Ferrándiz M J, Martín-Galiano A J, Arnanz C, Zimmerman T, de la Campa A G
Unidad de Genética Bacteriana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
Unidad de Genética Bacteriana, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain Presidencia. Consejo Superior de Investigaciones Científicas, Madrid, Spain
Antimicrob Agents Chemother. 2015 Nov 2;60(1):409-17. doi: 10.1128/AAC.02299-15. Print 2016 Jan.
We studied the transcriptomic response of Streptococcus pneumoniae to the fluoroquinolone moxifloxacin at a concentration that inhibits DNA gyrase. Treatment of the wild-type strain R6, at a concentration of 10× the MIC, triggered a response involving 132 genes after 30 min of treatment. Genes from several metabolic pathways involved in the production of pyruvate were upregulated. These included 3 glycolytic enzymes, which ultimately convert fructose 6-phosphate to pyruvate, and 2 enzymes that funnel phosphate sugars into the glycolytic pathway. In addition, acetyl coenzyme A (acetyl-CoA) carboxylase was downregulated, likely leading to an increase in acetyl-CoA. When coupled with an upregulation in formate acetyltransferase, an increase in acetyl-CoA would raise the production of pyruvate. Since pyruvate is converted by pyruvate oxidase (SpxB) into hydrogen peroxide (H2O2), an increase in pyruvate would augment intracellular H2O2. Here, we confirm a 21-fold increase in the production of H2O2 and a 55-fold increase in the amount of hydroxyl radical in cultures treated during 4 h with moxifloxacin. This increase in hydroxyl radical through the Fenton reaction would damage DNA, lipids, and proteins. These reactive oxygen species contributed to the lethality of the drug, a conclusion supported by the observed protective effects of an SpxB deletion. These results support the model whereby fluoroquinolones cause redox alterations. The transcriptional response of S. pneumoniae to moxifloxacin is compared with the response to levofloxacin, an inhibitor of topoisomerase IV. Levofloxacin triggers the transcriptional activation of iron transport genes and also enhances the Fenton reaction.
我们研究了肺炎链球菌在抑制DNA旋转酶的氟喹诺酮莫西沙星浓度下的转录组反应。以10倍MIC的浓度处理野生型菌株R6，处理30分钟后引发了涉及132个基因的反应。参与丙酮酸生成的几个代谢途径中的基因被上调。其中包括3种糖酵解酶，它们最终将6-磷酸果糖转化为丙酮酸，以及2种将磷酸糖导入糖酵解途径的酶。此外，乙酰辅酶A（acetyl-CoA）羧化酶被下调，可能导致乙酰辅酶A增加。当与甲酸乙酰转移酶的上调相结合时，乙酰辅酶A的增加会提高丙酮酸的产量。由于丙酮酸被丙酮酸氧化酶（SpxB）转化为过氧化氢（H2O2），丙酮酸的增加会增加细胞内H2O2。在这里，我们证实了在用莫西沙星处理4小时的培养物中，H2O2的产量增加了21倍，羟基自由基的量增加了55倍。通过芬顿反应产生的这种羟基自由基的增加会损害DNA、脂质和蛋白质。这些活性氧导致了药物的致死性，SpxB缺失所观察到的保护作用支持了这一结论。这些结果支持了氟喹诺酮类药物引起氧化还原改变的模型。将肺炎链球菌对莫西沙星的转录反应与对拓扑异构酶IV抑制剂左氧氟沙星的反应进行了比较。左氧氟沙星触发铁转运基因的转录激活，也增强了芬顿反应。
