Intravenous atrial natriuretic peptide prevents left ventricular remodeling in patients with first anterior acute myocardial infarction

Natriuretic Peptide Receptors (NPRs) as a Potential Target for the Treatment of Heart Failure

PURPOSE OF REVIEW

Heart failure is defined as a complex clinical syndrome that results from any structural or functional impairment of ventricular filling or ejection of blood. The natriuretic peptide is known to exert its biological action on the kidney, heart, blood vessels, renin-angiotensin system, autonomous nervous system, and central nervous system. The natriuretic peptide-natriuretic receptor system plays an important role in the regulation of blood pressure and body fluid volume through its pleiotropic effects.

RECENT FINDINGS

The clinical and animal studies suggest that natriuretic peptide-natriuretic receptors are important targets for the treatment of heart failure and other cardiovascular diseases. Even though attempts targeting natriuretic peptide receptors are underway for heart failure treatment, they seem insufficient despite the receptor systems' potential. This review summarizes natriuretic peptide-natriuretic receptor system's physiological actions and potential target for the treatment of heart failure. Natriuretic peptides play multiple roles in different parts of the body, almost all of the activities related to this receptor system appear to have the potential to be harnessed to treat heart failure or symptoms associated with heart failure.

Single-Dose Treatment with Rapamycin Preserves Post-Ischemic Cardiac Function through Attenuation of Fibrosis and Inflammation in Diabetic Rabbit

Robust activation of mTOR (mammalian target of rapamycin) signaling in diabetes exacerbates myocardial injury following lethal ischemia due to accelerated cardiomyocyte death with cardiac remodeling and inflammatory responses. We examined the effect of rapamycin (RAPA, mTOR inhibitor) on cardiac remodeling and inflammation following myocardial ischemia/reperfusion (I/R) injury in diabetic rabbits. Diabetic rabbits (DM) were subjected to 45 min of ischemia and 10 days of reperfusion by inflating/deflating a previously implanted hydraulic balloon occluder. RAPA (0.25 mg/kg, i.v.) or DMSO (vehicle) was infused 5 min before the onset of reperfusion. Post-I/R left ventricular (LV) function was assessed by echocardiography and fibrosis was evaluated by picrosirius red staining. Treatment with RAPA preserved LV ejection fraction and reduced fibrosis. Immunoblot and real-time PCR revealed that RAPA treatment inhibited several fibrosis markers (TGF-β, Galectin-3, MYH, p-SMAD). Furthermore, immunofluorescence staining revealed the attenuation of post-I/R NLRP3-inflammasome formation with RAPA treatment as shown by reduced aggregation of apoptosis speck-like protein with a caspase recruitment domain and active-form of caspase-1 in cardiomyocytes. In conclusion, our study suggests that acute reperfusion therapy with RAPA may be a viable strategy to preserve cardiac function with the alleviation of adverse post-infarct myocardial remodeling and inflammation in diabetic patients.

NPPA/atrial natriuretic peptide is an extracellular modulator of autophagy in the heart

NPPA/atrial natriuretic peptide (natriuretic peptide type A) exerts critical pleiotropic effects in the cardiovascular system, limiting cardiomyocyte hypertrophy and death, reducing cardiac fibrosis and promoting vascular integrity. However, the molecular mechanisms underlying these beneficial effects still need to be clarified. We demonstrated for the first time that macroautophagy/autophagy is involved in the local protective effects of NPPA in cardiomyocytes (CMs), both in vitro and in vivo. Exogenous NPPA rapidly activates autophagy in CMs through NPR1/type A natriuretic peptide receptor and PRKG/protein kinase G signaling and also increases cardiac autophagy in mice. Remarkably, endogenous NPPA is secreted by CMs in response to glucose deprivation or hypoxia, thereby stimulating autophagy through autocrine/paracrine mechanisms. NPPA preserves cell viability and reduces hypertrophy in response to stress through autophagy activation. In vivo, we found that Nppa knockout mice undergoing ischemia-reperfusion (I/R) show increased infarct size and reduced autophagy. Reactivation of autophagy by Tat-Beclin D11 limits I/R injury. We also found that the protective effects of NPPA in reducing infarct size are abrogated in the presence of autophagy inhibition. Mechanistically, we found that NPPA stimulates autophagy through the activation of TFEB (transcription factor EB). Our data suggest that NPPA is a novel extracellular regulator of autophagy in the heart.

Natriuretic Peptide-Based Novel Therapeutics: Long Journeys of Drug Developments Optimized for Disease States

Simple Summary

Natriuretic peptides are endogenous hormones produced in the heart and vascular endothelium, and they enable cardiorenal protective actions or bone growth via cGMP stimulation through their receptor guanylyl cyclase receptor A or B. To optimize the drug for each disease state, we must consider drug metabolism, delivery systems, and target receptor(s). This review summarizes attempts to develop novel natriuretic peptide-based therapeutics, including novel designer natriuretic peptides and oral drugs to enhance endogenous natriuretic peptides. We introduce some therapeutics that have been successful in clinical practice, as well as the prospective drug developments in the natriuretic peptide system for disease states.

Abstract

The field of natriuretic peptides (NPs) as an endocrine hormone has been developing since 1979. There are three peptides in humans: atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), which bind to the guanylyl cyclase-A (GC-A) receptor (also called natriuretic peptide receptor-A (NPR-A)), and C-type natriuretic peptide (CNP), which binds to the GC-B receptor (also called the NPR-B) and then synthesizes intracellular cGMP. GC-A receptor stimulation has natriuretic, vasodilatory, cardiorenal protective and anti-renin–angiotensin–aldosterone system actions, and GC-B receptor stimulation can suppress myocardial fibrosis and can activate bone growth before epiphyseal plate closure. These physiological effects are useful as therapeutics for some disease states, such as heart failure, hypertension, and dwarfism. To optimize the therapeutics for each disease state, we must consider drug metabolism, delivery systems, and target receptor(s). We review the cardiac NP system; new designer NPs, such as modified/combined NPs and modified peptides that can bind to not only NP receptors but receptors for other systems; and oral drugs that enhance endogenous NP activity. Finally, we discuss prospective drug discoveries and the development of novel NP therapeutics.

