The Colonic Mucosal MicroRNAs, MicroRNA-219a-5p and MicroRNA-338-3p, are Downregulated in Irritable Bowel Syndrome and are Associated with Barrier Function and MAPK signaling.

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Alterations in microRNA (miRNA) and in the intestinal barrier are putative risk factors for irritable bowel syndrome (IBS). We aimed to identify differentially expressed colonic mucosal miRNAs, their targets in IBS compared to healthy controls (HCs), and putative downstream pathways.29 IBS patients (15 IBS with constipation [IBS-C], 14 IBS with diarrhea [IBS-D]), and 15 age-matched HCs underwent sigmoidoscopy with biopsies. A nCounter array was used to assess biopsy associated miRNA levels. FDR<10% was considered significant. Real-time PCR (RT-PCR) was used to validate differentially expressed genes. To assess barrier function, trans-epithelial electrical resistance (TEER) and dextran flux assays were performed on Caco-2 intestinal epithelial cells that were transfected with miRNA-inhibitors or control inhibitors. Protein expression of barrier function associated genes was confirmed using western blots.Four out of 247 miRNAs tested were differentially expressed in IBS compared to HCs (FDR<10%). RT-PCR validation suggested decreased levels of miR-219a-5p and miR-338-3p in IBS (0.026 and p=0.004), and IBS-C (p=0.026 and 0.06) vs. HCs as the strongest associations. Inhibition of miR-219a-5p resulted in altered expression of proteasome/barrier function genes. Functionally, miR-219a-5p inhibition enhanced the permeability of intestinal epithelial cells as TEER was reduced (25-50%, p<0.05) and dextran flux was increased (p<0.01). Additionally, inhibition of miR-338-3p in cells caused alterations in the MAPK signaling pathway genes.Two microRNAs that potentially affect permeability and visceral nociception were identified to be altered in IBS patients. MiR-219a-5p and miR-338-3p potentially alter barrier function and visceral hypersensitivity via neuronal and MAPK signaling and could be therapeutic targets in IBS.

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Authors: Swapna Mahurkar-Joshi, Carl Robert Rankin, Elizabeth Jane Videlock, Artin Soroosh, Abhishek Verma, Ariela Khandadash, Dimitrios Iliopoulos, Charalabos Pothoulakis, Emeran A Mayer, Lin Chang