bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural Changes of Neuronal Mitochondria After Transient and Permanent Cerebral Ischemia
Authors: Solenski Nina J. , diPierro Charles G. , Trimmer Patricia A. , Kwan Aij-Li , Helms Gregory A.
Published: July 2002

Background and Purpose

—

Mitochondrial swelling is one of the most striking and initial ultrastructural changes after acute brain ischemia. The purpose of the present study was to examine the role of reperfusion of the cerebral cortex after transient focal cerebral ischemia on neuronal mitochondrial damage.

Methods

—

Male Sprague-Dawley rats (n=16) were subjected to either temporary or permanent occlusion of the middle cerebral artery and bilateral carotid arteries. Three experimental conditions were compared: group I, permanent ischemia (3, 5, and 24 hours); group II, transient ischemia (2, 24 hours of reperfusion); and sham surgery. Anesthetized rats were killed by cardiac perfusion, and brain tissue was removed ipsilaterally and contralaterally from the ischemic core section of the frontoparietal cortex. Fixed tissue was prepared for electron microscopic examination, and electron microscopic thin sections of random neurons were photographed. Perinuclear neuronal mitochondria were analyzed in a blinded manner for qualitative ultrastructural changes (compared with sham control) by 2 independent investigators using an objective grading system.

Results

—

Cortical neuronal mitochondria exposed to severe ischemic/reperfusion conditions demonstrated dramatic signs of injury in the form of condensation, increased matrix density, and deposits of electron-dense material followed by disintegration by 24 hours. In contrast, mitochondria exposed to an equivalent time of permanent ischemia demonstrated increasing loss of matrix density with pronounced swelling followed by retention of their shape by 24 hours.

Conclusions

—

Neuronal mitochondria undergoing transient versus permanent ischemia exhibit significantly different patterns of injury. Structural damage to neuronal mitochondria of the neocortex occurs more acutely and to a greater extent during the reperfusion phase in comparison to ischemic conditions alone. Further research is in progress to delineate the role of oxygen free radical production in the observed mitochondrial damage during postischemic reoxygenation.
Occurrence of Secondary Ischemic Events Among Persons With Atherosclerotic Vascular Disease
Authors: Vickrey Barbara G. , Rector Thomas S. , Wickstrom Steven L. , Guzy Peter M. , Sloss Elizabeth M. , Gorelick Philip B. , Garber Steven , McCaffrey Daniel F. , Dake Michael D. , Levin Regina A.
Published: July 2002

Background and Purpose

—

Few data exist for large managed care populations on the occurrence of subsequent acute ischemic events in persons with established atherosclerotic vascular disease. We estimated the occurrence of secondary stroke, acute myocardial infarction (AMI), and vascular deaths among 2 large, managed care samples.

Methods

—

With the use of
International Classification of Diseases, Ninth Revision, Clinical Modification
codes
,
patients aged ≥40 years and with stroke, AMI, or peripheral arterial disease (PAD) were identified from administrative data of UnitedHealthcare plans during 1995–1998. Stroke, AMI, and PAD cohorts were identified within a commercial insurance sample and a Medicare sample. Cumulative occurrences of subsequent stroke, AMI, or vascular death were estimated by survival analysis.

Results

—

In the stroke commercial cohort (n=1631; mean age, 62.1 years), cumulative occurrence of subsequent events was 4.2%, 6.5%, 9.8%, and 11.8% at 0.5, 1, 2, and 3 years, respectively; cumulative secondary event occurrence in the AMI commercial cohort (n=6458; mean age, 56.0 years) was 3.5%, 4.8%, 7.3%, and 8.5% and in the PAD commercial cohort (n=5813; mean age, 59.2 years) was 1.5%, 2.8%, 4.8%, and 6.5%, respectively. Cumulative secondary event occurrences were even higher in stroke (n=1518; mean age, 79.5 years), AMI (n=2197; mean age, 76.2 years), and PAD (n=5033; mean age, 76.6 years) cohorts of the Medicare sample: 18.1%, 17.0%, and 8.7%, respectively, at 3 years. More than 75% of each stroke cohort’s secondary events were strokes; more than 75% of each AMI cohort’s secondary events were AMIs. Of the PAD cohorts’ secondary events, 27% to 39% were strokes, 48% to 57% were AMIs, and 13% to 16% were vascular deaths.

Conclusions

—

Among these managed care enrollees with existing atherosclerotic vascular disease, subsequent ischemic events represent a significant symptomatic disease burden. Given these findings, it is very important to determine whether secondary prevention strategies are being effectively used to manage patients with diagnosed atherosclerosis.
l
-Arginine Augments Cardiac Vagal Control in Healthy Human Subjects
Authors: Chowdhary Saqib , Nuttall Sarah L. , Coote John H. , Townend Jonathan N.
Published: July 2002

Cardiac vagal control has prognostic significance in cardiac disease, but the control mechanisms of this system remain poorly understood. We have previously demonstrated a role for NO in promoting vagal control of heart rate in humans. Here we examine the influence of
l
-arginine, the substrate for NO synthase, on this mechanism in healthy human subjects. Eleven healthy volunteers (9 men; age, 20 to 25 years) underwent measurement of heart rate variability and baroreflex sensitivity before and during a systemic infusion of
l
-arginine (1 g/min; total, 30 g). To control for the fall in blood pressure, comparison was made with an infusion of the control vasodilator hydralazine. Stereospecificity of observed effects was investigated by infusion of
d
-arginine. Urinary nitrate and nitrite (NO
x
) and cGMP concentrations were measured as indexes of NO generation.
l
-Arginine infusion produced a drop in mean arterial pressure of 5 mm Hg. This fall in blood pressure was matched by hydralazine infusion and was not observed with either
d
-arginine or saline infusion. Although RR interval duration, heart rate variability, and baroreflex sensitivity all fell significantly with hydralazine, the same degree of baroreflex unloading with
l
-arginine produced an increase in RR interval duration and no change or even slight increases in heart rate variability and baroreflex sensitivity. In contrast,
d
-arginine produced falls in high-frequency indexes of heart rate variability compared with saline. Only
l
-arginine increased urinary NO
x
and cGMP excretion. In conclusion, these data demonstrate that short-term
l
-arginine infusion facilitates vagal control of heart rate in healthy humans, probably via increased NO synthesis.
Bradykinin Enhances Sympathetic Neurotransmission in Rat Blood Vessels
Authors: Kansui Yasuo , Fujii Koji , Goto Kenichi , Abe Isao
Published: July 2002

