Multiple Antibiotics Exert Delayed Effects against the Plasmodium falciparum Apicoplast

ABSTRACT Several classes of antibiotics exert antimalarial activity. The mechanisms of action of antibiotics against malaria parasites have been unclear, and prior studies have led to conflicting results, in part because they studied antibiotics at suprapharmacological concentrations. We examined the antimalarial effects of azithromycin, ciprofloxacin, clindamycin, doxycycline, and rifampin against chloroquine-resistant (W2) and chloroquine-sensitive (3D7) Plasmodium falciparum strains. At clinically relevant concentrations, rifampin killed parasites quickly, preventing them from initiating cell division. In contrast, pharmacological concentrations of azithromycin, ciprofloxacin, clindamycin, and doxycycline were relatively inactive against parasites initially but exerted a delayed death effect, in which the progeny of treated parasites failed to complete erythrocytic development. The drugs that caused delayed death did not alter the distribution of apicoplasts into developing progeny. However, the apicoplasts inherited by the progeny of treated parasites were abnormal. The loss of apicoplast function became apparent as the progeny of antibiotic-treated parasites initiated cell division, with the failure of schizonts to fully mature or for erythrocyte rupture to take place. These findings explain the slow antimalarial action of multiple antibiotics.

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Retargeting azithromycin analogues to have dual-modality antimalarial activity

BMC Biology ◽

10.1186/s12915-020-00859-4 ◽

2020 ◽

Vol 18 (1) ◽

Author(s):

Amy L. Burns ◽

Brad E. Sleebs ◽

Ghizal Siddiqui ◽

Amanda E. De Paoli ◽

Dovile Anderson ◽

...

Keyword(s):

Plasmodium Knowlesi ◽

Antimalarial Activity ◽

Treatment Strategies ◽

Food Vacuole ◽

Parasite Development ◽

Malaria Parasites ◽

Killing Activity ◽

Delayed Death ◽

Artemisinin Combination Therapies

Abstract Background Resistance to front-line antimalarials (artemisinin combination therapies) is spreading, and development of new drug treatment strategies to rapidly kill Plasmodium spp. malaria parasites is urgently needed. Azithromycin is a clinically used macrolide antibiotic proposed as a partner drug for combination therapy in malaria, which has also been tested as monotherapy. However, its slow-killing ‘delayed-death’ activity against the parasite’s apicoplast organelle and suboptimal activity as monotherapy limit its application as a potential malaria treatment. Here, we explore a panel of azithromycin analogues and demonstrate that chemical modifications can be used to greatly improve the speed and potency of antimalarial action. Results Investigation of 84 azithromycin analogues revealed nanomolar quick-killing potency directed against the very earliest stage of parasite development within red blood cells. Indeed, the best analogue exhibited 1600-fold higher potency than azithromycin with less than 48 hrs treatment in vitro. Analogues were effective against zoonotic Plasmodium knowlesi malaria parasites and against both multi-drug and artemisinin-resistant Plasmodium falciparum lines. Metabolomic profiles of azithromycin analogue-treated parasites suggested activity in the parasite food vacuole and mitochondria were disrupted. Moreover, unlike the food vacuole-targeting drug chloroquine, azithromycin and analogues were active across blood-stage development, including merozoite invasion, suggesting that these macrolides have a multi-factorial mechanism of quick-killing activity. The positioning of functional groups added to azithromycin and its quick-killing analogues altered their activity against bacterial-like ribosomes but had minimal change on ‘quick-killing’ activity. Apicoplast minus parasites remained susceptible to both azithromycin and its analogues, further demonstrating that quick-killing is independent of apicoplast-targeting, delayed-death activity. Conclusion We show that azithromycin and analogues can rapidly kill malaria parasite asexual blood stages via a fast action mechanism. Development of azithromycin and analogues as antimalarials offers the possibility of targeting parasites through both a quick-killing and delayed-death mechanism of action in a single, multifactorial chemotype.

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Synthesis and Antiplasmodial Activity of Novel Fosmidomycin Derivatives and Conjugates with Artemisinin and Aminochloroquinoline

Molecules ◽

10.3390/molecules25204858 ◽

2020 ◽

Vol 25 (20) ◽

pp. 4858 ◽

Cited By ~ 1

Author(s):

Despina Palla ◽

Antonia I. Antoniou ◽

Michel Baltas ◽

Christophe Menendez ◽

Philippe Grellier ◽

...

Keyword(s):

Drug Resistance ◽

Plasmodium Falciparum ◽

Infectious Diseases ◽

Antimalarial Activity ◽

Biological Evaluation ◽

Antiplasmodial Activity ◽

Malaria Parasites ◽

Antimalarial Agents ◽

New Compounds

Malaria, despite many efforts, remains among the most problematic infectious diseases worldwide, mainly due to the development of drug resistance by Plasmodium falciparum. The antibiotic fosmidomycin (FSM) is also known for its antimalarial activity by targeting the non-mevalonate isoprenoid synthesis pathway, which is essential for the malaria parasites but is absent in mammalians. In this study, we synthesized and evaluated against the chloroquine-resistant P. falciparum FcB1/Colombia strain, a series of FSM analogs, derivatives, and conjugates with other antimalarial agents, such as artemisinin (ART) and aminochloroquinoline (ACQ). The biological evaluation revealed four new compounds with higher antimalarial activity than FSM: two FSM-ACQ derivatives and two FSM-ART conjugates, with 3.5–5.4 and 41.5–23.1 times more potent activities than FSM, respectively.

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Antimalarial Benzoxaboroles Target Plasmodium falciparum Leucyl-tRNA Synthetase

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00820-16 ◽

2016 ◽

Vol 60 (8) ◽

pp. 4886-4895 ◽

Cited By ~ 31

Author(s):

Ebere Sonoiki ◽

Andres Palencia ◽

Denghui Guo ◽

Vida Ahyong ◽

Chen Dong ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Antimalarial Activity ◽

Multidrug Resistant ◽

Trna Synthetase ◽

Mechanisms Of Action ◽

Unnatural Amino Acid ◽

Leucine Incorporation ◽

Wild Type ◽

Content Type ◽

Editing Domain

ABSTRACTThere is a need for new antimalarials, ideally with novel mechanisms of action. Benzoxaboroles have been shown to be active against bacteria, fungi, and trypanosomes. Therefore, we investigated the antimalarial activity and mechanism of action of 3-aminomethyl benzoxaboroles againstPlasmodium falciparum. Two 3-aminomethyl compounds, AN6426 and AN8432, demonstrated good potency against cultured multidrug-resistant (W2 strain)P. falciparum(50% inhibitory concentration [IC50] of 310 nM and 490 nM, respectively) and efficacy against murinePlasmodium bergheiinfection when administered orally once daily for 4 days (90% effective dose [ED90], 7.4 and 16.2 mg/kg of body weight, respectively). To characterize mechanisms of action, we selected parasites with decreased drug sensitivity by culturing with stepwise increases in concentration of AN6426. Resistant clones were characterized by whole-genome sequencing. Three generations of resistant parasites had polymorphisms in the predicted editing domain of the gene encoding aP. falciparumleucyl-tRNA synthetase (LeuRS; PF3D7_0622800) and in another gene (PF3D7_1218100), which encodes a protein of unknown function. Solution of the structure of theP. falciparumLeuRS editing domain suggested key roles for mutated residues in LeuRS editing. Short incubations with AN6426 and AN8432, unlike artemisinin, caused dose-dependent inhibition of [14C]leucine incorporation by cultured wild-type, but not resistant, parasites. The growth of resistant, but not wild-type, parasites was impaired in the presence of the unnatural amino acid norvaline, consistent with a loss of LeuRS editing activity in resistant parasites. In summary, the benzoxaboroles AN6426 and AN8432 offer effective antimalarial activity and act, at least in part, against a novel target, the editing domain ofP. falciparumLeuRS.

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Synergy of Human Immunodeficiency Virus Protease Inhibitors with Chloroquine against Plasmodium falciparum In Vitro and Plasmodium chabaudi In Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01329-07 ◽

2008 ◽

Vol 52 (7) ◽

pp. 2653-2656 ◽

Cited By ~ 20

Author(s):

Zhengxiang He ◽

Li Qin ◽

Lili Chen ◽

Nanzheng Peng ◽

Jianlan You ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Plasmodium Falciparum ◽

Protease Inhibitors ◽

Plasmodium Chabaudi ◽

Malaria Parasites ◽

Human Immunodeficiency Virus Protease ◽

Immunodeficiency Virus ◽

Antimalarial Action

ABSTRACT The synergy of the activities between chloroquine and various human immunodeficiency virus protease inhibitors was investigated in chloroquine-resistant and -sensitive malaria parasites. In both in vitro and in vivo assay systems, ritonavir was found to be the most potent in potentiating the antimalarial action of chloroquine.

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Reaction of artemisinin with haemoglobin: implications for antimalarial activity

Biochemical Journal ◽

10.1042/bj20041170 ◽

2005 ◽

Vol 385 (2) ◽

pp. 409-418 ◽

Cited By ~ 52

Author(s):

Rangiah KANNAN ◽

Krishan KUMAR ◽

Dinkar SAHAL ◽

Shrikant KUKRETI ◽

Virander S. CHAUHAN

Keyword(s):

Ascorbic Acid ◽

Plasmodium Falciparum ◽

Malaria Parasite ◽

Competitive Inhibition ◽

Antimalarial Activity ◽

Food Vacuole ◽

Primary Target ◽

Reducing Environment ◽

Derivatives Of ◽

Antimalarial Action

Elucidation of the principal targets of the action of the antimalarial drug artemisinin is an ongoing pursuit that is important for understanding the action of this drug and for the development of more potent analogues. We have examined the chemical reaction of Hb with artemisinin. The protein-bound haem in Hb has been found to react with artemisinin much faster than is the case with free haem. It appears that the uptake of Hb and the accumulation of artemisinin into the food vacuole, together with the preferred reactivity of artemisinin with haem in Hb, may make Hb the primary target of artemisinin's antimalarial action. Both monoalkylated (HA) and dialkylated (HAA) haem derivatives of artemisinin have been isolated. These ‘haemarts’ bind to PfHRP II (Plasmodium falciparum histidine-rich protein II), inhibiting haemozoin formation, and possess a significantly decreased ability to oxidize ascorbic acid. The accelerated formation of HAA from Hb is expected to decrease the ratio of haem to its alkylated derivatives. The haemarts that are generated from ‘haemartoglobins’ may bring about the death of malaria parasite by a two-pronged effect of stalling the formation of haemozoin by the competitive inhibition of haem binding to its templates and creating a more reducing environment that is not conducive to the formation of haemozoin.

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Defining the Timing of Action of Antimalarial Drugs against Plasmodium falciparum

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01881-12 ◽

2013 ◽

Vol 57 (3) ◽

pp. 1455-1467 ◽

Cited By ~ 87

Author(s):

Danny W. Wilson ◽

Christine Langer ◽

Christopher D. Goodman ◽

Geoffrey I. McFadden ◽

James G. Beeson

Keyword(s):

Flow Cytometry ◽

Plasmodium Falciparum ◽

Inhibitory Activity ◽

Antimalarial Activity ◽

Trichostatin A ◽

Mechanisms Of Action ◽

Trophozoite Stage ◽

Merozoite Invasion ◽

Content Type

ABSTRACTMost current antimalarials for treatment of clinicalPlasmodium falciparummalaria fall into two broad drug families and target the food vacuole of the trophozoite stage. No antimalarials have been shown to target the brief extracellular merozoite form of blood-stage malaria. We studied a panel of 12 drugs, 10 of which have been used extensively clinically, for their invasion, schizont rupture, and growth-inhibitory activity using high-throughput flow cytometry and new approaches for the study of merozoite invasion and early intraerythrocytic development. Not surprisingly, given reported mechanisms of action, none of the drugs inhibited merozoite invasionin vitro. Pretreatment of erythrocytes with drugs suggested that halofantrine, lumefantrine, piperaquine, amodiaquine, and mefloquine diffuse into and remain within the erythrocyte and inhibit downstream growth of parasites. Studying the inhibitory activity of the drugs on intraerythrocytic development, schizont rupture, and reinvasion enabled several different inhibitory phenotypes to be defined. All drugs inhibited parasite replication when added at ring stages, but only artesunate, artemisinin, cycloheximide, and trichostatin A appeared to have substantial activity against ring stages, whereas the other drugs acted later during intraerythrocytic development. When drugs were added to late schizonts, only artemisinin, cycloheximide, and trichostatin A were able to inhibit rupture and subsequent replication. Flow cytometry proved valuable forin vitroassays of antimalarial activity, with the free merozoite population acting as a clear marker for parasite growth inhibition. These studies have important implications for further understanding the mechanisms of action of antimalarials, studying and evaluating drug resistance, and developing new antimalarials.

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In Vitro and In Vivo Properties of Ellagic Acid in Malaria Treatment

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01175-08 ◽

2008 ◽

Vol 53 (3) ◽

pp. 1100-1106 ◽

Cited By ~ 57

Author(s):

Patrice Njomnang Soh ◽

Benoît Witkowski ◽

David Olagnier ◽

Marie-Laure Nicolau ◽

Maria-Concepcion Garcia-Alvarez ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Ellagic Acid ◽

Antimalarial Activity ◽

Inhibitory Effect ◽

Oral Route ◽

Mechanisms Of Action ◽

The World ◽

Erythrocytic Cycle

ABSTRACT Malaria is one of the most significant causes of infectious disease in the world. The search for new antimalarial chemotherapies has become increasingly urgent due to the parasites’ resistance to current drugs. Ellagic acid is a polyphenol found in various plant products. In this study, antimalarial properties of ellagic acid were explored. The results obtained have shown high activity in vitro against all Plasmodium falciparum strains whatever their levels of chloroquine and mefloquine resistance (50% inhibitory concentrations ranging from 105 to 330 nM). Ellagic acid was also active in vivo against Plamodium vinckei petteri in suppressive, curative, and prophylactic murine tests, without any toxicity (50% effective dose by the intraperitoneal route inferior to 1 mg/kg/day). The study of the point of action of its antimalarial activity in the erythrocytic cycle of Plasmodium falciparum demonstrated that it occurred at the mature trophozoite and young schizont stages. Moreover, ellagic acid has been shown to potentiate the activity of current antimalarial drugs such as chloroquine, mefloquine, artesunate, and atovaquone. This study also proved the antioxidant activity of ellagic acid and, in contrast, the inhibitory effect of the antioxidant compound N-acetyl-l-cysteine on its antimalarial efficacy. The possible mechanisms of action of ellagic acid on P. falciparum are discussed in light of the results. Ellagic acid has in vivo activity against plasmodia, but modification of the compound could lead to improved pharmacological properties, principally for the oral route.

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