Shikonin alleviates choroidal neovascularization by inhibiting proangiogenic factor production from infiltrating macrophages.

Choroidal neovascularization (CNV), a feature of neovasular age-related macular degeneration (AMD), acts as a leading cause of vision loss in the elderly. Shikonin (SHI), a natural bioactive compound extracted from Chinese herb radix arnebiae, exerts anti-inflammatory and anti-angiogenic roles and also acts as a potential pyruvate kinase M2 (PKM2) inhibitor in macrophages. The major immune cells macrophages infiltrate the CNV lesions, where the production of pro-angiognic cytokines from macrophage facilitates the development of CNV. PKM2 contributes to the neovascular diseases. In this study, we found that SHI oral gavage alleviated the leakage, area and volume of mouse laser-induced CNV lesion and inhibited macrophage infiltration without ocular cytotoxicity. Moreover, SHI inhibited the secretion of pro-angiogenic cytokine, including basic fibroblast growth factor (FGF2), insulin-like growth factor-1 (IGF1), chemokine (C-C motif) ligand 2 (CCL2), placental growth factor and vascular endothelial growth factor (VEGF), from primary human macrophages by down-regulating PKM2/STAT3/CD163 pathway, indicating a novel potential therapy strategy for CNV.

Integrin-Linked Kinase Controls Choroidal Neovascularization by Recruitment of Endothelial Progenitor Cells.

Purpose: Vasculogenesis has been shown to contribute to the formation of choroidal neovascularization (CNV). However, the mechanism behind the recruitment of endothelial progenitor cells (EPC) to CNV is not well understood. Therefore, we were interested to know whether integrin-linked kinase (ILK) plays a role in recruiting EPC to CNV, and its possible mechanism. Methods: We investigated the effect of hypoxia on retinal pigment epithelium (RPE) cells expressing ILK, hypoxia-inducible factor 1α (HIF-1α), stromal-derived factor-1 (SDF-1), and vascular endothelial growth factor (VEGF), and we further examined the effect of ILK small interfering RNA (siRNA) on their expression. The function of ILK expressed by RPE on EPC in vitro with regard to angiogenic effect was also studied. In vivo, we determined the expression levels of the above factors in CNV. We also examined the role of ILK on their expression, on EPC recruiting, and on the growth of CNV. Results: We found that hypoxia strongly induced the expression of ILK, HIF-1α, SDF-1, and VEGF. Moreover, the silencing of ILK attenuated their expression. It also decreased the phosphorylation of protein kinase B (PKB/AKT) and extracellular regulated protein kinases (ERK) and nearly abolished the proliferation, migration, and adhesion of EPC to RPE cells. In vivo, we showed that these factors were upregulated in CNV. Inhibiting the expression of ILK prohibited the "homing" of EPC to CNV lesions and attenuated the growth of CNV. Conclusions: We demonstrate that ILK controls the development of CNV by regulating the recruitment of EPC to CNV lesions, possibly through ILK-dependent expression of SDF-1 and VEGF in RPE.

Cytochrome P450 Oxidase 2C Inhibition Adds to ω-3 Long-Chain Polyunsaturated Fatty Acids Protection Against Retinal and Choroidal Neovascularization.

OBJECTIVE: Pathological ocular neovascularization is a major cause of blindness. Increased dietary intake of ω-3 long-chain polyunsaturated fatty acids (LCPUFA) reduces retinal neovascularization and choroidal neovascularization (CNV), but ω-3 LCPUFA metabolites of a major metabolizing pathway, cytochrome P450 oxidase (CYP) 2C, promote ocular pathological angiogenesis. We hypothesized that inhibition of CYP2C activity will add to the protective effects of ω-3 LCPUFA on neovascular eye diseases. APPROACH AND RESULTS: The mouse models of oxygen-induced retinopathy and laser-induced CNV were used to investigate pathological angiogenesis in the retina and choroid, respectively. The plasma levels of ω-3 LCPUFA metabolites of CYP2C were determined by mass spectroscopy. Aortic ring and choroidal explant sprouting assays were used to investigate the effects of CYP2C inhibition and ω-3 LCPUFA-derived CYP2C metabolic products on angiogenesis ex vivo. We found that inhibition of CYP2C activity by montelukast added to the protective effects of ω-3 LCPUFA on retinal neovascularization and CNV by 30% and 20%, respectively. In CYP2C8-overexpressing mice fed a ω-3 LCPUFA diet, montelukast suppressed retinal neovascularization and CNV by 36% and 39% and reduced the plasma levels of CYP2C8 products. Soluble epoxide hydrolase inhibition, which blocks breakdown and inactivation of CYP2C ω-3 LCPUFA-derived active metabolites, increased oxygen-induced retinopathy and CNV in vivo. Exposure to selected ω-3 LCPUFA metabolites of CYP2C significantly reversed the suppression of both angiogenesis ex vivo and endothelial cell functions in vitro by the CYP2C inhibitor montelukast. CONCLUSIONS: Inhibition of CYP2C activity adds to the protective effects of ω-3 LCPUFA on pathological retinal neovascularization and CNV.

