Laser-induced Choroidal Neovascularization Mouse Research Articles

The Antiangiogenic Effects of Gold Nanoparticles on Experimental Choroidal Neovascularization in Mice.

The purpose of this study was to evaluate the antiangiogenic effect of gold nanoparticles (AuNPs) on experimental choroidal neovascularization (CNV) in mice. Choroidal neovascularization was induced by rupturing the Bruch's membrane using laser photocoagulation in C57BL/6 mice. The following day, intravitreal injections of AuNPs were administered. The control group received PBS injection of the same volume. Two weeks after laser injury, CNV lesions were evaluated by examination of choroidal flat-mounts using fluorescein-labeled dextran and immunofluorescence staining with isolectin B4. The effects of AuNPs on endothelial cell tube formation, proliferation, and cytotoxicity were evaluated using human umbilical vein endothelial cells (HUVECs) or human RPE cells. The activity of extracellular signal-regulated kinase (ERK)1/2, protein kinase B (Akt), and focal adhesion kinase (FAK) signaling pathways was also analyzed. The AuNPs reduced the extent of CNV. Mice treated with intravitreal AuNPs injections exhibited a 67.9% reduction in the extent of CNV lesions compared with the control group (P < 0.001). The size of the isolectin B4-labeled area was also significantly smaller in AuNP-treated groups compared with the control group (P < 0.001). Gold nanoparticles decreased vascular endothelial growth factor-induced HUVEC tube formation and proliferation but showed no RPE cell toxicity with the treatment doses administered. The phosphorylation of ERK1/2, Akt, and FAK in HUVECs was suppressed by AuNPs. Gold nanoparticles can inhibit laser-induced CNV in mice and may have an indication for the treatment of CNV.

Thy-1 Regulates VEGF-Mediated Choroidal Endothelial Cell Activation and Migration: Implications in Neovascular Age-Related Macular Degeneration.

PurposeThis study addresses the hypothesis that age-related stresses upregulate Thy-1 in choroidal endothelial cells (CECs) and contribute to CEC activation and migration, processes important in choroidal neovascularization (CNV).MethodsMeasurements were made of Thy-1 protein (Western blot) in CECs and Thy-1 mRNA (real time quantitative PCR) in CECs treated with VEGF, CCL11, or PBS or in RPE/choroids from young or old donors or lasered or nonlasered mice. Immunolabeled Thy-1 in ocular sections was compared from young versus old human donor eyes or those with or without neovascular AMD or from lasered versus nonlasered mice. Choroidal endothelial cells transfected with Thy-1 or control siRNA or pretreated with Thy-1 blocking peptide or control were stimulated with VEGF or 7-ketocholesterol (7-KC). Choroidal endothelial cell migration, proliferation, cytoskeletal stress fibers, Rac1 activation, and phosphorylated VEGF receptor 2 (VEGFR2), integrin β3, and Src were measured. Statistics were performed using ANOVA.ResultsThy-1 was expressed in retinal ganglion cells and in vascular endothelial-cadherin–labeled choroid and localized to human or mouse laser-induced CNV lesions. Thy-1 protein and mRNA were significantly increased in CECs treated with VEGF or CCL11 and in RPE/choroids from aged versus young donor eyes or from lasered mice versus nonlasered controls. Knockdown or inhibition of Thy-1 in CECs significantly reduced VEGF-induced CEC migration and proliferation, stress fiber formation and VEGFR2, Src, integrin β3 and Rac1 activation, and 7-KC–induced Rac1 and Src activation.ConclusionsThy-1 in CECs regulates VEGF-induced CEC activation and migration and links extracellular 7-KC to intracellular signaling. Future studies elucidating Thy-1 mechanisms in neovascular AMD are warranted.

Tissue Plasminogen Activator as an Antiangiogenic Agent in Experimental Laser-Induced Choroidal Neovascularization in Mice.

We investigate the antiangiogenic efficacy of tissue plasminogen activator (tPA) on experimental laser-induced choroidal neovascularization (CNV) in mice. After CNV was induced by laser photocoagulation in 92 C57BL/6J wild-type mice, tPA (4 or 40 international units [IU]/μl) or PBS was injected intravitreally immediately after laser injury. Fluorescein angiography was performed on day 7 to grade CNV leakage. The CNV volume was measured by confocal microscopy in eyes enucleated 7 days after laser injury. Immunohistochemical studies were performed 3 days after laser injury to evaluate fibrin/fibrinogen and CD31 expression. The possible adverse effects of tPA were assessed by electroretinography (ERG) and histology on day 7. Intravitreal administration of tPA significantly suppressed CNV leakage and CNV volume in a dose-dependent manner (P < 0.01). Intravitreal injection of tPA suppressed fibrin/fibrinogen and CD31 expression in laser-induced lesions. Histologic examination and ERG showed no evidence of retinal toxicity in eyes injected with tPA. Intravitreal injection of tPA suppressed fibrin/fibrinogen expression and laser-induced CNV. The current results suggested that tPA may be a potential therapeutic adjuvant for treating CNV.

Visible-Light Optical Coherence Tomography Angiography for Monitoring Laser-Induced Choroidal Neovascularization in Mice.

PurposeThis study sought to determine the earliest time-point at which evidence of choroidal neovascularization (CNV) could be detected with visible-light optical coherence tomography angiography (vis-OCTA) in a mouse model of laser-induced CNV.MethodsVisible light-OCTA was used to study laser-induced CNV at different time-points after laser injury to monitor CNV development and measure CNV lesion size. Measurements obtained from vis-OCTA angiograms were compared with histopathologic measurements from isolectin-stained choroidal flatmounts.ResultsChoroidal neovascularization area measurements between the vis-OCTA system and isolectin-stained choroidal flatmounts were significantly different in area for days 2 to 4 postlaser injury, and were not significantly different in area for days 5, 7, and 14. Choroidal neovascularization area measurements taken from the stained flatmounts were larger than their vis-OCTA counterparts for all time-points. Both modalities showed a similar trend of CNV size increasing from the day of laser injury until a peak of day 7 postlaser injury and subsequently decreasing by day 14.ConclusionsThe earliest vis-OCTA can detect the presence of aberrant vessels in a mouse laser-induced CNV model is 5 days after laser injury. Visible light-OCTA was able to visualize the maximum of the CNV network 7 days postlaser injury, in accordance with choroidal flatmount immunostaining. Visible light-OCTA is a reliable tool in both detecting the presence of CNV development, as well as accurately determining the size of the lesion in a mouse laser-induced CNV model.

Inhibition of RACK1 ameliorates choroidal neovascularization formation in vitro and in vivo

Choroidal neovascularization (CNV) occurs as a result of age-related macular degeneration (AMD) and causes severe vision loss among elderly patients. The receptor for activated C-kinase 1 (RACK1) serves as a scaffold protein which is recently found to promote angiogenesis. However, the impact of RACK1 on the vascular endothelial growth factor (VEGF) expression in endothelial cells and subsequent choroidal angiogenesis formation remains to be elucidated. In this study, we found that RACK1 and VEGF expression increased, and reached the peak at 7d in mouse CNV model by laser application. Furthermore, on RPE/choroid cryosections, RACK1 co-localized with CD31, suggesting that RACK1 was expressed in endothelial cells. In vitro, RF/6A cell hypoxia model showed that RACK1 expression was up-regulated in parallel with hypoxia-induced factor 1 (HIF-1α) and VEGF expression, reaching the peak at 6h. Silencing of RACK1 suppressed the invasion and tube formation activity of RF/6A cells in ARPE-19 and RF/6A co-culture system, possibly through VEGF signal pathway. Overexpression of RACK1 showed the opposite effect. Intravitreal injection of anti-RACK1 monoclonal antibody predominantly decreased RACK1 and VEGF expression in mouse laser-induced CNV model. Meanwhile, anti-RACK1 monoclonal antibody intravitreal injection also decreased incidence of CNV and leakage area. These data indicated that RACK1 promoted CNV formation via VEGF pathway. Additionally, anti-RACK1 monoclonal antibody significantly decreased CNV in mouse model and may have therapeutic potential in human CNV.

Edaravone is a free radical scavenger that protects against laser-induced choroidal neovascularization in mice and common marmosets

Choroidal neovascularization (CNV) is a main characteristic in exudative type of age-related macular degeneration (AMD). Our study aimed to evaluate the effects of edaravone, a free radical scavenger on laser-induced CNV. CNV was induced by laser photocoagulation to the subretinal choroidal area of mice and common marmosets. Edaravone was administered either intraperitoneally twice a day for 2 weeks or intravenously just once after laser photocoagulation. The effects of edaravone on laser-induced CNV were evaluated by fundus fluorescein angiography, CNV area measurements, and the expression of 4-hydroxy-2-nonenal (4-HNE) modified proteins, a marker of oxidative stress. Furthermore, the effects of edaravone on the production of H2O2-induced reactive oxygen species (ROS) and vascular endothelial growth factor (VEGF)-induced cell proliferation were evaluated using human retinal pigment epithelium cells (ARPE-19) and human retinal microvascular endothelial cells, respectively. CNV areas in the edaravone-treated group were significantly smaller in mice and common marmosets. The expression of 4-HNE modified proteins was upregulated 3 h after laser photocoagulation, and intravenously administered edaravone decreased it. In in vitro studies, edaravone inhibited H2O2-induced ROS production and VEGF-induced cell proliferation. These findings suggest that edaravone may protect against laser-induced CNV by inhibiting oxidative stress and endothelial cell proliferation.

A Mouse Model for Laser-induced Choroidal Neovascularization.

The mouse laser-induced choroidal neovascularization (CNV) model has been a crucial mainstay model for neovascular age-related macular degeneration (AMD) research. By administering targeted laser injury to the RPE and Bruch's membrane, the procedure induces angiogenesis, modeling the hallmark pathology observed in neovascular AMD. First developed in non-human primates, the laser-induced CNV model has come to be implemented into many other species, the most recent of which being the mouse. Mouse experiments are advantageously more cost-effective, experiments can be executed on a much faster timeline, and they allow the use of various transgenic models. The miniature size of the mouse eye, however, poses a particular challenge when performing the procedure. Manipulation of the eye to visualize the retina requires practice of fine dexterity skills as well as simultaneous hand-eye-foot coordination to operate the laser. However, once mastered, the model can be applied to study many aspects of neovascular AMD such as molecular mechanisms, the effect of genetic manipulations, and drug treatment effects. The laser-induced CNV model, though useful, is not a perfect model of the disease. The wild-type mouse eye is otherwise healthy, and the chorio-retinal environment does not mimic the pathologic changes in human AMD. Furthermore, injury-induced angiogenesis does not reflect the same pathways as angiogenesis occurring in an age-related and chronic disease state as in AMD. Despite its shortcomings, the laser-induced CNV model is one of the best methods currently available to study the debilitating pathology of neovascular AMD. Its implementation has led to a deeper understanding of the pathogenesis of AMD, as well as contributing to the development of many of the AMD therapies currently available.

Anti-angiogenic effect of ALS-L1023, an extract of Melissa officinalis L., on experimental choroidal neovascularization in mice.

The effect of ALS-L1023, an extract of Melissa officinalis L. (Labiatae; lemon balm) leaves, on experimental choroidal neovascularization (CNV) in mice was evaluated. C57BL/6 mice were given either vehicle or ALS-L1023 daily via oral gavage for 3 weeks (days 0-21). CNV was induced by rupturing Bruch's membrane using laser photocoagulation (day 7). Two weeks after laser injury (day 21), the CNV lesions were evaluated by an examination of choroidal flat mounts using fluorescein-labelled dextran, immunofluorescence staining with isolectin B4 and fluorescence angiography. The effects of ALS-L1023 on endothelial cell tube formation and the expression of phosphorylated extracellular signal-regulated kinase 1/2 were evaluated using human umbilical vein endothelial cells. The extent of CNV was reduced by ALS-L1023. Mice treated with 100 and 200 mg/kg/day of the material exhibited 44.3 and 68.1% reductions in the extent of CNV lesions, respectively, compared to the vehicle group (P < 0.001). The size of the isolectin B4-labelled area was also significantly decreased in the ALS-L1023-treated groups (P < 0.001). On fluorescein angiography, ALS-L1023-treated mice exhibited significantly less leakage of fluorescent material than did vehicle-treated mice. ALS-L1023 decreased vascular endothelial growth factor-induced human umbilical vein endothelial cell tube formation in a dose-dependent manner. The expression of phosphorylated extracellular signal-regulated kinase 1/2 was suppressed by ALS-L1023. The laser-induced CNV in mice can be inhibited by ALS-L1023. Therefore, it may have therapeutic potential for the treatment of diseases involving CNV.

