miR-146a and miR-146b Regulate Human Dendritic Cell Apoptosis and Cytokine Production by Targeting of TRAF6 and IRAK1 [Gene Regulation]

December 11th, 2014 by Park, H., Huang, X., Lu, C., Cairo, M. S., Zhou, X.

We have previously reported 27 differentially expressed miRNAs during human monocyte differentiation into immature dendritic cells (imDCs) and mature DCs (mDCs). However, their roles in DC differentiation and function remain largely elusive. Here, we report that miR-146a and miR-146b modulate DC apoptosis and cytokine production. Expression of miR-146a and miR-146b was significantly increased upon monocyte differentiation into imDCs and mDCs. Silencing of miR-146a and/or miR-146b in imDCs and mDCs significantly prevented DC from apoptosis whereas overexpressing miR-146a and/or miR-146b increased DC apoptosis. miR-146a and miR-146b expression in imDCs and mDCs was inversely correlated with TRAF6 and IRAK1 expression. Furthermore, siRNA silencing of TRAF6 and/or IRAK1 in imDCs and mDCs enhanced DC apoptosis. By contrast, lentivirus overexpression of TRAF6 and/or IRAK1 promoted DC survival. Moreover, silencing miR-146a and miR-146b expression had little effect on DC maturation but enhanced IL-12p70, IL-6, and TNF-α production as well as IFN-γ production by IL-12p70-mediated activation of natural killer (NK) cells, whereas miR-146a and miR-146b overexpression in mDCs reduced cytokine production. Silencing miR-146a and miR-146b in DCs also downregulated nuclear factor-κB (NF-κB) inhibitor IκBα and increased Bcl-2 expression. Our results have identified a new negative feedback mechanism involving the miR-146a/b-TRAF6/IRAK1-NF-κB axis in promoting DC apoptosis.