Melatonin Protects Against Mitochondrial Dyshomeostasis and Ovarian Damage Caused by Chronic Unpredictable Mild Stress Through the eIF2α-AFT4 Signaling Pathway in Mice.

Stress is an emotional state caused by an unexpected external environmental change or stimulus, and several experiments have demonstrated its negative impact on ovarian function, ultimately affecting reproductive ability. Melatonin (MT) has been shown to facilitate oocyte maturation and enhance ovarian function by regulating mitochondrial function. However, the specific effect and underlying molecular mechanisms of MT on stress-induced ovarian dysfunction remain largely unknown. In this study, we established a mouse model of chronic unpredictable mild stress (CUMS) to investigate its impact on ovarian function. Our findings revealed that CUMS led to premature ovarian insufficiency (POI) in mice, characterized by a reduction in follicle numbers and decreased levels of anti-Müllerian hormone (AMH) and bone morphogenetic protein 15 (BMP15). Furthermore, CUMS caused decreased expression of mitochondrial fission protein 1 (FIS1) and enhanced level of mitochondrial fusion protein optic atrophy 1(OPA1), mitofusin1(MFN1), as well as nucleus-encoded protein succinate dehydrogenase complex A (SDHA), reflecting mitochondrial dyshomeostasis. Additionally, CUMS resulted in excessive autophagy and apoptosis. However, MT reversed these effects and improved ovarian damage. Importantly, the protective effects of MT were mediated through the inhibition of the eIF2α-AFT4 pathway. Overall, this study provides valuable insights into the treatment of POI caused by CUMS.