Co-exposure of microcystin and nitrite enhanced spermatogenic disorders: The role of mtROS-mediated pyroptosis and apoptosis

Microcystins (MCs) and nitrites are coexisted in the environment and have reproductive toxicity. The combined toxic effect and mechanism of MCs and nitrite on spermatogenesis remain largely unclear. In the present study, co-exposure to microcystin-leucine arginine (MC-LR) and sodium nitrite (NaNO₂) aggravated testicular damage of Balb/c mice and mitochondrial impairment of spermatogonia, Sertoli cells, and sperm. Furthermore, MC-LR and NaNO₂ reduced sperm density with a synergistic effect. In addition, MC-LR and NaNO₂ synergistically induced oxidative stress in the reproductive system by decreasing superoxide dismutase (SOD) activity and glutathione (GSH) levels and increasing levels of mitochondrial reactive oxygen species (mtROS) and reactive oxygen species (ROS). More importantly, mitoquidone mesylate (MitoQ), an inhibitor of mtROS, blocked MC-LR and NaNO₂-induced spermatogonia and Sertoli cell apoptosis by inhibiting high expression of Bax, Fadd, Caspase-8, and cleaved-Caspase-3. On the other hand, MitoQ suppressed pyroptosis of Sertoli cells by inhibiting the expression of NLRP3, N-GSDMD, and cleaved-Caspase-1. Additionally, MitoQ alleviated co-exposure-induced sperm density reduction and organ index disorders in F1 generation mice. Together, co-exposure of MC-LR and NaNO₂ can enhance spermatogenic disorders by mitochondrial oxidative impairment-mediated germ cell death. This study emphasizes the potential risks of MC-LR and NaNO₂ on reproduction in realistic environments and highlights new insights into the cause and treatment of spermatogenic disorders.