RESUMO
The molecular mechanisms by which the malarial parasite has managed to develop resistance to many antimalarial drugs remain to be completely elucidated. Mutations in the pfmdr1 gene of Plasmodium falciparum, as well as an increase in pfmdr1 copy number, have been associated with resistance to the quinoline-containing antimalarial drugs. We investigated the mechanisms of drug resistance in Plasmodium using a collection of P. yoelii lines with different drug resistance profiles. The mdr1 gene of P. yoelii (pymdr1) was identified and characterized. A 2- to 3-fold increase in the pymdr1 gene copy number was observed in the P. yoelii ART line (artemisinin resistant) when compared with the NS parental line. The pymdr1 gene was mapped to a chromosome of 2.1 Mb in all lines analyzed. Reverse transcriptase-polymerase chain reaction and Western blot experiments confirmed the expression of the gene at the RNA and protein levels.
Assuntos
Antimaláricos/farmacologia , Artemisininas/farmacologia , Genes MDR/genética , Plasmodium yoelii/genética , Sequência de Aminoácidos , Animais , Western Blotting , Mapeamento Cromossômico , Resistência a Múltiplos Medicamentos/genética , Feminino , Dosagem de Genes , Expressão Gênica/genética , Genes MDR/fisiologia , Malária/tratamento farmacológico , Malária/parasitologia , Camundongos , Fases de Leitura Aberta/genética , Plasmodium yoelii/efeitos dos fármacos , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The rapid emergence of multidrug-resistant Plasmodium falciparum is a worldwide concern. Despite the magnitude of the problem, the mechanisms involved in this phenomenon are not well understood. One current proposal suggests that toxic heme molecules are degraded by glutathione (GSH), and that anti-malarial drugs, such as chloroquine (CQ), inhibit this degradation, thus implicating GSH in drug resistance. Furthermore, in some strains of Plasmodium berghei and P. falciparum, chloroquine resistance is accompanied by an increase in glutathione levels and increased activity in GSH-related enzymes. We are investigating the relationship between the gamma-glutamylcysteine synthetase (ggcs) gene, the rate-limiting enzyme in de novo synthesis of GSH, and drug resistance in P. berghei at the molecular level. In this report, we have demonstrated an increase in pbggcs mRNA levels associated with CQ and mefloquine (MFQ) resistance. In addition, the pbggcs gene locus structure was shown to be similar and localized to chromosome 8 in four parasite lines of P. berghei with different drug resistance profiles. This work suggests a link between increased GSH levels and drug resistance in Plasmodium.