摘要:

Integrins link the extracellular matrix to the cellular cytoskeleton and serve important roles in cell growth, differentiation, migration, and survival. Ablation of &bgr;1 integrin in all murine tissues results in peri-implantation embryonic lethality. To investigate the role of &bgr;1 integrin in the myocardium, we used Cre-LoxP technology to inactivate the &bgr;1 integrin gene exclusively in ventricular cardiac myocytes. Animals with homozygous ventricular myocyte &bgr;1 integrin gene excision were born in appropriate numbers and grew into adulthood. These animals had 18% of control levels of &bgr;1D integrin protein in the heart and displayed myocardial fibrosis. High-fidelity micromanometer-tipped catheterization of the intact 5-week-old &bgr;1 integrin knockout mice showed depressed left ventricular basal and dobutamine-stimulated contractility and relaxation (LV dP/dtmaxand LV dP/dtmin) as compared with control groups (n=8 to 10 of each,P<0.01). Hemodynamic loading imposed by 7 days of transverse aortic constriction showed that the &bgr;1 integrin knockout mice were intolerant of this stress as they had 53% survival versus 88% in controls (n=15 each). By 6 months of age, mice with depressed ventricular expression of &bgr;1 integrin developed a dilated cardiomyopathy that was not evident in any control animals and had patchy decrease in glucose metabolism as determined by positron emission tomography. Myocyte membrane integrity as determined via Evan’s blue dye staining was disrupted in the &bgr;1 integrin knockout mice. This model provides strong evidence for the importance of &bgr;1 integrin in cardiac form and function and indicates that integrins can be linked to development of cardiomyopathies.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Activation of protease-activated receptor (PAR)-2 has been proposed to be protective in myocardial ischemia/reperfusion (I/R) injury, an effect possibly related to an action on the coronary vasculature. Therefore, we investigated the effects of PAR2 activation on coronary tone in isolated perfused rat hearts and elucidated the mechanisms of any observed effects. Although having a negligible effect on ventricular contractility, the PAR2 activating peptide SLIGRL produced an endothelium-dependent coronary vasodilatation (ED50=3.5 nmol). Following I/R injury, the response to SLIGRL was selectively preserved, whereas the dilator response to acetylcholine was converted to constriction. Trypsin also produced a vasodilator dose-response curve that was biphasic in nature (ED50-1=0.36 U, ED50-2=38.71 U). Desensitization of PAR2 receptors indicated that the high potency phase was mediated by PAR2. Removal of the endothelium but not treatment with L-NAME (300 &mgr;mol/L), indomethacin (5 &mgr;mol/L), or oxyhemoglobin (10 &mgr;mol/L) inhibited the response to SLIGRL and trypsin. Treatment with the K+-channel blockers TEA (10 mmol/L), charybdotoxin (20 nmol/L)/apamin (100 nmol/L), or elevated potassium (20 mmol/L) significantly suppressed responses. Similarly, inhibition of lipoxygenase with nordihydroguaiaretic acid (1 &mgr;mol/L), eicosatetraynoic acid (1 &mgr;mol/L), or baicalein (10 &mgr;mol/L), desensitization of C-fibers using capsaicin (1 &mgr;mol/L, 20 minutes), or blockade of vanilloid (VR1) receptors using capsazepine (3 &mgr;mol/L) inhibited the responses. This study shows, for the first time, that PAR2 activation causes endothelium-dependent coronary vasodilation that is preserved after I/R injury and is not mediated by NO or prostanoids, but involves the release of an endothelium-derived hyperpolarizing factor (EDHF), possibly a lipoxygenase-derived eicosanoid, and activation of VR1 receptors on sensory C-fibers.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

