Antimalarial Exposure Delays Plasmodium falciparum Intra-Erythrocytic Cycle and Drives Drug Transporter Genes Expression

Background: Multi-drug resistant Plasmodium falciparum is a major obstacle to malaria control and is emerging as a complex phenomenon. Mechanisms of drug evasion based on the intracellular extrusion of the drug and/or modification of target proteins have been described. However, cellular mechanisms related with metabolic activity have also been seen in eukaryotic systems, e. g. cancer cells. Recent observations suggest that such mechanism may occur in P. falciparum. Methodology/Principal Findings: We therefore investigated the effect of mefloquine exposure on the cell cycle of three P. falciparum clones (3D7, FCB, W2) with different drug susceptibilities, while investigating in parallel the expression of four genes coding for confirmed and putative drug transporters (pfcrt, pfmdr1, pfmrp1 and pfmrp2). Mefloquine induced a previously not described dose and clone dependent delay in the intra-erythrocytic cycle of the parasite. Drug impact on cell cycle progression and gene expression was then merged using a non-linear regression model to determine specific drug driven expression. This revealed a mild, but significant, mefloquine driven gene induction up to 1.5 fold. Conclusions/Significance: Both cell cycle delay and induced gene expression represent potentially important mechanisms for parasites to escape the effect of the antimalarial drug.Swedish Development Cooperation Agency - Department for Research Cooperation [SWE 2005 - 0017, SWE 2005 - 4596, SWE-2007-174, SWE-2005-4027]; Fundacao para a Ciencia e Tecnologia (FCT)/Ministerio da Ciencia e Ensino Superior, Portugal - MCES [SFRH/BD/28393/2006, SFRH/BD/28368/2006]