脂多糖诱导急性肺损伤大鼠肺泡灌洗液明胶酶活性的变化

Changes of Activities of Gelatinases in Bronchoalveolar Lavage Fluid from Rats with Lipopolysaccaride-induced Acute Lung Injury

目的 :探讨明胶酶在脂多糖 (LPS)诱导的急性肺损伤 (ALI)中的作用。方法 :以LPS静脉注射建立ALI模型。将 32只大鼠随机分为正常组及LPS静脉注射后 2、4及 6h组。检测肺通透指数 (LPI)、PaO2 /FiO2 和组织病理学评分 ,以评估肺损伤严重程度。采用明胶酶谱法测量明胶酶活性。以免疫组织化学法观察肺组织IV型胶原。结果 :LPS静脉注射后 ,4及 6h组肺通透指数显著高于正常组 (P <0 .0 1) ,组织病理学呈ALI改变 ;LPS作用 2h时MMP 2 (明胶酶A)活性较正常组升高 (P <0 .0 1) ,并持续至 6h ;MMP 9(明胶酶B)在正常组几乎检测不到 ,而在 2h组发现其活性 ,在 4及 6h组进一步显著升高 (P <0 .0 1)。相关分析表明 ,MMP 9活性与PaO2 /FiO2 、LPI、肺组织病理学评分显著相关 (r分别为 - 0 .6 9、0 .80、0 .71,均P <0 .0 5 )。MMP 2与肺组织病理学评分相关 (r=0 .5 0 ,P <0 .0 5 )。IV型胶原染色显示LPS导致基底膜的破坏。结论 :胶原酶 (MMP 2 ,MMP 9) ,可通过破坏基底膜而参与内毒素诱导急性肺损伤的病理过程。

Objective:To investigate the role of gelatinases in the pathogenesis of acute lung injury (ALI) induced by lipopolysaccaride (LPS). Methods:Thirty-two rats were randomly divided into saline control group and different LPS groups (2 h, 4 h and 6 h after LPS challenge). Lung injury was quantified by measurements of PaO 2/FiO 2, lung permeability index (LPI) and histopathologic scoring. Samples obtained from bronchoalveolar lavage (BAL) fluid were compared for the presence of gelatinases by gelatin zymography. Immunohistochemical staining of the type-Ⅳ collagen was performed on sections of lung specimens. Results: The animals treated with LPS for 4 h and 6 h had developed ALI with respiratory failure as evidenced by a decrease of PaO 2/FIO 2 and an increase of LPI and histopathologic total lung injury score (all P<0.01 versus the control group). MMP-2 (gelatinase A) activity was significantly increased at 2nd h after LPS (P< 0.01 versus the control group), and not further changed at 4th h or 6th h after LPS (P>0.05 versus 2 h group). MMP-9 (gelatinase B) was not essentially detectable in rats treated with saline, but great in rats treated with LPS for 2 h, and further enhanced at 4th h and 6th h after LPS (P<0.01 versus 2 h group). MMP-9 activity was significantly correlated with PaO 2/FiO 2, LPI and the histopathologic total lung injury score (r=-0.69, r=0.80, r=0.71, respectively, all P<0.05). MMP-2 activity had a correlation with the histopathologic total lung injury score (r=0.50, P<0.05 ). Staining for type Ⅳ collagen showed the basement membrane (BM) in lung tissue was disrupted by LPS whereas no disruption was detected in the control group. Conclusion:Gelatinases (MMP-2 and MMP-9) play a role in the pathogenesis of LPS-induced acute lung injury, at least in part, through the degradation of the basement membrane in lung tissue.