title: NADPH oxidase-derived superoxide destabilizes lipopolysaccharide-induced interleukin 8 mRNA via p38, extracellular signal-regulated kinase mitogen-activated protein kinase, and the destabilizing factor tristetraprolin.
abstract: Expression of inflammatory cytokines is regulated by transcriptional and posttranscriptional mechanisms. We previously showed that NADPH oxidase-derived superoxide induces inflammatory mediators in response to tumor necrosis factor α (TNF-α) and lipopolysaccharide (LPS). In this study, we examined the role of endothelial NADPH oxidase in the regulation of mRNA stability of three inflammatory mediators: interleukin (IL) 8, IL-6, and intercellular adhesion molecule 1 (ICAM-1). Tumor necrosis factor α increased mRNA stability of ICAM-1, IL-8, and IL-6 by a p38 mitogen-activated protein kinase (MAPK)-dependent mechanism, but this did not involve NADPH oxidase. Surprisingly, whereas LPS treatment alone did not alter stability of these molecules, the antioxidant N-acetyl-L-cysteine; the flavine inhibitor diphenylene iodonium; short interfering RNA against Nox2, Nox4; and the p22(phox) subunit of NADPH oxidase all enhanced IL-8 mRNA stability in LPS-treated cells, indicating that LPS induced destabilization through NADPH oxidase. This occurred by a mechanism that involved extracellular signal-regulated kinase 1/2, p38 MAPK, and the mRNA-destabilizing factor tristetraprolin. On the other hand, N-acetyl-L-cysteine decreased mRNA stability of ICAM-1 and IL-6 in LPS-treated cells and IL-6 and ICAM-1 in TNF-α-treated cells. In conclusion, NADPH oxidase contributes to destabilization of IL-8 mRNA stability and propose a model for the complex underlying mechanism, which is dependent upon agonist (LPS vs. TNF-α) and target molecule (IL-8 vs. IL-6 and ICAM-1) and involves tristetraprolin, p38, and extracellular signal-regulated kinase 1/2 MAPK.
authors.affiliation: Critical Care Division, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Imad
authors.initials: I
authors.lastname: Al Ghouleh
authors.forename: Sheldon
authors.initials: S
authors.lastname: Magder
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D016209:Interleukin-8 / Q000235:genetics*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D019255:NADPH Oxidases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013481:Superoxides / Q000378:metabolism*; D051816:Tristetraprolin / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D016209:Interleukin-8; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D051816:Tristetraprolin; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D018799:Intercellular Adhesion Molecule-1; D019255:NADPH Oxidases; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases