Tu1713 Role of miR-19b-Targeting SOCS3 in Modulating Production of Chemokine in Colonic Epithelial Cells and Is Associated With the Pathogenesis of Crohn's Disease

Abstract

Background: To date, the role of IL-17C and its specific receptor subunit IL-17RE in inflammatory bowel disease (IBD) settings is entirely based on murine models. Therefore, the aim of this study was to analyze the role of the novel IL-17 family member IL-17C and its receptor IL-17RE in human IBD. Methods: IL-17C expression in intestinal epithelial cells (IEC) was analyzed by qPCR, immunoblotting, immunohistochemistry, EMSA, RNA interference and pharmacological or antibody-mediated inhibition. IL-17C protein and mRNA expression in IBD patient samples was assessed by ELISA, qPCR and immunohistochemistry. IL-17C serum levels were correlated to IL23R genotype status. Results: IL-17A amplifies IL-17C expression in human IEC upon TNF-α stimulation; this depends on TNFα-activated NF-κB, ERK-1/2 and p38 MAP kinases, and IL-17A-activated Akt kinase, MCPIP and C/EBP-δ pathways. IL-17C serum levels are elevated in patients with ulcerative colitis (UC) (P=0.008). IL-17C mRNA is increased in inflamed colonic sections of IBD patients (P=0.005) and correlates significantly with the mRNA expression of Th1 cytokines (e.g., IFN-γ; P<0.01) and Th17 cytokines (e.g., IL-17A, IL-23, CCL20; P<0.01). Genotyping revealed that UC patients carrying a minor allele of the IL23R SNP rs134351 have decreased IL-17C serum levels (P=0.037). Immunohistochemistry displayed increased IL-17C and IL17RE staining in IBD patients with active disease, compared to IBD patients in remission and healthy controls. Chromogranin A-positive IEC are major producers of IL-17C in the colon, whereas the IL-17RE subunit was only present on lamina propria mononuclear cells but not in IEC. In vitro experiments suggested that IEC lines are not responsive to IL-17C stimulation, even when combined with other cytokines, such as IL-22. Conclusions: This is the first comprehensive study involving human IBD patients which demonstrates an upregulation of the novel IL-17C-IL-17RE cytokine ligand-receptor pair during active human IBD. In contrast to murine models, IL-17RE expression is confined to lamina propria leukocytes and not epithelial cells; specialized chromogranin A-positive cells are among the major producers of IL-17C in the epithelium. Our data indicate that serum IL-17C is modulated by IL23R genotype status. In addition, our data reveal potential novel targets for the pharmacological modulation of epithelium-derived IL-17C.