Extracellular signal regulated kinase and SMAD signaling both mediate the angiotensin II driven progression towards overt heart failure in homozygous TGR(mRen2)27

Pectins from various sources inhibit galectin-3-related cardiac fibrosis

PURPOSE OF THE STUDY

A major challenge in cardiology remains in finding a therapy for cardiac fibrosis. Inhibition of galectin-3 with pectins attenuates fibrosis in animal models of heart failure. The purpose of this study is to identify pectins with the strongest galectin-3 inhibitory capacity. We evaluated the in vitro inhibitory capacity, identified potent pectins, and tested if this potency could be validated in a mouse model of myocardial fibrosis.

METHODS

Various pectin fractions were screened in vitro. Modified rhubarb pectin (EMRP) was identified as the most potent inhibitor of galectin-3 and compared to the well-known modified citrus pectin (MCP). Our findings were validated in a mouse model of myocardial fibrosis, which was induced by angiotensin II (Ang II) infusion.

RESULTS

Ang II infusion was associated with a 4-5-fold increase in fibrosis signal in the tissue of the left ventricle, compared to the control group (0•22±0•10 to 1•08±0•53%; P < 0•001). After treatment with rhubarb pectin, fibrosis was reduced by 57% vs. Ang II alone while this reduction was 30% with the well-known MCP (P = NS, P < 0•05). Treatment was associated with a reduced cardiac inflammatory response and preserved cardiac function.

CONCLUSION

The galectin-3 inhibitor natural rhubarb pectin has a superior inhibitory capacity over established pectins, substantially attenuates cardiac fibrosis, and preserves cardiac function in vivo. Bioactive pectins are natural sources of galectin-3 inhibitors and may be helpful in the prevention of heart failure or other diseases characterized by fibrosis.

FUNDING

Dr. Meijers is supported by the Mandema-Stipendium of the Junior Scientific Masterclass 2020-10, University Medical Center Groningen and by the Netherlands Heart Foundation (Dekkerbeurs 2021)Dr. de Boer is supported by the Netherlands Heart Foundation (CVON SHE-PREDICTS-HF, grant 2017-21; CVON RED-CVD, grant 2017-11; CVON PREDICT2, grant 2018-30; and CVON DOUBLE DOSE, grant 2020B005), by a grant from the leDucq Foundation (Cure PhosphoLambaN induced Cardiomyopathy (Cure-PLaN), and by a grant from the European Research Council (ERC CoG 818715, SECRETE-HF).

The effects of liraglutide and dapagliflozin on cardiac function and structure in a multi-hit mouse model of heart failure with preserved ejection fraction

AIMS

Heart failure with preserved ejection fraction (HFpEF) is a multifactorial disease that constitutes several distinct phenotypes, including a common cardiometabolic phenotype with obesity and type 2 diabetes mellitus. Treatment options for HFpEF are limited, and development of novel therapeutics is hindered by the paucity of suitable preclinical HFpEF models that recapitulate the complexity of human HFpEF. Metabolic drugs, like glucagon-like peptide receptor agonist (GLP-1 RA) and sodium-glucose co-transporter 2 inhibitors (SGLT2i), have emerged as promising drugs to restore metabolic perturbations and may have value in the treatment of the cardiometabolic HFpEF phenotype. We aimed to develop a multifactorial HFpEF mouse model that closely resembles the cardiometabolic HFpEF phenotype, and evaluated the GLP-1 RA liraglutide (Lira) and the SGLT2i dapagliflozin (Dapa).

METHODS AND RESULTS

Aged (18-22 months old) female C57BL/6J mice were fed a standardized chow (CTRL) or high-fat diet (HFD) for 12 weeks. After 8 weeks HFD, angiotensin II (ANGII), was administered for 4 weeks via osmotic mini pumps. HFD + ANGII resulted in a cardiometabolic HFpEF phenotype, including obesity, impaired glucose handling, and metabolic dysregulation with inflammation. The multiple hit resulted in typical clinical HFpEF features, including cardiac hypertrophy and fibrosis with preserved fractional shortening but with impaired myocardial deformation, atrial enlargement, lung congestion, and elevated blood pressures. Treatment with Lira attenuated the cardiometabolic dysregulation and improved cardiac function, with reduced cardiac hypertrophy, less myocardial fibrosis, and attenuation of atrial weight, natriuretic peptide levels, and lung congestion. Dapa treatment improved glucose handling, but had mild effects on the HFpEF phenotype.

CONCLUSIONS

We developed a mouse model that recapitulates the human HFpEF disease, providing a novel opportunity to study disease pathogenesis and the development of enhanced therapeutic approaches. We furthermore show that attenuation of cardiometabolic dysregulation may represent a novel therapeutic target for the treatment of HFpEF.

Radiological assessment of effectiveness of soluble RAGE in attenuating Angiotensin II-induced LVH mouse model using in vivo 9.4T MRI

We investigated the effectiveness of soluble Receptor for Advanced Glycation Endproducts (sRAGE) in attenuating angiotensin II (AngII)-induced left ventricular hypertrophy (LVH) using in vivo 9.4T cine-magnetic resonance imaging (CINE-MRI). Mice were divided into four groups: AngII (n = 9), saline (n = 10), sRAGE (n = 10), and AngII + sRAGE (n = 10). CINE-MRI was performed in each group after administration of the AngII or sRAGE, and CINE-MR images were analyzed to obtain parameters indicating cardiac anatomical and functional changes including end-diastolic and end-systolic blood volume, end-diastolic and end-systolic myocardial volume, ejection fraction, end-diastolic and end-systolic myocardial mass, and LV wall thickness. LVH observed in AngII group was significantly attenuated by sRAGE. These trends were also observed in histological analysis, demonstrating that cardiac function tracking using in vivo and real-time 9.4T MR imaging provides valuable information about the cardiac remodeling induced by AngII and sRAGE in an AngII-induced LV hypertrophy mice model.

Rodent heart failure models do not reflect the human circulating microRNA signature in heart failure

Introduction

We recently identified a set of plasma microRNAs (miRNAs) that are downregulated in patients with heart failure in comparison with control subjects. To better understand their meaning and function, we sought to validate these circulating miRNAs in 3 different well-established rat and mouse heart failure models, and correlated the miRNAs to parameters of cardiac function.

Methods

The previously identified let-7i-5p, miR-16-5p, miR-18a-5p, miR-26b-5p, miR-27a-3p, miR-30e-5p, miR-199a-3p, miR-223-3p, miR-423-3p, miR-423-5p and miR-652-3p were measured by means of quantitative real time polymerase chain reaction (qRT-PCR) in plasma samples of 8 homozygous TGR(mREN2)27 (Ren2) transgenic rats and 8 (control) Sprague-Dawley rats, 6 mice with angiotensin II-induced heart failure (AngII) and 6 control mice, and 8 mice with ischemic heart failure and 6 controls. Circulating miRNA levels were compared between the heart failure animals and healthy controls.

Results

Ren2 rats, AngII mice and mice with ischemic heart failure showed clear signs of heart failure, exemplified by increased left ventricular and lung weights, elevated end-diastolic left ventricular pressures, increased expression of cardiac stress markers and reduced left ventricular ejection fraction. All miRNAs were detectable in plasma from rats and mice. No significant differences were observed between the circulating miRNAs in heart failure animals when compared to the healthy controls (all P>0.05) and no robust associations with cardiac function could be found.

Conclusions

The previous observation that miRNAs circulate in lower levels in human patients with heart failure could not be validated in well-established rat and mouse heart failure models. These results question the translation of data on human circulating miRNA levels to experimental models, and vice versa the validity of experimental miRNA data for human heart failure.

Transforming growth factor β: A potential biomarker and therapeutic target of ventricular remodeling

Transforming growth factor β (TGF-β) is a multifunctional cytokine that is synthesized by many types of cells and regulates the cell cycle. Increasing evidence has led to TGF-β receiving increased and deserved attention in recent years because it may play a potentially novel and critical role in the development and progression of myocardial fibrosis and the subsequent progress of ventricular remodeling (VR). Numerous studies have highlighted a crucial role of TGF-β in VR and suggest potential therapeutic targets of the TGF-β signaling pathways for VR. Changes in TGF-β activity may elicit anti-VR activity and may serve as a novel therapeutic target for VR therapy. This review we discusses the smad-dependent signaling pathway, such as TGF-β/Smads, TGF-β/Sirtuins, TGF-β/BMP, TGF-β/miRNAs, TGF-β/MAPK, and Smad-independent signaling pathway of TGF-β, such as TGF-β/PI3K/Akt, TGF-β/Rho/ROCK,TGF-β/Wnt/β-catenin in the cardiac fibrosis and subsequent progression of VR. Furthermore, agonists and antagonists of TGF-β as potential therapeutic targets in VR are also described.

