Lactobacillus sakei K040706 evokes immunostimulatory effects on macrophages through TLR 2-mediated activation

Lactobacillus sakei K040706 is the most populous lactic acid bacteria (LAB) in over ripened Doenjang, a traditional Korean fermented soybean paste. In this study, we investigated the immunostimulating effects of L. sakei K040706 (K040706) in macrophages and in cyclophosphamide-induced immunosuppressed mice. Upon exposure to K040706, significant increases in phagocytic activity and in the productions of nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were observed in rIFN-γ-primed RAW 264.7 macrophages. K040706 also increased the expressions of inducible nitric oxide synthase (iNOS) at the protein and promoter binding levels, and the expressions of iNOS, TNF-α, and IL-6, at the mRNA level. In addition, K040706 significantly increased the transcriptional activities and DNA binding of nuclear factor-κB (NF-κB), which was accompanied by parallel enhancement of the nuclear translocation of p65 via the phosphorylations inhibitory kappa B-α (IκB-α) and IκB-kinase (IKK). On the other hand, pretreatment with NF-κB inhibitors reduced K040706-induced NO production in IFN-γ-primed RAW 264.7 macrophages. Furthermore, K040706 induced-NO production was completely abolished by anti-Toll-like receptor 2 (TLR2) antibody. In our cyclophosphamide-induced immunosuppressed mouse model, administration of K040706 restored thymus and spleen indices. Taken together, our findings suggest that K040706 improves immune function by regulating immunological parameters, such as, the productions of NO, TNF-α, and IL-6 via NF-κB activation, and by activating TLR2 in rIFN-γ-primed macrophages. In parallel, K040706 restored immunological parameters in cyclophosphamide-induced immunosuppressed mice and may warrant further evaluations as potential immunomodulatory agent.