<div><h4>Crosstalk of platelets with macrophages and fibroblasts aggravates inflammation, aortic wall stiffening and osteopontin release in abdominal aortic aneurysm.</h4><i>Wagenhäuser MU, Mulorz J, Krott KJ, Ehrenberg A, ... Schelzig H, Elvers M</i><br /><b>Aims</b><br />Abdominal aortic aneurysm (AAA) is a highly lethal disease with progressive dilatation of the abdominal aorta accompanied by degradation and remodelling of the vessel wall due to chronic inflammation. Platelets play an important role in cardiovascular diseases but their role in AAA is poorly understood.<br /><b>Methods and results</b><br />The present study revealed that platelets play a crucial role in promoting AAA through modulation of inflammation and degradation of the ECM. They are responsible for the up-regulation of SPP1 (osteopontin, OPN) gene expression in macrophages and aortic tissue, which triggers inflammation and remodeling but also platelet adhesion and migration into the abdominal aortic wall and the intraluminal thrombus (ILT). Further, enhanced platelet activation and pro-coagulant activity results in elevated gene expression of various cytokines, Mmp9 and Col1a1 in macrophages and Il-6 and Mmp9 in fibroblasts. Enhanced platelet activation and pro-coagulant activity was also detected in AAA patients. Further, we detected platelets and OPN in the vessel wall and in the ILT of patients who underwent open repair of AAA. Platelet depletion in experimental murine AAA reduced inflammation and ECM remodeling, with reduced elastin fragmentation and aortic diameter expansion. Of note, OPN co-localized with platelets, suggesting a potential role of OPN for the recruitment of platelets into the ILT and the aortic wall.<br /><b>Conclusion</b><br />In conclusion, our data strongly supports the potential relevance of anti-platelet therapy to reduce AAA progression and rupture in AAA patients.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 16 Nov 2023; epub ahead of print</small></div>

<div><h4>Acute heart failure: mechanisms and pre-clinical models-a Scientific Statement of the ESC Working Group on Myocardial Function.</h4><i>Ciccarelli M, Pires IF, Bauersachs J, Bertrand L, ... Thum T, Tocchetti CG</i><br /><AbstractText>While chronic heart failure (CHF) treatment has considerably improved patient prognosis and survival, the therapeutic management of acute heart failure (AHF) has remained virtually unchanged in the last decades. This is partly due to the scarcity of pre-clinical models for the pathophysiological assessment and, consequently, the limited knowledge of molecular mechanisms involved in the different AHF phenotypes. This scientific statement outlines the different trajectories from acute to CHF originating from the interaction between aetiology, genetic and environmental factors, and comorbidities. Furthermore, we discuss the potential molecular targets capable of unveiling new therapeutic perspectives to improve the outcome of the acute phase and counteracting the evolution towards CHF.</AbstractText><br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 14 Nov 2023; 119:2390-2404</small></div>

<div><h4>Targeting the apelin system for the treatment of cardiovascular diseases.</h4><i>Chapman FA, Maguire JJ, Newby DE, Davenport AP, Dhaun N</i><br /><AbstractText>Cardiovascular disease is the leading cause of death worldwide. Its prevalence is rising due to ageing populations and the increasing incidence of diseases such as chronic kidney disease, obesity and diabetes which are associated with elevated cardiovascular risk. Despite currently available treatments, there remains a huge burden of cardiovascular disease-associated morbidity for patients and healthcare systems, and newer treatments are needed. The apelin system, comprising the apelin receptor and its two endogenous ligands apelin and elabela, is a broad regulator of physiology that opposes the actions of the renin-angiotensin and vasopressin systems. Activation of the apelin receptor promotes endothelium-dependent vasodilatation and inotropy, lowers blood pressure and promotes angiogenesis. The apelin system appears to protect against arrhythmias, inhibits thrombosis and has broad anti-inflammatory and anti-fibrotic actions. It also promotes aqueous diuresis through direct and indirect (central) effects in the kidney. Thus, the apelin system offers therapeutic promise for a range of cardiovascular, kidney and metabolic diseases. This review will discuss current cardiovascular disease targets of the apelin system and future clinical utility of apelin receptor agonism.</AbstractText><br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 12 Nov 2023; epub ahead of print</small></div>

<div><h4>Contractility measurements for cardiotoxicity screening with ventricular myocardial slices of pigs.</h4><i>Shi R, Reichardt M, Fiegle DJ, Küpfer LK, ... Seidel T, Bruegmann T</i><br /><b>Aims</b><br />Cardiotoxicity is one major reason why drugs do not enter or are withdrawn from the market. Thus, approaches are required to predict cardiotoxicity with high specificity and sensitivity. Ideally, such methods should be performed within intact cardiac tissue with high relevance for humans and detect acute and chronic side effects on electrophysiological behaviour, contractility, and tissue structure in an unbiased manner. Herein, we evaluate healthy pig myocardial slices and biomimetic cultivation setups (BMCS) as a new cardiotoxicity screening approach.<br /><b>Methods and results</b><br />Pig left ventricular samples were cut into slices and spanned into BMCS with continuous electrical pacing and online force recording. Automated stimulation protocols were established to determine the force-frequency relationship (FFR), frequency dependence of contraction duration, effective refractory period (ERP), and pacing threshold. Slices generated 1.3 ± 0.14 mN/mm2 force at 0.5 Hz electrical pacing and showed a positive FFR and a shortening of contraction duration with increasing pacing rates. Approximately 62% of slices were able to contract for at least 6 days while showing stable ERP, contraction duration-frequency relationship, and preserved cardiac structure confirmed by confocal imaging and X-ray diffraction analysis. We used specific blockers of the most important cardiac ion channels to determine which analysis parameters are influenced. To validate our approach, we tested five drug candidates selected from the Comprehensive in vitro Proarrhythmia Assay list as well as acetylsalicylic acid and DMSO as controls in a blinded manner in three independent laboratories. We were able to detect all arrhythmic drugs and their respective mode of action on cardiac tissue including inhibition of Na+, Ca2+, and hERG channels as well as Na+/Ca2+ exchanger.<br /><b>Conclusion</b><br />We systematically evaluate this approach for cardiotoxicity screening, which is of high relevance for humans and can be upscaled to medium-throughput screening. Thus, our approach will improve the predictive value and efficiency of preclinical cardiotoxicity screening.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 02 Nov 2023; epub ahead of print</small></div>

