Pain Research Center, Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
Department of Anesthesiology, Cancer Center, Sun Yat-Sen University, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, PR China.
Pain. 2017 Nov;158(11):2169-2180. doi: 10.1097/j.pain.0000000000001018.
Oral Bulleyaconitine A (BLA) is effective for treating neuropathic pain in human patients, but the underlying mechanism is poorly understood. Here, we tested whether BLA blocked voltage-gated sodium channels (VGSCs) in dorsal root ganglion (DRG) neurons. Compelling evidence shows that voltage-gated sodium channels are upregulated in uninjured DRG neurons but downregulated in injured ones following peripheral nerve injury. We found that BLA preferably inhibited Na currents in uninjured DRG neurons in neuropathic rats. Compared to sham rats, IC50 values for resting and inactivated Na currents were 113 and 74 times lower in injured and uninjured neurons of L4-6 DRGs in spared nerve injury (SNI) rats (4.55 and 0.56 nM) and were 688 and 518 times lower in the uninjured L4 and L6 DRG neurons of L5 spinal nerve ligation (L5-SNL) rats. The use-dependent blockage of BLA on Na currents was more potent in neuropathic rats compared to sham rats. Bulleyaconitine A facilitated the inactivation of Na channels in each group. IC50 values for resting and inactivated tetrodotoxin-sensitive (TTX-S) channels were 1855 and 1843 times lower than those for TTX-resistant channels in the uninjured neurons of L5 spinal nerve ligation rats. The upregulation of protein kinase C was associated with the preferable effect of BLA on TTX-S Na channels in the uninjured DRG neurons. Local application of BLA onto L4-6 DRGs at 0.1 to 10 nM dose-dependently alleviated the mechanical allodynia and thermal hyperalgesia in L5 spinal nerve ligation model. Thus, preferable blockage of TTX-S Na channels in uninjured DRG neurons may contribute to BLA's antineuropathic pain effect.
口服草乌甲素 A(BLA)对治疗人类患者的神经性疼痛有效,但作用机制尚不清楚。在这里,我们测试了 BLA 是否能阻断背根神经节(DRG)神经元中的电压门控钠离子通道(VGSCs)。大量证据表明,电压门控钠离子通道在未受伤的 DRG 神经元中上调,而在外周神经损伤后则下调。我们发现,BLA 优先抑制神经性疼痛大鼠未受伤的 DRG 神经元中的钠离子电流。与假手术大鼠相比,在 spared nerve injury(SNI)大鼠的 L4-6 DRG 中,受伤和未受伤神经元的静息和失活钠离子电流的 IC50 值分别低 113 倍和 74 倍(4.55 和 0.56 nM),在 L5 脊神经结扎(L5-SNL)大鼠的 L4 和 L6 未受伤的 DRG 神经元中分别低 688 倍和 518 倍。与假手术大鼠相比,BLA 对钠离子电流的使用依赖性阻断在神经性疼痛大鼠中更为有效。草乌甲素 A 促进了各组钠离子通道的失活。在 L5 脊神经结扎大鼠未受伤的神经元中,静息和失活的四氢巴豆碱敏感(TTX-S)通道的 IC50 值比 TTX 抗性通道低 1855 倍和 1843 倍。蛋白激酶 C 的上调与 BLA 对未受伤的 DRG 神经元中 TTX-S Na 通道的偏好作用有关。在 0.1 至 10 nM 剂量范围内,局部应用 BLA 到 L4-6 DRG 可剂量依赖性地减轻 L5 脊神经结扎模型中的机械性痛觉过敏和热痛觉过敏。因此,未受伤的 DRG 神经元中 TTX-S Na 通道的优先阻断可能有助于 BLA 的抗神经病理性疼痛作用。