bluuebunny/crossref_metadata_2025 huggingface dataset:
Genome-Wide Linkage Analysis of Pulse Pressure in Mexican Americans
Authors: Atwood Larry D. , Samollow Paul B. , Hixson James E. , Stern Michael P. , MacCluer Jean W.
Published: June 2012

Pulse pressure, a measure of aortic stiffness, is a strong predictor of cardiovascular mortality. To locate genes that affect pulse pressure, we performed genetic analysis on randomly ascertained families in the San Antonio Family Heart Study. Pulse pressure was defined as the difference between systolic and diastolic blood pressures. Likelihood methods were used to construct a model that had both single-locus and polygenic components for 46 families (1308 individuals). The single-locus component included sex-specific and genotype-specific effects of both age and body mass index. Using this model, we then performed 2-point linkage analysis in 10 families (440 individuals) that were among the largest of the 46 families and that had been genotyped for 399 polymorphic markers. The model that contained only the polygenic component and simple effects of the covariates showed pulse pressure heritability of 0.21. When the single-locus component was added, the sex-specific and genotype-specific effects of age and body mass index were highly significant (P
<0.002). The full model accounted for 73% of the total variation of pulse pressure. Linkage analysis using this model with each marker revealed 4 markers with lod scores >1.9, which is the Lander-Kruglyak suggestive linkage standard.
D21S1440
had a lod score of 2.78 with a recombination fraction (θ) of 0.02.
D7S1799
had a lod score of 2.04 (θ=0.01),
D8S1100
had a lod score of 1.98 (θ=0.08), and
D18S844
had a lod score of 1.95 (θ=0.11). These results are highly correlated with results involving systolic blood pressure, indicating that pulse pressure may not be genetically distinct from systolic blood pressure.
p38 MAP Kinase Regulates Vascular Smooth Muscle Cell Collagen Synthesis by Angiotensin II in SHR But Not in WKY
Authors: Touyz Rhian M. , He Gang , El Mabrouk Mohammed , Schiffrin Ernesto L.
Published: June 2012

Vascular remodeling in hypertension is associated with cell growth and increased deposition of extracellular matrix components, particularly collagen. Mechanisms underlying these processes are unclear, but MAP kinases, particularly ERK1/2 and p38 MAP kinase, may be important. We studied the role of ERK1/2 and p38 MAP kinase in vascular smooth muscle cell (VSMC) collagen synthesis and growth mediated by angiotensin (Ang) II in spontaneously hypertensive rats (SHR). Cultured mesenteric VSMC from Wistar-Kyoto rats and SHR were used. Phosphorylation of ERK1/2 and p38 MAP kinase were assessed by Western blots with phosphospecific antibodies. Ang II–stimulated DNA and collagen synthesis were determined by measuring incorporation of
3
H-thymidine and
3
H-proline, respectively. mRNA expression of procollagen I and III was determined by reverse transcription–polymerase chain reaction. Ang II increased ERK1/2 and p38 MAP kinase phosphorylation. Responses were augmented in SHR. Effects were inhibited by irbesartan, a selective AT
1
antagonist, but not by PD123319, a selective AT
2
blocker. Ang II stimulated
3
H-thymidine and
3
H-proline incorporation. These actions were enhanced 2- to 3-fold in SHR. PD98059, selective inhibitor of the ERK1/2 pathway, attenuated Ang II–induced growth and collagen effects and normalized responses in SHR. SB212190, a selective p38 MAP kinase inhibitor, did not alter Ang II–elicited DNA synthesis but reduced collagen production and mRNA expression of procollagen I and III in SHR. These data demonstrate that (1) Ang II–mediated activation of p38 and ERK1/2 is increased in SHR, (2) augmented growth responses are generated by ERK1/2-dependent, p38 MAP kinase-independent pathways, and (3) p38 MAP kinase influences Ang II–induced collagen production in SHR but not in Wistar-Kyoto rats. These results indicate differential roles of ERK1/2 and p38 MAP kinase in AT
1
-stimulated VSMC growth and collagen production, which may contribute to vascular remodeling in hypertension.
Mitogenic and Antiapoptotic Actions of Hepatocyte Growth Factor Through ERK, STAT3, and Akt in Endothelial Cells
Authors: Nakagami Hironori , Morishita Ryuichi , Yamamoto Kei , Taniyama Yoshiaki , Aoki Motokuni , Matsumoto Kunio , Nakamura Toshikazu , Kaneda Yasufumi , Horiuchi Masatsugu , Ogihara Toshio
Published: June 2012

Hepatocyte growth factor (HGF), a member of the angiogenic growth factors, may play a pivotal role in the regulation of endothelial cells, inasmuch as HGF shows mitogenic and antiapoptotic actions in endothelial cells. Because the mechanism of these actions is still unclear, we examined the signal transduction system of HGF in human aortic endothelial cells. Treatment of endothelial cells with recombinant HGF (rHGF) resulted in a significant increase in DNA synthesis as assessed by thymidine incorporation. Importantly, phosphorylation of extracellular signal–related kinase (ERK) and Akt by rHGF was clearly observed. Thus, we further examined the effects of specific inhibitors of ERK or Akt on cell proliferation. Pretreatment with PD98059, a mitogen-activated protein kinase kinase inhibitor, significantly attenuated cell proliferation induced by rHGF, whereas inhibitors of phosphatidylinositol-3-OH kinase, wortmannin, and LY-294002, did not. Interestingly, treatment with rHGF significantly increased the phosphorylation of the signal transducers and activators of transcription (STAT)3 (Ser727), whereas PD98059 attenuated the phosphorylation of Ser727 induced by rHGF. In addition, treatment with rHGF significantly increased the promoter activity of c-fos
, which includes the
sis
-inducible element and serum response element, whereas PD98059 completely attenuated the activation of the c-
fos
promoter induced by rHGF. In contrast, inhibition of Akt by wortmannin and LY-294002 failed to inhibit the phosphorylation of STAT3 and c-
fos
activation. On the other hand, treatment with rHGF attenuated the increase in LDH release and caspase-3 activity induced by tumor necrosis factor-α stimulation. In contrast to DNA synthesis, wortmannin and LY-294002 markedly attenuated the decrease in caspase-3 activity mediated by rHGF, whereas PD98059 did not. Overall, the present study demonstrated that HGF stimulated cell proliferation through the ERK-STAT3 (Ser727) pathway and had an antiapoptotic action through the phosphatidylinositol-3-OH kinase–Akt pathway in human aortic endothelial cells. These findings provide new perspectives in the role of HGF in cardiovascular disease.
Workshop:
Mechanisms and Cardiovascular Damage in Hypertension
Authors: Luft Friedrich C.
Published: June 2012

Angiotensin (Ang) II is considered a regulatory hormone stimulating vascular smooth muscle cell constriction, aldosterone release from the adrenal gland, and sodium reabsorption in the renal tubule. Furthermore, Ang II may be formed and act locally as a chemokine, inducing tyrosine phosphorylation, cell growth, hypertrophy, and differentiation. In addition, evidence has recently accrued showing that Ang II is important in stimulating the production of reactive oxygen species and the activation of ancient inflammatory mechanisms. The transcription factor nuclear factor κ-B is pivotal to these processes. Nuclear factor κ-B activation stimulates the expression of a gene menagerie important to chemoattraction, surface adhesion molecule expression, coagulation, and inflammation. Anti-inflammatory interventions may have therapeutic utility.
20-Hydroxyeicosatetraenoic Acid Mediates Angiotensin II–Induced Phospholipase D Activation in Vascular Smooth Muscle Cells
Authors: Parmentier Jean-Hugues , Muthalif Mubarack M. , Nishimoto Andrew T. , Malik Kafait U.
Published: June 2012

Angiotensin II (Ang II) activates cytosolic phospholipase A
2
(cPLA
2
) and phospholipase D (PLD) in rabbit vascular smooth muscle cells (VSMCs). Ang II also activates ras/mitogen-activated protein (MAP) kinase in VSMCs; this activation is mediated by 20-hydroxyeicosatetraenoic acid (HETE) and 12(S)-HETE, which are metabolites of arachidonic acid generated by cytochrome P450 4A and lipoxygenase, respectively, produced on activation of cPLA
2
. The purpose of this study was to determine if Ang II–induced PLD activation in VSMCs is mediated through the ras/extracellular signal-regulating kinase (ERK) pathway by arachidonic acid metabolites that are generated consequent to cPLA
2
stimulation. Inhibitors of PLD (C
2
ceramide), phosphatidate phosphohydrolase (propranolol), and diacylglycerol lipase (RHC 80267) attenuated Ang II–induced arachidonic acid release. Ang II–induced PLD activation, as measured by [
3
H]phosphatidylethanol production, was inhibited by C
2
ceramide but not by propranolol or RHC 80267. Ang II–induced PLD activation was decreased by the inhibitor methyl arachidonylfluorophosphate (MAFP) and the antisense oligonucleotide of cPLA
2
. Inhibitors of lipoxygenases (baicalein) and cytochrome P450 4A (ODYA) attenuated Ang II–induced PLD activation. 20-HETE and 12(S)-HETE increased PLD activity. Inhibitors of ras farnesyltransferase (FPT III and BMS-191563) and MAP kinase kinase (UO126) attenuated the increase in PLD activity elicited by 20-HETE and Ang II. PLD2 was the main isoform activated by Ang II in VSMCs. These data suggest that the CYP4A metabolite 20-HETE, which is generated from arachidonic acid after cPLA
2
activation by Ang II, stimulates the ras/MAP kinase pathway, which in turn activates PLD2 and releases further arachidonic acid for prostaglandin synthesis through the phosphatidate phosphohydrolase/diacylglycerol lipase pathway.
Angiotensin II Signaling to Phospholipase D in Renal Microvascular Smooth Muscle Cells in SHR
Authors: Andresen Bradley T. , Jackson Edwin K. , Romero Guillermo G.
Published: June 2012

Angiotensin II (Ang II)–induced phospholipase D (PLD) activity is greater in aortic smooth muscle from spontaneously hypertensive rats (SHR) versus normotensive Wistar-Kyoto rats (WKY). Whether and how this signaling pathway is altered in preglomerular microvascular smooth muscle cells (PGSMCs), a cell type that may participate in genetic hypertension, is unknown. The goals of the present study were to determine in SHR and WKY PGSMCs the following: (1) whether Ang II induces PLD activity; (2) whether the effect of Ang II on PLD activity is greater in SHR; (3) which PLD isoform is stimulated by Ang II; (4) what signaling pathway mediates Ang II–induced PLD stimulation; and (5) whether the signaling pathways mediating Ang II–induced PLD activity are different in SHR and WKY. The EC
50
for Ang II–induced PLD stimulation in SHR was 10-fold lower than the EC
50
in WKY, and both were inhibited by L-158,805, an AT
1
antagonist. Inhibitors of phosphoinositol-3-kinase and protein kinase C did not block Ang II–induced PLD activity in SHR and WKY PGSMCs. Catalytically-inactive constructs of PLD2 and RhoA, but not PLD1, ADP ribosylation factor 1 (ARF1), ARF6, or ADP ribosylation factor nucleotide exchange factor (ARNO) blocked Ang II–induced PLD activity in SHR and WKY PGSMCs. Brefeldin A completely blocked Ang II–induced PLD activity in SHR but only slightly reduced Ang II–induced PLD activity in WKY PGSMCs. Therefore, we conclude that in PGSMCs, the effect of Ang II on PLD activity is (1) greater in SHR; (2) mediated by AT
1
receptors signaling to PLD2; (3) transduced primarily by Rho proteins; and (4) inhibited in SHR by brefeldin A.
Estradiol Metabolites Inhibit Endothelin Synthesis by an Estrogen Receptor-Independent Mechanism
Authors: Dubey Raghvendra K. , Jackson Edwin K. , Keller Paul J. , Imthurn Bruno , Rosselli Marinella
Published: June 2012

