bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypertension in β-Adducin–Deficient Mice
Authors: Marro Martín L. , Scremin Oscar U. , Jordan Maria C. , Huynh Ly , Porro Fabiola , Roos Kenneth P. , Gajović Srećko , Baralle Francisco E. , Muro Andrés F.
Published: June 2012

Abstract
—Polymorphic variants of the cytoskeletal protein adducin have been associated with hypertension in humans and rats. However, the direct role of this protein in modulating arterial blood pressure has never been demonstrated. To assess the effect of β-adducin on blood pressure, a β-adducin–deficient mouse strain (−/−) was studied and compared with wild-type controls (+/+). Aortic blood pressure was measured in nonanesthetized, freely moving animals with the use of telemetry implants. It is important to note that these mice have at least 98% of C57Bl/6 genetic background, with the only difference from wild-type animals being the β-adducin mutation. We found statistically significant higher levels of systolic blood pressure (mm Hg) (mean±SE values: −/−: 126.94±1.14, n=5; +/+: 108.06±2.34, n=6;
P
≤0.0001), diastolic blood pressure (−/−: 83.54±1.07; +/+: 74.87±2.23;
P
≤0.005), and pulse blood pressure (−/−: 43.32±1.10; +/+: 33.19±1.96;
P
≤0.001) in β-adducin–deficient mice. Western blot analysis showed that as a result of the introduced genetic modification, β-adducin was not present in heart protein extracts from −/− mice. Consequently, this deficiency produced a sharp decrease of α-adducin and a lesser reduction in γ-adducin levels. However, we found neither cardiac remodeling nor modification of the heart function in these animals. This is the first report showing direct evidence that hypertension is triggered by a mutation in the adducin gene family.
Evidence for a Gene Influencing Blood Pressure on Chromosome 17
Authors: Levy Daniel , DeStefano Anita L. , Larson Martin G. , O’Donnell Christopher J. , Lifton Richard P. , Gavras Haralambos , Cupples L. Adrienne , Myers Richard H.
Published: June 2012

Abstract
—Hypertension is a leading cause of morbidity and mortality. Efforts to identify hypertension genes have focused on 3 approaches: mendelian disorders, candidate genes, and genome-wide scans. Thus far, these efforts have not identified genes that contribute substantively to overall blood pressure (BP) variation in the community. A 10-centiMorgan (cM) density genome-wide scan was performed in the largest families from 2 generations of Framingham Heart Study participants. Heritability and linkage for long-term mean systolic and diastolic BP phenotypes were analyzed by use of
solar
software. Heritability estimates were based on BP measurements in 1593 families. Genotyping was performed on 1702 subjects from 332 large families, and BP data were available for 1585 (93%) genotyped subjects who contributed 12 588 longitudinal BP observations. The mean age was 47 years, and mean BP was 127/80 (systolic/diastolic) mm Hg. Long-term systolic and diastolic BP phenotypes had high heritability estimates, 0.57 and 0.56, respectively. For systolic BP, multipoint log-of-the-odds (LOD) scores >2.0 were located on chromosome 17 at 67 cM (LOD 4.7,
P
=0.0000016) and 94 cM (LOD 2.2). For diastolic BP, LOD scores >2.0 were identified on chromosome 17 (74 cM, LOD 2.1) and chromosome 18 (7 cM, LOD 2.1). Using a genome-wide scan, we found strong evidence for a BP quantitative trait locus on chromosome 17. Follow-up studies are warranted to identify the gene or genes in this quantitative trait locus that influence BP. Such knowledge could extend our understanding of the genetic basis of essential hypertension and have implications for the evaluation and treatment of patients with high BP.
Endogenous Circulating Sympatholytic Factor in Orthostatic Intolerance
Authors: Shapiro Robert E. , Winters Bradford , Hales Mariesa , Barnett Townsend , Schwinn Debra A. , Flavahan Nick , Berkowitz Dan E.
Published: June 2012

Abstract
—Sympathotonic orthostatic hypotension (SOH) is an idiopathic syndrome characterized by tachycardia, hypotension, elevated plasma norepinephrine, and symptoms of orthostatic intolerance provoked by assumption of an upright posture. We studied a woman with severe progressive SOH with blood pressure unresponsive to the pressor effects of α
1
-adrenergic receptor (AR) agonists. We tested the hypothesis that a circulating factor in this patient interferes with vascular adrenergic neurotransmission. Preincubation of porcine pulmonary artery vessel rings with patient plasma produced a dose-dependent inhibition of vasoconstriction to phenylephrine in vitro, abolished vasoconstriction to direct electrical stimulation, and had no effect on nonadrenergic vasoconstrictive stimuli (endothelin-1), PGF-2α (or KCl). Preincubation of vessels with control plasma was devoid of these effects. SOH plasma inhibited the binding of an α
1
-selective antagonist radioligand ([
125
I]HEAT) to membrane fractions derived from porcine pulmonary artery vessel rings, rat liver, and cell lines selectively overexpressing human ARs of the α
1B
subtype but not other AR subtypes (α
1A
and α
1D
). We conclude that a factor in SOH plasma can selectively and irreversibly inhibit adrenergic ligand binding to α
1B
ARs. We propose that this factor contributes to a novel pathogenesis for SOH in this patient. This patient’s syndrome represents a new disease entity, and her plasma may provide a unique tool for probing the selective functions of α
1
-ARs.
Proximal Sodium Reabsorption
Authors: Chiolero Arnaud , Maillard Marc , Nussberger Jurg , Brunner Hans-R. , Burnier Michel
Published: June 2012

Abstract
—The purpose of this study was to evaluate the contribution of renal sodium handling by the proximal tubule as an independent determinant of blood pressure responsiveness to salt in hypertension. We measured blood pressure (BP), renal hemodynamics, and segmental renal sodium handling (with lithium used as a marker of proximal sodium reabsorption) in 38 hypertensive patients and 27 normotensive subjects (15 young and 12 age-matched) on a high and low sodium diet. In control subjects, changing the diet from a low to a high sodium content resulted in no change in BP and increases in glomerular filtration rate (
P
<0.05), renal plasma flow (
P
<0.05), and fractional excretion of lithium (FE
Li
,
P
<0.01). In hypertensive patients, comparable variations of sodium intake induced an increase in BP with no change in renal hemodynamics and proximal sodium reabsorption. When analyzed by tertiles of their BP response to salt, salt-insensitive hypertensive patients of the first tertile disclosed a pattern of adaptation of proximal sodium reabsorption comparable to that of control subjects, whereas the most salt-sensitive patients of the third tertile had an inverse pattern with a high FE
Li
on low salt and a lower FE
Li
on high salt, suggesting an inappropriate modulation of proximal sodium reabsorption. The BP response to salt correlated positively with age (
r
=0.34,
P
=0.036) and negatively with the changes in FE
Li
(
r
=−0.37,
P
=0.029). In a multivariate analysis, the changes in FE
Li
were significantly and independently associated with the salt-induced changes in BP. These results suggest that proximal sodium reabsorption is an independent determinant of the BP response to salt in hypertension.
Baseline Characteristics in Relation to Electrocardiographic Left Ventricular Hypertrophy in Hypertensive Patients
Authors: Okin Peter M. , Devereux Richard B. , Jern Sverker , Kjeldsen Sverre E. , Julius Stevo , Dahlöf Björn
Published: June 2012

Abstract
—The Losartan Intervention For Endpoint (LIFE) reduction in hypertension study is a double-blind, prospective, parallel group study designed to compare the effects of losartan with those of atenolol on the reduction of cardiovascular morbidity and mortality. A total of 9194 patients with hypertension and ECG left ventricular hypertrophy (LVH) by Cornell voltage-duration product and/or Sokolow-Lyon voltage criteria were enrolled in the study, with baseline clinical and ECG data available in 8785 patients (54% women; mean age, 67±7 years). ECG LVH by Cornell voltage-duration product criteria was present in 5791 patients (65.9%) and by Sokolow-Lyon voltage in 2025 patients (23.1%). Compared with patients without ECG LVH by Cornell voltage-duration product criteria, patients with ECG LVH by this method were older; more obese; more likely to be female, white, and to have never smoked; more likely to be diabetic and have angina; and had slightly higher systolic, diastolic, and pulse blood pressures. In contrast, patients with ECG LVH by Sokolow-Lyon criteria were slightly younger; less obese; more likely to be male, black, and current smokers; less likely to have diabetes; more likely to have angina and a history of cerebrovascular disease; and had higher systolic and pulse blood pressure but slightly lower diastolic blood pressure than patients without ECG LVH by this method. By use of multivariate logistic regression analyses, presence of ECG LVH by Cornell voltage-duration product criteria was predominantly associated with higher body mass index, increased age, and female gender, whereas presence of ECG LVH by Sokolow-Lyon voltage criteria was predominantly related to lower body mass index, male gender, and black race. Thus, hypertensive patients who meet Cornell product and Sokolow-Lyon voltage criteria are associated with different, but potentially equally adverse, risk factor profiles.
Salt, Blood Pressure, and Human Health
Authors: Alderman Michael H.
Published: June 2012

Abstract
—The positive relation of sodium intake and blood pressure, first recognized a century ago, has been well established in ecological, epidemiological, and experimental human studies. Equally well established is the association of increasing blood pressure and cardiovascular morbidity and mortality. Indeed, the pharmacological capacity to reduce blood pressure has produced one of the great public health accomplishments of the 20th century. These two facts—the positive relation of blood pressure to strokes and heat attacks and the positive association of sodium intake to blood pressure—underlie the hypothesis that a reduction in sodium intake, by virtue of its hypotensive effect, might prevent strokes and heart attacks. Moreover, even if the effect on blood pressure were in the range of a 1- to 2-mm Hg decline in blood pressure for every 75- to 100-mmol difference in sodium intake, the impact of such a change, applied to the whole population, would be enormous. The problem with this appealing possibility is that a reduction in salt consumption of this magnitude has other—and sometimes adverse—health consequences. The question, therefore, is whether the beneficial hypotensive effects of sodium restriction will outweigh its hazards. Unfortunately, few data link sodium intake to health outcomes, and that which is available is inconsistent. Without knowledge of the sum of the multiple effects of a reduced sodium diet, no single universal prescription for sodium intake can be scientifically justified.
Mechanisms of Increased Susceptibility to Angiotensin II–Induced Apoptosis in Ventricular Cardiomyocytes of Spontaneously Hypertensive Rats
Authors: Ravassa Susana , Fortuño María Antonia , González Arantxa , López Begoña , Zalba Guillermo , Fortuño Ana , Díez Javier
Published: June 2012

