摘要:

Angiogenesis is implicated in the pathogenesis of cancer, rheumatoid arthritis, and atherosclerosis and in the treatment of coronary artery and peripheral vascular disease. Here, cholesterol-lowering agents, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, are shown to interfere with angiogenesis. In vivo, the HMG-CoA reductase inhibitor simvastatin dose-dependently inhibited capillary growth in both vascular endothelial growth factor–stimulated chick chorioallantoic membranes and basic fibroblast growth factor–stimulated mouse corneas. In vitro, the development of tubelike structures by human microvascular endothelial cells cultured on 3D collagen gels was inhibited at simvastatin concentrations similar to those found in the serum of patients on therapeutic doses of this agent. HMG-CoA reductase inhibitors interfered with angiogenesis via inhibition of the geranylgeranylation and membrane localization of RhoA. Simvastatin inhibited membrane localization of RhoA with a concentration dependence similar to that for the inhibition of tube formation, whereas geranylgeranyl pyrophosphate, the substrate for the geranylgeranylation of Rho, reversed the effect of simvastatin on tube formation and on the membrane localization of RhoA. Furthermore, tube formation was inhibited by GGTI, a specific inhibitor of the geranylgeranylation of Rho; by C3 exotoxin, which inactivates Rho; and by the adenoviral expression of a dominant-negative RhoA mutant. The expression of a dominant-activating RhoA mutant reversed the effect of simvastatin on tube formation. Finally, HMG-CoA reductase inhibitors inhibited signaling by vascular endothelial growth factor, Akt, and focal adhesion kinase, three RhoA-dependent pathways known to be involved in angiogenesis. This study demonstrates a new relationship between lipid metabolism and angiogenesis and an antiangiogenic effect of HMG-CoA reductase inhibitors with possible important therapeutic implications.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Sphingosine 1-phosphate (S1P), a lipid released from activated platelets, influences physiological processes in the cardiovascular system via activation of the endothelial differentiation gene (EDG/S1P) family of 7 transmembrane G protein–coupled receptors. In cultured vascular smooth muscle (VSM) cells, S1P signaling has been shown to stimulate proliferative responses; however, its role in vasoconstriction has not been examined. In the present study, the effects of S1P and EDG/S1P receptor expression were determined in rat VSM from cerebral artery and aorta. S1P induced constriction of cerebral artery, which was partly dependent on activation of p160ROCK(Rho-kinase). S1P also induced activation of RhoA in cerebral artery with a similar time course to contraction. In aorta, S1P did not produce a constriction or RhoA activation. In VSM myocytes from cerebral arteries, stimulation with S1P gives rise to a global increase in [Ca2+]i, initially generated via Ca2+release from the sarcoplasmic reticulum by an inositol 1,4,5-trisphosphate–dependent pathway. In aorta VSM, a small increase in [Ca2+]iwas observed after stimulation at higher concentrations of S1P. S1P induced activation of p42/p44mapkin aorta and cerebral artery VSM. Subtype-specific S1P receptor antibodies revealed that the expression of S1P3/EDG-3 and S1P2/EDG-5 receptors is 4-fold higher in cerebral artery compared with aorta. S1P1/EDG-1 receptor expression was similar in both types of VSM. Therefore, the ability of S1P to act as a vasoactive mediator is dependent on the activation of associated signaling pathways and may vary in different VSM. This differential signaling may be related to the expression of S1P receptor subtypes.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Perlecan is a heparan-sulfate proteoglycan abundantly expressed in pericellular matrices and basement membranes during development. Inactivation of the perlecan gene in mice is lethal at two developmental stages: around E10 and around birth. We report a high incidence of malformations of the cardiac outflow tract in perlecan-deficient embryos. Complete transposition of great arteries was diagnosed in 11 out of 15 late embryos studied (73%). Three of these 11 embryos also showed malformations of semilunar valves. Mesenchymal cells in the outflow tract were abnormally abundant in mutant embryos by E9.5, when the endocardial-mesenchymal transformation starts in wild-type embryos. At E10.5, mutant embryos lacked well-defined spiral endocardial