Yolk proteins of the schistosomiasis vector snail Biomphalaria glabrata revealed by multi-omics analysis.

Vitellogenesis is the most important process in animal reproduction, in which yolk proteins play a vital role. Among multiple yolk protein precursors, vitellogenin (Vtg) is a well-known major yolk protein (MYP) in most oviparous animals. However, the nature of MYP in the freshwater gastropod snail Biomphalaria glabrata remains elusive. In the current study, we applied bioinformatics, tissue-specific transcriptomics, ovotestis-targeted proteomics, and phylogenetics to investigate the large lipid transfer protein (LLTP) superfamily and ferritin-like family in B. glabrata. Four members of LLTP superfamily (BgVtg1, BgVtg2, BgApo1, and BgApo2), one yolk ferritin (Bg yolk ferritin), and four soma ferritins (Bg ferritin 1, 2, 3, and 4) were identified in B. glabrata genome. The proteomic analysis demonstrated that, among the putative yolk proteins, BgVtg1 was the yolk protein appearing in the highest amount in the ovotestis, followed by Bg yolk ferritin. RNAseq profile showed that the leading synthesis sites of BgVtg1 and Bg yolk ferritin are in the ovotestis (presumably follicle cells) and digestive gland, respectively. Phylogenetic analysis indicated that BgVtg1 is well clustered with Vtgs of other vertebrates and invertebrates. We conclude that, vitellogenin (BgVtg1), not yolk ferritin (Bg yolk ferritin), is the major yolk protein precursor in the schistosomiasis vector snail B. glabrata.

The anthelmintic meclonazepam activates a schistosome transient receptor potential channel.

Parasitic flatworms cause various clinical and veterinary infections that impart a huge burden worldwide. The most clinically impactful infection is schistosomiasis, a neglected tropical disease caused by parasitic blood flukes. Schistosomiasis is treated with praziquantel (PZQ), an old drug introduced over 40 years ago. New drugs are urgently needed, as while PZQ is broadly effective it suffers from several limitations including poor efficacy against juvenile worms, which may prevent it from being completely curative. An old compound that retains efficacy against juvenile worms is the benzodiazepine meclonazepam (MCLZ). However, host side effects caused by benzodiazepines preclude development of MCLZ as a drug and MCLZ lacks an identified parasite target to catalyze rational drug design for engineering out human host activity. Here, we identify a transient receptor potential ion channel of the melastatin subfamily, named TRPMMCLZ, as a parasite target of MCLZ. MCLZ potently activates Schistosoma mansoni TRPMMCLZ through engagement of a binding pocket within the voltage-sensor-like domain of the ion channel to cause worm paralysis, tissue depolarization, and surface damage. TRPMMCLZ reproduces all known features of MCLZ action on schistosomes, including a lower activity versus Schistosoma japonicum, which is explained by a polymorphism within this voltage-sensor-like domain-binding pocket. TRPMMCLZ is distinct from the TRP channel targeted by PZQ (TRPMPZQ), with both anthelmintic chemotypes targeting unique parasite TRPM paralogs. This advances TRPMMCLZ as a novel druggable target that could circumvent any target-based resistance emerging in response to current mass drug administration campaigns centered on PZQ.

Resveratrol protects against Schistosoma mansoni-induced liver fibrosis by targeting the Sirt-1/NF-κB axis.

