摘要:

Abstract—Cyclooxygenase (COX) is a prostanoid-synthesizing enzyme present in 2 isoforms: COX-1 and COX-2. Although it has long been hypothesized that prostanoids participate in cerebrovascular regulation, the lack of adequate pharmacological tools has led to conflicting results and has not permitted investigators to define the relative contribution of COX-1 and COX-2. We used the COX-1 inhibitor SC-560 and COX-1-null (COX-1−/−) mice to investigate whether COX-1 plays a role in cerebrovascular regulation. Mice were anesthetized (urethane and chloralose) and equipped with a cranial window. Cerebral blood flow (CBF) was measured by laser Doppler flowmetry or by the14C-iodoantipyrine technique with quantitative autoradiography. In wild-type mice, SC-560 (25 &mgr;mol/L) reduced resting CBF by 21±4% and attenuated the CBF increase produced by topical application of bradykinin (−59%) or calcium ionophore A23187 (−49%) and by systemic hypercapnia (−58%) (P<0.05 to 0.01). However, SC-560 did not reduce responses to acetylcholine or the increase in somatosensory cortex blood flow produced by vibrissal stimulation. In COX-1−/−mice, resting CBF assessed by14C-iodoantipyrine was reduced (−13% to −20%) in cerebral cortex and other telencephalic regions (P<0.05). The CBF increase produced by bradykinin, A23187, and hypercapnia, but not acetylcholine or vibrissal stimulation, were attenuated (P<0.05 to 0.01). The free radical scavenger superoxide dismutase attenuated responses to bradykinin and A23187 in wild-type mice but not in COX-1−/−mice, suggesting that COX-1 is the source of the reactive oxygen species known to mediate these responses. The data provide evidence for a critical role of COX-1 in maintaining resting vascular tone and in selected vasodilator responses of the cerebral microcirculation.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—Hearts of wild-type and insulin-like growth factor-1 overexpressing (Igf-1+/−) transgenic mice were subjected to Langendorff perfusions and progressive periods of ischemia followed by reperfusion. Apoptosis was measured by DNA nucleosomal cleavage and a hairpin probe labeling assay to detect single-base overhang. Transgenic hearts subjected to 20 minutes of ischemia and 4 hours of reperfusion (I/R) sustained a rate of apoptosis of 1.8±0.3% compared with 4.6±1.1% for wild-type controls (n=4;P<0.03). Phosphorylation of the protein kinase Akt/protein kinase B was elevated 6.2-fold in transgenic hearts at baseline and increased another 4.4-fold within 10 minutes of reperfusion, remaining elevated for up to 2 hours. I/R activated Akt in wild-type hearts but to a lesser extent (1.6±0.3-fold). Pretreatment of transgenic hearts with wortmannin immediately before and during ischemia eliminated reperfusion-mediated activation of Akt and neutralized the resistance to apoptosis. The stress-activated kinase p38 was also activated during ischemia and reperfusion in both wild-type and transgenic hearts. Perfusion with the p38 inhibitor SB203580 (10 &mgr;mol/L) blocked both p38 activation and phosphorylation of Akt and differentially modulated apoptosis in wild-type and transgenic hearts. Pretreatment with SB203580 reduced apoptosis in wild-type hearts but increased apoptosis in transgenic hearts. These results demonstrate that Akt phosphorylation during I/R is modulated by IGF-1 and prevents apoptosis in hearts that overexpress the IGF-1 transgene.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—During the development of an atherosclerotic plaque, mononuclear leukocytes infiltrate the artery wall through vascular endothelial cells (ECs). At the same time, arterial smooth muscle cells (SMCs) change from the physiological contractile phenotype to the secretory phenotype and migrate into the plaque. We investigated whether secretory SMCs released cytokines that stimulated ECs in a manner leading to increased leukocyte recruitment and thus might accelerate atheroma formation. SMCs and ECs were established in coculture on the opposite sides of a porous membrane, and the cocultured cells were incorporated into a flow-based assay for studying leukocyte adhesion. We found that coculture primed ECs so that their response to the inflammatory cytokine tumor necrosis factor-&agr; was amplified. ECs cocultured with SMCs supported greatly increased adhesion of flowing leukocytes and were sensitized to respond to tumor necrosis factor-&agr; at concentrations 10 000 times lower than ECs cultured alone. In addition, coculture altered the endothelial selectin adhesion molecules used for leukocyte capture. EC priming was attributable to the cytokine transforming growth factor-&bgr;1, which was proteolytically activated to a biologically active form by the serine protease plasmin. These results suggest a new role for secretory SMCs in the development of atheromatous plaque. We propose that paracrine interaction between ECs and SMCs has the potential to amplify leukocyte recruitment to sites of atheroma and exacerbate the inflammatory processes believed to be at the heart of disease progression.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

