Department of Pharmacy, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China.
Department of Gastroenterology, The Second Affiliated Hospital of Jiaxing University, Jiaxing, China.
J Cell Physiol. 2019 Nov;234(11):21089-21099. doi: 10.1002/jcp.28711. Epub 2019 Apr 29.
The present study was designed to investigate the mechanism of myeloid differentiation protein 2 (MD2) on intestinal mucosa destruction in mice with chronic colitis. Briefly, a chronic colitis mouse model was established by the administration of dextran sulfate sodium (DSS) in transgenic mice of MD2 overexpression (Transgenic, MD2-Tg) and C57BL/6 wild-type mice (MD2-WT). In addition, Caco-2 cells were cultured to form a monolayer cell model in vitro. The small interfering RNA was utilized to silence the MD2 gene in Caco-2 cells, and tumor necrosis factor-α (TNF-α) was used to establish the model of intestinal mucosal inflammation. After DSS induction, the intestinal mucosal tissue inflammation was more severe in MD2-Tg mice than MD2-WT. In addition, the intestinal mucosa was severely damaged, the intestinal mucosal permeability was increased, bacterial translocation was obvious, and the expression levels of MD2, MyD88, Toll-like receptor 4 (TLR4), and HMGB1 in mucosal tissues were significantly increased, while the expression levels of tight junction proteins, occludin, and claudin-1 were significantly lower in MD2-Tg mice compared with those in MD2-WT mice. TNF-α could induce inflammatory apoptosis in Caco-2 cell models. After MD2 silencing, the apoptotic level was decreased, the value of transepithelial electrical resistance was increased, the permeability of intestinal mucosa was decreased, the cellular expression levels of MD2, MyD88, TLR4, and HMGB1 were decreased, while the expression levels of tight junction proteins, occludin and claudin-1 were increased. MD2 could aggravate the destruction of intestinal mucosa in chronic colitis through the HMGB1-TLR4-MyD88 pathway.
本研究旨在探讨髓样分化蛋白 2（MD2）在慢性结肠炎小鼠肠道黏膜破坏中的作用机制。简要地说，通过在 MD2 过表达（转染，MD2-Tg）的转基因小鼠和 C57BL/6 野生型小鼠（MD2-WT）中给予葡聚糖硫酸钠（DSS）建立慢性结肠炎小鼠模型。此外，体外培养 Caco-2 细胞形成单层细胞模型。利用小干扰 RNA 沉默 Caco-2 细胞中的 MD2 基因，并用肿瘤坏死因子-α（TNF-α）建立肠道黏膜炎症模型。在 DSS 诱导后，MD2-Tg 小鼠的肠道黏膜组织炎症比 MD2-WT 更严重。此外，肠道黏膜严重受损，黏膜通透性增加，细菌易位明显，黏膜组织中 MD2、MyD88、Toll 样受体 4（TLR4）和高迁移率族蛋白 B1（HMGB1）的表达水平显著升高，而紧密连接蛋白 occludin 和 claudin-1 的表达水平明显降低。TNF-α可诱导 Caco-2 细胞模型发生炎症性凋亡。沉默 MD2 后，凋亡水平降低，跨上皮电阻值增加，肠黏膜通透性降低，细胞中 MD2、MyD88、TLR4 和 HMGB1 的表达水平降低，而紧密连接蛋白 occludin 和 claudin-1 的表达水平升高。MD2 可能通过 HMGB1-TLR4-MyD88 通路加重慢性结肠炎时的肠道黏膜破坏。