<div><h4>The inhibition of inner mitochondrial fusion in hepatocytes reduces NAFL and improves metabolic profile during obesity by modulating bile acid conjugation.</h4><i>Da Dalt L, Moregola A, Svecla M, Pedretti S, ... Scorrano L, Norata GD</i><br /><b>Background:</b><br/>and aim</b><br />Mitochondria are plastic organelles that continuously undergo biogenesis, fusion, fission, and mitophagy to control cellular energy metabolism, calcium homeostasis, hormones, sterols and bile acids (BAs) synthesis. Here we evaluated how the impairment of mitochondrial fusion in hepatocytes affect diet induced liver steatosis and obesity.<br /><b>Methods and results</b><br />Male mice selectively lacking the key protein involved in inner mitochondrial fusion, OPA1, (OPA1ΔHep) on a High Fat Diet (HFD) for 20 weeks. OPA1ΔHep mice were protected from the development of hepatic steatosis and obesity because of reduced lipid absorption; a profile which was accompanied by increased respiratory exchange ratio in vivo, suggesting a preference for carbohydrate in OPA1ΔHep in agreement with the defect in mitochondrial fusion. At the molecular level, this phenotype emerged as a consequence of poor mitochondrial-peroxisome-ER tethering in OPA1 deficient hepatocytes thus impairing bile acid conjugation and therefore its release in the bile, thus impacting lipid absorption from the diet. Concordantly the liver of NAFLD subjects presented an increased expression of OPA1 and of the network of proteins involved in mitochondrial when compared to controls.<br /><b>Conclusion</b><br />Patients with NAFLD present increased expression of proteins involved in mitochondrial fusion in the liver. The selective inhibition of liver mitochondrial fusion observed in hepatocyte OPA1 deficient mice protects mice from HFD-induced metabolic dysfunction by reducing lipid dietary absorption and bile acid secretion as a consequence of reduced liver mitochondria-peroxisome-ER tethering.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 31 Oct 2023; epub ahead of print</small></div>

<div><h4>Deletion of adipocyte NOS3 potentiates high-fat diet-induced hypertension and vascular remodeling via chemerin.</h4><i>Man AWC, Zhou Y, Reifenberg G, Camp A, ... Xia N, Li H</i><br /><b>Aims</b><br />Obesity is an epidemic that is a critical contributor to hypertension and other cardiovascular diseases. Current paradigms suggest that endothelial nitric oxide synthase (eNOS/NOS3) in the vessel wall is the primary regulator of vascular function and blood pressure. However, recent studies have revealed the presence of eNOS/NOS3 in the adipocytes of white adipose tissues and perivascular adipose tissues (PVATs). The current understanding of the role of adipocyte NOS3 is based mainly on studies using global knockout models. The present study aimed to elucidate the functional significance of adipocyte NOS3 for vascular function and blood pressure control.<br /><b>Methods and results</b><br />We generated an adipocyte-specific NOS3 knockout mouse line using adiponectin promotor-specific Cre-induced gene inactivation. Control and adipocyte-specific NOS3 knockout (A-NOS3 KO) mice were fed a high-fat diet (HFD). Despite less weight gain, A-NOS3 KO mice exhibited a significant increase in blood pressure after HFD feeding, associated with exacerbated vascular dysfunction and remodeling. A-NOS3 KO mice also showed increased expression of signature markers of inflammation and hypoxia in the PVATs. Among the differentially expressed adipokines, we have observed an upregulation of a novel adipokine, chemerin, in A-NOS3 KO mice. Chemerin was recently reported to link obesity and vascular dysfunction. Treatment with chemerin neutralizing antibody normalized the expression of remodeling markers in the aorta segments cultured in serum from HFD-fed A-NOS3 KO mice ex vivo.<br /><b>Conclusions</b><br />These data suggest that NOS3 in adipocytes is vital in maintaining vascular homeostasis; dysfunction of adipocyte NOS3 contributes to obesity-induced vascular remodeling and hypertension.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 28 Oct 2023; epub ahead of print</small></div>

<div><h4>Exercise-induced circular RNA circUtrn is required for cardiac physiological hypertrophy and prevents myocardial ischemia-reperfusion injury.</h4><i>Wang L, Feng J, Feng X, Meng D, ... Sluijter JPG, Xiao J</i><br /><b>Aims</b><br />Regular exercise training benefits cardiovascular health and effectively reduces the risk for cardiovascular disease. Circular RNAs (circRNAs) play important roles in cardiac pathophysiology. However, the role of circRNAs in response to exercise training and biological mechanisms responsible for exercise-induced cardiac protection remain largely unknown.<br /><b>Methods and results</b><br />RNA sequencing was used to profile circRNA expression in adult mouse cardiomyocytes which were isolated from mice with or without exercise training. Exercised-induced circRNA - circUtrn was significantly increased in swimming-trained adult mouse cardiomyocytes. In vivo, circUtrn was found to be required for exercise-induced physiological cardiac hypertrophy. CircUtrn inhibition abolished the protective effects of exercise on myocardial ischemia/reperfusion remodeling. CircUtrn overexpression prevented myocardial ischemia/reperfusion-induced acute injury and pathological cardiac remodeling. In vitro, overexpression of circUtrn promoted H9 human embryonic stem cell-induced cardiomyocytes growth and survival via protein phosphatase PP5. Mechanistically, circUtrn directly bound to PP5 and regulated the stability of PP5 in an ubiquitin-proteasome-dependent manner. Hypoxia-inducible factor 1α-dependent splicing factor SF3B1 acted as an upstream regulator of circUtrn in cardiomyocytes.<br /><b>Conclusions</b><br />The circRNA CircUtrn is upregulated upon exercise training in the heart. Overexpression of circUtrn can prevent myocardial I/R-induced injury and pathological cardiac remodeling.<br /><b>Translational perspective</b><br />CircRNA circUtrn is required for the development of exercise-induced physiological cardiac hypertrophy. CircUtrn inhibition abolished the protective effects of exercise on I/R remodeling. Moreover, circUtrn overexpression prevented myocardial I/R-induced acute injury and pathological cardiac remodeling. Our findings suggest that circUtrn elevation and its protective role against I/R injury may hold a therapeutic promise in I/R injury and pathological cardiac remodeling.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 28 Oct 2023; epub ahead of print</small></div>

<div><h4>Plasma adiponectin levels and risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction: large scale observational and Mendelian randomization evidence.</h4><i>Nielsen MB, Çolak Y, Benn M, Mason A, Burgess S, Nordestgaard BG</i><br /><b>Aims</b><br />Adiponectin may play an important protective role in heart failure and associated cardiovascular diseases. We hypothesized that plasma adiponectin is associated observationally and causally, genetically with risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction.<br /><b>Methods and results</b><br />In the Copenhagen General Population Study, we examined 30,045 individuals with plasma adiponectin measurements observationally and 96,903 individuals genetically in one-sample Mendelian randomization analyses using five genetic variants explaining 3% of the variation in plasma adiponectin. In the HERMES, UK Biobank, The Nord-Trøndelag Health Study(HUNT), deCODE, the Michigan Genomics Initiative(MGI), DiscovEHR, and the AFGen consortia, we performed two-sample Mendelian randomization analyses in up to 1,030,836 individuals using 12 genetic variants explaining 14% of the variation in plasma adiponectin.In observational analyses modelled linearly, a 1 unit log-transformed higher plasma adiponectin was associated with a hazard ratio of 1.51(95% confidence interval:1.37-1.66) for heart failure, 1.63(1.50-1.78) for atrial fibrillation, 1.21(1.03-1.41) for aortic valve stenosis, and 1.03(0.93-1.14) for myocardial infarction; levels above the median were also associated with increased risk of myocardial infarction, and non-linear U-shaped associations were more apparent for heart failure, aortic valve stenosis, and myocardial infarction in less-adjusted models. Corresponding genetic, causal risk ratios were 0.92(0.65-1.29), 0.87(0.68-1.12), 1.55(0.87-2.76), and 0.93(0.67-1.30) in one-sample Mendelian randomization analyses, and no significant associations were seen for non-linear one-sample Mendelian randomization analyses; corresponding causal risk ratios were 0.99(0.89-1.09), 1.00(0.92-1.08), 1.01(0.79-1.28), and 0.99(0.86-1.13) in two-sample Mendelian randomization analyses, respectively.<br /><b>Conclusion</b><br />Observationally, elevated plasma adiponectin was associated with increased risk of heart failure, atrial fibrillation, aortic valve stenosis, and myocardial infarction. However, genetic evidence did not support causality for these associations.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 28 Oct 2023; epub ahead of print</small></div>

<div><h4>Point mutations in RyR2 Ca2+ binding residues of human cardiomyocytes cause cellular remodeling of cardiac EC-coupling.</h4><i>Xia Y, Zhang XH, Yamaguchi N, Morad M</i><br /><b>Aims</b><br />CRISPR/Cas9 gene-edits of cardiac ryanodine receptor (RyR2) in human induced pluripotent stem cells derived-cardiomyocytes (hiPSC-CMs) provides a novel platform for introducing mutations in RyR2 Ca2+ binding residues and examining the resulting EC-coupling remodeling consequences.<br /><b>Methods and results</b><br />Ca2+-signaling phenotypes of mutations in RyR2 Ca2+ binding site residues associated with cardiac arrhythmia (RyR2-Q3925E) or not proven to cause cardiac pathology (RyR2-E3848A) were determined using ICa- and caffeine-triggered Ca2+ releases in voltage-clamped and TIRF-imaged wild type (WT) and mutant cardiomyocytes infected with SR-targeted ER-GCaMP6 probe. 1) ICa- and caffeine-triggered Fura-2 or ER-GCaMP6 signals were suppressed, even when ICa was significantly enhanced in Q3925E and E3848A mutant cardiomyocyte; 2) Spontaneous beating (Fura-2 Ca2+-transients) persisted in mutant cells without the SR-release signals; 3) While 5-20mM caffeine failed to trigger Ca2+-release in voltage-clamped mutant-cells, only ∼20% to ∼70% of intact myocytes responded respectively to caffeine; 4) 20mM caffeine-transients, however, activated slowly, were delayed, and variably suppressed by 2-APB, FCCP, or ruthenium red.<br /><b>Conclusion</b><br />Mutating RyR2 Ca2+ binding residues, irrespective of their reported pathogenesis, suppressed both ICa- and caffeine-triggered Ca2+ releases, suggesting interaction between Ca2+ and caffeine binding-sites. Enhanced transmembrane calcium influx and remodeling of EC-coupling pathways may underlie the persistence of spontaneous beating in CICR-suppressed mutant myocytes.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 27 Oct 2023; epub ahead of print</small></div>

<div><h4>Efficacy of pharmacological and interventional treatment for resistant hypertension-a network meta-analysis.</h4><i>Tian Z, Vollmer Barbosa C, Lang H, Bauersachs J, Melk A, Schmidt BMW</i><br /><b>Aims</b><br />Resistant hypertension is associated with a high risk of cardiovascular disease, chronic kidney disease and mortality. Yet, its management is challenging. This study aims to establish the comparative effectiveness of pharmacologic and interventional treatments by conducting a network meta-analysis.<br /><b>Methods and results</b><br />MEDLINE, Cochrane Register of Controlled Trials and Web of Science Core Collection were systematically searched in March 2022. Randomized controlled trials comparing treatment options for management of resistant hypertension were included. Outcomes were blood pressure changes, measured in the office and in 24 h ambulatory blood pressure measurement. We applied a frequentist random effects model to perform a network meta-analysis combining placebo medication and sham procedure as the reference comparator.From 4771 records, 24 studies met the inclusion criteria with 3458 included patients in total. 12 active treatment alternatives (spironolactone, doxazosin, β-blocker, clonidine, darusentan, guanfacine, various types of renal sympathetic denervation, lifestyle intervention, continuous positive airway pressure, and baroreflex activation therapy) were analyzed. Among all comparators, spironolactone had the highest-ranking probability and was considered the most effective treatment to reduce office systolic blood pressure (-13.30 mmHg [-17.89; -8.72]; P < 0.0001) and 24 h systolic blood pressure (-8.46 mmHg [-12.54; -4.38]; P < 0.0001) in patients with resistant hypertension. Lifestyle interventions were the most effective non-pharmacological treatment, lowering office systolic blood pressure by -7.26 mmHg [-13.73; -0.8], whereas baroreflex activation therapy lowered office systolic blood pressure by -7.0 [-18.59; 4.59]. RDN lowered office systolic blood pressure by -5.64 mmHg [-12.95; 1.66] and -3.79 mmHg [-11.39; 3.8] depending on the type of the procedure.<br /><b>Conclusion</b><br />Among all pharmacologic and interventional treatments, spironolactone is the most effective in reducing blood pressure in patients with resistant hypertension. More comparative trials and especially trials with long-term follow up are needed. In the meanwhile, we have to conclude that a combination of spironolactone and lifestyle modification are the most effective treatments in resistant hypertension.<br /><b>Translational perspective</b><br />Management of resistant hypertension is a multifaceted approach. Selection of adequate antihypertensive treatment must consider comorbidity, risk profiles, character and preference of patients. In most circumstances, aldosterone antagonism is an important therapeutic option that might even gain more importance with the new drugs on the horizon. Further head-to-head studies are necessary to determine whether new developing pharmacological treatments offer greater efficacy in blood pressure reduction with a better safety profile than spironolactone. Long-term follow up could provide more insights into efficacy of renal denervation versus aldosterone antagonists in reducing major cardiovascular events in the real-life setting.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 27 Oct 2023; epub ahead of print</small></div>

