Rudolf-Boehm-Institute of Pharmacology and Toxicology, Medical Faculty, University of Leipzig, Leipzig, Germany.
Br J Pharmacol. 2012 Sep;167(1):48-66. doi: 10.1111/j.1476-5381.2012.01987.x.
In mammalian cells, the anti-parasitic drug ivermectin is known as a positive allosteric modulator of the ATP-activated ion channel P2X4 and is used to discriminate between P2X4- and P2X7-mediated cellular responses. In this paper we provide evidence that the reported isoform selectivity of ivermectin is a species-specific phenomenon.
Complementary electrophysiological and fluorometric methods were applied to evaluate the effect of ivermectin on recombinantly expressed and on native P2X7 receptors. A biophysical characterization of ionic currents and of the pore dilation properties is provided.
Unexpectedly, ivermectin potentiated currents in human monocyte-derived macrophages that endogenously express hP2X7 receptors. Likewise, currents and Ca(2+) influx through recombinant human (hP2X7) receptors were potently enhanced by ivermectin at submaximal or saturating ATP concentrations. Since intracellular ivermectin did not mimic or prevent its activity when applied to the bath solution, the binding site of ivermectin on hP2X7 receptors appears to be accessible from the extracellular side. In contrast to currents through P2X4 receptors, ivermectin did not cause a delay in hP2X7 current decay upon ATP removal. Interestingly, NMDG(+) permeability and Yo-Pro-1 uptake were not affected by ivermectin. On rat or mouse P2X7 receptors, ivermectin was only poorly effective, suggesting a species-specific mode of action.
The data indicate a previously unrecognized species-specific modulation of human P2X7 receptors by ivermectin that should be considered when using this cell-biological tool in human cells and tissues.
在哺乳动物细胞中，抗寄生虫药物伊维菌素被认为是 ATP 激活离子通道 P2X4 的正别构调节剂，用于区分 P2X4 和 P2X7 介导的细胞反应。本文提供了证据表明，伊维菌素报道的亚型选择性是一种种属特异性现象。
应用互补的电生理学和荧光法评估伊维菌素对重组表达和天然 P2X7 受体的影响。提供了对离子电流和孔扩张特性的生物物理特征描述。
出乎意料的是，伊维菌素增强了人单核细胞衍生巨噬细胞中内源性表达 hP2X7 受体的电流。同样，在亚最大或饱和 ATP 浓度下，伊维菌素也能强烈增强重组人（hP2X7）受体的电流和Ca(2+) 内流。由于细胞内伊维菌素在应用于浴液溶液时不能模拟或阻止其活性，因此伊维菌素在 hP2X7 受体上的结合位点似乎可从细胞外侧进入。与 P2X4 受体的电流不同，伊维菌素在 ATP 去除时不会导致 hP2X7 电流衰减延迟。有趣的是，NMDG(+)通透性和 Yo-Pro-1 摄取不受伊维菌素影响。在大鼠或小鼠 P2X7 受体上，伊维菌素的作用效果较差，表明存在种属特异性作用模式。
这些数据表明，伊维菌素对人 P2X7 受体具有先前未被认识到的种属特异性调节作用，在人类细胞和组织中使用这种细胞生物学工具时应考虑到这一点。
