bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversibility of
PRKAG2
Glycogen-Storage Cardiomyopathy and Electrophysiological Manifestations
Authors: Wolf Cordula M. , Arad Michael , Ahmad Ferhaan , Sanbe Atsushi , Bernstein Scott A. , Toka Okan , Konno Tetsuo , Morley Gregory , Robbins Jeffrey , Seidman J.G. , Seidman Christine E. , Berul Charles I.
Published: December 2007

Background—

PRKAG2
mutations cause glycogen-storage cardiomyopathy, ventricular preexcitation, and conduction system degeneration. A genetic approach that utilizes a binary inducible transgenic system was used to investigate the disease mechanism and to assess preventability and reversibility of disease features in a mouse model of glycogen-storage cardiomyopathy.

Methods and Results—

Transgenic (Tg) mice expressing a human N488I
PRKAG2
cDNA under control of the tetracycline-repressible α-myosin heavy chain promoter underwent echocardiography, ECG, and in vivo electrophysiology studies. Transgene suppression by tetracycline administration caused a reduction in cardiac glycogen content and was initiated either prenatally (Tg
OFF(E-8 weeks)
) or at different time points during life (Tg
OFF(4–16 weeks)
, Tg
OFF(8–20 weeks)
, and Tg
OFF(>20 weeks)
). One group never received tetracycline, expressing transgene throughout life (Tg
ON
). Tg
ON
mice developed cardiac hypertrophy followed by dilatation, ventricular preexcitation involving multiple accessory pathways, and conduction system disease, including sinus and atrioventricular node dysfunction.

Conclusions—

Using an externally modifiable transgenic system, cardiomyopathy, cardiac dysfunction, and electrophysiological disorders were demonstrated to be reversible processes in
PRKAG2
disease. Transgene suppression during early postnatal development prevented the development of accessory electrical pathways but not cardiomyopathy or conduction system degeneration. Taken together, these data provide insight into mechanisms of cardiac
PRKAG2
disease and suggest that glycogen-storage cardiomyopathy can be modulated by lowering glycogen content in the heart.
Nanoparticle PET-CT Imaging of Macrophages in Inflammatory Atherosclerosis
Authors: Nahrendorf Matthias , Zhang Hanwen , Hembrador Sheena , Panizzi Peter , Sosnovik David E. , Aikawa Elena , Libby Peter , Swirski Filip K. , Weissleder Ralph
Published: December 2007

Background—

Macrophages participate centrally in atherosclerosis, and macrophage markers (eg, CD68, MAC-3) correlate well with lesion severity and therapeutic modulation. On the basis of the avidity of lesional macrophages for polysaccharide-containing supramolecular structures such as nanoparticles, we have developed a new positron emission tomography (PET) agent with optimized pharmacokinetics to allow in vivo imaging at tracer concentrations.

Methods and Results—

A dextranated and DTPA-modified magnetofluorescent 20-nm nanoparticle was labeled with the PET tracer
64
Cu (1 mCi/0.1 mg nanoparticles) to yield a PET, magnetic resonance, and optically detectable imaging agent. Peak PET activity 24 hours after intravenous injection into mice deficient in apolipoprotein E with experimental atherosclerosis mapped to areas of high plaque load identified by computed tomography such as the aortic root and arch and correlated with magnetic resonance and optical imaging. Accumulated dose in apolipoprotein E–deficient aortas determined by gamma counting was 260% and in carotids 392% of respective wild-type organs (
P
<0.05 both). Autoradiography of aortas demonstrated uptake of the agent into macrophage-rich atheromata identified by Oil Red O staining of lipid deposits. The novel nanoagent accumulated predominantly in macrophages as determined by fluorescence microscopy and flow cytometry of cells dissociated from aortas.

Conclusions—

This report establishes the capability of a novel trimodality nanoparticle to directly detect macrophages in atherosclerotic plaques. Advantages include improved sensitivity; direct correlation of PET signal with an established biomarker (CD68); ability to readily quantify the PET signal, perform whole-body vascular surveys, and spatially localize and follow the trireporter by microscopy; and clinical translatability of the agent given similarities to magnetic resonance imaging probes in clinical trials.
Deoxycorticosterone Acetate Salt Hypertension in Apolipoprotein E
−/−
Mice Results in Accelerated Atherosclerosis
Authors: Weiss Daiana , Taylor W. Robert
Published: December 2007

Previous studies have shown that administration of angiotensin II to atherosclerosis-prone animal models results in an increase in the extent of atherosclerosis and that this effect may be independent of changes in blood pressure. We sought to determine whether atherosclerosis was increased in the setting of a low renin model of hypertension. Apolipoprotein E–deficient mice were made hypertensive using the deoxycorticosterone acetate salt model. We found that this resulted in a dramatic increase in the atherosclerotic lesion area in the setting of either a low- or high-fat diet. In the hypertensive animals, we observed an increase in angiotensin II staining that was localized to the adventitial macrophages. The increase in atherosclerosis was inhibited by administration of an angiotensin receptor antagonist, an angiotensin-converting enzyme inhibitor, or a renin inhibitor. In addition, blood pressure reduction, with either a calcium channel blocker or hydralazine, reduced the extent of atherosclerosis indicating an important contribution of the mechanical effects of elevated blood pressure. These data suggest that, even in the setting of hypertension that is not associated with activation of the systemic renin-angiotensin system, local generation of angiotensin II within the arterial wall may be of pathophysiological relevance to the development of atherosclerosis.
Angiotensin II Type 2 Receptors and Nitric Oxide Sustain Oxygenation in the Clipped Kidney of Early Goldblatt Hypertensive Rats
Authors: Palm Fredrik , Connors Stephanie G. , Mendonca Margarida , Welch William J. , Wilcox Christopher S.
Published: December 2007

Angiotensin-converting enzyme inhibitors (ACEIs) decrease the glomerular filtration rate and renal blood flow in the clipped kidneys of early 2-kidney, 1-clip Goldblatt hypertensive rats, but the consequences for oxygenation are unclear. We investigated the hypothesis that angiotensin II type 1 or angiotensin II type 2 receptors or NO synthase mediate renal oxygenation responses to ACEI. Three weeks after left renal artery clipping, kidney function, oxygen (O
2
) use, renal blood flow, renal cortical blood flow, and renal cortical oxygen tension (P
o
2
) were measured after acute administration of an ACEI (enalaprilat) and after acute administration of ACEI following acute administration of an angiotensin II type 1 or angiotensin II type 2 receptor blocker (candesartan or PD-123,319) or an NO synthase blocker (
N
G
-nitro-
l
-arginine methyl ester with control of renal perfusion pressure) and compared with mechanical reduction in renal perfusion pressure to the levels after ACEI. The basal renal cortical P
o
2
of clipped kidneys was significantly lower than contralateral kidneys (35±1 versus 51±1 mm Hg; n=40 each). ACEI lowered renal venous P
o
2
, cortical P
o
2
, renal blood flow, glomerular filtration rate, and cortical blood flow and increased the renal vascular resistance in the clipped kidney, whereas mechanical reduction in renal perfusion pressure was ineffective. PD-123,319 and
N
G
-nitro-
l
-arginine methyl ester, but not candesartan, reduced the P
o
2
of clipped kidneys and blocked the fall in P
o
2
with acute ACEI administration. In conclusion, oxygen availability in the clipped kidney is maintained by angiotensin II generation, angiotensin II type 2 receptors, and NO synthase. This discloses a novel mechanism whereby angiotensin can prevent hypoxia in a kidney challenged with a reduced perfusion pressure.
Angiotensin-Converting Enzyme C-Terminal Catalytic Domain Is the Main Site of Angiotensin I Cleavage In Vivo
Authors: Fuchs Sebastien , Xiao Hong D. , Hubert Christine , Michaud Annie , Campbell Duncan J. , Adams Jonathan W. , Capecchi Mario R. , Corvol Pierre , Bernstein Kenneth E.
Published: December 2007

Angiotensin-converting enzyme (ACE) plays a central role in the production of the vasoconstrictor angiotensin II. ACE is a single polypeptide, but it contains 2 homologous and independent catalytic domains, each of which binds zinc. To understand the in vivo role of these 2 domains, we used gene targeting to create mice with point mutations in the ACE C-domain zinc-binding motif. Such mice, termed ACE13/13, produce a full-length ACE protein with tissue expression identical to wild-type mice. Analysis of ACE13/13 mice showed that they produce ACE having only N-domain catalytic activity, as determined by the hydrolysis of domain specific substrates and by chloride sensitivity. ACE13/13 mice have blood pressure and blood angiotensin II levels similar to wild-type mice. However, plasma renin concentration is increased 2.6-fold and blood angiotensin I levels are increased 7.5-fold. Bradykinin peptide levels are not different from wild-type levels. ACE13/13 mice have a reduced increase of blood pressure after intravenous infusion of angiotensin I. ACE13/13 mice have a normal renal structure, but they are not able to concentrate urine after dehydration as effectively as wild-type mice. This study shows that the C-domain of ACE is the predominant site of angiotensin I cleavage in vivo. Although mice lacking C-domain activity have normal physiology under laboratory conditions, they respond less well to the stress of dehydration.
Arterioventricular Coupling and Ventricular Efficiency After Antihypertensive Therapy
Authors: Osranek Martin , Eisenach John H. , Khandheria Bijoy K. , Chandrasekaran Krishnaswamy , Seward James B. , Belohlavek Marek
Published: December 2007

Patients with hypertension exhibit impaired energetic coupling between the ventricle and the arterial system, leading to reduced cardiac mechanic efficiency and exercise capacity. We tested whether blood pressure normalization with current antihypertensive therapy can improve arterioventricular coupling. Eighteen hypertensive patients without other cardiovascular disease were examined before and after antihypertensive therapy. Transthoracic echocardiography was performed. Central aortic pressure waveforms, including end-systolic pressure, were derived from radial artery applanation tonometry. Afterload was increased with isometric handgrip exercise. Central aortic end-systolic pressure and ventricular volumes at rest and handgrip were used to calculate ventricular elastance, effective arterial elastance, arterioventricular coupling (effective arterial elastance/ventricular elastance), and mechanical efficiency. After 142±67 days, systolic blood pressure decreased from 150.9±14.6 to 119.8±9.2 mm Hg (
P
<0.00001), diastolic blood pressure from 85.9±14.8 to 68.8±8.4 mm Hg (
P
=0.00002), and cardiac output from 5.8±1.7 to 4.9±1.8 L/min (
P
=0.03). Resting left ventricular end-systolic volume, ejection fraction, and septal thickness did not change. Ventricular elastance increased from 1.7±1.0 to 3.2±1.4 mm Hg/mL (
P
=0.00002), whereas effective arterial elastance decreased from 1.4±0.5 to 1.2±0.4 mm Hg/mL (
P
=0.02). Effective arterial elastance/ventricular elastance decreased in all patients, from 1.1±0.8 to 0.4±0.2 (
P
=0.0002). Efficiency improved at rest (72.9±5.8% versus 83.5±5.7%;
P
<0.00001) and during handgrip (63.5±7.8% versus 78.9±7.1%;
P
<0.00001). In hypertensive patients, optimal brachial and central blood pressure reduction shifts arterioventricular coupling from cardiac output maximization to ventricular mechanical efficiency optimization. This occurs before significant changes in ventricular geometry and may be responsible for early clinical improvements.
Gene Expression Pattern in Biomechanically Stretched Cardiomyocytes
Authors: Frank Derk , Kuhn Christian , Brors Benedikt , Hanselmann Christiane , Lüdde Mark , Katus Hugo A. , Frey Norbert
Published: December 2007