Bradykinin evokes endothelium-dependent relaxation in some vascular beds; on the other hand, the possibility has been demonstrated that in certain organs, such as the adrenal medulla or atria, bradykinin may enhance transmitter release from the sympathetic nerves. We hypothesized that bradykinin may also enhance postganglionic sympathetic neurotransmission in blood vessels. To test this hypothesis, we recorded excitatory junction potentials (EJPs), a measure of sympathetic purinergic neurotransmission, in rat mesenteric resistance arteries with a conventional microelectrode technique. EJPs were elicited by repetitive perivascular nerve stimulation (1 Hz, 20 to 50 V, 30 to 60 μs, 11 pulses). In this preparation, bradykinin (10
−7
or 10
−6
mol/L) significantly enhanced the amplitude of EJPs without altering the resting membrane potential. This effect of bradykinin was blocked by Hoe 140, a bradykinin B2 receptor antagonist, but not by des-Arg
9
,[Leu
8
]-bradykinin, a bradykinin B1 receptor antagonist. The cyclooxygenase inhibitor indomethacin or NO synthase inhibitor
N
G
-nitro-
l
-arginine did not alter the effect of bradykinin. Captopril, an ACE inhibitor, but not candesartan, an angiotensin II type 1 receptor antagonist, enhanced the action of a low concentration (10
−8
mol/L) of bradykinin on EJPs. These findings suggest that in rat mesenteric resistance arteries, bradykinin enhances sympathetic purinergic neurotransmission, presumably through presynaptic bradykinin B2 receptors. The clinical relevance of the present findings remains unclear; however, the fact that the ACE inhibitor, but not the angiotensin II type 1 receptor antagonist, enhanced the action of bradykinin on sympathetic neurotransmission may warrant further investigation.
Angiotensin II Suppression in Humans by the Orally Active Renin Inhibitor Aliskiren (SPP100)
Authors: Nussberger Juerg , Wuerzner Grégoire , Jensen Chris , Brunner Hans R.
Published: July 2002

Renin is the main determinant of angiotensin (Ang) II levels. It, therefore, always appeared desirable to reduce Ang II levels by direct inhibition of renin. So far, specific renin inhibitors lacked potency and/or oral availability. We tested the new orally active nonpeptidic renin inhibitor SPP100 (Aliskiren, an octanamide with a 50% inhibitory concentration [IC50] in the low nanomolar range) in 18 healthy volunteers on a constant 100 mmol/d sodium diet using a double-blind, 3-way crossover protocol. In 3 periods of 8 days, separated by wash-outs of 6 days, each volunteer received 2 dosage levels of Aliskiren (low before high; 40 and 80 or 160 and 640 mg/d) and randomized placebo or 20 mg enalapril. Aliskiren was well tolerated. Not surprisingly, blood pressure and heart rate remained unchanged in these normotensive subjects. There was a dose-dependent decrease in plasma renin activity, Ang I, and Ang II following single doses of Aliskiren starting with 40 mg. Inhibition was still marked and significant after repeated dosing with maximal decreases in Ang II levels by 89% and 75% on Days 1 and 8, respectively, when the highest dose of Aliskiren was compared with placebo. At the same time, mean plasma active renin was increased 16- and 34-fold at the highest dose of Aliskiren. Plasma drug levels of Aliskiren were dose-dependent with maximal concentrations reached between 3 to 6 hours after administration; steady state was reached between 5 and 8 days after multiple dosing. Less than 1% of dose was excreted in the urine. Plasma and urinary aldosterone levels were decreased after doses of Aliskiren ≥80 mg and after enalapril. Aliskiren at 160 and 640 mg enhanced natriuresis on Day 1 by +45% and +62%, respectively, compared with placebo (100%, ie, 87±11 mmol/24h) and enalapril (+54%); kaliuresis remained unchanged. In conclusion, the renin inhibitor Aliskiren dose-dependently decreases Ang II levels in humans following oral administration. The effect is long-lasting and, at a dose of 160 mg, is equivalent to that of 20 mg enalapril. Aliskiren has the potential to become the first orally active renin inhibitor that provides a true alternative to ACE-inhibitors and Ang II receptor antagonists in therapy for hypertension and other cardiovascular and renal diseases.
Central Pulse Pressure and Mortality in End-Stage Renal Disease
Authors: Safar Michel E. , Blacher Jacques , Pannier Bruno , Guerin Alain P. , Marchais Sylvain J. , Guyonvarc’h Pierre-Marie , London Gérard M.
Published: July 2002

