New strategic approach to develop therapeutic agent for diabetic retinopathy by regulation of apoptosis of retinal vascular cells and neurons

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We investigated the pathophysiological aspects of diabetic retinopathy, focusing on the cellular damage. The apoptosis of retinal cell components (retinal neurons and retinal vascular cells) is caused by various insults including oxidative stress. To evaluate the cell damage by oxidative stress, we observed the expression of 8-hydroxydeoxyguanosine (8-OHdG) and NOx in the eyes with diabetic retinopathy in human eyes. NOx is a marker for NO production, and 8-OHdG is a biological marker of DNA damage due to oxidative stress. 8-OHdG and NOx levels in the human vitreous specimens were measured by ELISA. The vitreous specimens were obtained during the vitreous surgeries from the eyes with proliferative diabetic retinopathy (PDR), branch retinal vein occulusion (BRVO), or macular hole and/or epiretinal membrane (MH/ERM)), after securing the written permission from the subjects. This study has been approved by Ethical Committee of Yamagata University Faculty of Medicine. The mean vitreal conc … More entration of NOx and 8-OHdG in the eyes with PDR was significantly higher than those with BRVO and MH/ERM. The expression of 8-OHdG was observed immunohistochemically in the retinas of the noromal rats and the DM model rats. The expression of 8-OHdG was detected mainly in ganglion cell layer of the STZ rat eyes. Taken together, oxidative damage was more significant in the diabetic eyes than in the BRVO or the MH/ERM eyes. These results suggest that anti-oxidant agents are very good candidates for therapeutic agents for diabetic retinopathy.We investigated the other approach to develop new therapeutic agents for diabetic retinopathy. In diabetic retinopathy, the production of diacylglycerol (DG) is increased and activates protein kinase C(PKC), which is involved in the signal transduction pathways from various growth factors. Diacylglycerol kinase (DGK) phosphorylates DG, which is degraded into phosphatidic acid (PA), and regulates the intracytoplasmic signal transduction by regulating DG level and inositol-phospholipid turnover. We observed the expression patterns of DGK isoforms and cytokines to investigate the clinical significance of DGK during the pathogenesis of diabetic retinopathy. In the retinal specimens from Streptozotocin induced rats (STZ) and Spontaneously Diabetic Torii (SDT) rats (supplied by the courtesy of Torii Pharmaceutical Co., Ltd., Tokyo, Japan), the expression of DGK isoforms and cytokines (VEGF, IL-6, Angiotensin II, TGF_1,2, and PEDF) was observed immunohistochemically and by Western blotting. The expression patterns and expression levels of DGK, VEGF, IL-6 and angiotensin-II changes in DM model rat retina in comparison with the normal control The expression of DGK and IL-6 was mainly detected in the retinal vessels, and angiotensin-II was observed in the vessels and the inner nuclear layer in the diabetic retina. VEGF expression increased in whole layere of the diabetic retina. It is possible that DGK and VEGF are involved in the pathogenesis in the early stage of DMR, and are good targets to develop new therapeutic agents for diabetic retinopathy. Less