The Action of the Hexokinase Inhibitor 2-deoxy-d-glucose on Cryptosporidium parvum and the Discovery of Activities against the Parasite Hexokinase from Marketed Drugs

Emerging therapeutic avenues against Cryptosporidium: A comprehensive review

Cryptosporidium is among the top causes of life-threatening diarrheal infection in public health and livestock sectors. Despite its high prevalence and economic importance, currently, there is no vaccine. Control of this protozoan is difficult due to the excretion of many resistant oocysts in the feces of the infected host, which contaminate the environment. Paromomycin shows inconsistent results and isn't considered a reliable therapy for cryptosporidiosis. Nitazoxanide (NTZ), the only FDA-approved drug against this parasite, is less productive in impoverished children and PLWHA (people living with HIV/AIDS). The absence of mitochondria and apicoplast, its unique location inside enterocytes separated by parasitophorous vacuole, and, most importantly, challenges in its genetic manipulations are some hurdles to the drug-discovery process. A library of compounds has been tested against Cryptosporidium during in vitro and in vivo trials. However, there has still not been sufficient success in finding the drug of choice against this parasite. Recent genome editing technologies based on CRISPR/Cas-9 have explored the functions of the vital genes by producing transgenic parasites that help to screen a collection of compounds to find target-specific drugs, provided the sufficient availability of in vitro culturing platforms, efficient transfection methods, and analytic techniques. The use of herbal remedies against Cryptosporidium is also an emerging area of interest with sufficient clinical success due to enhanced concern regarding anthelmintic resistance. Here, we highlighted present treatment options with their associated limitations, the use of genetic tools and natural products against it to find safe, effective, and inexpensive drugs to control the ever-increasing global burden of this disease.

Treating cryptosporidiosis: A review on drug discovery strategies

Despite several decades of research on therapeutics, cryptosporidiosis remains a major concern for human and animal health. Even though this field of research to assess antiparasitic drug activity is highly active and competitive, only one molecule is authorized to be used in humans. However, this molecule was not efficacious in immunocompromised people and the lack of animal therapeutics remains a cause of concern. Indeed, the therapeutic arsenal needs to be developed for both humans and animals. Our work aims to clarify research strategies that historically were diffuse and poorly directed. This paper reviews in vitro and in vivo methodologies to assess the activity of future therapeutic compounds by screening drug libraries or through drug repurposing. It focuses on High Throughput Screening methodologies (HTS) and discusses the lack of knowledge of target mechanisms. In addition, an overview of several specific metabolic pathways and enzymatic activities used as targets against Cryptosporidium is provided. These metabolic processes include glycolytic pathways, fatty acid production, kinase activities, tRNA elaboration, nucleotide synthesis, gene expression and mRNA maturation. As a conclusion, we highlight emerging future strategies for screening natural compounds and assessing drug resistance issues.

D-mannose alleviates intervertebral disc degeneration through glutamine metabolism

BACKGROUND

Intervertebral disc degeneration (IVDD) is a multifaceted condition characterized by heterogeneity, wherein the balance between catabolism and anabolism in the extracellular matrix of nucleus pulposus (NP) cells plays a central role. Presently, the available treatments primarily focus on relieving symptoms associated with IVDD without offering an effective cure targeting its underlying pathophysiological processes. D-mannose (referred to as mannose) has demonstrated anti-catabolic properties in various diseases. Nevertheless, its therapeutic potential in IVDD has yet to be explored.

METHODS

The study began with optimizing the mannose concentration for restoring NP cells. Transcriptomic analyses were employed to identify the mediators influenced by mannose, with the thioredoxin-interacting protein (Txnip) gene showing the most significant differences. Subsequently, small interfering RNA (siRNA) technology was used to demonstrate that Txnip is the key gene through which mannose exerts its effects. Techniques such as colocalization analysis, molecular docking, and overexpression assays further confirmed the direct regulatory relationship between mannose and TXNIP. To elucidate the mechanism of action of mannose, metabolomics techniques were employed to pinpoint glutamine as a core metabolite affected by mannose. Next, various methods, including integrated omics data and the Gene Expression Omnibus (GEO) database, were used to validate the one-way pathway through which TXNIP regulates glutamine. Finally, the therapeutic effect of mannose on IVDD was validated, elucidating the mechanistic role of TXNIP in glutamine metabolism in both intradiscal and orally treated rats.

RESULTS

In both in vivo and in vitro experiments, it was discovered that mannose has potent efficacy in alleviating IVDD by inhibiting catabolism. From a mechanistic standpoint, it was shown that mannose exerts its anti-catabolic effects by directly targeting the transcription factor max-like protein X-interacting protein (MondoA), resulting in the upregulation of TXNIP. This upregulation, in turn, inhibits glutamine metabolism, ultimately accomplishing its anti-catabolic effects by suppressing the mitogen-activated protein kinase (MAPK) pathway. More importantly, in vivo experiments have further demonstrated that compared with intradiscal injections, oral administration of mannose at safe concentrations can achieve effective therapeutic outcomes.

CONCLUSIONS

In summary, through integrated multiomics analysis, including both in vivo and in vitro experiments, this study demonstrated that mannose primarily exerts its anti-catabolic effects on IVDD through the TXNIP-glutamine axis. These findings provide strong evidence supporting the potential of the use of mannose in clinical applications for alleviating IVDD. Compared to existing clinically invasive or pain-relieving therapies for IVDD, the oral administration of mannose has characteristics that are more advantageous for clinical IVDD treatment.

Unlocking the mystery of the feeder organelle and versatile energy metabolism in Cryptosporidium parvum

Xu and colleagues recently revealed the critical role of Cryptosporidium's feeder organelle in nutrient uptake, showcasing the parasite's ability to harness glucose and glucose-6-phosphate from host cells. This illuminates the sophisticated energy metabolism and survival strategies of the parasite, highlighting potential therapeutic targets.

Anti-Cryptosporidial Drug-Discovery Challenges and Existing Therapeutic Avenues: A "One-Health" Concern

Cryptosporidiosis is the leading cause of life-threatening diarrheal infection, especially in infants. Oocysts contaminate the environment, and also, being a zoonotic disease, cryptosporidiosis is a threat to One Health. Nitazoxanide is the only FDA-approved drug, effective only in immunocompetent adults, and is not safe for infants. The absence of mitochondria and apicoplast, the presence of an electron-dense band (ED band), hindrances in its genetic and phenotypic manipulations, and its unique position inside the host cell are some challenges to the anti-cryptosporidial drug-discovery process. However, many compounds, including herbal products, have shown efficacy against Cryptosporidium during in vitro and in vivo trials. Still, the "drug of choice" against this protozoan parasite, especially in immunocompromised individuals and infants, has not yet been explored. The One-Health approach addresses this issue, focusing on the intersection of animal, human, and environmental health. The objective of this review is to provide knowledge about novel anti-cryptosporidial drug targets, available treatment options with associated limitations, and possible future shifts toward natural products to treat cryptosporidiosis. The current review is organized to address the treatment and prevention of cryptosporidiosis. An anti-cryptosporidial drug that is effective in immunocompromised individuals and infants is a necessity of our time.

Anti-Cryptosporidium parvum activity of Artemisia judaica L. and its fractions: in vitro and in vivo assays

Background

This study investigates the toxic activity of Artemisia judaica ethanolic extract (ArEx) as well as its phenolic fraction (ArPh), and terpenoid fraction (ArT) against Cryptosporidium parvum (C. parvum) oocysts.

Methods

Over a 4 months period, estimation of the total phenolic (TPC), total flavonoids (TFC), and total terpenoids contents (TTC) in ArEx; investigation of the in vitro antioxidant activity of ArEx, ArPh, and ArT; evaluation of ArEx, ArPh, and ArT toxic activity against C. parvum oocysts using MTT assay; parasitological analysis on ArPh-treated C. parvum oocysts and comet assay were performed both in vitro and in vivo (infectivity).

