Genomic and non-genomic effects of dexamethasone on equine peripheral blood neutrophils

• Published in: Veterinary immunology and immunopathology Vol. 128; no. 1-3; pp. 126 - 131
• Main Authors: Lecoq, L., Vincent, P., Lavoie-Lamoureux, A., Lavoie, J.-P.
• Format: Journal Article Web Resource
• Language: English
• Published: Netherlands Elsevier B.V 15.03.2009; Amsterdam: Elsevier; Elsevier BV
• Subjects: Animals; anti-inflammatory activity; Anti-Inflammatory Agents; Anti-Inflammatory Agents - pharmacology; biochemical mechanisms; Dactinomycin; Dactinomycin - pharmacology; Dexamethasone; Dexamethasone - pharmacology; Diffusion Chambers, Culture; Dose-Response Relationship, Drug; drug evaluation; drug therapy; Female; Flow-cytometry; gene expression; Gene Expression Profiling - veterinary; Gene Expression Regulation - drug effects; General Veterinary; Genomics; Glucocorticoids; horse diseases; horses; Horses - blood; Horses - genetics; Horses - immunology; IL-8; immune response; immune system; Immunology; inflammation; Life sciences; messenger RNA; Médecine vétérinaire & santé animale; neutrophils; Neutrophils - drug effects; normal values; receptors; respiratory tract diseases; RT-PCR; RU486; Sciences du vivant; synthetic glucocorticoids; Tetradecanoylphorbol Acetate; Tetradecanoylphorbol Acetate - pharmacology; transcriptional activation; Veterinary (all); Veterinary medicine & animal health; Glucocorticoids; IL-8; RU486; RT-PCR; Flow-cytometry
• ISSN: 0165-2427; 1873-2534; 1873-2534
• DOI: 10.1016/j.vetimm.2008.10.303

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. Dexamethasone (DEX), a potent synthetic glucocorticoid, inhibits the functions of equine peripheral blood neutrophils through both genomic and non-genomic effects. Six healthy adult mixed breed female horses. To assess the genomic effects of DEX, peripheral blood neutrophils were isolated using a gradient technique and incubated 6h with 100ng/ml LPS and 10−6M DEX alone, or combined with the glucocorticoid receptor (GR) inhibitor RU486 (10−5M). Messenger RNA for IL-8, TNF-α and TLR-4 were measured using real-time RT-PCR. The non-genomic effects of DEX were studied in neutrophils incubated with 5μM dichlorodihydrofluorescein (DCF) and 10−6M DEX 5, 10 and 15min prior to being stimulated with 5ng/ml phorbol myristate acetate. Neutrophils were similarly co-incubated with DEX (10−6M, 15min) and RU486 (10−5M) to evaluate the contribution of the GR to these effects. The oxidation of DCF was studied using flow-cytometry. Neutrophils stimulation with LPS resulted in a significant increase in IL-8, TNF-α 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 15min of incubation (p<0.0001). Those effects were mediated through the GRs. DEX exerts anti-inflammatory effects on equine peripheral blood neutrophils through both genomic and non-genomic pathways.