Role of HSP72 in alleviating heat stress-induced damage in Sertoli cells of dairy bulls.

Abstract

Sertoli cells (SCs), the essential functional units of the testis, are responsible for supporting spermatogenesis. Heat stress impairs SCs by triggering oxidative injury, apoptosis, and ferroptosis, consequently suppressing spermatogenesis. Nevertheless, the dynamic alterations of SCs upon sustained heat stress remain poorly defined. Although HSP72 is recognized to exert a vital pro-survival function under heat stress, its detailed molecular mechanism remains largely elusive. The present study aimed to investigate the protective effect of HSP72 against heat stress-induced damage in SCs. Our results revealed that heat stress treatment for 1-6 h markedly suppressed cell viability, with a highly significant elevation in the apoptotic rate observed at the 6-h time point. Furthermore, either knockdown of Hsp72 or perturbation of the components of its functional complex markedly increased cellular susceptibility to heat stress, wherein a significant rise in apoptosis was detected as early as 1 h post heat exposure. We additionally evaluated the influence of heat stress on cell proliferation; prolonged heat stress for 6 h caused highly significant repression of cell proliferation, and Hsp72 knockdown resulted in pronounced proliferation inhibition regardless of heat stress exposure status. Further mechanistic assays demonstrated that HSP72 depletion dramatically upregulated P21 expression, leading to cell cycle arrest at the G₂ phase. Moreover, intracellular galactosidase activity was significantly elevated following 1-6 h of heat stress, and HSP72 silencing further increased the percentage of galactosidase-positive cells. Collectively, these findings highlight the crucial protective role of HSP72 in counteracting heat stress-elicited cellular injury, laying a fundamental theoretical foundation for alleviating heat-induced cellular damage.