Contribution of Increased Expression of Yin Yang 2 to Development of Cardiomyopathy.

Yin Yang 2 (YY2) is a member of the Yin Yang family of transcription factors. Although the bioactivity of YY2 has been previously studied, its role in cardiovascular diseases is not known. We observed the increased expression of YY2 in failing human hearts compared with control hearts, raising the question of whether YY2 is involved in the pathogenesis of cardiomyopathy. To investigate the potential contribution of YY2 to the development of cardiomyopathy, we crossed two independent transgenic (Tg) mouse lines, pCAG-YY2-Tg+and alpha-myosin heavy chain-cre (α-MHC-Cre), to generate two independent double transgenic (dTg) mouse lines in which the conditional cardiomyocyte-specific expression of YY2 driven by the α-MHC promoter was mediated by Cre recombinase, starting at embryonic day 9.0. In dTg mice, we observed partial embryonic lethality and hearts with defective cardiomyocyte proliferation. Surviving dTg mice from both lines developed cardiomyopathy and heart failure that occurred with aging, showing different degrees of severity that were associated with the level of transgene expression. The development of cardiomyopathy was accompanied by increased levels of cardiac disease markers, apoptosis, and cardiac fibrosis. Our studies further revealed that the Cre-mediated cardiomyocyte-specific increase in YY2 expression led to increased levels of Beclin 1 and LC3II, indicating that YY2 is involved in mediating autophagic activity in mouse hearts in vivo. Also, compared with control hearts, dTg mouse hearts showed increased JNK activity. Because autophagy and JNK activity are important for maintaining cardiac homeostasis, the dysregulation of these signaling pathways may contribute to YY2-induced cardiomyopathy and heart failure in vivo.

Frequency Gradient Within Coronary Sinus Predicts the Long-Term Outcome of Persistent Atrial Fibrillation Catheter Ablation.

BACKGROUND: The coronary sinus (CS), as a junction of the atria, contributes to atrial fibrillation (AF) by developing unstable reentry, and isolating the atria by ablation at the CS could terminate AF. The present study evaluated whether AF activities at the CS in a subset of patients contributed to AF maintenance and predicted clinical outcome of ablation. METHODS AND RESULTS: We studied 122 consecutive patients who had a first-time radiofrequency ablation for persistent AF. Bipolar electrograms were obtained from multiple regions of the left atrium by a Lasso mapping catheter before ablation. Pulmonary vein isolation terminated AF in 12 patients (9.8%). Sequential stepwise ablation was conducted in pulmonary vein isolation nontermination patients and succeeded in 22 patients (18%). In the stepwise termination group, AF frequency in the proximal CS (CSp) was significantly higher (10.2±2.1 Hz versus 8.3±1.8 Hz, P<0.001), and the ratio of distal CS (CSd) to proximal CS (CSd/CSp ratio, 56.6%±10.11% versus 70.7%±9.8%, P<0.001) was significantly lower than that in the nontermination group. The stepwise logistic regression analysis indicated that the CSd/CSp ratio was an independent predictor with an odds ratio of 1.131 (95%CI 1.053-1.214; P=0.001). With a cutoff of 67%, the patients with lower CSd/CSp ratios had significantly better index and long-term outcomes than those with higher ratios during a follow-up of 46±18 months. CONCLUSIONS: Rapid repetitive activities in the musculature of the proximal CS may contribute to maintenance of AF after pulmonary vein isolation alone in persistent AF. A cutoff at 67%, of the CSd/CSp frequency ratio might be an indicator to stratify the subset of patients who might benefit from CS ablation.

Hyper-SUMOylation of the Kv7 potassium channel diminishes the M-current leading to seizures and sudden death.

