The role of enterocytes in the intestinal barrier function and antigen uptake

Avian intestinal ultrastructure changes provide insight into the pathogenesis of enteric diseases and probiotic mode of action

Epithelial damage and loss of barrier integrity occur following intestinal infections in humans and animals. Gut health was evaluated by electron microscopy in an avian model that exposed birds to subclinical necrotic enteritis (NE) and fed them a diet supplemented with the probiotic Bacillus amyloliquefaciens strain H57 (H57). Scanning electron microscopy of ileal mucosa revealed significant villus damage, including focal erosions of epithelial cells and villous atrophy, while transmission electron microscopy demonstrated severe enterocyte damage and loss of cellular integrity in NE-exposed birds. In particular, mitochondria were morphologically altered, appearing irregular in shape or swollen, and containing electron-lucent regions of matrix and damaged cristae. Apical junctional complexes between adjacent enterocytes were significantly shorter, and the adherens junction was saccular, suggesting loss of epithelial integrity in NE birds. Segmented filamentous bacteria attached to villi, which play an important role in intestinal immunity, were more numerous in birds exposed to NE. The results suggest that mitochondrial damage may be an important initiator of NE pathogenesis, while H57 maintains epithelium and improves the integrity of intestinal mucosa. Potential actions of H57 are discussed that further define the mechanisms responsible for probiotic bacteria’s role in maintaining gut health.

Oral Biologic Delivery: Advances Toward Oral Subunit, DNA, and mRNA Vaccines and the Potential for Mass Vaccination During Pandemics

Oral vaccination enables pain-free and self-administrable vaccine delivery for rapid mass vaccination during pandemic outbreaks. Furthermore, it elicits systemic and mucosal immune responses. This protects against infection at mucosal surfaces, which may further enhance protection and minimize the spread of disease. The gastrointestinal (GI) tract presents a number of prospective mucosal inductive sites for vaccine targeting, including the oral cavity, stomach, and small intestine. However, currently available oral vaccines are effectively limited to live-attenuated and inactivated vaccines against enteric diseases. The GI tract poses a number of challenges,including degradative processes that digest biologics and mucosal barriers that limit their absorption. This review summarizes the approaches currently under development and future opportunities for oral vaccine delivery to established (intestinal) and relatively new (oral cavity, stomach) mucosal targets. Special consideration is given to recent advances in oral biologic delivery that offer promise as future platforms for the administration of oral vaccines.

Role of enterocyte-specific gene polymorphisms in response to adjuvant treatment for stage III colorectal cancer

OBJECTIVES

The enterocyte subtype of colorectal cancer (CRC) responds favorably to oxaliplatin-based adjuvant treatment for stage III CRC. We examined the clinical significance of single-nucleotide polymorphisms (SNPs) in enterocyte-related genes MS4A12 and CDX2 in response to adjuvant treatment for stage III CRC.

PATIENTS AND METHODS

A total of 350 patients with stage III CRC were included: 274 received adjuvant treatment with surgical resection (discovery cohort) and 76 received surgery alone (control cohort). In the discovery cohort, 68 patients received FOLFOX and 206 received oral fluoropyrimidine. SNPs were analyzed by PCR-based direct sequencing.

RESULTS

In the discovery cohort, the MS4A12 rs4939378 G/G variant was associated with lower 5-year survival than any A allele [70% vs. 90%, univariate: hazard ratio (HR) 2.29, 95% confidence interval (CI) 1.03-5.06, P = 0.035; multivariate: HR 2.58, 95% CI 1.15-5.76, P = 0.021]. Patients with the CDX2 rs3812863 G/G variant had better overall survival than those with any A allele, although this was not significant in multivariate analysis (5 year-survival: 95% vs. 82%, univariate: HR 0.34, 95% CI 0.12-0.97, P = 0.034; multivariate: HR 0.39, 95% CI 0.13-1.11, P = 0.078). The SNPs did not show significant association with overall survival in the control cohort, and significant interaction was observed between MS4A12 genotypes and groups (P = 0.007).

CONCLUSIONS

Our findings suggest that MS4A12 and CDX2 gene polymorphisms may predict outcome in stage III CRC. However, the clinical significance of SNPs for response to oxaliplatin may differ by tumor stage.

CdsH Contributes to the Replication of Salmonella Typhimurium inside Epithelial Cells in a Cysteine-Supplemented Medium

Salmonella Typhimurium is a facultative, intracellular pathogen whose products range from self-limited gastroenteritis to systemic diseases. Food ingestion increases biomolecules' concentration in the intestinal lumen, including amino acids such as cysteine, which is toxic in a concentration-dependent manner. When cysteine's intracellular concentration reaches toxic levels, S. Typhimurium expresses a cysteine-inducible enzyme (CdsH), which converts cysteine into pyruvate, sulfide, and ammonia. Despite this evidence, the biological context of cdsH's role is not completely clear, especially in the infective cycle. Since inside epithelial cells both cdsH and its positive regulator, ybaO, are overexpressed, we hypothesized a possible role of cdsH in the intestinal phase of the infection. To test this hypothesis, we used an in vitro model of HT-29 cell infection, adding extra cysteine to the culture medium during the infective process. We observed that, at 6 h post-invasion, the wild type S. Typhimurium proliferated 30% more than the ΔcdsH strain in the presence of extra cysteine. This result shows that cdsH contributes to the bacterial replication in the intracellular environment in increased concentrations of extracellular cysteine, strongly suggesting that cdsH participates by increasing the bacterial fitness in the intestinal phase of the S. Typhimurium infection.

In Vitro Studies Toward the Use of Chitin as Nutraceutical: Impact on the Intestinal Epithelium, Macrophages, and Microbiota

SCOPE

Chitin, the most abundant polysaccharide found in nature after cellulose, is known for its ability to support wound healing and to lower plasma-oxidized low-density lipoprotein (LDL) levels. Studies have also revealed immunomodulatory potential but contradicting results are often impossible to coalesce through usage of chitin of different or unknown physicochemical consistency. In addition, only a limited set of cellular models have been used to test the bioactivity of chitin.

METHODS AND RESULTS

Chitin is investigated with well-defined physicochemical consistency for its immunomodulatory potency using THP-1 macrophages, impact on intestinal epithelial barrier using Caco-2 cells, and fermentation by fecal-derived microbiota. Results show that chitin with a degree of acetylation (DA) of ≈83%, regardless of size, does not affect the intestinal epithelial barrier integrity. Large-sized chitin significantly increases acetic acid production by gut microbiota without altering the composition. Exposure of small-sized chitin to THP-1 macrophages lead to significantly increased secretion of IL-1β, IL-8, IL-10, and CXCL10 in a multi-receptor and clathrin-mediated endocytosis dependent manner.

CONCLUSIONS

These findings indicate that small-sized chitin does not harm the intestinal barrier nor affects SCFA secretion and microbiota composition, but does impact immune activity which could be beneficial to subjects in need of immune support or activation.

Cell fate specification and differentiation in the adult mammalian intestine

Intestinal stem cells at the bottom of crypts fuel the rapid renewal of the different cell types that constitute a multitasking tissue. The intestinal epithelium facilitates selective uptake of nutrients while acting as a barrier for hostile luminal contents. Recent discoveries have revealed that the lineage plasticity of committed cells - combined with redundant sources of niche signals - enables the epithelium to efficiently repair tissue damage. New approaches such as single-cell transcriptomics and the use of organoid models have led to the identification of the signals that guide fate specification of stem cell progeny into the six intestinal cell lineages. These cell types display context-dependent functionality and can adapt to different requirements over their lifetime, as dictated by their microenvironment. These new insights into stem cell regulation and fate specification could aid the development of therapies that exploit the regenerative capacity and functionality of the gut.

The Ethanolamine-Sensing Transcription Factor EutR Promotes Virulence and Transmission during Citrobacter rodentium Intestinal Infection

Enteric pathogens exploit chemical and nutrient signaling to gauge their location within a host and control expression of traits important for infection. Ethanolamine-containing molecules are essential in host physiology and play important roles in intestinal processes. The transcription factor EutR is conserved in the Enterobacteriaceae and is required for ethanolamine sensing and metabolism. In enterohemorrhagic Escherichia coli (EHEC) O157:H7, EutR responds to ethanolamine to activate expression of traits required for host colonization and disease; however, the importance of EutR to EHEC intestinal infection has not been examined. Because EHEC does not naturally colonize or cause disease in mice, we employed the natural murine pathogen Citrobacter rodentium as a model of EHEC virulence to investigate the importance of EutR in vivo EHEC and C. rodentium possess the locus of enterocyte effacement (LEE), which is the canonical virulence trait of attaching and effacing pathogens. Our findings demonstrate that ethanolamine sensing and EutR-dependent regulation of the LEE are conserved in C. rodentium Moreover, during infection, EutR is required for maximal LEE expression, colonization, and transmission efficiency. These findings reveal that EutR not only is important for persistence during the primary host infection cycle but also is required for maintenance in a host population.

Anisakis simplex products impair intestinal epithelial barrier function and occludin and zonula occludens-1 localisation in differentiated Caco-2 cells

BACKGROUND

Anisakis spp. are nematode parasites found in a wide range of marine organisms. Human beings may accidentally become infected, showing the symptoms of anisakiasis and allergic responses. There has been evidence of increased intestinal permeability in A. simplex-sensitized subjects and that specific IgE titres increase in some allergic patients when fishery products are re-introduced into their diet. The aims of this work were to study the effect of A. simplex crude extract on the intestinal integrity and permeability by using Caco-2 cell monolayer. To analyse the capacity of Ani s 4 allergen to cross the epithelial barrier.

METHODOLOGY/PRINCIPAL FINDINGS

Cellular bioenergetics, transepithelial electrical resistance, viability, permeability, reactive oxygen species generation and immunofluorescent staining of tight junction proteins were analysed. A. simplex crude extract compromises the Caco-2 cell monolayer integrity in a dose-dependent manner. This effect is detected at 1 hour of culture and integrity is recovered after 24 hours of culture. The epithelial barrier disruption is accompanied by an increase in paracellular permeability and reactive oxygen species production and by a delocalization of occludin and zonula occludens-1. Finally, Ani s 4, a thermostable and resistant to digestion allergen with cystatin activity, is able to cross the epithelial barrier in Caco-2 monolayer and reach a cumulative mean percentage of 22.7% of total concentration in the basolateral side after 24 hours of culture.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate that A. simplex induces an early and reversible alteration of integrity and permeability of Caco-2 cell monolayer and that an underlying mechanism of this effect would involve the oxidative stress and disruption of epithelial tight junctions. Additionally, it has been shown that Ani s 4 allergen is able to cross the epithelial barrier. These findings could explain the increased intestinal permeability observed in Anisakis-sensitized patients, the changes over time in IgE sensitization to A. simplex allergens, and the specific IgE persistence in Anisakis allergy.

Production and characterization of avian crypt-villus enteroids and the effect of chemicals

BACKGROUND

Three-dimensional models of cell culture such as organoids and mini organs accord better advantage over regular cell culture because of their ability to simulate organ functions hence, used for disease modeling, metabolic research, and the development of therapeutics strategies. However, most advances in this area are limited to mammalian species with little progress in others such as poultry where it can be deployed to study problems of agricultural importance. In the course of enterocyte culture in chicken, we observed that intestinal mucosal villus-crypts self-repair and form spheroid-like structures which appear to be useful as ex vivo models to study enteric physiology and diseases.

RESULTS

The villus-crypts harvested from chicken intestinal mucosa were cultured to generate enteroids, purified by filtration then re cultured with different chemicals and growth factors to assess their response based on their morphological dispositions. Histochemical analyses using marker antibodies and probes showed the enteroids consisting different cell types such as epithelial, goblet, and enteroendocrine cells typical to villi and retain functional characteristics of intestinal mucosa.

CONCLUSIONS

We present a simple procedure to generate avian crypt-villous enteroids containing different cell types. Because the absorptive cells are functionally positioned outwards, similar to the luminal enterocytes, the cells have better advantages to interact with the factors present in the culture medium. Thus, the enteroids have the potential to study the physiology, metabolism, and pathology of the intestinal villi and can be useful for preliminary screenings of the factors that may affect gut health in a cost-effective manner and reduce the use of live animals.

Intestinal Organoids Generated from Human Pluripotent Stem Cells

The gastrointestinal system is one of the most complex organ systems in the human body, and consists of numerous cell types originating from three germ layers. To understand intestinal development and homeostasis and elucidate the pathogenesis of intestinal disorders, including unidentified diseases, several in vitro models have been developed. Human pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have remarkable developmental plasticity and possess the potential for a wide variety of applications. Three-dimensional organs, termed organoids and produced in vitro by PSCs, contain not only epithelium but also mesenchymal tissue and partially recapitulate intestinal functions. Such intestinal organoids have begun to be applied in disease models and drug development and have contributed to a detailed analysis of molecular interactions and findings in the synergistic development of biomedicine for human digestive organs. In this review, we describe gastrointestinal organoid technology derived from PSCs and consider its potential applications.

The relevance of a digestibility evaluation in the allergenicity risk assessment of novel proteins. Opinion of a joint initiative of COST action ImpARAS and COST action INFOGEST

The current allergenicity assessment of novel proteins is based on the EFSA GMO guidance. Recently, EFSA launched a new guidance document on allergenicity assessment of GM plants (2017). This document describes, amongst other topics, the new scientific and regulatory developments on in vitro protein digestibility tests. The EFSA GMO Panel stated that for in vitro protein digestibility tests, additional investigations are needed before any additional recommendation in the form of guidance can be provided. To this end, an interim phase is considered necessary to evaluate the revisions to the in vitro gastrointestinal digestion test, proposed by EFSA. This prompted the establishment of a joint workshop through two COST Action networks: COST Action ImpARAS and COST Acton INFOGEST. In 2017, a workshop was organised to discuss the relevance of digestion in allergenicity risk assessment and how to potentially improve the current methods and readouts. The outcome of the workshop is that there is no rationale for a clear readout that is predictive for allergenicity and we suggest to omit the digestion test from the allergenicity assessment strategy for now, and put an effort into filling the knowledge gaps as summarized in this paper first.

A soluble and highly fermentable dietary fiber with carbohydrases improved gut barrier integrity markers and growth performance in F18 ETEC challenged pigs1

This study aimed to evaluate the effects of a source of dietary soluble (SF) and insoluble fiber (IF) without or with exogenous carbohydrases (xylanase, β-glucanase, and pectinase) on diarrhea incidence, selected immune responses, and growth performance in enterotoxigenic Escherichia coli (ETEC)-challenged pigs. Sixty weaned pigs (6.9 ± 0.1 kg BW, ~23 d of age) were blocked by initial BW and placed in individual pens. Pens were randomly assigned to one of six treatments (n = 10 per treatment), including a nonchallenged control (NC), a positive challenge control (PC), the PC + a soluble fiber diet (10% sugar beet pulp) without (SF-) or with carbohydrases (SF+), and PC + an IF diet (15% corn distillers dried grains with solubles) without (IF-) or with carbohydrases (IF+). The control diet was primarily based on corn and soybean meal with 13.5% whey powder. The two sources of fiber were added at the expense of cornstarch in the control diet. Pigs were orally inoculated with 6 mL hemolytic F18 ETEC (~3.5 × 109 cfu/mL) or sham infected with 6 mL phosphate-buffered saline on day 7 (0 d postinoculation, dpi) postweaning. All ETEC challenged pigs were confirmed to be genetically susceptible to F18 ETEC. Pigs had free access to feed and water throughout the 14-d trial. Pig BW and feed intake were recorded on dpi -7, 0, and 7 or 8. Fecal swabs were collected on dpi -7, 0, 1, 2, 3, 5, and 7 or 8 to evaluate hemolytic E. coli shedding. Fecal score was visually ranked daily postchallenge to evaluate diarrhea incidence. Blood samples were collected on dpi -1, 3, and 7 or 8 at necropsy and intestinal tissues were collected at necropsy. Pigs on PC had lower dpi 1 to 7 ADG and ADFI than those on NC (P < 0.05). Compared with PC pigs, SF+ pigs had greater ADG during both pre- and postchallenge period (P < 0.05). The IF- increased postchallenge diarrhea incidence compared with PC (P < 0.05). Pigs on SF- had lower ileal E. coli attachment than PC (P < 0.05). The SF+ reduced haptoglobin and IF+ reduced C-reactive protein on dpi 3 compared with PC (P < 0.05). Compared with PC pigs, SF+ pigs tended to have lower ileal tumor necrosis factor alpha and greater ileal occludin (OCLN) mRNA (P < 0.10) and had greater (P < 0.05) colonic OCLN mRNA levels. Collectively, IF- increased incidence of diarrhea and fecal E. coli shedding compared with PC. The SF+ pigs had improved growth compared with PC pigs, likely due in part to a reduction in inflammatory intermediates.

The role of autophagy in maintaining intestinal mucosal barrier

The intestinal mucosal barrier is the first line to defense against luminal content penetration and performs numerous biological functions. The intestinal epithelium contains a huge surface that is lined by a monolayer of intestinal epithelial cells (IECs). IECs are dominant mediators in maintaining intestinal homeostasis that drive diverse functions including nutrient absorption, physical segregation, secretion of antibacterial peptides, and modulation of immune responses. Autophagy is a cellular self-protection mechanism in response to various stresses, and accumulating studies have revealed its importance in participating physiological processes of IECs. The regulatory effects of autophagy depend on the specific IEC types. This review aims to elucidate the myriad roles of autophagy in regulating the functions of different IECs (stem cells, enterocytes, goblet cells, and Paneth cells), and present the progress of autophagy-targeting therapy in intestinal diseases. Understanding the involved mechanisms can provide new preventive and therapeutic strategies for gastrointestinal dysfunction and diseases.

Innate and adaptive immunity in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most frequent and devastating gastrointestinal disease of premature infants. Although the precise mechanisms are not fully understood, NEC is thought to develop following a combination of prematurity, formula feeding, and adverse microbial colonization. Within the last decade, studies increasingly support an important role of a heightened mucosal immune response initiating a pro-inflammatory signaling cascade, which can lead to the disruption of the intestinal epithelium and translocation of pathogenic species. In this review, we first describe the cellular composition of the intestinal epithelium and its critical role in maintaining epithelial integrity. We then discuss cell signaling during NEC, specifically, toll-like receptors and nucleotide oligomerization domain-like receptors. We further review cytokines and cellular components that characterize the innate and adaptive immune systems and how they interact to support or modulate NEC development.

A method to culture chicken enterocytes and their characterization

Enterocytes function as both absorptive and protective components of intestine that come in close contact with a variety of enteric factors, such as dietary, microbial, and parasites, that have potential to affect the organismal health. Understanding how enterocytes interact with this complex array of factors may help improve gut health particularly in the context of poultry production where it is also linked to food safety issues. The enterocyte in vitro culture can help screen different factors and their interactions with microbiome, and potentially be utilized in the development of interventions strategies for pathogens such as antibiotic alternatives. We developed a method to culture primary chicken enterocytes and conducted their characterization using cytochemical and proteomic methods, and investigated their potential to respond to different chemical stimuli. Using selected micronutrients, microbial toxins, and metabolic modulators, we assessed their effects on the viability and morphological changes in enterocytes. We found that whereas some nutritional factors (calcitriol, retinoic acid) produced different morphological changes, toxins such as aflatoxin B1 and deoxynivalenol produced enterocyte degeneration and death, and the bacterial lipopolysaccharide had very little effect compared on the basis of their mass. Both cyclic AMP and phorbol myristate acetate exhibited some cachectic effects on enterocytes with the later showing more severe changes. Thyroxin induced distinct morphological changes making the cells more cuboidal and Na-butyrate produced no significant change in morphology. The cytochemical and proteomic characterization suggest that these enterocytes largely belong to epithelial cell categories which may be amenable to analysis of biochemical paths and mechanisms of action of different factors that affect these cells. Based on these results we conclude that chicken enterocyte culture can be a useful in vitro model to study intestinal physiology.

Immunomodulatory Effects of Probiotics on Cytokine Profiles

Probiotics confer immunological protection to the host through the regulation, stimulation, and modulation of immune responses. Researchers have shifted their attention to better understand the immunomodulatory effects of probiotics, which have the potential to prevent or alleviate certain pathologies for which proper medical treatment is as yet unavailable. It has been scientifically established that immune cells (T- and B-cells) mediate adaptive immunity and confer immunological protection by developing pathogen-specific memory. However, this review is intended to present the recent studies on immunomodulatory effects of probiotics. In the early section of this review, concepts of probiotics and common probiotic strains are focused on. On a priority basis, the immune system, along with mucosal immunity in the human body, is discussed in this study. It has been summarized that a number of species of Lactobacillus and Bifidobacterium exert vital roles in innate immunity by increasing the cytotoxicity of natural killer cells and phagocytosis of macrophages and mediate adaptive immunity by interacting with enterocytes and dendritic, Th1, Th2, and Treg cells. Finally, immunomodulatory effects of probiotics on proinflammatory and anti-inflammatory cytokine production in different animal models have been extensively reviewed in this paper. Therefore, isolating new probiotic strains and investigating their immunomodulatory effects on cytokine profiles in humans remain a topical issue.

Hydrophobically modified chitosan nanoliposomes for intestinal drug delivery

Background

Encapsulation of hydrophilic drugs within liposomes can be challenging.

Methods

A novel chitosan derivative, O-palmitoyl chitosan (OPC) was synthesized from chitosan and palmitoyl chloride using methane-sulfonic acid as a solvent. The success of synthesis was confirmed by Fourier transform infra-red (FT-IR) spectroscopy and proton NMR spectroscopy (H-NMR). Liposomes encapsulating ferrous sulphate as a model hydrophilic drug for intestinal delivery were prepared with or without OPC inclusion (Lipo-Fe and OPC-Lipo-Fe).

Results

Entrapment of iron was significantly higher in OPC containing liposomes compared to controls. Quantitative iron absorption from the OPC liposomes was significantly higher (1.5-fold P<0.05) than free ferrous sulphate controls. Qualitative uptake analysis by confocal imaging using coumarin-6 dye loaded liposomes also indicated higher cellular uptake and internalization of the OPC-containing liposomes.

Conclusion

These findings suggest that addition of OPC during liposome preparation creates robust vesicles that have improved mucoadhesive and absorption enhancing properties. The chitosan derivative OPC therefore provides a novel alternative for formulation of delivery vehicles targeting intestinal absorption.

Recent advances of polysaccharide-based nanoparticles for oral insulin delivery

Diabetes mellitus is a highly prevalent metabolic and chronic disease affecting millions of people in the world. The most common route of insulin therapy is the subcutaneous injection due to its low bioavailability and enzymatic degradation. The search for effective and high patient compliance insulin delivery systems has been a major challenge over many decades. The polysaccharide-based nanoparticles as delivery vehicles for insulin oral administration have recently attracted substantial interests. The present review highlights the recent advances on the development of nanoparticles prepared from polysaccharides, including chitosan, alginate, dextran and glucan, for oral delivery of insulin, overcoming multiple barriers in gastrointestinal tract. The aims of this review are first to summarize the strategies that have been applied in the past 5 years to fabricate polysaccharide-based nanoparticles for insulin oral delivery, and then to provide in-depth understanding on the mechanisms by which such nanoparticles protect insulin against degradation in the digestive tract and provide sustained release to enhance mucus permeation and transepithelial transport of insulin administered via oral route.

Effects of dietary inclusion of Moringa oleifera leaves on growth and some systemic and mucosal immune parameters of seabream

The effect of the dietary incorporation of drumstick, Moringa oleifera, leaf meal (MOL; 0, 5, 10 and 15%) on the growth, feed utilization, some skin mucus and systemic immune parameters and intestinal immune-related gene expression in gilthead seabream (Sparus aurata) specimens. The experiment lasted 4 weeks. The results revealed that MOL can be incorporated in S. aurata diet up to 10% with no significant negative effect on growth and feed utilization. However, there was a significant decrease with MOL at a level of 15% after 2 weeks of feeding. The systemic immune status of fish fed with the different levels of MOL showed an improvement in head kidney leucocyte phagocytosis, respiratory burst and peroxidase activities. Also, serum humoral components, including protease, ACH₅₀ and lysozyme activities and IgM level, increased with MOL inclusion especially at the 5% level. MOL at 5% improved skin-mucosal immunity such as protease, antiprotease, peroxidase and lysozyme activities. Moreover, the feeding of MOL revealed an upregulation of the intestinal mucosal immunity genes (lyso and c3), tight junction proteins (occludin and zo-1) and anti-inflammatory cytokines (tgf-β) with a downregulation of pro-inflammatory cytokine (tnf-α). Therefore, it is recommended to incorporate MOL in S. aurata diets at a level of 5% for the best immune status or 10% for the high growth performance and acceptable immune surveillance. Graphical abstract ᅟ.

Evolving understanding of neonatal necrotizing enterocolitis

PURPOSE OF REVIEW

Necrotizing enterocolitis (NEC) is a devastating disease that predominately affects premature neonates. The pathogenesis of NEC is multifactorial and poorly understood. Risk factors include low birth weight, formula-feeding, hypoxic/ischemic insults, and microbial dysbiosis. This review focuses on our current understanding of the diagnosis, management, and pathogenesis of NEC.

RECENT FINDINGS

Recent findings identify specific mucosal cell types as potential therapeutic targets in NEC. Despite a broadly accepted view that bacterial colonization plays a key role in NEC, characteristics of bacterial populations associated with this disease remain elusive. The use of probiotics such as lactobacilli and bifidobacteria has been studied in numerous trials, but there is a lack of consensus regarding specific strains and dosing. Although growth factors found in breast milk such as epidermal growth factor and heparin-binding epidermal growth factor may be useful in disease prevention, developing new therapeutic interventions in NEC critically depends on better understanding of its pathogenesis.

SUMMARY

NEC is a leading cause of morbidity and mortality in premature neonates. Recent data confirm that growth factors and certain bacteria may offer protection against NEC. Further studies are needed to better understand the complex pathogenesis of NEC.

Effects of dietary threonine supplementation on intestinal barrier function and gut microbiota of laying hens

The effects of supplemental dietary threonine (Thr) on laying performance, expression of intestinal mucin 2 (MUC2) and secretory IgA (sIgA), and intestinal microbiota of laying hens fed a low CP diet were investigated. A total of 240 Lohmann Brown laying hens, 28 wk of age, was allocated to 3 dietary treatments, each of which included 5 replicates of 16 hens. Hens were fed a control diet (16% CP), a low CP diet (14% CP), or a low CP diet supplemented with 0.3% L-Thr for 12 weeks. Chemical analyses of the diets for Thr are 0.49, 0.45, and 0.69%, respectively. Lowering dietary CP impaired egg production and egg mass of laying hens. Dietary Thr supplementation to the low CP diet increased (P < 0.05) egg production and egg mass. In addition, ileal sIgA contents and MUC2 and sIgA mRNA expression were increased (P < 0.05) by dietary Thr addition. Dietary CP reduction reduced (P < 0.05) intestinal bacterial diversity, whereas dietary Thr supplementation to the low CP diet recovered the bacteria diversity and significantly increased the abundance of potential beneficial bacteria. In conclusion, dietary Thr supplementation to a low CP diet could affect intestinal health and hence productivity via regulating intestinal mucin and sIgA expression, and microbial population of laying hens.

