ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—Primary pulmonary hypertension (PPH) is a disease of unknown etiology characterized by lumen-obliterating endothelial cell proliferation and vascular smooth muscle hypertrophy of the small precapillary pulmonary arteries. Because the vascular lesions are homogeneously distributed throughout the entire lung, we propose that a tissue fragment of the lung is representative of the whole lung. RNA extracted from the fragments is likely to provide meaningful information regarding the changes in gene expression pattern in PPH when compared with structurally normal lung tissue. We hypothesize that the lung tissue gene expression pattern of patients with PPH has a characteristic profile when compared with the gene expression pattern of structurally normal lungs and that this characteristic gene expression profile provides new insights into the pathobiology of PPH. Using oligonucleotide microarray technology, we characterized the expression pattern in the lung tissue obtained from 6 patients with primary pulmonary hypertension (PPH)—including 2 patients with the familial form of PPH (FPPH)—and from 6 patients with histologically normal lungs. For the data analysis, gene clusters were generated and the gene expression pattern differences between PPH and normal lung tissue and between PPH and FPPH lung tissue were compared. All PPH lung tissue samples showed a decreased expression of genes encoding several kinases and phosphatases, whereas several oncogenes and genes coding for ion channel proteins were upregulated in their expression. Importantly, we could distinguish by pattern comparison between sporadic PPH and FPPH, because alterations in the expression of transforming growth factor-&bgr; receptor III, bone morphogenic protein 2, mitogen-activated protein kinase kinase 5, RACK 1, apolipoprotein C-III, and the gene encoding the laminin receptor 1 were only found in the samples from patients with sporadic PPH, but not in FPPH samples. We conclude that the microarray gene expression technique is a new and useful molecular tool that provides novel information pertinent to a better characterization and understanding of the pathobiology of the distinct clinical phenotypes of pulmonary hypertension.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—The aim of this study was to assess the capability of MRI to characterize systolic and diastolic function in normal and chronically failing mouse hearts in vivo at rest and during inotropic stimulation. Applying an ECG-gated FLASH-cine sequence, MRI at 7 T was performed at rest and after administration of 1.5 &mgr;g/g IP dobutamine. There was a significant increase of heart rate, cardiac output, and ejection fraction and significant decrease of end-diastolic and end-systolic left ventricular (LV) volumes (P<0.01 each) in normal mice during inotropic stimulation. In mice with heart failure due to chronic myocardial infarction (MI), MRI at rest revealed gross LV dilatation. There was a significant decrease of LV ejection fraction in infarcted mice (29%) versus sham mice (58%). Mice with MI showed a significantly reduced maximum LV ejection rate (P<0.001) and LV filling rate (P<0.01) and no increase of LV dynamics during dobutamine action, indicating loss of contractile and relaxation reserve. In 4-month-old transgenic mice with cardiospecific overexpression of the &bgr;1-adrenergic receptor, which at this early stage do not show abnormalities of resting cardiac function, LV filling rate failed to increase after dobutamine stress (transgenic, 0.19±0.03 &mgr;L/ms; wild type, 0.36±0.01 &mgr;L/ms;P<0.01). Thus, MRI unmasked diastolic dysfunction during dobutamine stress. Dobutamine-stress MRI allows noninvasive assessment of systolic and diastolic components of heart failure. This study shows that MRI can demonstrate loss of inotropic and lusitropic response in mice with MI and can unmask diastolic dysfunction as an early sign of cardiac dysfunction in a transgenic mouse model of heart failure.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—ATP-sensitive potassium (KATP) channels were discovered in ventricular cells, but their roles in the heart remain mysterious. KATPchannels have also been found in numerous other tissues, including vascular smooth muscle. Two pore-forming subunits, Kir6.1 and Kir6.2, contribute to the diversity of KATPchannels. To determine which subunits are operative in the cardiovascular system and their functional roles, we characterized the effects of pharmacological K+channel openers (KCOs, ie, pinacidil, P-1075, and diazoxide) in Kir6.2-deficient mice. Sarcolemmal KATPchannels could be recorded electrophysiologically in ventricular cells from Kir6.2+/+(wild-type [WT]) but not from Kir6.2−/−(knockout [KO]) mice. In WT ventricular cells, pinacidil induced an outward current and action potential shortening, effects that were blocked by glibenclamide, a KATPchannel blocker. KO ventricular cells exhibited no response to KCOs, but gene transfer of Kir6.2 into neonatal ventricular cells rescued the electrophysiological response to P-1075. In terms of contractile function, pinacidil decreased force generation in WT but not KO hearts. Pinacidil and diazoxide produced concentration-dependent relaxation in both WT and KO aortas precontracted with norepinephrine. In addition, pinacidil induced a glibenclamide-sensitive current of similar magnitude in WT and KO aortic smooth muscle cells and comparable levels of hypotension in anesthetized WT and KO mice. In both WT and KO aortas, only Kir6.1 mRNA was expressed. These findings indicate that the Kir6.2 subunit mediates the depression of cardiac excitability and contractility induced by KCOs; in contrast, Kir6.2 plays no discernible role in the arterial tree.