The role of the P2X7 receptor in radiation-induced salivary gland inflammation and dysfunction

项目摘要：美国每年诊断出超过60，000例头颈癌， 治疗包括手术和放疗。放射治疗会对附近的正常组织造成附带损伤， 特别是唾液腺，这导致慢性唾液分泌不足和口腔干燥。目前仅限 存在姑息治疗选择，因此放射诱导的唾液腺功能障碍背后的机制 应进一步调查。众所周知，辐射导致活性氧的产生 (ROS)导致促炎信号（即细胞因子、类花生酸）的分泌以募集免疫细胞 帮助组织修复P2X7受体（P2X7R）在唾液腺上皮细胞上高度表达，介导ROS， 白细胞介素-1 β和前列腺素E2的产生，并在辐射后被激活。P2X7R是一种嘌呤能 由高水平细胞外ATP（> 100 μ M）激活的受体，通常在炎症期间分泌。 虽然已经在辐射后研究了选定数量的细胞因子和类花生酸，但是细胞因子和类花生酸的网络是不稳定的。 炎症信号和吞噬细胞活性尚未完全阐明，P2X7 R在炎症中的作用也未完全阐明。 这些途径。该提案的目标是评估炎症信号的整合网络， 诱导的下游信号级联，主要的吞噬细胞类型和P2X7R在 这些过程在放射线照射后的唾液腺。我们假设辐射引起的 唾液腺功能障碍的发生是由于P2X7R介导的促炎信号传导， 巨噬细胞是唾液组织中主要的吞噬细胞类型。为了验证这个假设，我们将 无偏地量化炎症信号的完整网络（即，细胞因子和类二十烷酸）产生的唾液 上皮细胞后辐射暴露，并确定下游途径诱导这些信号 通过评估受体结合和细胞内信号级联的激活。此外，我们将评估 主要的吞噬细胞群，吞噬后产生的炎症信号， 放射诱导的凋亡细胞，并确定放射后组织驻留巨噬细胞的活性。的 P2X7R的作用将通过将野生型小鼠的拟议实验结果与 P2X7R敲除（P2X7R-/-）或P2X7R拮抗剂（A438079）处理的小鼠。以前的工作表明， P2X7R敲低允许小鼠在辐射后持续的唾液功能和P2X7R的抑制 拮抗剂可能被证明是一种新的治疗靶点，用于在放射治疗期间保护正常组织。 该项目的长期结果将提供对急性和慢性 放射损伤后唾液上皮细胞发生炎症反应，并揭示了 P2X7受体在辐射诱导的炎症中的作用。这可能会影响唾液腺研究以外的领域， 这些结果应该可以扩展到其他类型的组织和组织损伤形式。

Project Abstract: Over 60,000 cases of head and neck cancer are diagnosed in the US annually with typical treatment including surgery and radiation. Radiation therapy causes collateral damage to nearby normal tissues, particularly the salivary glands, which results in chronic hyposalivation and xerostomia. Currently only limited palliative treatment options exist, therefore the mechanisms behind radiation-induced salivary gland dysfunction should be investigated further. It is well-established that radiation causes production of reactive oxygen species (ROS), which leads to secretion of pro-inflammatory signals (i.e. cytokines, eicosanoids) to recruit immune cells to aid in tissue repair. The P2X7 receptor (P2X7R) is highly expressed on salivary epithelial cells, mediates ROS, interleukin-1 and prostaglandin E2 production and is activated following radiation. P2X7R is a purinergic receptor activated by high levels of extracellular ATP (>100M) that are often secreted during inflammation. While a select number of cytokines and eicosanoids have been investigated following radiation, the network of inflammatory signals and phagocytic cell activity has not been fully elucidated, nor has the role of the P2X7R in these pathways. The goal of this proposal is to evaluate the integrated network of inflammatory signals, the downstream signaling cascades induced, the predominant phagocytic cell type and the role of the P2X7R in these processes in the salivary gland following radiation exposure. We hypothesize that radiation-induced salivary gland dysfunction occurs due to P2X7R-mediated pro-inflammatory signaling, and tissue-resident macrophages are the predominant phagocytic cell type in salivary tissue. To test this hypothesis, we will unbiasedly quantify the full network of inflammatory signals (i.e., cytokines and eicosanoids) produced by salivary epithelial cells following radiation exposure and determine downstream pathways induced by these signals through evaluation of receptor binding and activation of intracellular signaling cascades. Further, we will evaluate the predominant phagocytic cell population, the inflammatory signals generated following engulfment of radiation-induced apoptotic cells and determine the activity of tissue-resident macrophages post-radiation. The role of the P2X7R will be determined by comparing the results of the proposed experiments of wild type mice to that of P2X7R knockout (P2X7R-/-) or P2X7R antagonist (A438079)-treated mice. Previous work has shown that P2X7R knockdown allows for sustained salivary function following radiation in mice and inhibition with the P2X7R antagonist may prove to be a novel therapeutic target for normal tissue preservation during radiation therapy. The long-term outcomes of this project will provide an unbiased understanding of the acute and chronic inflammatory response occurring in salivary epithelial cells following radiation damage and uncover the role of the P2X7 receptor in radiation-induced inflammation. This may impact fields beyond salivary gland research, as these results should be expandable to other types of tissues and forms of tissue damage.