Glycated high-density lipoprotein regulates reactive oxygen species and reactive nitrogen species in endothelial cells.
ABSTRACT Nonenzymatic glycosylation of plasma proteins may contribute to the excess risk of developing atherosclerosis in patients with diabetes mellitus. Although it is believed that high-density lipoprotein (HDL) is glycosylated at an increased level in diabetic individuals, little is known about a possible linkage between glycated HDL and endothelial dysfunction in diabetes. To clarify whether glucose-modified HDL affects the function of endothelial cells, we first examined herein the level of H(2)O(2) generation from cultured human aortic endothelial cells (HAECs) exposed to a glycated oxidized HDL (gly-ox-HDL) prepared in vitro. Incubation for 48 hours with 100 microg/mL of gly-ox-HDL induced significant release of H(2)O(2) from cells and gly-ox-HDL-induced H(2)O(2) formation was inhibited in the presence of diphenyleneiodonium, an inhibitor of NADPH oxidase. In addition, stimulation of HAECs with gly-ox-HDL for 48 hours elicited a marked downregulation of catalase and Cu(2+), Zn(2+)-superoxide dismutase (CuZn-SOD), suggesting H(2)O(2) formation by gly-ox-HDL to be due to a disturbance involving oxidant and antioxidant enzymes in the cells. Treatment of HAECs with gly-ox-HDL attenuated the expression of endothelial nitric oxide synthase (eNOS), but not inducible nitric oxide synthase (iNOS), and this was followed by decreased production of nitric oxide (NO) by the cells. Furthermore, in vitro experiments with glycated HDL (gly-HDL) in the presence of 2 mmol/L EDTA and Cu(2+)-oxidized HDL suggested the effect of gly-HDL on endothelial function to be possibly potentiated by additional oxidative modification. Taking all of the above findings together, gly-ox-HDL may lead to the deterioration of vascular function through altered production of reactive oxygen species and reactive nitrogen species in endothelial cells.
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ABSTRACT: The endothelial cell layer plays a major role in the development and progression of atherosclerosis. Endothelial NO synthase (eNOS) produces nitric oxide (NO) from L-arginine. NO can rapidly react with reactive oxygen species to form peroxynitrite. This reduces NO availability, impairs vasodilatation, and mediates proinflammatory and prothrombotic processes such as leukocyte adhesion and platelet aggregation. In the vessel wall, specific NAD(P)H oxidase complexes are major sources of reactive oxygen species. These NAD(P)H oxidases can transfer electrons across membranes to oxygen and generate superoxide anions. The short-lived superoxide anion rapidly dismutates to hydrogen peroxide, which can further increase the production of reactive oxygen species. This can lead to uncoupling of eNOS switching enzymatic activity from NO to superoxide production. This review describes the structure and regulation of different NAD(P)H oxidase complexes. We will also focus on NO/superoxide anion balance as modulated by hemodynamic forces, vasoconstrictors, and oxidized low-density lipoprotein. We will then summarize the recent advances defining the role of nitric oxide and NAD(P)H oxidase-derived reactive oxygen species in the development and progression of atherosclerosis. In conclusion, novel mechanisms affecting the vascular NO/superoxide anion balance will allow the development of therapeutic strategies in the treatment of cardiovascular diseases.Antioxidants & Redox Signaling 04/2009; 11(7):1711-31. · 8.20 Impact Factor
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ABSTRACT: Abnormal high-density lipoproteins (HDL) metabolism is a major cardiovascular risk factor in type 2 diabetes mellitus (DM2). Lecithin:cholesterol acyltransferase (LCAT) increases HDL size by transferring 2-acyl groups from lecithin or phosphatidylethanolamine to unesterified cholesterol. The purpose of this study was to determine the independent correlates of LCAT activity in DM2 patients. A total of 45 (male: 20) consecutive adult DM2 patients aging 50.0+/-7.0 years (range: 40-64 years) with a median diabetes duration of 4 years (range: 2-18) were studied. Exclusion criteria were: smoking, positive history of cardiovascular, thyroid, renal or liver disease, pregnancy, treatment with metformin, insulin, lipid lowering drugs, angiotensin-converting enzyme inhibitors, aspirin or antioxidant supplements. Univariate and multivariate analyses were performed. From a comprehensive list of variables studied, only HbA1c (rho=-0.951) and oxidized LDL (rho=-0.779) had statistically significant correlation with LCAT activity (p<0.001). These two variables were themselves strongly correlated to each other (rho=0.809, p<0.001). To eliminate potential confounding effects, we performed multivariate analysis, where HbA1c emerged as a strong independent predictor of LCAT activity (adjusted OR=-0.928, p<0.001). Glycemia-induced glycation of HDL decreases LCAT activity. The fact that HbA1c is an accurate measure of glycation and can therefore reflect glycated HDL levels explains the association found in the present study. In conclusion, HbA1c provides an easy-to-assess, accurate measure of LCAT activity in DM2.Diabetes research and clinical practice 07/2008; 81(1):38-41. · 2.74 Impact Factor
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ABSTRACT: BACKGROUND: Diabetic HDL had diminished capacity to stimulate endothelial cell (EC) proliferation, migration, and adhesion to extracellular matrix. The mechanism of such dysfunction is poorly understood and we therefore sought to determine the mechanistic features of diabetic HDL dysfunction. METHODOLOGY/PRINCIPAL FINDINGS: We found that the dysfunction of diabetic HDL on human umbilical vein endothelial cells (HUVECs) was associated with the down regulation of the HDL receptor protein, SR-BI. Akt-phosphorylation in HUVECs was induced in a biphasic manner by normal HDL. While diabetic HDL induced Akt phosphorylation normally after 20 minutes, the phosphorylation observed 24 hours after diabetic HDL treatment was reduced. To determine the role of SR-BI down regulation on diminished EC responses of diabetic HDL, Mouse aortic endothelial cells (MAECs) were isolated from wild type and SR-BI (-/-) mice, and treated with normal and diabetic HDL. The proliferative and migratory effects of normal HDL on wild type MAECs were greatly diminished in SR-BI (-/-) cells. In contrast, response to diabetic HDL was impaired in both types suggesting diminished effectiveness of diabetic HDL on EC proliferation and migration might be due to the down regulation of SR-BI. Additionally, SR-BI down regulation diminishes diabetic HDL's capacity to activate Akt chronically. CONCLUSIONS/SIGNIFICANCE: Diabetic HDL was dysfunctional in promoting EC proliferation, migration, and adhesion to matrix which was associated with the down-regulation of SR-BI. Additionally, SR-BI down regulation diminishes diabetic HDL's capacity to activate Akt chronically.PLoS ONE 01/2012; 7(11):e48530. · 3.73 Impact Factor