Foster J A, Rich C B, Miller M F
Department of Biology, Syracuse University, New York 13244-1220.
J Biol Chem. 1990 Sep 15;265(26):15544-9.
Disruption and degradation of interstitial elastic fibers are significant characteristics of pulmonary emphysema. In order to examine the responses of elastogenic cells to the conditions mimicking degradation of interstitial pulmonary elastin, rat pulmonary fibroblast cultures were used as an in vitro model. Second passage fibroblasts were divided into two different environmental situations to represent cells adjacent to and remote from the site of elastase-digested matrix. One set of cell cultures was briefly digested with pancreatic elastase. The resultant digest was then added back incrementally to the medium of elastase-digested cell cultures and to the medium of a second set of undigested cultures. Both sets of cell cultures remained viable and metabolically active during these treatments (96 h of incubation) as judged by protein synthesis, cell number, and steady-state levels of beta-actin mRNA. However, the two sets of cultures exhibited opposite responses in elastin gene expression with addition of increasing amounts of the elastase digest. The elastase-digested cultures exhibited a 200% increase in extractable soluble elastin and a 186% increase in tropoelastin mRNA with the addition of increasing amounts of the elastase digest to the medium. Conversely, the amount of soluble elastin recovered from the undigested cultures decreased 75%, and the steady-state level of tropoelastin mRNA decreased 63%. Soluble elastin peptides generated from oxalic acid treatment of purified elastin were shown to decrease tropoelastin mRNA in undigested cell cultures in the same manner as the elastase digest. Based on these data, we propose that pulmonary fibroblast elastin gene expression can be controlled coordinately by the state of the extracellular matrix and solubilized peptides derived from that matrix. Such integrated regulation may serve to localize elastin repair mechanisms.
肺间质弹性纤维的破坏和降解是肺气肿的显著特征。为了研究弹性生成细胞对模拟肺间质弹性蛋白降解条件的反应，将大鼠肺成纤维细胞培养物用作体外模型。第二代成纤维细胞被分为两种不同的环境情况，以代表与弹性蛋白酶消化基质部位相邻和远离的细胞。一组细胞培养物用胰弹性蛋白酶短暂消化。然后将所得消化物逐步添加回弹性蛋白酶消化的细胞培养物培养基和另一组未消化培养物的培养基中。通过蛋白质合成、细胞数量和β-肌动蛋白mRNA的稳态水平判断，在这些处理过程中（96小时孵育），两组细胞培养物均保持存活且代谢活跃。然而，随着弹性蛋白酶消化物添加量的增加，两组培养物在弹性蛋白基因表达上表现出相反的反应。随着向培养基中添加越来越多的弹性蛋白酶消化物，弹性蛋白酶消化的培养物中可提取的可溶性弹性蛋白增加了200%，原弹性蛋白mRNA增加了186%。相反，从未消化培养物中回收的可溶性弹性蛋白量减少了75%，原弹性蛋白mRNA的稳态水平降低了63%。草酸处理纯化弹性蛋白产生的可溶性弹性蛋白肽在未消化的细胞培养物中以与弹性蛋白酶消化物相同的方式降低原弹性蛋白mRNA。基于这些数据，我们提出肺成纤维细胞弹性蛋白基因表达可由细胞外基质的状态和源自该基质的可溶性肽协同控制。这种整合调节可能有助于定位弹性蛋白修复机制。
