Cytopathic effects of Tritrichomonas foetus on bovine oviduct cells

Ultrastructural and Functional Analysis of a Novel Extra-Axonemal Structure in Parasitic Trichomonads

Trichomonas vaginalis and Tritrichomonas foetus are extracellular flagellated parasites that inhabit humans and other mammals, respectively. In addition to motility, flagella act in a variety of biological processes in different cell types, and extra-axonemal structures (EASs) have been described as fibrillar structures that provide mechanical support and act as metabolic, homeostatic, and sensory platforms in many organisms. It has been assumed that T. vaginalis and T. foetus do not have EASs. However, here, we used complementary electron microscopy techniques to reveal the ultrastructure of EASs in both parasites. Such EASs are thin filaments (3-5 nm diameter) running longitudinally along the axonemes and surrounded by the flagellar membrane, forming prominent flagellar swellings. We observed that the formation of EAS increases after parasite adhesion on the host cells, fibronectin, and precationized surfaces. A high number of rosettes, clusters of intramembrane particles that have been proposed as sensorial structures, and microvesicles protruding from the membrane were observed in the EASs. Our observations demonstrate that T. vaginalis and T. foetus can connect to themselves by EASs present in flagella. The protein VPS32, a member of the ESCRT-III complex crucial for diverse membrane remodeling events, the pinching off and release of microvesicles, was found in the surface as well as in microvesicles protruding from EASs. Moreover, we demonstrated that the formation of EAS also increases in parasites overexpressing VPS32 and that T. vaginalis-VPS32 parasites showed greater motility in semisolid agar. These results provide valuable data about the role of the flagellar EASs in the cell-to-cell communication and pathogenesis of these extracellular parasites.

Cytotoxicity profile of Cronobacter species isolated from food and clinical specimens in Brazil

AIMS

The objective of this study was to evaluate the cytotoxic activity of Cronobacter strains isolated from foods (n = 50) and clinical samples (n = 6) in Brazil and genotype selected strains (n = 18) using multi-locus sequence typing (MLST) METHODS AND RESULTS: The cytotoxic activity of C. sakazakii (n = 29), C. dublinensis (n = 13), C. malonaticus (n = 6), C. turicensis (n = 6) and C. muytjensii (n = 2) was screened using Vero, RK13, Hep2c, NCTC clone 929 and BHK-21 cell lines. Selected Cronobacter strains were assigned to C. sakazakii ST 21, C. turicensis ST 252, C. sakazakii ST 647, and three newly assigned STs: C. turicensis STs 738-740. The maximum death caused by non-heat-treated filtrates was 20·4, 86·2, 47·0 and 84·0%, in Vero, RK13, Hep2c and NCTC clone 929 cells, respectively. These were caused by C. sakazakii strains C291 and C292 (ST 494) which had been isolated during neonatal Cronobacter meningitis infection, and C110 (ST 395) isolated from flaxseed flour. Thermal treatment (100°C/20 min) significantly reduced the cytotoxicity activity in NCTC clone 929 and Vero cells (P ≤ 2 × 10^-6 ), but not in RK13 (P = 0·12) and Hep2c (P = 0·85), indicating the cytotoxin(s) were probably proteinaceous. Electron microscopy revealed that cytotoxic compounds from C. sakazakii induced several cell death characteristics, including loss of cell-cell contact, microvilli reduction and cellular lysis. Autophagic vacuoles and mitochondrial damage were the most common ultrastructural features observed.

CONCLUSIONS

It was concluded that Cronobacter strains, especially C. sakazakii, could produce heat-labile cytotoxic compounds in cell filtrates.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study providing insights into the pathogenesis of the Cronobacter genus. Cytotoxins were identified in excreted filtrates of C. sakazakii strains isolated from food and clinical specimens. The presence of Cronobacter strains that can produce cytotoxins in foods can be a potential threat to human health and highlight the need for high levels of hygiene.

Is Trichomonas tenax a Parasite or a Commensal?

Trichomonas tenax is considered a commensal organism found under poor oral hygiene conditions. T. tenax presents morphological similarities with T. vaginalis, and there are doubts concerning whether this protist is a parasite and whether it is a genetic variant of T. vaginalis. This study aimed to investigate the capacity of T. tenax to cause mammalian cell damage and compare its cytotoxicity with that of T. vaginalis. Protozoan-host cell interaction assays were performed with Madin-Darby canine kidney, HeLa, and gum cells and 3D spheroids, which were examined by scanning electron and transmission electron microscopy. Cellular viability experiments were also performed. T. tenax attached and had different forms when interacting with mammalian cells and caused damage with time-dependent host-cell viability. We observed that T. tenax produced plasma membrane projections and phagocytosed portions of the mammalian cells. In addition, T. tenax caused membrane blebbing and apoptotic bodies in HeLa cells, thus inducing cell death. Spheroids were also used in interaction assays with T. tenax and they were damaged by these cells. This study shows that T. tenax fulfills the requisites of a parasite, causing damage to different mammalian cells and behaving similarly to T. vaginalis when in contact with target cells in vitro.

Cysteine protease activity of feline Tritrichomonas foetus promotes adhesion-dependent cytotoxicity to intestinal epithelial cells

Trichomonads are obligate protozoan parasites most renowned as venereal pathogens of the reproductive tract of humans and cattle. Recently, a trichomonad highly similar to bovine venereal Tritrichomonas foetus but having a unique tropism for the intestinal tract was recognized as a significant cause of colitis in domestic cats. Despite a high prevalence, worldwide distribution, and lack of consistently effective drugs for treatment of the infection, the cellular mechanisms of T. foetus pathogenicity in the intestinal tract have not been examined. The aims of this study were to determine the pathogenic effect of feline T. foetus on porcine intestinal epithelial cells, the dependence of T. foetus pathogenicity on adhesion of T. foetus to the intestinal epithelium, and the identity of mediators responsible for these effects. Using an in vitro coculture approach to model feline T. foetus infection of the intestinal epithelium, these studies demonstrate that T. foetus promotes a direct contact-dependent activation of intestinal epithelial cell apoptosis signaling and progressive monolayer destruction. Moreover, these pathological effects were demonstrated to be largely dependent on T. foetus cell-associated cysteine protease activity. Finally, T. foetus cysteine proteases were identified as enabling cytopathic effects by promoting adhesion of T. foetus to the intestinal epithelium. The present studies are the first to examine the cellular mechanisms of pathogenicity of T. foetus toward the intestinal epithelium and support further investigation of the cysteine proteases as virulence factors in vivo and as potential therapeutic targets for ameliorating the pathological effects of intestinal trichomonosis.

Cooperative roles of biological flow and surface topography in guiding sperm migration revealed by a microfluidic model

Successful reproduction in mammals requires sperm to swim against a fluid flow and through the long and complex female reproductive tract before reaching the egg in the oviduct. Millions of them do not make it. Despite their clinical importance, the roles played in sperm migration by the diverse biophysical and biochemical microenvironments within the reproductive tract are largely unknown. In this article, we present the development of a double layer microfluidic device that recreates two important biophysical environments within the female reproductive tract: fluid flow and surface topography. The unique feature of the device is that it enables one to study the cooperative roles of fluid flow and surface topography in guiding sperm migration. Using bull sperm as a model system, we found that microfluidic grooves embedded on a channel surface facilitate sperm migration against fluid flow. These findings suggest ways to design in vitro fertilization devices to treat infertility and to develop non-invasive contraceptives that use a microarchitectural design to entrap sperm.

N-Propargylated isatin-Mannich mono- and bis-adducts: synthesis and preliminary analysis of in vitro activity against Tritrichomonas foetus

Cu(I)Cl promoted synthesis of N-propargylated-isatin Mannich mono- and bis-adducts with an extension towards the synthesis of N-propargylated-isatin-7-chloroquinoline conjugates was described. The synthesized scaffolds were evaluated for their in vitro activity against the veterinary protozoal pathogen Tritrichomonas foetus and cytotoxicity against human prostate (PC-3) cancer cell line. The preliminary evaluation data revealed the enhancement in the activity profiles with the introduction of 7-chloroquinoline ring with the most active conjugates 7a, 7c and 7d exhibiting an IC₅₀ of 22.2, 11.3 and 24.5 μM respectively against T. foetus and minimal toxicity against human prostate (PC-3) cell lines.

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Cu(I)Cl promoted synthesis of N-propargylated-isatin Mannich mono- and bis-adducts.

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Introduction of 7-chloro-quinoline moiety remarkably enhanced the activity against Tritrichomonas foetus.

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The most active and non-cytotoxic compound exhibited an IC₅₀ value 11.3 μM.

IL-10 release by bovine epithelial cells cultured with Trichomonas vaginalis and Tritrichomonas foetus

Trichomonas vaginalis and Tritrichomonas foetus are parasitic protists of the human and bovine urogenital tracts, respectively. Several studies have described the cytotoxic effects of trichomonads on urogenital tract epithelial cells. However, little is known about the host cell response against trichomonads. The aim of this study was to determine whether T. foetus and T. vaginalis stimulated the release of the cytokine interleukin (IL)-10 from cultured bovine epithelial cells. To characterise the inflammatory response induced by these parasites, primary cultures of bovine oviduct epithelial cells were exposed to either T. vaginalis or T. foetus. Within 12 h after parasite challenge, supernatants were collected and cytokine production was analysed. Large amounts of IL-10 were detected in the supernatants of cultures that had been stimulated with T. foetus. Interestingly, T. vaginalis induced only a small increase in the release of IL-10 upon exposure to the same bovine cells. Thus, the inflammatory response of the host cell is species-specific. Only T. foetus and not T. vaginalis induced the release of IL-10 by bovine oviduct epithelial cells.

Ultrastructural features of Tritrichomonas mobilensis and comparison with Tritrichomonas foetus

Tritrichomonas mobilensis is an intestinal parasite of squirrel monkeys. There are few reports concerning the morphological aspects of this parasite. In addition, the taxonomic relationship between T. mobilensis and Tritrichomonas foetus, a serious pathogen that causes bovine and feline trichomonosis, has been questioned. For this reason, in the present study, we examined and compared both tritrichomonads with regard to their morphology, ultrastructure, endocytic activity and cytotoxicity when in the presence of host cells. Electron microscopy demonstrated consistent morphological differences between the hydrogenosomes of both parasites. Moreover, T. mobilensis and T. foetus had striking differences in their endocytic behavior. Thus, this work provides additional data that support the hypothesis that T. mobilensis is a distinct species from T. foetus.