Structural Basis for Blocking Sugar Uptake into the Malaria Parasite Plasmodium falciparum.

Plasmodium species, the causative agent of malaria, rely on glucose for energy supply during blood stage. Inhibition of glucose uptake thus represents a potential strategy for the development of antimalarial drugs. Here, we present the crystal structures of PfHT1, the sole hexose transporter in the genome of Plasmodium species, at resolutions of 2.6 Å in complex with D-glucose and 3.7 Å with a moderately selective inhibitor, C3361. Although both structures exhibit occluded conformations, binding of C3361 induces marked rearrangements that result in an additional pocket. This inhibitor-binding-induced pocket presents an opportunity for the rational design of PfHT1-specific inhibitors. Among our designed C3361 derivatives, several exhibited improved inhibition of PfHT1 and cellular potency against P. falciparum, with excellent selectivity to human GLUT1. These findings serve as a proof of concept for the development of the next-generation antimalarial chemotherapeutics by simultaneously targeting the orthosteric and allosteric sites of PfHT1.

Multi-Level Biomarkers for Early Diagnosis of Ischaemic Stroke: A Systematic Review and Meta-Analysis.

Blood biomarkers hold potential for the early diagnosis of ischaemic stroke (IS). We aimed to evaluate the current weight of evidence and identify potential biomarkers and biological pathways for further investigation. We searched PubMed, EMBASE, the Cochrane Library and Web of Science, used R package meta4diag for diagnostic meta-analysis and applied Gene Ontology (GO) analysis to identify vital biological processes (BPs). Among 8544 studies, we included 182 articles with a total of 30,446 participants: 15675 IS, 2317 haemorrhagic stroke (HS), 1798 stroke mimics, 846 transient ischaemic attack and 9810 control subjects. There were 518 pooled biomarkers including 203 proteins, 114 genes, 108 metabolites and 88 transcripts. Our study generated two shortlists of biomarkers for future research: one with optimal diagnostic performance and another with low selection bias. Glial fibrillary acidic protein was eligible for diagnostic meta-analysis, with summary sensitivities and specificities for differentiating HS from IS between 3 h and 24 h after stroke onset ranging from 73% to 80% and 77% to 97%, respectively. GO analysis revealed the top five BPs associated with IS. This study provides a holistic view of early diagnostic biomarkers in IS. Two shortlists of biomarkers and five BPs warrant future investigation.

Intraperitoneal versus intranasal administration of lipopolysaccharide in causing sepsis severity in a murine model: a preliminary comparison.

Community-acquired respiratory infection is the commonest cause of sepsis presenting to emergency departments. Yet current experimental animal models simulate peritoneal sepsis with intraperitoneal (I.P.) injection of lipopolysaccharide (LPS) as the predominant route. We aimed to compare the progression of organ injury between I.P. LPS and intranasal (I.N.) LPS in order to establish a better endotoxemia murine model of respiratory sepsis. Eight weeks old male BALB/c mice received LPS-Escherichia coli doses at 0.15, 1, 10, 20, 40 and 100 mg per kg body weight (e.g. LPS-10 is a dose of 10 mg/kg body weight). Disease severity was monitored by a modified Mouse Clinical Assessment Score for Sepsis (M-CASS; range 0-21). A M-CASS score ≥ 10 or a weight reduction of ≥ 20%, was used as a criterion for euthanasia. The primary outcome was the survival rate (either no death or no need for euthanasia). The progression of disease was specified as M-CASS, body weight, blood glucose, histopathological changes to lung, liver, spleen, kidney, brain and heart tissues. Survival rate in I.P. LPS-20 mice was 0% (2/3 died; 1/3 euthanized with M-CASS > 10) at 24 h. Survival rate in all doses of I.N. LPS was 100% (20/20; 3-4 per group) at 96 h. 24 h mean M-CASS post-I.P. LPS-10 was 6.4/21 significantly higher than I.N. LPS-10 of 1.7/21 (Unpaired t test, P < 0.05). Organ injury was present at 96 h in the I.P. LPS-10 group: lung (3/3; 100%), spleen (3/3; 100%) and liver (1/3; 33%). At 24 h in the I.P. LPS-20 group, kidney injury was observed in the euthanized mouse. At 96 h in the post-I.N. LPS-20 group, only lung injury was observed in 2/3 (67%) mice (Kruskal-Wallis test with Dunn's, P < 0.01). At 24 h in the post-I.N. LPS-100 group all (4/4) mice had evidence of lung injury. Variable doses of I.N. LPS in mice produced lung injury but did not produce sepsis. Higher doses of I.P. LPS induced multi-organ injury but not respiratory sepsis. Lethal models of respiratory virus, e.g., influenza A, might provide alternative avenues that can be explored in future research.

An appraisal of studies using mouse models to assist the biomarker discovery for sepsis prognosis.

Introduction: Clinicians need reliable outcome predictors to improve the prognosis of septic patients. Mouse models are widely used in sepsis research. We aimed to review how mouse models were used to search for novel prognostic biomarkers of sepsis in order to optimize their use for future biomarker discovery. Methods: We searched PubMed from 2012 to July 2022 using "((sepsis) AND (mice)) AND ((prognosis) OR (prognostic biomarker))". Results: A total of 412 publications were retrieved. We selected those studies in which mouse sepsis was used to demonstrate prognostic potential of biomarker candidates and/or assist the subsequent evaluation in human sepsis for further appraisal. The most frequent models were lipopolysaccharide (LPS) injection and caecal ligation and puncture (CLP) using young male mice. Discovery technologies applied on mice include setting survival and nonsurvivable groups, detecting changes of biomarker levels and measuring physiological parameters during sepsis. None of the biomarkers achieved sufficient clinical performance for clinical use. Conclusions: The number of studies and strategies using mouse models to discover prognostic biomarkers of sepsis are limited. Current mouse models need to be further optimized to better conform to human sepsis. Current biomarker platforms do not achieve predictive performance for clinical use.

Responses of nitrous oxide fluxes to autumn freeze-thaw cycles in permafrost peatlands of the Da Xing'an Mountains, Northeast China.

Climate warming has intensified changes of permafrost freeze-thaw process and postponed the starting period of soil freezing, which significantly affected the processes of N2O production and emission from the soils. However, responses of soil N2O fluxes to freeze-thaw cycles (FTCS) during autumn freezing period in permafrost peatlands in field remain unclear. Therefore, the static chamber-GC techniques were used to explore the effects of autumn FTCS on N2O fluxes in the three permafrost peatlands [Calamagrostis angustifolia peatland (CA), Larix gmelini-Sphagnum swamp (LS), and Eriophorum vaginatum peatland (EV)] in Da Xing'an Mountains, Northeast China, from September to November 2019. The response peaks of N2O fluxes to autumn FTCS in CA (29.22 ± 14.90 µg m-2 h-1) and EV (19.70 ± 7.26 µg m-2 h-1) occurred in the autumn FTCS prophase, whereas LS (11.33 ± 0.90 µg m-2 h-1) appeared in the autumn FTCS metaphase. CA (394.90 µg m-2) and EV (497.82 µg m-2) acted as a N2O source, and LS (- 1321.43 µg m-2) was a N2O sink. The effects of autumn FTCS on N2O fluxes were significantly different (p < 0.001) in the three permafrost peatlands. N2O emissions during autumn FTCS were mainly driven by soil NH4+-N0-50 cm, DOC30-40 cm and 40-50 cm content and soil NO3--N0-50 cm content. The results implied that autumn FTCS could stimulate soil N2O emissions in permafrost peatlands and confirmed the important contribution of N2O emissions during autumn FTCS to annual nitrogen budget. This study could improve the accuracy of regional estimates of annual nitrogen budget.

1-Methyl-1H-pyrazole-5-carboxamide Derivatives Exhibit Unexpected Acute Mammalian Toxicity.

A series of 1-methyl-1H-pyrazole-5-carboxamides were synthesized as potent inhibitors of the parasitic nematode of sheep, Haemonchus contortus. These compounds did not show overt cytotoxicity to a range of mammalian cell lines under standard in vitro culture conditions, had high selectivity indices, and were progressed to an acute toxicity study in a rodent model. Strikingly, acute toxicity was observed in mice. Experiments measuring cellular respiration showed a dose-dependent inhibition of mitochondrial respiration. Under these conditions, potent cytotoxicity was observed for these compounds in rat hepatocytes suggesting that the potent acute mammalian toxicity of this chemotype is most likely associated with respiratory inhibition. In contrast, parasite toxicity was not correlated to acute toxicity or cytotoxicity in respiring cells. This paper highlights the importance of identifying an appropriate in vitro predictor of in vivo toxicity early on in the drug discovery pipeline, in particular assessment for in vitro mitochondrial toxicity.

A perspective on the discovery of selected compounds with anthelmintic activity against the barber's pole worm-Where to from here?

Parasitic roundworms (nematodes) cause substantial morbidity and mortality in animals worldwide. Anthelmintic treatment is central to controlling these worms, but widespread resistance to most of the commercially available anthelmintics for veterinary and agricultural use is compromising control, such that there is an urgency to discover new and effective drugs. The purpose of this article is to review information on parasitic nematodes, the treatment and control of parasitic nematode infections and aspects of discovering new anthelmintics in the context of anthelmintic resistance problems, and then to discuss some progress that our group has made in identifying selected compounds with activity against nematodes. The focus of our recent work has been on discovering new chemical entities and known drugs with anthelmintic activities against Haemonchus contortus as well as other socioeconomically important parasitic nematodes for subsequent development. Using whole worm-based phenotypic assays, we have been screening compound collections obtained via product-development-partnerships and/or collaborators, and active compounds have been assessed for their potential as anthelmintic candidates. Following the screening of 15,333 chemicals from five distinct compound collections against H. contortus, we have discovered one new chemical entity (designated SN00797439), two human kinase inhibitors (SNS-032 and AG-1295), 14 tetrahydroquinoxaline analogues, one insecticide (tolfenpyrad) and two tolfenpyrad (pyrazole-5-carboxamide) derivatives (a-15 and a-17) with anthelmintic activity in vitro. Some of these 20 'hit' compounds have selectivity against H. contortus in vitro when compared to particular human cell lines. In our opinion, some of these compounds could represent starting points for 'lead' development. Accordingly, the next research steps to be pursued include: (i) chemical optimisation of representative chemicals via structure-activity relationship (SAR) evaluations; (ii) assessment of the breadth of spectrum of anthelmintic activity on a range of other parasitic nematodes, such as strongyloids, ascaridoids, enoplids and filarioids; (iii) detailed investigations of the absorption, distribution, metabolism, excretion and toxicity (ADMET) of optimised chemicals with broad nematocidal or nematostatic activity; and (iv) establishment of the modes of action of lead candidates.

Synthesis and structure-activity relationship study of pyrrolidine-oxadiazoles as anthelmintics against Haemonchus contortus.

Parasitic roundworms (nematodes) are significant pathogens of humans and animals and cause substantive socioeconomic losses due to the diseases that they cause. The control of nematodes in livestock animals relies heavily on the use of anthelmintic drugs. However, their extensive use has led to a widespread problem of drug resistance in these worms. Thus, the discovery and development of novel chemical entities for the treatment of parasitic worms of humans and animals is needed. Herein, we describe our medicinal chemistry optimization efforts of a phenotypic hit against Haemonchus contortus based on a pyrrolidine-oxadiazole scaffold. This led to the identification of compounds with potent inhibitory activities (IC50 = 0.78-22.4 µM) on the motility and development of parasitic stages of H. contortus, and which were found to be highly selective in a mammalian cell counter-screen. These compounds could be used as suitable chemical tools for drug target identification or as lead compounds for further optimization.

Novel 1-Methyl-1 H-pyrazole-5-carboxamide Derivatives with Potent Anthelmintic Activity.

A phenotypic screen of two different libraries of small molecules against the motility and development of the parasitic nematode Haemonchus contortus led to the identification of two 1-methyl-1 H-pyrazole-5-carboxamide derivatives. Medicinal chemistry optimization targeted modifications of the left-hand side, middle section, and right-hand side of the hybrid structure of these two hits to elucidate the structure-activity relationship (SAR). Initial SAR around these hits allowed for the iterative and directed assembly of a focused set of 30 analogues of their hybrid structure. Compounds 10, 17, 20, and 22 were identified as the most potent compounds, inhibiting the development of the fourth larval (L4) stage of H. contortus at sub-nanomolar potencies while displaying strong selectivity toward the parasite when tested in vitro against the human MCF10A cell line. In addition, compounds 9 and 27 showed promising activity against a panel of other parasitic nematodes, including hookworms and whipworms.

Tetrahydroquinoxalines induce a lethal evisceration phenotype in Haemonchus contortus in vitro.

In the present study, the anthelmintic activity of a human tyrosine kinase inhibitor, AG-1295, and 14 related tetrahydroquinoxaline analogues against Haemonchus contortus was explored. These compounds were screened against parasitic larvae - exsheathed third-stage (xL3) and fourth-stage (L4) - using a whole-organism screening assay. All compounds were shown to have inhibitory effects on larval motility, development and growth, and induced evisceration through the excretory pore in xL3s. The estimated IC50 values ranged from 3.5 to 52.0 µM for inhibition of larval motility or development. Cytotoxicity IC50 against human MCF10A cells was generally higher than 50 µM. Microscopic studies revealed that this eviscerated (Evi) phenotype occurs rapidly (<20 min) and relates to a protrusion of internal tissues and organs (evisceration) through the excretory pore in xL3s; severe pathological damage in L4s as well as a suppression of larval growth in both stages were also observed. Using a relatively low concentration (12.5 µM) of compound m10, it was established that the inhibitor has to be present for a relatively short time (between 30 h and 42 h) during in vitro development from xL3 to L4, to induce the Evi phenotype. Increasing external osmotic pressure prevented evisceration and moulting, and xL3s remained unaffected by the test compound. These results point to a mode of action involving a dysregulation of morphogenetic processes during a critical time-frame, in agreement with the expected behaviour of a tyrosine kinase inhibitor, and suggest potential for development of this compound class as nematocidal drugs.

Structure-Activity Relationship Studies of Tolfenpyrad Reveal Subnanomolar Inhibitors of Haemonchus contortus Development.

Recently, we have discovered that the registered pesticide, tolfenpyrad, unexpectedly and potently inhibits the development of the L4 larval stage of the parasitic nematode Haemonchus contortus with an IC50 value of 0.03 µM while displaying good selectivity, with an IC50 of 37.9 µM for cytotoxicity. As a promising molecular template for medicinal chemistry optimization, we undertook anthelmintic structure-activity relationships for this chemical. Modifications of the left-hand side (LHS), right-hand side (RHS), and middle section of the scaffold were explored to produce a set of 57 analogues. Analogues 25, 29, and 33 were shown to be the most potent compounds of the series, with IC50 values at a subnanomolar level of potency against the chemotherapeutically relevant fourth larval (L4) stage of H. contortus. Selected compounds from the series also showed promising activity against a panel of other different parasitic nematodes, such as hookworms and whipworms.

Proteomic identification of galectin-11 and 14 ligands from Haemonchus contortus.

Haemonchus contortus is the most pathogenic nematode of small ruminants. Infection in sheep and goats results in anaemia that decreases animal productivity and can ultimately cause death. The involvement of ruminant-specific galectin-11 (LGALS-11) and galectin-14 (LGALS-14) has been postulated to play important roles in protective immune responses against parasitic infection; however, their ligands are unknown. In the current study, LGALS-11 and LGALS-14 ligands in H. contortus were identified from larval (L4) and adult parasitic stages extracts using immobilised LGALS-11 and LGALS-14 affinity column chromatography and mass spectrometry. Both LGALS-11 and LGALS-14 bound more putative protein targets in the adult stage of H. contortus (43 proteins) when compared to the larval stage (two proteins). Of the 43 proteins identified in the adult stage, 34 and 35 proteins were bound by LGALS-11 and LGALS-14, respectively, with 26 proteins binding to both galectins. Interestingly, hematophagous stage-specific sperm-coating protein and zinc metalloprotease (M13), which are known vaccine candidates, were identified as putative ligands of both LGALS-11 and LGALS-14. The identification of glycoproteins of H. contortus by LGALS-11 and LGALS-14 provide new insights into host-parasite interactions and the potential for developing new interventions.

Optimization of Novel 1-Methyl-1 H-Pyrazole-5-carboxamides Leads to High Potency Larval Development Inhibitors of the Barber's Pole Worm.

A phenotypic screen of a diverse library of small molecules for inhibition of the development of larvae of the parasitic nematode Haemonchus contortus led to the identification of a 1-methyl-1 H-pyrazole-5-carboxamide derivative with an IC50 of 0.29 µM. Medicinal chemistry optimization targeted modifications on the left-hand side (LHS), middle section, and right-hand side (RHS) of the scaffold in order to elucidate the structure-activity relationship (SAR). Strong SAR allowed for the iterative and directed assembly of a focus set of 64 analogues, from which compound 60 was identified as the most potent compound, inhibiting the development of the fourth larval (L4) stage with an IC50 of 0.01 µM. In contrast, only 18% inhibition of the mammary epithelial cell line MCF10A viability was observed, even at concentrations as high as 50 µM.

Screening of the 'Open Scaffolds' collection from Compounds Australia identifies a new chemical entity with anthelmintic activities against different developmental stages of the barber's pole worm and other parasitic nematodes.

The discovery and development of novel anthelmintic classes is essential to sustain the control of socioeconomically important parasitic worms of humans and animals. With the aim of offering novel, lead-like scaffolds for drug discovery, Compounds Australia released the 'Open Scaffolds' collection containing 33,999 compounds, with extensive information available on the physicochemical properties of these chemicals. In the present study, we screened 14,464 prioritised compounds from the 'Open Scaffolds' collection against the exsheathed third-stage larvae (xL3s) of Haemonchus contortus using recently developed whole-organism screening assays. We identified a hit compound, called SN00797439, which was shown to reproducibly reduce xL3 motility by ≥ 70%; this compound induced a characteristic, "coiled" xL3 phenotype (IC50 = 3.46-5.93 µM), inhibited motility of fourth-stage larvae (L4s; IC50 = 0.31-12.5 µM) and caused considerable cuticular damage to L4s in vitro. When tested on other parasitic nematodes in vitro, SN00797439 was shown to inhibit (IC50 = 3-50 µM) adults of Ancylostoma ceylanicum (hookworm) and first-stage larvae of Trichuris muris (whipworm) and eventually kill (>90%) these stages. Furthermore, this compound completely inhibited the motility of female and male adults of Brugia malayi (50-100 µM) as well as microfilariae of both B. malayi and Dirofilaria immitis (heartworm). Overall, these results show that SN00797439 acts against genetically (evolutionarily) distant parasitic nematodes i.e. H. contortus and A. ceylanicum [strongyloids] vs. B. malayi and D. immitis [filarioids] vs. T. muris [enoplid], and, thus, might offer a novel, lead-like scaffold for the development of a relatively broad-spectrum anthelmintic. Our future work will focus on assessing the activity of SN00797439 against other pathogens that cause neglected tropical diseases, optimising analogs with improved biological activities and characterising their targets.

Screening of the 'Stasis Box' identifies two kinase inhibitors under pharmaceutical development with activity against Haemonchus contortus.

BACKGROUND: In partnership with the Medicines for Malaria Venture (MMV), we screened a collection ('Stasis Box') of 400 compounds (which have been in clinical development but have not been approved for illnesses other than neglected infectious diseases) for inhibitory activity against Haemonchus contortus, in order to attempt to repurpose some of the compounds to parasitic nematodes. METHODS: We assessed the inhibition of compounds on the motility and/or development of exsheathed third-stage (xL3s) and fourth-stage (L4) larvae of H. contortus using a whole-organism screening assay. RESULTS: In the primary screen, we identified compound MMV690767 (also known as SNS-032) that inhibited xL3 motility by ~70% at a concentration of 20 µM after 72 h as well as compound MMV079840 (also known as AG-1295), which induced a coiled xL3 phenotype, with ~50% inhibition on xL3 motility. Subsequently, we showed that SNS-032 (IC50 = 12.4 µM) and AG-1295 (IC50 = 9.92 ± 1.86 µM) had a similar potency to inhibit xL3 motility. Although neither SNS-032 nor AG-1295 had a detectable inhibitory activity on L4 motility, both compounds inhibited L4 development (IC50 values = 41.24 µM and 7.75 ± 0.94 µM for SNS-032 and AG-1295, respectively). The assessment of the two compounds for toxic effects on normal human breast epithelial (MCF10A) cells revealed that AG-1295 had limited cytotoxicity (IC50 > 100 µM), whereas SNS-032 was quite toxic to the epithelial cells (IC50 = 1.27 µM). CONCLUSIONS: Although the two kinase inhibitors, SNS-032 and AG-1295, had moderate inhibitory activity on the motility or development of xL3s or L4s of H. contortus in vitro, further work needs to be undertaken to chemically alter these entities to achieve the potency and selectivity required for them to become nematocidal or nematostatic candidates.

Assessing the anthelmintic activity of pyrazole-5-carboxamide derivatives against Haemonchus contortus.

BACKGROUND: In this study, we tested five series of pyrazole-5-carboxamide compounds (n = 55) for activity against parasitic stages of the nematode Haemonchus contortus (barber's pole worm), one of the most pathogenic parasites of ruminants. METHODS: In an optimised, whole-organism screening assay, using exsheathed third-stage (xL3) and fourth-stage (L4) larvae, we measured the inhibition of larval motility and development of H. contortus. RESULTS: Amongst the 55 compounds, we identified two compounds (designated a-15 and a-17) that reproducibly inhibit xL3 motility as well as L4 motility and development, with IC50 values ranging between ~3.4 and 55.6 µM. We studied the effect of these two 'hit' compounds on mitochondrial function by measuring oxygen consumption. This assessment showed that xL3s exposed to each of these compounds consumed significantly less oxygen and had less mitochondrial activity than untreated xL3s, which was consistent with specific inhibition of complex I of the respiratory electron transport chain in arthropods. CONCLUSIONS: The present findings provide a sound basis for future work, aimed at identifying the targets of compounds a-15 and a-17 and establishing the modes of action of these chemicals in H. contortus.

Screening of the 'Pathogen Box' identifies an approved pesticide with major anthelmintic activity against the barber's pole worm.

There is a substantial need to develop new medicines against parasitic diseases via public-private partnerships. Based on high throughput phenotypic screens of largely protozoal pathogens and bacteria, the Medicines for Malaria Venture (MMV) has recently assembled an open-access 'Pathogen Box' containing 400 well-curated chemical compounds. In the present study, we tested these compounds for activity against parasitic stages of the nematode Haemonchus contortus (barber's pole worm). In an optimised, whole-organism screening assay, using exsheathed third-stage (xL3) and fourth-stage (L4) larvae, we measured the inhibition of larval motility, growth and development of H. contortus. We also studied the effect of the 'hit' compound on mitochondrial function by measuring oxygen consumption. Among the 400 Pathogen Box compounds, we identified one chemical, called tolfenpyrad (compound identification code: MMV688934) that reproducibly inhibits xL3 motility as well as L4 motility, growth and development, with IC50 values ranging between 0.02 and 3 µM. An assessment of mitochondrial function showed that xL3s treated with tolfenpyrad consumed significantly less oxygen than untreated xL3s, which was consistent with specific inhibition of complex I of the respiratory electron transport chain in arthropods. Given that tolfenpyrad was developed as a pesticide and has already been tested for absorption, distribution, excretion, biotransformation, toxicity and metabolism, it shows considerable promise for hit-to-lead optimisation and/or repurposing for use against H. contortus and other parasitic nematodes. Future work should assess its activity against hookworms and other pathogens that cause neglected tropical diseases.