Compound C inhibits vascular smooth muscle cell proliferation in an AMPK‐independent manner

Compound C (6‐[4‐(2‐piperidin‐1‐yl‐ethoxy)‐phenyl]‐3‐pyridin‐4‐yl‐pyrazolo[1,5‐a]‐pyrimidine) is a cell‐permeable inhibitor of adenosine monophosphate‐activated protein kinase (AMPK) that has been reported to block the growth of various cell lines. In the present study, we investigated whether compound C regulates the proliferation of cultured rat aortic smooth muscle cells (SMCs). Treatment of SMCs with serum stimulated a time‐dependent increase in cell proliferation that was blocked by compound C (0.02–10μM) in a concentration‐dependent fashion, independent of any change in cell viability. The anti‐proliferative action of compound C was not mimicked or affected by the knockdown of AMPK. Moreover, pharmacological activation of AMPK with 5‐aminoimidazole‐4‐carboxamide‐1‐beta‐D‐ribofuranoside (AICAR) also inhibited the proliferation of SMCs. Flow cytometry experiments indicated that compound C arrested SMCs in the G0/G1 phase of the cell cycle. This was associated with a decrease in cyclin D1 and cyclin A protein expression, a decrease in retinoblastoma protein phosphorylation, and an increase in p21 protein expression. In conclusion, this study identifies compound C as novel AMPK‐independent inhibitor of vascular SMC proliferation that may have therapeutic potential in treating occlusive vascular disease. Supported by NIH grants HL59976 and HL74966.