Achasova, K. | bioRxiv Science

bioRxiv2026

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

BackgroundIntestinal barrier dysfunction is a hallmark of inflammatory bowel diseases (IBD). This condition causes intoxication and immune hyperactivation. Understanding the events underlying epithelial barrier disruption during chronic inflammation is key to developing barrier-restoring therapies. Filamentous actin (F-actin) is essential for maintaining polarity and junctional integrity. However, the contribution of F-actin dynamics to IBD-associated barrier dysfunction remains unclear. ObjectiveWe aimed to examine actin cytoskeleton integrity during chronic colitis across mouse models and human patients and identify potential regulators of cytoskeleton dynamics. DesignF-actin and junctional proteins were analyzed in three models of chronic colitis (Muc2 KO, DSS-induced colitis, adoptive transfer colitis) using confocal microscopy. Claudin-3 interactors were identified by immunoprecipitation and proteomics. Intestinal organoids were used to assess the effect of F-actin disruption on barrier integrity. Metabolomic and gene expression analyses identified candidate pathways, further validated by chemical inhibition. Biopsies from patients with ulcerative colitis (UC) were examined using transmission electron microscopy and confocal microscopy. ResultsDisrupted actin dynamics emerged as a critical driver of epithelial barrier dysfunction in chronic colitis. An imbalance between polymeric and monomeric actin impaired barrier integrity in vivo and in 3D organoids. Immunoprecipitation identified actin and associated factors as the primary interactors of claudin-3 with reduced interaction during inflammation. Ceramide metabolism was revealed as a potential regulator of F-actin and intestinal barrier. In UC patients, we confirmed concurrent disruption of junctions and F-actin. ConclusionsF-actin dysregulation contributes to barrier dysfunction in IBD and targeting its modulators, including ceramide biosynthesis, represents a novel therapeutic strategy. WHAT IS ALREADY KNOWN ON THIS TOPICO_LIEpithelial damage and increased paracellular permeability are key characteristics of inflammatory bowel diseases. C_LIO_LIParacellular permeability is partially attributed to the downregulation of junction proteins but this mechanism does not explain all clinical observations. C_LIO_LIIn the Muc2 KO mouse model of chronic colitis, F-actin organization and membrane localization of tight junction protein claudin-3 are disrupted, although protein expression levels remain unchanged. C_LI WHAT THIS STUDY ADDSO_LIF-actin dynamics is impaired in the intestinal epithelium across three different mouse models of chronic colitis and IBD patients. C_LIO_LIDisruption of F-actin dynamics leads to impaired membrane localization of tight and adherens junction proteins and increased intestinal epithelial permeability in vivo and in colonic organoids. C_LIO_LIInhibition of ceramide biosynthesis rescues F-actin polymerization and intestinal barrier integrity in mouse chronic colitis models. C_LI HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICYO_LITargeting F-actin dynamics is a promising approach to improve gut epithelial integrity. C_LIO_LI"Ceramide-F-actin-junction" axis is proposed as one of the mechanisms behind epithelial barrier disruption in colitis. Therapeutic targeting of this axis represents a promising path for restoring gut integrity. C_LI

cell biology↗

bioRxiv2022

Colitis-associated intestinal microbiota regulates brain glycine and host behavior in mice.

Inflammatory bowel diseases (IBD) are chronic and relapsing inflammatory disorders of the gastrointestinal tract with complex etiology and no strategies for complete cure. IBD are often complicated by mental disorders like anxiety and depression, indicating substantial shifts in the gut-brain axis. However, the mechanisms connecting IBD to mental diseases are still under debate. Here we use Muc2 mutant mouse model of chronic colitis to uncouple the effects of the intestinal microbiota on host behavior from chronic inflammation in the gut. Muc2 mutant male mice exhibit high exploratory activity, reduced anxiety-related behaviors, impaired sensorimotor gating, and altered social preference towards males and females. Microbial transfer to wild-type mice via littermate co-housing shows that colitis-associated microbiota rather than inflammation per se defines behavioral features in Muc2 colitis model. Metagenomic profiling and combination of antibiotic treatments revealed that bacterial species Akkermansia muciniphila is associated with the behavioral phenotype in mutants, and that its intestinal abundance correlates with social preference towards males. Metabolomic analysis together with pharmacological inhibition of Gly and NMDA receptors helped us to determine that brain glycine is responsible for the behavioral phenotype in Muc2 mice. Blood and brain metabolic profiles suggest that microbiota-dependent changes in choline metabolism might be involved in regulation of central glycine neurotransmission. Taken together, our data demonstrates that colitis-associated microbiota controls anxiety, sensorimotor gating and social behavior via metabolic regulation of the brain glycinergic system, providing new venues to combat neurological complications of IBD.

animal behavior and cognition↗