NRSF-GNAO1-CaMK2 axis exacerbates cardiac remodeling and progresses heart failure by impairing Ca2+ homeostasis

Background

In the development of heart failure, pathological intracellular signaling reactivates fetal cardiac genes, which leads to maladaptive remodeling and cardiac dysfunction. We previously reported that a transcriptional repressor, neuron restrictive silencer factor (NRSF) represses fetal cardiac genes and maintains normal cardiac function under normal conditions, while hypertrophic stimuli de-repress this NRSF mediated repression via activation of CaMKII. Molecular mechanisms by which NRSF maintains cardiac systolic function remains to be determined, however.

Purpose

To elucidate how NRSF maintains normal cardiac homeostasis and identify the novel therapeutic targets for heart failure.

Methods and results

We generated cardiac-specific NRSF knockout mice (NRSF cKO), and found that these NRSF cKO showed cardiac dysfunction and premature deaths accompanied with lethal arrhythmias, as was observed in our previously reported cardiac-specific dominant-negative mutant of NRSF transgenic mice (dnNRSF-Tg).

By cDNA microarray analysis of dnNRSF-Tg and NRSF-cKO, we identified that expression of Gnao1 gene encoding Gαo, a member of inhibitory G proteins, was commonly increased in ventricles of both types of mice.

ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay identified that NRSF transcriptionally regulates Gnao1 gene expression.

Genetic Knockdown of Gαo in dnNRSF-Tg and NRSF-cKO by crossing these mice with Gnao1 knockout mice ameliorated the reduced systolic function, increased arrhythmogenicity and reduced survival rates.

Transgenic mice expressing a human GNAO1 in their hearts (GNAO1-Tg) showed progressive cardiac dysfunction with cardiac dilation. Ventricles obtained from GNAO1-Tg have increased phosphorylation level of CaMKII and increased expression level of endogenous mouse Gnao1 gene. These data suggest that increased cardiac expression of Gαo is sufficient to induce pathological Ca2+-dependent signaling and cardiac dysfunction, and that Gαo forms a positive regulatory circuit with CaMKII and NRSF.

Electrophysiological analysis in ventricular myocytes of dnNRSF-Tg revealed that impaired Ca2+ handling via alterations in localized L-type calcium channel (LTCC) activities; decreased T-tubular and increased surface sarcolemmal LTCC activities, underlies Gαo-mediated cardiac dysfunction.

Furthermore, we also identified increased expression of Gαo in ventricles of two different heart failure mice models, mice with transverse aortic constriction and mice carrying a mutant cardiac troponin T, and confirmed that genetic reduction of Gαo prevented the progression of cardiac dysfunction in both types of mice.

Conclusions

Increased expression of Gαo, induced by attenuation of NRSF-mediated repression forms a pathological circuit via activation of CaMKII. This circuit exacerbates cardiac remodeling and progresses heart failure by impairing Ca2+ homeostasis. Gαo is a potential therapeutic target for heart failure.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Grants-in –Aid for Scientific Research from the Japan Society for the Promotion of Science

4968Increased Gao expression underlies cardiac dysfunction and lethal arrhythmias accompanied with abnormal Ca2+ handling

Background

We previously demonstrated that a transcriptional repressor, neuron restrictive silencer factor (NRSF), maintains normal cardiac function and electrical stability. Transgenic mice expressing a dominant-negative mutant of NRSF in their hearts (dnNRSF-Tg) exhibit systolic dysfunction with cardiac dilation and premature death due to lethal arrhythmias like human dilated cardiomyopathy (DCM). Underlining mechanisms remain to be elucidated, however.

Purpose

We studied underling mechanisms by which NRSF maintains normal cardiac function to identify novel therapeutic targets for heart failure.

Methods and results

We generated cardiac-specific NRSF knockout mice (NRSFcKO) and confirmed that cardiac phenotypes of NRSFcKO are similar to those of dnNRSF-Tg.

cDNA microarray analysis revealed that cardiac gene expression of GNAO1 that encodes Gαo, a member of inhibitory G protein Gαi family, is increased in both dnNRSF-Tg and NRSFcKO ventricles.

We confirmed that GNAO1 is a direct target of NRSF through ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay.

In dnNRSF-Tg, pharmacological inhibition of Gαo with pertussis toxin improved systolic dysfunction and knockdown of Gαo by crossing with GNAO1 knockout mice improved not only systolic function but also frequency of ventricular arrhythmias and survival rates.

Electrophysiological and biochemical analysis in ventricular myocytes obtained from dnNRSF-Tg demonstrated that genetic reduction of Gαo ameliorated abnormalities in Ca2+ handling, which include increased current density in surface sarcolemmal L-type Ca2+ channel, reduced content of sarcoplasmic reticulum Ca2+ and lowered peak of Ca2+ transient. Furthermore, genetic reduction of Gαo attenuated increased phosphorylation levels of CAMKII in dnNRSF-Tg ventricles, which presumably underlies the improvement in Ca2+ handling. In addition, we identified increased Gαo expression in ventricles of heart failure model mice induced by transverse aortic constriction and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gαo ameliorated cardiac dysfunction.

Figure 1

Conclusions

We found that increased expression of Gαo, induced by attenuation of NRSF-mediated repression, plays a crucial role in the progression of cardiac dysfunction and lethal arrhythmias by evoking Ca2+ handling abnormality. These data demonstrate that Gαo is a potential therapeutic target for heart failure.

Prognostic factors of clear renal cell carcinoma in pT1a cases

e16064

Background: The proportion of clear cell renal cell carcinoma (CRCC) cases diagnosed at pT1a is known to be increasing significantly. Although their prognosis is excellent in general, some cases show distant metastasis. Most of proposed prognostic factors are based on mainly large sized CRCC data. The prognostic factors for small sized CRCC, especially for pT1a cases, aren't well described. Methods: Three hundred three pT1a CRCC cases were retrieved from authors’ institution files. All cases were reviewed by the single uropathologist (T. Tsuzuki). For each case, the following pathological parameters were analyzed: patient age, tumor location (upper, middle, low), Furhman grade, presence of capsule, presence of lympho-vascular invasion, growth pattern (expansive or infiltrating), presence of scar, presence of hemorrhage, and presence of necrosis. Results: Male to female ratio was 4.4. Patient's age ranged from 21 to 85 years (median: 59 years). Follow up duration ranged from one to 225 months (median: 59 months). 35 cases showed distant metastasis. The 5-year and 10-year cause specific survival rate were 96.9%, 93.0%. The 5-year and 10-year recurrence free survival rate were 91.8%, 83.9%. Furhman grade (grade 1+2+3 vs. 4), presence of lympho-vascular invasion, infiltrating growth pattern, and presence of necrosis were statistical significant (p < 0.0001). Conclusions: Furhman grade (less than 3 vs. 4), presence of lympho-vascular invasion, growth pattern, and presence of necrosis can be prognostic factors in CRCC in pTa cases. Growth pattern, which is unrecognized concept for prognosis, can be a new prognostic factor in CRCC.

No significant financial relationships to disclose.

Two molecular forms of adrenomedullin in congenital heart disease

To investigate the pathophysiological role of two forms of adrenomedullin (AM), a mature AM (AM-m) and a glycine-extended AM (AM-Gly), in congenital heart disease, we measured plasma levels of AM in patients with cyanotic heart disease, high pulmonary blood flow without pulmonary hypertension (PH), high pulmonary blood flow with PH, Fontan procedure, intracardiac repair without complication, and intracardiac repair with PH and control subjects. Plasma AM-m and AM-Gly were increased only for cyanotic heart disease (2.5 +/- 1.3 pmol/L, p < 0.001; 13.1 +/- 6.2 pmol/L, p < 0.05) and intracardiac repair with PH (2.3 +/- 1.5 pmol/L, p < 0.01; 13.0 +/- 7.0 pmol/L, p < 0.05) compared with control (1.0 +/- 1.4 and 8.6 +/- 1.3 pmol/L, respectively). They were similarly correlated with mean systemic arterial pressure (r = -0.40 and -0.37 respectively; p < 0.001), mixed venous oxygen saturation (r = -0.60 and -0.50; p < 0.0001), systemic arterial oxygen saturation (SA(sat)) (r = -0.56 and -0.46; p < 0.0001), and pulmonary arterial resistance (Rp) (r = 0.41 and 0.38; p < 0.005). Multiple regression analysis revealed that SA(sat) and Rp were independently correlated with AM. Interestingly, the venous AM-m level was significantly higher than the arterial AM-m, suggesting that the mature form is extracted in pulmonary circulation, whereas there were no venoarterial differences in AM-Gly. These results suggest that plasma AM-m and AM-Gly are similarly regulated and the main clearance site of AM-m is the lung in patients with congenital heart disease.

Role of increased circulating and renal adrenomedullin in rats with malignant hypertension

Although it has been reported that the circulating adrenomedullin (AM) level is elevated in hypertension and renal failure, the pathophysiological significance of circulating and intrarenal AM in malignant hypertension remains unknown. We investigated the circulating and intrarenal AM system in rats with malignant hypertension by measuring the plasma level, renal tissue level, and mRNA abundance of AM and the mRNA abundance of AM receptor. We also investigated the effects of intravenously infused calcitonin gene-related peptide (CGRP)-(8-37), an antagonist of AM, on the hemodynamics and renal tubular function. We studied the following four groups: control Wistar-Kyoto rats (WKY), control spontaneously hypertensive rats (C-SHR), salt-loaded SHR (S-SHR), and DOCA-salt SHR (D-SHR). After 3 wk of DOCA treatment, D-SHR developed malignant hypertension. D-SHR were characterized by higher blood pressure, kidney weight, urinary protein excretion and blood urea nitrogen, and lower creatinine clearance compared with the other three groups. The plasma AM level and urinary excretion of AM were markedly higher in D-SHR than in the other three groups. In the kidney, the tissue AM level and the expression of AM mRNA in the renal medulla were significantly increased in D-SHR compared with the other three groups, whereas there were no significant differences in these levels in the renal cortex among the four groups. In the renal AM receptor system, the expression of the gene for receptor activity modifying protein 3 was significantly increased in the renal medulla in D-SHR compared with the other three groups. An immunohistochemical study revealed that AM immunostaining in renal collecting duct cells and distal tubules was more intense in D-SHR than in the other three groups. After CGRP-(8-37) infusion, blood pressure increased significantly and urinary sodium excretion and urine flow decreased significantly only in D-SHR. These results suggest that the increased circulating AM and renal AM and the increased expression of the mRNA for AM and its receptor may at least partly compensate for the malignant hypertensive state in certain forms of malignant hypertension via the hypotensive, natriuretic, and diuretic actions of AM.

Two molecular forms of plasma adrenomedullin during tilt test in healthy subjects

There is accumulating evidence suggesting that adrenomedullin (AM) may participate in the regulation of circulatory homeostasis and pathophysiology of cardiovascular disease. A recent study revealed that two molecular forms of AM, an active form of mature AM (AM-m) and an intermediate inactive form of glycine-extended AM (AM-Gly), circulate in human plasma. The object of the present study was to evaluate the effect of orthostasis on a time course of two molecular forms of plasma AM and to compare them with the behavior of other vasoactive hormones. Twelve healthy male volunteers were studied. The experimental protocol consisted of 20 min of supine rest, tilting at 70 degrees for 20 min, and then 20 min of supine rest. Blood pressure and heart rate were measured every minute. Blood samples were obtained before, at 2 and 18 min during the tilt test, and 2 and 18 min after the test for the measurements of vasoacting hormones and hematocrit. Blood pressure and heart rate were slightly increased earlier during tilting and then remained elevated until the end of the test. The increase in heart rate and blood pressure returned to normal levels early after the tilt test. Plasma epinephrine and norepinephrine significantly increased during the tilt test. These hormones returned to normal levels 18 min after the test. The plasma renin activity, antidiuretic hormone and dopamine were also increased by the end of the tilt test, whereas plasma atrial natriuretic peptide was significantly decreased after the tilt test. Hematocrit increased slightly in the early phase of the tilt test and was further increased by the end of the test. In contrast, plasma AM-Gly or AM-m did not change during the tilt test or the recovery period. Nitric oxide metabolites did not change, either. There were no significant relationships between plasma catecholamines and AM. Plasma brain natriuretic peptide did not change during the tilt test or the recovery period, either. These results suggest that the two molecular forms of AM, AM-m and AM-Gly in plasma, did not respond to the short term tilting stress. These findings may support the hypothesis that plasma AM is secreted in a constitutive manner from the vascular wall.

Left ventricular mass relates to average systolic blood pressure, but not loss of circadian blood pressure in stable hemodialysis patients: an ambulatory 48-hour blood pressure study

Although left ventricular hypertrophy (LVH) is a common complication which contributes substantially to high cardiovascular mortality and morbidity in end-stage renal failure, whether changes in blood pressure and alterations of circadian variation of blood pressure occur between the hemodialysis (HD) day and the interdialytic day, and if so, whether they influence the left ventricular mass (LVM) remain unknown. Thirty-five consecutive stable patients who had had a hematocrit value greater than 25% for the previous 6 months, who had been on the same antihypertensive drugs during this period, and who underwent HD 3 times a week were included. Echocardiograms were recorded after HD and then ambulatory blood pressure monitoring was recorded every hour for 48 h. The mean interdialytic body weight gain was less than 5% of dry weight. Patients with LVH had a higher average systolic blood pressure (SBP) at predialysis, postdialysis, on the HD day and on the interdialytic day than those without LVH despite the higher antihypertensive therapy rate. The majority of patients with LVH showed concentric hypertrophy and higher plasma natriuretic peptide levels. Irrespective of the presence of LVH, the average blood pressure value did not change between the HD day and the interdialytic day, and a loss of circadian blood pressure variation was observed on both the HD and interdialytic days. Univariate analysis revealed that LVM was significantly correlated with the average SBP at predialysis, postdialysis, on the HD day, on the interdialytic day and over 48 h (r= 0.48, r=0.61, r=0.67, r=0.67, r=0.73, respectively; all p<0.05). Multiple regression analysis revealed that 48-h SBP was independently associated with the LVM index. These results suggest that neither the loss of circadian blood pressure variation nor the changes of blood pressure between the HD and interdialytic days was of major etiologic importance in the development of LVH, and that the absolute value of the 48-hour average SBP may be an important risk factor for concentric LVH in stable HD patients.

