Chiara Troffa

Effect of the HMG-CoA Reductase Inhibitors on Blood Pressure in Patients With Essential Hypertension and Primary Hypercholesterolemia

Certain hydroxymethylglutaryl coenzyme A reductase inhibitors, ie, statins, may cause vasodilation by restoring the endothelial dysfunction that frequently accompanies hypertension and hypercholesterolemia. Several studies have found that a blood pressure reduction is associated with the use of statins, but conclusive evidence from controlled trials is lacking. After an 8-week placebo and diet run-in period, 30 persons with moderate hypercholesterolemia and untreated hypertension (total cholesterol 6.29+/-0.52 mmol/L, systolic and diastolic blood pressure 149+/-6 and 97+/-2 mm Hg) were randomized in a double-blind manner to placebo or pravastatin (20 to 40 mg/d) in a crossover design. In 25 participants who completed the 32-week trial, pravastatin decreased total and LDL cholesterol (both -1.09 mmol/L, P=0.001), systolic and diastolic blood pressure (-8 and -5 mm Hg, both P=0.001), and pulse pressure (-3 mm Hg, P=0.011) and blunted the blood pressure increase caused by the cold pressor test (-4 mm Hg, P=0.005) compared with placebo. It also reduced the level of circulating endothelin-1 (P=0.001). The blood pressure results were virtually unchanged in stratified analyses according to gender and age and in intention-to-treat analyses that included the 5 patients who dropped out of the study. When the participants were taking either placebo or pravastatin, blood pressure was not significantly correlated with total or LDL cholesterol or with circulating endothelin-1. Pravastatin decreases systolic, diastolic, and pulse pressures in persons with moderate hypercholesterolemia and hypertension. This antihypertensive effect may contribute to the documented health benefits of certain statins.

Genomewide association study using a high-density single nucleotide polymorphism array and case-control design identifies a novel essential hypertension susceptibility locus in the promoter region of endothelial NO synthase

Essential hypertension is a multifactorial disorder and is the main risk factor for renal and cardiovascular complications. The research on the genetics of hypertension has been frustrated by the small predictive value of the discovered genetic variants. The HYPERGENES Project investigated associations between genetic variants and essential hypertension pursuing a 2-stage study by recruiting cases and controls from extensively characterized cohorts recruited over many years in different European regions. The discovery phase consisted of 1865 cases and 1750 controls genotyped with 1M Illumina array. Best hits were followed up in a validation panel of 1385 cases and 1246 controls that were genotyped with a custom array of 14 055 markers. We identified a new hypertension susceptibility locus (rs3918226) in the promoter region of the endothelial NO synthase gene (odds ratio: 1.54 [95% CI: 1.37–1.73]; combined P=2.58 · 10−13). A meta-analysis, using other in silico/de novo genotyping data for a total of 21 714 subjects, resulted in an overall odds ratio of 1.34 (95% CI: 1.25–1.44; P=1.032 · 10−14). The quantitative analysis on a population-based sample revealed an effect size of 1.91 (95% CI: 0.16–3.66) for systolic and 1.40 (95% CI: 0.25–2.55) for diastolic blood pressure. We identified in silico a potential binding site for ETS transcription factors directly next to rs3918226, suggesting a potential modulation of endothelial NO synthase expression. Biological evidence links endothelial NO synthase with hypertension, because it is a critical mediator of cardiovascular homeostasis and blood pressure control via vascular tone regulation. This finding supports the hypothesis that there may be a causal genetic variation at this locus.

Effects of Hoe 140, a bradykinin B2‐receptor antagonist, on renal function in conscious normotensive rats

1 . The present study was designed to determine if endogenous kinins are involved in the regulation of arterial blood pressure and renal function in conscious rats given deoxycorticosterone enantate (DOC, 25 mg kg−1, s.c., weekly) or vehicle for two weeks. 2 . The bradykinin B2‐receptor antagonist, d‐Arg[Hyp3,Thi5,d‐Tic7,Oic8]‐bradykinin (Hoe 140), at a dose of 300 μg kg−1, s.c., blocked the hypotensive effect of 300 ng kg−1 bradykinin i.a., but it did not alter the blood pressure lowering action of 300 ng kg−1 acetylcholine or prostaglandin E2. Inhibition of the response to bradykinin persisted up to 6 h after the administration of Hoe 140. 3 . Administration of 300 μg kg−1 Hoe 140 s.c. four times a day did not alter mean blood pressure, renal blood flow, or renal function in rats given DOC‐vehicle. However, it decreased urinary volume by 70% (from 48.2 ± 3.8 to 14.3 ± 3.7 ml 24 h−1, P < 0.01) and urinary secretion of sodium by 54% (from 1.02 ± 0.05 to 0.47 ± 0.16 mmol 24 h−1, P < 0.01) and potassium by 30% (from 2.93 ± 0.15 to 2.04 ± 0.15 mmol 24 h−1, P < 0.05) in DOC‐treated rats. Mean blood pressure, glomerular filtration rate and total renal blood flow remained unchanged. 4 . Our results suggest that endogenous kinins play a role in the regulation of renal excretion of water and sodium in the presence of elevated levels of DOC.

