Effects And Mechanisms Of GPR91on VEGF Expression In Retina Of Diabetic Rats

ObjectiveTo establish a diabetic rat model and observe the effects of G protein-coupledreceptor91(GPR91) on regulating vascular endothelial growth factor (VEGF) expressionand the pathological changes in retina of diabetic rats。To further explore the mechanism ofGPR91on VEGF expression in retina of diabetic rats and provide the basement for genetreatment of diabetic retinopathy (DR).MethodsHealthy male Sprague Dawley (SD) rats were selected in this study. The diabetic ratsmodel was induced by the peritoneal injection of streptozocin (STZ) at one time. Constructa lentiviral vector of shRNA of rat GPR91and scrambled shRNA lentiviral particles.Accumulation of succinate in different time of diabetic rats was assessed by gaschromatography-mass spectrometry (GC-MS). Western blotting and immunofluorescencewere detected the expression of GPR91, p-ERK1/2, COX-2in the diabetic rats. At14weeks diabetic retinas, the ultrastructure and function of the retinal vessel were assessedusing haematoxylin and eosin (HE) staining, transmission electron microscopy (TEM) andEvans blue dye permeability. qPCR was detected the mRNA levels of the COX-2andVEGF. PGE2and VEGF release was observed by the ELISA analysis.ResultsSuccinate exhibited abundant accumulation in diabetic rat retinas compared to thecontrol group (P<0.01), however the GPR91expression has no significant difference. Inthe14-week diabetic rats, the retinal telangiectatic vessels, the basement membranethicknessand Evans blue dye permeability were attenuated by treatment with GPR91 shRNA, but the damage to the inner nuclear layer was not attenuated in the GPR91shRNAgroup. The expression of p-ERK1/2, COX-2, PGE2and VEGF in diabetic rats wasincreased compared to the non-diabetic rats. The upregulation in p-ERK1/2, COX-2, PGE2and VEGF expression were significantly blocked by intravitreal injection of LV.shGPR91(P<0.01). Furthermore, intravitreal injection of U0126or NS-398significantly blocked theupregulation of COX-2, PGE2and VEGF release (P<0.01).Conlusion(1) Successfully established animal model of diabetes in rats and observed theaccumulation of succinic acid in the retina of diabetic rats, GPR91mainly located in nerveganglion cells and the expression of VEGF secretion increased.(2) Construct a lentiviral vector of GPR91shRNA and explore the effect of GPR91onthe VEGF secretion and improve the retinal microvascular lesion in the early stage of theDR.(3) GPR91regulated the VEGF release may be by activating ERK1/2/COX-2/PGE2in the early stage of the DR.