WITHDRAWN: Inhibition of NADPH oxidase up-regulates connexin 43 and ameliorates electrical remodeling in rabbits with heart failure

Antiarrhythmic efficacy of CPUY102122, a multiple ion channel blocker, on rabbits with ischemia/reperfusion injury

BACKGROUND

The antiarrhythmic potential of a novel multichannel blocker CPUY102122 (CY22) was investigated in the present study.

METHODS

The effect of CY22 on rapid delayed rectifier potassium channel current (IKr) was studied using whole-cell patch clamp techniques in Chinese Hamster Ovary cells stably expressing human Ether-à-go-go-Related Gene. We further evaluated the antioxidant effects of CY22 and demonstrated the reversal of connexin down-regulation in the development of cardiac ventricular arrhythmias, which was produced using coronary ligation/reperfusion in rabbits. CY22 and Amiodarone were administered 30min prior to the procedure. Next, electrocardiograms were recorded, protein expression of left ventricular Connexin43 (Cx43), non-phosphorylation-Cx43 (np-Cx43), Rac-1 and gp-91[phox] were assayed using Western blot analysis, microstructural changes in the myocardium were observed and redox system activity was assayed.

RESULTS

CY22 inhibited IKr in a concentration-dependent manner with IC50 value of 2.8±0.8μmol/L. CY22 treatment significantly decreased T-wave amplitude and QTc arrhythmic scores and ameliorated the shape of the infarcted myocardium compared to the model group. CY22 decreased the serum levels of creatine kinase, lactate dehydrogenase, and myocardial levels of malondialdehyde, as well as increased superoxide dismutase activity. Cx43 expression in the left ventricle was significantly increased by CY22 treatment, which significantly decreased np-43 expression, Rac-1 activity and gp-91[phox] protein expression.

CONCLUSIONS

These results indicated that CY22 has both antiarrhythmic and cardiovascular protective effects partly by blocking IKr, the production of antioxidants and protection of Cx43.

NADPH oxidase-dependent oxidative stress in the failing heart: From pathogenic roles to therapeutic approach

Heart failure (HF) occurs when the adaptation mechanisms of the heart fail to compensate for stress factors, such as pressure overload, myocardial infarction, inflammation, diabetes, and cardiotoxic drugs, with subsequent ventricular hypertrophy, fibrosis, myocardial dysfunction, and chamber dilatation. Oxidative stress, defined as an imbalance between reactive oxygen species (ROS) generation and the capacity of antioxidant defense systems, has been authenticated as a pivotal player in the cardiopathogenesis of the various HF subtypes. The family of NADPH oxidases has been investigated as a key enzymatic source of ROS in the pathogenesis of HF. In this review, we discuss the importance of NADPH oxidase-dependent ROS generation in the various subtypes of HF and its implications. A better understanding of the pathogenic roles of NADPH oxidases in the failing heart is likely to provide novel therapeutic strategies for the prevention and treatment of HF.

Functional consequences of abnormal Cx43 expression in the heart

The major gap junction protein expressed in the heart, connexin43 (Cx43), is highly remodeled in the diseased heart. Usually, Cx43 is down-regulated and heterogeneously redistributed to the lateral sides of cardiomyocytes. Reverse remodeling of the impaired Cx43 expression could restore normal cardiac function and normalize electrical stability. In this review, the reduced and heterogeneous Cx43 expression in the heart will be addressed in hypertrophic, dilated and ischemic cardiomyopathy together with its functional consequences of conduction velocity slowing, dispersed impulse conduction, its interaction with fibrosis and propensity to generate arrhythmias. Finally, different therapies are discussed. Treatments aimed to improve the Cx43 expression levels show new potentially anti-arrhythmic therapies during heart failure, but those in the context of acute ischemia can be anti-arrhythmogenic at the cost of larger infarct sizes. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.