Stretch-activated channels in the heart: Their role in arrhythmias and potential as antiarrhythmic drug targets

Amiodarone inhibits arrhythmias in hypertensive rats by improving myocardial biomechanical properties

The prevalence of arrhythmia in patients with hypertension has gradually attracted widespread attention. However, the relationship between hypertension and arrhythmia still lacks more attention. Herein, we explore the biomechanical mechanism of arrhythmia in hypertensive rats and the effect of amiodarone on biomechanical properties. We applied micro-mechanics and amiodarone to stimulate single ventricular myocytes to compare changes of mechanical parameters and the mechanism was investigated in biomechanics. Then we verified the expression changes of genes and long non-coding RNAs (lncRNAs) related to myocardial mechanics to explore the effect of amiodarone on biomechanical properties. The results found that the stiffness of ventricular myocytes and calcium ion levels in hypertensive rats were significantly increased and amiodarone could alleviate the intracellular calcium response and biomechanical stimulation. In addition, experiments showed spontaneously hypertensive rats were more likely to induce arrhythmia and preoperative amiodarone intervention significantly reduced the occurrence of arrhythmias. Meanwhile, high-throughput sequencing showed the genes and lncRNAs related to myocardial mechanics changed significantly in the spontaneously hypertensive rats that amiodarone was injected. These results strengthen the evidence that hypertension rats are prone to arrhythmia with abnormal myocardial biomechanical properties. Amiodarone effectively inhibit arrhythmia by improving the myocardial biomechanical properties and weakening the sensitivity of mechanical stretch stimulation.

An increased TREK-1-like potassium current in ventricular myocytes during rat cardiac hypertrophy

To elucidate the expression and identify the functional changes of 2 pore domain potassium channel TREK-1 during cardiac hypertrophy in rats, left ventricular hypertrophy was induced by subcutaneous injection with isoproterenol. Western blot was used to detect the expression of TREK-1 channel protein, and inside-out and whole-cell recordings were used to record TREK-1 currents. The results showed that TREK-1 protein expression in endocardium was slightly higher than that in epicardium in control left ventricles. However, it was obviously upregulated by 89.8% during hypertrophy, 2.3-fold higher than in epicardium. Mechanical stretch, intracellular acidification, and arachidonic acid could activate a TREK-1-like current in cardiomyocytes. The slope conductances of cardiac TREK-1 and CHO/TREK-1 channels were 123 ± 7 and 113 ± 17 pS, respectively. The TREK-1 inhibitor L-3-n-butylphthalide (10 μM) reduced the currents in CHO/TREK-1 cells, normal cardiomyocytes, and hypertrophic cardiomyocytes by 48.5%, 54.3%, and 55.5%, respectively. The percentage of L-3-n-butylphthalide-inhibited outward whole-cell current in hypertrophic cardiomyocytes (23.7%) was larger than that in normal cardiomyocytes (14.2%). The percentage of chloroform-activated outward whole-cell current in hypertrophic cardiomyocytes (58.3%) was also larger than normal control (40.2%). Our results demonstrated that in hypertrophic rats, TREK-1 protein expression in endocardium was specifically increased and the ratio of TREK-1 channel current in cardiac outward currents was also enhanced. TREK-1 might balance potassium ion flow during hypertrophy and might be a potential drug target for heart protection.