The predictive values of beta1 -adrenergic and M2 muscarinic receptor autoantibodies for sudden cardiac death in patients with chronic heart failure

Association between anti-SSA autoantibodies and conduction disturbances in heart failure

BACKGROUND

Conduction disturbances play an important role in the occurrence and development of heart failure (HF). Studies suggest autoantibodies may attack the conduction system. However, whether autoantibodies are associated with conduction disturbances in patients with HF is unclear.

OBJECTIVE

The purpose of this study was to assess whether anti-SSA, anti-Ro/Sjögren syndrome-related antigen A antibodies known for congenital atrioventricular block (AVB), is associated with conduction disturbances in patients with HF.

METHODS

This retrospective observational study used data from patients with HF who were admitted to Beijing Anzhen Hospital between January 2018 and June 2022. Patients who were tested for anti-SSA and had undergone electrocardiographic examination during hospitalization were included. Conduction disturbances, including AVB, bundle branch block (BBB), and intraventricular conduction delay, were confirmed by a cardiologist blinded to anti-SSA status. Univariate and multivariable logistic regression analyses were performed to assess the association between anti-SSA and conduction disturbances.

RESULTS

A total of 766 patients were included in this study, of whom 70 (9.1%) were anti-SSA positive. Subjects who were anti-SSA positive showed a higher prevalence of AVB (20% vs 10.6%) and BBB (27.3 % vs 10.9 %), including both left BBB and right BBB (all P <.05). After adjusting for known risk factors, anti-SSA was independently associated with AVB (odds ratio [OR] 2.42; 95% confidence interval [CI] 1.18-5.43; P = .03) and BBB (OR 3.15; 95% CI 1.68-5.89; P <.001).

CONCLUSION

Anti-SSA is independently associated with AVB and BBB in patients with HF. Further study of the role of autoantibodies in the development of conduction abnormalities in patients with HF to generate possible targeted treatments is required.

A case report of a rare genetic mutation (LMNA-C.185G>C, p.Arg62Pro) associated with dilated cardiomyopathy in a Han Chinese child

Dilated cardiomyopathy (DCM) remains an enigmatic myocardial disorder characterized either by enlargement of either the left or right ventricle or both and reduced contractility, posing a significant burden on pediatric populations as a leading cause of cardiac-related mortality and morbidity. This paper presents a compelling case of DCM in a Han Chinese child whose genomic analysis unveiled a novel LMNA-C.185G>C (p.Arg62Pro) variant. Over a meticulous 3-year clinical follow-up, spanning ten outpatient consultations and hospital admissions since the initial diagnosis, the patient exhibited a progressive emergence of various cardiac conduction anomalies closely mirroring LMNA-associated phenotypes. Delving into a comprehensive review of the patient's 14-year medical journey and familial history, antecedent signs of muscular dystrophy (MD) predated DCM onset. Familial scrutiny revealed a lineage marred by muscular atrophy, with the patient's maternal grandmother having a history of muscular dystrophy and an episode of DCM, necessitating cardiac transplantation in the patient's uncle at age 37. This scenario illuminates the intricate interplay between LMNA-associated diseases and genetic predisposition. Timely identification of etiological triggers stands paramount in DCM management. Beyond conventional genetic scrutiny, leveraging novel serum biomarkers such as anti-heart muscle antibodies (AHA) remarkably enhanced diagnostic precision. Notably, personalized therapeutic interventions comprising prednisolone regimens and intravenous immunoglobulin infusions precipitated marked amelioration in heart failure symptoms and serum biomarker profiles. It is noteworthy to identify this novel genetic locus within the Han Chinese populace, underscoring the imperative of expanding the LMNA mutation repository within this demographic cohort. Early recognition of clinical manifestations and etiological cues in pediatric DCM heralds a paradigm shift in risk prognostication and individualized therapeutic interventions, underscoring the profound significance of precision medicine in combating rare familial cardiomyopathies.

