Secretion of Thioredoxin Peroxidase Protein of Cat Liver Fluke Opisthorchis felineus during Modeling of Experimental Opisthorchiasis

Proteomic characterization of Opisthorchis felineus exosome-like vesicles and their uptake by human cholangiocytes

The epidemiologically important food-borne trematode Opisthorchis felineus infests the liver biliary tract of fish-eating mammals and causes disorders, including bile duct neoplasia. Many parasitic species release extracellular vesicles (EVs) that mediate host-parasite interaction. Currently, there is no information on O. felineus EVs. Using gel electrophoresis followed by liquid chromatography coupled with tandem mass spectrometry, we aimed to characterize the proteome of EVs released by the adult O. felineus liver fluke. Differential abundance of proteins between whole adult worms and EVs was assessed by semiquantitative iBAQ (intensity-based absolute quantification). Imaging, flow cytometry, inhibitor assays, and colocalization assays were performed to monitor the uptake of the EVs by H69 human cholangiocytes. The proteomic analysis reliably identified 168 proteins (at least two peptides matched a protein). Among major proteins of EVs were ferritin, tetraspanin CD63, helminth defense molecule 1, globin 3, saposin B type domain-containing protein, 60S ribosomal protein, glutathione S-transferase GST28, tubulin, and thioredoxin peroxidase. Moreover, as compared to the whole adult worm, EVs proved to be enriched with tetraspanin CD63, saposin B, helminth defense molecule 1, and Golgi-associated plant pathogenesis-related protein 1 (GAPR1). We showed that EVs are internalized by human H69 cholangiocytes via clathrin-dependent endocytosis, whereas phagocytosis and caveolin-dependent endocytosis do not play a substantial role in this process. Our study describes for the first time proteomes and differential abundance of proteins in whole adult O. felineus worms and EVs released by this food-borne trematode. Studies elucidating the regulatory role of individual components of EVs of liver flukes should be continued to determine which components of EV cargo play the most important part in the pathogenesis of fluke infection and in a closely linked pathology: bile duct neoplasia. SIGNIFICANCE: The food-borne trematode Opisthorchis felineus is a pathogen that causes hepatobiliary disorders in humans and animals. Our study describes for the first time the release of EVs by the liver fluke O. felineus, their microscopic and proteomic characterization, and internalization pathways by human cholangiocytes. Differential abundance of proteins between whole adult worms and EVs was assessed. EVs are enriched with canonical EV markers as well as parasite specific proteins, i.e. tetraspanin CD63, saposin B, helminth defense molecule 1, and others. Our findings will form the basis of the search for potential immunomodulatory candidates with therapeutic potential in the context of inflammatory diseases, as well as novel vaccine candidates.

Wound healing approach based on excretory-secretory product and lysate of liver flukes

Exogenous bioactive peptides are considered promising for the wound healing therapy in humans. In this regard, parasitic trematodes proteins may potentially become a new perspective agents. Foodborne trematode Opisthorchis felineus is widespread in Europe and has the ability to stimulate proliferation of bile duct epithelium. In this study, we investigated skin wound healing potential of O. felineus proteins in mouse model. C57Bl/6 mice were inflicted with superficial wounds with 8 mm diameter. Experimental groups included several non-specific controls and specific treatment groups (excretory-secretory product and lysate). After 10 days of the experiment, the percentage of wound healing in the specific treatment groups significantly exceeded the control values. We also found that wound treatment with excretory-secretory product and worm lysate resulted in: (i) inflammation reducing, (ii) vascular response modulating, (iii) type 1 collagen deposition promoting dermal ECM remodeling. An additional proteomic analysis of excretory-secretory product and worm lysate samples was revealed 111 common proteins. The obtained data indicate a high wound-healing potential of liver fluke proteins and open prospects for further research as new therapeutic approaches.

Similarities and differences among the Opisthorchiidae liver flukes: insights from Opisthorchis felineus

The foodborne liver trematode Opisthorchis felineus (Rivolta, 1884) is a member of the triad of phylogenetically related epidemiologically important Opisthorchiidae trematodes, which also includes O. viverrini (Poirier, 1886) and Clonorchis sinensis (Loos, 1907). Despite similarity in the life cycle, Opisthorchiidae liver flukes also have marked differences. Two species (O. viverrini and C. sinensis) are recognized as Group 1A biological carcinogens, whereas O. felineus belongs to Group 3A. In this review, we focus on these questions: Are there actual differences in carcinogenicity among these 3 liver fluke species? Is there an explanation for these differences? We provide a recent update of our knowledge on the liver fluke O. felineus and highlight its differences from O. viverrini and C. sinensis. In particular, we concentrate on differences in the climate of endemic areas, characteristics of the life cycle, the range of intermediate hosts, genomic and transcriptomic features of the pathogens, and clinical symptoms and morbidity of the infections in humans. The discussion of these questions can stimulate new developments in comparative studies on the pathogenicity of liver flukes and should help to identify species-specific features of opisthorchiasis and clonorchiasis pathogenesis.

Global changes in gene expression related to Opisthorchis felineus liver fluke infection reveal temporal heterogeneity of a mammalian host response

The food-borne trematode Opisthorchis felineus colonizes bile ducts of the liver of fish-eating mammals including humans. Among chronically infected individuals, this opisthorchiasis involves hepatobiliary problems, including chronic inflammation, periductal fibrosis, biliary intraepithelial neoplasia, and even cholangiocarcinoma. Despite numerous studies at the pathomorphological level, the systemic response and cellular pathogenesis of these disorders are not well studied.

To conduct in-depth research and to gain insights into the mechanism by which O. felineus infection causes precancerous liver lesions, we (i) applied a next-generation-sequencing–based technology (high-throughput mRNA sequencing) to identify differentially expressed genes in the liver of golden hamsters infected with O. felineus at 1 and 3 months postinfection and (ii) verified the most pronounced changes in gene expression by western blotting and immunohistochemistry.

A total of 2151 genes were found to be differentially expressed between uninfected and infected hamsters (“infection” factor), whereas 371 genes were differentially expressed when we analyzed “time × infection” interaction. Cluster analysis revealed that sets of activated genes of cellular pathways were different between acute (1 month postinfection) and chronic (3 months postinfection) opisthorchiasis. This enriched KEGG pathways were “Cell adhesion molecules”, “Hippo signaling”, “ECM-receptor interaction”, “Cell cycle”, “TGF-beta”, and “P53 signaling”. Moreover, epithelial–mesenchymal transition was the most enriched (q-value = 2.2E-07) MSigDB hallmark in the set of differentially expressed genes of all O. felineus–infected animals. Transcriptomic data were supported by the results of western blotting and immunohistochemistry revealing the upregulation of vimentin, N-cadherin, and α-smooth muscle actin postinfection.

Our data expand knowledge about global changes in gene expression in the O. felineus–infected host liver and contribute to understanding the biliary neoplasia associated with the liver fluke infection.

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A total of 2151 genes were found to be differentially expressed during the infection.

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Epithelial-Mesenchymal Transition was the most enriched process in the infected animals.

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Different pathways were activated between acute and chronic opisthorchiasis.

The pathogenic potential of the combined action of chronic Opisthorchis felineus infection and repeated social defeat stress in C57BL/6 mice

Parasitic food-borne diseases and chronic social stress are frequent attributes of day-to-day human life. Therefore, our aim was to model the combined action of chronic Opisthorchis felineus infection and repeated social defeat stress in C57BL/6 mice. Histological examination of the liver revealed inflammation sites, pronounced periductal fibrosis, and cholangiofibrosis together with proliferation of bile ducts and hepatocyte dystrophy in the infected mice, especially in the stress-exposed ones. Simultaneously with liver pathology, we detected significant structural changes in the cerebral cortex. Immunohistochemical analysis of the hippocampus indicated the highest increase in numerical density of Iba 1-, IL-6-, iNOS-, and Arg1-positive cells in mice simultaneously subjected to the two adverse factors. The number of GFAP-positive cells rose during repeated social defeat stress, most strongly in the mice subjected to both infection and stress. Real-time PCR analysis showed that the expression of genes Aif1 and Il6 differed among the analysed brain regions (hippocampus, hypothalamus, and frontal cortex) and depended on the adverse factors applied. In addition, among the brain regions, there was no consistent increase or decrease in these parameters when the two adverse treatments were combined: (i) in the hippocampus, there was upregulation of Aif1 and no change in Il6 expression; (ii) in the hypothalamus, expression levels of Aif1 and Il6 were not different from controls; and (iii) in the frontal cortex, Aif1 expression did not change while Il6 expression increased. It can be concluded that a combination of two long-lasting adverse factors, O. felineus infection and repeated social defeat stress, worsens not only the hepatic but also brain state, as evidenced behaviorally by disturbances of the startle response in mice.

Inhibition of Opisthorchis felineus glutathione-dependent prostaglandin synthase by resveratrol correlates with attenuation of cholangiocyte neoplasia in a hamster model of opisthorchiasis

Food-borne trematodiases represent major neglected parasitic diseases. Trematodes of the family Opisthorchiidae including Opisthorchis felineus, Opisthorchis viverrini and Clonorchis sinensis are ranked eight on the global list of the 24 most prevalent food-borne parasites. Chronic O. felineus infection symptoms include precancerous lesions with the potential for malignancy. In recent decades, liver flukes of the family Opisthorchiidae have been extensively scientifically explored, however despite this the molecular mechanisms of O. felineus pathogenicity and its carcinogenic potential have not been studied. Opisthorchis felineus glutathione-dependent prostaglandin synthase (GST σ) is the major component of the excretory-secretory product of this liver fluke. We hypothesised that the activity of this enzyme is involved in the infection pathogenesis, including the formation of precancerous lesions. To test this hypothesis and to gain insights into the mechanisms of precancerous lesion formation, we (i) investigated whether excretory parasitic GST σ retains its enzymatic activity, (ii) tested resveratrol (RSV) as a possible inhibitor of this enzyme, and (iii) assessed biliary neoplasia and oxidative DNA damage as well as the expression of neoplasia and fibrogenesis marker genes after prolonged administration of RSV in a hamster model. RSV was found to inhibit GST σ enzymatic activity in a dose-dependent manner (R = 0.85, P < 0.001; half-maximal effective dose (ED₅₀) = 48.6 μM). Prolonged administration of RSV significantly suppressed high-grade biliary neoplasia (P = 0.008), attenuated upregulation of hyperplasia and fibrogenesis-related genes (Tgfb, α-SMA and CK7), and decreased the elevated oxidative DNA damage. Taking into account that RSV can influence a wide range of pathways, further research is needed to confirm the role of GST σ in O. felineus pathogenicity. Nevertheless, the chemopreventive effect of RSV targeting biliary neoplasia formation might be useful for improving the outcomes in infected populations and represents a compelling rationale for RSV testing in combination chemotherapy of opisthorchiasis.

Characteristics of liver fibrosis associated with chronic Opisthorchis felineus infection in Syrian hamsters and humans

The food-borne liver trematode Opisthorchis felineus causes severe liver damage, including fibrosis. This study shows a comparison of the characteristics between cholangiofibrosis and periductal fibrosis in infected people and in the golden hamster as an experimental model. Comparative evaluation was carried out regarding collagen composition, the number of basic-producing cells, and extracellular-matrix degradation. The results revealed that characteristics of chronic opisthorchiasis due to O. felineus infection in humans and in Syrian hamsters are similar and include well-pronounced development of fibrotic complications in the liver parenchyma. Besides, a difference in fibrogenesis development was demonstrated between chronic O. felineus infection and noninfectious cholecystitis. In this study, we for the first time compared fibrogenesis between humans and model animals against the background of chronic O. felineus infection.

Opisthorchis felineus infection provokes time-dependent accumulation of oxidative hepatobiliary lesions in the injured hamster liver

Opisthorchiasis caused by food-borne trematode Opisthorchis felineus is a substantial public health problem, with 17 million persons infected worldwide. This chronic disease is associated with hepatobiliary inflammation, cholangiocyte dysplasia, cholangiofibrosis, intraepithelial neoplasia, and even cholangiocarcinoma among chronically infected individuals. To provide first insights into the mechanism by which O. felineus infection causes precancerous liver lesions, we investigated the level of oxidative stress (lipid peroxidation byproducts and 8-hydroxy-2′-deoxyguanosine) as well as the time course profiles of chronic inflammation and fibrogenesis markers in the dynamics of opisthorchiasis from 1 month to 1.5 years postinfection in an experimental model based on golden hamsters Mesocricetus auratus. For the first time, we showed that O. felineus infection provokes time-dependent accumulation of oxidative hepatobiliary lesions in the injured liver of hamsters. In particular, over the course of infection, lipid peroxidation byproducts 4-hydroxynonenal and malondialdehyde were upregulated; these changes in general correlate with the dynamics of hepatic histopathological changes. We detected macrophages with various immunophenotypes and elevated levels of CD68, COX2, and CD163 in the O. felineus–infected animals. Meanwhile, there was direct time-dependent elevation of TNF-α (R = 0.79; p < 0.001) and CD163 protein levels (R = 0.58; p = 0.022). We also provide quantitative data about epithelial hyperplasia marker CK7 and a marker of myofibroblast activation (α smooth muscle actin). Our present data provide first insights into the histopathological mechanism by which O. felineus infection causes liver injuries. These findings support the inclusion of O. felineus in Group 1 of biological carcinogens.