中性粒细胞胶原酶在内毒素性急性肺损伤中的作用

The role of neutrophil collagenase in acute lung injury induced by endotoxin

目的 研究中性粒细胞胶原酶(MMP-8)在内毒素(LPS)致急性肺损伤(ALI)中的作用。方法 30只SD大鼠以LPS静脉注射建立ALI模型,随机分为对照组及LPS静注后2、4、6、8 h组,取肺组织免疫组化法观察MMP-8和Ⅰ型胶原表达的变化,检测肺组织中CrossLaps蛋白含量以及髓过氧化物酶(MPO)活性、肺湿/干重比(W/D)、肺通透指数、肺内中性粒细胞数的变化。结果 LPS静脉注射后,4、6、8 h组MMP-8含量、CrossLaps蛋白含量、MPO活性、肺湿/干重比(W/D)、肺通透指数、肺内中性粒细胞数显著性高于对照组(P<0.01),Ⅰ型胶原表达相应减少(P<0.01)。结论 MMP-8介导了中性粒细胞对Ⅰ型胶原的降解作用,与ALI的发生密切相关。

Objective In the LPS-induced acute lung injury (ALI) there is massive accumulation of neutrophils in the lung. The effect of neutrophil collagenase on the degradation of lung matrix collagen ig still unknown. The aim of this study was to investigate the role of neutrophil collagenase in LPS-induced ALI.Methods Thirty SD rats of either sex weighing 190 ± 40 g were randomly divided into five groups of 6 animals : group 1 control and group 2-5 LPS. In LPS groups animals were anesthetized with intraperitoneal 3% pentobarbital 30 mg·kg-1. Right jugular vein was cannulated. LPS (O55: B5 Sigma USA) 5 mg·kg-1 was injected iv. The animals were sacrificed at 2 h (group 2), 4 h (group 3), 6 h( group 4) and 8 h( group 5) after iv LPS administration. Bronchoalveolar lavage was performed immediately with 3 ml of normal saline. The fluid washed out was collected and subjected to hypothermic centrifugation (3000 r·min-1, 10 min 4℃) . The supernatant was collected for determination of its protein content. Lung tissue was obtained for determination of myeloperoxidase (MPO) activity, expression of matrix metallo-proteinase-8 (MMP-8) , CrossLaps protein content (the degradation product of type Ⅰ collagen) and wet/dry lung weight ratio(W/D), and microscopic examination. Pulmonary permeability index was calculated (protein content in bronchoalveolar wash-out fluid / plasma protein concentration) .Results At 4, 6 and 8 h after iv LPS administration (in group 3-5) the MMP-8 expression, crosslaps protein content, MPO activity, W/D and lung permeability index were significantly increased as compared with those in control group ( P < 0.01) Microscopic examination showed massive neutrophil infiltration in lung parenchyma and alveoli. Conclusion The typeⅠ collagen degradation induced by neutrophils is through MMP-8 which may play an important role in the process of LPS-induced ALI.