Inhibitor kappaB and nuclear factor kappaB in granulocyte-macrophage colony-stimulating factor antagonism of dexamethasone suppression of the macrophage response to Aspergillus fumigatus conidia.
BACKGROUND
The dexamethasone (DEX) immunosuppressive effect on macrophage killing activity and cytokine production in response to Aspergillus fumigatus conidia is antagonized by granulocyte-macrophage colony-stimulating factor (GM-CSF). The molecular mechanism is unknown. We postulated that this antagonism is mediated by inhibitor kappaB (I kappaB) induction by DEX and is opposed by acceleration of I kappaB degradation by GM-CSF with or without conidia stimulation, with corresponding effects on translocation and activation of nuclear factor kappa B (NF-kappaB).


METHODS
We studied 2 types of cells, resident peritoneal macrophages from CD-1 mice and the murine macrophage RAW264.7 cell line. Cells were unstimulated or stimulated with conidia and simultaneously treated with DEX, GM-CSF, or DEX plus GM-CSF, for 2-4 hours. I kappaB degradation and NF-kappaB activation were assessed by Western blot.


RESULTS
Macrophages stimulated with conidia alone increased NF-kappaB translocation. DEX increased I kappaB levels in cytoplasm and blocked translocation of NF-kappaB to the nucleus in unstimulated and conidia-stimulated macrophages. Conversely, GM-CSF decreased I kappaB levels. GM-CSF reversed the effect of DEX on I kappaB levels. NF-kappaB levels were minimal in DEX-treated macrophage nuclear extracts, compared with those from GM-CSF-treated and GM-CSF plus DEX-treated macrophages.


CONCLUSIONS
GM-CSF can reverse the DEX immunosuppressive effect by enhancing I kappaB degradation and promoting NF-kappaB translocation. This would allow macrophage production of proinflammatory cytokines, facilitating resistance to aspergillosis.
Choi
Jung-Hyun
JH
California Institute for Medical Research, San Jose, USA.
Brummer
Elmer
E
Kang
Young Jun
YJ
Jones
Patricia P
PP
Stevens
David A
DA
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D001228:Aspergillosis / Q000276:immunology* / Q000382:microbiology; D001232:Aspergillus fumigatus / Q000276:immunology*; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D003907:Dexamethasone / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D052002:NF-kappa B p50 Subunit / Q000032:analysis / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D013172:Spores, Fungal / Q000276:immunology
D000893:Anti-Inflammatory Agents; D003907:Dexamethasone; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D047908:Intracellular Signaling Peptides and Proteins; D052002:NF-kappa B p50 Subunit; D011506:Proteins; C454819:Nfkbid protein, mouse; C073701:Nfkb1 protein, mouse