靶向PD-1的小分子镇痛肽构建及活性研究

慢性痛是一种常见的难治性疾病，镇痛多肽对慢性痛治疗效果显著，为临床治疗提供新的方法。研究发现，肿瘤免疫治疗领域的关键性分子程序性细胞死亡蛋白-1（PD-1）在背根神经节、脊髓和大脑皮层中表达，并参与疼痛的调节。PD-L1激活PD-1，诱发SHP-1磷酸化、抑制Na+通道和活化K+通道，抑制疼痛信号的转导，为镇痛新药的研发提供新的思路。本项目利用分子对接技术和钙成像，筛选出2−3条具有镇痛潜力的PD-1靶向肽。预实验表明，PD-1靶向肽H20在急性/慢性炎症痛和内脏痛中表现出强效的镇痛作用。在Pd1基因敲除小鼠的内脏痛模型与WT小鼠SHP-1抑制剂拮抗实验中，H20的镇痛效果大幅度衰减，证实H20主要通过激活PD-1与下游SHP-1信号通路抑制疼痛。本项目将从分子、细胞、组织及行为学等多个层面，对PD-1靶向肽的镇痛活性和适用范围展开研究，以期获得可应用于新药研发的肽类先导化合物。

Chronic pain presents a major economic and social burden; millions of individuals are suffering from various pains worldwide. Current medications have limited analgesic effects on chronic pain and several adverse effects. Developing new analgesic drugs with improved properties is thus a major focus in pharmacological research. More and more evidence has shown that analgesic peptides could provide effective therapy for chronic pain with a low risk of adverse side effects. The programmed cell death protein 1 (PD-1) and programmed cell death ligand-1 (PD-L1) are key immunosuppressive molecules regulating the adaptive immune response. In recent years, monoclonal antibodies and small molecular drugs, which disrupt the PD-L1/PD-1 interaction, have harvested promising results in cancer immunotherapy. Previously, expression of PD-1 is observed in dorsal root ganglia, spinal cord, and cerebral cortex. Activation of PD-1 by PD-L1 could evoke significant analgesia in acute and chronic pain. PD-1 has been considered to be one of the most promising targets for pain control. In this application, we use molecular docking technology and calcium imaging to screen nonapeptides with high PD-1 binding ability and analgesic potential. Our preliminary results have been shown that intrathecal injection of H20 (H-Ile-Ser-Tyr-Gly-Gly-Ala-Asp-Tyr-Lys-OH) produced potent analgesia in the formalin, acetic acid writhing, and carrageenan-induced inflammatory pain test. However, H20 was insufficient in Pd1-/- mice. The potent antinociception of H20 was abolished by SHP-1 inhibitor sodium stibogluconate (SSG) in the acetic acid writhing test. The analgesic effects and applicable scope of the promising peptide targeting PD-1 will be studied in the molecular, cellular, tissue, and behavioral tests to obtain lead compounds for addressing the critical need for effective pain relief.