Genistein attenuates choroidal neovascularization.

Genistein is a dietary-derived flavonoid abundantly present in soybeans and known to possess various biological effects including anti-inflammation and anti-angiogenic activity. To investigate the effects of genistein on intraocular neovascularization, we used an animal model of laser-induced choroidal neovascularization (CNV). Male C57BL/6J mice were treated in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. CNV was induced by laser photocoagulation. The animals were fed a mixture diet containing 0.5% genistein or a control diet ad libitum for 7 days before laser photocoagulation and the treatment was continued until the end of the study. Seven days after laser injury, the size of CNV lesions was quantified. Retinal pigment epithelium (RPE)-choroid complex was also harvested 1 or 3 days after laser injury and the level of monocyte chemoattractant protein (MCP)-1, intercellular adhesion molecule (ICAM)-1, and matrix metalloproteinase (MMP)-9 were measured by enzyme-linked immunosorbent assay. Expression levels of Ets-1 and F4/80 were examined by real-time PCR. A significant decrease in CNV size was observed in animals treated with genistein (15441.9±1511.8 µm(2)) compared to control mice (21074.0±1940.7µm(2), P<.05). Genistein significantly reduced the protein level of MCP-1, ICAM-1, and MMP-9 in the RPE-choroid complex (P<.05). In addition, genistein suppressed the expression levels of Ets-1 and F4/80 (P<.05). The current data indicate the anti-angiogenic property of genistein during CNV formation.

An angiotensin-converting enzyme inhibitor modulates stromal-derived factor-1 through CD26/dipeptidyl peptidase IV to inhibit laser-induced choroidal neovascularization.

PURPOSE: Stromal-derived factor (SDF)-1 is a chemokine that recruits bone marrow-derived endothelial precursor cells (EPCs) for choroidal neovascularization (CNV) development. Angiotensin-converting enzyme (ACE) inhibitors mediate the compensatory effects of ACE and CD26/dipeptidyl peptidase IV (DPP IV), which results in the degradation and inactivation of SDF-1 in vivo. ACE inhibitors, such as imidapril, exhibit potential antiangiogenic effects on laser-induced CNV in mice. The role that this imidapril-mediated effect plays in modulating SDF-1 signals has not been defined. The present study assessed the effect of the CD26/SDF-1 signaling pathway on the inhibitory effect of imidapril in CNV development. METHODS: CNV was induced in C57BL/6J mice by focally rupturing Bruch's membrane using a 532-nm diode laser. The animals were pretreated with PBS, imidapril, diprotin-A (a DPP IV antagonist), or imidapril plus diprotin-A for 5 days before photocoagulation. Treatments were continued daily for 14 days following the laser induction. The normal control group did not undergo laser rupture or receive treatment. CD26 activity was measured using a substrate conversion assay and flow cytometry. SDF-1 levels in both the blood and the bone marrow were measured using an enzyme-linked immunosorbent assay, and the number of circulating endothelial progenitor cells (EPCs) and leukocytes was quantified. Functional analyses of circulating SDF-1 were performed using actin polymerization blood biomarker assays, and the CNV-related responses were evaluated using fluorescein angiography and isolectin-B4-labeled flatmounts. RESULTS: Imidapril directly amplified CD26 activity and had a minor effect on the number of CD26+ cells in the bone marrow. However, decreased CD26 activity in the plasma was secondary to a decrease in the number of circulating CD26+ cells and blood leukocytes. Furthermore, imidapril increased SDF-1 concentrations in the peripheral circulation via CD26-induced degradation of SDF-1 in the bone marrow, an effect that coincided with elevated numbers of circulating EPCs. CD26-mediated SDF-1 inactivation was demonstrated by a decrease in SDF-1-induced actin polymerization in the whole blood of imidapril-treated mice. Imidapril markedly decreased angiographic leakage and CNV size. CD26 inhibition completely blocked the CD26/SDF-1 signaling pathway in vivo and reduced the antiangiogenic effect of imidapril. CONCLUSIONS: These results strongly suggest that the antiangiogenic effects of imidapril on laser-induced CNV partially involve the modulation of the CD26/SDF-1 signaling pathway.

