Introduction:
Heart failure (HF) remains a prevalent and life-threatening condition, impacting over 64 million people globally. Patients with HF are at increased risk of fatal arrhythmias, largely due to persistent activation of the sympathetic nervous system. This chronic activation, intended to compensate for reduced cardiac output, results in sustained beta-adrenergic cAMP signaling in cardiomyocytes (CM), which disturbs intracellular Ca2+-homeostasis and facilitates the development of arrhythmias. Phosphodiesterase 2 (PDE2), being upregulated in HF, may counteract these pro-arrhythmic effects when allosterically activated by cGMP, by increasing its cAMP hydrolytic activity. PDE2 activating cGMP can be synthesized by membrane-bound guanylyl cyclases (pGC-A, pGC-B) in CM. In this context, our study investigates the antiarrhythmic potential of pGC-B stimulation with C-type natriuretic peptide (CNP) and dual activation of pGC-A/B with the designer natriuretic peptide Cenderitide in isolated ventricular CM of mice with HF.
Materials and Methods:
HF was induced in control mice (PDE2-WT) and mice with CM-specific PDE2 knockout (PDE2-KO) using a 60% high-fat diet (HFD) and the NO-synthase inhibitor L-NAME (0.5 g/L) in drinking water for 5 weeks. Cardiac function was evaluated by echocardiography. The regulation of pGC-A/B expression was studied in cardiac tissues from human HF patients and in isolated CM from mice with HF using Western blot. In ventricular CMs, pro-arrhythmic spontaneous Ca2+-waves (SCWs) and Ca2+-sparks (CaSp) were quantified using fluorescent Ca2+-indicators Fluo-4 and Fura-2 in Ca2+-imaging techniques, while single-cell contractility was assessed by video-based analysis of sarcomere shortening.
Results:
A combined HFD and L-NAME treatment over five weeks induced both metabolic and hemodynamic stress in mice, resulting in increased body weight, elevated mean arterial pressure, and diastolic dysfunction with enhanced E/E’ in PDE2-WT and PDE2-KO. Interestingly, PDE2-KO showed reduced systolic heart function compared to PDE2-WT. Analysis of ventricular tissue from patients with HF revealed a selective upregulation of pGC-B, whereas pGC-A levels remained unchanged compared to non-failing controls. A similar expression pattern was observed in CM of mice with HF, where expression of pGC-B was significantly increased, and pGC-A decreased relative to healthy control mice. Functionally, beta-adrenergic stimulation with isoprenaline (ISO) markedly triggered pro-arrhythmic SCWs and CaSP in diseased PDE2-WT. Interestingly, both arrhythmogenic Ca2+-signals were substantially attenuated by CNP. This antiarrhythmic effect was abolished by PDE2 inhibition with BAY 60-7550, and was absent in CM of PDE2-KO with HF. Similarly, the pGC-A/B co-stimulation via Cenderitide reduced ISO-induced CaSp in CM of diseased PDE2-WT. PDE2 inhibition or genetic PDE2 deletion prevented the cardioprotective effect of Cenderitide. Importantly, both CNP and Cenderitide clearly enhanced cellular contraction amplitudes in CM of PDE2-WT with HF.
Conclusion:
By cGMP-mediated PDE2 activation, CNP and Cenderitide significantly reduced cAMP-dependent pro-arrhythmic Ca2+-signals and improved CM contraction in mice with HF, offering a novel antiarrhythmic approach for HF patients.
