Genomic and non-genomic effects of dexamethasone on equine peripheral blood neutrophils.
BACKGROUND
Glucocorticoids have potent anti-inflammatory properties and are frequently used for the treatment of domestic animal species, including horses. They induce a down-regulation of multiple inflammatory pathways through both genomic and non-genomic effects. Currently, little is known on the effects of glucocorticoids on equine peripheral blood neutrophils.


OBJECTIVE
Dexamethasone (DEX), a potent synthetic glucocorticoid, inhibits the functions of equine peripheral blood neutrophils through both genomic and non-genomic effects.


METHODS
Six healthy adult mixed breed female horses.


METHODS
To assess the genomic effects of DEX, peripheral blood neutrophils were isolated using a gradient technique and incubated 6 h with 100 ng/ml LPS and 10(-6) M DEX alone, or combined with the glucocorticoid receptor (GR) inhibitor RU486 (10(-5) M). Messenger RNA for IL-8, TNF-alpha and TLR-4 were measured using real-time RT-PCR. The non-genomic effects of DEX were studied in neutrophils incubated with 5 microM dichlorodihydrofluorescein (DCF) and 10(-6) M DEX 5, 10 and 15 min prior to being stimulated with 5 ng/ml phorbol myristate acetate. Neutrophils were similarly co-incubated with DEX (10(-6) M, 15 min) and RU486 (10(-5) M) to evaluate the contribution of the GR to these effects. The oxidation of DCF was studied using flow-cytometry.


RESULTS
Neutrophils stimulation with LPS resulted in a significant increase in IL-8, TNF-alpha and TLR-4 mRNA expressions (p<0.0001); incubation with DEX significantly down-regulated this process (p<0.0001). DEX significantly reduced oxidation of DCF after 10 and 15 min of incubation (p<0.0001). Those effects were mediated through the GRs.


CONCLUSIONS
DEX exerts anti-inflammatory effects on equine peripheral blood neutrophils through both genomic and non-genomic pathways.
Lecoq
L
L
Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, 3200 Sicotte, Saint-Hyacinthe, Québec, Canada J2S 7C6.
Vincent
P
P
Lavoie-Lamoureux
A
A
Lavoie
J-P
JP
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D015194:Diffusion Chambers, Culture; D004305:Dose-Response Relationship, Drug; D005260:Female; D020869:Gene Expression Profiling / Q000662:veterinary*; D005786:Gene Expression Regulation / Q000187:drug effects*; D023281:Genomics; D006736:Horses / Q000097:blood* / Q000235:genetics / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000893:Anti-Inflammatory Agents; D003609:Dactinomycin; D003907:Dexamethasone; D013755:Tetradecanoylphorbol Acetate