Cario E, Gerken G, Podolsky D K
Division of Gastroenterology & Hepatology, University Hospital of Essen and Medical School/University of Duisburg-Essen, Essen, Germany.
Gastroenterology. 2007 Apr;132(4):1359-74. doi: 10.1053/j.gastro.2007.02.056. Epub 2007 Feb 25.
BACKGROUND & AIMS: Toll-like receptors (TLRs) represent a class of transmembrane pattern recognition receptors essential for microbial recognition and control of innate immune responses. Commensal bacteria play an important role in maintaining tolerance and active stability of the intestinal epithelial barrier by suppressing intestinal inflammation, yet the mechanisms of action are unknown. The aim of this study was to determine the functional relevance of TLR2 to control tight junction (TJ)-associated intestinal epithelial barrier integrity to balance mucosal homeostasis against inflammatory stress-induced damage.
TLR2 ligand (synthetic Pam(3)Cys-SK4 [PCSK])-induced activation of signaling cascades and TJ-associated distribution was assessed by using Western blotting and confocal microscopy combined with functional transfection and inhibitor studies in model intestinal epithelial cell (IEC) lines (IEC-6, Caco-2) or primary IEC cultured short-term ex vivo. DSS colitis was induced by standard protocol in wild-type, TLR2-/-, and MyD88-/- mice. Spontaneous apoptosis was assessed by terminal deoxinucleotidyl-transferase-mediated dUTP-biotin nick end-labeling.
Data from in vitro and ex vivo models of intestinal epithelial cells revealed that TLR2 stimulation effectively preserves TJ-associated barrier assembly against stress-induced damage through promotion of PI3K/Akt-mediated cell survival via MyD88. Furthermore, in vivo studies underscored that TLR2-mediated TJ regulation critically determines susceptibility to intestinal injury and inflammation. Inflammatory stress in mice deficient of TLR2 or MyD88 induced early TJ-associated disruption interrelated with anti-apoptotic failure of the intestinal epithelial barrier. Oral treatment of colitis with the TLR2 ligand PCSK significantly suppressed mucosal inflammation and apoptosis by efficiently restoring TJ-associated integrity of the intestinal epithelium in vivo.
TLR2 may provide a target to pharmacologically modulate mucosal injury and intestinal inflammation.
Toll样受体（TLRs）是一类跨膜模式识别受体，对于微生物识别和先天性免疫反应的控制至关重要。共生细菌通过抑制肠道炎症在维持肠道上皮屏障的耐受性和活性稳定性方面发挥重要作用，但其作用机制尚不清楚。本研究的目的是确定TLR2在控制紧密连接（TJ）相关的肠道上皮屏障完整性以平衡黏膜稳态抵抗炎症应激诱导损伤方面的功能相关性。
通过蛋白质免疫印迹法和共聚焦显微镜，结合在模型肠上皮细胞系（IEC-6、Caco-2）或短期体外培养的原代IEC中的功能转染和抑制剂研究，评估TLR2配体（合成的Pam(3)Cys-SK4 [PCSK]）诱导的信号级联激活和TJ相关分布。通过标准方案在野生型、TLR2-/-和MyD88-/-小鼠中诱导葡聚糖硫酸钠（DSS）结肠炎。通过末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记法评估自发凋亡。
来自肠上皮细胞体外和离体模型的数据显示，TLR2刺激通过MyD88促进PI3K/Akt介导的细胞存活，有效保护TJ相关的屏障组装免受应激诱导的损伤。此外，体内研究强调，TLR2介导的TJ调节关键决定了对肠道损伤和炎症的易感性。TLR2或MyD88缺陷小鼠中的炎症应激诱导早期TJ相关破坏，这与肠上皮屏障的抗凋亡失败相关。用TLR2配体PCSK口服治疗结肠炎可通过有效恢复体内肠上皮TJ相关的完整性，显著抑制黏膜炎症和凋亡。
TLR2可能为药理学调节黏膜损伤和肠道炎症提供一个靶点。
