Cardiac gene therapy with PDE2A limits ventricular remodeling, dysfunction and arrhythmias promoted in mice by chronic infusion with catecholamines

Abstract

Chronic ß-AR activation is detrimental because it promotes cardiac remodeling and leads to heart failure (HF). Multiple cyclic nucleotide phosphodiesterases (PDEs) finely tune ß-AR responses by degrading and compartmentalizing cAMP. PDE2A is upregulated in HF, and PDE2A-transgenic mice are protected against catecholamine-induced arrhythmias. Since chronic treatment with PDE inhibitors increases mortality in HF and PDE2 overexpression seems cardioprotective, we postulated that decreasing cAMP levels by overexpressing PDE2A in the heart using gene therapy may have therapeutic effects. C57BL/6N male mice were injected with serotype 9 adeno-associated viruses (AAV9, 10e12 viral particles) encoding for PDE2A, or luciferase (LUC). Two weeks later, mice were implanted with osmotic pumps infusing NaCl or isoprenaline (Iso) and phenylephrine (IP, 30 mg/kg/day each) for 2 weeks. Cardiac function was assessed by echocardiography, susceptibility to arrhythmias by catheter-mediated ventricular pacing after Iso (1.5 mg/kg) and atropine (1 mg/kg) injection. Ventricular cardiomyocytes were isolated, loaded with 1 μM Fura-2AM and stimulated at 1 Hz to record calcium transients (CaT), sarcomere shortening (SS) and pro-arrhythmogenic spontaneous calcium waves (SCW). In LUC mice, IP treatment increased left ventricular weight over body weight ratio by 35 ± 5.7% ( P = 0.0001) and decreased ejection fraction by 29 ± 2.4% ( P < 0.0001). Both parameters were improved in animals subjected to AAV9-PDE2A injection ( P = 0.039 and P = 0.0003, respectively) increasing by ∼10 fold PDE2A levels. Ventricular tachycardias were triggered in IP-LUC mice ( P = 0.016) but not in animals treated with AAV9-PDE2A. In isolated myocytes from control mice, ß-AR stimulation (3 nM Iso) increased SS by 355% and CaT by 86% ( P < 0.0001). These inotropic effects were blunted in cells from IP treated animals with SS increasing by 157% ( P = 0.0002, vs. LUC-NaCl) and CaT by only 55% ( P = 0.06 vs. IP-LUC at baseline). However, the Iso effects were preserved in cardiomyocytes from animals injected with AAV9-PDE2A (SS: P < 0.0001, CaT: P < 0.0001 vs. IP-PDE2A at baseline), which exhibited less SCW upon maximal ß-AR stimulation (Iso, 100 nM, P = 0.02 vs. IP-LUC). Our results suggest that gene therapy with PDE2A limits cardiac hypertrophy and dysfunction induced by catecholamines as well as ventricular arrhythmias.