Purification and characterization of Taenia crassiceps cysticerci thioredoxin: insight into thioredoxin-glutathione-reductase (TGR) substrate recognition

A Physiological Approach to Explore How Thioredoxin-Glutathione Reductase (TGR) and Peroxiredoxin (Prx) Eliminate H2O2 in Cysticerci of Taenia

Peroxiredoxins (Prxs) and glutathione peroxidases (GPxs) are the main enzymes of the thiol-dependent antioxidant systems responsible for reducing the H2O2 produced via aerobic metabolism or parasitic organisms by the host organism. These antioxidant systems maintain a proper redox state in cells. The cysticerci of Taenia crassiceps tolerate millimolar concentrations of this oxidant. To understand the role played by Prxs in this cestode, two genes for Prxs, identified in the genome of Taenia solium (TsPrx1 and TsPrx3), were cloned. The sequence of the proteins suggests that both isoforms belong to the class of typical Prxs 2-Cys. In addition, TsPrx3 harbors a mitochondrial localization signal peptide and two motifs (-GGLG- and -YP-) associated with overoxidation. Our kinetic characterization assigns them as thioredoxin peroxidases (TPxs). While TsPrx1 and TsPrx3 exhibit the same catalytic efficiency, thioredoxin-glutathione reductase from T. crassiceps (TcTGR) was five and eight times higher. Additionally, the latter demonstrated a lower affinity (>30-fold) for H2O2 in comparison with TsPrx1 and TsPrx3. The TcTGR contains a Sec residue in its C-terminal, which confers additional peroxidase activity. The aforementioned aspect implies that TsPrx1 and TsPrx3 are catalytically active at low H2O2 concentrations, and the TcTGR acts at high H2O2 concentrations. These results may explain why the T. crassiceps cysticerci can tolerate high H2O2 concentrations.

Evaluation of recombinant glutathione transferase 26 kDa, thioredoxin-1, and endophilin B1 of Taenia solium in the diagnosis of human neurocysticercosis

Neurocysticercosis caused by Taenia solium larvae is a neglected disease that persists in several countries, including Mexico, and causes a high disability-adjusted life year burden. Neuroimaging tools such as computed tomography and magnetic resonance imaging are the most efficient for its detection, but low availability and high costs in most endemic regions limit their use. Serological methods such as lentil lectin-purified glycoprotein enzyme-linked immunoelectrotransfer blot antibody detection and monoclonal antibody-based enzyme-linked immunosorbent assays for HP10 antigen detection have been useful in supporting the diagnosis of this disease. We evaluated three T. solium recombinant antigens: glutathione transferase of 26 kDa (Ts26GST); thioredoxin-1 (TsTrx-1), and endophilin B1 (TsMEndoB1) by EITB. These are antigenic proteins antigenic, abundant in excretion/secretion products of the parasite, and do not cross-react with homologous host proteins. Ts26GST and TsTrx-1 showed sensitivity of 79 and 88%, specificity of 86 and 97%, PPV of 83 and 97% and NPV of 82 and 91%, respectively, for neurocysticercosis diagnosis. The recombinant antigens allowed the diagnosis of 70% (Ts26GST) and 80% (TsTrx-1) of patients having only one cysticercus. Further studies on specific regions of these proteins could improve T. solium diagnostics.

Cloning and characterization of Thioredoxin 1 from the Cnidarian Hydra

Thioredoxins, small disulphide-containing redox proteins, play an important role in the regulation of cellular thiol redox balance through their disulfide reductase activity. In this study, we have identified, cloned, purified and characterized thioredoxin 1 (HvTrx1) from the Cnidarian Hydra vulgaris Ind-Pune. Bioinformatics analysis revealed that HvTrx1 contains an evolutionarily conserved catalytic active site CGPC and shows a closer phylogenetic relationship with vertebrate Trx1. Optimum pH and temperature for enzyme activity of purified HvTrx1 was found to be pH 7.0 and 25 °C respectively. Enzyme activity decreased significantly at acidic or alkaline pH as well as at higher temperatures. HvTrx1 was found to be expressed ubiquitously in whole mount in situ hybridization. Treatment of Hydra with hydrogen peroxide (H2O2), a highly reactive oxidizing agent, led to a significant increase in gene expression and enzyme activity of Trx1. Further experiments using PX12, an inhibitor of Trx1, indicated that Trx1 plays an important role in regeneration in Hydra. Finally, by using growth assay in E. coli and wound healing assay in human colon cancer cells, we demonstrate that HvTrx1 is functionally active in both prokaryotic and eukaryotic heterologous systems.

Protein expression profile of Taenia crassiceps cysticerci related to Th1- and Th2-type responses in the mouse cysticercosis model

The intraperitoneal cysticercosis model with the Taenia crassiceps ORF strain in female BALB/cAnN mice has been widely used to study the immune response in cysticercosis. During early infection (2 weeks), the host develops a non-permissive Th1 response, whereas during late infection (8 weeks), molecules from the cysticerci induce a Th2 response that is permissive to parasite growth. The modulation of the Th2 response is induced by molecules excreted/secreted by the larval stage of the parasite. However, there is limited information regarding the response of cysticerci to the mouse immunological environment during infection. The proteomic profiles in T. crassiceps ORF cysticerci when faced with the mouse Th1 and Th2 responses were analyzed through two-dimensional gel electrophoresis (2DE), and the differential expression of proteins was evaluated. Thirteen proteins, whose differential expression varied between 70% and 100%, were selected randomly. Protein identification by MALDI-TOF MS and BLAST showed that the proteins were related to folding, signaling, enzymatic activities, cell-movement regulation, cell-cell interactions, motility, carbohydrate metabolism, detoxification, and redox regulation processes. Notably, some of the proteins can act as antigenic-protective molecules and elicit a weak Th1 response; however, most are involved in the avoidance of the immune system, which leads to a Th2 response, or apoptosis. The findings indicate the process by which T. crassiceps cysticerci responds based on the host environment and provides novel insights into the mechanism by which this facilitates its establishment and persistence in the mouse. Furthermore, these proteins could be used as targets for drug and vaccine development.

The Architecture of Thiol Antioxidant Systems among Invertebrate Parasites

The use of oxygen as the final electron acceptor in aerobic organisms results in an improvement in the energy metabolism. However, as a byproduct of the aerobic metabolism, reactive oxygen species are produced, leaving to the potential risk of an oxidative stress. To contend with such harmful compounds, living organisms have evolved antioxidant strategies. In this sense, the thiol-dependent antioxidant defense systems play a central role. In all cases, cysteine constitutes the major building block on which such systems are constructed, being present in redox substrates such as glutathione, thioredoxin, and trypanothione, as well as at the catalytic site of a variety of reductases and peroxidases. In some cases, the related selenocysteine was incorporated at selected proteins. In invertebrate parasites, antioxidant systems have evolved in a diversity of both substrates and enzymes, representing a potential area in the design of anti-parasite strategies. The present review focus on the organization of the thiol-based antioxidant systems in invertebrate parasites. Differences between these taxa and its final mammal host is stressed. An understanding of the antioxidant defense mechanisms in this kind of parasites, as well as their interactions with the specific host is crucial in the design of drugs targeting these organisms.