Damage of large arteries is a major factor in the high cardiovascular morbidity and mortality of patients with end-stage renal disease (ESRD). Increased aortic pulse wave velocity (PWV) and brachial pulse pressure (PP) are the principal arterial markers of cardiovascular mortality described in these patients. Whether central (carotid) PP and brachial-carotid PP amplification may predict all-cause (including cardiovascular) mortality has never been investigated. A cohort of 180 patients with ESRD who were undergoing hemodialysis was studied between January 1990 and March 2000. The mean duration of follow-up was 52±36 months (mean±SD). Mean age at entry was 51.5±16.3 years. Seventy deaths occurred, including both cardiovascular and noncardiovascular fatal events. At entry, patients underwent carotid PP measurements (pulse wave analysis), echocardiography, and aortic PWV (Doppler ultrasonography), together with standard clinical and biochemical analyses. On the basis of Cox analyses, after adjustment of age, time on dialysis before inclusion, and previous cardiovascular events, 3 factors emerged as predictors of all-cause mortality: carotid PP, brachial/carotid PP, and aortic PWV. Adjusted hazard ratios for 1-SD increments were 1.4 (1.1 to 1.8) for carotid PP, 0.5 (0.3 to 0.8) for brachial/carotid PP, and 1.3 (1.0 to 1.7) for PWV. Brachial blood pressure, including PP, had no predictive value for mortality after adjustment. These results provide the first direct evidence that in patients with ESRD, the carotid PP level and, mostly, the disappearance of PP amplification are strong independent predictors of all-cause (including cardiovascular) mortality.
Cationic Amino Acid Transport in the Renal Medulla and Blood Pressure Regulation
Authors: Kakoki Masao , Wang Weili , Mattson David L.
Published: July 2002

Previous studies have indicated that NO synthesis in isolated inner medullary collecting duct cells is reduced by cationic amino acids that compete with
l
-arginine for cellular uptake. In the present study, we investigated the effects of chronic renal medullary infusion of cationic amino acids on renal NO concentration and mean arterial pressure (MAP) in Sprague-Dawley rats. Renal medullary infusion of
l
-ornithine (50 μg/kg per min) or
l
-lysine (50 μg/kg per min) markedly decreased NO in the medulla (vehicle, 124±11 nmol/L;
l
-ornithine, 45±4 nmol/L;
l
-lysine, 42±6 nmol/L) and increased MAP (vehicle, 111±7 mm Hg;
l
-ornithine, 143±6 mm Hg;
l
-lysine, 148±3 mm Hg) after 5 days of infusion. In contrast, intravenous infusion of the same dose of
l
-ornithine or
l
-lysine for 5 days increased plasma concentration to levels similar to those observed with intramedullary infusion but did not change NO in the medulla or alter MAP. Furthermore, the NO-suppressing and hypertensive effects of medullary interstitial infusion of
l
-ornithine (50 μg/kg per min) were attenuated by simultaneous infusion of
l
-arginine (500 μg/kg per min; NO, 97±10 nmol/L; MAP, 124±3 mm Hg). A 5-day infusion of an antisense oligonucleotide against CAT-1 (18-mer, 8.3 nmol/h) significantly decreased CAT-1 protein in the medulla, decreased NO in the medulla (scrambled oligo, 124±10 nmol/L; antisense oligo, 67±11 nmol/L), and increased MAP (scrambled oligo, 113±2 mm Hg; antisense oligo, 130±2 mm Hg). These results suggest that uptake of
l
-arginine by cationic amino acid transport systems in the renal medulla plays an important role in the regulation of medullary NO and MAP in rats.
In Search of Cardiovascular Candidate Genes
Authors: Deschepper Christian F. , Boutin-Ganache Isabelle , Zahabi Ahmad , Jiang Zhibin
Published: July 2002

Most cardiovascular traits of interest can be defined as “complex traits,” with the first step in the identification of genetic factors affecting such traits being the detection of quantitative trait loci (QTLs). Animal models have proven particularly useful in this regard. However, only very few of the QTLs identified to date have led to the identification of candidate genes. We describe an example of our own work where the combination of anatomical and a biochemical intermediate phenotypes have led to the identification of the natriuretic peptide precursor A (
Nppa
) gene as a candidate gene for left ventricular hypertrophy (LVH). Combined with the power of comparative genetics, these strategies will continue to improve the chances of finding candidate genes for cardiovascular traits such as susceptibility to heart diseases, hypertension, and hypertension-induced end-organ damage.
Prorenin-Induced Myocyte Proliferation
Authors: Saris Jasper J. , van den Eijnden Mark M.E.D. , Lamers Jos M.J. , Saxena Pramod R. , Schalekamp Maarten A.D.H. , Danser A.H. Jan
Published: July 2002

Cardiomyocytes bind, internalize, and activate prorenin, the inactive precursor of renin, via a mannose 6-phosphate receptor (M6PR)–dependent mechanism. M6PRs couple directly to G-proteins. To investigate whether prorenin binding to cardiomyocytes elicits a response, and if so, whether this response depends on angiotensin (Ang) II, we incubated neonatal rat cardiomyocytes with 2 nmol/L prorenin and/or 150 nmol/L angiotensinogen, with or without 10 mmol/L M6P, 1 μmol/L eprosartan, or 1 μmol/L PD123319 to block M6P and AT
1
and AT
2
receptors, respectively. Protein and DNA synthesis were studied by quantifying [
3
H]-leucine and [
3
H]-thymidine incorporation. For comparison, studies with 100 nmol/L Ang II were also performed. Neither prorenin alone, nor angiotensinogen alone, affected protein or DNA synthesis. Prorenin plus angiotensinogen increased [
3
H]-leucine incorporation (+21±5%, mean±SEM,
P
<0.01), [
3
H]-thymidine incorporation (+29±6%,
P
<0.01), and total cellular protein (+14±3%,
P
<0.01), whereas Ang II increased DNA synthesis only (+34±7%,
P
<0.01). Eprosartan, but not PD123319 or M6P, blocked the effects of prorenin plus angiotensinogen as well as the effects of Ang II. Medium Ang II levels during prorenin and angiotensinogen incubation were <1 nmol/L. In conclusion, prorenin binding to M6PRs on cardiomyocytes per se does not result in enhanced protein or DNA synthesis. However, through Ang II generation, prorenin is capable of inducing myocyte hypertrophy and proliferation. Because this generation occurs independently of M6PRs, it most likely depends on the catalytic activity of intact prorenin in the medium (because of temporal prosegment unfolding) rather than its intracellular activation. Taken together, our results do not support the concept of Ang II generation in cardiomyocytes following intracellular prorenin activation.
Signaling Mechanisms of Heparin-Binding Epidermal Growth Factor-Like Growth Factor in Vascular Smooth Muscle Cells
Authors: Reynolds Cherilynn M. , Eguchi Satoru , Frank Gerald D. , Motley Evangeline D.
Published: July 2002

