miRNAs as regulators of extracellular TLRs in bacterial infections

The detection of pathogens by the immune system is facilitated through various cellular interactions and molecules, including pattern recognition receptors that activate signaling pathways in response to the pathogen. Among the most studied receptors are Toll-like receptors, which are activated upon ligand recognition and are considered the first event in innate immunity. The transcriptional response of TLRs in infected cells is modified by pathogens, where miRNAs, which are post-transcriptional regulators of gene expression, play a role. We review some bacteria that alter the signaling cascade of extracellular TLRs and the co-participation of miRNAs, most of which are analyzed downstream, and a very low percentage act as ligands of the TLRs. There is an increase in knowledge of the regulation of miRNAs by bacteria; however, the functional complexity of miRNAs has hindered progress in utilizing them as biomarkers or for therapeutic purposes.