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P2X7受体敲除对小鼠骨癌痛的影响

赵欣, 刘慧珠, 张玉秋^*

复旦大学脑科学研究院，上海 200032

摘要

癌痛是临床晚期恶性肿瘤患者常见的临床表现之一。其中，以肺癌、乳腺癌和前列腺癌等骨转移引起疼痛尤为严
重。P2X7受体是ATP门控离子通道型嘌呤能受体的一个亚型，在脊髓背角主要表达在胶质细胞。P2X7受体激活可以促进胶
质细胞释放多种炎症介质，介导脊髓中枢敏化。该受体在炎症痛及神经病理性疼痛中的作用已多有报道，但在癌痛中的作
用尚有争议。本研究采用C57BL/6J小鼠股骨骨髓腔内接种Lewis肺癌细胞所诱导的骨癌痛小鼠模型，分析对比了野生型小鼠和P2X7受体基因敲除(P2rx7−/−)小鼠骨癌痛的发生、发展。野生型C57BL/6J小鼠股骨骨髓腔内接种Lewis肺癌细胞后，患侧后肢分别在第7和14天开始出现明显的触诱发痛和热痛过敏，并呈进行性加重；CatWalk步态分析显示骨癌第21和28天，小鼠患侧脚印面积明显减小，站立时相持续时间缩短，举步时相持续时间显著延长；组织病理学结果显示受累骨骨髓腔有大量肿瘤细胞浸润，骨髓质正常结构消失，伴有髓质骨和皮质骨的破坏。与研究设计时的预期相反，P2rx7−/−小鼠接种瘤细胞后，患肢痛行为检测结果与野生型小鼠相似，甚至在CatWalk步态分析检测值变化发生的时间上较野生小鼠有所提前。这与本研究组前期在大鼠骨癌痛模型观察到的阻断P2X7受体明显对抗骨癌痛的结果完全不同，提示P2X7受体在大、小鼠骨癌痛中可能发挥不同的作用，并再次提示疾病动物模型上的研究结果与人类疾病机理之间还存在巨大差异。

关键词： 骨癌痛; 小鼠; P2X7受体; 基因敲除; 小胶质细胞

Effect of P2X7 receptor knock-out on bone cancer pain in mice

ZHAO Xin, LIU Hui-Zhu, ZHANG Yu-Qiu^*

Institutes of Brain Science, Fudan University, Shanghai 200032, China

Abstract

Cancer pain is one of the most common symptoms in patients with late stage cancer. Lung, breast and prostate carcinoma are the most common causes of pain from osseous metastasis. P2X7 receptor (P2X7R) is one of the subtypes of ATP-gated purinergic
ion channel family, predominately distributed in microglia in the spinal cord. Activation of P2X7Rs in the spinal dorsal horn has been associated with release of proinflammatory cytokines from glial cells, causing increased neuronal excitability and exaggerated nociception. Mounting evidence implies a critical role of P2X7R in inflammatory and neuropathic pain. However, whether P2X7R is involved in cancer pain remains controversial. Here we established a bone cancer pain model by injecting the Lewis lung carcinoma cells into the femur bone marrow cavity of C57BL/6J wild-type mice (C57 WT mice) and P2X7R knockout mice (P2rx7−/− mice) to explore the role of P2X7R in bone cancer pain. Following intrafemur carcinoma inoculation, robust mechanical allodynia and thermal hyperalgesia in C57 WT mice were developed on day 7 and 14, respectively, and persisted for at least 28 days in the ipsilateral hindpaw
of the affected limb. CatWalk gait analysis showed significant decreases in the print area and stand phase, and a significant increase in swing phase in the ipsilateral hindpaw on day 21 and 28 after carcinoma cells inoculation. Histopathological sections
(hematoxylin and eosin stain) showed that the bone marrow of the affected femur was largely replaced by invading tumor cells, and the femur displayed medullary bone loss and bone destruction on day 28 after inoculation. Unexpectedly, no significant changes in bone cancer-induced hypersensitivity of pain behaviors were found in P2rx7−/− mice, and the changes of pain-related values in CatWalk gait analysis even occurred earlier in P2rx7−/− mice, as compared with C57 WT mice. Together with our previous study in rats that blockade of P2X7R significantly alleviated bone cancer pain, it is implied that P2X7R may play different roles in bone cancer pain in different species (e.g. rat vs mouse). These results implicated a huge difference between the pathophysiology discovered in the experimental animal models and that of human disease.

Key words: bone cancer pain; mice; P2X7 receptor; gene knockout; microglia

收稿日期：　　录用日期：

通讯作者：张玉秋　　E-mail: yuqiuzhang@fudan.edu.cn

引用本文：

赵欣, 刘慧珠, 张玉秋. P2X7受体敲除对小鼠骨癌痛的影响[J]. 生理学报 2016; 68 (3): 224-232.

ZHAO Xin, LIU Hui-Zhu, ZHANG Yu-Qiu. Effect of P2X7 receptor knock-out on bone cancer pain in mice. Acta Physiol Sin 2016; 68 (3): 224-232 (in Chinese with English abstract).