bluuebunny/crossref_metadata_2025 huggingface dataset:
Circulating Microparticles From Patients With Myocardial Infarction Cause Endothelial Dysfunction
Authors: Boulanger Chantal M. , Scoazec Alexandra , Ebrahimian Talin , Henry Patrick , Mathieu Eric , Tedgui Alain , Mallat Ziad
Published: September 2007

Background

Shed membrane microparticles circulate in the peripheral blood of nonischemic (NI) patients and patients with myocardial infarction (MI). We investigated whether or not these microparticles would affect endothelium-dependent responses.

Methods and Results

Rat aortic rings with endothelium were exposed for 24 hours to circulating microparticles isolated from 7 patients with NI syndromes and 19 patients with acute MI. Endothelium-dependent relaxations to acetylcholine were not affected by high concentrations of microparticles from NI patients (
P
=0.80). However, significant impairment was observed in preparations exposed to microparticles from patients with MI at low and high concentrations, corresponding to 0.7-fold and 2-fold circulating plasma levels (
P
=0.05 and 0.001, respectively). Impairment was not affected by diclofenac (
P
=0.47), nor by the cell-permeable superoxide dismutase mimetic Mn(III)tetra(4-benzoic acid) porphyrin chloride (
P
=0.33), but it was abolished by endothelium removal or by N
ω
monomethyl-
l
-arginine. Relaxations to the calcium ionophore ionomycin were decreased in rings exposed to microparticles from MI patients (
P
=0.05 and 0.009 for low and high concentrations, respectively), but microparticles from NI patients had no effect (
P
=0.81). Finally, high concentrations of microparticles from MI patients affected neither endothelium-independent relaxation to sodium nitroprusside (
P
=0.59) nor expression of the endothelial nitric oxide synthase (
P
=0.43).

Conclusions

Circulating microparticles from patients with MI selectively impair the endothelial nitric oxide transduction pathway and, therefore, could contribute to the general vasomotor dysfunction observed after MI, even in angiographically normal arteries.
Single Nucleotide Polymorphisms in Multiple Novel Thrombospondin Genes May Be Associated With Familial Premature Myocardial Infarction
Authors: Topol Eric J. , McCarthy Jeanette , Gabriel Stacey , Moliterno David J. , Rogers William J. , Newby L. Kristin , Freedman Matt , Metivier Jennifer , Cannata Ruth , O’Donnell Christopher J. , Kottke-Marchant Kandice , Murugesan Gurunathan , Plow Edward F. , Stenina Olga , Daley George Q.
Published: September 2007

Background

Recent advances in high-throughput genomics technology have expanded our ability to catalogue allelic variants in large sets of candidate genes related to premature coronary artery disease.

Methods and Results

A total of 398 families were identified in 15 participating medical centers; they fulfilled the criteria of myocardial infarction, revascularization, or a significant coronary artery lesion diagnosed before 45 years in men or 50 years in women. A total of 62 vascular biology genes and 72 single-nucleotide polymorphisms were assessed. Previously undescribed variants in 3 related members of the thrombospondin protein family were prominent among a small set of single-nucleotide polymorphisms that showed a statistical association with premature coronary artery disease. A missense variant of thrombospondin 4 (A387P) showed the strongest association, with an adjusted odds ratio for myocardial infarction of 1.89 (
P
=0.002 adjusted for covariates) for individuals carrying the P allele. A variant in the 3′ untranslated region of thrombospondin-2 (change of thymidine to guanine) seemed to have a protective effect against myocardial in individuals homozygous for the variant (adjusted odds ratio of 0.31;
P
=0.0018). A missense variant in thrombospondin-1 (N700S) was associated with an adjusted odds ratio for coronary artery disease of 11.90 (
P
=0.041) in homozygous individuals, who also had the lowest level of thrombospondin-1 by plasma assay (
P
=0.0019).

Conclusions

This large-scale genetic study has identified the potential of multiple novel variants in the thrombospondin gene family to be associated with familial premature myocardial infarction. Notwithstanding multiple caveats, thrombospondins specifically and high-throughput genomic technology in general deserve further study in familial ischemic heart disease.
New Approaches to Antiarrhythmic Therapy, Part I
Authors:   Members of the Sicilian Gambit
Published: September 2007

Cardiac arrhythmias complicate many diseases affecting the heart and circulation, and they incorporate a multiplicity of underlying mechanisms. The evolution of scientific knowledge has made the complex changes produced by cardiovascular disease sufficiently understood at the organ, cellular, and molecular levels such that there is a diversity of therapeutic targets for pharmacological therapy and/or prevention. Moreover, the approach of rational drug design in mechanism-specific and disease-specific fashions facilitates the targeting of therapy using the methods of molecular, structural, and translational biology. Additional approaches, using similar drug design strategies but based on gene therapy and transcriptional and translational modification, are on the horizon. Hence, there is reason to be optimistic regarding the design, testing, and clinical availability of novel antiarrhythmic therapies.
Platelet Glycoprotein IIb/IIIa Inhibitors Reduce Mortality in Diabetic Patients With Non–ST-Segment-Elevation Acute Coronary Syndromes
Authors: Roffi Marco , Chew Derek P. , Mukherjee Debabrata , Bhatt Deepak L. , White Jennifer A. , Heeschen Christopher , Hamm Christian W. , Moliterno David J. , Califf Robert M. , White Harvey D. , Kleiman Neal S. , Théroux Pierre , Topol Eric J.
Published: September 2007

Background

Diabetes mellitus is a major risk factor for adverse outcomes after acute coronary syndromes (ACS). Because this disease may be associated with increased platelet aggregation, we investigated whether diabetic patients with ACS derive particular benefit from platelet glycoprotein (GP) IIb/IIIa receptor inhibition.

Methods and Results

We performed a meta-analysis of the diabetic populations enrolled in the 6 large-scale platelet GP IIb/IIIa inhibitor ACS trials: PRISM, PRISM-PLUS, PARAGON A, PARAGON B, PURSUIT, and GUSTO IV. Among 6458 diabetic patients, platelet GP IIb/IIIa inhibition was associated with a significant mortality reduction at 30 days, from 6.2% to 4.6% (OR 0.74; 95% CI 0.59 to 0.92;
P
=0.007). Conversely, 23 072 nondiabetic patients had no survival benefit (3.0% versus 3.0%). The interaction between platelet GP IIb/IIIa inhibition and diabetic status was statistically significant (
P
=0.036). Among 1279 diabetic patients undergoing percutaneous coronary intervention (PCI) during index hospitalization, the use of these agents was associated with a mortality reduction at 30 days from 4.0% to 1.2% (OR 0.30; 95% CI 0.14 to 0.69;
P
=0.002).

Conclusions

This meta-analysis, including the entire large-scale trial experience of intravenous platelet GP IIb/IIIa inhibitors for the medical management of non–ST-segment-elevation ACS, shows that these agents may significantly reduce mortality at 30 days in diabetic patients. Although not based on a randomized assessment, the survival benefit appears to be of greater magnitude in patients undergoing PCI. Therefore, the use of platelet GP IIb/IIIa inhibitors should be strongly considered in diabetic patients with ACS.
Clinical Correlates and Reference Intervals for Pulmonary Artery Systolic Pressure Among Echocardiographically Normal Subjects
Authors: McQuillan Brendan M. , Picard Michael H. , Leavitt Marcia , Weyman Arthur E.
Published: September 2007

Background

Data in normal human subjects on the factors affecting pulmonary artery systolic pressure (PASP) are limited. We determined the correlates of and established a reference range for PASP as determined by Doppler transthoracic echocardiography (TTE) from a clinical echocardiographic database of 102 818 patients, of whom 15 596 (15%) had a normal Doppler TTE study.

Methods and Results

A normal TTE was based on normal cardiac structure and function during complete Doppler TTE studies. The PASP was calculated by use of the modified Bernoulli equation, with right atrial pressure assumed to be 10 mm Hg. Among TTE normal subjects, 3790 subjects (2432 women, 1358 men) from 1 to 89 years old had a measured PASP. The mean PASP was 28.3±4.9 mm Hg (range 15 to 57 mm Hg). PASP was independently associated with age, body mass index (BMI), male sex, left ventricular posterior wall thickness, and left ventricular ejection fraction (
P
<0.001). The estimated upper 95% limit for PASP among lower-risk subjects was 37.2 mm Hg. A PASP >40 mm Hg was found in 6% of those >50 years old and 5% of those with a BMI >30 kg/m
2
.

Conclusions

Among 3790 echocardiographically normal subjects, PASP was associated with age, BMI, sex, wall thickness, and ejection fraction. Of these subjects, 28% had a PASP >30 mm Hg, and the expected upper limit of PASP may include 40 mm Hg in older or obese subjects. These findings support the use of age- and BMI-corrected values in establishing the expected normal range for PASP.
Double-Blind, Randomized Trial of an Anti-CD18 Antibody in Conjunction With Recombinant Tissue Plasminogen Activator for Acute Myocardial Infarction
Authors: Baran Kenneth W. , Nguyen Michel , McKendall George R. , Lambrew Costas T. , Dykstra Gary , Palmeri Sebastian T. , Gibbons Raymond J. , Borzak Steven , Sobel Burton E. , Gourlay Steven G. , Rundle Amy Chen , Gibson C. Michael , Barron Hal V.
Published: September 2007

Background

Inhibition of leukocyte adhesion can reduce myocardial infarct size in animals. This study was designed to define the safety and efficacy of a recombinant, humanized, monoclonal antibody to the CD18 subunit of the β2 integrin adhesion receptors (rhuMAb CD18), in reducing infarct size in patients treated with a thrombolytic agent.

Methods and Results

The Limitation of Myocardial Infarction following Thrombolysis in Acute Myocardial Infarction Study (LIMIT AMI) was a randomized, double-blind, placebo-controlled, multicenter study conducted in 60 centers in the United States and Canada. A total of 394 subjects who presented within 12 hours of symptom onset with ECG findings (ST-segment elevation) consistent with AMI were treated with recombinant tissue plasminogen activator and were also given an intravenous bolus of 0.5 or 2.0 mg/kg rhuMAb CD18 or placebo. Coronary angiography was performed at 90 minutes, 12-lead ECGs were obtained at baseline, 90, and 180 minutes, and resting sestamibi scans were performed at ≥120 hours. Adjunctive angioplasty and use of glycoprotein IIb/IIIa antiplatelet agents at the time of angiography were discretionary. There were no treatment effects on coronary blood flow, infarct size, or the rate of ECG ST-segment elevation resolution, despite the expected induction of peripheral leukocytosis. A slight trend toward an increase in bacterial infections was observed with rhuMAb CD18 (
P
=0.33).

Conclusions

RhuMAb CD18 was well tolerated but not effective in modifying cardiac end points.
Balloon-Protected Carotid Artery Stenting
Authors: Tübler Thilo , Schlüter Michael , Dirsch Olaf , Sievert Horst , Bösenberg Ilka , Grube Eberhard , Waigand Jürgen , Schofer Joachim
Published: September 2007

Background

Carotid artery stenting (CAS) has been advocated as an alternative to endarterectomy. To prevent cerebral atheroembolism during CAS, distal balloon occlusion of the target artery increasingly is employed during the procedure. A correlation of the size of captured particles with the incidence of periprocedural neurological complications (PNCs) has not been attempted.

