O-GlcNAc糖基化调控肺泡上皮细胞衰老参与特发性肺纤维化发病的分子机制研究

The incidence of idiopathic pulmonary fibrosis (IPF) is significantly increasing as increased age, indicating IPF is a aging related diseases. Among them, the senescence of alveolar epithelial cell plays an important role on the pathogenesis of IPF, but its specific molecular mechanism has not been fully elucidated. The glycosylation of protein is an important pathway for protein modification after translation and is involved in sorts of biological processes including gene transcription, signal transduction and cell growth and differentiation, and others. Abnormal modification of O-GlcNAc glycosylation is associated with age-related neurodegenerative disease. Our previous study found that among senescent alveolar epithelial cells and lung tissue samples from IPF patients, the level of O-GlcNAc glycosylation significantly decreased; otherwise the expression of endoplasmic reticulum stress related protein, and aging-related markers p21 and SA-β-Gal changed reversely. We speculate that through endoplasmic reticulum stress, decreased level of O-GlcNAc glycosylation, mediates alveolar epithelial cell to senescence, and then contributes to the development of idiopathic pulmonary fibrosis. In this project, using gene manipulation and specific pathway inhibitors, regulating O-GlcNAc glycosylation in the animal and cellular model, we clarify the role of O-GlcNAc glycosylation in the process and development of IPF, reveal that underlying molecular mechanism regarding O-GlcNAc glycosylation mediates the senescence of alveolar epithelial cells by endoplasmic reticulum stress. In future, this project will provide theoretical basis for targeted therapy and intervention treatment in view of the molecular mechanism of epithelial cells senescence.

特发性肺纤维化（IPF）发病率随着年龄增加而明显增高，提示IPF是一种衰老相关性疾病。肺泡上皮细胞衰老在IPF发病发挥了重要作用，其具体分子机制尚未阐明。糖基化修饰参与了基因转录、信号转导和细胞生长与分化等生物学过程， O-GlcNAc 糖基化修饰异常与衰老相关的神经退行性疾病发生有关。我们前期研究发现，在肺泡上皮细胞衰老模型和IPF肺组织标本中的蛋白质O-GlcNAc糖基化水平明显下降，但内质网应激相关蛋白与p21，SA-β-Gal等衰老标记明显增高。我们推测，O-GlcNAc糖基化水平降低，通过内质网应激介导肺泡上皮细胞衰老，参与IPF发生和发展。本项目拟用基因操控及特异性通路抑制剂等方法，调控O-GlcNAc糖基化水平，在动物及细胞水平，阐明O-GlcNAc糖基化在IPF发生和发展中作用，揭示其介导肺泡上皮细胞衰老分子机制，为将来针对上皮细胞衰老的靶点治疗和干预提供理论依据。

特发性肺纤维化（Idiopathic pulmonary fibrosis，IPF）是一种特殊形式的慢性、进行性、纤维化间质性肺炎; IPF的发病率随着年龄增加而明显升高，提示IPF是一种衰老相关性疾病，但导致肺泡上皮细胞衰老分子机制尚未完全阐明。内质网应激水平与增龄相关，且内质网应激在IPF发病过程中发挥了重要的作用。.蛋白质O-GlcNAc修饰，是指单个N-乙酰葡萄糖胺(N-acetylglucosamine, GlcNAc)以O-糖苷键与蛋白质的丝氨酸（Ser）/苏氨酸（Thr）的羟基相连。O-GlcNAc修饰由OGT（O-GlcNActransferase）和OGA（O-GlcNAcase）分别调节。O-GlcNAc修饰及信号通过动态可逆调节细胞内代谢和信号通路, 从而对各种应激压力做出迅速的反应。既往研究证实调控O-GlcNAc信号可减轻缺血缺氧诱导的内质网应激引起心肌细胞死亡。但肺泡上皮细胞的O-GlcNAc信号与内质网应激，衰老之间相互联系，及O-GlcNAc信号在IPF发病过程中的作用及分子机制尚不清楚。.我们对IPF及小鼠肺纤维化肺组织研究证实，肺纤维化肺组织中的O-GlcNAc，OGT和OGA蛋白表达异常；而内质网应激状态及衰老明显升高。在博来霉素（BLM）和衣霉素（TM）诱导的内质网应激及肺泡上皮细胞的细胞衰老中，发现O-GlcNAc，OGT和OGA下降，而内质网应激（GRP78、p-eIPF2α、XBP-1、CHOP)及衰老指标（P21，P16）表达增加。敲减OGA基因肺泡上皮细胞的O-GlcNAc升高趋势；用BLM诱导敲减OGA肺泡上皮细胞，肺泡上皮细胞的P21，GRP78、p-eIF2α和CHOP表达明显增加。敲减GRP78基因的肺泡上皮细胞经BLM诱导，其P21较无效敲减加降低，同时p-eIF2α磷酸化水平降低，提示抑制GRP78表达，可部分减轻肺泡上皮细胞的内质网应激和衰老。.肺纤维化肺组织O-GlcNAc，OGT和OGA蛋白表达异常,提示O-GlcNAc信号通路参与了特发性肺纤维化发病。O-GlcNAc信号通过调控肺泡上皮细胞的内质网应激和衰老。这些结果为O-GlcNAc信号通路与ER应激和衰老之间可能的相互作用提供了新的见解，并可能部分解释O-GlcNAc信号通路在肺纤维化发病中的作用及机制。