Neuron-macrophage cross-talk in the intestine plays a crucial role in the maintenance of tissue homeostasis and the modulation of immune responses throughout life. Here, we describe how gut neuron-macrophage interactions shift macrophage phenotype and function from early development to adulthood and how this cross-talk modulates the macrophage function in response to infection and inflammation. We highlight how a neural microenvironment instructs a neuron-associated macrophage phenotype in the gut and show that their phenotype may resemble nerve-associated macrophages in other organs. Finally, we note that the loss of neuron-associated macrophages or a shift in their phenotype can contribute to enteric neurodegeneration in the gastrointestinal tract, causing gut motility disorders.

The signaling mechanisms of nucleotides and nucleosides have been extensively studied over the past decades in various conditions affecting distinct organs and tissues. It is well-established that purinergic receptors are expressed in healthy tissues, with expression levels often increasing under pathological conditions. These receptors play crucial roles in numerous physiological and pathological processes, including inflammation, tissue repair, and cellular signaling. However, the purinergic context in the esophagus and its associated pathologies remains poorly understood, representing a significant gap in current knowledge. In this review, we compiled and analyzed the available data on the involvement of P2 purinergic receptors in esophageal diseases, such as gastroesophageal reflux disease and esophageal carcinoma. Specifically, we discuss the pharmacological modulation, functional characterization, and expression patterns of these receptors in various esophageal cell lines and immune tissue samples, under both healthy and pathological conditions. Understanding the mechanisms of action and signaling pathways involving P2 purinergic receptors in the esophagus can offer valuable insights into their biological roles and emphasize their potential as therapeutic targets for future clinical applications.

There is a huge gap in our understanding of the human ENS and translating data from mice to humans that is important when developing targeted therapeutics. The ENS or "human little brain in the gut" is easily accessible for study in GI surgical or biopsy samples. This mini review is focused on the use of human gut specimens in translating laboratory data on ENS and enteric neuropathies in neurogastroenterology and motility from mice to humans. Availability of viable human gut samples, in combination with technological advances in innovative recording techniques and new in vitro models provide powerful ways to study neural activity and secretomotor function or monitor motility in health and disease with exquisite sophistication and precision. Electrophysiological recordings, optical recordings with voltage-sensitive dyes, or Ca2+ imaging (in adult or fetal gut) is used to study neural activity in human ENS in health and disease. 'First in man patch clamp recordings' is possible in isolated networks of human myenteric ganglia, opening the door for patch-seq. The human ENS at single cell resolution (snRNA-seq) revealed cell-diversity, similarities and differences between human and mouse in vitro. Visceral afferent recordings are used for mechanosensation and pain signaling in humans. Stem cell therapies may hold future promise for patients with enteric neuropathies. A greater focus on the human ENS and enteric neuropathies (i.e. IBS, FD, postoperative ileus, CIPO, chronic constipation, Hirschsprung Disease, infection, gastroparesis, Parkinson's disease, IBD, visceral pain) is one important step for consideration in developing potential therapeutics before proceeding to more expensive and complex clinical trials in patients to treat GI Disorders and Diseases.

Neuro-immune interactions within barrier organs, such as lung, gut, and skin, are crucial in regulating tissue homeostasis, inflammatory responses, and host defence. Our rapidly advancing understanding of peripheral neuroimmunology is transforming the field of barrier tissue immunology, offering a fresh perspective for developing therapies for complex chronic inflammatory disorders affecting barrier organs. However, most studies have primarily examined interactions between the peripheral nervous system and the immune system from a neuron-focused perspective, while glial cells, the nonneuronal cells of the nervous system, have received less attention. Glial cells were long considered as mere bystanders, only supporting their neuronal neighbours, but recent discoveries mainly on enteric glial cells in the intestine have implicated these cells in immune-regulation and inflammatory disease pathogenesis. In this review, we will highlight the bi-directional interactions between peripheral glial cells and the immune system and discuss the emerging immune regulatory functions of glial cells in barrier organs.

Enteric glia are a unique type of peripheral neuroglia that accompany neurons in the enteric nervous system (ENS) of the digestive tract. The ENS displays integrative neural circuits that are capable of governing moment-to-moment gut functions independent of input from the central nervous system. Enteric glia are interspersed with neurons throughout these intrinsic gut neural circuits and are thought to fulfill complex roles directed at maintaining homeostasis in the neuronal microenvironment and at neuroeffector junctions in the gut. Changes to glial functions contribute to a wide range of gastrointestinal diseases, but the precise roles of enteric glia in gut physiology and pathophysiology are still under examination. This review summarizes current concepts regarding enteric glial development, diversity, and functions in health and disease.

Colon anastomotic leakage (CAL) is a postoperative complication originating from disturbed colon anastomotic healing (CAH). Wound healing involves several well-coordinated stages, which have not been comprehensively studied for CAH or CAL. This study aims to provide transcriptional profiles of different intestinal layers of anastomotic tissues throughout distinct healing stages and to identify CAL-related genes.

Proximal colon anastomosis was constructed with 8 interrupted sutures in mice. Six hours, 24 h and 72 h after surgery, anastomotic complications were assessed. Transcriptional profiles of inner (mucosa and submucosa) and outer (muscularis externa) layer of the anastomotic and naive control tissues were analyzed with 3' bulk mRNA sequencing to identify the layer-specific healing and leakage pathways. Selective target genes differing between CAL and CAH were measured for their protein expression.

Our data indicate that the mucosa/submucosa and muscularis externa enter inflammation stage at 6 h, proliferation stage at 24 h and tissue remodeling stage at 72 h during CAH. We observed that transcription profiles of the mucosa/submucosa, but not the muscularis externa, differ between CAH and CAL. Particularly, genes related to extracellular remodeling (including Col18a1 and Col16a1) and wound healing (Pdpn and Timp1) showed lower expression in the mucosa/submucosa of CAL tissue compared to CAH. Conformingly, protein levels for collagens as well IL-34 were decreased in CAL, while the TGF-β-pseudo-receptor BAMBI was increased in CAL compared to CAH tissues.

Mucosa/submucosa and muscularis externa are mostly in synchronization during the inflammation, proliferation, and extracellular remodeling stages during CAH. Transcriptional profiles within the anastomotic mucosa/submucosa differ between CAH and CAL in genes related to extracellular modelling and wound healing, indicating that genes of these pathways may contribute to CAL.

Colonic motility dysfunction is a common symptom of ulcerative colitis (UC), significantly affecting patients' quality of life. Evidence suggests that glial cell line-derived neurotrophic factor (GDNF) plays a role in restoring colonic function.

To investigate whether GDNF enhances aberrant colonic motility in mice with experimental colitis via connexin 43 (Cx43).

An experimental colitis model was induced in male C57BL/6 mice using dextran sodium sulfate (DSS). The measurement of colonic transit time was conducted, and colon tissues were evaluated through transmission electron microscopy and hematoxylin and eosin staining. The mice were treated with exogenous GDNF and Gap 19, a selective Cx43 inhibitor. The Cx43 and GDNF levels were detected via immunofluorescence, immunohistochemistry, and real-time polymerase chain reaction. The levels of inflammatory markers, including interleukin-1β, tumor necrosis factor-α, interleukin-6, and C-reactive protein, were quantified using enzyme-linked immunosorbent assay.

Experimental colitis was successfully induced using DSS, and the findings exhibited that the colonic transit time was significantly delayed in colitis mice relative to the UC group (P < 0.01). GDNF treatment improved colonic transit time and alleviated intestinal inflammation in DSS-induced colitis mice (P < 0.05). In the UC + Gap19 + GDNF group, colitis symptoms, colonic transit time, and inflammatory marker levels remained comparable to those in the UC group, indicating that the therapeutic effects of GDNF in UC mice were blocked by Gap 19.

GDNF improves colonic motility in mice with experimental colitis through a partially Cx43-mediated mechanism. GDNF holds promise as a therapeutic option for improving colonic motility in patients with colitis.

The Enteric Nervous System is composed of a vastly interconnected network of neurons and glial cells that coordinate to regulate homeostatic gut function including intestinal motility, nutrient sensing, and mucosal barrier immunity. Enteric Glial Cells (EGCs) are a heterogeneous cell population located throughout the gastrointestinal tract and have well described roles in regulating intestinal immune responses. Enteric Glial Cells have been suggested to act as nonconventional antigen presenting cells via the Major Histocompatibility Complex II (MHC II), though this has not been confirmed functionally. Here, we investigate the capability of EGCs to present antigen on MHC I and MHC II using in vitro antigen presentation assays performed with primary murine EGC cultures. We found that EGCs are capable of functional antigen presentation on MHC I, including antigen cross-presentation, but are not capable of functional antigen presentation on MHC II. We also determined EGC cell surface MHC I and MHC II expression levels by flow cytometry during intestinal inflammation during Dextran Sodium Sulfate-induced colitis or acute Toxoplasma gondii infection. We found that EGCs upregulate MHC I during acute T. gondii infection and induce low-level MHC II expression. These findings suggest that EGCs may be important in the regulation of CD8+ T cell responses via MHC I mediated antigen (cross) presentation but may not be relevant for MHC II-mediated antigen presentation.

Current studies pictured the enteric nervous system and macrophages as modulators of neuroimmune processes in the inflamed gut. Expanding this view, we investigated the impact of enteric neuron-macrophage interactions on postoperative trauma and subsequent motility disturbances, i.e., postoperative ileus. In the early postsurgical phase, we detected strong neuronal activation, followed by transcriptional and translational signatures indicating neuronal death and synaptic damage. Simultaneously, our study revealed neurodegenerative profiles in macrophage-specific transcriptomes after postoperative trauma. Validating the role of resident and monocyte-derived macrophages, we depleted macrophages by CSF-1R-antibodies and used CCR2-/- mice, known for reduced monocyte infiltration, in POI studies. Only CSF-1R-antibody-treated animals showed decreased neuronal death and lessened synaptic decay, emphasizing the significance of resident macrophages. In human gut samples taken early and late during abdominal surgery, we substantiated the mouse model data and found reactive and apoptotic neurons and dysregulation in synaptic genes, indicating a species' overarching mechanism. Our study demonstrates that surgical trauma activates enteric neurons and induces neurodegeneration, mediated by resident macrophages, introducing neuroprotection as an option for faster recovery after surgery.

Enteric glia are the partners of neurons in the enteric nervous system throughout the gastrointestinal tract. Roles fulfilled by enteric glia are diverse and contribute to maintaining intestinal homeostasis through interactions with neurons, immune cells, and the intestinal epithelium. Glial influences optimize physiological gut processes such as intestinal motility and epithelial barrier integrity through actions that regulate the microenvironment of the enteric nervous system, the activity of enteric neurons, intestinal epithelial functions, and immune response. Changes to glial phenotype in disease switch glial functions and contribute to intestinal inflammation, dysmotility, pain, neuroplasticity, and tumorigenesis. This review summarizes current concepts regarding the physiological roles of enteric glial cells and their potential contributions to gut disease. The discussion is focused on recent evidence that suggests important glial contributions to gastrointestinal health and pathophysiology.

Neuroglia are a heterogenous population of cells in the nervous system. In the central nervous system, this group is classified into astrocytes, oligodendrocytes, and microglia. Neuroglia in the peripheral nervous system are divided into Schwann cells and enteric glia. These groups of cells display considerable differences in their developmental origin, morphology, function, and regional abundance. Compared to animal models, human neuroglia differ in their transcriptomic profile, morphology, and function. Investigating the physiology of healthy or diseased human neuroglia in vivo is challenging due to the inaccessibility of the tissue. Therefore, researchers have developed numerous in vitro models attempting to replicate the natural tissue environment. Earlier models made use of postmortem, postsurgical, or fetal tissue to establish human neuroglial cells in vitro, either as a pure population of the desired cell type or as organotypic slice cultures. Advancements in human stem cell differentiation techniques have greatly enhanced the possibilities for creating in vitro models of human neuroglia. This chapter provides an overview of the current models used to study the functioning and development of human neuroglia in vitro, both in health and disease.

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Postoperative ileus (POI) is a condition marked by a temporary suppression of gastrointestinal motility following abdominal surgery. The mechanism of POI encompasses various factors and is characterized by two phases: the early neurogenic phase involving both adrenergic and non-adrenergic neural pathways; the later immune-mediated phase is characterized by a sterile inflammatory response that lasts several days. Activation of muscularis macrophages triggers a sterile inflammatory process that results in dysfunction of the enteric nervous system (ENS) and a reversible inhibition of gastrointestinal motility.

In this minireview, recent insights in the pathophysiological mechanisms underlying POI and potential new therapeutic strategies are described.

Enteric glia are a heterogeneous population of peripheral glia within the enteric nervous system and play pivotal roles in gut homeostasis, tissue integrity, coordination of motility, and intestinal immune responses. Under physiological conditions, they communicate with enteric neurons to control intestinal motility. In contrast, enteric glia undergo reactive changes in response to inflammatory signals during enteric neuroinflammation and participate in immune control. In this state, these glia are called reactive enteric glia, which promote cytokine and chemokine secretion and perpetuate immune cell recruitment, thereby affecting disease progression. Interestingly, reactive glia exhibit a huge plasticity and adapt to or shape the immune environment towards a resolving phenotype during inflammation and neuropathies. Recent studies revealed a bidirectional communication between enteric glia and resident and infiltrating immune cells under healthy conditions and in the context of inflammation-based intestinal disorders and neuropathies. While recent reviews give a superb general overview of enteric glial reactivity, we herein discuss the latest evidence on enteric glial reactivity in two prominent inflammatory conditions: acute postoperative inflammation, resulting in postoperative ileus, and chronic inflammation in inflammatory bowel diseases. We define their plasticity during inflammation and the interplay between reactive enteric glia and intestinal macrophages. Finally, we sketch important questions that should be addressed to clarify further the impact of enteric glial reactivity on intestinal inflammation.

Postoperative ileus (POI) is a common complication after abdominal surgery with high morbidity, which hinders patient recovery, prolongs hospitalization, and increases healthcare costs. Therefore, POI has become a global public health challenge. POI triggering is multifactorial. Autonomic and hormonal mechanisms are generally involved in POI pathogenesis. Recent studies have shown that beta adrenergic signaling of enteric glia is a POI trigger. Currently, the status quo, trends, and frontiers of global research on POI remain unclear.

To explore the current status, trends, and frontiers of POI research from 2011 to the present based on bibliometric analysis.

Publications published on POI research from 2011 to 2023 were retrieved on June 1, 2023, from the Web of Science Core Collection. CiteSpace 6.2.R2 and VOSviewer were used to conduct bibliometric visualization.

In total, 778 POI records published from 2011 to 2023 were retrieved. Over the past few decades, the annual cumulative number of related articles has linearly increased, with China and the United States of America contributing prominently. All publications were from 59 countries and territories. China and the University of Bonn were the top contributing country and institution, respectively. Neurogastroenterology & Motility was the most prolific journal. The Journal of Gastrointestinal Surgery had the highest number of citations. Wehner Sven was the most productive author. Burst keywords (e.g., colon, prolonged ileus, acupuncture, paralytic ileus, pathophysiology, rectal cancer, gastrointestinal function, risk) and a series of reference citation bursts provided evidence for the research frontiers in recent years.

This study demonstrates trends in the published literature on POI and provides new insights for researchers. It emphasizes the importance of multidisciplinary cooperation in the development of this field.

