ANGII Initiated HSF2 Trans-Activating HIF-1α Through Induction of ER Stress to Promote Cardiac Hypertrophy

Heat shock factor 2 (HSF2) and hypoxia-inducible factor 1α are activated by angiotensin II (ANGII) in cardiomyocytes. The endoplasmic reticulum (ER) stress plays a critical role in cardiac hypertrophy. Moreover, HIF-1α is known to be regulated by HSF2 in tumour cells. In this study, we hypothesised and clarified whether HSF2 trans-activated HIF-1α through initiation of ER stress in hypertrophic cardiomyocytes. Myocardial hypertrophy was induced by the treatment of ANGII. Expression of the gene or protein was assessed by applying RT-PCR, WB, ICC and IHC. Luciferase and CHIP were applied to detect the transcription of HIF-1α by HSF2. Both in vitro and in vivo, the expression of HIF-1α, ER stress markers and HSF2 was increased in ANGII-treated hypertrophic cardiomyocytes. Blocking ER stress suppressed the expression of HSF2 and HIF-1α in ANGII-treated cardiomyocytes. Silencing HSF2 inhibited HIF-1α, thereby reducing hypertrophy but had no effect on ER stress. Similarly, silencing HIF-1α reduced hypertrophy without affecting ER stress or HSF2 expression. HSF2 transcriptionally activated HIF-1α. We concluded that ER stress induced by ANGII activates HSF2, which then trans-activates HIF-1α, promoting cardiac hypertrophy.