Iron and Inflammatory Cytokines Synergistically Induce Colonic Epithelial Cell Ferroptosis in Colitis

Inflammatory bowel disease (IBD) is an inflammatory disease that occurs to the intestinal tract. Many patients with IBD often develop anemia and often receive oral iron supplementation. Many of them develop non-compliance with oral iron therapy, but the mechanisms are not well understood. We interrogated whether colonic epithelial iron overload impacts cell viability and disease severity. We observed increased expression of iron importers and iron accumulation in mature colonocytes in dextran sulfate sodium (DSS)-induced acute colitis and in humans with active colitis. Administration of hepcidin increased epithelial iron overload and aggravated colonic inflammation in DSS-treated mice and IL10^-/- mice. Hepcidin-induced iron accumulation increased colonic epithelial death, which was prevented by treatment with Trolox, a vitamin E analog and a scavenger of lipid peroxides. By using cultured Caco-2 cells, we showed that iron and inflammatory cytokines (TNF-α and IL-1β) induced a synergistic increase in the number of necrotic cells. We then showed that the combined treatment by hepcidin and cytokines increased labile iron content and lipid peroxidation in Caco-2 cells. Moreover, liproxstatin-1, a ferroptosis inhibitor, and deferoxamine, an iron chelator, both abolished the hepcidin/cytokines induced death of Caco-2 cells, suggesting ferroptosis. We further elucidated that inflammatory cytokines promote lipid peroxidation and ferroptosis by inducing NOX1-dependent exhaustion of reduced glutathione (GSH). Collectively, our findings demonstrate that the inflammatory context predisposes colonic epithelial cells to iron overload mediated ferroptosis, exacerbating colonic inflammation.