Benoit R, Rowe S, Watkins S C, Boyle P, Garrett M, Alber S, Wiener J, Rowe M I, Ford H R
Department of Surgery, University of Pittsburgh School of Medicine and The Children's Hospital of Pittsburgh, Pennsylvania 15213, USA.
Shock. 1998 Jul;10(1):43-8. doi: 10.1097/00024382-199807000-00008.
Numerous reports suggest that endotoxin (LPS) may play a central role in triggering the inflammatory cascade that leads to the systemic inflammatory response syndrome. Although conditions that promote bacterial translocation in vivo may also facilitate direct translocation of LPS, the exact mechanisms by which LPS crosses the intestinal barrier to reach the systemic circulation are unknown. This study was designed to determine whether pure endotoxin could pass across injured rat ileal mucosa in the Ussing chamber. Sprague-Dawley rats were subjected to mild or severe hemorrhagic shock following carotid artery cannulation, and then resuscitated. Control animals underwent carotid artery cannulation only (sham-shock). Bacterial translocation to the mesenteric lymph nodes, liver, or spleen was measured after 24 h. Transmucosal passage of fluorescein isothiocyanate (FITC)-labeled E. coli C-25, or FITC-conjugated LPS was measured in the Ussing chamber. Intestinal membranes were examined by light and confocal laser microscopy. Severe hemorrhagic shock resulted in a 60% mortality rate and a 100% incidence of bacterial translocation in surviving animals. Sham-shock rats had a 100% survival rate and a 33% incidence of bacterial translocation. Transmucosal passage of FITC-E. coli C-25 was similar in both groups; however, passage of FITC-LPS was never detected. Histologic analysis confirmed mucosal injury to the intestinal epithelium of rats subjected to severe hemorrhagic shock, and confocal laser microscopy demonstrated passage of FITC-E. coil C-25, but not of FITC-LPS across the ileal membranes. Disruption of the intestinal epithelium with a potent mucolytic agent did not result in significant increase in transmucosal passage of FITC-LPS. We conclude that pure LPS does not pass across the intestinal mucosa in vitro. Transmucosal passage of LPS in vivo may be due, at least in part, to the release of bacterial cell wall fragments containing LPS from killed bacteria that had previously translocated.
众多报告表明，内毒素（脂多糖，LPS）可能在引发导致全身炎症反应综合征的炎症级联反应中起核心作用。尽管促进体内细菌易位的情况也可能促使LPS直接易位，但LPS穿过肠屏障进入体循环的确切机制尚不清楚。本研究旨在确定纯内毒素是否能在Ussing chamber中穿过损伤的大鼠回肠黏膜。将Sprague-Dawley大鼠进行颈动脉插管后给予轻度或重度失血性休克，然后进行复苏。对照动物仅进行颈动脉插管（假休克）。24小时后测量细菌向肠系膜淋巴结、肝脏或脾脏的易位情况。在Ussing chamber中测量异硫氰酸荧光素（FITC）标记的大肠杆菌C-25或FITC偶联的LPS的跨黏膜转运情况。通过光学显微镜和共聚焦激光显微镜检查肠膜。重度失血性休克导致存活率为60%，存活动物中细菌易位发生率为100%。假休克大鼠存活率为10%，细菌易位发生率为33%。两组中FITC-大肠杆菌C-25的跨黏膜转运情况相似；然而，从未检测到FITC-LPS的转运。组织学分析证实重度失血性休克大鼠的肠上皮存在黏膜损伤，共聚焦激光显微镜显示FITC-大肠杆菌C-25穿过回肠膜，但FITC-LPS未穿过。用强效黏液溶解剂破坏肠上皮并未导致FITC-LPS跨黏膜转运显著增加。我们得出结论，纯LPS在体外不会穿过肠黏膜。LPS在体内的跨黏膜转运可能至少部分归因于先前易位的死亡细菌释放出含有LPS的细菌细胞壁片段。
