Signaling mechanisms involved in the activation of arachidonic acid metabolism in human astrocytoma cells by tumor necrosis factor-α:: Phosphorylation of cytosolic phospholipase A2 and transactivation of cyclooxygenase-2
Signaling mechanisms involved in the activation of arachidonic acid metabolism in human astrocytoma cells by tumor necrosis factor-α:: Phosphorylation of cytosolic phospholipase A2 and transactivation of cyclooxygenase-2
复制标题
DOI：
10.1046/j.1471-4159.1999.0731641.x
复制
发表时间：
1999-10-01
影响因子：
4.7
通讯作者：
Nieto, ML
中科院分区：
文献类型：
--
作者：
Hernández, M;Bayón, Y;Nieto, ML
肿瘤坏死因子-α (TNF-α) 是一种细胞因子，通过激活丝裂原激活蛋白激酶 (MAP 激酶) 级联和核因子 kappa B (NF-kappa B) 等转录因子来引发细胞反应。由于这些元件在参与胞质磷脂酶 A(2) (cPLA(2)) 和环氧合酶-2 (COX-2) 激活的信号传导机制中发挥核心作用，因此测定了 TNF-α 对 1321N1 星形细胞瘤细胞中花生四烯酸 (AA) 代谢的影响。 TNF-α 产生 cPLA(2) 磷酸化，随后 c-Jun N 末端激酶 (JNK) 和 p38-MAP 激酶均被激活，这与 [H-3]AA 的释放相关。相反，TNF-α 不会激活细胞外信号调节激酶（MAP 激酶）p42，也不会引发有丝分裂反应。通过反相 HPLC 对 [H-3]AA 代谢物进行分析表明，添加 TNF-α 后第一小时内释放的所有 [H-3]AA 均以真正的 AA 形式洗脱，而在添加 TNF-α 后 24 小时获得的样品中，25% 的 [H-3]AA 已转化与对照细胞中仅 9% 的 COX 产物相比，根据 RT-PCR 研究和 COX-2 蛋白免疫印迹判断，TNF-α 产生了 COX-2 表达的增加，以及 NF-κ B 的持久激活。这些数据表明，TNF-α 在星形细胞瘤细胞中产生 p38-MAP 激酶和 JNK 的早期激活，随后 cPLA(2) 磷酸化并释放AA。另一方面，NF-κ B 的激活可以解释 COX-2 表达的诱导和前列腺素生成的延迟。
Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that elicits cell responses by activating the mitogen-activated protein kinase (MAP kinase) cascade and transcription factors such as nuclear factor-kappa B (NF-kappa B). As these elements play a central role in the mechanisms of signaling involved in the activation of cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase-2 (COX-2), the effect of TNF-alpha on arachidonate (AA) metabolism in 1321N1 astrocytoma cells was assayed. TNF-alpha produced a phosphorylation of cPLA(2), which was preceded by an activation of both c-Jun N-terminal kinase (JNK) and p38-MAP kinase, and this was associated with the release of [H-3]AA. In contrast, TNF-alpha did not activate the extracellular signal-regulated kinase (MAP kinase) p42, nor did it elicit a mitogenic response, Analysis of [H-3]AA metabolites by reverse-phase HPLC showed that all of the [H-3]AA released during the first hour after TNF-alpha addition eluted as authentic AA, whereas in samples obtained at 24 h after addition of TNF-alpha, 25% of the [H-3]AA had been converted into COX products as compared with only 9% in control cells, In keeping with these findings, TNF-alpha produced an increase of COX-2 expression, as judged from both RT-PCR studies and immunoblot of COX-2 protein, and a long-lasting activation of NF-kappa B. These data show that TNF-alpha produces in astrocytoma cells an early activation of both p38-MAP kinase and JNK, which is followed by the phosphorylation of cPLA(2) and the release of AA. On the other hand, the activation of NF-kappa B may explain the induction of the expression of COX-2 and the delayed generation of prostanoids.