<div><h4>RBPMS regulates cardiomyocyte contraction and cardiac function through RNA alternative splicing.</h4><i>Gan P, Wang Z, Bezprozvannaya S, McAnally JR, ... Liu N, Olson EN</i><br /><b>Aims</b><br />RNA binding proteins play essential roles in mediating RNA splicing and are key post-transcriptional regulators in the heart. Our recent study demonstrated that RBPMS (RNA-binding protein with multiple splicing) is crucial for cardiac development through modulating mRNA splicing, but little is known about its functions in the adult heart. In this study, we aim to characterize the postnatal cardiac function of Rbpms and its mechanism of action.<br /><b>Methods and results</b><br />We generated a cardiac-specific knockout mouse line, and found that cardiac-specific loss of Rbpms caused severe cardiomyocyte contractile defect, leading to dilated cardiomyopathy and early lethality in adult mice. We showed that RBPMS associates with spliceosome factors and other RNA binding proteins that are important in cardiac function, such as RBM20 by proximity-dependent Biotin Identification (BioID) assay and mass spectrometry. We performed paired-end RNA sequencing and RT-PCR and found that RBPMS regulates alternative splicing of genes associated with sarcomere structure and function, such as Ttn, Pdlim5 and Nexn, generating new protein isoforms. Using a minigene splicing reporter assay, we determined that RBPMS regulates target gene splicing through recognizing tandem intronic CAC motifs. We also showed that RBPMS knockdown in human induced pluripotent stem cell-derived cardiomyocytes impaired cardiomyocyte contraction.<br /><b>Conclusion</b><br />This study identifies RBPMS as an essential regulator of cardiomyocyte contraction and cardiac function by modulating sarcomeric gene alternative splicing.<br /><b>Translational perspective</b><br />RNA binding proteins are associated with cardiovascular diseases through modulating RNA post-transcriptional modifications. Our previous study revealed that Rbpms deficiency caused noncompaction cardiomyopathy and patent ductus arteriosus in mouse. Our current study demonstrates that Rbpms mainly regulates cardiomyocyte contraction in the adult heart, and cardiac-specific Rbpms knockout leads to dilated cardiomyopathy and heart failure. RBPMS mediates the alternative splicing of key sarcomeric components in the adult heart, including Ttn, Pdlim5 and Nexn. These findings indicate that RBPMS is an essential regulator of cardiac function, and a better understanding of its function will provide new therapeutic opportunities for cardiovascular diseases.<br /><br />© Published by Oxford University Press on behalf of the European Society of Cardiology 2023.<br /><br /><small>Cardiovasc Res: 27 Oct 2023; epub ahead of print</small></div>

<div><h4>Canonical Wnt pathway and the LDL receptor superfamily in neuronal cholesterol homeostasis and function.</h4><i>Borrell-Pages M, Luquero A, Vilahur G, Padró T, Badimon L</i><br /><b>Objective</b><br />There is little information on the regulation of cholesterol homeostasis in the brain. Whether cholesterol crosses the blood-brain barrier is under investigation, but the present understanding is that cholesterol metabolism in the brain is independent from that in peripheral tissues. Lipoprotein receptors from the LDL receptor family (LRPs) have key roles in lipid particle accumulation in cells involved in vascular and cardiac pathophysiology, however, their function on neural cells is unknown.<br /><b>Approach and results</b><br />The expression of LRP5 and components and targets of its downstream signaling pathway, the canonical WNT pathway including β-catenin, LEF1, VEGF, OPN MMP7 and ADAM10 is analyzed in brains of Wt and Lrp5-/- mice and in a neuroblastoma cell line. LRP5 expression is increased in a time-dependent and dose-dependent manner after lipid loading in neuronal cells; however it does not participate in cholesterol homeostasis as shown by intracellular lipid accumulation analyses. Neurons challenged with stausporin and H2O2 display an anti-apoptotic protective role for LRP5.<br /><b>Conclusions</b><br />We show for the first time that neurons can accumulate intracellular lipids and that lipid uptake is performed mainly by the LDLR while CD36, LRP1, and LRP5 do not play a major role. We also show that LRP5 triggers the canonical WNT pathway in neuronal cells to generate pro-survival signals. Finally we show, that Lrp5-/- mice have maintained expression of LRP5 only in the brain supporting the biological plausible concept of the need of brain LRP5 to elicit pro-survival processes and embryonic viability.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 26 Oct 2023; epub ahead of print</small></div>

<div><h4>TNF-α protects from exacerbated myocarditis and cardiac death by suppressing expansion of activated heart-reactive CD4+ T cells.</h4><i>Rolski F, Tkacz K, Węglarczyk K, Kwiatkowski G, ... Kania G, Błyszczuk P</i><br /><b>Background:</b><br/>and aims</b><br />Tumour necrosis factor α (TNF-α) represents a classical proinflammatory cytokine and its increased levels positively correlate with the severity of many cardiovascular diseases. Surprisingly, some heart failure patients receiving high doses of anti- TNF-α antibodies showed serious health worsening. This work aimed to examine the role of TNF-α signalling on the development and progression of myocarditis and heart-specific autoimmunity.<br /><b>Methods and results</b><br />Mice with genetic deletion of TNF-α (Tnf+/- and Tnf-/-) and littermate controls (Tnf+/+) were used to study myocarditis in the inducible and the transgenic T cell receptor (TCR-M) models. Tnf+/- and Tnf-/- mice immunized with α-myosin heavy chain peptide (αMyHC) showed reduced myocarditis incidence but the susceptible animals developed extensive inflammation in the heart. In the TCR-M model, defective TNF-α production was associated with increased mortality at a young age due to cardiomyopathy and cardiac fibrosis. We could confirm that TNF-α as well as the secretome of antigen-activated heart-reactive effector CD4+ T (Teff) cells effectively activated the adhesive properties of cardiac microvascular endothelial cells (cMVECs). Our data suggested that TNF-α produced by endothelial in addition to Teff cells promoted leucocyte adhesion to activated cMVECs. Analysis of CD4+ T lymphocytes from both models of myocarditis showed a strongly increased fraction of Teff cells in hearts, spleens, and in the blood of Tnf+/- and Tnf-/- mice. Indeed, antigen-activated Tnf-/- Teff cells showed prolonged long-term survival and TNF-α cytokine-induced cell death of heart-reactive Teff.<br /><b>Conclusions</b><br />TNF-α signalling promotes myocarditis development by activating cardiac endothelial cells. However, in the case of established disease, TNF-α protects from exacerbating cardiac inflammation by inducing activation-induced cell death of heart-reactive Teff. These data might explain the lack of success of standard anti-TNF-α therapy in heart failure patients and open perspectives for T cell-targeted approaches.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 25 Oct 2023; epub ahead of print</small></div>

