Publications by authors named "Mohd Imtiaz Nawaz"

28 Publications

  • Page 1 of 1

CD146/Soluble CD146 Pathway Is a Novel Biomarker of Angiogenesis and Inflammation in Proliferative Diabetic Retinopathy.

Invest Ophthalmol Vis Sci 2021 Jul;62(9):32

University Hospitals, UZ Gasthuisberg, Leuven, Belgium.

Purpose: Inflammation, angiogenesis and fibrosis are pathological hallmarks of proliferative diabetic retinopathy (PDR). The CD146/sCD146 pathway displays proinflammatory and proangiogenic properties. We investigated the role of this pathway in the pathophysiology of PDR.

Methods: Vitreous samples from 41 PDR and 27 nondiabetic patients, epiretinal fibrovascular membranes from 18 PDR patients, rat retinas, human retinal microvascular endothelial cells (HRMECs) and human retinal Müller glial cells were studied by ELISA, Western blot analysis, immunohistochemistry and immunofluorescence microscopy analysis. Blood-retinal barrier breakdown was assessed with fluorescein isothiocyanate-conjugated dextran.

Results: sCD146 and VEGF levels were significantly higher in vitreous samples from PDR patients than in nondiabetic patients. In epiretinal membranes, immunohistochemical analysis revealed CD146 expression in leukocytes, vascular endothelial cells and myofibroblasts. Significant positive correlations were detected between numbers of blood vessels expressing CD31, reflecting angiogenic activity of PDR, and numbers of blood vessels and stromal cells expressing CD146. Western blot analysis showed significant increase of CD146 in diabetic rat retinas. sCD146 induced upregulation of phospho-ERK1/2, NF-κB , VEGF and MMP-9 in Müller cells. The hypoxia mimetic agent cobalt chloride, VEGF and TNF-α induced upregulation of sCD146 in HRMECs. The MMP inhibitor ONO-4817 attenuated TNF-α-induced upregulation of sCD146 in HRMECs. Intravitreal administration of sCD146 in normal rats significantly increased retinal vascular permeability and induced significant upregulation of phospho-ERK1/2, intercellular adhesion molecule-1 and VEGF in the retina. sCD146 induced migration of HRMECs.

Conclusions: These results suggest that the CD146/sCD146 pathway is involved in the initiation and progression of PDR.
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http://dx.doi.org/10.1167/iovs.62.9.32DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8300056PMC
July 2021

Evaluation of Proteoforms of the Transmembrane Chemokines CXCL16 and CX3CL1, Their Receptors, and Their Processing Metalloproteinases ADAM10 and ADAM17 in Proliferative Diabetic Retinopathy.

Front Immunol 2020 20;11:601639. Epub 2021 Jan 20.

Laboratory of Molecular Immunology, Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium.

The transmembrane chemokine pathways CXCL16/CXCR6 and CX3CL1/CX3CR1 are strongly implicated in inflammation and angiogenesis. We investigated the involvement of these chemokine pathways and their processing metalloproteinases ADAM10 and ADAM17 in the pathophysiology of proliferative diabetic retinopathy (PDR). Vitreous samples from 32 PDR and 24 non-diabetic patients, epiretinal membranes from 18 patients with PDR, rat retinas, human retinal Müller glial cells and human retinal microvascular endothelial cells (HRMECs) were studied by enzyme-linked immunosorbent assay, immunohistochemistry and Western blot analysis. angiogenesis assays were performed and the adherence of leukocytes to CXCL16-stimulated HRMECs was assessed. CXCL16, CX3CL1, ADAM10, ADAM17 and vascular endothelial growth factor (VEGF) levels were significantly increased in vitreous samples from PDR patients. The levels of CXCL16 were 417-fold higher than those of CX3CL1 in PDR vitreous samples. Significant positive correlations were found between the levels of VEGF and the levels of CXCL16, CX3CL1, ADAM10 and ADAM17. Significant positive correlations were detected between the numbers of blood vessels expressing CD31, reflecting the angiogenic activity of PDR epiretinal membranes, and the numbers of blood vessels and stromal cells expressing CXCL16, CXCR6, ADAM10 and ADAM17. CXCL16 induced upregulation of phospho-ERK1/2, p65 subunit of NF-κB and VEGF in cultured Müller cells and tumor necrosis factor-α induced upregulation of soluble CXCL16 and ADAM17 in Müller cells. Treatment of HRMECs with CXCL16 resulted in increased expression of intercellular adhesion molecule-1 (ICAM-1) and increased leukocyte adhesion to HRMECs. CXCL16 induced HRMEC proliferation, formation of sprouts from HRMEC spheroids and phosphorylation of ERK1/2. Intravitreal administration of CXCL16 in normal rats induced significant upregulation of the p65 subunit of NF-κB, VEGF and ICAM-1 in the retina. Our findings suggest that the chemokine axis CXCL16/CXCR6 and the processing metalloproteinases ADAM10 and ADAM17 might serve a role in the initiation and progression of PDR.
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http://dx.doi.org/10.3389/fimmu.2020.601639DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7854927PMC
June 2021

Apocynin ameliorates NADPH oxidase 4 (NOX4) induced oxidative damage in the hypoxic human retinal Müller cells and diabetic rat retina.

Mol Cell Biochem 2021 May 30;476(5):2099-2109. Epub 2021 Jan 30.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

NADPH oxidase (NOX) is a main producers of reactive oxygen species (ROS) that may contribute to the early pathogenesis of diabetic retinopathy (DR). ROS has harmful effects on endogenous neuro-survival factors brain-derived neurotrophic factor (BDNF) and sirtuin 1 (SIRT1) are necessary for the growth and survival of the retina. The role of NOX isoforms NOX4 in triggering ROS in DR is not clear. Here we determine the protective effects of a plant-derived NOX inhibitor apocynin (APO) on NOX4-induced ROS production which may contribute to the depletion of survival factors BDNF/SIRT1 or cell death in the diabetic retinas. Human retinal Müller glial cells (MGCs) were treated with hypoxia mimetic agent cobalt chloride (CoCl) in the absence or presence of APO. Molecular analysis demonstrates that NOX4 is upregulated in CoCl-treated MGCs and in the diabetic retinas. Increased NOX4 was accompanied by the downregulation of BDNF/SIRT1 expression or in the activation of apoptotic marker caspase-3. Whereas, APO treatment downregulates NOX4 and subsequently upregulates BDNF/SIRT1 or alleviate caspase-3 expression. Accordingly, in the diabetic retina we found a positive correlation in NOX4 vs ROS (p = 0.025; R = 0.488) and caspase-3 vs ROS (p = 0.04; R = 0.428); whereas a negative correlation in BDNF vs ROS (p = 0.009; R = 0.596) and SIRT1 vs ROS (p = 0.0003; R = 0.817) respectively. Taken together, NOX4-derived ROS could be a main contributor in downregulating BDNF/SIRT1 expression or in the activation of caspase-3. Whereas, APO treatment may minimize the deleterious effects occurring due to hyperglycemia and/or diabetic mimic hypoxic condition in early pathogenesis of DR.
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http://dx.doi.org/10.1007/s11010-021-04071-yDOI Listing
May 2021

The Autocrine FGF/FGFR System in both Skin and Uveal Melanoma: FGF Trapping as a Possible Therapeutic Approach.

