Atrial Natriuretic Peptide Expression Research Articles

Vitamin D receptor activation, left ventricular hypertrophy and myocardial fibrosis

Left ventricular hypertrophy (LVH), a common complication in chronic kidney disease (CKD), is associated with high cardiovascular mortality. The aim of this experimental study was to analyze the effect of different vitamin D receptor activators (VDRAs) on both LVH and myocardial fibrosis in chronic renal failure (CRF). Male Wistar rats with CRF, carried out by 7/8 nephrectomy, were treated intraperitoneally with equivalent doses of VDRAs (calcitriol, paricalcitol and alfacalcidol, 5 days per week) during 4 weeks. A placebo group (CRF + vehicle) and a Sham group with normal renal function served as controls. Biochemical, morphological, functional and molecular parameters associated with LVH were evaluated, as well as cardiac fibrosis, collagen I, transforming growth factor β1 (TGFβ1) and matrix metalloproteinase-1 (MMP1) expression. All VDRAs treatment prevented LVH, with values of cardiomyocyte size, LV wall and septum thickness and heart-body weight ratio similar to those observed in the Sham group. At molecular levels, all VDRAs attenuated atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression compared with CRF + vehicle. The phosphorylation of ERK1/2, a signal for activating growth, was stimulated in the CRF + vehicle group; VDRAs use prevented this activation. Paricalcitol was the only VDRA used that maintained in the normal range all parameters associated with myocardial fibrosis (total collagen, collagen I, TGFβ1 and MMP1). Our findings demonstrated that the three VDRAs used induced similar changes in bone metabolic parameters and LVH. In addition, paricalcitol was the only VDRA which showed a relevant beneficial effect in the reduction of myocardial fibrosis, a key factor in the myocardial dysfunction in CKD patients.

Abstract 385: Tenascin-C Worsens Myocardial Inflammation and Fibrosis by Enhancing Macrophage Activation via NF-kappaB in Mouse Hypertensive Heart

Background and Aim: Tenascin-C (TN-C) is an extracellular matrix glycoprotein, not detected in normal adult heart but it expresses under various pathological conditions. We have previously reported in the enhanced TN-C production and accumulation of macrophages in the perivascular lesions of angiotensin II (AgII)-induced cardiac fibrosis mouse model. To clarify the role of TN-C in molecular mechanism, we analyzed the effect of TN-C in hypertensive heart utilizing wild-type (WT) and TN-C knock-out (TNKO) mice. Furthermore, to assess whether TN-C is involved in macrophage activation, we investigated in vitro study using macrophages isolated from the peritoneal cavity of WT mice. Methods and Results: Balb/c WT and TNKO mice were treated with 560 ng/kg body weight/min AgII subcutaneously by osmotic minipump for 4 weeks (WT/AgII and TNKO/AgII), and analyzed histological and molecular biological approaches. AgII treatment increased blood pressure, heart weight/body weight ratio, atrial and brain natriuretic peptide expression level and sizes of cardiomyocytes, but no significant differences were detected between WT/AgII and TNKO/AgII mice. In WT/AgII mice, interstitial collagen fibers (10.29±5.09% vs. WT: 4.6±1.56%, p<0.001) and accumulation of mac-3 positive macrophages (50±15.13 vs. WT: 6±2.55 cells/section, p<0.001) were observed at perivascular regions, and expression levels of interleukin (IL)-6 (1.85±0.39 fold, p<0.05) and monocyte chemoattractant protein (MCP)-1 (3.20±0.53 fold, p<0.001) were up-regulated. These changes were significantly reduced in TNKO/AgII mice. In vitro, TN-C accelerated macrophage migration in the presence of MCP-1. Western blotting and Immunofluorescence staining indicated that TN-C activated rapidly NF-kappaB. RT-PCR analysis demonstrated that TN-C up-regulated IL-6 mRNA on NF-kappaB dependent manner (39.90±18.10 fold, p<0.01). Integrin αVβ3 antagonist P11 suppressed these changes. Conclusion: The present study clearly demonstrated that TN-C aggravates inflammation and fibrosis in hypertensive heart by upregulation of IL-6 productions by activating NF-kappaB via integrin αVβ3 on macrophage.

Diabetes mellitus impairs cardiac remodeling and oxidative stress and activates fetal gene program in aged spontaneously hypertensive rats

Purpose: The combination of systemic arterial hypertension and Diabetes Mellitus (DM) induces greater cardiac remodeling than either condition alone. However, this association has been poorly addressed in senescent rats. Therefore, this study aimed to analyze the influence of streptozotocin-induced DM on ventricular remodeling and oxidative stress in aged Spontaneously Hypertensive Rats (SHR). Methods: Fifty 18 month old male SHR were divided into two groups: control (CTL, n=25) and diabetic (DM, n=25). DM was induced by streptozotocin (40 mg/kg, i.p.). After nine weeks, the rats underwent echocardiography and myocardial functional study in Left Ventricular (LV) isolated papillary muscle preparations. LV samples were obtained to measure myocyte diameters, interstitial collagen fraction, hydroxyproline concentration, and gene expression of Atrial Natriuretic Peptide (ANP) and α- and β-Myosin Heavy Chain (MyHC) isoforms. Serum oxidative stress was assessed by measuring lipid hydroperoxide concentration and superoxide dismutase and glutathione peroxidase activities. Statistics: Student's t test or Mann-Whitney test, p<0.05. Results: DM group presented higher blood glucose (487±29 vs. 89.1±21.1 mg/dL) and lower body weight (277±26 vs. 339±38 g). Systolic blood pressure did not differ between groups (CTL: 193±34; DM: 201±36 mmHg). Echocardiography showed LV and left atrial dilation, LV diastolic and relative wall thickness decrease, and LV systolic and diastolic function impairment in DM. Papillary muscle study showed decreased myocardial contractility and contractile reserve in DM. Myocyte diameters and myocardial interstitial collagen fraction and hydroxyproline concentration did not differ between groups. Increased serum pro-oxidant activity and gene expression of ANP (CTL: 1.00±0.38; DM: 1.88±0.69) and β/α-MyHC ratio (CTL: 1.20±0.60; DM: 2.26±0.94) were observed in DM. Conclusion: Diabetes mellitus induces cardiac dilation and functional impairment, increases oxidative stress and activates fetal gene program in aged spontaneously hypertensive rats. Support: CAPES and CNPq.

GW24-e2121 Adenosine monophosphate-activated protein kinase attenuates cardiomyocyte hypertrophy through regulation of FOXO3a/MAFbx signalling pathway

ObjectivesTo examine the inhibitory effects of adenosine monophosphate-activated protein kinase (AMPK) activation on cardiomyocyte hypertrophy in vitro and to investigate the underlying molecular mechanisms.MethodsCultured neonatal rat cardiomyocytes were treated with...

Puerarin attenuates pressure overload-induced cardiac hypertrophy

BackgroundPuerarin is the most abundant isoflavonoid in kudzu root. It has been used to treat angina pectoris and myocardial infarction clinically. However, little is known about the effect of puerarin on cardiac hypertrophy. MethodsAortic banding (AB) was performed to induce cardiac hypertrophy in mice. Puerarin premixed in diets was administered to mice after one week of AB. Echocardiography and catheter-based measurements of hemodynamic parameters were performed at 7 weeks after starting puerarin treatment (8 weeks post-surgery). The extent of cardiac hypertrophy was also evaluated by pathological and molecular analyses of heart samples. Cardiomyocyte apoptosis was assessed by measuring Bax and Bcl-2 protein expression and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. In addition, the inhibitory effect of puerarin (1μM, 5μM, 10μM, 20μM, 40μM) on mRNA expression of atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in Ang II (1μM)-stimulated H9c2 cells was investigated using quantitative real-time reverse transcription-polymerase chain reaction. ResultsEchocardiography and catheter-based measurements of hemodynamic parameters at 7 weeks revealed the amelioration of systolic and diastolic abnormalities. Puerarin also decreased cardiac fibrosis in AB mice. Moreover, the beneficial effect of puerarin was associated with the normalization in gene expression of hypertrophic and fibrotic markers. Further studies showed that pressure overload significantly induced the activation of phosphoinositide 3-kinase (PI3K)/Akt signaling and c-Jun N-terminal kinase (JNK) signaling, which was blocked by puerarin treatment. Cardiomyocyte apoptosis and induction of Bax in response to AB were suppressed by puerarin. Furthermore, the increased mRNA expression of ANP and BNP induced by Ang II (1μM) was restrained to a different extent by different concentrations of puerarin. ConclusionPuerarin may have an ability to retard the progression of cardiac hypertrophy and apoptosis which is probably mediated by the blockade of PI3K/Akt and JNK signaling pathways.

The expression and role of activin A and follistatin in heart failure rats after myocardial infarction

Activin A, a member of the transforming growth factor-β superfamily, is involved in inflammatory response and fibrosis [ [1] Wang Y. Cui X. Tai G. et al. A critical role of activin A in maturation of mouse peritoneal macrophages in vitro and in vivo. Cell Mol Immunol. 2009; 6: 387-392 Crossref PubMed Scopus (31) Google Scholar ]. Follistatin (FST) as an activin binding protein is widely expressed in various tissues and blocks the role of activin by preventing activin from binding to activin receptor (ActR) [ [2] Fang L. Wang Y.N. Cui X.L. et al. The role and mechanism of action of activin A in neurite outgrowth of chicken embryonic dorsal root ganglia. J Cell Sci. 2012; 125: 1500-1507 Crossref PubMed Scopus (30) Google Scholar ]. Activin A and follistatin generally co-express in tissues and the imbalance of activin A–follistatin system is involved in remodeling and repair of tissues. For example, overexpression of activin A in the skin of transgenic mice caused dermal fibrosis and epidermal hyperthickening, whereas the overexpressed follistatin significantly reduced granulation tissue formation and scar area [ 3 Munz B. Smola H. Engelhardt F. et al. Overexpression of activin A in the skin of transgenic mice reveals new activities of activin in epidermal morphogenesis, dermal fibrosis and wound repair. EMBO J. 1999; 18: 5205-5215 Crossref PubMed Scopus (189) Google Scholar , 4 Wankell M. Munz B. Hubner G. et al. Impaired wound healing in transgenic mice overexpressing the activin antagonist follistatin in the epidermis. EMBO J. 2001; 20: 5361-5372 Crossref PubMed Scopus (146) Google Scholar ]. It has been reported that expressions of activin A and its receptors increased after myocardial infarction and activin A induced expressions of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and matrix metalloproteinase-9 (MMP-9), which were known to play important roles in myocardial remodeling and fibrosis [ [5] Yndestad A. Ueland T. Øie E. et al. Elevated levels of activin A in heart failure: potential role in myocardial remodeling. Circulation. 2004; 109: 1379-1385 Crossref PubMed Scopus (137) Google Scholar ]. The latest study has reported that follistatin-like 3, a member of follistatin family, is upregulated in ischemic injury of heart and attenuates stress-induced myocardial hypertrophy [ [6] Shimano M. Ouchi N. Nakamura K. et al. Cardiac myocyte-specific ablation of follistatin-like 3 attenuates stress-induced myocardial hypertrophy. J Biol Chem. 2011; 286: 9840-9848 Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar ].

Cyclical stretch induces structural changes in atrial myocytes

Atrial fibrillation (AF) often occurs in the presence of an underlying disease. These underlying diseases cause atrial remodelling, which make the atria more susceptible to AF. Stretch is an important mediator in the remodelling process. The aim of this study was to develop an atrial cell culture model mimicking remodelling due to atrial pressure overload. Neonatal rat atrial cardiomyocytes (NRAM) were cultured and subjected to cyclical stretch on elastic membranes. Stretching with 1 Hz and 15% elongation for 30 min. resulted in increased expression of immediate early genes and phosphorylation of Erk and p38. A 24-hr stretch period resulted in hypertrophy-related changes including increased cell diameter, reinduction of the foetal gene program and cell death. No evidence of apoptosis was observed. Expression of atrial natriuretic peptide, brain natriuretic peptide and growth differentiation factor-15 was increased, and calcineurin signalling was activated. Expression of several potassium channels was decreased, suggesting electrical remodelling. Atrial stretch-induced change in skeletal α-actin expression was inhibited by pravastatin, but not by eplerenone or losartan. Stretch of NRAM results in elevation of stress markers, changes related to hypertrophy and dedifferentiation, electrical remodelling and cell death. This model can contribute to investigating the mechanisms involved in the remodelling process caused by stretch and to the testing of pharmaceutical agents.

Expression and localization of atrial natriuretic peptide and its receptors in rat spiral ganglion neurons

Spiral ganglion neurons (SGNs) are the primary auditory neurons in the inner ear, conveying auditory information between sensory hair cells and the central nervous system. Atrial natriuretic peptide (ANP), acting through specific receptors, is a regulatory peptide required for a variety of cardiac and neuronal functions. While the localization of ANP and its receptors (NPR-A and NPR-C) in the inner ear has been widely studied, there is only limited information regarding their localization in cochlear SGNs and their regulatory roles during primary auditory neurotransmission. Here we have investigated the presence of ANP and its receptors in the cochlear spiral ganglion of the postnatal rat using immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. ANP and its receptors are expressed in the cochlear SGNs at both the mRNA and protein level, and co-localize in the cochlear SGNs as shown by immunofluorescence. Our research provides a direct evidence for the presence and synthesis of ANP as well as its receptors in the cochlear SGNs, suggesting a possible role for ANP in modulating the neuronal functions of SGNs via its receptors.

Signaling mechanisms of a water soluble curcumin derivative in experimental type 1 diabetes with cardiomyopathy

BackgroundCurcumin exhibits anti-diabetic activities, induces heme-oxygenase-1 (HO-1) and is an inhibitor of transcriptional co-activator p300. A novel water soluble curcumin derivative (NCD) has been developed to overcome low invivo bioavailability of curcumin. We evaluated the effect of the NCD on signaling mechanisms involved in cardiomyocyte hypertrophy and studied whether its action is mediated via inducible HO-1.Materials and methodsRats were divided into controls, controls receiving NCD, diabetic, diabetic receiving NCD, diabetic receiving pure curcumin, diabetic receiving HO inhibitor, zinc protoporphyrin IX (ZnPP IX) and diabetic receiving NCD and ZnPP IX. NCD and curcumin were given orally. After 45 days, cardiac physiologic parameters, plasma glucose, insulin, glycated hemoglobin (GHb), HO-1 gene expression and HO activity in pancreas and cardiac tissues were assessed. Gene expression of p300, atrial natriuretic peptide (ANP) and myocyte enhancer factor 2 (MEF2A and MEF2C) were studied.ResultsNCD and curcumin decreased plasma glucose, GHb and increased insulin levels significantly in diabetic rats. This action may be partially mediated by induction of HO-1 gene. HO-1 gene expression and HO activity were significantly increased in diabetic heart and pancreas. Diabetes upregulated the expression of ANP, MEF2A, MEF2C and p300. NCD and curcumin prevented diabetes-induced upregulation of these parameters and improved left ventricular function. The effect of the NCD was better than the same dose of curcumin.

ANP-NPRA Signaling Pathway - A Potential Therapeutic Target for the Treatment of Malignancy

It was well established that the atrial natriuretic peptide (ANP)/natriuretic peptide receptor-A (NPRA) signaling pathway controls natriuretic, diuretic, vasorelaxant, and anti-proliferative responses in the regulation of the human cardiovascular system by previous studies. Yet in recent years, more and more evidence has shown that the ANP/NPRA signaling pathway plays an important role in human cancer. For example, NPRA is abundantly expressed on tumorigenic mouse and human prostate cancer (PCa) cells, but not in nontumorigenic prostate epithelial cells and down-regulation of NPRA-induced apoptosis in PCa cells. Dexamethasone can increase the expression of ANP markedly, and that is the reason why dexamethasone is the cornerstone in the treatment of multiple myeloma. NPRA deficiency can substantially protect C57BL/6 mice from lung, skin, and ovarian cancers. These results strongly suggest ANP and NPRA may play an anti-cancer and carcinogenesis role, respectively, and this signaling pathway could be a more potent target for cancer therapy. In light of these new insights, this review will summarize the structures, functions, and their regulation by cell signaling, and their different impacts on tumors.

Establishment of Mouse Embryonic Stem Cell and Effects of Herbal Medicine on Induction of Cardiomyocyte Differentiation

This study was conducted to investigate the effects of Woohwangcheungsimweun (ox bezoar), deer antlers, and wild ginseng on induction of cardiomyocyte differentiation using the established mouse embryonic stem (ES) cells. The expression of atrial natriuretic peptide (ANP) was highest in Woohwangcheungsimweun treatment group. The expression of rabbit anti-GATA-4(GATA-4) and troponin (TnI) were highest in wild ginseng and Woohwangcheungsimweun treatment groups, respectively. Fluorescence activated cell sorting (FACS) analysis showed that the expression of ANP was highest in Dimethyl sulfoxide(DMSO) and Woohwangcheungsimweun treatment groups. The expression of GATA-4 was relatively high in wild ginseng treatment group. The expression of TnI was highest in Woohwangcheungsimweun treatment group. In the gene expression analysis, DMSO greatly inhibited GATA-4 expression to 25% of control. Woohwangcheungsimweun treatment caused to increase cTnI and cardiac ANP expression significantly. Wild ginseng extract upregulated GATA-4 gene expression. In conclusion, DMSO widely used as cardiomyocyte differentiation inducer did not show significant effects on the expression of ANP, GATA-4 and TnI in this study. Woohwangcheungsimweun showed upregulation of ANP and TnI expression. Wild ginseng extract showed greater effects than DMSO on GATA-4 expression. These results might suggest that the combination of Woohwangcheungsimweun and wild ginseng extract treatment can be expected to increase expressions of all three genes.

Resveratrol improves myocardial ischemia and ischemic heart failure in mice by antagonizing the detrimental effects of fractalkine*

To test the hypothesis that resveratrol would improve cardiac remodeling by inhibiting the detrimental effects of fractalkine. We previously reported that fractalkine exacerbates heart failure. Furthermore, this study sought to determine whether resveratrol targets fractalkine to improve myocardial ischemia and cardiac remodeling. Randomized and controlled laboratory investigation. Research laboratory. Neonatal rat cardiac cells and C57BL/6 mice. Cardiac cells were treated with recombinant mouse soluble fractalkine for 24 hrs or pretreated with 25 µM resveratrol. Cardiomyocytes were exposed to anoxia/reoxygenation, H2O2, or pretreatment with resveratrol. Ex vivo murine hearts were perfusioned with soluble fractalkine or pretreated with resveratrol after global ischemia. Mice were subjected to the left coronary artery ligation to induce myocardial infarction and randomized to treatment with resveratrol or vehicle alone for 42 days. In a murine myocardial infarction model, we found that resveratrol increased survival and delayed the progression of cardiac remodeling evaluated by serial echocardiography. At 6 wks, the heart weight/body weight ratio, lung weight/body weight ratio, and old infarct size were significantly smaller in resveratrol-treated mice than in untreated myocardial infarction mice. In cultures of neonatal rat cells, exposure to soluble fractalkine increased the atrial natriuretic peptide expression by cardiomyocytes, matrix metalloproteinase-9 and procollagen expression by fibroblasts, and intercellular adhesion molecule-1 expression by microvascular endothelial cells, while it decreased autophagy in cardiomyocytes. All these effects were blocked by coculture with resveratrol. The methyl thiazolyl tetrazolium assay showed that soluble fractalkine reduced the viability of cultured cardiomyocytes during exposure to anoxia/reoxygenation or H2O2, while pretreatment with resveratrol blocked this effect. Perfusion of ex vivo murine hearts with soluble fractalkine after global ischemia led to an increase of infarct size, which was prevented by pretreatment with resveratrol. Resveratrol alleviates the deleterious effects of fractalkine on myocardial ischemia and thus reduces subsequent cardiac remodeling.

Enhanced phosphoinositide 3-kinase(p110α) activity prevents diabetes-induced cardiomyopathy and superoxide generation in a mouse model of diabetes

Diabetic cardiomyopathy is characterised by diastolic dysfunction, oxidative stress, fibrosis, apoptosis and pathological cardiomyocyte hypertrophy. Phosphoinositide 3-kinase (PI3K)(p110α) is a cardioprotective kinase, but its role in the diabetic heart is unknown. The aim of this study was to assess whether PI3K(p110α) plays a critical role in the induction of diabetic cardiomyopathy, and whether increasing PI3K(p110α) activity in the heart can prevent the development of cardiac dysfunction in a setting of diabetes. Type 1 diabetes was induced with streptozotocin in adult male cardiac-specific transgenic mice with increased PI3K(p110α) activity (constitutively active PI3K [p110α], caPI3K] or decreased PI3K(p110α) activity (dominant-negative PI3K [p110α], dnPI3K) and non-transgenic (Ntg) mice for 12weeks. Cardiac function, histological and molecular analyses were performed. Diabetic Ntg mice displayed diastolic dysfunction and increased cardiomyocyte size, expression of atrial and B-type natriuretic peptides (Anp, Bnp), fibrosis and apoptosis, as well as increased superoxide generation and increased protein kinase C β2 (PKCβ2), p22 ( phox ) and apoptosis signal-regulating kinase 1 (Ask1) expression. Diabetic dnPI3K mice displayed an exaggerated cardiomyopathy phenotype compared with diabetic Ntg mice. In contrast, diabetic caPI3K mice were protected against diastolic dysfunction, pathological cardiomyocyte hypertrophy, fibrosis and apoptosis. Protection in diabetic caPI3K mice was associated with attenuation of left ventricular superoxide generation, attenuated Anp, Bnp, PKCβ2, Ask1 and p22 ( phox ) expression, and elevated AKT. Further, in cardiomyocyte-like cells, increased PI3K(p110α) activity suppressed high glucose-induced superoxide generation and enhanced mitochondrial function. These results demonstrate that reduced PI3K activity accelerates the development of diabetic cardiomyopathy, and that enhanced PI3K(p110α) activity can prevent adverse cardiac remodelling and dysfunction in a setting of diabetes.

Chronic intermittent hypoxia exposure improves left ventricular contractility in transgenic mice with heart failure

We previously reported the unexpected finding that 4 wk of exposure to intermittent hypoxia (IH), which simulates the hypoxic stress of obstructive sleep apnea, improved LV cardiac function in healthy, lean C57BL/6J mice. The purpose of the present study was to assess the impact of 4 wk of IH on cardiac function in a transgenic murine model that exhibits a natural history of heart failure. We hypothesized that IH exposure would exacerbate cardiac decompensation in heart failure. Adult male FVB (wild type) and transgenic mice with cardiac overexpression of tumor necrosis factor α (TNF-αTG) at 10-12 wk of age were exposed to 4 wk of IH (nadir inspired oxygen 5-6% at 60 cycles/h for 12 h during light period) or intermittent air (IA) as control. Cardiac function was assessed by echocardiography and pressure-volume loop analyses, and mRNA and protein expression were performed on ventricular homogenates. TNF-αTG mice exposed to IA exhibited impaired LV contractility and increased LV dilation associated with markedly elevated cardiac expression of atrial natriuretic peptide and brain natriuretic peptide compared with wild-type mice. When wild-type FVB mice were exposed to IH, they exhibited increases in arterial pressure and dP/dt(max), consistent with our previous report in C57BL/6J mice. Surprisingly, we found that TNF-αTG mice exposed to IH showed a reduction in end-diastolic volume (38.7 ± 3.8 to 22.2 ± 2.1 ul; P < 0.01) and an increase in ejection fraction (29.4 ± 2.5 to 41.9 ± 3.1%; P < 0.05). In contrast to our previous study in C56Bl/6J mice, neither FVB nor TNF-αTG mice exhibited an upregulation in β-adrenergic expression or cAMP in response to IH exposure. We conclude that 4 wk of exposure to IH in mice induces adaptive responses that improve cardiac function in not only healthy animals but also in animals with underlying heart failure.

Aldosterone inhibits the fetal program and increases hypertrophy in the heart of hypertensive mice.

BackgroundArterial hypertension (AH) induces cardiac hypertrophy and reactivation of “fetal” gene expression. In rodent heart, alpha-Myosin Heavy Chain (MyHC) and its micro-RNA miR-208a regulate the expression of beta-MyHC and of its intronic miR-208b. However, the role of aldosterone in these processes remains unclear.Methodology/Principal FindingsRT-PCR and western-blot were used to investigate the genes modulated by arterial hypertension and cardiac hyperaldosteronism. We developed a model of double-transgenic mice (AS-Ren) with cardiac hyperaldosteronism (AS mice) and systemic hypertension (Ren). AS-Ren mice had increased (x2) angiotensin II in plasma and increased (x2) aldosterone in heart. Ren and AS-Ren mice had a robust and similar hypertension (+70%) versus their controls. Anatomical data and echocardiography showed a worsening of cardiac hypertrophy (+41%) in AS-Ren mice (P<0.05 vs Ren). The increase of ANP (x 2.5; P<0.01) mRNA observed in Ren mice was blunted in AS-Ren mice. This non-induction of antitrophic natriuretic peptides may be involved in the higher trophic cardiac response in AS-Ren mice, as indicated by the markedly reduced cardiac hypertrophy in ANP-infused AS-Ren mice for one month. Besides, the AH-induced increase of ßMyHC and its intronic miRNA-208b was prevented in AS-Ren. The inhibition of miR 208a (−75%, p<0.001) in AS-Ren mice compared to AS was associated with increased Sox 6 mRNA (x 1.34; p<0.05), an inhibitor of ßMyHC transcription. Eplerenone prevented all aldosterone-dependent effects.Conclusions/SignificanceOur results indicate that increased aldosterone in heart inhibits the induction of atrial natriuretic peptide expression, via the mineralocorticoid receptor. This worsens cardiac hypertrophy without changing blood pressure. Moreover, this work reveals an original aldosterone-dependent inhibition of miR-208a in hypertension, resulting in the inhibition of β-myosin heavy chain expression through the induction of its transcriptional repressor Sox6. Thus, aldosterone inhibits the fetal program and increases cardiac hypertrophy in hypertensive mice.

