Forsøksdyr: The role of CaMKII-oxidation in development of arrhythmias


Godkjenningsdato 21.12.2018

Ischemic heart disease and heart failure share a common defect that predisposes to ventricular tachyarrhythmias and sudden Cardiac Death (SCD): Both conditions involve a dysfunction of the ryanodine receptor (RyR), a key protein in cardiac Ca2+ homeostasis. This dysfunction makes the heart vulnerable to adrenergic stress which might initiate ventricular extrasystoles and tachycardias. Further insight in the role of RyR in ventricular arrhythmias is needed to improve survival and prevention of SCD. Such insight might come from animal models of conditions with increased risk of arrhythmias. One condition of special interest is cathecolaminergic polymorphic ventricular tachycardia (CPVT).

Hypothesis:
Reduced level of oxidized CaMKII (ox-CaMKII) prevents ventricular arrhythmias while preserving beneficial effects of exercise training in CPVT1 and conditions with RyR dysfunction.

Methods:
Several mouse models will be employed to elucidate the role of ox-CaMKII in ischemic heart disease, heart failure and CPVT. The project will involve three genetic mutations (CaMKII MMVV, RyR R2474S and PLB KO). In vivo interventions will comprise coronary artery ligation, aortic banding, exercise training, echocardiography, pressure-volume-measurements and telemetric ECG-survaillance. The use of proper anesthesia and analgesia will minimize the burden on laboratory animals as a result of in vivo interventions. Cardiac tissue will be used for cellular experiments to characterize Ca2+ handling in isolated ventricular cardiomyocytes by whole-cell Ca2+ imaging and confocal microscopy. Protein abundance including ox-CaMKII, as well as THR286-phosphorylated CaMKII, phosphorylated RyR and other key Ca2+ handling proteins will be measured by western blotting, while the functional impact will be tested in cellular experiments with CaMKII-inhibitors and antioxidants.

This study requires 7972 mice.

The experimental procedures in this study will be carried out by experienced co-workers to minimize the number of animals needed. The experimental procedures are continuously improved by keeping up to date with recent publications and through communication with experienced researchers. The mechanisms involved in heart failure and arrhythmia-development, and the beneficial effects of exercise training are multifactorial, complex and highly unknown. Therefore, the use of experimental animal models is the most reliable way to understand the mechanisms involved these diseases. In vitro experiments cannot replace the complex processes involved in the patophysiology of arrhythmias and in exercise training.