Activation of RhoA and Inhibition of Myosin Phosphatase as Important Components in Hypertension in Vascular Smooth Muscle

Seko, Tetsuya; M, Ito; Kureishi, Yasuko; Okamoto, Ryuji; Moriki, Nobuyuki; Onishi, Katsuya; Isaka, Naoki; Hartshorne, David J.; Nakano, Takeshi

doi:10.1161/01.res.0000059987.90200.44

Cited by 301 publications

(289 citation statements)

References 51 publications

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“…33 In addition, ATV treatment reduced the levels of activated RhoA in rat aorta in experimental models of hypertension induced by angiotensin II infusion. 33,34 Finally, a previous report showing that expression of SM-specific genes downstream of the RhoA-ROCK cascade, such as myocardin, desmin, SM ␣-actin, and SM22, was inhibited by ATV treatment in human fetal penile SMCs 16 provides further support to our conclusions.…”

Section: Discussionsupporting

confidence: 83%

Atorvastatin Inhibits Myocardin Expression in Vascular Smooth Muscle Cells

Jiang²,

Yin³

et al. 2012

Hypertension

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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...

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Section: Discussionsupporting

confidence: 83%

Atorvastatin Inhibits Myocardin Expression in Vascular Smooth Muscle Cells

Jiang²,

Yin³

et al. 2012

Hypertension

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“…A decrease in MLC phosphatase activity increases phosphorylation of myosin and therefore contributes to smooth muscle contraction at low levels of intracellular Ca 2ϩ concentration. Strong evidence suggests that increased Rho/Rho kinase-dependent Ca 2ϩ sensitization contributes to hypertension and inhibition of Rho or Rho kinase reduces blood pressure (33,42). Some heterotrimetric G protein-coupled receptor (GPCR) agonists, including angiotensin II (ANG II) and endothelin (ET)-1, induce smooth muscle contraction through both intracellular Ca 2ϩ -dependent and Rho/Rho kinase-mediated Ca 2ϩ -independent signaling pathways (24,26).…”

mentioning

confidence: 99%

Activation of Rho/Rho kinase signaling pathway by reactive oxygen species in rat aorta

Jin

Zhao

Webb

2004

American Journal of Physiology-Heart and Circulatory Physiology

224

186

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. Activation of Rho/Rho kinase signaling pathway by reactive oxygen species in rat aorta. Am J Physiol Heart Circ Physiol 287: H1495-H1500; 2004; 10.1152/ajpheart.01006.2003.-Evidence indicates that both the Rho/ Rho kinase signaling pathway and reactive oxygen species (ROS) such as superoxide and H 2O2 are involved in the pathogenesis of hypertension. This study aimed to determine whether ROS-induced vascular contraction is mediated through activation of Rho/Rho kinase. Rat aortic rings (endothelium denuded) were isolated and placed in organ chambers for measurement of isometric force development. ROS were generated by a xanthine (X)-xanthine oxidase (XO) mixture. The antioxidants tempol (3 mM) and catalase (1,200 U/ml) or the XO inhibitor allopurinol (400 M) significantly reduced X/XOinduced contraction. A Rho kinase inhibitor, (ϩ)-(R)-trans-4-(1-aminoethyl-N-4-pyridil)cyclohexanecarboxamide dihydrochloride (Y-27632), decreased the contraction in a concentration-dependent manner; however, the Ca 2ϩ -independent protein kinase C inhibitor rottlerin did not have an effect on X/XO-induced contraction. Phosphorylation of the myosin light chain phosphatase target subunit (MYPT1) was increased by ROS, and preincubation with Y-27632 blocked this increased phosphorylation. Western blotting for cytosolic and membrane-bound fractions of Rho showed that Rho was increased in the membrane fraction by ROS, suggesting activation of Rho. These observations demonstrate that ROS-induced Ca 2ϩ sensitization is through activation of Rho and a subsequent increase in Rho kinase activity but not Ca 2ϩ -independent PKC. myosin light chain phosphatase; smooth muscle contraction; antioxidants CONTRACTION OF SMOOTH MUSCLE is regulated by both Ca 2ϩ -dependent and Ca 2ϩ -independent (Ca 2ϩ sensitization) mechanisms. A rise in intracellular Ca 2ϩ levels leads to myosin light chain (MLC) kinase activation, resulting in an increase in MLC phosphorylation. Importantly, MLC phosphorylation can also be increased through inhibition of MLC phosphatase, which augments smooth muscle force generation without a change in intracellular Ca 2ϩ (38).In recent years, studies have revealed that the small GTPase Rho and its downstream target Rho kinase mediate the Ca 2ϩ sensitization of smooth muscle contraction (37). The exchange of bound GDP for GTP activates Rho and stimulates its translocation from cytosol to membrane. Rho-GTP phosphorylates Rho kinase, which inhibits MLC phosphatase activity by phosphorylation of the MLC phosphatase target subunit (MYPT1). A decrease in MLC phosphatase activity increases phosphorylation of myosin and therefore contributes to smooth muscle contraction at low levels of intracellular Ca 2ϩ concentration. Strong evidence suggests that increased Rho/Rho kinase-dependent Ca 2ϩ sensitization contributes to hypertension and inhibition of Rho or Rho kinase reduces blood pressure (33, 42). Some heterotrimetric G protein-coupled receptor (GPCR) agonists, including angiotensin II (ANG II) and endothelin (ET)-1, induce smooth mus...

