Lactobacillus paracasei modulates LPS-induced inflammatory cytokine release by monocyte-macrophages via the up-regulation of negative regulators of NF-kappaB signaling in a TLR2-dependent manner

The application of the probiotic lactobacillus is suggested in the treatment of some inflammatory diseases of intestines due to its potential ability to attenuate inflammation. However, the mechanism is not completely understood. In PBMCs, Lactobacillus paracasei (L. Paracasei) down-regulated the LPS-induced production of TNF-alpha and IL-6. Using a macrophage-like differentiated THP-1 cell line induced by PMA, we investigated the effect of L paracasei on the production of pro-inflammatory cytokines by monocytemacrophages. Treatment of the differentiated THP-1 cells with L paracasei either concurrently with or before LPS challenge attenuated the LPS-induced secretion of TNF-alpha and IL-1 beta. This effect was due to a decrease in 1 kappa B phosphorylation and NF-kappa B nuclear translocation. Furthermore, treatment of the differentiated THP-1 cells with L. paracasei induced the expression of negative regulators of the NF-kappa B signaling pathway, including the deubiquitinating enzyme A20, suppressor of cytokine signaling (SOCS) 1, SOCS3, and IL-I receptor-associated kinase (IRAK) 3. Pretreatment with an IRAK4 inhibitor suppressed the L paracasei-induced expression of these negative regulators and further increased the LPS-mediated expressions of TNF-alpha and IL-1 beta. Moreover, treatment with an antibody against Toll-like receptor (TLR) 2 reversed the effect of L paracasei on inducing negative regulators and inhibiting TNF-alpha and IL 1 beta productions. Our findings suggest that L. paracasei inhibits the production of pro-inflammatory cytokines by monocyte-macrophages via the induction of negative regulators of the NF-kappa B signaling pathway in a TLR2-IRAK4-dependent manner. (C) 2017 Elsevier Ltd. All rights reserved.