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A J Bitonti

Publications and source records attributed to A J Bitonti.

At least 37 records · Page 2Linked to original sources
PubMed1991

Irreversible inhibition of S-adenosylmethionine decarboxylase in Plasmodium falciparum-infected erythrocytes: growth inhibition in vitro.

Blocking spermidine and spermine synthesis in Plasmodium falciparum-infected erythrocytes with irreversible inhibitors of S-adenosylmethionine decarboxylase (AdoMet DC; EC 4.1.1.50), prevented the growth of the parasite in vitro. The most potent of these compounds, MDL 73811, inhibited growth of chloroquine-sensitive and -resistant strains of P. falciparum equally, with an IC50 of 2-3 microM. Other structurally related compounds also inhibited parasite proliferation, but to a lesser degree, determined apparently by their potency for inhibition of AdoMet DC. The growth inhibition by MDL 73811 could be alleviated by incubating infected erythrocytes with spermidine and spermine, but not putrescine. Parasites treated with the drug were arrested at the trophozoite stage of the erythrocytic cycle and had putrescine levels which were elevated by about 3- to 4-fold. Treatment of crude extracts of purified parasites with 1 microM MDL 73811 inhibited AdoMet DC activity by greater than 90%. These biochemical changes in P. falciparum-infected cells were consistent with AdoMet DC inhibition being the primary effect of MDL 73811 treatment.

Adenosylmethionine Decarboxylase↗
PubMed1991

Antitrypanosomal effects of polyamine biosynthesis inhibitors correlate with increases in Trypanosoma brucei brucei S-adenosyl-L-methionine.

We reported recently that administration of ([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxyadenosine (MDL 73811), an enzyme-activated irreversible inhibitor of S-adenosyl-L-methionine decarboxylase (AdoMetDC; EC 4.1.1.50), a key enzyme in the synthesis of spermidine, cures African trypanosome infections in mice. The precise mechanism of action of MDL 73811 was not clear because a rapid disappearance of trypanosomes from the bloodstream of treated rats occurred before significant depletion of spermidine. Administration of MDL 73811 to Trypanosoma brucei brucei-infected rats resulted in a 70% decrease in parasitaemia within 1 h and a complete disappearance of parasites by 5 h. The reduction in parasitaemia was accompanied by complete inhibition of AdoMetDC activity by 10 min after injection of MDL 73811; inhibition was sustained for at least 4 h. Polyamine levels in trypanosomes were unaffected during the first 1 h in which the marked decrease in parasitaemia was observed, but parasite AdoMet levels increased 20-fold within this time. In contrast, exposure of cultured mammalian cells to MDL 73811 resulted in only a 1.5-2-fold increase in AdoMet levels over a 6 h time course. Experiments with inhibitors of ornithine decarboxylase (ODC) also suggested that the increased AdoMet levels might be an important factor for antitrypanosomal efficacy. Trypanosomes taken from rats treated for 36 h with eflornithine, an inhibitor of ODC, were depleted of putrescine and had markedly decreased spermidine levels. These organisms also had less than 10% of control AdoMetDC activity, and had elevated decarboxy AdoMet (greater than 4000-fold) and AdoMet (up to 50-fold) levels. The methyl ester of alpha-monofluromethyl-3,4-dehydro-ornithine (delta-MFMO-CH3), which cures murine T. b. brucei infections, and the ethyl ester analogue of this compound (delta-MFMO-C2H5), which does not cure this infection, become ODC inhibitors upon hydrolysis and thus were tested for their effects on trypanosomal polyamines, AdoMet and decarboxy AdoMet levels. Although both esters of delta-MFMO depleted trypanosomal polyamines, AdoMet and decarboxy AdoMet levels were elevated in T. b. brucei from infected mice treated with delta-MFMO-CH3 but not in parasites from mice treated with the delta-MFMO-C2H5. These data suggest that inhibition of AdoMetDC, either directly with MDL 73811 or indirectly with inhibitors of ODC, apparently leads to a trypanosome-specific elevation of AdoMet. It is possible that major changes in AdoMet, rather than changes in polyamines, may be responsible for the antitrypanosomal effects of these drugs.

Adenosylmethionine Decarboxylase↗
PubMed1991

Antimalarial polyamine analogues.

