title: Is the expression of genes encoding enzymes of glutathione (GSH) metabolism involved in chloroquine resistance in Plasmodium chabaudi parasites?
abstract: The genes encoding enzymes involved in glutathione (GSH) metabolism may modulate responses to antimalarial drugs, but the role of most of them in antimalarial drug resistance has scarcely been investigated. Using an in silico/PCR combined approach, we have isolated from Plasmodium chabaudi, full sequences of five Plasmodium falciparum gene orthologues involved in GSH metabolism: the gamma-glutamylcysteine synthetase (Pc-gammagcs), glutathione-synthetase (Pc-gs), glutathione peroxidase (Pc-gpx), glutathione reductase (Pc-gr) and glutathione-S-transferase (Pc-gst). DNA sequencing of these genes from drug sensitive parasites, P. chabaudi AS (0CQ), and ones isolated from parasite lines that show genetically stable resistance to chloroquine (CQ) at low, intermediate and high levels, AS (3CQ), AS (15CQ) and AS (30CQ), respectively, revealed no point mutations in the resistant parasites. We used these sequences to design internal oligonucleotide primers to compare relative mRNA amounts of these genes between all P. chabaudi clones, in untreated mice or following CQ treatment with sub-curative doses, by real-time PCR. Analysis of three independent experiments revealed that transcription levels of the Pc-gammagcs, Pc-gs, Pc-gpx, Pc-gr and Pc-gst genes were not changed between chloroquine sensitive and resistant parasite clones, and that treatment with chloroquine did not induce an alteration in the expression of these genes in sensitive or resistant parasites. We concluded that chloroquine resistance in this species is determined by a mechanism that is independent of these genes, and most likely, of GSH metabolism.
authors.affiliation: Centro de Malária e Outras Doenças Tropicais/IHMT/UEI Malária, Rua da Junqueira 96, 1349-008 Lisbon, Portugal.
authors.forename: Isabel D
authors.initials: ID
authors.lastname: Ferreira
authors.forename: Fátima
authors.initials: F
authors.lastname: Nogueira
authors.forename: Sofia T
authors.initials: ST
authors.lastname: Borges
authors.forename: Virgilio E
authors.initials: VE
authors.lastname: do Rosário
authors.forename: Pedro
authors.initials: P
authors.lastname: Cravo
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage / Q000494:pharmacology*; D002738:Chloroquine / Q000008:administration & dosage / Q000494:pharmacology*; D004351:Drug Resistance; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism; D005981:Glutathione Synthase / Q000235:genetics / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D008288:Malaria / Q000469:parasitology; D051379:Mice; D008969:Molecular Sequence Data; D016788:Plasmodium chabaudi / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics
chemical_list: D000962:Antimalarials; D002738:Chloroquine; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D005721:Glutamate-Cysteine Ligase; D005981:Glutathione Synthase; D005978:Glutathione