Migration and proliferation of vascular smooth muscle cells (VSMCs) are two events involved in atherosclerosis, restenosis after balloon angioplasty, and stenosis of grafted vessels. Platelet-derived growth factor (PDGF) found in stenotic vessels is known to induce migration of VSMCs. VSMCs express both α- and β-adrenergic receptors on their surface, and blood vessels are innervated by the adrenergic nervous system and exposed to circulating epinephrine. We examined the role of these receptors on PDGF-induced migration of VSMCs. VSMCs were cultured from saphenous vein segments. Migration was stimulated by PDGF. Effect of pretreatment of VSMCs with the β-agonist isoproterenol, the α-agonist phenylephrine, or forskolin on PDGF-induced migration was examined with a modified Boyden chamber. Cell migration was quantitated by spectrophotometry. Intracellular cyclic AMP was determined by radioimmunoassay. PDGF significantly induced VSMC migration. Isoproterenol (0.1 and 1.0 μM) inhibited PDGF-induced migration by 30 per cent and 50 per cent, respectively. Forskolin (10 μM) completely blocked PDGF-induced migration. The migration inhibition by isoproterenol or forskolin was associated with a significant elevation of intracellular cyclic AMP. In contrast, phenylephrine had no effect on PDGF-induced migration or on cyclic AMP. Activation of β-adrenergic receptors and the consequent rise in intracellular cyclic AMP inhibits migration of VSMCs induced by PDGF. These results are consistent with the notion that adrenergic agonists with substantial β-receptor affinity, such as isoproterenol, can inhibit smooth muscle cell migration.
Intimal injury in vivo activates vascular smooth muscle cell migration and explant outgrowth in vitro.
