Reflections on the biochemistry of Echinococcus: past, present and future

Anti-parasitic effects of resveratrol on protoscolices and hydatid cyst layers

The main goal of the current study was to evaluate the effectiveness of resveratrol (RESV) on protoscolices and hydatid cysts of Echinococcus granolosus. Echinococcus granolosus protoscolices and hydatid cyst were exposed to RPMI, DMSO, formalin, mebendazole, and different concentrations of RESV in vitro. Then, viability, GGT, and caspase-3 activity of protoscolices were evaluated using light microscopy, colorimetric, and enzymatic assay, respectively. Tissue changes and expression of caspase-3 apoptosis were analyzed on the hydatid cyst wall by histologic and immunohistochemistry methods. The cell toxicity effect of RESV was evaluated on mouse PBMCs by Annexin V-FITC assay. The RESV-treated protoscolices showed loss of viability, increased gamma-glutamyl transpeptidase, and caspase-3 activity with significant differences compared to all control groups (P < 0.05). Dose and time dependence of mortality, GGT, and caspase-3 enzymatic activity was confirmed in the protoscolices of Echinococcus granulosus treated by RESV. Also, the tissue changes and apoptosis were prominent in RESV-treated hydatid cyst layers; however, tissue changes were only time-dependent, and RESV concentration had no apparent effect on tissue. In cell toxicity evaluation, RESV is safe without any significant apoptosis induction from 31.5 to 250 μg/ml; however, it was significant at 350 and 500 μg/ml in PBMCs.

Molecular Characterization and Haplotype Analyses of Lung Hydatid Cyst Isolates of Cattle and First Report of Echinococcus canadensis (G6/G7) in Cattle Isolates in Turkey

PURPOSE

Cystic echinococcosis (CE) is a zoonotic disease, caused by parasite known as Echinococcus granulosus sensu lato complex, leading to substantial economic losses in rural areas with public health problems. This study was carried out to understand the haplotypic profiles of the partial mitochondrial cytochrome c oxidase (mt-CO1) gene of cattle lung hydatid cyst samples which were obtained from two provinces in Turkey.

METHODS

In this study, forty (n = 40) hydatid cyst samples from the lungs of slaughtered cattle were obtained. The germinal layers were taken separately for each individual cyst then stored in 70% ethanol. From each individual cyst sample, total genomic DNA was extracted. Amplification of the partial mt-CO1 gene (875 bp) was performed using a specific primer set by PCR, and then, the amplicons were sequenced. All sequences were analyzed individually, followed by alignment, and haplotype and phylogenetic analyses were then performed.

RESULTS

By the sequence alignment process, 39 out of the 40 sequences were characterized as E. granulosus sensu stricto. However, one of them was matched with E. canadensis (G6/G7). The haplotype analyses of the E. granulosus s.s. isolates were arranged in a star-like orientation with a main haplotype, which was separated from other haplotypes by 1-10 mutation steps, and 26 haplotypes were identified. In the mt-CO1 sequences, 29 polymorphic sites were determined, and 34.5% (10/29) of them were parsimony informative.

CONCLUSIONS

The findings of this study provide the first report of E. canadensis (G6/G7 genotype) among cattle in Turkey.

Identification of Newly Synthesized Proteins by Echinococcus granulosus Protoscoleces upon Induction of Strobilation

Background

The proteins responsible for the key molecular events leading to the structural changes between the developmental stages of Echinococcus granulosus remain unknown. In this work, azidohomoalanine (AHA)-specific labeling was used to identify proteins expressed by E. granulosus protoscoleces (PSCs) upon the induction of strobilar development.

Methodology/Principal Findings

The in vitro incorporation of AHA with different tags into newly synthesized proteins (NSPs) by PSCs was analyzed using SDS-PAGE and confocal microscopy. The LC-MS/MS analysis of AHA-labeled NSPs by PSCs undergoing strobilation allowed for the identification of 365 proteins, of which 75 were differentially expressed in comparison between the presence or absence of strobilation stimuli and 51 were expressed exclusively in either condition. These proteins were mainly involved in metabolic, regulatory and signaling processes.

Conclusions/Significance

After the controlled-labeling of proteins during the induction of strobilar development, we identified modifications in protein expression. The changes in the metabolism and the activation of control and signaling pathways may be important for the correct parasite development and be target for further studies.

In the life cycle of the parasite Echinococcus granulosus, hydatid cysts produce the pre-adult form, which has the ability to either differentiate into an adult worm (strobilation) or dedifferentiate into a secondary hydatid cyst. We used different protein tags that allowed for the visualization and purification of proteins produced specifically after the induction of strobilar development to identify proteins that might be involved in this process (temporally controlled and context-dependent). As a result, we found proteins that are involved in important processes during development, such as energy metabolism, control pathways and cellular communication. We believe that these results will be useful for the development of scientific approaches to controlling and preventing cystic hydatid disease.

