Functional analysis of autoantibodies against ADP/ATP carrier from dilated cardiomyopathy

Overview of imaging in adult- and childhood-onset Takayasu arteritis

Takayasu Arteritis is an idiopathic large vessel vasculitis, that affects young adults and children and can lead to ischemia and end-organ damage. Vascular imaging is crucial for diagnosis, assessment of disease extent and management of the disease. In this article, we critically review evidence for the clinical use of the different imaging modalities conventional angiography, magnetic resonance imaging, computed tomography, Doppler ultrasound and ¹⁸fluorodeoxyglucose positron emission tomography. We thereby focus on their clinical applicability, challenges and specific use in children.

Autoimmune Calcium Channelopathies and Cardiac Electrical Abnormalities

Patients with autoimmune diseases are at increased risk for developing cardiovascular diseases, and abnormal electrocardiographic findings are common. Voltage-gated calcium channels play a major role in the cardiovascular system and regulate cardiac excitability and contractility. Particularly, by virtue of their localization and expression in the heart, calcium channels modulate pace making at the sinus node, conduction at the atrioventricular node and cardiac repolarization in the working myocardium. Consequently, emerging evidence suggests that calcium channels are targets to autoantibodies in autoimmune diseases. Autoimmune-associated cardiac calcium channelopathies have been recognized in both sinus node dysfunction atrioventricular block in patients positive for anti-Ro/La antibodies, and ventricular arrhythmias in patients with dilated cardiomyopathy. In this review, we discuss mechanisms of autoimmune-associated calcium channelopathies and their relationship with the development of cardiac electrical abnormalities.

Circulating miR-185 might be a novel biomarker for clinical outcome in patients with dilated cardiomyopathy

B cells contribute to the development of dilated cardiomyopathy (DCM) by inducing myocyte injuries and myocardial fibrosis. Our recent research indicated that microRNA (miR) -185 participated in human B-cell activation. Thus, this study was aimed to explore the relationship between miR-185 and DCM progression. Forty-one healthy volunteers and fifty newly diagnosed DCM patients were enrolled. The levels of plasma miR-185, TNF-α secreting B cells, and anti-heart autoantibody were detected. We found that the mean levels of plasma miR-185 in DCM patients were significantly higher than those in healthy controls. Furthermore, these DCM patients could be divided into miR-185^high and miR-185^low groups according to the cluster distribution. During one-year follow-up period, the miR-185^high group showed apparent improvements in left ventricular ejection fraction, left ventricular end diastolic diameter, and NT-proBNP, accompanied by significant declines in both cardiovascular mortality and total admissions for heart failure re-hospitalizations. In addition, the levels of anti-β1-AR antibody and TNF-α secreting B cells were also reduced in miR-185^high group. These findings suggested that high miR-185 levels might be associated with a favorable prognosis by repressing B cell function in DCM. The findings of this study need to be confirmed with larger sample size and longer duration of observation.

Increased frequency of follicular helper T cells in mice viral myocarditis is relevant with anti-ANT antoantibody

BACKGROUND

Recently, a new subset of CD4(+)T helper cell termed Follicular helper T cells (Tfh), which play a pivotal role in B cell activation and differentiation in lymphoid structures, has been reported to participate in some certain autoimmune diseases. But whether Tfh cells are involved in the pathogenesis of VMC remains unclear.

METHODS

Male BALB/c mice were intraperitoneally (i.p) infected with CVB3 to establish VMC models. Control mice were treated with phosphate-buffered saline i.p. On 0, 1, 2, 3, 4, 6 weeks post injection, frequencies of splenic Tfh cells were determined by flow cytometric analysis, productions of IL-21 and anti-adenine nucleotide translocator(ANT) autoantibody were detected by enzyme-linked immunosorbent assay. To further investigate the effects of Tfh cells, VMC mice were treated with Anti-IL-21 neutralizing antibody. Heart pathology was examined histologically, the frequencies of Tfh cells and the expressions of anti-ANT autoantibody were investigated after anti-IL-21 intervention. Spearman analysis was used to evaluate the relationship between the frequencies of Tfh cells and IL-21 levels with anti-ANT autoantibody.

