Akiyasu Baba

Leukemia Inhibitory Factor, a Potent Cardiac Hypertrophic Cytokine, Activates the JAK/STAT Pathway in Rat Cardiomyocytes

Leukemia inhibitory factor (LIF) is a member of the interleukin-6 family of cytokines, which induces a wide range of responses in a variety of cells. The aim of this study was to investigate whether LIF induces cardiomyocyte hypertrophy and transmits signals through the JAK/STAT (indicating just another kinase/signal transducer and activator of transcription) pathway in primary cultured neonatal rat cardiomyocytes. LIF increased protein content and [3H]phenylalanine uptake in cardiomyocytes in a dose-dependent manner. LIF (10(3) U/mL) induced rapid tyrosine phosphorylation of gp130, JAK1, JAK2, STAT1, and STAT3 but not Tyk2 or STAT2. LIF also induced autokinase activity of JAK1 in a time-dependent manner. Gel shift assays for interferon gamma activation site/interferon-stimulated responsive element and sis-inducible element (SIE) revealed that LIF induced dimerization of STAT1 and STAT3 and formation of sis-inducing factor complexes, which subsequently interacted with SIE in the promoter. Preincubation with anti-STAT1 and anti-STAT3 antibodies inhibited the binding of SIF complexes. In conclusion, LIF induces cardiac hypertrophy and directly stimulates the JAK/STAT pathway in cardiomyocytes.

Autoantibodies against the second extracellular loop of beta1-adrenergic receptors predict ventricular tachycardia and sudden death in patients with idiopathic dilated cardiomyopathy

OBJECTIVES We sought to define the clinical and long-term prognostic implications of autoantibodies that act against the second extracellular loop of beta1-adrenergic receptors (ARs) in patients with idiopathic dilated cardiomyopathy (IDC). BACKGROUND Although autoantibodies directed against various domains of beta-ARs are found in patients with IDC, only a subgroup against the second extracellular domain of beta1-ARs exerts intrinsic sympathomimetic-like actions on human beta-ARs. It is suggested that the autoantibodies take part in the pathophysiology of IDC and may affect long-term prognosis of patients with this disorder. METHODS Sera from 104 patients with IDC were screened for autoantibodies that act against the second extracellular loop of beta1-ARs by enzyme-linked immunosorbent assay, using a synthetic peptide corresponding to the domain. Relations of the autoantibodies to clinical variables and long-term prognosis were assessed by multivariate analysis. RESULTS Autoantibodies were detected in 40 patients (38%). Multifocal ventricular premature contractions (p < 0.01) and ventricular tachycardia (VT; p < 0.01) were more common in autoantibody-positive than in autoantibody-negative patients, although no differences in cardiac function or neurohormonal levels were demonstrated. The presence of autoantibodies (p = 0.001) and a low left ventricular ejection fraction (LVEF <30%; p = 0.02) were independent predictors of VT. Sudden death was independently predicted by the presence of autoantibodies (p = 0.03), as well as by LVEF <30% (p = 0.01), whereas total mortality was predicted only by LVEF <30% (p = 0.001). CONCLUSIONS Autoantibodies directed against the second extracellular loop of beta1-ARs were closely related to serious ventricular arrhythmias in patients with IDC, and the presence of autoantibodies independently predicted sudden death. These autoantibodies may contribute to electrical instability in patients with IDC.

Autoimmunity Against the Second Extracellular Loop of β1-Adrenergic Receptors Induces β-Adrenergic Receptor Desensitization and Myocardial Hypertrophy In Vivo

Abstract— Although immunoapheresis removing autoantibodies against the second extracellular domain of &bgr;1-adrenergic receptors (ARs) improves cardiac function in patients with cardiomyopathy, the underlying mechanisms have not been defined. We examined the role of autoimmunity against the domain in the development of cardiac dysfunction in vivo. Japanese white rabbits were immunized with a synthetic peptide corresponding to the second extracellular loop of &bgr;1-AR once a month with (&bgr;+biso rabbits, n=10) or without (&bgr; rabbits, n=13) bisoprolol treatment (2 mg/kg per day). Control rabbits received vehicle without bisoprolol treatment (n=13). Autoantibodies of IgG isotype against the domain were persistently detected in &bgr; and &bgr;+biso rabbits. Purified IgG from sera of &bgr; and &bgr;+biso rabbits increased cAMP production in a rabbit cardiac membrane preparation, which was blocked by bisoprolol. At 3 months, &bgr;-AR uncoupling with increased G protein-coupled receptor kinase 5 (GRK5) expression was found in &bgr; rabbits. At 6 months, left ventricular hypertrophy was noted with hemodynamic derangements in &bgr; rabbits. This was accompanied by decreased &bgr;1-AR density and increased inhibitory G protein and GRK5 expression, which were related to marked decrease in membrane cAMP production. These changes in &bgr; rabbits at 6 months were prevented in &bgr;+biso rabbits. There was no difference in the plasma norepinephrine concentration in the 3 groups over the observation period. Thus, autoimmunity against the second extracellular loop of &bgr;1-ARs induced profound &bgr;-AR desensitization and myocardial hypertrophy in vivo, associated with cardiac dysfunction. Sustained sympathomimetic-like actions of autoantibodies against the domain may be partly responsible for these changes.

Autoantibodies produced against sarcolemmal Na-K-ATPase: possible upstream targets of arrhythmias and sudden death in patients with dilated cardiomyopathy

OBJECTIVES We sought to test the hypothesis that autoantibodies (Abs) produced against sarcolemmal Na-K-ATPase play a role in the development of ventricular tachycardia (VT) and cardiac sudden death in patients with dilated cardiomyopathy (DCM). BACKGROUND Autoimmunity is one of the mechanisms of pathogenesis of DCM as well as virus infection and genetic predisposition. METHODS One hundred patients with DCM and age-matched control subjects (CTL) were screened for Abs produced against Na-K-ATPase by using enzyme-linked immunosorbent assay. RESULTS Abs were detected in 26 DCM and 2 CTL patients. Na-K-ATPase activity in the presence of patient IgG was lower in DCM with Abs than without Abs, but there was no difference between two groups in CTL. Western blots showed that Abs recognized the alpha subunit of Na-K-ATPase, and 3H-ouabain bindings in the presence of patient IgG showed that dissociation constant was higher in DCM with Abs than without Abs. No difference existed between subjects with regard to age, gender, New York Heart Association functional class, cardiac function, or neurohormone levels, except for plasma norepinephrine, which was higher in patients with Abs than without Abs. VTs were more common in patients with Abs than without Abs, and multiple logistic regression analysis demonstrated that the presence of Abs, but not plasma norepinephrine, was an independent predictor for the occurrence of VT. Cardiac sudden death was independently predicted by the presence of Abs, as well as poor systolic function. CONCLUSION We conclude that there are Abs produced against sarcolemmal Na-K-ATPase in patients with DCM and that Abs could be responsible for the electrical instability in some cases.

Effectiveness of carvedilol alone versus carvedilol + pimobendan for severe congestive heart failure ∗

Pimobendan is a new inotropic agent with phosphodiesterase-inhibiting and calcium-sensitizing effects that increase contractility with minimal increase in oxygen consumption.1‐5 We hypothesized that short-term administration of pimobendan in the early phase of b-blocker therapy would be beneficial in alleviating exacerbation of congestive heart failure (CHF) resulting in withdrawal for patients with severe CHF. The present study investigated the effects of short-term coadministration of pimobendan during introduction of carvedilol therapy on the clinical outcome, left ventricular contractile function, and neurohormone and cytokine levels compared with conventional carvedilol therapy in a randomized fashion in patients with severe CHF. ••• For the present study patients with New York Heart Association (NYHA) class III/IV symptomatic CHF who had multiple episodes of decompensated heart failure and a left ventricular ejection fraction of ,40% on radionuclide ventriculography or contrast ventriculography were enrolled. They were treated with conventional medical treatment including digitalis glycosides, diuretics, and angiotensin-converting enzyme (ACE) inhibitors. Exclusion criteria included a heart rate of ,50 beats/min, systolic blood pressure of ,90 mm Hg, significant bradyarrhythmias or atrioventricular block, serum creatinine of .3.0 mg/dl, and the presence of stenotic valvular heart disease, alcohol abuse, active myocarditis, or hypertrophic obstructive cardiomyopathy. Plasma creatinine phosphokinase level determination and scintigraphic assessment were performed to exclude myocarditis in the absence of biopsy samples. The study protocol was approved by an institutional review committee, and informed consent was obtained from all patients who participated in the study.

Specific immunoadsorption therapy using a tryptophan column in patients with refractory heart failure due to dilated cardiomyopathy.

Background: Certain cardiac‐specific autoantibodies found in patients with dilated cardiomyopathy (DCM) play a role in mediating myocardial damage and fatal ventricular arrhythmias resulting in sudden cardiac death. Immunoadsorption therapy (IA) is one of the therapeutic tools to remove such autoantibodies. Clinical studies from Germany have shown that nonspecific IA using columns loaded by sheep antihuman IgG or protein A improved hemodynamic data and affected favorably cardiac function and survival in patients with heart failure (HF) due to DCM. The goal of this study is to determine if IA therapy using the high‐profile tryptophan column, which has high affinity for IgG3 subclass, affects favorably cardiac function in patients with severe HF who are refractory to conventional therapy. Methods and Results: IA therapy was conducted in 16 patients with DCM (age 53 ± 4, male 8, New York Heart Association functional class III/IV, mean ejection fraction 18 ± 2%). Study subjects had autoantibodies directed against either β1‐adrenergic or M2‐muscarinic receptors. Plasma brain natriuretic peptide levels were significantly decreased after IA (P = 0.016). Plasma inflammatory cytokines including interleukin‐6 and tumor necrosis factor‐α did not change after each session of IA. Six‐minute walk distance was significantly increased after IA (P = 0.01). Left ventricular ejection fraction increased by 3% 3 months after IA (P = 0.039). Conclusions: Our initial experience demonstrated safety and short‐term efficacy of IA using a new IgG3‐specific tryptophan column for patients with advanced HF due to DCM. Long‐term follow‐up is needed to confirm the effects on cardiac function and morbidity/mortality in such patients. J. Clin. Apheresis, 2011.

A Pilot Study on the Role of Autoantibody Targeting the β1-Adrenergic Receptor in the Response to β-blocker Therapy for Congestive Heart Failure

BACKGROUND Autoantibodies directed against the beta1-adrenergic receptor exert agonist-like actions by inducing receptor uncoupling and cause myocardial damage as well as fatal ventricular arrhythmias. Previous studies have shown that beta-blockers can modulate these actions of the autoantibodies. We investigated the influence of such autoantibodies in patients with congestive heart failure (CHF) receiving beta-blocker therapy. METHODS AND RESULTS Eighty-two CHF patients were randomly assigned to treatment with metoprolol or carvedilol for 16 weeks. Autoantibodies were detected in 20 patients (24%) by enzyme-linked immunosorbent assay. Left ventricular function in response to beta-blocker therapy did not differ significantly by the presence of the autoantibody in global analysis. However, changes of the left ventricular end-diastolic dimension (P = .04), end-systolic dimension (P < .01), and ejection fraction on radionuclide ventriculography (P = .02) were significantly larger in autoantibody-positive patients than antibody-negative patients. Changes in the plasma level of brain natriuretic peptide tended to be larger in autoantibody-positive patients (P = .09). The increase of heart rate normalized by the increase of plasma norepinephrine during exercise (an index of adrenergic responsiveness) showed a greater decrease in autoantibody-positive patients than autoantibody-negative patients (P = .035). CONCLUSION Our data suggest that beta-blocker therapy might be more effective in CHF patients with autoantibodies targeting the beta1-adrenergic receptor.

Erythrocyte Na+, K+-ATPase activity in patients with congestive heart failure.

In order to determine if the Na+, K+-ATPase activity in erythrocyte membranes is altered in congestive heart failure, and to examine its clinical significance with respect to other clinical variables, erythrocyte Na+, K+-ATPase activity was measured in 51 patients with left ventricular ejection fractions <40% (coronary artery disease, n=26; dilated cardiomyopathy, n=25) and 24 control patients. Na+, K+-ATPase activity was lower in both coronary artery disease and dilated cardiomyopathy groups than control group even in the absence of digitalis use. There was a significant inverse correlation between Na+, K+-ATPase activity and plasma norepinephrine. The presence of non-sustained ventricular tachycardia was associated with a lower Na+, K+-ATPase activity in both groups with congestive heart failure without digitalis use than those without ventricular tachycardia. Plasma norepinephrine was higher in patients with non-sustained ventricular tachycardia than those without in the coronary artery disease group, but not in the dilated cardiomyopathy group. Na+, K+-ATPase activity may be helpful in predicting electrophysiologic instability in patients with heart failure.

Autoantibodies in atrial fibrillation: actor, biomaker or bystander?

Atrial fibrillation (AF) is one of the most common arrhythmias in patients with congestive heart failure, although the underlying mechanism has still to be determined. There is increasing evidence to suggest that autoimmunity may play an important role in the pathogenesis of AF. To date, at least three types of autoantibody have been found in AF: the anti-myosin heavy chain autoantibody, the anti-M2 muscarinic receptor autoantibody and the anti-heat shock protein autoantibody. The question is: are these autoantibodies actors, biomakers or merely bystanders? How much knowledge do we have?

Isoform-specific alterations in cardiac and erythrocyte Na+ ,K+-ATPase activity induced by norepinephrine

BACKGROUND Myocardial Na+,K+-ATPase activities are decreased in congestive heart failure because of an increase in plasma norepinephrine levels, but it is difficult to monitor the activities in the clinical setting. METHODS AND RESULTS This study investigated whether erythrocyte Na+,K+-ATPase activity can reflect myocardial enzyme activity and whether isoform-specific alterations occur in the presence of catecholamine. Na+,K+-ATPase activity was measured by the colorimetric method by using the left ventricular myocardium and erythrocytes prepared from eight rabbits given norepinephrine for 7 days and from eight control rabbits that received saline. The protein levels of total catalytic subunit and alpha1- or alpha3-isoform of Na+,K+-ATPase were determined by Western blot analysis. Na+,K+-ATPase activity was lower in both myocardium and erythrocytes from norepinephrine-treated rabbits than control rabbits (P < .01 and P < .01, respectively). There was a close correlation in Na+,K+-ATPase activity between myocardium and erythrocytes (r = .963). Total catalytic subunit protein level was lower in myocardium from norepinephrine-treated rabbits than control rabbits, but the alpha1-isoform level was similar between the two groups. The alpha3-isoform level was lower in norepinephrine-treated rabbits than control rabbits. In erythrocytes, alpha1-isoform was lower in norepinephrine-treated rabbits than control rabbits. CONCLUSIONS Na+,K+-ATPase activity in myocardium could be reflected in erythrocyte membrane, although there was a difference in isoform-specific regulation between the two.