A review of the renal and neurohormonal effects of B-type natriuretic peptide

Emerging pathways of communication between the heart and non-cardiac organs

The breakthrough discovery of cardiac natriuretic peptides provided the first direct demonstration of the connection between the heart and the kidneys for the maintenance of sodium and volume homeostasis in health and disease. Yet, little is still known about how the heart and other organs cross-talk. Here, we review three physiological mechanisms of communication linking the heart to other organs through: i) cardiac natriuretic peptides, ii) the microRNA-208a/mediator complex subunit-13 axis and iii) the matrix metalloproteinase-2 (MMP-2)/C-C motif chemokine ligand-7/cardiac secreted phospholipase A2 (sPLA2) axis – a pathway which likely applies to the many cytokines, which are cleaved and regulated by MMP-2. We also suggest experimental strategies to answer still open questions on the latter pathway. In short, we review evidence showing how the cardiac secretome influences the metabolic and inflammatory status of non-cardiac organs as well as the heart.

Effects of recombinant human brain natriuretic peptide on the prognosis of patients with acute anterior myocardial infarction undergoing primary percutaneous coronary intervention: a prospective, multi-center, randomized clinical trial

BACKGROUND

This study aims to investigate the effects of recombinant human brain natriuretic peptide (rhBNP) on serum enzyme data, cardiac function parameters and cardiovascular events in patients with acute anterior myocardial infarction (MI).

METHODS

A total of 421 patients with acute anterior or extensive anterior MI were collected from 20 hospitals. These patients were randomly divided into two groups: rhBNP and control groups. Both groups of patients received primary percutaneous coronary intervention (PCI) within the effective time window. In the rhBNP group, rhBNP administration (0.01 µg/kg/min, 48-72 successive hours) was performed as early as possible after hospital admission. Prior to and one or seven days after PCI, serum concentrations of cardiac troponin (cTnT), creatine kinase-MB (CK-MB) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured. At seven days and 6 months after PCI, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDd) and stroke volume (SV) were measured using 2D Doppler echocardiography. MACEs that occurred during hospitalization and within 6 months after PCI were recorded.

RESULTS

At postoperative days one and seven, serum concentrations of cTnT were significantly lower in the rhBNP group than in the control group. At postoperative day one, serum concentrations of CK-MB were significantly lower in the rhBNP group than in the control group. At postoperative day seven, serum concentrations of NT-proBNP were significantly lower in the rhBNP group than in the control group, and LVEF was significantly greater in the rhBNP group than in the control group. At postoperative 6 months, LVEDd was significantly lower in the rhBNP group compared with the control group. In addition, SV and LVEF were significantly greater in the rhBNP group than in the control group. By postoperative month 6, the incidence of composite cardiovascular events (16.0% vs. 26.0%, P=0.012), cardiac death (7.0% vs.13.5%, P=0.030), and particularly cardiac death + re-hospitalization for congestive heart failure (13.1% vs. 25.5%, P=0.001) were significantly lower in the rhBNP group than in the control group.

CONCLUSIONS

Early intravenous rhBNP administration after PCI significantly lowered the serum concentrations of cTnT and NT-proBNP, increased LVEDd, SV and LVEF, and reduced MACEs, including cardiac death, in patients with acute anterior MI undergoing PCI.

Recombinant human brain natriuretic peptide attenuates LPS-induced cellular injury in human fetal lung fibroblasts via inhibiting MAPK and NF-κB pathway activation

Inflammatory responses are vital in lung injury diseases, particularly acute respiratory distress syndrome (ARDS). Recombinant human brain natriuretic peptide (rhBNP) has been shown to exhibit anti‑inflammatory effects in vivo in our previous studies. The present study aimed to investigate the mechanisms underlying the anti‑inflammatory effects of rhBNP on lipopolysaccharide (LPS)-induced human fetal lung fibroblasts (HFL-1). The results showed that LPS induced a significant increase in the leakage of lactate dehydrogenase and the secretion of interleukin (IL)‑1β. Activation of p38, extracellular-signal regulated kinase (ERK) 1/2, c‑Jun NH2-terminal kinase (JNK) mitogen‑activated protein kinases (MAPK)s, and nuclear factor (NF)‑κB in HFL‑1 cells was also observed following treatment with LPS. Treatment with rhBNP (0.1 µM) reduced the production of IL‑1β at the protein and mRNA levels. Moreover, rhBNP decreased the phosphorylation of p38, ERK1/2 and JNK induced by LPS. However, the JNK inhibitor, SP600125, significantly inhibited LPS‑induced IL‑1β production. These results indicate that the inhibition of IL‑1β by may dependent upon the JNK signaling pathway. The LPS‑induced NF‑κB activation was also suppressed by rhBNP, and IL‑1β production was inhibited by the NF‑κB inhibitor. Furthermore, NF‑κB activation was attenuated by the JNK inhibitor, indicating that NF‑κB activation was dependent on the JNK signaling pathway. The present study suggests that rhBNP exhibits an anti‑inflammatory effect on LPS‑induced HFL‑1 cell injury via the inhibition of MAPK and NF‑κB signaling pathways and may exhibit therapeutic potential for acute lung injury and ARDS.

Preprocedural N-terminal pro-brain natriuretic peptide (NT-proBNP) is similar to the Mehran contrast-induced nephropathy (CIN) score in predicting CIN following elective coronary angiography

BACKGROUND

N-terminal pro-brain natriuretic peptide (NT-proBNP) has been associated with important risk factors for contrast-induced nephropathy (CIN). However, few studies have investigated the predictive value of NT-proBNP itself. This study investigated whether levels of preprocedural NT-proBNP could predict CIN after elective coronary angiography as effectively as the Mehran CIN score.

METHODS AND RESULTS

We retrospectively observed 2248 patients who underwent elective coronary angiography. The predictive value of preprocedural NT-proBNP for CIN was assessed by receiver operating characteristic and multivariable logistic regression analysis. The 50 patients (2.2%) who developed CIN had higher Mehran risk scores (9.5 ± 5.1 versus 4.8 ± 3.8), and higher preprocedural levels of NT-proBNP (5320 ± 7423 versus 1078 ± 2548 pg/mL, P<0.001). Receiver operating characteristic analysis revealed that NT-proBNP was not significantly different from the Mehran CIN score in predicting CIN (C=0.7657 versus C=0.7729, P=0.8431). An NT-proBNP cutoff value of 682 pg/mL predicted CIN with 78% sensitivity and 70% specificity. Multivariable analysis suggested that, after adjustment for other risk factors, NT-proBNP >682 pg/mL was significantly associated with CIN (odds ratio: 4.007, 95% CI: 1.950 to 8.234; P<0.001) and risk of death (hazard ratio: 2.53; 95% CI: 1.49 to 4.30; P=0.0006).

CONCLUSIONS

Preprocedural NT-proBNP >682 pg/mL was significantly associated with the risk of CIN and death. NT-proBNP, like the Mehran CIN score, may be another useful and rapid screening tool for CIN and death risk assessment, identifying subjects who need therapeutic measures to prevent CIN.

Changes in cardiac aldosterone and its synthase in rats with chronic heart failure: an intervention study of long-term treatment with recombinant human brain natriuretic peptide

The physiological mechanisms involved in isoproterenol (ISO)-induced chronic heart failure (CHF) are not fully understood. In this study, we investigated local changes in cardiac aldosterone and its synthase in rats with ISO-induced CHF, and evaluated the effects of treatment with recombinant human brain natriuretic peptide (rhBNP). Sprague-Dawley rats were divided into 4 different groups. Fifty rats received subcutaneous ISO injections to induce CHF and the control group (n=10) received equal volumes of saline. After establishing the rat model, 9 CHF rats received no further treatment, rats in the low-dose group (n=8) received 22.5 μg/kg rhBNP and those in the high-dose group (n=8) received 45 μg/kg rhBNP daily for 1 month. Cardiac function was assessed by echocardiographic and hemodynamic analysis. Collagen volume fraction (CVF) was determined. Plasma and myocardial aldosterone concentrations were determined using radioimmunoassay. Myocardial aldosterone synthase (CYP11B2) was detected by quantitative real-time PCR. Cardiac function was significantly lower in the CHF group than in the control group (P<0.01), whereas CVF, plasma and myocardial aldosterone, and CYP11B2 transcription were significantly higher than in the control group (P<0.05). Low and high doses of rhBNP significantly improved hemodynamics (P<0.01) and cardiac function (P<0.05) and reduced CVF, plasma and myocardial aldosterone, and CYP11B2 transcription (P<0.05). There were no significant differences between the rhBNP dose groups (P>0.05). Elevated cardiac aldosterone and upregulation of aldosterone synthase expression were detected in rats with ISO-induced CHF. Administration of rhBNP improved hemodynamics and ventricular remodeling and reduced myocardial fibrosis, possibly by downregulating CYP11B2 transcription and reducing myocardial aldosterone synthesis.

