Reduction–oxidation (redox) state constitutes such a potential signaling mechanism for the regulation of an inflammatory signal associated with oxidative stress. Exposure of alveolar epithelial cells to ascending ΔpO₂ regimen±reactive oxygen species (ROS)-generating systems induced a dose-dependent release of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. Similarly, the Escherichia coli-derived lipopolysaccharide-endotoxin (LPS) up-regulated cytokine biosynthesis in a dose- and time-dependent manner. Irreversible inhibition of γ-glutamylcysteine synthetase, the rate-limiting enzyme in the biosynthesis of glutathione (GSH), by l-buthionine-(S,R)-sulfoximine (BSO), induced the accumulation of ROS and augmented ΔpO₂ and LPS-mediated release of cytokines. Analysis of the molecular mechanism implicated revealed an inhibitory-κB (IκB-α)/nuclear factor-κB (NF-κB)-independent pathway in mediating redox-dependent regulation of inflammatory cytokines. BSO stabilized cytosolic IκB-α and down-regulated its phosphorylation, thereby blockading NF-κB activation, yet it augmented cytokine secretion. Glutathione depletion is associated with the augmentation of oxidative stress-mediated inflammatory state in a ROS-dependent mechanism and the IκB-α/NF-κB pathway is redox-sensitive but differentially involved in regulating redox-dependent regulation of cytokines.