Elia J Duh

Johns Hopkins University, Baltimore, Maryland, United States

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Publications (53)271.98 Total impact

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    ABSTRACT: Retinal ischemia results in neuronal degeneration and contributes to the pathogenesis of multiple blinding diseases. Recently, the fumaric acid ester dimethyl fumarate (DMF) has been FDA-approved for the treatment of multiple sclerosis, based on its neuroprotective and anti-inflammatory effects. Its potential role as a neuroprotective agent for retinal diseases has received little attention. In addition, DMF’s mode of action remains elusive, although studies have suggested nuclear factor erythroid 2-related factor 2 (Nrf2) activation as an important mechanism. Here we investigated the neuroprotective role of monomethyl fumarate (MMF), the biologically active metabolite of DMF, in retinal ischemia-reperfusion (I/R) injury, and examined the role of Nrf2 in mediating MMF action. Wild-type C57BL/6J and Nrf2 knockout (KO) mice were subjected to 90 min of retinal ischemia followed by reperfusion. Mice received daily intraperitoneal injection of MMF. Inflammatory gene expression was measured using quantitative reverse transcription PCR (qRT-PCR) at 48 h after I/R injury. Seven days after I/R, qRT-PCR for Nrf2 target gene expression, immunostaining for Müller cell gliosis and cell loss in the ganglion cell layer (GCL), and electroretinography for retinal function were performed. The results of this study confirmed that MMF reduces retinal neurodegeneration in an Nrf2-dependent manner. MMF treatment significantly increased the expression of Nrf2-regulated antioxidative genes, suppressed inflammatory gene expression, reduced Müller cell gliosis, decreased neuronal cell loss in the GCL, and improved retinal function measured by electroretinogram (ERG) after retinal I/R injury in wild-type mice. Importantly, these MMF-mediated beneficial effects were not observed in Nrf2 KO mice. These results indicate that fumaric acid esters (FAEs) exert a neuronal protective function in the retinal I/R model and further validate Nrf2 modulation as a major mode of action of FAEs. This suggests that DMF and FAEs could be a potential therapeutic agent for activation of the Nrf2 pathway in retinal and possibly systemic diseases.
    No preview · Article · Dec 2015 · Journal of Neuroinflammation
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    ABSTRACT: Delayed revascularization of ischemic neural tissue is a major impediment to preservation of function in central nervous system (CNS) diseases including stroke and ischemic retinopathies. Therapeutic strategies allowing rapid revascularization are greatly needed to reduce ischemia-induced cellular damage and suppress harmful pathologic neovascularization. However, key mechanisms governing vascular recovery in ischemic CNS, including regulatory molecules governing the transition from tissue injury to tissue repair, are largely unknown. NF-E2-related factor 2 (Nrf2) is a major stress-response transcription factor well known for its cell-intrinsic cytoprotective function. However, its role in cell-cell crosstalk is less appreciated. Here we report that Nrf2 is highly activated in ischemic retina and promotes revascularization by modulating neurons in their paracrine regulation of endothelial cells. Global Nrf2 deficiency strongly suppresses retinal revascularization and increases pathologic neovascularization in a mouse model of ischemic retinopathy. Conditional knockout studies demonstrate a major role for neuronal Nrf2 in vascular regrowth into avascular retina. Deletion of neuronal Nrf2 results in semaphorin 6A (Sema6A) induction in hypoxic/ischemic retinal ganglion cells in a hypoxia-inducible factor-1 alpha (HIF-1α)-dependent fashion. Sema6A expression increases in avascular inner retina and colocalizes with Nrf2 in human fetal eyes. Extracellular Sema6A leads to dose-dependent suppression of the migratory phenotype of endothelial cells through activation of Notch signaling. Lentiviral-mediated delivery of Sema6A small hairpin RNA (shRNA) abrogates the defective retinal revascularization in Nrf2-deficient mice. Importantly, pharmacologic Nrf2 activation promotes reparative angiogenesis and suppresses pathologic neovascularization. Our findings reveal a unique function of Nrf2 in reprogramming ischemic tissue toward neurovascular repair via Sema6A regulation, providing a potential therapeutic strategy for ischemic retinal and CNS diseases.
    No preview · Article · Nov 2015 · Proceedings of the National Academy of Sciences
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    ABSTRACT: Endothelial cells play a major role in the initiation and perpetuation of the inflammatory process in health and disease, including their pivotal role in leukocyte recruitment. The role of pro-inflammatory transcription factors in this process has been well-described, including NF-κB. However, much less is known regarding transcription factors that play an anti-inflammatory role in endothelial cells. Myocyte enhancer factor 2 C (MEF2C) is a transcription factor known to regulate angiogenesis in endothelial cells. Here, we report that MEF2C plays a critical function as an inhibitor of endothelial cell inflammation. Tumor necrosis factor (TNF)-α inhibited MEF2C expression in endothelial cells. Knockdown of MEF2C in endothelial cells resulted in the upregulation of pro-inflammatory molecules and stimulated leukocyte adhesion to endothelial cells. MEF2C knockdown also resulted in NF-κB activation in endothelial cells. Conversely, MEF2C overexpression by adenovirus significantly repressed TNF-α induction of pro-inflammatory molecules, activation of NF-κB, and leukocyte adhesion to endothelial cells. This inhibition of leukocyte adhesion by MEF2C was partially mediated by induction of KLF2. In mice, lipopolysaccharide (LPS)-induced leukocyte adhesion to the retinal vasculature was significantly increased by endothelial cell-specific ablation of MEF2C. Taken together, these results demonstrate that MEF2C is a novel negative regulator of inflammation in endothelial cells and may represent a therapeutic target for vascular inflammation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · Jun 2015 · Journal of Cellular Physiology
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    ABSTRACT: To determine whether scatter and grid laser photocoagulation (laser) adds benefit to ranibizumab injections in patients with macular edema from retinal vein occlusion (RVO) and to compare 0.5-mg with 2.0-mg ranibizumab. Randomized, double-masked, controlled clinical trial. Thirty-nine patients with central RVO (CRVO) and 42 with branch RVO (BRVO). Subjects were randomized to 0.5 mg or 2.0 mg ranibizumab every 4 weeks for 24 weeks and re-randomized to pro re nata ranibizumab plus laser or ranibizumab alone. Mean change from baseline best-corrected visual acuity (BCVA) at week 24 for BCVA at weeks 48, 96, and 144 for second randomization. Mean improvement from baseline BCVA at week 24 was 15.5 and 15.8 letters in the 0.5-mg and 2.0-mg CRVO groups, and 12.1 and 14.6 letters in the 0.5-mg and 2.0-mg BRVO groups. For CRVO, but not BRVO, there was significantly greater reduction from baseline mean central subfield thickness (CST) in the 2.0-mg versus 0.5-mg group (396.1 vs. 253.5 μm; P = 0.03). For the second randomization in CRVO patients, there was no significant difference from week 24 BCVA in the ranibizumab plus laser versus the ranibizumab only groups at week 48 (-3.3 vs. 0.0 letters), week 96 (+0.69 vs. -1.6 letters), or week 144 (+0.4 vs. -6.7 letters), and a significant increase from week 24 mean CST at week 48 (+94.7 vs. +15.2 μm; P = 0.05) but not weeks 96 or 144. For BRVO, there was a significant reduction from week 24 mean BCVA in ranibizumab plus laser versus ranibizumab at week 48 (-7.5 vs. +2.8; P < 0.01) and week 96 (-2.0 vs. +4.8; P < 0.03), but not week 144, and there were no differences in mean CST change from week 24 at weeks 48, 96, or 144. Laser failed to increase edema resolution or to reduce the ranibizumab injections between weeks 24 and 144. In patients with macular edema resulting from RVO, there was no short-term clinically significant benefit from monthly injections of 2.0-mg versus 0.5-mg ranibizumab injections and no long-term benefit in BCVA, resolution of edema, or number of ranibizumab injections obtained by addition of laser treatment to ranibizumab. Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
    No preview · Article · May 2015 · Ophthalmology
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    Full-text · Article · Mar 2015 · Diabetes
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    ABSTRACT: Retinal ischemia plays a critical role in multiple vision-threatening diseases and leads to death of retinal neurons, particularly ganglion cells. Oxidative stress plays an important role in this ganglion cell loss. Nrf2 (NF-E2-related factor 2) is a major regulator of the antioxidant response, and its role in the retina is increasingly appreciated. We investigated the potential retinal neuroprotective function of Nrf2 after ischemia-reperfusion (I-R) injury. In an experimental model of retinal I/R, Nrf2 knockout mice exhibited much greater loss of neuronal cells in the ganglion cell layer than wild-type mice. Primary retinal ganglion cells (RGCs) isolated from Nrf2 knockout mice exhibited decreased cell viability compared to wild-type RGCs, demonstrating the cell-intrinsic protective role of Nrf2. The retinal neuronal cell line 661W exhibited reduced cell viability following siRNA-mediated knockdown of Nrf2 under conditions of oxidative stress, and this was associated with exacerbation of increase in reactive oxygen species (ROS). The synthetic triterpenoid CDDO-Im (2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide), a potent Nrf2 activator, inhibited ROS increase in cultured 661W under oxidative stress conditions and increased neuronal cell survival after I/R injury in wild-type, but not Nrf2, knockout mice. Our findings indicate that Nrf2 exhibits a retinal neuroprotective function in I-R and suggest that pharmacologic activation of Nrf2 could be a therapeutic strategy. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · Feb 2015 · Journal of Neurochemistry
