The Existing Drug Nifuroxazide as an Antischistosomal Agent: In Vitro, In Vivo, and In Silico Studies of Macromolecular Targets

Anthelmintic Potential of Conjugated Long-Chain Fatty Acids Isolated from the Bioluminescent Mushroom Neonothopanus gardneri

With praziquantel being the sole available drug for schistosomiasis, identifying novel anthelmintic agents is imperative. A chemical investigation of the fruiting body of the bioluminescent mushroom Neonothopanus gardneri Berk. resulted in the isolation of new conjugated long-chain fatty acids (8E,10E,12S,13S)-12,13-dihydroxy-7-oxo-octadeca-8,10-dienoic acid (1) and (7S,8S,9E,11E)-7,8-dihydroxy-13-oxo-octadeca-9,11-dienoic acid (2) and three previously described compounds, (7R,8R,9Z)-7,8-dihydroxyoctadec-9-enoic acid (3), (2E)-dec-2-ene-1,10-dioic acid (4), and a ketolactone marasmeno-1,15-dione (5). Their planar structures were elucidated based on 1D and 2D NMR and MS/MS spectroscopic analyses. Compound 3 displayed significant antiparasitic activity against Schistosoma mansoni ex vivo (EC50 < 10 μM). No toxicity was observed in mammalian cells or Caenorhabditis elegans.

In Vitro and In Vivo Evaluation of the Antischistosomal Activity of Polygodial and 9-Deoxymuzigadial Isolated from Drimys brasiliensis Branches

In the present study, the hexane extract from branches of Drimys brasiliensis (Winteraceae) displayed potent activity against Schistosoma mansoni parasites (100% mortality of the worms at 200 μg/mL). Bioactivity-guided fractionation afforded, in addition to the previously reported bioactive sesquiterpene 3,6-epidioxy-bisabola-1,10-diene, two chemically related drimane sesquiterpenes-polygodial (1) and 9-deoxymuzigadial (2). The anti-S. mansoni effects for compounds 1 and 2 were determined in vitro, with compound 1 demonstrating significant potency (EC50 value of 10 μM for both male and female worms), while 2 was inactive. Cytotoxicity assays against Vero cells revealed no toxicity for either compound (CC50 > 200 μM). Additionally, an in silico analysis was conducted using the SwissADME platform for 1, revealing that this natural sesquiterpene exhibited adherence to several ADME parameters and no PAINS violations. Finally, in vivo studies with S. mansoni-infected mice treated with compound 1 demonstrated a 44.0% reduction in worm burden, accompanied by decreases in egg production of 71.8% in feces and 69.5% in intestines. These findings highlight the potential of polygodial (1) as a promising prototype for schistosomiasis treatment.

Exploration of innovative drug repurposing strategies for combating human protozoan diseases: Advances, challenges, and opportunities

Protozoan infections (e.g., malaria, trypanosomiasis, and toxoplasmosis) pose a considerable global burden on public health and socioeconomic problems, leading to high rates of morbidity and mortality. Due to the limited arsenal of effective drugs for these diseases, which are associated with devastating side effects and escalating drug resistance, there is an urgent need for innovative antiprotozoal drugs. The emergence of drug repurposing offers a low-cost approach to discovering new therapies for protozoan diseases. In this review, we summarize recent advances in drug repurposing for various human protozoan diseases and explore cost-effective strategies to identify viable new treatments. We highlight the cross-applicability of repurposed drugs across diverse diseases and harness common chemical motifs to provide new insights into drug design, facilitating the discovery of new antiprotozoal drugs. Challenges and opportunities in the field are discussed, delineating novel directions for ongoing and future research.

Atomic force microscopy reveals morphological and mechanical properties of schistosoma mansoni tegument

Schistosoma mansoni, an intravascular parasitic worm and the causative agent of schistosomiasis, relies on its tegument (outer layer) for survival and host interaction. This study explored the morphology and mechanical properties of S. mansoni tegument using Atomic Force Microscopy (AFM). Notably, we employed the PeakForce Quantitative Nanomechanical Mapping (PF-QNM) mode in air, enabling simultaneous acquisition of 3D topography and mechanical property contrasts (adhesion, elastic modulus). Additionally, nanoindentation (AFM contact mode) was performed on female worm tegument for elastic modulus measurement. Both techniques revealed an elastic modulus range of fractions or units of GPa for the tegument. Interestingly, mechanical property maps, particularly adhesion contrast, displayed a recurring pattern of light and dark bands. We also measured the depth of annular furrows on the female tegument, finding an average of 128 ± 10 nm. These findings establish AFM, particularly PF-QNM, as a valuable tool to characterize S. mansoni tegument properties, offering insights for future investigations into parasite biology and its response to immunological or pharmacological challenges.

