Human Congestive Heart Failure Research Articles

Invited Commentary

Mitral annuloplasty ring dehiscence may occur in 1% to 10% of all mitral surgeries, but can have severe and potentially fatal consequences when it does. In this issue of The Annals, Pierce and colleagues [1Pierce E.L. Siefert A.W. Paul D.M. et al.How local annular force and collagen density govern mitral annuloplasty ring dehiscence risk.Ann Thorac Surg. 2016; 102: 518-526Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar] examine the mechanisms underlying mitral annuloplasty ring dehiscence. In this manuscript, “How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence Risk,” Pierce and colleagues examine causative factors governing mitral annular ring suture dehiscence in a sheep model. Possible mechanisms contributing to dehiscence such as cyclic force, loading, annular flexion, and left ventricular pressures, among others, were quantified and correlated with relative collagen density differences at multiple points around the mitral ovine annulus. From this data, a propensity for mitral annular suture pull out and force margins of safety was developed. The results showed that the anterior annular holding strength exceeded posterior annular holding strength and that the overall pullout force required exhibited a strong correlation to local collagen density. Surprisingly, trigonal sutures were less secure (less resistant to pullout) than would have been predicted or thought by the authors, due to a combination of reduced collagen in the trigonal area and higher overall annular rigidity. This goes against popular belief that the trigones are the most secure area. This finding reinforces their finding that the inter-trigonal anterior annular tissue may be a superior anchor for a mitral annular ring. This fact may help guide clinicians in selection of type of ring (complete versus partial) and for future rings and mitral prostheses. Furthermore, this manuscript is also important as it brings up more questions to be considered. For example, ring dehiscence appears to be more common in the tricuspid annular position than mitral. What are the corresponding pullout forces in the tricuspid position? Are there significant differences between the ovine and the human annulus? What happens to pullout force when the annulus is overdistended and dilated, as is often seen in human congestive heart failure. All of these questions should be examined carefully as our field moves forward to possible percutaneous therapy for mitral and tricuspid disease. Data such as in the present manuscript will help with the technology of percutaneous implantations of mitral and tricuspid rings when annular ring implantation technique no longer includes direct visualization. The scientific quantitation of long-held popular beliefs in cardiac surgery is well warranted. The questioning and validation or abandonment of our standard practice should be a continual quality process. It is in this manner that we will best serve our future mitral patients. How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence RiskThe Annals of Thoracic SurgeryVol. 102Issue 2PreviewAnnuloplasty ring dehiscence is a well described mode of mitral valve repair failure. Defining the mechanisms underlying dehiscence may facilitate its prevention. Full-Text PDF

Inverse Correlation between Heart Rate Variability and Heart Rate Demonstrated by Linear and Nonlinear Analysis

The dynamical fluctuations in the rhythms of biological systems provide valuable information about the underlying functioning of these systems. During the past few decades analysis of cardiac function based on the heart rate variability (HRV; variation in R wave to R wave intervals) has attracted great attention, resulting in more than 17000-publications (PubMed list). However, it is still controversial about the underling mechanisms of HRV. In this study, we performed both linear (time domain and frequency domain) and nonlinear analysis of HRV data acquired from humans and animals to identify the relationship between HRV and heart rate (HR). The HRV data consists of the following groups: (a) human normal sinus rhythm (n = 72); (b) human congestive heart failure (n = 44); (c) rabbit sinoatrial node cells (SANC; n = 67); (d) conscious rat (n = 11). In both human and animal data at variant pathological conditions, both linear and nonlinear analysis techniques showed an inverse correlation between HRV and HR, supporting the concept that HRV is dependent on HR, and therefore, HRV cannot be used in an ordinary manner to analyse autonomic nerve activity of a heart.

Chronobiology and Pharmacologic Modulation of the Renin-Angiotensin-Aldosterone System in Dogs: What Have We Learned?

Congestive heart failure (CHF) is a primary cause of morbidity and mortality with an increasing prevalence in human and canine populations. Recognition of the role of renin-angiotensin-aldosterone system (RAAS) overactivation in the pathophysiology of CHF has led to significant medical advances. By decreasing systemic vascular resistance and angiotensin II (AII) production, angiotensin-converting enzyme (ACE) inhibitors such as benazepril improve cardiac hemodynamics and reduce mortality in human and dog CHF patients. Although several experiments have pointed out that efficacy of ACE inhibitors depends on the time of administration, little attention is paid to the optimum time of dosing of these medications. A thorough characterization of the chronobiology of the renin cascade has the potential to streamline the therapeutic management of RAAS-related diseases and to help determining the optimal time of drug administration that maximizes efficacy of ACE inhibitors, while minimizing the occurrence of adverse effects. We have developed an integrated pharmacokinetic-pharmacodynamic model that adequately captures the disposition kinetics of the paradigm drug benazeprilat, as well as the time-varying changes of systemic renin-angiotensin-aldosterone biomarkers, without and with ACE inhibition therapy. Based on these chronobiological investigations, the optimal efficacy of ACE inhibitors is expected with bedtime dosing. The data further show that benazepril influences the dynamics of the renin-angiotensin-aldosterone cascade, resulting in a profound decrease in AII and aldosterone (ALD), while increasing renin activity for about 24h. From the results of recent investigations in human, it is hypothesized that reduction of AII and ALD is one of the drivers of increased survival and improved quality of life in dogs receiving ACE inhibitors. To support and consolidate this hypothesis, additional efforts should be directed toward the collection of circulating RAAS peptides in spontaneous cases of canine CHF. If such a link could be established, profiling of these biomarkers could support determination of the severity of heart failure, complement clinical and echocardiographic findings, and be used for therapeutic drug monitoring purposes.

The Role of Transcription Factors in the Formation of an Arrhythmogenic Substrate in Congestive Human Heart Failure

Human congestive heart failure is accompanied by structural and electrical alterations leading to the development of an arrhythmogenic substrate. This substrate is associated with the "sudden cardiac death" due to ventricular tachycardia or ventricular fibrillation. Multiple studies link distinct transcription factors to the transcriptional regulation of genes related to the formation of an arrhythmogenic substrate. In addition to cardiac hypertrophy the up- or downregulation of ion channels, calcium-handling proteins, and proteins forming gap junctions play a pivotal role in the progression of heart failure. This review summarizes the transcriptional regulation of selected genes implicated in the formation of an arrhythmogenic substrate. In this context we provide an overview of relevant transcription factors, activating stimuli and pathways, the evidence of binding to respective elements in the promoter of target genes and the associated mRNA regulation in animal models. Finally, possible therapeutic consequences are discussed.

Phosphoproteome mapping of cardiomyocyte mitochondria in a rat model of heart failure

Mitochondria are complex organelles essential to cardiomyocyte survival. Protein phosphorylation is emerging as a key regulator of mitochondrial function. In the study reported here, we analyzed subsarcolemmal (SSM) mitochondria harvested from rats who have received 4weeks of aldosterone/salt treatment to simulate the neurohormonal profile of human congestive heart failure. Our objective was to obtain an initial qualitative inventory of the phosphoproteins in this biologic system. SSM mitochondria were harvested, and the phosphoproteome was analyzed with a gel-free bioanalytical platform. Mitochondrial proteins were digested with trypsin, and the digests were enriched for phosphopeptides with immobilized metal ion affinity chromatography. The phosphopeptides were analyzed by ion trap liquid chromatography-tandem mass spectrometry, and the phosphoproteins identified via database searches. Based on MS/MS and MS(3) data, we characterized a set of 42 phosphopeptides that encompassed 39 phosphorylation sites. These peptides mapped to 26 proteins, for example, long-chain specific acyl-CoA dehydrogenase, Complex III subunit 6, and mitochondrial import receptor TOM70. Collectively, the characterized phosphoproteins belong to diverse functional modules, including bioenergetic pathways, protein import machinery, and calcium handling. The phosphoprotein panel discovered in this study provides a foundation for future differential phosphoproteome profiling toward an integrated understanding of the role of mitochondrial phosphorylation in heart failure.

