Short-term pravastatin mediates growth inhibition and apoptosis, independently of Ras, via the signaling proteins p27Kip1 and P13 kinase.
Growth factor-stimulated DNA synthesis in a variety of cell lines has been shown to be decreased after overnight (or longer) treatment with the 3-hydroxy-3-methylglutaryl CoA reductase inhibitors, the statins. Although this anti-mitogenic effect had been presumed to be the result of the impairment of Ras lipidation, a stable modification (T1/2 approximately 20 h), this study provides new data demonstrating that brief (approximately 1 h) pretreatment of rat vascular smooth muscle cells with 100 microM pravastatin before platelet-derived growth factor-BB (PDGF-BB) stimulation results in attenuation of DNA synthesis through a Ras-independent mechanism. PDGF-BB-stimulated PDGF-beta receptor tyrosine phosphorylation, Ras activity, and mitogen-activated protein/extracellular signal-regulated kinase activity are unaffected by from 10 min to 1 h of pravastatin incubation, while Raf activity is markedly increased after 1 h of pravastatin. Phosphatidylinositol-3 kinase activity and phosphorylation of its downstream effector Akt are decreased after 1 h pravastatin incubation. Rho is stabilized by pravastatin, and ADP-ribosylation of Rho by C3 exoenzyme decreases PDGF-stimulated phosphatidylinositol-3 kinase activity, mimicking the effect of pravastatin on this signaling protein. Levels of the cyclin-dependent kinase inhibitor p27Kip1 are increased when cells were preincubated with pravastatin for 1 h and then exposed to PDGF, and apoptosis is induced by pravastatin incubation times as short as 1 to 4 h. Thus, short-term, high-dose pravastatin inhibits vascular smooth muscle cell growth and induces apoptosis independently of Ras, likely by means of the drug's effect on p27Kip1, mediated by Rho and/or phosphatidylinositol-3 kinase. This work demonstrates for the first time that the statins may be therapeutically useful when applied for short periods of time such that potential toxicity of long-term statin use (such as chronic Ras inhibition) may be avoided, suggesting future therapeutic directions for statin research.
Weiss
R H
RH
Department of Internal Medicine, University of California, Davis 95616, USA. rhweiss@ucdavis.edu
Ramirez
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Joo
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D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D000077214:Becaplermin; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017035:Pravastatin / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D025521:Tumor Suppressor Proteins; D018631:ras Proteins / Q000378:metabolism
C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008869:Microtubule-Associated Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000077214:Becaplermin; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D018631:ras Proteins; D017035:Pravastatin