ATRIAL STRETCH-DEPENDENT TUMOR NECROSIS FACTOR-MEDIATED ADVERSE ATRIAL REMODELING AND ATRIAL ARRHYTHMIA INDUCIBILITY IN A MOUSE MODEL OF AORTIC REGURGITATION

Abstract

<h3>BACKGROUND</h3> Atrial fibrillation (AF) is the most common sustained supraventricular arrhythmia worldwide, with its incidence linked to cardiovascular (CV) disease and, paradoxically, endurance exercise. Most conditions linked to AF are associated with elevated atrial pressures and stretch, which are powerful stimuli for atrial hypertrophy, fibrosis, and inflammation. We previously established adverse atrial changes and arrhythmogenesis required the pro-inflammatory and mechanosensitive cytokine tumor necrosis factor (TNF) in intense swim exercised mice. Thus, we hypothesize that stretch-mediated TNF-dependent signaling may provide a unifying mechanism linking AF in exercise and disease. <h3>METHODS AND RESULTS</h3> We developed a clinically-relevant mouse model of aortic regurgitation (AR), which is characterized by diastolic volume overload and elevated left ventricular end-diastolic (LVEDPs) and atrial pressures, to study atrial stretch-dependent TNF-mediated AF pathogenesis. AR was induced by retrograde puncture of the aortic valve in 8-week-old CD1 wild-type and whole-body TNF knockout (TNF-/-) mice. Four weeks after regurgitation, AR resulted in volume overload-mediated progressive LV dilatation, functional impairment, hypertrophy, and elevated LVEDPs in the absence of ventricular arrhythmia inducibility in both groups. In wild-type mice, AR resulted in adverse atrial remodeling, characterized by atrial hypertrophy and fibrosis, decreased conduction velocity, reduced atrial effective refractory period and action potential duration, and increased in vivo and ex vivo AF susceptibility. By contrast, TNF-/- prevented AR-induced adverse atrial remodeling and arrhythmia inducibility, independent of ventricular changes. <h3>CONCLUSION</h3> Our results establish that adverse atrial remodeling and AF vulnerability with AR requires TNF, providing a mechanistic link between elevated atrial pressures, adverse remodeling, and AF susceptibility with CV disease and exercise.