Citations

Background: C-type natriuretic peptide (CNP), a 22-amino-acid peptide and a ligand of the natriuretic peptide receptor-B (NPR-B), exhibits venodilating, anti-fibrotic, and vascular-regenerating properties but limited renal actions. A Mayo-designed chimeric peptide, CD-NP, which consists of CNP and the C-terminus of Dendroaspis NP, was synthesized to test the hypothesis that CD-NP would possess CNP-like properties with an improved pharmacodynamic profile. Methods: Normal anesthetized dogs were given CD-NP 50 ng/kg/min (n = 10) or an equimolar dose of CNP 29.3 ng/kg/min (n = 9) i.v. for 75 min. Hemodynamic, renal, and hormonal data were obtained pre-infusion (pre-I), at 30 and 60 min I, and post-I, and were compared both within group vs pre-I (mean ± SE, P< 0.05*, < 0.01 † ) and between groups ( P < 0.05 ‡ , < 0.01 § , < 0.001 ¶ ). Plasma BNP was measured by radioimmunoassay. Results: CD-NP resulted in greater increases in plasma cGMP (7±.4 to 25±3 †¶ to 36±3 †¶ to 23±3 †¶ pmol/ml), urinary cGMP excretion (978±145, 3170±205 †¶ , 5919±616 †¶ , 3077±298 †¶ pmol/min) vs CNP (8±.8, 10±.6 † , 11±.7 † , 8±.5 pmol/ml; 976±110, 1104±115, 1317±103, 998±101 pmol/min, respectively). CD-NP also increased urine Na + excretion (19±4, 168±24 †§ , 237±26 †¶ , 96±12 † μEq/min), urine flow (0.2±.1, 1.3±.2 † , 1.8±.3 † , 0.8±.2 † ml/min), and GFR (37±2 ‡ , 48±3 † , 51±3 † , 53±4 † ml/min) vs CNP (36±12, 68±10, 85±26, 81±25 μEq/min; 0.4±.1, 0.9±.2, 1.2±.3*, 0.9±.3 ml/min; 52±5, 53±7, 50±4, 49±6 ml/min, respectively). CD-NP reduced PCWP (5.7±.7, 4.1±1*, 3.2±.7 † , 4.3±.8 mmHg), RAP (1.8±.4, 1.1±.4 † , 0.9±.5 †§ , 1.3±.5 § mmHg), PAP (12±.6, 10±.4*, 10±.6, 11±.7 mmHg) vs CNP (6±.6, 5±.8, 6±.8, 7±.9 † mmHg; 2.6±.3, 2.5±.3 to 2.9±.3 to 3.5±.5 † mmHg; 13±1, 12±1, 12±1, 13±1 mmHg, respectively). Mean blood pressure was unchanged in either group. CD-NP increased circulating BNP during infusion vs CNP (40±4 vs 18±2 pg/ml, P<0.001). Conclusion: This study demonstrates the successful transformation of CNP to a CNP-like peptide with enhanced natriuretic, diuretic, GFR-enhancing, and cardiac-unloading actions. CD-NP may also promote increases in plasma BNP which via the NPR-A receptor may contribute to its biological actions. The therapeutic potential of CD-NP in heart failure warrants further studies.

Background: B-type natriuretic peptide (BNP) signals via particulate guanylyl cyclase (pGC) and cyclic guanosine monophosphate (cGMP). In heart failure (HF), BNP reduces cardiac filling pressures and in selected patients augments sodium excretion and glomerular filtration rate (GFR). Studies have established that pGC and soluble guanylyl cyclase (sGC), the main target of nitric oxide (NO), can be compartmentalized with both enzymes affecting distinct intracellular cGMP pools, resulting in different biological actions. Importantly, sGC may be oxidized in disease states like HF making it unresponsive to NO and nitrovasodilators. BAY 58 –2667 (BAY) is a novel NO and heme independent sGC activator that preferentially stimulates oxidized sGC. We hypothesized that adding direct sGC stimulation with BAY to pGC activation with BNP in HF would enhance vasodilation and cardiac unloading without attenuating the distinct renal actions of BNP. Methods: Severe HF was induced by tachypacing in 13 dogs. On day 11, cardiorenal function was assessed in an acute study under anesthesia at baseline and with intravenous BNP (50 ng/kg/min) alone or in combination with BAY (0.3 ug/kg/min). Results: BNP significantly increased urine flow (UV), urinary sodium excretion (UNaV), GFR, renal blood flow (RBF) and systemic vascular resistance (SVR) and decreased cardiac output (CO), mean arterial pressure (MAP), right atrial pressure (RAP) and pulmonary capillary wedge pressure (PCWP). Despite a greater decrease in MAP compared to BNP, BAY+BNP resulted in similar increases in UNaV, UV and GFR. Dual pGC and sGC stimulation resulted in greater decreases in SVR, RAP and PCWP together with an augmentation of CO compared to BNP alone. Conclusion: Particulate GC activation with BNP in experimental HF enhances renal function and leads to renal but not systemic vasodilation. Addition of the sGC stimulator BAY provides systemic vasodilation, greater cardiac unloading, and augmented CO. Despite a larger decrease in MAP, additional sGC stimulation does not impair the renal actions observed with pGC stimulation alone. These findings support coactivation of sGC with BAY and pGC with BNP as a novel and beneficial therapeutic strategy in HF to optimize activation of distinct GC enzymes and cGMP.

