Department of Pharmacology, The Key Laboratory of Pharmacology and Toxicology for New Drugs, Hebei Medical University, Shijiazhuang, 050017, China.
The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, 050017, China.
Acta Pharmacol Sin. 2021 Feb;42(2):218-229. doi: 10.1038/s41401-020-0467-6. Epub 2020 Aug 3.
Aconitine (ACO), a main active ingredient of Aconitum, is well-known for its cardiotoxicity. However, the mechanisms of toxic action of ACO remain unclear. In the current study, we investigated the cardiac effects of ACO and mesaconitine (MACO), a structurally related analog of ACO identified in Aconitum with undocumented cardiotoxicity in guinea pigs. We showed that intravenous administration of ACO or MACO (25 μg/kg) to guinea pigs caused various types of arrhythmias in electrocardiogram (ECG) recording, including ventricular premature beats (VPB), atrioventricular blockade (AVB), ventricular tachycardia (VT), and ventricular fibrillation (VF). MACO displayed more potent arrhythmogenic effect than ACO. We conducted whole-cell patch-clamp recording in isolated guinea pig ventricular myocytes, and observed that treatment with ACO (0.3, 3 μM) or MACO (0.1, 0.3 μM) depolarized the resting membrane potential (RMP) and reduced the action potential amplitude (APA) and durations (APDs) in a concentration-dependent manner. The ACO- and MACO-induced AP remodeling was largely abolished by an I blocker tetrodotoxin (2 μM) and partly abolished by a specific Na/K pump (NKP) blocker ouabain (0.1 μM). Furthermore, we observed that treatment with ACO or MACO attenuated NKP current (I) and increased peak I by accelerating the sodium channel activation with the EC of 8.36 ± 1.89 and 1.33 ± 0.16 μM, respectively. Incubation of ventricular myocytes with ACO or MACO concentration-dependently increased intracellular Na and Ca concentrations. In conclusion, the current study demonstrates strong arrhythmogenic effects of ACO and MACO resulted from increasing the peak I via accelerating sodium channel activation and inhibiting the I. These results may help to improve our understanding of cardiotoxic mechanisms of ACO and MACO, and identify potential novel therapeutic targets for Aconitum poisoning.
乌头碱（ACO）是乌头属植物的主要活性成分，以其心脏毒性而闻名。然而，ACO 的毒性作用机制尚不清楚。在本研究中，我们研究了 ACO 和中乌头碱（MACO）的心脏效应，MACO 是乌头属植物中发现的与 ACO 结构相关的类似物，在豚鼠中具有未记录的心脏毒性。我们表明，静脉给予豚鼠 25μg/kg 的 ACO 或 MACO 会导致心电图（ECG）记录中的各种类型的心律失常，包括室性早搏（VPB）、房室传导阻滞（AVB）、室性心动过速（VT）和心室颤动（VF）。MACO 比 ACO 显示出更强的致心律失常作用。我们在分离的豚鼠心室肌细胞中进行全细胞膜片钳记录，观察到 ACO（0.3、3μM）或 MACO（0.1、0.3μM）处理以浓度依赖性方式去极化静息膜电位（RMP）并降低动作电位幅度（APA）和动作电位时程（APD）。ACO 和 MACO 诱导的 AP 重塑主要被 I 型阻断剂河豚毒素（2μM）消除，部分被特异性 Na/K 泵（NKP）阻断剂哇巴因（0.1μM）消除。此外，我们观察到 ACO 或 MACO 处理会减弱 NKP 电流（I）并通过加速钠通道激活增加峰值 I，ACO 和 MACO 的 EC 分别为 8.36±1.89μM 和 1.33±0.16μM。培养的心室肌细胞中 ACO 或 MACO 浓度依赖性地增加细胞内 Na 和 Ca 浓度。总之，本研究表明 ACO 和 MACO 具有很强的致心律失常作用，这是通过加速钠通道激活和抑制 I 来增加峰值 I 引起的。这些结果可能有助于提高我们对 ACO 和 MACO 心脏毒性机制的理解，并为乌头碱中毒的潜在新治疗靶点提供依据。
