Signaling pathways of Periplaneta americana peptide resist H2O2-induced apoptosis in pig-ovary granulosa cells through FoxO1

Granulosa cell apoptosis induced by oxidative stress is an important cause of follicular atresia. Our previous studies found that Periplaneta americana peptide (PAP) decreased H2O2-induced apoptosis of pig-ovary granulosa cells (PGCs) through FoxO1. The aim of this study is to investigate the signaling pathways involved in PAP resistance against H2O2-induced apoptosis of PGCs. PGCs obtained from the follicles of non-estrous Duroc × Landrace × Yorkshire gilts (5 months old, 50-55 kg) were treated with H2O2 and PAP, or together with inhibitors against PI3K and JNK, and then collected for ROS levels and SOD activities detection, TUNEL staining, qRT-PCR, western blotting, immunofluorescence or coimmunoprecipitation. Results showed that the increased ROS levels and decreased activities of SOD caused by H2O2 stimulation were reversed by PAP. Additionally, PAP downregulated the differential abundance of mRNA of Bax and FasL, thus inhibiting H2O2-induced apoptosis of PGCs. PAP significantly reduces p-JNK expression and increases the p-FoxO1/FoxO1 expression ratio, thereby decreasing caspase-3 expression and cell apoptosis in H2O2-induced PGCs. PAP promotes the combination of FoxO1 with the 14-3-3 protein, increases FoxO1 translocation to the cytoplasm, and decreases FoxO1 acetylation. Therefore, PAP regulates FoxO1 expression through the JNK/FoxO1 signaling pathway and effects the translocation of FoxO1 to the cytoplasm by the FoxO1 interaction with 14-3-3, enabling reversal of the H2O2-induced apoptosis of PGCs. Acetylation of FoxO1 is also involved in the antiapoptotic effect of PAP.