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    ABSTRACT: We recently demonstrated that 12/15-lipoxygenase (LOX) derived metabolites, hydroxyeicosatetraenoic acids (HETEs), contribute to diabetic retinopathy (DR) via NADPH oxidase (NOX) and disruption of the balance in retinal levels of the vascular endothelial growth factor (VEGF) and Pigment Epithelium-Derived Factor (PEDF). Here, we test whether PEDF ameliorates retinal vascular injury induced by HETEs and the underlying mechanisms. Furthermore, we pursue the causal relationship between LOX-NOX system and regulation of PEDF expression during DR. For these purposes, we used an experimental eye model in which normal mice were injected intravitreally with 12/15HETE with/without PEDF. Thereafter, Fluorescein Angiography (FA) was used to evaluate the vascular leakage, followed by Optical coherence tomography (OCT) to assess the presence of angiogenesis. FA and OCT reported an increased vascular leakage and pre-retinal neovascularization, respectively, in response to 12-HETE that were not observed in PEDF-treated group. Moreover, PEDF significantly attenuated the increased levels of vascular cell and intercellular adhesion molecules, VCAM-1 and ICAM-1, elicited by 12-HETE injection. Accordingly, the direct relationship between HETE and PEDF has been explored through in-vitro studies using Müller cells (rMCs) and human retinal endothelial cells (HRECs). The results showed that HETEs triggered the secretion of TNF-α and IL-6, as well as activation of NFκB in rMCs and significantly increased permeability and reduced zonula occludens protein-1 (ZO-1) immunoreactivity in HRECs. All these effects were prevented in PEDF-treated cells. Furthermore, interest in PEDF regulation during DR has been expanded to include NOX system. Retinal PEDF was significantly restored in diabetic mice treated with NOX inhibitor, apocynin, or lacking NOX2 up to 80% of the control level. Collectively, our findings suggest that interfering with LOX-NOX signaling opens up a new direction for treating DR by restoring endogenous PEDF that carries out multilevel vascular protective functions.
    No preview · Article · Jan 2015 · Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids
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    ABSTRACT: Purpose: Chronic inflammation is a critical process in pterygium development and progression, including promotion of angiogenesis. Vascular endothelial cells (ECs) actively participate in and regulate inflammation. Pterygium research has uncovered multiple inflammatory cytokines that are upregulated, but there has been minimal focus on EC activation. The Receptor for Advanced Glycation Endproducts (RAGE), a major proinflammatory molecule expressed in the vascular endothelium and other cell types, is a major instigator of endothelial cell activation. In this study, we explored the hypothesis that RAGE is upregulated in ECs in pterygium. To this end, we examined RAGE expression and immunolocalization in human pterygium and normal conjunctival tissue, with a particular interest in assessing endothelial RAGE.
    Full-text · Article · Dec 2014 · Molecular vision
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    ABSTRACT: A new diabetic mouse strain, the Akita.PlGF knockout ((-/-)), was generated to study the role of placental growth factor (PlGF) in the pathogenesis of diabetic retinopathy (DR). PlGF deletion did not affect blood glucose but reduced the body weight of Akita.PlGF(-/-) mice. Diabetes-induced retinal cell death, capillary degeneration, pericyte loss, and blood-retinal barrier breakdown were prevented in these mice. Protein expression of PlGF was upregulated by diabetes, particularly in vascular cells. Diabetes-induced degradation of ZO-1 and VE-cadherin was reversed due to PlGF deficiency; their expression was correlated with that of sonic hedgehog and angiopoietin-1. PlGF deletion in Akita mice resulted in an increased Akt phosphorylation. Diabetes-activated HIF1α-VEGF pathway, including expression of HIF1α , VEGF, VEGFR1-3 and the extent of phospho (p)-VEGFR1, p-VEGFR2 , and p-eNOS, was inhibited in the retinas of diabetic PlGF(-/-) mice. However, expression of ICAM-1, VCAM-1, CD11b, and CD18 was not inhibited by PlGF deletion, nor was retinal leukostasis. These results suggest that PlGF is critical for the development of DR and its genetic deletion protects the retina from diabetic damage. The protective mechanisms are associated with the Akt activation and HIF1α-VEGF pathway inhibition, but independent of retinal leukostasis in the retinas of diabetic PlGF(-/-) mice.
