3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors upregulate inducible NO synthase expression and activity in vascular smooth muscle cells.
Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase ameliorate atherosclerosis by both cholesterol-dependent and cholesterol-independent mechanisms. We examined whether HMG-CoA reductase inhibitors affect the expression and activity of inducible NO synthase (iNOS) in cultured rat aortic vascular smooth muscle (VSM) cells. Atorvastatin (34 to 68 micromol/L) markedly increased nitrite production, an increase that was essentially abrogated by the NO synthase inhibitor N(G)-monomethyl-L-arginine (500 micromol/L). Activity of iNOS, determined by the conversion of L-arginine to L-citrulline, increased 9-fold after atorvastatin treatment. Western blot and semiquantitative reverse transcriptase-polymerase chain reaction revealed that atorvastatin (34 to 68 micromol/L) strongly upregulated iNOS protein and mRNA levels, respectively. These concentrations of atorvastatin did not cause cytotoxicity, as judged by the cell survival rate. Similarly, simvastatin and lovastatin (34 micromol/L) caused robust upregulation of the iNOS protein level. Transfection experiments demonstrated that the -1034- to 88-bp human iNOS promoter was strongly induced by atorvastatin (34 micromol/L). Electromobility and supershift assays using a nuclear factor-kappaB (NF-kappaB) consensus oligonucleotide and nuclear extracts from VSM cells as well as transfection studies using an NF-kappaB reporter plasmid suggested that the transcriptional activation of the iNOS gene by atorvastatin is not mediated via the NF-kappaB pathway. We conclude that HMG-CoA reductase inhibitors potently upregulate iNOS expression and activity in VSM cells, at least in part, by transcriptional mechanisms that do not depend on transcription factor NF-kappaB. These effects might have important implications for the impact of HMG-CoA reductase inhibitors on atherosclerosis.
Kolyada
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AY
Department of Medicine, Tufts University School of Medicine, Division of Nephrology and the Tupper Research Institute, New England Medical Center, Boston, Massachusetts, USA.
Fedtsov
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A
Madias
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NE
D000818:Animals; D000069059:Atorvastatin; D002478:Cells, Cultured; D006538:Heptanoic Acids / Q000494:pharmacology*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011401:Promoter Regions, Genetic; D011758:Pyrroles / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015533:Transcriptional Activation; D015854:Up-Regulation
D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D016328:NF-kappa B; D011758:Pyrroles; D012333:RNA, Messenger; D000069059:Atorvastatin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat