Sodium fluoride induces apoptosis through reactive oxygen species-mediated endoplasmic reticulum stress pathway in Sertoli cells

Excessive fluoride exposure is known to contribute to reproductive system dysfunction, ultimately leading to pathological damage and apoptosis in cells. Although both oxidative and endoplasmic reticulum (ER) stresses have been implicated in fluorosis, the signaling pathways and their roles in sodium fluoride (NaF)-induced apoptosis of Sertoli cells have been sparsely described. In this study, oxidative damage, ER stress, and apoptosis were analyzed after Sertoli cells were treated with varying doses of NaF for 24 hr. Moreover, the antioxidant N-acetylcysteine (NAC) and pro-apoptotic transcription factor CHOP knockdown were used to clarify the precise interplay between reactive oxygen species (ROS), ER stress and their roles in NaF-induced apoptosis in Sertoli cells. The present study indicated that NaF significantly decreased cell viability and induced apoptosis in Sertoli cells. In addition, NaF exposure facilitated the accumulation of ROS and increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) in Sertoli cells. Treatment with NAC caused remarkable recovery from these NaF-induced responses. Meanwhile, excessive NaF triggered ER stress as evidenced by up-regulated glucose-regulated protein 78 kDa (GRP78), PKR-like ER kinase (PERK), phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α) and CCAAT/enhancer-binding protein-homologous protein (CHOP), without affecting total eukaryotic translation initiation factor 2α (eIF2α). NAC effectively blocked the activation of ER stress, suggesting that NaF-induced ROS is an early event that triggers ER stress. Taken together, the results demonstrate that the ROS-mediated ER stress pathway is the crucial mechanistic event involved in NaF-induced apoptosis of Sertoli cells.

In this article, the mode of primary cultured Sertoli cells from rat testis was used. The aim of this study was to investigate the role of ROS-dependent ER stress in fluoride-induced apoptosis. Oxidative damage markers (ROS levels and Nrf2 nuclear translocation), ER stress markers (GRP78, PERK, eIF2α, phospho-eIF2α and CHOP) and apoptosis were analyzed after Sertoli cells were treated with varying doses of sodium fluoride (NaF) for 24 hr. Moreover, N-acetylcysteine (NAC) and CCAAT/enhancer-binding protein-homologous protein (CHOP) knockdown were used to strengthen the findings concerning relationships between ROS, ER stress and apoptosis in this study. A better understanding of this process may provide us new insights into the mechanism of fluorosis in reproductive lesions.Figure optionsDownload as PowerPoint slide