Losartan versus enalapril in dogs asymptomatic carriers of myxomatous degeneration of mitral valve

The myxomatous mitral valve degeneration (DMVM) is the most common heart disease in dogs. The treatment of congestive heart failure (CHF) from DMVM is based on the use of angiotensin-converting enzyme inhibitors (ACE inhibitor) Receptor antagonists of angiotensin II (ARBs) promote complete blockade of angiotensin II, and are used in the treatment of CHF in humans, but is not common in dogs. The objective of this research was to compare the clinical responses of dogs carriers DMVM treated with enalapril-ACE inhibitors, losartan-ARBs. Thirteen dogs with DMVM and ICC class Ib were randomized into two groups as follows: G1-enalapril and G2-losartan. On physical examination, electrocardiogram and blood pressure were measured on days 0, 14, 28 and 56 after the begging of treatment. Radiographic measure, Vertebral Heart Size-VHS and ecodopplercardiográficas variables were obtained on days 0 and 56. Data were subjected to analysis of variance with repeated measures. There was no difference (P>0.05) for ecodopplercardiográficas, electrocardiographic and radiographic variables between the groups studied. In relation to time, there was a decrease (P <0.05) of the VHS, duration of the P wave and the QRS complex variables. We conclude that losartan acts similarly to enalapril in the initial treatment (first 56 days) of dogs with DMVM class Ib and II of the CHF.

Renal and Hormonal Effects of Systemic Nitric Oxide Inhibition in Patients With Congestive Heart Failure and in Healthy Control Subjects

BackgroundThe significance of basal renal nitric oxide (NO) availability in the regulation of renal perfusion and sodium excretion in human congestive heart failure (CHF) has not been described previously. Methods and ResultsWe studied the effects of acute systemic NO synthesis inhibition with NG-monomethyl-L-arginine (L-NMMA) in 12 patients with CHF and 10 healthy control subjects (CON) in a randomized placebo-controlled study. Effect parameters were renal plasma flow (RPF), renal vascular resistance (RVR), glomerular filtration rate (GFR), urine sodium excretion and plasma levels of vasoactive hormones. L-NMMA was associated with a significant decrease in RPF (CON-LNMMA: −13 ± 3% [P = .014]; CHF-LNMMA: −17 ± 7% [P = .017]) and a profound increase in RVR in both CHF and CON (CON-LNMMA: +26 ± 6% [P = .009]; CHF-LNMMA: +37 ± 70% [P = .005]). Significant decreases in sodium excretion were found in both CHF-LNMMA and CON-LNMMA. Relative changes from baseline were not statistically different between CHF-LNMMA and CON-LNMMA. After L-NMMA, RPF values correlated inversely with plasma aldosterone in CHF-LNMMA (P = .01). L-NMMA induced an increase in A-type natriuretic peptide (ANP) only in CHF-LNMMA (+18 ± 8%; P = .035), which correlated significantly with basal ANP levels (P = .034). ConclusionsThere was no difference in the renal response to L-NMMA in CHF vs CON, suggesting that the impact of NO on renal perfusion and sodium excretion is maintained in stable CHF. We suggest that NO influences the release of ANP during high levels of atrial stretch in CHF.

Potent inhibition of L-type Ca2+ currents by a Rad variant associated with congestive heart failure

Ca2+ influx via L-type voltage-gated Ca2+ channels supports the plateau phase of ventricular action potentials and is the trigger for excitation–contraction (EC) coupling in the myocardium. Rad, a member of the RGK (Rem, Rem2, Rad, Gem/Kir) family of monomeric G proteins, regulates ventricular action potential duration and EC coupling gain through its ability to inhibit cardiac L-type channel activity. In this study, we have investigated the potential dysfunction of a naturally occurring Rad variant (Q66P) that has been associated with congestive heart failure in humans. Specifically, we have tested whether Rad Q66P limits, or even eliminates, the inhibitory actions of Rad on CaV1.2 and CaV1.3, the two L-type channel isoforms known to be expressed in the heart. We have found that mouse Rad Q65P (the murine equivalent of human Rad Q66P) inhibits L-type currents conducted by CaV1.2 or CaV1.3 channels as potently as wild-type Rad (>95% inhibition of both channels). In addition, Rad Q65P attenuates the gating movement of both channels as effectively as wild-type Rad, indicating that the Q65P substitution does not differentially impair any of the three described modes of L-type channel inhibition by RGK proteins. Thus, we conclude that if Rad Q66P contributes to cardiomyopathy, it does so via a mechanism that is not related to its ability to inhibit L-type channel-dependent processes per se. However, our results do not rule out the possibility that decreased expression, mistargeting or altered regulation of Rad Q66P may reduce the RGK protein’s efficacy in vivo.

Particulate Matter Induces Cardiac Arrhythmias via Dysregulation of Carotid Body Sensitivity and Cardiac Sodium Channels

The mechanistic links between exposure to airborne particulate matter (PM) pollution and the associated increases in cardiovascular morbidity and mortality, particularly in people with congestive heart failure (CHF), have not been identified. To advance understanding of this issue, genetically engineered mice (CREB(A133)) exhibiting severe dilated cardiomyopathic changes were exposed to ambient PM collected in Baltimore. CREB(A133) mice, which display aberrant cardiac physiology and anatomy reminiscent of human CHF, displayed evidence of basal autonomic aberrancies (compared with wild-type mice) with PM exposure via aspiration, producing significantly reduced heart rate variability, respiratory dysynchrony, and increased ventricular arrhythmias. Carotid body afferent nerve responses to hypoxia and hyperoxia-induced respiratory depression were pronounced in PM-challenged CREB(A133) mice, and denervation of the carotid bodies significantly reduced PM-mediated cardiac arrhythmias. Genome-wide expression analyses of CREB(A133) left ventricular tissues demonstrated prominent Na(+) and K(+) channel pathway gene dysregulation. Subsequent PM challenge increased tyrosine phosphorylation and nitration of the voltage-gated type V cardiac muscle α-subunit of the Na(+) channel encoded by SCN5A. Ranolazine, a Na(+) channel modulator that reduces late cardiac Na(+) channel currents, attenuated PM-mediated cardiac arrhythmias and shortened PM-elongated QT intervals in vivo. These observations provide mechanistic insights into the epidemiologic findings in susceptibility of human CHF populations to PM exposure. Our results suggest a multiorgan pathobiology inherent to the CHF phenotype that is exaggerated by PM exposure via heightened carotid body sensitivity and cardiac Na(+) channel dysfunction.

β-Adrenergic receptor blockade reduces endoplasmic reticulum stress and normalizes calcium handling in a coronary embolization model of heart failure in canines

Alterations in calcium homeostasis in the endoplasmic/sarcoplasmic reticulum (ER) cause ER stress that ultimately may affect ventricular function. However, the role of ER stress in β-blocker therapy for congestive heart failure (CHF) has not been studied. This study examined ER stress in CHF and evaluated its role in β-blocker therapy in a canine model of ischaemic CHF. CHF was created by daily coronary embolization in chronically instrumented dogs. After oral administration of β-blocker metoprolol or vehicle for 12 weeks, Ca(2+) transport proteins including sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), ryanodine receptor (RyR2), Na(+)-Ca(2+) exchanger (NCX1), Ca(2+) storage protein calreticulin (CRT), and phospholamban were evaluated by Western blot analysis. Cellular levels of ER stress marker, phosphorylated eukaryotic initiation factor 2α (eIF2α-P), were also examined. Compared with the vehicle-treated group, metoprolol caused significantly improved cardiac function, restored the proteins of SERCA2a, NCX1, and CRT, increased phosphorylated phospholamban, reversed protein kinase A hyperphosphorylation of RyR2, and resulted in normalized ER stress marker eIF2α-P and reduced DNA damage. Our results suggest that ER stress could be induced by abnormal Ca(2+) homeostasis in CHF. The restoration of calcium-handling protein function and resultant decrease in ER stress might, in part, explain the beneficial effects of β-blockade observed in CHF. Whether this mechanism occurs in other animal CHF models or human CHF warrants further study.

Cardiovascular Changes During Maturation and Ageing in Male and Female Spontaneously Hypertensive Rats

Cardiovascular remodeling leading to heart failure is common in the elderly. Testing effective pharmacological treatment of human heart failure requires a suitable animal model that adequately mimics the human disease state. This study has characterized the structural, functional, and electrical characteristics of the cardiovascular system throughout the lifespan in male and female spontaneously hypertensive rats (SHRs), a genetic model of chronic hypertension-induced cardiovascular remodeling, and age- and gender-matched normotensive controls, to determine whether ageing SHRs mimic the changes seen in ageing humans. Both the ageing male and female SHRs developed progressive hypertension, ventricular hypertrophy, left ventricular fibrosis, action potential prolongation without impaired glucose tolerance. Male SHRs from 15 months of age exhibited left ventricular wall thinning and chamber dilation, together with systolic and diastolic dysfunction and increased cardiac stiffness and increased erythrocyte superoxide production, which were not present in the female SHRs. Ageing male SHRs in contrast to the female SHRs, better mimic the chronic heart failure in humans produced by chronic hypertension. Ageing male SHRs could then be used to investigate proposed therapeutic interventions for chronic congestive heart failure in humans.

Enhancement of proteasome function by PA28α overexpression protects against oxidative stress

The principal function of the proteasome is targeted degradation of intracellular proteins. Proteasome dysfunction has been observed in experimental cardiomyopathies and implicated in human congestive heart failure. Measures to enhance proteasome proteolytic function are currently lacking but would be beneficial in testing the pathogenic role of proteasome dysfunction and could have significant therapeutic potential. The association of proteasome activator 28 (PA28) with the 20S proteasome may play a role in antigen processing. It is unclear, however, whether the PA28 plays any important role outside of antigen presentation, although up-regulation of PA28 has been observed in certain types of cardiomyopathy. Here, we show that PA28α overexpression (PA28αOE) stabilized PA28β, increased 11S proteasomes, and enhanced the degradation of a previously validated proteasome surrogate substrate (GFPu) in cultured neonatal rat cardiomyocytes. PA28αOE significantly attenuated H(2)O(2)-induced increases in the protein carbonyls and markedly suppressed apoptosis in cultured cardiomyocytes under basal conditions or when stressed by H(2)O(2). We conclude that PA28αOE is sufficient to up-regulate 11S proteasomes, enhance proteasome-mediated removal of misfolded and oxidized proteins, and protect against oxidative stress in cardiomyocytes, providing a highly sought means to increase proteasomal degradation of abnormal cellular proteins.

Imbalance of Matrix Metalloproteinases/Tissue Inhibitor of Metalloproteinase-1 and Loss of Fibronectin Expression in Patients with Congestive Heart Failure

Objective: Previous studies have demonstrated that an imbalance of matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinase-1 (TIMP-1) and a loss of fibronectin are associated with postmyocardial infarction remodeling in rats. The present study was designed to examine this issue in patients with congestive heart failure (CHF). Methods: We measured plasma levels and the cardiac protein expression of MMPs/TIMP-1 and fibronectin in 39 patients with CHF and 38 controls. Results: Plasma levels of MMP-2, MMP-3, and MMP-9 tended to be higher in patients with CHF (NYHA II: 276 ± 18, 613 ± 118, and 245 ± 43 µg/l, respectively; NYHA III: 302 ± 20, 850 ± 132, and 310 ± 39 µg/l, respectively; NYHA IV: 367 ± 15, 998 ± 99, and 392 ± 27 µg/l, respectively) than in controls (213 ± 23, 485 ± 102, and 158 ± 31 µg/l, respectively), while the plasma TIMP-1 level tended to be lower in patients with CHF (NYHA II: 126 ± 12 µg/l, NYHA III: 83 ± 11 µg/l, and NYHA IV: 61 ± 12 µg/l) than in controls (208 ± 15 µg/l). Interestingly, the changes in protein expression of MMPs/TIMP-1 were consistent with their plasma concentration. Furthermore, the fibronectin level in the patients with CHF was significantly lower than in the controls. Conclusions: These data suggest that human CHF is associated with an imbalance of MMPs/TIMP-1 and a concurrent loss of fibronectin.

Symbolic analysis detects alterations of cardiac autonomic modulation in congestive heart failure rats

Congestive heart failure (CHF) is associated with neurohumoral activation. Only very few studies have examined the progression of autonomic dysfunction in CHF in humans and scanty data are available in animal models of CHF. This study was performed to assess the changes in cardiac autonomic modulation during the progression of CHF in a rat model, using an innovative analysis of heart rate variability. Progression of cardiovascular autonomic dysfunction was assessed in a rat model of CHF induced by coronary artery ligation. Spectral and symbolic analyses were performed on heart period (approximated with pulse interval, PI) and systolic arterial pressure (SAP) signals, acquired ~2 and ~4 weeks after the surgical procedure. As CHF developed, symbolic analysis revealed a decrease of rhythmical physiological sympathetic modulation, as indicated by the reduction of the percentage of stable patterns. In addition, symbolic analysis revealed that runs of short–long–short and/or long–short–long PI values and high–low–high and/or low–high–low SAP values were more and more frequent as CHF progressed. On the contrary, spectral analysis of PI and SAP series was not able to detect any impairment of autonomic regulation. Indeed, low frequency and high frequency powers derived from both PI and SAP series were not significantly changed. These data indicate that the autonomic cardiovascular modulation is altered during the progression of CHF and that symbolic analysis seems to be more suitable than spectral analysis to describe alterations of heart period dynamics and of cardiovascular regulation in this animal model of CHF.