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“…We speculate that Rho-kinase inhibitors may provide greater CBF benefit in acute stroke in the presence of pathologic activation of vascular Rho/Rho-kinase, such as in hyperlipidemia, diabetes, hypertension, and hyperhomocysteinemia Seko et al, 2003;Shah and Singh 2006;Zhu et al, 2003). Therefore, Rho-kinase inhibition may present a novel therapeutic opportunity during acute stroke.…”

Section: Discussionmentioning

confidence: 98%

Rho-Kinase Inhibition Acutely Augments Blood Flow in Focal Cerebral Ischemia via Endothelial Mechanisms

Shin

Salomone

Potts

et al. 2006

J Cereb Blood Flow Metab

106

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Rho-kinase is a serine threonine kinase that increases vasomotor tone via its effects on both endothelium and smooth muscle. Rho-kinase inhibition reduces cerebral infarct size in wild type, but not endothelial nitric oxide synthase deficient (eNOS À/À ) mice. The mechanism may be related to Rho-kinase activation under hypoxic/ischemic conditions and impaired vasodilation because of downregulation of eNOS activity. To further implicate Rho-kinase in impaired vascular relaxation during hypoxia/ischemia, we exposed isolated vessels from rat and mouse to 60 mins of hypoxia, and showed that hypoxia reversibly abolished acetylcholine-induced eNOS-dependent relaxation, and that Rho-kinase inhibitor hydroxyfasudil partially preserved this relaxation during hypoxia. We, therefore, hypothesized that if hypoxia-induced Rho-kinase activation acutely impairs vasodilation in ischemic cortex, in vivo, then Rho-kinase inhibitors would acutely augment cerebral blood flow (CBF) as a mechanism by which they reduce infarct size. To test this, we studied the acute cerebral hemodynamic effects of Rho-kinase inhibitors in ischemic core and penumbra during distal middle cerebral artery occlusion (dMCAO) in wild-type and eNOS À/À mice using laser speckle flowmetry. When administered 60 mins before or immediately after dMCAO, Rho-kinase inhibitors hydroxyfasudil and Y-27632 reduced the area of severely ischemic cortex. However, hydroxyfasudil did not reduce the area of CBF deficit in eNOS À/À mice, suggesting that its effect on CBF within the ischemic cortex is primarily endothelium-dependent, and not mediated by its direct vasodilator effect on vascular smooth muscle. Our results suggest that Rho-kinase negatively regulates eNOS activity in acutely ischemic brain, thereby worsening the CBF deficit. Therefore, rapid nontranscriptional upregulation of eNOS activity by small molecule inhibitors of Rho-kinase may be a viable therapeutic approach in acute stroke.

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Activation of RhoA and Inhibition of Myosin Phosphatase as Important Components in Hypertension in Vascular Smooth Muscle

Cited by 301 publications

References 51 publications

Atorvastatin Inhibits Myocardin Expression in Vascular Smooth Muscle Cells

Atorvastatin Inhibits Myocardin Expression in Vascular Smooth Muscle Cells

Activation of Rho/Rho kinase signaling pathway by reactive oxygen species in rat aorta

Rho-Kinase Inhibition Acutely Augments Blood Flow in Focal Cerebral Ischemia via Endothelial Mechanisms

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