Journal: J Mol Cell Cardiol

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Abstract

Blockade of sodium‑calcium exchanger via ORM-10962 attenuates cardiac alternans.

Szlovák J, Tomek J, Zhou X, Tóth N, ... Rodriguez B, Nagy N

Repolarization alternans, a periodic oscillation of long-short action potential duration, is an important source of arrhythmogenic substrate, although the mechanisms driving it are insufficiently understood. Despite its relevance as an arrhythmia precursor, there are no successful therapies able to target it specifically. We hypothesized that blockade of the sodium‑calcium exchanger (NCX) could inhibit alternans. The effects of the selective NCX blocker ORM-10962 were evaluated on action potentials measured with microelectrodes from canine papillary muscle preparations, and calcium transients measured using Fluo4-AM from isolated ventricular myocytes paced to evoke alternans. Computer simulations were used to obtain insight into the drug\'s mechanisms of action. ORM-10962 attenuated cardiac alternans, both in action potential duration and calcium transient amplitude. Three morphological types of alternans were observed, with differential response to ORM-10962 with regards to APD alternans attenuation. Analysis of APD restitution indicates that calcium oscillations underlie alternans formation. Furthermore, ORM-10962 did not markedly alter APD restitution, but increased post-repolarization refractoriness, which may be mediated by indirectly reduced L-type calcium current. Computer simulations reproduced alternans attenuation via ORM-10962, suggesting that it is acts by reducing sarcoplasmic reticulum release refractoriness. This results from the ORM-10962-induced sodium‑calcium exchanger block accompanied by an indirect reduction in L-type calcium current. Using a computer model of a heart failure cell, we furthermore demonstrate that the anti-alternans effect holds also for this disease, in which the risk of alternans is elevated. Targeting NCX may therefore be a useful anti-arrhythmic strategy to specifically prevent calcium driven alternans.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 27 Dec 2020; epub ahead of print
Szlovák J, Tomek J, Zhou X, Tóth N, ... Rodriguez B, Nagy N
J Mol Cell Cardiol: 27 Dec 2020; epub ahead of print | PMID: 33383036
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Abstract

Soluble epoxide hydrolase deficiency attenuates lipotoxic cardiomyopathy via upregulation of AMPK-mTORC mediated autophagy.

Wang L, Zhao D, Tang L, Li H, ... Wang J, Huang H

Obesity-driven cardiac lipid accumulation can progress to lipotoxic cardiomyopathy. Soluble epoxide hydrolase (sEH) is the major enzyme that metabolizes epoxyeicosatrienoic acids (EETs), which have biological activity of regulating lipid metabolism. The current study explores the unknown role of sEH deficiency in lipotoxic cardiomyopathy and its underlying mechanism. Wild-type and Ephx2 knock out (sEH KO) C57BL/6 J mice were fed with high-fat diet (HFD) for 24 weeks to induce lipotoxic cardiomyopathy animal models. Palmitic acid (PA) was utilized to induce lipotoxicity to cardiomyocytes for in vitro study. We found sEH KO, independent of plasma lipid and blood pressures, significantly attenuated HFD-induced myocardial lipid accumulation and cardiac dysfunction in vivo. HFD-induced lipotoxic cardiomyopathy and dysfunction of adenosine 5\'-monophosphate-activated protein kinase-mammalian target of rapamycin complex (AMPK-mTORC) signaling mediated lipid autophagy in heart were restored by sEH KO. In primary neonatal mouse cardiomyocytes, both sEH KO and sEH substrate EETs plus sEH inhibitor AUDA treatments attenuated PA-induced lipid accumulation. These effects were blocked by inhibition of AMPK or autophagy. The outcomes were supported by the results that sEH KO and EETs plus AUDA rescued HFD- and PA-induced impairment of autophagy upstream signaling of AMPK-mTORC, respectively. These findings revealed that sEH deficiency played an important role in attenuating myocardial lipid accumulation and provided new insights into treating lipotoxic cardiomyopathy. Regulation of autophagy via AMPK-mTORC signaling pathway is one of the underlying mechanisms.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 26 Dec 2020; epub ahead of print
Wang L, Zhao D, Tang L, Li H, ... Wang J, Huang H
J Mol Cell Cardiol: 26 Dec 2020; epub ahead of print | PMID: 33378686
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Abstract

Pathophysiology and pharmacological management of pulmonary and cardiovascular features of COVID-19.

Hamouche W, Bisserier M, Brojakowska A, Eskandari A, ... Goukassian DA, Hadri L

The first confirmed case of novel Coronavirus Disease 2019 (COVID-19) in the United States was reported on January 20, 2020. As of November 24, 2020, close to 12.2 million cases of COVID-19 was confirmed in the US, with over 255,958 deaths. The rapid transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), its unusual and divergent presentation has strengthened the status of COVID-19 as a major public health threat. In this review, we aim to 1- discuss the epidemiological data from various COVID-19 patient cohorts around the world and the USA as well the associated risk factors; 2- summarize the pathophysiology of SARS-CoV-2 infection and the underlying molecular mechanisms for the respiratory and cardiovascular manifestations; 3- highlight the potential treatments and vaccines as well as current clinical trials for COVID-19.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print
Hamouche W, Bisserier M, Brojakowska A, Eskandari A, ... Goukassian DA, Hadri L
J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print | PMID: 33373644
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Abstract

Mechanisms underlying age-associated manifestation of cardiac sodium channel gain-of-function.

Nowak MB, Poelzing S, Weinberg SH

Cardiac action potentials are initiated by sodium ion (Na) influx through voltage-gated Na channels. Na channel gain-of-function (GOF) can arise in inherited conditions due to mutations in the gene encoding the cardiac Na channel, such as Long QT syndrome type 3 (LQT3). LQT3 can be a \"concealed\" disease, as patients with LQT3-associated mutations can remain asymptomatic until later in life; however, arrhythmias can also arise early in life in LQT3 patients, demonstrating a complex age-associated manifestation. We and others recently demonstrated that cardiac Na channels preferentially localize at the intercalated disc (ID) in adult cardiac tissue, which facilitates ephaptic coupling and formation of intercellular Na nanodomains that regulate pro-arrhythmic early afterdepolarization (EAD) formation in tissue with Na channel GOF. Several properties related to ephaptic coupling vary with age, such as cell size and Na channel and gap junction (GJ) expression and distribution: neonatal cells have immature IDs, with Na channels and GJs primarily diffusively distributed, while adult myocytes have mature IDs with preferentially localized Na channels and GJs. Here, we perform an in silico study varying critical age-dependent parameters to investigate mechanisms underlying age-associated manifestation of Na channel GOF in a model of guinea pig cardiac tissue. Simulations predict that total Na current conductance is a critical factor in action potential duration (APD) prolongation. We find a complex cell size/ Na channel expression relationship: increases in cell size (without concurrent increases in Na channel expression) suppress EAD formation, while increases in Na channel expression (without concurrent increases in cell size) promotes EAD formation. Finally, simulations with neonatal and early age-associated parameters predict normal APD with minimal dependence on intercellular cleft width; however, variability in cellular properties can lead to EADs presenting in early developmental stages. In contrast, for adult-associated parameters, EAD formation is highly dependent on cleft width, consistent with a mechanism underlying the age-associated manifestation of the Na channel GOF.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print
Nowak MB, Poelzing S, Weinberg SH
J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print | PMID: 33373643
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Abstract

Adverse effects of hydroxychloroquine and azithromycin on contractility and arrhythmogenicity revealed by human engineered cardiac tissues.

Wong AO, Gurung B, Wong WS, Mak SY, ... Li RA, Hajjar RJ

The coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic as declared by World Health Organization (WHO). In the absence of an effective treatment in early 2020, different drugs with unknown effectiveness, including antimalarial hydroxychloroquine (HCQ), with or without concurrent administration with azithromycin (AZM), have been tested for treating COVID-19 patients with developed pneumonia. However, the efficacy and safety of HCQ and/or AZM have been questioned by recent clinical reports. Direct effects of these drugs on the human heart remain very poorly defined. To better understand the mechanisms of action of HCQ +/- AZM, we employed bioengineered human ventricular cardiac tissue strip (hvCTS) and anisotropic sheet (hvCAS) assays, made with human pluripotent stem cell (hPSC)-derived ventricular cardiomyocytes (hvCMs), which have been designed for measuring cardiac contractility and electrophysiology, respectively. Our hvCTS experiments showed that AZM induced a dose-dependent negative inotropic effect which could be aggravated by HCQ; electrophysiologically, as revealed by the hvCAS platform, AZM prolonged action potentials and induced spiral wave formations. Collectively, our data were consistent with reported clinical risks of HCQ and AZM on QTc prolongation/ventricular arrhythmias and development of heart failure. In conclusion, our study exposed the risks of HCQ/AZM administration while providing mechanistic insights for their toxicity. Our bioengineered human cardiac tissue constructs therefore provide a useful platform for screening cardiac safety and efficacy when developing therapeutics against COVID-19.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print
Wong AO, Gurung B, Wong WS, Mak SY, ... Li RA, Hajjar RJ
J Mol Cell Cardiol: 25 Dec 2020; epub ahead of print | PMID: 33373642
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Abstract

Elevated EZH2 in ischemic heart disease epigenetically mediates suppression of Na1.5 expression.

