bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk and Predictors of Stroke After Myocardial Infarction Among the Elderly
Authors: Lichtman Judith H. , Krumholz Harlan M. , Wang Yun , Radford Martha J. , Brass Lawrence M.
Published: July 2002

Background
—

Stroke is an important outcome after acute myocardial infarction. Studies that have examined this relationship have largely excluded older patients, even though half of stroke admissions occur among patients 75 years of age and older.

Methods and Results
—

Among 111 023 medicare patients discharged with a principal diagnosis of acute myocardial infarction during an 8-month period in 1994 to 1995, we identified hospital admissions for ischemic stroke within 6 months of discharge. The rate of admission was 2.5% within 6 months. Independent predictors of ischemic stroke were age ≥75 years, black race, no aspirin at discharge, frailty, prior stroke, atrial fibrillation, diabetes, hypertension, and history of peripheral vascular disease. To identify individuals at increased risk for stroke, a risk stratification score was constructed from identified factors. The 6-month stroke admission rate for patients with a score of 4 or higher (≈20% of the total sample) was ≈4%.

Conclusions
—

The risk of stroke after myocardial infarction is substantial, with about 1 in 40 patients suffering an ischemic stroke within 6 months of discharge. Simple clinical factors can predict the risk of stroke and, based on these factors, we identified 20% of older patients who have a 1 in 25 chance of being hospitalized for a stroke within 6 months of discharge.
Pulmonary Vein Isolation for Paroxysmal and Persistent Atrial Fibrillation
Authors: Oral Hakan , Knight Bradley P. , Tada Hiroshi , Özaydın Mehmet , Chugh Aman , Hassan Sohail , Scharf Christoph , Lai Steve W.K. , Greenstein Radmira , Pelosi Frank , Strickberger S. Adam , Morady Fred
Published: July 2002

Background
—

The pulmonary veins (PVs) have been demonstrated to often play an important role in generating atrial fibrillation (AF). The purpose of this study was to determine the safety and efficacy of segmental PV isolation in patients with paroxysmal or persistent AF.

Methods and Results
—

In 70 consecutive patients (mean age, 53±11 years) with paroxysmal (58) or persistent (12) AF, segmental PV isolation guided by ostial PV potentials was performed. The left superior, left inferior, and right superior PVs were targeted for isolation in all patients, and the right inferior PV was isolated in 20 patients. Among the 230 targeted PVs, 217 (94%) were completely isolated, with a mean of 6.5±4.2 minutes of radiofrequency energy applied at a maximum power setting of 35 W. A second PV isolation procedure was performed in 6 patients (9%). At 5 months of follow-up, 70% of patients with paroxysmal and 22% of patients with persistent AF were free from recurrent AF (
P
<0.001), and 83% of patients with paroxysmal AF were either free of symptomatic AF or had significant improvement. Among various clinical characteristics, only paroxysmal AF was an independent predictor of freedom from recurrence of AF (
P
<0.05). One patient developed unilateral quadrantopsia after the procedure. There were no other complications.

Conclusions
—

With a segmental isolation approach that targets at least 3 PVs, a clinically satisfactory result can be achieved in >80% of patients with paroxysmal AF. The clinical efficacy of pulmonary vein isolation is much lower when AF is persistent than when it is paroxysmal.
Vascular Endothelial Growth Factor Is Necessary in the Development of Arteriosclerosis by Recruiting/Activating Monocytes in a Rat Model of Long-Term Inhibition of Nitric Oxide Synthesis
Authors: Zhao Qingwei , Egashira Kensuke , Inoue Shujiro , Usui Makoto , Kitamoto Shiro , Ni Weihua , Ishibashi Minako , Hiasa Ken-ichi , Ichiki Toshihiro , Shibuya Masabumi , Takeshita Akira
Published: July 2002

Background
—

It remains unclear whether vascular endothelial growth factor (VEGF) is a proarteriosclerotic or an antiarteriosclerotic factor. We recently reported that long-term inhibition of nitric oxide by administering
Nω
-nitro-
l
-arginine methyl ester (L-NAME) induces coronary vascular inflammation and arteriosclerosis.

Methods and Results
—

We used this animal model to investigate the role of VEGF in arteriosclerosis. We blocked VEGF activity in vivo by transfecting with plasmid DNA encoding the murine soluble
FLT-1
(
sFLT-1
) gene into thigh muscle. Soluble
FLT-1
can suppress VEGF activity both by sequestering VEGF and by functioning as a dominant-negative inhibitor of VEGF receptors. We observed vascular inflammation associated with increased VEGF expression within 3 days of L-NAME administration, which was prevented by pretreatment with ACE inhibitor, angiotensin II receptor antagonist, or neutralizing monocyte chemoattractant protein-1 antibody. The
sFLT-1
gene transfer attenuated the early vascular inflammation and prevented late arteriosclerosis. The
sFLT-1
gene transfer also inhibited increased expression of monocyte chemoattractant protein-1 and transforming growth factor-β, indicating creation of a positive feedback loop to cause arteriosclerosis.

Conclusions
—

VEGF is necessary in the development of arteriosclerosis by mediating monocyte recruitment and activation in this model.
Validation of Collateral Fractional Flow Reserve by Myocardial Perfusion Imaging
Authors: Matsuo Hitoshi , Watanabe Sachiro , Kadosaki Tohru , Yamaki Takahiko , Tanaka Shinichiro , Miyata Shuusaku , Segawa Tomonori , Matsuno Yukihiko , Tomita Masaaki , Fujiwara Hisayoshi
Published: July 2002

Background
—

Collateral fractional flow reserve (FFR

coll

) is an index to quantify collateral blood flow, derived from coronary pressure measurements. Although well defined theoretically, its direct validation by myocardial perfusion imaging has not been established so far. Validating this index by myocardial perfusion imaging is the main aim of this study.

Methods and Results
—

Twenty-four consecutive patients with stable angina and single left anterior descending artery stenosis underwent simultaneous measurement of aortic pressure (P

a

), coronary wedge pressure (P

w

), and central venous pressure (P

v

) during balloon inflation. FFR

coll

was calculated and compared with the extent and severity of the defect during coronary occlusion using
99m
Tc-sestamibi imaging at balloon inflation of the respective coronary artery. Although the pressure-derived collateral indexes (P

w

, P

w

/P

a

, and FFR

coll

) ranged widely, they were closely correlated with extent and severity scores of the nuclear occlusion images and superior to the ECG for that purpose. Of all parameters, FFR

coll

correlated best with the severity score at imaging (
r
=−0.88), followed by the P

w

/P

a

ratio (
r
=−0.74) or P

w

alone (
r
=−0.69).

Conclusions
—

FFR

coll

, calculated from coronary pressure during balloon occlusion, is highly correlated with the extent and severity of the defect at myocardial perfusion of the territory of the occluded artery and can be used for quantitative assessment of collateral blood flow in conscious humans.
Vascular Gene Transfer of Phosphomimetic Endothelial Nitric Oxide Synthase (S1177D) Using Ultrasound-Enhanced Destruction of Plasmid-Loaded Microbubbles Improves Vasoreactivity
Authors: Teupe Claudius , Richter Sergio , Fisslthaler Beate , Randriamboavonjy Voahanginirina , Ihling Christian , Fleming Ingrid , Busse Rudi , Zeiher Andreas M. , Dimmeler Stefanie
Published: July 2002

Background
—

Local gene therapy has enormous potential for the treatment of vascular disease. We determined whether diagnostic ultrasound-mediated destruction of plasmid-loaded albumin microbubbles is a feasible and efficient technique for local vascular gene delivery. For gene transfer, we used a phosphomimetic, active endothelial nitric oxide synthase (eNOS) construct in which Ser1177 was replaced by aspartic acid (S1177D) and exhibits a 2-fold higher basal activity than the wild-type enzyme.

Methods and Results
—

Gas-filled microbubbles (3.0±1.2 μm) were created by sonication of 5% human albumin in the presence of plasmid DNA encoding for
LacZ
or eNOS S1177D. Porcine coronary arteries were perfused with DNA-loaded albumin microbubbles in vitro, exposed to diagnostic ultrasound (5 seconds), and incubated for a further 24 hours. Detection of the β-galactosidase in
LacZ
-transfected vessels revealed a predominant staining of endothelial cells without any functional impairment of vasoreactivity. Western blotting demonstrated the expression of the eNOS S1177D construct in extracts from the transfected segments. Vascular responsiveness was tested with prostaglandin F
2α
and the NOS inhibitor

N
ω

nitro-
l
-arginine. Compared with segments treated with the expression plasmid alone, the contractile response to prostaglandin F
2α
was impaired in segments transfected with eNOS S1177D, whereas the contractile response to the administration of

N
ω

nitro-
l
-arginine was markedly enhanced.

Conclusions
—

Ultrasound-mediated destruction of eNOS S1177D DNA-loaded albumin microbubbles is a feasible and efficient method for vascular gene transfection. Transfection resulted in significant protein expression and enhanced NO-mediated relaxation of bradykinin-stimulated porcine coronary arteries.
Intravenous Pulse Administration of Cyclophosphamide Is an Effective and Safe Treatment for Sensitized Cardiac Allograft Recipients
Authors: Itescu Silviu , Burke Elizabeth , Lietz Katherine , John Ranjit , Mancini Donna , Michler Robert , Rose Eric , Oz Mehmet , Edwards Niloo
Published: July 2002

Background

—

The proportion of cardiac transplant recipients with preexisting sensitization to HLA alloantigens has been increasing. Sensitization prolongs duration to obtaining a donor and predicts poorer long-term allograft survival because of increased risk of cellular rejections. We investigated the effect of cyclophosphamide pulse therapy in sensitized cardiac allograft recipients.

Methods and Results

—

Pretransplant and posttransplant outcomes were compared between 88 cardiac allograft recipients at risk for sensitization and 26 sensitized recipients treated with intravenous cyclophosphamide pulse therapy together with intravenous immune globulin before transplant and as part of a cyclosporine-based triple immunosuppressive regimen after transplant. Preformed IgG anti-HLA antibodies predicted longer duration to transplantation, earlier cellular rejection, and 2.7-fold higher cumulative rejection frequency (
P
=0.002). Before transplant, cyclophosphamide reduced waiting time and mortality to levels in nonsensitized patients. After transplant, cyclophosphamide prevented induction of IgG anti-HLA class II antibodies and interleukin-2 receptor–positive T-cell outgrowth from biopsy sites (both
P
<0.01), prolonged the rejection-free interval (
P
=0.009), and reduced cumulative rejections to levels in nonsensitized patients (
P
=0.003). By multivariable analysis, the risk of rejection was 3.7-fold higher in patients treated with mycophenolate mofetil than patients treated with cyclophosphamide (
P
=0.019). There were no differences in infectious or other significant complications.

Conclusions

—

Immunosuppression incorporating intravenous cyclophosphamide before and after transplantation is safe and highly effective in sensitized cardiac transplant recipients. When used after transplantation as part of triple immunosuppression, cyclophosphamide is superior to mycophenolate mofetil in reducing rejection. The mechanism may involve prevention of diversification of the recipient immune response to donor HLA class II molecules.
Relationship Between Lipid Levels and Clinical Outcomes in the Long-Term Intervention With Pravastatin in Ischemic Disease (LIPID) Trial
Authors: Simes R. John , Marschner Ian C. , Hunt David , Colquhoun David , Sullivan David , Stewart Ralph A.H. , Hague Wendy , Keech Anthony , Thompson Peter , White Harvey , Shaw John , Tonkin Andrew
Published: July 2002

Background

—

The Long-Term Intervention with Pravastatin in Ischemic Disease (LIPID) trial showed that pravastatin significantly reduced mortality and coronary heart disease (CHD) events in 9014 patients with known CHD and total cholesterol 4.0 to 7.0 mmol/L at baseline. Secondary objectives included assessment of CHD event reduction according to lipid levels.

