B-type Natriuretic Peptide Treatment Research Articles

Chronic B-Type Natriuretic Peptide Therapy Prevents Atrial Electrical Remodeling in a Rabbit Model of Atrial Fibrillation.

Atrial fibrillation (AF) is an important and growing clinical problem. Current pharmacological treatments are unsatisfactory. Electrical remodeling has been identified as one of the principal pathophysiological mechanisms that promote AF, but there are no effective therapies to prevent or correct electrical remodeling in patients with AF. In AF, cardiac production and circulating levels of B-type natriuretic peptide (BNP) are increased. However, its functional significance in AF remains to be determined. We assessed the hypotheses that chronic BNP treatment may prevent the altered electrophysiology in AF, and preventing AF-induced activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) may play a role. Forty-four rabbits were randomly divided into sham, rapid atrial pacing (RAP at 600 beats/min for 3 weeks), RAP/BNP, and sham/BNP groups. Rabbits in the RAP/BNP and sham/BNP groups received subcutaneous BNP (20 μg/kg twice daily) during the 3-week study period. HL-1 cells were subjected to rapid field stimulation for 24 hours in the presence or absence of BNP, KN-93 (a CaMKII inhibitor), or KN-92 (a nonactive analog of KN-93). We compared atrial electrical remodeling-related alterations in the ion channel/function/expression of these animals. We found that only in the RAP group, AF inducibility was significantly increased, atrial effective refractory periods and action potential duration were reduced, and the density of ICa, L and Ito decreased, while IK1 increased. The changes in the expressions of Cav1.2, Kv4.3, and Kir2.1 and currents showed a similar trend. In addition, in the RAP group, the activation of CaMKIIδ and phosphorylation of ryanodine receptor 2 and phospholamban significantly increased. Importantly, these changes were prevented in the RAP/BNP group, which were further validated by in vitro studies. Chronic BNP therapy prevents atrial electrical remodeling in AF. Inhibition of CaMKII activation plays an important role to its anti-AF efficacy in this model.

172. B-Type Natriuretic Peptide Gene Therapy as a Novel Early Treatment for Familial Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common familial cardiomyopathy, with the prevalence between 0.2 to 0.5%. HCM presents as an increase in left ventricular mass with thickening of the interventricular septum (IVS), myocellular disarray, interstitial fibrosis, heart rhythm abnormalities, and sudden death, necessitating therapeutic intervention. HCM is commonly caused by mutations in genes MYH7, MYBPC3, TNNT2, and TNNI3.The cardiac hormone, B-type natriuretic peptide (BNP) is a guanylyl cyclase A (GC-A) agonist. Physiological effects of BNP include natriuresis, vasodilation and blood pressure-lowering action. Additionally, BNP shows direct cardioprotective properties including anti-hypertrophic and anti-fibrotic effects, independently of its anti-hypertensive effects. We have recently found that genetic BNP ablation results in progressive cardiac hypertrophy with upregulation in HCM-associated genes in rats. In the current study, we tested the hypothesis that sustained BNP treatment with novel gene delivery of BNP may preserve cardiac function and structure in HCM in a mouse model of HCM.We used transgenic HCM mice expressing a mutated α-myosin heavy chain. Adeno-associated virus serotype 9 (AAV9) vectors were utilized to exploit their natural myocardial tropism. Three groups of mice were treated via tail-vein injections at four weeks of age (week one of study); Group 1, No HCM control (C57bl/6, no transgenic α-myosin heavy chain, n=6); Group 2, Untreated HCM mice with transgenic α-myosin heavy chain (PBS treated, n=10); Group 3, AAV9-BNP vector-treated HCM mice (n=6). To observe therapeutic benefit we assayed non-invasive blood pressure, myocardial architecture and remodeling (echocardiography), exercise capacity (treadmills), and any cardiorenal interplay through renal parameters. At 6, 9, 12, 15 and 25 weeks after AAV vector administration, left ventricular mass by echo was significantly higher in the untreated HCM group than the AAV-BNP-treated HCM and wildtype C57bl/6 mice. Significant increases in IVS and posterior wall thickness were also observed in control HCM group. At 11, 19, and 25 weeks after AAV vector administration, exercise capacity, monitored by treadmill tolerance, was significantly lower in the control HCM group than the AAV-BNP-treated HCM mice. No significant changes were seen in urine outputs. HCMAAV9-BNP treated mice showed a trend towards a lower blood pressure than both C57bl/6 and HCM mice.Our data demonstrate that AAV9-mediated BNP over-expression blocks progressive left ventricular enlargement and improves exercise capacity in a mouse model of HCM. The present study supports the BNP/GC-A/cGMP axis as a novel therapeutic target for the treatment of HCM.

0312 : Lebetin 2, a snake venom natriuretic-like peptide and BNP exert cardioprotective effects against ischemia-reperfusion injury in vivo

Myocardial infarction (MI) is associated with inflammatory promoting cell death and subsequent fibrosis leading to cardiac dysfunction. Here, we aimed at testing if Lebetin 2 (L2), a snake venom-derived natriuretic peptide and B-type natriuretic peptide (BNP), modulate inflammatory response to ischemia-reperfusion (IR) injury in rats. All rats were submitted to 30min ischemia. To study the acute effects of natriuretic peptides, rats underwent 90min reperfusion. IR-induced inflammation and fibrosis were studied after 48h or 10 days of reperfusion, respectively. Rats were treated either with saline, 50μg/kg BNP or 100μg/kg L2, administered before reperfusion. Infarct size (IS) and fibrosis were evaluated using planimetry. Inflammation was assessed by studying leukocyte and macrophage infiltration after CD45 and MCR1/CD68 immunostainings respectively, and by quantification of capillary proliferation after CD31 immunostaining. BNP and L2 significantly decreased IS after acute IR (–60% and –40%, p <0.01) and also 10 days post-IR (-60% and –80%, p <0.01). Both natriuretic peptides reduced cardiac fibrosis by 35% for BNP and 60% for L2 ( p <0.05). In inflammation studies, leukocyte and macrophage infiltration in the area at risk was reduced after BNP treatment (–20% and –35% respectively, p <0.05), and after L2 treatment (-30% and –90% respectively, p <0.05), compared to non treated group. BNP decreased capillary proliferation (–41%, p <0.01), when this was increased after L2 treatment (49%, p <0.01). Our results demonstrate that BNP and L2 have cardioprotective effects during myocardial ischemia by reducing infarct size and post-ischemic fibrosis. The beneficial effects of both drugs are due, at least, to inhibition of IR-induced inflammation by reducing leukocyte and macrophage infiltration. However, BNP and L2 seem to have opposite effects on capillary proliferation during IR. The author hereby declares no conflict of interest

8. Guanylyl Cyclase A-Targeted Gene Therapy Ameliorates Disease Progression in Autosomal Recessive Polycystic Kidney Disease

