Abstract
Probiotic–host interaction can be cell-to-cell or through metabolite production. Dead (inactive) organisms could interact with the host, leading to local effects and possible health benefits. This research examined the effects of live and heat-inactivated Bifidobacterium animalis subsp. lactis, BB-12 (BB-12) and Lactobacillus rhamnosus GG (LGG) on cultured Caco-2 cells focusing on epithelial integrity and production of inflammatory mediators. Live organisms increased transepithelial electrical resistance (TEER), a barrier-integrity marker, with LGG having a greater effect than BB-12. When mildly heat-treated, both organisms had a more modest effect on TEER than when alive. When they were heat-inactivated, both organisms had only a limited effect on TEER. Neither live nor heat-inactivated organisms affected production of six inflammatory mediators produced by Caco-2 cells compared to control conditions. Pre-treatment with heat-inactivated LGG or BB-12 did not alter the decline in TEER caused by exposure to an inflammatory cocktail of cytokines. However, pre-treatment of Caco-2 cells with heat-inactivated organisms alone or their combination decreased the production of interleukin (IL)-6, IL-18, and vascular endothelial growth factor. To conclude, while the live organisms improve the epithelial barrier using this model, neither live nor heat-inactivated organisms directly elicit an inflammatory response by the epithelium. Pre-treatment with heat-inactivated BB-12 or LGG can reduce some components of the response induced by an inflammatory stimulus.
Highlights
The World Health Organization defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” [1]
B. animalis subsp. lactis, BB-12 by more than three logs, whereas 6 min exposure at this temperature resulted in no live B. animalis subsp. lactis, BB-12 remaining
For L. rhamnosus GG, the results of the current study suggest that those metabolic products may be more important for the interaction with epithelial cells than the physical interaction with components of the bacterial cell wall
Summary
The World Health Organization defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” [1]. Dead or inactive organisms could interact with the host and be functional, conferring health benefits, and would not carry the risk of infection. In vitro studies showed that the anti-inflammatory effects of live and heat-killed B. breve were comparable in peripheral blood mononuclear cells isolated from patients with ulcerative colitis [11]. We examined the effects of live and heat-inactivated B. animalis subsp. lactis, BB-12 and L. rhamnosus GG on cultured
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