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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have shown previously that increased extracellular osmolality stimulates expression and promoter activity of the type A natriuretic peptide receptor (NPR-A) gene in rat inner medullary collecting duct (IMCD) cells through a mechanism that involves activation of p38 mitogen-activated protein kinase (MAPK). The serum and glucocorticoid inducible kinase (Sgk) is thought to participate in the regulation of sodium handling in distal tubular segments. We sought to determine whether this kinase might be involved in the osmotic stimulation of NPR-A gene promoter activity. Exposure of cultured IMCD cells to an additional 75 mmol/L NaCl in culture media (final osmolality 475 mosm/kg) resulted in an approximately 4-fold increase in Sgk1 protein levels after 7 hours. The Sgk1 induction was almost completely inhibited by the p38 MAPK inhibitor SB203580, indicating that NaCl activates Sgk1 through the p38 MAPK pathway. Transient transfection of a mouse Sgk1 expression vector along with a -1590 NPR-A luciferase reporter resulted in an approximately 3-fold increment in reporter activity, which was significantly reduced by cotransfection with a kinase-dead Sgk1 mutant. The NaCl-dependent induction was partially blocked (approximately 40% inhibition) by cotransfection of the kinase-dead Sgk1 mutant. Neither Sgk1 nor the kinase-dead mutant had any effect on endothelial nitric oxide synthase (eNOS) promoter activity, and the Sgk1 mutant and 8-bromo-cyclic guanosine monophosphate were, to some degree, additive in reducing osmotically stimulated NPR-A promoter activity. Collectively, these data imply that Sgk1 operates over an eNOS-independent, p38 MAPK-dependent pathway in mediating osmotic induction of the NPR-A gene promoter.
Hypertension 2004 Apr
PMID:Sgk1 mediates osmotic induction of NPR-A gene in rat inner medullary collecting duct cells. 1500 40

This study aimed to characterize the vasorelaxing effects of ANP, BNP and CNP in isolated renal resistance arteries (RRA) from wild-type mice and mice with either systemic (GC-A -/-) or smooth muscle-restricted deletion of GC-A (SMC GC-A KO). In RRA from wild-type (GC-A +/+) mice natriuretic peptides (NP) induced concentration-dependent vasorelaxations with the rank order of potency ANP>BNP>CNP. In RAA obtained from mice with systemic or smooth muscle-restricted deletion of GC-A, the effects of ANP and BNP were abolished. In contrast, CNP induced concentration-dependent vasorelaxations of GC-A -/- and SMC GC-A KO RRA. However, the efficacy of CNP for vasorelaxation was markedly diminished compared with wild-type RRA. Such changes in CNP responsiveness did not affect large arteries as the aorta and they were not due to vascular changes secondary to chronic arterial hypertension in GC-A -/- mice. Unaltered vasorelaxing effects of acetylcholine and sodium nitroprusside demonstrated unaltered function of downstream targets regulated by cGMP in vascular smooth muscle. An increased expression of the clearance receptor (NPR-C) or diminished expression of GC-B were not found to account for the differences in CNP responsiveness. In conclusion, observations in isolated aortic rings do not necessarily allow conclusions concerning the physiology of natriuretic peptides in the smaller resistance size arteries. Changes at the GC-B receptor level are likely to explain the diminished responsiveness of GC-A-deficient RRA to CNP.
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PMID:Diverging vasorelaxing effects of C-type natriuretic peptide in renal resistance arteries and aortas of GC-A-deficient mice. 1509 94

Cardiac hypertrophy is associated with ventricular arrhythmias and sudden death. The molecular mechanisms that predispose the hypertrophied heart to arrhythmias are not well understood. In mice, deletion of the gene coding for the atrial natriuretic peptide receptor, guanylyl cyclase A (GC-A-/-), causes arterial hypertension, cardiac hypertrophy and sudden death. We used this mouse model to study molecular mechanisms of arrhythmias in the hypertrophied heart. Right and left ventricular monophasic action potential durations (APD) were recorded in isolated, Langendorff-perfused hearts during pacing from the right atrium and ventricle. The atrioventricular (AV) node was ablated to provoke bradycardia. Intracellular Ca(2+) transients were measured in isolated INDO-1 loaded ventricular myocytes. Cardiac expression of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) was analyzed by western blotting. Polymorphic ventricular arrhythmias (pVT) occurred spontaneously after mechanical AV block in 20/45 hearts from 12-month-old GC-A-/- mice (P < 0.05), but neither in age-matched GC-A+/+ hearts nor in hearts from 3-month-old mice of either genotype. Triggered activity preceded pVT. APD were prolonged and systolic Ca(i)(2+) levels were increased in GC-A-/- hearts independently of age. In 12-month-old GC-A-/- hearts only, dispersion of APD and expression levels of CaMKII were increased. CaMKII expression was particularly increased in hearts with pVT. Direct inhibition of CaMKII activation by KN93 (0.5 or 2 microM) or inhibition of Ca(2+)/calmodulin-dependent activation of CaMKII by W-7 (25 microM) suppressed pVT in GC-A-/- hearts (P < 0.05) while prolonging APD. The combination of increased CaMKII activity and altered action potential characteristics facilitates ventricular arrhythmias in hypertrophic GC-A-/- hearts.
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PMID:Ventricular arrhythmias, increased cardiac calmodulin kinase II expression, and altered repolarization kinetics in ANP receptor deficient mice. 1513 64

The crucial functions of atrial natriuretic peptide (ANP) and endothelial nitric oxide/NO in the regulation of arterial blood pressure have been emphasized by the hypertensive phenotype of mice with systemic inactivation of either the guanylyl cyclase-A receptor for ANP (GC-A-/-) or endothelial nitric-oxide synthase (eNOS-/-). Intriguingly, similar levels of arterial hypertension are accompanied by marked cardiac hypertrophy in GC-A-/-, but not in eNOS-/-, mice, suggesting that changes in local pathways regulating cardiac growth accelerate cardiac hypertrophy in the former and protect the heart of the latter. Our recent observations in mice with conditional, cardiomyocyte-restricted GC-A deletion demonstrated that ANP locally inhibits cardiomyocyte growth. Abolition of these local, protective effects may enhance the cardiac hypertrophic response of GC-A-/- mice to persistent increases in hemodynamic load. Notably, eNOS-/- mice exhibit markedly increased cardiac ANP levels, suggesting that increased activation of cardiac GC-A can prevent hypertensive heart disease. To test this hypothesis, we generated mice with systemic inactivation of eNOS and cardiomyocyte-restricted deletion of GC-A by crossing eNOS-/- and cardiomyocyte-restricted GC-A-deficient mice. Cardiac deletion of GC-A did not affect arterial hypertension but significantly exacerbated cardiac hypertrophy and fibrosis in eNOS-/- mice. This was accompanied by marked cardiac activation of both the mitogen-activated protein kinase (MAPK) ERK 1/2 and the phosphatase calcineurin. Our observations suggest that local ANP/GC-A/cyclic GMP signaling counter-regulates MAPK/ERK- and calcineurin/nuclear factor of activated T cells-dependent pathways of cardiac myocyte growth in hypertensive eNOS-/- mice.
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PMID:Local atrial natriuretic peptide signaling prevents hypertensive cardiac hypertrophy in endothelial nitric-oxide synthase-deficient mice. 1579 9

Natriuretic peptides are a family of structurally related but genetically distinct hormones/paracrine factors that regulate blood volume, blood pressure, ventricular hypertrophy, pulmonary hypertension, fat metabolism, and long bone growth. The mammalian members are atrial natriuretic peptide, B-type natriuretic peptide, C-type natriuretic peptide, and possibly osteocrin/musclin. Three single membrane-spanning natriuretic peptide receptors (NPRs) have been identified. Two, NPR-A/GC-A/NPR1 and NPR-B/GC-B/NPR2, are transmembrane guanylyl cyclases, enzymes that catalyze the synthesis of cGMP. One, NPR-C/NPR3, lacks intrinsic enzymatic activity and controls the local concentrations of natriuretic peptides through constitutive receptor-mediated internalization and degradation. Single allele-inactivating mutations in the promoter of human NPR-A are associated with hypertension and heart failure, whereas homozygous inactivating mutations in human NPR-B cause a form of short-limbed dwarfism known as acromesomelic dysplasia type Maroteaux. The physiological effects of natriuretic peptides are elicited through three classes of cGMP binding proteins: cGMP-dependent protein kinases, cGMP-regulated phosphodiesterases, and cyclic nucleotide-gated ion channels. In this comprehensive review, the structure, function, regulation, and biological consequences of natriuretic peptides and their associated signaling proteins are described.
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PMID:Natriuretic peptides, their receptors, and cyclic guanosine monophosphate-dependent signaling functions. 1629 70

We have previously shown that the partial disruption of the gene for atrial natriuretic peptide (ANP) results in a salt-sensitive phenotype. The present study examined the possibility that alterations in either the ANP natriuretic pathway or endothelin (ET) system in the kidney of the salt-challenged ANP +/- mouse was responsible for its salt-sensitive phenotype. Plasma ANP levels and renal cGMP activity were increased in response to a salt load in both ANP +/+ and +/- mice. However, the mRNA expression of proANP was found to be increased only in the ANP +/- kidney along with its guanylyl cyclase-linked receptor, NPRA; the upregulation of NPRA mRNA was limited to the renal medulla. This suggests that the renal ANP pathway remains capable of responding to a salt load in the ANP +/- animal, but may be compensating for other dysfunctional pathways. We also report a significant increase in renal ET-1 mRNA and ETA receptor protein expression in medulla and cortex of the salt-treated, ANP +/- mouse, but not its wild-type counterpart. In fact, ETA expression decreased in the renal cortex of the ANP +/+ salt-treated animal. The ETB receptor expression was not affected by diet in either genotype. We hypothesize that the salt-sensitive hypertension in the ANP +/- mouse is exacerbated, and possibly driven by the vasoconstrictive effects resulting from an upregulated ET-1/ETA pathway.
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PMID:A potential role for the endothelin ETA receptor in salt-sensitive hypertension of the proANP gene-disrupted mouse. 1633 84

Disruption of the guanylyl cyclase-A/natriuretic peptide receptor-A (GC-A/NPRA) gene leads to elevated arterial blood pressure and congestive heart failure in mice lacking NPRA. This study was aimed at determining whether Npr1 (coding for GC-A/NPRA) gene copy number affects adrenal ANG II and aldosterone (Aldo) levels in a gene-dose-dependent manner in Npr1 gene-targeted mice. Adrenal ANG II and Aldo levels increased in 1-copy mice compared with 2-copy mice, but decreased in 3-copy and 4-copy mice. In contrast, renal ANG II levels decreased in 1-copy (25%), 3-copy (38%), and 4-copy (39%) mice compared with 2-copy mice. The low-salt diet stimulated adrenal ANG II and Aldo levels in 1-copy (20 and 2,441%), 2-copy (15 and 2,339%), 3-copy (20 and 424%), and 4-copy (31 and 486%) mice, respectively. The high-salt diet suppressed adrenal ANG II and Aldo levels in 1-copy (46 and 29%) and 2-copy (38 and 17%) mice. On the other hand, the low-salt diet stimulated renal ANG II levels in 1-copy (45%), 2-copy (45%), 3-copy (59%), and 4-copy (48%) mice. However, the high-salt diet suppressed renal ANG II levels in 1-copy (28%) and 2-copy (27%) mice. In conclusion, NPRA signaling antagonizes adrenal ANG II and Aldo levels in a gene-dose dependent manner. Increased adrenal ANG II and Aldo levels may play an important role in elevated arterial blood pressure and progressive hypertension, leading to renal and vascular injury in Npr1 gene-disrupted mice.
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PMID:Guanylyl cyclase/natriuretic peptide receptor-A gene disruption causes increased adrenal angiotensin II and aldosterone levels. 1738 76

Dendroaspis natriuretic peptide (DNP) is a newly-described natriuretic peptide which lowers blood pressure via vasodilation. The natriuretic peptide clearance receptor (NPR-C) removes natriuretic peptides from the circulation, but whether DNP interacts with human NPR-C directly is unknown. The purpose of this study was to test the hypothesis that DNP binds to NPR-C. ANP, BNP, CNP, and the NPR-C ligands AP-811 and cANP(4-23) displaced [(125)I]-ANP from NPR-C with pM-to-nM K(i) values. DNP displaced [(125)I]-ANP from NPR-C with nM potency, which represents the first direct demonstration of binding of DNP to human NPR-C. DNP showed high pM affinity for the GC-A receptor and no affinity for GC-B (K(i)>1000 nM). DNP was nearly 10-fold more potent than ANP at stimulating cGMP production in GC-A expressing cells. Blockade of NPR-C might represent a novel therapeutic approach in augmenting the known beneficial actions of DNP in cardiovascular diseases such as hypertension and heart failure.
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PMID:Dendroaspis natriuretic peptide binds to the natriuretic peptide clearance receptor. 1747 16