RESULTS

The percentage of Tfh cells significantly increased in VMC mice from 1 W to 6 W, the serum level of IL-21 and ANT autoantibody were also significantly increased in VMC mice. Neutralization of IL-21 with anti-IL-21 can ameliorate the myocardium inflammation, decrease Tfh cells and ANT autoantibody after IL-21 antibody intervention compared with those of the control (P < 0.05). Both of the frequencies of Tfh cells and IL-21 levels were positively correlated with anti-ANT antibody levels (R = 0.758, P < 0.05; R = 0.88, P < 0.01, respectively).

CONCLUSIONS

Those results suggest that Tfh cells and IL-21 might involve in the pathogenesis of VMC and play an important role in anti-ANT autoantibody production. Targeting the Tfh cell and IL-21 may be a new therapeutic target for the treatment of CVB3-induced VMC.

Increased circulating T‑helper 22 cells in patients with dilated cardiomyopathy

Recently, the newly determined interleukin (IL)‑22‑producing T-helper (Th) 22 cell has been implicated to be involved in the pathogenesis of autoimmune diseases. However, its role in the pathogenesis of dilated cardiomyopathy (DCM) has yet to be elucidated. A total of 30 patients with DCM and 30 healthy controls were enrolled in the present study. The levels of Th22, Th17 and Th1 cells in the peripheral blood were analyzed by flow cytometry. Levels of plasma IL‑22 and autoantibody adenine nucleotide translocator (ANT) were assessed using the ELISA. The key transcription factor of Th22, aryl hydrocarbon receptor (AHR), was assessed using quantitative polymerase chain reaction. Additionally, clinical data on the brain natriuretic peptide (BNP), C‑reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were collected. In comparison with those in the control group, significantly elevated levels of Th22, Th17 and Th1 cells were detected in patients with DCM (all P<0.01). Similarly, elevated mRNA levels of peripheral AHR were detected in patients with DCM. The percentage of Th22 cells was higher in ANT‑positive compared with ANT‑negative patients with DCM. The levels of BNP and CRP, but not ESR, showed a significant positive correlation with those of Th22 cells. With regard to the concentrations of plasma IL‑22, no statistical difference was found between patients with DCM and the healthy controls, nor did it demonstrate a statistical correlation with the percentage of Th22 cells. In conclusion, the present study showed that patients with DCM, particularly those of the ANT autoantibody positive subjects, exhibit elevated levels of peripheral Th22 cells, indicating that a Th22 immune response may be implicated in the pathogenesis of DCM.

Relevance of molecular mimicry in the mediation of infectious myocarditis

Heart disease, the leading cause of death in humans, is estimated to affect one in four American adults in some form. One predominant cause of heart failure in young adults is myocarditis, which can lead to the development of dilated cardiomyopathy, a major indication for heart transplantation. Environmental microbes, including viruses, bacteria, and fungi that are otherwise innocuous, have the potential to induce inflammatory heart disease. As the list is growing, it is critical to determine the mechanisms by which microbes can trigger heart autoimmunity and, importantly, to identify their target antigens. This is especially true as microbes showing structural similarities with the cardiac antigens can predispose to heart autoimmunity by generating cross-reactive immune responses. In this review, we discuss the relevance of molecular mimicry in the mediation of infectious myocarditis.

Regulatory T cells and Th17 cells in viral infections: implications for multiple sclerosis and myocarditis

In immune-mediated diseases, Treg and proinflammatory Th17 cells have been suggested to play either suppressor (beneficial) or effector (detrimental) roles, respectively. Tissue damage in viral infections can be caused by direct viral replication or immunopathology. Viral replication can be enhanced by anti-inflammatory responses and suppressed by proinflammatory responses. However, Tregs could suppress proinflammatory responses, reducing immunopathology, while Th17 cell-induced inflammation may enhance immunopathology. Here, the roles of Treg and Th17 cells depend on whether tissue damage is caused by direct virus replication or immunopathology, which differ depending on the virus, disease stage and host immune background. Although the precise mechanisms of tissue damage in multiple sclerosis and myocarditis are unclear, both viral replication and immune effector cells have been proposed to cause pathogenesis. Personalized medicine that alters the balance between Treg and Th17 cells may ameliorate viral pathology during infections.

