BNP Gene Expression Research Articles

Cardiac Natriuretic Peptide Profiles in Chronic Hypertension by Single or Sequentially Combined Renovascular and DOCA-Salt Treatments.

The involvement of natriuretic peptides was studied during the hypertrophic remodeling transition mediated by sequential exposure to chronic hemodynamic overload. We induced hypertension in rats by pressure (renovascular) or volume overload (DOCA-salt) during 6 and 12 weeks of treatment. We also studied the consecutive combination of both models in inverse sequences: RV 6 weeks/DS 6 weeks and DS 6 weeks/RV 6 weeks. All treated groups developed hypertension. Cardiac hypertrophy and left ventricular ANP gene expression were more pronounced in single DS than in single RV groups. BNP gene expression was positively correlated with left ventricular hypertrophy only in RV groups, while ANP gene expression was positively correlated with left ventricular hypertrophy only in DS groups. Combined models exhibited intermediate values between those of single groups at 6 and 12 weeks. The latter stimulus associated to the second applied overload is less effective than the former to trigger cardiac hypertrophy and to increase ANP and BNP gene expression. In addition, we suggest a correlation of ANP synthesis with volume overload and of BNP synthesis with pressure overload-induced hypertrophy after a prolonged treatment. Volume and pressure overload may be two mechanisms, among others, involved in the differential regulation of ANP and BNP gene expression in hypertrophied left ventricles. Plasma ANP levels reflect a response to plasma volume increase and volume overload, while circulating BNP levels seem to be regulated by cardiac BNP synthesis and ventricular hypertrophy.

63. AMELIORATION OF CARDIAC HYPERTROPHY BIOMARKERS BY DECAFFEINATED LIGHT ROASTED GREEN COFFEE EXTRACT IN METABOLIC SYNDROME RAT MODEL

Background: Metabolic syndrome is associated with increased prevalence of cardiac hypertrophy. The effect of coffee consumption on cardiovascular outcome is still controversial due to its caffeine content. Objective: This study aimed to investigate the effect of light roasted decaffeinated green coffee extract (GCE) on amelioration of cardiac hypertrophy biomarkers in metabolic syndrome rat model Methods: Twenty five metabolic syndrome rat model were divided into GCE 100, 200, 250 group, normal control (NC) and metabolic syndrome (MS) group. Rats in the GCE groups were treated once daily with green coffee extract at a dose of 100, 200, and 250 mg/bw.t respectively. The extract was given for 9 weeks through oral gavage. The metabolic syndrome parameters were measured every two weeks by colorimetric method. Blood pressure was determined by tail cuff blood pressure recorder. Angiotensin 2 level was analysed by ELISA method. Cardiac TNFα, IL6, NFKβ, RAC1 and BNP gene expression was analysed by RT-PCR methods. Results: The metabolic syndrome parameters were significantly in all GCE groups after administration of green coffee extract for 9 weeks. The lowest angiotensin 2 level were observed in GCE 250 group compared to that of MS and GCE 100 and 200 group. The cardiac TNFα, IL6, NFKβ, RAC1 and BNP gene expression were significantly lower in all GCE group (p < 0.000) compared to that of MS group. However, in GCE 100 group the expression of those genes was the lowest among all GCE groups. Conclusion: This study suggested that the administration of GCE 100 mg/bw.t ameliorated angiotensin 2 level and cardiac hypertrophy biomarker in metabolic syndrome rat model.

Musa balbisiana Fruit Rich in Polyphenols Attenuates Isoproterenol-Induced Cardiac Hypertrophy in Rats via Inhibition of Inflammation and Oxidative Stress.

Musa balbisiana Colla (Family: Musaceae), commonly known as banana and native to India and other parts of Asia, is very rich in nutritional value and has strong antioxidant potential. In the present study, we have developed Musa balbisiana (MB) fruit pulp powder and evaluated its cardioprotective effect in cardiac hypertrophy, which is often associated with inflammation and oxidative stress. An ultra-high-pressure liquid chromatography-mass spectrometer (UPLC-MS/MS) has been used for the detection and systematic characterization of the phenolic compounds present in Musa balbisiana fruit pulp. The cardioprotective effect of MB was evaluated in a rat model of isoproterenol- (ISO-) induced cardiac hypertrophy by subcutaneous administration of isoproterenol (5 mg/kg−1/day−1), delivered through an alzet minipump for 14 days. Oral administration of MB fruit pulp powder (200 mg/kg/day) significantly (p < 0.001) decreased heart weight/tail length ratio and cardiac hypertrophy markers like ANP, BNP, β-MHC, and collagen-1 gene expression. MB also attenuated ISO-induced cardiac inflammation and oxidative stress. The in vivo data were further confirmed in vitro in H9c2 cells where the antihypertrophic and anti-inflammatory effect of the aqueous extract of MB was observed in the presence of ISO and lipopolysaccharide (LPS), respectively. This study strongly suggests that supplementation of dried Musa balbisiana fruit powder can be useful for the prevention of cardiac hypertrophy via the inhibition of inflammation and oxidative stress.

Sex differences in the response to angiotensin II receptor blockade in a rat model of eccentric cardiac hypertrophy.

Background. Men and women differ in their susceptibility to cardiovascular disease, though the underlying mechanism has remained elusive. Heart disease symptoms, evolution and response to treatment are often sex-specific. This has been studied in animal models of hypertension or myocardial infarction in the past but has received less attention in the context of heart valve regurgitation. The aim of the study was to evaluate the development of cardiac hypertrophy (CH) in response to left ventricle (LV) volume overload (VO) caused by chronic aortic valve regurgitation (AR) in male and female rats treated or not with angiotensin II receptor blocker (ARB), valsartan. We studied eight groups of Wistar rats: male or female, AR or sham-operated (sham) and treated or not with valsartan (30 mg/kg/day) for 9 weeks starting one week before AR surgical induction.Results. As expected, VO from AR resulted for both male and female rats in significant LV dilation (39% vs. 40% end-diastolic LV diameter increase, respectively; p < 0.0001) and CH (53% vs. 64% heart weight increase, respectively; p < 0.0001) compared to sham. Sex differences were observed in LV wall thickening in response to VO. In untreated AR males, relative LV wall thickness (a ratio of wall thickness to end-diastolic diameter) was reduced compared to sham, whereas this ratio in females remained unchanged. ARB treatment did not prevent LV dilation in both male and female animals but reversed LV wall thickening in females. Systolic and diastolic functions in AR animals were altered similarly for both sexes. ARB treatment did not improve systolic function but helped normalizing diastolic parameters such as left atrial mass and E wave slope in female AR rats. Increased LV gene expression of Anp and Bnp was normalized by ARB treatment in AR females but not in males. Other hypertrophy gene markers (Fos, Trpc6, Klf15, Myh6 and Myh7) were not modulated by ARB treatment. The same was true for genes related to LV extracellular matrix remodeling (Col1a1, Col3a1, Fn1, Mmp2, Timp1 and Lox). In summary, ARB treatment of rats with severe AR blocked the female-specific hypertrophic response characterized by LV chamber wall thickening. LV dilation, on the other hand, was not significantly decreased by ARB treatment. This also indicates that activation of the angiotensin II receptor is probably more involved in the early steps of LV remodeling caused by AR in females than in males.

Abstract 523: Myocardial Hypertrophy and Fibrosis Regulated by Nogo-ROCK-norepinephrine Transporter Signaling Pathway in Spontaneously Hypertensive Rats

Objective: To investigate the regulation of Nogo/ROCK- norepinephrine transporter (NET) signaling pathway on myocardial hypertrophy and fibrosis in spontaneously hypertensive rats (SHR). Methods: Twenty male SHR rats aged 7-week-old were randomly divided into four groups: control group (n=5), NEP1-40 group (n=5), fasudil group (n=5) and fluoxetine group (n=5), and fed for 7 weeks. Left ventricular mass (LVW) was separated and weighed. Left ventricular mass index (LVMI) was calculated. Real-time quantitative PCR was used to detect the gene expression of myocardial hypertrophy and fibrosis and NET. Results: Compared with the control group, the left ventricular mass index (LVMI), the gene expression of ANP, BNP andβ-MHC were significantly increased in NEP1-40 group, and were significantly decreased in Fasudil group. Compared with the control group, the gene expression of CTGF, Collagen I and Collagen III increased significantly in NEP1-40 group, while decreased significantly in Fasudil group. Compared with the control group, the gene expression of norepinephrine transporter (NET) significantly increased in fasudil group. Compared with the control group, the gene expression of ANP, BNP, β-MHC, CTGF and Collagen I were significantly increased in fluoxetine group. Conclusion: Nogo/ROCK-NET signaling pathway is involved in the regulation of myocardial hypertrophy and fibrosis in spontaneously hypertensive rats.

Angiotensin‐(1‐7) Prevents Thyroid Hormone‐induced Cardiomyocyte Hypertrophy by FOXO3 Signaling Pathway

It is well‐known that high levels of thyroid hormone promote cardiomyocyte hypertrophy, which in part is mediated by activation of Renin‐Angiotensin System (RAS). Recent study of our group demonstrated that the contralateral RAS axis (ACE2/Angiotensin‐(1–7)/Mas receptor) is also involved in this cardiac hypertrophy model and that transgenic rats overexpressing circulating levels of Angiotensin‐(1‐7) (Ang‐(1‐7)) present an improvement of cardiac function and attenuation of cardiac hypertrophy. However, the molecular mechanisms involved in these Ang‐(1‐7) actions have not been fully elucidated. The aim of this study was to investigate if the anti‐hypertrophic effect of Ang‐(1‐7) also occurs in isolated cardiomyocytes, as well as the involvement of the Foxo3 signaling pathway for these effects. All experiments were approved by the Ethics Committee on Animal Experimentation of ICB‐USP (n030/12/CEUA). Primary cardiomyocytes cultures obtained from neonatal rats were treated with triiodothyronine (T3) (15nM) and/or Angiotensin‐(1‐7) (Ang‐(1‐7)) (100nM). All data were analyzed by ANOVA followed by Tukey's post hoc test, and values of P&lt;0.05 were considered statistically significant. The Ang‐(1‐7) treatment prevented the cardiomyocyte hypertrophy induced by T3, which was confirmed by reduction cell surface area, L‐[3,4,5‐3H] leucine incorporation and BNP gene expression. Combined treatment with the MAS receptor antagonist (A779, 100nM) impaired the anti‐hypertrophic effect of Ang‐(1‐7). Regarding molecular mechanisms, although Ang‐(1‐7) treatment did not impair the rapid activation of Akt promoted by T3, Ang‐(1‐7) treatment reduced the phosphorylation of Foxo3 (inactive form) and promoted the nuclear accumulation of Foxo3 in cardiomyocytes, indicating the activation of this protein. Collectively, these findings indicate an important cardioprotective effect of Ang‐(1‐7) in isolated cardiomycoytes treated with T3, occurring via MAS receptor and with possible participation of Foxo3.Support or Funding InformationFoundation for the Support of Research in the State of São Paulo (FAPESP) and National Council of Technological and Scientific Development (CNPq).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

PO-173 The Effects of Interval Exercise on oxidative stress and Smyd1-related myocardial hypertrophy in Rats with Myocardial Infarction

Objective This study was carried out to investigate interval exercise on Smyd1 expression and F-actin sarcomere assembly in non-infarcted myocardium of normal and myocardial infarction(MI) rats and its possible mechanism.&#x0D; Methods Male SD rats were randomly divided into normal control group (C), normal interval exercise group (CE), sham-operated group (S), MI group (MI), MI with interval exercise group (ME) and MI with ROS Tempol group (MT), n=10. MI model was established by left anterior descending coronary artery ligation. Interval exercise was carried out on a small animal treadmill. MT group was given an oral solution of Tempol (2mmol/L). Hemodynamics was performed to evaluate cardiac function. HE and Masson staining were used to analyze the cross-sectional area (CSA) of cardiomyocytes and collagen volume fraction, respectively. T-SOD and MDA kits were used to detect oxidative stress. H9C2 cells were treated with H2O2. Immunofluorescence staining was used to determine Smyd1 expression and F-actin sarcomere assembly. RT-qPCR and Western blotting were used to detect the gene or protein expression of Smyd1, Trx1, Hsp90, MuRF1, cTnI, α-actinin and BNP.&#x0D; Results Smyd1, Trx1, Hsp90, MuRF1 and BNP expression in the peri-infarcted area were up-regulated, but cTnI and α-actinin expression and F-actin assembly were decreased. The cardiac function was reduced. Both interval exercise and Tempol intervention significantly increase the CSA and expression of Smyd1, Trx1, cTnI and α-actinin, improve the antioxidation capacity and F-actin sarcomere assembly and cardiac function, reduce the expression of Hsp90, MuRF1, BNP and ROS level, and inhibit the fibrosis of myocardium. The oxidative stress level was closely related to the Smyd1 expression. Improvement of cardiac function were correlated with Smyd1 expression. H2O2 can induce oxidative stress injuries of H9C2, and its closely related to cardiomyocytes oxidative stress level and Smyd1 expression.&#x0D; Conclusions Interval exercise could promote antioxidant capability and physiological cardiomyocyte hypertrophy, regulate the expression of Smyd1, Hsp90 and MuRF1 in infarcted heart; so as to improve the cardiac function. Smyd1 may participate in pathologic hypertrophy of cardiomyocytes caused by oxidative stress.