A host of growth factors have been implicated in vascular pathologies; one such factor is heparin-binding epidermal growth factor-like growth factor (HB-EGF). Although HB-EGF has been shown to stimulate mitogenesis and chemotaxis of vascular smooth muscle cells (VSMC), its signaling mechanism remains undefined. In this study, we examined possible signal transduction pathways by which HB-EGF leads to mitogenesis in cultured rat VSMC. HB-EGF induced phosphorylation of the EGF receptor (EGFR) with maximum phosphorylation at 0.5 to 1 minute, whereas erbB4, the other receptor to which HB-EGF binds, was not activated on HB-EGF stimulation. HB-EGF induced a time- and concentration-dependent phosphorylation of mitogen-activated protein kinase (MAPK; p42/44 MAPK, extracellular signal-regulating kinase [ERK] 1/2). It also activated Akt and p70S6 kinase (p70S6K) but not p38 MAPK. HB-EGF-induced phosphorylation of these kinases was blocked by the EGFR kinase inhibitor AG1478. To investigate signaling molecules involved in HB-EGF-induced DNA synthesis, we pretreated VSMC with the specific ERK kinase mitogen-activated kinase (MEK) inhibitor PD98059 and the phosphatidylinositol 3-kinase inhibitor LY294002. These inhibitors significantly blocked HB-EGF-induced DNA synthesis. PD98059 inhibited HB-EGF-induced ERK activation, whereas it had no effect on Akt activation by HB-EGF. By contrast, LY294002 inhibited HB-EGF-induced Akt and p70S6K activation without effecting ERK activation by HB-EGF. These results demonstrate that HB-EGF-induced mitogenesis requires both ERK and phosphatidylinositol 3-kinase (Akt and p70S6K) pathways activated through EGFR, thereby providing a new mechanistic insight by which HB-EGF contributes to vascular remodeling.
Endothelin-1–Induced Enhancement of Coronary Smooth Muscle Contraction via MAPK-Dependent and MAPK-Independent [Ca
2+
]
i
Sensitization Pathways
Authors: Cain Ashley E. , Tanner Dennis M. , Khalil Raouf A.
Published: July 2002

Endothelin-1 (ET-1) has been implicated in coronary vasospasm by enhancing coronary vasoconstriction to vasoactive eicosanoids, and a role for protein kinase C (PKC) activation has been suggested. However, the cellular mechanisms downstream from PKC activation are unclear. We investigated whether physiological concentrations of ET-1 enhance coronary smooth muscle contraction by activating a PKC-mediated signaling pathway involving tyrosine phosphorylation and activation of mitogen-activated protein kinase (MAPK). Cell contraction was measured in smooth muscle cells isolated from porcine coronary artery, [Ca
2+
]
i
was measured in fura-2 loaded cells, and tissue fractions were examined for reactivity with anti-phosphotyrosine (P-Tyr) and anti-MAPK antibodies using immunoprecipitation and immunoblot analysis. In Hanks’ solution (1 mmol/L Ca
2+
), ET-1 (10 pmol/L) did not increase basal [Ca
2+
]
i
(81±2 nmol/L) but caused cell contraction (10%) that was inhibited by calphostin C (10
−6
mol/L), inhibitor of PKC, tyrphostin (10
−6
mol/L), inhibitor of tyrosine kinase, and PD098059 (10
−6
mol/L), inhibitor of MAPK kinase. The vasoactive eicosanoid prostaglandin F
2α
(PGF
2α
; 10
−7
mol/L) caused increases in cell contraction (11%) and [Ca
2+
]
i
(122±9 nmol/L) that were inhibited by the Ca
2+
channel blocker verapamil (10
−6
mol/L) but not by calphostin C, tyrphostin, or PD098059. Pretreatment with ET-1 for 10 minutes enhanced cell contraction to PGF
2α
(33%) with no additional increase in [Ca
2+
]
i
(124±10 nmol/L). Activation of PKC by phorbol 12-myristate 13-acetate (PMA; 10
−7
mol/L) caused cell contraction and enhanced PGF
2α
contraction (32%) with no additional increase in [Ca
2+
]
i
(126±9 nmol/L). The ET-1– and PMA-induced enhancement of PGF
2α
contraction was abolished by verapamil or calphostin C but not by tyrphostin or PD098059. ET-1 and PMA caused significant increases in tyrosine phosphorylation of MAPK that were inhibited by calphostin C, tyrphostin, and PD098059. PGF
2α
did not cause any additional increases in tyrosine phosphorylation of MAPK in tissues untreated or pretreated with ET-1 or PMA. Thus, physiological concentrations of ET-1 activate a Ca
2+
-independent PKC-mediated signaling pathway that involves tyrosine phosphorylation and activation of MAPK. The enhancement of PGF
2α
-induced coronary smooth muscle contraction by ET-1 involves additional activation of a Ca
2+
-sensitive PKC-mediated pathway but not tyrosine phosphorylation or activation of MAPK. The MAPK-dependent and MAPK-independent signaling pathways represent possible cellular mechanisms by which ET-1 could enhance coronary vasoconstriction to vasoactive eicosanoids in coronary vasospasm.
Calcium-Dependent Synthesis of Prostacyclin in ATP-Stimulated Venous Endothelial Cells
Authors: Choi Jaehwa , Hammer Leah W. , Hester Robert L.
Published: July 2002

