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Human African trypanosomiasis: pharmacological re-engagement with a neglected disease. Br J Pharmacol 2007; 152:1155-71. [PMID: 17618313 DOI: 10.1038/sj.bjp.0707354] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This review discusses the challenges of chemotherapy for human African trypanosomiasis (HAT). The few drugs registered for use against the disease are unsatisfactory for a number of reasons. HAT has two stages. In stage 1 the parasites proliferate in the haemolymphatic system. In stage 2 they invade the central nervous system and brain provoking progressive neurological dysfunction leading to symptoms that include the disrupted sleep wake patterns that give HAT its more common name of sleeping sickness. Targeting drugs to the central nervous system offers many challenges. However, it is the cost of drug development for diseases like HAT, that afflict exclusively people of the world's poorest populations, that has been the principal barrier to new drug development and has led to them becoming neglected. Here we review drugs currently registered for HAT, and also discuss the few compounds progressing through clinical trials. Finally we report on new initiatives that might allow progress to be made in developing new and satisfactory drugs for this terrible disease.
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202
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Heby O, Persson L, Rentala M. Targeting the polyamine biosynthetic enzymes: a promising approach to therapy of African sleeping sickness, Chagas' disease, and leishmaniasis. Amino Acids 2007; 33:359-66. [PMID: 17610127 DOI: 10.1007/s00726-007-0537-9] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Accepted: 02/01/2007] [Indexed: 12/11/2022]
Abstract
Trypanosomatids depend on spermidine for growth and survival. Consequently, enzymes involved in spermidine synthesis and utilization, i.e. arginase, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC), spermidine synthase, trypanothione synthetase (TryS), and trypanothione reductase (TryR), are promising targets for drug development. The ODC inhibitor alpha-difluoromethylornithine (DFMO) is about to become a first-line drug against human late-stage gambiense sleeping sickness. Another ODC inhibitor, 3-aminooxy-1-aminopropane (APA), is considerably more effective than DFMO against Leishmania promastigotes and amastigotes multiplying in macrophages. AdoMetDC inhibitors can cure animals infected with isolates from patients with rhodesiense sleeping sickness and leishmaniasis, but have not been tested on humans. The antiparasitic effects of inhibitors of polyamine and trypanothione formation, reviewed here, emphasize the relevance of these enzymes as drug targets. By taking advantage of the differences in enzyme structure between parasite and host, it should be possible to design new drugs that can selectively kill the parasites.
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Affiliation(s)
- O Heby
- Department of Molecular Biology, Umeå University, Umeå, Sweden.
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203
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Gonzalez JL, Stephens CE, Wenzler T, Brun R, Tanious FA, Wilson WD, Barszcz T, Werbovetz KA, Boykin DW. Synthesis and antiparasitic evaluation of bis-2,5-[4-guanidinophenyl]thiophenes. Eur J Med Chem 2007; 42:552-7. [PMID: 17178177 DOI: 10.1016/j.ejmech.2006.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Revised: 11/12/2006] [Accepted: 11/16/2006] [Indexed: 11/27/2022]
Abstract
A series of bis-2,5-[4-guanidinophenyl]thiophenes were prepared in a five step process starting from 2,5-bis[trimethylstannyl]thiophene. The compounds were evaluated in vitro against Trypanosoma brucei rhodesiense (T. b. r.), Plasmodium falciparum (P. f.), Leshmania donovani (L. d.) and Trypanasoma cruzi (T. c.), and in vivo against T. b. r. Certain compounds show promising in vitro activity against T. b. r. and P. f. and have superior in vivo activity against T. b. r. to that of pentamidine and furamidine.
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Affiliation(s)
- Jose L Gonzalez
- Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University, University Plaza, Atlanta, GA 30303-3083, USA
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204
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Comini MA, Krauth-Siegel RL, Flohé L. Depletion of the thioredoxin homologue tryparedoxin impairs antioxidative defence in African trypanosomes. Biochem J 2007; 402:43-9. [PMID: 17040206 PMCID: PMC1783994 DOI: 10.1042/bj20061341] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In trypanosomes, the thioredoxin-type protein TXN (tryparedoxin) is a multi-purpose oxidoreductase that is involved in the detoxification of hydroperoxides, the synthesis of DNA precursors and the replication of the kinetoplastid DNA. African trypanosomes possess two isoforms that are localized in the cytosol and in the mitochondrion of the parasites respectively. Here we report on the biological significance of the cTXN (cytosolic TXN) of Trypanosoma brucei for hydroperoxide detoxification. Depending on the growth phase, the concentration of the protein is 3-7-fold higher in the parasite form infecting mammals (50-100 microM) than in the form hosted by the tsetse fly (7-34 microM). Depletion of the mRNA in bloodstream trypanosomes by RNA interference revealed the indispensability of the protein. Proliferation and viability of cultured trypanosomes were impaired when TXN was lowered to 1 muM for more than 48 h. Although the levels of glutathione, glutathionylspermidine and trypanothione were increased 2-3.5-fold, the sensitivity against exogenously generated H2O2 was significantly enhanced. The results prove the essential role of the cTXN and its pivotal function in the parasite defence against oxidative stress.
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Affiliation(s)
- Marcelo A Comini
- Centre of Biochemistry, Heidelberg University, Im Neuenheimer Feld 504, D-69120, Heidelberg, Germany.
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205
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Holloway GA, Baell JB, Fairlamb AH, Novello PM, Parisot JP, Richardson J, Watson KG, Street IP. Discovery of 2-iminobenzimidazoles as a new class of trypanothione reductase inhibitor by high-throughput screening. Bioorg Med Chem Lett 2007; 17:1422-7. [PMID: 17194585 PMCID: PMC3428904 DOI: 10.1016/j.bmcl.2006.11.090] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 11/21/2006] [Accepted: 11/30/2006] [Indexed: 11/26/2022]
Abstract
A high-throughput screening campaign of a library of 100,000 lead-like compounds identified 2-iminobenzimidazoles as a novel class of trypanothione reductase inhibitors. These 2-iminobenzimidazoles display potent trypanocidal activity against Trypanosoma brucei rhodesiense, do not inhibit closely related human glutathione reductase and have low cytotoxicity against mammalian cells.
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Affiliation(s)
- Georgina A. Holloway
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
| | - Jonathan B. Baell
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
| | - Alan H. Fairlamb
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, Wellcome Trust Biocentre, University of Dundee, Dundee, Scotland, UK
| | - Patrizia M. Novello
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
| | - John P. Parisot
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
| | - John Richardson
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, Wellcome Trust Biocentre, University of Dundee, Dundee, Scotland, UK
| | - Keith G. Watson
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
| | - Ian P. Street
- The Walter and Eliza Hall Institute of Medical Research, Biotechnology Centre, 4 Research Avenue, La Trobe Research and Development Park, Bundoora, Vic. 3086, Australia
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206
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Scory S, Stierhof YD, Caffrey CR, Steverding D. The cysteine proteinase inhibitor Z-Phe-Ala-CHN2 alters cell morphology and cell division activity of Trypanosoma brucei bloodstream forms in vivo. KINETOPLASTID BIOLOGY AND DISEASE 2007; 6:2. [PMID: 17328798 PMCID: PMC1810305 DOI: 10.1186/1475-9292-6-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 02/28/2007] [Indexed: 11/25/2022]
Abstract
Background Current chemotherapy of human African trypanosomiasis or sleeping sickness relies on drugs developed decades ago, some of which show toxic side effects. One promising line of research towards the development of novel anti-trypanosomal drugs are small-molecule inhibitors of Trypanosoma brucei cysteine proteinases. Results In this study, we demonstrate that treatment of T. brucei-infected mice with the inhibitor, carbobenzoxy-phenylalanyl-alanine-diazomethyl ketone (Z-Phe-Ala-CHN2), alters parasite morphology and inhibits cell division. Following daily intra-peritoneal administration of 250 mg kg-1 of Z-Phe-Ala-CHN2 on days three and four post infection (p.i.), stumpy-like forms with enlarged lysosomes were evident by day five p.i. In addition, trypanosomes exposed to the inhibitor had a 65% greater protein content than those from control mice. Also, in contrast to the normal 16% of parasites containing two kinetoplasts – a hallmark of active mitosis, only 4% of trypanosomes exposed to the inhibitor were actively dividing, indicating cell cycle-arrest. Conclusion We suggest that inhibition of endogenous cysteine proteinases by Z-Phe-Ala-CHN2 depletes the parasite of essential nutrients necessary for DNA synthesis, which in turn, prevents progression of the cell cycle. This arrest then triggers differentiation of the long-slender into short-stumpy forms.