Dynamic detection of N-terminal pro-B-type natriuretic peptide helps to predict the outcome of patients with major trauma

INTRODUCTION

NT-proBNP and BNP have been demonstrated to be prognostic markers in cardiac disease and sepsis. However, the prognostic value and the dynamic changes of BNP or NT-proBNP in trauma patients remain unclear. The present study was conducted to investigate the dynamic changes of NT-proBNP in patients with major trauma (injury severity score ≥16), determine whether NT-proBNP could be used as a simple index to predict mortality in major trauma patients.

METHODS

This prospective observational study included 60 patients with major trauma. Serum NT-proBNP levels were measured on the 1st, 3rd and 7th day after injury The NT-proBNP levels in survivors were compared with those in non-survivors. The efficacy of NT-proBNP to predict survival was analyzed using receiver operating characteristic curves. An analysis of correlations between NT-proBNP and various factors, including injury severity score, Glasgow coma score, acute physiology and chronic health evaluation II, central venous pressure, creatine kinase-MB, cardiac troponin I and procalcitonin (PCT) was performed. NT-proBNP levels in patients with traumatic brain injury were compared with those in patients without traumatic brain injury. A comparison of NT-proBNP levels between patients with and without sepsis was also performed at each time point.

RESULTS

NT-proBNP levels in non-survivors were significantly higher than those in survivors at all the indicated time points. In the group of non-survivors, NT-proBNP levels on the 7th day were markedly higher than those on the 1st day. In contrast, NT-proBNP levels in survivors showed a reduction over time. The efficacy of NT-proBNP to predict survival was analyzed using ROC curves, and there was no difference in the area under the ROC between NT-proBNP and APACHE II/ISS at the three time points. A significant correlation was found between NT-proBNP and ISS on the 1st day, NT-proBNP and CK-MB, Tn-I and APACHE II on the 3rd day, NT-proBNP and PCT on the 7th day. There were no significant differences in NT-proBNP levels between patients with or without brain trauma at all the indicated time points. NT-proBNP levels in patients with sepsis were significantly higher than those in patients without sepsis at all the indicated time points.

CONCLUSION

These findings suggest that dynamic detection of serum NT-proBNP might help to predict death in patients with major trauma. A high level of NT-proBNP at admission or maintained for several days after trauma indicates poor survival.

The heart as an endocrine organ

The concept of the heart as an endocrine organ arises from the observation that the atrial cardiomyocytes in the mammalian heart display a phenotype that is partly that of endocrine cells. Investigations carried out between 1971 and 1983 characterised, by virtue of its natriuretic properties, a polypeptide referred to atrial natriuretic factor (ANF). Another polypeptide isolated from brain in 1988, brain natriuretic peptide (BNP), was subsequently characterised as a second hormone produced by the mammalian heart atria. These peptides were associated with the maintenance of extracellular fluid volume and blood pressure. Later work demonstrated a plethora of other properties for ANF and BNP, now designated cardiac natriuretic peptides (cNPs). In addition to the cNPs, other polypeptide hormones are expressed in the heart that likely act upon the myocardium in a paracrine or autocrine fashion. These include the C-type natriuretic peptide, adrenomedullin, proadrenomedullin N-terminal peptide and endothelin-1. Expression and secretion of ANF and BNP are increased in various cardiovascular pathologies and their levels in blood are used in the diagnosis and prognosis of cardiovascular disease. In addition, therapeutic uses for these peptides or related substances have been found. In all, the discovery of the endocrine heart provided a shift from the classical functional paradigm of the heart that regarded this organ solely as a blood pump to one that regards this organ as self-regulating its workload humorally and that also influences the function of several other organs that control cardiovascular function.