Zhao L, You T, Lu Y, Lin S, Li F, Xu H

Suppression of the cardiac sodium channel Na1.5 leads to fatal arrhythmias in ischemic heart disease (IHD). However, the transcriptional regulation of Na1.5 in cardiac ischemia is still unclear. Our studies are aimed to investigate the expression of enhancer of zeste homolog 2 (EZH2) in IHD and regulation of cardiac Na1.5 expression by EZH2. Human heart tissue was obtained from IHD and non-failing heart (NFH) patients; mouse heart tissue was obtained from the peri-infarct zone of hearts with myocardial infarction (MI) and hearts with a sham procedure. Protein and mRNA expression were measured by immunoblotting, immunostaining, and qRT-PCR. Protein-DNA binding and promoter activity were analyzed by ChIP-qPCR and luciferase assays, respectively. Na channel activity was assessed by whole-cell patch clamp recordings. EZH2 and H3K27me3 were increased while Na1.5 expression was reduced in IHD hearts and in mouse MI hearts compared to the controls. Reduced Na1.5 and increased EZH2 mRNA levels were observed in mouse MI hearts. A selective EZH2 inhibitor, GSK126 decreased H3K27me3 and elevated Na1.5 in HL-1 cells. Silencing of EZH2 expression decreased H3K27me3 and increased Na1.5 in these cells. EZH2 and H3K27me3 were enriched in the promoter regions of Scn5a and were decreased by treatment with EZH2 siRNA. GSK126 inhibited the enrichment of H3K27me3 in the Scn5a promoter and enhanced Scn5a transcriptional activity. GSK126 significantly increased Na channel activity. Taken together, EZH2 is increased in ischemic hearts and epigenetically suppresses Scn5a transcription by H3K27me3, leading to decreased Na1.5 expression and Na channel activity underlying the pathogenesis of arrhythmias.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 24 Dec 2020; epub ahead of print
Zhao L, You T, Lu Y, Lin S, Li F, Xu H
J Mol Cell Cardiol: 24 Dec 2020; epub ahead of print | PMID: 33370552
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Abstract

Suppression of canonical TGF-β signaling enables GATA4 to interact with H3K27me3 demethylase JMJD3 to promote cardiomyogenesis.

Riching AS, Danis E, Zhao Y, Cao Y, ... Buttrick PM, Song K

Direct reprogramming of fibroblasts into cardiomyocytes (CMs) represents a promising strategy to regenerate CMs lost after ischemic heart injury. Overexpression of GATA4, HAND2, MEF2C, TBX5, miR-1, and miR-133 (GHMT2m) along with transforming growth factor beta (TGF-β) inhibition efficiently promote reprogramming. However, the mechanisms by which TGF-β blockade promotes cardiac reprogramming remain unknown. Here, we identify interactions between the histone H3 lysine 27 trimethylation (H3K27me3) demethylase JMJD3, the SWI/SNF remodeling complex subunit BRG1, and cardiac transcription factors. Furthermore, canonical TGF-β signaling regulates the interaction between GATA4 and JMJD3. TGF-β activation impairs the ability of GATA4 to bind target genes and prevents demethylation of H3K27 at cardiac gene promoters during cardiac reprogramming. Finally, a mutation in GATA4 (V267M) that is associated with congenital heart disease exhibits reduced binding to JMJD3 and impairs cardiomyogenesis. Thus, we have identified an epigenetic mechanism wherein canonical TGF-β pathway activation impairs cardiac gene programming, in part by interfering with GATA4-JMJD3 interactions.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 23 Dec 2020; 153:44-59
Riching AS, Danis E, Zhao Y, Cao Y, ... Buttrick PM, Song K
J Mol Cell Cardiol: 23 Dec 2020; 153:44-59 | PMID: 33359755
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Abstract

Considerations for using isolated cell systems to understand cardiac metabolism and biology.

McNally LA, Altamimi TR, Fulghum K, Hill BG

Changes in myocardial metabolic activity are fundamentally linked to cardiac health and remodeling. Primary cardiomyocytes, induced pluripotent stem cell-derived cardiomyocytes, and transformed cardiomyocyte cell lines are common models used to understand how (patho)physiological conditions or stimuli contribute to changes in cardiac metabolism. These cell models are helpful also for defining metabolic mechanisms of cardiac dysfunction and remodeling. Although technical advances have improved our capacity to measure cardiomyocyte metabolism, there is often heterogeneity in metabolic assay protocols and cell models, which could hinder data interpretation and discernment of the mechanisms of cardiac (patho)physiology. In this review, we discuss considerations for integrating cardiomyocyte cell models with techniques that have become relatively common in the field, such as respirometry and extracellular flux analysis. Furthermore, we provide overviews of metabolic assays that complement XF analyses and that provide information on not only catabolic pathway activity, but biosynthetic pathway activity and redox status as well. Cultivating a more widespread understanding of the advantages and limitations of metabolic measurements in cardiomyocyte cell models will continue to be essential for the development of coherent metabolic mechanisms of cardiac health and pathophysiology.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 20 Dec 2020; 153:26-41
McNally LA, Altamimi TR, Fulghum K, Hill BG
J Mol Cell Cardiol: 20 Dec 2020; 153:26-41 | PMID: 33359038
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Abstract

Nano-scale morphology of cardiomyocyte t-tubule/sarcoplasmic reticulum junctions revealed by ultra-rapid high-pressure freezing and electron tomography.

Rog-Zielinska EA, Moss R, Kaltenbacher W, Greiner J, ... Kohl P, Cannell MB

Detailed knowledge of the ultrastructure of intracellular compartments is a prerequisite for our understanding of how cells function. In cardiac muscle cells, close apposition of transverse (t)-tubule (TT) and sarcoplasmic reticulum (SR) membranes supports stable high-gain excitation-contraction coupling. Here, the fine structure of this key intracellular element is examined in rabbit and mouse ventricular cardiomyocytes, using ultra-rapid high-pressure freezing (HPF, omitting aldehyde fixation) and electron microscopy. 3D electron tomograms were used to quantify the dimensions of TT, terminal cisternae of the SR, and the space between SR and TT membranes (dyadic cleft). In comparison to conventional aldehyde-based chemical sample fixation, HPF-preserved samples of both species show considerably more voluminous SR terminal cisternae, both in absolute dimensions and in terms of junctional SR to TT volume ratio. In rabbit cardiomyocytes, the average dyadic cleft surface area of HPF and chemically fixed myocytes did not differ, but cleft volume was significantly smaller in HPF samples than in conventionally fixed tissue; in murine cardiomyocytes, the dyadic cleft surface area was higher in HPF samples with no change in cleft volume. In both species, the apposition of the TT and SR membranes in the dyad was more likely to be closer than 10 nm in HPF samples compared to CFD, presumably resulting from avoidance of sample shrinkage associated with conventional fixation techniques. Overall, we provide a note of caution regarding quantitative interpretation of chemically-fixed ultrastructures, and offer novel insight into cardiac TT and SR ultrastructure with relevance for our understanding of cardiac physiology.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 19 Dec 2020; epub ahead of print
Rog-Zielinska EA, Moss R, Kaltenbacher W, Greiner J, ... Kohl P, Cannell MB
J Mol Cell Cardiol: 19 Dec 2020; epub ahead of print | PMID: 33359037
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Abstract

The role of β-adrenergic system remodeling in human heart failure: A mechanistic investigation.

Mora MT, Gong JQX, Sobie EA, Trenor B

β-adrenergic receptor antagonists (β-blockers) are extensively used to improve cardiac performance in heart failure (HF), but the electrical improvements with these clinical treatments are not fully understood. The aim of this study was to analyze the electrophysiological effects of β-adrenergic system remodeling in heart failure with reduced ejection fraction and the underlying mechanisms. We used a combined mathematical model that integrated β-adrenergic signaling with electrophysiology and calcium cycling in human ventricular myocytes. HF remodeling, both in the electrophysiological and signaling systems, was introduced to quantitatively analyze changes in electrophysiological properties due to the stimulation of β-adrenergic receptors in failing myocytes. We found that the inotropic effect of β-adrenergic stimulation was reduced in HF due to the altered Ca dynamics resulting from the combination of structural, electrophysiological and signaling remodeling. Isolated cells showed proarrhythmic risk after sympathetic stimulation because early afterdepolarizations appeared, and the vulnerability was greater in failing myocytes. When analyzing coupled cells, β-adrenergic stimulation reduced transmural repolarization gradients between endocardium and epicardium in normal tissue, but was less effective at reducing these gradients after HF remodeling. The comparison of the selective activation of β-adrenergic isoforms revealed that the response to β-adrenergic receptors stimulation was blunted in HF while β-adrenergic receptors downstream effectors regulated most of the changes observed after sympathetic stimulation. In conclusion, this study was able to reproduce an altered β-adrenergic activity on failing myocytes and to explain the mechanisms involved. The derived predictions could help in the treatment of HF and guide in the design of future experiments.

Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 13 Dec 2020; 153:14-25
Mora MT, Gong JQX, Sobie EA, Trenor B
J Mol Cell Cardiol: 13 Dec 2020; 153:14-25 | PMID: 33326834
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Abstract

Ubiquitin-like protein FAT10 suppresses SIRT1-mediated autophagy to protect against ischemic myocardial injury.

Wan R, Yuan P, Guo L, Shao J, ... Jiang X, Hong K

Autophagy plays a deleterious role in ischemic myocardial injury. The deacetylase SIRT1 is a well-established regulator of autophagy that can be modified by the ubiquitin-like protein SUMO1. Our previous work demonstrated that another ubiquitin-like protein, FAT10, exerts cardioprotective effects against myocardial ischemia by stabilizing the caveolin-3 protein; however, the effects of FAT10 on autophagy through SIRT1 are unclear. Here, we constructed a Fat10-knockout rat model to evaluate the role of FAT10 in autophagy. In vivo and in vitro assays confirmed that FAT10 suppressed autophagy to protect the heart from ischemic myocardial injury. Mechanistically, FAT10 was mainly involved in the regulation of the autophagosome formation process. FAT10 affected autophagy through modulating SIRT1 degradation, which resulted in reduced SIRT1 nuclear translocation and inhibited SIRT1 activity via its C-terminal glycine residues. Notably, FAT10 competed with SUMO1 at the K734 modification site of SIRT1, which further reduced LC3 deacetylation and suppressed autophagy. Our findings suggest that FAT10 inhibits autophagy by antagonizing SIRT1 SUMOylation to protect the heart from ischemic myocardial injury. This is a novel mechanism through which FAT10 regulates autophagy as a cardiac protector.

Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 08 Dec 2020; 153:1-13
Wan R, Yuan P, Guo L, Shao J, ... Jiang X, Hong K
J Mol Cell Cardiol: 08 Dec 2020; 153:1-13 | PMID: 33307094
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Abstract

Downregulation of the zinc transporter SLC39A13 (ZIP13) is responsible for the activation of CaMKII at reperfusion and leads to myocardial ischemia/reperfusion injury in mouse hearts.

Wang J, Cheng X, Zhao H, Yang Q, Xu Z

While Zn dyshomeostasis is known to contribute to ischemia/reperfusion (I/R) injury, the roles of zinc transporters that are responsible for Zn homeostasis in the pathogenesis of I/R injury remain to be addressed. This study reports that ZIP13 (SLC39A13), a zinc transporter, plays a role in myocardial I/R injury by modulating the Ca signaling pathway rather than by regulating Zn transport. ZIP13 is downregulated upon reperfusion in mouse hearts or in H9c2 cells at reoxygenation. Ca but not Zn was responsible for ZIP13 downregulation, implying that ZIP13 may play a role in I/R injury through the Ca signaling pathway. In line with our assumption, knockout of ZIP13 resulted in phosphorylation (Thr) of Ca-calmodulin-dependent protein kinase (CaMKII), indicating that downregulation of ZIP13 leads to CaMKII activation. Further studies showed that the heart-specific knockout of ZIP13 enhanced I/R-induced CaMKII phosphorylation in mouse hearts. In contrast, overexpression of ZIP13 suppressed I/R-induced CaMKII phosphorylation. Moreover, the heart-specific knockout of ZIP13 exacerbated myocardial infarction in mouse hearts subjected to I/R, whereas overexpression of ZIP13 reduced infarct size. In addition, knockout of ZIP13 induced increases of mitochondrial Ca, ROS, mitochondrial swelling, decrease in the mitochondrial respiration control rate (RCR), and dissipation of mitochondrial membrane potential (ΔΨm) in a CaMKII-dependent manner. These data suggest that downregulation of ZIP13 at reperfusion contributes to myocardial I/R injury through activation of CaMKII and the mitochondrial death pathway.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 08 Dec 2020; 152:69-79
Wang J, Cheng X, Zhao H, Yang Q, Xu Z
J Mol Cell Cardiol: 08 Dec 2020; 152:69-79 | PMID: 33307093
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Abstract

Gut microbiome - A potential mediator of pathogenesis in heart failure and its comorbidities: State-of-the-art review.

Mamic P, Chaikijurajai T, Tang WHW

Gut microbiome (GMB) has been increasingly recognized as a contributor to development and progression of heart failure (HF), immune-mediated subtypes of cardiomyopathy (myocarditis and anthracycline-induced cardiotoxicity), response to certain cardiovascular drugs, and HF-related comorbidities, such as chronic kidney disease, cardiorenal syndrome, insulin resistance, malnutrition, and cardiac cachexia. Gut microbiome is also responsible for the \"gut hypothesis\" of HF, which explains the adverse effects of gut barrier dysfunction and translocation of GMB on the progression of HF. Furthermore, accumulating evidence has suggested that gut microbial metabolites, including short chain fatty acids, trimethylamine N-oxide (TMAO), amino acid metabolites, and bile acids, are mechanistically linked to pathogenesis of HF, and could, therefore, serve as potential therapeutic targets for HF. Even though there are a variety of proposed therapeutic approaches, such as dietary modifications, prebiotics, probiotics, TMAO synthesis inhibitors, and fecal microbial transplant, targeting GMB in HF is still in its infancy and, indeed, requires further preclinical and clinical evidence. In this review, we aim to highlight the role gut microbiome plays in HF pathophysiology and its potential as a novel therapeutic target in HF.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 07 Dec 2020; epub ahead of print
Mamic P, Chaikijurajai T, Tang WHW
J Mol Cell Cardiol: 07 Dec 2020; epub ahead of print | PMID: 33307092
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Abstract

Mep1a contributes to Ang II-induced cardiac remodeling by promoting cardiac hypertrophy, fibrosis and inflammation.

Ge W, Hou C, Zhang W, Guo X, ... Zhao H, Wang J

Pathological cardiac remodeling, characterized by excessive deposition of extracellular matrix proteins and cardiac hypertrophy, leads to the development of heart failure. Meprin α (Mep1a), a zinc metalloprotease, previously reported to participate in the regulation of inflammatory response and fibrosis, may also contribute to cardiac remodeling, although whether and how it participates in this process remains unknown. Here, in this work, we investigated the role of Mep1a in pathological cardiac remodeling, as well as the effects of the Mep1a inhibitor actinonin on cardiac remodeling-associated phenotypes. We found that Mep1a deficiency or chemical inhibition both significantly alleviated TAC- and Ang II-induced cardiac remodeling and dysfunction. Mep1a deletion and blocking both attenuated TAC- and Ang II-induced heart enlargement and increases in the thickness of the left ventricle anterior and posterior walls, and reduced expression of pro-hypertrophic markers, including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and myosin heavy chain beta (β-MHC). In addition, Mep1a deletion and blocking significantly inhibited TAC- and Ang II-induced cardiac fibroblast activation and production of extracellular matrix (ECM). Moreover, in Mep1a mice and treatment with actinonin significantly reduced Ang II-induced infiltration of macrophages and proinflammatory cytokines. Notably, we found that in vitro, Mep1a is expressed in cardiac myocytes and fibroblasts and that Mep1a deletion or chemical inhibition both markedly suppressed Ang II-induced hypertrophy of rat or mouse cardiac myocytes and activation of rat or mouse cardiac fibroblasts. In addition, blocking Mep1a in macrophages reduced Ang II-induced expression of interleukin (IL)-6 and IL-1β, strongly suggesting that Mep1a participates in cardiac remodeling processes through regulation of inflammatory cytokine expression. Mechanism studies revealed that Mep1a mediated ERK1/2 activation in cardiac myocytes, fibroblasts and macrophages and contributed to cardiac remodeling. In light of our findings that blocking Mep1a can ameliorate cardiac remodeling via inhibition of cardiac hypertrophy, fibrosis, and inflammation, Mep1a may therefore serve as a strong potential candidate for therapeutic targeting to prevent cardiac remodeling.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 07 Dec 2020; 152:52-68
Ge W, Hou C, Zhang W, Guo X, ... Zhao H, Wang J
J Mol Cell Cardiol: 07 Dec 2020; 152:52-68 | PMID: 33301800
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Abstract

Mitochondrial Ca, redox environment and ROS emission in heart failure: Two sides of the same coin?

Cortassa S, Juhaszova M, Aon MA, Zorov DB, Sollott SJ

Heart failure (HF) is a progressive, debilitating condition characterized, in part, by altered ionic equilibria, increased ROS production and impaired cellular energy metabolism, contributing to variable profiles of systolic and diastolic dysfunction with significant functional limitations and risk of premature death. We summarize current knowledge concerning changes of intracellular Na and Ca control mechanisms during the disease progression and their consequences on mitochondrial Ca homeostasis and the shift in redox balance. Absent existing biological data, our computational modeling studies advance a new \'in silico\' analysis to reconcile existing opposing views, based on different experimental HF models, regarding variations in mitochondrial Ca concentration that participate in triggering and perpetuating oxidative stress in the failing heart and their impact on cardiac energetics. In agreement with our hypothesis and the literature, model simulations demonstrate the possibility that the heart\'s redox status together with cytoplasmic Na concentrations act as regulators of mitochondrial Ca levels in HF and of the bioenergetics response that will ultimately drive ATP supply and oxidative stress. The resulting model predictions propose future directions to study the evolution of HF as well as other types of heart disease, and to develop novel testable mechanistic hypotheses that may lead to improved therapeutics.

Published by Elsevier Ltd.

J Mol Cell Cardiol: 06 Dec 2020; 151:113-125
Cortassa S, Juhaszova M, Aon MA, Zorov DB, Sollott SJ
J Mol Cell Cardiol: 06 Dec 2020; 151:113-125 | PMID: 33301801
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Abstract

Mitochondrial Ca in heart failure: Not enough or too much?

O\'Rourke B, Ashok D, Liu T

Ca serves as a ubiquitous second messenger mediating a variety of cellular processes including electrical excitation, contraction, gene expression, secretion, cell death and others. The identification of the molecular components of the mitochondrial Ca influx and efflux pathways has created a resurgent interest in the regulation of mitochondrial Ca balance and its physiological and pathophysiological roles. While the pace of discovery has quickened with the availability of new cellular and animal models, many fundamental questions remain to be answered regarding the regulation and functional impact of mitochondrial Ca in health and disease. This review highlights several experimental observations pertaining to key aspects of mitochondrial Ca homeostasis that remain enigmatic, particularly whether mitochondrial Ca signaling is depressed or excessive in heart failure, which will determine the optimal approach to therapeutic intervention.

Copyright © 2019. Published by Elsevier Ltd.

J Mol Cell Cardiol: 04 Dec 2020; epub ahead of print
O'Rourke B, Ashok D, Liu T
J Mol Cell Cardiol: 04 Dec 2020; epub ahead of print | PMID: 33290770
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Abstract

Proximity to injury, but neither number of nuclei nor ploidy define pathological adaptation and plasticity in cardiomyocytes.

Hesse M, Bednarz R, Carls E, Becker C, ... Fleischmann BK, Gilsbach R

The adult mammalian heart consists of mononuclear and binuclear cardiomyocytes (CMs) with various ploidies. However, it remains unclear whether a variation in ploidy or number of nuclei is associated with distinct functions and injury responses in CMs, including regeneration. Therefore, we investigated transcriptomes and cellular as well as nuclear features of mononucleated and binucleated CMs in adult mouse hearts with and without injury. To be able to identify the role of ploidy we analyzed control and failing human ventricular CMs because human CMs show a larger and disease-sensitive degree of polyploidization. Using transgenic Myh6-H2BmCh to identify mononucleated and binucleated mouse CMs, we found that cellular volume and RNA content were similar in both. On average nuclei of mononuclear CMs showed a 2-fold higher ploidy, as compared to binuclear CMs indicating that most mononuclear CMs are tetraploid. After myocardial infarction mononucleated and binucleated CMs in the border zone of the lesion responded with hypertrophy and corresponding changes in gene expression, as well as a low level of induction of cell cycle gene expression. Human CMs allowed us to study a wide range of polyploidy spanning from 2n to 16n. Notably, basal as well as pathological gene expression signatures and programs in failing CMs proved to be independent of ploidy. In summary, gene expression profiles were induced in proximity to injury, but independent of number of nuclei or ploidy levels in CMs.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 04 Dec 2020; 152:95-104
Hesse M, Bednarz R, Carls E, Becker C, ... Fleischmann BK, Gilsbach R
J Mol Cell Cardiol: 04 Dec 2020; 152:95-104 | PMID: 33290769
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Abstract

The cardiac methylome: A hidden layer of RNA modifications to regulate gene expression.

