Ornithine decarboxylase or gamma-glutamylcysteine synthetase overexpression protects Leishmania (Vianna) guyanensis against antimony

- ODC- or GSH1-overexpressing L. guyanensis are more resistant to SbIII.
- DFMO and BSO sensitize LgWT and ODC and GSH1-overexpressors to SbIII.
- DFMO and BSO increase the antileishmanial effect of SbIII.
- ODC and GSH1 are implicated in SbIII-resistance in New World Leishmania.

Trypanosomatids present a unique mechanism for detoxification of peroxides that is dependent on trypanothione (bisglutathionylspermidine). Ornithine decarboxylase (ODC) and γ-glutamylcysteine synthetase (GSH1) produce molecules that are direct precursors of trypanothione. In this study, Leishmania guyanensis odc and gsh1 overexpressor cell lines were generated to investigate the contribution of these genes to the trivalent antimony (SbIII)-resistance phenotype. The ODC- or GSH1-overexpressors parasites presented an increase of two and four-fold in SbIII-resistance index, respectively, when compared with the wild-type line. Pharmacological inhibition of ODC and GSH1 with the specific inhibitors α-difluoromethylornithine (DFMO) and buthionine sulfoximine (BSO), respectively, increased the antileishmanial effect of SbIII in all cell lines. However, the ODC- and GSH1-overexpressor were still more resistant to SbIII than the parental cell line. Together, our data shows that modulation of ODC and GSH1 levels and activity is sufficient to affect L. guyanensis susceptibility to SbIII, and confirms a role of these genes in the SbIII-resistance phenotype.

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