Circulation research
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Circulation research · Sep 2001
Thrombin suppresses endothelial nitric oxide synthase and upregulates endothelin-converting enzyme-1 expression by distinct pathways: role of Rho/ROCK and mitogen-activated protein kinase.
An imbalance of nitric oxide and endothelin plays an important role in cardiovascular disease. Thrombin exerts profound effects on endothelial function. The present study investigated the molecular mechanisms by which thrombin regulates endothelial nitric oxide synthase (eNOS) and endothelin-converting enzyme (ECE)-1 expression in human endothelial cells. ⋯ Treatment of rat aorta with thrombin overnight impaired endothelium-dependent relaxations but not endothelium-independent relaxations. Thus, thrombin suppresses eNOS and upregulates ECE-1 expression via Rho/ROCK and ERK pathway, respectively. These effects of thrombin may be important for endothelial dysfunction in cardiovascular disease, particularly during acute coronary episodes.
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Circulation research · Aug 2001
Review Comparative StudyClinical imaging of the high-risk or vulnerable atherosclerotic plaque.
The study of atherosclerotic disease during its natural history and after therapeutic intervention will enhance our understanding of disease progression and regression and aid in selecting appropriate treatments. Several invasive and noninvasive imaging techniques are available to assess atherosclerotic vessels. ⋯ We will present the different imaging modalities that have been used for the direct assessment of the carotid, aortic, and coronary atherosclerotic plaques. We will review in detail the use of high-resolution, multicontrast magnetic resonance for the noninvasive imaging of vulnerable plaques and the characterization of plaques in terms of their various components (ie, lipid, fibrous, calcium, or thrombus).
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Circulation research · Aug 2001
Role for endothelin-1-induced superoxide and peroxynitrite production in rebound pulmonary hypertension associated with inhaled nitric oxide therapy.
Our previous studies have demonstrated that inhaled nitric oxide (NO) decreases nitric oxide synthase (NOS) activity in vivo and that this inhibition is associated with rebound pulmonary hypertension upon acute withdrawal of inhaled NO. We have also demonstrated that inhaled NO elevates plasma endothelin-1 (ET-1) levels and that pretreatment with PD156707, an ETA receptor antagonist, blocks the rebound hypertension. The objectives of this study were to further elucidate the role of ET-1 in the rebound pulmonary hypertension upon acute withdrawal of inhaled NO. ⋯ The nitration of eNOS was also reduced by 40% in PD156707-treated lambs (P<0.05). These data suggest that the reduction of NOS activity associated with inhaled NO therapy may involve ETA receptor-mediated superoxide production. ETA receptor antagonists may prevent rebound pulmonary hypertension by protecting endogenous eNOS activity during inhaled NO therapy.
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Circulation research · Aug 2001
Acetylcholine, bradykinin, opioids, and phenylephrine, but not adenosine, trigger preconditioning by generating free radicals and opening mitochondrial K(ATP) channels.
It has been assumed that all G(i)-coupled receptors trigger the protective action of preconditioning by means of an identical intracellular signaling pathway. To test this assumption, rabbit hearts were isolated and perfused with Krebs buffer. All hearts were subjected to a 30-minute coronary artery occlusion followed by 120 minutes of reperfusion. ⋯ In contrast, protection by adenosine or its analog N(6)-(2-phenylisopropyl) adenosine could not be blocked by either MPG or 5-HD. Therefore, whereas most of the tested agonists trigger protection by a pathway that requires opening of mitochondrial K(ATP) channels and production of free radicals, the protective action of adenosine is not dependent on either of these steps. Hence, it cannot be assumed that all G(i)-coupled receptors use the same signal transduction pathways to trigger preconditioning.
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Circulation research · Jul 2001
Sarcoplasmic reticulum Ca(2+) atpase (SERCA) 1a structurally substitutes for SERCA2a in the cardiac sarcoplasmic reticulum and increases cardiac Ca(2+) handling capacity.
Ectopic expression of the sarcoplasmic reticulum (SR) Ca(2+) ATPase (SERCA) 1a pump in the mouse heart results in a 2.5-fold increase in total SERCA pump level. SERCA1a hearts show increased rates of contraction/relaxation and enhanced Ca(2+) transients; however, the cellular mechanisms underlying altered Ca(2+) handling in SERCA1a transgenic (TG) hearts are unknown. In this study, using confocal microscopy, we demonstrate that SERCA1a protein traffics to the cardiac SR and structurally substitutes for the endogenous SERCA2a isoform. ⋯ However, TG myocytes had a greater rate of spontaneous ryanodine receptor opening as measured by spark frequency. Whole-cell L-type Ca(2+) current density was reduced by approximately 50%, whereas the time course of inactivation was unchanged in TG myocytes. These studies provide important evidence that SERCA1a can substitute both structurally and functionally for SERCA2a in the heart and that SERCA1a overexpression can be used to enhance SR Ca(2+) transport and cardiac contractility.