Cathepsin proteases promote angiogenic sprouting and laser-induced choroidal neovascularisation in mice.

Cysteine cathepsins are a family of proteases involved in intracellular protein turnover and extracellular matrix degradation. Cathepsin B (Ctsb) and cathepsin Z (Ctsz) promote tumorigenesis and Ctsb is a known modulator of tumor angiogenesis. We therefore investigated the angiomodulatory function of these cathepsins in vitro as well as in a mouse model of laser-induced choroidal neovascularization (laser-CNV). Ctsb(-/-), Ctsz(-/-), Ctsb/Ctsz double-knockout (Ctsb/z DKO), and wild type (WT) mice underwent argon laser treatment to induce choroidal neovascularization (CNV). The neovascularized area was quantified individually for each lesion at 14 days after laser coagulation. In vitro the effects of cathepsin inhibitors on angiogenesis were analysed by endothelial cell (EC) spheroid sprouting and EC invadosome assays. Retinas from cathepsin KO mice did not show gross morphological abnormalities. In the laser CNV model, however, Ctsb/z DKO mice displayed a significantly reduced neovascularized area compared to WT (0.027 mm(2) vs. 0.052 mm(2); p = 0.012), while single knockouts did not differ significantly from WT. In line, VEGF-induced EC spheroid sprouting and invadosome formation were not significantly altered by a specific cathepsin B inhibitor alone, but significantly suppressed when more than one cathepsin was inhibited. Our results demonstrate that laser-CNV formation is significantly reduced in Ctsb/z DKO mice. In line, EC sprouting and invadosome formation are blunted when more than one cathepsin is inhibited in vitro. These results reveal an angiomodulatory potential of cathepsins with partial functional redundancies between different cathepsin family members.

Specific inhibition of serine/arginine-rich protein kinase attenuates choroidal neovascularization.

PURPOSE: To investigate the applicability of serine/arginine-rich protein kinase (SRPK)-specific inhibitor, SRPIN340, for attenuation of choroidal neovascularization (CNV) formation using a mouse model. METHODS: Laser photocoagulation was performed to induce CNV in C57BL/6J mice, followed by intravitreal injection of SRPIN340 or vehicle. Seven days after the treatment, the CNV size was evaluated using a flatmount technique. Protein levels of vascular endothelial growth factor (VEGF) and inflammation-associated molecules, such as monocyte chemoattractant protein (MCP)-1 and intercellular adhesion molecule (ICAM)-1, in the retinal pigment epithelium-choroid complex were measured with enzyme-linked immunosorbent assay. Expression levels of total Vegf, exon 8a-containing Vegf isoforms, and F4/80 (a specific marker for macrophage) were assessed using real-time PCR. RESULTS: SRPIN340 inhibited CNV formation in a dose-dependent manner. Compared with the vehicle, SRPIN340 significantly decreased the protein levels of VEGF, MCP-1, ICAM-1, and consequently inhibited macrophage infiltration. Furthermore, SRPIN340 suppressed the gene expression levels of total Vegf and exon 8a-containing Vegf isoforms. CONCLUSIONS: SRPIN340, a specific inhibitor of SRPK, suppressed Vegf expression and attenuated CNV formation. Our data suggest the possibility that SRPIN340 is applicable for neovascular age-related macular degeneration as a novel chemical therapeutics.

Antiangiogenic effects of axitinib, an inhibitor of vascular endothelial growth factor receptor tyrosine kinase, on laser-induced choroidal neovascularization in mice.

