Varied role of the gut epithelium in mucosal homeostasis

Rapamycin promotes the intestinal barrier repair in ulcerative colitis via the mTOR/PBLD/AMOT signaling pathway

Intestinal barrier dysfunction characterized by the functional loss of the intestinal epithelium's tight junction (TJ) barrier is a key factor in the pathogenesis of ulcerative colitis (UC). Although rapamycin, an mTOR (mechanistic target of rapamycin) inhibitor, has shown promise in inducing clinical remission and mucosal healing in inflammatory bowel disease, its underlying mechanism remains elusive. Thus, this study investigated the role of the mTOR pathway in regulating the intestinal barrier. To investigate the molecular mechanism regulating the intestinal barrier, specific intestinal epithelial phenazine biosynthesis-like domain-containing protein (PBLD)-deficient (PBLDIEC-/-) mice and control wild-type (WT) mice were intraperitoneally injected with rapamycin or MHY1485. To determine the relevance of the findings for UC, we analyzed transcriptome data and single-cell expression profiles from public databases and intestinal mucosal tissues obtained from patients with active UC or colon cancer. We observed that mTOR activation in the intestinal epithelium of patients with active UC. Moreover, in vivo, rapamycin markedly increased the expressions of PBLD and TJ proteins and reduced intestinal inflammation in mice with dextran sulfate sodium-induced enteritis. However, the therapeutic efficacy of rapamycin was notably reduced in PBLDIEC-/- mice. In vitro, rapamycin influenced PBLD expression by modulating the nuclear transcription of transcription factor EB (TFEB). Angiomotin (AMOT) could directly bind to PBLD, and rapamycin could not effectively increase the expression of TJ proteins after the knockdown of PBLD or AMOT. In summary, the administration of rapamycin is a potential treatment for UC, and targeting the mTOR/PBLD/AMOT axis is a potential novel approach for UC treatment.

Comprehensive analysis of circular RNAs in porcine small intestine epithelial cells associated with susceptibility to Escherichia coli F4ac diarrhea

BACKGROUND

Diarrhea is one of the most common diseases in pig industry, which seriously threatens the health of piglets and causes huge economic losses. Enterotoxigenic Escherichia coli (ETEC) F4 is regarded as the most important cause of diarrhea in piglets. Some pigs are naturally resistant to those diarrheas caused by ETEC-F4, because they have no F4 receptors (F4R) on their small intestine epithelial cells that allow F4 fimbriae adhesion. Circular RNA (circRNA) has been shown to play an important regulatory role in the pathogenesis of disease. We hypothesized that circRNAs may also regulate the adhesion of piglet small intestinal epithelial cells to ETEC F4 fimbriae. However, the circRNA expression profiles of piglets with different Enterotoxigenic Escherichia coli F4 fimbriae (ETEC-F4ac) adhesion phenotypes are still unclear, and the intermediate regulatory mechanisms need to be explored. Hence, the present study assessed the circRNA expression profiling in small intestine epithelial cells of eight male piglets with different ETEC-F4 adhesion phenotypes and ITGB5 genotypes to unravel their regulatory function in susceptibility to ETEC-F4ac diarrhea. Piglets were divided into two groups: non-adhesive group (n = 4) with CC genotype and adhesive group (n = 4) with TT genotype.

RESULTS

The RNA-seq data analysis identified 13,199 circRNAs from eight samples, most of which were exon-derived. In the small intestine epithelial cells, 305 were differentially expressed (DE) circRNAs between the adhesive and non-adhesive groups; of which 46 circRNAs were upregulated, and 259 were downregulated. Gene ontology and KEGG enrichment analysis revealed that most significantly enriched DE circRNAs' host genes were linked to cytoskeletal components, protein phosphorylation, cell adhesion, ion transport and pathways (such as adherens junction, gap junction) associated with ETEC diarrhea. The circRNA-miRNA-mRNA interaction network was also constructed to elucidate their underlying regulatory relationships. Our results identified several candidate circRNAs that affects susceptibility to ETEC diarrhea. Among them, circ-SORBS1 can adsorb ssc-miR-345-3p to regulate the expression of its host gene SORBS1, thus improving cell adhesion.

CONCLUSION

Our results provided insights into the regulation function of circRNAs in susceptibility to ETEC diarrhea of piglets, and enhanced our understanding of the role of circRNAs in regulating ETEC diarrhea, and reveal the great potential of circRNA as a diagnostic marker for susceptibility of ETEC diarrhea in piglets.

Pro-inflammatory Polarization of Macrophages Causes Intestinal Inflammation in Low-Birth-Weight Piglets and Mice

BACKGROUND

Low-birth-weight (LBW) animals suffer from intestinal damage and inflammation in their early life.

OBJECTIVES

The aim of this study was to investigate the role of macrophages in intestinal inflammation in LBW piglets and mice.

METHODS

Major genes involved in intestinal barrier function such as claudin-1, zonula occludens-1 (ZO-1), occludin, and mucin 2 and inflammatory cytokines such as IL-1β, TNF-α, IL-10, and IL-13 were evaluated in 21-day-old, normal birth weight (NBW) and LBW piglets and mice. Macrophage markers such as CD16/32, CD163, and CD206 were also assessed by immunofluorescence and flow cytometry. Polarized and unpolarized macrophages were further transferred into NBW and LBW mice, followed by evaluation of intestinal permeability and inflammation.

RESULTS

Claudin-1 mRNA in LBW piglets as well as claudin-1, occludin, ZO-1 and mucin 2 mRNAs in LBW mice was significantly downregulated. IL-1β and TNF-α were significantly upregulated in LBW piglets (P < 0.05). LBW mice showed a reduced expression of IL-10 and IL-13 (P < 0.05), with a heightened IL-6 level (P < 0.01) in the jejunum. CD16, a marker for M1 macrophages, was significantly elevated in the jejunum of LBW piglets, whereas CD163, a marker for M2 macrophages, was significantly decreased (P < 0.05). Similarly, LBW mice had more CD11b+CD16/32+ M1 macrophages (P < 0.05) and fewer CD206+ M2 macrophages (P < 0.01) than NBW mice. Moreover, transfer of M1 macrophages exacerbated intestinal inflammation in LBW mice. Furthermore, two major glycolysis-associated genes, hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA), were significantly upregulated in LBW piglets and mice (P < 0.05).

CONCLUSIONS

This study revealed for the first time that the intestinal macrophages are polarized towards a pro-inflammatory phenotype in LBW piglets and mice, contributing to intestinal inflammation. The findings of this study provide new options for the management of intestinal inflammation in LBW animals.

