Polyamine content of Pneumocystis carinii and response to the ornithine decarboxylase inhibitor DL-alpha-difluoromethylornithine.
AUTOR(ES)
Merali, S
RESUMO
Difluoromethylornithine (DFMO; eflornithine hydrochloride [Ornidyl]), a suicide inhibitor of the key polyamine biosynthesis enzyme ornithine decarboxylase (ODC), is effective in treating Pneumocystis carinii pneumonia, a common opportunistic infection associated with AIDS. Despite DFMO's specificity for ODC, the reason for its selective toxicity against P. carinii is unknown since both host and parasite are dependent on the same enzyme for polyamine biosynthesis. A new high-performance liquid chromatography method was used with P. carinii cells isolated from infected rat lungs to measure polyamine content, to confirm the presence of ODC, and to examine the effect of DFMO on polyamine concentrations. Putrescine, spermidine, and spermine were found to be present at 2.00 +/- 0.54, 1.26 +/- 0.51, and 1.59 +/- 0.91 nmol (mg of protein)-1, respectively, neither unusually high nor low values. ODC's specific activity was 79 +/- 11 pmol (mg of protein)-1 h-1, again not a remarkable value. However, the rates of both DFMO-induced polyamine depletion and subsequent repletion upon DFMO removal were unusually high. A 3-h exposure to 1 mM DFMO in vitro caused the depletion of putrescine, spermidine, and spermine to levels 12, 29, and 16%, respectively, of that of control cells. After DFMO removal and incubation for 1 h in serum-free media, polyamine levels returned to 78, 88, and 64%, respectively, of that of the control cells not exposed to DFMO. Since such depletions and repletions usually occur over periods of days rather than hours, these rapid changes may provide a clue to the selective action of DFMO against P. carinii and may guide the development of new compounds and an optimal drug administration schedule for DFMO.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=163241Documentos Relacionados
- Efficacy of DL-alpha-difluoromethylornithine in a rat model of Pneumocystis carinii pneumonia.
- Deferoxamine and eflornithine (DL-alpha-difluoromethylornithine) in a rat model of Pneumocystis carinii pneumonia.
- Continuous infusion of DL-alpha-difluoromethylornithine and improved efficacy against a rat model of Pneumocystis carinii pneumonia.
- Alterations in ornithine decarboxylase characteristics account for tolerance of Trypanosoma brucei rhodesiense to D,L-alpha-difluoromethylornithine.
- alpha-Difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, inhibits tumor promoter-induced polyamine accumulation and carcinogenesis in mouse skin.