Inhibition of CCN5 Protects Against Apoptosis and Endoplasmic Reticulum Stress in Bisphenol A-Induced Sertoli Cells via p38/JNK MAPK Signaling Pathway

Bisphenol A (BPA) is the most common endocrine disruptor that has toxicity to the reproductive system and male infertility. However, the underlying mechanisms of BPA's toxicity to Sertoli cells remain poorly understood. Cellular communication network factor 5 (CCN5) is reported to regulate cell proliferation, apoptosis, and differentiation. Our study demonstrated a significant elevation of CCN5 expression in the testis of nonobstructive azoospermia patients and TM4 Sertoli cells exposed to BPA. Knockdown of CCN5 reduced apoptotic cells after BPA treatment, as determined by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. Cells exposed to BPA showed increased expressions of Bax and cleaved poly(ADP-ribose) polymerase, decreased expression of Bcl-2, as well as elevated activities of caspase-3 and caspase-9 in BPA-induced TM4 cells, which were reversed by CCN5 inhibition. Loss of CCN5 declined phosphorylation of protein kinase R-like endoplasmic reticulum kinase and eukaryotic translation initiation factor 2A and decreased activating transcription factor 4 and C/EBP-homologous protein in BPA-treated cells. Furthermore, silencing CCN5 blocked BPA-induced phosphorylation of p38 and c-Jun N-terminal kinase (JNK). Administration of anisomycin, a mitogen-activated protein kinase (MAPK) activator, reversed the effects of CCN5 knockdown on BPA-induced endoplasmic reticulum (ER) stress and apoptosis. Taken together, CCN5 promotes apoptosis and ER stress in Sertoli cells exposed to BPA by activating the p38/JNK MAPK signaling pathway.