<div><h4>Prdm16 mutation determines sex-specific cardiac metabolism and identifies two novel cardiac metabolic regulators.</h4><i>Kühnisch J, Theisen S, Dartsch J, Fritsche-Guenther R, ... Hubner N, Klaassen S</i><br /><b>Aims</b><br />Mutation of the PRDM16 gene causes human dilated and non-compaction cardiomyopathy. The PRDM16 protein is a transcriptional regulator that affects cardiac development via Tbx5 and Hand1, thus regulating myocardial structure. The biallelic inactivation of Prdm16 induces severe cardiac dysfunction with post-natal lethality and hypertrophy in mice. The early pathological events that occur upon Prdm16 inactivation have not been explored.<br /><b>Methods and results</b><br />This study performed in-depth pathophysiological and molecular analyses of male and female Prdm16csp1/wt mice that carry systemic, monoallelic Prdm16 gene inactivation. We systematically assessed early molecular changes through transcriptomics, proteomics, and metabolomics. Kinetic modelling of cardiac metabolism was performed in silico with CARDIOKIN. Prdm16csp1/wt mice are viable up to 8 months, develop hypoplastic hearts, and diminished systolic performance that is more pronounced in female mice. Prdm16csp1/wt cardiac tissue of both sexes showed reductions in metabolites associated with amino acid as well as glycerol metabolism, glycolysis, and the tricarboxylic acid cycle. Prdm16csp1/wt cardiac tissue revealed diminished glutathione (GSH) and increased inosine monophosphate (IMP) levels indicating oxidative stress and a dysregulated energetics, respectively. An accumulation of triacylglycerides exclusively in male Prdm16csp1/wt hearts suggests a sex-specific metabolic adaptation. Metabolic modelling using CARDIOKIN identified a reduction in fatty acid utilization in males as well as lower glucose utilization in female Prdm16csp1/wt cardiac tissue. On the level of transcripts and protein expression, Prdm16csp1/wt hearts demonstrate an up-regulation of pyridine nucleotide-disulphide oxidoreductase domain 2 (Pyroxd2) and the transcriptional regulator pre-B-cell leukaemia transcription factor interacting protein 1 (Pbxip1). The strongest concordant transcriptional up-regulation was detected for Prdm16 itself, probably through an autoregulatory mechanism.<br /><b>Conclusions</b><br />Monoallelic, global Prdm16 mutation diminishes cardiac performance in Prdm16csp1/wt mice. Metabolic alterations and transcriptional dysregulation in Prdm16csp1/wt affect cardiac tissue. Female Prdm16csp1/wt mice develop a more pronounced phenotype, indicating sexual dimorphism at this early pathological window. This study suggests that metabolic dysregulation is an early event in the PRDM16 associated cardiac pathology.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 16 Oct 2023; epub ahead of print</small></div>

<div><h4>Empagliflozin improves cardiac energetics during ischaemia/reperfusion by directly increasing cardiac ketone utilisation.</h4><i>Chase D, Eykyn TR, Shattock MJ, Chung YJ</i><br /><b>Aim</b><br />Empagliflozin (EMPA), a potent inhibitor of the renal sodium-glucose cotransporter 2 (SGLT2) and an effective treatment for type-2 diabetes, has been shown to have cardioprotective effects, independent of improved glycaemic control. Several non-canonical mechanisms have been proposed to explain these cardiac effects, including increasing circulating ketone supply to the heart. This study aims to test whether EMPA directly alters cardiac ketone metabolism independent of supply.<br /><b>Methods and results</b><br />The direct effects of EMPA on cardiac function and metabolomics were investigated in Langendorff rat heart perfused in buffer containing 5 mM glucose, 4 mM β-hydroxybutyrate (βHb) and 0.4 mM intralipid, subject to low flow ischaemia/reperfusion. Cardiac energetics were monitored in situ using 31P NMR spectroscopy. Steady-state 13C-labelling was performed by switching 12C substrates for 13C1 glucose or 13C4 βHb, and 13C incorporation into metabolites determined using 2D 1H-13C HSQC NMR spectroscopy. EMPA treatment improved left ventricular developed pressure during ischaemia and reperfusion compared to vehicle-treated hearts. In EMPA-treated hearts, total ATP and PCr levels, and Gibbs free energy for ATP hydrolysis were significantly higher during ischaemia and reperfusion. EMPA treatment did not alter the incorporation of 13C from glucose into glycolytic products lactate or alanine neither during ischaemia nor reperfusion. In ischaemia, EMPA led to a decrease in 13C1 glucose incorporation and a concurrent increase in 13C4 βHb incorporation into TCA intermediates succinate, citrate, and glutamate. During reperfusion, the concentration of metabolites originating from 13C1 glucose was similar to vehicle but those originating from 13C4 βHb remained elevated in EMPA treated hearts.<br /><b>Conclusions</b><br />Our findings indicate that EMPA causes a switch in metabolism away from glucose oxidation towards increased ketone utilisation in the rat heart, thereby improving function and energetics both during ischaemia and recovery during reperfusion. This preference of ketone utilisation over glucose was observed under conditions of constant supply of substrate, suggesting that EMPA acts directly by modulating cardiac substrate preference, independent of substrate availability. The mechanisms underlying our findings are currently unknown, warranting further study.<br /><b>Translational perspective</b><br />Heart failure remains a huge clinical burden. Clinical trials of SGLT2 inhibitors in patients with diabetes and heart failure have reported significant cardio-protection from EMPA treatment that appears independent of improved glycaemic control. The direct cardiac effect of EMPA in modulating ketone metabolism observed in this study raises the potential for EMPA to be used as a therapy for heart failure in both diabetic and non-diabetic patients alike.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 11 Oct 2023; epub ahead of print</small></div>