Results

The ArEx TPC, TFC, and TTC was 52.6 ± 3.1 mgGAE/g, 64.5 ± 3.1 mg QE/g, and 9.5 ± 1.1 mg Linol/g, respectively. Regarding the phytochemical in vitro antioxidant activity, the ArPh exhibited the highest antioxidant activity compared to the ArEx and ArT. The ArPh showed promising free radical scavenging activity of DPPH and ABTS^•+ with IC₅₀ values of 47.27 ± 1.86 μg/mL and 66.89 ± 1.94 μg/mL, respectively. Moreover, the FRAP of ArPh was 2.97 ± 0.65 mMol Fe⁺²/g while its TAC was 46.23 ± 3.15 mg GAE/g. The ArPh demonstrated toxic activity against C. parvum oocysts with a potent IC₅₀ value of 31.6 μg/mL compared to ArT (promising) and ArEx (non-effective). ArPh parasitological analysis demonstrated MIC₉₀ at 1000 μg/ml and effective oocysts destruction on count and morphology. ArPh fragmented oocysts nuclear DNA in comet assay. Beginning at 200 μg/mL, ArPh-treated oocysts did not infect mice.

Conclusion

To combat C. parvum infection, the phenolic fraction of A. judaica L. shows promise as an adjuvant therapy or as a source of potentially useful lead structures for drug discovery.

Cryptosporidium parvumcompetes with the intestinal epithelial cells for glucose and impairs systemic glucose supply in neonatal calves

Cryptosporidiosis is one of the main causes of diarrhea in children and young livestock. The interaction of the parasite with the intestinal host cells has not been characterized thoroughly yet but may be affected by the nutritional demand of the parasite. Hence, we aimed to investigate the impact of C. parvum infection on glucose metabolism in neonatal calves. Therefore, N = 5 neonatal calves were infected with C. parvum on the first day of life, whereas a control group was not (N = 5). The calves were monitored clinically for one week, and glucose absorption, turnover and oxidation were assessed using stable isotope labelled glucose. The transepithelial transport of glucose was measured using the Ussing chamber technique. Glucose transporters were quantified on gene and protein expression level using RT-qPCR and Western blot in the jejunum epithelium and brush border membrane preparations. Plasma glucose concentration and oral glucose absorption were decreased despite an increased electrogenic phlorizin sensitive transepithelial transport of glucose in infected calves. No difference in the gene or protein abundance of glucose transporters, but an enrichment of glucose transporter 2 in the brush border was observed in the infected calves. Furthermore, the mRNA for enzymes of the glycolysis pathway was increased indicating enhanced glucose oxidation in the infected gut. In summary, C. parvum infection modulates intestinal epithelial glucose absorption and metabolism. We assume that the metabolic competition of the parasite for glucose causes the host cells to upregulate their uptake mechanisms and metabolic machinery to compensate for the energy losses.

Past, current, and potential treatments for cryptosporidiosis in humans and farm animals: A comprehensive review

The intracellular protozoan parasite of the genus Cryptosporidium is among the leading causes of waterborne diarrheal disease outbreaks throughout the world. The parasite is transmitted by ingestion of infective oocysts that are highly stable in the environment and resistant to almost all conventional disinfection methods and water treatments. Control of the parasite infection is exceedingly difficult due to the excretion of large numbers of oocysts in the feces of infected individuals that contaminate the environment and serve as a source of infection for susceptible hosts including humans and animals. Drug development against the parasite is challenging owing to its limited genetic tractability, absence of conventional drug targets, unique intracellular location within the host, and the paucity of robust cell culture platforms for continuous parasite propagation. Despite the high prevalence of the parasite, the only US Food and Drug Administration (FDA)-approved treatment of Cryptosporidium infections is nitazoxanide, which has shown moderate efficacy in immunocompetent patients. More importantly, no effective therapeutic drugs are available for treating severe, potentially life-threatening cryptosporidiosis in immunodeficient patients, young children, and neonatal livestock. Thus, safe, inexpensive, and efficacious drugs are urgently required to reduce the ever-increasing global cryptosporidiosis burden especially in low-resource countries. Several compounds have been tested for both in vitro and in vivo efficacy against the disease. However, to date, only a few experimental compounds have been subjected to clinical trials in natural hosts, and among those none have proven efficacious. This review provides an overview of the past and present anti-Cryptosporidium pharmacotherapy in humans and agricultural animals. Herein, we also highlight the progress made in the field over the last few years and discuss the different strategies employed for discovery and development of effective prospective treatments for cryptosporidiosis.

