Involvement of thiol metabolism in resistance to glucantime in Leishmania tropica.
Clinical resistance to pentavalent antimonials, in the form of pentostam (sodium stibogluconate) or glucantime (N-methylglucamine antimoniate), has long been recognized as a problem in Leishmaniasis. However, the mechanisms of resistance are unclear. We selected in vitro a Leishmania tropica line resistant to 1.2 mg/mL of Sb(V) of glucantime (GLU-R10). The cell line has a stable phenotype for at least 6 months and a resistance index of 1400-fold. The resistant line has no cross-resistance to pentostam or to SbCl3 and SbCl5. The resistance to glucantime was reverted by buthionine sulfoximine (BSO) and chlorambucil (CLB); however, thiol analyses by HPLC of wild-type and GLU-R10 cell lines, in the presence or absence of the drug, showed no differences between these two cell lines. The resistant line had a DNA amplification shown as a circular extrachromosomal element (G-circle) of approximately 22 kb. However, the specific probes for gamma-glutamyl cysteine synthetase, ornithine decarboxylase and trypanothione reductase did not recognize the G-circle amplified in the GLU-R10. The G-circle did not arise from the H region and was not related with P-glycoprotein Pgp-MDR- or Pgp-MRP-like genes. Northern blot analysis of the G-circle showed that a single transcript of approximately 6 kb was overexpressed in the resistant line. Molecular characterization of the G-circle would lead to the determination of the gene(s) involved in resistance to glucantime in Leishmania.
Arana
F E
FE
Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Granada, Spain.
Pérez-Victoria
J M
JM
Repetto
Y
Y
Morello
A
A
Castanys
S
S
Gamarro
F
F
D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002699:Chlorambucil / Q000494:pharmacology; D004351:Drug Resistance; D007895:Leishmania tropica / Q000187:drug effects*; D008536:Meglumine / Q000494:pharmacology*; D000077485:Meglumine Antimoniate; D009942:Organometallic Compounds / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
D000981:Antiprotozoal Agents; D009942:Organometallic Compounds; D013438:Sulfhydryl Compounds; D002699:Chlorambucil; D019328:Buthionine Sulfoximine; D008536:Meglumine; D000077485:Meglumine Antimoniate