Homeostasis and inflammation in the intestine

Curcumin utilizes the anti-inflammatory response pathway to protect the intestine against bacterial invasion

BACKGROUND/OBJECTIVES

Curcumin, a major component of the Curcuma species, contains antioxidant and anti-inflammatory properties. Although it was found to induce apoptosis in cancer cells, the functional role of curcumin as well as its molecular mechanism in anti-inflammatory response, particularly in intestinal cells, has been less investigated. The intestine epithelial barrier is the first barrier and the most important location for the substrate coming from the lumen of the gut.

SUBJECTS/METHODS

We administered curcumin treatment in the human intestinal epithelial cell lines, T84 and Caco-2. We examined endoplasmic reticulum (ER) stress response by thapsigargin, qPCR of XBP1 and BiP, electrophysiology by wild-type cholera toxin in the cells.

RESULTS

In this study, we showed that curcumin treatment reduces ER stress and thereby decreases inflammatory response in human intestinal epithelial cells. In addition, curcumin confers protection without damaging the membrane tight junction or actin skeleton change in intestine epithelial cells. Therefore, curcumin treatment protects the gut from bacterial invasion via reduction of ER stress and anti-inflammatory response in intestinal epithelial cells.

CONCLUSIONS

Taken together, our data demonstrate the important role of curcumin in protecting the intestine by modulating ER stress and inflammatory response post intoxication.

Endoplasmic reticulum stress and unfolded protein response in inflammatory bowel disease

In eukaryotic cells, protein folding and modification in the endoplasmic reticulum (ER) is highly sensitive to disturbances of homeostasis. The accumulation of unfolded and misfolded proteins in the ER lumen, termed ER stress, activates intracellular signaling pathways to resolve the protein-folding defect. This unfolded protein response (UPR) increases the capacity of ER protein folding, reduces global protein synthesis, and activates ER-associated protein degradation. If ER stress is too severe or chronic, or the UPR is compromised and not able to restore ER protein-folding homeostasis, numerous apoptotic signaling pathways are activated. Preclinical and clinical studies in the past decade indicate that ER stress and the UPR have a significant impact on the pathogenesis of inflammatory bowel disease. Paneth and goblet cells, 2 epithelial cell populations in the gut, rely on a robust ER function for protein folding and secretion. Several immune cells are orchestrated by ER stress and the UPR for differentiation, activation, migration, and survival. In addition, a variety of exogenous and endogenous molecules in the intestinal lumen affect ER function, making ER stress and the UPR relevant cellular signals in intestinal homeostasis. Recent studies demonstrated that unresolved ER stress and/or dysregulated UPR may cause inflammatory bowel disease by inducing epithelial cell death, impairing mucosal barrier function, and activating proinflammatory response in the gut. With our increased understanding of ER stress in inflammatory bowel disease pathogenesis, it is now possible to develop novel therapies to improve ER protein-folding homeostasis and target-specific UPR pathways in cells residing in the intestinal mucosa.

The gut microbiota engages different signaling pathways to induce Duox2 expression in the ileum and colon epithelium

The epithelium is a first line of defense against microorganisms in the gut. Reactive oxygen species (ROS) have an important role in controlling the normal gut microbiota and pathogenic bacteria. Dual oxidase 2 (DUOX2) is an important source of hydrogen peroxide in the small and large intestine, and the gut microbiota induces Duox2 expression. Here, we investigated the microbial regulation of Duox2 expression. We found that Duox2 was expressed by intestinal epithelial cells mainly in the tip of the epithelium. Duox2 expression was strongly induced by the presence of a normal microbiota in mice, but not when germ-free mice were colonized with various commensal bacteria. Duox2 expression was more rapidly induced by the gut microbiota in the colon than in the ileum. Furthermore, we showed that regulation of Duox2 expression in the ileum involved TIR-domain-containing adaptor protein including interferon-β (TRIF) and canonical nuclear factor-κB p50/p65 signaling, whereas regulation of Duox2 expression in the colon involved MyD88 and the p38 pathway. Collectively, these data indicate that the gut microbiota uses two distinct signaling pathways to induce Duox2 expression in the ileum and colon epithelium.

CD69 is the crucial regulator of intestinal inflammation: a new target molecule for IBD treatment?

CD69 has been identified as an early activation marker of lymphocytes. However, recent work has indicated that CD69 plays an essential role for the regulation of inflammatory processes. Particularly, CD69 is highly expressed by lymphocytes at mucosal sites being constantly exposed to the intestinal microflora (one of the nature's most complex and most densely populated microbial habitats) and food antigens, while only a small number of circulating leukocytes express this molecule. In this review we will discuss the role of CD69 in mucosal tissue and consider CD69 as a potential target for the development of novel treatments of intestinal inflammation.

Endoplasmic reticulum stress in intestinal epithelial cell function and inflammatory bowel disease

In eukaryotic cells, perturbation of protein folding homeostasis in the endoplasmic reticulum (ER) causes accumulation of unfolded and misfolded proteins in the ER lumen, which activates intracellular signaling pathways termed the unfolded protein response (UPR). Recent studies have linked ER stress and the UPR to inflammatory bowel disease (IBD). The microenvironment of the ER is affected by a myriad of intestinal luminal molecules, implicating ER stress and the UPR in proper maintenance of intestinal homeostasis. Several intestinal cell populations, including Paneth and goblet cells, require robust ER function for protein folding, maturation, and secretion. Prolonged ER stress and impaired UPR signaling may cause IBD through: (1) induction of intestinal epithelial cell apoptosis, (2) disruption of mucosal barrier function, and (3) induction of the proinflammatory response in the gut. Based on our increased understanding of ER stress in IBD, new pharmacological approaches can be developed to improve intestinal homeostasis by targeting ER protein-folding in the intestinal epithelial cells (IECs).

Perturbations of mucosal homeostasis through interactions of intestinal microbes with myeloid cells

Mucosal surfaces represent the largest areas of interactions of the host with its environment. Subsequently, the mucosal immune system has evolved complex strategies to maintain the integrity of the host by inducing protective immune responses against pathogenic and tolerance against dietary and commensal microbial antigens within the broad range of molecules the intestinal epithelium is exposed to. Among many other specialized cell subsets, myeloid cell populations - due to their strategic location in the subepithelial lamina propria - are the first ones to scavenge and process these intestinal antigens and to send consecutive signals to other immune and non-immune cell subsets. Thus, myeloid cell populations represent attractive targets for clinical intervention in chronic inflammatory bowel diseases (IBDs) such as ulcerative colitis (UC) and Crohn's disease (CD) as they initiate and modulate inflammatory or regulatory immune response and shape the intestinal T cell pool. Here, we discuss the interactions of the intestinal microbiota with dendritic cell and macrophage populations and review in this context the literature on four promising candidate molecules that are critical for the induction and maintenance of intestinal homeostasis on the one hand, but also for the initiation and propagation of chronic intestinal inflammation on the other.

Bacterial uracil modulates Drosophila DUOX-dependent gut immunity via Hedgehog-induced signaling endosomes

Genetic studies in Drosophila have demonstrated that generation of microbicidal reactive oxygen species (ROS) through the NADPH dual oxidase (DUOX) is a first line of defense in the gut epithelia. Bacterial uracil acts as DUOX-activating ligand through poorly understood mechanisms. Here, we show that the Hedgehog (Hh) signaling pathway modulates uracil-induced DUOX activation. Uracil-induced Hh signaling is required for intestinal expression of the calcium-dependent cell adhesion molecule Cadherin 99C (Cad99C) and subsequent Cad99C-dependent formation of endosomes. These endosomes play essential roles in uracil-induced ROS production by acting as signaling platforms for PLCβ/PKC/Ca2+-dependent DUOX activation. Animals with impaired Hh signaling exhibit abolished Cad99C-dependent endosome formation and reduced DUOX activity, resulting in high mortality during enteric infection. Importantly, endosome formation, DUOX activation, and normal host survival are restored by genetic reintroduction of Cad99C into enterocytes, demonstrating the important role for Hh signaling in host resistance to enteric infection.

Maturation of the enteric mucosal innate immune system during the postnatal period

The innate immune system instructs the host on microbial exposure and infection. This information is critical to mount a protective innate and adaptive host response to microbial challenge, but is also involved in homeostatic and adaptive processes that adjust the organism to meet environmental requirements. This is of particular importance for the neonatal host during the transition from the protected fetal life to the intense and dynamic postnatal interaction with commensal and pathogenic microorganisms. Here, we discuss both adaptive and developmental mechanisms of the mucosal innate immune system that prevent inappropriate stimulation and facilitate establishment of a stable homeostatic host-microbial interaction after birth.

Implication of fructans in health: immunomodulatory and antioxidant mechanisms

Previous studies have shown that fructans, a soluble dietary fiber, are beneficial to human health and offer a promising approach for the treatment of some diseases. Fructans are nonreducing carbohydrates composed of fructosyl units and terminated by a single glucose molecule. These carbohydrates may be straight or branched with varying degrees of polymerization. Additionally, fructans are resistant to hydrolysis by human digestive enzymes but can be fermented by the colonic microbiota to produce short chain fatty acids (SCFAs), metabolic by-products that possess immunomodulatory activity. The indirect role of fructans in stimulating probiotic growth is one of the mechanisms through which fructans exert their prebiotic activity and improve health or ameliorate disease. However, a more direct mechanism for fructan activity has recently been suggested; fructans may interact with immune cells in the intestinal lumen to modulate immune responses in the body. Fructans are currently being studied for their potential as "ROS scavengers" that benefit intestinal epithelial cells by improving their redox environment. In this review, we discuss recent advances in our understanding of fructans interaction with the intestinal immune system, the gut microbiota, and other components of the intestinal lumen to provide an overview of the mechanisms underlying the effects of fructans on health and disease.

The probiotic mixture VSL#3 dampens LPS-induced chemokine expression in human dendritic cells by inhibition of STAT-1 phosphorylation

VSL#3, a mixture of 8 different probiotic bacteria, has successfully been used in the clinic to treat Ulcerative Colitis. We previously identified the modulation of chemokines as a major mechanism in the protective effect of the VSL#3 in a mouse model of colitis. This was supported by invitro studies that implicated a role for VSL#3 in the suppression of LPS-induced chemokine production by mouse bone marrow-derived dendritic cells (DC). Herein, we validated these findings employing human monocyte-derived DC. Stimulation of human DC with LPS, VSL#3, or a combination of both resulted in their maturation, evident from enhanced expression of activation markers on the cell-surface, as well as the induction of various chemokines and cytokines. Interestingly, a set of LPS-induced chemokines was identified that were suppressed by VSL#3. These included CXCL9, CXCL10, CCL2, CCL7, and CCL8. In silico approaches identified STAT-1 as a dominant regulator of these chemokines, and this was confirmed by demonstrating that LPS-induced phosphorylation of this transcription factor was inhibited by VSL#3. This indicates that VSL#3 may contribute to the control of inflammation by selective suppression of STAT-1 induced chemokines.

Exploring the physiology and pathology of aging in the intestine of Drosophila melanogaster

The gastrointestinal tract, due to its role as a digestive organ and as a barrier between the exterior and interior milieus, is critically impacted by dietary, environmental, and inflammatory conditions that influence health and lifespan. Work in flies is now uncovering the multifaceted molecular mechanisms that control homeostasis in this tissue, and establishing its central role in health and lifespan of metazoans. The Drosophila intestine has thus emerged as a productive, genetically accessible model to study various aspects of the pathophysiology of aging. Studies in flies have characterized the maintenance of regenerative homeostasis, the development of immune senescence, the loss of epithelial barrier function, the decline in metabolic homeostasis, as well as the maintenance of epithelial diversity in this tissue. Due to its fundamental similarity to vertebrate intestines, it can be anticipated that findings obtained in this system will have important implications for our understanding of age-related changes in the human intestine. Here, I review recent studies exploring age-related changes in the fly intestine, and their insight into the regulation of health and lifespan of the animal.

Human adipose-derived stem cells attenuate inflammatory bowel disease in IL-10 knockout mice

Inflammatory bowel disease (IBD) is a complex immunological disorder characterized by chronic inflammation caused mainly by unknown factors. The interleukin-10 knockout (IL-10 KO) mouse is a well-established murine model of IBD which develops spontaneous intestinal inflammation that resembles Crohn's disease. In the present study, human adipose-derived mesenchymal stem cells (hAMSCs) were administrated to IL-10 KO mice to evaluate the anti-inflammatory effects of hAMSCs that may attenuate the progress of or treat IBD. After IBD was induced by feeding the IL-10 KO mouse a 125-250 ppm piroxicam mixed diet for 1 week, 2×10(6) hAMSCs were injected into the peritoneum and the mice were switched to a normal diet. After 1 week, the mice were sacrificed and tissue samples were harvested. Tissue scores for inflammation and inflammation-related genes expression were determined. The hAMSC-treated group showed significantly reduced inflammatory changes in histological analysis. Reverse transcription-PCR analysis showed that RANTES, Toll-like receptor 9, and IL-4 expression levels were not significantly different between the groups while IL-12, INF-γ, and TNF-α levels were significantly decreased in the hAMSC treated group. hAMSC attenuated IBD in the IL-10 KO mice by suppressing inflammatory cytokine expression, was mediated by the type 1 helper T cell pathway. Even though only a single injection of hAMSCs was delivered, the effect influenced chronic events associated with inflammatory changes and demonstrated that hAMSCs are a powerful candidate for IBD therapy.