Methods and Results

In a 4-center, phase-1 trial, 54 patients (46 men; age, 69±8 years) underwent 58 CAS procedures using the PercuSurge GuardWire system for distal protection. Aspirated debris was sent for histological/cytological analysis. Stent placement was successful in all cases. Mean balloon occlusion time was 10.4±4.0 minutes (range, 3.0 to 22.0 minutes). Three patients (5.2%) experienced PNCs: 1 prolonged reversible ischemic neurological deficit that resolved in ≤48 hours, 1 stroke, and 1 transient ischemic attack. Relevant particles (those with an area ≥10 000 μm
2
) were found in 48 aspirates (83%). The median number of particles, their maximum diameter, and their maximum area were all significantly higher in the aspirates obtained during procedures associated with PNCs than in aspirates obtained during procedures not associated with PNCs. However, pronounced overlap in the distributions (PNCs versus no PNCs) of the number and maximum diameter of particles precluded any predictive inferences. In contrast, a maximum particle area >800 000 μm
2
(>0.8 mm
2
) was associated with a 60% chance of having a PNC.

Conclusions

Despite balloon protection, PNCs occurred in 5.2% of patients who underwent CAS procedures. The maximum area of aspirated particles seems to be an indicator of increased risk for PNCs.
Reversal of Cardiogenic Shock by Percutaneous Left Atrial-to-Femoral Arterial Bypass Assistance
Authors: Thiele Holger , Lauer Bernward , Hambrecht Rainer , Boudriot Enno , Cohen Howard A. , Schuler Gerhard
Published: September 2007

Background
—

Recovery of myocardial function after revascularization of acutely occluded coronary arteries may require several days. During this critical time, patients in cardiogenic shock may have low output. A newly developed percutaneous left ventricular assist device (VAD) may offer effective treatment for these patients by providing active circulatory support.

Methods and Results
—

Between May 2000 and May 2001, VADs were implanted in 18 consecutive patients who had cardiogenic shock after myocardial infarction. The device was connected to the patient’s circulation by insertion of a 21F venous cannula into the left atrium by transseptal puncture; blood was returned to the iliac artery through an arterial cannula. Mean duration of cardiac assistance was 4±3 days. Mean flow of the VAD was 3.2±0.6 L/min. Before support, cardiac index was 1.7±0.3 L/min per m
2
and improved to 2.4±0.6 L/min per m
2
(
P
<0.001). Mean blood pressure increased from 63±8 mm Hg to 80±9 mm Hg (
P
<0.001). Pulmonary capillary wedge pressure, central venous pressure, and pulmonary artery pressure were reduced from 21±4, 13±4, and 31±8 mm Hg to 14±4, 9±3, and 23±6 mm Hg (all
P
<0.001), respectively. Overall 30-day mortality rate was 44%.

Conclusions
—

A newly developed VAD can be rapidly deployed in the catheterization laboratory setting. This device provides up to 4.0 L/min of assisted cardiac output, which may aid to revert cardiogenic shock. The left ventricle is unloaded by diverting blood from the left atrium to the systemic circulation, making recovery more likely after an ischemic event. The influence of this device on long-term prognosis warrants further investigation.
Activation Delay After Premature Stimulation in Chronically Diseased Human Myocardium Relates to the Architecture of Interstitial Fibrosis
Authors: Kawara Tokuhiro , Derksen Richard , de Groot Joris R. , Coronel Ruben , Tasseron Sara , Linnenbank André C. , Hauer Richard N.W. , Kirkels Hans , Janse Michiel J. , de Bakker Jacques M.T.
Published: September 2007

Background
—

Progressive activation delay starting at long coupling intervals of premature stimuli has been shown to correlate with sudden cardiac death in patients with hypertrophic cardiomyopathy. The purpose of this study was to elucidate the mechanism of increased activation delay in chronically diseased myocardium.

Methods and Results
—

High-resolution unipolar mapping (105, 208, or 247 recording sites with interelectrode distances of 0.8, 0.5, or 0.3 mm, respectively) of epicardial electrical activity was carried out during premature stimulation in 11 explanted human hearts. The hearts came from patients who underwent heart transplantation and were in the end stage of heart failure (coronary artery disease, 4; hypertrophic cardiomyopathy, 1; and dilated cardiomyopathy, 6). Eight hearts were Langendorff-perfused. Epicardial sheets were taken from the remaining hearts and studied in a tissue bath. Activation maps and conduction curves were constructed and correlated with histology. Conduction curves revealing prominent increase of activation delay were associated with zones of dense, patchy fibrosis with long fibrotic strands. Dense, diffuse fibrosis with short fibrotic strands only marginally affected conduction curves. The course of conduction curves in patchy fibrotic areas greatly depended on the direction of propagation relative to fiber direction.

Conclusions
—

The study demonstrates that in chronically diseased human myocardium, nonuniform anisotropic characteristics imposed by long fibrotic strands cause a progressive increase of activation delay, starting at long coupling intervals of premature stimuli. The increase strongly depends on the direction of the wave front with respect to fiber direction and the architecture of fibrosis.
Myocardial Contractile Function and Heart Rate in Mice With Myocyte-Specific Overexpression of Endothelial Nitric Oxide Synthase
Authors: Brunner Friedrich , Andrew Penelope , Wölkart Gerald , Zechner Rudolf , Mayer Bernd
Published: September 2007

Background
—

The major source of nitric oxide (NO) in the heart is the constitutive form of NO synthases (eNOS, NOS III) that is expressed in vascular endothelium and cardiac myocytes. NO mediates endothelium-dependent vasodilation and may modulate cardiac function. We examined the role of NO in hearts from transgenic (TG) mice overexpressing eNOS exclusively in cardiac myocytes.