PURPOSE: To investigate the effects of axitinib, an inhibitor of vascular endothelial growth factor receptors, on choroidal neovascularization (CNV) in an animal model of neovascular age-related macular degeneration (AMD). METHODS: Experimental CNV lesions were induced in C57BL/6 mice by laser photocoagulation. Beginning 1 day after CNV induction, mice were treated with axitinib (5 mg/kg/day) or vehicle for 2 weeks. In other groups of mice, axitinib or vehicle treatment was started 7 days after the laser application to determine the effect of the drug on established CNV. Untreated mice were used as a baseline group. Two weeks after laser injury, the extent of CNV was assessed from choroidal flat mounts perfused with fluorescein-labeled dextran. Immunofluorescence staining with isolectin IB4 was also used to quantify the CNV lesions. RESULTS: Orally administered axitinib inhibited CNV growth in the laser-induced CNV model. Axitinib caused a 70.1% inhibition of CNV lesions compared to vehicle-treatment (p < 0.001). Axitinib also caused a significant regression of established CNV, reducing the area by 71.1% compared to vehicle treatment (p < 0.001). Moreover, immunofluorescence staining showed that the area of isolectin IB4 labeled vessels was smaller in the axitinib-treated group compared to the vehicle-treated group (p < 0.001). CONCLUSIONS: Axitinib effectively inhibits the progression of CNV in an experimental animal model. These results suggest that axitinib could constitute a therapeutic alternative for the treatment of neovascular AMD.

Bone marrow-derived mesenchymal cells and MMP13 contribute to experimental choroidal neovascularization.

In this study, we evaluate the potential involvement of collagenase-3 (MMP13), a matrix metalloproteinase (MMP) family member, in the exudative form of age-related macular degeneration characterized by a neovascularisation into the choroid. RT-PCR analysis revealed that human neovascular membranes issued from patients with AMD expressed high levels of Mmp13. The contribution of MMP13 in choroidal neovascularization (CNV) formation was explored by using a murine model of laser-induced CNV and applying it to wild-type mice (WT) and Mmp13-deficient mice (Mmp13 ( -/- ) mice). Angiogenic and inflammatory reactions were explored by immunohistochemistry. The implication of bone marrow (BM)-derived cells was determined by BM engraftment into irradiated mice and by injecting mesenchymal stem cells (MSC) isolated from WT BM. The deficiency of Mmp13 impaired CNV formation which was fully restored by WT BM engraftment and partially rescued by several injections of WT MSC. The present study sheds light on a novel function of MMP13 during BM-dependent choroidal vascularization and provides evidence for a role for MSC in the pathogenesis of CNV.

Reduced choroidal neovascular membrane formation in cyclooxygenase-2 null mice.

PURPOSE: To assess the degree of laser-induced choroidal neovascular membrane formation in wild-type (WT) and COX-2 null mice and to measure vascular endothelial growth factor (VEGF), interleukin (IL)-1ß, and tumor necrosis factor (TNF)-α levels in the retina and choroid. METHODS: Four laser burns were placed in each eye of WT and COX-2 null mice to induce choroidal neovascularization. Fluorescein angiography (FA) was performed at 14 days, and retinal pigment epithelium-choroid-sclera (choroidal) flat mounts were prepared. The retina and choroid were isolated from WT and COX-2 null mice at 24, 72, and 168 hours after laser photocoagulation and from unlasered eyes and were tested for VEGF, IL-1ß, and TNF-α. RESULTS: COX-2 null mice demonstrated 58% (P = 0.001) and 48% (P = 0.001) reductions in CNV formation on FA and choroidal flat mounts, respectively, compared with WT mice. For unlasered mice, mean VEGF concentrations in the retina and choroid were 1.2 ± 0.42 pg/mg protein for WT but only 0.42 ± 0.2 pg/mg protein for COX-2 null mice (P < 0.05). After laser photocoagulation, WT mice showed significantly greater VEGF and IL-ß expression in the retina and choroid by 168 hours (P < 0.05) and 72 hours (P < 0.05), respectively, compared with COX-2 null mice. CONCLUSIONS: COX-2 null mice exhibited significantly less choroidal neovascular membrane formation associated with reduced expression of VEGF. The results of this study suggest that COX-2 modulates VEGF expression in CNV and implicates a potential therapeutic role for nonsteroidal anti-inflammatory drugs.