Agonist-like autoantibodies against calcium channel in patients with dilated cardiomyopathy

The calcium channel may be an important target in the autoimmune pathogenesis of dilated cardiomyopathy (DCM). The presence and function of serum autoantibodies against calcium channels (CC-AAbs) in patients with DCM were studied. Calcium-channel AAbs were detected in 80 patients with DCM and 80 controls by enzyme-linked immunosorbent assay (ELISA). Calcium-channel AAbs were further purified by affinity chromatography for characterization by immunoblotting and immunofluorescence. Voltage-clamp experiments were performed to identify the function of CC-AAbs. The presence of CC-AAbs was shown effectively by ELISA, and CC-AAbs were able specifically to bind to the calcium channel on the myocyte, confirmed by immunoblotting and immunofluorescence. Calcium currents were enhanced by CC-AAbs on Xenopus oocytes expressing human Ca(V)1.2 channels, which suggested CC-AAbs in patients with DCM were agonist-like. Our results suggest there are novel agonist-like CC-AAbs in patients with DCM. Calcium-channel AAbs might play an important role in the pathogenesis of DCM.

Arrhythmogenic autoantibodies against calcium channel lead to sudden death in idiopathic dilated cardiomyopathy

AIMS

Calcium channel plays an important role in the autoimmune pathogenesis of idiopathic dilated cardiomyopathy (DCM). Autoantibodies have emerged as a new upstream target of sudden death in DCM. We sought to validate the hypothesis that autoantibodies against l-type calcium channel (CC-AAbs) are arrhythmogenic and lead to sudden death in patients with DCM.

METHODS AND RESULTS

We investigated sudden death and ventricular arrhythmias in 80 patients with DCM in a prospective, case follow-up survey. During a follow-up of 32 (SD 8) months, CC-AAbs-positive patients not only had a higher incidence of ventricular tachycardia (VT) but also a higher incidence of sudden death than CC-AAbs-negative patients (for VT: 59.0 vs. 24.4%, P = 0.002 and for sudden death: 20.5 vs. 4.9%, P = 0.045). Further univariate and multivariate analyses showed that the occurrence of CC-AAbs was the strongest independent predictor for sudden death (odds ratio: 10.20, 95% confidence interval: 2.43-36.78, P = 0.0027). Experimental studies in ex vivo systems using affinity-purified CC-AAbs from patients demonstrated that CC-AAbs were able to induce VT by prolongation of action potential duration (APD) and triggered activity by early afterdepolarization (EAD).

CONCLUSION

Our results demonstrate for the first time to our knowledge that there is a high incidence of sudden death and VT in CC-AAbs-positive patients with DCM. Furthermore, experimental data from ex vivo systems suggest that CC-AAbs might induce VT by prolongation of APD and triggered activity by EAD.

Profiling humoral autoimmune repertoire of dilated cardiomyopathy (DCM) patients and development of a disease-associated protein chip

Dilated cardiomyopathy (DCM) is a myocardial disease characterized by progressive depression of myocardial contractile function and ventricular dilatation. Thirty percent of DCM patients belong to the inherited genetic form; the rest may be idiopathic, viral, autoimmune, or immune-mediated associated with a viral infection. Disturbances in humoral and cellular immunity have been described in cases of myocarditis and DCM. A number of autoantibodies against cardiac cell proteins have been identified in DCM. In this study, we have profiled the autoantibody repertoire of plasma from DCM patients against a human protein array consisting of 37,200 redundant, recombinant human proteins and performed qualitative and quantitative validation of these putative autoantigens on protein microarrays to identify novel putative DCM specific autoantigens. In addition to analyzing the whole IgG autoantibody repertoire, we have also analyzed the IgG3 antibody repertoire in the plasma samples to study the characteristics of IgG3 subclass antibodies. By combining screening of a protein expression library with protein microarray technology, we have detected 26 proteins identified by the IgG antibody repertoire and 6 proteins bound by the IgG3 subclass. Several of these autoantibodies found in plasma of DCM patients, such as the autoantibody against the Kv channel-interacting protein, are associated with heart failure.

Gadolinium-enhanced Three-dimensional MR Angiography of Takayasu Arteritis

Takayasu arteritis is a form of large vessel vasculitis with a possible autoimmune origin that may cause stenosis of the aorta and its major branches. Six types of Takayasu arteritis are recognized; the type depends on whether the ascending aorta, descending thoracic aorta, abdominal aorta, aortic cervicobrachial branches, or renal arteries are affected. The coronary and pulmonary arteries are also sometimes involved. Clinical features of the disease include diminished or absent pulses, claudication, hypertension, and mesenteric angina. Conventional angiography has been the standard imaging tool for diagnosis and evaluation of Takayasu arteritis, although it demonstrates only the lumen of the vessel. Less invasive cross-sectional methods such as computed tomographic angiography and, more recently, three-dimensional magnetic resonance (MR) angiography can effectively demonstrate thickening of the vessel wall, which may be the earliest manifestation of the disease, occurring before stenosis and dilatation. MR imaging in particular allows better soft-tissue differentiation and can show other signs of inflammation, including mural edema and increased mural vascularity. Other advantages of MR imaging are the lack of iodinated contrast material or ionizing radiation.

