Effect of theophylline on CD11b and L-selectin expression and density of eosinophils and neutrophils in vitro

The nonspecific phosphodiesterase inhibitor theophylline, widely used in asthma therapy, may cause a decrease in inflammatory responses of airways, In asthma, eosinophils migrate to the airway wall and become activated, Activated eosinophils are characterized by low cell density, as well as increased expression of CD11b and reduced expression of L-selectin, two adhesion molecules involved in transendothelial migration, To study the anti-inflammatory effect of theophylline on granulocyte adhesion molecules in vitro, the platelet-activating factor (PAF)-induced density shift was determined by density centrifugation and the modulation of CD11b and L-selectin expression by how cytometry on eosinophils and neutrophils in human whole blood, A relatively high concentration of theophylline (10(-3) M) inhibited the increase in the percentage of hypodense eosinophils and neutrophils in whole-blood samples after PAF stimulation in vitro. A more pharmacological concentration (10(-4) M) inhibited the CD11b upregulation and L-selectin shedding induced by PAF (10(-7) M) on both eosinophils and neutrophils. The effect of isoproterenol on the inhibitory effect of theophylline was mainly additive, but a small synergistic effect could not be excluded, In conclusion theophylline can attenuate eosinophil and neutrophil activation in vitro at the level of adhesion molecule expression and changes in cell density, This may have implications for transendothelial migration of these cells in asthma

Changes in CD11b and L-selectin expression on eosinophils are mediated by human lung fibroblasts in vitro

Eosinophilic airway infiltration is a central feature in asthma. Eosinophils recovered from bronchoalveolar fluid show an activated phenotype, e.g., increased CD11b and decreased L-selectin expression. We investigated whether lung fibroblasts are able to activate eosinophils in vitro, and if so, which activating factor is most important. CD11b and L-selectin expression of isolated peripheral blood eosinophils were measured by flow cytometry after coculture with normal lung fibroblasts or their conditioned medium. We found that eosinophil CD11b expression increased (154% and 210%, p <0.05) and L-selectin expression decreased (59% and 35.5%, p <0.05) on eosinophils compared with baseline (100%) after 4 and 24 h of coculture with interleukin-1-beta (IL-1 beta)-stimulated fibroblasts, respectively. Conditioned medium of stimulated fibroblasts also increased CD11b expression, but to a smaller extent (p <0.05). L-selectin expression of eosinophils in cocultures was not different from that of eosinophils in conditioned medium. Only anti-granulocyte/macrophage colony-stimulating factor (anti-GM-CSF) reduced the activation of eosinophils in conditioned medium to almost basal levels (p <0.05). An increase in CD11b expression is mediated by cytokines as well as direct cell contact, whereas a decrease in L-selectin expression is only mediated by cytokines. GM-CSF released by fibroblasts is an important factor in the modulation of both CD11b and L-selectin expression. These results show that lung fibroblasts can activate eosinophils by both adhesive interactions and by soluble factors