Li X, Hales K H, Watanabe G, Lee R J, Pestell R G, Hales D B
Department of Physiology & Biophysics, University of Illinois at Chicago 60612-7342, USA.
Endocrine. 1997 Jun;6(3):317-24. doi: 10.1007/BF02820509.
The immunostimulant tumor necrosis factor-alpha (TNF alpha), produced by monocytes/macrophages in response to inflammatory disorders, regulates gene expression in part through induction of mitogen-activated protein kinases (MAPKs), including the stress-activated protein kinase (SAPK) (c-Jun N-terminal kinase [JNK]) and the extracellular signal-regulated kinases (ERKs). In testicular Leydig cells, the induction of steroidogenesis by cAMP is inhibited by TNF alpha. To examine the potential mechanisms governing the mutual inhibition between cAMP and TNF alpha in Leydig cells, the intracellular signaling pathways that contribute to AP-1-dependent gene expression were examined in the mouse MA-10 Leydig cell line. TNF alpha induced SAPK activity sixfold at 15 min, and the PKC inhibitor calphostin C reduced the induction of SAPK by 30%. cAMP induced SAPK activity twofold but reduced TNF alpha-induced SAPK activity. ERK activity was inhibited by both cAMP and TNFa. TNFa increased c-Jun protein, but only weakly induced FOS proteins (c-Fos, FosB, Fra-1, and Fra-2) whereas cAMP increased the abundance of several FOS proteins (c-Fos, FosB, Fra-1, and Fra-2), with little effect on c-Jun levels. AP-1 binding activity, assessed using electrophoretic mobility shift assays, was increased twofold by TNF alpha and fivefold by cAMP. Cyclic AMP alone induced AP-1-responsive reporter (p3TPLUX) activity threefold after 2 h with peak effect of 4-fold at 4 hr. AP-1 reporter was not induced by TNF alpha alone but in the presence of cAMP, TNF alpha induced AP-1 reporter activity 12-fold. In conclusion, TNF alpha and cAMP induce distinct components that separately contribute to the modulation of AP-1 activity in MA-10 cells.
免疫刺激因子肿瘤坏死因子-α（TNFα）由单核细胞/巨噬细胞针对炎症性疾病产生，部分通过诱导丝裂原活化蛋白激酶（MAPK）来调节基因表达，其中包括应激激活蛋白激酶（SAPK）（c-Jun氨基末端激酶[JNK]）和细胞外信号调节激酶（ERK）。在睾丸间质细胞中，cAMP诱导的类固醇生成受到TNFα的抑制。为了研究间质细胞中cAMP和TNFα之间相互抑制的潜在机制，在小鼠MA-10间质细胞系中检测了有助于AP-1依赖性基因表达的细胞内信号通路。TNFα在15分钟时使SAPK活性增加了6倍，PKC抑制剂钙泊三醇C使SAPK的诱导降低了30%。cAMP使SAPK活性增加了2倍，但降低了TNFα诱导的SAPK活性。ERK活性受到cAMP和TNFα两者的抑制。TNFα增加了c-Jun蛋白，但仅微弱诱导FOS蛋白（c-Fos、FosB、Fra-1和Fra-2），而cAMP增加了几种FOS蛋白（c-Fos、FosB、Fra-1和Fra-2）的丰度，对c-Jun水平影响很小。使用电泳迁移率变动分析评估的AP-1结合活性，TNFα使其增加了2倍，cAMP使其增加了5倍。单独的环磷酸腺苷（cAMP）在2小时后使AP-1反应性报告基因（p3TPLUX）活性增加了3倍，在4小时时达到峰值效应4倍。单独的TNFα未诱导AP-1报告基因，但在存在cAMP的情况下，TNFα诱导AP-1报告基因活性增加了12倍。总之，TNFα和cAMP诱导不同的成分，分别有助于调节MA-10细胞中的AP-1活性。
