bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Liability in Stroke
Authors: Bak Søren , Gaist David , Sindrup Søren Hein , Skytthe Axel , Christensen Kaare
Published: July 2002

Background and Purpose
—

Few studies have assessed the overall importance of genetic factors on stroke risk, and the results have been contradictory. We used a large, population-based twin register and nationwide registries of death and hospitalization with long-term follow-up to estimate the effect of genetic factors on the risk of stroke.

Methods
—

Through the population-based Danish Twin Register, we identified same-sex twin pairs born in 1870 through 1952 for whom at least 1 twin was recorded under a stroke diagnosis in the Register of Causes of Death or the Danish National Discharge Register. From the day of the first stroke event in each twin pair, the live co-twins were followed up for stroke. In survival analyses, we estimated the age- and sex-adjusted effect of zygosity on the risk of stroke death or hospitalization for stroke. Concordance rates, tetrachoric correlations, and heritability were also assessed.

Results
—

Thirty-five of 351 monozygotic pairs (10%) and 34 of 639 dizygotic pairs (5%) were concordant for stroke death. The age- and sex-adjusted relative risk of stroke death in monozygotic compared with dizygotic co-twins was 2.1 (95% CI, 1.3 to 3.3). The probandwise concordance rates were 0.18 (95% CI, 0.14 to 0.22) for monozygotic and 0.10 (95% CI, 0.08 to 0.13) for dizygotic pairs. Thirty-three of 309 monozygotic pairs (11%) and 39 of 560 dizygotic pairs (7%) were concordant for stroke hospitalization or stroke death. The age- and sex-adjusted relative risk of stroke hospitalization or stroke death in monozygotic compared with dizygotic co-twins was 1.5 (95% CI, 0.9 to 2.4). The probandwise concordance rates were 0.19 (95% CI, 0.15 to 0.24) for monozygotic and 0.13 (95% CI, 0.10 to 0.16) for dizygotic pairs. The heritability estimates were 0.32 for the liability to stroke death and 0.17 for the liability to stroke hospitalization or stroke death.

Conclusions
—

The observed increased risk of stroke death and stroke hospitalization in monozygotic compared with dizygotic co-twins suggests that genetic factors increase the risk of stroke and that the size of this effect is moderate.
Stroke Prevention Therapy Beyond Antithrombotics: Unifying Mechanisms in Ischemic Stroke Pathogenesis and Implications for Therapy
Authors: Gorelick Philip B.
Published: July 2002

Background

—

It is estimated that about half of cardiovascular disease risk is explained by conventional risk factors. The realization that atherosclerosis is an inflammatory disease has led to a search for new stroke and cardiovascular disease risk factors and treatments. As such, the vulnerable atherosclerotic plaque has become the main focus for new medical strategies for plaque stabilization and stroke prevention.

Summary of Review

—

In this invited review, I discuss inflammation as a possible risk factor for stroke, unifying mechanisms in ischemic stroke pathogenesis, and new avenues for stroke prevention—statin agents, angiotensin-converting enzyme inhibitors, and vitamins. These new stroke prevention therapies may help to reduce inflammation, serve to stabilize the atherosclerotic plaque, or act by other protective mechanisms.

Conclusion

—

Beyond the traditional antithrombotic agents, statin agents, angiotensin-converting enzyme inhibitors, and vitamins may prove to be important additions to our armamentarium for stroke prevention.
Inhibitory Effect With Antisense Mitogen-Activated Protein Kinase Oligodeoxynucleotide Against Cerebral Vasospasm in Rats
Authors: Satoh Motoyoshi , Parent Andrew D. , Zhang John H.
Published: July 2002

Background and Purpose
—

Mitogen-activated protein kinase (MAPK) may be associated with the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). This study aimed to clarify the role of MAPK expression and activation during cerebral vasospasm and to evaluate the therapeutic effect on cerebral vasospasm using an antisense MAPK oligodeoxynucleotide (ODN).

Methods
—

Antisense MAPK, sense MAPK, or scrambled ODN was injected into the rats intracisternally. We used a single-hemorrhage experimental SAH model to assess vasospasm in the basilar arteries at 30 minutes, 1 day, and 2 days after SAH by cross-sectional area measurement and other histological parameters. Immunohistochemistry and Western blot analysis were used to quantify MAPK expression and activation. In addition, a double-hemorrhage rat SAH model was used to test the effect of post-SAH treatment with antisense MAPK ODN.

Results
—

Antisense MAPK therapy significantly inhibited cerebral vasospasm when compared with sense MAPK or scrambled ODN treatment on day 2. The immunohistochemistry and Western blotting performed in the basilar artery of rats that received antisense MAPK ODN demonstrated inhibition of MAPK and phosphorylated MAPK on day 2. In post-SAH treatment study, antisense ODN reduced MAPK and phosphorylated MAPK in the basilar artery and attenuated cerebral vasospasm.

Conclusions
—

MAPK activation, but not expression, might be implicated with sustained smooth muscle contraction during cerebral vasospasm after SAH. This study suggests that antisense MAPK ODN strategy is an effective treatment against cerebral vasospasm.
Protective Vasomotor Effects of In Vivo Recombinant Endothelial Nitric Oxide Synthase Gene Expression in a Canine Model of Cerebral Vasospasm
Authors: Khurana Vini G. , Smith Leslie A. , Baker Timothy A. , Eguchi Daihiko , O’Brien Timothy , Katusic Zvonimir S.
Published: July 2002

Background and Purpose

—

Post-subarachnoid hemorrhage (SAH) cerebral vasospasm is a potentially devastating condition whose pathogenesis involves impaired nitric oxide (NO) bioavailability. We aimed to determine whether recombinant endothelial NO synthase (eNOS) gene expression may protect vasomotor function and prevent vasospasm in a canine experimental SAH model.