Methods and Results
—

Three independent TG lines with varying levels of NOS activity were selected, and the hearts were isolated and retrogradely perfused at constant flow. We found that NO is positively inotropic in spontaneously beating hearts from wild-type (WT) mice, whereas hearts overexpressing eNOS had reduced basal contractility that was partially reversed by NOS blockade. Heart rate was not altered. Acetylcholine (10 to 1000 nmol/L) increased contractility in unstimulated hearts and decreased contractility after β-adrenergic stimulation with norepinephrine, and these responses were identical in WT and TG hearts. Finally, resting systolic intracellular calcium (Ca
2+
i
) tended to be lower in TG than in WT hearts, and the beat-to-beat responsiveness to Ca
2+
i
was reduced in hearts with eNOS overexpression.

Conclusions
—

High levels of endogenous myocyte-derived NO blunt myofilament Ca
2+
sensitivity. The similar effects of acetylcholine on contractility and heart rate, as well as the identical basal intrinsic heart rate in WT and TG hearts, provide a solid argument against NO as an important modulator of neurohormonal control of myocardial function.
Enhanced Angiotensin II Activity in Heart Failure
Authors: Opie Lionel H. , Sack Michael N.
Published: September 2007

Abstract
—There are strong data favoring the pathogenic role of angiotensin II type 1 receptor (AT
1
) activation with subsequent promotion of myocyte growth and cardiac fibrosis in the development of cardiac hypertrophy and heart failure. An emerging hypothesis suggests that the activity of the angiotensin II type 2 receptor (AT
2
) may counterregulate AT
1
receptor effects during cardiac development and during the evolution of cardiac hypertrophy and heart failure. In this review, we examine the potential role of AT
2
activity in the context of this hypothesis. In contrast to the counterregulatory hypothesis, studies in mice with an overabundance of, or a deficiency in, the AT
2
receptor do not suggest that AT
2
signaling is essential for cardiac development. Moreover, the proposed antigrowth effects of AT
2
receptor signaling in pathological cardiac hypertrophy could not be shown in two mice models both deficient in AT
2
receptors. The role of AT
2
receptor signaling in cardiac fibrosis is, however, still debatable because of conflicting data in the same two studies. In angiotensin II–evoked apoptosis in cardiomyocytes, the proposed proapoptotic role of AT
2
activity could not be confirmed. Furthermore, in the progression from the bench to bedside, the results of two large clinical trials in heart failure, namely ELITE II and Val-HeFT, can be explained without ascribing a major protective role to the unopposed activity of the AT
2
receptor in the failing myocardium. In this review, we conclude that the collective evidence does not strongly support a net beneficial effect of AT
2
stimulation in the diseased myocardium.
Diazoxide-Induced Cardioprotection Requires Signaling Through a Redox-Sensitive Mechanism
Authors: Forbes Robert A. , Steenbergen Charles , Murphy Elizabeth
Published: September 2007

Abstract
—Diazoxide, a selective opener of the mitochondrial ATP-sensitive potassium channel, has been shown to elicit tolerance to ischemia in cardiac myocytes and in perfused heart. However, the mechanism of this cardioprotection is poorly understood. Because reactive oxygen species (ROS) are recognized as important intracellular signaling molecules and have been implicated in ischemic preconditioning, we examined diazoxide-induced ROS production in adult cardiomyocytes. Cells treated with 50 μmol/L diazoxide showed a 173% increase in ROS production relative to baseline. 5-Hydroxydecanoate was found to attenuate the diazoxide-induced increase in ROS generation. The diazoxide-induced increase in ROS also was abrogated by the addition of either the antioxidant
N
-acetylcysteine (NAC) or
N
-mercaptopropionylglycine. We also examined the ability of NAC to block the protective effects of diazoxide in the perfused rat heart. After 20 minutes of global ischemia and 20 minutes of reflow, hearts perfused with 100 μmol/L diazoxide before ischemia showed significantly improved postischemic contractile function relative to untreated hearts (84% versus 29% of initial left ventricular developed pressure, respectively). Hearts treated with diazoxide in the presence of 4 mmol/L NAC recovered 53% of initial left ventricular developed pressure, whereas hearts treated with NAC alone recovered 46% of preischemic function. Using
31
P NMR spectroscopy, we found that, similar to preconditioning, diazoxide significantly attenuated ischemia-induced intracellular acidification and enhanced post- ischemic recovery of phosphocreatine levels, both of which were blocked by cotreatment with NAC. These data suggest that the cardioprotective actions of diazoxide are mediated by generation of a pro-oxidant environment.
Cardiovascular Proteomics
Authors: Arrell D. Kent , Neverova Irina , Van Eyk Jennifer E.
Published: September 2007

Abstract
—The development of proteomics is a timely one for cardiovascular research. Analyses at the organ, subcellular, and molecular levels have revealed dynamic, complex, and subtle intracellular processes associated with heart and vascular disease. The power and flexibility of proteomic analyses, which facilitate protein separation, identification, and characterization, should hasten our understanding of these processes at the protein level. Properly applied, proteomics provides researchers with cellular protein “inventories” at specific moments in time, making it ideal for documenting protein modification due to a particular disease, condition, or treatment. This is accomplished through the establishment of species- and tissue-specific protein databases, providing a foundation for subsequent proteomic studies. Evolution of proteomic techniques has permitted more thorough investigation into molecular mechanisms underlying cardiovascular disease, facilitating identification not only of modified proteins but also of the nature of their modification. Continued development should lead to functional proteomic studies, in which identification of protein modification, in conjunction with functional data from established biochemical and physiological methods, has the ability to further our understanding of the interplay between proteome change and cardiovascular disease.
Long-Chain Acyl–Coenzyme A Esters and Fatty Acids Directly Link Metabolism to K
ATP
Channels in the Heart
Authors: Liu Gong Xin , Hanley Peter J. , Ray John , ürgen Daut;
Published: September 2007

Abstract
—ATP-sensitive K (K
ATP
) channels are inhibited by cytosolic ATP, a defining property that implicitly links these channels to cellular metabolism. Here we report a direct link between fatty acid metabolism and K
ATP
channels in cardiac muscle cells. Long-chain (LC) acyl–coenzyme A (CoA) esters are synthesized from fatty acids and serve as the principal metabolic substrates of the heart. We have studied the effects of LC acyl-CoA esters and LC fatty acids on K
ATP
channels of isolated guinea pig ventricular myocytes and compared them with the effects of phosphatidylinositol 4,5-bisphosphate (PIP
2
). Application of oleoyl-CoA (0.2 or 1 μmol/L), a naturally occurring acyl-CoA ester, to the cytosolic side of excised patches completely prevented rundown of K
ATP
channels, but not of Kir2 channels. The open probability of K
ATP
channels measured in the presence of oleoyl-CoA or PIP
2
was voltage dependent, increasing with depolarization. Oleoyl-CoA greatly reduced the ATP sensitivity of K
ATP
channels. At a concentration of 2 μmol/L, oleoyl-CoA increased the half-maximal inhibitory concentration of ATP >200-fold. The time course of the decrease in ATP sensitivity was much faster during application of oleoyl-CoA than during application of PIP
2
. The effects of PIP
2
, but not of oleoyl-CoA, were inhibited by increasing Ca
2+
to 1 mmol/L. Oleate (C18:1; 10 μmol/L), the precursor of oleoyl-CoA, inhibited K
ATP
channels activated by oleoyl-CoA. Palmitoleoyl-CoA and palmitoleate (C16:1) exerted similar reciprocal effects. These findings indicate that LC fatty acids and their CoA-linked derivatives may be key physiological modulators of K
ATP
channel activity in the heart.
Tissue-Specific Patterns of Gap Junctions in Adult Rat Atrial and Ventricular Cardiomyocytes In Vivo and In Vitro
Authors: Kostin Sawa , Schaper Jutta
Published: September 2007

Abstract
—To verify the hypothesis that tissue-specific patterns of gap junctions (GJs) are determined by intrinsic factors within myocytes forming different cardiac tissues, we have compared by quantitative transmission electron microscopy (TEM) the structural features of GJs in adult rat atrial myocytes (AMs) and ventricular myocytes (VMs) in vivo with those in developing GJs in cultured AMs and VMs in vitro. Quantitative TEM data revealed a 3-fold increase in the number of developing GJs per intercalated disk in both AMs and VMs from 6 to 15 days in culture. However, at days 12 and 15, the percentage of GJ length per intercalated disk and mean GJ length were 2-fold higher in VMs than in AMs. Measurements of connexin43 GJs by confocal microscopy confirmed TEM data and demonstrated respectively 2- and 4.5-fold greater mean values of GJ length and area in VMs than in AMs. These differences are attributable to the development of large GJs (>3 μm) in VMs, closely resembling those observed in VMs in vivo. Although large GJs in cultured VMs comprised ≈14% of the total number of GJs, their contribution to total GJ length and area constituted >60% and 85%, respectively. In marked contrast, the number of large GJs in AMs both in vitro and in vivo was <1% from the total number of GJs. These data confirm our hypothesis and provide the first evidence that tissue-specific patterns of GJs in AMs and VMs are determined primarily by intrinsic factors within cardiac myocytes and are developmentally regulated.
MinK-Related Peptide 1 Associates With Kv4.2 and Modulates Its Gating Function
Authors: Zhang Mei , Jiang Min , Tseng Gea-Ny
Published: September 2007

Abstract—Inherited mutations and a polymorphism in minK-related peptide 1 (MiRP1) have been linked to congenital or acquired long-QT syndrome, pointing to the importance of MiRP1 in maintaining the cardiac electrical stability. We tested whether MiRP1 could affect the function of Kv4.x (x=2 and 3), the major pore-forming (α) subunits of transient outward (Ito) channels in the heart. We used theXenopusoocyte expression system to examine the effects of MiRP1 on Kv4.x channel gating kinetics and current amplitude and correlated these effects with MiRP1 expression level. MiRP1 slowed the rates of Kv4.2 activation and inactivation and shifted the voltage dependence of channel gating in the positive direction. These effects had a similar “dose” dependence: they plateaued at a cRNA ratio (MiRP1:Kv4.2) of 13:1, with half-maximum effects at estimated cRNA ratios of 2 to 4. On the other hand, MiRP1 had no significant effects on Kv4.2 current amplitude in the same range of expression level. When expressed at a comparable low level, MiRP1 had similar (although smaller) effects on Kv4.3 but could not modulate Kv1.4 (another α subunit ofItochannels in the heart). Kv4.2 could be coimmunoprecipitated with epitope-tagged MiRP1, indicating that the 2 could form a stable complex. Our data suggest that MiRP1 may serve as a regulatory (β) subunit ofItochannels in the heart. This is supported by the observation that MiRP1 induced an “overshoot” of Kv4.2 current amplitude during channel recovery from inactivation, similar to the overshoot ofItodescribed for human epicardial myocytes.
Null Mutation of Connexin43 Causes Slow Propagation of Ventricular Activation in the Late Stages of Mouse Embryonic Development
Authors: Vaidya Dhananjay , Tamaddon Houman S. , Lo Cecilia W. , Taffet Steven M. , Delmar Mario , Morley Gregory E. , Jalife José
Published: September 2007