Cancers (Basel) 2019 Sep 4;11(9). Epub 2019 Sep 4.

Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy.

Fibroblast growth factors (FGFs) play non-redundant autocrine/paracrine functions in various human cancers. The Cancer Genome Atlas (TCGA) data mining indicates that high levels of FGF and/or FGF receptor (FGFR) expression are associated with reduced overall survival, chromosome 3 monosomy and mutation in human uveal melanoma (UM), pointing to the FGF/FGFR system as a target for UM treatment. Here, we investigated the impact of different FGF trapping approaches on the tumorigenic and liver metastatic activity of liver metastasis-derived murine melanoma B16-LS9 cells that, similar to human UM, are characterized by a distinctive hepatic tropism. In vitro and in vivo experiments demonstrated that the overexpression of the natural FGF trap inhibitor long-pentraxin 3 (PTX3) inhibits the oncogenic activity of B16-LS9 cells. In addition, B16-LS9 cells showed a reduced tumor growth and liver metastatic activity when grafted in PTX3-overexpressing transgenic mice. The efficacy of the FGF trapping approach was confirmed by the capacity of the PTX3-derived pan-FGF trap small molecule NSC12 to inhibit B16-LS9 cell growth in vitro, in a zebrafish embryo orthotopic tumor model and in an experimental model of liver metastasis. Possible translational implications for these observations were provided by the capacity of NSC12 to inhibit FGF signaling and cell proliferation in human UM Mel285, Mel270, 92.1, and OMM2.3 cells. In addition, NSC12 caused caspase-3 activation and PARP cleavage followed by apoptotic cell death as well as -catenin degradation and inhibition of UM cell migration. Together, our findings indicate that FGF trapping may represent a novel therapeutic strategy in UM.
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http://dx.doi.org/10.3390/cancers11091305DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770058PMC
September 2019

CoFe2 O4 -ZnO nanoparticles for rapid microwave-assisted tryptic digestion of phosphoprotein and phosphopeptide analysis by matrix-assisted laser desorption/ionization mass spectrometry.

Rapid Commun Mass Spectrom 2016 07;30(13):1443-53

Department of Chemistry and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, 70 Lien-Hai Road, Kaohsiung, 80424, Taiwan.

Rationale: Phosphorylation is a post-translational modification of proteins that plays very important role in a large number of biological processes. However, despite recent advancements in phosphoproteome research, large-scale detection and characterization of phosphopeptides by mass spectrometry (MS) is still a challenging task due to the low abundance of phosphopeptides and sub-stoichiometric nature of phosphorylation sites. On-particle microwave-assisted trypsin digestion of phosphoproteins and enrichment of phosphopeptides is an effective method for identification/characterization of phosphopeptides. Magnetic nanoparticles typically can absorb microwave radiation and generate heat in order to resolve complex phosphproteins and to enhance the digestion rate and capture the phosphopeptides on their modified surfaces.

Methods: In this study, we used a cheap and efficient method for rapid microwave-assisted tryptic digestion of phosphoproteins and simultaneous enrichment of phosphopeptides using CoFe2 O4 -ZnO magnetic nanoparticles. Using this technique, the digestion time of phosphoproteins can be reduced and the phosphopeptides can be quickly analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). For the first time, we have applied CoFe2 O4 -ZnO magnetic nanoparticles for enrichment of phosphopeptides from standard phosphoproteins (β-casein and ovalbumin), complex samples (human serum and egg white) and a protein mixture of β-casein and BSA (1:100).

Results: Our results demonstrate that the capture efficiency of CoFe2 O4 -ZnO nanoparticles for β-casein and ovalbumin in MALDI-TOFMS is very high (detection limits 0.2 fmol and 20 fmol, respectively). The CoFe2 O4 -ZnO nanoparticles have high affinity for phosphopeptide enrichment for β-casein in complex mixtures with BSA at 1:10 and 1:100 molar ratios in the microwave within 30 s.

Conclusions: Compared with other reported magnetic nanoparticles, the CoFe2 O4 -ZnO nanoparticles are easy to prepare and handle, and can save time in the phosphopeptide enrichment procedure, making these nanoparticle a good choice for highly sensitive phosphopeptide enrichment. Copyright © 2016 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/rcm.7559DOI Listing
July 2016

Upregulation of Thrombin/Matrix Metalloproteinase-1/Protease-Activated Receptor-1 Chain in Proliferative Diabetic Retinopathy.

Curr Eye Res 2016 12 3;41(12):1590-1600. Epub 2016 Jun 3.

d Department of Microbiology and Immunology , Rega Institute for Medical Research, University of Leuven , KU Leuven , Belgium.

Purpose: Selective proteolytic activation of protease-activated receptor-1 (PAR1) by thrombin and matrix metalloproteinase-1 (MMP-1) plays a central role in enhancing angiogenesis. We investigated the expression levels of thrombin, MMP-1, and PAR1 and correlated these levels with vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR). In addition, we examined the expression of PAR1 and thrombin in the retinas of diabetic rats and PAR1 in human retinal microvascular endothelial cells (HRMEC) following exposure to high-glucose, the proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and the hypoxia mimetic agent cobalt chloride (CoCl).

Methods: Vitreous samples from 32 PDR and 23 nondiabetic patients, epiretinal membranes from 10 patients with PDR, retinas of rats, and HRMEC were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and Western blot analysis. An assay for in vitro cell migration angiogenesis was performed in HRMEC.

Results: In epiretinal membranes, PAR1 was expressed in vascular endothelial cells, CD45-expressing leukocytes, and myofibroblasts. ELISA and Western blot assays revealed significant increases in the expression levels of thrombin, MMP-1, and VEGF in vitreous samples from PDR patients compared to nondiabetic controls. Significant positive correlations were found between the levels of VEGF and the levels of thrombin (r = 0.41; p = 0.006) and MMP-1 (r = 0.66; p < 0.0001). Significant increases of cleaved PAR1 (approximately 50 kDa) and the proteolytically active thrombin (approximately 50 kDa) were detected in rat retinas after induction of diabetes. The proinflammatory cytokines IL-1β and TNF-α, but not high-glucose and CoCl, induced upregulation of cleaved PAR1 (approximately 30 kDa) in HRMEC. In addition, thrombin and MMP-1 induced VEGF in HRMEC and vorapaxar, a PAR1 inhibitor, inhibited thrombin-induced migration in HRMEC.

