Takagi H, Ochoa M S, Zhou L, Helfman T, Murata H, Falanga V
University of Miami School of Medicine, Department of Dermatology and Cutaneous Surgery, Florida 33136, USA.
J Clin Invest. 1995 Nov;96(5):2120-5. doi: 10.1172/JCI118265.
The pathogenesis of the eosinophilia myalgia syndrome (EMS) remains unclear. Several abnormal constituents have been found in the L-tryptophan lots responsible for the illness, particularly, 1,1-ethylidenebis[L-tryptophan], also called peak E or EBT, and 3-phenylamino-alanine or peak 5. However, the role of these contaminants in the pathogenesis of EMS and in the development of fibrosis is unknown. We now report that peak E, a dimer of L-tryptophan, is a potent stimulus for human dermal fibroblast DNA and collagen synthesis. Peak E (0.1-1.0 microM) increased DNA synthesis up to four-fold (P = 0.0001) in a dose-dependent manner (r = 0.987). When added to monolayer cultures for 2 to 24 h, peak E (0.5 to 100 microM) caused a progressive, more than threefold increase in alpha 1(I) procollagen mRNA levels and collagenous protein. No increase in procollagen mRNA levels was found after the addition of another major L-tryptophan contaminant, peak 5, or with L-tryptophan itself. Transient transfection with a 2.5-kb alpha 1(I) procollagen promoter-luciferase construct showed that peak E causes a twofold upregulation of promoter activity (P = 0.022). Contraction of collagen gels, consisting of human dermal fibroblasts incorporated into a type I collagen lattice, was enhanced two-fold by exposure to peak E (P = 0.001). We conclude that a major constituent of contaminated batches of L-tryptophan, peak E, is a potent stimulus for fibroblast activation and collagen synthesis. This stimulatory action of peak E may provide a direct mechanism for the development of fibrosis in EMS.
嗜酸性粒细胞增多性肌痛综合征（EMS）的发病机制尚不清楚。在引发该病的L-色氨酸批次中发现了几种异常成分，特别是1,1-亚乙基双[L-色氨酸]，也称为E峰或EBT，以及3-苯基氨基丙氨酸或5峰。然而，这些污染物在EMS发病机制和纤维化发展中的作用尚不清楚。我们现在报告，E峰，一种L-色氨酸二聚体，是人类皮肤成纤维细胞DNA和胶原蛋白合成的有力刺激物。E峰（0.1 - 1.0 microM）以剂量依赖性方式（r = 0.987）使DNA合成增加高达四倍（P = 0.0001）。当添加到单层培养物中2至24小时时，E峰（0.5至100 microM）导致α1（I）前胶原mRNA水平和胶原蛋白含量逐渐增加超过三倍。添加另一种主要的L-色氨酸污染物5峰或L-色氨酸本身后，未发现前胶原mRNA水平增加。用2.5 kb的α1（I）前胶原启动子 - 荧光素酶构建体进行瞬时转染表明，E峰导致启动子活性上调两倍（P = 0.022）。由掺入I型胶原晶格中的人类皮肤成纤维细胞组成的胶原凝胶的收缩，通过暴露于E峰而增强了两倍（P = 0.001）。我们得出结论，受污染的L-色氨酸批次的主要成分E峰是成纤维细胞活化和胶原蛋白合成的有力刺激物。E峰的这种刺激作用可能为EMS中纤维化的发展提供直接机制。
