The natriuretic peptide system: kidney and cardiovascular effects

Unveiling the pathogenic mechanisms of NPR2 missense variants: insights into the genotype-associated severity in acromesomelic dysplasia and short stature

Introduction: Natriuretic peptide receptor 2 (NPR2 or NPR-B) plays a central role in growth development and bone morphogenesis and therefore loss-of-function variations in NPR2 gene have been reported to cause Acromesomelic Dysplasia, Maroteaux type 1 and short stature. While several hypotheses have been proposed to underlie the pathogenic mechanisms responsible for these conditions, the exact mechanisms, and functional characteristics of many of those variants and their correlations with the clinical manifestations have not been fully established. Methods: In this study, we examined eight NPR2 genetic missense variants (p.Leu51Pro, p.Gly123Val, p.Leu314Arg, p.Arg318Gly, p.Arg388Gln, p.Arg495Cys, p.Arg557His, and p.Arg932Cys) Acromesomelic Dysplasia, Maroteaux type 1 and short stature located on diverse domains and broadly classified as variants of uncertain significance. The evaluated variants are either reported in patients with acromesomelic dysplasia in the homozygous state or short stature in the heterozygous state. Our investigation included the evaluation of their expression, subcellular trafficking and localization, N-glycosylation profiles, and cyclic guanosine monophosphate (cGMP) production activity. Results and Discussion: Our results indicate that variants p.Leu51Pro, p.Gly123Val, p.Leu314Arg, p.Arg388Gln have defective cellular trafficking, being sequestered within the endoplasmic reticulum (ER), and consequently impaired cGMP production ability. Conversely, variants p.Arg318Gly, p.Arg495Cys, and p.Arg557His seem to display a non-statistically significant behavior that is slightly comparable to WT-NPR2. On the other hand, p.Arg932Cys which is located within the guanylyl cyclase active site displayed normal cellular trafficking profile albeit with defective cGMP. Collectively, our data highlights the genotype-phenotype relationship that might be responsible for the milder symptoms observed in short stature compared to acromesomelic dysplasia. This study enhances our understanding of the functional consequences of several NPR2 variants, shedding light on their mechanisms and roles in related genetic disorders which might also help in their pathogenicity re-classification.

Neprilysin Inhibition in the Prevention of Anthracycline-Induced Cardiotoxicity

Anthracycline-induced cardiotoxicity (AIC) poses a clinical challenge in the management of cancer patients. AIC is characterized by myocardial systolic dysfunction and remodeling, caused by cardiomyocyte DNA damage, oxidative stress, mitochondrial dysfunction, or renin-angiotensin-aldosterone system (RAAS) dysregulation. In the past decade, after positive results of a PARADIGM-HF trial, a new class of drugs, namely angiotensin receptor/neprilysin inhibitors (ARNi), was incorporated into the management of patients with heart failure with reduced ejection fraction. As demonstrated in a variety of preclinical studies of cardiovascular diseases, the cardioprotective effects of ARNi administration are associated with decreased oxidative stress levels, the inhibition of myocardial inflammatory response, protection against mitochondrial damage and endothelial dysfunction, and improvement in the RAAS imbalance. However, data on ARNi's effectiveness in the prevention of AIC remains limited. Several reports of ARNi administration in animal models of AIC have shown promising results, as ARNi prevented ventricular systolic dysfunction and electrocardiographic changes and ameliorated oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, and the inflammatory response associated with anthracyclines. There is currently an ongoing PRADAII trial aimed to assess the efficacy of ARNi in patients receiving breast cancer treatment, which is expected to be completed by late 2025.

Hemodynamic phenotyping of transgenic rats with ubiquitous expression of an angiotensin-(1-7)-producing fusion protein

Activation of the angiotensin (Ang)-converting enzyme (ACE) 2/Ang-(1-7)/MAS receptor pathway of the renin-angiotensin system (RAS) induces protective mechanisms in different diseases. Herein, we describe the cardiovascular phenotype of a new transgenic rat line (TG7371) that expresses an Ang-(1-7)-producing fusion protein. The transgene-specific mRNA and the corresponding protein were shown to be present in all evaluated tissues of TG7371 with the highest expression in aorta and brain. Plasma Ang-(1-7) levels, measured by radioimmunoassay (RIA) were similar to control Sprague-Dawley (SD) rats, however high Ang-(1-7) levels were found in the hypothalamus. TG7371 showed lower baseline mean arterial pressure (MAP), assessed in conscious or anesthetized rats by telemetry or short-term recordings, associated with increased plasma atrial natriuretic peptide (ANP) and higher urinary sodium concentration. Moreover, evaluation of regional blood flow and hemodynamic parameters with fluorescent microspheres showed a significant increase in blood flow in different tissues (kidneys, mesentery, muscle, spleen, brown fat, heart and skin), with a resulting decrease in total peripheral resistance (TPR). TG7371 rats, on the other hand, also presented increased cardiac and global sympathetic tone, increased plasma vasopressin (AVP) levels and decreased free water clearance. Altogether, our data show that expression of an Ang-(1-7)-producing fusion protein induced a hypotensive phenotype due to widespread vasodilation and consequent fall in peripheral resistance. This phenotype was associated with an increase in ANP together with an increase in AVP and sympathetic drive, which did not fully compensate the lower blood pressure (BP). Here we present the hemodynamic impact of long-term increase in tissue expression of an Ang-(1-7)-fusion protein and provide a new tool to investigate this peptide in different pathophysiological conditions.

The Impact of the Nitric Oxide (NO)/Soluble Guanylyl Cyclase (sGC) Signaling Cascade on Kidney Health and Disease: A Preclinical Perspective

Chronic Kidney Disease (CKD) is a highly prevalent disease with a substantial medical need for new and more efficacious treatments. The Nitric Oxide (NO), soluble guanylyl cyclase (sGC), cyclic guanosine monophosphate (cGMP) signaling cascade regulates various kidney functions. cGMP directly influences renal blood flow, renin secretion, glomerular function, and tubular exchange processes. Downregulation of NO/sGC/cGMP signaling results in severe kidney pathologies such as CKD. Therefore, treatment strategies aiming to maintain or increase cGMP might have beneficial effects for the treatment of progressive kidney diseases. Within this article, we review the NO/sGC/cGMP signaling cascade and its major pharmacological intervention sites. We specifically focus on the currently known effects of cGMP on kidney function parameters. Finally, we summarize the preclinical evidence for kidney protective effects of NO-donors, PDE inhibitors, sGC stimulators, and sGC activators.

