Department of Neurobiology, Harvard Medical School, Boston, Massachusetts.
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
Mol Pharmacol. 2023 Apr;103(4):221-229. doi: 10.1124/molpharm.122.000593. Epub 2023 Jan 12.
Sodium channel inhibitors used as local anesthetics, antiarrhythmics, or antiepileptics typically have the property of use-dependent inhibition, whereby inhibition is enhanced by repetitive channel activation. For targeting pain, Nav1.8 channels are an attractive target because they are prominent in primary pain-sensing neurons, with little or no expression in most other kinds of neurons, and a number of Nav1.8-targeted compounds have been developed. We examined the characteristics of Nav1.8 inhibition by one of the most potent Nav1.8 inhibitors so far described, A-887826, and found that when studied with physiologic resting potentials and physiologic temperatures, inhibition had strong "reverse use dependence", whereby inhibition was relieved by repetitive short depolarizations. This effect was much stronger with A-887826 than with A-803467, another Nav1.8 inhibitor. The use-dependent relief from inhibition was seen in both human Nav1.8 channels studied in a cell line and in native Nav1.8 channels in mouse dorsal root ganglion (DRG) neurons. In native Nav1.8 channels, substantial relief of inhibition occurred during repetitive stimulation by action potential waveforms at 5 Hz, suggesting that the phenomenon is likely important under physiologic conditions. SIGNIFICANCE STATEMENT: Nav1.8 sodium channels are expressed in primary pain-sensing neurons and are a prime current target for new drugs for pain. This work shows that one of the most potent Nav1.8 inhibitors, A-887826, has the unusual property that inhibition is relieved by repeated short depolarizations. This "reverse use dependence" may reduce inhibition during physiological firing and should be selected against in drug development.
钠离子通道抑制剂被用作局部麻醉剂、抗心律失常药或抗癫痫药,通常具有使用依赖性抑制的特性,即抑制作用通过重复的通道激活而增强。为了靶向疼痛,Nav1.8 通道是一个有吸引力的目标,因为它们在主要的疼痛感觉神经元中表现突出,在大多数其他类型的神经元中表达很少或没有,并且已经开发了许多靶向 Nav1.8 的化合物。我们研究了迄今为止描述的最有效的 Nav1.8 抑制剂之一 A-887826 对 Nav1.8 抑制的特性,发现当在生理静息电位和生理温度下研究时,抑制具有强烈的“反向使用依赖性”,即通过重复的短去极化来缓解抑制。与另一种 Nav1.8 抑制剂 A-803467 相比,这种效应在 A-887826 中要强得多。这种由使用引起的抑制缓解作用在细胞系中研究的人类 Nav1.8 通道和小鼠背根神经节 (DRG) 神经元中的天然 Nav1.8 通道中都有观察到。在天然 Nav1.8 通道中,在以 5 Hz 的动作电位波形进行重复刺激期间,观察到抑制作用有明显的缓解,这表明该现象在生理条件下可能很重要。意义声明:Nav1.8 钠离子通道在主要的疼痛感觉神经元中表达,是新型疼痛药物的主要当前靶点。这项工作表明,最有效的 Nav1.8 抑制剂之一 A-887826 具有不寻常的特性,即抑制作用通过重复的短去极化来缓解。这种“反向使用依赖性”可能会减少生理放电期间的抑制作用,在药物开发中应加以避免。
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