| Objective: Diabetes is one of the most popular chronic disease in clinic.With the improvement of people’s material standard of living, the unhealthylife style which is mainly characterized by overnutrition, lack of exercises,overweight and obesity increasingly popular. The incidence and mortality ratesof Diabetes have shown a gradual increase over the past few years. Diabeteshas became the third leading cause of death after cancer and cardiovasculardisease. Diabetic retinopathy (DR) which is one of the most commonmicrangium complications of diabetes has caused more than10,000people ofblindness each year. The pathogenesis of DR is very complex and has not beenelucidated completely so far. In recent years, many studies suggest thatoxidative stress is a common pathway of chronic complications in thedevelopment and progression of diabetes. In high glucose condition in vivo,the system of peroxidation and antioxidation has been destroyed, theabsorbance capacity of oxygen radical has been declined, tissue and cells havebeen injured. Retina tissue which is rich in polyunsaturated fatty acids makesthe highest intake of the oxygen molecules in the blood. Consequently, it ismore sensitive to oxidative stress. The breakdown of the blood-retinal barrierand neovascularization of retina are the fundamental pathology characteristicsof DR. The development and progression of novascularization is a challengein clinic. It could cause vitreous hemorrhage and retina detachment latterly,and result in progressive deterioration of vision. Vascular endothelial growthfactor (VEGF) and pigment epithelium-derived factor (PEDF) wererespectively considered as the typical representative of vascular systemstimulating factor and vascular system inhibiting factor. The balance betweenthe two is crucial to the neovascularization. Studies have shown that high glucose could change the expression of VEGF and PEDF which retinalpigment epithelium (RPE) cells secreted, and promote the proliferation of RPEcells. With the exploration of oxidative stress and cytokine theory in thepathogenesis of DR, we believe that looking for more effective antioxidantdrugs and recovering the balance between vascular system stimulating factorand vascular system inhibiting factor is essential to improving the the qualityof life for patients. lipoic acid (LA) is rich in a variety of food. As a powerfulantioxygen, it is widely used. In our experiment, different concentrations ofalpha-lipoic-acid(α-LA) effect human retinal pigment epithelial (HRPE)cells48hours cultured with high glucose in vitro, in order to investigate thechanges of cell morphology, cell activity, oxidative stress levels and theexpression of VEGF and PEDF. Then we study the protective effect of α-LAto HRPE cells in high glucose and further explorer the effect and mechanismsof α-LA on DR.Methods: The HRPE cells were cultured and randomly divided intoseven groups:(1) normal control group (glucose5.56mmol/L),(2) highglucose group (glucose30mmol/L),(3) mannitol contorl group (5.56mmol/Llow glucose and24.44mmol/L mannitol),(4) α-LA-treated group: highglucose30mmol/L and α-LA50μmol/L,(5) α-LA-treated group: highglucose30mmol/L and α-LA100μmol/L,(6) α-LA-treated group: highglucose30mmol/L and α-LA200μmol/L,(7)α-LA-treated group: highglucose30mmol/L and α-LA300μmol/L. They were exposed toexperimental conditions for48hours. The cells of exponential phase ofgrowth were harvested for the following experiment. The effect of α-LA onthe cell activity in high glucose was observed by MTT assay, themalondialdehyde(MDA), superoxide dismutase(SOD) and glutathione(GSH)are measured by colorimetry, the level of VEGF and PEDF was measured byenzyme-linked immunosorbent assay (ELISA).Results:1Compared with normal control group, the cell viability of HRPE cellscultured by high glucose was significantly inhibited (P <0.05), there was no significant difference in cell viability between mannitol control group andnormal control group, α-LA(50,100,200,300μmol/L)can significantlyincrease the cell viability of HRPE cells cultured by high glucose in adose-dependent manner (P <0.05).2Compared with normal control group, after cultured by high glucose,the expression of MDA content was significantly increased (P<0.05), whileSOD, GSH levels were obviously reduced (P<0.05), mannitol did not affectthose indexes; after intervened by α-LA, compared with the high glucosegroup, the expression activity of SOD, GSH were increased(P<0.05), theMDA level was decreased. The changes are obviously different from highglucose group in a dose-dependent manner.The difference has statisticalsignificance between α-LA-treated groups and the normal controlgroup(P<0.05).3Compared with normal control group, the VEGF level significantlyincreased and PEDF significantly decreased in high glucose group; mannitoldid not affect the expression of target protein, α-LA (50,100,200,300μmol/L)significantly decreased the expression of VEGF protein and increased PEDFprotein in a dose-dependent manner(P＜0.05), The difference has statisticalsignificance between α-LA-treated groups and the normal control group(P＜0.05).Conclusion:1High glucose can decrease the cell viability of HRPE cells, enhance thelevel of oxidative stress, and can lead to increase VEGF secreted by HRPEcells and decrease PEDF then take part in DR.2A certain concentration of α-LA may inhibit the oxidative stress level ofHRPE cells, reduce the secretion of VEGF and increased PEDF secretion. Itmay play a protective role in HRPE cells injury caused by high glucose. α-LAcould inhibit the oxidative stress level so that it could inhibit DR pathologicalneovascularization through regulating the balance between VEGF and PEDF.So it provides a theoretical basis of α-LA to clinical application. |
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