Welgus H G, Connolly N L, Senior R M
J Clin Invest. 1986 May;77(5):1675-81. doi: 10.1172/JCI112485.
Human monocytic tumor cells of the U937 cell line contain substantial quantities of two neutrophil neutral proteinases, elastase and cathepsin G, raising the question of whether their presence reflects an expression of transformation or whether normal monocytes undergo a developmental stage in which they produce certain neutrophil proteinases. To address this issue, we examined U937 cells for production of collagenase, since human alveolar macrophages release fibroblast-like collagenase, an enzyme that is distinct from neutrophil collagenase. Using an immunoassay that utilized antibody to skin fibroblast collagenase, we found that U937 cells secreted barely detectable quantities of enzyme, 10-12 ng/10(6) cells per 24 h, under basal conditions. Upon incubation with 10 nM 12-o-tetradecanoyl-phorbol-13-acetate (TPA), however, collagenase release increased 200-fold, comparable to the amount secreted by phorbol-stimulated human fibroblasts. Metabolic labeling and immunoprecipitation confirmed the enhanced synthesis of U937 cell collagenase upon TPA exposure. This enzyme activity further resembled fibroblast collagenase and differed from neutrophil collagenase by exhibiting preferential cleavage of monomeric type III collagen relative to type I. As previously observed with human alveolar macrophages, U937 cells also released a protein identical to the collagenase inhibitor produced by human skin fibroblasts, a molecule not associated with neutrophils. Release of this inhibitor increased 10-fold with TPA exposure. In contrast to collagenase and collagense inhibitor, TPA-treated U937 cells contained only 10-15% as much elastase and cathepsin G activities as control cells. Thus, TPA-induced differentiation modified the presence of these enzymes in the direction of their content in normal monocytes. Since the neutral proteinase profile of undifferentiated U937 cells resembles that of neutrophils and changes markedly after cellular differentiation to one that is characteristic of monocytes, these data suggest that neutrophilic proteinases may be produced by normal monocytes during the early stages of their differentiation.
U937细胞系的人单核细胞肿瘤细胞含有大量的两种中性粒细胞中性蛋白酶，即弹性蛋白酶和组织蛋白酶G，这就提出了一个问题，即它们的存在是反映了转化的表现，还是正常单核细胞经历了一个产生某些中性粒细胞蛋白酶的发育阶段。为了解决这个问题，我们检测了U937细胞中胶原酶的产生情况，因为人肺泡巨噬细胞会释放成纤维细胞样胶原酶，这是一种与中性粒细胞胶原酶不同的酶。使用一种利用抗皮肤成纤维细胞胶原酶抗体的免疫测定法，我们发现，在基础条件下，U937细胞分泌的酶量几乎检测不到，每24小时每10⁶个细胞分泌10 - 12 ng。然而，用10 nM 12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）孵育后，胶原酶的释放增加了200倍，与佛波醇刺激的人成纤维细胞分泌的量相当。代谢标记和免疫沉淀证实了TPA处理后U937细胞胶原酶的合成增加。这种酶活性进一步类似于成纤维细胞胶原酶，与中性粒细胞胶原酶不同的是，它对单体III型胶原的切割优先于I型胶原。正如之前在人肺泡巨噬细胞中观察到的那样，U937细胞还释放了一种与人皮肤成纤维细胞产生的胶原酶抑制剂相同的蛋白质，这种分子与中性粒细胞无关。TPA处理后，这种抑制剂的释放增加了10倍。与胶原酶和胶原酶抑制剂相反，TPA处理的U937细胞中的弹性蛋白酶和组织蛋白酶G活性仅为对照细胞的10% - 15%。因此，TPA诱导的分化使这些酶的存在朝着正常单核细胞中的含量方向改变。由于未分化的U937细胞的中性蛋白酶谱类似于中性粒细胞，并且在细胞分化后显著改变为单核细胞的特征谱，这些数据表明中性粒细胞蛋白酶可能在正常单核细胞分化的早期阶段产生。
