Effect of acute mucosal exposure to Lactobacillus rhamnosus GG on human colonic smooth muscle cells

Aim: To define whether human colonic mucosa exposure to Lactobacillus rhamnosus GG (LGG), American Type Culture Collection (ATCC) 53103, may influence intestinal muscle cell contractility. Methods: Human colon specimens were obtained from disease-free margins of resected segments for cancer. The mucosa and submucosa, after dissection, were scaled between 2 chambers, with the luminal side of the mucosa facing upward and covered with 5 mL of Krebs solution and the submucosal side facing downward into 20 mL of Krebs solution. LGG or normal undernatant (N-undernatant) were added to the luminal side of the mucosa for 30 minutes. Smooth muscle cells (SMCs), isolated from the circular muscle layer, were exposed to undernatant for 30 minutes from the submucosal chamber of mucosa that was either preexposed to N-undernatant or to LGG (36 x 10(-9) colony forming units/mL) (LGG-undernatant). Acetylcholine (Ach) dose-response was obtained for SMCs. Results: SMCs exposed to N-undernatant presented a dose-response to Ach (maximal contraction: 32% +/- 5% with 1-mu M Ach) that is similar to unstimulated SMCs. Exposure to LGG-undernatant resulted both in an 18% +/- 3% cell shortening and a 78% +/- 7% inhibition of maximal Ach-induced contraction. When SMCs were directly exposed to LGG, a significant impairment of contraction (70% +/- 5%, compared with control cells) and a dose-dependent and time-dependent shortening were observed. Conclusions: After acute exposure of colonic mucosa to LGG, a significant shortening of SMCs is observed that possibly contributes to the reduced contractile response to Ach. Further studies are needed to establish the mechanisms of this effect that could account for the clinical efficacy of probiotics in intestinal disorders.