Objective:To investigate the ameliorate effect and underlying mechanism of Xueshuantong for Injection (Lyophilized,注射用血栓通,XST) in streptozocin (STZ)-induced diabetic retinopathy (DR) rats.Methods:Diabetes mellitus (DM) model was induced by intraperitoneal (i.p.) injection of STZ (60 mg/kg) in Sprague-Dawley rats.Diabetic rats were randomized into 3 groups (n=10) according to a random number table,including DM,XST50 and XST100 groups.XST treatment groups were daily i.p.injected with 50 or 100 mg/kg XST for 60 days,respectively.The control and DM groups were given i.p.injection with saline.Blood glucose level and body weight were recorded every week.Histological changes in the retina tissues were observed with hematoxylin-eosin staining.Apoptosis and inflammation related factors,including cleaved caspase-3,glial fibrillary acidic protein (GFAP),tumor necrosis factor-α (TNF-α) and intercellular cell adhesion molecule-1 (ICAM-1) were detected by Western blot or real-time polymerase chain reaction.Then,the levels of advanced glycation end product (AGE) and its receptor (RAGE) were investigated.Tight junctions proteins(Zonula occludens-1 (ZO-1),Occludin and Claudin-5) of blood-retinal barrier were detected by Western blot.The levels of retinal fibrosis,transforming growth factor-β 1 (TGF-β 1)-Smad2/3 signaling pathway were evaluated at last.Results:There was no significant difference in the body weight and blood glucose level between XST and DM groups (P＞0.05).Compared with the DM group,XST treatment significantly increased the retinal thickness of rats (P＜0.05 or P＜0.01),and suppressed cleaved caspase-3 expression (P＜0.01).XST increased the protein expressions of ZO-1,Occludin and Claudin-5 and decreased the mRNA expressions of matrix metalloproteinase 2(MMP-2) and MMP-9 (P＜0.05 or P＜0.01).Moreover,XST significantly reduced the productions of AGE and RAGE proteins in the retina of rats (P＜0.05 or P＜0.01),suppressed the over-expression of TNF-α,and decreased the elevated level of ICAM-1 in retina of rats (P＜0.05 or P＜0.01).XST significantly reduced the levels of α-smooth muscle actin (α-SMA),connective tissue growth factor (CTGF),TGF-β 1 and phosphorylation of Smad2/3 protein in rats (P＜0.05 or P＜0.01).Conclusions:XST had protective effects on DR with possible mechanisms of inhibiting the inflammation and apoptosis,up-regulating the expression of tight junction proteins,suppressing the productions of AGE and RAGE proteins,and blocking the TGF-β /Smad2/3 signaling pathway.XST treatment might play a role for the future therapeutic strategy against DR.