Atrial natriuretic peptide: A possible mediator involved in dexamethasone’s inhibition of cell proliferation in multiple myeloma

Atrial natriuretic peptide (ANP) has been recognized for several decades for its role of regulating blood pressure. Recently, cumulating evidences show that ANP plays an anticancer role in various solid tumors via blocking the kinase cascade of Ras-MEK1/2-ERK1/2 with the result of inhibition of DNA synthesis. ANP, as well as its receptors (NPR-A and NPR-C) has been identified present in the embryonic stem cell and a wide range of cancer cells. Various lymphoid organs, such as lymph nodes, have been detected the presence of ANP. Multiple myeloma (MM), though the therapies have evolved significantly, is still an incurable disease as B lymphocyte cell neoplasm. Dexamethasone is the cornerstone in treatment of MM via inactivation of Ras-MEK1/2-ERK1/2 cascade reaction. Coincidently, dexamethasone can increase the expression of ANP markedly. Nevertheless, the role of ANP in MM is unclear. Based on these results above, we raise the hypothesis that ANP is involved in mediating dexamethasone’s inhibition of proliferation in MM cells, which suggests that ANP may be a potential agent to treat MM.

A novel player in cellular hypertrophy: Giβγ/PI3K-dependent activation of the RacGEF TIAM-1 is required for α1-adrenoceptor induced hypertrophy in neonatal rat cardiomyocytes

Activation of α(1)-adrenoceptors (α(1)-AR) by high catecholamine levels, e.g. in heart failure, is thought to be a driving force of cardiac hypertrophy. In this context several downstream mediators and cascades have been identified to potentially play a role in cardiomyocyte hypertrophy. One of these proteins is the monomeric G protein Rac1. However, until now it is unclear how this essential G protein is activated by α(1)-AR agonists and what are the downstream targets inducing cellular growth. By using protein-based as well as pharmacological inhibitors and the shRNA technique, we demonstrate that in neonatal rat cardiomyocytes (NRCM) Rac1 is activated via a cascade involving the α(1A)-AR subtype, G(i)βγ, the phosphoinositide-3'-kinase and the guanine nucleotide exchange factor Tiam1. We further demonstrate that this signaling induces an increase in protein synthesis, cell size and atrial natriuretic peptide expression. We identified the p21-activated kinase 2 (PAK2) as a downstream effector of Rac1 and were able to link this cascade to the activation of the pro-hypertrophic kinases ERK1/2 and p90RSK. Our data thus reveal a prominent role of the α(1A)-AR/G(i)βγ/Tiam1-mediated activation of Rac1 and its effector PAK2 in the induction of hypertrophy in NRCM.

Curcumin prevents diabetic cardiomyopathy in streptozotocin-induced diabetic rats: Possible involvement of PKC–MAPK signaling pathway

