Human colonic myogenic dysfunction induced by mucosal lipopolysaccharide translocation and oxidative stress

Background: Impairment of gastrointestinal motility is frequently observed in patients with severe infection. Aim: To assess whether exposure of human colonic mucosa to pathogenic lipopolysaccharide affects smooth muscle contractility. Methods: Human colonic mucosa and submucosa were sealed between two chambers, with the luminal side facing upwards and covered with Krebs solution, with or without lipopolysaccharide from a pathogenic strain of Escherichia coli (0111:B4; 1000 ng/mL), and with the submucosal side facing downwards into Krebs. The solution on the submuco sal side was collected following 30-min muco sal exposure to Krebs without (N-undernatant) or with lipopolysaccharide (lipopolysaccharide undernatant). Undernatants were tested for lipopolysaccharide and hydrogen peroxide levels and for their effects on smooth muscle cells in the presence of catalase, indomethacin or MG132. Results: Smooth muscle cells incubated with N-undernatant had a maximal contraction of 32 + 5% that was reduced by 62.9 + 12% when exposed to lipopolysaccharide undernatant. Inhibition of contraction was reversed by catalase, indomethacin and MG132. Lipopolysaccharide levels were higher in the lipopolysaccharide undernatant (2.7 + 0.7 ng/mL) than in N-undernatant (0.45 + 0.06 ng/mL) as well as hydrogen peroxide levels (133.75 + 15.9 vs 82 + 7.5 nM respectively). Conclusions: Acute exposure of colonic mucosa to pathogenic lipopolysaccharide impairs muscle cell contractility owing to both lipopolysaccharide mucosal translocation and production of free radicals. (C) 2013 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.