Abstract 524: Anti-Proliferative and Pro-Apoptotic Effects of Statins in Human Pulmonary Artery Smooth Muscle Cells
Background: Pulmonary arterial hypertension (PAH) is a progressive disease, involving aberrant regulation of proliferation and apoptosis in pulmonary artery smooth muscle cells (PASMCs). HMG-CoA reductase inhibitors (statins) have broad biological (pleiotropic) effects and simva-statin rescues rats with established pulmonary hypertension. We therefore sought to establish whether statins regulate human PASMC proliferation and apoptosis.
Methods: Distal PASMCs were derived from surgical samples of human lung (n = 11). Anti-proliferative effects of simvastatin, atorvastatin, mevastatin and pravastatin were determined by measuring [3H-methyl]-thymidine uptake, cell proliferation and matrix metalloproteinase-9 (MMP-9) production. Apoptosis and transforming growth factor-β1 (TGF-β1)-stimulated endothelin-1 (ET-1) production were assessed by measuring cytoplasmic histone associated DNA fragments, propidium iodide (PI) labelling and ET-1 in conditioned medium. Intracellular signalling was explored using mevalonate (MVA), geranylgeranylpyrophosphate (GGPP), farnesylpyrophos-phate (FPP) and inhibitors of geranylgeranyl transferase (GGTI-2133) and farnesyl transferase (FTI-277).
Results: Lipophilic but not lipophobic statins attenuated DNA synthesis and cell proliferation in a concentration-dependent manner (0.01 to 10 μM). Lipophilic statins also induced apoptosis, measured by increased DNA fragmentation and sub-diploid population of PI-labelled cells, and the pan-caspase inhibitor z-VAD-fmk was protective. Lipophilic statins inhibited both ET-1 release and MMP-9 production. MVA (100 μM) and GGPP (10 μM), but not FPP, reversed these effects, which were mimicked by GGTI-2133 (10 μM, P<0.05), indicating signalling via geranylgeranylated proteins. The Rho kinase inhibitor Y27632 (10 μM) also attenuated ET-1 release (60±10 % inhibition, n=6, P<0.001) and promoted DNA fragmentation, consistent with involvement of the mevalonate pathway.
Conclusions: Statins have anti-proliferative and pro-apoptotic effects in human PASMCs that are dependent, at least in part, on mevalonate and isoprenylation. If replicated in vivo, these effects support a role for lipophilic statins in the management of PAH.