Dystrophin conferral using human endothelium expressing HLA-E in the non-immunosuppressive murine model of Duchenne muscular dystrophy

Human leukocyte antigen (HLA)-E is a non-classical major histocompatibility complex class I (Ib) molecule, which plays an important role in immunosuppression. In this study, we investigated the immunomodulating effect of HLA-E in a xenogeneic system, using human placental artery-derived endothelial (hPAE) cells expressing HLA-E in a mouse model. In vitro cell lysis analysis by primed lymphocytes in combination with siRNA transfection showed that HLA-E is necessary for inhibition of the immune response. Similarly, in vivo cell implantation analysis with siRNA-mediated down-regulation of HLA-E demonstrates that HLA-E is involved in immunosuppression. As hPAE cells efficiently transdifferentiate into myoblasts/myocytes in vitro, we transplanted the cells into mdx mice, a model of Duchenne muscular dystrophy. hPAE cells conferred dystrophin to myocytes of the ‘immunocompetent' mdx mice with extremely high efficiency. These findings suggest that HLA-E-expressing cells with a myogenic potential represent a promising source for cell-based therapy of patients with muscular dystrophy

Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome

Objectives.We examined the modulatory effects of autonomic nervous system and antiarrhythmic drugs on the ST segment in patients with Brugada syndrome to gain an insight into the mechanism of ST segment elevation.Background.Right bundle branch block, ST segment elevation and ventricular tachyarrhythmias define a distinct clinical and electrocardiographic (ECG) syndrome (Brugada syndrome). However, the mechanism of ST segment elevation and the causes of this syndrome are unknown.Methods.The study included four patients in whom structural heart or coronary artery disease was excluded by noninvasive and invasive tests. High take-off ST segment elevation of either the coved or saddle-back type in precordial leads V1, V2and V3was seen in all patients. Three patients experienced recurrent episodes of syncope or aborted sudden cardiac death, and the remaining patient had palpitation. Autonomic receptor stimulation and blockade and intravenous administration of antiarrhythmic drugs were performed during sinus rhythm while the 12-lead ECG was recorded. Metaiodobenzylguanidine (MIBG) scanning and Holter monitoring were also performed.Results.Beta-adrenoceptor stimulation by intravenous isoproterenol consistently reduced (≥0.1 mV) ST segment elevation at or 80 ms after the J point in all four patients. Selective alphaadrenoceptor stimulation by intravenous norepinephrine in the presence of propranolol or by intravenous methoxamine consistently augmented, whereas alpha-adrenoceptor blockade reduced, ST segment elevation in three patients. Intracoronary acetylcholine or intravenous edrophonium or neostigmine augmented ST segment elevation without inducing coronary spasm in three of four patients. Class IA antiarrhythmic drugs also consistently augmented (three patients), whereas class IB drugs had no effect on (two patients) ST segment elevation. No abnormality was found on MIBG imaging or heart rate variability in three patients, suggesting that autonomic dysfunction is not a primary disease process. Class IA drugs had no effect on ST segment in three control patients, suggesting that the ST segment elevation seen in patients with Brugada syndrome in response to the drugs is not a nonspecific response.Conclusions.ST segment elevation in patients with Brugada syndrome was augmented by selective stimulation of alphaadrenoceptors or muscarinic receptors or by class IA drugs but was mitigated by beta-adrenoceptor stimulation or alphaadrenoceptor blockade. These responses might be explained by postulating the presence of an area of early repolarization or a local “depolarized” area in the ventricle causing ST segment elevation in this syndrome. Because only a small number of patients were studied, these possibilities need further evaluation

Autoimmunity against the second extracellular loop of beta1-adrenergic receptors induces early afterdepolarization and decreases in K-channel density in rabbits

AbstractObjectivesWe sought to define the electrophysiologic property of the rabbit heart associated with autoimmunity against the second extracellular loop of the beta1-adrenergic receptor.BackgroundSudden death of patients with cardiomyopathy, probably due to lethal ventricular arrhythmias, can be predicted by the presence of autoantibodies against the second extracellular loop of the beta1-adrenergic receptor.MethodsRabbits were immunized by repetitive subcutaneous administration of a synthetic peptide corresponding to the second extracellular loop of beta1-adrenergic receptors (beta group; n = 30) for a mean of 4.2 months. Control rabbits received only vehicle (control group; n = 30).ResultsOne of the rabbits in the beta group died suddenly during the observation period, but none of the control animals died. The prevalence of sustained ventricular tachycardia was significantly higher in the beta group (beta: 4 of 27 vs. control: 0 of 30), and a standard microelectrode experiment revealed prolongation of the action potential duration (APD) in the right ventricular papillary muscle (beta: 156 ± 5 ms vs. control: 131 ± 4 ms; p < 0.05). Early afterdepolarization (EAD) was observed in one rabbit in the beta group (1 of 26), but not in any animals in the control group (0 of 17). A dose of 100 nmol/l of E-4031 induced EAD in the beta group (10 of 10), but not in the control group, except for one rabbit (1 of 10). The whole-cell, patch-clamp experiment on left ventricular M cells showed significant decreases in transient outward current (Ito1) (−43%) and slowly activated delayed rectifier current (IKs) densities (−33%), whereas the inward-rectifying K current (IK1) and rapidly activated delayed rectifier current (IKr) densities remained unchanged.ConclusionsLong-term immunization against the second extracellular loop of the beta1-adrenergic receptor caused EAD and APD prolongation and decreased the K-channel density, suggesting that an arrhythmic substrate via autoimmune mechanisms is present in cardiomyopathic patients who have autoantibodies directed against the receptors