Background: Renal dysfunction has emerged as an important independent prognostic factor in patients with heart failure (HF). Cardiac resynchronization therapy (CRT) improves functional status and left ventricular (LV) function in HF patients with ventricular dyssynchrony. We hypothesized that CRT would also improve glomerular filtration rate as estimated by the abbreviated MDRD equation (eGFR) in patients with reduced eGFR. Methods: This is a retrospective analysis of the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) study, which evaluated CRT in HF patients with NYHA class III–IV, ejection fraction ≤35%, QRS ≥130 ms, and stable medical regimen. Patients were evaluated before implantation and 6 months after randomization to control (CRT device OFF, n=225) or CRT (n=228). Patients were categorized according to their baseline eGFR: ≥90 (category A), 60≤eGFR<90 (category B), and 30≤eGFR<60 (category C) mL/min per 1.73m 2 . Changes in eGFR were also correlated with changes in other parameters in univariate analysis. Results: At baseline, reduced eGFR was associated with ischemic etiology, increased age, mitral regurgitation, and neurohumoral activation. CRT increased LV ejection fraction and decreased LV volumes and mitral regurgitation in all categories. Importantly, CRT improved eGFR (p=0.003) and reduced blood urea nitrogen (p=0.008) compared to control in category C, but not A (p=0.75/p=0.41) and B (p=0.43/p=0.89). In addition, only in category C did atrial natriuretic peptide decrease, suggesting reduced atrial distention and filling pressures with CRT in this group with impaired eGFR. In univariate analysis, changes in eGFR correlated weakly but significantly with changes in aldosterone (r=−0.22), plasma renin activity (r=−0.19, norepinephrine (r=−0.16), and mean blood pressure (r=+0.14), a pattern consistent with reduced neurohumoral activation due to increased systemic and renal perfusion pressure. Conclusions: CRT increased eGFR and reduced blood urea nitrogen in HF patients with reduced baseline eGFR. By improving cardiac function, CRT can indirectly improve renal function, underscoring the importance of cardiorenal interaction and providing another mechanism for the beneficial effects of CRT.

BACKGROUND: AlbuBNP is a novel recombinant human BNP serum albumin fusion protein which possesses a significantly longer elimination half-life compared to BNP. To date, it remains unclear if this novel protein which represents a single molecule of BNP synthesized with the carrier protein albumin can enter the post glomerular/tubular system due to the fusion of BNP to albumin and mediate renal actions. We hypothesized that this fusion protein will have potent renal actions and possess prolonged renal hemodynamic enhancing and excretory properties based upon its unique structure as compared to native BNP. METHODS: We compared the cardiorenal and humoral actions of intravenous(IV) bolus of administration of AlbuBNP (Cardeva, CoGenesys, Rockville MD) (5 mg/kg, n=7) and Human BNP (Phoenix Pharmaceutical, Belmont CA) (25 μ g/Kg, n=5) in two groups of normal anesthetized dogs. * p<0.05 RESULTS: Single IV bolus of AlbuBNP resulted in a sustained increase in plasma cGMP (5±1 to 9±2 pmol/ml*) and urinary cGMP excretion (1136±113 to 2556±417 pmol/min*), markers of the biological activity of BNP, which remained elevated at the termination of the experiment at 270 minutes. In contrast, with human BNP, both plasma and urinary cGMP peaked at 30 minutes and returned to baseline by 150 minutes. In a similar fashion, there was a sustained increase in natriuresis (39±12 to 159±38 μEq/min*), diuresis (0.2±0.1 to 1.1±0.3 ml/min*), renal blood flow (220±22 to 301±33 ml/min*), and glomerular filtration rate (34±2 to 62±13 ml/min*) with AlbuBNP while with human BNP, these renal effects peaked at 30 minutes and returned to baseline by 150 minutes. Furthermore, there was a gradual and sustained suppression of plasma aldosterone (7.8±2 to 3.6±1 ng/dL*) with AlbuBNP. Likewise, there was a more sustained reduction of cardiac filling pressures with AlbuBNP as compared to human BNP. CONCLUSION: We report for the first time that this newly developed BNP/albumin fusion protein has a more prolonged and sustained renal enhancing properties compared to human BNP. Thus, AlbuBNP (Cardeva) represents a novel long-acting renal enhancing and aldosterone suppressing drug which has therapeutic potential for the management of cardiovascular and renal diseases that should be defined in further studies.