Although Polycystic Kidney Disease (PKD) is a leading cause of renal and hepatic pathologies, there are limited therapies available. PKD presents with cystic manifestations leading to organ enlargement, loss of functional parenchyma, progressive organ dysfunction and hypertension, ultimately leading to organ failure.Cardiac B-type natriuretic peptide (BNP) is central in the control of intravascular volume by regulating water and sodium homeostasis. Additionally, BNP has been characterized to counteract several key properties contributing to cystic disease progression such as; inhibiting fibroblast proliferation, preventing monocyte chemotaxis, antagonizing vasopressin (AVP)-mediated water reabsorption, and preventing renin-angiotensin-aldosterone activation. Along with its blood pressure-lowering propensity, BNP presents a promising therapeutic strategy in hindering the progression of PKD.We investigated the therapeutic effect of vector mediated BNP expression in the rat model of ARPKD (PCK). Littermate PCK neonates received placebo, or single intraperitoneal injection of adeno-associated virus 9 (AAV9) vectors at 1.0E+12 genome copies/kg, under the control of an internal CMV promoter.Three months post treatment, kidney weight was significantly reduced (TKW/BW 12.6±1.7* vs 14.5±2.0) in treated PCK, along with a significant reduction in renal cyst burden. Blood and urine analysis confirmed decreased disease with BNP treatment, with a nearly 50% reduction in 24 hour urine output, (8.8±3* vs 13.2±1 mL/24-hr), higher creatinine clearance (eGFR: 0.51±0.1* vs 0.26±0.2 mL/min), decreased proteinuria (490±270* vs 270±190 mg/dL), and increased urine concentrations of sodium (130±39* vs 85±20 mmol/L) and potassium (395.8±41* vs 282.1±75 mmol/L) in treated PCK, compared to controls, respectively. Excretion of renal injury markers, kidney injury molecule-1 and lipocalin-2, was lower in BNP-treated rats compared to controls. BNP treatment also preserved glomerular architecture, retarded basement membrane thickening and glomerular sclerosis in PCK. Real-time RT-PCR analysis demonstrated that BNP treatment significantly reduced renal and hepatic expression of the fibrosis-associated genes; Collagen, fibronectin, and transforming growth factor β. Furthermore, liver protection, in BNP-treated PCK, was observed through decreased expression of fibrosis marker desmin, and galectin-3, along with decreased cyst-index. Additionally, echocardiography demonstrated preserved cardiac function with treatment (ejection fraction: 78±5 * vs 73±5%) at three months, though both groups remained normotensive.Together, these observations indicate that a single intraperitoneal AAV9 injection elicits therapeutic benefit in protecting against declining hepatic and renal function, remodeling of healthy parenchyma, and increased cyst burden, while providing cardiac protection. The present study further suggests that sustained GC-A activation provides a novel opportunity for the treatment of polycystic kidney and liver diseases.±±

B-type natriuretic peptide inhibits angiotensin II-induced proliferation and migration of pulmonary arterial smooth muscle cells

Pulmonary vascular remodeling, characterized by disordered proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), is a pathognomonic feature of pulmonary arterial hypertension. Thus, pharmacologic strategy targeting on anti-proliferation and anti-migration of PASMCs may have therapeutic implications for PAH. Here we investigated the effects and underlying mechanisms of B-type natriuretic peptide (BNP) on angiotensin II (Ang II)-induced proliferation and migration of PASMCs. Proliferation and migration of PASMCs cultured from Wistar rats were induced by Ang II, with or without BNP treatment. In addition, potential underlying mechanisms including cell cycle progression, Ca(2+) overload, reactive oxygen species (ROS) production, signal transduction of MAPK and Akt, and the cGMP/PKG pathway were examined. We found that BNP inhibited Ang II-induced PASMCs proliferation and migration dose dependently. BNP could also arrest the cell cycle progression in the G0/G1-phase. In addition, BNP attenuated intracellular calcium overload caused by Ang II. Moreover, Ang II-induced ROS production was mitigated by BNP, with associated down-regulation of NAD(P)H oxidase 1 (Nox1) and reduced mitochondrial ROS production. Finally, Ang II-activated MAPKs and Akt were also counteracted by BNP. Of note, all these effects of BNP were abolished by a PKG inhibitor (Rp-8-Br-PET-cGMPS). In conclusion, BNP inhibits Ang II-induced PASMCs proliferation and migration. These effects are potentially mediated by decreased calcium influx, reduced ROS production by Nox1 and mitochondria, and down-regulation of MAPK and Akt signal transduction, through the cGMP/PKG pathway. Therefore, this study implicates that BNP may have a therapeutic role in pulmonary vascular remodeling.

Attenuation of Monocyte Chemotaxis—A Novel Anti-inflammatory Mechanism of Action for the Cardio-protective Hormone B-Type Natriuretic Peptide

B-type natriuretic peptide (BNP) is a prognostic and diagnostic marker for heart failure (HF). An anti-inflammatory, cardio-protective role for BNP was proposed. In cardiovascular diseases including pressure overload-induced HF, perivascular inflammation and cardiac fibrosis are, in part, mediated by monocyte chemoattractant protein (MCP)1-driven monocyte migration. We aimed to determine the role of BNP in monocyte motility to MCP1. A functional BNP receptor, natriuretic peptide receptor-A (NPRA) was identified in human monocytes. BNP treatment inhibited MCP1-induced THP1 (monocytic leukemia cells) and primary monocyte chemotaxis (70 and 50 %, respectively). BNP did not interfere with MCP1 receptor expression or with calcium. BNP inhibited activation of the cytoskeletal protein RhoA in MCP1-stimulated THP1 (70 %). Finally, BNP failed to inhibit MCP1-directed motility of monocytes from patients with hypertension (n = 10) and HF (n = 6) suggesting attenuation of this anti-inflammatory mechanism in chronic heart disease. We provide novel evidence for a direct role of BNP/NPRA in opposing human monocyte migration and support a role for BNP as a cardio-protective hormone up-regulated as part of an adaptive compensatory response to combat excess inflammation.

Mechanical stretch up-regulates the B-type natriuretic peptide system in human cardiac fibroblasts: a possible defense against transforming growth factor-β mediated fibrosis

BackgroundMechanical overload of the heart is associated with excessive deposition of extracellular matrix proteins and the development of cardiac fibrosis. This can result in reduced ventricular compliance, diastolic dysfunction, and heart failure. Extracellular matrix synthesis is regulated primarily by cardiac fibroblasts, more specifically, the active myofibroblast. The influence of mechanical stretch on human cardiac fibroblasts’ response to pro-fibrotic stimuli, such as transforming growth factor beta (TGFβ), is unknown as is the impact of stretch on B-type natriuretic peptide (BNP) and natriuretic peptide receptor A (NPRA) expression. BNP, acting via NPRA, has been shown to play a role in modulation of cardiac fibrosis.Methods and resultsThe effect of cyclical mechanical stretch on TGFβ induction of myofibroblast differentiation in primary human cardiac fibroblasts and whether differences in response to stretch were associated with changes in the natriuretic peptide system were investigated. Cyclical mechanical stretch attenuated the effectiveness of TGFβ in inducing myofibroblast differentiation. This finding was associated with a novel observation that mechanical stretch can increase BNP and NPRA expression in human cardiac fibroblasts, which could have important implications in modulating myocardial fibrosis. Exogenous BNP treatment further reduced the potency of TGFβ on mechanically stretched fibroblasts.ConclusionWe postulate that stretch induced up-regulation of the natriuretic peptide system may contribute to the observed reduction in myofibroblast differentiation.

B‐type natriuretic peptide attenuates cardiac hypertrophy via the transforming growth factor‐β1/smad7 pathway in vivo and in vitro

1. Previously, we showed that long-term treatment of rats after myocardial infarction (MI) with B-type natriuretic peptide (BNP) prevented ventricular remodelling. However, it is unclear whether long-term BNP treatment affects cardiac hypertrophy and, if so, its mechanism of action. In the present study, we investigated the effects of long-term BNP treatment on cardiac hypertrophy and the molecular mechanisms involved. 2. Cardiac hypertrophy was established in rats by ligation of the left anterior descending coronary artery. After treatment with BNP (5 or 15 microg/kg per day) for 8 weeks, indices of cardiac hypertrophy were determined. In separate in vitro experiments, cardiomyocyte hypertrophy was induced by treatment of cardiomyocytes with 10(-6) mol/L angiotensin (Ang) II for 48 h and cell surface area and [(3)H] incorporation were measured. Transforming growth factor (TGF)-beta1 and smad7 mRNA and protein expression in vivo and in vitro were detected using reverse transcription-polymerase chain reaction and western blotting. 3. Long-term BNP treatment dose-dependently attenuated cardiac hypertrophy and improved cardiac function in rats after MI. Furthermore, BNP attenuated the upregulation of TGF-beta1 and downregulation of smad7 mRNA and protein expression. The in vitro experiments further proved that BNP inhibited cardiac hypertrophy and changes in the TGF-beta1/smad7 pathway, which were completely blocked by the cyclic GMP-dependent protein kinase (PKG) inhibitor, KT5823 (cells were treated with 10(-6) mol/L KT5823 for 48 h). 4. The results of the present study demonstrate that long-term treatment of rats with BNP dose-dependently attenuates cardiac hypertrophy and that this is associated with downregulation of TGF-beta1 and upregulation of smad7 via PKG signalling. Long-term BNP treatment may be a new therapeutic strategy to prevent cardiac hypertrophy and progression to heart failure.

Long-term Effects of B-type Natriuretic Peptide Infusion After Acute Myocardial Infarction in a Rat Model

The effects of exogenous B-type natriuretic peptide (BNP) on postmyocardial infarction (MI) are not known. We tested the hypothesis that in vivo infusion of BNP would improve cardiac function and affect left ventricular (LV) remodeling in an experimental model of MI. MI was induced by coronary ligation in rats and confirmed by echocardiography. 19 rats were randomized to 1 of 3 groups: sham (n = 7), MI + saline (n = 5), MI + BNP (400 ng.kg(-1).minute(-1)) (n = 7). Infusions were delivered for 7 days via venous catheters tunneled to an infusion pump. Rats were followed for 8 weeks. Echocardiography, hemodynamics, histology, and in vivo and ex vivo pressure-volume relationships were examined. LV systolic pressure, LV dP/dtmax, and infarct size improved with BNP treatment versus control MI group (132 +/- 4 vs.110 +/- 2 mm Hg, 8097 +/- 317 vs. 5816 +/- 378 mm Hg/s, 19.3% +/- 1.6% vs. 23.3% +/- 1.9%, respectively; all P < 0.05). Ex vivo end-diastolic pressure-volume relationship demonstrated reduced diastolic dysfunction after BNP therapy (P < 0.05 vs. control MI). Serum BNP levels confirmed delivery of BNP. We demonstrate beneficial effects on LV function and decreased LV remodeling with BNP infusion in an experimental model of acute MI.

Pretreatment with B-type Natriuretic Peptide Protects the Heart From Ischemia-Reperfusion Injury by Inhibiting Myocardial Apoptosis

The therapy for acute myocardial infarction (AMI) has been improved; yet, AMI remains a major cause of death and heart failure in industrialized countries. B-type natriuretic peptide (BNP), a hormone secreted from the heart, has been shown cardioprotective effects during myocardial ischemia/reperfusion. In the present study, we aimed to examine whether BNP could inhibit myocardial apoptosis during ischemia/reperfusion. Rabbits were randomly divided into three groups (12 animals for each group): sham-operated control and ischemia-reperfusion animals with or without BNP treatment. Occlusion of the left circumflex coronary for 45 min was followed by 3-h reperfusion with infusion of physiological saline (untreated group) or BNP (treated group) starting 5 min before reperfusion and throughout the whole reperfusion. The infarct size, measured by triphenyltetrazolium chloride staining, was reduced by 44% with BNP treatment (P < 0.01). Accordingly, serum levels of creatine kinase and lactate dehydrogenase were markedly reduced in BNP-treated group (P < 0.05) compared with the untreated group. BNP significantly attenuated apoptotic cells (TUNEL-positive cardiomyocyte nuclei) in the myocardium (P < 0.01). The BNP-mediated attenuation of apoptosis was associated with the increased expression of an anti-apoptotic protein Bcl-2 and the reduced expression of a pro-apoptotic protein Bax. Moreover, BNP treatment significantly decreased the magnitude of caspase-3 activation caused by myocardial ischemia-reperfusion. In conclusion, pretreatment with BNP shortly before the onset of reperfusion not only reduces necrosis, but also attenuates myocardial apoptosis. BNP appears to be an ideal pharmacological agent applied as an adjuvant therapy to current myocardial reperfusion strategies.

Effect of long-term B-type natriuretic peptide treatment on left ventricular remodeling and function after myocardial infarction in rats

Although short-term B-type natriuretic peptide (BNP) treatment has been shown to be effective for decompensated congestive heart failure, little is known about the effects of long-term BNP treatment in ventricular remodeling and heart failure in response to myocardial infarction. The aim of the present study was to investigate the effects of long-term BNP treament on ventricular remodeling and heart failure after myocardial infarction in rats. Myocardial infarction was induced by ligating the left anterior descending coronary artery. The surviving rats were randomly divided into four groups: 1) vehicle-treated myocardial infarction group (‘vehicle-treated group’), 2) rats treated with low-dose BNP (‘low BNP group’), 3) rats treated with high-dose BNP (‘high BNP group’), 4) sham-operated group. Eight weeks after the operation, rats were sacrificed. Compared with the sham-operated group, the vehicle-treated group had significantly higher collagen deposition and angiotensin II levels ( P < 0.01) and a significantly lower cardiac function ( P < 0.05). Both BNP-treated groups had significant improvement of these indexes compared with the vehicle-treated group ( P < 0.01). The high BNP group had significantly less collagen deposition and better cardiac function than the untreated and low BNP groups. Moreover, the mRNA and protein expression of TGFβ1 and Smad2 in the vehicle-treated group was significantly higher than in the sham-operated group ( P < 0.01). Both BNP-treated groups had a suppression of TGFβ1 and Smad2 expression ( P < 0.01). In conclusion, long-term treatment with BNP prevents ventricular remodeling and deterioration of cardiac function in a dose-dependent fashion, a process that may be associated with the inhibition of TGFβ1/ Smad2 signaling.

Emergency Physician Use of the B-Type Natriuretic Peptide Value and the Effect of Variance Between Commercial Assays in the Diagnosis and Treatment of Congestive Heart Failure

Introduction: B-type natriuretic peptide (BNP) is a diagnostic adjunct in congestive heart failure (CHF) patients. Little is known regarding how this test is utilized clinically and what affect it has on ED patient management. Most studies to date have utilized the Bio-Site assay, while newer marketed tests report up to a 20-30% variance from to this assay. Our objective was to first delineated how often BNP changes patient diagnosis, treatment or disposition and second to determine whether the reported variance in 2 commercial BNP tests has clinical relevancy.

B-type natriuretic peptide exerts broad functional opposition to transforming growth factor-beta in primary human cardiac fibroblasts: fibrosis, myofibroblast conversion, proliferation, and inflammation.

The natriuretic peptides, including human B-type natriuretic peptide (BNP), have been implicated in the regulation of cardiac remodeling. Because transforming growth factor-beta (TGF-beta) is associated with profibrotic processes in heart failure, we tested whether BNP could inhibit TGF-beta-induced effects on primary human cardiac fibroblasts. BNP inhibited TGF-beta-induced cell proliferation as well as the production of collagen 1 and fibronectin proteins as measured by Western blot analysis. cDNA microarray analysis was performed on RNA from cardiac fibroblasts incubated in the presence or absence of TGF-beta and BNP for 24 and 48 hours. TGF-beta, but not BNP, treatment resulted in a significant change in the RNA profile. BNP treatment resulted in a remarkable reduction in TGF-beta effects; 88% and 85% of all TGF-beta-regulated mRNAs were affected at 24 and 48 hours, respectively. BNP opposed TGF-beta-regulated genes related to fibrosis (collagen 1, fibronectin, CTGF, PAI-1, and TIMP3), myofibroblast conversion (alpha-smooth muscle actin 2 and nonmuscle myosin heavy chain), proliferation (PDGFA, IGF1, FGF18, and IGFBP10), and inflammation (COX2, IL6, TNFalpha-induced protein 6, and TNF superfamily, member 4). Lastly, BNP stimulated the extracellular signal-related kinase pathway via cyclic guanosine monophosphate-dependent protein kinase signaling, and two mitogen-activated protein kinase kinase inhibitors, U0126 and PD98059, reversed BNP inhibition of TGF-beta-induced collagen-1 expression. These findings demonstrate that BNP has a direct effect on cardiac fibroblasts to inhibit fibrotic responses via extracellular signal-related kinase signaling, suggesting that BNP functions as an antifibrotic factor in the heart to prevent cardiac remodeling in pathological conditions.