Salivary Acinar Cell Apoptosis: Regulation of p53 by Akt

描述（由申请人提供）：头颈癌放射治疗后发生的唾液腺功能减退降低了抗癌治疗的有效性，降低了这些患者的生活质量。该应用旨在了解γ辐照诱导的唾液腺细胞凋亡是否可以调节以防止唾液腺功能障碍。我们实验室的数据表明，25-30%的唾液腺泡细胞在单次5gy照射后24小时发生凋亡。对唾液腺中表达活化Akt的转基因小鼠进行头颈部辐照后，其细胞凋亡和唾液腺功能障碍减少。这些数据提示细胞凋亡可能导致辐照诱导的唾液腺功能障碍。基于这一线索，我们确定了激活Akt的分子是否可以抑制辐射诱导的唾液腺功能障碍。新数据表明，在辐照前注射胰岛素样生长因子-1 （IGF-1）可激活Akt，并抑制受辐照小鼠的唾液功能障碍。这是第一次证明辐照诱导的唾液腺功能障碍可以通过简单的预处理来预防。在本应用中，我们将确定IGF-1治疗的参数，以防止辐射诱导的唾液腺功能障碍。剂量、时间和IGF-1在预防连续照射引起的功能障碍中的反复治疗效果将被确定。我们已经证明激活的Akt通过Akt-> mdm2-> p53通路抑制唾液腺泡细胞的凋亡。我们假设IGF-1通过相同的途径抑制唾液腺泡细胞凋亡。我们建议在体外和体内进行论证。在用IGF-1和照射治疗小鼠唾液腺之前，将使用组织特异性重组来消除mdm2，以确认IGF-1抑制唾液腺功能障碍的途径。我们还假设IGF-1和myr-Aktl可能通过改变调节细胞凋亡的基因表达来抑制细胞凋亡。DNA微阵列将用于鉴定辐照后igf -1处理和myr-Akt1转基因小鼠唾液腺中表达改变的基因。我们可以通过载体过表达这些候选基因或siRNA载体消除这些基因的表达来检测这些候选基因在体外抑制细胞凋亡中的作用。这些研究将建立使用IGF-1预防唾液腺功能障碍的参数，确定IGF-1抑制唾液腺功能障碍的机制，并确定新的治疗靶点，可用于增强对唾液腺免受辐射诱导损伤的保护。建立临床前动物模型，开发预防辐射引起的唾液腺功能障碍的治疗方法，对口腔健康具有重要的临床意义。

DESCRIPTION (provided by applicant): The salivary gland hypofunction that occurs following irradiation for treatment of head and neck cancer decreases the effectiveness of anti-cancer therapies and diminishes the quality of life for these patients. This application is directed towards understanding whether gamma-irradiation induced apoptosis in the salivary gland can be modulated to prevent salivary gland dysfunction. Data from our lab indicate that 25-30% of salivary acinar cells are apoptotic 24 hours post irradiation with a single dose of 5 Gy. Head and neck irradiation of transgenic mice that express activated Akt in the salivary gland results in diminished apoptosis and salivary gland dysfunction following irradiation. These data suggest apoptosis may cause irradiation-induced salivary gland dysfunction. Based upon this lead we determined whether molecules that activate Akt can suppress irradiation-induced salivary gland dysfunction. New data demonstrates that injection of mice with insulin-like growth factor-1 (IGF-1) prior to irradiation activates Akt, and suppresses salivary dysfunction in irradiated mice. This is the first demonstration that irradiation-induced salivary gland dysfunction can be prevented by a simple pretreatment. In this application we will determine the parameters of treatment with IGF-1 that prevent irradiation-induced salivary gland dysfunction. Dose, timing, and the effect of repeated treatment with IGF-1 in preventing dysfunction resulting from serial irradiation will be determined. We have demonstrated that activated Akt suppresses apoptosis of salivary acinar cells by an Akt-> mdm2-> p53 pathway. We posit that IGF-1 suppresses salivary acinar cell apoptosis by this same pathway. We propose to demonstrate in vitro and in vivo. Tissue-specific recombination will be used to eliminate mdm2 from the salivary glands of mice prior to treatment with IGF-1 and irradiation to confirm the pathway by which IGF-1 functions to suppress salivary gland dysfunction. We also posit that IGF-1 and myr-Aktl may suppress apoptosis by altering the expression of genes that regulate apoptosis. DNA microarrays will be used to identify genes whose expression is altered in the salivary glands of IGF-1-treated and myr-Akt1 transgenic mice following irradiation. We can examine the role of these candidate genes in suppressing apoptosis in vitro using vectors to overexpress these genes, or siRNA vectors to eliminate expression of these genes. These studies will establish the parameters for the use of IGF-1 to prevent salivary gland dysfunction, identify the mechanism by which IGF-1 suppresses salivary gland dysfunction, and identify new therapeutic targets that could be used to enhance protection of the salivary gland from -irradiation-induced damage. The development of a pre-clinical animal model that allows development of therapies that prevent irradiation-induced salivary gland dysfunction is great clinical significance to oral health.