Massive Post-Obstructive Diuresis

Patient: Male, 8

Final Diagnosis: Post obstructive diuresis

Symptoms: Nausea • vomiting

Medication: —

Clinical Procedure: Surgical release of obstucted ureter

Specialty: Nephrology

Temporal changes in cardiac oxidative stress, inflammation and remodeling induced by exercise in hypertension: Role for local angiotensin II reduction

Exercise training reduces renin-angiotensin system (RAS) activation, decreases plasma and tissue oxidative stress and inflammation in hypertension. However, the temporal nature of these phenomena in response to exercise is unknown. We sought to determine in spontaneously hypertensive rats (SHR) and age-matched WKY controls the weekly effects of training on blood pressure (BP), plasma and left ventricle (LV) Ang II and Ang-(1–7) content (HPLC), LV oxidative stress (DHE staining), gene and protein expression (qPCR and WB) of pro-inflammatory cytokines, antioxidant enzymes and their consequence on hypertension-induced cardiac remodeling. SHR and WKY were submitted to aerobic training (T) or maintained sedentary (S) for 8 weeks; measurements were made at weeks 0, 1, 2, 4 and 8. Hypertension-induced cardiac hypertrophy was accompanied by acute plasma Ang II increase with amplified responses during the late phase of LV hypertrophy. Similar pattern was observed for oxidative stress markers, TNF alpha and interleukin-1β, associated with cardiomyocytes’ diameter enlargement and collagen deposition. SHR-T exhibited prompt and marked decrease in LV Ang II content (T₁vs T₄ in WKY-T), normalized oxidative stress (T₂), augmented antioxidant defense (T₄) and reduced both collagen deposition and inflammatory profile (T₈), without changing cardiomyocytes’ diameter and LV hypertrophy. These changes were accompanied by decreased plasma Ang II content (T₂-T₄) and reduced BP (T₈). SHR-T and WKY-T showed parallel increases in LV and plasma Ang-(1–7) content. Our data indicate that early training-induced downregulation of LV ACE-AngII-AT1 receptor axis is a crucial mechanism to reduce oxidative/pro-inflammatory profile and improve antioxidant defense in SHR-T, showing in addition this effect precedes plasma RAS deactivation.

Pulmonary vasodilation by phosphodiesterase 5 inhibition is enhanced and nitric oxide independent in early pulmonary hypertension after myocardial infarction

Myocardial infarction (MI) may result in pulmonary hypertension (PH). Inhibition of phosphodiesterase 5 (PDE5), the enzyme responsible for the breakdown of cGMP in vascular smooth muscle, has become part of the contemporary therapeutic armamentarium for pulmonary arterial hypertension and may also be beneficial for PH secondary to MI. Nitric oxide (NO) is an important activator of cGMP synthesis and can be enhanced in early PH and decreased in severe PH. In the present study, we investigated if PDE5 inhibition ameliorates pulmonary hemodynamics in swine with PH secondary to MI and whether NO is essential. The PDE5 inhibitor EMD360527 was administered in awake, chronically instrumented swine with or without MI. At rest, PDE5 inhibition produced pulmonary vasodilation as evidenced by a decrease in pulmonary vascular resistance, which was more pronounced in MI ( n = 5) compared with normal swine ( n = 10, P ≤ 0.01) and was accompanied by an increase in stroke volume in MI swine. Both pulmonary vasodilation and increased stroke volume were maintained during exercise, suggesting that this therapy may improve exercise capacity in patients with PH secondary to MI. Interestingly, prior inhibition of NO significantly enhanced ( P ≤ 0.01) pulmonary vasodilation by PDE5 inhibition in both normal ( n = 8) and MI swine ( n = 5, P ≤ 0.05 vs. normal). This suggests that the increased vasodilator responses to PDE5 inhibition after MI were not due to an increase in NO-induced cGMP production. These observations indicate that PDE5 inhibition represents an interesting pharmacotherapeutic approach in early PH after a recent MI to prevent overt PH. NEW & NOTEWORTHY This research article is the first to describe that pulmonary vasodilation to phosphodiesterase 5 inhibition is enhanced and nitric oxide independent in resting and exercising swine with pulmonary hypertension as a result of myocardial infarction. This suggests that phosphodiesterase 5 inhibition can normalize pulmonary hemodynamics in postcapillary pulmonary hypertension after a recent myocardial infarction and may improve exercise capacity.

Association between plasma proANP and hyperuricemia in Chinese Han women: a cross-sectional study

Background:

Association between pro-atrial natriuretic peptide (proANP) and hyperuricemia has not yet been investigated in population. This study aimed to examine the association in Chinese Han women.

Methods:

We measured plasma proANP, serum uric acid, and other traditional biomarkers in 1360 women older than 30 years residing in the Gusu district of Suzhou City. Association between plasma proANP and hyperuricemia was analyzed in women aged ≥45 years and those aged <45 years, respectively.

Results:

In women aged ≥45 years, the odds ratio (OR) [95% confidence interval (CI)] of hyperuricemia with high proANP (over the median) was 0.57 (0.34–0.97) compared to those with low proANP (p=0.040). After adjustment for age and other potential covariates, a high plasma proANP was associated with a decreased risk of hyperuricemia in women aged ≥45 years (OR 0.40; 95% CI, 0.19–0.84), when the highest and lowest categories were compared. In contrast, there was no association between plasma proANP and hyperuricemia in women aged <45 years. We did not observe a significant interaction between age and proANP (pinteraction=0.113). Sensitivity analyses further confirmed these age-specific findings.

Conclusions:

Plasma proANP was significantly and inversely associated with hyperuricemia in Chinese Han women aged ≥45 years. This study suggests that an increased plasma proANP should be a protective factor of hyperuricemia among middle-aged and old women.

Plasma proANP1-98 levels are positively associated with central obesity: A cross-sectional study in a general population of China

BACKGROUND

Atrial natriuretic peptide (ANP) and its prohormone activating enzyme are associated with central obesity, suggesting there may be a potential relationship between proANP_1-98 and central obesity. However, the association is still lack of population-based evidence. We explored the association in a general population of China.

METHODS

We measured plasma proANP_1-98, waist circumference and other traditional biomarkers in 2203 participants aged≥30y. Multivariate logistic regression models were used to determine the association between plasma proANP_1-98 and central obesity, and odds ratio (OR) and 95% confidence interval (CI) were calculated.

RESULTS

High proANP_1-98 was significantly associated with increased risk of central obesity in participants, and the multivariate adjusted OR (95% CI) of central obesity associated with the second, third and fourth quartiles of proANP_1-98 were 1.33 (1.03-1.72), 1.69 (1.31-2.19) and 1.76 (1.35-2.29), respectively, compared with the lowest quartile of proANP_1-98. There was a dose-response relationship between proANP_1-98 and risk of central obesity among the participants (P_trend<0.001). Sensitivity analyses further confirmed these associations. Adding proANP_1-98 to a model containing conventional risk factors improved discriminatory power of central obesity (as shown by significant improvement in continuous NRI and IDI).

CONCLUSIONS

Contrary to known reduced ANP levels in central obesity, we found that plasma proANP_1-98 was positively associated with central obesity, suggesting that elevated plasma proANP_1-98 may be a marker or a risk factor for central obesity.

Neuronal nitric oxide synthase in hypertension - an update

Hypertension is a prevalent condition worldwide and is the key risk factor for fatal cardiovascular complications, such as stroke, sudden cardiac death and heart failure. Reduced bioavailability of nitric oxide (NO) in the endothelium is an important precursor for impaired vasodilation and hypertension. In the heart, NO deficiency deteriorates the adverse consequences of pressure-overload and causes cardiac hypertrophy, fibrosis and myocardial infarction which lead to fatal heart failure and sudden cardiac death. Recent consensus is that both endothelial and neuronal nitric oxide synthases (eNOS or NOS3 and nNOS or NOS1) are the constitutive sources of NO in the myocardium. Between the two, nNOS is the predominant isoform of NOS that controls intracellular Ca²⁺ homeostasis, myocyte contraction, relaxation and signaling pathways including nitroso-redox balance. Notably, our recent research indicates that cardiac eNOS protein is reduced but nNOS protein expression and activity are increased in hypertension. Furthermore, nNOS is induced by the interplay between angiotensin II (Ang II) type 1 receptor (AT1R) and Ang II type 2 receptor (AT2R), mediated by NADPH oxidase and reactive oxygen species (ROS)-dependent eNOS activity in cardiac myocytes. nNOS, in turn, protects the heart from pathogenesis via positive lusitropy in hypertension. Soluble guanylate cyclase (sGC)-cGMP/PKG-dependent phosphorylation of myofilament proteins are novel targets of nNOS in hypertensive myocardium. In this short review, we will endeavor to overview new findings of the up-stream and downstream regulation of cardiac nNOS in hypertension, shed light on the underlying mechanisms which may be of therapeutic value in hypertensive cardiomyopathy.

Rehabilitation Enablement in Chronic Heart Failure-a facilitated self-care rehabilitation intervention in patients with heart failure with preserved ejection fraction (REACH-HFpEF) and their caregivers: rationale and protocol for a single-centre pilot randomised controlled trial

INTRODUCTION

The Rehabilitation EnAblement in CHronic Heart Failure in patients with Heart Failure (HF) with preserved ejection fraction (REACH-HFpEF) pilot trial is part of a research programme designed to develop and evaluate a facilitated, home-based, self-help rehabilitation intervention to improve self-care and quality of life (QoL) in heart failure patients and their caregivers. We will assess the feasibility of a definitive trial of the REACH-HF intervention in patients with HFpEF and their caregivers. The impact of the REACH-HF intervention on echocardiographic outcomes and bloodborne biomarkers will also be assessed.

METHODS AND ANALYSIS

A single-centre parallel two-group randomised controlled trial (RCT) with 1:1 individual allocation to the REACH-HF intervention plus usual care (intervention) or usual care alone (control) in 50 HFpEF patients and their caregivers. The REACH-HF intervention comprises a REACH-HF manual with supplementary tools, delivered by trained facilitators over 12 weeks. A mixed methods approach will be used to assess estimation of recruitment and retention rates; fidelity of REACH-HF manual delivery; identification of barriers to participation and adherence to the intervention and study protocol; feasibility of data collection and outcome burden. We will assess the variance in study outcomes to inform a definitive study sample size and assess methods for the collection of resource use and intervention delivery cost data to develop the cost-effectiveness analyses framework for any future trial. Patient outcomes collected at baseline, 4 and 6 months include QoL, psychological well-being, exercise capacity, physical activity and HF-related hospitalisation. Caregiver outcomes will also be assessed, and a substudy will evaluate impact of the REACH-HF manual on resting global cardiovascular function and bloodborne biomarkers in HFpEF patients.

ETHICS AND DISSEMINATION

The study is approved by the East of Scotland Research Ethics Service (Ref: 15/ES/0036). Findings will be disseminated via journals and presentations to clinicians, commissioners and service users.

TRIAL REGISTRATION NUMBER

ISRCTN78539530; Pre-results .

Clinical effectiveness and cost-effectiveness of the Rehabilitation Enablement in Chronic Heart Failure (REACH-HF) facilitated self-care rehabilitation intervention in heart failure patients and caregivers: rationale and protocol for a multicentre randomised controlled trial

INTRODUCTION

The Rehabilitation EnAblement in CHronic Heart Failure (REACH-HF) trial is part of a research programme designed to develop and evaluate a health professional facilitated, home-based, self-help rehabilitation intervention to improve self-care and health-related quality of life in people with heart failure and their caregivers. The trial will assess the clinical effectiveness and cost-effectiveness of the REACH-HF intervention in patients with systolic heart failure and impact on the outcomes of their caregivers.

METHODS AND ANALYSIS

A parallel two group randomised controlled trial with 1:1 individual allocation to the REACH-HF intervention plus usual care (intervention group) or usual care alone (control group) in 216 patients with systolic heart failure (ejection fraction <45%) and their caregivers. The intervention comprises a self-help manual delivered by specially trained facilitators over a 12-week period. The primary outcome measure is patients' disease-specific health-related quality of life measured using the Minnesota Living with Heart Failure questionnaire at 12 months' follow-up. Secondary outcomes include survival and heart failure related hospitalisation, blood biomarkers, psychological well-being, exercise capacity, physical activity, other measures of quality of life, patient safety and the quality of life, psychological well-being and perceived burden of caregivers at 4, 6 and 12 months' follow-up. A process evaluation will assess fidelity of intervention delivery and explore potential mediators and moderators of changes in health-related quality of life in intervention and control group patients. Qualitative studies will describe patient and caregiver experiences of the intervention. An economic evaluation will estimate the cost-effectiveness of the REACH-HF intervention plus usual care versus usual care alone in patients with systolic heart failure.

ETHICS AND DISSEMINATION

The study is approved by the North West-Lancaster Research Ethics Committee (ref 14/NW/1351). Findings will be disseminated via journals and presentations to publicise the research to clinicians, commissioners and service users.

TRIAL REGISTRATION NUMBER

ISRCTN86234930; Pre-results.

Carperitide Increases the Need for Renal Replacement Therapy After Cardiovascular Surgery

OBJECTIVES

Acute kidney injury is a common complication after aortic surgery. Carperitide, a human atrial natriuretic peptide, was reported to be effective for preventing acute kidney injury after cardiac surgery. However, most studies were from single centers, and results of meta-analyses are subject to publication bias. The aim of the present study was to investigate whether carperitide preserved renal function in patients undergoing cardiovascular surgery.

DESIGN

Retrospective cohort study.

SETTING

Participating hospitals (N = 281) in a national database from 2010 to 2013.

PARTICIPANTS

Adult patients (N = 47,032) who underwent cardiovascular surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The main intervention variable investigated was the use of carperitide on the day of surgery. Assessed outcomes included receiving renal replacement therapy within 21 days of surgery and in-hospital mortality. Data were available for 47,032 patients, of whom 2,186 (4.6%) received carperitide on the day of surgery. Multivariate logistic regression analysis revealed that carperitide was significantly associated with a greater likelihood of receiving renal replacement therapy within 21 days of surgery, but not with in-hospital mortality.

CONCLUSIONS

In patients undergoing cardiovascular surgery, carperitide significantly increased the odds of receiving renal replacement therapy within 21 days after surgery.

Collecting duct principal cell transport processes and their regulation

The principal cell of the kidney collecting duct is one of the most highly regulated epithelial cell types in vertebrates. The effects of hormonal, autocrine, and paracrine factors to regulate principal cell transport processes are central to the maintenance of fluid and electrolyte balance in the face of wide variations in food and water intake. In marked contrast with the epithelial cells lining the proximal tubule, the collecting duct is electrically tight, and ion and osmotic gradients can be very high. The central role of principal cells in salt and water transport is reflected by their defining transporters-the epithelial Na(+) channel (ENaC), the renal outer medullary K(+) channel, and the aquaporin 2 (AQP2) water channel. The coordinated regulation of ENaC by aldosterone, and AQP2 by arginine vasopressin (AVP) in principal cells is essential for the control of plasma Na(+) and K(+) concentrations, extracellular fluid volume, and BP. In addition to these essential hormones, additional neuronal, physical, and chemical factors influence Na(+), K(+), and water homeostasis. Notably, a variety of secreted paracrine and autocrine agents such as bradykinin, ATP, endothelin, nitric oxide, and prostaglandin E2 counterbalance and limit the natriferic effects of aldosterone and the water-retaining effects of AVP. Considerable recent progress has improved our understanding of the transporters, receptors, second messengers, and signaling events that mediate principal cell responses to changing environments in health and disease. This review primarily addresses the structure and function of the key transporters and the complex interplay of regulatory factors that modulate principal cell ion and water transport.

Function of cGMP-dependent protein kinase II in volume load-induced diuresis

Atrial natriuretic peptide (ANP)/cGMPs cause diuresis and natriuresis. Their downstream effectors beyond cGMP remain unclear. To elucidate a probable function of cGMP-dependent protein kinase II (cGKII), we investigated renal parameters in different conditions (basal, salt diets, starving, water load) using a genetically modified mouse model (cGKII-KO), but did not detect any striking differences between WT and cGKII-KO. Thus, cGKII is proposed to play only a marginal role in the adjustment of renal concentration ability to varying salt loads without water restriction or starving conditions. When WT mice were subjected to a volume load (performed by application of a 10-mM glucose solution (3% of BW) via feeding needle), they exhibited a potent diuresis. In contrast, urine volume was decreased significantly in cGKII-KO. We showed that AQP2 plasma membrane (PM) abundance was reduced for about 50% in WT upon volume load, therefore, this might be a main cause for the enhanced diuresis. In contrast, cGKII-KO mice almost completely failed to decrease AQP2-PM distribution. This significant difference between both genotypes is not induced by an altered p-Ser256-AQP2 phosphorylation, as phosphorylation at this site decreases similarly in WT and KO. Furthermore, sodium excretion was lowered in cGKII-KO mice during volume load. In summary, cGKII is only involved to a minor extent in the regulation of basal renal concentration ability. By contrast, cGKII-KO mice are not able to handle an acute volume load. Our results suggest that membrane insertion of AQP2 is inhibited by cGMP/cGKII.

Acute kidney injury and critical cardiac disease

The field of cardiac intensive care continues to advance in tandem with congenital heart surgery. The survival of patients with critical congenital heart disease is seldom in question. Consequently, the focus has now shifted to that of morbidity reduction and eventual elimination. Acute kidney injury (AKI) after cardiac surgery is associated with adverse outcomes, including prolonged intensive care and hospital stays, diminished quality of life, and increased long-term mortality. Acute kidney injury occurs frequently, complicating 30% to 40% of adult and pediatric cardiac surgeries. Patients who require dialysis are at high risk of mortality, but even minor degrees of postoperative AKI portend a significant increase in mortality and morbidity.

Comparison and evaluation of cardiac biomarkers in patients with intermittent claudication: results from the CAVASIC study

BACKGROUND

Plasma concentrations of the peptides midregional proadrenomedullin (MR-proADM), midregional proatrial natriuretic peptide (MR-proANP), and C-terminal endothelin-1 precursor fragment (CT-proET-1) are increased in various cardiovascular conditions. However, there is limited information about the association and comparative performance of these peptides in peripheral arterial disease (PAD).

METHODS

The associations of MR-proADM, MR-proANP, and CT-proET-1 plasma concentrations with symptomatic PAD were investigated in the CAVASIC (Cardiovascular Disease in Intermittent Claudication) Study. Study participants were a male cohort of 238 patients with a diagnosis of intermittent claudication (IC) and 245 age- and diabetes-matched controls. Results were compared to those for N-terminal pro-B-type natriuretic peptide (NT-proBNP).

RESULTS

Each increase of MR-proADM, MR-proANP, and CT-proET-1 by 1 SD was significantly associated with symptomatic PAD: odds ratio (OR) = 1.78 (95% CI, 1.41-2.25, P < 0.001), OR = 1.32 (95% CI, 1.06-1.66, P = 0.014), and OR = 1.80 (95% CI, 1.43-2.28, P < 0.001), respectively. The association remained significant for all 3 markers after additional adjustment for log C-reactive protein, serum creatinine, HDL cholesterol, and current smoking. When one adjusts for log NT-proBNP and excluding individuals with prevalent cardiovascular disease, MR-proADM and CT-proET-1 still predicted symptomatic PAD. Extended adjustment models including MR-proADM or CT-proET-1 showed significantly improved model fits compared to models including classical cardiac risk factors or NT-proBNP and led to significant reclassification (P < 0.05).

CONCLUSIONS

This study in a male cohort of patients with IC and age- and diabetes-matched controls indicates a significant association of high MR-proADM, MR-proANP, and CT-proET-1 concentrations with PAD. MR-proADM and CT-proET-1 provide additive information in comparison to NT-proBNP. Moreover, MR-proADM and CT-proET-1 significantly predict PAD in those patients and controls free from prevalent CVD.

Interaction of atrial natriuretic peptide and ouabain in the myocardium

Natriuretic peptides and digitalis-like compounds serve as regulators of homeostasis, including control of volume expansion and blood pressure. The aim of the present study was to explore possible interactions between atrial natriuretic peptide (ANP) and ouabain in the heart. ANP (1 nmol/L) had no effect in papillary muscle preparations from guinea pigs. Ouabain (1 µmol/L) induced positive inotropic effect. The addition of ANP prior to ouabain resulted in a significant decrease in the ouabain-induced positive inotropic effect, manifested as an attenuated increase in twitch maximal upward force slope and resting muscular tension. In addition, ANP caused an increase in Na+–K+-ATPase activity in heart microsomal preparations. The effect of ouabain on Na+–K+-ATPase activity was shown in a biphasic manner. Ouabain (0.01–1 nmol/L) had a small but significant increase on pump activity, but higher doses of ouabain inhibited activity. ANP attenuated ouabain-induced Na+–K+-ATPase activity. Furthermore, ouabain (50 nmol/L) or ANP (10 nmol/L) alone induced Akt activation in cardiomyocytes. However, ANP blocked ouabain-induced Akt activation. These results point to the existence of interactions between ANP and ouabain on Na+–K+-ATPase signaling and function in the heart, which may be mediated by regulation of Na+–K+-ATPase activity and (or) signal transduction mechanisms.

