Abstract：
Aflatoxin B1 (AFB1) is a widespread mycotoxin in food and feed. Although the liver is the main target organ of AFB1, the intestine is the first exposure organ to AFB1. However, the mechanism by which AFB1 induced intestinal barrier dysfunction via regulating the farnesoid X receptor (FXR)-mediated myosin light chain kinase (MLCK) signaling pathway has rarely been studied. In vivo, AFB1 exposure significantly decreased the small intestine length and increased the intestinal permeability. Meanwhile, AFB1 exposure markedly suppressed the protein expressions of FXR, ZO-1, occludin, and claudin-1 and enhanced the protein expression of MLCK. In vitro, AFB1 exposure induced intestinal barrier dysfunction by the elevation in the FITC-Dextran 4 kDa flux and inhibition in the transepithelial electrical resistance in a dose-dependent manner. In addition, AFB1 exposure downregulated the mRNA and protein expressions of FXR, ZO-1, occludin, and claudin-1, redistributed the ZO-1 protein, and enhanced the protein expressions of MLCK and p-MLC. However, fexaramine (Fex, FXR agonist) pretreatment markedly reversed the AFB1-induced FXR activity reduction, MLCK protein activation, and intestinal barrier impairment in vitro and in vivo. Moreover, pretreatment with the inhibition of MLCK with ML-7 significantly alleviated the AFB1-induced intestinal barrier dysfunction and tight junction disruption in vitro. In conclusion, AFB1 induced intestinal barrier impairment via regulating the FXR-mediated MLCK signaling pathway in vitro and in vivo and provided novel insights to prevent mycotoxin poisoning in the intestine.
摘要：
黄曲霉毒素B1(AFB1)是一种广泛存在于食品和饲料中的霉菌毒素。尽管肝脏是AFB1的主要靶器官，但肠是AFB1的第一个暴露器官。然而,AFB1通过调节法尼醇X受体（FXR）介导的肌球蛋白轻链激酶（MLCK）信号通路而引起肠屏障功能障碍的机制研究甚少。在体内,AFB1暴露显着降低了小肠长度并增加了肠通透性。同时,AFB1暴露显著抑制FXR的蛋白表达，ZO-1，闭塞蛋白，和claudin-1并增强MLCK的蛋白表达。体外，AFB1暴露通过FITC-Dextran4kDa通量的升高和以剂量依赖性方式抑制跨上皮电阻来诱导肠屏障功能障碍。此外,AFB1暴露下调FXR的mRNA和蛋白表达，ZO-1，闭塞蛋白，和claudin-1，重新分配ZO-1蛋白，并增强MLCK和p-MLC的蛋白表达。然而,fexaramine(Fex,FXR激动剂)预处理显著逆转AFB1诱导的FXR活性降低，MLCK蛋白激活，和体内外肠道屏障损伤。此外，用ML-7抑制MLCK预处理可显着减轻AFB1诱导的肠屏障功能障碍和紧密连接破坏。总之,AFB1通过在体外和体内调节FXR介导的MLCK信号通路诱导肠屏障损伤，为预防肠道真菌毒素中毒提供了新的见解。
