Mitochondrial-derived peptide Humanin protects granulosa cells under oxidative conditions

In brief: Redox imbalance compromises granulosa cell survival and follicle fate. This study identifies the mitochondrial-derived peptide Humanin (HN) as a cytoprotective factor that protects granulosa cells under oxidative condItions. Abstract: Granulosa cell function is essential for proper ovarian physiology. Redox imbalance compromises granulosa cell survival, thereby impacting follicle fate within the ovary. Humanin (HN), a small mitochondrial-derived peptide, exerts cytoprotective effects in several tissues under pro-oxidant conditions. The present study aimed to evaluate the cytoprotective effects of HN under oxidative conditions in granulosa cells, using a human granulosa cell line (KGN) and an in-vitro rat ovary culture to assess its action within the ovarian microenvironment. KGN cells showed a significant increase in endogenous HN mRNA expression in response to oxidative conditions induced by H2O2. Upon oxidative insult, exogenous HN enhanced cellular antioxidant capacity by significantly increasing catalase activity levels, without modifying superoxide dismutase expression or activity, or redox status in KGN cells. Importantly, HN significantly decreased H2O2-induced granulosa cell apoptosis in KGN cells, as determined by the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. This protective effect was associated with modulation of key apoptosis-related genes, including reduced expression of BAX and the caspase-3 precursor (CASP3), while BCL2 expression remained unchanged. Consistently, in rat ovaries, HN protected granulosa cells of antral follicles under oxidative conditions. In conclusion, our findings support a cytoprotective role of HN in granulosa cells under oxidative conditions, which may contribute to the maintenance of antral follicle survival within the ovarian microenvironment.