Establishment of a role of reactive oxygen species as a second messenger

我们研究的作用，活性氧（ROS）作为第二信使使用大鼠新生心肌细胞和成纤维细胞。在血管紧张素Ⅱ刺激下，心肌细胞内有三种MAP激酶（ERK、JNK和p38 MAPK）被激活。在三种MAP激酶中，JNK和p38 MAPK以ROS依赖的方式被激活，而ERK则不被激活。我们详细研究了导致JNK激活的信号通路，并发现了以下结果。血管紧张素受体可直接激活G_家族G蛋白的异源三聚体G_&lt;α12&gt;和G_&lt;α13&gt;<12>，G_（12）家族G蛋白可激活小G蛋白Rho。然后，Rho激活另一个小G蛋白Rae，Rac增加NADPH氧化酶，导致ROS产生。抑制ROS的产生抑制血管紧张素刺激诱导的肥大。这些结果表明，ROS通过JNK和p38 MAPK激活间接介导了肥大反应。另一方面，据信心脏成纤维细胞通过NFAT和其他转录因子的活化产生细胞因子而参与纤维化。当心脏成纤维细胞被血管紧张素II刺激时，观察到NFAT转录激活以ROS依赖的方式。然而，核转位的NFAT不受清除ROS。我们分析了NEAT激活途径，证明G_&lt;α12&gt;和G_&lt;α13&gt;介导的ROS产生参与了JNK的激活，而JNK激活了NFAT依赖的转录激活所必需的另一个因子。这些结果表明，G_<12>家族G蛋白调节ROS的产生，ROS在JNK激活中起重要作用。

We examined the role of reactive oxygen species (ROS) as a second messenger using rat neonatal cardiac myocytes and fibroblasts. When cardiac myocytes were stimulated by angiotensin II, three MAP kinases (ERK, JNK and p38 MAPK) were activated. Among three MAP kinases, JNK and p38 MAPK but not ERK were activated in a ROS-dependent manner. We examined the signaling pathway leading to JNK activation in detail, and have found the following results. Heterotrimeric G_<α12> and G_<α13> that belong to G_<12> family G proteins were directly activated by angiotensin receptor stimulation, and G12 family G proteins activated small G protein Rho. Then, Rho activated another small G protein Rae, and Rac increased NADPH oxidase that resulted in ROS production. Inhibition of ROS production suppressed hypertrophy induced by angiotensin stimulation. These results suggested that ROS indirectly mediated hypertrophic responses through JNK and p38 MAPK activation. On the other hand, it is believed that cardiac fibroblasts are involved in fibrosis by production of cytokines through activation of NFAT and other transcriptional factors. When cardiac fibroblasts were stimulated by angiotensin II, NFAT transcriptional activation was observed in a ROS-dependent manner. However, nuclear translocation of NFAT was not affected by elimination of ROS. We analyzed NEAT activation pathway and demonstrated that G_<α12>- and G_<α13>-mediated ROS production is involved in JNK activation, and JNK activated another factor that is necessary for NFAT-dependent transcriptional activation. These results indicated that G_<12> family G proteins regulate ROS production, and ROS play an essential role of JNK activation.