Rho and Rho kinase mediate thrombin-stimulated vascular smooth muscle cell DNA synthesis and migration

Relationship between Inflammation and Vasospastic Angina

Coronary artery spasm (CAS) is a dynamic coronary stenosis causing vasospastic angina (VSA). However, VSA is a potentially lethal medical condition with multiple presentations, including sudden cardiac death. Despite investigations to explore its pathogenesis, no single mechanism has been found to explain the entire process of VSA occurrence. The roles of elevated local and systemic inflammation have been increasingly recognized in VSA. Treatment strategies to decrease local and systemic inflammation deserve further investigation.

Paxillin controls actin stress fiber formation and migration of vascular smooth muscle cells by directly binding to the active Fyn

Rho-kinase (ROK)-mediated migration of vascular smooth muscle cells plays a crucial role in cardiovascular diseases. Previously we demonstrated Fyn tyrosine kinase as an upstream molecule of ROK to mediate actin stress fiber formation that plays an important role in cell migration, but the molecular mechanism between the two kinases was unclear. To discover a novel signaling molecule that exists between Fyn and ROK, we identified paxillin acting downstream of the active Fyn by combined use of pulldown assay and mass spectrometry. Immunofluorescence staining confirmed co-localization of Fyn and paxillin at the ends of actin stress fibers in human coronary artery smooth muscle cells (CASMCs). Surface plasmon resonance assay demonstrated direct binding between constitutively active Fyn (CA-Fyn) and N-terminus of paxillin (N-pax). The sphingosylphosphorylcholine (SPC)-induced ROK activation, actin stress fiber formation and cell migration were inhibited by paxillin knockdown, which were rescued by full-length paxillin (FL-pax) but not N-pax. N-pax co-localized with CA-Fyn at the cytosol and overexpression of N-pax inhibited the SPC-induced actin stress fiber formation and cell migration, indicating that the direct binding of FL-pax and CA-Fyn at the ends of actin stress fibers is essential for the ROK-mediated actin stress fiber formation and cell migration. Paxillin, as a novel signalling molecule, mediates the SPC-induced actin stress fiber formation and migration in human CASMCs via the Fyn/paxillin/ROK signalling pathway by direct binding of active Fyn.

Nelumbo nucifera leaf polyphenol extract and gallic acid inhibit TNF-α-induced vascular smooth muscle cell proliferation and migration involving the regulation of miR-21, miR-143 and miR-145

Nelumbo nucifera leaf water extract (NLE) attenuates high-fat diet (HFD)-induced rabbit atherosclerosis, but its mechanism of action and the relevant compounds remain unclear. Modulating the proliferation and migration of vascular smooth muscle cells (VSMCs) may be an enforceable strategy for atherosclerosis prevention. Therefore, we investigated the potential mechanisms of N. nucifera leaf polyphenol extract (NLPE) and its active ingredient gallic acid (GA) in VSMC proliferation and migration. A7r5 rat aortic VSMCs were provoked using 50 ng mL-1 tumor necrosis factor (TNF)-α; the NLPE or GA reduced the TNF-α-induced migration by inhibiting the transforming protein RhoA/cell division cycle protein 42 pathway. The NLPE or GA suppressed the TNF-α-induced VSMC proliferation by inhibiting the Ras pathway and increasing the expression of phosphatase and tensin homolog (PTEN), kinase suppressor of Ras 2, and inducible nitric oxide synthase. The NLPE or GA increased PTEN expression by downregulating microRNA (miR)-21 expression and reduced Ras and RhoA expression by upregulating miR-143 and miR-145 expression. The NLPE and GA use potentially prevents atherosclerosis by inhibiting the VSMC migration and proliferation. The mechanisms involve the regulation of the miRNA in PTEN, the Ras/extracellular-signal-regulated kinase pathway, and Rho family proteins.

CREB depletion in smooth muscle cells promotes medial thickening, adventitial fibrosis and elicits pulmonary hypertension

Levels of the cAMP-responsive transcription factor, CREB, are reduced in medial smooth muscle cells in remodeled pulmonary arteries from hypertensive calves and rats with chronic hypoxia-induced pulmonary hypertension. Here, we show that chronic hypoxia fails to promote CREB depletion in pulmonary artery smooth muscle cells or elicit significant remodeling of the pulmonary arteries in mice, suggesting that sustained CREB expression prevents hypoxia-induced pulmonary artery remodeling. This hypothesis was tested by generating mice, in which CREB was ablated in smooth muscle cells. Loss of CREB in smooth muscle cells stimulated pulmonary artery thickening, right ventricular hypertrophy, profound adventitial collagen deposition, recruitment of myeloid cells to the adventitia, and elevated right ventricular systolic pressure without exposure to chronic hypoxia. Isolated murine CREB-null smooth muscle cells exhibited serum-independent proliferation and hypertrophy in vitro and medium conditioned by CREB-null smooth muscle cells stimulated proliferation and expression of extracellular matrix proteins by adventitial fibroblasts. We conclude that CREB governs the pathologic switch from homeostatic, quiescent smooth muscle cells to proliferative, synthetic cells that drive arterial remodeling contributing to the development or pulmonary hypertension.

Coagulation factor XI induces Ca2+ response and accelerates cell migration in vascular smooth muscle cells via proteinase-activated receptor 1

Activated coagulation factor XI (FXIa) is a serine proteinase that plays a key role in the intrinsic coagulation pathway. The analysis of FXI-knockout mice has indicated the contribution of FXI to the pathogenesis of atherosclerosis. However, the underlying mechanism remains unknown. We hypothesized that FXIa exerts vascular smooth muscle effects via proteinase-activated receptor 1 (PAR₁). Fura-2 fluorometry revealed that FXIa elicited intracellular Ca²⁺ signal in rat embryo aorta smooth muscle A7r5 cells. The influx of extracellular Ca²⁺ played a greater role in generating Ca²⁺ signal than the Ca²⁺ release from intracellular stores. The FXIa-induced Ca²⁺ signal was abolished by the pretreatment with atopaxar, an antagonist of PAR₁, or 4-amidinophenylmethanesulfonyl fluoride (p-APMSF), an inhibitor of proteinase, while it was also lost in embryonic fibroblasts derived from PAR₁^-/- mice. FXIa cleaved the recombinant protein containing the extracellular region of PAR₁ at the same site (R45/S46) as that of thrombin, a canonical PAR₁ agonist. The FXIa-induced Ca²⁺ influx was inhibited by diltiazem, an L-type Ca²⁺ channel blocker, and by siRNA targeted to Ca_V1.2. The FXIa-induced Ca²⁺ influx was also inhibited by GF109203X and rottlerin, inhibitors of protein kinase C. In a wound healing assay, FXIa increased the rate of cell migration by 2.46-fold of control, which was partly inhibited by atopaxar or diltiazem. In conclusion, FXIa mainly elicits the Ca²⁺ signal via the PAR₁/Ca_V1.2-mediated Ca²⁺ influx and accelerates the migration in vascular smooth muscle cells. The present study provides the first evidence that FXIa exerts a direct cellular effect on vascular smooth muscle.

Myeloperoxidase aggravates pulmonary arterial hypertension by activation of vascular Rho-kinase

Pulmonary arterial hypertension (PAH) remains a disease with limited therapeutic options and dismal prognosis. Despite its etiologic heterogeneity, the underlying unifying pathophysiology is characterized by increased vascular tone and adverse remodeling of the pulmonary circulation. Myeloperoxidase (MPO), an enzyme abundantly expressed in neutrophils, has potent vasoconstrictive and profibrotic properties, thus qualifying as a potential contributor to this disease. Here, we sought to investigate whether MPO is causally linked to the pathophysiology of PAH. Investigation of 2 independent clinical cohorts revealed that MPO plasma levels were elevated in subjects with PAH and predicted adverse outcome. Experimental analyses showed that, upon hypoxia, right ventricular pressure was less increased in Mpo-/- than in WT mice. The hypoxia-induced activation of the Rho-kinase pathway, a critical subcellular signaling pathway yielding vasoconstriction and structural vascular remodeling, was blunted in Mpo-/- mice. Mice subjected to i.v. infusion of MPO revealed activation of Rho-kinase and increased right ventricular pressure, which was prevented by coinfusion of the Rho-kinase inhibitor Y-27632. In the Sugen5416/hypoxia rat model, PAH was attenuated by the MPO inhibitor AZM198. The current data demonstrate a tight mechanistic link between MPO, the activation of Rho-kinase, and adverse pulmonary vascular function, thus pointing toward a potentially novel avenue of treatment.

Loss of SPRR3 in ApoE-/- mice leads to atheroma vulnerability through Akt dependent and independent effects in VSMCs

Vascular smooth muscle cells (VSMCs) represent important modulators of plaque stability in advanced lesions. We previously reported that loss of small proline-rich repeat protein 3 (Sprr3), leads to VSMC apoptosis in a PI3K/Akt-dependent manner and accelerates lesion progression. Here, we investigated the role of Sprr3 in modulating plaque stability in hyperlipidemic ApoE^-/- mice. We show that loss of Sprr3 increased necrotic core size and reduced cap collagen content of atheromas in brachiocephalic arteries with evidence of plaque rupture and development of intraluminal thrombi. Moreover, Sprr3^-/-ApoE^-/- mice developed advanced coronary artery lesions accompanied by intraplaque hemorrhage and left ventricle microinfarcts. SPRR3 is known to reduce VSMC survival in lesions by promoting their apoptosis. In addition, we demonstrated that Sprr3^-/- VSMCs displayed reduced expression of procollagen in a PI3K/Akt dependent manner. SPRR3 loss also increased MMP gelatinase activity in lesions, and increased MMP2 expression, migration and contraction of VSMCs independently of PI3K/Akt. Consequently, Sprr3 represents the first described VSMC modulator of each of the critical features of cap stability, including VSMC numbers, collagen type I synthesis, and protease activity through Akt dependent and independent pathways.

Na+, HCO3--cotransporter NBCn1 increases pHi gradients, filopodia, and migration of smooth muscle cells and promotes arterial remodelling

AIMS

Arterial remodelling can cause luminal narrowing and obstruct blood flow. We tested the hypothesis that cellular acid-base transport facilitates proliferation and migration of vascular smooth muscle cells (VSMCs) and enhances remodelling of conduit arteries.

METHODS AND RESULTS

[Formula: see text]-cotransport via NBCn1 (Slc4a7) mediates net acid extrusion and controls steady-state intracellular pH (pHi) in VSMCs of mouse carotid arteries and primary aortic explants. Carotid arteries undergo hypertrophic inward remodelling in response to partial or complete ligation in vivo, but the increase in media area and thickness and reduction in lumen diameter are attenuated in arteries from NBCn1 knock-out compared with wild-type mice. With [Formula: see text] present, gradients for pHi (∼0.2 units magnitude) exist along the axis of VSMC migration in primary explants from wild-type but not NBCn1 knock-out mice. Knock-out or pharmacological inhibition of NBCn1 also reduces filopodia and lowers initial rates of VSMC migration after scratch-wound infliction. Interventions to reduce H(+)-buffer mobility (omission of [Formula: see text] or inhibition of carbonic anhydrases) re-establish axial pHi gradients, filopodia, and migration rates in explants from NBCn1 knock-out mice. The omission of [Formula: see text] also lowers global pHi and inhibits proliferation in primary explants.

CONCLUSION

Under physiological conditions (i.e. with [Formula: see text] present), NBCn1-mediated [Formula: see text] uptake raises VSMC pHi and promotes filopodia, VSMC migration, and hypertrophic inward remodelling. We propose that axial pHi gradients enhance VSMC migration whereas global acidification inhibits VSMC proliferation and media hypertrophy after carotid artery ligation. These findings support a key role of acid-base transport, particularly via NBCn1, for development of occlusive artery disease.

Emerging roles for vascular smooth muscle cell exosomes in calcification and coagulation

Vascular smooth muscle cell (VSMC) phenotypic conversion from a contractile to 'synthetic' state contributes to vascular pathologies including restenosis, atherosclerosis and vascular calcification. We have recently found that the secretion of exosomes is a feature of 'synthetic' VSMCs and that exosomes are novel players in vascular repair processes as well as pathological vascular thrombosis and calcification. Pro-inflammatory cytokines and growth factors as well as mineral imbalance stimulate exosome secretion by VSMCs, most likely by the activation of sphingomyelin phosphodiesterase 3 (SMPD3) and cytoskeletal remodelling. Calcium stress induces dramatic changes in VSMC exosome composition and accumulation of phosphatidylserine (PS), annexin A6 and matrix metalloproteinase-2, which converts exosomes into a nidus for calcification. In addition, by presenting PS, VSMC exosomes can also provide the catalytic surface for the activation of coagulation factors. Recent data showing that VSMC exosomes are loaded with proteins and miRNA regulating cell adhesion and migration highlight VSMC exosomes as potentially important communication messengers in vascular repair. Thus, the identification of signalling pathways regulating VSMC exosome secretion, including activation of SMPD3 and cytoskeletal rearrangements, opens up novel avenues for a deeper understanding of vascular remodelling processes.

Phosphodiesterase inhibitor KMUP-3 displays cardioprotection via protein kinase G and increases cardiac output via G-protein-coupled receptor agonist activity and Ca(2+) sensitization

KMUP-3 (7-{2-[4-(4-nitrobenzene) piperazinyl]ethyl}-1, 3-dimethylxanthine) displays cardioprotection and increases cardiac output, and is suggested to increase cardiac performance and improve myocardial infarction. To determine whether KMUP-3 improves outcomes in hypoperfused myocardium by inducing Ca(2+) sensitization to oppose protein kinase (PK)G-mediated Ca(2+) blockade, we measured left ventricular systolic blood pressure, maximal rates of pressure development, mean arterial pressure and heart rate in rats, and measured contractility and expression of PKs/RhoA/Rho kinase (ROCK)II in beating guinea pig left atria. Hemodynamic changes induced by KMUP-3 (0.5-3.0 mg/kg, intravenously) were inhibited by Y27632 [(R)-(+)-trans-4-1-aminoethyl)-N-(4-Pyridyl) cyclohexane carboxamide] and ketanserin (1 mg/kg, intravenously). In electrically stimulated left guinea pig atria, positive inotropy induced by KMUP-3 (0.1-100μM) was inhibited by the endothelial NO synthase (eNOS) inhibitors N-nitro-l-arginine methyl ester (L-NAME) and 7-nitroindazole, cyclic AMP antagonist SQ22536 [9-(terahydro-2-furanyl)-9H-purin-6-amine], soluble guanylyl cyclase (sGC) antagonist ODQ (1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one), RhoA inhibitor C3 exoenzyme, β-blocker propranolol, 5-hydroxytryptamine 2A antagonist ketanserin, ROCK inhibitor Y27632 and KMUP-1 (7-{2-[4-(2-chlorobenzene) piperazinyl]ethyl}-1, 3-dimethylxanthine) at 10μM. Western blotting assays indicated that KMUP-3 (0.1-10μM) increased PKA, RhoA/ROCKII, and PKC translocation and CIP-17 (an endogenous 17-kDa inhibitory protein) activation. In spontaneous right atria, KMUP-3 induced negative chronotropy that was blunted by 7-nitroindazole and atropine. In neonatal myocytes, L-NAME inhibited KMUP-3-induced eNOS phosphorylation and RhoA/ROCK activation. In H9c2 cells, Y-27632 (50μM) and PKG antagonist KT5823 [2,3,9,10,11,12-hexahydro-10R- methoxy-2,9-dimethyl-1-oxo-9S,12R-epoxy-1H-diindolo(1,2,3-fg:3',2',1'-kl) pyrrolo(3,4-i)(1,6)benzodiazocine-10-carboxylic acid, methyl ester] (3μM) reversed KMUP-3 (1-100μM)-induced Ca(2+)-entry blockade. GPCR agonist activity of KMUP-3 appeared opposed to KMUP-1, and increased cardiac output via Ca(2+) sensitization, and displayed cardioprotection via cyclic GMP/PKG-mediated myocardial preconditioning in animal studies.

Light and Dark of Reactive Oxygen Species for Vascular Function: 2014 ASVB (Asian Society of Vascular Biology)

Vascular-derived hydrogen peroxide (H2O2) serves as an important signaling molecule in the cardiovascular system and contributes to vascular homeostasis. H2O2 is a second messenger, transducing the oxidative signal into biological responses through posttranslational protein modification. The balance between oxidant and antioxidant systems regulates intracellular redox status, and their imbalance causes oxidative or reductive stress, leading to cellular damage in cardiovascular systems. Excessive H2O2 deteriorates vascular functions and promotes vascular disease through multiple pathways. The RhoA/Rho-kinase pathway plays an important role in various fundamental cellular functions, including production of excessive reactive oxygen species, leading to the development of cardiovascular diseases. Rho-kinase (ROCK1 and ROCK2) belongs to the family of serine/threonine kinases and is an important downstream effector of the small GTP-binding protein RhoA. Rho-kinase plays a crucial role in the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, stroke, and heart failure. Thus, Rho-kinase inhibitors may be useful for the treatment of cardiovascular diseases in humans. In this review, we will briefly discuss the roles of vascular-derived H2O2 and review the recent progress in the translational research on the therapeutic importance of the Rho-kinase pathway in cardiovascular medicine.

Rho-associated protein kinase inhibitor, Y-27632, significantly enhances cell adhesion and induces a delay in G1 to S phase transition in rabbit corneal endothelial cells

Human corneal endothelial cells are a non-proliferative cell type. As a result of the increase in corneal endothelium disease, increasing numbers of studies have been conducted in order to promote corneal endothelial cell proliferation. The aim of the present study was to investigate the proliferative effects of Rho-associated protein kinase inhibitor, Y-27632, on rabbit corneal endothelial cells (rCECs). Y-27632 (1, 10 or 30 μM) was added at two different time points to two groups of rCECs. The first group received Y-27632 when rCECs were initially plated, and the second following 72 h of cell growth. Cell morphology and cell adhesion ratios were subsequently observed using light microscopy. A cell counting kit was used to measure the number of viable cells that adhered to culture plates. Cell cycle transitions and levels of Annexin V-positive apoptotic cells were detected using flow cytometry. Cells treated with 1 μM Y-27632 and 10 μM Y-27632 retained their cell shape. At a concentration of 30 μM Y-27632, the cell shape became irregular. Cell adhesion ratios, in 1 μM Y-27632 (36.84%), 10 μM Y-27632 (84.21%) and 30 μM Y-27632 (84.21%) were higher than the adhesion ratio in the control group (P<0.01). The optical densities of rCECs treated with 10 μM or 30 μM Y-27632 following 72 h of cell growth was less than that of the control cells (P<0.01), but higher than that of cells which received Y-27632 at the time of plating (P<0.01). Flow cytometry results also demonstrated that there was a delay in G1 to S phase cell cycle progression in rCECs following administration of 10 μM Y-27632 (P<0.01). Cell apoptosis was inhibited when 10 μM Y-27632 was added, at the time of cell plating, as well as when added following 72 h of cell growth (P<0.01). At a concentration of 10 μM Y-27632, there was an improvement in cell adhesion and an inhibition of the cell cycle in rabbit corneal endothelial cells. In conclusion, Y-27632 has different effects on rCECs when administered at varying concentrations and at particular stages of cell growth.

Structure, Function, Pharmacology, and Therapeutic Potential of the G Protein, Gα/q,11

G protein coupled receptors (GPCRs) are one of the major classes of cell surface receptors and are associated with a group of G proteins consisting of three subunits termed alpha, beta, and gamma. G proteins are classified into four families according to their α subunit; Gα_i, Gα_s, Gα_12/13, and Gα_q. There are several downstream pathways of Gα_q of which the best known is upon activation via guanosine triphosphate (GTP), Gα_q activates phospholipase Cβ, hydrolyzing phosphatidylinositol 4,5-biphosphate into diacylglycerol and inositol triphosphate and activating protein kinase C and increasing calcium efflux from the endoplasmic reticulum. Although G proteins, in particular, the Gα_q/11 are central elements in GPCR signaling, their actual roles have not yet been thoroughly investigated. The lack of research of the role on Gα_q/11 in cell biology is partially due to the obscure nature of the available pharmacological agents. YM-254890 is the most useful Gα_q-selective inhibitor with antiplatelet, antithrombotic, and thrombolytic effects. YM-254890 inhibits Gα_q signaling pathways by preventing the exchange of guanosine diphosphate for GTP. UBO-QIC is a structurally similar compound to YM-254890, which can inhibit platelet aggregation and cause vasorelaxation in rats. Many agents are available for the study of signaling downstream of Gα_q/11. The role of G proteins could potentially represent a novel therapeutic target. This review will explore the range of pharmacological and molecular tools available for the study of the role of Gα_q/11 in GPCR signaling.

Mulberry water extracts inhibit atherosclerosis through suppression of the integrin-β₃/focal adhesion kinase complex and downregulation of nuclear factor κB signaling in vivo and in vitro

Previous studies have shown that mulberry water extracts (MWEs), which contain polyphenolic compounds, have an antiatherosclerotic effect in vivo and in vitro through stimulating apoptosis of vascular smooth muscle cells (VSMCs). Histological analysis was performed on atherosclerotic lesions from high-cholesterol diet (HCD)-fed rabbits after treatment with 0.5-1% MWEs for 10 weeks. Immunohistochemistry showed that the expressions of SMA, Ras, and matrix metalloproteinase-2 in the VSMCs were dose-dependently inhibited after MWE treatment. The antimigratory effects of MWEs on A7r5 VSMCs were assessed by western blot analysis of migration-related proteins, visualization of F-actin cytoskeleton, and reverse transcription polymerase chain reaction. The results showed that MWEs inhibited VSMC migration through reducing interactions of the integrin-β3/focal adhesion kinase complex, alterations of the cytoskeleton, and downregulation of glycogen synthase kinase 3β/nuclear factor κB signaling. Taken together, MWEs inhibited HCD-induced rabbit atherogenesis through blocking VSMC migration via reducing interactions of integrin-β3 and focal adhesion kinase and downregulating migration-related proteins.

Mixed-lineage kinase 3 deficiency promotes neointima formation through increased activation of the RhoA pathway in vascular smooth muscle cells

OBJECTIVE

Mitogen-activated protein kinase pathways play an important role in neointima formation secondary to vascular injury, in part by promoting proliferation of vascular smooth muscle cells (VSMC). Mixed-lineage kinase 3 (MLK3) is a mitogen-activated protein kinase kinase kinase that activates multiple mitogen-activated protein kinase pathways and has been implicated in regulating proliferation in several cell types. However, the role of MLK3 in VSMC proliferation and neointima formation is unknown. The aim of this study was to determine the function of MLK3 in the development of neointimal hyperplasia and to elucidate the underlying mechanisms.

APPROACH AND RESULTS

Neointima formation was analyzed after endothelial denudation of carotid arteries from wild-type and MLK3-deficient mice. MLK3 deficiency promoted injury-induced neointima formation and increased proliferation of primary VSMC derived from aortas isolated from MLK3-deficient mice compared with wild-type mice. Furthermore, MLK3 deficiency increased the activation of p63Rho guanine nucleotide exchange factor, RhoA, and Rho kinase in VSMC, a pathway known to promote neointimal hyperplasia, and reconstitution of MLK3 expression attenuated Rho kinase activation. Furthermore, cJun NH2-terminal kinase activation was decreased in MLK3-deficient VSMC, and proliferation of wild-type but not MLK3 knockout cells treated with a cJun NH2-terminal kinase inhibitor was attenuated.