G protein-coupled receptor-mediated autophagy in health and disease

G protein-coupled receptors (GPCRs) constitute the largest and most diverse superfamily of mammalian transmembrane proteins. These receptors are involved in a wide range of physiological functions and are targets for more than a third of available drugs in the market. Autophagy is a cellular process involved in degrading damaged proteins and organelles and in recycling cellular components. Deficiencies in autophagy are involved in a variety of pathological conditions. Both GPCRs and autophagy are essential in preserving homeostasis and cell survival. There is emerging evidence suggesting that GPCRs are direct regulators of autophagy. Additionally, autophagic machinery is involved in the regulation of GPCR signalling. The interplay between GPCR and autophagic signalling mechanisms significantly impacts on health and disease; however, there is still an incomplete understanding of the underlying mechanisms and therapeutic implications in different tissues and disease contexts. This review aims to discuss the interactions between GPCR and autophagy signalling. Studies on muscarinic receptors, beta-adrenoceptors, taste receptors, purinergic receptors and adhesion GPCRs are summarized, in relation to autophagy.

β1 Adrenergic Receptor Autoantibodies and IgG Subclasses: Current Status and Unsolved Issues

A wide range of anti-myocardial autoantibodies have been reported since the 1970s. Among them, autoantibodies against the β1-adrenergic receptor (β1AR-AAb) have been the most thoroughly investigated, especially in dilated cardiomyopathy (DCM). Β1AR-Aabs have agonist effects inducing desensitization of β1AR, cardiomyocyte apoptosis, and sustained calcium influx which lead to cardiac dysfunction and arrhythmias. Β1AR-Aab has been reported to be detected in approximately 40% of patients with DCM, and the presence of the antibody has been associated with worse clinical outcomes. The removal of anti-myocardial autoantibodies including β1AR-AAb by immunoadsorption is beneficial for the improvement of cardiac function for DCM patients. However, several studies have suggested that its efficacy depended on the removal of AAbs belonging to the IgG3 subclass, not total IgG. IgG subclasses differ in the structure of the Fc region, suggesting that the mechanism of action of β1AR-AAb differs depending on the IgG subclasses. Our previous clinical research demonstrated that the patients with β1AR-AAb better responded to β-blocker therapy, but the following studies found that its response also differed among IgG subclasses. Further studies are needed to elucidate the possible pathogenic role of IgG subclasses of β1AR-AAbs in DCM, and the broad spectrum of cardiovascular diseases including HF with preserved ejection fraction.

Prognostic Value of β1 Adrenergic Receptor Autoantibody and Soluble Suppression of Tumorigenicity-2 in Patients With Acutely Decompensated Heart Failure

Background

Both β1 adrenergic receptor autoantibody (β1-AA) and soluble suppression of tumorigenicity-2 (sST2) take a role in the pathological remodeling of heart failure. However, limited studies investigated the correlation between the expression of β1-AA and sST2 in patients with acutely decompensated heart failure (ADHF).

Objective

To explore the correlation between β1-AA and sST2, and evaluate their prognostic value in patients with ADHF.

Methods

Patients who were admitted for ADHF were included. The N-terminal pro-brain natriuretic peptide (NT-proBNP), sST2, and β1-AA in blood samples were tested at hospital admission and then followed up for assessing the outcomes. Pearson correlation analysis was used to explore the correlation between β1-AA and sST2. The effects of β1-AA, sST2, or the combination of them on the all-cause mortality of patients with ADHF were assessed by Multivariate Cox regression analysis.

Results

There were 96 patients with ADHF and 96 control populations enrolled. The β1-AA was significantly higher in ADHF than in the control group (0.321 ± 0.06 vs. 0.229 ± 0.04, P = 0.000). Pearson correlation analysis showed that β1-AA was positively correlated with sST2 (r = 0.593), NT-proBNP (r = 0.557), Procalcitonin (r = 0.176), and left ventricular end-diastolic diameter (r = 0.315), but negatively correlated with triglycerides (r = −0.323), and left ventricular ejection fraction (r = −0.430) (all P < 0.05) in ADHF. Patients with ADHF, complicated with both high β1-AA and sST2, showed the highest all-cause mortality during an average of 25.5 months of follow-up. Multivariate Cox regression showed the combination of both high β1-AA and sST2 independently correlated with the all-cause mortality after adjustment for other risk factors (hazard ratio 3.348, 95% CI 1.440 to 7.784, P = 0.005). After adding with β1-AA and sST2, the area under the curves for the prognostic all-cause mortality could increase from 0.642 to 0.748 (P = 0.011).

Conclusion

The β1-AA is positively correlated with sST2 in patients with ADHF. Elevated plasma β1-AA and sST2 level in patients with ADHF are associated with poorer prognoses.

LRP6 Polymorphisms Is Associated With Sudden Cardiac Death in Patients With Chronic Heart Failure in the Chinese Han Population

Low-density lipoprotein receptor-related protein 6 (LRP6) plays a critical role in cardiovascular homeostasis. The deficiency of LRP6 is associated with a high risk of arrhythmias. However, the association between genetic variations of LRP6 and sudden cardiac death (SCD) remains unknown. This study aims to explore the association between common variants of LRP6 and the prognosis of chronic heart failure (CHF) patients. From July 2005 to December 2009, patients with CHF were enrolled from 10 hospitals in China. The single-nucleotide polymorphism (SNP) rs2302684 was selected for the evaluation of the effect of LRP6 polymorphisms on the survival in patients with CHF. A total of 1,437 patients with CHF were finally included for the analysis. During a median follow-up of 61 months (range 0.4–129 months), a total of 546 (38.0%) patients died, including 201 (36.8%) cases with SCD and 345 (63.2%) cases with non-SCD. Patients carrying A allele of rs2302684 had an increased risk of all-cause death (adjusted HR 1.452, 95% CI 1.189–1.706; P &lt; 0.001) and SCD (adjusted HR 1.783, 95% CI 1.337–2.378; P &lt; 0.001). Therefore, the SNP rs2302684 T&gt;A in LRP6 indicated higher risks of all-cause death and SCD in patients with CHF. LRP6 could be added as a novel predictor of SCD and might be a potential therapeutic target in the prevention of SCD in the CHF population.

Sympatho-adrenergic mechanisms in heart failure: new insights into pathophysiology

The sympathetic nervous system is activated in the setting of heart failure (HF) to compensate for hemodynamic instability. However, acute sympathetic surge or sustained high neuronal firing rates activates β-adrenergic receptor (βAR) signaling contributing to myocardial remodeling, dysfunction and electrical instability. Thus, sympatho-βAR activation is regarded as a hallmark of HF and forms pathophysiological basis for β-blocking therapy. Building upon earlier research findings, studies conducted in the recent decades have significantly advanced our understanding on the sympatho-adrenergic mechanism in HF, which forms the focus of this article. This review notes recent research progress regarding the roles of cardiac β2AR or α1AR in the failing heart, significance of β1AR-autoantibodies, and βAR signaling through G-protein independent signaling pathways. Sympatho-βAR regulation of immune cells or fibroblasts is specifically discussed. On the neuronal aspects, knowledge is assembled on the remodeling of sympathetic nerves of the failing heart, regulation by presynaptic α2AR of NE release, and findings on device-based neuromodulation of the sympathetic nervous system. The review ends with highlighting areas where significant knowledge gaps exist but hold promise for new breakthroughs.

Role of Anti-Beta-1-Adrenergic Receptor Antibodies in Cardiac Dysfunction in Patients with Cirrhotic Cardiomyopathy

Cirrhotic cardiomyopathy (CCM) is a recognized complication of cirrhosis and is associated with poor outcomes, especially under challenges such as surgery/liver transplantation. However, the mechanism is not clear, and the treatment is not specific. The present study aimed to evaluate the role of anti-β₁-adrenergic receptor antibodies (anti-β1-AR) in CCM. We enrolled 3 groups: healthy controls, cirrhotic patients without CCM, and patients with CCM. We found that the anti-β1-AR levels in the CCM group were significantly higher than that in the non-CCM group; anti-β1-AR was positively correlated to NT-proBNP, negatively correlated to left ventricular ejection fraction, fractional shortening ((r =  - 0.466, P < 0.05), and the ratio of peak early (E wave) and atrial (A wave) flow velocities (E/A (r =  - 0.475, P < 0.05) in CCM patients. Anti-β1-AR is a useful predictive biomarker for the presence of CCM and eventually may also have therapeutic implications. Clinical Trials Registration: Chinese Clinical Trials No. ChiCTR 2,000,037,730.

