Ethanol extract of Dendrobium chrysotoxum Lindl ameliorates diabetic retinopathy and its mechanism.

Diabetic retinopathy (DR) is the most common and serious complication of diabetes mellitus (DM). The present study investigates the amelioration of ethanol extract of Dendrobium chrysotoxum Lindl (DC) on streptozotocin (STZ)-induced DR and its engaged mechanism. Retinal immunofluorescence staining with cluster of differentiation 31 (CD31) demonstrated that DC (30-300 mg/kg) decreased the increased retinal vessels in STZ-induced diabetic rats. Retinal histopathological observation also showed that retinal vessels were decreased in DC-treated diabetic rats. DC decreased the increased retinal mRNA expression of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2) in diabetic rats, and DC also decreased the elevated serum VEGF level. Immunohistochemical staining further evidenced that DC decreased VEGF and VEGFR2 expression in retinas. Retinal mRNA expression of matrix metalloproteinase (MMP) 2/9 was decreased in DC (300 mg/kg)-treated diabetic rats. Serum levels of MMP 2/9, basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) A/B, insulin-like growth factor 1 (IGF-1), interleukin 1β (IL-1β), and IL-6 were all decreased in DC-treated diabetic rats. In addition, DC decreased the increased phosphorylation of p65 and the increased expression of intercellular adhesion molecule-1 (ICAM-1). In conclusion, DC can alleviate retinal angiogenesis during the process of DR via inhibiting the expression of VEGF/VEGFR2, and some other pro-angiogenic factors such as MMP 2/9, PDGF A/B, bFGF, IGF-1. In addition, DC can also ameliorate retinal inflammation via inhibiting NFκB signaling pathway.