肿瘤组织和中脑导水管周围灰质P2X7受体在大鼠骨癌痛机制中作用研究

Cancer pain is one of the most common complications in advanced cancer patients but without an efficient analgesia treatment in clinical. The midbrain periaqueductal gray (PAG) is a crucial site in the pain modulation systems. The purinergic P2X7 receptor activation is closely related to the mechanisms of tumor development and metastasis. The accumulating evidence suggests that the P2X7 receptor also plays an important role in the inflammatory and neuropathic pain modulation. However, it is currently debated whether P2X7 receptor activation is involved in the mechanisms of cancer pain. In our previous works, we have found the expression of P2X7 receptor was upregulated in the ventrolateral periaqueductal gray (vlPAG) neurons in cancer-induced bone pain rats. We rationally hypothesized that the activation of vlPAG neuronal P2X7 receptor plays a role in the mechanisms of bone cancer pain development and maintenance. To try to test this hypothesis, a rat model of bone cancer pain will be used and a series of behavioral, morphological, molecular biological and electrophysiological techniques will be adopted in a combination of in vivo and in vitro experiments for exploring the underlying mechanisms. In the current study, we aim to verify the following assumptions: 1）the tumor tissue P2X7 receptor activation causes electrophysiological changes of primary somatosensory cortex (SI) neurons in the firing sequence and field potential; 2) the activation of the vlPAG P2X7 receptors promotes the glutamate and/or D-serine release in the vlPAG followed by NMDA receptor activation, and incurs a decreased opioid receptor function, eventually leads to the development of a bone cancer pain status. We also attempt to clarify the relevant molecular mechanisms. This study can deepen the understanding of the P2X7 receptor activation in bone cancer pain mechanism, which provides new ideas and new perspectives for clinical bone cancer pain managements.

癌性疼痛是晚期癌症患者常见并发症但临床镇痛治疗效果欠佳。中脑导水管周围灰质（PAG）是机体疼痛调制的关键部位；P2X7受体活化介入疼痛调制以及肿瘤生长、转移机制。本课题组发现骨癌痛大鼠PAG神经元P2X7受体表达增多，推测PAG神经元P2X7受体激活可能参与大鼠骨癌痛机制。本研究采用骨癌痛模型大鼠，综合运用行为学、形态学、分子生物学以及电生理学方法分别探讨外周肿瘤组织和PAG神经元P2X7受体激活在大鼠骨癌痛机制中的作用。求证：①肿瘤组织中P2X7受体激活引起大鼠初级躯体感觉皮层神经元放电序列改变；②PAG神经元P2X7受体激活后通过促进谷氨酸/D-丝氨酸释放激活NMDA受体，NMDA受体与阿片受体相互作用引起阿片受体功能下调，最终导致骨癌痛的形成和维持，并对其相关的分子机制进行研究。本研究可加深对P2X7受体在骨癌痛机制中作用的认识，有助于拓展以P2X7受体为靶点的新的癌性疼痛镇痛策略。

骨癌痛（BCP）是晚期肿瘤患者常见的并发症，临床镇痛效果欠佳。中脑导水管周围灰质（PAG）是疼痛调制的关键部位；P2X7受体激活介入疼痛调制以及肿瘤生长、转移机制。本研究主要完成以下工作。.一、建立骨癌痛模型大鼠，运用行为学、形态学、分子生物学以及电生理学方法，研究证实①PAG神经元P2X7受体激活后通过促进D-丝氨酸释放激活NMDA受体，进而产生镇痛作用；②骨癌痛大鼠初级躯体感觉皮层神经元放电序列改变，导致骨癌痛的形成和维持。.二、对临床癌痛镇痛的常用药物的镇痛机制进行研究。神经妥乐平是临床常用的针对慢性病理性疼痛的镇痛药。观察BCP大鼠多次腹腔注射不同剂量神经妥乐平可缓解BCP大鼠的疼痛行为，剂量依赖性的提高BCP大鼠机械痛阈值，vlPAG中5-HT7受体和P2X3受体阳性细胞数和蛋白水平；同时，神经妥乐平可降低BCP大鼠初级体感皮层神经元的放电频率。曲马多（tramadol）是一种中枢阿片受体镇痛药。研究发现，BCP大鼠腹腔注射不同剂量的曲马多后呈剂量依赖的促进P2X7受体在vlPAG的表达，同时缓解骨癌痛大鼠的疼痛行为学表现、疼痛阈值提高。本研究结果为临床癌性疼痛镇痛中运用神经妥乐平和曲马多提供了理论支持。.三、糖尿病神经病理性疼痛大鼠PAG中星型胶质细胞激活，表达和功能上调；给予神经妥乐平治疗后，PAG中星型胶质细胞激活减少，大鼠疼痛缓解；.四、本研究证实在炎症性疼痛、神经病理性疼痛中，PAG以及脊髓背角P2X7受体激活对疼痛信息的调制作用。.本课题研究结果以论著形式发表SCI文章4篇，北图核心期刊文章6篇以及科技核心期刊文章2篇，获得实用新型专利授权3项。