Reciprocal Regulation of Myocardial microRNAs and Messenger RNA in Human Cardiomyopathy and Reversal of the microRNA Signature by Biomechanical Support

Much has been learned about transcriptional control of cardiac gene expression in clinical and experimental congestive heart failure (CHF), but less is known about dynamic regulation of microRNAs (miRs) in CHF and during CHF treatment. We performed comprehensive microarray profiling of miRs and messenger RNAs (mRNAs) in myocardial specimens from human CHF with (n=10) or without (n=17) biomechanical support from left ventricular assist devices in comparison to nonfailing hearts (n=11). Twenty-eight miRs were upregulated >2.0-fold (P<0.001) in CHF, with nearly complete normalization of the heart failure miR signature by left ventricular assist device treatment. In contrast, of 444 mRNAs that were altered by >1.3-fold in failing hearts, only 29 mRNAs normalized by as much as 25% in post-left ventricular assist device hearts. Unsupervised hierarchical clustering of upregulated miRs and mRNAs with nearest centroid analysis and leave-1-out cross-validation revealed that combining the miR and mRNA signatures increased the ability of RNA profiling to serve as a clinical biomarker of diagnostic group and functional class. These results show that miRs are more sensitive than mRNAs to the acute functional status of end-stage heart failure, consistent with important functions for regulated miRs in the myocardial response to stress. Combined miR and mRNA profiling may have superior potential as a diagnostic and prognostic test in end-stage cardiomyopathy.

Synthesis and Evaluation of a Series of 99mTc(CO)3+ Lisinopril Complexes for In Vivo Imaging of Angiotensin-Converting Enzyme Expression

In animal models of cardiac disease and in human congestive heart failure, expression of angiotensin-converting enzyme (ACE) is upregulated in the failing heart and has been associated with disease progression leading to cardiac failure and fibrosis. To develop probes for imaging ACE expression, a series of di(2-pyridylmethyl)amine (D) chelates capable of binding M(CO)3+ (M = technetium, rhenium) was conjugated to lisinopril by acylation of the epsilon-amine of the lysine residue with a series of di(2-pyridylmethylamino)alkanoic acids where the distance of the chelator from the lisinopril core was investigated by varying the number of methylene spacer groups to produce di(2-pyridylmethyl)amine(Cx)lisinopril analogs: D(C4)lisinopril, D(C5)lisinopril, and D(C8)lisinopril. The inhibitory activity of each rhenium complex was evaluated in vitro against purified rabbit lung ACE and was shown to vary directly with the length of the methylene spacer: Re[D(C8)lisinopril], inhibitory concentration of 50% (IC50) = 3 nM; Re[D(C5)lisinopril], IC50 = 144 nM; and Re[D(C4)lisinopril], IC50 = 1,146 nM, as compared with lisinopril, IC50 = 4 nM. The in vivo specificity for ACE was determined by examining the biodistribution of the 99mTc-[D(C8)lisinopril] analog in rats with and without pretreatment with unlabeled lisinopril. Uptake in the lungs, a tissue that constitutively expresses ACE, was 15.2 percentage injected dose per gram at 10 min after injection and was dramatically reduced by pretreatment with lisinopril, supporting ACE-mediated binding in vivo. Planar anterior imaging analysis of 99mTc-[D(C8)lisinopril] corroborated these data. Thus, high-affinity 99mTc-labeled ACE inhibitor has been designed with potency similar to that of lisinopril and has been demonstrated to specifically localize to tissues that express ACE in vivo. This agent may be useful in monitoring ACE as a function of disease progression in relevant diseases such as heart failure.

Catenins and connexin43 gap junction remodelling in human congestive heart failure

We have recently shown that connexin43 (Cx43) gap junction remodelling in human congestive heart failure is associated with increased interaction of Cx43 with ZO-1. The action of ZO-1 in regulating this remodelling is proposed to involve other connexin-interacting partners, in particular adhesion junction proteins. Double-label immunoconfocal microscopy in human left ventricular myocytes shows that a proportion of the signal for the adhesion junction proteins β-catenin and γ-catenin co-localise with Cx43 at the intercalated disk.

Drug development for treatment of cardiac arrhythmias: targeting the gap junctions

reentrant excitation ([12][1]) is likely the most important mechanism for serious life-threatening arrhythmias. Traditionally, a major focus of antiarrhythmic drug development has been to explore the actions of drugs designed to block conduction in reentrant pathways(s). During the latter part of

SKELETAL MUSCLE ATROPHY, BONE LOSS, AND OXIDATIVE STRESS IN RATS WITH ALDOSTERONISM.

Purpose Congestive heart failure (CHF) is a syndrome composed of symptoms and signs arising from congested organs and hypoperfused tissues; it is mediated by a salt-avid state based on an activation of the circulating renin-angiotensin-aldosterone system (RAAS). Beyond this classic perspective, CHF also features a systemic illness with oxidative stress and progressive loss of soft tissues and bone that eventuates in a wasting syndrome termed cardiac cachexia. Pathophysiologic responses contributing to this illness are under investigation. Methods and Results To simulate one aspect of RAAS activation and to address musculoskeletal health in aldosteronism, 8-week-old male Sprague-Dawley rats weighing 253 ± 11 g were treated for 4 weeks with aldosterone (ALDO, 0.75 μg/h) and 1% NaCl in their drinking water (ALDOST) to raise plasma ALDO levels to those found in human CHF. These levels are accompanied by secondary hyperparathyroidism (SHPT) due to ionized hypocalcemia and hypomagnesemia resulting from increased urinary and fecal excretion of Ca2+ and Mg2+. We monitored body weight; skeletal muscle total Ca2+, and morphology, including scarring (a marker of necrosis) and the presence of myocyte apoptosis (TUNEL assay); tibial bone mineral density (BMD) and content (BMC) and strength to flexor stress; plasma α1-antiproteinase activity (AP), an inverse correlate of oxidative stress; and plasma parathyroid hormone (PTH). Compared with age-/gender-matched untreated controls, with ALDOST we found (mean ± SEM) inadequate weight gain (81 ± 5 vs 22 ±6 g), accompanied by increased (p Conclusions Aldosteronism in rats is accompanied by SHPT with skeletal muscle Ca2+ overloading and atrophy, but not myocyte death, a loss of bone minerals with reduced strength to resist flexor stress, and the appearance of oxidative stress. In human CHF, aldosteronism may contribute to its progressive wasting.

SPIRONOLACTONE IN THE PREVENTION OF SKELETAL MUSCLE ATROPHY AND BONE LOSS IN RATS WITH ALDOSTERONISM.

Purpose Congestive heart failure (CHF), with its classic signs and symptoms, has its origins rooted in a salt-avid state mediated largely by effector hormones of the renin-angiotensin-aldosterone system (RAAS). CHF is accompanied by a systemic illness that features oxidative stress and a progressive loss of soft tissues and bone that eventuates in a wasting syndrome termed cardiac cachexia. To simulate the inappropriate (relative to dietary Na+) aldosteronism found in human CHF, rats receive aldosterone (0.75 μg/h), together with 1% NaCl in drinking water (ALDOST). Skeletal muscle wasting and bone loss are found in ALDOST and associated with secondary hyperparathyroidism (SHPT). Herein we hypothesized that these responses could be attenuated by cotreatment with spironolactone (Spiro), an ALDO receptor antagonist. Methods and Results Eight-week-old male Sprague-Dawley rats received ALDOST alone for 4 weeks or together with Spiro (150 mg/kg/d by gavage). We monitored: body weight and skeletal muscle morphology, including scarring, a marker of myocyte necrosis, and the presence of apoptosis (TUNEL assay); femoral bone mineral density (BMD) and content (BMC); plasma α1-antiproteinase activity (AP), an inverse correlate of oxidative stress; and plasma parathyroid hormone (PTH). Compared with age-/gender-matched controls, with ALDOST we found (mean ± SEM): inadequate weight gain (81 ± 5 vs 22 ± 6 g; p Conclusions In rats with aldosteronism, cotreatment with an ALDO receptor antagonist, Spiro, prevents the appearance of SHPT and accompanying skeletal muscle atrophy, bone loss, and oxidative stress. The use of Spiro in human CHF may offer advantages that extend beyond its diuretic properties.