Lipopolysaccharide induces Rac1-dependent reactive oxygen species formation and coordinates tumor necrosis factor-α secretion through IKK regulation of NF-κB
Lipopolysaccharide induces Rac1-dependent reactive oxygen species formation and coordinates tumor necrosis factor-α secretion through IKK regulation of NF-κB
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DOI：
10.1074/jbc.m102061200
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发表时间：
2001-08-10
影响因子：
4.8
通讯作者：
Engelhardt, JF
中科院分区：
文献类型：
--
作者：
Sanlioglu, S;Williams, CM;Engelhardt, JF
活性氧（reactive oxygen species，ROS）是机体在多种环境胁迫下产生的重要第二信使。在这种情况下，细胞内ROS的变化可以激活信号转导途径，影响细胞对环境的反应。在脓毒症中，对细菌毒素的动态促炎细胞反应（例如，脂多糖或LPS）导致广泛的器官损伤和死亡。本研究首次证明，Rac 1（一种GTP结合蛋白）的激活和随后ROS的产生构成了参与巨噬细胞LPS攻击后NF κ B介导的肿瘤坏死因子-α（TNF α）分泌的主要途径。Rac 1的显性负突变体的表达。（N17 Rac 1）减少LPS刺激后Rac 1活化、ROS形成、NF κ B活化和TNF α分泌。相比之下，Rac 1的显性活性形式（V12 Rac 1）的表达在不存在LPS刺激的情况下模拟这些效应。IKK α和IKK β都是LPS激活的Rac 1所需的下游调节剂，因为IKK显性突变体（IKK α KM或IKK β KA）的表达显著降低了NF κ B依赖性TNF α的分泌。此外，使用CD 14阻断抗体的研究表明，Rac 1通过不依赖于CD 14的途径诱导TNF α分泌。然而，当CD 14和Rac 1途径均被抑制时，LPS诱导的TNF α分泌的最大治疗抑制发生。我们的研究结果表明，靶向Rac 1和CD 14依赖性途径可能是一个有用的治疗策略，在脓毒症的过程中减弱促炎细胞因子的反应。
Reactive oxygen species (ROS) are important second messengers generated in response to many types of environmental stress. In this setting, changes in intracellular ROS can activate signal transduction pathways that influence how cells react to their environment. In sepsis, a dynamic proinflammatory cellular response to bacterial toxins (e.g., lipopolysaccharide or LPS) leads to widespread organ damage and death. The present study demonstrates for the first time that the activation of Rac1 (a GTP-binding protein), and the subsequent production of ROS, constitutes a major pathway involved in NF kappaB-mediated tumor necrosis factor-alpha (TNF alpha) secretion following LPS challenge in macrophages. Expression of a dominant negative mutant of Rac1. (N17Rac1) reduced Rac1 activation, ROS formation, NF kappaB activation, and TNF alpha secretion following LPS stimulation. In contrast, expression of a dominant active form of Rac1 (V12Rac1) mimicked these effects in the absence of LPS stimulation. IKK alpha and IKK beta were both required downstream modulators of LPS-activated Rac1, since the expression of either of the IKK dominant mutants (IKK alpha KM or IKK beta KA) drastically reduced NF kappaB-dependent TNF alpha secretion. Moreover, studies using CD14 blocking antibodies suggest that Rac1 induces TNF alpha secretion through a pathway independent of CD14. However, a maximum therapeutic inhibition of LPS-induced TNF alpha secretion occurred when both CD14 and Rac1 pathways were inhibited. Our results suggest that targeting both Rac1- and CD14-dependent pathways could be a useful therapeutic strategy for attenuating the proinflammatory cytokine response during the course of sepsis.