Lactobacillus plantarum extracellular metabolites: In vitro assessment of probiotic effects on normal and cancerogenic human cells

Supernatants obtained from four Lactobacillus plantarum strains were evaluated for their effects on normal and cancerogenic human cells. After growing bacteria in human cell culture media for 24 h, two fractions containing extracellular components with low (<10 kDa) and high (>10 kDa) molecular mass were generated by ultrafiltration. Proliferation tests were done on H4, CaCo-2, Melanoma and TLT cells. The <10 kDa fraction obtained from two of the tested strains significantly increased proliferation of H4 cells by increasing the proportion of cells in G2/M cell cycle phase. The active components causing proliferation of H4 cells were confirmed to be of protein origin. Different active components (not affected by a protease), from the <10 kDa samples decreased the proliferation of cancerogenic CaCo-2 and Melanoma cells. The <10 kDa fraction also increased transepithelial electrical resistance of H4 cells and decreased secretion of pro-inflammatory cytokines IL-6 and IL-8 in a co-cultured model of H4/TLT cells under inflammatory conditions.