The Sphingosine-1-Phosphate/Sphingosine-1-Phosphate Receptor 2 Axis in Intestinal Epithelial Cells Regulates Intestinal Barrier Function During Intestinal Epithelial Cells-CD4+T-Cell Interactions

Background/Aims: Epithelial cells line the intestinal mucosa and form an important barrier for maintaining host health. This study aimed to explore the mechanism of the Sphingosine-1-phosphate (S1P)/Sphingosine-1-phosphate receptor 2 (S1PR2) pathway in intestinal epithelial cells (IECs) that participate in the intestinal barrier function. Methods: In this study, we constructed a knockout of the S1PR2 gene in mice, and Dextra sulfate sodium (DSS) was used to induce colitis. We isolated IECs from wild type (WT) and S1PR2(-/-) mice, and the endogenous expression of S1PR2 and Zonula occludens 1 (ZO-1) in IEC were detected by Western blot. Next, the major histocompatibility complex II (MHC-II) expression was analyzed by reverse transcription quantitative real-time (RT-qPCR) and flow cytometry. The in vivo and in vitro intestinal permeability were evaluated by serum fluorescein isothiocyanate (FITC) concentration. The tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) levels in cell suspension were analyzed by enzyme-linked immuno sorbent assay (ELISA). A carboxyfluorescein diacetate succinimidyl ester (CFSE) assay was used to detect the T-cell proliferation in a co-culture system. Results: The intestinal mucosal barrier damage in S1PR2(-/-) mice was more severe than in the WT mice, and there were more CD4-q-cells in the colon tissue of DSS-treated S1PR2(-/-) mice. Either the mouse colon carcinoma cell line (CT26. WT) or the IECs upregulated MHC-II expression, which then promoted CD4(+)T-cell proliferation. The S1P/S1PR2 pathway controlled MHC-II expression to regulate CD4(+)T-cell proliferation via the extracellular signal-regulated kinase (ERK) pathway. In addition, the IFN-gamma that was secreted by CD4(+)T-cells increased DSS-induced damage of intestinal epithelial cell barrier function. ZO-1 expression was increased by SIP in CT26.WT cells, while S1PR2 antagonist JTE-013 expression was downregulated. However, in CT26.WTsi-S1R2 cells, SIP had no effect on ZO-1 expression. Conclusions: The S1P/S1PR2 axis in IECs mediated CD4(+)T-cell activation via the ERK pathway and MHC-II expression to regulate intestinal barrier function. (C) 2018 The Author(s) Published by S. Karger AG, Basel