A pathway for the regulation of vascular tone appears to involve coupling between integrins and extracellular matrix proteins or their fragments and the subsequent modulation of ion movement across the smooth muscle cell membrane. Here, we report that the activation of L-type voltage-activated Ca2+channels occurs through a novel interaction of &agr;4&bgr;1integrin with peptides containing the Leu-Asp-Val (LDV) integrin–binding sequence, which is found in the CS-1 region of an alternately spliced fibronectin variant. Experiments were conducted on arterioles isolated from rat skeletal muscle. Arterioles exhibited sustained concentration-dependent vasoconstriction to LDV peptides but not to Leu-Glu-Val (LEV) control peptides. The constriction was associated with increased smooth muscle cell [Ca2+]i, as measured by using fura 2. The response could be inhibited with a function-blocking anti–&agr;4integrin antibody. Removal of the endothelium did not alter the vasoconstrictor response. Further experiments demonstrated that the vasoconstriction was abolished by the L-type Ca2+channel inhibitor nifedipine and the Src family kinase inhibitor PP2. In studies of isolated smooth muscle cells using whole-cell patch-clamp methods, the L-type current was enhanced by the LDV but not LEV peptide and was blocked by PP2 or antibodies to &agr;4integrin. Collectively, these data indicate that activation of &agr;4&bgr;1integrin leads to enhanced influx of Ca2+through L-type channels by activating a tyrosine kinase pathway, leading to vasoconstriction. Involvement of integrins in the modulation of vascular tone may be particularly important in vascular responses to mechanical signals, such as pressure and flow, and to tissue injury after damage to the extracellular matrix.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Versican is an extracellular matrix (ECM) proteoglycan that is synthesized as multiple splice variants. In a recent study, we demonstrated that retroviral-mediated overexpression of the variant V3, which lacks chondroitin sulfate (CS) chains, altered arterial smooth muscle cell (ASMC) phenotype in short-term cell culture. We now report that V3-overexpressing ASMCs exhibit significantly increased expression of tropoelastin and increased formation of elastic fibers in long-term cell cultures. In addition, V3-overexpressing ASMCs seeded into ballooned rat carotid arteries continued to overexpress V3 and, at 4 weeks after seeding, produced a highly structured neointima significantly enriched in elastic fiber lamellae. In contrast to the hydrated, myxoid neointima produced by rounded or stellate vector-alone–transduced cells, V3-expressing cells produced a compact and highly ordered neointima, which contained elongated ASMCs that were arranged in parallel arrays and separated by densely packed collagen bundles and elastic fibers. These results indicate that a variant of versican is involved in elastic fiber assembly and may represent a novel therapeutic approach to facilitate the formation of elastic fibers.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

A central role for leukocytes in neointimal hyperplasia after arterial injury is suspected. However, the relative importance of neutrophils and monocytes in balloon or stent-induced injury are not well understood, and mechanistic targeting of leukocyte recruitment or function is crude. We determined the temporal and spatial distribution of different leukocytes after balloon and stent-induced injury in primate iliac arteries. Based on these data, we targeted neutrophil and monocyte recruitment selectively after angioplasty or stent implantation and demonstrated that monocyte-specific blockade achieved via blockade of the MCP-1 receptor CCR2, was effective at reducing neointimal hyperplasia after stenting. In contrast, combined neutrophil and monocyte blockade achieved by targeting the leukocyte &bgr;2-integrin &bgr;-subunit CD18 was required to reduce neointimal hyperplasia after balloon injury. Distinct patterns of leukocyte infiltration in balloon versus stent-injured arteries predict distinct mechanisms for antiinflammatory strategies targeting neutrophils or monocytes in primates and may assist design of effective clinical strategies for optimizing vascular interventions.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Angiotensin II infusion causes endothelial dysfunction by increasing NAD(P)H oxidase-mediated vascular superoxide production. However, it remains to be elucidated how in vivo angiotensin II treatment may alter the expression of the gp91phoxisoforms and the endothelial nitric oxide synthase (NOS III) and subsequent signaling events and whether, in addition to the NAD(P)H oxidase, NOS III contributes to vascular superoxide formation. We therefore studied the influence of in vivo angiotensin II treatment (7 days) in rats on endothelial function and on the expression of the NAD(P)H oxidase subunits p22phox, nox1, nox4, and gp91phoxand NOS III. Further analysis included the expression of NO-downstream targets, the soluble guanylyl cyclase (sGC), the cGMP-dependent protein kinase I (cGK-I), and the expression and phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) at Ser239 (P-VASP). Angiotensin II caused endothelial dysfunction and increased vascular superoxide. Likewise, we found an increase in vascular protein kinase C (PKC) activity, in the expression of nox1 (6- to 7-fold), gp91phox(3-fold), p22phox(3-fold), NOS III mRNA, and protein. NOS-inhibition withNG-nitro-l-arginine decreased superoxide in vessels from angiotensin II-treated animals, compatible with NOS-uncoupling. Vascular NO assessed with electron paramagnetic resonance was markedly reduced. Likewise, a decrease in sGC-expression and P-VASP levels was found. In vivo PKC-inhibition with chelerythrine reduced angiotensin II-induced superoxide production and markedly inhibited upregulation of NAD(P)H oxidase subunits. We therefore conclude that angiotensin II-induced increases in the activity and the expression of NAD(P)H oxidase are at least in part PKC-dependent. NADPH oxidase-induced superoxide production may trigger NOS III uncoupling, leading to impaired NO/cGMP signaling and to endothelial dysfunction in this animal model. The full text of this article is available at http://www.circresaha.org.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID