Vivekananda J, Lin A, Coalson J J, King R J
Department of Physiology, University of Texas Health Science Center at San Antonio 78284-7756.
J Biol Chem. 1994 Oct 7;269(40):25057-61.
Although transforming growth factor-alpha (TGF-alpha) is widely distributed in transformed cells and in some normal cells and much is known about its structure and metabolism, there is little information about its physiological actions. TGF-alpha is not thought to be synthesized by nontransformed fibroblasts, but it is thought to be a mitogen for these and epithelial cells (Derynck, R. (1986) J. Cell. Biochem. 32, 293-304). We report here that fibroblasts obtained from hamsters with oxidant-induced lung injury release TGF-alpha at levels comparable with those reported for transformed cells. In conditioned media, one isoform of 18 kDa was recognized by a monoclonal antibody to mature TGF-alpha; five isoforms ranging from 18 to 42 kDa were recognized in cell lysates. Conditioned media from these fibroblasts stimulated tyrosine phosphorylation of the epidermal growth factor (EGF)/TGF-alpha receptor, competed with radioactive EGF for binding sites on A431 cells, and were mitogenic for mesenchymal and epithelial cells. This mitogenic activity could be almost completely blocked by anti-TGF-alpha. Conditioned media from normal lung fibroblasts exhibited none of these activities. Using normal lung fibroblasts, we found that TGF-alpha synthesis could be induced in vitro with 25 nmol/ml EGF, suggesting that the induction in vivo may have been due, in part, to a stimulation by EGF (or TGF-alpha) released by other cell types such as alveolar macrophages recruited to the injury site. TGF-alpha is, in general, a mitogen for epithelial cells (Derynck, 1986); more specific to acute injury in the lung, it may affect the proliferation (Ryan, R. M., Mineo-Kuhn, M. M., Kromer, C. M., and Finkelstein, J. N. (1994) Am. J. Physiol. 266, L17-L23) and metabolic activities (Whitsett, J. A., Weaver, T. E., Lieberman, M. A., Clark, J. G., and Daugherty, C. (1987) J. Biol. Chem. 262, 7908-7913) of alveolar epithelial type II cells. This is, we believe, the first report of a fibroblast-derived TGF-alpha induced with oxidant injury. If this response was ubiquitously manifested in other tissues, then fibroblast-derived TGF-alpha might be an important determinant of the epithelial and mesenchymal hyperplasia commonly observed in tissue repair.
尽管转化生长因子α（TGF-α）广泛分布于转化细胞和一些正常细胞中，且对其结构和代谢已有很多了解，但关于其生理作用的信息却很少。非转化的成纤维细胞不被认为能合成TGF-α，但它被认为是这些细胞和上皮细胞的促有丝分裂原（德里恩克，R.（1986年）《细胞生物化学杂志》32卷，293 - 304页）。我们在此报告，从患有氧化剂诱导性肺损伤的仓鼠中获取的成纤维细胞释放TGF-α的水平与报道的转化细胞中的水平相当。在条件培养基中，一种18 kDa的同工型可被针对成熟TGF-α的单克隆抗体识别；在细胞裂解物中可识别出五种分子量在18至42 kDa之间的同工型。这些成纤维细胞的条件培养基刺激表皮生长因子（EGF）/TGF-α受体的酪氨酸磷酸化，与放射性EGF竞争A431细胞上的结合位点，并且对间充质细胞和上皮细胞具有促有丝分裂作用。这种促有丝分裂活性几乎可被抗TGF-α完全阻断。正常肺成纤维细胞的条件培养基不表现出这些活性。利用正常肺成纤维细胞，我们发现用25 nmol/ml EGF可在体外诱导TGF-α合成，这表明体内的诱导可能部分归因于被招募到损伤部位的其他细胞类型如肺泡巨噬细胞释放的EGF（或TGF-α）的刺激。一般来说，TGF-α是上皮细胞的促有丝分裂原（德里恩克，1986年）；对于肺中的急性损伤更具特异性的是，它可能影响肺泡II型上皮细胞的增殖（瑞安，R.M.，米内奥 - 库恩，M.M.，克罗默，C.M.，和芬克尔斯坦，J.N.（1994年）《美国生理学杂志》266卷，L17 - L23页）和代谢活性（惠特塞特，J.A.，韦弗，T.E.，利伯曼，M.A.，克拉克，J.G.，和多尔蒂，C.（1987年）《生物化学杂志》262卷，7908 - 7913页）。我们认为，这是关于氧化剂损伤诱导成纤维细胞源性TGF-α的首次报道。如果这种反应在其他组织中普遍存在，那么成纤维细胞源性TGF-α可能是组织修复中常见的上皮和间充质增生的重要决定因素。
