Department of Chemistry, University of Delhi, Delhi 110007, India.
J Antimicrob Chemother. 2012 Dec;67(12):2882-91. doi: 10.1093/jac/dks322. Epub 2012 Sep 3.
Antibiotic resistance in bacterial pathogens is a serious clinical problem. Novel targets are needed to combat increasing drug resistance in Escherichia coli. Our objective is to demonstrate that 2-(3,4-dimethoxyphenyl)-5-[5-(4-methylpiperazin-1-yl)-1H-benzimidazol-2yl]-1H-benzimidazole (DMA) inhibits E. coli DNA topoisomerase I more strongly than human topoisomerase I. In addition, DMA is non-toxic to mammalian cells at antibiotic dosage level.
In the present study, we have established DMA as an antibacterial compound by determining MICs, post-antibiotic effects (PAEs) and MBCs for different standard as well as clinical strains of E. coli. We have described the differential catalytic inhibitory mechanism of bis-benzimidazole, DMA, for human and E. coli topoisomerase I and topoisomerase II by performing different assays, including relaxation assays, cleavage-religation assays, DNA unwinding assays, ethidium bromide displacement assays, decatenation assays and DNA gyrase supercoiling assays.
DMA significantly inhibited bacterial growth at a very low concentration, but did not affect human cell viability at higher concentrations. Activity assays showed that it preferentially targeted E. coli topoisomerase I over human topoisomerase I, topoisomerase II and gyrase. Cleavage-religation assays confirmed DMA as a poison inhibitor of E. coli topoisomerase I. This study illuminates new properties of DMA, which may be further modified to develop an efficient topoisomerase inhibitor that is selective towards bacterial topoisomerase I.
This is the first report of a bis-benzimidazole acting as an E. coli topoisomerase I inhibitor. DMA is a safe, non-cytotoxic molecule to human cells at concentrations that are needed for antibacterial activity.
细菌病原体的抗生素耐药性是一个严重的临床问题。需要寻找新的靶标来对抗大肠杆菌日益增加的耐药性。我们的目标是证明 2-(3,4-二甲氧基苯基)-5-[5-(4-甲基哌嗪-1-基)-1H-苯并咪唑-2-基]-1H-苯并咪唑（DMA）对大肠杆菌 DNA 拓扑异构酶 I 的抑制作用强于人拓扑异构酶 I。此外，DMA 在抗生素剂量水平下对哺乳动物细胞无毒。
在本研究中，我们通过确定不同标准和临床大肠杆菌菌株的 MIC、抗生素后效应（PAE）和 MBC，将 DMA 确立为一种抗菌化合物。我们通过不同的实验，包括松弛实验、切割-连接实验、DNA 解旋实验、溴化乙锭置换实验、解连环实验和 DNA 回旋酶超螺旋化实验，描述了双苯并咪唑 DMA 对人源和大肠杆菌拓扑异构酶 I 和拓扑异构酶 II 的差异催化抑制机制。
DMA 以非常低的浓度显著抑制细菌生长，但在较高浓度下不影响人细胞活力。活性实验表明，它优先靶向大肠杆菌拓扑异构酶 I，而不是人拓扑异构酶 I、拓扑异构酶 II 和回旋酶。切割-连接实验证实 DMA 是大肠杆菌拓扑异构酶 I 的毒物抑制剂。本研究阐明了 DMA 的新特性，这些特性可能进一步修饰，以开发出对细菌拓扑异构酶 I 具有选择性的高效拓扑异构酶抑制剂。
这是第一个报道双苯并咪唑作为大肠杆菌拓扑异构酶 I 抑制剂的报告。DMA 在抗菌活性所需的浓度下是一种对人细胞安全、无毒的非细胞毒性分子。
