Olli Vuolteenaho

Circulating and cardiac levels of apelin, the novel ligand of the orphan receptor APJ, in patients with heart failure.

The orphan receptor APJ and its recently identified endogenous ligand, apelin, are expressed in the heart. However, their importance in the human cardiovascular system is not known. This study shows that apelin-like immunoreactivity is abundantly present in healthy human heart and plasma. Gel filtration HPLC analysis revealed that atrial and plasma levels of high molecular weight apelin, possibly proapelin, were markedly higher than those of mature apelin-36 itself. As assessed by quantitative RT-PCR analysis, left ventricular apelin mRNA levels were increased 4.7-fold in chronic heart failure (CHF) due to coronary heart disease (p<0.01) and 3.3-fold due to idiopathic dilated cardiomyopathy (p<0.05), whereas atrial apelin mRNA levels were unchanged. Atrial and plasma apelin-like immunoreactivity as well as atrial and ventricular APJ receptor mRNA levels were significantly decreased in CHF. Our results suggest that a new cardiac regulatory peptide, apelin, and APJ receptor may contribute to the pathophysiology of human CHF.

Atrial natriuretic polypeptides (ANP): Rat atria store high molecular weight precursor but secrete processed peptides of 25–35 amino acids

A radioimmunoassay was developed for rat atrial natriuretic polypeptides. Using the radioimmunoassay and gel filtration in reducing and dissociating conditions, extracts of rat atria were found to contain mainly a 15000-dalton immunoreactive material, probably corresponding to pronatriodilatin. However, when isolated beating atria were incubated in plasma-free conditions, the secreted immunoreactive material consisted almost exclusively of 2500-3500-dalton peptide(s). These results show that rat atrial cells secrete a low molecular weight natriuretic peptide which is highly active, but store the less active large molecular weight form(s).

Hypoxia inducible factor regulates the cardiac expression and secretion of apelin

Apelin and its G‐protein‐coupled receptor APJ have various beneficial effects on cardiac function and blood pressure. The mechanisms that regulate apelin gene expression are not known. Because apelin gene expression has been shown to increase in cardiac ischemia, we investigated if apelin (Apln) gene expression was sensitive to hypoxia. Here we show that hypoxia increases the apelin expression in rat myocardium and in cultured cardiomyocytes. Pharmacological activation of hypoxia inducible factor by desferrioxamine (DFO) or expression of a constitu‐tively active form of HIF‐1α increased apelin expression in cardiomyocyte cultures. The induction of apelin by hypoxia was abolished on transient expression of the HIF inhibitory PAS protein in cardiomyocytes. Increased apelin expression induced by hypoxia or DFO was accompanied by the processing of the cellular storage form proapelin into smaller apelin peptides and increased secretion of these biologically active forms of apelin. In a rat in vivo model, acute myocardial infarction (24 h) led to a transient increase in ventricular apelin mRNA levels. Our results indicate that apelin gene is regulated by hypoxia in cardiac myocytes via the HIF pathway, suggesting a role for apelin as a potential marker for acute cardiac hypoxia with a possible compensatory role in myocardial tissue suffering from oxygen deprivation.—Ronkainen V.‐P., Ronkainen, J. J., Hanninen, S. L., Leskinen, H., Ruas, J. L., Pereira, T., Poellinger, L., Vuolteenaho, O., Tavi P. Hypoxia inducible factor regulates the cardiac expression and secretion of apelin. FASEB J. 21, 1821–1830 (2007)

Natriuretic Peptides and Mortality After Stroke

Background and Purpose— Measurement of natriuretic peptides provides prognostic information in various patient populations. The prognostic value of natriuretic peptides among patients with acute stroke is not known, although elevated peptide levels have been observed. Methods— A series of 51 patients (mean age, 68±11years) with first-ever ischemic stroke underwent a comprehensive clinical examination and measurements of plasma atrial natriuretic peptides (N-ANP) and brain natriuretic peptides (N-BNP) in the acute phase of stroke. The patients were followed-up for 44±21 months. Risk factors for all-cause mortality were assessed. Control populations, matched for gender and age, consisted of 51 patients with acute myocardial infarction (AMI) and 25 healthy subjects. Results— Plasma concentrations of N-ANP (mean±SD, 988±993 pmol/L) and N-BNP (751±1608 pmol/L) in the stroke patients were at the same level as those in the AMI patients (NS for both), but significantly higher than those of the healthy subjects (358±103 pmol/L, P<0.001 and 54±26 pmol/L, P<0.01, respectively). Elevated levels of N-ANP and N-BNP predicted mortality after stroke (risk ratio [RR] 4.3, P<0.01 and RR 3.9, P<0.01, respectively) and after AMI (P<0.05), and remained independent predictors of death after stroke even after adjustment for age, diabetes, coronary artery disease, and medication (RR 3.9, P<0.05 and RR 3.7, P<0.05, respectively). Conclusion— Plasma levels of natriuretic peptides are elevated in the acute phase of stroke and predict poststroke mortality.

Ultrasonographic and Biochemical Markers of Human Fetal Cardiac Dysfunction in Placental Insufficiency

Background— Placental insufficiency may lead to fetal cardiovascular compromise. We sought to determine whether ultrasonographic parameters of fetal cardiovascular function correlate with umbilical arterial levels of biochemical markers of myocardial dysfunction and damage in placental insufficiency. Methods and Results— In 48 fetuses with placental insufficiency, umbilical artery blood was obtained at delivery for assessment of N-terminal peptide of proatrial natriuretic peptide (NT-proANP) and cardiac troponin-T (cTnT). Group 1 fetuses (n=12) had normal NT-proANP and cTnT serum concentrations. Group 2 fetuses (n=25) showed increased NT-proANP (>1145 pmol/L) and normal cTnT values. Group 3 fetuses (n=11) had increased NT-proANP and cTnT (>0.10 ng/mL) levels. The ultrasonographic parameters of fetal cardiovascular function were compared between the groups. Pulsatility indices for veins of the ductus venosus, left hepatic vein, and inferior vena cava correlated significantly with NT-proANP levels. In group...

Adrenomedullin gene expression in the rat heart is stimulated by acute pressure overload: blunted effect in experimental hypertension.

The levels of adrenomedullin (ADM), a newly discovered vasodilating and natriuretic peptide, are elevated in plasma and ventricular myocardium in human congestive heart failure suggesting that cardiac synthesis may contribute to the plasma concentrations of ADM. To examine the time course of induction and mechanisms regulating cardiac ADM gene expression, we determined the effect of acute and short-term cardiac overload on ventricular ADM mRNA and immunoreactive ADM (ir-ADM) levels in conscious rats. Acute pressure overload was produced by infusion of arginine8-vasopressin (AVP, 0.05μ g/kg/min,iv) for 2 h into 12-week-old hypertensive TGR(mREN-2)27 rats and normotensive Sprague-Dawley (SD) rats. Hypertension and marked left ventricular hypertrophy were associated with 2.2-times higher ir-ADM levels in the left ventricular epicardial layer (178 ± 36 vs. 81 ± 23 fmol/g, P < 0.05) and 2.6-times higher ir-ADM levels in the left ventricular endocardial layer (213 ± 23 vs. 83 ± 22 fmol/g, P < 0.01). The infusio...Somatostatin (SRIF) acts on specific membrane receptors to inhibit exocrine and endocrine pancreatic functions. Five SRIF receptor genes have been cloned, producing six receptor proteins (sst-s). We used a recently developed antibody to localize the sst2A splice variant in the rat pancreas. Western blots identified the sst2A receptor as an 90 kDa glycosylated protein in pancreatic tissue. In tyramide-amplified immunostainings all acinar cells, and the glucagon and pancreatic polypeptide immunoreactive cells (A and PP, respectively) were intensely labeled for sst2A, while no signal was detected in SRIF producing (D) cells. A very few insulin immunoreactive (B) cells were also labeled for sst2A, but the signal in these cells was lower than in exocrine, A or PP cells. Absorption of the sst2A antibody with the receptor peptide abolished specific staining in both immunoblots and tissue sections (negative control). These studies are the first to localize any SRIF receptor subtype in the rat pancreas. The specific localization of sst2A receptor in acinar, A and PP cells if confirmed in humans, would suggest that subtype specific analogs will be useful for the therapeutic regulation of exocrine and/or endocrine pancreatic secretion.

Natriuretic peptides as markers of cardiotoxicity during doxorubicin treatment for non-Hodgkin's lymphoma

Abstract:  Thirty adult patients with non‐Hodgkins lymphoma who were planned to receive up to 8–10 cycles of CHOP (cyclophosphamide, doxorubicin, vincristine and prednisolone) to a cumulative doxorubicin dose of 400–500 mg/m2 were studied to evaluate the value of serial plasma atrial natriuretic peptide (ANP), N‐terminal pro‐ANP (NT‐proANP) and brain natriuretic peptide (BNP) measurements in the early detection of doxorubicin‐induced left ventricular dysfunction. Plasma levels of natriuretic peptides were measured before every treatment course and 4 wk after the last one. Cardiac function was monitored with serial radionuclide ventriculography. Twenty‐eight patients were evaluable for cardiotoxicity. Clinical heart failure developed in 2 patients (7%). Left ventricular ejection fraction (LVEF) decreased from 58.0 ± 1.3% to 49.6 ± 1.7% (p<0.001). Plasma levels of ANP increased from 16.4 ± 1.3 pmol/l to 22.7 ± 2.4 pmol/l (p = 0.002), NT‐proANP from 288 ± 22 to 380 ± 42 pmol/l (p = 0.019) and BNP from 3.3 ±0.4 to 8.5 ± 2.0 pmol/l (p =0.020). There was a significant correlation between the increase in plasma ANP and the decrease in LVEF (r = ‐0.447, p = 0.029), and a trend towards significance between the increase in NT‐proANP and the decrease in LVEF (r=‐0.390, p = 0.059). The decrease in LVEF started very early and could already be seen after the cumulative doxorubicin dose of 200 mg/m2, whereas the increase in plasma natriuretic peptides was not evident until the cumulative doxorubicin dose of 400 mg/m2. Our results show that neuroendocrine activation — increased concentrations of plasma natriuretic peptides — occurs when left ventricular function has reduced substantially and its compensatory capacity has been exceeded resulting in atrial and ventricular overload. Thus, serial natriuretic peptide measurements cannot be used in predicting the impairment of left ventricular function. On the other hand, our study suggests that natriuretic peptides are useful in the detection of subclinical left ventricular dysfunction in patients receiving doxorubicin therapy.

