磷脂酰丝氨酸外翻和磷脂氧化在凋亡细胞被吞噬细胞清除过程中的协作效应

COOPERATION EFFECT OF EXTERNALIZED PHOSPHATIDYLSERINE AND OXIDIZED PHOSPHOLIPIDS ON CLEARANCE OF APOPTOTIC CELLS BY MACROPHAGES

为探讨磷脂酰丝氨酸(phosphatidylserine,PS)外翻和磷脂氧化在凋亡细胞被吞噬细胞清除中的作用,用脂质体整合的方法将不同的磷脂整合到红细胞上或用N-乙酰马来酰胺(N-ethylmaleimide,NEM)预处理红细胞然后整合磷脂,制备含不同凋亡信号的红细胞模型,测定巨噬细胞对整合不同磷脂信号红细胞的结合率和吞噬率。结果表明,单独整合PS或用NEM处理造成PS外翻,可显著性提高巨噬细胞对红细胞的结合率,但对吞噬率没有影响;同时整合PS和氧化磷脂(氧化PS或氧化磷脂酰胆碱(phosphatidylcholine,PC)),或用NEM处理造成PS外翻后再整合氧化PS或氧化PC,不仅可显著提高巨噬细胞对红细胞的结合率,而且可显著性提高吞噬率。这些结果提示PS外翻可能参与了巨噬细胞对凋亡细胞的结合,而磷脂氧化可能启动了巨噬细胞对凋亡细胞的吞噬,二者协作才可能完成巨噬细胞对凋亡细胞的清除。

To investigate the role of externalized phosphatidylserine （PS） and oxidized phospholipids on the clearance of apoptotic cells by macrophage, red blood cells （RBCs） containing different apoptotic signals （externalized PS or/and oxidized phospholipids）were prepared by incubation of normal or N-ethylmaleimide pre-treated RBCs with liposomes containing PS or/and oxidized phospholipids, the ratio of binding and phagocytosis of these modified RBCs by mouse peritoneal macrophages were measured by counting binding or phagocytotic positive macrophages under microscope. The results showed that PS externalization alone caused either by incorporation with liposome containing PS or by pre-treatment with N-ethylmaleimide significantly increased the ratio of binding by macrophages, but had no significantly influence on the ratio of phagocytosis. However, when both PS and oxidized phospholipids （either oxidized PS or oxidized phosphatidylcholine） were incorporated into normal RBCs or oxidized phospholipids were incorporated into N-ethylmaleimide pre-treated RBCs, not only the ratio of binding by macrophages increased significantly, but also the ratio of phagocytosis significantly increased. These results imply that externalization of PS might be responsible for the binding of apoptotic cells with macrophage, and oxidized phospholipids might trigger the further phagocytosis. The cooperation of them is required for the clearance of apoptotic cells by macrophages.