Objective-A thick endothelial glycocalyx provides the endothelial surface with a nonadherent shield. Oxidized LDL (Ox-LDL) degrades the endothelial glycocalyx. We hypothesized that glycocalyx degradation stimulates leukocyteendothelial cell adhesion, whereas intravascular supplementation with sulfated polysaccharides reconstitutes the endothelial glycocalyx and attenuates Ox-LDL-induced leukocyte-endothelial cell adhesion. Methods and Results-Degradation of the endothelial glycocalyx by local microinjection of heparitinase (10 to 50 U/mL) into mouse cremaster venules dose-dependently increased the number of adherent leukocytes. Systemic administration of Ox-LDL (0.4 mg/100 g body weight) induced 10.1Ϯ0.9 adherent leukocytes/100 m at 60 minutes. In the venules perfused with 500-kDa dextran sulfate (1 mg/mL), the number of adherent leukocytes at 60 minutes after Ox-LDL bolus application was not influenced (9.2Ϯ1.0 leukocytes/100 m). However, the venules locally perfused with heparan sulfate (10 mg/mL) or heparin (1 mg/mL) displayed a significantly lower number of adherent leukocytes induced by Ox-LDL: 5.1Ϯ0.7 and 5.4Ϯ0.9 leukocytes/100 m, respectively (PϽ0.05). Fluorescently labeled heparan sulfate and heparin, but not dextran sulfate, attached to the venule luminal surface after Ox-LDL administration. Key Words: glycocalyx Ⅲ leukocytes Ⅲ oxidized LDL Ⅲ heparin T he endothelial glycocalyx provides the endothelial surface with a negatively charged coating that contributes to the antiadhesive nature of the endothelial cell surface. 1,2 In the presence of inflammatory stimuli, the endothelial surface loses its nonadhesiveness because of the activation of adhesion molecules and becomes accessible to leukocytes. There is evidence that activation of adhesion molecules is associated with changes in the cell-surface glycocalyx. 2-4 Indeed, the glycocalyx occupies a large domain at the endothelial surface, 5,6 which most probably influences the adhesion process. In this investigation, we studied the effect of endothelial glycocalyx condition on leukocyte-endothelial cell adhesion. Conclusions-EndothelialUnderstanding the role of the endothelial glycocalyx in leukocyte-endothelial cell adhesion has direct relevance for atherosclerosis-related conditions, such as hypercholesterolemia and the plasma presence of oxidized lipoproteins, which are associated with increased leukocyte recruitment 7,8 and degradation of the endothelial glycocalyx. 9 -11 Noteworthy, early modifications of endothelial cells during diet-induced hypercholesterolemia are represented by a decreased thickness and anionic charge of the endothelial glycocalyx and by changes in its biochemical composition. 9,10 Degradation of the endothelial glycocalyx is also induced by oxidized LDL (Ox-LDL in clinically relevant doses and is associated with a parallel increase in endothelial surface adhesiveness. 11 The first aim of the present study was to induce a primary alteration of the thickness and charge of the endothelial glycocalyx by enzyme treatment and to inves...

Oxygen-derived free radicals mediate the disruption of the EC surface layer and increase vascular wall adhesiveness by Ox-LDL.

Proteoglycans and plasma proteins bound to the endothelial cell glycocalyx are essential for vascular function, but at the same time, they lower capillary tube hematocrit by reducing capillary volume available to flowing blood. Because oxidized low-density lipoproteins (oxLDL) reduce the effective thickness of the glycocalyx (Vink H, Constantinescu AA, and Spaan JAE. Circulation 101: 1500-1502, 2000), we designed the present study to determine whether this is caused by pathological degradation of glycocalyx constituents or increased glycocalyx deformation by elevated shear forces of flowing blood. Capillaries from the right cremaster muscle of 24 hamsters were examined by using intravital microscopy after systemic administration of normal LDL (n = 4), moderate oxLDL (6-h oxidation with CuSO(4), n = 7), severe oxLDL (18-h oxidation, n = 5), and moderate oxLDL plus superoxide dismutase (SOD) and catalase (n = 8). Capillary tube hematocrit increased from 0.16 +/- 0.03 to 0.37 +/- 0.05 and from 0.15 +/- 0.01 to 0.31 +/- 0.03 after moderate oxLDL and severe oxLDL, respectively. These changes were paralleled by increases in red blood cell flux from 8.7 +/- 1.9 to 13.8 +/- 3 and from 10.7 +/- 2.1 to 16.3 +/- 3.2 cells/s after moderate oxLDL and severe oxLDL, respectively, in the absence of changes in anatomic capillary diameter. Red blood cell velocity, as a measure for the shear forces on the glycocalyx, was not affected by oxLDL, whereas tissue pretreatment with SOD and catalase completely abolished the effects of oxLDL on glycocalyx thickness, capillary hematocrit, and red blood cell flux. We conclude that elevation of capillary tube hematocrit by oxLDL reflects degradation of the endothelial glycocalyx by oxygen-derived free radicals.

NCT00476281.