Regulation of nuclear factor-kappa B, activator protein-1, and glutathione levels by tumor necrosis factor-alpha and dexamethasone in alveolar epithelial cells.
The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensitive transcription factors such as nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1), which regulate the genes for proinflammatory mediators and protective antioxidant genes. GSH, a ubiquitous tripeptide thiol, is a vital intra- and extracellular protective antioxidant against oxidative stress, which plays a key role in the control of proinflammatory processes in the lungs. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS), which consists of a catalytic heavy and a regulatory light subunit. The promoter regions of the human gamma-GCS subunits contain AP-1, NF-kappa B, and antioxidant response elements and are regulated by oxidants, growth factors, inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), and anti-inflammatory agent (dexamethasone) in lung cells. TNF-alpha depletes intracellular GSH, concomitant with an increase in oxidised glutathione levels in alveolar epithelial cells. TNF-alpha also induces the activation of NF-kappa B and AP-1 and the subsequent increase in gamma-GCS heavy subunit transcription in these cells. Dexamethasone depleted both basal and TNF-alpha-stimulated GSH levels by down-regulating the gamma-GCS-heavy subunit transcription via a mechanism involving AP-1 (c-Jun). The existence of this fine tuning between the redox GSH levels and the activation of transcription factors may determine the balance of transcription for proinflammatory and antioxidant gamma-GCS genes in inflammation. More studies are required to understand the signalling mechanism of the redox regulation of NF-kappa B and AP-1 and gene transcription in inflammation. This could lead to the development of therapeutic strategies based on the pharmacological manipulation of the production of this important antioxidant in inflammation.
Rahman
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Elegi and Colt Research Laboratories, Department of Respiratory Medicine, University of Edinburgh, Edinburgh EH8 9AG Scotland, Scotland, UK. ir@srvl.med.ed.ac.uk
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology*; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008171:Lung Diseases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione