Dept. of Physiology, University of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA.
Am J Physiol Cell Physiol. 2011 Feb;300(2):C256-65. doi: 10.1152/ajpcell.00272.2010. Epub 2010 Dec 1.
We investigated the role of reactive oxygen species (ROS) in promoting cell survival during oxidative stress induced by the inflammatory mediator tumor necrosis factor-α (TNF-α) in cerebral microvascular endothelial cells (CMVEC) from newborn piglets. Nox4 is the major isoform of NADPH oxidase responsible for TNF-α-induced oxidative stress and apoptosis in CMVEC. We present novel data that Nox4 NADPH oxidase-derived ROS also initiate a cell survival mechanism by increasing production of a gaseous antioxidant mediator carbon monoxide (CO) by constitutive heme oxygenase-2 (HO-2). TNF-α rapidly enhanced endogenous CO production in a superoxide- and NADPH oxidase-dependent manner in CMVEC with innate, but not with small interfering RNA (siRNA)-downregulated Nox4 activity. CORM-A1, a CO-releasing compound, inhibited Nox4-mediated ROS production and enhanced cell survival in TNF-α-challenged CMVEC. The ROS-induced CO-mediated survival mechanism requires functional interactions between the protein kinase B/Akt and extracellular signal-related kinase (ERK)/p38 MAPK signaling pathways activated by TNF-α. In Akt siRNA-transfected CMVEC and in cells with pharmacologically inhibited Akt, Erk1/2, and p38 mitogen-activated protein kinase (MAPK) activities, CORM-A1 was no longer capable of blocking Nox4 activation and apoptosis caused by TNF-α. Overall, Nox4 NADPH oxidase-derived ROS initiate both death and survival pathways in TNF-α-challenged CMVEC. The ROS-dependent cell survival pathway is mediated by an endogenous antioxidant CO, which inhibits Nox4 activation via a mechanism that includes Akt, ERK1/2, and p38 MAPK signaling pathways. The ability of CO to inhibit TNF-α-induced ERK1/2 and p38 MAPK activities in an Akt-dependent manner appears to be the key element in ROS-dependent survival of endothelial cells during TNF-α-mediated brain inflammatory disease.
我们研究了活性氧（ROS）在促炎介质肿瘤坏死因子-α（TNF-α）诱导的新生仔猪脑微血管内皮细胞（CMVEC）氧化应激过程中促进细胞存活的作用。Nox4 是 NADPH 氧化酶的主要同工型，负责 TNF-α 诱导的 CMVEC 氧化应激和细胞凋亡。我们提供了新的数据，表明 Nox4 NADPH 氧化酶衍生的 ROS 还通过增加组成型血红素氧合酶-2（HO-2）产生气态抗氧化介质一氧化碳（CO）来启动细胞存活机制。TNF-α 以超氧化物和 NADPH 氧化酶依赖的方式迅速增强 CMVEC 内源性 CO 的产生，而不是用小干扰 RNA（siRNA）下调 Nox4 活性。CO 释放化合物 CORM-A1 抑制 Nox4 介导的 ROS 产生并增强 TNF-α 挑战的 CMVEC 中的细胞存活。ROS 诱导的 CO 介导的存活机制需要 TNF-α 激活的蛋白激酶 B/Akt 和细胞外信号相关激酶（ERK）/p38 MAPK 信号通路之间的功能相互作用。在 Akt siRNA 转染的 CMVEC 和用药物抑制 Akt、Erk1/2 和 p38 丝裂原激活蛋白激酶（MAPK）活性的细胞中，CORM-A1 不再能够阻断 TNF-α 引起的 Nox4 激活和细胞凋亡。总体而言，Nox4 NADPH 氧化酶衍生的 ROS 在 TNF-α 挑战的 CMVEC 中启动死亡和存活途径。ROS 依赖性细胞存活途径是由内源性抗氧化剂 CO 介导的，CO 通过包括 Akt、ERK1/2 和 p38 MAPK 信号通路在内的机制抑制 Nox4 激活。CO 以 Akt 依赖的方式抑制 TNF-α 诱导的 ERK1/2 和 p38 MAPK 活性的能力似乎是 ROS 依赖性内皮细胞在 TNF-α 介导的脑炎症疾病中存活的关键因素。