Hsp90/Cdc37 assembly modulates TGFβ receptor-II to act as a profibrotic regulator of TGFβ signaling during cardiac hypertrophy

Cardiac hypertrophy is accompanied by excessive collagen deposition in the heart. Despite painstaking research on this fatal disease, the precise role of molecular chaperones in myocardial fibrosis has not yet been elucidated. In this study, we have analyzed the mechanism by which Heat shock protein 90 (Hsp90)/Cell division cycle 37 (Cdc37) assembly modulates cardiac hypertrophy associated fibrosis. For the in vitro hypertrophy model, Angiotensin II (AngII) treated cultured adult cardiac fibroblasts were used, whereas the in vivo hypertrophy model was generated by renal artery ligation in adult male Wistar rats (Rattus norvegicus). Pretreatment with the Hsp90 inhibitor or the blocking of Hsp90-Cdc37 interactions during pressure overload hypertrophy resulted in ubiquitin-mediated proteasomal degradation of TGFβ receptor-II (TβR-II) leading to termination of TGFβ mediated signaling. In both cases significant reduction in collagen synthesis was observed revealing the Hsp90/Cdc37 complex as an integral profibrotic component of TGFβ signaling during cardiac hypertrophy.

Taxifolin protects against cardiac hypertrophy and fibrosis during biomechanical stress of pressure overload

Cardiac hypertrophy is a key pathophysiological component to biomechanical stress, which has been considered to be an independent and predictive risk factor for adverse cardiovascular events. Taxifolin (TAX) is a typical plant flavonoid, which has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. However, very little is known about whether TAX can influence the development of cardiac hypertrophy. In vitro studies, we found that TAX concentration-dependently inhibited angiotensin II (Ang II) induced hypertrophy and protein synthesis in cardiac myocytes. Then we established a mouse model by transverse aortic constriction (TAC) to further confirm our findings. It was demonstrated that TAX prevented pressure overload induced cardiac hypertrophy in mice, as assessed by ventricular mass/body weight, echocardiographic parameters, myocyte cross-sectional area, and the expression of ANP, BNP and β-MHC. The excess production of reactive oxygen species (ROS) played critical role in the development of cardiac hypertrophy. TAX arrested oxidative stress and decreased the expression of 4-HNE induced by pressure overload. Moreover, TAX negatively modulated TAC-induced phosphorylation of ERK1/2 and JNK1/2. Further studies showed that TAX significantly attenuated left ventricular fibrosis and collagen synthesis through abrogating the phosphorylation of Smad2 and Smad2/3 nuclear translocation. These results demonstrated that TAX could inhibit cardiac hypertrophy and attenuate ventricular fibrosis after pressure overload. These beneficial effects were at least through the inhibition of the excess production of ROS, ERK1/2, JNK1/2 and Smad signaling pathways. Therefore, TAX might be a potential candidate for the treatment of cardiac hypertrophy and fibrosis.

Exendin-4 protects against post-myocardial infarction remodelling via specific actions on inflammation and the extracellular matrix

Glucagon-like peptide-1 (GLP-1) is an insulin-releasing hormone clinically exploited for glycaemic control in diabetes, which also confers acute cardioprotection and benefits in experimental/clinical heart failure. We specifically investigated the role of the GLP-1 mimetic, exendin-4, in post-myocardial infarction (MI) remodelling, which is a key contributor to heart failure. Adult female normoglycaemic mice underwent coronary artery ligation/sham surgery prior to infusion with exendin-4/vehicle for 4 weeks. Metabolic parameters and infarct sizes were comparable between groups. Exendin-4 protected against cardiac dysfunction and chamber dilatation post-MI and improved survival. Furthermore, exendin-4 modestly decreased cardiomyocyte hypertrophy/apoptosis but markedly attenuated interstitial fibrosis and myocardial inflammation post-MI. This was associated with altered extracellular matrix (procollagen IαI/IIIαI, connective tissue growth factor, fibronectin, TGF-β₃) and inflammatory (IL-10, IL-1β, IL-6) gene expression in exendin-4-treated mice, together with modulation of both Akt/GSK-3β and Smad2/3 signalling. Exendin-4 also altered macrophage response gene expression in the absence of direct actions on cardiac fibroblast differentiation, suggesting cardioprotective effects occurring secondary to modulation of inflammation. Our findings indicate that exendin-4 protects against post-MI remodelling via preferential actions on inflammation and the extracellular matrix independently of its established actions on glycaemic control, thereby suggesting that selective targeting of GLP-1 signalling may be required to realise its clear therapeutic potential for post-MI heart failure.

Klotho and phosphate are modulators of pathologic uremic cardiac remodeling

Cardiac dysfunction in CKD is characterized by aberrant cardiac remodeling with hypertrophy and fibrosis. CKD is a state of severe systemic Klotho deficiency, and restoration of Klotho attenuates vascular calcification associated with CKD. We examined the role of Klotho in cardiac remodeling in models of Klotho deficiency-genetic Klotho hypomorphism, high dietary phosphate intake, aging, and CKD. Klotho-deficient mice exhibited cardiac dysfunction and hypertrophy before 12 weeks of age followed by fibrosis. In wild-type mice, the induction of CKD led to severe cardiovascular changes not observed in control mice. Notably, non-CKD mice fed a high-phosphate diet had lower Klotho levels and greatly accelerated cardiac remodeling associated with normal aging compared with those on a normal diet. Chronic elevation of circulating Klotho because of global overexpression alleviated the cardiac remodeling induced by either high-phosphate diet or CKD. Regardless of the cause of Klotho deficiency, the extent of cardiac hypertrophy and fibrosis correlated tightly with plasma phosphate concentration and inversely with plasma Klotho concentration, even when adjusted for all other covariables. High-fibroblast growth factor-23 concentration positively correlated with cardiac remodeling in a Klotho-deficient state but not a Klotho-replete state. In vitro, Klotho inhibited TGF-β1-, angiotensin II-, or high phosphate-induced fibrosis and abolished TGF-β1- or angiotensin II-induced hypertrophy of cardiomyocytes. In conclusion, Klotho deficiency is a novel intermediate mediator of pathologic cardiac remodeling, and fibroblast growth factor-23 may contribute to cardiac remodeling in concert with Klotho deficiency in CKD, phosphotoxicity, and aging.

AKIP1, a cardiac hypertrophy induced protein that stimulates cardiomyocyte growth via the Akt pathway

Cardiac adaptation to unremitting physiological stress typically involves hypertrophic growth of cardiomyocytes, a compensatory response that often fails and causes heart disease. Gene array analysis identified AKIP1 (A Kinase Interacting Protein 1) as a hypertrophic gene and we therefore hypothesized a potential role in the hypertrophic response. We show for the first time that both AKIP1 mRNA and protein levels increased in hypertrophic cardiomyocytes under conditions of sustained cardiac stress, including pressure overload and after myocardial infarction and in vitro in phenylephrine (PE) stimulated neonatal rat ventricular cardiomyocytes (NRVCs). AKIP1 overexpression in NRVCs markedly stimulated hypertrophic growth responses, including significantly increased cell size, augmented cytoskeletal organization and protein synthesis. Although, AKIP1 was not essential for PE induced hypertrophy in NRVCs, it did potentiate neurohormonal induced protein synthesis. AKIP1 did, however, not induce expression of pathological marker genes like ANP and β-MHC. ERK and Akt kinase signaling pathways have been linked to hypertrophy and AKIP1 specifically induced phosphorylation of Akt. This phosphorylation of Akt was essential for activation of ribosomal rpS6 and translation elongation factor eEF2 and this readily explains the increased protein synthesis. Akt inhibition fully blocked AKIP1 induced hypertrophy, showing that this pathway is critically involved. In conclusion, our results show that AKIP1 is induced in hypertrophic hearts and can stimulate adaptive cardiomyocyte growth, which involves Akt signaling.

Regression effect of hepatocyte nuclear factor 4α on liver cirrhosis in rats

OBJECTIVE

The aim of this study was to determine whether cirrhosis could be reversed after treated with hepatocyte nuclear factor 4α (HNF4α), a key transcriptional regulator of hepatocyte differentiation and function.

METHODS

Early and advanced stages of liver cirrhosis were induced by thioacetamide (TAA) administration. The adenovirus carrying HNF4α gene was injected into cirrhotic rats via the tail vein. The effect of HNF4α on cirrhosis was evaluated by histological and immunohistochemical examination.