Rajan KS, Ramasamy S, Garikipati VNS, Suvekbala V

Post-transcriptional RNA modification has been observed in all kingdoms of life and more than a hundred different types of RNA modifications decorate the chemical and topological properties of these ribose nucleotides. These RNA modifications can potentially alter the RNA structure and also affect the binding affinity of proteins, thus regulating the mRNA stability as well as translation. Emerging evidence suggest that these modifications are not static, but are dynamic; vary upon different cues and are cell-type or tissue-specific. The cardiac transcriptome is not exceptional to such RNA modifications and is enriched with the abundant base methylation such as N-methyladenosine (mA) and also 2\'-O-Methylation (Nm). In this review we will focus on the technologies available to map these modifications and as well as the contribution of these post-transcriptional modifications during various pathological conditions of the heart.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 02 Dec 2020; 152:40-51
Rajan KS, Ramasamy S, Garikipati VNS, Suvekbala V
J Mol Cell Cardiol: 02 Dec 2020; 152:40-51 | PMID: 33279505
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Abstract

Inhibition of endoplasmic reticulum stress mediates the ameliorative effect of apelin on vascular calcification.

Li Y, Li Y, Li Y, Yang Z, ... Wang X, Teng X
Aims
Apelin is the endogenous ligand of G protein-coupled receptor APJ and play an important role in the regulation of cardiovascular homeostasis. We aimed to investigate whether apelin ameliorates vascular calcification (VC) by inhibition of endoplasmic reticulum stress (ERS).
Methods and results
VC model in rats was induced by nicotine plus vitamin D, while calcification of vascular smooth muscle cell (VSMC) was induced by beta-glycerophosphate. Alizarin Red S staining showed dramatic calcium deposition in the aorta of rats with VC, while calcium contents and ALP activity also increased in calcified aorta. Protein levels of apelin and APJ were decreased in the calcified aorta. In rats with VC, apelin treatment significantly ameliorated aortic calcification, compliance and stimulation of ERS. The ameliorative effect of apelin on VC and ERS was also observed in calcified VSMCs. ERS stimulator (tunicamycin or DTT) blocked the beneficial effect of apelin. Apelin treatment activated the PI3K/Akt signaling, blockage of which by wortmannin or inhibitor IV prevented the ameliorative effect of apelin, while ERS inhibitor 4-PBA rescued the blockade effect of wortmannin. Akt-induced GSK inhibition prevented the phosphorylation of PERK and IRE1, and the activation of these two major ERS branches. F13A blocked the ameliorative effect of apelin on VC and ERS, which was reversed by treatment with 4-PBA or Akt activator SC79
Conclusions:
Apelin ameliorated VC by binding to APJ and then prevented ERS activation by stimulating Akt signaling. These results might provide new target for therapy and prevention of VC.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 02 Dec 2020; 152:17-28
Li Y, Li Y, Li Y, Yang Z, ... Wang X, Teng X
J Mol Cell Cardiol: 02 Dec 2020; 152:17-28 | PMID: 33279504
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Impact:
Abstract

Precision medicine for heart failure based on molecular mechanisms: The Research Achievement Award Lecture.

Nomura S, Komuro I

Heart failure is a leading cause of death, and the number of patients with heart failure continues to increase worldwide. To realize precision medicine for heart failure, its underlying molecular mechanisms must be elucidated. In this review summarizing the \"The Research Achievement Award Lecture\" of the 2019 XXIII ISHR World Congress held in Beijing, China, we would like to introduce our approaches for investigating the molecular mechanisms of cardiac hypertrophy, development, and failure, as well as discuss future perspectives.

Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 30 Nov 2020; 152:29-39
Nomura S, Komuro I
J Mol Cell Cardiol: 30 Nov 2020; 152:29-39 | PMID: 33275937
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Impact:
Abstract

What we know about cardiomyocyte dedifferentiation.

Zhu Y, Do VD, Richards AM, Foo R

Cardiomyocytes (CMs) lost during cardiac injury and heart failure (HF) cannot be replaced due to their limited proliferative capacity. Regenerating the failing heart by promoting CM cell-cycle re-entry is an ambitious solution, currently vigorously pursued. Some genes have been proven to promote endogenous CM proliferation, believed to be preceded by CM dedifferentiation, wherein terminally differentiated CMs are initially reversed back to the less mature state which precedes cell division. However, very little else is known about CM dedifferentiation which remains poorly defined. We lack robust molecular markers and proper understanding of the mechanisms driving dedifferentiation. Even the term dedifferentiation is debated because there is no objective evidence of pluripotency, and could rather reflect CM plasticity instead. Nonetheless, the significance of CM transition states on cardiac function, and whether they necessarily lead to CM proliferation, remains unclear. This review summarises the current state of knowledge of both natural and experimentally induced CM dedifferentiation in non-mammalian vertebrates (primarily the zebrafish) and mammals, as well as the phenotypes and molecular mechanisms involved. The significance and potential challenges of studying CM dedifferentiation are also discussed. In summary, CM dedifferentiation, essential for CM plasticity, may have an important role in heart regeneration, thereby contributing to the prevention and treatment of heart disease. More attention is needed in this field to overcome the technical limitations and knowledge gaps.

Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 30 Nov 2020; 152:80-91
Zhu Y, Do VD, Richards AM, Foo R
J Mol Cell Cardiol: 30 Nov 2020; 152:80-91 | PMID: 33275936
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Impact:
Abstract

BRD4 inhibition by JQ1 prevents high-fat diet-induced diabetic cardiomyopathy by activating PINK1/Parkin-mediated mitophagy in vivo.

Mu J, Zhang D, Tian Y, Xie Z, Zou MH

BRD4 is a member of the BET family of epigenetic regulators. Inhibition of BRD4 by the selective bromodomain inhibitor JQ1, alleviates thoracic aortic constriction-induced cardiac hypertrophy and heart failure. However, whether BRD4 inhibition by JQ1 has therapeutic effect on diabetic cardiomyopathy, a major cause of heart failure in patients with Type 2 diabetes, remains unknown. Here, we discover a novel link between BRD4 and PINK1/Parkin-mediated mitophagy during diabetic cardiomyopathy. Upregulation of BRD4 in diabetic mouse hearts inhibits PINK1/Parkin-mediated mitophagy, resulting in accumulation of damaged mitochondria and subsequent impairment of cardiac structure and function. BRD4 inhibition by JQ1 improves mitochondrial function, and repairs the cardiac structure and function of the diabetic heart. These effects depended on rewiring of the BRD4-driven transcription and repression of PINK1. Deletion of Pink1 suppresses mitophagy, exacerbates cardiomyopathy, and abrogates the therapeutic effect of JQ1 on diabetic cardiomyopathy. Our results illustrate a valid therapeutic strategy for treating diabetic cardiomyopathy by inhibition of BRD4.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 29 Nov 2020; 149:1-14
Mu J, Zhang D, Tian Y, Xie Z, Zou MH
J Mol Cell Cardiol: 29 Nov 2020; 149:1-14 | PMID: 32941882
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Impact:
Abstract

Increased mast cell density is associated with decreased fibrosis in human atrial tissue.

Legere SA, Haidl ID, Castonguay MC, Brunt KR, ... Marshall JS,

Fibrotic remodelling of the atria is poorly understood and can be regulated by myocardial immune cell populations after injury. Mast cells are resident immune sentinel cells present in the heart that respond to tissue damage and have been linked to fibrosis in other settings. The role of cardiac mast cells in fibrotic remodelling in response to human myocardial injury is controversial. In this study, we sought to determine the association between mast cells, atrial fibrosis, and outcomes in a heterogeneous population of cardiac surgical patients, including a substantial proportion of coronary artery bypass grafting patients. Atrial appendage from patients was assessed for collagen and mast cell density by histology and by droplet digital polymerase chain reaction (ddPCR) for mast cell associated transcripts. Clinical variables and outcomes were also followed. Mast cells were detected in human atrial tissue at varying densities. Histological and ddPCR assessment of mast cells in atrial tissue were closely correlated. Patients with high mast cell density had less fibrosis and lower severity of heart failure classification or incidence mortality than patients with low mast cell content. Analysis of a homogeneous population of coronary artery bypass graft patients yielded similar observations. Therefore, evidence from this study suggests that increased atrial mast cell populations are associated with decreased clinical cardiac fibrotic remodelling and improved outcomes, in cardiac surgery patients.

Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:15-26
Legere SA, Haidl ID, Castonguay MC, Brunt KR, ... Marshall JS,
J Mol Cell Cardiol: 29 Nov 2020; 149:15-26 | PMID: 32931784
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Impact:
Abstract

Nestin represents a potential marker of pulmonary vascular remodeling in pulmonary arterial hypertension associated with congenital heart disease.

Zhou JJ, Li H, Qian YL, Quan RL, ... Jing XL, He JG
Objective
Reportedly, nestin was re-expressed in proliferative synthetic-type pulmonary artery smooth muscle cells (PASMCs) and obligatory for PASMC proliferation in pulmonary arterial hypertension (PAH). Accordingly, nestin is increased in pulmonary vascular lesions of congenital heart disease (CHD)-associated PAH patients. We tested the hypothesis whether nestin was re-expressed in proliferative synthetic-type PASMCs and associated with pulmonary vascular remodeling in CHD-PAH.
Materials and methods
Nestin expression was tested using lung tissues from CHD-PAH patients and monocrotaline (MCT) plus aortocaval (AV) shunt-induced PAH rats, human PASMCs (HPASMCs), and pulmonary artery endothelial cells (PAECs) and PASMCs from MCT-AV-induced PAH rats. The role and possible mechanism of nestin on HPASMC proliferation, apoptosis, cell cycle and migration were investigated by assays of CCK-8, EdU, TUNEL, flow cytometry, transwell chamber and immunoblotting assays.
Results
Nestin was solely expressed in proliferative synthetic-type PASMCs, but rarely detected in PAECs. Nestin was barely detected in normal pulmonary arterioles and occlusive pulmonary vascular lesions. Its expression was robustly increased in developing pulmonary vasculature, but returned to normal levels at the late stage of pulmonary vascular remodeling in lung tissues from CHD-PAH patients and MCT-AV-induced PAH rats. Besides, nestin peaks were consistent with the histological features in lung tissues of MCT-AV-induced PAH rats. Moreover, nestin overexpression effectively promoted HPASMC phenotypic transformation, proliferation, apoptosis resistance and migration via enhancing Wnt/β-catenin activation.
Conclusions
These data indicated that nestin was re-expressed in proliferative synthetic-type PASMCs and might represent a potential marker of pulmonary vascular remodeling in CHD-PAH.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:41-53
Zhou JJ, Li H, Qian YL, Quan RL, ... Jing XL, He JG
J Mol Cell Cardiol: 29 Nov 2020; 149:41-53 | PMID: 32950539
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Impact:
Abstract

Inhibition of Pyk2 and Src activity improves Cx43 gap junction intercellular communication.

