This study aimed to investigate the protective effects and underlying mechanism of seaweed polysaccharide (SWP) on intestinal epithelial barrier dysfunction induced by E. coli in an IPEC-J2 model. A preliminary study was done to screen optimum SWP concentrations by cell viability, cytotoxicity, apoptosis and proliferation evaluation. The regular study was conducted to evaluate the protective effects of SWP against E. coli challenge via the analysis of transepithelial electrical resistance (TEER), tight junction proteins, NF-κB signalling pathway, proinflammatory cytokines and the E. coli adhesion and invasion. Our results show that 4 h E. coli challenge down-regulated tight junction proteins expression, decreased TEER, activated NF-κB signalling pathway and increased proinflammatory response, which indicates that the E. coli infection model was well-established. Pre-treatment with 240 μg/ml SWP for 24 h alleviated the 4 h E. coli -induced intestinal epithelial barrier dysfunction, as evidenced by the up-regulated expression of Occludin, Claudin-1 and ZO-1 at both mRNA and protein level and the increased TEER of IPEC-J2 cells. Pre-incubation with 240 μg/ml SWP for 24 h inhibited the activation of the NF-κB signalling pathway by 4 h E. coli challenge, including the decreased mRNA expression of TLR-4, MyD88, IκBα, p-65, as well as the reduced ratio of protein expression of p-p65/p65. Also, pre-treatment with 240 μg/ml SWP for 24 h decreased proinflammatory response (IL-6 and TNF-α) induced by 4 h E. coli challenge and decreased the E. coli adhesion and invasion. In conclusion, SWP mitigated intestinal barrier dysfunction caused by E. coli through NF-κB pathway in IPEC-J2 cells and 240 μg/ml SWP exhibited better effect. Our results also provide a fundamental basis for SWP in reducing post-weaning diarrhoea of weaned piglets, especially under E. coli -infected or in-feed antibiotic-free conditions.

中文翻译：

---

海藻多糖通过抑制猪肠上皮细胞NF-κB通路减轻产肠毒素大肠杆菌诱导的肠屏障功能障碍

本研究旨在探讨海藻多糖 (SWP) 在IPEC-J2 模型中对大肠杆菌诱导的肠上皮屏障功能障碍的保护作用及其潜在机制。进行了初步研究，通过细胞活力、细胞毒性、细胞凋亡和增殖评估来筛选最佳 SWP 浓度。定期研究通过分析跨上皮电阻 (TEER)、紧密连接蛋白、NF-κB 信号通路、促炎细胞因子和大肠杆菌粘附和侵袭来评估 SWP 对大肠杆菌攻击的保护作用。我们的结果表明 4 h大肠杆菌挑战下调紧密连接蛋白的表达，降低 TEER，激活 NF-κB 信号通路并增加促炎反应，这表明大肠杆菌感染模型已经建立。用 240 μg/ml SWP 预处理 24 小时可减轻 4 小时大肠杆菌诱导的肠上皮屏障功能障碍，这可以通过 Occludin、Claudin-1 和 ZO-1 在 mRNA 和蛋白质水平上的表达上调来证明和 IPEC-J2 细胞的 TEER 增加。用 240 μg/ml SWP 预孵育 24 小时可抑制 4 小时大肠杆菌对 NF-κB 信号通路的激活挑战，包括 TLR-4、MyD88、IκBα、p-65 的 mRNA 表达降低，以及 p-p65/p65 的蛋白质表达比率降低。此外，用 240 μg/ml SWP 预处理 24 小时可降低 4 小时大肠杆菌攻击诱导的促炎反应（IL-6 和 TNF-α）并降低大肠杆菌粘附和侵袭。总之，SWP通过 IPEC-J2 细胞中的 NF-κB 途径减轻大肠杆菌引起的肠道屏障功能障碍，240 μg/ml SWP 表现出更好的效果。我们的结果还为 SWP 减少​​断奶仔猪断奶后腹泻提供了基本依据，尤其是在大肠杆菌感染或饲料中不含抗生素的条件下。