Effect of carperitide on the 1 year prognosis of patients with acute decompensated heart failure

Aims

Acute heart failure (AHF) is a clinical syndrome with a poor prognosis and a major public health concern worldwide. The aim of this study was to investigate whether carperitide administration improves the 1 year prognosis of patients with AHF and to check whether there is an optimal dose of the drug.

Methods and results

We analysed the data of COOPERATE‐HF‐J (the Consortium for Pooled Data Analysis regarding Hospitalized Patients with Heart Failure in Japan), combining two cohorts (NARA‐HF and REALITY‐AHF), which included 2435 patients with acute decompensated heart failure. The patients were divided into no carperitide (NO‐ANP, n = 1098); very low‐dose carperitide (VLD‐ANP, <0.02 μg/kg/min, n = 593); and low‐dose carperitide groups (LD‐ANP, ≥0.02 μg/kg/min, n = 744). The primary endpoint was cardiovascular mortality within 1 year after admission. The secondary endpoints were all‐cause mortality and rehospitalization due to worsening heart failure within 1 year after admission. The median carperitide doses in the VLD‐ANP and LD‐ANP groups were 0.013 and 0.025 μg/kg/min, respectively. Kaplan–Meier analysis showed that cardiovascular mortality and all‐cause mortality were significantly lower in the LD‐ANP group than in the NO‐ANP and VLD‐ANP groups (P < 0.001 and P = 0.002, respectively). Multivariable Cox regression analysis for cardiovascular and all‐cause mortality revealed that LD‐ANP was significantly associated with lower cardiovascular and all‐cause mortality within 1 year after admission, even after adjusting other covariates (hazard ratio: 0.696 and 0.791, 95% confidence interval: 0.513–0.944 and 0.628–0.997, P = 0.020 and 0.047, respectively).

Conclusions

Low‐dose carperitide was significantly associated with lower cardiovascular and all‐cause mortality within 1 year after admission. Our results suggest the necessity for well‐designed randomized controlled trials to determine the doses of carperitide that could improve clinical outcomes in patients with AHF.

[The no-Reflow Phenomenon During Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction due to Massive Coronary Thrombosis. Pathogenesis and Predictors of no-Reflow]

Despite successful and timely revascularization of the infarct-related artery, myocardial tissue remains underperfused in some patients. This condition is known as the no-reflow phenomenon, which is associated with a worse prognosis. The first part of the systematic review on no-reflow focuses on description of the no-reflow pathogenesis and predictors. This phenomenon has a complicated, multifactorial pathogenesis, including distal embolization, ischemic injury, reperfusion injury, and a component of individual predisposition. Meanwhile, this phenomenon undergoes spontaneous regression in some patients. Several studies have demonstrated the role of definite biomarkers and clinical indexes as risk predictors for no-reflow. The significance of each pathogenetic component of no-reflow is suggested to be different in different patients, which may warrant an individualized approach in the treatment.

The Role of False Tendons in Left Ventricular Remodeling and Secondary Mitral Regurgitation After Acute Myocardial Infarction

BACKGROUND

Left ventricular false tendons (LVFT) are common structures visualized on transthoracic echocardiography (TTE). The present study tested the hypothesis that LVFT, via a possible 'constraint' mechanism, attenuate left ventricular (LV) remodeling and secondary mitral regurgitation after acute myocardial infarction.

METHODS

Seventy-one patients admitted to the Coronary Care Unit following an ST-elevation (n = 63) or non-ST-elevation (n = 8) myocardial infarction were analyzed; 29 (41%) had LVFT, and 42 (59%) did not (no-LVFT). All had a TTE and at least 1 follow-up study after revascularization. The χ² analysis, Student's t-test, and Mann Whitney U test were used for the statistical analyses.

RESULTS

The mean age (64 vs. 66 years), left ventricular ejection fraction (LVEF) (41% vs. 39%), left ventricular end-diastolic diameter (LVEDd) index (23 mm/m² for both), and prevalence of ≥ moderate secondary/functional mitral regurgitation (MR) (17% vs. 14%) were similar between the LVFT and no-LVFT groups. At 1-year follow-up, there was no significant difference in chamber remodeling amongst the LVFT versus no-LVFT group when assessed by: 1) ≥ 10% decrease in the relative LVEF (24% vs. 26%; p = 0.83); 2) ≥ 10% increase in the LVEDd index (41% vs. 38%, p = 0.98); and, 3) ≥ 10% increase in the LV mass index (48% vs. 41%, p = 0.68). There was no difference in the prevalence of ≥ moderate secondary/functional MR (17% vs. 12%, p = 0.77). Outcomes remained similar when stratifying by LVFT morphology or ischemic territory.

CONCLUSIONS

In patients with mild to moderate LV dysfunction and normal chamber size, LVFT do not affect the development of LV remodeling or secondary/functional MR post-myocardial infarction.

The Role of Natriuretic Peptides in the Regulation of Cardiac Tolerance to Ischemia/Reperfusion and Postinfarction Heart Remodeling

In the past 10 years, mortality from acute myocardial infarction has not decreased despite the widespread introduction of percutaneous coronary intervention. The reason for this situation is the absence in clinical practice of drugs capable of preventing reperfusion injury of the heart with high efficiency. In this regard, noteworthy natriuretic peptides (NPs) which have the infarct-limiting effect, prevent reperfusion cardiac injury, prevent adverse post-infarction remodeling of the heart. Atrial natriuretic peptide does not have the infarct-reducing effect in rats with alloxan-induced diabetes mellitus. NPs have the anti-apoptotic and anti-inflammatory effects. There is indirect evidence that NPs inhibit pyroptosis and autophagy. Published data indicate that NPs inhibit reactive oxygen species production in cardiomyocytes, aorta, heart, kidney and the endothelial cells. NPs can suppress aldosterone, angiotensin II, endothelin-1 synthesize and secretion. NPs inhibit the effects aldosterone, angiotensin II on the post-receptor level through intracellular signaling events. NPs activate guanylyl cyclase, protein kinase G and protein kinase A, and reduce phosphodiesterase 3 activity. NO-synthase and soluble guanylyl cyclase are involved in the cardioprotective effect of NPs. The cardioprotective effect of natriuretic peptides is mediated via activation of kinases (AMPK, PKC, PI3 K, ERK1/2, p70s6 k, Akt) and inhibition of glycogen synthase kinase 3β. The cardioprotective effect of NPs is mediated via sarcolemmal K_ATP channel and mitochondrial K_ATP channel opening. The cardioprotective effect of brain natriuretic peptide is mediated via MPT pore closing. The anti-fibrotic effect of NPs may be mediated through inhibition TGF-β1 expression. Natriuretic peptides can inhibit NF-κB activity and activate GATA. Hemeoxygenase-1 and peroxisome proliferator-activated receptor γ may be involved in the infarct-reducing effect of NPs. NPs exhibit the infarct-limiting effect in patients with acute myocardial infarction. NPs prevent post-infarction remodeling of the heart. To finally resolve the question of the feasibility of using NPs in AMI, a multicenter, randomized, blind, placebo-controlled study is needed to assess the effect of NPs on the mortality of patients after AMI.

