Structure-activity studies of dicationically substituted bis-benzimidazoles against Giardia lamblia: correlation of antigiardial activity with DNA binding affinity and giardial topoisomerase II inhibition

Bell, Constance A.; Dykstra, Christine C.; Naiman, Noreen; Cory, Michael; Fairley, Terri A.; Tidwell, Richard R.

doi:10.1128/aac.37.12.2668

Cited by 100 publications

(71 citation statements)

References 19 publications

(37 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the basis of the results of those studies, nine dicationic-substituted bis-benzimidazoles with potent minor groove-binding properties were examined for their in vitro activities against G. lamblia. The results of that analysis showed a strong correlation between in vitro antigiardial activity, DNA-binding affinity, and the ability to inhibit the catalytic activity of giardial DNA topoisomerase 11 (4). This correlation suggested that the antiparasitic activity of the bis-benzimidazoles is linked to DNA binding and further suggested that inhibition of giardial DNA topoisomerase II is a factor in drug activity.…”

Section: Resultsmentioning

confidence: 71%

“…There was no evidence of either an intercalative or a covalent interaction of these compounds with nucleic acids. The antigiardiasis study also revealed a convincing correlation between antitopoisomerase II activity and in vitro activity against G. lamblia for the dicationic bis-benzimidazoles (r2 = 0.91) (4). It is unclear whether these compounds manifest their antiparasitic activity primarily by binding to DNA, topoisomerase, or the enzyme-DNA binary complex.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Selective inhibition of topoisomerases from Pneumocystis carinii compared with that of topoisomerases from mammalian cells

Dykstra

McClernon

Elwell

et al. 1994

Antimicrob Agents Chemother

Self Cite

View full text Add to dashboard Cite

Type I and II topoisomerase activities were partially purified from Pneumocystis carinii. The catalytic (strand-passing) activities of both enzymes were selectively inhibited by members of a series of dicationicsubstituted bis-benzimidazoles compared with those of topoisomerases of mammalian (calf thymus) origin.The most active inhibitors of the parasite enzymes were also highly effective in an in vivo animal model of P.carinii pneumonia. Selected dicationic-substituted bis-benzimidazoles also strongly inhibited the induction of the topoisomerase I-and 11-mediated cleavable complex, suggesting that the biologically active DNA minor groove-binding molecules inhibit the enzyme-DNA binding step of the topoisomerase reaction sequence. The apparent selectivities for the parasite enzymes and the low levels of toxicity to mammalian cells for the biologically active bis-benzimidazoles suggest that these compounds hold promise as effective therapeutic agents in the treatment of a life-threatening AIDS-related disease, P. carinii pneumonia.Dicationic-substituted aromatic molecules related to pentamidine have long been known to be effective antiparasitic agents (35). Recent studies have found that a number of direct analogs of pentamidine have activity against Pneumocystis carinii (19), Giardia lamblia (3), Toxoplasma gondii (25), Cryptosporidium parvum (7), Leishmania amazonensis subsp. mexicana (5), and Plasmodium falciparum (5). A strong correlation was observed between compound activity against G. lamblia in vitro and DNA-binding ability (3). On the basis of those initial results, studies of antiparasitic compounds were extended to a series of compounds with much stronger DNA-binding affinities, the dicationic bis-benzimidazoles. As observed with the pentamidine analogs, a strong correlation was found between DNA binding strength and antigiardial activity for the bisbenzimidazole series [r2 = 0.96 versus calf thymus DNA and i2 = 0.97 versus poly(dA) * (dT)](4). Other studies confirmed that the effective antigiardial compounds were strong DNA minor groove-binding agents with an AT base pair preference (14). Molecular modeling calculations in that study showed that the DNA-binding strength for this class of compound depended on the radius of curvature on the basis of four defined moieties within the molecules, the distance between cationic moieties, the electronic effects from cationic substituents, and hydrogen bonding. There was no evidence of either an intercalative or a covalent interaction of these compounds with nucleic acids. The antigiardiasis study also revealed a convincing correlation between antitopoisomerase II activity and in vitro activity against G. lamblia for the dicationic bis-benzimidazoles (r2 = 0.91) (4). It is unclear whether these compounds manifest their antiparasitic activity primarily by binding to DNA, topoisomerase, or the enzyme-DNA binary complex.As part of a continuing investigation to determine the mechanism of the anti-P. carinii action of these dicationic molecules and to develop new ag...

show abstract

Section: Resultsmentioning

confidence: 71%

mentioning

confidence: 99%

Selective inhibition of topoisomerases from Pneumocystis carinii compared with that of topoisomerases from mammalian cells

Dykstra

McClernon

Elwell

et al. 1994

Antimicrob Agents Chemother

Self Cite

View full text Add to dashboard Cite

show abstract

“…These features include: 1) although five chromosomal bands was demonstrated by PFGE, no condensed chromosomal structures have been observed so far [10], which might suggest that it has no transition between chromatin and chromosome; 2) no nucleoli have been identified and its rRNA transcription and processing are not localized to certain regions of the nuclei [10,16,17]. Given the fact that enzymic activities of type II DNA topoisomerase were previously detected from G. lamblia, what are the characteristics of its type II DNA topoisomerase(s) and the gene(s) in the organism [18]? Is its type II enzymes eukaryotic type or prokaryotic type (gyrase, and Top IV or Top VI)?…”

Section: Introductionmentioning

confidence: 99%

Identification, characteristic and phylogenetic analysis of type II DNA topoisomerase gene in Giardia lamblia

Wen

Chen

et al. 2005

Cell Res

View full text Add to dashboard Cite

The genes encoding type II DNA topoisomerases were investigated in Giardia lamblia genome, and a type IIA gene, GlTop 2 was identified. It is a single copy gene with a 4476 bp long ORF without intron. The deduced amino acid sequence shows strong homology to eukaryotic DNA Top 2. However, some distortions were found, such as six insertions in the ATPase domain and the central domain, a ~100 aa longer central domain; a ~200 aa shorter C-terminal domain containing rich charged residues. These features revealed by comparing with Top 2 of the host, human, might be helpful in exploiting drug selectivity for antigiardial therapy. Phylogenetic analysis of eukaryotic enzymes showed that kinetoplastids, plants, fungi, and animals were monophyletic groups, and the animal and fungi lineages shared a more recent common ancestor than either did with the plant lineage; microsporidia grouped with fungi. However, unlike many previous phylogenetic analyses, the "amitochondriate" G. lamblia was not the earliest branch but diverged after mitochondriate kinetoplastids in our trees. Both the finding of typical eukaryotic type IIA topoisomerase and the phylogenetic analysis suggest G. lamblia is not possibly as primitive as was regarded before and might diverge after the acquisition of mitochondria. This is consistent with the recent discovery of mitochondrial remnant organelles in G. lamblia.

show abstract

“…10), indicating that another cytotoxic target exists. One suggested cytotoxic target of pentamidine and several other biscationic minor-groove binding drugs is topoisomerase II (5,8,18). In addition, pentamidine has been suggested to block the splicing of group I introns in P. carinii, C. albicans, and S. cerevisiae cells (41,43).…”

Section: Discussionmentioning

confidence: 99%

Molecular Characterization of Recombinant Pneumocystis carinii Topoisomerase I: Differential Interactions with Human Topoisomerase I Poisons and Pentamidine

Dross¹,

Sanders²

2002

Antimicrob Agents Chemother

View full text Add to dashboard Cite

The Pneumocystis carinii topoisomerase I-encoding gene has been cloned and sequenced, and the expressed enzyme interactions with several classes of topoisomerase I poisons have been characterized. The P. carinii topoisomerase I protein contains 763 amino acids and has a molecular mass of ca. 90 kDa. The expressed enzyme relaxes supercoiled DNA to completion and has no Mg 2؉ requirement. Cleavage assays reveal that both the human and P. carinii enzymes form covalent complexes in the presence of camptothecin, Hoechst 33342, and the terbenzimidazole QS-II-48. As with the human enzyme, no cleavage is stimulated in the presence of 4,6-diamidino-2-phenylindole (DAPI) or berenil. A yeast cytotoxicity assay shows that P. carinii topoisomerase I is also a cytotoxic target for the mixed intercalative plus minor-groove binding drug nogalamycin. In contrast to the human enzyme, P. carinii topoisomerase I is resistant to both nitidine and potent protoberberine human topoisomerase I poisons. The differences in the sensitivities of P. carinii and human topoisomerase I to various topoisomerase I poisons support the use of the fungal enzyme as a molecular target for drug development. Additionally, we have characterized the interaction of pentamidine with P. carinii topoisomerase I. We show, by catalytic inhibition, cleavage, and yeast cytotoxicity assays, that pentamidine does not target topoisomerase I.Pneumocystis carinii pneumonia (PCP) is an opportunistic infection common in immune compromised individuals (35, 48). The incidence of this infection has decreased dramatically in individuals infected with human immunodeficiency virus due to the use of highly active antiretroviral therapy. However, in human immunodeficiency virus-infected individuals and cancer patients with CD4 cell counts lower than 200/l, long-term prophylaxis with the standard PCP drug combination sulfamethoxazole-trimethoprim (co-trimoxazole) is recommended (2). Continued use of co-trimoxazole in the treatment of Plasmodium falciparum, Escherichia coli, and Streptococcus pneumoniae infections is associated with the generation of point mutations in the dihydropteroate synthase gene, which confers resistance to sulfonamides. Such resistance has been seen in P. carinii-infected individuals (31,36,37,42). Therefore, novel antipneumocystis agents must be developed to address these concerns.Topoisomerases from a variety of organisms have been effective targets for cytotoxic drug development. These nuclear enzymes modulate the topology of DNA during processes such as transcription, replication, and recombination. Type I topoisomerases cleave a single DNA strand and allow "controlled rotation" of the strand to relieve torsional stress one linking number at a time (9,30,56). The type II enzymes cleave both DNA strands and change the linking number by two by passing intact, double-stranded DNA through the cut (reviewed in references 10 and 14). In the presence of certain drugs, topoisomerases are converted into cytotoxic molecules. Camptothecin (CPT) reversibly traps ...

show abstract

Structure-activity studies of dicationically substituted bis-benzimidazoles against Giardia lamblia: correlation of antigiardial activity with DNA binding affinity and giardial topoisomerase II inhibition

Cited by 100 publications

References 19 publications

Selective inhibition of topoisomerases from Pneumocystis carinii compared with that of topoisomerases from mammalian cells

Selective inhibition of topoisomerases from Pneumocystis carinii compared with that of topoisomerases from mammalian cells

Identification, characteristic and phylogenetic analysis of type II DNA topoisomerase gene in Giardia lamblia

Molecular Characterization of Recombinant Pneumocystis carinii Topoisomerase I: Differential Interactions with Human Topoisomerase I Poisons and Pentamidine

Contact Info

Product

Resources

About