Abstract Background The dysbiosis of the intestinal microbiome in post-cholecystectomy (PC) patients often leads to various intestinal complications. However, both clinical and basic studies suggest that colitis rarely occurs in the PC host, and microbial dysbiosis cannot explain this phenomenon. Our previous research found that macrophages phenotypic remodeling plays a pivotal role in regulating intestinal inflammation in PC mice, but the mechanism has not been elucidated. Methods An animal model of colitis after cholecystectomy was established, and the effect of cholecystectomy on the intestinal immunocytes and intestinal inflammation was evaluated. Gene conditional knockout mice were constructed to determine the effect of m6 A modification regulators on macrophage homeostasis and intestinal inflammation after cholecystectomy. MeRIP-seq and RNA-seq analysis were performed to identify the downstream target. Bone marrow-derived macrophages (BMDM) were isolated for in vitro functional validation. Results Cholecystectomy ameliorated DSS-induced murine colitis, reduced the infiltration of M1 macrophages in the lamina propria, and inhibited the expression of METTL3 in macrophages. Macrophage-specific deletion of Mettl3 mice were more resistant to DSS-induced colitis than were wild-type mice after cholecystectomy. In vivo and in vitro studies confirmed that Mettl3 deletion skewed macrophages towards M2 activation. Mechanistically, Irakm, a negative regulator of TLR4 signaling, was identified as a target of METTL3-mediated m6 A modification. METTL3 deficiency led to a higher level of IRAKM, which ultimately suppressed TLR signaling–mediated macrophage activation. Macrophage-specific deletion of Irakm mice were more susceptible to DSS-induced colitis than were wild-type mice after cholecystectomy. Colon-infiltrating M1 macrophages from Irakmfl/flLyz2Cre mice dramatically increased compared with those from their counterpart Irakmfl/fl mice. Additionally, deletion of IRAKM in BMDMs induced NF-κB activation and facilitated M1 polarization. Conclusion Collectively, this study highlights the function of m6A in regulating macrophage homeostasis and identifies potential targets in remodeling intestinal immune microenvironment after cholecystectomy. Conflict of interest: Dr. Zhang, Yang: No conflict of interest Xu, Jun: No conflict of interest Liu, Yulan: No conflict of interest
Zhang et al. (Thu,) studied this question.