Methods and Results

—

We investigated the relationships of baseline and on-study lipids with subsequent CHD events in separate Cox models. Treatment effect on CHD event reduction was examined by baseline lipids and after adjustment for on-study lipid levels. Baseline lipids were significant predictors of CHD events. The adjusted relative risk per mmol/L (on placebo) was 1.24 (
P
=0.004) for total cholesterol, 1.28 (
P
=0.002) for low-density lipoprotein cholesterol, and 0.52 (
P
=0.004) for high-density lipoprotein cholesterol. Apolipoproteins A1 and B were strong predictors (each
P
=0.001). Pravastatin reduced the risk of the composite outcome of fatal CHD or nonfatal myocardial infarction by 24% (95% confidence interval [CI], 15% to 32%) and the expanded end point of fatal CHD, nonfatal myocardial infarction, unstable angina, or coronary revascularization by 17% (95% CI, 10% to 24%). Similar relative effects were observed for different categories of baseline lipids. The proportion of treatment effect explained by on-study lipid levels was 67% (95% CI, 27% to 106%) for the composite and 97% (95% CI, 49% to 145%) for the expanded end point. The most important lipids associated with event reduction were apolipoprotein B, low-density lipoprotein cholesterol, and the combination of total and high-density lipoprotein cholesterol.

Conclusions

—

Changes in lipid levels can explain all or most of the observed benefit of pravastatin. Some treatment effect may also be mediated through nonlipid changes.
Effects of Cariporide and Losartan on Hypertrophy, Calcium Transients, Contractility, and Gene Expression in Congestive Heart Failure
Authors: Loennechen Jan P. , Wisløff Ulrik , Falck Geir , Ellingsen Øyvind
Published: July 2002

Background

—

The purpose of this study was to compare long-term effects of cariporide with those of losartan in postinfarction heart failure.

Methods and Results

—

Female Sprague-Dawley rats with large myocardial infarctions and sham controls were randomized to losartan, cariporide, or placebo after 7 days and treated for 49 days. Cardiac function was assessed by echocardiography and measurement of left ventricular pressures, and gene expression was assessed by competitive reverse transcription–polymerase chain reaction. Cell dimensions, shortening, and relaxation were determined by videomicroscopy and calcium transients by fura 2. Losartan reduced postinfarction systolic and diastolic left ventricular dilation (by 24% and 31%, respectively), left and right ventricular weight (by 22% and 26%, respectively), and cardiomyocyte hypertrophy length and width (by 62% and 54%, respectively). Induction of myocardial atrial natriuretic peptide decreased 66%. Cariporide did not affect postinfarction hypertrophy or atrial natriuretic peptide. Losartan and cariporide respectively improved reduced cellular contractility (55% and 30%) and reduced elevated systolic (86% and 27%) and diastolic (49% and 43%) calcium. Losartan and cariporide respectively reduced prolonged time to 50% relaxation (66% and 25%) and time to 50% calcium reduction (55% and 53%).

Conclusions

—

Losartan and cariporide improve cardiomyocyte contractility and calcium regulation in chronic heart failure. Losartan has salutary effects on postinfarction remodeling and gene expression, whereas cariporide is neutral.
Left Ventricular Volume Reduction by Radiofrequency Heating of Chronic Myocardial Infarction in Patients With Congestive Heart Failure
Authors: Victal Octavio A. , Teerlink John R. , Gaxiola Efrain , Wallace Arthur W. , Najar Sergio , Camacho David H. , Gutierrez Augustin , Herrera Gabriel , Zuniga Gustavo , Mercado-Rios Fausto , Ratcliffe Mark B.
Published: July 2002

Background

—

Myocardial infarct expansion and left ventricular (LV) remodeling are integral components in the evolution of chronic heart failure and predict morbidity and mortality. Radiofrequency (RF) heating and patch placement of chronic LV aneurysms caused a sustained reduction in LV infarct area and volume in an ovine infarct model. This study evaluated the effect of RF heating and epicardial patch as an adjunct to coronary artery bypass graft on LV volumes in patients with prior myocardial infarction, evidence of akinetic/dyskinetic scar, and LV ejection fraction ≤40%.

Methods and Results

—

Ten patients (3 female; mean age, 64±11 years) scheduled for coronary artery bypass graft were enrolled (Canadian Cardiovascular Society angina class 2.1±1.1; New York Heart Association class 3.1±0.5). Intraoperative digital photography demonstrated an acute 39% reduction in infarct area (n=5;
P
=0.01), and transesophageal ECGs demonstrated a 16% acute reduction in LV end-diastolic volumes (n=9;
P
=0.002) after RF treatment. There were no intraoperative or procedure-related postoperative complications, and during an average follow-up of >180 days, there have been no safety issues. All patients had complete relief of their angina and improvement in exercise tolerance. Serial transthoracic ECGs over the 6 months of follow-up after RF treatment demonstrated persistent reductions in LV end-diastolic volume (29%;
P
<0.0001) and LV end-systolic volume (37%;
P
<0.0001) with improved ejection fraction (
P
<0.02).

