Cardioprotection afforded by NF-kappaB ablation is associated with activation of Akt in mice overexpressing TNF-alpha

When selectively overexpressed in mouse heart, TNF-alpha effects the development of a cardiomyopathy that closely mimics that seen in human failing hearts. It has been suggested that two intracellular signaling pathways, the Akt protein kinase and the NF-kappaB transcription factor, mediated TNF-alpha signaling. The present experiments assessed the effects of TNF-alpha overexpression on these two target proteins in vivo. We measured cardiac Akt kinase phosphorylation and NF-kappaB activity in mice overexpressing TNF-alpha (TNF1.6). Both basal and insulin-stimulated Akt phosphorylation were reduced by almost 70% by TNF-alpha overexpression. By contrast, NF-kappaB was robustly activated. These effects were absent when TNF-alpha receptor 1 (TNFR1) was selectively ablated. Cardiomyocyte-specific overexpression of the dominant-negative inhibitory kappaB protein transgene and subsequent inhibition of NF-kappaB activity attenuated the effects of TNF-alpha on Akt phosphorylation. NF-kappaB inhibition also significantly improved fractional shortening and diminished ventricular hypertrophy and survival without affecting infiltrative inflammation or cytokine expression. Thus, while overexpression of TNF-alpha effected a marked Akt inhibition and NF-kappaB activation in mouse hearts, inhibition of NF-kappaB offered salutary benefits mediated at least in part through activation of Akt.

Treating heart failure with enhanced external counterpulsation (EECP): design of the Prospective Evaluation of EECP in Heart Failure (PEECH) trial

BACKGROUND

Enhanced external counterpulsation (EECP) treatment can improve exercise tolerance in patients with ischemic heart disease; however, the possible benefits of EECP in patients with stable heart failure (HF) and left ventricular dysfunction (LVD) are unclear. An open pilot study showed significant increases in exercise tolerance in HF patients undergoing EECP. Thus a larger, controlled study of EECP in patients with stable HF (New York Heart Association [NYHA] classes II and III) and LVD was undertaken.

METHODS AND RESULTS

The PEECH trial is a controlled, randomized, single-blind, parallel-group, multicenter study of 187 patients with symptomatic but stable HF (NYHA classes II and III) and an LV ejection fraction < or =35% was designed to assess the efficiency of EECP in patients with stable HF. Medical therapy is optimized in all patients based on the recommendations of the Heart Failure Society of America ("Usual Care"), and then randomized between 2 treatment groups; UC or EECP (35 hours over 7 weeks).

CONCLUSION

Efficacy measures include standard exercise tolerance tests on a treadmill (modified Naughton protocol), with measurements of peak oxygen uptake and exercise duration time; quality of life questionnaires; NYHA classification; and neurohormonal markers of HF.

Myocardial Expression of Fas and Recovery of Left Ventricular Function in Patients With Recent-Onset Cardiomyopathy

OBJECTIVES

This study aimed to evaluate the role of gene expression for predicting myocardial recovery in recent-onset cardiomyopathy.

BACKGROUND

Apoptosis may limit ventricular recovery. We examined the myocardial expression of Fas, Fas ligand (FasL), tumor necrosis factor (TNF)-alpha, and TNF receptor 1 (TNFR1), and myocardial recovery in patients from the multicenter Intervention in Myocarditis and Acute Cardiomyopathy (IMAC) study.

METHODS

Endomyocardial biopsy samples were obtained in 20 patients with recent-onset (<6 months) idiopathic dilated cardiomyopathy (left ventricular ejection fraction [LVEF] < or =0.40). The LVEF was assessed at baseline and at 6 and 12 months by nuclear scans. Myocardial expression was assessed by ribonuclease (RNase) protection, normalized to a constitutively active gene (glyceraldehydes 3-phosphate dehydrogenase [GAPDH]) and reported as percent GAPDH expression. The change in LVEF at 6 and 12 months was compared by tertiles of expression.

RESULTS

For all patients (14 men, 6 women; age 46.5 +/- 10.7 years), the mean LVEF was 0.28 +/- 0.05 at baseline and 0.40 +/- 0.14 at six months. Patients in the highest tertile of Fas expression had minimal improvement at six months (DeltaEF = 0.03 +/- 0.05) when compared with the intermediate (DeltaEF = 0.10 +/- 0.13) and lowest tertiles (DeltaEF = 0.21 +/- 0.11, change in LVEF by tertile, p = 0.006). A similar relationship was seen with TNFR1 expression (highest tertile, DeltaEF = 0.06 +/- 0.07; lowest tertile, DeltaEF = 0.21 +/- 0.11, p = 0.02). In contrast with Fas and TNFR1, expression of TNF-alpha and FasL did not predict recovery of LV function.

CONCLUSIONS

In cardiomyopathy of recent onset, increased expression of Fas and TNFR1 was associated with minimal recovery of LV function. Apoptosis limits myocardial recovery, and represents a potential target for therapeutic intervention.

17 Beta-estradiol improves survival in male mice with cardiomyopathy induced by cardiac-specific tumor necrosis factor-alpha overexpression

A transgenic mouse model of congestive heart failure (CHF) consequent to cardiac-specific overexpression of tumor necrosis factor-alpha (TNF-alpha) (TNF1.6) displays marked sex-related phenotypic differences. To clarify the potential contributions of estrogen to these sex-specific differences, male TNF1.6 mice were treated with 17beta- estradiol (E2). E2 treatment started at 25 +/- 1 days old (group A), but not at 36 +/- 2 days old (group B), significantly improved survival rate (p < 0.05). Furthermore, ventricular weight/body weight ratio was significantly decreased by E2 treatment in group A (p < 0.05). Echocardiography revealed that E2-treated hearts in group A exhibited less left ventricular dilatation (p < 0.05) relative to untreated male TNF1.6 mice (control). Moreover, in group A, E2 treatment partially reversed basal and isoproterenol-stimulated fractional shortening in TNF1.6 mice (p < 0.05). The cardiac content of TNF-alpha and interleukin-1beta (IL-1beta) was not changed by E2 treatment regardless of the timing of treatment. Thus, E2 exposure prior to puberty can limit the severity of cardiomyopathy in male TNF1.6 mice.

Cardiac-specific blockade of NF-κB in cardiac pathophysiology: differences between acute and chronic stimuli in vivo

The role of NF-κB in cardiac physiology and pathophysiology has been difficult to delineate due to the inability to specifically block NF-κB signaling in the heart. Cardiac-specific transgenic models have recently been developed that repress NF-κB activation by preventing phosphorylation at specific serine residues of the inhibitory κB (IκB) protein isoform IκBα. However, these models are unable to completely block NF-κB because of a second signaling pathway that regulates NF-κB function via Tyr42 phosphorylation of IκBα. We report the development of transgenic (3M) mouse lines that express the mutant IκBα(S32A,S36A,Y42F)in a cardiac-specific manner. NF-κB activation in cardiomyopathic TNF-1.6 mice is completely blocked by the 3M transgene but only partially blocked (70–80%) by the previously described double-mutant 2M [IκBα(S32A,S36A)] transgene, which demonstrates the action of two proximal pathways for NF-κB activation in TNF-α-induced cardiomyopathy. In contrast, after acute stimuli including administration of TNF-α and ischemia-reperfusion (I/R), NF-κB activation is blocked in both 2M and 3M transgenic mice. This result suggests that phosphorylation of the regulatory Ser32 and Ser36 predominantly mediates NF-κB activation in these situations. We show that infarct size after I/R is reduced by 70% in 3M transgenic mice, which conclusively demonstrates that NF-κB is involved in I/R injury. In summary, we have engineered novel transgenic mice that allow us to distinguish two major proximal pathways for NF-κB activation. Our results demonstrate that the serine and tyrosine phosphorylation pathways are differentially activated during different pathophysiological processes (cardiomyopathy and I/R injury) and that NF-κB contributes to infarct development after I/R.

Selective disruption of MMP-2 gene exacerbates myocardial inflammation and dysfunction in mice with cytokine-induced cardiomyopathy

Tumor necrosis factor-alpha (TNF-alpha) plays a pathophysiological role in the development and progression of heart failure. Matrix metalloproteinase (MMP)-2 is involved in extracellular matrix remodeling. Recent evidence suggests a protective role for this protease against tissue inflammation. Although MMP-2 is upregulated in the failing heart, little is known about its pathophysiological role. We thus hypothesized that ablation of the MMP-2 gene could affect cardiac remodeling and failure in TNF-alpha-induced cardiomyopathy. We crossed transgenic mice with cardiac-specific overexpression of TNF-alpha (TG) with MMP-2 knockout (KO) mice. Four groups of male and female mice were studied: wild-type (WT) with wild MMP-2 (WT/MMP(+/+)), WT with MMP-2 KO (WT/MMP(-/-)), TNF-alpha TG with wild MMP-2 (TG/MMP(+/+)), and TG with MMP-2 KO (TG/MMP(-/-)). The upregulation of MMP-2 zymographic activity in TG/MMP(+/+) mice was completely abolished in TG/MMP(-/-) mice, and other MMPs and tissue inhibitors of metalloproteinase were comparable between groups. Survival was shorter for male TG/MMP(-/-) than TG/MMP(+/+) mice. Female TG/MMP(-/-) mice were more severely affected than TG/MMP(+/+) mice with diminished cardiac function. Myocardial TNF-alpha and other proinflammatory cytokines were increased in TG/MMP(+/+) mice, and this increase was similarly observed in TG/MMP(-/-) mice. The extent of myocardial infiltrating cells including macrophages was greater in TG/MMP(-/-) than in TG/MMP(+/+) mice. Selective ablation of the MMP-2 gene reduces survival and exacerbates cardiac failure in association with the increased level of myocardial inflammation. MMP-2 may play a cardioprotective role in the pathogenesis of cytokine-induced cardiomyopathy.

Blockade of NF-κB improves cardiac function and survival without affecting inflammation in TNF-α-induced cardiomyopathy

OBJECTIVE

NF-kappaB, a key transcription factor that regulates inflammatory processes, has been shown to be activated in the failing human heart with enhanced expression of proinflammatory cytokines. In the present study, we assessed the hypothesis that cardiotoxic effects of proinflammatory cytokines are mediated by the activation of NF-kappaB.

METHODS

Transgenic mice with cardiac-specific overexpression of TNF-alpha were used as a model of cytokine-induced cardiomyopathy. To block the activation of NF-kappaB, transgenic mice (TG/p50(+/+)) were crossed with knockout mice in which the p50 subunit of NF-kappaB was disrupted (WT/p50(-/-)).

RESULTS

The electrophoretic mobility shift assay demonstrated that NF-kappaB was activated in the myocardium of TG/p50(+/+) mice, while it was completely abolished in TG/p50(-/-) mice. Male TG mice died of congestive heart failure earlier than females, where the disruption of the p50 subunit significantly improved the survival. Compared with TG/p50(+/+) mice, TG/p50(-/-) mice showed a significant reduction of ventricular dilatation and hypertrophy with preserved fractional shortening. Although the myocardial expression of proinflammatory cytokines or infiltration of inflammatory cells was not affected, increased expression and activity of MMP-9 were significantly suppressed in TG/p50(-/-) mice.

CONCLUSION

Blockade of NF-kappaB activation did not ameliorate myocardial inflammation but improved cardiac function and survival in male TNF-alpha TG mice. An inhibition of NF-kappaB may be a new therapeutic strategy for cardiac remodeling and heart failure, especially when proinflammatory cytokines are activated.

Implantable cardioverter defibrillators and cardiac resynchronization therapy in patients with left ventricular dysfunction: randomized trial evidence through 2004

Although many studies have shown that implantable cardioverter defibrillator (ICD) therapy improves the survival of patients with significant left ventricular dysfunction, the magnitude of effectiveness of ICD therapy in clinically defined subgroups remains uncertain. Similarly, although studies have shown an improvement in patients' hemodynamics and quality of life with cardiac resynchronization therapy (CRT), there is a continuing uncertainty about the effect of CRT on patients' survival and the magnitude of improvement in quality of life with this therapy. On August 24, 2004, an ad hoc group of experts representing clinical cardiovascular medicine, biostatistics, economics, and health policy were joined by representatives of the Food and Drug Administration, Centers for Medicare and Medicaid Services (Baltimore, Md), Agency for Healthcare Research and Quality (Rockville, Md), and the device industry for a 1-day round table to review the available clinical trial evidence on the effect of ICD therapy in the primary prevention of sudden cardiac death and the effect of CRT in patients with congestive heart failure. The meeting was organized by the Duke Clinical Research Institute, Durham, NC, and funded in part by the Agency for Healthcare Research and Quality. This document summarizes the evidence reviewed at that meeting and the discussions of that evidence.

Atrial contractile dysfunction, fibrosis, and arrhythmias in a mouse model of cardiomyopathy secondary to cardiac-specific overexpression of tumor necrosis factor-{alpha}

Transgenic mice overexpressing the inflammatory cytokine TNF-alpha in the heart develop a progressive heart failure syndrome characterized by biventricular dilatation, decreased ejection fraction, decreased survival compared with non-transgenic littermates, and earlier pathology in males. TNF-alpha mice (TNF1.6) develop atrial arrhythmias on ambulatory telemetry monitoring that worsen with age and are more severe in males. We performed in vivo electrophysiological testing in transgenic and control mice, ex vivo optical mapping of voltage in the atria of isolated perfused TNF1.6 hearts, and in vitro studies on isolated atrial muscle and cells to study the mechanisms that lead to the spontaneous arrhythmias. Programmed stimulation induces atrial arrhythmias (n = 8/32) in TNF1.6 but not in control mice (n = 0/37), with a higher inducibility in males. In the isolated perfused hearts, programmed stimulation with single extra beats elicits reentrant atrial arrhythmias (n = 6/6) in TNF1.6 but not control hearts due to slow heterogeneous conduction of the premature beats. Lowering extracellular Ca(2+) normalizes conduction and prevents the arrhythmias. Atrial muscle and cells from TNF1.6 compared with control mice exhibit increased collagen deposition, decreased contractile function, and abnormal systolic and diastolic Ca(2+) handling. Thus abnormalities in action potential propagation and Ca(2+) handling contribute to the initiation of atrial arrhythmias in this mouse model of heart failure.

Phospholamban gene ablation improves calcium transients but not cardiac function in a heart failure model

Decreased amplitude and slower kinetics of cardiomyocyte intracellular calcium (Ca(i)(2+)) transients may underlie the diminished cardiac function observed in heart failure. These alterations occur in humans and animals with heart failure, including the TNF1.6 mouse model, in which heart failure arises from cardiac-specific overexpression of tumor necrosis factor alpha (TNF alpha).

OBJECTIVE

Since ablation of phospholamban expression (PLBKO) removes inhibition of the sarcoplasmic reticulum (SR) Ca(2+) pump, enhances SR Ca(2+) uptake and increases contractility, we assessed whether ablation of phospholamban expression could improve cardiac function, limit remodeling, and improve survival in the TNF1.6 model of heart failure.

METHODS

We bred PLBKO with TNF1.6 mice and characterized the progeny for survival, cardiac function (echocardiography), cardiac remodeling (hypertrophy, dilation, fibrosis), and Ca(2+)(i) transients and contractile function of isolated cardiomyocytes.

RESULTS

PLB ablation did not improve survival, cardiac function, or limit cardiac chamber dilation and hypertrophy in TNF1.6 mice (TKO mice). However, contractile function and Ca(2+)(i) transients (amplitude and kinetics) of isolated TKO cardiomyocytes were markedly enhanced. This discordance between unimproved cardiac function, and enhanced Ca(2+)(i) cycling and cardiomyocyte contractile parameters may arise from a continued overexpression of collagen and decreased expression of gap junction proteins (connexin 43) in response to chronic TNF alpha stimulation.

CONCLUSIONS

Enhancement of intrinsic cardiomyocyte Ca(2+)(i) cycling and contractile function may not be sufficient to overcome several parallel pathophysiologic processes present in the failing heart.

