Yiping Sun1, Ying Xie2, Luping Du2, Jingwu Sun3, Zhiqiang Liu2. 1. Department of Cardiac Surgery, the Affiliated Zhongshan Hospital of Fudan University, Xuhui, Shanghai, China. 2. Department of Physiology and Pathophysiology, School of Basic Medical Science, Tianjin Medical University, Heping, Tianjin, China. 3. Department of Cardiology, the Affiliated Hospital of Binzhou Medical University, Binzhou, Shandong, China.
Abstract
BACKGROUND: Myocardial infarction (MI) remains the most common cause of heart failure (HF) worldwide. For almost 50 years, HF has been recognized as a determinant of adverse prognosis after MI, but efforts to promote myocardial repair have failed to be translated into clinical therapies. AIMS: In this study, we investigated the effects of BRD4 on cardiac function and the underlying mechanism. MATERIAL AND METHODS: The in vivo rat model of AMI and in vitro neonatal cardiomyocytes were established and cultured respectively, the BRD4 and NPPA/NPPB expression levels were detected by qPCR and Western blot, and interaction of BRD4 with acetylation RelA or NPPA/B promoters were examined by co-immunoprecipitation and chromatin immunoprecipitation assays, respectively. RESULTS: We found that BRD4 protein expression was significantly increased in cardiomyocytes of MI rat model and cardiomyocytes under hypoxia, accompanied by the expression of natriuretic peptide A (NPPA) and natriuretic peptide B (NPPB). Functionally, knockdown of BRD4 greatly downregulated the NPPA and NPPB in vivo and in vitro, improved the hemodynamic and biometric parameters in rat with heart failure, as well as decreased the apoptosis occurrence. In vitro studies further demonstrated that BRD4 bound with acetylated RelA to enhance the activation of NF-κb signaling, which resulted in activation of NPPA and NPPB transcriptions. CONCLUSIONS: Taken together, our findings suggest that inhibition of BRD4 attenuated cardiomyocyte apoptosis via NF-κB pathway in myocardial infarction, and this study sheds light on developing new strategies to overcome myocardial damage.
BACKGROUND:Myocardial infarction (MI) remains the most common cause of heart failure (HF) worldwide. For almost 50 years, HF has been recognized as a determinant of adverse prognosis after MI, but efforts to promote myocardial repair have failed to be translated into clinical therapies. AIMS: In this study, we investigated the effects of BRD4 on cardiac function and the underlying mechanism. MATERIAL AND METHODS: The in vivo rat model of AMI and in vitro neonatal cardiomyocytes were established and cultured respectively, the BRD4 and NPPA/NPPB expression levels were detected by qPCR and Western blot, and interaction of BRD4 with acetylation RelA or NPPA/B promoters were examined by co-immunoprecipitation and chromatin immunoprecipitation assays, respectively. RESULTS: We found that BRD4 protein expression was significantly increased in cardiomyocytes of MI rat model and cardiomyocytes under hypoxia, accompanied by the expression of natriuretic peptide A (NPPA) and natriuretic peptide B (NPPB). Functionally, knockdown of BRD4 greatly downregulated the NPPA and NPPB in vivo and in vitro, improved the hemodynamic and biometric parameters in rat with heart failure, as well as decreased the apoptosis occurrence. In vitro studies further demonstrated that BRD4 bound with acetylated RelA to enhance the activation of NF-κb signaling, which resulted in activation of NPPA and NPPB transcriptions. CONCLUSIONS: Taken together, our findings suggest that inhibition of BRD4 attenuated cardiomyocyte apoptosis via NF-κB pathway in myocardial infarction, and this study sheds light on developing new strategies to overcome myocardial damage.