No abstract

Background: Lactoferrin, a type of glycoprotein, is contained in exocrine fluids such as tears, breast milk, sweat, and saliva, and is known to have anti-microbial, antioxidant, and anti-cancer effects. In the ophthalmological field, topical administration of lactoferrin has been reported to have a therapeutic effect in a murine dry eye model. Hypoxia-inducible factor (HIF) regulates various gene expressions under hypoxia, including vascular endothelial growth factor (VEGF), and is considered as an alternative target for neovascular ocular diseases such as age-related macular degeneration (AMD). We previously screened natural products and identified lactoferrin as a novel HIF inhibitor. In this study, we confirmed that lactoferrin has an HIF inhibitory effect and a therapeutic effect in a murine model of neovascular AMD.Methods: HIF inhibitory effects of lactoferrin were evaluated using a luciferase assay and western blotting in vitro. The quantified volume of choroidal neovascularization (CNV) induced by laser irradiation was compared with oral lactoferrin administration or conditional tissue specific Hif1a knockout mice.Results: Lactoferrin administration showed a significant HIF inhibitory effect in the retinal neuronal cells. Oral administration of lactoferrin or conditional Hif1a gene deletion significantly reduced CNV volume compared to controls.Conclusions: Lactoferrin has a therapeutic effect in a laser CNV model by suppressing the retinal HIF activity.

Background: Age-related macular degeneration (AMD) is the leading cause of blindness and can be classified into two types called atrophic AMD (dry AMD) and neovascular AMD (wet AMD). Dry AMD is characterized by cellular degeneration of the retinal pigment epithelium, choriocapillaris, and photoreceptors. Wet AMD is characterized by the invasion of abnormal vessels from the choroid. Although anti-vascular endothelial growth factor (VEGF) therapy has a potent therapeutic effect against the disease, there is a possibility of chorio-retinal atrophy and adverse systemic events due to long-term robust VEGF antagonism. We focused on hypoxia-inducible factor (HIF) regulation of VEGF transcription, and report the suppressive effects of HIF inhibition against ocular phenotypes in animal models. Many of the known HIF inhibitors are categorized as anti-cancer drugs, and their systemic side effects are cause for concern in clinical use. In this study, we explored food ingredients that have HIF inhibitory effects and verified their effects in an animal model of AMD. Methods: Food ingredients were screened using a luciferase assay. C57BL6/J mice were administered the Garcinia cambogia extract (Garcinia extract) and hydroxycitric acid (HCA). Choroidal neovascularization (CNV) was induced by laser irradiation. Results: Garcinia extract and HCA showed inhibitory effects on HIF in the luciferase assay. The laser CNV model mice showed significant reduction of CNV volume by administering Garcinia extract and HCA. Conclusions: Garcinia extract and HCA showed therapeutic effects in a murine AMD model.

Neovascular retinal degeneration is a leading cause of blindness in advanced countries. Anti-vascular endothelial growth factor (VEGF) drugs have been used for neovascular retinal diseases; however, anti-VEGF drugs may cause the development of chorioretinal atrophy in chronic therapy as they affect the physiological amount of VEGF needed for retinal homeostasis. Hypoxia-inducible factor (HIF) is a transcription factor inducing VEGF expression under hypoxic and other stress conditions. Previously, we demonstrated that HIF was involved with pathological retinal angiogenesis in murine models of oxygen-induced retinopathy (OIR), and pharmacological HIF inhibition prevented retinal neovascularization by reducing an ectopic amount of VEGF. Along with this, we attempted to find novel effective HIF inhibitors. Compounds originally isolated from mushroom-forming fungi were screened for prospective HIF inhibitors utilizing cell lines of 3T3, ARPE-19 and 661W. A murine OIR model was used to examine the anti-angiogenic effects of the compounds. As a result, 2-azahypoxanthine (AHX) showed an inhibitory effect on HIF activation and suppressed Vegf mRNA upregulation under CoCl2-induced pseudo-hypoxic conditions. Oral administration of AHX significantly suppressed retinal neovascular tufts in the OIR model. These data suggest that AHX could be a promising anti-angiogenic agent in retinal neovascularization by inhibiting HIF activation.