Statin-induced inhibition of the Rho-signaling pathway activates PPARα and induces HDL apoA-I
Geneviève Martin, Hélène Duez, Christophe Blanquart, Vincent Berezowski, Philippe Poulain, Jean-Charles Fruchart, Jamila Najib-Fruchart, Corine Glineur, Bart Staels
Geneviève Martin, Hélène Duez, Christophe Blanquart, Vincent Berezowski, Philippe Poulain, Jean-Charles Fruchart, Jamila Najib-Fruchart, Corine Glineur, Bart Staels
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Statin-induced inhibition of the Rho-signaling pathway activates PPARα and induces HDL apoA-I

Abstract

Statins are inhibitors of the rate-limiting enzyme in cholesterol synthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. In addition to reducing LDL cholesterol, statin treatment increases the levels of the antiatherogenic HDL and its major apolipoprotein apoA-I. Here, we investigated the molecular mechanisms of apoA-I regulation by statins. Treatment with statins increased apoA-I mRNA levels in human HepG2 hepatoma cells, and this effect was reversed by the addition of mevalonate, implicating HMG-CoA reductase as the relevant target of these drugs. Pretreatment with Actinomycin D abolished the increase of apoA-I mRNA, indicating that statins act at the transcriptional level. Indeed, statins increased the human apoA-I promoter activity in transfected cells, and we have identified a statin response element that coincides with a PPARα response element known to confer fibrate responsiveness to this gene. The statin effect could be abolished not only by mevalonate, but also by geranylgeranyl pyrophosphate, whereas inhibition of geranylgeranyl transferase activity or treatment with an inhibitor of the Rho GTP-binding protein family increased PPARα activity. Using dominant negative forms of these proteins, we found that Rho A itself mediates this response. Because cotreatment with statins and fibrates activated PPARα in a synergistic manner, these observations provide a molecular basis for combination treatment with statins and fibrates in coronary heart disease.

Authors

Geneviève Martin, Hélène Duez, Christophe Blanquart, Vincent Berezowski, Philippe Poulain, Jean-Charles Fruchart, Jamila Najib-Fruchart, Corine Glineur, Bart Staels

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Statins induce apoA-I gene expression at the transcriptional level in He...
Statins induce apoA-I gene expression at the transcriptional level in HepG2 cells by inhibition of HMG-CoA reductase. (a) Statins induce apoA-I mRNA in HepG2 cells in a dose-dependent manner. HepG2 cells were treated for 24 hours with the indicated doses of cerivastatin or pitavastatin or appropriate solvent in serum-free medium. RNA levels were quantified as described in Methods and expressed (means ± SD, n = 3/point) relative to the untreated control set at 1. Values without a common superscript are significantly different, P < 0.05. R.A.U., relative arbitrary units. (b) Statins induce apoA-I mRNA in HepG2 cells in a time-dependent manner. HepG2 cells were treated for 3, 6, 12, or 24 hours with 5 μM of cerivastatin, or pitavastatin, or appropriate solvent in serum-free medium. RNA levels were quantified as described in Methods and expressed relative to the untreated controls at each time point set at 1. (c) Mevalonate reverses the induction of apoA-I mRNA by statins. HepG2 cells were treated for 24 hours with cerivastatin (5 μM) and/or mevalonate (Mev.; 3 mM) or appropriate solvent in serum-free medium. (d) Statins regulate apoA-I gene expression in HepG2 cells at the transcriptional level. HepG2 cells were treated for 24 hours with cerivastatin (5 μM) or appropriate solvent in serum-free medium. Actinomycin D (Act. D; 5 μg/ml) was added to the medium 90 minutes before treatment. For all, total RNA (10 μg) was subjected to Northern blot analysis using human apoA-I and 36B4 cDNA probes.