Gut microbial functional maturation and succession during human early life

The evolutional trajectory of gut microbial colonization from birth has been shown to prime for health later in life. Here, we combined cultivation-independent 16S rRNA gene sequencing and metaproteomics to investigate the functional maturation of gut microbiota in faecal samples from full-term healthy infants collected at 6 and 18 months of age. Phylogenetic analysis of the metaproteomes showed that Bifidobacterium provided the highest number of distinct protein groups. Considerable divergences between taxa abundance and protein phylogeny were observed at all taxonomic ranks. Age had a profound effect on early microbiota where compositional and functional diversity of less dissimilar communities increased with time. Comparisons of the relative abundances of proteins revealed the transition of taxon-associated saccharolytic and fermentation strategies from milk and mucin-derived monosaccharide catabolism feeding acetate/propanoate synthesis to complex food-derived hexoses fuelling butanoate production. Furthermore, co-occurrence network analysis uncovered two anti-correlated modules of functional taxa. A low-connected Bifidobacteriaceae-centred guild of facultative anaerobes was succeeded by a rich club of obligate anaerobes densely interconnected around Lachnospiraceae, underpinning their pivotal roles in microbial ecosystem assemblies. Our findings establish a framework to visualize whole microbial community metabolism and ecosystem succession dynamics, proposing opportunities for microbiota-targeted health-promoting strategies early in life.

Nutritional management of the foal with diarrhoea

Diarrhoea is a common problem in the neonatal and suckling foal. In certain circumstances supplemental nutrition is necessary depending on the age of foal, severity of diarrhoea and presence of other systemic manifestations. Nutritional supplementation can be provided either enterally or parenterally. Enteral nutrition is superior to parenteral nutrition because it is the most natural and physiologically sound means to provide nutritional support. Parenteral nutrition may be warranted if the foal is unable to receive or tolerate enteral nutrition. Dextrose alone or with amino acids and lipids can provide appropriate nutrition when enteral feeding is not tolerated. As soon as the foal stabilises enteral feeding can be reintroduced.

Salmonella enterica Serovar Typhimurium Strategies for Host Adaptation

Bacterial pathogens must sense and respond to newly encountered host environments to regulate the expression of critical virulence factors that allow for niche adaptation and successful colonization. Among bacterial pathogens, non-typhoidal serovars of Salmonella enterica, such as serovar Typhimurium (S. Tm), are a primary cause of foodborne illnesses that lead to hospitalizations and deaths worldwide. S. Tm causes acute inflammatory diarrhea that can progress to invasive systemic disease in susceptible patients. The gastrointestinal tract and intramacrophage environments are two critically important niches during S. Tm infection, and each presents unique challenges to limit S. Tm growth. The intestinal tract is home to billions of commensal microbes, termed the microbiota, which limits the amount of available nutrients for invading pathogens such as S. Tm. Therefore, S. Tm encodes strategies to manipulate the commensal population and side-step this nutritional competition. During subsequent stages of disease, S. Tm resists host immune cell mechanisms of killing. Host cells use antimicrobial peptides, acidification of vacuoles, and nutrient limitation to kill phagocytosed microbes, and yet S. Tm is able to subvert these defense systems. In this review, we discuss recently described molecular mechanisms that S. Tm uses to outcompete the resident microbiota within the gastrointestinal tract. S. Tm directly eliminates close competitors via bacterial cell-to-cell contact as well as by stimulating a host immune response to eliminate specific members of the microbiota. Additionally, S. Tm tightly regulates the expression of key virulence factors that enable S. Tm to withstand host immune defenses within macrophages. Additionally, we highlight the chemical and physical signals that S. Tm senses as cues to adapt to each of these environments. These strategies ultimately allow S. Tm to successfully adapt to these two disparate host environments. It is critical to better understand bacterial adaptation strategies because disruption of these pathways and mechanisms, especially those shared by multiple pathogens, may provide novel therapeutic intervention strategies.

Tenofovir disoproxil fumarate loaded PLGA nanoparticles for enhanced oral absorption: Effect of experimental variables and in vitro, ex vivo and in vivo evaluation

In this study, PLGA based nanoparticles of tenofovir disoproxil fumarate (TDF) were designed for enhancing its oral absorption. To develop PLGA based TDF nanoparticles with the goal of minimum particle size and maximum entrapment efficiency statistical optimization techniques (factorial design and response surface methodology) were employed. The optimized nanoparticles were characterized for size, shape, charge and physical state. Further, the stability, cytotoxicity and metabolic protective effect of the nanoparticles were evaluated. Single dose pharmacokinetic study in rats was conducted to evaluate the oral absorption of the designed nanoparticles. Ex vivo everted gut sac studies were performed to evaluate the role of active uptake mechanisms in the absorption of the designed nanoparticles. The results showed that the statistical models employed could determine the interaction effects of the critical factors which were used in the optimization of the nanoparticles. The optimized nanoparticles with a particle size of 218±3.85nm and an entrapment efficiency of 57.3±1.6%. The nanoparticles were able to increase the AUC of tenofovir by 5.8 fold. It was observed that active uptake mechanisms predominantly via clathrin-mediated uptake played a key role in increasing the oral absorption of TDF.

Isolevuglandins as a gauge of lipid peroxidation in human tumors

The cellular production of free radicals or reactive oxygen species (ROS) can lead to protein, lipid or DNA modifications and tumor formation. The cellular lipids undergo structural changes through the actions of enzymes (e.g. cyclooxygenases) or free radicals to form a class of compounds called Isolevuglandins (IsoLGs). The recruitment and continued exposure of tissue to ROS and IsoLGs causes increased cell proliferation, mutagenesis, loss of normal cell function and angiogenesis. The elevated concentration of ROS in cancerous tissues suggests that these mediators play an important role in cancer development. We hypothesized that tumors with elevated ROS levels would similarly possess an increased concentration of IsoLGs when compared with normal tissue. Using D11, an ScFv recombinant antibody specific for IsoLGs, we utilized immunohistochemistry to visualize the presence of IsoLG in human tumors compared to normal adjacent tissue (NAT) to the same tumor. We found that IsoLG concentrations were elevated in human breast, colon, kidney, liver, lung, pancreatic and tongue tumor cells when compared to NAT and believe that IsoLGs can be used as a gauge indicative of lipid peroxidation in tumors.