RESULTS

Early stage of cirrhosis was remarkably resolved by HNF4α to a nearly-normal extent and advanced cirrhosis was partially ameliorated in vivo. The enforced expression of HNF4α downregulated profibrogenic factors remarkably including α-smooth muscle actin (α-SMA), transforming growth factor (TGF)-β1, fibroblast-specific protein (FSP)-1, collagen I and III. In vivo and in vitro studies revealed that HNF4α administration inhibited extracellular signal-regulated kinase (ERK) signaling pathway through the downregulation of phosphorated ERK and phosphorated JunD. In addition, HNF4α readjusted the balance between extracellular matrix deposition and degradation through the upregulation of matrix metalloproteinase and downregulation of its inhibitors. Moreover, HNF4α treatment inhibited angiogenesis as determined by CD31 and CD34 immunostaining.

CONCLUSIONS

Our findings broaden the knowledge on the reversibility of different stages of cirrhosis as HNF4α could present a promising alternative for the treatment of liver cirrhosis.

LOXL4 is induced by transforming growth factor β1 through Smad and JunB/Fra2 and contributes to vascular matrix remodeling

Transforming growth factor β1 (TGF-β1) is a pleiotropic factor involved in the regulation of extracellular matrix (ECM) synthesis and remodeling. In search for novel genes mediating the action of TGF-β1 on vascular ECM, we identified the member of the lysyl oxidase family of matrix-remodeling enzymes, lysyl oxidase-like 4 (LOXL4), as a direct target of TGF-β1 in aortic endothelial cells, and we dissected the molecular mechanism of its induction. Deletion mapping and mutagenesis analysis of the LOXL4 promoter demonstrated the absolute requirement of a distal enhancer containing an activator protein 1 (AP-1) site and a Smad binding element for TGF-β1 to induce LOXL4 expression. Functional cooperation between Smad proteins and the AP-1 complex composed of JunB/Fra2 accounted for the action of TGF-β1, which involved the extracellular signal-regulated kinase (ERK)-dependent phosphorylation of Fra2. We furthermore provide evidence that LOXL4 was extracellularly secreted and significantly contributed to ECM deposition and assembly. These results suggest that TGF-β1-dependent expression of LOXL4 plays a role in vascular ECM homeostasis, contributing to vascular processes associated with ECM remodeling and fibrosis.

Animal models of cardiorenal syndrome: a review

The incidence of heart failure and renal failure is increasing and is associated with poor prognosis. Moreover, these conditions do often coexist and this coexistence results in worsened outcome. Various mechanisms have been proposed as an explanation of this interrelation, including changes in hemodynamics, endothelial dysfunction, inflammation, activation of renin-angiotensin-aldosterone system, and/or sympathetic nervous system. However, the exact mechanisms initializing and maintaining this interaction are still unknown. In many experimental studies on cardiac or renal dysfunction, the function of the other organ was either not addressed or the authors failed to show any decline in its function despite histological changes. There are few studies in which the dysfunction of both heart and kidney function has been described. In this review, we discuss animal models of combined cardiorenal dysfunction. We show that translation of the results from animal studies is limited, and there is a need for new and better models of the cardiorenal interaction to improve our understanding of this syndrome. Finally, we propose several requirements that a new animal model should meet to serve as a tool for studies on the cardiorenal syndrome.

Cardiac remodeling during and after renin-angiotensin system stimulation in Cyp1a1-Ren2 transgenic rats

This study investigated renin-angiotensin system (RAS)-induced cardiac remodeling and its reversibility in the presence and absence of high blood pressure (BP) in Cyp1a1-Ren2 transgenic inducible hypertensive rats (IHR). In IHR (pro)renin levels and BP can be dose-dependently titrated by oral administration of indole-3-carbinol (I3C). Young (four-weeks old) and adult (30-weeks old) IHR were fed I3C for four weeks (leading to systolic BP >200 mmHg). RAS-stimulation was stopped and animals were followed-up for a consecutive period. Cardiac function and geometry was determined echocardiographically and the hearts were excised for molecular and immunohistochemical analyses. Echocardiographic studies revealed that four weeks of RAS-stimulation incited a cardiac remodeling process characterized by increased left ventricular (LV) wall thickness, decreased LV volumes, and shortening of the left ventricle. Hypertrophic genes were highly upregulated, whereas in substantial activation a fibrotic response was absent. Four weeks after withdrawal of I3C, (pro)renin levels were normalized in all IHR. While in adult IHR BP returned to normal, hypertension was sustained in young IHR. Despite the latter, myocardial hypertrophy was fully regressed in both young and adult IHR. We conclude that (pro)renin-induced severe hypertension in IHR causes an age-independent fully reversible myocardial concentric hypertrophic remodeling, despite a continued elevated BP in young IHR.

Suicidal erythrocyte death, eryptosis, as a novel mechanism in heart failure-associated anaemia

AIMS

Suicidal death of erythrocytes (eryptosis) is characterized by cell shrinkage and exposure of phosphatidylserine (PS) residues at the cell surface. Excessive eryptosis may lead to anaemia. We aimed to study the role of eryptosis in heart failure (HF)-associated anaemia.

METHODS AND RESULTS

We measured eryptosis in rodent models of HF. Typical measures of eryptosis including PS-exposure, increased intracellular Ca(2+) levels, and decreased cell volume were determined by flow cytometry. Transgenic REN2 rats displayed mild anaemia which was associated with a two-fold increase in erythrocyte PS-exposure when compared with Sprague Dawley (SD) control rats (P < 0.01). Upon stimulation with eryptotic triggers such as oxidative stress, hyperosmotic shock and energy depletion, eryptosis was more prominent in REN2 as shown by increased PS-exposure, cytosolic Ca(2+) influx, and cell shrinkage (P < 0.05 vs. SD). Increasing cytosolic Ca(2+) levels resulted in a stronger increase in PS-exposure in REN2 erythrocytes (P < 0.01 vs. SD). Accordingly, inhibition of Ca(2+) entry blunted the increased PS-exposure upon oxidative stress. The REN2 rats had significantly higher reticulocytes (REN2: 10.6 ± 2.3%; SD: 5.4 ± 0.1%; P < 0.05) and erythrocyte turnover was increased, indicated by increased clearance of eryptotic erythrocytes. Eryptosis was also increased in a rat model of hypertensive cardiac remodelling (uninephrectomized rats implanted with deoxycorticosterone acetate pellets), in mice after transverse aortic constriction, as well as in a small proof-of-concept study in human HF patients.

CONCLUSION

Eryptosis is increased during HF development and could contribute to HF-associated anaemia. Eryptosis may therefore become a novel target for therapy in HF-associated anaemia.

Genetic and pharmacological inhibition of galectin-3 prevents cardiac remodeling by interfering with myocardial fibrogenesis

BACKGROUND

Galectin-3 has been implicated in the development of organ fibrosis. It is unknown whether it is a relevant therapeutic target in cardiac remodeling and heart failure.

METHODS AND RESULTS

Galectin-3 knock-out and wild-type mice were subjected to angiotensin II infusion (2.5 µg/kg for 14 days) or transverse aortic constriction for 28 days to provoke cardiac remodeling. The efficacy of the galectin-3 inhibitor N-acetyllactosamine was evaluated in TGR(mREN2)27 (REN2) rats and in wild-type mice with the aim of reversing established cardiac remodeling after transverse aortic constriction. In wild-type mice, angiotensin II and transverse aortic constriction perturbations caused left-ventricular (LV) hypertrophy, decreased fractional shortening, and increased LV end-diastolic pressure and fibrosis (P<0.05 versus control wild type). Galectin-3 knock-out mice also developed LV hypertrophy but without LV dysfunction and fibrosis (P=NS). In REN2 rats, pharmacological inhibition of galectin-3 attenuated LV dysfunction and fibrosis. To elucidate the beneficial effects of galectin-3 inhibition on myocardial fibrogenesis, cultured fibroblasts were treated with galectin-3 in the absence or presence of galectin-3 inhibitor. Inhibition of galectin-3 was associated with a downregulation in collagen production (collagen I and III), collagen processing, cleavage, cross-linking, and deposition. Similar results were observed in REN2 rats. Inhibition of galectin-3 also attenuated the progression of cardiac remodeling in a long-term transverse aortic constriction mouse model.

CONCLUSIONS

Genetic disruption and pharmacological inhibition of galectin-3 attenuates cardiac fibrosis, LV dysfunction, and subsequent heart failure development. Drugs binding to galectin-3 may be potential therapeutic candidates for the prevention or reversal of heart failure with extensive fibrosis.

Atrial tachyarrhythmia in Rgs5-null mice

AIMS

The aim of this study was to elucidate the effects of regulator of G-protein signaling 5 (Rgs5), a negative regulator of G protein-mediated signaling, on atrial repolarization and tachyarrhythmia (ATA) in mice.

METHODS AND RESULTS

In present study, the incidence of ATA were increased in Rgs5(-/-) Langendorff-perfused mouse hearts during program electrical stimulation (PES) (46.7%, 7 of 15) and burst pacing (26.7%, 4 of 15) compared with wild-type (WT) mice (PES: 7.1%,1 of 14; burst:7.1%,1 of 14) (P<0.05). And the duration of ATA also shown longer in Rgs5(-/-) heart than that in WT, 2 out of 15 hearts exhibited sustained ATA (>30 s) but none of them observed in WT mice. Atrial prolonged repolarization was observed in Rgs5(-/-) hearts including widened P wave in surface ECG recording, increased action potential duration (APD) and atrial effective refractory periods (AERP), all of them showed significant difference with WT mice (P<0.05). At the cellular level, whole-cell patch clamp recorded markedly decreased densities of repolarizing K(+) currents including I(Kur) (at +60 mV: 14.0±2.2 pF/pA) and I(to) (at +60 mV: 16.7±1.3 pA/pF) in Rgs5(-/-) atrial cardiomyocytes, compared to those of WT mice (at +60 mV I(to): 20.4±2.0 pA/pF; I(kur): 17.9±2.0 pF/pA) (P<0.05).

CONCLUSION

These results suggest that Rgs5 is an important regulator of arrhythmogenesis in the mouse atrium and that the enhanced susceptibility to atrial tachyarrhythmias in Rgs5(-/-) mice may contribute to abnormalities of atrial repolarization.

Regulation of the (pro)renin-renin receptor in cardiac remodelling

The (pro)renin-renin receptor [(P)RR] was discovered as an important novel component of the renin-angiotensin system (RAS). The functional significance of (P)RR is widely studied in renal and vascular pathologies and has sparked interest for a potential role in cardiovascular disease. To investigate the role of (P)RR in cardiac pathophysiology, we aimed to assess (P)RR regulation in adverse cardiac remodelling of the failing heart. In particular, we evaluated the expression of (P)RR in different models of heart failure and across different species. Significantly increased levels of (P)RR mRNA were found in post-myocardial infarcted (MI) hearts of rats (1.6-fold, P < 0.05) and mice (5-fold, P < 0.01), as well as in transgenic rats with overexpression of the mouse renin gene (Ren2) (2.2-fold, P < 0.01). Moreover, we observed a strong increase of (P)RR expression in hearts of dilated cardiomyopathy (DCM) patients (5.3-fold, P < 0.001). Because none of the tested commercially available antibodies appeared to detect endogenous (P)RR, a (P)RR-specific polyclonal antibody was generated to study (P)RR protein levels. (P)RR protein levels were significantly increased in the post-MI rat heart (1.4-fold, P < 0.05) as compared to controls. Most interestingly in DCM patients, a significant 8.7-fold (P < 0.05) increase was observed. Thus, protein expression paralleled gene expression. These results demonstrate that (P)RR expression is strongly up-regulated both in rodent models of heart failure and in the failing human heart, hinting to a potential role for (P)RR in cardiac pathophysiology.

Angiotensin II-induced pro-fibrotic effects require p38MAPK activity and transforming growth factor beta 1 expression in skeletal muscle cells

Fibrotic disorders are typically characterised by excessive connective tissue and extracellular matrix (ECM) deposition that preclude the normal healing of different tissues. Several skeletal muscle dystrophies are characterised by extensive fibrosis. Among the factors involved in skeletal muscle fibrosis is angiotensin II (Ang-II), a key protein of the renin-angiotensin system (RAS). We previously demonstrated that myoblasts responded to Ang-II by increasing the ECM protein levels mediated by AT-1 receptors, implicating an Ang-II-induced reactive oxygen species (ROS) by a NAD(P)H oxidase-dependent mechanism. In this paper, we show that in myoblasts, Ang-II induced the increase of transforming growth factor beta 1 (TGF-β1) and connective tissue growth factor (CTGF) expression through its AT-1 receptor. This effect is dependent of the NAD(P)H oxidase (NOX)-induced ROS, as indicated by a decrease of the expression of both pro-fibrotic factors when the ROS production was inhibited via the NOX inhibitor apocynin. The increase in pro-fibrotic factors levels was paralleled by enhanced p38MAPK and ERK1/2 phosphorylation in response to Ang-II. However, only the p38MAPK activity was critical for the Ang-II-induced fibrotic effects, as indicated by the decrease in the Ang-II-induced TGF-β1 and CTGF expression and fibronectin levels by SB-203580, an inhibitor of the p38MAPK, but not by U0126, an inhibitor of ERK1/2 phosphorylation. Furthermore, we showed that the Ang-II-dependent p38MAPK activation, but not the ERK1/2 phosphorylation, was necessary for the NOX-derived ROS. In addition, we demonstrated that TGF-β1 expression was required for the Ang-II-induced pro-fibrotic effects evaluated by using SB-431542, an inhibitor of TGF-βRI kinase activity, and by knocking down TGF-β1 levels by shRNA technique. These results strongly suggest that the fibrotic response to Ang-II is mediated by the AT-1 receptor and requires the p38MAPK phosphorylation, NOX-induced ROS, and TGF-β1 expression increase mediated by Ang-II in skeletal muscle cells.

Oral administration of an angiotensin-converting enzyme 2 activator ameliorates diabetes-induced cardiac dysfunction

We evaluated the hypothesis that activation of endogenous angiotensin-converting enzyme (ACE) 2 would improve cardiac dysfunction induced by diabetes. Ten days after diabetes induction (streptozotocin, 50 mg/kg, i.v.), male Wistar rats were treated with the ACE2 activator 1-[[2-(dimethylamino)ethyl]amino]-4-(hydroxymethyl)-7-[[(4-methylphenyl)sulfonyl]oxy]-9H-xanthen-9-one (XNT, 1 mg/kg/day, gavage) or saline (control) for 30 days. Echocardiography was performed to analyze the cardiac function and kinetic fluorogenic assays were used to determine cardiac ACE and ACE2 activities. Cardiac ACE2, ACE, Mas receptor, AT(1) receptor, AT(2) receptor and collagen types I and III mRNA and ACE2, ACE, Mas, AT(1) receptor, AT(2) receptor, ERK1/2, Akt, AMPK-α and AMPK-β(1) protein were measured by qRT-PCR and western blotting techniques, respectively. Histological sections of hearts were analyzed to evaluate the presence of hypertrophy and fibrosis. Diabetic animals presented hyperglycemia and diastolic dysfunction along with cardiac hypertrophy and fibrosis. XNT treatment prevented further increase in glycemia and improved the cardiac function, as well as the hypertrophy and fibrosis. These effects were associated with increases in cardiac ACE2/ACE ratios (activity: ~26%; mRNA: ~113%; and protein: ~188%) and with a decrease in AT(1) receptor expression. Additionally, XNT inhibited ERK1/2 phosphorylation and prevented changes in AMPK-α and AMPK-β(1) expressions. XNT treatment did not induce any significant change in AT(2) receptor and Akt expression. These results indicate that activation of intrinsic cardiac ACE2 by oral XNT treatment protects the heart against diabetes-induced dysfunction through mechanisms involving ACE, ACE2, ERK1/2, AMPK-α and AMPK-β(1) modulations.

Transgenic overexpression of the adenine nucleotide translocase 1 protects cardiomyocytes against TGFβ1-induced apoptosis by stabilization of the mitochondrial permeability transition pore

AIMS

Since adenine nucleotide translocase 1 (ANT1) overexpression improved cardiac function in rats with activated renin-angiotensin system (RAS) and angiotensin II is known to enhance transforming growth factor β (TGFβ) signaling in cardiomyocytes, we assumed that ANT1 might modulate the classical TGFβ/SMAD pathway. We therefore investigated whether the cardioprotective effect of ANT1 overexpression suppresses TGFβ(1)-induced apoptosis, whether mitochondrial permeability transition pore (MPTP) regulation is involved, and SMAD signaling pathway is affected.

METHODS AND RESULTS

Ventricular cardiomyocytes isolated from wild-type (WT) and ANT1 transgenic rats were treated with the apoptosis-inducing agent TGFβ(1) (1 ng/ml). TGFβ(1) treatment of WT cells enhanced the number of apoptotic cells by 31.8 ± 11.7% (p<0.01 vs. WT) measured by chromatin condensation. Apoptosis was blocked by 1μM cyclosporine A and by ANT1 overexpression. The protecting effect of ANT1 overexpression on TGFβ(1)-induced apoptosis was verified by reduced caspase 3/7 activity and increased Bcl-2 expression. In addition, TGFβ(1) decreased mitochondrial membrane potential as measured by JC-1 staining by 18.0 ± 3.7% in WT cardiomyocytes, but only by 7.2 ± 2.8% (p<0.05 vs. WT) in ANT1 cardiomyocytes. Cyclosporine A also attenuated the decline in mitochondrial membrane potential under TGFβ(1) in WT cardiomyocytes. Determination of MPTP opening by Calcein assay in isolated cardiomyocytes and calcium retention assay in isolated mitochondria revealed a reduced open probability of MPTP after ANT1 overexpression. In addition to the effects of ANT1 on MPTP opening we investigated if ANT1 may interfere with the classical TGFβ signaling pathway. Interestingly, ANT1-transgenic cardiomyocytes expressed less TGFβ receptor II than WT cells. However, SMAD2 phosphorylation was already enhanced without TGFβ(1) stimulation in these cells. Although no additional increase in SMAD2 phosphorylation was detectable after TGFβ(1) treatment, SMAD signaling was still responsive to TGFβ(1) indicated by an upregulation of SMAD7, a TGFβ(1) target protein.

CONCLUSION

Heart-specific overexpression of ANT1 leads to a reduced apoptotic response to TGFβ(1) by preservation of the mitochondrial membrane potential, resistance to MPTP opening and altered TGFβ signaling.

Identification of hypertrophy- and heart failure-associated genes by combining in vitro and in vivo models

Heart failure (HF) is a complex disease involving multiple changes including cardiomyocyte hypertrophy (growth). Here we performed a set of screens in different HF and hypertrophy models to identify differentially expressed genes associated with HF and/or hypertrophy. Hypertensive Ren2 rats and animals with postmyocardial infarction (post-MI) HF were used as in vivo HF models, and neonatal rat cardiomyocytes treated with hypertrophy inducing hormones phenylephrine, endothelin-1, and isoproterenol were used as in vitro models. This combined approach revealed a robust set of genes that were differentially expressed both in vitro and in vivo. This included known genes like NPPA (ANP) and FHL1, but also novel genes not previously associated with hypertrophy/HF. Among these are PTGIS, AKIP1, and Dhrs7c, which could constitute interesting targets for further investigations. We also identified a number of in vivo specific genes and these appeared to be enriched for fibrosis, wounding, and stress responses. Therefore a number of novel genes within this in vivo specific list could be related to fibroblasts or other noncardiomyocytes present in the heart. We also observed strong differences between the two HF rat models. For example KCNE1 was strongly upregulated in Ren2, but not in post-MI HF rats, suggesting possible etiology-specific differences. Moreover, Gene Ontology analysis revealed that genes involved in fatty acid oxidation were specifically down regulated in the post-MI group only. Together these results show that combining multiple models, both in vivo and in vitro, can provide a robust set of hypertrophy/HF-associated genes. Moreover it provides insight in the differences between the different etiology models and neurohormonal effects.

Renal effects of long-term darbepoetin alpha treatment in hypertensive TGR(mRen2)27 rats

INTRODUCTION

Erytropoietin (EPO) has cytoprotective and angiogenic properties and has a beneficial effect in ischaemic conditions. Since the development of renal interstitial abnormalities are often associated with ischaemia, we studied the effects of the long-acting EPO analogue darbepoetin alpha (DA) on kidney damage in TGR(mRen2)27 (Ren2) rats.

MATERIALS AND METHODS

Ren2 rats were randomised to DA or vehicle (VEH) or to DA + angiotensin converting enzyme inhibitor (ACEi) or VEH + ACEi. Sprague Dawley (SD) rats served as controls. Blood pressure was measured weekly and 24-h urine was collected to measure proteinuria. Blood samples were collected for creatinine and haematocrit. Kidneys were studied for inflammation and pre-fibrosis. Renal mRNA expression was studied for EPO, EPO-receptor, collagen-3α1 and kidney injury molecule-1 (KIM-1).

RESULTS

DA had no effect on SBP, serum creatinine and proteinuria. Interstitial and glomerular α-SMA expression was significantly increased in Ren2. ACEi but not DA improved the increased renal inflammatory and pro-fibrotic profile in Ren2 rats. DA on top of ACEi further reduced glomerular α-SMA and KIM-1 expression.

CONCLUSION

Long-term DA treatment has no beneficial effects on renal structural and functional changes in TGR(mRen2)27 rats in the time frame studied and the dose provided.

DHRS7c, a novel cardiomyocyte-expressed gene that is down-regulated by adrenergic stimulation and in heart failure

AIMS

Although cardiac diseases account for the highest mortality and morbidity rates in Western society, there is still a considerable gap in our knowledge of genes that contribute to cardiac (dys)function. Here we screened for gene expression profiles correlated to heart failure.

METHODS AND RESULTS

By expression profiling we identified a novel gene, termed DHRS7c, which was significantly down-regulated by adrenergic stimulation and in heart failure models. Dhrs7c is a short chain dehydrogenase/reductase (SDR) and is localized to the endo/sarcoplasmic reticulum. Dhrs7c is strongly conserved in vertebrates, and mRNA and protein expression levels were highest in heart and skeletal muscle followed by skin, but were not detectable in other organs. In vitro, both α- and β-adrenergic stimulation repressed Dhrs7c expression in neonatal cardiomyocytes and this could be mimicked by the direct activation of protein kinase C and adenylate cyclase, the respective intracellular targets of these hormones. In contrast, endothelin-1, which also provoked strong hypertrophy development in vitro, did not repress Dhrs7c expression. The latter suggests adrenergic specificity and indicates that down-regulation is not a prerequisite for hypertrophy development. In vivo adrenergic stimulation could also down-regulate Dhrs7c expression. Finally, we confirmed that expression was also down-regulated in two different models of failure and, importantly, also in biopsies from human heart failure patients.

CONCLUSION

Our results show that the expression of Dhrs7c, a novel endo/sarcoplasmic reticulum-localized SDR, is inversely correlated with adrenergic stimulation and heart failure development.

Metformin improves cardiac function in a nondiabetic rat model of post-MI heart failure

Metformin is the first choice drug for the treatment of patients with diabetes, but its use is debated in patients with advanced cardiorenal disease. Epidemiological data suggest that metformin may reduce cardiac events, in patients both with and without heart failure. Experimental evidence suggests that metformin reduces cardiac ischemia-reperfusion injury. It is unknown whether metformin improves cardiac function (remodeling) in a long-term post-MI remodeling model. We therefore studied male, nondiabetic, Sprague-Dawley rats that were subjected to either myocardial infarction (MI) or sham operation. Animals were randomly allocated to treatment with normal water or metformin-containing water (250 mg·kg(-1)·day(-1)). At baseline, 6 wk, and 12 wk, metabolic parameters were analyzed and oral glucose tolerance tests (OGTT) were performed. Echocardiography and hemodynamic parameters were assessed 12 wk after MI. In the MI model, infarct size was significantly smaller after 12-wk metformin treatment (29.6 ± 3.2 vs. 38.0 ± 2.2%, P < 0.05). Moreover, metformin resulted in less left ventricular dilatation (6.0 ± 0.4 vs. 7.6 ± 0.6 mm, P < 0.05) and preservation of left ventricular ejection fraction (65.8 ± 3.7% vs. 48.6 ± 5.6%, P < 0.05) compared with MI control. The improved cardiac function was associated with decreased atrial natriuretic peptide mRNA levels in the metformin-treated group (50% reduction compared with MI, P < 0.05). Insulin resistance did not occur during cardiac remodeling (as indicated by normal OGTT) and fasting glucose levels and the pattern of the OGTT were not affected by metformin. Molecular analyses suggested that altered AMP kinase phosphorylation status and low insulin levels mediate the salutary effects of metformin. Altogether our results indicate that metformin may have potential to attenuate heart failure development after myocardial infarction, in the absence of diabetes and independent of systemic glucose levels.

Urotensin-2 promotes collagen synthesis via ERK1/2-dependent and ERK1/2-independent TGF-β1 in neonatal cardiac fibroblasts

U2 (urotensin-2) is the most potent vasoconstrictor in mammals which is involved in cardiac remodelling, including cardiac hypertrophy and cardiac fibrosis. Although the cellular mechanisms of the U2-induced vasoconstriction have been extensively studied, the signalling pathways involved in U2-induced TGF-β1 (transforming growth factor-β1) expression and collagen synthesis remain unclear. In this study, we show that U2 promoted collagen synthesis and ERK1/2 (extracellular signal-regulated kinase 1/2) activation in neonatal cardiac fibroblasts. The U2-induced collagen synthesis and TGF-β1 production were significantly but not completely inhibited by blocking ERK1/2. Both ERK1/2 inhibitor and TGF-β1 antibody could separately inhibit U2-induced collagen synthesis, and the synergistic inhibition effect was observed by blocking ERK1/2 and TGF-β1 simultaneously. These data suggest that U2 promotes collagen synthesis via ERK1/2-dependent and independent TGF-β1 pathway in neonatal cardiac fibroblasts.

Heart failure-associated anemia: bone marrow dysfunction and response to erythropoietin

Heart failure (HF)-associated anemia is common and has a poor outcome. Because bone marrow (BM) dysfunction may contribute to HF-associated anemia, we first investigated mechanisms of BM dysfunction in an established model of HF, the transgenic REN2 rat, which is characterized by severe hypertrophy and ventricular dilatation and SD rats as controls. Secondly, we investigated whether stimulation of hematopoiesis with erythropoietin (EPO) could restore anemia and BM dysfunction. After sacrifice, erythropoietic precursors (BFU-E) were isolated from the BM and cultured for 10 days. BFU-E were quantified and transcript abundance of genes involved in erythropoiesis were assayed. Number of BFU-E were severely decreased in BM of REN2 rats compared to SD rats (50 ± 6.2 vs. 6.4 ± 1.7, p < 0.01). EPO treatment increased hematocrit in the SD-EPO group (after 6 weeks, 49 ± 1 vs. 58 ± 1%, p < 0.01); however, in the mildly anemic REN2 rats, there was no effect (43 ± 1 vs. 44 ± 1%). This was paralleled by a 67% decrease in BFU-E in BM of REN2 rats compared to SD (p < 0.01). EPO significantly improved BFU-E in both SD and REN2 but could not restore this to control levels in the REN2 rats. Expression of several genes involved in differentiation (LMO2), mobilization (SDF-1), and iron incorporation (transferrin receptor) of the BM were differentially expressed in REN2 rats compared to SD rats, and EPO did not normalize this. Altogether, these results suggest that BM dysfunction is an important contributor to HF-associated anemia and that EPO is not an effective agent to treat HF-associated anemia.

Atrial fibrillation induces myocardial fibrosis through angiotensin II type 1 receptor-specific Arkadia-mediated downregulation of Smad7

RATIONALE

Tachycardia-induced atrial fibrosis is a hallmark of structural remodeling of atrial fibrillation (AF). The molecular mechanisms underlying the AF-induced atrial fibrosis remain unclear.

OBJECTIVE

To determine the role of angiotensin II (Ang II)/Ang II type 1 (AT(1)) receptor-coupled transforming growth factor (TGF)-β(1)/Smad signaling pathway in the AF-induced atrial fibrosis.

METHODS AND RESULTS

Rapid atrial pacing (1000 ppm) was applied to the left atrium of rabbit heart to induce atrial fibrillation and fibrosis. Quantitative PCR and Western blot analysis revealed that rapid atrial pacing caused a marked increase in the expression of Ang II, TGF-β(1), phosphorylated Smad2/3 (P-Smad2/3), Arkadia, and hydroxyproline synthesis. However, the expression of Smad7, a key endogenous antagonist of the TGF-β(1)/Smad-mediated fibrosis, was significantly decreased. These changes were dose-dependently reversed by AT(1) receptor antagonist losartan, implicating the involvement of AF-induced release of Ang II and activation of AT(1) receptor-specific pathway. In the adult rabbit cardiac fibroblasts, Ang II increased the expression of TGF-β(1), P-Smad2/3, Smad4, Arkadia, and collagen I synthesis and significantly reduced Smad7 expression. These effects of Ang II were reversed by losartan but not by the AT(2) antagonist (PD123319). In addition, extracellular signal-regulated kinase inhibitor and anti-TGF-β(1) antibody also blocked the Ang II-induced downregulation of Smad7. Silencing of Smad7 gene by small interfering RNA abolished the antagonism of losartan on the fibrogenic effects of Ang II on cardiac fibroblasts, whereas overexpression of Smad7 blocked Ang II-induced increase in collagen I synthesis.

CONCLUSIONS

Ang II/AT(1) receptor-specific activation of Arkadia-mediated poly-ubiquitination and degradation of Smad7 may decrease the inhibitory feedback regulation of TGF-β(1)/Smad signaling and serves as a key mechanism for AF-induced atrial fibrosis.

Galectin-3 in cardiac remodeling and heart failure

Galectin-3 is a member of the galectin family, which consists of animal lectins that bind β-galactosides. Recently, a role for galectin-3 in the pathophysiology of heart failure has been suggested. It was observed that galectin-3 is specifically upregulated in decompensated heart failure compared with compensated heart failure in animal models of heart failure. This has been associated with activation of fibroblasts and macrophages, which are a hallmark of cardiac remodeling. Therefore, galectin-3 may be a culprit biomarker in heart failure. Initial clinical observations indicate that galectin-3 may be a useful biomarker for decompensated heart failure, with incremental value over well-used “pressure-dependent” biomarkers, such as B-type natriuretic peptide. Future studies should focus on galectin-3 biology to better address the usefulness of galectin-3 as a biomarker and probe the usefulness of anti-galectin-3 therapy in treating heart failure.

Syndecan-1 amplifies angiotensin II-induced cardiac fibrosis

Syndecan-1 (Synd1) is a transmembrane heparan sulfate proteoglycan that functions as a coreceptor for various growth factors and modulates signal transduction. The present study investigated whether Synd1, by affecting growth factor signaling, may play a role in hypertension-induced cardiac fibrosis and dysfunction. Expression of Synd1 was increased significantly in mouse hearts with angiotensin II-induced hypertension, which was spatially related to cardiac fibrosis. Angiotensin II significantly impaired fractional shortening and induced cardiac fibrosis in wild-type mice, whereas these effects were blunted in Synd1-null mice. Angiotensin II significantly increased cardiac expression of connective tissue growth factor and collagen type I and III in wild-type mice, which was blunted in Synd1-null mice. These findings were confirmed in vitro, where angiotensin II induced the expression of both connective tissue growth factor and collagen I in fibroblasts. The absence of Synd1 in either Synd1-null fibroblasts, after knockdown of Synd1 by short hairpin RNA, or after inhibition of heparan sulfates by protamine attenuated this increase, which was associated with reduced phosphorylation of Smad2. In conclusion, loss of Synd1 reduces cardiac fibrosis and dysfunction during angiotensin II-induced hypertension.

Inhibition of extracellular signal-regulated kinase 1 by adenovirus mediated small interfering RNA attenuates hepatic fibrosis in rats

Extracellular signal-regulated kinase 1 (ERK1) is a critical part of the mitogen-activated protein kinase signal transduction pathway, which is involved in hepatic fibrosis. However, the effect of down-regulation of ERK1 on hepatic fibrosis has not been reported. Here, we induced hepatic fibrosis in rats with dimethylnitrosamine administration or bile duct ligation. An adenovirus carrying small interfering RNA targeting ERK1 (AdshERK1) was constructed to determine its effect on hepatic fibrosis, as evaluated by histological and immunohistochemical examination. Our results demonstrated that AdshERK1 significantly reduced the expression of ERK1 and suppressed proliferation and levels of fibrosis-related genes in hepatic stellate cells in vitro. More importantly, selective inhibition of ERK1 remarkably attenuated the deposition of the extracellular matrix in fibrotic liver in both fibrosis models. In addition, both hepatocytes and biliary epithelial cells were proven to exert the ability to generate the myofibroblasts depending on the insults of the liver, which were remarkably reduced by AdshERK1. Furthermore, up-regulation of ERK1 paralleled the increased expression of transforming growth factor beta1 (TGF-beta1), vimentin, snail, platelet-derived growth factor-BB (PDGF-BB), bone morphogenetic protein 4 (BMP4), and small mothers against decapentaplegic-1 (p-Smad1), and was in reverse correlation with E-cadherin in the fibrotic liver. Nevertheless, inhibition of ERK1 resulted in the increased level of E-cadherin in parallel with suppression of TGF-beta1, vimentin, snail, PDGF-BB, BMP4, and p-Smad1. Interestingly, AdshERK1 treatment promoted hepatocellular proliferation.

CONCLUSION

Our study provides the first evidence for AdshERK1 suppression of hepatic fibrosis through the reversal of epithelial-mesenchymal transition of both hepatocytes and biliary epithelial cells without interference of hepatocellular proliferation. This suggests that ERK1 is implicated in hepatic fibrogenesis and selective inhibition of ERK1 by small interfering RNA may present a novel option for hepatic fibrosis treatment.

Galectin-3: a novel mediator of heart failure development and progression

Galectins are a family of soluble beta-galactoside-binding lectins that play many important regulatory roles in inflammation, immunity, and cancer. Recently, a role for galectin-3 in the pathophysiology of heart failure (HF) has been suggested. Numerous studies have demonstrated the up-regulation of galectin-3 in hypertrophied hearts, its stimulatory effect on macrophage migration, fibroblast proliferation, and the development of fibrosis. The latter observation is particularly relevant as cardiac remodelling is an important determinant of the clinical outcome of HF and is linked to disease progression and poor prognosis. Because galectin-3 expression is maximal at peak fibrosis and virtually absent after recovery, routine measurement in patients with HF may prove valuable to identify those patients at highest risk for readmission or death, thus enabling physicians to tailor the level of care to individual patient needs. This review summarizes the most recent advances in galectin-3 research, with an emphasis on the role galectin-3 plays in the development and progression of HF.

SMAD-proteins as a molecular switch from hypertrophy to apoptosis induction in adult ventricular cardiomyocytes

Heart failure development goes along with a transition from hypertrophic growth to apoptosis induction. In adult cardiomyocytes SMAD proteins are only activated under apoptotic, but not under hypertrophic conditions and are increased at the transition to heart failure. Therefore, SMADs could be candidates that turn the balance from hypertrophic growth to apoptosis resulting in heart failure development. To test this hypothesis we infected isolated rat ventricular cardiomyocytes with adenovirus encoding SMAD4 (AdSMAD4) and investigated the impact of SMAD4 overexpression on the development of apoptosis and hypertrophy under stimulation with phenylephrine (PE). Infection of cardiomyocytes with AdSMAD4 significantly enhanced SMAD-binding activity while apoptosis after 24 and 36 h infection did not rise. But when SMAD4 overexpressing cardiomyocytes were incubated with PE (10 microM), the number of apoptotic cells increased (Ctrl: 94.97 +/- 6.91%; PE: 102.48 +/- 4.78% vs. AdSMAD4 + PE: 118.64 +/- 3.28%). Furthermore expression of caspase 3 as well as bax/bcl2 ratio increased in SMAD4 overexpressing, PE-stimulated cardiomyocytes. In addition, the effects of SMAD4 overexpression on PE-induced hypertrophic growth were analyzed. Protein synthesis 36 h after AdSMAD4 infection was comparable to control cells, whereas the increase in protein synthesis stimulated by phyenylephrine was significantly reduced in SMAD4 overexpressing cells (134.28 +/- 10.02% vs. 100.57 +/- 8.86%). SMAD4 triggers the transition from hypertrophy to apoptosis in ventricular cardiomyocytes. Since SMADs are increased under several pathophysiological conditions in the heart, it can be assumed that it triggers apoptosis induction and therefore contributes to negative remodeling and heart failure progression.

Effect of renin inhibition and AT1R blockade on myocardial remodeling in the transgenic Ren2 rat

Angiotensin II (Ang II) stimulation of the Ang type 1 receptor (AT(1)R) facilitates myocardial remodeling through NADPH oxidase-mediated generation of oxidative stress. Components of the renin-angiotensin system constitute an autocrine/paracrine unit in the myocardium, including renin, which is the rate-limiting step in the generation of Ang II. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo renin inhibition and/or AT(1)R blockade in a rodent model of chronically elevated tissue Ang II levels, the transgenic (mRen2)27 rat (Ren2). The Ren2 overexpresses the mouse renin transgene with resultant hypertension, insulin resistance, and cardiovascular damage. Young (6- to 7-wk-old) heterozygous (+/-) male Ren2 and age-matched Sprague-Dawley rats were treated with the renin inhibitor aliskiren, which has high preferential affinity for human and mouse renin, an AT(1)R blocker, irbesartan, or placebo for 3 wk. Myocardial NADPH oxidase activity and immunostaining for NADPH oxidase subunits and 3-nitrotyrosine were evaluated and remodeling changes assessed by light and transmission electron microscopy. Blood pressure, myocardial NADPH oxidase activity and subunit immunostaining, 3-nitrotyrosine, perivascular fibrosis, mitochondrial content, and markers of activity were significantly increased in Ren2 compared with SD littermates. Both renin inhibition and blockade of the AT(1)R significantly attenuated cardiac functional and structural alterations, although irbesartan treatment resulted in greater reductions of both blood pressure and markers of oxidative stress. Collectively, these data suggest that both reduce changes driven, in part, by Ang II-mediated increases in NADPH oxidase and, in part, increases in blood pressure.

Angiotensin II-mediated oxidative stress promotes myocardial tissue remodeling in the transgenic (mRen2) 27 Ren2 rat

Angiotensin II (ANG II) contributes to cardiac remodeling, hypertrophy, and left ventricular dysfunction. ANG II stimulation of the ANG type 1 receptor (AT(1)R) generates reactive oxygen species via NADPH oxidase, which facilitates this hypertrophy and remodeling. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo AT(1)R blockade (AT(1)B) (valsartan) or superoxide dismutase/catalase mimetic (tempol) treatment in a rodent model of chronically elevated tissue levels of ANG II, the transgenic (mRen2) 27 rat (Ren2). Ren2 rats overexpress the mouse renin transgene with resultant hypertension, insulin resistance, proteinuria, and cardiovascular damage. Young (6-7 wk old) male Ren2 and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Heart tissue NADPH oxidase (NOX) activity and immunohistochemical analysis of subunits NOX2, Rac1, and p22(phox), heart tissue malondialdehyde, and insulin-stimulated protein kinase B (Akt) activation were measured. Structural changes were assessed with cine MRI, transmission electron microscopy, and light microscopy. Increases in septal wall thickness and altered systolic function (cine MRI) were associated with perivascular fibrosis and increased mitochondria in Ren2 on light and transmission electron microscopy (P < 0.05). AT(1)B, but not tempol, reduced blood pressure (P < 0.05); significant improvements were seen with both AT(1)B and tempol on NOX activity, subunit expression, malondialdehyde, and insulin-mediated activation/phosphorylation of Akt (each P < 0.05). Collectively, these data suggest cardiac oxidative stress-induced structural and functional changes are driven, in part, by AT(1)R-mediated increases in NADPH oxidase activity.

Rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitor, decreases cardiac oxidative stress and remodeling in Ren2 transgenic rats

Angiotensin-II (Ang-II)-stimulated increases in nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase activity and oxidative stress are known to play a key role in cardiac remodeling. Inhibition of isoprenylation and activation of small G proteins, such as Rac1, a component of NADPH oxidase, may mediate the antioxidant actions of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). In this study, we investigated the effects of rosuvastatin on cardiac oxidative stress and remodeling in transgenic rats (Ren2) overexpressing the mouse renin gene with elevated cardiac levels of Ang-II. We treated 6- to 7-wk-old Ren2 rats and age-matched Sprague-Dawley (SD) rats with rosuvastatin (10 mg/kg.d) or vehicle for 3 wk. At the end of the treatment period, left ventricular mass, wall thickness, ejection fraction (by echocardiography), and cardiac remodeling (by light microscopy and immunohistochemistry) were assessed. In addition, myocardial content of nitrotyrosine, malondialdehyde, NADPH-oxidase subunits (gp91(phox), p40(phox), and p22(phox)), and Rac1 were analyzed by immunochemistry. Systolic blood pressure was significantly higher in Ren2 rats, compared with SD rats (P < 0.05); rosuvastatin had no significant effect on systolic blood pressure in either group. In Ren2, but not SD rats, rosuvastatin significantly improved the ventricular ejection fraction, cardiac hypertrophy, and perivascular fibrosis (P < 0.05). In addition, rosuvastatin administration significantly decreased the accentuated myocardial gp91(phox), p40(phox), p22(phox), and Rac1 expression. These changes were accompanied by a parallel reduction in myocardial lipid peroxidation (nitrotyrosine and malondialdehyde content) (P < 0.05). These results suggest that in vivo statin treatment through its direct actions on the heart reduces oxidative stress and remodeling including ventricular mass regression in the Ang-II-dependent Ren2 model.

p38 Mitogen-Activated Protein Kinase Inhibition Ameliorates Angiotensin II–Induced Target Organ Damage

We investigated whether or not p38 mitogen-activated protein kinase inhibition ameliorates angiotensin II–induced target organ damage. We used double transgenic rats harboring both human renin and angiotensinogen genes (dTGRs). dTGR, with or without p38 inhibitor (BIRB796; 30 mg/kg per day in the diet), and nontransgenic Sprague–Dawley rats were studied in 2 protocols. In protocol 1 (week 7), systolic blood pressure of untreated dTGRs was 204±4 mm Hg, but partially reduced after BIRB796 treatment (166±7 mm Hg), whereas Sprague–Dawley rats were normotensive. The cardiac hypertrophy index was unchanged in untreated and BIRB796-treated dTGRs. The β-myosin heavy chain expression of BIRB796-treated hearts was significantly lower in BIRB796 compared with dTGRs, indicating a delayed switch to the fetal isoform. BIRB796 treatment significantly reduced cardiac fibrosis, connective tissue growth factor, tumor necrosis factor-α, interleukin-6, and macrophage infiltration. Albuminuria was not reduced in BIRB796-treated dTGRs. Tubular and glomerular damage with tumor necrosis factor-α expression was unaltered, although serum creatinine and cystatin C were normalized. Renal macrophage infiltration, fibrosis, and vessel damage were reduced. In protocol 2 (week 8), we focused on mortality and arrhythmogenic electrical remodeling. Mortality of untreated dTGRs was 100% but was reduced to 10% in the BIRB796 group. Cardiac magnetic field mapping showed prolongation of depolarization and repolarization in untreated dTGRs compared with Sprague–Dawley rats with a partial reduction by BIRB796. Programmed electrical stimulation elicited ventricular tachycardias in 81% of untreated dTGRs but only in 48% of BIRB796-treated dTGRs. In conclusion, BIRB796 improved survival, target organ damage, and arrhythmogenic potential in angiotensin II–induced target organ damage.

Rodent models of heart failure

Heart failure, a complex disorder with heterogeneous aetiologies remains one of the most threatening diseases known. It is a clinical syndrome attributable to a multitude of factors that begins with the compensatory response known as hypertrophy, followed by a decompensated state that finally results in heart failure. Given the lack of a unified theory of heart failure, future research efforts are required to unify and synthesize our current understanding of the multiple mechanisms that control remodelling in heart under various stress conditions. During the past few decades, use of animal models has provided new insights into the complex pathogenesis of this syndrome. Rodents have contributed significantly in the understanding of the pathogenesis and progression of heart failure. With the advent of the transgenic era, rodent models have revolutionized preclinical research associated with heart failure. These models combined with physiological measurements of cardiac hemodynamics, are expected to yield more valuable information regarding the molecular mechanisms of heart failure and aid in the discovery of novel therapeutic targets. However, all animal models used have advantages and limitations, and the issues determining transfer from preclinical to clinical require critical evaluation. The present review focuses upon rodent models of heart failure.

Decorin-mediated Transforming Growth Factor-β Inhibition Ameliorates Adverse Cardiac Remodeling

BACKGROUND

Implantation of a left ventricular assist device (LVAD) has been shown to induce regression of fibrosis in patients with congestive heart failure (CHF) and improve myocardial function. The mechanism of reverse remodeling after mechanical circulatory support (MCS), however, has not been fully characterized. In this study we examined the anti-fibrotic effects of decorin, an extracellular matrix (ECM) proteoglycan, on the transforming growth factor-beta (TGF-beta) pathway.

METHODS

Human myocardial tissue samples were obtained from patients undergoing LVAD implantation and again following subsequent transplantation after a sustained period of MCS. The specimens were examined by utilizing different molecular and histologic techniques, including human cardiac fibroblast in vitro studies. We assessed gene expression, mRNA and protein levels.

RESULTS

We found a significant decrease in interstitial fibrosis after MCS, with a decrease in collagen mRNA transcription rates, serving as an indirect measurement of collagen synthesis. Both the mRNA and protein levels of decorin were significantly increased after a period of MCS. Decorin mRNA was up-regulated by 44% after MCS (p < 0.01), which paralleled the increase in interstitial decorin deposition (p < 0.001). In addition, p-SMAD2, a molecular marker downstream of the TGF-beta pathway, was found to be inactivated after MCS (p < 0.02). Moreover, cultured human cardiac fibroblasts exposed to TGF-beta demonstrated decreased collagen production when exogenous decorin was added (p < 0.03).

CONCLUSIONS

The decorin molecule is potentially involved in reverse cardiac remodeling, by directly inhibiting the TGF-beta pathway and its pro-fibrotic effects on the failing human heart.

Induction of kidney injury molecule-1 in homozygous Ren2 rats is attenuated by blockade of the renin-angiotensin system or p38 MAP kinase

Kidney injury molecule-1 (Kim-1) is associated with ischemic and proteinuric tubular injury; however, whether dysregulation of the renin-angiotensin system (RAS) can also induce Kim-1 is unknown. We studied Kim-1 expression in homozygous Ren2 rats, characterized by renal damage through excessive RAS activation. We also investigated whether antifibrotic treatment (RAS blockade or p38 MAP kinase inhibition) would affect Kim-1 expression. At 7 wk of age, homozygous Ren2 rats received a nonhypotensive dose of candesartan (0.05 mg x kg(-1) x day(-1) sc) or the p38 inhibitor SB-239063 (15 mg x kg(-1) x day(-1) sc) for 4 wk; untreated Ren2 and Sprague-Dawley (SD) rats served as controls. Kim-1 mRNA and protein expression were determined by quantitative PCR and immunohistochemistry, respectively, and related to markers of prefibrotic renal damage. Urinary Kim-1 was measured in 8-wk-old Ren2 and SD rats with and without angiotensin-converting enzyme inhibition (ramipril, 1 mg x kg(-1) x day(-1) in drinking water for 4 wk). Untreated Ren2 rats showed a >20-fold increase in renal Kim-1 mRNA (expressed as Kim-1-to-GAPDH ratio): 75.5 +/- 43.6 vs. 3.1 +/- 1.0 in SD rats (P < 0.01). Candesartan and SB-239063 strongly reduced Kim-1 mRNA: 3.1 +/- 1.5 (P < 0.01) and 9.8 +/- 4.2 (P < 0.05), respectively. Kim-1 protein expression in damaged tubules paralleled mRNA expression. Kim-1 expression correlated with renal osteopontin, alpha-smooth muscle actin, and collagen III expression and with tubulointerstitial fibrosis. Damaged tubular segments expressing activated p38 also expressed Kim-1. Urinary Kim-1 was increased in Ren2 vs. SD (458 +/- 70 vs. 27 +/- 2 pg/ml, P < 0.01) rats and abolished in Ren2 rats treated with ramipril (33 +/- 5 pg/ml, P < 0.01). Kim-1 is associated with development of RAS-mediated renal damage. Antifibrotic treatment through RAS blockade or p38 MAP kinase inhibition reduced Kim-1 in the homozygous Ren2 model.

Imatinib Attenuates End-Organ Damage in Hypertensive Homozygous TGR(mRen2)27 Rats

Imatinib specifically inhibits receptor tyrosine kinase signaling and is clinically used to treat leukemia. Receptor tyrosine kinases not only mediate tumor growth but also initiate adverse signaling in heart failure. We investigated whether imatinib, by inhibiting the platelet-derived growth factor receptor-beta (PDGFRbeta), prevents cardiac and renal damage in TGR(mRen2)27 (Ren2) rats. Eight-week-old male homozygous Ren2 and Sprague Dawley rats were treated either with imatinib (30 mg/kg; STI-571) or placebo for 8 weeks (Ren2 n=12 for each group; Sprague Dawley n=6 for each group). Imatinib did not affect blood pressure or left ventricular (LV) hypertrophy in both groups. Imatinib attenuated the decline in fractional shortening (imatinib versus Ren2 placebo 45+/-4.5% versus 32+/-3%; n=7-11; P<0.05) and in diastolic function in Ren2 rats (baseline diastolic dP/dt corrected for systolic blood pressure Ren2 imatinib versus Ren2 placebo 38.6+/-0.67 versus 35.3+/-0.41 [1 . s(-1)]; n=7-11; P<0.05). This was associated with decreased cardiac fibrosis and decreased activation of PDGFRbeta and extracellular signal-regulated kinase 1/2. Renal microvascular hypertrophy and perivascular fibrosis in Ren2 rats were significantly decreased by imatinib. In vitro, imatinib blocked angiotensin II-induced activation of the PDGFRbeta and significantly decreased fibroblast proliferation and collagen production. In conclusion, imatinib did not affect LV hypertrophy but attenuated the decline in cardiac function and reduced renal microvascular damage associated with reduced activation of the PDGFRbeta. The simultaneous improvement in both heart and kidneys suggests that inhibition of the PDGFRbeta has broad protective effects that may provide novel avenues for a blood pressure-independent protection against end-organ damage.