Phosphatase inhibitors BVT-948 and alexidine dihydrochloride inhibit sexual development of the malaria parasite Plasmodium berghei

Background

With the emergence of resistance to front-line antimalarials, there is an urgent need to develop new medicines, including those targeting sexual development. This study aimed to assess the activity of a panel of phosphatase inhibitors against the sexual development of Plasmodium berghei and evaluate their potential as transmission-blocking agents.

Methods

Twenty-five compounds were screened for transmission-blocking activity in vitro using the P. berghei ookinete culture assay. The inhibitory effects on male gametogenesis, gamete-ookinete, and zygote-ookinete formation were evaluated. The transmission-blocking activity of two compounds was evaluated using an in vivo mosquito feeding assay. Their cytotoxic effects were assessed on the human cell line HepG2.

Results

Twelve compounds inhibited P. berghei ookinete formation with an IC₅₀ < 10 μM. Two compounds, BVT-948 and alexidine dihydrochloride, significantly inhibited different developmental stages from gametogenesis through ookinete maturation. They also showed a substantial in vivo transmission-blocking activity by the mosquito feeding assay.

Conclusions

Some phosphatase inhibitors effectively inhibited Plasmodium sexual development and exhibited evident transmission-blocking activity, suggesting that phosphatases are valid targets for antimalarial development.

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BVT-948 and alexidine·2HCl inhibit sexual developmental stages of Plasmodium.

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BVT-948 and alexidine·2HCl show a substantial transmission-blocking activity.

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BVT-948 and alexidine·2HCl show a relatively low cytotoxicity to HepG2 cells.

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Phosphatases are valid targets for antimalarial development.

2-Deoxy-D-glucose and combined 2-Deoxy-D-glucose/albendazole exhibit therapeutic efficacy against Echinococcus granulosus protoscoleces and experimental alveolar echinococcosis

2-Deoxy-D-glucose (2-DG) is a glucose analog used as a promising anticancer agent. It exerts its effects by inhibiting the glycolytic energy metabolism to deplete cells of energy. The larval stage of Echinococcus relies on glycolysis for energy production. Therefore, in this study, we investigated the in vitro and in vivo efficacy of 2-DG against the larval stage of Echinococcus granulosus and E. multilocularis. 2-DG exhibited significant time- and dose-dependent effects against in vitro cultured E. granulosus protoscoleces and E. multilocularis metacestodes. A daily oral administration of 500 mg/kg 2-DG in E. multilocularis-infected mice effectively reduced the weight of metacestodes. Notably, the combination treatment, either 2-DG (500 mg/kg/day) + albendazole (ABZ) (200 mg/kg/day) or 2-DG (500 mg/kg/day) + half-dose of ABZ (100 mg/kg/day), exhibited a potent therapeutic effect against E. multilocularis, significantly promoting the reduction of metacestodes weight compared with the administration of 2-DG or ABZ alone. Furthermore, the combination significantly promoted apoptosis of the cells of metacestodes and inhibited glycolysis in metacestodes, compared with the administration of 2-DG or ABZ alone. In conclusion, 2-DG exerts an effective activity against the larval stage of Echinococcus. Thus, it may be a promising anti-Echinococcus drug, and its combination with ABZ may provide a new strategy for the treatment of echinococcosis in humans.

Echinococcosis is a serious but neglected helminthic zoonosis caused by the larval stage of Echinococcus granulosus and E. multilocularis. At present, clinical pharmacotherapy of echinococcosis, such as albendazole (ABZ) and mebendazole, has limited effectiveness. Thus, the development of novel therapeutic drugs for human echinococcosis is urgently needed. 2-Deoxy-D-glucose (2-DG) is a glucose analog used as a promising anticancer agent, and it exerts its effects by inhibiting the glycolytic energy metabolism to deplete cells of energy. Echinococcus in the host depends on glycolysis for energy production and glycolysis intermediates for other metabolic processes. Therefore, in this study, we investigated the efficacy of 2-DG against Echinococcus. 2-DG exerted an effective in vitro and in vivo activity against E. granulosus protoscoleces and E. multilocularis metacestodes, and the combination of this drug with ABZ further improved the therapeutic effect. Therefore, 2-DG can be developed as a promising anti-Echinococcus drug, and its combination with ABZ may provide a new strategy for the treatment of human echinococcosis in the future.

Cryptosporidium parvum Pyruvate Kinase Inhibitors With in vivo Anti-cryptosporidial Efficacy

Cryptosporidium parvum is a highly prevalent protozoan parasite that causes a diarrheal disease in humans and animals worldwide. Thus far, the moderately effective nitazoxanide is the only drug approved by the United States Food and Drug Administration for treating cryptosporidiosis in immunocompetent humans. However, no effective drug exists for the severe disease seen in young children, immunocompromised individuals and neonatal livestock. C. parvum lacks the Krebs cycle and the oxidative phosphorylation steps, making it dependent solely on glycolysis for metabolic energy production. Within its glycolytic pathway, C. parvum possesses two unique enzymes, the bacterial-type lactate dehydrogenase (CpLDH) and the plant-like pyruvate kinase (CpPyK), that catalyze two sequential steps for generation of essential metabolic energy. We have previously reported that inhibitors of CpLDH are effective against C. parvum, both in vitro and in vivo. Herein, we developed an in vitro assay for the enzymatic activity of recombinant CpPyK protein and used it to screen a chemical compound library for inhibitors of CpPyK’s activity. The identified inhibitors were tested (at non-toxic concentrations) for efficacy against C. parvum using in vitro assays, and an in vivo mouse infection model. We identified six CpPyK inhibitors that blocked in vitro growth and proliferation of C. parvum at low micromolar concentrations (EC₅₀ values ranging from 10.29 to 86.01 μM) that were non-toxic to host cells. Among those six compounds, two (NSC252172 and NSC234945) were found to be highly efficacious against cryptosporidiosis in immunocompromised mice at a dose of 10 mg/kg body weight, with very significant reduction in parasite load and amelioration of intestinal pathologies. Together, these findings have unveiled inhibitors for an essential molecular target in C. parvum and demonstrated their efficacy against the parasite in vitro and in vivo. These inhibitors are, therefore, potential lead-compounds for developing efficacious treatments for cryptosporidiosis.

Ebselen, a multi-target compound: its effects on biological processes and diseases

Ebselen is a well-known synthetic compound mimicking glutathione peroxidase (GPx), which catalyses some vital reactions that protect against oxidative damage. Based on a large number of in vivo and in vitro studies, various mechanisms have been proposed to explain its actions on multiple targets. It targets thiol-related compounds, including cysteine, glutathione, and thiol proteins (e.g., thioredoxin and thioredoxin reductase). Owing to this, ebselen is a unique multifunctional agent with important effects on inflammation, apoptosis, oxidative stress, cell differentiation, immune regulation and neurodegenerative disease, with anti-microbial, detoxifying and anti-tumour activity. This review summarises the current understanding of the multiple biological processes and molecules targeted by ebselen, and its pharmacological applications.

Phenotypic screening techniques for Cryptosporidium drug discovery

Introduction: Two landmark epidemiological studies identified Cryptosporidium spp. as a significant cause of diarrheal disease in pediatric populations in resource-limited countries. Notably, nitazoxanide is the only approved drug for treatment of cryptosporidiosis but shows limited efficacy. As a result, many drug discovery efforts have commenced to find improved treatments. The unique biology of Cryptosporidium presents challenges for traditional drug discovery methods, which has inspired new assay platforms to study parasite biology and drug screening. Areas covered: The authors review historical advancements in phenotypic-based assays and techniques for Cryptosporidium drug discovery, as well as recent advances that will define future drug discovery. The reliance on phenotypic-based screens and repositioning of phenotypic hits from other pathogens has quickly created a robust pipeline of potential cryptosporidiosis therapeutics. The latest advances involve new in vitro culture methods for oocyst generation, continuous culturing capabilities, and more physiologically relevant assays for testing compounds. Expert opinion: Previous phenotypic screening techniques have laid the groundwork for recent cryptosporidiosis drug discovery efforts. The resulting improved methodologies characterize compound activity, identify, and validate drug targets, and prioritize new compounds for drug development. The most recent improvements in phenotypic assays are poised to help advance compounds into clinical development.