P2X receptors, a subfamily of ligand-gated ion channels activated by extracellular ATP, are implicated in various physiopathological processes, including inflammation, pain perception, and immune and respiratory regulations. Structural determinations using crystallography and cryo-EM have revealed that the extracellular three-dimensional architectures of different P2X subtypes across various species are remarkably identical, greatly advancing our understanding of P2X activation mechanisms. However, structural studies yield paradoxical architectures of the intracellular domain (ICD) of different subtypes (e.g., P2X3 and P2X7) at the apo state, and the role of the ICD in P2X functional regulation remains unclear. Here, we propose that the P2X3 receptor's ICD has an apo state conformation similar to the open state but with a less tense architecture, containing allosteric sites that influence P2X3's physiological and pathological roles. Using covalent occupancy, engineered disulfide bonds and voltage-clamp fluorometry, we suggested that the ICD can undergo coordinated motions with the transmembrane domain of P2X3, thereby facilitating channel activation. Additionally, we identified a novel P2X3 enhancer, PSFL77, and uncovered its potential allosteric site located in the 1α3β domain of the ICD. PSFL77 modulated pain perception in P2rx3+/+, but not in P2rx3-/-, mice, indicating that the 1α3β, a "tunable" region implicated in the regulation of P2X3 functions. Thus, when P2X3 is in its apo state, its ICD architecture is fairly ordered rather than an unstructured outward folding, enabling allosteric modulation of the signaling of P2X3 receptors.

The precise mechanism underlying the therapeutic effects of dihydroartemisinin (DHA) in alleviating colitis remains incompletely understood. A strong correlation existed between the elevation of glial fibrillary acidic protein (GFAP)+/S100 calcium binding protein B (S100β)+ enteric glial cells (EGCs) in inflamed colonic tissues and the disruption of the intestinal epithelial barrier (IEB) and gut vascular barrier (GVB) observed in chronic colitis. DHA demonstrated efficacy in restoring the functionality of the dual gut barrier while concurrently attenuating intestinal inflammation. Mechanistically, DHA inhibited the transformation of GFAP+ EGCs into GFAP+/S100β+ EGCs while promoting the differentiation of GFAP+/S100β+ EGCs back into GFAP+ EGCs. Furthermore, DHA induced apoptosis in GFAP+/S100β+ EGCs by inducing cell cycle arrest at the G0/G1 phase. The initial mechanism is further validated that DHA regulates EGC heterogeneity by improving dysbiosis in colitis. These findings underscore the multifaceted therapeutic potential of DHA in ameliorating colitis by improving dysbiosis, modulating EGC heterogeneity, and preserving gut barrier integrity, thus offering promising avenues for novel therapeutic strategies for inflammatory bowel diseases.

Nucleosides and purine nucleotides serve as transmitter and modulator agents that extend their functions beyond the cell. In this context, purinergic signaling plays a crucial role in regulating energy homeostasis and modulating metabolic alterations in tumor cells. Therefore, it is essential to consider the pharmacological targeting of purinergic receptors (PUR), which encompass the expression and inhibition of P1 receptors (metabotropic adenosine receptors) as well as P2 receptors (extracellular ATP/ADP) comprising P2X and P2Y receptors. Thus, the pharmacological interaction between inhibitors (such as RNA, monoclonal antibodies, and small molecules) and PUR represents a key aspect in facilitating the development of therapeutic interventions. Moreover, this review explores recent advancements in pharmacological inhibitors and the regulation of innate and adaptive immunity of PUR, specifically in relation to immunological and inflammatory responses. These responses encompass the release of pro-inflammatory cytokines (PIC), the production of reactive oxygen and nitrogen species (ROS and RNS), the regulation of T cells, and the activation of inflammasomes in all human leukocytes.

Enteric glial cells are important players in the control of motility, intestinal barrier integrity and inflammation. During inflammation, they switch into a reactive phenotype enabling them to release inflammatory mediators, thereby shaping the inflammatory environment. While a plethora of well-established in vivo models exist, cell culture models necessary to decipher the mechanistic pathways of enteric glial reactivity are less well standardized. In particular, the composition of extracellular matrices (ECM) can massively affect the experimental outcome. Considering the growing number of studies involving primary enteric glial cells, a better understanding of their homeostatic and inflammatory in vitro culture conditions is needed.

We examined the impact of different ECMs on enteric glial culture purity, network morphology and immune responsiveness. Therefore, we used immunofluorescence and brightfield microscopy, as well as 3' bulk mRNA sequencing. Additionally, we compared cultured cells with in vivo enteric glial transcriptomes isolated from Sox10iCreERT2Rpl22HA/+ mice.

We identified Matrigel and laminin as superior over other coatings, including poly-L-ornithine, different lysines, collagens, and fibronectin, gaining the highest enteric glial purity and most extended glial networks expressing connexin-43 hemichannels allowing intercellular communication. Transcriptional analysis revealed strong similarities between enteric glia on Matrigel and laminin with enrichment of gene sets supporting neuronal differentiation, while cells on poly-L-ornithine showed enrichment related to cell proliferation. Comparing cultured and in vivo enteric glial transcriptomes revealed a 50% overlap independent of the used coating substrates. Inflammatory activation of enteric glia by IL-1β treatment showed distinct coating-dependent gene expression signatures, with an enrichment of genes related to myeloid and epithelial cell differentiation on Matrigel and laminin coatings, while poly-L-ornithine induced more gene sets related to lymphocyte differentiation.

