bluuebunny/crossref_metadata_2025 huggingface dataset:
G Protein β3 Subunit Gene Variant and Blood Pressure Variation in Canadian Oji-Cree
Authors: Hegele Robert A. , Harris Stewart B. , Hanley Anthony J. G. , Cao Henian , Zinman Bernard
Published: June 2012

Abstract
—The subunits of the heterotrimeric G proteins are attractive candidate gene products for both susceptibility to essential hypertension and interindividual variation in blood pressure. There is alternative splicing of exon 9 of the gene encoding the β3 subunit of heterotrimeric G proteins (
GNB3
) associated with a C→T change at nucleotide 825, which activates a cryptic splice site. The 825T allele results in a gene product that is 41 amino acids smaller than the wild-type gene product. G protein heterotrimers containing the shorter variant are more reactive than those containing the wild type, and the 825T allele appears to be associated with essential hypertension. To evaluate whether this variant is associated with hypertension or blood pressure in other human samples, we genotyped 447 young adult Oji-Cree for the
GNB3
C825T variation. We found that the frequency of the
GNB3
825T allele was 0.501 in the Oji-Cree, which is considerably higher than the frequency observed in whites. Furthermore, genetic variation of the
GNB3
nucleotide 825 was significantly associated with variation in systolic pressure but not diastolic pressure. Specifically, subjects with the 825T/T genotype had significantly lower systolic pressure than subjects with the 825C/T and 825C/C genotypes; the association was independent of sex. Furthermore, the 825T allele frequency tended to be higher in subjects who took antihypertensive medications than in subjects who did not (0.571 versus 0.496;
P
=NS), although this young sample had relatively few subjects with hypertension. The findings support an association of variation in this gene with variation in blood pressure.
Early Cardiac Changes After Menopause
Authors: Schillaci Giuseppe , Verdecchia Paolo , Borgioni Claudia , Ciucci Antonella , Porcellati Carlo
Published: June 2012

Abstract
—The mechanisms underlying the increased cardiovascular risk after menopause are incompletely known. To investigate whether menopause may induce left ventricular structural and functional adaptations in normotensive and hypertensive women, we compared in a case-control setting (1) 76 untreated hypertensive premenopausal women with 76 postmenopausal women and (2) 30 normotensive premenopausal women with 30 postmenopausal women. Subjects were individually matched by age (±5 years; range, 45 to 55), clinic systolic blood pressure (±5 mm Hg), and body mass index (±2 kg×m
−2
). All subjects underwent 24-hour blood pressure monitoring and M-mode echocardiography. Age, clinic and daytime blood pressure, body mass index, and smoking habits did not differ between the paired groups. After menopause, blood pressure fall from day to night was lower in both normotensives (10/15% versus 16/21%) and hypertensives (12/17% versus 16/21%) (all
P
<0.01). Menopause was also associated with a greater left ventricular relative wall thickness (38.8% versus 35.1% in normotensives, 40.2% versus 37.5% in hypertensives) and a reduced midwall fractional shortening (17.3% versus 18.6% in normotensives, 16.6% versus 17.9% in hypertensives) (all
P
<0.05). We conclude that menopause is associated with blunted day-night blood pressure reduction, impaired left ventricular systolic performance, and concentric left ventricular geometric pattern. These finding are independent of presence or absence of high blood pressure.
Dual Inhibition of Neutral Endopeptidase and Angiotensin-Converting Enzyme in Rats With Hypertension and Diabetes Mellitus
Authors: Tikkanen Tuula , Tikkanen Ilkka , Rockell Melinda D. , Allen Terri J. , Johnston Colin I. , Cooper Mark E. , Burrell Louise M.
Published: June 2012

Abstract
—It has been suggested that combined inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) may lower blood pressure more effectively than either treatment alone, independent of the degree of salt and volume status or the activity of the renin-angiotensin system. The effects of NEP inhibition in hypertension associated with diabetes mellitus are largely unknown. We therefore compared ACE inhibition, NEP inhibition, and dual NEP/ACE inhibition in diabetic hypertensive rats. Spontaneously hypertensive rats (SHR) aged 9 to 10 weeks were injected with either streptozotocin (45 mg/kg) or citrate buffer and randomized to receive either the ACE inhibitor captopril (25 mg/kg BID), the NEP inhibitor SCH 42495 (30 mg/kg BID), the dual NEP/ACE inhibitor S 21402 (25 or 50 mg/kg BID), or vehicle by gavage for 4 weeks. A group of diabetic SHR was also allocated to receive the combination of SCH 42495 (30 mg/kg BID) and captopril (25 mg/kg BID). The degree of renal NEP inhibition was determined by autoradiography, and plasma renin activity (PRA) was determined by radioimmunoassay. In diabetic SHR, the dual NEP/ACE inhibitor (50 mg/kg BID), as well as the combination of the NEP inhibitor and the ACE inhibitor, reduced systolic blood pressure more effectively than the ACE inhibitor (
P
<0.001) or the NEP inhibitor (
P
<0.001) alone. In nondiabetic SHR, the dual NEP/ACE inhibitor and the ACE inhibitor were equally effective, while the NEP inhibitor had only slight blood pressure–lowering effects. Relative heart weight decreased in parallel to the changes in blood pressure. Renal NEP was clearly inhibited (70% to 92%;
P
<0.001) by both the NEP inhibitor and the dual NEP/ACE inhibitor. Both the ACE inhibitor and the dual NEP/ACE inhibitor increased PRA, but the stimulating effect of dual NEP/ACE inhibition on PRA was less than that observed with ACE inhibition alone (
P
<0.05). Albuminuria in diabetic SHR was lower during treatment with both the dual NEP/ACE inhibitor (50 mg/kg BID) and the combination of NEP inhibition and ACE inhibition compared with vehicle treatment (
P
<0.05). In conclusion, the present study shows that hypertension in SHR with streptozotocin-induced diabetes is modulated by natriuretic peptides and thus is sensitive to NEP inhibition. The increased efficacy of dual NEP/ACE inhibition on blood pressure in diabetic SHR, compared with ACE or NEP inhibition alone, suggests that this therapeutic approach may prove beneficial in the treatment of hypertension associated with diabetes mellitus and other forms of volume-dependent hypertension.
Serum Angiotensinogen Concentration in Relation to Gonadal Hormones, Body Size, and Genotype in Growing Young People
Authors: Pratt J. Howard , Ambrosius Walter T. , Tewksbury Duane A. , Wagner Mary Ann , Zhou Lifen , Hanna Mark P.
Published: June 2012

