Plasminogen Activator Inhibitor-1 Overexpression in Nonproliferative Diabetic Retinopathy

doi:10.1006/exer.1996.0112

Experimental Eye Research

Volume 63, Issue 3, September 1996, Pages 233-244

https://doi.org/10.1006/exer.1996.0112 Get rights and content

Abstract

Plasminogen activator inhibitor-1 is secreted bidirectionally by endothelial cells, acts as the primary regulator of fibrinolysis and as a key modulator of extracellular matrix proteolysis. Elevated serum levels of plasminogen activator inhibitor-1 are observed in serum of diabetic individuals. We investigated whether plasminogen activator inhibitor-1 is overexpressed in capillaries of diabetic donors with non-proliferative retinopathy compared to non-diabetic donors. We also assessed plasminogen activator inhibitor-1 expression in an animal model of retinopathy induced by exposing rabbit retinas to insulin-like growth factor-I. Colloidal gold immunocytochemistry was used to quantify plasminogen activator-1 antigen in donor retinas from diabetic subjects (n=10) and control subjects (n=10). This technique was also used to examine expression of plasminogen activator inhibitor-1 for correlation with retinal changes in the insulin-like growth factor-I-induced retinopathy model (n=14). Plasminogen activator inhibitor-1 immunoreactivity was significantly increased in the retinas of all diabetic subjects as compared to controls. In the rabbit model, the expression of plasminogen activator inhibitor-1 immunoreactivity correlated with pathological retinal changes. In both the diabetic human and insulin-like growth factor-I-injected rabbit, overproduction of plasminogen activator inhibitor-1 was seen within the lumen of capillaries, within the cytoplasm of endothelial cells and in the basement membrane and extracellular matrix surrounding these capillaries. Minimal plasminogen activator inhibitor-1 was detected in the retinas of non-diabetics and in control rabbits injected with either heat-inactivated insulin-like growth factor-I or balanced salt solution. These studies support the conclusion that plasminogen activator inhibitor-1 is overexpressed in the retinal capillaries of diabetics with non-proliferative diabetic retinopathy and in rabbits with insulin-like growth factor-I-induced retinopathy.

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Cited by (43)

