OXIDIZED LOW-DENSITY LIPOPROTEINS FACILITATE LEUKOCYTE ADHESION TO AORTIC INTIMA WITHOUT AFFECTING ENDOTHELIUM-DEPENDENT RELAXATION - ROLE OF P-SELECTIN

Inflammatory cell deposition in atherosclerotic blood vessels has been thought to relate to loss of endothelium-derived nitric oxide (NO), T o examine whether cell deposition correlates temporally with the loss of NO activity, rat aortic rings were incubated with buffer, native LD L (n-LDL), oxidized LDL (ox-LDL), or the endothelium-derived relaxing factor synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAM E) for 2 hours, and vascular contractile response to norepinephrine an d relaxant response to acetylcholine, thrombin, and calcium ionophore A23,187 were examined. Thereafter, the rings were exposed to biotin-fl uorescein isothiocyanate-labeled fluorescent or unlabeled leukocytes f or 30 minutes. Cell adhesion was quantitated by fluorescent microscopy as well as by scanning electron microscopy. Incubation with n-LDL or ox-LDL did not affect either the contractile or the relaxant response of rings. However, leukocyte adhesion increased markedly in all ox-LDL -treated rings but not in those treated with n-LDL. Thus, leukocyte ad hesion occurred independent of NO activity. In keeping with this conce pt, pretreatment of rings with the NO precursor L-arginine failed to i nfluence leukocyte adhesion to rings incubated with ox-LDL. Treatment of rings with L-NAME also resulted in adhesion of a large number of le ukocytes. Furthermore, all rings treated with ox-LDL or L-NAME demonst rated marked expression of P-selectin leukocyte adhesion molecules, de termined by immunohistochemistry. Pretreatment of rings with the P-sel ectin blocking antibody PB1.3 markedly decreased deposition of leukocy tes in rings exposed to ox-LDL, These data show that cell adhesion to vascular intima exposed to ox-LDL shows no temporal relation with atte nuation of NO activity, although inhibition of NO synthesis leads to l eukocyte deposition. P-selectin expression on vascular rings exposed t o ox-LDL appears to be the basis of leukocyte deposition.