c-Jun N-terminal kinases (JNKs) mediate pro-inflammatory actions of microglia.
The activation and function of c-Jun N-terminal kinases (JNKs) were investigated in primary microglia cultures from neonatal rat brain, which express all three JNK isoforms. Lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), and thrombin preparations induced a rapid and lasting activation of JNKs in the cytoplasm. In the nucleus, the activation patterns were rather complex. In untreated microglia, the small pool of nuclear JNKs was strongly activated, while the high-affinity JNK substrate c-Jun was only weakly phosphorylated. Stimulation with LPS increased the total amount of nuclear JNKs and the phosphorylation of the transcription factor c-Jun. Levels of activated JNKs in the nucleus, however, rapidly decreased. Analysis of the nuclear JNK isoforms revealed that the amount of JNK1 declined, while JNK2 increased, and the weakly expressed JNK3 did not vary. This observation suggests that JNK2 is mainly responsible for the activation of c-Jun in this context. Upstream of JNKs, LPS induced a lasting activation of the constitutively present JNK kinase MKK4. The function of JNKs in LPS-triggered cellular reactions was investigated using SP600125 (0.5-5 microM), a direct inhibitor of JNKs. Inhibition of JNKs reduced the LPS-induced metabolic activity and induction of the AP-1 target genes cyclooxygenase-2 (Cox-2), TNF-alpha, monocyte chemoattractant protein-1 (MCP-1), and interleukin-6 (IL-6) in response to LPS, while ERK1/2 and p38 alpha had a more pronounced effect on LPS-induced cellular enlargement than JNKs. In summary, JNKs are essential mediators of relevant pro-inflammatory functions in microglia with different contributions of the JNK isoforms.
Waetzig
Vicki
V
Institute of Pharmacology, University Hospital Kiel, 24105 Kiel, Germany.
Czeloth
Karen
K
Hidding
Ute
U
Mielke
Kirsten
K
Kanzow
Moritz
M
Brecht
Stephan
S
Goetz
Mario
M
Lucius
Ralph
R
Herdegen
Thomas
T
Hanisch
Uwe-Karsten
UK
D000818:Animals; D000831:Animals, Newborn; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000201:enzymology; D004660:Encephalitis / Q000139:chemically induced / Q000201:enzymology* / Q000503:physiopathology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism / Q000494:pharmacology; D005911:Gliosis / Q000139:chemically induced / Q000201:enzymology* / Q000503:physiopathology; D018836:Inflammation Mediators / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D017628:Microglia / Q000187:drug effects / Q000201:enzymology*; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D013917:Thrombin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000494:pharmacology
D018925:Chemokines; D004791:Enzyme Inhibitors; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D016755:Proto-Oncogene Proteins c-jun; D014409:Tumor Necrosis Factor-alpha; D048056:Mitogen-Activated Protein Kinase 9; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048055:Mitogen-Activated Protein Kinase 8; D048051:p38 Mitogen-Activated Protein Kinases; D013917:Thrombin