title: The Nrf2-inducible antioxidant defense in astrocytes can be both up- and down-regulated by activated microglia:Involvement of p38 MAPK.
abstract: The effects of microglia-conditioned medium (MCM) on the inducible Nrf2 system in astrocyte-rich cultures were investigated by determination of glutathione (GSH) levels, γglutamylcysteine ligase (γGCL) activity, the protein levels of Nrf2, Keap1, the modulatory subunit of γGCL (γGCL-M) and activated MAP kinases (ERK1/2, JNK and p38). Microglia were either cultured for 24 h in serum-free culture medium to achieve microglia-conditioned medium from non-activated cells (MCM(0) ), used as control condition, or activated with different concentrations (0.1-1,000 ng mL(-1) ) of lipopolysaccharide (LPS) to produce MCM(0.1-1,000) . Acute exposure (24 h) to MCM(100) increased GSH, γGCL activity, the protein levels of γGCL-M, Nrf2, and activated JNK and ERK1/2 in astrocyte-rich cultures. In contrast, treatment with MCM(10) for 24 h decreased components of the Nrf2 system in parallel with activation of p38 MAPK. Stimulation of the Nrf2 system by tBHQ was partly intact after 24 h but blocked after 72 h treatment with MCM(10) and MCM(100) . This down-regulation after 72 h correlated with activation of p38 MAPK and lack of ERK1/2 and JNK activation. The negative effects were partly reversed by an inhibitor of p38 which restored tBHQ mediated protection against oxidative stress. In conclusion, the study showed a negative effect of MCM(10) on the inducible anti-oxidant defense in astrocyte-rich cultures at both 24 and 72 h that correlated with activation of p38 and was partly reversed by a p38 inhibitor. A transient protective effect of MCM(100) on astrocyte-rich cultures against H(2)O(2) toxicity was observed at 24 h which coincided with activation of JNK and ERK1/2.
authors.affiliation: Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, University of Gothenburg, Sweden. Fernando.correa@medkem.gu.se
authors.forename: Fernando
authors.initials: F
authors.lastname: Correa
authors.forename: Elin
authors.initials: E
authors.lastname: Ljunggren
authors.forename: Carina
authors.initials: C
authors.lastname: Mallard
authors.forename: Michael
authors.initials: M
authors.lastname: Nilsson
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Weber
authors.forename: Mats
authors.initials: M
authors.lastname: Sandberg
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D015153:Blotting, Western; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017077:Culture Media, Conditioned; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D006873:Hydroquinones; D051267:NF-E2-Related Factor 2; C018855:2-tert-butylhydroquinone; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005978:Glutathione