CONCLUSIONS

We demonstrate that MLK3 limits RhoA activation and injury-induced neointima formation by binding to and inhibiting the activation of p63Rho guanine nucleotide exchange factor, a RhoA activator. In MLK3-deficient cells, activation of p63Rho guanine nucleotide exchange factor proceeds in an unchecked manner, leading to a net increase in RhoA pathway activation. Reconstitution of MLK3 expression restores MLK3/p63Rho guanine nucleotide exchange factor interaction, which is attenuated by feedback from activated cJun NH2-terminal kinase.

Rho/Rho-associated coiled-coil forming kinase pathway as therapeutic targets for statins in atherosclerosis

SIGNIFICANCE

The 3-hydroxy-methylglutaryl coenzyme A reductase inhibitors or statins are important therapeutic agents for lowering serum cholesterol levels. However, recent studies suggest that statins may exert atheroprotective effects beyond cholesterol lowering. These so-called "pleiotropic effects" include effects of statins on vascular and inflammatory cells. Thus, it is important to understand whether other signaling pathways that are involved in atherosclerosis could be targets of statins, and if so, whether individuals with "overactivity" of these pathways could benefit from statin therapy, regardless of serum cholesterol level.

RECENT ADVANCES

Statins inhibit the synthesis of isoprenoids, which are important for the function of the Rho/Rho-associated coiled-coil containing kinase (ROCK) pathway. Indeed, recent studies suggest that inhibition of the Rho/ROCK pathway by statins could lead to improved endothelial function and decreased vascular inflammation and atherosclerosis. Thus, the Rho/ROCK pathway has emerged as an important target of statin therapy for reducing atherosclerosis and possibly cardiovascular disease.

CRITICAL ISSUES

Because atherosclerosis is both a lipid and an inflammatory disease, it is important to understand how inhibition of Rho/ROCK pathway could contribute to statins' antiatherosclerotic effects.

FUTURE DIRECTIONS

The role of ROCKs (ROCK1 and ROCK2) in endothelial, smooth muscle, and inflammatory cells needs to be determined in the context of atherogenesis. This could lead to the development of specific ROCK1 or ROCK2 inhibitors, which could have greater therapeutic benefits with less toxicity. Also, clinical trials will need to be performed to determine whether inhibition of ROCKs, with and without statins, could lead to further reduction in atherosclerosis and cardiovascular disease.

Chronic allograft rejection: A significant hurdle to transplant success

The state-of-the-art immunosuppression drugs do not ensure indefinite transplant survival, and most transplants are continuously lost to chronic rejection even years posttransplantation. This form of rejection is responsible for long-term failure of transplanted organs. The mechanisms involved in development of chronic rejection are not well-understood. One of the main features of chronic rejection is progressive luminal narrowing of graft vessels, which results in compromised blood flow, ischemia, cell death, and finally graft failure. All the existing immunosuppressive regimens are targeting acute rejection, and at present there is no available therapy for prevention of chronic rejection. Chronic rejection involves two major, but interrelated responses: The first is the host immune response against the transplant mediated primarily by alloreactive T and B cells, and the second is injury and repair of the graft (vasculopathy of graft vessels). Here we focus on recent advances in understanding the cellular and molecular aspects of chronic transplant vasculopathy and function of macrophages, topics pivotal for development of novel antichronic rejection therapies.

Inhibition of phosphatidylinositol 3-kinase/Akt signaling attenuates hypoxia-induced pulmonary artery remodeling and suppresses CREB depletion in arterial smooth muscle cells

Hypoxia-induced pulmonary hypertension is characterized by progressive remodeling of the pulmonary artery (PA) system and loss of the transcription factor, cAMP response element binding protein (CREB) in PA smooth muscle cells (SMCs). Previous in vitro studies suggested that platelet-derived growth factor, a mitogen produced in the hypoxic arterial wall, elicits loss of CREB in medial SMCs via the PI3K/Akt pathway. These events trigger switching of SMCs from a quiescent, contractile phenotype to a proliferative, migratory, dedifferentiated, and synthetic phenotype, which contributes to PA thickening. Here, we investigated whether inhibition of PI3K or Akt could attenuate arterial remodeling in the lung and prevent CREB loss in PA medial SMCs in rats subjected to chronic hypoxia. Inhibition of either enzyme-blunted hypoxia-induced PA remodeling and SMC CREB depletion and diminished SMC proliferation and collagen deposition. Inhibition of Akt, but not PI3K, suppressed muscularization of distal arterioles and blunted right ventricular hypertrophy. Interestingly, mean PA pressure was elevated equally by hypoxia in untreated and inhibitor-treated groups but was normalized acutely by the Rho kinase inhibitor, Fasudil. We conclude that PI3K and Akt inhibitors can attenuate hypoxia-induced PA remodeling and SMC CREB depletion but fail to block the development of pulmonary hypertension because of their inability to repress Rho kinase-mediated vasoconstriction.

Mulberry 1-deoxynojirimycin pleiotropically inhibits glucose-stimulated vascular smooth muscle cell migration by activation of AMPK/RhoB and down-regulation of FAK

Mulberry 1-deoxynojirimycin (DNJ), an inhibitor of α-glucosidase, has been reported to help prevent diabetes mellitus and suppress lipid accumulation. The aim of this study was to determine whether mulberry DNJ has pleiotropic effects on the development of atherosclerosis. The mechanisms by which mulberry DNJ might inhibit migration of A7r5 vascular smooth muscle cells (VSMCs) under hyperglycemic conditions mimicking diabetes were investigated. The antimigratory effects of DNJ on VSMCs were assessed by Western blot analysis of migration-related proteins and by electric cell-substrate impedance sensing (ECIS) and visualization of F-actin cytoskeleton. Two pathways of DNJ-mediated inhibition of VSMC migration were identified. The first involved AMPK activation to inhibit fatty acid synthase (FASN) and Akt activity and then RhoB activation to inhibit nuclear factor-κB (NF-κB) and matrix metalloproteinase-2 (MMP) activity. The second involved inhibition of focal adhesion kinase (FAK), Ras, and RhoA activity leading to inhibition of F-actin activity.

Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects

Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.

Novel role for p21-activated kinase 2 in thrombin-induced monocyte migration

To understand the role of thrombin in inflammation, we tested its effects on migration of THP-1 cells, a human monocytic cell line. Thrombin induced THP-1 cell migration in a dose-dependent manner. Thrombin induced tyrosine phosphorylation of Pyk2, Gab1, and p115 RhoGEF, leading to Rac1- and RhoA-dependent Pak2 activation. Downstream to Pyk2, Gab1 formed a complex with p115 RhoGEF involving their pleckstrin homology domains. Furthermore, inhibition or depletion of Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, or Pak2 levels substantially attenuated thrombin-induced THP-1 cell F-actin cytoskeletal remodeling and migration. Inhibition or depletion of PAR1 also blocked thrombin-induced activation of Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, and Pak2, resulting in diminished THP-1 cell F-actin cytoskeletal remodeling and migration. Similarly, depletion of Gα12 negated thrombin-induced Pyk2, Gab1, p115 RhoGEF, Rac1, RhoA, and Pak2 activation, leading to attenuation of THP-1 cell F-actin cytoskeletal remodeling and migration. These novel observations reveal that thrombin induces monocyte/macrophage migration via PAR1-Gα12-dependent Pyk2-mediated Gab1 and p115 RhoGEF interactions, leading to Rac1- and RhoA-targeted Pak2 activation. Thus, these findings provide mechanistic evidence for the role of thrombin and its receptor PAR1 in inflammation.

