Emerging roles of microRNAs in the regulation of Toll-like receptor (TLR)-signaling

Toll-like receptors (TLRs) are evolutionarily conserved molecules that detect exogenous and endogenous molecular patterns and trigger both the innate and adaptive immune systems to initiate a pathogen-specific immune response and eliminate the threat. However, sustained, or prolonged activation of the immune system disrupts immunological homeostasis and leads to chronic or acute inflammatory diseases. MicroRNAs (miRNAs) can intervene in the initiation and modulation of the complex immunoregulatory networks via regulating the expression of TLRs and multiple components of TLR-signaling pathways including signaling proteins, transcription factors, and cytokines. Moreover, the aberrant expression of TLRs can induce the expression of several miRNAs which in turn regulate the expression of TLR signaling components and TLR-induced cytokines. The present review aims to highlight the emerging roles of miRNA in the regulation of TLR signaling, the interaction between the miRNAs and TLRs, and their implication in inflammatory diseases.