Abstract
Probiotic bacteria alleviate many gastrointestinal symptoms, but the current trend of combining bacteria for additional benefit may make their effects more complex. We characterize four probiotics and their combination in terms of pathogen adhesion, barrier function, cell death, and inflammatory response in Helicobacter pylori-infected epithelial cells. H. pylori-infected Caco-2 cells were pretreated with Lactobacillus rhamnosus GG, Lactobacillus rhamnosus Lc705, Propionibacterium freudenreichii subsp. shermanii Js, Bifidobacterium breve Bb99, or all four organisms in combination. We evaluated the adhesion of H. pylori by in situ immunofluorescence; epithelial barrier function by measurement of transepithelial resistance; apoptosis by measurement of caspase 3 activation; cell membrane leakage by measurement of lactate dehydrogenase release; and inflammation by measurement of interleukin-8 (IL-8), IL-10, prostaglandin E(2) (PGE(2)), and leukotriene B(4) (LTB(4)) release. All probiotics inhibited H. pylori adhesion. L. rhamnosus GG, L. rhamnosus Lc705, P. freudenreichii subsp. shermanii Js, and the combination inhibited H. pylori-induced cell membrane leakage. L. rhamnosus GG, L. rhamnosus Lc705, and the combination initially improved epithelial barrier function but increased the H. pylori-induced barrier deterioration after incubation for 24 to 42 h. L. rhamnosus GG, L. rhamnosus Lc705, and P. freudenreichii subsp. shermanii Js inhibited H. pylori-induced IL-8 release, whereas L. rhamnosus GG, L. rhamnosus Lc705, and B. breve Bb99 suppressed PGE(2) release. None of these anti-inflammatory effects persisted when the probiotics were used in combination. The combination thus increased the levels of IL-8, PGE(2), and LTB(4) released from H. pylori-infected epithelial cells. The proinflammatory actions of the individual components dominated the anti-inflammatory effects when the probiotic bacteria were used in combination. Our results stress that the therapeutic response can be optimized if probiotic strains are characterized before they are used in combination.