Cooperativity between Oxidants and Tumor Necrosis Factor in the Activation of Nuclear Factor (NF)-

The transcription factor nuclear factor (NF)k B 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)a to activate NFk B 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 I k Ba did not change after exposure to ROS/RNS, whereas a rapid depletion of I k Ba was observed in cells exposed to TNF. In addition, the proteosome inhibitor MG132 did not affect activation of NFk B by ROS/RNS, whereas it abolished the TNF response. Transfection of a dominant negative Ras construct prevented the activation of NFk B by ROS/RNS, demonstrating the requirement for Ras in the activation of NFk B by oxidants. In contrast, TNF activated NFk B 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 NFk B by both oxidants and TNF, whereas the MEK–ERK pathway negatively regulates NFk B. 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 NFk B–regulated genes important in the development of inflammatory diseases. Janssen-Heininger, Y. M. W., I. Macara, and B. T. Mossman. 1999. Cooperativity between oxidants and tumor necrosis factor in the activation of nuclear factor (NF) k B: requirement of Ras/mitogen-activated protein kinases in the activation of NFk B by oxidants. Am. J. Respir. Cell Mol. Biol. 20:942–952.