Enterocyte TLR4 mediates phagocytosis and translocation of bacteria across the intestinal barrier
Enterocyte TLR4 mediates phagocytosis and translocation of bacteria across the intestinal barrier
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DOI：
10.4049/jimmunol.176.5.3070
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发表时间：
2006-03-01
影响因子：
4.4
通讯作者：
Hackam, David J.
中科院分区：
文献类型：
--
作者：
Neal, Matthew D.;Leaphart, Cynthia;Hackam, David J.
细菌穿过肠屏障的移位在全身性脓毒症的发病机制中是重要的，尽管细菌移位发生的机制在很大程度上仍然未知。我们假设，细菌易位穿过完整的屏障后发生的细菌内化肠细胞在一个过程中类似的吞噬作用，TLR 4是需要这个过程。我们现在表明，Fc γ RIIa转染的肠细胞可以内化IgG调理红细胞到肌动蛋白丰富的杯子，证实这些肠细胞具有吞噬作用所需的分子机制。我们进一步表明，肠细胞可以内化大肠杆菌进入吞噬体，细菌保持细胞内活力，TLR 4是需要这个过程发生。发现TLR 4信号传导对于上皮细胞的吞噬作用是必要的和充分的，因为IEC-6肠上皮细胞能够内化LPS包被但未热包被的乳胶颗粒，并且因为MD 2/TLR 4转染的人内皮肾（HEK）-293细胞获得内化E.而未转染的HEK-293细胞和携带P712 H突变的显性阴性TLR 4转染的HEK-293细胞则没有。LIPS不诱导膜皱褶或巨胞饮在肠细胞，排除其在细菌内化的作用。引人注目的是，与TLR 4突变的小鼠相比，野生型小鼠体内革兰氏阴性菌内化到肠细胞中，以及细菌穿过肠上皮到肠系膜淋巴结的易位显著更大。这些数据表明细菌易位发生的新机制，并表明TLR 4在此过程中肠细胞吞噬细菌的关键作用。
Translocation of bacteria across the intestinal barrier is important in the pathogenesis of systemic sepsis, although the mechanisms by which bacterial translocation occurs remain largely unknown. We hypothesized that bacterial translocation across the intact barrier occurs after internalization of the bacteria by enterocytes in a process resembling phagocytosis and that TLR4 is required for this process. We now show that Fc gamma RIIa-transfected enterocytes can internalize IgG-opsonized erythrocytes into actin-rich cups, confirming that these enterocytes have the molecular machinery required for phagocytosis. We further show that enterocytes can internalize Escherichia coli into phagosomes, that the bacteria remain viable intracellularly, and that TLR4 is required for this process to occur. TLR4 signaling was found to be necessary and sufficient for phagocytosis by epithelial cells, because IEC-6 intestinal epithelial cells were able to internalize LPS-coated, but hot uncoated, latex particles and because MD2/TLR4-transfected human endothelial kidney (HEK)-293 cells acquired the capacity to internalize E. coli, whereas nontransfected HEK-293 cells and HEK-293 cells transfected with dominant-negative TLR4 bearing a P712H mutation did not. LIPS did not induce membrane ruffling or macropinocytosis in enterocytes, excluding their role in bacterial internalization. Strikingly, the internalization of Gram-negative bacteria into enterocytes in vivo, and the translocation of bacteria across the intestinal epithelium to mesenteric lymph nodes were significantly greater in wild-type mice as compared with mice having mutations in TLR4. These data suggest a novel mechanism by which bacterial translocation occurs and suggest a critical role for TLR4 in the phagocytosis of bacteria by enterocytes in this process.