Methods

—

Recombinant adenoviral vectors (5×10

9

plaque-forming units/animal) encoding genes for eNOS (AdeNOS) and β-galactosidase (AdLacZ) or vehicle were injected into the cerebrospinal fluid (CSF) of dogs on day −1 (ie, 24 hours before the first intra-CSF injection of blood on day 0). Cerebral angiography was performed at day 0 (baseline) and day 7 (immediately before death), and tissues were harvested for additional studies.

Results

—

Western analysis and immunohistochemistry detected recombinant eNOS exclusively in cerebral arteries isolated from AdeNOS-transduced dogs, and in this group of animals CSF NO concentrations were significantly elevated by day 2. Analysis of day 7 versus day 0 cerebral angiograms for each group revealed significant spasm at the basilar artery midpoint in AdLacZ-transduced and nontransduced dogs but not in AdeNOS-transduced dogs. Isometric force recording of basilar arteries isolated from AdeNOS-transduced dogs showed significantly augmented relaxations to bradykinin and reduced contractions to endothelin-1.

Conclusions

—

Our results suggest that expression of recombinant eNOS in the adventitia of cerebral arteries may contribute toward protection against post-SAH vasospasm.
New Insights Into Brain Damage in Stroke-Prone Rats
Authors: Guerrini Uliano , Sironi Luigi , Tremoli Elena , Cimino Mauro , Pollo Bianca , Calvio Anna Maria , Paoletti Rodolfo , Asdente Maria
Published: July 2002

Background and Purpose

—

The spontaneously hypertensive stroke-prone rat (SHRSP) is an animal model for a complex form of cerebrovascular pathology. MRI provides an efficient and noninvasive tool for studying the time course of brain damage. The aim of this study was to gain new insights into the pathological phenomena responsible for the occurrence of brain injury in SHRSP with the use of the apparent diffusion coefficient of water (ADC), one of the most efficient MRI parameters for detecting brain abnormalities. To this end, the pattern of ADC variation observed in SHRSP was compared with that of focal ischemia induced in both SHRSP and Sprague-Dawley rats.

Methods

—

Four groups of animals were studied: SHRSP developing spontaneous brain lesions fed with a salt-loaded (n=15, group 1) or standard diet (n=3, group 2) and Sprague-Dawley rats (n=8, group 3) and SHRSP (n=8, group 4) with permanent middle cerebral artery occlusion. ADC maps and T2-weighted images of brains were performed by MRI. After the rats were killed, the brains were removed and histologically processed.

Results

—

There was no decrease in ADC during spontaneous stroke in the SHRSP fed with a normal or salt-enriched diet, while both the SHRSP and Sprague-Dawley rats with middle cerebral artery occlusion showed a marked decrease that lasted for 24 to 48 hours.

Conclusions

—

Cerebral ischemia cannot be considered a major factor in the onset of spontaneous brain lesions in SHRSP, which show only vasogenic edema after the beginning of the damage with no evidence of metabolic impairment.
Validation of a Weight-Based Nomogram for the Use of Intravenous Heparin in Transient Ischemic Attack or Stroke
Authors: Toth Cory , Voll Chris
Published: July 2002

Background and Purpose

—

Intravenous heparin therapy is often used in patients presenting with transient ischemic attack (TIA) or stroke as either bridging therapy for anticoagulation with warfarin or primary therapy in suspected intracranial arterial dissection, crescendo TIAs, or suspected hypercoagulable states. We attempted to validate the use of a weight-based nomogram for heparin-adjusted therapy during hospital admission of patients with TIA or stroke.

Methods

—

A prospective, single-blinded, randomized, clinical trial was undertaken to compare the use of a specially designed, weight-based heparin nomogram against the traditional method of physician-ordered heparin therapy for patients admitted with TIA or stroke. The trial was not designed to examine the efficacy of heparin therapy but to examine the use of the nomogram for labor requirements, costs of monitoring, safety, length of heparin therapy, and user-friendliness.

Results

—

Pretreatment clinical factors were comparable between those randomized to use of the nomogram (n=101) and to usual care (n=105). Nomogram patients had a significantly lower first activated partial thromboplastin time than nonnomogram patients (60.6±16.8 versus 69.8±28.7 seconds). Patients treated by nomogram achieved a therapeutic range of anticoagulation sooner than nonnomogram patients (13.4±17.0 versus 17.9±14.1 hours). The fraction of time during which anticoagulation was therapeutic was significantly greater in patients on nomogram therapy (74±25% versus 67±26%). Nomogram patients also had significantly fewer supratherapeutic coagulation results, significantly fewer dose adjustment mistakes, significantly fewer calls to house staff regarding anticoagulation, and significantly fewer total complications than nonnomogram patients. The times required for discontinuation of heparin and discharge from hospital were not significantly different. A survey of house staff and nursing staff showed a preference for nomogram use.

Conclusions

—

The heparin nomogram is a user-friendly method of maintaining heparin infusions and is associated with improved anticoagulation measures, fewer total complications related to heparin therapy, fewer mistakes in heparin dosage adjustment, and decreased labor on the part of house staff and nursing staff.
Functional Walk Tests in Individuals With Stroke
Authors: Eng Janice J. , Chu Kelly S. , Dawson Andrew S. , Kim C.Maria , Hepburn Katherine E.
Published: July 2002

Background and Purpose
—

Functional walk tests such as the 6- and 12-Minute Walk Test (ie, 6MWT and 12MWT, respectively) are submaximal measures used to determine functional capacity in individuals with compromised ability. The purpose of this study was to determine the relationship between these walk tests and measures of exertion (perceived and myocardial), in addition to impairment in individuals with stroke. The relationship among the 6MWT, 12MWT, and the more traditionally assessed measure of self-paced gait speed (generally assessed over a short distance, eg, 10 m) was also evaluated.

