Gut Inflammation Hijacked by RNA Modification Driving Harmful Immune Cells

Ulcerative colitis (UC) is a chronic, debilitating inflammatory bowel disease with incompletely understood molecular drivers. Identifying new molecular targets could open doors to more precise treatments, particularly ones that modulate the immune cells central to intestinal inflammation.

This study focused on SerpinB5, a member of the serine protease inhibitor family previously linked to macrophage behavior. Using patient data, RNA-sequencing datasets (including GSE224758), and the GeneCards database, researchers confirmed that SerpinB5 is significantly upregulated in UC patients, TNF-α-stimulated colonic epithelial cells, and DSS-induced mouse models of UC.

The team demonstrated that knocking down SerpinB5 reduced TNF-α-induced apoptosis, cellular senescence (measured by SA-β-Gal staining and p53/p16 expression), inflammatory cytokine release, oxidative stress, and the proportion of pro-inflammatory M1 macrophages (CD11b+CD86+). In mice, SerpinB5 knockdown also alleviated colitis severity. Mechanistically, SerpinB5 was found to activate the NF-κB inflammatory pathway by interacting with the ubiquitin ligase adaptor FBXO32, confirmed through GST pull-down and co-immunoprecipitation assays.

Upstream regulation was traced to the m6A methyltransferase METTL3, which deposits m6A modifications onto SerpinB5 mRNA. The m6A reader protein YTHDF1 then recognizes these marks and stabilizes SerpinB5 mRNA, increasing its expression. MeRIP-qPCR, RNA pull-down, and RIP assays validated this METTL3/m6A/YTHDF1 axis.

These findings establish a coherent pathway — METTL3 → m6A modification → YTHDF1-stabilized SerpinB5 → FBXO32 → NF-κB → M1 macrophage polarization — that aggravates UC. SerpinB5 emerges as a promising therapeutic target, though further clinical validation is needed.