ABSTRACT
The peroxisome proliferator-activated receptor-γ (PPARγ) is an important regulator of lipid and glucose metabolism, and its activation is reported to suppress the progression of atherosclerosis. We have reported that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) activate PPARγ in macrophages. However, it is not yet known whether statins activate PPARγ in other vascular cells. In the present study, we investigated whether statins activate PPARγ in smooth muscle cells (SMCs) and endothelial cells (ECs) and thus mediate anti-atherosclerotic effects. Human aortic SMCs (HASMCs) and human umbilical vein ECs (HUVECs) were used in this study. Fluvastatin and pitavastatin activated PPARγ in HASMCs, but not in HUVECs. Statins induced cyclooxygenase-2 (COX-2) expression in HASMCs, but not in HUVECs. Moreover, treatment with COX-2-siRNA abrogated statin-mediated PPARγ activation in HASMCs. Statins suppressed migration and proliferation of HASMCs, and inhibited lipopolysaccharide-induced expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) in HASMCs. These effects of statins were abrogated by treatment with PPARγ-siRNA. Treatment with statins suppressed atherosclerotic lesion formation in Apoe(-/-) mice. In addition, transcriptional activity of PPARγ and CD36 expression were increased, and the expression of MCP-1 and TNF-α was decreased, in the aorta of statin-treated Apoe(-/-) mice. In conclusion, statins mediate anti-atherogenic effects through PPARγ activation in SMCs. These effects of statins on SMCs may be beneficial for the prevention of atherosclerosis.
Subject(s)
Atherosclerosis/drug therapy , Atherosclerosis/metabolism , Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use , PPAR gamma/metabolism , Animals , Aorta/pathology , Apolipoproteins E/deficiency , Apolipoproteins E/metabolism , Atherosclerosis/enzymology , Atherosclerosis/pathology , Cell Movement/drug effects , Cell Proliferation/drug effects , Chemokine CCL2/metabolism , Cyclooxygenase 2/metabolism , Disease Progression , Fatty Acids, Monounsaturated/pharmacology , Fluvastatin , Human Umbilical Vein Endothelial Cells/drug effects , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Indoles/pharmacology , Lipopolysaccharides , Mice, Inbred C57BL , Myocytes, Smooth Muscle/drug effects , Myocytes, Smooth Muscle/metabolism , Myocytes, Smooth Muscle/pathology , NF-kappa B/metabolism , Tumor Necrosis Factor-alpha/metabolismABSTRACT
OBJECTIVE: Nifedipine, an L-type calcium channel blocker, protects against the progression of atherosclerosis. We investigated the molecular basis of the antiatherosclerotic effect of nifedipine in macrophages and apolipoprotein E-deficient mice. METHODS AND RESULTS: In macrophages, nifedipine increased peroxisome proliferator-activated receptor-gamma (PPARgamma) activity without increasing PPARgamma-binding activity. Amlodipine, another L-type calcium channel blocker, and 1,2-bis-(o-aminophenoxy)-ethane-N,N,-N',N'-tetraacetic acid tetraacetoxy-methyl ester (BAPTA-AM), a calcium chelator, decreased PPARgamma activity, suggesting that nifedipine does not activate PPARgamma via calcium channel blocker activity. Inactivation of extracellular signal-regulated kinase 1/2 suppressed PPARgamma2-Ser112 phosphorylation and induced PPARgamma activation. Nifedipine suppressed extracellular signal-regulated kinase 1/2 activation and PPARgamma2-Ser112 phosphorylation, and mutating PPARgamma2-Ser112 to Ala abrogated nifedipine-mediated PPARgamma activation. These results suggested that nifedipine inhibited extracellular signal-regulated kinase 1/2 activity and PPARgamma2-Ser112 phosphorylation, leading to PPARgamma activation. Nifedipine inhibited lipopolysaccharide-induced monocyte chemoattractant protein-1 expression and induced ATP-binding cassette transporter A1 mRNA expression, and these effects were abrogated by small interfering RNA for PPARgamma. Furthermore, in apolipoprotein E-deficient mice, nifedipine treatment decreased atherosclerotic lesion size, phosphorylation of PPARgamma2-Ser112 and extracellular signal-regulated kinase 1/2, and monocyte chemoattractant protein-1 mRNA expression and increased ATP-binding cassette transporter A1 expression in the aorta. CONCLUSIONS: Nifedipine unlike amlodipine inhibits PPARgamma-Ser phosphorylation and activates PPARgamma to suppress monocyte chemoattractant protein-1 expression and induce ATP-binding cassette transporter A1 expression in macrophages. These effects may induce antiatherogenic effects in hypertensive patients.
