Echinococcus granulosus: heterogeneity and differential expression of superoxide dismutases

Assessment of oxidative stress and tissue damage in Echinococcus granulosus naturally infected bovine liver

Echinococcus granulosus is a zoonotic parasite infects many livestock species, especially cattle, sheep, goat and buffalo, causing cystic echinococcosis. The aim of this study was to demonstrate the presence of the parasite and parasitic tissue damage histopathologically and to determine the role of oxidative stress in the tissue damage through the immunohistochemical detection of the oxidative damage-marker malondialdehyde (MDA) and the antioxidant response-marker superoxide dismutase (SOD). The material of the study consisted of 20 liver samples with Echinococcus cysts and 10 E.granulosus- negative healthy liver samples obtained from different cattle at various times from slaughterhouses in Kırıkkale province, Turkey. Histopathologically, Echinococcus cysts of various sizes were observed along with the surrounding fibrous connective tissue. Giant cells, mononuclear cells, and eosinophilic leukocytes were found between the fibrous connective tissue and the cyst. In the parenchymal tissue distant from the cyst, inflammatory changes were observed, including vacuolation and necrosis in hepatocytes, congestion and dilation sinusoidal capillaries. Immunohistochemically, MDA immunopositivity was observed in both hepatocytes surrounding the cyst and areas distant from the cyst, while SOD immunopositivity was mainly detected in fibrous connective tissue and hepatocytes surrounding the Echinococcus cysts. A significant increase in MDA immunoreactivity was observed in E.granulosus s.l.-infected livers. Although no statistically significant change was observed in SOD immunopositivity in the liver tissues with cystic echinococcosis, regional variations were noted. Germinal layer (GL) of Echinococcus cyst showed immunopositive staining for MDA, while laminated layer (LL) exhibited immunonegative staining. To the authors' best understanding, this study represents a pioneering effort in showcasing and evaluating the immunoreactivities of MDA and SOD within the liver tissue afflicted with Echinococcus cysts. Simultaneously, the examination extends to encompass tissue damage and the infiltration of inflammatory cells. This study highlights the role of oxidative stress in the pathogenesis of Cystic Echinococcosis (CE) and the need for further investigation of antioxidant defense mechanisms and their regional variations.

Unraveling oxidative stress response in the cestode parasite Echinococcus granulosus

Cystic hydatid disease (CHD) is a worldwide neglected zoonotic disease caused by Echinococcus granulosus. The parasite is well adapted to its host by producing protective molecules that modulate host immune response. An unexplored issue associated with the parasite's persistence in its host is how the organism can survive the oxidative stress resulting from parasite endogenous metabolism and host defenses. Here, we used hydrogen peroxide (H₂O₂) to induce oxidative stress in E. granulosus protoescoleces (PSCs) to identify molecular pathways and antioxidant responses during H₂O₂ exposure. Using proteomics, we identified 550 unique proteins; including 474 in H₂O₂-exposed PSCs (H-PSCs) samples and 515 in non-exposed PSCs (C-PSCs) samples. Larger amounts of antioxidant proteins, including GSTs and novel carbonyl detoxifying enzymes, such as aldo-keto reductase and carbonyl reductase, were detected after H₂O₂ exposure. Increased concentrations of caspase-3 and cathepsin-D proteases and components of the 26S proteasome were also detected in H-PSCs. Reduction of lamin-B and other caspase-substrate, such as filamin, in H-PSCs suggested that molecular events related to early apoptosis were also induced. We present data that describe proteins expressed in response to oxidative stress in a metazoan parasite, including novel antioxidant enzymes and targets with potential application to treatment and prevention of CHD.

Praziquantel induced oxidative stress and apoptosis-like cell death in Raillietina echinobothrida

Praziquantel (PZQ) is an anthelmintic drug used against trematode and cestode parasites of humans and veterinary animals. Since praziquantel was introduced as a broadspectrum anthelmintic, numerous studies described its successful use against helminth parasites, but its exact mechanism of action is feebly understood. Therefore, the present study was carried out to evaluate the possible role of PZQ induced oxidative stress in apoptosis-like cell death in the poultry tapeworm Raillietina echinobothrida. Parasite viability assay revealed a time-dependent reduction in the worm viability compared to the control. Transmission electron microscopy showed typical apoptotic features like condensed nucleus, damaged nuclear envelope and altered mitochondrial membrane in PZQ exposed parasites. Results revealed chromatin condensation and DNA fragmentation in PZQ exposed parasites. There was a notable decline in the level of glutathione and glutathione-s-transferase activity leading to the augmented generation of reactive oxygen species. This led to the alterations in the mitochondrial membrane potential with increased active caspase-3/7, confirms the involvement of mitochondria in the event. The present study suggests that PZQ exerts oxidative stress leading to apoptosis-like events in the parasites resulting their death.

A transcriptomic analysis of Echinococcus granulosus larval stages: implications for parasite biology and host adaptation

Background

The cestode Echinococcus granulosus - the agent of cystic echinococcosis, a zoonosis affecting humans and domestic animals worldwide - is an excellent model for the study of host-parasite cross-talk that interfaces with two mammalian hosts. To develop the molecular analysis of these interactions, we carried out an EST survey of E. granulosus larval stages. We report the salient features of this study with a focus on genes reflecting physiological adaptations of different parasite stages.

Methodology/Principal Findings

We generated ∼10,000 ESTs from two sets of full-length enriched libraries (derived from oligo-capped and trans-spliced cDNAs) prepared with three parasite materials: hydatid cyst wall, larval worms (protoscoleces), and pepsin/H⁺-activated protoscoleces. The ESTs were clustered into 2700 distinct gene products. In the context of the biology of E. granulosus, our analyses reveal: (i) a diverse group of abundant long non-protein coding transcripts showing homology to a middle repetitive element (EgBRep) that could either be active molecular species or represent precursors of small RNAs (like piRNAs); (ii) an up-regulation of fermentative pathways in the tissue of the cyst wall; (iii) highly expressed thiol- and selenol-dependent antioxidant enzyme targets of thioredoxin glutathione reductase, the functional hub of redox metabolism in parasitic flatworms; (iv) candidate apomucins for the external layer of the tissue-dwelling hydatid cyst, a mucin-rich structure that is critical for survival in the intermediate host; (v) a set of tetraspanins, a protein family that appears to have expanded in the cestode lineage; and (vi) a set of platyhelminth-specific gene products that may offer targets for novel pan-platyhelminth drug development.

Conclusions/Significance

This survey has greatly increased the quality and the quantity of the molecular information on E. granulosus and constitutes a valuable resource for gene prediction on the parasite genome and for further genomic and proteomic analyses focused on cestodes and platyhelminths.

Cestodes are a neglected group of platyhelminth parasites, despite causing chronic infections to humans and domestic animals worldwide. We used Echinococcus granulosus as a model to study the molecular basis of the host-parasite cross-talk during cestode infections. For this purpose, we carried out a survey of the genes expressed by parasite larval stages interfacing with definitive and intermediate hosts. Sequencing from several high quality cDNA libraries provided numerous insights into the expression of genes involved in important aspects of E. granulosus biology, e.g. its metabolism (energy production and antioxidant defences) and the synthesis of key parasite structures (notably, the one exposed to humans and livestock intermediate hosts). Our results also uncovered the existence of an intriguing set of abundant repeat-associated non-protein coding transcripts that may participate in the regulation of gene expression in all surveyed stages. The dataset now generated constitutes a valuable resource for gene prediction on the parasite genome and for further genomic and proteomic studies focused on cestodes and platyhelminths. In particular, the detailed characterization of a range of newly discovered genes will contribute to a better understanding of the biology of cestode infections and, therefore, to the development of products allowing their efficient control.

Enzymatic antioxidant systems in helminth parasites

Parasitic helminths have a coexistence with mammalian hosts whereby they survive for several years in known hostile conditions of their hosts. Many explanations exist describing how these parasitic helminths are able to survive. In the last years, a lot of studies have focused on both enzymatic and non-enzymatic antioxidant systems now shown to exist in these parasites and which may serve as defence tactics against the host-generated oxygen radicals. The relevance of antioxidant enzymes is confirmed by the fact that some of these molecules represent putative protective anti-parasite vaccines (i.e. in schistosomiasis). This review tries to compile what is known to date of the enzymatic antioxidant systems in selected parasitic helminths.

DNA damage, RAD9 and fertility/infertility of Echinococcus granulosus hydatid cysts

Hydatidosis, caused by the larval stage of the platyhelminth parasite Echinococcus granulosus, affects human and animal health. Hydatid fertile cysts are formed in intermediate hosts (human and herbivores) producing protoscoleces, the infective form to canines, at their germinal layers. Infertile cysts are also formed, but they are unable to produce protoscoleces. The molecular mechanisms involved in hydatid cysts fertility/infertility are unknown. Nevertheless, previous work from our laboratory has suggested that apoptosis is involved in hydatid cyst infertility and death. On the other hand, fertile hydatid cysts can resist oxidative damage due to reactive oxygen and nitrogen species. On these foundations, we have postulated that when oxidative damage of DNA in the germinal layers exceeds the capability of DNA repair mechanisms, apoptosis is triggered and hydatid cysts infertility occurs. We describe a much higher percentage of nuclei with oxidative DNA damage in dead protoscoleces and in the germinal layer of infertile cysts than in fertile cysts, suggesting that DNA repair mechanisms are active in fertile cysts. rad9, a conserved gene, plays a key role in cell cycle checkpoint modulation and DNA repair. We found that RAD9 of E. granulosus (EgRAD9) is expressed at the mRNA and protein levels. As it was found in other eukaryotes, EgRAD9 is hyperphosphorylated in response to DNA damage. Our results suggest that molecules involved in DNA repair in the germinal layer of fertile hydatid cysts and in protoscoleces, such as EgRAD9, may allow preserving the fertility of hydatid cysts in the presence of ROS and RNS.

Activity of antioxidative defense enzymes in the blood of patients with liver echinococcosis

Background/Aim. Chronic echinococcocal disease is the parasite human disease caused by the penetration of larval (asexual) stages of the canine tapeworm (Echinococcus granulosus) in the liver of humans. After the penetration of the parasite, the host organism react by activating complement- depending immune response. The aim of this study was to elucidate the influence of larval form of Echinococcus granulosus in the liver on the activity of antioxidative defense enzymes in the blood of patients before and after the surgical intervention. Methods. We investigated the activity of antioxidative defense enzymes: copper/zinc containing superoxide dismutase (CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) in the blood of patients before and after the surgical intervention in respect to the controls, clinically healthy persons. Results. Our results showed that the activity of the GSH-Px was significantly decreased in the plasma of the patients with echinocococal disease before the surgery in respect to the controls. The activity of GST was significantly higher in the blood of the patients after the surgery in comparison to the controls. Conclusion. Chronic liver echinoccocal disease caused significant changes of some antioxidative defense enzymes, first of all Se-dependent enzyme GSH-Px, which could be a suitabile biomarker in the biochemical evaluation of the disease. This work represents a first comprehensive study of the activity of antioxidative defense enzymes in cronic liver echinococcocosis in the patients before and after the surgical intervention in respect to the clinically healthy persons.

Unusual electrophoretic patterns for phosphoglucomutase and fumarase in a population of Lecithochirium rufoviride (Trematoda: Hemiuridae), a parasite of Conger conger

Electrophoretic analyses of phosphoglucomutase (PGM) and fumarase (FH) in a population of Lecithochirium rufoviride parasitizing Conger conger, revealed 2 independent activity zones for each enzyme on starch gel electrophoresis. However, some individuals exhibited only 1 activity zone for 1 or both enzymes. The banding patterns observed strongly suggest that (1) PGM is coded by 2 polymorphic loci, Pgm-1 (expressed in all individuals) with allelic frequencies not significantly different from those expected under Hardy-Weinberg equilibrium, and Pgm-2 (expressed in a subset of individuals); and (2) FH is coded by 2 loci, Fh-2 (monomorphic and expressed in all individuals) and Fh-1 (expressed in a subset of individuals). A high degree of concordance (88.75%) was observed between the expression and nonexpression of Pgm-2 and Fh-1. The most likely explanations for these findings are either variation in enzyme expression with developmental stage or the presence of null alleles at high frequencies in the population.