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.

Abstract

A number of bis(benzyl)polyamine analogs were found to be potent inhibitors ofboth chloroquine-resistant and chloroquine-sensitive strains of the human malaria parasite Plasmodiumfalciparum in vitro (IC50 values = 0.2-14MM).Administration of one of the compounds, MDL 27695, which is N,N'-bis{3-[(phenylmethyl)aminolpropyl}-1,7-diaminoheptane (C6H5CH2NH(CH2)3NH(CH2)7NH(CH2)3NHCH2C6HS), at 10-15 mg/kg i.p. three times per day for 3 days in combination with 2% x-difluoromethylornithine (DFMO; eflornithine) (1). Radical departure from the chemical classes of compounds effective in the past is needed to circumvent the problems of cross-resistance between drugs. We have studied an approach to the chemotherapy of malaria that involves the disruption of the biosynthesis and/or intracellular function of the polyamines-putrescine, spermidine, and spermine.The polyamines are important regulators of growth and differentiation in a wide variety of cell types including parasitic protozoa (2). a-Difluoromethylomithine (DFMO; eflornithine), an irreversible inhibitor of the first enzyme in polyamine biosynthesis, ornithine decarboxylase, inhibits the proliferation of a number of human-infective parasites, including P. falciparum (3,4). We have recently shown that DFMO also inhibits the growth of Plasmodium berghei in mice but does not cure these infections (5).Another approach to interference with polyamine biosynthesis and function, which has been applied successfully in cancer cells (6), takes advantage of the ability of the natural polyamines (7,8) and nonphysiological polyamine analogs (9, 10) to suppress ornithine decarboxylase activity in the cell and also possibly to block the intracellular function of the natural polyamines by displacing them from critical binding sites, such as appear to be present on DNA (11). In this approach, it is preferred that the polyamine analogs not subserve the normal physiological roles of putrescine, spermidine, and spermine, because then they would simply replace the natural polyamines and growth inhibition would not occur. We now report on a series of bis(benzyl)polyamine analogs that have marked antimalarial activity against both chloroquine-sensitive and chloroquine-resistant P. falciparum in vitro and, when administered in combination with DFMO, cure murine malaria. Trager and Jensen (14). Maintenance cultures, in 25-cm2 flasks at 370C, contained a 6% suspension of human (type 0+) erythrocytes in RPMI 1640 medium supplemented with 10% human serum, 25 mM Hepes, and 0.2% NaHCO3 with a gaseous phase of 90% N2/5% 02/5% CO2. Cultures were fed daily with fresh medium and were subcultured twice weekly by 10-to 20-fold dilutions with fresh human erythrocytes. MATERIALS AND METHODSMicrotiter Cultures for Drug Testing. Drug testing in vitro was carried out using standard procedures (15). In the 96-well microtiter cultures P.falciparum (FCR-3/Gambia strain) was at a starting parasitemia of =0.5% in a 1% suspension of erythrocytes in a total volume of 0.2 ml. Test compounds were dissolve...

Xanthine oxidase inhibits growth of Plasmodium falciparum in human erythrocytes in vitro.

“…Purine is released from red cells almost exclusively in the form ofhypoxanthine (23,24), and is thus susceptible to oxidation by xanthine oxidase present in the medium. Failure of 1 x 10-7 M chloroquine to abolish parasite growth is indicative of chloroquine resistance (31). Thus, we have demonstrated that a chloroquine-resistant strain ofP.…”

“…These morphological changes are reversed by provision ofsufficient hypoxanthine to overcome the deficiency. Growth arrest at the same developmental stage is produced by a-difluoromethylornithine, an inhibitor of polyamine synthesis, which prevents DNA replication (31). In this case, normal maturation of schizonts is restored by putrescine rescue (32).…”

Inhibition of host cell invasion and intracellular replication of Trypanosoma cruzi by N,N'-bis(benzyl)-substituted polyamine analogs

“…N,N'-Di-substituted tetraamines with the general formula RNH(CH2)XNH (CH2)YNH(CH2)NINHR have been reported to suppress the growth of several pathogenic protozoans (e.g., Leishmania donovani, Plasmodium falciparum, and Plasmodium berghei) in vitro and in infected animals (2)(3)(4) and could be suitable for exploring the role that polyamines and polyamine biosynthesis plays in T. cnuzi infection. In this work, we used two N,N'-bis(benzyl)-substituted polyamine analogs and studied their effects on T. cnuzi infectivity and replication using an in vitro model system of mammalian host cell infection.…”

Implicações estruturais de mutantes da piridoxal quinase de Plasmodium falciparum

“…DFMO, a derivative of the amino acid ornithine, inhibits the enzyme irreversibly by an alkylation of its active site. A combination of DFMO and bis(benzyl)polyamines revealed a curative effect in rodent malaria [61]. Moreover DFMO reveals a more prominent role due to its effectiveness against Trypanosoma brucei gambiense, the agent of the West African Sleeping Sickness [62][63][64].…”

“…These molecules have to be detoxified. While the parasite possesses a variety of anti-oxidative defense mechanisms [9,[60][61][62][63], none of them addresses singlet oxygen. Recently it was demonstrated that PLP is involved in the protection against 1 O 2 in P. falciparum [58,64], which has been attributed to the catalysis of the plasmodial PLP synthase complex as validated by protein interference experiments using transgenically modified parasites [64].…”