Cooperativity between oxidants and tumor necrosis factor in the activation of nuclear factor (NF)-kappaB: requirement of Ras/mitogen-activated protein kinases in the activation of NF-kappaB by oxidants.
The transcription factor nuclear factor (NF)-kappaB is activated by oxidative stress or cytokines and is critical to the activation of inflammatory genes. Here, we report that hydrogen peroxide or 3-morpholinosydnonimine, which simultaneously releases nitric oxide and superoxide, synergize with the cytokine tumor necrosis factor (TNF)-alpha to activate NF-kappaB in rat lung epithelial cells, suggesting that signaling pathways elicited by reactive oxygen species (ROS)/reactive nitrogen species (RNS) are different from TNF-induced signaling. These findings were substantiated by observations that levels of IkappaB-alpha did not change after exposure to ROS/RNS, whereas a rapid depletion of IkappaB-alpha was observed in cells exposed to TNF. In addition, the proteosome inhibitor MG132 did not affect activation of NF-kappaB by ROS/RNS, whereas it abolished the TNF response. Transfection of a dominant negative Ras construct prevented the activation of NF-kappaB by ROS/RNS, demonstrating the requirement for Ras in the activation of NF-kappaB by oxidants. In contrast, TNF activated NF-kappaB in a Ras-independent fashion. Evaluation of members of the mitogen-activated protein kinase (MAPK) family as downstream effectors of Ras revealed the requirement of MAPK/ extracellular-regulated kinase (ERK) kinase kinase (MEKK)1 and c-Jun N-terminal kinases in the induction of NF-kappaB by both oxidants and TNF, whereas the MEK-ERK pathway negatively regulates NF-kappaB. Our findings demonstrate that cytokines and oxidants cooperate in the activation of transcription factors through distinct pathways, and suggest that anti-inflammatory and antioxidant therapies may be required in concert to prevent the activation of NF-kappaB-regulated genes important in the development of inflammatory diseases.
Janssen-Heininger
Y M
YM
Department of Pathology, University of Vermont Medical Alumni Building, Burlington, Vermont; and The Center for Cell Signaling, University of Virginia, Charlottesville, Virginia, USA.
Macara
I
I
Mossman
B T
BT
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D020672:I-kappa B Proteins; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D018384:Oxidative Stress; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D018631:ras Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; C002385:linsidomine; D006861:Hydrogen Peroxide; D008981:Molsidomine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018631:ras Proteins