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Adrenomedullin as a Novel Antimigration Factor of Vascular Smooth Muscle Cells

The present study investigated the effect of adrenomedullin, a novel vasorelaxant peptide, on the migration of cultured rat vascular smooth muscle cells (SMCs) by using the Boyden-chamber method. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)–BB strongly stimulated SMC migration. Adrenomedullin clearly inhibited SMC migration stimulated with 5% and 10% FCS in a concentration-dependent manner. The migration induced by 10 and 25 ng/mL PDGF-BB was also inhibited by adrenomedullin in a concentration-dependent manner. Inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration was paralleled by an increase in the cellular level of cAMP. In fact, the percent increase in cAMP level was strongly correlated with the percent decrease in migration activity of SMCs after treatment with adrenomedullin. 8-Bromo cAMP, a cAMP analogue, reproduced the inhibition by adrenomedullin of FCS- and PDGF-induced SMC migration. An activator of adenylate cyclase, forskolin, also reduced FCS- and PDGF-induced SMC migration. These data indicate that adrenomedullin inhibits the migration of SMCs stimulated with FCS and PDGF, probably through a cAMP-dependent process. On the basis of these results and the finding that adrenomedullin is synthesized in and secreted from vascular endothelial cells, adrenomedullin may play a role as a local antimigration factor in some pathophysiological states.

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Antioxidants Improve Impaired Insulin-Mediated Glucose Uptake and Prevent Migration and Proliferation of Cultured Rabbit Coronary Smooth Muscle Cells Induced by High Glucose

Background—To explore the role of intracellular oxidative stress in high glucose–induced atherogenesis, we examined the effect of probucol and/or α-tocopherol on the migration and growth characteristics of cultured rabbit coronary vascular smooth muscle cells (VSMCs).

Methods and Results—Chronic high-glucose-medium (22.2 mmol/L) treatment increased platelet-derived growth factor (PDGF)-BB–mediated VSMC migration, [3H]thymidine incorporation, and cell number compared with VSMCs treated with normal-glucose medium (5.6 mmol/L+16.6 mmol/L mannose). Probucol and α-tocopherol significantly suppressed high glucose–induced increase in VSMC migration, cell number, and [3H]thymidine incorporation. Probucol and α-tocopherol suppressed high glucose–induced elevation of the cytosolic ratio of NADH/NAD+, phospholipase D, and membrane-bound protein kinase C activation. Probucol, α-tocopherol, and calphostin C improved the high glucose–induced suppression of insulin-mediated [3H]deoxyglucose uptake. Chronic high-glucose treatment increased the oxidative stress, which was significantly suppressed by probucol, α-tocopherol, suramin, and calphostin C.

Conclusions—These findings suggest that probucol and α-tocopherol may suppress high glucose–induced VSMC migration and proliferation via suppression of increases in the cytosolic ratio of free NADH/NAD+, phospholipase D, and protein kinase C activation induced by high glucose, which result in reduction in intracellular oxidative stress.