Effects of autoantibodies removed by immunoadsorption from patients with dilated cardiomyopathy on neonatal rat cardiomyocytes

SNHG16 accelerates the proliferation of primary cardiomyocytes by targeting miRNA-770-5p

The present study aimed to clarify the influence of long non-coding RNA small nuclear host gene 16 (lncRNA SNHG16) on cardiomyocyte proliferation following ischemia/reperfusion injury (IRI) and the potential mechanism. An IRI model in mice was established by performing ligation of the anterior descending coronary artery (LAD). Primary cardiomyocytes were isolated from newborn mice and subjected to H₂O₂ treatment to mimic in vitro IRI. Relative levels of SNHG16 and miRNA-770-5p in both in vivo and in vitro IRI models were examined. The regulatory effects of SNHG16 and miRNA-770-5p on the proliferative ability of H₂O₂-treated cardiomyocytes were assessed by Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assay. The binding relationship between SNHG16 and miRNA-770-5p was verified through dual-luciferase reporter gene assay. It is found that SNHG16 was time-dependently downregulated in the IRI models. Overexpression of SNHG16 enhanced the proliferative ability of the cardiomyocytes. miRNA-770-5p was found to be a direct target of SNHG16. Moreover, SNHG16 was able to negatively regulate the miRNA-770-5p level. Overexpression of miRNA-770-5p partially reversed the role of SNHG16 on accelerating cardiomyocyte proliferation. Collectively, SNHG16 accelerates the proliferative ability of cardiomyocytes following IRI by negatively regulating miRNA-770-5p.

Autoantibodies and cardiovascular dysfunction: cause or consequence?

There has been a long history of the exploration into autoimmunity as a possible pathogenic factor of cardiovascular diseases from unknown cause represented by dilated cardiomyopathy (DCM). Autoantibodies (AAbs) have emerged either as humoral responses provoked by the release of "self-antigens" due to tissue damage or dysregulated humoral immunity itself. The pathogenic roles of some AAbs have been suggested by the findings from basic research using in vitro and in vivo disease models as well as clinical studies including immunoadsorption studies removing AAbs from patients with DCM. In this context, the importance of AAbs belonging to IgG3 subclass has also been implicated. In this review article, we summarize the findings accumulated to date regarding AAbs which have been considered to be involved in the pathology of DCM or pregnancy-related cardiovascular disease. Furthermore, we discuss the significance of AAbs as a possible cause of DCM and their potential roles as a novel therapeutic target.

Dedifferentiated fat cells convert to cardiomyocyte phenotype and repair infarcted cardiac tissue in rats

Adipose tissue-derived stem cells have been demonstrated to differentiate into cardiomyocytes and vascular endothelial cells. Here we investigate whether mature adipocyte-derived dedifferentiated fat (DFAT) cells can differentiate to cardiomyocytes in vitro and in vivo by establishing DFAT cell lines via ceiling culture of mature adipocytes. DFAT cells were obtained by dedifferentiation of mature adipocytes from GFP-transgenic rats. We evaluated the differentiating ability of DFAT cells into cardiomyocytes by detection of the cardiac phenotype markers in immunocytochemical and RT-PCR analyses in vitro. We also examined effects of the transplantation of DFAT cells into the infarcted heart of rats on cardiomyocytes regeneration and angiogenesis. DFAT cells expressed cardiac phenotype markers when cocultured with cardiomyocytes and also when grown in MethoCult medium in the absence of cardiomyocytes, indicating that DFAT cells have the potential to differentiate to cardiomyocyte lineage. In a rat acute myocardial infarction model, transplanted DFAT cells were efficiently accumulated in infarcted myocardium and expressed cardiac sarcomeric actin at 8 weeks after the cell transplantation. The transplantation of DFAT cells significantly (p<0.05) increased capillary density in the infarcted area when compared with hearts from saline-injected control rats. We demonstrated that DFAT cells have the ability to differentiate to cardiomyocyte-like cells in vitro and in vivo. In addition, transplantation of DFAT cells led to neovascuralization in rats with myocardial infarction. We propose that DFAT cells represent a promising candidate cell source for cardiomyocyte regeneration in severe ischemic heart disease.

Autoimmunity and idiopathic dilated cardiomyopathy: where we stand?

Idiopathic dilated cardiomyopathy (DCM) with its heterogeneous phenotype and genotype remains one of the leading causes of severe heart failure particularly in the younger. Even in the elderly, it appears around 15% of heart failure is due to DCM. Despite great improvements in heart failure therapy, prognoses remains poor. One of the most important reasons is that the present heart failure management is aimed mostly at restoration of neurohormonal balance, rather than targeting primary causes of the disease. As a matter of fact, a substantial subgroup of DCM and chronic heart failure is accompanied by autoimmune mechanism, in particular a wide spectrum of autoantibodies. For almost two decades, the autoimmune hypothesis has been considered a "fairy tale". Today, we have better understanding of autoimmune mechanism in DCM. This focused issue is aimed to summarize what has happened in the last two decades in the context of basic understanding of underlying mechanisms and clinical relevance.

Immunoadsorption as treatment option in dilated cardiomyopathy

Abnormalities of the cellular and humoral immune system have been described in patients with dilated cardiomyopathy (DCM). Various circulating cardiac autoantibodies have been detected among DCM patients. Circulating antibodies are extractable by immunoadsorption (IA). Recent open controlled pilot studies have consequently shown that removal of circulating antibodies by IA induces improvement of cardiac function in DCM. IA, furthermore, decreases myocardial inflammation. In vitro data indicate that cardiodepressive antibodies play an important role in cardiac dysfunction of DCM patients; removal of these antibodies may accordingly represent the essential mechanism of IA in DCM. Furthermore, detection of cardiodepressive antibodies predicts hemodynamic benefits during IA. These antibodies belong to immunoglobulin G subclass 3. Recent data indicate that newly detected sarcolemmal Fc(gamma) receptors IIa are involved in the functional effects of cardiac autoantibodies.

The diagnostic role of autoantibodies in the prediction of organ-specific autoimmune diseases

Due to their pathogenetic role, many serum autoantibodies can be detected a long time before the clinical onset and during the course of organ-specific autoimmune diseases. For these reasons, autoantibodies can be used as predictive markers of an ongoing disease (in healthy subjects) and of disease activity and severity (in ill patients). The new multiplex diagnostic technologies introduced recently in laboratory medicine allow the simultaneous detection of several different autoantibodies and can be used for screening purposes in open populations or high-risk groups. This review examines the various autoantibodies of demonstrated predictive role in organ-specific autoimmune diseases and it introduces the state-of-the-art in the detection of multiple autoantibodies with proteomic systems.

Antibodies with beta-adrenergic activity from chronic chagasic patients modulate the QT interval and M cell action potential duration

AIMS

The aim of this study was to investigate whether the sera from chronic chagasic patients (CChPs) with beta-1 adrenergic activity (Ab-beta) can modulate ventricular repolarization. Beta-adrenergic activity has been described in CChP. It increases the L-type calcium current and heart rate in isolated hearts, but its effects on ventricular repolarization has not been described.

METHODS AND RESULTS

In isolated rabbit hearts, under pacing condition, QT interval was measured under Ab-beta perfusion. Beta-adrenergic activity was also tested in guinea pig ventricular M cells. Furthermore, the immunoglobulin fraction (IgG-beta) of the Ab-beta was tested on Ito, ICa, and Iks currents in rat, rabbit, and guinea pig myocytes, respectively. Beta-adrenergic activity shortened the QT interval. This effect was abolished in the presence of propranolol. In addition, sera from CChP without beta-adrenergic activity (Ab-beta) did not modulate QT interval. The M cell action potential duration (APD) was reversibly shortened by Ab-beta. Atenolol inhibited this effect of Ab-beta, and Ab- did not modulate the AP of M cells. Ito was not modulated by isoproterenol nor by IgG-beta. However, IgG-beta increased ICa and IKs.

CONCLUSION

The shortening of the QT interval and APD in M cells and the increase of IKs and ICa induced by IgG-beta contribute to repolarization changes that may trigger malignant ventricular arrhythmias observed in patients with chronic chagasic or idiopathic cardiomyopathy.

Anti-beta1-adrenergic receptor autoantibodies in patients with chronic Chagas heart disease

Chronic Chagas heart disease (cChHD), a chronic manifestation of the Trypanosoma cruzi infection, is characterized by high antibody levels against the C-terminal region of the ribosomal P proteins (i.e. peptide R13, EEEDDDMGFGLFD) which bears similarity with the second extracellular loop of beta1-adrenergic receptor (beta1-AR, peptide H26R HWWRAESDEARRCYNDPKCCDFVTNR). Because it has not been demonstrated clearly that IgGs from cChHD patients bind to native human beta1-AR, the aim of this study was to investigate further the physical interaction between cChHD IgGs and the human beta1-AR. Immunofluorescence assays demonstrated the binding of these antibodies to the receptor expressed on stably transfected cells, together with a beta1-AR agonist-like effect. In addition, immunoadsorption of the serum samples from cChHD patients with a commercially available matrix, containing peptides representing the first and the second extracellular loop of the beta1-AR, completely abolished reactivity against the H26R peptide and the physiological response to the receptor. The follow-up of this specificity after in vitro immunoadsorption procedures suggests that this treatment might be used to diminish significantly the serum levels of anti-beta1-AR antibodies in patients with Chagas heart disease.

Pathological importance of anti-G-protein coupled receptor autoantibodies

Anti-cardiac receptor autoantibodies have been studied intensively last 10 years. A growing evidence, both in vitro and in vivo and both clinical and experimental studies, have supported that these anti-cardiac receptor autoantibodies, mainly anti-beta1 adrenoceptor autoantibodies, play a very important pathophysiological role, at least partly, in the development of idiopathic dilated cardiomyopathy. This concise review article will only summarize studies done in rabbits with consideration of other articles in this focused issue.