Calpain-2调控IL-6介导Nav1.6钠通道异常表达参与紫杉醇诱导的痛觉过敏

Studies have shown that calpain-2(a calcium-dependent cysteine protease) levels are higher in colorectal tumors resistant to chemotherapy. Paclitaxel chemotherapy frequently induces neuropathic pain during and often persisting after therapy. Our previous work have revealed that calpain-2 contributed to neuropathic pain following motor nerve injury by regulating tumor necrosis factor-α(TNF-a) and interleukin-6 (IL-6) expression. However, its role in paclitaxel-induced hyperalgesia is still unknown. In our preliminary experiments, we found that intrathecal administration of IL-6 neutralizing antibody significantly alleviated the up-regulation of Nav1.6 by L5 ventral root transection (L5-VRT); the protein level of calpain-2、IL-6 and Nav1.6 in DRGs and spinal dorsal horn were markedly increased in paclitaxel model; pre-treatment with calpain inhibitor MDL28170 blocked the mechanical allodynia in bilateral hind paws in paclitaxel model. These results suggest the important role of calpain-2 in paclitaxel-induced neuropathic pain. We will further investigate that① in paclitaxel-induced pain model, whether the abnormal expression of Nav1.6 produces an effect on neuronal excitability in DRGs and spinal ventral horn and affects behavior; ②whether calpain-2 increases Nav1.6 expression via upregulating the protein level of IL-6 associated with neuropathic pain induced by paclitaxel. The present project aims to reveal the roles and mechanisms of calpain-2 in paclitaxel-induced hyperalgesia and to provide a new target for clinical therapy.

高表达钙依赖性蛋白酶（Calpain-2）的患者易抵抗化疗药的作用，而紫杉醇在临床治疗肿瘤时常伴神经病理性疼痛。我们曾发现calpain-2可通过调控肿瘤坏死因子（TNF-α）和白细胞介素-6（IL-6）的表达参与运动神经损伤（L5-VRT）诱导的慢性痛，但其是否参与紫杉醇诱导的痛过敏尚无报导。我们预实验发现在L5-VRT模型中抑制IL-6可缓解DRG内Nav1.6上调，而在紫杉醇痛模型中calpain-2、IL-6及Nav1.6均显著增加，抑制calpain-2可阻断紫杉醇诱导的痛过敏，提示calpain-2可能参与紫杉醇痛过敏的诱导。本项目拟进一步明确在紫杉醇痛模型中：①Nav1.6对脊髓和DRG神经元兴奋性及痛行为的影响；②calpain-2是否通过IL-6调控Nav1.6的异常表达，旨在揭示calpain-2参与紫杉醇诱导的痛过敏的作用机制，为防治化疗药后痛过敏的发生提供新靶点。

紫杉醇的抗肿瘤效果显著，但引起的长时间的痛觉过敏反应制约了其使用。以往研究发现神经免疫炎症在神经病理性疼痛中发挥重要作用，以往研究发现calpain可通过调节细胞因子IL-6参与运动神经损伤引起的痛觉过敏。本项目观察了calpain在紫杉醇诱导的神经病理性疼痛中发挥的作用，并探究calpain与炎性细胞因子及Nav1.6的上下游调控关系，同时分析了不同痛觉过敏模型中Nav1.6和IL-6和TNF-α在前扣带皮层中枢的表达情况。实验结果提示紫杉醇痛模型中脊髓背角内calpain酶早期即被激活，同时Nav1.6和IL-6及TNF-α表达显著增加。预先使用Calpain抑制剂MDL28170可阻断紫杉醇诱导的痛过敏。干扰calpain-1可显著削弱Nav1.6、IL-6和TNF-α的增加，并抑制小胶质细胞的激活。同时，不同的神经病理性疼痛模型中，炎性细胞因子及Nav1.6在参与疼痛调控的一级皮层区域前扣带皮层内表达活跃。实验结果提示calpain-炎性细胞因子-钠通道蛋白级联反应可诱导紫杉醇引起的痛觉过敏的发生，calpain可能成为防治紫杉醇引起的痛觉过敏的新靶点。

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