The P2X7 receptor for ATP as a therapeutic target in the prevention of radiation-induced salivary gland dysfunction

总结 尽管头颈部鳞状细胞癌（HNSCC）放射治疗的技术进步， 电离辐射（IR）后对周围正常组织如唾液腺的附带损伤仍然存在 这对这些患者来说是一个严重的问题，并严重降低了他们的生活质量。据估计，95%以上的 HNSCC患者在放疗后表现出口干和唾液腺功能减退， 这些患者在完成放射治疗后继续遭受数月至数年的痛苦。缺乏治疗 预防IR诱导的口腔干燥症或恢复唾液功能的选择是复杂的， 介导慢性IR诱导的唾液功能障碍的潜在机制。我们以前的研究 证明了细胞外ATP（eATP）的作用，这是受损组织中的一种关键“警报”分子， 对于IR诱导的唾液功能障碍，可以通过药理学或遗传学阻断eATP的P2X7R来抑制， 从而赋予唾液腺显著的放射防护作用。此外，我们的研究表明， 从P2X7R拮抗作用维持正常的唾液分泌到IR后30天，尽管更长的时间段 与IR诱导的慢性口干症和唾液功能障碍的治疗相关的药物尚未研究。 我们的最终目标是使用P2X7R拮抗剂作为辐射防护剂，以保留头部唾液腺功能 以及接受放射治疗的颈部癌症患者，尽管关于是否 P2X7R拮抗剂将干扰通过放疗实现的肿瘤消退，并且拟议的研究将 解决这一知识差距。本提案的总体目标是开发一种使用P2X7R的方法 拮抗剂预防头颈癌放疗患者IR诱导的唾液功能障碍 而不抑制IR诱导的HNSCC肿瘤消退。成功完成这一提案将大大 加速将这种新的药理学方法转化为接受IR治疗的人类患者， 头颈癌将努力实现以下具体目标： Specific Aim 1将开发一种在受辐射的同基因小鼠中使用P2X7R拮抗作用的辐射防护方法。 保留唾液腺功能和抗肿瘤反应的HNSCC小鼠模型。 具体目标2将研究P2X7R拮抗作用对放射性损伤的辐射保护作用的持久性。 开发治疗放疗后HNSCC患者中发生的慢性唾液腺功能障碍的方法。 具体目标3将评估eATP释放和P2X7R下游嘌呤组信号传导的贡献 在小鼠和人唾液腺器官型培养物中激活IR诱导的唾液腺功能障碍 以确定替代的辐射防护靶点，并将小鼠的发现转化为人类。

Summary Despite technological advancements in head and neck squamous cell carcinoma (HNSCC) radiotherapies, collateral damage to surrounding normal tissues such as salivary glands following ionizing radiation (IR) remains a significant problem for these patients and severely diminishes their quality of life. It is estimated that >95% of HNSCC patients exhibit xerostomia and salivary gland hypofunction following the irradiation regimen and >73% of these patients continue to suffer for months to years after completion of radiotherapy. The lack of treatment options to prevent IR-induced xerostomia or recover salivary function is compounded by a limited understanding of the underlying mechanisms that mediate chronic IR-induced salivary dysfunction. Our previous studies demonstrate the action of extracellular ATP (eATP), a key “alarmin” molecule in damaged tissue that contributes to IR-induced salivary dysfunction, can be inhibited by pharmacological or genetic blockade of P2X7Rs for eATP, thereby conferring significant radioprotection to salivary glands. In addition, our studies show that radioprotection from P2X7R antagonism maintains normal salivary output through day 30 post-IR, although longer time periods relevant to the treatment of IR-induced chronic xerostomia and salivary dysfunction have not been investigated. Our ultimate goal is to use P2X7R antagonists as radioprotective agents to retain salivary gland function in head and neck cancer patients undergoing radiotherapy, although there is little information available on whether P2X7R antagonists will interfere with tumor regression achieved by radiotherapy, and proposed studies will address this gap in knowledge. The overall goal of this proposal is to develop an approach using P2X7R antagonism to prevent IR-induced salivary dysfunction in head and neck cancer patients receiving radiotherapy without inhibiting the IR-induced regression of HNSCC tumors. Successful completion of this proposal will greatly accelerate translation of this novel pharmacological approach to human patients undergoing IR therapies for head and neck cancer. The following specific aims will be pursued: Specific Aim 1 will develop a radioprotective approach using P2X7R antagonism in an irradiated syngeneic mouse model of HNSCC that preserves salivary gland function and anti-tumor responses. Specific Aim 2 will investigate the durability of the radioprotective effects of P2X7R antagonism towards developing an approach for chronic salivary dysfunction that occurs in HNSCC patients following radiotherapy. Specific Aim 3 will evaluate the contribution of eATP release and purinomic signaling downstream of P2X7R activation to IR-induced salivary gland dysfunction in mouse and human salivary gland organotypic cultures towards identifying alternative radioprotective targets and translating findings in mice to humans.