GDNF通过激活Ret介导信号通路参与骨癌痛-吗啡耐受的机制研究

Patients with cancer often suffer from chronic pain. Bone cancer pain is one of the most severe pain. Morphine is the first choice in the treatment of moderate to severe cancer pain. However, antinociceptive tolerance resulted from chronic administration restrains the use of morphine. The mechanism of morphine tolerance is still unclear. There are plenty of studies focused on the role of glial cell line-derived neurotrophic factor (GDNF) in the neuropathic pain and morphine dependence, and the efficient approach that delivery GDNF to the central nervous system has been one of the major topic of study. Nevertheless, the role and the mechanism of GDNF in the morphine tolerance is unknown. To further the previous proteomics work, we investigate the role of GDNF in morphine antinociceptive tolerance on the rats with chronic bone cancer pain. There are growing bodies of studies induced the morphine tolerance on the rats with bone cancer pain, which was relevant to the clinical status. In the preliminary study, we found that the expression of GDNF was significant reduced in the morphine tolerant rats with bone cancer pain compared to that in normal control, and intrathecal injection of GDNF reversed the morphine antinociceptive tolerance. Thus, we plan to do further studies on the expression of GDNF in spinal and dorsal root ganglia, relationships of receptor complex of GDNF and downstream signal pathway in cell and the electrophysiology changes in the development of morphine tolerance. The objective of the project is to explain the role of GDNF in the development of morphine tolerance in bone cancer pain, and provide basic research data for the development of new drugs.

骨癌痛为最严重的癌性疼痛之一。吗啡是治疗中重度癌痛的一线药物，吗啡耐受限制了其临床应用。胶质细胞源性神经营养因子（GDNF）在神经病理性疼痛及吗啡慢性处理中的作用受到广泛的关注，其在中枢神经系统有效的给药方式是研究的热点。GDNF参与吗啡镇痛耐受的机理仍不明确。在蛋白质组学研究的基础上，我们应用更加接近临床的骨癌痛大鼠模型研究GDNF在慢性吗啡耐受中的作用机制。预实验发现，骨癌痛-吗啡耐受大鼠脊髓GDNF表达较正常组大鼠明显降低，鞘内注射GDNF可逆转大鼠吗啡镇痛耐受。本项目拟研究GDNF在骨癌痛-吗啡耐受中的作用部位及神经细胞类型，探索GDNF激活Ret导致下游MAPK、PI3K及SFK信号通路的改变，观察脊髓神经元电生理特征改变，以阐明脊髓及背根神经节GDNF在骨癌痛-吗啡耐受中的作用及其机制，为研发新药提供实验依据。

恶性肿瘤是世界性的医疗及社会难题，是目前导致中国患者死亡的首要病因。癌性疼痛机制复杂，临床治疗效果不佳，严重影响患者生活质量。吗啡是治疗中重度癌痛的一线药物，然而长期应用吗啡后伴随的吗啡耐受及成瘾严重限制了其临床应用。胶质细胞源性神经营养因子（GDNF）在神经病理性疼痛及吗啡慢性处理中的作用受到广泛的关注，其在中枢神经系统有效的给药方式是研究的热点。GDNF参与吗啡镇痛耐受的机理仍不明确。在本项目研究中，我们首先发现骨癌痛大鼠脊髓GDNF表达降低，伴随脊髓星形胶质细胞及小胶质细胞激活，神经元兴奋性升高。我们通过鞘内注射慢病毒载体恢复骨癌痛大鼠脊髓GDNF表达后其胶质细胞激活及神经元兴奋性升高缓解，足底皮肤热痛敏及机械痛敏减轻。癌性疼痛包括痛觉过敏、持续性自发痛及爆发痛。本研究发现鞘内注射GDNF 可以缓解痛觉过敏但对持续性自发痛无效。同时，我们发现骨癌痛大鼠脊髓MOR表达下调，吗啡的镇痛效能下降。鞘内注射GDNF 可以逆转骨癌痛大鼠MOR表达下调，减缓吗啡耐受。通过上述研究，明确了GDNF在大鼠骨癌痛及吗啡耐受中的作用及可能的机制，为预防及控制骨癌痛提供了新的治疗思路。