Hepatic schistosomiasis is a prevalent form of chronic liver disease that drastically affects human health. Nevertheless, an antifibrotic drug that could suppress the development of hepatic fibrosis does not exist yet. The current study aimed to evaluate the effect of resveratrol, a natural polyphenol with multiple biological activities, on Schistosoma mansoni (S. mansoni)-induced hepatic fibrosis and delineate the underlying molecular mechanism. Swiss male albino mice were randomly assigned into infected and non-infected groups. Hepatic schistosomiasis infection was induced via exposure to S. mansoni cercariae. 6 weeks later, resveratrol was administrated either as 20 mg/kg/day or 100 mg/kg/day for 4 weeks to two infected groups. Another group received vehicle and served as infected control group. At the end of the study, portal hemodynamic, biochemical, and histopathological evaluation of liver tissues were conducted. Remarkably, resveratrol significantly reduced portal pressure, portal and mesenteric flow in a dose-dependent manner. It improved several key features of hepatic injury as evidenced biochemically by a significant reduction of bilirubin and liver enzymes, and histologically by amelioration of the granulomatous and inflammatory reactions. In line, resveratrol reduced the expression of pro-inflammatory markers; TNF-α, IL-1ß and MCP-1 mRNA, together with fibrotic markers; collagen-1, TGF-ß1 and α-SMA. Moreover, resveratrol restored SIRT1/NF-κB balance in hepatic tissues which is the main switch-off control for all the fibrotic and inflammatory mechanisms. Taken together, it can be inferred that resveratrol possesses a possible anti-fibrotic effect that can halt the progression of hepatic schistosomiasis via targeting SIRT1/ NF-κB signaling.

Hemocyte-like cells in larvae of the freshwater snail Biomphalaria glabrata (Mollusca: Panpulmonata).

Despite undergoing development within a germfree egg capsule, embryos and larvae of the freshwater snail Biomphalaria glabrata possess passive immune protection in the form of parentally-derived antimicrobial proteins in the perivitelline fluid. However, the point at which larvae begin to form their own internal defense system (IDS), which consists of both plasma proteins and hemocytes, is not known. In this study, hemocyte-like cells were observed in mechanically-disrupted late trochophores and veligers of the BS-90 strain of B. glabrata. These cells showed the properties of glass adherence, spreading, motility, and binding and phagocytosing polystyrene microspheres. No hemocyte-like cells were recovered from the early trochophore stage, and therefore their formation first occurs during subsequent maturation. Numbers of hemocyte-like cells increased during larval development. Although the functional significance of these cells is not known, they may represent the initial cellular component of the IDS.

Divide, conquer and reconstruct: How to solve the 3D structure of recalcitrant Micro-Exon Gene (MEG) protein from Schistosoma mansoni.

Micro-Exon Genes are a widespread class of genes known for their high variability, widespread in the genome of parasitic trematodes such as Schistosoma mansoni. In this study, we present a strategy that allowed us to solve the structures of three alternatively spliced isoforms from the Schistoma mansoni MEG 2.1 family for the first time. All isoforms are hydrophobic, intrinsically disordered, and recalcitrant to be expressed in high yield in heterologous hosts. We resorted to the chemical synthesis of shorter pieces, before reconstructing the entire sequence. Here, we show that isoform 1 partially folds in a-helix in the presence of trifluoroethanol while isoform 2 features two rigid elbows, that maintain the peptide as disordered, preventing any structuring. Finally, isoform 3 is dominated by the signal peptide, which folds into a-helix. We demonstrated that combining biophysical techniques, like circular dichroism and nuclear magnetic resonance at natural abundance, with in silico molecular dynamics simulation for isoform 1 only, was the key to solve the structure of MEG 2.1. Our results provide a crucial piece to the puzzle of this elusive and highly variable class of proteins.

Defining an optimal control for RNAi experiments with adult Schistosoma mansoni.

In parasites such as Schistosoma mansoni, gene knockdown by RNA interference (RNAi) has become an indispensable tool for functional gene characterization. To distinguish target-specific RNAi effects versus off-target effects, controls are essential. To date, however, there is still no general agreement about suitable RNAi controls, which limits the comparability between studies. To address this point, we investigated three selected dsRNAs for their suitability as RNAi controls in experiments with adult S. mansoni in vitro. Two dsRNAs were of bacterial origin, the neomycin resistance gene (neoR) and the ampicillin resistance gene (ampR). The third one, the green fluorescent protein gene (gfp), originated from jellyfish. Following dsRNA application, we analyzed physiological parameters like pairing stability, motility, and egg production as well as morphological integrity. Furthermore, using RT-qPCR we evaluated the potential of the used dsRNAs to influence transcript patterns of off-target genes, which had been predicted by si-Fi (siRNA-Finder). At the physiological and morphological levels, we observed no obvious changes in the dsRNA treatment groups compared to an untreated control. However, we detected remarkable differences at the transcript level of gene expression. Amongst the three tested candidates, we suggest dsRNA of the E. coli ampR gene as the most suitable RNAi control.

Dissection of schistosome tissues under LC-MS compatible preservative conditions for quantitative proteomics.

Schistosomes are blood flukes with specialised tissues and organs, each one playing a pivotal role in perpetuating the parasite life cycle. Herein, we describe a detailed methodology for preserving the proteome of adult Schistosoma mansoni worms during manual dissection for enrichment of tissues associated with the parasite's alimentary tract. We provide step-by-step directions for specimen storage and dissection while in preservative solution, tissue homogenisation, protein extraction and digestion using a methodology fully compatible with downstream quantitative liquid chromatography-mass spectrometry analysis. Our methodology uses label-free and QconCAT-based absolute quantification for detection of S. mansoni oesophageal gland products proposed as vaccine candidates. Through stabilisation of the proteome and minimising sample degradation during dissection our approach has allowed us to access the hidden proteome of target tissues not readily available from total lysates because of their small volume. This protocol can be replicated or adapted to other Schistosoma species lacking quantitative proteomics characterisation of specialised tissues for discovery of proteins with potential diagnostic and therapeutic utility.

Descriptive Analysis of Transient-State Observations for Thioredoxin/Glutathione Reductase (Sec597Cys) from Schistosoma mansoni.

Thioredoxin/glutathione reductase from Schistosoma mansoni (SmTGR) catalyzes the reduction of both oxidized thioredoxin and glutathione with electrons from reduced nicotinamide adenine dinucleotide phosphate (NADPH). SmTGR is a drug target for the treatment of Schistosomiasis, an infection caused by Schistosoma platyhelminths residing in the blood vessels of the host. Schistosoma spp. are reliant on TGR enzymes as they lack catalase and so use reduced thioredoxin and glutathione to regenerate peroxiredoxins consumed in the detoxification of reactive oxygen species. SmTGR is a flavin adenine dinucleotide (FAD)-dependent enzyme, and we have used the flavin as a spectrophotometric reporter to observe the movement of electrons within the enzyme. The data show that NADPH fractionally reduces the active site flavin with an observed rate constant estimated in this study to be ∼3000 s-1. The flavin then reoxidizes by passing electrons at a similar rate to the proximal Cys159-Cys154 disulfide pair. The dissociation of NADP+ occurs with a rate of ∼180 s-1, which induces the deprotonation of Cys159, and this coincides with the accumulation of an intense FAD-thiolate charge transfer band. It is proposed that the electrons then pass to the Cys596-Cys597 disulfide pair of the associated subunit in the dimer with a net rate constant of ∼2 s-1. (Note: Cys597 is Sec597 in wild-type (WT) SmTGR.) From this position, the electrons can be passed to oxidized thioredoxin or further into the protein to reduce the Cys28-Cys31 disulfide pair of the originating subunit of the dimer. From the Cys28-Cys31 center, electrons can then pass to oxidized glutathione that has a binding site directly adjacent.

Molecular characterization of thioester-containing proteins in Biomphalaria glabrata and their differential gene expression upon Schistosoma mansoni exposure.

