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DOP87 SUCNR1 a novel key protagonist in fistula development

C. Bauset1, L. Gisbert-Ferrandiz1, D. Ortiz-Masia2, S. Coll1, C. Mamie3, M. Scharl3, S. Calatayud1, M.D. Barrachina1, J. Cosín-Roger4

1Department of Pharmacology, Universidad de Valencia, Valencia, Spain, 2Department of Medicine, Universidad de Valencia, Valencia, Spain, 3Department of Gastroenterology, UniversitatsSpital Zurich, Zurich, Switzerland, 4Department of Endocrinology and Metabolism, Hospital Dr. Peset, Valencia, Spain

Background

Intestinal fistula is a common complication in CD patients whose aetiology is still not well-characterised. It is associated with an exacerbated inflammation and epithelial-to-mesenchymal transition (EMT), a process which allows a switch from epithelial towards a fibrotic behaviour. We have recently reported that SUCNR1 mediates intestinal inflammation and fibrosis1 but its role in fistula has not yet been analysed. Therefore, we aim to analyse the role of SUCNR1 in EMT and in fistula formation.

Methods

Intestinal resections were obtained from CD and non-IBD patients. Fistula specimens were identified by the surgeons and collected from B3-CD patients. The expression of SUCNR1 and EMT markers was analysed by qPCR and the protein expression of SUCNR1 by immunohistochemistry. HT-29 cells were treated with succinate (0,0.1,0.5,1,5 mM) or TGF-β (5 ng/ml) during 48 h and transfected with SUCNR1 siRNA. Expression of EMT markers was analysed by qPCR and western blot. Intestinal fibrosis was induced in vivo using the heterotopic transplant model in WT and Sucnr1−/− mice and expression of EMT markers was analysed by qPCR and by confocal microscopy. Statistical analysis was performed with one-way ANOVA followed by Newman–Keuls test. Correlations were analysed with the Spearman’s coefficient.

Results

In intestinal resections from B3-CD patients, SUCNR1 mRNA expression was significantly increased when compared with B2-CD or non-IBD controls and it correlates positively with the mRNA expression of Snail1 and Snail2 and negatively with that of E-Cadherin. In the fistula tract, SUCNR1 is expressed in intestinal epithelial cells and lamina propria cells of the submucosa with a higher intensity in cells close to the fistula tract than in more distant areas. Succinate induced, in a dose–response manner, a significant increase in Vimentin, Snail1 and Snail2 expression and a reduction in E-cadherin expression. This effect was completely abolished when SUCNR1 was transiently knocked-down. WT-grafts 7 days after surgery exhibited: (a) an increase in gene and protein expression of SUCNR1, (b) an increase in the expression of Vimentin, Snail1 and Snail2 and a significant reduction in E-Cadherin compared with WT-grafts at day 0. Of interest, KO-grafts at day 7 failed to exhibited changes in the expression of Vimentin, Snail1, Snail2 or E-Cadherin.

Conclusion

SUCNR1 is increased specifically in the fistula tract of B3-CD patients. It mediates EMT in intestinal epithelial cells and in a murine model of fibrosis. Hence, SUCNR1 might be a potential pharmacological target for fistula treatment.

Reference:

Mucosal Immunol. 2019;12(1):178–187.

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