Biomechanical stress ie, attributable to pressure overload, leads to cardiac hypertrophy and may ultimately cause heart failure. Yet, it is still unclear how mechanical stress is sensed and transduced on the molecular level. To systematically elucidate the underlying signal transduction pathways, we analyzed the gene expression profile of stretched cardiomyocytes on a genome-wide scale in comparison with other inducers of hypertrophy such as pharmacological stimulation. Neonatal rat ventricular cardiomyocytes were either stretched biaxially or stimulated with phenylephrine (PE), both resulting in a similar degree of hypertrophy. Microarray analyses revealed 164 genes >2.0-fold up- and 21 genes <0.5-fold downregulated (
P
<0.01). Differential expression was confirmed by real-time polymerase chain reaction. Genes of the “fetal gene program” such as BNP were induced by both stretch (4.2×) and PE (2.9×). We also verified upregulation of known stretch-responsive genes, including HSP70 (20.9×) and c-myc (3.0×). Moreover, several genes were found to be preferentially induced by stretch, such as the cardioprotective cytokine GDF15 (24.8×) and heme oxygenase 1 (Hmox1, 10.8×; both confirmed on protein level). Neither PE nor endothelin-1 upregulated GDF15 and Hmox1, whereas angiotensin II significantly induced both genes. Conversely, the AT
1
receptor blocker irbesartan markedly blunted stretch-mediated GDF15 and Hmox1 upregulation, suggesting that the angiotensin receptor tranduces the biomechanical induction of these genes. In conclusion, we report a comprehensive gene expression profile of cardiomyocytes subjected to biomechanical stress in comparison with pharmacologically induced hypertrophy. Our data imply that a stretch-specific gene program exists, which is mediated, at least in part, by angiotensin II–dependent signaling.
Protective Effect of Dietary Potassium Against Vascular Injury in Salt-Sensitive Hypertension
Authors: Kido Makiko , Ando Katsuyuki , Onozato Maristela L. , Tojo Akihiro , Yoshikawa Masahiro , Ogita Teruhiko , Fujita Toshiro
Published: December 2007

Hypertensive cardiovascular damage is accelerated by salt loading but counteracted by dietary potassium supplementation. We suggested recently that antioxidant actions of potassium contribute to protection against salt-induced cardiac dysfunction. Therefore, we examined whether potassium supplementation ameliorated cuff-induced vascular injury in salt-sensitive hypertension via suppression of oxidative stress. Four-week–old Dahl salt-sensitive rats were fed a normal-salt (0.3% NaCl), high-salt (8% NaCl), or high-salt plus high-potassium (8% KCl) diet for 5 weeks, and some of the rats fed a high-salt diet were also given antioxidants. One week after the start of the treatments, a silicone cuff was implanted around the femoral artery. Examination revealed increased cuff-induced neointimal proliferation with adventitial macrophage infiltration in arteries from salt-loaded Dahl salt-sensitive rats compared with that in arteries from non–salt-loaded animals (intima/media ratio: 0.471±0.070 versus 0.302±0.037;
P
<0.05), associated with regional superoxide overproduction and reduced nicotinamide-adenine dinucleotide phosphate oxidase activation and mRNA overexpression. On the other hand, simultaneous potassium supplementation attenuated salt-induced neointimal hyperplasia (intima/media ratio: 0.205±0.012;
P
<0.001), adventitial macrophage infiltration, superoxide overproduction, and reduced nicotinamide-adenine dinucleotide phosphate oxidase activation and overexpression. Antioxidants, which decrease vascular oxidative stress, also reduced neointima formation induced by salt excess. In conclusion, high-potassium diets seems to have a protective effect against the development of vascular damage induced by salt loading mediated, at least in part, through suppression of the production of reactive oxygen species probably generated by reduced nicotinamide-adenine dinucleotide phosphate oxidase.
Telmisartan Inhibits CD4-Positive Lymphocyte Migration Independent of the Angiotensin Type 1 Receptor via Peroxisome Proliferator-Activated Receptor-γ
Authors: Walcher Daniel , Hess Katharina , Heinz Philipp , Petscher Kerstin , Vasic Dusica , Kintscher Ulrich , Clemenz Markus , Hartge Martin , Raps Katrin , Hombach Vinzenz , Marx Nikolaus
Published: December 2007

Migration of CD4-positive lymphocytes into the vessel wall represents an important step in early atherogenesis. Telmisartan is an angiotensin type 1 receptor (AT1R) blocker with peroxisome proliferator-activated receptor (PPAR)-γ–activating properties. The present study examined the effect of telmisartan on CD4-positive cell migration and the role of PPARγ in this context. CD4-positive lymphocytes express both the AT1R and PPARγ. Stimulation of CD4-positive lymphocytes with stromal cell-derived factor (SDF)-1 leads to a 4.1±3.1-fold increase in cell migration. Pretreatment of cells with telmisartan reduces this effect in a concentration-dependent manner to a maximal 1.6±0.7-fold induction at 10 μmol/L of telmisartan (
P
<0.01 compared with SDF-1–treated cells; n=22). Three different PPARγ activators, rosiglitazone, pioglitazone, and GW1929, had similar effects, whereas eprosartan, a non-PPARγ–activating AT1R blocker, did not affect chemokine-induced lymphocyte migration. Telmisartan’s effect on CD4-positive lymphocyte migration was mediated through an early inhibition of chemokine-induced phosphatidylinositol 3-kinase activity. Downstream, telmisartan inhibited F-actin formation, as well as intercellular adhesion molecule-3 translocation. Transfection of CD4-positive lymphocytes with PPARγ small interfering RNA abolished telmisartan’s effect on migration, whereas blockade of the AT1R had no such effect. Telmisartan inhibits chemokine-induced CD4-positive cell migration independent of the AT1R via PPARγ. These data provide a novel mechanism to explain how telmisartan modulates lymphocyte activation by its PPARγ-activating properties.
Beneficial Effects of Pioglitazone on Hypertensive Cardiovascular Injury Are Enhanced by Combination With Candesartan
Authors: Nakamura Taishi , Yamamoto Eiichiro , Kataoka Keiichiro , Yamashita Takuro , Tokutomi Yoshiko , Dong Yi-Fei , Matsuba Shinji , Ogawa Hisao , Kim-Mitsuyama Shokei
Published: December 2007

