摘要:

Abstract—Integrins play an important role in vascular smooth muscle cell (VSMC) migration, a crucial event in the development of restenosis and atherosclerosis. Transforming growth factor-&bgr; (TGF-&bgr;) is highly expressed in restenotic and atherosclerotic lesions, and known to induce integrin expression. Peroxisome proliferator-activated receptor &agr; (PPAR&agr;), a member of the nuclear receptor superfamily, regulates gene expression in a variety of vascular cells. We investigated the effects of PPAR&agr; ligands on TGF-&bgr;–induced &bgr;3and &bgr;5integrin expression and potential interaction between PPAR&agr; and TGF-&bgr; signaling. PPAR&agr; ligands WY-14643 (100 &mgr;mol/L) and 5,8,11,14-eicosatetranoic acid (ETYA, 50 &mgr;mol/L) inhibited TGF-&bgr;–induced &bgr;5integrin protein expression by 72±6.8% and 73±7.1%, respectively (bothP<0.05). TGF-&bgr;–stimulated &bgr;3integrin expression was not affected by PPAR&agr; ligands. Both PPAR&agr; ligands also suppressed TGF-&bgr;–induced &bgr;5integrin mRNA levels. PPAR&agr; ligands inhibited TGF-&bgr;–inducible transcription of &bgr;5integrin by an interaction with a TGF-&bgr; response element between nucleotides −63 and −44, which contains a Sp1/Sp3 transcription factor binding site. Nuclear complexes binding to the TGF-&bgr; response region contained Sp1/Sp3 and TGF-&bgr;–regulated Smad 2, 3, and 4 transcription factors. TGF-&bgr;–stimulated Sp1/Smad4 nuclear complex formation was inhibited by WY-14643 and ETYA with a parallel induction of PPAR&agr;/Smad4 interactions. However, in vitro pull-down experiments failed to demonstrate direct binding between PPAR&agr;/Smad4. Both PPAR&agr; ligands blocked PDGF-directed migration of TGF-&bgr;–pretreated VSMCs, a process mediated, in part, by &bgr;5integrins. The present study demonstrates that PPAR&agr; activators inhibit TGF-&bgr;–induced &bgr;5integrin transcription in VSMCs through a novel indirect interaction between ligand-activated PPAR&agr; and the TGF-&bgr;–regulated Smad4 transcription factors. 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

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Recent studies have identified the importance of proinflammatory mediators in the development and progression of heart failure. The growing appreciation of the pathophysiological consequences of sustained expression of proinflammatory mediators in preclinical and clinical heart failure models culminated in a series of multicenter clinical trials that used “targeted” approaches to neutralize tumor necrosis factor in patients with moderate to advanced heart failure. However, these targeted approaches have resulted in worsening heart failure, thereby raising a number of important questions about what role, if any, proinflammatory cytokines play in the pathogenesis of heart failure. This review will summarize the tremendous growth of knowledge that has taken place in this field, with a focus on what we have learned from the negative clinical trials, as well as the potential direction of future research in this area.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—The Notch family of receptors and ligands plays an important role in cell fate determination, vasculogenesis, and organogenesis. Mutations of the Notch-3 receptor result in an arteriopathy that predisposes to early-onset stroke. However, the functional role of the Notch signaling pathway in adult vascular smooth muscle cells (VSMCs) is poorly characterized. This study documents that the Notch-3 receptor, the ligand Jagged-1, and the downstream transcription factor, HESR-1, are expressed in the normal adult rat carotid artery, and that this expression is modulated after vascular injury. In cultured VSMCs, both angiotensin II and platelet-derived growth factor (PDGF) markedly downregulated Notch-3 and Jagged-1 through ERK-dependent signaling mechanisms and prevented the glycosylation of Jagged-1. The downregulation of Jagged-1 and Notch-3 was associated with a decrease in CBF-1–mediated gene transcription activation and a fall in the mRNA levels of the downstream target transcription factor HESR-1. To test the hypothesis that the Notch pathway was coupled to growth regulation, we generated VSMC lines overexpressing the constitutively active form of Notch-3 (A7r5-N3IC). These cells exhibited a biphasic growth behavior in which the growth rate was retarded during the subconfluent phase and failed to decelerate at postconfluence. The lack of cell-cycle arrest in postconfluent A7r5-N3IC was associated with an attenuated upregulation of the cell-cycle inhibitor p27kiprelative to control cells. This study documents the regulation of the Jagged-1 and Notch-3 genes in VSMCs by growth factor stimulation as well as a role for Notch-3 as a determinant of VSMC growth.