Toll-like receptor expression in crypt epithelial cells, putative stem cells and intestinal myofibroblasts isolated from controls and patients with inflammatory bowel disease

The aim of our studies was to investigate the expression of Toll-like receptor (TLR)-2 and TLR-4 (and in some studies TLR-5) in myofibroblasts and small and large intestinal crypt epithelial cells from control patients and those affected by Crohn's disease and ulcerative colitis. Isolated and disaggregated crypt epithelial cells and monolayers of myofibroblasts were used for studies by reverse transcription–polymerase chain reaction (RT–PCR), real-time RT–PCR, flow cytometry, immunocytochemistry and Western blot analysis. Compared to control cells, crypt epithelial cells isolated from active ulcerative colitis and Crohn's disease colonic mucosal samples showed significantly higher expression of TLR-2 and TLR-4 transcripts and protein (on the cell surface). There was also enhanced expression of TLR-4 in crypt cells from ileal Crohn's disease. Expression of TLR-2 and TLR-4 transcripts in crypt epithelial cells isolated from inflamed mucosa of distal ulcerative colitis did not differ significantly from such cells obtained from the normal proximal colon. Crypt epithelial cells with side population characteristics (putative stem cells) also expressed transcripts and protein for TLR-2, TLR-4 and TLR-5. Colonic myofibroblast expression of these TLRs was much weaker than in crypt epithelial cells. In conclusion, enhanced TLR-2 and TLR-4 expression by crypt epithelial cells in active inflammatory bowel disease likely reflects greater ability to respond to microbial products. Results from our studies using mucosal samples from patients with distal ulcerative colitis suggest that the enhanced expression of these TLRs could be constitutive. TLR-2, TLR-4 and TLR-5 expression by stem cells imply ability to respond to distinct bacterial products.

SIM2 maintains innate host defense of the small intestine

The single-minded 2 (SIM2) protein is a basic helix-loop-helix transcription factor regulating central nervous system (CNS) development in Drosophila. In humans, SIM2 is located within the Down syndrome critical region on chromosome 21 and may be involved in the development of mental retardation phenotype in Down syndrome. In this study, knockout of SIM2 expression in mice resulted in a gas distention phenotype in the gastrointestinal tract. We found that SIM2 is required for the expression of all cryptdins and numerous other antimicrobial peptides (AMPs) expressed in the small intestine. The mechanism underlying how SIM2 controls AMP expression involves both direct and indirect regulations. For the cryptdin genes, SIM2 regulates their expression by modulating transcription factor 7-like 2, a crucial regulator in the Wnt/β-catenin signaling pathway, while for other AMP genes, such as RegIIIγ, SIM2 directly activates their promoter activity. Our results establish that SIM2 is a crucial regulator in controlling expression of intestinal AMPs to maintain intestinal innate immunity against microbes.

Interaction of Streptococcus agalactiae and Cellular Innate Immunity in Colonization and Disease

Streptococcus agalactiae (Group B streptococcus, GBS) is highly adapted to humans, where it is a normal constituent of the intestinal and vaginal flora. Yet, GBS has highly invasive potential and causes excessive inflammation, sepsis, and death at the beginning of life, in the elderly and in diabetic patients. Thus, GBS is a model pathobiont that thrives in the healthy host, but has not lost its potential virulence during coevolution with mankind. It remains incompletely understood how the innate immune system contains GBS in the natural niches, the intestinal and genital tracts, and which molecular events underlie breakdown of mucocutaneous resistance. Newborn infants between days 7 and 90 of life are at risk of a particularly striking sepsis manifestation (late-onset disease), where the transition from colonization to invasion and dissemination, and thus from health to severe sepsis is typically fulminant and not predictable. The great majority of late-onset sepsis cases are caused by one clone, GBS ST17, which expresses HvgA as a signature virulence factor and adhesin. In mice, HvgA promotes the crossing of both the mucosal and the blood–brain barrier. Expression levels of HvgA and other GBS virulence factors, such as pili and toxins, are regulated by the upstream two-component control system CovR/S. This in turn is modulated by acidic epithelial pH, high glucose levels, and during the passage through the mouse intestine. After invasion, GBS has the ability to subvert innate immunity by mechanisms like glycerinaldehyde-3-phosphate-dehydrogenase-dependent induction of IL-10 and β-protein binding to the inhibitory phagocyte receptors sialic acid binding immunoglobulin-like lectin 5 and 14. On the host side, sensing of GBS nucleic acids and lipopeptides by both Toll-like receptors and the inflammasome appears to be critical for host resistance against GBS. Yet, comprehensive models on the interplay between GBS and human immune cells at the colonizing site are just emerging.

The laminin response in inflammatory bowel disease: protection or malignancy?

Laminins (LM), basement membrane molecules and mediators of epithelial-stromal communication, are crucial in tissue homeostasis. Inflammatory Bowel Diseases (IBD) are multifactorial pathologies where the microenvironment and in particular LM play an important yet poorly understood role in tissue maintenance, and in cancer progression which represents an inherent risk of IBD. Here we showed first that in human IBD colonic samples and in murine colitis the LMα1 and LMα5 chains are specifically and ectopically overexpressed with a concomitant nuclear p53 accumulation. Linked to this observation, we provided a mechanism showing that p53 induces LMα1 expression at the promoter level by ChIP analysis and this was confirmed by knockdown in cell transfection experiments. To mimic the human disease, we induced colitis and colitis-associated cancer by chemical treatment (DSS) combined or not with a carcinogen (AOM) in transgenic mice overexpressing LMα1 or LMα5 specifically in the intestine. We demonstrated that high LMα1 or LMα5 expression decreased susceptibility towards experimentally DSS-induced colon inflammation as assessed by histological scoring and decrease of pro-inflammatory cytokines. Yet in a pro-oncogenic context, we showed that LM would favor tumorigenesis as revealed by enhanced tumor lesion formation in both LM transgenic mice. Altogether, our results showed that nuclear p53 and associated overexpression of LMα1 and LMα5 protect tissue from inflammation. But in a mutation setting, the same LM molecules favor progression of IBD into colitis-associated cancer. Our transgenic mice represent attractive new models to acquire knowledge about the paradoxical effect of LM that mediate either tissue reparation or cancer according to the microenvironment. In the early phases of IBD, reinforcing basement membrane stability/organization could be a promising therapeutic approach.

