Synergistic expression of inducible nitric oxide synthase by phorbol ester and interferon-gamma is mediated through NF-kappaB and ERK in microglial cells.
A proinflammatory cytokine IFN-gamma stimulates microglia in the injured brain; however, signaling pathways for IFN-gamma-mediated microglia activation are not well characterized. In the present study, a protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) acts in concert with IFN-gamma to enhance nitric oxide (NO) production in murine microglial BV2 cells by synergistically increasing expression of inducible NO synthase (iNOS). The synergistic NO production by PMA was in part decreased by a PKC inhibitor Gö6976. PMA alone induced activation of nuclear factor-kappa B (NF-kappaB) and extracellular signal-regulated kinase (ERK) of mitogen-activated protein kinases (MAPKs) subtypes, whereas IFN-gamma alone had little effect. PMA and IFN-gamma synergistically enhanced activity of NF-kappaB, but not ERK. The inhibitors of NF-kappaB (pyrrolidine dithiocarbamate, PDTC) and ERK (1,4-diamino-2,3-dicyano-1,4 bis[2-aminophenylthio]butadiene; U0126) markedly decreased synergistic NO production in BV2 cells treated with IFN-gamma and PMA in combination. We found further that co-treatment with IFN-gamma and PMA synergistically induced interferon regulatory factor-1 (IRF-1), which is the major transcription factor for IFN-gamma-mediated iNOS expression. The present results demonstrate the cooperative interaction of multiple signaling pathways in the induction of NO production in activated microglial cells, and suggest that the functional interplay of these pathways may be important for the onset of microglia-mediated inflammatory responses in brain.
Han
Inn-Oc
IO
Research Institute, National Cancer Center, Goyang, Gyeonggi, Republic of Korea.
Kim
Hee-Sun
HS
Kim
Hyoung-Chun
HC
Joe
Eun-Hye
EH
Kim
Won-Ki
WK
D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D015151:Immunoblotting; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D010750:Phosphoproteins / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D016328:NF-kappa B; D010750:Phosphoproteins; D012333:RNA, Messenger; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate