Methotrexate is highly potent against pyrimethamine-resistant Plasmodium vivax

Discovery of harmiprims, harmine-primaquine hybrids, as potent and selective anticancer and antimalarial compounds

Although cancer and malaria are not etiologically nor pathophysiologically connected, due to their similarities successful repurposing of antimalarial drugs for cancer and vice-versa is known and used in clinical settings and drug research and discovery. With the growing resistance of cancer cells and Plasmodium to the known drugs, there is an urgent need to discover new chemotypes and enrich anticancer and antimalarial drug portfolios. In this paper, we present the design and synthesis of harmiprims, hybrids composed of harmine, an alkaloid of the β-carboline type bearing anticancer and antiplasmodial activities, and primaquine, 8-aminoquinoline antimalarial drug with low antiproliferative activity, covalently bound via triazole or urea. Evaluation of their antiproliferative activities in vitro revealed that N-9 substituted triazole-type harmiprime was the most selective compound against MCF-7, whereas C1-substituted ureido-type hybrid was the most active compound against all cell lines tested. On the other hand, dimeric harmiprime was not toxic at all. Although spectrophotometric studies and thermal denaturation experiments indicated binding of harmiprims to the ds-DNA groove, cell localization showed that harmiprims do not enter cell nucleus nor mitochondria, thus no inhibition of DNA-related processes can be expected. Cell cycle analysis revealed that C1-substituted ureido-type hybrid induced a G1 arrest and reduced the number of cells in the S phase after 24 h, persisting at 48 h, albeit with a less significant increase in G1, possibly due to adaptive cellular responses. In contrast, N-9 substituted triazole-type harmiprime exhibited less pronounced effects on the cell cycle, particularly after 48 h, which is consistent with its moderate activity against the MCF-7 cell line. On the other hand, screening of their antiplasmodial activities against the erythrocytic, hepatic, and gametocytic stages of the Plasmodium life cycle showed that dimeric harmiprime exerts powerful triple-stage antiplasmodial activity, while computational analysis showed its binding within the ATP binding site of PfHsp90.

Repurposing of existing therapeutics to combat drug-resistant malaria

In the era of drug repurposing, speedy discovery of new therapeutic options for the drug-resistant malaria is the best available tactic to reduce the financial load and time in the drug discovery process. Six anticancer drugs, three immunomodulators and four antibiotics were selected for the repositioning against experimental malaria owing to their mode of action and published literature. The efficacy of existing therapeutics was evaluated against chloroquine-resistant in vitro and in vivo strains of Plasmodium falciparum and P. yoelii, respectively. All the pre-existing FDA-approved drugs along with leptin were primarily screened against chloroquine-resistant (PfK1) and drug-sensitive (Pf3D7) strains of P. falciparum using SYBR green-based antiplasmodial assay. Cytotoxic profiling of these therapeutics was achieved on Vero and HepG2 cell lines, and human erythrocytes. Percent blood parasitemia and host survival was determined in chloroquine-resistant P. yoelii N67-infected Swiss mice using appropriate doses of these drugs/immunomodulators. Antimalarial screening together with cytotoxicity data revealed that anticancer drugs, idelalisib and 5-fluorouracil acquired superiority over their counterparts, regorafenib, and tamoxifen, respectively. ROS-inducer anticancer drugs, epirubicin and bleomycin were found toxic for the host. Immunomodulators (imiquimod, lenalidomide and leptin) were safest but less active in in vitro system, however, in P. yoelii-infected mice, they exhibited modest parasite suppression at their respective doses. Among antibiotics, moxifloxacin exhibited better antimalarial prospective than levofloxacin, roxithromycin and erythromycin. 5-Fluorouracil, imiquimod and moxifloxacin displayed 97.64, 81.18 and 91.77 % parasite inhibition in treated animals and attained superiority in their respective groups thus could be exploited further in combination with suitable antimalarials.

Prevalence of Periodontal Disease and Periodontopathic Bacteria in Anti-Cyclic Citrullinated Protein Antibody-Positive At-Risk Adults Without Arthritis

IMPORTANCE

The prevalence of periodontitis is increased in patients with rheumatoid arthritis (RA) and periodontopathic bacteria can citrullinate proteins. Periodontitis may, therefore, be an initiator of RA and a target for prevention. Periodontal disease and periodontal bacteria have not been investigated in at-risk individuals with RA autoimmunity but no arthritis.

OBJECTIVE

To examine periodontal disease and periodontopathic bacteria in anti-cyclic citrullinated protein (anti-CCP) antibody-positive at-risk individuals without arthritis.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study took place at a teaching hospital from April 27, 2015, to May 8, 2017. Forty-eight anti-CCP-positive individuals without arthritis (CCP+ at-risk) were recruited nationally. Twenty-six patients with early RA (ERA) and 32 healthy control individuals were recruited locally. Data were analyzed between June 1, 2017, and December 1, 2017.

INTERVENTIONS

Periodontal assessment and examination of joints using ultrasonography.

MAIN OUTCOMES AND MEASURES

Prevalence of diseased periodontal sites, clinical periodontitis, and periodontal inflamed surface area in CCP+ at-risk individuals compared with patients with ERA and healthy individuals matched for age and smoking. Paired-end sequencing of DNA from subgingival plaque from diseased and healthy periodontal sites was performed and DNA was profiled and analyzed.

RESULTS

A total of 48 CCP+ at-risk individuals (mean [SD] age, 51.9 [11.4] years; 31 [65%] female), 26 patients with ERA (mean [SD] age, 54.4 [16.7] years; 14 [54%] female), and 32 healthy individuals (mean [SD] age, 49.4 [15.3] years; 19 [59%] female) were recruited. Of 48 CCP+ at-risk individuals, 46 had no joint inflammation on ultrasonography. Thirty-five CCP+ at-risk individuals (73%), 12 healthy individuals (38%), and 14 patients with ERA (54%) had clinical periodontitis. The median (interquartile range) percentage of periodontal sites with disease was greater in CCP+ at-risk individuals compared with healthy individuals (3.3% [0%-11.3%] vs 0% [0%-0.7%]) and similar to patients with ERA (1.1% [0%-13.1%]). Median (interquartile range) periodontal inflamed surface area was higher in CCP+ at-risk individuals compared with healthy individuals (221 mm2 [81-504 mm2] vs 40 mm2 [12-205 mm2]). Patients with CCP+ at-risk had increased relative abundance of Porphyromonas gingivalis (but not Aggregatibacter actinomycetemcomitans) at healthy periodontal sites compared with healthy individuals (effect size, 3.00; 95% CI, 1.71-4.29) and patients with ERA (effect size, 2.14; 95% CI, 0.77-3.52).

CONCLUSIONS AND RELEVANCE

This study found increased prevalence of periodontitis and P gingivalis in CCP+ at-risk individuals. This suggests periodontitis and P gingivalis are associated with disease initiation and could be targets for preventive interventions in RA.

The Potential Use of Methotrexate in the Treatment of Cutaneous Leishmaniasis: In Vitro Assays against Sensitive and Meglumine Antimoniate-resistant Strains of Leishmania tropica

BACKGROUND

The present study aimed to evaluate the effect of methotrexate (MTX) alone and in combination with meglumine antimoniate (MA, Glucantime) against sensitive and MA-resistant Leishmania tropica stages in vitro.

METHODS

The present study was carried out in 2014 in Leishmaniasis Research Center at School of Medicine, Kerman University of Medical sciences, Kerman, Iran. The effects of MTX alone and along with MA on promastigote and amastigote stages of sensitive (SS) and MA-resistant (RS) L. tropica strains have been evaluated using a colorimetric MTT assay and in a macrophage model, respectively. In addition, the inhibitory effect of MTX on the Leishmania invasion of murine macrophages was assessed in promastigotes of both strains of L. tropica. Sensitive and MA resistant L. tropica are referred to those isolates that are responsive or non-responsive to one or two courses of treatment by MA systemically and/or intralesionally, respectively.

RESULTS

The findings of OD and IC50 showed that MTX plus MA (SS: 16.1 μg/ml, RS: 39.8 μg/ml) had a higher anti-leishmanial effect than MA (SS: 52.2 μg/ml, RS: 170 μg/ml) or MTX alone (SS: 22.2 μg/ml, RS: 51.4 μg/ml) on promastigotes of both strains of L. tropica. The MTX plus MA caused a significant decrease (P<0.05) in the mean infection rate (MIR) and the mean number of amastigotes in each macrophage compared with positive control. Infectivity of promastigotes is significantly (P<0.05) reduced when it was preincubated with MTX.

CONCLUSION

This study indicated high potency and a synergistic effect of MTX on MA in inhibiting the growth rateof promastigote and amastigote stages of sensitive and meglumine antimoniate-resistant L. tropica. Further works are needed to evaluate the anti-leishmanial effects of MTX on L. tropica using a clinical setting.

Major involvement of bacterial components in rheumatoid arthritis and its accompanying oxidative stress, systemic inflammation and hypercoagulability

We review the evidence that infectious agents, including those that become dormant within the host, have a major role to play in much of the etiology of rheumatoid arthritis and the inflammation that is its hallmark. This occurs in particular because they can produce cross-reactive (auto-)antigens, as well as potent inflammagens such as lipopolysaccharide that can themselves catalyze further inflammagenesis, including via β-amyloid formation. A series of observables coexist in many chronic, inflammatory diseases as well as rheumatoid arthritis. They include iron dysregulation, hypercoagulability, anomalous morphologies of host erythrocytes, and microparticle formation. Iron dysregulation may be responsible for the periodic regrowth and resuscitation of the dormant bacteria, with concomitant inflammagen production. The present systems biology analysis benefits from the philosophical idea of "coherence," that reflects the principle that if a series of ostensibly unrelated findings are brought together into a self-consistent narrative, that narrative is thereby strengthened. As such, we provide a coherent and testable narrative for the major involvement of (often dormant) bacteria in rheumatoid arthritis.

An integrative analysis of small molecule transcriptional responses in the human malaria parasite Plasmodium falciparum

Background

Transcriptional responses to small molecules can provide insights into drug mode of action (MOA). The capacity of the human malaria parasite, Plasmodium falciparum, to respond specifically to transcriptional perturbations has been unclear based on past approaches. Here, we present the most extensive profiling to date of the parasite’s transcriptional responsiveness to thirty-one chemically and functionally diverse small molecules.

Methods

We exposed two laboratory strains of the human malaria parasite P. falciparum to brief treatments of thirty-one chemically and functionally diverse small molecules associated with biological effects across multiple pathways based on various levels of evidence. We investigated the impact of chemical composition and MOA on gene expression similarities that arise between perturbations by various compounds. To determine the target biological pathways for each small molecule, we developed a novel framework for encoding small molecule effects on a spectra of biological processes or GO functions that are enriched in the differentially expressed genes of a given small molecule perturbation.

Results

We find that small molecules associated with similar transcriptional responses contain similar chemical features, and/ or have a shared MOA. The approach also revealed complex relationships between drugs and biological pathways that are missed by most exisiting approaches. For example, the approach was able to partition small molecule responses into drug-specific effects versus non-specific effects.

Conclusions

Our work provides a new framework for linking transcriptional responses to drug MOA in P. falciparum and can be generalized for the same purpose in other organisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2165-1) contains supplementary material, which is available to authorized users.

Methylene blue inhibits the asexual development of vivax malaria parasites from a region of increasing chloroquine resistance

OBJECTIVES

Methylene blue, once discarded due to its unsettling yet mild side effects, has now found a renewed place in the pharmacopoeia of modern medicine. The continued spread of drug-resistant Plasmodium vivax and Plasmodium falciparum has also led to a recent re-examination of methylene blue's potent antimalarial properties. Here we examine the ex vivo susceptibility profile of Plasmodium spp. isolates to methylene blue; the isolates were from a region on the Thai-Myanmar border where there are increasing rates of failure when treating vivax malaria with chloroquine.

METHODS

To do this we used a newly developed ex vivo susceptibility assay utilizing flow cytometry and a portable flow cytometer with a near-UV laser.

RESULTS

P. vivax (median methylene blue IC50 3.1 nM, IQR 1.7-4.3 nM) and P. falciparum (median methylene blue IC50 1.8 nM, IQR 1.6-2.3 nM) are susceptible to methylene blue treatment at physiologically relevant levels. Unfortunately, the addition of chloroquine to combination treatments with methylene blue significantly reduces the ex vivo effectiveness of this molecule.

CONCLUSIONS

Our data support further efforts to employ methylene blue as a safe, low-cost antimalarial to treat drug-resistant malaria.

Small molecule screen for candidate antimalarials targeting Plasmodium Kinesin-5

Plasmodium falciparum and vivax are responsible for the majority of malaria infections worldwide, resulting in over a million deaths annually. Malaria parasites now show measured resistance to all currently utilized drugs. Novel antimalarial drugs are urgently needed. The Plasmodium Kinesin-5 mechanoenzyme is a suitable "next generation" target. Discovered via small molecule screen experiments, the human Kinesin-5 has multiple allosteric sites that are "druggable." One site in particular, unique in its sequence divergence across all homologs in the superfamily and even within the same family, exhibits exquisite drug specificity. We propose that Plasmodium Kinesin-5 shares this allosteric site and likewise can be targeted to uncover inhibitors with high specificity. To test this idea, we performed a screen for inhibitors selective for Plasmodium Kinesin-5 ATPase activity in parallel with human Kinesin-5. Our screen of nearly 2000 compounds successfully identified compounds that selectively inhibit both P. vivax and falciparum Kinesin-5 motor domains but, as anticipated, do not impact human Kinesin-5 activity. Of note is a candidate drug that did not biochemically compete with the ATP substrate for the conserved active site or disrupt the microtubule-binding site. Together, our experiments identified MMV666693 as a selective allosteric inhibitor of Plasmodium Kinesin-5; this is the first identified protein target for the Medicines of Malaria Venture validated collection of parasite proliferation inhibitors. This work demonstrates that chemical screens against human kinesins are adaptable to homologs in disease organisms and, as such, extendable to strategies to combat infectious disease.

