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Purpose: Müller glial-mesenchymal transition (GMT) is reported as the fibrogenic mechanism promoted by TGF-β-SNAIL axis in Müller cells transdifferentiated into myofibroblasts. Here we show the multifaceted involvement of TGF-β in diabetic fibrovascular proliferation via Müller GMT and VEGF-A production., Methods: Surgically excised fibrovascular tissues from the eyes of patients with proliferative diabetic retinopathy were processed for immunofluorescence analyses of TGF-β downstream molecules. Human Müller glial cells were used to evaluate changes in gene and protein expression with real-time quantitative PCR and ELISA, respectively. Immunoblot analyses were performed to detect TGF-β signal activation., Results: Müller glial cells in patient fibrovascular tissues were immunopositive for GMT-related molecular markers, including SNAIL and smooth muscle protein 22, together with colocalization of VEGF-A and TGF-β receptors. In vitro administration of TGF-β1/2 upregulated TGFB1 and TGFB2, both of which were suppressed by inhibitors for nuclear factor-κB, glycogen synthase kinase-3, and p38 mitogen-activated protein kinase. Of the various profibrotic cytokines, TGF-β1/2 application exclusively induced Müller glial VEGFA mRNA expression, which was decreased by pretreatment with small interfering RNA for SMAD2 and inhibitors for p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Supporting these findings, TGF-β1/2 stimulation to Müller cells increased the phosphorylation of these intracellular signaling molecules, all of which were also activated in Müller glial cells in patient fibrovascular tissues., Conclusions: This study underscored the significance of Müller glial autoinduction of TGF-β as a pathogenic cue to facilitate diabetic fibrovascular proliferation via TGF-β-driven GMT and VEGF-A-driven angiogenesis.

Purpose: Acrolein, a highly reactive unsaturated aldehyde, is known to facilitate glial cell migration, one of the pathological hallmarks in diabetic retinopathy. However, cellular mechanisms of acrolein generation in retinal glial cells remains elusive. In the present study, we investigated the role and regulation of spermine oxidase (SMOX), one of the enzymes related to acrolein generation, in retinal glial cells under hypoxic condition., Methods: Immunofluorescence staining for SMOX was performed using sections of fibrovascular tissues obtained from patients with proliferative diabetic retinopathy. Expression levels of polyamine oxidation enzymes including SMOX were analyzed in rat retinal Müller cell line 5 (TR-MUL5) cells under either normoxic or hypoxic conditions. The transcriptional activity of Smox in TR-MUL5 cells was evaluated using the luciferase assay. Levels of acrolein-conjugated protein, Nε-(3-formyl-3,4-dehydropiperidino) lysine adduct (FDP-Lys), and hydrogen peroxide were measured., Results: SMOX was localized in glial cells in fibrovascular tissues. Hypoxia induced SMOX production in TR-MUL5 cells, which was suppressed by silencing of hypoxia-inducible factor-1α (Hif1a), but not Hif2a. Transcriptional activity of Smox was regulated through HIF-1 binding to hypoxia response elements 2, 3, and 4 sites in the promoter region of Smox. Generation of FDP-Lys and hydrogen peroxide increased in TR-MUL5 cells under hypoxic condition, which was abrogated by SMOX inhibitor MDL72527., Conclusions: The current data demonstrated that hypoxia regulates production of SMOX, which plays a role in the generation of oxidative stress inducers, through HIF-1α signaling in Müller glial cells under hypoxic condition.

Purpose: To investigate the effect of the unsaturated aldehyde acrolein on retinal glial cell migration., Methods: Müller glial cell markers expression in TR-MUL5 were confirmed by RT-PCR and immunostaining. Cell viability and migration rate of TR-MUL5 cells were assessed after the stimulation with acrolein. DNA microarray analysis was performed to analyze changes in the expression levels of migration-related genes in Müller glial cells stimulated with acrolein. Real-time PCR and ELISA were performed to validate DNA microarray analysis results. Inhibitors of C-X-C motif chemokine ligand 1 (CXCL1), one of the genes highly upregulated after the exposure to acrolein, and blockers of its receptor, CXCR2, were used to investigate the role of the CXCL1-CXCR2 axis on glial cell migration. CXCL1 concentration was measured in vitreous fluid samples obtained from proliferative diabetic retinopathy (PDR) and nondiabetic control eyes. CXCL1 and CXCR2 expression in glial cells of fibrovascular tissues obtained from PDR patients was examined by immunostaining., Results: At a high concentration, acrolein (100 μM) significantly decreased cell viability. However, in moderate, sublethal concentrations (25-50 μM), acrolein induced cell migration and substantially increased the production of CXCL1 in TR-MUL5 cells. CXCL1 concentration was significantly elevated in vitreous fluids of PDR patients, and CXCL1 and CXCR2 were present in glial cells in fibrovascular tissues of PDR patients. CXCL1 stimulation increased glial cell migration in a dose-dependent manner, which was abrogated by the neutralization of the CXCL1-CXCR2 axis., Conclusions: Our data demonstrate that acrolein promotes retinal Müller glial cell migration by enhancing CXCL1 production.

Purpose: To investigate the effect of the vascular adhesion protein-1 (VAP-1) inhibitor RTU-1096 on retinal morphologic changes and ocular inflammation after retinal laser photocoagulation in mice., Methods: C57BL/6JJcl mice were fed a diet containing RTU-1096, a specific inhibitor for VAP-1, or a control diet ad libitum for 7 days. Laser photocoagulation was performed on the peripheral retina of the animals. The semicarbazide sensitive amine oxidase (SSAO) activities in plasma and chorioretinal tissues were measured. Optical coherence tomography (OCT) images were acquired before and at 1, 3, and 7 days after laser photocoagulation, and thickness of the individual retinal layers was measured. Intravitreal leukocyte infiltration was assessed by histologic analysis. The expression level of intercellular adhesion molecule-1 (ICAM-1) in retinal tissues were examined by quantitative real-time PCR., Results: One day after laser photocoagulation, the thickness of the outer nuclear layer (ONL) increased in the laser group compared with in the control group, and RTU-1096 administration abrogated the ONL thickening. Histologic analysis and OCT observation revealed that laser photocoagulation caused infiltration of inflammatory cells and the appearance of hyperreflective foci at the vitreoretinal surface, both of which were suppressed by RTU-1096 administration. In addition, systemic administration of RTU-1096 reduced upregulation of the leukocyte adhesion molecules ICAM-1 in the retina., Conclusions: The current data indicate that VAP-1/SSAO inhibition may be a potential therapeutic strategy for the prevention of macular edema secondary to scatter laser photocoagulation in patients with ischemic retinal diseases such as diabetic retinopathy.

