Therapeutic Potential of Tpl2 (Tumor Progression Locus 2) Inhibition on Diabetic Vasculopathy Through the Blockage of the Inflammasome Complex

Arterioscler Thromb Vasc Biol. 2021 Jan;41(1):e46-e62. doi: 10.1161/ATVBAHA.120.315176. Epub 2020 Nov 12.

Abstract

Objective: Diabetic retinopathy, one of retinal vasculopathy, is characterized by retinal inflammation, vascular leakage, blood-retinal barrier breakdown, and neovascularization. However, the molecular mechanisms that contribute to diabetic retinopathy progression remain unclear. Approach and Results: Tpl2 (tumor progression locus 2) is a protein kinase implicated in inflammation and pathological vascular angiogenesis. Nε-carboxymethyllysine (CML) and inflammatory cytokines levels in human sera and in several diabetic murine models were detected by ELISA, whereas liquid chromatography-tandem mass spectrometry analysis was used for whole eye tissues. The CML and p-Tpl2 expressions on the human retinal pigment epithelium (RPE) cells were determined by immunofluorescence. Intravitreal injection of pharmacological inhibitor or NA (neutralizing antibody) was used in a diabetic rat model. Retinal leukostasis, optical coherence tomography, and H&E staining were used to observe pathological features. Sera of diabetic retinopathy patients had significantly increased CML levels that positively correlated with diabetic retinopathy severity and foveal thickness. CML and p-Tpl2 expressions also significantly increased in the RPE of both T1DM and T2DM diabetes animal models. Mechanistic studies on RPE revealed that CML-induced Tpl2 activation and NADPH oxidase, and inflammasome complex activation were all effectively attenuated by Tpl2 inhibition. Tpl2 inhibition by NA also effectively reduced inflammatory/angiogenic factors, retinal leukostasis in streptozotocin-induced diabetic rats, and RPE secretion of inflammatory cytokines. The attenuated release of angiogenic factors led to inhibited vascular abnormalities in the diabetic animal model.

Conclusions: The inhibition of Tpl2 can block the inflammasome signaling pathway in RPE and has potential clinical and therapeutic implications in diabetes-associated retinal microvascular dysfunction.

Keywords: Nε-carboxymethyllysine; cytokine; diabetic retinopathy; inflammasome; inflammation; neovascularization; retinal pigment epithelium; tumor progression locus 2.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Angiogenesis Inhibitors / pharmacology*
  • Animals
  • Cells, Cultured
  • Cross-Sectional Studies
  • Databases, Factual
  • Diabetes Mellitus, Experimental / complications
  • Diabetes Mellitus, Experimental / diagnosis
  • Diabetes Mellitus, Experimental / enzymology
  • Diabetes Mellitus, Type 1 / complications
  • Diabetes Mellitus, Type 1 / diagnosis
  • Diabetes Mellitus, Type 1 / enzymology
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / diagnosis
  • Diabetes Mellitus, Type 2 / enzymology
  • Diabetic Retinopathy / enzymology
  • Diabetic Retinopathy / etiology
  • Diabetic Retinopathy / pathology
  • Diabetic Retinopathy / prevention & control*
  • Female
  • Humans
  • Inflammasomes / antagonists & inhibitors*
  • Inflammasomes / metabolism
  • MAP Kinase Kinase Kinases / antagonists & inhibitors*
  • MAP Kinase Kinase Kinases / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • Pregnancy
  • Prospective Studies
  • Protein Kinase Inhibitors / pharmacology*
  • Proto-Oncogene Proteins / antagonists & inhibitors*
  • Proto-Oncogene Proteins / metabolism
  • Retinal Neovascularization / enzymology
  • Retinal Neovascularization / etiology
  • Retinal Neovascularization / pathology
  • Retinal Neovascularization / prevention & control*
  • Retinal Pigment Epithelium / drug effects*
  • Retinal Pigment Epithelium / enzymology
  • Retinal Pigment Epithelium / pathology
  • Signal Transduction

Substances

  • Angiogenesis Inhibitors
  • Inflammasomes
  • Protein Kinase Inhibitors
  • Proto-Oncogene Proteins
  • MAP Kinase Kinase Kinases
  • MAP3K8 protein, human
  • Map3k8 protein, mouse