Pathophysiology of viral myocarditis: the role of humoral immune response

The pathophysiology of viral myocarditis is still a matter of debate. Humoral autoimmunity in postviral heart disease remains an attractive but complex hypothesis. Antigenic mimicry with or without cytolytic antibody properties has been shown to play a role in the immunopathogenesis of myocarditis with respect to sarcolemmal/myolemmal epitopes (including the beta-receptor), myosin and some mitochondrial proteins including the antinucleotide translocator (ANT)-carrier and dihydrolipoamid dehydrogenase. Today, refined two-dimensional Western blots are able to identify receptors and enzymes that are target of a humoral immune response or the consequence of an "immunization process." A humoral immune response to an invading agent will most likely lead to immunodestruction first. After conversion to IgG, the continuing antibody response may indicate the healing or healed process and last for many years or life-long. This paper reviews our present knowledge on the humoral immune response in myocarditis and its interplay with the viral agents and the other components of the immune system.

Possible association of HLA-DRB1 gene with the autoantibody against myocardial mitochondria ADP/ATP carrier in dilated cardiomyopathy

To probe the genetic background and immunopathogenesis of dilated cardiomyopathy (DCM) 77 patients with DCM, HLA-DRB1 gene polymorphism were analyzed by using the polymerase chain reaction/sequence specific primer (PCR/SSP) technique and autoantibody against myocardial mitochondria ADP/ATP carrier were examined by using the Immunoblot analysis. The frequency of HLA-DRB1*0901 allele was significantly higher in DCM patients in which autoantibody against ADP/ATP carrier of myocardial mitochondria is positive in contrast with those in which the autoantibody is negative (25.46% vs 3.45%, P < 0.05), the relative risk (RR) being 9.56. The other frequencies of HLA-DRB1 alleles have no significant difference in the antibody positive group and negative group. It is possible that a subset of DCM patients may exist in which autoimmunity is associated with genetic factors.

Experimental study on AT1-receptor-peptide-induced myocardial immune damage in rat

In order to investigate the immunological damage in rat immunized with AT1-receptor peptide, 18 male Wistar rats were divided into two groups: immunized-group (n = 12), each rat was immunized with 150 micrograms AT1-receptor peptide coupled to bovine serum albumin, together with Freund's adjuvant. Control group (n = 6), sham-immunized, "immunized liquid" was same as immunized-group except AT1-receptor peptide. Systolic blood pressure (SBP) was measured by using the tail-cuff technique, antibody against AT1-receptor peptide detected by using ELISA method, and left ventricular myocardium and renal cortex sections were observed under light and electron microscopy. There was no significant difference in SBP and light microscopic observation of the tissue sections between the immunized-group and control group. The O.D. value of anti-AT1-receptor peptide antiserum was significantly higher in the immunized-group than in the rats before immunization and control group (P < 0.01). Positive rate in the immunized-group was 100%, while 0% in the control group. Ultramicroscopic morphology showed potential myocardial injury, including: increase in number of mitochondria, swelling of many mitochondria with reduction in number or absence of their cristae and cristolysis, disorder of the cardiac myofibrils, and myofibrillar disruption and myocytolysis. And lysosomes were increased in renal tubular epithelia. The AT1-receptor peptide could induce to generate the antibody against AT1-receptor peptide and lead to myocardial and renal damage in rats.

Antimyosin autoantibodies are associated with deterioration of systolic and diastolic left ventricular function in patients with chronic myocarditis

OBJECTIVES

The study evaluates the clinical course and the development of systolic and diastolic left ventricular function in patients with chronic myocarditis with or without autoantibodies against cardiac myosin.

BACKGROUND

Patients with myocarditis often show autoantibodies against cardiac myosin. The clinical and pathophysiologic significance of these antimyosin autoantibodies (AMAAB) is yet unknown. The results from studies comparing the clinical course and the development of left ventricular function in patients with chronic myocarditis with or without AMAAB are not yet available.