Autoantibodies against M5-muscarinic and beta1-adrenergic receptors in periodontitis patients

Autoantibodies against muscarinic and beta₁-adrenergic receptors are considered a potential cause and/or risk factor for chronic heart failure. Association of periodontitis with such autoantibodies and with impaired heart function has been observed in patients exposed to endemic Chagas' disease, which triggers by itself cardiomyopathy and receptor immunization.Here we studied the association between periodontitis, markers of cardiac injury and receptor autoimmunization in periodontitis patients (n = 147) not exposed to Chagas' disease. The autoantibodies were determined by IgG binding to native intact muscarinic and beta₁-adrenergic receptors or to a cyclic peptide mimicking the disease-relevant conformational autoepitope presented by the active beta₁-adrenergic receptor. Possible cardiac injury and inflammatory status were judged by serum levels of proBNP/Troponin I and CRP/IL-6, respectively. These parameters were analysed in healthy and periodontally diseased individuals as well as before and after periodontal therapy.Patients with periodontitis had significantly (p < 0.001) higher levels of autoantibodies against M₅-muscarinic and beta₁-adrenergic receptors, which further increased following periodontal therapy. Receptor autoantibodies were associated with increased inflammatory status but not with increased markers of cardiac injury. Thus, our data indicate that periodontitis triggers systemic inflammation, which is associated with receptor autoimmunization, and, independently thereof, with cardiac injury.

Diagnostic and prognostic value of autoantibodies against β1-adrenoreceptors in patients with heart failure following acute myocardial infarction: A 5-year prospective study

A number of studies have suggested that autoantibodies against β₁-adrenoreceptors (β₁R-AAbs) have an important role in pathophysiological processes of heart failure. The aim of the present study was to determine whether β₁R-AAbs are implicated in cardiac dysfunction following acute myocardial infarction (AMI) and their association with prognosis. A total of 33 cases with systolic heart failure (SHF), 49 with diastolic heart failure (DHF) and 44 with normal heart function following AMI were recruited. β₁R-AAbs were detected by ELISA and major adverse cardiac events (MACEs) were recorded during the 5-year follow-up. The positive rate of β₁R-AAbs in the SHF group (45.5%) was significantly higher compared with that in the DHF (22.4%; P<0.05) and normal (15.9%; P<0.05) groups. The area under the receiver operating characteristics curve for the diagnosis of SHF was 0.630 (95% CI: 0.514–0.747, P=0.026). During a median follow-up period of 51.0±15.4 months, the positive rate of β₁R-AAbs in the MACEs group was significantly higher compared with that in the non-MACEs group (P<0.05). Multivariate logistic regression analysis indicated that the left ventricular ejection fraction and diabetes were independent predictors of 5-year MACEs following AMI, whereas β₁R-AAbs were not. Kaplan-Meier analysis revealed that the cumulative MACEs-free survival rate was the lowest in the SHF group, followed by the DHF and normal groups (P<0.05). Therefore, β₁R-AAbs were indicated to be of value for early diagnosis of SHF after AMI but not as independent predictors for the prognosis of patients with AMI.

The relationship between β1 -adrenergic and M2 -muscarinic receptor autoantibodies and hypertrophic cardiomyopathy

NEW FINDINGS

What is the central question of this study? The concentrations of β₁ -adrenergic receptor and M₂ -muscarinic receptor autoantibodies in hypertrophic cardiomyopathy (HCM) patients and the relationship between the cardiac autoantibodies and clinical manifestations of HCM have rarely been reported. What is the main finding and its importance? We found that the concentrations of the two autoantibodies in HCM patients were significantly higher than those in control subjects. Furthermore, we found that the concentrations of the two autoantibodies could reflect myocardial injury and diastolic dysfunction in HCM patients to some extent and might be involved in the occurrence of arrhythmia. These findings might be valuable in exploration of the mechanisms of occurrence and progression of HCM.

