Reactive oxygen species and proinflammatory cytokine signaling in endothelial cells: effect of selenium supplementation.

The release of superoxide (O(2)(*-)) and hydrogen peroxide (H(2)O(2)), induced by tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1beta), has been studied in the endothelial cell line ECV 304 in the presence and absence of selenium (Se) supplementation. Both cytokines elicit the production of both species. Selenium supplementation, which increases Se-enzyme activity, decreases the amount of H(2)O(2) but not O(2)(*-) detectable in the extracellular medium. Inhibition of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by diphenyliodonium (DPI) or phenylarsine oxide (PAO), largely prevents O(2)(*-) production, whereas H(2)O(2) remains above the amount accounted for by disproportion of residual O(2)(*-). Thus, a fraction of H(2)O(2) found in the medium, derives from an intracellular pool, which is under control of selenium-dependent peroxidases. This is further supported by the observation that in Se-supplemented cells, the rate of intracellular glutathione (GSH) depletion induced by cytokine treatment is faster and more extensive. Because Se supplementation decreases cytokine-induced NF-kappaB activity, whereas added H(2)O(2) is inactive and catalase does not affect the activation induced by TNF-alpha, it is concluded that only intracellularly generated H(2)O(2) has a role in transcription factor activation by both TNF-alpha and IL-1beta.