A series of novel tetraamines of the general formula RNH(CH2)xNH(CH2)yNH(CH2)xNHR was synthesized and examined for activity against growth of Plasmodium falciparum in vitro. Within the series, dibenzyl analogues (R = benzyl) were found to be the most effective growth inhibitors, with IC50 values of about 10(-6) M. Further modifications of the tetraamine provided the optimum chain length for antimalarial activity of y = 7, x = 3. Compound 8 (MDL 27,695) with the structure y = 7, x = 3, R = benzyl, in combination with the ornithine decarboxylase inhibitor alpha-(difluoromethyl)ornithine, resulted in radical cures when tested against experimental Plasmodium berghei infections in mice. The structure-activity relationships of the series are discussed.

Animals↗
PubMed1991

Suppression of Leishmania donovani by oral administration of a bis(benzyl)polyamine analog.

We reported previously that intraperitoneal administration of a bis(benzyl)polyamine analog, MDL 27,695, suppressed both pentavalent antimony (Sbv)-susceptible and -resistant Leishmania donovani in vivo. The present studies were performed to optimize parasite suppression by parenteral administration and to evaluate the efficacy of oral treatment with MDL 27,695. L. donovani infections in BALB/c mice were suppressed greater than 99% after intraperitoneal dosing for 20 days with a total dose of 150 mg of MDL 27,695 per kg of body weight or 560 mg of Sbv per kg. Suppression was not increased by a total dose of 400 mg of MDL 27,695 per kg given for 20 days. In mice treated for 2, 4, or 7 days with either MDL 27,695 or Sbv (total doses of 60, 120, and 210 mg/kg, respectively), more liver parasites were killed with MDL 27,695 than with Sbv. Assessment of livers posttreatment showed that parasite killing continued for at least 3 days in MDL 27,695-treated mice but not for longer than 1 day in Sbv-treated mice. Intramuscular administration of drugs resulted in 92% parasite suppression by MDL 27,695 (15 mg/kg three times per day for 5 days) and 64% suppression by Sbv (60 mg/kg once per day for 5 days). Dosing of mice by oral gavage with 100 mg of MDL 27,695 per kg twice per day for 14 days resulted in 99.7% parasite suppression, and the 50% effective dose was approximately 11 mg of MDL 27,695 per kg. MDL 27,695 represents an effective new drug potentially useful for oral or parenteral treatment of visceral leishmaniasis.

Animals↗
PubMed1990

Antimalarial activity of a 4',5'-unsaturated 5'-fluoroadenosine mechanism-based inhibitor of S-adenosyl-L-homocysteine hydrolase.

A 4',5'-unsaturated 5'-fluoroadenosine inhibitor of S-adenosyl-L-homocysteine hydrolase (SAH hydrolase; EC 3.3.1.1), MDL 28842, was found to inhibit markedly the growth of Plasmodium falciparum in vitro and Plasmodium berghei in mice. Inhibition of P. berghei growth was associated with a large increase in the concentration of S-adenosyl-L-homocysteine (SAH) in the erythrocytes of the mice treated with MDL 28842. This increase in SAH was due apparently to inhibition of the mouse erythrocyte SAH hydrolase activity, because SAH hydrolase activity was undetectable in either P. berghei or P. falciparum isolated from infected erythrocytes, although enzyme activity was readily detected in mouse erythrocyte extracts. Therefore, MDL 28842 probably inhibits plasmodial growth indirectly by adversely changing the milieu of the host erythrocyte. SAH hydrolase represents a worthwhile target for the future development of potent inhibitors for the chemotherapy of malaria.

Adenosine↗
PubMed1990

bis(benzyl)polyamine analogues are substrates for a mammalian cell-transport system which is distinct from the polyamine-transport system.

Bis(benzyl)polyamine analogues (e.g. NN'-bis(3-[(phenylmethyl)amino]propyl)-1,8-diamino-octane [C6H5CH2NH-(CH2)3NH(CH2)8NH(CH2)3NHCH2C6H5]) have previously been shown to regulate polyamine biosynthesis and growth of rat hepatoma (HTC) cells. Saturable uptake of the analogues, the ability of other bis(benzyl)polyamine analogues to compete for this uptake and the trans-acceleration of this uptake in pre-loaded cells indicate that these novel compounds are accumulated through the action of a transport system in HTC cells. A mutant Chinese-hamster-ovary (CHO) cell line, CHOMG, which lacks a functional polyamine-transport system, exhibited saturable bis(benzyl)polyamine uptake identical with that observed in the parental CHO cells, which have normal polyamine transport. The uptake of the analogue by both CHOMG and CHO cells was competitively inhibited by other bis(benzyl)polyamine analogues, but was insensitive to excess spermine. Treatment with alpha-difluoromethylornithine, an inhibitor of polyamine biosynthesis, resulted in the enhancement of spermine uptake in CHO cells but did not alter the uptake of a bis(benzyl)polyamine analogue by either CHO or CHOMG cells. Thus it appears that bis(benzyl)polyamine analogues are substrates for a mammalian-cell-transport system distinct from the polyamine-transport system.

Animals↗
PubMed1990

Bis(benzyl)polyamine analogs as novel substrates for polyamine oxidase.

N,N'-Bis(benzyl)polyamine analogs were found to be substrates for highly purified polyamine oxidase. Metabolism of these analogs was apparently dependent on molecular O2 and resulted in the formation of benzaldehyde, H2O2, and a polyamine analog with free terminal amines. The debenzylation reaction was optimal between pH 9 and 10, identical to the pH optimum for polyamine oxidase activity when N1-acetylspermine was used as the substrate. On a molecular sieve column the debenzylating activity co-eluted with N1-acetylspermine oxidizing activity, at an apparent molecular mass of approximately 65 kDa. The purified enzyme also appeared to have a molecular mass of approximately 65 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Debenzylation of the bis(benzyl)polyamines was competitively inhibited by N1-acetylspermine and N1-acetylspermidine. The specific irreversible inhibitor of polyamine oxidase, N1,N4-bis(buta-2,3-dienyl)butanediamine also inhibited the debenzylation, whereas inhibitors of diamine and monoamine oxidases did not. The evolution of benzaldehyde from bis(benzyl)polyamine analogs by polyamine oxidase allowed the development of a simple rapid spectrophotometric assay for use in the measurement of polyamine oxidase activity in partially purified tissue or cell extracts. Further, metabolism of a bis(benzyl)polyamine analog by polyamine oxidase was found to be an important element in the growth inhibitory properties of the compound in a mouse model of malaria.

Animals↗
PubMed1990

Alpha-difluoromethylornithine resistance in Leishmania donovani is associated with increased ornithine decarboxylase activity.

The promastigote form of Leishmania donovani is sensitive to growth inhibition by DL-alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase (ODC), the first enzyme of the polyamine biosynthetic pathway, with an EC50 value of approximately 30 microM. Exposure of a wild type (DI700) cell population to gradually increasing concentrations of DFMO resulted in the selection of a strain of Leishmania, DFMO-10, which was capable of proliferating in 10 mM DFMO. DFMO-10 cells possessed an EC50 value for DFMO greater than 4 mM, and were cross-resistant to alpha-methylornithine, alpha-monofluoromethyl-3,4-dehydroornithine methyl ester, and delta-methyl-acetylenic putrescine, three other inhibitors of ODC activity. DI700 and DFMO-10 cells accumulated and/or transported [3H]DFMO and a spectrum of basic, neutral, and acidic amino acids at comparative rates. However, the DFMO-resistant Leishmania, if suspended in culture medium in the absence of DFMO for several days, expressed up to 15-fold greater levels of ODC activity than did wild-type cells. The overexpressed ODC in mutant cells appeared kinetically normal, since the ODC activities from DI700 and DFMO-10 cells possessed similar apparent Km values for ornithine and were equally sensitive to inactivation by DFMO. Incubation of extracts of DFMO-10 cells, but not of wild-type parental cells, with [3H]DFMO for 1 h resulted in the labeling of a polypeptide, presumably ODC, which migrated with a molecular weight of 76,000 +/- 4000 on SDS-gel electrophoretograms. As a consequence of the elevated ODC activities, the levels of putrescine in mutant cells released from DFMO exposure were also elevated by about 15-fold over those of wild-type cells, although spermidine levels in DI700 and DFMO-10 cells were similar. In the absence of prolonged selective pressure, the resistance to DFMO, the ODC activity, and the putrescine levels of DFMO-10 cells all returned to those of wild type cells, indicating that the mutant phenotype of DFMO-selected L. donovani was unstable.

Affinity Labels↗
PubMed1990

Polyamine analogues with antitumor activity.

A series of tetraamines derived from 1,8-diaminooctane was prepared and tested as antitumor agents. The reaction of 1,8-diaminooctane with acrylonitrile gave N,N'-bis(cyanoethyl)-1,8-diaminooctane, which was reduced to tetraamine 20. Alkylation of the terminal nitrogen atoms of the tetra-Boc derivative of this compound by methyl or ethyl halide followed by removal of the Boc groups gave the bis(alkyl)polyamines 26a and 26b, respectively. These three compounds exhibit promising antitumor activity in the mouse L1210 leukemia model. Coadministration of a polyamine oxidase inhibitor potentiated the antitumor activity.

Animals↗
PubMed1990

Suppression of both antimony-susceptible and antimony-resistant Leishmania donovani by a bis(benzyl)polyamine analog.

It was recently demonstrated that a bis(benzyl)polyamine analog (MDL 27695; N,N'-bis(3-[(phenylmethyl)amino]propyl)-1,7-diaminoheptane) possessed potent antimalarial activity in vitro and in vivo (A. J. Bitonti, J. A. Dumont, T. L. Bush, M. L. Edwards, D. M. Stemerick, P. P. McCann, and A. Sjoerdsma, Proc. Natl. Acad. Sci. USA 86:651-655, 1989). We now report that MDL 27695 also has potent antileishmanial activity, eliminating 77 to 100% of Leishmania donovani amastigotes from mouse peritoneal macrophages in vitro at 1 microM. Administration of 15 mg of MDL 27695 per kg three times per day for 5 days to L. donovani-infected mice suppressed parasite burdens in liver, spleen, and bone marrow by 83 to 96, 90, and 87%, respectively, and by 99.9% in livers of mice given the same dose two times per day for 10 days. Liver parasites were suppressed 74% in L. donovani-infected hamsters treated three times per day for 4 days with 5 mg of MDL 27695 per kg. The 50% effective doses for MDL 27695 were 2.5 mg/kg in mice and about 1 mg/kg in hamsters. In hamsters, MDL 27695 was equally effective against both antimony-susceptible and antimony-resistant L. donovani, suggesting a different mechanism of action for the two types of drugs. Coadministration of N1,N4-bis(butadienyl)-butanediamine (MDL 72527) to mice to inhibit host polyamine oxidase, and hence the formation of oxidative metabolites of MDL 27695, did not affect the antileishmanial activity of MDL 27695. Thus, the mechanism of action of MDL 27695 does not appear to be related to its oxidation to toxic metabolites but may involve interference with DNA and RNA syntheses as found previously in Plasmodium falciparum (Bitonti et al., Proc. Natl. Acad. Sci. USA 86:651-655, 1989).

Animals↗
PubMed1990

Cure of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense infections in mice with an irreversible inhibitor of S-adenosylmethionine decarboxylase.

A structural analog, 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxy adenosine (MDL 73811), of decarboxy S-adenosyl-L-methionine, the product of the reaction catalyzed by S-adenosyl-L-methionine (AdoMet) decarboxylase (DC), was found to inhibit Trypanosoma brucei brucei AdoMet DC. The inhibition was time dependent (tau 50, 0.3 min), exhibited pseudo-first-order kinetics (Ki, 1.5 microM), and was apparently irreversible. The natural substrate of the reaction, AdoMet, protected the enzyme from inactivation, suggesting that MDL 73811 was directed at the enzyme active site and was probably catalytically activated. Administration of MDL 73811 to T. b. brucei-infected rats resulted in rapid inhibition of AdoMet DC activity, a decrease in spermidine, and an increase in putrescine in the trypanosomes isolated from treated rats. Treatment of T. b. brucei-infected mice with MDL 73811 (20 mg/kg of body weight intraperitoneally twice daily for 4 days) resulted in cures of the trypanosome infections. Additionally, drug-resistant T. brucei rhodesiense infections in mice were cured by either a combination of MDL 73811 (50 mg/kg intraperitoneally three times per day for 5 days) and relatively low oral doses of alpha-difluoromethylornithine or MDL 73811 (50 mg/kg per day for 7 days) administered alone in implanted miniosmotic pumps. These data suggest that MDL 73811 and, perhaps, other inhibitors of AdoMet DC have potential for therapeutic use in various forms of African trypanosomiasis.

Adenosylmethionine Decarboxylase↗
PubMed1989

Regulation of polyamine biosynthesis in rat hepatoma (HTC) cells by a bisbenzyl polyamine analogue.

A bisbenzyl polyamine analogue, MDL 27695, rapidly repressed ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (AdoMet DC) activity and depleted polyamines in rat hepatoma (HTC) cells. The suppression of ODC and AdoMet DC activity was temporally related to metabolism of MDL 27695 by intracellular polyamine oxidase to a free-amine analogue, MDL 26752, which, when added directly to HTC cells, suppressed ODC activity and polyamine biosynthesis more rapidly and to a greater extent than did the bisbenzyl analogue. The ODC suppression caused by MDL 27695 was completely blocked by the addition of a polyamine oxidase inhibitor to the HTC-cell cultures along with MDL 27695. These data suggested that MDL 27695 acted as a prodrug, with metabolism to an active analogue being necessary for ODC repression to occur. MDL 27695 and MDL 26752 completely abolished division of HTC cells when added to cultures at 1 microM. This established them as being among the most potent antiproliferative polyamine analogues yet described. MDL 27695 has also been shown to possess significant antimalarial effects both in vitro and in vivo, and it is possible that the marked suppression of polyamine biosynthesis described herein may contribute to its anti-malarial effects as well as its antiproliferative effects in mammalian cells.

Adenosylmethionine Decarboxylase↗
PubMed1989

Trypanosoma brucei brucei: regulation of ornithine decarboxylase in procyclic forms and trypomastigotes.

Ornithine decarboxylase (ODC) activity was measured in procyclic forms of Trypanosoma brucei brucei grown in semidefined medium. ODC activity rapidly increased in late log-phase cells which were resuspended in fresh medium. A biphasic induction curve similar to that observed in mammalian cells was observed over an 18-hr period. ODC activity increased 4.5- to 25-fold over control levels measured at zero time. Actinomycin D and cycloheximide inhibited induction by greater than 90%. Polyamines at a level not inhibitory to growth (10 microM) inhibited ODC induction, but only by 30-50%, late in the induction period. Putrescine inhibited the first peak of induction and suppressed activity at 14 hr by 75%. Polyamine analogs such as bis(ethyl)spermidine were not effective suppressors of ODC activity. The half-life of ODC in procyclic forms grown in the presence of cycloheximide was greater than 6 hr, while that of bloodstream trypomastigotes in mice treated with cycloheximide was 5 hr. A single dose of the ODC inhibitor DL-alpha-difluoromethylornithine given to infected rats or mice suppressed trypanosome ODC activity greater than 90% for more than 7 hr. These studies indicate that although trypanosome ODC increases rapidly under log growth conditions, it is less susceptible to fluctuation and external control than the enzyme from mammalian sources. The latter may be a factor in the clinical efficacy of ODC inhibitors.

Animals↗
PubMed1989

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.

A number of bis(benzyl)polyamine analogs were found to be potent inhibitors of both chloroquine-resistant and chloroquine-sensitive strains of the human malaria parasite Plasmodium falciparum in vitro (IC50 values = 0.2-14 microM). Administration of one of the compounds, MDL 27695, which is N,N'-bis(3-[(phenylmethyl)amino]propyl)-1,7-diaminoheptane (C6H5CH2NH(CH2)3NH(CH2)7NH(CH2)3NHCH2C6H5), at 10-15 mg/kg i.p. three times per day for 3 days in combination with 2% alpha-difluoromethylornithine (DFMO; eflornithine) in drinking water effected cures of 47/54 mice infected with Plasmodium berghei. Cured mice were found to be immune upon rechallenge with the same P. berghei strain 4 months after the initial infection and drug-induced cure. MDL 27695 rapidly inhibited the incorporation of [3H]hypoxanthine into P. falciparum RNA and DNA, whereas the incorporation of [3H]isoleucine was not affected until much later. We conclude, therefore, that the major cytotoxic event may be direct binding of MDL 27695 to DNA with subsequent disruption of macromolecular biosynthesis and cell death. These compounds offer a lead in the search for new agents for chemotherapy of malaria.

Animals↗
PubMed1988

Reversal of chloroquine resistance in malaria parasite Plasmodium falciparum by desipramine.

Desipramine and several other tricyclic antidepressant drugs reverse chloroquine resistance in Plasmodium falciparum in vitro at concentrations observed in the plasma of human patients treated for depression. Reversal of resistance is associated with increased chloroquine accumulation in the parasite, probably because of inhibition of a putative chloroquine efflux pump. When owl monkeys (Aotus lemurinus lemurinus) infected with chloroquine-resistant Plasmodium falciparum were treated with chloroquine plus desipramine, their parasitemias were rapidly suppressed. Desipramine was found to be one of the most effective compounds yet described for the reversal of chloroquine resistance both in vitro and in vivo.

Animals↗