ABSTRACT

Increasing attention is being given to the role of immunological mechanisms in the development of heart failure. The purpose of this study was to investigate the concentration of serum β₁ -adrenergic receptor autoantibody (β₁ -AAb) and M₂ -muscarinic receptor autoantibody (M₂ -AAb) in patients with hypertrophic cardiomyopathy (HCM), and the relationship between β₁ -AAb, M₂ -AAb and clinical indices. One hundred and thirty-four patients with HCM were recruited consecutively into the HCM group. Forty healthy subjects were assigned as the normal controls (NCs). Serum samples were collected to measure the concentrations of β₁ -AAb and M₂ -AAb by enzyme-linked immunosorbent assay. The clinical data of HCM patients were collected. The serum concentrations of β₁ -AAb and M₂ -AAb of HCM patients were significantly higher than those of NCs. In HCM patients, those with a left atrial diameter ≥50 mm or moderate-to-severe mitral regurgitation had significantly higher concentrations of the two autoantibodies. Patients with a history of syncope had higher concentrations of β₁ -AAb. Female patients and patients with a family history of sudden cardiac death or atrial fibrillation had higher concentrations of M₂ -AAb. Maximal wall thickness, interventricular septum thickness and resting left ventricular outflow tract gradient were positively correlated with log β₁ -AAb or log M₂ -AAb in HCM patients. In conclusion, the serum concentrations of β₁ -AAb and M₂ -AAb of HCM patients were significantly higher than those of NCs. Being female, syncope, a family history of sudden death, atrial fibrillation, left atrial diameter ≥50 mm, moderate-to-severe mitral regurgitation, maximal wall thickness, interventricular septum thickness and resting left ventricular outflow tract gradient may affect the concentrations of the two autoantibodies.

Doberman pinschers present autoimmunity associated with functional autoantibodies: A model to study the autoimmune background of human dilated cardiomyopathy

Background

Autoimmunity associated with autoantibodies against the β1-adrenergic receptor (β1-AAB) is increasingly accepted as the driver of human dilated cardiomyopathy (DCM). Unfortunately, there is a lack of animal models to extend the knowledge about β1-AAB autoimmunity in DCM and to develop appropriate treatment strategies.

Objectives

To introduce an animal model, we investigated the β1-AAB associated autoimmunity in Doberman Pinscher (DP) with dilated cardiomyopathy, which has similarities to human DCM.

Materials and methods

Eighty-seven DP with cardiomyopathy in terms of pathological ECG and echocardiography (DoCM) and 31 dogs (at enrollment) without DoCM (controls) were analyzed for serum activity of β1-AAB with a bioassay that records the chronotropic response of spontaneously beating cultured neonatal rat cardiomyocytes to the DP’s IgG. To locate the receptor binding site of β1-AAB and the autoantibody’s sensitivity to inhibition, competing experiments with related blockers were performed with the bioassay. In controls that developed DoCM during follow-up, β1-AAB were analyzed during progress.

Results

Fifty-nine (67.8%) DoCM dogs and 19 (61.3%) controls were β1-AAB positive. Of the controls that developed DoCM, 8 were β1-AAB positive (p = 0.044 vs. dogs remaining in the control group); their β1-AAB activity increased with the cardiomyopathy progress (p<0.02). To supplement DoCM group with the 9 animals which developed cardiomyopathy in the follow up, a more pronounced β1-AAB positivity became visible in the DoCM group (p = 0.066).

Total and cardiac mortality were higher in β1-AAB positive DP (p = 0.002; p = 0037). The dogs’ β1-AAB recognized a specific epitope on the second extracellular receptor and were sensitive to inhibition by drugs already successfully tested to inhibit the corresponding human autoantibody.

Conclusions

Doberman Pinschers presented β1-AAB associated autoimmunity, similar as in the pathogenesis of human DCM. Consequently, DP could compensate the lack of animal models for the investigation of β1-AAB autoimmunity in human DCM.

Autoantibodies for Cardiac Channels and Sudden Cardiac Death and its Relationship to Autoimmune Disorders

Background:

Sudden Cardiac Death (SCD) is an unexpected death caused by heart dys-function. Autoantibodies against cardiac proteins may be potentially involved in the occurrence and progression of cardiac disease and SCD. The first report on the role of autoantibodies in idiopathic dilated cardiomyopathy appeared in the 1980s. In recent years new studies on the effects of the pres-ence of specific autoantibodies and their relationship to ventricular arrhythmias and SCD were pub-lished. The purpose of the current mini-review is to analyze the results of the research studies focused on the relationship between anti-cardiomyocyte autoantibodies and SCD with respect to autoimmune disorders.

Conclusion:

According to our analysis, more research is needed to understand the role of these auto-antibodies against cardiac proteins in the SCD pathogenesis, and potentially employ this knowledge for improving prognosis of SCD.

Roles of Host Immunity in Viral Myocarditis and Dilated Cardiomyopathy

The pathogenesis of viral myocarditis includes both the direct damage mediated by viral infection and the indirect lesion resulted from host immune responses. Myocarditis can progress into dilated cardiomyopathy that is also associated with immunopathogenesis. T cell-mediated autoimmunity, antibody-mediated autoimmunity (autoantibodies), and innate immunity, working together, contribute to the development of myocarditis and dilated cardiomyopathy.

A standardised FACS assay based on native, receptor transfected cells for the clinical diagnosis and monitoring of β1-adrenergic receptor autoantibodies in human heart disease

BACKGROUND

Autoantibodies against β1-adrenergic receptors (β1AR) that stimulate cardiac cAMP-production play a causal role in the pathogenesis of human heart failure. Patients can be subjected to specific therapies, if the presence of potentially cardio-noxious β1AR-autoantibodies is reliably diagnosed. This requires assessment of IgG-interactions with the native β1AR because β1AR-autoantibodies target a conformational epitope inadequately presented by denatured receptors or linear peptides. Here, we report on a standardised diagnostic procedure for the assessment of β1AR-autoantibodies in heart failure patients, which is based on IgG-binding to native human β1AR.

METHODS

Good laboratory practice (GLP)-conform measurement of β1AR-autoantibodies was based on flow-cytometric quantification of differential IgG-binding to native HT1080 cells overexpressing biofluorescent human β1AR or not. Receptor-specific IgG-binding was derived from IgG-related median fluorescence of β1AR-positive cells corrected for background staining of β1AR-negative cells admixed to each measurement. The slope of IgG binding at two different concentrations was used as measure for the titre/avidity of β1AR-autoantibodies.

RESULTS

Sensitivity and specificity of the novel procedure for high β1AR-autoantibody levels in dilated cardiomyopathy patients (n=40, NYHA class III-IV) relative to n=40 matched healthy subjects was >90%. It was similar to functional assays considered the gold standard and vastly superior to existing screening-procedures employing fixed cells or linear receptor-peptides as auto-antigenic targets. Inter-assay scatter was 7%-15% and linear dilution recovery was within ±10% of expected values throughout.

CONCLUSIONS

The novel assay possibly provides a tool to determine true prevalence and clinical impact of β1AR-autoantibodies. Furthermore, it may serve as companion diagnostic for therapies specifically directed at β1AR-autoantibodies.

Proliferation in cardiac fibroblasts induced by β1-adrenoceptor autoantibody and the underlying mechanisms

Chronic sustained stimulation of β-adrenoceptor is closely related to cardiac fibrosis which is bad for cardiac function. Growing evidence showed that the high prevalence of β₁-adrenoceptor autoantibody (β₁-AA) in the sera of patients with various types of cardiovascular diseases decreased cardiac function. In the current study, we demonstrated that β₁-AA impaired the cardiac function evaluated by echocardiography and that β₁-AA triggered cardiac fibrosis in terms of increased expression of α-smooth muscle actin as the marker of myofibroblast and collagen deposition in a passive β₁-AA immunized mice model during 16 weeks. Further, we showed that β₁-AA activated β₁-AR/cAMP/PKA pathway and promoted proliferation in primary cardiac fibroblasts through specific binding to β₁-AR but not to β₂-AR. Moreover, β₁-AA was also likely to promote proliferation in cardiac fibroblasts through activating p38MAPK and ERK1/2 as p38MAPK inhibitor SB203580 and ERK1/2 inhibitor PD98059 partially reversed the proliferative effect. The persistent activating signalling of PKA and P38MAPK in 1 h induced by β₁-AA was associated with lacking agonist-induced desensitization phenomena. The conditioned medium from β₁-AA-stimulated cardiac fibroblasts induced cardiomyocyte apoptosis, which indicated that β₁-AA changed the secretion of cardiac fibroblasts contributing to cardiac injury. These findings will contribute to our understanding of the pathological mechanisms of β₁-AA.

Antibodies to β adrenergic and muscarinic cholinergic receptors in patients with Chronic Fatigue Syndrome

Infection-triggered disease onset, chronic immune activation and autonomic dysregulation in CFS point to an autoimmune disease directed against neurotransmitter receptors. Autoantibodies against G-protein coupled receptors were shown to play a pathogenic role in several autoimmune diseases. Here, serum samples from a patient cohort from Berlin (n=268) and from Bergen with pre- and post-treatment samples from 25 patients treated within the KTS-2 rituximab trial were analysed for IgG against human α and β adrenergic, muscarinic (M) 1-5 acetylcholine, dopamine, serotonin, angiotensin, and endothelin receptors by ELISA and compared to a healthy control cohort (n=108). Antibodies against β2, M3 and M4 receptors were significantly elevated in CFS patients compared to controls. In contrast, levels of antibodies against α adrenergic, dopamine, serotonin, angiotensin, and endothelin receptors were not different between patients and controls. A high correlation was found between levels of autoantibodies and elevated IgG1-3 subclasses, but not with IgG4. Further patients with high β2 antibodies had significantly more frequently activated HLA-DR+ T cells and more frequently thyreoperoxidase and anti-nuclear antibodies. In patients receiving rituximab maintenance treatment achieving prolonged B-cell depletion, elevated β2 and M4 receptor autoantibodies significantly declined in clinical responder, but not in non-responder. We provide evidence that 29.5% of patients with CFS had elevated antibodies against one or more M acetylcholine and β adrenergic receptors which are potential biomarkers for response to B-cell depleting therapy. The association of autoantibodies with immune markers suggests that they activate B and T cells expressing β adrenergic and M acetylcholine receptors. Dysregulation of acetylcholine and adrenergic signalling could also explain various clinical symptoms of CFS.

Calcium channel autoantibodies predicted sudden cardiac death and all-cause mortality in patients with ischemic and nonischemic chronic heart failure

The purpose of this study was to evaluate whether CC-AAbs levels could predict prognosis in CHF patients. A total of 2096 patients with CHF (841 DCM patients and 1255 ICM patients) and 834 control subjects were recruited. CC-AAbs were detected and the relationship between CC-AAbs and patient prognosis was analyzed. During a median follow-up time of 52 months, there were 578 deaths. Of these, sudden cardiac death (SCD) occurred in 102 cases of DCM and 121 cases of ICM. The presence of CC-AAbs in patients was significantly higher than that of controls (both P < 0.001). Multivariate analysis revealed that positive CC-AAbs could predict SCD (HR 3.191, 95% CI 1.598–6.369 for DCM; HR 2.805, 95% CI 1.488–5.288 for ICM) and all-cause mortality (HR 1.733, 95% CI 1.042–2.883 for DCM; HR 2.219, 95% CI 1.461–3.371 for ICM) in CHF patients. A significant association between CC-AAbs and non-SCD (NSCD) was found in ICM patients (HR = 1.887, 95% CI 1.081–3.293). Our results demonstrated that the presence of CC-AAbs was higher in CHF patients versus controls and corresponds to a higher incidence of all-cause death and SCD. Positive CC-AAbs may serve as an independent predictor for SCD and all-cause death in these patients.

A common NOS1AP genetic polymorphism, rs12567209 G>A, is associated with sudden cardiac death in patients with chronic heart failure in the Chinese Han population

BACKGROUND

Variants in NOS1AP associated with cardiac repolarization and sudden cardiac death (SCD) in coronary artery disease have been reported. Whether they are related to mortality and QTc interval in chronic heart failure (CHF) has not been investigated.

METHODS AND RESULTS

A total of 1,428 patients with CHF and 480 control subjects were genotyped for 6 SNPs of NOS1AP, and the genetic associations with mortality as well as QTc interval were analyzed. During a median follow-up period of 52 months, 467 patients (32.70%) died, of which deaths 169 (36.19%) were SCD. The A allele of rs12567209 was associated with greater risk of all-cause death and SCD (hazard ratio [HR] 1.381, 95% confidence interval [CI] 1.124-1.698 [P = .002], and HR 1.645, 95% CI 1.184-2.287 [P = .003], respectively). After adjusting for other risk factors, significant differences remained (HR 1.309, 95% CI 1.054-1.624 [P = .015], and HR 1.601, 95% CI 1.129-2.271 [P = .008]). The A allele was also associated with prolongation of QTc interval by 4.04 ms in the entire population (P = .026).

