Restoring Salivary Gland Function by Reducing Nucleotide-induced Inflammation

描述(申请人提供)：唾液腺功能障碍影响数以百万计的美国人，他们的生活质量受到口腔干燥、口腔细菌感染、营养不良和其他与唾液产生减少相关的疾病的严重影响。唾液分泌减少在干燥综合征(SS)中最为常见，这是一种病因不明的自身免疫性外分泌病，唾液分泌减少后，唾液腺中的淋巴细胞渗入，最终导致组织变性。此外，唾液腺发炎和唾液腺萎缩是γ辐射用于治疗头颈癌的一种意外副作用。了解唾液腺炎症早期事件的机制将有助于确定目前无法治疗唾液腺退化的治疗方案。现在人们已经很好地认识到，细胞内高水平的核苷酸，特别是 三磷酸腺苷是细胞在病理条件下对炎症、应激或创伤做出的反应。我们的研究侧重于了解唾液腺炎症和退化所涉及的ATP依赖机制。我们团队最近的工作表明，唾液腺炎症可以通过激活P2X7受体(P2X7R)来启动，P2X7R是一种ATP门控的非选择性阳离子通道，也可以促进几种慢性疾病的炎症和细胞凋亡，包括类风湿性关节炎、肺纤维化以及神经退行性和炎症性肠病。这项建议中提出的初步研究表明，当我们最初开发的一种高亲和力的P2X7R配体BzATP灌流到P2X7R-/-小鼠的颌下腺(SMG)时，与对照组小鼠相比，中性粒细胞向颌下腺(SMG)的募集显著减少。因此，我们将利用原代分离的唾液腺细胞和野生型和P2X7R-/-小鼠唾液腺炎症的导管结扎模型来阐明与P2X7R相关的炎症反应是否在功能性SMG变性中发挥重要作用及其相关机制(特定目标1)。其他研究将把这些结果扩展到辐射诱导的唾液腺损伤(特异性目标2)和自身免疫性外分泌病(特异性目标3)的小鼠模型，其中P2X7R-/-小鼠和P2X7R选择性拮抗剂的可用性(目前处于治疗类风湿性关节炎和脊髓损伤的临床试验中)将使我们能够直接检查体内P2X7R功能的降低是否可以延缓唾液腺退化。因此，这些研究的总体目标是评估抑制P2X7R活性是否可以保护小鼠的唾液腺免受各种形式的组织损伤，这最终将是开发治疗人类唾液功能障碍的关键。

DESCRIPTION (provided by applicant): Salivary gland dysfunction affects millions of Americans whose quality of life is severely impacted by dry mouth, oral bacterial infections, poor nutrition, and other disorders that are associated with decreased saliva production. Loss of saliva production is most common in Sjögren's syndrome (SS), an autoimmune exocrinopathy of unknown etiology in which decreased saliva production is followed by lymphocytic infiltration of the salivary gland and ultimately tissue degeneration. In addition, salivary gland inflammation and hyposalivation is an unintended side effect of γ-radiation used for the treatment of head and neck cancers. Understanding the mechanisms underlying early events in salivary gland inflammation will help identify currently-unavailable therapeutic options to treat salivary gland degeneration. It is now well recognized that high levels of intracellular nucleotides, particularly ATP, are released from cells under pathological conditions in response to inflammation, stress or trauma. Our research has focused on understanding the ATP- dependent mechanisms involved in salivary gland inflammation and degeneration. Recent work by our group indicates that salivary gland inflammation can be initiated by activation of the P2X7 receptor (P2X7R), an ATP- gated, non-selective cation channel that also promotes inflammation and cell apoptosis in several chronic diseases, including rheumatoid arthritis, lung fibrosis, and neurodegenerative and inflammatory bowel diseases. Preliminary studies presented in this proposal indicate that neutrophil recruitment to duct-ligated submandibular gland (SMG) is significantly reduced in P2X7R-/- mice compared to control mice when the glands were perfused with BzATP, a high affinity P2X7R ligand that we initially developed. Therefore, we will utilize primary isolated salivary gland cells and the duct ligation model of salivary gland inflammation in wild type and P2X7R-/- mice to elucidate whether inflammatory responses associated with the P2X7R play a significant role in functional SMG degeneration and the mechanisms involved (Specific Aim 1). Other studies will extend these results to mouse models of radiation-induced salivary gland damage (Specific Aim 2) and autoimmune exocrinopathy (Specific Aim 3), where the availability of the P2X7R-/- mouse and P2X7R-selective antagonists (currently in clinical trials for the treatment of rheumatoid arthritis and spinal cord injury) will enable us to directly examine whether decreases in P2X7R function in vivo can retard salivary gland degeneration. Thus, the overall goal of these studies is to evaluate whether inhibition of P2X7R activity can protect the salivary gland from various forms of tissue damage in mice, which ultimately will be essential for developing treatments for human salivary dysfunction.