Chi Ming Wei

Endothelin in human congestive heart failure

BACKGROUND Although recent investigations report the elevation of plasma endothelin (ET) in congestive heart failure (CHF), it remains unclear if this elevation is that of the biologically active peptide ET-1 or of its precursor big-ET. Furthermore, it is unclear if such elevation is associated with increased myocardial ET and if the molecular form from cardiac tissue is altered ET. Last, it remains to be established whether circulating ET is increased at the earliest stage of CHF in patients with asymptomatic left ventricular dysfunction and correlates with the magnitude of ventricular dysfunction. METHODS AND RESULTS The present study was designed to investigate concentrations and molecular forms of ET in plasma and cardiac tissue in healthy subjects and CHF patients with New York Heart Association (NYHA) class I through IV using cardiac radionuclide angiogram, cardiac myocardial biopsy, radioimmunoassay, gel permeation chromatography (GPC), and immunohistochemical staining (IHCS). Plasma ET was increased only in patients with moderate (NYHA class III) or severe (NYHA class IV) CHF compared with healthy subjects and individuals with asymptomatic (NYHA class I) or mild (NYHA class II) CHF. The elevation of circulating ET in CHF showed a negative correlation with left ventricular ejection fraction and cardiac index and a positive correlation with functional class and left ventricular end-diastolic volume index. GPC demonstrated that immunoreactive plasma ET was ET-1 in healthy subjects and both mature ET-1 and its precursor big-ET in severe CHF patients, with big-ET the predominant molecular form. Cardiac tissue concentrations and IHCS revealed ET presence in healthy atrial and ventricular tissue, which were not different in severe CHF. GPC revealed that the molecular form of cardiac ET was ET-1 in both healthy and CHF hearts. CONCLUSIONS The present study establishes for the first time that the elevation of plasma ET in severe human CHF represents principally elevation of big-ET. Second, ET is present in healthy and failing myocardia, and its activity by both immunohistochemistry and radioimmunoassay is not changed in CHF. Furthermore, the elevated plasma ET is characteristic of severe CHF and not asymptomatic or mild CHF. In addition, the degree of plasma elevation of ET correlates with the magnitude of alterations in cardiac hemodynamics and functional class. The present study confirms and extends previous investigations of ET in human CHF and establishes the evolution of circulating and local cardiac ET in the spectrum of human CHF.

Differential atrial and ventricular expression of myocardial BNP during evolution of heart failure

Although brain natriuretic peptide (BNP) of myocardial origin is important in cardiovascular and renal function and as a marker of cardiac dysfunction, the expression of BNP in atrial and ventricular myocardium remains controversial both under normal conditions and in heart failure. We therefore determined left atrial and left ventricular (LV) gene expression and tissue concentration as well as circulating BNP during the evolution of rapid ventricular pacing-induced congestive heart failure (CHF) in the dog. Early LV dysfunction after 10 days of pacing was characterized by impaired LV function but maintained arterial pressure, and overt CHF after 38 days of pacing was characterized by further impaired LV function and decreased systemic arterial pressure. Under normal conditions, cardiac BNP mRNA and cardiac tissue BNP were of atrial origin. In early LV dysfunction, BNP mRNA and tissue BNP were markedly increased in the left atrium in association with an increase in circulating BNP but remained below or at the limit of detection in the LV. In overt CHF, BNP mRNA was further increased in the left atrium and first increased in the LV, together with an increase in LV tissue BNP and a further increase in circulating BNP. In the progression of CHF, early LV dysfunction is characterized by a selective increase in atrial BNP expression in association with increased circulating BNP. Overt CHF is characterized by an additional recruitment of ventricular BNP expression and a further increase in circulating BNP. These studies provide important new insight into the local and temporal regulation of cardiac BNP gene expression during the progression of heart failure and underscore the predominant endocrine role of atrial myocardium under normal conditions and in early LV dysfunction.Although brain natriuretic peptide (BNP) of myocardial origin is important in cardiovascular and renal function and as a marker of cardiac dysfunction, the expression of BNP in atrial and ventricular myocardium remains controversial both under normal conditions and in heart failure. We therefore determined left atrial and left ventricular (LV) gene expression and tissue concentration as well as circulating BNP during the evolution of rapid ventricular pacing-induced congestive heart failure (CHF) in the dog. Early LV dysfunction after 10 days of pacing was characterized by impaired LV function but maintained arterial pressure, and overt CHF after 38 days of pacing was characterized by further impaired LV function and decreased systemic arterial pressure. Under normal conditions, cardiac BNP mRNA and cardiac tissue BNP were of atrial origin. In early LV dysfunction, BNP mRNA and tissue BNP were markedly increased in the left atrium in association with an increase in circulating BNP but remained below or at the limit of detection in the LV. In overt CHF, BNP mRNA was further increased in the left atrium and first increased in the LV, together with an increase in LV tissue BNP and a further increase in circulating BNP. In the progression of CHF, early LV dysfunction is characterized by a selective increase in atrial BNP expression in association with increased circulating BNP. Overt CHF is characterized by an additional recruitment of ventricular BNP expression and a further increase in circulating BNP. These studies provide important new insight into the local and temporal regulation of cardiac BNP gene expression during the progression of heart failure and underscore the predominant endocrine role of atrial myocardium under normal conditions and in early LV dysfunction.

