MicroRNA-144 suppresses the expression of cytokines through targeting RANKL in the matured immune cells.

To investigate whether the microRNA-144 (miR-144) had immune regulation effect on matured immune cells, we firstly used quantitative RT-PCR (qRT-PCR) to detect the expression changes of miR-144 between the matured and immature dendritic cells (DCs), macrophages, and the peripheral blood mononuclear cells (PBMCs). Then we went on inspecting the expression changes of TNF-α, IL-1β, IL-6 and IL-23 in the matured DCs treated with miR-144 mimics or inhibitors using qRT-PCR, and also performed western blot to test phosphorylation state of ERK, JNK, p38 and p65 in these cells. Next, TargetScan was conducted to forecast the target gene of miR-144, receptor activator for nuclear factor-κB ligand (RANKL), and double luciferase reporter system was applied to research their banding sites. We also determined the expression changes of RANKL in the DCs treated with miR-144 mimics or inhibitors using qRT-PCR and ELISA, respectively. The siRNA of RANKL was synthesized and transfected into DCs to inspect how the immune regulation effect of miR-144 was conducted to inhibit the expression of TNF-α using qRT-PCR, and lastly we used flow cytometry to investigate whether this effect applied to Th17 cells. As results, we found that miR-144 was down-regulated in the matured DCs, macrophages and PBMCs of liver transplantation patients, and the miR-144 mimics could inhibit the expression levels of TNF-α, IL-1β, IL-6 and IL-23 in the matured DCs. Furthermore, miR-144 interacted with RANKL at position 679-685 of RANKL 3'UTR, and suppressed the translation of RANKL mRNA to realize the negative-regulation. Besides, the silence of RANKL enhanced the suppression effect of miR-144 on TNF-α and this immune regulation effect was applied to Th17 cells, too. In conclusion, this study clearly illustrated that miR-144 could inhibit the expression of cytokine in matured immune cells through suppressing the translation of RANKL mRNA.