Smad2/3 regulates IL-6R m6A methylation through METTL3 to influence inflammatory responses in hemorrhoidal disease

OBJECTIVE: This study investigates METTL3's function and mechanisms in hemorrhoidal disease-related inflammation. METHODS: A rat model of hemorrhoidal disease was induced in vivo using croton oil. Human monocytic leukemia cells THP-1 were induced into macrophages using phorbol myristate acetate, and then lipopolysaccharide (LPS) was used to induce an inflammatory phenotype in the macrophages. The pathological changes in the rectal and anal tissues of rats were evaluated using the rectoanal coefficient and HE staining. Key gene and protein expression levels were detected using RT-qPCR, Western blotting, immunofluorescence, and immunohistochemistry. RESULTS: METTL3 expression was significantly upregulated in hemorrhoidal tissues and LPS-induced macrophages, and its knockdown alleviated rectal-anal lesions in hemorrhoidal rats. Silencing METTL3 suppressed the expression of M1 polarization markers (iNOS, CD80, CD86) while increasing IL-10 and reducing TNF-α, IL-1β, and IL-6 levels in hemorrhoidal tissues and LPS-stimulated macrophages. Furthermore, LPS treatment enhanced Smad2/3 and IL-6R expression in macrophages, and positive correlations were observed between the expression of Smad2, Smad3, and METTL3, as well as between METTL3 and IL-6R. Mechanistically, nuclear-translocated Smad2/3 bound to METTL3 to promote its expression. The resulting elevated METTL3 then promoted IL-6R expression via m6A modification, driving macrophage activation and ultimately exacerbating the inflammatory response in hemorrhoidal disease. CONCLUSION: This work demonstrates that the Smad2/3-induced METTL3 drives hemorrhoidal inflammation via m6A modification of IL-6R, presenting a novel intervention target.