Glycosylation Mediates Up-regulation of a Potent Antiangiogenic and Proatherogenic Protein, Thrombospondin-1, by Glucose in Vascular Smooth Muscle Cells

Abstract

Thrombospondins are matricellular proteins that regulate cell-cell and cell-matrix interactions (1, 2). Recent genetic association studies link the thrombospondin (TSP) 2 protein family to the development of atherosclerotic lesions (3-10). TSP-1 was found in early atherosclerotic lesions (11), in injured vascular walls (12,13), and in cardiac allografts where its expression correlated with the degree of vasculopathy (14). The genetic disruption of TSP-1 reduced the atherosclerotic lesion area in the mouse model of atherosclerosis and suggested an important role for TSP-1 in the evolution of plaque and its composition (15). In both in vivo and in vitro studies TSP-1 induced proliferation of vascular smooth muscle cells (SMC) (16,17), and both TSP-1 and TSP-2 inhibited growth of endothelial cells (18 -21); both effects are considered proatherogenic.Previous studies have documented increased TSP-1 levels in the plasma and kidneys of diabetic patients and diabetic animal models (22-25). In mesangial cells, the level of TSP-1 was upregulated by glucose by a transcriptional mechanism (26 -28). We have recently reported increased levels of TSP-1 in the blood vessels of diabetic animals (29). Moreover, TSP-1 was up-regulated by high glucose in vitro in major cell types from large blood vessels. These observations suggest that TSP-1 represents an important link between diabetes, hyperglycemia, and accelerated atherogenesis.A large number of clinical studies and trials have conclusively identified hyperglycemia as an independent risk factor for development of both micro-and macrovascular complications (30 -33). Recently, the Epidemiology of Diabetes Intervention and Complications study reported that, as compared with conventional therapy, intensive glycemic control reduced the risk of the most serious cardiovascular events such as heart attacks, stroke, and death by nearly 60%. These findings clearly underscore the importance of hyperglycemia as a critical player in the development of pathogenic complications associated with diabetes. Glucose regulates the expression of a number of vascular * This work was supported by National Institutes of Health Grants R01 DK067532, K01 DK62128, and P50 HL077107, American Heart Association Grant 0565284B, and funds from the Lerner Research Institute (Cleveland Clinic) (to O. I. S.) and by National Institutes of Health Grant R01 45418 (to P. B.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Cell Type-specific Post-transcriptional Regulation of Production of the Potent Antiangiogenic and Proatherogenic Protein Thrombospondin-1 by High Glucose

“…Change in Osmolarity Regulates TSP-1 Production-The transcriptional increase of TSP-1 mRNA that we observed in all cell types is dependent on the intracellular glucose metabolism; cell-impermeable sorbitol and L-glucose used as osmolarity control failed to up-regulate TSP-1 mRNA (26,31). In contrast, the regulation of protein production by UTR of TSP-1 mRNA in response to high glucose is regulated by a change in osmolarity; biologically inactive cell-impermeable L-glucose had a similar effect on luciferase production regulated by TSP-1 UTR and on the endogenous TSP-1 levels (Fig.…”

“…TSP-1 was up-regulated by glucose stimulation in all major vascular wall cell types from large vessels (EC, smooth muscle cells, and fibroblasts) in vitro (26). Both the protein and mRNA for TSP-1 were rapidly upregulated after stimulation of cells with 10 -30 mM D-glucose but not biologically inactive L-glucose or sorbitol (26,31). In addition to our published data, similar experiments have been performed in human pulmonary artery EC, several isolates of human aortic EC, and human coronary artery EC with similar results (Fig.…”

Glucose and insulin modify thrombospondin 1 expression and secretion in primary adipocytes from diet-induced obese rats

“…This stimulation seems to be mediated by glycosylation of specific nuclear proteins that participate in the hexosamine pathway of glucose catabolism [34]. However, in another report from the same investigation group, a cell-type specific modulation by HG treatment was observed [2].…”

Role of UDP-N-Acetylglucosamine (GlcNAc) and O-GlcNAcylation of Hyaluronan Synthase 2 in the Control of Chondroitin Sulfate and Hyaluronan Synthesis

“…3 ϫ 10 5 cells were seeded in 35-mm dishes, and after 6 h, SmGm2 medium was replaced with DMEM (Euroclone) supplemented with 0.2% FBS. After 48 h to induce quiescence, the medium was changed to low glucose (5 mM) DMEM/F-12 with 10% FBS, and the cells were treated without or with 2 mM GlcN, 40 M 6-diazo-5-oxoleucine (DON), 5 mM alloxan, 100 M O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAC), or 1 mM 4-methylumbelliferone (4-MU) for 24 h (all from Sigma) to modulate protein O-GlcNAcylation (26). In some experiments, NIH3T3 cells were used and grown to confluence in DMEM supplemented with 10% FBS and 1% Glutamax (Lonza).…”

“…cose and treated with 2 mM GlcN, which is known to induce protein O-GlcNAcylation in the same cells (26).…”