Recent studies suggest that the ANP (atrial natriuretic peptide)/NPRA (type A natriuretic peptide receptor) system modulates ventricular remodelling and cardiac hypertrophy in hypertension in Western populations. In the present study, we tested for any association between two SNPs (single nucleotide polymorphisms) in the ANP gene (one in the promoter and one exonic) with cardiac hypertrophy. We tested the hypothesis in 2118 hypertensive patients, including 945 with LVH [LV (left ventricular) hypertrophy] and 1173 without LVH, as well as 816 healthy control subjects. All subjects were genotyped for the -A2843G and A188G polymorphisms. We found that the GG genotype at position -2843 conferred a 2.2-fold risk for LVH compared with the AA or AG genotypes, including septal wall thickness (11.8+/-1.4 mm for GG compared with 10.9+/-1.4 and 10.7+/-1.3 mm for AA and AG respectively; P<0.01), posterior wall thickness (11.8+/-2.8 mm for GG compared with 10.6+/-1.2 and 10.6+/-1.4 mm for AA and AG respectively; P<0.01), LV mass index (62.7+/-13.6 g/m(2.7) for GG compared with 57.9+/-8.6 and 57.8+/-8.4 g/m(2.7) for AA and AG respectively; P<0.05) and relative wall thickness (50.7+/-10.8% for GG compared with 44.3+/-7.3 and 43.5+/-6.8% for AA and AG respectively; P<0.05). Plasma levels of ANP were significantly lower in the hypertensive patients with LVH carrying the GG genotypes compared with those carrying the AA or AG genotypes (P<0.01). No association of GG genotype with echocardiographic variables and plasma ANP levels was identified in hypertensive patients without LVH and in control subjects (P>0.05). No significant association between the A188G genotype and echocardiographic variables was found in either hypertensive patients or controls (P>0.05). In conclusion, our findings indicate that the -A2843G polymorphism in the ANP gene promoter might be a genetic risk factor for the development of LVH in patients with hypertension.
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PMID:Atrial natriuretic peptide gene promoter polymorphism is associated with left ventricular hypertrophy in hypertension. 1767 26

Guanylyl cyclase (GC)-A (natriuretic peptide receptor [NPR]-1), the receptor for atrial and brain natriuretic peptide, is important in the regulation of blood pressure in animal models and, possibly, in humans. In this study, we examined the association between dinucleotide repeat polymorphism within the 5'-flanking region of the GC-A gene and essential hypertension in a group of Japanese subjects. By genotyping 177 hypertensive and 170 normotensive subjects, we identified 5 allele types with 6, 9, 10, 11 and 12 CT dinucleotide repeats, respectively, around position -293, upstream of the ATG codon in the human GC-A gene. The frequency of the (CT)n=6 allele was significantly higher among hypertensive than normotensive subjects, while the frequencies of the other allele types did not differ between the two groups. We also examined the linkage between G/A polymorphism at position -77 (rs13306004), downstream of the (CT)n polymorphism, and found that the (CT)n=6 allele was tightly linked to an A at position -77, while all other (CT)n alleles were linked to G. Promoter-reporter analyses carried out in cultured human aortic smooth muscle cells using a luciferase gene fused to the 5'-flanking region of the GC-A gene revealed that the promoter containing (CT)n=6 drove less transcriptional activity than that containing (CT)n=10. Finally, site-directed mutation showed that the (CT)n and G/A polymorphisms act synergistically to affect GC-A promoter activity. Our results thus define the (CT)n polymorphism in the 5'-flanking region of the GC-A gene as a potent and novel susceptibility marker for hypertension.
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PMID:Association of CT dinucleotide repeat polymorphism in the 5'-flanking region of the guanylyl cyclase (GC)-A gene with essential hypertension in the Japanese. 1836 23


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