ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Formation of the coronary vessels is a fundamental event in heart development. Congenital abnormalities in the coronary system can have major deleterious effects on heart function. It is also possible that subtle variation in the patterning of coronary vessels has significant but uncharacterized effects on myocardial structure and function. In addition, generation of the coronary vascular system represents a complex system for analysis of regulation of cell fate determination, cell and epithelial migration, epithelial/mesenchymal transition, and patterning of a complex three-dimensional structure. In this review, we present the descriptive embryology of this process as well as the recent data that shed light on the unique developmental mechanisms underlying generation of coronary vessels. This review also attempts to identify areas where additional research is needed and highlights the questions that must be answered for a meaningful understanding of coronary vessel development.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—The focal pattern of atherosclerotic lesions in arterial vessels suggests that local blood flow patterns are important factors in atherosclerosis. Although disturbed flows in the branches and curved regions are proatherogenic, laminar flows in the straight parts are atheroprotective. Results from in vitro studies on cultured vascular endothelial cells with the use of flow channels suggest that integrins and the associated RhoA small GTPase play important roles in the mechanotransduction mechanism by which shear stress is converted to cascades of molecular signaling to modulate gene expression. By interacting dynamically with extracellular matrix proteins, the mechanosensitive integrins activate RhoA and many signaling molecules in the focal adhesions and cytoplasm. Through such mechanotransduction mechanisms, laminar shear stress upregulates genes involved in antiapoptosis, cell cycle arrest, morphological remodeling, and NO production, thus contributing to the atheroprotective effects. This review summarizes some of the recent findings relevant to these mechanotransduction mechanisms. These studies show that integrins play an important role in mechanosensing in addition to their involvement in cell attachment and migration.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—In response to pathophysiological stress, the adult heart undergoes hypertrophic enlargement characterized by an increase in the cross-sectional area of individual myofibers. Although cardiac hypertrophy is initially a compensatory response, sustained hypertrophy is a leading predictor for the development of heart failure. At the molecular level, disease-related stimuli invoke endocrine, paracrine, and autocrine regulatory circuits, which directly influence cardiomyocyte hypertrophy, in part, through membrane bound G protein–coupled receptors and receptor tyrosine kinases. These membrane receptors activate intermediate signal transduction pathways within the cytoplasm such as mitogen-activated protein kinases (MAPKs), protein kinase C (PKC), and calcineurin, which directly modify transcriptional regulatory factors promoting alterations in cardiac gene expression. This review will weigh an increasing body of literature implicating the intermediate signaling pathway consisting of MEK1 and extracellular signal-regulated kinases (ERK1/2) as important regulators of cardiac hypertrophy and myocyte survival. The MEK1-ERK1/2 pathway likely occupies a central regulatory position in the signaling hierarchy of a cardiac myocyte given its unique ability to respond to virtually every characterized hypertrophic agonist and stress stimuli examined to date and based on its ability to promote myocyte growth in vitro and in vivo.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Apoptotic cell death is an important mode of cell loss contributing to heart dysfunction. To analyze the importance of the E2F-dependent regulation of gene transcription in cardiomyocyte apoptosis, the function of cell cycle factors impinging on the retinoblastoma protein (pRb)/E2F pathway was investigated. In isolated neonatal ventricular myocytes, apoptotic cell death induced by hypoxia (deferoxamine, 100 &mgr;mol/L) specifically activated cyclin-dependent kinases (cdks) 2 and 3. Apoptotic cell death was inhibited by ectopic expression of cdk inhibitors p21CIPand p27KIP1but not p16INK4. In addition, apoptosis was also abrogated by forced expression of kinase dead mutant proteins of cdk2/3 but not of cdk4/6. Introduction of cdk inhibitors or dominant-negative cdk2/3 blocked pRb hyperphosphorylation and abrogated E2F-dependent gene transcription, including that of the E2F-responsive genes of proapoptotic caspase 3 and caspase 7. Moreover, introduction of constitutively active pRb and transcriptionally inert mutant E2F1/DP1 efficiently protected cardiomyocytes from apoptosis. In conclusion, these data demonstrate that cdk-specific inactivation of pRb and the subsequent activation of E2F-dependent gene transcription are required for cardiomyocyte apoptosis.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Although Purkinje fibers (PFs) play an important role in cardiac electrophysiology, almost nothing is known about the expression of ion-channel subunits in PFs. We applied competitive reverse transcription–polymerase chain reaction, Western blotting, and immunocytochemistry to compare the expression of ion-channel subunit mRNA and protein in canine PFs versus ventricular muscle (VM). For transient outward current–related subunits, Kv4.2 was not detected, and Kv1.4 expression was extremely low. Kv4.3 expression was of the same order for VM and PFs. The tetraethylammonium chloride–sensitive subunit Kv3.4 was expressed much more strongly in PFs than in VM, and Kv channel–interacting protein transcript expression was 25-fold stronger in VM than in PFs. For delayed rectifiers, ERG and KvLQT1 expression was lower in PFs at both mRNA and protein levels. Although minK transcripts were more numerous in PFs, minK protein was significantly more strongly expressed in VM. L-type Ca2+current &agr;-subunit (CaV1.2) and Na+-Ca2+exchanger proteins were more strongly expressed in VM than in PFs. For T-type Ca2+current, CaV3.1, CaV3.2, and CaV3.3 transcripts were all more strongly expressed in PFs. For the nonselective cation current, hyperpolarization-activated cation channel 1 (HCN1) expression was subquantifiable, HCN2 transcript expression was comparable in PFs and VM, and HCN4 mRNA expression was strong in PFs but below the detection threshold in VM. HCN2 and HCN4 protein expression was much stronger in PFs than in VM. We conclude that ion-channel subunit expression in PFs differs from that in VM in ways that are consistent with, and shed light on the molecular basis of, well-recognized fundamental PF ionic properties.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Under ischemic conditions, the vessel wall recruits inflammatory cells. Human aortic endothelial cells (HAECs) exposed to hypoxia followed by reoxygenation produce monocyte chemoattractant protein-1 (MCP-1); however, most experiments have been performed in the presence of nutrient deprivation (ND). We hypothesized that ND rather than hypoxia mediates endothelial MCP-1 production during ischemia, and that the small GTP-binding protein Rac1 and reactive oxygen species (ROS) are involved in this process. ND was generated by shifting HAECs from 10% to 1% FBS. Superoxide production by HAECs was increased 6 to 24 hours after ND, peaking at 18 hours. MCP-1 production was increased over a similar time frame, but peaked later at 24 hours. These effects were blocked by treatment with antioxidants such as superoxide dismutase mimetic andN-acetylcysteine (NAC), or NADPH oxidase inhibitors, DPI and gp91ds-tat. Superoxide and MCP-1 production were enhanced by RacV12 (constitutively active) in the absence of ND, and were inhibited by RacN17 (dominant-negative) adenoviral transduction under ND, suggesting that the small G-protein Rac1 is required. In conclusion, ND, an important component of ischemia, is sufficient to induce MCP-1 production by HAECs, and such production requires a functional Rac1, redox-dependent pathway.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Transforming growth factor-&bgr; (TGF-&bgr;) increases expression of endothelial nitric oxide synthase (eNOS), although the precise mechanism by which it does so is unclear. We report that Smad2, a transcription factor activated by TGF-&bgr;, mediates TGF-&bgr; induction of eNOS in endothelial cells. TGF-&bgr; induces Smad2 translocation from cytoplasm to nucleus, where it directly interacts with a specific region of the eNOS promoter. Overexpression of Smad2 increases basal levels of eNOS, and further increases TGF-&bgr; stimulation of eNOS expression. Ectopic expression of Smurf, an antagonizer of Smad2, decreases Smad2 expression and blocks TGF-&bgr; induction of eNOS. Because Smad2 can interact with a variety of transcription factors, coactivators, and corepressors, Smad2 may thus act as an integrator of multiple signals in the regulation of eNOS expression.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Estrogen receptor (ER)&agr; mediates many of the effects of estrogen on the vascular endothelium. The purpose of the present study was to determine whether estrogen modifies endothelial ER&agr; expression. In experiments in cultured ovine endothelial cells, physiological concentrations of 17&bgr;-estradiol (E2, 10−10to 10−8mol/L) caused an increase in ER&agr; protein abundance that was evident after 6 hours of hormone exposure. Shorter (2-hour) E2treatment caused ER&agr; downregulation. In contrast to the upregulation in ER&agr; after long-term E2, the expression of the other ER isoform, ER&bgr;, was downregulated. Both nonselective ER antagonism with ICI 182,780 and the inhibition of gene transcription with actinomycin D blocked the increase in ER&agr; with E2. In studies using the human ER&agr; gene promoter P-1 coupled to luciferase, an increase in ER&agr; gene transcription was evident in endothelial cells within 4 hours of E2exposure. The transcriptional activation was fully blocked by ICI 182,780, whereas the specific ER&bgr; antagonist RR-tetrahydrochrysene yielded partial blockade. Overexpression of ER&agr; or ER&bgr; caused comparable 10- and 8-fold increases, respectively, in ER&agr; promoter activation by E2.Thus, long-term exposure to E2upregulates ER&agr; expression in endothelial cells through the actions of either ER&agr; or ER&bgr; on ER&agr; gene transcription; in contrast, E2causes ER&bgr; downregulation in the endothelium. We postulate that E2-induced changes in ER&agr; and ER&bgr; expression modify the effects of the hormone on vascular endothelium.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—The Gq protein-coupled receptor agonists phenylephrine (PE) and endothelin-1 (ET-1) induce cardiac hypertrophy and stimulate protein synthesis in cardiomyocytes. This study aims to investigate how they activate mRNA translation in adult cardiomyocytes. PE and ET-1 do not activate protein kinase B but stimulate Ras and Erk, and their ability to activate protein synthesis was blocked by inhibition of Ras or MEK and by rapamycin, which inhibits mTOR (mammalian target of rapamycin). These agonists activated ribosomal protein S6 kinase 1 (S6K1) and induced phosphorylation of eIF4E-binding protein-1 (4E-BP1) and its release from eIF4E. These effects were blocked by inhibitors of MEK. Furthermore, adenovirus-mediated expression of constitutively-active MEK1 caused activation of S6K1, phosphorylation of 4E-BP1, and activation of protein synthesis in a rapamycin-sensitive manner. Expression of N17Ras inhibited the regulation of S6K1 and protein synthesis by GqPCR agonists. These data point to a signaling pathway involving Ras and MEK that acts, with mTOR, to control regulatory translation factors and activate protein synthesis. This study provides new insights into the mechanisms underlying the stimulation of protein synthesis by hypertrophic agents in heart.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID