P2X7R: a novel therapeutic target in implant loosening

摘要 临床骨科中最常见的问题之一仍然是由于 炎性骨溶解。植入物中的磨损颗粒刺激巨噬细胞产生炎症 细胞因子，诱导局部骨溶解，抑制骨溶解的成骨修复。我们的长期目标是 发现新的潜在机制，从而为患者确定新的治疗靶点 “无菌松动”。这个R21 A1应用程序将测试细胞外ATP(EATP)的总体假设 增加骨科磨损颗粒的生物活性。 与总体假设一致，我们的初步结果表明，磨粒刺激 巨噬细胞释放三磷酸腺苷。EATP是已知的P2X7R的唯一配体，而P2X7R是主要的巨噬细胞 EATP水平升高的受体。EATP刺激P2X7R可增加某些类型的炎症，但 以前没有在“无菌松动”中进行过研究。因此，目标1(原则证明目标)将决定 EATP和P2X7R如何影响磨粒的生物活性。 EATP刺激P2X7R可以激活NLRP3炎症体，而NLRP3炎症体是 主要负责将PRO-IL1？和PRO-IL18加工成活性细胞因子，以应对磨损颗粒。 然而，NLRP3炎症体必须在激活之前被激活。我们的初步结果表明 磨损颗粒既可以激活NLRP3炎症小体，也可以激活NLRP3炎症小体。我们之前已经证明了 细菌病原体相关分子模式(PAMPs)的粘附性大大增加了生物 粒子的活度。因此，目标2(机械目标)将决定磨粒(与和)如何 无粘附性PAMPs)影响ATP释放、P2X7R和NLRP3炎症体。 高特异性、类药物的P2X7R拮抗剂可以减轻动物模型中的炎症，并已进入临床 其他炎症性疾病的试验。因此，目标3(翻译目标)将决定 P2X7R拮抗剂对磨粒生物活性的影响。 这个项目是R21机制的理想选择：它的风险很高，因为以前没有关于 EATP或P2X7R在“无菌松动”中的作用它具有高影响力的潜力，因为P2X7R 在其他炎症条件的临床试验中，拮抗剂耐受性良好。我们队拥有 该公司拥有必要的专业知识，因此具有得天独厚的优势，能够高效地完成该项目。

SUMMARY One of the most common problems in clinical orthopaedics continues to be “aseptic loosening” due to inflammatory osteolysis. Wear particles from the implants stimulate macrophages to produce inflammatory cytokines, which induce local osteolysis and inhibit osteogenic repair of the osteolysis. Our long-term goal is to discover novel underlying mechanisms and thereby identify novel therapeutic targets for patients with “aseptic loosening”. This R21 A1 application will test the overall hypothesis that extracellular ATP (eATP) increases the biologic activity of orthopaedic wear particles. Consistent with the overall hypothesis, our preliminary results indicate that wear particles stimulate macrophages to release ATP. eATP is the only known ligand for P2X7R, which is the primary macrophage receptor for elevated levels of eATP. Stimulation of P2X7R by eATP increases some types of inflammation but has not previously been studied in “aseptic loosening”. Aim 1 (proof-of-principle aim) will therefore determine how eATP and P2X7R affect the biologic activity of wear particles. Stimulation of the P2X7R by eATP can activate the NLRP3 inflammasome and the NLRP3 inflammasome is primarily responsible for processing pro-IL1ß and pro-IL18 to the active cytokines in response to wear particles. However, the NLRP3 inflammasome must be primed prior to activation. Our preliminary results suggest that wear particles can both prime and activate the NLRP3 inflammasome. We previously showed that the adherence of bacterial pathogen-associate molecular patterns (PAMPs) substantially increases the biologic activity of the particles. Aim 2 (mechanistic aim) will therefore determine how wear particles (with and without adherent PAMPs) affect ATP release, the P2X7R, and the NLRP3 inflammasome. Highly-specific, drug-like antagonists of P2X7R can reduce inflammation in animal models and are in clinical trials for other inflammatory conditions. Aim 3 (translational aim) will therefore determine the effects of antagonists of P2X7R on biologic activity of the wear particles. This project is ideal for the R21 mechanism: It is high risk because there are no previous studies on the effects of eATP or P2X7R in “aseptic loosening”. It has the potential for high impact because the P2X7R antagonists were well tolerated in clinical trials for other inflammatory conditions. Our team possesses the necessary expertise and thus is uniquely positioned to efficiently complete this project.