Abstract
—Previous findings have shown that hypotensive doses of losartan prevent the excess of apoptosis present in the hypertrophied left ventricle of adult spontaneously hypertensive rats (SHR). This study was designed to determine whether angiotensin II facilitates apoptosis in cardiomyocytes of adult SHR. Primary cultures of ventricular cardiomyocytes from 30-week-old normotensive Wistar-Kyoto rats (WKY) and SHR with left ventricular hypertrophy were exposed to 10
−
9
mol/L angiotensin II for 24 hours. Apoptotic cells were assessed by terminal deoxynucleotidyl transferase assay and confirmed by Annexin V detection. The expression of Bax-α, Bcl-2, p53
,
and caspase-3 proteins was assessed by Western blot assays. The expression of
BAX
gene was assessed by Northern blot. Angiotensin II increased (
P
<0.01) cardiomyocyte apoptosis, and this effect was higher (
P
<0.001) in SHR cells than in WKY cells. Whereas losartan (10
−
7
mol/L) blocked the apoptotic effect of the octapeptide in cells from the two strains of rats, PD123319 (10
−
7
mol/L) inhibited angiotensin II–mediated apoptosis only in SHR cells. Angiotensin II stimulated (
P
<0.01) Bax-α protein, and this effect was higher (
P
<0.01) in SHR cells than in WKY cells. Angiotensin II did not modify Bcl-2, p53, and BAX mRNA in cells from the two strains of rats. Angiotensin II induced a similar increase (
P
<0.05) in the ratio caspase-3/procaspase-3 (an index of caspase-3 activation) in cardiomyocytes from the two strains of rats. The present in vitro results indicate that SHR cardiomyocytes exhibit enhanced susceptibility to angiotensin II–induced apoptosis. Ligand binding to angiotensin II type 1 and type 2 receptors leading to changes in posttranscriptional processing of Bax-α and accumulation of this proapoptotic protein may be involved in the abnormal response of SHR cardiomyocytes. These data support a role for angiotensin II in apoptosis observed in the left ventricle of these rats.
Retinal Neovascularization Is Prevented by Blockade of the Renin-Angiotensin System
Authors: Moravski Christina J. , Kelly Darren J. , Cooper Mark E. , Gilbert Richard E. , Bertram John F. , Shahinfar Shahnaz , Skinner Sandford L. , Wilkinson-Berka Jennifer L.
Published: June 2012

Both angiotensin II and vascular endothelial growth factor are angiogenic agents that have recently been implicated in the pathogenesis of proliferative diabetic retinopathy. In this study, retinal neovascularization was examined in a model of retinopathy of prematurity with the use of neonatal transgenic (mRen-2)27 rats, which overexpress renin in tissues, and Sprague-Dawley rats. Blockers of the renin-angiotensin system were administered during the neovascularization period. The ACE inhibitor lisinopril and the angiotensin type 1 receptor antagonist losartan both increased retinal renin levels and prevented inner retinal blood vessel growth. Quantitative in situ hybridization revealed that the expression of vascular endothelial growth factor and its type 2 receptor in the inner retina and proliferating blood vessels were increased in rats with retinopathy of prematurity. Lisinopril reduced both retinal vascular endothelial growth factor and its type 2 receptor mRNA in retinopathy of prematurity rats, whereas losartan had no effect. It is predicted that agents that interrupt the renin-angiotensin system may play an important role as retinoprotective agents in various forms of proliferative retinopathy.
Increased Arterial Intima-Media Thickness and In Vivo LDL Oxidation in Young Men With Borderline Hypertension
Authors: Toikka Jyri O. , Laine Hanna , Ahotupa Markku , Haapanen Arto , Viikari Jorma S. A. , Hartiala Jaakko J. , Raitakari Olli T
Published: June 2012

Abstract
—We used borderline hypertension as a model for prehypertension to examine the early influences of elevated blood pressure on subclinical atherosclerosis, lipoprotein oxidation, and cardiac adaptation. Healthy men (age 37±4 years) were classified prospectively into 2 groups on the basis of having either borderline hypertension (systolic 130 to 140 mm Hg or diastolic 85 to 89 mm Hg, n=16) or normal (<130/85 mm Hg, n=22) blood pressure values during the previous 2 years. The groups were matched for age, body size, and serum cholesterol levels. High-resolution ultrasound was used to measure intima-media thickness (IMT) of the carotid and brachial arteries, cardiac dimensions, and brachial artery endothelial function. Baseline low-density lipoprotein (LDL)-diene conjugation was measured as an estimate of in vivo LDL oxidation (ox-LDL). Compared with normotensive controls, men with borderline hypertension had higher IMT of the carotid artery (0.58±0.06 versus 0.75±0.07 mm,
P
<0.001) and IMT of the brachial artery (0.45±0.05 versus 0.57±0.07 mm,
P
<0.001), and increased levels of ox-LDL (29±9 versus 47±17 mol/L,
P
<0.001), but similar endothelial function. Left ventricular mass was similar in both groups, but there were significant differences in left ventricular geometry. In multivariate analyses, the predictors of carotid IMT were 24-hour systolic blood pressure (
P
<0.001) and ox-LDL (
P
=0.10). The current study demonstrates evidence of increased subclinical atherosclerosis and ox-LDL in borderline hypertension. These results are consistent with the idea that enhanced ox-LDL may be one of the pathophysiological events related to development of atherosclerosis in men with borderline elevated blood pressure.
Effect of Chronic Blockade of the Kallikrein-Kinin System on the Development of Hypertension in Rats
Authors: Rhaleb Nour-Eddine , Yang Xiao-Ping , Nanba Masahiko , Shesely Edward G. , Carretero Oscar A.
Published: June 2012

Abstract
—The kallikrein-kininogen-kinin system is an important vasodilator and vasodepressor component of the cardiovascular system. Acting mainly through B
2
receptors, kinins may counterbalance the pressor effect of angiotensin II, salt, and mineralocorticoids plus salt. Using rats lacking the bradykinin precursors low- and high-molecular-weight kininogen or a B
2
kinin receptor antagonist (icatibant), we investigated whether absence or blockade of the kallikrein-kinin system alters blood pressure (BP) in rats given (1) chronic infusion of Ang II, (2) a normal or high salt diet, or (3) chronic administration of deoxycorticosterone acetate (DOCA) plus salt. We confirmed the genotype and phenotype of Brown Norway Katholiek rats (BNK) and found that they had a G-to-A point mutation on the kininogen gene compared with Brown Norway (BN) and Sprague-Dawley (SD) rats, very low levels of high-molecular-weight kininogen (17±3 ng/mL) compared with BN and SD (1814±253 and 2397±302 ng/mL, respectively;
P
<0.01), and plasma low-molecular-weight kininogen concentrations below detectable limits compared with 1773±74 and 1781±140 ng/mL for BN and SD, respectively. Basal BP was the same in BNK and BN. Chronic infusion of icatibant did not alter BP in BN or Wistar rats. At doses that blocked the acute effect of bradykinin, icatibant did not potentiate the pressor effect of a chronic subpressor or pressor dose of angiotensin II in male and female Wistar rats nor that of a high salt diet (2%) plus unilateral nephrectomy in male Wistar rats. Moreover, blockade of the kallikrein-kininogen-kinin system in either BN rats given a very high dose of icatibant or kinin-deficient rats (BNK) did not potentiate the pressor effect of angiotensin II (nonpressor dose) or a high salt (3% NaCl) diet given for 2 weeks. Established DOCA-salt hypertension was not exaggerated in rats treated with icatibant but was partially attenuated by ramipril (1.5 mg · kg
−
1
· d
−
1
for 7 days;
P
<0.002). This antihypertensive effect was abolished by icatibant (
P
<0.002, ramipril versus ramipril plus icatibant). These results suggest that endogenous kinins do not participate in the maintenance of normal blood pressure or antagonize the development of hypertension induced by chronic infusion of angiotensin II, a high salt diet, or DOCA-salt. However, kinins appear to play an important role in the antihypertensive effect of angiotensin-converting enzyme inhibitors in DOCA-salt hypertension.
Salicylate Inhibits Phosphorylation of the Nonreceptor Tyrosine Kinases, Proline-Rich Tyrosine Kinase 2 and c-Src
Authors: Wang Zhongyan , Brecher Peter
Published: June 2012

Abstract
—The anti-inflammatory effects of salicylate are well known, but the intracellular mechanisms underlying those effects remain to be clarified and are not explained solely by an influence on cyclooxygenase activity. In the present study, we have used cardiac fibroblasts stimulated by either angiotensin II (Ang II) or platelet-derived growth factor (PDGF) to demonstrate an inhibitory effect of salicylate on the phosphorylation of the nonreceptor tyrosine kinases, proline-rich tyrosine kinase 2 (PYK2) and c-Src, by immunoprecipitation and immunoblotting methods. This inhibition was dose dependent, with a clear effect observed at concentrations between 5 and 20 mmol/L salicylate. Intracellular Ca
2+
chelation and protein kinase C (PKC) inhibition reduced Ang II and PDGF-induced PYK2 and c-Src phosphorylation. Salicylate significantly inhibited the phosphorylation of both of the tyrosine kinases activated by either ionophore A23187 or thapsigargin treatment, which led to an elevation of cytosolic Ca
2+
. Activation of PKC by phorbol ester phosphorylated both PYK2 and Src, and this effect also was attenuated by salicylate. In contrast, salicylate had no effect on either the transactivation of the epidermal growth factor receptor by Ang II or the phosphorylation of phospholipase C-γ by PDGF. These studies indicate a novel site of action for salicylate on PYK2 and c-Src phosphorylation and suggest that this inhibitory effect on these important signaling intermediates may be through a Ca
2+
- and PKC-dependent mechanism.
Neurovascular Contact of Cranial Nerve IX and X Root-Entry Zone in Hypertensive Patients
Authors: Hohenbleicher Henriette , Schmitz Stephan A. , Koennecke Hans-Christian , Offermann Ralf , Offermann Jens , Zeytountchian Helen , Wolf Karl-Jürgen , Distler Armin , Sharma Arya M.
Published: June 2012

Abstract
—Neurovascular contact of the left rostral ventrolateral medulla has been implicated in the pathogenesis of “essential” hypertension, and recent intervention studies suggest that surgical decompression of the ventrolateral medulla lowers blood pressure in these patients. We assessed the prevalence of this vascular anomaly in patients with essential hypertension by using an advanced MRI technique. We performed MRI of the brain stem in 125 hypertensive patients and in 105 age-matched, sex-matched, and body mass index–matched normotensive control subjects. Imaging of the root-entry zone of cranial nerves IX and X was performed by combining a high-resolution 3D constructive interference in steady-state sequence with a flow-sensitive time-of-flight technique, and images were independently assessed by 4 readers using predefined criteria. Left-sided neurovascular contact was found in 23% of the hypertensive patients and in 16% of the normotensive individuals (
P
=0.12). Blood pressure level, heart rate, and number of antihypertensive medications in treated hypertensive patients were similar among patients with positive, borderline, and negative brain stem findings. Our findings cast doubt on the importance of left-sided neurovascular contact as a frequent cause of essential hypertension or as a major factor determining the severity of hypertension in patients with this anomaly.
Inhibition of Neointima by Angiotensin-Converting Enzyme Inhibitor in Porcine Coronary Artery Balloon-Injury Model
Authors: Matsumoto Keiko , Morishita Ryuichi , Moriguchi Atsushi , Tomita Naruya , Aoki Motokuni , Sakonjo Hiroshi , Matsumoto Kunio , Nakamura Toshikazu , Higaki Jitsuo , Ogihara Toshio
Published: June 2012

Because hepatocyte growth factor (HGF) stimulates growth of endothelial cells exclusively without replication of vascular smooth muscle cells, we hypothesized that HGF may play a role in cardiovascular disease. In human vascular smooth muscle cells, angiotensin II suppressed local vascular HGF production in a dose-dependent manner. Using a rat balloon-injury carotid artery model, we demonstrated that blockade of angiotensin II inhibited neointimal formation, accompanied by a significant increase in local HGF production. However, the relation of vascular HGF to endothelial function was not clarified. Moreover, it is important to test the hypothesis in animal models that are more similar to human restenosis. Thus, in the present study, we used a porcine coronary artery balloon-injury model to study the role of angiotensin II in regulation of the local HGF system in vivo. Expression of HGF mRNA was significantly decreased in balloon-injured coronary arteries versus intact vessels. An angiotensin-converting enzyme (ACE) inhibitor (perindopril) significantly inhibited neointimal formation after balloon injury compared with vehicle (
P
<0.05). In addition, vasodilator response of balloon-injured coronary arteries to bradykinin was restored by perindopril treatment, whereas no vasodilator response was observed in balloon-injured vessels treated with vehicle. Vasodilator response of balloon-injured arteries induced by perindopril was completely abolished by
N
w
-nitro-
l
-arginine methyl ester. Of particular interest, vascular HGF mRNA was significantly increased in balloon-injured vessels treated with perindopril as compared with vehicle. Overall, the present study demonstrated that ACE inhibitor significantly inhibited neointimal formation, accompanied by significant improvement of endothelial dysfunction and a significant increase in local vascular HGF mRNA in vivo in a porcine coronary artery balloon-injury model. Given the strong mitogenic activity of HGF on endothelial cells, improvement of endothelial dysfunction by perindopril might be due to increased local HGF expression through enhancement of reendothelialization after balloon injury, in addition to its direct effect, ACE inhibition. Downregulation of the local vascular HGF system may play an important role in the pathogenesis of cardiovascular disease.
Signaling Events Mediating the Additive Effects of Oleic Acid and Angiotensin II on Vascular Smooth Muscle Cell Migration
Authors: Greene Eddie L. , Lu Gang , Zhang Da , Egan Brent M.
Published: June 2012

Obese hypertensive patients with cardiovascular risk factor clustering and increased risk for atherosclerotic disease have increased plasma nonesterified fatty acid levels, including oleic acid (OA), and a more active renin-angiotensin-aldosterone system. Vascular smooth muscle cell (VSMC) migration and proliferation participate in the development of atherosclerotic plaque. OA and angiotensin (Ang) II induce synergistic mitogenic responses in VSMCs through sequential signaling pathways dependent on the activation of protein kinase C (PKC), oxidants (reactive oxygen species, ROS), and extracellular signal-regulated kinase (ERK) activation. We tested the hypotheses that (1) OA and Ang II have additive or synergistic effects on VSMC migration and (2) PKC, ROS, and mitogen-activated protein kinase are critical signaling molecules. OA at 100 μmol/L increases VSMC migration 60±10% over control (
P
<0.001). Ang II (10
−
9
mol/L) increases VSMC migration by 62±13% and 73% over control, respectively (
P
<0.01). Coincubation of cells with OA and Ang II produces a nearly additive increase in VSMC cell migration at 107±20% (
P
<0.01). Increases in VSMC migration induced by OA alone and combined with Ang II were reduced by PKC inhibition and downregulation. VSMC migration in response to OA alone and with Ang II was also inhibited by
N
-acetyl-cysteine, MEK inhibition, and ERK antisense. VSMC migration in response to OA alone or combined with Ang II is dependent on activation of PKC, ROS, and ERK activation, further raising the possibility that increased plasma nonesterified fatty acids and an activated renin-angiotensin-aldosterone system in subjects with the risk factor cluster contribute to accelerated atherosclerosis through a PKC, ROS, and ERK-dependent signaling pathway.
Antisense Inhibition of Thyrotropin-Releasing Hormone Reduces Arterial Blood Pressure in Spontaneously Hypertensive Rats
Authors: García Silvia I. , Alvarez Azucena L. , Porto Patricia I. , Garfunkel Victoria M. , Finkielman Sammuel , Pirola Carlos J.
Published: June 2012

Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation. Recently, we described that the TRH precursor gene overexpression induces hypertension in the normal rat. In addition, we published that spontaneously hypertensive rats (SHR) have central extrahypothalamic TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. In the present study, we report that intracerebroventricular antisense (AS) treatment with a phosphorothioate oligonucleotide against the TRH precursor gene significantly diminished up to 72 hours and in a dose-dependent manner the increased diencephalic TRH content, whereas normalized systolic blood pressure (SABP) was present in the SHR compared with Wistar-Kyoto (WKY) rats. Although basal thyrotropin was higher in SHR compared with WKY rats and this difference disappeared after antisense treatment, no differences were observed in plasma T4 or T3 between strains with or without AS treatment, indicating that the effect of the AS on SABP was independent of the thyroid status. Because the encephalic renin-angiotensin system seems to be crucial in the development and/or maintenance of hypertension in SHR, we investigated the effect of antisense inhibition of TRH on that system and found that TRH antisense treatment significantly diminished the elevated diencephalic angiotensin II (Ang II) content in the SHR without any effect in control animals, suggesting that the Ang II system is involved in the TRH cardiovascular effects. To summarize, the central TRH system seems to be involved in the etiopathogenesis of hypertension in this model of essential hypertension.
Degeneration of Capsaicin-Sensitive Sensory Nerves Leads to Increased Salt Sensitivity Through Enhancement of Sympathoexcitatory Response
Authors: Wang Donna H. , Wu Wei , Lookingland Keith J.
Published: June 2012

We have previously shown that neonatal degeneration of capsaicin-sensitive sensory nerves renders a rat responsive to a salt load with an increase in blood pressure and a decrease in natriuretic response. To test the hypothesis that the enhanced sympathoexcitatory response to a high salt intake contributes to the development of hypertension in this model, newborn Wistar rats were given 50 mg/kg capsaicin and/or 80 mg/kg guanethidine subcutaneously. Control rats were treated with vehicle. After the weaning period, male rats were grouped as the following and given a high sodium diet (4%) for 2 weeks: capsaicin and guanethidine coadministration (CAP-GUA), capsaicin only (CAP), guanethidine only (GUA), and vehicle control (CON). Norepinephrine concentrations in the atrium were significantly lower in CAP-GUA and GUA than in CON rats (
P
<0.05). Twenty-four–hour urine and sodium excretions were significantly lower in CAP than in CAP-GUA, GUA, and CON rats (
P
<0.05). Mean arterial pressure (mm Hg) was significantly higher in CAP (180±10) than in CAP-GUA (106±1), GUA (133±5), and CON (122±3) rats (
P
<0.05). Thus, sympathectomy restores the natriuretic response to a high salt intake and prevents the development of salt-sensitive hypertension induced by sensory denervation. These data indicate that sensory nerves counterbalance the prohypertensive effect of the sympathetic nerves to maintain blood pressure within normal range during salt loading.
Role of Endothelin and Isoprostanes in Slow Pressor Responses to Angiotensin II
Authors: Ortiz Maria Clara , Sanabria Elisabeth , Manriquez Melissa C. , Romero Juan C. , Juncos Luis A.
Published: June 2012

We tested the hypothesis that angiotensin II (Ang II)–induced stimulations of endothelin (ET) and isoprostanes are implicated in the slow pressor responses to Ang II. We infused either vehicle (group 1) or Ang II (groups 2 to 4) intravenously at 5 ng/kg per minute via osmotic pumps for 15 days into Sprague-Dawley rats. Groups 3 and 4 received 30 mg/kg per day of either losartan (Ang II type 1 receptor blocker) or bosentan (ET

A

and ET

B

receptor blocker) in their drinking water. We measured systolic blood pressure (SBP) every 3 days during the infusion. Plasma levels of Ang II, ET, isoprostanes, and urinary nitrites were determined at 15 days. Vehicle infusion did not change SBP (from 138±13 to 136±2 mm Hg at day 15). Circulating Ang II, ET, and isoprostane levels were 35±9, 39±3, and 111±10 pg/mL, respectively, whereas urinary nitrites were 2.3±0.4 μg/d. Ang II increased SBP (from 133±10 to 158±8 mm Hg), plasma Ang II (179±77 pg/mL), and isoprostanes (156±19 pg/mL) without altering ET levels (38±5 pg/mL) or urinary nitrites (1.8±0.5 μg/d). Losartan prevented Ang II–induced increases in SBP and isoprostanes (SBP went from 137±5 to 120±4 mm Hg; isoprostanes were 115±15 pg/mL) while increasing urinary nitrite levels (5.2±1.1 μg/d). Losartan did not alter Ang II (141±57 pg/mL) or ET (40±4 pg/mL) levels. Bosentan also blocked Ang II–induced hypertension (from 135±4 to 139±3 mm Hg) but did not decrease isoprostanes (146±14 pg/mL). Ang II (63±11 pg/mL), ET levels (46±2 pg/mL), and urinary nitrites (2.8±0.4 μg/d) were not altered. In conclusion, our results suggest that low-dose Ang II increases isoprostanes via its Ang II type 1 receptor and causes an ET-dependent hypertension, without altering circulating ET levels.
Effects of Estradiol and Its Metabolites on Glomerular Endothelial Nitric Oxide Synthesis and Mesangial Cell Growth
Authors: Xiao Shen , Gillespie Delbert G. , Baylis Christine , Jackson Edwin K. , Dubey Raghvendra K.
Published: June 2012

Reduced nitric oxide synthesis by glomerular endothelial cells and increased proliferation of glomerular mesangial cells is associated with glomerular remodeling that leads to accelerated glomerulosclerosis. Estradiol induces nitric oxide synthesis and slows the progression of renal disease. Because the estradiol metabolites 2-hydroxyestradiol and 2-methoxyestradiol are more potent than estradiol in inhibiting growth of vascular smooth muscle cells, which are phenotypically similar to mesangial cells, we compared the effects of estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol on growth of glomerular mesangial cells and on basal nitric oxide synthesis by glomerular endothelial cells. In human glomerular mesangial cells, estradiol and its metabolites concentration-dependently (1 nmol/L to 10 μmol/L) inhibited serum (2.5%)-induced DNA synthesis, cell proliferation, and collagen synthesis with the order of potency being 2-methoxyestradiol > 2-hydroxyestradiol > estradiol. ICI182780 (100 μmol/L, an estrogen receptor antagonist) blocked the growth inhibitory effects of estradiol but not 2-hydroxyestradiol or 2-methoxyestradiol. Treatment with estradiol, but not 2-hydroxyestradiol and 2-methoxyestradiol, induced nitric oxide synthesis (
P
<0.05, assayed by the formation of
3
H-
l
-citrulline from
3
H-
l
-arginine) in human glomerular endothelial cells, and these effects were blocked by ICI182780 and L-NMA (a nitric oxide synthesis inhibitor). In conclusion, estradiol may attenuate glomerulosclerosis by inducing nitric oxide synthesis via an estrogen receptor–dependent mechanism and by conversion to 2-hydroxyestradiol and 2-methoxyestradiol, which inhibit glomerular mesangial cell proliferation independent of estrogen receptors.
Increased 2-Methoxyestradiol Production in Human Coronary Versus Aortic Vascular Cells
Authors: Zacharia Lefteris C. , Jackson Edwin K. , Gillespie Delbert G. , Dubey Raghvendra K.
Published: June 2012

Estradiol may be cardioprotective; however, the mechanisms involved remain unclear. Recent findings that estradiol attenuates neointima formation in estrogen receptor knockout mice suggest that the cardioprotective effects of estradiol may be mediated through estrogen receptor–independent mechanisms. Because 2-methoxyestradiol, an endogenous metabolite of estradiol with no affinity for estrogen receptors, is more potent than estradiol in inhibiting vascular smooth muscle cell growth, it is feasible that 2-methoxyestradiol mediates in part the cardioprotective effects of estradiol. To address this hypothesis, we examined the kinetics of 2-methoxyestradiol synthesis in vascular smooth muscle cells and endothelial cells. In human aortic smooth muscle cells, the V
max
,
K
m
, and V
max
/
K
m
ratio values for conversion of 2-hydroxyestradiol to 2-methoxyestradiol were 19±0.69 pmol · min
−1
per 10
6
cells, 0.52±0.085 μmol/L, and 44±4.9 pmol · min
−1
· μmol/L per 10
6
cells, respectively. In human coronary artery vascular smooth muscle cells, the V
max
,
K
m
, and V
max
/
K
m
ratio values for conversion of 2-hydroxyestradiol to 2-methoxyestradiol were 16±0.59 pmol · min
−1
per 10
6
cells, 0.23±0.011 μmol/L, and 69±3.6 pmol · min
−1
· μmol/L per 10
6
cells, respectively (all values significantly different compared with human aortic smooth muscle cells). Also, in human aortic versus coronary artery endothelial cells, the V
max
(33±0.24 versus 22±0.33 pmol · min
−1
per 10
6
cells, respectively),
K
m
(0.20±0.010 versus 0.099±0.014 μmol/L, respectively), and V
max
/
K
m
(163±7.7 versus 243±41 pmol · min
−1
· μmol/L per 10
6
cells, respectively) values were significantly different. Our results indicate that vascular smooth muscle and endothelial cells effectively metabolize 2-hydroxyestradiol to 2-methoxyestradiol. The lower
K
m
and higher V
max
/
K
m
ratio of human coronary versus aortic cells indicate a faster rate of local metabolism of 2-hydroxyestradiol to 2-methoxyestradiol in the coronary circulation at low levels of 2-hydroxyestradiol.
Inhibition of NO Synthesis Enhances Chronic Cardiovascular and Renal Actions of Leptin
Authors: Kuo Jay J. , Jones Oscar B. , Hall John E.
Published: June 2012

Acute studies suggest that leptin has pressor and depressor actions, including stimulation of sympathetic activity as well as increased release of NO from the vascular endothelium. The goal of this study was to examine the role of NO in modulating the chronic blood pressure, heart rate, and renal responses to hyperleptinemia, comparable to that found in obesity-induced hypertension. Male Sprague-Dawley rats were implanted with arterial and venous catheters, and mean arterial pressure and heart rate were monitored continuously 24 h/d. After a 4-day control period, the rats were infused with isotonic saline vehicle (n=6) or
N
G
-nitro-
l
-arginine methyl ester (L-NAME, 10 μg/kg per minute; n=9) to inhibit NO synthesis for 7 days. After 7 days of vehicle or L-NAME administration, leptin was infused intravenously for 7 days at a rate of 0.5 μg/kg per minute, followed by a leptin infusion at 1.0 μg/kg per minute for 7 days, along with vehicle or L-NAME. A 21-day infusion of L-NAME alone (n=6) served as a control for the L-NAME+leptin rats. Although the low dose of leptin alone did not significantly elevate arterial pressure, it raised the heart rate by 18±3 bpm. The higher leptin infusion rate raised arterial pressure from 96±3 to 104±3 mm Hg but did not increase the heart rate further. L-NAME+leptin increased arterial pressure by 40±6 mm Hg and heart rate by 79±19 bpm compared with pretreatment levels. In control L-NAME rats, mean arterial pressure increased by 31±4 mm Hg, whereas the heart rate was not altered significantly compared with pretreatment levels. Neither chronic leptin infusion alone nor L-NAME alone altered the glomerular filtration rate or renal plasma flow significantly, but L-NAME+leptin reduced glomerular filtration rate by 27±11% and renal plasma flow by 47±9%. These results indicate that impaired NO synthesis mildly enhances the chronic renal hemodynamic and hypertensive effects of leptin but markedly amplifies the tachycardia caused by hyperleptinemia.
Angiotensin II Increases Vesicular Trafficking in Brain Neurons
Authors: Wang Xianyu , Yang Hong , Raizada Mohan K.
Published: June 2012

Our previous studies have established that angiotensin (Ang) II stimulates the release, uptake, and synthesis of norepinephrine (NE) in brain neurons involving distinct signal transduction pathways. However, little is known if this NE neuromodulatory effect is a result of Ang II activation of vesicular trafficking in the catecholaminergic neurons. Thus, the aim of this study was to determine if Ang II influences movement of vesicles in live neurons. Dopamine–β-hydroxylase (DβH) fused to green fluorescence protein (GFP) has been used to trace vesicular movement in live neurons by confocal microscopy. Transfection by a plasmid containing GFP-DβH resulted in the expression of green fluorescence, representing ≈100 kDa GFP-DβH fusion protein. The fluorescence was predominantly localized in the perinuclear region of the neuronal soma, with a few neurites also depicting the fluorescence. Ang II caused a dramatic redistribution of fluorescence. The fluorescence was translocated to the neurites in a time-dependent manner. As a result, the number of neurites depicting fluorescence was significantly increased. The translocation was blocked by losartan, an Ang II type 1 receptor subtype–specific antagonist and not by
PD123319
, an Ang II type 2 receptor subtype antagonist. High-magnification confocal microscopic examination revealed that Ang II treatment resulted in a distal movement of certain fluorescent clusters in the neurites at an average rate of 0.84±0.2 μm/s. These observations suggest increased vesicular trafficking is a key signaling event in Ang II stimulation of NE neuromodulation.
Effect of
N-Acetyl-Seryl-Aspartyl-Lysyl-Proline on DNA and Collagen Synthesis in Rat Cardiac Fibroblasts
Authors: Rhaleb Nour-Eddine , Peng Hongmei , Harding Pamela , Tayeh Mahmoud , LaPointe Margot C. , Carretero Oscar A.
Published: June 2012

N
-Acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell entry into the S phase of the cell cycle and is normally present in human plasma. Ac-SDKP is exclusively hydrolyzed by ACE, and its plasma concentration is increased 5-fold after ACE inhibition in humans. We examined the effect of 0.05 to 100 nmol/L Ac-SDKP on 24-hour
3
H-thymidine incorporation (DNA synthesis) by cardiac fibroblasts both in the absence and presence of 5% FCS. Captopril (1 μmol/L) was added in all cases to prevent the degradation of Ac-SDKP. Treatment of cardiac fibroblasts with 5% FCS increased thymidine incorporation from a control value of 12 469±594 to 24 598±1051 cpm (
P
<0.001). Cotreatment with 1 nmol/L Ac-SDKP reduced stimulation to control levels (10 373±200 cpm,
P
<0.001). We measured hydroxyproline content and incorporation of
3
H-proline into collagenous fibroblast proteins and found that Ac-SDKP blocked endothelin-1 (10
−8
mol/L)–induced collagen synthesis in a biphasic and dose-dependent manner, causing inhibition at low doses, whereas high doses had little or no effect. It also blunted the activity of p44/p42 mitogen-activated protein kinase in a biphasic and dose-dependent manner in serum-stimulated fibroblasts, suggesting that the inhibitory effect of DNA and collagen synthesis may depend in part on blocking mitogen-activated protein kinase activity. Participation of p44/p42 in collagen synthesis was confirmed, because a specific inhibitor for p44/p42 activation (PD 98059, 25 μmol/L) was able to block endothelin-1–induced collagen synthesis, similar to the effect of Ac-SDKP. The fact that Ac-SDKP inhibits DNA and collagen synthesis in cardiac fibroblasts suggests that it may be an important endogenous regulator of fibroblast proliferation and collagen synthesis in the heart. Ac-SDKP may participate in the cardioprotective effect of ACE inhibitors by limiting fibroblast proliferation (and hence collagen production), and therefore it would reduce fibrosis in patients with hypertension.
Adverse Cardiac Effects of Salt With Fludrocortisone in Hypertension
Authors: Lim Pitt O. , Farquharson Colin A. J. , Shiels Paul , Jung Roland T. , Struthers Allan D. , MacDonald Thomas M.
Published: June 2012

The effect of salt on blood pressure (BP) is controversial. A more important question is whether salt can produce cardiac target-organ damage, irrespective of its effect on BP. We assessed the effect of salt with fludrocortisone on QT dispersion and echocardiographic left ventricular diastolic function in a prospective interventional study involving 29 hypertensive subjects with a raised aldosterone/renin ratio who were hospitalized for investigation of possible primary aldosteronism. Each subject over 4 days was given a total of 28.8 g (480 mmol) of sodium chloride and 1.5 mg of fludrocortisone with potassium supplementation. Baseline and posttreatment 12-lead ECGs and echocardiograms were obtained. There were no significant changes in body weight, pulse rate, or BP after treatment with salt and fludrocortisone. Plasma sodium was significantly increased from 141.4 (SD 2.1) to 142.6 (SD 2.4) mmol/L (
P
=0.001). QT and QTc dispersion both significantly increased: +19.6 (SD 16.5) ms (95% CI, 13.4 to 25.9) (
P
<0.001) and +19.8 (SD 20.9) ms (95% CI, 11.8 to 27.7) (
P
<0.001), respectively. There were no significant changes in (n=15) left ventricular dimensions or systolic function, but all diastolic filling indexes, including the preload-independent index, flow propagation velocity (55.49 [SD 10.91] to 48.96 [SD 11.40] cm/s,
P
=0.018) worsened, suggesting significant deterioration of left ventricular diastolic function with salt and fludrocortisone. In conclusion, a combination of salt with fludrocortisone increased QT dispersion and impaired left ventricular diastolic relaxation in hypertensive patients with high aldosterone/renin ratios. This raises the possibility that salt may have BP-independent adverse cardiac effects in susceptible hypertensive subjects.
Impaired Sodium Excretion During Mental Stress in Mild Essential Hypertension
Authors: Schneider Markus P. , Klingbeil Arnfried U. , Schlaich Markus P. , Langenfeld Matthias R. , Veelken Roland , Schmieder Roland E.
Published: June 2012

In hypertensive rats, environmental stress causes sodium retention by an exaggerated increase in renal sympathetic nerve activity, which is modulated by angiotensin II. We tested whether similar effects can be observed in humans. In 66 normotensive subjects (half of them with a family history of hypertension) and 36 subjects with mild essential hypertension, urinary sodium excretion and renal hemodynamics were examined at rest and during mental stress treated either with placebo or ACE inhibition in a double-blind, randomized, cross-over design. Despite a marked increase in glomerular filtration rate in response to mental stress (Δglomerular filtration rate, 4.3±7.7 mL/min in normotensives without versus 5.6±8.4 mL/min in normotensives with a family history versus 10.1±5.7 mL/min in patients with mild essential hypertension;
P
<0.002), the increase in urinary sodium excretion was blunted in patients with mild essential hypertension (Δurinary sodium excretion, 0.12±0.17 mmol/min versus 0.10±0.14 mmol/min versus 0.05±0.14 mmol/min;
P
<0.05). ACE inhibition corrected the natriuretic response to mental stress in subjects with mild essential hypertension (Δurinary sodium excretion, 0.05±0.14 mmol/min with placebo versus 0.13±0.19 mmol/min with ACE inhibition;
P
<0.01); thus, after ACE inhibition, urinary sodium excretion increased similarly in all 3 groups. In conclusion, impaired sodium excretion occurs during mental stress in human essential hypertension but not in subjects with positive family history of hypertension. This abnormality in sodium handling during activation of the sympathetic nervous system appears to be mediated by angiotensin II.