Abstract
—Multiple factors are thought to influence the level of circulating angiotensinogen (AGT). We showed previously that the serum AGT concentration was significantly related to body mass index (BMI) in a cohort of young people. In the present study, we studied whether levels of the gonadal hormones estradiol and testosterone might also predict the AGT level and might contribute to the BMI effect, since both the production of these hormones and BMI increase with age. In boys (n=127; mean±SD age, 14.7±1.9 years) and girls (n=104; age, 14.8±1.9 years) studied as a single group, we found a significant association of AGT level with level of estradiol (
P
=0.015) after adjustment for haplotype, age, race, testosterone concentration, and BMI. In girls studied alone, the level of AGT showed a significantly positive relation to level of testosterone (
P
=0.043), possibly a result of peripheral conversion of testosterone to estradiol, after adjustment for haplotype, age, race, estradiol concentration, and BMI. In boys, on the other hand, the level of testosterone was inversely related to AGT concentration (
P
=0.019), again after making adjustments for the other variables. Finally, in pairs of subjects matched for BMI, age, race, and gender where 1 member of each pair had either 1 or 2 copies of an
AGT
gene haplotype (T235 and −1074t) and the other member had no copy, the level of AGT was higher in the carrier of a haplotype in 24 of the 34 pairs (
P
<0.001). In conclusion, gonadal hormones are an additional influence on the circulating level of AGT in growing young people. In addition, with matching for BMI and other covariates, there is a strong association of
AGT
genotype with the serum level of AGT, emphasizing the importance of
AGT
gene expression as a determinant of the circulating level of AGT.
Proadrenomedullin N-Terminal 20 Peptide
Authors: Mahata Manjula , Mahata Sushil K. , Parmer Robert J. , O’Connor Daniel T.
Published: June 2012

Abstract
—Proadrenomedullin N-terminal 20 peptide (PAMP-[1-20]; ARLDVASEFRKKWNKWALSR-amide) is a potent hypotensive and catecholamine release–inhibitory peptide released from chromaffin cells. We studied the mechanism of PAMP action and how its function is linked to structure. We tested human PAMP-[1-20] on catecholamine secretion in PC12 pheochromocytoma cells and found it to be a potent, dose-dependent (IC
50
≈350 nmol/L) secretory inhibitor. Inhibition was specific for nicotinic cholinergic stimulation since PAMP-[1-20] failed to inhibit release by agents that bypass the nicotinic receptor. Nicotinic cationic (
22
Na
+
,
45
Ca
2+
) signal transduction was disrupted by this peptide, and potencies for inhibition of
22
Na
+
uptake and catecholamine secretion were comparable. Even high-dose nicotine failed to overcome the inhibition, suggesting noncompetitive nicotinic antagonism. N- and C-terminal PAMP truncation peptides indicated a role for the C-terminal amide and refined the minimal active region to the C-terminal 8 amino acids (WNKWALSR-amide), a region likely to be α-helical. PAMP also blocked (EC
50
≈270 nmol/L) nicotinic cholinergic agonist desensitization of catecholamine release, as well as desensitization of nicotinic signal transduction (
22
Na
+
uptake). Thus, PAMP may exert both inhibitory and facilitatory effects on nicotinic signaling, depending on the prior state of nicotinic stimulation. PAMP may therefore contribute to a novel, autocrine, homeostatic (negative-feedback) mechanism controlling catecholamine release.
Effects of Acute ACE Inhibition on Pulsatile Renin and Aldosterone Secretion and Their Synchrony
Authors: Fliser Danilo , Veldhuis Johannes D. , Dikow Ralf , Schmidt-Gayk Heinrich , Ritz Eberhard
Published: June 2012

Abstract
—Pulsatile (burstlike) secretion of renin and aldosterone is positively coupled with a short time lag of about 10 to 20 minutes. We investigated how acute interruption of the renin-angiotensin-aldosterone axis, ie, acute angiotensin-converting enzyme (ACE) inhibition, alters the pattern of renin and aldosterone secretion. Eight healthy men (mean age, 22±1 years) were studied while on standardized salt intake. They were allocated on 2 occasions in random order to injection of placebo or 1.25 mg of the ACE inhibitor enalaprilat. Blood samples were obtained every 10 minutes for 24 hours for measurement of plasma renin and aldosterone concentrations. The hormone concentration profiles were analyzed using a multiparameter deconvolution technique; basal (tonic) and pulsatile hormone secretion was assessed. The regularity of pulsatile hormone secretion was analyzed using approximate entropy (ApEn). Cross-correlation and cross-ApEn analysis of renin and aldosterone secretion were performed to assess synchrony. Acute ACE inhibition caused an immediate burst of renin release and, in addition, significantly (
P
<0.01) increased 24-hour pulsatile and total renin secretion. It did not affect basal (nonpulsatile) renin secretion. The amplitude of renin bursts and the mass of hormone secreted per burst were significantly (
P
<0.01) increased, whereas the burst frequency (ie, number of secretory events) was unchanged. ApEn analysis revealed significantly (
P
<0.05) more regular renin secretion after ACE inhibition. In contrast, neither basal nor pulsatile aldosterone secretion was affected by administration of enalaprilat. Cross-ApEn analysis documented not only a maintained pattern of reproducibility (ie, synchrony) but also greater conditional regularity between pulsatile renin and aldosterone secretions with acute ACE inhibition. However, the quantitative strength of hormone coupling (assessed by cross-correlation analysis) was markedly diminished by enalaprilat treatment. The present findings suggest that the renin-angiotensin-aldosterone axis may not be completely uncoupled by acute ACE inhibition or that pulsatile renin and aldosterone secretion is driven by a common signal generator that is unaffected by ACE inhibition. In addition, a background basal and pulsatile aldosterone secretion not regulated by the renin-angiotensin axis may exist.
Elevated Fos Expression in the Nucleus Tractus Solitarii Is Associated With Reduced Baroreflex Response in Spontaneously Hypertensive Rats
Authors: Chan Julie Y. H. , Chen Wan-Chi , Lee Hsien-Yang , Chan Samuel H. H.
Published: June 2012

Abstract
—We delineated the functional role of Fos protein at the nucleus tractus solitarii in the manifestation of reduced baroreceptor reflex control of heart rate during hypertension, using spontaneously hypertensive rats (SHR), stroke-prone SHR, Wistar-Kyoto rats, or Sprague-Dawley rats. Microinjection into the bilateral nucleus tractus solitarii of an antisense oligonucleotide that targets against the initiation codon of c-
fos
mRNA significantly potentiated the baroreceptor reflex in response to 30 minutes of sustained increase in blood pressure. Of particular note was the restoration of both the impaired sensitivity and capacity of baroreceptor reflex in SHR and stroke-prone SHR to levels comparable to those in normotensive rats. Likewise, the number of Fos-immunoreactive nuclei evoked by the sustained increase in blood pressure in the caudal nucleus tractus solitarii of SHR and stroke-prone SHR was reduced, after this antisense c-
fos
treatment, to the basal level exhibited by the normotensive animals. Control treatment with the corresponding sense oligonucleotide, an antisense oligonucleotide that targets against a different portion of the coding sequence of the c-
fos
mRNA or artificial cerebrospinal fluid, on the other hand, elicited no discernible effect on either the baroreceptor reflex response or the induced expression of Fos protein in the nucleus tractus solitarii by baroreceptor activation. We also found that the basal level of Fos expression in the caudal nucleus tractus solitarii was significantly elevated in the SHR and stroke-prone SHR. Together, these novel findings suggest that an elevated expression of basal Fos protein in the NTS during hypertension may be associated with the dysfunction in baroreceptor reflex control of heart rate.
Felodipine Inhibits Free-Radical Production by Cytokines and Glucose in Human Smooth Muscle Cells
Authors: Hishikawa Keiichi , Lüscher Thomas F.
Published: June 2012

Abstract
—An imbalance between nitric oxide (NO) and superoxide is importantly involved in the pathogenesis of vascular disease. Inflammatory stimuli and risk factors contribute to these alterations. Calcium antagonists and angiotensin-converting enzyme inhibitors are commonly used cardiovascular drugs. To clarify the effect of felodipine and ramiprilat on the balance of these free radicals, we stimulated human aortic smooth muscle cells (HASCs) with cytokines (human interleukin-1β, tumor necrosis factor-α, lipopolysaccharide, and/or interferon-γ) or high glucose in the presence and absence of these compounds. Felodipine, but not ramiprilat, concentration-dependently inhibited cytokine-induced NO production and NO synthase (NOS) mRNA induction. The antioxidant
N
-acetylcysteine also inhibited cytokine-induced NO production and induction of inducible NOS mRNA. Moreover, felodipine inhibited cytokine-induced superoxide production both in the presence and absence of an NOS inhibitor, suggesting that it acted as a superoxide scavenger and not as an inhibitor of inducible NOS induction. High glucose treatment (22 mmol/L for 48 hours) also significantly increased superoxide production in HASCs, and this increase was inhibited in a concentration-dependent manner by felodipine but not by ramiprilat. These results suggest that felodipine may exert vascular protective effects by suppressing free radical generation in human smooth muscle cells during activation of inflammatory mechanisms and diabetic conditions.
Basal and Stimulated Sympathetic Responses After Epinephrine
Authors: Stein C. Michael , He Huai B. , Wood Alastair J. J.
Published: June 2012

Abstract
—Delayed facilitation of norepinephrine release through the action of epinephrine (NE) at presynaptic β-adrenoceptors has been postulated to account for the delayed hemodynamic effects of epinephrine and to be a mechanism causally related to the development of hypertension. To determine whether a short-term increase in epinephrine concentrations resulted in subsequent facilitation of sympathetic responses, 9 healthy subjects (age, 21±0.9 years) were studied at rest and during physiological stress on 2 occasions when they received an infusion of either saline or epinephrine (20 ng/kg per minute) in random order. Heart rate, blood pressure, forearm blood flow, epinephrine concentrations, and NE spillover were measured at rest, during mental stress (Stroop test), and during a cold pressor test. Measurements were performed before, during the 1-hour infusion of epinephrine or placebo, and 1 hour after the infusion. A radioisotope dilution method was used to measure NE spillover. Hemodynamic measurements and NE spillover were increased during the infusion of epinephrine, but 1 hour after discontinuation of epinephrine there was no significant augmentation of hemodynamic or sympathetic responses. NE spillover 1 hour after saline or epinephrine infusion was similar (0.85±0.2 versus 0.87±0.2 μg/min;
P
=0.92). In addition, there was no delayed facilitation of stress-induced hemodynamic or NE responses after epinephrine. These findings do not support the hypothesis that epinephrine results in delayed facilitation of NE release.
Effect of Activation and Inhibition of the Renin-Angiotensin System on Plasma PAI-1
Authors: Brown Nancy J. , Agirbasli Mehmet A. , Williams Gordon H. , Litchfield W. Reid , Vaughan Douglas E.
Published: June 2012

Abstract
—Increased plasma renin activity (PRA) has been associated with an increased risk of myocardial infarction (MI), whereas angiotensin-converting enzyme (ACE) inhibition appears to reduce the risk of recurrent MI in patients with left ventricular dysfunction. These observations may be partially explained by an interaction between the renin-angiotensin system (RAS) and fibrinolytic system. To test this hypothesis, we examined the effect of salt depletion on tissue-type plasminogen activator (tPA) antigen and plasminogen activator inhibitor-1 (PAI-1) activity and antigen in normotensive subjects in the presence and absence of quinapril (40 mg BID). Under low (10 mmol/d) and high (200 mmol/d) salt conditions there was significant diurnal variation in PAI-1 antigen and activity and tPA antigen. Morning (8
am
through 2
pm
) PAI-1 antigen levels were significantly higher during low salt intake compared with high salt intake conditions (ANOVA, F=5.8,
P
=0.048). PAI-1 antigen correlated with aldosterone (
r
=0.56,
P
<10
−7
) during low salt intake. ACE inhibition significantly decreased 24-hour (ANOVA for 24 hours, F=6.7,
P
=0.04) and morning (F=24,
P
=0.002) PAI-1 antigen and PAI-1 activity (F=6.48,
P
=0.038) but did not alter tPA antigen. Thus, the mean morning PAI-1 antigen concentration was significantly higher during low salt intake than during either high salt intake or low salt intake and concomitant ACE inhibition (22.7±4.6 versus 16.1±3.3 and 16.3±3.7 ng/mL, respectively;
P
<0.05). This study provides evidence of a direct functional link between the RAS and fibrinolytic system in humans. The data suggest that ACE inhibition has the potential to reduce the incidence of thrombotic cardiovascular events by blunting the morning peak in PAI-1.
Blood Pressure in Spain
Authors: Banegas José R. , Rodríguez-Artalejo Fernando , de la Cruz Troca Juan José , Guallar-Castillón Pilar , del Rey Calero Juan
Published: June 2012

Abstract
—Distribution of blood pressure (as per US Joint National Committee VI classification and staging criteria) plus awareness, treatment, and control of hypertension were studied in a representative Spanish population sample of 2021 persons (age range, 35 to 64 years). Pressure was determined in accordance with World Health Organization guidelines. A total of 45.1% of subjects were hypertensive (≥140/≥90 mm Hg or undergoing drug therapy); 12% had isolated systolic hypertension, and 8.7% had isolated diastolic hypertension. Pulse pressure was 48.7 mm Hg. Heart rate was 81.4 bpm in untreated hypertensives and 78.9 bpm in normotensives (
P
<0.05). A substantial proportion of the community burden of blood pressure was attributable to stage 1 (28.3% of subjects), the most frequent category of hypertension, and to the high-normal blood pressure group (17% of subjects). A percentage breakdown showed that among hypertensives, 44.5% were aware of their condition; of these, 71.9% were undergoing drug therapy, and of those being treated, only 15.5% were controlled (5% of hypertensives). Not only are these figures consistent with the fact that Spain has a higher cerebrovascular mortality than other countries such as the United States, but they represent a great potential for improvement, particularly among those groups registering relatively worse data (younger men, rural residents, and unskilled professionals). A decrease of only 1 to 4 mm Hg in average blood pressure could reduce the prevalence of hypertension in Spain by 12.4% to 15.4%.
Mechanisms of FK 506–Induced Hypertension in the Rat
Authors: Takeda Yoshiyu , Miyamori Isamu , Furukawa Kenji , Inaba Satoru , Mabuchi Hiroshi
Published: June 2012

Abstract
—Tacrolimus (FK 506) is a powerful, widely used immunosuppressant. The clinical utility of FK 506 is complicated by substantial hypertension and nephrotoxicity. To clarify the mechanisms of FK 506–induced hypertension, we studied the chronic effects of FK 506 on the synthesis of endothelin-1 (ET-1), the expression of mRNA of ET-1 and endothelin-converting enzyme-1 (ECE-1), the endothelial nitric oxide synthase (eNOS) activity, and the expression of mRNA of eNOS and C-type natriuretic peptide (CNP) in rat blood vessels. In addition, the effect of the specific endothelin type A receptor antagonist FR 139317 on FK 506–induced hypertension in rats was studied. FK 506, 5 mg · kg
−1
· d
−1
given for 4 weeks, elevated blood pressure from 102±13 to 152±15 mm Hg and increased the synthesis of ET-1 and the levels of ET-1 mRNA in the mesenteric artery (240% and 230%, respectively). Little change was observed in the expression of ECE-1 mRNA and CNP mRNA. FK 506 decreased eNOS activity and the levels of eNOS mRNA in the aorta (48% and 55%, respectively). The administration of FR 139317 (10 mg · kg
−1
· d
−1
) prevented FK 506–induced hypertension in rats. These results indicate that FK 506 may increase blood pressure not only by increasing ET-1 production but also by decreasing NO synthesis in the vasculature.
TNF-α–Induced Migration of Vascular Smooth Muscle Cells Is MAPK Dependent
Authors: Goetze Stephan , Xi Xiao-Ping , Kawano Yasuko , Kawano Hiroaki , Fleck Eckart , Hsueh Willa A. , Law Ronald E.
Published: June 2012

Abstract
—Migration of vascular smooth muscle cells (VSMC) is a key event in neointimal formation and atherosclerosis that may be linked to the accumulation of inflammatory cells and release of chemotactic cytokines. Tumor necrosis factor-α (TNF-α) induces chemotaxis of inflammatory cells and fibroblasts, but little is known about chemotactic signaling by TNF-α in VSMC. The aim of this study was to investigate the role of TNF-α in VSMC migration and to elucidate the chemotactic signaling pathways mediating this action. TNF-α (50 to 400 U/mL) induced migration of cultured rat aortic VSMC in a dose-dependent manner. Because activation of the extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (MAPK) is known to be required in platelet-derived growth factor–directed and angiotensin II–directed migration of these cells, we used the MAPK-inhibitor PD98059 to determine if chemotactic signaling by TNF-α involves the MAPK pathway as well. We found that TNF-α–directed migration was substantially inhibited by PD98059. TNF-α (100 U/mL) transiently activated MAPK with a maximal induction 10 minutes after stimulation that returned to baseline levels by 2 hours after treatment. Only a single peak of increased MAPK activity was seen. PD98059 also blocked TNF-α–stimulated MAPK activation in a concentration-dependent manner, which is consistent with its inhibition of TNF-α–directed migration. To identify which TNF-α receptor is involved in TNF-α–induced MAPK activation, antibodies against the p55 TNF-α receptor-1 (TNF-R1) and the p75 TNF-α receptor-2 (TNF-R2) were used. VSMC express both receptors, but TNF-α–induced MAPK activation was inhibited only by the TNF-R1 antibody. The TNF-R2 antibody had no effect. Thiazolidinediones are known to inhibit TNF-α signaling in adipose tissue and attenuate platelet-derived growth factor–directed and angiotensin II–directed migration in VSMC. We therefore investigated the effects of the thiazolidinediones troglitazone (TRO) and rosiglitazone (RSG) on TNF-α–induced migration. Both TRO and RSG inhibited migration, but neither attenuated TNF-α–induced MAPK activation, indicating that their antimigration activity was exerted downstream of MAPK. These experiments provide the first evidence that early activation of MAPK is a crucial event in TNF-α–mediated signal transduction leading to VSMC migration. Moreover, inhibition of TNF-α–directed migration by the insulin sensitizers TRO and RSG underscores their potential as vasculoprotective agents.
Involvement of PYK2 in Angiotensin II Signaling of Vascular Smooth Muscle Cells
Authors: Eguchi Satoru , Iwasaki Hiroaki , Inagami Tadashi , Numaguchi Kotaro , Yamakawa Tadashi , Motley Evangeline D. , Owada Koji M. , Marumo Fumiaki , Hirata Yukio
Published: June 2012

Abstract
—PYK2, a recently identified Ca
2+
-sensitive tyrosine kinase, has been implicated in extracellular signal-regulated kinase (ERK) activation via several G protein–coupled receptors. We have reported that angiotensin II (Ang II) induces Ca
2+
-dependent transactivation of the epidermal growth factor receptor (EGFR) which serves as a scaffold for preactivated c-Src and downstream adaptors (Shc/Grb2), leading to ERK activation in cultured rat vascular smooth muscle cells (VSMC). Herein we demonstrate the involvement of PYK2 in this cascade. Ang II rapidly induced tyrosine phosphorylation of PYK2, whose effect was completely inhibited by an AT
1
receptor antagonist and an intracellular Ca
2+
chelator. A Ca
2+
ionophore also induced PYK2 tyrosine phosphorylation to a level comparable with that by Ang II, whereas phorbol ester–induced phosphorylation was less than that by Ang II. Moreover, PYK2 formed a complex coprecipitable with catalytically active c-Src after Ang II stimulation. Although a selective EGFR kinase inhibitor completely abolished Ang II–induced recruitment of Grb2 to EGFR and markedly attenuated Ang II–induced ERK activation, it had no effect on Ang II–induced PYK2 tyrosine phosphorylation or its association with c-Src and Grb2. These data suggest that the AT
1
receptor uses Ca
2+
-dependent PYK2 to activate c-Src, thereby leading to EGFR transactivation, which preponderantly recruits Grb2 in rat VSMC.
Atrial Natriuretic Peptide Gene Delivery Reduces Stroke-Induced Mortality Rate in Dahl Salt-Sensitive Rats
Authors: Lin Kuei-Fu , Chao Julie , Chao Lee
Published: June 2012

Abstract
—Atrial natriuretic peptide (ANP) is a powerful hormone with hypotensive, natriuretic, diuretic, and many other beneficial effects. Direct infusion of ANP in therapeutics has limited success because of its short half-life in the circulation. Our previous studies have shown that ANP gene delivery attenuates hypertension, cardiac hypertrophy, and renal injury in Dahl salt-sensitive (Dahl-SS) rats. To investigate the potential therapeutic value of ANP gene delivery on salt-induced stroke and cerebrovascular disorders, an adenovirus harboring the human ANP gene (Ad.RSV-cANP) was injected into Dahl-SS rats on a high salt diet. A single intravenous injection of the ANP gene caused a significant reduction of blood pressure that lasted for more than 3 weeks. A maximal blood pressure reduction of 28 mm Hg was observed 2 weeks after gene delivery as compared with that of control rats injected with adenovirus harboring the LacZ gene under the control of the Rous sarcoma virus promoter (Ad.RSV-LacZ). Immunoreactive human ANP can be detected in the heart, lung, kidney, and brain of rats after gene delivery. The stroke mortality rate of Dahl-SS rats was significantly decreased (from 54% to 17% at 3 weeks and from 70% to 50% at 4 weeks after ANP gene delivery as compared with rats injected with control virus). ANP gene delivery also significantly attenuates salt-induced aortic hypertrophy as evidenced by reduced thickness of the aortic wall. This is the first study to demonstrate the potential of ANP gene delivery in reducing the mortality rate caused by cerebrovascular disorders and stroke. Successful application of this technology may have potential value in treating individuals with a high risk of stroke.
Genetic Polymorphism of
CYP11B2
Gene and Hypertension in Japanese
Authors: Tamaki Shinji , Iwai Naoharu , Tsujita Yasuyuki , Kinoshita Masahiko
Published: June 2012

Abstract
—Low-renin hypertension is characterized by a high ratio of aldosterone to plasma renin activity (ALD/PRA), which may suggest inappropriately increased aldosterone biosynthesis. The genes for the enzymes involved in aldosterone synthesis may contribute to low-renin hypertension. We investigated the associations between genetic variations of
CYP11B2
(aldosterone synthase) T(−344)C and hypertension in 482 Japanese subjects. Subjects older than 50 years with a blood pressure <140/85 mm Hg were considered normotensive (n=227 subjects), and subjects younger than 65 years old with a BP >160/95 mm Hg were considered hypertensive (n=255 subjects). The frequency of the TC+CC genotypes in the normotensive group was significantly lower than in the hypertensive group. Logistic analysis on 482 subjects revealed that body mass index, gender, and the genotype of
CYP11B2
T(−344)C were significantly associated with hypertension. ALD and PRA were assessed in 97 subjects with hypertension, and the TC+CC genotypes were significantly associated with higher ALD/PRA. Sixty-five subjects with hypertension were assessed by 24-hour ambulatory blood pressure monitoring, and the frequency of nondippers (a difference in mean blood pressure of <10% between the daytime [6
am
to 9
pm
] and nighttime [9
pm
to 6
am
] hours) was significantly higher in subjects with the TC+CC (hetero+homo mutation) genotype than in subjects with the TT (wild-type) genotype. Echocardiographic assessment (n=136) revealed that the ratio of left ventricular end-diastolic dimension to height tended to be higher in subjects with the TC+CC genotype than in subjects with the TT genotype. The present study suggests that the (−344)C allele of the
CYP11B2
gene may be a genetic marker for low-renin hypertension in Japanese.
Novel
Cis
Element for Tissue-Specific Transcription of Rat Platelet-Derived Growth Factor β-Receptor Gene
Authors: Takata Yasunori , Kitami Yutaka , Fukuoka Tomikazu , Okura Takafumi , Hiwada Kunio
Published: June 2012

Abstract
—Platelet-derived growth factor (PDGF) and its receptors are widely expressed in several tissues in the stage of cellular growth and development. In adulthood, PDGF β-receptor (PDGFβR) is mainly detected in pathological conditions such as atherosclerotic lesions and injured vascular wall. The purpose of the present study was to elucidate the underlying mechanism of PDGFβR gene expression under pathological conditions in vascular smooth muscle cells (VSMC) and to identify the important
cis
elements responsible for tissue-specific gene transcription. Gel mobility shift assay and supershift assay indicated that the CCAAT motif located at −67 (C67) was mainly interacted with NF-YC, and this element drove the basal promoter activity of the gene as a putative promoter. On the other hand, another important sequence essential for the basal transcription was found at a 30-bp region (R30) spanning −150 to −121. To test whether R30 actually regulates the tissue-specific transcription of PDGFβR gene, electromobility shift pattern was compared between VSMC and hepatoma cell line (HTC). We obtained the result that DNA-protein complex seen only in nuclear extracts from HTC suppressed the promoter activity in HTC in a tissue-specific manner. Furthermore,
cis
element decoy transfection experiments for C67 and R30 also revealed that both elements were functionally important in mRNA expression of PDGFβR in VSMC. From these results, we concluded that the basal activity of PDGFβR gene expression was transactivated by the interaction or coordination of both C67 and R30, and the latter one mainly controlled the tissue-specific gene expression in VSMC.
Appropriate Regulation of Renin and Blood Pressure in 45-kb Human Renin/Human Angiotensinogen Transgenic Mice
Authors: Catanzaro Daniel F. , Chen Rong , Yan Yan , Hu Lufei , Sealey Jean E. , Laragh John H.
Published: June 2012

Abstract
—The renin-angiotensin system is normally subject to servo control mechanisms that suppress plasma renin levels in response to increased blood pressure and increase plasma renin levels when blood pressure falls. In most species, renin is rate limiting, and angiotensinogen circulates at a concentration close to the
K
m
, so varying the concentration of either can affect the rate of angiotensin formation. However, only the plasma renin level responds to changes in blood pressure and sodium balance to maintain blood pressure homeostasis. Therefore, the high plasma human renin levels and the hypertension of mice and rats containing both human renin and angiotensinogen transgenes indicate inappropriate regulation of renin and blood pressure. These anomalies led us to develop new lines of transgenic mice with a longer human renin gene fragment (45 kb) than earlier lines (13 to 15 kb). Unlike their predecessors, the 45-kb
hREN
mice secrete human renin only from the kidneys, and both the human and mouse renins respond appropriately to physiological stimuli. To determine whether blood pressure is also regulated appropriately, we crossed these new 45-kb
hREN
mice with mice containing the human angiotensinogen gene. All doubly transgenic mice were normotensive like their singly transgenic and nontransgenic littermates. Moreover, among doubly transgenic mice, both human and mouse plasma renin concentrations were suppressed relative to the singly transgenic 45-kb
hREN
mice. These findings demonstrate the importance of appropriate cell and tissue specificity of gene expression in constructing transgenic models and affirm the pivotal role played by renal renin secretion in blood pressure control.
β-Adrenergic Receptor Kinase-1 Levels in Catecholamine-Induced Myocardial Hypertrophy
Authors: Iaccarino Guido , Dolber Paul C. , Lefkowitz Robert J. , Koch Walter J.
Published: June 2012

