Substances released from probiotic L actobacillus rhamnosus GR ‐1 potentiate NF ‐κB activity in E scherichia coli ‐stimulated urinary bladder cells

L actobacillus rhamnosus GR ‐1 is a probiotic bacterium used to maintain urogenital health. The putative mechanism for its probiotic effect is by modulating the host immunity. Urinary tract infections ( UTI ) are often caused by uropathogenic E scherichia coli that frequently evade or suppress immune responses in the bladder and can target pathways, including nuclear factor‐kappaB ( NF ‐κ B ). We evaluated the role of L . rhamnosus GR ‐1 on NF ‐κ B activation in E . coli ‐stimulated bladder cells. Viable L . rhamnosus GR ‐1 was found to potentiate NF ‐κ B activity in E . coli ‐stimulated T 24 bladder cells, whereas heat‐killed lactobacilli demonstrated a marginal increase in NF ‐κ B activity. Surface components released by trypsin‐ or LiCl treatment, or the resultant heat‐killed shaved lactobacilli, had no effect on NF ‐κ B activity. Isolation of released products from L . rhamnosus GR ‐1 demonstrated that the induction of NF ‐κ B activity was owing to released product(s) with a relatively large native size. Several putative immunomodulatory proteins were identified, namely G ro EL , elongation factor T u and NLP / P 60. G ro EL and elongation factor T u have previously been shown to elicit immune responses from human cells. Isolating and using immune‐augmenting substances produced by lactobacilli is a novel strategy for the prevention or treatment of UTI caused by immune‐evading E . coli .