Test S T, Mitsuyoshi J
Children's Hospital Oakland Research Institute, California 94609, USA.
J Lab Clin Med. 1997 Aug;130(2):169-82. doi: 10.1016/s0022-2143(97)90093-7.
The aminophospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) are exposed on the outer membrane leaflet of deoxygenated and irreversibly sickled erythrocytes and senescent normal cells. PS exposure on erythrocytes results in the expression of procoagulant activity for the conversion of prothrombin to thrombin. Because liposomes or vesicles composed of aminophospholipids can activate the alternative pathway of complement, the possibility that increased exposure of PS and PE on intact erythrocytes would also make them capable of activating the alternative pathway was examined. Loss of normal membrane phospholipid asymmetry was induced by incubation of erythrocytes with calcium (Ca2+) and the calcium ionophore A23187. PS exposure on 60% of erythrocytes was confirmed by binding of fluorescein isothiocyanate-conjugated annexin V. Expression of procoagulant activity, measured with the Russell's viper venom clotting assay, was significantly increased on the Ca2+/A23187-treated erythrocytes. In addition, the erythrocytes became capable of activating the alternative pathway of complement, as judged by an increase in cell-bound C3b after incubation with serum and a decrease in alternative pathway hemolytic activity of the serum. The effect could be reversed by incubation of the Ca2+/A23187-treated erythrocytes under conditions that induced recovery of normal membrane phospholipid asymmetry. In contrast, tetrathionate-treated erythrocytes showed no increase in binding of annexin V and no procoagulant activity and failed to activate the alternative pathway of complement. These findings demonstrate that loss of phospholipid asymmetry in erythrocytes not only results in expression of procoagulant activity but also renders the cells capable of activating the alternative pathway of complement.
氨基磷脂磷脂酰丝氨酸（PS）和磷脂酰乙醇胺（PE）暴露于脱氧和不可逆镰状红细胞以及衰老正常细胞的外膜小叶。红细胞上PS的暴露导致凝血酶原转化为凝血酶的促凝活性表达。由于由氨基磷脂组成的脂质体或囊泡可激活补体替代途径，因此研究了完整红细胞上PS和PE暴露增加是否也会使其能够激活替代途径。通过用钙（Ca2+）和钙离子载体A23187孵育红细胞来诱导正常膜磷脂不对称性的丧失。通过异硫氰酸荧光素偶联的膜联蛋白V的结合证实60%的红细胞上有PS暴露。用罗素蝰蛇毒凝血试验测量，Ca2+/A23187处理的红细胞上促凝活性的表达显著增加。此外，红细胞能够激活补体替代途径，这可通过与血清孵育后细胞结合的C3b增加以及血清替代途径溶血活性降低来判断。通过在诱导正常膜磷脂不对称性恢复的条件下孵育Ca2+/A23187处理的红细胞，可以逆转这种效应。相比之下，连四硫酸盐处理的红细胞膜联蛋白V结合没有增加，没有促凝活性，也不能激活补体替代途径。这些发现表明红细胞中磷脂不对称性的丧失不仅导致促凝活性的表达，还使细胞能够激活补体替代途径。