Nifuroxazide Prevents Chikungunya Virus Infection Both In Vitro and In Vivo via Suppressing Viral Replication

Chikungunya virus (CHIKV) is a reemerging arbovirus causing disease on a global scale, and the potential for its epidemics remains high. CHIKV has caused millions of cases and heavy economic burdens around the world, while there are no available approved antiviral therapies to date. In this study, nifuroxazide, an FDA-approved antibiotic for acute diarrhea or colitis, was found to significantly inhibit a variety of arboviruses, although its antiviral activity varied among different target cell types. Nifuroxazide exhibited relatively high inhibitory efficiency in yellow fever virus (YFV) infection of the hepatoma cell line Huh7, tick-borne encephalitis virus (TBEV) and west nile virus (WNV) infection of the vascular endothelial cell line HUVEC, and CHIKV infection of both Huh7 cells and HUVECs, while it barely affected the viral invasion of neurons. Further systematic studies on the action stage of nifuroxazide showed that nifuroxazide mainly inhibited in the viral replication stage. In vivo, nifuroxazide significantly reduced the viral load in muscles and protected mice from CHIKV-induced footpad swelling, an inflammation injury within the arthrosis of infected mice. These results suggest that nifuroxazide has a potential clinical application as an antiviral drug, such as in the treatment of CHIKV infection.

The 3D pharmacophore modeling to explore new antischistosomal agents among US FDA approved drugs

Aim: To identify potential antischistosomal agents through 3D pharmacophore-based virtual screening of US FDA approved drugs.Materials & methods: A comprehensive virtual screening was conducted on a dataset of 10,000 FDA approved drugs, employing praziquantel as a template. Promising candidates were selected and assessed for their impact on Schistosoma mansoni viability in vitro and in vivo using S. mansoni infected mice.Results & conclusion: Among the selected drugs, betamethasone and doxazosin demonstrated in vitro efficacy, with effective concentration 50% (EC50) values ranging from 35 to 60 μM. In vivo studies revealed significant (>50%) reductions in worm burden for both drugs. These findings suggest that betamethasone and doxazosin hold promise for repurposing in treating schistosomiasis. Additionally, the study showcases a useful approach for identifying new antischistosomal drugs.

Antihistamines H1 as Potential Anthelmintic Agents against the Zoonotic Parasite Angiostrongylus cantonensis

Infections caused by parasitic helminths pose significant health concerns for both humans and animals. The limited efficacy of existing drugs underscores the urgent need for novel anthelmintic agents. Given the reported potential of antihistamines against various parasites, including worms, this study conducted a screening of clinically available antihistamines against Angiostrongylus cantonensis-a nematode with widespread implications for vertebrate hosts, including humans. Twenty-one anti-H1 antihistamines were screened against first-stage larvae (L1) of A. cantonensis obtained from the feces of infected rats. Standard anthelmintic drugs ivermectin and albendazole were employed for comparative analysis. The findings revealed four active compounds (promethazine, cinnarizine, desloratadine, and rupatadine), with promethazine demonstrating the highest potency (EC50 = 31.6 μM). Additionally, morphological analysis showed that antihistamines induced significant changes in larvae. To understand the mechanism of action, antimuscarinic activities were reported based on average pK i values for human muscarinic receptor (mAChR) subtypes of the evaluated compounds. Furthermore, an analysis of the physicochemical and pharmacodynamic properties of antihistamines revealed that their anthelmintic activity does not correlate with their activity at H1 receptors. This study marks the first documentation of antihistamines' activity against A. cantonensis, offering a valuable contribution to the quest for novel agents effective against zoonotic helminths.

In vitro and in vivo efficacy of the amiodarone and praziquantel combination against the blood fluke Schistosoma mansoni

Schistosomiasis, a widespread parasitic disease caused by the blood fluke of the genus Schistosoma, affects over 230 million people, primarily in developing countries. Praziquantel, the sole drug currently approved for schistosomiasis treatment, demonstrates effectiveness against patent infections. A recent study highlighted the antiparasitic properties of amiodarone, an anti-arrhythmic drug, exhibiting higher efficacy than praziquantel against prepatent infections. This study assessed the efficacy of amiodarone and praziquantel, both individually and in combination, against Schistosoma mansoni through comprehensive in vitro and in vivo experiments. In vitro experiments demonstrated synergistic activity (fractional inhibitory concentration index ≤0.5) for combinations of amiodarone with praziquantel. In a murine model of schistosomiasis featuring prepatent infections, treatments involving amiodarone (200 or 400 mg/kg) followed by praziquantel (200 or 400 mg/kg) yielded a substantial reduction in worm burden (60%-70%). Given the low efficacy of praziquantel in prepatent infections, combinations of amiodarone with praziquantel may offer clinical utility in the treatment of schistosomiasis.

Pharmacophore Virtual Screening Identifies Riboflavin as an Inhibitor of the Schistosome Cathepsin B1 Protease with Antiparasitic Activity

Schistosomiasis is a neglected disease of poverty that affects over 200 million people worldwide and relies on a single drug for therapy. The cathepsin B1 cysteine protease (SmCB1) of Schistosoma mansoni has been investigated as a potential target. Here, a structure-based pharmacophore virtual screening (VS) approach was used on a data set of approved drugs to identify potential antischistosomal agents targeting SmCB1. Pharmacophore (PHP) models underwent validation through receiver operating characteristics curves achieving values >0.8. The data highlighted riboflavin (RBF) as a compound of particular interest. A 1 μs molecular dynamics simulation demonstrated that RBF altered the conformation of SmCB1, causing the protease's binding site to close around RBF while maintaining the protease's overall integrity. RBF inhibited the activity of SmCB1 at low micromolar values and killed the parasite in vitro. Finally, in a murine model of S. mansoni infection, oral administration of 100 mg/kg RBF for 7 days significantly decreased worm burdens by ∼20% and had a major impact on intestinal and fecal egg burdens, which were decreased by ∼80%.

Considering ivermectin for treatment of schistosomiasis

Because of recent reports of praziquantel resistance in schistosome infections, there have been suggestions to employ ivermectin as a possible alternative, especially as its chemical composition is different from that of praziquantel, so cross-resistance is not expected. In order to ascertain possible damage and elimination of worms, we used ivermectin by oral gavage in infected mice, at a high dose (30.1 mg/kg, bordering toxicity). We also tested the efficacy of the drug at various times postinfection (PI), to check on possible effect on young and mature stages of the parasites. Thus, we treated mice on days 21 and 22 or on days 41 and 42 and even on days 21, 22, 41, and 42 PI. None of the treatment regimens resulted in cure rates or signs of lessened pathology in the mice. We also compared the effect of ivermectin to that of artemisone, an artemisinin derivative which had served us in the past as an effective anti-schistosome drug, and there was a stark difference in the artemisone's efficacy compared to that of ivermectin; while ivermectin was not effective, artemisone eliminated most of the worms, prevented egg production and granulomatous inflammatory response. We assume that the reported lack of activity of ivermectin, in comparison with praziquantel and artemisinins, originates from the difference in their mode of action. In wake of our results, we suggest that ivermectin is not a suitable drug for treatment of schistosomiasis.

Current drug strategies for the treatment and control of schistosomiasis

INTRODUCTION

Schistosomiasis, one of the current Neglected Tropical Diseases (NTDs) affects over 230 million people globally, with nearly 700 million at risk in more than 74 countries. Praziquantel (PZQ) has served as the primary treatment for the past four decades; however, its effectiveness is limited as it solely eliminates adult worms. In regions where infections are frequent, PZQ exhibits only temporary efficacy and has restricted potential to disrupt the prolonged transmission of the disease.

AREAS COVERED

A comprehensive exploration using the PubMed database was conducted to review current pharmacotherapy approaches for schistosomiasis. This review also encompasses recent research findings related to potential novel therapeutics and the repurposing of existing drugs.

EXPERT OPINION

Current schistosoma treatment strategies, primarily relying on PZQ, face challenges like temporary effectiveness and limited impact on disease transmission. Drug repurposing, due to economic constraints, is decisive for NTDs. Despite PZQ's efficacy, its failure to prevent reinfection highlights the need for complementary strategies, especially in regions with persistent environmental foci. Integrating therapies against diverse schistosome stages boosts efficacy and impedes resistance. Uncovering novel agents is essential to address resistance concerns in tackling this neglected tropical disease. Integrated strategies present a comprehensive approach to navigate the complex challenges.

In Situ Preparation of Dehydrodieugenol-Loaded Silver Nanoparticles and their Antischistosomal Activity

Schistosomiasis is a major neglected disease that imposes a substantial worldwide health burden, affecting approximately 250 million people globally. As praziquantel is the only available drug to treat schistosomiasis, there is a critical need to identify new anthelmintic compounds, particularly from natural sources. To enhance the activity of different natural products, one potential avenue involves its combination with silver nanoparticles (AgNP). Based on this approach, a one-step green method for the in situ preparation of dehydrodieugenol (DHDG) by oxidation coupling reaction using silver and natural eugenol is presented. AgNP formation was confirmed by UV-Vis spectroscopy due to the appearance of the surface plasmon resonance (SPR) band at 430 nm which is characteristic of silver nanoparticles. The nanoparticles were spherical with sizes in the range of 40 to 50 nm. Bioassays demonstrated that the silver nanoparticles loaded with DHDG exhibited significant anthelmintic activity against Schistosoma mansoni adult worms without toxicity to mammalian cells and an in vivo animal model (Caenorhabditis elegans), contributing to the development of new prototypes based on natural products for the treatment of schistosomiasis.

Small Schiff Base Molecules-A Possible Strategy to Combat Biofilm-Related Infections

Microorganisms participating in the development of biofilms exhibit heightened resistance to antibiotic treatment, therefore infections involving biofilms have become a problem in recent years as they are more difficult to treat. Consequently, research efforts are directed towards identifying novel molecules that not only possess antimicrobial properties but also demonstrate efficacy against biofilms. While numerous investigations have focused on antimicrobial capabilities of Schiff bases, their potential as antibiofilm agents remains largely unexplored. Thus, the objective of this article is to present a comprehensive overview of the existing scientific literature pertaining to small molecules categorized as Schiff bases with antibiofilm properties. The survey involved querying four databases (Web of Science, ScienceDirect, Scopus and Reaxys). Relevant articles published in the last 10 years were selected and categorized based on the molecular structure into two groups: classical Schiff bases and oximes and hydrazones. Despite the majority of studies indicating a moderate antibiofilm potential of Schiff bases, certain compounds exhibited a noteworthy effect, underscoring the significance of considering this type of molecular modeling when seeking to develop new molecules with antibiofilm effects.

Evaluating the Antischistosomal Activity of Dehydrodieugenol B and Its Methyl Ether Isolated from Nectandra leucantha-A Preclinical Study against Schistosoma mansoni Infection

Schistosomiasis, a parasitic disease affecting nearly 250 million individuals globally, poses a significant health challenge. With praziquantel being the sole available treatment and its limited efficacy in early stage infections, the identification of novel bioactive compounds becomes imperative. This study examines the potential of dehydrodieugenol B (1) and its methyl ether (2), derived from the leaves of the Brazilian Nectandra leucantha plant (Lauraceae), in combatting Schistosoma mansoni infections through a preclinical approach. Initially, compound 1 displayed noteworthy in vitro antiparasitic activity with an EC50 of 31.9 μM, showcasing low toxicity in mammalian cells and an in vivo animal model (Caenorhabditis elegans). Conversely, compound 2 exhibited no activity. In silico predictions pointed to favorable oral bioavailability and the absence of PAINS similarities. Subsequently, a single oral dose of 400 mg/kg of compound 1 or praziquantel was administered to mice infected with adult (patent infection) or immature parasites (prepatent infection). Remarkably, in prepatent infections, 1 resulted in a significant reduction (approximately 50%) in both worm and egg burden, while praziquantel reduced worm and egg numbers by 30%. The superior efficacy of dehydrodieugenol B (1) compared to praziquantel in premature infections holds the potential to advance the development of new molecular prototypes for schistosomiasis treatment.