Abstract
miRNAs are ubiquitous regulators of human biology. Parallel profiling of in vitro monocyte-to-Mφ and monocyte-to-DC differentiation revealed static, convergent, and divergent expression of miRNA. Bioinformatic and network analysis of differentially expressed miRNAs implicated miR-24, miR-30b, and miR-142-3p as negative regulators of intracellular signaling pathways, triggered not only by differentiation factors (M-CSF/GM-CSF/IL-4) but also from PRRs. Manipulation of miR-24, miR-30b, and miR-142-3p expression during the differentiation of mD-Mφ and mD-DC differentiation had minimal impact on the acquisition of phenotype but significantly abrogated the ability of these cells to mount inflammatory responses to pathogen-associated stimuli. Forced expression of these miRNAs, which are down-regulated during differentiation, inhibited release of inflammatory cytokines [TNF-α, IL-12(p40), IL-6] upon stimulation with LPS. Functional analysis revealed overlapping mechanisms of inhibition, including surface expression of TLR4/CD14/MD-1 and intracellular PKCα/NF-κB activation. Potential intermediary targets of the TLR4-NF-κB axis included members of the PI3K and MAPK families and PKC isoforms. These results demonstrate the requirement of miR-24, miR-30b, and miR-142-3p down-regulation for the generation of fully functional Mφs and DCs.