Together, changes in morphology, differentiation and immune activation of primary enteric glial cells proved a strong effect of the ECM. We identified Matrigel and laminin as pre-eminent substrates for murine enteric glial cultures. These new insights will help to standardize and improve enteric glial culture quality and reproducibility between in vitro studies in the future, allowing a better comparison of their functional role in enteric neuroinflammation.

Enteric glia have been recently recognized as key components of the colonic tumor microenvironment indicating their potential role in colorectal cancer pathogenesis. Although enteric glia modulate immune responses in other intestinal diseases, their interaction with the colorectal cancer immune cell compartment remains unclear. Through a combination of single-cell and bulk RNA-sequencing, both in murine models and patients, here we find that enteric glia acquire an immunomodulatory phenotype by bi-directional communication with tumor-infiltrating monocytes. The latter direct a reactive enteric glial cell phenotypic and functional switch via glial IL-1R signaling. In turn, tumor glia promote monocyte differentiation towards pro-tumorigenic SPP1+ tumor-associated macrophages by IL-6 release. Enteric glia cell abundancy correlates with worse disease outcomes in preclinical models and colorectal cancer patients. Thereby, our study reveals a neuroimmune interaction between enteric glia and tumor-associated macrophages in the colorectal tumor microenvironment, providing insights into colorectal cancer pathogenesis.

Enteric glial cells (EGCs) are an essential component of the enteric nervous system (ENS) and play key roles in gastrointestinal development, homeostasis, and disease. Derived from neural crest cells, EGCs undergo complex differentiation processes regulated by various signalling pathways. Being among the most dynamic cells of the digestive system, EGCs react to cues in their surrounding microenvironment and communicate with various cell types and systems within the gut. Morphological studies and recent single cell RNA sequencing studies have unveiled heterogeneity among EGC populations with implications for regional functions and roles in diseases. In gastrointestinal disorders, including inflammatory bowel disease (IBD), infections and cancer, EGCs modulate neuroplasticity, immune responses and tumorigenesis. Recent evidence suggests that EGCs respond plastically to the microenvironmental cues, adapting their phenotype and functions in disease states and taking on a crucial role. They exhibit molecular abnormalities and alter communication with other intestinal cell types, underscoring their therapeutic potential as targets. This review delves into the multifaceted roles of EGCs, particularly emphasizing their interactions with various cell types in the gut and their significant contributions to gastrointestinal disorders. Understanding the complex roles of EGCs in gastrointestinal physiology and pathology will be crucial for the development of novel therapeutic strategies for gastrointestinal disorders.

The enteric nervous system (ENS), consisting of neurons and glial cells, is situated along the gastrointestinal (GI) tract's wall and plays a crucial role in coordinating digestive processes. Recent research suggests that the optimal functioning of the GI system relies on intricate connections between the ENS, the intestinal epithelium, the immune system, the intestinal microbiome, and the central nervous system (CNS). Inflammatory bowel disease (IBD) encompasses a group of chronic inflammatory disorders, such as Crohn's disease (CD) and ulcerative colitis (UC), characterized by recurring inflammation and damage to the GI tract. This review explores emerging research in the dynamic field of IBD and sheds light on the potential role of ENS alterations in both the etiology and management of IBD. Specifically, we delve into IBD-induced enteric glial cell (EGC) activation and its implications for persistent enteric gliosis, elucidating how this activation disrupts GI function through alterations in the gut-brain axis (GBA). Additionally, we examine IBD-associated ENS alterations, focusing on EGC senescence and the acquisition of the senescence-associated secretory phenotype (SASP). We highlight the pivotal role of these changes in persistent GI inflammation and the recurrence of IBD. Finally, we discuss potential therapeutic interventions involving senotherapeutic agents, providing insights into potential avenues for managing IBD by targeting ENS-related mechanisms. This approach might represent a potential alternative to managing IBD and advance treatment of this multifaceted disease.

The enteric nervous system (ENS) is contained within two layers of the gut wall and is made up of neurons, immune cells, and enteric glia cells (EGCs) that regulate gastrointestinal (GI) function. EGCs in both inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) change in response to inflammation, referred to as reactive gliosis. Whether EGCs restricted to a specific layer or region within the GI tract alone can influence intestinal immune response is unknown. Using bulk RNA-sequencing and in situ hybridization, we identify G-protein coupled receptor Gpr37 , as a gene expressed only in EGCs of the myenteric plexus, one of the two layers of the ENS. We show that Gpr37 contributes to key components of LPS-induced reactive gliosis including activation of NF-kB and IFN-y signaling and response genes, lymphocyte recruitment, and inflammation-induced GI dysmotility. Targeting Gpr37 in EGCs presents a potential avenue for modifying inflammatory processes in the ENS.

Studies have confirmed that P2 purinergic receptors (P2X receptors and P2Y receptors) expressed in gastric cancer (GC) cells and GC tissues and correlates with their function. Endogenous nucleotides including ATP, ADP, UTP, and UDP, as P2 purinergic receptors activators, participate in P2 purinergic signal transduction pathway. These activated P2 purinergic receptors regulate the progression of GC mainly by mediating ion channels and intracellular signal cascades. It is worth noting that there is a difference in the expression of P2 purinergic receptors in GC, which may play different roles in the progression of GC as a tumor promoting factor or a tumor suppressor factor. Among them, P2 × 7, P2Y2 and P2Y6 receptors have certain clinical significance in patients with GC and may be used as biological molecular markers for the prediction of patients with GC. Therefore, in this paper, we discuss the functional role of nucleotide / P2 purinergic receptors signal axis in regulating the progression of GC and that these P2 purinergic receptors may be used as potential molecular targets for the prevention and treatment of GC.

Ischemic damage to the intestinal epithelial barrier, such as in necrotizing enterocolitis or small intestinal volvulus, is associated with higher mortality rates in younger patients. We have recently reported a powerful pig model to investigate these age-dependent outcomes in which mucosal barrier restitution is strikingly absent in neonates but can be rescued by direct application of homogenized mucosa from older, juvenile pigs by a yet-undefined mechanism. Within the mucosa, a postnatally developing network of enteric glial cells (EGCs) is gaining recognition as a key regulator of the mucosal barrier. Therefore, we hypothesized that the developing EGC network may play an important role in coordinating intestinal barrier repair in neonates. Neonatal and juvenile jejunal mucosa recovering from surgically induced intestinal ischemia was visualized by scanning electron microscopy and the transcriptomic phenotypes were assessed by bulk RNA sequencing. EGC network density and glial activity were examined by Gene Set Enrichment Analysis, three-dimensional (3-D) volume imaging, and Western blot and its function in regulating epithelial restitution was assessed ex vivo in Ussing chamber using the glia-specific inhibitor fluoroacetate (FA), and in vitro by coculture assay. Here we refine and elaborate our translational model, confirming a neonatal phenotype characterized by a complete lack of coordinated reparative signaling in the mucosal microenvironment. Furthermore, we report important evidence that the subepithelial EGC network changes significantly over the early postnatal period and demonstrate that the proximity of a specific functional population of EGC to wounded intestinal epithelium contributes to intestinal barrier restitution following ischemic injury.NEW & NOTEWORTHY This study refines a powerful translational pig model, defining an age-dependent relationship between enteric glia and the intestinal epithelium during intestinal ischemic injury and confirming an important role for enteric glial cell (EGC) activity in driving mucosal barrier restitution. This study suggests that targeting the enteric glial network could lead to novel interventions to improve recovery from intestinal injury in neonatal patients.

Retinitis pigmentosa (RP) and macular dystrophy (MD) cause severe retinal dysfunction, affecting 1 in 4000 people worldwide. This disease is currently assumed to be intractable, because effective therapeutic methods have not been established, regardless of genetic or sporadic traits. Here, we examined a RP mouse model in which the Prominin-1 (Prom1) gene was deficient and investigated the molecular events occurring at the outset of retinal dysfunction. We extracted the Prom1-deficient retina subjected to light exposure for a short time, conducted single-cell expression profiling, and compared the gene expression with and without stimuli. We identified the cells and genes whose expression levels change directly in response to light stimuli. Among the genes altered by light stimulation, Igf1 was decreased in rod photoreceptor cells and astrocytes under the light-stimulated condition. Consistently, the insulin-like growth factor (IGF) signal was weakened in light-stimulated photoreceptor cells. The recovery of Igf1 expression with the adeno-associated virus (AAV) prevented photoreceptor cell death, and its treatment in combination with the endothelin receptor antagonist led to the blockade of abnormal glial activation and the promotion of glycolysis, thereby resulting in the improvement of retinal functions, as assayed by electroretinography. We additionally demonstrated that the attenuation of mammalian/mechanistic target of rapamycin (mTOR), which mediates IGF signalling, leads to complications in maintaining retinal homeostasis. Together, we propose that combinatorial manipulation of distinct mechanisms is useful for the maintenance of the retinal condition.

More and more studies have revealed that P2 purinergic receptors play a key role in the progression of colorectal cancer (CRC). P2X and P2Y purinergic receptors can be used as promoters and regulators of CRC and play a dual role in the progression of CRC. CRC microenvironment is rich in ATP and its cleavage products (ADP, AMP, Ado), which act as activators of P2X and P2Y purinergic receptors. The activation of P2X and P2Y purinergic receptors regulates the progression of CRC mainly by regulating the function of immune cells and mediating different signal pathways. In this paper, we focus on the specific mechanisms and functional roles of P2X7, P2Y12, and P2Y2 receptors in the growth and progression of CRC. The antagonistic effects of these selective antagonists of P2X purinergic receptors on the growth, invasion, and metastasis of CRC were further discussed. Moreover, different studies have reported that P2X7 receptor can be used as an effective predictor of patients with CRC. All these indicate that P2 purinergic receptors are a key regulator of CRC. Therefore, antagonizing P2 purinergic receptors may be an innovative treatment for CRC.

Current evidence suggests that activation of glial and immune cells leads to increased production of proinflammatory mediators, creating a neuroinflammatory state. Neuroinflammation has been proven to be a fundamental mechanism in the genesis of acute pain and its transition to neuropathic and chronic pain. A noxious event that stimulates peripheral afferent nerve fibers may also activate pronociceptive receptors situated at the dorsal root ganglion and dorsal horn of the spinal cord, as well as peripheral glial cells, setting off the so-called peripheral sensitization and spreading neuroinflammation to the brain. Once activated, microglia produce cytokines, chemokines, and neuropeptides that can increase the sensitivity and firing properties of second-order neurons, upregulating the signaling of nociceptive information to the cerebral cortex. This process, known as central sensitization, is crucial for chronification of acute pain. Immune-neuronal interactions are also implicated in the lesser-known complex regulatory relationship between pain and opioids. Current evidence suggests that activated immune and glial cells can alter neuronal function, induce, and maintain pathological pain, and disrupt the analgesic effects of opioid drugs by contributing to the development of tolerance and dependence, even causing paradoxical hyperalgesia. Such alterations may occur when the neuronal environment is impacted by trauma, inflammation, and immune-derived molecules, or when opioids induce proinflammatory glial activation. Hence, understanding these intricate interactions may help in managing pain signaling and opioid efficacy beyond the classical pharmacological approach.

Enteric glia contribute to the pathophysiology of various intestinal immune-driven diseases, such as postoperative ileus (POI), a motility disorder and common complication after abdominal surgery. Enteric gliosis of the intestinal muscularis externa (ME) has been identified as part of POI development. However, the glia-restricted responses and activation mechanisms are poorly understood. The sympathetic nervous system becomes rapidly activated by abdominal surgery. It modulates intestinal immunity, innervates all intestinal layers, and directly interfaces with enteric glia. We hypothesized that sympathetic innervation controls enteric glia reactivity in response to surgical trauma.

Sox10iCreERT2/Rpl22HA/+ mice were subjected to a mouse model of laparotomy or intestinal manipulation to induce POI. Histological, protein, and transcriptomic analyses were performed to analyze glia-specific responses. Interactions between the sympathetic nervous system and enteric glia were studied in mice chemically depleted of TH+ sympathetic neurons and glial-restricted Sox10iCreERT2/JellyOPfl/+/Rpl22HA/+ mice, allowing optogenetic stimulation of β-adrenergic downstream signaling and glial-specific transcriptome analyses. A laparotomy model was used to study the effect of sympathetic signaling on enteric glia in the absence of intestinal manipulation. Mechanistic studies included adrenergic receptor expression profiling in vivo and in vitro and adrenergic agonism treatments of primary enteric glial cell cultures to elucidate the role of sympathetic signaling in acute enteric gliosis and POI.

With ~ 4000 differentially expressed genes, the most substantial enteric glia response occurs early after intestinal manipulation. During POI, enteric glia switch into a reactive state and continuously shape their microenvironment by releasing inflammatory and migratory factors. Sympathetic denervation reduced the inflammatory response of enteric glia in the early postoperative phase. Optogenetic and pharmacological stimulation of β-adrenergic downstream signaling triggered enteric glial reactivity. Finally, distinct adrenergic agonists revealed β-1/2 adrenoceptors as the molecular targets of sympathetic-driven enteric glial reactivity.

Enteric glia act as early responders during post-traumatic intestinal injury and inflammation. Intact sympathetic innervation and active β-adrenergic receptor signaling in enteric glia is a trigger of the immediate glial postoperative inflammatory response. With immune-activating cues originating from the sympathetic nervous system as early as the initial surgical incision, adrenergic signaling in enteric glia presents a promising target for preventing POI development.

Postoperative ileus (POI) is the cessation or reduction of gastrointestinal (GI) motility after surgery. Reactive enteric glial cells (EGCs) are critical for maintaining bowel function. However, the triggering mechanisms and downstream effects of reactive EGCs in POI were poorly understood. The goal of this current study was to investigate whether the inducible nitric oxide synthase (iNOS)-driven reactive EGCs participated in GI motility disorders and mechanisms underlying altered GI motility in POI. Intestinal manipulation (IM)-induced POI mice and iNOS-/- mice were used in the study. Longitudinal muscle and myenteric plexuses (LMMPs) from the distal small intestine were stained by immunofluorescence. Our results found that the GI motility disorders occurred in the IM-induced POI mice, and reactive EGCs were observed in LMMPs. Glial metabolic inhibitor gliotoxin fluorocitrate (FC) treatment or iNOS gene knockout attenuated GI motility dysfunction. In addition, we also found that FC treatment or iNOS gene knockout significantly inhibited the fluorescence intensity macrophage colony-stimulating factor (M-CSF), which reduced M2 phenotype macrophages activation in LMMPs of IM-induced POI mice. Our findings demonstrated that iNOS-driven reactive EGCs played a key role and were tightly linked to the MMs homeostasis in the POI mice. EGCs are emerging as a new frontier in neurogastroenterology and a potential therapeutic target.

The enteric nervous system is an autonomous neuronal circuit that regulates many processes far beyond the peristalsis in the gastro-intestinal tract. This circuit, consisting of enteric neurons and enteric glial cells, can engage in many intercellular interactions shaping the homeostatic microenvironment in the gut. Perhaps the most well documented interactions taking place, are the intestinal neuro-immune interactions which are essential for the fine-tuning of oral tolerance. In the context of intestinal disease, compelling evidence demonstrates both protective and detrimental roles for this bidirectional neuro-immune signaling. This review discusses the different immune cell types that are recognized to engage in neuronal crosstalk during intestinal health and disease. Highlighting the molecular pathways involved in the neuro-immune interactions might inspire novel strategies to target intestinal disease.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive types of cancer, characterized by the spreading of highly metastatic cancer cells, including invasion into surrounding nerves and perineural spaces. Nerves, in turn, can invade the tumor tissue and, through the secretion of neurotrophic factors, chemokines, and cytokines, contribute to PDAC progression. However, the contribution of the nerve-associated glial cells to PDAC progression is not well characterized.