BACKGROUND: C-type natriuretic peptide (CNP) is a 22-amino-acid peptide produced mainly in the endothelium with potent cardiac unloading and modest blood pressure lowering actions, but minimal renal actions. Based on our previous knowledge, we recently fused a 6 aa sequence from BNP to the C-terminus and a 5 aa sequence from ANP to the N-terminus of CNP. This novel hybrid peptide, CBA-NP, has cardiac unloading actions and mild hypotensive effects similar to CNP. Importantly however, the N and C terminus alterations resulted in potent renal excretory actions. here we test the hypothesis that the 3 aa GSM 15–17 in the disulfide-ring mediate the vascular and hypotensive actions. We therefore mutated GSM 15–17 to REA 15–17 , which we named ABC-NP and compared its in vivo and in vitro actions to CBA-NP. METHODS: We determined the cardiorenal and humoral actions of intravenous bolus administration of CBA-NP (n=5) and ABC-NP (n=5) at 25 microgram/Kg in 2 separate group of normal anesthetized dogs. We also assessed the cGMP response of both peptides in human aortic endothelial cells (HAEC), human cardiac fibroblast (HCF) and isolated canine glomeruli. * p<0.05 RESULTS: IV bolus administration of CBA-NP and ABC-NP resulted in diuresis* and natriuresis*. There was a significant decrease in mean arterial blood (MAP) pressure with CBA-NP (126±6 to113±7 mmHg*) but no change with ABC-NP(126±8 to126±8 mmHg) . In addition, the reduction in pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) was significantly greater with CBA-NP as compared to ABC-NP. cGMP generation in HAEC and HCF was minimal with ABC-NP and was significantly higher with CBA-NP*. In contrast, cGMP generation was similar in isolated glomeruli between the two peptides. CONCLUSION: Our studies demonstrates that mutation of three amino acid (aa) residues within the CNP ring of CBA-NP from GSM 15–17 to REA alters the vascular but not the renal excretory properties. Hence by this strategic mutation within the ring of CBA-NP, we have designed a renal specific peptide ABC-NP resulting in new sequence specific functional information which can be used to design organ specific therapeutic peptides with unique properties tailored for a specific disease state.

Background: Chronic renal insufficiency (CRI) is a strong predictor of increased mortality in the presence of heart failure (HF) and its prevalence has been increasing in the US. In addition, CRI is a major contributing factor to the progression of HF as it is associated with chronic volume overload, accelerated atherosclerosis and hypertension (HTN). The first aim of the current study was to evaluate the prevalence of CRI in an adult general population. The second aim was to address whether calculated glomerular filtration rate (cGFR) adds value to the cardiac biomarkers BNP and NT-proBNP in detecting early cardiac structural and functional impairments in the general population. Methods: From 1997 to 1999 medical history, physical examination, echocardiography, BNP (Biosite) and NT-proBNP (Roche) and serum creatinine (SCr) were obtained in 1,982 randomly selected residents of Olmsted County, MN >= 45 years (range 45 – 96 years). GFR was calculated using the Cockroft Gault equation. CRI was defined as a GFR < 60 ml/min. Cardiac structure and function were evaluated by in-depth echocardiographic examination. Results: The prevalence of cardiovascular co-morbidities was coronary atherosclerosis 12%, HTN 29.5% and diabetes mellitus 7.5%. The prevalence of CRI was 22.8% when cGFR was used for its detection. Importantly, by Chi-Square model, cGFR significantly increased the ability of BNP in detecting left ventricular hypertrophy (LVH) (p=0.004), increased relative wall thickness (p=0.0036), diastolic dysfunction (DDF) (p=0.0001) and HTN (p=0.0002). Similarly, when combined with NT-proBNP, cGFR increased the predictive power of detecting DDF (p=0.0001) and HTN (p=0.0366). Conclusion: This study reports a higher than predicted prevalence of CRI in this general US population equal to 23% and closely associated with the prevalence of HTN (29.5%). Importantly, this study also demonstrates that cGFR has additive predictive power when used in combination with two cardiac biomarkers of cardiac dysfunction and remodeling, BNP and NT-proBNP. These studies underscore the increasing burden of CRI in the general population and the utility of assessing cardiorenal function by combining renal and cardiac biomarkers in assessment of cardiac structure and function.

Introduction: The incidence of post-myocardial infarction (MI) heart failure (HF) is increasing in the elderly. Studies have demonstrated that B-type natriuretic peptide (BNP) mediates critical cardiorenal compensatory and protective actions through guanylyl cyclase receptor A and cGMP activation. Such actions include natriuresis, diuresis and suppression of adverse cardiorenal remodelling. Hypothesis: While the mechanism of this increased risk may be multifactorial, we hypothesized that an impairment of the compensatory protective BNP/cGMP axis in both the aged kidney and heart contributes to post-MI HF. Methods: 20 month old Fischer rats were randomized into two groups: Sham-operated (S) and MI(produced by left coronary artery ligation). Cardiorenal structure and function were assessed at 4 weeks and included mean arterial pressure(MAP), LV EF, LV chamber dimension, proteinuria, sodium (Na) excretion and fibrosis by picrosirius red staining. Plasma BNP and cGMP levels were assessed by RIA. Data presented as mean±SE,*P<0.05. Results: LV EF (S:78±2, MI:46±3 %*) was significantly reduced in aged MI rats, despite no difference in LV fibrosis in the remote region and no change in MAP compared to aged sham rats. Post-MI HF was evident and characterized by a significant reduction in Na excretion (S:0.20±0.03, MI:0.13±0.01 mEq/day*) as well as significant increases in LV dilatation (S:7.2±0.1, MI:8.3±0.2 mm*) and cardiac hypertrophy (S:2.78±0.06, MI:3.25±0.16 mg/g*) in aged MI rats. Notably, plasma BNP (S:9±1, MI:11±2 pg/ml) failed to increase and plasma cGMP (S:44±6, MI:27±3 mm*) was significantly reduced in the MI group. Importantly, MI in the aged rat resulted in a significant loss in total renal mass (S:2739±83, MI:2351±68 mg*), consistent with renal atrophy, while no changes in proteinuria or renal fibrosis were observed. Conclusions: Post-MI dysfunction of the protective BNP/cGMP axis in the aged rat was associated with various cardiorenal abnormalities including renal atrophy, which may contribute to the pathophysiology of HF. This pre-clinical model provides new insights into post-MI HF and may be used to examine therapeutic strategies using natriuretic peptides to protect the heart and kidney in the elderly post-MI population.

Introduction: ANP and BNP are cardiac hormones that have a natriuretic and diuretic role in heart failure (HF) through guanylyl cyclase receptor A (GC-A) and cGMP generation. C-type natriuretic peptide (CNP) is part of this hormone family and is produced in the heart and endothelium. The biologically active form, CNP-22, is known to have potent anti-remodeling properties through the activation of GC-B and cGMP, but lacks natriuretic actions. Recently we have identified that another larger CNP form, CNP-53, is elevated in the plasma of acute decompensated HF patients, however it unclear if CNP-53 possesses biological actions. Hypothesis: We hypothesized that CNP-53 would be biologically active in vivo and in vitro, and would stimulate GC-B specific cGMP production. Methods: HEK 293 cells over-expressing GC-A and GC-B and human cardiac fibroblasts (hCFs), in which GC-B are in abundance, were stimulated with CNP-53 for 10 minutes at a dose of (10-8M). Two groups of anesthetized rats (n=8) received a 75-minute infusion of normal saline vehicle (V) or CNP-53 (1 ug/kg/min) and then mean arterial pressure (MAP), sodium excretion and urinary and plasma cGMP were assessed. Results: CNP-53 significantly activated cGMP in GC-B HEK cells (75±9 vs. 0.4±0.1 pmol/well, p<0.05) and in hCFs (0.17±0.03 vs. 0.00±0.00 pmol/well, p<0.05) compared to no treatment. In contrast CNP-53 failed to generate cGMP in GC-A HEK cells. In vivo, CNP-53 decreased MAP compared to vehicle (V: 101±2, CNP-53: 94±2 mmHg, p<0.05). CNP-53 had a greater natriuretic effect compared vehicle (V: 0.86±0.11, CNP-53: 1.39±0.21 uEq/min, p<0.05). Urinary cGMP excretion (V: 33±6, CNP-53: 177±28 pmol/min, p<0.05) and plasma cGMP generation was also significantly higher with CNP-53 compared to vehicle (V: 9±2, CNP-53: 91±3 pmol/ml, p<0.05). Conclusions: CNP-53, a higher molecular form of CNP that was reported to be increased human HF plasma, is bioactive with GC-B specific cGMP generation in vitro. Moreover, infusion of CNP-53 generates significant urinary and plasma cGMP and has natriuretic actions with minimal hypotensive effects in vivo. This study advances our understanding of CNP biology and provides new insights into potential CNP therapeutic opportunities targeting the progression of HF.

Introduction: The cardiac atrium is an important endocrine organ which also releases natriuretic peptides (NPs). We reported that dysregulation of the proNP convertases, furin and corin, may disrupt NP progressing, causing atrial fibrosis in experimental heart failure (HF). Atrial fibrosis results in atrial arrhythmias and impairs the prognosis of human HF, therefore understanding mechanisms of atrial fibrosis may help in designing treatment strategies for HF. We sought to extend our studies into the entire NP system and global gene profiles including fibrotic and inflammatory pathways in experimental HF. Hypothesis: Components of the NP, pro-fibrotic and inflammatory system will be up-regulated in the atrium in HF. Methods: Experimental canine HF was induced by rapid right ventricular pacing at 240 bpm for 10 days. We examined hemodynamics, echo parameters, circulating neurohumoral factors, and global gene profiles using RT-PCR microarrays related to the NP system, fibrosis, growth factors, inflammation and cardiac hypertrophy in left atrium (LA) from normal and HF canines (n=4 of each). Results: Experimental HF was characterized by decreased % EF and LV radial strain, and increased circulating ANP, cGMP and aldosterone levels. HF LA weight significantly increased with fibrosis and interstitial edema compared to normals. Gene profile analyses showed increases in profibrotic cytokines and extracellular matrix related genes in LA. Increased ANP expression but also increased ANP degrading enzyme IDE and decreased proANP processing enzyme corin were also observed. Genes related to inflammatory cytokines such as TNF-alpha, members of the IL-6 family, MCP-1, and cell adhesion molecules were up-regulated in LA compared to normals. Conclusions: Experimental HF was characterized by on-going atrial fibrosis with increased circulating ANP levels. Although ANP gene expression increased in failing LA, impaired proANP processing and accelerated ANP degradation may impair any anti-fibrotic ANP effects. Further, atrium may be a source of inflammatory cytokines and pro-fibrotic growth factors which may advance organ damage in HF. Our studies suggest NP treatment, perhaps in a form less susceptible to IDE degradation, may be a novel therapeutic for HF.

Introduction: ProANP is a 108 amino acid (AA) prohormone which is produced in the atria and processed to the mature 28 AA ANP which activates the guanylyl cyclase receptor-A (GC-A) and its second messenger cGMP. ProANP is found in the human circulation but its bioavailability is undefined. Hypothesis: ProANP represents a novel cardiac peptide with more sustained natriuretic actions than either carperitide (ANP) or nesiritide (BNP). ProANP itself can activate GC-A in vitro and the proANP can be processed in human serum from normals and in patients with heart failure (HF). Methods: We examined the in vivo cardiorenal actions of proANP compared to ANP, BNP, or placebo in normal canines (667 pmol/kg, n=5/group). We determined cGMP activation of proANP, ANP and BNP in GC-A expressing HEK293 cells. ProANP processing and degradation was also defined in serum from normal subjects (n=13) and patients with HF (n=14) ex vivo. Results: ProANP had significantly greater diuretic and natriuretic properties with increased renal blood flow and sustained renal tubular actions compared to ANP or BNP in canines. ProANP also resulted in greater and more prolonged cardiac unloading than ANP, and much less hypotensive effects than BNP. The plasma half-life of proANP was 4.5 times longer than ANP and 3.8 times longer than BNP. ProANP itself stimulated cGMP generation in GC-A expressing HEK cells which was equal to ANP. ProANP was processed to ANP in fresh serum from normals as well as HF patients ex vivo and the processed peptide activated cGMP in GC-A expressing HEK cells. Conclusions: ProANP represents a novel GC-A activator with a longer half-life and greater natriuresis and diuresis than ANP and BNP and less hypotensive effects than BNP. The bioactivity of exogenous proANP may be through direct stimulation of GC-A, as well as through processing into ANP, as proANP is processed in the circulation of both normal and HF. As proANP circulates in the human circulation, proANP may represent a key circulating hormone in cardiorenal and blood pressure homeostasis as well as a potential innovative therapeutic beyond ANP (carperitide) or BNP (nesiritide) for cardiorenal diseases including HF.