B-type natriuretic peptide (BNP), not ANP, is the principal cardiac natriuretic peptide in vertebrates as revealed by comparative studies

The natriuretic peptide (NP) family consists of at least seven members; cardiac ANP, BNP and VNP and brain CNPs (CNP1-4). Phylogenetic and comparative genomic analyses showed that CNP4 is the ancestral molecule of the family, from which CNP3 and CNP1/2 were duplicated in this order, and that the three cardiac NPs were generated from CNP3 by tandem duplication. Seven members existed at the divergence of ray-finned fishes and lobe-finned fishes (tetrapods), but some of the NP genes have disappeared during the course of evolution. In ray-finned fishes, all three cardiac NPs exist in chondrostei and some migratory teleost species, but VNP is generally absent and ANP is absent in a group of teleosts (Beloniformes). In tetrapods, ANP and BNP are present in mammals and amphibians, but ANP is usually absent in reptiles and birds. Thus, BNP is a ubiquitous cardiac NP in bony fishes and tetrapods though elasmobranchs and cyclostomes have only CNP3/4 as a cardiac NP. Functional studies indicate that cardiac NPs are essential Na(+)-extruding hormones throughout vertebrates; they play critical roles in seawater (SW) adaptation in teleosts, while they are important volume-depleting hormones in mammals as water and Na(+) are regulated in parallel in terrestrial animals. In mammals, cardiac NPs become prominent in pathological conditions such as heart failure where they are used in diagnosis and treatment. Although the functional role of BNP has not yet been fully elucidated compared with ANP in non-mammalian vertebrates, it appears that BNP plays pivotal roles in the cardiovascular and body fluid regulation as shown in mammals. ANP has previously been recognized as the principal cardiac NP in mammals and teleosts, but comparative studies have revealed that BNP is the only cardiac NP that exists in all tetrapods and teleosts. This is an excellent example showing that comparative studies have created new insights into the molecular and functional evolution of a hormone family.

B-type natriuretic peptide in patients undergoing orthopaedic surgery: a prospective cohort study

BACKGROUND AND OBJECTIVE

Postoperative cardiac complications pose a substantial risk to patients undergoing orthopaedic surgery.

METHODS

B-type natriuretic peptide (BNP) was determined preoperatively in 270 patients undergoing scheduled orthopaedic surgery. The accuracy of BNP to predict the occurrence of in-hospital cardiac events was evaluated as the primary endpoint. Cardiac events at 1 year of follow-up were considered secondary endpoints.

RESULTS

Preoperative BNP levels were significantly higher in the four patients experiencing in-hospital cardiac events than in patients without events [median 306 pg ml(-1) (range 123-3958) vs. 35 pg ml(-1) (range 14-2074), P = 0.01]. In a receiver operating characteristic analysis for the prediction of in-hospital cardiac events, the area under the receiver operating characteristic curve for BNP was 0.86 (95% confidence interval 0.74-0.99). The optimal predictive accuracy was achieved with a BNP threshold of 174 pg ml(-1). Importantly, the combination of BNP and the American Society of Anesthesiologists score further improved this accuracy. Additionally, BNP retained a high predictive accuracy in the subgroup of patients with known cardiac diseases [area under the receiver operating characteristic curve 0.85 (95% confidence interval from 0.65 to <1)]. The area under the receiver operating characteristic curve for the prediction of long-term cardiac events by BNP was 0.71 (95% confidence interval 0.57-0.84).

CONCLUSION

In patients undergoing orthopaedic surgery, preoperative BNP levels can predict short-term and long-term postoperative cardiac events. Despite the paucity of endpoint events observed in this study, our results are in agreement with all prior investigations. BNP used in addition to an American College of Cardiology/American Heart Association guideline-based risk assessment might, therefore, be a useful tool in the preoperative evaluation of patients undergoing orthopaedic surgery.

Experimental models of duchenne muscular dystrophy: relationship with cardiovascular disease

Almost every boy that has Duchenne Muscular Dystrophy (DMD) will develop cardiac problems. Whereas, it used to be respiratory problems that was the main cause of death in these DMD boys; with the advent of better respiratory care it is now the cardiac involvement that is becoming the most common cause of their death. Once the heart is affected, there is progressive deterioration in the function of the heart over time. The main problem is the death of the cardiomyocytes. The cause of the cardiomyocyte death is due to the loss of dystrophin, this makes the sarcolemma more susceptible to damage, and leads to a cascade of calcium influx, calcium activated proteases and ultimately the death of the cardiomyocyte. The dead cardiomyocytes are replaced by fibrotic tissue, which results in a dilated cardiomyopathy (DCM) developing, which begins in the base of the left ventricle and progresses to involve the entire left ventricle. The treatments used for the DMD cardiomyopathy are based on ones designed for other forms of cardiac weakness and include ACE-inhibitors and β-blockers. New therapies based around the pathophysiology in DMD are now being introduced. This review will look at the pathophysiology of the cardiac problems in DMD and how the various animal models that are available can be used to design new treatment options for DMD boys.

Atrial natriuretic peptides and urodilatin modulate proximal tubule Na(+)-ATPase activity through activation of the NPR-A/cGMP/PKG pathway

The signaling pathway mediating modulation of Na(+)-ATPase of proximal tubule cells by atrial natriuretic peptides (ANP) and urodilatin through receptors located in luminal and basolateral membranes (BLM) is investigated. In isolated BLM, 10(-11)M ANP or 10(-11)M urodilatin inhibited the enzyme activity (50%). Immunodetection revealed the presence of NPR-A in BLM and LLC-PK1 cells. Both compounds increased protein kinase G (PKG) activity (80%) and this effect did not occur with 10(-6)M LY83583, a specific inhibitor of guanylyl cyclase. The inhibitory effect of these peptides on Na(+)-ATPase activity did not occur after addition of 10(-6)M KT5823, a specific inhibitor of PKG. LLC-PK1 cells were used to investigate if ANP and urodilatin change the activity of sodium pumps by luminal receptor interaction. ANP and urodilatin inhibited Na(+)-ATPase activity (50%), with maximal effect at 10(-10)M, similar to 10(-7)M db-cGMP, and did not occur with 10(-7)M LY83583, a guanylyl cyclase inhibitor. ANP and urodilatin specifically inhibit Na(+)-ATPase activity by activation of the cGMP/PKG pathway through NPR-A located in luminal membrane and BLM, increasing understanding of the mechanism of natriuretic peptides on renal sodium excretion, with proximal tubule Na(+)-ATPase one possible target.

Rationale and design of a randomised controlled trial evaluating the effectiveness of an exercise program to improve the quality of life of patients with heart failure in primary care: The EFICAR study protocol

BACKGROUND

Quality of life (QoL) decreases as heart failure worsens, which is one of the greatest worries of these patients. Physical exercise has been shown to be safe for people with heart failure. Previous studies have tested heterogeneous exercise programs using different QoL instruments and reported inconsistent effects on QoL. The aim of this study is to evaluate the effectiveness of a new exercise program for people with heart failure (EFICAR), additional to the recommended optimal treatment in primary care, to improve QoL, functional capacity and control of cardiovascular risk factors.

