Constant light exposure impairs embryonic development via disrupting oocyte cytoskeleton integrity and redox homeostasis

Environmental constant light exposure could induce biological rhythm disruption, which negatively induces metabolic syndrome, mood disorders, cognitive declines, chronic disease risk, and reproduction defects. Previous studies indicated that constant light exposure affected ovary function and oocyte quality. Here, we reported that melatonin supplementation effectively alleviated the adverse effects of constant light exposure on embryonic development by improving oocyte quality. Our results showed that constant light exposure reduced blastocyst formation during mouse embryo development, and the levels of DNA and histone methylation modifications of embryos were altered. This might be due to the low oocyte quality since we observed aberrant spindle formation, which might be caused by HDAC6-medicated tubulin acetylation for microtubule stability, and this further induced K-MT attachment defects for aneuploidy. Besides, spindle migration was disturbed due to ARP2-based actin assembly defects. Light exposure also led to oocyte elevated ROS level, DNA damage, and then activated LC3-based autophagy and disrupted lysosome function. Notably, in vivo melatonin supplementation effectively rescued these defects in the oocytes and embryos of the mice under constant light exposure. Collectively, our results suggested that melatonin preserved embryo development potential and epigenetic modifications under constant light exposure by maintaining oocyte redox homeostasis and cytoskeletal dynamics.