Downregulation of Orexin Receptor in Hypothalamic Paraventricular Nucleus Decreases Blood Pressure in Obese Zucker Rats.

Background Orexin and its receptors are critical regulating sympathetic vasomotor tone under physiological and pathophysiological conditions. Orexin receptor 1 ( OXR 1) is upregulated in the paraventricular nucleus ( PVN ) in the hypothalamus and contributes to increased sympathetic outflow in obese Zucker rats ( OZR s). We hypothesized that silencing OXR 1 expression in the PVN decreases heightened blood pressure and elevated sympathetic outflow in OZR s. Methods and Results An adeno-associated virus ( AAV ) vector containing a short hairpin RNA (sh RNA ) targeting rat OXR 1 was designed to silence OXR 1 expression in the PVN . The AAV - OXR 1-sh RNA or scrambled sh RNA was injected into the PVN in OZR s. The arterial blood pressure in free-moving OZR s was continuously monitored by using a telemetry approach. The firing activity of spinally projecting PVN neurons in rat brain slices was recorded 3 to 4 weeks after injection of viral vectors. The free-moving OZR s treated with AAV - OXR 1-sh RNA had markedly lower OXR 1 expression and lower mean arterial blood pressure, heart rate, and ratio of low- to high-frequency components of heart rate variability compared with OZR s treated with scrambled sh RNA . Furthermore, AAV - OXR 1-sh RNA treatment markedly reduced renal sympathetic nerve activity and attenuated sympathoexcitatory response induced by microinjection of orexin A into the PVN . In addition, treatment with AAV - OXR 1-sh RNA substantially decreased the basal firing activity of spinally projecting PVN neurons in OZR s and attenuated the excitatory effect of orexin A on the firing activity of these neurons. Conclusions These data suggest that chronic downregulation of OXR 1 expression in the PVN reduces sympathetic vasomotor tone in obesity-related hypertension.

A multi-ancestry genome-wide study incorporating gene-smoking interactions identifies multiple new loci for pulse pressure and mean arterial pressure.

Elevated blood pressure (BP), a leading cause of global morbidity and mortality, is influenced by both genetic and lifestyle factors. Cigarette smoking is one such lifestyle factor. Across five ancestries, we performed a genome-wide gene-smoking interaction study of mean arterial pressure (MAP) and pulse pressure (PP) in 129 913 individuals in stage 1 and follow-up analysis in 480 178 additional individuals in stage 2. We report here 136 loci significantly associated with MAP and/or PP. Of these, 61 were previously published through main-effect analysis of BP traits, 37 were recently reported by us for systolic BP and/or diastolic BP through gene-smoking interaction analysis and 38 were newly identified (P < 5 × 10-8, false discovery rate < 0.05). We also identified nine new signals near known loci. Of the 136 loci, 8 showed significant interaction with smoking status. They include CSMD1 previously reported for insulin resistance and BP in the spontaneously hypertensive rats. Many of the 38 new loci show biologic plausibility for a role in BP regulation. SLC26A7 encodes a chloride/bicarbonate exchanger expressed in the renal outer medullary collecting duct. AVPR1A is widely expressed, including in vascular smooth muscle cells, kidney, myocardium and brain. FHAD1 is a long non-coding RNA overexpressed in heart failure. TMEM51 was associated with contractile function in cardiomyocytes. CASP9 plays a central role in cardiomyocyte apoptosis. Identified only in African ancestry were 30 novel loci. Our findings highlight the value of multi-ancestry investigations, particularly in studies of interaction with lifestyle factors, where genomic and lifestyle differences may contribute to novel findings.

A comparison of the genetic and clinical risk factors for arterial hypertension between indigenous and non-indigenous people of the Shoria Mountain Region.

BACKGROUND: This study investigated the non-genetic and genetic risk factors for arterial hypertension (AH) in two ethnic groups living in the Mountain Shoria region: Shors and non-indigenous people. METHODS: Clinical and epidemiological study of compactly living population in the remote areas of the Mountain Shoria (Orton, Ust-Kabyrza, Sheregesh settlements, Kemerovo region). 1178 residents of these settlements were surveyed with the help of continuous sampling method; the sample consisted of adults (18 years and older). RESULTS: The prevalence of AH was lower in Shors (39.9% vs. 46.1%), mainly due to differences between men from the different groups: 33.2% vs. 45.8%. The percentage of people with AH, overweight, and obesity (including transabdominal obesity) in the different age groups did not differ between ethnicities. We identified statistically significant differences in the prevalence of hypertension according the two ethic groups according to age, body weight, and abdominal obesity. I/D ACE and ADRA2B polymorphisms were associated with AH. In DD ACE and DD ADRA2B carriers, there were fewer hypertensive patients in Shors than in non-indigenous people: 40.6% vs. 58.6% and 38.3% vs. 64.0%, respectively. In DD ACE carriers, more Shors had AH (60.0% vs. 37.1%). CONCLUSION: Among Shors, the following factors increased AH risk: female sex, age, hypercholesterolemia, hyperbetacholesterinemia, hypertriglyceridemia, obesity (including transabdominal obesity), glucose intolerance, and the DD ACE, CT MTHFR, and AA ADRB1 genotypes; among the non-indigenous population, the main factors were age, hypercholesterolemia, hyperbetacholesterinemia, hypoalfacholesterinemia, hypertriglyceridemia, obesity (including transabdominal obesity), and ID ACE genotype.