The effect of pioglitazone, a peroxisome proliferator-activated receptor γ agonist, on hypertensive cardiovascular injury is unknown. We examined the effect of pioglitazone on hypertensive cardiovascular injury and the significance of combination of pioglitazone with angiotensin type 1 receptor blocker. Stroke-prone spontaneously hypertensive rats (SHRSP) were orally given pioglitazone, candesartan, or combined pioglitazone and candesartan for 4 weeks to compare their effects on cardiovasucular injury. Pioglitazone, without lowering blood pressure, significantly suppressed cardiac inflammation and fibrosis and reduced vascular endothelial dysfunction, and these beneficial effects were associated with the reduction of superoxide by inhibition of cardiovascular NADPH oxidase. Thus, pioglitazone protects against hypertensive cardiovascular injury, by inhibiting reactive oxygen species (ROS). Combination of pioglitazone and candesartan suppressed cardiac hypertrophy, inflammation, and interstitial fibrosis of SHRSP to a greater extent than either monotherapy, and reduced vascular endothelial dysfunction of SHRSP more than either monotherapy. Furthermore, more beneficial effects of their combination on cardiovascular injury were associated with more reduction of NADPH oxidase–mediated cardiovascular ROS. To elucidate the underlying molecular mechanism, we examined cardiovascular NADPH oxidase subunits. Pioglitazone monotherapy significantly attenuated cardiovascular p22phoxand Rac1 in SHRSP, whereas pioglitazone combined with candesartan more attenuated p22phoxand significantly reduced Nox1. Thus, additive suppression of cardiovascular NADPH oxidase by the combination was attributed to its additive attenuation of p22phoxand Nox1 protein levels. In conclusion, we showed that pioglitazone protected against hypertensive cardiovascular damage, and the combination of pioglitazone and candesartan exerted more beneficial effects on hypertensive cardiovascular injury by more suppressing ROS.
Endothelial Dysfunction and the Development of Renal Injury in Spontaneously Hypertensive Rats Fed a High-Fat Diet
Authors: Knight Sarah F. , Quigley Jeffrey E. , Yuan Jianghe , Roy Siddhartha S. , Elmarakby Ahmed , Imig John D.
Published: December 2007

Obesity and hypertension have been identified as cardiovascular risk factors that contribute to the progression of end-stage renal disease. To examine the mechanisms by which a high-fat diet and hypertension contribute to endothelial dysfunction and renal injury, 8-week–old male spontaneously hypertensive rats and Wistar rats were fed a high-fat (36% fat) or a normal-fat (7% fat) diet for 10 weeks. The high-fat diet increased body weight in Wistar and hypertensive rats by 25 and 31 g, respectively. Systolic blood pressure was higher in the hypertensive rats compared with Wistar rats; however, blood pressure was unaltered by the high-fat diet. Afferent arteriole response to acetylcholine was impaired in the high-fat groups after just 3 weeks. Renal macrophage infiltration was increased in the hypertensive high-fat group compared with others, and monocyte chemoattractant protein-1 excretion was increased in both of the high-fat–fed groups. Renal PCR arrays displayed significant increases in 2 inflammatory genes in hypertensive rats fed a normal diet, 1 gene was increased in high-fat–fed Wistar rats, whereas 12 genes were increased in high-fat–fed hypertensive rats. Urinary albumin excretion was increased in the hypertensive rats compared with the Wistar rats, which was further exacerbated by the high-fat diet. Glomerular nephrin expression was reduced and desmin was increased by the high-fat diet in the hypertensive rats. Our results indicate that endothelial dysfunction precedes renal injury in normotensive and spontaneously hypertensive rats fed a high-fat diet, and hypertension with obesity induces a powerful inflammatory response and disruption of the renal filtration barrier.
Pulse Pressure Is Inversely Related to Aortic Root Diameter Implications for the Pathogenesis of Systolic Hypertension
Authors: Farasat S. Morteza , Morrell Christopher H. , Scuteri Angelo , Ting Chih-Tai , Yin Frank C.P. , Spurgeon Harold A. , Chen Chen-Huan , Lakatta Edward G. , Najjar Samer S.
Published: December 2007

Hypertension accelerates the age-associated increase in aortic root diameter (AoD), likely because of chronically elevated distending pressures. However, the pulsatile component of blood pressure may have a different relationship with AoD. We sought to assess the relationship between AoD and pulse pressure (PP) while accounting for left ventricular and central arterial structural and functional properties, which are known to influence PP. The study population was composed of 1256 individuals, aged 30 to 79 years (48% women and 48% hypertensive), none of whom were on antihypertensive medications. Blood pressure was measured in the sitting position with conventional sphygmomanometry. PP was calculated as the difference between systolic and diastolic blood pressures. AoD was measured at end diastole at the level of the sinuses of Valsalva with echocardiography. The relationship between AoD and PP was evaluated with multiple regression analyses. PP was 50±14 mm Hg in men and 54±18 mm Hg in women, and AoD was 31.9±3.5 mm in men and 28.9±3.5 mm in women. After adjusting for age, age
2
, height, weight, and mean arterial pressure, AoD was independently and inversely associated with PP in both sexes. After further adjustments for central arterial stiffness and wall thickness, reflected waves, and left ventricular geometry, AoD remained inversely associated with PP in both men (coefficient=−0.48;
P
=0.0003; model
R
2
=0.51) and women (coefficient=−0.40;
P
=0.01; model
R
2
=0.61). Thus, AoD is inversely associated with PP, suggesting that a small AoD may contribute to the pathogenesis of systolic hypertension. Longitudinal studies are needed to examine this possibility.
Oxidative Stress Causes Renal Dopamine D1 Receptor Dysfunction and Salt-Sensitive Hypertension in Sprague-Dawley Rats
Authors: Banday Anees A. , Lau Yuen-Sum , Lokhandwala Mustafa F.
Published: December 2007

