Objectives: Drug resistance in parasitic protozoa is an obstacle to successful chemotherapy. Understanding how pathogens respond to drugs is crucial in preventing resistance. Previously, we have shown that in Entamoeba histolytica, methionine γ-lyase (EhMGL) downregulation results in trifluoromethionine resistance. The transcriptional response, however, of this parasite to the drug is not known. In this study, we used microarray analysis to determine whether additional genes are involved.
Methods: The expression profiles of 9230 genes in wild-type and trifluoromethionine-resistant strains were compared. Episomal overexpression of EhBspA1 was performed to verify its role in trifluoromethionine resistance. The transcriptomes of a trifluoromethionine-resistant strain cultured with or without trifluoromethionine, an EhMGL gene-silenced strain, a strain with reduced susceptibility to metronidazole and a wild-type strain under cysteine-deprived conditions were compared to determine the specificity of the changes observed in the trifluoromethionine-resistant strain.
Results: The expression of 35 genes differed at least 3-fold between trifluoromethionine-resistant and wild-type strains. Some of the genes play roles in metabolism, the stress response and gene regulation. EhMGL and EhBspA1 were found to be highly downregulated and upregulated, respectively. Overexpression of EhBspA1 conferred partial resistance to trifluoromethionine. Comparative transcriptome analysis showed that genes modulated in trifluoromethionine-resistant strains were specific.
Conclusions: E. histolytica has few known resistance mechanisms against drugs. In this study, we showed that aside from EhMGL downregulation, induction of EhBspA1 plays a role in trifluoromethionine resistance. We also showed a unique set of induced genes that could represent the signature profile of trifluoromethionine resistance in E. histolytica.