急性肺损伤大鼠多形核白细胞L选择素变化及其在肺内扣押中的作用

目的 探讨急性肺损伤(ALI)大鼠循环血多形核白细胞(PMN)L选择素表达的变化及其于肺内扣押中的作用.方法 通过静脉注射内毒素(5 mg/kg)复制大鼠ALI模型,56只大鼠随机分为7组,每组8只.分别为(1)内毒素5 min组;(2)内毒素15 min组;(3)内毒素30 min组;(4)内毒素60 min组;(5)fucodin干预5 min组;(6)Fucodin干预15 min组静脉注射fucodin 5 mg/kg后,立即静脉注射内毒素5 mg/kg;(7)正常对照组静脉注射等量生理盐水替代内毒素.用免疫荧光间接法和流式细胞仪检测大鼠ALI过程中PMN L选择素蛋白表达的变化;用髓过氧化酶(MPO)分析法及组织学检查定量ALI过程中PMN于肺内的扣押量.结果 (1)PMN L 选择素的表达于静脉注射内毒素后5 min为7.8±1.6,与对照组(10.5±2.1)比较差异有显著性(P<0.05),静脉注射内毒素后15 min(2.9±0.5)、30 min(3.5±0.7)和60 min(4.9±0.7)与对照组比较差异更具显著性(P<0.01).(2)大鼠肺组织MPO活力于静脉注射内毒素后5 min (0.359±0.074) U/mg肺组织]、15 min (0.490±0.069) U/mg肺组织]、30 min (0.565±0.111 ) U/mg肺组织]、60 min (0.710±0.112) U/mg肺组织]与对照组(0.069±0.011) U/mg肺组织]比较差异有显著性(P<0.01);fucodin干预5 min组(0.391±0.071)U/mg肺组织]和对应时相点的内毒素组(0.359±0.074) U/mg肺组织]比较差异无显著性,fucodin干预15 min组(0.396±0.061) U/mg肺组织]和对应时相点的内毒素组(0.490±0.069) U/mg肺组织]比较差异有显著性(P<0.05).结论 (1)正常状态下L选择素在PMN表面呈结构性表达,内毒素致伤后PMN L选择素表达迅速减少,伤后15 min时最低,其后呈回升趋势.(2)内毒素性ALI大鼠PMN肺内的早期扣押可能是L选择素非依赖性的,但L选择素对维持肺PMN的持续扣押仍然是重要的.

Changes of L-selectin expression on polymorphonuclear leukocytes and its role during polymorphonuclear leukocytes sequestration in lungs of rats with acute lung injury

OBJECTIVE: To explore the changes of L-selectin protein expression on peripheral blood polymorphonuclear leukocytes (PMN) and their role during PMN sequestration in the lungs of rats with acute lung injury (ALI). METHODS: The model of ALI in rat was established by intravenous injection of E. Coli endotoxin (ET). The protein expression of L-selectin on peripheral blood PMNs was measured by immunofluorescence and flow cytometry. Myeloperoxidase (MPO) enzyme analysis and histology were employed to estimate the quantity of PMN sequestration in lungs of rats during ALI. RESULTS: (1) The protein expression of L-selectin on PMN after injection of ET (7.8 +/- 1.6) was all significantly lower than that in control group (10.5 +/- 2.1, P < 0.05). (2) MPO activity increased significantly after injection of ET in comparison with the control group 0.069 +/- 0.011) U/mg lung tissue, P < 0.01]. The difference was not significant between the fucodin treated 5 min group (0.391 +/- 0.071) U/mg lung tissue] and ET-treated 5 min group (0.359 +/- 0.074) U/mg lung tissue]. But MPO activity was significantly lower in fucodin-treated 15 min group (0.396 +/- 0.061) U/mg lung tissue] than that in ET-treated group at same time point (0.490 +/- 0.069) U/mg lung tissue, P < 0.05]. CONCLUSIONS: (1) In physiological state, L-selectin are consistently expressed on the surface of PMN membrane. The protein expression of L-selectin on PMNs reduces rapidly after injection of ET and is the lowest at 15 min, then gradually increases. (2) The early stage of PMN sequestration in lungs is not dependent on L-selectin, but L-selectin is still important for maintaining a continual PMN sequestration in lungs of rats with ALI.