Mononuclear Leukocytes Invade Rabbit Arterial Intima During Thickening Formation via CD18- and VLA-4–Dependent Mechanisms and Stimulate Smooth Muscle Migration

Abstract

The role of mononuclear leukocytes for the migration of smooth muscle cells (SMCs) during intimal thickening was investigated in the rabbit model of electrically stimulated carotid artery. The approach was to inhibit leukocyte entry into the arterial intima with antibodies against the adhesion molecules very late activation antigen-4 (VLA-4) and CD11/CD18. In electrically stimulated control rabbits treated either with saline or a nonspecific antibody, all types of granulocytes, monocytes, and lymphocytes migrated across an intact endothelium into the acellular subendothelial space, followed by the movement of SMCs from the media into the intima within 36 hours of applying electrical current. Treatment of the rabbits with monoclonal antibody (mAb) HP1/2 directed toward the α 4 subunit (CD49d) of VLA-4 inhibited mononuclear leukocyte invasion (consisting of monocytes and lymphocytes) by ≈70% compared with the IgG-treated control rabbits and completely abolished the minimal influx of basophils and eosinophils after 36 hours. Neutrophil infiltration, however, remained unaffected by anti–VLA-α 4 treatment. Under these conditions, SMC migration across the internal elastic lamina was reduced by 50%. The use of mAb HP1/2 together with mAb 60.3 (directed to the β 2 chain of CD11/CD18) completely abolished the influx of monocytes, lymphocytes, and all types of granulocytes into the arterial intima. This complete blockade of leukocyte infiltration resulted in a 70% reduction of intimal SMC accumulation. Together with our previous findings excluding neutrophils as stimulators of SMC migration, the present results indicate that mononuclear leukocytes promote lesion development by stimulating SMC migration.

Monoclonal Antibody Against Vascular Cell Adhesion Molecule-1 Inhibits Neointimal Formation After Periadventitial Carotid Artery Injury in Genetically Hypercholesterolemic Mice

“…25 In a cuff model with electrical stimulusinduced injury, mononuclear cell but not polymorphonuclear influx was shown to influence intimal thickening. 10 Although the present study was not designed to determine specific cell infiltrates, on the basis of previous results outlined above, 10,24 it is reasonable to speculate that polymorphonuclear influx does not significantly affect intimal thickening in the cuffinjury model. In the present report, the reduction of neointimal formation with antibody treatment was associated with reduced inflammatory infiltrates, suggesting further that monocyte/macrophage accumulation plays a role in promoting neointimal formation in injured arteries of apoE KO mice.…”

“…20 Reports correlating inflammatory infiltrates with neointimal thickening have substantially strengthened the notion that inflammation plays a significant role in the arterial response to injury. 9,10 Adhesion molecules, such as intercellular adhesion molecule (ICAM)-1 and VCAM-1, expressed by endothelial and smooth muscle cells, mediate inflammatory cell recruitment to sites of injury. 1,6 Arterial injury has been shown to increase ICAM-1 expression in rats.…”

“…Immune-mediated inflammation has also been implicated in this response, characterized by the influx of leukocytes, activation of SMCs, and neointimal formation. 9,10 We used the arterial wall injury model in the genetically mutated…”

Increased Expression of Adhesion Molecules in Uremic Atherosclerosis in Apolipoprotein-E–Deficient Mice

“…This is mainly due to selectin ligation, whereas the subsequent firm adhesion depends on interactions between Ig-like molecules (ICAM-1, VCAM-1) on the endothelium and integrins on the leukocyte surface. Knockout mice that lack E-selectin, ICAM-1, or VCAM-1 and mice treated with antibodies against adhesion molecules display reduced atherosclerosis (12)(13)(14)(25)(26)(27).…”

Effect of Cyclosporine on Arterial Balloon Injury Lesions in Cholesterol-Clamped Rabbits

“…In this latter model, an inflammatory reaction with mononuclear leukocytes eventually leads to smooth muscle cell migration and proliferation. 49,50 Although the lesions formed after balloon injury and transplantation have several common features, it is quite possible that the mechanism at work differs in the 2 situations. This is illustrated clearly in the present study by the inhibitory effect of cyclosporine on neointimal proliferation in the transplanted aorta, but not in the balloon-injured aorta.…”