Inhibition of hypoxia-inducible factor-1α and vascular endothelial growth factor by chrysin in experimental choroidal neovascularization

Abstract

Purpose: To determine the effects of a single intravitreal injection of chrysin to inhibit angiogenesis in an experimental rat model of choroidal neovascularization (CNV). Methods: A diode laser was used to break Bruch’s membrane in Brown Norway rats. One week later after laser photocoagulation, each rat was injected intravitreally with 5 µl of 15 mg/ml chrysin in the right eye and same amount of solvent solution in the left eye. The formation of CNV was evaluated according to the size and intensity of dye leakage by fluorescein angiography (FA) at 2 weeks. The effect of chrysin on CNV was assessed by FA score and histology. The expression level of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in retina/choroid complex was measured in both chrysin-treated eyes and control eyes. Results: In chrysin-treated eyes, the size and intensity of fluorescein dye leakage from CNV lesions decreased significantly compared with those in the control group (Mean CNV score, 2.34 ± 0.10 vs. 2.97 ± 0.09, p < 0.05 by unpaired t test). When each photocoagulated lesion was categorized into low or high leakage groups, the number of low leakage lesions was significantly greater in chysin-treated than in control eyes (p < 0.05, by Pearson chi-square test). The relative risk of control eyes developing high leakage lesions compared with chrysin-treated eyes was 2.03 (95% confidence interval, 1.46-2.83). The mean CVN thickness of chrysin-treated eyes was significantly thinner than that of control eyes (33.90 ± 0.89 μm vs. 38.50 ± 0.99 μm, p < 0.05 by unpaired t test). The mean HIF-1α and VEGF level in chrysin-treated eyes were significantly lower than those in control eyes (p < 0.05 in each protein analysis, by unpaired t test). Conclusion: Chrysin inhibited effectively laser-induced CNV in a rat model and downregulated HIF-1α and VEGF. Further studies are warranted to evaluate its potential as a candidate substance of therapy for wet age-related macular degeneration and other CNV associated vision-threatening conditions.