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Abstract—Although immunoapheresis removing autoantibodies against the second extracellular domain of &bgr;1-adrenergic receptors (ARs) improves cardiac function in patients with cardiomyopathy, the underlying mechanisms have not been defined. We examined the role of autoimmunity against the domain in the development of cardiac dysfunction in vivo. Japanese white rabbits were immunized with a synthetic peptide corresponding to the second extracellular loop of &bgr;1-AR once a month with (&bgr;+biso rabbits, n=10) or without (&bgr; rabbits, n=13) bisoprolol treatment (2 mg/kg per day). Control rabbits received vehicle without bisoprolol treatment (n=13). Autoantibodies of IgG isotype against the domain were persistently detected in &bgr; and &bgr;+biso rabbits. Purified IgG from sera of &bgr; and &bgr;+biso rabbits increased cAMP production in a rabbit cardiac membrane preparation, which was blocked by bisoprolol. At 3 months, &bgr;-AR uncoupling with increased G protein-coupled receptor kinase 5 (GRK5) expression was found in &bgr; rabbits. At 6 months, left ventricular hypertrophy was noted with hemodynamic derangements in &bgr; rabbits. This was accompanied by decreased &bgr;1-AR density and increased inhibitory G protein and GRK5 expression, which were related to marked decrease in membrane cAMP production. These changes in &bgr; rabbits at 6 months were prevented in &bgr;+biso rabbits. There was no difference in the plasma norepinephrine concentration in the 3 groups over the observation period. Thus, autoimmunity against the second extracellular loop of &bgr;1-ARs induced profound &bgr;-AR desensitization and myocardial hypertrophy in vivo, associated with cardiac dysfunction. Sustained sympathomimetic-like actions of autoantibodies against the domain may be partly responsible for these changes.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Cardiac-restricted expression of Cre recombinase can provoke lineage-specific gene excision in the myocardium. However, confounding early lethality may still preclude using loss-of-function models to study the postnatal heart. Here, we have tested whether inducible, heart-specific recombination can be triggered after birth by transgenic expression of a Cre fusion protein that incorporates a mutated progesterone receptor ligand binding domain (PR1) that is activated by the synthetic antiprogestin, RU486, but not by endogenous steroid hormones. CrePR1 driven by the &agr;-myosin heavy chain (&agr;MHC) promoter was expressed specifically in heart. Translocation of CrePR1 from cytoplasm to nuclei in ventricular myocytes was induced by RU486. To establish whether this approach can mediate cardiac-specific, drug-dependent excision between loxP sites in vivo, we mated &agr;MHC-CrePR1 mice with a ubiquitously expressed (ROSA26) Cre reporter line. Offspring harboring &agr;MHC-CrePR1 and/or the floxed allele were injected with RU486 versus vehicle, and the prevalence of &bgr;-galactosidase (&bgr;-gal)–positive cells was determined, indicative of Cre-mediated excision. Little or no baseline recombination was seen 1 week after birth. Cardiac-restricted, RU486-inducible recombination was demonstrated in bigenic mice at age 3 and 6 weeks, using each of 3 independent CrePR1 lines. Recombination in the absence of ligand paralleled the levels of CrePR1 protein expression and was more evident at 6 weeks. Thus, conditional, posttranslational activation of a Cre fusion protein can bypass potential embryonic and perinatal effects on the heart and permits inducible recombination in cardiac muscle. High levels of the chimeric Cre protein, in particular, were associated with progressive recombination in the absence of drug.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Flow-dependent dilation is a fundamental mechanism by which large arteries ensure appropriate blood supply to tissues. We investigated whether or not the vascular kallikrein-kinin system, especially tissue kallikrein (TK), contributes to flow-dependent dilation by comparing wild-type and TK-knockout mice in which the presence or absence of TK expression was verified. We examined in vitro changes in the outer diameter of perfused carotid arteries from TK+/+and TK−/−mice. In both groups, exogenous bradykinin caused a similar dilation that was abolished by the B2receptor antagonist HOE-140, as well as by the NO synthase inhibitorN&ohgr;-nitro-l-arginine methyl ester. However, purified kininogen dilated only TK+/+arteries, demonstrating the essential role of TK in the vascular formation of kinins. In TK+/+arteries, increasing intraluminal flow caused a larger endothelium-dependent dilation than that seen in TK−/−. In both strains the flow response was mediated by NO and by endothelium-derived hyperpolarizing factor, whereas in TK−/−vasoconstrictor prostanoids participated as well. HOE-140 impaired flow-dependent dilation in TK+/+arteries while showing no effect in TK−/−. This compound reduced the flow response in TK+/+arteries to a level similar to that in TK−/−. After NO synthase inhibition, HOE-140 no longer affected the response of TK+/+. Impaired flow-dependent dilation was also observed in arteries from knockout mice lacking bradykinin B2receptors as compared with wild-type animals. This study demonstrates the active contribution of the vascular kallikrein-kinin system to one-third of the flow-dependent dilation response via activation of B2receptors coupled to endothelial NO release.

ISSN:0009-7330    

出版商:OVID    

年代:2001

数据来源: OVID