Effect of endothelin on regional hemodynamics and renal function in awake normotensive rats

Summary: The effects of endothelin on regional hemodynamics and renal function were studied in awake normotensive rats. Intravenous injection of endothelin (700 pmol/kg) transiently lowered mean blood pressure (from 108 ± 2 to 84 ± 2 mm Hg, p < 0.01), due to a reduction in total vascular resistance (38 ± 1%, p < 0.01), and increased stroke volume (29 ± 5%, p < 0.01) and heart rate (from 399 ± 18 to 447 ± 18 bpm, p < 0.05); mesenteric and renal blood flow was reduced (37 ± 13, p < 0.05 and 63 ± 5%, p < 0.01), whereas carotid blood flow was increased (78 ± 5%, p < 0.01). This effect was followed by long-lasting hypertension due to increased total vascular resistance (112 ± 19%, p < 0.01); stroke volume, mesenteric, and renal blood flow were reduced (34 ± 5, 41 ± 4, and 58 ± 4%, respectively, p < 0.05) and carotid blood flow returned to basal levels. Bilateral nephrectomy enhanced the initial hypotensive effect. Pretreatment with nifedipine blocked the hypertensive effect, whereas bilateral nephrectomy did not. A subpressor dose of endothelin (70 pmol/kg) had no effect on stroke volume, mesenteric blood flow, glomerular filtration rate, and plasma renin activity; carotid blood flow was transiently increased (48 ± 16%, p < 0.05), then returned to basal levels; renal blood flow decreased (22 ± 6 and 15 ± 4% at 30 s and 10 min, respectively p < 0.05). Our data show a heterogeneity in the response of regional vascular beds to endothelin, the renal and mesenteric compartments being very sensitive to its vasoconstricting action. Endothelin, acting as paracrine or endocrine hormone, might have an important role in the pathogenesis of high blood pressure.

Low-dose infusion of atrial natriuretic factor in mild essential hypertension.

Intra-arterial blood pressure, cardiac output, heart rate, right heart indexes, urinary electrolytes, and urinary volume were monitored in eight patients with untreated (WHO Class I) essential hypertension. The patients were given synthetic atrial natriuretic factor (ANF) (99-126 alpha-hANP) at 1 and 2 pmol/kg/min in series (phases 1 and 2, 2 hours each dose) or vehicle (hemaccel) in random order on two separate occasions while on their usual diet. Arterial plasma ANF levels increased significantly from basal and time-matched placebo values from 25 +/- 2 and 28 +/- 3 pmol/l to 50 +/- 4 and 83 +/- 9 pmol/l at the end of phases 1 and 2, respectively (p less than 0.001). After 30 minutes during phase 2, systolic blood pressure decreased significantly by 20 +/- 4 mm Hg (p less than 0.001) from basal and time-matched placebo values and remained significantly reduced (-17 +/- 4 mm Hg, p less than 0.001) by the end of the recovery period (2 hours after infusions were completed). Pulmonary systolic blood pressure decreased by 5 +/- 1 mm Hg (phase 2, p less than 0.05). Cardiac output decreased by 0.5 +/- 0.1 l/min below baseline at the end of phase 2 of ANF infusion, whereas it increased significantly (p less than 0.02) by 0.6 +/- 0.1 l/min during vehicle infusion. Systemic diastolic, pulmonary diastolic, right atrial, and wedge pressures were not significantly changed during ANF or vehicle infusions, nor were pulmonary vascular resistance or heart rate altered. Systemic vascular resistance did not change significantly during both infusions, whereas during recovery, systemic vascular resistance decreased significantly after ANF infusion was discontinued (p less than 0.05). Microhematocrit levels increased dose dependently during ANF. The maximum increase was observed at the end of phase 2 (+4.7 +/- 1.7%), whereas the microhematocrit level decreased to -2.4 +/- 0.6% with vehicle (p less than 0.001) at the end of phase 2. Urinary sodium excretion increased significantly (p less than 0.02) by the end of phase 2 under ANF infusion (+38 +/- 15%), whereas it decreased (-10 +/- 6%) under placebo infusion by the end of phase 2. Urinary magnesium excretion was significantly increased during ANF infusion from phase 1 (p less than 0.02), whereas urinary potassium levels, calcium levels, creatinine levels, volume, and glomerular filtration rate did not differ significantly between the two infusions. Plasma renin, angiotensin II, aldosterone, and catecholamine concentrations did not change significantly during ANF or vehicle infusions.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of α1-Na,K-ATPase and Na,K,2Cl-Cotransporter Genes in Human Essential Hypertension

