Effect of Lactobacillus GG and conditioned media on IL-1β-induced IL-8 production in Caco-2 cells

Objective. To evaluate the anti-inflammatory effect of Lactobacillus casei rhamnosus GG (LGG) and its conditioned media (CM) in stimulated Caco-2 cells and to characterize the components of LGG that have the anti-inflammatory effect. Material and methods. Caco-2 cells were stimulated with IL-1 beta with or without LGG or LGG-CM. Production of IL-8 was measured by enzyme-linked immunosorbent assay (ELISA). The transcriptional activities of the IL-8 gene and the NF kappa-B-responsive gene were evaluated by a transient transfection of the luciferase reporter gene. The effect on I kappa B alpha degradation was evaluated by Western blot analysis. To determine the nature of the immunomodulatory molecules, the LGG was modified to the following: treated with antibiotics, 4% formaldehyde, incubation at 95 degrees C, or sonication. Results. We demonstrated that the pretreatment of Caco-2 cells with LGG significantly inhibited IL-1 beta-induced IL-8 production. Furthermore, LGG attenuated the IL-1 beta-induced transcriptional activation of the IL-8 gene and the NF-kappa B-responsive gene, and attenuated the IL-1 beta-induced I kappa B alpha degradation. Formaldehyde-fixed or antibiotics-treated LGG maintained the inhibitory effect, but heated LGG lost this effect. Sonicated LGG debris had a similar inhibitory effect with whole bacterial cells. LGG-CM attenuated IL-1 beta-induced IL-8 production. This effect was maintained even when the conditioned media were heated. Conclusions. LGG inhibited IL-1 beta-induced IL-8 production in Caco-2 and this effect occurred at the transcriptional level, at least in part, by inhibition of the NF-kappa B signaling pathway. Both the structural material of LGG and the soluble factor secreted from LGG inhibited the IL-1 beta-induced IL-8 production, and thus different substances may cause the effects.