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Biomedical subjects

C J Bacchi

Publications and source records attributed to C J Bacchi.

At least 73 records · Page 4Linked to original sources
PubMed1987

In vivo effects of difluoromethylornithine on trypanothione and polyamine levels in bloodstream forms of Trypanosoma brucei.

The effect of D,L-alpha-difluoromethylornithine (DFMO) on thiol and polyamine levels in Trypanosoma brucei was investigated by isolating trypanosomes from infected rats treated with DFMO for 12-48 h. Concentrations of thiols, polyamines and other amino-compounds were measured by an automated high-performance liquid chromatography method. The levels of DFMO in rat plasma (0.02-1.34 mM) is similar to that found in the parasites (0.27-0.99 mM), concentrations which exceed the Ki of DFMO for T. brucei ornithine decarboxylase. Treatment with DFMO increases intracellular levels of ornithine, S-adenosylmethionine and decarboxylated S-adenosylmethionine and decreases putrescine and spermidine. Putrescine is undetectable after 12 h treatment with DFMO and after 48 h spermidine is decreased by 76%. By 48 h, the spermidine-glutathione conjugates glutathionylspermidine and dihydrotrypanothione (bis(glutathionyl)spermidine) are also decreased by 41 and 66%, respectively. In contrast, levels of glutathione show a slight increase. These changes in metabolite levels are consistent with the biosynthetic pathway proposed for Crithidia fasciculata, where trypanothione is synthesized from spermidine and glutathione via the intermediates N1- and N8-glutathionyl-spermidine. Trypanothione is thought to have two important roles in trypanosomatid metabolism: the maintenance of intracellular thiols in the correct redox state and in the removal of hydrogen peroxide and other hydroperoxides. Thus, it is proposed that depletion of this metabolite may be an important contributory factor to the selective toxic effect of DFMO, particularly in its synergistic effect with other trypanocidal drugs.

Animals↗
PubMed1987

Synergism between 9-deazainosine and DL-alpha-difluoromethylornithine in treatment of experimental African trypanosomiasis.

Kinetoplastid hemoflagellates are sensitive to growth inhibition by various purine analogs. In this study the activities of 9-deazainosine (9-DINO), formycin B, and sinefungin were compared in experimental murine Trypanosoma brucei subsp. brucei infections, both singly and in combination with the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine (DFMO, eflornithine). Used singly, all of the purine analogs were able to suppress an acute T. brucei subsp. brucei infection. 9-DINO and formycin B were the most active. None of the purine analogs was curative when used singly against a strain causing chronic central nervous system infection. 9-DINO was highly effective when used in combination with DFMO in curing this central nervous system infection and another more stringent experimental infection. Neither sinefungin nor formycin B was active in combination with DFMO in curing the central nervous system experimental infection. 9-DINO was metabolized to phosphorylated derivatives of 9-deazaadenosine and 9-deazaguanosine by bloodstream trypomastigotes, but not by murine erythrocyte suspensions or kidney or liver homogenates--a potential rationale for the selectivity of the analog. These studies indicate that 9-DINO is a potent, nontoxic purine analog which, in combination with DFMO, is capable of late-stage cures of African trypanosomiasis.

Animals↗
PubMed1987

Effects of the ornithine decarboxylase inhibitors DL-alpha-difluoromethylornithine and alpha-monofluoromethyldehydroornithine methyl ester alone and in combination with suramin against Trypanosoma brucei brucei central nervous system models.

Two ornithine decarboxylase inhibitors, DL-alpha-difluoromethylornithine (eflornithine; DFMO) and a-monofluoromethyldehydroornithine methyl ester (delta MFMO X CH3) were compared in their ability to cure two distinct Trypanosoma brucei brucei central nervous system murine model infections. Both inhibitors cured the TREU 667 and LUMP 1001 isolates if used in combination with a single (20 mg/kg) injection of suramin, a trypanocide in current clinical use. The curative dose of delta MFMO X CH3 in combination with suramin was 1.09 g/kg/day, administered in the drinking water for 14 days; used with suramin, the curative dose of DFMO was 5.3 g/kg/day for 14 days (5 times the delta MFMO X CH3 dose required). In host animals, delta MFMO X CH3 was not toxic and was accumulated by trypanosomes 6-8 times faster than DFMO. Since DFMO by itself has been highly effective against T. b. gambiense infections in humans (12-15 g/day for 6 weeks) the present data suggest that delta MFMO X CH3 might be effective in a shorter regimen and at lower doses.

Animals↗
PubMed1986

Effect of putrescine on the respiration of Trypanosoma brucei brucei.

When bloodstream forms of Trypanosoma brucei brucei were exposed to exogenous putrescine for 24 h during in vitro culture, the rate of O2 consumption increased significantly in a concentration-related and time-dependent manner. Trypanosomes cultured with 100 microM DL-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, were depleted of intracellular putrescine, and the rate of O2 consumption decreased by more than 50%. This effect could be abrogated if 100 microM putrescine was also present. A similar pattern was observed in trypanosomes harvested from rats after 36 h of DFMO treatment. If such trypanosomes were placed in culture for 2 h with 100 microM putrescine, the rate of O2 consumption returned to that of controls. When an intraperitoneal injection of putrescine was given to infected rats 18 h after commencement of DFMO treatment, rates of O2 consumption in the trypanosomes were found to return to control values. The addition of putrescine, spermidine or Mg2+ did not affect rate of O2 consumption in enriched mitochondrial preparations. However, when putrescine was present throughout the preparation of mitochondrial fractions, there was an increase of 23% in O2 uptake, which was 23% higher than in the controls. Putrescine may modulate trypanosomal respiration by stabilizing mitochondrial membranes.

Animals↗
PubMed1986

Polyamine depletion following exposure to DL-alpha-difluoromethylornithine both in vivo and in vitro initiates morphological alterations and mitochondrial activation in a monomorphic strain of Trypanosoma brucei brucei.

DL-alpha-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase (ODC), rapidly depletes cells of intracellular putrescine. When administered to animals and humans, DFMO cures acute infections of trypanosomiasis. In order to determine if the mechanism of drug action is related to initiation of transformation and biochemical alterations subsequent to polyamine depletion, trypanosome morphology and mitochondrial activation were studied in a monomorphic strain of Trypanosoma brucei brucei. Exposure of trypanosomes to DFMO in vivo in infected rodents or in vitro in culture resulted in a depletion of intracellular putrescine and a cessation of cell division without specific cytotoxicity. These events were followed by a transformation of the long slender bloodstream form to a short stumpy form via an intermediate morphology. Putrescine, the product of the ODC reaction, abrogates this effect. When introduced into SDM-79 medium, the intermediate form is capable of further transformation to an "insect" procyclic trypomastigote whereas the long slender form and short stumpy form are not. Short stumpy forms are incapable of binary fission and have lost their infectivity for the vertebrate host. In addition, the mitochondrial marker enzyme, NAD diaphorase, was found only in the short stumpy and intermediate forms. We hypothesize that the short stumpy phenotype may not be a viable stage in the natural transformation of the trypanosome from its mammalian host to the insect vector.

Animals↗
PubMed1986

Inhibition of polyamine biosynthesis by alpha-difluoromethylornithine in African trypanosomes and Pneumocystis carinii as a basis of chemotherapy: biochemical and clinical aspects.

The symposium provided dramatic evidence of the value of the use of polyamine inhibition via alpha-difluoromethylornithine (DFMO, eflornithine) for advances in chemotherapy of Trypanosoma brucei gambiense sleeping sickness and Pneumocystis carinii pneumonia in acquired immune deficiency syndrome (AIDS) and also for further understanding the metabolic importance of the ubiquitous polyamines in these organisms.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Catalytic irreversible inhibition of Trypanosoma brucei brucei ornithine decarboxylase by substrate and product analogs and their effects on murine trypanosomiasis.

Ornithine decarboxylase from Trypanosoma brucei brucei was inhibited by several substrate (ornithine) and product (putrescine) analogs both in vitro and in vivo. Since alpha-difluoromethylornithine is effective for the treatment of experimental and clinical African trypanosomiasis, it was possible that the more potent ornithine and putrescine analogs might be more active in treating the disease. However, only alpha-monofluoromethyldehydroornithine methyl ester was more potent than alpha-difluromethylornithine against mouse trypanosomiasis and warrants further study in model infections.

Animals↗
PubMed1985

Stimulation of Rauscher leukemia virus DNA polymerase DNA-directed DNA synthesis by cationic trypanocides and polyamines.

Activated DNA-directed DNA synthesis catalyzed by Rauscher leukemia virus (RLV) and other type C mammalian retroviral DNA polymerases is uniquely stimulated by biologically active polyamines. Cationic trypanocides may act as antagonists of polyamine function. As described here, several cationic trypanocides stimulate RLV polymerase-catalyzed DNA-directed DNA synthesis at concentrations significantly inhibiting eukaryotic DNA polymerases. Such stimulation is negated by polyamines. Kinetic analysis of the stimulation of RLV DNA polymerase by three structurally dissimilar cationic trypanocides (Antrycide, Burroughs-Wellcome Compound 64A, and Bayer Compound 1694) suggests that such stimulation is, in part, due to a drug:DNA structural interaction resembling the polyamine:DNA structural complex recognized by the RLV DNA polymerase.

Cations↗
PubMed1984

Inhibitors of histamine metabolism in vitro and in vivo. Correlations with antitrypanosomal activity.

The effects of antimalarial and antitrypanosomal drugs on the activity of histamine N-methyl transferase and diamine oxidase in vitro, as well as diamine oxidation and histamine levels in vivo, were examined. Diamidine antitrypanosomal drugs which interfere with polyamine metabolism were found to be potent inhibitors both in vitro and in vivo. Antrycide ( quinapyramine ) and isometamidium were the best inhibitors of both enzymes. Ki values for histamine N-methyl transferase were 3 X 10(-8) M for both compounds, and the inhibition was competitive for histamine. Antrycide and isometamidium were both non-competitive inhibitors of diamine oxidase, having Ki values of 6 X 10(-9) M and 3 X 10(-9) M respectively. Isometamidium elevated histamine levels in rat kidney 2-fold and produced a long-term inhibition of putrescine oxidation in vivo. Among the compounds examined, only known active antitrypanosomal agents inhibited both histamine N-methyl transferase and diamine oxidase in vitro as well as putrescine oxidation in vivo. These observations suggest that the enzymes acting on histamine and putrescine as substrates can be used to select compounds which interfere with polyamine metabolism and that persistence of such compounds in vivo, as indicated by inhibition of putrescine oxidation, correlates with favorable chemotherapeutic properties as antitrypanosomal agents.

Amine Oxidase (Copper-Containing)↗
PubMed1984

Induction of ornithine decarboxylase in Leptomonas seymouri.

Ornithine decarboxylase, the initial enzyme of polyamine biosynthesis, was induced in vitro in Leptomonas seymouri, a parasite of Diptera, by resuspending stationary phase cells with fresh medium. Induction was biphasic with peaks at 2 and 8 h. Activity increased about 20-fold over 22 h under control conditions. Induction was completely blocked by cycloheximide and was suppressed by actinomycin D, alpha-amanitin, putrescine, spermidine and spermine. The enzyme half-life was 45 min in cells treated with cycloheximide 24 h post induction. These observations suggest the presence of a highly sensitive mechanism for regulation of ornithine decarboxylase as found in mammalian and other eukaryotic cells.

Amanitins↗
PubMed1984

New drug combination for experimental late-stage African trypanosomiasis: DL-alpha-difluoromethylornithine (DFMO) with suramin.

Using a previously described mouse model of late-stage African trypanosomiasis (i.e., involvement of the central nervous system), we demonstrate that a combination of DL-alpha-difluoromethylornithine (DFMO) and suramin is curative. In the curative protocol, DFMO is given as a 2% solution in the drinking water for 14 days and suramin is administered as a single dose (20 mg/kg intravenously) on day 1 of DFMO administration. Since: 1) DFMO has very low toxicity, 2) suramin is one of the least toxic of the presently used trypanocides, and 3) suramin and DFMO act synergistically in mouse models of both acute and late stage trypanosomiasis, we conclude that this combination offers special promise in the treatment of African trypanosomiasis in man.

Animals↗
PubMed1984

Antitumor phthalanilides active in acute and chronic Trypanosoma brucei brucei murine infections.

A series of phthalanilides and related compounds were tested on a short-term, fulminating, mouse infection of Trypanosoma brucei brucei (EATRO 110 isolate). The most effective compound was [4,4'-bis (4-methylimidazolin-2-yl)-terephthalanilide] which had a cure rate of 75% at 0.1 mg/kg body weight and 100% at 0.5 mg/kg when administered as three single daily intraperitoneal injections starting 24 hours post-infection. Several related phthalanilides and similarly substituted ureas showed definite but lower activity. In tests with a chronic neurotropic T. b. brucei isolate (TREU 667), cure rates greater than 90% were obtained with 10 or 25 mg/kg [4,4'-bis(4-methylimidazolin-2-yl)-terephthalanilide]. Cured animals survived for at least 200 days after infection with no evidence of recrudescence of parasitemia or of toxicity; blood or brain homogenates of cured animals were non-infective to immunosuppressed animals. These studies indicate that this series of compounds, previously studied as antitumor agents, should be re-examined as potential trypanocides.

Anilides↗
PubMed1983

In vivo effects of alpha-DL-difluoromethylornithine on the metabolism and morphology of Trypanosoma brucei brucei.

The EATRO 110 isolate of Trypanosoma brucei brucei was grown in rats for 60 h and the animals treated with the ornithine decarboxylase inhibitor alpha-DL-difluoromethylornithine 12 h or 36 h prior to sacrifice. Control untreated animals died 72-80 h after infection. Treated parasites were shorter and broader than the predominantly long slender forms found in untreated controls and many had two or more nuclei and kinetoplasts. Trypanosomes were purified from blood and examined for disruption of polyamine metabolism. ODC activity decreased by more than 99% after 12 h treatment and putrescine and spermidine levels also decreased dramatically. Spermine, not normally present in control cells, increased to detectable, low levels (less than 1 nmol mg-1 protein) after 36 h treatment. alpha-DL-Difluoromethylornithine-treated cells were unable to synthesize putrescine from [3H]ornithine but were able to convert [3H]putrescine + methionine to spermidine. 12-h treated parasites responded to polyamine depletion by assimilating radiolabeled polyamines in vitro at 2- to 4-times the rate of untreated cells. The metabolism of S-adenosylmethionine was also altered in treated parasites: decarboxylated S-adenosylmethionine increased more than 1000-fold over untreated cells while S-adenosylmethionine decarboxylase activity, associated with the formation of spermidine and spermine in other eukaryotes, paradoxically declined in treated cells. Synthesis of macromolecules was perturbed in treated parasites: rates of DNA and RNA synthesis declined 50-100%, while protein synthesis increased up to 4-fold in 36-h treated cells. alpha-DL-Difluoromethylornithine treatment progressively limits the parasites' ability to synthesize nucleic acids and blocks cytokinesis while inducing morphological changes resembling long slender leads to short stumpy transformation.

Animals↗
PubMed1983

Efficacy of combinations of difluoromethylornithine and bleomycin in a mouse model of central nervous system African trypanosomiasis.

DL-alpha-Difluoromethylornithine, a polyamine biosynthesis inhibitor, and bleomycin, a currently used antineoplastic agent, have each previously been shown to be curative for acute short-term infections of mice with Trypanosoma brucei brucei, an African trypanosome closely related to those that cause the human disease African sleeping sickness. These agents were tested singly and in combination in a previously described mouse model of sleeping sickness with demonstrable brain involvement. The original model is extended by using two additional strains of outbred mice and by demonstrating that melarsoprol, an arsenical and currently the only drug used for human African trypanosomiasis involving the brain, was also curative for these brain infections. Neither difluoromethylornithine nor bleomycin alone was curative for the brain infections; however, many combinations of the two drugs were found to be 100% curative with no evidence of immediate toxicity.

Animals↗