Abstract 171: T Cell Mediated Immune Responses Regulate Cardiac Remodeling and Survival in Pressure Overload Induced Heart Failure

Background: Clinical data support that inflammation and the improper regulation of the immune response are intimately associated with Heart Failure (HF), however, the type of immune response involved and whether it regulates cardiac remodeling remains largely unexplored. We hypothesize that T cell mediated immune responses and their recruitment into the heart influence cardiac remodeling and contribute to the pathogenesis of pressure overload induced HF. Methods and Results: Using quantitative flow cytometry we found that T cells infiltrated the heart as Wild-type mice (WT) developed systolic dysfunction and LV hypertrophy in response to transverse aortic constriction (TAC) (p&lt;0.01 TAC vs Sham). Real time imaging demonstrated that T cells from TAC mice adhered to activated heart endothelial cells in higher numbers than T cells from Sham mice under physiological flow conditions in vitro (P&lt;0.05) indicating a systemic T cell activation to pressure overload induced by TAC. Similarly, circulating T cells from patients with HF adhered more to activated human umbilical vein endothelial cells (HUVEC) than T cells from healthy volunteers. Based on these findings, we performed similar TAC studies in T cell deficient mice (TCRα -/- ). In contrast with WT TAC mice, TCRα -/- had preserved LV systolic and diastolic function (p&lt;0.01) determined by echocardiography and hemodynamic studies, reduced LV fibrosis (p&lt;0.001) and TGFβ1, collagen Iα and αSMA gene expression (p&lt;0.05), and reduced LV hypertrophy and gene expression of ANP and BNP (p&lt;0.05), but unaltered expression of SerCA. Remarkably, TCRα -/- had improved survival after 4 weeks of TAC [100%(16/16) TCRα -/- vs 73.7%(14/19) WT, p=0.023]. Ongoing studies will determine the mechanisms regulating T cell recruitment into the heart, the type of T cell response involved and its contribution to pathological remodeling of the heart. Conclusion: Our studies demonstrate that T cell immune responses and their recruitment into the LV contribute to the pathogenesis of pressure overload induced HF by mechanisms involving T cell regulation of cardiac hypertrophy and fibrosis, and open a window to develop novel therapeutic strategies to improve the structural, functional and molecular deficits of the failing heart.

Antihypertrophic effects of combined inhibition of the renin–angiotensin system (RAS) and neutral endopeptidase (NEP) in progressive, tachycardia-induced experimental heart failure

Vasopeptidase inhibition (VPI), a therapeutic strategy by dual inhibition of both ACE and neutral endopeptidase 24.11, has not shown a prognostic benefit over ACE inhibition in chronic severe heart failure (CHF). Nevertheless, the effects of early treatment by VPI on cardiac remodelling have not been well assessed. We analysed the effects of early chronic VPI (50mg/kg/day Omapatrilat) on cardiac remodelling and neurohumoral function during the progression of rapid ventricular pacing-induced heart failure in rabbits (early left ventricular dysfunction [ELVD]: 10days at 330bpm, CHF: further 10days at 360bpm). VPI-treated animals (ELVD-VPI n = 6; CHF-VPI n = 8) and placebo treated animals (ELVD n = 6; CHF n = 7) were compared with control rabbits (CTRL n = 5). LV fractional shortening (FS) and enddiastolic diameter (LVEDD) were assessed by echocardiography (12MHz probe). LV BNP- and LV IL-6 gene expression was analysed quantitatively by real time PCR. Neurohumoral function was assessed by ANP, cGMP, plasma renin activity (PRA) and Aldosterone. In ELVD, LVEDD and atrial mass were significantly increased (both p < 0.05). This increase was markedly attenuated by VPI (both p < 0.05 vs. placebo). CHF was associated with a further increase in atrial mass and an increase in LV mass (both p < 0.05), which was again attenuated by VPI (atrial mass, p < 0.05 vs. untreated). LV BNP mRNA was significantly increased in CHF (p < 0.05 vs. control), and chronic VPI completely abolished this increase in ELVD and significantly attenuated it in CHF (p < 0.05 vs. CHF-placebo). Beyond that, the increase of cGMP was augmented by chronic VPI (p < 0.05 vs. placebo in CHF) in heart failure and that of Aldosterone was attenuated (p < 0.05 vs. placebo in ELVD), whereas PRA was temporarily increased (p < 0.05 vs. placebo in ELVD). Combined inhibition of ACE and NEP by VPI significantly inhibits early cardiac remodelling and LV BNP gene expression. If initiated early enough, it may slow down cardiac remodelling and represents a promising therapeutic strategy in progressive heart failure.

Proteomic Profiling Implies Mitochondrial Dysfunction in Tachycardia-Induced Heart Failure

Background/ObjectivesMolecular mechanisms of congestive heart failure as reflected by alterations of protein expression patterns are still incompletely analyzed. We therefore investigated intraventricular (ie, left ventricular congestive heart failure [LV-CHF] vs. LV-control [CTRL], and right ventricular [RV]-CHF vs. RV-CTRL) and interventricular (ie, LV-CHF vs. RV-CHF, and LV-CTRL vs. RV-CTRL) protein expression differences in an animal model. MethodsThe model of rapid ventricular pacing in rabbits was combined with a proteomic approach using 2-dimensional gel electrophoresis. Identification of proteins was done by matrix-assisted laser desorption/ionization-tandem mass spectrometry (MALDI-MS/MS). ResultsRapid ventricular pacing-induced heart failure was characterized by LV dilatation, dysfunction, and hypotension as well as by increased BNP gene expression. By comparing LV-CHF vs. LV-CTRL, proteins were found to be underexpressed at 3 crucial points of cellular energy metabolism. In RV-CHF vs. RV-CTRL, proteins belonging to respiratory chain complexes were underexpressed, but additionally a disturbance in the nitric oxide–generating enzymatic apparatus was seen. Regarding the interventricular analyses, a stronger expression of energetic pathways was accompanied by an underexpression of contractile and stress response proteins in failing left vs. right ventricles. Finally, significant protein expression differences were found in LV-CTRL vs. RV-CTRL reflecting a higher expression of contractile, stress response, and respiratory chain proteins in LV tissue. ConclusionsIn tachycardia-induced heart failure, significant inter- and intraventricular protein expression patterns were found with a predominance of proteins, which are involved in cellular energy metabolism.

Uncoordinated regulation of atrial natriuretic factor and brain natriuretic peptide in lipopolysaccharide-treated Rats

We investigated the expression and secretion of the natriuretic peptides (NPs) ANF and BNP in lipopolysaccharide (LPS)-induced sepsis and its association with cytokines and other biologically active substances. LPS treatment increased plasma levels of ANF and BNP. The latter increase was larger than the increase in plasma ANF. LPS also increased cardiac content and gene expression of BNP but not of ANF. LPS treatment significantly increased gene expression cytokines, chemokines and proteases, which significantly correlated with BNP gene expression. SB203580, a p38 MAP kinase inhibitor, inhibited the elevation of BNP in plasma. The present work suggests that during inflammation, BNP gene expression and secretion is uniquely related to changes in gene expression in the absence of hemodynamic changes and hence differentiates ANF and BNP as biomarkers of cardiac disease.

Dipeptidyl peptidase IV inhibition improves cardiorenal function in overpacing‐induced heart failure

Recent studies indicate that brain natriuretic peptide (BNP(1-32)) may be truncated into BNP(3-32) by dipeptidyl peptidase IV (DPP4) and that BNP(3-32) has reduced biological activities compared with BNP(1-32). We investigated if DPP4 contributes to the cardiorenal alterations and to the attenuated response to BNP seen in heart failure. Haemodynamic and renal assessment was performed in 12 pigs at baseline, 4 weeks after pacing-induced heart failure, and during BNP infusion. They were randomized to either placebo or treatment with a DPP4 inhibitor, sitagliptin. After 4 weeks of pacing, heart rate was reduced compared with baseline in the sitagliptin group (60 ± 2 vs. 95 ± 16 b.p.m., P < 0.01), and an increase in stroke volume was observed in the sitagliptin group compared with placebo (+24 ± 6% vs. -17 ± 7%, P < 0.01). Glomerular filtration rate declined at week 4 compared with baseline in the placebo group (1.3 ± 0.4 vs. 2.3 ± 0.3 mL/kg/min, P < 0.01) but remained preserved in the sitagliptin group [1.8 ± 0.2 vs. 2.0 ± 0.3 mL/kg/min, P = NS (non-significant)]. In the sitagliptin group, BNP infusion improved end-systolic elastance (68 ± 5 vs. 31 ± 4 mmHg/kg/mL, P < 0.05), ventricular-arterial coupling, and mechanical efficiency. Compared with controls (n = 6), myocardial gene expression of BNP, interleukin-6, Na(+)-Ca(2+) exchanger, and calmodulin was up-regulated in the placebo group, but not in the sitagliptin group. In pacing-induced heart failure, DPP4 inhibition preserves the glomerular filtration rate, modulates stroke volume and heart rate, and potentiates the positive inotropic effect of exogenous BNP at no energy expense.

