The Nrf2-inducible antioxidant defense in astrocytes can be both up- and down-regulated by activated microglia:Involvement of p38 MAPK.

• 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.

Nyckelord

Analysis of Variance

Animals

Animals

Newborn

Astrocytes

cytology

drug effects

immunology

metabolism

Blotting

Western

Cell Survival

physiology

Cells

Cultured

Cerebral Cortex

cytology

drug effects

metabolism

Culture Media

Conditioned

Down-Regulation

drug effects

physiology

Extracellular Signal-Regulated MAP Kinases

metabolism

Glutathione

metabolism

Hydroquinones

pharmacology

JNK Mitogen-Activated Protein Kinases

metabolism

Microglia

cytology

drug effects

immunology

metabolism

NF-E2-Related Factor 2

metabolism

Oxidative Stress

drug effects

physiology

Rats

Rats

Sprague-Dawley

Up-Regulation

drug effects

physiology

p38 Mitogen-Activated Protein Kinases

metabolism

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