Thioredoxin Reduced Cardiomyocytes Apoptosis Induced By Diabetic Conditions

Abstract

Thioredoxin (TRX) is a class of redox proteins and functions in various biological processes, including differentiation, proliferation, and apoptosis. Although several studies have reported the anti-apoptotic roles of TRX both in vivo and in vitro, the exact role and mechanism of TRX in cardiomyocyte apoptosis under diabetic conditions remains largely unknown. PURPOSE: To investigate the role of TRX in apoptosis regulation after diabetic treatment both in vivo and in vitro. METHODS: We fed transgenic TRX C56BL/6 mice and wild type mice controls with normal diet or high-fat diet for 12 weeks, and measured mice body weight, glucose tolerance and insulin resistance. The apoptotic rate in the heart tissue with protein expressions of MAPKs and Bcl-2 family members were also measured. In addition, primary cultured mice cardiomyocytes were incubated in media with either low (5 mM) or high glucose (25 mM), with or without TRX si-RNA transfection. Apoptotic rate, expressions of MAPKs and Bcl-2 family members were measured. Finally, we constructed the luciferase reporter system to investigate the activation of AP-1 by TRX through JNK and c-Jun. RESULTS: Mice fed with high-fat diet showed obvious diabetic symptoms, including increased body weight (43±1.8 vs 35±2.1, p<0.05), impaired glucose tolerance, and occurrence of insulin resistance. High-fat diet also induced apoptosis in the heart tissues. Over-expression of TRX protected cells from apoptosis via regulating the Bcl-2 family through p38 MAPK and c-Jun/JNK pathway. In cell culture, high glucose environment mimicked the diabetic condition, which induced apoptosis in the cells. Silence of TRX exacerbated the phenomenon with altered MAPKs activities. At last, TRX directly regulated the activation of c-Jun and JNK through binding AP-1. CONCLUSION: TRX showed anti-apoptotic effects under diabetic conditions both in vivo and in vitro. The effects were mediated though modulating intrinsic apoptotic pathway via p38 MAPK and c-Jun/JNK signalings. Supported by Shanghai Key Laboratory of Human Sport Competence Development and Maintenance(Shanghai University of sport)(NO. 11DZ2261100)