Molecular Determinants of Oxidized Low-Density Lipoprotein–Induced Leukocyte Adhesion and Microvascular Dysfunction

Oxidized low-density lipoproteins (oxLDL) have been implicated in the leukocyte recruitment and microvascular dysfunction associated with atherosclerosis. The objectives of this study were to define the adhesion molecules that mediate oxLDL-induced leukocyte-endothelial cell adhesion and to determine whether leukocyte-endothelial cell adhesion contributes to the endothelial barrier dysfunction elicited by oxLDL. Leukocyte-endothelial cell adhesion and emigration, albumin extravasation, and mast cell degranulation were monitored in rat mesentery in response to native LDL (nLDL) or copper-oxidized LDL (oxLDL). Intra-arterial infusion of oxLDL but not nLDL elicited increases in leukocyte adherence and emigration, mast cell degranulation, and albumin leakage. The oxLDL-induced leukocyte adherence/emigration was attenuated by pretreatment with monoclonal antibodies directed against CD11/CD18, intercellular adhesion molecule-1, P-selectin, and L-selectin but not by pretreatment with a nonbinding monoclonal antibody. The albumin leakage and mast cell degranulation responses were attenuated by all of the same monoclonal antibodies except L-selectin. In addition, a peptide previously shown to inhibit leukocyte-endothelial cell adhesion in vitro also attenuated leukocyte adherence and mast cell degranulation in this model. These findings implicate CD11/ CD18, L-selectin, intercellular adhesion molecule-1, and P-selectin in the leukocyte recruitment elicited by oxLDL and invoke a role for adherent leukocytes in the accompanying increase in mast cell degranulation and albumin leakage.