Akademik Veri Yönetim Sistemi
JOURNAL OF BIOLOGICAL CHEMISTRY, cilt.276, sa.32, ss.30188-30198, 2001 (SCI-Expanded)
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.