MK-4 Ameliorates Post-Ovulatory Aging of Mouse Oocytes by Alleviating Iron Metabolism Disorder-Induced Oxidative Stress

Abstract

Post-ovulatory aging (POA) reduces oocyte quality, yet effective interventions remain limited. Here we demonstrate that early intervention with vitamin K2 (menaquinone-4 isoform, MK-4) alleviates POA by inhibiting iron-disorder-induced oxidative stress. Western blot revealed that the expressions of ferroptosis suppressor protein 1 (FSP1) and vitamin K epoxide reductase-like protein (VKORC1L1) were significantly decreased in mouse POA oocytes; however, MK-4 attenuated these changes. Further, MK-4 inhibited ferritinophagy by downregulating NCOA4 and LC3II, markedly restored ferritin level, reduced intracellular Fe²⁺ amount, thus attenuating oxidative stress. These results were characterized by reducing lipid peroxidation marker malondialdehyde (MDA) and acyl-CoA synthetase long chain family member 4 (ACSL4) expression, decreasing γ-H2AX and 8-Hydroxy-2′-deoxyguanosine (8-OHdG), and enhancing expression of the mitochondrial antioxidant enzyme superoxide dismutase 1 (SOD1). Additionally, MK-4 suppressed mitophagy by downregulating PINK1 and Parkin, and upregulating Rab7 improving mitochondrial membrane potential. Consequently, abnormalities in chromosomes, spindles, and the cytoskeleton were significantly ameliorated in POA oocytes receiving early MK-4 intervention. Notably, in vitro-aging oocytes expressed higher FSP1 and VKORC1L1 but lower ACSL4 and MDA versus the in vivo counterparts, suggesting a milder lipid peroxidation in vitro. Collectively, our findings uncover a novel anti-aging mechanism triggered by MK-4, highlighting its potential to establish a preventive strategy for female reproductive aging.