Action of an HMG CoA Reductase Inhibitor, Lovastatin, on Apoptosis of Untransformed and ts-SV40 Transformed Human Smooth Muscle Cells Derived from Saphenous Vein

The effect of lovastatin, an inhibitor of 3-hydroxymethyl-3-glutaryl coenzyme A (HMG CoA) reductase, was examined on human vascular smooth muscle cells (HVSMC). Untransformed HVSMC were obtained from saphenous vein and in addition an SV-40 transformed immortalized cell line (HVTs-SM1) derived from saphenous vein smooth muscle was also used. HVTs-SM1 cell proliferation and DNA synthesis were measured, and cell cycle analysis was performed by flow cytometry. Apoptosis in both cell types was assessed by a combination of flow cytometry, terminal deoxynucleotidyl transferase (TUNEL) reagent-based immunocytochemistry, DAPI staining, and DNA agarose gel electrophoresis. Lovastatin had no effect on apoptosis of HVSMC over 96 h in serum-free conditions or after stimulation with platelet-derived growth factor (PDGF-BB), although PDGF-BB increased apoptosis in HVSMC, and this was prevented by lovastatin. In HVTs-SM1 cells lovastatin inhibited cell proliferation and DNA synthesis and induced apoptosis in a time- and concentration-dependent manner. The effects of lovastatin on cell proliferation, DNA synthesis, and apoptosis were prevented by coincubation with mevalonate and geranylgeranyl pyrophosphate, but not by farnesyl pyrophosphate. Lovastatin does not induce apoptosis in saphenous vein HVSMC in culture and inhibits PDGF-BB-induced DNA synthesis and apoptosis. In contrast, in SV40 transformed immortalized HVTs-SM1 cells, lovastatin induces apoptosis and inhibits cell proliferation and DNA synthesis. The pro-apoptotic effects of lovastatin in SV40 transformed HVTs-SM1 cells may be related to the enhanced rate of proliferation or deregulation of the cell cycle in this cell line.