Estradiol inhibits endothelin-1 synthesis, an effect that may contribute to the cardiovascular protective effects of estradiol. Recent findings that estradiol inhibits neointima formation in mice lacking estrogen receptors suggests that the cardiovascular protective effects of estradiol may be mediated by means of an estrogen receptor-independent mechanism. Because 2-hydroxyestradiol and 2-methoxyestradiol, metabolites of estradiol with little/no affinity for estrogen receptors, are more potent than estradiol in inhibiting vascular smooth muscle cell growth, we investigated whether these metabolites also inhibit endothelin-1 synthesis by means of an receptor-independent mechanism. Treatment of porcine coronary artery endothelial cells for 4 to 24 hours with 0.001 to 1 μmol/L of estradiol, 2-hydroxyestradiol, or 2-methoxyestradiol concentration-dependently inhibited basal as well as serum-induced (2.5%), TNFα-induced (10 ng/mL), angiotensin II–induced (100 nmol/L), and thrombin-induced (4 U/mL) endothelin-1 synthesis. Estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol also inhibited serum-induced mitogen-activated protein kinase activity. As compared with estradiol, its metabolites were more potent in inhibiting endothelin-1 secretion and mitogen activated protein kinase activity. The inhibitory effects of 2-hydroxyestradiol and 2-methoxyestradiol on endothelin-1 release and mitogen-activated protein kinase activity were not blocked by ICI182780 (50 μmol/L), an estrogen receptor antagonist. Our findings indicate that the estradiol metabolites 2-hydroxyestradiol and 2-methoxyestradiol potently inhibit endothelin-1 synthesis by means of an estrogen receptor-independent mechanism. This effect of estradiol metabolites may be mediated by inhibition of mitogen activated protein kinase activity and may contribute to the cardioprotective effects of estradiol.
Nerve Growth Factor Enhances Calcitonin Gene-Related Peptide Expression in the Spontaneously Hypertensive Rat
Authors: Supowit Scott C. , Zhao Huawei , DiPette Donald J.
Published: June 2012

Calcitonin gene–related peptide (CGRP) expression is markedly reduced in dorsal root ganglia neurons in the spontaneously hypertensive rat (SHR). This decrease in such a potent vasodilator may contribute to the elevated blood pressure. Therefore, the purpose of this study was to determine whether stimulation of neuronal CGRP expression in SHR, by means of the administration of nerve growth factor, would lower the blood pressure. Nerve growth factor (10 nmol/L per kg/d, IP) was given to 12-week SHR (n=8 to 11/group) once a day for 1, 3, and 7 days. Control SHR received vehicle only. All rats were instrumented for CGRP receptor antagonist (CGRP
8–37
) administration (intravenous) and mean arterial pressure recording. Both the 1- and 3-day NGF treatments lowered the mean arterial pressure to 147±5 and 147±3 mm Hg, respectively, compared with controls (166±3 mm Hg). However, by day 7, the mean arterial pressure had returned to control levels (169±5 mm Hg). CGRP
8–37
administration produced a significant mean arterial pressure increase in all 3 nerve growth factor–treated groups (14±2, 10±2, and 13±2 mm Hg). CGRP mRNA levels in dorsal root ganglia were increased in the 3 neurotrophin-treated groups, whereas CGRP peptide content was higher at days 3 and 7. Therefore, nerve growth factor treatment of SHR can enhance neuronal CGRP expression. At days 1 and 3, nerve growth factor produces a depressor response that is primarily mediated by CGRP as evidenced by the pressor effect of CGRP
8–37.
At day 7, CGRP also plays a counterregulatory role, even though the mean arterial pressure has returned to control levels. This finding may result from a nerve growth factor–mediated upregulation of a pressor system that counteracts the hypotensive actions of CGRP. Thus, these data suggest that the decreased production of CGRP in SHR could contribute to the hypertension.
Workshop: Excess Growth and Apoptosis
Authors: Hamet Pavel , Thorin-Trescases Nathalie , Moreau Pierre , Dumas Pierre , Tea Ben-Sung , deBlois Denis , Kren Vladimir , Pravenec Michal , Kunes Jaroslav , Sun Yulin , Tremblay Johanne
Published: June 2012

Several groups including ours have demonstrated cardiac hyperplasia in neonates from genetically hypertensive rat strains. We have shown that similar problems exist in the kidney as well. More recently, we found that excessive heart and kidney weight is neonatally related to inhibition of apoptosis. Using recombinant inbred strains derived from a reciprocal cross between Brown Norway and spontaneously hypertensive rat progenitor strains, we mapped the inhibition of neonatal apoptosis to 2 distinct loci on chromosomes 1 (Myl 2) and 18 (Abrb 2). Positional candidate genes at these loci are being explored. These studies have also demonstrated that the loci determining kidney and heart weights in neonates are distinct from those determining increased organ weight in adults. The impact of blood pressure per se is also divergent because adult kidney weight is negatively correlated whereas heart weight is positively correlated with it. Analyses by extremes of low and high percentiles from fetal life to adulthood identified a single locus determining heart weight at Acaa on chromosome 8 in newborn (
P
=0.0003) and adult (
P
=0.016) rats. The Acaa region contains a DNA mismatch repair gene (
hMLH1
). The kinetics of neonatal growth through adulthood by prelabeling DNA with [
3
H]thymidine in pregnant mares showed that although the growth process is complex and nonlinear in the kidney of hypertensive rats, there is an increased turnover of cells, that is, reduced half-life of DNA. This observation is supported by the presence of shorter telomere fragments in kidneys of spontaneously hypertensive rats. These studies suggest that cardiovascular cells from hypertensive animals are subject to accelerated turnover, potentially leading to their accelerated aging.
Angiotensinogen Polymorphisms and Elevated Blood Pressure in the General Population
Authors: Sethi Amar A. , Nordestgaard Børge G. , Agerholm-Larsen Birgit , Frandsen Erik , Jensen Gorm , Tybjærg-Hansen Anne
Published: June 2012

In the present study, we tested the hypothesis that the Met235Thr and Thr174Met mutations were associated or not with elevated blood pressure. We genotyped 9100 women and men from the Danish general population, of whom 54% had elevated blood pressure. Of the 9100, 41% and 12% carried the Thr235 and Met174 mutations, respectively; the Met174 mutation always occurred on the same allele as the Thr235 mutation. On multifactorial logistic regression analysis, women homozygous for Thr235 versus noncarriers had an odds ratio for elevated blood pressure of 1.29 (95% CI 1.05 to 1.58), which increased to 1.50 (1.15 to 1.96) if they also were homozygous for Thr174 (noncarrier of Met174). Women homozygous for Thr235 also had an increased risk of isolated elevated systolic blood pressure (1.37; 1.02 to 1.84) and of mild blood pressure elevation (1.40; 1.10 to 1.77). We found no statistically significant association between elevated blood pressure and genotype in men or among genotype and systolic blood pressure, diastolic blood pressure, or pulse pressure in either gender. Homozygosity for both Thr235 and Thr174 was associated with a 10% increase in plasma angiotensinogen levels in both genders compared with homozygosity for Met235 and Thr174; however, systolic and diastolic blood pressures were positively correlated to plasma angiotensinogen levels in women only. In conclusion, in this large-scale study of the general population, double homozygosity for Thr235 and Thr174 in the angiotensinogen gene is associated with a 10% increase in angiotensinogen levels and is a risk factor for elevated blood pressure in women but not in men.
Early Alteration in Glomerular Reserve in Humans at Genetic Risk of Essential Hypertension
Authors: O’Connor Daniel T. , Tyrell Elizabeth A. , Kailasam Mala T. , Miller Lucy M. , Martinez Joseph A. , Henry Robert R. , Parmer Robert J. , Gabbai Francis B.
Published: June 2012

Essential hypertension has a familial predisposition, but the phenotype of elevated blood pressure has delayed penetrance. Because the kidney is a crucial determinant of blood pressure homeostasis, we studied early glomerular alterations in still-normotensive young subjects at genetic risk of hypertension. Thirty-nine normotensive adults (mean age 29 to 31 years), stratified by genetic risk (parental family history [FH]) of hypertension (26 with positive FH [FH+], 13 with negative FH [FH−]), underwent intravenous infusion of mixed amino acids. Before and during amino acid administration, we measured glomerular filtration rate (GFR), putative second messengers of amino acids (nitric oxide [NO·] metabolites and cGMP), serum insulin and amino acid concentrations, and the FE
Li
+ as an index of renal proximal tubular reabsorption. The FH+ group had a blunted GFR rise in response to amino acids (2.43±8.16% versus 31.0±13.4% rise,
P
=0.0126). The amino acid–induced change in GFR correlated (
r
=0.786,
P
<0.01) with the change in urinary NO· metabolite excretion; a diminished rise in urinary NO· metabolite excretion in the FH+ group (
P
=0.0105) suggested a biochemical mechanism for the different GFR responses between FH groups: a relative inability to convert arginine to NO·. The FH+ group had a far lower initial cGMP excretion at baseline (261±21.1 versus 579±84.9 nmol · h
−1
/1.73 m
2
,
P
=0.001), although cGMP did not change during the amino acid infusion (
P
=0.703). FH status, baseline GFR, and baseline serum insulin jointly predicted GFR response to amino acids (
P
=0.0013), accounting for ≈45% of the variance in GFR response. Decline in FE
Li
+, an inverse index of proximal tubular reabsorption, paralleled increase in GFR (
r
=−0.506,
P
=0.01), suggesting differences in proximal tubular reabsorption during amino acids between the FH groups. GFR response to amino acid infusion was blunted in the FH+ group despite significantly higher serum concentrations of 6 amino acids (arginine, isoleucine, leucine, methionine, phenylalanine, and valine) in the FH+ group, suggesting a novel form of insulin resistance (to the amino acid–translocating action of insulin) in FH+ subjects. We conclude that blunted glomerular filtration reserve in response to amino acids is an early-penetrance phenotype seen even in still-normotensive subjects at genetic risk of hypertension and is linked to impaired formation of NO· in the kidney. Corresponding changes in GFR and fractional excretion of Li
+
suggest that altered proximal tubular reabsorption after amino acids is an early pathophysiologic mechanism. Resistance to the amino acid–translocating actions of insulin may play a role in the biological response to amino acids in this setting. This glomerular reserve phenotype may be useful in genetic studies of renal traits preceding or predisposing to hypertension.
Effect of Valsartan on Angiotensin II–Induced Plasminogen Activator Inhibitor-1 Biosynthesis in Arterial Smooth Muscle Cells
Authors: Sironi Luigi , Calvio Anna Maria , Arnaboldi Lorenzo , Corsini Alberto , Parolari Alessandro , de Gasparo Marc , Tremoli Elena , Mussoni Luciana
Published: June 2012

Previous studies have shown that angiotensin II stimulates the synthesis of plasminogen activator inhibitor-1 in cultured vascular cells, which suggests that activation of the renin-angiotensin system may impair fibrinolysis. We have investigated the effects of angiotensin II and of valsartan, a recently developed angiotensin II antagonist that is highly specific and selective for the angiotensin II subtype 1 receptor, on plasminogen activator inhibitor-1 secretion by smooth muscle cells isolated from rat and human vessels. Angiotensin II induced a time- and concentration-dependent increase of plasminogen activator inhibitor activity in supernatants of rat aortic cells, which reached a plateau after 6 hours of incubation with 100 nmol/L angiotensin II (2.4±0.6-fold over control value;
P
<0.001). The angiotensin II–induced plasminogen activator inhibitor activity was inhibited, in a concentration-dependent manner, by valsartan with an IC
50
value of 21 nmol/L. Valsartan fully prevented the angiotensin II–induced increase in plasminogen activator inhibitor-1 protein and mRNA. Furthermore, angiotensin II doubled the secretion of plasminogen activator inhibitor-1 by smooth muscle cells obtained from human umbilical and internal mammary arteries, and valsartan fully prevented it. Angiotensin II did not affect the secretion of tissue plasminogen activator antigen by any of the cell systems tested. Thus, valsartan effectively inhibits angiotensin II–induced plasminogen activator inhibitor-1 secretion without affecting that of tissue plasminogen activator in arterial rat and human smooth muscle cells.
Angiotensin II–Induced Hypertension in Bradykinin B
2
Receptor Knockout Mice
Authors: C̆ervenka Ludĕk , Malý Jan , Karasová Ludmila , Šimová Marcela , Vítko Štefan , Hellerová Son̆a , Heller Jir̆í , El-Dahr Samir S.
Published: June 2012

The present study was performed to examine the role of endogenous bradykinin (BK) in the development of angiotensin II (Ang II)–induced hypertension in mice. BK B
2
receptor knockout (B
2
R
−/−
) and wild-type (B
2
R
+/+
) mice (22 to 26 g) were infused with either saline (SAL) or Ang II (40 ng/min) via an osmotic minipump implanted intraperitoneally. On day 12 after implantation, there was no difference in systolic blood pressure (SBP, tail-cuff plethysmography) between SAL/B
2
R
+/+
and SAL/B
2
R
−/−
mice (128±5 versus 133±6 mm Hg, n=24/group). In contrast, SBP was higher on day 12 of infusion in Ang II/B
2
R
−/−
than in Ang II/B
2
R
+/+
mice (173±6 versus 156±5 mm Hg;
P
<0.05, n=27 and 28). Mean arterial pressure (MAP) was also higher in anesthetized Ang II/B
2
R
−/−
mice than in Ang II/B
2
R
+/+
mice (139±3 versus 124±3 mm Hg;
P
<0.05, n=16 and 14). Unlike Ang II, long-term norepinephrine (NE) infusion via an osmotic minipump (45 ng/min) caused equivalent increases in SBP in B
2
R
+/+
and B
2
R
−/−
mice measured on day 12 after implantation (151±4 versus 149±5 mm Hg, n=9 and 8). MAP also did not differ on day 13 after implantation between NE/B
2
R
+/+
and NE/B
2
R
−/−
mice (120±6 versus 122±4 mm Hg, n=9 and 8). There were no differences in glomerular filtration rate and urinary sodium excretion among the groups. However, renal plasma flow (RPF) was lower in Ang II/B
2
R
−/−
mice than in Ang II/B
2
R
+/+
mice (2.34±0.06 versus 4.33±0.19 mL · min
−1
· g
−1
;
P
<0.05). Acute inhibition of NO synthase (NOS) with nitro-
l
-arginine-methyl ester (0.5 μg · g
−1
· min
−1
) in SAL/B
2
+/+
and SAL/B
2
−/−
mice caused equal increases in MAP (142±1 versus 145±1 mm Hg) and decreases in RPF (2.06±0.06 versus 2.12±0.15 mL · min
−1
· g
−1
). However, short-term NOS inhibition caused a greater increase in MAP of Ang II/B
2
R
+/+
mice than of Ang II/B
2
R
−/−
mice, such that MAP after NOS inhibition in Ang II/B
2
R
+/+
approached that of Ang II/B
2
R
−/−
mice (156±2 versus 159±2 mm Hg). These changes were associated with a decrease in RPF in Ang II/B
2
R
+/+
mice to values similar to those of Ang II/B
2
R
−/−
mice before NOS inhibition (2.12±0.09 versus 2.34±0.06 mL · min
−1
· g
−1
). These results demonstrate that the kallikrein-kinin system selectively buffers the vasoconstrictor activity of Ang II. Furthermore, the enhanced susceptibility of B
2
R
−/−
mice to Ang II–induced hypertension and renal vasoconstriction is likely due to an impaired ability to release NO by endogenous kinins.
Abnormal Platelet Function and Calcium Handling in Dahl Salt-Hypertensive Rats
Authors: Li Yun , Adachi Takeshi , Bolotina Victoria M. , Knowles Cathy , Ault Kenneth A. , Cohen Richard A.
Published: June 2012

Abstract
—The effect of dietary salt on platelet function and Ca
2+
homeostasis was studied in Dahl (DS) rats, a genetic model of salt-sensitive hypertension. DS rats were fed a high-salt (DSHS) or a low-salt diet (DSLS) for up to 4 weeks, and the effects of salt loading on systolic blood pressure, platelet P-selectin expression, and platelet Ca
2+
homeostasis were measured. The high-salt diet increased blood pressure and markedly increased the amount of ionomycin (IM)-releasable Ca
2+
in platelet intracellular stores (Ca
2+
/IM). The alteration in Ca
2+
stores was not prevented when the hypertension was prevented by treatment with hydralazine and reserpine. The Ca
2+
store filling during platelet exposure to 1 mmol/L Ca
2+
for 5 minutes and the rate of sarcoplasmic/endoplasmic Ca
2+
ATPase–dependent Ca
45
uptake were higher in DSHS compared with that in DSLS. There was a decrease in thrombin-induced Ca
2+
influx in platelets from DSHS; consistent with this, agonist-induced P-selectin expression was decreased. In DSLS, nitric oxide accelerated reloading of platelet Ca
2+
stores after their emptying by thrombin but failed to do so in DSHS. These results indicate that in DS rats, a high-salt diet increases sarcoplasmic/endoplasmic Ca
2+
ATPase activity and the Ca
2+
/IM but decreases the reuptake of Ca
2+
caused by nitric oxide. Decreases in Ca
2+
influx and platelet P-selectin expression might be explained by changes in intracellular Ca
2+
stores in DSHS rats, which apparently is a heritable response to a high-salt diet.
Dynamic Analysis of Renal Nerve Activity Responses to Baroreceptor Denervation in Hypertensive Rats
Authors: DiBona Gerald F. , Jones Susan Y.
Published: June 2012

Abstract
—Sinoaortic and cardiac baroreflexes exert important control over renal sympathetic nerve activity. Alterations in these reflex mechanisms contribute to renal sympathoexcitation in hypertension. Nonlinear dynamic analysis was used to examine the chaotic behavior of renal sympathetic nerve activity in normotensive Sprague-Dawley and Wistar-Kyoto rats and spontaneously hypertensive rats before and after complete baroreceptor denervation (sinoaortic and cardiac baroreceptor denervation). The peak interval sequence of synchronized renal sympathetic nerve discharge was extracted and used for analysis. In all rat strains, this yielded systems whose correlation dimensions converged to similar low values over the embedding dimension range of 10 to 15 and whose greatest Lyapunov exponents were positive. In Sprague-Dawley and Wistar-Kyoto rats, compete baroreceptor denervation was associated with decreases in the correlation dimensions (Sprague-Dawley: 2.42±0.04 to 2.16±0.04; Wistar-Kyoto: 2.44±0.04 to 2.34±0.04) and in the greatest Lyapunov exponents (Sprague-Dawley: 0.199±0.004 to 0.130±0.015; Wistar-Kyoto: 0.196±0.002 to 0.136±0.010). Spontaneously hypertensive rats had a similar correlation dimension, which was unaffected by complete baroreceptor denervation (2.42±0.02 versus 2.42±0.03), and a lower value for the greatest Lyapunov exponent, which decreased to a lesser extent after complete baroreceptor denervation (0.183±0.006 versus 0.158±0.006). These results indicate that removal of sinoaortic and cardiac baroreceptor regulation of renal sympathetic nerve activity is associated with a greater decrease in the chaotic behavior of renal sympathetic nerve activity in normotensive compared with hypertensive rats. This suggests that the central neural mechanisms that regulate renal sympathetic nerve activity in response to alterations in cardiovascular reflex inputs are different in spontaneously hypertensive rats from those in Sprague-Dawley and Wistar-Kyoto rats.
C-Type Natriuretic Peptide–Induced Vasodilation Is Dependent On Hyperpolarization in Human Forearm Resistance Vessels
Authors: Honing Marina L. H. , Smits Paul , Morrison Paul J. , Burnett John C. , Rabelink Ton J.
Published: June 2012

Abstract
—Animal studies have demonstrated that CNP causes endothelium-independent vasodilation, which is limited by neutral endopeptidase (NEP) activity. However, the vasodilating mechanism of CNP in humans is still unknown. Therefore, we investigated the vasodilator actions of CNP in human forearm resistance vessels before and after inhibition of nitric oxide (NO) and then prostacyclin production and after inhibition of Ca
2+
-dependent potassium channel activation and NEP activity. Three separate studies were performed. In each study, forearm blood flow was recorded by venous occlusion plethysmography in 8 healthy nonsmoking subjects. Brachial artery infusion of CNP (70, 140, 280, and 560 ng per 100 mL forearm volume per minute) caused significant forearm vasodilation in all studies (forearm blood flow from 3.94 to 8.50 mL per 100 mL forearm volume per minute). Inhibition of the endogenous generation of NO by
l
-
N
G
-monomethyl arginine (by use of the NO-clamp technique) did not block the maximal vasodilating effects of CNP (forearm blood flow from 3.69 to 6.93). In addition, when the cyclooxygenase system was inhibited by 600 mg of acetylsalicylic acid (aspirin) administered orally 30 minutes before start of measurements, the rise in forearm blood flow remained intact (forearm blood flow from 3.31 to 8.27 mL per 100 mL forearm volume per minute). However, inhibition of Ca
2+
-dependent potassium channels with tetraethylammonium chloride (0.1 mg per 100 mL forearm volume per minute) significantly attenuated vasodilation caused by CNP (forearm blood flow from 2.28 to 3.06 mL per 100 mL forearm volume per minute), which suggests that CNP opens vascular potassium channels. Vasodilation to all doses of CNP was significantly increased when activity of NEP was blocked with thiorphan (30 nmol/min), which suggests that NEP activity limits vasodilation of CNP. CNP is a dilator of human resistance vessels that mediates its effects through hyperpolarization of the vessel wall independent of the NO and prostaglandin system. Inhibition of local NEP activity increases CNP bioavailability. This may be of relevance to cardiovascular disease, given that vascular tone is well balanced between NO and an endothelium-derived hyperpolarizing factor, which suggests that in pathological situations, impaired NO activity can be compensated for by enhanced endothelium-derived hyperpolarizing factor release to maintain vascular homeostasis.
8-iso-Prostaglandin F
2α
Increases Expression of LOX-1 in JAR Cells
Authors: Halvorsen Bente , Staff Anne Cathrine , Henriksen Tore , Sawamura Tatsuya , Ranheim Trine
Published: June 2012

Abstract
—Lectinlike oxidized LDL receptor-1 (LOX-1), a cell-surface receptor for oxidized LDL (ox-LDL), is proposed to be involved in endothelial dysfunction and in the pathogenesis of atherosclerosis. Preeclampsia is a pregnancy complication diagnosed by hypertension and proteinuria, characterized by endothelial dysfunction, and supposedly caused by compounds from hypoxic uteroplacental tissues. A feature of preeclampsia is formation of foam cells in maternal arterial walls of gestational tissue (“acute atherosis”). Oxidative stress is believed to play a role in the pathophysiology of preeclampsia. 8-iso-prostaglandin F
2α
(8-iso-PGF
2α
) is a marker of oxidative stress in vivo, is biologically active in vitro, and is elevated in preeclamptic plasma and gestational tissue. In the present article, we hypothesized that 8-iso-PGF
2α
could induce the expression of LOX-1 in trophoblastic cells (JAR). We demonstrated augmented cellular uptake of
125
I-tyraminylcellobiose ox-LDL in JAR cells incubated with 8-iso-PGF
2α
(10 μmol/L) versus control cells. Ligand blots revealed an increased binding of ox-LDL to LOX-1 in JAR cells incubated with 8-iso-PGF
2α
(10 μmol/L). Incubation with 8-iso-PGF
2α
(10 μmol/L) also resulted in augmented LOX-1 protein levels (Western blots) and mRNA levels (Northern blots). JAR cells transfected with 3 copies of a nuclear factor-κB binding site demonstrated dose-dependent activation of the reporter gene luciferase after incubation with 8-iso-PGF
2α
(0 to 10 μmol/L). We also demonstrated increased accumulation of neutral fats in JAR cells incubated with 8-iso-PGF
2α
(10 μmol/L) and ox-LDL compared with controls by oil red O staining. We speculate a potential role of isoprostanes and LOX-1 in preeclampsia in the development of “acute atherosis” of gestational spiral arteries.
Aortic Root Dilatation at Sinuses of Valsalva and Aortic Regurgitation in Hypertensive and Normotensive Subjects
Authors: Palmieri Vittorio , Bella Jonathan N. , Arnett Donna K. , Roman Mary J. , Oberman Albert , Kitzman Dalane W. , Hopkins Paul N. , Paranicas Mary , Rao D. C. , Devereux Richard B.
Published: June 2012

Abstract
—The association of sinuses of Valsalva dilatation and aortic regurgitation with hypertension is disputed, and few data are available in population-based samples. We explored the relations of sinuses of Valsalva dilatation and aortic regurgitation to hypertension and additional clinical and echocardiographic data in 2096 hypertensive and 361 normotensive participants in the Hypertension Genetic Epidemiology Network study. Age and body surface area were used to predict aortic root diameter using published equations developed from a separated reference population. Aortic dilatation was defined as measured sinuses of Valsalva diameter exceeding the 97.5th percentile of the confidence interval of predicted diameter for age and body size. Aortic dilatation was present in 4.6% of the population. After adjustment for age and body surface area, mean aortic root diameter was larger in hypertensives with suboptimal blood pressure control than normotensives or hypertensives with optimal blood pressure control. In multivariate models, sinuses of Valsalva diameter was weakly positively related to diastolic blood pressure and to left ventricular mass independent of aortic regurgitation. Subjects with aortic dilatation were slightly older, were more frequently men, had higher left ventricular mass, and had lower left ventricular systolic chamber function independent of covariates. Sinuses of Valsalva dilatation was independently related to male gender, aortic valve fibrocalcification, and echocardiographic wall motion abnormalities but not to diastolic blood pressure (or history of hypertension in a separate model). The likelihood of aortic regurgitation increased with larger aortic root diameter, older age, female gender, presence of aortic valve fibrocalcification, and lower body mass index but not hypertension or diabetes. In a subsequent model, diastolic blood pressure was negatively related to aortic regurgitation independent of covariates. In a large population-based sample, sinuses of Valsalva diameter was only mildly larger in subjects with suboptimally controlled hypertension than in normotensives or well-controlled hypertensives, which did not result in differences in prevalence of aortic regurgitation among groups. Sinuses of Valsalva dilatation was associated with higher left ventricular mass and lower systolic function, which may contribute to higher cardiovascular risk in subjects with aortic root dilatation.
Cardiovascular Mortality in Hypertensive Men According to Presence of Associated Risk Factors
Authors: Thomas Frédérique , Rudnichi Annie , Bacri Anne-Marie , Bean Kathryn , Guize Louis , Benetos Athanase
Published: June 2012

Abstract
—To evaluate the risk of cardiovascular disease (CVD) mortality in hypertensive men according to the presence of associated risk factors (ARFs). The population was composed of 29 640 normotensive men without ARFs (reference group) and 60 343 hypertensive men (with and without ARFs) who had a standard health checkup at the Centre d’Investigations Préventives et Cliniques between 1978 and 1988. Mortality data for a mean period of 14 years were analyzed. The following ARFs were considered: total cholesterol ≥2.5 g/L, personal history of diabetes, smoking (current smokers), body mass index >28 kg/m
2
, and heart rate >80 bpm. CVD risk related to the presence of isolated hypertension (assessed in hypertensive subjects without ARFs versus the reference group) increased linearly from 15% at the age of 30 years to 134% at the age of 80 years. In hypertensive subjects, one additional ARF increased CVD risk by 56% (47% to 65%,
P
<0.01) in younger subjects but only by 4% (−8% to 17%,
P
=NS) in older subjects. The role of hypercholesterolemia and tobacco smoking in CVD mortality was significantly higher in hypertensive subjects aged <55 years than in hypertensive subjects aged ≥55 years (
P
<0.01), whereas the roles of tachycardia and obesity were not affected by age. In younger hypertensive subjects, evaluation of CVD risk and therapeutic strategies should target ARFs. In older subjects, the presence of high blood pressure levels seems to be the major determinant of CVD risk.
Selective Inhibition of the Renal Angiotensin Type 2 Receptor Increases Blood Pressure in Conscious Rats
Authors: Moore Allan F. , Heiderstadt Nicolas T. , Huang Esther , Howell Nancy L. , Wang Zhi-Qin , Siragy Helmy M. , Carey Robert M.
Published: June 2012

Abstract
—The angiotensin II type 2 (AT
2
) receptor is present in rat kidney; however, its function is not well understood. The purpose of this study was to evaluate the role of the AT
2
receptor in blood pressure (BP) regulation. The effects of selective inhibition of the renal AT
2
receptor with phosphorothioated antisense oligodeoxynucleotide (AS-ODN) were examined in conscious uninephrectomized rats. Oligodeoxynucleotides (AS-ODN or scrambled [S-ODN]) were infused directly into the renal interstitial space by using an osmotic pump at 1 μL/h for 7 days. Texas red–labeled AS-ODN was distributed in renal tubules in the infused but not the contralateral kidney of normal rats. Continuous renal interstitial infusion of the AS-ODN, but not S-ODN, caused a significant (
P
<0.01) increase in BP 1 to 5 days after the initiation of the infusion. AS-ODN–treated rats experienced an increase in systolic BP from 109±4 to 130±4 mm Hg (n=8,
P
<0.01), whereas S-ODN–treated (n=8) and vehicle-treated (n=8) rats did not show any significant change in BP. On day 5 of the oligodeoxynucleotide infusion, AS-ODN–treated rats exhibited a greater pressor response to systemic angiotensin II infusion (30 ng/kg per hour) than did S-ODN–treated rats (
P
<0.01). Renal interstitial fluid cGMP decreased from 11.9±0.8 to 3.6±0.5 pmol/mL (
P
<0.001), and bradykinin decreased from 0.05±0.05 to 0.18±0.03 ng/mL (
P
<0.001) in response to AS-ODN, but they were not significantly changed in response to S-ODN. To evaluate the effects of AS-ODN and S-ODN on AT
2
receptor expression, Western Blot analysis was performed on treated kidneys. Kidneys treated with AS-ODN had ≈40% less expression of AT
2
receptor than did kidneys treated with S-ODN or vehicle (
P
<0.05). These results suggest that AS-ODN directed selectively against the renal AT
2
receptor decreased receptor expression and caused an increase in BP. We conclude that the renal AT
2
receptor plays an important role in the regulation of BP via a bradykinin/cGMP vasodilator signaling cascade.
AT
1
Antisense Distinguishes Receptors Mediating Angiotensin II Actions in Solitary Tract Nucleus
Authors: Diz Debra I. , Westwood Brian , Averill David B.
Published: June 2012

