The involvement of L-gamma-glutamyl-L-cysteinyl-glycine (glutathione/GSH) in the mechanism of redox signaling mediating MAPK(p38)-dependent regulation of pro-inflammatory cytokine production.
Redox regulation of mitogen-activated protein kinase (MAPK(p38))-mediated pro-inflammatory cytokine production is not well characterized in the alveolar epithelium. It was hypothesized that the involvement of the MAPK(p38) pathway in regulating lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-alpha and interleukin-6 secretion is redox-sensitive and affected by NAC, an antioxidant and a precursor of glutathione, and L-buthionine-(S,R)-sulfoximine, an irreversible inhibitor of gamma-glutamylcysteine synthetase, the rate-limiting enzyme in GSH biosynthesis. Exposure of fetal alveolar type II epithelial cells to Escherichia coli-derived LPS induced, in a time-dependent manner, the phosphorylation/activation of MAPK(p38) (peak at 15min). In addition, LPS up-regulated the phosphorylation of MAPK(p38) in a dose-dependent manner. The effect of LPS on the MAPK(p38) pathway was associated with the activation of MAPK-activated protein kinase, which phosphorylated the small 27kDa heat-shock protein (Hsp27). LPS induced the phosphorylation of Hsp27 in a time- and dose-dependent manner. Selective blockage of the MAPK(p38) pathway by a pyridinyl-imidazole (SB-203580) abrogated LPS-induced release of TNF-alpha and IL-6. Pre-treatment with NAC reduced LPS-mediated secretion of TNF-alpha and IL-6. Incubation of cells with NAC induced intracellular accumulation of GSH, but reduced the concentration of GSSG. On the other hand, pre-treatment with BSO augmented LPS-mediated secretion of TNF-alpha and IL-6. In addition, BSO induced intracellular accumulation of GSSG, but reduced the concentration of GSH. Whereas NAC blocked the phosphorylation/activation of MAPK(p38), BSO amplified the LPS-mediated effect on MAPK(p38). These results indicated that intracellular redox signaling plays an important role in regulating LPS-induced activation of the MAPK(p38) pathway and MAPK(p38)-mediated regulation of LPS-dependent inflammatory cytokine production in the alveolar epithelium.
Haddad
John J
JJ
Oxygen Signaling Group, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Scotland, UK. jhaddad@itsa.ucsf.edu
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000096:biosynthesis; D019803:Glutathione Disulfide / Q000378:metabolism*; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D015850:Interleukin-6 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D000111:Acetylcysteine; D019328:Buthionine Sulfoximine; D016207:Cytokines; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D005978:Glutathione; D019803:Glutathione Disulfide; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D020928:Mitogen-Activated Protein Kinases; D009363:Neoplasm Proteins; D017346:Protein Serine-Threonine Kinases; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C486114:Hspb1 protein, rat