PTPN2 regulates bacterial clearance in a mouse model of enteropathogenic and enterohemorrhagic E. coli infection

Macrophages intimately interact with intestinal epithelial cells, but the consequences of defective macrophage-epithelial cell interactions for protection against enteric pathogens are poorly understood. Here, we show that in mice with a deletion in protein tyrosine phosphatase nonreceptor type 2 (PTPN2) in macrophages, infection with Citrobacter rodentium, a model of enteropathogenic and enterohemorrhagic E. coli infection in humans, promoted a strong type 1/IL-22-driven immune response, culminating in accelerated disease but also faster clearance of the pathogen. In contrast, deletion of PTPN2 specifically in epithelial cells rendered the epithelium unable to upregulate antimicrobial peptides and consequently resulted in a failure to eliminate the infection. The ability of PTPN2-deficient macrophages to induce faster recovery from C. rodentium was dependent on macrophage-intrinsic IL-22 production, which was highly increased in macrophages deficient in PTPN2. Our findings demonstrate the importance of macrophage-mediated factors, and especially macrophage-derived IL-22, for the induction of protective immune responses in the intestinal epithelium, and show that normal PTPN2 expression in the epithelium is crucial to allow for protection against enterohemorrhagic E. coli and other intestinal pathogens.

The hypoxic tissue microenvironment as a driver of mucosal inflammatory resolution

On the backdrop of all acute inflammatory processes lies the activation of the resolution response. Recent years have witnessed an emerging interest in defining molecular factors that influence the resolution of inflammation. A keystone feature of the mucosal inflammatory microenvironment is hypoxia. The gastrointestinal tract, particularly the colon, exists in a state of physiological hypoxia and during active inflammation, this hypoxic state is enhanced as a result of infiltrating leukocyte oxygen consumption and the activation of oxygen consuming enzymes. Most evidence suggests that mucosal hypoxia promotes the active resolution of inflammation through a variety of mechanisms, including extracellular acidification, purine biosynthesis/salvage, the generation of specialized pro-resolving lipid mediators (ie. resolvins) and altered chemokine/cytokine expression. It is now appreciated that infiltrating innate immune cells (neutrophils, eosinophils, macrophages) have an important role in molding the tissue microenvironment to program an active resolution response. Structural or functional dysregulation of this inflammatory microenvironment can result in the loss of tissue homeostasis and ultimately progression toward chronicity. In this review, we will discuss how inflammatory hypoxia drives mucosal inflammatory resolution and its impact on other microenvironmental factors that influence resolution.

Polyamines in Gut Epithelial Renewal and Barrier Function

Polyamines regulate a variety of physiological functions and are involved in pathogenesis of diverse human diseases. The epithelium of the mammalian gut mucosa is a rapidly self-renewing tissue in the body, and its homeostasis is preserved through well-controlled mechanisms. Here, we highlight the roles of cellular polyamines in maintaining the integrity of the gut epithelium, focusing on the emerging evidence of polyamines in the regulation of gut epithelial renewal and barrier function. Gut mucosal growth depends on the available supply of polyamines to the dividing cells in the crypts, and polyamines are also essential for normal gut epithelial barrier function. Polyamines modulate expression of various genes encoding growth-associated proteins and intercellular junctions via distinct mechanisms involving RNA-binding proteins and noncoding RNAs. With the rapid advance of polyamine biology, polyamine metabolism and transport are promising therapeutic targets in our efforts to protect the gut epithelium and barrier function in patients with critical illnesses.

Omega-3 Polyunsaturated Fatty Acids and the Intestinal Epithelium-A Review

Epithelial cells (enterocytes) form part of the intestinal barrier, the largest human interface between the internal and external environments, and responsible for maintaining regulated intestinal absorption and immunological control. Under inflammatory conditions, the intestinal barrier and its component enterocytes become inflamed, leading to changes in barrier histology, permeability, and chemical mediator production. Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) can influence the inflammatory state of a range of cell types, including endothelial cells, monocytes, and macrophages. This review aims to assess the current literature detailing the effects of ω-3 PUFAs on epithelial cells. Marine-derived ω-3 PUFAs, eicosapentaenoic acid and docosahexaenoic acid, as well as plant-derived alpha-linolenic acid, are incorporated into intestinal epithelial cell membranes, prevent changes to epithelial permeability, inhibit the production of pro-inflammatory cytokines and eicosanoids and induce the production of anti-inflammatory eicosanoids and docosanoids. Altered inflammatory markers have been attributed to changes in activity and/or expression of proteins involved in inflammatory signalling including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), peroxisome proliferator activated receptor (PPAR) α and γ, G-protein coupled receptor (GPR) 120 and cyclooxygenase (COX)-2. Effective doses for each ω-3 PUFA are difficult to determine due to inconsistencies in dose and time of exposure between different in vitro models and between in vivo and in vitro models. Further research is needed to determine the anti-inflammatory potential of less-studied ω-3 PUFAs, including docosapentaenoic acid and stearidonic acid.

PTPN2 Regulates Interactions Between Macrophages and Intestinal Epithelial Cells to Promote Intestinal Barrier Function

BACKGROUND & AIMS

The mechanisms by which macrophages regulate intestinal epithelial cell (IEC) barrier properties are poorly understood. Protein tyrosine phosphatase non-receptor type 2 (PTPN2) protects the IEC barrier from inflammation-induced disruption and regulates macrophage functions. We investigated whether PTPN2 controls interactions between IECs and macrophages to maintain intestinal barrier function.

METHODS

Human IEC (Caco-2BBe/HT-29.cl19a cells) and mouse enteroid monolayers were cocultured with human macrophages (THP-1, U937, primary monocyte-derived macrophages from patients with inflammatory bowel disease [IBD]) or mouse macrophages, respectively. We assessed barrier function (transepithelial electrical resistance [TEER] and permeability to 4-kDa fluorescently labeled dextran or 70-kDa rhodamine B-dextran) and macrophage polarization. We analyzed intestinal tissues from mice with myeloid cell-specific deletion of PTPN2 (Ptpn2-LysMCre mice) and mice without disruption of Ptpn2 (controls); some mice were given injections of a neutralizing antibody against interleukin (IL) 6. Proteins were knocked down in macrophages and/or IECs with small hairpin RNAs.

RESULTS

Knockdown of PTPN2 in either macrophages and/or IECs increased the permeability of IEC monolayers, had a synergistic effect when knocked down from both cell types, and increased the development of inflammatory macrophages in macrophage-IEC cocultures. Colon lamina propria from Ptpn2-LysMCre mice had significant increases in inflammatory macrophages; these mice had increased in vivo and ex vivo colon permeability to 4-kDa fluorescently labeled dextran and reduced ex vivo colon TEER. Nanostring analysis showed significant increases in the expression of IL6 in colon macrophages from Ptpn2-LysMCre mice. An IL6-blocking antibody reversed the effects of PTPN2-deficient macrophages, reducing the permeability of IEC monolayers in culture and in Ptpn2-LysMCre mice. Macrophages from patients with IBD carrying a single-nucleotide polymorphism associated with the disease (PTPN2 rs1893217) had the same features of PTPN2-deficient macrophages from mice, including reduced TEER and increased permeability in cocultures with human IEC or mouse enteroid monolayers, which were restored by anti-IL6.

CONCLUSIONS

PTPN2 is required for interactions between macrophages and IECs; loss of PTPN2 from either cell type results in intestinal barrier defects, and loss from both cell types has a synergistic effect. We provide a mechanism by which the PTPN2 gene variants compromise intestinal epithelial barrier function and increase the risk of inflammatory disorders such as IBD.

AMPK mediates inhibition of electrolyte transport and NKCC1 activity by reactive oxygen species

Reactive oxygen species such as H₂O₂ are believed to play a prominent role in the injury and loss of transport function that affect the intestinal epithelium in inflammatory conditions such as inflammatory bowel diseases. Defects in intestinal epithelial ion transport regulation contribute to dysbiosis and inflammatory phenotypes. We previously showed that H₂O₂ inhibits Ca²⁺-dependent Cl^- secretion across intestinal epithelial cells (IECs) via a phosphatidylinositol 3-kinase (PI3K)- and extracellular signal-regulated kinase (ERK)-dependent mechanism that occurs, at least in part, through inhibition of the basolateral Na⁺-K⁺-2Cl^- cotransporter NKCC1. NKCC1 governs Cl^- entry into crypt IECs and thus plays a critical role in maintaining the driving force for Cl^- secretion. Electrolyte transport consumes large amounts of cellular energy, and direct pharmacological activation of the cellular energy sensor AMP-activated protein kinase (AMPK) has been shown to inhibit a number of ion transport proteins. Here, we show that H₂O₂ activates AMPK in human IEC lines and ex vivo human colon. Moreover, we demonstrate that the inhibitory effect of H₂O₂ on Ca²⁺-dependent Cl^- secretion and NKCC1 activity is AMPK-dependent. This inhibitory effect is associated with a physical interaction between AMPK and NKCC1, as well as increased phosphorylation (Thr^212,217) of NKCC1, without causing NKCC1 internalization. These data identify a key role for AMPK-NKCC1 interaction as a point of convergence for suppression of colonic epithelial ion transport by inflammatory reactive oxygen species.NEW & NOTEWORTHY H₂O₂ inhibition of intestinal epithelial Ca²⁺-dependent Cl^- secretion involves recruitment of AMP-activated protein kinase (AMPK) downstream of ERK and phosphatidylinositol 3-kinase signaling pathways, physical interaction of AMPK with the Na⁺-K⁺-2Cl^- cotransporter NKCC1, and AMPK-dependent suppression of NKCC1-mediated electrolyte influx without causing NKCC1 internalization. It is intriguing that, in human intestinal epithelial cell lines and human colon, H₂O₂ activation of AMPK increased phosphorylation of NKCC1 residues required for promoting, not inhibiting, NKCC1 activity. These data identify an elevated complexity of AMPK regulation of NKCC1 in the setting of an inflammatory stimulus.

Special pro-resolving mediator (SPM) actions in regulating gastro-intestinal inflammation and gut mucosal immune responses

Surfaces covered by epithelial cells, termed mucosal surfaces, serve special functions as selectively permeable barriers that partition the host and the outside world. Given its close association to microbial antigens, the intestinal mucosa has evolved creative mechanisms to maintain homeostasis, to prevent excessive inflammatory responses, and to promote rapid and full inflammatory resolution. In recent years, an active role for the epithelium has been attributed to the local generation of specialized pro-resolving mediators (SPMs) in the maintenance of immunological homeostasis. In this brief review, we highlight evidence that the epithelium actively contributes to coordination and resolution of inflammation, principally through the generation of SPMs. These autacoids are derived from omega-6 and omega-3 polyunsaturated fatty acids. Acting through widely expressed G-protein coupled receptors, SPMs are implicated in the resolution of acute inflammation that manifests specific, epithelial-directed actions focused on mucosal-homeostasis, including regulation of leukocyte trafficking, the generation of antimicrobial peptides, the dampening of endotoxin signaling, and the attenuation of mucosal cytokine responses.

Mechanisms of Intestinal Epithelial Barrier Dysfunction by Adherent-Invasive Escherichia coli

Pathobiont expansion, such as that of adherent-invasive Escherichia coli (AIEC), is an emerging factor associated with inflammatory bowel disease. The intestinal epithelial barrier is the first line of defense against these pathogens. Inflammation plays a critical role in altering the epithelial barrier and is a major factor involved in promoting the expansion and pathogenesis of AIEC. AIEC in turn can exacerbate intestinal epithelial barrier dysfunction by targeting multiple elements of the barrier. One critical element of the epithelial barrier is the tight junction. Increasing evidence suggests that AIEC may selectively target protein components of tight junctions, leading to increased barrier permeability. This may represent one mechanism by which AIEC could contribute to the development of inflammatory bowel disease. This review article discusses potential mechanisms by which AIEC can disrupt epithelial tight junction function and intestinal barrier function.

Eicosanoid receptors: Targets for the treatment of disrupted intestinal epithelial homeostasis

The importance of cyclooxygenase and lipoxygenase pathways and the consequent eicosanoid synthesis in the physiology and pathophysiology of the intestinal epithelium is currently being established. Each eicosanoid (prostanoid, leukotriene, hydroxyeicosatetraenoic acid) preferentially recognizes one or more receptors coupled to one or more signal-transduction processes. This overview focuses on the role of eicosanoid receptors in the maintenance of intestinal epithelium physiology through the control of proliferation/differentiation/apoptosis processes. Furthermore, it is reported that the role of these receptors on the regulation of the barrier function of the intestinal epithelium have arisen through the regulation of absorption/secretion processes, tight-junction state and the control of the intestinal immune response. Also, this review considers the implication of AA cascade in the disruption of epithelial homeostasis during inflammatory bowel diseases and colorectal cancer as well as the therapeutic values and potential of the eicosanoid receptors as novel targets for the treatments of the pathologies above mentioned.