Zheng L, Trease AJ, Katsurada K, Spagnol G, ... Patel KP, Sorgen PL

Identification of proteins that interact with Cx43 has been instrumental in the understanding of gap junction (GJ) regulation. An in vitro phosphorylation screen identified that Protein tyrosine kinase 2 beta (Pyk2) phosphorylated purified Cx43CT and this led us to characterize the impact of this phosphorylation on Cx43 function. Mass spectrometry identified Pyk2 phosphorylates Cx43 residues Y247, Y265, Y267, and Y313. Western blot and immunofluorescence staining using HeLa cells, HEK 293 T cells, and neonatal rat ventricular myocytes (NRVMs) revealed Pyk2 can be activated by Src and active Pyk2 interacts with Cx43 at the plasma membrane. Overexpression of Pyk2 increases Cx43 phosphorylation and knock-down of Pyk2 decreases Cx43 phosphorylation, without affecting the level of active Src. In HeLa cells treated with PMA to activate Pyk2, a decrease in Cx43 GJ intercellular communication (GJIC) was observed when assayed by dye transfer. Moreover, PMA activation of Pyk2 could be inhibited by the small molecule PF4618433. This partially restored GJIC, and when paired with a Src inhibitor, returned GJIC to the no PMA control-level. The ability of Pyk2 and Src inhibitors to restore Cx43 function in the presence of PMA was also observed in NRVMs. Additionally, an animal model of myocardial infarction induced heart failure showed a higher level of active Pyk2 activity and increased interaction with Cx43 in ventricular myocytes. Src inhibitors have been used to reverse Cx43 remodeling and improve heart function after myocardial infarction; however, they alone could not fully restore proper Cx43 function. Our data suggest that Pyk2 may need to be inhibited, in addition to Src, to further (if not completely) reverse Cx43 remodeling and improve intercellular communication.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:27-40
Zheng L, Trease AJ, Katsurada K, Spagnol G, ... Patel KP, Sorgen PL
J Mol Cell Cardiol: 29 Nov 2020; 149:27-40 | PMID: 32956670
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Impact:
Abstract

Circadian influence on the microbiome improves heart failure outcomes.

Mistry P, Reitz CJ, Khatua TN, Rasouli M, ... Allen-Vercoe E, Martino TA

Myocardial infarction (MI) leading to heart failure (HF) is a major cause of death worldwide. Previous studies revealed that the circadian system markedly impacts cardiac repair post-MI, and that light is an important environmental factor modulating the circadian influence over healing. Recent studies suggest that gut physiology also affects the circadian system, but how it contributes to cardiac repair post-MI and in HF is not well understood. To address this question, we first used a murine coronary artery ligation MI model to reveal that an intact gut microbiome is important for cardiac repair. Specifically, gut microbiome disruption impairs normal inflammatory responses in infarcted myocardium, elevates adverse cardiac gene biomarkers, and leads to worse HF outcomes. Conversely, reconstituting the microbiome post-MI in mice with prior gut microbiome disruption improves healing, consistent with the notion that normal gut physiology contributes to cardiac repair. To investigate a role for the circadian system, we initially utilized circadian mutant Clock mice, revealing that a functional circadian mechanism is necessary for gut microbiome benefits on post-MI cardiac repair and HF. Finally, we demonstrate that circadian-mediated gut responses that benefit cardiac repair can be conferred by time-restricted feeding, as wake time feeding of MI mice improves HF outcomes, but these benefits are not observed in MI mice fed during their sleep time. In summary, gut physiology is important for cardiac repair, and the circadian system influences the beneficial gut responses to improve post-MI and HF outcomes.

Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:54-72
Mistry P, Reitz CJ, Khatua TN, Rasouli M, ... Allen-Vercoe E, Martino TA
J Mol Cell Cardiol: 29 Nov 2020; 149:54-72 | PMID: 32961201
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Impact:
Abstract

CaMKII exacerbates heart failure progression by activating class I HDACs.

Zhang M, Yang X, Zimmerman RJ, Wang Q, ... Jiang H, Feng N
Background
Persistent cardiac Ca/calmodulin dependent Kinase II (CaMKII) activation plays an essential role in heart failure development. However, the molecular mechanisms underlying CaMKII induced heart failure progression remains incompletely understood. Histone deacetylases (HDACs) are critical for transcriptional responses to stress, and contribute to expression of pathological genes causing adverse ventricular remodeling. Class I HDACs, including HDAC1, HDAC2 and HDAC3, promote pathological cardiac hypertrophy, whereas class IIa HDACs suppress cardiac hypertrophy. While it is known that CaMKII deactivates class IIa HDACs to enhance cardiac hypertrophy, the role of CaMKII in regulating class I HDACs during heart failure progression is unclear.
Methods and results
CaMKII increases the deacetylase activity of recombinant HDAC1, HDAC2 and HDAC3 via in vitro phosphorylation assays. Phosphorylation sites on HDAC1 and HDAC3 are identified with mass spectrometry. HDAC1 activity is also increased in cardiac-specific CaMKIIδ transgenic mice (CaMKIIδ-tg). Beyond post-translational modifications, CaMKII induces HDAC1 and HDAC3 expression. HDAC1 and HDAC3 expression are significantly increased in CaMKIIδ-tg mice. Inhibition of CaMKII by overexpression of the inhibitory peptide AC3-I in the heart attenuates the upregulation of HDAC1 after myocardial infarction surgery. Importantly, a potent HDAC1 inhibitor Quisinostat improves downregulated autophagy genes and cardiac dysfunction in CaMKIIδ-tg mice. In addition to Quisinostat, selective class I HDACs inhibitors, Apicidin and Entinostat, HDAC3 specific inhibitor RGFP966, as well as HDAC1 and HDAC3 siRNA prevent CaMKII overexpression induced cardiac myocyte hypertrophy.
Conclusion
CaMKII activates class I HDACs in heart failure, which may be a central mechanism for heart failure progression. Selective class I HDACs inhibition may be a novel therapeutic avenue to alleviate CaMKII hyperactivity induced cardiac dysfunction.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:73-81
Zhang M, Yang X, Zimmerman RJ, Wang Q, ... Jiang H, Feng N
J Mol Cell Cardiol: 29 Nov 2020; 149:73-81 | PMID: 32971072
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Impact:
Abstract

Glycogen synthase kinase-3β inhibition alleviates activation of the NLRP3 inflammasome in myocardial infarction.

Wang S, Su X, Xu L, Chang C, ... Zhang L, Han S

Inflammasome-promoted sterile inflammation following cardiac damage is critically implicated in heart dysfunction after myocardial infarction (MI). Glycogen synthase kinase-3 (GSK-3β) is a prominent mediator of the inflammatory response, and high GSK-3 activity is associated with various heart diseases. We investigated the regulatory mechanisms of GSK-3β in activation of the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in a rat model with successful induction of MI on days 2-28. An in vitro investigation was performed using newborn rat/human cardiomyocytes and fibroblast cultures under typical inflammasome stimulation and hypoxia treatment. GSK-3β inhibition markedly improved myocardial dysfunction and prevented remodeling, with parallel reduction in the parameters of NLRP3 inflammasome activation after MI. GSK-3β inhibition reduced NLRP3 inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes. GSK-3β\'s interaction with activating signal cointegrator (ASC) as well as GSK-3β inhibition reduced ASC phosphorylation and oligomerization at the tissues and cellular levels. Taken together, these data show that GSK-3β directly mediates NLRP3 inflammasome activation, causing cardiac dysfunction in MI.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 29 Nov 2020; 149:82-94
Wang S, Su X, Xu L, Chang C, ... Zhang L, Han S
J Mol Cell Cardiol: 29 Nov 2020; 149:82-94 | PMID: 32991876
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Impact:
Abstract

Single-cell protein expression of hiPSC-derived cardiomyocytes using Single-Cell Westerns.

Jabart E, Molho J, Sin K, Stansfield B, ... Wu JC, Churko JM

The ability to reprogram human somatic cells into human induced pluripotent stem cells (hiPSCs) has enabled researchers to generate cell types in vitro that have the potential to faithfully recapitulate patient-specific disease processes and phenotypes. hiPSC-derived cardiomyocytes (hiPSC-CMs) offer the promise of in vitro patient- and disease-specific models for drug testing and the discovery of novel therapeutic approaches for treating cardiovascular diseases. While methods to differentiate hiPSCs into cardiomyocytes have been demonstrated, the heterogeneity and immaturity of these differentiated populations have restricted their potential in reproducing human disease and the associated target cell phenotypes. These barriers may be overcome through comprehensive single-cell characterization to dissect the rich heterogeneity of hiPSC-CMs and to study the source of varying cell fates. In this study, we optimized and validated a new Single-Cell Western method to assess protein expression in hiPSC-CMs. To better understand distinct subpopulations generated from cardiomyocyte differentiations and to track populations at single-cell resolution over time, we measured and quantified the expression of cardiomyocyte subtype-specific proteins (MLC2V and MLC2A) using Single-Cell Westerns. By understanding their heterogeneity through single-cell protein expression and quantification, we may improve upon current cardiomyocyte differentiation protocols, generate hiPSC-CMs that are more representative of in vivo derived cardiomyocytes for disease modeling, and utilize hiPSC-CMs for regenerative medicine purposes. Single-Cell Westerns provide a robust platform for protein expression analysis at single-cell resolution.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 29 Nov 2020; 149:115-122
Jabart E, Molho J, Sin K, Stansfield B, ... Wu JC, Churko JM
J Mol Cell Cardiol: 29 Nov 2020; 149:115-122 | PMID: 33010256
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Abstract

Autotaxin inhibition reduces cardiac inflammation and mitigates adverse cardiac remodeling after myocardial infarction.