Role of c-Cbl-dependent regulation of phospholipase Cgamma1 activation in experimental choroidal neovascularization.

PURPOSE: Activation of phospholipase Cγ1 (PLCγ1) by vascular endothelial growth factor receptor (VEGFR)-2 is necessary for proliferation and tube formation of endothelial cells in vitro. Previous work has demonstrated that Casitas B-lineage lymphoma (c-Cbl) promotes ubiquitination of PLCγ1 and suppression of its tyrosine phosphorylation. This study was designed to evaluate the importance of PLCγ1 and c-Cbl in experimental choroidal neovascularization (CNV). METHODS: The role of PLCγ1 was studied in three models of angiogenesis: the endothelial cell culture system, the chorioallantoic membrane (CAM) assay, and the laser-induced CNV model. Endothelial cells were analyzed for the role of PLCγ1 in promoting tube formation. CAMs were incubated with pharmacologic agents that either inhibit or stimulate PLCγ1. CNV was induced in wild-type and c-Cbl-knockout mice, and the progression of CNV was evaluated by fluorescein angiography. RESULTS: Activation of PLCγ1 was necessary for tube formation of endothelial cells. PLCγ1 stimulation increased the growth of blood vessels and conversely, PLCγ1 inhibition decreased the growth of blood vessels in the CAM model. CNV lesions in the c-Cbl-knockout mice were significantly greater in number, more confluent, and increased in size with time, compared with those in the control wild-type mice. CONCLUSIONS: The data show that PLCγ1 plays an important role in angiogenesis. Loss of c-Cbl results in enhanced CNV in the eye. The study also shows that c-Cbl plays an important role in ocular angiogenesis, suggesting that modulation of c-Cbl activity or inhibition of PLCγ1 would be a compelling target for antiangiogenesis therapy.

Doxycycline-mediated inhibition of choroidal neovascularization.

PURPOSE: Doxycycline, a broad-spectrum antibiotic, has certain antiangiogenic properties and can inhibit matrix metalloproteinases (MMPs/gelatinases). The authors investigated the effects of doxycycline on choroidal neovascularization (CNV) and regulation of MMP-2 and -9 and pigment epithelium-derived factor (PEDF). METHODS: Doxycycline was orally administered to rats at 500, 50, 5, and 0.5 mg/kg/d; nontreated animals were used as controls. Experimental CNV was induced with laser 7 days after doxycycline treatment started. At 7 days after induction, animals were euthanatized, and eyes were collected. RPE/choroid flatmounts were labeled with isolectin IB4 to determine CNV lesion volumes using confocal microscopy and high-performance 3D imaging software. MMP-2, MMP-9, and PEDF protein levels were determined by ELISA. MMP catalytic activity was determined in solution using fluorogenic gelatin and peptide substrates, by gelatin zymography in SDS-PAGE, and by in situ fluorogenic substrate zymography in RPE/choroid sections. RESULTS: CNV complex lesion volumes decreased with doxycycline in a dose-response relationship. A dosage of 500 mg/kg/d caused a 70% inhibition of CNV complex volume compared with control animals. Doxycycline elevated PEDF levels in plasma and did not affect the active and pro-enzymes MMP-2 and MMP-9 levels. However, the in vitro enzymatic activities of purified MMP-2 and MMP-9 declined significantly with doxycycline. MMP-2, MMP-9, and gelatinolytic activities in situ increased early in CNV lesion development. Doxycycline treatments and exogenous additions inhibited gelatinolytic activities in CNV lesions. CONCLUSIONS: Doxycycline effectively hampered the progression of experimental CNV. The results suggest that orally administrated doxycycline can reach the choroid to attenuate proteolytic enzymes that remodel Bruch's membrane and promote the antiangiogenic PEDF to inhibit neovascularization.

Focal adhesion kinase signaling pathway participates in the formation of choroidal neovascularization and regulates the proliferation and migration of choroidal microvascular endothelial cells by acting through HIF-1 and VEGF expression in RPE cells.