Conclusions: Interactions among thrombin, MMP-1, PAR1, and VEGF might facilitate angiogenesis in PDR.
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http://dx.doi.org/10.3109/02713683.2016.1141964DOI Listing
December 2016

Coexpression of heparanase activity, cathepsin L, tissue factor, tissue factor pathway inhibitor, and MMP-9 in proliferative diabetic retinopathy.

Mol Vis 2016 30;22:424-35. Epub 2016 Apr 30.

Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.

Purpose: Heparanase cleaves heparan sulfate side chains of heparan sulfate proteoglycans, activity that is implicated in angiogenesis. Proteolytic cleavage of proheparanase by cathepsin L leads to the formation of catalytically active heparanase. We investigated the expression levels of heparanase enzymatic activity and correlated these with the levels of cathepsin L, the angiogenic factors tissue factor (TF) and matrix metalloproteinase-9 (MMP-9), and the angiostatic factor tissue factor pathway inhibitor (TFPI) in proliferative diabetic retinopathy (PDR).

Methods: Vitreous samples from 25 patients with PDR and 20 nondiabetic patients and epiretinal membranes from 12 patients with PDR were studied with enzyme-linked immunosorbent assay, western blot analysis, and immunohistochemistry.

Results: We observed a significant increase in the expression of heparanase activity in vitreous samples from patients with PDR compared to the nondiabetic controls (p=0.027). Significant positive correlations were found between the levels of heparanase activity and the levels of cathepsin L (r=0.51; p=0.001), TF (r=0.6; p<0.0001), and TFPI (r=0.49; p=0.001). The expression levels of cathepsin L (p=0.019), TF (p<0.0001), TFPI (p<0.0001), and MMP-9 (p=0.029) were significantly higher in the vitreous samples with detected heparanase activity compared to the vitreous samples with undetected heparanase activity. Western blot analysis demonstrated proteolytic cleavage of TFPI in the vitreous samples from patients with PDR. In the epiretinal membranes, cathepsin L, TF, and TFPI were expressed in vascular endothelial cells and CD45-expressing leukocytes. Significant positive correlations were detected between the number of blood vessels that expressed CD31 and the number of blood vessels that expressed TF (r=0.9; p<0.0001) and TFPI (r=0.81; p=0.001).

Conclusions: The coexpression of these angiogenesis regulatory factors suggests cross-talk between these factors and pathogenesis of PDR angiogenesis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851855PMC
November 2016

Upregulated Expression of Heparanase in the Vitreous of Patients With Proliferative Diabetic Retinopathy Originates From Activated Endothelial Cells and Leukocytes.

Invest Ophthalmol Vis Sci 2015 Dec;56(13):8239-47

Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.

Purpose: To determine and interrelate the levels of heparanase, syndecan-1, and VEGF in proliferative diabetic retinopathy (PDR), and to study the production of heparanase by human retinal microvascular endothelial cells (HRMEC) and its effect on HRMEC barrier function.

Methods: Vitreous samples from 33 PDR and 27 nondiabetic patients, epiretinal membranes from 16 patients with PDR and HRMEC were studied by enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot analysis. The effect of heparanase on HRMEC barrier function was evaluated by transendothelial electrical resistance.

Results: We showed a significant increase in the expression of heparanase, syndecan-1, and VEGF in vitreous samples from PDR patients compared with nondiabetic controls (P < 0.0001 for all comparisons). Significant positive correlations were found between the levels of heparanase and the levels of syndecan-1 (r = 0.75, P < 0.0001) and VEGF (r = 0.91, P < 0.0001) and between the levels of syndecan-1 and the levels of VEGF (r = 0.78, P < 0.0001). In epiretinal membranes, heparanase was expressed in vascular endothelial cells and CD45-expressing leukocytes. High-glucose, tumor necrosis factor alpha (TNF-α), and the combination of TNF-α and interleukin (IL)-1β, but not cobalt chloride induced upregulation of heparanase in HRMEC. Heparanase-reduced transendothelial electrical resistance of HRMEC.

Conclusions: Our findings suggest a link between heparanase, syndecan-1, and VEGF in the progression of PDR and that heparanase is a potential target for therapy of diabetic retinopathy.
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http://dx.doi.org/10.1167/iovs.15-18025DOI Listing
December 2015

Role of high-mobility group box-1 protein in disruption of vascular barriers and regulation of leukocyte-endothelial interactions.

J Recept Signal Transduct Res 2015 19;35(4):340-5. Epub 2014 Nov 19.

a Department of Ophthalmology , College of Medicine, King Saud University, and Dr. Nasser Al-Rasheed Research Chair in Ophthalmology , Riyadh , Saudi Arabia.

High-mobility group box-1 protein (HMGB1) is a highly conserved non-histone DNA-binding protein present in the nuclei and cytoplasm of nearly all cell types. The results from recent research provide evidence that HMGB1 is secreted into the extracellular milieu and acts as a pro-inflammatory cytokine and exhibits angiogenic effects to fire the immunological response against the pathological effects. Recently, a great deal of evidence has indicated the critical importance of HMGB1 in mediating vascular barriers dysfunction by modulating the expression of adhesion molecules, such as intercellular adhesion molecule-1, vascular cell adhesion protein 1 and E-selectin on the surface of endothelial cells. Such process promotes the adhesion and migration of leukocytes across the endothelium, leading to breakdown of vascular barriers (blood-brain barrier and blood-retinal barrier) via modulating the expression, content, phosphorylation, and distribution of tight junction proteins. Therefore, here we give an abridged review to understand the mechanistic link between HMGB1 and vascular barriers dysfunction, including interaction with cell-surface receptors and intracellular signaling pathways.
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http://dx.doi.org/10.3109/10799893.2014.984309DOI Listing
August 2016

The Chemokine Platelet Factor-4 Variant (PF-4var)/CXCL4L1 Inhibits Diabetes-Induced Blood-Retinal Barrier Breakdown.

Invest Ophthalmol Vis Sci 2015 Feb 24;56(3):1956-64. Epub 2015 Feb 24.

Laboratory of Molecular Immunology, Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Leuven, Belgium.

Purpose: To investigate the expression of platelet factor-4 variant (PF-4var/CXCL4L1) in epiretinal membranes from patients with proliferative diabetic retinopathy (PDR) and the role of PF-4var/CXCL4L1 in the regulation of blood-retinal barrier (BRB) breakdown in diabetic rat retinas and human retinal microvascular endothelial cells (HRMEC).

