Global gene expression profiling of Plasmodium falciparum in response to the anti-malarial drug pyronaridine

Abstract

Background: Pyronaridine (PN) and chloroquine (CQ) are structurally related anti-malarial drugs with primarily the same mode of action. However, PN is effective against several multidrug-resistant lines of Plasmodium falciparum, including CQ resistant lines, suggestive of important operational differences between the two drugs.

Methods: Synchronized trophozoite stage cultures of P. falciparum strain K1 (CQ resistant) were exposed to 50% inhibitory concentrations (IC50) of PN and CQ, and parasites were harvested from culture after 4 and 24 hours exposure. Global transcriptional changes effected by drug treatment were investigated using DNA microarrays.

Results: After a 4 h drug exposure, PN induced a greater degree of transcriptional perturbation (61 differentially expressed features) than CQ (10 features). More genes were found to respond to 24 h treatments with both drugs, and 461 features were found to be significantly responsive to one or both drugs across all treatment conditions. Filtering was employed to remove features unrelated to primary drug action, specifically features representing genes developmentally regulated, secondary stress/death related processes and sexual stage development. The only significant gene ontologies represented among the 46 remaining features after filtering relate to host exported proteins from multi-gene families.

Conclusions: The malaria parasite's molecular responses to PN and CQ treatment are similar in terms of the genes and pathways affected. However, PN appears to exert a more rapid response than CQ. The faster action of PN may explain why PN is more efficacious than CQ, particularly against CQ resistant isolates. In agreement with several other microarray studies of drug action on the parasite, it is not possible, however, to discern mechanism of drug action from the drug-responsive genes.

Figure 1

Chemical structures of Pyronaridine (PN) and Chloroquine (CQ).

Figure 2

All PN and CQ significant responsive features. The data from 463 features showing significant changes in expression identified from microarray analysis were clustered according to the average gene expression changes as rows and the drug treatments as columns. The colour key indicates the average log₂ fold changes in expression.

Figure 3

Correlation between K1 Trophozoite (22-24 h) and intraerythrocytic developmental cycle data for strain HB3.

Figure 4

PN and CQ responsive features after filtering of developmental and secondary responsive features. The data from 46 features which show significant changes in expression under CQ and/or PN exposure after filtering identified from microarray were clustered according to the average gene expression changes as rows and the drug treatments as columns. The colour key indicates the log₂ fold changes in expression. The feature oligo IDs and gene annotations (Plasmodb v8.0) are shown on the right.