Depolarization, Bacterial Membrane Composition, and the Antimicrobial Action of Ceragenins
Depolarization, Bacterial Membrane Composition, and the Antimicrobial Action of Ceragenins
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DOI：
10.1128/aac.00380-10
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发表时间：
2010-09-01
影响因子：
4.9
通讯作者：
Epand, Richard M.
中科院分区：
文献类型：
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作者：
Epand, Raquel F.;Pollard, Jake E.;Epand, Richard M.
cergenins是胆酸衍生的抗菌药物，模仿内源性抗菌肽的活性。cergenins靶向细菌膜，但这些相互作用的后果尚未完全阐明。使用大肠杆菌ML-35p突变菌株研究了外膜在允许革兰氏阴性菌进入胞质膜中的作用，该菌株经过工程设计，可以独立监测穿过内外膜的小分子通量。革蓝素CSA-8、CSA-13和CSA-54可使这种细菌的外膜通透，这表明外膜在阻止这些物质进入细胞质膜方面不起主要作用。然而，只有最有效的角朊蛋白CSA-13能够穿透内膜。有趣的是，CSA-8和CSA-54都没有在30分钟内引起细胞膜透性，即使浓度远高于细菌毒性所需的浓度。为了进一步评估膜相互作用的作用，我们测量了具有不同膜脂组成的革兰氏阳性细菌和革兰氏阴性细菌的膜去极化。我们发现，对于细胞质膜中含有高浓度的磷脂酰乙醇胺或不带电的脂质的细菌物种，在最小的杀菌浓度下，膜去极化大大增加。尽管膜脂成分影响杀菌效率，但只要药物能进入细胞质膜，膜去极化足以致死性。因此，我们建议，在针对细菌细胞质膜，重点放在膜去极化作为效力的指标。
Ceragenins are cholic acid-derived antimicrobial agents that mimic the activity of endogenous antimicrobial peptides. Ceragenins target bacterial membranes, yet the consequences of these interactions have not been fully elucidated. The role of the outer membrane in allowing access of the ceragenins to the cytoplasmic membrane of Gram-negative bacteria was studied using the ML-35p mutant strain of Escherichia coli that has been engineered to allow independent monitoring of small-molecule flux across the inner and outer membranes. The ceragenins CSA-8, CSA-13, and CSA-54 permeabilize the outer membrane of this bacterium, suggesting that the outer membrane does not play a major role in preventing the access of these agents to the cytoplasmic membrane. However, only the most potent of these ceragenins, CSA-13, was able to permeabilize the inner membrane. Interestingly, neither CSA-8 nor CSA-54 caused inner membrane permeabilization over a 30-min period, even at concentrations well above those required for bacterial toxicity. To further assess the role of membrane interactions, we measured membrane depolarization in Gram-positive bacteria with different membrane lipid compositions, as well as in Gram-negative bacteria. We found greatly increased membrane depolarization at the minimal bactericidal concentration of the ceragenins for bacterial species containing a high concentration of phosphatidylethanolamine or uncharged lipids in their cytoplasmic membranes. Although membrane lipid composition affected bactericidal efficiency, membrane depolarization was sufficient to cause lethality, providing that agents could access the cytoplasmic membrane. Consequently, we propose that in targeting bacterial cytoplasmic membranes, focus be placed on membrane depolarization as an indicator of potency.