The Transcription Factor Bach1 Plays an Important Role in Regulating Macrophage Ferroptosis Upon Iron Supplementation

Ferroptosis is a novel iron-mediated necrotic cell death pathway associated with accumulation of lipid peroxidation, reduced levels of glutathione (GSH) and glutathione peroxidase-4 (Gpx4). This form of cell death has been implicated in different diseases, including tuberculosis. Our group previously described that Mtb-induced macrophage necrosis is associated with hallmarks of ferroptosis, facilitating bacterial spread extracellularly. Nevertheless, the mechanisms underlying the effect of iron in modulating cell death remain poorly delineated. In this study, we used an iron overload model of ferroptosis on bone-marrow derived macrophages (BMDMs) to investigate molecular mediators of antioxidant generation and lipid peroxidation, and their role in modulating ferroptotic cell death. Our findings showed that BMDMs deficient in Nrf2, a transcription factor that regulates many antioxidant genes, were highly susceptible to iron-mediated ferroptosis. In the opposite direction, BMDMs deficient in lipoxygenase-5 (5-LO) as well as in Bach1, a Nrf2 suppressor, displayed enhanced resistance to the cytotoxic effects of iron overload. Interestingly, ~50% of the ferroptotic death triggered by iron supplementation was blocked by 5-LO deficiency while in Bach1-/- macrophage cultures this suppression reached ~94%. Together, these findings indicate that 5-LO plays a partial role in lipid peroxidation driven by iron overload and reveal Bach1 as a master regulator of ferroptosis in macrophages. This study additionally provides a conceptual basis for further investigation of the role of ferroptosis-induced cellular and tissue damage in Mtb infection.