Increased production of BDNF in colonic epithelial cells induced by fecal supernatants from diarrheic IBS patients

Abstract

Colonic brain-derived neurotrophic factor (BDNF) plays an essential role in pathogenesis of abdominal pain in diarrhea-predominant irritable bowel syndrome (IBS-D), but regulation on its expression remains unclear. We investigated the role of fecal supernatants (FSN) from IBS-D patients on regulating BDNF expression in colonic epithelial cells of human and mice. Using human Caco-2 cells, we found that IBS-D FSN significantly increased BDNF mRNA and protein levels compared to control FSN, which were remarkably suppressed by the serine protease inhibitor. To further explore the potential mechanisms, we investigated the impact of protease-activated receptor-2 (PAR-2) on BDNF expression. We found a significant increase in PAR-2 expression in Caco-2 after IBS-D FSN stimulation. Knockdown of PAR-2 significantly inhibited IBS-D FSN-induced upregulation of BDNF. Moreover, we found that phosphorylation of p38 MAPK, not NF-κB p65, contributed to PAR-2-mediated BDNF overexpression. To confirm these results, we intracolonically infused IBS-D or control FSN in mice and found that IBS-D FSN significantly elevated colonic BDNF and visceral hypersensitivity in mice, which were both suppressed by the inhibitor of serine protease or antagonist of PAR-2. Together, our data indicate that activation of PAR-2 signaling by IBS-D FSN promotes expression of colonic BDNF, thereby contributing to IBS-like visceral hypersensitivity.

Visceral hypersensitivity in inflammatory bowel diseases and irritable bowel syndrome: The role of proteases

“…Nafamostat mesilate or FUT-175 is a broad specificity serine protease inhibitor. In mice, visceral hypersensitivity induced by the intracolonic infusion of IBS-D fecal supernatants, could be suppressed when the supernatant was pre-incubated with nafamostat mesilate[65]. Similar results were observed by the group of Cenac et al[41] who used a similar, but slightly different experimental design.…”

Activation of cannabinoid 2 receptor relieves colonic hypermotility in a rat model of irritable bowel syndrome

“…These results are in agreement with previous reports on the close association between CB2 receptors and p38 MAPK inhibition, suggesting that CB2 receptors are coupled to MAPK through G proteins and regulate MAPK phosphorylation . Our data are also in line with the finding that p38 MAPK is required for the production of IBS‐like symptoms . Nitric oxide (NO), produced by nNOS, is a major GI inhibitory neurotransmitter .…”

Newly developed serine protease inhibitors decrease visceral hypersensitivity in a post‐inflammatory rat model for irritable bowel syndrome

“…Firstly, we opted for a direct in vivo treatment strategy, with a single i.p. injection of the animals, while preceding studies employed an in vitro treatment strategy (Cenac et al ., ; Wang et al ., ). Secondly, we are the first to demonstrate a positive outcome after a symptomatic treatment instead of a preventive treatment in earlier studies (Cenac et al ., ; Zhao et al ., ; Wang et al ., ).…”

“…Thirdly, the animal models used are different. Previous studies employed intracolonic administration in mice of supernatants from IBS patients (Cenac et al ., ; Wang et al ., ) or acute stress in rats (Zhao et al ., ) to induce visceral hypersensitivity, whereas we used an inflammation‐triggered, post‐colitis, model based on chemically induced colitis in rats. We provide further evidence for the role for the serine proteases tryptase and trypsin‐3 in this post‐inflammatory rat model for IBS, shown by the elevated mRNA expression and an increased number of mast cell tryptase‐positive cells.…”