Retinal capillary basement membrane thickening: Role in the pathogenesis of diabetic retinopathy
2021, Progress in Retinal and Eye Research
Citation Excerpt :
Taken together, these findings indicate increased activity of MMP-2 and MMP-9 during late stage development of DR. Therefore, it remains plausible that in early stages of DR, degradation of ECM components is decreased ultimately leading to thickening of the BM, while in the later stages of DR, increased local activity of MMP-2 and MMP-9 allows endothelial cell sprouting during neovascularization leading to angiogenesis (Abreu and de Brito Vieira, 2016; Mohammad and Siddiquei, 2012; Naduk-Kik and Hrabec, 2008). In parallel, several studies suggest that levels of plasminogen activator inhibitor-1 (PAI-1), a serine protease, which can lower matrix degradation of BM components such as laminin and fibronectin (Krag et al., 2005; Levin and Santell, 1987), are elevated in retinal microvessels of diabetic subjects (Lorenzi et al., 1998) and in the vitreous of non-proliferative DR patients (Grant et al., 1996). These findings support the suggestion that in early stages of DR, excess synthesis of ECM components may also be accompanied by decreased degradation, contributing to the overall thickening of the retinal vascular BM.
Vascular basement membrane (BM) thickening has been hailed over half a century as the most prominent histological lesion in diabetic microangiopathy, and represents an early ultrastructural change in diabetic retinopathy (DR). Although vascular complications of DR have been clinically well established, specific cellular and molecular mechanisms underlying dysfunction of small vessels are not well understood. In DR, small vessels develop insidiously as BM thickening occurs. Studies examining high resolution imaging data have established BM thickening as one of the foremost structural abnormalities of retinal capillaries. This fundamental structural change develops, at least in part, from excess accumulation of BM components. Although BM thickening is closely associated with the development of DR, its contributory role in the pathogenesis of DR is coming to light recently. DR develops over several years before clinical manifestations appear, and it is during this clinically silent period that hyperglycemia induces excess synthesis of BM components, contributes to vascular BM thickening, and promotes structural and functional lesions including cell death and vascular leakage in the diabetic retina. Studies using animal models show promising results in preventing BM thickening with subsequent beneficial effects. Several gene regulatory approaches are being developed to prevent excess synthesis of vascular BM components in an effort to reduce BM thickening. This review highlights current understanding of capillary BM thickening development, role of BM thickening in retinal vascular lesions, and strategies for preventing vascular BM thickening as a potential therapeutic strategy in alleviating characteristic lesions associated with DR.
Identification of genes related to proliferative diabetic retinopathy through RWR algorithm based on protein–protein interaction network
2018, Biochimica et Biophysica Acta - Molecular Basis of Disease
Citation Excerpt :
The herb andrographolide ameliorates DR via attenuating retinal angiogenesis and inflammation, during which Egr1 signaling pathway plays an important role [64]. As the downstream gene of Egr1 [65], SERPINE1 has been found that its upregulation in plasma was associated with the progression of DR [66,67]. The epithelial-mesenchymal transition (EMT) of retinal pigment epithelium cells plays a key role in PDR.
Proliferative diabetic retinopathy (PDR) is one of the most common complications of diabetes and can lead to blindness. Proteomic studies have provided insight into the pathogenesis of PDR and a series of PDR-related genes has been identified but are far from fully characterized because the experimental methods are expensive and time consuming. In our previous study, we successfully identified 35 candidate PDR-related genes through the shortest-path algorithm. In the current study, we developed a computational method using the random walk with restart (RWR) algorithm and the protein–protein interaction (PPI) network to identify potential PDR-related genes. After some possible genes were obtained by the RWR algorithm, a three-stage filtration strategy, which includes the permutation test, interaction test and enrichment test, was applied to exclude potential false positives caused by the structure of PPI network, the poor interaction strength, and the limited similarity on gene ontology (GO) terms and biological pathways. As a result, 36 candidate genes were discovered by the method which was different from the 35 genes reported in our previous study. A literature review showed that 21 of these 36 genes are supported by previous experiments. These findings suggest the robustness and complementary effects of both our efforts using different computational methods, thus providing an alternative method to study PDR pathogenesis.
Gemigliptin, a dipeptidyl peptidase-4 inhibitor, inhibits retinal pericyte injury in db/db mice and retinal neovascularization in mice with ischemic retinopathy
2015, Biochimica et Biophysica Acta - Molecular Basis of Disease
Citation Excerpt :
PAI-1 plays an important role in the development of diabetic retinopathy. High levels of PAI-1 have been observed in serum [39], vitreous [40] and retinal microvasculature [41] of patients with diabetes. Furthermore, the retinal vasculature of transgenic mice that overexpress PAI-1 exhibited an increase in the basal membranes and E/P ratio, similar to diabetic retinopathy [42].
Retinal pericyte loss and neovascularization are characteristic features of diabetic retinopathy. Gemigliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has shown robust blood-glucose lowering effects in type 2 diabetic patients, but its effects on diabetic retinopathy have not yet been reported. We evaluated the efficacy of gemigliptin on retinal vascular leakage in db/db mice, which is an animal model for type 2 diabetes, and neovascularization in oxygen-induced retinopathy (OIR) mice, which is an animal model for ischemic proliferative retinopathy. Gemigliptin (100 mg/kg/day) was orally administered to the db/db mice for 12 weeks. C57BL/6 mice on postnatal day 7 (P7) were exposed to 75% hyperoxia for 5 days, followed by exposure to room air from P12 to P17 to induce OIR. Gemigliptin (50 mg/kg/day) was intraperitoneally injected daily from P12 to P17. Retinal neovascularization was analyzed in flat-mounted retinas on P17. We determined the efficacy and possible mechanism of gemigliptin on high glucose-induced apoptosis of primary human retinal pericytes. The oral administration of gemigliptin for 4 months significantly ameliorated retinal pericyte apoptosis and vascular leakage in the db/db mice. Gemigliptin also ameliorated retinal neovascularization in the OIR mice. Gemigliptin attenuated the overexpression of plasminogen activator inhibitor-1 (PAI-1) in the retinas of diabetic and OIR mice. Gemigliptin and PAI-1 siRNA significantly inhibited pericyte apoptosis by inhibiting the overexpression of PAI-1, which is induced by high glucose. Our results suggest that gemigliptin has potent anti-angiogenic and anti-apoptotic activities via suppressing DPP-4 and PAI-1, and the results support the direct retinoprotective action of gemigliptin.