Abstract P143: Activation of GPR30 Attenuates Diastolic Dysfunction and LV Remodeling in Oophorectomized mRen2.Lewis Rats

The incidence of diastolic dysfunction increases in women after menopause but the mechanisms involved are not completely understood. GPR30 is a novel estrogen receptor expressed in various tissues including the heart. Studies have shown that activation of GPR30 by its agonist G1, improves contractile function and reduces infarct size in isolated rat and mouse hearts subjected to ischemia/reperfusion injury and attenuates diastolic dysfunction in a salt-sensitive rat model of hypertension. We hypothesized that the activation of GPR30 by G1 protects against the development of diastolic dysfunction and cardiac hypertrophy in oophorectomized mRen2.Lewis rats, an established model that emulates the cardiac phenotype of the postmenopausal woman. Surgical bilateral oophorectomy (OVX) was performed in female mRen2.Lewis rats at 4 weeks of age, and G1 (50 or 100 µg/kg/day) was given subcutaneously via minipump starting at 13 weeks of age for 2 weeks. Both doses of G1 significantly improved lusitropic function and structure, independent of changes in blood pressure. Compared to vehicle-treated OVX rats, G1 reduced the tissue Doppler-derived index of left ventricular filling pressure (E/e’), left ventricle mass, wall thickness, and the biomarkers of hypertrophy, ANF and BNP mRNA levels. Using cultured H9c2 cardiomyocytes, in vitro studies further showed that 1) G1 inhibited angiotensin (ANG) II-induced hypertrophy, evidenced by reductions in cell size, and ANF and BNP gene expression; 2) the antagonist of GPR30, G15, inhibited estrogen’s protective effects on ANG II-induced hypertrophy; and 3) G1 induced phosphorylation of Erk and Akt. These data demonstrate the protective role of GPR30 in a model of diastolic dysfunction and cardiac hypertrophy, and provide insight into the underlying mechanisms.

Sequencing and cardiac expression of natriuretic peptide receptors A and C in normal and heart failure pigs

Pharmacological treatments able to activate natriuretic receptors (NPRs) and inhibit cardiac remodelling in heart failure (HF) patients, are currently under investigation. To better understand the therapeutic potential of the NPRs activation is necessary to dispose of experimental models devoid of confounding effects. The pig constitutes an animal model largely used but its genome is not completely sequenced. Aims of this study were to sequence NPR-A and NPR-C in Sus scrofa and to evaluate ANP, BNP and NPRs mRNA expression in cardiac tissue of normal and HF minipigs in order to have a starting point for future studies devoted to check new potential drugs. Cardiac tissue was collected from adult male minipigs without ( n = 4) and with HF ( n = 5). Pig NPR-A (179 bp) and NPR-C (203 bp) mRNA were partially sequenced (GenBank n.: FJ518622, FJ518621). Compared to control, ANP and BNP gene expression resulted higher in all the cardiac chambers of HF heart. This increase is associated to a down-regulation of NPR-A and an up-regulation of NPR-C in HF. These sequences will provide a new tool to investigate the role of natriuretic peptides and of their receptors under physiological and pathological conditions and their response to therapeutic interventions.

Regulation and significance of atrial and brain natriuretic peptides as cardiac hormones

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are cardiac hormones. During cardiac development, their expression is a maker of cardiomyocyte differentiation and is under tight spatiotemporal regulation. After birth, however, their ventricular expression is only up-regulated in response to various cardiovascular diseases. As a result, analysis of ANP and BNP gene expression has led to discoveries of transcriptional regulators and signaling pathways involved in both cardiac differentiation and cardiac disease. Studies using genetically engineered mice have shed light on the molecular mechanisms regulating ANP and BNP gene expression, as well as the physiological and pathophysiological relevance of the cardiac natriuretic peptide system. In this review we will summarize what is currently known about their regulation and the significance of ANP and BNP as hormones derived from the heart.

