MicroRNAs: Regulators of TLR2-Mediated Probiotic Immune Responses

MicroRNAs (miRNAs) are similar in importance to transcription factors and critical to confer accuracy and robustness in gene expression programs and consequently, have emerged as controllers of the immune response. On the other hand, probiotic influence over immune responses against a wide spectrum of health conditions are widely studied but the mechanism for this modulation has not yet completely elucidated. One proposed mechanism involves the receptor-mediated interaction of dendritic cells with components of the cellular membrane and/or secreted peptides of probiotics ending with the production of cytokines. However, the cytokine response elicited by dendritic cells is largely strain-dependent, and not to the same extent. The signaling pathway involved must be tightly regulated in order to be precise and effective; proteins as TNF receptor-associated factor 6 (TRAF6), Interleukin-1 receptor-associated kinase 4 (IRAK4) and Interleukin-1 receptor-associated kinase 3 (IRAK3 or IRAKM) participate in an important way in the nuclear factor kappa B (NF-κB) signaling pathway, which is the main cascade activated in response to probiotics. These proteins can be regulated by miRNAs and alter the immune outcome. This review discusses the current understanding on the participation of miRNAs modulating the TLR2/NF-κB pathway in the innate immune response mediated by probiotics.