- Email: [email protected]
Inotropic effect of human b -type natriuretic peptide in the failing human heart
The Second Annual Scientific Meeting
•
HFSA
005
006
The Renal Response to Acute Neutral Endopeptidase Inhibition is Determined by the Severity of Heart Failure
S u b c u t a n e o u s B N P Administration in Experimental Mild Heart Failure: A N o v e l T h e r a p e u t i c S t r a t e g y
H H Chert, JA Schirger, W L C h a u , M Jougasaki, O Lisy, M M Redfield, PT Barclay, JC Burnett, Jr. M a y o Clinic, Rochester, M N , U S A
H H Chert, JA G r a n t h a m , JA Schirger, M Jougasaki, O Lisy, M M Redfield a n d JC Bumett, Jr. M a y o Clinic, Rochester, MINI, U S A
Mild heart failure (HE) is characterized by increases in circulating atrial natriuretic peptide (ANP) without activation of the renin-angiotensin-aldosterane system (RAAS) and a maintenance of sodium balance despite ventticular dysfimction. A hallmark of overt HF is the renal resistance to ANP, which may in part be secondary to the opposing actions of the RAAS, thus contl~buting to volume overload. In contrast, a preserved renal responsiveness to an activated ANP system is seen in mild HE. As neutral endopcptidase (NEP) is found in greatest abundance in the kidney and rapidly degrades ANP, we hypothesize that acute NEP inhibition in mild HF would potentiate the renal actions of ANP to a greater magnitude compared to overt ItF or to normal, consistent with a beneficial renal protective role for ANP in mild HF which would be attenuated in overt HF. We defined the renal actions of intravenous administration the NEP inhibitor, Candnxatrilat (8#g/Kg/min, Pfizer UK), in 3 groups of anesthetized dogs (Normal n=8, Mild HE n=6 and Overt CHF n=5). Mild I-IF was produced by rapid ventricular pacing at 180 bpm for 10 days and Overt HE at 245 bpm for 10 days. In response to NEP inhibition, urinary sodium excretion (Mild HF, 187 -+34; Normal, 86 -+23; Overt HE, 27_+9 IsEq/min; p<0.05) and glomerular filtration rate (GFR) (Mild HE, 54_+9;Normal, 29_+6; Overt HE, 24+_ 7 mi/min; p<0.05) were greatest in Mild HE compared to Normal and Overt HE. The increase in GFR observed only in Mild HE, was associated with an increase in renal blood flow and decreases in renal vascular resistance and distal fractional sodium reabsorption. Urinm'y ANP excretion (Mild HF, 288-+65; Normal, 43+-11; Overt HE, 119+13 pg/min; p<0.05) and cCMP excretion (Mild HF, 3106+564; Normal, 804-+201; Overt HE 864-+502 pmol/min; p<0.05), both markers for renal ANP action, were greatest ha Mild HE vs Normal or Overt I-IF. Plasma ANP and cGMP were unchanged in all three groups with NEP inhibition. These studies demonstrate for the first lime that NEP inhibition has unique and enhanced natriuretic and renal hemodynamic actions in mild ItF as compared to normal, and that these enhanced renal actions are attenuated in overt HE. These studies underscore the potential therapeutic role for NEP inhibition in mild HE by enhancing the renal actions of endogenous ANP in the absence of an activated RAAS.
19
(Rochester, MN, /_/SA) Brain natriuretic peptide (BNP) is a 32-amino acid protein with vasodilating, natriuretic, renin-angiotensin-aldosterone (RAAS) inhibiting and lnsitropic properties. Recent clinical studies have demonstrated that acute intravanous (IV) administration of BNP in human chronic heart failure (HF) imiquoly reduces cardiac filling pressures and increases sodium excretion. However, the need for IV administration has limited the widespread and chronic use of BNP in CHF. The current study was designed to develop a novel strategy to deliver BNP by subcutaneous (SQ) administration, testing the hypothesis that SQ BNP would increase plasma BNP and its second messenger cGMP, enhance renal hemodynamics, sodium excretion (UNaV) and reduce cardiac filling pressures without activation of the RAAS. SQ canine BNP was administered acutely, 5/zg/kg in a canine model of mild FIF produced by 10 days of rapid ventricular pacing at 180 bpm (n=5) and chronically 5~tg/kg tid (n=4) for 10 days throughout the development of HF. Plasma BNP (51_+25 to 296+136 pg/ml, p<0.05) and cGMP ( 16+3 to 29_+3pmol/ml, p<0.05) increased and peaked at 30 minutes and were maintained for 120 minutes after acute subcutaneous administration. These humoral responses were associated with increases in UNaV (36+_11 to 272+-64 ~teq/min, p<0.05) and renal blood flow (145±34 to 209-+28 ml/inin, p<0.05) and decreases in distal fi'actional sodium reabsorption (96.7-+1.0 to 87.2+-0.9 %, p<0.05) and renal vascular resistance (0.9±0.2 to 0.5~:0.1 mmHg/1/min, p<0,05). Pulmonary capillary wedge pressure (PCWP) (16~3 to 12~:3 mmHg, p<0.05) and right atrial pressure (RAP) (1.3~0.3 to 0.5:L0.3 mmHg, p<0.05) decreased with no changes in arterial pressure or cardiac output. Despite natriuresis and decreases in cardiac filling pressures, no activation of the RAAS was observed. Chronic SQ BNP resulted in increased UNaV (107:L54vs 28±7 peq/min, p<0.05) and decreased RAP (-0.3±0.9 vs 1.9± 0.3 mmHg, p<0.05) and PCWP (8.0~-2.0 vs 14.5:t-1.2mmHg, p<0.05) compared to untreated HF. This study demonstrates for the first time that acute and chronic subcutaneous administration of BNP in a model of mild HE result in elevation of plasma BNP and its second messenger cGMP with natriuresis and reduction hi cardiac filling pressures in the absence of activation of the RAA8. This investigation supports a novel strategy for SQ BNP in the management of HE.
007
008
Superoxide Anion Mediates Norepinephrine-Induced Hypertrophy, but not Contractility, in Adult Rat Ventricular
Inotropic Effect of Human B-Type Natriuretic Peptide in the Failing Human Heart
Myocytes l a y K. An-fin, D a v i d R. Pimentel, Jing W a n g , D o n n y L.F. C h a n g , Patrick J. Pagano*, Wilson S. Colucci, D o u g l a s B.Sawyer, *Henry F o r d H o s p i t a l , Detroit, MI a n d Boston U n i v e r s i t y Medical Center, Boston, MA
Robert L. Roden, Koji A s a n o , Scott W i c h m a n , Erin H o o v e r , Michael R. Bristow a n d William T. A b r a h a m . U n i v e r s i t y of C o l o r a d o H e a l t h Sciences Center, Denver, C o l o r a d o a n d the U n i v e r s i t y of Cincinnati College of Medicine, Cincinnati, O H
In cardiac myocytes norpinephrine (NE) is both a potent inotropic agonist and a stimulus for hypertrophy in vivo and in vitro. Reactive oxygen species are known signaling intermediates of growth pathways in other cell systems (e.g. vascular cells), and we have found that increased superoxide anion, alone, can trigger hypertrophy and apoptosis in cardiac myocytes. We therefore tested the role of oxidative stress, specifically, increased superoxide anion, as a mediator of NE-induced hypertrophy and contraction in isolated adult rat ventricolar myocytes (ARVM) in primary culture. Exposure to NE (1 gin) for 48 hr. caused a 54 +/- 6% increase (n=4; p<0.001) in SH-leucine incorporation, an 88% increase in total protein content (n=2), and a 130% increase in ANF expression by northern blot (n=2). This hypertrophic response to NE was inhibited by the superoxide dismutase mimetic MnTMPyP (50 ~tM), which abolished the NE-stimulated increase in SH-leucine incorporation (10 +/- 12%; p<0.02; n=4) and total protein content (-30%; n=2). MnTMPyP also decreased NE-stimulated ANF expression by 50% (n=2). Using a video edgedetection system, we measured the effect of MnTMPyP on NE-stimulated contraction in paced myocytes (5Hz, 37°C). Exposure to MnTMPyP (24 hrs) had no effect on baseline contractility or the response to NE (n=6). Thus, superoxlde anion appears to mediate NE-stimulated myocyte hypertrophy, but has no effect on 13-adrenergic receptor-mediated contraction. These data therefore suggest an increase in superoxide anion may mediate the hypertrophic, but not the eontractile, effects of NE. Thus, superoxide anion may play a central role in mediating the effects of NE on myocyte remodeling. These data further provide a mechanism by which sympathetic inhibition could exert salutary effects in heart failure.
