Effects of glucocorticoids on the airways.

Glucocorticoids can affect every stage of inflammatory and immunological reactivity. They influence the movement and distribution of lymphocytes, neutrophils and eosinophils in quite low concentrations and decrease the accumulation of these cells at inflammatory sites. The functional capabilities of these cells are relatively resistant to steroids. Steroids also inhibit the leakage of fluid and cells from capillary beds. Glucocorticosteroids have recently been shown to stimulate the synthesis of a protein called lipomodulin or macrocortin, which inhibits the activity of phospholipase A2. As a consequence of this effect the phospholipid methylation in the cell membrane is inhibited, as is the arachidonic acid cascade. This decreases neutrophil and macrophage chemotaxis, histamine release from mast cells and basophils as well as bronchospasm and inflammatory oedema mediated by leukotrienes.