Prostacyclin is a powerful vasodilator that is released from vascular endothelial cells. Previous studies in our laboratory have indicated that arachidonic acid metabolites from venous endothelium play an important role in the dilation of adjacent arterioles during muscle stimulation. Furthermore, recent studies have suggested that ATP released from red blood cells during hypoxia stimulates dilation of arterioles. We tested the hypothesis that an ATP-induced increase in intracellular Ca
2+
in venous endothelium promotes prostacyclin synthesis. Small branches of femoral veins were isolated from male golden hamsters, placed in a 1 mL bath, and cannulated for perfusion with 3-(
N
-morpholino) propanesulfonic acid (MOPS)-buffered physiological salt solution at 37°C. Prostacyclin synthesis was determined by enzyme immunoassay of bath solution. Perfusion of veins with ATP increased prostacyclin synthesis from 50±5 to 627±46 pg/mL (n=49). ATP-induced prostacyclin synthesis was inhibited by removal of extracellular Ca
2+
, chelation of intracellular Ca
2+
with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) (10 μmol/L for 10 minutes), and preincubation with cytosolic phospholipase A
2
(PLA
2
) inhibitors, AACOCF
3
, and bromoenol lactone. Changes in intracellular Ca
2+
in cultured human venous endothelial cells were assessed by fura-2 spectrofluorometry. ATP induced a transient Ca
2+
peak within seconds, and the subsequent Ca
2+
plateau was abolished by removal of extracellular Ca
2+
. An increase in prostacyclin synthesis was detected in these cells 2 minutes after application of ATP. These findings suggest that the ATP-induced increase in intracellular Ca
2+
stimulates prostacyclin synthesis in venous endothelial cells.
Role of Methoxyestradiols in the Growth Inhibitory Effects of Estradiol on Human Glomerular Mesangial Cells
Authors: Dubey Raghvendra K. , Gillespie Delbert G. , Keller Paul J. , Imthurn Bruno , Zacharia Lefteris C. , Jackson Edwin K.
Published: July 2002

Metabolism of locally applied 17β-estradiol (estradiol) to methoxyestradiols contributes to the growth inhibiting effects of estradiol on vascular smooth muscle cells via an estrogen receptor (ER)-independent mechanism. Because vascular smooth muscle cells are phenotypically similar to glomerular mesangial cells, it is feasible that estradiol inhibits glomerular mesangial cell growth via a similar mechanism, and this possibility was investigated. In human glomerular mesangail cells, estradiol concentration dependently (1 to 100 nmol/L) inhibited serum-induced proliferation (cell number) and DNA (
3
[H]-thymidine incorporation) and collagen (
3
[H]-proline incorporation) synthesis. The inhibitory effects of estradiol were mimicked by 2-hydroxyestradiol and 2-methoxyestradiol, metabolites of estradiol with little affinity for ERs. 2-Hydroxyestradiol and 2-methoxyestradiol were more potent growth inhibitors than estradiol. The inhibitory effects of estradiol were enhanced by CYP450 inducers 3-methylcholanthrene (10 μmol/L) and phenobarbital (10 μmol/L) and blocked by the CYP450 inhibitor 1-aminobenzotriazole (10 μmol/L). The growth inhibitory effects of estradiol were also blocked by quercetin (10 μmol/L) and OR 486 (10 μmol/L) inhibitors of catechol-O-methyltransferase (converts catecholestradiols to methoxyestradiols). ICI182780 (ER antagonist with ER binding affinity similar to estradiol) blocked the growth inhibitory effects of estradiol (1 to 100 nmol/L) only at concentrations (>50 μmol/L) that inhibited estradiol metabolism to catecholestradiols. The growth inhibitory effects of 2-hydroxyestradiol were abrogated by quercetin and OR486 (two structurally dissimilar catechol-O-methyltransferase inhibitors), but not by ICI182780. However, the growth inhibitory effects of 2-methoxyestradiol were unaltered by catechol-O-methyltransferase inhibitors and ICI182780. In conclusion, our findings provide the first evidence that methoxyestradiols mediate the growth inhibitory effects of locally applied estradiol on glomerular mesangial cell growth via an ER-independent mechanism.
Perindopril Alters Vascular Angiotensin-Converting Enzyme, AT
1
Receptor, and Nitric Oxide Synthase Expression in Patients With Coronary Heart Disease
Authors: Zhuo Jia Long , Mendelsohn Frederick A.O. , Ohishi Mitsuru
Published: July 2002

Angiotensin-converting enzyme inhibitors (ACEi) reduce cardiovascular morbidity and mortality by improving coronary perfusion, reducing ventricular hypertrophy and remodeling, and preventing progression of coronary atherosclerosis. However, the cellular mechanisms underlying the beneficial effects of ACEi are not fully understood. We studied the in vivo effects of ACE inhibition with perindopril on cellular expression of ACE, AT
1
receptors and 2 nitric oxide synthase (NOS) isoforms, endothelial (eNOS) and inducible NOS (iNOS), in human blood vessels using quantitative in vitro autoradiography and immunocytochemistry. Seven patients with ischemic heart disease were treated with perindopril (4 mg/d) for up to 5 weeks before elective coronary bypass surgery, whereas controls did not receive the ACEi (n=7). Perindopril decreased plasma ACE by 70% and the plasma angiotensin II to angiotensin I ratio by 57% and reduced vascular ACE to approximately 65% of control levels in both endothelium and adventitia. By contrast, AT
1
receptor binding in vascular smooth muscle cells was increased by 80% in patients treated with perindopril as confirmed by immunocytochemistry. eNOS was expressed primarily in endothelial cells, whereas little iNOS expression occurred in vascular smooth muscle cells of untreated patients. Both eNOS and iNOS expression seemed to increase during perindopril treatment. These results suggest that suppression of angiotensin II formation in the vascular wall and increased expression of eNOS and iNOS during ACE inhibition may be beneficial in reversing endothelial dysfunction in patients with cardiovascular disease. Because vascular AT
1
receptor expression is increased during chronic ACE inhibition, more clinical studies are required to determine whether it is necessary to combine ACE inhibitors and AT
1
receptor antagonists in clinical management of heart failure, coronary heart disease, and hypertension
Lower Blood Pressure in Floxed Angiotensinogen Mice After Adenoviral Delivery of Cre-Recombinase
Authors: Stec David E. , Keen Henry L. , Sigmund Curt D.
Published: July 2002

