Formononetin alleviates ulcerative colitis via reshaping the balance of M1/M2 macrophage polarization in a gut microbiota-dependent manner

Abstract

BackgroundUlcerative colitis (UC), a type of inflammatory bowel disease, presents substantial challenges in clinical treatment due to the limitations of current medications. Formononetin (FN), a naturally compound with widespread availability, exhibits anti-inflammatory, antioxidant, and immunomodulatory properties. PurposeThis study aimed to investigate the efficacy of FN against UC and its potential regulatory mechanism. MethodsHere, dextran sulfate sodium (DSS) was employed to replicate experimental colitis in mice with concomitant FN treatment. The distribution and localisation of CD68 and F4/80 macrophages in colonic tissues were visualized by immunofluorescence, their chemokine and inflammatory cytokine concentrations were determined by ELISA, and macrophages and M1/M2 subpopulations were determined by flow cytometry. Additionally, 16 s rRNA and LC-MS techniques were used to detect the colonic intestinal microbiota and metabolite profiles, respectively. Correlation analyses was performed to clarify the interactions between differential bacteria, metabolites and M1/M2 macrophages, and pseudo sterile mice were constructed by depletion of gut flora with quadruple antibiotics, followed by faecal microbial transplantation to evaluate its effects on colitis and M1/M2 macrophage polarisation. ResultsFN dose-dependently alleviated clinical symptoms and inflammatory injury in colonic tissues of colitis mice, with its high-dose efficacy comparable to that of 5-ASA. Concurrently, FN not only inhibited inflammatory infiltration of macrophages and their M1/M2 polarisation balance in colitis mice, but also improved the composition of colonic microbiota and metabolite profiles. However, FN lost its protective effects against DSS-induced colitis and failed to restore the equilibrium of M1/M2 macrophage differentiation following intestinal flora depletion through quadruple antibiotic treatment. Importantly, fecal microbiota transplantation from FN-treated mice restored FN's protective effects against DSS-induced colitis and reestablished its regulatory role in M1/M2 macrophage polarization. ConclusionCollectively, FN ameliorated UC through modulating the balance of M1/M2 macrophage polarization in a gut microbiota-dependent manner.