Alexeev, E. | Search bioRxiv

bioRxiv2025

TL1A overexpression in Crohn's Disease and mice alters Paneth cells and microbiota promoting ileal inflammation

Paneth cells regulate host-microbial homeostasis and defects in autophagy and host defense pathways have been associated with inflammatory bowel diseases (IBD). Genetic variants in TL1A (TNFSF15) and its receptor DR3 (TNFRSF25) have been associated with IBD. TL1A expression is increased in IBD patients, particularly in TL1A risk allele carriers. However, effects of TL1A on Paneth cells, resident microbiota, and development of ileitis remain unknown. TL1A overexpression in mice induces Paneth cell hyperplasia and morphological abnormalities preceding the development of ileitis. In Crohns disease (CD) patients, ileal TL1A expression was associated with abnormal Paneth cell phenotypes. We confirmed direct effects of TL1A on Paneth cells in human iPSC-derived human intestinal organoids and mouse Paneth cell-enriched organoids. Resident microbiota was required for TL1A-mediated Paneth cell dysfunction, and ileitis. Tl1a-tg mice were enriched in short chain fatty acid-producing bacteria and the metabolite acetate. Acetate supplementation in WT or Tl1a-tg mice caused ileal inflammation, suggesting that acetate is sufficient to cause ileitis. DR3-deficiency in Paneth cells resulted in Paneth cell abnormalities and microbiome composition changes. Our findings provide a mechanistic link between overexpression of TL1A in CD patients, Paneth cell dysfunction, and enrichment of acetate-producing bacteria and acetate that promotes ileal inflammation. Brief SummaryOverexpression of TL1A drives Paneth cell dysfunction in Crohns Disease and mice leading to microbial and metabolomic changes that promote small bowel inflammation.

immunology↗

bioRxiv2023

Microbiota-dependent indole production is required for the development of collagen-induced arthritis

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model we identify alterations in tryptophan metabolism, and specifically indole, that correlate with disease. We demonstrate that both bacteria and dietary tryptophan are required for disease, and indole supplementation is sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1{beta}; splenic ROR{gamma}t+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colon lymphocytes to indole increased expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a novel therapeutic pathway for RA and SpA.

immunology↗