The development of diabetic cardiomyopathy is accompanied with a high membrane-bound protein kinase C (PKC) levels. Curcumin is a naturally occurring compound which is known to inhibit PKC activity. However, the effects of curcumin on ameliorating diabetic cardiomyopathy are still undefined. We evaluated whether curcumin treatment is associated with the modulation of PKC-α and -β2-mitogen-activated protein kinase (MAPK) pathway in experimental diabetic cardiomyopathy. Diabetes was induced in male Sprague–Dawley rats by streptozotocin (STZ). Curcumin (100mg/kg/day) was started three weeks after STZ injection and was given for 8weeks. We demonstrate that curcumin significantly prevented diabetes-induced translocation of PKC-α and -β2 to membranous fraction and diabetes-induced increased phosphorylation of p38MAPK and extracellular regulated-signal kinase (ERK)1/2 in left ventricular tissues of diabetic rats. Curcumin treatment also markedly decreased NAD(P)H oxidase subunits (p67phox, p22phox, gp91phox), growth factors (transforming growth factor-β, osteopontin) and myocyte enhancer factor-2 protein expression as well as inhibited NF-κB activity at nuclear level. Furthermore, curcumin decreased the mRNA expression of transcriptional coactivator p300 and atrial natriuretic peptide, decreased accumulation of ECM protein and reversed the increment of superoxide production in left ventricular tissues, as evidenced by dihydroethidium staining. It is also significantly lowered plasma glucose and attenuated oxidative stress, as determined by lipid peroxidation and activity of anti-oxidant enzyme, and as a result attenuated cardiomyocyte hypertrophy, myocardial fibrosis and left ventricular dysfunction. Taken together, it is suggested that curcumin by inhibiting PKC-α and -β2-MAPK pathway may be useful as an adjuvant therapy for the prevention of diabetic cardiomyopathy.

Renal, retinal and cardiac changes in type 2 diabetes are attenuated by macitentan, a dual endothelin receptor antagonist

AimsDiabetes is known to cause alteration of the endothelin (ET) system. We have previously demonstrated that ETs regulate augmented production of extracellular matrix proteins causing structural alterations in type 1 diabetes. Here we investigated the effects of macitentan, an orally-active, tissue-targeting dual ET receptor antagonist on chronic complications in type 2 diabetes. Main methodsdb/db mice and their age- and sex-matched controls were examined after 2 and 4months of diabetes. Groups of diabetic animals were treated with oral macitentan (25mg/kg/day). The animals were monitored with respect to body weight and blood glucose. Urine analyses were performed for albumin. Cardiac hemodynamic studies were carried out. Renal, cardiac and retinal tissues were analyzed for ET-1, transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), fibronectin (FN), extradomain B containing FN (EDB+FN) and collagen α-I (IV) mRNA. Cardiac atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were measured. Protein expressions were measured by ELISA and Western blot. Microscopic analyses were performed in the kidneys. Key findingsDiabetic animals showed hyperglycemia, increased urinary albumin and augmented serum creatinine levels. Diabetes caused increased renal, cardiac and retinal ET-1, TGF-β1, VEGF, FN, EDB+FN, collagen α-I(IV) mRNA expression along with increased FN and collagen protein and NF-κB activation. Diabetic mice also demonstrated mesangial expansion, cardiac dysfunction and increased expression of ANP and BNP. Treatment with macitentan attenuated such abnormalities. SignificanceThese experiments confirmed that ET system plays a significant role in the pathogenesis of chronic complications in type 2 diabetes. Such diabetes induced changes can be reduced macitentan therapy.

Aging Aggravates Cardiac Dysfunction in Severe, but not in Mild, Pressure‐Overload

The aging heart undergoes structural and functional alterations, that are reminiscent of changes observed in the failing heart, and which thus may increase the vulnerability of the aging heart to develop heart failure. To investigate the effect of aging on left ventricular (LV) hypertrophy and dysfunction we subjected mice at 3, 12 and 24 mo of age to 8 wk of pressure‐overload produced by transverse aortic constriction (TAC), either mild (mTAC) or severe (sTAC).Aging affected cardiac geometry and function in sham mice, demonstrated by increases in LV weight (~26%) and diameter (~8%) and by decreases in LVdP/dt at 40 mmHg (dP/dtP40) (~13%) and in dP/dtmin (~26%) in 24 mo versus 3 mo old mice (all p&lt;0.05). mTAC produced compensated LV hypertrophy (30–40%) with minimal signs of LV dysfunction, which was similar in all age groups. sTAC resulted in ~75% LV hypertrophy, LV dilation (~20%), global dysfunction and pulmonary congestion in all age groups. However, aging aggravated the responses to sTAC, demonstrated by a further decrease in dP/dtP40 (~30%) and dP/dtmin (~30%) and elevation of lung fluid weight (~27%) and right ventricular weight (~31%) in 24 mo versus 3 mo old mice (all p&lt;0.05). The TAC‐induced increase in expression of atrial natriuretic peptide (ANP) was also most pronounced in the older age groups. In conclusion, the effects of severe pressure‐overload on cardiac hypertrophy and function are aggravated by aging.