Methods: Rats were treated intravitreally with PF-4var/CXCL4L1 or the anti-vascular endothelial growth factor (VEGF) agent bevacizumab on the first day after diabetes induction. Blood-retinal barrier breakdown was assessed in vivo with fluorescein isothiocyanate (FITC)-conjugated dextran and in vitro in HRMEC by transendothelial electrical resistance and FITC-conjugated dextran cell permeability assay. Occludin, vascular endothelial (VE)-cadherin, hypoxia-inducible factor (HIF)-1α, VEGF, tumor necrosis factor (TNF)-α, receptor for advanced glycation end products (RAGE), caspase-3 levels, and generation of reactive oxygen species (ROS) were assessed by Western blot, enzyme-linked immunosorbent assays, or spectrophotometry.

Results: In epiretinal membranes, vascular endothelial cells and stromal cells expressed PF-4var/CXCL4L1. In vitro, HRMEC produced PF-4var/CXCL4L1 after stimulation with a combination of interleukin (IL)-1β and TNF-α, and PF-4var/CXCL4L1 inhibited VEGF-mediated hyperpermeability in HRMEC. In rats, PF-4var/CXCL4L1 was as potent as bevacizumab in attenuating diabetes-induced BRB breakdown. This effect was associated with upregulation of occludin and VE-cadherin and downregulation of HIF-1α, VEGF, TNF-α, RAGE, and caspase-3, whereas ROS generation was not altered.

Conclusions: Our findings suggest that increasing the intraocular PF-4var/CXCL4L1 levels early after the onset of diabetes protects against diabetes-induced BRB breakdown.
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http://dx.doi.org/10.1167/iovs.14-16144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4365984PMC
February 2015

The tumor necrosis factor superfamily members TWEAK, TNFSF15 and fibroblast growth factor-inducible protein 14 are upregulated in proliferative diabetic retinopathy.

Ophthalmic Res 2015 7;53(3):122-30. Epub 2015 Feb 7.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Purpose: Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and tumor necrosis factor superfamily member 15 (TNFSF15), members of the TNF superfamily, play important roles in the modulation of inflammation and neovascularization. TWEAK activity is mediated via binding to fibroblast growth factor-inducible molecule 14 (Fn14). We investigated the expression of TWEAK, Fn14 and TNFSF15 and the correlation between TWEAK levels and the levels of the inflammatory biomarker soluble intercellular adhesion molecule-1 (sICAM-1) in proliferative diabetic retinopathy (PDR). In addition, we examined the expression of FN14 and TNFSF15 in retinas of diabetic rats.

Methods: Vitreous samples from 34 PDR and 23 nondiabetic patients were studied by enzyme-linked immunosorbent assay and Western blot analysis. Epiretinal membranes from 14 patients with PDR were studied by immunohistochemistry. The retinas of rats were examined by Western blot analysis.

Results: We identified a significant increase in the expression of TWEAK, Fn14, TNFSF15 and sICAM-1 in vitreous samples from PDR patients compared to controls. A significant positive correlation was found between levels of TWEAK and levels of sICAM-1 (r = 0.3, p = 0.02). In epiretinal membranes, TWEAK and TNFSF15 protein expression was confined to vascular endothelial cells, monocytes/macrophages and myofibroblasts. Significant positive correlations were observed between the number of blood vessels expressing CD34 and the number of blood vessels expressing TWEAK (r = 0.670; p = 0.017) and TNFSF15 (r = 0.784; p = 0.001). The expression level of TNFSF15 was upregulated in the retinas of diabetic rats, whereas Fn14 was not upregulated.

Conclusions: Our findings suggest that TNFSF15 and the TWEAK/Fn14 pathway are novel mediators involved in persistent inflammation and modulation of pathological neovascularization associated with PDR.
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http://dx.doi.org/10.1159/000369300DOI Listing
September 2015

Expression of bioactive lysophospholipids and processing enzymes in the vitreous from patients with proliferative diabetic retinopathy.

Lipids Health Dis 2014 Dec 11;13:187. Epub 2014 Dec 11.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Background: The bioactive lysophospholipids phosphatidic acid (PA), lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been implicated in mediating cell migration, proliferation and apoptosis, inflammation, angiogenesis and fibrosis. This study was conducted to measure the levels of PA, LPA, LPA-producing enzymes phospholipase A1/A2 (PLA1A/PLA2, respectively) and acylgylycerol kinase (AGK), the S1P receptor S1PR1, the S1P catabolising enzyme S1P lyase (SPL) and 5-lipoxygenase in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR). In addition, we investigated the correlations between the levels of PA and LPA and the levels of the inflammatory and endothelial dysfunction biomarker soluble vascular cell adhesion molecule-1 (sVCAM-1).

Methods: Vitreous samples from 34 PDR and 29 nondiabetic patients were studied by biochemical and enzyme-linked immunosorbent assays and Western blot analysis.

Results: PA, LPA and sVCAM-1 levels in vitreous samples from PDR patients were significantly higher than those in nondiabetic patients. Significant correlations were observed between levels of LPA and levels of PA and sVCAM-1. Western blot analysis revealed a significant increase in the expression of PLA1A, AGK, S1PR1 and SPL in vitreous samples from PDR patients compared to nondiabetic controls, whereas PLA2 and 5-lipoxygenase were not detected.

Conclusions: Our findings suggest that the enzymatic activities of PLA1A and AGK might be responsible for increased synthesis of LPA in PDR and that PLA1A, but not PLA2 is responsible for deacylation of PA to generate LPA. S1PR1 and SPL might regulate inflammatory, angiogenic and fibrogenic responses in PDR.
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http://dx.doi.org/10.1186/1476-511X-13-187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293108PMC
December 2014

S100A4 is upregulated in proliferative diabetic retinopathy and correlates with markers of angiogenesis and fibrogenesis.

Mol Vis 2014 10;20:1209-24. Epub 2014 Sep 10.

Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Belgium.

Purpose: The calcium-binding protein S100A4 is implicated in cancer cell invasion and metastasis, the stimulation of angiogenesis, the progression of fibrosis, and inflammatory disorders. We investigated the expression of S100A4 and correlated it with clinical disease activity as well as with the levels of osteopontin (OPN), soluble syndecan-1, and vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR). To reinforce the findings at the functional level, we examined the expressions of S100A4 and OPN in the retinas of diabetic rats and in human retinal microvascular endothelial cells (HRMECs) following exposure to VEGF and the proinflammatory cytokine tumor necrosis factor-α (TNF-α).

Methods: Vitreous samples from 30 PDR and 30 nondiabetic patients, epiretinal membranes from 14 patients with PDR, the retinas of rats, and HRMECs were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, western blot analysis, and co-immunoprecipitation.