Defensins, lectins, mucins, and secretory immunoglobulin A: microbe-binding biomolecules that contribute to mucosal immunity in the human gut

In the intestine, the mucosal immune system plays essential roles in maintaining homeostasis between the host and microorganisms, and protecting the host from pathogenic invaders. Epithelial cells produce and release a variety of biomolecules into the mucosa and lumen that contribute to immunity. In this review, we focus on a subset of these remarkable host-defense factors - enteric α-defensins, select lectins, mucins, and secretory immunoglobulin A - that have the capacity to bind microbes and thereby contribute to barrier function in the human gut. We provide an overview of the intestinal epithelium, describe specialized secretory cells named Paneth cells, and summarize our current understanding of the biophysical and functional properties of these select microbe-binding biomolecules. We intend for this compilation to complement prior reviews on intestinal host-defense factors, highlight recent advances in the field, and motivate investigations that further illuminate molecular mechanisms as well as the interplay between these molecules and microbes.

The Role of Mucosal Immunity in the Pathogenesis of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most devastating gastrointestinal disease of prematurity. Although the precise cause is not well understood, the main risk factors thought to contribute to NEC include prematurity, formula feeding, and bacterial colonization. Recent evidence suggests that NEC develops as a consequence of intestinal hyper-responsiveness to microbial ligands upon bacterial colonization in the preterm infant, initiating a cascade of aberrant signaling events, and a robust pro-inflammatory mucosal immune response. We now have a greater understanding of important mechanisms of disease pathogenesis, such as the role of cytokines, immunoglobulins, and immune cells in NEC. In this review, we will provide an overview of the mucosal immunity of the intestine and the relationship between components of the mucosal immune system involved in the pathogenesis of NEC, while highlighting recent advances in the field that have promise as potential therapeutic targets. First, we will describe the cellular components of the intestinal epithelium and mucosal immune system and their relationship to NEC. We will then discuss the relationship between the gut microbiota and cell signaling that underpins disease pathogenesis. We will conclude our discussion by highlighting notable therapeutic advancements in NEC that target the intestinal mucosal immunity.

Defensins, lectins, mucins, and secretory immunoglobulin A: microbe-binding biomolecules that contribute to mucosal immunity in the human gut

In the intestine, the mucosal immune system plays essential roles in maintaining homeostasis between the host and microorganisms, and protecting the host from pathogenic invaders. Epithelial cells produce and release a variety of biomolecules into the mucosa and lumen that contribute to immunity. In this review, we focus on a subset of these remarkable host-defense factors - enteric α-defensins, select lectins, mucins, and secretory immunoglobulin A - that have the capacity to bind microbes and thereby contribute to barrier function in the human gut. We provide an overview of the intestinal epithelium, describe specialized secretory cells named Paneth cells, and summarize our current understanding of the biophysical and functional properties of these select microbe-binding biomolecules. We intend for this compilation to complement prior reviews on intestinal host-defense factors, highlight recent advances in the field, and motivate investigations that further illuminate molecular mechanisms as well as the interplay between these molecules and microbes.

Biocompatibility study of quaternized chitosan on the proliferation and differentiation of Caco-2 cells as an in vitro model of the intestinal barrier

The development of different chitosan derivatives for medical applications has increased recently. Among these chitosan derivatives, quaternized chitosan was designed to improve the solubility of chitosan in biological fluids for oral drug delivery while retaining the cationic character for mucoadhesion. However, the biocompatibility of quaternized chitosan on the human intestine is unknown. In this study, we aimed to examine the potential biological effects of quaternized chitosan on the intestinal barrier, in terms of cell proliferation and cell differentiation, using the Caco-2 cell line as an in vitro model. The lower the degree of substitution of quaternized chitosan, the lower the cytotoxic and anti-proliferative effect on Caco-2 cells. In addition, the anti-proliferative effect of quaternized chitosan might induce a cell cycle disturbance and differentiation delay. Long-term continuous exposure (9 days) to quaternized chitosan caused a delay in differentiation of the Caco-2 cells even at non-cytotoxic quaternized chitosan doses (0.005% (w/v)), as shown by the low level of alkaline phosphatase in the quaternized chitosan–treated group compared to the control cells. In contrast, short-term discontinuous exposure to quaternized chitosan (0.005% (w/v) for 4 h/day over 9 days) that more realistically mimics the daily intestinal exposure did not inhibit the intestinal differentiation of Caco-2 cells. Thus, the use of a low degree of substitution and a low concentration of quaternized chitosan resulted in a good biocompatibility to the intestinal barrier supporting the potential usefulness of quaternized chitosan in the application of an oral drug delivery system.

Novel approaches: Tissue engineering and stem cells--In vitro modelling of the gut

In many intestinal diseases, the function of the epithelial lining is impaired. In this review, we describe the recent developments of in vitro intestinal stem cell cultures. When these stem cells are grown in 3D structures (organoids), they provide a model of the intestinal epithelium, which is closely similar to the growth and development of the in vivo gut. This model provides a new tool to study various diseases of malabsorption in functional detail and therapeutic applications, which could not be achieved with traditional cell lines. First, we describe the organization and function of the healthy small intestinal epithelium. Then, we discuss the establishment of organoid cultures and how these structures represent the healthy epithelium. Finally, we discuss organoid cultures as a tool for studying intrinsic properties of the epithelium, as a model for intestinal disease, and as a possible source for stem cell transplantations.

Manganese deficiency or excess caused the depression of intestinal immunity, induction of inflammation and dysfunction of the intestinal physical barrier, as regulated by NF-κB, TOR and Nrf2 signalling, in grass carp (Ctenopharyngodon idella)

Intestinal mucosal immune components and mRNA levels of inflammatory cytokines, tight junction proteins, antioxidant enzymes and related signalling molecules in young grass carp (Ctenopharyngodon idellus) under dietary manganese (Mn) deficiency or excess were investigated. Fish were fed the diets containing graded levels of Mn [3.65-27.86 mg Mn kg(-1) diet] for 8 weeks. The results demonstrated that Mn deficiency significantly decreased the lysozyme and acid phosphatase (ACP) activities, up-regulated tumour necrosis factor α (TNF-α), interleukin 8 and the signalling factor nuclear factor-κB p65, and down-regulated interleukin 10 (IL-10), transforming growth factor β1, inhibitor of signalling factors κB-α and target of rapamycin mRNA levels in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI). However, Mn deficiency did not change the C3 content in the PI, whereas it decreased the C3 contents in the MI and DI. Additionally, Mn depletion also resulted in significantly low mRNA levels for tight junction proteins (claudin-b, claudin-c, claudin-15, occludin and zonula occludens-1), antioxidant enzymes (MnSOD, GPx and CAT) and NF-E2-related factor-2 in the intestines of fish. Excessive Mn exhibited toxic effects similar to Mn deficiency, where optimal Mn contents reversed those indicators. In conclusion, Mn deficiency or excess causes the depression of intestinal immunity, induction of inflammation and dysfunction of the intestinal physical barrier relating to NF-κB, TOR and Nrf2 signalling in grass carp. Furthermore, quadratic regression analysis at 95% maximum response of lysozyme and acid phosphatase activities in the distal intestine of young grass carp revealed the optimum dietary Mn levels to be 8.90 and 8.99 mg kg(-1) diet, respectively.