Phenotypic Characterization of EIF2AK4 Mutation Carriers in a Large Cohort of Patients Diagnosed Clinically With Pulmonary Arterial Hypertension.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a rare disease with an emerging genetic basis. Heterozygous mutations in the gene encoding the bone morphogenetic protein receptor type 2 (BMPR2) are the commonest genetic cause of PAH, whereas biallelic mutations in the eukaryotic translation initiation factor 2 alpha kinase 4 gene (EIF2AK4) are described in pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis. Here, we determine the frequency of these mutations and define the genotype-phenotype characteristics in a large cohort of patients diagnosed clinically with PAH. METHODS: Whole-genome sequencing was performed on DNA from patients with idiopathic and heritable PAH and with pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis recruited to the National Institute of Health Research BioResource-Rare Diseases study. Heterozygous variants in BMPR2 and biallelic EIF2AK4 variants with a minor allele frequency of <1:10 000 in control data sets and predicted to be deleterious (by combined annotation-dependent depletion, PolyPhen-2, and sorting intolerant from tolerant predictions) were identified as potentially causal. Phenotype data from the time of diagnosis were also captured. RESULTS: Eight hundred sixty-four patients with idiopathic or heritable PAH and 16 with pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis were recruited. Mutations in BMPR2 were identified in 130 patients (14.8%). Biallelic mutations in EIF2AK4 were identified in 5 patients with a clinical diagnosis of pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis. Furthermore, 9 patients with a clinical diagnosis of PAH carried biallelic EIF2AK4 mutations. These patients had a reduced transfer coefficient for carbon monoxide (Kco; 33% [interquartile range, 30%-35%] predicted) and younger age at diagnosis (29 years; interquartile range, 23-38 years) and more interlobular septal thickening and mediastinal lymphadenopathy on computed tomography of the chest compared with patients with PAH without EIF2AK4 mutations. However, radiological assessment alone could not accurately identify biallelic EIF2AK4 mutation carriers. Patients with PAH with biallelic EIF2AK4 mutations had a shorter survival. CONCLUSIONS: Biallelic EIF2AK4 mutations are found in patients classified clinically as having idiopathic and heritable PAH. These patients cannot be identified reliably by computed tomography, but a low Kco and a young age at diagnosis suggests the underlying molecular diagnosis. Genetic testing can identify these misclassified patients, allowing appropriate management and early referral for lung transplantation.

Familial aggregation of albuminuria and arterial hypertension in an Aboriginal Australian community and the contribution of variants in ACE and TP53.

BACKGROUND: Aboriginal Australians are at high risk of cardiovascular, metabolic and renal diseases, resulting in a marked reduction in life expectancy when compared to the rest of the Australian population. This is partly due to recognized environmental and lifestyle risk factors, but a contribution of genetic susceptibility is also likely. METHODS: Using results from a comprehensive survey of one community (N = 1350 examined individuals), we have tested for familial aggregation of plasma glucose, arterial blood pressure, albuminuria (measured as urinary albumin to creatinine ratio, UACR) and estimated glomerular filtration rate (eGFR), and quantified the contribution of variation at four candidate genes (ACE; TP53; ENOS3; MTHFR). RESULTS: In the subsample of 357 individuals with complete genotype and phenotype data we showed that both UACR (h2 = 64%) and blood pressure (sBP h2 = 29%, dBP, h2 = 11%) were significantly heritable. The ACE insertion-deletion (P = 0.0009) and TP53 codon72 polymorphisms (P = 0.003) together contributed approximately 15% of the total heritability of UACR, with an effect of ACE genotype on BP also clearly evident. CONCLUSIONS: While the effects of the ACE insertion-deletion on risk of renal disease (especially in the setting of diabetes) are well recognized, this is only the second study to implicate p53 genotype as a risk factor for albuminuria - the other being an earlier study we performed in a different Aboriginal community (McDonald et al., J Am Soc Nephrol 13: 677-83, 2002). We conclude that there are significant genetic contributions to the high prevalence of chronic diseases observed in this population.

Heritabilities and genetic correlations of pulmonary arterial pressure and performance traits in Angus cattle at high altitude.

Pulmonary arterial pressure (PAP) is an indicator trait for pulmonary hypertension and for the risk of developing high-altitude disease (HAD) in cattle. Pulmonary arterial pressures provide a tool for selection of breeding cattle for tolerance to high altitude in mountainous regions of the United States. The objective of this study was to evaluate relationships between growth performance traits and yearling PAP (42.4 ± 9.9 mmHg; = 5,776; elevation 2,150 m) using data from 1993 to 2014 in the John E. Rouse Colorado State University Beef Improvement Center (CSU-BIC) Angus herd. The breeding program used sires ( = 299) from both low- and high-elevation environments. We hypothesized that little to no genetic relationship exists between PAP and birth weight (BWT; direct and maternal), weaning weight (WW; direct and maternal), yearling weight (YW; direct and maternal), and postweaning gain (PWG). Historic selection of natural service sires from within the herd required a PAP of ≤ 42 mmHg. Outside AI sires ( = 156) used in this breeding program were not PAP tested and therefore were used with little knowledge of these sires' high-altitude adaptability. Performance traits (± SD) routinely recorded included BWT (36.2 ± 5.1 kg; = 8,695), WW (213.5 ± 31.8 kg; = 8,010), YW (345.6 ± 83.8 kg; = 5,580), and PWG (122.0 ± 63.7 kg; = 5,449), where PWG represented the total weight gained from weaning to yearling age. Four-trait analyses using REML were conducted with an animal model. The heritability estimates (± SE) for PAP (0.26 ± 0.03), BWT direct (0.42 ± 0.04) and maternal (0.14 ± 0.02), WW direct (0.29 ± 0.04) and maternal (0.19 ± 0.03), YW direct (0.45 ± 0.04) and maternal (0.23 ± 0.03), and PWG (0.14 ± 0.02) were in the range of those reported in previous literature. Estimates of genetic correlations (± SE) revealed weak relationships between PAP and direct and maternal BWT, direct and maternal WW, direct and maternal YW, and PWG of 0.15 ± 0.09, 0.14 ± 0.10, 0.23 ± 0.09, -0.01 ± 0.10, 0.12 ± 0.08, 0.00 ± 0.09, and -0.10 ± 0.10, respectively. The results of this study suggest that selection for lower PAP measures should have minimal influence on the growth performance of yearling Angus bulls and heifers at the CSU-BIC, supporting our hypothesis.

Epigenetic regulation of insulin-like growth factor signaling: A novel insight into the pathophysiology of neonatal pulmonary hypertension.

Burdened by high morbidity and mortality, neonatal pulmonary hypertension (PH) is a life-threatening pathophysiological condition that progressively elevates the mean pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). Pulmonary vascular remodeling and vasoconstriction are recognized pathophysiological features of the disease. Neonatal PH is a serious pathological condition in which persistent PH of the newborn causes hypoxemia and right-to-left extrapulmonary shunting of blood flow, leading to right heart failure and serious life-threatening complications. Recently, the role of growth factors in the pathogenesis of neonatal PH has attracted much attention. Here we provide an update on the ongoing research regarding the epigenetic regulation of the insulin growth factor (IGF)-1/IGF-1 receptor pathway, with insight into the potential regulatory role such regulation in the pathogenesis of neonatal PH.

Viral transduction of renin rapidly establishes persistent hypertension in diverse murine strains.

Mice provide a unique platform to dissect disease pathogenesis, with the availability of recombinant inbred strains and diverse genetically modified strains. Leveraging these reagents to elucidate the mechanisms of hypertensive tissue injury has been hindered by difficulty establishing persistent hypertension in these inbred lines. ANG II infusion provides relatively short-term activation of the renin-angiotensinogen system (RAS) with concomitant elevated arterial pressure. Longer-duration studies using renin transgenic mice are powerful models of chronic hypertension, yet are limited by the genetic background on which the transgene exists and the exposure throughout development. The present studies characterized hypertension produced by transduction with a renin-coding adeno-associated virus (ReninAAV). ReninAAV mice experienced elevated circulating renin with concurrent elevations in arterial pressure. Following a single injection of ReninAAV, arterial pressure increased on average +56 mmHg, an increase that persisted for at least 12 wk in three distinct and widely used strains of adult mice: 129/S6, C56BL/6, and DBA/2J. This was accomplished without surgical implantation of pumps or complex breeding and backcrossing. In addition, ReninAAV mice developed pathophysiological changes associated with chronic hypertension, including increased heart weight and albuminuria. Thus ReninAAV provides a unique tool to study the onset of and effects of persistent hypertension in diverse murine models. This model should facilitate our understanding of the pathogenesis of hypertensive injury.

A Kinase-Independent Function of c-Src Mediates p130Cas Phosphorylation at the Serine-639 Site in Pressure Overloaded Myocardium.

Early work in pressure overloaded (PO) myocardium shows that integrins mediate focal adhesion complex formation by recruiting the adaptor protein p130Cas (Cas) and nonreceptor tyrosine kinase c-Src. To explore c-Src role in Cas-associated changes during PO, we used a feline right ventricular in vivo PO model and a three-dimensional (3D) collagen-embedded adult cardiomyocyte in vitro model that utilizes a Gly-Arg-Gly-Asp-Ser (RGD) peptide for integrin stimulation. Cas showed slow electrophoretic mobility (band-shifting), recruitment to the cytoskeleton, and tyrosine phosphorylation at 165, 249, and 410 sites in both 48 h PO myocardium and 1 h RGD-stimulated cardiomyocytes. Adenoviral mediated expression of kinase inactive (negative) c-Src mutant with intact scaffold domains (KN-Src) in cardiomyocytes did not block the RGD stimulated changes in Cas. Furthermore, expression of KN-Src or kinase active c-Src mutant with intact scaffold function (A-Src) in two-dimensionally (2D) cultured cardiomyocytes was sufficient to cause Cas band-shifting, although tyrosine phosphorylation required A-Src. These data indicate that c-Src's adaptor function, but not its kinase function, is required for a serine/threonine specific phosphorylation(s) responsible for Cas band-shifting. To explore this possibility, Chinese hamster ovary cells that stably express Cas were infected with either ß-gal or KN-Src adenoviruses and used for Cas immunoprecipitation combined with mass spectrometry analysis. In the KN-Src expressing cells, Cas showed phosphorylation at the serine-639 (human numbering) site. A polyclonal antibody raised against phospho-serine-639 detected Cas phosphorylation in 24-48 h PO myocardium. Our studies indicate that c-Src's adaptor function mediates serine-639 phosphorylation of Cas during integrin activation in PO myocardium.

IGF-1 signaling in neonatal hypoxia-induced pulmonary hypertension: Role of epigenetic regulation.

Pulmonary hypertension is a fatal disease characterized by a progressive increase in pulmonary artery pressure accompanied by pulmonary vascular remodeling and increased vasomotor tone. Although some biological pathways have been identified in neonatal hypoxia-induced pulmonary hypertension (PH), little is known regarding the role of growth factors in the pathogenesis of PH in neonates. In this study, using a model of hypoxia-induced PH in neonatal mice, we demonstrate that the growth factor insulin-like growth factor-1 (IGF-1), a potent activator of the AKT signaling pathway, is involved in neonatal PH. After exposure to hypoxia, IGF-1 signaling is activated in pulmonary endothelial and smooth muscle cells in vitro, and the IGF-1 downstream signal pAKT(S473) is upregulated in lungs of neonatal mice. We found that IGF-1 regulates ET-1 expression in pulmonary endothelial cells and that IGF-1 expression is regulated by histone deacetylases (HDACs). In addition, there is a differential cytosine methylation site in the IGF-1 promoter region in response to neonatal hypoxia. Moreover, inhibition of HDACs with apicidin decreases neonatal hypoxia-induced global DNA methylation levels in lungs and specific cytosine methylation levels around the pulmonary IGF-1 promoter region. Finally, HDAC inhibition with apicidin reduces chronic hypoxia-induced activation of IGF-1/pAKT signaling in lungs and attenuates right ventricular hypertrophy and pulmonary vascular remodeling. Taken together, we conclude that IGF-1, which is epigenetically regulated, is involved in the pathogenesis of pulmonary hypertension in neonatal mice. This study implicates a novel HDAC/IGF-1 epigenetic pathway in the regulation of hypoxia-induced PH and warrants further study of the role of IGF-1 in neonatal pulmonary hypertensive disease.

The Dahl salt-sensitive rat is a spontaneous model of superimposed preeclampsia.

The mechanisms of the pathogenesis of preeclampsia, a leading cause of maternal morbidity and death worldwide, are poorly understood in part due to a lack of spontaneous animal models of the disease. We hypothesized that the Dahl salt-sensitive (S) rat, a genetic model of hypertension and kidney disease, is a spontaneous model of superimposed preeclampsia. The Dahl S was compared with the Sprague-Dawley (SD) rat, a strain with a well-characterized normal pregnancy, and the spontaneously hypertensive rat (SHR), a genetic model of hypertension that does not experience a preeclamptic phenotype despite preexisting hypertension. Mean arterial pressure (MAP, measured via telemetry) was elevated in the Dahl S and SHR before pregnancy, but hypertension was exacerbated during pregnancy only in Dahl S. In contrast, SD and SHR exhibited significant reductions in MAP consistent with normal pregnancy. Dahl S rats exhibited a severe increase in urinary protein excretion, glomerulomegaly, increased placental hypoxia, increased plasma soluble fms-like tyrosine kinase-1 (sFlt-1), and increased placental production of tumor necrosis factor-α (TNF-α). The Dahl S did not exhibit the expected decrease in uterine artery resistance during late pregnancy in contrast to the SD and SHR. Dahl S pups and litter sizes were smaller than in the SD. The Dahl S phenotype is consistent with many of the characteristics observed in human superimposed preeclampsia, and we propose that the Dahl S should be considered further as a spontaneous model to improve our understanding of the pathogenesis of superimposed preeclampsia and to identify and test new therapeutic targets for its treatment.

Renal cyst growth is the main determinant for hypertension and concentrating deficit in Pkd1-deficient mice.

We have bred a Pkd1 floxed allele with a nestin-Cre expressing line to generate cystic mice with preserved glomerular filtration rate to address the pathogenesis of complex autosomal dominant polycystic kidney disease (ADPKD) phenotypes. Hypertension affects about 60% of these patients before loss of renal function, leading to significant morbimortality. Cystic mice were hypertensive at 5 and 13 weeks of age, a phenotype not seen in noncystic controls and Pkd1-haploinsufficient animals that do not develop renal cysts. Fractional sodium excretion was reduced in cystic mice at these ages. Angiotensinogen gene expression was higher in cystic than noncystic kidneys at 18 weeks, while ACE and the AT1 receptor were expressed in renal cyst epithelia. Cystic animals displayed increased renal cAMP, cell proliferation, and apoptosis. At 24 weeks, mean arterial pressure and fractional sodium excretion did not significantly differ between the cystic and noncystic groups, whereas cardiac mass increased in cystic mice. Renal concentrating deficit is also an early finding in ADPKD. Maximum urine osmolality and urine nitrite excretion were reduced in 10-13- and 24-week-old cystic mice, deficits not found in haploinsufficient and noncystic controls. A trend of higher plasma vasopressin was observed in cystic mice. Thus, cyst growth most probably plays a central role in early-stage ADPKD-associated hypertension, with activation of the intrarenal renin-angiotensin system as a key mechanism. Cyst expansion is also likely essential for the development of the concentrating deficit in this disease. Our findings are consistent with areas of reduced perfusion in the kidneys of patients with ADPKD.

ß2-Adrenoceptor gene variants affect vasopressor requirements in patients after thoracic epidural anaesthesia.

BACKGROUND: While the ß2-adrenoceptor pathway is essential for cardiovascular regulation, the impact of ADRB2 gene variations on circulatory responses is unclear, possibly due to neural compensatory mechanisms. We tested the hypotheses that (i) sympathetic block by thoracic epidural anaesthesia (TEA) unmasks the influence on arterial pressure of genetic variations and (ii) vasopressor requirements during TEA depend on ADRB2 gene variation. METHODS: Ninety-three elective patients undergoing abdominal surgery were included prospectively. After epidural bupivacaine 0.5% (15 mg test dose+50 mg), arterial pressure, heart rate, and progression of sensory block were measured for 20 min in the supine awake state and for 20 min after standardized anaesthetic induction of general anaesthesia. The primary endpoint was cumulative dose of the α-adrenoreceptor agonist phenylephrine administered to sustain a mean arterial pressure >70 mm Hg. The ADRB2 polymorphisms Arg16Gly and Gln27Glu were genotyped using Slowdown-PCR. RESULTS: After TEA, 86 (93%) patients required phenylephrine. The mean dosages (sd) were significantly different between the ADRB2 genotypes [Arg16Arg 357 µg (326), Arg16Gly 776 µg (449), Gly16Gly 600 µg (443), P=0.036; Gln27Gln 356 µg (254), Gln27Glu 639 µg (354), Glu27Glu 577 µg (388), P=0.007]. Multiple linear regression analysis revealed that age, male gender, rostral extent of sensory block, lower arterial pressure before TEA, and ADRB2 Glu27 allele together explained 37% of phenylephrine dosage variation, with genetic variants being the second most important predictor (10%; P<0.001). CONCLUSIONS: The ADRB2 Glu27 allele is an independent predictor of arterial hypotension and vasopressor requirements after TEA. Neural block can unmask genetic influences on neurohumoral regulation. Clinical trial registration DRKS00005260.