Choroidal neovascularization (CNV) is one of the most frequent causes of severe and progressive vision loss, while its pathogenesis is still poorly understood. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, plays a crucial role in linking signals initiated by both the extracellular matrix (ECM) and soluble signaling factors and controls essential cellular processes. Extensive evidence has shown that FAK is activated in angiogenic response. This study aims to investigate the effect of FAK on CNV formation. The Brown-Norway (BN) rats underwent laser rupture of Bruch's membrane to induce CNV and were then killed at 1, 3, 7, and 14 days following laser injury. Immunofluorescence and Western blot were processed to detect FAK protein. Retinal pigment epithelial (RPE) cells were cultured under hypoxia and RNA interference (RNAi) technique was used to knock down the FAK gene in RPE cells. Expression of hypoxia inducible factor-1 (HIF-1alpha) and vascular endothelial growth factor (VEGF) in RPE cells were investigated by RT-PCR and Western blot. Two kinds of coculture models were used to observe the effects of specific blockade of FAK in RPE cells on the proliferation and migration of choroidal microvascular endothelial cells (CECs), respectively. FAK was highly expressed in the rat RPE-choroid tissue after photocoagulation. In vitro experiment showed that FAK was involved in hypoxia signaling in cultured RPE cells. The absence of FAK effectively reduced the expression of hypoxia-induced HIF-1alpha and VEGF in RPE cells, resulting in the inhibition of proliferation and migration of CECs. Our results suggest that FAK pathway activation plays a role in the development of CNV, and regulates the proliferation and migration of CECs by acting through HIF-1 and then up-regulating the expression of the angiogenic factor VEGF in RPE cells. It is reasonable to propose that FAK siRNA will potentially provides a means to attenuate the strong stimuli for neovascularization in CNV-dependent disorders, which could present a therapeutically relevant strategy for the inhibition of CNV.

Expression of cyclooxygenase-2 in choroidal neovascular membranes from age-related macular degeneration patients.

PURPOSE: The objective of this study was to investigate the expression of cyclooxygenase (COX)-2 in human choroidal neovascular membranes. METHODS: Paraffin-embedded sections of choroidal neovascular membranes excised from 16 patients with wet age-related macular degeneration were used for this study. Sections were subjected to immunohistochemistry using a monoclonal mouse antihuman COX-2 antibody. Staining was classified as either negative or positive in retinal pigment epithelial cells, vascular endothelial cells, and fibroblasts. Serial sections were stained for vimentin expression to confirm tissue antigenicity. RESULTS: Eleven of 16 (69%) choroidal neovascular membranes stained positive for COX-2 in retinal pigment epithelial cells, with 6 (38%) of these also expressing COX-2 in vascular endothelial cells and 6 (38%) in fibroblasts. None of the sections that were negative for COX-2 in the retinal pigment epithelial cells showed COX-2 expression in the other cell types assessed. There was a statistically significant difference (P = 0.0097) in the mean ages between the COX-2 positive group (65.6 years) and COX-2 negative group (76.8 years) as determined by a two-tailed, unpaired Student's t-test. CONCLUSION: The expression of COX-2 in human choroidal neovascular membranes suggests a possible role for this modulator in age-related macular degeneration pathogenesis. The age-dependent expression observed is novel and warrants further investigation.

Increased choroidal neovascularization following laser induction in mice lacking lysyl oxidase-like 1.

PURPOSE: Age-related degradation of the elastic lamina in Bruch's membrane may have a permissive effect on the growth of choroidal neovascularization (CNV). This study investigated the influence of defective elastic fiber maintenance in the development of laser-induced CNV. METHODS: A mouse lacking lysyl oxidase-like (LOXL)-1, an enzyme essential for elastin polymerization, was studied. The morphologic characteristics of the elastic lamina within Bruch's membrane were examined in mutant and wild-type (WT) eyes. Laser-induced CNV was evaluated by fluorescein angiography and choroidal flat mounts. Immunohistochemistry for elastin was performed on the CNV lesions, and vascular endothelial growth factor (VEGF) levels were determined by ELISA. Soluble elastin and matrix metalloproteinase (MMPs) levels were also analyzed by immunoblotting. RESULTS: The elastic lamina of Bruch's membrane in the LOXL1-deficient mice was fragmented and less continuous than in the WT controls. The mutant mice showed increased levels of soluble elastin peptides and reduced elastin polymer deposition in neovascular membranes. Significantly larger CNV with greater leakage on fluorescein angiography developed in mutant mice. VEGF levels in the RPE/choroid were higher in the knockout mice on days 7 and 14 after laser (P < 0.05). MT1-MMP (MMP14) was also elevated after laser in the LOXL1 mutant eyes compared to the WT controls. CONCLUSIONS: These results show that a systemic defect in elastic fiber deposition affects Bruch's membrane integrity and leads to more aggressive CNV growth. The latter may be partially mediated by abnormal signaling from the accumulation of soluble elastin peptides.