The role of glycosylation in IBD

A number of genetic and immunological studies give impetus for investigating the role of glycosylation in IBD. Experimental mouse models have helped to delineate the role of glycosylation in intestinal mucins and to explore the putative pathogenic role of glycosylation in colitis. These experiments have been extended to human studies investigating the glycosylation patterns of intestinal mucins as well as levels of glycans of serum glycoproteins and expression of glycan receptors. These early human studies have generated interesting hypotheses regarding the pathogenic role of glycans in IBD, but have generally been restricted to fairly small underpowered studies. Decreased glycosylation has been observed in the intestinal mucus of patients with IBD, suggesting that a defective inner mucus layer might lead to increased bacterial contact with the epithelium, potentially triggering inflammation. In sera, decreased galactosylation of IgG has been suggested as a diagnostic marker for IBD. Advances in glycoprofiling technology make it technically feasible and affordable to perform high-throughput glycan pattern analyses and to build on previous work investigating a much wider range of glycan parameters in large numbers of patients.

Contribution of TLR signaling to the pathogenesis of colitis-associated cancer in inflammatory bowel disease

In the intestine a balance between proinflammatory and repair signals of the immune system is essential for the maintenance of intestinal homeostasis. The innate immunity ensures a primary host response to microbial invasion, which induces an inflammatory process to localize the infection and prevent systemic dissemination of pathogens. The key elements of this process are the germline encoded pattern recognition receptors including Toll-like receptors (TLRs). If pathogens cannot be eliminated, they may elicit chronic inflammation, which may be partly mediated via TLRs. Additionally, chronic inflammation has long been suggested to trigger tissue tumorous transformation. Inflammation, the seventh hallmark of cancer, may affect all phases of tumor development, and evade the immune system. Inflammation acts as a cellular stressor and may trigger DNA damage or genetic instability. Furthermore, chronic inflammation can provoke genetic mutations and epigenetic mechanisms that promote malignant cell transformation. Colorectal cancers in inflammatory bowel disease patients are considered typical examples of inflammation-related cancers. Although data regarding the role of TLRs in the pathomechanism of cancer-associated colitis are rather conflicting, functionally these molecules can be classified as "largely antitumorigenic" and "largely pro-tumorigenic" with the caveat that the underlying signaling pathways are mainly context (i.e., organ-, tissue-, cell-) and ligand-dependent.

Biological pathways involved in the development of inflammatory bowel disease

Apoptosis, autophagy and necrosis are three distinct functional types of the mammalian cell death network. All of them are characterized by a number of cell's morphological changes. The inappropriate induction of cell death is involved in the pathogenesis of a number of diseases.Pathogenesis of inflammatory bowel diseases (ulcerative colitis, Crohn's disease) includes an abnormal immunological response to disturbed intestinal microflora. One of the most important reason in pathogenesis of chronic inflammatory disease and subsequent multiple organ pathology is a barrier function of the gut, regulating cellular viability. Recent findings have begun to explain the mechanisms by which intestinal epithelial cells are able to survive in such an environment and how loss of normal regulatory processes may lead to inflammatory bowel disease (IBD).This review focuses on the regulation of biological pathways in development and homeostasis in IBD. Better understanding of the physiological functions of biological pathways and their influence on inflammation, immunity, and barrier function will simplify our expertice of homeostasis in the gastrointestinal tract and in upgrading diagnosis and treatment.

Linking immunity, epigenetics, and cancer in inflammatory bowel disease

Most of what is known about the pathogenesis of inflammatory bowel disease (IBD) pertains to complex interplay between host genetics, immunity, and environmental factors. Epigenetic modifications play pivotal roles in intestinal immunity and mucosal homeostasis as well as mediating gene-environment interactions. In this article, we provide a historical account of epigenetic research either directly related or pertinent to the pathogenesis and management of IBD. We further collate emerging evidence supporting roles for epigenetic mechanisms in relevant aspects of IBD biology, including deregulated immunity, host-pathogen recognition and mucosal integrity. Finally, we highlight key epigenetic mechanisms that link chronic inflammation to specific IBD comorbidities, including colitis-associated cancer and discuss their potential utility as novel biomarkers or pharmacologic targets in IBD therapy.

Promoting longevity by maintaining metabolic and proliferative homeostasis

Aging is characterized by a widespread loss of homeostasis in biological systems. An important part of this decline is caused by age-related deregulation of regulatory processes that coordinate cellular responses to changing environmental conditions, maintaining cell and tissue function. Studies in genetically accessible model organisms have made significant progress in elucidating the function of such regulatory processes and the consequences of their deregulation for tissue function and longevity. Here, we review such studies, focusing on the characterization of processes that maintain metabolic and proliferative homeostasis in the fruitfly Drosophila melanogaster. The primary regulatory axis addressed in these studies is the interaction between signaling pathways that govern the response to oxidative stress, and signaling pathways that regulate cellular metabolism and growth. The interaction between these pathways has important consequences for animal physiology, and its deregulation in the aging organism is a major cause for increased mortality. Importantly, protocols to tune such interactions genetically to improve homeostasis and extend lifespan have been established by work in flies. This includes modulation of signaling pathway activity in specific tissues, including adipose tissue and insulin-producing tissues, as well as in specific cell types, such as stem cells of the fly intestine.

Integration of UPRER and oxidative stress signaling in the control of intestinal stem cell proliferation

The Unfolded Protein Response of the endoplasmic reticulum (UPR^ER) controls proteostasis by adjusting the protein folding capacity of the ER to environmental and cell-intrinsic conditions. In metazoans, loss of proteostasis results in degenerative and proliferative diseases and cancers. The cellular and molecular mechanisms causing these phenotypes remain poorly understood. Here we show that the UPR^ER is a critical regulator of intestinal stem cell (ISC) quiescence in Drosophilamelanogaster. We find that ISCs require activation of the UPR^ER for regenerative responses, but that a tissue-wide increase in ER stress triggers ISC hyperproliferation and epithelial dysplasia in aging animals. These effects are mediated by ISC-specific redox signaling through Jun-N-terminal Kinase (JNK) and the transcription factor CncC. Our results identify a signaling network of proteostatic and oxidative stress responses that regulates ISC function and regenerative homeostasis in the intestinal epithelium.

