Effects of Pentamidine on Polyamine Level and Biosynthesis in Wild-Type, Pentamidine-Treated, and Pentamidine-ResistantLeishmania

Polyamine biosynthesis was studied in wild-type promastigotes ofLeishmania donovaniandLeishmania amazonensistreated with pentamidine and in the parasites resistant to this drug. Treatment of wild-type clones with low pentamidine concentrations for 24 hr provoked a strong decrease in arginine, ornithine, and putrescine pools, while the level of intracellular spermidine remained unchanged. In these cells, the activity of the enzyme ornithine decarboxylase was found to be decreased. Compared to wild-type cells, resistant clones had a lower level of putrescine, higher pools of arginine and ornithine, and a similar spermidine content. Analysis by Western blot and DFMO-binding showed reduced amount of ornithine decarboxylase. Furthermore, in the resistant cells, the kinetic parameters of the enzyme spermidine synthase were markedly changed, showing increased affinity to putrescine and decreased affinity to pentamidine. Thus, it seems that polyamine biosynthesis pathway is a target of pentamidine inLeishmaniaand is altered in resistant clones.