1 Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff CF10 3XF; 2 Institute of Biomedical and Life Sciences, Division of Infection and Immunity, University of Glasgow, Glasgow G12 8QQ, UK; 3 Swiss Tropical Institute, Socinstrasse 57, CH-4002 Basel, Switzerland
Received 30 August 2002; returned 10 January 2003; revised 23 January 2003; accepted 29 April 2003
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Abstract |
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Keywords: Plasmodium falciparum, malaria, parasites, protozoa, polyamine metabolism
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Introduction |
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Polyamines are essential for cell proliferation and differentiation. Interference with their biosynthesis or function can block cellular growth and the polyamine pathway has been investigated with regard to anticancer therapy.5 Malaria parasites have a great propensity for rapid proliferation, and interference with polyamine function in these cells is likely to be detrimental. Eflornithine, used in conjunction with bis(benzyl)polyamine analogues, cured rodent malaria models,6 although used alone eflornithine has no curative affect in human malaria. An S-adenosylmethionine decarboxylase inhibitor, methylglyoxalbis(guanyl) hydrazone (MGBG), blocked growth of the erythrocytic stages of Plasmodium falciparum in vitro.7 Moderate antiplasmodial activity was also seen with a series of N-alkylated putrescine derivatives,8 and dicyclohexylamine, an inhibitor of spermidine biosynthesis, also showed antiplasmodial activity.9
We previously reported a series of 1,3,5-triazine-substituted polyamine analogues, which were developed specifically to interfere with polyamine metabolism in African trypanosomes.10 Several of the compounds showed marked trypanocidal activity. We report here the evaluation of the activity of this series against P. falciparum in vitro.
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Materials and methods |
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After 48 h, 50 µL of [3H]hypoxanthine (0.5 µCi) was added to each well of the plate. The plates were incubated for a further 24 h under the same conditions. The plates were then harvested with a Betaplate cell harvester (Wallac, Zurich, Switzerland), and the red blood cells were transferred onto a glass fibre filter and then washed with distilled water. The dried filters were inserted into a plastic foil with 10 mL of scintillation fluid, and counted in a Betaplate liquid scintillation counter (Wallac). IC50 values were calculated from sigmoidal inhibition curves using Microsoft Excel.
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Results |
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Discussion |
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However, it is currently not clear how these triazine-substituted polyamine analogues actually exert their action. In rodents, Plasmodium yoelii-infected erythrocytes have been shown to have enhanced polyamine uptake.13 The parasites may induce specific transporters for these metabolites and Plasmodium knowlesi-infected erythrocytes have been shown to have an up-regulated putrescine-specific uptake system.14 It is also possible that the triazine-substituted analogues are preferentially taken into Plasmodium-infected erythrocytes via the new permeation pathway that is induced at the plasma membrane of infected erythrocytes.15 It will be of interest to determine how these analogues enter infected erythrocytes and exert a toxic effect on the parasites. We cannot rule out the possibility that the compounds are oxidized by serum components prior to exerting a toxic effect. Interestingly, it has recently been shown that pentamidine and other diamidine compounds are active against malaria parasites grown in vitro,16 with efficacy in the submicromolar range. It has been proposed that diamidines exert their plasmocidal effect by binding to ferriprotoporphyrin IX and preventing the polymerization of haem that accumulates to toxic levels in these parasites. It is feasible that the triazine-substituted polyamine analogues could act in a similar fashion. Further work is required to elucidate modes of action of these compounds.13
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Acknowledgements |
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Footnotes |
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References |
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2 . Wongsrichanalai, C., Pickard, A. L., Wernsdorfer, W. H. et al. (2002). Epidemiology of drug-resistant malaria. Lancet Infectious Diseases 2, 20918.[CrossRef][ISI][Medline]
3 . Laurence, J., Marton, L. J. & Pegg, A. E. (1995). Polyamines as targets for therapeutic intervention. Annual Review of Pharmacology and Toxicology 35, 5591.[CrossRef][ISI][Medline]
4 . Bacchi, C. J., Nathan, H. C., Hutner, S. H. et al. (1980). Polyamine metabolism: a potential therapeutic target in trypanosomes. Science 210, 3324.[ISI][Medline]
5 . Barrett, S. V. & Barrett, M. P. (2000). Anti-sleeping sickness drugs and cancer chemotherapy. Parasitology Today 16, 79.[CrossRef][ISI][Medline]
6 . Bitonti, A. J., Dumont, J. A., Bush, T. L. et al. (1989). Bis(benzyl)polyamine analogs inhibit the growth of chloroquine-resistant human malaria parasites (Plasmodium falciparum) in vitro and in combination with alpha-difluoromethylornithine cure murine malaria. Proceedings of the National Academy of Sciences, USA 86, 6515.[Abstract]
7 . Wright, P. S., Byers T. L., Cross-Doersen, D. E. et al. (1991). Irreversible inhibition of S-adenosylmethionine decarboxylase in Plasmodium falciparum-infected erythrocytes: growth inhibition in vitro. Biochemical Pharmacology 41, 17138.[CrossRef][ISI][Medline]
8 . Slater, L. A., McMonagle, F. A., Phillips, R. S. et al. (1998). Antimalarial activity of unsaturated putrescine derivatives. Annals of Tropical Medicine and Parasitology 92, 2717.[CrossRef][ISI][Medline]
9 . Kaiser, A., Gottwald, A., Wiersch, C. et al. (2001). Effect of drugs inhibiting spermidine biosynthesis and metabolism on the in vitro development of Plasmodium falciparum. Parasitology Research 87, 96372.[ISI][Medline]
10 . Klenke, B., Stewart, M., Barrett, M. P. et al. (2001). Synthesis and biological evaluation of s-triazine substituted polyamines as potential new anti-trypanosomal drugs. Journal of Medicinal Chemistry 44, 344052.[CrossRef][ISI][Medline]
11 . Desjardins, R. E., Canfield, C. J., Haynes, D. et al. (1979). Quantitative assessment of antimalarial activity in vitro by a semiautomated microdilution technique. Antimicrobial Agents and Chemotherapy 16, 7108.[ISI][Medline]
12 . Matile, H. & Pink, J. R. L. (1990). Plasmodium falciparum malaria parasite cultures and their use in immunology. In Immunological Methods (Lefkovits, I. & Pernis, B., Eds), pp. 22134. Academic Press, San Diego, CA, USA.
13 . Muller, S., Coombs, G. H. & Walter, R. D. (2001). Targeting polyamines of parasitic protozoa in chemotherapy. Trends in Parasitology 17, 2429.[CrossRef][ISI][Medline]
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Singh, S., Puri, S. K., Singh, S. K. et al. (1997). Characterization of simian malarial parasite (Plasmodium knowlesi)-induced putrescine transport in rhesus monkey erythrocytes. A novel putrescine conjugate arrests in vitro growth of simian malarial parasite (Plasmodium knowlesi) and cures multidrug resistant murine malaria (Plasmodium yoelii) infection in vivo. Journal of Biological Chemistry 272, 1350611.
15 . Kirk, K., Staines, H. M., Martin, R. E. et al. (1999). Transport properties of the host cell membrane. Novartis Foundation Symposium 226, 5566; discussion 6673.
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Stead, A. M., Bray, P. G., Edwards, I. G. et al. (2001). Diamidine compounds: selective uptake and targeting in Plasmodium falciparum. Molecular Pharmacology 59, 1298306.
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