PTD-FNK Alleviated Heat Stress-Induced Apoptosis of Boar Sertoli Cells via the PI3K/AKT Pathway.

Heat stress (HS) impairs boar reproductive capacity via damaging Sertoli cells (SCs) and disrupting the integrity of the blood-testis barrier (BTB). This present study investigated the protective effects and underlying molecular mechanisms of PTD-FNK against HS-induced injury in porcine SCs. A HS model (43 °C, 1 h) was established, and 0.1 nM was determined as the optimal working concentration of PTD-FNK. Results showed that PTD-FNK effectively reversed HS-induced BTB disruption by restoring the expression levels of tight junction proteins (Claudin-1, Occludin, ZO-1, and Cx43) to baseline levels (p < 0.05). Concurrently, PTD-FNK alleviated HS-induced oxidative stress by enhancing total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity, while reducing malondialdehyde (MDA) content (p < 0.05). It also suppressed HS-triggered apoptosis by downregulating the expression of pro-apoptotic proteins (Caspase-3/8/9 and Bax) and upregulating the anti-apoptotic protein Bcl-2 (p < 0.05). Furthermore, PTD-FNK maintained cellular homeostasis by regulating mitochondrial dynamics-restoring mitochondrial membrane potential (MMP) and balancing the expression of fusion-related protein Mfn1 and fission-related protein Drp1.Transcriptomic and LY294002 experiments confirmed PTD-FNK exerted effects via the PI3K/AKT pathway, modulating ID3, H2AX, DDIT3, CDKN1C, RAD51, and TP53. Thus, PTD-FNK protects SCs from HS through multi-target regulation dependent on PI3K/AKT, providing a novel strategy for boar reproductive health under HS.