Hallbeck A L, Walz T M, Wasteson A
Department of Biomedicine and Surgery, Division of Cell Biology, University of Linkoping, Sweden.
Biosci Rep. 2001 Jun;21(3):325-39. doi: 10.1023/a:1013238300100.
We have previously reported that the human monocytoid cell line U-937-1 constitutively expresses transforming growth factor-alpha (TGF-alpha) and that the steady-state levels of TGF-alpha mRNA as well as TGF-alpha protein release increase when U-937-1 cells are differentiated towards monocytes/macrophages. Interleukin-6 (IL-6), which has been shown to have growth-stimulatory effects on a number of cell types, has recently been shown to enhance TGF-alpha expression in keratinocytes. In the present study we investigated whether TGF-alpha expression in macrophage-like cells could be regulated by IL-6 using U-937-1 cells as a model system of monocyte/macrophage differentiation. U-937-1 cells were differentiated with retinoic acid (RA), vitamin D3 (Vit-D3) or phorbol-12-myristate-13-acetate (PMA) for 4 days and were then treated with human recombinant IL-6 (1000 IU/ml) for up to 24 hr. Northern blot analysis revealed that cells differentiated with PMA, inducing the phenotype of a secretory macrophage, markedly increased their TGF-alpha mRNA levels (2.7-fold) when treated with IL-6; the response was maximal at 6 hr and remained high at 12 hr. The expression of the TGF-alpha gene was accompanied by release of TGF-alpha protein into the cell culture medium, irrespective of differentiating agent, as demonstrated by enzyme-linked immunosorbent assay (ELISA), as well as by surface expression of pro-TGF-alpha as determined by indirect immunofluorescent cytometry. However, the superinduction of the TGF-alpha gene by IL-6 in cells differentiated with PMA was not accompanied by any increase in TGF-alpha protein release or pro-TGF-alpha surface expression. We conclude that since IL-6 causes increased steady-state levels of TGF-alpha mRNA in macrophage-like cells, it may prime these cells for production of this growth factor. Furthermore, we have shown that the IL-6 receptor complex is functional in U-937-1 cells induced to differentiate towards a secretory macrophage by treatment with PMA.
我们之前报道过人单核细胞样细胞系U - 937 - 1组成性表达转化生长因子α（TGF -α），并且当U - 937 - 1细胞向单核细胞/巨噬细胞分化时，TGF -α mRNA的稳态水平以及TGF -α蛋白释放会增加。白细胞介素-6（IL - 6）已被证明对多种细胞类型具有生长刺激作用，最近还被证明可增强角质形成细胞中TGF -α的表达。在本研究中，我们以U - 937 - 1细胞作为单核细胞/巨噬细胞分化的模型系统，研究了IL - 6是否能调节巨噬细胞样细胞中TGF -α的表达。U - 937 - 1细胞用视黄酸（RA）、维生素D3（Vit - D3）或佛波醇-12 -肉豆蔻酸酯-13 -乙酸酯（PMA）分化4天，然后用人重组IL - 6（1000 IU/ml）处理长达24小时。Northern印迹分析显示，用PMA分化诱导出分泌性巨噬细胞表型的细胞，在用IL - 6处理时其TGF -α mRNA水平显著增加（2.7倍）；反应在6小时时最大，并在12小时时保持较高水平。TGF -α基因的表达伴随着TGF -α蛋白释放到细胞培养基中，这与分化剂无关，通过酶联免疫吸附测定（ELISA）以及间接免疫荧光细胞术测定的前体TGF -α的表面表达证明了这一点。然而，在用PMA分化的细胞中，IL - 6对TGF -α基因的超诱导并没有伴随着TGF -α蛋白释放或前体TGF -α表面表达的任何增加。我们得出结论，由于IL - 6导致巨噬细胞样细胞中TGF -α mRNA的稳态水平增加，它可能使这些细胞为产生这种生长因子做好准备。此外，我们已经表明，IL - 6受体复合物在通过PMA处理诱导向分泌性巨噬细胞分化的U - 937 - 1细胞中具有功能。