Schistosomiasis is a disease caused by trematode parasites of the genus Schistosoma that affects approximately 200 million people worldwide. Schistosomiasis has been a persistent problem in endemic areas as there is no vaccine available, currently used anti-helmintic medications do not prevent reinfection, and most concerning, drug resistance has been documented in laboratory and field isolates. Thus, alternative approaches to curtail this human disease are warranted. Understanding the immunobiology of the obligate intermediate host of these parasites, which include the freshwater snail Biomphalaria glabrata, may facilitate the development of novel methods to stop or reduce transmission to humans. Molecules from the thioester-containing protein (TEP) superfamily have been shown to be involved in immunological functions in many animals including corals and humans. In this study we identified, characterized, and compared TEP transcripts and their expression upon S. mansoni exposure in resistant and susceptible strains of B. glabrata snails. Results showed the expression of 11 unique TEPs in B. glabrata snails. These transcripts present high sequence identity at the nucleotide and putative amino acid levels between susceptible and resistant strains. Further analysis revealed differences in several TEPs' constitutive expression levels between resistant and susceptible snail strains, with C3-1, C3-3, and CD109 having higher constitutive expression levels in the resistant (BS90) strain, whereas C3-2 and TEP-1 showed higher constitutive expression levels in the susceptible (NMRI) strain. Furthermore, TEP-specific response to S. mansoni miracidia exposure reiterated their differential expression, with resistant snails upregulating the expression of both TEP-4 and TEP-3 at 2 h and 48 h post-exposure, respectively. Further understanding the diverse TEP genes and their functions in invertebrate animal vectors will not only expand our knowledge in regard to this ancient family of immune proteins, but also offer the opportunity to identify novel molecular targets that could aid in the efforts to develop control methods to reduce schistosomiasis transmission.

Comparative proteome analysis of the tegument of male and female adult Schistosoma mansoni.

The tegument, as the surface layer of adult male and female Schistosoma spp. represents the protective barrier of the worms to the hostile environment of the host bloodstream. Here we present the first comparative analysis of sex-specific tegument proteins of paired or virgin Schistosoma mansoni. We applied a new and highly sensitive workflow, allowing detection of even low abundance proteins. Therefore, a streptavidin-biotin affinity purification technique in combination with single pot solid-phase enhanced sample preparation was established for subsequent LC-MS/MS analysis. We were able to identify 1519 tegument proteins for male and female virgin and paired worms and categorized them by sex. Bioinformatic analysis revealed an involvement of female-specific tegument proteins in signaling pathways of cellular processes and antioxidant mechanisms. Male-specific proteins were found to be enriched in processes linked to phosphorylation and signal transduction. This suggests a task sharing between the sexes that might be necessary for survival in the host. Our datasets provide a basis for further studies to understand and ultimately decipher the strategies of the two worm sexes to evade the immune system.

Inhibition of Schistosoma mansoni carbonic anhydrase by the antiparasitic drug clorsulon: X-ray crystallographic and in vitro studies.

Clorsulon is an anthelmintic drug that is clinically used against Fasciola hepatica. Due to the presence of two sulfonamide moieties in its core nucleus, which are well recognized as zinc-binding groups, it was proposed that it may be efficacious in the inhibition of parasite carbonic anhydrases (CAs). Proteomic analyses revealed the presence of CA in the tegument of Schistosoma mansoni, and recently the druggability of this target was explored by testing the inhibitory activities of several sulfonamide-based derivatives. According to the principles of drug repurposing, the aim was to demonstrate a putative new mechanism of action of clorsulon and thus widen its antiparasitic spectrum. For this purpose, the inhibitory activity and isoform selectivity of clorsulon was studied using human CA I and S. mansoni CA, revealing different modes of binding of clorsulon that explain its inhibitory potency against the two enzymes. The information obtained in this study could be crucial in the design of more active and selective derivatives.

Schistosome TRPML channels play a role in neuromuscular activity and tegumental integrity.

Schistosomiasis is a neglected tropical disease caused by parasitic flatworms of the genus Schistosoma. Mono-therapeutic treatment of this disease with the drug praziquantel, presents challenges such as inactivity against immature worms and inability to prevent reinfection. Importantly, ion channels are important targets for many current anthelmintics. Transient receptor potential (TRP) channels are important mediators of sensory signals with marked effects on cellular functions and signaling pathways. TRPML channels are a class of Ca2+-permeable TRP channels expressed on endolysosomal membranes. They regulate lysosomal function and trafficking, among other functions. Schistosoma mansoni is predicted to have a single TRPML gene (SmTRPML) with two splice variants differing by 12 amino acids. This study focuses on exploring the physiological properties of SmTRPML channels to better understand their role in schistosomes. In mammalian cells expressing SmTRPML, TRPML activators elicit a rise in intracellular Ca2+. In these cells, SmTRPML localizes both to lysosomes and the plasma membrane. These same TRPML activators elicit an increase in adult worm motility that is dependent on SmTRPML expression, indicating a role for these channels in parasite neuromuscular activity. Suppression of SmTRPML in adult worms, or exposure of adult worms to TRPML inhibitors, results in tegumental vacuolations, balloon-like surface exudates, and membrane blebbing, similar to that found following TRPML loss in other organisms. Together, these findings indicate that SmTRPML may regulate the function of the schistosome endolysosomal system. Further, the role of SmTRPML in neuromuscular activity and in parasite tegumental integrity establishes this channel as a candidate anti-schistosome drug target.

