HSP70 Enhances Heat-induced Lactate Production In Cultured Immature Boar Sertoli Cells

Heat stress has adverse effects on spermatogenesis in many mammal species. Lactate produced by Sertoli cells(SCs) provides a substrate for developing germ cells and plays an antiapoptotic role in the process of spermatogenesis. Heat shock proteins(HSPs) have also an antiapoptotic effect to response to heat stress. However, it is unclear whether HSPs exert an antiapoptotic effect via regulating heat-induced lactate production in cultured immature boar SCs.In this study, we used immature boar about 20 d as the experimental material, and cultured immature SCs in the condition of 32 °C incubator for 48 h for the subsequent treatment. The condition of heat treatment is 43 °C incubator for 30 min, and then SCs were put back in 32 °C incubator for recovery(0, 12, 24, 36 or 48 h). All the cells and culture medium were collected to detect lactate production, mRNA and protein level of relative enzymes.These results were as followed:(1) Heat stress stimulated SCs lactate production in time dependence with the maximum level(119% of control) at 24 h after heat stress.(2) Among all GLUTs and LDHs detected, two major regulatory enzymes, glucose transporter 3(GLUT3) and lactate dehydrogenase A(LDHA), were associated with in lactate production. Heat shock protein70(HSP70) is the most significant changed HSPs in all HSPs detected in immature boar SCs after heat stress.(3) Heat stress induced the expression of SLC2A3(GLUT3) and LDHA in time-dependence. Both mRNA level reached maximum at 12 h after heat treatment, protein level reached maximum at 24 h after heat treatment.(4) Heat stress induced the mRNA expression of HSP70.2(HSP70) immediately at 0 h after heat treatment. And the maximum protein level of HSP70 reached at 24 h after heat treatment.(5) Both quercetin, an inhibitor of HSP70, and HSP70.2 siRNA reduced mRNA and protein level of SLC2A3 and LDHA, resulting in lower lactate production after heat stress.These results showed that HSP70 enhances the expression of SLC2A3 and LDHA in heat stress induced lactate production in cultured immature boar SCs. This study provides an insight that HSP70 exerts an antiapoptotic effect in spermatogenesis.