Madamanchi N R, Bukoski R D, Runge M S, Rao G N
Division of Cardiology, University of Texas Medical Branch, Galveston 77555, USA.
Oncogene. 1998 Jan 22;16(3):417-22. doi: 10.1038/sj.onc.1201551.
We have previously demonstrated that arachidonic acid activates extracellular signal-regulated protein kinases (ERKs) group of mitogen-activated protein kinases (MAPKs) in vascular smooth muscle cells (VSMC). To understand the role of arachidonic acid in cellular signaling events, we have now studied its effect on jun N-terminal kinases (JNKs) group of MAPKs in VSMC. Arachidonic acid activated JNK1 in a time- and concentration-dependent manner with maximum effects at 10 min and 50 microM. Induced activation of JNK1 by arachidonic acid is specific as other fatty acids such as linoleic and stearic acids had no such effect. Indomethacin and nordihydroguaiaretic acid (NDGA), potent inhibitors of the cyclooxygenase (COX) and the lipoxygenase (LOX)/monooxygenase (MOX) pathways, respectively, had no effect on arachidonic acid activation of JNK1 suggesting that the observed phenomenon is independent of its metabolism through either pathway. However, 12-hydroperoxyeicosatetraenoic acid (12-HpETE), the LOX metabolite of arachidonic acid significantly induced JNK1 activity. Protein kinase C (PKC) depletion by prolonged treatment of VSMC with phorbol 12-myristate 13-acetate (PMA) resulted in partial decrease in the responsiveness of JNK1 to arachidonic acid suggesting a role for both PKC-dependent and -independent mechanisms in the activation of JNK1 by this important fatty acid. On the other hand, the responsiveness of JNK1 to 12-HpETE was completely abolished in PKC-depleted cells, suggesting a major role for PKC in 12-HpETE-induced JNK1 activation. IL-1beta and TNF-alpha activated JNK1 in a time-dependent manner with maximum effect at 10 min. Desensitization of JNK1 by arachidonic acid significantly reduced its responsiveness to both the cytokines. In addition, 4-bromophenacyl bromide (4-BPB), a potent and selective inhibitor of phospholipase A2 (PLA2), significantly attenuated the cytokine-induced activation of JNK1. Together, these results show that (1) arachidonic acid and its LOX metabolite, 12-HpETE, activate JNK1 in VSMC, (2) PKC-dependent and -independent mechanisms play a role in the activation of JNK1 by arachidonic acid and 12-HpETE, and (3) arachidonic acid mediates, at least partially, the cytokine-induced activation of JNK1.
我们之前已经证明，花生四烯酸可激活血管平滑肌细胞（VSMC）中丝裂原活化蛋白激酶（MAPK）的细胞外信号调节蛋白激酶（ERK）组。为了解花生四烯酸在细胞信号转导事件中的作用，我们现在研究了其对VSMC中MAPK的Jun氨基末端激酶（JNK）组的影响。花生四烯酸以时间和浓度依赖性方式激活JNK1，在10分钟和50微摩尔时作用最强。花生四烯酸诱导的JNK1激活具有特异性，因为其他脂肪酸如亚油酸和硬脂酸没有这种作用。分别作为环氧化酶（COX）和脂氧合酶（LOX）/单加氧酶（MOX）途径的强效抑制剂的吲哚美辛和去甲二氢愈创木酸（NDGA），对花生四烯酸激活JNK1没有影响，这表明观察到的现象与其通过任一途径的代谢无关。然而，花生四烯酸的脂氧合酶代谢产物12-氢过氧化二十碳四烯酸（12-HpETE）显著诱导JNK1活性。用佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）长时间处理VSMC导致蛋白激酶C（PKC）耗竭，从而使JNK1对花生四烯酸的反应性部分降低，这表明PKC依赖性和非依赖性机制在这种重要脂肪酸激活JNK1中均起作用。另一方面，在PKC耗竭的细胞中，JNK1对12-HpETE的反应性完全丧失，这表明PKC在12-HpETE诱导的JNK1激活中起主要作用。白细胞介素-1β（IL-1β）和肿瘤坏死因子-α（TNF-α）以时间依赖性方式激活JNK1，在10分钟时作用最强。花生四烯酸使JNK1脱敏显著降低了其对这两种细胞因子的反应性。此外，磷脂酶A2（PLA2）的强效选择性抑制剂4-溴苯甲酰溴（4-BPB）显著减弱了细胞因子诱导的JNK1激活。总之，这些结果表明：（1）花生四烯酸及其脂氧合酶代谢产物12-HpETE可激活VSMC中的JNK1；（2）PKC依赖性和非依赖性机制在花生四烯酸和12-HpETE激活JNK1中起作用；（3）花生四烯酸至少部分介导细胞因子诱导的JNK1激活。