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Affiliation(s)
- Stefan Scory
- Abteilung Parasitologie, Hygiene-Institut der Ruprecht Karls-Universität, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - York-Dieter Stierhof
- Abteilung Membranbiochemie, Max-Planck-Institut für Biologie, Corrensstraße 38, 72076 Tübingen, Germany
- Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität, Auf der Morgenstelle 1, 72076 Tübingen, Germany
| | - Conor R Caffrey
- Abteilung Tropenhygiene und Öffentliches Gesundheitswesen, Hygiene-Institut der Ruprecht Karls-Universität, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
- Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biomedical Research, Byers Hall, University of California San Francisco, 1700 4th Street, San Francisco, CA94158-2330, USA
| | - Dietmar Steverding
- Abteilung Parasitologie, Hygiene-Institut der Ruprecht Karls-Universität, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
- Present address: BioMedical Research Centre, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK
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207
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Steverding D. The proteasome as a potential target for chemotherapy of African trypanosomiasis. Drug Dev Res 2007. [DOI: 10.1002/ddr.20188] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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208
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Barrett MP, Gilbert IH. Targeting of toxic compounds to the trypanosome's interior. ADVANCES IN PARASITOLOGY 2006; 63:125-83. [PMID: 17134653 DOI: 10.1016/s0065-308x(06)63002-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Drugs can be targeted into African trypanosomes by exploiting carrier proteins at the surface of these parasites. This has been clearly demonstrated in the case of the melamine-based arsenical and the diamidine classes of drug that are already in use in the treatment of human African trypanosomiasis. These drugs can enter via an aminopurine transporter, termed P2, encoded by the TbAT1 gene. Other toxic compounds have also been designed to enter via this transporter. Some of these compounds enter almost exclusively through the P2 transporter, and hence loss of the P2 transporter leads to significant resistance to these particular compounds. It now appears, however, that some diamidines and melaminophenylarsenicals may also be taken up by other routes (of yet unknown function). These too may be exploited to target new drugs into trypanosomes. Additional purine nucleoside and nucleobase transporters have also been subverted to deliver toxic agents to trypanosomes. Glucose and amino acid transporters too have been investigated with a view to manipulating them to carry toxins into Trypanosoma brucei, and recent work has demonstrated that aquaglyceroporins may also have considerable potential for drug-targeting. Transporters, including those that carry lipids and vitamins such as folate and other pterins also deserve more attention in this regard. Some drugs, for example suramin, appear to enter via routes other than plasma-membrane-mediated transport. Receptor-mediated endocytosis has been proposed as a possible way in for suramin. Endocytosis also appears to be crucial in targeting natural trypanocides, such as trypanosome lytic factor (TLF) (apolipoprotein L1), into trypanosomes and this offers an alternative means of selectively targeting toxins to the trypanosome's interior. Other compounds may be induced to enter by increasing their capacity to diffuse over cell membranes; in this case depending exclusively on selective activity within the cell rather than selective uptake to impart selective toxicity. This review outlines studies that have aimed to exploit trypanosome nutrient uptake routes to selectively carry toxins into these parasites.
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Affiliation(s)
- Michael P Barrett
- Division of Infection & Immunity, Institute of Biomedical and Life Sciences, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, UK
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209
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Dawson A, Gibellini F, Sienkiewicz N, Tulloch LB, Fyfe PK, McLuskey K, Fairlamb AH, Hunter WN. Structure and reactivity of Trypanosoma brucei pteridine reductase: inhibition by the archetypal antifolate methotrexate. Mol Microbiol 2006; 61:1457-68. [PMID: 16968221 PMCID: PMC1618733 DOI: 10.1111/j.1365-2958.2006.05332.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The protozoan Trypanosoma brucei has a functional pteridine reductase (TbPTR1), an NADPH-dependent short-chain reductase that participates in the salvage of pterins, which are essential for parasite growth. PTR1 displays broad-spectrum activity with pterins and folates, provides a metabolic bypass for inhibition of the trypanosomatid dihydrofolate reductase and therefore compromises the use of antifolates for treatment of trypanosomiasis. Catalytic properties of recombinant TbPTR1 and inhibition by the archetypal antifolate methotrexate have been characterized and the crystal structure of the ternary complex with cofactor NADP+ and the inhibitor determined at 2.2 A resolution. This enzyme shares 50% amino acid sequence identity with Leishmania major PTR1 (LmPTR1) and comparisons show that the architecture of the cofactor binding site, and the catalytic centre are highly conserved, as are most interactions with the inhibitor. However, specific amino acid differences, in particular the placement of Trp221 at the side of the active site, and adjustment of the beta6-alpha6 loop and alpha6 helix at one side of the substrate-binding cleft significantly reduce the size of the substrate binding site of TbPTR1 and alter the chemical properties compared with LmPTR1. A reactive Cys168, within the active site cleft, in conjunction with the C-terminus carboxyl group and His267 of a partner subunit forms a triad similar to the catalytic component of cysteine proteases. TbPTR1 therefore offers novel structural features to exploit in the search for inhibitors of therapeutic value against African trypanosomiasis.
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Affiliation(s)
| | | | | | | | | | | | | | - William N Hunter
- *For correspondence. E-mail ; Tel. (+44) 1382 385745; Fax (+44) 1382 345764
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210
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Bosch J, Robien MA, Mehlin C, Boni E, Riechers A, Buckner FS, Van Voorhis WC, Myler PJ, Worthey EA, DeTitta G, Luft JR, Lauricella A, Gulde S, Anderson LA, Kalyuzhniy O, Neely HM, Ross J, Earnest TN, Soltis M, Schoenfeld L, Zucker F, Merritt EA, Fan E, Verlinde CLMJ, Hol WGJ. Using fragment cocktail crystallography to assist inhibitor design of Trypanosoma brucei nucleoside 2-deoxyribosyltransferase. J Med Chem 2006; 49:5939-46. [PMID: 17004709 DOI: 10.1021/jm060429m] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The 1.8 A resolution de novo structure of nucleoside 2-deoxyribosyltransferase (EC 2.4.2.6) from Trypanosoma brucei (TbNDRT) has been determined by SADa phasing in an unliganded state and several ligand-bound states. This enzyme is important in the salvage pathway of nucleoside recycling. To identify novel lead compounds, we exploited "fragment cocktail soaks". Out of 304 compounds tried in 31 cocktails, four compounds could be identified crystallographically in the active site. In addition, we demonstrated that very short soaks of approximately 10 s are sufficient even for rather hydrophobic ligands to bind in the active site groove, which is promising for the application of similar soaking experiments to less robust crystals of other proteins.
