Effect of Lactobacillus reuteri on cell viability and PGE2 production in human gingival fibroblasts

Emerging evidence suggests that probiotic therapy can play a role in the prevention and management of oral inflammatory diseases through immunomodulation and downregulation of the inflammatory cascade. The aim of this in vitro study was to investigate the viability of human gingival fibroblasts (HGF) and its production of prostaglandin E-2 (PGE(2)), when exposed to supernatants of twomixed Lactobacillus reuteri strains (ATCC PTA 5289 and DSM 17938). The experiments were conducted in the presence and absence of the proinflammatory cytokine IL-1 beta. L. reuteri strains were grown and the bacterial supernatant was collected. The cell-free supernatant was diluted to concentrations equivalent to the ones produced by 0.5 to 5.0 x 10(7) CFU/mL bacteria. Cell viability was assessed with the MTT colorimetric assay and the amount of PGE(2) in the cell culture medium was determined using the monoclonal enzyme immune assay kits. Our findings showed that none of the L. reuteri supernatants were cytotoxic or affected the viability ofHGF. The most concentrated bacterial supernatant stimulated the production of PGE(2) by the gingival cells in a significant way in the presence of IL-1 beta (p < 0.05), suggesting that bacterial products secreted from L. reuteri might play a role in the resolution of inflammation in HGF. Thus, our findings justify further investigations on the influence of probiotic bacteria on gingival inflammatory reactions.