Serum can overcome contact inhibition in confluent human pulmonary artery smooth muscle cells

Pulmonary artery endothelial cells (PAEC) in an intact vessel are continually exposed to serum, but unless injured, do not proliferate, constrained by confluence. In contrast, pulmonary artery smooth muscle cells (PASMC) attain, and maintain, confluence in the presence of minimal serum, protected from serum's stimulatory effects except when the endothelial barrier becomes more permeable. We hypothesized therefore, that confluent PASMC may be less constrained by contact inhibition in the presence of serum than PAEC and tested this idea by exposing confluent non-transformed human PAEC and PASMC to media containing increasing concentrations of fetal bovine serum (FBS) and determining cell growth over 7 days. PAEC that had attained confluence in low serum did not proliferate even when exposed to 5% serum, the highest concentration tested. In contrast, PASMC that attained confluence in low serum did proliferate once serum levels were increased, an effect that was dose dependent. Consistent with this observation, PASMC had more BrdU incorporation and a greater percentage of cells in S phase in 5% compared to 0.2% FBS, whereas no such difference was seen in PAEC. These results suggest that confluent human PAEC are resistant to the stimulatory effects of serum, whereas confluent PASMC can proliferate when serum levels are increased, an effect mediated in part by differences in phosphoinositide 3-kinase activation. This observation may be relevant to understanding the PASMC hyperplasia observed in humans and animals with pulmonary hypertension in which changes in endothelial permeability due to hypoxia or injury expose the underlying smooth muscle to serum.

ROCK inhibitor enhances adhesion and wound healing of human corneal endothelial cells

Maintenance of corneal transparency is crucial for vision and depends mainly on the endothelium, a non-proliferative monolayer of cells covering the inner part of the cornea. When endothelial cell density falls below a critical threshold, the barrier and “pump” functions of the endothelium are compromised which results in corneal oedema and loss of visual acuity. The conventional treatment for such severe disorder is corneal graft. Unfortunately, there is a worldwide shortage of donor corneas, necessitating amelioration of tissue survival and storage after harvesting. Recently it was reported that the ROCK inhibitor Y-27632 promotes adhesion, inhibits apoptosis, increases the number of proliferating monkey corneal endothelial cells in vitro and enhance corneal endothelial wound healing both in vitro and in vivo in animal models. Using organ culture human cornea (N = 34), the effect of ROCK inhibitor was evaluated in vitro and ex vivo. Toxicity, corneal endothelial cell density, cell proliferation, apoptosis, cell morphometry, adhesion and wound healing process were evaluated by live/dead assay standard cell counting method, EdU labelling, Ki67, Caspase3, Zo-1 and Actin immunostaining. We demonstrated for the first time in human corneal endothelial cells ex vivo and in vitro, that ROCK inhibitor did not induce any toxicity effect and did not alter cell viability. ROCK inhibitor treatment did not induce human corneal endothelial cells proliferation. However, ROCK inhibitor significantly enhanced adhesion and wound healing. The present study shows that the selective ROCK inhibitor Y-27632 has no effect on human corneal endothelial cells proliferative capacities, but alters cellular behaviours. It induces changes in cell shape, increases cell adhesion and enhances wound healing ex vivo and in vitro. Its absence of toxicity, as demonstrated herein, is relevant for its use in human therapy.

Cyclooxygenase-2-derived prostaglandin E₂ promotes injury-induced vascular neointimal hyperplasia through the E-prostanoid 3 receptor

RATIONALE

Vascular smooth muscle cell (VSMC) migration and proliferation are the hallmarks of restenosis pathogenesis after angioplasty. Cyclooxygenase (COX)-derived prostaglandin (PG) E₂ is implicated in the vascular remodeling response to injury. However, its precise molecular role remains unknown.

OBJECTIVE

This study investigates the impact of COX-2-derived PGE₂ on neointima formation after injury.

METHODS AND RESULTS

Vascular remodeling was induced by wire injury in femoral arteries of mice. Both neointima formation and the restenosis ratio were diminished in COX-2 knockout mice as compared with controls, whereas these parameters were enhanced in COX-1>COX-2 mice, in which COX-1 is governed by COX-2 regulatory elements. PG profile analysis revealed that the reduced PGE₂ by COX-2 deficiency, but not PGI2, could be rescued by COX-1 replacement, indicating COX-2-derived PGE₂ enhanced neointima formation. Through multiple approaches, the EP3 receptor was identified to mediate the VSMC migration response to various stimuli. Disruption of EP3 impaired VSMC polarity for directional migration by decreasing small GTPase activity and restricted vascular neointimal hyperplasia, whereas overexpression of EP3α and EP3β aggravated neointima formation. Inhibition or deletion of EP3α/β, a Gαi protein-coupled receptor, activated the cAMP/protein kinase A pathway and decreased activation of RhoA in VSMCs. PGE₂ could stimulate phosphatidylinositol 3-kinase/Akt/glycogen synthase kinase3β signaling in VSMCs through Gβγ subunits on EP3α/β activation. Ablation of EP3 suppressed phosphatidylinositol 3-kinase signaling and reduced GTPase activity in VSMCs and altered cell polarity and directional migration.

CONCLUSIONS

COX-2-derived PGE₂ facilitated the neointimal hyperplasia response to injury through EP3α/β-mediated cAMP/protein kinase A and phosphatidylinositol 3-kinase pathways, indicating EP3 inhibition may be a promising therapeutic strategy for percutaneous transluminal coronary angioplasty.

The activation of proteinase-activated receptor-1 (PAR1) promotes gastric cancer cell alteration of cellular morphology related to cell motility and invasion

Cell motility proceeds by cycles of edge protrusion, adhesion and retraction. Whether these functions are coordinated by biochemical or biomechanical processes is unknown. Tumor invasion and metastasis is directly related to cell motility. We showed that stimulation of proteinase-activated receptor-1 (PAR1) can trigger an array of responses that would promote tumor cell growth and invasion. Thus, we examined aspects of PAR1 activation related to cell morphological change that might contribute to cell motility. We established a PAR1 stably transfected MKN45 gastric cancer cell line (MKN45/PAR1). We examined morphological changes, Rho family activation and overexpression of cytoskeletal protein in cells exposed to PAR1 agonists (α-thrombin and TFLLR-NH2). MKN45/PAR1 grows with an elongated and polarized morphology, extending pseudopodia at the leading edge. However, in the presence of PAR1 antagonist, MKN45/PAR1 did not show any changes in cell shape upon addition of either α-thrombin or TFLLR-NH2. Activated PAR1 induced RhoA and Rac1 phosphorylation, and subsequent overexpression of myosin IIA and filamin B which are stress fiber components that were identified by PMF analysis of peptide mass data obtained by MALDI-TOF/MS measurement. Upon stimulation of MKN45/PAR1 for 24 h with either α-thrombin or TFLLR-NH2, the distribution of both myosin IIA and filamin B proteins shifted to being distributed throughout the cytoplasm to the membrane, with more intense luminescence signals than in the absence of stimulation. These results demonstrate that PAR1 activation induces cell morphological change associated with cell motility via Rho family activation and cytoskeletal protein overexpression, and has a critical role in gastric cancer cell invasion and metastasis.

Pericytes regulate vascular basement membrane remodeling and govern neutrophil extravasation during inflammation

During inflammation polymorphonuclear neutrophils (PMNs) traverse venular walls, composed of the endothelium, pericyte sheath and vascular basement membrane. Compared to PMN transendothelial migration, little is known about how PMNs penetrate the latter barriers. Using mouse models and intravital microscopy, we show that migrating PMNs expand and use the low expression regions (LERs) of matrix proteins in the vascular basement membrane (BM) for their transmigration. Importantly, we demonstrate that this remodeling of LERs is accompanied by the opening of gaps between pericytes, a response that depends on PMN engagement with pericytes. Exploring how PMNs modulate pericyte behavior, we discovered that direct PMN-pericyte contacts induce relaxation rather than contraction of pericyte cytoskeletons, an unexpected response that is mediated by inhibition of the RhoA/ROCK signaling pathway in pericytes. Taking our in vitro results back into mouse models, we present evidence that pericyte relaxation contributes to the opening of the gaps between pericytes and to the enlargement of the LERs in the vascular BM, facilitating PMN extravasation. Our study demonstrates that pericytes can regulate PMN extravasation by controlling the size of pericyte gaps and thickness of LERs in venular walls. This raises the possibility that pericytes may be targeted in therapies aimed at regulating inflammation.

Therapeutic implications of endothelin and thrombin G-protein-coupled receptor transactivation of tyrosine and serine/threonine kinase cell surface receptors

Objectives

This review discusses the latest developments in G protein coupled receptor (GPCR) signalling related to the transactivation of cell surface protein kinase receptors and the therapeutic implications.

