KN-93, A CaMKII inhibitor, suppresses ventricular arrhythmia induced by LQT2 without decreasing TDR

Area of Science:

• Cardiovascular Physiology
• Pharmacology
• Cardiac Electrophysiology

Background:

• Abnormal transmural dispersion of repolarization (TDR) is crucial in severe ventricular arrhythmias like Torsades de Pointes (TDP) in Long-QT (LQT) syndrome.
• Ca2+/calmodulin-dependent protein kinase II (CaMKII) is implicated in cardiac arrhythmogenesis.

Purpose of the Study:

• To investigate the effects of KN-93, a CaMKII inhibitor, on repolarization heterogeneity and arrhythmias in an in vitro rabbit model of LQT2.
• To determine if CaMKII inhibition can prevent TDP by targeting early afterdepolarizations (EADs).

Main Methods:

• Utilized an in vitro rabbit cardiac wedge model mimicking LQT2 using E-4031 and hypokalemic, hypomagnesaemic Tyrode's solution.
• Recorded monophasic action potentials from epicardial and endocardial tissues.
• Administered KN-93 (a CaMKII inhibitor) as a pretreatment to assess its antiarrhythmic effects.

Main Results:

• E-4031 successfully induced LQT2 model characteristics, including prolonged QT interval, increased Tp-e, elevated Tp-e/QT, and heightened TDR.
• The LQT2 model exhibited increased incidence of EADs, R-on-T extrasystoles, and TDP.
• Pretreatment with KN-93 significantly inhibited EADs, R-on-T extrasystoles, and TDP without affecting QT interval, Tp-e, or Tp-e/QT.

Conclusions:

• KN-93, a CaMKII inhibitor, effectively suppresses EADs, which are triggers for TDP in the LQT2 model.
• CaMKII inhibition offers a potential therapeutic strategy for LQT2-induced TDP by targeting EADs without altering TDR.