Oral lactobacilli reduce cytotoxicity and cytokine release from peripheral blood mononuclear cells exposed to Aggregatibacter actinomycetemcomitans subtypes in vitro.
Abstract Background: This study evaluated the effect of oral lactobacilli on the cytotoxicity and cytokine release from peripheral blood mononuclear cells (PBMC) when exposed to Aggregatibacter actinomycetemcomitans subtypes in vitro. The supernatants and cell wall extracts (CWEs) of eight A. actinomycetemcomitans strains, representing different subtypes, and three Lactobacillus strains were used. The PBMC cells from six blood donors were exposed to supernatants and CWEs of A. actinomycetemcomitans or Lactobacillus strains alone or combinations and untreated cells as control. The cytotoxicity was determined by trypan blue exclusion-method and IL-1β secretion by ELISA. TNF-α, IL-6 and IL-8 secretions were measured using Bioplex Multiplex Immunoassay. Results: Supernatants or CWEs from all bacterial strains showed cytotoxicity and IL-1β secretion and the subtypes of A. actinomycetemcomitans showed generally a significantly higher effect on PBMC´s than that of the Lactobacillus strains. Two highly toxic A. actinomycetemcomitans strains (JP2 and JP2-like) induced a higher response than all other strains. Two non-serotypable strains (NS1 and NS2) showed a weaker although significant effect than other A. actinomycetemcomitans or Lactobacillus strains tested. CWEs showed generally a higher effect on PBMC´s than the supernatants. When combined, Lactobacillus significantly reduced the toxicity and IL-1β secretion induced by A. acinomycetemcomitans. The effect varied between the subtypes and the reduction was highest for the JP2 and JP2-like strains. The Lactobacillus paracasei strain SD1 had a higher reducing effect that the other Lactobacillus strains. This strain had a consistent reducing effect on all subtypes of A. actinomycetemcomitans cytotoxicity, and release of IL-1β and TNF-α from PBMC´s of the blood donors. A strong and significant variation in cytokine release between the 6 blood donors was noticed. Conclusions: Lactobacillus spp and L. paracasei strain SD1 in particular, showed a significant reducing interaction with A. actinomycetemcomitans toxicity and release of cytokines in vitro.