Photodynamic therapy induces caspase-dependent apoptosis in rat CNV model.

PURPOSE: To investigate the mechanism of cell death in laser-induced choroidal neovascularization (CNV) after photodynamic therapy (PDT). METHODS: PDT was performed in Brown-Norway rats using laser light at a wavelength of 689 nm, irradiance of 600 mW/cm(2), and fluence of 25 J/cm(2) after intravenous injection of verteporfin at the doses of 3, 6, and 12 mg/m(2). Apoptotic cells in CNV were detected by TUNEL assay at 1, 3, 6, 15, 24, and 48 hours after PDT. Caspase activation at 1, 3, 6, 15, and 24 hours after PDT was determined by immunohistochemistry (IHC) with a cleaved caspase-3 or -9 antibody. Akt activity was determined by Western blot and IHC with a phosphorylated-Akt (pAkt) antibody. To investigate the roles of Akt in PDT-induced apoptosis, insulin-like growth factor (IGF)-1, an Akt activator, with or without wortmannin, an inhibitor of PI3K-Akt pathway, was injected into the vitreous before PDT. RESULTS: The number of TUNEL-positive cells in CNV increased at 3 hours after PDT and peaked at 6 hours, showing a dose dependence of verteporfin. Caspase activation was detected in TUNEL-positive cells. Dephosphorylation of Akt in CNV occurred within 1 hour. IGF-1 significantly activated Akt and suppressed the number of TUNEL-positive cells in CNV, and the effects of IGF-1 were diminished by wortmannin. CONCLUSIONS: PDT induced caspase-dependent apoptosis in CNV. These results suggest that PDT leads to dephosphorylation of Akt and subsequent activation of the caspase-dependent pathway. Understanding the intracellular signaling mechanisms of apoptosis in PDT may lead to more selective and effective treatment of CNV secondary to age-related macular degeneration.

Matrix metalloproteinases in human choroidal neovascular membranes excised following verteporfin photodynamic therapy.

AIM: To evaluate expression of proangiogenic matrix metalloproteinases (MMP) 2 and 9 at distinct intervals after verteporfin photodynamic therapy (PDT) in human choroidal neovascular membranes (CNV) secondary to age-related macular degeneration (AMD). METHODS: Retrospective review of an interventional case series of 49 patients who underwent removal of CNV. Twenty-six patients were treated with PDT 3 to 383 days prior to surgery. Twenty-three CNV without previous treatment were used as controls. CNV were stained for CD34, cytokeratin 18, endostatin, MMP-2 and MMP-9 by immunohistochemistry. RESULTS: CNV without previous therapy disclosed MMP-2, MMP-9 in RPE-Bruch's membrane, vessels and stroma in different intensities. Three days after PDT, MMP-9 expression was significantly weaker in stroma (p = 0.0019). Endostatin was significantly reduced in vessels (p<0.001). At longer post-PDT intervals, a significant increase of MMP-9 in stroma (p = 0.037) and of endostatin in RPE-Bruch's membrane (p = 0.02), vessels (p = 0.005) and stroma (p<0.001) were disclosed. No significant changes in MMP-2 expression were detected. CONCLUSIONS: PDT induced an early, temporary decrease in MMP-9 and endostatin expression. At longer intervals, MMP-9 increase is possibly associated with the angiogenic process responsible for recurrence after PDT. MMP-9, however, acts as a double-edged sword by concomitant induction of endostatin, an endogenous inhibitor of angiogenesis.

Reduced photoreceptor damage after photodynamic therapy through blockade of nitric oxide synthase in a model of choroidal neovascularization.

