Cryptosporidium parvum disrupts intestinal epithelial barrier function via altering expression of key tight junction and adherens junction proteins

The influence of selected gastrointestinal parasites on apoptosis in intestinal epithelial cells

Studies on the parasite–host interaction may provide valuable information concerning the modulation of molecular mechanisms as well as of the host immune system during infection. To date, it has been demonstrated that intestinal parasites may affect, among others, the processes of digestion in the gastrointestinal system of the host, thus limiting the elimination of the parasite, the immune response as well as inflammation. However, the most recent studies suggest that intestinal parasites may also affect modulation of the apoptosis pathway of the host. The present paper presents the latest scientific information on the influence of intestinal parasite species (Blastocystis sp., Giardia sp., Cryptosporidium sp., Trichuris sp., Entamoeba histolytica, Nippostrongylus brasiliensis, Heligmosomoides polygyrus) on the molecular mechanisms of apoptosis in intestinal epithelial cells. This paper stresses that the interdependency between the intestinal parasite and the host results from the direct effect of the parasite and the host’s defense reactions, which lead to modulation of the apoptosis pathways (intrinsic and extrinsic). Moreover, the present paper presents the role of proteins involved in the mechanisms of apoptosis as well as the physiological role of apoptosis in the host’s intestinal epithelial cells.

Effects of Aluminum on the Integrity of the Intestinal Epithelium: An in Vitro and in Vivo Study

BACKGROUND

Aluminum (Al) is the most abundant and ubiquitous metal in the environment. The main route of human exposure to Al is through food and water intake. Although human exposure to Al is common, the influence of Al on the gastrointestinal tract remains poorly understood.

OBJECTIVES

We aimed to further understand the toxic effect of Al and to elucidate the underlying cellular mechanisms in the intestinal barrier.

METHODS

The human intestinal epithelial cell line HT-29 and C57BL6 mice were exposed to AlCl3 at 0-16 mM (1-24h) and 5-50mg/kg body weight (13 weeks), respectively. In cell culture experiments, intracellular oxidative stress, inflammatory protein and gene expression, and intestinal epithelial permeability were measured. In animal studies, histological examination, gene expression, and myeloperoxidase (MPO) activity assays were conducted.

RESULTS

Cellular oxidative stress level (superoxide production) in AlCl3-treated cells (4 mM, 3h) was approximately 38-fold higher than that of the control. Both protein and mRNA expression of tight junction (TJ) components (occludin and claudin-1) in AlCl3-treated cells (1-4 mM, 24h) was significantly lower than that of the control. Transepithelial electrical resistance (TEER) decreased up to 67% in AlCl3-treated cells (2 mM, 24h) compared with that of the control, which decreased approximately 7%. Al activated extracellular signal-regulated kinase 1/2 and nuclear factor-kappa B (NF-κB), resulting in mRNA expression of matrix metalloproteinase-9, myosin light-chain kinase, and inflammatory cytokines [tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and IL-6] in HT-29 cells. Moreover, oral administration of AlCl3 to mice induced pathological alteration, MPO activation, and inflammatory cytokine (TNF-α, IL-1β, and IL-6) production in the colon.

CONCLUSION

Al induced epithelial barrier dysfunction and inflammation via generation of oxidative stress, down-regulation of the TJ proteins, and production of inflammatory cytokines in HT-29 cells. In addition, Al induced toxicity in the colon by increasing the levels of inflammatory cytokines and MPO activity and induced histological damage in a mouse model. Our data suggest that Al may be a potential risk factor for human intestinal diseases. https://doi.org/10.1289/EHP5701.

Cryptosporidium Infection: Epidemiology, Pathogenesis, and Differential Diagnosis

Cryptosporidium is a protozoan that infects a wide variety of vertebrates, including humans, causing acute gastroenteritis. The disease manifests with abdominal pain and diarrhea similar to that of choleric infection. In the immunocompromised hosts, the parasite causes prolonged infections that can also be fatal. For this reason, cryptosporidiosis is considered one of riskiest opportunistic infections for patients with acquired immunodeficiency syndrome. The best way to control the infection in these patients is setting up sensitive and specific diagnostic tests for epidemiological surveillance and morbidity reduction. Here, we summarized the general aspects of Cryptosporidium infection focusing on available diagnostic tools used for the diagnosis of cryptosporidiosis. Molecular methods currently available for its detection and progress in the development of new diagnostics for cryptosporidiosis are also discussed.

Disruption of gut integrity and permeability contributes to enteritis in a fish-parasite model: a story told from serum metabolomics

Background

In the animal production sector, enteritis is responsible for serious economic losses, and intestinal parasitism is a major stress factor leading to malnutrition and lowered performance and animal production efficiency. The effect of enteric parasites on the gut function of teleost fish, which represent the most ancient bony vertebrates, is far from being understood. The intestinal myxozoan parasite Enteromyxum leei dwells between gut epithelial cells and causes severe enteritis in gilthead sea bream (Sparus aurata), anorexia, cachexia, growth impairment, reduced marketability and increased mortality.

Methods

This study aimed to outline the gut failure in this fish-parasite model using a multifaceted approach and to find and validate non-lethal serum markers of gut barrier dysfunction. Intestinal integrity was studied in parasitized and non-parasitized fish by immunohistochemistry with specific markers for cellular adhesion (E-cadherin) and tight junctions (Tjp1 and Cldn3) and by functional studies of permeability (oral administration of FITC-dextran) and electrophysiology (Ussing chambers). Serum samples from parasitized and non-parasitized fish were analyzed using non-targeted metabolomics and some significantly altered metabolites were selected to be validated using commercial kits.

Results

The immunodetection of Tjp1 and Cldn3 was significantly lower in the intestine of parasitized fish, while no strong differences were found in E-cadherin. Parasitized fish showed a significant increase in paracellular uptake measured by FITC-dextran detection in serum. Electrophysiology showed a decrease in transepithelial resistance in infected animals, which showed a diarrheic profile. Serum metabolomics revealed 3702 ions, from which the differential expression of 20 identified compounds significantly separated control from infected groups in multivariate analyses. Of these compounds, serum inosine (decreased) and creatine (increased) were identified as relevant and validated with commercial kits.

Conclusions

The results demonstrate the disruption of tight junctions and the loss of gut barrier function, a metabolomic profile of absorption dysfunction and anorexia, which further outline the pathophysiological effects of E. leei.

Decreased SLC26A3 expression and function in intestinal epithelial cells in response to Cryptosporidium parvum infection

The protozoan parasite Cryptosporidium parvum (CP) causes cryptosporidiosis, a diarrheal disease worldwide. Infection in immunocompetent hosts typically results in acute, self-limiting, or recurrent diarrhea. However, in immunocompromised individuals infection can cause fulminant diarrhea, extraintestinal manifestations, and death. To date, the mechanisms underlying CP-induced diarrheal pathogenesis are poorly understood. Diarrheal diseases most commonly involve increased secretion and/or decreased absorption of fluid and electrolytes. We and others have previously shown impaired chloride absorption in infectious diarrhea due to dysregulation of SLC26A3 [downregulated in adenoma (DRA)], the human intestinal apical membrane Cl^-/HCO3- exchanger protein. However, there are no studies on the effects of CP infection on DRA activity. Therefore, we examined the expression and function of DRA in intestinal epithelial cells in response to CP infection in vitro and in vivo. CP infection (0.5 × 10⁶ oocysts/well in 24-well plates, 24 h) of Caco-2 cell monolayers significantly decreased Cl^-/HCO3- exchange activity (measured as DIDS-sensitive ¹²⁵I uptake) as well as DRA mRNA and protein levels. Substantial downregulation of DRA mRNA and protein was also observed following CP infection ex vivo in mouse enteroid-derived monolayers and in vivo in the ileal and jejunal mucosa of C57BL/6 mice for 24 h. However, at 48 h after infection in vivo, the effects on DRA mRNA and protein were attenuated and at 5 days after infection DRA returned to normal levels. Our results suggest that impaired chloride absorption due to downregulation of DRA could be one of the contributing factors to CP-induced acute, self-limiting diarrhea in immunocompetent hosts.

The Role of Probiotics and Prebiotics in the Prevention and Treatment of Obesity

Obesity is a global pandemic complex to treat due to its multifactorial pathogenesis-an unhealthy lifestyle, neuronal and hormonal mechanisms, and genetic and epigenetic factors are involved. Scientific evidence supports the idea that obesity and metabolic consequences are strongly related to changes in both the function and composition of gut microbiota, which exert an essential role in modulating energy metabolism. Modifications of gut microbiota composition have been associated with variations in body weight and body mass index. Lifestyle modifications remain as primary therapy for obesity and related metabolic disorders. New therapeutic strategies to treat/prevent obesity have been proposed, based on pre- and/or probiotic modulation of gut microbiota to mimic that found in healthy non-obese subjects. Based on human and animal studies, this review aimed to discuss mechanisms through which gut microbiota could act as a key modifier of obesity and related metabolic complications. Evidence from animal studies and human clinical trials suggesting potential beneficial effects of prebiotic and various probiotic strains on those physical, biochemical, and metabolic parameters related to obesity is presented. As a conclusion, a deeper knowledge about pre-/probiotic mechanisms of action, in combination with adequately powered, randomized controlled follow-up studies, will facilitate the clinical application and development of personalized healthcare strategies.

Enhancement of connexin30.3 expression in mouse embryonic stem cell line EB3 in response to cell-cell contacts

To clarify the potential role of gap junction in cell-cell contact response, the expression of connexin30.3 gene (Cx30.3), a specifically expressed isoform in undifferentiated state of mouse embryonic stem (ES) cell line EB3 was investigated under different cell-cell contact conditions. ES cells were cultured by hanging drop culture method to increase cell-cell contact frequency. As control, a single cell culture was conducted. After culture for 12 h, the Cx30.3 expression level in hanging drop culture reached 1.73-fold that of the control (p < 0.001). By contrast, connexin43 gene (Cx43), a ubiquitously expressed gene, showed no difference between both cultures. The experiment of E-cadherin inhibition and β-catenin knockdown suggested the action of E-cadherin upstream of the Cx30.3 regulating pathway. The cell-cell contacts with different cell lines such as HeLa cells and B16/BL6 caused no effect on the Cx30.3 in ES cells. These suggest a potential role of Cx30.3 as a cell-cell contact signal mediator partially regulated by E-cadherin signaling.