Renal dopamine plays an important role in maintaining sodium homeostasis and blood pressure (BP) during increased sodium intake. The present study was carried out to determine whether renal dopamine D1 receptor (D1R) dysfunction contributes to increase in salt sensitivity during oxidative stress. Male Sprague-Dawley rats, divided into various groups, received tap water (vehicle); 1% NaCl (high salt [HS]);
l
-buthionine sulfoximine (BSO), an oxidant; and HS plus BSO with or without Tempol, an antioxidant, for 12 days. Compared with vehicle, HS intake increased urinary dopamine production and decreased basal renal Na/K-ATPase activity but did not affect BP. BSO-treated rats exhibited oxidative stress and a mild increase in BP. In these rats, D1R expression and G protein coupling were reduced, and SKF38393, a D1R agonist, failed to inhibit Na/K-ATPase activity and promote sodium excretion. Concomitant administration of BSO and HS caused oxidative stress, D1R dysfunction, and a marked increase in BP. Although renal dopamine production was increased, it failed to reduce the basal Na/K-ATPase activity in these animals. Treatment of BSO plus HS rats with Tempol decreased oxidative stress and restored endogenous, as well as exogenous, D1R agonist-mediated Na/K-ATPase inhibition and normalized BP. In conclusion, during HS intake, the increased dopamine production via Na/K-ATPase inhibition prevents an increase in BP. During oxidative stress, D1R function is defective, and there is mild hypertension. However, in the presence of oxidative stress, HS intake causes marked elevation in BP, which results from a defective renal D1R function leading to the failure of dopamine to inhibit Na/K-ATPase and promote sodium excretion.
Cellular Stretch Increases Superoxide Production in the Thick Ascending Limb
Authors: Garvin Jeffrey L. , Hong Nancy J.
Published: December 2007

Superoxide (O
2
−
) is an important regulator of kidney function. We have recently shown that luminal flow stimulates O
2
−
production in the thick ascending limb (TAL), attributable in part to mechanical factors. Stretch, pressure and shear stress all change when flow increases in the TAL. We hypothesized that stretch rather than shear stress or pressure per se stimulates O
2
−
production by TALs. We measured O
2
−
production in isolated perfused rat TALs using fluorescence microscopy and dihydroethidium. Tubules were perfused with a Na-free solution to eliminate the confounding effect of Na transport. Flow induced an increase in O
2
−
production from 29±4 to 90±8 AU/s (
P
<0.002; n=5). The response to flow is rapidly reversible. O
2
−
production by TALs perfused at 10 nL/min decreased from 113±6 to 25±10 AU/s (
P
<0.003; n=4) 15 minutes after flow was stopped. Increasing pressure and stretch in the absence of shear stress caused a significant increase in O
2
−
production (40±6 to 118±17 AU/s;
P
<0.02; n=5). In contrast, eliminating shear stress had no effect (107±9 versus 108±10 AU/s; n=5). Increasing stretch by 27±2% in the presence of flow while reducing pressure stimulated O
2
−
production from 66±7 to 84±9 AU/s (29±8%;
P
<0.02; n=5). Tempol inhibited this increase (n=5). We conclude that increasing stretch rather than pressure or shear stress accounts for the mechanical aspect of flow-induced O
2
−
production in the TAL. Stretch of the TAL during hypertension, diabetes, and salt loading may contribute to renal damage.
Insulin in the Brain Increases Gain of Baroreflex Control of Heart Rate and Lumbar Sympathetic Nerve Activity
Authors: Pricher Mollie P. , Freeman Korrina L. , Brooks Virginia L.
Published: December 2007

Chronic central administration of insulin increases the gain of baroreflex control of heart rate, but whether baroreflex control of the sympathetic nervous system is similarly affected is unknown. The sites and mechanisms by which brain insulin influences the baroreflex are also unclear. Therefore, the present study tested the hypothesis that acute infusion of insulin into the brain ventricles of urethane-anesthetized rats increases gain of baroreflex control of heart rate and lumbar sympathetic nerve activity and that this action is gender specific. Furthermore, to identify the location within the brain that mediates these effects, insulin was infused into either the lateral ventricle or the fourth ventricle. Lateral ventricular insulin infusion increased the gain of baroreflex control of heart rate (2.1±0.3 to 4.0±0.6 bpm/mm Hg;
P
<0.05) and sympathetic activity (2.3±0.3% to 4.8±1.1% control/mm Hg;
P
<0.05) within 60 to 90 minutes; however, the increase in heart rate gain was similar in males and females. Increases in the maximum of baroreflex control of heart rate (395±10 to 452±13 bpm;
P
<0.05) and of sympathetic activity (156±13% to 253±22% control;
P
<0.05) were also observed. In contrast, fourth ventricular insulin infusion failed to alter baroreflex function. In conclusion, increases in brain insulin act acutely in the forebrain to enhance gain of baroreflex control of heart rate and lumbar sympathetic nerve activity.
Osteopontin in Rat Renal Fibroblasts
Authors: Irita Jun , Okura Takafumi , Kurata Mie , Miyoshi Ken-ichi , Fukuoka Tomikazu , Higaki Jitsuo
Published: December 2007

Osteopontin (OPN), a proinflammatory cytokine, plays an important role in renal fibrosis. We reported that plasma OPN levels were higher in patients with primary aldosteronism than with essential hypertension. However, the regulatory mechanism of OPN by aldosterone remains unclear. Here, we report the transcriptional regulation of OPN expression by aldosterone and the functional effects of aldosterone-mediated OPN transcription in renal fibroblasts. Aldosterone induced OPN expression in a dose-dependent manner with significant responses at 10 nmol/L (1.6±0.2-fold of controls,
P
<0.05, n=5) and elicited maximal effects at 10 μmol/L (3.5±0.4-fold of controls,
P
<0.01, n=5). Aldosterone increased OPN expression in a time-dependent manner with a maximal effect after 48 hours (2.7±0.3-fold of controls,
P
<0.01, n=5). This effect was abolished by the mineralocorticoid receptor (MR) antagonist spironolactone. Luciferase promoter deletion assays identified a novel
cis
regulatory element (−2153 to −1758) in the OPN promoter that is responsive to aldosterone. This element contains an activator protein-1 (AP-1) and nuclear factor kappa B (NFκB) site. Electrophoretic mobility shift assays, supershift assays, and chromatin immunoprecipitation assays identified both AP-1 and NFκB as the DNA binding proteins induced by aldosterone with spironolactone inhibiting aldosterone-induced AP-1 or NFκB activity. OPN-siRNA inhibited completely the induction of cell proliferation, type I, III, and IV collagen synthesis by aldosterone. These results indicate that aldosterone induced MR-mediated OPN expression through AP-1 and NFκB activation and suggest that aldosterone plays an important role in renal fibrosis through the induction of OPN.
Metabolic Syndrome and Vascular Alterations in Normotensive Subjects at Risk of Diabetes Mellitus
Authors: Ghiadoni Lorenzo , Penno Giuseppe , Giannarelli Chiara , Plantinga Yvonne , Bernardini Melania , Pucci Laura , Miccoli Roberto , Taddei Stefano , Salvetti Antonio , Del Prato Stefano
Published: December 2007

We evaluated the possible association between early vascular abnormalities and the metabolic syndrome (MS) in 77 normotensive subjects (mean age: 50 years) at risk of developing diabetes for family history of diabetes, obesity, or impaired fasting glucose. Fifty healthy subjects were recruited as controls. MS was defined according to the ATP III criteria. Brachial artery endothelium-dependent and -independent vasodilation were assessed as flow-mediated dilation (FMD) and response to glyceryl trinitrate (GTN, 25 μg sublingual), respectively, by automatic computerized edge detection system. Carotid-femoral pulse wave velocity (PWV) and radial augmentation index (AIx) were assessed by applanation tonometry. PWV was significantly (
P
<0.01) higher in subjects with MS (n=29, 9.0±1.9 m/s) as compared with those without MS (n=48, 7.7±1.2 m/s) and controls (7.2±1.5 m/s). FMD was significantly (
P
<0.05) reduced in both subjects with (5.8±2.7%) and without MS (6.1±3.7%) as compared with controls (6.9±2.5%). No significant differences were found for response to GTN and AIx. PWV and FMD were significantly (
P
<0.05) affected by increasing number of MS components. Among the components of the MS, only blood pressure significantly affected PWV, whereas blood pressure and fasting glucose influenced FMD. Logistic regression analysis showed that MS was associated with increased risk of altered PVW (odd ratio: 7.95, confidence limits: 1.06 to 69.11), whereas only blood pressure component was significantly related with increased risk of impaired FMD (odd ratio: 3.60, confidence limits: 1.01 to 12.78). In conclusion, in normotensive subjects at risk of developing diabetes mellitus, the presence of MS is associated with a selective alteration of central PWV.
Dietary n-3 Polyunsaturated Fatty Acids and Direct Renin Inhibition Improve Electrical Remodeling in a Model of High Human Renin Hypertension
Authors: Fischer Robert , Dechend Ralf , Qadri Fatimunnisa , Markovic Marija , Feldt Sandra , Herse Florian , Park Joon-Keun , Gapelyuk Andrej , Schwarz Ines , Zacharzowsky Udo B. , Plehm Ralph , Safak Erdal , Heuser Arnd , Schirdewan Alexander , Luft Friedrich C. , Schunck Wolf-Hagen , Muller Dominik N.
Published: December 2007

We compared the effect n-3 polyunsaturated fatty acids (PUFAs) with direct renin inhibition on electrophysiological remodeling in angiotensin II–induced cardiac injury. We treated double-transgenic rats expressing the human renin and angiotensinogen genes (dTGRs) from week 4 to 7 with n-3 PUFA ethyl-esters (Omacor; 25-g/kg diet) or a direct renin inhibitor (aliskiren; 3 mg/kg per day). Sprague-Dawley rats were controls. We performed electrocardiographic, magnetocardiographic, and programmed electrical stimulation. Dietary n-3 PUFAs increased the cardiac content of eicosapentaenoic and docosahexaenoic acid. At week 7, mortality in dTGRs was 31%, whereas none of the n-3 PUFA- or aliskiren-treated dTGRs died. Systolic blood pressure was modestly reduced in n-3 PUFA-treated (180±3 mm Hg) compared with dTGRs (208±5 mm Hg). Aliskiren-treated dTGRs and Sprague-Dawley rats were normotensive (110±3 and 119±6 mm Hg, respectively). Both n-3 PUFA–treated and untreated dTGRs showed cardiac hypertrophy and increased atrial natriuretic peptide levels. Prolonged QRS and QT
c
intervals and increased T-wave dispersion in dTGRs were reduced by n-3 PUFAs or aliskiren. Both treatments reduced arrhythmia induction from 75% in dTGRs to 17% versus 0% in Sprague-Dawley rats. Macrophage infiltration and fibrosis were reduced by n-3 PUFAs and aliskiren. Connexin 43, a mediator of intermyocyte conduction, was redistributed to the lateral cell membranes in dTGRs. n-3 PUFAs and aliskiren restored normal localization to the intercalated disks. Thus, n-3 PUFAs and aliskiren improved electrical remodeling, arrhythmia induction, and connexin 43 expression, despite a 70-mm Hg difference in blood pressure and the development of cardiac hypertrophy.
Conversion of Renal Angiotensin II to Angiotensin III Is Critical for AT
2
Receptor–Mediated Natriuresis In Rats
Authors: Padia Shetal H. , Kemp Brandon A. , Howell Nancy L. , Fournie-Zaluski Marie-Claude , Roques Bernard P. , Carey Robert M.
Published: December 2007

