Inhibitor κB and Nuclear Factor κB in Granulocyte‐Macrophage Colony‐Stimulating Factor Antagonism of Dexamethasone Suppression of the Macrophage Response toAspergillus fumigatusConidia

Abstract

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 kB (IkB) induction by DEX and is opposed by acceleration of IkB degradation by GM-CSF with or without conidia stimulation, with corresponding effects on translocation and activation of nuclear factor kB (NF-kB).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. IkB degradation and NF-kB activation were assessed by Western blot.Results. Macrophages stimulated with conidia alone increased NF-kB translocation. DEX increased IkB levels in cytoplasm and blocked translocation of NF-kB to the nucleus in unstimulated and conidia-stimulated macrophages. Conversely, GM-CSF decreased IkB levels. GM-CSF reversed the effect of DEX on IkB levels. NF-kB levels were minimal in DEX-treated macrophage nuclear extracts, compared with those from GM-CSF-treated and GM-CSF plus DEX-treated macrophages.Conclusion. GM-CSF can reverse the DEX immunosuppressive effect by enhancing IkB degradation and promoting NF-kB translocation. This would allow macrophage production of proinflammatory cytokines, facilitating resistance to aspergillosis.

Reduced Nicotinamide Adenine Dinucleotide Phosphate Oxidase-Independent Resistance to Aspergillus fumigatus in Alveolar Macrophages

“…3, network C). Our Ingenuity analysis results support the importance of NF-B in aspergillosis immunity, as reduced nuclear NF-B translocation in macrophages was previously implicated in increased susceptibility to infection following dexamethazone treatment (54), and in sepsis (55). Our data are also consistent with a role for both NF-B and p38 MAPK in dendritic cells following contact with A. fumigatus (56).…”

CD4+T Cells Mediate the Protective Effect of the Recombinant Asp f3-Based Anti-Aspergillosis Vaccine

“…For vaccinated immunosuppressed animals, the inhibited effector cell could receive a strong local stimulus (cytokines) delivered by a fungus-recognizing, vaccine-primed CD4 ϩ T cell. Similarly, it was shown that treatment with granulocyte macrophage colony-stimulating factor can reverse the immunosuppressive effect of dexa- methasone by enhancing degradation of IB (14). A T-cellderived cytokine stimulus such as IFN-␥ could likewise lead to activation of IB kinases (IKK) in the effector cell (45), to an extent that even increased numbers of corticosteroid-induced IB molecules become sufficiently phosphorylated and degraded.…”

Immunomodulation Therapy for Invasive Aspergillosis: Discussion on Myeloid Growth Factors, Recombinant Cytokines, and Antifungal Drug Immune Modulation

“…Interestingly, cortisone acetate leads to longer (7 days) macrophage suppression, compared with approximately 4 days of suppression noted with dexamethasone [37]. GM-CSF restores steroid-induced loss of antifungal microconidia activity by augmenting proinflammatory cytokine production by alveolar macrophages [37] and by enhanced degradation of inhibitor kappa B and by relegating nuclear factor kappa B translocation [38]. Similarly, mononuclear cell response to fungal hyphal damage is abrogated by dexamethasone treatment; GM-CSF can reverse this effect by supplementing superoxide anion release and monocytemacrophage-assisted damage to Aspergillus fumigatus hyphae [39,40].…”

“…Furthermore, dexamethasone has been show to compromise macrophage antifungal activity by induction of inhibitor kappa B and via blocking translocation and activation of nuclear factor kappa B [38]. Interestingly, cortisone acetate leads to longer (7 days) macrophage suppression, compared with approximately 4 days of suppression noted with dexamethasone [37].…”