Inhibition of tumor necrosis factor receptor-1-mediated pathways has beneficial effects in a murine model of postischemic remodeling

The aim of the present study was to investigate the importance of tumor necrosis factor (TNF)-alpha receptor-1 (TNFR1)-mediated pathways in a murine model of myocardial infarction and remodeling. One hundred and ninety-four wild-type (WT) and TNFR1 gene-deleted (TNFR1KO) mice underwent left coronary artery ligation to induce myocardial infarction. On days 1, 3, 7, and 42, mice underwent transesophageal echocardiography. Hearts were weighed, and the left ventricle (LV) was assayed for matrix metalloproteinase (MMP)-2 and -9 activity and for tissue inhibitor of MMP (TIMP)-1 and -2 expression. Deletion of the TNFR1 gene substantially improved survival because no deaths were observed in TNFR1KO mice versus 56.4% and 18.2% in WT males and females, respectively (P < 0.002). At 42 days, LV remodeling, assessed by LV function (fractional area change of 31.9 +/- 7.9%, 32.2 +/- 7.7%, and 21.6 +/- 7.1% in TNFR1KO males, TNFR1KO females, and WT females, respectively, P < 0.04), and hypertrophy (heart weight-to-body weight ratios of 5.435 +/- 0.986, 5.485 +/- 0.677, and 6.726 +/- 0.704 mg/g, P < 0.04) were ameliorated in TNFR1KO mice. MMP-9 activity was highest at 3 days postinfarction and was highest in WT males (1.9 +/- 0.4 4, 3.6 +/- 0.24, 1.15 +/- 0.28, and 1.3 +/- 1.2 ng/100 microg protein, respectively, in TNFR1KO males, WT males, TNFR1KO females, and WT females, respectively, P < 0.002), whereas at 3 days TIMP-1 mRNA fold upregulation compared with type- and sex-matched controls was lowest in WT males (138.32 +/- 13.05, 46.74 +/- 5.43, 186.09 +/- 28.07, and 101.76 +/- 22.48, respectively, P < 0.002). MMP-2 and TIMP-2 increased similarly in all infarcted groups. These findings suggest that the benefits of TNFR1 ablation might be attributable at least in part to the attenuation of cytokine-mediated imbalances in MMP-TIMP activity.

Clinical characteristics of vesnarinone

Congestive heart failure is a common condition with a poor prognosis. Its high rates of morbidity and mortality produce a huge societal burden. Current pharmacological treatment approaches are based on angiotensin-converting enzyme inhibitors, diuretics and digoxin, but up to 5% of patients may have refractory disease with persistent symptoms at rest. Such patients with advanced-stage disease may be candidates for treatment with the novel agent vesnarinone, a mixed phosphodiesterase inhibitor and ion-channel modifier that has modest, dose-dependent, positive inotropic activity, but minimal negative chronotropic activity. Vesnarinone improves ventricular performance most in patients with the worst degree of heart failure. However, before the initiation of vesnarinone therapy, risk-benefit profiles in individual patients should be considered, because in two large-scale studies [i.e. of the high dosage used in the Vesnarinone Study Group Trial (VSGT), and of both dosages used in the Vesnarinone Trial (VEST)] a dose-dependent increase in mortality was identified for vesnarinone 30-120 mg/day. The two studies also found significant vesnarinone-induced, short-term improvements in quality of life (QOL) in patients with refractory end-stage heart failure. Such patients are the most willing to trade-off a slightly increased risk of mortality for improved QOL. It is thus in these patients with refractory end-stage heart failure that vesnarinone may ultimately establish an important treatment role. However, detailed further investigation of the overall place of vesnarinone in heart failure management, with particular reference to the clinical potential of vesnarinone plus beta-blocker combination therapy, for example, is certainly warranted.