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—By subtractive hybridization, we found a significant increase in H11 kinase transcript in large mammalian models of both ischemia/reperfusion (stunning) and chronic pressure overload with hypertrophy. Because this gene has not been characterized in the heart, the goal of the present study was to determine the function of H11 kinase in cardiac tissue, both in vitro and in vivo. In isolated neonatal rat cardiac myocytes, adenoviral-mediated overexpression of H11 kinase resulted in a 37% increase in protein/DNA ratio, reflecting hypertrophy. A cardiac-specific transgene driven by the &agr;MHC-promoter was generated, which resulted in an average 7-fold increase in H11 kinase protein expression. Transgenic hearts were characterized by a 30% increase of the heart weight/body weight ratio, by the reexpression of a fetal gene program, and by concentric hypertrophy with preserved contractile function at echocardiography. This phenotype was accompanied by a dose-dependent activation of Akt/PKB and p70S6kinase, whereas the MAP kinase pathway was unaffected. Thus, H11 kinase represents a novel mediator of cardiac cell growth and hypertrophy.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Sarcoplasmic reticulum (SR) Ca2+transport proteins, especially ryanodine receptors (RyR) and their accessory protein FKBP12.6, have been implicated as major players in the pathogenesis of heart failure (HF), but their role remain controversial. We used the tachycardia-induced canine model of HF and human failing hearts to investigate the density and major functional properties of RyRs, SERCA2a, and phospholamban (PLB), the main proteins regulating SR Ca2+transport. Intracellular Ca2+is likely to play a role in the contractile dysfunction of HF because the amplitude and kinetics of the [Ca2+]itransient were reduced in HF. Ca2+uptake assays showed 44±8% reduction of Vmaxin canine HF, and Western blots demonstrated that this reduction was due to decreased SERCA2a and PLB levels. Human HF showed a 30±5% reduction in SERCA2a, but PLB was unchanged. RyRs from canine and human HF displayed no major structural or functional differences compared with control. The Poof RyRs was the same for control and HF over the range of pCa 7 to 4. Subconductance states, which predominate in FKBP12.6-stripped RyRs, were equally frequent in control and HF channels. An antibody that recognizes phosphorylated RyRs yields equal intensity for control and HF channels. Further, phosphorylation of RyRs by PKA did not appear to change the RyR/FKBP12.6 association, suggesting minor &bgr;-adrenergic stimulation of Ca2+release through this mechanism. These results support a role for SR in the pathogenesis of HF, with abnormal Ca2+uptake, more than Ca2+release, contributing to the depressed and slow Ca2+transient characteristic of HF.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—The [Ca2+]itransient of ventricular myocytes during normal excitation-contraction coupling is the summation of primary Ca2+release events, which originate at the junction of the sarcoplasmic reticulum (SR) and the T-tubular system. Studies in small mammals have shown a high density of release sites, but little is known of larger mammals. We have studied the spatial distribution of SR Ca2+release in pig ventricular myocytes using a confocal microscopy. In 69 of 107 cells, large inhomogeneities of Ca2+release were observed along the longitudinal scan line. Areas where the increase of [Ca2+]iwas delayed (time to 50% of peak F/F0[where F indicates fluorescence intensity, and F0indicates F at rest] was 26±1 ms in delayed areas versus 11±2 ms in early areas) and smaller (peak F/F0was 2.27±0.10 for delayed areas versus 2.69±0.13 for early areas; n=13 cells,P<0.05) could be up to 26 &mgr;m wide. The sum of all delayed areas could make up to 55% of the line scan. The spatial pattern was constant during steady-state stimulation and was not altered by enhancing Ca2+channel opening or SR Ca2+content (Bay K8644, isoproterenol). Imaging of sarcolemmal membranes revealed several areas devoid of T tubules, but SR Ca2+release channels were homogeneously distributed. In contrast, compared with pig myocytes, mouse myocytes had a very dense T-tubular network, no large inhomogeneities of release, and a faster rate of rise of [Ca2+]i. In conclusion, in pig ventricular myocytes, areas of delayed release are related to regional absence of T tubules but not ryanodine receptors. This lower number of functional couplons contributes to a slower overall rate of rise of [Ca2+]i.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—The mechanism of oxygen-induced cerebral vasoconstriction has been sought for more than a century. Using genetically altered mice to enhance or disrupt extracellular superoxide dismutase (EC-SOD, SOD3), we tested the hypothesis that this enzyme plays a critical role in the physiological response to oxygen in the brain by regulating nitric oxide (NO·) availability. Cerebral blood flow responses in these genetically altered mice to changes in Po2demonstrate that SOD3 regulates equilibrium between superoxide (·O2−) and NO·, thereby controlling vascular tone and reactivity in the brain. That SOD3 opposes inactivation of NO·is shown by absence of vasoconstriction in response to Po2in the hyperbaric range in SOD3+/+mice, whereas NO-dependent relaxation is attenuated in SOD3−/−mutants. Thus, EC-SOD promotes NO·vasodilation by scavenging ·O2−while hyperoxia opposes NO·and promotes constriction by enhancing endogenous ·O2−generation and decreasing basal vasodilator effects of NO·.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID