F-actin dynamics couples sphingolipid metabolism to epithelial barrier integrity in chronic colitis

Intestinal barrier dysfunction is a hallmark of gastrointestinal disorders, including inflammatory bowel diseases (IBD). In IBD, the disruption of the gut barrier causes fluid loss and persistent immune response. Understanding the cellular events underlying epithelial barrier disruption during chronic inflammation is essential for targeting increased intestinal permeability. Filamentous actin (F-actin) destabilization accompanied by metabolic dysfunction has previously been reported in the Muc2 knockout colitis model; however, the mechanistic contribution of these defects to chronic intestinal barrier loss remains unclear. Here, we identify impaired cytoskeleton dynamics as a critical driver of intestinal barrier dysfunction in chronic colitis. An imbalance between polymeric and monomeric actin disrupts the epithelial barrier in both a 3D organoid system and in vivo. Actin and associated factors were identified as primary interactors of claudin-3, and this interaction was reduced under chronic inflammatory conditions in vivo. Further analysis revealed ceramide metabolism as a potential metabolic regulator of actin dynamics and barrier integrity during chronic inflammation. Consistently, intestinal samples from IBD patients showed concurrent disruption of tight and adherens junctions and reduced F-actin levels. Together, these findings reveal F-actin dynamics as one of the key mechanisms of barrier dysfunction in IBD and highlight ceramide metabolism as a potential therapeutic target in IBD.