TASK-1通道所参与的局麻药心脏毒性作用机制

Although modern local anesthetics (LAs) are generally safe, risks persist and toxic reactions remain a problem with accidental intravascular injection, inadvertent intrathecal injection, or administration of an excessive systemic dose of these drugs. It is clear that the major mechanism accounting for LA-induced regional anesthesia involves inhibition of voltage-gated sodium (NaV) channels, but it is not certain that inhibition of NaV channels can account for systemic toxic effects of the drugs, for example the initial CNS excitation and proconvulsive actions. It is increasingly recognized that LAs at toxicologically relevant concentrations are not selective Na+ channel blockers but also block other ion channels such as inward rectifier K+ channel, delayed rectifier K+ channel, transient outward K+ channel, ATP-sensitive K+ channel and L-Ca2+ channel. Our previous findings suggest that TASK channels are an important molecular target for central toxic effects of LAs. TASK-1, expressed in mouse ventricular cardiomyocytes and in the conduction system of the murine heart, contributes to a rapidly activating, non-inactivating K+ current component (IKur, IKp or Iss) in the repolarization phase of the action potential. It has been shown that TASK-1 inhibitor carbamyl-PAF causes abnormal automaticity, plateau phase arrest of the action potential, and early afterdepolarizations in isolated murine ventricular myocytes. Our previous study shows TASK-1 channel is most sensitive to the inhibition by LAs compared to homomeric TASK-3 and heteromeric TASK-1/TASK-3 channels. According to those previous results, the inhibition of TASK-1 channel in ventricular cardiomyocytes may affect their action potential replorization, leading to ventricular arrhythmias. We therefore hypothesize that TASK-1 may also be a molecular target for cardiotoxicity of LAs. To testify the hypothesis, the effects of different concentrations of LAs on cardiac electrophysiological activity will be compared between wild type and TASK-1 deleted mice using patch clamp in isolated ventricular cardiomyocytes and in vivo ventricular monophasic action potential and electrocardiogram recordings. In the project, we will explore the possible role of TASK-1 channel in modulation of LA cardiotoxicity, providing a new target for further understanding mechanisms of LA cardiotoxicity and for development of new LA compounds with reduced cardiotoxicity.

局麻药(LAs)一般使用安全，但在临床中发生全身性毒性反应的风险仍然存在。LAs的毒性作用机制不能完全用其作用机制即对钠通道的阻滞来解释。我们的前期研究证实TASK通道是LAs引起CNS毒性作用的重要靶位。TASK-1在小鼠的心脏传导系统和心室肌中均有表达并在心室肌细胞动作电位的复极中具有重要作用。LAs对TASK-1具有抑制效应，而TASK-1的抑制可影响心室肌细胞动作电位的复极，可能会导致室性心律失常的发生，由此我们推测TASK-1通道可能也是LAs心脏毒性作用的靶位。为了检验这一假设的成立，我们将应用膜片钳、单相动作电位和ECG记录技术，比较不同浓度LAs对野生型和TASK-1基因剔除型小鼠离体的心室肌细胞及在体心脏电生理活动的影响，探讨TASK-1在LAs心脏毒性作用中所参与的机制，为LAs心脏毒性作用机制的进一步认识提供新的理论依据，为新型毒性小的LAs的开发提供新的方向。

局麻药(LAs)一般使用安全，但在临床中发生全身性毒性反应的风险仍然存在。LAs的毒性作用机制不能完全用其作用机制即对钠通道的阻滞来解释。TASK-1在小鼠的心脏传导系统和心室肌中均有表达并在心室肌细胞动作电位的复极中具有重要作用。LAs对TASK-1具有抑制效应，而TASK-1的抑制可影响心室肌细胞动作电位的复极，可能会导致室性心律失常的发生，由此我们推测TASK-1通道可能也是LAs心脏毒性作用的靶位。为了检验这一假设的成立，我们应用膜片钳、单向动作电位和ECG记录技术，比较不同剂量LAs对野生型和TASK-1基因剔除型小鼠在体心脏电生理活动的影响。研究结果显示：1）TASK-1通道在小鼠的心脏中广泛表达；在心脏中，TASK-1通道相对于其它K2P 通道的表达更为丰富；2）在细胞水平上不同浓度LAs对TASK-1电流产生剂量依赖性抑制作用；3）毒性剂量的LAs引起了小鼠ECG QRS波时程和QT间期的延长，TASK-1基因的剔除抑制了毒性剂量LAs对小鼠ECG QRS波时程和QT间期的影响；4）毒性剂量的LAs引起了小鼠单向动作电位 APD90的延长，TASK-1基因的剔除抑制了毒性剂量LAs对小鼠单向动作电位 APD90的影响；5）毒性剂量的LAs引起了可引起小鼠死亡，TASK-1基因的剔除降低了小鼠的死亡率。以上研究结果表明：1）TASK-1通道是LAs的心脏毒性作用靶位；2）LAs所致的心脏毒性的作用机制是通过抑制心肌上TASK-1通道延长ECG QRS波时程和QT间期及单向动作电位的APD90而导致心律失常；3）不同LAs所致的心脏毒性的大小与其对心肌上TASK-1通道的抑制程度有关：布比卡因对TASK-1通道的抑制程度最大，所致的心脏毒性也最大；而利多卡因对TASK-1通道的抑制程度相对较小，其心脏毒性也较小。本研究为LAs心脏毒性作用机制的进一步认识提供新的理论依据，为新型毒性小的LAs的开发提供新的方向。