Results: ELISA revealed a significant increase in the expressions of S100A4, OPN, soluble syndecan-1, and VEGF in vitreous samples from PDR patients compared to nondiabetic controls (p = 0.001; <0.001; <0.001; <0.001, respectively). Significant positive correlations were found between the levels of S100A4, OPN (r = 0.52, p = <0.001), soluble syndecan-1 (r = 0.37, p = 0.012), and VEGF (r = 0.29, p = 0.044). In epiretinal membranes, S100A4 was expressed in the vascular endothelial cells and stromal CD45-expressing leukocytes. A significant positive correlation was detected between the number of blood vessels expressing CD31 and the number of stromal cells expressing S100A4 (r = 0.77, p = 0.001). Western blot analysis revealed a significant increase in the expressions of S100A4 and both intact and cleaved OPN in vitreous samples from PDR patients compared to nondiabetic controls, as well as in the retinas of diabetic rats. Co-immunoprecipitation studies revealed a positive interaction between S100A4 and the receptor for advanced glycation end products (RAGE) in the retinas of diabetic rats. TNF-α-but not VEGF-induced the upregulations of S100A4 and both intact and cleaved OPN in HRMECs.

Conclusions: S100A4 represents a valuable vitreous marker molecule in the pathogenesis of PDR and might become a new target for the treatment of PDR.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4160443PMC
December 2015

The angiogenic biomarker endocan is upregulated in proliferative diabetic retinopathy and correlates with vascular endothelial growth factor.

Curr Eye Res 2015 Mar 28;40(3):321-31. Epub 2014 May 28.

Department of Ophthalmology, College of Medicine, King Saud University , Riyadh , Saudi Arabia and.

Purpose/aim: Endocan is a proteoglycan specifically secreted by endothelial cells, is a marker of angiogenesis and endothelial cell activation in response to proangiogenic signals. The aim of this study was to measure the levels of endocan in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and to correlate its levels with clinical disease activity and the levels of the angiogenic biomarkers vascular endothelial growth factor (VEGF), soluble vascular endothelial-cadherin (sVE-cadherin) and soluble endoglin (sEng). In addition, we investigated the expression of endocan and correlated it with the level of vascularization in PDR epiretinal membranes.

Materials And Methods: Vitreous samples from 44 PDR and 29 non-diabetic patients were studied by enzyme-linked immunosorbent assay. Epiretinal membranes from 14 patients with PDR were studied by immunohistochemistry.

Results: Endocan, VEGF, sVE-cadherin and sEng levels were significantly higher in PDR patients than in non-diabetic patients (p < 0.001; p = 0.002; p < 0.001; p = 0.001, respectively). Endocan levels were significantly higher in patients with active PDR than in patients with inactive PDR and non-diabetic patients (p < 0.001). There were significant positive correlations between endocan levels and the levels of VEGF (r = 0.574, p < 0.001) and sVE-cadherin (r = 0.498, p < 0.001). In epiretinal membranes, vascular endothelial cells and myofibroblasts expressed endocan. There was a significant positive correlation between the number of blood vessels expressing CD34 and the number of blood vessels expressing endocan (r = 0.933, p < 0.001).

Conclusions: Our findings suggest that upregulation of endocan expression in PDR could be a reflection of endothelial cell activation associated with angiogenesis.
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http://dx.doi.org/10.3109/02713683.2014.921312DOI Listing
March 2015

The proinflammatory cytokine high-mobility group box-1 mediates retinal neuropathy induced by diabetes.

Mediators Inflamm 2014 10;2014:746415. Epub 2014 Mar 10.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

To test the hypothesis that increased expression of proinflammatory cytokine high-mobility group box-1 (HMGB1) in epiretinal membranes and vitreous fluid from patients with proliferative diabetic retinopathy and in retinas of diabetic rats plays a pathogenetic role in mediating diabetes-induced retinal neuropathy. Retinas of 1-month diabetic rats and HMGB1 intravitreally injected normal rats were studied using Western blot analysis, RT-PCR and glutamate assay. In addition, we studied the effect of the HMGB1 inhibitor glycyrrhizin on diabetes-induced biochemical changes in the retina. Diabetes and intravitreal injection of HMGB1 in normal rats induced significant upregulation of HMGB1 protein and mRNA, activated extracellular signal-regulated kinase 1 and 2 (ERK1/2), cleaved caspase-3 and glutamate; and significant downregulation of synaptophysin, tyrosine hydroxylase, glutamine synthetase, and glyoxalase 1. Constant glycyrrhizin intake from the onset of diabetes did not affect the metabolic status of the diabetic rats, but it significantly attenuated diabetes-induced upregulation of HMGB1 protein and mRNA, activated ERK1/2, cleaved caspase-3, and glutamate. In the glycyrrhizin-fed diabetic rats, the decrease in synaptophysin, tyrosine hydroxylase, and glyoxalase 1 caused by diabetes was significantly attenuated. These findings suggest that early retinal neuropathy of diabetes involves upregulated expression of HMGB1 and can be ameliorated by inhibition of HMGB1.
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http://dx.doi.org/10.1155/2014/746415DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964896PMC
December 2014

Relationship between vitreous levels of matrix metalloproteinases and vascular endothelial growth factor in proliferative diabetic retinopathy.

PLoS One 2013 31;8(12):e85857. Epub 2013 Dec 31.

Rega Institute for Medical Research, Department of Microbiology and Immunology, University of Leuven, KU Leuven, Belgium.

To investigate which matrix metalloproteinases (MMPs) are more likely to be involved in the angiogenic process in proliferative diabetic retinopathy (PDR), we measured the levels of MMPs in the vitreous fluid from patients with PDR and controls and correlated these levels with the levels of vascular endothelial growth factor (VEGF). Vitreous samples from 32 PDR and 24 nondiabetic patients were studied by mosaic multiplex MMPs enzyme-linked immunosorbent assay (ELISA), single ELISA, Western blot and zymography analysis. Epiretinal membranes from 11 patients with PDR were studied by immunohistochemistry. MMP-8 and MMP-13 were not detected. ELISA, Western blot and gelatin ymography assays revealed significant increases in the expression levels of MMP-1, MMP-7, MMP-9 and VEGF in vitreous samples from PDR patients compared to nondiabetic controls, whereas MMP-2 and MMP-3 were not upregulated in vitreous samples from PDR patients. Significant correlations existed between ELISA and zymography assays for the quantitation of MMP-2 (r=0.407; p=0.039) and MMP-9 (r=0.711; p<0.001). Significant correlations were observed between levels of VEGF and levels of MMP-1 (r=0.845; P<0.001) and MMP-9 (r=0.775; p<0.001), and between levels of MMP-1 and MMP-9 (r=0.857; p<0.001). In epiretinal membranes, cytoplasmic immunoreactivity for MMP-9 was present in vascular endothelial cells and stromal monocytes/macrophages and neutrophils. Our findings suggest that among the MMPs measured, MMP-1 and MMP-9 may contribute to the angiogenic switch in PDR.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0085857PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3877391PMC
August 2014

High-mobility group box-1 induces decreased brain-derived neurotrophic factor-mediated neuroprotection in the diabetic retina.

Mediators Inflamm 2013 20;2013:863036. Epub 2013 May 20.

Department of Ophthalmology, College of Medicine, King Saud University, King Abdulaziz University Hospital, Old Airport Road, PO Box 245, Riyadh 11411, Saudi Arabia.