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Affiliation(s)
- Jürgen Bosch
- Department of Biochemistry, Division of Infectious Disease, and Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
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211
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Vickers TJ, Orsomando G, de la Garza RD, Scott DA, Kang SO, Hanson AD, Beverley SM. Biochemical and genetic analysis of methylenetetrahydrofolate reductase in Leishmania metabolism and virulence. J Biol Chem 2006; 281:38150-8. [PMID: 17032644 DOI: 10.1074/jbc.m608387200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Methylenetetrahydrofolate reductase (MTHFR; EC 1.5.1.20) is the sole enzyme responsible for generation of 5-methyltetrahydrofolate, which is required for methionine synthesis and provision of methyl groups via S-adenosylmethionine. Genome analysis showed that Leishmania species, unlike Trypanosoma brucei and Trypanosoma cruzi, contain genes encoding MTHFR and two distinct methionine synthases. Leishmania MTHFR differed from those in other eukaryotes by the absence of a C-terminal regulatory domain. L. major MTHFR was expressed in yeast and recombinant enzyme was produced in Escherichia coli. MTHFR was not inhibited by S-adenosylmethionine and, uniquely among folate-metabolizing enzymes, showed dual-cofactor specificity with NADH and NADPH under physiological conditions. MTHFR null mutants (mthfr(-)) lacked 5-methyltetrahydrofolate, the most abundant intracellular folate, and could not utilize exogenous homocysteine for growth. Under conditions of methionine limitation mthfr(-) mutant cells grew poorly, whereas their growth was normal in standard culture media. Neither in vitro MTHFR activity nor the growth of mthfr(-) mutants or MTHFR overexpressors were differentially affected by antifolates known to inhibit parasite growth via targets beyond dihydrofolate reductase and pteridine reductase 1. In a mouse model of infection mthfr(-) mutants showed good infectivity and virulence, indicating that sufficient methionine is available within the parasitophorous vacuole to meet the needs of the parasite.
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Affiliation(s)
- Tim J Vickers
- Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
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212
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Ismail MA, Arafa RK, Brun R, Wenzler T, Miao Y, Wilson WD, Generaux C, Bridges A, Hall JE, Boykin DW. Synthesis, DNA affinity, and antiprotozoal activity of linear dications: Terphenyl diamidines and analogues. J Med Chem 2006; 49:5324-32. [PMID: 16913722 DOI: 10.1021/jm060470p] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Diamidines 10a-g and 18a,b were obtained from dinitriles 9a-g and 15a,b by treatment with lithium trimethylsilylamide or upon hydrogenation of bis-O-acetoxyamidoximes. Dinitriles 9a-g were prepared via Suzuki reactions between arylboronic acids and arylnitriles. Potential prodrugs 12a-f and 17 were prepared via methylation of the diamidoximes 11a-f and 16a. Significant DNA affinities for rigid-rod molecules were observed. Compounds 10a, 10b, 10d, 18a, and 18b show IC50 values of 5 nM or less against Trypanosoma brucei rhodesiense (T. b. r.) and 10a, 10b, 10e, 18a, and 18b gave similar ones against Plasmodium falciparum (P.f.). The dications, 10a, 10d, 10f, and 10g are more active than furamidine in vivo. The prodrugs are only moderately effective on oral administration. Mouse liver microsome bioconversion of the methamidoxime prodrugs is significantly reduced from that of pafuramidine and suggests that the in vivo efficacy of these prodrugs is, in part, due to poor bioconversion.
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Affiliation(s)
- Mohamed A Ismail
- Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303-3083, USA
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213
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Abstract
The utility of the two docking programs DOCK and AutoDock in studying the binding of small molecules to the minor groove of B-DNA is examined. The AutoDock program is found to be more effective in both pose prediction and ranking of known binders over random compounds, and this superior performance is shown to be because of the scoring functions rather than the sampling algorithms.
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Affiliation(s)
- David A Evans
- Cancer Research UK Biomolecular Structure Group, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, UK
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214
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Chaudhuri M, Ott RD, Hill GC. Trypanosome alternative oxidase: from molecule to function. Trends Parasitol 2006; 22:484-91. [PMID: 16920028 DOI: 10.1016/j.pt.2006.08.007] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Revised: 07/06/2006] [Accepted: 08/04/2006] [Indexed: 10/24/2022]
Abstract
Trypanosome alternative oxidase (TAO) is the cytochrome-independent terminal oxidase of the mitochondrial electron transport chain. TAO is a diiron protein that transfers electrons from ubiquinol to oxygen, reducing the oxygen to water. The mammalian bloodstream forms of Trypanosoma brucei depend solely on TAO for respiration. The inhibition of TAO by salicylhydroxamic acid (SHAM) or ascofuranone is trypanocidal. TAO is present at a reduced level in the procyclic form of T. brucei, where it is engaged in respiration and is also needed for developmental processes. Alternative oxidases similar to TAO have been found in a wide variety of organisms but not in mammals, thus rendering TAO an important chemotherapeutic target for African trypanosomiasis.
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Affiliation(s)
- Minu Chaudhuri
- Division of Microbial Pathogenesis and Immune Response, Department of Biomedical Sciences, Meharry Medical College, Nashville, TN 37208, USA.
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215
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Merschjohann K, Steverding D. In vitro growth inhibition of bloodstream forms of Trypanosoma brucei and Trypanosoma congolense by iron chelators. KINETOPLASTID BIOLOGY AND DISEASE 2006; 5:3. [PMID: 16914038 PMCID: PMC1563472 DOI: 10.1186/1475-9292-5-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 08/16/2006] [Indexed: 12/02/2022]
Abstract
African trypanosomes exert significant morbidity and mortality in man and livestock. Only a few drugs are available for the treatment of trypanosome infections and therefore, the development of new anti-trypanosomal agents is required. Previously it has been shown that bloodstream-form trypanosomes are sensitive to the iron chelator deferoxamine. In this study the effect of 13 iron chelators on the growth of Trypanosoma brucei, T. congolense and human HL-60 cells was tested in vitro. With the exception of 2 compounds, all chelators exhibited anti-trypanosomal activities, with 50% inhibitory concentration (IC50) values ranging between 2.1 – 220 μM. However, the iron chelators also displayed cytotoxicity towards human HL-60 cells and therefore, only less favourable selectivity indices compared to commercially available drugs. Interfering with iron metabolism may be a new strategy in the treatment of trypanosome infections. More specifically, lipophilic iron-chelating agents may serve as lead compounds for novel anti-trypanosomal drug development.
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Affiliation(s)
- Karin Merschjohann
- Department of Parasitology, Ruprecht-Karls-University, 69120 Heidelberg, Germany
| | - Dietmar Steverding
- Department of Parasitology, Ruprecht-Karls-University, 69120 Heidelberg, Germany
- Biomedical Research Centre, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK
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216
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Lanteri CA, Stewart ML, Brock JM, Alibu VP, Meshnick SR, Tidwell RR, Barrett MP. Roles for theTrypanosoma bruceiP2 Transporter in DB75 Uptake and Resistance. Mol Pharmacol 2006; 70:1585-92. [PMID: 16912218 DOI: 10.1124/mol.106.024653] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A novel trypanocide, 2,5-bis(4-amidinophenyl)furan (DB75), in its prodrug amidoxime-derivative form, 2,5-bis(4-amidinophenyl)furan-bis-O-methylamidoxime (DB289), is in trials as the first orally administered drug for human African trypanosomiasis. DB75 is a diamidine. Resistance to some diamidines correlates to loss of uptake via the P2 aminopurine transporter. We show here that uptake of DB75 into Trypanosoma brucei also occurs principally via the P2 transporter. Uptake of tritiated DB75 occurred via a high-affinity (K(m app), 3.2 microM) carriermediated route that was inhibited by adenosine, adenine, and pentamidine, all known substrates of the P2 transporter. Trypanosomes lacking the TbAT1 gene that encodes the P2 transporter demonstrated an 11-fold reduction in sensitivity to DB75 when measured under controlled in vitro conditions. These knockout cells were also less sensitive to DB75 than wild-type cells in mice. Initial uptake rates of DB75 into the Deltatbat1 knockout cell line were greatly reduced compared with rates in wild-type cells. A trypanosome cell line selected in vitro for DB75 resistance was shown to have lost P2-mediated DB75 uptake. The TbAT1 gene was mapped to chromosome V of the T. brucei genome and the DB75-resistant parasites were shown to have deleted both alleles of this gene. Fluorescence microscopy of DB75-treated trypanosomes revealed that DB75 fluorescence localizes rapidly within the DNA-containing organelles of wild-type trypanosomes, whereas no fluorescence was observed in Deltatbat1-null parasites or in the parasites selected for resistance to DB75.
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Affiliation(s)
- Charlotte A Lanteri
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, The Glasgow Biomedical Research Centre, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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217
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Chackal-Catoen S, Miao Y, Wilson WD, Wenzler T, Brun R, Boykin DW. Dicationic DNA-targeted antiprotozoal agents: naphthalene replacement of benzimidazole. Bioorg Med Chem 2006; 14:7434-45. [PMID: 16889966 DOI: 10.1016/j.bmc.2006.07.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 07/03/2006] [Accepted: 07/07/2006] [Indexed: 10/24/2022]
Abstract
A series of naphthalene analogues of highly active benzimidazole diamidines were synthesized using sequential Stille and Suzuki coupling reactions for preparation of the bis-nitrile intermediates. All of the diamidines showed strong DNA affinities as judged by high DeltaTm values with poly(dA-dT). The dicationic compounds were quite active in vitro versus Trypanosoma brucei rhodesiense (T. b. r.) exhibiting IC50 values ranging from 4 to 98 nM. These compounds were also active versus Plasmodium falciparum (P. f.) giving IC50 values ranging from 4 to 33 nM. Two of the compounds showed good activity in vivo in the STIB900 model for acute African trypanosomiasis; one gave 3/4 cures and the other gave 4/4 cures on ip dosage of 20 mg/kg for 4 days. The amidoxime prodrugs of the naphthalene analogues were essentially ineffective.
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Affiliation(s)
- Sarah Chackal-Catoen
- Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303-3083, USA
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218
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Mathis AM, Holman JL, Sturk LM, Ismail MA, Boykin DW, Tidwell RR, Hall JE. Accumulation and intracellular distribution of antitrypanosomal diamidine compounds DB75 and DB820 in African trypanosomes. Antimicrob Agents Chemother 2006; 50:2185-91. [PMID: 16723581 PMCID: PMC1479144 DOI: 10.1128/aac.00192-06] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The aromatic diamidine pentamidine has long been used to treat early-stage human African trypanosomiasis (HAT). Two analogs of pentamidine, DB75 and DB820, have been shown to be more potent and less toxic than pentamidine in murine models of trypanosomiasis. The diphenyl furan diamidine, DB75, is the active metabolite of the prodrug DB289, which is currently in phase III clinical trials as a new orally active candidate drug to treat first-stage HAT. The new aza analog, DB820, is the active diamidine of the prodrug DB844, currently undergoing preclinical evaluation as a new candidate to treat HAT of the central nervous system. The exact mechanisms of antitrypanosomal activity of aromatic dications remain poorly understood, with multiple mechanisms hypothesized. Pentamidine is known to be actively transported into trypanosomes and binds to DNA within the nucleus and kinetoplast. A long-hypothesized mechanism of action has been that DNA binding ultimately leads to interference with DNA-associated enzymes. Both DB75 and DB820 are intensely fluorescent, which provides an important tool for determining the kinetics of accumulation and intracellular distribution in trypanosomes. We show in the current study that DB75 and DB820 rapidly accumulate and strongly concentrate within trypanosomes, with intracellular concentrations over 15,000-fold higher than mouse plasma concentrations. Both compounds initially accumulate in the DNA-containing nucleus and kinetoplast, but at later time points, they concentrate in non-DNA-containing cytoplasmic organelles. Analyses of the kinetics of uptake and intracellular distribution are necessary to begin to define antitrypanosomal mechanisms of action of DB75, DB820, and other aromatic diamidines.
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Affiliation(s)
- Amanda M Mathis
- Division of Molecular Pharmaceutics, School of Pharmacy, University of North Carolina, Chapel Hill, Chapel 27599, USA
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219
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Hayeshi R, Masimirembwa C, Mukanganyama S, Ungell ALB. The potential inhibitory effect of antiparasitic drugs and natural products on P-glycoprotein mediated efflux. Eur J Pharm Sci 2006; 29:70-81. [PMID: 16846720 DOI: 10.1016/j.ejps.2006.05.009] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 05/03/2006] [Accepted: 05/29/2006] [Indexed: 11/27/2022]
Abstract
The potential inhibitory effect on P-glycoprotein (Pgp) by antiparasitic drugs and natural compounds was investigated. Compounds were screened for Pgp interaction based on inhibition of Pgp mediated [3H]-taxol transport in Caco-2 cells. Bidirectional transport of selected inhibitors was further evaluated to identify potential Pgp substrates using the Caco-2 cells. Of 21 antiparasitics tested, 14 were found to inhibit Pgp mediated [3H]-taxol with K(iapp) values in the range 4-2000 microM. The antimalarial quinine was the most potent inhibitor with a K(iapp) of 4 microM. Of the 12 natural compounds tested, 3 inhibited [3H]-taxol transport with K(iapp) values in the range 50-400 microM. Quinine, amodiaquine, chloroquine, flavone, genistein, praziquantel, quercetin and thiabendazole were further investigated in bidirectional transport assays to determine whether they were substrates for Pgp. Transport of quinine in the secretory direction exceeded that in the absorptive direction and was saturable, suggesting quinine being a Pgp substrate. The rest of the compounds inhibiting Pgp showed no evidence of being Pgp substrates. In conclusion, we have demonstrated that a substantial number of antiparasitic and natural compounds, in a range of concentrations, are capable of inhibiting Pgp mediated [3H]-taxol efflux in Caco-2 cells, without being substrates and this may have implications for drug interactions with Pgp.
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Affiliation(s)
- Rose Hayeshi
- Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe
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220
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Athri P, Wenzler T, Ruiz P, Brun R, Boykin DW, Tidwell R, Wilson WD. 3D QSAR on a library of heterocyclic diamidine derivatives with antiparasitic activity. Bioorg Med Chem 2006; 14:3144-52. [PMID: 16442293 DOI: 10.1016/j.bmc.2005.12.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 11/24/2005] [Accepted: 12/16/2005] [Indexed: 11/26/2022]
Abstract
African trypanosomes, Trypanosoma brucei rhodesiense (TBR) and Trypanosoma brucei gambiense (TBG), affect hundreds of thousands of lives in tropical regions of the world. The toxicity of the diamidine pentamidine, an effective drug against TBG, necessitates the design of better drugs. An orally effective prodrug of the diamidine, furamidine (DB75), presently scheduled for phase III clinical trials, has excellent activity against TBG with toxicity lower than that of pentamidine. As part of an effort to develop additional and improved diamidines against African trypanosomes, CoMFA and CoMSIA 3D QSAR analyses have been conducted with furamidine and a set of 25 other structurally related compounds. Two different alignment strategies, based on a putative kinetoplast DNA minor groove target, were used. Due to conserved electrostatic properties across the compounds, models that used only steric and electronic properties did not perform well in predicting biological results. An extended CoMSIA model with additional descriptors for hydrophobic, donor, and acceptor properties had good predictive ability with a q2=0.699, r2=0.974, SEE, standard error of estimate=0.1, and F=120.04. The results have been used as a guide to design compounds that, potentially, have better activity against African trypanosomes.