Plasma brain natriuretic peptide levels in chronic hemodialysis patients: influence of coronary artery disease

A noninvasive biochemical testing method for early detection and monitoring the condition of cardiac complications in hemodialysis (HD) patients would be useful and might lead to improved survival. The aim of this study is to clarify the pathophysiological significance of plasma brain natriuretic peptide (BNP) levels in HD patients with and without coronary artery disease (CAD). We measured plasma atrial natriuretic peptide (ANP) and BNP levels on Monday, Wednesday, and Friday before and after HD in 28 consecutive patients who underwent HD three times weekly. In addition, we measured plasma ANP and BNP levels in 21 HD patients with CAD and 27 HD patients without CAD and studied the relationships between BNP levels and cardiac function and clinical variables. Plasma ANP levels significantly decreased after HD on Monday, Wednesday, and Friday, and predialysis plasma ANP levels on Monday were significantly greater than those on other days. Plasma BNP levels did not change after HD on Monday; however, they significantly decreased after HD on Wednesday and FRIDAY: Predialysis plasma BNP levels on Monday were greater than those on other days, and postdialysis plasma BNP levels on Monday were greater than predialysis plasma BNP levels on WEDNESDAY: Plasma BNP levels in HD patients with CAD were significantly greater than those in HD patients without CAD and significantly correlated with left ventricular (LV) ejection fraction (r = -0.69), end-diastolic volume index (r = 0.59), and end-systolic volume index (r = 0.84) determined by left ventriculography. Conversely, plasma BNP levels in HD patients without CAD significantly correlated with LV mass index (r = 0.54) determined by echocardiography and mean systolic blood pressure (r = 0.72) determined by 48-hour ambulatory blood pressure monitoring. These results suggest the following: (1) plasma BNP levels before and after HD in chronic HD patients directly correlate with the degree of body fluid retention, and the day of the week on which the sample is obtained should be considered for its evaluation; (2) plasma BNP levels reflect LV function in HD patients with CAD; and (3) plasma BNP levels reflect LV mass and blood pressure in HD patients without CAD.

Effects of TCV-116 on expression of NOS and adrenomedullin in failing heart of Dahl salt-sensitive rats

We examined the effects of TCV-116, an angiotensin II type 1 receptor antagonist, on endothelial-cell nitric oxide synthase (eNOS), inducible NOS (iNOS), and adrenomedullin (ADM) expression in the left ventricle (LV) and evaluated these relation to myocardial remodeling in failing heart of Dahl salt-sensitive hypertensive rats (DS) fed a high-salt diet. TCV-116 (DSHF-T, 5 mg/kg/day, subdepressor dose) or vehicle (DSHF-V) were given from left ventricular hypertrophy to heart failure stage for 7 weeks. Markedly increased left ventricular end-diastolic diameter and reduced fractional shortening in DSHF-V was significantly ameliorated in DSHF-T. The eNOS mRNA and protein in the LV was significantly suppressed in DSHF-V compared with control rats (DR-C), and significantly increased in DSHF-T compared with DSHF-V. The iNOS mRNA and protein, ADM mRNA and immunoreactive ADM contents, and type I collagen mRNA in the LV were significantly increased in DSHF-V compared with DR-C, and significantly decreased in DSHF-T compared with DSHF-V. DSHF-V showed a significant increase of the wall-to-lumen ratio, perivascular fibrosis, and myocardial fibrosis, with all these parameters being significantly improved by TCV-116. In conclusion, myocardial remodeling and heart failure in DS rats fed a high-salt diet were significantly ameliorated by a subdepressor dose of TCV-116, which may be due to a increased in eNOS and a decreased in iNOS mRNA and protein expression in the LV. Moreover, the ADM mRNA and immunoreactive ADM contents are upregulated in failing heart of DS rats fed a high-salt diet, and increased ADM expression may have a role in the defense mechanism against further cardiac dysfunction and impaired myocardial remodeling.

Molecular forms of plasma and urinary adrenomedullin in normal, essential hypertension and chronic renal failure

OBJECTIVES

Human adrenomedullin precursor is converted to glycine-extended adrenomedullin (AM-Gly), an intermediate inactive form of adrenomedullin. Subsequently, AM-Gly is converted to active form of mature adrenomedullin (AM-m). The aim of the present study was to investigate (i) whether sex or age influences plasma and urinary AM-m and AM-Gly levels in normal subjects; (ii) the daytime variability of plasma AM-m and AM-Gly levels in normal subjects; (iii) AM-m and AM-Gly levels and its ratio in plasma and urine in normal subjects, individuals with essential hypertension (HT), and chronic renal failure (CRF); and (iv) the ratio of AM-m and AM-total (T) in plasma of various veins and aorta.

METHODS

We measured plasma levels and urinary excretions of AM-m, AM-Gly and AM-T (AM-m + AM-Gly) by recently developed immunoradiometric assay in normal subjects (n = 81), HT (n = 28) and CRF (n = 30). We also determined the molecular forms of plasma adrenomedullin taken from various sites during angiography in patients with suspected renovascular hypertension (n = 9).

RESULTS

There were no differences in plasma and urinary excretions of two molecular forms of adrenomedullin among sexes or ages in normal subjects. There was no daytime variation of plasma two molecular forms of adrenomedullin in normal subjects. Plasma AM-m, AM-Gly and AM-T levels were increased in patients with HT and CRF compared with normal subjects, whereas urinary AM-m, AM-Gly and AM-T excretions were decreased in patients with HT and CRF compared with normal subjects. Urinary AM-m: AM-T ratios were significantly higher than plasma AM-m: AM-T ratios. Plasma AM-m and AM-T levels taken from various veins were similar, and they were significantly higher than those of aorta, although there were no differences in plasma AM-Gly levels between aorta and veins.

CONCLUSIONS

These results suggest that in normal subjects, and individuals with HT and CRF: (i) plasma and urinary excretions of AM-m and AM-Gly are not affected by age or sex; (ii) AM-m in parallel with AM-Gly is increased; (iii) urine contains a higher percentage of active adrenomedullin than plasma; and (iv) plasma AM-m may be partly metabolized in the lung.

Effect of a hypocaloric diet on adrenomedullin and natriuretic peptides in obese patients with essential hypertension

We examined the effect of a hypocaloric diet on adrenomedullin (AM), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) in 12 obese patients with essential hypertension (age, 48-81 years; body mass index, 26-34 kg/m2). For the initial week, a standard diet of 2000 kcal/day was given, followed by 3 weeks of a hypocaloric diet of 850 kcal/day, with a constant intake of sodium. The patients lost 3.7 +/- 0.2 kg body weight during the hypocaloric diet period (p < 0.0001). The decrease in blood pressure during the study period was 10.3 +/- 3.6 mmHg systole (p = 0.017) and 4.2 +/- 3.2 mmHg diastole (NS). Plasma AM concentration was decreased significantly from 4.88 +/- 0.46 to 3.97 +/- 0.38 pmol/l by the hypocaloric diet (p = 0.004). Plasma ANP and BNP concentrations were also decreased significantly by the hypocaloric diet (p = 0.042 for each). These results demonstrate, for the first time, that plasma AM concentration as well as plasma ANP and BNP concentrations are decreased by a hypocaloric diet in obese patients with essential hypertension. These vasodilator peptides may act against further elevation in blood pressure in obese patients with essential hypertension.

Alterations of intrarenal adrenomedullin and its receptor system in heart failure rats

Calcitonin receptor-like receptor/receptor activity-modifying protein 2 (CRLR/RAMP2) and CRLR/RAMP3 complexes have been reported to be specific adrenomedullin (AM) receptors. In the present study, we evaluated the pathophysiological significance of renal AM and its receptor system in aortocaval shunt (ACS) rats. Renal AM levels were measured serially during 5 weeks after the operation. Renal gene expressions of AM, CRLR, RAMP2, and RAMP3 were measured at 2 weeks (decompensated phase) and 5 weeks (compensated phase) after the operation. Immunohistochemical localizations of renal AM were also evaluated. Furthermore, the relations between urinary sodium excretion (UNaV) and renal AM levels were evaluated. Renal AM levels were higher in ACS than in control animals only at 1, 2, and 3 weeks after the operation. At 2 weeks after the operation, renal AM mRNA expression was also higher in ACS than in control animals. CRLR, RAMP2, and RAMP3 mRNAs were expressed in the kidney, but there were no differences between the 2 groups. Immunohistochemistry revealed the positive AM immunostaining within the renal tubular cells, and it was more intense in ACS than in control animals. There were significant correlations between UNaV and renal AM levels. At 5 weeks after the operation, there were no differences in mRNA levels of AM, CRLR, RAMP2, and RAMP3 between the 2 groups. There was a significant correlation between UNaV and medullary AM levels. The present findings suggest that increased renal AM levels in decompensated heart failure, presumably due to increased AM production in renal tubules, in part, are involved in the regulation of sodium excretion.

[Plasma brain natriuretic peptide as a prognostic indicator in patients with primary pulmonary hypertension]

BACKGROUND

Plasma brain natriuretic peptide (BNP) level increases in proportion to the degree of right ventricular dysfunction in pulmonary hypertension. We sought to assess the prognostic significance of plasma BNP in patients with primary pulmonary hypertension.

METHODS AND RESULTS

Plasma BNP was measured in 60 patients with primary pulmonary hypertension at diagnostic catheterization, together with atrial natriuretic peptide, norepinephrine, and epinephrine. Measurements were repeated in 53 patients after a mean follow-up period of 3 months. Forty-nine of the patients received intravenous or oral prostacyclin. During a mean follow-up period of 24 months, 18 patients died of cardiopulmonary causes. According to multivariate analysis, baseline plasma BNP was an independent predictor of mortality. Patients with a supramedian level of baseline BNP (> or = 150 pg/ml) had a significantly lower survival rate than those with an inframedian level, according to Kaplan-Meier survival curves (p < 0.05). Plasma BNP in survivors decreased significantly during the follow-up (217 +/- 38 to 149 +/- 30 pg/ml, p < 0.05), whereas that in nonsurvivors increased (365 +/- 77 to 544 +/- 68 pg/ml, p < 0.05). Thus, survival was strikingly worse for patients with a supramedian value of follow-up BNP (> or = 180 pg/ml) than for those with an inframedian value (p < 0.0001).

CONCLUSIONS

A high level of plasma BNP, and in particular, a further increase in plasma BNP during follow-up, may have a strong, independent association with increased mortality in patients with primary pulmonary hypertension.

Elevation of two molecular forms of adrenomedullin in plasma and urine in patients with acute myocardial infarction treated with early coronary angioplasty

Adrenomedullin (AM) has vasodilatory, diuretic and natriuretic actions. Two molecular forms of AM circulate in human plasma: an active, mature form of AM (AM-m) and an intermediate, inactive, glycine-extended form of AM (AM-Gly). In the present study we investigated the pathophysiological significance of the two molecular forms of AM in plasma and urine in patients with acute myocardial infarction. We serially measured venous and arterial plasma levels and urinary excretion of AM-m, AM-Gly and total AM (Am-T; =AM-m+AM-Gly) over 2 weeks using our recently developed immunoradiometric assay in 26 consecutive patients with acute myocardial infarction and in age-matched normal controls, and studied the relationships between AM levels and clinical parameters. Plasma AM-m, AM-Gly and AM-T levels were increased on admission in patients with acute myocardial infarction compared with age-matched normal controls. Levels of AM-m, AM-Gly and AM-T in plasma reached a peak 24 h after the onset of symptoms. Plasma AM-m, AM-Gly and AM-T levels were significantly correlated with plasma levels of brain natriuretic peptide and pulmonary arterial pressure. Plasma AM-Gly levels in the vein were similar to those in the artery, whereas plasma AM-m levels were significantly lower in the artery than in the vein. Urinary excretion of AM-m, AM-Gly and AM-T was also increased on admission, and reached a peak at 12 h after the onset of symptoms. Urinary excretion of AM-m and AM-Gly was significantly correlated with urinary sodium excretion. The AM-m/AM-T ratio was significantly higher in the urine than in the vein or artery. AM-m levels were significantly correlated with AM-Gly levels in both the urine and plasma; however, there were no significant correlations between plasma and urinary AM levels. The results suggest that levels of both molecular forms of AM are increased in the urine as well as in the plasma in the acute phase of myocardial infarction. Since AM exerts potent cardiovascular and renal effects, increased concentrations of AM in plasma and urine in the acute phase of myocardial infarction may be involved in the defence mechanism against further elevations of peripheral and pulmonary vascular resistance and oliguria in acute myocardial infarction.

The active molecular form of plasma adrenomedullin is extracted in the pulmonary circulation in patients with mitral stenosis: possible role of adrenomedullin in pulmonary hypertension

Adrenomedullin (AM), a novel hypotensive peptide, preferentially dilates pulmonary vessels rather than systemic vessels. This suggests the possibility that AM is a circulating hormone which participates in regulation of the pulmonary circulation. A recent study revealed that two molecular forms of AM, i.e. a mature, active form of AM (AM-m) and an intermediate, inactive, glycine-extended form of AM (AM-Gly), circulate in human plasma. In the present study we investigated the production and clearance sites and pathophysiological significance of the two molecular forms of AM in the pulmonary circulation in patients with mitral stenosis. We measured the plasma levels of AM-m and total AM (AM-T; AM-m+AM-Gly) using a recently developed specific immunoradiometric assay, and thus calculated plasma AM-Gly levels, in blood samples obtained from the femoral vein, pulmonary artery, left atrium and aorta of 28 consecutive patients with mitral stenosis (20 females and eight males; age 53+/-10 years). Patients with mitral stenosis had significantly higher venous concentrations of AM-T, AM-Gly and AM-m than age-matched normal controls (AM-T, 15.9+/-2.5 and 10.6+/-2.1 pmol/l respectively; AM-Gly, 14.0+/-2.1 and 9.8+/-1.9 pmol/l respectively; AM-m, 1.9+/-0.6 and 1.1+/-0.3 pmol/l respectively; each P<0.001). There was a significant decrease in the concentrations of AM-m and AM-T between the pulmonary artery and the left atrium (AM-T, 16.1+/-2.7 and 14.0+/-2.4 pmol/l respectively; AM-m, 2.0+/-0.6 and 0.7+/-0.2 pmol/l respectively; each P<0.001); however, there were no differences in plasma AM-Gly levels between the pulmonary artery and the left atrium (14.1+/-2.3 and 13.5+/-2.3 pmol/l respectively). The venous concentrations of AM-m, AM-Gly and AM-T showed similar correlations with mean pulmonary artery pressure (AM-T, r=0.67; AM-Gly, r=0.63; AM-m, r=0.59; each P<0.001) and total pulmonary vascular resistance (AM-T, r=0.77; AM-Gly, r=0.70; AM-m, r=0.75; each P<0.001). These results suggest that the plasma concentration of AM-m is increased in parallel with those of AM-Gly and AM-T, and that the main site for clearance of AM-m from the plasma is the lung; the extracted AM-m in the lungs may help to attenuate the increased pulmonary arterial resistance in secondary pulmonary hypertension due to mitral stenosis.

Urocortin, a member of the corticotropin-releasing factor family, in normal and diseased heart

In the present study we investigated the form of expression, action, second messenger, and the cellular location of urocortin, a member of the corticotropin-releasing factor (CRF) family, in the heart. Urocortin mRNA, as shown by quantitative RT-PCR analysis, is expressed in the cultured rat cardiac nonmyocytes (NMC) as well as myocytes (MC) in the heart, whereas CRF receptor type 2beta (CRF-R2beta), presumed urocortin receptor mRNA, is predominantly expressed in MC compared with NMC. Urocortin mRNA expression is higher in left ventricular (LV) hypertrophy than in normal LV, whereas CRF-R2beta mRNA expression is markedly depressed in LV hypertrophy compared with normal LV. Urocortin more potently increased the cAMP levels in both MC and NMC than did CRF, and its effect was more potent in MC than in NMC. Urocortin significantly increased protein synthesis by [(14)C]Phe incorporations and atrial natriuretic peptide secretion in MC and collagen and increased DNA synthesis by [(3)H]prolin and [(3)H]Thy incorporations in NMC. An immunohistochemical study revealed that urocortin immunoreactivity was observed in MC in the normal human heart and that it was more intense in the MC of the human failing heart than in MC of the normal heart. These results, together with the recent evidence of urocortin for positive inotropic action, suggest that increased urocortin in the diseased heart may modulate the pathophysiology of cardiac hypertrophy or failing heart, at least in part, via cAMP signaling pathway.

Haemodynamic and hormonal effects of adrenomedullin in patients with pulmonary hypertension

OBJECTIVE

To investigate whether infusion of adrenomedullin, a potent vasorelaxant peptide, has beneficial haemodynamic and hormonal effects in patients with pulmonary hypertension.

PATIENTS AND DESIGN

The haemodynamic and hormonal responses to intravenous infusion of adrenomedullin (0.05 microgram/kg/min) or placebo were examined in 13 patients with precapillary pulmonary hypertension.

RESULTS

Infusion of adrenomedullin produced a 44% increase in cardiac index (mean (SD) 1.8 (0.2) to 2.6 (0.3) l/min/m(2), p < 0. 05) and a 32% decrease in pulmonary vascular resistance (19.7 (1.4) to 13.4 (1.3) units, p < 0.05), with a 4% reduction in mean pulmonary arterial pressure (62 (4) to 59 (4) mm Hg, NS). Adrenomedullin also decreased mean systemic arterial pressure (81 (3) to 72 (4) mm Hg, p < 0.05) and increased heart rate (73 (4) to 79 (4) beats/min, p < 0.05). Adrenomedullin decreased plasma aldosterone (9.8 (2.5) to 7.1 (1.5) ng/dl, p < 0.05) without significant changes in plasma renin activity. Plasma atrial and brain natriuretic peptides tended to decrease with adrenomedullin, although these changes did not reach significance. The haemodynamic and hormonal variables remained unchanged during placebo infusion.

CONCLUSIONS

Intravenous adrenomedullin has beneficial haemodynamic and hormonal effects in patients with precapillary pulmonary hypertension.

Gene transfer of human prostacyclin synthase ameliorates monocrotaline-induced pulmonary hypertension in rats

BACKGROUND

Prostacyclin is a potent vasodilator that also inhibits platelet adhesion and cell growth. We investigated whether in vivo gene transfer of human prostacyclin synthase (PGIS) ameliorates monocrotaline (MCT)-induced pulmonary hypertension in rats.

METHODS AND RESULTS

The cDNA encoding PGIS was intratracheally transfected into the lungs of rats by the hemagglutinating virus of Japan-liposome method. Rats transfected with control vector lacking the PGIS gene served as controls. Three weeks after MCT injection, mean pulmonary arterial pressure and total pulmonary resistance had increased significantly; the increases were significantly attenuated in PGIS gene-transfected rats compared with controls [mean pulmonary arterial pressure, 31+/-1 versus 35+/-1 mm Hg (-12%); total pulmonary resistance, 0.087+/-0.01 versus 0.113+/-0.01 mm Hg x mL x min(-1) x kg(-1) (-23%), both P:<0.05]. Systemic arterial pressure and heart rate were unaffected. Histologically, PGIS gene transfer inhibited the increase in medial wall thickness of peripheral pulmonary arteries that resulted from MCT injection. PGIS immunoreactivity was intense predominantly in the bronchial epithelium and alveolar cells. Lung tissue levels of 6-keto-PGF(1alpha), a stable metabolite of prostacyclin, were significantly increased for >/=1 week after transfer of PGIS gene. The Kaplan-Meier survival curves demonstrated that repeated transfer of PGIS gene every 2 weeks increased survival rate in MCT rats (log-rank test, P:<0.01).

CONCLUSIONS

Intratracheal transfer of the human PGIS gene augmented pulmonary prostacyclin synthesis, ameliorated MCT-induced pulmonary hypertension, and thereby improved survival in MCT rats.

Production and clearance sites of two molecular forms of adrenomedullin in human plasma

Human adrenomedullin (AM) precursor is converted to glycine-extended AM (AM-Gly), an inactive intermediate form of AM. Subsequently, AM-Gly is converted to active mature AM (AM-m) by enzymatic amidation. A recent study showed that two molecular forms of adrenomedullin (AM) are present in human plasma. In this study we investigated the production and clearance sites of two molecular forms of adrenomedullin in humans. We measured plasma levels of AM-m and AM-Total (T) (AM-m+AM-Gly) by immunoradiometric assay and calculated plasma levels of AM-Gly in blood samples taken from various sites during cardiac catheterization in patients with ischemic heart disease. Plasma AM-m levels were significantly lower in left-sided sites after passing through pulmonary circulation than in right-sided sites, whereas there were no significant differences in AM-Gly levels between left-sided sites and right-sided sites. These results suggest that AM-m produced in many organs is released into veins and that the main clearance sites of AM-m are the lungs. Considering that AM preferentially dilates pulmonary vessels rather than systemic vessels, a possible role of this peptide is suggested in the regulation of pulmonary vascular tonus.

Plasma brain natriuretic peptide as a prognostic indicator in patients with primary pulmonary hypertension

BACKGROUND

Plasma brain natriuretic peptide (BNP) level increases in proportion to the degree of right ventricular dysfunction in pulmonary hypertension. We sought to assess the prognostic significance of plasma BNP in patients with primary pulmonary hypertension (PPH).

METHODS AND RESULTS

Plasma BNP was measured in 60 patients with PPH at diagnostic catheterization, together with atrial natriuretic peptide, norepinephrine, and epinephrine. Measurements were repeated in 53 patients after a mean follow-up period of 3 months. Forty-nine of the patients received intravenous or oral prostacyclin. During a mean follow-up period of 24 months, 18 patients died of cardiopulmonary causes. According to multivariate analysis, baseline plasma BNP was an independent predictor of mortality. Patients with a supramedian level of baseline BNP (>/=150 pg/mL) had a significantly lower survival rate than those with an inframedian level, according to Kaplan-Meier survival curves (P<0.05). Plasma BNP in survivors decreased significantly during the follow-up (217+/-38 to 149+/-30 pg/mL, P<0. 05), whereas that in nonsurvivors increased (365+/-77 to 544+/-68 pg/mL, P<0.05). Thus, survival was strikingly worse for patients with a supramedian value of follow-up BNP (>/=180 pg/mL) than for those with an inframedian value (P<0.0001).

CONCLUSIONS

A high level of plasma BNP, and in particular, a further increase in plasma BNP during follow-up, may have a strong, independent association with increased mortality rates in patients with PPH.

Effects of cardiotrophin-1 on hemodynamics and endocrine function of the heart

Cardiotrophin-1 (CT-1), a member of the interleukin-6 superfamily of cytokines, possesses hypertrophic actions and atrial natriuretic peptide (ANP)-producing activity in vitro. The goal of our study is to elucidate whether CT-1 affects the cardiovascular system in vivo. Intravenous injection of CT-1 (4-100 microg/kg) in conscious rats evoked significant declines in blood pressure and reflex increases in heart rate (HR) in a dose-dependent manner. CT-1 induced no significant change in cardiac output (from 260.7 +/- 11.0 to 264.7 +/- 26.6 ml. min(-1). kg(-1), P = not significant), which was compatible with the results from isolated perfused rat hearts; HR, change in pressure over time, left ventricular developed pressure, and perfusion pressure were unaffected. Northern blot and RT-PCR analyses revealed that CT-1 increased expression of inducible nitric oxide synthase (iNOS) in lung and aorta but not in heart or liver. Pretreatment with aminoguanidine, a specific iNOS inhibitor, inhibited both iNOS mRNA production and the depressor effect of CT-1. Interestingly, CT-1 increased ventricular expression of ANP and brain natriuretic peptide (BNP). The data demonstrate that CT-1 elicits its hypotensive effect via a nitric oxide-dependent mechanism and that CT-1 induces ANP and BNP mRNA expression in vivo.

Preservation of the right atrial appendage improves reduced plasma atrial natriuretic peptide levels after the maze procedure

OBJECTIVES

The present study was conducted to determine whether preservation of the right atrial appendage lessens the decrease of plasma atrial natriuretic peptide levels after the maze procedure and whether the increase of plasma atrial natriuretic peptides improves the ability of the kidneys to excrete the fluid load after the operation.

METHODS

We evaluated 42 patients who underwent the maze procedure. The right atrial appendage was preserved in 22 patients but not in 20. Blood samples were obtained before and after the operation for measurement of atrial natriuretic peptides. To evaluate the influence of atrial natriuretic peptides on the ability of the kidneys, we also measured body weight, fluid balance, and the doses of furosemide and dopamine administered after the operation.

RESULTS

The restoration to sinus rhythm at 1 month after was comparable in the two groups. Plasma atrial natriuretic peptide levels significantly increased after the operation in patients in whom the right atrial appendage was preserved (1 day after: 23.4 +/- 17.8 vs 3 days after: 42.7 +/- 23.6 and 7 days after: 36.3 +/- 23.7 pg/mL, P <.05) but not in patients in whom the right atrial appendage was not preserved (1 day after: 20.0 +/- 19.6, 3 days after: 28.5 +/- 19.3, and 7 days after: 23.0 +/- 16.1 pg/mL). Furthermore, plasma atrial natriuretic peptide levels were significantly lower in patients in whom the right atrial appendage was not preserved than in patients in whom the right atrial appendage was preserved at 3 and 7 days after the operation. The fluid balance during the first 7 days of the postoperative period was comparable in the two groups, although the total dose of dopamine used in the same period was significantly smaller in patients in whom the right atrial appendage was preserved than in patients in whom the right atrial appendage was not preserved (155.3 +/- 119.0 vs 244.9 +/- 129.0 microg/kg, P <.05).

CONCLUSIONS

The present study showed that preservation of the right atrial appendage lessens the decrease of plasma atrial natriuretic peptide levels after the maze procedure and that increased plasma atrial natriuretic peptides may improve the ability of the kidneys to excrete the fluid load after the operation.

Cardiac adrenomedullin gene expression and peptide accumulation after acute myocardial infarction in rats

Plasma adrenomedullin (AM) has been shown to increase in the early phase of acute myocardial infarction (MI). However, little information is available regarding cardiac AM synthesis after MI. Accordingly, we examined the time course of ventricular AM production and potential stimulation of AM in the infarcted and noninfarcted regions in MI rats produced by coronary artery ligation. Compared with sham-operated rats, the ventricular AM peptide level 6 h after MI increased 1.5-fold in the infarcted region and 1.7-fold in the noninfarcted region in association with increased left ventricular end-diastolic pressure (EDP). Northern blot analysis also showed marked induction of AM gene expression in the infarcted region (11-fold) and the noninfarcted region (6-fold) 6 h after MI. The AM peptide level in the infarcted region reached its peak (2. 6-fold) 1 wk postinfarction and thereafter decreased to normal. In the noninfarcted region, however, the AM level remained elevated for at least 4 wk. Immunohistochemical studies demonstrated that intense immunostaining for AM was limited to myocytes in both the infarcted and noninfarcted regions. Interestingly, the AM level in the noninfarcted region correlated positively with infarct size (r = 0. 40, P < 0.01) and EDP (r = 0.52, P < 0.001). An oral angiotensin-converting enzyme inhibitor suppressed the overproduction of AM 1 wk postinfarction in association with decreases in EDP and mean arterial pressure. In summary, cardiac AM synthesis was rapidly induced in both the infarcted and noninfarcted regions after MI. The subsequent ventricular AM in the two regions demonstrated different time-concentration curves during 4 wk after MI. AM may be synthesized predominantly by cardiac myocytes, but not by fibroblasts, at least in part, in association with increased ventricular load after MI.

Force-length relationship in dogs as a measure of protective effect of imidapril on regional myocardial ischemia and reperfusion injury

Our laboratory previously reported that the end-systolic force-length relationship of the left ventricle provides a better method of evaluating myocardial contractile properties than the left ventricular end-systolic pressure-volume relationship, because it avoids deficiencies of the latter parameter such as dependence of its slope (E(max)) on the volume intercept (V(0)). The slope (E(c)) of the left ventricular end-systolic force-length relationship represents the contractility of functioning myocardium, while its length intercept (L(0)) reflects the length of non-functioning myocardium. However, the effect of regional myocardial ischemia on these parameters, as evaluated by the force-length relationship, remains unknown. To clarify the effects of regional ischemia and angiotensin-converting enzyme inhibition on the myocardium during ischemia-reperfusion, the changes in E(c) and L(0) were determined in anesthetized open-chest dogs. (1) Control group (n=26): Before and after 15 min of complete coronary artery occlusion, as well as after 15 min of reperfusion, left ventricular pressure and volume were simultaneously recorded during inferior vena cava occlusion. The left ventricular force-length relationship was obtained from the pressure and volume of three cylindrical segments of the ventricle, and E(c) and L(0) were calculated. (2) Imidapril group (n=14): Imidaprilat (1 microg/kg/min) was continuously infused from 30 min before ischemia to the end of the experiment, and the same procedures were followed as in the control group. Fourteen out of the 26 dogs (54%) in the control group died of reperfusion-induced ventricular arrhythmias, while only two of the 14 dogs (14%) in the imidapril group did so (P<0.05). In the control group, E(c) was increased during ischemia and remained at the same level after reperfusion. However, E(c) was not altered in the imidapril group. Although L(0) was increased during ischemia and decreased after reperfusion in both groups, the percent increase of L(0) in the imidapril group was significantly smaller than in the control group (8% vs. 32%, P<0.05). With the improvement of these indices, the bradykinin concentration of coronary venous blood increased in the imidapril group (P<0.01). These findings suggest that regional myocardial ischemia increased the average contractility of overall functioning myocardium despite the increased non-functioning myocardium. Moreover, imidapril has a cardioprotective effect against ischemia-reperfusion injury by decreasing infarct size, and through the antiarrhythmic effect and the reversal of increased overall contractility.

Hemodynamic, renal, and hormonal effects of adrenomedullin infusion in patients with congestive heart failure

BACKGROUND

Experimental studies have shown that adrenomedullin (AM) causes vasodilatation, diuresis, and a positive inotropic effect. In humans, however, whether infusion of AM has beneficial effects in congestive heart failure (CHF) remains unknown.

METHODS AND RESULTS

Hemodynamic, renal, and hormonal responses to intravenous infusion of human AM (0.05 microg. kg(-1). min(-1)) were examined in 7 patients with CHF and 7 normal healthy subjects (NL). In NL group, AM significantly decreased mean arterial pressure (-16 mm Hg, P<0. 05) and increased heart rate (+12 bpm, P<0.05). In CHF group, AM also decreased mean arterial pressure (-8 mm Hg, P<0.05) and increased heart rate (+5 bpm, P<0.05), but to a much lesser degree (P<0.05 versus NL). AM markedly increased cardiac index (CHF, +49%; NL, +39%, P<0.05) while decreasing pulmonary capillary wedge pressure (CHF, -4 mm Hg; NL, -2 mm Hg, P<0.05). AM significantly decreased mean pulmonary arterial pressure only in CHF (-4 mm Hg, P<0.05). AM increased urine volume (CHF, +48%; NL, +62%, P<0.05) and urinary sodium excretion (CHF, +42%; NL, +75%, P<0.05). Only in CHF, plasma aldosterone significantly decreased during (-28%, P<0.05) and after (-36%, P<0.05) AM infusion. These parameters remained unchanged in 7 patients with CHF and 6 healthy subjects who received placebo.

CONCLUSIONS

Intravenous infusion of AM has beneficial hemodynamic and renal effects in patients with CHF.

Ventricular adrenomedullin concentration is a sensitive biochemical marker for volume and pressure overload in rats

This study was designed to investigate the pathophysiological significance of adrenomedullin (AM) concentration in volume- and pressure-overloaded cardiac hypertrophy. We measured ventricular AM concentrations and compared them with changes of alpha-actin and myosin heavy chain (MHC) mRNA isoforms after the creation of an aortocaval (AC) shunt as a volume-overload model or the injection of monocrotaline (MCT) as a pressure-overload model, respectively. The left ventricular AM levels after the creation of AC shunt and the right ventricular AM levels after the injection of MCT were significantly increased and correlated with changes of the alpha-actin and MHC mRNA isoforms. However, the ventricular AM mRNA expressions were increased and correlated with ventricular AM concentrations only in the AC shunt model. These results suggest that the ventricular AM levels are upregulated in both the volume- and pressure-overloaded cardiac hypertrophy by differential transcriptional regulation and that the ventricular AM may be a biochemical marker for the volume and pressure overload to the ventricle.

Inhibitory regulation of hypertrophy by endogenous atrial natriuretic peptide in cultured cardiac myocytes

Atrial natriuretic peptide (ANP) may function as an endogenous regulator of cardiac hypertrophy, because the natriuretic peptide receptor has been found in the heart and because mice lacking its receptor have been shown to have a markedly elevated ventricular mass. We examined the role of endogenous ANP in cardiac hypertrophy in vitro. The effects of the blockade of endogenous ANP by its receptor antagonist, HS-142-1, on cell hypertrophy were investigated with the use of cultured neonatal rat ventricular myocytes. HS-142-1 increased the basal and phenylephrine (PE, 10(-5) mol/L)-stimulated protein syntheses in a concentration-dependent manner (1 to 300 microg/mL). A significant increase in the cell size of myocytes was also induced by this antagonist. In addition, the expression levels of skeletal alpha-actin, beta-myosin heavy chain, and ANP genes, markers of hypertrophy, were partially elevated by treatment with HS-142-1 (100 microg/mL) under nonstimulated or PE-stimulated conditions. A cGMP-specific phosphodiesterase inhibitor, zaprinast (5x10(-4) mol/L), and a cGMP analogue (10(-4) mol/L) suppressed the basal and PE-stimulated protein syntheses. Our observations suggest that endogenous ANP inhibits cardiac myocyte hypertrophy under basal and PE-stimulated conditions, probably through a cGMP-dependent process. ANP may play a role as an autocrine factor in the regulation of cardiac myocyte growth.

Effects of adrenomedullin on cultured rat cardiac myocytes and fibroblasts

The direct effects of adrenomedullin, a novel vasorelaxant peptide, on protein synthesis and atrial natriuretic peptide release in myocytes and on DNA and collagen syntheses in fibroblasts were examined using cultured ventricular cardiocytes. The protein synthesis of cardiac myocytes was not affected by adrenomedullin under non-stimulated conditions. Endothelin-1-induced protein synthesis in myocytes was slightly but significantly elevated by adrenomedullin. Likewise, the secretion of atrial natriuretic peptide from myocytes stimulated by endothelin-1 was increased by adrenomedullin. In cardiac fibroblasts, adrenomedullin clearly inhibited DNA synthesis and collagen production in a dose-dependent manner under both basal and angiotensin II-stimulated conditions. DNA and collagen syntheses by cardiac fibroblasts were suppressed by both 8-bromo cAMP and forskolin. Furthermore, a cAMP-specific phosphodiesterase inhibitor decreased DNA and collagen syntheses in fibroblasts and enhanced the inhibitory effects of adrenomedullin on these syntheses. Our observations suggest that adrenomedullin has opposite effects on cultured cardiac myocytes and fibroblasts and that the effects of adrenomedullin at least on fibroblasts are probably mediated through a cAMP-dependent pathway. As adrenomedullin is produced and secreted from both types of cardiac cells, adrenomedullin may play a role as an autocrine/paracrine modulator in the process of cardiac remodeling, mainly by suppressing mitogenesis and collagen synthesis in fibroblasts.

Adrenomedullin and atrial natriuretic peptide concentrations in normal pregnancy and pre-eclampsia

Adrenomedullin (AM) is a peptide that elicits a long-lasting vasorelaxant activity, while atrial natriuretic peptide (ANP) has also been shown to be a potent vasodilatory agent. To clarify the possible role of AM and ANP in the physiology of pregnancy and pathophysiology of pre-eclampsia, we measured plasma concentrations of these peptides in non-pregnant women, normal pregnant women and women with pre-eclampsia. A gradual increase in plasma AM was observed as pregnancy progressed. The plasma AM concentrations during the second trimester (12.7 +/- 1.4 fmol/ml) were significantly elevated, in comparison with the non-pregnant follicular phase (6.4 +/- 0.61 fmol/ml), luteal phase (6.0 +/- 0.49 fmol/ml), and the first trimester (6.5 +/- 0.8 fmol/ml). The plasma AM concentrations of the third trimester (21.5 +/- 1.4 fmol/ml) were significantly elevated when compared with those of the second trimester (P < 0.05). Northern blot analysis confirmed the expression of the AM mRNA transcript (1.6 kb) in third trimester placentas. In comparison with those observed at term (25.3 +/- 4.5 fmol/ml), the plasma concentrations were significantly reduced post-partum (6.4 +/- 0.6 fmol/ml). In the third trimester, plasma AM concentrations did not differ significantly between women with pre-eclampsia (17.2 +/- 2.3 fmol/ml) and normal pregnant women. In contrast, the plasma ANP concentrations in pre-eclampsia (39.5 +/- 7. 1 pg/ml) were significantly elevated when compared with those of the normal third trimester (14.4 +/- 1.4 pg/ml) (P < 0.05). ANP concentrations were reasonably constant throughout the pregnancy.

Elevated plasma levels of adrenomedullin in congenital cyanotic heart disease

Adrenomedullin is a novel hypotensive peptide originally isolated from human pheochromocytoma. Accumulating evidence suggests the possible involvement of adrenomedullin in the physiology of the pulmonary circulation and the pathophysiology of hypoxaemia. The aim of the present study was to investigate the pathophysiological significance of adrenomedullin in hypoxaemia caused by congenital cyanotic heart disease. Subjects were 16 patients with congenital cyanotic heart disease aged 0.8-10 years (Group C) and 12 age-matched control subjects (patients with coronary artery dilatation after Kawasaki disease; Group N). Plasma adrenomedullin concentrations were measured, using radioimmunoassay, in femoral venous, pulmonary arterial and pulmonary venous blood obtained during cardiac catheterization. Plasma adrenomedullin concentrations in Group C were significantly (3-fold) higher than those in Group N at all sampling sites. In Group C, plasma adrenomedullin concentrations in pulmonary venous blood were significantly lower than those in pulmonary arterial blood. Pulmonary uptake of adrenomedullin in Group C was significantly greater than that in Group N. Patients with congenital cyanotic heart disease showed elevated plasma adrenomedullin concentrations and an increased uptake of adrenomedullin in the pulmonary circulation, which may act to dilate pulmonary vessels and increase pulmonary blood flow to alleviate hypoxaemia. Intrinsically increased adrenomedullin levels may function as a compensatory mechanism for hypoxaemia in congenital cyanotic heart disease.

Effects of long-term treatment with pimobendan on neurohumoral factors in patients with non-ischemic chronic moderate heart failure

To evaluate the effects of the addition of pimobendan to an optimal basic regimen on plasma levels of neurohumoral factors in patients with non-ischemic, moderate heart failure during 2-year follow-up. This prospective, observational study involved 16 patients with non-ischemic, moderate heart failure [New York Heart Association (NYHA) functional class IIM-III] receiving an optimal basic regimen of digitalis, diuretics and angiotensin-converting enzyme inhibitor. Eight patients (Group P) were also administered pimobendan at a dose of 2.5 or 5 mg daily, while the other 8 served as controls (Group C). After 3 months of pimobendan administration, the plasma levels of norepinephrine and atrial natriuretic peptide and brain natriuretic peptide decreased and left ventricular ejection fraction improved. After 1 year, the cardiac symptoms, assessed using the Specific Activity Scale as well as the NYHA functional class, improved and the left ventricular end-diastolic diameter decreased. These improvements in Group P were maintained for 2 years. However, in Group C, the cardiac symptoms and the neurohumoral factor levels remained unchanged or deteriorated during this study, and one patient died of heart failure. Long-term combination therapy with the optimal basic regimen and pimobendan has potentially beneficial effects on neurohumoral factor levels and cardiac symptoms in patients with non-ischemic, chronic moderate heart failure.

Ventricular adrenomedullin levels correlate with the extent of cardiac hypertrophy in rats

We investigated the pathophysiological significance of adrenomedullin (AM) in the development of left ventricular hypertrophy (LVH). LVH was produced by aortic banding (AB) in rats. The left ventricular weight/body weight (LV/BW) ratio, ventricular AM peptide and mRNA levels, and hemodynamics were measured at 1, 3, 7, and 21 days after the operation. Both LV/BW ratio and ventricular AM levels showed a significant increase from 1 day after the operation in the AB rats versus the sham-operated rats. Both increased in a time-dependent manner. The ventricular AM levels correlated with the LV/BW ratio (r=0.76, P<0.01). The AM mRNA levels were highly expressed at 1 day after the operation in the AB rats but showed no difference from 3 to 21 days after the operation between the AB and sham groups. The plasma AM levels showed a peak at 1 day after the operation in both groups. Then, we treated AB rats with an angiotensin-converting enzyme inhibitor (quinapril) in 2 doses (1 and 10 mg. kg-1. d-1) for 21 days. The quinapril treatment attenuated similarly both the LV/BW ratio and the ventricular AM levels. We also assessed the effects of AM and hydralazine administration for 7 days on the LV/BW ratio and hemodynamics of AB rats. Both AM and hydralazine administration reduced the blood pressure by approximately 10% compared with the nontreated AB rats, but a reduction of the LV/BW ratio was observed only in the AM-treated group (P<0.05). These results suggest that ventricular AM levels are elevated by chronic pressure overload in a time-dependent manner concomitant with the extent of LVH and that AM may play a pathophysiological role in the development of LVH in chronic pressure overload.

Plasma adrenomedullin as an indicator of prognosis after acute myocardial infarction

OBJECTIVE

To elucidate whether prognosis after acute myocardial infarction can be predicted by measuring plasma adrenomedullin, a novel vasorelaxant peptide.

PATIENTS AND DESIGN

Plasma adrenomedullin concentrations on day 2 after myocardial infarction were measured in 113 patients with myocardial infarction with other clinical and haemodynamic variables related to mortality.

RESULTS

During a mean follow up period of 25 months, 16 patients died of cardiac causes. Plasma adrenomedullin concentrations on day 2 increased significantly in patients with myocardial infarction compared with controls (mean (SD), 12.3 (8.8) v 4.9 (1.0) pmol/l, p < 0.001). Plasma adrenomedullin correlated negatively with left ventricular ejection fraction on admission (r = -0.47, p < 0.001), although it did not significantly correlate with any other haemodynamic variable. By univariate Cox proportional hazards analysis, plasma adrenomedullin, age, coronary reperfusion, maximum creatine kinase concentrations, pulmonary congestion, pulmonary capillary wedge pressure, cardiac index, and left ventricular ejection fraction were all significantly related to mortality. Among the non-invasive variables, only plasma adrenomedullin was an independent predictor of mortality after myocardial infarction (p < 0.05). The Kaplan-Meier survival curves based on the median plasma adrenomedullin concentration (10.3 pmol/l) showed that patients with high plasma adrenomedullin had a higher mortality than those with low plasma adrenomedullin (p < 0.01).

CONCLUSIONS

Plasma adrenomedullin on day 2 after myocardial infarction is strongly associated with long term mortality, and thus may complement standard prognostic indicators.

Differential roles of endothelin-1 in the development of secondary pulmonary hypertension in patients with left heart failure with or without acute exacerbation

BACKGROUND

The aim of this study was to investigate the contribution of endothelin-1 (ET-1) to the development of secondary pulmonary hypertension (PH) in patients with left heart failure (HF).

METHODS AND RESULTS

The subjects were 40 patients with left HF with (group 1; n = 20) and without (group 2; n = 20) acute exacerbation. Before treatment, the ET-1 level in the pulmonary capillary wedge region was three times greater in patients of group 2 than group 1, although there was no significant difference in mean pulmonary artery pressure (mPAP) or pulmonary vascular resistance index (PVRI) between the two groups. Also, the ET-1 level significantly correlated with mPAP and PVRI for both groups, but with different slopes of the regression lines. After treatment of group 1, the extent of reduction in the ET-1 level significantly correlated with that in mPAP and in PVRI, whereas the ET-1 level itself correlated with mPAP, with the regression lines approximating those of group 2.

CONCLUSIONS

Our findings suggest that ET-1 may have differential roles in the development of secondary PH in patients with left HF with or without acute exacerbation.