Biology subjects

Guler, J. L.

Publications and source records attributed to Guler, J. L..

2 recordsLinked to original sources

bioRxiv2018

Leveraging the effects of chloroquine on resistant malaria parasites for combination therapies

Malaria is a major global health problem, with the Plasmodium falciparum protozoan parasite causing the most severe form of the disease. Prevalence of drug-resistant P. falciparum highlights the need to understand the biology of resistance and to identify novel combination therapies that are effective against resistant parasites. Resistance has compromised the therapeutic use of many antimalarial drugs, including chloroquine, and limited our ability to treat malaria across the world. Fortunately, chloroquine resistance comes at a fitness cost to the parasite; this can be leveraged in developing combination therapies or to reinstate use of chloroquine. To understand biological changes induced by chloroquine treatment, we compared transcriptomics data from chloroquine-resistant parasites in the presence or absence of the drug. Using both linear models and a genome-scale metabolic network reconstruction of the parasite to interpret the expression data, we identified targetable pathways in resistant parasites. This study identified an increased importance of lipid synthesis, glutathione production/cycling, isoprenoids biosynthesis, and folate metabolism in response to chloroquine. We identified potential drug targets for chloroquine combination therapies. Significantly, our analysis suggests that the combination of chloroquine and sulfadoxine-pyrimethamine or fosmidomycin may be more effective against chloroquine-resistant parasites than either drug alone; further studies will explore the use of these drugs as chloroquine resistance blockers. Additional metabolic weaknesses were found in glutathione generation and lipid synthesis during chloroquine treatment. These processes could be targeted with novel inhibitors to reduce parasite growth and reduce the burden of malaria infections. Thus, we identified metabolic weaknesses of chloroquine-resistant parasites and propose targeted chloroquine combination therapies.

microbiology↗

bioRxiv2017

Methods matter: Influential purification and analysis parameters for intracellular parasite metabolomics

Metabolomics is increasingly popular for the study of many pathogens. For the malaria parasite, Plasmodium falciparum, both targeted and untargeted metabolite detection has improved our understanding of pathogenesis, host-parasite interactions, and antimalarial drug treatment and resistance. However, purification and analysis procedures for performing metabolomics on intracellular pathogens have not been explored. Here, we investigate the impact of host contamination on the metabolome when preparing samples using standard methods. We purified in vitro grown ring stage intra-erythrocytic P. falciparum parasites for untargeted metabolomics studies; the small size of this developmental stage amplifies the challenges associated with metabolomics studies as the ratio between host and parasite biomass is maximized. Following metabolite identification and data preprocessing, we investigated whether host contributions could be corrected post hoc using various normalization approaches (including double stranded DNA, total protein, or parasite number). We conclude that normalization parameters have large effects on differential abundance analysis and recommend the thoughtful selection of these parameters. However, normalization does not remove the contribution from the parasites extracellular environment (culture media and host erythrocyte). In fact, we found that extra-parasite material is as influential on the metabolome as treatment with a potent antimalarial drug with known metabolic effects (artemisinin). Because of this influence, we could not detect significant changes associated with drug treatment. Instead, we identified metabolites predictive of host and media contamination that can be used to assess sample purification. Our findings provide a basis for development of improved experimental and analytical methods for future metabolomics studies of intracellular organisms.

microbiology↗