Protective effect of inulin on LPS-induced intestinal smooth muscle impairment: a proteomic approach.

BACKGROUND AND AIM : Fructans, such as inulin, are dietary fibers which stimulate gastro-intestinal function acting as prebiotics. We recently demonstrated the protective effect of inulin on LPS-induced damage of colonic smooth muscle in an ex vivo experimental model, which seems to be related to presence of oxidative stress. In the present study, the protective role of inulin against LPS-induced oxidative stress was evaluated on colonic mucosa using a proteomic approach. MATERIAL AND METHODS : Human colonic mucosa and submucosa, obtained from disease-free margins of resected segments for cancer, were sealed between two chambers containing Krebs solution, with the luminal side of the mucosa overlayed with 5 ml of Krebs, or 100 µg/mL LPS solution, or 100 µg/mL LPS +100 mg/mL inulin Fructafit IQ (LPS+INU). The biological system was kept oxygenated for 30 min at 37°C. iTRAQ based analysis was used to separate and compare the total soluble proteomes from human colonic mucosa and submucosa treated. Each sample was labelled by one of four reagents of the iTRAQ 4-plex and then combined into one aliquote. Triplicate labelling were performed, which showed a high level of reproducibility. RESULTS : Inulin exposure was able to restore, in human colonic mucosa, the LPS-dependent alteration of some proteins involved in the host response and in the intestinal smooth muscle contraction (ZG16, CALM1/MLCK/MYL signaling pathway) and to reduce the upregulation of two proteins involved in the radical-mediated oxidative stress induced by LPS (APEX1, CCT7). Moreover the administration of inulin entails a higher level of some detoxification enzymes (MT2A, GSTK1, and UGT2B4) with respect to LPS treatment. Consistently inulin exposure to colonic mucosa and submucosa was also able to restore the LPS-induced alteration of intestinal smooth muscle contraction as well as it was able to prevent the oxidative damages of LPS-exposed tissues. CONCLUSIONS : Our preliminary data suggest that the exposure of colonic mucosa to inulin is able to prevent LPS-dependent altered expression of some key proteins which promote intestinal motility and the host response, reducing the radical-mediated oxidative stress