Tripathi H, Al-Darraji A, Abo-Aly M, Peng H, ... Smyth SS, Abdel-Latif A
Objective
Acute myocardial infarction (AMI) initiates pathological inflammation which aggravates tissue damage and causes heart failure. Lysophosphatidic acid (LPA), produced by autotaxin (ATX), promotes inflammation and the development of atherosclerosis. The role of ATX/LPA signaling nexus in cardiac inflammation and resulting adverse cardiac remodeling is poorly understood.
Approach and results
We assessed autotaxin activity and LPA levels in relation to cardiac and systemic inflammation in AMI patients and C57BL/6 (WT) mice. Human and murine peripheral blood and cardiac tissue samples showed elevated levels of ATX activity, LPA, and inflammatory cells following AMI and there was strong correlation between LPA levels and circulating inflammatory cells. In a gain of function model, lipid phosphate phosphatase-3 (LPP3) specific inducible knock out (Mx1-Plpp3) showed higher systemic and cardiac inflammation after AMI compared to littermate controls (Mx1-Plpp3); and a corresponding increase in bone marrow progenitor cell count and proliferation. Moreover, in Mx1- Plpp3 mice, cardiac functional recovery was reduced with corresponding increases in adverse cardiac remodeling and scar size (as assessed by echocardiography and Masson\'s Trichrome staining). To examine the effect of ATX/LPA nexus inhibition, we treated WT mice with the specific pharmacological inhibitor, PF8380, twice a day for 7 days post AMI. Inhibition of the ATX/LPA signaling nexus resulted in significant reduction in post-AMI inflammatory response, leading to favorable cardiac functional recovery, reduced scar size and enhanced angiogenesis.
Conclusion
ATX/LPA signaling nexus plays an important role in modulating inflammation after AMI and targeting this mechanism represents a novel therapeutic target for patients presenting with acute myocardial injury.

Published by Elsevier Ltd.

J Mol Cell Cardiol: 29 Nov 2020; 149:95-114
Tripathi H, Al-Darraji A, Abo-Aly M, Peng H, ... Smyth SS, Abdel-Latif A
J Mol Cell Cardiol: 29 Nov 2020; 149:95-114 | PMID: 33017574
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Impact:
Abstract

Protective role of ErbB3 signaling in myeloid cells during adaptation to cardiac pressure overload.

Yin H, Favreau-Lessard AJ, deKay JT, Herrmann YR, ... Sawyer DB, Ryzhov S
Background
Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood. This study investigated the role of ErbB3 receptors in the regulation of early adaptive response using a mouse model of transverse aortic constriction (TAC) for non-ischemic cardiomyopathy.
Methods and results
TAC surgery was performed in groups of age- and sex-matched myeloid cell-specific ErbB3-deficient mice (ErbB3) and control animals (ErbB3). The number of cardiac CD45 immune cells, CD11b myeloid cells, Ly6G neutrophils, and Ly6C monocytes was determined using flow cytometric analysis. Five days after TAC, survival was dramatically reduced in male but not female ErbB3 mice or control animals. The examination of lung weight to body weight ratio suggested that acute pulmonary edema was present in ErbB3 male mice after TAC. To determine the cellular and molecular mechanisms involved in the increased mortality in ErbB3 male mice, cardiac cell populations were examined at day 3 post-TAC using flow cytometry. Myeloid cells accumulated in control but not in ErbB3 male mouse hearts. This was accompanied by increased proliferation of Sca-1 positive non-immune cells (endothelial cells and fibroblasts) in control but not ErbB3 male mice. No significant differences in intramyocardial accumulation of myeloid cells or proliferation of Sca-1 cells were found between the groups of ErbB3 and ErbB3 female mice. An antibody-based protein array analysis revealed that IGF-1 expression was significantly downregulated only in ErbB3 mice hearts compared to control animals after TAC.
Conclusion
Our data demonstrate the crucial role of myeloid cell-specific ErbB3 signaling in the cardiac accumulation of myeloid cells, which contributes to the activation of cardiac endothelial cells and fibroblasts and development of an early adaptive response to cardiac pressure overload in male mice.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 27 Nov 2020; 152:1-16
Yin H, Favreau-Lessard AJ, deKay JT, Herrmann YR, ... Sawyer DB, Ryzhov S
J Mol Cell Cardiol: 27 Nov 2020; 152:1-16 | PMID: 33259856
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Impact:
Abstract

Three-dimensional chromatin organization in cardiac development and disease.

Bertero A, Rosa-Garrido M

Recent technological advancements in the field of chromatin biology have rewritten the textbook on nuclear organization. We now appreciate that the folding of chromatin in the three-dimensional space (i.e. its 3D \"architecture\") is non-random, hierarchical, and highly complex. While 3D chromatin structure is partially encoded in the primary sequence and thereby broadly conserved across cell types and states, a substantial portion of the genome seems to be dynamic during development or in disease. Moreover, there is growing evidence that at least some of the 3D structure of chromatin is functionally linked to gene regulation, both being modulated by and impacting on multiple nuclear processes (including DNA replication, transcription, and RNA splicing). In recent years, these new concepts have nourished several investigations about the functional role of 3D chromatin topology dynamics in the heart during development and disease. This review aims to provide a comprehensive overview of our current understanding in this field, and to discuss how this knowledge can inform further research as well as clinical practice.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 23 Nov 2020; 151:89-105
Bertero A, Rosa-Garrido M
J Mol Cell Cardiol: 23 Nov 2020; 151:89-105 | PMID: 33242466
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Impact:
Abstract

Cardiac epigenetics: Driving signals to the cardiac epigenome in development and disease.

Robinson EL, Anene-Nzelu CG, Rosa-Garrido M, Foo RSY

Conrad Waddington\'s famous illustration of a ball poised at the top of an undulating epigenetic landscape is often evoked when one thinks of epigenetics. Although the original figure was a metaphor for gene regulation during cell fate determination, we now know that epigenetic regulation is important for the homeostasis of every tissue and organ in the body. This is evident in the cardiovascular system, one of the first organs to develop and one whose function is vital to human life. Epigenetic mechanisms are central in regulating transcription and signaling programs that drive cardiovascular disease and development. The epigenome not only instructs cell and context specific gene expression signatures, but also retains \"memory\" of past events and can pass it down to subsequent generations. Understanding the various input and output signals from the cardiac epigenome is crucial for unraveling the molecular underpinnings of cardiovascular disease and development. This knowledge is useful for patient risk stratification, understanding disease pathophysiology, and identifying novel approaches for cardiac regeneration and therapy. In this special issue, a series of high-quality reviews and original research articles examining the field of cardiac epigenetics will broaden our insights into this fundamental aspect of molecular and cellular cardiology. Topics include DNA methylation, histone modifications, chromatin architecture, transcription factors, and long non-coding RNA biology in the diverse cell types that comprise the cardiovascular system. We hope that our readers will expand their horizons and be challenged to envision innovative strategies to further probe the epigenome and develop diagnostic and therapeutic solutions for cardiovascular pathologies.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 20 Nov 2020; 151:88
Robinson EL, Anene-Nzelu CG, Rosa-Garrido M, Foo RSY
J Mol Cell Cardiol: 20 Nov 2020; 151:88 | PMID: 33232681
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Impact:
Abstract

Diabetes changes gene expression but not DNA methylation in cardiac cells.

Lother A, Bondareva O, Saadatmand AR, Pollmeier L, ... Hein L, Gilsbach R
Background
Diabetes mellitus is a worldwide epidemic that causes high mortality due to cardiovascular complications, in particular heart failure. Diabetes is associated with profound pathophysiological changes in the heart. The aim of this study was to investigate the impact of diabetes on gene expression and DNA methylation in cardiac cells.
Methods and results
Transcriptome analysis of heart tissue from mice with streptozotocin-induced diabetes revealed only 39 genes regulated, whereas cell type-specific analysis of the diabetic heart was more sensitive and more specific than heart tissue analysis and revealed a total of 3205 differentially regulated genes in five cell types. Whole genome DNA methylation analysis with basepair resolution of distinct cardiac cell types identified highly specific DNA methylation signatures of genic and regulatory regions. Interestingly, despite marked changes in gene expression, DNA methylation remained stable in streptozotocin-induced diabetes. Integrated analysis of cell type-specific gene expression enabled us to assign the particular contribution of single cell types to the pathophysiology of the diabetic heart. Finally, analysis of gene regulation revealed ligand-receptor pairs as potential mediators of heterocellular interaction in the diabetic heart, with fibroblasts and monocytes showing the highest degree of interaction.
Conclusion
In summary, cell type-specific analysis reveals differentially regulated gene programs that are associated with distinct biological processes in diabetes. Interestingly, despite these changes in gene expression, cell type-specific DNA methylation signatures of genic and regulatory regions remain stable in diabetes. Analysis of heterocellular interactions in the diabetic heart suggest that the interplay between fibroblasts and monocytes is of pivotal importance.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 13 Nov 2020; 151:74-87
Lother A, Bondareva O, Saadatmand AR, Pollmeier L, ... Hein L, Gilsbach R
J Mol Cell Cardiol: 13 Nov 2020; 151:74-87 | PMID: 33197445
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Impact:
Abstract

Remodeling of the mA landscape in the heart reveals few conserved post-transcriptional events underlying cardiomyocyte hypertrophy.

Hinger SA, Wei J, Dorn LE, Whitson BA, ... He C, Accornero F

Regulation of gene expression plays a fundamental role in cardiac stress-responses. Modification of coding transcripts by adenosine methylation (mA) has recently emerged as a critical post-transcriptional mechanism underlying heart disease. Thousands of mammalian mRNAs are known to be mA-modified, suggesting that remodeling of the mA landscape may play an important role in cardiac pathophysiology. Here we found an increase in mA content in human heart failure samples. We then adopted genome-wide analysis to define all mA-regulated sites in human failing compared to non-failing hearts and identified targeted transcripts involved in histone modification as enriched in heart failure. Further, we compared all mA sites regulated in human hearts with the ones occurring in isolated rat hypertrophic cardiomyocytes to define cardiomyocyte-specific mA events conserved across species. Our results identified 38 shared transcripts targeted by mA during stress conditions, and 11 events that are unique to unstressed cardiomyocytes. Of these, further evaluation of select mRNA and protein abundances demonstrates the potential impact of mA on post-transcriptional regulation of gene expression in the heart.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 11 Nov 2020; 151:46-55
Hinger SA, Wei J, Dorn LE, Whitson BA, ... He C, Accornero F
J Mol Cell Cardiol: 11 Nov 2020; 151:46-55 | PMID: 33188779
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Impact:
Abstract

Heart failure impairs the mechanotransduction properties of human cardiac pericytes.

