Probiotic bacteria isolated from human breast milk inhibits murine colorectal cancer and modulates mirnas that regulate IL-1 beta - and IL-6

Probiotic lactic acid bacteria are known for their ability to modulate the immune system. The objective of this study was to elucidate the modulatory effect of the probiotic bacteria (Lactobacillus plantarum), isolated from breast milk of lactating Egyptian women, on IL-6 and IL-1 beta as well as their regulating miRNAs in Azoxymethane (AOM) / dextran sulfate sodium (DSS)-induced colon carcinoma in mice. The expression of IL-1 beta and IL-6 in colonic tissue were determined by real time PCR and ELISA. Compared with DSS/AOM group, the inflammatory symptoms and histological damages of colonic mucosa in L. plantarum-treated group were significantly improved, the expression level and protein concentration of IL-1 beta, in colonic tissue were significantly reduced and it was combined with up-regulation of IL-6 expression level and protein concentration. L. plantarum-administration resulted in decreased aberrant crypt foci in DSS/AOM group. The investigation of the miR-21a, miR-155 and miR-146a expressions, which regulate IL-6 and IL-1 beta expression, indicated that both of miR-21a and miR-146a was depressed by L. plantarum-administration in healthy and in DSS/AOM group, while miR-155 expression was induced by L. plantarum-administration in 7 healthy and in DSS/AOM group. In conclusion, our findings suggested that L. plantarum administration modulated the inflammatory cytokines and inhibited CRC through reducing the expression and the protein concentration of pro-inflammatory cytokine IL-1 beta and inducing the expression and the protein concentration of anti-inflammatory cytokineIL-6. These results were triggered by the inhibition of miR-146a-5p and miR-21 expressions, which are responsible for IL-6 induction and IL-1 beta reduction.