Lactobacillus casei DG decreases LPS-induced nitricoxcide and enteroglial-S100B secretion in human intestinalbiopsies

Objective: Enteroglial derived S100B protein plays an active role 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 lipopolysaccharides (LPS)-induced iNOS protein expression, nitric oxide (NO) and S100B secretion from human intestinal biopsies. Methods: Rectal biopsies from 3 healthy subjects undergoing screening for colorectal cancer were stimulated with LPS (10 lg mL-1) and/or with LC-DG (108 bacteria mL-1), as follows: experiment A) stimulation with LPS starts at 0 h and end at 5 h (0–5 h); B) LC-DG 0–5 h; C) LC-DG 0–5 h + LPS 2.5–5 h; D) LPS 0–5 h + LC-DG 2.5–5 h; E) LPS 0–5 h + LC-DG 0–5 h. 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, LPS (experiment A), but not LC-DG (experiment B), significantly increased S100B secretion (+1.8 ± 0.5 fold increase vs control; P < 0.05). With experiments C, D and E S100B secretion was not increased respect to control. In parallel, incubation with LPS (experiment A) led to a significant increase of iNOS protein expression (+2.0 ± 0.3 fold increase vs control; P < 0.05) and of NO secretion (+2.9 ± 0.7 fold increase vs control; P < 0.05), that was not observed with LC-DG (experiment B). With experiments C, D and E iNOS expression and NO secretion were similar to control. Conclusion: We show that the probiotic LC-DG decreases LPS-induced NO secretion in human biopsies by inhibiting iNOS protein expression. This effect may be mediated by EGCs since LC-DG also decreases LPS-induced enteroglial-derived S100B protein secretion.