Aims To investigate whether probiotics and/or prebiotics attenuate Salmonella typhimurium induced NF-κB activation via Smad7 and IκBα expression in the human colorectal epithelial CaCO2 cells; to determine the molecular mechanisms of preventive effects of probiotics on intestinal infection.
Material and methods CaCO2 cells were administered probiotic (Lactobicillus acidophilus) and/or prebiotic (inulin supplemented with oligofructose). Subsequently, the cells were infected with S. typhimurium. The culture supernatants and cell lysates were collected for cytokine determination and western blot analysis. The CaCO2 cells were also transfected with plasmids containing Smads or NF-κB responsive reporter luciferase. After transfection, supernatants from cells were collected for luciferase assay. Involvement of miR-21 (Smad7 silencer) from supernatants of infected cells in the presence or absence of probiotics was determined.
Results The probiotics significantly suppressed NF-κB activation elevated by S. typhimurium. IL-8 mRNA was significantly lower in probiotics pretreated CaCO2 cells compared with the cells infected with S. typhimurium alone. Synbiotics showed strongly suppressed effects on IL-8 and TNF-α gene transcriptions elevated by S. typhimurium. Pretreatment of probiotics increased IκBα expression level. Consistent with IκBα expression, pretreatment of probiotics increased 7 folds of Smad3/4 activity. The protein expressions of TGF-β and Smad7 in S. typhimurium infected cells with or without probiotics were determined by immunoblotting. Compared to S. typhimurium infection alone, pretreatment with probiotics and synbiotics induced 20 and 4 folds of miR 21 expressions, respectively.
Conclusions The experimental results showed that probiotics effectively attenuated Salmonella-induced intestinal inflammation in human intestinal CaCO2 cells via TGF-β1/Smads and TGF-β1/miR21 signalling pathway.