Glial cells in the gut

Berberine decreases S100B generation to regulate gut vascular barrier permeability in mice with burn injury

Context: Berberine (BBR) can regulate enteric glial cells (EGCs) and the gut vascular barrier (GVB).Objective: To explore whether BBR regulates GVB permeability via the S100B pathway.Materials and methods: GVB hyperpermeability in C57BL/6J mice was induced by burns or S100B enema. BBR (25 or 50 mg/kg/d, 3 d) was gavaged preburn. S100B monoclonal antibody (S100BmAb) was i.v. injected postburn. Mouse intestinal microvascular endothelial cells (MIMECs) were treated with S100B, S100B plus BBR, or Z-IETD-FMK. GVB permeability was assayed by FITC-dextran, S100B by ELISA, caspase-8, β-catenin, occludin and PV-1 by immunoblot.Results: Burns elevated S100B in serum and in colonic mucosa to a peak (147.00 ± 4.95 ng/mL and 160.30 ± 8.50 ng/mg, respectively) at 36 h postburn, but BBR decreased burns-induced S100B in serum (126.20 ± 6.30 or 90.60 ± 3.78 ng/mL) and in mucosa (125.80 ± 12.40 or 91.20 ± 8.54 ng/mg). Burns raised GVB permeability (serum FITC-dextran 111.40 ± 8.56 pg/mL) at 48 h postburn, but BBR reduced GVB permeability (serum FITC-dextran 89.20 ± 6.98 or 68.60 ± 5.50 ng/mL). S100B enema (1 μM) aggravated burns-raised GVB permeability (142.80 ± 8.07 pg/mL) and PV-1, but the effect of S100B was antagonized by BBR. Z-IETD-FMK (5 μM) increased S100B-induced permeability to FITC-dextran (205.80 ± 9.70 to 263.80 ± 11.04 AUs) while reducing β-catenin in MIMECs. BBR (5 μM) reduced S100B-induced permeability (104.20 ± 9.65 AUs) and increased caspase-8, β-catenin and occludin.Discussion and conclusion: BBR decreases burns-induced GVB hyperpermeability via modulating S100B/caspase-8/β-catenin pathway and may involve EGCs.

Global research status and trends of enteric glia: a bibliometric analysis

Background

Enteric glia are essential components of the enteric nervous system. Previously believed to have a passive structural function, mounting evidence now suggests that these cells are indispensable for maintaining gastrointestinal homeostasis and exert pivotal influences on both wellbeing and pathological conditions. This study aimed to investigate the global status, research hotspots, and future directions of enteric glia.

Methods

The literature on enteric glia research was acquired from the Web of Science Core Collection. VOSviewer software (v1.6.19) was employed to visually represent co-operation networks among countries, institutions, and authors. The co-occurrence analysis of keywords and co-citation analysis of references were conducted using CiteSpace (v6.1.R6). Simultaneously, cluster analysis and burst detection of keywords and references were performed.

Results

A total of 514 publications from 36 countries were reviewed. The United States was identified as the most influential country. The top-ranked institutions were University of Nantes and Michigan State University. Michel Neunlist was the most cited author. "Purinergic signaling" was the largest co-cited reference cluster, while "enteric glial cells (EGCs)" was the cluster with the highest number of co-occurring keywords. As the keyword with the highest burst strength, Crohns disease was a hot topic in the early research on enteric glia. The burst detection of keywords revealed that inflammation, intestinal motility, and gut microbiota may be the research frontiers.

Conclusion

This study provides a comprehensive bibliometric analysis of enteric glia research. EGCs have emerged as a crucial link between neurons and immune cells, attracting significant research attention in neurogastroenterology. Their fundamental and translational studies on inflammation, intestinal motility, and gut microbiota may promote the treatment of some gastrointestinal and parenteral disorders.

Neuroimmune Connectomes in the Gut and Their Implications in Parkinson's Disease

The gastrointestinal tract is the largest immune organ and it receives dense innervation from intrinsic (enteric) and extrinsic (sympathetic, parasympathetic, and somatosensory) neurons. The immune and neural systems of the gut communicate with each other and their interactions shape gut defensive mechanisms and neural-controlled gut functions such as motility and secretion. Changes in neuroimmune interactions play central roles in the pathogenesis of diseases such as Parkinson's disease (PD), which is a multicentric disorder that is heterogeneous in its manifestation and pathogenesis. Non-motor and premotor symptoms of PD are common in the gastrointestinal tract and the gut is considered a potential initiation site for PD in some cases. How the enteric nervous system and neuroimmune signaling contribute to PD disease progression is an emerging area of interest. This review focuses on intestinal neuroimmune loops such as the neuroepithelial unit, enteric glial cells and their immunomodulatory effects, anti-inflammatory cholinergic signaling and the relationship between myenteric neurons and muscularis macrophages, and the role of α-synuclein in gut immunity. Special consideration is given to the discussion of intestinal neuroimmune connectomes during PD and their possible implications for various aspects of the disease.

Enteric glial cells aggravate the intestinal epithelial barrier damage by secreting S100β under high-altitude conditions

Damage to the intestinal epithelial barrier (IEB) has been reported under high-altitude (HA) conditions and may be responsible for HA-associated gastrointestinal (GI) disorders. However, this pathogenetic mechanism does not fully explain the GI stress symptoms, such as flatulence and motility diarrhea, which accompany the IEB damage under HA conditions, especially for the people exposed to HA acutely. In the present study, we collected the blood samples from the people who lived at HA and found the concentration of enteric glial cells (EGCs)-associated biomarkers increased significantly. HA mouse model was then established and the results revealed that EGCs were involved in IEB damage. Zona occludens (ZO)-1, occludin, and claudin-1 expression was negatively correlated with that of glial fibrillary acidic protein (GFAP) and S100β under HA conditions. In order to learn more about how EGCs influence IEB, the in vitro EGC and MODE-K hypoxia experiments that used hypoxic stimulation for simulating in vivo exposure to HA was performed. We found that hypoxia increased S100β secretion in EGCs. And MODE-K cells cultured in medium conditioned by hypoxic EGCs showed low ZO-1, occludin, and claudin-1 levels of expression. Furthermore, treatment of MODE-K cells with recombinant mouse S100β resulted in diminished levels of ZO-1, occludin, and claudin-1 expression. Thus, HA exposure induces greater S100β secretion by EGCs, which aggravates the damage to the IEB. This study has revealed a novel mechanism of IEB damage under HA conditions, and suggest that EGCs may constitute a fresh avenue for the avoidance of GI disorders at HA.

Effects of experimental ulcerative colitis on myenteric neurons in P2X7-knockout mice

This study aimed to investigate the distal colon myenteric plexus and enteric glial cells (EGCs) in P2X7 receptor-deficient (P2X7-/-) animals after the induction of experimental ulcerative colitis. 2,4,6-Trinitrobenzene sulfonic acid (TNBS) was injected into the distal colon of C57BL/6 (WT) and P2X7 receptor gene-deficient (P2X7-/-, KO) animals. Distal colon tissues in the WT and KO groups were analyzed 24 h and 4 days after administration. The tissues were analyzed by double immunofluorescence of the P2X7 receptor with neuronal nitric oxide synthase (nNOS)-immunoreactive (ir), choline acetyltransferase (ChAT)-ir, and PGP9.5 (pan neuronal)-ir, and their morphology was assessed by histology. The quantitative analysis revealed 13.9% and 7.1% decreases in the number of P2X7 receptor-immunoreactive (ir) per ganglion in the 24 h-WT/colitis and 4 day-WT/colitis groups, respectively. No reduction in the number of nNOS-ir, choline ChAT-ir, and PGP9.5-ir neurons per ganglion was observed in the 4 day-KO/colitis group. In addition, a reduction of 19.3% in the number of GFAP (glial fibrillary acidic protein)-expressing cells per ganglion was found in the 24 h-WT/colitis group, and a 19% increase in the number of these cells was detected in the 4 day-WT/colitis group. No profile area changes in neurons were observed in the 24 h-WT and 24 h-KO groups. The 4 day-WT/colitis and 4 day-KO/colitis groups showed increases in the profile neuronal areas of nNOS, ChAT, and PGP9.5. The histological analysis showed hyperemia, edema, or cellular infiltration in the 24 h-WT/colitis and 4 day-WT/colitis groups. Edema was observed in the 4 day-KO/colitis group, which showed no histological changes compared with the 24 h-KO/colitis group. We concluded that ulcerative colitis differentially affected the neuronal classes in the WT and KO animals, demonstrating the potential participation and neuroprotective effect of the P2X7 receptor in enteric neurons in inflammatory bowel disease.

Effect of the gut microbiota and their metabolites on postoperative intestinal motility and its underlying mechanisms

Gut microbiota is closely related to human health and disease because, together with their metabolites, gut microbiota maintain normal intestinal peristalsis. The use of antibiotics or opioid anesthetics, or both, during surgical procedures can lead to dysbiosis and affect intestinal motility; however, the underlying mechanisms are not fully known. This review aims to discuss the effect of gut microbiota and their metabolites on postoperative intestinal motility, focusing on regulating the enteric nervous system, 5-hydroxytryptamine neurotransmitter, and aryl hydrocarbon receptor.

The emerging science of Glioception: Contribution of glia in sensing, transduction, circuit integration of interoception

Interoception is the process by which the nervous system regulates internal functions to achieve homeostasis. The role of neurons in interoception has received considerable recent attention, but glial cells also contribute. Glial cells can sense and transduce signals including osmotic, chemical, and mechanical status of extracellular milieu. Their ability to dynamically communicate "listening" and "talking" to neurons is necessary to monitor and regulate homeostasis and information integration in the nervous system. This review introduces the concept of "Glioception" and focuses on the process by which glial cells sense, interpret and integrate information about the inner state of the organism. Glial cells are ideally positioned to act as sensors and integrators of diverse interoceptive signals and can trigger regulatory responses via modulation of the activity of neuronal networks, both in physiological and pathological conditions. We believe that understanding and manipulating glioceptive processes and underlying molecular mechanisms provide a key path to develop new therapies for the prevention and alleviation of devastating interoceptive dysfunctions, among which pain is emphasized here with more focused details.

Effects of probenecid and brilliant blue G on rat enteric glial cells following intestinal ischemia and reperfusion

The P2X7 receptor participates in several intracellular events and acts with the pannexin-1 channel. This study examined the effects of probenecid (PB) and brilliant blue G (BBG), which are antagonists of the pannexin-1 channel and P2X7 receptor, respectively, on rat ileum enteric glial cells after on ischemia and reperfusion. The ileal vessels were occluded for 45 min with nontraumatic vascular tweezers, and reperfusion was performed for periods of 24 h and 14 and 28 days. After ischemia (IR groups), the animals were treated with BBG (BG group) or PB (PB group). The double-labeling results demonstrated the following: the P2X7 receptor was present in enteric glial cells (S100β) and enteric neurons positive for HuC/D; enteric glial cells exhibited different phenotypes; some enteric glial cells were immunoreactive to only S100β or GFAP; and the pannexin-1 channel was present in enteric glial cells (GFAP). Density (in cells/cm²) analyses showed that the IR group exhibited a decrease in the number of cells immunoreactive for the P2X7 receptor, pannexin-1, and HuC/D and that treatment with BBG or PB resulted in the recovery of the numbers of these cells. The number of glial cells (S100β and GFAP) was higher in the IR group, and the treatments decreased the number of these cells to the normal value. However, the PB group did not exhibit recovery of S100β-positive glia. The cell profile area (μm²) of S100β-positive enteric glial cells decreased to the normal value after BBG treatment, whereas no recovery was observed in the PB group. The ileum contractile activity was decreased in the IR group and returned to baseline in the BG and PB groups. BBG and PB can effectively induce the recovery of neurons and glia cells and are thus potential therapeutic agents in the treatment of gastrointestinal tract diseases.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

Effect of Reactive EGCs on Intestinal Motility and Enteric Neurons During Endotoxemia

Paralytic ileus is common in patients with septic shock, causing high morbidity and mortality. Enteric neurons and enteric glial cells (EGCs) regulate intestinal motility. However, little is known about their interaction in endotoxemia. This study aimed to investigate whether reactive EGCs had harmful effects on enteric neurons and participated in intestinal motility disorder in mice during endotoxemia. Endotoxemia was induced by the intraperitoneal injection of lipopolysaccharide (LPS) in mice. Fluorocitrate (FC) was administered before LPS injection to inhibit the reactive EGCs. The effects of reactive EGCs on intestinal motility were analyzed by motility assays in vivo and colonic migrating motor complexes ex vivo. The number of enteric neurons was evaluated by immunofluorescent staining of HuCD, nNOS, and ChAT in vivo. In addition, we stimulated EGCs with IL-1β and TNF-α in vitro and cultured the primary enteric neurons in the conditioned medium, detecting the apoptosis and morphology of neurons through staining TUNEL, cleaved caspase-3 protein, and anti-β-III tubulin. Intestinal motility and peristaltic reflex were improved by inhibiting reactive EGCs in vivo. The density of the neuronal population in the colonic myenteric plexus increased significantly, while the reactive EGCs were inhibited, especially the nitrergic neurons. In vitro, the enteric neurons cultured in the conditioned medium of reactive EGCs had a considerably higher apoptotic rate, less dendritic complexity, and fewer primary neurites. Reactive enteric glial cells probably participated in paralytic ileus by damaging enteric neurons during endotoxemia. They might provide a novel therapeutic strategy for intestinal motility disorders during endotoxemia or sepsis.

Enteric glia: extent, cohesion, axonal contacts, membrane separations and mitochondria in Auerbach's ganglia of guinea pigs

Studied by electron microscopy and morphometry, Auerbach’s ganglia comprise nerve cell bodies that occupy ~ 40% of volume; of the neuropil, little over 30% is neural processes (axons, dendrites) and little less than 30% is glia (cell bodies, processes). The amount of surface membrane of neural elements only marginally exceeds that of glia. Glial cells extend laminar processes radially between axons, reaching the ganglion’s surface with specialized membrane domains. Nerve cells and glia are tightly associated, eliminating any free space in ganglia. Glia expands maximally its cell membrane with a minimum of cytoplasm, contacting a maximal number of axons, which, with their near-circular profile, have minimal surface for a given volume. Shape of glia is moulded by the neural elements (predominantly concave the first, predominantly convex the second); the glia extends its processes to maximize contact with neural elements. Yet, a majority of axons is not reached by glia and only few are wrapped by it. Despite the large number of cells, the glia is not sufficiently developed to wrap around or just contact many of the neural elements. Mitochondria are markedly fewer in glia than in neurons, indicating a lower metabolic rate. Compactness of ganglia, their near-circular profile, absence of spaces between elements and ability to withstand extensive deformation suggest strong adhesion between the cellular elements, holding them together and keeping them at a fixed distance. Many axonal varicosities, with vesicles and membrane densities, abut on non-specialized areas of glia, suggesting the possibility of neurotransmitters being released outside synaptic sites.

Pathophysiology of Diverticular Disease: From Diverticula Formation to Symptom Generation

Diverticular disease is a common clinical problem, particularly in industrialized countries. In most cases, colonic diverticula remain asymptomatic throughout life and sometimes are found incidentally during colonic imaging in colorectal cancer screening programs in otherwise healthy subjects. Nonetheless, roughly 25% of patients bearing colonic diverticula develop clinical manifestations. Abdominal symptoms associated with diverticula in the absence of inflammation or complications are termed symptomatic uncomplicated diverticular disease (SUDD). The pathophysiology of diverticular disease as well as the mechanisms involved in the shift from an asymptomatic condition to a symptomatic one is still poorly understood. It is accepted that both genetic factors and environment, as well as intestinal microenvironment alterations, have a role in diverticula development and in the different phenotypic expressions of diverticular disease. In the present review, we will summarize the up-to-date knowledge on the pathophysiology of diverticula and their different clinical setting, including diverticulosis and SUDD.

Immunohistochemical visualisation of the enteric nervous system architecture in the germ-free piglets

The enteric nervous system (ENS), considered as separate branch of the autonomic nervous system, is located throughout the length of the gastrointestinal tract as a series of interconnected ganglionic plexuses. Recently, the ENS is getting more in the focus of gastrointestinal research. For years, the main interest and research was aimed to the enteric neurons and their functional properties in normal conditions, less attention has been paid to the germ-free animals. Germ-free (GF) piglets have clear microbiological background and are reared in sterile environment. GF piglets are regarded as clinically relevant models for studying of human diseases, as these piglets' manifest similar clinical symptoms to humans. In this study we briefly summarised the main characteristics in immunohistochemical distribution of ENS elements in the wall of jejunum and colon of germ-free piglets.

Enteric Glia and Enteric Neurons, Associated

Peripheral neurons are never found alone and are invariably accompanied by glial cells, with which they are intimately associated in compact, highly deformable structures.Myenteric ganglia of the guinea-pig, examined in situ by electron microscopy, show that in their neuropil (axons and dendrites, and glial cells and processes) the glia constitutes almost half of the volume and almost half of membrane extent.In the glia, the expanse of the cell membrane predominates over that of their cytoplasm, the opposite being the case with the neural elements.The profile of the glial elements is passive and is dictated by the surrounding elements, mainly the axons, and hence it is predominantly concave.The enteric glia is widely developed; however, it is not sufficient to form a full wrapping around all neurons and around all axons (unlike what is found in other autonomic ganglia).Glial processes are radially expanding laminae, irregularly tapering, branching, and penetrating between axons.Some processes have a specialized termination attached to the basal lamina of the ganglion.Mitochondria are markedly more abundant in neural element that in the glia (up to a factor of 2).Many expanded axons, laden with vesicles clustered beneath membrane sites, abut on glial cells and processes, while these show no matching structural specializations.

Enteric glial cell heterogeneity regulates intestinal stem cell niches

The high turnover and regenerative capacity of the adult intestine relies on resident stem cells located at the bottom of the crypt. The enteric nervous system consists of an abundant network of enteric glial cells (EGCs) and neurons. Despite the close proximity of EGCs to stem cells, their in vivo role as a stem cell niche is still unclear. By analyzing the mouse and human intestinal mucosa transcriptomes at the single-cell level, we defined the regulation of EGC heterogeneity in homeostasis and chronic inflammatory bowel disease. Ablation of EGC subpopulations revealed that the repair potential of intestinal stem cells (ISCs) is regulated by a specific subset of glial fibrillary acidic protein (GFAP)⁺ EGCs. Mechanistically, injury induces expansion of GFAP⁺ EGCs, which express several WNT ligands to promote LGR5⁺ ISC self-renewal. Our work reveals the dynamically regulated heterogeneity of EGCs as a key part of the intestinal stem cell niche in regeneration and disease.

Automatic chronic degenerative diseases identification using enteric nervous system images

Studies recently accomplished on the Enteric Nervous System have shown that chronic degenerative diseases affect the Enteric Glial Cells (EGC) and, thus, the development of recognition methods able to identify whether or not the EGC are affected by these type of diseases may be helpful in its diagnoses. In this work, we propose the use of pattern recognition and machine learning techniques to evaluate if a given animal EGC image was obtained from a healthy individual or one affect by a chronic degenerative disease. In the proposed approach, we have performed the classification task with handcrafted features and deep learning-based techniques, also known as non-handcrafted features. The handcrafted features were obtained from the textural content of the ECG images using texture descriptors, such as the Local Binary Pattern (LBP). Moreover, the representation learning techniques employed in the approach are based on different Convolutional Neural Network (CNN) architectures, such as AlexNet and VGG16, with and without transfer learning. The complementarity between the handcrafted and non-handcrafted features was also evaluated with late fusion techniques. The datasets of EGC images used in the experiments, which are also contributions of this paper, are composed of three different chronic degenerative diseases: Cancer, Diabetes Mellitus, and Rheumatoid Arthritis. The experimental results, supported by statistical analysis, show that the proposed approach can distinguish healthy cells from the sick ones with a recognition rate of 89.30% (Rheumatoid Arthritis), 98.45% (Cancer), and 95.13% (Diabetes Mellitus), being achieved by combining classifiers obtained on both feature scenarios.

A Novel Role of A2AR in the Maintenance of Intestinal Barrier Function of Enteric Glia from Hypoxia-Induced Injury by Combining with mGluR5

During acute intestinal ischemia reperfusion (IR) injury, the intestinal epithelial barrier (IEB) function is often disrupted. Enteric glial cells (EGCs) play an important role in maintaining the integrity of IEB functions. However, how EGCs regulate IEB function under IR stimulation is unknown. The present study reveals that the adenosine A_2A receptor (A_2AR) is important for mediating the barrier-modulating roles of EGCs. A_2AR knockout (KO) experiments revealed more serious intestinal injury in A_2AR KO mice than in WT mice after IR stimulation. Moreover, A_2AR expression was significantly increased in WT mice when challenged by IR. To further investigate the role of A_2AR in IEB, we established an in vitro EGC-Caco-2 co-culture system. Hypoxia stimulation was used to mimic the process of in vivo IR. Treating EGCs with the CGS21680 A_2AR agonist attenuated hypoxia-induced intestinal epithelium damage through up-regulating ZO-1 and occludin expression in cocultured Caco-2 monolayers. Furthermore, we showed that A_2AR and metabotropic glutamate receptor 5 (mGluR5) combine to activate the PKCα-dependent pathway in conditions of hypoxia. This study shows, for the first time, that hypoxia induces A_2AR-mGluR5 interaction in EGCs to protect IEB function via the PKCα pathway.

Human resident gut microbe Bacteroides thetaiotaomicron regulates colonic neuronal innervation and neurogenic function

BACKGROUND AND AIMS

As the importance of gut-brain interactions increases, understanding how specific gut microbes interact with the enteric nervous system (ENS), which is the first point of neuronal exposure becomes critical. Our aim was to understand how the dominant human gut bacterium Bacteroides thetaiotaomicron (Bt) regulates anatomical and functional characteristics of the ENS.

METHODS

Neuronal cell populations, as well as enteroendocrine cells, were assessed in proximal colonic sections using fluorescent immunohistochemistry in specific pathogen-free (SPF), germ-free (GF) and Bt conventionalized-germ-free mice (Bt-CONV). RNA expression of tight junction proteins and toll-like receptors (TLR) were measured using qPCR. Colonic motility was analyzed using in vitro colonic manometry.

RESULTS

Decreased neuronal and vagal afferent innervation observed in GF mice was normalized by Bt-CONV with increased neuronal staining in mucosa and myenteric plexus. Bt-CONV also restored expression of nitric oxide synthase expressing inhibitory neurons and of choline acetyltransferase and substance P expressing excitatory motor neurons comparable to those of SPF mice. Neurite outgrowth and glial cells were upregulated by Bt-CONV. RNA expression of tight junction protein claudin 3 was downregulated while TLR2 was upregulated by Bt-CONV. The enteroendocrine cell subtypes L-cells and enterochromaffin cells were reduced in GF mice, with Bt-CONV restoring L-cell numbers. Motility as measured by colonic migrating motor complexes (CMMCs) increased in GF and Bt-CONV.

CONCLUSION

Bt, common gut bacteria, is critical in regulating enteric neuronal and enteroendocrine cell populations, and neurogenic colonic activity. This highlights the potential use of this resident gut bacteria for maintaining healthy gut function.

Enteric glia as a source of neural progenitors in adult zebrafish

The presence and identity of neural progenitors in the enteric nervous system (ENS) of vertebrates is a matter of intense debate. Here, we demonstrate that the non-neuronal ENS cell compartment of teleosts shares molecular and morphological characteristics with mammalian enteric glia but cannot be identified by the expression of canonical glial markers. However, unlike their mammalian counterparts, which are generally quiescent and do not undergo neuronal differentiation during homeostasis, we show that a relatively high proportion of zebrafish enteric glia proliferate under physiological conditions giving rise to progeny that differentiate into enteric neurons. We also provide evidence that, similar to brain neural stem cells, the activation and neuronal differentiation of enteric glia are regulated by Notch signalling. Our experiments reveal remarkable similarities between enteric glia and brain neural stem cells in teleosts and open new possibilities for use of mammalian enteric glia as a potential source of neurons to restore the activity of intestinal neural circuits compromised by injury or disease.

Mycotoxins and the Enteric Nervous System

Mycotoxins are secondary metabolites produced by various fungal species. They are commonly found in a wide range of agricultural products. Mycotoxins contained in food enter living organisms and may have harmful effects on many internal organs and systems. The gastrointestinal tract, which first comes into contact with mycotoxins present in food, is particularly vulnerable to the harmful effects of these toxins. One of the lesser-known aspects of the impact of mycotoxins on the gastrointestinal tract is the influence of these substances on gastrointestinal innervation. Therefore, the present study is the first review of current knowledge concerning the influence of mycotoxins on the enteric nervous system, which plays an important role, not only in almost all regulatory processes within the gastrointestinal tract, but also in adaptive and protective reactions in response to pathological and toxic factors in food.

Preterm birth and sustained inflammation: consequences for the neonate

Almost half of all preterm births are caused or triggered by an inflammatory process at the feto-maternal interface resulting in preterm labor or rupture of membranes with or without chorioamnionitis (“first inflammatory hit”). Preterm babies have highly vulnerable body surfaces and immature organ systems. They are postnatally confronted with a drastically altered antigen exposure including hospital-specific microbes, artificial devices, drugs, nutritional antigens, and hypoxia or hyperoxia (“second inflammatory hit”). This is of particular importance to extremely preterm infants born before 28 weeks, as they have not experienced important “third-trimester” adaptation processes to tolerate maternal and self-antigens. Instead of a balanced adaptation to extrauterine life, the delicate co-regulation between immune defense mechanisms and immunosuppression (tolerance) to allow microbiome establishment is therefore often disturbed. Hence, preterm infants are predisposed to sepsis but also to several injurious conditions that can contribute to the onset or perpetuation of sustained inflammation (SI). This is a continuing challenge to clinicians involved in the care of preterm infants, as SI is regarded as a crucial mediator for mortality and the development of morbidities in preterm infants. This review will outline the (i) role of inflammation for short-term consequences of preterm birth and (ii) the effect of SI on organ development and long-term outcome.

Abdominal Massage Reduces Visceral Hypersensitivity via Regulating GDNF and PI3K/AKT Signal Pathway in a Rat Model of Irritable Bowel Syndrome

Changes in gut motility and visceral hypersensitivity are two major features of irritable bowel syndrome (IBS). Current drug treatments are often poorly efficacious, with many side effects for patients with IBS. Complementary therapies, such as acupuncture or abdominal massage, have received more attention in recent years. In this study, a rat model of IBS with diarrhea (IBS-D) was established by instillation of acetic acid from the colon. The effects of abdominal massage on changes in gut motility, visceral hypersensitivity, and the possible mechanism were investigated. Continuous abdominal massage could decrease the stool consistency score and increase the efflux time of glass beads compared with model groups, while also decreasing mast cell counts in IBS-D rats. The mRNA and protein expressions of neuronal nitric oxide synthase (nNOS), choline acetyl transferase (CHAT), and protein gene product 9.5 (PGP9.5) were significantly upregulated by continuous abdominal massage compared with model groups. Continuous abdominal massage also improved the ultrastructure of enteric glial cells (EGCs) by decreasing the number of mitochondria and increasing the level of the heterochromatin. Meanwhile, continuous abdominal massage could upregulate the expression of glial cell line-derived neurotrophic factor (GDNF) and P-Akt/Akt. Furthermore, it could reduce visceral hypersensitivity and improve the IBS-D symptoms by regulating the phosphoinositide 3-kinase (PI3K)-Akt pathway, which would provide a novel method for the treatment of IBS-D in the clinical setting.

Pentamidine niosomes thwart S100B effects in human colon carcinoma biopsies favouring wtp53 rescue

S100B protein bridges chronic mucosal inflammation and colorectal cancer given its ability to activate NF-kappaB transcription via RAGE signalling and sequestrate pro-apoptotic wtp53. Being an S100B inhibitor, pentamidine antagonizes S100B-wtp53 interaction, restoring wtp53-mediated pro-apoptotic control in cancer cells in several types of tumours. The expression of S100B, pro-inflammatory molecules and wtp53 protein was evaluated in human biopsies deriving from controls, ulcerative colitis and colon cancer patients at baseline (a) and (b) following S100B targeting with niosomal PENtamidine VEhiculation (PENVE), to maximize drug permeabilization in the tissue. Cultured biopsies underwent immunoblot, EMSA, ELISA and biochemical assays for S100B and related pro-inflammatory/pro-apoptotic proteins. Exogenous S100B (0.005-5 μmol/L) alone, or in the presence of PENVE (0.005-5 μmol/L), was tested in control biopsies while PENVE (5 μmol/L) was evaluated on control, peritumoral, ulcerative colitis and colon cancer biopsies. Our data show that S100B level progressively increases in control, peritumoral, ulcerative colitis and colon cancer enabling a pro-inflammatory/angiogenic and antiapoptotic environment, featured by iNOS, VEGF and IL-6 up-regulation and wtp53 and Bax inhibition. PENVE inhibited S100B activity, reducing its capability to activate RAGE/phosphor-p38 MAPK/NF-kappaB and favouring its disengagement with wtp53. PENVE blocks S100B activity and rescues wtp53 expression determining pro-apoptotic control in colon cancer, suggesting pentamidine as a potential anticancer drug.

Dangerous Liaison: Helicobacter pylori, Ganglionitis, and Myenteric Gastric Neurons: A Histopathological Study

Chronic inflammation induced by Helicobacter pylori (H. pylori) infection plays a major role in development of gastric cancer. However, recent findings suggested that progression of inflammation and neoplastic transformation in H. pylori infection are more complex than previously believed and could involve different factors that modulate gastric microenvironment and influence host-pathogen interaction. Among these factors, gastric myenteric plexus and its potential adaptive changes in H. pylori infection received little attention. This study is aimed at identifying the impact of H. pylori-associated gastritis on number and morphology of nerve cells in the stomach. The distribution of density, inflammation, and programmed cell death in neurons was immunohistochemically assessed in full-thickness archival tissue samples obtained from 40 patients with H. pylori infection who underwent surgery for gastric cancer and were compared with findings on samples collected from 40 age- and sex-matched subjects without bacteria. Overall, significant differences were noted between H. pylori-positive and H. pylori-negative patients. The analysis of tissue specimens obtained from those with infection revealed higher density and larger surface of the myenteric nervous plexus, as well as a significant increase in the number of gastric neuronal cell bodies and glial cells compared to controls. A predominant CD3-immunoreactive T cell infiltrate confined to the myenteric plexus was observed in infected subjects. The presence of mature B lymphocytes, plasma cells, and eosinophils was also noted, but to a lesser extent, within the ganglia. Myenteric ganglionitis was associated with degeneration and neuronal loss. Our results represent the first histopathological evidence supporting the hypothesis that H. pylori-induced gastric inflammation may induce morphological changes in myenteric gastric ganglia. These findings could help gain understanding of some still unclear aspects of pathogenesis of H. pylori infection, with the possibility of having broader implications for gastric cancer progression.

Nerve growth factor and Tropomyosin receptor kinase A are increased in the gastric mucosa of patients with functional dyspepsia

Background

Nerve growth factor (NGF) and enteric glial cells (EGCs) are associated with visceral hypersensitivity and gastrointestinal motility disorder, which may represent the pathogenesis of functional dyspepsia (FD). This study aimed to investigate the expression of NGF, its high affinity receptor tropomyosin receptor kinase A (TrkA) and the EGC activation marker glial fibrillary acidic protein (GFAP) in the gastric mucosa of patients with FD and the association of these proteins with dyspeptic symptoms.

Methods

Gastric mucosal biopsies taken from 27 FD patients (9 epigastric pain syndrome (EPS) patients, 7 postprandial distress syndrome (PDS) patients and 11 EPS overlap PDS patients) and 26 control subjects were used for analysis. The expression of NGF, TrkA and GFAP was examined, and the association of these proteins with dyspeptic symptoms, including epigastric pain, postprandial fullness, early satiation and epigastric burning, was analysed.

Results

The expression levels of NGF, TrkA, and GFAP in the gastric mucosa were significantly higher in the EPS group, the PDS group, and the EPS overlap PDS group than in the healthy control group. There was no significant difference between the FD subgroups. TrkA colocalized with GFAP, which indicated that TrkA was localized to EGCs, and the expression of TrkA in EGCs was significantly higher in the FD group than in the control group. Changes in the expression of NGF, TrkA, and GFAP were positively correlated with epigastric pain, postprandial fullness and early satiation but had no significant relationship with epigastric burning.

Conclusions

The increased expression of gastric NGF, TrkA and GFAP might be involved in FD pathophysiology and symptom perception.

Induction of brain-derived neurotrophic factor in enteric glial cells stimulated by interleukin-1β via a c-Jun N-terminal kinase pathway

Brain-derived neurotrophic factor exhibits neurotropic and neuroprotective functions and is increased in the colonic mucosa of patients with irritable bowel syndrome in correlation with the severity and frequency of abdominal pain. However, there are no reports of brain-derived neurotrophic factor expression in enteric glial cells. We evaluated the mRNA and protein expressions of brain-derived neurotrophic factor in enteric glial cells and culture medium and levels of mitogen-activated protein kinase after stimulation with interleukin-1β. Brain-derived neurotrophic factor mRNA expression was increased by interleukin-1β (3.125-75 ng/ml) and time-dependently increased 3-fold (24 h) and 4-fold (48 h) by interleukin-1β (50 ng/ml). Pro- and mature brain-derived neurotrophic factor proteins were both significantly increased at 48 h by interleukin-1β. However, the mature form was predominant in the cultured medium. Interleukin-1β increased phosphorylated-p38 mitogen-activated protein kinase expressions 2-fold higher at 5 and 15 min, and also phosphorylated-c-Jun N-terminal kinase expression 5-fold at 5 min and 10-fold at 15 min. Prior treatment with phosphorylated-c-Jun N-terminal kinase inhibitors decreased interleukin-1β-induced brain-derived neurotrophic factor by 50%. Thus, brain-derived neurotrophic factor expression was induced by interleukin-1β in enteric glial cells via a phosphorylated-c-Jun N-terminal kinase pathway, which might affect the enteric nervous system during stress.

Schwann cell plasticity-roles in tissue homeostasis, regeneration, and disease

How tissues are maintained over a lifetime and repaired following injury are fundamental questions in biology with a disruption to these processes underlying pathologies such as cancer and degenerative disorders. It is becoming increasingly clear that each tissue has a distinct mechanism to maintain homeostasis and respond to injury utilizing different types of stem/progenitor cell populations depending on the insult and/or with a contribution from more differentiated cells that are able to dedifferentiate to aid tissue regeneration. Peripheral nerves are highly quiescent yet show remarkable regenerative capabilities. Remarkably, there is no evidence for a classical stem cell population, rather all cell-types within the nerve are able to proliferate to produce new nerve tissue. Co-ordinating the regeneration of this tissue are Schwann cells (SCs), the main glial cells of the peripheral nervous system. SCs exist in architecturally stable structures that can persist for the lifetime of an animal, however, they are not postmitotic, in that following injury they are reprogrammed at high efficiency to a progenitor-like state, with these cells acting to orchestrate the nerve regeneration process. During nerve regeneration, SCs show little plasticity, maintaining their identity in the repaired tissue. However, once free of the nerve environment they appear to exhibit increased plasticity with reported roles in the repair of other tissues. In this review, we will discuss the mechanisms underlying the homeostasis and regeneration of peripheral nerves and how reprogrammed progenitor-like SCs have broader roles in the repair of other tissues with implications for pathologies such as cancer.

Berberine ameliorates non-steroidal anti-inflammatory drugs-induced intestinal injury by the repair of enteric nervous system

The study was to detect the role of GDNF, PGP9.5 (a neuronal marker), and GFAP (EGCs' marker) in the mechanism of non-steroidal anti-inflammatory drugs (NSAIDs) related to intestinal injury and to clarify the protective effect of berberine in the treatment of NSAID-induced small intestinal disease. Forty male SD rats were divided randomly into five groups (A-E): Group A: control group; Group B: model group received diclofenac sodium 7.5 mg/(kg*day) for 5 days; Group C-E: berberine low, medium and high dose groups were treated by 7.5 mg/(kg*day) diclofenac sodium for 5 days then received berberine 25 mg/(kg*day), 50 mg/(kg*day), and 75 mg/(kg*day), respectively, between the sixth and eighth day. Intestinal mucosa was taken on the ninth day to observe the general, histological injuries, and to measure the intestinal epithelial thickness. Then, immunohistochemistry was performed to detect the expression of PGP9.5 and GFAP, and Western blot was performed to detect GDNF expression. The histological score and the general score in the model group were, respectively, 5.75 ± 1.04 and 4.83 ± 0.92. Scores in berberine medium and high berberine group were lower compared with the model group (P < 0.05). The intestinal epithelial thickness in the model group was lower than in the control group and the berberine groups (P < 0.05). PGP9.5, GFAP, and GDNF content in the model group and the three berberine groups were significantly lower than in the control groups (P < 0.05). PGP9.5, GFAP, and GDNF content in the control group and the three berberine groups were higher compared with the model groups (P < 0.05). Berberine can protect the intestinal mucosa of NSAID users, and the mechanism is associated with the reparation of the enteric nervous system via upregulating the expression of PGP9.5, GFAP, and GDNF.

Enteric glial cells immunoreactive for P2X7 receptor are affected in the ileum following ischemia and reperfusion

The aim of this study was to analyze the effect of ischemia and reperfusion injury (IS) on enteric glial cells (EGCs) and neurons immunoreactive for the P2X7 receptor. Intestinal ischemia was induced by obstructing blood flow in the ileal vessels for 35 min. Afterwards, the vessels were reperfused for 14 days. Tissues were prepared for immunohistochemical labeling of P2X7 receptor, HuC/D (Hu) (pan-neuronal marker) and S100β (glial marker); HuC/D (Hu) and glial fibrillary acidic protein (GFAP, glial marker)/DAPI (nuclear marker); or S100β and GFAP/DAPI. Qualitative and quantitative analyses of colocalization, density, profile area and cell proliferation were performed via fluorescence and confocal laser scanning microscopy. The quantitative analyses revealed that a) neurons and EGCs were immunoreactive for P2X7 receptor; b) the P2X7 receptor immunoreactive cells and Hu immunoreactive neurons were reduced after 0 h and 14 days of reperfusion; c) the S100β and GFAP immunoreactive EGCs were increased; d) the profile area of S100β immunoreactive EGCs was increased by IS; e) few GFAP immunoreactive proliferated at 14 days of reperfusion; f) distinct populations of glial cells can be discerned: S100β⁺/GFAP⁺ cells, S100β⁺/GFAP^- cells and S100β^-/GFAP ⁺ cells; g) histological analysis revealed less alterations in the epithelium cells in the IS groups and h) myeloperoxidase reaction revealed increased of the neutrophils in the lamina propria in the IS groups. This study showed that IS is associated with significant neuronal loss, increase of glial cells and altered purinergic receptor expression and that these changes may contribute to intestinal disorders.

Impact of Maternal Malnutrition on Gut Barrier Defense: Implications for Pregnancy Health and Fetal Development

Small intestinal Paneth cells, enteric glial cells (EGC), and goblet cells maintain gut mucosal integrity, homeostasis, and influence host physiology locally and through the gut-brain axis. Little is known about their roles during pregnancy, or how maternal malnutrition impacts these cells and their development. Pregnant mice were fed a control diet (CON), undernourished by 30% vs. control (UN), or fed a high fat diet (HF). At day 18.5 (term = 19), gut integrity and function were assessed by immunohistochemistry and qPCR. UN mothers displayed reduced mRNA expression of Paneth cell antimicrobial peptides (AMP; Lyz2, Reg3g) and an accumulation of villi goblet cells, while HF had reduced Reg3g and mucin (Muc2) mRNA and increased lysozyme protein. UN fetuses had increased mRNA expression of gut transcription factor Sox9, associated with reduced expression of maturation markers (Cdx2, Muc2), and increased expression of tight junctions (TJ; Cldn-7). HF fetuses had increased mRNA expression of EGC markers (S100b, Bfabp, Plp1), AMP (Lyz1, Defa1, Reg3g), and TJ (Cldn-3, Cldn-7), and reduced expression of an AMP-activator (Tlr4). Maternal malnutrition altered expression of genes that maintain maternal gut homeostasis, and altered fetal gut permeability, function, and development. This may have long-term implications for host-microbe interactions, immunity, and offspring gut-brain axis function.

Targeting strategies for chemotherapy-induced peripheral neuropathy: does gut microbiota play a role?

Chemotherapy-induced peripheral neuropathy (CIPN) is a progressive, often irreversible condition that produces severe neurological deficits. Emerging data suggest that chemotherapy also exerts detrimental effects on gut microbiota composition and intestinal permeability, contributing to dysbiosis and inflammation. Compared with other complications associated with chemotherapy, such as diarrhoea and mucositis, CIPN is of particular concern because it is the most common reason for terminating or suspending treatment. However, specific and effective curative treatment strategies are lacking. In this review, we provide an update on current preclinical and clinical understandings about the role of gut microbiota in CIPN. The gut microbiota serves as an intersection between the microbiome-gut-brain and the neuroimmune-endocrine axis, forming a complex network that can directly or indirectly affect key components involved in the manifestations of CIPN. Herein, we discuss several potential mechanisms within the context of the networks and summarize alterations in gut microbiome induced by chemotherapeutic drugs, providing great potential for researchers to target pathways associated with the gut microbiome and overcome CIPN.

Advances in morphologic study of enteric glial cells

As an important part of the intestinal nervous system, enteric glial cells are about four times as many as intestinal neurons. Furthermore, a large population of astrocyte-like glial cells populate gut muscle layers and the intestinal mucosa, and mounting new evidence points toward enteric glial cells as an active participant in gut pathology. They are similar in morphology and function to the astrocytes of the central nervous system and play an important role in nutrition, supporting gastrointestinal nerve, maintaining gastrointestinal homeostasis, and regulating gastrointestinal function. Because of their complex and diverse roles in the intestinal tract, they have become the focus of research. As the study of their functional mechanism has been extensively deepened, the research methods for intestinal glial cells are also on constant progress and improvement, especially in studying their morphology. This paper mainly introduces the morphological characteristics of enteric glial cells under the conditions of gastrointestinal physiology and pathology, so as to provide a reference for the future study of enteric glial cells and promote the development of this field.

Corrected pair correlation functions for environments with obstacles

Environments with immobile obstacles or void regions that inhibit and alter the motion of individuals within that environment are ubiquitous. Correlation in the location of individuals within such environments arises as a combination of the mechanisms governing individual behavior and the heterogeneous structure of the environment. Measures of spatial structure and correlation have been successfully implemented to elucidate the roles of the mechanisms underpinning the behavior of individuals. In particular, the pair correlation function has been used across biology, ecology, and physics to obtain quantitative insight into a variety of processes. However, naively applying standard pair correlation functions in the presence of obstacles may fail to detect correlation, or suggest false correlations, due to a reliance on a distance metric that does not account for obstacles. To overcome this problem, here we present an analytic expression for calculating a corrected pair correlation function for lattice-based domains containing obstacles. We demonstrate that this obstacle pair correlation function is necessary for isolating the correlation associated with the behavior of individuals, rather than the structure of the environment. Using simulations that mimic cell migration and proliferation we demonstrate that the obstacle pair correlation function recovers the short-range correlation known to be present in this process, independent of the heterogeneous structure of the environment. Further, we show that the analytic calculation of the obstacle pair correlation function derived here is significantly faster to implement than the corresponding numerical approach.

Functional Probiotic Assessment and In Vivo Cholesterol-Lowering Efficacy of Weissella sp. Associated with Arid Lands Living-Hosts

The research and the selection of novel probiotic strains from novel niches are receiving increased attention on their proclaimed health benefits to both humans and animals. This study aimed to evaluate the functional properties of Weissella strains from arid land living-hosts and to select strains with cholesterol-lowering property in vitro and in vivo, for use as probiotics. They were assessed for acid and bile tolerance, antibiotic susceptibility, membrane properties, antibacterial activity, antiadhesive effect against pathogens to host cell lines, and cholesterol assimilation in vitro. Our results showed that the majority of strains revealed resistance to gastrointestinal conditions. All the strains were nonhemolytic and sensitive to most of the tested antibiotics. They also exhibited high rates of autoaggregation and some of them showed high coaggregation with selected pathogens and high adhesion ability to two different cell lines (Caco-2 and MIM/PPk). Particularly, W. halotolerans F99, from camel feces, presented a broad antibacterial spectrum against pathogens, reduced Enterococcus faecalis and Escherichia coli adhesion to Caco-2 cells, and was found to reduce, in vitro, the cholesterol level by 49 %. Moreover, W. halotolerans F99 was evaluated for the carbohydrate utilization as well as the serum lipid metabolism effect in Wistar rats fed a high-cholesterol diet. W. halotolerans F99 showed an interesting growth on different plant-derivative oligosaccharides as sole carbon sources. Compared with rats fed a high-fat (HF) diet without Weissella administration, total serum cholesterol, low-density lipoprotein cholesterol, and triglycerides levels were significantly (p<0.001) reduced in W. halotolerans F99-treated HF rats, with no significant change in high-density lipoprotein cholesterol HDL-C levels. On the basis of these results, this is the first study to report that W. halotolerans F99, from camel feces, can be developed as cholesterol-reducing probiotic strain. Further studies may reveal their potential and possible biotechnological and probiotic applications.

Expression profile of some neuronal and glial cell markers in the ovine ileal enteric nervous system during prenatal development

The enteric nervous system (ENS) is a network of neurons and glia found in the gut wall and governs this gastrointestinal function independently from the central nervous system (CNS). ENS comprises the myenteric plexus (MP) and the submucous plexus (SP). In this study, we examined the expression profile of neurofilament heavy chain (NF-H), neuron-specific enolase (NSE), calcyclin (S100A6), vimentin and glial fibril acidic protein (GFAP) in ovine ileal enteric neurons and enteric glia cells (EGCs) during prenatal development using an immunohistochemical method. The material of the study consisted of 15 different fetal ileum tissues obtained between days 60 and 150 of pregnancy. NF-H was observed in the majority of ganglion cells in SP and MP throughout the fetal period. It was determined that there was no NF-H reaction in some ganglion cells in Peyer's patches of internal submucosal plexus (ISPF). In the early stage of pregnancy (60-90 days), there was no expression of NSE and S1006 in ileum. After this period, NSE and S1006 were expressed in the ganglion cells of the plexus, indicating an increase in the amount of expression towards the end of pregnancy. In the early period, vimentin expression was only detected in intramuscular interstitial cells (ICs) (60-90 days), but later (90-150 days) it was also seen in the cells around the ganglion cells in the plexus. On days 60-90 of gestation, GFAP expression only occurred in MP, but in later stages, staining was also detected in SP. In the plexus, an immunoreactivity was present in EGCs forming a network around the ganglion cell. During the last period of gestation (120-150 days), the number of GFAP-positive plexus increased, with the majority of these stained cells being observed in MP. Interestingly, weak staining or reaction did not occur in ISPF, unlike other plexuses. In conclusion, this is the first study that demonstrated the expression of NF-H, vimentin, S100A6, NSE and glial fibril acidic protein (GFAP) in ovine ileal ENS in the prenatal period. In the last period of gestation (120-150 days), the expression profile of ENS was similar to that of adult animals. The expression of the used markers increased toward the end of pregnancy. Our results suggest that neurons and EGCs show heterogeneity, and GFAP and NF-H cannot be used as panenteric glial or panneuronal markers, respectively. We also demonstrated, for the first time, the prenatal expression of S100A6 in enteric neurons and the possibility of using this protein for the identification of enteric neurons.

Immunopathological and molecular basis of functional dyspepsia and current therapeutic approaches

INTRODUCTION

Functional dyspepsia (FD) is widespread with 20% prevalence worldwide and a significant economic burden due to health care cost and constraints on daily activities of patients. Despite extensive investigation, the underlying causes of dyspepsia in a majority of patients remain unknown. Common complaints include abdominal discomfort, pain, burning, nausea, early satiety, and bloating. Motor dysfunction of the gut was long considered a major cause, but recent investigations suggest immune-based pathophysiological and molecular events in the duodenum are more probable contributing factors. Areas Covered: Inflammatory mediators and immune cells including duodenal eosinophils, intraepithelial lymphocytes, and T-cells have been implicated in the underlying cause of disease process, as have genetic factors. In this article, we critically reviewed findings, identified gaps in knowledge and suggested future directions for further investigation to identify targets and develop better therapeutic approaches. Expert commentary: Impaired gastric accommodation, slow gastric emptying, and increased visceral sensitivity have long been thought of as main causal factors of FD. However, more recent identification of eosinophilic degranulation and recruitment of T cells that induce mild duodenal inflammation are giving rise to new insights into immune-mediated pathophysiology. These insights offer promising avenues to explore for immune-mediated therapy in the future.

Enteric glia: Diversity or plasticity?

Glial cells of the enteric nervous system correspond to a unique glial lineage distinct from other central and peripheral glia, and form a vast and abundant network spreading throughout all the layers of the gastrointestinal wall. Research over the last two decades has demonstrated that enteric glia regulates all major gastrointestinal functions via multiple bi-directional crosstalk with enteric neurons and other neighboring cell types. Recent studies propose that enteric glia represents a heterogeneous population associated with distinct localization within the gut wall, phenotype and activity. Compelling evidence also indicates that enteric glial cells are capable of plasticity leading to phenotypic changes whose pinnacle so far has been shown to be the generation of enteric neurons. While alterations of the glial network have been heavily incriminated in the development of gastrointestinal pathologies, enteric glial cells have also recently emerged as an active player in gut-brain signaling. Therefore, the development of tools and techniques to better appraise enteric glia heterogeneity and plasticity will undoubtedly unveil critical regulatory mechanisms implicated in gut health and disease, as well as disorders of the gut-brain axis.

Palmitate lipotoxicity in enteric glial cells: Lipid remodeling and mitochondrial ROS are responsible for cyt c release outside mitochondria

Enteric glial cells (EGCs) are components of the enteric nervous system, an organized structure that controls gut functions. EGCs may be vulnerable to different agents, such as bacterial infections that could alter the intestinal epithelial barrier, allowing bacterial toxins and/or other agents possessing intrinsic toxic effect to access cells. Palmitate, known to exhibit lipotoxicity, is released in the gut during the digestion process. In this study, we investigated the lipotoxic effect of palmitate in cultured EGCs, with particular emphasis on palmitate-dependent intracellular lipid remodeling. Palmitate but not linoleate altered mitochondrial and endoplasmic reticulum lipid composition. In particular, the levels of phosphatidic acid, key precursor of phospholipid synthesis, increased, whereas those of mitochondrial cardiolipin (CL) decreased; in parallel, phospholipid remodeling was induced. CL remodeling (chains shortening and saturation) together with palmitate-triggered mitochondrial burst, caused cytochrome c (cyt c) detachment from its CL anchor and accumulation in the intermembrane space as soluble pool. Palmitate decreased mitochondrial membrane potential and ATP levels, without mPTP opening. Mitochondrial ROS permeation into the cytosol and palmitate-induced ER stress activated JNK and p38, culminating in Bim and Bax overexpression, factors known to increase the outer mitochondrial membrane permeability. Overall, in EGCs palmitate produced weakening of cyt c-CL interactions and favoured the egress of the soluble cyt c pool outside mitochondria to trigger caspase-3-dependent viability loss. Elucidating the mechanisms of palmitate lipotoxicity in EGCs may be relevant in gut pathological conditions occurring in vivo such as those following an insult that may damage the intestinal epithelial barrier.

Octreotide modulates the expression of somatostatin receptor subtypes in inflamed rat jejunum induced by Cryptosporidium parvum

Somatostatins are proteins that are involved in gastrointestinal function. However, little is known with regard to somatostatin receptor subtype (SSTR) expression changes that occur in the jejunum during low-grade inflammation and during subsequent octreotide treatment. The aim of the present study was to investigate the expression of SSTRs in the jejunums of Cryptosporidium parvum (C. parvum)-infected rats by immunohistochemisty, reverse transcription (RT) PCR and quantitative real-time RT-PCR assays. Five-day-old suckling Sprague-Dawley rats (n = 15 for each group) were orally gavaged with 105 Nouzilly isolate (NoI) oocysts. Rats then received 50 μg/kg/day of octreotide by intraperitoneal injection from day 10 to day 17 post-infection. Animals were sacrificed on days 7 and 14 post-infection for immunohistochemical analysis and on days 14, 35 and 50 for mRNA expression analysis of SSTR subtypes. Histological analysis of jejunum tissues demonstrated infection of C. parvum along the villus brush border on day 7 post-infection and infection clearance by day 14 post-infection. Real-time PCR analysis indicated that in the inflamed jejunum, a significant increase in SSTR1 and SSTR2 expression was observed on day 14 post-infection. Octreotide therapy down-regulated the expression of SSTR2 on day 37 post-infection but significantly increased expression of SSTR1, SSTR2 and SSTR3 on day 50 post-infection. The results indicate that specific SSTRs may regulate the inflammatory pathway in the rat intestinal inflammation model.

Copper sulphate forms in piglet diets: Microbiota, intestinal morphology and enteric nervous system glial cells

The objective of this study was to evaluate dietary supplementation with different copper sulphate (CuSO₄ ) forms on small intestine microanatomy and large intestine microbiota. Ninety weaned piglets were divided into three experimental groups: control diet (CTR), with no added CuSO₄ and diets supplemented with 150 ppm of CuSO₄ in protected (150P) and unprotected form (150UP). After 18 days of dietary treatment, six piglets per treatment were randomly selected and sacrificed. Duodenum villi length and crypt depths were higher (P < 0.001) in the animals fed 150UP than other groups. Glial fibrillary acidic protein (GFAP), a marker for enteric glial cells, was unaffected by dietary treatments. The total bacteria and Enterobacteriaceae bacteria counts were lower (P < 0.05) in cecum of animals fed 150P in comparison with the other two groups. In the colon the Streptococci spp were lower (P < 0.001) in both CuSO₄ supplemented groups than controls. The obtained results revealed a modulation of intestinal structure and microbiota exerted by the studied CuSO₄ dietary supplementation. The present data show that dietary supplementation with 150UP in the first period post-weaning may assist in restoring the gut morphology, improving duodenal structure.

Increased population of immature enteric glial cells in the resected proximal ganglionic bowel of Hirschsprung's disease patients

BACKGROUND

Enteric glial cells are essential for normal gastrointestinal function. Abnormalities in glial structure, development, or function lead to disturbances in gastrointestinal physiology. Fatty acid-binding protein 7 (FABP7) is a marker of immature enteric glial cells, whereas S100 is expressed only by mature glial cells. Patients with Hirschsprung's disease (HSCR) often suffer from dysmotility and enterocolitis despite proper surgery. We designed this study to determine the distribution and expression of glial cells in patients with HSCR compared to normal controls.

METHODS

We investigated FABP7, S100, and PGP 9.5 expressions in both the ganglionic and aganglionic bowel of patients with HSCR (n = 6) versus normal control colon (n = 6). Protein distribution was assessed by using immunofluorescence and confocal microscopy. Gene and protein expressions were quantified using quantitative real-time polymerase chain reaction (qPCR), Western blot analysis, and densitometry.

RESULTS

qPCR and Western blot analysis demonstrated a significantly increased FABP7 expression in ganglionic specimens compared to control specimen (P < 0.05). Confocal microscopy revealed FABP7⁺ glia cells lie under the colonic epithelium and in close apposition to enteric neurons in the ganglionic bowel.

CONCLUSIONS

The significantly increased number of immature enteric glial cells (EGCs) in the ganglionic bowel of HSCR patients may have adverse effect on the function of enteric neurons and intestinal barrier and thus predispose these patients to intestinal motility problems and enterocolitis.

Expression of Ecto-nucleoside Triphosphate Diphosphohydrolases-2 and -3 in the Enteric Nervous System Affects Inflammation in Experimental Colitis and Crohn's Disease

OBJECTIVE

Recent studies have suggested that the enteric nervous system can modulate gut immunity. Ecto-nucleoside triphosphate diphosphohydrolases [E-NTPDases] regulate purinergic signalling by sequential phosphohydrolysis of pro-inflammatory extracellular adenosine 5'-triphosphate [ATP]. Herein, we test the hypothesis that E-NTPDases modulate gut inflammation via neuro-immune crosstalk.

DESIGN

We determined expression patterns of NTPDase2 and NTPDase3 in murine and human colon. Experimental colitis was induced by dextran sodium sulphate [DSS] in genetically engineered mice deficient in NTPDase2 or NTPDase3. We compared plasma adenosine diphosphatase [ADPase] activity from Crohn's patients and healthy controls, and linked the enzyme activity to Crohn's disease activity.

RESULTS

NTPDase2 and -3 were chiefly expressed in cells of the enteric nervous system in both murine and human colon. When compared with wild type, DSS-induced colitis was exacerbated in Entpd2, and to a lesser extent, Entpd3 null mice as measured by disease activity score and histology, and marked anaemia was seen in both. Colonic macrophages isolated from Entpd2 null mice displayed a pro-inflammatory phenotype compared with wild type. In human plasma, Crohn's patients had decreases in ADPase activity when compared with healthy controls. The drop in ADPase activity was likely associated with changes in NTPDase2 and -3, as suggested by inhibitor studies, and were correlated with Crohn's disease activity.

CONCLUSIONS

NTPDase2 and -3 are ecto-enzymes expressed in the enteric nervous system. Both enzymes confer protection against gut inflammation in experimental colitis and exhibit alterations in Crohn's disease. These observations suggest that purinergic signalling modulated by E-NTPDases governs neuro-immune interactions that are relevant in Crohn's disease.

The enteric nervous system is a potential autoimmune target in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) in young adults that has serious negative socioeconomic effects. In addition to symptoms caused by CNS pathology, the majority of MS patients frequently exhibit gastrointestinal dysfunction, which was previously either explained by the presence of spinal cord lesions or not directly linked to the autoimmune etiology of the disease. Here, we studied the enteric nervous system (ENS) in a B cell- and antibody-dependent mouse model of MS by immunohistochemistry and electron microscopy at different stages of the disease. ENS degeneration was evident prior to the development of CNS lesions and the onset of neurological deficits in mice. The pathology was antibody mediated and caused a significant decrease in gastrointestinal motility, which was associated with ENS gliosis and neuronal loss. We identified autoantibodies against four potential target antigens derived from enteric glia and/or neurons by immunoprecipitation and mass spectrometry. Antibodies against three of the target antigens were also present in the plasma of MS patients as confirmed by ELISA. The analysis of human colon resectates provided evidence of gliosis and ENS degeneration in MS patients compared to non-MS controls. For the first time, this study establishes a pathomechanistic link between the well-established autoimmune attack on the CNS and ENS pathology in MS, which might provide a paradigm shift in our current understanding of the immunopathogenesis of the disease with broad diagnostic and therapeutic implications.

Toll-Like Receptor 4 Modulates Small Intestine Neuromuscular Function through Nitrergic and Purinergic Pathways

Objective: Toll-like receptors (TLRs) play a pivotal role in the homeostatic microflora-host crosstalk. TLR4-mediated modulation of both motility and enteric neuronal survival has been reported mainly for colon with limited information on the role of TLR4 in tuning structural and functional integrity of enteric nervous system (ENS) and in controlling small bowel motility. Methods: Male TLR4 knockout (TLR4^-/-, 9 ± 1 weeks old) and sex- and age-matched wild-type (WT) C57BL/6J mice were used for the experiments. Alterations in ENS morphology and neurochemical code were assessed by immunohistochemistry whereas neuromuscular function was evaluated by isometric mechanical activity of ileal preparations following receptor and non-receptor-mediated stimuli and by gastrointestinal transit. Results: The absence of TLR4 induced gliosis and reduced the total number of neurons, mainly nNOS⁺ neurons, in ileal myenteric plexus. Furthermore, a lower cholinergic excitatory response with an increased inhibitory neurotransmission was found together with a delayed gastrointestinal transit. These changes were dependent on increased ileal non-adrenergic non-cholinergic (NANC) relaxations mediated by a complex neuronal-glia signaling constituted by P2X7 and P2Y1 receptors, and NO produced by nNOS and iNOS. Conclusion: We provide novel evidence that TLR4 signaling is involved in the fine-tuning of P2 receptors controlling ileal contractility, ENS cell distribution, and inhibitory NANC neurotransmission via the combined action of NO and adenosine-5'-triphosphate (ATP). For the first time, this study implicates TLR4 at regulating the crosstalk between glia and neurons in small intestine and helps to define its role in gastrointestinal motor abnormalities during dysbiosis.

Submucosal neurons and enteric glial cells expressing the P2X7 receptor in rat experimental colitis

The aim of this study was to evaluate the effect of ulcerative colitis on the submucosal neurons and glial cells of the submucosal ganglia of rats. 2,4,6-Trinitrobenzene sulfonic acid (TNBS; colitis group) was administered in the colon to induce ulcerative colitis, and distal colons were collected after 24h. The colitis rats were compared with those in the sham and control groups. Double labelling of the P2X7 receptor with calbindin (marker for intrinsic primary afferent neurons, IPANs, submucosal plexus), calretinin (marker for secretory and vasodilator neurons of the submucosal plexus), HuC/D and S100β was performed in the submucosal plexus. The density (neurons per area) of submucosal neurons positive for the P2X7 receptor, calbindin, calretinin and HuC/D decreased by 21%, 34%, 8.2% and 28%, respectively, in the treated group. In addition, the density of enteric glial cells in the submucosal plexus decreased by 33%. The profile areas of calbindin-immunoreactive neurons decreased by 25%. Histological analysis revealed increased lamina propria and decreased collagen in the colitis group. This study demonstrated that ulcerative colitis affected secretory and vasodilatory neurons, IPANs and enteric glia of the submucosal plexus expressing the P2X7 receptor.

Purinergic signaling during intestinal inflammation

Inflammatory bowel disease (IBD) is a devastating disease that is associated with excessive inflammation in the intestinal tract in genetically susceptible individuals and potentially triggered by microbial dysbiosis. This illness markedly predisposes patients to thrombophilia and chronic debility as well as bowel, lymphatic, and liver cancers. Development of new therapies is needed to re-establish long-term immune tolerance in IBD patients without increasing the risk of opportunistic infections and cancer. Aberrant purinergic signaling pathways have been implicated in disordered thromboregulation and immune dysregulation, as noted in the pathogenesis of IBD and other gastrointestinal/hepatic autoimmune diseases. Expression of CD39 on endothelial or immune cells allows for homeostatic integration of hemostasis and immunity, which are disrupted in IBD. Our focus in this review is on novel aspects of the functions of CD39 and related NTPDases in IBD. Regulated CD39 activity allows for scavenging of extracellular nucleotides, the maintenance of P2-receptor integrity and coordination of adenosinergic signaling responses. CD39 together with CD73, serves as an integral component of the immunosuppressive machinery of dendritic cells, myeloid cells, T and B cells. Genetic inheritance and environental factors closely regulate the levels of expression and phosphohydrolytic activity of CD39, both on immune cells and released microparticles. Purinergic mechanisms associated with T regulatory and supressor T helper type 17 cells modulate disease activity in IBD, as can be modeled in experimental colitis. As a recent example, upregulation of CD39 is dependent upon ligation of the aryl hydrocarbon receptor (AHR), as with natural ligands such as bilirubin and 2-(1' H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Decreased expression of CD39 and/or dysfunctional AHR signaling, however, abrogates the protective effects of immunosuppressive AHR ligands. These factors could also serve as biomarkers of disease activity in IBD. Heightened thrombosis, inflammation, and immune disturbances as seen in IBD appear to be associated with aberrant purinergic signaling. Ongoing development of therapeutic strategies augmenting CD39 ectonucleotidase bioactivity via cytokines or AHR ligands offers promise for management of thrombophilia, disordered inflammation, and aberrant immune reactivity in IBD.

VPAC Receptor Subtypes Tune Purinergic Neuron-to-Glia Communication in the Murine Submucosal Plexus

The enteric nervous system (ENS) situated within the gastrointestinal tract comprises an intricate network of neurons and glia which together regulate intestinal function. The exact neuro-glial circuitry and the signaling molecules involved are yet to be fully elucidated. Vasoactive intestinal peptide (VIP) is one of the main neurotransmitters in the gut, and is important for regulating intestinal secretion and motility. However, the role of VIP and its VPAC receptors within the enteric circuitry is not well understood. We investigated this in the submucosal plexus of mouse jejunum using calcium (Ca²⁺)-imaging. Local VIP application induced Ca²⁺-transients primarily in neurons and these were inhibited by VPAC1- and VPAC2-antagonists (PG 99-269 and PG 99-465 respectively). These VIP-evoked neural Ca²⁺-transients were also inhibited by tetrodotoxin (TTX), indicating that they were secondary to action potential generation. Surprisingly, VIP induced Ca²⁺-transients in glia in the presence of the VPAC2 antagonist. Further, selective VPAC1 receptor activation with the agonist ([K15, R16, L27]VIP(1-7)/GRF(8-27)) predominantly evoked glial responses. However, VPAC1-immunoreactivity did not colocalize with the glial marker glial fibrillary acidic protein (GFAP). Rather, VPAC1 expression was found on cholinergic submucosal neurons and nerve fibers. This suggests that glial responses observed were secondary to neuronal activation. Trains of electrical stimuli were applied to fiber tracts to induce endogenous VIP release. Delayed glial responses were evoked when the VPAC2 antagonist was present. These findings support the presence of an intrinsic VIP/VPAC-initiated neuron-to-glia signaling pathway. VPAC1 agonist-evoked glial responses were inhibited by purinergic antagonists (PPADS and MRS2179), thus demonstrating the involvement of P2Y₁ receptors. Collectively, we showed that neurally-released VIP can activate neurons expressing VPAC1 and/or VPAC2 receptors to modulate purine-release onto glia. Selective VPAC1 activation evokes a glial response, whereas VPAC2 receptors may act to inhibit this response. Thus, we identified a component of an enteric neuron-glia circuit that is fine-tuned by endogenous VIP acting through VPAC1- and VPAC2-mediated pathways.