Purpose: To quantitatively evaluate the pulse waveform changes in macular choroidal blood flow by using laser speckle flowgraphy (LSFG) with regression of acute central serous chorioretinopathy (CSC)., Methods: This retrospective observational case series included 20 eyes of 20 patients with acute CSC. Laser speckle flowgraphy was performed at baseline and after 6 months. On the LSFG monochrome map, automatically divided 5 × 5 grid segments within the macula were classified into predominantly delayed filling (PDF) or minimally or no delayed filling (MDF) areas according to the degree of choroidal filling delay on early-phase indocyanine green angiography. The average mean blur rate (MBR) and the pulse waveform parameters, including the skew and blowout time (BOT), were compared between the total PDF and MDF areas during follow-up., Results: The average MBR significantly decreased in both PDF (P = 0.005) and MDF (P < 0.001) areas during follow-up; in both areas, the skew decreased (P < 0.001 and P = 0.006, respectively) and BOT increased (P < 0.001 for each), showing significant reduction in vascular resistance at 6 months. The degree of the changes in the skew and BOT was significantly larger (P = 0.02 and P < 0.001, respectively) in the PDF area than in the MDF area., Conclusions: Changes in the skew and BOT, indices for vascular resistance, confirmed the involvement of circulatory disturbance at the acute stage of CSC. The present findings suggested that the pathogenesis of CSC stems from imbalanced distribution of choroidal blood flow due to augmented vascular resistance.

Purpose: To investigate the alteration of vitreal N-glycans in patients with proliferative diabetic retinopathy (PDR)., Methods: Plasma and vitreous samples were collected from 17 patients (10 females and 7 males) with PDR (PDR group) and 17 nondiabetic patients (8 females and 9 males) with epiretinal membrane (ERM) and idiopathic macular hole (MH) (non-diabetes mellitus [DM] group). Profiles of N-glycans were analyzed by a glycoblotting-based high-throughput protocol that we recently developed. Human retinal microvascular endothelial cells (HRMECs) were cultivated with culture media containing either low glucose (5 mM) or high glucose (25 mM), and expression levels of sialyltransferases were analyzed by real-time PCR and ELISA., Results: Amount of N-glycans in the vitreous fluid of the PDR group was significantly higher than that of the non-DM group (495.5 ± 37.4 vs. 142.7 ± 30.8 pmol/100 μg protein, P < 0.005), whereas there was no significant difference in the plasma samples between the PDR and the non-DM group. In addition, profile analysis showed that N-glycans with sialic acids increased in the vitreous of the PDR group (328.4 ± 25.8 pmol/100 μg protein) compared to the non-DM group (92.1 ± 21.2 pmol/100 μg protein, P < 0.0005). Expression levels of sialyltransferases ST3GAL1 and ST3GAL4 were upregulated in the HRMECs after high-glucose stimulation. Consistent with the real-time PCR data, high-glucose stimulation elevated the protein levels of ST3GAL1 (117.4 ± 14.9 pg/mg, P < 0.01) and ST3GAL4 (6.1 ± 0.9 pg/mg, P < 0.05) in the HRMECs compared with the cells cultured with low-glucose culture media (ST3GAL1, 64.4 ± 5.8 pg/mg; ST3GAL4, 3.8 ± 0.3 pg/mg)., Conclusions: Our data demonstrate distinct changes in the N-glycan profile and an increase in sialylated N-glycans in eyes with PDR.

