1. Redox/ROS regulation of lipopolysaccharide-induced mitogen-activated protein kinase (MAPK) activation and MAPK-mediated TNF-alpha biosynthesis.
- Author
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Haddad JJ and Land SC
- Subjects
- Acetylcysteine pharmacology, Animals, Culture Techniques, Dose-Response Relationship, Drug, Enzyme Activation, Female, Glutathione metabolism, Intracellular Signaling Peptides and Proteins, Mitogen-Activated Protein Kinases antagonists & inhibitors, Mitogen-Activated Protein Kinases physiology, Oxidation-Reduction, Phosphorylation drug effects, Pregnancy, Protein Serine-Threonine Kinases metabolism, Pulmonary Alveoli cytology, Pulmonary Alveoli drug effects, Pulmonary Alveoli enzymology, Rats, Rats, Sprague-Dawley, Signal Transduction drug effects, p38 Mitogen-Activated Protein Kinases, Lipopolysaccharides pharmacology, Mitogen-Activated Protein Kinases metabolism, Reactive Oxygen Species metabolism, Tumor Necrosis Factor-alpha biosynthesis
- Abstract
Redox and ROS regulation of MAPK-mediated TNF-alpha biosynthesis is not well characterized. It was hypothesized that the involvement of the MAPK pathway in regulating LPS-mediated TNF-alpha secretion is redox-dependent, NF-kappaB-sensitive and attenuated by N-acetyl-L-cysteine (NAC) and other antioxidants. In alveolar epithelial cells, LPS induced a time- and dose-dependent phosphorylation of MAPK(p38). This was associated with the activation of MAPK-activated protein kinase, which phosphorylated the small heat-shock protein, Hsp27. MAPK(p38) inhibition (SB-203580) abrogated LPS-induced TNF-alpha production. MAPK(ERK) blockade (PD-98059) attenuated TNF-alpha secretion, an effect synergistically amplified in the presence of SB-203580. Regulation of NF-kappaB by selective inhibitors revealed that this pathway is partially involved in regulating LPS-mediated TNF-alpha secretion. Whereas the proteasome inhibitor, MG-132, had no effect on LPS-mediated TNF-alpha production, CAPE, sulfasalazine and SN-50, a cell-permeant NF-kappaB inhibitor, attenuated but did not abrogate TNF-alpha biosynthesis. LPS up-regulated ROS, an effect abrogated by 4'-hydroxy-3'-methoxy-acetophenone and NAC, which reduced TNF-alpha secretion, induced the accumulation of GSH, reduced the concentration of GSSG, and blockaded the phosphorylation/activation of MAPK(p38) pathway. ROS induced MAPK(p38) phosphorylation and selective antioxidants, including the permeant GSH precursor, gamma-GCE, reduced ROS-dependent MAPK(p38) phosphorylation. These results indicate that the MAPK pathway and MAPK-mediated regulation of TNF-alpha production is redox-dependent, GSH-mediated and requires, at least in part, a NF-kappaB/ROS-sensitive mechanism.
- Published
- 2002
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