Recent experimental evidence suggests a role for tissue renin-angiotensin systems in the development of hypertension. To test the importance of tissue renin-angiotensin systems in the development and maintenance of angiotensin II-dependent hypertension, we generated a transgenic model in which exon 2 of the human angiotensinogen gene is flanked by loxP sites (hAGT
flox
) so that this region of the gene can be deleted by the cre-recombinase. Double transgenic human renin and hAGT
flox
(R
+
/A
+flox
) mice of two independent lines exhibited elevated blood pressure. Acute administration of an adenovirus containing cre-recombinase (Adcre) lowered blood pressure by 30 mm Hg over a 4-day period as measured with fluid filled catheters. The chronic effect of Adcre administration on blood pressure was determined by radiotelemetry in a separate group of R
+
/A
+flox
mice. Blood pressure decreased by 25 mm Hg from baseline by day 8 post-Adcre, but increased on each day thereafter until it was 90% of baseline by day 21 post-Adcre. Expression analysis indicated the absence of detectable hAGT mRNA in the liver at day 5 post-Adcre, but reappeared at normal levels at days 14 to 21 post-Adcre. These studies suggest that Adcre is effective for acute, but not chronic, elimination of hepatic hAGT. Chronic elimination of hepatic hAGT will likely require the use of transgenic mice endogenously expressing cre-recombinase in the liver.
Preproendothelin-1 Gene Polymorphism Is Related to a Change in Vascular Reactivity in the Human Mammary Artery In Vitro
Authors: Iglarz Marc , Benessiano Joëlle , Philip Ivan , Vuillaumier-Barrot Sandrine , Lasocki Sigismond , Hvass Ulrich , Durand Geneviève , Desmonts Jean-Marie , Lévy Bernard I. , Henrion Daniel
Published: July 2002

A gene polymorphism of preproendothelin-1 (a G-to-T transversion that predicts a Lys/Asn change at codon 198) associated with an increased risk of hypertension has been recently described in patients carrying the T allele. No study has yet determined the impact of this polymorphism on vascular reactivity, although a functional role for endothelin-1 in the pathophysiology of hypertension has been clarified. At subthreshold concentrations, endothelin-1 and angiotensin II induce a potentiation of α-adrenergic–dependent vascular tone caused by an increased sensitivity of the contractile apparatus to calcium. We investigated phenylephrine-induced tone and its amplification by endothelin-1 and angiotensin II in human mammary artery rings in vitro. Contractions to phenylephrine (0.1 to 100 μmol) and endothelin-1 (0.1 to 300 nmol) were not significantly different in rings from GT/TT (n=27) and GG (n=21) patients. A subthreshold concentration of endothelin-1 (10 pmol) potentiated a phenylephrine-induced contraction (eg, 44±12% increase in tone with phenylephrine 1 μmol/L,
P
<0.001) that was significantly higher in the GT/TT group than in the GG group (eg, 44±12% versus 82±11%,
P
<0.01). A similar effect on response to phenylephrine was observed with a subthreshold concentration of angiotensin II. We also found a higher response to calcium in arteries from GT/TT patients. Endothelium-dependent or -independent relaxations were unaffected by the genotype. These data suggest that the preproendothelin-1 gene polymorphism is associated with a higher potentiating effect of endothelin-1 and angiotensin II, probably in relation with higher calcium sensitivity. These changes in vascular reactivity might help to understand the relations between this polymorphism and cardiovascular disorders.
Nitric Oxide Produced by THAL Nitric Oxide Synthase Inhibits TGF
Authors: Wang Hong , Carretero Oscar A. , Garvin Jeffrey L.
Published: July 2002

Nitric oxide (NO) produced by neuronal NO synthase (nNOS) in the macula densa decreases tubuloglomerular feedback (TGF). NO produced by NOS in the thick ascending limb (THAL) inhibits NaCl transport. We hypothesized that NO produced by NOS in the THAL reaches the macula densa and inhibits TGF. Rabbit afferent arterioles and attached macula densa were simultaneously microperfused in vitro. TGF response was determined by measuring afferent arteriole diameter before and after increasing NaCl in the macula densa perfusate. When the nNOS inhibitor 7-nitroindazole (7-NI) (10 μmol/L) was added to the macula densa lumen, it increased TGF from 2.3±0.2 to 3.5±0.5 μm (
P
<0.02; n=6). In the presence of 7-NI,

N
ω

-nitro-
l
-arginine methyl ester (L-NAME) (1 mmol/L) enhanced TGF from 2.6±0.3 to 4.0±0.5 μm (
P
<0.02; n=6) when the macula densa was perfused orthograde via the THAL, whereas it had no effect on TGF when the macula densa was perfused retrograde via the distal tubule (DT). Inhibition of macula densa soluble guanylate cyclase with LY83583 (1 μmol/L) blocked the effect of NO produced by THAL NOS when the macula densa was perfused via the THAL. We concluded that NO produced by THAL NOS acts as a paracrine factor, reaching the macula densa and inhibiting TGF.
Function and Regulation of Endothelin-1 and Its Receptors in Salt Sensitive Hypertension Induced by Sensory Nerve Degeneration
Authors: Ye Diana Z. , Wang Donna H.
Published: July 2002