Rolle IG, Crivellari I, Zanello A, Mazzega E, ... Cesselli D, Beltrami AP

The prominent impact that coronary microcirculation disease (CMD) exerts on heart failure symptoms and prognosis, even in the presence of macrovascular atherosclerosis, has been recently acknowledged. Experimental delivery of pericytes in non-revascularized myocardial infarction improves cardiac function by stimulating angiogenesis and myocardial perfusion. Aim of this work is to verify if pericytes (Pc) residing in ischemic failing human hearts display altered mechano-transduction properties and to assess which alterations of the mechano-sensing machinery are associated with the observed impaired response to mechanical cues.
Results:
Microvascular rarefaction and defects of YAP/TAZ activation characterize failing human hearts. Although both donor (D-) and explanted (E-) heart derived cardiac Pc support angiogenesis, D-Pc exert this effect significantly better than E-Pc. The latter are characterized by reduced focal adhesion density, decreased activation of the focal adhesion kinase (FAK)/ Crk-associated substrate (CAS) pathway, low expression of caveolin-1, and defective transduction of extracellular stiffness into cytoskeletal stiffening, together with an impaired response to both fibronectin and lysophosphatidic acid. Importantly, Mitogen-activated protein kinase kinase inhibition restores YAP/TAZ nuclear translocation.
Conclusion:
Heart failure impairs Pc mechano-transduction properties, but this defect could be reversed pharmacologically.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 04 Nov 2020; 151:15-30
Rolle IG, Crivellari I, Zanello A, Mazzega E, ... Cesselli D, Beltrami AP
J Mol Cell Cardiol: 04 Nov 2020; 151:15-30 | PMID: 33159916
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Impact:
Abstract

Calcium influx through the mitochondrial calcium uniporter holocomplex, MCU.

Boyman L, Greiser M, Lederer WJ

Ca flux into the mitochondrial matrix through the MCU holocomplex (MCU) has recently been measured quantitatively and with milliseconds resolution for the first time under physiological conditions in both heart and skeletal muscle. Additionally, the dynamic levels of Ca in the mitochondrial matrix ([Ca]) of cardiomyocytes were measured as it was controlled by the balance between influx of Ca into the mitochondrial matrix through MCU and efflux through the mitochondrial Na / Ca exchanger (NCLX). Under these conditions [Ca] was shown to regulate ATP production by the mitochondria at only a few critical sites. Additional functions attributed to [Ca] continue to be reported in the literature. Here we review the new findings attributed to MCU function and provide a framework for understanding and investigating mitochondrial Ca influx features, many of which remain controversial. The properties and functions of the MCU subunits that constitute the holocomplex are challenging to tease apart. Such distinct subunits include EMRE, MCUR1, MICUx (i.e. MICU1, MICU2, MICU3), and the pore-forming subunits (MCU). Currently, the specific set of functions of each subunit remains non-quantitative and controversial. The more contentious issues are discussed in the context of the newly measured native MCU Ca flux from heart and skeletal muscle. These MCU Ca flux measurements have been shown to be a highly-regulated, tissue-specific with femto-Siemens Ca conductances and with distinct extramitochondrial Ca ([Ca]) dependencies. These data from cardiac and skeletal muscle mitochondria have been examined quantitatively for their threshold [Ca] levels and for hypothesized gatekeeping function and are discussed in the context of model cell (e.g. HeLa, MEF, HEK293, COS7 cells) measurements. Our new findings on MCU dependent matrix [Ca] signaling provide a quantitative basis for on-going and new investigations of the roles of MCU in cardiac function ranging from metabolic fuel selection, capillary blood-flow control and the pathological activation of the mitochondrial permeability transition pore (mPTP). Additionally, this review presents the use of advanced new methods that can be readily adapted by any investigator to enable them to carry out quantitative Ca measurements in mitochondria while controlling the inner mitochondrial membrane potential, ΔΨ.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 01 Nov 2020; epub ahead of print
Boyman L, Greiser M, Lederer WJ
J Mol Cell Cardiol: 01 Nov 2020; epub ahead of print | PMID: 33147447
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Abstract

DCA-TGR5 signaling activation alleviates inflammatory response and improves cardiac function in myocardial infarction.

Wang J, Zhang J, Lin X, Wang Y, ... Jiang C, Xu M
Aims
The progression of myocardial infarction (MI) involves multiple metabolic disorders. Bile acid metabolites have been increasingly recognized as pleiotropic signaling molecules that regulate multiple cardiovascular functions. G protein-coupled bile acid receptor (TGR5) is one of the receptors sensing bile acids to mediate their biological functions. In this study, we aimed to elucidate the effects of bile acids-TGR5 signaling pathways in myocardial infarction (MI).
Methods and results
Blood samples of AMI patients or control subjects were collected and plasma was used for bile acid metabolism analysis. We discovered that bile acid levels were altered and deoxycholic acid (DCA) was substantially reduced in the plasma of AMI patients. Mice underwent either the LAD ligation model of MI or sham operation. Both MI and sham mice were gavaged with 10 mg/kg/d DCA or vehicle control since 3-day before the operation. Cardiac function was assessed by ultrasound echocardiography, infarct area was evaluated by TTC staining and Masson trichrome staining. Administration of DCA improved cardiac function and reduced ischemic injury at the 7th-day post-MI. The effects of DCA were dependent on binding to its receptor TGR5. Tgr5 mice underwent the same MI model. Cardiac function deteriorated and infarct size was increased at the 7th-day post-MI, which were not savaged by DCA administration. Moreover, DCA inhibited interleukin (IL)-1β expression in the infarcted hearts, and ameliorated IL-1β activation at 1-day post-MI. DCA inhibited NF-κB signaling and further IL-1β expression in cultured neonatal mouse cardiomyocytes under hypoxia as well as cardio-fibroblasts with the treatment of LPS.
Conclusions
DCA-TGR5 signaling pathway activation decreases inflammation and ameliorates heart function post-infarction. Strategies that control bile acid metabolism and TGR5 signaling to ameliorate the inflammatory responses may provide beneficial effects in patients with myocardial infarction.

Copyright © 2020. Published by Elsevier Ltd.

J Mol Cell Cardiol: 30 Oct 2020; 151:3-14
Wang J, Zhang J, Lin X, Wang Y, ... Jiang C, Xu M
J Mol Cell Cardiol: 30 Oct 2020; 151:3-14 | PMID: 33130149
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Abstract

Interleukin-1α dependent survival of cardiac fibroblasts is associated with StAR/STARD1 expression and improved cardiac remodeling and function after myocardial infarction.

Razin T, Melamed-Book N, Argaman J, Galin I, ... Leor J, Orly J
Aims
One unaddressed aspect of healing after myocardial infarction (MI) is how non-myocyte cells that survived the ischemic injury, keep withstanding additional cellular damage by stress forms typically arising during the post-infarction inflammation. Here we aimed to determine if cell survival is conferred by expression of a mitochondrial protein novel to the cardiac proteome, known as steroidogenic acute regulatory protein, (StAR/STARD1). Further studies aimed to unravel the regulation and role of the non-steroidogenic cardiac StAR after MI.
Methods and results
Following permanent ligation of the left anterior descending coronary artery in mouse heart, timeline western blot analyses showed that StAR expression corresponds to the inflammatory response to MI. Following the identification of StAR in mitochondria of cardiac fibroblasts in culture, confocal microscopy immunohistochemistry (IHC) identified StAR expression in left ventricular (LV) activated interstitial fibroblasts, adventitial fibroblasts and endothelial cells. Further work with the primary fibroblasts model revealed that interleukin-1α (IL-1α) signaling via NF-κB and p38 MAPK pathways efficiently upregulates the expression of the Star gene products. At the functional level, IL-1α primed fibroblasts were protected against apoptosis when exposed to cisplatin mimicry of in vivo apoptotic stress; yet, the protective impact of IL-1α was lost upon siRNA mediated StAR downregulation. At the physiological level, StAR expression was nullified during post-MI inflammation in a mouse model with global IL-1α deficiency, concomitantly resulting in a 4-fold elevation of apoptotic fibroblasts. Serial echocardiography and IHC studies of mice examined 24 days after MI revealed aggravation of LV dysfunction, LV dilatation, anterior wall thinning and adverse tissue remodeling when compared with loxP control hearts.
Conclusions
This study calls attention to overlooked aspects of cellular responses evolved under the stress conditions associated with the default inflammatory response to MI. Our observations suggest that LV IL-1α is cardioprotective, and at least one mechanism of this action is mediated by induction of StAR expression in border zone fibroblasts, which renders them apoptosis resistant. This acquired survival feature also has long-term ramifications on the heart recovery by diminishing adverse remodeling and improving the heart function after MI.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 29 Oct 2020; epub ahead of print
Razin T, Melamed-Book N, Argaman J, Galin I, ... Leor J, Orly J
J Mol Cell Cardiol: 29 Oct 2020; epub ahead of print | PMID: 33130150
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Abstract

Comprehensive evaluation of electrophysiological and 3D structural features of human atrial myocardium with insights on atrial fibrillation maintenance mechanisms.

