Role of Retinal Capillary Stiffness in Diabetic Retinopathy

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PROJECT ABSTRACT Diabetic retinopathy (DR) is a major, potentially blinding, microvascular complication of diabetes and the leading cause of vision loss in the working-age population. Although current clinical therapies aim to resolve the advanced stages of DR, there is a recognition that more effective DR management can be achieved by tackling the disease at the early stage. Diabetes-induced retinal inflammation is strongly implicated in the pathogenesis of DR. Retinal endothelial activation (ICAM-1 expression) plays a major role in inflammation because inhibiting ICAM-1 alone blocks retinal capillary leukostasis, hyperpermeability, and degeneration associated with DR. But precisely how retinal endothelial cells (ECs) become activated in diabetes is not properly understood. Since diabetes has been strongly associated with increased stiffness of the aorta and arteries, which undergo chronic inflammation, we asked whether diabetes also leads to stiffening of retinal capillaries and, if so, whether the increased capillary stiffness promotes retinal inflammation in diabetes. Our preliminary data has revealed that retinal capillaries in diabetic mice are significantly stiffer than those in normal mice, which correlates with increased lysyl oxidase (LOX) expression. Pharmacological inhibition of LOX-dependent capillary stiffening alone blocks retinal endothelial ICAM-1 associated with diabetes. Our preliminary studies have also revealed that this stiffness-dependent control of retinal inflammation in diabetes is mediated by the mechanosensitive and proinflammatory small GTPase Rho and its downstream effector ROCK, which is markedly upregulated in retinal capillaries of diabetic mice and HG-treated retinal EC cultures. Based on these observations, we hypothesize that diabetes leads to LOX-dependent stiffening of retinal capillaries and elevated Rho/ROCK that, in turn, promotes NF-kB-mediated endothelial ICAM-1 expression and retinal inflammation associated with early DR. The objective of this proposal is to uncover the link between diabetes, retinal capillary stiffness, endothelial mechanotransduction, and retinal inflammation. To achieve this goal, we will pursue the following specific aims. Aim 1: To fully examine the effects of pharmacologic and genetic inhibition of LOX on retinal capillary stiffening-dependent inflammation and vascular lesions of early DR; Aim 2: To determine the extent to which diabetes-induced biochemical changes in the retina contribute to LOX-dependent retinal capillary stiffening; and Aim 3: To delineate the mechanotransduction mechanism underlying capillary stiffening-dependent retinal inflammation in diabetes.