On Blastocystis secreted cysteine proteases: a legumain-activated cathepsin B increases paracellular permeability of intestinal Caco-2 cell monolayers

An Update on Blastocystis: Possible Mechanisms of Blastocystis-Mediated Colorectal Cancer

Blastocystis is an anaerobic parasite that colonizes the intestinal tract of humans and animals. When it was first discovered, Blastocystis was considered to be a normal flora with beneficial effects on human health, such as maintaining gut hemostasis and improving intestinal barrier integrity. Later, with increasing research on Blastocystis, reports showed that Blastocystis sp. is associated with gastrointestinal disorders, colorectal cancer (CRC), and neurological disorders. The association between Blastocystis sp. and CRC has been confirmed in several countries. Blastocystis sp. can mediate CRC via similar mechanisms to CRC-associated bacteria, including infection-mediated inflammation, increased oxidative stress, induced gut dysbiosis, and damage to intestinal integrity, leading to a leaky gut. IL-8 is the main inflammatory cytokine released from epithelial cells and can promote CRC development. The causal association of Blastocystis sp. with other diseases needs further investigation. In this review, we have provided an update on Blastocystis sp. and summarized the debate about the beneficial and harmful effects of this parasite. We have also highlighted the possible mechanisms of Blastocystis-mediated CRC.

Unveiling Blastocystis epidemiology in Morocco: subtype diversity among clinical patients with and without gastrointestinal manifestations in the Meknes region

Blastocystis is an intestinal protist frequently identified in humans and other animals, though its clinical significance remains controversial. This study aimed to determine the prevalence and genetic diversity of Blastocystis in faecal samples from symptomatic (n = 55) and asymptomatic (n = 50) individuals seeking medical care in Meknes, Morocco. Detection of the protist was accomplished through coproparasitological examination and culture in Jones medium. Culture-positive samples were subjected to molecular analyses (PCR and Sanger sequencing) based on sequences of the small subunit ribosomal RNA gene. Epidemiological questionnaires on demographics and potential risk factors were collected from participating patients. The overall Blastocystis infection rate was 51.4% (54/105), with no differences between symptomatic (52.7%, 29/55) and asymptomatic (50.0%, 25/50) individuals. Sequence analyses identified three Blastocystis subtypes, with ST3 being the most prevalent (42.0%), followed by ST1 (34.0%), and ST2 (12.0%). Regarding intra-subtype diversity, allele 4 was found within ST1; alleles 11/12 and alleles 34/36 (alone or in combination) were identified within ST2 and ST3 respectively. Allele 34 in ST3 (40.8%) and allele 4 in ST1 (34.7%) were the most common genetic variants circulating in the surveyed clinical population. A statistically significant association between ST2 and the presence of flatulence was observed. This is the first study assessing the epidemiology and genetic diversity of Blastocystis sp. in the Meknes region, Morocco.

Extracellular Cysteine Proteases of Key Intestinal Protozoan Pathogens-Factors Linked to Virulence and Pathogenicity

Intestinal diseases caused by protistan parasites of the genera Giardia (giardiasis), Entamoeba (amoebiasis), Cryptosporidium (cryptosporidiosis) and Blastocystis (blastocystosis) represent a major burden in human and animal populations worldwide due to the severity of diarrhea and/or inflammation in susceptible hosts. These pathogens interact with epithelial cells, promoting increased paracellular permeability and enterocyte cell death (mainly apoptosis), which precede physiological and immunological disorders. Some cell-surface-anchored and molecules secreted from these parasites function as virulence markers, of which peptide hydrolases, particularly cysteine proteases (CPs), are abundant and have versatile lytic activities. Upon secretion, CPs can affect host tissues and immune responses beyond the site of parasite colonization, thereby increasing the pathogens' virulence. The four intestinal protists considered here are known to secrete predominantly clan A (C1- and C2-type) CPs, some of which have been characterized. CPs of Giardia duodenalis (e.g., Giardipain-1) and Entamoeba histolytica (EhCPs 1-6 and EhCP112) degrade mucin and villin, cause damage to intercellular junction proteins, induce apoptosis in epithelial cells and degrade immunoglobulins, cytokines and defensins. In Cryptosporidium, five Cryptopains are encoded in its genome, but only Cryptopains 4 and 5 are likely secreted. In Blastocystis sp., a legumain-activated CP, called Blastopain-1, and legumain itself have been detected in the extracellular medium, and the former has similar adverse effects on epithelial integrity and enterocyte survival. Due to their different functions, these enzymes could represent novel drug targets. Indeed, some promising results with CP inhibitors, such as vinyl sulfones (K11777 and WRR605), the garlic derivative, allicin, and purified amoebic CPs have been obtained in experimental models, suggesting that these enzymes might be useful drug targets.

Lipid Accumulation in Blastocystis Increases Cell Damage in Co-Cultured Cells

Blastocystis hominis is an intestinal protozoan that is often neglected, despite causing abdominal pain and diarrhea. Previous research has demonstrated that lipids can be synthesized by B. hominis or can accumulate in growth medium, but their function and mechanisms in the pathogenesis of Blastocystis remain unclear. Our study found that lipid-rich Blastocystis ST7-B can increase inflammation and disrupt Caco-2 cells more than the same parasite without the lipovenoes supplement. Additionally, the cysteine protease of Blastocystis, a virulence factor, is upregulated and has higher activity in lipid-rich Blastocystis. In order to better understand the effects of lipids on Blastocystis pathogenesis, we treated lipid-lowering pravastatin during Blastocystis ST7-B culturing with a lipovenoes supplement, which decreased the lipid levels of the Blastocystis and reduced the Blastocystis-induced inflammation and cell disruption of Caco-2 cells. We also analyzed the fatty acid composition and possible synthesis pathway in Blastocystis ST7-B, finding significantly higher ratios of arachidonic acid, oleic acid, and palmitic acid than in the other lipid components in lipid-rich Blastocystis ST7-B. These results suggest that lipids play a significant role in the pathogenesis of Blastocystis and provide important information on the molecular mechanisms of and potential treatments for Blastocystis infection.

Can increased intestinal permeability and low-grade endotoxemia be the triggering pathogenesis in isolated coronary artery ectasia?

PURPOSE

Isolated coronary artery ectasia (ICAE) is a rare coronary artery disease (CAD) encountered during coronary angiography. Although many mechanisms have been suggested today that may be associated with ICAE, the underlying pathogenesis has not been fully understood. In this study, we aimed to reveal the possible relationship between intestinal permeability and ICAE.

METHODS

Of the 12 850 patients who underwent coronary angiography, 138 consecutive patients with ICAE and 140 age- and sex-matched subjects with normal coronary arteries as the control group and 140 subjects with stenotic CAD were included in the study.

RESULTS

Serum zonulin and lipopolysaccharide levels were significantly higher in patients with ICAE than in the control group and CAD group. Additionally, zonulin and lipopolysaccharide levels were significantly higher in the CAD group than in the ICAE group. In the correlation analysis, serum zonulin levels were correlated with the mean diameter and length of the ecstatic segment. In multivariate analysis, zonulin and lipopolysaccharide were identified as independent predictors for ICAE.

CONCLUSION

These results suggest that there may be a pathophysiological relationship between increased intestinal permeability and ICAE.

The synthesis of extracellular vesicles by the protistan parasite Blastocystis

Blastocystis is a genus of single-celled protist belonging to the stramenopile group. Prior studies have shown that isolates of Blastocystis subtype 7 (ST7) induced higher levels of intestinal epithelial cell damage and gut microbiota dysbiosis in comparison to other subtypes in in vivo and in vitro settings. Prior research has shown a link between gut dysbiosis and exposure to extracellular vesicles (EVs) produced by pathogenic microorganisms. This study demonstrates a protocol for the isolation of EVs from Blastocystis ST7 via ultracentrifugation. Nanoparticle tracking analysis and transmission electron microscopy were used to assess EV size and morphology. The protein content of isolated EVs was assessed by mass spectrophotometry and the presence of EV markers were evaluated by Western blotting. Finally, the EVs were cocultured with prominent human gut microbiome species to observe their effect on prokaryote growth. Our data shows that Blastocystis ST7 secretes EVs that are similar in morphology to previously characterized EVs from other organisms and that these EVs contain a limited yet unique protein cargo with functions in host-parasite intercellular communication and cell viability. This cargo may be involved in mediating the effects of Blastocystis on its surrounding environment.

Variations in active proteases of Blastocystis sp. obtained from water and animal isolates from the Philippines

Blastocystis sp. is a commonly encountered gut protozoan with unclear pathogenicity. The presence of proteases in this organism may be related to its potential pathogenicity or other physiological differences. This study aimed to identify the various proteases that may be present in different subtypes (STs) of Blastocystis sp. using azocasein assay and gelatin zymography. In this study, cysteine, serine, aspartic protease, metalloproteases, and unknown proteases were identified in Blastocystis sp. cultures obtained from animal and water samples belonging to ST1-ST5 and ST7. Azocasein assay and gelatin zymography were conducted on different batches of protease extracts, which showed varying results. Cysteine protease was the most commonly encountered. Protease activity in general is not associated with ST or source (animal or water). However, the presence of cysteine protease alone was associated with animal samples, whereas the presence of more than two protease types was associated with water samples. Azocasein assay and gelatin zymography were conducted on different batches of protease extracts, which showed varying results. Protease activity and the types present may change over time. Blastocystis sp. shows high protease diversity, including possible novel types.

