Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa
Anaerobiosis-Induced Loss of Cytotoxicity Is Due to Inactivation of Quorum Sensing in Pseudomonas aeruginosa
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DOI：
10.1128/iai.01361-10
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发表时间：
2011-07-01
影响因子：
3.1
通讯作者：
Yoon, Sang Sun
中科院分区：
文献类型：
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作者：
Lee, Kang-Mu;Yoon, Mi Young;Yoon, Sang Sun
铜绿假单胞菌是一种临床重要的机会性致病菌，可引起囊性纤维化患者的慢性呼吸道感染。目前的文献表明，在CF的呼吸道粘液中存在氧分压降低的腔隙。然而，这种机会性病原体在这种条件下的毒力特征在很大程度上是未知的。从厌氧培养获得的标准实验室铜绿假单胞菌PAO1株的无细胞上清液，而不是有氧培养获得的无细胞培养上清，未能杀死A549人呼吸道上皮细胞。进一步的研究表明，这种对厌氧菌细胞毒性的降低是由于弹性酶的分泌受到抑制，弹性酶是一种受铜绿假单胞菌群体感应(QS)控制的毒力因子。LacZ-Report融合分析和实时定量聚合酶链式反应(RT-PCR)分析都表明，与有氧生长相比，在厌氧生长过程中，编码弹性蛋白酶的lasB基因的转录水平显著降低。此外，在相同的厌氧生长条件下，LASI/R QS系统控制的其他基因，如rHLR、vqsR、mvfR和rsaL的转录也受到抑制。重要的是，3-oxo-C-12-HSL(PAI-1)是介导LASI/R QS系统诱导的自身诱导剂分子，在厌氧生长过程中其合成减少了22倍，而介导RhlI/R QS的C-4-HSL(PAI-2)在相同的生长条件下是检测不到的。外源自身诱导剂可以恢复lasB基因的转录，PAI-2在恢复lasB基因转录方面比PAI-1或假单胞菌喹诺酮信号(PQS)更有效。综上所述，这些结果表明，厌氧剥夺了铜绿假单胞菌通过QS调节其毒力的能力，这种错误的调节减弱了这种重要病原体的致病潜力。
Pseudomonas aeruginosa, an opportunistic pathogen of clinical importance, causes chronic airway infections in patients with cystic fibrosis (CF). Current literature suggests that pockets with reduced oxygen tension exist in the CF airway mucus. However, virulence features of this opportunistic pathogen under such conditions are largely unknown. Cell-free supernatant of the standard laboratory P. aeruginosa strain PAO1 obtained from anaerobic culture, but not aerobic culture, failed to kill A549 human airway epithelial cells. Further investigation revealed that this reduced cytotoxicity upon anaerobiosis was due to the suppressed secretion of elastase, a virulence factor controlled by P. aeruginosa quorum sensing (QS). Both a lacZ-reporter fusion assay and quantitative real-time PCR (RT-PCR) analysis demonstrated that transcription of the elastase-encoding lasB gene was substantially decreased during anaerobic growth compared with aerobic growth. Moreover, transcription of other genes controlled by the LasI/R QS system, such as rhlR, vqsR, mvfR, and rsaL, was also repressed under the same anaerobic growth conditions. Importantly, synthesis of 3-oxo-C-12-HSL (PAI-1), an autoinducer molecule that mediates induction of the LasI/R QS system, was >22-fold decreased during anaerobic growth while C-4-HSL (PAI-2), which mediates RhlI/R QS, was nondetectable under the same growth conditions. Transcription of the lasB gene was restored by exogenous supplementation with autoinducers, with PAI-2 more effective than PAI-1 or Pseudomonas quinolone signal (PQS) at restoring transcription of the lasB gene. Together, these results suggest that anaerobiosis deprives P. aeruginosa of the ability to regulate its virulence via QS and this misregulation attenuates the pathogenic potential of this important pathogen.