IRP1 deficiency promotes fibroblast activation through iron dysregulation: protective modulation by H₂S

Iron is indispensable for core physiological processes, and intracellular iron homeostasis is tightly governed by iron regulatory protein 1 (IRP1). Hydrogen sulfide (H₂S), an endogenous gasotransmitter with well-established antioxidant and cytoprotective activities, remains poorly characterized for its regulatory roles in IRP1-dependent iron metabolism and fibroblast activation. Herein, we employed primary mouse embryonic fibroblasts (MEFs) to interrogate the functional crosstalk between NaHS (a H₂S donor) and IRP1 governing iron balance and profibrotic responses. Our results reveal that IRP1 ablation or iron supplementation elevates the labile iron pool, triggers oxidative stress, and enhances cell adhesion, proliferation, and expression of profibrotic genes. Exogenous NaHS supplementation reduced labile iron accumulation and rescued iron-evoked cellular abnormalities, with this beneficial effect predominantly observed in wild-type MEFs. Mechanistically, NaHS upregulated IRP1 aconitase activity without altering the expression of transferrin receptor 1 or ferritin heavy chain. Although IRP1 deficiency and iron overload boosted endogenous H₂S production, neither manipulation changed the protein abundance of three major H₂S-synthesizing enzymes: cystathionine gamma-lyase (CSE), cystathionine beta-synthase, and 3-mercaptopyruvate sulfurtransferase. In vivo, intravenous iron administration elicited markedly greater cardiac profibrotic gene expression in CSE-knockout mice relative to wild-type littermates. Taken together, these data establish that H₂S mitigates iron overload and subsequent fibrosis driven by IRP1 dysfunction, pointing toward promising therapeutic strategies for iron imbalance-associated fibrotic disorders.