Pang V., Chen Y., Chen M.
Department of Animal Science and Technology, National Taiwan University, Taiwan

Lactobacillus kefiranofaciens M1 and Lb. mali APS1, previously isolated from different kefir grains in our lab, are potential probiotic strains. Both strains demonstrated an anti-colitis effect in vitro and in vivo. Lb. kefiranofaciens M1 was also proven to possess immunoregulatory ability on sustaining intestinal homeostasis, anti-allergic and anti-asthmatic effects. In further mechanism study, we found that the putative receptor for recognition of Lb. kefiranofaciens M1 in intestinal epithelial layers was Toll-like receptor (TLR)-2. Dendritic cells (DCs), also existing in the epithelial barrier, are professional antigen-presenting cells and act as messengers between innate and adaptive immune systems. When receiving foreign antigen and becoming mature, they migrate to the draining lymph nodes and mediate to convert naïve lymphocytes into effector T cell or regulatory T (Treg) cell. The relationship between DCs and benefits of our probiotic strains are still remain unclear.

Thus, we isolated BMDCs from C57BL/6 mice and co-culture with different dosages of Lb. kefiranofaciens M1 or Lb. mali APS1 to understand the role of DCs on health benefits of the probiotic strains.To further investigate the immunomodulatory activity of DCs activated by these two probiotic strains, we evaluated their capacity to regulate T cell functions, including cytokine profiles as well as proliferation of allogenic T cell in a mixed lymphocytes reaction. Furthermore, we investigated the signal transduction pathways engaged by these two strains, including pattern recognition receptor TLRs and mitogen-activated protein kinases (MAPK) pathway using anti-TLR2 and specific inhibitors of p38MAPK, JNK and MEK1/2.

Results indicated that both live and heat-killed bacteria of these two strains could stimulate phenotypic maturation of DCs and up-regulate surface expression of CD40, CD80, CD86 which are co-stimulatory molecules of DC maturation, as well as major histocompatibility complex (MHC) class II. These two strains markedly enriched production of IL-12, TNF-α, IL-6 and IL-10 secreted by BMDCs in a dose-dependent manner. On the other hand, their supernatant may not interact with DCs.We found that probiotic-stimulated DC could induce CD4+ T cell proliferation when DC: T cell =1:10. Besides, live Lb. mali could promote T cells to secrete more IL-10 rather than IFN- production, indicating that CD4+ T cells may differentiate into Treg cells when receiving Lb. mali, as consistent to the result of alleviating inflammation symptoms in DSS-induced colitis mice from our previous studies. With p38MAPK and JNK inhibitors, CD80 and CD86 mfi of probiotic-induced DC maturation were downregulated while MEK1/2 was not. However, there was a large decrease of IL-10 and IL-6 production by blocking JNK of DC among all the other inhibitor groups, thus JNK pathway is most likely involved in modulating DC biological functions by our strains.

As both of the live and heat-killed bacteria differentially modulate DC activation, the following step is to know which components participate in immunoregulation. This study elucidates that DCs may be the important route for Lb. kefiranofaciens M1 and Lb. mali APS1 to interact with immune system and influence T cell shaping, resulting in amelioration of various immune disorders.

Keywords: Dendritic cell, Lactobacillus, Kefir, Immunoregulation, Probiotics, MAPK pathway

Pang V., Chen Y., Chen M. (2016). The immunomodulatory properties of probiotic strains on dendritic cell functions.  Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 110.). IPC2016

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