Purpose: Extranodal marginal zone B-cell lymphoma (EMZL) is the most common subtype of conjunctival lymphoma, though its molecular mechanisms of pathogenesis are largely unknown. We attempted to explore the association of the renin-angiotensin system (RAS) and (pro)renin receptor ([P]RR) in the pathogenesis of conjunctival lymphoma., Methods: Surgically removed conjunctiva EMZL samples were used for gene expression, and immunohistochemical and immunofluorescence analyses of (P)RR and RAS components. Human B-lymphoblast IM-9 cells were treated with prorenin or angiotensin II (Ang II), and gene expression levels were analyzed using real-time quantitative PCR (qPCR). In addition, immunofluorescence analysis of EMZL samples was used to evaluate the in vivo expression of those components., Results: Gene expression and immunohistochemical analyses revealed the expression of RAS components, including (P)RR and angiotensin II type 1 receptor (AT1R), in EMZL tissues. Double-labeling analyses demonstrated that (P)RR and AT1R were detected in cells positive for CD20, a marker for B-cells, where they colocalized with prorenin and angiotensinogen, respectively. Prorenin stimulation of human B-lymphoblast IM-9 cells increased mRNA expression levels of fibroblast growth factor 2 (FGF2), while angiotensin II treatment upregulated the expression levels of basigin (BSG), matrix metallopeptidase (MMP)2, 9, and 14, which were abolished by (P)RR and AT1R blockades, respectively. Immunofluorescence analyses of clinical samples showed colocalizations of (P)RR and AT1R with the products of these upregulated genes., Conclusions: The present study suggests that activation of (P)RR and AT1R is associated with the pathogenesis of conjunctival EMZL by stimulating the production of FGF2 and MMPs., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To study the retinal degeneration caused by decreased proteasomal activity in β5t transgenic (β5t-Tg) mice, an animal model of senescence acceleration., Methods: β5t-Tg mice and age-matched littermate control (WT) mice were used. Proteasomal activities and protein level of poly-ubiquitinated protein in retinal extracts were quantified. Fundus images of β5t-Tg mice were taken and their features were assessed. For histologic evaluation, the thicknesses of inner nuclear layer (INL), outer nuclear layer (ONL), and photoreceptor outer segment (OS) were measured. For functional analysis, ERG was recorded under scotopic and photopic illumination conditions. Immunofluorescence (IF) staining and TUNEL were performed to investigate the mechanism of photoreceptor degeneration., Results: Chymotrypsin-like activity was partially suppressed in retinal tissues of β5t-Tg mice. Retinal degenerative changes with arterial attenuation were present in β5t-Tg, but not in WT mice. Inner nuclear layer thickness showed no significant change between β5t-Tg and WT mice at 1, 3, 6, and 9 months of age. By contrast, thicknesses of ONL and OS in β5t-Tg mice were significantly decreased at 3, 6, and 9 months compared with those in WT mice. Electroretinograms showed decrease of scotopic a-wave amplitude in β5t-Tg mice. The number of TUNEL-positive cells in ONL were significantly increased in β5t-Tg mice and colocalized with apoptosis-inducing factor, but not with cleaved caspase-3 and -9, indicating that the photoreceptor cell death was induced via a caspase-independent pathway., Conclusions: The current data showed that impaired proteasomal function causes photoreceptor degeneration., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To examine the expression of VEGF in extranodal marginal zone B-cell lymphoma (EMZL) and reactive lymphoid hyperplasia (RLH) of human ocular adnexa, and analyze the correlation with the intratumoral microvessel density (MVD)., Methods: Twenty-two EMZL and 16 RLH tissues were examined in this study. Paraformaldehyde-fixed, paraffin-embedded tissue sections were processed for immunohistochemistry with antibodies against VEGF and CD20. Vascular endothelial growth factor expression was analyzed using the ELISA and RT-PCR in the EMZL tissues. Microvessel density was determined based on the immunoreactivity for anti-CD34 antibody., Results: Vascular endothelial growth factor immunoreactivity was detected in the cytoplasm of lymphoid cells in EMZL and RLH. ELISA and RT-PCR confirmed VEGF protein and mRNA expressions in the EMZL tissue, respectively. Vascular endothelial growth factor-immunopositive rate in B-cells was significantly higher in 12 conjunctival EMZLs than four RLHs (P < 0.01) and 10 orbital EMZLs than 12 RLHs (P < 0.05). The MVD showed a significant positive correlation with the VEGF-immunopositive rate in conjunctival and orbital EMZLs., Conclusions: This study demonstrated increased VEGF expression in human conjunctival and orbital EMZL compared with that in RLH, suggesting that VEGF plays a significant role in the pathogenesis and tumor angiogenesis of ocular adnexal lymphoma., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To investigate the antiangiogenic properties of tissue kallikrein in a murine model of laser-induced choroidal neovascularization (CNV)., Methods: CNV was induced in male C57BL/6J mice by laser photocoagulation. The animals received daily subcutaneous injections of tissue kallikrein (50 μg/kg) or vehicle control for 2 days before the laser photocoagulation, and this treatment continued until sample collection. Seven days after laser injury, the CNV size was quantified. The levels of monocyte chemoattractant protein (MCP)-1, intercellular adhesion molecule (ICAM)-1, and interleukin (IL)-6 were assessed by enzyme-linked immunosorbent assay 3 days after laser injury. Cleavage of mouse VEGF with tissue kallikrein was assessed in vivo and in vitro. The protein levels of bradykinin were assessed in the RPE-choroid complexes and hearts., Results: A significant decrease in CNV size was observed in animals treated with tissue kallikrein (27,168.3 ± 2432.2 μm(2)) compared with vehicle-treated controls (36,374.6 ± 3204.1 μm(2), P < 0.05). Tissue kallikrein treatment significantly reduced MCP-1, ICAM-1, and IL-6 levels in RPE-choroid complexes. Furthermore, immunoblotting showed the bands, presumably corresponding to the fragmented VEGF(164) protein, in the samples of both mouse VEGF preincubated with tissue kallikrein and RPE-choroid complexes obtained from animals treated with tissue kallikrein. In addition, bradykinin was unchanged in the RPE-choroid complexes of animals treated with tissue kallikrein, whereas the level of bradykinin was increased in the heart obtained from these experimental animals., Conclusions: The current data indicate that kallikrein exhibits antiangiogenic properties by cleaving VEGF(164) in a laser-induced CNV model.

Purpose: To examine the expression of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR)-2 in enucleated eyes with Coats' disease., Methods: Formalin-fixed, paraffin-embedded tissue sections from nine globes with Coats' disease were submitted for hematoxylin and eosin staining and immunohistochemistry with anti-VEGF and VEGFR antibodies., Results: Histologically, the enucleated eyes demonstrated the presence of macrophage infiltration and cholesterol clefts in the subretinal space. There were marked retinal vascular abnormalities, including dilated vessels with hyalinized vessel walls in six globes. Exudative retinal detachment was noted in all globes. VEGF immunoreactivity was observed in macrophages infiltrating the subretinal space, and in the detached retina including several blood vessels. VEGF-positivity in macrophages was significantly higher in cases containing retinal vessel abnormalities than those without the abnormalities (P < 0.01). VEGFR-2 immunoreactivity was detected in endothelial cells lining the abnormal retinal vessels, where VEGFR-1 or VEGFR-3 was not expressed., Conclusions: Immunoreactivity for VEGF and VEGFR-2 was detected in macrophages and endothelia of abnormal vessels in eyes with Coats' disease. These results suggest that anti-VEGF approach is a promising therapy for patients with Coats' disease.