In the kidney, angiotensin II (Ang II) is metabolized to angiotensin III (Ang III) by aminopeptidase A (APA). In turn, Ang III is metabolized to angiotensin IV by aminopeptidase N (APN). Renal interstitial (RI) infusion of Ang III, but not Ang II, results in angiotensin type-2 receptor (AT
2
R)-mediated natriuresis. This response is augmented by coinfusion of PC-18, a specific inhibitor of APN. The present study addresses the hypotheses that Ang II conversion to Ang III is critical for the natriuretic response. Sprague-Dawley rats received systemic angiotensin type-1 receptor (AT
1
R) blockade with candesartan (CAND; 0.01 mg/kg/min) for 24 hours before and during the experiment. After a control period, rats received either RI infusion of Ang II or Ang II+PC-18. The contralateral kidney received a RI infusion of vehicle in all rats. Mean arterial pressure (MAP) was monitored, and urinary sodium excretion rate (U
Na
V) was calculated separately from experimental and control kidneys for each period. In contrast to Ang II–infused kidneys, U
Na
V from Ang II+PC-18-infused kidneys increased from a baseline of 0.03±0.01 to 0.09±0.02 μmol/min (
P
<0.05). MAP was unchanged by either infusion. RI addition of PD-123319, an AT
2
R antagonist, inhibited the natriuretic response. Furthermore, RI addition of EC-33, a selective APA inhibitor, abolished the natriuretic response to Ang II+PC-18. These data demonstrate that RI addition of PC-18 to Ang II enables natriuresis mediated by the AT
2
R, and that conversion of Ang II to Ang III is critical for this response.
Low Concentrations of Sphingosylphosphorylcholine Enhance Pulmonary Artery Vasoreactivity
Authors: Snetkov Vladimir A. , Thomas Gavin D. , Teague Bonnie , Leach Richard M. , Shaifta Yasin , Knock Greg A. , Aaronson Philip I. , Ward Jeremy P.T.
Published: December 2007

Sphingosylphosphorylcholine (SPC) is a powerful vasoconstrictor, but in vitro its EC
50
is ≈100-fold more than plasma concentrations. We examined whether subcontractile concentrations of SPC (≤1 μmol/L) modulated vasoreactivity of rat intrapulmonary arteries using myography and measurement of intracellular [Ca
2+
]. SPC (1 μmol/L) had no effect on force or intracellular [Ca
2+
] on its own, but dramatically potentiated constrictions induced by ≈25 mmol/L [K
+
], such that at 40 minutes, force and intracellular [Ca
2+
] (Fura PE3 340/380 ratio) were increased by 429±96% and 134±26%, respectively. The potentiation was stereospecific, apparent at concentrations >100 nmol/L of SPC, and independent of the endothelium, 2-aminoethoxydiphenylborane–sensitive Ca
2+
entry, and Rho kinase. It was abolished by the phospholipase C inhibitor U73122, the broad spectrum protein kinase C (PKC) inhibitor Ro31-8220, and the PKCδ inhibitor rottlerin, but not by Gö6976, which is ineffective against PKCδ. The potentiation could be attributed to enhancement of Ca
2+
entry. SPC also potentiated the responses to prostaglandin F
2α
and U436619, which activate a 2-aminoethoxydiphenylborane sensitive nonselective cation channel in intrapulmonary arteries. In this case, potentiation was partially inhibited by diltiazem but abolished by 2-aminoethoxydiphenylborane, Ro31-8220, and rottlerin. SPC (1 μmol/L) caused translocation of PKCδ to the perinuclear region and cytoskeleton of cultured intrapulmonary artery smooth muscle cells. We present the novel finding that low, subcontractile concentrations of SPC potentiate Ca
2+
entry in intrapulmonary arteries through both voltage-dependent and independent pathways via a receptor-dependent mechanism involving PKCδ. This has implications for the physiological role of SPC, especially in cardiovascular disease, where SPC is reported to be elevated.
Early Neutrophilia Is Associated With Volume of Ischemic Tissue in Acute Stroke
Authors: Buck Brian H. , Liebeskind David S. , Saver Jeffrey L. , Bang Oh Young , Yun Susan W. , Starkman Sidney , Ali Latisha K. , Kim Doojin , Villablanca J. Pablo , Salamon Noriko , Razinia Tannaz , Ovbiagele Bruce
Published: December 2007

Background and Purpose—

Few data exist on the relationship between differential subpopulations of peripheral leukocytes and early cerebral infarct size in ischemic stroke. Using diffusion-weighted MR imaging (DWI), we assessed the relationship of early total and differential peripheral leukocyte counts and volume of ischemic tissue in acute stroke.

Methods—

All included patents had laboratory investigations and neuroimaging collected within 24 hours of stroke onset. Total peripheral leukocyte counts and differential counts were analyzed individually and by quartiles. DWI lesions were outlined using a semiautomated threshold technique. The relationship between leukocyte quartiles and DWI infarct volumes was examined using multivariate quartile regression.

Results—

173 patients met study inclusion criteria. Median age was 73 years. Total leukocyte counts and DWI volumes showed a strong correlation (Spearman rho=0.371,
P
<000.1). Median DWI volumes (mL) for successive neutrophil quartiles were: 1.3, 1.3, 3.2, and 20.4 (
P
for trend <0.001). Median DWI volumes (mL) for successive lymphocyte quartiles were: 3.2, 8.1, 1.3, and 1.5 (
P
=0.004). After multivariate analysis, larger DWI volume remained strongly associated with higher total leukocyte and neutrophil counts (both probability values <0.001), but not with lymphocyte count (
P
=0.4971). Compared with the lowest quartiles, DWI volumes were 8.7 mL and 12.9 mL larger in the highest quartiles of leukocyte and neutrophil counts, respectively.

Conclusions—

Higher peripheral leukocyte and neutrophil counts, but not lymphocyte counts, are associated with larger infarct volumes in acute ischemic stroke. Attenuating neutrophilic response early after ischemic stroke may be a viable therapeutic strategy and warrants further study.
Intravenous Rosuvastatin for Acute Stroke Treatment
Authors: Prinz Vincent , Laufs Ulrich , Gertz Karen , Kronenberg Golo , Balkaya Mustafa , Leithner Christoph , Lindauer Ute , Endres Matthias
Published: December 2007

Background and Purpose—

Statins exert rapid cholesterol-independent vasoprotective effects. Here, we tested whether postevent treatment with intravenously (i.v.) administered rosuvastatin improves acute stroke outcome in mice.