Optimization of an Image-Guided Laser-Induced Choroidal Neovascularization Model in Mice.

The mouse model of laser-induced choroidal neovascularization (CNV) has been used in studies of the exudative form of age-related macular degeneration using both the conventional slit lamp and a new image-guided laser system. A standardized protocol is needed for consistent results using this model, which has been lacking. We optimized details of laser-induced CNV using the image-guided laser photocoagulation system. Four lesions with similar size were consistently applied per eye at approximately double the disc diameter away from the optic nerve, using different laser power levels, and mice of various ages and genders. After 7 days, the mice were sacrificed and retinal pigment epithelium/choroid/sclera was flat-mounted, stained with Isolectin B4, and imaged. Quantification of the area of the laser-induced lesions was performed using an established and constant threshold. Exclusion criteria are described that were necessary for reliable data analysis of the laser-induced CNV lesions. The CNV lesion area was proportional to the laser power levels. Mice at 12-16 weeks of age developed more severe CNV than those at 6-8 weeks of age, and the gender difference was only significant in mice at 12-16 weeks of age, but not in those at 6-8 weeks of age. Dietary intake of omega-3 long-chain polyunsaturated fatty acid reduced laser-induced CNV in mice. Taken together, laser-induced CNV lesions can be easily and consistently applied using the image-guided laser platform. Mice at 6-8 weeks of age are ideal for the laser-induced CNV model.

Intravitreal inhibition of complement C5a reduces choroidal neovascularization in mice.

To investigate the influence of complement component C5a inhibition on laser-induced choroidal neovascularization (CNV) in mice using a C5a specific L-aptamer. In C57BL/6 J mice CNV was induced by argon-laser, C5a-inhibitor (NOX-D20) was intravitreally injected in three concentrations: 0.3, 3.0, and 30 mg/ml. The unPEGylated derivate (NOX-D20001) was applied at 3.0 mg/ml; the vehicle (5 % glucose) was injected in controls. Vascular leakage was evaluated using fluorescence angiography, CNV area was examined immunohistochemically. Activated immune cells surrounding the CNV lesion and potential cytotoxicity were analyzed. Compared to controls, CNV areas were significantly reduced after NOX-D20 injection at a concentration of 0.3 and 3.0 mg/ml (p = 0.042; p = 0.016). NOX-D20001 significantly decreased CNV leakage but not the area (p = 0.007; p = 0.276). At a concentration of 30 mg/ml, NOX-D20 did not reveal significant effects on vascular leakage or CNV area (p = 0.624; p = 0.121). The amount of CD11b positive cells was significantly reduced after treatment with 0.3 and 3.0 mg/ml NOX-D20 (p = 0.027; p = 0.002). No adverse glial cell proliferation or increased apoptosis were observed at effective dosages. Our findings demonstrate that the targeted inhibition of complement component C5a reduces vascular leakage and neovascular area in laser-induced CNV in mice. NOX-D20 was proven to be an effective and safe agent that might be considered as a therapeutic candidate for CNV treatment. The deficiency of activated immune cells highlights promising new aspects in the pathology of choroidal neovascularization, and warrants further investigations.

The effect of triamcinolone acetonide on laser-induced choroidal neovascularization in mice using a hypoxia visualization bio-imaging probe.