Purpose: Vascular adhesion protein (VAP)-1, a multifunctional molecule with adhesive and enzymatic properties, is expressed at the surface of vascular endothelial cells of mammals. It also exists as a soluble form (sVAP-1), which is implicated in oxidative stress via its enzymatic activity. This study explores a link between increased level of sVAP-1 and oxidative stress in proliferative diabetic retinopathy (PDR) with a focus on mechanistic components to form sVAP-1 by shedding from retinal endothelial cells., Methods: Protein levels of sVAP-1 and N epsilon-(hexanoyl)lysine (HEL), an oxidative stress marker, in the vitreous samples from patients with PDR or non-PDR were measured by ELISA. The mechanism of VAP-1 shedding under diabetic condition, exposure to high glucose and/or inflammatory cytokines, was explored using cultured retinal capillary endothelial cells., Results: Protein level of sVAP-1 was increased and correlated with HEL in the vitreous fluid of patients with PDR. Retinal capillary endothelial cells released sVAP-1 when stimulated with high glucose or inflammatory cytokines, such as TNF-α and IL-1β in vitro. Furthermore, matrix metalloproteinase-2 and -9, type IV collagenases, were the key molecules to mediate the protein cleavage of VAP-1 from retinal capillary endothelial cells., Conclusions: Our data for the first time provide evidence on the link between sVAP-1 and type IV collagenases in the pathogenesis of PDR.

Purpose: AMP-activated protein kinase (AMPK) is a sensor of cellular energy status. The purpose of the present study was to elucidate the roles of AMPK in the pathogenesis of diabetic retinopathy using the known AMPK activators resveratrol and AICAR (5-aminoimidazole-4-carboxamide ribonucleoside) in a mouse model., Methods: C57BL/6 mice with streptozotocin-induced diabetes were treated with resveratrol orally at 50 mg/kg for 7 days or with AICAR intraperitoneally at 100 mg/kg 24 hours before death. Retinal protein levels of phosphorylated and total AMPK, phosphorylated nuclear factor (NF)-κB p65, intercellular adhesion molecule (ICAM)-1, and vascular endothelial growth factor (VEGF) were evaluated by Western blot analysis or enzyme-linked immunosorbent assay. Retinal activity of sirtuin (SIRT)1 was measured by deacetylase fluorometric assay. Leukocyte adhesion to the retinal vasculature was examined with a concanavalin A lectin perfusion-labeling technique., Results: Induction of diabetes in mice led to retinal AMPK dephosphorylation, which was significantly reversed by either resveratrol or AICAR. Either resveratrol or AICAR significantly reversed SIRT1 deactivation and NF-κB phosphorylation, both of which were induced in the diabetic retina. Administration of resveratrol to diabetic mice significantly reduced diabetes-induced retinal leukocyte adhesion, together with retinal expression of ICAM-1 and VEGF., Conclusions: The present findings reveal that diabetes-induced retinal inflammation stems from downregulation of the AMPK pathway, leading subsequently to SIRT1 deactivation and NF-κB activation. The data also suggest the potential use of the AMPK activator resveratrol as a therapeutic agent for diabetic retinopathy.

Purpose: To investigate the influence of deficiency in superoxide dismutase (SOD) 1, a major antioxidative enzyme, on retinal ganglion cells (RGCs)., Methods: In the SOD1 total knockout (SOD1-deficient) mice, the level of superoxide anion was measured using dihydroethidium. The number of RGCs was counted in both the retinal sections and the flat-mount retinas after retrograde labeling. Thickness of nerve fiber layer (NFL) was measured in the sections, and the amount of neurofilament protein was measured by immunoblot analysis. Pattern electroretinogram (ERG), which reflects the function of retinal ganglion cells, dark-adapted ERG, and cone ERG were performed. The intraocular pressure (IOP) was measured with an induction-impact tonometer. The levels of SOD-1 and -2 were measured by ELISA, in the serum of 47 newly diagnosed consecutive normal tension glaucoma (NTG) patients and 44 consecutive control subjects., Results: The level of superoxide anion in the RGC layer was significantly higher in 24-week-old SOD1-deficient mice than in wild-type mice. The RGC number was significantly reduced in 24-week-old SOD1-deficient mice, although they were not in 8-week-old mice. The NFL thickness and neurofilament protein were reduced in 24-week-old SOD1-deficient mice. The amplitude of pattern ERG was significantly reduced, although dark-adapted and cone ERGs showed no impairment, in 24-week-old SOD1-deficient mice. The IOP level was not changed in the SOD1-deficient mice. The serum level of SOD1, but not SOD2, was significantly lower in the NTG patients than in the healthy controls., Conclusions: SOD1 deficiency causes RGC vulnerability, which may be involved in the underlying condition of NTG.

Purpose: To investigate the role of reactive oxygen species (ROS) as the prime initiators of the angiogenic response after alkali injury of the cornea and observe the effects of antioxidants in preventing angiogenesis., Methods: The corneal epithelia of SOD-1-deficient mice or wild-type (WT) mice were removed after application of 0.15 N NaOH to establish the animal model of alkali burn. ROS production was semiquantitatively measured by dihydroethidium (DHE) fluorescence. Angiogenesis was visualized by CD31 immunohistochemistry. The effects of the specific NF-κB inhibitor DHMEQ, the antioxidant N-acetyl-L-cysteine (NAC), and hydrogen (H2) solution were observed., Results: ROS production in the cornea was enhanced immediately after alkali injury, as shown by increased DHE fluorescence (P<0.01). NF-κB activation and the upregulation of vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1) were significantly enhanced (P<0.01), leading to a significantly larger area of angiogenesis. Angiogenesis in SOD-1-/- mice corneas were significantly higher in WT mice (P<0.01), confirming the role of ROS. Pretreatment with the specific NF-κB inhibitor DHMEQ or the antioxidant NAC significantly reduced corneal angiogenesis by downregulating the NF-κB pathway (P<0.01) in both WT and SOD-1-/- mice. Furthermore, we showed that irrigation of the cornea with hydrogen (H2) solution significantly reduced angiogenesis after alkali-burn injury (P<0.01)., Conclusions: Immediate antioxidant therapy with H2-enriched irrigation solution is a new potent treatment of angiogenesis in cornea to prevent blindness caused by alkali burn.