Acute study of clinical effectiveness of nesiritide in decompensated heart failure: nesiritide redux

Nesiritide, a synthetic drug form of human B-type natriuretic peptide, is approved for the early treatment of dyspnea in acute decompensated heart failure. Meta-analyses suggested a risk of worsening renal insufficiency and mortality with its use. Therefore, the Acute Study of Clinical Effectiveness in Decompensated Heart Failure (ASCEND-HF) was designed as a prospective, multicenter, double-blind, randomized trial to examine the use of nesiritide in this common, morbid, and often lethal clinical condition. Two coprimary end points, dyspnea and 30-day hospital readmission or death, were chosen to examine symptomatic response and objective outcomes, respectively. Preliminary reports from ASCEND-HF investigators suggest no significant improvement in symptoms or clinical outcomes, although no adverse effect on mortality or renal function was noted. We recommend the continued use of nesiritide in acute decompensated heart failure as an individualized case-based therapy to those patients who meet criteria for treatment and are expected to receive benefit from its use.

Efficacy and safety of nesiritide in patients with acute decompensated heart failure

Acute decompensated heart failure is a common clinical problem with associated poor outcomes. Over the last decade, attention to this area has greatly increased, with a focus on medical therapies that may safely offer improvement in acute symptoms and early outcomes. Previous therapies that focused on increased inotropy have generally failed to improve symptoms without adverse consequences. Thus, attention towards vasodilators and natriuretic peptides, such as nesiritide, has increased owing to nesiritide's symptomatic improvement and unique mechanism of improvement in hemodynamics. However, the pathophysiology of acute decompensated heart failure is complex and the impact of nesiritide on important clinical end points, beyond symptomatic and hemodynamic improvement, is unknown.

Molecular and physiological effects of nesiritide

BACKGROUND

Nesiritide (Natrecor, Janssen-Ortho Inc, Canada), or recombinant human B-type natriurtic peptide (BNP), is a molecule identical in structure to endogenous BNP-32. This peptide is secreted from cardiac myocytes in response to volume and pressure overload. While high levels of circulating BNP are measured by commercially available assays during acute decompensated heart failure (ADHF), the detection of alternate, potentially more active, but undermeasured forms of BNP needs to be considered.

AIM

The present review summarizes the molecular and physiological effects of nesiritide in the setting of hospitalized patients with ADHF. In particular, an overview of the molecular structure and circulating isoforms of BNP is given, followed by a discussion of the vasodilatory, renal, antagonistic neurohormonal, pulmonary, anti-inflammatory and cardiac remodelling effects of recombinant human BNP.

SUMMARY

Nesiritide has beneficial effects in the treatment of ADHF that go beyond the traditional goals of reducing pulmonary capillary wedge pressure, preload and afterload, and relieving symptoms of dyspnea. Therefore, the unique pharmacological profile of this medication provides an additional treatment option for Canadian patients with ADHF.

Perinatal profile of ventricular overload markers in congenital diaphragmatic hernia

BACKGROUND

In congenital diaphragmatic hernia (CDH), pulmonary hypertension increases right ventricle (RV) afterload, which could impair heart function and contribute to poor outcome for most affected infants. Nevertheless, the real significance of vascular pulmonary alterations in perinatal hemodynamics is largely unknown. It is defined that ventricular pressure overload induces increased myocardium gene expression of B-type natriuretic peptide (BNP) and components of the renin-angiotensinogen and endothelin (ET)-1 systems. Our aim was to evaluate perinatal myocardium expression of these genes associated with ventricular pressure overload in a nitrofen-induced CDH rat model.

METHODS

In the nitrofen-induced CDH rat model, fetuses from dated pregnant Sprague-Dawley rats at 15.5, 17.5, 19.5 and 21.5 days postcoitum as well as newborn pups were assigned to 3 experimental groups: control, nitrofen (exposed to nitrofen, without CDH), and CDH (exposed to nitrofen, with CDH). Myocardial samples collected from the RV and left ventricle (LV) were processed for quantification of messenger RNA (mRNA) of BNP, angiotensinogen, and ET-1.