To determine the role of endothelin-1 (ET-1) and its receptors in salt-sensitive hypertension induced by sensory nerve degeneration, selective ET
A
antagonist (ABT-627) and ET
B
antagonist (A-192621) were used. Newborn Wistar rats were given vehicle or 50 mg/kg capsaicin subcutaneously on the first and second days of life. After the weaning period, male rats were divided into eight groups, and subjected to the following treatments for 2 weeks: control + normal salt diet (Con+NS, 0.5%), control + high salt diet (Con+HS, 4%), control + high salt diet + ABT-627 (Con+HS+ABT-627), control + high salt diet + A-192621 (Con+HS+A-192621), capsaicin + normal salt diet (Cap+NS), capsaicin + high salt diet (Cap+HS), capsaicin + high salt diet + ABT-627 (Cap+HS+ABT-627), capsaicin + high salt diet + A-192621 (Cap+HS+A-192621). Both ABT-627 (5 mg/kg/d) and A-192621 (30 mg/kg/d) were given by oral gavage twice a day. Mean arterial pressure (MAP, mm Hg) was higher in Con+HS+A-192621 (141±11) than in Con+NS (94±10), Con+HS (95±5), and Con+HS+ABT-627 (97±6) (
P
<0.05). MAP was also higher in Cap+HS (152±6) and Cap+HS+A-192621 (180±7) than in Cap+NS (99±3) and Cap+HS+ABT-627 (104±5) (
P
<0.05), and it was higher in Cap+HS+A-192621 than in Cap+HS (
P
<0.05). Enzyme immunometric assay showed that ET-1 plasma concentration (pg/mL) was higher in Con+HS+A-192621 (7.59±0.78) than in Con+NS (2.68±0.56), Con+HS (2.50±0.92), and Con+HS+ABT-627 (3.54±0.79) (
P
<0.05). ET-1 plasma concentration was also higher in Cap+HS (8.95±2.16), Cap+HS+ABT-627 (9.82±1.22) and Cap+HS+A-192621 (10.97±0.57) than in Cap+NS (3.06±0.73) (
P
<0.05). We conclude that blockade of the ET
A
receptor prevents the development of salt sensitive hypertension induced by sensory nerve degeneration, indicating that activation of the ET
A
receptor by increased plasma ET-1 level contributes to elevation of blood pressure in this model. In contrast, blockade of the ET
B
receptor leads to an increase in blood pressure in both normal and sensory nerve degenerated rats fed a high salt diet. These results suggest that ET
B
plays an antihypertensive role in response to high salt intake under both normal and sensory nerve degenerated conditions.
Renal Resistance Index and Progression of Renal Disease
Authors: Radermacher Jörg , Ellis Sebastian , Haller Hermann
Published: July 2002

The progression of renal disease depends on various clinical parameters such as hypertension and proteinuria. We recently showed that an increased renal resistance index measured by duplex ultrasound is associated with a poor prognosis in patients with renal artery stenosis. We now prospectively tested the hypothesis that a high renal resistance index (≥80) predicts progression of renal disease in patients without renal artery stenosis. In 162 patients newly diagnosed with renal disease, the resistance index (1−[enddiastolic velocity/maximum systolic velocity]*100) was measured in segmental arteries of both kidneys. Creatinine clearance was measured at baseline, at 3, 6, and 12 months, and then at yearly intervals thereafter (mean follow-up 3±1.4 years). The combined endpoint was a decrease of creatinine clearance by ≥50%, end-stage renal disease with replacement therapy, or death. Twenty-five patients (15%) had a renal resistance index value ≥80 at baseline. Nineteen (76%) had a decline in renal function; 16 (64%) progressed to dialysis, and 6 (24%) died. In comparison, in patients with renal resistance index values <80, 13 (9%) had a decline in renal function, only 7 (5%) became dialysis-dependent, and 2 (1%) died (
P
<0.001). In a multivariate regression analysis, only proteinuria and resistance index were independent predictors of declining renal function. A renal resistance index value of ≥80 reliably identifies patients at risk for progressive renal disease.
Hypoxia Inducible Double Plasmid System for Myocardial Ischemia Gene Therapy
Authors: Tang Yi , Jackson MaShira , Qian Keping , Phillips M. Ian
Published: July 2002

Coronary artery disease frequently involves repeated bouts of myocardial ischemia. To automatically up-regulate the cardioprotective transgenes under hypoxic ischemia, a “vigilant vector” gene therapy system was developed and tested in a rat embryonic myocardial cell line (H9c2). In the vigilant vector, a hypoxia response element-incorporated promoter was used as a switch to turn on the gene expression in response to hypoxic signal. Furthermore, a novel double plasmid system was designed to elevate the potency of the vigilant vector. Instead of putting the promoter and the reporter gene in the same plasmid (single plasmid system), we separated them into two plasmids: the transactivator plasmid and reporter plasmid (double plasmid system). The hypoxia response element (HRE)-incorporated promoter increased the expression of a chimeric transcription factor consisting of the yeast GAL4 DNA binding domain and the human nuclear (transcription) factor-κB (NF-κB) p65 activation domain. The powerful chimeric regulator binds specifically to the upstream activating sequence for GAL4 in the reporter plasmid and activates the transcription of the transgene. Our experiments showed that the HRE-mediated expression could quickly increase 2.08±0.75-fold within 6 hours of hypoxia and further augmented 7.12±1.52-fold when the hypoxia condition was prolonged to 24 hours. The hypoxia-inducible double plasmid system dramatically amplified the transgene expression under both hypoxia and normoxia by 412.79±185.27-fold and 205.35±65.44-fold, respectively, relative to the single plasmid system. From these results, we concluded that this hypoxia inducible double plasmid system could be used therapeutically to switch on genes that have proven beneficial effects in myocardial ischemia.
Tonin and Kallikrein in the Brain of Transgenic Rat Line Expressing Human Tissue Kallikrein
Authors: Lomez Eliane S.L. , Araujo Ronaldo C. , Bader Michael , Pesquero Joao B. , Pesquero Jorge L.
Published: July 2002