Conclusions

—

RF heating and patch placement in these 10 patients resulted in acute reduction in infarct area and ventricular volumes that were maintained 180 days after procedure. This technique may reduce the incidence of congestive heart failure and mortality in these patients and warrants investigation in larger clinical trials.
Myofilament Calcium Sensitivity in Skinned Rat Cardiac Trabeculae
Authors: Konhilas John P. , Irving Thomas C. , de Tombe Pieter P.
Published: July 2002

The increase in myofilament Ca
2+
responsiveness on an increase in sarcomere length (SL) is, in part, the cellular basis for Frank-Starling’s law of the heart. It has been suggested that a decrease in myofilament lattice spacing (LS) in response to an increase in SL underlies this phenomenon. This hypothesis is supported by previous studies in which reduced muscle width induced by osmotic compression was associated with an increase in Ca
2+
sensitivity, mimicking those changes observed with an increase in SL. To evaluate this hypothesis, we directly measured LS by synchrotron x-ray diffraction as function of SL in skinned rat cardiac trabeculae bathed in 0% to 6% dextran solutions (MW 413 000). We found that EC
50
, [Ca
2+
] at which force is half-maximal, at SL between 1.95 and 2.25 μm did not vary in proportion to LS when 3% or 6% dextran solutions were applied. We also found that moderate compression (1% dextran) of skinned trabeculae at SL=2.02 μm reduced LS (LS=42.29±0.14 nm) to match that of uncompressed fibers at a long SL (SL=2.19 μm; LS=42.28±0.15 nm). Whereas increasing SL from 2.02 to 2.19 μm significantly increased Ca
2+
sensitivity as indexed by the EC
50
parameter (2.87±0.11 μmol/L to 2.52±0.12 μmol/L), similar reduction in myofilament lattice spacing achieved by compression with 1% dextran did not alter Ca
2+
sensitivity (2.87±0.10 μmol/L) at the short SL. We conclude that alterations in myofilament lattice spacing may not be the mechanism that underlies the sarcomere length–induced alteration of calcium sensitivity in skinned myocardium.
Cardiac-Specific Overexpression of Inducible Nitric Oxide Synthase Does Not Result in Severe Cardiac Dysfunction
Authors: Heger Jacqueline , Gödecke Axel , Flögel Ulrich , Merx Marc W. , Molojavyi Andrei , Kühn-Velten W. Nikolaus , Schrader Jürgen
Published: July 2002

Nitric oxide (NO), a potent regulator of myocardial contractility, has been implicated in the development of heart failure; however, no study exists describing the relation between expression of inducible nitric oxide synthase (iNOS), formation of NO in vivo, and cardiac contractility. We have therefore generated transgenic (TG) mice overexpressing iNOS under the cardiospecific α-myosin heavy chain (α-MHC) promoter. In vitro, iNOS activity in hearts of two transgenic lines was 260- to 400-fold above controls (wild type [WT]), but TG mice were viable and appeared normal. Ventricular mass/body weight ratio did not differ; heart rate and cardiac output as well as mean arterial blood pressure were decreased by 10%. NO
x
levels of hearts and blood of TG mice were 2.5- and 2-fold above WT controls, respectively. In the isolated heart, release of the NO oxidation products nitrate and nitrite, an index of in vivo NOS activity, was 40-fold over WT. However, cardiac hemodynamics and levels of ATP and phosphocreatine were unaltered. The high iNOS activity was associated with reduced cardiac
l
-arginine in TG hearts to only 15% of the WT, indicating limited substrate availability, whereas
l
-citrulline was 20-fold elevated. Our findings demonstrate that the heart can tolerate high levels of iNOS activity without detrimental functional consequences. The concept that iNOS-derived NO is the triggering factor in the pathomechanism leading to heart failure therefore needs to be reevaluated.
Molecular Pathogenesis of the Antiphospholipid Syndrome
Authors: Rand Jacob H.
Published: July 2002

The antiphospholipid (aPL) syndrome is an acquired autoimmune disorder of unknown etiology in which patients present with thrombosis together with laboratory evidence for antibodies in blood that recognize anionic phospholipid-protein complexes. The main antigenic target for the aPL antibodies has been identified to be β
2
glycoprotein I (β
2
GPI), a phospholipid-binding protein. The high affinity of aPL antibody-β
2
GPI complex for phospholipid membranes seems to be a critical step in the mechanism of this disease. This review focuses on some of the major mechanisms that have been proposed to explain this disorder.
Secretory Phospholipase A
2
Elicits Proinflammatory Changes and Upregulates the Surface Expression of Fas Ligand in Monocytic Cells
Authors: Hernández Marita , Fuentes Lucía , Fernández Avilés Francisco Javier , Crespo Mariano Sánchez , Nieto María Luisa
Published: July 2002

Type IIA secretory phospholipase A
2
(sPLA
2
) is an acute-phase reactant that plays a role in atherogenesis and is expressed in atherosclerotic arterial walls displaying inflammatory features. This generates a relevant question addressing the biological effects of this enzyme on monocytic cells, in view of the role of these cells in the inflammatory process associated with atherosclerosis. sPLA
2
produced a mild activation of the p42 mitogen-activated protein module of the mitogen-activated protein kinase (MAPK) cascade and a prominent activation of c-Jun N-terminal kinase in THP-1 monocytes. This activation showed both an early and a late peak, different from that elicited by tumor necrosis factor-α (TNF-α), which only showed the first peak. This was accompanied by activation of arachidonate metabolism, as judged from both the activation of the cytosolic phospholipase A
2
(cPLA
2
) and the induction of cyclooxygenase-2 (COX-2) expression. sPLA
2
also elicited the production of monocyte chemoattractant protein-1 (MCP-1) and showed a synergistic effect with TNF-α on both COX-2 induction and MCP-1 production. sPLA
2
upregulated the expression of Fas ligand at the cell surface, but it did not influence Fas expression nor cell survival of monocytes. In summary, these data indicate that some of the atherogenic effects of sPLA
2
can be exerted by engagement of an sPLA
2
-binding structure on monocytic cells, most probably the M-type receptor for sPLA
2
, which produces the activation of the MAPK cascade, induces a proinflammatory phenotype, and upregulates the cell surface expression of Fas ligand.
Alterations of Myocardial Dynamic Stiffness Implicating Abnormal Crossbridge Function in Human Mitral Regurgitation Heart Failure
Authors: Mulieri L.A. , Barnes W. , Leavitt B.J. , Ittleman F.P. , LeWinter M.M. , Alpert N.R. , Maughan D.W.
Published: July 2002