Key findings

Multiple GPCRs have been known to transactivate protein tyrosine kinase receptors for almost two decades. More recently it has been discovered that GPCRs can also transactivate protein serine/threonine kinase receptors such as that for transforming growth factor (TGF)-β. Using the model of proteoglycan synthesis and glycosaminoglycan elongation in human vascular smooth muscle cells which is a component of an in vitro model of atherosclerosis, the dual tyrosine and serine/threonine kinase receptor transactivation pathways appear to account for all of the response to the agonists, endothelin and thrombin.

Summary

The broadening of the paradigm of GPCR receptor transactivation explains the broad range of activities of these receptors and also the efficacy of GPCR antagonists in cardiovascular therapeutics. Deciphering the mechanisms of transactivation with the aim of identifying a common therapeutic target remains the next challenge.

Increased leukocyte Rho-associated coiled-coil containing protein kinase activity predicts the presence and severity of coronary vasospastic angina

OBJECTIVE

Although inhibition of Rho-associated coiled-coil containing protein kinase (ROCK) has been shown to prevent coronary vasospastic angina (CVA), direct evidence linking ROCK activity and CVA is lacking. Accordingly, we investigated whether ROCK activity is an independent marker for CVA and is altered after treatment with antispastic medications.

METHODS AND RESULTS

We prospectively studied 31 Taiwanese patients who were diagnosed with CVA and 33 control subjects. Subject demographics were recorded, and blood samples were obtained at baseline in all participants and in CVA patients after 3 months of antispastic treatment. Compared with control subjects, leukocyte ROCK activity was greater in CVA patients (136% versus 91%, P<0.001). A cutoff value for leukocyte ROCK activity of 104% predicted the presence of CVA with specificity and sensitivity rates of 88% and 84%, respectively. ROCK activity increased with the severity of CVA (P for trend<0.001). Following 3-month treatment of antispastic agents, leukocyte ROCK activity, high-sensitivity C-reactive protein, and interleukin-6 levels were reduced by 43%, 42% and 27%, respectively (P<0.05 for all).

CONCLUSIONS

Increased levels of leukocyte ROCK activity independently predicted the presence of CVA and correlated with CVA severity. Treatment with antispastic agents substantially reduced the level of leukocyte ROCK activity.

Cardioprotective effect of a combination of Rho-kinase inhibitor and p38 MAPK inhibitor on cardiovascular remodeling and oxidative stress in Dahl rats

AIM

Rho-kinase plays a critical role in various cellular functions. p38 mitogen-activated protein kinase (p38 MAPK) plays a central role in the inflammatory cytokine response to immune challenge. We evaluated the effects of a combination of fasudil, a Rho-kinase inhibitor, and FR167653, a p38 MAPK inhibitor, on cardiovascular remodeling, inflammation, and oxidative stress in Dahl salt-sensitive hypertensive (DS) rats.

METHODS

DS and Dahl salt-resistant (DR) rats were fed a high-salt diet at 6 weeks of age. Vehicle, fasudil (100 mg/kg per day), FR167653 (2 mg/kg per day), and a combination of fasudil and FR167653 were administered to 6-week-old DS rats for 5 weeks.

RESULTS

At the age of 11 weeks, in the left ventricle, DS rats were characterized by increased myocardial fibrosis, phosphorylation of p38 MAPK, and myosin phosphatase targeting subunit (MYPT-1), and NAD(P)H oxidase p22(phox), p47(phox), gp91(phox), tumor necrosis factor-α and interleukin-1β expression compared with DR rats. Fasudil improved cardiovascular remodeling, inflammation, NAD(P)H oxidase subunits, and phosphorylation of p38 MAPK and MYPT-1. FR167653 also similarly ameliorated these indices but not MYPT-1 phosphorylation. Compared with either agent alone, a combination of fasudil and FR167653 was more effective for the improvement of myocardial damage, inflammation and oxidative stress.

CONCLUSION

These findings suggest that the Rho-kinase and p38 MAPK pathways may play a pivotal role in ventricular hypertrophy; thus, we obtained the first evidence that a combination of Rho-kinase inhibitor and p38 MAPK inhibitor may provide a potential therapeutic target in hypertension with cardiovascular remodeling.

Platelet receptor gain-of-function single nucleotide polymorphisms in carotid and vertebral stenosis patients

The role of platelet receptor gain-of-function single nucleotide polymorphisms (SNP) in cardiovascular disease is controversial. We hypothesised that certain SNPs may accelerate the development of carotid artery stenosis. The intronic PAR-1 receptor intervening sequence-14 A/T (IVSn-14 A/T) polymorphism and three additional platelet receptor polymorphisms, i.e. GPIa (807C/T), GPIbα (5T/C) and HPA-1a/HPA-1b (Pl (A1/A2)) of GPIIIa were studied. The interaction of SNPs with conventional risk factors including male gender, hypertension, high cholesterol, diabetes, advanced age and smoking were investigated. The hypothesis was tested in 114 well-characterised patients with symptomatic carotid or vertebral stenosis from the British CAVATAS population and compared the results with 97 unrelated controls. The allele frequency of the platelet gain-of-function SNP was not significantly different in the CAVATAS population as compared to controls (PAR-1A/T (P = 0.13), GPIa C/T (P = 0.25), GPIIIa HPA-1a/HPA-1b (PlA1/A2) (P = 0.66) and GPIb T/C (P = 0.20)). In the subgroup of smokers, however, the prothrombotic GPIbα C mutated allele was found in a significantly higher frequency in the patient as compared to the control group (P = 0.04). Contrary to the primary hypothesis, the PAR-1A/T SNP as well as the other SNPs tested were not over- or underrepresented in the CAVATAS population. However, a significantly increased prevalence of GPIb-α (5C/T) was found in the subgroup of smokers and may represent an important cofactor in this patient group of our hypothesis-generating study.

Signaling mechanisms that regulate smooth muscle cell differentiation

Extensive studies over the last 30 years have demonstrated that vascular smooth muscle cell (SMC) differentiation and phenotypic modulation is controlled by a dynamic array of environmental cues. The identification of the signaling mechanisms by which these environmental cues regulate SMC phenotype has been more difficult because of our incomplete knowledge of the transcription mechanisms that regulate SMC-specific gene expression. However, recent advances in this area have provided significant insight, and the goal of this review is to summarize the signaling mechanisms by which extrinsic cues control SMC differentiation.

Protective effects of Y-27632 on hypoxia/reoxygenation-induced intestinal injury in newborn rats

BACKGROUND/PURPOSE

Necrotizing enterocolitis (NEC) is a major cause of mortality in neonates and is associated with a disruption in the protective intestinal barrier. The precise cause of NEC is elusive. However, ischemia/reperfusion injury of the intestine has been considered a major contributing factor. We examined the role of Y-27632, a selective Rho-kinase inhibitor, on a hypoxia/reoxygenation (H/R)-induced intestinal injury of newborn rat pups.

METHODS

Hypoxia/reoxygenation was achieved by placing rat pups in an airtight chamber aerated with 95% N(2) + 5% CO(2) for 10 minutes followed by 10-minute 100% oxygen. Forty newborn rat pups were randomly allocated into 4 groups. Group 1 served as untreated controls. The pups in group 2 were subjected to H/R only. In groups 3 and 4, the rats were treated with intraperitoneal injection of 0.3 and 3 mg kg(-1) day(-1) of Y-27632 for 5 days following H/R, respectively. The pups were killed 6 days following the H/R injury. Intestine specimens were evaluated for histopathology and biochemical investigation.

RESULTS

The microscopic lesions in H/R rat pups were virtually the same as those seen in neonatal NEC, with severe destruction of villi and crypts. Hypoxia/reoxygenation resulted in significant elevation in malondialdehyde levels, but decreased tissue nitric oxide levels (P < .05). Protective effects of Y-27632 on H/R-induced intestinal injury of newborn rat pups were observed with a significant decrease in the intestinal injury score, suppression in malondialdehyde levels, and increase in nitric oxide levels (P < .05).