Andrographolide ameliorates diabetic retinopathy by inhibiting retinal angiogenesis and inflammation
2015, Biochimica et Biophysica Acta - General Subjects
Citation Excerpt :
Serpine1, also named plasminogen activator inhibitor 1, is a rapid inhibitor of tissue plasminogen (tPA) and acts as the primary regulator of fibrinolysis, which is critically involved in modulating extracellular matrix proteolysis [38]. Recent studies demonstrate that the increased plasma serpine1 content is associated with the progression of DR [39,40]. TF, a transmembrane glycoprotein, is involved in regulating blood coagulation, and recent reports demonstrate its potential regulation of angiogenesis [41,42].
Andrographolide (Andro) is the main compound distributed in medicinal herb Andrographis paniculata. This study aims to observe the amelioration of Andro on streptozotocin (STZ)-induced diabetic retinopathy (DR) in mice.
STZ-induced non-proliferative DR (NPDR) for 2 months and proliferative DR (PDR) for 5 month in C57BL/6 mice were used in this study, respectively. Retinal vessels were observed by immunofluorescence staining for cluster of differentiation 31 (CD31). Evans blue permeation assay was used to detect the breakdown of blood-retinal barrier (BRB). Real-time PCR and immune-blot were used to detect mRNA and protein expression. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β.
Retinal immunofluorescence staining with CD31 showed that Andro reduced the increased retinal vessels in STZ-induced PDR mice. Evans blue permeation results demonstrated that Andro attenuated the breakdown of BRB in STZ-induced NPDR mice. In STZ-induced PDR mice, Andro decreased the increased vascular endothelial growth factor (VEGF) in serum and vitreous cavity, and reduced the increased retinal mRNA expression of VEGF and its receptors. In STZ-induced NPDR mice, Andro abrogated the nuclear translocation of nuclear factor κB (NF-κB) p65 and early growth response-1 (Egr-1), and reduced the increased phospho-NF-κBp65, -inhibitor of kappa B (IκB), and -IκB kinase (IKK). Andro also decreased the increased serum and retinal mRNA expression of TNF-α, IL-6, IL-1β, serpine1, and tissue factor (TF).
Andro ameliorates DR via attenuating retinal angiogenesis and inflammation, and VEGF, NF-κB, and Egr1 signaling pathways all play important roles in this process.
Low shear stress up-regulation of proinflammatory gene expression in human retinal microvascular endothelial cells
2013, Experimental Eye Research
The vascular endothelium responds to shear stress generated by blood flow and changes functions to regulate blood flow and maintain tissue homeostasis. Recently, we found that arteriolar high shear stress leads to increased expression of vasodilatory and antithrombotic genes in human retinal microvascular endothelial cells (HRMECs). However, it is unknown whether low shear stress, which is induced by hypoperfusion particularly in the retinal venules where leukocyte–endothelial interactions mainly occur, affects the retinal endothelial function. We studied the effect of low shear stress on proinflammatory gene expression in HRMECs. The cells were cultured on glass plates and exposed to laminar shear stresses of 0 (static), 1.5 (relatively low flow), and 15 dyne/cm² (relatively high flow) for 24 h using parallel plate-type flow-loading devices. The mRNA expressions of adhesion molecules, cytokines and chemokines, and procoagulant factors were evaluated using real-time reverse-transcription polymerase chain reaction. HRMECs exposed to 1.5 dyne/cm² significantly up-regulated the mRNA expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin. The cells exposed to 1.5 dyne/cm² of stress also had increased cytokine/chemokine mRNA expression, i.e., interleukin (IL)-6, IL-8, platelet-derived growth factor-B, and monocyte chemotactic protein-1. Procoagulant factors, i.e., tissue factor and plasminogen activator inhibitor-1 mRNA, increased significantly with exposure to 1.5 dyne/cm² of stress. Our results showed that relatively low shear stress causes up-regulation of proinflammatory genes in HRMECs, suggesting that decreased shear stress due to vascular hypoperfusion might change the phenotypic characterization of the retinal vascular endothelium and be associated with leukocyte–endothelial interactions.
Mouse models of diabetic retinopathy
2013, Drug Discovery Today: Disease Models
Citation Excerpt :
Plasmin degrades fibrin and blood basement membrane components [54]. PAI-1 is increased in diabetic eye suggesting a role of this inhibitor in the pathogenesis of diabetic retinopathy [55]. Transgenic mice overexpressing human PAI-1 under the control of the murine metallothionein I promoter showed thickened blood basement membrane and loss of pericytes [56].
Despite many years of clinical and laboratory investigation, diabetic retinopathy remains the leading cause of vision impairment among working-aged people. Mouse models have been valuable tools in further understanding the pathophysiology of diabetic retinopathy and discovering and assessing new potential therapeutic agents. However, although numerous diabetic mouse models have been developed, none of these models replicates all the key features of human diabetic retinopathy. In this review, we summarize and update the list of mouse diabetic and diabetic-like models that have been generated.

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^f1: For correspondence at: Division of Endocrinology and Metabolism, Box 100226, University of Florida, Gainesville, FL 32610-0226, U.S.A.

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Regular articlePlasminogen Activator Inhibitor-1 Overexpression in Nonproliferative Diabetic Retinopathy

Abstract

Regular article
Plasminogen Activator Inhibitor-1 Overexpression in Nonproliferative Diabetic Retinopathy