Methods
—

Twenty-five community-dwelling individuals with stroke were evaluated for the following: 12MWT distance, 6MWT distance, self-paced gait speed over 8 m, plantarflexion strength, Berg Balance Scale, Ashworth Scale of Spasticity, and Chedoke-McMaster Stroke Assessment. Heart rate (HR), rate-pressure product (RPP), and perceived exertion were assessed during the functional walk tests. Correlational analysis quantified the relationship between gait, impairment measures, and physiological responses during the functional walk tests.

Results
—

HR reached a steady state after 6 minutes and reflected a moderate exercise intensity of 63% of age-predicted maximum HR. The 6MWT, 12MWT, and self-paced gait speed were all highly correlated with one another (
r
>0.90) and were all also related to the severity of impairments. The functional walk distances did not relate either to perceived exertion or actual exertion (increase in the myocardial oxygen demand as measured by RPP).

Conclusions
—

Stroke-specific impairments are the major limitations to the distance walked in individuals with stroke. If the functional walk test is used to assess performance of an individual over time (eg, in response to an intervention), we recommend that both exertion (eg, increase in RPP or HR) and distance be measured.
Stroke Risk Factor Profiles in African American Women
Authors: Worrall Bradford B. , Johnston Karen C. , Kongable Gail , Hung Elena , Richardson DeJuran , Gorelick Philip B.
Published: July 2002

Background and Purpose

—

If sex differences in stroke risk factor profiles exist among African Americans in the United States, prevention strategies will need to reflect those differences. African Americans and women have been underrepresented in stroke prevention studies. The purpose of this study was to determine whether medical and lifestyle factors differ among women and men who have enrolled in the African-American Antiplatelet Stroke Prevention Study (AAASPS).

Methods

—

We performed a planned exploratory analysis of differences in baseline characteristics and risk factors between women and men enrolled in AAASPS, a double-blind, randomized, multicenter, controlled trial. Frequencies of vascular risk factors and related conditions, medical therapies, stroke subtypes, and vascular territories were compared between women and men by 1-way ANOVA and Fisher’s exact test where appropriate.

Results

—

A total of 1087 African American patients (574 women, 513 men) enrolled between December 1995 and June 1999. Women had higher rates of hypertension, diabetes, family history of stroke, and no reported leisure exercise. Men had higher rates of smoking and heavy alcohol use. Few differences were noted in proportions of stroke subtype or proportions receiving preventive therapy.

Conclusions

—

AAASPS represents the largest enrollment of African American women in a recurrent stroke prevention study. Our data suggest that African American women in a clinical trial differ from men in the frequency of key vascular risk factors. Although limited, these data provide an important first characterization of sex differences in African Americans with stroke.
Expression and Function of Recombinant S1179D Endothelial Nitric Oxide Synthase in Canine Cerebral Arteries
Authors: Akiyama Masahiko , Eguchi Daihiko , Weiler Deborah , O’Brien Timothy , Kovesdi Imre , Scotland Ramona S. , Sessa William C. , Katusic Zvonimir S.
Published: July 2002

Background and Purpose

—

Bovine endothelial nitric oxide synthase (eNOS) is phosphorylated directly by the protein kinase Akt at serine 1179. Mutation of this residue to the negatively charged aspartate (S1179DeNOS) increases nitric oxide (NO) production constitutively in the absence of agonist stimulus. The present study was designed to determine the effect of mutant S1179DeNOS gene expression on vasomotor function of canine cerebral arteries.

Methods

—

Isolated basilar and middle cerebral arteries were exposed ex vivo (30 minutes at 37°C) to an adenoviral vector (10
10
plaque-forming units per milliliter) encoding the S1179DeNOS gene (AdCMVS1179DeNOS), the wild-type eNOS gene (AdCMVeNOS), or the green fluorescent protein (GFP) reporter gene (AdCMVGFP). Twenty-four hours after transduction, arteries were suspended in an organ chamber for isometric force recording, and levels of cGMP were measured by radioimmunoassay.

Results

—

Transgene protein expression was detected mainly in the vascular adventitia. In AdCMVS1179DeNOS-transduced arteries, basal levels of cGMP were significantly elevated compared with those in control (nontransduced), AdCMVGFP-, or AdCMVeNOS-transduced vessels (n=8;
P
<0.01). The elevation of cGMP was abolished by a NOS inhibitor,
N
G
-nitro-
l
-arginine methyl ester (L-NAME), or by incubation in the calcium-free medium in the presence of calcium chelators. In AdCMVS1179DeNOS-transduced arteries, contractions to endothelin-1 (10
−10
to 10
−8
mol/L) were significantly reduced compared with those in control and AdCMVGFP-transduced arteries (n=7;
P
<0.05). The vasoconstrictor effect of endothelin-1 was restored in the presence of the NOS inhibitor L-NAME.

Conclusions

—

Our results suggest that in cerebral arteries, expression of recombinant S1179DeNOS increases basal production of NO and inhibits the vasoconstrictor effect of endothelin-1. This effect may have therapeutic application in prevention and treatment of cerebrovascular diseases.
Temporal Profile of Enhanced Vulnerability of the Postthrombotic Brain to Secondary Embolic Events
Authors: Danton Gary H. , Prado Ricardo , Watson Brant D. , Dietrich W. Dalton
Published: July 2002

Background and Purpose

—

Patients with vascular or cardiac disease may experience recurrent thrombosis and embolization to the cerebral vasculature. Transient distal platelet accumulation after common carotid artery thrombosis (CCAT) leads to hemodynamic, metabolic, and molecular events that may influence the response of the postthromboembolic brain to secondary emboli. We investigated the effect of repeated embolic episodes on histopathological outcome at various time intervals using a clinically relevant model of embolic stroke.

Methods

—

Six groups of rats underwent either photochemically induced CCAT followed by sham surgery or 2 episodes of CCAT separated by 10 minutes or 1, 3, 5, or 7 days. Outcome measures included routine histopathological analysis and determination of the number of infarct loci and their total volume.

Results

—

Rats that underwent a second CCAT at 1, 3, or 5 days after the first insult had 20 to 30 times larger infarct volumes than rats in the single-CCAT group (
P
<0.05). In addition, rats in the 10-minute and 1-, 3-, and 5-day groups had 2 to 3 times as many infarcts as those in the single-CCAT group (
P
<0.05). Infarcts produced by double insults commonly extended through the neuraxis and were necrotic, edematous, and sometimes hemorrhagic.

Conclusions

—

A prior thromboembolic event puts the brain at risk for severe infarction after a second embolic event. These findings cannot be explained solely by a greater number of infarcts. Elucidating pathomechanisms responsible for the vulnerability of the postthromboembolic brain may provide targets for new treatment strategies to prevent the severe consequences of embolic stroke.
Cardiac and Renal Effects of Growth Hormone in Volume Overload–Induced Heart Failure
Authors: Pagel Ines , Langenickel Thomas , Höhnel Klaus , Philipp Sebastian , Nüssler Andreas K. , Blum Werner F. , Aubert Michel L. , Dietz Rainer , Willenbrock Roland
Published: July 2002

Growth hormone (GH) application is a new strategy in the treatment of heart failure. However, clinical and experimental investigations have shown contradictory effects of GH on cardiac performance. We tested the hypothesis that GH could improve cardiac and renal function in volume overload–induced heart failure. The effect of 4 weeks of GH treatment (2 mg/kg daily) was investigated in Wistar rats with aortocaval shunt. GH application did not influence left ventricular contractility and end-diastolic pressure in rats with aortocaval shunt. In contrast, GH treatment normalized impaired diuresis (vehicle 10.8±0.6 mL/d, GH 15.8±0.7 mL/d;
P
<0.05) and sodium excretion (vehicle 1.5±0.1 mmol/d, GH 2.2±0.1 mmol/d;
P
<0.001) in shunt-operated rats, with a similar increase of fractional sodium excretion. The urinary excretion of cGMP, the second messenger of atrial natriuretic peptide and NO, was higher in animals with shunts than in sham-operated animals and was further increased by GH (vehicle 293±38 nmol/d, GH 463±57 nmol/d;
P
<0.01). Although the atrial natriuretic peptide plasma levels were unchanged after GH, the excretion of NO metabolites (nitrate/nitrite) was elevated (vehicle 2020±264 nmol/d, GH 2993±375 nmol/d;
P
<0.05) in parallel with increased renal mRNA levels of inducible NO synthase 2. The changes of renal function after GH and the increased excretion of NO metabolites and cGMP were abolished by simultaneous treatment with the NO synthase inhibitor
N
G
-nitro-
l
-arginine methyl ester. GH treatment did not influence cardiac function in rats with aortocaval shunts. However, GH improved renal function by increasing diuresis and sodium excretion. The responsible mechanism might be the enhanced activity of the renal NO system.
Emerging Excitatory Role of Cardiovascular Sympathetic Afferents in Pathophysiological Conditions
Authors: Malliani Alberto , Montano Nicola
Published: July 2002

There is sound experimental evidence that cardiovascular sympathetic afferent fibers mediate cardiovascular reflexes largely excitatory in nature with positive-feedback characteristics. This afferent neural channel is likely to normally participate in the neural regulation of cardiovascular function. The hypothesis, which is the core of this article, is that in some pathophysiological conditions, sympathetic overactivity may be partly due to an emerging excitatory reflex action of cardiovascular sympathetic afferents. In fact, the early phase of congestive heart failure can be characterized by an increase in arterial pressure and heart rate and/or by a diastolic dysfunction, leaving unchanged the cardiac output; in these conditions, in which no baroreceptor deactivation should occur, it is possible that cardiovascular sympathetic afferents with sensory endings in the thoracic low-pressure areas, highly responsive to volume loading, are responsible for mediating the reflex sympathetic excitation. Similarly, during acute myocardial infarction, ventricular sympathetic afferents are likely to mediate a reflex sympathetic overactivity, which is known to facilitate sudden death. Finally, numerous reports have described in essential arterial hypertension an increased sympathetic activity that may be due, at least in part, to the reinforcing action of sympathosympathetic reflexes. Thus, in pathophysiological conditions, cardiovascular sympathetic afferents would mediate a reflex sympathetic overactivity independently of baroreceptive mechanisms, and such an absence of a homeostatic purpose would provide a better rationale for some beneficial effects of therapeutic correction.
Enhanced Nitric Oxide Inactivation and Protein Nitration by Reactive Oxygen Species in Renal Insufficiency
Authors: Vaziri Nosratola D. , Ni Zhenmin , Oveisi Fariba , Liang Kaihui , Pandian Raj
Published: July 2002

Chronic renal failure (CRF) is associated with oxidative stress which promotes production of reactive carbonyl compounds and lipoperoxides leading to the accumulation of advanced glycation and lipoxidation end products. Reactive oxygen species (ROS) avidly reacts with nitric oxide (NO) producing cytotoxic reactive nitrogen species capable of nitrating proteins and damaging other molecules. This study tested the hypothesis that CRF results in enhanced ROS-mediated NO inactivation and protein nitration which can be ameliorated with antioxidant therapy. Male Sprague Dawley rats were randomized to CRF (5/6 nephrectomy) and sham-operated controls and fed either a regular diet (vitamin E, 40 U/Kg food) or an antioxidant-fortified diet (vitamin E, 5000 U/Kg food) for 6 weeks. Blood pressure, plasma malondialdehyde (MDA), tissue NO synthase (NOS) isoforms, tissue nitrotyrosine (the footprint of NO interaction with ROS), and vascular tissue NO production were determined. CRF resulted in marked elevations of blood pressure, plasma MDA, and tissue nitrotyrosine abundance, but did not change plasma L-arginine level. This was coupled with depressed vascular tissue NO production and reduced immunodetectable NOS proteins in the vascular, renal, and cardiac tissues. Antioxidant therapy ameliorated the CRF-induced hypertension, improved vascular tissue NO production, lowered tissue nitrotyrosine burden, and reversed downregulations of NOS isoforms. In contrast, antioxidant therapy had no effects in the controls. CRF is associated with oxidative stress which promotes NO inactivation by ROS leading to functional NO deficiency, hypertension, and widespread accumulation of protein nitration products. Amelioration of oxidative stress by high-dose vitamin E enhances NO availability, improves hypertension, lowers protein nitration products, and increases NOS expression and vascular NO production in CRF animals.
Methoxyestradiols Mediate the Antimitogenic Effects of Locally Applied Estradiol on Cardiac Fibroblast Growth
Authors: Dubey Raghvendra K. , Gillespie Delbert G. , Zacharia Lefteris C. , Rosselli Marinella , Imthurn Bruno , Jackson Edwin K.
Published: July 2002

