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Note: Pseudomonas aeruginosa Induces Type-III-Secretion-Mediated Apoptosis of Macrophages and Epithelial Cells

机译:注意:铜绿假单胞菌诱导III型分泌介导的巨噬细胞和上皮细胞凋亡。

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摘要

Pseudomonas aeruginosa is a gram-negative opportunistic pathogen that is cytotoxic towards a variety of eukaryotic cells. To investigate the effect of this bacterium on macrophages, we infected J774A.1 cells and primary bone-marrow-derived murine macrophages with the P. aeruginosa strain PA103 in vitro. PA103 caused type-III-secretion-dependent killing of macrophages within 2 h of infection. Only a portion of the killing required the putative cytotoxin ExoU. By three criteria, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assays, cytoplasmic nucleosome assays, and Hoechst staining, the ExoU-independent but type-III-secretion-dependent killing exhibited features of apoptosis. Extracellular bacteria were capable of inducing apoptosis, and some laboratory and clinical isolates of P. aeruginosa induced significantly higher levels of this form of cell death than others. Interestingly, HeLa cells but not Madin-Darby canine kidney cells were susceptible to type-III-secretion-mediated apoptosis under the conditions of these assays. These findings are consistent with a model in which the P. aeruginosa type III secretion system transports at least two factors that kill macrophages: ExoU, which causes necrosis, and a second, as yet unidentified, effector protein, which induces apoptosis. Such killing may contribute to the ability of this organism to persist and disseminate within infected patients.
机译:铜绿假单胞菌是革兰氏阴性机会病原体,对多种真核细胞具有细胞毒性。为了研究这种细菌对巨噬细胞的作用,我们在体外用铜绿假单胞菌菌株PA103感染了J774A.1细胞和原代骨髓的鼠巨噬细胞。 PA103在感染后2小时内导致了III型分泌依赖性巨噬细胞的杀死。仅一部分杀伤需要推定的细胞毒素ExoU。通过三个标准,末端脱氧核苷酸转移酶介导的dUTP-生物素缺口末端标记测定,胞质核小体测定和Hoechst染色,ExoU独立但III型分泌依赖的杀伤表现出凋亡的特征。细胞外细菌能够诱导细胞凋亡,某些铜绿假单胞菌的实验室和临床分离株比其他铜绿假单胞菌诱导这种细胞死亡的水平高得多。有趣的是,在这些检测条件下,HeLa细胞而不是Madin-Darby犬肾细胞对III型分泌介导的细胞凋亡敏感。这些发现与其中铜绿假单胞菌III型分泌系统转运至少两个杀死巨噬细胞的因子的模型一致:ExoU引起坏死,而第二个尚未发现的效应蛋白诱导细胞凋亡。此类杀伤可能有助于该生物体在感染患者体内持久和传播的能力。

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