Abstract
—Connexin43 (Cx43) is the principal connexin isoform in the mouse ventricle, where it is thought to provide electrical coupling between cells. Knocking out this gene results in anatomic malformations that nevertheless allow for survival through early neonatal life. We examined electrical wave propagation in the left (LV) and right (RV) ventricles of isolated Cx43 null mutated (Cx43
−/−
), heterozygous (Cx43
+/
−
), and wild-type (WT) embryos using high-resolution mapping of voltage-sensitive dye fluorescence. Consistent with the compensating presence of the other connexins, no reduction in propagation velocity was seen in Cx43
−/−
ventricles at postcoital day (dpc) 12.5 compared with WT or Cx43
+/
−
ventricles. A gross reduction in conduction velocity was seen in the RV at 15.5 dpc (in cm/second, mean [1 SE confidence interval], WT 9.9 [8.7 to 11.2], Cx43
+/
−
9.9 [9.0 to 10.9], and Cx43
−/−
2.2 [1.8 to 2.7;
P
<0.005]) and in both ventricles at 17.5 dpc (in RV, WT 8.4 [7.6 to 9.3], Cx43
+/
−
8.7 [8.1 to 9.3], and Cx43
−/−
1.1 [0.1 to 1.3;
P
<0.005]; in LV, WT 10.1 [9.4 to 10.7], Cx43
+/
−
8.3 [7.8 to 8.9], and Cx43
−/−
1.7 [1.3 to 2.1;
P
<0.005]) corresponding with the downregulation of Cx40. Cx40 and Cx45 mRNAs were detectable in ventricular homogenates even at 17.5 dpc, probably accounting for the residual conduction function. Neonatal knockout hearts were arrhythmic in vivo as well as ex vivo. This study demonstrates the contribution of Cx43 to the electrical function of the developing mouse heart and the essential role of this gene in maintaining heart rhythm in postnatal life.
Arrhythmogenesis and Contractile Dysfunction in Heart Failure
Authors: Pogwizd Steven M. , Schlotthauer Klaus , Li Li , Yuan Weilong , Bers Donald M.
Published: September 2007

Abstract
—Ventricular arrhythmias and contractile dysfunction are the main causes of death in human heart failure (HF). In a rabbit HF model reproducing these same aspects of human HF, we demonstrate that a 2-fold functional upregulation of Na
+
-Ca
2+
exchange (NaCaX) unloads sarcoplasmic reticulum (SR) Ca
2+
stores, reducing Ca
2+
transients and contractile function. Whereas β-adrenergic receptors (β-ARs) are progressively downregulated in HF, residual β-AR responsiveness at this critical HF stage allows SR Ca
2+
load to increase, causing spontaneous SR Ca
2+
release and transient inward current carried by NaCaX. A given Ca
2+
release produces greater arrhythmogenic inward current in HF (as a result of NaCaX upregulation), and ≈50% less Ca
2+
release is required to trigger an action potential in HF. The inward rectifier potassium current (
I
K1
) is reduced by 49% in HF, and this allows greater depolarization for a given NaCaX current. Partially blocking
I
K1
in control cells with barium mimics the greater depolarization for a given current injection seen in HF. Thus, we present data to support a novel paradigm in which changes in NaCaX and
I
K1
, and residual β-AR responsiveness, conspire to greatly increase the propensity for triggered arrhythmias in HF. In addition, NaCaX upregulation appears to be a critical link between contractile dysfunction and arrhythmogenesis.
Calcineurin Pathway Is Required for Endothelin-1–Mediated Protection Against Oxidant Stress–Induced Apoptosis in Cardiac Myocytes
Authors: Kakita Tsuyoshi , Hasegawa Koji , Iwai-Kanai Eri , Adachi Souichi , Morimoto Tatsuya , Wada Hiromichi , Kawamura Teruhisa , Yanazume Tetsuhiko , Sasayama Shigetake
Published: September 2007

Abstract
—Endothelin-1 (ET-1) acts not only as a growth-promoting peptide but also as a potent survival factor against myocardial cell apoptosis. However, the signaling pathways leading to myocardial cell protection by ET-1 are poorly understood. Using a culture system of primary cardiac myocytes derived from neonatal rats, we show in the present study that ET-1 almost completely blocked the hydrogen peroxide–induced increase in the percentage of TdT-mediated dUTP-biotin nick-end labeling–positive myocytes. Apoptosis inhibition by ET-1 was confirmed by cytofluorometric analysis as well as by examination of the ladder formation, morphological features, and caspase-3 cleavage. We have found that ET-1 converts the nuclear factor of activated T lymphocytes (NFATc) in cardiac myocytes into high-mobility forms and translocates cytoplasmic NFATc to the nuclei. In addition, ET-1 stimulates the interaction between NFATc and the cardiac-restricted zinc-finger protein GATA4 in these cells. The immunosuppressants cyclosporin A and FK506, which antagonize calcineurin, negated the inhibitory effect of ET-1 on apoptosis. Calcineurin activation de novo was sufficient to inhibit hydrogen peroxide–induced apoptosis. ET-1 induced the expression of an antiapoptotic protein bcl-2 in cardiac myocytes in a cyclosporin A–dependent manner, but it did not alter the expression of bax. Cyclosporin A also attenuated the ET-1–stimulated transcription of the bcl-2 gene in these cells. These findings demonstrate that the calcineurin pathway is required for the inhibitory effect of ET-1 on oxidant stress–induced apoptosis in cardiac myocytes.
Overexpression of Ref-1 Inhibits Hypoxia and Tumor Necrosis Factor–Induced Endothelial Cell Apoptosis Through Nuclear Factor-κB–Independent and –Dependent Pathways
Authors: Hall Jennifer L. , Wang Xiaohong , Van Adamson  , Zhao Ying , Gibbons Gary H.
Published: September 2007

