Propionate alleviated colitis by modulating iron homeostasis to inhibit ferroptosis and macrophage polarization.

Ulcerative colitis (UC) is a relapsing inflammatory bowel disease with limited effective treatment options. Ferroptosis, characterized by lipid peroxidation-induced cellular death, is involved in UC pathogenesis. Propionic acid, a short-chain fatty acid, has demonstrated therapeutic potential in alleviating numerous conditions; however, its role and underlying mechanisms in UC remain unclear. In this study, we analyzed ferroptosis in UC patients using datasets from the GEO database and established an experimental colitis model to evaluate the therapeutic effects of propionate. We assessed the markers of inflammation and ferroptosis. Our findings revealed that ferroptosis occurred in the colonic tissue of UC patients and mouse colitis model. Propionate effectively alleviated UC symptoms, reduced pro-inflammatory cytokines, and regulated iron homeostasis. At a dose of 100 mM, propionate promoted intestinal epithelial regeneration, while 400 mM inhibited ferroptosis significantly. Mechanistic studies demonstrated that propionate increased the expression of transferrin receptor 1 (TFR1) and ferritin heavy chain 1 (FTH1) in a dose-dependent manner, which was associated with reduced hypoxia-inducible factor 1α (HIF-1α) expression. Moreover, after inhibition of HIF-1α, the therapeutic effects of propionate on colonic symptoms were found to be similar. Furthermore, propionate promoted the polarization of macrophages to the M2 type. Our results indicate that propionate regulates HIF-mediated expression of TFR1 and FTH1 to modulate iron homeostasis, promote epithelial regeneration, inhibit ferroptosis, and regulate macrophage differentiation. These results strongly support the potential use of propionate in the clinical treatment of UC.