CONCLUSIONS

In this experimental study, Y-27632 significantly attenuated H/R-induced intestinal injury. These findings indicate that inhibition of Rho-kinase may offer a novel therapeutic approach in the treatment of NEC.

Activation of NADPH oxidase 1 increases intracellular calcium and migration of smooth muscle cells

Redox-dependent migration and proliferation of vascular smooth muscle cells (SMCs) are central events in the development of vascular proliferative diseases; however, the underlying intracellular signaling mechanisms are not fully understood. We tested the hypothesis that activation of Nox1 NADPH oxidase modulates intracellular calcium ([Ca(2+)](i)) levels. Using cultured SMCs from wild-type and Nox1 null mice, we confirmed that thrombin-dependent generation of reactive oxygen species requires Nox1. Thrombin rapidly increased [Ca(2+)](i), as measured by fura-2 fluorescence ratio imaging, in wild-type but not Nox1 null SMCs. The increase in [Ca(2+)](i) in wild-type SMCs was inhibited by antisense to Nox1 and restored by expression of Nox1 in Nox1 null SMCs. Investigation into potential mechanisms by which Nox1 modulates [Ca(2+)](i) showed that thrombin-induced inositol triphosphate generation and thapsigargin-induced intracellular calcium mobilization were similar in wild-type and Nox1 null SMCs. To examine the effects of Nox1 on Ca(2+) entry, cells were either bathed in Ca(2+)-free medium or exposed to dihydropyridines to block L-type Ca(2+) channel activity. Treatment with nifedipine or removal of extracellular Ca(2+) reduced the thrombin-mediated increase of [Ca(2+)](i) in wild-type SMCs, whereas the response in Nox1 null SMCs was unchanged. Sodium vanadate, an inhibitor of protein tyrosine phosphatases, restored the thrombin-induced increase of [Ca(2+)](i) in Nox1 null SMCs. Migration of SMCs was impaired with deficiency of Nox1 and restored with expression of Nox1 or the addition of sodium vanadate. In summary, we conclude that Nox1 NADPH oxidase modulates Ca(2+) mobilization in SMCs, in part through regulation of Ca(2+) influx, to thereby promote cell migration.

Rho-kinase: important new therapeutic target in cardiovascular diseases

Rho-kinase (ROCKs) belongs to the family of serine/threonine kinases and is an important downstream effector of the small GTP-binding protein RhoA. There are two isoforms of Rho-kinase, ROCK1 and ROCK2, and they have different functions with ROCK1 for circulating inflammatory cells and ROCK2 for vascular smooth muscle cells. It has been demonstrated that the RhoA/Rho-kinase pathway plays an important role in various fundamental cellular functions, including contraction, motility, proliferation, and apoptosis, leading to the development of cardiovascular disease. The important role of Rho-kinase in vivo has been demonstrated in the pathogenesis of vasospasm, arteriosclerosis, ischemia-reperfusion injury, hypertension, pulmonary hypertension, stroke, and heart failure. Furthermore, the beneficial effects of fasudil, a selective Rho-kinase inhibitor, have been demonstrated for the treatment of several cardiovascular diseases in humans. Thus the Rho-kinase pathway is an important new therapeutic target in cardiovascular medicine.

Alteration of enzyme expressions in mevalonate pathway: possible role for cardiovascular remodeling in spontaneously hypertensive rats

BACKGROUND

The mevalonate pathway is an important metabolic pathway that plays a key role in multiple cellular processes. The aim of this study was to define whether the enzyme expression in mevalonate pathway changes during cardiovascular remodelling in spontaneously hypertensive rats (SHR).

METHODS AND RESULTS

Hearts and thoracic aortas were removed for the study of cardiovascular remodeling in SHR and Wistar-Kyoto rats (WKY). The protein expression of the enzymes in hearts, aortas and livers was analyzed by western blot. The histological measurements showed that the mass and the size of cardiomyocytes, the media thickness and the media cross-sectional area (MCSA) of the thoracic aorta were all increased in SHR since 3 weeks of age. In the heart, there was overexpression of some enzymes, including 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), farnesyl diphosphate synthase (FDPS), and geranylgeranyltransferase type I (GGTase-I), and downregulation of squalene synthetase (SQS) in SHR since 3 weeks of age. In the aorta, besides similar expressions of HMGR, SQS, FDPS and GGTase-I as in the heart, there was upregulation of farnesyltransferase α at 16 and 25 weeks of age and of farnesyltransferase β in 25-weeks-old SHR. Western blot demonstrated overexpression of HMGR and downregulation of SQS in SHR livers at all ages tested.

CONCLUSIONS

The cardiovascular remodeling of SHR preceded the development of hypertension, and altered expression of several key enzymes in the mevalonate pathway may play a potential pathophysiological role in cardiovascular remodeling.

Mechanics and regulation of cell shape during the cell cycle

Many cell types undergo dramatic changes in shape throughout the cell cycle. For individual cells, a tight control of cell shape is crucial during cell division, but also in interphase, for example during cell migration. Moreover, cell cycle-related cell shape changes have been shown to be important for tissue morphogenesis in a number of developmental contexts. Cell shape is the physical result of cellular mechanical properties and of the forces exerted on the cell. An understanding of the causes and repercussions of cell shape changes thus requires knowledge of both the molecular regulation of cellular mechanics and how specific changes in cell mechanics in turn effect global shape changes. In this chapter, we provide an overview of the current knowledge on the control of cell morphology, both in terms of general cell mechanics and specifically during the cell cycle.

Chronic treatment with PDGF-BB and endothelin-1 synergistically induces vascular hyperplasia and loss of contractility in organ-cultured rat tail artery

OBJECTIVE

In this study, we examined the synergistic effects of the two potent pathogenic factors, platelet-derived growth factor-BB (PDGF-BB) and endothelin-1 (ET-1) to induce vascular hyperplasia using ex vivo organ-culture system.

METHODS AND RESULTS

In organ-cultured rat tail arteries, concomitant treatment with 100 ng/ml PDGF-BB and 300 nM ET-1 for 4 days induced medial hyperplasia with increased smooth muscle cell proliferation. Concomitant treatment with PDGF-BB (10-300 nM) and ET-1 (30 nM-1 μM) dose-dependently suppressed contractile responses to high K(+) and norepinephrine. This dyscontractility was accompanied by decreased α-actin protein expression. In all series of experiments, concomitant treatment with PDGF-BB and ET-1 exhibited stronger effects than sole treatment with PDGF-BB (100 ng/ml) or ET-1 (300 nM). Western blot analysis revealed that concomitant treatment with PDGF-BB and ET-1 synergistically phosphorylated extracellular signal-regulated kinase 1 and 2 (ERK1/2), Akt, and a downstream target of mammalian target of rapamycin (mTOR), p70 ribosomal S6 kinase in cultured artery. Consistently, a MAPK/ERK kinase (MEK) inhibitor, PD98059 (30 μM), a phosphoinositide 3-kinase (PI3K) inhibitor, LY294002, and an mTOR inhibitor, rapamycin (30 nM), partially restored PDGF-BB and ET-1-induced hyperplastic changes.

CONCLUSIONS

We evidenced for the first time at tissue level that PDGF-BB and ET-1 synergistically accelerate vascular smooth muscle hyperplastic changes and lose its contractility, at least partially through ERK1/2, Akt, and mTOR activation.

Simvastatin inhibits glucose-stimulated vascular smooth muscle cell migration involving increased expression of RhoB and a block of Ras/Akt signal

BACKGROUND

Diabetic patients are at high risk to develop atherosclerotic cardiovascular disease and have a higher restenotic rate after percutaneous coronary intervention (PCI). Statins improve cardiovascular outcome and reduce restenosis after PCI by inhibiting proliferation and migration of vascular smooth muscle cells (VSMCs). But the effect of statins on diabetes without dyslipidemia was still not fully understood. Our previous study has demonstrated that simvastatin inhibits VSMC proliferation in high glucose status without dyslipidemia, inducing a G0/G1 phase cell cycle growth arrest by acting on multiple steps upstream of pRb, including inhibition of CDK2/4 expression and upregulation of p53, p21, p16, and p27.

METHOD

Following our previous study, we investigated the mechanism of simvastatin inhibition of VSMC migration in a diabetes-like model (A7r5 cells under high glucose conditions without dyslipidemia).

RESULTS

Under high glucose conditions, simvastatin dose-dependently inhibited VSMC migration, decreased PI3K/Akt pathway activity, reduced c-Raf and Ras expression, increased RhoB but not RhoA, Rac1, and Cdc2 expression, dose-dependently inhibited MMP-2, but not MMP-9, activity, and dose-dependently inhibited NF-κB activity.

CONCLUSION

The inhibition of VSMC migration under high glucose conditions was via two different pathways. The first pathway is mevalonate-related but not RhoA protein-related and involves suppression of Ras and PI3K/Akt signals. The second pathway is not mevalonate-related and involves increasing RhoB expression directly.

RhoA phosphorylation induces Rac1 release from guanine dissociation inhibitor alpha and stimulation of vascular smooth muscle cell migration

Although overactivation of RhoA is recognized as a common component of vascular disorders, the molecular mechanisms regulating RhoA activity in vascular smooth muscle cells (VSMC) are still unclear. We have previously shown that in VSMC, RhoA is phosphorylated on Ser188 by nitric oxide (NO)-stimulated cGMP-dependent kinase (PKG), which leads to RhoA-Rho kinase pathway inhibition. In this study, we showed that expression of phosphoresistant RhoA mutants prevented the stimulation of VSMC migration and adhesion induced by NO-PKG pathway activation. In contrast, under basal conditions, phosphomimetic RhoA mutants stimulated VSMC adhesion and migration through a signaling pathway requiring Rac1 and the Rho exchange factor Vav3. RhoA phosphorylation or phosphomimetic RhoA mutants induced Rac1 activation but did not activate Vav3. Indeed, phosphorylated RhoA or phosphomimetic mutants trapped guanine dissociation inhibitor α (GDIα), leading to the release of Rac1 and its translocation to the membrane, where it was then activated by the basal Vav3 nucleotide exchange activity. In vivo, RhoA phosphorylation induced by PKG activation in the aortas of rats treated with sildenafil induced dissociation of Rac1 from GDIα and activation of the Rac1 signaling pathway. These results suggest that the phosphorylation of RhoA represents a novel potent and physiological GDIα displacement factor that leads to Rac1 activation and regulation of Rac1-dependent VSMC functions.

Revisited and revised: is RhoA always a villain in cardiac pathophysiology?

The neonatal rat ventricular myocyte model of hypertrophy has provided tremendous insight with regard to signaling pathways regulating cardiac growth and gene expression. Many mediators thus discovered have been successfully extrapolated to the in vivo setting, as assessed using genetically engineered mice and physiological interventions. Studies in neonatal rat ventricular myocytes demonstrated a role for the small G-protein RhoA and its downstream effector kinase, Rho-associated coiled-coil containing protein kinase (ROCK), in agonist-mediated hypertrophy. Transgenic expression of RhoA in the heart does not phenocopy this response, however, nor does genetic deletion of ROCK prevent hypertrophy. Pharmacologic inhibition of ROCK has effects most consistent with roles for RhoA signaling in the development of heart failure or responses to ischemic damage. Whether signals elicited downstream of RhoA promote cell death or survival and are deleterious or salutary is, however, context and cell-type dependent. The concepts discussed above are reviewed, and the hypothesis that RhoA might protect cardiomyocytes from ischemia and other insults is presented. Novel RhoA targets including phospholipid regulated and regulating enzymes (Akt, PI kinases, phospholipase C, protein kinases C and D) and serum response element-mediated transcriptional responses are considered as possible pathways through which RhoA could affect cardiomyocyte survival.

UTP controls cell surface distribution and vasomotor activity of the human P2Y2 receptor through an epidermal growth factor receptor-transregulated mechanism

Extracellular nucleotides transmit signals into the cells through the P2 family of cell surface receptors. These receptors are amply expressed in human blood vessels and participate in vascular tone control; however, their signaling mechanisms remain unknown. Here we show that in smooth muscle cells of isolated human chorionic arteries, the activation of the P2Y(2) receptor (P2Y(2)R) induces not only its partition into membrane rafts but also its rapid internalization. Cholesterol depletion with methyl-beta-cyclodextrin reduced the association of the agonist-activated receptor into membrane rafts but did not affect either the UTP-mediated vasoconstrictions or the vasomotor responses elicited by both serotonin and KCl. Ex vivo perfusion of human chorionic artery segments with 1-10 mum UTP, a selective P2Y(2)R agonist, displaced the P2Y(2)R localization into membrane rafts within 1 min, a process preceded by the activation of both RhoA and Rac1 GTPases. AG1478, a selective and potent inhibitor of the epidermal growth factor receptor tyrosine kinase activity, not only blocked the UTP-induced vasomotor activity but also abrogated both RhoA and Rac1 activation, the P2Y(2)R association with membrane rafts, and its internalization. Altogether, these results show for the first time that the plasma membrane distribution of the P2Y(2)R is transregulated by the epidermal growth factor receptor, revealing an unsuspected functional interplay that controls both the membrane distribution and the vasomotor activity of the P2Y(2)R in intact human blood vessels.

Rho kinase: an important mediator of atherosclerosis and vascular disease

Atherosclerosis is a complex inflammatory process characterized by the cross-talk between excessive inflammation and lipid accumulation. In the past few years, compelling evidence suggests that statins can decrease vascular inflammation and attenuate the development of atherosclerosis through their so-called "pleiotropic effects". These cholesterol-independent effects are predominantly due to their ability to inhibit isoprenoid synthesis. In particular, inhibition of geranylgeranylpyrophosphate synthesis leads to inhibition of Rho and its downstream target, Rho-kinase (ROCK). Thus, one of the beneficial effects of statin therapy could be due to inhibitory effects on ROCK. ROCK is involved in mediating diverse cellular functions such as smooth muscle contraction, cell migration and proliferation. While increased ROCK activity is associated with endothelial dysfunction, cerebral ischemia, coronary vasospasms and metabolic syndrome, the inhibition of ROCK by statins or selective ROCK inhibitors leads to up-regulation of endothelial nitric oxide synthase (eNOS), decreased vascular inflammation, and reduced atherosclerotic plaque formation. This review will focus on the impact of ROCK in cardiovascular disease and its contributory role to vascular inflammation and the atherosclerosis.

Cyclic GMP kinase and RhoA Ser188 phosphorylation integrate pro- and antifibrotic signals in blood vessels

Vascular fibrosis is a major complication of hypertension and atherosclerosis, yet it is largely untreatable. Natriuretic peptides (NPs) repress fibrogenic activation of vascular smooth muscle cells (VSMCs), but the intracellular mechanism mediating this effect remains undetermined. Here we show that inhibition of RhoA through phosphorylation at Ser188, the site targeted by the NP effector cyclic GMP (cGMP)-dependent protein kinase I (cGK I), is critical to fully exert antifibrotic potential. cGK I(+/-) mouse blood vessels exhibited an attenuated P-RhoA level and concurrently increased RhoA/ROCK signaling. Importantly, cGK I insufficiency caused dynamic recruitment of ROCK into the fibrogenic programs, thereby eliciting exaggerated vascular hypertrophy and fibrosis. Transgenic expression of cGK I-unphosphorylatable RhoA(A188) in VSMCs augmented ROCK activity, vascular hypertrophy, and fibrosis more prominently than did that of wild-type RhoA, consistent with the notion that RhoA(A188) escapes the intrinsic inhibition by cGK I. Additionally, VSMCs expressing RhoA(A188) became refractory to the antifibrotic effects of NPs. Our results identify cGK I-mediated Ser188 phosphorylation of RhoA as a converging node for pro- and antifibrotic signals and may explain how diminished cGMP signaling, commonly associated with vascular malfunction, predisposes individuals to vascular fibrosis.