Use of a wearable defibrillator in terminating tachyarrhythmias in patients at high risk for sudden death: results of the WEARIT/BIROAD

The automatic ICD improves survival in patients with a history of sudden cardiac arrest. However, some patients do not meet the guidelines for ICD implantation or are unable to receive an implantable device. This study tested the hypothesis that these patients could benefit from a wearable cardioverter defibrillator. Patients with symptomatic heart failure and an ejection fraction of <0.30 (WEARIT Study) or patients having complications associated with high risk for sudden death after a myocardial infarction or bypass surgery not receiving an ICD for up to 4 months (BIROAD Study) were enrolled into two studies. After a total of 289 patients had been enrolled in the trial (177 in WEARIT and 112 in BIROAD), prespecified safety and effectiveness guidelines had been met. Six (75%) of eight defibrillation attempts were successful. Six inappropriate shock episodes occurred during 901 months of patient use (0.67% unnecessary shocks per month of use). Twelve deaths occurred during the study 6 sudden deaths: 5 not wearing and 1 incorrectly wearing the device). Most patients tolerated the device although 68 patients quit due to comfort issues or adverse reactions. The results of the present study suggest that a wearable defibrillator is beneficial in detecting and effectively treating ventricular tachyarrhythmias in patients at high risk for sudden death who are not clear candidates for an ICD and may be useful as a bridge to transplantation or ICD in some patients.

Assessment of infarct size and myocardial function in mice using transesophageal echocardiography

BACKGROUND

Because transthoracic echocardiography (TTE) has significant limitations in assessing changes consequent to myocardial infarction (MI) in mice, we studied two novel methods to characterize such infarcts.

METHODS

Large MIs were produced by proximal left coronary artery ligation, and small MIs by distal left coronary artery ligation. Serum cardiac troponin I levels were measured 24 hours postoperatively. At 2 weeks, mice underwent transesophageal echocardiography (TEE) and TTE. Infarct sizes were determined histologically.

RESULTS

Surviving mice were classified according to infarct size. TEE identified all histologically proven large infarcts, and 4 of 5 small infarcts. TTE identified 4 of 5 large infarcts, but only 1 of 5 small infarcts. TEE-derived fractional area change, but not TTE-estimated left ventricular fractional shortening, was significantly different among large, small, and sham infarcts. Cardiac troponin I showed excellent correlation with infarct size and mortality.

CONCLUSIONS

Cardiac troponin I was found to predict infarct size and mortality, whereas TEE proved superior to TTE in determining infarct size and/or myocardial function in a murine MI model. These tools should provide more accurate assessments in preclinical studies of ischemic cardiomyopathy.

Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure

BACKGROUND

We tested the hypothesis that prophylactic cardiac-resynchronization therapy in the form of biventricular stimulation with a pacemaker with or without a defibrillator would reduce the risk of death and hospitalization among patients with advanced chronic heart failure and intraventricular conduction delays.

METHODS

A total of 1520 patients who had advanced heart failure (New York Heart Association class III or IV) due to ischemic or nonischemic cardiomyopathies and a QRS interval of at least 120 msec were randomly assigned in a 1:2:2 ratio to receive optimal pharmacologic therapy (diuretics, angiotensin-converting-enzyme inhibitors, beta-blockers, and spironolactone) alone or in combination with cardiac-resynchronization therapy with either a pacemaker or a pacemaker-defibrillator. The primary composite end point was the time to death from or hospitalization for any cause.

RESULTS

As compared with optimal pharmacologic therapy alone, cardiac-resynchronization therapy with a pacemaker decreased the risk of the primary end point (hazard ratio, 0.81; P=0.014), as did cardiac-resynchronization therapy with a pacemaker-defibrillator (hazard ratio, 0.80; P=0.01). The risk of the combined end point of death from or hospitalization for heart failure was reduced by 34 percent in the pacemaker group (P<0.002) and by 40 percent in the pacemaker-defibrillator group (P<0.001 for the comparison with the pharmacologic-therapy group). A pacemaker reduced the risk of the secondary end point of death from any cause by 24 percent (P=0.059), and a pacemaker-defibrillator reduced the risk by 36 percent (P=0.003).

CONCLUSIONS

In patients with advanced heart failure and a prolonged QRS interval, cardiac-resynchronization therapy decreases the combined risk of death from any cause or first hospitalization and, when combined with an implantable defibrillator, significantly reduces mortality.