Gene Structure of a New Cardiac Peptide Hormone: A Model for Heart-Specific Gene Expression1

Volume excess and mechanical load lead to the induction of the endocrine activity of the heart. The increased production and secretion of A- and B-type natriuretic peptides (ANP and BNP), in turn, unload the heart due to their physiological effects. To find out the mechanisms of cardiac-specific expression and sensitivity to mechanical stimuli of the natriuretic peptide genes, we have used salmon (Salmo salar) as our model organism, because osmoregulating fish have a particularly well developed defense mechanism against volume excess. We have previously cloned a complementary DNA from salmon heart encoding a novel vasorelaxant cardiac hormone, salmon cardiac peptide (sCP). Its production is restricted to the heart, and its release is very sensitive to mechanical load. We have now cloned the gene encoding sCP. The structure of the gene suggests that sCP may represent an ancestral form of the mammalian natriuretic peptides. Remarkably, despite the large phylogenetic distance, the sCP promoter is as effective as mammalian ANP promoters in cultured neonatal rat atrial cardiomyocytes. Therefore, structural and functional comparisons of the promoters of sCP and ANP provide an excellent means of identifying the elements and transcription factors required for atrial-specific gene expression and the regulation of the endocrine function of the heart. Isolation of the protein product of sCP gene from salmon atrium demonstrated that the storage form of sCP is the prohormone of 126 amino acids. The final processing of the prohormone appears to take place during exocytosis of the secretory granules, as the released and circulating form is the biologically active 29-amino acid sCP.

Natriuretic peptides during the development of doxorubicin-induced left ventricular diastolic dysfunction

Abstract. Nousiainen T, Vanninen E, Jantunen E, Puustinen J, Remes J, Rantala A, Vuolteenaho O, Hartikainen J (Kuopio University Hospital, Kuopio; Satakunta Central Hospital, Pori; University of Oulu, Oulu, Finland). Natriuretic peptides during the development of doxorubicin‐induced left ventricular diastolic dysfunction. J Intern Med 2002; 251: 228–234.

Endothelin-1 Is Involved in Stretch-Induced Early Activation of B-Type Natriuretic Peptide Gene Expression in Atrial but Not in Ventricular Myocytes Acute Effects of Mixed ETA/ETB and AT1 Receptor Antagonists In Vivo and In Vitro

BACKGROUND The precise role of paracrine and autocrine factors in mechanical load-induced activation of cardiac gene expression is unknown. Here we report the effects of endothelin-1 (ET-1) and angiotensin II (Ang II) receptor antagonism on acute pressure overload-induced activation of cardiac B-type natriuretic peptide (BNP) gene expression in spontaneously hypertensive rats (SHRs) in vivo and on mechanical stretch-induced increase in atrial BNP gene expression in vitro. METHODS AND RESULTS Acute pressure overload produced in conscious SHRs by infusion of arginine8-vasopressin (0.05 microg x kg(-1) x min(-1)) for 2 hours resulted in an increase in BNP mRNA levels in the left ventricle as well as in the atrium. Bolus injections of bosentan (mixed ET(A)/ET(B) receptor antagonist, 10 mg/kg I.V.) but not losartan (AT1 receptor antagonist, 10 mg/kg I.V.) blocked the increase of the BNP mRNA levels produced by pressure overload in the left atria, whereas the elevation of BNP mRNA levels was similar (a 1.9-fold increase) in the left ventricles of vehicle-, losartan-, and bosentan-infused SHRs. In an isolated perfused rat heart preparation, infusion of bosentan (1 micromol/L) for 2 hours inhibited the mechanical stretch-induced increase in BNP mRNA levels in the right atria, whereas an AT1 receptor antagonist, CV-11974 (10 nmol/L), had no effect. CONCLUSIONS The findings of the present study demonstrate that Ang II and ET-1 are not obligatorily required for stretch to trigger the increased BNP gene expression in ventricular myocytes in vivo. In contrast, mechanical load on the atrial myocytes did initiate an ET-1-dependent expression of BNP gene showing that endogenous ET-1 production differentially regulates BNP gene expression in atrial and ventricular myocytes.