Compound C inhibits vascular smooth muscle cell proliferation and migration in an AMP-activated protein kinase-independent fashion

6-[4-(2-Piperidin-1-yl-ethoxy)-phenyl]-3-pyridin-4-yl-pyrazolo[ 1,5-a] pyrimidine (compound C) is a cell-permeable pyrrazolopyrimidine derivative that acts as a potent inhibitor of AMPactivated protein kinase (AMPK). Although compound C is often used to determine the role of AMPK in various physiological processes, it also evokes AMPK-independent actions. In the present study, we investigated whether compound C influences vascular smooth muscle cell (SMC) function through the AMPK pathway. Treatment of rat aortic SMCs with compound C (0.02-10 μM) inhibited vascular SMC proliferation and migration in a concentration-dependent fashion. These actions of compound C were not mimicked or affected by silencing AMPKα expression or infecting SMCs with an adenovirus expressing a dominant-negative mutant of AMPK. In contrast, the pharmacological activator of AMPK 5-aminoimidazole-4-carboxamide-1-β-D- ribofuranoside inhibited the proliferation and migration of SMCs in a manner that was strictly dependent on AMPK activity. Flow cytometry experiments revealed that compound C arrested SMCs in the G₀/G₁ phase of the cell cycle, and this was associated with a decrease in cyclin D1 and cyclin A protein expression and retinoblastoma protein phosphorylation and an increase in p21 protein expression. Finally, local perivascular delivery of compound C immediately after balloon injury of rat carotid arteries markedly attenuated neointima formation. These studies identify compound C as a novel AMPK-independent regulator of vascular SMC function that exerts inhibitory effects on SMC proliferation and migration and neointima formation after arterial injury. Compound C represents a potentially new therapeutic agent in treating and preventing occlusive vascular disease.