Epithelial transport of immunogenic and toxic gliadin peptides in vitro

Scope

Celiac disease is an autoimmune disorder caused by failure of oral tolerance against gluten in genetically predisposed individuals. The epithelial translocation of gluten-derived gliadin peptides is an important pathogenetic step; the underlying mechanisms, however, are poorly understood. Thus, we investigated the degradation and epithelial translocation of two different gliadin peptides, the toxic P31–43 and the immunogenic P56–68. As the size, and hence, the molecular weight of peptides might have an effect on the transport efficiency we chose two peptides of the same, rather short chain length.

Methods and Results

Fluorescence labeled P31–43 and P56–68 were synthesized and studied in a transwell system with human enterocytes. Fluorometric measurements were done to reveal antigen translocation and flow cytometry as well as confocal microscopy were used to investigate cellular uptake of peptides. Structural changes of these peptides were analysed by MALDI-TOF-MS. According to fluorescence intensities, significantly more P31–43 compared to P56–68 was transported through the enterocyte layer after 24 h incubation. In contrast to previous reports, however, mass spectrometric data do not only show a time-dependent cleavage of the immunogenic P56–68, but we observed for the first time the degradation of the toxic peptide P31–43 at the apical side of epithelial cells.

Conclusion

Considering the degradation of gliadin peptides by enterocytes, measurement of fluorescence signals do not completely represent translocated intact gliadin peptides. From our experiments it is obvious that even short peptides can be digested prior to the translocation across the epithelial barrier. Thus, the chain length and the sensibility to degradations of gliadin peptides as well as the integrity of the epithelial barrier seem to be critical for the uptake of gliadin peptides and the subsequent inflammatory immune response.

Emerging micro- and nanotechnology based synthetic approaches for insulin delivery

Insulin is essential for type 1 and advanced type 2 diabetics to maintain blood glucose levels and prolong lives. The traditional administration requires frequent subcutaneous insulin injections that are associated with poor patient compliance, including pain, local tissue necrosis, infection, and nerve damage. Taking advantage of emerging micro- and nanotechnologies, numerous alternative strategies integrated with chemical approaches for insulin delivery have been investigated. This review outlines recent developments in the controlled delivery of insulin, including oral, nasal, pulmonary, transdermal, subcutaneous and closed-loop insulin delivery. Perspectives from new materials, formulations and devices at the micro- or nano-scales are specifically surveyed. Advantages and limitations of current delivery methods, as well as future opportunities and challenges are also discussed.

Hydrolysates of glycated and heat-treated peanut 7S globulin (Ara h 1) modulate human gut microbial proliferation, survival and adhesion

AIMS

Evaluation of an effect of glycation of Ara h 1 on proliferation and survival rate and adhesion of intestinal Enterococcus faecalis, Escherichia coli and Lactobacillus acidophilus.

METHODS AND RESULTS

Pure Ara h 1 heated at three different temperature conditions (G37, G60 and C145°C) in the presence or absence of glucose was subjected to enzymatic hydrolysis. Impacts of Ara h 1 hydrolysates on the bacterial proliferation, survival rate and adhesion to Caco-2 cells in mono and heterogeneous cultures were studied with fluorescent techniques: DAPI, LIVE/DEAD staining and FISH. Examined hydrolysates hindered proliferation of E. coli and Ent. faecalis with simultaneous decrease in their survival. Maillard reaction (MR, glycation) of Ara h 1 did not alter the effect of hydrolysates on bacterial proliferation rate. Hydrolysates modified at 60 and 145°C with glucose altered the profile of immobilized bacteria, mostly by lowering the number of adhering E. coli and promoting the adhesion of bacteria from genera Lactobacillus and Enterococcus.

CONCLUSIONS

Ara h1 hydrolysates processed in various ways demonstrated their strong modulatory effect on bacterial proliferation, survival rate and adhesion.

SIGNIFICANCE AND IMPACT OF THE STUDY

Reducing the adhesion of opportunistic bacteria by hydrolysates of Ara h 1 glycated at 60 and 145°C, together with modulation of immobilization of beneficial lactobacilli and enterococci, may be of relevance in terms of the physiological status of the intestinal barrier.

Transmigration route of Campylobacter jejuni across polarized intestinal epithelial cells: paracellular, transcellular or both?

Intact intercellular junctions and cellular matrix contacts are crucial structural components for the formation and maintenance of epithelial barrier functions in humans to control the commensal flora and protect against intruding microbes. Campylobacter jejuni is one of the most important zoonotic pathogens causing food-borne gastroenteritis and potentially more severe diseases such as reactive arthritis or Guillain–Barré syndrome. Crossing the intestinal epithelial barrier and host cell invasion by C. jejuni are considered to represent the primary reasons of gut tissue damage in humans and various animal model systems including monkeys, piglets, rabbits, hamsters and ferrets. C. jejuni is also able to invade underlying tissues such as the lamina propria, can enter the bloodstream, and possibly reach distinct organs such as spleen, liver or mesenteric lymph nodes. However, the molecular mechanisms as well as major bacterial and host cell factors involved in these activities are poorly understood. Various models exist by which the pathogen can trigger its own transmigration across polarized intestinal epithelial cells in vitro, the paracellular and/or transcellular mechanism. Recent studies suggest that bacterial factors such as flagellum, serine protease HtrA and lipooligosaccharide LOS may play an active role in bacterial transmigration. Here we review our knowledge on transmigration of C. jejuni as well as some other Campylobacter species, and discuss the pros and cons for the route(s) taken to travel across polarized epithelial cell monolayers. These studies provide fresh insights into the infection strategies employed by this important pathogen.

EutR is a direct regulator of genes that contribute to metabolism and virulence in enterohemorrhagic Escherichia coli O157:H7

Ethanolamine (EA) metabolism is a trait associated with enteric pathogens, including enterohemorrhagic Escherichia coli O157:H7 (EHEC). EHEC causes severe bloody diarrhea and hemolytic uremic syndrome. EHEC encodes the ethanolamine utilization (eut) operon that allows EHEC to metabolize EA and gain a competitive advantage when colonizing the gastrointestinal tract. The eut operon encodes the transcriptional regulator EutR. Genetic studies indicated that EutR expression is induced by EA and vitamin B12 and that EutR promotes expression of the eut operon; however, biochemical evidence for these interactions has been lacking. We performed EA-binding assays and electrophoretic mobility shift assays (EMSAs) to elucidate a mechanism for EutR gene regulation. These studies confirmed EutR interaction with EA, as well as direct binding to the eutS promoter. EutR also contributes to expression of the locus of enterocyte effacement (LEE) in an EA-dependent manner. We performed EMSAs to examine EutR activation of the LEE. The results demonstrated that EutR directly binds the regulatory region of the ler promoter. These results present the first mechanistic description of EutR gene regulation and reveal a novel role for EutR in EHEC pathogenesis.

Probiotics, prebiotics and immunomodulation of gut mucosal defences: homeostasis and immunopathology

Probiotics are beneficial microbes that confer a realistic health benefit on the host, which in combination with prebiotics, (indigestible dietary fibre/carbohydrate), also confer a health benefit on the host via products resulting from anaerobic fermentation. There is a growing body of evidence documenting the immune-modulatory ability of probiotic bacteria, it is therefore reasonable to suggest that this is potentiated via a combination of prebiotics and probiotics as a symbiotic mix. The need for probiotic formulations has been appreciated for the health benefits in "topping up your good bacteria" or indeed in an attempt to normalise the dysbiotic microbiota associated with immunopathology. This review will focus on the immunomodulatory role of probiotics and prebiotics on the cells, molecules and immune responses in the gut mucosae, from epithelial barrier to priming of adaptive responses by antigen presenting cells: immune fate decision-tolerance or activation? Modulation of normal homeostatic mechanisms, coupled with findings from probiotic and prebiotic delivery in pathological studies, will highlight the role for these xenobiotics in dysbiosis associated with immunopathology in the context of inflammatory bowel disease, colorectal cancer and hypersensitivity.

Nimodipine nanocrystals for oral bioavailability improvement: role of mesenteric lymph transport in the oral absorption

PURPOSE

We had conducted a comprehensive study on preparation, characterization and pharmacokinetics of nimodipine nanocrystals for oral administration previously, and nimodipine nanocrystals displayed lower dissolution profiles but higher bioavailability than Nimotop(®). In this study, we aimed at elucidating the reasons of unfavorable in vitro in vivo correlation for NMD nanocrystals and Nimotop(®) with a hypothesis that special oral absorption mechanism was involved in the absorption of nimodipine nanocrystals.

METHODS

Investigations of oral absorption mechanism of the nanocrystals were performed on everted gut sac models, lymphatically (mesenteric lymph duct) cannulated SD rats, Caco-2 cell monolayers and chylomicron flow blocking rats, respectively.

RESULTS

The permeability of nanocrystals in duodenum, ileum and colon was not superior to that of Nimotop(®), suggestive of special absorption mechanisms involved. Exudates of nanocrystals from enterocytes were detected in mesenteric lymphatic fluids using a transmission electron microscope, and the bioavailability was only about half of the control after the mesenteric lymph was blocked. The nanocrystals were taken up by enterocytes via macropinocytosis and caveolin-mediated endocytosis pathways.

CONCLUSIONS

It was impossible to establish a favorable in vitro in vivo correlation for NMD nanocrystals and Nimotop(®), because portions of the nanocrystals underwent macropinocytosis and caveolin-mediated endocytosis by enterocytes as intact nanocrystal forms, then bypassed the liver first-pass metabolism.

[EHEC carriage in ruminants and probiotic effects]

Enterohaemorrhagic Escherichia coli (EHEC) are Shiga-Toxin producing E. coli (STEC) that cause human outbreaks which can lead to a severe illness such as haemolytic-uraemic syndrome (HUS), particularly in young children. The gastrointestinal tract of cattle and other ruminants is the principal reservoir of EHEC strains and outbreaks have been associated with direct contact with the farm environment, and with the consumption of meat, dairy products, water and fruit or vegetable contaminated with ruminant manure. Several outbreaks occurred these last years in France. In Brazil, although STEC carriage in ruminants is important, human cases due to EHEC are fairly rare. In order to reduce EHEC survival in the ruminant gastrointestinal tract and thus limit contamination of food products, it is necessary to determine the mechanisms underlying EHEC persistence in this ecosystem with the aim of developing nutritional or ecological strategies. The effect of probiotics has been tested in vitro on the growth and survival of EHEC strains and in vivo on the animal carriage of these strains. Various studies have then shown that lactic bacteria or non-pathogenic E. coli strains were able to limit EHEC fecal shedding. In addition, understanding EHEC physiology in the ruminant gut is also critical for limiting EHEC shedding. We found that EHEC O157:H7 is able to use ethanolamine and mucus-derived sugars as nitrogen and carbon sources, respectively. Thus, these substrates represent an ecological niche for EHEC and their utilization confers a competitive growth advantage to these pathogens as they use them more rapidly than the bacteria belonging to the resident intestinal microbiota. Understanding EHEC metabolism and ecology in the bovine intestinal tract will allow proposing probiotic strains to compete with EHEC for nutrients and thus decrease the sanitary risk.

Digestion of kiwifruit fiber

Dietary fiber affects the digestion and absorption of nutrients in the gastrointestinal tract. Moreover, it is generally believed that fiber largely escapes digestion in the human small intestine and is therefore mainly a substrate for microbial fermentation in the hindgut. Kiwifruit is a food naturally high in dietary fiber, yet the impact of dietary kiwifruit on nutrient availability has not been reported. The digestion of kiwifruit has been investigated but only in in vitro digestion studies. With its naturally high nonstarch polysaccharide content, it would be expected that kiwifruit would possess the characteristics of a good source of fiber for nutrition and health. Kiwifruit contains soluble and nonsoluble fiber components, both of which would be expected to affect the physical attributes of digesta as it transits the gastrointestinal tract. This chapter summarizes fiber digestion in general and current knowledge of kiwifruit fiber digestion in the gastrointestinal tract.

Truncated VP28 as oral vaccine candidate against WSSV infection in shrimp: an uptake and processing study in the midgut of Penaeus monodon

Several oral vaccination studies have been undertaken to evoke a better protection against white spot syndrome virus (WSSV), a major shrimp pathogen. Formalin-inactivated virus and WSSV envelope protein VP28 were suggested as candidate vaccine components, but their uptake mechanism upon oral delivery was not elucidated. In this study the fate of these components and of live WSSV, orally intubated to black tiger shrimp (Penaeus monodon) was investigated by immunohistochemistry, employing antibodies specific for VP28 and haemocytes. The midgut has been identified as the most prominent site of WSSV uptake and processing. The truncated recombinant VP28 (rec-VP28), formalin-inactivated virus (IVP) and live WSSV follow an identical uptake route suggested as receptor-mediated endocytosis that starts with adherence of luminal antigens at the apical layers of gut epithelium. Processing of internalized antigens is performed in endo-lysosomal compartments leading to formation of supra-nuclear vacuoles. However, the majority of WSSV-antigens escape these compartments and are transported to the inter-cellular space via transcytosis. Accumulation of the transcytosed antigens in the connective tissue initiates aggregation and degranulation of haemocytes. Finally the antigens exiting the midgut seem to reach the haemolymph. The nearly identical uptake pattern of the different WSSV-antigens suggests that receptors on the apical membrane of shrimp enterocytes recognize rec-VP28 efficiently. Hence the truncated VP28 can be considered suitable for oral vaccination, when the digestion in the foregut can be bypassed.