Purpose: CD44 is a cell-surface adhesion molecule and receptor for hyaluronan (HA), one of the major extracellular matrix components. The purpose of the present study was to clarify a role of HA and CD44 in the development of choroidal neovascularization (CNV)., Methods: Laser photocoagulation was used to induce CNV in C57BL/6 mice or CD44-deficient mice. The mRNA expression of CD44 and HA synthase (HAS)-2 in the retinal pigment epithelium (RPE)-choroid complex was evaluated by DNA microarray and real-time RT-PCR analyses 3 days after laser treatment. HA synthesis and CD44 expression were examined by immunohistochemistry 1 week after photocoagulation. Mice with laser-induced CNV were systemically administered the HA synthesis inhibitor 4-methylumbelliferone (MU) or an anti-CD44-neutralizing antibody. The response of CNV was analyzed by volumetric measurements 1 week after photocoagulation. Macrophage infiltration into CNV lesions was evaluated by real-time RT-PCR for F4/80 3 days after laser-induced injury., Results: The induction of CNV led to a significant increase in expression of CD44 and HAS2 mRNA. HA and CD44 were immunopositive in the CNV lesions. Compared with vehicle treatment, the systemic application of MU significantly attenuated CNV volume in a dose-dependent fashion, together with macrophage infiltration into the lesions. Consistently, antibody-based blockade of CD44 resulted in a significant reduction of CNV volume, compared with the isotype control. In contrast, genetic ablation of CD44 significantly augmented CNV formation together with HA accumulation and macrophage infiltration, compared with wild-type mice., Conclusions: These results indicate a significant role of HA and its receptor CD44 in the development of CNV.

Purpose: Resveratrol is known as one of the antioxidant polyphenols contained in red wine and grape skin. The purpose of the present study was to investigate the role of resveratrol in ocular inflammation in endotoxin-induced uveitis (EIU)., Methods: EIU was induced in male C57/B6 mice at the age of 6 weeks by a single intraperitoneal injection of lipopolysaccharide (LPS). Animals had received oral supplementation of resveratrol at the doses of 5, 50, 100, or 200 mg/kg for 5 days until LPS injection. Twenty-four hours after LPS administration, leukocyte adhesion to the retinal vasculature was examined with a concanavalin A lectin perfusion-labeling technique. Retinal and retinal pigment epithelium (RPE)-choroidal levels of intercellular adhesion molecule (ICAM)-1, monocyte chemotactic protein (MCP)-1, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nuclear translocation of nuclear factor (NF)-kappaB p65 were evaluated by enzyme-linked immunosorbent assay. Retinal and RPE-choroidal activities of silent information regulator two ortholog (SIRT) 1 were measured by deacetylase fluorometric assay., Results: Resveratrol pretreatment led to significant and dose-dependent suppression of leukocyte adhesion to retinal vessels of EIU mice compared with vehicle application. Protein levels of MCP-1 and ICAM-1 in the retina and the RPE-choroid of EIU animals were significantly reduced by resveratrol administration. Importantly, resveratrol-treated animals showed significant decline of retinal 8-OHdG generation and nuclear NF-kappaB P65 translocation, both of which were upregulated after EIU induction. RPE-choroidal SIRT1 activity, reduced in EIU animals, was significantly augmented by treatment with resveratrol., Conclusions: Resveratrol prevented EIU-associated cellular and molecular inflammatory responses by inhibiting oxidative damage and redox-sensitive NF-kappaB activation.

Purpose: Lutein has been the focus of recent study as a possible therapeutic approach for retinal diseases, but the molecular mechanism of its neuroprotective effect remains to be elucidated. The aim of this study was to investigate, with the use of a mouse endotoxin-induced uveitis (EIU) model, the neuroprotective effects of lutein against retinal neural damage caused by inflammation., Methods: EIU was induced by intraperitoneal injection of lipopolysaccharide (LPS). Each animal was given a subcutaneous injection of lutein or vehicle three times: concurrently with and 3 hours before and after the LPS injection. Analysis was carried out 24 hours after EIU induction. Levels of rhodopsin protein and STAT3 activation were analyzed by immunoblotting. Lengths of the outer segments of the photoreceptor cells were measured. Dark-adapted full-field electroretinograms were recorded. Oxidative stress in the retina was analyzed by dihydroethidium and fluorescent probe. Expression of glial fibrillary acidic protein (GFAP) was shown immunohistochemically., Results: The EIU-induced decrease in rhodopsin expression followed by shortening of the outer segments and reduction in a-wave amplitude were prevented by lutein treatment. Levels of STAT3 activation, downstream of inflammatory cytokine signals, and reactive oxygen species (ROS), which are both upregulated during EIU, were reduced by lutein. Pathologic change of Müller glial cells, represented by GFAP expression, was also prevented by lutein., Conclusions: The present data revealed that the antioxidant lutein was neuroprotective during EIU, suggesting a potential approach for suppressing retinal neural damage during inflammation.

Purpose: To study whether corticosteroids protect photoreceptors when combined with photodynamic therapy (PDT) in a laser-induced model of choroidal neovascularization (CNV)., Methods: PDT was performed in 36 Brown-Norway rats 2 weeks after laser induction of CNV. The expressional change of several cytokines and chemokines in the CNV lesions after PDT was measured by real-time PCR in combination with laser-capture microdissection. Immunostaining for monocyte chemoattractant protein (MCP)-1, C-C chemokine receptor 2(CCR2), interleukin (IL)-1beta, and myeloperoxidase(MPO) were performed. To study the effect of corticosteroids in combination with PDT, either dexamethasone (100 mg/kg) or control was injected intraperitoneally 1 hour before PDT. Animals were killed 24 hours or 1 week after PDT. CNV was examined by fluorescein angiography and choroidal flatmount. Photoreceptor degeneration was evaluated by TUNEL assay., Results: MCP-1 and IL-1beta was increased in CNV lesions 24 hours after PDT. CCR2 was also expressed in laser-induced CNV but did not increase after PDT. Twenty-four hours after PDT, MPO-positive cells were noted in the CNV lesions. Dexamethasone-treated animals had significantly fewer TUNEL-positive cells in the photoreceptor layer than did the control animals (P < 0.05) after PDT. Fluorescein angiographic grading of CNV closure 6 days after PDT showed a closure rate in the dexamethasone-treated group of 31% (15/48 lesions) compared to 10% (4/42 lesions) in the control group (P < 0.05). CNV size was significantly smaller in the dexamethasone-treated group 1 week after PDT compared with the control (P < 0.05)., Conclusions: Systemic administration of dexamethasone combined with PDT reduces photoreceptor apoptosis, increases angiographic closure, and reduces CNV size compared with PDT alone in a rat model.

