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Redox/ROS regulation of lipopolysaccharide-induced mitogen-activated protein kinase (MAPK) activation and

J J Haddad1, S C Land

  • 1Oxygen Signalling Group, Centre for Research into Human Development, Tayside Institute of Child Health, Faculty of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY. haddadj@anesthesia.ucsf.edu

British Journal of Pharmacology
|January 30, 2002
PubMed

Insights

Reactive oxygen species (ROS) and glutathione (GSH) regulate mitogen-activated protein kinase (MAPK)-mediated tumor necrosis factor-alpha (TNF-alpha) production. Antioxidants and GSH modulate this pathway, impacting inflammatory responses.

Area of Science:

  • Cellular Biology
  • Immunology
  • Biochemistry

Background:

  • Tumor necrosis factor-alpha (TNF-alpha) plays a crucial role in inflammatory responses.
  • The precise mechanisms regulating TNF-alpha biosynthesis, particularly the involvement of mitogen-activated protein kinase (MAPK) pathways and redox status, remain incompletely understood.

Purpose of the Study:

  • To investigate the role of redox regulation and reactive oxygen species (ROS) in MAPK-mediated TNF-alpha production.
  • To determine the involvement of the NF-kappaB pathway in lipopolysaccharide (LPS)-induced TNF-alpha secretion.
  • To elucidate the impact of antioxidants on these pathways.

Main Methods:

  • Utilized alveolar epithelial cells stimulated with LPS.
  • Employed specific inhibitors for MAPK pathways (SB-203580 for p38, PD-98059 for ERK) and NF-kappaB.
  • Assessed protein phosphorylation, TNF-alpha secretion, ROS levels, and glutathione (GSH/GSSG) concentrations.
  • Investigated the effects of antioxidants like N-acetyl-L-cysteine (NAC) and gamma-glutamylcysteine (gamma-GCE).

Main Results:

  • LPS induced time- and dose-dependent phosphorylation of MAPK(p38) and subsequent TNF-alpha production, which was abrogated by p38 inhibition.
  • MAPK(ERK) blockade attenuated TNF-alpha secretion, with synergistic effects when combined with p38 inhibition.
  • NF-kappaB pathway was partially involved, as indicated by attenuation of TNF-alpha by specific inhibitors (CAPE, sulfasalazine, SN-50).
  • LPS upregulated ROS, which was reduced by antioxidants (NAC, 4'-hydroxy-3'-methoxy-acetophenone).
  • Antioxidants reduced TNF-alpha secretion, increased GSH, decreased GSSG, and blocked MAPK(p38) phosphorylation.
  • ROS directly induced MAPK(p38) phosphorylation, and antioxidants, including gamma-GCE, reduced this effect.

Conclusions:

  • The MAPK pathway and its regulation of TNF-alpha production are redox-dependent.
  • Glutathione (GSH) plays a critical role in mediating these redox-dependent processes.
  • A NF-kappaB/ROS-sensitive mechanism is partially involved in LPS-mediated TNF-alpha secretion.

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