Unpacking ‘Artemisinin Resistance’

Frontiers in superbug management: innovating approaches to combat antimicrobial resistance

Anti-microbial resistance (AMR) is a global health issue causing significant mortality and economic burden. Pharmaceutical companies' discontinuation of research hinders new agents, while MDR pathogens or "superbugs" worsen the problem. Superbugs pose a threat to common infections and medical procedures, exacerbated by limited antibiotic development and rapid antibiotic resistance. The rising tide of antimicrobial resistance threatens to undermine progress in controlling infectious diseases. This review examines the global proliferation of AMR, its underlying mechanisms, and contributing factors. The study explores various methodologies, emphasizing the significance of precise and timely identification of resistant strains. We discuss recent advancements in CRISPR/Cas9, nanoparticle technology, light-based techniques, and AI-powered antibiogram analysis for combating AMR. Traditional methods often fail to effectively combat multidrug-resistant bacteria, as CRISPR-Cas9 technology offers a more effective approach by cutting specific DNA sequences, precision targeting and genome editing. AI-based smartphone applications for antibiogram analysis in resource-limited settings face challenges like internet connectivity, device compatibility, data quality, energy consumption, and algorithmic limitations. Additionally, light-based antimicrobial techniques are increasingly being used to effectively kill antibiotic-resistant microbial species and treat localized infections. This review provides an in-depth overview of AMR covering epidemiology, evolution, mechanisms, infection prevention, control measures, antibiotic access, stewardship, surveillance, challenges and emerging non-antibiotic therapeutic approaches.

Antimalarial mechanism of action of the natural product 9-methoxystrobilurin G

The natural product 9-methoxystrobilurin G (9MG) from Favolaschia spp basidiomycetes is a potent and selective antimalarial. The mechanism of action of 9MG is unknown. We induced 9MG resistance in Plasmodium falciparum 3D7 and Dd2 strains and identified mutations associated with resistance by genome sequencing. All 9MG-resistant clones possessed missense mutations in the cytochrome b (CYTB) gene, a key component of mitochondrial complex III. The mutations map to the quinol oxidation site of CYTB, which is also the target of antimalarials such as atovaquone. In a complementary approach to identify protein targets of 9MG, a photoactivatable derivative of 9MG was synthesized and applied in chemoproteomic-based target profiling. Three components of mitochondrial complex III (QCR7, QCR9, and COX15) were specifically enriched consistent with 9MG targeting CYTB and complex III function in P. falciparum. Inhibition of complex III activity by 9MG was confirmed by ubiquinone cytochrome c reductase assay using P. falciparum extract. The findings from this study may be useful for developing novel antimalarials targeting CYTB.

An Overview of the Recent Advances in Antimicrobial Resistance

Antimicrobial resistance (AMR), frequently considered a major global public health threat, requires a comprehensive understanding of its emergence, mechanisms, advances, and implications. AMR's epidemiological landscape is characterized by its widespread prevalence and constantly evolving patterns, with multidrug-resistant organisms (MDROs) creating new challenges every day. The most common mechanisms underlying AMR (i.e., genetic mutations, horizontal gene transfer, and selective pressure) contribute to the emergence and dissemination of new resistant strains. Therefore, mitigation strategies (e.g., antibiotic stewardship programs-ASPs-and infection prevention and control strategies-IPCs) emphasize the importance of responsible antimicrobial use and surveillance. A One Health approach (i.e., the interconnectedness of human, animal, and environmental health) highlights the necessity for interdisciplinary collaboration and holistic strategies in combating AMR. Advancements in novel therapeutics (e.g., alternative antimicrobial agents and vaccines) offer promising avenues in addressing AMR challenges. Policy interventions at the international and national levels also promote ASPs aiming to regulate antimicrobial use. Despite all of the observed progress, AMR remains a pressing concern, demanding sustained efforts to address emerging threats and promote antimicrobial sustainability. Future research must prioritize innovative approaches and address the complex socioecological dynamics underlying AMR. This manuscript is a comprehensive resource for researchers, policymakers, and healthcare professionals seeking to navigate the complex AMR landscape and develop effective strategies for its mitigation.

Characterization of antimalarial activity of artemisinin-based hybrid drugs

In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and drug-resistant Plasmodium falciparum parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state.

3D printing of multi-unit gastro-retentive tablets for the pulsatile release of artesunate

Pulsatile drug delivery is hardly achieved by conventional gastro-retentive dosage forms. Artesunate as a typical anti-malaria medicine needs oral pulsatile release. Here, artesunate-loaded pulsatile-release multi-unit gastro-retentive tablets (APGTs) were prepared with a semi-solid extrusion three-dimensional (3D) printing method. An APGT was composed of three units: artesunate-loaded immediate and delayed release units and a block unit. The matrix of the immediate/delayed release units consisted of polyvinylpyrrolidone (PVP) K30 and croscarmellose sodium, which improved the rapid release of artesunate when contacting water. The block unit consisted of octadecanol, hydroxypropyl methyl cellulose K15M, PVP K30, and poloxamer F68. APGTs showed multi-phase release in simulated gastric liquids (SGLs). The first immediate release phase continued for 1 h followed by a long block phase for 7 h. The second rapid release phase was initiated when the eroded holes in the block unit extended to the inner delayed release unit, and this phase continued for about 14 h. Low-density APGTs could ensure their long-term floating in the stomach. Oral APGTs remained in the rabbit stomach for about 20 h. 3D printing provides a new strategy for the preparation of oral pulsatile-release tablets.

Combating antimicrobial resistance in malaria, HIV and tuberculosis

Antimicrobial resistance poses a significant threat to the sustainability of effective treatments against the three most prevalent infectious diseases: malaria, human immunodeficiency virus (HIV) infection and tuberculosis. Therefore, there is an urgent need to develop novel drugs and treatment protocols capable of reducing the emergence of resistance and combating it when it does occur. In this Review, we present an overview of the status and underlying molecular mechanisms of drug resistance in these three diseases. We also discuss current strategies to address resistance during the research and development of next-generation therapies. These strategies vary depending on the infectious agent and the array of resistance mechanisms involved. Furthermore, we explore the potential for cross-fertilization of knowledge and technology among these diseases to create innovative approaches for minimizing drug resistance and advancing the discovery and development of new anti-infective treatments. In conclusion, we advocate for the implementation of well-defined strategies to effectively mitigate and manage resistance in all interventions against infectious diseases.

Emergence, transmission dynamics and mechanisms of artemisinin partial resistance in malaria parasites in Africa

Malaria, mostly due to Plasmodium falciparum infection in Africa, remains one of the most important infectious diseases in the world. Standard treatment for uncomplicated P. falciparum malaria is artemisinin-based combination therapy (ACT), which includes a rapid-acting artemisinin derivative plus a longer-acting partner drug, and standard therapy for severe P. falciparum malaria is intravenous artesunate. The efficacy of artemisinins and ACT has been threatened by the emergence of artemisinin partial resistance in Southeast Asia, mediated principally by mutations in the P. falciparum Kelch 13 (K13) protein. High ACT treatment failure rates have occurred when resistance to partner drugs is also seen. Recently, artemisinin partial resistance has emerged in Rwanda, Uganda and the Horn of Africa, with independent emergences of different K13 mutants in each region. In this Review, we summarize our current knowledge of artemisinin partial resistance and focus on the emergence of resistance in Africa, including its epidemiology, transmission dynamics and mechanisms. At present, the clinical impact of emerging resistance in Africa is unclear and most available evidence suggests that the efficacies of leading ACTs remain excellent, but there is an urgent need to better appreciate the extent of the problem and its consequences for the treatment and control of malaria.

Whole genome sequencing identifies novel mutations in malaria parasites resistant to artesunate (ATN) and to ATN + mefloquine combination

Introduction

The global evolution of resistance to Artemisinin-based Combination Therapies (ACTs) by malaria parasites, will severely undermine our ability to control this devastating disease.

Methods

Here, we have used whole genome sequencing to characterize the genetic variation in the experimentally evolved Plasmodium chabaudi parasite clone AS-ATNMF1, which is resistant to artesunate + mefloquine.

Results and discussion

Five novel single nucleotide polymorphisms (SNPs) were identified, one of which was a previously undescribed E738K mutation in a 26S proteasome subunit that was selected for under artesunate pressure (in AS-ATN) and retained in AS-ATNMF1. The wild type and mutated three-dimensional (3D) structure models and molecular dynamics simulations of the P. falciparum 26S proteasome subunit Rpn2 suggested that the E738K mutation could change the toroidal proteasome/cyclosome domain organization and change the recognition of ubiquitinated proteins. The mutation in the 26S proteasome subunit may therefore contribute to altering oxidation-dependent ubiquitination of the MDR-1 and/or K13 proteins and/or other targets, resulting in changes in protein turnover. In light of the alarming increase in resistance to artemisin derivatives and ACT partner drugs in natural parasite populations, our results shed new light on the biology of resistance and provide information on novel molecular markers of resistance that may be tested (and potentially validated) in the field.

Emerging roles of the epitranscriptome in parasitic protozoan biology and pathogenesis

RNA modifications (epitranscriptome) - such as N6-methyladenosine (m6A), 5-methylcytosine (m5C), and pseudouridine (Ψ) - modulate RNA processing, stability, interaction, and translation, thereby playing critical roles in the development, replication, virulence, metabolism, and life cycle adaptations of parasitic protozoa. Here, we summarize potential homologs of the major human RNA modification regulatory factors in parasites, outline current knowledge on how RNA modifications affect parasitic protozoa, highlight the regulation of RNA modifications and their crosstalk, and discuss current progress in exploring RNA modifications as potential drug targets. This review contributes to our understanding of epitranscriptomic regulation of parasitic protozoa biology and pathogenesis and provides new perspectives for the treatment of parasitic diseases.

Click-chemistry synergic MXene-functionalized flexible skeleton membranes for accurate recognition and separation

Membrane-based technology with accurate-recognition and specific-transmission has been regarded as one of the most promising strategies in environmental protection and energy conservation. However, membrane technique still faces challenges of "trade-off effect" between high selectivity and permeation flux within organic-aqueous mixed matrix. Here, well-intergrown click-chemistry synergic MXene-functionalized flexible skeleton membranes has been prepared in this strategy, enabling size-exclusion&structure selectivity by uniform location array imprinting unit and transport performance towards specific medicinal molecules of artemisinin (Ars). The well-assembled ultrathin cascade-type MXene layer guarantees the narrow interlayer nanochannels and the flexible skeleton modified mesoporous SiO2 nanoparticles provide active reaction platform for the construction of selective recognition space. The resulting membranes demonstrated outstanding selective separation performance with permeability factor that artesunate (Aru) /Ars and dihydro-artemisinin (d-Ars) / Ars of 3.17 and 2.89 and permeation flux of 1173.25 L·m-2·h-1·bar-1. Besides, combined with antibacterial durability, recycling performance, high separation performance in mobile phase stability of CMFMs, it is anticipated that this work hopefully opens a new avenue for efficient chiral separation to medicinal molecules, exhibiting broad potential for practical application.

Analysis of complementarities between nanomedicine and phytodrugs for the treatment of malarial infection

The use of nanocarriers in medicine, so-called nanomedicine, is one of the most innovative strategies for targeting drugs at the action site and increasing their activity index and effectiveness. Phytomedicine is the oldest traditional method used to treat human diseases and solve health problems. The recent literature on the treatment of malaria infections using nanodelivery systems and phytodrugs or supplements has been analyzed. For the first time, in the present review, a careful look at the considerable potential of nanomedicine in promoting phytotherapeutic efficacy was done, and its key role in addressing a translation through a significant reduction of the current burden of malaria in many parts of the world has been underlined.

Molecular Interactions Identified by Two-Dimensional Analysis-Detailed Insight into the Molecular Interactions of the Antimalarial Artesunate with the Target Structure β-Hematin by Means of 2D Raman Correlation Spectroscopy

A thorough understanding of the interaction of endoperoxide antimalarial agents with their biological target structures is of utmost importance for the tailored design of future efficient antimalarials. Detailed insights into molecular interactions between artesunate and β-hematin were derived with a combination of resonance Raman spectroscopy, two-dimensional correlation analysis, and density functional theory calculations. Resonance Raman spectroscopy with three distinct laser wavelengths enabled the specific excitation of different chromophore parts of β-hematin. The resonance Raman spectra of the artesunate-β-hematin complexes were thoroughly analyzed with the help of high-resolution and highly sensitive two-dimensional correlation spectroscopy. Spectral changes in the peak properties were found with increasing artesunate concentration. Changes in the low-frequency, morphology-sensitive Raman bands indicated a loss in crystallinity of the drug-target complexes. Differences in the high-wavenumber region were assigned to increased distortions of the planarity of the structure of the target molecule due to the appearance of various coexisting alkylation species. Evidence for the appearance of high-valent ferryl-oxo species could be observed with the help of differences in the peak properties of oxidation-state sensitive Raman modes. To support those findings, the relaxed ground-state structures of ten possible covalent mono- and di-meso(Cm)-alkylated hematin-dihydroartemisinyl complexes were calculated using density functional theory. A very good agreement with the experimental peak properties was achieved, and the out-of-plane displacements along the lowest-frequency normal coordinates were investigated by normal coordinate structural decomposition analysis. The strongest changes in all data were observed in vibrations with a high participation of Cm-parts of β-hematin.

Investigations on the Novel Antimalarial Ferroquine in Biomimetic Solutions Using Deep UV Resonance Raman Spectroscopy and Density Functional Theory

Deep ultraviolet (DUV) resonance Raman experiments are performed, investigating the novel, promising antimalarial ferroquine (FQ). Two buffered aqueous solutions with pH values of 5.13 and 7.00 are used, simulating the acidic and neutral conditions inside a parasite's digestive vacuole and cytosol, respectively. To imitate the different polarities of the membranes and interior, the buffer's 1,4-dioxane content was increased. These experimental conditions should mimic the transport of the drug inside malaria-infected erythrocytes through parasitophorous membranes. Supporting density functional theory (DFT) calculations on the drug's micro-speciation were performed, which could be nicely assigned to shifts in the peak positions of resonantly enhanced high-wavenumber Raman signals at λ_exc = 257 nm. FQ is fully protonated in polar mixtures like the host interior and the parasite's cytoplasm or digestive vacuole (DV) and is only present as a free base in nonpolar ones, such as the host's and parasitophorous membranes. Additionally, the limit of detection (LoD) of FQ at vacuolic pH values was determined using DUV excitation wavelengths at 244 and 257 nm. By applying the resonant laser line at λ_exc = 257 nm, a minimal FQ concentration of 3.1 μM was detected, whereas the pre-resonant excitation wavelength 244 nm provides an LoD of 6.9 μM. These values were all up to one order of magnitude lower than the concentration found for the food vacuole of a parasitized erythrocyte.

A Water-Soluble Polymer-Lumefantrine Conjugate for the Intravenous Treatment of Severe Malaria

Uncomplicated malaria is effectively treated with oral artemisinin-based combination therapy (ACT). Yet, there is an unmet clinical need for the intravenous treatment of the more fatal severe malaria. There is no combination intravenous therapy for uncomplicated due to the nonavailability of a water-soluble partner drug for the artemisinin, artesunate. The currently available treatment is a two-part regimen split into an intravenous artesunate followed by the conventional oral ACT . In a novel application of polymer therapeutics, the aqueous insoluble antimalarial lumefantrine is conjugated to a carrier polymer to create a new water-soluble chemical entity suitable for intravenous administration in a clinically relevant formulation . The conjugate is characterized by spectroscopic and analytical techniques, and the aqueous solubility of lumefantrine is determined to have increased by three orders of magnitude. Pharmacokinetic studies in mice indicate that there is a significant plasma release of lumefantrine and production its metabolite desbutyl-lumefantrine (area under the curve of metabolite is ≈10% that of the parent). In a Plasmodium falciparum malaria mouse model, parasitemia clearance is 50% higher than that of reference unconjugated lumefantrine. The polymer-lumefantrine shows potential for entering the clinic to meet the need for a one-course combination treatment for severe malaria.

Antimalarial activity and sensitization of chrysosplenetin against artemisinin-resistant genotype Plasmodium berghei K173 potentially via dual-mechanism of maintaining host P-glycoprotein homeostasis mediated by NF-κB p52 or PXR/CAR signaling pathways and regulating heme/haemozoin metabolism

This study investigated antimalarial efficacy and sensitization of chrysosplenetin against artemisinin-resistant Plasmodium berghei K173 and potential molecular mechanism. Our data indicated a risk of artemisinin resistance because a higher parasitaemia% and lower inhibition% under artemisinin treatment against resistant parasites than those in the sensitive groups were observed. Two non-antimalarial components, verapamil and chrysosplentin, being P-gp inhibitors, possessed a strong efficacy against resistant parasites but it was not the case for Bcrp inhibitor novobiocin. Artemisinin-chrysosplenetin combination improved artemisinin susceptibility of resistant P. berghei. Artemisinin activated intestinal P-gp and Abcb1/Abcg2 expressions and suppressed Bcrp whereas chrysosplenetin reversed them. Resistant parasite infection led to a decreased haemozoin in organs or an increased heme in peripheral bloods compared with the sensitives; however, that in Abcb1-deficient knockout (KO)-resistant mice reversely got increased or decreased versus wild type (WT)-resistant animals. Chrysosplenetin as well as rifampin (nuclear receptor agonist) increased the transcription levels of PXR/CAR while showed a versatile regulation on hepatic and enternal PXR/CAR in WT- or KO-sensitive or -resistant parasites. Oppositely, hepatic and enteric NF-κB p52 mRNA decreased conformably in WT but increased in KO-resistant mice. NF-κB pathway potentially involved in the mechanism of chrysosplenetin on inhibiting P-gp expressions while PXR/CAR play a more complicated role in this mechanism.

Decreased susceptibility of Plasmodium falciparum to both dihydroartemisinin and lumefantrine in northern Uganda

Artemisinin partial resistance may facilitate selection of Plasmodium falciparum resistant to combination therapy partner drugs. We evaluated 99 P. falciparum isolates collected in 2021 from northern Uganda, where resistance-associated PfK13 C469Y and A675V mutations have emerged, and eastern Uganda, where these mutations are uncommon. With the ex vivo ring survival assay, isolates with the 469Y mutation (median survival 7.3% for mutant, 2.5% mixed, and 1.4% wild type) and/or mutations in Pfcoronin or falcipain-2a, had significantly greater survival; all isolates with survival >5% had mutations in at least one of these proteins. With ex vivo growth inhibition assays, susceptibility to lumefantrine (median IC₅₀ 14.6 vs. 6.9 nM, p < 0.0001) and dihydroartemisinin (2.3 vs. 1.5 nM, p = 0.003) was decreased in northern vs. eastern Uganda; 14/49 northern vs. 0/38 eastern isolates had lumefantrine IC₅₀ > 20 nM (p = 0.0002). Targeted sequencing of 819 isolates from 2015-21 identified multiple polymorphisms associated with altered drug susceptibility, notably PfK13 469Y with decreased susceptibility to lumefantrine (p = 6 × 10^-8) and PfCRT mutations with chloroquine resistance (p = 1 × 10^-20). Our results raise concern regarding activity of artemether-lumefantrine, the first-line antimalarial in Uganda.

The influence of biological, epidemiological, and treatment factors on the establishment and spread of drug-resistant Plasmodium falciparum

The effectiveness of artemisinin-based combination therapies (ACTs) to treat Plasmodium falciparum malaria is threatened by resistance. The complex interplay between sources of selective pressure-treatment properties, biological factors, transmission intensity, and access to treatment-obscures understanding how, when, and why resistance establishes and spreads across different locations. We developed a disease modelling approach with emulator-based global sensitivity analysis to systematically quantify which of these factors drive establishment and spread of drug resistance. Drug resistance was more likely to evolve in low transmission settings due to the lower levels of (i) immunity and (ii) within-host competition between genotypes. Spread of parasites resistant to artemisinin partner drugs depended on the period of low drug concentration (known as the selection window). Spread of partial artemisinin resistance was slowed with prolonged parasite exposure to artemisinin derivatives and accelerated when the parasite was also resistant to the partner drug. Thus, to slow the spread of partial artemisinin resistance, molecular surveillance should be supported to detect resistance to partner drugs and to change ACTs accordingly. Furthermore, implementing more sustainable artemisinin-based therapies will require extending parasite exposure to artemisinin derivatives, and mitigating the selection windows of partner drugs, which could be achieved by including an additional long-acting drug.

The Advances of Broad-Spectrum and Hot Anti-Coronavirus Drugs

Coronaviruses, mainly including severe acute respiratory syndrome virus, severe acute respiratory syndrome coronavirus 2, Middle East respiratory syndrome virus, human coronavirus OC43, chicken infectious bronchitis virus, porcine infectious gastroenteritis virus, porcine epidemic diarrhea virus, and murine hepatitis virus, can cause severe diseases in humans and livestock. The severe acute respiratory syndrome coronavirus 2 is infecting millions of human beings with high morbidity and mortality worldwide, and the multiplicity of swine epidemic diarrhea coronavirus in swine suggests that coronaviruses seriously jeopardize the safety of public health and that therapeutic intervention is urgently needed. Currently, the most effective methods of prevention and control for coronaviruses are vaccine immunization and pharmacotherapy. However, the emergence of mutated viruses reduces the effectiveness of vaccines. In addition, vaccine developments often lag behind, making it difficult to put them into use early in the outbreak. Therefore, it is meaningful to screen safe, cheap, and broad-spectrum antiviral agents for coronaviruses. This review systematically summarizes the mechanisms and state of anti-human and porcine coronavirus drugs, in order to provide theoretical support for the development of anti-coronavirus drugs and other antivirals.

Ferroptosis plays an essential role in the antimalarial mechanism of low-dose dihydroartemisinin

The activation of artemisinin and its derivatives (ARTs) to generate ROS and other free radicals is mainly heme- or ferrous iron-dependent. ARTs induce ferroptosis in tumor cells, although the involvement of ferroptosis in malaria remains unclear. We found that three typical inducers of ferroptosis (erastin, RSL3 and sorafenib) could effectively mimic DHA inhibition on the growth of blood-stage parasites, which exhibited synergistic or nearly additive interactions in vitro with DHA, while the combination of DHA with ferroptosis inhibitors (deferoxamine, liproxstatin-1) had an obvious antagonistic effect. DHA, similar to ferroptosis inducers, can simultaneously induce the accumulation of ferroptosis-associated cellular labile iron and lipid peroxide. However, deferoxamine and liproxstatin-1 reduced the increase in ferrous iron and lipid peroxide caused by DHA. These results suggested that ferroptosis might be an effective way to induce cell death in parasites and could be a primary mechanism by which DHA kills parasites, with almost 50% contribution at low concentrations. These results provide a new strategy for antimalarial drug screening and clinical medication guidance.

Artemisinin resistance in the malaria parasite, Plasmodium falciparum, originates from its initial transcriptional response

The emergence and spread of artemisinin-resistant Plasmodium falciparum, first in the Greater Mekong Subregion (GMS), and now in East Africa, is a major threat to global malaria elimination ambitions. To investigate the artemisinin resistance mechanism, transcriptome analysis was conducted of 577 P. falciparum isolates collected in the GMS between 2016–2018. A specific artemisinin resistance-associated transcriptional profile was identified that involves a broad but discrete set of biological functions related to proteotoxic stress, host cytoplasm remodelling, and REDOX metabolism. The artemisinin resistance-associated transcriptional profile evolved from initial transcriptional responses of susceptible parasites to artemisinin. The genetic basis for this adapted response is likely to be complex.

Transcriptomic analysis of isolates from the malaria parasite (Plasmodium falciparum) in the Greater Mekong Subregion of Southeast Asia identifies gene expression patterns that are correlated with resistance to a common anti-malaria drug, artemisinin.

A Nanodrug Coated with Membrane from Brain Microvascular Endothelial Cells Protects against Experimental Cerebral Malaria

Human malaria is a global life-threatening infectious disease. Cerebral malaria (CM) induced by Plasmodium falciparum parasites accounts for 90% of malaria deaths. Treating CM is challenging due to inadequate treatment options and the development of drug resistance. We describe a nanoparticle formulation of the antimalarial drug dihydroartemisinin that is coated in a biomimetic membrane derived from brain microvascular endothelial cells (BMECs) and test its therapeutic efficacy in a mouse model of experimental cerebral malaria (ECM). The membrane-coated nanoparticle drug has a prolonged drug-release profile and enhanced dual targeting killing efficacy toward parasites residing in red blood cells (iRBCs) and iRBCs obstructed in the BMECs (for both rodent and human). In a mice ECM model, the nanodrug protects the brain, liver, and spleen from infection-induced damage and improves the survival rate of mice. This so-called nanodrug offers new insight into engineering nanoparticle-based therapeutics for malaria and other parasitic pathogen infections.

Reactive Oxygen Species as the Brainbox in Malaria Treatment

Several measures are in place to combat the worldwide spread of malaria, especially in regions of high endemicity. In part, most common antimalarials, such as quinolines and artemisinin and its derivatives, deploy an ROS-mediated approach to kill malaria parasites. Although some antimalarials may share similar targets and mechanisms of action, varying levels of reactive oxygen species (ROS) generation may account for their varying pharmacological activities. Regardless of the numerous approaches employed currently and in development to treat malaria, concerningly, there has been increasing development of resistance by Plasmodium falciparum, which can be connected to the ability of the parasites to manage the oxidative stress from ROS produced under steady or treatment states. ROS generation has remained the mainstay in enforcing the antiparasitic activity of most conventional antimalarials. However, a combination of conventional drugs with ROS-generating ability and newer drugs that exploit vital metabolic pathways, such antioxidant machinery, could be the way forward in effective malaria control.

Discovery of novel inhibitors targeting Plasmodium knowlesi dihydrofolate reductase using molecular docking and molecular dynamics simulation

Plasmodium knowlesi, recognized as the fifth Plasmodium parasite, is the least studied malaria parasite. It is a significant cause of morbidity and mortality in the South-East Asia region. Enzymes of folate synthesis, especially dihydrofolate reductase (DHFR), is a well-approved drug target in other Plasmodium species, but its role in Plasmodium knowlesi is poorly studied. This work characterizes PkDHFR as a drug target and identifies inhibitors that can withstand the upcoming problem of resistance. The 3D structure of the PkDHFR target is modelled using comparative modelling, and further, it is refined and validated using energy minimization and torsional angle analysis methods. We extracted 13 compounds from DrugBank and ZINC databases using the "target similarity search" criteria. These compounds were categorized based on their binding affinity (-4.49 to -10.08 kcal/mol) and pose prediction against the active site of PkDHFR. Later on, the top 5 PkDHFR-compound complexes with high or equivalent binding affinity to its natural ligand (dihydrofolate) have undergone for dynamics. The simulation experiments reveal the higher stability of DB00563-PkDHFR complex and less conformational fluctuations and share a similar degree of compactness throughout the simulation trajectory. The MM/GBSA calculation of free energy of DB00563 is also the least (-72.84 kcal/mol) compared to others. Furthermore, the flexible side chain of DB00563 can bind and block the active site of PkDHFR more efficiently. Thus, the identified drug may be considered as a potential candidate for treating P. knowlesi malaria.

Suspected Plasmodium falciparum resistance to artesunate in Cameroon: A case report

Malaria in pregnancy is associated with adverse maternal and perinatal outcomes. The first-line treatment for severe malaria in the second and third trimesters of pregnancy is parenteral artesunate, according to WHO recommendations. Resistance of Plasmodium falciparum to artesunate has not yet been noted in our country. We report a case highly suspicious of such. A pregnant woman presented with the clinical signs of malaria. After paraclinical confirmation of the diagnosis, she was admitted and injectable artesunate was given for 72 h at the recommended dosage, with antipyretic without any improvement. Artesunate was therefore replaced by parenteral quinine, with favourable evolution. Resistance of Plasmodium falciparum to artesunate might be present in our country. This patient provides a warning about possible artesunate resistance, and this calls for careful monitoring of other cases of malaria been treated with this drug to ascertain the possibility of resistant cases.

Dihydroartemisinin Inhibits mTORC1 Signaling by Activating the AMPK Pathway in Rhabdomyosarcoma Tumor Cells

Dihydroartemisinin (DHA), an anti-malarial drug, has been shown to possess potent anticancer activity, partly by inhibiting the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) signaling. However, how DHA inhibits mTORC1 is still unknown. Here, using rhabdomyosarcoma (RMS) as a model, we found that DHA reduced cell proliferation and viability in RMS cells, but not those in normal cells, which was associated with inhibition of mTORC1. Mechanistically, DHA did not bind to mTOR or FK506 binding protein 12 (FKBP12). In addition, DHA neither inhibited insulin-like growth factor-1 receptor (IGF-1R), phosphoinositide 3-kinase (PI3K), and extracellular signal-regulated kinase ½ (Erk1/2), nor activated phosphatase and tensin homolog (PTEN) in the cells. Rather, DHA activated AMP-activated protein kinase (AMPK). Pharmacological inhibition of AMPK, ectopic expression dominant negative or kinase-dead AMPK, or knockdown of AMPKα attenuated the inhibitory effect of DHA on mTORC1 in the cells. Additionally, DHA was able to induce dissociation of regulatory-associated protein of mTOR (raptor) from mTOR and inhibit mTORC1 activity. Moreover, treatment with artesunate, a prodrug of DHA, dose-dependently inhibited tumor growth and concurrently activated AMPK and suppressed mTORC1 in RMS xenografts. The results indicated that DHA inhibits mTORC1 by activating AMPK in tumor cells. Our finding supports that DHA or artesunate has a great potential to be repositioned for treatment of RMS.

Superoxide: A major role in the mechanism of action of essential antimalarial drugs

Understanding the mode of action of antimalarials is central to optimizing their use and the discovery of new therapeutics. Currently used antimalarials belong to a limited series of chemical structures and their mechanisms of action are coutinuously debated. Whereas the involvement of reactive species that in turn kill the parasites sensitive to oxidative stress, is accepted for artemisinins, little is known about the generation of such species in the case of quinolines or hydroxynaphtoquinone. Moreover, the nature of the reactive species involved has never been characterized in Plasmodium-infected erythrocytes. The aim of this work was to determine and elucidate the production of the primary radical, superoxide in Plasmodium-infected erythrocytes treated with artemisinin, dihydroartemisinin, chloroquine and atovaquone, as representatives of three major classes of antimalarials. The intracellular generation of superoxide was quantified by liquid chromatography coupled to mass spectrometry (LC-MS). We demonstrated that artemisinins, atovaquone and to a lesser extent chloroquine, generate significant levels of superoxide radicals in Plasmodium falciparum sensitive strains. More so, the production of superoxide was lowered in chloroquine-resistant strain of Plasmodium treated with chloroquine. These results consolidate the knowledge about the mechanism of action of these different antimalarials and should be taken into consideration in the design of future drugs to fight drug-resistant parasites.

Implicating extracellular vesicles in Plasmodium falciparum artemisinin resistance development

Plasmodium falciparum malaria remains a disease of significant public health impact today. With the risk of emerging artemisinin resistance stalling malaria control efforts, the need to deepen our understanding of the parasite's biology is dire. Extracellular vesicles (EVs) are vital to the biology of P. falciparum and play a role in the pathogenesis of malaria. Recent studies have also shown that EVs may play a role in the development of artemisinin resistance in P. falciparum. Here, we highlight evidence on EVs in P. falciparum biology and malaria pathogenesis and argue that there is sufficient ground to propose a role for EVs in the development of P. falciparum artemisinin resistance. We suggest that EVs are actively secreted functional organelles that contribute to cellular homeostasis in P. falciparum-infected red blood cells under artemisinin pressure. Further exploration of this hypothesized EVs-based molecular mechanism of artemisinin resistance will aid the discovery of novel antimalarial therapies.

Study towards improving artemisinin-based combination therapies

Covering: Up to 2020 Artemisinin has made a significant contribution towards global malaria control since its initial discovery. Countless lives have been saved by this unique and miraculous molecule. In 2006, artemisinin-based combination therapies (ACTs) were recommended by the World Health Organization (WHO) as the first-line treatment for uncomplicated malaria infection and have since remained as the mainstays of the antimalarial treatment. Even so, substantial efforts to pursue better curative effects for the treatment of malaria have never ceased, particularly with regards to the circumstances surrounding the appearance of delayed clearance of malaria parasites by 3 day ACT treatments in South-East Asian countries. Strategies to further optimize artemisinin-based therapies, including synthesizing better artemisinin derivatives, developing advanced drug delivery systems, and diversifying artemisinin partner drugs, have been proposed over the past few years. Here, we provide an updated account of the continuous efforts in improving ACTs for better efficacy in curing malarial infection.

Antiplasmodial activity of sulfonylhydrazones: in vitro and in silico approaches

Malaria is still a life-threatening public health issue, and the upsurge of resistant strains requires continuous generation of active molecules. In this work, 35 sulfonylhydrazone derivatives were synthesized and evaluated against Plasmodium falciparum chloroquine-sensitive (3D7) and resistant (W2) strains. The most promising compound, 5b, had an IC₅₀ of 0.22 μM against W2 and was less cytotoxic and 26-fold more selective than chloroquine. The structure-activity relationship model, statistical analysis and molecular modeling studies suggested that antiplasmodial activity was related to hydrogen bond acceptor count, molecular weight and partition coefficient of octanol/water and displacement of frontier orbitals to the heteroaromatic ring beside the imine bond. This study demonstrates that the synthesized molecules with a simple scaffold allow the hit-to-lead process for new antimalarials to commence.

The potential of artemisinins as anti-obesity agents via modulating the immune system

Artemisinin and its derivatives are the most effective antimalarial drugs. Besides anti-malarial activity, artemisinin and its derivatives have displayed wide-spectrum bioactivities such as anti-parasite, anti-tumor, and anti-obesity effects. Obesity is an epidemic worldwide which is a big threat to human health, but there are only a few approved anti-obesity drugs in the world. Also, these drugs are efficient to limited patients partly because their safety and efficacy are questioned. Anti-inflammatory therapies may be valuable in obesity treatment since growing evidence shows chronic metabolic inflammation is implicated in metabolic disease pathogenesis. As artemisinin and its derivatives display effective anti-inflammatory and immunoregulatory properties with less toxicity, it provides an insight for novel drug development in obesity therapeutic strategies via immune-regulatory mechanisms. In this review, the potential of artemisinin and its derivatives to treat various metabolic diseases such as obesity and diabetes is discussed.

Stochastic Protein Alkylation by Antimalarial Peroxides

Antimalarial peroxides such as the phytochemical artemisinin or the synthetic ozonides arterolane and artefenomel undergo reductive cleavage of the pharmacophoric peroxide bond by ferrous heme, released by parasite hemoglobin digestion. The generated carbon-centered radicals alkylate heme in an intramolecular reaction and proteins in an intermolecular reaction. Here, we determine the proteinaceous alkylation signatures of artemisinin and synthetic ozonides in Plasmodium falciparum using alkyne click chemistry probes to identify target proteins by affinity purification and mass spectrometry-based proteomics. Using stringent controls and purification procedures, we identified 25 P. falciparum proteins that were alkylated by the antimalarial peroxides in a peroxide-dependent manner, but the alkylation patterns were more random than we had anticipated. Moreover, there was little overlap in the alkylation signatures identified in this work and those disclosed in previous studies. Our findings suggest that alkylation of parasite proteins by antimalarial peroxides is likely to be a nonspecific, stochastic process.

Artemisinin and its derivatives; ancient tradition inspiring the latest therapeutic approaches against malaria

Artemisinin (ART) is an endoperoxide sesquiterpene lactone, commonly used in the treatment of malaria. Although it was isolated from Artemisia annua L., a plant widely applied in Chinese Traditional Medicine, its mechanism of action remains uncertain and its clinical use is still limited due to its low solubility, its poor bioavailability and short in vivo half-life. Over time, several studies have been aimed towards the discovery of potent ART derivatives that could overcome clinical drawbacks. In this review, we focus on the multifaced aspects of ART and on the efforts spent to improve its pharmacological profile that so far culminated in the discovery of more effective drugs. Lastly, we outline the new perspectives in the ART-derivatives scenario.

Artemisinin-Resistant Malaria as a Global Catastrophic Biological Threat

The global spread of artemisinin resistance brings with it the threat of incurable malaria. Already, this disease threatens over 219 million lives per year and causes 5-6% losses in GDP in endemic areas, even with current advances in prevention and treatment. This chapter discusses the currently tenuous position we are in globally, and the impact that could be seen if artemisinin treatment is lost, whether due to the unchecked spread of K13 mutations or poor global investment in treatment and prevention advances. Artemisinin is the backbone of current ACT treatment programs and severe malarial treatment; without it, the success of future malaria eradication programs will be in jeopardy.

Artemisone and Artemiside Are Potent Panreactive Antimalarial Agents That Also Synergize Redox Imbalance in Plasmodium falciparum Transmissible Gametocyte Stages

The emergence of resistance toward artemisinin combination therapies (ACTs) by the malaria parasite Plasmodium falciparum has the potential to severely compromise malaria control. Therefore, the development of new artemisinins in combination with new drugs that impart activities toward both intraerythrocytic proliferative asexual and transmissible gametocyte stages, in particular, those of resistant parasites, is urgently required. We define artemisinins as oxidant drugs through their ability to oxidize reduced flavin cofactors of flavin disulfide reductases critical for maintaining redox homeostasis in the malaria parasite. Here we compare the activities of 10-amino artemisinin derivatives toward the asexual and gametocyte stages of P. falciparum parasites. Of these, artemisone and artemiside inhibited asexual and gametocyte stages, particularly stage V gametocytes, in the low-nanomolar range. Further, treatment of both early and late gametocyte stages with artemisone or artemiside combined with the pro-oxidant redox partner methylene blue displayed notable synergism. These data suggest that modulation of redox homeostasis is likely an important druggable process, particularly in gametocytes, and this finding thereby enhances the prospect of using combinations of oxidant and redox drugs for malaria control.

Novel Peroxides as Promising Anticancer Agents with Unexpected Depressed Antimalarial Activity

Twenty six peroxides belonging to bridged 1,2,4,5-tetraoxanes, bridged 1,2,4-trioxolanes (ozonides), and tricyclic monoperoxides were evaluated for their in vitro antimalarial activity against Plasmodium falciparum (3D7) and for their cytotoxic activities against immortalized human normal fibroblast (CCD19Lu), liver (LO₂ ), and lung (BEAS-2B) cell lines as well as human liver (HepG2) and lung (A549) cancer-cell lines. Synthetic ozonides were shown to have the highest cytotoxicity on HepG2 (IC₅₀ =0.19-0.59 μm), and some of these compounds selectively targeted liver cancer (selectivity index values for compounds 13 a and 14 a are 20 and 28, respectively) at levels that, in some cases, were higher than those of paclitaxel, artemisinin, and artesunic acid. In contrast some ozonides showed only moderate antimalarial activity against the chloroquine-sensitive 3D7 strain of P. falciparum (IC₅₀ from 2.76 to 24.2 μm; 12 b, IC₅₀ =2.76 μm; 13 a, IC₅₀ =20.14 μm; 14 a, IC₅₀ =6.32 μm). These results suggest that these derivatives have divergent mechanisms of action against cancer cells and malaria-infected cells. A cyclic voltammetry study of the peroxides was performed, but most of the compounds did not show direct correlation in oxidative capacity-activity. Our findings offer a new source of antimalarial and anticancer agents through structural modification of peroxide compounds.

Drug resistance in protozoan parasites

As with all other anti-infectives (antibiotics, anti-viral drugs, and anthelminthics), the limited arsenal of anti-protozoal drugs is being depleted by a combination of two factors: increasing drug resistance and the failure to replace old and often shamefully inadequate drugs, including those compromised by (cross)-resistance, through the development of new anti-parasitics. Both factors are equally to blame: a leaking bathtub may have plenty of water if the tap is left open; if not, it will soon be empty. Here, I will reflect on the factors that contribute to the drug resistance emergency that is unfolding around us, specifically resistance in protozoan parasites.

Dihydroartemisinin inhibits EMT induced by platinum-based drugs via Akt-Snail pathway

Artemisinin and its derivatives exhibit a high activity against a range of cancer cell types both in vitro and in vivo. In clinical practice, platinum-based anti-cancer chemotherapy is widely used to treat tumors. However, a large proportion of patients receiving these treatments will relapse because of metastasis and drug resistance. The purpose of this study is to explore the combinational anti-metastatic effect of platinum-based drugs and dihydroartemisinin (DHA). Both DDP and oxaliplatin (OXA) at low doses could induce epithelial–mesenchymal transition (EMT) in HCC. Meanwhile, co-administration of DHA could enhance DDP and OXA chemosensitivity in HCC and reverse drug resistance. DHA reversed the morphological changes induced by DDP or OXA and reversed the changes in EMT biomarkers induced by DDP and OXA in HCC in vitro and in vivo via AKT–Snail signaling. DHA significantly increased platinum-based drug sensitivity and suppressed EMT induced by platinum-based drugs via AKT–Snail signaling in HCC. DHA is expected to become the new adjuvant for chemotherapy.