CONCLUSIONS

The A allele of rs12567209 in NOS1AP may serve as an independent predictor of all-cause death and SCD in patients with CHF, it is also associated with prolonged QTc interval in the Chinese Han population.

Autoantibodies against the β3-adrenoceptor protect from cardiac dysfunction in a rat model of pressure overload

β₃-adrenoceptors (β₃-ARs) mediate a negative inotropic effect in human ventricular cardiomyocytes, which is opposite to that of β₁- and β₂-ARs. It has been previously demonstrated that autoantibodies against the β_1/β₂-AR exist in the sera of some patients with heart failure (HF) and these autoantibodies display agonist-like effects. Our aim in this study was to observe whether autoantibodies against the β₃-AR (β₃-AR Abs) exist in the sera of patients with HF and to assess the effects of β₃-AR Abs on rat model of pressure overload cardiomyopthy. In the present study, the level of β₃-AR Abs in the sera of HF patients was screened by ELISA. β₃-AR Abs from HF patients were administrated to male adult rats with abdominal aortic banding (AAB), and the cardiac function was measured by echocardiographic examination and hemodynamic studies. The biological effects of this autoantibody on cardiomyocytes were evaluated using a motion-edge detection system, intracellular calcium transient assay, and patch clamp techniques. Compared to healthy subjects, the frequency of occurrence and titer of β₃-AR Abs in the sera of HF patients were greatly increased, and β₃-AR Abs could prevent LV dilation and improve the cardiac function of rats with AAB. β₃-AR Abs exhibited negative chronotropic and inotropic effects and were accompanied by a decreased intracellular Ca²⁺ transient and membrane L-type Ca²⁺ current in cardiomyocytes. Our results demonstrated the existence of β₃-AR Abs in the sera of patients with HF and found that this autoantibody could alleviate the cardiac dysfunction induced by pressure-overload in AAB rats.

Impact of human autoantibodies on β1-adrenergic receptor conformation, activity, and internalization

Aims

Autoantibodies against second extracellular loops of β₁-adrenergic receptors frequent in dilated cardiomyopathy confer myocardial dysfunction presumably via cAMP stimulation. Here, we investigate the autoantibody impact on receptor conformation and function.

Methods and results

IgG was prepared from patients with dilated cardiomyopathy, matched healthy donors (10 each) or commercial IgG preparations (2). IgG binding to β₁-adrenergic receptor peptides was detected in 5 of 10 patients and 2 of 10 controls. IgG colocalization with the native receptor was detected in 8 of 10 patients and 1 of 10 controls (10 of 10 patients and 7 of 10 controls at >30 mg IgG/L). All IgGs exhibiting receptor colocalization triggered changes in receptor conformation (determined with fluorescent sensors) not stringently correlated to cAMP stimulation, suggesting the induction of more or less active receptor conformations. Receptor-activating IgG was detected in 8 of 10 patients but only 1 of 10 controls. In addition, IgG from 8 of 10 patients and 3 of 10 controls attenuated receptor internalization (measured by total internal reflection fluorescence microscopy). IgG-inducing inactive receptor conformations had no effect on subsequent cAMP stimulation by isoproterenol. IgG-inducing active receptor conformations dampened or augmented subsequent cAMP stimulation by isoproterenol, depending on whether receptor internalization was attenuated or not. Corresponding IgG effects on the basal beating rate and chronotropic isoproterenol response of embryonic human cardiomyocytes were observed.

Conclusions

(i) Autoantibodies trigger conformation changes in the β₁-adrenergic receptor molecule. (ii) Some also attenuate receptor internalization. (iii) Combinations thereof increase the basal beating rate of cardiomyocytes and optionally entail dampening of their chronotropic catecholamine responses. (iv) The latter effects seem specific for patient autoantibodies, which also have higher levels.