Anti-IL17A Halts the Onset of Diabetic Retinopathy in Type I and II Diabetic Mice.

There are ~463 million diabetics worldwide, and more than half have diabetic retinopathy. Yet, treatments are still lacking for non-proliferative diabetic retinopathy. We and others previously provided evidence that Interleukin-17A (IL-17A) plays a pivotal role in non-proliferative diabetic retinopathy. However, all murine studies used Type I diabetes models. Hence, it was the aim of this study to determine if IL-17A induces non-proliferative diabetic retinopathy in Type II diabetic mice, as identified for Type I diabetes. While examining the efficacy of anti-IL-17A as a potential therapeutic in a short-term Type I and a long-term Type II diabetes model; using different routes of administration of anti-IL-17A treatments. Retinal inflammation was significantly decreased (p < 0.05) after Type I-diabetic mice received 1 intravitreal injection, and Type II-diabetic mice received seven intraperitoneal injections of anti-IL-17A. Further, vascular tight junction protein Zonula Occludens-1 (ZO-1) was significantly decreased in both Type I and II diabetic mice, which was significantly increased when mice received anti-IL-17A injections (p < 0.05). Similarly, tight junction protein Occludin degradation was halted in Type II diabetic mice that received anti-IL-17A treatments. Finally, retinal capillary degeneration was halted 6 months after diabetes was confirmed in Type II-diabetic mice that received weekly intraperitoneal injections of anti-IL-17A. These findings provide evidence that IL-17A plays a pivotal role in non-proliferative diabetic retinopathy in Type II diabetic mice, and suggests that anti-IL-17A could be a good therapeutic candidate for non-proliferative diabetic retinopathy.

IL-17A Enhances Retinal Neovascularization.

Retinal neovascularization occurs in proliferative diabetic retinopathy, neovascular glaucoma, and age-related macular degeneration. This type of retinal pathology normally occurs in the later stages of these ocular diseases and is a prevalent cause of vision loss. Previously, we determined that Interleukin (IL)-17A plays a pivotal role in the onset and progression of non-proliferative diabetic retinopathy in diabetic mice. Unfortunately, none of our diabetic murine models progress to proliferative diabetic retinopathy. Hence, the role of IL-17A in vascular angiogenesis, neovascularization, and the onset of proliferative diabetic retinopathy was unclear. In the current study, we determined that diabetes-mediated IL-17A enhances vascular endothelial growth factor (VEGF) production in the retina, Muller glia, and retinal endothelial cells. Further, we determined that IL-17A can initiate retinal endothelial cell proliferation and can enhance VEGF-dependent vascular angiogenesis. Finally, by utilizing the oxygen induced retinopathy model, we determined that IL-17A enhances retinal neovascularization. Collectively, the results of this study provide evidence that IL-17A plays a pivotal role in vascular proliferation in the retina. Hence, IL-17A could be a potentially novel therapeutic target for retinal neovascularization, which can cause blindness in multiple ocular diseases.

Inhibition of CD40-TRAF6-dependent inflammatory activity halts the onset of diabetic retinopathy in streptozotocin-diabetic mice.

Diabetes initiates inflammation that can impair the retinal vasculature, and lead to diabetic retinopathy; one of the leading causes of blindness. Inflammatory pathways have been examined as potential therapeutic targets for diabetic retinopathy, but there is still a need for early-stage treatments. We hypothesized that the CD40-TNF Receptor Associated Factor 6 (TRAF6) axis plays a pivotal role in the onset of diabetic retinopathy, and that the CD40-TRAF6 axis would be a prime therapeutic target for early-stage non-proliferative diabetic retinopathy. The CD40-TRAF6 complex can initiate NFκB activation, inflammation, and tissue damage. Further, CD40 and TRAF6 are constitutively expressed on Muller glia, and upregulated in the diabetic retina. Yet the role of the CD40-TRAF6 complex in the onset of diabetic retinopathy is still unclear. In the current study, we examined the CD40-TRAF6 axis in diabetic retinopathy using a small molecule inhibitor (SMI-6877002) on streptozotocin-induced diabetic mice. When CD40-TRAF6-dependent inflammation was inhibited, retinal vascular leakage and capillary degeneration was ameliorated in diabetic mice. Collectively, these data suggest that the CD40-TRAF6 axis plays a pivotal role in the onset of diabetic retinopathy, and could be a novel therapeutic target for early diabetic retinopathy.

Retinal Inflammation, Oxidative Stress, and Vascular Impairment Is Ablated in Diabetic Mice Receiving XMD8-92 Treatment.

The global number of diabetics continues to rise annually. As diabetes progresses, almost all of Type I and more than half of Type II diabetics develop diabetic retinopathy. Diabetic retinopathy is a microvascular disease of the retina, and is the leading cause of blindness in the working-age population worldwide. With such a significant health impact, new drugs are required to halt the blinding threat posed by this visual disorder. The cause of diabetic retinopathy is multifactorial, and an optimal therapeutic would halt inflammation, cease photoreceptor cell dysfunction, and ablate vascular impairment. XMD8-92 is a small molecule inhibitor that blocks inflammatory activity downstream of ERK5 (extracellular signal-related kinase 5) and BRD4 (bromodomain 4). ERK5 elicits inflammation, is increased in Type II diabetics, and plays a pathologic role in diabetic nephropathy, while BRD4 induces retinal inflammation and plays a role in retinal degeneration. Further, we provide evidence that suggests both pERK5 and BRD4 expression are increased in the retinas of our STZ (streptozotocin)-induced diabetic mice. Taken together, we hypothesized that XMD8-92 would be a good therapeutic candidate for diabetic retinopathy, and tested XMD8-92 in a murine model of diabetic retinopathy. In the current study, we developed an in vivo treatment regimen by administering one 100 µL subcutaneous injection of saline containing 20 µM of XMD8-92 weekly, to STZ-induced diabetic mice. XMD8-92 treatments significantly decreased diabetes-mediated retinal inflammation, VEGF production, and oxidative stress. Further, XMD8-92 halted the degradation of ZO-1 (zonula occludens-1), which is a tight junction protein associated with vascular permeability in the retina. Finally, XMD8-92 treatment ablated diabetes-mediated vascular leakage and capillary degeneration, which are the clinical hallmarks of non-proliferative diabetic retinopathy. Taken together, this study provides strong evidence that XMD8-92 could be a potentially novel therapeutic for diabetic retinopathy.

Aryl Hydrocarbon Receptor Agonist VAF347 Impedes Retinal Pathogenesis in Diabetic Mice.

Diabetic retinopathy is the leading cause of blindness in the working-age population worldwide. Although the cause of diabetic retinopathy is multifactorial, IL-17A is a prevalent inflammatory cytokine involved in the promotion of diabetes-mediated retinal inflammation and the progression of diabetic retinopathy. The primary source of IL-17A is Th17 cells, which are T helper cells that have been differentiated by dendritic cells in a proinflammatory cytokine environment. Aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that can manipulate dendritic cell maturation, halt the production of IL-6 (a proinflammatory cytokine), and suppress Th17 cell differentiation. In the current study, we examined the efficacy of an AhR agonist, VAF347, as a potential therapeutic for the onset of non-proliferative diabetic retinopathy in streptozotocin (STZ)-induced diabetic C57BL/6 mice. We determined that diabetes-mediated leukostasis, oxidative stress, and inflammation in the retina of STZ-diabetic mice were all significantly lower when treated with the AhR agonist VAF347. Furthermore, when VAF347 was subcutaneously injected into STZ-diabetic mice, retinal capillary degeneration was ameliorated, which is the hallmark of non-proliferative diabetic retinopathy in this diabetes murine model. Collectively, these findings provide evidence that the AhR agonist VAF347 could be a potentially novel therapeutic for non-proliferative diabetic retinopathy.

RORγt Inhibitor-SR1001 Halts Retinal Inflammation, Capillary Degeneration, and the Progression of Diabetic Retinopathy.

Diabetic retinopathy is a diabetes-mediated retinal microvascular disease that is the leading cause of blindness in the working-age population worldwide. Interleukin (IL)-17A is an inflammatory cytokine that has been previously shown to play a pivotal role in the promotion and progression of diabetic retinopathy. Retinoic acid-related orphan receptor gammaT (RORγt) is a ligand-dependent transcription factor that mediates IL-17A production. However, the role of RORγt in diabetes-mediated retinal inflammation and capillary degeneration, as well as its potential therapeutic attributes for diabetic retinopathy has not yet been determined. In the current study, we examined retinal inflammation and vascular pathology in streptozotocin-induced diabetic mice. We found RORγt expressing cells in the retinal vasculature of diabetic mice. Further, diabetes-mediated retinal inflammation, oxidative stress, and retinal endothelial cell death were all significantly lower in RORγt-/- mice. Finally, when a RORγt small molecule inhibitor (SR1001) was subcutaneously injected into diabetic mice, retinal inflammation and capillary degeneration were ameliorated. These findings establish a pathologic role for RORγt in the onset of diabetic retinopathy and identify a potentially novel therapeutic for this blinding disease.

Diabetes induces IL-17A-Act1-FADD-dependent retinal endothelial cell death and capillary degeneration.

PURPOSE: Diabetes leads to progressive complications such as diabetic retinopathy, which is the leading cause of blindness within the working-age population worldwide. Interleukin (IL)-17A is a cytokine that promotes and progresses diabetes. The objective of this study was to determine the role of IL-17A in retinal capillary degeneration, and to identify the mechanism that induces retinal endothelial cell death. These are clinically meaningful abnormalities that characterize early-stage non-proliferative diabetic retinopathy. METHODS: Retinal capillary degeneration was examined in vivo using the streptozotocin (STZ) diabetes murine model. Diabetic-hyperglycemia was sustained for an 8-month period in wild type (C57BL/6) and IL-17A-/- mice to elucidate the role of IL-17A in retinal capillary degeneration. Further, ex vivo studies were performed in retinal endothelial cells to identify the IL-17A-dependent mechanism that induces cell death. RESULTS: It was determined that diabetes-induced retinal capillary degeneration was significantly lower in IL-17A-/- mice. Further, retinal endothelial cell death occurred through an IL-17A/IL-17R ➔ Act1/FADD signaling cascade, which caused caspase-mediated apoptosis. CONCLUSION: These are the first findings that establish a pathologic role for IL-17A in retinal capillary degeneration. Further, a novel IL-17A-dependent apoptotic mechanism was discovered, which identifies potential therapeutic targets for the early onset of diabetic retinopathy.

Diabetes-mediated IL-17A enhances retinal inflammation, oxidative stress, and vascular permeability.

Diabetic retinopathy is a prevailing diabetes complication, and one of the leading causes of blindness worldwide. IL-17A is a cytokine involved in the onset of diabetic complications. In the current study, we examined the role of IL-17A in the development of retinal inflammation and long-term vascular pathology in diabetic mice. We found IL-17A expressing T cells and neutrophils in the retinal vasculature. Further, the IL-17A receptor was expressed on Muller glia, retinal endothelial cells, and photoreceptors. Finally, diabetes-mediated retinal inflammation, oxidative stress, and vascular leakage were all significantly lower in IL-17A-/- mice. These are all clinically meaningful abnormalities that characterize the onset of diabetic retinopathy.