<div><h4>Circulating GDF11 exacerbates myocardial injury in mice and associates with increased infarct size in humans.</h4><i>Kraler S, Balbi C, Vdovenko D, Lapikova-Bryhinska T, ... Lüscher TF, Akhmedov A</i><br /><b>Aims</b><br />The heart rejuvenating effects of circulating growth differentiation factor 11 (GDF11), a TGF-β superfamily member that shares 90% homology with myostatin (MSTN), remains controversial. Here, we aimed to probe the role of GDF11 in acute myocardial infarction (MI), a frequent cause of heart failure and premature death during ageing.<br /><b>Methods and results</b><br />In contrast to endogenous Mstn, myocardial Gdf11 declined during the course of ageing, and was particularly reduced following ischaemia/reperfusion (I/R) injury, suggesting a therapeutic potential of GDF11-signalling in MI. Unexpectedly, boosting systemic Gdf11 by recombinant GDF11 (rGDF11) delivery (0.1 mg/kg BW over 30 days) prior to myocardial I/R augmented myocardial infarct size in C57BL/6 mice irrespective of their age, predominantly by accelerating pro-apoptotic signalling. While intrinsic cardioprotective signalling pathways remained unaffected by high circulating GDF11, targeted transcriptomics and immunomapping studies focusing on GDF11-associated downstream targets revealed attenuated Nkx2-5 expression confined to CD105 expressing cells, with pro-apoptotic activity, as assessed by caspase-3 levels, being particularly pronounced in adjacent cells, suggesting a possible indirect effect. Finally, by harnessing a highly-specific and validated LC-MS/MS based assay, we show that in prospectively recruited patients with MI circulating GDF11 but not MSTN levels incline with age. Moreover, GDF11 levels were particularly elevated in those at high risk for adverse outcomes following the acute event, with circulating GDF11 emerging as an independent predictor of myocardial infarct size, as estimated by standardized peak creatine kinase-MB levels.<br /><b>Conclusion</b><br />Our data challenge the initially reported rejuvenating effects of circulating GDF11 and suggest that high levels of systemic GDF11 exacerbate myocardial injury in mice and humans alike. Our results suggest that persistently high GDF11 levels during ageing may contribute to the age-dependent loss of cardioprotective mechanisms and thus poor outcomes following acute MI.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 23 Sep 2023; epub ahead of print</small></div>

<div><h4>Targeted activation of hERG channels rescues electrical instability induced by the hERG R56Q+/- Long QT Syndrome variant.</h4><i>Venkateshappa R, Hunter DV, Muralidharan P, Nagalingam RS, ... Tibbits GF, Claydon TW</i><br /><b>Aims</b><br />Long QT Syndrome Type 2 (LQTS2) is associated with inherited variants in the cardiac hERG K+ channel. However, the pathogenicity of hERG channel gene variants is often uncertain. Using CRISPR-Cas9 gene-edited hiPSC-derived cardiomyocytes (hiPSC-CMs), we investigated the pathogenic mechanism underlying the LQTS-associated hERG R56Q variant, and its phenotypic rescue by the type 1 hERG activator, RPR260243.<br /><b>Methods and results</b><br />These approaches enable characterization of the unclear causative mechanism of arrhythmia in the R56Q variant (an N-terminal PAS domain mutation that primarily accelerates channel deactivation) and translational investigation of the potential for targeted pharmacologic manipulation of hERG deactivation. Using perforated patch clamp electrophysiology of single hiPSC-CMs, programmed electrical stimulation showed that the hERG R56Q variant does not significantly alter the mean APD90. However, the R56Q variant increases the beat-to-beat variability in APD90 during pacing at constant cycle lengths, enhances the variance of action potential duration (APD90) during rate transitions, and increases the incidence of 2:1 block. During paired S1-S2 stimulations measuring electrical restitution properties, the R56Q variant was also found to increase the variability in rise time and duration of the response to premature stimulations. Application of the hERG channel activator, RPR260243, reduces the APD variance in hERG R56Q hiPSC-CMs, reduces the variability in responses to premature stimulations, and increases the post-repolarization refractoriness.<br /><b>Conclusion</b><br />Based on our findings, we propose that the hERG R56Q variant leads to heterogeneous APD dynamics, which could result in spatial dispersion of repolarization and increased risk for re-entry without significantly affecting the average APD90. Furthermore, our data highlight the antiarrhythmic potential of targeted slowing of hERG deactivation gating, which we demonstrate increases protection against premature action potentials and reduces electrical heterogeneity in hiPSC-CMs.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 21 Sep 2023; epub ahead of print</small></div>

<div><h4>Iron deficiency in myocardial ischemia: molecular mechanisms and therapeutic perspectives.</h4><i>Corradi F, Masini G, Bucciarelli T, De Caterina R</i><br /><AbstractText>Systemic iron deficiency (SID), even in the absence of anemia, worsens the prognosis and increases mortality in heart failure (HF). Recent clinical-epidemiological studies, however, have shown that a myocardial iron deficiency (MID) is frequently present in cases of severe HF even in the absence of SID and without anemia. In addition, experimental studies have shown a poor correlation between the state of systemic and myocardial iron. MID in animal models may lead to severe mitochondrial dysfunction, alterations of mitophagy and mitochondrial biogenesis, with profound alterations in cardiac mechanics and the occurrence of a fatal cardiomyopathy, all effects prevented by intravenous administration of iron. This shifts the focus to the myocardial state of iron, in the absence of anemia, as an important factor in prognostic worsening and mortality in HF. There is now epidemiological evidence that SID worsens prognosis and mortality also in patients with acute and chronic coronary heart disease, and experimental evidence that MID aggravates acute myocardial ischemia as well as post-ischemic remodeling. Intravenous administration of ferric carboxymaltose or ferric dextrane improves post-ischemic adverse remodeling. We here review such evidence, propose that MID worsens ischemia/reperfusion injury, and discuss possible molecular mechanisms, such as chronic hyperactivation of HIF1-α; exacerbation of cytosolic and mitochondrial calcium overload, amplified increase of mitochondrial [NADH]/[NAD+] ratio, and depletion of energy status and NAD+ content with inhibition of sirtuin 1-3 activity. Such evidence now portrays iron metabolism as a core factor not only in heart failure, but also in myocardial ischemia.</AbstractText><br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 19 Sep 2023; epub ahead of print</small></div>