ridges, and the excess of mesenchymal cells obstructed sometimes the outflow tract lumen. Most of this anomalous mesenchyme expressed the smooth muscle cell-specific &agr;-actin isoform, a marker of the neural crest in the outflow tract of the mouse. In wild-type embryos, perlecan is present in the basal surface of myocardium and endocardium, as well as surrounding presumptive neural crest cells. We suggest that the excess of mesenchyme at the earlier stages of conotruncal development precludes the formation of the spiral ridges and the rotation of the septation complex in order to achieve a concordant ventriculoarterial connection. The observed mesenchymal overpopulation might be due to an uncontrolled migration of neural crest cells, which would arrive prematurely to the heart. Thus, perlecan is involved in the control of the outflow tract mesenchymal population size, underscoring the importance of the extracellular matrix in cardiac morphogenesis.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We used a genetic approach to determine whether increasing the level of A3adenosine receptors (A3ARs) expressed in the heart confers protection against ischemia without causing cardiac pathology. We generated mice carrying one (A3tg.1) or six (A3tg.6) copies of a transgene consisting of the cardiomyocyte-specific &agr;-myosin heavy chain gene promoter and the A3AR cDNA. A3tg.1 and A3tg.6 mice expressed 12.7±3.15 and 66.3±9.4 fmol/mg of the high-affinity G protein–coupled form of the A3AR in the myocardium, respectively. Extensive morphological, histological, and functional analyses demonstrated that there were no apparent abnormalities in A3tg.1 transgenic mice compared with nontransgenic mice. In contrast, A3tg.6 mice exhibited dilated hearts, expression of markers of hypertrophy, bradycardia, hypotension, and systolic dysfunction. When A3tg mice were subjected to 30 minutes of coronary occlusion and 24 hours of reperfusion, infarct size was reduced ≈30% in A3tg.1 mice and ≈40% in A3tg.6 mice compared with nontransgenic littermates. The reduction in infarct size in the transgenic mice was not related to differences in risk region size, systemic hemodynamics, or body temperature, indicating that the cardioprotection was a result of increased A3AR signaling in the ischemic myocardium. The results demonstrate that low-level expression of A3ARs in the heart provides effective protection against ischemic injury without detectable adverse effects, whereas higher levels of A3AR expression lead to the development of a dilated cardiomyopathy.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) improve endothelial function. We determined whether withdrawal of statin therapy affects endothelium-dependent relaxation in mice and studied the underlying mechanism. Mice were treated with daily injections of cerivastatin (2 mg/kg per day SC), atorvastatin (1 and 10 mg/kg per day SC), or placebo. Vascular reactivity was studied in aortic rings from these mice after 10 days of treatment and after cessation of therapy for several days. Both statins improved endothelium-dependent relaxation to acetylcholine. Compared with control, withdrawal of statin treatment transiently (from day 4 to 7) attenuated endothelium-dependent relaxation. In vessels from animals subjected to atorvastatin withdrawal, the antioxidant tiron restored relaxations. Vascular superoxide anion generation was unaffected by statin therapy but was increased during withdrawal. In mice lacking the gp91phox subunit of the NADPH oxidase, no attenuation of acetylcholine-induced relaxation and no increase in superoxide generation were observed after withdrawal of atorvastatin. In human umbilical vein endothelial cells, statins, which decrease the membrane association of NADPH oxidase–activating Rac-1, increased the activity of this GTPase in whole-cell lysates. Withdrawal of statins induced a translocation of Rac-1 from the cytosol to the membrane and transiently increased NADPH-induced lucigenin chemiluminescence in membrane preparations. Rac-1 inactivation byClostridium difficiletoxin B inhibited the cerivastatin-induced oxygen radical production in human umbilical vein endothelial cells. These observations indicate that the withdrawal of statins induces endothelial dysfunction. The underlying mechanism involves activation of a gp91phox-containing NADPH oxidase by Rac-1 and the subsequent scavenging of endothelium-derived NO by superoxide anions generated from this enzyme.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID