Ragland B D, Ashley L S, Vaux D L, Petri W A
Department of Medicine, University of Virginia, Charlottesville 22908.
Exp Parasitol. 1994 Nov;79(3):460-7. doi: 10.1006/expr.1994.1107.
Amebic destruction of neutrophils and macrophages is contact-dependent. Adherence is mediated by a galactose-specific surface lectin on the amebic membrane. The pathway by which contact-dependent cytolysis of the target cell occurs is unknown. We hypothesized that target cell death is due to the triggering of apoptosis (programmed cell death) by the amebae. The purpose of this study was to determine whether target cell DNA is fragmented into a ladder pattern characteristic of apoptosis and to test whether overexpression of Bcl-2, a protein that confers resistance to apoptotic death from some stimuli, blocks target cell killing. The murine myeloid cell line FDC-P1 transfected with a retrovirus construct expressing the Bcl-2 protein was shown to be resistant to the apoptotic death that the parental line undergoes upon growth factor deprivation. 51Cr-labeled FDC-P1 control or bcl-2-transfected cells were incubated with Entamoeba histolytica (4:1 cell/ameba ratio) and killing of the cells was assessed by 51Cr release. Both cell lines were susceptible to contact-dependent killing. Death induced by the amebae in the bcl-2-transfected cells resulted in a DNA ladder fragmentation pattern (using [125I]iododeoxyuridine-labeled target cell DNA) identical to that seen in the control cells undergoing apoptosis upon growth factor withdrawal. Target cell DNA fragmentation was inhibited by blocking adherence with galactose. Our data suggest that target cell killing by E. histolytica can occur via Bcl-2-independent apoptotic mechanism.
阿米巴对中性粒细胞和巨噬细胞的破坏是接触依赖性的。黏附由阿米巴细胞膜上的一种半乳糖特异性表面凝集素介导。靶细胞接触依赖性细胞溶解发生的途径尚不清楚。我们推测靶细胞死亡是由于阿米巴触发了细胞凋亡（程序性细胞死亡）。本研究的目的是确定靶细胞DNA是否断裂成细胞凋亡特有的梯形模式，并测试Bcl-2（一种对某些刺激诱导的凋亡性死亡具有抗性的蛋白质）的过表达是否能阻止靶细胞被杀伤。用表达Bcl-2蛋白的逆转录病毒构建体转染的小鼠髓样细胞系FDC-P1，对亲代细胞系在生长因子剥夺时所经历的凋亡性死亡具有抗性。将51Cr标记的FDC-P1对照细胞或bcl-2转染细胞与溶组织内阿米巴一起孵育（细胞/阿米巴比例为4:1），通过51Cr释放评估细胞的杀伤情况。两种细胞系都易受接触依赖性杀伤。在bcl-2转染细胞中，由阿米巴诱导的死亡导致DNA梯形断裂模式（使用[125I]碘脱氧尿苷标记的靶细胞DNA），与在生长因子撤除时发生凋亡的对照细胞中所见的模式相同。通过用半乳糖阻断黏附可抑制靶细胞DNA断裂。我们的数据表明，溶组织内阿米巴对靶细胞的杀伤可通过不依赖Bcl-2的凋亡机制发生。