Estradiol inhibits cardiac fibroblast growth and may protect against cardiac remodeling associated with heart disease. However, the mechanisms by which estradiol attenuates cardiac fibroblast growth remain unclear. Because cardiac fibroblasts express cytochrome P450s (CYP450s) and catechol-O-methyltransferase (COMT) capable of converting estradiol to hydroxyestradiols and methoxyestradiols, respectively, and because hydroxyestradiols and methoxyestradiols (estradiol metabolites with little affinity for estrogen receptors) are potent inhibitors of cardiac fibroblast growth, we hypothesized that the antimitogenic effects of estradiol are mediated via hydroxyestradiols and/or methoxyestradiols. The inhibitory effects of estradiol (1 to 100 nmol/L) on serum-stimulated
3
H-thymidine incorporation (DNA synthesis),
3
H-proline incorporation (collagen synthesis), and cell number (proliferation) were enhanced (
P
<0.005) by CYP450 inducers 3-methylcholanthrene (10 μmol/L) and phenobarbital (10 μmol/L). Moreover, the inhibitory effects of estradiol were blocked by the CYP450 inhibitor 1-aminobenzotriazole (10 μmol/L) and the COMT inhibitors quercetin (10 μmol/L) and OR486 (10 μmol/L). In contrast to estradiol, the modulators of CYP450 and COMT were poor ligands for estrogen receptors (binding affinity ≤0.0001% versus estradiol). In cardiac fibroblasts, both quercetin and OR486 inhibited the metabolism of hydroxyestradiol to methoxyestradiol and blocked the inhibitory effects of hydroxyestradiol on cardiac fibroblast proliferation and DNA and collagen synthesis. The abrogating effects of quercetin and OR486 on the metabolism and antimitogenic effects of 2-hydroxyestradiol were mimicked by 20 μmol/L norepinephrine and isoproterenol, substrates for COMT. Our findings provide evidence that estradiol can inhibit cardiac fibroblast growth via an estrogen receptor–independent pathway that involves the local metabolism of estradiol to methoxyestradiols.
In Vivo Evidence for Antioxidant Potential of Estrogen in Microvessels of Female Spontaneously Hypertensive Rats
Authors: Dantas Ana Paula V. , Tostes Rita C.A. , Fortes Zuleica B. , Costa Sonia G. , Nigro Dorothy , Carvalho Maria Helena C.
Published: July 2002

In studies conducted in vitro, it has been demonstrated that estrogen has an antioxidant potential that may contribute to its protective effects on the cardiovascular system. However, the antioxidant effect of estrogen in vivo has not been demonstrated. To address this issue, in this study the effects of estrogen on oxidative stress were evaluated in microvessels studied in vivo. Oxidative stress was evaluated by using intravital microscopy in mesenteric arterioles from female spontaneously hypertensive rats (SHR) in physiological estrous (OE), ovariectomized (OVX), OVX treated with estradiol (E
2
), or estradiol + progesterone (E/P). The mesenteries were superfused with hydroethidine, a reduced and nonfluorescent precursor of ethidium bromide (EB). In the presence of reactive oxygen species, hydroethidine is transformed intracellularly in EB, which binds to DNA and can be detected by its red fluorescence. The percentage of EB-positive nuclei along the arteriolar wall in OVX (28.4±4.3) was significantly increased compared with OE (14.2±3.9;
P
<0.05). The OVX overproduction of oxyradicals was attenuated by E
2
(15.7±2.2) and E/P (14.8±0.8). Treatment with the superoxide dismutase mimetic MnTMPyP attenuated by 75% the oxidation of hydroethidine in both OE and OVX. Conversely, mannitol, that decomposes hydroxyl radical, and L-NAME, a nitric oxide synthase inhibitor, had no significant effects on hydroethidine oxidation. No differences on hydrogen peroxide plasma concentration were observed among the groups, suggesting that superoxide anion is the most likely oxyradical involved in the increased oxidative stress observed in OVX. The treatment of mesenteries with diphenyleneiodonium (DPI), an nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase inhibitor, but not with oxypurinol, a xanthine-oxidase inhibitor, produced a significant reduction of oxyradical generation in OVX microvessels and a slight decrease in those from OE. Chronic treatment of female SHR with losartan caused similar decreases in oxyradicals in both OE and OVX, whereas diclofenac and verapamil had no effects. Together these data suggest that estrogen reduces superoxide anion bioavailability in vivo. The antioxidant effect of estrogen, which can contribute to a less pronounced endothelial dysfunction in female SHR, may be dependent on a direct modulatory action of estrogen on NADPH activity.
Important Role of Rho-kinase in the Pathogenesis of Cardiovascular Inflammation and Remodeling Induced by Long-Term Blockade of Nitric Oxide Synthesis in Rats
Authors: Kataoka Chu , Egashira Kensuke , Inoue Shujiro , Takemoto Masao , Ni Weihua , Koyanagi Masamichi , Kitamoto Shiro , Usui Makoto , Kaibuchi Kozo , Shimokawa Hiroaki , Takeshita Akira
Published: July 2002