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Affiliation(s)
- Prashanth Athri
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
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221
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Steverding D. A new initiative for the development of new diagnostic tests for human African trypanosomiasis. KINETOPLASTID BIOLOGY AND DISEASE 2006; 5:1. [PMID: 16638141 PMCID: PMC1464096 DOI: 10.1186/1475-9292-5-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Accepted: 04/25/2006] [Indexed: 11/25/2022]
Abstract
Human African trypanosomiasis is a threat to millions of people living in sub-Saharan countries and is fatal unless treated. At present, the serological and parasitological tests used in the field for diagnosis of sleeping sickness have low specificity and sensitivity. There is clearly an urgent need for accurate tools for both diagnosis and staging of the disease. The Foundation for Innovative New Diagnostics and the World Health Organization have announced that they will collaborate to develop and evaluate new diagnostic tests for human African trypanosomiasis.
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Affiliation(s)
- Dietmar Steverding
- Biomedical Research Centre, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK.
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222
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Göringer HU, Homann M, Zacharias M, Adler A. RNA aptamers as potential pharmaceuticals against infections with African trypanosomes. Handb Exp Pharmacol 2006:375-93. [PMID: 16594626 DOI: 10.1007/3-540-27262-3_19] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Protozoal pathogens cause symptomatic as well as asymptomatic infections. They have a worldwide impact, which in part is reflected in the long-standing search for antiprotozoal chemotherapy. Unfortunately, effective treatments for the different diseases are by and large not available. This is especially true for African trypanosomiasis, also known as sleeping sickness. The disease is an increasing problem in many parts of sub-Saharan Africa, which is due to the lack of new therapeutics and the increasing resistance against traditional drugs such as melarsoprol, berenil and isometamidium. Considerable progress has been made over the past 10 years in the development of nucleic acid-based drug molecules using a variety of different technologies. One approach is a combinatorial technology that involves an iterative Darwinian-type in vitro evolution process, which has been termed SELEX for "systematic evolution of ligands by exponential enrichment". The procedure is a highly efficient method of identifying rare ligands from combinatorial nucleic acid libraries of very high complexity. It allows the selection of nucleic acid molecules with desired functions, and it has been instrumental in the identification of a number of synthetic DNA and RNA molecules, so-called aptamers that recognize ligands of different chemical origin. Aptamers typically bind their target with high affinity and high specificity and have successfully been converted into pharmaceutically active compounds. Here we summarize the recent examples of the SELEX technique within the context of identifying high-affinity RNA ligands against the surface of the protozoan parasite Trypanosoma brucei, which is the causative agent of sleeping sickness.
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Affiliation(s)
- H U Göringer
- Genetics, Darmstadt University of Technology, Schnittspahnstr. 10, 64287 Darmstadt, Germany.
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223
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Wu D, George TG, Hurh E, Werbovetz KA, Dalton JT. Pre-systemic metabolism prevents in vivo antikinetoplastid activity of N1,N4-substituted 3,5-dinitro sulfanilamide, GB-II-150. Life Sci 2006; 79:1081-93. [PMID: 16643960 DOI: 10.1016/j.lfs.2006.03.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/07/2006] [Accepted: 03/08/2006] [Indexed: 11/18/2022]
Abstract
We previously showed that N1-phenyl-3,5-dinitro-N4,N4-di-n-butylsulfanilamide (denoted GB-II-150) possesses selective antimicrotubule activity against Leishmania donovani and Trypanosoma brucei in vitro [Bhattacharya, G., Herman, J., Delfin, D., Salem, M.M., Barszcz, T., Mollet, M., Riccio, G., Brun, R., Werbovetz, K.A., 2004. Synthesis and antitubulin activity of N(1)- and N(4)-substituted 3,5-dinitro sulfanilamides against African trypanosomes and Leishmania. Journal of Medicinal Chemistry 47, 1823-1832]. When GB-II-150 was administered orally to male Sprague-Dawley rats, extensive first-pass metabolism of the compound was observed and the oral bioavailability was zero. GB-II-150 displayed a half-life of 170 min and a clearance of 31.5 mL/min/kg in rats when administered intravenously. In vitro metabolism studies indicated that less than 5% of GB-II-150 remained intact after a 60-min incubation with rat liver S9 fraction. As expected, the compound was extensively metabolized, with the major products resulting from N1-ring oxidation, N4-alkane oxidation, N4-oxidation, and nitro reduction. These data indicate that GB-II-150 undergoes rapid and extensive first-pass metabolism, precluding the attainment of effective systemic drug concentrations and explaining the lack of in vivo antitrypanosomal activity of this compound.
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Affiliation(s)
- Di Wu
- Division of Pharmaceutics, College of Pharmacy, The Ohio State University, 500 West 12th Avenue, Columbus, OH 43210, USA.
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224
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Ismail MA, Boykin DW. Synthesis of deuterium and15N-labelled 2,5-Bis[5-amidino-2-pyridyl]furan and 2,5-Bis[5-(methoxyamidino)-2-pyridyl]furan. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.1111] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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225
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Fèvre EM, Picozzi K, Jannin J, Welburn SC, Maudlin I. Human African Trypanosomiasis: Epidemiology and Control. ADVANCES IN PARASITOLOGY 2006; 61:167-221. [PMID: 16735165 DOI: 10.1016/s0065-308x(05)61005-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Human African trypanosomiasis (HAT), or sleeping sickness, describes not one but two discrete diseases: that caused by Trypanosoma brucei rhodesiense and that caused by T. b. gambiense. The Gambian form is currently a major public health problem over vast areas of central and western Africa, while the zoonotic, Rhodesian form continues to present a serious health risk in eastern and southern Africa. The two parasites cause distinct clinical manifestations, and there are significant differences in the epidemiology of the diseases caused. We discuss the differences between the diseases caused by the two parasites, with an emphasis on disease burden, reservoir hosts, transmission, diagnosis, treatment and control. We analyse how these differences impacted on historical disease control trends and how they can inform contemporary treatment and control options. We consider the optimal ways in which to devise HAT control policies in light of the differing biology and epidemiology of the parasites, and emphasise, in particular, the wider aspects of control policy, outlining the responsibilities of individuals, governments and international organisations in control programmes.
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Affiliation(s)
- E M Fèvre
- Centre for Infectious Diseases, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian, EH25 9RG, UK
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226
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Dardonville C. Recent advances in antitrypanosomal chemotherapy: patent literature 2002 – 2004. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.15.9.1241] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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227
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Ismail MA, Batista-Parra A, Miao Y, Wilson WD, Wenzler T, Brun R, Boykin DW. Dicationic near-linear biphenyl benzimidazole derivatives as DNA-targeted antiprotozoal agents. Bioorg Med Chem 2005; 13:6718-26. [PMID: 16099661 DOI: 10.1016/j.bmc.2005.07.024] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Accepted: 07/20/2005] [Indexed: 11/29/2022]
Abstract
A series of near-linear biphenyl benzimidazole diamidines 5a-h were synthesized from their respective diamidoximes (4a-h), through the bis-O-acetoxyamidoxime, followed by hydrogenation in glacial acetic acid/ethanol in the presence of Pd-C. Compounds 4a-h were obtained in three steps, starting with the Suzuki coupling reaction of the appropriate haloarylcarbonitriles 1a-g or 4-bromo-2-fluorobenzaldehyde with 4-formylphenylboronic acid or 4-cyanophenylboronic acid to form the anticipated 4-formylbiphenyl carbonitrile analogues 2a-h. Subsequent condensation of the formyl derivatives 2a-h with 3,4-diaminobenzonitrile in the presence of sodium bisulfite or 1,4-benzoquinone gave the desired dinitriles 3a-h, the precursors for 4a-h. All the diamidines showed strong DNA affinities, as judged by high Delta Tm values with poly(dA.dT)2) The compounds were quite active in vitro versus Trypanosoma brucei rhodesiense, giving IC50 values ranging from 3 to 37 nM. These compounds were even more active versus Plasmodium falciparum, exhibiting IC50 values ranging from 0.5 to 23 nM. The compounds showed moderate to good activity in vivo in the STIB900 model for acute African trypanosomiasis. The most active compounds 5b and e gave 3/4 cures on an IP dosage of 20 mg/kg.
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Affiliation(s)
- Mohamed A Ismail
- Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303-3083, USA
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228
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Campbell NH, Evans DA, Lee MPH, Parkinson GN, Neidle S. Targeting the DNA minor groove with fused ring dicationic compounds: comparison of in silico screening and a high-resolution crystal structure. Bioorg Med Chem Lett 2005; 16:15-9. [PMID: 16263285 DOI: 10.1016/j.bmcl.2005.10.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Accepted: 10/12/2005] [Indexed: 01/27/2023]
Abstract
The crystal structure of the DNA minor groove biphenyl benzimidazole diamidine ligand DB819 has been determined, bound to the DNA sequence d(CGCGAATTCGCG)(2), at a resolution of 1.36 Angstrom. Conditions for reliable in silico docking that reproduce the observed position of the ligand in the minor groove have been determined.
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Affiliation(s)
- Nancy H Campbell
- Cancer Research UK Biomolecular Structure Group, The School of Pharmacy, University of London, London WC1N 1AX, UK
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229
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Kunz S, Beavo JA, D'Angelo MA, Flawia MM, Francis SH, Johner A, Laxman S, Oberholzer M, Rascon A, Shakur Y, Wentzinger L, Zoraghi R, Seebeck T. Cyclic nucleotide specific phosphodiesterases of the kinetoplastida: a unified nomenclature. Mol Biochem Parasitol 2005; 145:133-5. [PMID: 16280178 DOI: 10.1016/j.molbiopara.2005.09.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 09/22/2005] [Accepted: 09/27/2005] [Indexed: 01/26/2023]
Affiliation(s)
- Stefan Kunz
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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230
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Arafa RK, Brun R, Wenzler T, Tanious FA, Wilson WD, Stephens CE, Boykin DW. Synthesis, DNA affinity, and antiprotozoal activity of fused ring dicationic compounds and their prodrugs. J Med Chem 2005; 48:5480-8. [PMID: 16107146 DOI: 10.1021/jm058190h] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dicationic guanidine, N-alkylguanidine, and reversed amidine derivatives of fused ring systems have been synthesized from their corresponding bis-amines. DNA binding studies suggest that the diguanidines and the N-alkyl diguanidines fluorenes bind in the minor groove in a manner similar to that of the previously reported dicationic carbazole derivatives. The diguanidines and the N-alkyl diguanidines showed promising in vitro activity against both Trypanosoma brucei rhodesiense and Plasmodium falciparum. Promising in vivo biological results were obtained for the dicationic N-isopropylguanidino-9H-fluorene, giving 4/4 cures of the treated animals in the STIB900 animal model for African trypanosomiasis. The N-methyl analogue showed high activity as well. In addition, with the goal of enhancing the oral bioavailability, two novel classes of potential guanidine prodrugs were prepared. The N-alkoxyguanidine derivatives were not effective as prodrugs. In contrast, a number of the carbamates showed promising activity. The value of the carbamate prodrugs was clearly demonstrated by the results, which gave 4/4 cures on oral administration in the STIB900 mouse model.
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Affiliation(s)
- Reem K Arafa
- Department of Chemistry and Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30303-3083, USA
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231
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Schüttelkopf AW, Hardy LW, Beverley SM, Hunter WN. Structures of Leishmania major pteridine reductase complexes reveal the active site features important for ligand binding and to guide inhibitor design. J Mol Biol 2005; 352:105-16. [PMID: 16055151 DOI: 10.1016/j.jmb.2005.06.076] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Revised: 06/29/2005] [Accepted: 06/30/2005] [Indexed: 11/23/2022]
Abstract
Pteridine reductase (PTR1) is an NADPH-dependent short-chain reductase found in parasitic trypanosomatid protozoans. The enzyme participates in the salvage of pterins and represents a target for the development of improved therapies for infections caused by these parasites. A series of crystallographic analyses of Leishmania major PTR1 are reported. Structures of the enzyme in a binary complex with the cofactor NADPH, and ternary complexes with cofactor and biopterin, 5,6-dihydrobiopterin, and 5,6,7,8-tetrahydrobiopterin reveal that PTR1 does not undergo any major conformational changes to accomplish binding and processing of substrates, and confirm that these molecules bind in a single orientation at the catalytic center suitable for two distinct reductions. Ternary complexes with cofactor and CB3717 and trimethoprim (TOP), potent inhibitors of thymidylate synthase and dihydrofolate reductase, respectively, have been characterized. The structure with CB3717 reveals that the quinazoline moiety binds in similar fashion to the pterin substrates/products and dominates interactions with the enzyme. In the complex with TOP, steric restrictions enforced on the trimethoxyphenyl substituent prevent the 2,4-diaminopyrimidine moiety from adopting the pterin mode of binding observed in dihydrofolate reductase, and explain the inhibition properties of a range of pyrimidine derivates. The molecular detail provided by these complex structures identifies the important interactions necessary to assist the structure-based development of novel enzyme inhibitors of potential therapeutic value.
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Affiliation(s)
- Alexander W Schüttelkopf
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
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232
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Ariza A, Vickers TJ, Greig N, Fairlamb AH, Bond CS. Crystallization and preliminary X-ray analysis of Leishmania major glyoxalase I. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:769-72. [PMID: 16511153 PMCID: PMC1952357 DOI: 10.1107/s174430910502169x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 07/06/2005] [Indexed: 11/11/2022]
Abstract
Glyoxalase I (GLO1) is a putative drug target for trypanosomatids, which are pathogenic protozoa that include the causative agents of leishmaniasis. Significant sequence and functional differences between Leishmania major and human GLO1 suggest that it may make a suitable template for rational inhibitor design. L. major GLO1 was crystallized in two forms: the first is extremely disordered and does not diffract, while the second, an orthorhombic form, produces diffraction to 2.0 A. Molecular-replacement calculations indicate that there are three GLO1 dimers in the asymmetric unit, which take up a helical arrangement with their molecular dyads arranged approximately perpendicular to the c axis. Further analysis of these data are under way.
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Affiliation(s)
- Antonio Ariza
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Tim J. Vickers
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Neil Greig
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Alan H. Fairlamb
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Charles S. Bond
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
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233
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Berriman M, Ghedin E, Hertz-Fowler C, Blandin G, Renauld H, Bartholomeu DC, Lennard NJ, Caler E, Hamlin NE, Haas B, Böhme U, Hannick L, Aslett MA, Shallom J, Marcello L, Hou L, Wickstead B, Alsmark UCM, Arrowsmith C, Atkin RJ, Barron AJ, Bringaud F, Brooks K, Carrington M, Cherevach I, Chillingworth TJ, Churcher C, Clark LN, Corton CH, Cronin A, Davies RM, Doggett J, Djikeng A, Feldblyum T, Field MC, Fraser A, Goodhead I, Hance Z, Harper D, Harris BR, Hauser H, Hostetler J, Ivens A, Jagels K, Johnson D, Johnson J, Jones K, Kerhornou AX, Koo H, Larke N, Landfear S, Larkin C, Leech V, Line A, Lord A, Macleod A, Mooney PJ, Moule S, Martin DMA, Morgan GW, Mungall K, Norbertczak H, Ormond D, Pai G, Peacock CS, Peterson J, Quail MA, Rabbinowitsch E, Rajandream MA, Reitter C, Salzberg SL, Sanders M, Schobel S, Sharp S, Simmonds M, Simpson AJ, Tallon L, Turner CMR, Tait A, Tivey AR, Van Aken S, Walker D, Wanless D, Wang S, White B, White O, Whitehead S, Woodward J, Wortman J, Adams MD, Embley TM, Gull K, Ullu E, Barry JD, Fairlamb AH, Opperdoes F, Barrell BG, Donelson JE, Hall N, Fraser CM, Melville SE, El-Sayed NM. The genome of the African trypanosome Trypanosoma brucei. Science 2005; 309:416-22. [PMID: 16020726 DOI: 10.1126/science.1112642] [Citation(s) in RCA: 1257] [Impact Index Per Article: 66.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.
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Affiliation(s)
- Matthew Berriman
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.
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234
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Docampo R, de Souza W, Miranda K, Rohloff P, Moreno SNJ. Acidocalcisomes - conserved from bacteria to man. Nat Rev Microbiol 2005; 3:251-61. [PMID: 15738951 DOI: 10.1038/nrmicro1097] [Citation(s) in RCA: 314] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Recent work has shown that acidocalcisomes, which are electron-dense acidic organelles rich in calcium and polyphosphate, are the only organelles that have been conserved during evolution from prokaryotes to eukaryotes. Acidocalcisomes were first described in trypanosomatids and have been characterized in most detail in these species. Acidocalcisomes have been linked with several functions, including storage of cations and phosphorus, polyphosphate metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis and osmoregulation. Here, we review acidocalcisome ultrastructure, composition and function in different trypanosomatids and other organisms.
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Affiliation(s)
- Roberto Docampo
- Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, Georgia 30602, USA.
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235
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Deterding A, Dungey FA, Thompson KA, Steverding D. Anti-trypanosomal activities of DNA topoisomerase inhibitors. Acta Trop 2005; 93:311-6. [PMID: 15715983 DOI: 10.1016/j.actatropica.2005.01.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Revised: 01/07/2005] [Accepted: 01/12/2005] [Indexed: 11/24/2022]
Abstract
Only four drugs are available for chemotherapy of human African sleeping sickness with undesirable toxic side effects. The development of new anti-trypanosomal drugs is, therefore, urgently required. In this study, 15 DNA topoisomerase inhibitors, including approved anti-cancer drugs, were tested for in vitro activity against bloodstream forms of Trypanosoma brucei and human leukaemia HL-60 cells. All compounds exhibited anti-trypanosomal activity, with ED50 values ranging between 3 nM and 30 microM, and MIC values between 100 nM and >100 microM. The trypanocidal activities of the most effective DNA topoisomerase inhibitors, aclarubicin, doxorubicin and mitoxantrone, were comparable with those of commercial anti-trypanosomal drugs. These data support the use of DNA topoisomerase inhibitors as lead compounds for anti-trypanosomal drug development.
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Affiliation(s)
- Alexander Deterding
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, United Kingdom
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236
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Moyersoen J, Choe J, Fan E, Hol WGJ, Michels PAM. Biogenesis of peroxisomes and glycosomes: trypanosomatid glycosome assembly is a promising new drug target. FEMS Microbiol Rev 2005; 28:603-43. [PMID: 15539076 DOI: 10.1016/j.femsre.2004.06.004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 06/14/2004] [Accepted: 06/15/2004] [Indexed: 10/26/2022] Open
Abstract
In trypanosomatids (Trypanosoma and Leishmania), protozoa responsible for serious diseases of mankind in tropical and subtropical countries, core carbohydrate metabolism including glycolysis is compartmentalized in peculiar peroxisomes called glycosomes. Proper biogenesis of these organelles and the correct sequestering of glycolytic enzymes are essential to these parasites. Biogenesis of glycosomes in trypanosomatids and that of peroxisomes in other eukaryotes, including the human host, occur via homologous processes involving proteins called peroxins, which exert their function through multiple, transient interactions with each other. Decreased expression of peroxins leads to death of trypanosomes. Peroxins show only a low level of sequence conservation. Therefore, it seems feasible to design compounds that will prevent interactions of proteins involved in biogenesis of trypanosomatid glycosomes without interfering with peroxisome formation in the human host cells. Such compounds would be suitable as lead drugs against trypanosomatid-borne diseases.
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Affiliation(s)
- Juliette Moyersoen
- Research Unit for Tropical Diseases, Christian de Duve Institute of Cellular Pathology and Laboratory of Biochemistry, Université Catholique de Louvain, ICP-TROP 74.39, Avenue Hippocrate 74, B-1200 Brussels, Belgium
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237
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Téllez-Valencia A, Olivares-Illana V, Hernández-Santoyo A, Pérez-Montfort R, Costas M, Rodríguez-Romero A, López-Calahorra F, Tuena De Gómez-Puyou M, Gómez-Puyou A. Inactivation of triosephosphate isomerase from Trypanosoma cruzi by an agent that perturbs its dimer interface. J Mol Biol 2004; 341:1355-65. [PMID: 15321726 DOI: 10.1016/j.jmb.2004.06.056] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Revised: 06/10/2004] [Accepted: 06/14/2004] [Indexed: 11/17/2022]
Abstract
We characterized by crystallographic, calorimetric and biochemical methods the action of a low molecular weight compound, 3-(2-benzothiazolylthio)-1-propanesulfonic acid (compound 8) that binds to the dimer interface of triosephosphate isomerase from Trypanosoma cruzi (TcTIM) and thereby abolishes its function with a high level of selectivity. The kinetics of TcTIM inactivation by the agent and isothermal titration calorimetry experiments showed that the binding of two molecules of the compound per enzyme is needed for inactivation. The binding of the first molecule is endothermic, and that of the second exothermic. Crystals of TcTIM in complex with one molecule of the inactivating agent that diffracted to a resolution of 2A were obtained. The compound is at the dimer interface at less than 4A from residues of the two subunits. Compound 8 is more effective at low than at high protein concentrations, indicating that it perturbs the association between the two TcTIM monomers. Calorimetric and kinetic data of experiments in which TcTIM was added to a solution of the inactivating agent showed that at low concentrations of the compound, inactivation is limited by binding, whereas at high concentrations of the agent, the events that follow binding become rate-limiting. The portion of the interface of TcTIM that binds the benzothiazole derivative and its equivalent region in human TIM differs in amino acid composition and hydrophobic packing. Thus, we show that by focusing on protein-protein interfaces, it is possible to discover low molecular weight compounds that are selective for enzymes from parasites.
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Affiliation(s)
- Alfredo Téllez-Valencia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D.F., 04510 México
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238
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Mallena S, Lee MPH, Bailly C, Neidle S, Kumar A, Boykin DW, Wilson WD. Thiophene-Based Diamidine Forms a “Super” AT Binding Minor Groove Agent. J Am Chem Soc 2004; 126:13659-69. [PMID: 15493923 DOI: 10.1021/ja048175m] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The DNA minor groove is the interaction site for many enzymes and transcription control proteins and as a result, development of compounds that target the minor groove is an active research area. In an effort to develop biologically active minor groove agents, we are preparing and exploring the DNA interactions of a systematic set of diamidine derivatives with a powerful array of methods including DNase I footprinting, biosensor-SPR methods, and X-ray crystallography. Surprisingly, conversion of the parent phenyl-furan-phenyl diamidine to a phenyl-thiophene-benzimidazole derivative yields a compound with over 10-fold-increased affinity for the minor groove at AT sequences. Single conversion of the furan to a thiophene or a phenyl to benzimidazole does not cause a similar increase in affinity. X-ray results indicate a small bond angle difference between the C-S-C angle of thiophene and the C-O-C angle of furan that, when amplified out to the terminal amidines of the benzimidazole compounds, yields a very significant difference in the positions of the amidines and their DNA interaction strength.
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Affiliation(s)
- Sirish Mallena
- Department of Chemistry, Georgia State University, P.O. Box 4098, Atlanta, Georgia 30302-4098, USA
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239
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Vickers TJ, Greig N, Fairlamb AH. A trypanothione-dependent glyoxalase I with a prokaryotic ancestry in Leishmania major. Proc Natl Acad Sci U S A 2004; 101:13186-91. [PMID: 15329410 PMCID: PMC516525 DOI: 10.1073/pnas.0402918101] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Indexed: 11/18/2022] Open
Abstract
Glyoxalase I forms part of the glyoxalase pathway that detoxifies reactive aldehydes such as methylglyoxal, using the spontaneously formed glutathione hemithioacetal as substrate. All known eukaryotic enzymes contain zinc as their metal cofactor, whereas the Escherichia coli glyoxalase I contains nickel. Database mining and sequence analysis identified putative glyoxalase I genes in the eukaryotic human parasites Leishmania major, Leishmania infantum, and Trypanosoma cruzi, with highest similarity to the cyanobacterial enzymes. Characterization of recombinant L. major glyoxalase I showed it to be unique among the eukaryotic enzymes in sharing the dependence of the E. coli enzyme on nickel. The parasite enzyme showed little activity with glutathione hemithioacetal substrates but was 200-fold more active with hemithioacetals formed from the unique trypanosomatid thiol trypanothione. L. major glyoxalase I also was insensitive to glutathione derivatives that are potent inhibitors of all other characterized glyoxalase I enzymes. This substrate specificity is distinct from that of the human enzyme and is reflected in the modification in the L. major sequence of a region of the human protein that interacts with the glycyl-carboxyl moiety of glutathione, a group that is conjugated to spermidine in trypanothione. This trypanothione-dependent glyoxalase I is therefore an attractive focus for additional biochemical and genetic investigation as a possible target for rational drug design.
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Affiliation(s)
- Tim J Vickers
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, DD1 5EH Dundee, Scotland
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240
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Vickers TJ, Wyllie S, Fairlamb AH. Leishmania major elongation factor 1B complex has trypanothione S-transferase and peroxidase activity. J Biol Chem 2004; 279:49003-9. [PMID: 15322082 DOI: 10.1074/jbc.m407958200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the Trypanosomatidae, trypanothione has subsumed many of the roles of glutathione in defense against chemical and oxidant stress. Crithidia fasciculata lacks glutathione S-transferase, but contains an unusual trypanothione S-transferase activity that is associated with eukaryotic translation elongation factor 1B (eEF1B). Here we describe the cloning, expression, and reconstitution of the purified alpha, beta, and gamma subunits of eEF1B from Leishmania major. Individual subunits lacked trypanothione S-transferase activity. Only eEF1B, formed by reconstitution or co-expression of the three subunits, was able to conjugate a variety of electrophilic substrates to trypanothione or glutathionylspermidine, but not glutathione. In contrast to the C. fasciculata eEF1B, the L. major enzyme also displayed peroxidase activity against a variety of organic hydroperoxides. The enzyme showed no activity with hydrogen peroxide and greatest activity with linoleic acid hydroperoxide (1 unit mg(-1)). Kinetic studies suggest a ternary complex mechanism, with Km values of 140 mum for trypanothione and 7.4 mm for cumene hydroperoxide and kcat=25 s(-1). Immunofluorescence studies indicate that the enzyme may be localized to the surface of the endoplasmic reticulum. These results suggest that, in addition to its role in protein synthesis, the Leishmania eEF1B may help protect the parasite from lipid peroxidation.
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Affiliation(s)
- Tim J Vickers
- Division of Biological Chemistry and Molecular Microbiology, Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, United Kingdom
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241
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Vickers TJ, Fairlamb AH. Trypanothione S-transferase activity in a trypanosomatid ribosomal elongation factor 1B. J Biol Chem 2004; 279:27246-56. [PMID: 15073172 PMCID: PMC3428924 DOI: 10.1074/jbc.m311039200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trypanothione is a thiol unique to the Kinetoplastida and has been shown to be a vital component of their antioxidant defenses. However, little is known as to the role of trypanothione in xenobiotic metabolism. A trypanothione S-transferase activity was detected in extracts of Leishmania major, L. infantum, L. tarentolae, Trypanosoma brucei, and Crithidia fasciculata, but not Trypanosoma cruzi. No glutathione S-transferase activity was detected in any of these parasites. Trypanothione S-transferase was purified from C. fasciculata and shown to be a hexadecameric complex of three subunits with a relative molecular weight of 650,000. This enzyme complex was specific for the thiols trypanothione and glutathionylspermidine and only used 1-chloro-2,4-dinitrobenzene from a range of glutathione S-transferase substrates. Peptide sequencing revealed that the three components were the alpha, beta, and gamma subunits of ribosomal eukaryotic elongation factor 1B (eEF1B). Partial dissociation of the complex suggested that the S-transferase activity was associated with the gamma subunit. Moreover, Cibacron blue was found to be a tight binding inhibitor and reactive blue 4 an irreversible time-dependent inhibitor that covalently modified only the gamma subunit. The rate of inactivation by reactive blue 4 was increased more than 600-fold in the presence of trypanothione, and Cibacron blue protected the enzyme from inactivation by 1-chloro-2,4-dinitrobenzene, confirming that these dyes interact with the active site region. Two eEF1Bgamma genes were cloned from C. fasciculata, but recombinant C. fasciculata eEF1Bgamma had no S-transferase activity, suggesting that eEF1Bgamma is unstable in the absence of the other subunits.
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Affiliation(s)
- Tim J. Vickers
- Division of Biological Chemistry and Molecular Microbiology, The Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
| | - Alan H. Fairlamb
- Division of Biological Chemistry and Molecular Microbiology, The Wellcome Trust Biocentre, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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242
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Zsila F, Bikadi Z, Simonyi M. Circular dichroism spectroscopic studies reveal pH dependent binding of curcumin in the minor groove of natural and synthetic nucleic acids. Org Biomol Chem 2004; 2:2902-10. [PMID: 15480453 DOI: 10.1039/b409724f] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For the first time, an interaction between the non-toxic, cancer chemopreventive agent curcumin and both natural and synthetic DNA duplexes has been demonstrated by using circular dichroism (CD) and absorption spectroscopy techniques. Upon addition of curcumin to calf thymus DNA, poly(dG-dC).poly(dG-dC) and poly(dA-dT).poly(dA-dT) solutions, an intense positive induced CD band centered around 460-470 nm was observed depending on the actual pH and Na+ ion concentration of the medium; no CD signal was obtained, however, with single stranded poly(dC). Interaction of curcumin with calf thymus DNA was observed already at pH 6.5 in contrast with poly(dG-dC).poly(dG-dC) which induces no extrinsic Cotton effect above a pH value of 5. The protonated, Hoogsteen base-paired structure of poly(dG-dC).poly(dG-dC) is necessary for curcumin binding while the alternating AT-rich polymer formed complexes with curcumin only at certain Na+ concentrations. Evaluation of the spectral data and molecular modeling calculations suggested that curcumin, this dietary polyphenolic compound binds in the minor groove of the double helix. The mechanism of the induced CD activity, the effects of the pH and Na+ ions on the ligand binding and conformation of the double helix are discussed in detail. As well as being an essentially new phenolic minor groove binder agent curcumin is also a promising molecular probe to study biologically important, pH and cation induced conformational polymorphisms of nucleic acids.
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Affiliation(s)
- Ferenc Zsila
- Institute of Biomolecular Chemistry, Chemical Research Center, H-1525, Budapest, P.O. Box 17, Hungary.
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