Mechtcheriakova D, Schabbauer G, Lucerna M, Clauss M, Binder B R, Hofer E
Department of Vascular Biology and Thrombosis Research, VIRCC, University of Vienna, A-1235 Vienna, Austria.
FASEB J. 2001 Jan;15(1):230-242. doi: 10.1096/fj.00-0247com.
Tissue factor (TF) has been shown to be up-regulated in endothelial cells by the inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) as well as by the main angiogenic factor VEGF. Since both stimuli induce the transcription factor EGR-1, which is critically involved in TF gene regulation, we used EGR-1-dependent TF induction as a model to identify potential cross-talks between the various signal transduction cascades initiated by VEGF and TNF-alpha. The data show that at the MAP kinase level, VEGF mainly activates ERK1/2 and p38 MAP kinases in human endothelial cells. TNF-alpha is able to activate all three MAP kinase cascades as well as the classical inflammatory IkappaB/NFkappaB pathway. Furthermore, the MEK/ERK module of MAP kinases appears to act as the convergence point of VEGF- and TNF-alpha-initiated signaling cascades, which lead to the activation of EGR-1 and subsequent TF expression, whereas the upstream signals are distinct. We found that induction of TF by VEGF via EGR-1 is strongly PKC dependent. The TNF-alpha-initiated MEK/ERK cascade connected to EGR-1 and TF expression is clearly less sensitive to PKC inhibition. TNF-alpha-mediated activation of MEK/ERK and EGR-1 can be blocked by adenoviral expression of a dominant negative mutant of IKK2, whereas the VEGF signaling pathway is unaffected. Thus, our data demonstrate a new link between the classical inflammatory IKK/IkappaB and the MEK/ERK cascades triggered by TNF-alpha. The additional finding that EGF induces ERK and EGR-1 in a PKC-independent manner and that this signal is not sufficient to up-regulate TF emphasizes the importance of a VEGF-specific signaling pattern for the induction of TF.
组织因子（TF）已被证明在炎症细胞因子肿瘤坏死因子α（TNF-α）以及主要血管生成因子血管内皮生长因子（VEGF）作用下，在内皮细胞中表达上调。由于这两种刺激均能诱导转录因子早期生长反应因子1（EGR-1），而EGR-1在TF基因调控中起关键作用，我们以EGR-1依赖的TF诱导作为模型，来确定由VEGF和TNF-α引发的各种信号转导级联之间潜在的相互作用。数据显示，在丝裂原活化蛋白激酶（MAP激酶）水平，VEGF主要激活人内皮细胞中的细胞外信号调节激酶1/2（ERK1/2）和p38 MAP激酶。TNF-α能够激活所有三条MAP激酶级联以及经典的炎症性IκB/核因子κB（NFκB）途径。此外，MAP激酶的丝裂原活化蛋白激酶/细胞外信号调节激酶（MEK/ERK）模块似乎是VEGF和TNF-α引发的信号级联的汇聚点，这些级联导致EGR-1的激活及随后的TF表达，而上游信号是不同的。我们发现VEGF通过EGR-1诱导TF强烈依赖蛋白激酶C（PKC）。与EGR-1和TF表达相关的TNF-α引发的MEK/ERK级联对PKC抑制明显不敏感。TNF-α介导的MEK/ERK和EGR-1的激活可被IKK2显性负性突变体的腺病毒表达所阻断，而VEGF信号通路不受影响。因此，我们的数据证明了经典炎症性IKK/IκB与TNF-α引发的MEK/ERK级联之间的新联系。另外的发现是，表皮生长因子（EGF）以不依赖PKC的方式诱导ERK和EGR-1，且该信号不足以上调TF，这强调了VEGF特异性信号模式对TF诱导的重要性。