To test the hypothesis that brain-derived neurotrophic factor-(BDNF-) mediated neuroprotection is reduced by high-mobility group box-1 (HMGB1) in diabetic retina, paired vitreous and serum samples from 46 proliferative diabetic retinopathy and 34 nondiabetic patients were assayed for BDNF, HMGB1, soluble receptor for advanced glycation end products (sRAGE), soluble intercellular adhesion molecule-1 (sICAM-1), monocyte chemoattractant protein-1 (MCP-1), and TBARS. We also examined retinas of diabetic and HMGB1 intravitreally injected rats. The effect of the HMGB1 inhibitor glycyrrhizin on diabetes-induced changes in retinal BDNF expressions was studied. Western blot, ELISA, and TBARS assays were used. BDNF was not detected in vitreous samples. BDNF levels were significantly lower in serum samples from diabetic patients compared with nondiabetics, whereas HMGB1, sRAGE, sICAM-1, and TBARS levels were significantly higher in diabetic serum samples. MCP-1 levels did not differ significantly. There was significant inverse correlation between serum levels of BDNF and HMGB1. Diabetes and intravitreal administration of HMGB1 induced significant upregulation of the expression of HMGB1, TBARS, and cleaved caspase-3, whereas the expression of BDNF and synaptophysin was significantly downregulated in rat retinas. Glycyrrhizin significantly attenuated diabetes-induced downregulation of BDNF. Our results suggest that HMGB1-induced downregulation of BDNF might be involved in pathogenesis of diabetic retinal neurodegeneration.
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http://dx.doi.org/10.1155/2013/863036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3671668PMC
December 2013

Neurotrophins and neurotrophin receptors in proliferative diabetic retinopathy.

PLoS One 2013 7;8(6):e65472. Epub 2013 Jun 7.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Neurotrophins (NTs) are emerging as important mediators of angiogenesis and fibrosis. We investigated the expression of the NTs nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) and their receptors TrkA, TrkB, and TrkC in proliferative diabetic retinopathy (PDR). As a comparison, we examined the expression of NTs and their receptors in the retinas of diabetic rats. Vitreous samples from 16 PDR and 15 nondiabetic patients were studied by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). Epiretinal membranes from 17 patients with PDR were studied by immunohistochemistry. Rats were made diabetic with a single high dose of streptozotocin and retinas of rats were examined by Western blot analysis. Western blot analysis revealed a significant increase in the expression of NT-3 and NT-4 and the shedding of receptors TrkA and TrkB in vitreous samples from PDR patients compared to nondiabetic controls, whereas NGF and BDNF and the receptor TrkC were not detected with the use of Western blot analysis and ELISA. In epiretinal membranes, vascular endothelial cells and myofibroblasts expressed NT-3 and the receptors TrkA, TrkB and TrkC in situ, whereas NT-4 was not detected. The expression levels of NT-3 and NT-4 and the receptors TrkA and TrkB, both in intact and solubilized forms, were upregulated in the retinas of diabetic rats, whereas the receptor TrkC was not detected. Co-immunoprecipitation studies revealed binding between NT-3 and the receptors TrkA and TrkB in the retinas of diabetic rats. Our findings in diabetic eyes from humans and rats suggest that the increased expression levels within the NT-3 and NT-4/Trk axis are associated with the progression of PDR.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065472PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3676317PMC
January 2014

Angiogenic and vasculogenic factors in the vitreous from patients with proliferative diabetic retinopathy.

J Diabetes Res 2013 10;2013:539658. Epub 2013 Mar 10.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia ; Department of Ophthalmology, King Abdulaziz University Hospital, Old Airport Road, P.O. Box 245, Riyadh 11411, Saudi Arabia.

This study was conducted to determine levels of angiogenic and endothelial progenitor cell mobilizing (vasculogenic) factors in vitreous fluid from proliferative diabetic retinopathy (PDR) patients and correlate their levels with clinical disease activity. Vascular endothelial growth factor (VEGF), soluble vascular endothelial growth factor receptor-2 (sVEGFR-2), stem cell factor (SCF), soluble c-kit (s-kit), endothelial nitric oxide synthase (eNOS), and prostaglandin E2 (PGE2) levels were measured by ELISA in vitreous samples from 34 PDR and 15 nondiabetic patients. eNOS was not detected. VEGF, sVEGFR-2, SCF, and s-kit levels were significantly higher in PDR with active neovascularization compared with quiescent PDR and nondiabetic patients (P < 0.001; 0.007; 0.001; <0.001, resp.). In contrast, PGE2 levels were significantly higher in nondiabetic patients compared with PDR patients (P < 0.001). There were significant correlations between levels of sVEGFR-2 versus SCF (r = 0.950, P < 0.001), sVEGFR-2 versus s-kit (r = 0.941, P < 0.001), and SCF versus s-kit (r = 0.970, P < 0.001). Our findings suggest that upregulation of VEGF, sVEGFR-2, SCF, and s-kit supports the contributions of angiogenesis and vasculogenesis in pathogenesis of PDR.
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http://dx.doi.org/10.1155/2013/539658DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3647558PMC
May 2013

Novel drugs and their targets in the potential treatment of diabetic retinopathy.

Med Sci Monit 2013 Apr 26;19:300-8. Epub 2013 Apr 26.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Diabetic retinopathy (DR) is the most common complication of diabetes. It causes vision loss, and the incidence is increasing with the growth of the diabetes epidemic worldwide. Over the past few decades a number of clinical trials have confirmed that careful control of glycemia and blood pressure can reduce the risk of developing DR and control its progression. In recent years, many treatment options have been developed for clinical management of the complications of DR (e.g., proliferative DR and macular edema) using laser-based therapies, intravitreal corticosteroids and anti-vascular endothelial growth factors, and vitrectomy to remove scarring and hemorrhage, but all these have limited benefits. In this review, we highlight and discuss potential molecular targets and new approaches that have shown great promise for the treatment of DR. New drugs and strategies are based on targeting a number of hyperglycemia-induced metabolic stress pathways, oxidative stress and inflammatory pathways, the renin-angiotensin system, and neurodegeneration, in addition to the use of stem cells and ribonucleic acid interference (RNAi) technologies. At present, clinical trials of some of these newer drugs in humans are yet to begin or are in early stages. Together, the new therapeutic drugs and approaches discussed may control the incidence and progression of DR with greater efficacy and safety.
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http://dx.doi.org/10.12659/MSM.883895DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659065PMC
April 2013

Neurodegeneration and neuroprotection in diabetic retinopathy.

Int J Mol Sci 2013 Jan 28;14(2):2559-72. Epub 2013 Jan 28.

Department of Biochemistry, Faculty of Science, King Saud University, Riyadh 11415, Saudi Arabia.

