Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil.
Int J Antimicrob Agents. 2011 May;37(5):449-56. doi: 10.1016/j.ijantimicag.2010.11.031. Epub 2011 Feb 2.
Trypanosomatids present unusual organelles, such as the kinetoplast that contains the mitochondrial DNA arranged in catenated circles. The nucleus of these protozoa presents distinct domains during interphase as well as a closed mitosis. DNA topoisomerases modulate the topological state of DNA by regulating supercoiling of the double-stranded DNA during replication, transcription, recombination and repair. Because topoisomerases play essential roles in cellular processes, they constitute a potential target for antitumour and antimicrobial drugs. In this study, the effects of various topoisomerase inhibitors and DNA-binding drugs were tested on the cellular proliferation and ultrastructure of the Trypanosoma cruzi epimastigote form Blastocrithidia culicis was used as a comparative model, which has a more relaxed kinetoplast DNA (kDNA) organization. The results showed that the eukaryotic topoisomerase I inhibitors camptothecin and rebeccamycin were the most effective compounds in the arrest of T. cruzi proliferation. Of the eukaryotic topoisomerase II inhibitors, mitoxantrone, but not merbarone, was effective against cell proliferation. The prokaryotic topoisomerase II inhibitors norfloxacin and enoxacin targeted the kinetoplast specifically, thus promoting ultrastructural kDNA rearrangement in B. culicis. Of the DNA-binding drugs, berenil caused remarkable kDNA disorganization. With the exception of camptothecin, there have been no previous evaluations of the compounds tested here on trypanosomatid ultrastructure. In conclusion, inhibitors of the same class may have different effects on trypanosomatid proliferation and ultrastructure. The results obtained in this work may help to reveal the mechanism of action of different topoisomerase inhibitors in trypanosomatids.
锥虫呈现出不寻常的细胞器，例如含有以链状排列的线粒体 DNA 的动基体。这些原生动物的核在有丝分裂间期和封闭有丝分裂中呈现出明显的结构域。DNA 拓扑异构酶通过调节复制、转录、重组和修复过程中双链 DNA 的超螺旋来调节 DNA 的拓扑状态。由于拓扑异构酶在细胞过程中发挥着重要作用，它们构成了抗肿瘤和抗微生物药物的潜在靶标。在这项研究中，测试了各种拓扑异构酶抑制剂和 DNA 结合药物对 Trypanosoma cruzi 锥形体的细胞增殖和超微结构的影响。 Blastocrithidia culicis 被用作比较模型，其动基体 DNA（kDNA）组织更为松弛。结果表明，真核拓扑异构酶 I 抑制剂喜树碱和瑞贝卡霉素是阻止 T. cruzi 增殖的最有效化合物。在真核拓扑异构酶 II 抑制剂中，米托蒽醌而不是美贝罗酮对细胞增殖有效。原核拓扑异构酶 II 抑制剂诺氟沙星和恩诺沙星特异性靶向动基体，从而促进 B. culicis 中 kDNA 的超微结构重排。在 DNA 结合药物中，贝伦那导致明显的 kDNA 解聚。除喜树碱外，这里测试的化合物以前从未在锥虫体的超微结构上进行过评价。总之，同一类抑制剂可能对锥虫体的增殖和超微结构有不同的影响。本工作获得的结果可能有助于揭示不同拓扑异构酶抑制剂在锥虫体中的作用机制。