METHODS/DESIGN

Multicenter clinical trial in which 600 patients with heart failure in NYHA class II-IV will be randomized to two parallel groups: EFICAR and control. After being recruited, through the reference cardiology services, in six health centres from the Spanish Primary Care Prevention and Health Promotion Research Network (redIAPP), patients are followed for 1 year after the beginning of the intervention. Both groups receive the optimized treatment according to the European Society of Cardiology guidelines. In addition, the EFICAR group performs a 3 month supervised progressive exercise program with an aerobic (high-intensity intervals) and a strength component; and the programme continues linked with community resources for 9 months. The main outcome measure is the change in health-related QoL measured by the SF-36 and the Minnesota Living with Heart Failure Questionnaires at baseline, 3, 6 and 12 months. Secondary outcomes considered are changes in functional capacity measured by the 6-Minute Walking Test, cardiac structure (B-type natriuretic peptides), muscle strength and body composition. Both groups will be compared on an intention to treat basis, using multi-level longitudinal mixed models. Sex, age, social class, co-morbidity and cardiovascular risk factors will be considered as potential confounding and predictor variables.

DISCUSSION

A key challenges of this study is to guarantee the safety of the patients; however, the current scientific evidence supports the notion of there being no increase in the risk of decompensation, cardiac events, hospitalizations and deaths associated with exercise, but rather the opposite. Safety assurance will be based on an optimized standardised pharmacological therapy and health education for all the participants.

TRIAL REGISTRATION

Clinical Trials.gov Identifier: NCT01033591.

Role of B-type natriuretic peptide in epoxyeicosatrienoic acid-mediated improved post-ischaemic recovery of heart contractile function

AIMS

This study examined the functional role of B-type natriuretic peptide (BNP) in epoxyeicosatrienoic acid (EET)-mediated cardioprotection in mice with targeted disruption of the sEH or Ephx2 gene (sEH null).

METHODS AND RESULTS

Isolated mouse hearts were perfused in the Langendorff mode and subjected to global no-flow ischaemia followed by reperfusion. Hearts were analysed for recovery of left ventricular developed pressure (LVDP), mRNA levels, and protein expression. Naïve hearts from sEH null mice had similar expression of preproBNP (Nppb) mRNA compared with wild-type (WT) hearts. However, significant increases in Nppb mRNA and BNP protein expression occurred during post-ischaemic reperfusion and correlated with improved post-ischaemic recovery of LVDP. Perfusion with the putative EET receptor antagonist 14,15-epoxyeicosa-5(Z)-enoic acid prior to ischaemia reduced the preproBNP mRNA in sEH null hearts. Inhibitor studies demonstrated that perfusion with the natriuretic peptide receptor type-A (NPR-A) antagonist, A71915, limited the improved recovery in recombinant full-length mouse BNP (rBNP)- and 11,12-EET-perfused hearts as well as in sEH null mice. Increased expression of phosphorylated protein kinase C epsilon and Akt were found in WT hearts perfused with either 11,12-EET or rBNP, while mitochondrial glycogen synthase kinase-3beta was significantly lower in the same samples. Furthermore, treatment with the phosphoinositide 3-kinase (PI3K) inhibitor wortmannin abolished improved LVDP recovery in 11,12-EET-treated hearts but not did significantly inhibit recovery of rBNP-treated hearts.

CONCLUSION

Taken together, these data indicate that EET-mediated cardioprotection involves BNP and PI3K signalling events.

Regulation of renin release by local and systemic factors

The renin-angiotensin system (RAS) is critically involved in the regulation of the salt and volume status of the body and blood pressure. The activity of the RAS is controlled by the protease renin, which is released from the renal juxtaglomerular epithelioid cells into the circulation. Renin release is regulated in negative feedback-loops by blood pressure, salt intake, and angiotensin II. Moreover, sympathetic nerves and renal autacoids such as prostaglandins and nitric oxide stimulate renin secretion. Despite numerous studies there remained substantial gaps in the understanding of the control of renin release at the organ or cellular level. Some of these gaps have been closed in the last years by means of gene-targeted mice and advanced imaging and electrophysiological methods. In our review, we discuss these recent advances together with the relevant previous literature on the regulation of renin release.

Endogenous B-type natriuretic peptide: a limb of the regulatory response to acutely decompensated heart failure

Acutely decompensated heart failure (ADHF) represents an episodic failure of cardiorenal homeostasis that may resolve with upregulation of natriuretic peptides, bradykinin, and certain prostacyclins. B-type natriuretic peptide (BNP) has multiple favorable effects, including vasodilation, diuresis, natriuresis, and inhibition of vascular endothelial proliferation and cardiac fibrosis. By antagonizing the effects of activation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system in volume overload, the endogenous BNP response may help rescue patients from episodic ADHF. Although knowledge of BNP physiology is expanding, we still have limited understanding of the heterogeneity of proBNP-derived molecules, including active 32 amino acid BNP and less active junk BNP forms. Emerging evidence suggests that in ADHF, the endogenous BNP response is overwhelmed by neurohormonal activation. This relative BNP deficiency may also be accompanied by physiologic resistance to BNP. Additionally, abnormalities of BNP production may result in a lower proportion of active BNP relative to less active forms that may also be detected by point-of-care tests. Improved detection of the various BNP species may clarify these concepts and facilitate improved clinical management of ADHF.

Renal effects of ularitide in patients with decompensated heart failure

BACKGROUND

Renal function frequently deteriorates in decompensated heart failure (DHF) patients, and one determinant is reduced renal blood flow. This may, in part, result from low cardiac output (CO), reduced mean arterial pressure (MAP), and venous congestion. The combined impact of both venous congestion (elevated right atrial pressure [RAP]) and low MAP are reflected by a reduced pressure gradient MAP-RAP. This study investigated the renal effects of ularitide, a synthetic version of the renal natriuretic peptide urodilatin in DHF patients.

METHODS

In SIRIUS II, a double-blind phase II trial, 221 patients hospitalized for DHF (with dyspnea at rest or minimal activity, cardiac index <or=2.5 L/min per square meter, and pulmonary artery wedge pressure >or=18 mm Hg) were randomized to a single 24-hour infusion of ularitide (7.5, 15, or 30 ng/kg per minute) or placebo added to standard therapy.

RESULTS

Estimated glomerular filtration rate, serum creatinine, creatinine clearance, and blood urea nitrogen (BUN) were not impaired by ularitide throughout infusion and during a 2-day follow-up period. At 24 hours, 15 ng/kg per minute ularitide reduced BUN levels (-4.07 +/- 12.30 vs -0.20 +/- 7.50 for placebo, P < .05). Ularitide at 15 and 30 ng/kg per minute rapidly elevated CO with sustained effects. Although 15 ng/kg per minute ularitide preserved the pressure gradient MAP-RAP, 30 ng/kg per minute ularitide reduced MAP-RAP by -7.8 +/- 10.6 mm Hg vs -2.4 +/- 9.8 mm Hg for placebo (P < .01, at 6 hours). A strong inverse correlation between MAP-RAP and BUN levels (Corr = -0.50579, P = .00015) was observed with 15 ng/kg per minute ularitide.

CONCLUSIONS

Single 24-hour infusions of ularitide at 15 ng/kg per minute preserved short-term renal function in DHF patients possibly by both elevating CO and maintaining the MAP-RAP pressure gradient.