A transgenic rat line harboring the human tissue kallikrein gene was investigated for expression and activity of tonin and kallikrein in different regions of the brain. The introduction of the transgene into the rat genome produced a significant augmentation of the expression levels and activity of rat tissue kallikrein. The possibility that human kallikrein does not hydrolyze the rat substrate is probably responsible for the augmented expression of the rat enzyme. On the other hand, although expression of tonin was significantly reduced, tonin activity was not altered in most brain structures, except for cerebellum and neurohypophysis.
Prevention of Hypertension, Insulin Resistance, and Oxidative Stress by α-Lipoic Acid
Authors: Midaoui Adil EL , de Champlain Jacques
Published: July 2002

The aim of the present study was to investigate whether a dietary supplementation of α-lipoic acid could prevent blood pressure elevation, insulin resistance, and the increase in aorta superoxide anion production in a new experimental model of hypertension associated with insulin resistance. Sprague-Dawley rats were given 10%
d
-glucose in their drinking water combined either with a normal chow diet or with an α-lipoic acid–supplemented diet and were compared with control rats during 3 weeks. Oxidative stress was evaluated by measuring the aortic superoxide anion production using the lucigenin chemiluminescence method. Increases in blood pressure, insulin resistance, and aorta superoxide production observed in glucose-fed rats were prevented by the supplementation of the diet with lipoic acid. Positive correlations were found between aortic superoxide production and blood pressure, between insulin resistance and blood pressure, or between superoxide production and insulin resistance. Moreover, a decrease in the activity of plasma glutathione peroxidase observed in the glucose-fed rats was prevented by lipoic acid treatment. These findings demonstrate that high-glucose feeding rapidly induced hypertension and insulin resistance in association with the induction of a vascular oxidative stress. The antihypertensive action and the prevention of insulin resistance by lipoic acid appears to be associated to its antioxidative properties because it prevented the increase in oxidative stress, as reflected by the normalization of superoxide anion production in aorta and the prevention of the fall in the activity of glutathione peroxidase in the glucose-fed rats.
Trophic Effects of the Cyclooxygenase-2 Product Prostaglandin E
2
in Cardiac Myocytes
Authors: Mendez Mariela , LaPointe Margot C.
Published: July 2002

Interleukin-1β (IL-1β), a proinflammatory cytokine, induces cyclooxygenase-2 (COX-2) in cultured neonatal ventricular myocytes (NVMs), resulting in the preferential production of prostaglandin E
2
(PGE
2
). To explain the preferential PGE
2
release by myocytes, we studied whether its specific synthase, PGE
2
synthase (PGES), is also induced by IL-1β. Because COX-2 has been extensively associated with cell growth, we questioned whether PGE
2
plays a role in cardiac cell growth. IL-1β–treated myocytes showed induction of PGES protein and mRNA by Western blot and reverse transcription–polymerase chain reaction, respectively. Immunofluorescence studies revealed perinuclear localization of COX-2 and PGES in IL-1β–treated myocytes. Exogenous PGE
2
increased protein synthesis in NVMs, as indicated by a 1.6-fold increase in [
3
H]leucine incorporation, comparable to the known hypertrophic factor phenylephrine (1.6-fold). Because PGE
2
exerts different effects through 4 receptor subtypes (EP
1
, EP
2
, EP
3
, and EP
4
), we investigated whether these receptors are functional in myocytes. Treatment of NVMs with the selective EP
1
/EP
3
agonist sulprostone significantly increased protein synthesis (1.7-fold), whereas the EP
1
/EP
2
antagonist AH6809 blocked this effect by 43%. In contrast, AH6809 had no effect on PGE
2
-induced protein synthesis. Regarding second messengers, sulprostone had no effect on cAMP, whereas PGE
2
increased it. We concluded that (1) PGE
2
production requires the induction of its specific synthase; (2) in myocytes, the inducible enzymes COX-2 and PGES are perinuclear; and (3) PGE
2
and sulprostone induce cardiac myocyte growth but seem to activate a different subset of EP receptors.
Discovery of a Spontaneous Genetic Mouse Model of Preeclampsia
Authors: Davisson Robin L. , Hoffmann Darren S. , Butz Genelle M. , Aldape Gilbert , Schlager Gunther , Merrill David C. , Sethi Sanjeev , Weiss Robert M. , Bates James N.
Published: July 2002

Preeclampsia remains a leading cause of maternal and fetal morbidity and mortality but has an unknown etiology. Women with elevated baseline blood pressure have an increased risk of this disorder. We hypothesized that BPH/5 mice, an inbred mouse strain with mildly elevated blood pressure, would develop a pregnancy-induced hypertensive syndrome. Nonpregnant female BPH/5 and C57BL/6 mice underwent thoracic aortic implantation of telemeters. After 7 days of recovery and 5 days of baseline mean arterial blood pressure (MAP) recording, strain-matched timed matings were carried out. MAP was recorded continuously during pregnancy and for 1 week after birth. In separate mice in metabolic cages, urinary protein was tracked, followed by renal histological analysis. Before pregnancy, the BPH/5 strain had elevated baseline MAP compared with the C57BL/6 strain, but both strains had similar total urinary protein levels and renal histology. MAP remained stable in both groups during the first 2 weeks of pregnancy. However, at the start of the last trimester, MAP began to rise further in the BPH/5 mice; it rose to peak levels just before delivery and returned to prepregnancy levels by 2 days after delivery. This was accompanied by late-gestational proteinuria and progressive glomerulosclerosis. No changes were observed in the C57BL/6 group except for a small decrease in MAP at mid gestation. The BPH/5 group delivered significantly smaller litters despite normal numbers of fetuses early in gestation, and longitudinal ultrasound studies documented fetal demise before the onset of hypertension and renal disease. This is the first report of an animal model that spontaneously develops a syndrome that bears close resemblance to preeclampsia, and it should have an impact on our understanding of the pathophysiology of this disorder.