摘要:

The vascular endothelial growth factor receptor Flk-1/KDR is highly expressed during development and almost disappears in adult tissues. Despite its biological relevance, little is known about the molecular mechanisms controlling its expression. In the present work, it is shown that cAMP response element binding protein (CREB) and nuclear factor-&kgr;B (NF-&kgr;B)–related antigens bind specific sequences in the Flk-1/KDR promoter. Functional studies demonstrate that cAMP represses whereas tumor necrosis factor-&agr;, an activator of NF-&kgr;B, stimulates promoter activity. Histone acetyltransferases (HATs) P/CAF and CBP/p300 together with p65/RelA, the catalytic subunit of NF-&kgr;B, increase Flk-1/KDR promoter activity 10- to 20-fold. Consistently, inhibition by cAMP is reverted by increasing intracellular HATs and is completely abolished by site-specific mutagenesis of the cAMP response element. In contrast, specific mutations in the NF-&kgr;B response element abolish responsiveness to p65/RelA and HATs without affecting cAMP-dependent repression. These results suggest that opposing signaling pathways, activating NF-&kgr;B or CREB and requiring HAT molecules, control Flk-1/KDR promoter activity. The full text of this article is available at http://www.circresaha.org. (Circ Res. 2000;86:e110-e117.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Connexins, the protein molecules forming gap junction channels, are reduced in number or redistributed from intercalated disks to lateral cell borders in a variety of cardiac diseases. This “gap junction remodeling” is considered to be arrhythmogenic. Using a simple model of human ventricular myocardium, we found that quantitative remodeling data extracted from the literature gave rise to only small to moderate changes in conduction velocity and the anisotropy ratio. Especially for longitudinal conduction, cytoplasmic resistivity (and thus cellular geometry) is much more important than commonly realized. None of the remodeling data gave rise to slow conduction on the order of a few centimeters per second. (Circ Res. 2000;86:1193-1197.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Preclinical studies in animal models and early results of clinical trials in patients suggest that intramuscular injection of naked plasmid DNA encoding vascular endothelial growth factor (VEGF) can promote neovascularization of ischemic tissues. Such neovascularization has been attributed exclusively to sprout formation of endothelial cells derived from preexisting vessels. We investigated the hypothesis that VEGF gene transfer may also augment the population of circulating endothelial progenitor cells (EPCs). In patients with critical limb ischemia receiving VEGF gene transfer, gene expression was documented by a transient increase in plasma levels of VEGF. A culture assay documented a significant increase in EPCs (219%,P<0.001), whereas patients who received an empty vector had no change in circulating EPCs, as was the case for volunteers who received saline injections (VEGF versus empty vector,P<0.001; VEGF versus saline,P<0.005). Fluorescence-activated cell sorter analysis disclosed an overall increase of up to 30-fold in endothelial lineage markers KDR (VEGF receptor-2), VE-cadherin, CD34, &agr;v&bgr;3, and E-selectin after VEGF gene transfer. Constitutive overexpression of VEGF in patients with limb ischemia augments the population of circulating EPCs. These findings support the notion that neovascularization of human ischemic tissues after angiogenic growth factor therapy is not limited to angiogenesis but involves circulating endothelial precursors that may home to ischemic foci and differentiate in situ through a process of vasculogenesis. (Circ Res. 2000;86:1198-1202.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Atherosclerotic lesions can be induced in rabbits and mice immunized with heat shock protein 65 (HSP65). In the current study, we investigated the role of interleukin (IL)-4 in the HSP65- andMycobacterium tuberculosis(MT)–induced models that exhibit an inflammatory phenotype. Fatty streak formation in IL-4–knockout (IL-4 KO) mice immunized with HSP65 or MT was significantly reduced when compared with lesions in wild-type C57BL/6 mice. However, when injected with control (HSP-free) adjuvant, no differences were evident in the lesion size between wild-type and the IL-4 KO mice. Next, we studied comparatively the extent of humoral and cellular immune responses to HSP65 in the IL-4 KO and wild-type mice, as those are thought to be influential in murine atherosclerosis. Anti-HSP65 antibody levels were reduced in the HSP65-immunized IL-4 KO mice as compared with their wild-type littermates, whereas no differences were evident between the groups with respect to the primary cellular immune response to HSP65. Other than the absence of IL-4 in the knockout mice, the pattern of secreting cytokines interferon-&ggr; and IL-10 in concanavalin A–primed splenocytes was similar between the groups. HSP65-primed inguinal lymphocytes from IL-4 KO mice immunized with HSP65 secreted higher levels of interferon-&ggr; (previously shown to be proatherogenic in vivo) as compared with their wild-type controls. 12-/15-Lipoxygenase expression, known to be regulated by IL-4 and to contribute to murine atherosclerosis, in the lesions was not influenced by the immunization protocol used or by IL-4 disruption. Thus, IL-4 may prove a principal cytokine in the progression of early “inflammatory” atherosclerotic lesions and may serve as a target for immunomodulation. (Circ Res. 2000;86:1203-1210.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

