Atorvastatin Inhibits Myocardin Expression in Vascular Smooth Muscle Cells

Abstract

Abstract-Atorvastatin (ATV), an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, is widely prescribed as a lipid-lowering drug. It also inhibits the RhoA-Rho-associated kinase pathway in vascular smooth muscle (SM) cells and critically inhibits SM function. Myocardin is a coactivator of serum response factor, which upregulates SM contractile proteins. The RhoA-Rho-associated kinase pathway, which directly triggers SM contraction, also increases myocardin gene expression. Therefore, we investigated whether ATV inhibits myocardin gene expression in SM cells. In mice injected with ATV (IP 20 g/g per day) for 5 days, myocardin gene expression was significantly downregulated in aortic and carotid arterial tissues with decreased expression of myocardin target genes SM ␣-actin and SM22. Correspondingly, the contractility of aortic rings in mice treated with ATV or the Rho-associated kinase inhibitor Y-27632 was reduced in response to treatment with either KCl or phenylephrine. In cultured mouse and human aortic SM cells, KCl treatment stimulated the expression of myocardin, SM ␣-actin, and SM22. These stimulatory effects were prevented by ATV treatment. ATV-induced inhibition of myocardin expression was prevented by pretreatment with either mevalonate or geranylgeranylpyrophosphate but not farnesylpyrophosphate. Treatment with Y-27632 mimicked ATV effects on the gene expression of myocardin, SM ␣-actin, and SM22, further suggesting a role for the RhoA-Rho-associated kinase pathway in ATV effects. Furthermore, ATV treatment inhibited RhoA membrane translocation and activation; these effects were prevented by pretreatment with mevalonate. We conclude that ATV inhibits myocardin gene expression in vivo and in vitro, suggesting a novel mechanism for ATV inhibition of vascular contraction. Statins inhibit production of isoprenoid intermediates in the cholesterol biosynthetic pathway, such as farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), to reduce posttranslational modifications of several intracellular signaling proteins, including nuclear lamins, Ras, Rho, Rac, and Rap. 1-3 The Ras and Rho GTPase family members are the major substrates for posttranslational modification by prenylation. 4 These small GTP-binding proteins cycle between the inactive GDP-bound state and active GTP-bound state and play critical roles in the regulation of the actin cytoskeleton and intracellular signaling pathways. It has been shown that statins regulate subcellular location 1 and activation of Ras and Rho. 5 The inhibitory effect of statins on prenylation of these small G proteins, for example, RhoA, and, therefore, the RhoA-Rho-associated kinase (ROCK) pathway, is known to contribute to protection of the cardiovascular system beyond their cholesterol-lowering effects. 6 It is well known that the ROCK pathway stimulates contraction through inhibition of myosin light-chain phosphatase or phosphorylation of myosin light chain 20. 7,8 Statins attenuate spontaneous smooth muscle (SM) tone through inhibition of the...

Rho/Rho-Associated Coiled-Coil Forming Kinase Pathway as Therapeutic Targets for Statins in Atherosclerosis

“…This effect was again mimicked by inhibition of Rho or ROCK (135). Atorvastatin prevented KCl-induced upregulation of myocardin and its downstream targets SM)actin and SM22, the contractile proteins in VSMCs (92). Again this effect was reversed by mevalonate or GGPP, but not FPP, and mimicked by the ROCK inhibitor Y-27632.…”

Suppression of the Rho/Rho-Kinase Pathway and Prevention of Cerebral Vasospasm by Combination Treatment with Statin and Fasudil After Subarachnoid Hemorrhage in Rabbit

“…GGPP geranylgeranylates Rho-GDP, which is activated by Rho-GEF. Therefore, decreased GGPP induces the inhibition of RhoA [12, 13]. …”

The cellular origin of laminin determines its role in blood pressure regulation

“…Since SMA and SM22α contribute to the contractile property of SMCs [11,25,26], we examined their expression levels in our laminin-deficient mice. Both SMA and SM22α were expressed in Ctr aorta (Fig.…”