Loss of proper protein homeostasis (proteostasis) as well as increased production of reactive oxygen species (ROS) is a hallmark of aging. In complex metazoans, these processes can result in proliferative diseases and cancers. The protein folding capacity of the endoplasmic reticulum (ER) is monitored and maintained by the unfolded protein response of the ER (UPR^ER). In this study, we identify a coordinated role of UPR^ER and oxidative stress signaling in regulating the proliferation of intestinal stem cells (ISCs). We find that the ER-stress responsive transcription factor Xbp1 and the ER-associated degradation pathway component Hrd1 are sufficient and required cell autonomously in ISCs to limit their proliferative activity. This function is dependent on the activities of the stress sensor JNK and the redox-responsive transcription factor CncC, which we have previously identified as regulators of ISC proliferation. We further show here that promoting ER homeostasis in aging ISCs is sufficient to limit age-associated epithelial dysplasia. Our results establish the integration of UPR^ER and oxidative stress signaling as a central mechanism promoting regenerative homeostasis in the intestinal epithelium.

Guidelines on the use of extracorporeal photopheresis

BACKGROUND

After the first investigational study on the use of extracorporeal photopheresis for the treatment of cutaneous T-cell lymphoma was published in 1983 with its subsequent recognition by the FDA for its refractory forms, the technology has shown significant promise in the treatment of other severe and refractory conditions in a multi-disciplinary setting. Among the major studied conditions are graft versus host disease after allogeneic bone marrow transplantation, systemic sclerosis, solid organ transplant rejection and inflammatory bowel disease.

MATERIALS AND METHODS

In order to provide recognized expert practical guidelines for the use of this technology for all indications the European Dermatology Forum (EDF) proceeded to address these questions in the hands of the recognized experts within and outside the field of dermatology. This was done using the recognized and approved guidelines of EDF for this task.

RESULTS AND CONCLUSION

These guidelines provide at present the most comprehensive available expert recommendations for the use of extracorporeal photopheresis based on the available published literature and expert consensus opinion.

Domino effect of hypomagnesemia on the innate immunity of Crohn’s disease patients

Digestive diseases play major role in development and complications of other disorders including diabetes. For example, Crohn’s disease (CD) is an inflammatory bowel disease associated with Mycobacterium avium subspecies paratuberculosis. The inflammation is a complex process that involves the activity of both innate and adaptive immune responses. CD lesions are primarily due to T cell response, however; innate immune response has a significant role in initiating its pathogenesis. Toll-like receptors and NOD-like receptors promote the activity of nuclear factor (NF)-κB pathway for cytokines production. This results in the production of high levels of tumor necrosis factor-α, interleukin (IL)-1β and IL-6. Moreover, intestinal inflammation of CD is related to increased activity of NMDA receptors and the release of substance P. Imbalanced magnesium homeostasis in CD is a frequent finding in CD, Diabetes and others. The loss of such a major mineral affects many physiological processes in the body including its role as an immunomodulator. This review aims to (1) describe the significance of hypomagnesemia in the release of pro-inflammatory mediators in CD; (2) demonstrate effects of magnesium on pathways like NF-κB; (3) address the role of hypomagnesemia in the activity of CD; and (4) examine possible future research to establish a standard magnesium supplementation strategy; helping patients with CD or other disorders to maintain a sustained remission.

Immunomodulation by gut microbiota: role of Toll-like receptor expressed by T cells

A close relationship exists between gut microbiota and immune responses. An imbalance of this relationship can determine local and systemic immune diseases. In fact the immune system plays an essential role in maintaining the homeostasis with the microbiota that normally resides in the gut, while, at the same time, the gut microbiota influences the immune system, modulating number and function of effector and regulatory T cells. To achieve this aim, mutual regulation between immune system and microbiota is achieved through several mechanisms, including the engagement of toll-like receptors (TLRs), pathogen-specific receptors expressed on numerous cell types. TLRs are able to recognize ligands from commensal or pathogen microbiota to maintain the tolerance or trigger the immune response. In this review, we summarize the latest evidences about the role of TLRs expressed in adaptive T cells, to understand how the immune system promotes intestinal homeostasis, fights invasion by pathogens, and is modulated by the intestinal microbiota.

Gut microbiota-generated metabolites in animal health and disease

Gut microbiota is found in virtually any metazoan, from invertebrates to vertebrates. It has long been believed that gut microbiota, more specifically, the activity of the microbiome and its metabolic products, directly influence a variety of aspects in metazoan physiology. However, the exact molecular relationship among microbe-derived gut metabolites, host signaling pathways, and host physiology remains to be elucidated. Here we review recent discoveries regarding the molecular links between gut metabolites and host physiology in different invertebrate and vertebrate animal models. We describe the different roles of gut microbiome activity and their metabolites in regulating distinct host physiology and the molecular mechanisms by which gut metabolites cause physiological homeostasis via regulating specific host signaling pathways. Future studies in this direction using different animal models will provide the key concepts to understanding the evolutionarily conserved chemical dialogues between gut microbiota and metazoan cells and also human diseases associated with gut microbiota and metabolites.

Soluble CD83 ameliorates experimental colitis in mice

The physiological balance between pro- and anti-inflammatory processes is dysregulated in inflammatory bowel diseases (IBD) as in Crohn's disease and ulcerative colitis. Conventional therapy uses anti-inflammatory and immunosuppressive corticosteroids to treat acute-phase symptoms. However, low remission rate and strong side effects of these therapies are not satisfying. Thus, there is a high medical need for new therapeutic strategies. Soluble CD83, the extracellular domain of the transmembrane CD83 molecule, has been reported to have interesting therapeutic and immunosuppressive properties by suppressing dendritic cell (DC)-mediated T-cell activation and inducing tolerogenic DCs. However, the expression and function of CD83 in IBD is still unknown. Here, we show that CD83 expression is upregulated by different leukocyte populations in a chemical-induced murine colitis model. Furthermore, in this study the potential of sCD83 to modulate colitis using an experimental murine colitis model was investigated. Strikingly, sCD83 ameliorated the clinical disease symptoms, drastically reduced mortality, and strongly decreased inflammatory cytokine expression in mesenteric lymph nodes and colon. The infiltration of macrophages and granulocytes into colonic tissues was vigorously inhibited. Mechanistically, we could show that sCD83-induced expression of indolamine 2,3-dioxygenase is essential for its protective effects.

Adipocyte inflammation is essential for healthy adipose tissue expansion and remodeling

Chronic inflammation constitutes an important link between obesity and its pathophysiological sequelae. In contrast to the belief that inflammatory signals exert a fundamentally negative impact on metabolism, we show that proinflammatory signaling in the adipocyte is in fact required for proper adipose tissue remodeling and expansion. Three mouse models with an adipose tissue-specific reduction in proinflammatory potential were generated that display a reduced capacity for adipogenesis in vivo, while the differentiation potential is unaltered in vitro. Upon high-fat-diet exposure, the expansion of visceral adipose tissue is prominently affected. This is associated with decreased intestinal barrier function, increased hepatic steatosis, and metabolic dysfunction. An impaired local proinflammatory response in the adipocyte leads to increased ectopic lipid accumulation, glucose intolerance, and systemic inflammation. Adipose tissue inflammation is therefore an adaptive response that enables safe storage of excess nutrients and contributes to a visceral depot barrier that effectively filters gut-derived endotoxin.

Stress, inflammation, and defense of homeostasis

Inflammation is traditionally considered a defense response induced by infection or injury. However, inflammation can also be induced by tissue stress and malfunction in the absence of infection or overt tissue damage. Here we discuss the relationship between homeostasis, stress responses, and inflammation. Stress responses have cell-autonomous and cell-extrinsic components, the latter contributing to tissue level adaptation to stress conditions. Inflammation can be thought of as the extreme end of a spectrum that ranges from homeostasis to stress response to bona fide inflammatory response. Inflammation can be triggered by two types of stimuli: extreme deviations of homeostasis or challenges that cause a disruption of homeostasis. This perspective may help to explain qualitative differences and functional outcomes of diverse inflammatory responses.

Fecal microbiome analysis as a diagnostic test for diverticulitis

Disease-specific variations in intestinal microbiome composition have been found for a number of intestinal disorders, but little is known about diverticulitis. The purpose of this study was to compare the fecal microbiota of diverticulitis patients with control subjects from a general gastroenterological practice and to investigate the feasibility of predictive diagnostics based on complex microbiota data. Thirty-one patients with computed tomography (CT)-proven left-sided uncomplicated acute diverticulitis were included and compared with 25 control subjects evaluated for a range of gastrointestinal indications. A high-throughput polymerase chain reaction (PCR)-based profiling technique (IS-pro) was performed on DNA isolates from baseline fecal samples. Differences in bacterial phylum abundance and diversity (Shannon index) of the resulting profiles were assessed by conventional statistics. Dissimilarity in microbiome composition was analyzed with principal coordinate analysis (PCoA) based on cosine distance measures. To develop a prediction model for the diagnosis of diverticulitis, we used cross-validated partial least squares discriminant analysis (PLS-DA). Firmicutes/Bacteroidetes ratios and Proteobacteria load were comparable among patients and controls (p = 0.20). The Shannon index indicated a higher diversity in diverticulitis for Proteobacteria (p < 0.00002) and all phyla combined (p = 0.002). PCoA based on Proteobacteria profiles resulted in visually separate clusters of patients and controls. The diagnostic accuracy of the cross-validated PLS-DA regression model was 84 %. The most discriminative species derived largely from the family Enterobacteriaceae. Diverticulitis patients have a higher diversity of fecal microbiota than controls from a mixed population, with the phylum Proteobacteria defining the difference. The analysis of intestinal microbiota offers a novel way to diagnose diverticulitis.

Disruption of epithelial barrier by quorum-sensing N-3-(oxododecanoyl)-homoserine lactone is mediated by matrix metalloproteinases

The intestinal epithelium forms a selective barrier maintained by tight junctions (TJs) and separating the luminal environment from the submucosal tissues. N-acylhomoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence homeostasis of the host intestinal epithelium. In the present study, we evaluated the regulatory mechanisms affecting the impact of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on barrier function of human intestinal epithelial Caco-2 cells. Treatment with C12-HSL, but not with C4-HSL, perturbed Caco-2 barrier function; the effect was associated with decreased levels of the TJ proteins occludin and tricellulin and their delocalization from the TJs. C12-HSL also induced matrix metalloprotease (MMP)-2 and MMP-3 activation via lipid raft- and protease-activated receptor (PAR)-dependent signaling. Pretreatment with lipid raft disruptors, PAR antagonists, or MMP inhibitors restored the C12-HSL-induced loss of the TJ proteins and increased permeability of Caco-2 cell monolayers. These results indicate that PAR/lipid raft-dependent MMP-2 and -3 activation followed by degradation of occludin and tricellulin are involved in C12-HSL-induced alterations of epithelial paracellular barrier functions.

Aging of the mammalian gastrointestinal tract: a complex organ system

Gastrointestinal disorders are a major cause of morbidity in the elderly population. The gastrointestinal tract is the most complex organ system; its diverse cells perform a range of functions essential to life, not only secretion, digestion, absorption and excretion, but also, very importantly, defence. The gastrointestinal tract acts not only as a barrier to harmful materials and pathogens but also contains the vast number of beneficial bacterial populations that make up the microbiota. Communication between the cells of the gastrointestinal tract and the central nervous and endocrine systems modifies behaviour; the organisms of the microbiota also contribute to this brain-gut-enteric microbiota axis. Age-related physiological changes in the gut are not only common, but also variable, and likely to be influenced by external factors as well as intrinsic aging of the cells involved. The cellular and molecular changes exhibited by the aging gut cells also vary. Aging intestinal smooth muscle cells exhibit a number of changes in the signalling pathways that regulate contraction. There is some evidence for age-associated degeneration of neurons and glia of the enteric nervous system, although enteric neuronal losses are likely not to be nearly as extensive as previously believed. Aging enteric neurons have been shown to exhibit a senescence-associated phenotype. Epithelial stem cells exhibit increased mitochondrial mutation in aging that affects their progeny in the mucosal epithelium. Changes to the microbiota and intestinal immune system during aging are likely to contribute to wider aging of the organism and are increasingly important areas of analysis. How changes of the different cell types of the gut during aging affect the numerous cellular interactions that are essential for normal gut functions will be important areas for future aging research.

