Diabetic retinopathy: current understanding, mechanisms, and treatment strategiesDiabetic retinopathy (DR) causes significant visual loss on a global scale. Treatments for the vision-threatening complications of diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) have greatly improved over the past decade. However, additional therapeutic options are needed that take into account pathology associated with vascular, glial, and neuronal components of the diabetic retina. Recent work indicates that diabetes markedly impacts the retinal neurovascular unit and its interdependent vascular, neuronal, glial, and immune cells. This knowledge is leading to identification of new targets and therapeutic strategies for preventing or reversing retinal neuronal dysfunction, vascular leakage, ischemia, and pathologic angiogenesis. These advances, together with approaches embracing the potential of preventative or regenerative medicine, could provide the means to better manage DR, including treatment at earlier stages and more precise tailoring of treatments based on individual patient variations.
Diabetic Retinopathy: A Position Statement by the American Diabetes AssociationDiabetic retinopathy diagnostic assessment and treatment options have improved dramatically since the 2002 American Diabetes Association Position Statement (1). These improvements include the widespread adoption of optical coherence tomography to assess retinal thickness and intraretinal pathology and wide-field fundus photography to reveal clinically silent microvascular lesions. Treatment of diabetic macular edema is now achieved by intravitreous injection of anti–vascular endothelial growth factor agents, and the same drugs are now used for proliferative diabetic retinopathy. Improvements in medications and devices for the systemic therapy of diabetes have also improved the ability of patients to optimize their metabolic control. This Position Statement incorporates these recent developments for the use of physicians and patients.
Diabetic retinopathy is a highly specific neurovascular complication of both type 1 and type 2 diabetes, the prevalence of which strongly correlates to both the duration of diabetes and level of glycemic control. A pooled meta-analysis involving 35 studies conducted worldwide from 1980 to 2008 estimated global prevalence of any diabetic retinopathy and proliferative diabetic retinopathy (PDR) among patients to be 35.4% and 7.5%, respectively (2). Diabetic retinopathy is the most frequent cause of new cases of blindness among adults aged 20–74 years in developed countries. Glaucoma, cataracts, and other disorders of the eye occur earlier and more frequently in people with diabetes.
In addition to diabetes duration, factors that increase the risk of or are associated with retinopathy include chronic hyperglycemia (3,4), nephropathy (5), hypertension (6), and dyslipidemia (7). Intensive diabetes management with the goal of achieving near-normoglycemia has been shown in large prospective randomized studies to prevent and/or delay the onset and progression of diabetic retinopathy (8,9).
Lowering blood pressure has been shown to decrease retinopathy progression in people with type 2 diabetes, although tight targets (systolic blood pressure <120 mmHg) do …
Tumor necrosis factor alpha activates human immunodeficiency virus type 1 through induction of nuclear factor binding to the NF-kappa B sites in the long terminal repeat.Elia J. Duh, Wendy Maury, T M Folks et al.|Proceedings of the National Academy of Sciences|1989 Expression of human immunodeficiency virus type 1 (HIV-1) can be activated in a chronically infected T-cell line (ACH2 cells) by a cytokine, human tumor necrosis factor alpha (TNF-alpha). TNF-alpha treatment of ACH2 cells resulted in an increase in steady-state levels of HIV RNA and HIV transcription. Gel mobility shift assays demonstrated that the transcriptional activation of the HIV long terminal repeat (LTR) by TNF-alpha was associated with the induction of a nuclear factor(s) binding to the NF-kappa B sites in the LTR. Deletion of the NF-kappa B sites from the LTR eliminated activation by TNF-alpha in T cells transfected with plasmids in which the HIV LTR directed the expression of the bacterial chloramphenicol acetyltransferase gene. Thus, TNF-alpha appears to activate HIV RNA and virus production by ACH2 cells through the induction of transcription-activating factors that bind to the NF-kappa B sequences in the HIV LTR.
Tumor necrosis factor alpha induces expression of human immunodeficiency virus in a chronically infected T-cell clone.T M Folks, Kathleen A. Clouse, J. Shawn Justement et al.|Proceedings of the National Academy of Sciences|1989 Tumor necrosis factor alpha (TNF-alpha), also known as cachectin, was demonstrated to induce the expression of human immunodeficiency virus (HIV) in a chronically infected T-cell clone (ACH-2). Concentrations of recombinant TNF-alpha as low as 50 pg/ml induced a significant increase over background of HIV expression in the ACH-2 cells as determined by supernatant reverse transcriptase activity. The HIV-inducing effects of TNF-alpha could not be explained by toxic effects on the cells. In addition, both the uninfected parental cell line (A3.01) and the infected ACH-2 cells were shown to have high-affinity receptors for TNF-alpha. Transient-transfection experiments demonstrated that the inductive effects of TNF-alpha were due to specific activation of the HIV long terminal repeat. These studies provide evidence that TNF-alpha may play a role in the mechanisms of pathogenesis of HIV infection.
Vascular Endothelial Growth Factor–Induced Retinal Permeability Is Mediated by Protein Kinase C In Vivo and Suppressed by an Orally Effective β-Isoform–Selective InhibitorIncreased vascular permeability and excessive neovascularization are the hallmarks of endothelial dysfunction, which can lead to diabetic macular edema and proliferative diabetic retinopathy in the eye. Vascular endothelial growth factor (VEGF) is an important mediator of ocular neovascularization and a known vasopermeability factor in nonocular tissues. In these studies, we demonstrate that intravitreal injection of VEGF rapidly activates protein kinase C (PKC) in the retina at concentrations observed clinically, inducing membrane translocation of PKC isoforms alpha, betaII, and delta and >threefold increases in retinal vasopermeability in vivo. The effect of VEGF on retinal vascular permeability appears to be mediated predominantly by the beta-isoform of PKC with >95% inhibition of VEGF-induced permeability by intravitreal or oral administration of a PKC beta-isoform-selective inhibitor that did not inhibit histamine-mediated effects. These studies represent the first direct demonstration that VEGF can increase intraocular vascular permeability through activation of PKC in vivo and suggest that oral pharmacological therapies involving PKC beta-isoform-selective inhibitors may prove efficacious for the treatment of VEGF-associated ocular disorders such as diabetic retinopathy.