Diabetic retinopathy is widely considered to be a neurovascular disease. This is in contrast to its previous identity as solely a vascular disease. Early in the disease progression of diabetes, the major cells in the neuronal component of the retina consist of retinal ganglion cells and glial cells, both of which have been found to be compromised. A number of retinal function tests also indicated a functional deficit in diabetic retina, which further supports dysfunction of neuronal cells. As an endocrinological disorder, diabetes alters metabolism both systemically and locally in several body organs, including the retina. A growing body of evidences indicates increased levels of excitotoxic metabolites, including glutamate, branched chain amino acids and homocysteine in cases of diabetic retinopathy. Also present, early in the disease, are decreased levels of folic acid and vitamin-B12, which are potential metabolites capable of damaging neurons. These altered levels of metabolites are found to activate several metabolic pathways, leading to increases in oxidative stress and decreases in the level of neurotrophic factors. As a consequence, they may damage retinal neurons in diabetic patients. In this review, we have discussed those potential excitotoxic metabolites and their implications in neuronal damage. Possible therapeutic targets to protect neurons are also discussed. However, further research is needed to understand the exact molecular mechanism of neurodegeneration so that effective neuroprotection strategies can be developed. By protecting retinal neurons early in diabetic retinopathy cases, damage of retinal vessels can be protected, thereby helping to ameliorate the progression of diabetic retinopathy, a leading cause of blindness worldwide.
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http://dx.doi.org/10.3390/ijms14022559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3588002PMC
January 2013

Reduced levels of brain derived neurotrophic factor (BDNF) in the serum of diabetic retinopathy patients and in the retina of diabetic rats.

Cell Mol Neurobiol 2013 Apr 28;33(3):359-67. Epub 2012 Dec 28.

Department of Biochemistry, College of Science, King Saud University, Riyadh, 11415, Saudi Arabia.

Diabetic retinopathy (DR) is widely recognized as a neurovascular disease. Retina, being a neuronal tissue of the eye, produces neurotrophic factors for its maintenance. However, diabetes dysregulates their levels and thereby may damage the retina. Among neurotrophins, brain derived neurotrophic factor (BDNF) is the most abundant in the retina. In this study, we investigated the level of BDNF in the serum of patients with DR and also in the serum and retina of streptozotocin-induced diabetic rats. The level of BDNF was significantly decreased in the serum of proliferative diabetic retinopathy patients as compared to that of non-diabetic healthy controls (25.5 ± 8.5-10.0 ± 8.1 ng/ml, p < 0.001) as well as compared to that of diabetic patients with no retinopathy (21.8 ± 4.7-10.0 ± 8.1 ng/ml, p < 0.001), as measured by ELISA techniques. The levels of BDNF in the serum and retina of diabetic rats were also significantly reduced compared to that of non-diabetic controls (p < 0.05). In addition, the expression level of tropomyosin-related kinase B (TrkB) was significantly decreased in diabetic rat retina compared to that of non-diabetic controls as determined by Western blotting technique. Caspase-3 activity was increased in diabetic rat retina after 3 weeks of diabetes and remained elevated until 10 weeks, which negatively correlated with the level of BDNF (r = -0.544, p = 0.013). Our results indicate that reduced levels of BDNF in diabetes may cause apoptosis and neurodegeneration early in diabetic retina, which may lead to neuro-vascular damage later in DR.
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http://dx.doi.org/10.1007/s10571-012-9901-8DOI Listing
April 2013

High-mobility group box-1 and endothelial cell angiogenic markers in the vitreous from patients with proliferative diabetic retinopathy.

Mediators Inflamm 2012 16;2012:697489. Epub 2012 Oct 16.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11411, Saudi Arabia.

The aim of this study was to measure the levels of high-mobility group box-1 (HMGB1) in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and to correlate its levels with clinical disease activity and the levels of vascular endothelial growth factor (VEGF), the angiogenic cytokine granulocyte-colony-stimulating factor (G-CSF), the endothelial cell angiogenic markers soluble vascular endothelial-cadherin (sVE-cadherin), and soluble endoglin (sEng). Vitreous samples from 36 PDR and 21 nondiabetic patients were studied by enzyme-linked immunosorbent assay. HMGB1, VEGF, sVE-cadherin, and sEng levels were significantly higher in PDR patients than in nondiabetics (P = 0.008; <0.001; <0.001; 0.003, resp.). G-CSF was detected in only 3 PDR samples. In the whole study group, there was significant positive correlation between the levels of HMGB1, and sVE-cadherin (r = 0.378, P = 0.007). In PDR patients, there was significant negative correlation between the levels of sVE-cadherin and sEng (r = -0.517, P = 0.0005). Exploratory regression analysis identified significant associations between active PDR and high levels of VEGF (odds ratio = 76.4; 95% confidence interval = 6.32-923) and high levels of sEng (odds ratio = 6.01; 95% confidence interval = 1.25-29.0). Our findings suggest that HMGB1, VEGF, sVE-cadherin and sEng regulate the angiogenesis in PDR.
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http://dx.doi.org/10.1155/2012/697489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3478750PMC
February 2013

Osteopontin and other regulators of angiogenesis and fibrogenesis in the vitreous from patients with proliferative vitreoretinal disorders.

Mediators Inflamm 2012 29;2012:493043. Epub 2012 Sep 29.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi

The aim of this study was to determine the levels of the angiogenic and fibrogenic factors osteopontin (OPN), high-mobility group box-1 (HMGB1), and connective tissue growth factor (CTGF) and the antiangiogenic and antifibrogenic pigment epithelium-derived factor (PEDF) in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and rhegmatogenous retinal detachment with no PVR (RD). Vitreous samples from 48 PDR, 17 PVR and 30 RD patients were studied by enzyme-linked immunosorbent assay. OPN, HMGB1, CTGF, and PEDF levels were significantly higher in PDR patients than in RD patients (P < 0.001; 0.002; <0.001; <0.001, resp.). CTGF and PEDF levels were significantly higher in PVR patients than in RD patients (P < 0.001; 0.004, resp.). Exploratory logistic regression analysis identified significant associations between PDR and high levels of HMGB1, CTGF and PEDF, between PDR with active neovascularization and high levels of CTGF and PEDF, and between PDR with traction retinal detachment and high levels of HMGB1. In patients with PDR, there were significant correlations between the levels of PEDF and the levels of OPN (r = 0.544, P = 0.001), HMGB1 (r = 0.719, P < 0.001), and CTGF (r = 0.715, P < 0.001). In patients with PVR, there were significant correlations between the levels of OPN and the levels of HMGB1 (r = 0.484, P = 0.049) and PEDF (r = 0.559, P = 0.02). Our findings suggest that OPN, HMGB1, and CTGF contribute to the pathogenesis of proliferative vitreoretinal disorders and that increased levels of PEDF may be a response to counterbalance the activity of angiogenic and fibrogenic factors in PDR and PVR.
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http://dx.doi.org/10.1155/2012/493043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3465918PMC
February 2013

Expression of lysophosphatidic acid, autotaxin and acylglycerol kinase as biomarkers in diabetic retinopathy.