PURPOSE: To investigate the role of nitric oxide synthase (NOS) in photoreceptor degeneration associated with photodynamic therapy (PDT) in a laser-induced model of choroidal neovascularization (CNV). METHODS: PDT was performed in monkey and Brown Norway rats with laser-induced CNV. L-NAME, a NOS inhibitor, or saline was injected intraperitoneally in rats with CNV. An NO donor, or saline, was injected intravitreously into normal rats. Photoreceptor apoptosis was evaluated by TUNEL and electron microscopy. NOS, ED-1, and cleaved-caspase-3 (c-casp-3) expression were determined by immunohistochemistry. CNV lesions were examined by fluorescence angiography and choroidal flat mount. RESULTS: TUNEL and electron microscopy showed photoreceptor apoptosis after PDT. In rats, there were significantly more TUNEL-positive cells in the photoreceptors 24 hours after PDT, whereas in the CNV lesions there were more TUNEL-positive cells 6 hours after PDT. C-casp-3 was detected in the CNV lesions but not in the photoreceptors after PDT. There was no difference in the numbers of ED-1-positive macrophages before and after PDT. However, inducible NOS (iNOS) was increased after PDT in macrophages. Intravitreous injection of the NO donor without PDT also induced substantial photoreceptor apoptosis. L-NAME-treated animals had significantly fewer TUNEL-positive cells in the photoreceptors than saline-treated animals after PDT (P < 0.05). There were no differences in CNV size and leakage between L-NAME- and saline-treated groups. CONCLUSIONS: iNOS expression in macrophages contributes to PDT-induced photoreceptor degeneration. NOS inhibition reduces PDT-induced photoreceptor degeneration without compromising the treatment effect of PDT in an experimental model of CNV.

Role of urokinase inhibitors in choroidal neovascularization.

Cell migration is a critical step in the angiogenesis cascade that involves proteolysis of the basement membrane and extracellular matrix around existing blood vessels. The urokinase plasminogen activator (uPA) system has been involved in cellular invasion, angiogenesis and tumor growth. Similar expression of urokinase and its receptor (uPAR) is seen in both retinal and choroidal neovascularization. Significant inhibition of choroidal neovascularization (CNV) has been observed when cell surface associated uPA-uPAR activity is prevented with a specific inhibitor of this proteinase system. As the current treatments of CNV are not optimal, the urokinase-uPAR system appears to be an attractive target for alternative pharamacological therapy for CNV.

Inhibition of retinal and choroidal neovascularization by a novel KDR kinase inhibitor.

PURPOSE: Inhibition of vascular endothelial growth factor (VEGF) signaling has shown great promise for the treatment of ocular neovascular disease. Current anti-VEGF therapies in late-stage development, while efficacious, require dosing by frequent intravitreal injections that are inconvenient to patients. VEGF signaling inhibitors that demonstrate more convenient dosing regimens could lead to the improved treatment of neovascular diseases such as wet age related macular degeneration (AMD) and proliferative diabetic retinopathy (PDR). Here we describe the assessment of a KDR (VEGFR2) kinase inhibitor in two well-established models of ocular neovascularization following oral administration. METHODS: A novel KDR kinase inhibitor was dosed by oral gavage for 12 days at 0, 10, 30, or 100 mg/kg in an adult male Brown Norway rat laser induced choroidal neovascularization (CNV) model. The areas of CNV lesions were quantitated by fluorescence image analysis of FITC-dextran perfused animals. The kinase inhibitor was also assessed in a rat oxygen induced retinopathy (OIR) model in which neonatal rats were placed in an oxygen chamber that delivered alternating 24 h cycles of 50% and 10% oxygen for 14 days. After 14 days of oxygen treatment, the animals were returned to room air and dosed orally for 7 days with 0, 10, or 30 mg/kg kinase inhibitor. The extent of retinal neovascularization was assessed by counting pre-retinal neovascular nuclei on histological sections. RESULTS: At doses of 100 mg/kg, the KDR kinase inhibitor resulted in a 98% reduction in lesion size in the rat CNV model. 30 mg/kg doses of the inhibitor showed a 70% and 80% reduction in lesion size in the laser CNV and OIR models, respectively. CONCLUSIONS: Oral dosing of the described KDR kinase inhibitor effectively inhibits neovascularization in two well-established animal models of ocular neovascularization. These data suggest that compounds of this class may prove to be useful for the treatment of a variety of ocular neovascular diseases using a convenient oral dosing regimen.