Lactobacillus casei Zhang modulate cytokine and Toll-like receptor expression and beneficially regulate PolyI:C-induced immune responses in RAW264.7 macrophages.

Lactobacilli are frequently used as probiotics due to their health-benefiting effects. Lactobacillus casei Zhang (LcZ), exhibiting favorite probiotic properties, was isolated from koumiss. In this study, we assessed the immunomodulating effects of LcZ on cytokine and toll-like receptor expression in RAW264.7 macrophages. Our results showed that live LcZ promoted the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and interferon (IFN)-β. The transcription of inducible nitric oxide synthase (iNOS) was also enhanced by viable LcZ. The immunostimulating effects of live LcZ were significantly attenuated in heat-killed LcZ. Live LcZ promoted TLR2 mRNA transcription, while heat-killed LcZ enhanced the transcription of TLR2, TLR3, TLR4 and TLR9. Furthermore, Live LcZ significantly suppressed polyinosinic:polycytidylic acid (PolyI:C)-stimulated NO, iNOS and TNF-α expression while enhancing the expression of IFN-β. We found that PolyI:C-induced IRF-3 reporter gene activity was significantly up-regulated by Live LcZ. These results suggest that Lactobacillus casei Zhang keep the innate immune system alert by increasing the transcription of toll-like receptors and enhancing the production of pro-inflammatory mediators and type I IFN in macrophages. The synergistic effect of live LcZ with PolyI:C on IFN-β expression is associated with increased activities of IRF-3. Lactobacillus casei Zhang has the potential to be used as an adjuvant against viral infections.