Acta Diabetol 2013 Jun 4;50(3):363-71. Epub 2012 Aug 4.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

The proinflammatory lysophosphatidic acid (LPA) is a potent activator of several transcriptional factors and signaling pathways and a potent modulator of genes involved in inflammation, angiogenesis and fibrosis. This study was conducted to measure the levels of LPA and LPA-producing enzymes, autotaxin (ATX) and acylglycerol kinase (AGK) in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and to correlate their levels with clinical disease activity and the level of vascular endothelial growth factor (VEGF). In addition, we examined the expression of ATX, AGK and VEGF receptor-2 (VEGFR-2) in the retinas of diabetic rats. Vitreous samples from 42 PDR and 35 nondiabetic patients were studied by enzyme-linked immunosorbent assay. Vitreous samples and retinas of rats were examined by Western blot analysis. VEGF, LPA and AGK levels in vitreous samples from PDR patients were significantly higher than those in control patients without diabetes (p < 0.001 for all comparisons). ATX levels in PDR with active neovascularization and inactive PDR were significantly lower than those in nondiabetic patients (p = 0.045). Mean VEGF and AGK levels in PDR with active neovascularization were significantly higher than those in inactive PDR and nondiabetic patients (p < 0.001 for both comparisons). A significant correlation was observed between levels of VEGF and levels of AGK in PDR patients (r = 0.954; p < 0.001). Western blot analysis revealed a significant increase in the expression of AGK and VEGFR-2 in vitreous samples and the retinas of diabetic rats compared to nondiabetic controls, whereas ATX was significantly downregulated. Our findings suggest that ATX-AGK-LPA signaling axis might be an important player in the development and progression of diabetic retinopathy.
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http://dx.doi.org/10.1007/s00592-012-0422-1DOI Listing
June 2013

Recent advances in understanding the biochemical and molecular mechanism of diabetic retinopathy.

J Diabetes Complications 2012 Jan-Feb;26(1):56-64. Epub 2012 Jan 5.

Department of Ophthalmology, College of Medicine, King Saud University, KAUH, Riyadh, KSA.

One of the major complications in patients with diabetes is diabetic retinopathy (DR), a leading cause of blindness worldwide. It takes several years before any clinical signs of retinopathy appear in diabetic patients, which gives an ample opportunity for scientists to uncover biochemical and molecular mechanism implicated early in the development and progression of the disease. During the past few decades, research progress has been made in investigating the pathophysiology of the disease; however, due to nonavailability of human retinal samples at different stages of the disease and also due to lack of a proper animal model of DR, the exact molecular mechanism has not been elucidated, making therapeutic a difficult task. In this review article, we have discussed a number of diabetes-induced metabolites such as glucose, lipids, amino acids, and other related factors and molecules that are implicated in the pathophysiology of the DR. Furthermore, we have highlighted neurodegeneration and regulation of neurotrophic factors, being recognized as early events that may be involved in the pathology of the disease in the course of DR. An understanding of the biochemical and molecular changes especially early in the diabetic retina may lead to new and effective therapies towards prevention and amelioration of DR, which is important for the millions of individuals who already have or are likely to develop the disease before a cure becomes available.
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http://dx.doi.org/10.1016/j.jdiacomp.2011.11.004DOI Listing
July 2012

Angiogenesis regulatory factors in the vitreous from patients with proliferative diabetic retinopathy.

Acta Diabetol 2013 Aug 25;50(4):545-51. Epub 2011 Sep 25.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia,

We determined the levels of the endogenous angiogenesis inhibitors soluble vascular endothelial growth factor receptor-1 (sVEGFR-1), thrombospondin (TSP)-1 and TSP-2 in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and correlated their levels with clinical disease activity and the levels of vascular endothelial growth factor (VEGF). Vitreous samples from 30 PDR and 25 nondiabetic patients were studied by enzyme-linked immunosorbent assay. TSP-1 was not detected. VEGF and TSP-2 levels were significantly higher in PDR with active neovascularization compared with inactive PDR and nondiabetic patients (P < 0.001 for both comparisons). VEGF, sVEGFR-1 and TSP-2 levels were significantly higher in PDR with hemorrhage compared with PDR without hemorrhage and nondiabetic patients (P = 0.0063; 0.0144; <0.001, respectively). VEGF and sVEGFR-1 levels were significantly higher in PDR without traction retinal detachment (TRD) compared with PDR with TRD and nondiabetic patients (P = 0.038; 0.022, respectively). TSP-2 levels were significantly higher in PDR with TRD compared with PDR without TRD and nondiabetic patients (P < 0.001). There was a significant correlation between levels of VEGF and sVEGFR-1 (r = 0.427, P = 0.038). Our findings suggest that upregulation of sVEGFR-1 and TSP-2 may be a protective mechanism against progression of angiogenesis associated with PDR. TSP-2 might be associated with TRD.
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http://dx.doi.org/10.1007/s00592-011-0330-9DOI Listing
August 2013

High-mobility group box-1 and biomarkers of inflammation in the vitreous from patients with proliferative diabetic retinopathy.

Mol Vis 2011 6;17:1829-38. Epub 2011 Jul 6.

Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.

Purpose: To measure levels of high-mobility group box -1 (HMGB1) and soluble receptor for advanced glycation end products (sRAGE) in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and to correlate their levels with clinical disease activity and the levels of the inflammatory biomarkers monocyte chemoattractant protein-1 (MCP-1), soluble intercellular adhesion molecule-1 (sICAM-1), interleukin-1β (IL-1β), and granulocyte macrophage colony-stimulating factor (GM-CSF). In addition, we examined the expression of HMGB1 in the retinas of diabetic mice.

Methods: Vitreous samples from 29 PDR and 17 nondiabetic patients were studied by enzyme-linked immunosorbent assay. Retinas of mice were examined by immunofluorescence analysis and western blotting.

Results: HMGB1 was detected in all vitreous samples and sRAGE was detected in 5 PDR samples. IL-1β was detected in 3PDR samples and GM-CSF was not detected. Mean HMGB1 levels in PDR with active neovascularization were twofold and threefold higher than that in inactive PDR and nondiabetic patients, respectively. Mean HMGB1 levels in PDR patients with hemorrhage were significantly higher than those in PDR patients without hemorrhage and nondiabetic patients (p=0.0111). There were significant correlations between levels of HMGB1 and levels of MCP-1 (r=0.333, p=0.025) and sICAM-1 (r=0.548, p<0.001). HMGB1 expression was also upregulated in the retinas of diabetic mice.

Conclusions: Subclinical chronic inflammation might contribute to the progression of PDR.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3137555PMC
December 2011
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