The therapeutic effect of B-type natriuretic peptides in acute decompensated heart failure

B-type natriuretic peptide (BNP) exhibits roles in natriuresis and diuresis, making it an ideal drug that may aid in diuresing a fluid-overloaded patient with poor or worsening renal function. Several randomized clinical trials have tested the hypothesis that infusions of pharmacological doses of BNP to acute heart failure (HF) patients may enhance decongestion and preserve renal function in this clinical setting. Unfortunately, none of these have demonstrated beneficial outcomes. The current challenge for BNP research in acute HF lies in addressing a failure of concept and a reluctance to abandon an ineffective research model. Future success will necessitate a detailed understanding of the mechanism of action of BNP, as well as better integration of basic and clinical science.

Cardiovascular Pleiotropic Effects of Natriuretic Peptides

Atrial natriuretic peptide (ANP) is a cardiac hormone belonging to the family of natriuretic peptides (NPs). ANP exerts diuretic, natriuretic, and vasodilatory effects that contribute to maintain water–salt balance and regulate blood pressure. Besides these systemic properties, ANP displays important pleiotropic effects in the heart and in the vascular system that are independent of blood pressure regulation. These functions occur through autocrine and paracrine mechanisms. Previous works examining the cardiac phenotype of loss-of-function mouse models of ANP signaling showed that both mice with gene deletion of ANP or its receptor natriuretic peptide receptor A (NPR-A) developed cardiac hypertrophy and dysfunction in response to pressure overload and chronic ischemic remodeling. Conversely, ANP administration has been shown to improve cardiac function in response to remodeling and reduces ischemia-reperfusion (I/R) injury. ANP also acts as a pro-angiogenetic, anti-inflammatory, and anti-atherosclerotic factor in the vascular system. Pleiotropic effects regarding brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) were also reported. In this review, we discuss the current evidence underlying the pleiotropic effects of NPs, underlying their importance in cardiovascular homeostasis.

Natriuretic Peptides in Cardiac Anesthesia and Intensive Care

Natriuretic peptides, predominantly B-type, are widely used in cardiology as prognostic and diagnostic biomarkers or, much less often, as a substantive treatment tool. They are hormones that are produced mainly in the myocardium in response to overload and ischemia, and their level quite accurately reflects the degree of myocardial dysfunction. Although their use in cardiac anesthesia and intensive care setting seems to be very beneficial for assessing the risk of acute disturbance of myocardial function or its laboratory monitoring, the actual significance of natriuretic peptides in this area is not yet recognized. This is due to the lack of clear diagnostic and prognostic values for these biomarkers supported by high-quality researches. On the basis of the available data, main advantages, existing difficulties, and most effective ways of using natriuretic peptides for determining the risk of heart surgery and assessing the severity of sepsis, pneumonia, and other critical conditions have been discussed in this review. In addition, the expediency of using natriuretic peptides as target parameters for goal-oriented therapy and as a substantive tool for treatment is considered.

Circadian regulation of renal function

The kidneys regulate many vital functions that require precise control throughout the day. These functions, such as maintaining sodium balance or regulating arterial pressure, rely on an intrinsic clock mechanism that was commonly believed to be controlled by the central nervous system. Mounting evidence in recent years has unveiled previously underappreciated depth of influence by circadian rhythms and clock genes on renal function, at the molecular and physiological level, independent of other external factors. The impact of circadian rhythms in the kidney also affects individuals from a clinical standpoint, as the loss of rhythmic activity or clock gene expression have been documented in various cardiovascular diseases. Fortunately, the prognostic value of examining circadian rhythms may prove useful in determining the progression of a kidney-related disease, and chronotherapy is a clinical intervention that requires consideration of circadian and diurnal rhythms in the kidney. In this review, we discuss evidence of circadian regulation in the kidney from basic and clinical research in order to provide a foundation on which a great deal of future research is needed to expand our understanding of circadian relevant biology.

Gallic acid increases atrial natriuretic peptide secretion and mechanical dynamics through activation of PKC

AIMS

Gallic acid (GA) protects against myocardial ischemia-reperfusion (I/R) injury, prevents cardiac hypertrophy and fibrosis, and has anti-inflammatory activity in the heart. However, its effects in regulating atrial natriuretic peptide (ANP) secretion are unknown. The aim of this study was to determine the function of GA in regulating ANP secretion and atrial dynamics in rat atria.

KEY FINDINGS

GA (0.01, 0.05, and 0.1μmol/L) significantly increased atrial ANP secretion and induced positive inotropy dose-dependently. GA (0.1μmol/L) also increased plasma level of ANP and hemodynamics in rats. These effects were accompanied by upregulation of atrial protein kinase C subtypes β and ε (PKC_β and PKC_ε), which was completely blocked by LY333531 and EAVSLKPT, antagonists of protein PKC_β and PKC_ε, respectively. GA-induced ANP secretion was also attenuated by Gö6983 but not rottlerin, antagonists of PKC_α and PKC_δ, and the positive inotropy was reversed by Gö6983. U-73122, a phospholipase C (PLC) antagonist, mitigated the effects of GA on ANP secretion and mechanical dynamics and downregulated Phospho-PLC_β at Ser⁵³⁷ (pPLC_β S537), Phospho-PLC_β at Ser¹¹⁰⁵ (pPLC_β S1105), PKC_β and PKC_ε levels, whereas KN62, an inhibitor of Ca²⁺/calmodulin-dependent kinase II, was not modified the GA-induced ANP secretion and suppressed GA-induced mechanical dynamics.

SIGNIFICANCE

GA promotes ANP secretion and effects positive inotropy with regard to mechanical dynamics through the activation of PLC-PKC signaling in rat atria.

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.

Atrial natriuretic peptide down-regulates neutrophil recruitment on inflamed endothelium by reducing cell deformability and resistance to detachment force

BACKGROUND

Recombinant atrial natriuretic peptide (ANP) is administered in patients with acute heart failure in Japan to improve renal function and hemodynamics, but its anti-inflammatory effect on activated leukocytes may also contribute to its therapeutic efficacy.

OBJECTIVE

Examine unconventional role of ANP in neutrophil adhesion to inflamed endothelium.

METHODS

Human neutrophils were perfused over endothelial monolayers in a microfluidic lab-chip assay. Cell rheology was assessed by micropipette aspiration to assess changes in cortical tension and viscosity. Fluorescence microscopy was applied to measure adhesive contact area and β2-integrin focal bond formation.

RESULTS

ANP inhibited neutrophil rolling and firm adhesion without influencing the upregulation of cellular adhesion molecules on endothelium or the regulation of high affinity CD18 and shedding of L-selectin during neutrophil activation. Exposed to fluid shear, integrin mediated arrest was disrupted with ANP treatment, which elicited formation of long tethers and diminished cell spreading and contact. This correlated with a ∼40% increase in neutrophil viscosity and a reduction in the adhesive footprint.

CONCLUSIONS

A decrease in cell deformation and neutrophil flattening with ANP results in fewer integrin bond clusters, which translates to higher tensile forces and impaired adhesion strengthening and cell detachment.

Recombinant Atrial Natriuretic Peptide Prevents Aberrant Ca2+ Leakage through the Ryanodine Receptor by Suppressing Mitochondrial Reactive Oxygen Species Production Induced by Isoproterenol in Failing Cardiomyocytes

Catecholamines induce intracellular reactive oxygen species (ROS), thus enhancing diastolic Ca²⁺ leakage through the ryanodine receptor during heart failure (HF). However, little is known regarding the effect of atrial natriuretic peptide (ANP) on ROS generation and Ca²⁺ handling in failing cardiomyocytes. The aim of the present study was to clarify the mechanism by which an exogenous ANP exerts cardioprotective effects during HF. Cardiomyocytes were isolated from the left ventricles of a canine tachycardia-induced HF model and sham-operated vehicle controls. The degree of mitochondrial oxidized DNA was evaluated by double immunohistochemical (IHC) staining using an anti-VDAC antibody for the mitochondria and an anti-8-hydroxy-2′-deoxyguanosine antibody for oxidized DNA. The effect of ANP on ROS was investigated using 2,7-dichlorofluorescin diacetate, diastolic Ca²⁺ sparks assessed by confocal microscopy using Fluo 4-AM, and the survival rate of myocytes after 48 h. The double IHC study revealed that isoproterenol (ISO) markedly increased oxidized DNA in the mitochondria in HF and that the ISO-induced DNA damage was markedly inhibited by the co-presence of ANP. ROS production and Ca²⁺ spark frequency (CaSF) were increased in HF compared to normal controls, and were further increased in the presence of ISO. Notably, ANP significantly suppressed both ISO-induced ROS and CaSF without changing sarcoplasmic reticulum Ca²⁺ content in HF (p<0.01, respectively). The survival rate after 48 h in HF was significantly decreased in the presence of ISO compared with baseline (p<0.01), whereas it was significantly improved by the co-presence of ANP (p<0.01). Together, our results suggest that ANP strongly suppresses ISO-induced mitochondrial ROS generation, which might correct aberrant diastolic Ca²⁺ sparks, eventually contributing to the improvement of cardiomyocyte survival in HF.

Clinical Implication of Atrial and Brain Natriuretic Peptide in Coronary Artery Bypass Grafting

Atrial natriuretic peptide and brain natriuretic peptide are known to be indices for heart failure. Atrial natriuretic peptide and brain natriuretic peptide changes in off-pump and on-pump coronary artery bypass grafting is hypothesized to be correlated to clinical implications of coronary artery bypass grafting. 20 consecutive off-pump and 20 consecutive on-pump coronary artery bypass grafting patients were studied. Perioperative atrial natriuretic peptide and brain natriuretic peptide values were measured and statistically analyzed in terms of 14 factors related to myocardial damage and recovery. Postoperative atrial natriuretic peptide plateaued on the third postoperative day and it decreased gradually down to the preoperative level by one month in the off-pump group. Postoperative brain natriuretic peptide plateaued, showed very slow decrease and it never reached down to the preoperative level. The peak brain natriuretic peptide level was correlated with aortic cross-clamp time, postoperative pleural effusion, and postoperative atrial fibrillation ( p < 0.01). The atrial natriuretic peptide change reflected surgical prevention of ventricular remodeling. Brain natriuretic peptide > 450 μg·mL−1 had strong predictive power for atrial fibrillation and pleural effusion and is a useful marker for management of coronary surgery patients.

Is enhancing cGMP-PKG signalling a promising therapeutic target for heart failure with preserved ejection fraction?

Heart failure with preserved ejection fraction, i.e. HFpEF, is highly prevalent in ageing populations, accounting for more than 50 % of all cases of heart failure in Western societies, and is closely associated with comorbidities such as obesity, diabetes and arterial hypertension. However, all large multicentre trials of potential HFpEF treatments conducted to date have failed to produce positive outcomes. These disappointing results suggest that a 'one size fits all' strategy may be ill-suited to HFpEF and support the use of tailored, personalised therapeutic approaches with specific treatments designed for specific comorbidity-related HFpEF phenotypes. The accumulation of a multitude of cardiovascular comorbidities over time leads to increased systemic inflammation, oxidative stress and coronary microvascular endothelial inflammation, eventually resulting in degradation of cyclic guanosine monophosphate (cGMP) via multiple pathways, thereby reducing protein kinase G (PKG) activity. The importance of cGMP-PKG pathway modulation is supported by growing evidence that suggests that this pathway may be a promising therapeutic target, evidence that is mainly based on its role in the phosphorylation of the giant cytoskeletal protein titin. This review will focus on the preclinical and early clinical evidence in the field of cGMP-enhancing therapies and PKG activation.

Interplay Between Adiponectin and Pro-Atrial Natriuretic Peptide and Prognosis in Patients With ST-Segment Elevation Myocardial Infarction

Natriuretic peptides (NPs) may regulate adipocyte metabolism including adiponectin. Infusion of atrial natriuretic peptide (ANP) increases plasma adiponectin in patients with heart failure. However, this relation has not been examined in a clinical setting or in myocardial infarction (MI). Accordingly, we investigated the interplay between proANP and adiponectin and the prognostic implications in patients with MI. We prospectively included 680 patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention from September 2006 to December 2008. Blood samples were drawn immediately before percutaneous coronary intervention. Additionally, we included 40 patients with 4 obtained blood samples during STEMI. Adiponectin and proANP were measured in all plasma samples. All patients were followed for 5 years. End points were all-cause mortality (n = 137) and the combined end point (n = 170) of major adverse cardiovascular events (MACEs). Plasma adiponectin and proANP were strongly associated at admission (r = 0.34, p <0.001). In patients with increasing proANP during STEMI, adiponectin also increased (0.5 ± 0.3 vs -0.1 ± 0.1 mg/L, p = 0.026). During follow-up, patients with higher adiponectin at admission had increased risk of all-cause mortality and MACE (both, p <0.001). After adjustment for confounding risk factors by Cox regression analysis, adiponectin remained an independent predictor of all-cause mortality and MACE: hazard ratio 1.31 (95% confidence interval 1.07 to 1.60; p = 0.009) and 1.31 (95% confidence interval 1.09 to 1.57; p = 0.004), respectively, for each SD increase. However, the association vanished when proANP was included in the analysis. In conclusion, adiponectin is associated with an increased risk of all-cause mortality and MACE. However, concomitantly elevated proANP levels appear to confound the association between adiponectin and worsened outcome.

Molecular Screen Identifies Cardiac Myosin-Binding Protein-C as a Protein Kinase G-Iα Substrate

BACKGROUND

Pharmacological activation of cGMP-dependent protein kinase G I (PKGI) has emerged as a therapeutic strategy for humans with heart failure. However, PKG-activating drugs have been limited by hypotension arising from PKG-induced vasodilation. PKGIα antiremodeling substrates specific to the myocardium might provide targets to circumvent this limitation, but currently remain poorly understood.

METHODS AND RESULTS

We performed a screen for myocardial proteins interacting with the PKGIα leucine zipper (LZ)-binding domain to identify myocardial-specific PKGI antiremodeling substrates. Our screen identified cardiac myosin-binding protein-C (cMyBP-C), a cardiac myocyte-specific protein, which has been demonstrated to inhibit cardiac remodeling in the phosphorylated state, and when mutated leads to hypertrophic cardiomyopathy in humans. GST pulldowns and precipitations with cGMP-conjugated beads confirmed the PKGIα-cMyBP-C interaction in myocardial lysates. In vitro studies demonstrated that purified PKGIα phosphorylates the cMyBP-C M-domain at Ser-273, Ser-282, and Ser-302. cGMP induced cMyBP-C phosphorylation at these residues in COS cells transfected with PKGIα, but not in cells transfected with LZ mutant PKGIα, containing mutations to disrupt LZ substrate binding. In mice subjected to left ventricular pressure overload, PKGI activation with sildenafil increased cMyBP-C phosphorylation at Ser-273 compared with untreated mice. cGMP also induced cMyBP-C phosphorylation in isolated cardiac myocytes.

CONCLUSIONS

Taken together, these data support that PKGIα and cMyBP-C interact in the heart and that cMyBP-C is an anti remodeling PKGIα kinase substrate. This study provides the first identification of a myocardial-specific PKGIα LZ-dependent antiremodeling substrate and supports further exploration of PKGIα myocardial LZ substrates as potential therapeutic targets for heart failure.

B-type natriuretic peptide and heart failure: what can we learn from clinical trials?

The B-type natriuretic peptide (BNP) may favour natriuresis and diuresis, making it an ideal drug to aid in diuresing a fluid-overloaded patient with poor or worsening renal function. Several randomized clinical trials have tested the hypothesis that infusions of pharmacological doses of BNP to acute heart failure (HF) patients may enhance decongestion and preserve renal function in this clinical setting. Unfortunately, none of these has resulted in a better outcome. The current challenge for BNP research in acute HF lies in a failure of concept and reluctance to abandon a demonstrably ineffectual research model. Future success will necessitate a detailed understanding of the mechanism of action of BNP as well as a better integration of basic and clinical science.

Natriuretic Peptides and Cardiometabolic Health

Natriuretic peptides are cardiac-derived hormones with a range of protective functions, including natriuresis, diuresis, vasodilation, lusitropy, lipolysis, weight loss, and improved insulin sensitivity. Their actions are mediated through membrane-bound guanylyl cyclases that lead to production of the intracellular second-messenger cyclic guanosine monophosphate. A growing body of evidence demonstrates that genetic and acquired deficiencies of the natriuretic peptide system can promote hypertension, cardiac hypertrophy, obesity, diabetes mellitus, the metabolic syndrome, and heart failure. Clinically, natriuretic peptides are robust diagnostic and prognostic markers, and augmenting natriuretic peptides is a target for therapeutic strategies in cardiometabolic disease. This review will summarize current understanding and highlight novel aspects of natriuretic peptide biology.

Pharmacologic Therapy for Reducing Myocardial Infarct Size in Clinical Trials

In patients with acute ST-segment elevation myocardial infarction, early, successful, and durable reperfusion therapy optimizes the likelihood of favorable outcomes. Fibrinolysis and primary percutaneous coronary intervention improve survival compared to no reperfusion therapy in large part by reducing infarct size (IS) and preserving left ventricular ejection fraction. There is direct correlation between IS and clinical outcomes. In this article, we will review some of the more promising pharmacological agents geared toward reduction in IS, discuss the major pathways that can lead to this desirable outcome, and evaluate the results of clinical trials performed with these and other compounds.

Carperitide induces coronary vasodilation and limits infarct size in canine ischemic hearts: role of NO

Carperitide is effective for heart failure (HF) owing to its diuretic and vasodilatory effects. This recombinant peptide may also have direct cardioprotective effects because carperitide reduces the severity of heart failure and limits infarct size. Because coronary vasodilation is an important cardioprotective treatment modality, we investigated whether carperitide increased coronary blood flow (CBF) and improved myocardial metabolic and contractile dysfunction during ischemia in canine hearts. We also tested whether carperitide is directly responsible for limiting the infarct size. We infused carperitide at 0.025-0.2 μg kg(-1) min(-1) into the canine coronary artery. A minimum dose of 0.1 μg kg(-1) min(-1) was required to obtain maximal vasodilation. To test the effects of carperitide on ischemic hearts, we reduced perfusion pressure in the left anterior descending coronary artery such that CBF decreased to one-third of the baseline value. At 10 min after carperitide was infused at a dose of 0.1 μg kg(-1) min(-1), we observed increases in CBF, fractional shortening (FS) and pH levels in coronary venous blood without concomitant increases in cardiac nitric oxide (NO) levels; these changes were attenuated using either the atrial natriuretic peptide receptor antagonist HS-142-1 or the NO synthase inhibitor L(ω)-nitroarginine methyl ester (L-NAME). Cyclic guanosine monophosphate (GMP) levels in the coronary artery were elevated in response to carperitide that also limited the infarct size after 90 min of ischemia and subsequent reperfusion. Again, these effects were blunted by L-NAME. Carperitide increases CBF, reduces myocardial contractile and metabolic dysfunction and limits infarct size. In addition, NO is necessary for carperitide-induced vasodilation and cardioprotection in ischemic hearts.

Effect of direct renin inhibitor on left ventricular remodeling in patients with primary acute myocardial infarction

Some patients with acute myocardial infarction (AMI) have a poor prognosis due to left ventricular remodeling (LVR), resulting in the recurrence of congestive heart failure even when therapy with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II type 1 receptor blockers (ARBs) has been initiated. We investigated the effect of early administration of the direct renin inhibitor (DRI) aliskiren in combination with an ACEI or an ARB on LVR using cardiac magnetic resonance (CMR) imaging in patients with AMI.Twenty-one consecutive patients were treated with an ACEI or an ARB (non-DRI group), and another 21 consecutive patients received aliskiren 150 mg/day combined with an ACEI or an ARB (DRI group). CMR imaging was performed 7 days after AMI and 10 months later.CMR imaging revealed no significant changes in LV end-systolic volume, LV end-diastolic volume, or LV ejection fraction between the patients with and without DRI aliskiren. In the DRI group, plasma renin activity was significantly lower in both the acute and chronic phases; however, aldosterone levels were significantly lower in the acute but not the chronic phase.A low dose of aliskiren may be insufficient to maintain suppression of aldosterone under current standard therapies with an ACEI or an ARB and β-blocker in patients with primary AMI, and results in no attenuation of LVR.

Novel vasodilators in heart failure

Heart failure is an important public health problem that is increasing in prevalence throughout the world. Not only is this condition common, but it is associated with significant morbidity and mortality as well as high costs to medical care systems. Vasodilator drugs help unload the heart and may have other effects that could benefit heart failure patients. Consequently, they have emerged as an important therapeutic approach for patients with this condition. Novel vasodilator therapies that are currently in development target new pathways, potentially giving clinicians alternate options for improving outcomes in this vulnerable population. This review focuses on investigational drugs that have the ability to dilate blood vessels amongst their therapeutic properties. These drugs include the natriuretic peptides that activate particulate guanylate cyclase, the novel agent cinaciguat that activates the soluble guanylate cyclase system, and finally a recombinant form of the naturally occurring vasodilating agent relaxin, a hormone that mediates many of the changes that allows the cardiovascular system to successfully adapt to pregnancy.

Inhibition of the Renin-Angiotensin System Reduces the Rise in Serum Aldosterone in Acute Coronary Syndrome Patients with Preserved Left Ventricular Function: Observations from the AVANT GARDE-TIMI 43 Trial

BACKGROUND

Acute coronary syndrome (ACS) activates neurohormonal pathways, including elevations in circulating aldosterone, with deleterious cardiovascular effects. We aimed to determine if early, more complete renin-angiotensin-aldosterone system inhibition (RAASI) in post-ACS patients without ventricular dysfunction or heart failure would result in a graded reduction in aldosterone concentrations.

METHODS

We performed serial measurement of serum aldosterone within the Aliskiren and Valsartan to Reduce NT-proBNP via Renin-Angiotensin-Aldosterone-System Blockade (AVANT GARDE)–Thrombolysis in Myocardial Infarction (TIMI) 43 trial, a randomized double-blind, placebo controlled trial of RAASI by valsartan, aliskiren, or both in post-ACS patients with preserved ventricular function but increased natriuretic peptides. Aldosterone was measured at randomization and week 8.

RESULTS

Median aldosterone concentrations were comparable across treatment arms at baseline (9.26 ng/dL; interquartile range 7.12–12.76; n = 1073). In the placebo group, there was a significant increase in aldosterone over 8 weeks (19.7% rise, 2.20 (0.36) ng/dL, P &lt; 0.0001) that was significantly reduced across active RAASI therapies (1.36 (0.39) ng/dL with aliskiren; 1.02 (0.37) ng/dL with valsartan; and 0.85 (0.37) ng/dL with combination therapy, P trend = 0.008). Compared to placebo, RAASI monotherapy resulted in a pooled relative absolute aldosterone change of −1.01 (0.45) ng/dL (P = 0.026 vs placebo), and combination therapy resulted in a relative absolute aldosterone change of −1.35 (0.52) ng/dL (P = 0.01 vs placebo). No significant difference in aldosterone concentrations was achieved between dual vs single RAASI (P = 0.47).

CONCLUSIONS

In ACS patients with preserved ventricular function but increased natriuretic peptides, serum aldosterone rises over time and is blunted by more complete RAASI. The clinical implications and role for RAASI in this population warrant further investigation.

Left ventricular false tendons: anatomic, echocardiographic, and pathophysiologic insights

Left ventricular (LV) false tendons are chordlike structures that traverse the LV cavity. They attach to the septum, to the papillary muscles, or to the free wall of the ventricle but not to the mitral valve. They are found in approximately half of human hearts examined at autopsy. Although it has been more than 100 years since their initial description, the functional significance of these structures remains largely unexplored. It has been suggested that they retard LV remodeling by tethering the walls to which they are attached, but there are few data to substantiate this. Some studies have suggested that false tendons reduce the severity of functional mitral regurgitation by stabilizing the position of the papillary muscles as the left ventricle enlarges. LV false tendons may also have deleterious effects and have been implicated in promoting membrane formation in discrete subaortic stenosis. This article reviews current understanding of the anatomy, echocardiographic characteristics, and pathophysiology of these structures.

Early results of human atrial natriuretic peptide infusion in non-dialysis patients with chronic kidney disease undergoing isolated coronary artery bypass grafting: the NU-HIT trial for CKD-II

BACKGROUND

Chronic kidney disease (CKD) is an important risk factor for cardiac surgery. In the most recently reported NU-HIT trial for CKD with CKD patients underwent coronary artery bypass grafting (CABG) as subjects, carperitide was reported to be effective in terms of renal function. In the present study, a subanalysis was performed on patients registered in the NU-HIT trial for CKD from the standpoint of renin-angiotensin system, natriuresis and renal function.

METHODS

303 patients with CKD who underwent isolated CABG were divided into a group that received carperitide infusion and another group without carperitide. The renin activity, angiotensin-II, aldosterone, urine-sodium, urine- creatinine, fractional sodium excretion, renal failure index, and BNP levels.

RESULTS

There were significant lower in hANP group than the placebo group, in angiotensin-II at one day postoperatively, and in aldosterone from 0 day to one month postoperatively. FENa was significantly lower in the hANP group at 3 day and one week postoperatively.

CONCLUSIONS

In on pump isolated CABG patients with CKD, carperitide showed a potent natriuretic action and inhibited the renin-angiotensin system, suggesting that it prevented deterioration of postoperative renal function. Our findings raise new possibilities for the perioperative and postoperative management of patients undergoing surgery with cardiopulmonary bypass.

Atrial natriuretic peptide exerts protective action against angiotensin II-induced cardiac remodeling by attenuating inflammation via endothelin-1/endothelin receptor A cascade

We aimed to investigate whether atrial natriuretic peptide (ANP) attenuates angiotensin II (Ang II)-induced myocardial remodeling and to clarify the possible molecular mechanisms involved. Thirty-five 8-week-old male Wistar-Kyoto rats were divided into control, Ang II, Ang II + ANP, and ANP groups. The Ang II and Ang II + ANP rats received 1 μg/kg/min Ang II for 14 days. The Ang II + ANP and ANP rats also received 0.1 μg/kg/min ANP intravenously. The Ang II and Ang II + ANP rats showed comparable blood pressure. Left ventricular fractional shortening and ejection fraction were lower in the Ang II rats than in controls; these indices were higher (P < 0.001) in the Ang II + ANP rats than in the Ang II rats. In the Ang II rats, the peak velocity of mitral early inflow and its ratio to atrial contraction-related peak flow velocity were lower, and the deceleration time of mitral early inflow was significantly prolonged; these changes were decreased by ANP. Percent fibrosis was higher (P < 0.001) and average myocyte diameters greater (P < 0.01) in the Ang II rats than in controls. ANP decreased both myocardial fibrosis (P < 0.01) and myocyte hypertrophy (P < 0.01). Macrophage infiltration, expression of mRNA levels of collagen types I and III, monocyte chemotactic protein-1, and a profibrotic/proinflammatory molecule, tenascin-C (TN-C) were increased in the Ang II rats; ANP significantly decreased these changes. In vitro, Ang II increased expression of TN-C and endothelin-1 (ET-1) in cardiac fibroblasts, which were reduced by ANP. ET-1 upregulated TN-C expression via endothelin type A receptor. These results suggest that ANP may protect the heart from Ang II-induced remodeling by attenuating inflammation, at least partly through endothelin 1/endothelin receptor A cascade.

Physiology and clinical significance of natriuretic hormones

The natriuretic system consists of the atrial natriuretic peptide (ANP) and four other similar peptides including the wrongly named brain natriuretic peptide (BNP). Chemically they are small peptide hormones predominantly secreted by the cardiac myocytes in response to stretching forces. The peptide hormones have multiple renal, hemodynamic, and antiproliferative effects through three different kinds of natriuretic receptors. Clinical interest in these peptide hormones was initially stimulated by the use of these peptides as markers to differentiate cardiac versus noncardiac causes of breathlessness. Subsequently work has been done on using these peptides to prognosticate patients with acute and chronic heart failure and those with acute myocardial infraction. Synthetic forms of both atrial- and brain-natriuretic peptides have been studied and approved for use in acute heart failure with mixed results. This review focuses on the biochemistry and physiology of this fascinating hormone system and the clinical application of these hormones.

Mid-regional pro-atrial natriuretic peptide as a prognostic marker for all-cause mortality in patients with symptomatic coronary artery disease

In the present study, we investigated the prognostic value of MR-proANP (mid-regional pro-atrial natriuretic peptide). We consecutively evaluated a catheterization laboratory cohort of 2700 patients with symptomatic CAD (coronary artery disease) [74.1% male; ACS (acute coronary syndrome), n=1316; SAP (stable angina pectoris), n=1384] presenting to the Cardiology Department of a large primary care hospital, all of whom underwent coronary angiography. Serum MR-proANP and other laboratory markers were sampled at the time of presentation or in the catheterization laboratory. Clinical outcome was assessed by hospital chart analysis and telephone interviews. The primary end point was all-cause death at 3 months after enrolment. Follow-up data were complete in 2621 patients (97.1%). Using ROC (receiver operating characteristic) curves, the AUC (area under the curve) of 0.73 [95% CI (confidence interval), 0.67-0.79] for MR-proANP was significantly higher compared with 0.58 (95% CI, 0.55-0.62) for Tn-I (troponin-I; DeLong test, P=0.0024). According to ROC analysis, the optimal cut-off value of MR-proANP was at 236 pmol/l for all-cause death, which helped to find a significantly increased rate of all-cause death (n=76) at 3 months in patients with elevated baseline concentrations (≥236 pmol/l) compared with patients with a lower concentration level in Kaplan-Meier survival analysis (log rank, P<0.001). The predictive performance of MR-proANP was independent of other clinical variables or cardiovascular risk factors, and superior to that of Tn-I or other cardiac biomarkers (all: P<0.0001). MR-proANP may help in the prediction of all-cause death in patients with symptomatic CAD. Further studies should verify its prognostic value and confirm the appropriate cut-off value.

Targeting reperfusion injury in acute myocardial infarction: a review of reperfusion injury pharmacotherapy

INTRODUCTION

Acute myocardial infarction (AMI) (secondary to lethal ischemia-reperfusion [IR]) contributes to much of the mortality and morbidity from ischemic heart disease. Currently, the treatment for AMI is early reperfusion; however, this itself contributes to the final myocardial infarct size, in the form of what has been termed 'lethal reperfusion injury'. Over the last few decades, the discovery of the phenomena of ischemic preconditioning and postconditioning, as well as remote preconditioning and remote postconditioning, along with significant advances in our understanding of the cardioprotective pathways underlying these phenomena, have provided the possibility of successful mechanical and pharmacological interventions against reperfusion injury.

AREAS COVERED

This review summarizes the evidence from clinical trials evaluating pharmacological agents as adjuncts to standard reperfusion therapy for ST-elevation AMI.

EXPERT OPINION

Reperfusion injury pharmacotherapy has moved from bench to bedside, with clinical evaluation and ongoing clinical trials providing us with valuable insights into the shortcomings of current research in establishing successful treatments for reducing reperfusion injury. There is a need to address some key issues that may be leading to lack of translation of cardioprotection seen in basic models to the clinical setting. These issues are discussed in the Expert opinion section.

M-atrial natriuretic peptide: a novel antihypertensive protein therapy

The natriuretic peptides, specifically atrial natriuretic peptide (ANP), are increasingly recognized to play a fundamental role in blood pressure (BP) regulation. This role in BP regulation reflects the pluripotent cardiorenal actions of ANP, which include diuresis, enhancement of renal blood flow and glomerular filtration rate, systemic vasodilatation, suppression of aldosterone, and inhibition of the sympathetic nervous system. These actions of ANP, in addition to recent human studies demonstrating an association of higher plasma ANP with lower risk of hypertension, support the development of an ANP-based therapy for hypertension. M-ANP is a novel ANP-based peptide that is resistant to proteolytic degradation and possesses greater BP-lowering, renal function-enhancing, and aldosterone-suppressing properties than native ANP. In an animal model of hypertension, M-ANP lowers BP via multiple mechanisms, including vasodilatation, diuresis, and inhibition of aldosterone. Importantly, M-ANP enhances both glomerular filtration rate and renal blood flow despite reductions in BP. The pluripotent BP-lowering actions and concomitant enhancement of renal function associated with M-ANP are highly attractive characteristics for an antihypertensive agent and underscore the therapeutic potential of M-ANP. M-ANP currently is heading into clinical testing, which may advance this novel strategy for human hypertension.

Differences in hemodynamic responses between intravenous carperitide and nicorandil in patients with acute heart failure syndromes

While recent guidelines for the treatment of acute heart failure syndromes (AHFS) recommend pharmacotherapy with vasodilators in patients without excessively low blood pressure (BP), few reports have compared the relative efficiency of vasodilators on hemodynamics in AHFS patients. The present study aimed to assess the differences in hemodynamic responses between intravenous carperitide and nicorandil in patients with AHFS. Thirty-eight consecutive patients were assigned to receive 48-h continuous infusion of carperitide (n = 19; 0.0125-0.05 μg/kg/min) or nicorandil (n = 19; 0.05-0.2 mg/kg/h). Hemodynamic parameters were estimated at baseline, and 2, 24, and 48 h after drug administration using echocardiography. After 48 h of infusion, systolic BP was significantly more decreased in the carperitide group compared with that in the nicorandil group (22.1 ± 20.0 % vs 5.3 ± 10.4 %, P = 0.003). While both carperitide and nicorandil significantly improved hemodynamic parameters, improvement of estimated pulmonary capillary wedge pressure was greater in the carperitide group (38.2 ± 14.5 % vs 26.5 ± 18.3 %, P = 0.036), and improvement of estimated cardiac output was superior in the nicorandil group (52.1 ± 33.5 % vs 11.4 ± 36.9 %, P = 0.001). Urine output for 48 h was greater in the carperitide group, but not to a statistically significant degree (4203 ± 1542 vs 3627 ± 1074 ml, P = 0.189). Carperitide and nicorandil were differentially effective in improving hemodynamics in AHFS patients. This knowledge may enable physicians in emergency wards to treat and manage patients with AHFS more effectively and safely.

Relationship between status of plasma atrial natriuretic peptide and heart rate variability in human subjects

A relationship may exist between plasma atrial natriuretic peptide (P-ANP) and heart rate variability (HRV), which reflects the activity of the autonomic nervous system. We performed a survey in human subjects to examine the relationship between P-ANP and HRV parameters. Three ethnic groups (Han, Uygur, and Kazakh) provided blood and urine samples and underwent 24-h ambulatory blood pressure monitoring and 24-h ECG recording (24-h Holter ECG). There was a positive correlation between P-ANP and HF, as well as a negative correlation between P-ANP and the LF/HF ratio, in all subjects from the 3 ethnic groups. There was no association of BP with any of the blood, urinary, and HRV parameters. Our results suggested the possibility of a relationship between P-ANP and HRV, which reflects autonomic activity. These findings are consistent with the previous report of a close relationship between ANP and cardiac parasympathetic and/or sympathetic activity.

Molecular mechanisms underlying cardiac antihypertrophic and antifibrotic effects of natriuretic peptides

Natriuretic peptides (NPs) exert well-characterized protective effects on the cardiovascular system, such as vasorelaxation, natri- and diuresis, increase of endothelial permeability, and inhibition of renin-angiotensin-aldosterone system. It has been reported that they also possess antihypertrophic and antifibrotic properties and contribute actively to cardiac remodeling. As a consequence, they are involved in several aspects of cardiovascular diseases. Antihypertrophic and antifibrotic actions of NPs appear to be mediated by specific signaling pathways within a more complex cellular network. Elucidation of the molecular mechanisms underlying the effects of NPs on cardiac remodeling represents an important research objective in order to gain more insights on the complex network leading to cardiac hypertrophy, ventricular dysfunction, and transition to heart failure, and in the attempt to develop novel therapeutic agents. The aim of the present article is to review well-characterized molecular mechanisms underlying the antihypertrophic and antifibrotic effects of NPs in the heart that appear to be mainly mediated by guanylyl cyclase type A receptor. In particular, we discuss the calcineurin/NFAT, the sodium exchanger NHE-1, and the TGFβ1/Smad signaling pathways. The role of guanylyl cyclase type B receptor, along with the emerging functional significance of natriuretic peptide receptor type C as mediators of CNP antihypertrophic and antifibrotic actions in the heart are also considered.