    Full-text · Article · Sep 2014 · Diabetes
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    ABSTRACT: Although much is known about the pathophysiological processes contributing to diabetic retinopathy (DR), the role of protective pathways has received less attention. The transcription factor nuclear factor erythroid-2-related factor 2 (also known as NFE2L2 or NRF2) is an important regulator of oxidative stress and also has anti-inflammatory effects. The objective of this study was to explore the potential role of NRF2 as a protective mechanism in DR. Retinal expression of NRF2 was investigated in human donor and mouse eyes by immunohistochemistry. The effect of NRF2 modulation on oxidative stress was studied in the human Müller cell line MIO-M1. Non-diabetic and streptozotocin-induced diabetic wild-type and Nrf2 knockout mice were evaluated for multiple DR endpoints. NRF2 was expressed prominently in Müller glial cells and astrocytes in both human and mouse retinas. In cultured MIO-M1 cells, NRF2 inhibition significantly decreased antioxidant gene expression and exacerbated tert-butyl hydroperoxide- and hydrogen peroxide-induced oxidative stress. NRF2 activation strongly increased NRF2 target gene expression and suppressed oxidant-induced reactive oxygen species. Diabetic mice exhibited retinal NRF2 activation, indicated by nuclear translocation. Superoxide levels were significantly increased by diabetes in Nrf2 knockout mice as compared with wild-type mice. Diabetic Nrf2 knockout mice exhibited a reduction in retinal glutathione and an increase in TNF-α protein compared with wild-type mice. Nrf2 knockout mice exhibited early onset of blood-retina barrier dysfunction and exacerbation of neuronal dysfunction in diabetes. These results indicate that NRF2 is an important protective factor regulating the progression of DR and suggest enhancement of the NRF2 pathway as a potential therapeutic strategy.
    No preview · Article · Nov 2013 · Diabetologia
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    ABSTRACT: To determine the percentage of ranibizumab-treated patients with retinal vein occlusion (RVO) who had resolution of edema for at least 6 months after the last injection, along with factors and outcomes that correlate with resolution. Post hoc analysis of open-label clinical trial. Twenty patients with branch RVO (BRVO) and 20 with central RVO (CRVO) received ranibizumab monthly for 3 months and as needed for recurrent/persistent macular edema, no more frequently than every 2 months. Patients still requiring injections after month 40 received scatter and grid laser photocoagulation to try to reduce the need for injections. Main outcome measures included the percentage of patients who had resolution of edema, change in best-corrected visual acuity (BCVA) from baseline, and change in area of retinal nonperfusion in central subfields. Nine patients with BRVO (45%) had edema resolution from injections alone after a mean of 20.2 months, 4 resolved after addition of laser, 4 were unresolved through 72 months, and 3 exited prior to resolution. Five patients with CRVO (25%) resolved from injections alone after a mean of 14.0 months, 8 remained unresolved through 72 months despite addition of laser, and 7 exited prior to resolution. For BRVO or CRVO, there was a negative correlation between posterior retinal nonperfusion area and BCVA at months 18, 24, and 36 (P < .05). In patients with RVO, infrequent ranibizumab injections to control edema may not be sufficient to prevent progression of retinal nonperfusion, which may contribute to loss of visual gains.
