PERK regulates Nrf2/ARE antioxidant pathway against dibutyl phthalate-induced mitochondrial damage and apoptosis dependent of reactive oxygen species in mouse spermatocyte-derived cells

Abstract

Dibutyl phthalate (DBP)-induced germ cell apoptosis contributes to male reproductive toxicity, however, the primary target organelle of DBP or the molecular events triggered by DBP to initiate germ cell apoptosis remain unclear. Our previous studies demonstrated DBP could stimulate the production of intracellular reactive oxygen species (ROS), which served as an upstream mediator of activation of endoplasmic reticulum (ER) stress in mouse spermatocyte-derived GC-2 cells. In the present study, the impacts of DBP-induced ROS generation on the mitochondria-related damage and the associations between ER stress and mitochondrial-related damage were investigated in GC-2 cells. We observed significant decreases of mitochondrial mass, mtDNA copy number, COX IV protein level, and ATP level in DBP-treated GC-2 cells in a dose-dependent manner. And DBP activated mitochondrial-related apoptosis, indicated by the elevation of cytoplasmic cytochrome C (Cyt C) and the activation of caspase-9/3 cascade. Pretreatment with antioxidant melatonin obviously attenuated DBP-induced mitochondrial damage and mitochondrial-dependent apoptosis in GC-2 cells, indicating the role of ROS in DBP-caused testicular toxicity. In response to oxidative stress, the Nrf2/ARE axis was activated in DBP-treated GC-2 cells to counteract ROS overproduction and subsequent mitochondrial damage. Further experiments showed DBP treatment increased the phosphorylated expression of ER stress-related protein PERK. GSK2606414, a specific inhibitor of PERK, partly attenuated the expression of Nrf2. And both DBP-induced mitochondrial damage in GC-2 cells and mitochondrial-dependent apoptosis of the germ cells in rat testes were further aggravated by PERK inhibition. Taken together, our data suggest that PERK regulates the Nrf2/ARE antioxidant pathway functioning as a self-defense mechanism against ROS-related mitochondrial damage induced by DBP in male germ cells.

Keywords: Dibutyl phthalate; Mitochondrial damage; Nrf2/ARE axis; PERK; Reactive oxygen species.