Purpose: Azurocidin, released by neutrophils during leukocyte-endothelial interaction, is a main cause of neutrophil-evoked vascular leakage. Its role in the retina, however, is unknown., Methods: Brown Norway rats received intravitreal injections of azurocidin and vehicle control. Blood-retinal barrier (BRB) breakdown was quantified using the Evans blue (EB) dye technique 1, 3, and 24 hours after intravitreal injection. To block azurocidin, aprotinin was injected intravenously before the intravitreal injections. To investigate whether azurocidin plays a role in vascular endothelial growth factor (VEGF)-induced BRB breakdown, rats were treated intravenously with aprotinin, followed by intravitreal injection of VEGF(164). BRB breakdown was quantified 24 hours later. To investigate whether azurocidin may mediate BRB breakdown in early diabetes, aprotinin or vehicle was injected intravenously each day for 2 weeks to streptozotocin-induced diabetic rats, and BRB breakdown was quantified., Results: Intravitreal injection of azurocidin (20 microg) induced a 6.8-fold increase in vascular permeability compared with control at 1-3 hours (P < 0.05), a 2.7-fold increase at 3 to 5 hours (P < 0.01), and a 1.7-fold increase at 24 hours (P < 0.05). Aprotinin inhibited azurocidin-induced BRB breakdown by more than 95% (P < 0.05). Furthermore, treatment with aprotinin significantly suppressed VEGF-induced BRB breakdown by 93% (P < 0.05) and BRB breakdown in early experimental diabetes by 40.6% (P < 0.05)., Conclusions: Azurocidin increases retinal vascular permeability and is effectively blocked by aprotinin. The inhibition of VEGF-induced and early diabetic BRB breakdown with aprotinin indicates that azurocidin may be an important mediator of leukocyte-dependent BRB breakdown secondary to VEGF. Azurocidin may become a new therapeutic target in the treatment of retinal vascular leakage, such as during diabetic retinopathy.

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.

Purpose: To investigate the role of eicosapentaenoic acid (EPA), the major omega-3 polyunsaturated fatty acid (PUFA), in the development of choroidal neovascularization (CNV), together with underlying molecular mechanisms., Methods: Six-week-old C57BL/6 mice were fed with laboratory chow with 5% EPA or the omega-6 PUFA linoleic acid (LA) for 4 weeks. Laser photocoagulation was performed to induce CNV, and the volume of CNV tissue was evaluated by volumetric measurements. The expression and production of intercellular adhesion molecule (ICAM)-1, monocyte chemotactic protein (MCP)-1, vascular endothelial growth factor (VEGF) and interleukin (IL)-6 in the retinal pigment epithelium (RPE)-choroid in vivo, and stimulated b-End3 endothelial cells and RAW264.7 macrophages in vitro were evaluated by RT-PCR and ELISA. Fatty acid composition in the serum and the RPE-choroid was analyzed by gas chromatography and high-performance liquid chromatography, respectively. Serum levels of C-reactive protein (CRP), IL-6, VEGF, MCP-1, and soluble ICAM-1 were examined by ELISA., Results: The CNV volume in EPA-fed animals was significantly suppressed compared with that in control mice, whereas the LA-rich diet did not affect CNV. The mRNA expression and protein levels of ICAM-1, MCP-1, VEGF, and IL-6 after CNV induction were significantly reduced in EPA-supplemented mice. In vitro, EPA application led to significant inhibition of mRNA and protein levels of ICAM-1 and MCP-1 in endothelial cells and VEGF and IL-6 in macrophages. EPA-fed mice exhibited significantly higher levels of EPA and lower levels of the omega-6 PUFA arachidonic acid in the serum and the RPE-choroid than control animals. EPA supplementation also led to significant reduction of serum levels of IL-6 and CRP after CNV induction., Conclusions: The present study demonstrates for the first time that an EPA-rich diet results in significant suppression of CNV and CNV-related inflammatory molecules in vivo and in vitro. These results suggest that frequent consumption of omega-3 PUFAs may prevent CNV and lower the risk of blindness due to age-related macular degeneration.

Purpose: Angiotensin-converting enzyme (ACE), also known as kininase II, functions not only to convert angiotensin I to angiotensin II, but also to cleave bradykinin into inactive fragments. Thus, ACE inhibition causes the tissue accumulation of bradykinin, exerting either of two opposite effects: anti- or proangiogenic. The purpose of the present study was to investigate the role of bradykinin in the development of choroidal neovascularization (CNV), with or without ACE inhibition., Methods: Laser photocoagulation was used to induce CNV in wild-type C57BL/6J mice and angiotensin II type 1 receptor (AT1-R)-deficient mice. Wild-type mice were pretreated with the ACE inhibitor imidapril, with or without the bradykinin B2 receptor (B2-R) antagonist icatibant daily for 6 days before photocoagulation, and the treatment was continued daily until the end of the study. CNV response was analyzed by volumetric measurements using confocal microscopy 1 week after laser injury. The mRNA and protein levels of vascular endothelial growth factor (VEGF), intercellular adhesion molecule (ICAM)-1, and monocyte chemotactic protein (MCP)-1 in the retinal pigment epithelium-choroid complex were examined by RT-PCR and ELISA, respectively., Results: ACE inhibition led to significant suppression of CNV development to the level seen in AT1-R-deficient mice. B2-R blockade together with high-dose but not low-dose ACE inhibition resulted in more potent suppression of CNV than did ACE inhibition alone. B2-R blockade alone exhibited little or no effect on CNV. VEGF, ICAM-1, and MCP-1 levels, elevated by CNV induction, were significantly suppressed by ACE inhibition. VEGF but not ICAM-1 or MCP-1 levels were further attenuated by B2-R blockade with ACE inhibition., Conclusions: These results suggest a limited contribution of the kallikrein-kinin system to the pathogenesis of CNV, in which the renin-angiotensin system plays more essential roles for facilitating angiogenesis. The present study indicates the possibility of ACE inhibition as a novel therapeutic strategy to inhibit CNV.