R-praziquantel integrated population pharmacokinetics in preschool- and school-aged African children infected with Schistosoma mansoni and S. haematobium and Lao adults infected with Opisthorchis viverrini.

Racemic praziquantel (PZQ) is the standard treatment for schistosomiasis and liver fluke infections (opisthorchiasis and clonorchiasis). The development of an optimal pediatric formulation and dose selection would benefit from a population pharmacokinetic (popPK) model. A popPK model was developed for R-PZQ, the active enantiomer of PZQ, in 664 subjects, 493 African children (2-15 years) infected with Schistosoma mansoni and S. haematobium, and 171 Lao adults (15-78 years) infected with Opisthorchis viverrini. Racemate tablets were administered as single doses of 20, 40 and 60 mg/kg in children and 30, 40 and 50 mg/kg in 129 adults, and as 3 × 25 mg/kg apart in 42 adults. Samples collected by the dried-blood-spot technique were assayed by LC-MS/MS. A two-compartment disposition model, with allometric scaling and dual first-order and transit absorption, was developed using Phoenix™ software. Inversely parallel functions of age described the apparent oral bioavailability (BA) and clearance maturation in children and ageing in adults. BA decreased slightly in children with dose increase, and by 35% in adults with multiple dosing. Crushing tablets for preschool-aged children increased the first-order absorption rate by 64%. The mean transit absorption time was 70% higher in children. A popPK model for R-PZQ integrated African children over 2 years of age with schistosomiasis and Lao adults with opisthorchiasis, and should be useful to support dose optimization in children. In vitro hepatic and intestinal metabolism data would help refining and validating the model in younger children as well as in target ethnic pediatric and adult groups.

Identification of potential inhibitors of Schistosoma mansoni purine nucleoside phosphorylase from neolignan compounds using molecular modelling approaches.

Schistosomiasis is a parasitic disease that is part of the neglected tropical diseases (NTDs), which cause significant levels of morbidity and mortality in millions of people throughout the world. The enzyme purine nucleoside phosphorylase from Schistosoma mansoni (SmPNP) represents a potential target for discovering new agents, and neolignans stand out as an important class of compounds. In this work, molecular modeling studies and biological assays of a set of neolignans were conducted against the PNP enzymes of the parasite and the human homologue (HssPNP). The results of the molecular docking described that the neolignans showed good complementarity by the active site of SmPNP. Molecular dynamics (MD) studies revealed that both complexes (Sm/HssPNP - neolignan compounds) were stable by analyzing the root mean square deviation (RMSD) values, and the binding free energy values suggest that the selected structures can interact and inhibit the catalytic activity of the SmPNP. Finally, the biological assay indicated that the selected neolignans presented a better molecular profile of inhibition compared to the human enzyme, as these ligands did not have the capacity to inhibit enzymatic activity, indicating that these compounds are promising candidates and that they can be used in future research in chemotherapy for schistosomiasis.Communicated by Ramaswamy H. Sarma.

The Schistosoma mansoni nuclear receptor FTZ-F1 maintains esophageal gland function via transcriptional regulation of meg-8.3.

Schistosomes infect over 200 million of the world's poorest people, but unfortunately treatment relies on a single drug. Nuclear hormone receptors are ligand-activated transcription factors that regulate diverse processes in metazoans, yet few have been functionally characterized in schistosomes. During a systematic analysis of nuclear receptor function, we found that an FTZ-F1-like receptor was essential for parasite survival. Using a combination of transcriptional profiling and chromatin immunoprecipitation (ChIP), we discovered that the micro-exon gene meg-8.3 is a transcriptional target of SmFTZ-F1. We found that both Smftz-f1 and meg-8.3 are required for esophageal gland maintenance as well as integrity of the worm's head. Together, these studies define a new role for micro-exon gene function in the parasite and suggest that factors associated with the esophageal gland could represent viable therapeutic targets.

Identification of novel modulators of a schistosome transient receptor potential channel targeted by praziquantel.

Given the worldwide burden of neglected tropical diseases, there is ongoing need to develop novel anthelmintic agents to strengthen the pipeline of drugs to combat these burdensome infections. Many diseases caused by parasitic flatworms are treated using the anthelmintic drug praziquantel (PZQ), employed for decades as the key clinical agent to treat schistosomiasis. PZQ activates a flatworm transient receptor potential (TRP) channel within the melastatin family (TRPMPZQ) to mediate sustained Ca2+ influx and worm paralysis. As a druggable target present in many parasitic flatworms, TRPMPZQ is a promising target for a target-based screening campaign with the goal of discovering novel regulators of this channel complex. Here, we have optimized methods to miniaturize a Ca2+-based reporter assay for Schistosoma mansoni TRPMPZQ (Sm.TRPMPZQ) activity enabling a high throughput screening (HTS) approach. This methodology will enable further HTS efforts against Sm.TRPMPZQ as well as other flatworm ion channels. A pilot screen of ~16,000 compounds yielded a novel activator of Sm.TRPMPZQ, and numerous potential blockers. The new activator of Sm.TRPMPZQ represented a distinct chemotype to PZQ, but is a known chemical entity previously identified by phenotypic screening. The fact that a compound prioritized from a phenotypic screening campaign is revealed to act, like PZQ, as an Sm.TRPMPZQ agonist underscores the validity of TRPMPZQ as a druggable target for antischistosomal ligands.

Fifty years of the schistosome tegument: discoveries, controversies, and outstanding questions.

The unique multilaminate appearance of the tegument surface of schistosomes was first described in 1973, in one of the earliest volumes of the International Journal for Parasitology. The present review, published almost 50 years later, traces the development of our knowledge of the tegument, starting with those earliest cytological advances, particularly the surface plasma membrane-membranocalyx complex, through an era of protein discovery to the modern age of protein characterization, aided by proteomics. More recently, analysis of single cell transcriptomes of schistosomes is providing insight into the organisation of the cell bodies that support the surface syncytium. Our understanding of the tegument, notably the nature of the proteins present within the plasma membrane and membranocalyx, has provided insights into how the schistosomes interact with their hosts but many aspects of how the tegument functions remain unanswered. Among the unresolved aspects are those concerned with maintenance and renewal of the surface membrane complex, and whether surface proteins and membrane components are recycled. Current controversies arising from investigations about whether the tegument is a source of extracellular vesicles during parasitism, and if it is covered with glycolytic enzymes, are evaluated in the light of cytological and proteomic knowledge of the layer.

Histone deacetylase 8 interacts with the GTPase SmRho1 in Schistosoma mansoni.

BACKGROUND: Schistosoma mansoni histone deacetylase 8 (SmHDAC8) has elicited considerable interest as a target for drug discovery. Invalidation of its transcripts by RNAi leads to impaired survival of the worms in infected mice and its inhibition causes cell apoptosis and death. To determine why it is a promising therapeutic target the study of the currently unknown cellular signaling pathways involving this enzyme is essential. Protein partners of SmHDAC8 were previously identified by yeast two-hybrid (Y2H) cDNA library screening and by mass spectrometry (MS) analysis. Among these partners we characterized SmRho1, the schistosome orthologue of human RhoA GTPase, which is involved in the regulation of the cytoskeleton. In this work, we validated the interaction between SmHDAC8 and SmRho1 and explored the role of the lysine deacetylase in cytoskeletal regulation. METHODOLOGY/PRINCIPAL FINDINGS: We characterized two isoforms of SmRho1, SmRho1.1 and SmRho1.2. Co- immunoprecipitation (Co-IP)/Mass Spectrometry (MS) analysis identified SmRho1 partner proteins and we used two heterologous expression systems (Y2H assay and Xenopus laevis oocytes) to study interactions between SmHDAC8 and SmRho1 isoforms. To confirm SmHDAC8 and SmRho1 interaction in adult worms and schistosomula, we performed Co-IP experiments and additionally demonstrated SmRho1 acetylation using a Nano LC-MS/MS approach. A major impact of SmHDAC8 in cytoskeleton organization was documented by treating adult worms and schistosomula with a selective SmHDAC8 inhibitor or using RNAi followed by confocal microscopy. CONCLUSIONS/SIGNIFICANCE: Our results suggest that SmHDAC8 is involved in cytoskeleton organization via its interaction with the SmRho1.1 isoform. The SmRho1.2 isoform failed to interact with SmHDAC8, but did specifically interact with SmDia suggesting the existence of two distinct signaling pathways regulating S. mansoni cytoskeleton organization via the two SmRho1 isoforms. A specific interaction between SmHDAC8 and the C-terminal moiety of SmRho1.1 was demonstrated, and we showed that SmRho1 is acetylated on K136. SmHDAC8 inhibition or knockdown using RNAi caused extensive disruption of schistosomula actin cytoskeleton.

Homology modelling, molecular dynamics simulation and docking evaluation of ß-tubulin of Schistosoma mansoni.

Schistosomiasis is one of the neglected diseases causing considerable morbidity and mortality throughout the world. Microtubules with its main component, tubulin play a vital role in helminthes including schistosomes. Benzimidazoles represent potential drug candidates by binding ß-tubulin. The study aimed to generate a homology model for the ß-tubulin of S. mansoni using the crystal structure of O visaries (Sheep) ß-tubulin (PDB ID: 3N2G D) as a template, then different ß-tubulin models were generated and two previously reported benzimidazole derivatives (NBTP-F and NBTP-OH) were docked to the generated models, the binding results indicated that both S. mansoni, S. haematobium were susceptible to the two NBTP derivatives. Additionally, three mutated versions of S. mansoni ß-tubulin wild-type were generated and the mutation (F185Y) seems to slightly enhance the ligand binding. Dynamics simulation experiments showed S. haematobium ß-tubulin is highly susceptible to the tested compounds; similar to S. mansoni, moreover, mutated models of S. mansoni ß-tubulin altered its NBTPs susceptibility. Moreover, additional seven new benzimidazole derivatives were synthesized and tested by molecular docking on the generated model binding site of S. mansoni ß-tubulin and were found to have good interaction inside the pocket.

Neurological impairment caused by Schistosoma mansoni systemic infection exhibits early features of idiopathic neurodegenerative disease.

Schistosomiasis, a neglected tropical disease caused by trematodes of the Schistosoma genus, affects over 250 million people around the world. This disease has been associated with learning and memory deficits in children, whereas reduced attention levels, impaired work capacity, and cognitive deficits have been observed in adults. Strongly correlated with poverty and lack of basic sanitary conditions, this chronic endemic infection is common in Africa, South America, and parts of Asia and contributes to inhibition of social development and low quality of life in affected areas. Nonetheless, studies on the mechanisms involved in the neurological impairment caused by schistosomiasis are scarce. Here, we used a murine model of infection with Schistosoma mansoni in which parasites do not invade the central nervous system to evaluate the consequences of systemic infection on neurologic function. We observed that systemic infection with S. mansoni led to astrocyte and microglia activation, expression of oxidative stress-induced transcription factor Nrf2, oxidative damage, Tau phosphorylation, and amyloid-ß peptide accumulation in the prefrontal cortex of infected animals. We also found impairment in spatial learning and memory as evaluated by the Morris water maze task. Administration of anthelmintic (praziquantel) and antioxidant (N-acetylcysteine plus deferoxamine) treatments was effective in inhibiting most of these phenotypes, and the combination of both treatments had a synergistic effect to prevent such changes. These data demonstrate new perspectives toward the understanding of the pathology and possible therapeutic approaches to counteract long-term effects of systemic schistosomiasis on brain function.