Gene expression profiling during the transition to failure in TNF-α over-expressing mice demonstrates the development of autoimmune myocarditis☆

Transgenic mice with cardiac-specific over-expression of tumor necrosis factor-alpha (TNF1.6) progress to dilated heart failure. A significant inflammatory response precedes functional deterioration, and may contribute to cardiac damage in this model. To evaluate the underlying molecular mechanisms, we assessed the gene expression in six groups of mouse hearts defined by age, gender, and phenotype (n = 3/group) using Affymetrix microarray analysis. Phenotype was defined as compensated (in young TNF1.6) or decompensated (in older TNF1.6) via echocardiogram. Of the >1000 transcripts altered in the compensated hearts (fold change > 2, P < 0.05 vs. wild-type (WT)), 102 were identified as immune response genes, 20 of which function in antigen presentation and processing. When comparing the compensated and decompensated hearts, >50 genes were differentially regulated, including seven immunoglobulin genes. Real-time reverse transcriptase-polymerase chain reaction and cDNA microarray confirmed the Affymetrix data. Mac3+ macrophages, CD4+ T and CD45/B220+ B-cells were identified in both compensated and decompensated hearts. However, a large amount of IgG was found deposited in areas devoid of B-lymphocytes in the myocardium of decompensated TNF1.6 mice; no such accumulation was seen in the compensated or age-matched controls. Furthermore, nuclei density analyses showed a two-fold increase in the myocardium of both compensated and decompensated TNF1.6 mice (vs. WT). This study suggests that TNF-alpha over-expression activates not only the inflammatory response, but also humoral immune responses within the transgenic hearts. The autoimmune response occurs concomitantly with cardiac decompensation and may participate in triggering the transition to failure in TNF1.6 mice.

Tumor necrosis factor receptors 1 and 2 differentially regulate survival, cardiac dysfunction, and remodeling in transgenic mice with tumor necrosis factor-alpha-induced cardiomyopathy

BACKGROUND

Tumor necrosis factor (TNF)-alpha plays a pathophysiological role in heart failure. Although both TNF receptor 1 (TNFR1) and 2 (TNFR2) are present in the heart, comparatively little is known about the role of TNFR2.

METHODS AND RESULTS

We bred TNFR1-knockout (KO) or TNFR2KO mice to transgenic (TG) mice with cardiac-specific overexpression of TNF-alpha and analyzed resultant progeny. Six groups of male and female mice were studied: wild type (WT) with wild receptors (WT/W), TG with wild receptors (TG/W), TG with heterozygous receptor KO (TG/R1+/- or TG/R2+/-), and TG with homozygous receptor KO (TG/R1-/- or TG/R2-/-). Both male and female TG mice displayed cardiac hypertrophy, dilation, and reduced cardiac function. Male TG mice were more severely affected than genotypically matched females and died of heart failure at a younger age. Survival, cardiac function, and remodeling of TG/R1+/- and TG/R1-/- mice were improved relative to TG/W mice in both males and females. However, the survival of female TG/R2+/- and TG/R2-/- mice was worse than that of TG/W mice, with increased left ventricular dimension and left ventricular weight/body weight ratios. The cardiac TNF-alpha protein level was upregulated in TG/R1-/- and TG/R2-/- compared with TG/W mice, whereas the level of TNF receptors was not downregulated in TG/W relative to WT/W mice.

CONCLUSIONS

Ablation of the TNFR2 gene exacerbates heart failure and reduces survival, whereas ablation of TNFR1 blunts heart failure and improves survival. Signaling via TNFR2 may play a cardioprotective role in the pathogenesis of cytokine-mediated heart failure.

Selective versus nonselective beta-blockade for heart failure therapy: are there lessons to be learned from the COMET trial?

The recently reported COMET trial found that the beta1/beta2/alpha1 receptor blocking agent carvedilol given in a relatively high beta1-receptor blocking dose regimen was superior in mortality reduction to immediate release metoprolol given in a relatively low beta1-receptor blocking dose schedule. We analyze the problems with the trial design of COMET from the standpoint of comparing 2 therapeutic agents at different positions on a common dose-response curve, and discuss the theoretical reasons why postjunctional adrenergic receptor blockade that is in addition to beta1-receptor antagonism will likely produce only minimal or no incremental benefit in chronic heart failure.