Repositioning: the fast track to new anti-malarial medicines?

BACKGROUND

Repositioning of existing drugs has been suggested as a fast track for developing new anti-malarial agents. The compound libraries of GlaxoSmithKline (GSK), Pfizer and AstraZeneca (AZ) comprising drugs that have undergone clinical studies in other therapeutic areas, but not achieved approval, and a set of US Food and Drug Administration (FDA)-approved drugs and other bio-actives were tested against Plasmodium falciparum blood stages.

METHODS

Molecules were tested initially against erythrocytic co-cultures of P. falciparum to measure proliferation inhibition using one of the following methods: SYBR®I dye DNA staining assay (3D7, K1 or NF54 strains); [(3)H] hypoxanthine radioisotope incorporation assay (3D7 and 3D7A strain); or 4',6-diamidino-2-phenylindole (DAPI) DNA imaging assay (3D7 and Dd2 strains). After review of the available clinical pharmacokinetic and safety data, selected compounds with low μM activity and a suitable clinical profile were tested in vivo either in a Plasmodium berghei four-day test or in the P. falciparum Pf3D7(0087/N9) huSCID 'humanized' mouse model.

RESULTS

Of the compounds included in the GSK and Pfizer sets, 3.8% (9/238) had relevant in vitro anti-malarial activity while 6/100 compounds from the AZ candidate drug library were active. In comparison, around 0.6% (24/3,800) of the FDA-approved drugs and other bio-actives were active. After evaluation of available clinical data, four investigational drugs, active in vitro were tested in the P. falciparum humanized mouse model: UK-112,214 (PAF-H1 inhibitor), CEP-701 (protein kinase inhibitor), CEP-1347 (protein kinase inhibitor), and PSC-833 (p-glycoprotein inhibitor). Only UK-112,214 showed significant efficacy against P. falciparum in vivo, although at high doses (ED90 131.3 mg/kg [95% CI 112.3, 156.7]), and parasitaemia was still present 96 hours after treatment commencement. Of the six actives from the AZ library, two compounds (AZ-1 and AZ-3) were marginally efficacious in vivo in a P. berghei model.

CONCLUSIONS

Repositioning of existing therapeutics in malaria is an attractive proposal. Compounds active in vitro at μM concentrations were identified. However, therapeutic concentrations may not be effectively achieved in mice or humans because of poor bio-availability and/or safety concerns. Stringent safety requirements for anti-malarial drugs, given their widespread use in children, make this a challenging area in which to reposition therapy.

Field-based flow cytometry for ex vivo characterization of Plasmodium vivax and P. falciparum antimalarial sensitivity

Ex vivo antimalarial sensitivity testing in human malaria parasites has largely depended on microscopic determination of schizont maturation. While this microscopic method is sensitive, it suffers from poor precision and is laborious. The recent development of portable, low-cost cytometers has allowed us to develop and validate a simple, field-optimized protocol using SYBR green and dihydroethidium for the accurate and objective determination of antimalarial drug sensitivity in freshly isolated Plasmodium vivax and Plasmodium falciparum.

The folate metabolic network of Falciparum malaria

The targeting of key enzymes in the folate pathway continues to be an effective chemotherapeutic approach that has earned antifolate drugs a valuable position in the medical pharmacopoeia. The successful therapeutic use of antifolates as antimalarials has been a catalyst for ongoing research into the biochemistry of folate and pterin biosynthesis in malaria parasites. However, our understanding of the parasites folate metabolism remains partial and patchy, especially in relation to the shikimate pathway, the folate cycle, and folate salvage. A sizeable number of potential folate targets remain to be characterised. Recent reports on the parasite specific transport of folate precursors that would normally be present in the human host awaken previous hypotheses on the salvage of folate precursors or by-products. As the parasite progresses through its life-cycle it encounters very contrasting host cell environments that present radically different metabolic milieus and biochemical challenges. It would seem probable that as the parasite encounters differing environments it would need to modify its biochemistry. This would be reflected in the folate homeostasis in Plasmodium. Recent drug screening efforts and insights into folate membrane transport substantiate the argument that folate metabolism may still offer unexplored opportunities for therapeutic attack.

Human ex vivo studies on asexual Plasmodium vivax: the best way forward

The lack of a continuous culture method for Plasmodium vivax has given the impression that investigations on this important species are severely curtailed. However, the use of new or improved ex vivo methods and tools to study fresh and thawed isolates from vivax malaria patients is currently providing useful data on P. vivax, such as sensitivity to antimalarial drugs, invasion mechanisms and pathobiology. This review discusses a practical framework for conducting ex vivo studies on the asexual erythrocytic stages of P. vivax and considers the synergies between ex vivo defined phenotypes, ex vivo derived 'omic' studies and in vivo clinical studies.