Groupe Cœur et Ischémie, Université de Caen, Caen, France.
Br J Pharmacol. 2012 Apr;165(7):2354-64. doi: 10.1111/j.1476-5381.2011.01715.x.
Hypoxia and subsequent re-oxygenation are associated with cardiac arrhythmias such as early afterdepolarizations (EADs), which may be partly explained by perturbations in cytosolic calcium concentration. Transient receptor potential melastatin 4 (TRPM4), a calcium-activated non-selective cation channel, is functionally expressed in the heart. Based on its biophysical properties, it is likely to participate in EADs. Hence, modulators of TRPM4 activity may influence arrhythmias. The aim of this study was to investigate the possible anti-arrhythmic effect of 9-phenanthrol, a TRPM4 inhibitor in a murine heart model of hypoxia and re-oxygenation-induced EADs.
Mouse heart was removed, and the right ventricle was pinned in a superfusion chamber. After a period of normoxia, the preparation was superfused for 2 h with a hypoxic solution and then re-oxygenated. Spontaneous electrical activity was investigated by intracellular microelectrode recordings.
In normoxic conditions, the ventricle exhibited spontaneous action potentials. Application of the hypoxia and re-oxygenation protocol unmasked hypoxia-induced EADs, the occurrence of which increased under re-oxygenation. The frequency of these EADs was reduced by superfusion with either flufenamic acid, a blocker of Ca(2+) -dependent cation channels or with 9-phenanthrol. Superfusion with 9-phenanthrol (10(-5) or 10(-4) mol·L(-1) ) caused a dramatic dose-dependent abolition of EADs.
Hypoxia and re-oxygenation-induced EADs can be generated in the mouse heart model. 9-Phenanthrol abolished EADs, which strongly suggests the involvement of TRPM4 in the generation of EAD. This identifies non-selective cation channels inhibitors as new pharmacological candidates in the treatment of arrhythmias.
缺氧及随后的复氧与心脏性心律失常有关，如早期后除极（EAD），这在一定程度上可以通过细胞溶质钙离子浓度的波动来解释。瞬时受体电位 melastatin 4（TRPM4）是一种钙激活的非选择性阳离子通道，在心脏中具有功能性表达。根据其生物物理特性，它可能参与 EAD 的发生。因此，TRPM4 活性的调节剂可能会影响心律失常。本研究旨在探讨 9-菲咯啉（一种 TRPM4 抑制剂）在缺氧和复氧诱导的 EAD 小鼠心脏模型中的抗心律失常作用。
取出小鼠心脏，将右心室固定在灌流室中。在正常氧合期后，用缺氧溶液灌流 2 小时，然后再复氧。通过细胞内微电极记录来研究自发电活动。
在正常氧合条件下，心室呈现自发性动作电位。应用缺氧和复氧方案揭示了缺氧诱导的 EAD，复氧时 EAD 的发生增加。用氟芬那酸（一种钙依赖性阳离子通道阻滞剂）或 9-菲咯啉灌流可减少这些 EAD 的发生频率。用 9-菲咯啉（10⁻⁵或 10⁻⁴ mol·L⁻¹ ）灌流可引起 EAD 的显著剂量依赖性消除。
在小鼠心脏模型中可以产生缺氧和复氧诱导的 EAD。9-菲咯啉消除了 EAD，这强烈表明 TRPM4 参与了 EAD 的产生。这确定了非选择性阳离子通道抑制剂作为心律失常治疗的新的药理学候选药物。
