Inhibitory effect of insulin-like growth factor binding protein-related protein 1 on retinal angiogenesis via ERK signaling pathway

Abstract

Objective: To explore the inhibitory effect of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1), a novel anti-angiogenic factor, on retinal angiogenesis and its underlying molecular mechanisms. Methods: Experimental study. C57BL/6J mice were classified into three groups: control group (n=24), oxygen-induced retinopathy (OIR) non-intervention group (n=24) and OIR intervention group (n=72). The OIR mouse model was established using improved Smith's methods (n= 96). Twelve-day-old mice in the OIR intervention group were randomly assigned into three groups receiving intravitreal injection of recombinant mouse IGFBP-rP1 (50 μg/L, 100 μg/L and 200 μg/L, respectively). Five days later, the proliferative neovascular responses were estimated by quantifying the new vessel area relative to the total retinal area in flattening retinas stained by high molecular FITC-Dextran and counting the number of neovascular cell nuclei breaking through the internal limiting membrane (ILM) in cross-sections. Retinal phosphor-ERK1/2 (p-ERK1/2), ERK1/2 and vascular endothelial growth factor (VEGF) protein expression was assessed by Western blot. Results: In the fluorescence angiograms, irregular neovascularization and fluorescence leakage were observed in the OIR model. In the OIR non-intervention group, the expression of p-ERK1/2 and VEGF was significantly up-regulated in comparison with the control group (t=100.068, P=0.000. t=6.526, P=0.003). The area ratios of new retinal vessels and the number of neovascular cell nuclei in mice receiving intravitreal injection of recombinant mouse IGFBP-rP1 both decreased significantly (F=1920, P=0.000. F=852.387, P=0.000), following the down-regulation of retinal p-ERK1/2 protein expression (F=859.587, P=0.000) and VEGF protein expression (F=24.301, P= 0.000) in a dose-dependent manner (P<0.05). There was no significant difference in ERK1/2 protein expression (P>0.05). Conclusions: IGFBP-rP1 inhibits retinal angiogenesis by blocking ERK signaling pathway and down-regulating VEGF expression. This highlights the potential importance of IGFBP-rP1 serving as a target of gene therapy for retinal neovascularization. (Chin J Ophthalmol, 2017, 53: 207-211).