Usefulness of Exchanged Protein Directly Activated by cAMP (Epac)1-Inhibiting Therapy for Prevention of Atrial and Ventricular Arrhythmias in Mice

Abstract

Background: It has been suggested that protein directly activated by cAMP (Epac), one of the downstream signaling molecules of β-adrenergic receptor (β-AR), may be an effective target for the treatment of arrhythmia. However, there have been no reports on the anti-arrhythmic effects or cardiac side-effects of Epac1 inhibitors in vivo. Methods and Results: In this study, the roles of Epac1 in the development of atrial and ventricular arrhythmias are examined. In addition, we examined the usefulness of CE3F4, an Epac1-selective inhibitor, in the treatment of the arrhythmias in mice. In Epac1 knockout (Epac1-KO) mice, the duration of atrial fibrillation (AF) was shorter than in wild-type mice. In calsequestrin2 knockout mice, Epac1 deficiency resulted in a reduction of ventricular arrhythmia. In both atrial and ventricular myocytes, sarcoplasmic reticulum (SR) Ca 2+ leak, a major trigger of arrhythmias, and spontaneous SR Ca 2+ release (SCR) were attenuated in Epac1-KO mice. Consistently, CE3F4 treatment significantly prevented AF and ventricular arrhythmia in mice. In addition, the SR Ca 2+ leak and SCR were significantly inhibited by CE3F4 treatment in both atrial and ventricular myocytes. Importantly, cardiac function was not significantly affected by a dosage of CE3F4 sufficient to exert anti-arrhythmic effects. Conclusions: These findings indicated that Epac1 is involved in the development of atrial and ventricular arrhythmias. CE3F4, an Epac1-selective inhibitor, prevented atrial and ventricular arrhythmias in mice.

Effects of occlusal disharmony on susceptibility to atrial fibrillation in mice

“…More importantly, increased P wave duration was recently demonstrated to be a potent indicator of paroxysmal AF susceptibility and a discriminator of paroxysmal AF history not only in humans, but also in mice 32 . We thus examined the effects of BO on AF susceptibility in mice in terms of the duration of AF induced by transesophageal burst pacing 22 , 33 – 35 (Fig. 2 C).…”

“…While a surface ECG was recorded using electrode in a lead-II configuration, a 1.1-French catheter electrode (EPR800; Millar Instruments, Houston, TX, USA) was carefully advanced and fixed at the esophageal position dorsal to the left atrium. Induction of AF was conducted by applying transesophageal atrial burst pacing for 10 s at a stimulation amplitude of 1.5 mA with 10 ms cycle lengths and a pulse width of 3 ms. AF was defined according to the following criteria: (i) loss of P wave, (ii) irregular R-R interval, and (iii) duration greater than 2 s, which have already been adopted for AF in mice induced by rapid transesophageal atrial pacing by us 33 – 35 and other groups 58 , 59 . Further, after the screening of AF induction based on these criteria by a single technician who was blind to information about the experimental groups, the diagnosis was always re-checked by an expert on cardiac physiology.…”

“…The murine atrial surface area is < 35 mm 2 , and therefore it may be difficult to sustain a micro-reentrant atrial tachyarrhythmia in an intact normal mouse. However, the AF mouse model induced by transesophageal atrial burst pacing can be used to evaluate mechanisms of arrhythmia using molecular and genetic approaches 22 , 33 – 35 , 58 , 59 . On the other hand, large animal models are needed for the macrostudy of atrial arrhythmia, and such studies have greatly contributed to our understanding of the underlying mechanisms.…”

The Epac1 Protein: Pharmacological Modulators, Cardiac Signalosome and Pathophysiology

“…Recent functional analyses of genetically engineered mouse models further demonstrated that Epac1 deficiency resulted in reduced susceptibility to atrial fibrillation (the most common sustained cardiac arrhythmia) and ventricular arrhythmia [58]. Consistently, the Epac1-selective inhibitor CE3F4 shortened the duration of the pacing-induced atrial fibrillation and reduced the incidence of sympathetic activation-induced ventricular arrhythmias, suggesting that Epac1 pharmacological inhibition was an effective strategy in the prevention of arrhythmia [78].…”

The Role of Epac in Cancer Progression

“…Although the safety of drugs that act on Epac has not been well-investigated in a cancer setting, their side effects are reported to be minimal when used for cardiovascular diseases. In fact, studies suggest that the use Epac modulators poses a lower risk for heart failure than beta-blockers [157]. Likewise, these drugs have the potential to become alternative pain management medications to opioids due to their lesser complications [25].…”