Chronic inhibition of endothelial NO synthesis by the administration of
N
G
-nitro-
l
-arginine methyl ester (L-NAME) to rats induces early vascular inflammation (monocyte infiltration into coronary vessels and monocyte chemoattractant protein-1 expression) as well as subsequent arteriosclerosis. The small GTPase Rho controls cell adhesion, motility, and proliferation and is activated by several growth factors such as angiotensin II. We investigated the effect of a specific inhibitor of Rho-kinase, Y-27632, in rats treated with L-NAME to determine the role of the Rho/Rho-kinase pathway in the development of arteriosclerosis. We found here increased activity of Rho/Rho-kinase after L-NAME administration and its prevention by angiotensin II type 1 receptor blockade. Hydralazine or lecithinized superoxide dismutase (l-SOD) did not affect Rho/Rho-kinase activity. Co-treatment with Y-27632 did not affect the L-NAME-induced increase in cardiovascular tissue ACE activity or L-NAME-induced decrease in plasma NO concentrations, but did prevent the L-NAME-induced early inflammation and late coronary arteriosclerosis. In addition, Y-27632 prevented the increased gene expression of monocyte chemoattractant protein-1 and transforming growth factor-β1 as well as cardiac fibrosis and glomerulosclerosis. These findings suggest that increased activity of Rho/Rho-kinase pathway mediated via the angiotensin II type 1 receptor may thus be important in the pathogenesis of early vascular inflammation and late remodeling induced by chronic inhibition of NO synthesis. The beneficial effects of Rho-kinase inhibition are not mediated by restoration of NO production. The Rho-kinase pathway could be a new therapeutic target for treatment of vascular diseases.
Altered Nitric Oxide Synthase 3 Distribution in Mesenteric Arteries of Hypertensive Rats
Authors: Sullivan Jennifer C. , Pollock David M. , Pollock Jennifer S.
Published: July 2002

A high-salt (HS) diet and angiotensin II (Ang II) are both associated with the development of hypertension and impaired endothelial function. We hypothesize that alterations in nitric oxide synthase (NOS) activity or subcellular localization of NOS 3 protein may contribute to endothelial dysfunction in salt-dependent hypertension. To test this hypothesis, two models of salt-dependent hypertension were studied: DOCA-salt and Ang II. For Ang II hypertension, rats were divided into 4 groups: control on normal or HS diet, Ang II-infused on normal or HS diet. The mesenteric arterial bed was isolated and frozen in liquid nitrogen. Frozen arteries were homogenized and separated into cytosolic and particulate fractions. NOS activity was assayed by determining the conversion of
3
H-arginine to
3
H-citrulline in the absence and presence of the NOS inhibitor, Nω-nitro-
l
-arginine. NOS 3 protein expression was significantly increased in the cytosol of arteries from DOCA-salt compared with placebo rats and in Ang II-infused and Ang HS rats compared with control. NOS 3 expression in the particulate fraction was comparable among all groups. NOS activity (pmol/30 min/total protein) was significantly increased in the cytosolic fraction of arteries from DOCA-salt rats compared with placebo and in Ang HS rats compared with control. NOS activity was comparable in the particulate fraction in all rat groups. In conclusion, there is an altered subcellular distribution of NOS 3 in salt-dependent hypertension that may contribute to the development of hypertension and endothelial dysfunction.
Cytochrome P450-Dependent Eicosapentaenoic Acid Metabolites Are Novel BK Channel Activators
Authors: Lauterbach Birgit , Barbosa-Sicard Eduardo , Wang Mong-Heng , Honeck Horst , Kärgel Eva , Theuer Jürgen , Schwartzman Michal L. , Haller Hermann , Luft Friedrich C. , Gollasch Maik , Schunck Wolf-Hagen
Published: July 2002

P450-dependent arachidonic acid (AA) metabolites regulate arterial tone by modulating calcium-activated (BK) potassium channels in vascular smooth muscle cells (VSMC). Because eicosapentaenoic acid (EPA) has been reported to improve vascular function, we tested the hypothesis that P450-dependent epoxygenation of EPA produces alternative vasoactive compounds. We synthesized the 5 regioisomeric epoxyeicosattrienoic acids (EETeTr) and examined them for effects on K
+
currents in rat cerebral artery VSMCs with the patch-clamp technique. 11(R),12(S)-epoxyeicosatrienoic acid (50 nmol/L) was used for comparison and stimulated K
+
currents 6-fold at +60 mV. However, 17(R),18(S)-EETeTr elicited a more than 14-fold increase. 17(S),18(R)-EET and the remaining four regioisomers were inactive. The effect of 17(R),18(S)-EETeTr was blocked by tetraethylammonium but not by 4-aminopyridine. VSMCs expressed P450s 4A1 and 4A3. Recombinant P450 4A1 hydroxylated EPA at C-19 and C-20 and epoxygenated the 17,18-double bond, yielding the R, S- and S, R-enantiomers in a ratio of 64:36. We conclude that 17(R),18(S)-EETeTr represents a novel, potent activator of BK potassium channels. Furthermore, this metabolite can be directly produced in VSMCs. We suggest that 17(R),18(S)-EETeTr may function as an important hyperpolarizing factor, particularly with EPA-rich diets.
Selective Gene Transfer to Key Cardiovascular Regions of the Brain: Comparison of Two Viral Vector Systems
Authors: Sinnayah Puspha , Lindley Timothy E. , Staber Patrick D. , Cassell Martin D. , Davidson Beverly L. , Davisson Robin L.
Published: July 2002

