Roxithromycin is an inhibitor of human coronary artery smooth muscle cells proliferation: a potential ability to prevent coronary heart disease.

Roxithromycin (RXM), a macrolide antibiotic, is used in clinical trials to address secondary prevention of coronary heart disease. However, the effects of RXM on human coronary artery smooth muscle cells (CASMC) proliferation remain unclear. Human CASMC were stimulated with growth medium containing 5% fetal bovine serum and growth factors. RXM at 1 or 10 microg/ml, which are relevant to the therapeutic plasma levels, significantly suppressed mitogen-induced CASMC proliferation, assessed by WST-1 assay and cell counting. Flow cytometry analysis demonstrated that RXM suppressed mitogen-induced G1 to S progression on cell cycle. Western blot showed that RXM inhibited phosphorylation of retinoblastoma gene products, reduced protein levels of cyclin D1 and A, and restored downregulation of cyclin-dependent kinase (CDK) inhibitor p27kip1. The activities of CDK4 and CDK2 were suppressed by RXM without affecting their protein levels. When transfected with both IkappaB kinase alpha and beta constructs as nuclear factor-kappa B (NF-kappaB) activator, CASMC entered S phase at 24 h, and RXM inhibited it. Electrophoretic mobility shift assay and immunostaining of NF-kappaB p65 demonstrated that RXM inhibited mitogen-induced NF-kappaB activation. These results indicate that RXM is an inhibitor of human CASMC proliferation through modulating cell cycle regulatory proteins and inhibiting NF-kappaB signaling pathway.