Targeting malaria parasites with novel derivatives of azithromycin
Ontology highlight
ABSTRACT:
ORGANISM(S): Plasmodium Falciparum
TISSUE(S): Blood
DISEASE(S): Malaria
PROVIDER: ST002309 | MetabolomicsWorkbench |
REPOSITORIES: MetabolomicsWorkbench
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Project description:IntroductionThe spread of artemisinin resistant Plasmodium falciparum parasites is of global concern and highlights the need to identify new antimalarials for future treatments. Azithromycin, a macrolide antibiotic used clinically against malaria, kills parasites via two mechanisms: 'delayed death' by inhibiting the bacterium-like ribosomes of the apicoplast, and 'quick-killing' that kills rapidly across the entire blood stage development.MethodsHere, 22 azithromycin analogues were explored for delayed death and quick-killing activities against P. falciparum (the most virulent human malaria) and P. knowlesi (a monkey parasite that frequently infects humans).ResultsSeventeen analogues showed improved quick-killing against both Plasmodium species, with up to 38 to 20-fold higher potency over azithromycin after less than 48 or 28 hours of treatment for P. falciparum and P. knowlesi, respectively. Quick-killing analogues maintained activity throughout the blood stage lifecycle, including ring stages of P. falciparum parasites (<12 hrs treatment) and were >5-fold more selective against P. falciparum than human cells. Isopentenyl pyrophosphate supplemented parasites that lacked an apicoplast were equally sensitive to quick-killing analogues, confirming that the quick killing activity of these drugs was not directed at the apicoplast. Further, activity against the related apicoplast containing parasite Toxoplasma gondii and the gram-positive bacterium Streptococcus pneumoniae did not show improvement over azithromycin, highlighting the specific improvement in antimalarial quick-killing activity. Metabolomic profiling of parasites subjected to the most potent compound showed a build-up of non-haemoglobin derived peptides that was similar to chloroquine, while also exhibiting accumulation of haemoglobin-derived peptides that was absent for chloroquine treatment.DiscussionThe azithromycin analogues characterised in this study expand the structural diversity over previously reported quick-killing compounds and provide new starting points to develop azithromycin analogues with quick-killing antimalarial activity.
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Project description:Hemangioblasts are known as the common precursors for primitive hematopoietic and endothelial lineages. Their existence has been supported mainly by the observation that both cell types develop in close proximity and by in vitro differentiation and genetic studies. However, more compelling evidence will arise from tracking their cell fates using a lineage-specific marker. We report the identification of a hemangioblast-specific enhancer (Hb) located in the cis-regulatory region of chick Cerberus gene (cCer) that is able to direct the expression of enhanced green fluorescent protein (eGFP) to the precursors of yolk sac blood and endothelial cells in electroporated chick embryos. Moreover, we present the Hb-eGFP reporter as a powerful live imaging tool for visualizing hemangioblast cell fate and blood island morphogenesis. We hereby introduce the Hb enhancer as a valuable resource for genetically targeting the hemangioblast population as well as for studying the dynamics of vascular and blood cell development. We used microarray analysis of Hb-eGFP expressing cells to verify the expression of hemangioblast-specific genes in this cell population. In order to characterize the gene expression profile of the Hb-eGFP-positive population, we have isolated Hb-eGFP-positive cells and compared their expression profile with the control RFP-positive population. In brief, chicken embryos were electroporated at HH3 with Hb-eGFP and pCAGGS-RFP reporter constructs, observed under a fluorescence stereoscope and harvested at stage HH5-6 into three groups of four embryos each. Embryos were dissociated into single cell suspensions and the eGFP-positive and eGFP-negative/RFP-positive cell populations were sorted by Fluorescence Activated Cell Sorting (FACS). Cell populations were collected simultaneously into two different tubes, containing RNAlater (Ambion) and subsequently used for RNA extraction. Total RNA was isolated from triplicates of each population, evaluated for RNA integrity, reverse transcribed, amplified and hybridized against six Affymetrix Chicken Genome microarrays.
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