title: Endothelial cell phagocytosis of senescent neutrophils decreases procoagulant activity.
abstract: Abundant senescent neutrophils traverse the vascular compartment and may contribute to pathologic conditions. For example, they become procoagulant when undergoing apoptosis and may contribute to thrombosis or inflammation. Our previous studies demonstrated a dominant clearance pathway in which the neutrophils can be phagocytosed by liver macrophages. The aim of this study was to explore an alternate pathway of neutrophil clearance by endothelial cells. Phagocytosis of the neutrophils by endothelial cells was performed using various experimental approaches includingflow cytometry, confocal microscopy and electron microscopy assays in vitro and in vivo. Procoagulant activity of cultured neutrophils was evaluated by coagulation time, factor Xase and prothrombinase assays. Lactadherin functioned as a novel probe for the detection of phosphatidylserine on apoptotic cells, an opsonin (bridge) between apoptotic cell and phagocyte for promoting phagocytosis, and an efficient anticoagulant for inhibition of factor Xase and thrombin formation. When cultured, purified human neutrophils spontaneously entered apoptosis and developed procoagulant activity that was directly related to the degree of phosphatidylserine exposure. Co-culture of aged neutrophils and endothelial cells resulted in phagocytosis of the neutrophils and prolonged coagulation time. Lactadherin diminished the procoagulant activity and increased the rate of neutrophil clearance. In vivo, neutrophils were sequestered by endothelial cells after blockade of Kupffer cells, a process that was dependent upon both phosphatidylserine exposure and P-selectin expression. Thus, the ability of endothelial cells to clear senescent neutrophils may limit the procoagulant and/or inflammatory impact of these cells.
authors.affiliation: Department of Medicine, The First Affiliated Hospital, Harbin Medical University, 23 Youzheng Street, Nangang District, Harbin 150001, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Gao
authors.forename: Rui
authors.initials: R
authors.lastname: Xie
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.forename: Jin
authors.initials: J
authors.lastname: Zhou
authors.forename: Shuchuan
authors.initials: S
authors.lastname: Liu
authors.forename: Fenglin
authors.initials: F
authors.lastname: Cao
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.forename: Ruishuang
authors.initials: R
authors.lastname: Ma
authors.forename: Yu
authors.initials: Y
authors.lastname: Si
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Yayan
authors.initials: Y
authors.lastname: Bi
authors.forename: Gary E
authors.initials: GE
authors.lastname: Gilbert
authors.forename: Jialan
authors.initials: J
authors.lastname: Shi
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D017209:Apoptosis; D002417:Cattle; D016922:Cellular Senescence; D003029:Coagulants / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry; D042783:Endothelial Cells / Q000166:cytology*; D005434:Flow Cytometry; D006801:Humans; D007249:Inflammation; D008297:Male; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008894:Milk Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000737:chemistry; D009504:Neutrophils / Q000166:cytology* / Q000378:metabolism; D010586:Phagocytes / Q000166:cytology; D010587:Phagocytosis; D010718:Phosphatidylserines / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution
chemical_list: D000954:Antigens, Surface; D003029:Coagulants; C098942:MFGE8 protein, human; D008894:Milk Proteins; D009363:Neoplasm Proteins; D010718:Phosphatidylserines; D003546:Cysteine Endopeptidases; C030910:cancer procoagulant