The prognostic value of autoantibodies against β1-adrenoceptor and cardiac troponin-I for clinical outcomes in STEMI

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.

Expression Levels of MicroRNA-146b and Anti-Cardiac Troponin I in Serum of Children with Viral Myocarditis and Their Clinical Significance

Background

To investigate the expression levels of microRNA-146b (miR-146b) and cardiac troponin I (anti-cTnI) in serum of children with viral myocarditis and their clinical significance.

Methods

Forty-eight children with viral myocarditis (patient group) and 40 healthy physical examinees (healthy group), who were diagnosed in Jinan City People's Hospital Affiliated to Shandong First Medical University, China from Feb 2018 to May 2019, were enrolled as study subjects. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect the level of miR-146b in serum of children. ELISA was used to detect the expression of anti-cTnI in serum of children. Pearson was used to analyze the correlation between the level of miR-146b and the level of anti-cTnI, and the factors affecting the prognosis.

Results

The levels of miR-146b and anti-cTnI in serum of children in patient group were statistically significantly higher than those of healthy group (P<0.01). The AUC of miR-146b was 0.741, (95% CI: 0.638-0.843), the specificity was 62.50%, the sensitivity was 82.50%, and the AUC of anti-cTnI was 0.720 (95% CI: 0.608-0.832), the specificity was 64.58% and the sensitivity was 92.50%. The level of miR-146b was positively correlated with the level of anti-cTnI (r=0.601, P<0.05). CK-MB, LVEF, miR-146b and anti-cTnI expression were independent risk factors affecting the prognosis.

Conclusion

The levels of miR-146b and anti-cTnI increased in serum of patients with viral myocarditis. They were related to the degree of myocardial injury, which indicated that miR-146b and anti-cTnI might be involved in the pathological process of viral myocarditis.

Autoantibodies Against β1-Adrenoceptor Exaggerated Ventricular Remodeling by Inhibiting CTRP9 Expression

Background

Autoantibodies against the second extracellular loop of the β₁‐adrenoceptor (β₁‐AA) act similarly to agonist of β₁‐adrenergic receptor, which plays an important role in the pathophysiological characteristics of ventricular remodeling. Recently, considerable lines of evidence have suggested that CTRP9 (C1q tumor necrosis factor–related protein 9) is a potent cardioprotective cardiokine and protects the heart from ventricular remodeling. The aim of this study was to determine the role of CTRP9 in ventricular remodeling induced by β₁‐AA.

Methods and Results

Blood samples were collected from 131 patients with coronary heart disease and 131 healthy subjects. The serum levels of β₁‐AA and CTRP9 were detected using ELISA. The results revealed that CTRP9 levels in β₁‐AA–positive patients were lower than those in β₁‐AA–negative patients, and serum CTRP9 concentrations were inversely correlated with β₁‐AA. β₁‐AA monoclonal antibodies (β₁‐AAmAbs) were administered in mice with and without rAAV9‐cTnT‐Full Ctrp9‐FLAG virus for 8 weeks. Reverse transcription–polymerase chain reaction/Western analysis showed that cardiomyocyte CTRP9 expression was significantly reduced in β₁‐AAmAb–treated mice. Moreover, compared with the β₁‐AAmAb alone group, cardiac‐specific CTRP9 overexpression improved cardiac function, attenuated adverse remodeling, and ameliorated cardiomyocyte apoptosis and fibrosis. Mechanistic studies demonstrated that CTRP9 overexpression decreased the levels of G‐protein–coupled receptor kinase 2 and promoted the activation of AMP‐dependent kinase pathway. However, cardiac‐specific overexpression of CTRP9 had no effect on the levels of cAMP and protein kinase A activity elevated by β₁‐AAmAb.

Conclusions

This study provides the first evidence that the long‐term existence of β₁‐AAmAb suppresses cardiac CTRP9 expression and exaggerates cardiac remodeling, suggesting that CTRP9 may be a novel therapeutic target against pathologic remodeling in β₁‐AA–positive patients with coronary heart disease.

Pro-remodeling effect of autoantibody against β1-adrenoceptor on cardiomyocytes involves T cells dysfunction under the pathological condition of heart failure

Autoantibody against β₁-adrenoceptor (β₁-AA) has been shown to be closely linked to the aggravation of heart failure. Removal of β₁-AA remarkably attenuated patients' cardiac dysfunction. We found that β₁-AA induced rat heart failure with increased CD4⁺ T cells. However, whether or not β₁-AA interacts with T cells isolated from heart failure patients remains unknown. Twenty-one β₁-AA-negative heart failure patients were divided into those taking β-adrenergic blocker and those not. The effects of β₁-AA monoclonal antibodies (β₁-AAmAb) on T cells proliferation were detected using the CCK-8 assay. IFN-γ and IL-4 production by human T cells were measured by after the administration of β₁-AAmAb. The levels of cardiomyocyte apoptosis and hypertrophy were detected after co-cultured with the supernatant of T cells pre-stimulated by β₁-AAmAb. It was found that β₁-AAmAb promoted T cell proliferation via the β₁-AR/cAMP/PKA pathway in patients who not take β-blocker. β₁-AAmAb inhibited the characteristic cytokine secretion of Th1, IFN-γ, but had no significant effect on the Th2 cytokine IL-4. Supernatant resulted from the T cells pre-treated with β₁-AAmAb induced cardiomyocytes remodeling, as evidenced by increased levels of cardiomyocytes apoptosis and hypertrophy. We propose that heart failure is likely to be an interference factor for Th-mediated immunity, and the presence of β₁-AAmAb may aggravate this effect and deteriorate concomitant inflammatory injury in cardiomyocytes, partially via β₁-AR/cAMP/PKA pathway.

Anti-cardiac troponin antibodies in clinical human disease: a systematic review

Anti-cardiac troponin antibodies have been studied in different types of clinical diseases and in healthy populations. A systematic review of published data on anti-troponin antibodies was carried out (search performed on PubMed, ISI Web of Knowledge and Scopus databases). From title and abstract analysis, thirty-three articles were included that met the pre-specified criteria; after full-text analysis, nine articles were excluded. Most studies assessed anti-troponin I antibodies. The prevalence of anti-cardiac troponin antibodies in healthy individuals ranged from 0.0% to 20.0%. The prevalence of anti-troponin I autoantibodies in dilated cardiomyopathy (DCM) ranged from 7.0% to 22.2%. Other conditions under study were myocardial infarction, ischemic cardiomyopathy (ICM), peripartum cardiomyopathy (PPCM), Chagas disease, Emery-Dreifuss muscular dystrophy (EDMD) and renal transplantation. In the different patient populations studied, anti-cardiac troponin antibodies have been shown to be either positively or negatively associated with prognostic and clinical features. In what concerns a possible value as biomarkers, these assays have not emerged up to the present moment as important aids for practical clinical decisions in cardiac or other types of patients. In what concerns pathophysiology, anti-cardiac troponin autoantibodies may play a role in different diseases. It can be speculated that these antibodies could be involved in perpetuating some degree of cardiac injury after an event, such as myocardial infarction or PPCM.