Abstract
—Pressure overload ventricular hypertrophy is accompanied by dysfunctional β-adrenergic receptor signaling due to increased levels of the β-adrenergic receptor kinase-1, which phosphorylates and desensitizes β-adrenergic receptors. In this study, we examined whether increased β-adrenergic receptor kinase 1 expression is associated with myocardial hypertrophy induced by adrenergic stimulation. With use of implanted mini-osmotic pumps, we treated mice with isoproterenol, phenylephrine, or vehicle to distinguish between α
1
- and β-adrenergic stimulation. Both treatments resulted in cardiac hypertrophy, but only isoproterenol induced significant increases in β-adrenergic receptor kinase-1 protein levels and activity. Similarly, in isolated adult rat cardiac myocytes, 24 hours of isoproterenol stimulation resulted in a significant 2.8-fold increase in β-adrenergic receptor kinase-1 protein levels, whereas 24 hours of phenylephrine treatment did not alter β-adrenergic receptor kinase-1 expression. Our results indicate that increased β-adrenergic receptor kinase-1 is not invariably associated with myocardial hypertrophy but apparently is controlled by the state of β-adrenergic receptor activation.
Differential Expression of Renal Nitric Oxide Synthase Isoforms During Pregnancy in Rats
Authors: Alexander Barbara T. , Miller M. Todd , Kassab Salah , Novak Jackie , Reckelhoff Jane F. , Kruckeberg Walter C. , Granger Joey P.
Published: June 2012

Abstract
—Alterations in nitric oxide (NO) production have been suggested to play a role in mediating changes in renal function during normal pregnancy and in pregnancy-induced hypertension. Although NO production is enhanced during normal pregnancy, the mechanisms for the increase are unknown. The purpose of this study was to determine whether the elevation in NO production during pregnancy is associated with increases in renal expression of endothelial (eNOS), inducible (iNOS), and neuronal (nNOS) nitric oxide synthases. To achieve this goal we examined systemic and renal hemodynamics, urinary excretion of nitrate/nitrite, and renal protein expression of the three NOS isoforms in prepregnant rats, pregnant rats at days 6, 13, and 19 of gestation and at day 4 postpartum. Mean arterial pressure decreased by 14% in late pregnancy whereas the glomerular filtration rate and renal plasma flow increased by 21% and 24%, respectively, in mid pregnancy. Excretion of nitrate/nitrite increased throughout pregnancy with a 3.4-fold increase present at day 19 (12.2±0.7 to 41.1±1.3 μmol/24 h). Renal eNOS protein expression decreased by 39% during pregnancy with the lowest level resulting at day 19 and returning to virgin levels by day 4 post partum. In contrast, renal iNOS and nNOS protein expression increased 31% and 25%, respectively, with highest expression occurring for both at day 13 of pregnancy. These data suggest that the increased NO production and renal hemodynamics associated with pregnancy in rats may be caused by the upregulation of iNOS and nNOS in the kidney.
Renal Intramedullary Infusion of
l
-Arginine Prevents Reduction of Medullary Blood Flow and Hypertension in Dahl Salt-Sensitive Rats
Authors: Miyata Noriyuki , Cowley Allen W.
Published: June 2012

Abstract
—A role for reduced renal nitric oxide production has been proposed as a mechanism responsible for hypertension in Dahl “salt-sensitive” rats. The present study had 2 goals: first, to determine the relationship between changes in mean arterial pressure and renal cortical and medullary blood flows in unanesthetized Dahl/Rapp salt-sensitive (S) and Dahl/Rapp salt-resistant (R) rats as daily salt intake was increased from 0.4% to 4.0%; second, to determine if delivery of
l
- or
d
-arginine into the renal medulla of Dahl S rats would change the responses to high salt. Optical fibers were implanted into the renal cortex and inner medulla for daily recording of cortical and medullary blood flows using laser-Doppler flowmetry. Indwelling aortic catheters were used to record arterial pressure. Increasing salt intake to 4.0% in Dahl S rats increased mean arterial pressure from 128±2.0 to 155±5.0 mm Hg by day 5 of high salt diet; medullary blood flow was reduced 13% by day 2, 24% by day 3 (
P
<0.05), and 31% by day 5 (
P
<0.05), whereas cortical blood flow was unchanged. In Dahl R rats, mean arterial pressure averaged 117±5 mm Hg during the 0.4% salt control period and remained unchanged (as did cortical and medullary blood flows) during 5 days of 4.0% salt intake. Dahl S rats that received medullary
l
-arginine (300 μg · kg
–1
· min
–1
) exhibited no changes of mean arterial pressure or regional renal blood flow during the 5 days of 4.0% salt intake. Medullary infusion of
d
-arginine (300 μg · kg
–1
· min
–1
) did not prevent the development of hypertension in Dahl S rats that received 4.0% salt. The results are consistent with the view that Dahl S rats have a reduced capacity to generate nitric oxide within the renal medulla under conditions of high salt, which the administration of
l
-arginine can normalize. Furthermore, early reductions of medullary blood flow in Dahl S rats with high salt intake probably contribute to the development of hypertension.
Prolonged L-Arginine on Cardiovascular Mass and Myocardial Hemodynamics and Collagen in Aged Spontaneously Hypertensive Rats and Normal Rats
Authors: Susic Dinko , Francischetti Aloisio , Frohlich Edward D.
Published: June 2012

Abstract
—This study was designed to examine whether L-arginine could prevent hypertension- and age-related impairment of coronary hemodynamics and cardiac fibrosis in aged (80-week-old) rats. To differentiate between hypertension- and age-related changes, the study was performed in both normotensive Wistar-Kyoto rats (WKYs) and spontaneously hypertensive rats (SHR). Male 1-year-old rats of both strains were divided into 2 groups and given either placebo or L-arginine (1.2 g/L) in drinking water. After 6 months, systemic and coronary hemodynamics (radionuclide-labeled microspheres), right and left ventricular and aortic mass indexes, and ventricular hydroxyproline (an estimate of collagen) concentrations were determined. In the aged WKYs, L-arginine did not affect any of the examined variables except slightly reducing total peripheral resistance. In contrast, L-arginine diminished arterial pressure, total peripheral resistance, and left ventricular and aortic mass indexes in the SHRs; it also increased coronary flow reserve and reduced minimal coronary flow resistance and myocardial hydroxyproline concentration. These findings demonstrated that L-arginine ameliorated adverse cardiovascular effects of hypertension in aged SHRs, as demonstrated by reduced arterial pressure and total peripheral resistance, diminished left ventricular mass and collagen content, and improved coronary hemodynamics. There were no important effects in the old WKYs.
Handling
22
NaCl by the Blood-Brain Barrier and Kidney
Authors: Simchon Shlomoh , Manger William , Golanov Eugene , Kamen Jacob , Sommer George , Marshall Chris H.
Published: June 2012

