Bakowska J, Adamson I Y
Department of Pathology, University of Manitoba, Winnipeg, Canada.
J Pathol. 1998 Jul;185(3):319-23. doi: 10.1002/(SICI)1096-9896(199807)185:3<319::AID-PATH114>3.0.CO;2-L.
Basement membrane degradation can be indicative of tissue injury, but the process may also release matrix-bound cytokines to stimulate cell regeneration. To investigate this process, acute lung injury was induced in rats by intratracheal bleomycin and animals were killed from 3 days to 8 weeks later. The lungs were lavaged with saline to collect bronchoalveolar lavage (BAL) fluid and cell proliferation was assessed by pulse incorporation of tritiated thymidine. Bleomycin induced rapid inflammation with increased cell numbers and protein levels in BAL. Collagen degradation products were also increased in BAL fluid from 3 days to 4 weeks. Incubating samples of BAL fluid with radiolabelled collagens I and IV showed that high levels of activity, particularly for the degradation of type IV collagen, were present as early as 3 days post-bleomycin and persisted over the 8-week period. Zymograms demonstrated the highest level of gelatinase A (MMP-2) activity in BAL fluid in the first 2 weeks after bleomycin. Coincident with peak basement membrane degradative activity was the onset of a phase of epithelial cell proliferation, as measured by labelled nuclei in autoradiographs. The results show that enzymes capable of degrading the alveolar basement membrane are secreted early in the lung injury phase and that their presence in BAL fluid can be used as a measure of alveolar wall damage. It is possible that this enzyme action may release bound cytokines from the basement membrane, since maximal gelatinase activity correlates with alveolar epithelial cell proliferation.
基底膜降解可能表明组织损伤，但该过程也可能释放与基质结合的细胞因子以刺激细胞再生。为了研究这一过程，通过气管内注射博来霉素在大鼠中诱导急性肺损伤，并在3天至8周后处死动物。用生理盐水灌洗肺部以收集支气管肺泡灌洗（BAL）液，并通过氚标记胸腺嘧啶核苷的脉冲掺入来评估细胞增殖。博来霉素诱导快速炎症，BAL中的细胞数量和蛋白质水平增加。从3天到4周，BAL液中的胶原降解产物也增加。将BAL液样品与放射性标记的I型和IV型胶原一起孵育表明，早在博来霉素注射后3天就存在高水平的活性，特别是对于IV型胶原的降解，并且在8周期间持续存在。酶谱分析表明，博来霉素注射后的前2周，BAL液中明胶酶A（MMP-2）活性水平最高。与基底膜降解活性峰值一致的是上皮细胞增殖阶段的开始，这通过放射自显影片中的标记细胞核来测量。结果表明，能够降解肺泡基底膜的酶在肺损伤早期就会分泌，并且它们在BAL液中的存在可以用作肺泡壁损伤的指标。由于最大明胶酶活性与肺泡上皮细胞增殖相关，这种酶的作用可能会从基底膜释放结合的细胞因子。
