Regulation of thrombospondin-1 expression by glucose

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Description (provided by applicant): Vascular complications account for the greatest numbers of deaths in diabetic patients. However, the molecular mechanisms responsible for these complications remain poorly understood. We recently reported that the expression of thrombospondin-1 (TSP-1) is strikingly elevated in large vessels of Zucker rats, an animal model of type 2 diabetes, both in basal conditions and in response to injury, suggesting a role for this protein in the accelerated atherosclerosis and increased restenosis in this animal model and diabetic patients. TSP-1 has a number of well-documented proatherogenic properties, including genetic and biochemical evidence, and is also one of the most potent antiangiogenic agents, a function directly relevant to diabetic complications. Our preliminary data indicated that TSP-1 expression is regulated by glucose at the transcriptional level and suggested possible signaling pathways for this activation. We will test the hypothesis that specific signaling and transcriptional molecular mechanisms rapidly activated by acute stimulation of arterial smooth muscle cells (SMC) with high glucose mediate the increased expression of TSP-1 in the wall of large blood vessels and provide a link between hyperglycemia and accelerated atherogenesis. The overall goal of the proposed project is to elucidate specific signaling and transcriptional mechanisms responsible for the upregulation of TSP-1 expression by glucose in SMC and to test whether that increased expression of TSP-1 in the vascular wall contributes to the development of atherosclerotic lesions. The long-term objective is to uncover the hyperglycemia-induced molecular mechanisms that lead to development of vascular complications. Specific Aims are: 1. To identify the promoter region of the TSP-1 gene and nuclear factors responsible for the upregulation of TSP-1 by glucose; 2. To identify signaling pathways involved in regulation of TSP-1 expression by glucose; 3. To demonstrate directly in the transgenic mouse model that increased expression of TSP-1 in the vascular wall contributes to the development of atherosclerotic lesions. The results of these experiments will: 1) identify targets for the regulation of TSP-1, a potent antiangiogenic and proatherogenic protein that may contribute to vascular diabetic complications; 2) provide additional information about the molecular mechanisms of the effects of glucose in SMC; and 3) demonstrate directly that TSP-1 may serve as a link between diabetes and vascular complications.