Anti-inflammatory properties of dairy lactobacilli

Background: The intestinal microbiota plays an important role in human health through the modulation of innate immune responses. While selected commensal bacteria are marketed in specific probiotic products to control these responses, relatively little is known about the immune modulation potential of dairy bacteria that have principally been selected for their fermentation properties. The modulation of innate immune responses may reduce chronic inflammation in inflammatory bowel diseases like ulcerative colitis. Methods: A collection of dairy Lactobacillus delbrueckii strains was screened for immune modulation effects in vitro through the quantification of nuclear factor kappa B (NF-kappa B) activation in a human intestinal epithelial cell line. Selected bacterial strains were then tested in vivo in a mouse dextran sodium sulfate (DSS) colitis model. Results: All L. delbrueckii strains tested showed anti- inflammatory effects in vitro, to an extent that varied between strains. These effects rely on bacterial surface exposed proteins and affect the central part of the NF-kappa B activation pathway. One of the selected strains significantly reduced the macroscopic and microscopic symptoms of DSS- induced colitis in the mouse intestinal tract, diminished body weight loss, and improved survival. Conclusions: The results of this study show that dairy lactobacilli that often are part of a regular diet can modulate innate immune responses, and may thus affect health more than generally thought. One of the strains tested alleviated the symptoms of DSS-induced colitis in mice, a model of human ulcerative colitis.