<div><h4>Cardiomyocyte and endothelial cells play distinct roles in the tumor necrosis factor (TNF)-dependent atrial responses and increased atrial fibrillation vulnerability induced by endurance exercise training in mice.</h4><i>Lakin R, Polidovitch N, Yang S, Parikh M, ... Christoffels VM, Backx PH</i><br /><b>Aims</b><br />Endurance exercise is associated with an increased risk of atrial fibrillation (AF). We previously established that adverse atrial remodeling and AF susceptibility induced by intense exercise in mice requires the mechanosensitive and pro-inflammatory cytokine tumor necrosis factor (TNF). The cellular and mechanistic basis for these TNF-mediated effects is unknown.<br /><b>Methods and results</b><br />We studied the impact of TNF excision, in either atrial cardiomyocytes or endothelial cells (using Cre-recombinase expression controlled by Nppa or Tie2 promoters, respectively), on the cardiac responses to six weeks of intense swim exercise training. TNF ablation, in either cell type, had no impact on the changes in heart rate, autonomic tone or left ventricular structure and function induced by exercise training. Tnf excision in atrial cardiomyocytes did, however, prevent atrial hypertrophy, fibrosis, and macrophage infiltration as well as conduction slowing and increased AF susceptibility arising from exercise training. By contrast, endothelial-specific excision only reduced the training-induced atrial hypertrophy. Consistent with these cell-specific effects of Tnf excision, the loss of TNF in cardiomyocytes was able to prevent the activation of p38MAPKinase, a strain-dependent downstream mediator of TNF signaling, without affecting the atrial stretch as assessed by atrial pressures induced by exercise. Despite TNF\'s established role in innate immune responses and inflammation, neither acute nor chronic exercise training caused measurable NLRP3 inflammasome activation.<br /><b>Conclusions</b><br />Our findings demonstrate that adverse atrial remodeling and AF vulnerability induced by intense exercise requires TNF in atrial cardiomyocytes whereas the impact of endothelial-derived TNF is limited to hypertrophy modulation. The implications of the cell autonomous effects of TNF and crosstalk between cells in the atria are discussed.<br /><b>Translational perspective</b><br />Endurance sport is associated with atrial fibrillation (AF) and mouse models show intense exercise training promotes atrial hypertrophy, fibrosis, inflammation, and AF vulnerability, which requires the mechanosensitive inflammatory cytokine tumor necrosis factor (TNF). We demonstrate that Tnf ablation in atrial cardiomyocytes protects fully against atrial changes induced by exercise, whereas endothelial-specific ablation only prevents atrial hypertrophy. Since atrial filling pressures increase markedly during exercise and most clinical conditions linked to AF (hypertension, heart failure, valvular/metabolic diseases), we discuss how atrial stretch may mediate cell autonomous effects of TNF and arrhythmogenic tissue changes in the atria.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 15 Sep 2023; epub ahead of print</small></div>

<div><h4>Metabolic targeting of platelets to combat thrombosis: dawn of a new paradigm?</h4><i>Flora GD, Nayak MK, Ghatge M, Chauhan AK</i><br /><AbstractText>Current antithrombotic therapies used in clinical settings either target the coagulation pathways or platelet activation receptors (P2Y12 or GPIIb/IIIa), as well as the cyclooxygenase (COX) enzyme through aspirin. However, they are associated with bleeding risk and are not suitable for long-term use. Thus, novel strategies which provide broad protection against platelet activation with minimal bleeding risks are required. Regardless of the nature of agonist stimulation, platelet activation is an energy-intensive and ATP-driven process characterized by metabolic switching towards a high rate of aerobic glycolysis, relative to oxidative phosphorylation (OXPHOS). Consequently, there has been considerable interest in recent years in investigating whether targeting metabolic pathways in platelets, especially aerobic glycolysis and OXPHOS, can modulate their activation, thereby preventing thrombosis. This review briefly discusses the choices of metabolic substrates available to platelets that drive their metabolic flexibility. We have comprehensively elucidated the relevance of aerobic glycolysis in facilitating platelet activation and the underlying molecular mechanisms that trigger this switch from OXPHOS. We have provided a detailed account of the antiplatelet effects of targeting vital metabolic checkpoints such as pyruvate dehydrogenase kinases (PDKs) and pyruvate kinase M2 (PKM2) that preferentially drive the pyruvate flux to aerobic glycolysis. Furthermore, we discuss the role of fatty acids, and glutamine oxidation in mitochondria and their subsequent role in driving OXPHOS and platelet activation. While the approach of targeting metabolic regulatory mechanisms in platelets to prevent their activation is still in a nascent stage, accumulating evidence highlights its beneficial effects as a potentially novel antithrombotic strategy.</AbstractText><br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 14 Sep 2023; epub ahead of print</small></div>

<div><h4>Predictive metabolites for incident myocardial infarction: a two-step meta-analysis of individual patient data from six cohorts comprising 7,897 individuals from the the COnsortium of METabolomic Studies.</h4><i>Nogal A, Alkis T, Lee Y, Kifer D, ... Yu B, Menni C</i><br /><b>Aims</b><br />Myocardial infarction (MI) is a major cause of death and disability worldwide. Most metabolomics studies investigating metabolites predicting MI are limited by the participant number and/or the demographic diversity. We sought to identify biomarkers of incident MI in the Consortium of Metabolomics Studies (COMETS).<br /><b>Methods and results</b><br />We included 7,897 individuals aged on average 66 years from six intercontinental cohorts with blood metabolomic profiling (n = 1,428 metabolites, of which 168 were present in at least 3 cohorts with over 80% prevalence) and MI information (1,373 cases). We performed a two-stage Individual Patients Data meta-analysis. We first assessed the associations between circulating metabolites and incident MI for each cohort adjusting for traditional risk factors, and then performed a fixed effect inverse-variance meta-analysis to pull the results together. Finally, we conducted a pathway enrichment analysis to identify potential pathways linked to MI.On meta-analysis, 56 metabolites including 21 lipids and 17 amino acids were associated with incident MI after adjusting for multiple testing (false discovery rate, FDR < 0.05), and 10 were novel. The largest increased risk was observed for the carbohydrate mannitol/sorbitol (HR [95% CI] = 1.40[1.26-1.56], p-value < 0.001), whereas the largest decrease in risk was found for glutamine (HR [95% CI] = 0.74[0.67-0.82], p-value < 0.001). Moreover, the identified metabolites were significantly enriched (corrected p-value < 0.05) in pathways previously linked with cardiovascular diseases, including aminoacyl-tRNA biosynthesis.<br /><b>Conclusions</b><br />In the most comprehensive metabolomics study of incident MI to date, 10 novel metabolites were associated with MI. Metabolite profiles might help to identify high-risk individuals before disease onset. Further research is needed to fully understand the mechanisms of action and elaborate pathway findings.<br /><b>Translational perspective</b><br />In the largest meta-analyses covering six international cohorts, we identify 10 novel and 46 known metabolites associated with incident MI, that can be used to identify at-risk individuals before disease onset. Our results improve our understanding of the molecular changes that take place in MI development and provide potential novel targets for clinical prediction and a deeper understanding of causal mechanisms.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 14 Sep 2023; epub ahead of print</small></div>