Candida albicans infection leads to barrier breakdown and a MAPK/NF-κB mediated stress response in the intestinal epithelial cell line C2BBe1

Intestinal epithelial cells (IEC) form a tight barrier to the gut lumen. Paracellular permeability of the intestinal barrier is regulated by tight junction proteins and can be modulated by microorganisms and other stimuli. The polymorphic fungus Candida albicans, a frequent commensal of the human mucosa, has the capacity of traversing this barrier and establishing systemic disease within the host. Infection of polarized C2BBe1 IEC with wild-type C. albicans led to a transient increase of transepithelial electric resistance (TEER) before subsequent barrier disruption, accompanied by a strong decline of junctional protein levels and substantial, but considerably delayed cytotoxicity. Time-resolved microarray-based transcriptome analysis of C. albicans challenged IEC revealed a prominent role of NF-κB and MAPK signalling pathways in the response to infection. Hence, we inferred a gene regulatory network based on differentially expressed NF-κB and MAPK pathway components and their predicted transcriptional targets. The network model predicted activation of GDF15 by NF-κB was experimentally validated. Furthermore, inhibition of NF-κB activation in C. albicans infected C2BBe1 cells led to enhanced cytotoxicity in the epithelial cells. Taken together our study identifies NF-κB activation as an important protective signalling pathway in the response of epithelial cells to C. albicans.

Protein tyrosine phosphatase non-receptor type 2 and inflammatory bowel disease

Genome wide association studies have associated single nucleotide polymorphisms within the gene locus encoding protein tyrosine phosphatase non-receptor type 2 (PTPN2) with the onset of inflammatory bowel disease (IBD) and other inflammatory disorders. Expression of PTPN2 is enhanced in actively inflamed intestinal tissue featuring a marked up-regulation in intestinal epithelial cells. PTPN2 deficient mice suffer from severe intestinal and systemic inflammation and display aberrant innate and adaptive immune responses. In particular, PTPN2 is involved in the regulation of inflammatory signalling cascades, and critical for protecting intestinal epithelial barrier function, regulating innate and adaptive immune responses, and finally for maintaining intestinal homeostasis. On one hand, dysfunction of PTPN2 has drastic effects on innate host defence mechanisms, including increased secretion of pro-inflammatory cytokines, limited autophagosome formation in response to invading pathogens, and disruption of the intestinal epithelial barrier. On the other hand, PTPN2 function is crucial for controlling adaptive immune functions, by regulating T cell proliferation and differentiation as well as maintaining T cell tolerance. In this way, dysfunction of PTPN2 contributes to the manifestation of IBD. The aim of this review is to present an overview of recent findings on the role of PTPN2 in intestinal homeostasis and the impact of dysfunctional PTPN2 on intestinal inflammation.

Role of protein tyrosine phosphatases in regulating the immune system: implications for chronic intestinal inflammation

Current hypothesis suggests that genetic, immunological, and bacterial factors contribute essentially to the pathogenesis of inflammatory bowel disease. Variations within the gene loci encoding protein tyrosine phosphatases (PTPs) have been associated with the onset of inflammatory bowel disease. PTPs modulate the activity of their substrates by dephosphorylation of tyrosine residues and are critical for the regulation of fundamental cellular signaling processes. Evidence emerges that expression levels of PTPN2, PTPN11, and PTPN22 are altered in actively inflamed intestinal tissue. PTPN2 seems to be critical for protecting intestinal epithelial barrier function, regulating innate and adaptive immune responses and finally for maintaining intestinal homeostasis. These observations have been confirmed in PTPN2 knockout mice in vivo. Those animals are clearly more susceptible to intestinal and systemic inflammation and feature alterations in innate and adaptive immune responses. PTPN22 controls inflammatory signaling in lymphocytes and mononuclear cells resulting in aberrant cytokine secretion pattern and autophagosome formation. PTPN22 deficiency in vivo results in more severe colitis demonstrating the relevance of PTPN22 for intestinal homeostasis in vivo. Of note, loss of PTPN22 promotes mitogen-activated protein kinase-induced cytokine secretion but limits secretion of nuclear factor κB-associated cytokines and autophagy in mononuclear cells. Loss of PTPN11 is also associated with increased colitis severity in vivo. In summary, dysfunction of those PTPs results in aberrant and uncontrolled immune responses that result in chronic inflammatory conditions. This way, it becomes more and more evident that dysfunction of PTPs displays an important factor in the pathogenesis of chronic intestinal inflammation, in particular inflammatory bowel disease.

IBD candidate genes and intestinal barrier regulation

Technological advances in the large scale analysis of human genetics have generated profound insights into possible genetic contributions to chronic diseases including the inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis. To date, 163 distinct genetic risk loci have been associated with either Crohn's disease or ulcerative colitis, with a substantial degree of genetic overlap between these 2 conditions. Although many risk variants show a reproducible correlation with disease, individual gene associations only affect a subset of patients, and the functional contribution(s) of these risk variants to the onset of IBD is largely undetermined. Although studies in twins have demonstrated that the development of IBD is not mediated solely by genetic risk, it is nevertheless important to elucidate the functional consequences of risk variants for gene function in relevant cell types known to regulate key physiological processes that are compromised in IBD. This article will discuss IBD candidate genes that are known to be, or are suspected of being, involved in regulating the intestinal epithelial barrier and several of the physiological processes presided over by this dynamic and versatile layer of cells. This will include assembly and regulation of tight junctions, cell adhesion and polarity, mucus and glycoprotein regulation, bacterial sensing, membrane transport, epithelial differentiation, and restitution.

The gut microbiota and developmental programming of the testis in mice

Nutrients and environmental chemicals, including endocrine disruptors, have been incriminated in the current increase in male reproductive dysfunction, but the underlying mechanisms remain unknown. The gastrointestinal tract represents the largest surface area exposed to our environment and thereby plays a key role in connection with exposure of internal organs to exogenous factors. In this context the gut microbiome (all bacteria and their metabolites) have been shown to be important contributors to body physiology including metabolism, cognitive functions and immunity. Pivotal to male reproduction is a proper development of the testis, including the formation of the blood-testis barrier (BTB) that encapsulates and protects germ cells from stress induced environmental cues, e.g. pathogenic organisms and xenobiotics. Here we used specific pathogen free (SPF) mice and germ-free (GF) mice to explore whether gut microbiota and/or their metabolites can influence testis development and regulation of BTB. Lumen formation in the seminiferous tubules, which coincides with the development of the BTB was delayed in the testes of GF mice at 16 days postpartum. In addition, perfusion experiments (Evans blue) demonstrated increased BTB permeability in these same mice. Reduced expressions of occludin, ZO-2 and E-cadherin in GF testis suggested that the microbiota modulated BTB permeability by regulation of cell-cell adhesion. Interestingly, exposure of GF mice to Clostridium Tyrobutyricum (CBUT), which secrete high levels of butyrate, restored the integrity of the BTB and normalized the levels of cell adhesion proteins. Moreover, the GF mice exhibited lower serum levels of gonadotropins (LH and FSH) than the SPF group. In addition, the intratesticular content of testosterone was lower in GF compared to SPF or CBUT animals. Thus, the gut microbiome can modulate the permeability of the BTB and might play a role in the regulation of endocrine functions of the testis.