Local modulation of the natriuretic peptide system in the rat remnant kidney

The natriuretic peptide (NP) system plays a central role in the renal adaptations to acute volume expansion. However, the modulation of the NP system in chronic renal insufficiency (CRI) remains to be elucidated. In the present study, we evaluated cardiac haemodynamics, plasma type-B natriuretic peptide (BNP) levels and the expression of natriuretic peptide receptor A (NPR-A) and NPR-C in the renal cortex (RC) and medulla (RM) of Sham and (3/4) nephrectomized ((3/4)nx) rats, up to 26 weeks after surgery. Male Wistar-Han rats (190-220 g; n = 49) were randomly assigned to (3/4)nx or Sham surgery. Two, 10 and 26 weeks after surgery, non-invasive blood pressure (BP) and left ventricular (LV) haemodynamics were performed, and urine and blood were collected for metabolic studies and plasma BNP determination. In addition, tissue samples from RC and RM were obtained for NPR-A and NPR-C quantification (RT-PCR and western blotting) as well as NPR-A immunodetection. In (3/4)nx rats, the progressive interstitial fibrosis and tubular atrophy were accompanied by a time-dependent increase of BP and impaired natriuretic response to volume expansion (VE). This was accompanied in (3/4)nx rats by an early and time-dependent elevation of BNP circulating levels that was not associated with cardiac dysfunction or increased myocardial BNP gene expression. In (3/4)nx rats, NPR-A expression in the remnant RM was consistently reduced at 2, 10 and 26 weeks, and this was accompanied by an increase in NPR-C expression in the remnant RC from (3/4)nx rats. BP elevation and compromised natriuretic response to VE in (3/4)nx rats is associated with increased circulating BNP levels in the absence of cardiac dysfunction. This is accompanied in (3/4)nx rats by both impaired NPR-A expression in the RM and upregulation of NPR-C in the RC suggesting a novel mechanism for NP resistance in CRI.

Molecular Forms of BNP and ANP and gene expression of processing enzyme in atrium and ventricle in heart failure rat

Object: Recent studies suggest that there are several molecular forms of plasma BNP in patients with heart failure. However, precise mechanism remains unknown. Methods: The atrial and ventricular tissue levels of BNP1-45(alpha-BNP), BNP1-95(gamma-BNP), ANP1-28(alpha-ANP), and ANP1-126(gamma-ANP) were determined by radioimmunoassay following extraction with a Sep-Pak C18 cartridge and gel-filtration in control and Dahl salt-sensitive heart failure rat. We also measured mRNA levels of ANP, BNP, corin and furin, processing enzyme of ANP and BNP, in atrial and ventricular tissue by real-time PCR analysis.

Head-to-head comparison of BNP and IL-6 as markers of clinical and experimental heart failure: Superiority of BNP

Activation of BNP and IL-6 are hallmarks of left ventricular (LV) dysfunction and congestive heart failure (CHF). To assess the relative activation of BNP and IL-6 in clinical and experimental heart failure, we performed a human study in which plasma N-terminal proBNP (NT-proBNP) and IL-6 were measured in a large group of patients in the chronic phase after myocardial infarction (MI) and an animal study in which LV gene expression of BNP and IL-6 was assessed in rapid ventricular pacing-induced heart failure. In the human study, NT-proBNP and IL-6 were measured by non-extracted, enzyme-linked immunoassay in 845 subjects ( n = 468 outpatients after MI, MONICA MI register Augsburg; and 377 siblings without MI, control). NT-proBNP (295 ± 23 pg/mL vs. CTRL 84 ± 8, P < 0.05) and IL-6 (2.7 ± 0.1 pg/mL vs. CTRL 2.1 ± 0.1, P < 0.05) were both elevated in subjects with MI. These increases were particularly pronounced in the presence of concomitant CHF (both P < 0.01 vs. CTRL) and LV dysfunction (EF < 45%, both P < 0.05 vs. CTRL). However, NT-proBNP was significantly correlated with several cardiac structural and functional parameters (EF, LVMI, history of MI, CHF symptoms; all P < 0.05) upon regression analysis whereas IL-6 was only correlated with history of MI ( P < 0.001). Accordingly, MI subjects with symptomatic LV dysfunction were detected by NT-proBNP with a greater sensitivity, specificity, and ROC-area (85%, 88%, and 0.87, respectively) as compared to IL-6 (69%, 53%, and 0.67, respectively). In the animal study, IL-6 and BNP expression were both significantly elevated in CHF (both P < 0.05) but with a much greater absolute activation of BNP. In addition, BNP mRNA expression displayed a stronger inverse correlation with LV function ( r = −0.74; P < 0.001) than IL-6 ( r = −0.53; P = 0.001) and was a markedly more sensitive and specific molecular marker of LV dysfunction (sensitivity 91%, specificity 100%, ROC-area 0.94) than IL-6 (sensitivity 74%, specificity 83%, ROC-area 0.87). Our animal study provides evidence that IL-6 expression is activated in heart failure but to a significantly lesser degree than that of BNP. Both the stronger expression of BNP and the better correlation with LV function provide the molecular basis for a diagnostic superiority of NT-proBNP in clinical LV dysfunction and heart failure.