Mitral regurgitation (MR) causes ventricular dilation, a blunted myocardial force-frequency relation, and increased crossbridge force-time integral (FTI). The mechanism of FTI increase was investigated using sinusoidal length perturbation analysis to compare crossbridge function in skinned left ventricular (LV) epicardial muscle strips from 5 MR and 5 nonfailing (NF) control hearts. Myocardial dynamic stiffness was modeled as 3 parallel viscoelastic processes. Two processes characterize intermediate crossbridge cycle transitions,
B
(work producing) and
C
(work absorbing) with Q
10
s of 4 to 5. No significant differences in moduli or kinetic constants of these processes were observed between MR and NF. The third process,
A
, characterizes a nonenzymatic (Q
10
=0.9) work-absorbing viscoelasticity, whose modulus increases sigmoidally with [Ca
2+
]. Effects of temperature, crossbridge inhibition, or variation in [MgATP] support associating the calcium-dependent portion of
A
with the structural “backbone” of the myosin crossbridge. Extension of the conventional sinusoidal length perturbation analysis allowed using the A modulus to index the lifetime of the prerigor, AMADP crossbridge. This index was 75% greater in MR than in NF (
P
=0.02), suggesting a mechanism for the previously observed increase in crossbridge FTI. Notably, the
A
-process modulus was inversely correlated (
r
2
=0.84,
P
=0.03) with in vivo LV ejection fraction in MR patients. The longer prerigor dwell time in MR may be clinically relevant not only for its potential role as a compensatory mechanism (increased economy of tension maintenance and increased resistance to ventricular dilation) but also for a potentially deleterious effect (reduced elastance and ejection fraction).
FGF2
Signaling Is Required for the Development of Neuronal Circuits Regulating Blood Pressure
Authors: Dono Rosanna , Faulhaber Jörg , Galli Antonella , Zuniga Aimée , Volk Tilmann , Texido Gemma , Zeller Rolf , Ehmke Heimo
Published: July 2002

Fibroblast growth factor 2 (FGF2) signaling is involved in angiogenesis, vascular contractility, and cardiac hypertrophy. Mice lacking a functional
FGF2
gene (FGF2
−/−
) are hypotensive, but the primary physiological role of FGF2 in cardiovascular homeostasis remained unknown. Using a chicken
FGF2
(
cFGF2
) transgene under control of the
Wnt-1
promotor, we selectively re-expressed FGF2 in the developing nervous system of FGF2
−/−
(transgenic FGF2 mutant) embryos. Expression of the
cFGF2
transgene in the developing nervous system, including its autonomic region, was limited to the period between embryonic day 9.5 and 14.5. Significantly, no
FGF2
re-expression was detected in developing heart and blood vessels. Pharmacological analysis revealed a normalization of the blood pressure response to isoproterenol-induced vasodilation in adult transgenic FGF2 mutant mice. In addition, the hypotensive phenotype was rescued in 1 line (of 2) transgenic FGF2 mutant adult mice having expressed higher levels of cFGF2 proteins during nervous system development. These genetic studies indicate that FGF2 signaling is essential for complete development of the neural circuitry required for central regulation of blood pressure, whereas it appears dispensable for blood pressure control in the healthy adult. The full text of this article is available at http://www.circresaha.org.
Ca
2+
Signaling in Cardiac Myocytes Overexpressing the α
1
Subunit of L-Type Ca
2+
Channel
Authors: Song Long-Sheng , Guia António , Muth James N. , Rubio Marta , Wang Shi-Qiang , Xiao Rui-Ping , Josephson Ira R. , Lakatta Edward G. , Schwartz Arnold , Cheng Heping
Published: July 2002

Voltage-gated L-type Ca
2+
channels (LCCs) provide Ca
2+
ingress into cardiac myocytes and play a key role in intracellular Ca
2+
homeostasis and excitation-contraction coupling. We investigated the effects of a constitutive increase of LCC density on Ca
2+
signaling in ventricular myocytes from 4-month-old transgenic (Tg) mice overexpressing the α
1
subunit of LCC in the heart. At this age, cells were somewhat hypertrophic as reflected by a 20% increase in cell capacitance relative to those from nontransgenic (Ntg) littermates. Whole cell
I
Ca
density in Tg myocytes was elevated by 48% at 0 mV compared with the Ntg group. Single-channel analysis detected an increase in LCC density with similar conductance and gating properties. Although the overexpressed LCCs triggered an augmented SR Ca
2+
release, the “gain” function of EC coupling was uncompromised, and SR Ca
2+
content, diastolic cytosolic Ca
2+
, and unitary properties of Ca
2+
sparks were unchanged. Importantly, the enhanced
I
Ca
entry and SR Ca
2+
release were associated with an upregulation of the Na
+
-Ca
2+
exchange activity (indexed by the half decay time of caffeine-elicited Ca
2+
transient) by 27% and SR Ca
2+
recycling by ≈35%. Western analysis detected a 53% increase in the Na
+
-Ca
2+
exchanger expression but no change in the abundance of ryanodine receptor (RyR), SERCA2, and phospholamban. Analysis of
I
Ca
kinetics suggested that SR Ca
2+
release-dependent inactivation of LCCs remains intact in Tg cells. Thus, in spite of the modest cardiac hypertrophy, the overexpressed LCCs form functional coupling with RyRs, preserving both orthograde and retrograde Ca
2+
signaling between LCCs and RyRs. These results also suggest that a modest but sustained increase in Ca
2+
influx triggers a coordinated remodeling of Ca
2+
handling to maintain Ca
2+
homeostasis.
Frequency Analysis of Ventricular Fibrillation in Swine Ventricles
Authors: Valderrábano Miguel , Yang Junzhong , Omichi Chikaya , Kil John , Lamp Scott T. , Qu Zhilin , Lin Shien-Fong , Karagueuzian Hrayr S. , Garfinkel Alan , Chen Peng-Sheng , Weiss James N.
Published: July 2002

