MicroRNA-31-3p Is Involved in Substance P (SP)-Associated Inflammation in Human Colonic Epithelial Cells and Experimental Colitis

Substance P (SP) mediates colitis. SP signaling regulates the expression of several miRNAs, including miR-31-3p, in human colonocytes. However, the role of miR-31-3p in colitis and the underlying mechanisms has not been elucidated. We performed real-time PCR analysis of miR-31-3p expression in human colonic epithelial cells overexpressing neurokinin-1 receptor (NCM460 NK-1R) in response to SP stimulation and in NCM460 cells after IL-6, IL8, tumor necrosis factor (TNF)-α, and interferon-γ exposure. Functions of miR-31-3p were tested in NCM460-NK-1R cells and the trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) models of colitis. Targets of miRNA-31-3p were confirmed by Western blot analysis and luciferase reporter assay. Jun N-terminal kinase inhibition decreased SP-induced miR-31-3p expression. miR-31-3p expression was increased in both TNBS- and DSS-induced colitis and human colonic biopsies from ulcerative colitis, compared with controls. Intracolonic administration of a miR-31-3p chemical inhibitor exacerbated TNBS- and DSS-induced colitis and increased colonic TNF-α, CXCL10, and chemokine (C-C motif) ligand 2 (CCL2) mRNA expression. Conversely, overexpression of miR-31-3p ameliorated the severity of DSS-induced colitis. Bioinformatic, luciferase reporter assay, and Western blot analyses identified RhoA as a target of miR-31-3p in NCM460 cells. Constitutive activation of RhoA led to increased expression of CCL2, IL6, TNF-α, and CXCL10 in NCM460-NK-1R cells on SP stimulation. Our results reveal a novel SP-miR-31-3p-RhoA pathway that protects from colitis. The use of miR-31-3p mimics may be a promising approach for colitis treatment.