Reprint of: Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Sphingomyelin and phosphatidylcholine contrarily affect the induction of apoptosis in intestinal epithelial cells

SCOPE

The major alimentary sources for the plasma membrane lipid sphingomyelin (SM) are dairy products, eggs, and meat. We recently reported that the SM metabolite ceramide induces cathepsin D mediated apoptosis in murine intestinal epithelial cells (IECs) and increases inflammation in acute colitis. We investigated the impact of SM and phosphatidylcholine on apoptosis in human IECs and point out BH3-interacting death agonist (BID) as link between cathepsin D and apoptosis.

METHODS AND RESULTS

HT-29 and isolated human IECs were stimulated with SM or phosphatidylcholine. SM treatment resulted in increased apoptosis. Phosphatidylcholine showed contrary effects. Western revealed higher amounts of cathepsin D and BID activation upon lipid stimulation. Western blotting revealed BID activation through SM in both an induced and a spontaneous mouse model of colitis.

CONCLUSION

Dietary phospholipids may induce or abolish apoptosis in IECs and seem to play a role in the pathogenesis of inflammatory bowel diseases. This nutritional factor might be considered when evaluating the pathogenesis of inflammatory bowel diseases. Effects of SMase- and SM treatment on inflammation in dextran sulfate sodium induced animal models of colitis and in vitro experiments are discussed as controversial. Variable sources of SM, feeding techniques, and mouse strains might play a role.

The inflammatory tissue microenvironment in IBD

A current view of the inflammatory bowel diseases (IBDs) includes the luminal triggering of innate immune disease in a genetically susceptible host. Given the unique anatomy and complex environment of the intestine, local microenvironmental cues likely contribute significantly to both disease progression and resolution in IBD. Compartmentalized tissue and microbe populations within the intestine result in significant metabolic shifts within these tissue microenvironments. During active inflammatory disease, metabolic demands often exceed supply, resulting in localized areas of metabolic stress and diminished oxygen delivery (hypoxia). There is much recent interest in harnessing these microenvironmental changes to the benefit of the tissue, including targeting these pathways for therapy of IBD. Here, we review the current understanding of metabolic microenvironments within the intestine in IBD, with discussion of the advantages and disadvantages of targeting these pathways to treat patients with IBD.

In vitro cell and tissue models for studying host-microbe interactions: a review

Ideally, cell models should resemble the in vivo conditions; however, in most in vitro experimental models, epithelial cells are cultivated as monolayers, in which the establishment of functional epithelial features is not achieved. To overcome this problem, co-culture experiments with probiotics, dendritic cells and intestinal epithelial cells and three-dimensional models attempt to reconcile the complex and dynamic interactions that exist in vivo between the intestinal epithelium and bacteria on the luminal side and between the epithelium and the underlying immune system on the basolateral side. Additional models include tissue explants, bioreactors and organoids. The present review details the in vitro models used to study host-microbe interactions and explores the new tools that may help in understanding the molecular mechanisms of these interactions.

Integrated stress response-altered pro-inflammatory signals in mucosal immune-related cells

Various cells are associated with the integrated stress response (ISR) that leads to translation arrest via phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2. Pathogenic insults or nutritional imbalance in the mucosal tissues including the intestinal, airway, and genitourinary epithelia can cause ISRs, which have been linked to different mucosal inflammatory responses and subsequent systemic diseases. In particular, translational arrest caused by the early recognition of luminal microbes as well as nutritional status allows the human body to mount appropriate responses and maintain homeostasis both at the cellular and systemic levels. However, an over- or reduced ISR can create pathogenic conditions such as inflammation and carcinogenesis. This present review explores the association between eIF2α kinase-linked pathways and mucosal or systemic pro-inflammatory signals activated by xenobiotic insults (such as ones caused by microbes or nutritional abnormalities). Understanding ISR-modulated cellular alterations will provide progressive insights into approaches for treating human mucosal inflammatory and metabolic disorders.

Activated fluid transport regulates bacterial-epithelial interactions and significantly shifts the murine colonic microbiome

Within the intestinal mucosa, epithelial cells serve multiple functions to partition the lumen from the lamina propria. As part of their natural function, intestinal epithelial cells actively transport electrolytes with passive water movement as a mechanism for mucosal hydration. Here, we hypothesized that electrogenic Cl(-) secretion, and associated mucosal hydration, influences bacterial-epithelial interactions and significantly influences the composition of the intestinal microbiota. An initial screen of different epithelial secretagogues identified lubiprostone as the most potent agonist for which to define these principles. In in vitro studies using cultured T84 cells, lubiprostone decreased E. coli translocation in a concentration-dependent manner (p < 0.001) and decreased S. typhimurium internalization and translocation by as much as 71 ± 6% (p < 0.01). Such decreases in bacterial translocation were abolished by inhibition of electrogenic Cl(-) secretion and water transport using the Na/K/Cl(-) antagonist bumetanide (p < 0.01). Extensions of these findings to microbiome analysis in vivo revealed that lubiprostone delivered orally to mice fundamentally shifted the intestinal microbiota, with notable changes within the Firmicutes and Bacteroidetes phyla of resident colonic bacteria. Such findings document a previously unappreciated role for epithelial Cl(-) secretion and water transport in influencing bacterial-epithelial interactions and suggest that active mucosal hydration functions as a primitive innate epithelial defense mechanism.

Antimicrobial aspects of inflammatory resolution in the mucosa: a role for proresolving mediators

Mucosal surfaces function as selectively permeable barriers between the host and the outside world. Given their close proximity to microbial Ags, mucosal surfaces have evolved sophisticated mechanisms for maintaining homeostasis and preventing excessive acute inflammatory reactions. The role attributed to epithelial cells was historically limited to serving as a selective barrier; in recent years, numerous findings implicate an active role of the epithelium with proresolving mediators in the maintenance of immunological equilibrium. In this brief review, we highlight new evidence that the epithelium actively contributes to coordination and resolution of inflammation, principally through the generation of anti-inflammatory and proresolution lipid mediators. These autacoids, derived from ω-6 and ω-3 polyunsaturated fatty acids, are implicated in the initiation, progression, and resolution of acute inflammation and display specific, epithelial-directed actions focused on mucosal homeostasis. We also summarize present knowledge of mechanisms for resolution via regulation of epithelial-derived antimicrobial peptides in response to proresolving lipid mediators.

Regulation of homeostasis and inflammation in the intestine

The gastrointestinal tract is the largest immune interface with the environment. Exposure to large numbers of dietary and microbial antigens requires complex and highly regulated immune responses by different mucosal cell types, which result in the induction and maintenance of intestinal homeostasis. Defects in this equilibrium can disrupt the homeostatic mechanisms and lead to chronic intestinal inflammation. We review the cell populations and mechanisms involved in the control of intestinal homeostasis and inflammation, focusing on inflammatory bowel diseases. We describe some aspects of gut immunity that could alter the delicate balance between inflammatory and tolerogenic responses and result in chronic gastrointestinal tract inflammation in patients.

Endoplasmic reticulum stress-activated C/EBP homologous protein enhances nuclear factor-kappaB signals via repression of peroxisome proliferator-activated receptor gamma

Endoplasmic reticulum (ER) stress is a causative factor of inflammatory bowel diseases. ER stress mediators, including CCAAT enhancer-binding protein (C/EBP) homologous protein (CHOP), are elevated in intestinal epithelia from patients with inflammatory bowel diseases. The present study arose from the question of how chemical ER stress and CHOP protein were associated with nuclear factor-κB (NF-κB)-mediated epithelial inflammatory response. In a human intestinal epithelial cell culture model, chemical ER stresses induced proinflammatory cytokine interleukin-8 (IL-8) expression and the nuclear translocation of CHOP protein. CHOP was positively involved in ER-activated IL-8 production and was negatively associated with expression of peroxisome proliferator-activated receptor γ (PPARγ). ER stress-induced IL-8 production was enhanced by NF-κB activation that was negatively regulated by PPARγ. Mechanistically, ER stress-induced CHOP suppressed PPARγ transcription by sequestering C/EBPβ and limiting availability of C/EBPβ binding to the PPARγ promoter. Due to the CHOP-mediated regulation of PPARγ action, ER stress can enhance proinflammatory NF-κB activation and maintain an increased level of IL-8 production in human intestinal epithelial cells. In contrast, PPARγ was a counteracting regulator of gut inflammatory response through attenuation of NF-κB activation. The collective results support the view that balances between CHOP and PPARγ are crucial for epithelial homeostasis, and disruption of these balances in mucosal ER stress can etiologically affect the progress of human inflammatory bowel diseases.

Role of Toll-like receptors in the development of immunotolerance mediated by probiotics

Commensal bacteria are important in intestinal homeostasis and appear to play a role in early tolerance to foreign antigens. The requirement for homeostatic balance between tolerance and immunity poses a unique regulatory challenge to mucosal immune systems. Dysregulation of this balance can contribute to the pathogenesis of numerous inflammatory conditions such as inflammatory bowel diseases. The primary response to these bacteria is triggered by pattern recognition receptors (PRR), which bind pathogen-associated molecular patterns (PAMP). PRR comprise Toll-like receptors (TLR), nucleotide-binding oligomerization domains, adhesion molecules and lectins. Probiotics are living commensal micro-organisms of the intestinal tract with clinically documented health effects in human subjects. They are known to affect the gastrointestinal tract and the associated immune system and to have numerous effects on intestinal function and immune responses, including immunotolerance. This last effect appears to be mediated via regulatory T-cell activation by intestinal dendritic cells and the low activation of T-helper 1 and 2 (Th1 and Th2) cell inflammatory responses. However, the precise mechanisms of probiotic activity remain poorly understood. The aim of the present work was to review the function of TLR in the development of immunotolerance and examine the specific role of probiotics in the regulation of tolerance to antigens.

The multifaceted influence of the mucosal microflora on mucosal dendritic cell responses

Over the last decade, it has become apparent that the complex interactions between components of the mucosal microflora and the mucosal immune system can involve either direct contact with dendritic cells in the lamina propria or, alternatively, contact with epithelial cells lining the mucosa that then influence the function of dendritic cells. Although in some cases these interactions involve signaling specific to particular organisms and in others, to classes of organisms, a common theme is that signaling is invariably channeled through receptors that address many organisms or all organisms such as the pattern-recognition receptors TLR and NLR. Here, I review this information with the intention of identifying how the mucosal microflora influences specific functions of the mucosal immune system such the production of particular cytokines as well as broader functions such as the maintenance of mucosal immune homeostasis and host defense.

Potentiation of flagellin responses in gut epithelial cells by interferon-gamma is associated with STAT-independent regulation of MyD88 expression

Flagellin acting via TLR5 (Toll-like receptor 5) is a key regulator of the host response to the gut microbial flora in both health and disease. The present study has investigated regulation of flagellin-TLR5 signalling in human colonocytes (HT29-19A) by IFNgamma (interferon-gamma), a cytokine released early in the inflammatory process which has multiple effects on gut epithelial function that may facilitate abnormal responses to enteric bacteria. Flagellin induced a dose-dependent secretion of chemokines CXCL8 and CCL2 in the human colonocyte line, HT29-19A. Exposure to IFNgamma did not induce chemokine secretion, but markedly potentiated responses to flagellin, increasing CXL8 gene expression and protein secretion by approx. 4-fold. Potentiation by IFNgamma was independent of changes in TLR5 and was associated with a rapid, sustained increase in expression of the downstream adaptor molecule MyD88 (myeloid differentiation factor 88). Knockdown of MyD88 expression using siRNA (small interfering RNA) abolished flagellin-dependent CXCL8 secretion and the potentiating effect of IFNgamma. Exposure of non-transformed mouse and human colonocytes to IFNgamma also increased MyD88 expression. STAT (signal transducer and activator of transcription) 1 knockdown and use of the broad-spectrum JAK (Janus kinase)-STAT inhibitor AG490 had no effect on IFNgamma-mediated up-regulation of MyD88. The findings of the present study suggest that IFNgamma sensitizes colonic epithelial cells to bacterial flagellin via a largely STAT-independent up-regulation of MyD88 expression leading to increased secretion of immunomodulatory factors. These results indicate that epithelial responses to flagellin are potentiated by IFNgamma, most likely mediated by increased MyD88 expression. The present study adds to our understanding of the spectrum of effects of this cytokine on gut epithelium that may contribute to bacterial-driven inflammation in the gut.

Biomarkers of human gastrointestinal tract regions

Dysregulation of intestinal epithelial cell performance is associated with an array of pathologies whose onset mechanisms are incompletely understood. While whole-genomics approaches have been valuable for studying the molecular basis of several intestinal diseases, a thorough analysis of gene expression along the healthy gastrointestinal tract is still lacking. The aim of this study was to map gene expression in gastrointestinal regions of healthy human adults and to implement a procedure for microarray data analysis that would allow its use as a reference when screening for pathological deviations. We analyzed the gene expression signature of antrum, duodenum, jejunum, ileum, and transverse colon biopsies using a biostatistical method based on a multivariate and univariate approach to identify region-selective genes. One hundred sixty-six genes were found responsible for distinguishing the five regions considered. Nineteen had never been described in the GI tract, including a semaphorin probably implicated in pathogen invasion and six novel genes. Moreover, by crossing these genes with those retrieved from an existing data set of gene expression in the intestine of ulcerative colitis and Crohn's disease patients, we identified genes that might be biomarkers of Crohn's and/or ulcerative colitis in ileum and/or colon. These include CLCA4 and SLC26A2, both implicated in ion transport. This study furnishes the first map of gene expression along the healthy human gastrointestinal tract. Furthermore, the approach implemented here, and validated by retrieving known gene profiles, allowed the identification of promising new leads in both healthy and disease states.

Regulation of serum amyloid A3 (SAA3) in mouse colonic epithelium and adipose tissue by the intestinal microbiota

The gut microbiota has been proposed as an environmental factor that affects the development of metabolic and inflammatory diseases in mammals. Recent reports indicate that gut bacteria-derived lipopolysaccharide (LPS) can initiate obesity and insulin resistance in mice; however, the molecular interactions responsible for microbial regulation of host metabolism and mediators of inflammation have not been studied in detail. Hepatic serum amyloid A (SAA) proteins are markers and proposed mediators of inflammation that exhibit increased levels in serum of insulin-resistant mice. Adipose tissue-derived SAA3 displays monocyte chemotactic activity and may play a role in metabolic inflammation associated with obesity and insulin resistance. To investigate a potential mechanistic link between the intestinal microbiota and induction of proinflammatory host factors, we performed molecular analyses of germ-free, conventionally raised and genetically modified Myd88-/- mouse models. SAA3 expression was determined to be significantly augmented in adipose (9.9+/-1.9-fold; P<0.001) and colonic tissue (7.0+/-2.3-fold; P<0.05) by the presence of intestinal microbes. In the colon, we provided evidence that SAA3 is partially regulated through the Toll-like receptor (TLR)/MyD88/NF-kappaB signaling axis. We identified epithelial cells and macrophages as cellular sources of SAA3 in the colon and found that colonic epithelial expression of SAA3 may be part of an NF-kappaB-dependent response to LPS from gut bacteria. In vitro experiments showed that LPS treatments of both epithelial cells and macrophages induced SAA3 expression (27.1+/-2.5-fold vs. 1.6+/-0.1-fold, respectively). Our data suggest that LPS, and potentially other products of the indigenous gut microbiota, might elevate cytokine expression in tissues and thus exacerbate chronic low-grade inflammation observed in obesity.

Between celiac disease and irritable bowel syndrome: the "no man's land" of gluten sensitivity

The repertoire of gastrointestinal (GI) symptoms is finite; however, the etiologies and mechanisms underlying symptom generation and perception are diverse and, in many cases, unknown. This review examines the clinical and experimental evidence exploring the putative relationship between gluten sensitivity (GS) and the generation of GI symptoms. It explores the hypothesis that, in a proportion of patients, GS causes functional bowel disorder (FBD)-like symptoms. We propose a model for investigating and understanding the induction of GI symptoms and dysfunction by gluten in FBD and organic disease. We hypothesize that, even in the absence of fully developed celiac disease, gluten can induce symptoms similar to FBD. We discuss the hypothesis that GS and post-infectious irritable bowel syndrome (IBS) provide two triggers that can explain at least part of the spectrum that constitutes IBS, further advancing an understanding of the role of mucosal responses to luminal factors in FBDs. We propose that the animal model of GS in human leukocyte antigen (HLA)- DQ8 mice allows investigation of mucosal pathophysiological changes that occur before the onset of full-blown inflammation in a GS host. A better understanding of how gluten can cause symptoms in sensitive individuals will illuminate the interaction between host genotype, diet, and intestinal microbiota in generating one of the most common GI conditions.

Mechanisms involved in alleviation of intestinal inflammation by bifidobacterium breve soluble factors

OBJECTIVES

Soluble factors released by Bifidobacterium breve C50 (Bb) alleviate the secretion of pro-inflammatory cytokines by immune cells, but their effect on intestinal epithelium remains elusive. To decipher the mechanisms accounting for the cross-talk between bacteria/soluble factors and intestinal epithelium, we measured the capacity of the bacteria, its conditioned medium (Bb-CM) and other Gram(+) commensal bacteria to dampen inflammatory chemokine secretion.

METHODS

TNFalpha-induced chemokine (CXCL8) secretion and alteration of NF-kappaB and AP-1 signalling pathways by Bb were studied by EMSA, confocal microscopy and western blotting. Anti-inflammatory capacity was also tested in vivo in a model of TNBS-induced colitis in mice.

RESULTS

Bb and Bb-CM, but not other commensal bacteria, induced a time and dose-dependent inhibition of CXCL8 secretion by epithelial cells driven by both AP-1 and NF-kappaB transcription pathways and implying decreased phosphorylation of p38-MAPK and IkappaB-alpha molecules. In TNBS-induced colitis in mice, Bb-CM decreased the colitis score and inflammatory cytokine expression, an effect reproduced by dendritic cell conditioning with Bb-CM.

CONCLUSIONS

Bb and secreted soluble factors contribute positively to intestinal homeostasis by attenuating chemokine production. The results indicate that Bb down regulate inflammation at the epithelial level by inhibiting phosphorylations involved in inflammatory processes and by protective conditioning of dendritic cells.

Contribution of intestinal epithelial cells to innate immunity of the human gut--studies on polarized monolayers of colon carcinoma cells

The aim was to establish an in vitro model for studies of innate defence mechanisms of human intestinal epithelium. Ultrastructural characterization and determination of mRNA expression levels for apical glycocalyx and mucous components showed that polarized, tight monolayers of the colon carcinoma cell lines T84 and Caco2 acquire the features of mature- and immature columnar epithelial cells, respectively. Polarized monolayers were challenged with non-pathogenic Gram+ and Gram- bacteria from the apical side and the proinflammatory cytokines interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) from the basolateral side. Immune responses were estimated as changes in mRNA expression levels for the mucous component mucin-2 (MUC2), the glycocalyx components carcinoembryonic antigen (CEA), CEA-related cell adhesion molecule-1 (CEACAM1), CEACAM6, CEACAM7 and MUC3, the antimicrobial factors human beta-defensin-1 (hBD1), hBD2, hBD3 and lysozyme, the chemokine IL-8 and the cytokines IL-6 and TNF-alpha. Tight monolayer cells were generally unresponsive to bacterial challenge, but increased their hBD2 levels when challenged with Bacillus megaterium. T84 cells also increased their TNF-alpha levels upon bacterial challenge. Tight monolayer cells responded to cytokine challenge suggesting awareness of basolateral attack. TNF-alpha induced significantly increased levels of IL-8 and TNF-alpha itself in both cell lines suggesting recruitment and activation of immune cells in the underlying mucosa in vivo. Cytokine challenge also increased levels of CEACAM1, which includes two functionally different forms, CEACAM1-L and CEACAM1-S. In T84 cells, IFN-gamma was selective for CEACAM1-L while TNF-alpha upregulated both forms. Increased CEACAM1 expression may influence epithelial function and communication between epithelial cells and intraepithelial lymphocytes.

The effect of preoperative weight loss and body mass index on postoperative outcome in patients with esophagogastric carcinoma

Studies have shown that weight loss is associated with adverse outcomes in all treatment modalities for esophagogastric carcinoma. Because of the increased prevalence of obesity and the effectiveness of perioperative nutrition, a number of patients are now obese or have normal body mass index (BMI) at the time of treatment. We investigated the relationship between weight loss, BMI, and outcome of surgery for patients with esophagogastric carcinoma. Data were collected over a 38-month period for all patients diagnosed with operable esophagogastric cancer at two UK centers. All patients underwent resection by a single Consultant Upper Gastrointestinal Surgeon and the use of perioperative jejunal feeding was universal. Ninety-three patients (57 male) underwent esophagogastric resection; 48 had no preoperative weight loss (34 with a BMI > 25 and 14 with a BMI < 25). Forty-five patients had preoperative weight loss (20 with BMI > 25 and 25 with BMI < 25). There was no significant difference in complication rates, median hospital stay, or mortality between the four groups. A significantly higher number of patients displaying preoperative weight loss were found to have stage III disease, but difference in survival of up to 3 years did not reach statistical significance on multivariate analysis. Preoperative weight loss and low BMI did not significantly influence the complication rate, perioperative mortality rate, length of hospital stay, or short-term prognosis. We conclude that preoperative weight loss can not be reliably used as an independent predictor of poor outcome in patients undergoing surgery for esophagogastric carcinoma. However, patients with preoperative weight loss and low BMI are more likely to have advanced disease.

Enteral and parenteral nutrition distinctively modulate intestinal permeability and T cell function in vitro

BACKGROUND

Nutritional support is an established element of therapy for various indications. However, its impact on the mucosal barrier function is not well understood.

AIM OF THE STUDY

We investigated the influence of EN and PN on intestinal epithelial cells and peripheral blood (PBMC) and lamina propria mononuclear cells (LPMC), all of which are involved in the mucosal defense against bacterial translocation and systemic inflammation.

METHODS

Integrity of epithelial cells was measured as transepithelial electrical resistance (TER) of confluent Caco-2 monolayers in the presence of 1% EN, PN and a parenteral amino acid mixture (AM). To determine wound healing capacities, an established migration model with IEC-6 cells was used. Furthermore, we investigated apoptosis, cell activation, proliferation and cytokine secretion of Caco-2, HT29 and of stimulated PBMC and LPMC cultured with or without 1 and 5% EN, AM or PN.

RESULTS

We demonstrated that EN, AM and PN promoted the integrity of the epithelial monolayer and reconstituted epithelial cell continuity TGF-beta-dependently and -independently. Interestingly, only PN induced apoptosis and decreased the mitochondrial membrane potential. The activation status of PBMC was significantly reduced by EN and AM. Specifically, EN leads to an increased apoptosis rate, inhibited cell cycle progression and increased pro-inflammatory cytokine secretion. Both EN and PN reduced the activation status and the release of pro- and anti-inflammatory cytokines.

CONCLUSIONS

Our study provides evidence that by promoting wound healing and regulating T cell function, EN, AM, and PN potently interact with the intestinal barrier and immune system, thus justifying its use in diseases accompanied by impaired mucosal barrier function.

PMNs facilitate translocation of platelets across human and mouse epithelium and together alter fluid homeostasis via epithelial cell-expressed ecto-NTPDases

Mucosal diseases are often characterized by an inflammatory infiltrate that includes polymorphonuclear leukocytes (PMNs), monocytes, lymphocytes, and platelets. A number of studies have suggested that the interaction of platelets with leukocytes has an essential proinflammatory role. Here, we examined whether platelets migrate across mucosal epithelium, as PMNs are known to do, and whether platelets influence epithelial cell function. Initial studies revealed that human platelets did not efficiently transmigrate across human epithelial cell monolayers. However, in the presence of human PMNs, platelet movement across the epithelium was proportional to the extent of PMN transmigration, and strategies that blocked PMN transmigration diminished platelet movement. Furthermore, platelet-PMN comigration was observed in intestinal tissue derived from human patients with inflammatory bowel disease (IBD). The translocated platelets were found to release large quantities of ATP, which was metabolized to adenosine via a 2-step enzymatic reaction mediated by ecto-nucleotidases, including CD73 and ecto-nucleoside triphosphate diphosphohydrolases (ecto-NTPDases), expressed on the apical membrane of the intestinal epithelial cells. In vitro studies and a mouse model of intestinal inflammation were employed to define a mechanism involving adenosine-mediated induction of electrogenic chloride secretion, with concomitant water movement into the intestinal lumen. These studies demonstrate that ecto-NTPDases are expressed on the apical membrane of epithelial cells and are involved in what we believe to be a previously unappreciated function for platelets in the inflamed intestine, which might promote bacterial clearance under inflammatory conditions.

Indigestible Material Attenuated Changes in Apoptosis in the Fasted Rat Jejunal Mucosa

We have previously demonstrated that fasting induced apoptosis and decreased cell proliferation in the rat intestinal mucosa. The aim was to investigate the effect of expanded polystyrene as indigestible material on apoptosis and cell proliferation in rat small intestinal mucosa during fasting. Male SD rats were divided into 3 groups. The first group was fed with chow and water ad libitum. The second group fasted for 72 hrs. The third group was fasted for 24 hrs and was fed expanded polystyrene. Intestinal apoptosis was evaluated by percent fragmented DNA assay, terminal deoxynucleotidyl transferase–mediated dUDP-biotin nick end-labeling (TUNEL) staining, and caspase-3 assay. Cell proliferation was analyzed by 5-bromo-2′-deoxyuridine (5-BrdU) uptake. Truncal vagotomy was performed to evaluate a role of the central nervous system. In the 72-hr fasted rat, mucosal height of the rat jejunum was decreased to 73% of that in rats fed ad libitum, and this decrease was partly restored to 90% in rats fed expanded polystyrene. The fragmented DNA was increased in fasted rats (28.0%) when compared with that in rats fed ad libitum (2.6%). The increase in fragmented DNA in fasted rats was recovered by feeding them expanded polystyrene (8.3%). TUNEL staining confirmed this result. The effect of polystyrene on apoptosis was decreased by truncal vagotomy. Expression of cleaved caspase-3 was increased in fasted rats, which was then decreased by feeding of expanded polystyrene. In contrast to apoptosis, feeding of expanded polystyrene had no reconstructive effect on 5-BrdU uptake in the intestinal epithelium, which was decreased by fasting to 60% of that in rats fed ad libitum. In conclusion, feeding of indigestible material partly restored the decrease in intestinal mucosal length in the fasted rats through the apoptotic pathway without any influence on BrdU uptake. Further exploration focused on the mechanism of this effect of indigestible material is required.