METHODS

Thirty-three patients with biopsy proven chronic myocarditis underwent analysis of AMAAB, right and left heart catheterization and left ventriculography at baseline and after six months. Left ventricular volumes and ejection fraction as well as the time constant of left ventricular relaxation "tau" and the constant of myocardial stiffness "b" were determined at baseline and at follow-up.

RESULTS

In 17 (52%) patients, AMAAB could be detected at baseline. After six months, AMAAB were still found in 13 (76%) initially antibody-positive patients. No initially antibody-negative (n = 16) patient developed AMAAB during follow-up. Clinical symptoms improved slightly in antibody-negative patients and remained stable in antibody-positive patients. Left ventricular ejection fraction developed significantly better in antibody-negative patients (+8.9 +/- 10.1%) compared with antibody-positive patients (-0.1 +/- 9.4%) (p < 0.012). Stroke volume (SV) and stroke volume index (SVI) also improved in antibody-negative patients (SV: +20 +/- 31 ml; SVI: +10 +/- 17 ml) compared with antibody-positive patients (SV: -14 +/- 43 ml; SVI: -8 +/- 22 ml) (SV: p < 0.015; SVI: p < 0.016). Left ventricular end-diastolic and end-systolic volumes and the time constant of left ventricular relaxation "tau" did not change significantly different in antibody-positive and antibody-negative patients. The constant of myocardial stiffness "b" improved significantly in antibody-negative patients (-6.1 +/- 10.8) compared with antibody-positive patients (+7.3 +/- 22.6) (p < 0.040). Analyzing only the persistently antibody-positive patients yielded essentially the same results.

CONCLUSIONS

Antimyosin autoantibodies are associated with worse development of left ventricular systolic function and diastolic stiffness in patients with chronic myocarditis.

HLA-DRB1 gene polymorphism in patients with dilated cardiomyopathy

To probe into the genetic background and immunopathogenesis of dilated cardiomyopathy (DCM), HLA-DRB1 gene polymorphism in 68 patients with DCM and 175 normal control subjects were analyzed by using the polymerase chain reaction/sequence specific primer (PCR/SSP) techniques. It was found that the frequencies of HLA-DRB1* 15 and HLA-DRB1* 03 alleles were significantly lower in DCM patients than those in normal controls (14.71% vs 29.71% and 4.41% vs 15.43%, respectively), the relative risks (RR) in the DCM patients being 0.41 and 0.25, respectively, all P < 0.05. However, the frequencies of HLA-DRB1* 11 and HLA-DRB1* 12 alleles were significantly higher in the DCM patients than in controls (29.4% vs 12.00% and 36.76% vs 12.57%, respectively) with the RR in the DCM patients being 3.06 and 4.04, respectively, all P < 0.01. These findings further demonstrated that immunogenetics might play a predominant pathogenetic role in partial DCM patients.

Interventional study of diltiazem in dilated cardiomyopathy: a report of multiple centre clinical trial in China. Chinese Cooperative Group of Diltiazem Intervention Trial in Dilated Cardiomyopathy

The aim of this study was to determine the interventional effects of diltiazem on autoantibody mediated myocardial damage in dilated cardiomyopathy (DCM). 221 patients with DCM in 16 hospitals were included in the multiple centre clinical trial from January 1995 to November 1996, using the diltiazem or placebo based on the background therapy for heart failure. Patients were randomly divided into groups for a single blind trial, followed by observation for an average of 7.4 months. After treatment, the heart function of 84% of patients in the diltiazem group recovered to grade I or II, but this occurred for 64% of patients in the placebo group. Heart-thorax ratio was decreased from 0.59+/-0.07 to 0.56+/-0.07 and the left ventricular end-diastolic dimension (LVEDd) from 65.40+/-8.60 mm to 61.12+/-9.86 mm, the left ventricular ejection fraction (EF) was increased from 35.75+/-10.78% to 42.52%+/-11.41% (P<0.01) in the diltiazem group (n=114). The above parameters were not significantly changed in the placebo group (n=107). Mortality was 3.5% in the diltiazem group and 11.2% in the placebo group (P<0.05). Further analysis also shows that LVEDd were reduced and EF were obviously elevated in patients with DCM of LVEDd <70 mm, but the above parameters weren't improved in patients of LVEDd >70 mm. The study suggests that diltiazem is safe and effective in the treatment of DCM, the action mechanism might be intervention in antibody-mediated myocardial damage and protection of myocardium. Diltiazem is suitable for the treatment of the early stage in DCM.