    No preview · Article · Oct 2013 · American Journal of Ophthalmology
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    ABSTRACT: Angiogenesis, in which new blood vessels form via endothelial cell (EC) sprouting from existing vessels, is a critical event in embryonic development and multiple disease processes. Many insights have been made into key EC receptors and ligands/growth factors that govern sprouting angiogenesis, but intracellular molecular mechanisms of this process are not well understood. NF-E2-related factor 2 (Nrf2) is a transcription factor well-known for regulating the stress response in multiple pathologic settings, but its role in development is less appreciated. Here, we show that Nrf2 is increased and activated during vascular development. Global deletion of Nrf2 resulted in reduction of vascular density as well as EC sprouting. This was also observed with specific deletion of Nrf2 in ECs, but not with deletion of Nrf2 in the surrounding nonvascular tissue. Nrf2 deletion resulted in increased delta-like ligand 4 (Dll4) expression and Notch activity in ECs. Blockade of Dll4 or Notch signaling restored the vascular phenotype in Nrf2 KOs. Constitutive activation of endothelial Nrf2 enhanced EC sprouting and vascularization by suppression of Dll4/Notch signaling in vivo and in vitro. Nrf2 activation in ECs suppressed Dll4 expression under normoxia and hypoxia and inhibited Dll4-induced Notch signaling. Activation of Nrf2 blocked VEGF induction of VEGFR2-PI3K/Akt and downregulated HIF-2α in ECs, which may serve as important mechanisms for Nrf2 inhibition of Dll4 and Notch signaling. Our data reveal a function for Nrf2 in promoting the angiogenic sprouting phenotype in vascular ECs.
    Preview · Article · Sep 2013 · Proceedings of the National Academy of Sciences
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    ABSTRACT: Vision loss from ischemic retinopathies commonly results from the accumulation of fluid in the inner retina [macular edema (ME)]. Although the precise events that lead to the development of ME remain under debate, growing evidence supports a role for an ischemia-induced hyperpermeability state regulated, in part, by VEGF. Monthly treatment with anti-VEGF therapies is effective for the treatment of ME but results in a major improvement in vision in a minority of patients, underscoring the need to identify additional therapeutic targets. Using the oxygen-induced retinopathy mouse model for ischemic retinopathy, we provide evidence showing that hypoxic Müller cells promote vascular permeability by stabilizing hypoxia-inducible factor-1α (HIF-1α) and secreting angiogenic cytokines. Blocking HIF-1α translation with digoxin inhibits the promotion of endothelial cell permeability in vitro and retinal edema in vivo. Interestingly, Müller cells require HIF-but not VEGF-to promote vascular permeability, suggesting that other HIF-dependent factors may contribute to the development of ME. Using gene expression analysis, we identify angiopoietin-like 4 (ANGPTL4) as a cytokine up-regulated by HIF-1 in hypoxic Müller cells in vitro and the ischemic inner retina in vivo. ANGPTL4 is critical and sufficient to promote vessel permeability by hypoxic Müller cells. Immunohistochemical analysis of retinal tissue from patients with diabetic eye disease shows that HIF-1α and ANGPTL4 localize to ischemic Müller cells. Our results suggest that ANGPTL4 may play an important role in promoting vessel permeability in ischemic retinopathies and could be an important target for the treatment of ME.
    Full-text · Article · Aug 2013 · Proceedings of the National Academy of Sciences
  • Elia J Duh

    No preview · Article · Jun 2013 · Investigative ophthalmology & visual science
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    ABSTRACT: Intravitreal injection of biodegradable nanoparticles (NP) holds promise for gene therapy and drug delivery to the back of the eye. In some cases, including gene therapy, NP need to diffuse rapidly from the site of injection in order to reach targeted cell types in the back of the eye, whereas in other cases it may be preferred for the particles to remain at the injection site and slowly release drugs that may then diffuse to the site of action. We studied the movements of polystyrene (PS) nanoparticles of various sizes and surface chemistries in fresh bovine vitreous. PS NP as large as 510 nm rapidly penetrated the vitreous gel when coated with polyethylene glycol (PEG), whereas the movements of NP 1190 nm in diameter or larger were highly restricted regardless of surface chemistry owing to steric obstruction. PS NP coated with primary amine groups (-NH(2)) possessed positively charged surfaces at the pH of bovine vitreous (pH = 7.2), and were immobilized within the vitreous gel. In comparison, PS NP coated with -COOH (possessing negatively charged surfaces) in the size range of 100-200 nm and at particle concentrations below 0.0025% (w/v) readily diffused through the vitreous meshwork; at higher concentrations (~0.1% w/v), these nanoparticles aggregated within vitreous. Based on the mobility of different sized PS-PEG NP, we estimated the average mesh size of fresh bovine vitreous to be ~550 ± 50 nm. The bovine vitreous behaved as an impermeable elastic barrier to objects sized 1190 nm and larger, but as a highly permeable viscoelastic liquid to non-adhesive objects smaller than 510 nm in diameter. Guided by these studies, we next sought to examine the transport of drug- and DNA-loaded nanoparticles in bovine vitreous. Biodegradable NP with diameter of 227 nm, composed of a poly(lactic-co-glycolic acid) (PLGA)-based core coated with poly(vinyl alcohol) rapidly penetrated vitreous. Rod-shaped, highly-compacted CK(30)PEG(10k)/DNA with PEG coating (neutral surface charge; diameter ~60 nm) diffused rapidly within vitreous. These findings will help guide the development of nanoparticle-based therapeutics for the treatment of vision-threatening ocular diseases.