Abstract
— We hypothesized that a redox-sensitive transcription factor, redox factor-1 (Ref-1) (HAP1, APE, and APEX), was critical in the regulation of endothelial cell survival in response to hypoxia and cytokines, including tumor necrosis factor (TNF)-α. Hypoxia resulted in a significant decrease in Ref-1 protein expression in both human umbilical vein endothelial cells and calf pulmonary artery endothelial cells. The hypoxia-induced decrease in Ref-1 expression was followed by a significant induction of apoptosis as measured by caspase 3 activity and nuclear morphology. Transient upregulation of Ref-1 significantly inhibited hypoxia-induced apoptosis. However, deletion of the redox-sensitive domain of Ref-1 abolished the antiapoptotic effect. We postulated that the antiapoptotic effects of Ref-1 were mediated through nuclear factor-κB (NF-κB). However, blockade of NF-κB with a dominant-negative IκB (S32A/S36A) expression vector had no effect on Ref-1–mediated survival under hypoxic conditions. The second aim of this study was to test the cytoprotective ability of Ref-1 upregulation in response to TNF-induced apoptosis. Ref-1 inhibition of TNF-induced death was associated with a significant potentiation of NF-κB activity. Deletion of the redox-sensitive domain of Ref-1 significantly inhibited TNF-induced NF-κB activation. Moreover, loss of the redox-sensitive domain also abolished the antiapoptotic effect of Ref-1 in response to TNF. To test whether Ref-1 induced activation of NF-κB was necessary to promote survival, we blocked NF-κB activity with a dominant-negative IκB (S32A/S36A). Indeed, blockade of NF-κB activity abolished the ability of Ref-1 to rescue TNF-induced apoptosis. In conclusion, upregulation of Ref-1 promotes endothelial cell survival in response to hypoxia and TNF through NF-κB–independent and NF-κB–dependent signaling cascades, respectively. Moreover, it seems that Ref-1 may act as a critical cofactor, mediating the TNF-induced NF-κB response in the vascular endothelium.
Model for Hypoxic Pulmonary Vasoconstriction Involving Mitochondrial Oxygen Sensing
Authors: Waypa Gregory B. , Chandel Navdeep S. , Schumacker Paul T.
Published: September 2007

Abstract
—We tested whether mitochondria function as the O
2
sensor underlying hypoxic pulmonary vasoconstriction (HPV). In buffer-perfused rat lungs, rotenone, myxothiazol, and diphenyleneiodonium, which inhibit mitochondria in the proximal region of the electron transport chain (ETC), abolished HPV without attenuating the response to U46619. Cyanide and antimycin A inhibit electron transfer in the distal region of the ETC, but they did not abolish HPV. Cultured pulmonary artery (PA) myocytes contract in response to hypoxia or to U46619. The hypoxic response was abolished while the response to U46619 was maintained in mutant (ρ
0
) PA myocytes lacking a mitochondrial ETC. To test whether reactive oxygen species (ROS) derived from mitochondria act as signaling agents in HPV, the antioxidants pyrrolidinedithiocarbamate and ebselen and the Cu,Zn superoxide dismutase inhibitor diethyldithiocarbamate were used. These abolished HPV without affecting contraction to U46619, suggesting that ROS act as second messengers. In cultured PA myocytes, oxidation of intracellular 2′,7′-dichlorofluorescin diacetate (DCFH) dye increased under 2% O
2
, indicating that myocytes increase their generation of H
2
O
2
during hypoxia. This was attenuated by myxothiazol, implicating mitochondria as the source of increased ROS during HPV. These results indicate that mitochondrial ATP is not required for HPV, that mitochondria function as O
2
sensors during hypoxia, and that ROS generated in the proximal region of the ETC act as second messengers in the response.
Increased Expression of Protease-Activated Receptor-2 (PAR2) and PAR4 in Human Coronary Artery by Inflammatory Stimuli Unveils Endothelium-Dependent Relaxations to PAR2 and PAR4 Agonists
Authors: Hamilton Justin R. , Frauman Albert G. , Cocks Thomas M.
Published: September 2007

Abstract—Protease-activated receptor (PAR)1 and PAR2 are expressed on vascular endothelial cells and mediate endothelium-dependent relaxation in several species, and PAR4 agonists cause similar responses in rat aortas. To date, only PAR1 has been reported to mediate relaxation of human arteries despite endothelial cell expression of both PAR1 and PAR2 in these tissues. Because inflammatory stimuli increase PAR2 expression in human endothelial cells in culture, the present study investigated the effect of similar stimuli on PARs in human isolated coronary arteries (HCAs). In HCA ring segments suspended for isometric tension measurements, the selective PAR1-activating peptide, TFLLR (0.01 to 10 μmol/L), caused endothelium-dependent relaxation of precontracted preparations. Little or no change in vascular tension was elicited by either the PAR2- or PAR4-activating peptides, SLIGKV and GYPGQV, respectively (up to 100 μmol/L). Exposure of HCAs to interleukin (IL)-1α (1 ng/mL, 12 hours) or tumor necrosis factor-α (3 nmol/L, 12 hours) did not affect PAR1 expression but increased PAR2 and PAR4 mRNA levels by ≈5- and 4-fold, respectively, as determined by quantitative polymerase chain reaction. Similar IL-1α treatment did not affect TFLLR-induced relaxations but revealed significant endothelium-dependent relaxations to SLIGKV (100 μmol/L, 61.4±6.7%) and GYPGQV (100 μmol/L, 34.8±6.4%). These studies are the first to demonstrate functional PAR2 and PAR4 in human arteries in situ. The selective upregulation of PAR2 and PAR4 expression and the increased vascular response in HCAs after exposure to inflammatory stimuli suggest a role for these endothelial receptors during inflammation.
Number and Migratory Activity of Circulating Endothelial Progenitor Cells Inversely Correlate With Risk Factors for Coronary Artery Disease
Authors: Vasa Mariuca , Fichtlscherer Stephan , Aicher Alexandra , Adler Klaudia , Urbich Carmen , Martin Hans , Zeiher Andreas M. , Dimmeler Stefanie
Published: September 2007