Male-specific region of the Y chromosome and cardiovascular risk: phylogenetic analysis and gene expression studies.

OBJECTIVE: Haplogroup I of male-specific region of the human Y chromosome is associated with 50% increased risk of coronary artery disease. It is not clear to what extent conventional cardiovascular risk factors and genes of the male-specific region may explain this association. APPROACH AND RESULTS: A total of 1988 biologically unrelated men from 4 white European populations were genotyped using 11 Y chromosome single nucleotide polymorphisms and classified into 13 most common European haplogroups. Approximately 75% to 93% of the haplotypic variation of the Y chromosome in all cohorts was attributable to I, R1a, and R1b1b2 lineages. None of traditional cardiovascular risk factors, including body mass index, blood pressures, lipids, glucose, C-reactive protein, creatinine, and insulin resistance, was associated with haplogroup I of the Y chromosome in the joint inverse variance meta-analysis. Fourteen of 15 ubiquitous single-copy genes of the male-specific region were expressed in human macrophages. When compared with men with other haplogroups, carriers of haplogroup I had ≈ 0.61- and 0.64-fold lower expression of ubiquitously transcribed tetratricopeptide repeat, Y-linked gene (UTY) and protein kinase, Y-linked, pseudogene (PRKY) in macrophages (P=0.0001 and P=0.002, respectively). CONCLUSIONS: Coronary artery disease predisposing haplogroup I of the Y chromosome is associated with downregulation of UTY and PRKY genes in macrophages but not with conventional cardiovascular risk factors.

Deletion of cyclooxygenase-2 in the mouse increases arterial blood pressure with no impairment in renal NO production in response to chronic high salt intake.

Experiments were designed to test the hypothesis that cyclooxygenase-2 (COX-2) activity attenuates the blood pressure increase during high NaCl intake by stimulation of endothelial nitric oxide synthase (eNOS)-mediated NO synthesis in the kidney medulla. COX-2(-/-) (C57BL6) an COX-2(+/+) mice were fed a diet with 0.004% (low salt, LS) or 4% (high salt, HS) NaCl for 18 days. Arterial blood pressure was recorded continuously using indwelling catheters. Food and water intake and diuresis were measured in metabolic cages. Urine osmolality and excretion of electrolytes, cGMP, cAMP, and NOx were determined, as well as plasma NOx and cGMP. There was a significant dependence of blood pressure on salt intake and genotype: COX-2(-/-) exhibited higher blood pressure than COX-2(+/+) both on HS and LS intake. COX-2(+/+) littermates displayed an increase in blood pressure on HS versus LS (102.3 ± 1.1 mmHg vs. 91.9 ± 0.9 mmHg) day and night. The mice exhibited significant blood pressure increases during the awake phase (night) that were larger in COX-2(-/-) on HS diet compared with COX-2(+/+). Water intake, diuresis, Na(+), and osmolyte excretions and NOx and cGMP excretions were significantly and similarly elevated with HS in COX-2(-/-) and COX-2(+/+). In summary, C57BL6 mice exhibit a salt intake-dependent increase in arterial blood pressure with increased renal NO production. COX-2 activity has a general lowering effect on arterial blood pressure. COX-2 dampens NaCl-induced increases in arterial blood pressure in the awake phase. In conclusion, COX-2 activity attenuates the changes in nocturnal blood pressure during high salt intake, and COX-2 activity is not necessary for increased renal nitric oxide formation during elevated NaCl intake.

Tubuloglomerular feedback and renal function in mice with targeted deletion of the type 1 equilibrative nucleoside transporter.

A(1) adenosine receptors (A1AR) are required for the modulation of afferent arteriolar tone by changes in luminal NaCl concentration implying that extracellular adenosine concentrations need to change in synchrony with NaCl. The present experiments were performed in mice with a null mutation in the gene for the major equilibrative nucleoside transporter ENT1 to test whether interference with adenosine disposition by cellular uptake of adenosine may modify TGF characteristics. Responses of stop flow pressure (P(SF)) to maximum flow stimulation were measured in mice with either C57Bl/6 or SWR/J genetic backgrounds. Maximum flow stimulation reduced P(SF) in ENT1(-/-) compared with wild-type (WT) mice by 1.6 ± 0.4 mmHg (n = 28) and 5.8 ± 1.1 mmHg (n = 17; P < 0.001) in C57Bl/6 and by 1.4 ± 0.4 mmHg (n = 15) and 9 ± 1.5 mmHg (n = 9; P < 0.001) in SWR/J. Plasma concentrations of adenosine and inosine were markedly higher in ENT1(-/-) than WT mice (ado: 1,179 ± 78 and 225 ± 48 pmol/ml; ino: 179 ± 24 and 47.5 ± 9 pmol/ml). Renal mRNA expressions of the four adenosine receptors, ENT2, and adenosine deaminase were not significantly different between WT and ENT1(-/-) mice. No significant differences of glomerular filtration rate or mean arterial blood pressure were found while plasma renin concentration, and heart rates were significantly lower in ENT1(-/-) animals. In conclusion, TGF responsiveness is significantly attenuated in the absence of ENT1, pointing to a role of nucleoside transport in the NaCl-synchronous changes of extracellular adenosine levels in the juxtaglomerular apparatus interstitium.

Heart failure with preserved ejection fraction: chronic low-intensity interval exercise training preserves myocardial O2 balance and diastolic function.

We have previously reported chronic low-intensity interval exercise training attenuates fibrosis, impaired cardiac mitochondrial function, and coronary vascular dysfunction in miniature swine with left ventricular (LV) hypertrophy (Emter CA, Baines CP. Am J Physiol Heart Circ Physiol 299: H1348-H1356, 2010; Emter CA, et al. Am J Physiol Heart Circ Physiol 301: H1687-H1694, 2011). The purpose of this study was to test two hypotheses: 1) chronic low-intensity interval training preserves normal myocardial oxygen supply/demand balance; and 2) training-dependent attenuation of LV fibrotic remodeling improves diastolic function in aortic-banded sedentary, exercise-trained (HF-TR), and control sedentary male Yucatan miniature swine displaying symptoms of heart failure with preserved ejection fraction. Pressure-volume loops, coronary blood flow, and two-dimensional speckle tracking ultrasound were utilized in vivo under conditions of increasing peripheral mean arterial pressure and ß-adrenergic stimulation 6 mo postsurgery to evaluate cardiac function. Normal diastolic function in HF-TR animals was characterized by prevention of increased time constant of isovolumic relaxation, normal LV untwisting rate, and enhanced apical circumferential and radial strain rate. Reduced fibrosis, normal matrix metalloproteinase-2 and tissue inhibitors of metalloproteinase-4 mRNA expression, and increased collagen III isoform mRNA levels (P < 0.05) accompanied improved diastolic function following chronic training. Exercise-dependent improvements in coronary blood flow for a given myocardial oxygen consumption (P < 0.05) and cardiac efficiency (stroke work to myocardial oxygen consumption, P < 0.05) were associated with preserved contractile reserve. LV hypertrophy in HF-TR animals was associated with increased activation of Akt and preservation of activated JNK/SAPK. In conclusion, chronic low-intensity interval exercise training attenuates diastolic impairment by promoting compliant extracellular matrix fibrotic components and preserving extracellular matrix regulatory mechanisms, preserves myocardial oxygen balance, and promotes a physiological molecular hypertrophic signaling phenotype in a large animal model resembling heart failure with preserved ejection fraction.

Chronic treatment with tempol does not significantly ameliorate renal tissue hypoxia or disease progression in a rodent model of polycystic kidney disease.

In the present study, we tested whether polycystic kidney disease (PKD) is associated with renal tissue hypoxia and oxidative stress, which, in turn, contribute to the progression of cystic disease and hypertension. Lewis polycystic kidney (LPK) rats and Lewis control (Lewis) rats were treated with tempol (1 mmol/L in drinking water) from 3 to 13 weeks of age or remained untreated. The LPK rats developed polyuria, uraemia and proteinuria. At 13 weeks of age, LPK rats had greater mean arterial pressure (1.5-fold), kidney weight (sixfold) and plasma creatinine (3.5-fold) than Lewis rats. Kidneys from LPK rats were cystic and fibrotic. Renal hypoxia was evidenced by staining for pimonidazole adducts and hypoxia-inducible factor (HIF)-1α in cells lining renal cysts and upregulation of HIF-1α and its downstream targets vascular endothelial growth factor (VEGF), glucose transporter-1 (Glut-1) and heme oxygenase 1 (HO-1). However, total HO activity did not differ greatly between kidney tissue from LPK compared with Lewis rats. Renal oxidative and/or nitrosative stress was evidenced by ninefold greater immunofluorescence for 3-nitrotyrosine in kidney tissue from LPK compared with Lewis rats and a > 10-fold upregulation of mRNA for p47phox and gp91phox. Total renal superoxide dismutase (SOD) activity was sevenfold less and expression of SOD1 mRNA was 70% less in kidney tissue from LPK compared with Lewis rats. In LPK rats, tempol treatment reduced immunofluorescence for 3-nitrotyrosine and HIF1A mRNA while upregulating VEGF and p47phox mRNA expression, but otherwise had little impact on disease progression, renal tissue hypoxia or hypertension. Our findings do not support the hypothesis that oxidative stress drives hypoxia and disease progression in PKD.