It has been suggested from frequency analysis that cardiac fibrillation is driven by stable intramural reentry, with wavebreak occurring due to failure of 1:1 propagation. We tested this hypothesis with a combined experimental and theoretical approach. Optical mapping was performed on epicardial, endocardial, and transmural cut surfaces of fibrillating swine ventricles. Wavelets were characterized, the frequency content of optical signals analyzed, and space-time plots (STPs) constructed to detect Wenckebach-like conduction. The findings were compared with simulations in 2D and 3D cardiac tissue using the Luo-Rudy action potential model. The incidence of reentry in the cut transmural surface (11.8% in right ventricle, 14.3% in left ventricle) was similar to that on the endocardial surface (13.1%,
P
=NS) but greater than on the epicardial surface (7.7%,
P
<0.01). Frequency spectra of optically recorded membrane voltage were organized into spatial domains with the same dominant frequency, but these domains were nonstationary. In STPs, pseudo-2:1 conduction block was caused by double potentials arising when reentry occurred on the recording site rather than true Wenckebach conduction. The latter was observed in 11 of 166 STPs but did not occur at borders of high-to-low frequency domains. In simulations, similar findings were obtained when action potential duration (APD) restitution slope was steep. Stationary dominant frequency domains with Wenckebach conduction patterns were observed only in the presence of shallow APD restitution slope and marked nonuniform tissue heterogeneity. In conclusion, stable intramural reentry as the engine of fibrillation was not observed. Our findings support the idea that dynamic wavebreak plays a fundamental role in the generation and maintenance of ventricular fibrillation.
C/EBP-β Mediates iNOS Induction by Hypoxia in Rat Pulmonary Microvascular Smooth Muscle Cells
Authors: Teng Xingwu , Li Dechun , Catravas John D. , Johns Roger A.
Published: July 2002

Exposure of rats to 10% O
2
for 4 days caused pulmonary hypertension and induced expression of both inducible nitric oxide synthase (iNOS) and CCAAT box enhancer binding protein-β (C/EBP-β) in rat lung. Electrophoretic mobility shift assays (EMSAs) showed that exposure to 1% O
2
increased the C/EBP-β binding in rat pulmonary microvascular smooth muscle cells (rPSMs). To test the hypothesis that C/EBP-β participates in hypoxia-induced iNOS expression in rPSMs, a C/EBP motif at −910 bp of rat iNOS promoter was mutated. rPSMs transfected with the rat iNOS promoter and exposed to 1% O
2
for 24 hours had significantly increased wild-type iNOS promoter activity. The hypoxia-induced promoter activity was abolished by the C/EBP motif mutation. Thus, C/EBP-β mediates, at least in part, hypoxia-induced iNOS expression in rPSMs.
Effect of ATP-Sensitive Potassium Channel Inhibition on Resting Coronary Vascular Responses in Humans
Authors: Farouque H. M. Omar , Worthley Stephen G. , Meredith Ian T. , Skyrme-Jones R. Andrew P. , Zhang Michael J.
Published: July 2002

Experimental data suggest that vascular ATP-sensitive potassium (K
ATP
) channels regulate coronary blood flow (CBF), but their role in regulating human CBF is unclear. We sought to determine the contribution of K
ATP
channels to resting conduit vessel and microvascular function in the human coronary circulation. Twenty-five patients (19 male/6 female, aged 56±12 years) were recruited. Systemic and coronary hemodynamics were assessed in 20 patients before and after K
ATP
channel inhibition with graded intracoronary glibenclamide infusions (4, 16, and 40 μg/min), in an angiographically smooth or mildly stenosed coronary artery following successful elective percutaneous coronary intervention to another vessel. Coronary blood velocity was measured with a Doppler guidewire and CBF calculated. Adenosine-induced hyperemia was determined following bolus intracoronary adenosine injection (24 μg). Time control studies were undertaken in 5 patients. Compared with vehicle infusion (0.9% saline), glibenclamide reduced resting conduit vessel diameter from 2.5±0.1 to 2.3±0.1 mm (
P
<0.01), resting CBF by 17% (
P
=0.05), and resting CBF corrected for rate pressure-product by 18% (
P
=0.01) in a dose-dependent manner. A corresponding 24% increase in coronary vascular resistance was noted at the highest dose (
P
<0.01). No alteration to resting CBF was noted in the time control studies. Glibenclamide reduced peak adenosine-induced hyperemia (
P
=0.01) but did not alter coronary flow reserve. Plasma insulin increased from 5.6±1.2 to 7.6±1.3 mU/L (
P
=0.02); however, plasma glucose was unchanged. Vascular K
ATP
channels are involved in the maintenance of basal coronary tone but may not be essential to adenosine-induced coronary hyperemia in humans.
Na
+
-Ca
2+
Exchange Current and Submembrane [Ca
2+
] During the Cardiac Action Potential
Authors: Weber Christopher R. , Piacentino Valentino , Ginsburg Kenneth S. , Houser Steven R. , Bers Donald M.
Published: July 2002

