A proteomic analysis of bovine blood neutrophils after administration of dexamethasone

Glucocorticoids downregulate several neutrophil functions in cattle, although the molecular mechanisms remain incompletely understood. In bovine neutrophils cultured for 18 hours, 10-6 M dexamethasone reduced oxidative burst and CD18 expression. The culture conditions were subsequently used to study the effects of dexamethasone on the proteins of bovine neutrophils in vitro. Dexamethasone administration altered amounts of 22 of 355 neutrophil proteins visible by 2D electrophoresis. In four calves treated in vivo with 1mg/kg dexamethasone sodium phosphate, 22 of the 193 proteins were altered in whole cell lysates. Dexamethasone treatment was associated with downregulation of phospholipase A2, cathelicidin 1, and annexin 1, in addition to upregulation of beta-adrenergic receptor kinase 2 and purine nucleoside phosphorylase. These findings suggest that glucocorticoids might be immunomodulatory in part by altering amounts of various functional proteins.