Hypoxic stress is a risk factor of ocular neovascularization. Hypoxia visualization may provide clues regarding the underlying cause of angiogenesis. Recently, we developed a hypoxia-specific probe, protein transduction domain-oxygen-dependent degradation domain-HaloTag-Rhodamine (POH-Rhodamine). In this study, we observed the localization of HIF-1α proteins by immunohistochemistry and the fluorescence of POH-Rhodamine on RPE-choroid flat mounts. Moreover, we compared the localization of POH-Rhodamine with pimonidazole which is a standard reagent for detecting hypoxia. Next, we investigated the effects of triamcinolone acetonide (TAAC) against visual function that was evaluated by recording electroretinogram (ERG) and choroidal neovascularization (CNV) development. Mice were given laser-induced CNV using a diode laser and treated with intravitreal injection of TAAC. Finally, we investigated POH-Rhodamine on CNV treated with TAAC. In this study, the fluorescence of POH-Rhodamine and HIF-1α were co-localized in laser-irradiated sites, and both the POH-Rhodamine and pimonidazole fluorescent areas were almost the same. Intravitreal injection of TAAC restored the reduced ERG b-wave but not the a-wave and decreased the mean CNV area. Furthermore, the area of the POH-Rhodamine-positive cells decreased. These findings indicate that POH-Rhodamine is useful for evaluating tissue hypoxia in a laser-induced CNV model, suggesting that TAAC suppressed CNV through tissue hypoxia improvement.

AAV2 Delivery of Flt23k Intraceptors Inhibits Murine Choroidal Neovascularization

Long-term inhibition of extracellular vascular endothelial growth factor (VEGF) in the treatment of age-related macular degeneration (AMD) may induce retinal neuronal toxicity and risk other side effects. We developed a novel strategy which inhibits retinal pigment epithelium (RPE)-derived VEGF, sparing other highly sensitive retinal tissues. Flt23k, an intraceptor inhibitor of VEGF, was able to inhibit VEGF in vitro. Adeno-associated virus type 2 (AAV2)-mediated expression of Flt23k was maintained for up to 6 months postsubretinal injection in mice. Flt23k was able to effectively inhibit laser-induced murine choroidal neovascularization (CNV). VEGF levels in the RPE/choroid complex decreased significantly in AAV2.Flt23k treated eyes. Neither retinal structure detected by Heidelberg Spectralis nor function measured by electroretinography (ERG) was adversely affected by treatment with AAV2.Flt23k. Hence AAV2.Flt23k can effectively maintain long-term expression and inhibit laser-induced CNV in mice through downregulation of VEGF while maintaining a sound retinal safety profile. These findings suggest a promising novel approach for the treatment of CNV.

Effects of transforming growth factor-β on the laser-induced choroidal neovascularization in mice

Objective To investigate the effects of transforming growth factor-β (TGF-β) in choroidal neovascularization (CNV) induced by laser in mice.Methods Eighty male C57BL/6J mice at the age of 6-8 weeks old were randomly divided into the normal control,photocoagulation model,photocoagulation with phosphate buffered saline (PBS control group) and photocoagulation with TGF-β receptor inhibitor groups (TGF-β receptor inhibitor group),twenty mice of each group.Fundus argon laser photocoagulation was performed in the photocoagulation model group,PBS control group and TGF-β receptor inhibitor group to induce CNV.One week,two,three and four weeks after the laser procedure,fundus fluorescein angiography (FFA) was carried out in the normal control or photocoagulation model groups to observe CNV formation dynamically.Western blot was used to analyze the expressions of TGF-β in the retina from the mice of normal control or photocoagulation model groups,and VEGF or TNF-α in the retina of normal control,PBS control or TGF-β receptor inhibitor groups.The CNV areas of each group were evaluated by using fluorescein stain on retinal pigment epithelium (RPE)/choroid flat mounts after two weeks of photocoagulation.Results The FFA results showed the retinal vessels centered on the optic disc and arranged radially,while the choroidal vascular present network distribution in the normal control mice.Significant leakage of fluorescein showed discoid strong fluorophore in photocoagulation sites of retina at one week after photocoagulation.The quantitative analysis results of Western blot demonstrated that the TGF-β protein expression levels in retina of photocoagulation model mice gradually increased with time passing.The protein expression levels of TGF-β were significant differences in the photocoagulation model group comparing with the normal control group (F=13.042,P＜0.05).The protein expression levels of TNF-α (F=14.721,17.509) and VEGF (F=18.890,11.251) increased significantly in retina of PBS control or TGF-β receptor inhibitor groups when compared with that of normal control group at one week,two,three and four weeks after photocoagulation,and the differences were both statistically significant (P＜0.05).Compared with PBS control group,the protein levels of TNF-α and VEGF in retina from TGF-β receptor inhibitor group were significantly reduced,the differences was statistically significant (F=21.321,16.160,P＜0.05).Two weeks after laser photocoagulation,a distinct reduction in CNV lesion size in the TGF-β receptor inhibitor group mice when compared to PBS or normal control groups,the differences was statically significant (F=4.482,P＜0.05).Conclusion TGF β may promote CNV formation by up-regulating both TNF α and VEGF protein expressions,the application of its specific inhibitor is able to reduce CNV progression. Key words: Choroidal neovascularization/physiopathology; Transforming growth factor beta/ agonists; Tumor necrosis factor-alpha; Vascular endothelial growth factors; Animal experimentation

Interleukin-18 induces retinal pigment epithelium degeneration in mice.

To examine the effectiveness of interleukin-18 (IL-18) on choroidal neovascularization (CNV) and retinal pigment epithelium (RPE) in humans and mice. Serum IL-18 levels in patients with wet and dry AMD who were older than 50 years were measured and compared with those of age-matched controls. In mice, laser photocoagulation was performed in the retina to induce experimental CNV, and CNV volume was measured in eyes injected with recombinant IL-18 (rIL-18) and IL-18 neutralizing antibody (nIL-18Ab) compared with those injected with control. Tube formation assay was performed on human retinal endothelial cells (HREC) with rIL-18 administration in vitro. After subretinal injection of rIL-18, fundus change in the injected eyes was evaluated; active caspase-3 level was measured in the RPE/choroid complex, and tight junction integrity in RPE was visualized by zonula occludens-1 (ZO-1) staining. Serum IL-18 levels in dry AMD patients were higher than those in control. Mouse rIL-18 or nIL-18Ab did not induce significant change in CNV volume compared with controls or change tube formation in HREC. Subretinal injection of rIL-18 induced retinal degeneration in the mice fundus; ZO-1 staining showed considerably disturbed RPE structure, and active caspase-3 expression was significantly higher after rIL-18 induction. Interleukin-18 did not show a pro- or antiangiogenic effect on mouse laser-induced CNVs (laser-CNVs), whereas it directly induced RPE cell apoptosis in the mouse eye. Our results suggested that IL-18 is associated with dry AMD, but not with wet AMD.

Blockage of tissue factor ameliorates the lesion of laser-induced choroidal neovascularization in mice

Choroidal neovascularization (CNV) occurs as a result of age-related macular degeneration (AMD) and causes severe vision loss among elderly patients. High expression of tissue factor (TF) was found in the retinas of AMD patients. In this study, we used anti-TF monoclonal antibody to test the effect of the TF blockage on experimental CNV induced by laser photocoagulation of retina in mice. Anti-TF monoclonal antibody or vehicle was administered intravitreally at day 1, 2 or 3 after laser application. We found that TF expression increased, and reached the peak at the 3rd week after the after laser application. Anti-TF monoclonal antibody can predominantly decrease the expression of TF, VEGF and F4/80, and reduced the area of CNV. Anti-TF monoclonal antibody also decreased incidence of CNV and leakage area. There were no pathological changes in the liver, heart, brain or kidney tissue. We conclude that TF plays an important role in CNV and anti-TF monoclonal antibody significantly decreases CNV in mouse model and anti-TF monoclonal antibody may have therapeutic potential in AMD.

Suppression of choroidal neovascularization through inhibition of APE1/Ref-1 redox activity.

The redox function of APE1/Ref-1 is a key regulator in pathological angiogenesis, such as retinal neovascularization and tumor growth. In this study, we examined whether inhibition of APE1/Ref-1 redox function by a small molecule inhibitor E3330 suppresses experimental choroidal neovascularization (CNV) in vitro and in vivo. Primate choroid endothelial cells (CECs) received treatment of 0 to 100 μM E3330 alone or cotreatment of E3330 and 500 μg/mL anti-VEGF antibody bevacizumab. Choroid endothelial cell angiogenic function was examined by cell proliferation, migration, and tube formation assays. The effects of E3330 on NF-κB and STAT3 signaling pathways were determined by reporter gene assay, Western blot, and ELISA. Laser-induced CNV mouse model was used to test the effects of E3330 in vivo. Potential toxicity of E3330 was evaluated by TUNEL assay. The E3330 of 25 to 100 μM dose-dependently suppressed CEC proliferation, migration, and tube formation, in the absence of noticeable cell toxicity. Lower doses of E3330 (10-20 μM) reduced the transcriptional activity of NF-κB and STAT3 without affecting protein phosphorylation of both molecules. At the same time, E3330 downregulated MCP-1 production in CECs. The antiangiogenic effect of E3330 was comparable and additive to bevacizumab. The E3330 effectively attenuated the progression of laser-induced CNV in mice after a single intravitreal injection. The APE1/Ref-1 redox function regulates multiple transcription factors and inflammatory molecules, and is essential for CEC angiogenesis. Specific inhibition of APE1/Ref-1 redox function with E3330 may represent a promising novel treatment for wet AMD.

Protective role of glutathione peroxidase 4 in laser-induced choroidal neovascularization in mice.

PurposeTo evaluate the influence of glutathione peroxidase 4 (GPx4) expression in retinal pigment epithelium (RPE)/choroid tissue using a mouse model of laser-induced choroidal neovascularization (CNV).MethodsIn this study, GPx4+/−, GPx4+/+, and GPx4-overexpressing transgenic mice were created for comparison. The mRNA and protein expression of vascular endothelial growth factor (VEGF)-A in RPE/choroid tissue were evaluated before and after CNV induction by laser. Moreover, we investigated the changes in the VEGF-A mRNA level in RPE/choroid tissue in the CNV model that have not been clearly shown previously. Lipid peroxidation in RPE/choroid tissue was evaluated by immunohistochemistry using antibody against 4-hydroxy-2-nonenal. To investigate the protective role of GPx4, the size of laser-induced CNV was compared on day 7 among the mice expressing different levels of GPx4.ResultsIn the laser-induced CNV mouse model, laser treatment reduced the VEGF-A mRNA level in RPE/choroid tissue, while it increased the VEGF-A protein level. Evaluation of VEGF-A expression in RPE/choroid tissue of the GPx4+/−, GPx4+/+, and GPx4 transgenic mice revealed that GPx4 increased the VEGF-A protein level under physiological conditions (i.e., without laser treatment), while GPx4 suppressed the increase in the VEGF-A protein level under pathological conditions (i.e., after CNV induction by laser). In addition, GPx4 reduced the CNV size in a dose-dependent manner in vivo. ConclusionsGPx4 suppresses the increase in the VEGF-A protein level, which occurs during the development of pathological CNV, thus partly explaining the protective effect of GPx4 against CNV.

Angiopoietin-1 Suppresses Choroidal Neovascularization and Vascular Leakage

To investigate the role of angiopoietin-1 (Ang1) in choroidal neovascularization (CNV) and vascular leakage. We generated laser-induced CNV in mice and measured the size of CNV and vascular leakage after intravitreal administration of Ang1. The expressions and distributions of endothelial junctional proteins were analyzed using immunohistochemistry and Western blot. Moreover, we compared the sizes of CNV and vascular leakage in Ang1-overexpressing, Ang1-deficient, and their littermate control mice. In addition, following the transplantation of GFP(+) bone marrow cells into these Ang1-genetically modified mice, we evaluated the recruitment of VEGF-A producing macrophages from the bone marrow after CNV induction. Intravitreal administration of Ang1 was as effective as VEGF-Trap in inhibiting CNV formation. Furthermore, Ang1 suppressed vascular leakage by increasing endothelial junctional proteins, which was more effective than VEGF-Trap. Genetic deletion of Ang1 exacerbated, while overexpression of Ang1 suppressed CNV formation and vascular leakage. We attribute these Ang1-induced, anti-angiogenic, and anti-leakage effects to its inhibitory actions against the recruitment and infiltration of VEGF-A-producing macrophages from bone marrow into the inflammatory lesions. Ang1 supplementation can be established as a therapeutic strategy to suppress the CNV formation and vascular leakage by inhibiting the recruitment of angiogenic macrophages and tightening the endothelial junctions.

