Induction of apoptosis in human T cells by Actinobacillus actinomycetemcomitans cytolethal distending toxin is a consequence of G2 arrest of the cell cycle
Induction of apoptosis in human T cells by Actinobacillus actinomycetemcomitans cytolethal distending toxin is a consequence of G2 arrest of the cell cycle
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DOI：
10.4049/jimmunol.167.1.435
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发表时间：
2001-07-01
影响因子：
4.4
通讯作者：
Demuth, DR
中科院分区：
文献类型：
--
作者：
Shenker, BJ;Hoffmaster, RH;Demuth, DR
我们以前已经表明，放线共生放线杆菌产生的免疫抑制因子编码的cdtB基因，这是同源的几个革兰氏阴性菌表达的细胞致死性膨胀毒素（CDT）的家庭。此外，我们已经表明CdtB通过诱导细胞周期的G（2）停滞来损害淋巴细胞功能。我们现在报道CdtB以及从表达所有三种A.伴随放线菌cdt基因（rCdtABC）诱导细胞凋亡。用CdtB或rCdtABC预处理淋巴细胞导致活化淋巴细胞在72和96 h的DNA片段化。在未活化的细胞中未诱导DNA片段化。流式细胞术分析的Cdt处理的淋巴细胞表明，细胞大小的减少和核凝聚的增加。在CdtB或rCdtABC预处理的细胞中，线粒体功能也受到干扰。观察到线粒体Ag（Apo 2.7）的表达增加，沿着线粒体渗透性过渡状态发展的证据;这包括跨膜电位降低和活性氧产生增加。活化的半胱天冬酶级联反应，这是一个重要的生化特征的凋亡过程中，也观察到在Cdt处理的淋巴细胞。bcl-2基因在人B类淋巴母细胞系JY中的过表达导致Cdt诱导的凋亡减少。有趣的是，Bcl-2过表达并不阻断Cdt诱导的G2期阻滞。我们的研究结果与Cdt蛋白的免疫抑制功能的影响进行了讨论。免疫学杂志，2001年。
We have previously shown that Actinobacillus actinomycetemcomitans produces an immunosuppressive factor that is encoded by the cdtB gene, which is homologous to a family of cytolethal distending toxins (Cdt) expressed by several Gram-negative bacteria. Moreover, we have shown that CdtB impairs lymphocyte function by inducing G(2) arrest of the cell cycle. We now report that both CdtB as well as an extract prepared from an Escherichia coli strain that expresses all three of the A. actinomycetemcomitans cdt genes (rCdtABC) induce apoptosis. Pretreatment of lymphocytes with either CdtB or rCdtABC leads to DNA fragmentation in activated lymphocytes at 72 and 96 h. No DNA fragmentation was induced in nonactivated cells. Flow cytometric analysis of the Cdt-treated lymphocytes demonstrates a reduction in cell size and an increase in nuclear condensation. Mitochondrial function was also perturbed in cells pretreated with either CdtB or rCdtABC. An increase in the expression of the mitochondria Ag, Apo 2.7, was observed along with evidence of the development of a mitochondrial permeability transition state; this includes a decrease in the transmembrane potential and elevated generation of reactive oxygen species. Activation of the caspase cascade, which is an important biochemical feature of the apoptotic process, was also observed in Cdt-treated lymphocytes. Overexpression of the bcl-2 gene in the human B lymphoblastoid cell line, JY, led to a decrease in Cdt-induced apoptosis. Interestingly, Bcl-2 overexpression did not block Cdt-induced G2 arrest. The implications of our results with respect to the immunosuppressive functions of Cdt proteins are discussed. The Journal of Immunology, 2001.