Artemisinins

Facile synthesis of vanillin-based novel bischalcones identifies one that induces apoptosis and displays synergy with Artemisinin in killing chloroquine resistant Plasmodium falciparum

The inherent affinity of natural compounds for biological receptors has been comprehensively exploited with great success for the development of many drugs, including antimalarials. Here the natural flavoring compound vanillin has been used as an economical precursor for the synthesis of a series of novel bischalcones whose in vitro antiplasmodial activities have been evaluated against erythrocytic stages of Plasmodium falciparum. Bischalcones 9, 11 and 13 showed promising antiplasmodial activity {Chloroquine (CQ) sensitive Pf3D7 IC₅₀ (μM): 2.0, 1.5 and 2.5 respectively}but only 13 displayed potent activities also against CQ resistant PfDd2 and PfIndo strains exhibiting resistance indices of 1.4 and 1.5 respectively. IC₉₀ (8 μM) of 13 showed killing activity against ring, trophozoite and schizont stages. Further, 13 initiated the cascade of reactions that culminates in programmed cell death of parasites including translocation of phosphatidylserine from inner to outer membrane leaflet, loss of mitochondrial membrane potential, activation of caspase like enzyme, DNA fragmentation and chromatin condensation. The combinations of 13 + Artemisinin (ART) exhibited strong synergy (ΣFIC₅₀:0.46 to 0.58) while 13 + CQ exhibited mild synergy (ΣFIC₅₀: 0.7 to 0.98) to mild antagonism (ΣFIC₅₀: 1.08 to 1.23) against PfIndo. In contrast, both combinations showed marked antagonism against Pf3D7(ΣFIC₅₀: 1.33 to 3.34). These features of apoptosis and strong synergy with Artemisinin suggest that bischalcones possess promising antimalarial drug-like properties and may also act as a good partner drugs for artemisinin based combination therapies (ACTs) against Chloroquine resistant P. falciparum.

Oxidative stress and protein damage responses mediate artemisinin resistance in malaria parasites

Due to their remarkable parasitocidal activity, artemisinins represent the key components of first-line therapies against Plasmodium falciparum malaria. However, the decline in efficacy of artemisinin-based drugs jeopardizes global efforts to control and ultimately eradicate the disease. To better understand the resistance phenotype, artemisinin-resistant parasite lines were derived from two clones of the 3D7 strain of P. falciparum using a selection regimen that mimics how parasites interact with the drug within patients. This long term in vitro selection induced profound stage-specific resistance to artemisinin and its relative compounds. Chemosensitivity and transcriptional profiling of artemisinin-resistant parasites indicate that enhanced adaptive responses against oxidative stress and protein damage are associated with decreased artemisinin susceptibility. This corroborates our previous findings implicating these cellular functions in artemisinin resistance in natural infections. Genomic characterization of the two derived parasite lines revealed a spectrum of sequence and copy number polymorphisms that could play a role in regulating artemisinin response, but did not include mutations in pfk13, the main marker of artemisinin resistance in Southeast Asia. Taken together, here we present a functional in vitro model of artemisinin resistance that is underlined by a new set of genetic polymorphisms as potential genetic markers.

Molecular targets and anti-cancer potential of escin

Escin is a mixture of triterpenoid saponins extracted from the horse chestnut tree, Aesculus hippocastanum. Its potent anti-inflammatory and anti-odematous properties makes it a choice of therapy against chronic venous insufficiency and odema. More recently, escin is being actively investigated for its potential activity against diverse cancers. It exhibits anti-cancer effects in many cancer cell models including lung adenocarcinoma, hepatocellular carcinoma and leukemia. Escin also attenuates tumor growth and metastases in various in vivo models. Importantly, escin augments the effects of existing chemotherapeutic drugs, thereby supporting the role of escin as an adjunct or alternative anti-cancer therapy. The beneficial effects of escin can be attributed to its inhibition of proliferation and induction of cell cycle arrest. By regulating transcription factors/growth factors mediated oncogenic pathways, escin also potentially mitigates chronic inflammatory processes that are linked to cancer survival and resistance. This review provides a comprehensive overview of the current knowledge of escin and its potential as an anti-cancer therapy through its anti-proliferative, pro-apoptotic, and anti-inflammatory effects.

Activities of 11-Azaartemisinin and N-Sulfonyl Derivatives against Asexual and Transmissible Malaria Parasites

Dihydroartemisinin (DHA), either used in its own right or as the active drug generated in vivo from the other artemisinins in current clinical use-artemether and artesunate-induces quiescence in ring-stage parasites of Plasmodium falciparum (Pf). This induction of quiescence is linked to artemisinin resistance. Thus, we have turned to structurally disparate artemisinins that are incapable of providing DHA on metabolism. Accordingly, 11-azaartemisinin 5 and selected N-sulfonyl derivatives were screened against intraerythrocytic asexual stages of drug-sensitive Pf NF54 and drug-resistant K1 and W2 parasites. Most displayed appreciable activities against all three strains, with IC₅₀ values <10.5 nm. The p-trifluoromethylbenzenesulfonyl-11-azaartemisinin derivative 11 [(4'-trifluoromethyl)benzenesulfonylazaartemisinin] was the most active, with IC₅₀ values between 2 and 3 nm. The compounds were screened against Pf NF54 early and transmissible late intraerythrocytic-stage gametocytes using luciferase and parasite lactate dehydrogenase (pLDH) assays. The 2'-thienylsulfonyl derivative 16 (2'-thiophenesulfonylazaartemisinin) was notably active against late-stage (IV-V) gametocytes with an IC₅₀ value of 8.7 nm. All compounds were relatively nontoxic to human fetal lung WI-38 fibroblasts, showing selectivity indices of >2000 toward asexual parasites. Overall, the readily accessible 11-azaartemisinin 5 and the sulfonyl derivatives 11 and 16 represent potential candidates for further development, in particular for transmission blocking of artemisinin-resistant parasites.

More insights into the pharmacological effects of artemisinin

Artemisinin is one of the most widely prescribed drugs against malaria and has recently received increased attention because of its other potential biological effects. The aim of this review is to summarize recent discoveries of the pharmaceutical effects of artemisinin in basic science along with its mechanistic action, as well as the intriguing results of recent clinical studies, with a focus on its antitumor activity. Scientific evidence indicates that artemisinin exerts its biological activity by generating reactive oxygen species that damage the DNA, mitochondrial depolarization, and cell death. In the present article review, scientific evidence suggests that artemisinin is a potential therapeutic agent for various diseases. Thus, this review is expected to encourage interested scientists to conduct further preclinical and clinical studies to evaluate these biological activities.

Chemoprevention by artesunate in a preclinical model of colorectal cancer involves down regulation of β-catenin, suppression of angiogenesis, cellular proliferation and induction of apoptosis

Use of anti-inflammatory drugs is well known to decrease the risk of colorectal cancer, one of the most common causes of cancer related mortality. In view of anti-inflammatory property of artesunate reported in various experimental models, the present study was carried out to evaluate its efficacy in rat model where colon carcinogenesis was induced by 1, 2 dimethylhydrazine (DMH). A time course study revealed that two injections of DMH given at an interval of one week resulted in appearance of multiple plaque lesions and aberrant crypt foci in the colon with a peak effect occurring at the end of 8 weeks. An efficacy study carried out with daily oral administration of artesunate (50 and 150 mg/kg) and aspirin (60 mg/kg) showed a marked reduction in pre-neoplastic changes with a significant decrease in the number of aberrant crypt foci, crypt multiplicity and restoration of histoarchitecture. Both the drugs down regulated β-catenin signaling, reduced the levels of angiogenic markers like VEGF, MMP-9 and inhibited cellular proliferation. The anti-cancer effect of these drugs was concomitant with the pro-apoptotic effect as revealed by increased DNA fragmentation, TUNEL positivity and Bax/Bcl₂ immunoreactivity. This is the first study to evaluate the inhibitory effect of artesunate on pre-neoplastic changes in colon where its chemopreventive effect was found to be comparable to that of aspirin. Our study strengthens the previous findings and shows that it has a preventive and therapeutic potential in the treatment of colon cancer.

The Effects of Artemisinin on the Cytolytic Activity of Natural Killer (NK) Cells

Artemisinin, a chemical compound used for the treatment of malaria, has been known to show anti-cancer activity. However, the effect of this chemical on natural killer (NK) cells, which are involved in tumor killing, remains unknown. Here, we demonstrate that artemisinin exerts a potent anti-cancer effect by activating NK cells. NK-92MI cells pre-treated with artemisinin were subjected to a cytotoxicity assay using K562 cells. The results showed that artemisinin significantly enhances the cytolytic activity of NK cells in a dose-dependent manner. Additionally, the artemisinin-enhanced cytotoxic effect of NK-92MI cells on tumor cells was accompanied by the stimulation of granule exocytosis, as evidenced by the detection of CD107a expression in NK cells. Moreover, this enhancement of cytotoxicity by artemisinin was also observed in human primary NK cells from peripheral blood. Our results suggest that artemisinin enhances human NK cell cytotoxicity and degranulation. This is the first evidence that artemisinin exerts antitumor activity by enhancing NK cytotoxicity. Therefore, these results provide a deeper understanding of the action of artemisinin and will contribute to the development and application of this class of compounds in cancer treatment strategies.

In vitro and in vivo delivery of artemisinin loaded PCL-PEG-PCL micelles and its pharmacokinetic study

Artemisinin (ART) is a natural anti-malarial sesquiterpene lactone with anticancer properties, but its application is limited because of its low water solubility. To increase the bioavailability and water solubility of ART, we synthesized three series of poly (ɛ-caprolactone)-poly (ethylene glycol)-poly (ɛ-caprolactone) (PCL-PEG-PCL) tri-block copolymers. The structure of the copolymers was characterized by HNMR, FTIR, DSC and GPC techniques. ART was encapsulated inside micelles by a nanoprecipitation method which leading to the formation of ART/PCL-PEG-PCL micelles. The obtained micelles were characterized by DLS and AFM technique. The results showed that the average size of micelles was about 83.22 nm. ART was encapsulated into PCL-PEG-PCL micelles with encapsulation efficacy of 89.23 ± 1.41%. In vivo results demonstrated that this formulation significantly increased drug accumulation in tumours. Pharmacokinetic study in rats revealed that in vivo drug exposure of ART was significantly increased and prolonged by intravenously administering ART-loaded micelles when compared with the same dose of free ART. The MTT assay showed that bare PCL-PEG-PCL micelles is non-toxic to MCF7 and 4T1 cancer cell lines whereas the ART/PCL-PEG-PCL micelles showed a specific toxicity to both cancer cell lines. Therefore, the polymeric micellar formulation of ART based copolymer could provide a desirable process for ART delivery.

Comparative analysis of the safety and tolerability of fixed-dose artesunate/amodiaquine versus artemether/lumefantrine combinations for uncomplicated falciparum malaria in pregnancy: a randomized open label study

A comparative clinical study was conducted to evaluate the safety and tolerability of two commonly used fixed dose artemisinin-based combinations for the treatment of uncomplicated Plasmodium falciparum malaria in the second and third trimester of pregnancy. To achieve this, a total of 155 participants were recruited for the study. Eighty of these were drawn from pregnant women who came for routine antenatal care while 40 nonpregnant participants were recruited from apparently healthy females in the community. Eighty pregnant participants with uncomplicated P. falciparum malaria were randomized into artesunate/amodiaquine (AA) and artemether/lumefantrine (AL) treatment arms while 40 nonpregnant and 35 nonmalarious pregnant women were used as control. The interventional groups received standard fixed dose combinations of AA (100/270 mg) daily or AL (20/120 mg) twice daily for 3 days. Blood samples were collected on day 4 and patients were followed-up closely to ascertain the safety of the drugs. The study showed a significant (p<0.0001) elevation of alkaline phosphatase in the AA and AL group compared to the nonpregnant control and a significant (p<0.05) elevation of alanine transaminase and aspartate transaminase level in the AL combination group when compared with the AA group. The elevated hepatic enzymes were within the normal range for pregnancy and were not clinically significant. Adverse event rate was higher in the AA group (n=28 [70%]) when compared to the AL group (n=4 [10%]) although the drugs were well-tolerated in both treatment arms. In conclusion, the use of these combinations is safe in the second and third trimester of pregnancy. However, we recommend active pharmacovigilance and spontaneous drug reporting of the agents in order to continuously monitor safety in the vastly heterogeneous population.

Antischistosomal activity of hederacochiside C against Schistosoma japonicum harbored in experimentally infected animals

The present study was undertaken to investigate whether hederacochiside C (HSC) possesses antischistosomal effects and anti-inflammatory response activities in Schistosoma japonicum-infected mice. Different concentrations of HSC were administrated to the mice infected by schistosomula or adult worm by intravenous injection twice a day for five consecutive days. The total worm burden, female worm burden, and the egg burden in liver of mice treated with 400 mg/kg HSC were fewer than those in non-treated ones. Murine immune responses following HSC treatment were investigated using enzyme-linked immunosorbent assays (ELISA). Our results indicated that 200 mg/kg HSC could reduce the expression of IgG, tumor necrosis factor (TNF)-α, interleukin (IL)-4 and IL-17 in comparison to infected group, exhibiting best immunomodulatory effects. In addition, scanning electron microscopical examination revealed that male worms treated with HSC lost their normal surface architecture since its surface showed extensive swelling, erosion, and peeling in tegumental regions. Remarkable amelioration was noticed in histopathological investigations, and 200 mg/kg HSC treatment could reduce the size of granulomatous inflammatory infiltrations in the liver which was reflected in nearly normalization of liver architecture. These results suggested that HSC had potential antischistosomal activity and provided a basis for subsequent experimental.

Herbicidal properties of antimalarial drugs

The evolutionary relationship between plants and the malarial parasite Plasmodium falciparum is well established and underscored by the P. falciparum apicoplast, an essential chloroplast-like organelle. As a result of this relationship, studies have demonstrated that herbicides active against plants are also active against P. falciparum and thus could act as antimalarial drug leads. Here we show the converse is also true; many antimalarial compounds developed for human use are highly herbicidal. We found that human antimalarial drugs (e.g. sulfadiazine, sulfadoxine, pyrimethamine, cycloguanil) were lethal to the model plant Arabidopsis thaliana at similar concentrations to market herbicides glufosinate and glyphosate. Furthermore, the physicochemical properties of these herbicidal antimalarial compounds were similar to commercially used herbicides. The implications of this finding that many antimalarial compounds are herbicidal proffers two novel applications: (i) using the genetically tractable A. thaliana to reveal mode-of-action for understudied antimalarial drugs, and (ii) co-opting antimalarial compounds as a new source for much needed herbicide lead molecules.

Syntheses of 7-dehydrocholesterol peroxides and their improved anticancer activity and selectivity over ergosterol peroxide

Three 7-dehydrocholesterol peroxides were photochemically prepared and their anticancer activity was studied.

Endoperoxide Drug Cross-Resistance Patterns for Plasmodium falciparum Exhibiting an Artemisinin Delayed-Clearance Phenotype

The ring-stage susceptibility assay was modified to quantify the susceptibilities of multiple strains of control and delayed-clearance phenotype (DCP) Plasmodium falciparum strains to seven endoperoxide antimalarial drugs. The susceptibility of all of the DCP lines to six of the drugs was lower than that of the controls. In contrast, DCP parasites did not show reduced susceptibility to the synthetic endoperoxide drug OZ439. These data show that it is possible to circumvent emerging artemisinin resistance with a modified endoperoxide drug.

Si-Accumulation In Artemisia annua Glandular Trichomes Increases Artemisinin Concentration, but Does Not Interfere In the Impairment of Toxoplasma gondii Growth

Artemisia annua is used as a source of artemisinin, a potent therapeutic agent used for the treatment of infectious diseases, chiefly malaria. However, the low concentration (from 0.01 to 1.4% of dried leaf matter) of artemisinin in the plant obtained with the traditional cropping system makes it a relatively expensive drug, especially in developing countries. Considering that artemisinin and silicon (Si) are both stored in A. annua glandular trichomes, and that Si accumulation has never been investigated, this study aimed to look into Si effects on A. annua trichome artemisinin concentration, and whether leaf infusion from Si-treated A. annua plants is able to control Toxoplasma gondii growth. T. gondii is the etiologic agent of toxoplasmosis, a zoonotic parasitic disease whose traditional treatment shows significant side effects. The experimental design consisted of A. annua seedlings randomly planted in soil treated with different doses of calcium/magnesium silicate (0, 200, 400, 800, and 1600 kg ha^-1). Analysis of foliar macronutrients showed significant increases of nitrogen content only at the highest dose of silicate. Foliar micronutrients, Si concentrations, and plant height were not affected by any of the silicate doses. However, the dose of 400 kg ha^-1 of silicate increased the trichome size, which in turn raised artemisinin concentration in leaves and the infusion. In contrast, the 800 and 1600 kg ha^-1 doses dramatically decreased artemisinin concentration. HeLa cell treatment with the infusion of A. annua grown in soil treated with 400 kg ha^-1 of silicate decreased parasite proliferation in a dose-dependent manner when the treatment was carried out after or along with T. gondii infection. However, this effect was similar to A. annua grown in soil without silicate treatment. Thus, it can be concluded that, even though Si applied to the soil at 400 kg ha^-1 has a positive effect on the A. annua glandular trichome size and the artemisinin concentration, this outcome cannot be directly associated with the efficiency of A. annua infusion on T. gondii growth, suggesting that other components from A. annua leaves could be acting in synergy with artemisinin.

Probucol dramatically enhances dihydroartemisinin effect in murine malaria

Background

Artemisinin-based combination therapy (ACT) has been adopted as national policy for the first-line treatment in large number of malaria-endemic regions. However, artemisinin-resistant parasites have emerged and are spreading, with slow-cleaning parasites being reported in patients treated with ACT. It means that more parasites are exposed to the partner drug alone and the risk of developing resistant parasites against the partner drug is increasing. Therefore, the development of a new method to enhance the effect of artemisinin is required. In this study, the potential effect of probucol as a combination drug of dihydroartemisinin (DHA), an artemisinin derivative, was examined.

Methods

C57BL/6 J mice infected with Plasmodium yoelii XL-17 were treated with probucol and/or DHA. The mice were fed with a probucol mixed diet from 2 weeks before infection and through infection period. DHA was injected to mice three to 5 days post infection once a day. In addition, 0.5 % (w/w) probucol was mixed with vitamin E supplemented diet (800 mg/kg) and fed to mice infected with P. yoelii XL-17 to examine the mechanisms of probucol on murine malaria. Furthermore, 8-OHdG, a biomarker of oxidized DNA, was detected in infected red blood cells (iRBC) taken from infected mice by immunofluorescent staining.

Results

With dose-dependent manner, both probucol and DHA decreased parasitaemia and increased survival rate of mice infected with P. yoelii XL-17. A significantly larger amount of 8-OHdG was detected in iRBC taking from probucol-treated mice than control mice. In addition, a large amount of vitamin E supplementation eliminated the effect of probucol against P. yoelii XL-17 infection and lowered the effect of probucol on host plasma vitamin E concentration. The effective doses for probucol and DHA were 0.5 % and 30 mg/kg, respectively, in each single treatment. While the combination treatment of 0.25 % probucol and 7.5 mg/kg DHA was effective in all mice from P. yoelii XL-17 infection.

Conclusion

This study demonstrated that probucol has some impact on malaria by oxidative stress through the induction of host plasma vitamin E deficiency. Moreover, the effective dose of DHA on malaria was decreased by prophylactic treatment of probucol. This finding indicates that probucol might be a candidate for a prophylactic treatment drug to enhance the effect of DHA.

Methylene Homologues of Artemisone: An Unexpected Structure-Activity Relationship and a Possible Implication for the Design of C10-Substituted Artemisinins

We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with divinyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds.

Repetitive live sporozoites inoculation under arteether chemoprophylaxis confers protection against subsequent sporozoite challenge in rodent malaria model

Inoculation with live sporozoites under prophylactic antimalarial cover (CPS-immunization) represents an alternate approach to develop sterile, reproducible, and long-term protection against malaria. Here, we have employed arteether (ART), a semi synthetic derivative of artemisinin to explore its potential as a chemoprophylaxis candidate in CPS approach and systematically compared the protective potential of arteether with mefloquine, azithromycin and primaquine. Blood stage patency and quantitative RT-PCR of liver stage parasite load were monitored as primary key end-points for protection against malaria challenge infection. For this purpose, sequential exposures of Plasmodium yoelii sporozoites under prophylactic treatment with arteether (ART), mefloquine (MFQ), azithromycin (AZ) or primaquine (PQ) was conducted in experimental Swiss mice. Our results show that during the first three sequential exposures (1st, 2nd and 3rd challenge) no marked difference in the blood stage patency was observed between control and CPS-ART group. However, delayed patency was recorded following 4th sporozoite challenge and mice enjoyed sterile protection after 5th sporozoite challenge. A similar response was observed in CPS-MFQ group, whereas earlier protection was recorded in CPS-AZ group i.e., after 4th sprozoite challenge. However, mice under PQ cover did not show any protection/delay in patency even after five sequential sporozoite inoculations, possibly due to inhibition of liver stage development. Furthermore, protection acquired by CPS-immunization is stage-specific as the protected mice remained susceptible to challenge with blood stage parasites. In short, the present study demonstrates that sporozoite administration under ART, MFQ or AZ treatment confers strong protection against subsequent sporozoite infection and the acquired response is dependent on the presence of liver stage parasites.

Mechanism of dihydroartemisinin-induced apoptosis in prostate cancer PC3 cells: An iTRAQ-based proteomic analysis

AIMS

Prostate cancer (PCa) is one of the most common cancers in men in the world. Advanced PCa, especially castration-resistant PCa (CRPC), is difficult to cure. There is an urgent need to develop novel agents for CPRC. Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin and is a well-known antimalarial drug. DHA has been documented to be a potential anticancer agent for PCa. However, the mechanisms underlying the anticancer activity of DHA are still unknown.

MAIN METHODS

Proteomics analysis based on iTRAQ technology was performed to determine the protein profile changes in human prostate cancer PC3 cells treated by DHA, and apoptosis was detected by flow cytometry and transmission electron microscopy.

KEY FINDINGS

DHA induced obvious apoptosis in PC3 cells. Using iTRAQ technology, we found 86 differentially expressed proteins linked to the cytotoxicity of DHA in PC3 cells. Gene ontology analysis showed the differentially expressed proteins were mainly associated with the protein synthesis and translation. Protein interaction network analysis and KEGG pathway analysis revealed altered aminoacyl-tRNA biosynthesis and metabolic pathways. Moreover, one candidate protein, heat shock protein HSP70 (HSPA1A), was identified by western blot analysis.

SIGNIFICANCE

Our results indicate that multiple mechanisms involved in the anticancer activity of DHA in PC3 cells. Decreased HSP70 expression may have an important role in DHA-induced apoptosis in PC3 cells. Our data also provide novel insights into the anticancer mechanisms of DHA.

Plasmodium falciparum kelch 13: a potential molecular marker for tackling artemisinin-resistant malaria parasites

Although artemisinin combination therapies have been deployed as a first-line treatment for uncomplicated malaria in almost all endemic countries, artemisinin-resistant parasites have emerged and have gradually spread across the Greater Mekong subregions. There is growing concern that the resistant parasites may migrate to or emerge indigenously in sub-Saharan Africa, which might provoke a global increase in malaria-associated morbidity and mortality. Therefore, development of molecular markers that enable identification of artemisinin resistance with high sensitivity is urgently required to combat this issue. In 2014, a potential artemisinin-resistance responsible gene, Plasmodium falciparum kelch13, was discovered. Here, we review the genetic features of P. falciparum kelch13 and discuss its related resistant mechanisms and potential as a molecular marker.

The wisdom of crowds and the repurposing of artesunate as an anticancer drug

Artesunate, a semi-synthetic and water-soluble artemisinin-derivative used as an anti-malarial agent, has attracted the attention of cancer researchers due to a broad range of anti-cancer activity including anti-angiogenic, immunomodulatory and treatment-sensitisation effects. In addition to pre-clinical evidence in a range of cancers, a recently completed randomised blinded trial in colorectal cancer has provided a positive signal for further clinical investigation. Used perioperatively artesunate appears to reduce the rate of disease recurrence - and the Neo-Art trial, a larger Phase II RCT, is seeking to confirm this positive effect. However, artesunate is a generic medication, and as with other trials of repurposed drugs, the Neo-Art trial does not have commercial sponsorship. In an innovative move, the trial is seeking funds directly from members of the public via a crowd-funding strategy that may have resonance beyond this single trial.

Artemisinin nanoformulation suitable for intravenous injection: Preparation, characterization and antimalarial activities

More than 40 years after its discovery, artemisinin has become the most promising antimalarial agent. However, no intravenous formulation is available due to its poor aqueous solubility. Here, we report the preparation, characterization, and in vitro and in vivo biological evaluation of biodegradable albumin-bound artemisinin nanoparticles. The nanoparticles were prepared by a combination of a bottom-up and a top-down processes and characterized by different spectroscopic techniques. The preparation process was optimized to develop a nanoformulation with the smallest possible diameter and good homogeneity suitable for intravenous injection enabling direct contact of artemisinin with infected erythrocytes. Chemically and physically stable artemisinin nanoparticles were obtained with excellent entrapment efficiency. In in vitro experiments, the artemisinin nanoformulation was interestingly more effective than non-formulated artemisinin. In Plasmodiumm falciparum-infected 'humanized' mice, the nanoparticles proved to be highly effective with 96% parasitemia inhibition at 10mg/kg/day, prolonging mean survival time without recrudescence. This nanoparticulate albumin-bound system allows the intravenous administration of artemisinin for the first time without harsh organic solvents or cosolvents with 100% bioavailability.

A comparative study on the impact of two artemisinin derivatives, artemether and artesunate, on the female reproductive system of Fasciola hepatica

An in vivo study in the laboratory rat model has been carried out to monitor changes to the female reproductive system in adult Fasciola hepatica following treatment with the artemisinins, artemether and artesunate. Rats infected with the triclabendazole (TCBZ)-resistant Sligo isolate were dosed orally with artemether at a concentration of 200mg/kg and flukes recovered at 24, 48 and 72 h post-treatment (pt). Rats infected with the TCBZ-resistant Oberon isolate were dosed orally with artesunate at a concentration of 200mg/kg and flukes recovered 24, 48, 72 and 96 h pt. The flukes were processed for histological and transmission electron microscope (TEM) examination of the uterus, Mehlis' gland, ovary and vitellaria. After treatment with artemether, egg production had become abnormal by 72 h pt, with free vitelline cells and masses of shell protein material within the uterus; spermatozoa were absent. The Mehlis' gland and ovary retained a normal morphology over the 3-day period. A change in the cell population in the vitelline follicles was seen at 48 h pt, with a decline in the number of immature cells. This became more marked by 72 h and the follicles became progressively vacuolated over the 3-day period. At the TEM level, there were changes in the immature vitelline cells at 24h pt, as evidenced by a decrease in shell protein production and the presence of lipid droplets and abnormal mitochondria. Spaces in the follicles separated the cells from each other. The changes became progressively more severe with time, so that, by 72 h pt, the follicles were very disrupted, containing cells in the advanced stages of apoptotic breakdown. In extreme cases, the follicles were scarcely recognisable and had become filled with cellular debris. Fine structural changes to the vitelline cells induced by artesunate treatment were similar to those described for artemether, but generally occurred more quickly and were greater; this was particularly true of the swelling of the ger cisternae. Overall, the results have shown that artemisinin treatment has a severe impact on egg production by TCBZ-resistant flukes, an effect that is mediated by disruption of the vitelline cells.

Artemisinin-naphthoquine for treating uncomplicated Plasmodium falciparum malaria

BACKGROUND

The World Health Organization (WHO) recommends artemisinin-based combination therapy (ACT) for treating people with Plasmodium falciparum malaria. Five combinations are currently recommended, all administered over three days. Artemisinin-naphthoquine is a new combination developed in China, which is being marketed as a one-day treatment. Although shorter treatment courses may improve adherence, the WHO recommends at least three days of the short-acting artemisinin component to eliminate 90% P. falciparum parasites in the bloodstream, before leaving the longer-acting partner drug to clear the remaining parasites.

OBJECTIVES

To evaluate the efficacy and safety of the artemisinin-naphthoquine combination for treating adults and children with uncomplicated P. falciparum malaria.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) published in The Cochrane Library; MEDLINE; EMBASE; and LILACS up to January 2015. We also searched the metaRegister of Controlled Trials (mRCT) using 'malaria' and 'arte* OR dihydroarte*' as search terms.

SELECTION CRITERIA

Randomized controlled trials comparing artemisinin-naphthoquine combinations with established WHO-recommended ACTs for the treatment of adults and children with uncomplicated malaria due to P. falciparum.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for eligibility and risk of bias, and extracted data. We analysed primary outcomes in line with the WHO 'Protocol for assessing and monitoring antimalarial drug efficacy' and compared drugs using risk ratios (RR) and 95% confidence intervals (CI). Secondary outcomes were effects on gametocytes, haemoglobin, and adverse events. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Four trials, enrolling 740 adults and children, met the inclusion criteria. Artemisinin-naphthoquine was administered as a single dose (two trials), as two doses given eight hours apart (one trial), and once daily for three days (one trial), and compared to three-day regimens of established ACTs. Three additional small pharmaceutical company trials have been carried out. We have requested the data but have not received a response from the company. Artemisinin-naphthoquine versus artemether-lumefantrineIn three small trials from Benin, Côte d'Ivoire, and Papua New Guinea, both combinations had a very low incidence of treatment failure at Day 28, and there were no differences demonstrated in PCR-unadjusted, or PCR-adjusted treatment failure (three trials, 487 participants, low quality evidence). Only the single study from Papua New Guinea followed participants up to Day 42, and the number of treatment failures remained very low with both combinations (one trial, 186 participants, very low quality evidence). Artemisinin-naphthoquine versus dihydroartemisinin-piperaquineIn a single small trial from Indonesia, treatment failure at Day 28 and Day 42 was very low in both groups with no differences demonstrated (one trial, 144 participants, very low quality evidence).

AUTHORS' CONCLUSIONS

The results of these few trials of artemisinin-naphthoquine are promising, but further trials from multiple settings are required to reliably demonstrate the relative efficacy and safety compared to established ACTs. Future trials should be adequately powered to demonstrate non-inferiority, and regimens incorporating three days of the artemisinin component are probably preferable to the one-day regimens.

Mutual action of anticancer and antiparasitic drugs: are there any shared targets?

ABSTRACT 

Parasites and cancers have some common features. It has been shown that some parasites interfere with tumor growth. In addition, they both have common antigens such as the Tn antigen. A communal action of anticancer and antiparasitic drugs has been reported. This shared action may be related to common targets for these drugs in cancers and parasites. In this paper, mutual action of anticancer and antiparasitic drugs, with the aim of discussing shared targets of these drugs, has been reviewed.

Artemisinin induces hormonal imbalance and oxidative damage in the erythrocytes and uterus but not in the ovary of rats

Artemisinin is an antimalarial drug previously reported to induce neurotoxicity and embryotoxicity in animal models. This study investigated the erythrocytes and reproductive toxicity potentials of artemisinin in female rats. Animals were randomly divided into four study groups of eight rats each. The control group (group I) received corn oil, the vehicle, while groups II-IV were orally exposed to 7, 35 and 70 mg kg(-1) day(-1) of artemisinin, respectively, by gastric intubation for 7 consecutive days. Subsequently, we evaluated the impact of artemisinin on the endocrine environment and selected markers of oxidative damage and antioxidant status of the erythrocytes, ovary and uterus. Artemisinin significantly increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels and decreased catalase, glutathione peroxidase and superoxide dismutase activities in erythrocytes and uterus of rats compared with control group (p < 0.05). However, artemisinin did not alter ovarian MDA, H2O2, glutathione levels and catalase activity, while ovarian and uterine histological assessment revealed absence of visible lesions. Moreover, artemisinin significantly decreased follicle-stimulating hormone and increased progesterone levels compared with control (p < 0.05). Thus, these data suggest that in the absence of malarial parasite infection, artemisinin induced hormonal imbalance and oxidative damage in the erythrocytes and uterus but spared the ovary of rats.

In silico profiling of Escherichia coli and Saccharomyces cerevisiae as terpenoid factories

Background

Heterologous microbial production of rare plant terpenoids of medicinal or industrial interest is attracting more and more attention but terpenoid yields are still low. Escherichia coli and Saccharomyces cerevisiae are the most widely used heterologous hosts; a direct comparison of both hosts based on experimental data is difficult though. Hence, the terpenoid pathways of E. coli (via 1-deoxy-D-xylulose 5-phosphate, DXP) and S. cerevisiae (via mevalonate, MVA), the impact of the respective hosts metabolism as well as the impact of different carbon sources were compared in silico by means of elementary mode analysis. The focus was set on the yield of isopentenyl diphosphate (IPP), the general terpenoid precursor, to identify new metabolic engineering strategies for an enhanced terpenoid yield.

Results

Starting from the respective precursor metabolites of the terpenoid pathways (pyruvate and glyceraldehyde-3-phosphate for the DXP pathway and acetyl-CoA for the MVA pathway) and considering only carbon stoichiometry, the two terpenoid pathways are identical with respect to carbon yield. However, with glucose as substrate, the MVA pathway has a lower potential to supply terpenoids in high yields than the DXP pathway if the formation of the required precursors is taken into account, due to the carbon loss in the formation of acetyl-CoA. This maximum yield is further reduced in both hosts when the required energy and reduction equivalents are considered. Moreover, the choice of carbon source (glucose, xylose, ethanol or glycerol) has an effect on terpenoid yield with non-fermentable carbon sources being more promising. Both hosts have deficiencies in energy and redox equivalents for high yield terpenoid production leading to new overexpression strategies (heterologous enzymes/pathways) for an enhanced terpenoid yield. Finally, several knockout strategies are identified using constrained minimal cut sets enforcing a coupling of growth to a terpenoid yield which is higher than any yield published in scientific literature so far.

Conclusions

This study provides for the first time a comprehensive and detailed in silico comparison of the most prominent heterologous hosts E. coli and S. cerevisiae as terpenoid factories giving an overview on several promising metabolic engineering strategies paving the way for an enhanced terpenoid yield.

Dihydroartemisinin suppresses ovalbumin-induced airway inflammation in a mouse allergic asthma model

Asthma is a complex disease characterized by reversible airway obstruction, airway hyper-responsiveness (AHR) and chronic inflammation of the airways. Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, has been shown to possess antimalarial and antitumor activities, but whether it can be used in asthma treatment has not been investigated. In this study, we attempted to determine whether DHA regulates inflammatory mediators in the ovalbumin (OVA)-induced mouse asthma model. BALB/c mice were sensitized and challenged by OVA to induce chronic airway inflammation. The intragastrical administration of DHA at 30 mg/kg significantly decreased the number of infiltrating inflammatory cells, T-helper type 2 (Th2) cytokines, OVA-specific immunoglobulin E (IgE) and AHR. Treatment with DHA also attenuated OVA-induced mRNA expression of Muc5ac and chitinase 3-like protein 4 (Ym2) in lung tissues. In addition, lung histopathological studies revealed that DHA inhibited inflammatory cell infiltration and mucus hypersecretion. Then signal transduction studies showed that DHA significantly inhibited extracellular signal-regulated protein kinase (ERK), p38 mitogen-activated protein kinase phosphorylation. DHA also inhibited nuclear factor-κB (NF-κB) activation via the inhibition of phosphorylation of IκBα. These findings provide new insight into the immunopharmacological role of DHA in terms of its effects in a mouse model of asthma.

Artemisinin based combination therapy in travel medicine

A steadily increasing number of Western travellers are exposed to malaria. Also, numbers of migrants from malarious areas are increasing. Fast and effective treatment options are needed to ensure effective malaria treatment in these groups in the future. Artemisinin combinations are well tolerated and have shown high efficacy in malaria endemic areas. Since 2001, 42 malaria endemic countries, 23 of them in Africa, have adopted artemisinin based combination therapies recommended by WHO. An additional 14 countries are in the process of changing their malaria treatment policy. Studies in non-immune travellers confirm a rapid parasite clearance time and very low rate of side effects. Outpatient clinics and hospitals in non-endemic countries should have standard operating procedures for diagnosing and managing patients with malaria. In this setting, artemisinin combinations should be available for treatment of uncomplicated malaria as they are clearly superior to any other oral antimalarial in their fast reduction of parasite biomass and in decreasing clinical symptoms. Also, they are the drugs of choice for travellers who are advised to carry stand-by emergency treatment during their journey.

Anti-allergic action of anti-malarial drug artesunate in experimental mast cell-mediated anaphylactic models

BACKGROUND

Allergy is an acquired hypersensitivity reaction of the immune system mediated by cross-linking of allergen-specific IgE-bound high-affinity IgE receptors, leading to immediate mast cell degranulation. Artesunate is a semi-synthetic derivative of artemisinin, an active component of the medicinal plant Artemisia annua. Artesunate is a clinically effective anti-malarial drug and has recently been shown to attenuate allergic asthma in mouse models. This study investigated potential anti-allergic effects of artesunate in animal models of IgE-dependent anaphylaxis.

METHODS

Anti-allergic actions of artesunate were evaluated in passive cutaneous anaphylaxis and passive systemic anaphylaxis mouse models, and in ovalbumin-induced contraction of bronchial rings isolated from sensitized guinea pigs. Direct mast cell-stabilizing effect of artesunate was examined in RBL-2H3 mast cell line and in mature human cultured mast cells. Anti-allergic signaling mechanisms of action of artesunate in mast cells were also investigated.

RESULTS

Artesunate prevented IgE-mediated cutaneous vascular hyperpermeability, hypothermia, elevation in plasma histamine level, and tracheal tissue mast cell degranulation in mice in a dose-dependent manner. In addition, artesunate suppressed ovalbumin-mediated guinea pig bronchial smooth muscle contraction. Furthermore, artesunate concentration-dependently blocked IgE-mediated degranulation of RBL-2H3 mast cells and human culture mast cells. Artesunate was found to inhibit IgE-induced Syk and PLCγ1 phosphorylation, production of IP(3) , and rise in cytosolic Ca(+2) level in mast cells.

CONCLUSIONS

We report here for the first time that artesunate possesses anti-allergic activity by blocking IgE-induced mast cell degranulation, providing a foundation for developing artesunate for the treatment of allergic asthma and other mast cell-mediated allergic disorders.

Artesunate Exerts a Direct Effect on Endothelial Cell Activation and NF-κB Translocation in a Mechanism Independent of Plasmodium Killing

Artemisinin and its derivates are an important class of antimalarial drug and are described to possess immunomodulatory activities. Few studies have addressed the effect of artesunate in the murine malaria model or its effect on host immune response during malaria infection. Herein, we study the effect of artesunate treatment and describe an auxiliary mechanism of artesunate in modulating the inflammatory response during experimental malaria infection in mice. Treatment with artesunate did not reduce significantly the parasitemia within 12 h, however, reduced BBB breakdown and TNF-α mRNA expression in the brain tissue of artesunate-treated mice. Conversely, mefloquine treatment was not able to alter clinical features. Notably, artesunate pretreatment failed to modulate the expression of LFA-1 in splenocytes stimulated with parasitized red blood cells (pRBCs) in vitro; however, it abrogated the expression of ICAM-1 in pRBC-stimulated endothelial cells. Accordingly, a cytoadherence in vitro assay demonstrated that pRBCs did not adhere to artesunate-treated vascular endothelial cells. In addition, NF-κB nuclear translocation in endothelial cells stimulated with pRBCs was impaired by artesunate treatment. Our results suggest that artesunate is able to exert a protective effect against the P. berghei-induced inflammatory response by inhibiting NF-κB nuclear translocation and the subsequent expression of ICAM-1.

Randomized trials of artemisinin-piperaquine, dihydroartemisinin-piperaquine phosphate and artemether-lumefantrine for the treatment of multi-drug resistant falciparum malaria in Cambodia-Thailand border area

Background

Drug resistance of falciparum malaria is a global problem. Sulphadoxine/pyrimethamine-resistant and mefloquine-resistant strains of falciparum malaria have spread in Southeast Asia at lightning speed in 1980s-1990s, and the Cambodia-Thailand border is one of the malaria epidemic areas with the most severe forms of multi-drug resistant falciparum malaria.

Methods

Artemisinin-piperaquine (AP), dihydroartemisinin-piperaquine phosphate (DHP) and artemether-lumefantrine (AL) were used to treat 110, 55 and 55 uncomplicated malaria patients, respectively. The total dosage for adults is 1,750 mg (four tablets, twice over 24 hours) of AP, 2,880 mg (eight tablets, four times over two days) of DHP, and 3,360 mg (24 tablets, six times over three days) of AL. The 28-day cure rate, parasite clearance time, fever clearance time, and drug tolerance of patients to the three drugs were compared. All of the above methods were consistent with the current national guidelines.

Results

The mean parasite clearance time was similar in all three groups (66.7 ± 21.9 hrs, 65.6 ± 27.3 hrs, 65.3 ± 22.5 hrs in AP, DHP and AL groups, respectively), and there was no remarkable difference between them; the fever clearance time was also similar (31.6 ± 17.7 hrs, 34.6 ± 21.8 hrs and 36.9 ± 15.4 hrs, respectively). After following up for 28-days, the cure rate was 95.1%(97/102), 98.2%(54/55) and 82.4%(42/51); and the recrudescence cases was 4.9%(5/102), 1.8%(1/55) and 17.6%(9/51), respectively. Therefore, the statistical data showed that 28-day cure rate in AP and DHP groups was superior to AL group obviously.

The patients had good tolerance to all the three drugs, and some side effects (anoxia, nausea, vomiting, headache and dizziness) could be found in every group and they were self-limited; patients in control groups also had good tolerance to DHP and AL, there was no remarkable difference in the three groups.

Conclusions

AP, DHP and AL all remained efficacious treatments for the treatment of falciparum malaria in Cambodia-Thailand border area. However, in this particular setting, the AP regimen turned out to be favourable in terms of efficacy and effectiveness, simplicity of administration, cost and compliance.

Trial Registration

The trial was registered at Chinese Clinical Trial Register under identifier 2005L01041.