Estrogens Protect against AKI by Regulating Ferroptosis Sensitivity

Background: Epidemiological studies demonstrated that premenopausal women experience less episodes of acute kidney injury (AKI) than males, and that estrogen supplementation protects concomitantly in menopause. This falls in line with the known phenomenon that female mice are protected against ischemia/reperfusion injury. However, molecular mechanisms of this phenomenon remain ill-defined. As ferroptosis, an iron-dependent form of regulated necrosis, plays a crucial role in the pathogenesis of AKI, we hypothesized that estrogens modulate sensitivity to ferroptosis. Methods: The effects of estrogens on ferroptosis sensitivity were investigated in various cell culture assays. Mechanistic insights were derived from western blots, and confirmed by CRISRP-mediated knock-outs. Radical trapping mechanisms were tested in cell free systems, whereas translational relevance was established via isolated renal tubules of various species. Complex murine studies tested proposed mechanisms in AKI models. Results: 17-beta-estradiol (E2) protected against ferroptosis and associated lipid peroxidation in cell culture. Mechanistically, E2 quinone derivates 2OH and 4OH were identified as potent lipophilic radical trapping antioxidants, which were regenerated by the oxidoreductase FSP1 (AIFM2). Interestingly, inhibition of FSP1 sensitized female cells to ferroptosis and increased the E2 doses required for protection. Furthermore, E2 induced several antiferroptotic programs via genomic functions, including increased expression of FSP1, generation of hydropersulfides, and downregulation of ether lipids via reduced AGPS expression. Knock-out studies confirmed the functional relevance of these mechanisms in cell culture, whereas isolated tubuli from several mammalian species demonstrated the conservation of these mechanisms. Studies utilizing the murine IRI model proved the functional relevance of these mechanisms upon AKI. Conclusion: In summary, we describe the molecular underpinnings of ferroptosis resistance in female mammals. These findings may explain epidemiological data on female resistance to AKI, and could lead the path to sex-specific interventions in prevention and treatment of human AKI. Funding: Government Support – Non-U.S.