Honokiol Attenuates Choroidal Neovascularization by Inhibiting the Hypoxia-Inducible Factor-α/Vascular Endothelial Growth Factor Axis via Nuclear Transcription Factor-Kappa B Activation.

PURPOSE: Honokiol is a lignan isolated from Magnolia officinalis and exhibits anti-angiogenic properties. This study was conducted to investigate the role of honokiol in choroidal neovascularization. METHODS: C57BL/6 mice were treated with honokiol at 10-20 mg/kg by daily intraperitoneal injection from day 1 to 6 after laser photocoagulation. ARPE-19 cells were cultured under hypoxic conditions with or without the presence of honokiol. After laser photocoagulation and honokiol treatment, hematoxylin and eosin staining, immunofluorescence and fundus fluorescein angiography were used to analyze the effect of honokiol on choroidal neovascularization formation. Quantitative real-time PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, luciferase assay, and chromatin immunoprecipitation were performed to explore the mechanism of honokiol in the pathological process of choroidal neovascularization. Finally, the role of honokiol on the human choroidal vascular endothelial cells was detected by using 5-ethynyl-20-deoxyuridine assay, Transwell and Tube formation assays. RESULTS: The results of hematoxylin and eosin staining and immunofluorescence suggested that honokiol reduced the thickness, length, and area of choroidal neovascularization lesions in laser-induced choroidal neovascularization mouse model. Fundus fluorescein angiography showed that choroidal neovascularization leakage was reduced in honokiol group and the concentration of 20 mg/kg showed better effects. Mechanism studies have shown that honokiol exerted inhibitory effects on choroidal neovascularization by inactivating hypoxia-inducible factor-1α/vascular endothelial growth factor axis through the nuclear transcription factor-kappa B signaling pathway. The same results were obtained in ARPE-19 cells under hypoxic conditions. Furthermore, the conditional medium of retinal pigmented epithelial cells promoted the proliferation, migration, and tube formation of human choroidal vascular endothelial cells, while honokiol reversed these. CONCLUSION: We demonstrated that honokiol attenuated choroidal neovascularization formation by inactivating the hypoxia-inducible factor-1α/vascular endothelial growth factor axis through nuclear transcription factor-kappa B signaling pathway.

Regulator of G-protein signaling 1 promotes choroidal neovascularization in age-related macular degeneration.

Background: Age-related macular degeneration (AMD) is the leading cause of blindness, and is associated with oxidative stress and the development of new blood vessels. At present, the main clinical treatment for AMD includes intraocular injection of vascular endothelial growth factor (VEGF). However, treatment includes repeated injections with significant side-effects. Therefore, new treatment options are required. The aim of the present study was to discover the new treatment target of AMD from the gene level. Methods: The Gene Expression Omnibus (GEO) database was used to analyze the differential gene expression in AMD, and the regulator of G-protein signaling 1 (RGS1) was obtained by bioassay. Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used to detect the expression levels of RGS1, VEGF, and other related molecules in human microvascular endothelial cells (HMECs) under different conditions. Cell viability, apoptosis, and proliferation of HMECs were measured by Cell Counting Kit-8 proliferation assay. Immunofluorescence and immunohistochemistry detected the interaction between RGS1, platelet endothelial cell adhesion molecule-1, and VEGF. Results: RGS1 was found to closely associated with the proliferation of vascular endothelial cells, and therefore, with angiogenesis. The expression of RGS1, VEGF, and platelet endothelial cell adhesion molecule-1 was upregulated in laser model mice and hypoxia model HMECs. Knockout of RGS1 inhibits the expression of VEGF and HMEC proliferation, thereby inhibiting AMD angiogenesis. Conclusions: Our results support the use of RGS1 as a new potential target for the future treatment of AMD.

TNF-α released from retinal Müller cells aggravates retinal pigment epithelium cell apoptosis by upregulating mitophagy during diabetic retinopathy.

Retinal pigment epithelium (RPE) cell damage, including mitophagy-associated cell apoptosis, accelerates the pathogenesis of diabetic retinopathy (DR), a common complication of diabetes that causes blindness. Müller cells interact with RPE cells via pro-inflammatory cytokines, such as tumor necrosis factor α (TNF-α). Herein, we investigated the role of the RPE cell epidermal growth factor receptor (EGFR)/p38 mitogen-activated protein kinase (p38)/nuclear factor kappa B (NF-κB) pathway in Müller cell-derived TNF-α-induced mitophagy-associated apoptosis during DR. Our results showed that TNF-α released from Müller cells activated the EGFR/p38/NF-κB/p62 pathway to increase mitophagy and apoptosis in RPE cells under high glucose (HG) conditions. Additionally, blockade of the TNF-α/EGFR axis alleviates blood-retina barrier breakdown in diabetic mice. Our data further illustrate the effects of the Müller cell inflammatory response on RPE cell survival, implying potential molecular targets for DR treatment.