Induction of phospholipid hydroperoxide glutathione peroxidase in human polymorphonuclear neutrophils and HL60 cells stimulated with TNF-α

Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is characterized as an important enzyme for protecting cells from oxidative stress-induced apoptosis and regulating the production of leukotrienes and prostanoids in cells overexpressing PHGPx. We studied whether the expression level of PHGPx fluctuates in polymorphonuclear leukocytes (PMNs) which were exposed to reactive oxygen species (ROS) and inflammatory cytokines at an inflammation site. Human peripheral PMNs up-regulated the expression level of PHGPx following culture with TNF-α, but not with IL-1β, IL-8, and GRO. The up-regulated PHGPx expression was also observed in neutrophil-like cells that differentiated from the human leukemia cell line HL60 only after stimulation with TNF-α. However, macrophage-like differentiated HL60 cells and other cell lines, A498, ECV304, HeLa, U937, and HEK293, showed no increase in the PHGPx expression. This up-regulation of PHGPx was inhibited by treatment with the anti-oxidants, pyrrolidine dithiocarbamate, and N-acetyl-l-cysteine, and by inhibitors of NFκB and Src kinases. The stimulation of neutrophil-like differentiated HL60 cells with TNF-α induced activation of NFκB and c-Src kinase, and the activation was attenuated by treatment with the anti-oxidants. Up-regulation in neutrophil-like HL60 cells was also observed following exposure to H2O2. These results indicate that activation of NFκB and/or Src kinases through ROS signaling may be involved in the up-regulation of the PHGPx in human PMNs stimulated by TNF-α.