Glucocorticiod And Glucocorticiod Cytosolic Receptors Antagonist Effect On The Trend Of Apoptotic Eosinophils.

Backround:Eosinophils are the major effector cells in the pathophysilogy of bronchial asthma, which are associated with airway inflammation, airway remolding, and airway hyperresponsiveness of asthma, so eliminating eosinophils is crucial to the control of airway inflammation. Researches indicated that eosinophils could be recognized and ingested as intact cells by macrophage or airway epithelial cells after apoptosis, which play an important role in the resolution of inflammation in the asthmatic lung for preventing release of inflammatory mediators and cytotoxic substances from eosinophils. Recently researches have represented glococorticoids not only can accelerate the eosinophils apoptosis, but also could improve airway epithelial cell englufing apoptotic eosinophils, which may represent a potential therapeutic target in the control of asthmatic inflammation, However, little is known of the pathways. Phagocytosis of apoptptic cells not only effectively dispose of inflammatory cells, but also can degrade inflammatory state of phagocyte. In macrophages, apoptotic cell uptake prevents the release of pro-inflammatory mediators, and promotes the release of anti-inflammtory cytokines. Whether epithelial cells, like macrophages, can be degrade inflammatory cytokines secretory after engulfing apoptotic eosinophils is deserved to more discussion.Objective:To investigate the effects of glucocorticoid and glucocorticoid cytosolic receptors antagonist RU38486 on the phagocytosis of apoptotic eosinophils by A549 cells,and the time character of the effect of glucocorticoid ; Also to observe the change of releasing IL-6 and IL-8 from A549 cell after phagocytosis of apoptotic eosinophils.Methods :CD15 positive eosinophils were seperated from normal human peripheral vein blood by magneticactivated separation column. After cultured for 48 hours, eosinophils were assessed for apoptosis by morphological assessment and binding of annexin V-FITC. apoptotic eosinophils were added to A549 cells which was pretreated with dexamethasone or RU38486 for engulfment .After engulfment apoptotic eosinophils were stained for peroxidase with o-dianisidine and A549 cells were stained with haematoxylin. Inverted microscope of Olympus and Digital Photography frame Grabber of Diagnostic Instruments-Spot insight were used to observe dynamic engulfment phenomena. Calculate the ratio of engulfment under the light microscope with the cells which were be fixed and stained. IL-6 and IL-8 in the supernatant from A549 cells were measured using radioimmunoassay kit.Results:1 ) The capacity of engulfment of A549 cells started enhancing at the 1h of preincubation with dexamethasone, reached the highest at the 4h of preincubation,At the 8h,24h of preincubation the capacity of engulfment evidently reduced.2 ) Glucocorticoid cytosolic receptors antagonist RU38486 inhibited the improved engulfment ability by dexamethasone.3)Phagocytosing apoptotic eosinophils did not change the release of IL-6 and IL-8,but can inhibited the release of IL-6 and IL-8 from A549 cells stimulated by lipopolysaccharide.4)Increasely uptaking by dexamethasone also did not agitate the release of IL-6 and IL-8 from A549 cells. Conclusion:1)Dexamethasome improve the phagocyte capacity for apoptotic eosinophils of A549 cells by glucocorticoid cytosolic receptors, and the effect presents time-dependently.2)Phagocytosis of apoptotic eosinphils can degrade inflammatory reflection, so it is likely to be critical in the control of asthma inflammation.