Essential hypertension is a common disease the genetic determinants of which have been difficult to unravel because of its clinical heterogeneity and complex, multifactorial, polygenic etiology. Based on our observations that α1-Na,K-ATPase ( ATP1A1 ) and renal-specific, bumetanide-sensitive Na,K,2Cl-cotransporter ( NKCC2 ) genes interactively increase susceptibility to hypertension in the Dahl salt-sensitive hypertensive (Dahl S) rat model, we investigated whether parallel molecular genetic mechanisms might exist in human essential hypertension in a relatively genetic homogeneous cohort in northern Sardinia. Putative ATP1A1-NKCC2 gene interaction was tested by comparing hypertensive patients (blood pressure [BP] >165/95 mm Hg) with normotensive controls age >60 years with BP <140/85 mm Hg. Genotype analysis with microsatellite markers revealed conformation to Hardy-Weinberg proportions for 6 alleles of both ATP1A1 ( D1S453 ) and NKCC2 ( NKCGT7 ) markers, respectively. Two-by-six χ2 analysis of alleles identified overrepresentation of ATP1A1 No. 4 and NKCC2 No. 4 alleles, respectively, in hypertensives compared with controls. With a qualitative trait framework, single-gene analysis detected association of both the ATP1A1 No. 4 allele ( P =0.004, χ2=8.094, df =1) and the NKCC2 No. 4 allele ( P =0.0002, χ2=14.279, df =1) with moderate to severe hypertension. Digenic analysis revealed that ATP1A1 No. 4– NKCC2 No. 4 allele interaction increases susceptibility to hypertension ( P <0.0001, χ2=22.3, df =1) beyond levels obtained in single-gene analysis. Analysis was also performed in a quantitative trait framework with BP as the continuous trait parameter. Digenic analysis of ATP1A1 No. 4– NKCC2 No. 4 allele interaction revealed significant association with systolic (1-way ANOVA, P =0.000076) and diastolic ( P =0.00099) BP. Interaction was corroborated by 2×2 factorial ANOVA for interaction (systolic BP interaction term, P <0.05, diastolic BP interaction term, P =0.035). The data are compelling that ATP1A1 and NKCC2 genes are candidate interacting hypertension-susceptibility loci in human essential hypertension and affirm gene interaction as an important genetic mechanism underlying hypertension susceptibility. Although corroboration in other cohorts and identification of functionally significant mutations are imperative next steps, the data provide a genotype-stratification scheme, with 4-fold predictive value (odds ratio, 4.28; 95% confidence interval, 2.29 to 8.0), which could help decipher the complex genetics of essential hypertension.

Brain kinins are responsible for the pressor effect of intracerebroventricular captopril in spontaneously hypertensive rats.

The role of the brain kallikrein-kinin system in the regulation of arterial blood pressure of normotensive and spontaneously hypertensive rats was evaluated. Intracerebroventricular administration of the kinin antagonist [DArg0]Hyp3-Thi5,8[DPhe7]bradykinin caused no change in mean blood pressure in Wistar-Kyoto, Sprague-Dawley, or spontaneously hypertensive rats. The antagonist proved to be very potent in blocking the pressor effect of intracerebroventricular bradykinin (32 +/- 3 vs. 3 +/- 1 mm Hg, p less than 0.01). It was specific, as the pressor effect induced by other unrelated peptides was similar during the infusion of either vehicle or kinin antagonist (angiotensin II, 25 +/- 4 vs. 26 +/- 2 mm Hg; prostaglandin E2, 48 +/- 3 vs. 47 +/- 8 mm Hg; norepinephrine, 17 +/- 2 vs. 18 +/- 2 mm Hg; leucine-enkephaline, 15 +/- 2 vs. 16 +/- 1 mm Hg; neurotensin, 18 +/- 2 vs. 19 +/- 1 mm Hg; substance P, 19 +/- 2 vs. 19 +/- 2 mm Hg). Intracerebroventricular administration of 1 mg captopril, an inhibitor of kininase II (one of the enzymes responsible for kinin degradation), caused no change in mean blood pressure in normotensive rats, whereas it increased mean blood pressure by 44 +/- 9 mm Hg (p less than 0.01) in spontaneously hypertensive rats. This increase in mean blood pressure was blocked and then reversed into a hypotensive effect (22 +/- 6 mm Hg, p less than 0.05) during the infusion of kinin antagonist. Our data suggest that the pressor effect induced by intracerebroventricular captopril is due to a transient elevation in endogenous brain kinin levels, supporting the hypothesis that the brain kallikrein-kinin system plays a role in the central regulation of blood pressure in spontaneously hypertensive rats.

Association of ATP1A1 and Dear Single-Nucleotide Polymorphism Haplotypes With Essential Hypertension Sex-Specific and Haplotype-Specific Effects

Essential hypertension remains a major risk factor for cardiovascular and cerebrovascular diseases. As a complex multifactorial disease, elucidation of susceptibility loci remains elusive. ATP1A1 and Dear are candidate genes for 2 closely linked rat chromosome-2 blood pressure quantitative trait loci. Because corresponding human syntenic regions are on different chromosomes, investigation of ATP1A1 (chromosome [chr]-1p21) and Dear (chr-4q31.3) facilitates genetic analyses of each blood pressure quantitative trait locus in human hypertension. Here we report the association of human ATP1A1 (P<0.000005) and Dear (P<0.03) with hypertension in a relatively isolated, case/control hypertension cohort from northern Sardinia by single-nucleotide polymorphism haplotype analysis. Sex-specific haplotype analyses detected stronger association of both loci with hypertension in males than in females. Haplotype trend-regression analyses support ATP1A1 and Dear as independent susceptibility loci and reveal haplotype-specific association with hypertension and normotension, thus delineating haplotype-specific subsets of hypertension. Although investigation in other cohorts needs to be performed to determine genetic effects in other populations, haplotype subtyping already allows systematic stratification of susceptibility and, hence, clinical heterogeneity, a prerequisite for unraveling the polygenic etiology and polygene–environment interactions in essential hypertension. As hypertension susceptibility genes, coexpression of ATP1A1 and Dear in both renal tubular cells and vascular endothelium suggest a cellular pathogenic scaffold for polygenic mechanisms of hypertension, as well as the hypothesis that ATP1A1 and/or Dear could contribute to the known renal and vascular endothelial dysfunction associated with essential (polygenic) hypertension.

Bradykinin B2-receptor blockade facilitates deoxycorticosterone-salt hypertension.

The contribution of endogenous kinins to the regulation of blood pressure, urinary volume, and renal sodium excretion was evaluated in Wistar rats on high sodium intake by using the new bradykinin receptor antagonist Hoe 140 (D-Arg,[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin). Neither Hoe 140 (3 nmol/hr s.c. for 4 weeks) nor its vehicle altered systolic blood pressure (tail-cuff plethysmography) or renal function in rats given saline solution (0.15 mol/L NaCl) to drink ad libitum. Four-week administration of deoxycorticosterone (DOC), combined with high sodium intake and uninephrectomy, increased systolic blood pressure from 127 +/- 3 to 160 +/- 3 mm Hg (p < 0.01). When long-term infusion of Hoe 140 was combined with DOC, high sodium intake, and uninephrectomy, systolic blood pressure rose from 127 +/- 3 to 175 +/- 3 mm Hg (p < 0.01). The hypertensive effect was greater in the Hoe 140 group (48 +/- 4 versus 33 +/- 3 mm Hg in controls, p < 0.05). This difference was confirmed by direct measurement of mean blood pressure (Hoe 140 group, 154 +/- 4 mm Hg; vehicle group, 139 +/- 4 mm Hg; p < 0.05). The antagonist blunted the increase in urinary volume induced by salt load and DOC in uninephrectomized rats, whereas it did not alter the increase in urinary sodium excretion. These results suggest that endogenous kinins do not play a major role in the regulation of normal blood pressure in sodium-loaded rats, whereas they may attenuate the hypertensive effect induced by long-term administration of mineralocorticoids and salt in uninephrectomized rats.

Haplotypes of the adrenergic system predict the blood pressure response to β-blockers in women with essential hypertension

AIMS To analyze the association of haplotypes of the adrenergic system with essential hypertension and with the blood pressure response to beta-blockers. MATERIALS & METHODS In 1112 never-treated essential hypertension patients and 203 normotensive controls, tightly linked SNPs of beta-adrenergic receptors (ADRB1 - Ser49Gly and Arg389Gly; ADRB2 - Cys19Arg, Gly16Arg and Gln27Glu) and the G-protein beta3-subunit (GNB3 - A3882C, G5249A and C825T) were genotyped. Association of haplotypes with essential hypertension and with the blood pressure response to atenolol 50 mg twice daily in a subgroup of essential hypertension patients (n = 340) was evaluated (Haploview 3.2). RESULTS No SNPs or haplotypes were associated with essential hypertension. In females only, GNB3 SNPs and haplotypes were associated with the blood pressure response (p < 0.05). CONCLUSION Our study confirmed the sex-specific association of GNB3 with the blood pressure response to atenolol with no substantial advantage of the analysis of haplotypes over SNPs.