| Objective：Diabetic Retinopathy (DR) is a occlusive,proliferous intraretinal microangiopathy,one of the most common and serious microvascular complications of the diabetes mellitus (DM),and the main cause of blindness.Today,with the diabetes patients increased,strengthening the role of preventing diabetic retinopathy has become a matter of top priority. Up to now,the pathogenesis about diabetic retinopathy is not clear,but in recent years, diacylglycerol (DAG)/protein kinase C (PKC) signal pathway has drawn more attention which was considered to playing an important role during the appearance and development of diabetic retinopathy.Hyperglycemia triggers increased intracellular levels of diacylglycerol the agonists to protein kinase C.The elevated activation of protein kinase C leads to the biochemical changes in retina include many abnormal vascular and cellular processes and deregulations such as cellular dysfunction,capillary basement membrane thickening,vascular permeability and angiogenesis.Heat shock protein (HSP) is a conservative protein family during the organisms evolution, various kinds of factors can induce its production.The protein of the family has a variety of biological function, and also acts as an important molecular partner. HSP27is one of the member in the family of small HSP.It expresses with a low level in normal cells, but when there is a stimulator, the expression increase and play the role of the antioxidant injury.The PKC inhibitors had been found in many plants.Catechin was the main ingredient of the pharmacology function extracted from natural plant. For its Phenolic hydroxyl,it can react easily in oxidation, polymerization, condensation, et al. It has better antioxidant ability to eliminate free radicals, and it was safety, non-toxic, usage, and has many kinds of biological function as anticancer,resistance of gene mutations, antibacterial,antiphlogosis,resistance to atherosclerosis,buck,hypoglycemic and so on.Studies had found that the catechins can protect the optic nerve from injure [1].But there was no a research had been reported about the catechins effect in diabetic retinopathy.This study was established to investigate the alteration of protein kinase C (PKC) and heat shock protein27(HSP27)in diabetic rats, and the effect of Catechin on the expression of PKC and HSP27in diabetic rats.Methods:54healthy male SD rats,each weighting175±15g,were randomly divided into three groups:the normal control group(normal group)(18rats,36eyes),diabetic control group (control group)(18rats,36eyes) and treated with Catechin group (treated group)(18rats,36eyes). Diabetes model established:rats in control group and treated group received a single intraperitoneal injection of65mg/kg streptozotocin(STZ) after an overnight fast. Rats with blood glucose levels>16.7mmol/L72hours later were deemed diabetic while the rats with blood glucose level less than16.7mmol/L were excluded.All rats were kept with free access to water and food.The rats of treated group was irrigated the catechin(200mg/kg)diluted in distilled water through stomach once a day while the rats in normal and control group irrigated with distilled water.Record the change of blood glucose and weight weekly. After the success of the model,anesthetize6rats of each group with hydration chlorine aldehyde in2weeks,4weeks,8weeks, quickly take off the double eyes, Randomly chose one eye, cut the eye ball along the equator in anatomical microscope, remove the cornea and lens,remove vitreous with cold saline,detach the retinal with ophthalmic microscopic tweezers.The detached retina tissue was used for examining PKC expression through ELISA method.The other eye was quickly fixed in stationary liquid for24h,used for immunohistochemical observations of HSP27changes, the results was record with the form of mean±standard deviation.SPSS13.0was used to analyse the data.Results: 1. Changes in body weight and Blood Glucose Levels:During the experiment process,diabetic rats body weights lost, the body weights were significantly lower in control and treated rats at2and4weeks compared with the normal group in different time points(2w p<0.05,p<0.01;4w and8w p<0.01); At2weeks and4weeks, there were no significant difference between the treated group and the control group (p>0.05), at8weeks, the weight loss degree in treated rats was lighter than control group (p<0.05).After the success induction of Diabetes model, the blood glucose levels of the rats in control and treated group were significantly elevated compared with the normal group in different time points,(p<0.01),there were no statistically significant between the treated and control group at2weeks and4weeks (p>0.05), at8weeks blood glucose level in treated group was reduced significantly than the control group.(p<0.01).2.The change of PKC activity in retinal tissue:At2weeks,4weeks,8weeks,the expression of PKC was significantly elevated in the cytomembrane of retina tissue in the control group compared with the normal group (P<0.01),but there were no significant difference between the treated group and control group at2weeks and4weeks(P>0.05);At8weeks,the expression of PKC was significantly reduced in the cytomembrane of retina tissue in the treated group compared with the control group (P<0.01).However, there was no significant difference in the PKC expression in the cytoplasm at2week,4week,8week among each other group(p>0.05).3.Change of the HSP27expression in rat retina tissue among each group:Hsp27was expressed primarily in the the ganglion cell layer and the retina nerve fiber layer.The cytoplasm with HSP27expressed was claybank.HSP27was not obviously positively expressed in the rest of the retina. There was only little positive expression in the normal group. At2weeks,4weeks and8weeks,positive expression of HSP27in retina tissue was increased in the control group and treated group compared with the normal group (p<0.01);Positive expression of HSP27in retina tissue was increased in the treated group compared with the control group at2weeks and4weeks(p <0.05),but there was no significant difference at8weeks (p>0.05)Conclusion:1.PKC activity in cytomembrane and the expression of the HSP27enhanced in diabetic rats retinal.2.The application of catechin can restrain the PKC activity in the diabetic rats retinal tissue and stimulate the expression of HSP27in the early stage of diabetic retinopathy3.The application of catechin can reduce blood glucose level in diabetic rats and improve the symptoms such as polydipsia,polyphagia,polyuria and weight loss.4.Catechin can delay the development of diabetic retinopathy and has a certain treatment function on diabetic retinopathy. |
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