The systemic renin-angiotensin system (RAS) plays a critical role in cardiovascular (CV) homeostasis. All components of the RAS are also known to be produced cell-specifically within specific brain regions, although the role of the brain RAS relative to the systemic RAS has remained a puzzle due to the difficulty of dissecting these two systems. Selectively targeting these regions with genes that modify the RAS could help unravel this puzzle. We compared the ability of adenovirus (Ad) and lentivirus (feline immunodeficiency virus, FIV) vectors to mediate gene delivery in vivo to the supraoptic nucleus (SON) and subfornical organ (SFO), two important CV control regions known to express the various RAS genes. SON or SFO of adult C57BL/6 mice (n=37) were stereotaxically injected with replication-deficient recombinant Ad or FIV harboring a β-galactosidase (β-gal) reporter gene. At 1, 3, or 8 weeks post-injection, brain sections were processed for β-Gal activity, double immunofluorescence to verify cell-type specificity of viral transduction, or immunohistochemical detection of inflammatory mediators. Our results demonstrate that: (1) murine SFO and SON can be selectively targeted for gene transfer in vivo;(2) FIV mediated neuron-specific gene delivery, whereas Ad transduced both neuronal and glial cell types in SFO and SON; (3) Ad injected into the SON transduced neurons within the SFO through retrograde transport, whereas FIV did not; (4) β-gal activity remained stable for 3 weeks but then declined by 8 weeks with Ad, while minimal decline occurred with FIV; (5) FIV did not cause inflammatory responses, whereas infiltrate was detectable in Ad-injected SFO and SON. These vectors are potentially important tools for dissecting the cell- and site-specific components of the brain RAS and other important CV regulatory systems within this circuitry, and may have therapeutic applications for centrally mediated CV diseases.
Mechanism by Which Superoxide Potentiates Tubuloglomerular Feedback
Authors: Ren YiLin , Carretero Oscar A. , Garvin Jeffrey L.
Published: July 2002

The macula densa detects changes in NaCl concentration in tubular fluid and transmits a feedback signal, known as tubuloglomerular feedback (TGF), which helps to control glomerular afferent arteriole resistance. We and other investigators have reported that synthesis of NO in the macula densa inhibits TGF. NO can be scavenged by superoxide (O
−
2
) to form peroxynitrite, effectively reducing the bioavailability of NO; there is growing evidence that O
−
2
regulates vascular tone in the kidney. We hypothesized that O
−
2
produced in the macula densa enhances TGF and this effect acts only in an autocrine manner within the cells of the macula densa. Afferent arterioles and attached macula densas from Sprague-Dawley rats were simultaneously microperfused in vitro and TGF response examined before and after perfusing the tubular lumen, bath, or vascular lumen with a superoxide scavenger. The macula densa was perfused with solutions containing either 5 mmol/L Na
+
and 3 mmol/L Cl
−
(low NaCl) or 80 mmol/L Na
+
and 77 mmol/L Cl
−
(high NaCl) while keeping pressure in the afferent arteriole constant at 60 mm Hg. When 10
−4
M Tempol, a stable membrane-permeant superoxide dismutase (SOD) mimetic, was added to the tubular lumen, it inhibited TGF by 56% (before Tempol: TGF, 3.2±0.3 μm; after Tempol: TGF, 1.4±0.2 μm; n=6;
P
<0.05, control versus Tempol). Adding Tempol to the bath inhibited TGF by 48% (before Tempol: TGF, 2.5±0.25 μm; after Tempol: TGF, 1.3±0.18 μm; n=6;
P
<0.05). However, adding Tempol to the vessel lumen did not change TGF response significantly (before Tempol: TGF, 2.7±0.37 μm; after Tempol: TGF, 3.2±0.25 μm; n=7;
P
=0.25). When 300 U/mL of the enzyme SOD, which is not membrane-permeant, was added to either the tubular lumen or bath, it had no effect on TGF response. Finally, to determine whether the effect of O
−
2
in the macula densa is mediated by its scavenging of NO, 7-nitroindazole (7-NI) was added to the macula densa to inhibit neuronal nitric oxide synthase (nNOS). In the presence of 7-NI, Tempol had no effect (7-NI only: TGF, 3.0±0.4 μm; 7-NI plus Tempol: TGF, 2.8±0.5 μm; n=6;
P
=0.343). Our findings suggest that (1) reducing O
−
2
increases the bioavailability of NO, which inhibits TGF, (2) both O
−
2
and NO act within the macula densa, and (3) O
−
2
appears to have no effect on its own.
The Y Chromosome Effect on Blood Pressure in Two European Populations
Authors: Charchar Fadi J. , Tomaszewski Maciej , Padmanabhan Sandosh , Lacka Beata , Upton Mark N. , Inglis Gordon C. , Anderson Niall H. , McConnachie Alex , Zukowska-Szczechowska Ewa , Grzeszczak Wladyslaw , Connell John M.C. , Watt Graham C.M. , Dominiczak Anna F.
Published: July 2002

Higher blood pressure (BP) in males compared with females is well documented and is thought to be influenced in part by the Y chromosome. To examine whether there is an association between BP and a polymorphic
Hin
dIII biallelic marker in the nonrecombining region of the Y chromosome, we genotyped 155 males from a Polish study group and 762 males from a Scottish study group. We also tested for possible interaction between the Y chromosome and a mutation in the steroidogenic factor binding site of the aldosterone synthase gene by genotyping the same group from Scotland. There was no significant difference in age or body mass index between 2 Y chromosome genotypes in both study groups. Men with the
Hin
dIII(+) genotype had significantly higher systolic and diastolic pressures than those with the
Hin
dIII(−) genotype in both the Polish and Scottish studies. This difference between the genotypes was 5.27 mm Hg (
P
=0.0014) and 3.14 mm Hg (
P
=0.0005) for adjusted systolic BP and 2.6 mm Hg (
P
=0.0045) and 1.44 mm Hg (
P
=0.0084) for adjusted diastolic BP in the Polish and the Scottish studied, respectively. On binary logistic regression analysis, males with the
Hin
dIII(+)/TT SF1 genotype combination had an odds ratio for elevated BP of 3.92 (CI 1.21 to 12.68,
P
=0.023). Our results indicate that the Y chromosome harbors a locus or loci that contribute to BP variation in hypertensive and normotensive men. The polymorphism in the aldosterone synthase gene may interact with the Y chromosome to increase the odds of an individual’s developing higher BP.
Heart Rate and Blood Pressure Quantitative Trait Loci for the Airpuff Startle Reaction
Authors: Jaworski Rebecca L. , Jirout Martin , Closson Shamara , Breen Laura , Flodman Pamela L. , Spence M. Anne , Kren Vladimir , Krenova Drahomira , Pravenec Michal , Printz Morton P.
Published: July 2002

