Intestinal bile salt nuclear receptor FXR protects from inflammatory bowel disease potential

Intestinal bile salt nuclear receptor FXR protects from inflammatory bowel disease: potential therapeutic implications.
R.M.Gadaleta1,2,3, K.J. van Erpecum1, B. Oldenburg 1, E.C.L. Willemsen2, S. Murzilli3, L.W.J.Klomp2, P.D. Siersema1, A. Moschetta3 ,S.W.C. van Mil2.
1Department of Gastroenterology and Hepatology, 2Laboratory of Metabolic and Endocrine Diseases and Netherlands Metabolomics Centre,UMC Utrecht, The Netherlands; 3Laboratory of Lipid Metabolism and Cancer, Consorzio Mario Negri Sud, S.ta Maria Imbaro (Ch), Italy
Bile salt nuclear receptor Farnesoid X Receptor (FXR) was recently implicated in intestinal antibacterial defense and barrier function. We aimed to study its role in pathogenesis of inflammatory bowel disease. Colitis was induced in Wild Type (WT) and FXR knockout (ko) mice (n=8 to 10) by Dextran Sodium Sulphate (DSS: 2.5% in drinking water, 10 days) with or without synthetic FXR ligand 6-Ethyl Chenodeoxycholic Acid (6ECDCA: 5 mg/kg/day, 13 days, starting 3 days before DSS). Colitis symptoms were checked daily and intestinal permeability (FITC-dextran assay), bile salt composition (HPLC), histology and colonic inflammatory gene expression (Q-PCR) determined. mRNA expression of FXR and target genes was determined in patient biopsies. Underlying mechanisms were explored in complementary in vitro experiments. 6ECDCA-treated WT but not FXR ko mice were protected from DSS-induced colitis, as shown by highly significant reduction of body weight loss, rectal bleeding, colonic shortening, normalization of intestinal permeability, 49% reduction in blinded histological score and 55% reduction in goblet cell loss. Only in 6ECDCA-treated WT mice, mRNA levels of pro-inflammatory genes (IL-1β, IL-6, IL-10 and MCP-1) were strongly down-regulated while antibacterial defense gene iNOS was upregulated. 6ECDCA was enriched in both WT and FXR ko mice (10% and 5% of total bile salts, respectively). However intestinal expression of FXR target genes FGF15 and SHP was increased 4.5- and 19-fold with 6ECDCA treatment only in WT mice. In patients with quiescent Crohn colitis (n=17), mRNA expression of FXR and SHP was significantly altered compared to patients with ulcerative colitis (n=16) or healthy controls (n=17). In differentiated CaCo2 cells grown on trans-well plates, FXR activation by GW4064 prevented DSS-dependent loss of integrity of the monolayer. In differentiated HT29 cells, TNFα-induced 20-fold increase of IL-1βexpression was abolished by GW4064-dependent FXR activation. In reporter assays, GW4064 prevented TNFα-induced NF-κB activity in HEK293 cells transfected with WT FXR, but no effect was achieved with FXR mutant W469A (defective in Ligand Binding Domain), indicating FXR-mediated inhibition of NF-κB signalling. In conclusion, FXR activation protects against experimental murine colitis, supposedly by preserving the intestinal barrier and inhibiting NF-κB activity. Currently available FXR agonists may offer new therapeutic strategies for inflammatory bowel disease.。