Mikhailov AV, Kalyanasundaram A, Li N, Scott SS, ... Hummel JD, Fedorov VV

Atrial fibrillation (AF) occurrence and maintenance is associated with progressive remodeling of electrophysiological (repolarization and conduction) and 3D structural (fibrosis, fiber orientations, and wall thickness) features of the human atria. Significant diversity in AF etiology leads to heterogeneous arrhythmogenic electrophysiological and structural substrates within the 3D structure of the human atria. Since current clinical methods have yet to fully resolve the patient-specific arrhythmogenic substrates, mechanism-based AF treatments remain underdeveloped. Here, we review current knowledge from in-vivo, ex-vivo, and in-vitro human heart studies, and discuss how these studies may provide new insights on the synergy of atrial electrophysiological and 3D structural features in AF maintenance. In-vitro studies on surgically acquired human atrial samples provide a great opportunity to study a wide spectrum of AF pathology, including functional changes in single-cell action potentials, ion channels, and gene/protein expression. However, limited size of the samples prevents evaluation of heterogeneous AF substrates and reentrant mechanisms. In contrast, coronary-perfused ex-vivo human hearts can be studied with state-of-the-art functional and structural technologies, such as high-resolution near-infrared optical mapping and contrast-enhanced MRI. These imaging modalities can resolve atrial arrhythmogenic substrates and their role in reentrant mechanisms maintaining AF and validate clinical approaches. Nonetheless, longitudinal studies are not feasible in explanted human hearts. As no approach is perfect, we suggest that combining the strengths of direct human atrial studies with high fidelity approaches available in the laboratory and in realistic patient-specific computer models would elucidate deeper knowledge of AF mechanisms. We propose that a comprehensive translational pipeline from ex-vivo human heart studies to longitudinal clinically relevant AF animal studies and finally to clinical trials is necessary to identify patient-specific arrhythmogenic substrates and develop novel AF treatments.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 28 Oct 2020; 151:56-71
Mikhailov AV, Kalyanasundaram A, Li N, Scott SS, ... Hummel JD, Fedorov VV
J Mol Cell Cardiol: 28 Oct 2020; 151:56-71 | PMID: 33130148
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Abstract

Combined high-throughput library screening and next generation RNA sequencing uncover microRNAs controlling human cardiac fibroblast biology.

Schimmel K, Stojanović SD, Huang CK, Jung M, ... Fiedler J, Thum T
Background
Myocardial fibrosis is a hallmark of the failing heart, contributing to the most common causes of deaths worldwide. Several microRNAs (miRNAs, miRs) controlling cardiac fibrosis were identified in recent years; however, a more global approach to identify miRNAs involved in fibrosis is missing.
Methods and results
Functional miRNA mimic library screens were applied in human cardiac fibroblasts (HCFs) to identify annotated miRNAs inducing proliferation. In parallel, miRNA deep sequencing was performed after subjecting HCFs to proliferating and resting stimuli, additionally enabling discovery of novel miRNAs. In-depth in vitro analysis confirmed the pro-fibrotic nature of selected, highly conserved miRNAs miR-20a-5p and miR-132-3p. To determine downstream cellular pathways and their role in the fibrotic response, targets of the annotated miRNA candidates were modulated by synthetic siRNA. We here provide evidence that repression of autophagy and detoxification of reactive oxygen species by miR-20a-5p and miR-132-3p explain some of their pro-fibrotic nature on a mechanistic level.
Conclusion
We here identified both miR-20a-5p and miR-132-3p as crucial regulators of fibrotic pathways in an in vitro model of human cardiac fibroblast biology.

Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 27 Oct 2020; 150:91-100
Schimmel K, Stojanović SD, Huang CK, Jung M, ... Fiedler J, Thum T
J Mol Cell Cardiol: 27 Oct 2020; 150:91-100 | PMID: 33127387
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Abstract

Selective changes in cytosolic β-adrenergic cAMP signals and L-type Calcium Channel regulation by Phosphodiesterases during cardiac hypertrophy.

Abi-Gerges A, Castro L, Leroy J, Domergue V, Fischmeister R, Vandecasteele G


Background:
In cardiomyocytes, phosphodiesterases (PDEs) type 3 and 4 are the predominant enzymes that degrade cAMP generated by β-adrenergic receptors (β-ARs), impacting notably the regulation of the L-type Ca current (I). Cardiac hypertrophy (CH) is accompanied by a reduction in PDE3 and PDE4, however, whether this affects the dynamic regulation of cytosolic cAMP and I is not known. Methods and Results CH was induced in rats by thoracic aortic banding over a time period of five weeks and was confirmed by anatomical measurements. Left ventricular myocytes (LVMs) were isolated from CH and sham-operated (SHAM) rats and transduced with an adenovirus encoding a Förster resonance energy transfer (FRET)-based cAMP biosensor or subjected to the whole-cell configuration of the patch-clamp technique to measure I. Aortic stenosis resulted in a 46% increase in heart weight to body weight ratio in CH compared to SHAM. In SHAM and CH LVMs, a short isoprenaline stimulation (Iso, 100 nM, 15 s) elicited a similar transient increase in cAMP with a half decay time (t) of ~50 s. In both groups, PDE4 inhibition with Ro 20-1724 (10 μM) markedly potentiated the amplitude and slowed the decline of the cAMP transient, this latter effect being more pronounced in SHAM (t ~ 250 s) than in CH (t ~ 150 s, P < 0.01). In contrast, PDE3 inhibition with cilostamide (1 μM) had no effect on the amplitude of the cAMP transient and a minimal effect on its recovery in SHAM, whereas it potentiated the amplitude and slowed the decay in CH (t ~ 80 s). Iso pulse stimulation also elicited a similar transient increase in I in SHAM and CH, although the duration of the rising phase was delayed in CH. Inhibition of PDE3 or PDE4 potentiated I amplitude in SHAM but not in CH. Besides, while only PDE4 inhibition slowed down the decline of I in SHAM, both PDE3 and PDE4 contributed in CH.
Conclusion:
These results identify selective alterations in cytosolic cAMP and I regulation by PDE3 and PDE4 in CH, and show that the balance between PDE3 and PDE4 for the regulation of β-AR responses is shifted toward PDE3 during CH.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 24 Oct 2020; 150:109-121
Abi-Gerges A, Castro L, Leroy J, Domergue V, Fischmeister R, Vandecasteele G
J Mol Cell Cardiol: 24 Oct 2020; 150:109-121 | PMID: 33184031
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Abstract

Mutation location of HCM-causing troponin T mutations defines the degree of myofilament dysfunction in human cardiomyocytes.

Schuldt M, Johnston JR, He H, Huurman R, ... Pinto JR, van der Velden J
Background
The clinical outcome of hypertrophic cardiomyopathy patients is not only determined by the disease-causing mutation but influenced by a variety of disease modifiers. Here, we defined the role of the mutation location and the mutant protein dose of the troponin T mutations I79N, R94C and R278C.
Methods and results
We determined myofilament function after troponin exchange in permeabilized single human cardiomyocytes as well as in cardiac patient samples harboring the R278C mutation. Notably, we found that a small dose of mutant protein is sufficient for the maximal effect on myofilament Ca-sensitivity for the I79N and R94C mutation while the mutation location determines the magnitude of this effect. While incorporation of I79N and R94C increased myofilament Ca-sensitivity, incorporation of R278C increased Ca-sensitivity at low and intermediate dose, while it decreased Ca-sensitivity at high dose. All three cTnT mutants showed reduced thin filament binding affinity, which coincided with a relatively low maximal exchange (50.5 ± 5.2%) of mutant troponin complex in cardiomyocytes. In accordance, 32.2 ± 4.0% mutant R278C was found in two patient samples which showed 50.0 ± 3.7% mutant mRNA. In accordance with studies that showed clinical variability in patients with the exact same mutation, we observed variability on the functional single cell level in patients with the R278C mutation. These differences in myofilament properties could not be explained by differences in the amount of mutant protein.
Conclusions
Using troponin exchange in single human cardiomyocytes, we show that TNNT2 mutation-induced changes in myofilament Ca-sensitivity depend on mutation location, while all mutants show reduced thin filament binding affinity. The specific mutation-effect observed for R278C could not be translated to myofilament function of cardiomyocytes from patients, and is most likely explained by other (post)-translational troponin modifications. Overall, our studies illustrate that mutation location underlies variability in myofilament Ca-sensitivity, while only the R278C mutation shows a highly dose-dependent effect on myofilament function.

Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.

J Mol Cell Cardiol: 23 Oct 2020; 150:77-90
Schuldt M, Johnston JR, He H, Huurman R, ... Pinto JR, van der Velden J
J Mol Cell Cardiol: 23 Oct 2020; 150:77-90 | PMID: 33148509
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Abstract

HSF1 functions as a key defender against palmitic acid-induced ferroptosis in cardiomyocytes.

Wang N, Ma H, Li J, Meng C, ... Zhang H, Wang K

Palmitic acid (PA)-induced myocardial injury is considered a critical contributor to the development of obesity and type 2 diabetes mellitus (T2DM)-related cardiomyopathy. However, the underlying mechanism has not been fully understood. Here, we demonstrated that PA induced the cell death of H9c2 cardiomyoblasts in a dose- and time-dependent manner, while different ferroptosis inhibitors significantly abrogated the cell death of H9c2 cardiomyoblasts and primary neonatal rat cardiomyocytes exposed to PA. Mechanistically, PA decreased the protein expression levels of both heat shock factor 1 (HSF1) and glutathione peroxidase 4 (GPX4) in a dose- and time-dependent manner, which were restored by different ferroptosis inhibitors. Overexpression of HSF1 not only alleviated PA-induced cell death and lipid peroxidation but also improved disturbed iron homeostasis by regulating the transcription of iron metabolism-related genes (e.g., Fth1, Tfrc, Slc40a1). Additionally, PA-blocked GPX4 protein expression was evidently restored by HSF1 overexpression. Inhibition of endoplasmic reticulum (ER) stress rather than autophagy contributed to HSF1-mediated GPX4 expression. Moreover, GPX4 overexpression protected against PA-induced ferroptosis, whereas knockdown of GPX4 reversed the anti-ferroptotic effect of HSF1. Consistent with the in vitro findings, PA-challenged Hsf1 mice exhibited more serious ferroptosis, increased Slc40a1 and Fth1 mRNA expression, decreased GPX4 and TFRC expression and enhanced ER stress in the heart compared with Hsf1 mice. Altogether, HSF1 may function as a key defender against PA-induced ferroptosis in cardiomyocytes by maintaining cellular iron homeostasis and GPX4 expression.

Copyright © 2020 Elsevier Ltd. All rights reserved.

J Mol Cell Cardiol: 21 Oct 2020; 150:65-76
Wang N, Ma H, Li J, Meng C, ... Zhang H, Wang K
J Mol Cell Cardiol: 21 Oct 2020; 150:65-76 | PMID: 33098823
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This program is still in alpha version.