ENTEROGLIAL DERIVED-S100B PROTEIN IS INVOLVED IN THE PROTECTIVE EFFECT OF LACTOBACILLUS CASEI DG ON PATHOGEN-INDUCED NITRIC OXIDE PRODUCTION IN HUMAN INTESTINAL BIOPSIES

Background and aim: Enteroglial derived S100B protein is involved in nitric oxide (NO)-dependent gut inflammation. Previous data show that pathogen bacteria are able to induce S100B release from enteroglial cells (EGCs). Whether probiotics are able to counteract these effects is not established yet. We aimed to study the effects of Lactobacillus Casei DG (LC-DG) on Enteroinvasive Escherichia Coli (EIEC)-induced iNOS protein expression, nitric oxide (NO) and S100B secretion from human intestinal biopsies. Material and methods: Rectal biopsies from 6 healthy subjects undergoing screening for colorectal cancer were stimulated with EIEC (≈108 bacteria/mL), with LC-DG (≈108 bacteria/mL) and with 3 different combination of LC-DG plus EIEC (LC-DG added contemporarily, before or after EIEC stimulation), respectively. To test EGCs stimulation, S100B release was evaluated by ELISA assay. Nitrite assay and Western Blot analysis were used to evaluate NO release and iNOS expression, respectively, in stimulated biopsies compared to unstimulated biopsies (control). Data are expressed as mean±SD of 6 independent experiments. Results: In rectal biopsies, EIEC, but not LC-DG, significantly increased S100B secretion (+1.8±0.4 fold increase vs control; p<0.05). When LC-DG was added to biopsy before, after or together with EIEC, S100B secretion was not significantly increased respect to control. In parallel, incubation with EIEC alone led to a significant increase of iNOS protein expression (+2.3±0.5 fold increase vs control; p<0.05) and of NO secretion (+1.7±0.3 fold increase vs control; p<0.05), that was not observed with LC-DG alone. When LC-DG was added to biopsy before, after or together with EIEC, iNOS expression and NO secretion were not significantly different to control. Conclusions: We show that the probiotic LC-DG is able to counteract the effect of the pathogen EIEC decreasing NO secretion in human biopsies by inhibiting iNOS protein expression. EGCs may be involved in this effect since LC-DG also decreases EIEC-induced enteroglial-derived S100B protein secretion.