Abstract
—Recent studies provide increasing evidence that postnatal neovascularization involves bone marrow–derived circulating endothelial progenitor cells (EPCs). The regulation of EPCs in patients with coronary artery disease (CAD) is unclear at present. Therefore, we determined the number and functional activity of EPCs in 45 patients with CAD and 15 healthy volunteers. The numbers of isolated EPCs and circulating CD34/kinase insert domain receptor (KDR)-positive precursor cells were significantly reduced in patients with CAD by ≈40% and 48%, respectively. To determine the influence of atherosclerotic risk factors, a risk factor score including age, sex, hypertension, diabetes, smoking, positive family history of CAD, and LDL cholesterol levels was used. The number of risk factors was significantly correlated with a reduction of EPC levels (
R
=−0.394,
P
=0.002) and CD34-/KDR-positive cells (
R
=−0.537,
P
<0.001). Analysis of the individual risk factors demonstrated that smokers had significantly reduced levels of EPCs (
P
<0.001) and CD34-/KDR-positive cells (
P
=0.003). Moreover, a positive family history of CAD was associated with reduced CD34-/KDR-positive cells (
P
=0.011). Most importantly, EPCs isolated from patients with CAD also revealed an impaired migratory response, which was inversely correlated with the number of risk factors (
R
=−0.484,
P
=0.002). By multivariate analysis, hypertension was identified as a major independent predictor for impaired EPC migration (
P
=0.043). The present study demonstrates that patients with CAD revealed reduced levels and functional impairment of EPCs, which correlated with risk factors for CAD. Given the important role of EPCs for neovascularization of ischemic tissue, the decrease of EPC numbers and activity may contribute to impaired vascularization in patients with CAD. The full text of this article is available at http://www.circresaha.org.
Cardiac-Specific Expression of Heme Oxygenase-1 Protects Against Ischemia and Reperfusion Injury in Transgenic Mice
Authors: Yet Shaw-Fang , Tian Rong , Layne Matthew D. , Wang Zhi Yuan , Maemura Koji , Solovyeva Maria , Ith Bonna , Melo Luis G. , Zhang Lunan , Ingwall Joanne S. , Dzau Victor J. , Lee Mu-En , Perrella Mark A.
Published: September 2007

Heme oxygenase (HO)-1 degrades the pro-oxidant heme and generates carbon monoxide and antioxidant bilirubin. We have previously shown that in response to hypoxia, HO-1–null mice develop infarcts in the right ventricle of their hearts and that their cardiomyocytes are damaged by oxidative stress. To test whether HO-1 protects against oxidative injury in the heart, we generated cardiac-specific transgenic mice overexpressing different levels of HO-1. By use of a Langendorff preparation, hearts from transgenic mice showed improved recovery of contractile performance during reperfusion after ischemia in an HO-1 dose–dependent manner. In vivo, myocardial ischemia and reperfusion experiments showed that infarct size was only 14.7% of the area at risk in transgenic mice compared with 56.5% in wild-type mice. Hearts from these transgenic animals had reduced inflammatory cell infiltration and oxidative damage. Our data demonstrate that overexpression of HO-1 in the cardiomyocyte protects against ischemia and reperfusion injury, thus improving the recovery of cardiac function.
Acetylcholine, Bradykinin, Opioids, and Phenylephrine, but not Adenosine, Trigger Preconditioning by Generating Free Radicals and Opening Mitochondrial K
ATP
Channels
Authors: Cohen Michael V. , Yang Xi-Ming , Liu Guang S. , Heusch Gerd , Downey James M.
Published: September 2007

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. Risk area was measured with fluorescent particles and infarct size with triphenyltetrazolium chloride staining. Control hearts showed 29.1±2.8% infarction of the risk zone. A 5-minute infusion of acetylcholine (0.55 mmol/L) beginning 15 minutes before the 30-minute occlusion resulted in significant protection (9.2±2.7% infarction). This protection could be blocked by administration of 300 μmol/L
N
-2-mercaptopropionyl glycine (MPG), a free radical scavenger, or by 200 μmol/L 5-hydroxydecanoate (5-HD), a mitochondrial K
ATP
antagonist, for 15 minutes beginning 5 minutes before the acetylcholine infusion (35.2±3.9% and 27.8±2.4% infarction, respectively). Similar protection was observed with other known triggers, ie, bradykinin (0.4 μmol/L), morphine (0.3 μmol/L), and phenylephrine (0.1 μmol/L), and in each case protection was completely abrogated by either MPG or 5-HD. 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.
Functional Consequences of Integrin Gene Mutations in Mice
Authors: Bouvard Daniel , Brakebusch Cord , Gustafsson Erika , Aszódi Attila , Bengtsson Therese , Berna Alejandro , Fässler Reinhard
Published: September 2007

Integrins are cell-surface receptors responsible for cell attachment to extracellular matrices and to other cells. The application of mouse genetics has significantly increased our understanding of integrin function in vivo. In this review, we summarize the phenotypes of mice carrying mutant integrin genes and compare them with phenotypes of mice lacking the integrin ligands.