Calcium-Calmodulin Kinase II Is the Common Factor in Calcium-Dependent Cardiac Expression and Secretion of A- and B-Type Natriuretic Peptides

Peptides derived from the precursor of A- and B-type natriuretic peptides (ANP and BNP) are powerful clinical markers of cardiac hypertrophy and dysfunction. It is known that many stimuli affecting the intracellular calcium concentration also induce ANP and BNP secretion. It was our intention to study the mechanisms by which calcium regulates the secretion of ANP and BNP. The effects of pacing and calcium-calmodulin kinase II activity on natriuretic peptide secretion were studied in isolated perfused rat atria and cultured rat neonatal cardiomyocytes. In isolated rat atrium pacing induced an increase in diastolic, systolic, and averaged intracellular free calcium concentration and a frequency-dependent increase in the secretion of both ANP and BNP. The molar ratio of the secreted natriuretic peptides (ANP to BNP) remained nearly constant ( approximately 1000) at all the pacing frequencies tested (1, 3, 6, and 8 Hz). Calmodulin kinase II inhibitor KN-93 (3 mum) did not affect intracellular free calcium concentration but showed a frequency-dependent inhibitory effect on ANP and BNP secretion without a change in ANP to BNP ratio. In the neonatal cardiomyocytes, KN-93 (3 mum) suppressed the secretion and gene expression of both ANP and BNP. Overexpression of constitutively active (T286D) or nuclear (delta(B)) calcium-calmodulin kinase II induced an increase in ANP and BNP gene expression. The results indicate that the calcium-dependent secretion and gene expression of A- and B-type natriuretic peptides are similarly regulated by calmodulin kinase II-dependent mechanisms. This is a plausible mechanism contributing to exercise-induced natriuretic peptide secretion and the augmented secretion in heart dysfunction due to impaired calcium handling.

Fetal Cardiac Natriuretic Peptide Expression and Cardiovascular Hemodynamics in Endotoxin-Induced Acute Cardiac Dysfunction in Mouse

We hypothesized that, in acute endotoxin-induced fetal cardiac dysfunction, atrial (ANP) and B-type (BNP) natriuretic peptide mRNA expressions are increased in proportion to the severity of fetal cardiovascular compromise in mouse. To investigate in vitro the effect of endotoxin-induced inflammation on cardiac natriuretic peptide expression, fetal hearts were harvested at 15-16 d of gestation and incubated for 6 h with lipopolysaccharide (LPS). To examine the relationship between fetal cardiovascular compromise and cardiac natriuretic peptide expression in endotoxin-induced cardiac dysfunction in the in vivo model, fetuses received intra-amniotically 25 microL LPS (10 microg/mL) or 25 microL of 0.9% saline. Fetal Doppler ultrasonography was performed before and six hours after the injections. In in vitro cultured fetal hearts, LPS induced the production of proinflammatory cytokines without affecting the basal expressions of natriuretic peptides. In the in vivo model, Doppler ultrasonography revealed severe cardiac dysfunction after LPS injection. No significant changes in ANP or atrial BNP mRNA were found. The fetal ventricular BNP mRNA levels were about 2.6-fold in the LPS group compared with the control group. Decreased fetal cardiac outflow mean velocity, increased proportion of isovolumetric contraction time of the cardiac cycle, and increased pulsatility indices of the descending aorta and inferior vena cava were related to elevated ventricular BNP mRNA levels. Our results show that LPS did not increase the mRNA expression of natriuretic peptides in cultured fetal hearts. In contrast, fetal ventricular BNP gene expression was increased in proportion to the severity of the hemodynamic compromise in vivo.