The growth of blood and lymphatic vasculature is mediated in part by secreted polypeptides of the vascular endothelial growth factor (VEGF) family. The prototype VEGF binds VEGF receptor (VEGFR)-1 and VEGFR-2 and is angiogenic, whereas VEGF-C, which binds to VEGFR-2 and VEGFR-3, is either angiogenic or lymphangiogenic in different assays. We used an adenoviral gene transfer approach to compare the effects of these growth factors in adult mice. Recombinant adenoviruses encoding human VEGF-C or VEGF were injected subcutaneously into C57Bl6 mice or into the ears of nude mice. Immunohistochemical analysis showed that VEGF-C upregulated VEGFR-2 and VEGFR-3 expression and VEGF upregulated VEGFR-2 expression at 4 days after injection. After 2 weeks, histochemical and immunohistochemical analysis, including staining for the lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), the vascular endothelial marker platelet-endothelial cell adhesion molecule-1 (PECAM-1), and the proliferating cell nuclear antigen (PCNA) revealed that VEGF-C induced mainly lymphangiogenesis in contrast to VEGF, which induced only angiogenesis. These results have significant implications in the planning of gene therapy using these growth factors.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—The platelet-derived growth factor (PDGF) ligands and their receptors have been implicated as critical regulators of the formation of arterial lesions after tissue injury. SU9518 (3[5-{5-bromo-2-oxo-1,2-dihydroindol-3-ylidenemethyl}-2,4-dimethyl-1H-pyrrol-3-yl]propionic acid) is a novel synthetic indolinone that potently and selectively inhibits the cellular PDGF receptor kinase and PDGF receptor-induced cell proliferation. Inhibition of PDGF receptor phosphorylation in cell-based assays occurs within 5 minutes after drug exposure and persists for >6 hours after drug removal. The pharmacokinetics indicate plasma levels that exceeded the effective concentration required to inhibit the PDGF receptor in cells for up to 8 hours or 7 days after a single oral or subcutaneous administration, respectively. In the rat balloon arterial injury-induced stenosis model, once-daily oral or once-weekly subcutaneous administration of SU9518 reduced intimal thickening of the carotid artery (ratio of neointimal to medial area, 1.94±0.38 versus 1.03±0.29 [P<0.01] 2.21±0.32 versus 1.34±0.45 [P<0.01], respectively). These studies provide the rationale to evaluate PDGF receptor tyrosine kinase inhibitors, including inhibitors related to the indolinone, SU9518, for the treatment of arterial restenosis.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—Retinoids are derivatives of vitamin A and powerful inhibitors of cell proliferation and inflammation. Angiotensin II (Ang II) contributes to vascular lesions by promoting cell growth of vascular smooth muscle cells (VSMCs). Therefore, we examined whether retinoids interfere with the proproliferative actions of Ang II in VSMCs via AT1receptor-dependent or activator protein-1 (AP-1)-dependent mechanisms. VSMCs express retinoid receptor proteins, ie, retinoic acid receptor (RAR) &agr; and retinoid X receptor (RXR) &agr;. Long-term exposure to 1 &mgr;mol/L all-transretinoic acid (RA) dose-dependently inhibited Ang II-induced cell proliferation (P<0.005) as well as DNA and protein synthesis (P<0.001). All-transRA blocked Ang II stimulation of transforming growth factor-&bgr;1mRNA (P<0.005). All-transRA inhibition of vascular VSMC growth was mediated both via RAR- and RXR-dependent pathways, as shown by receptor-specific synthetic retinoids. Transfection experiments revealed that inhibition of AP-1-dependent gene transcription is one mechanism by which all-transRA inhibits Ang II action. RAR&agr; cotransfection enhanced the anti-AP-1 effects of all-transRA dose-dependently. AP-1 activity was similarly inhibited by cotransfection with either RAR&agr; or RXR&agr;. Ang II-induced gene expression of c-fos was abrogated by all-transRA treatment (P<0.005). In VSMCs, all-transRA downregulated AT1receptor mRNA (P<0.01) and reduced Bmax(P<0.001). All-transRA repressed Ang II-stimulated AT1receptor promoter activity. The all-transRA inhibitory effect was abolished when the AP-1 consensus site on the AT1receptor promoter was deleted. Our findings demonstrate that retinoids are potent inhibitors of the actions of Ang II on VSMCs. The findings support the notion that retinoids may interfere with proliferative vascular disease.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID