Abstract：
Noxious pain signals are transduced in the peripheral nervous system as action potentials, which rely on the activities of voltage-gated sodium channels (NaVs). Blocking NaVs is thus a valuable strategy for pain treatment. Here, we report the characterization of a novel NaVs antagonist, 2-(2-(diethylamino)ethyl)indeno[1,2,3-de]phthalazin-3(2H)-one (C65780), and investigation of its action mechanisms. C65780 inhibited the resting NaV1.7, NaV1.8, and NaV1.9 channels with IC50s of 11.3 ± 0.4 μM, 2.7 ± 0.3 μM and 19.2 ± 2.3 μM, respectively. Mechanistic analysis revealed that C65780 quickly bound to its high-affinity receptor site in NaV1.7 as formed by the fast inactivation process and stabilized the channels in a slowly recovering state, for which it facilitated NaV1.7 channels\' inactivation by shifting their inactivation-voltage relationship in the hyperpolarizing direction, increasing the plateau proportion of inactivated channels, and blunting their time-dependent recovery. The slow inactivation of NaV1.7, however, is not involved in the action of C65780. In DRG neurons, C65780 also inhibited activity of NaVs, thus dampening neuronal excitability. These effects parlayed into a broad efficacy of orally administrated C65780 in various models of pain, with an efficacy comparable to the antidepressant/neuropathic pain drug Amitriptyline. Excitingly, C65780 demonstrated weaker inactivated state inhibition of related NaV1.4 and NaV1.5 channels compared to amitriptyline, and no toxicity or inhibition of locomotion in a forced-swimming test was observed in mice at pain-relieving doses. These results demonstrate that C65780 acts by trapping NaVs in the inactivated and slowly-recovering state to produce pain relief and may represent an excellent starting compound for developing analgesics.
摘要：
有害的疼痛信号在周围神经系统中被转换为动作电位，依赖于电压门控钠通道(Navs)的活性。因此,阻断NaV是疼痛治疗的有价值的策略。这里,我们报道了一种新型NaVs拮抗剂的表征，2-(2-(二乙基氨基)乙基)茚并[1,2,3-de]萘嗪-3(2H)-酮(C65780),并调查其作用机制。C65780抑制静止的NaV1.7，NaV1.8和NaV1.9通道，IC50为11.3±0.4μM，2.7±0.3μM和19.2±2.3μM，分别。机制分析显示，C65780迅速结合到其在NaV1.7中的高亲和力受体位点，如快速失活过程所形成的，并使通道稳定在缓慢恢复的状态，它通过在超极化方向上改变它们的失活-电压关系来促进NaV1.7通道失活，增加失活通道的高原比例，削弱了他们依赖时间的恢复。然而，NaV1.7的缓慢失活，不参与C65780的操作。在DRG神经元中，C65780还抑制了NaVs的活性，从而抑制神经元的兴奋性.这些效果表现为口服C65780在各种疼痛模型中的广泛功效，疗效与抗抑郁药/神经性疼痛药物阿米替林相当。令人兴奋的是,与阿米替林相比，C65780对相关的NaV1.4和NaV1.5通道的失活状态抑制较弱，在缓解疼痛剂量的小鼠中，在强迫游泳试验中没有观察到毒性或运动抑制。这些结果表明,C65780通过捕获处于失活和缓慢恢复状态的NaV来产生疼痛缓解,并且可以代表用于开发镇痛药的优异起始化合物。
