Diabetic Neuropathy: Implications for Wound Repair

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DESCRIPTION (provided by applicant): This proposal explores cell signaling pathways that occur between cutaneous sensory nerve fibers and endothelial cells in response to cutaneous injury. Our previous data suggest that nerve-derived neuropeptides contribute to the normal wound repair process. In contrast, non-healing chronic ulcers associated with diabetes mellitus are characterized by microangiopathy and decreased innervations. Based on encouraging data during the past funding period we continue to explore our hypothesis that in patients with diabetes mellitus, hyperglycemia and hyperlipidemia impair microvascular endothelial cell response to nerve-derived neuropeptides and endothelial cell production of necessary inflammatory mediators. These abnormalities contribute to impaired response to cutaneous injury. We will test our hypothesis by addressing the following Aims: Aim 1: To determine the effects of hyperglycemia and matrix glycosylation on microvascular endothelial cells responses. Hyperglycemia can directly alter cellular responses and can indirectly alter cellular response by extracellular matrix molecule glycosylation. We will determine whether hyperglycemia and/or matrix molecule glycosylation alters SP-induced endothelial cell mediator synthesis, cytoskeleton organization, integrin expression and intracellular signaling. Aim 2: To determine the effect of elevated fatty acid levels on endothelial cell responses. Hyperlipidemia is strongly associated with complications in diabetes mellitus. We will determine whether elevated fatty acids alone or as Triglycerides alter SP-induced endothelial cell mediator synthesis, cytoskeleton organization, integrin expression or intracellular signaling. Aim 3: To determine the anti-oxidant regulation of microvascular endothelial cell response to hyperglycemia & hyperlipidemia. Oxidative stress due to hyperlipidemia may alter cellular response to injury. We will continue our studies of effects of antioxidants, vitamin E, vitamin C and n-acetyl cysteine on cellular responses under hyperlipidemic and hyperglycemic conditions. Aim 4: To determine whether restoration of neuropeptide activity improves wound repair in diabetic mice. We will use several approaches to evaluate the roles of neuropeptides in wound repair. Using an excisional wound repair model in hyperglycemic db/db mice, we will replace substance P and inhibit neutral endopeptidases activity. We will also test the effects of antioxidants in this murine wound model.