Effect of atrial natriuretic peptide on left ventricular remodelling in patients with acute myocardial infarction

Atrial natriuretic peptide (ANP) is a member of the natriuretic peptide family that exerts various biological effects via acting on the receptor-guanylyl cyclase system, increasing the content of intracellular cyclic guanosine monophosphate (cGMP). ANP was first identified as a diuretic/natriuretic and vasodilating hormone, but subsequent studies revealed that ANP has a very important function in the inhibition of the renin-angiotensin-aldosterone system (RAAS), endothelin synthesis, and sympathetic nerve activity. Evidence is also accumulating from recent work that ANP exerts its cardioprotective functions not only as a circulating hormone but also as a local autocrine and/or paracrine factor. ANP inhibits apoptosis and hypertrophy of cardiac myocytes, and inhibits proliferation and fibrosis of cardiac fibroblasts. Reperfusion of the ischaemic myocardium by percutaneous coronary intervention (PCI) reduces the infarct size and improves left ventricular (LV) function in patients with acute myocardial infarction (AMI). However, the benefits of PCI in AMI are limited by reperfusion injury. Animal studies have shown that ANP inhibits ischaemia/reperfusion injury, and reduces infarct size. We and others have recently shown that the intravenous administration of ANP inhibits RAAS, sympathetic nerve activity and reperfusion injury, prevents LV remodelling, and improves LV function in patients with AMI. ANP has a variety of cardioprotective effects and is considered to be a very promising adjunct drug for the reperfusion therapy in patients with AMI.

B-Type Natriuretic Peptide Decreases Gastric Emptying and Absorption

Natriuretic peptides have been shown to decrease contractility of isolated gastric smooth muscle cells. However there is a paucity of research showing whether this effect has functional significance in the whole animal. The objective of this study was to test whether intravenously administered B-type Natriuretic Peptide (BNP) has an effect on gastric emptying and/or absorption in a whole animal mouse model. C57BL/6-Wild-type (WT) and Natriuretic Peptide Receptor type A (NPR-A) knockout (KO) mice were used in these studies. Gastric contractility was examined in anesthetized mice before and after BNP vs. vehicle injection. Gastric emptying of gavage fed 70 Kilo Dalton (kDa) FITC-dextran and absorption of 4 kDa FITC-dextran were compared in BNP vs. vehicle treated conscious WT and KO mice. BNP decreased gastric contractility (measured in change in intragastric pressure) from 2.26 ± 0.29 to 1.44 ± 0.11 mmHg ( P < 0.05), pressure returned to 2.08 ± 0.17 after 5 BNP half-lives ( P < 0.05). There was no significant change in the vehicle or KO. BNP also decreased gastric emptying in WT mice compared to vehicle, 87.8 ± 0.8% vs. 97.3 ± 1.04% ( P < 0.05) and this effect showed a dose-response relationship. In KO mice emptying was 95.8 ± 0.5% (BNP) vs. 91.7 ± 0.7% (Vehicle) ( P > 0.05). The absorption in WT mice was 28.2 ± 7.8 (relative fluorescence units) for BNP vs. 91 ± 25.9 for vehicle ( P < 0.05). For KO mice absorption was 64.3 ± 14.9 for BNP vs. 60.6 ± 17.4 for vehicle ( P > 0.05). The results show that BNP decreases intragastric pressure, emptying and absorption by acting via the NPR-A receptor. We postulate that this effect is aimed at decreasing preload through decreased water and electrolyte absorption from the GI tract and may also be responsible for the symptoms of impaired gastrointestinal function observed in heart failure patients.

Use of B-type natriuretic peptide in the risk stratification of acute exacerbations of COPD

BACKGROUND

In patients with COPD, prognosis might be determined at least in part by the extent of cardiac stress induced by hypoxia and pulmonary arterial hypertension.

METHODS

B-type natriuretic peptide (BNP), a quantitative marker of cardiac stress, was determined in 208 consecutive patients presenting to the emergency department with an acute exacerbation of COPD (AECOPD). The accuracy of BNP to predict death at a 2-year follow-up was evaluated as the primary end point. The need for intensive care and in-hospital mortality were determined as secondary end points.

RESULTS

BNP levels were significantly elevated during the acute exacerbation compared to recovery (65 pg/mL; interquartile range [IQR], 34 to 189 pg/mL; vs 45 pg/mL; IQR, 25 to 85 pg/mL; p < 0.001), particularly in those patients requiring ICU treatment (105 pg/mL; IQR, 66 to 553 pg/mL; vs 60 pg/mL; IQR, 31 to 169 pg/mL; p = 0.007). In multivariate Cox regression analysis, BNP accurately predicted the need for ICU care (hazard ratio, 1.13; 95% confidence interval [CI], 1.03 to 1.24 for an increase in BNP of 100 pg/mL; p = 0.008). In a receiver operating characteristic analysis to evaluate the potential of BNP levels to predict short-term and long-term mortality rates, areas under the curve were 0.55 (SD, 0.71; 95% CI, 0.41 to 0.68) and 0.56 (SD, 0.53; 95% CI, 0.45 to 0.66, respectively).

CONCLUSIONS

In patients with AECOPD, BNP levels independently predict the need for intensive care. However, BNP levels failed to adequately predict short-term and long-term mortality rates in AECOPD patients.

Renal expression of the brain and muscle isoforms of glycogen phosphorylase in different cell types

Kidney contains glycogen. Glycogen is degraded by glycogen phosphorylase (GP). This enzyme comes in three isoforms, one of which, the brain isozyme (GP BB), is known to occur in kidney. Its pattern of distribution in rat kidney was studied in comparison to that of the muscle isoform (GP MM) with the aim to see if for GP BB and GP MM there were functional similarities in brain and kidney. In immunoblotting and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) experiments, both isozymes and their respective mRNAs were found in kidney homogenates. GP BB was immunocytochemically detected in collecting ducts which were identified by the marker protein aquaporin-2. GP MM was localized exclusively in interstitial cells of cortex and outer medulla. These cells were identified as fibroblasts by their expression of 5'-ectonucleotidase (cortex) or by their morphology (outer medulla). The physiological role of both isozymes is discussed in respect to local demands of energy and of proteoglycan building blocks.

Hypertensive renal vascular disease and cardiovascular endpoints

PURPOSE OF REVIEW

Hypertension involves the entire cardiovascular system, and hypertensive vascular disease may promote and exacerbate cardiac and renal dysfunction. We discuss the coexistence of cardiorenal disease as a manifestation of vascular involvement in hypertension, and the relationship of biomarkers of renal vascular involvement in hypertension with cardiovascular endpoints.

RECENT FINDINGS

Markers of renal dysfunction, especially microalbuminuria, have been considered recently as potent predictors of cardiovascular morbidity and mortality in all explored populations, including hypertensive individuals. Microalbuminuria, per se, is related to vascular injury and to the increased glomerular permeability of albumin as a direct manifestation of renal vascular involvement in hypertension, a systemic vascular disease. Left ventricular hypertrophy in hypertension develops even before proteinuria or impairment of renal function. Factors including anemia, inflammation and hyperuricemia are either induced or exacerbated by renal vascular disease, and each of these may exert additional influence in determining the increased incidence of cardiovascular events with progressive renal dysfunction.

