Control of macrophage autophagy by miR-384-5p in the development of diabetic encephalopathy.

The molecular development of diabetic encephalopathy remains ill-defined. Recently, we reported that elimination of inflammatory macrophages alleviated the progress and severity of diabetic encephalopathy. Here, we studied the underlying mechanism. Inflammatory macrophages were isolated from the brain of the mice that received i.p. injection of streptozotocin (STZ) to develop diabetes 6 weeks before, and showed enhanced autophagy activity, seemingly through augmentation of Beclin-1 levels. However, the increases in Beclin-1 levels did not result from enhanced gene transcription, but appeared to result from suppression of a Beclin-1-inhibitory microRNA, miR-384-5p. Overexpression of miR-384-5p in the inflammatory macrophages through an adeno-associated virus mediated gene transfer system significantly reduced inflammatory macrophages in the diabetic brain, resulting in attenuation of the STZ-induced decreases in brain malondialdehyde, catalase and superoxidase anion-positive cells, and the STZ-induced increases in brain nitric oxide. Thus, these data suggest that downregulation of miR-384-5p in the inflammatory macrophages may enhance macrophage autophagy and contribute to the development of diabetic encephalopathy, which may be suppressed by re-expression of miR-384-5p in macrophages.