Regulation of L-selectin and CD18 on bovine neutrophils by glucocorticoids: effects of cortisol and dexamethasone

Abstract

The responsiveness of bovine neutrophil L-selectin and CD18 to in vivo glucocorticoid administration was characterized by flow cytometric analysis. Blood was sampled intensively from dairy cows treated for 3 days with placebo, cortisol, or dexamethasone. Immunostaining was performed on whole blood (100 microliters) that was left unstimulated or was stimulated with platelet-activating factor (PAF; 1 microgram/ml blood) prior to incubation with fluorescein isothiocyanate-conjugated monoclonal antibodies against L-selectin and CD18. Results were expressed as the percentage of positive-staining cells and as mean fluorescence intensity (MFI) of those cells. Total leukocyte count and leukocyte differentials were also performed on all blood samples. Dexamethasone caused nearly complete down-regulation of L-selectin (P < .01) on the surface of gated cells and reduced to half the MFI of CD18 (P < .01). Compared with values for the placebo group, dexamethasone began to cause L-selectin down-regulation within 8 h after the first injection and these effects persisted until 48 h after the third injection. This was correlated in time with an acute reduction in the proportion of cells that stained positive for L-selectin (from 98% before dexamethasone injections to a low of 17% by 40 h after the first injection). Dexamethasone also caused leukocytosis and neutrophilia during this time interval. In contrast, CD18 down-regulation was delayed until 16 h after the second dexamethasone injection and persisted for roughly 8 days. However, at no time during the experiment did dexamethasone influence the proportion of gated cells staining positive for CD18 (always 100%). Effects of cortisol were generally similar in pattern to those of dexamethasone but were more subtle and more readily detected when PAF was added to blood prior to immunostaining. These results strongly suggest that one mechanism of the anti-inflammatory action of glucocorticoids is to induce dramatic down-regulation of L-selectin and CD18 adhesion molecules on blood neutrophils.

Evaluation of L-selectin expression and assessment of protein tyrosine phosphorylation in bovine polymorphonuclear neutrophil leukocytes around parturition

“…Treatment with dexamethasone and cortisol resulted in down-regulation of membrane bound L-selectin [4] on resting and activated PMN. Burton and Kehrli [3] also observed that glucocorticoidmediated down regulation of membrane bound L-selectin and CD18 on PMN increased mammary gland susceptibility to Staphylococcus aureus following experimental challenge.…”

Effect of Corticosteroids and Neuropeptides on the Expression of Defensins in Bovine Tracheal Epithelial Cells

“…The effects of dexamethasone on bovine neutrophil function are generally thought to be immunosuppressive: reducing phagocytosis (36), antibody-dependent cell-mediated cytotoxicity (36,38), and generation of reactive-oxygen species (25,36,38). In particular, dexamethasone downregulates neutrophil cell surface expression of the adhesion molecule L-selectin (CD62L) (7,25) and the ␤ 2 -integrin CD18 (7), which should intuitively reduce neutrophil extravasation. Conversely, there is evidence that dexamethasone enhances chemotactic ability, as neutrophils taken from dexamethasone-treated cattle show increased migration to C5a and IL-8 (1).…”

The effects of a single injection of dexamethasone-21-isonicotinate on the lymphocyte functions of dairy cows at two weeks post partum

“…Decreased margination of neutrophils might be caused by the recognized ability of corticosteroids to reduce neutrophil adhesion to the vascular endothelium. This effect is well explained by the decreased expression of adhesion molecules of the L-selectin and β 2 -integrin (CD18) families on neutrophils [7,9,23] in combination with the inhibition of the expression of endothelial-leukocyte adhesion molecule 1 (ELAM-1) and intercellular adhesion molecule 1 (ICAM-1) [12]. Although these changes impair neutrophil migration kinetics, which increase susceptibility to infectious diseases, such as bovine mastitis, they require additional immunological investigations.…”

“…Glucocorticosteroids have been shown to cause leukocytosis involving neutrophilia and lymphopenia [36], suppression of leukocyte blastogenesis [26,30,33] and to change T-lymphocyte subpopulation patterns [2,8,16]. The increase in the number of circulating neutrophils following the administration of glucocorticosteroids has been well explained by the down-regulation of L-selectin and adhesion molecules of the β2-integrin family on these cells, resulting in an impaired ability of neutrophils to leave the circulation [9,23]. In addition, an increased release of neutrophils from bone marrow has been observed following the administration of corticosteroids [32].…”