The effects of anti-asthma drugs on the phagocytic clearance of apoptotic eosinophils by A549 cells

SummaryBackgroundPhagocytic clearance of apoptotic eosinophils plays an important role in the successful resolution of asthmatic inflammation. To our knowledge, there is limited information available on the effects of anti-asthma drugs on the ingestion of apoptotic eosinophils by bronchial epithelial cells.AimsTo evaluate the effects of dexamethasone, aminophylline and terbutaline on the ingestion of apoptotic eosinophils by A549 cells.MethodsEosinophils were purified by CD15 and CD16-dependent immunomagnetic selection from peripheral blood of five normal donors. The capacity of phagocytosis of apoptotic eosinophils by A549 cells were assessed under the microscope. IL-6 and IL-8 released from A549 cells to the culture supernatants were measured by RIA.ResultsDexamethasone enhanced the phagocytic capacity of A549 cells and inhibited the production of IL-6 and IL-8 from A549 cells stimulated by LPS. Interestingly, aminophylline and terbutaline could not only down-regulate the ingestion of apoptotic eosinophils by A549 cells in a time- and dose-dependent manner, but also decrease IL-6 and IL-8 secretion by A549 cells induced by LPS.ConclusionsThe present study showed that all of the investigated anti-asthmatic drugs including dexamethasone, aminophylline and terbutaline play an anti-inflammatory effect by decreasing the release of IL-6 and IL-8 induced by LPS. On the other hand, they may have a different effect on the phagocytosis of apoptotic eosinophils by A549 cells, i.e., dexamethasone promotes the uptake of apoptotic eosinophils while aminophylline and terbutaline inhibit the ingestion of apoptotic eosinophils. These results revealed a novel aspect of dexamethasone, aminophylline and terbutaline in the treatment of asthma.