NOD-like receptors in intestinal homeostasis and epithelial tissue repair

The intestinal epithelium constitutes a dynamic physical barrier segregating the luminal content from the underlying mucosal tissue. Following injury, the epithelial integrity is restored by rapid migration of intestinal epithelial cells (IECs) across the denuded area in a process known as wound healing. Hence, through a sequence of events involving restitution, proliferation and differentiation of IECs the gap is resealed and homeostasis reestablished. Relapsing damage followed by healing of the inflamed mucosa is a hallmark of several intestinal disorders including inflammatory bowel diseases (IBD). While several regulatory peptides, growth factors and cytokines stimulate restitution of the epithelial layer after injury, recent evidence in the field underscores the contribution of innate immunity in controlling this process. In particular, nucleotide-binding and oligomerization domain-like receptors (NLRs) play critical roles in sensing the commensal microbiota, maintaining homeostasis, and regulating intestinal inflammation. Here, we review the process of intestinal epithelial tissue repair and we specifically focus on the impact of NLR-mediated signaling mechanisms involved in governing epithelial wound healing during disease.

The cytosolic bacterial peptidoglycan sensor Nod2 affords stem cell protection and links microbes to gut epithelial regeneration

The intestinal crypt is a site of potential interactions between microbiota products, stem cells, and other cell types found in this niche, including Paneth cells, and thus offers a potential for commensal microbes to influence the host epithelium. However, the complexity of this microenvironment has been a challenge to deciphering the underlying mechanisms. We used in vitro cultured organoids of intestinal crypts from mice, reinforced with in vivo experiments, to examine the crypt-microbiota interface. We find that within the intestinal crypt, Lgr5(+) stem cells constitutively express the cytosolic innate immune sensor Nod2 at levels much higher than in Paneth cells. Nod2 stimulation by its bona fide agonist, muramyl-dipeptide (MDP), a peptidoglycan motif common to all bacteria, triggers stem cell survival, which leads to a strong cytoprotection against oxidative stress-mediated cell death. Thus, gut epithelial restitution is Nod2 dependent and triggered by the presence of microbiota-derived molecules.

Reconceiving autoimmunity: An overview

Three interconnected positions are advocated: (1) although serving as a useful model, the immune self does not exist as such; (2) instead of a self/nonself demarcation, the immune system 'sees' itself, i.e., it does not ignore the 'self' or attack the 'other;' but exhibits a spectrum of responses, which when viewed from outside the system appear as discrimination of 'self' and 'nonself' based on certain criteria of reactivity. When immune reactions are conceived in terms of normal physiology and open exchange with the environment, where borders dividing host and foreign are elusive and changing, host defense is only part of the immune system's functions, which actually comprise two basic tasks: protection, i.e., to preserve host integrity, and maintenance of organismic identity. And thus (3) if the spectrum of immunity is enlarged, differentiating low reactive 'autoimmune' reactions from activated immune responses against the 'other' is only a matter of degree. Simply, all immunity is 'autoimmunity,' and the pathologic state of immunity directed at normal constituents of the organism is a particular case of dis-regulation, which appropriately is designated, autoimmune. Other uses of 'autoimmunity' and its congeners function as the semantic remnants of Burnet's original self/nonself theory and should be replaced. A new nomenclature is proposed, concinnity, which more accurately designates the physiology of the animal's ordinary housekeeping economy mediated by the immune system than 'autoimmunity' when used to describe such normal functions.

Microbial community profiling of human saliva using shotgun metagenomic sequencing

Human saliva is clinically informative of both oral and general health. Since next generation shotgun sequencing (NGS) is now widely used to identify and quantify bacteria, we investigated the bacterial flora of saliva microbiomes of two healthy volunteers and five datasets from the Human Microbiome Project, along with a control dataset containing short NGS reads from bacterial species representative of the bacterial flora of human saliva. GENIUS, a system designed to identify and quantify bacterial species using unassembled short NGS reads was used to identify the bacterial species comprising the microbiomes of the saliva samples and datasets. Results, achieved within minutes and at greater than 90% accuracy, showed more than 175 bacterial species comprised the bacterial flora of human saliva, including bacteria known to be commensal human flora but also Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae, and Gamma proteobacteria. Basic Local Alignment Search Tool (BLASTn) analysis in parallel, reported ca. five times more species than those actually comprising the in silico sample. Both GENIUSand BLAST analyses of saliva samples identified major genera comprising the bacterial flora of saliva, but GENIUS provided a more precise description of species composition, identifying to strain in most cases and delivered results at least 10,000 times faster. Therefore, GENIUS offers a facile and accurate system for identification and quantification of bacterial species and/or strains in metagenomic samples.

Shrinkage of the human core microbiome and a proposal for launching microbiome biobanks

ABSTRACT: 

The Human Microbiome Project (HMP) revealed the significance of the gut microbiome in promoting health. Disruptions in microbiome composition are associated with the pathogenesis of numerous diseases. The indigenous microflora has co-evolved with humans for millions of years and humans have preserved the inherited microbiomes through consumption of fermented foods and interactions with environmental microbes. Through modernization, traditional foods were abandoned, native food starters were substituted with industrial products, vaccines and antibiotics were used, extreme hygiene measures were taken, the rate of cesarean section increased, and breast feeding changed into formula. These factors have reduced human exposure to microbial symbionts and led to shrinkage of the core microbiome. Reduction in microbiome biodiversity can compromise the human immune system and predispose individuals to several modern diseases. This article suggests launching microbiome biobanks for archiving native microbiomes, supervising antibiotic use, probiotic design and native starter production, as well as advertising a revisit to native lifestyles.

Silibinin modulates caudal-type homeobox transcription factor (CDX2), an intestine specific tumor suppressor to abrogate colon cancer in experimental rats

To authenticate the colon cancer preventive potential of silibinin, the efficacy of silibinin needs to be tested by evaluating an organ-specific biomarker. The aim of this study was to evaluate the impact of silibinin on the colonic expression of the caudal-type homeobox transcription factor (CDX2) an intestine specific tumor suppressor gene and its downstream targets in the colon of rats challenged with 1,2 dimethyl hydrazine (DMH). Rats of groups 1 and 2 were treated as control and silibinin control. Rats under groups 3 and 4 were given DMH (20 mg/kg body weight (b.w.) subcutaneously) once a week for 15 consecutive weeks from the 4th week of the experimental period. In addition, group 4 rats alone were treated with silibinin (50 mg/kg b.w. per os) everyday throughout the study period of 32 weeks. Histological investigation and messenger RNA and protein expression studies were performed in the colonic tissues of experimental rats. Findings of the study revealed that DMH administration significantly decreased the expression of CDX2 and Guanylyl cyclase C ( GCC) in the colon of experimental rats. Further the decreased levels of CDX2 protein, colonic mucin content, and increased number of mast cells in the colon of DMH alone-administered rats reflects the onset of carcinogenesis. The pathological changes caused due to CDX2 suppression were attenuated by silibinin supplementation.

Restoring the gut microbiome for the treatment of inflammatory bowel diseases

Fecal microbiota transplantation (FMT) is considered to be a highly successful therapy for recurrent and refractory Clostridium difficile infection (CDI) based on recent clinical trials. The pathogenesis of inflammatory bowel diseases (IBD) is thought to be due in part to perturbations in the gut microflora that disrupt homeostasis. FMT restores essential components of the microflora which could reverse the inflammatory processes observed in IBD. Case reports and series for the treatment of IBD by FMT have shown promise with regards to treatment success and safety despite the limitations of the reporting. Future studies will determine the optimal delivery and preparation of stool as well as the conditions under which the recipient will derive maximal benefit. The long term consequences of FMT with regards to infection, cancer, auto-immune, and metabolic diseases are not known and will require continued regulation and study. Despite these limitations, FMT may be beneficial for the treatment of ulcerative colitis and Crohn’s disease, particularly those with concurrent CDI or with pouchitis.

High abundance of Escherichia during the establishment of fecal microbiota in Brazilian children

The sequence of bacterial events that occurs during the colonization of the gastrointestinal tract may affect the future health of the host. A clear understanding of the colonization process of the human neonatal gut in developing countries is lacking because the few available studies were mostly performed using culture techniques. Using molecular approaches, this study analyzed the fecal microbiota of children of low socioeconomic status in São Paulo, Brazil, during their first year of life. We collected fecal samples of healthy children at 3, 6, and 12 months of life. Total DNA was extracted directly from feces, and the bacteria-specific primers 27F-1492R were used to construct 16S rRNA libraries. Clones were randomly selected and partially sequenced. The main phylogenetic groups identified at 3 months were Streptococcus, unidentified bacteria, and Escherichia. At 6 months, Escherichia remained predominant, while the unidentified bacterial population increased significantly. At 12 months, a more complex composition of fecal microbiota was observed, represented by unidentified bacteria and microorganisms found at low rates at earlier ages. The genus Escherichia remained the most abundant microorganism (34% relative abundance and 75% prevalence). Principal component analysis (PCA) revealed changes in the composition of the microbiota at 6 months and an increase of diversity at 12 months of life. Bifidobacterium was identified by quantitative PCR (qPCR) and showed a high incidence in the microbiota at 3 months. The present results corroborate the global observation of inter-individual variability with an early establishment of microbial complexity at the end of the first year of life and highlight the presence of the Escherichia as abundant in microbiota composition of this group of children.

Phosphorylation of eIF2α is dispensable for differentiation but required at a posttranscriptional level for paneth cell function and intestinal homeostasis in mice

BACKGROUND

Recent studies link endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) to inflammatory bowel disease. Altered eIF2α phosphorylation (eIF2α-P), a regulatory hub of the UPR, was observed in mucosal tissue of patients with inflammatory bowel disease. In this study, we examined the mechanistic role of eIF2α-P in intestinal epithelial cell (IEC) function and intestinal homeostasis in mice.

METHODS

We generated mice with villin-Cre-mediated conditional expression of nonphosphorylatable Ser51Ala mutant eIF2α in IECs (AA mice). We analyzed AA mice under normal conditions and on challenge with oral infection of Salmonella Typhimurium or dextran sulfate sodium-induced colitis.

RESULTS

Loss of eIF2α-P did not affect the normal proliferation or differentiation of IECs. However, AA mice expressed decreased secretory proteins including lysozyme, suggesting eIF2α-P is required for Paneth cell function. The ultrastructure of AA Paneth cells exhibited a reduced number of secretory granules, a fragmented ER, and distended mitochondria under normal conditions. UPR gene expression was defective in AA IECs. Translation of Paneth cell specific messenger RNAs encoding lysozyme and cryptidins was significantly defective leading to the observed granule-deficient phenotype, which was associated with reduced ribosomal recruitment of these messenger RNAs to the ER membrane. Consequently, AA mice were more susceptible to oral Salmonella infection and dextran sulfate sodium-induced colitis.

CONCLUSIONS

We conclude eIF2α phosphorylation is required for the normal function of intestinal Paneth cells and mucosal homeostasis by activating UPR signaling and promoting messenger RNA recruitment to the ER membrane for translation.

Role of Th17 Cells in the Pathogenesis of Human IBD

The gastrointestinal tract plays a central role in immune system, being able to mount efficient immune responses against pathogens, keeping the homeostasis of the human gut. However, conditions like Crohn's disease (CD) or ulcerative colitis (UC), the main forms of inflammatory bowel diseases (IBD), are related to an excessive and uncontrolled immune response against normal microbiota, through the activation of CD4(+) T helper (Th) cells. Classically, IBD was thought to be primarily mediated by Th1 cells in CD or Th2 cells in UC, but it is now known that Th17 cells and their related cytokines are crucial mediators in both conditions. Th17 cells massively infiltrate the inflamed intestine of IBD patients, where they produce interleukin- (IL-) 17A and other cytokines, triggering and amplifying the inflammatory process. However, these cells show functional plasticity, and they can be converted into either IFN- γ producing Th1 cells or regulatory T cells. This review will summarize the current knowledge regarding the regulation and functional role of Th17 cells in the gut. Deeper insights into their plasticity in inflammatory conditions will contribute to advancing our understanding of the mechanisms that regulate mucosal homeostasis and inflammation in the gut, promoting the design of novel therapeutic approaches for IBD.

Early life events influence whole-of-life metabolic health via gut microflora and gut permeability

The capacity of our gut microbial communities to maintain a stable and balanced state, termed 'resilience', in spite of perturbations is vital to our achieving and maintaining optimal health. A loss of microbial resilience is observed in a number of diseases including obesity, diabetes and metabolic syndrome. There are large gaps in our understanding of why an individual's co-evolved microflora consortium fail to develop resilience thereby establishing a trajectory towards poor metabolic health. This review examines the connections between the developing gut microbiota and intestinal barrier function in the neonate, infant and during the first years of life. We propose that the effects of early life events on the gut microflora and permeability, whilst it is in a dynamic and vulnerable state, are fundamental in shaping the microbial consortia's resilience and that it is the maintenance of resilience that is pivotal for metabolic health throughout life. We review the literature supporting this concept suggesting new potential research directions aimed at developing a greater understanding of the longitudinal effects of the gut microflora on metabolic health and potential interventions to recalibrate the 'at risk' infant gut microflora in the direction of enhanced metabolic health.