Purpose: Recently, it was revealed that the inhibition of nonproteolytic activation of prorenin led to significant suppression of ocular inflammation in endotoxin-induced uveitis. The purpose of the present study was to investigate whether nonproteolytically activated prorenin plays a role in ischemia-induced retinal neovascularization., Methods: C57BL/6 neonatal mice were reared in an 80% concentration of oxygen from postnatal (P) day 7 to P12, followed by room-air breathing to P17 to induce ischemia-initiated retinal neovascularization. Tissue localization of activated prorenin and prorenin receptor was examined by immunohistochemistry. Animals received intraperitoneal injections of handle-region peptide (HRP), a decoy peptide corresponding to the handle region of prorenin, which inhibits prorenin receptor-mediated upregulation of the renin-angiotensin system (RAS). A concanavalin A lectin perfusion-labeling technique was used to evaluate the areas of physiologic and pathologic retinal new vessels and the number of leukocytes adhering to the vasculature. Retinal mRNA expression and protein levels of intercellular adhesion molecule (ICAM)-1, vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)-1, and VEGFR-2 were examined by RT-PCR and ELISA., Results: Retinal vessels in ischemic retinopathy eyes were positive for activated prorenin and prorenin receptor. Pathologic, but not physiologic, retinal neovascularization was significantly attenuated in HRP-treated mice compared with vehicle- or control peptide-treated animals. The number of adherent leukocytes was also significantly reduced. Retinal mRNA expression and protein levels of ICAM-1, VEGF, VEGFR-1, and VEGFR-2 in ischemic retinopathy were also significantly suppressed by the application of HRP., Conclusions: The present findings suggest that nonproteolytic activation of prorenin selectively promotes pathologic, but not physiologic, retinal neovascularization through the inflammatory processes related to pathologic neovascularization.

Purpose: A recent study revealed that angiotensin receptor signaling mediates ocular inflammation and neovascularization. It was also found that prorenin undergoes nonproteolytic activation leading to upregulation of the renin-angiotensin system (RAS) when prorenin receptor interacts specifically with the handle region of prorenin. The purpose of the present study was to elucidate the role of the receptor-dependent nonproteolytic activation of prorenin in ocular inflammation in endotoxin-induced uveitis (EIU)., Methods: EIU was induced in Long-Evans rats by a single intraperitoneal injection of 100 microg lipopolysaccharide (LPS). Tissue localization of total prorenin, prorenin receptor, and activated prorenin in the EIU retina was examined by immunohistochemistry. To inhibit the prorenin receptor-mediated upregulation of the RAS, a decoy handle-region peptide (HRP) was intraperitoneally administered 24 hours before and immediately after the injection of LPS. Twenty-four hours after LPS injection, leukocyte adhesion to the retinal vasculature was evaluated with a concanavalin A lectin perfusion-labeling technique. In addition, leukocyte infiltration into the vitreous cavity and protein concentration in the anterior chamber were also measured. Retinal mRNA and protein levels of intercellular adhesion molecule (ICAM)-1, interleukin (IL)-6, and C-C chemokine ligand (CCL) 2/monocyte chemotactic protein (MCP)-1 were examined by RT-PCR and ELISA., Results: Retinal vessels in rats with EIU were strongly positive for total prorenin, prorenin receptor, and activated prorenin. Systemic treatment with HRP resulted in dose- and time-dependent inhibition of the leukocyte adhesion and infiltration and the protein leakage, all of which were increased by the induction of EIU. Retinal mRNA expression and protein levels of ICAM-1, CCL2/MCP-1 and IL-6, induced in rats with EIU, were also significantly suppressed with application of HRP., Conclusions: These findings demonstrate for the first time that nonproteolytically activated prorenin plays a significant role in the development of ocular inflammation in the EIU model. The present study suggests the potential use of HRP, a decoy peptide binding to the prorenin receptor, as a therapeutic agent to reduce ocular inflammation.

Purpose: Fibrovascular tissue formation in diabetic retinopathy necessitates not only angiogenic activity but also proteolytic activity, which is at least in part attributable to the induction of membrane-type 1 matrix metalloproteinase (MT1-MMP) in retinal glial cells. However, little is known about the triggers for MT1-MMP induction in the diabetic retina. In the present study, the effect of tissue hypoxia on MT1-MMP expression in retinal glial cells was investigated., Methods: Retinal glial cells were isolated from the rabbit retina and cultured under either normoxic (20% O(2)) or hypoxic (1% O(2)) conditions in the presence or absence of the inhibitor for vascular endothelial growth factor (VEGF) receptor signal transduction or a neutralizing antibody against VEGF. The expression level of MT1-MMP in retinal glial cells was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR, Western blot analysis and immunocytochemistry. Expression of VEGF and VEGF receptors, VEGFR-1 and VEGFR-2, was also examined by RT-PCR., Results: RT-PCR and real-time PCR analyses showed a 2.3-fold induction of MT1-MMP expression in retinal glial cells under hypoxic conditions. VEGF, especially its isoform VEGF(165), and VEGFR-2 were also upregulated in retinal glial cells by hypoxia, and hypoxia-induced MT1-MMP expression was inhibited in the presence of the VEGFR-2 inhibitor SU1498 or the anti-VEGF antibody., Conclusions: Hypoxia can induce MT1-MMP expression in retinal glial cells, and the hypoxia-induced expression of MT1-MMP is mediated by VEGF in an autocrine fashion.

