DNA氧化损伤激活的PARP-1/NF-kB信号通路在Barrett食管发生中的作用机制研究

Barrett’s esophagus (BE) is a major complication of gastroesophageal reflux disease (GERD), also an important precursor lesion for the development of esophageal adenocarcinoma (EAC). However, the cellular origin of BE and the signaling pathways of Barrett’s metaplasia remain unclear. Acidic/alkaline reflux-induced chronic inflammation and oxidative stress are important pathological features of BE, both of which can cause oxidative DNA damage and genomic instability. However, it has not been reported that chronic inflammation and oxidative stress are involved in the process of BE formation. Our previous study indicated that there were inflammatory infiltration and DNA damage in the BE tissue, the expression of PARP-1 and NF-kB in BE epithelial cells were increased. It’s well established that the PARP-1-catalyzed poly(ADP-ribose) (PAR) level determines the sensitivity and repair efficiency to DNA damage. In addition, the epithelial progenitor cells in esophagus are the most important candidates of BE cellular origin. Previous studies showed that the differentiation of esophageal epithelial progenitor cells was well regulated by BMP4 pathway and p63. Thus we speculate that the acid-alkali-mediated oxidative stress in esophageal epithelial cells activate PARP-1/NF-kB, which promotes the differentiation of esophageal epithelial progenitor cells into BE epithelial cells by suppressing BMP4 pathway and p63. Meanwhile, incomplete DNA repair may be one of the important reasons that cause EAC from BE. In this study, we are going to treat esophageal progenitor cells with bile acid and H2O2 in vitro, to observe the PARP-1 induced BE differentiation of esophageal progenitor cells and DNA damage repair. We are going to compare the level of PAR, DNA damage, cell differentiation, and the expression of BE markers in esophageal epithelial progenitor cells with or without bile acid and H2O2 treatment. By establishment of the GERD mice model, we will further confirm that the PAPR-1-dependent multiple signaling pathways (PARP-1/NF-kB/BMP4/p63, PARP-1/PAR/PARG) are involved in the progression of BE by regulating both metaplasia and DNA damage repair. PARP-1 inhibitor will be applied to the GERD model in vivo. And we will compare its effect on the prevention of metaplasia and BE formation with proton pump inhibitors and anti-reflux surgery, and observe the effect on the prevention of metaplasia and BE formation. Eventually, the potential method and intervention for BE formation in the early diagnosis and therapy will be explored, especially for tumor prevention.

Barrett食管(Barrett's esophagus,BE)是胃食管反流病的严重并发症和特殊癌前病变，但BE的细胞起源和形成机制尚不明确。反流介导的慢性炎症和氧化应激是BE的重要病理特征，二者均可导致DNA损伤，但是否介导BE化生和癌变过程尚无确切报道。我们前期发现：BE中存在炎性浸润和DNA损伤，BE组织和上皮细胞中PARP-1/NF-kB表达上调。食管上皮干细胞被认为是BE可能的细胞来源，正常食管上皮干细胞向鳞状上皮的有序分化受BMP4通路及p63调控。据此推测：慢性炎症和氧化损伤诱导的PARP-1/NF-kB高表达，通过抑制BMP4/p63扰乱了食管上皮正常分化，促进向BE柱状细胞异向分化。本研究观察PARP-1介导的这一信号通路调控食管上皮分化过程和DNA损伤修复作用；在细胞和动物模型中干扰PARP-1，论证PAPR-1依赖的食管干细胞分化参与BE发生，探索BE潜在干预方式。

胃食管反流病（Gastroesophageal reflux disease, GERD）是指胃、十二指肠内容物反流入食管引起不适症状和/或食管粘膜病理改变的一类临床状态, 长期GERD可导致Barrett食管等癌前病变甚至食管癌，但Barrett食管发生的细胞起源及分子机制尚不完全清楚。已有充分的研究表明PARP-1参与氧化应激、促进炎症反应，GERD本身即为反复发生的慢性氧化损伤、炎性刺激反应过程，PARP-1通过氧化应激诱导下游通路激活，产生的具体作用可能是多方面的。炎症过程中，细胞环境受到炎症诱导的ROS增加导致氧化DNA损伤及更加严重的DNA双链断裂，PARP-1作为DNA损伤重要的级联和修复蛋白，在识别DNA损伤、启动修复过程中激活并发挥重要作用。本课题研究目标拟采用细胞学及分子生物学实验，通过氧化应激、酸/碱刺激和转染和分子靶向抑制剂等技术进行体外实验，在细胞水平验证诱导食管上皮祖细胞向柱状上皮细胞异向分化；通过靶向PARP-1抑制剂Olaparib降低PARP-1活性，观察氧化应激下Barrett食管柱状上皮细胞，检测PARP-1/NF-kB/BMP4/p63通路表达变化和氧化损伤的程度，明确Barrett食管柱状上皮细胞能否通过降低NF-kB转录水平进而提高BMP4/p63表达，实现Barrett食管柱状上皮细胞逆向转化为正常鳞状上皮细胞。明确PARP-1在Barrett食管形成和进展过程中发挥的作用。通过该项目的实施，我们通过转录组测序寻找到了鹅去氧胆酸处理后的Barrett细胞基因表达水平变化。同时分选LGR5+食管腺癌细胞并进行转录组测序。发现其中核糖体相关基因富集在两种情况中均存在。通过免疫共沉淀和荧光共定位证明PARP1与Notch1相互作用。PARP1抑制剂处理后，核糖体基因表达发生改变。表明PARP1与Notch1介导的核糖体基因表达可能是胃食管反流向食管腺癌恶性转化的关键分子事件。