Abstract
—We previously reported that inappropriate renal vasoconstriction in Dahl salt-sensitive (DS) rats fed high NaCl diets may cause sodium retention. The present study examined the distribution and elimination of
22
Na in DS and Dahl salt-resistant (DR) rats, and we determined whether an abnormality in renal function might also cause sodium retention in DS rats. Following an intravenous bolus of 4 μCi
22
NaCl in prehypertensive DS and DR rats with similar blood pressures on low (0.23%) or high (8% for 4 days) NaCl diets, urinary clearance of
22
Na in 1 hour was about 4 times less in DS than DR rats, and renal retention of
22
Na was up to 8 times greater in DS than DR rats (
P
<0.01), suggesting that a renal functional defect may contribute to salt retention in DS rats; however, its uptake in tail artery, heart, lungs, liver, and spleen was similar in DS and DR rats. Uptake in brain was up to 5 times greater in DS than DR rats (
P
<0.01). Cerebrospinal fluid
22
Na radioactivity (in counts per minute) revealed that the blood-brain barrier is 5 to 8 times more permeable to sodium in DS than DR rats (
P
<0.01). Cerebrospinal fluid volume and brain water content increased significantly (
P
<0.01) in DS but not DR rats on an 8% NaCl diet. Intracerebroventricular bolus injection of 0.06 mL of 4.5 mol/L NaCl acutely and transiently induced the same degree of hypertension in DR and DS rats, whereas similar volume injections of isotonic saline, 4.5 mol/L Na-acetate, or 4.5 mol/L NaBr did not produce hypertension in either strain. We conclude that functional abnormalities in DS rat kidneys may cause retention of NaCl and that an increased blood-brain barrier permeability to NaCl may enhance its access to sites in the brain that are then activated and induce hypertension.
Insulin-Mediated Vasodilation and Glucose Uptake Are Functionally Linked in Humans
Authors: Cleland Stephen J. , Petrie John R. , Ueda Shinichiro , Elliott Henry L. , Connell John M. C.
Published: June 2012

Abstract
—Intra-arterial infusion of insulin in physiological doses causes forearm vasodilation which is augmented by co-infusion of
d
-glucose, leading us to speculate that local insulin-mediated vasodilation may depend on insulin-mediated glucose uptake. We have examined the relationship between whole-body insulin sensitivity and forearm vasodilation in response to local infusion of insulin/glucose, thus avoiding any confounding effects of sympathetic stimulation on peripheral blood flow. Eighteen healthy, normotensive male volunteers (age, 26±5.4 years) attended on two separate occasions for measurement of: (1) whole-body insulin sensitivity with use of the hyperinsulinemic euglycemic clamp; (2) forearm vasodilation in response to an intra-arterial infusion of insulin/glucose with use of bilateral venous occlusion plethysmography. Insulin-mediated glucose uptake (M) for the group (mean±SD) was 10.0±2.2 mg · kg
−1
· min
−1
, and the percentage change in forearm blood flow ratio (%FBFR) for the group (median, interquartile range) was 28.2% (13.6, 48.6). In univariate analysis, M was significantly correlated with %FBFR (
r
s
=0.60,
P
<0.05), but not with body mass index (BMI) (
r
s
=−0.42), age (
r
=−0.39) or mean arterial pressure (
r
=0.13). In multiple regression analysis, %FBFR remained a significant independent predictor of M (
R
2
(adj)=0.48,
t
=3.23,
P
<0.01) in a model involving BMI, age, and blood pressure. These data support the concept of a significant functional relationship between insulin’s metabolic and vascular actions, possibly at an endothelial level.
Hyperglycemia and Angiotensin-Mediated Control of the Renal Circulation in Healthy Humans
Authors: Osei Suzette Y. , Price Deborah A. , Fisher Naomi D. L. , Porter Lisa , Laffel Lori M. B. , Hollenberg Norman K.
Published: June 2012

Abstract
—Type 1 and type 2 diabetics have an enhanced renal vasodilator response to angiotensin-converting enzyme (ACE) inhibition despite suppressed plasma renin activity (PRA), indicating possible activation of the intrarenal renin angiotensin system. To investigate the role of hyperglycemia, we evaluated the renal hemodynamic response to ACE inhibition in 9 healthy subjects in high-salt balance after steady-state hyperglycemia (8.4±1 mmol/L) was achieved via intravenous glucose administration. Renal plasma flow (RPF) and glomerular filtration rate (GFR) responses to captopril and to angiotensin II (Ang II) were measured as paraminohippuric acid and inulin clearances. Hyperglycemia produced a significant increase in RPF of 117 mL · min
−1
· 1.73 m
−2
after 90 minutes but not GFR. Administration of captopril at a dose of 25 mg during glucose infusion led to an increase in RPF of 173±24 mL · min
−1
· 1.73 m
−2
(
P
<0.01) but did not significantly change RPF in the absence of hyperglycemia (7±21 mL · min
−1
· 1.73 m
−2
). Captopril did not alter GFR in the presence or absence of hyperglycemia. Ang II infusion during hyperglycemia decreased RPF by 45±16 mL · min
−1
· 1.73 m
−2
, and this was significantly enhanced by captopril (−98±26 mL · min
−1
· 1.73 m
−2
,
P
<0.05). In contrast, there was no enhancement of the vasoconstrictor response to Ang II in the absence of hyperglycemia. PRA did not change with hyperglycemia. Enhancement of renal vasodilation during hyperglycemia by captopril without alteration of PRA suggests activation of the intrarenal renin angiotensin system.