<div><h4>Atrial fibrillation-associated electrical remodelling in human induced pluripotent stem cell-derived atrial cardiomyocytes: a novel pathway for antiarrhythmic therapy development.</h4><i>Seibertz F, Rubio T, Springer R, Popp F, ... Zimmermann WH, Voigt N</i><br /><b>Background:</b><br/>and aims</b><br />Atrial fibrillation (AF) is associated with tachycardia-induced cellular electrophysiology alterations which promote AF chronification and treatment resistance. Development of novel antiarrhythmic therapies is hampered by the absence of scalable experimental human models that reflect AF-associated electrical remodelling. Therefore, we aimed to assess if AF-associated remodelling of cellular electrophysiology can be simulated in human atrial-like cardiomyocytes derived from induced pluripotent stem cells in the presence of retinoic acid (iPSC-aCM), and atrial engineered human myocardium (aEHM) under short term (24 h) and chronic (7 d) tachypacing (TP).<br /><b>Methods and results</b><br />First, 24-hour electrical-pacing at 3 Hz was used to investigate whether AF-associated remodelling in iPSC-aCM and aEHM would ensue. Compared to controls (24 h, 1 Hz pacing) TP-stimulated iPSC-aCM presented classical hallmarks of AF-associated remodelling: (1) decreased L-type Ca2+ current (ICa, L) and (2) impaired activation of acetylcholine-activated inward-rectifier K+ current (IK, ACh). This resulted in action potential shortening and an absent response to the M-receptor agonist carbachol in both iPSC-aCM and aEHM subjected to TP. Accordingly, mRNA expression of the channel-subunit Kir3.4 was reduced. Selective IK, ACh blockade with tertiapin reduced basal inward-rectifier K+ current only in iPSC-aCM subjected to TP, thereby unmasking an agonist-independent constitutively-active IK, ACh. To allow for long-term TP, we developed iPSC-aCM and aEHM expressing the light-gated ion-channel f-Chrimson. The same hallmarks of AF-associated remodelling were observed after optical-TP. In addition, continuous TP (7 days) led to (1) increased amplitude of inward rectifier K+ current (IK1), (2) hyperpolarization of the resting membrane potential, (3) increased AP-amplitude and upstroke velocity as well as (4) reversibly impaired contractile function in aEHM.<br /><b>Conclusions</b><br />Classical hallmarks of AF-associated remodelling were mimicked through TP of iPSC-aCM and aEHM. The use of the ultrafast f-Chrimson depolarizing ion channel allowed us to model the time-dependence of AF-associated remodelling in vitro for the first time. The observation of electrical remodelling with associated reversible contractile dysfunction offers a novel platform for human-centric discovery of antiarrhythmic therapies.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.<br /><br /><small>Cardiovasc Res: 07 Sep 2023; epub ahead of print</small></div>

<div><h4>Single-nuclear transcriptome profiling identifies persistent fibroblast activation in hypertrophic and failing human hearts of patients with longstanding disease.</h4><i>Kattih B, Boeckling F, Shumliakivska M, Tombor L, ... Zeiher AM, Dimmeler S</i><br /><b>Aims</b><br />Cardiac fibrosis drives the progression of heart failure in ischemic and hypertrophic cardiomyopathy. Therefore, the development of specific antifibrotic treatment regimens to counteract cardiac fibrosis is of high clinical relevance. Hence, this study examined the presence of persistent fibroblast activation during longstanding human heart disease at a single-cell resolution to identify putative therapeutic targets to counteract pathological cardiac fibrosis in patients.<br /><b>Methods and results</b><br />We used single nuclei RNA sequencing with human tissues from 2 samples of one healthy donor, 5 hypertrophic and 2 failing hearts. Unsupervised sub-clustering of 7,110 nuclei led to the identification of 7 distinct fibroblast clusters.Deconvolution of cardiac fibroblast heterogeneity revealed a distinct population of human cardiac fibroblasts with a molecular signature of persistent fibroblast activation and a transcriptional switch towards a profibrotic extracellular matrix composition in patients with established cardiac hypertrophy and heart failure. This subcluster was characterized by high expression of POSTN, RUNX1, CILP and a target gene AEBP1 (all p < 0.001). Strikingly, elevated circulating AEBP1 blood level were also detected in a validation cohort of patients with confirmed cardiac fibrosis and hypertrophic cardiomyopathy by cardiac magnetic resonance imaging (p < 0.01). Since endogenous AEBP1 expression was increased in patients with established cardiac hypertrophy and heart failure, we assessed the functional consequence of siRNA mediated AEBP1 silencing in human cardiac fibroblasts. Indeed, AEBP1 silencing reduced proliferation, migration, as well as fibroblast contractile capacity and α-SMA gene expression, which is a hallmark of fibroblast activation (all p < 0.05). Mechanistically, the antifibrotic effects of AEBP1 silencing were linked to TGFβ pathway modulation.<br /><b>Conclusion</b><br />Together, this study identifies persistent fibroblast activation in patients with longstanding heart disease, which might be detected by circulating AEBP1 and therapeutically modulated by its targeted silencing in human cardiac fibroblasts.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 30 Aug 2023; epub ahead of print</small></div>

<div><h4>PDE4D mediates impaired β-adrenergic receptor signaling in the sinoatrial node in mice with hypertensive heart disease.</h4><i>Dorey TW, McRae MD, Belke DD, Rose RA</i><br /><b>Aims</b><br />The sympathetic nervous system increases HR by activating β-adrenergic receptors (β-ARs) and increasing cAMP in sinoatrial node (SAN) myocytes while phosphodiesterases (PDEs) degrade cAMP. Chronotropic incompetence, the inability to regulate heart rate (HR) in response to sympathetic nervous system activation, is common in hypertensive heart disease; however, the basis for this is poorly understood. The objective of this study was to determine the mechanisms leading to chronotropic incompetence in mice with angiotensin II (AngII) induced hypertensive heart disease.<br /><b>Methods and results</b><br />C57BL/6 mice were infused with saline or AngII (2.5 mg/kg/day for 3 weeks) to induce hypertensive heart disease. Heart rate (HR) and SAN function in response to the β-AR agonist isoproterenol (ISO) were studied in vivo using telemetry and electrocardiography, in isolated atrial preparations using optical mapping, in isolated SAN myocytes using patch-clamping, and using molecular biology. AngII-infused mice had smaller increases in HR in response to physical activity and during acute ISO injection. Optical mapping of the SAN in AngII-infused mice demonstrated impaired increases in conduction velocity and altered conduction patterns in response to ISO. Spontaneous AP firing responses to ISO in isolated SAN myocytes from AngII-infused mice were impaired due to smaller increases in diastolic depolarization (DD) slope, hyperpolarization activated current (If), and L-type Ca2+ current (ICa, L). These changes were due to increased localization of PDE4D surrounding β1- and β2-ARs in the SAN, increased SAN PDE4 activity, and reduced cAMP generation in response to ISO. Knockdown of PDE4D using a virus-delivered shRNA or inhibition of PDE4 with rolipram normalized SAN sensitivity to β-AR stimulation in AngII-infused mice.<br /><b>Conclusions</b><br />AngII-induced hypertensive heart disease results in impaired HR responses to β-AR stimulation due to upregulation of PDE4D and reduced effects of cAMP on spontaneous AP firing in SAN myocytes.<br /><br />© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.<br /><br /><small>Cardiovasc Res: 29 Aug 2023; epub ahead of print</small></div>