title: Involvement of annexin I in the dexamethasone-mediated upregulation of A549 cells phagocytosis of apoptotic eosinophils.
abstract: Phagolysis of apoptotic eosinophils plays an important role in the successful resolution of asthmatic inflammation. However, little is known about underlying mechanisms. Our aim is to investigate whether annexin I is involved in the dexamethasone-mediated enhancement of phagolysis of apoptotic eosinophils by A549 cells. Phagocytosis of apoptotic eosinophils by A549 cells was visualized under laser confocal scanning microscopy. The effect of dexamethasone and TNF-alpha treatment on surface annexin I expression on A549 cells was assayed by Western blot. Eosinophils were purified under sterile conditions from periphery blood of five normal donors. A549 cells were visually assessed for apoptotic eosinophil phagocytosis by microscope. The concentration of interleukin 6 (IL-6), IL-8 and TGF-beta(1) released by A549 cells to the culture supernatants was measured by RIA or ELISA. Dexamethasone upregulated apoptotic eosinophils phagocytosis by A549 cells in a time-dependent manner, which correlated with annexin I surface expression. Annexin I mAb abolished dexamethasone-mediated enhancement of apoptotic eosinophil phagocytosis by A549 cells. Phagocytosis of apoptotic eosinophils did not change IL-6, IL-8 and TGF-beta(1) release from A549 cells. These results suggest that annexin I is involved in upregulating of dexamethasone-mediated phagocytosis of apoptotic eosinophils by A549 cells. Furthermore, the phagocytic clearance of apoptotic eosinophils did not increase proinflammatory responses.
authors.affiliation: Department of Pulmonary, Anhui Geriatrics Institute, The First Affiliated Hospital of Anhui Medical University, Jixi Road 218, Hefei 230022 PR China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.forename: Jiong
authors.initials: J
authors.lastname: Wang
authors.forename: Hou-Fu
authors.initials: HF
authors.lastname: Guo
authors.forename: Rong-Yu
authors.initials: RY
authors.lastname: Liu
mesh_terms: D017305:Annexin A1 / Q000276:immunology / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology; D045744:Cell Line, Tumor; D016207:Cytokines / Q000276:immunology / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004804:Eosinophils / Q000166:cytology / Q000276:immunology*; D006801:Humans; D010587:Phagocytosis; D015854:Up-Regulation
chemical_list: D017305:Annexin A1; D016207:Cytokines; D003907:Dexamethasone