SUMMARY

The development and progression of vascular disease is the primary determinant in the progressive cardiac and renal dysfunction observed in hypertension and, therefore, is the underlying mechanism of the overall clinical manifestations of cardiorenal disease. Commonly used biomarkers of renal and vascular function are important tools for determination of the progression and, hence, management of hypertensive disease and its complications.

Regulation of atrial natriuretic peptide secretion by a novel Ras-like protein

Atrial cardiomyocytes, neurons, and endocrine tissues secrete neurotransmitters and peptide hormones via large dense-core vesicles (LDCVs). We describe a new member of the Ras family of G-proteins, named RRP17, which is expressed specifically in cardiomyocytes, neurons, and the pancreas. RRP17 interacts with Ca²⁺-activated protein for secretion-1 (CAPS1), one of only a few proteins known to be associated exclusively with LDCV exocytosis. Ectopic expression of RRP17 in cardiomyocytes enhances secretion of atrial natriuretic peptide (ANP), a regulator of blood pressure and natriuresis. Conversely, genetic deletion of RRP17 in mice results in dysmorphic LDCVs, impaired ANP secretion, and hypertension. These findings identify RRP17 as a component of the cellular machinery involved in regulated secretion within the heart and potential mediator of the endocrine influence of the heart on other tissues.

Atrial natriuretic peptide (ANP)-granules in the guinea pig atrial and auricular cardiocytes: an immunocytochemical and ultrastructural morphometric comparative study

The atrial natriuretic peptide (ANP) is a peptide hormone that is mainly produced in the cardiac atria, where it is stored within granules. It is known that the four regions of the atrial-auricular complex (two atria and two auricles) produce and store ANP in the granules. However, no report has been presented comparing the presence of ANP, and the number and diameter of atrial granules in the atria and auricles. ANP immunoreactivity was detected in cardiocytes from the four regions of the atrial-auricular complex. No differences were observed among the regions. The number of granules was greatest in the right atrium followed by the left atrium and left auricle and right auricle, in this order. The diameter of granules in the cardiocytes was significantly largest in the right atrium and reduced via the left auricle to the left atrium and right auricle. Both the number and diameter of the granules are larger in the right atrium in comparison with the other regions of the atrial-auricular complex, which leads to the supposition that this region is the one that most synthesizes and stores the ANP.

Right ventricular failure complicating heart failure: pathophysiology, significance, and management strategies

Right heart failure most commonly results from the complication of left heart failure (systolic or nonsystolic dysfunction) or pulmonary hypertension. Over the past decade, greater attention has been paid to the role of right ventricular failure in the morbidity and mortality associated with cardiomyopathy and pulmonary hypertension. The right ventricle is distinct from the left ventricle not only in its spatial localization, but also in its response to increased afterload and signaling mechanisms. This article discusses the role of right ventricular failure in the setting of heart failure as well as the clinical diagnosis and management of right ventricular failure.

B-type natriuretic peptide: a critical review

Natriuretic peptides have been used as tools for diagnosis and risk stratification in patients with heart failure, myocardial infarction, and unstable coronary syndromes, as well as in the general population. The biology of intra-assay and intraindividual variations of plasma natriuretic peptide levels is still not clearly understood despite their broad adoption in clinical practice. Interpretation of plasma natriuretic peptide levels therefore requires availability of the clinical context as well as considerations of various confounders. It is clear that high plasma natriuretic peptide levels can be highly suggestive of underlying myocardial disease, although a specific underlying cause cannot be identified based on the test results. The potential use of natriuretic peptide levels to monitor and guide patient management or detect subclinical disease states is currently under investigation.

Emerging drugs for acute and chronic heart failure: current and future developments

Heart failure continues to be a major public health issue. Although angiotensin-converting enzyme inhibitors and beta-adrenergic blockers have been broadly used as evidence-based therapies in heart failure, morbidity and mortality remains high. Furthermore, treatment for acute decompensated heart failure and diastolic heart failure (or 'heart failure with preserved ejection fraction') is far from perfect. This review provides a broad overview of some of the novel compounds under investigation for the treatment of heart failure. Novel strategies include drugs that aim to alleviate congestion and improve hemodynamics, drugs that preserve renal function, drugs that reduce arterial and myocardial stiffness, drugs that module myocardial contractility, drugs that affect metabolic and hormonal balance, and drugs that act on existing and novel physiologic targets.

[B-type natriuretic hormone--diagnostic and prognostic cardiovascular biomarker]

Brain natriuretic hormone and N-terminal-probrain natriuretic hormone are equally important cardiovascular biomarkers. Moderately increased brain natriuretic hormone level is a reliable predictor of preclinical, asymptomatic left ventricular dysfunction. Low brain natriuretic hormone levels are extensively used to rule out acute heart failure. Increased brain natriuretic hormone is associated to age, left ventricular hypertrophy, left atrial volume, atrial fibrillation, myocardial ischemia, renal failure, pulmonary hypertension, acute pulmonary embolism and progressive aortic stenosis. In chronic heart failure only high brain natriuretic hormone values support the diagnosis. High brain natriuretic hormone level, however, is an important overall cardiovascular prognostic biomarker. In the near future brain natriuretic hormone appears to be an interesting new therapeutic modality.

Influence of controlled hypotension using esmolol and sodium nitroprusside on natriuretic peptides in patients undergoing endonasal sinus surgery

BACKGROUND AND OBJECTIVE

Atrial and brain natriuretic peptide, synthesized by cardiac myocytes, are mediators secreted secondary to cardiac volume expansion and increased filling pressure. The study was designed to assess serum concentration of atrial and brain natriuretic peptide in patients undergoing endonasal sinus surgery receiving controlled hypotension.

METHODS

We studied 45 patients without cardiovascular history, scheduled for elective endonasal sinus surgery. Patients were allocated to one of three groups: controlled hypotension was induced either by using esmolol (n = 15) or sodium nitroprusside (n = 15) with a mean arterial pressure of 50-55 mmHg. In the control group (n = 15), mean arterial pressure was adjusted to 70-80 mmHg. Atrial and brain natriuretic peptides were measured preoperatively (T1), at the end of surgery (T2), 2 h (T3), 24 h (T4) and 48 h (T5) postoperatively.

RESULTS

Preoperative atrial and brain natriuretic peptide plasma levels were within normal ranges and similar between all groups. Patients treated with esmolol (atrial natriuretic peptide: 2.46 +/- 0.75 microg mL(-1) brain natriuretic peptide: 4.34 +/- 3.06 microg mL(-1)) and sodium nitropusside (atrial natriuretic peptide: 2.48 +/- 0.92 microg mL(-1); brain natriuretic peptide: 4.49 +/- 3.21 microg mL(-1)) showed significantly lower concentrations of atrial and brain natriuretic peptide at T2 and T3 compared with controls (atrial natriuretic peptide: 5.31 +/- 2.32 microg mL(-1); brain natriuretic peptide: 13.26 +/- 8.98 microg mL(-1)) , P < 0.01) as well as a reduction in blood loss and duration of surgery.

CONCLUSIONS

Controlled hypotension decreases the release of natriuretic peptides in cardiovascular healthy patients. This effect may be contributed to by changes in cardiac filling pressure due to lower systemic resistance and diminished perfusion pressure.