In Vitro Anti-Echinococcal and Metabolic Effects of Metformin Involve Activation of AMP-Activated Protein Kinase in Larval Stages of Echinococcus granulosus

Metformin (Met) is a biguanide anti-hyperglycemic agent, which also exerts antiproliferative effects on cancer cells. This drug inhibits the complex I of the mitochondrial electron transport chain inducing a fall in the cell energy charge and leading 5'-AMP-activated protein kinase (AMPK) activation. AMPK is a highly conserved heterotrimeric complex that coordinates metabolic and growth pathways in order to maintain energy homeostasis and cell survival, mainly under nutritional stress conditions, in a Liver Kinase B1 (LKB1)-dependent manner. This work describes for the first time, the in vitro anti-echinococcal effect of Met on Echinococcus granulosus larval stages, as well as the molecular characterization of AMPK (Eg-AMPK) in this parasite of clinical importance. The drug exerted a dose-dependent effect on the viability of both larval stages. Based on this, we proceeded with the identification of the genes encoding for the different subunits of Eg-AMPK. We cloned one gene coding for the catalytic subunit (Eg-ampkɑ) and two genes coding for the regulatory subunits (Eg-ampkβ and Eg-ampkγ), all of them constitutively transcribed in E. granulosus protoscoleces and metacestodes. Their deduced amino acid sequences show all the conserved functional domains, including key amino acids involved in catalytic activity and protein-protein interactions. In protoscoleces, the drug induced the activation of AMPK (Eg-AMPKɑ-P¹⁷⁶), possibly as a consequence of cellular energy charge depletion evidenced by assays with the fluorescent indicator JC-1. Met also led to carbohydrate starvation, it increased glucogenolysis and homolactic fermentation, and decreased transcription of intermediary metabolism genes. By in toto immunolocalization assays, we detected Eg-AMPKɑ-P¹⁷⁶ expression, both in the nucleus and the cytoplasm of cells as in the larval tegument, the posterior bladder and the calcareous corpuscles of control and Met-treated protoscoleces. Interestingly, expression of Eg-AMPKɑ was observed in the developmental structures during the de-differentiation process from protoscoleces to microcysts. Therefore, the Eg-AMPK expression during the asexual development of E. granulosus, as well as the in vitro synergic therapeutic effects observed in presence of Met plus albendazole sulfoxide (ABZSO), suggest the importance of carrying out chemoprophylactic and clinical efficacy studies combining Met with conventional anti-echinococcal agents to test the potential use of this drug in hydatidosis therapy.

Echinococcus granulosus tegumental enzymes as in vitro markers of pharmacological damage: a biochemical and molecular approach

Cystic echinococcosis is a chronic, complex, and neglected disease. Novel therapeutical tools are needed to optimize human treatment. A number of compounds have been investigated, either using in vitro cultured parasites and/or applying in vivo rodent models. Although some of these compounds showed promising activities in vitro, and to some extent also in the rodent models, they have not been translated into clinical applications. Membrane enzyme activities in culture supernatants of treated protoscoleces with calcium modulator drugs and anthelmintic drugs were measured and provided an indication of compound efficacy. This work describes for the first time the detection of alkaline phosphatase, gamma-glutamyl-transpeptidase and acetylcholinesterase activities in supernatants of in vitro treated Echinococcus granulosus protoscoleces. Marked differences on the enzymatic activities in supernatants from drug treated cultures were detected. We demonstrated that those genes that show the highest degree of conservation when compared to orthologs, are constitutively and highly expressed in protoscoleces and metacestodes. Due to high sensibility and the lack of activity in supernatants of intact protoscoleces, gamma-glutamyl-transpeptidase is proposed as the ideal viability marker during in vitro pharmacological studies against E. granulosus protoscoleces.

Host-parasite relationship in cystic echinococcosis: an evolving story

The larval stage of Echinococcus granulosus causes cystic echinococcosis, a neglected infectious disease that constitutes a major public health problem in developing countries. Despite being under constant barrage by the immune system, E. granulosus modulates antiparasite immune responses and persists in the human hosts with detectable humoral and cellular responses against the parasite. In vitro and in vivo immunological approaches, together with molecular biology and immunoproteomic technologies, provided us exciting insights into the mechanisms involved in the initiation of E. granulosus infection and the consequent induction and regulation of the immune response. Although the last decade has clarified many aspects of host-parasite relationship in human cystic echinococcosis, establishing the full mechanisms that cause the disease requires more studies. Here, we review some of the recent developments and discuss new avenues in this evolving story of E. granulosus infection in man.

Hepatic gene expression profile in mice perorally infected with Echinococcus multilocularis eggs

Background

Alveolar echinococcosis (AE) is a severe chronic hepatic parasitic disease currently emerging in central and eastern Europe. Untreated AE presents a high mortality (>90%) due to a severe hepatic destruction as a result of parasitic metacestode proliferation which behaves like a malignant tumor. Despite this severe course and outcome of disease, the genetic program that regulates the host response leading to organ damage as a consequence of hepatic alveolar echinococcosis is largely unknown.

Methodology/Principal Findings

We used a mouse model of AE to assess gene expression profiles in the liver after establishment of a chronic disease status as a result of a primary peroral infection with eggs of the fox tapeworm Echinococcus multilocularis. Among 38 genes differentially regulated (false discovery rate adjusted p≤0.05), 35 genes were assigned to the functional gene ontology group <immune response>, while 3 associated with the functional group <intermediary metabolism>. Upregulated genes associated with <immune response> could be clustered into functional subgroups including <macrophages>, <APCs>, <lymphocytes, chemokines and regulation>, <B-cells> and <eosinophils>. Two downregulated genes related to <lymphocytes, chemokines and regulation> and <intermediary metabolism>, respectively. The <immune response> genes either associated with an <immunosupression> or an <immunostimulation> pathway. From the overexpressed genes, 18 genes were subsequently processed with a Custom Array microfluidic card system in order to assess respective expression status at the mRNA level relative to 5 reference genes (Gapdh, Est1, Rlp3, Mdh-1, Rpl37) selected upon a constitutive and stable expression level. The results generated by the two independent tools used for the assessment of gene expression, i.e., microarray and microfluidic card system, exhibited a high level of congruency (Spearman correlation rho = 0.81, p = 7.87e-5) and thus validated the applied methods.

Conclusions/Significance

Based on this set of biomarkers, new diagnostic targets have been made available to predict disease status and progression. These biomarkers may also offer new targets for immuno-therapeutic intervention.