Synthetic human B-type or brain natrimetic peptide (hBNP) is currently seeking FDA approval as a therapeutic agent to be used in treating patients with congestive heart failure. Several reports have demonstrated hBNP's favorable hemodynamic effects including: a reduction in blood pressure, systemic vascular resistance, and vemricular filling pressnres with an associated increase in cardiac output. While previous studies have suggested that hBNP improves cardiac function principally by unloading the heart, none have ruled out the possibility of a direct inotropic effect. Therefore, we tested this hypothesis on ventricular myoeardium obtained from 9 explanted failing human hearts. Right ventricular 1400 trabeculae were hung in a tissue muscle bath and allowed to equilibrate in ~BNP Tyrede's solution at 37°C. The trabecttfae ~Control were stimulated at a frequency of 1 Hz -a-Dobutabmine and net maximal tension response was "~ 20000 measured following cumulative doses of hBNP (1 n M - 1 toM) in the absence or presence (not shown) of increased adenylyl cyclase activity through -200 Drug Concentration forskolin augmentation. For comparison, isoprotcrenol and dobotamine (each 1 nM - 1 ~M) were administered to identically prepared tsabecalae from the 9 hearts, "!0<0.05 vs. vehicle controls, Relative to vehicle controls, lfl3NP produced no change in systolic tension either in the absence or presence of heightened adenylyl cyclase activity, while both dobutamine and isoproterenol increased net systolic tension (as expected) hi a dose-related manner. Conclusion: These results suggest that the favorable hemodymamic effects of td3NP in human heart failure are not due to a direct positive inetropic effect on ventricular myecardium.
~1000 ¢o6~ ~sloproterenol
•
HFSA
005
006
The Renal Response to Acute Neutral Endopeptidase Inhibition is Determined by the Severity of Heart Failure
S u b c u t a n e o u s B N P Administration in Experimental Mild Heart Failure: A N o v e l T h e r a p e u t i c S t r a t e g y
H H Chert, JA Schirger, W L C h a u , M Jougasaki, O Lisy, M M Redfield, PT Barclay, JC Burnett, Jr. M a y o Clinic, Rochester, M N , U S A
H H Chert, JA G r a n t h a m , JA Schirger, M Jougasaki, O Lisy, M M Redfield a n d JC Bumett, Jr. M a y o Clinic, Rochester, MINI, U S A
Mild heart failure (HE) is characterized by increases in circulating atrial natriuretic peptide (ANP) without activation of the renin-angiotensin-aldosterane system (RAAS) and a maintenance of sodium balance despite ventticular dysfimction. A hallmark of overt HF is the renal resistance to ANP, which may in part be secondary to the opposing actions of the RAAS, thus contl~buting to volume overload. In contrast, a preserved renal responsiveness to an activated ANP system is seen in mild HE. As neutral endopcptidase (NEP) is found in greatest abundance in the kidney and rapidly degrades ANP, we hypothesize that acute NEP inhibition in mild HF would potentiate the renal actions of ANP to a greater magnitude compared to overt ItF or to normal, consistent with a beneficial renal protective role for ANP in mild HF which would be attenuated in overt HF. We defined the renal actions of intravenous administration the NEP inhibitor, Candnxatrilat (8#g/Kg/min, Pfizer UK), in 3 groups of anesthetized dogs (Normal n=8, Mild HE n=6 and Overt CHF n=5). Mild I-IF was produced by rapid ventricular pacing at 180 bpm for 10 days and Overt HE at 245 bpm for 10 days. In response to NEP inhibition, urinary sodium excretion (Mild HF, 187 -+34; Normal, 86 -+23; Overt HE, 27_+9 IsEq/min; p<0.05) and glomerular filtration rate (GFR) (Mild HE, 54_+9;Normal, 29_+6; Overt HE, 24+_ 7 mi/min; p<0.05) were greatest in Mild HE compared to Normal and Overt HE. The increase in GFR observed only in Mild HE, was associated with an increase in renal blood flow and decreases in renal vascular resistance and distal fractional sodium reabsorption. Urinm'y ANP excretion (Mild HF, 288-+65; Normal, 43+-11; Overt HE, 119+13 pg/min; p<0.05) and cCMP excretion (Mild HF, 3106+564; Normal, 804-+201; Overt HE 864-+502 pmol/min; p<0.05), both markers for renal ANP action, were greatest ha Mild HE vs Normal or Overt I-IF. Plasma ANP and cGMP were unchanged in all three groups with NEP inhibition. These studies demonstrate for the first lime that NEP inhibition has unique and enhanced natriuretic and renal hemodynamic actions in mild ItF as compared to normal, and that these enhanced renal actions are attenuated in overt HE. These studies underscore the potential therapeutic role for NEP inhibition in mild HE by enhancing the renal actions of endogenous ANP in the absence of an activated RAAS.
19
(Rochester, MN, /_/SA) Brain natriuretic peptide (BNP) is a 32-amino acid protein with vasodilating, natriuretic, renin-angiotensin-aldosterone (RAAS) inhibiting and lnsitropic properties. Recent clinical studies have demonstrated that acute intravanous (IV) administration of BNP in human chronic heart failure (HF) imiquoly reduces cardiac filling pressures and increases sodium excretion. However, the need for IV administration has limited the widespread and chronic use of BNP in CHF. The current study was designed to develop a novel strategy to deliver BNP by subcutaneous (SQ) administration, testing the hypothesis that SQ BNP would increase plasma BNP and its second messenger cGMP, enhance renal hemodynamics, sodium excretion (UNaV) and reduce cardiac filling pressures without activation of the RAAS. SQ canine BNP was administered acutely, 5/zg/kg in a canine model of mild FIF produced by 10 days of rapid ventricular pacing at 180 bpm (n=5) and chronically 5~tg/kg tid (n=4) for 10 days throughout the development of HF. Plasma BNP (51_+25 to 296+136 pg/ml, p<0.05) and cGMP ( 16+3 to 29_+3pmol/ml, p<0.05) increased and peaked at 30 minutes and were maintained for 120 minutes after acute subcutaneous administration. These humoral responses were associated with increases in UNaV (36+_11 to 272+-64 ~teq/min, p<0.05) and renal blood flow (145±34 to 209-+28 ml/inin, p<0.05) and decreases in distal fi'actional sodium reabsorption (96.7-+1.0 to 87.2+-0.9 %, p<0.05) and renal vascular resistance (0.9±0.2 to 0.5~:0.1 mmHg/1/min, p<0,05). Pulmonary capillary wedge pressure (PCWP) (16~3 to 12~:3 mmHg, p<0.05) and right atrial pressure (RAP) (1.3~0.3 to 0.5:L0.3 mmHg, p<0.05) decreased with no changes in arterial pressure or cardiac output. Despite natriuresis and decreases in cardiac filling pressures, no activation of the RAAS was observed. Chronic SQ BNP resulted in increased UNaV (107:L54vs 28±7 peq/min, p<0.05) and decreased RAP (-0.3±0.9 vs 1.9± 0.3 mmHg, p<0.05) and PCWP (8.0~-2.0 vs 14.5:t-1.2mmHg, p<0.05) compared to untreated HF. This study demonstrates for the first time that acute and chronic subcutaneous administration of BNP in a model of mild HE result in elevation of plasma BNP and its second messenger cGMP with natriuresis and reduction hi cardiac filling pressures in the absence of activation of the RAA8. This investigation supports a novel strategy for SQ BNP in the management of HE.
007
008
Superoxide Anion Mediates Norepinephrine-Induced Hypertrophy, but not Contractility, in Adult Rat Ventricular
Inotropic Effect of Human B-Type Natriuretic Peptide in the Failing Human Heart
Myocytes l a y K. An-fin, D a v i d R. Pimentel, Jing W a n g , D o n n y L.F. C h a n g , Patrick J. Pagano*, Wilson S. Colucci, D o u g l a s B.Sawyer, *Henry F o r d H o s p i t a l , Detroit, MI a n d Boston U n i v e r s i t y Medical Center, Boston, MA
Robert L. Roden, Koji A s a n o , Scott W i c h m a n , Erin H o o v e r , Michael R. Bristow a n d William T. A b r a h a m . U n i v e r s i t y of C o l o r a d o H e a l t h Sciences Center, Denver, C o l o r a d o a n d the U n i v e r s i t y of Cincinnati College of Medicine, Cincinnati, O H
In cardiac myocytes norpinephrine (NE) is both a potent inotropic agonist and a stimulus for hypertrophy in vivo and in vitro. Reactive oxygen species are known signaling intermediates of growth pathways in other cell systems (e.g. vascular cells), and we have found that increased superoxide anion, alone, can trigger hypertrophy and apoptosis in cardiac myocytes. We therefore tested the role of oxidative stress, specifically, increased superoxide anion, as a mediator of NE-induced hypertrophy and contraction in isolated adult rat ventricolar myocytes (ARVM) in primary culture. Exposure to NE (1 gin) for 48 hr. caused a 54 +/- 6% increase (n=4; p<0.001) in SH-leucine incorporation, an 88% increase in total protein content (n=2), and a 130% increase in ANF expression by northern blot (n=2). This hypertrophic response to NE was inhibited by the superoxide dismutase mimetic MnTMPyP (50 ~tM), which abolished the NE-stimulated increase in SH-leucine incorporation (10 +/- 12%; p<0.02; n=4) and total protein content (-30%; n=2). MnTMPyP also decreased NE-stimulated ANF expression by 50% (n=2). Using a video edgedetection system, we measured the effect of MnTMPyP on NE-stimulated contraction in paced myocytes (5Hz, 37°C). Exposure to MnTMPyP (24 hrs) had no effect on baseline contractility or the response to NE (n=6). Thus, superoxlde anion appears to mediate NE-stimulated myocyte hypertrophy, but has no effect on 13-adrenergic receptor-mediated contraction. These data therefore suggest an increase in superoxide anion may mediate the hypertrophic, but not the eontractile, effects of NE. Thus, superoxide anion may play a central role in mediating the effects of NE on myocyte remodeling. These data further provide a mechanism by which sympathetic inhibition could exert salutary effects in heart failure.
Synthetic human B-type or brain natrimetic peptide (hBNP) is currently seeking FDA approval as a therapeutic agent to be used in treating patients with congestive heart failure. Several reports have demonstrated hBNP's favorable hemodynamic effects including: a reduction in blood pressure, systemic vascular resistance, and vemricular filling pressnres with an associated increase in cardiac output. While previous studies have suggested that hBNP improves cardiac function principally by unloading the heart, none have ruled out the possibility of a direct inotropic effect. Therefore, we tested this hypothesis on ventricular myoeardium obtained from 9 explanted failing human hearts. Right ventricular 1400 trabeculae were hung in a tissue muscle bath and allowed to equilibrate in ~BNP Tyrede's solution at 37°C. The trabecttfae ~Control were stimulated at a frequency of 1 Hz -a-Dobutabmine and net maximal tension response was "~ 20000 measured following cumulative doses of hBNP (1 n M - 1 toM) in the absence or presence (not shown) of increased adenylyl cyclase activity through -200 Drug Concentration forskolin augmentation. For comparison, isoprotcrenol and dobotamine (each 1 nM - 1 ~M) were administered to identically prepared tsabecalae from the 9 hearts, "!0<0.05 vs. vehicle controls, Relative to vehicle controls, lfl3NP produced no change in systolic tension either in the absence or presence of heightened adenylyl cyclase activity, while both dobutamine and isoproterenol increased net systolic tension (as expected) hi a dose-related manner. Conclusion: These results suggest that the favorable hemodymamic effects of td3NP in human heart failure are not due to a direct positive inetropic effect on ventricular myecardium.
~1000 ¢o6~ ~sloproterenol