OP027 SUCNR1 receptor mediates intestinal fibrosis

Abstract

Intestinal fibrosis is a common complication associated with Crohn’s Disease (CD) which cannot be reverted with any drug and forces repeated surgery. It has been reported that succinate, a metabolite accumulated in inflammatory pathologies, plays an important role in the activation of synovial fibroblasts and hepatic stellate cells through its receptor called SUCNR1 or GPR91. We aim to analyse the relevance of SUCNR1 receptor in intestinal fibrosis. Intestinal resections from CD patients and colon carcinoma patients were obtained and the expression of SUCNR1 and α-sma were analysed by immunostaining. Primary intestinal fibroblasts from human resections or from colon of wild-type (WT) or SUCNR1−/− (KO) mice were isolated, maintained in culture and treated with different concentrations (0, 0.1, 0.5, 1, and 5 mM) of succinate for 24 h. Intestinal fibrosis was induced in vivo introducing one intestinal graft from WT or KO mice into the neck of a receptor mice for 7 days. The expression of pro-fibrotic markers was analysed by qPCR. Sirius Red staining was performed and the collagen layer was quantified using ImageJ. Results are expressed by mean ± SEM (n ≥ 5). Statistical analysis was performed with one-way ANOVA followed by Newman–Keuls test. Correlations were analysed with the Spearman coefficient. SUCNR1 is expressed in epithelial cells and α-sma+ cells of intestinal resections from CD patients. The SUCNR1 expression positively and significantly correlates with the expression of α-sma (r = 0.759, p < 0.0001, n = 24) and colA1 (r = 0.82, p < 0.001, n = 24). In primary fibroblasts isolated from CD patients (13.54 ± 4.6) the expression of SUCNR1 was significantly higher than in those obtained from control patients (2.07 ± 0.86). In these cells, succinate induced the expression of profibrotic markers such as ColA1, α-sma, Tgfb, and TIMP1 in a dose-response manner. This profibrotic effect of succinate was also observed in fibroblasts from WT mice and it was completely reverted in fibroblasts obtained from KO mice. The murine model of intestinal fibrosis in vivo revealed that: (a) the thickness of the collagen layer was significantly reduced in colons from KO mice compared with those from WT mice; (b) the expression of pro-fibrotic markers such as colA1, α-sma and vimentin was also significantly reduced in colons from KO mice vs. colons from WT mice (19.7 ± 10.1 vs. 69.8 ± 26.6, 0.9 ± 0.1 vs. 2.5 ± 0.5, 1.7 ± 0 vs. 12.4 ± 0.3, respectively). An increased expression of SUCNR1 receptor is detected in fibroblasts from CD patients the activation of which induces a pro-fibrotic effect. This receptor mediates murine intestinal fibrosis and we propose its blockade as a new pharmacological target in CD treatment.