RESULTS

The perinatal expression of BNP, angiotensinogen, and ET-1 mRNA in the RV and LV of the control group revealed daily changes. During gestation, the expression of BNP and angiotensinogen mRNA underwent significant oscillation compared with control in both nitrofen-exposed fetuses, although we cannot identify significant differences between the nitrofen and CDH groups. After birth, we found a significant increasing expression of all studied genes only in the RV of CDH pups.

CONCLUSIONS

Perinatal myocardial quantification of BNP, angiotensinogen, and ET-1 mRNA levels suggests that both nitrofen-exposed and control pups revealed prenatal variations of expression of the studied genes. Moreover, CDH is associated with significant molecular alterations only in the RV after birth.

Relation of B-type natriuretic peptide to left ventricular wall stress as assessed by cardiac magnetic resonance imaging in patients with dilated cardiomyopathy

Ventricular loading conditions are crucial determinants of cardiac function and prognosis in heart failure. B-type natriuretic peptide (BNP) is mainly stored in the ventricular myocardium and is released in response to an increased ventricular filling pressure. We examined, therefore, the hypothesis that BNP serum concentrations are related to ventricular wall stress. Cardiac magnetic resonance imaging (MRI) was used to assess left ventricular (LV) mass and cardiac function of 29 patients with dilated cardiomyopathy and 5 controls. Left ventricular wall stress was calculated by using a thick-walled sphere model, and BNP was assessed by immunoassay. LV mass (r = 0.73, p < 0.001) and both LV end-diastolic (r = 0.54, p = 0.001) and end-systolic wall stress (r = 0.66, p < 0.001) were positively correlated with end-diastolic volume. LV end-systolic wall stress was negatively related to LV ejection fraction (EF), whereas end-diastolic wall stress was not related to LVEF. BNP concentration correlated positively with LV end-diastolic wall stress (r = 0.50, p = 0.002). Analysis of variance revealed LV end-diastolic wall stress as the only independent hemodynamic parameter influencing BNP (p < 0.001). The present approach using a thick-walled sphere model permits determination of mechanical wall stress in a clinical routine setting using standard cardiac MRI protocols. A correlation of BNP concentration with calculated LV stress was observed in vivo. Measurement of BNP seems to be sufficient to assess cardiac loading conditions. Other relations of BNP with various hemodynamic parameters (e.g., EF) appear to be secondary. Since an increased wall stress is associated with cardiac dilatation, early diagnosis and treatment could potentially prevent worsening of the outcome.

Effects of ambient air pollution on functional status in patients with chronic congestive heart failure: a repeated-measures study

BACKGROUND

Studies using administrative data report a positive association between ambient air pollution and the risk of hospitalization for congestive heart failure (HF). Circulating levels of B-type natriuretic peptide (BNP) are directly associated with cardiac hemodynamics and symptom severity in patients with HF and, therefore, serves as a marker of functional status. We tested the hypothesis that BNP levels would be positively associated with short-term changes in ambient pollution levels among 28 patients with chronic stable HF and impaired systolic function.

METHODS

BNP was measured in whole blood at 0, 6, and 12 weeks. We used linear mixed models to evaluate the association between fine particulate matter (PM2.5), carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and black carbon and log(BNP). Lags of 0 to 3 days were considered in separate models. We calculated the intraclass correlation coefficient and within-subject coefficient of variation as measures of reproducibility.

RESULTS

We found no association between any pollutant and measures of BNP at any lag. For example, a 10 microg/m3 increase in PM2.5 was associated with a 0.8% (95% CI: -16.4, 21.5; p = 0.94) increase in BNP on the same day. The within-subject coefficient of variation was 45% on the natural scale and 9% on the log scale.

CONCLUSION

These results suggest that serial BNP measurements are unlikely to be useful in a longitudinal study of air pollution-related acute health effects. The magnitude of expected ambient air pollution health effects appears small in relation to the considerable within-person variability in BNP levels in this population.

Controversy and Conflict in the Treatment of Acute Decompensated Heart Failure: Limited Role for Nesiritide

The use of nesiritide for acute decompensated heart failure (ADHF) has been clouded with controversy since its approval in 2001. Extensive marketing and many review articles have established this drug as a safe and superior product to current standards. However, its safety has been called into question by the results of a meta-analysis, and its superiority of important outcomes (length of stay, mortality, decreased readmission rate) has never been proved by a randomized trial against agents with similar vasodilator properties (e.g., nitroglycerin). A review of the available literature on nesiritide in the areas of mortality, renal effects, retrospective studies, use in off-label indications, length of stay, and mortality is presented and illustrates why its use should be limited or even eliminated. After review of this article, the reader should be able to answer the question--if nesiritide had never been approved for use in patients with ADHF, would we have missed it?--with a negative reply.

Administration of brain natriuretic peptide improves cardiac function following operations using extracorporeal circulation in an animal model

The critical phase during cardiosurgical procedures is weaning the diseased heart from the ECC (extracorporeal circulation). Post-ischaemic heart failure sometimes requires the administration of inotropic and/or vasconstrictive agents. The natriuretic peptides influence pre- and after-load through their natriuretic, diuretic and vasodilating actions. To date, there are only a few reports describing the therapeutic effect of BNP (brain natriuretic peptide) administration during cardiosurgical procedures. The aim of the present study was to evaluate the effect of BNP administration following ECC in an animal model. Surgery was performed on 20 pigs using ECC. A 30-min ischaemic episode was simulated. Following de-clamping, BNP was administered to the BNP group (n=10) by an i.v. (intravenous) bolus at 0.3 microg x kg(-1) of body weight x min(-1), followed by an infusion at a rate of 0.015 microg x kg(-1) of body weight x min(-1) for 60 min. The animals in the control group (n=10) received a saline solution instead of BNP. Haemodynamic and clinical chemistry parameters as well as the amount of catecholamines that were required were measured. All of the animals in the BNP group had a significantly better cardiac output and cardiac index at the end of the experiment. Seven out of 10 animals from the control group required catecholamines, whereas only one animal from the BNP group did. Creatine kinase levels were significantly lower in the BNP group. Systemic vascular resistance was markedly lower in the BNP group. In conclusion, administration of BNP is highly effective in treating post-ischaemic heart failure following ECC. Haemodynamics are greatly improved, and there is almost no need for pharmacological support.

Beyond diuretics: management of volume overload in acute heart failure syndromes

Diuretics are an established foundation of therapy for patients with chronic heart failure (HF) as well as for those hospitalized for treatment of acute HF syndromes. Despite the accepted use of diuretics in acute HF syndromes, treatment patterns with diuretics vary widely, and there are no data from randomized studies on the benefit of diuretics on morbidity or mortality in patients hospitalized with acute HF syndromes. Additional pharmacologic therapies that complement or replace diuretics in this setting, especially in patients with diuretic resistance, include positive inotropes, nitrovasodilators, and natriuretic peptides, but data are likewise lacking on important clinical outcomes. Ultrafiltration has also been used as a nonpharmacologic strategy to treat patients with acute HF syndromes who exhibit resistance to diuretics. Effective monitoring of volume status with newer modalities may allow more selective use of diuretics and diuretic-like modalities, but additional randomized trial data are clearly needed to establish ideal strategies to promote volume removal in acute HF syndromes.

Neurohormones and heart failure: the importance of aldosterone

Heart failure is a major cause of cardiovascular morbidity and mortality and its incidence is on the increase. The pathophysiology of heart failure is multi-factorial but recent studies suggest that aldosterone plays an important and independent role in its progression. Emerging evidence now suggests that aldosterone exerts renal-independent effects. It binds to its mineralocorticoid receptor to produce direct effects on the myocardium and vasculature, leading to damaging processes such as hypertrophy, necrosis, fibrosis and endothelial dysfunction, factors known to contribute to the pathophysiology of heart failure. Mineralocorticoid receptor antagonists have thus emerged as a new paradigm for the treatment of heart failure. The benefits of these agents on both morbidity and mortality when used in patients with chronic symptomatic heart failure have been demonstrated by recent trials.