Na
+
-Ca
2+
exchange (NCX) is crucial in the regulation of [Ca
2+
]
i
and cardiac contractility, but key details of its dynamic function during the heartbeat are not known. In the present study, we assess how NCX current (
I
NCX
) varies during a rabbit ventricular action potential (AP). First, we measured the steady-state voltage and [Ca
2+
]
i
dependence of
I
NCX
under conditions when [Ca
2+
]
i
was heavily buffered. We then used this relationship to infer the submembrane [Ca
2+
]
i
([Ca
2+
]
sm
) sensed by NCX during a normal AP and [Ca
2+
]
i
transient (when the AP was interrupted to produce an
I
NCX
tail current). The [Ca
2+
]
i
dependence of
I
NCX
at −90 mV allowed us to convert the peak inward
I
NCX
tail currents to [Ca
2+
]
sm
. Peak [Ca
2+
]
sm
measured via this technique was >3.2 μmol/L within <32 ms of the AP upstroke (versus peak [Ca
2+
]
i
of 1.1 μmol/L at 81 ms measured with the global Ca
2+
indicator indo-1). The voltage and [Ca
2+
]
sm
dependence of
I
NCX
allowed us to infer
I
NCX
during the normal AP and Ca
2+
transient. The early rise in [Ca
2+
]
sm
causes
I
NCX
to be inward for the majority of the AP. Thus, little Ca
2+
influx via NCX is expected under physiological conditions, but this can differ among species and in pathophysiological conditions.
Early Expression of Myocardial HIF-1α in Response to Mechanical Stresses
Authors: Kim Chan-Hyung , Cho Young-Suk , Chun Yang-Sook , Park Jong-Wan , Kim Myung-Suk
Published: July 2002

Vascular endothelial growth factor (VEGF) expression is upregulated by hypoxia-inducible factor-1 (HIF-1) in ischemic tissues and growing tumors. Normally, HIF-1 activity depends on the amount of HIF-1α subunit, which is tightly regulated by the oxygen tension. In the myocardium, VEGF expression has been shown to be induced under nonhypoxic conditions by mechanical stresses. However, the cellular mechanism of stress-mediated VEGF induction remains unclear. Therefore, we examined the possible involvement of HIF-1 in stress-mediated VEGF induction in rat hearts. In this study, we increased the left ventricular wall tension using 3 different methods, namely by inducing regional ischemia, by expanding an intraventricular balloon, and by producing hemodynamic overload using an aortocaval shunt. In all cases, HIF-1α accumulated in the nuclei of cardiac myocytes in the early phase, and this was followed by VEGF induction. Phosphatidylinositol 3-kinase (PI3K)–dependent Akt phosphorylation was found to be activated by mechanical stress and completely blocked by wortmannin (a PI3K inhibitor). Moreover, the stress-mediated induction of HIF-1α and VEGF was suppressed by gadolinium (a stretch-activated channel inhibitor), wortmannin, and rapamycin (a FRAP inhibitor). Our results suggest that HIF-1α plays an important role in the induction of VEGF in nonischemic and mechanically stressed myocardium, and that this is regulated by stretch-activated channels and the PI3K/Akt/FRAP pathway. Moreover, this signaling pathway, which induces HIF-1α, seems to play an important role in the adaptation of the myocardium to stresses. The full text of this article is available at http://www.circresaha.org.
Early Loss of Thrombomodulin Expression Impairs Vein Graft Thromboresistance
Authors: Kim Antony Y. , Walinsky Peter L. , Kolodgie Frank D. , Bian Ce , Sperry Jason L. , Deming Clayton B. , Peck Eric A. , Shake Jay G. , Ang Gregory B. , Sohn Richard H. , Esmon Charles T. , Virmani Renu , Stuart R. Scott , Rade Jeffrey J.
Published: July 2002

Thrombosis is the major cause of early vein graft failure. Our aim was to determine whether alterations in the expression of the anticoagulant proteins, thrombomodulin (TM) and the endothelial cell protein C receptor (EPCR), impair endothelial thromboresistance that may contribute to vein graft failure. Immunohistochemical staining of autologous rabbit vein graft sections revealed that the expression of TM, but not EPCR, was reduced significantly early after graft implantation. Western blot analysis revealed that TM expression was reduced by >95% during the first 2 weeks after implantation, with gradual but incomplete recovery by 42 days. This resulted in up to a 95% reduction in the capacity of the grafts to activate protein C and was associated with an increase in bound thrombin activity, which peaked on day 7 at 28.7±3.8 mU/cm
2
and remained elevated for more than 14 days. Restoration of TM expression using adenovirus vector-mediated gene transfer significantly enhanced the capacity of grafts to activate protein C and reduced bound thrombin activity on day 7 to levels comparable to that of normal veins (5.7±0.4 versus 5.2±1.1 mU/cm
2
, respectively,
P
=0.74). Surprisingly, neointima formation was not affected by this inhibition of local thrombin activity. These data suggest that the early loss of TM expression significantly impairs vein graft thromboresistance and results in enhanced local thrombin generation. Although enhanced local thrombin generation may predispose to early vein graft failure due to thrombosis, it does not seem to contribute significantly to late vein graft failure due to neointimal hyperplasia.
A Role for the β-Catenin/T-Cell Factor Signaling Cascade in Vascular Remodeling
Authors: Wang Xiaohong , Xiao Yan , Mou Yongshan , Zhao Ying , Blankesteijn W. Matthijs , Hall Jennifer L.
Published: July 2002

β-Catenin and T cell factor (Tcf) are distal components of the highly conserved Wnt pathway that govern cell fate and proliferation in lower organisms. Thus, we hypothesized that the regulation of β-catenin and Tcf played a critical role in vascular remodeling. The first objective was to define β-catenin expression in vascular smooth muscle cells (VSMCs) after balloon injury. Indeed, β-catenin mRNA and protein were significantly elevated 7 days after balloon injury in the rat carotid artery. We hypothesized that β-catenin accumulation in response to vascular injury inhibited VSMC apoptosis. In line with our hypothesis, transfection of a degradation-resistant β-catenin transgene into rat VSMCs significantly inhibited apoptosis. Accumulation of β-catenin also resulted in a 10-fold increase in the activation of Tcf. To test if Tcf was necessary to confer β-catenin–induced survival, loss of function studies were carried out with a dominant negative Tcf-4 transgene lacking the β-catenin binding domain, Tcf4(N31). Indeed, loss of Tcf-4 activity abolished β-catenin–induced survival. We further postulated that β-catenin and Tcf promoted cell cycle progression by activating cyclin D1, a target gene of Tcf-4. β-Catenin activated cyclin D1, and this activation was partially blocked with loss of Tcf-4. In parallel, blockade of Tcf-4 resulted in inhibition of [
3
H]thymidine incorporation and partial blockade of the G1-S phase transition. In conclusion, β-catenin and Tcf-4 play a dual role in vascular remodeling by inhibiting VSMC apoptosis and promoting proliferation.
The Na
+
-Ca
2+
Exchanger Is Essential for the Action of Cardiac Glycosides
Authors: Reuter Hannes , Henderson Scott A. , Han Tieyan , Ross Robert S. , Goldhaber Joshua I. , Philipson Kenneth D.
Published: July 2002

The widely accepted model to explain the positive inotropic effect of cardiac glycosides invokes altered Na
+
-Ca
2+
exchange activity secondary to Na
+
pump inhibition. However, proof of this model is lacking and alternative mechanisms have been proposed. We directly tested the role of the Na
+
-Ca
2+
exchanger in the action of the glycoside ouabain using Na
+
-Ca
2+
exchanger knockout mice. Ablation of the exchanger is embryonic lethal, but contractility can be studied in embryonic heart tubes at day 9.5 postcoitum. Heart tubes isolated from homozygous Na
+
-Ca
2+
exchanger knockout mice (NCX
−/−
) display surprisingly normal Ca
2+
transients. Removal of extracellular Na
+
induces Ca
2+
overload in wild-type heart tubes but does not alter the Ca
2+
transients of NCX
−/−
heart tubes. Similarly, ouabain, at levels causing Ca
2+
overload in wild-type heart tubes, has no effect on NCX
−/−
heart tubes. We conclude that in embryonic mouse myocytes the Na
+
-Ca
2+
exchanger is absolutely required for the effect of cardiac glycosides on Ca
2+
i
.
Protease-Activated Receptor-2 Activation Causes EDHF-Like Coronary Vasodilation
Authors: McLean Peter G. , Aston Daniel , Sarkar David , Ahluwalia Amrita
Published: July 2002

Activation of protease-activated receptor (PAR)-2 has been proposed to be protective in myocardial ischemia/reperfusion (I/R) injury, an effect possibly related to an action on the coronary vasculature. Therefore, we investigated the effects of PAR2 activation on coronary tone in isolated perfused rat hearts and elucidated the mechanisms of any observed effects. Although having a negligible effect on ventricular contractility, the PAR2 activating peptide SLIGRL produced an endothelium-dependent coronary vasodilatation (ED
50
=3.5 nmol). Following I/R injury, the response to SLIGRL was selectively preserved, whereas the dilator response to acetylcholine was converted to constriction. Trypsin also produced a vasodilator dose-response curve that was biphasic in nature (ED
50-1
=0.36 U, ED
50-2
=38.71 U). Desensitization of PAR2 receptors indicated that the high potency phase was mediated by PAR2. Removal of the endothelium but not treatment with L-NAME (300 μmol/L), indomethacin (5 μmol/L), or oxyhemoglobin (10 μmol/L) inhibited the response to SLIGRL and trypsin. Treatment with the K
+
-channel blockers TEA (10 mmol/L), charybdotoxin (20 nmol/L)/apamin (100 nmol/L), or elevated potassium (20 mmol/L) significantly suppressed responses. Similarly, inhibition of lipoxygenase with nordihydroguaiaretic acid (1 μmol/L), eicosatetraynoic acid (1 μmol/L), or baicalein (10 μmol/L), desensitization of C-fibers using capsaicin (1 μmol/L, 20 minutes), or blockade of vanilloid (VR1) receptors using capsazepine (3 μmol/L) inhibited the responses. This study shows, for the first time, that PAR2 activation causes endothelium-dependent coronary vasodilation that is preserved after I/R injury and is not mediated by NO or prostanoids, but involves the release of an endothelium-derived hyperpolarizing factor (EDHF), possibly a lipoxygenase-derived eicosanoid, and activation of VR1 receptors on sensory C-fibers.
L-Type Ca
2+
Currents Overlapping Threshold Na
+
Currents
Authors: Piacentino Valentino , Gaughan John P. , Houser Steven R.
Published: July 2002

Phosphorylation of Na channels has been suggested to increase their Ca permeability. Termed “slip-mode conductance” (SMC), this hypothesis predicts that Ca influx via protein kinase A (PKA)-modified Na channels can induce sarcoplasmic reticulum (SR) Ca release. We tested this hypothesis by determining if SR Ca release is graded with
I
Na
in the presence of activated PKA (with Isoproterenol, ISO). V
m
,
I
m
, and [Ca]
i
were measured in feline (n=26) and failing human (n=19) ventricular myocytes. Voltage steps from −70 through −40 mV were used to grade
I
Na
. Na channel antagonists (tetrodotoxin), L-type Ca channel (
I
Ca,L
) antagonists (nifedipine, cadmium, verapamil), and agonists (Bay K 8644, FPL 64176) were used to separate SMC from
I
Ca,L
. In the absence of ISO,
I
Na
was associated with SR Ca release in human but not feline myocytes. After ISO, graded
I
Na
was associated with small amounts of SR Ca release in feline myocytes and the magnitude of release increased in human myocytes.
I
Na
-related SR Ca release was insensitive to tetrodotoxin (n=10) but was blocked by nifedipine (n=10) and cadmium (n=3). SR Ca release was induced over the same voltage range in the absence of ISO with Bay K 8644 and FPL 64176 (n=9). Positive voltage steps (to 0 mV) to fully activate Na channels (SMC) in the presence of ISO and Verapamil only caused SR Ca release when block of
I
Ca,L
was incomplete. We conclude that PKA-mediated increases in
I
Ca,L
and SR Ca loading can reproduce many of the experimental features of SMC.