P0137 Primary bile acids promote epithelial necroptosis via Stat1 signaling
Authors: Hu K , Leistl S , Wieser L , Chiriac M , Rauh M , Neurath M , Günther C 
Published: January 2025

Abstract

Background
Gut barrier dysfunction and microbial dysbiosis play a crucial role in the pathogenesis of Inflammatory Bowel Disease (IBD), including Ulcerative colitis (UC) and Crohn´s disease (CD)1. Although IBD is marked by dynamic changes in the intestinal microbiome, little is known about the corresponding changes in the gut metabolism, the molecular interface between the host and its microbiota. In CD, changes in bile acid (BA) metabolism and composition have been observed, with a notable the enrichment of the primary BA chenodeoxycholic acid (CDCA) specifically in CD2, suggesting a potential involvement in disease pathogenesis. However, it is still poorly understood how BAs influence epithelial homeostasis.

Methods
Serum bile acid (BA) profiles of CD patients and healthy controls were analyzed using BA-targeted metabolomics. Data normalization and statistical analyses were performed to identify significant differences in BA composition between groups. Human ileal organoids were established from biopsy samples obtained from CD patients, while murine small intestinal organoids were derived from wildtype, Stat1-/-, and farnesoid X receptor (FXR) deficient mice. Bulk RNA sequencing was performed on organoids treated with CDCA to investigate transcriptional changes and identify molecular mechanisms underlying CDCA-induced toxicity. A cell death inhibitor screen was applied to delineate the pathways contributing to CDCA-induced IEC toxicity.

Results
Our findings reveal a significant difference in BA profiles between CD patients and healthy controls, with a notable enrichment of the primary BA, CDCA, in CD patients. CDCA exerts a pronounced toxic effect on both human and murine small intestinal organoids (SIO) in a dose-dependent manner, whereas the secondary BA, deoxycholic acid (DCA), does not. Importantly, the cytotoxicity of CDCA was markedly reduced when it was conjugated with glycine or taurine, suggesting that conjugation mitigates CDCA's impact on IEC viability.
Mechanistically, CDCA disrupts BA signaling pathways, enhances the interferon (IFN) response, and activates cell death pathways within SIO models. CDCA specifically promotes epithelial necroptosis via STAT1 signaling, highlighting a pathway through which CDCA may exacerbate epithelial damage in CD. Therapeutically, both tofacitinib (Tofa) and glucocorticoids (GCs) demonstrate a protective effect, significantly suppressing the CDCA-induced IFN response. These findings suggest that modulation of BA signaling and inhibition of the IFN response may be promising strategies to protect intestinal epithelial integrity in CD patients.

Conclusion
These findings suggest that modulation of BA signaling may be promising strategies to protect intestinal epithelial integrity in CD patients.

References
1.Liso M,De Santis S,Verna G, et al. A Specific Mutation in Muc2 Determines Early Dysbiosis in Colitis-Prone Winnie Mice. Inflamm Bowel Dis. 2020;26 (4):546-556. doi:10.1093/ibd/izz279
2.Franzosa EA,Sirota-Madi A,Avila-Pacheco J, et al. Gut microbiome structure and metabolic activity in inflammatory bowel disease. Nat Microbiol. 2019;4 (2):293-305. doi:10.1038/s41564-018-0306-4