Matak Ivica, Tékus Valéria, Bölcskei Kata, Lacković Zdravko, Helyes Zsuzsanna
Department of Pharmacology, University of Zagreb School of Medicine, Zagreb, Croatia.
Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, Pécs, Hungary; János Szentágothai Research Center, University of Pécs, Pécs, Hungary.
Neuroscience. 2017 Sep 1;358:137-145. doi: 10.1016/j.neuroscience.2017.06.040. Epub 2017 Jul 1.
The antinociceptive action of botulinum toxin type A (BoNT/A) has been demonstrated in behavioral animal studies and clinical settings. It was shown that this effect is associated with toxin activity in CNS, however, the mechanism is not fully understood. Substance P (SP) is one of the dominant neurotransmitters in primary afferent neurons transmitting pain and itch. Thus, here we examined association of SP-mediated transmission and BoNT/A antinociceptive action by employing gene knockouts. Antinociceptive activity of intraplantarly (i.pl.) injected BoNT/A was examined in mice lacking the gene encoding for SP/neurokinin A (tac1) or SP-preferred receptor neurokinin 1 (tac1r), compared to control C57Bl/6J wild type animals. BoNT/A action was assessed in inflammatory pain induced by formalin and CFA, and neuropathic pain induced by partial sciatic nerve ligation. BoNT/A activity in CNS was examined by c-Fos and BoNT/A-cleaved SNAP-25 immunohistochemistry. In wild type mice, acute (formalin-evoked) and chronic pain (neuropathic and inflammatory) was reduced by peripherally injected BoNT/A. In tac1 and tac1r knockout mice, BoNT/A exerted no analgesic effect. In control animals BoNT/A reduced the formalin-evoked c-Fos expression in lumbar dorsal horn, while in knockout mice the c-Fos expression was not reduced. After peripheral toxin injection, cleaved SNAP-25 occurred in lumbar dorsal horn in all animal genotypes. BoNT/A antinociceptive activity is absent in animals lacking the SP and neurokinin 1 receptor encoding genes, in spite of presence of toxin's enzymatic activity in central sensory regions. Thus, we conclude that the integrity of SP-ergic system is necessary for the antinociceptive activity of BoNT/A.
A型肉毒杆菌毒素（BoNT/A）的抗伤害感受作用已在动物行为研究和临床环境中得到证实。研究表明，这种作用与毒素在中枢神经系统中的活性有关，然而，其机制尚未完全明确。P物质（SP）是传递疼痛和瘙痒的初级传入神经元中的主要神经递质之一。因此，我们通过基因敲除技术研究了SP介导的传递与BoNT/A抗伤害感受作用之间的关联。与对照C57Bl/6J野生型动物相比，在缺乏编码SP/神经激肽A（tac1）或SP优先受体神经激肽1（tac1r）基因的小鼠中，检测了经足底（i.pl.）注射的BoNT/A的抗伤害感受活性。在福尔马林和完全弗氏佐剂（CFA）诱导的炎性疼痛以及坐骨神经部分结扎诱导的神经性疼痛中评估了BoNT/A的作用。通过c-Fos和BoNT/A切割的SNAP-25免疫组织化学检测毒素在中枢神经系统中的活性。在野生型小鼠中，外周注射BoNT/A可减轻急性（福尔马林诱发）和慢性疼痛（神经性和炎性）。在tac1和tac1r基因敲除小鼠中，BoNT/A没有镇痛作用。在对照动物中，BoNT/A可降低福尔马林诱发的腰段背角c-Fos表达，而在基因敲除小鼠中，c-Fos表达未降低。外周注射毒素后，所有动物基因型的腰段背角均出现切割的SNAP-25。尽管毒素在中枢感觉区域具有酶活性，但缺乏编码SP和神经激肽1受体基因的动物中不存在BoNT/A的抗伤害感受活性。因此，我们得出结论，SP能系统的完整性对于BoNT/A的抗伤害感受活性是必要的。