    No preview · Article · Jan 2013 · Journal of Controlled Release
  • Shuang Wang · James K Park · Elia J Duh
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    ABSTRACT: Proliferative diabetic retinopathy (PDR), characterized by pathologic retinal angiogenesis, is a major cause of blindness in the USA and globally. Treatments targeting vascular endothelial growth factor (VEGF) have emerged as a beneficial part of the therapeutic armamentarium for this condition, highlighting the utility of identifying and targeting specific pathogenic molecules. There continues to be active research into the molecular players regulating retinal angiogenesis, including pro-angiogenic factors, anti-angiogenic factors, and integrins and matrix proteinases. New insights have been especially prominent regarding molecules which regulate specialized endothelial cells called tip cells, which play a lead role in endothelial sprouting. Together, these research efforts are uncovering new, important molecular regulators of retinal angiogenesis, which provide fertile areas for therapeutic exploration. This review discusses potential molecular targets, with an emphasis towards newer targets.
    No preview · Article · May 2012 · Current Diabetes Reports
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    ABSTRACT: Ischemic retinopathies, including retinopathy of prematurity and diabetic retinopathy, are major causes of blindness. Both have two phases, vessel loss and consequent hypoxia-driven pathologic retinal neovascularization, yet relatively little is known about the transcription factors regulating these processes. Myocyte enhancer factor 2 (MEF2) C, a member of the MEF2 family of transcription factors that plays an important role in multiple developmental programs, including the cardiovascular system, seems to have a significant functional role in the vasculature. We, therefore, generated endothelial cell (EC)-specific MEF2C-deficient mice and explored the role of MEF2C in retinal vascularization during normal development and in a mouse model of oxygen-induced retinopathy. Ablation of MEF2C did not cause appreciable defects in normal retinal vascular development. However, MEF2C ablation in ECs suppressed vessel loss in oxygen-induced retinopathy and strongly promoted vascular regrowth, consequently reducing retinal avascularity. This finding was associated with suppression of pathologic retinal angiogenesis and blood-retinal barrier dysfunction. MEF2C knockdown in cultured retinal ECs using small-interfering RNAs rescued ECs from death and stimulated tube formation under stress conditions, confirming the endothelial-autonomous and antiangiogenic roles of MEF2C. HO-1 was induced by MEF2C knockdown in vitro and may play a role in the proangiogenic effect of MEF2C knockdown on retinal EC tube formation. Thus, MEF2C may play an antiangiogenic role in retinal ECs under stress conditions, and modulation of MEF2C may prevent pathologic retinal neovascularization.
    Preview · Article · Apr 2012 · American Journal Of Pathology
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    ABSTRACT: Endothelial cell dysfunction is a critical component of ocular diseases such as age-related macular degeneration and diabetic retinopathy. An important limitation in endothelial cell research is the difficulty in achieving efficient transfection of these cells. A new polymer library was here synthesized and utilized to find polymeric nanoparticles that can transfect macrovascular (human umbilical vein, HUVECs) and microvascular (human retinal, HRECs) endothelial cells. Nanoparticles were synthesized that can achieve transfection efficiency of up to 85% for HRECs and 65% for HUVECs. These nanoparticle systems enable high levels of expression while avoiding problems associated with viral gene delivery. The polymeric nanoparticles also show cell-specific behavior, with a high correlation between microvascular and macrovascular transfection (R(2) = 0.81) but low correlation between retinal endothelial and retinal epithelial transfection (R(2) = 0.21). These polymeric nanoparticles can be used in vitro as experimental tools and potentially in vivo to target and treat vascular-specific diseases. FROM THE CLINICAL EDITOR: Polymeric nanoparticles were synthesized with the goal of transfecting endothelial cells, which are commonly considered difficult targets. The authors report excellent transfection efficiency of up to 85% for human retinal and 65% for human umbilical vein endothelial cells. These NPs can be used in vitro as experimental tools and potentially in vivo to target and treat vascular-specific diseases.
    Full-text · Article · Feb 2012 · Nanomedicine: nanotechnology, biology, and medicine
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    ABSTRACT: Retinal angiogenesis is a major cause of blindness in ischemic retinopathies including diabetic retinopathy and retinopathy of prematurity. Integrin αvβ3 is a promising therapeutic target for ocular angiogenesis, modulating the pro-angiogenic actions of multiple growth factors. In this study, we sought to determine the effects of the integrin αvβ3 antagonist tetra-iodothyroacetic acid (tetrac) on the angiogenic actions of VEGF and erythropoietin (EPO) in cultured human retinal endothelial cells. In addition, we investigated the effect of tetrac and a nanoparticulate formulation of tetrac on retinal angiogenesis in vivo, in the mouse oxygen-induced retinopathy (OIR) model. Tetrac inhibitory activity was evaluated in human retinal endothelial cells treated with VEGF and/or EPO. Endothelial cell proliferation, migration, and tube formation were assessed, in addition to phosphorylation of ERK1/2. For the studies of the oxygen-induced retinopathy model, C57BL/6 mice were exposed to 75% oxygen from postnatal day (P)7 to P12, and then returned to room air. Tetrac and tetrac-nanoparticle (tetrac-NP) were administered at P12 and P15 by either intraperitoneal or intravitreal injection. Retinal neovascularization was quantitated at P18. Tetrac significantly inhibited pro-angiogenic effects of VEGF and/or EPO on retinal endothelial cells, indicating that the angiogenic effects of both growth factors are dependent on integrin αvβ3. Retinal neovascularization in the OIR model was significantly inhibited by both tetrac and tetrac-NP. These results indicate that the integrin αvβ3 antagonist, tetrac, is an effective inhibitor of retinal angiogenesis. The ability of tetrac to inhibit the pro-angiogenic effect of both VEGF and EPO on retinal endothelial cells suggests that tetrac (and antagonism of integrin αvβ3) is a viable therapeutic strategy for proliferative diabetic retinopathy.
    No preview · Article · Nov 2011 · Experimental Eye Research
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    ABSTRACT: Retinal ischemia-reperfusion (I/R) involves an extensive increase in reactive oxygen species as well as proinflammatory changes that result in significant histopathologic damage, including neuronal and vascular degeneration. Nrf2 has a well-known cytoprotective role in many tissues, but its protective function in the retina is unclear. We investigated the possible role of Nrf2 as a protective mechanism in retinal ischemia-reperfusion injury using Nrf2(-/-) mice. I/R resulted in an increase in retinal levels of superoxide and proinflammatory mediators, as well as leukocyte infiltration of the retina and vitreous, in Nrf2(+/+) mice. These effects were greatly accentuated in Nrf2(-/-) mice. With regard to histopathologic damage, Nrf2(-/-) mice exhibited loss of cells in the ganglion cell layer and markedly accentuated retinal capillary degeneration, as compared to wild-type. Treatment with the Nrf2 activator CDDO-Me increased antioxidant gene expression and normalized I/R-induced superoxide in the retina in wild-type but not Nrf2(-/-) mice. CDDO-Me treatment abrogated retinal capillary degeneration induced by I/R in wild-type but not Nrf2(-/-) mice. These studies indicate that Nrf2 is an important cytoprotective mechanism in the retina in response to ischemia-reperfusion injury and suggest that pharmacologic induction of Nrf2 could be a new therapeutic strategy for retinal ischemia-reperfusion and other retinal diseases.
    No preview · Article · Jul 2011 · Free Radical Biology and Medicine

Publication Stats

3k Citations
271.98 Total Impact Points

Institutions

  • 2001-2015
    • Johns Hopkins University
      • • Wilmer Eye Institute
      • • Department of Medicine
      Baltimore, Maryland, United States
  • 2013
    • Johns Hopkins Medicine
      Baltimore, Maryland, United States
  • 2002
    • Harvard University
      Cambridge, Massachusetts, United States
  • 1998
    • Joslin Diabetes Center
      • William P. Beetham Eye Institute
      Boston, Massachusetts, United States