To investigate the kinetic parameters of the crossbridge cycle that regulate force and shortening in cardiac muscle, we compared the mechanical properties of cardiac trabeculae with either ATP or 2-deoxy-ATP (dATP) as the substrate for contraction. Comparisons were made in trabeculae from untreated rats (predominantly V1 myosin) and those treated with propylthiouracil (PTU; V3 myosin). Steady-state hydrolytic activity of cardiac heavy meromyosin (HMM) showed that PTU treatment resulted in >40% reduction of ATPase activity. dATPase activity was >50% elevated above ATPase activity in HMM from both untreated and PTU-treated rats.Vmaxof actin-activated hydrolytic activity was also >50% greater with dATP, whereas theKmfor dATP was similar to that for ATP. This indicates that dATP increased the rate of crossbridge cycling in cardiac muscle. Increases in hydrolytic activity were paralleled by increases of 30% to 80% in isometric force (Fmax), rate of tension redevelopment (ktr), and unloaded shortening velocity (Vu) in trabeculae from both untreated and PTU-treated rats (at maximal Ca2+activation), and F-actin sliding speed in an in vitro motility assay (Vf). These results contrast with the effect of dATP in rabbit psoas and soleus fibers, where Fmaxis unchanged even thoughktr,Vu, andVfare increased. The substantial enhancement of mechanical performance with dATP in cardiac muscle suggests that it may be a better substrate for contractility than ATP and warrants exploration of ribonucleotide reductase as a target for therapy in heart failure. (Circ Res. 2000;86:1211-1217.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

To test the hypothesis that activation of the protein kinase C (PKC) &egr; isoform leads to cardiac hypertrophy without failure, we studied transgenic mice with cardiac-specific overexpression of a constitutively active mutant of the PKC&egr; isoform driven by an &agr;–myosin heavy chain promoter. In transgenic mice, the protein level of PKC&egr; in heart tissue was increased 9-fold. There was a 6-fold increase of the membrane/cytosol ratio, and PKC activity in the membrane fraction was 4.2-fold compared with wild-type mice. The heart weight was increased by 28%, and upregulation of the mRNA for &bgr;-myosin heavy chain and &agr;-skeletal actin was observed in transgenic mouse hearts. Echocardiography demonstrated increased anterior and posterior wall thickness with normal left ventricular function and dimensions, indicating concentric cardiac hypertrophy. Isolated cardiomyocyte mechanical function was slightly decreased, and Ca2+signals were markedly depressed in transgenic mice, suggesting that myofilament sensitivity to Ca2+was increased. No differences were observed in either the levels of cardiac Ca2+-handling proteins or the degree of cardiac regulatory protein phosphorylation between wild-type and transgenic mice. Unlike mice with PKC&bgr;2overexpression, transgenic mice with cardiac-specific overexpression of the active PKC&egr; mutant demonstrated concentric hypertrophy with normal in vivo cardiac function. Thus, PKC isoforms may play differential functional roles in cardiac hypertrophy and failure. (Circ Res. 2000;86:1218-1223.)

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID