IGF-1/PI3K/PKB通路介导自噬调控放射性涎腺功能损伤的作用及机制

Autophagy, the process by which cells recycle cytoplasm and dispose of excess or defective organelles, plays different roles in radiation induced tissue and organs damage. It may protect the body, or in contrast, aggravate the damage. Therefore, autophagy, as a double-edged sword with therapeutic potential, becomes the focus of research in recent years. Our previous study showed that there was an up-regulation of autophagy-related genes and proteins in the acute stage of radiation induced salivary gland hypofunction, which indicated an increase of autophagy level. Also, we observed that the expression of IGF-1 binding protein-3 (IGFBP3) was significantly reduced. The functional study verified that the secretion function of acini was decreased. Altogether these preliminary results suggest that autophagy is involved in the pathophysiology of radiation induced salivary gland hypofunction. However, the exact role of autophagy in the etiology of radiation induced salivary gland hypofunction and its regulation mechanism is unknown. Therefore, we hypothesize that increased autophagy level plays a critical role in the etiology of radiation induced salivary gland hypofunction and IGF-1/PI3K/PKB pathway regulates this process. To test this hypothesis, we will firstly evaluate the alteration of autophagy levels after irradiation and its relationship with IGF-1/PI3K/PKB pathway and acini secretion function. Next the autophagy levels will be up- or down-regulated by IGF-1/PI3K/PKB pathway, and the secretion function will be quantitatively assessed. Then, we tend to prevent radiation induced salivary gland hypofunction by regulation of autophagy in vivo using the animal mode of rabbit salivary gland injury after fractionated radiotherapy, which was firstly published by our research group in 2012. Finally, we will assess the relationship between the autophagy levels and salivary gland function in patients receiving radiotherapy for head and neck cancers. The present study will test our hypothesis and illustrate the role of autophagy in radiation induced salivary gland hypofunction and its molecular regulation mechanism during this process.

自噬在不同组织的放射应答中起不同作用：既可能是机体自我保护机制，也可能是加重放射损伤的因素。如何利用自噬的"两面性"，舍弊取利，是自噬研究的焦点。我们前期研究表明：涎腺放射后自噬基因及蛋白上调，自噬水平上调，IGF-1结合蛋白IGFBP3表达降低，腺泡分泌功能减弱。由此推断：自噬在放射性涎腺损伤的发病中发挥一定作用。然而，自噬是否为放射损伤发生的主要因素，其调控机制如何，这些关键问题尚待探讨。本课题拟在前期研究基础上，进一步探讨放射后自噬水平改变及对涎腺细胞性状、分泌功能的影响；阐明IGF-1/PI3K/PKB通路调控放射后涎腺细胞自噬的分子机制；通过课题组首创的分割放射后涎腺功能损伤动物模型，体内研究IGF-1/PI3K/PKB信号通路介导自噬预防放射性涎腺损伤的作用；最后，临床验证放射后涎腺自噬水平与功能损伤相关的结论。课题将揭示自噬在放射性涎腺功能损伤中所扮演的角色及其调控分子机制。

自噬在机体不同组织的放射应答中起不同作用：既可能是机体自我保护机制，也可能是加重放射损伤的因素。自噬在肿瘤放疗中的作用已有很多报道，然而，自噬对正常组织，尤其是涎腺组织在放射中的作用机制尚有待研究。IGF-1/PI3K/PKB信号通路是调控自噬的主要通路。因此，本课题针对IGF-1/PI3K/PKB信号通路和自噬在涎腺组织放射性损伤中的作用机制进行研究。主要研究内容包括：IGF-1/PI3K/PKB通路相关因子在涎腺细胞放射前后的表达变化研究；放射后涎腺细胞自噬水平改变及对细胞性状、分泌功能的影响；调控IGF-1/PI3K/PKB通路对涎腺细胞放射后自噬的影响；调控自噬预防分割放射后涎腺功能损伤的动物实验研究；涎腺病理与自噬关系的临床转化研究。结果表明，涎腺放射后自噬基因及蛋白上调，自噬水平上调，IGF-1/PI3K/PKB通路是该过程的主要调控通路。 IGF-1/PI3K/PKB调控的自噬影响涎腺肌上皮细胞功能，从而影响腺泡的分泌功能。 IGF-1/PI3K/PKB及自噬与涎腺病理密切相关。该项目有助于揭示涎腺组织对放射的应答，自噬对放射性涎腺损伤的作用机制，涎腺病理与自噬的关系，IGF-1/PI3K/PKB调控自噬在涎腺组织放射性损伤及病理状态中的重要作用等，同时为进一步的深入研究提供实验依据和理论基础。