Purpose: To examine whether the angiotensin II type 1 receptor (AT1-R) signaling plays a role in ocular inflammation in endotoxin-induced uveitis (EIU)., Methods: EIU was induced in C57BL/6 mice by a single intraperitoneal injection of 150 mug lipopolysaccharide (LPS). Tissue localization, mRNA expression, and protein levels of AT1-R in murine retinas were examined by immunohistochemistry, RT-PCR, and Western blot analyses, respectively. Telmisartan, an AT1-R antagonist widely used as an antihypertensive agent, was administered intraperitoneally at a dose of 10 mg/kg daily for 5 days until the injection of LPS. Twenty-four hours after administration, leukocyte adhesion to the retinal vasculature was evaluated with a concanavalin A lectin perfusion-labeling technique. Retinal mRNA and protein levels of intercellular adhesion molecule (ICAM)-1 were examined by RT-PCR and ELISA, respectively. Protein concentration and inflammatory cells in the aqueous humor were also measured., Results: Retinal vessels were positive for AT1-R. In mice with EIU, retinal AT1-R mRNA and protein levels were significantly increased when compared to the normal control. EIU animals also showed significant increases in the number of inflammatory cells infiltrating the anterior chamber and adhering to the retinal vessels and in retinal ICAM-1 levels. Administration of telmisartan to EIU mice resulted in significant suppression of retinal ICAM-1 expression and leukocyte adhesion and infiltration compared with vehicle treatment. Protein concentration in the aqueous humor of telmisartan-treated EIU mice tended to be lower than that of vehicle-treated EIU mice, but the difference was not statistically significant., Conclusions: AT1-R signaling blockade inhibited retinal ICAM-1 upregulation and leukocyte adhesion and infiltration in the EIU model. These results suggest the potential use of an AT1-R antagonist as a therapeutic agent to reduce ocular inflammation.

Purpose: To investigate the anti-inflammatory and anti-angiogenic effects of telmisartan, an angiotensin II type 1 receptor (AT1-R) antagonist, on ischemia-induced retinal neovascularization., Methods: C57BL/6 neonatal mice were reared in an 80% concentration of oxygen from postnatal day (P)7 to P12, followed by room-air breathing until P17, to induce ischemia-initiated retinal neovascularization (i.e., a murine model of ischemic retinopathy). Tissue localization of AT1-R was examined by immunohistochemistry for murine retinal wholemounts and human fibrovascular tissues excised at vitrectomy for proliferative diabetic retinopathy. Animals received intraperitoneal injection of telmisartan or vehicle. A concanavalin A lectin perfusion-labeling technique was used to evaluate the areas of physiological and pathologic retinal new vessels and the number of leukocytes adhering to the vasculature. Retinal mRNA and protein levels of intercellular adhesion molecule (ICAM)-1, vascular endothelial growth factor receptor (VEGFR)-1, and VEGFR-2 were examined by RT-PCR and ELISA., Results: Vessels in human fibrovascular tissues and the murine retinas were positive for AT1-R. Pathologic (P < 0.01), but not physiologic (P > 0.05), retinal neovascularization was significantly suppressed in telmisartan-treated mice compared with vehicle-treated animals. The number of adherent leukocytes (P < 0.01) was also significantly reduced, together with retinal ICAM-1 levels (P < 0.01) in the telmisartan-treated group compared with the control group. No significant difference was detected in retinal VEGFR-2 levels between the two groups, whereas retinal VEGFR-1 levels in the telmisartan-treated group were significantly (P < 0.05) lower than in the vehicle-treated group., Conclusions: The present findings suggest that the AT1-R signaling blockade leads to the selective suppression of pathologic, but not physiological, retinal neovascularization through the inhibition of the inflammatory processes related to pathologic neovascularization.

Purpose: To investigate the matrix metalloproteinase (MMP) species and their activation associated with the pathogenesis of proliferative diabetic retinopathy (PDR)., Methods: Sandwich enzyme immunoassays were used to measure concentrations of MMP-1, -2, -3, -7, -8, -9, and -13 in vitreous samples from patients with PDR and nondiabetic vitreoretinal diseases. To evaluate activation ratios of the zymogen of MMP-2 (proMMP-2) and -9 (proMMP-9) in the vitreous samples and fibrovascular tissues, gelatin zymography was performed. Production and tissue localization of MMP-2, membrane type 1-MMP (MT1-MMP), tissue inhibitor of metalloproteinases (TIMP)-2, and MMP-9 in the fibrovascular tissues were examined by immunohistochemistry. mRNA expression of MT1-MMP in the tissues was determined by reverse transcription-polymerase chain reaction (RT-PCR)., Results: Among the seven different MMPs examined in the vitreous samples, only the levels of MMP-2 and -9 were significantly higher in the PDR samples than in the control. However, activation ratios of proMMP-2 (10.6% +/- 11.8%) and proMMP-9 (2.5% +/- 5.1%) in PDR vitreous samples were low and not significantly different from those of the control. In contrast, high activation ratios of proMMP-2 (54.3% +/- 13.6%) and notable activation of proMMP-9 (19.5% +/- 7.8%) were observed in the fibrovascular tissues. Immunohistochemical study demonstrated the localization of MMP-2 and -9 in the endothelial cells and glial cells of the fibrovascular tissues. MMP-2 was colocalized with MT1-MMP and TIMP-2, which are an activator and an activation-enhancing factor, respectively, for proMMP-2. RT-PCR analysis indicated the gene expression of MT1-MMP in the tissues., Conclusions: These data demonstrate that proMMP-2 is efficiently activated in the fibrovascular tissues of PDR, probably through interaction with MT1-MMP and TIMP-2, and suggest the possibility that the activity of MMP-2 and MT1-MMP is involved in the formation of the fibrovascular tissues.