Baicalein Reduces Inflammatory Process in a Rodent Model of Diabetic Retinopathy

PURPOSE. This study was designed to elucidate the role of inflammatory process in diabetic retinopathy and to investigate the effect of baicalein treatment on diabetic rat. METHODS. Retinal microglial cells were identified with CD11b antibody, and retinal Muller cells were identified with glial fibrillary acidic protein (GFAP). The gene expression of interleukin (IL)-18, tumor necrosis factor (TNF)-alpha, and IL-1 beta was examined by quantitative real-time PCR. The expression of GFAP and vascular endothelial growth factor ( VEGF) was examined by quantitative real-time PCR, immunohistochemistry, and Western blot analysis. Vascular permeability was measured in vivo by bovine serum albumin conjugated with FITC. Baicalein was given by oral administration (150 mg/kg/d) with an animal feeding needle beginning 5 days after streptozotocin (STZ) injection. RESULTS. By 24 weeks after onset of diabetes, microglial cells were activated and proliferated, and Muller cells upregulated their GFAP and VEGF expression. Pro-inflammatory factors, including IL-18, TNF-alpha, and IL-1 beta, were significantly upregulated. Obvious vascular leakage and abnormality were demonstrated, and ganglion cell loss was significant. Baicalein treatment ameliorated diabetes-induced microglial activation and pro-inflammatory expression, reduced the GFAP and VEGF expression from Muller cells, and significantly reduced vascular abnormality and ganglion cell loss within the retina. CONCLUSIONS. Inflammatory process, characterized by microglial activation and Muller cells dysfunction, was implicated in STZ-induced diabetic retinopathy. Baicalein treatment ameliorated inflammatory process, and therefore inhibited vascular abnormality and neuron loss in diabetic retinas. (Invest Ophthalmol Vis Sci. 2009;50:2319-2327) DOI:10.1167/iovs.08-2642