miR-124 Regulates Amadori-Glycated Albumin-Induced Retinal Microglial Activation and Inflammation by Targeting Rac1

PURPOSE. To characterize whether the activation of Rac1 is involved in the inflammatory effects produced by Amadori-glycated albumin (AGA) in retinal microglia and to further explore the pathologic pathways of AGA-induced retinal microglial activation and inflammation via a microRNA-dependent mechanism. METHODS. Primary rat retinal microglia were separated and cultured. The levels of TNF-alpha mRNA and soluble TNF-alpha produced by the retinal microglia in response to AGA were measured with quantitative RT-PCR (qRT-PCR) and ELISA. In addition, the GTPase activity of Rac1 was measured using a Rac activation assay kit. Luciferase reporter assays were used to validate the regulation of a putative target of microRNA-124 (miR-124). RESULTS. Amadori-glycated albumin significantly stimulated the expression of TNF-alpha mRNA and protein in cultured retinal microglial cells in a dose- and time-dependent manner. MicroRNA-124 expression was consistently suppressed by AGA, and the inhibitory effect was controlled by histone deacetylases (HDACs). Amadori-glycated albumin induced an increase in Rac1 activation in a dose- and time-dependent manner. Furthermore, our data indicated that Rac1 activation-mediated reactive oxygen species production stimulates p65 NF-kappa B phosphorylation and induces TNF-alpha release from retinal microglial cells. Finally, we demonstrated that miR-124 directly controls Rac1 expression. CONCLUSIONS. The current study indicated that AGA-induced retinal microglial activation and inflammation occur via a miR-124-dependent mechanism.