CARDIAC SECRETION OF ADRENOMEDULLIN IN HUMAN HEART FAILURE

Adrenomedullin (ADM) is a newly discovered endogenous vasorelaxing and natriuretic peptide. Recently, we have reported that plasma ADM is increased in severe congestive heart failure (CHF) in humans and that increased immunohistochemical staining is observed in the failing human ventricular myocardium. The present study was designed to test the hypothesis that the failing human ventricle secretes ADM and that circulating ADM progressively increases with the severity of clinical CHF. Plasma ADM was significantly increased in human CHF (39.8 +/- 3.6 pg/ml, P < 0.001 vs. normal) as compared with normal subjects (14.4 +/- 2.7 pg/ml). Plasma ADM was increased in mild CHF (NYHA class II, 30.1 +/- 3.4 pg/ml, P < 0.01 vs. normal), moderate CHF (NYHA class III, 31.5 +/- 3.0 pg/ml, P < 0.01 vs. normal), and severe CHF (NYHA class IV, 66.1 +/- 9.4 pg/ml, P < 0.001 vs. normal). In 13 patients with CHF in whom plasma samples were obtained from aorta (AO), coronary sinus (CS) and anterior interventricular vein (AIV), there was a significant step-up in plasma ADM between AO and AIV (50.6 +/- 9.3 pg/ml and 62.1 +/- 11.1 pg/ml, respectively, P < 0.01) and between AO and CS (50.6 +/- 9.3 pg/ml and 58.6 +/- 11.4 pg/ml, respectively, P < 0.05). The current study demonstrates that the failing human heart secretes ADM in human CHF suggesting contribution to the increase in plasma ADM, and indicates for the first time an additional endocrine system of cardiac origin which is activated in human CHF and may function in cardiorenal regulation.

Circulating and tissue endothelin immunoreactivity in hypercholesterolemic pigs.

BackgroundHypercholesterolemia is characterized by a coronary vasoconstrictive response to the endothelium-dependent vasodilator acetylcholine. This abnormality may be due to reduced synthesis of endothelium-derived relaxing factor and/or enhanced synthesis and release of an endothelium-derived contracting factor. Endothelin is an endothelium-derived vasoconstrictor and mitogenic peptide that is present in normal plasma, and its circulating concentrations are elevated in disease states that are characterized by abnormal endothelium-dependent relaxation to acetylcholine. The current studies were designed to test the hypotheses that experimental hypercholesterolemia results in elevation of plasma and tissue endothelin immunoreactivity and that the abnormal acetylcholine-evoked coronary vasoconstriction in the hypercholesterolemic animals is associated with further elevation of plasma endothelin. Methods and ResultsPlasma concentrations and molecular forms of endothelin immunoreactivity were determined following 2% cholesterol diet for 4 months in pigs and during intracoronary acetylcholine administration. Second, we assessed the presence of endothelin in the coronary vascular wall by using immunohistochemistry. Hypercholesterolemia elevated plasma endothelin concentration and enhanced coronary artery tissue endothelin immunoreactivity. The endothelium-dependent vasodilator acetylcholine further increases plasma endothelin in hypercholesterolemia in association with coronary vasoconstriction. The predominant molecular form of endothelin in hypercholesterolemia is the biological active endothelin-l. ConclusionThis study suggests a role for endothelin as an early participant and a marker for the endothelial dysfunction in hypercholesterolemia as well as a participant in the atherogenic process.

Immunohistochemical localization of adrenomedullin in canine heart and aorta

Adrenomedullin (ADM) is a new endogenous hypotensive and vasorelaxing peptide that may play an important role in the regulation of cardiovascular function. Although ADM was originally isolated from pheochromocytoma, ADM-like immunoreactivity has also been widely detected in various tissues, including the cardiovascular system. Based upon the reports that ADM mRNA and ADM-like immunoreactivity are present in the heart, the present study was designed to investigate the immunohistochemical localization of ADM in the canine heart and aorta. In the canine heart, immunohistochemical examination revealed positive immunostaining within the myocardia in both atria and ventricles. ADM immunoreactivity was observed within the cytoplasm of myocardium, and was widely distributed in the peripheral cytoplasm. ADM immunoreactivity was more intense in the atria than in the ventricles. In the canine aorta, vascular smooth muscle cells of the aorta and vasa vasorum were also immunopositive for ADM. ADM immunoreactivity was mostly localized in the perinuclear position within the smooth muscle cells. There was no immunoreactivity in endothelium, endocardium, epicardium, adventitia, or connective tissues. The current study demonstrates for the first time that immunoreactive ADM by immunohistochemistry is present in the cardiovascular system. As ADM has hypotensive and vasorelaxing actions and circulates in the body, ADM is a cardiovascular peptide hormone that may play an important role in the regulation of cardiovascular system.

Vasonatrin peptide: a unique synthetic natriuretic and vasorelaxing peptide.

This study reports the cardiovascular and renal actions of a novel and newly synthesized 27-amino acid peptide termed vasonatrin peptide (VNP). VNP is a chimera of atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP). This synthetic peptide possesses the 22-amino acid structure of CNP, which is a cardiovascular selective peptide of endothelial origin and is structurally related to ANP. VNP also possesses the five-amino acid COOH terminus of ANP. The current study demonstrates both in vitro and in vivo that VNP possesses the venodilating actions of CNP, the natriuretic actions of ANP, and unique arterial vasodilating actions not associated with either ANP or CNP.

Genetic Expression of Endothelial Nitric Oxide Synthase in Human Atrial Myocardium

OBJECTIVE To investigate the expression of endothelial nitric oxide synthase (eNOS) in human cardiac tissues. DESIGN We attempted to determine the genetic expression and localization of eNOS in normal human atrial tissue. MATERIAL AND METHODS In normal human right atrial tissues from five donors during cardiac transplantation, eNOS expression and localization were assessed by using Northern blot analysis, in situ hybridization, and immunohistochemical staining. RESULTS Northern blot analysis and in situ hybridization demonstrated that eNOS messenger RNA is present in cardiomyocytes. Positive immunohistochemical staining was observed in the cytoplasm of cardiomyocytes. CONCLUSION These studies show for the first time the genetic expression and distribution of eNOS in human atrial myocardium and suggest that the eNOS mediated paracrine and autocrine pathway may participate in the control of myocardial function in humans.

C-type natriuretic peptide-mediated coronary vasodilation: role of the coronary nitric oxide and particulate guanylate cyclase systems.

OBJECTIVES We tested the hypothesis that C-type natriuretic peptide (CNP) mediates coronary vasodilation through activation of cyclic guanosine monophosphate (cGMP) by way of particulate guanylate cyclase. BACKGROUND CNP has known peripheral vasodilator properties, and preliminary data have suggested that it can function as a coronary vasodilator. METHODS The actions of CNP were studied in instrumented dogs and in organ chamber rings in the presence and absence of a known antagonist to particulate guanylate cyclase, HS-142-1. Additionally, the actions of HS-142-1 were tested on acetylcholine-mediated coronary vasodilation, and immunohistochemical staining was utilized to localize the presence of CNP in the coronary endothelium. RESULTS CNP relaxed isolated coronary arteries with (mean +/- SEM 45.9 +/- 7%*) and without (72.0 +/- 7%*) an endothelium (*p < 0.05 for CNP effect alone, p < 0.05 for endothelium vs. no endothelium with CNP). Intracoronary infusions increased coronary blood flow (baseline, 64.6 +/- 5.1 ml/min; CNP-5, 79.9 +/- 6.1*; CNP-20, 103.3 +/- 13.6* [*p < 0.05 vs. baseline value]) and reduced coronary vascular resistance (baseline, 1.6 +/- 0.3 mm Hg/ml per min; CNP-5, 1.4 +/- 0.3*; CNP-20, 1.2 +/- 0.3*). Intracoronary injections increased coronary blood flow (delta baseline coronary flow, 30 +/- 9* ml/min [*p < 0.05]). HS-142-1 significantly attenuated these increases (delta coronary flow, 30 +/- 9* ml/min [CNP] to 14 +/- 6 [CNP + HS-142-1] [p < 0.05 CNP vs. CNP + HS-142-1]) and the relaxation of organ chamber rings (56 +/- 7% [CNP] to 18 +/- 6% [HS-142-1 + CNP]). Finally, CNP was localized to the coronary endothelium and smooth muscle by immunohistochemical staining. CONCLUSIONS CNP functions as a coronary vasodilator through activation of cGMP by way of particulate guanylate cyclase. CNP-mediated coronary vasodilation is attenuated by intracoronary HS-142-1. Intracoronary HS-142-1 does not affect acetylcholine-mediated coronary vasodilation. These observations support a role for exogenous CNP as a potent coronary vasodilator.

Atrial natriuretic peptide and C-type natriuretic peptide in spontaneously hypertensive rats and their vasorelaxing actions in vitro.

The present study determined circulating concentrations of atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) and also investigated the vasorelaxing action of ANP and CNP on isolated contracted aorta. We also defined the vasorelaxing action of a novel and newly synthesized 27-amino acid chimera of ANP and CNP termed vasonatrin peptide (VNP), which we compared with ANP and CNP in WKY rats and SHR. Plasma and urinary cyclic GMP and sodium excretion were also investigated. Plasma ANP was increased in SHR in contrast to no change in circulating CNP. Plasma and urinary cyclic GMP and sodium excretion were no different between WKY rats and SHR. In WKY rats maximal relaxations to VNP in aortic rings without endothelium were greater than those to ANP and CNP. In SHR aortic rings the potency of VNP relaxation was preserved, the actions of ANP were enhanced, and the actions of CNP were markedly impaired. In association with these vasorelaxing actions, these data suggest that (1) circulating CNP is not different in SHR and WKY rats, but the aortic relaxing action of CNP is markedly impaired in SHR; (2) endogenous plasma ANP is significantly increased in SHR without associated increases in plasma or urinary cyclic GMP; (3) there is an increase in aortic relaxation to exogenous ANP in SHR; and (4) VNP has a potent endothelium-independent aortic relaxing action in both WKY rats and SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal role of the endogenous natriuretic peptide system in acute congestive heart failure

BACKGROUND Atrial and brain natriuretic peptides exert renal and cardiovascular actions through binding to the natriuretic peptide-A receptor, while C-type natriuretic peptide mediates actions that occur through binding to the natriuretic peptide-B receptor, with subsequent generation of cyclic guanosine monophosphate. This study determined responses of circulating atrial natriuretic peptides in experimental acute heart failure and addressed the hypothesis that elevated circulating atrial natriuretic peptides serve a homeostatic role in regulating sodium excretion and that this action is localized to the glomerulus and distal nephron, sites rich in natriuretic peptide-A receptors. METHODS AND RESULTS Studies were performed in the absence and presence of HS-142-1, an inhibitor of the natriuretic peptide receptors. Two groups of anesthetized dogs underwent induction of acute heart failure by rapid ventricular pacing, as characterized by decreases in cardiac output and increases in filling pressures with associated elevation of endogenous atrial natriuretic peptides secondary to increases in atrial stretch. In group 1 (n = 5, vehicle intrarenal bolus), despite acute heart failure-mediated decreases in cardiac output, sodium excretion was preserved with maintenance of the glomerular filtration rate and distal fractional sodium reabsorption. In group 2 (n = 5), in response to the natriuretic peptide receptor antagonist, HS-142-1 (0.5 mg/kg intrarenal bolus), sodium excretion (17.0 +/- 4.4 to 5.9 +/- 3.2 microEq/min; P < .05) and glomerular filtration rate decreased (33.0 +/- 3.6 to 21.0 +/- 3.9 mL/min; P < .05) and distal fractional sodium reabsorption increased (98.0 +/- 0.63 to 99.3 +/- 0.25%; P < .05), in association with a decrease in plasma cyclic guanosine monophosphate (13.0 +/- 3.5 to 6.6 +/- 2.9 pmol/mL; P < .05) and renal cyclic guanosine monophosphate generation (1,216 +/- 421 to 466 +/- 208 pmol/min; P < .05). CONCLUSIONS This study supports a functionally significant role for the endogenous natriuretic peptide system in preserving sodium homeostasis and glomerular filtration rate in acute heart failure.