Sudden unexplained death in epilepsy (SUDEP) is the most common cause of premature mortality in epilepsy and was linked to mutations in ion channels; however, genes within the channel protein interactome might also represent pathogenic candidates. Here we show that mice with partial deficiency of Sentrin/SUMO-specific protease 2 (SENP2) develop spontaneous seizures and sudden death. SENP2 is highly enriched in the hippocampus, often the focus of epileptic seizures. SENP2 deficiency results in hyper-SUMOylation of multiple potassium channels known to regulate neuronal excitability. We demonstrate that the depolarizing M-current conducted by Kv7 channel is significantly diminished in SENP2-deficient hippocampal CA3 neurons, primarily responsible for neuronal hyperexcitability. Following seizures, SENP2-deficient mice develop atrioventricular conduction blocks and cardiac asystole. Both seizures and cardiac conduction blocks can be prevented by retigabine, a Kv7 channel opener. Thus, we uncover a disease-causing role for hyper-SUMOylation in the nervous system and establish an animal model for SUDEP.

The early stage of the atrial electroanatomic remodeling as substrates for atrial fibrillation in hypertensive patients.

BACKGROUND: Hypertension is one of the most important risk factors for atrial fibrillation (AF). Recent studies suggest right atrial remodeling in hypertensive patients may be associated with increased inducibility of AF. This study sought to characterize the electroanatomic features of left and right atria and pulmonary veins (PVs) in hypertensive patients. METHODS AND RESULTS: A prospective observational study was conducted on patients who underwent ablation for paroxysmal supraventricular tachycardia or paroxysmal AF. Electrophysiological features of the PVs and atria, including event-related potentials, conduction time, and inducibility and vulnerability of AF, were characterized during cardiac catheterization. Anatomic and hemodynamic features were assessed by using echocardiographic and computer tomography imaging. When 15 hypertensive patients with paroxysmal supraventricular tachycardia were compared with 17 normotensive patients with paroxysmal supraventricular tachycardia, the hypertensive patients had significantly shortened PV event-related potentials with increased dispersions (P<0.001) but slightly prolonged atrial event-related potentials (P=NS) and had prolonged interatrial and intra-atrial conduction times (P<0.001). Additionally, the hypertensive patients had increased vulnerability and inducibility of AF and prolonged duration of induced AF (P<0.01). All of these changes were more pronounced in hypertensive patients with paroxysmal AF. Anatomically, compared with the normotensive patients, the diameters of 4 PVs in the hypertensive patients with paroxysmal supraventricular tachycardia were significantly enlarged (P<0.01) and became more remarkable in hypertensive patients with paroxysmal AF (P<0.0001), although the diameter and volume index of the left atrium among 3 groups were similar. CONCLUSIONS: The hypertensive patients showed electroanatomic changes associated with increased vulnerability to AF, including shortened event-related potentials with increased dispersion, prolonged conduction time, and increased PV diameter, but these changes were not appreciated in the atria. Additionally, these changes became more dramatic in hypertensive patients with paroxysmal AF.

Engineered endothelial progenitor cells that overexpress prostacyclin protect vascular cells.

Prostacyclin (PGI2) is a potent vasodilator and important mediator of vascular homeostasis; however, its clinical use is limited because of its short (<2-min) half-life. Thus, we hypothesize that the use of engineered endothelial progenitor cells (EPCs) that constitutively secrete high levels of PGI2 may overcome this limitation of PGI2 therapy. A cDNA encoding COX-1-10aa-PGIS, which links human cyclooxygenase-1 (COX-1) to prostacyclin synthase (PGIS), was delivered via nucleofection into outgrowth EPCs derived from rat bone marrow mononuclear cells. PGI2-secreting strains (PGI2-EPCs) were established by continuous subculturing of transfected cells under G418 selection. Genomic PCR, RT-PCR, and Western blot analyses confirmed the overexpression of COX-1-10aa-PGIS in PGI2-EPCs. PGI2-EPCs secreted significantly higher levels of PGI2 in vitro than native EPCs (P < 0.05) and showed higher intrinsic angiogenic capability; conditioned medium (CM) from PGI2-EPCs promoted better tube formation than CM from native EPCs (P < 0.05). Cell- and paracrine-mediated in vitro angiogenesis was attenuated when COX-1-10aa-PGIS protein expression was knocked down. Whole-cell patch-clamp studies showed that 4-aminopyridine-sensitive K(+) current density was increased significantly in rat smooth muscle cells (rSMCs) cocultured under hypoxia with PGI2-EPCs (7.50 ± 1.59 pA/pF; P < 0.05) compared with rSMCs cocultured with native EPCs (3.99 ± 1.26 pA/pF). In conclusion, we successfully created EPC strains that overexpress an active novel enzyme resulting in consistent secretion of PGI2. PGI2-EPCs showed enhanced intrinsic proangiogenic properties and provided favorable paracrine-mediated cellular protections, including promoting in vitro angiogenesis of native EPCs and hyperpolarization of SMCs under hypoxia.

A ZASP missense mutation, S196L, leads to cytoskeletal and electrical abnormalities in a mouse model of cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM) is a primary disease of the heart muscle associated with sudden cardiac death secondary to ventricular tachyarrhythmias and asystole. However, the molecular pathways linking DCM to arrhythmias and sudden cardiac death are unknown. We previously identified a S196L mutation in exon 4 of LBD3-encoded ZASP in a family with DCM and sudden cardiac death. These findings led us to hypothesize that this mutation may precipitate both cytoskeletal and conduction abnormalities in vivo. Therefore, we investigated the role of the ZASP4 mutation S196L in cardiac cytoarchitecture and ion channel biology. METHODS AND RESULTS: We generated and analyzed transgenic mice with cardiac-restricted expression of the S196L mutation. We also performed cellular electrophysiological analysis on isolated S196L cardiomyocytes and protein-protein interaction studies. Ten month-old S196L mice developed hemodynamic dysfunction consistent with DCM, whereas 3-month-old S196L mice presented with cardiac conduction defects and atrioventricular block. Electrophysiological analysis on isolated S196L cardiomyocytes demonstrated that the L-type Ca(2+) currents and Na(+) currents were altered. The pull-down assay demonstrated that ZASP4 complexes with both calcium (Ca(v)1.2) and sodium (Na(v)1.5) channels. CONCLUSIONS: Our findings provide new insight into the mechanisms by which mutations of a structural/cytoskeletal protein, such as ZASP, lead to cardiac functional and electric abnormalities. This work represents a novel framework to understand the development of conduction defects and arrhythmias in subjects with cardiomyopathies, including DCM.

Potassium magnesium supplementation for four weeks improves small distal artery compliance and reduces blood pressure in patients with essential hypertension.

It has been postulated that the loss of arterial compliance may precede cardiovascular diseases, and that arterial compliance is an important parameter to consider when evaluating arterial diseases such as essential hypertension (EH) and the effects of antihypertensive treatment. In all, 133 EH patients and 147 healthy subjects were enrolled in this study. Large arterial compliance (C1) and small arterial compliance (C2) were measured by the CVProfilor DO-2020 CardioVascular Profiling System. Thirty-five patients randomly received magnesium potassium supplementation (magnesium, 70.8 mg/d; potassium, 217.2 mg/d) for four weeks, and 32 patients received lacidipin (4 mg/d) as a control. Before and after the four weeks, blood pressure, C1, and C2 were measured. It was found that arterial compliance was significantly lower in EH patients compared with healthy subjects (C1: 12.53 +/- 0.33 vs. 15.63 +/- 0.30 ml/mmHg x 10, p < 0.01;C2: 3.79 +/- 0.17 vs. 5.69 +/- 0.25 ml/mmHg x 100, p < 0.01). On lacidipine, systolic and diastolic BP decreased 13.27 +/- 1.76 mm Hg and 6.33 +/- 1.55 mm Hg, and C1 and C2 compliance values increased 25.05% +/- 4.49% and 34.50% +/- 7.40%, respectively. On K+ and Mg2+ supplementation, systolic and diastolic BP decreased 7.83 +/- 1.87 mm Hg and 3.67 +/- 1.03 mm Hg, and C1 and C2 compliance values increased 12.44% +/- 4.43% and 45.25% +/- 6.67%, respectively. Decreases in systemic vascular resistance (mean arterial pressure divided by cardiac output) by 11.9% and 16.6 % (p < 0.01) were seen between the drug-induced changes, respectively. Both large arterial compliance and small arterial compliance were decreased in essential hypertension patients. In essential hypertension patients, magnesium and potassium supplementation could improve small arterial compliance, while lacidipine improved large arterial compliance significantly.