ABSTRACT
Background The special pathological change of diabetic retinopathy(DR)is microvascular disorder.Angiopoietin-like protein 2(Ang-2)is a new protein associated with genesis of blood vessels.Quercetin has multiple pharmacological action,including improving the microcircularion and the permeability of blood capillary.However,the action mechanism of Ang-2 on DR was unclear.Objective The present study was to investigate the effects of quercetin on Ang-2 and its receptor Tie2 expression in retina with diabetes mellitus.Methods Sixty clean male Wistar rats were randomized into 7 groups and 10 rats for each group,and 10 rats served as blank control group.Streptozotocin of 35 mg/kg was intraperitoneally injected in 60 rats to establish the diabetic models.Quercetins encapsulated by liposome with the doses of 50,150 and 250 mg/(kg · d)(3-5 ml)were used to gavage in different groups of models for 12 weeks,and normal saline solution and calcium dobesilate were used at the same fashion as the negative control group and positive control group,respectively.Twelve weeks later,the animals were sacrificed and retinas were isolated.Expressions of Ang-2 protein and Tie2 mRNA in retinas were detected by ELISA and RT-PCR,respectively.The usage and rearing of the animals complied with the Regulations for the Administration of Affair Concerning Experimental Animals by State Sciences and Technology Commission.Results ELISA showed that the A450 of Ang-2 in 150 and 250 mg/(kg · d)quercetin groups was 0.796±0.057 and 0.842±0.043 respectively and was lower than that negative group(1.012±0.046),showing statistically significant differences(q =2.95,2.698,P＜0.05).RT-PCR assay showed that expression of Tie2 mRNA(Tie2 mRNA/GAPDH mRNA)in retinas was 0.712±0.092 and 0.821±0.087,presenting statistically significant differences in comparison with negative group(1.182±0.098)(q =3.497,2.852,P＜0.05).The expression levels of Ang-2 and Tie2 mRNA in retina were lowest in 150 mg/(kg · d)quercetin group.Conclusions Quercetin can improve the retinal microcirculation by downregulating the expressions of Ang-2 and its receptor in early period of diabetic rats.