In vivo expression of angiotensin-(1-7) lowers blood pressure and improves baroreflex function in transgenic (mRen2)27 rats.

Transgenic (mRen2)27 rats are hypertensive with impaired baroreflex sensitivity for control of heart rate compared with Hannover Sprague-Dawley rats. We assessed blood pressure and baroreflex function in male hemizygous (mRen2)27 rats (30-40 weeks of age) instrumented for arterial pressure recordings and receiving into the cisterna magna either an Ang-(1-7) fusion protein or a control fusion protein (CTL-FP). The maximum reduction in mean arterial pressure achieved was -38 ± 7 mm Hg on day 3, accompanied by a 55% enhancement in baroreflex sensitivity in Ang-(1-7) fusion protein-treated rats. Both the high-frequency alpha index (HF-α) and heart rate variability increased, suggesting increased parasympathetic tone for cardiac control. The mRNA levels of several components of the renin-angiotensin system in the dorsal medulla were markedly reduced including renin (-80%), neprilysin (-40%), and the AT1a receptor (-40%). However, there was a 2-fold to 3-fold increase in the mRNA levels of the phosphatases PTP-1b and dual-specificity phosphatase 1 in the medulla of Ang-(1-7) fusion protein-treated rats. Our finding that replacement of Ang-(1-7) in the brain of (mRen2)27 rats reverses in part the hypertension and baroreflex impairment is consistent with a functional deficit of Ang-(1-7) in this hypertensive strain. We conclude that the increased mRNA expression of phosphatases known to counteract the phosphoinositol 3 kinase and mitogen-activated protein kinases, and the reduction of renin and AT1a receptor mRNA levels may contribute to the reduction in arterial pressure and improvement in baroreflex sensitivity in response to Ang-(1-7).

Papel de la sensibilidad a la sal y los polimorfismos genéticos como determinantes de la modificación de los factores de riesgo cardiovascular durante la pérdida de peso en sujetos con sobrepeso u obesidad / Role of salt sensitivity and genetic polymorphisms as determinants of the modification of cardiovascular risk factors during weight loss in overweight or obese subjects

El incremento de la ingesta de sal no siempre se acompaña de un aumento en la presión arterial; aquellos sujetos que así lo hacen, son denominados Sal Sensibles (SS), mientras que los que no, se denominan Sal Resistentes (SR). La sensibilidad a la sal se ha asociado con mayor riesgo cardiometabólico y es más frecuente en los sujetos obesos hipertensos, sin embargo, no todos los obesos son SS y se desconoce como se origina este fenotipo. Debido a que la obesidad es un estado proinflamatorio, se propone que es necesario cierto grado y/o tiempo de obesidad para ser SS. Es por ello, que en esta investigación se evaluó el cambio en el tiempo de las interleuquinas 6, 10 y 18 (IL-6, IL-10 e IL-18), adiponectina, leptina, glicemia, lípidos, insulina, depuración de creatinina, microalbuminuria, ADMA, metabolitos urinarios del óxido nrico (NO), y además se estudió la prevalencia de los polimorfismos genéticos más frecuentemente asociados a riesgo cardiometabólico de la IL-6, 10,18, y de la sintasa de NO endotelial (eNOS), en sujetos SR (n=11) y SS (n=17), con sobrepeso u obesidad grado I, que fueron sometidos por 18 semanas a dieta y ejercicio. Se encontró que la pérdida de peso revertió el estado SS, el cual fue mas evidente en los sujetos que tenían más tiempo de obesidad, mayor concentración de insulina y ADMA sanguíneo, menor excreción urinaria de los metabolito del NO, mayor índice IL-6/ circunferencia abdominal y presentaban al alelo ä"del polimorfismo 4ab de la eNOS, por lo que se concluye que la sensibilidad a la sal pudiera ser producto de la interacción entre los componentes inflamatorios, vasculares y metabólicos y probablemente sea modulada por el polimorfismo 4ab de la eNOS