Methods—

129/SV wild-type mice were subjected to 1-hour filamentous middle cerebral artery occlusion (MCAo), followed by reperfusion, and were postevent treated with i.v. or intraperitoneal (i.p.) rosuvastatin given up to 6 hours after MCAo (dose range 0.02 to 20 mg kg
−1
body weight).

Results—

Rosuvastatin, when administered i.v., significantly reduced lesion size when given up to 4 hours after MCAo and in doses as low as 0.2 mg kg
−1
. In contrast, i.p. administration provided protection only when given directly on reperfusion at a dose of 20 mg kg
−1
but not at lower doses or later time points. Lesion protection was evident as late as 5 days after brain ischemia and was associated with functional improvements in the pole-test and wire-hanging test (2.0 mg kg
−1
dose). Neuroprotection with i.v. rosuvastatin was achieved with peak plasma concentrations <0.5 ng ml
−1
(ie, with 0.2 mg kg
−1
) and was associated with increased levels of phosphorylated Akt kinase and endothelial nitric oxide synthase in the vasculature.

Conclusions—

Rosuvastatin, given intravenously at pharmacologically relevant concentrations, protects from focal brain ischemia up to 4 hours after an event. In our opinion, the development of an intravenous statin formulation is warranted for acute stroke trials with statins in humans.
Stroke Awareness in Brazil
Authors: Pontes-Neto Octávio Marques , Silva Gisele Sampaio , Feitosa Marley Ribeiro , de Figueiredo Nathalie Lôbo , Fiorot José Antonio , Rocha Talitha Nery , Massaro Ayrton Roberto , Leite João Pereira
Published: December 2007

Background and Purpose—

Stroke is the leading cause of death in Brazil. This community-based study assessed lay knowledge about stroke recognition and treatment and risk factors for cerebrovascular diseases and activation of emergency medical services in Brazil.

Methods—

The study was conducted between July 2004 and December 2005. Subjects were selected from the urban population in transit about public places of 4 major Brazilian cities: São Paulo, Salvador, Fortaleza, and Ribeirão Preto. Trained medical students, residents, and neurologists interviewed subjects using a structured, open-ended questionnaire in Portuguese based on a case presentation of a typical patient with acute stroke at home.

Results—

Eight hundred fourteen subjects were interviewed during the study period (53.9% women; mean age, 39.2 years; age range, 18 to 80 years). There were 28 different Portuguese terms to name stroke. Twenty-two percent did not recognize any warning signs of stroke. Only 34.6% of subjects answered the correct nationwide emergency telephone number in Brazil (#192). Only 51.4% of subjects would call emergency medical services for a relative with symptoms of stroke. In a multivariate analysis, individuals with higher education called emergency medical services (
P
=0.038, OR=1.5, 95%, CI: 1.02 to 2.2) and knew at least one risk factor for stroke (
P
<0.05, OR=2.0, 95% CI: 1.2 to 3.2) more often than those with lower education.

Conclusions—

Our study discloses alarming lack of knowledge about activation of emergency medical services and availability of acute stroke treatment in Brazil. These findings have implications for public health initiatives in the treatment of stroke and other cardiovascular emergencies.
Tight Link Between Our Sense of Limb Ownership and Self-Awareness of Actions
Authors: Baier Bernhard , Karnath Hans-Otto
Published: December 2007

Background and Purpose—

Hemiparetic stroke patients with disturbed awareness for their motor weakness (anosognosia for hemiparesis/-plegia [AHP]) may exhibit further abnormal attitudes toward or perceptions of the affected limb(s). The present study investigated the clinical relationship and the anatomy of such abnormal attitudes and AHP.

Methods—

In a new series of 79 consecutively admitted acute stroke patients with right brain damage and hemiparesis/ -plegia, different types of abnormal attitudes toward the hemiparetic/plegic limb (asomatognosia, somatoparaphrenia, anosodiaphoria, misoplegia, personification, kinaesthetic hallucinations, supernumerary phantom limb) were investigated.

Results—

Ninty-two percent of the patients with AHP showed additional “disturbed sensation of limb ownership” (DSO) for the paretic/plegic limb. The patients had the feeling that their contralesional limb(s) do not belong to their body or even belong to another person. Analysis of lesion location revealed that the right posterior insula is a crucial structure involved in these phenomena.

Conclusions—

DSO for hemiparetic/-plegic limbs and AHP are tightly linked both clinically and anatomically. The right posterior insula seems to be a crucial structure involved in the genesis of our sense of limb ownership and self-awareness of actions.
Diffusion-Weighted Imaging in Stroke Attributable to Internal Carotid Artery Dissection
Authors: Bonati Leo H. , Wetzel Stephan G. , Gandjour Joubin , Baumgartner Ralf W. , Lyrer Philippe A. , Engelter Stefan T.
Published: December 2007

Background and Purpose—

In stroke attributable to spontaneous dissection of the internal carotid artery (sICAD), arterial patency may influence the pattern and extent of cerebral ischemia.

Methods—

In 40 consecutive patients with stroke caused by sICAD, we compared the number, size and pattern of cerebral diffusion-weighted imaging lesions between patients with stenotic sICAD (n=15) and occlusive sICAD (n=25).

Results—

Patients with stenotic sICAD had more ischemic lesions (median 5, interquartile range 1 to 10) than patients with occlusive sICAD (2, 1 to 3;
P
=0.014). Lesion diameters were larger in occlusive sICAD (62, 50 to 99 mm) than in stenotic sICAD (25, 10 to 50 mm;
P
=0.007). Border-zone infarction occurred only in stenotic sICAD (7/15, 47%). Most patients with occlusive sICAD had territorial infarcts (22/25, 88%).

Conclusions—

In stroke attributable to sICAD, diffusion-weighted imaging characteristics may be influenced by the patency of the carotid artery. Differences in the pathogenesis of cerebral ischemia might exist between patients with stenotic and those with occlusive sICAD.