Laser-Induced Choroidal Neovascularization in Mice Attenuated by Deficiency in the Apelin-APJ System

To investigate the role of the apelin-APJ system in the development of choroidal neovascularization (CNV). Experimental CNV was induced by laser photocoagulation in wild-type (WT), apelin-deficient (apelin-KO), and apelin receptor (APJ)-deficient (APJ-KO) mice. The gene expression levels of angiogenic or inflammatory factors were determined by quantitative real-time reverse transcription-polymerase chain reaction. APJ expression in CNV lesions was examined by immunohistochemistry. The sizes of the CNV lesions in the three mouse models were measured and compared histologically using isolectin B4 staining. Macrophage recruitment was measured by flow cytometric analysis. Proliferation of endothelial cells was determined using the alamar Blue assay. Laser photocoagulation significantly increased expression of apelin and APJ in the retina-retinal pigment epithelium (RPE) complex. APJ immunoreactive cells were found in the CNV lesions and colocalized with platelet endothelial cell adhesion molecule-1, an endothelial cell marker. The sizes of the CNV lesions in apelin-KO or APJ-KO mice decreased significantly compared with those in the WT mice. Macrophages in the RPE complex of the apelin-KO mice, in which gene expression of the inflammatory factors was almost equal to that in WT mice, were recruited as a result of laser photocoagulation to the same degree as in WT mice. In addition, apelin small and interfering RNA (siRNA) suppressed proliferation of endothelial cells independently of vascular endothelial growth factor (VEGF) receptor 2 signaling, while VEGF increased expression of apelin and APJ in human umbilical vein endothelial cells. The results suggested that the apelin-APJ system contributes to CNV development partially independent of the VEGF pathway.

Oxidative Stress Sensitizes Retinal Pigmented Epithelial (RPE) Cells to Complement-mediated Injury in a Natural Antibody-, Lectin Pathway-, and Phospholipid Epitope-dependent Manner

Uncontrolled activation of the alternative complement pathway (AP) is thought to be associated with age-related macular degeneration. Previously, we have shown that in retinal pigmented epithelial (RPE) monolayers, oxidative stress reduced complement inhibition on the cell surface, resulting in sublytic complement activation and loss of transepithelial resistance (TER), but the potential ligand and pathway involved are unknown. ARPE-19 cells were grown as monolayers on transwell plates, and sublytic complement activation was induced with H2O2 and normal human serum. TER deteriorated rapidly in H2O2-exposed monolayers upon adding normal human serum. Although the effect required AP activation, AP was not sufficient, because elimination of MASP, but not C1q, prevented TER reduction. Reconstitution experiments to unravel essential components of the lectin pathway (LP) showed that both ficolin and mannan-binding lectin can activate the LP through natural IgM antibodies (IgM-C2) that recognize phospholipid cell surface modifications on oxidatively stressed RPE cells. The same epitopes were found on human primary embryonic RPE monolayers. Likewise, mouse laser-induced choroidal neovascularization, an injury that involves LP activation, could be increased in antibody-deficient rag1(-/-) mice using the phospholipid-specific IgM-C2. In summary, using a combination of depletion and reconstitution strategies, we have shown that the LP is required to initiate the complement cascade following natural antibody recognition of neoepitopes, which is then further amplified by the AP. LP activation is triggered by IgM bound to phospholipids. Taken together, we have defined novel mechanisms of complement activation in oxidatively stressed RPE, linking molecular events involved in age-related macular degeneration, including the presence of natural antibodies and neoepitopes.