Evaluation of ferrocenyl phosphines a<i>s potent antimalarials</i>targeting the digestive vacuole function of<i>Plasmodium falciparum</i>

Subramanian, Gomathy Sandhya; Sadeer, Abdul; Mukherjee, Kalyani; Kojima, Tadayuki; Tripathi, Pallavi; Naidu, Renugah; Tay, Shan Wen; Pang, Jia; Pullarkat, Sumod A.; Chandramohanadas, Rajesh

doi:10.1039/c8dt04263b

Cited by 14 publications

(12 citation statements)

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“…Trophozoite stage parasites (24-26 hpi) (or schizonts at 40-42 hpi for E64 and heparin) grown in CD71 + and CD71 - host cells were incubated with the drugs, along with non-treated infected RBCs. New infections were counted in the next cycle (after 50-52 h post drug treatment) and/or post invasion (20 h after treatment), for heparin and E64, followed by IC 50 determination 26 . We observed comparable response and IC 50 values between parasites infected into CD71 + and CD71 - cells for most drugs ( Supplemental Table 1 ) including chloroquine.…”

Section: Resultsmentioning

confidence: 99%

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Reticulocyte Infection Leads to Altered Behaviour, Drug Sensitivity and Host Cell Remodelling byPlasmodium falciparum

Chandramohanadas

Naidu²,

Chu³

et al. 2019

Preprint

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29Plasmodia are host-specific, both at the organism and cellular levels. During asexual 30 development, Plasmodium spp. infect cells of erythroid lineage, with an overall 31 propensity towards reticulocytes. This applies to even Plasmodium (P.) falciparum, the 32 most common causative agent of human malaria, implications of which remain 33 unexplored. Herein, for the first time, we characterize the developmental stages and 34 features of P. falciparum cultured in vitro in young reticulocytes (CD71 + ) in comparison to 35 standard normocyte (CD71 -) cultures. We demonstrate that there are notable differences 36 in the patterns of invasion, development and sensitivity to potent antimalarials (such as 37 artemisinin and dihydroartemisinin) for parasites residing in CD71 + reticulocytes. 38Through a transcriptomic approach, we report that P. falciparum parasites are able to 39 sense the host cell environment, and calibrate their metabolic and host cell remodelling 40 pathways through differential gene expression. These results form an exciting avenue on 41 which hitherto unexplored interactions between Plasmodium spp and different stages of 42 host red blood cells could be investigated in the broader contexts of drug resistance, 43 host tropism and zoonosis. 45Author Summary 46Parasites causing malaria infect red blood cells for development and proliferation during 47 asexual development. This asexual erythrocytic stage determines higher parasite 48 densities and eventual disease manifestation. Although the most virulent species of 49 Plasmodium infecting humans known as Plasmodium falciparum is able to infect red 50 blood cells of all ages, these parasites show a preference for younger blood cells. Of 51 note, the biochemical and biophysical properties of young and adult red blood cells vary 52 significantly. Herein, we undertook a comparative profiling of invasion process, parasite 53 development and drug response of Plasmoddium falciparum in two host cells: young red 54 blood cells (reticulocytes) and mature red blood cells (normocytes). We demonstrate that 55 P. falciparum infects human reticulocytes with higher affinity and demonstrate differential 56 3 sensitivity to drugs such as artemisinin while they reside within reticulocytes. 57Furthermore, we show that P. falciparum is able to detect differences in host 58 environment and adapt to it by changing the expression of genes required for host cell 59 remodelling. 61 Introduction 62Plasmodium infection and associated mortality remain an important concern to the 63 developing world with 218 million malaria cases and ~450,000 deaths annually 1 64 (https://www.who.int/malaria/publications/world-malaria-report-2018/en/). 65Widespread drug-resistance 2-3 and evolution of newer phenotypes; influenced by factors 66 such as changing availability and distribution of insect vector 4 , haematological 67 malignancies(1, 2) 5-6 (thalassemia, sickle cell anaemia, G6PD deficiency etc), providing 68 protective immunity to certain populations 7 , adversely impact malaria eradic...

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Section: Resultsmentioning

confidence: 99%

“…Three trained researchers counted the slides independently, data represents experiments performed in triplicates. IC 50 values were determined using GraphPad Prism according to the recommended protocol for nonlinear regression of a log(inhibitor)-versus-response curve 26 . An unpaired t-test was applied to ensure statistical significance.…”

Section: Methodsmentioning

confidence: 99%

Reticulocyte Infection Leads to Altered Behaviour, Drug Sensitivity and Host Cell Remodelling byPlasmodium falciparum

Chandramohanadas

Naidu²,

Chu³

et al. 2019

Preprint

Self Cite

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“…Parasitemia was scored using flow cytometry (Accuri C6 sampler; BD Biosciences, Singapore) after the paraformaldehyde-fixed parasites were stained with Hoechst (Hoechst 33342; Thermo Fisher Scientific, Inc.). In parallel, Giemsa-stained smears were microscopically examined to match the smear findings with the flow cytometry results and to record the phenotypic characteristics arising from drug treatment, as established previously (46,53). EC 50 determination of Pathogen Box molecules against P. falciparum.…”

Section: Methodsmentioning

confidence: 99%

Whole-Cell Phenotypic Screening of Medicines for Malaria Venture Pathogen Box Identifies Specific Inhibitors of Plasmodium falciparum Late-Stage Development and Egress

Patra

Hingamire

Belekar

et al. 2020

Antimicrob Agents Chemother

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We report a systematic, cellular phenotype-based antimalarial screening of the Medicines for Malaria Venture Pathogen Box collection, which facilitated the identification of specific blockers of late-stage intraerythrocytic development of Plasmodium falciparum. First, from standard growth inhibition assays, we identified 173 molecules with antimalarial activity (50% effective concentration [EC50] ≤ 10 μM), which included 62 additional molecules over previously known antimalarial candidates from the Pathogen Box. We identified 90 molecules with EC50 of ≤1 μM, which had significant effect on the ring-trophozoite transition, while 9 molecules inhibited the trophozoite-schizont transition and 21 molecules inhibited the schizont-ring transition (with ≥50% parasites failing to proceed to the next stage) at 1 μM. We therefore rescreened all 173 molecules and validated hits in microscopy to prioritize 12 hits as selective blockers of the schizont-ring transition. Seven of these molecules inhibited the calcium ionophore-induced egress of Toxoplasma gondii, a related apicomplexan parasite, suggesting that the inhibitors may be acting via a conserved mechanism which could be further exploited for target identification studies. We demonstrate that two molecules, MMV020670 and MMV026356, identified as schizont inhibitors in our screens, induce the fragmentation of DNA in merozoites, thereby impairing their ability to egress and invade. Further mechanistic studies would facilitate the therapeutic exploitation of these molecules as broadly active inhibitors targeting late-stage development and egress of apicomplexan parasites relevant to human health.

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“…Parasitemia was scored using flow cytometry (Accuri C6 sampler, BD biosciences Singapore) after staining with Hoechst dye (Hoechst 33342, Thermo Fisher). In parallel, Giemsa-stained thin smears were microscopically examined to match with flow cytometry results and to record phenotypic characteristics arising from drug treatment, as established previously 17–18 .…”

Section: Methodsmentioning

confidence: 99%

“…Tachyzoite stage RH strain T. gondii were cultured in the laboratory as previously reported 18 . When exposed to the calcium ionophore A23187, intracellular tachyzoites are known to rapidly rupture the parasitophorous vacuole and egress out of the host cells 23–25 .…”

Section: Methodsmentioning

confidence: 99%

Whole Cell Phenotypic Screening Of MMV Pathogen Box identifies Specific Inhibitors of Plasmodium falciparum merozoite maturation and egress

Patra

Hingamire

Belekar

et al. 2019

Preprint

Self Cite

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30We report a systematic, cellular phenotype-based antimalarial screening of the MMV Pathogen Box 31 collection, which facilitated the identification of specific blockers of late stage intraerythrocytic 32 Plasmodium falciparum maturation. First, from standard growth inhibition asays, we discovered 62 33 additional antimalarials (EC 50 ≤ 10µM) over previously known antimalarial candidates from Pathogen 34 Box. A total of 90 potent molecules (EC 50 ≤ 1µM) were selected for evaluating their stage-specific 35 effects during the intra-erythrocytic development of P. falciparum. None of these molecules had 36 significant effect on ring-trophozoite transition, 10 molecules inhibited trophozoite-schizont transition, 37 and 21 molecules inhibited schizont-ring transition at 1µM. These compounds were further validated 38 in secondary assays by flow cytometry and microscopic imaging of treated cells to prioritize 12 39 molecules as potent and selective blockers of schizont-ring transition. Seven of these were found to 40 strongly inhibit calcium ionophore induced egress of Toxoplasma gondii, a related apicomplexan 41 parasite, suggesting that the inhibitors may be acting via similar mechanism in the two parasites, 42 which can be further exploited for target identification studies. Two of these molecules, with previously 43 unknown mechanism of action, MMV020670 and MMV026356, were found to induce fragmentation of 44 DNA in developing merozoites. Further mechanistic studies would facilitate therapeutic exploitation of 45 these molecules as broadly active inhibitors targeting development and egress of apicomplexan 46 parasites relevant to human health. 47 48 49 Despite technological advancements and improved knowledge on disease manifestation and 69 pathogen biology, progress in therapeutic development has been slower than expected for human 70 infectious diseases affecting the developing world. In addition to limited financial prospects, 71 pharmaceutical companies remain under significant pressure to address high attrition rates. In this 72 context, repurposing of old drugs is becoming a viable alternative through the exploitation of known 73 compounds with established mechanisms thereby shortening the time window between efficacy 74 testing to pharmacophore optimization 1-3 to eventual application. In recent efforts to speed up the 75 process of drug development against various pathogenic diseases, a collaborative model of public-76 private partnerships (PPPs) facilitated through Medicines for Malaria Venture (MMV: mmv.org) was 77 formed. This resulted in well-characterized drug-like small molecule libraries being made accessible 78 to academics worldwide, for the purpose of identifying novel bioactivities against various tropical 79 disease pathogens and conducting focused mechanistic studies. In 2015, the consortium launched 80 the open access "Pathogen Box" consisting of 400 drug-like small molecules, included 26 reference 81 compounds, with confirmed bioactivity against at least one of the neglected disease pathogens ...

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Evaluation of ferrocenyl phosphines as potent antimalarialstargeting the digestive vacuole function ofPlasmodium falciparum

Abstract: Ferrocenyl phosphines targeting the digestive vacuole function of the malaria parasite, Plasmodium falciparum.

Cited by 14 publications

References 56 publications

Reticulocyte Infection Leads to Altered Behaviour, Drug Sensitivity and Host Cell Remodelling byPlasmodium falciparum

Reticulocyte Infection Leads to Altered Behaviour, Drug Sensitivity and Host Cell Remodelling byPlasmodium falciparum

Whole-Cell Phenotypic Screening of Medicines for Malaria Venture Pathogen Box Identifies Specific Inhibitors of Plasmodium falciparum Late-Stage Development and Egress

Whole Cell Phenotypic Screening Of MMV Pathogen Box identifies Specific Inhibitors of Plasmodium falciparum merozoite maturation and egress

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