Abstract
—Angiotensin (Ang) II receptors in the solitary tract nucleus (nTS) are located on vagal sensory-afferent fiber terminals as well as on neuronal cell bodies. Results from in vitro slice preparations indicate that ≈50% of the neuronal excitatory actions of Ang II result from actions at presynaptic receptors. The differential contribution of actions on fiber terminals versus neuronal cell soma to the cardiovascular effects of Ang II in the nTS is not known. We used antisense oligonucleotides to the angiotensin type 1 (AT
1
) receptor, which should reduce receptors on neurons within the injection site but not those on fiber terminals projecting to the nTS. Ang II injections (250 fmol/30 nL) into the nTS reduced blood pressure by 14±1 mm Hg and heart rate by 13±1 bpm (n=8) in male Sprague-Dawley rats anesthetized with chloralose/urethane. Although there was still a significant fall in pressure that was induced by Ang II at 90 and 150 minutes after AT
1
antisense (164 pmol/120 nL) was injected into the nTS, the response was blunted 50% (
P
<0.01). Heart rate responses were completely blocked at the 150-minute time point. Scrambled sequence oligonucleotides did not alter Ang II responses at any time. There was a 40% reduction in
125
I[Sar
1
Thr8]-Ang II binding when antisense-injected and noninjected sides of the nTS were compared with receptor autoradiography. This finding is consistent with the continued presence of AT
1
receptors on afferent fibers. This unique strategy illustrates that both presynaptic fiber terminals and nTS neurons are involved in the blood pressure lowering actions of Ang II, whereas heart rate responses are largely due to actions directly on nTS neurons and activation of vagal efferent pathways.
Role of Brain Angiotensin II on Somatosensory-Induced Antinatriuresis in Hypertensive Rats
Authors: Huang Chunlong , Johns Edward J.
Published: June 2012

Abstract
—The aim of this investigation was to compare the contribution of brain angiotensin II in mediating the transmission of a somatosensory stimulus within the brain to generate a renal sympathetic nerve–dependent antidiuresis and antinatriuresis in normotensive Wistar rats and stroke-prone spontaneously hypertensive rats (SHRSP). In anesthetized Wistar rats, stimulation of somatosensory receptors by subcutaneous capsaicin increased blood pressure by 9%, had no effect on renal hemodynamics, but decreased urinary flow and sodium excretion by 30% to 40%. These antidiuretic and antinatriuretic, but not blood pressure, responses were absent after intracerebroventricular losartan administration to block angiotensin II type 1 receptors. By contrast, in the SHRSP, although subcutaneous capsaicin raised blood pressure and renal blood flow, neither glomerular filtration rate, urinary flow, nor sodium excretion changed, and this pattern of responses was unaffected after intracerebroventricular losartan. However, an intracerebroventricular infusion of angiotensin II increased basal blood pressure and fluid output, and the capsaicin challenge elicited vasopressor, antidiuretic, and antinatriuretic responses similar in magnitude to those observed in the Wistar rats. The capsaicin challenge in the SHRSP also caused a slowly developing, long-lasting fall in blood pressure and fluid excretion. These findings show that angiotensin II is a necessary component in the somatorenal reflex in normotensive rats but that endogenous angiotensin II is unable to exert this role in SHRSP.
Effects of an Angiotensin-Converting Enzyme Inhibitor and a β-Blocker on Cerebral Arteriolar Dilatation in Hypertensive Rats
Authors: Chillon Jean-Marc , Baumbach Gary L.
Published: June 2012

Abstract
—We examined the effects of the angiotensin-converting enzyme inhibitor perindopril and the β-blocker propranolol on dilator responses of cerebral arterioles in chronic hypertension. Dilator responses to acute hypotension were examined in untreated Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) that were untreated or treated for 3 months with a low (0.3 mg · kg
−1
· day
−1
) or a high (2 mg · kg
−1
· day
−1
) dose of perindopril or a dose of propranolol (250 mg · kg
−1
· day
−1
) alone or in combination with the low dose of perindopril. Pressure (servo-null) and diameter were measured in cerebral arterioles during acute reductions in arterial pressure both before and during maximal dilatation (EDTA). The high dose of perindopril or the combination of propranolol and perindopril normalized cerebral arteriolar pressure (52±2 [mean±SEM], 49±2 mm Hg versus 50±2 mm Hg in WKY and 96±3 mm Hg in untreated SHRSP;
P
<0.05). In contrast, the low dose of perindopril or propranolol alone did not normalize arteriolar pressure (74±2 mm Hg and 58±3 mm Hg). Both the low and high doses of perindopril improved autoregulatory dilatation, maximal dilatation, and dilator reserve of cerebral arterioles in SHRSP, with the low dose of perindopril being almost as effective as the high dose of perindopril. Propranolol alone did not significantly improve dilator function of cerebral arterioles. Furthermore, dilator function of cerebral arterioles was not further improved by the addition of propranolol to the low dose of perindopril. These findings suggest that angiotensin-converting enzyme inhibitors, such as perindopril, may be more effective than propranolol in attenuating the impairment of cerebral autoregulatory vasodilatation, maximal dilatation, and dilator reserve during treatment of chronic hypertension.