The role of PDE2 as a potential target for antiarrhythmic therapy in cardiovascular diseases

Abstract

Background and aim: Patients with heart failure and myocardial infarction have a significant risk of ventricular arrhythmia and sudden cardiac death, contributing to ∼20% of total deaths worldwide. However, pharmacological therapy of life-threatening arrhythmia remains limited and challenging. Consequently, there is a strong medical need for novel antiarrhythmic pharmacotherapy approaches that can effectively address fatal arrhythmias and reduce mortality rates. There is increasing evidence for cardioprotective effects of C-type natriuretic peptide (CNP) generating the intracellular second messenger cyclic guanosine monophosphate (cGMP) via its guanylyl cyclase receptor. While cGMP is proposed to mediate beneficial effects in the diseased myocardium, the second messenger cyclic adenosine monophosphate (cAMP) downstream of the chronically activated β-adrenoceptors provoke detrimental effects, such as cardiac remodelling and arrhythmia generation. Importantly, phosphodiesterase type 2 (PDE2) plays a crucial role in mediating the negative crosstalk between cGMP and cAMP signalling pathways within cardiomyocytes. As the only phosphodiesterase that is allosterically activated by cGMP to increase its cAMP-hydrolysing activity, PDE2 regulates the balance between these two signalling molecules. The aim of this study was to investigate the potential antiarrhythmic effect of CNP-cGMP-induced PDE2 stimulation at both organ and animal level in physiological as well as pathophysiological conditions.

Material & methods: Hearts from mouse models with cardiomyocyte-specific PDE2 overexpression (PDE2 OE) or deletion (PDE2 KO) were isolated and subjected to ischemia/reperfusion (I/R) injuries using a Langendorff perfusion system. Thereby, the left descending coronary artery was ligated for 30 minutes to induce ischemia, followed by 30 minutes of reperfusion after removing the occlusion. The incidence of arrhythmic events during the reperfusion phase was examined following PDE2 activation with CNP or PDE2 inhibition with BAY 60-7550 using ex vivo ECG electrodes. To assess the potential antiarrhythmic effects of PDE2 modulation under pathophysiological conditions, two different experimental models were induced in mice: (i) Heart failure (HF) was induced through a 5-week regimen including a high-fat diet and the administration of the NO-synthase inhibitor L-NAME in drinking water to mediate metabolic and hypertensive stress, and (ii) diabetes was induced via 5 consecutive streptozotocin (STZ) i.p. injections, leading to the destruction of pancreatic β-cells and subsequent development of diabetes over a four-week period. In addition to ex vivo arrhythmia quantification after I/R, in vivo arrhythmia development was conducted by implanting ECG telemeters and provoking arrhythmias with double injections of the β-adrenoceptor agonist isoprenaline (Iso). Additionally, atrial arrhythmia induction protocols were established to evaluate the development of atrial fibrillation (AF) using two different pacing protocols on the right atrium. The S1S2 protocol was used to detect the effective refractory period of the atria and the burst pacing protocol to determine the inducibility of AF, with simultaneous recording of monophasic action potentials from the left atrium.

Results: WT hearts perfused with CNP exhibited a significant reduction in the number of arrhythmic events following I/R compared to control hearts. Importantly, this antiarrhythmic effect of CNP was reversed by pharmacological inhibition of PDE2 with BAY 60-7550 (Cachorro et al., 2023). Interestingly, no differences in arrhythmia development were observed between control and perfusion with BAY (Wagner et al., 2021). In contrast, inhibition of PDE3 resulted in markedly increased number of arrhythmic events compared to control. Hearts with cardiomyocyte-specific PDE2 deletion displayed a significantly higher incidence of arrhythmias after I/R, including ventricular extrasystole, bigeminy, and tachycardia. However, in vivo experiments did not demonstrate increased arrhythmia development after acute β-adrenergic stress in PDE2 KO mice with HF potentially due to desensitization of chronically activated β-adrenergic receptors in this pathophysiological model. Furthermore, hearts from diabetic mice exhibited a significantly higher number of arrhythmic events ex vivo, although those with PDE2 OE were protected against diabetes-induced arrhythmias compared to diabetic controls. However, the established pacing protocols revealed a low AF induction rate in ex vivo perfused mouse hearts, limiting the ability to observe a significant antiarrhythmic effect of CNP. Nonetheless, control hearts perfused with CNP plus BAY or with cardiac-specific deletion of PDE2 showed a trend towards increased AF compared to WT hearts and those perfused with CNP alone. Under diabetic conditions, PDE2 KO mice also displayed a trend to have higher AF inducibility compared to control diabetic hearts. As observed under physiological conditions, simultaneous perfusion of diabetic hearts with CNP plus BAY also showed a trend to have enhanced AF development compared to CNP or control perfusion.

Conclusions: In conclusion, the findings of this study provide strong evidence that cGMP-induced PDE2 activation plays a crucial role in protecting the heart from ventricular arrhythmias in both physiological and pathophysiological conditions. Thus, CNP-mediated PDE2 stimulation could provide a novel therapeutic strategy to reduce life-threatening arrhythmias. However, further research should be performed to elucidate the effects of PDE2 stimulation on other tissues expressing PDE2, such as fibroblasts, neurons, endothelial cells, or circulating immune cells. Additionally, the impact of CNP-induced cGMP on the protein kinase G (PKG) pathway in cardiomyocytes should be investigated. The results of this work may provide a new approach for the development of novel antiarrhythmic therapies targeting the CNP-PDE2 axis, improving clinical outcomes for patients with HF and myocardial infarction.

Date of Award	12 Jul 2024
Original language	English
Awarding Institution	King's College London
Supervisor	Manuel Mayr (Supervisor) & Susanne Bergmann (Supervisor)