Exosomes secreted by Blastocystis subtypes affect the expression of proinflammatory and anti-inflammatory cytokines (TNFα, IL-6, IL-10, IL-4)

Background

Blastocystis sp. is a common intestinal parasite, possibly responsible for diarrhea, vomiting and nausea, abdominal pain, and irritable bowel syndrome. However, many studies focused on this issue due to the uncertainty of its pathogenic potential. The extracellular vesicles (EVs) are significant mediators for cellular communication, carrying biological molecules such as proteins, lipids, and nucleic acids. Compared with other parasites, little is known about the Blastocystis EVs. Hence the present investigation was done.

Methods

The Blastocystis parasites were cultured in the DMEM medium, and a 550–585 bp fragment was amplified using PCR, and sequencing was done. A commercial kit was used for exosome extraction and dynamic light scattering (DLS), flow cytometry (CD63, CD81 markers), and electron microscopy tests to determine their morphology. The human leukemia monocytic cell line (THP-1) was exposed to Blastocystis EVs. Next, the expression of proinflammatory and anti-inflammatory cytokines, including IL-4, IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α), were measured using quantitative PCR.

Results

Exosomes were extracted from ST1-3 Blastocystis sp. According to the DLS assay, the size of the exosomes was in the range of 30–100 nm. Electron microscopy images and CD63 and CD81 markers also confirmed the exosome's size, structure, and morphology. According to real-time PCR results, ST1-derived exosomes caused IL-6 and TNF-α upregulation and IL-10 and IL-4 downregulation, ST2- and ST3-derived exosomes downregulated IL-10, and ST3-derived exosomes caused IL-6 upregulation. There is a statistically significant difference (P ≤ 0.05).

Conclusion

To our knowledge, this is the first report of the release of exosome-like vesicles by the human parasite, Blastocystis, and the provided information demonstrates the role of this parasite, particularly ST1 on proinflammatory and anti-inflammatory cytokines and navigating the host response.

The Infection, Coinfection, and Abundance of Intestinal Protozoa Increase the Serum Levels of IFABP2 and TNF-α in Patients With Rheumatoid Arthritis

Protozoa, nematodes, and platyhelminths are of clinical interest due to their role on the modulation of the immune responses. To determine the frequency of infection by intestinal parasites as well as the status of single or mixed infection (coinfection) and its relation with inflammation and intestinal permeability markers in patients with rheumatoid arthritis (RA), a cross-sectional study was conducted in 18 women diagnosed with RA. A fecal sample of each participant was analyzed for parasitic identification. The DAS28-erythrocyte sedimentation rate score, as well as the serum levels of TNF-α, IL-10, IL-17A, and the intestinal fatty-acid binding protein 2 (IFABP2), was determined through the ELISA technique. The T CD4+ and CD8+ lymphocytes' proportions were determined by flow cytometry. In this study, 50% (n = 9) of the total sample tested were positive to the presence of intestinal protozoa (27% by single infection and 22.2% by coinfection). Blastocystis sp. and Endolimax nana were the most frequently identified protozoa. The serum levels of IFABP2 were increased in patients with infection by protozoa, mainly in those individuals with coinfection and a larger abundance of Blastocystis sp. We found that coinfection by protozoa was related to higher levels of TNF-α and higher frequency of T CD4+ lymphocytes, mainly in patients under antirheumatic treatment. Infection by intestinal protozoa is associated with increased intestinal permeability in patients with RA; thus, infection, coinfection, and abundance of intestinal protozoa should be clinically screened because they could be an associated factor to the clinical variability of the disease.

Modulation of microRNAs and claudin-7 in Caco-2 cell line treated with Blastocystis sp., subtype 3 soluble total antigen

Background

Blastocystis sp., is a eukaryote of the large intestine, which is reported from almost all countries. The pathogenesis of this protist is not clear. The current study aimed to analyze the effects of Blastocystis sp., ST3 soluble total antigen (B3STA) on the microRNAs (miRNAs) involved in the gut permeability and also pro-inflammatory cytokines, occludin, and claudin-7.

Methods

Blastocystis sp., ST3 isolated from stool sample was purified, and its soluble total antigen was extracted using freeze and thawing. The Caco-2 cell line was treated with B3STA for 24 h and the expression levels of mir-16, mir-21, mir-29a, mir-223, and mir-874 were analyzed. In addition, the expression levels of il-8, il-15, occludin, and claudin-7 genes were assessed.

Results

B3STA significantly upregulated the expression of mir-223, and mir-874, and downregulated mir-29a. The expression of mir-16 and mir-21 was not significant. In addition, the expression of il-8 and il-15 was not significant. B3STA significantly decreased the expression level of claudin-7 (P-value < 0.0001), but the expression of occludin was not significant. Our results showed significant correlation between all studied miRNAs, except mir-29a, with downregulation of claudin-7.

Conclusions

This is the first study investigating the effects of Blastocystis sp., ST3 isolated from symptomatic subjects on the expression levels of miRNAs involved in the gut permeability. Our results demonstrated that B3STA may change miRNA expression, which are involved in the gut barrier integrity, and downregulates claudin-7, which is known as sealing factor.

The Relationship between the Mechanism of Sarcopenia and Exercise Based on Data Mining

Due to the increasing prosperity of human life science and technology, many huge research results have been obtained, and the scientific research of molecular biology is developing rapidly. Therefore, the output of biological genome data has increased exponentially, which constitutes a huge amount of data analysis. The seemingly chaotic and massive amount of data information actually contains a large amount of data and information of great key scientific significance and value. Therefore, this kind of genomic data information not only contains the information content that describes the characteristics of human life but also contains the information content that can express the essence of the biological organism. It includes macroeconomic information that can reflect the basic structure and capabilities of living organisms and microinformation in related fields of molecular biology. This massive amount of genetic data is usually closely related to each other, can influence each other, and does not exist alone. In the article, the causes of uncertain data and the classification of uncertain data are introduced, and the basic concepts and related algorithms of data mining are explained. Focusing on the research and analysis of abnormal point detection and clustering algorithms in uncertain data mining technology, this paper solves the problem of how to obtain more diverse and accurate outlier detection and cluster analysis results in uncertain data. The results showed that whether it was related to obesity or not, the Lp(a) level of the sarcopenia group was significantly higher than that of the nonsarcopenia group. At the same time, the correlation analysis showed that ASM/height was negatively correlated with Lp(a). ASM/height is one of the criteria for diagnosing sarcoidosis, and it is also the core of the analysis. Among the 1956 tumor patients collected in this study, 432 had sarcopenia, accounting for 22.08%, and the incidence of sarcopenia in patients with gastrointestinal tumors increased.

Association of Blastocystis ST6 with higher protease activity among symptomatic subjects

BACKGROUND

Blastocystis sp. is an anaerobic intestinal protozoan parasite of humans and a wide range of animals worldwide. In the current study the correlation between the cysteine protease activity of clinical samples of Blastocystis sp. ST1-3 and 6 with the levels of pro-inflammatory cytokines was evaluated.

METHODS

Stool samples were collected from subjects with or without clinical symptoms. All samples were cultivated in DMEM medium. The bacteria were eliminated or reduced in Blastocystis sp. positive samples subtypes 1-3 and 6 by a variety of antibiotics and consecutive sub-cultures. To prepare parasite lysate, 1 × 105 Blastocystis sp. from each isolate were harvested and lysed using freeze-thaw. Protease activity of each isolate was measured and the gene expression of pro-inflammatory biomarkers in HT-29 cell line sensed by isolates was investigated using quantitative Real-time PCR.

RESULTS

Protease activity assay showed inter- and intra-subtype variations among subtypes regarding the presence of symptoms, while the protease activity of symptomatic isolates was higher than asymptomatic isolates. The highest and lowest levels of protease activity were seen in ST6 and ST2, respectively. However, patterns of the expression of pro-inflammatory biomarkers in HT-29 cell line was different regarding the presence of symptoms and time points. There was no significant correlation between protease activity of different subtypes with the expression levels of pro-inflammatory biomarkers.

CONCLUSIONS

Our study indicated a higher protease activity among isolates from symptomatic compared to asymptomatic subjects, suggesting functional role for proteases in clinical symptoms due to Blastocystis sp. The lack of correlation between the levels of expression of pro-inflammatory biomarkers with subtypes regarding the presence of clinical symptoms proposes the importance of host-related factors in presentation of clinical symptoms.

Prokaryotic and Eukaryotic Fecal Microbiota in Irritable Bowel Syndrome Patients and Healthy Individuals Colonized With Blastocystis

Blastocystis is the most frequently isolated protozoan from human stool. Its role in human health is still debated, and a high prevalence was reported in irritable bowel syndrome (IBS) subjects, suggesting a potential link with microbiota. In the present study, we aimed to investigate prokaryotic and eukaryotic microbiota in both IBS-C (constipated) and healthy individuals. We recruited 35 IBS-C patients and 23 healthy subjects, from which 12 and 11 carried Blastocystis, respectively. We performed 16S and 18S rRNA high-throughput sequencing on feces. Whereas we did not observe differences between infected and non-infected controls, several phyla were significantly modified in IBS-C patients according to the presence of Blastocystis. Tenericutes phylum and Ruminococcaceae family were especially increased in Blastocystis carriers. Furthermore, colonization with Blastocystis was associated with discrete changes in the microbial eukaryome, particularly among the Fungi taxa. Depending on the group of patients considered, the mycobiota changes do not go in the same direction and seem more deleterious in the IBS-C group. These results encourage further in vivo and in vitro investigations concerning the role of Blastocystis in the gut environment.

The neglected role of Blastocystis sp. and Giardia lamblia in development of irritable bowel syndrome: A systematic review and meta-analysis

The possible role of Blastocystis sp. and Giardia lamblia infections in the development of irritable bowel syndrome (IBS) has long been controversial. In this study, we conducted a systematic review and meta-analysis to investigate whether these protozoan infections are associated with IBS development. We systematically searched international databases for all studies that reported these protozoa in IBS patients published by May 10, 2021. Studies were included in the review if they were observational studies with confirmed patients with IBS (in case-control and cross-sectional studies) or parasitic infections (cohort studies) with an appropriate control group. Pooled odds ratios (ORs) and 95% confidence intervals were estimated using a random-effects meta-analysis model for included studies. A total of 32 papers (42 datasets), including 29 papers (31 datasets) for Blastocystis sp./IBS and 11 papers (11 datasets) for G. lamblia/IBS met the eligibility criteria. Our results indicated that the individuals with Blastocystis sp. infection were significantly at a higher risk of IBS development (OR, 1.78; 95%CI, 1.29-2.44). Moreover, cohort studies indicated a significant positive association between G. lamblia infection and IBS risk (OR, 5.47; 95%CI, 4.23-7.08); while an increasing but no statistically significant risk was observed in case-control studies (OR, 1.19; 95%CI, 0.75-1.87). Our findings suggested that Blastocystis sp. and G. lamblia infections are associated with the increased risk of developing IBS. Despite these results, further studies are needed to determine the effect of these protozoa on IBS development.

Prevalence and molecular subtyping of Blastocystis in patients with Clostridium difficile infection, Singapore

Background

Blastocystis is a common anaerobic colonic protist in humans with controversial pathogenicity. Clostridium difficile (C. difficile) is the commonest cause of infectious diarrhea in healthcare settings. The prevalence and subtype (ST) characteristics of Blastocystis in patients with C. difficile infection (CDI) are rarely documented. Therefore, the present study was conducted to investigate the prevalence and subtype characteristics of Blastocystis in patients with suspicion of CDI in Singapore.

Methods

Fecal samples were collected from 248 patients presenting with suspected CDI from a single tertiary hospital in Singapore. C. difficile was diagnosed through positive glutamate dehydrogenase (GDH) with or without toxin A/B using enzyme immunoassay methods. The prevalence and subtype genetic characteristics of Blastocystis were determined by polymerase chain reaction (PCR) amplification and analysis of the barcode region of the SSU rRNA gene.

Results

The proportion of C. difficile in patients with healthcare-associated diarrhea in this study was 44% (109/248). Among the 109 C. difficile-positive patients, 59 (54.1%, 59/109) tested positive for toxigenic C. difficile, which was considered CDI. Based on the sequence analyses of the barcode region of the SSU rRNA gene, 10.1% (25/248) of the patients were found to be Blastocystis-positive, and three subtypes were identified: ST7 (64%, 16/25), ST1 (20%, 5/25), and ST3 (16%, 4/25). Remarkably, we found five patients with Blastocystis and C. difficile coinfection, and further subtype analysis showed two with ST7, two with ST1, and one with ST3.

Conclusions

To the best of our knowledge, this is the first study to investigate the subtype distributions of Blastocystis in patients with CDI in Singapore. We found ST7 to be the predominant subtype in diarrheal patients. The pathogenicity of ST7 has been strongly suggested in previous in vitro and mouse model experiments, further confirming its potential pathogenicity to humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04749-8.

The roles of parasite-derived extracellular vesicles in disease and host-parasite communication

In recent years, several parasites have been shown to interact with their hosts through intra- and inter-community communication mechanisms, which were identified to be mediated by extracellular vesicles (EVs) through various uptake mechanisms. EVs are a heterogenous group of nanoparticles (~30-5000 nm) classified into three main types according to their size and biogenesis. EVs contain proteins, lipids, nucleic acids and metabolites from the cell of origin which are essential for genetic exchange, biomarker identification and diagnosis of pathological diseases. As important "forward lines of parasite infectivity", the parasite-secreted EVs function as information transmitters in the early-stage of host-parasite interaction and subsequent host-cell colonization. For this review, we summarize from the literature the relevance of EVs to the pathogenesis and development of human parasitic protistan diseases such as giardiasis, leishmaniasis, amoebiasis, malaria and Blastocystis-mediated gut pathology. Specific in vitro and in vivo interactions of the parasite-EVs and the host, with the reported cellular and immunological outcomes are discussed in this review. EVs have great potential to be further developed as diagnostic, immunomodulation and therapeutic alternatives to fill the knowledge gaps in the current parasitic diseases discussed in this review. Nanomedicine and vaccine development could be explored, with the utilization and/or modification of the parasitic EVs as novel treatment and prevention strategies.

Influence of Proton Pump Inhibitors and Histamine Receptor 2 Antagonists on Blastocystis ST3 and Selected Microorganisms of Intestinal Microbiota In Vitro

INTRODUCTION

Proton pump inhibitors (PPIs) and histamine receptor 2 (H2) antagonists are commonly prescribed medications. Association between PPIs and alteration of the gut microbiota has been reported. Blastocystis, the most common intestinal protozoan worldwide, occurs in both healthy and symptomatic people with gastrointestinal or cutaneous disorders, with controversial pathogenicity. The current study was aimed to investigate the influence of PPIs and H2 blockers on the in vitro proliferation of selected intestinal bacteria, fungi, and protozoa.

METHODS

Cultures of Lactobacillus rhamnosus, Escherichia coli, Enterococcus faecium, Candida albicans, and Blastocystis subtype 3 were treated with different concentrations of respective medications in vitro, and the numbers of microorganisms were quantified and compared.

RESULTS

Pantoprazole and esomeprazole exerted a significant inhibition on Blastocystis and C. albicans, especially at higher concentrations, which were even more effective than metronidazole. On the other hand, treatment with pantoprazole caused an increase in proliferation of L. rhamnosus and E. coli. There was no influence of H2 blockers on the examined microorganisms.

DISCUSSION

PPIs, such as pantoprazole, can be a potential treatment in the prophylaxis or eradication of Blastocystis and C. albicans.

Tight Junctions as a Key for Pathogens Invasion in Intestinal Epithelial Cells

Tight junctions play a major role in maintaining the integrity and impermeability of the intestinal barrier. As such, they act as an ideal target for pathogens to promote their translocation through the intestinal mucosa and invade their host. Different strategies are used by pathogens, aimed at directly destabilizing the junctional network or modulating the different signaling pathways involved in the modulation of these junctions. After a brief presentation of the organization and modulation of tight junctions, we provide the state of the art of the molecular mechanisms leading to permeability breakdown of the gut barrier as a consequence of tight junctions’ attack by pathogens, including bacteria, viruses, fungi, and parasites.

New insights into the interactions between Blastocystis, the gut microbiota, and host immunity

The human gut microbiota is a diverse and complex ecosystem that is involved in beneficial physiological functions as well as disease pathogenesis. Blastocystis is a common protistan parasite and is increasingly recognized as an important component of the gut microbiota. The correlations between Blastocystis and other communities of intestinal microbiota have been investigated, and, to a lesser extent, the role of this parasite in maintaining the host immunological homeostasis. Despite recent studies suggesting that Blastocystis decreases the abundance of beneficial bacteria, most reports indicate that Blastocystis is a common component of the healthy gut microbiome. This review covers recent finding on the potential interactions between Blastocystis and the gut microbiota communities and its roles in regulating host immune responses.

Fecal dysbiosis associated with colonic hypersensitivity and behavioral alterations in chronically Blastocystis-infected rats

BACKGROUND

Infectious gastroenteritis is a risk factor for the development of post-infectious Irritable Bowel Syndrome (PI-IBS). Recent clinical studies reported a higher prevalence of the intestinal parasite Blastocystis in IBS patients. Using a rat model, we investigated the possible association between Blastocystis infection, colonic hypersensitivity (CHS), behavioral disturbances and gut microbiota changes.

METHODS

Rats were orally infected with Blastocystis subtype 4 (ST4) cysts, isolated from human stool samples. Colonic sensitivity was assessed by colorectal distension and animal behavior with an automatic behavior recognition system (PhenoTyper), the Elevated Plus Maze test and the Forced Swimming tests. Feces were collected at different time points after infection to study microbiota composition by 16 S rRNA amplicon sequencing and for short-chain fatty acid (SFCA) analysis.

RESULTS

Blastocystis-infected animals had non-inflammatory CHS with increased serine protease activity. Infection was also associated with anxiety- and depressive-like behaviors. Analysis of fecal microbiota composition showed an increase in bacterial richness associated with altered microbiota composition. These changes included an increase in the relative abundance of Oscillospira and a decrease in Clostridium, which seem to be associated with lower levels of SCFAs in the feces from infected rats.

CONCLUSIONS

Our findings suggest that experimental infection of rats with Blastocystis mimics IBS symptoms with the establishment of CHS related to microbiota and metabolic shifts.

Development and Evaluation of Modified Cryopreservation for Long-Term Storage of Blastocystis Subtypes 1-3 and 6

BACKGROUND

Blastocystis is a protozoan parasite living in the intestine of humans and a wide range of animals. Although Blastocystis grows in several cultivation media, axenification and serial cultivations for long time are the main challenges of the researchers. Therefore, the long-term storage of subtypes/strains of Blastocystis using cryopreservation provides a suitable source of this parasite for the physiological, biochemical, and biological studies.

METHODS

In the current study, seven xenic isolates including two separated isolates from ST1-3 and one isolate from ST6 were cryopreserved using a standard method with minor modifications. After 3 months, all isolates were recovered and cultivated in DMEM medium.

RESULTS

The findings of the method showed all seven isolates were successfully recovered in DMEM medium. In addition, all isolates remained viable after several sub-cultures.

CONCLUSIONS

It seems that cryopreservation is a simple method that can provide a suitable condition for the long-term storage of Blastocystis.

The influence of probiotic bacteria and human gut microorganisms causing opportunistic infections on Blastocystis ST3

BACKGROUND

Blastocystis subtype 3 is an intestinal protist present in humans throughout the world with a controversial pathogenic potential. It has been suggested that probiotic bacteria inhibit the multiplication of gut protozoans, while others are beneficial for their development. This study aimed to evaluate the efficacy of the lactic acid bacteria Lactobacillus rhamnosus, Lactococcus lactis and Enterococcus faecium in Blastocystis ST3 eradication and the relevance of the intestinal microorganisms Escherichia coli, Candida albicans and Candida glabrata in protozoan proliferation. Blastocystis xenic and axenic culture was co-incubated with the above-mentioned microorganisms and their cell free supernatants at different concentrations in vitro. The number of protozoan cells was counted every day.

RESULTS

Both experiments, with xenic and axenic cultures, showed Blastocystis inhibition by L. rhamnosus and L. lactis and their supernatants from the 2nd day of co-incubation. Furthermore, co-incubation with both E. faecium and E. coli showed a beneficial influence on Blastocystis during the first 2 days. Only after 3 days did the above-mentioned bacteria start to inhibit Blastocystis growth in both cultures. The supernatant containing the metabolites of E. coli was effective to a lesser degree. Compared to the control samples, co-incubation with both C. albicans and C. glabrata showed a faster decrease in Blastocystis proliferation, but this was not statistically significant.

CONCLUSIONS

This study has shown the potential of using L. rhamnosus and L. lactis, as well as E. faecium as a prophylactic treatment against Blastocystis colonization or as an additional treatment regimen in combination with standard drugs.

Is the genetic variability of Cathepsin B important in the pathogenesis of Blastocystis spp.?

The potential role of Blastocystis as a pathogen is controversial because it is found in both symptomatic and asymptomatic carriers. Since Cathepsin B has been identified as a main virulence factor that contributes to the pathogenesis of this parasite, the purpose of this study was to analyze the genetic polymorphisms of cathepsin B from Blastocystis from patients with irritable bowel syndrome and from asymptomatic carriers. DNA from fecal samples of both groups, which were previously genotyped by 18S sequencing, was used to amplify a fragment of the cathepsin B gene. Phylogenetic reconstructions were performed and some genetic population indexes were obtained. Amplicons of 27 samples (15 cases, 10 controls, and two commercial ATCC strains) were obtained and analyzed. Phylogenetic reconstructions using nucleotides or inferred amino acid sequences did not separate between cases or controls or among subtypes. Regarding the values of genetic variability, we found that the haplotype and nucleotide diversity indexes of cathepsin B from cases and controls were similar to the values of 18S from controls. By contrast, 18S from cases showed low variability, suggesting that the genetic variability of cathepsin B was not related to the symptomatology of Blastocystis carriers. However, since no polymorphisms related to cases or controls were found, it is logical to assume that the potential damage caused by Blastocystis in situ may be due to unclear mechanisms of Cathepsin B regulation and expression that should be studied in future studies.

Extreme genome diversity in the hyper-prevalent parasitic eukaryote Blastocystis

Blastocystis is the most prevalent eukaryotic microbe colonizing the human gut, infecting approximately 1 billion individuals worldwide. Although Blastocystis has been linked to intestinal disorders, its pathogenicity remains controversial because most carriers are asymptomatic. Here, the genome sequence of Blastocystis subtype (ST) 1 is presented and compared to previously published sequences for ST4 and ST7. Despite a conserved core of genes, there is unexpected diversity between these STs in terms of their genome sizes, guanine-cytosine (GC) content, intron numbers, and gene content. ST1 has 6,544 protein-coding genes, which is several hundred more than reported for ST4 and ST7. The percentage of proteins unique to each ST ranges from 6.2% to 20.5%, greatly exceeding the differences observed within parasite genera. Orthologous proteins also display extreme divergence in amino acid sequence identity between STs (i.e., 59%-61% median identity), on par with observations of the most distantly related species pairs of parasite genera. The STs also display substantial variation in gene family distributions and sizes, especially for protein kinase and protease gene families, which could reflect differences in virulence. It remains to be seen to what extent these inter-ST differences persist at the intra-ST level. A full 26% of genes in ST1 have stop codons that are created on the mRNA level by a novel polyadenylation mechanism found only in Blastocystis. Reconstructions of pathways and organellar systems revealed that ST1 has a relatively complete membrane-trafficking system and a near-complete meiotic toolkit, possibly indicating a sexual cycle. Unlike some intestinal protistan parasites, Blastocystis ST1 has near-complete de novo pyrimidine, purine, and thiamine biosynthesis pathways and is unique amongst studied stramenopiles in being able to metabolize α-glucans rather than β-glucans. It lacks all genes encoding heme-containing cytochrome P450 proteins. Predictions of the mitochondrion-related organelle (MRO) proteome reveal an expanded repertoire of functions, including lipid, cofactor, and vitamin biosynthesis, as well as proteins that may be involved in regulating mitochondrial morphology and MRO/endoplasmic reticulum (ER) interactions. In sharp contrast, genes for peroxisome-associated functions are absent, suggesting Blastocystis STs lack this organelle. Overall, this study provides an important window into the biology of Blastocystis, showcasing significant differences between STs that can guide future experimental investigations into differences in their virulence and clarifying the roles of these organisms in gut health and disease.

Blastocystis: how do specific diets and human gut microbiota affect its development and pathogenicity?

Blastocystis is an enteric parasite that inhabits the gastrointestinal tract of humans and many animals. This emerging parasite has a worldwide distribution. It is often identified as the most common eukaryotic organism reported in human fecal samples. This parasite is recognized and diagnosed more often than ever before. Furthermore, some strains develop resistance against currently recommended drugs, such as metronidazole; therefore, the use of natural remedies or special diets has many positive aspects that may address this problem. The goal of this review is to compare natural treatments and various diets against the efficacy of drugs, and describe their influence on the composition of the gut microbiota, which affects Blastocystis growth and the occurrence of symptoms. This article reviews important work in the literature, including the classification, life cycle, epidemiology, pathogenesis, pathogenicity, genetics, biology, and treatment of Blastocystis. It also includes a review of the current knowledge about human gut microbiota and various diets proposed for Blastocystis eradication. The literature has revealed that garlic, ginger, some medical plants, and many spices contain the most effective organic compounds for parasite eradication. They work by inhibiting parasitic enzymes and nucleic acids, as well as by inhibiting protein synthesis. The efficacy of any specific organic compound depends on the Blastocystis subtype, and, consequently, on its immunity to treatment. In conclusion, the article discusses the findings that human gut microbiota composition triggers important mechanisms at the molecular level, and, thus, has a crucial influence on the parasitic pathogenicity.