The airpuff startle reaction is a probe of sensori-autonomic processing and is useful for studies of genetic control of stress-induced cardiovascular activity. Using a Wistar-Kyoto-Spontaneously Hypertensive Rat F2 cross, we reported an airpuff-elicited strain-dependent and trial-dependent bradycardia, the absence of which cosegregated with hypertension. Here, we use the mapping power of the HXB-BXH recombinant inbred rat strains (n=23) to locate quantitative trait loci (QTL) for this and associated cardiovascular phenotypes. Rats (12 weeks old), with indwelling femoral arterial catheters, were subjected to repeated airpuff startle stimuli (100 ms, 12.5 psi, 28 trials). Basal mean arterial pressure (MAP), delta MAP, and delta heart rate response to airpuff stimuli were analyzed as the average over 28 trials. There was a significant strain effect on the cardiovascular phenotypes measured. One QTL for the bradycardia elicited by the first airpuff stimulus was identified on chromosome 2 (D2rat 62/63; logarithm of odds [LOD] 2.9) mapping near a reported blood pressure locus. Further QTL were identified for basal MAP (RN08), stimulus-elicited tachycardia on trials 2 to 5 (RNO1 and RNO10), and delta MAP (RNO6). Our results indicate that chromosomes 1, 2, and 10 are involved in heart rate responses to airpuff startle stimulus, and chromosomes 6 and 8 are involved in pressor responses. This study is the first to identify stress-related heart rate loci and provides additional support for our prior cosegregation results. Furthermore, we have established the utility of this experimental paradigm to identify loci responsible for cardiovascular regulation during stress in genetic hypertensive models.
Regulation of Cyclooxygenase- and Cytochrome P450-Derived Eicosanoids by Heme Oxygenase in the Rat Kidney
Authors: Botros Fady T. , Laniado-Schwartzman Michal , Abraham Nader G.
Published: July 2002

Heme oxygenase enzymes (HO-1 and HO-2) catalyze the conversion of heme to biliverdin, free iron, and carbon monoxide (CO). Heme and products derived from its metabolism potentially influence renal function and blood pressure by affecting the expression and/or activity of hemeproteins, including cytochrome P450 (CYP4A) monooxygenases and cyclooxygenases (COX-1 and COX-2). We studied HO isoform expression and examined the effect of HO-1 induction by SnCl
2
on CYP4A and COX expression and activity in the rat kidney. HO-1 protein levels in kidney tissues from untreated rats were barely detectable, whereas HO-2 protein was expressed in all kidney structures examined and its levels were higher in the outer medulla followed by the inner medulla/papilla and cortex. HO-2 expression along the nephron followed its regional distribution, ie, the highest levels were detected in the medullary thick ascending limb (mTAL) and inner medullary collecting ducts followed by proximal tubules. SnCl
2
Treatment did not significantly affect HO-2 expression or distribution; however, it markedly increased HO-1 protein in the inner and outer medulla, specifically, in the inner medullary collecting ducts and mTAL. CYP4A expression and 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis were the highest in the outer medulla followed by the cortex and inner medulla/papilla. SnCl
2
treatment reduced cortical and inner medullary CYP4A protein levels by 60% and 50% and inhibited 20-HETE synthesis by 90% and 60%, respectively. Despite a significant induction of HO-1 protein in the outer medulla, CYP4A expression and 20-HETE synthesis were hardly affected. SnCl
2
treatment did not affect COX-1 expression but markedly reduced cortical and medullary COX-2 protein levels. We conclude that HO isoform expression is segmented within the kidney and along the nephron and that treatment with an HO-1 inducer suppressed the levels of CYP4A and COX-2 proteins in a tissue-specific manner with concomitant effects on their activity. Such interactions may play an important role in the regulation of renal function.
Sympathetic Activation in Adipose Tissue and Skeletal Muscle of Hypertensive Rats
Authors: Cabassi Aderville , Vinci Simonetta , Cantoni Anna Maria , Quartieri Fabio , Moschini Luigi , Cavazzini Stefania , Cavatorta Angelo , Borghetti Alberico
Published: July 2002

The activation of the sympathetic nervous system is a common feature of arterial hypertension and other cardiovascular diseases. This activation might be dependent on an altered baroreflex control of vascular resistance of which the inhibitory response on sympathetic activity appears impaired. The aim of the study was to monitor during the natural course of arterial hypertension in spontaneously hypertensive (SHR) and age-matched Wistar Kyoto (WKY) rats (5, 16, 30, and 54 weeks of age) the peripheral sympathetic activity expressed as interstitial norepinephrine (NE) release and as tyrosine hydroxylase (TH) activity, the rate-limiting enzyme of NE synthesis, in the differently baroreflex-controlled subcutaneous adipose tissues and skeletal muscles. Blood pressure and plasma NE in SHR were similar to WKY at 5 weeks of age but increased at all other ages. Body weight was similar in both 5-week-old rats but reduced in SHR at all other ages. The interstitial NE levels were greater in both SHR tissues at all ages as compared with WKY. In adipose tissue of SHR, TH activity was higher at all ages as compared with WKY, whereas TH activity in skeletal muscle was higher only after the development of hypertension. These data show that in both SHR tissues, an increase of interstitial NE release is always present during its lifespan. This suggests that increased sympathetic activation in the SHR model is not specific to baroreflex-controlled tissues such as skeletal muscle but involves also subcutaneous adipose tissue, the sympathetic efferents of which are independent from baroreflexes.