Two murine PDAC cell lines were cultured with the conditioned media (CM) of primary enteric glial cells or IMS32 Schwann cells (SCs). Different properties of PDAC cells, such as invasiveness, migratory capacity, and resistance to gemcitabine, were measured by RT-qPCR, microscopy, and MTT assays. Using a neuronal cell line, the observed effects were confirmed to be specific to the glial lineage.

Compared to the control medium, PDAC cells in the glial cell-conditioned medium showed increased invasiveness and migratory capacity. These cells showed reduced E-cadherin and increased N-cadherin and Vimentin levels, all markers of epithelial-mesenchymal transition (EMT). Primary enteric glial cell CM inhibited the proliferation of PDAC cells but preserved their viability, upregulated transcription factor Snail, and increased their resistance to gemcitabine. The conditioned medium generated from the IMS32 SCs produced comparable results.

Our data suggest that glial cells can increase the metastatic potential of PDAC cells by increasing their migratory capacity and inducing epithelial-to-mesenchymal transition, a re-programming that many solid tumors use to undergo metastasis. Glial cell-conditioned medium also increased the chemoresistance of PDAC cells. These findings may have implications for future therapeutic strategies, such as targeting glial cell-derived factor signaling in PDAC.

Binge or chronic alcohol consumption causes neuroinflammation and leads to alcohol use disorder (AUD). AUD not only affects the central nervous system (CNS) but also leads to pathologies in the peripheral and enteric nervous systems (ENS). Thus, understanding the mechanism of the immune signaling to target the effector molecules in the signaling pathway is necessary to alleviate AUD. Growing evidence shows that excessive alcohol consumption can activate neuroimmune cells, including microglia, and change the status of neurotransmitters, affecting the neuroimmune system. Microglia, like peripheral macrophages, are an integral part of the immune defense and represent the reticuloendothelial system in the CNS. Microglia constantly survey the CNS to scavenge the neuronal debris. These cells also protect parenchymal cells in the brain and spinal cord by repairing nerve circuits to keep the nervous system healthy against infectious and stress-derived agents. In an activated state, they become highly dynamic and mobile and can modulate the levels of neurotransmitters in the CNS. In several ways, microglia, enteric glial cells, and macrophages are similar in terms of causing inflammation. Microglia also express most of the receptors that are constitutively present in macrophages. Several receptors on microglia respond to the inflammatory signals that arise from danger-associated molecular patterns (DAMPs), pathogen-associated molecular patterns (PAMPs), endotoxins (e.g., lipopolysaccharides), and stress-causing molecules (e.g., alcohol). Therefore, this review article presents the latest findings, describing the roles of microglia and enteric glial cells in the brain and gut, respectively, and their association with neurotransmitters, neurotrophic factors, and receptors under the influence of binge and chronic alcohol use, and AUD.

ET-1 signalling modulates intestinal motility and inflammation, but the role of ET-1/ETB receptor signalling is poorly understood. Enteric glia modulate normal motility and inflammation. We investigated whether glial ETB signalling regulates neural-motor pathways of intestinal motility and inflammation.

We studied ETB signalling using: ETB drugs (ET-1, SaTX, BQ788), activity-dependent stimulation of neurons (high K+ -depolarization, EFS), gliotoxins, Tg (Ednrb-EGFP)EP59Gsat/Mmucd mice, cell-specific mRNA in Sox10CreERT2 ;Rpl22-HAflx or ChATCre ;Rpl22-HAflx mice, Sox10CreERT2 ::GCaMP5g-tdT, Wnt1Cre2 ::GCaMP5g-tdT mice, muscle tension recordings, fluid-induced peristalsis, ET-1 expression, qPCR, western blots, 3-D LSM-immunofluorescence co-labelling studies in LMMP-CM and a postoperative ileus (POI) model of intestinal inflammation.

In the muscularis externa ETB receptor is expressed exclusively in glia. ET-1 is expressed in RiboTag (ChAT)-neurons, isolated ganglia and intra-ganglionic varicose-nerve fibres co-labelled with peripherin or SP. ET-1 release provides activity-dependent glial ETB receptor modulation of Ca2+ waves in neural evoked glial responses. BQ788 reveals amplification of glial and neuronal Ca2+ responses and excitatory cholinergic contractions, sensitive to L-NAME. Gliotoxins disrupt SaTX-induced glial-Ca2+ waves and prevent BQ788 amplification of contractions. The ETB receptor is linked to inhibition of contractions and peristalsis. Inflammation causes glial ETB up-regulation, SaTX-hypersensitivity and glial amplification of ETB signalling. In vivo BQ788 (i.p., 1 mg·kg-1 ) attenuates intestinal inflammation in POI.

Enteric glial ET-1/ETB signalling provides dual modulation of neural-motor circuits to inhibit motility. It inhibits excitatory cholinergic and stimulates inhibitory nitrergic motor pathways. Amplification of glial ETB receptors is linked to muscularis externa inflammation and possibly pathogenic mechanisms of POI.

Enteric glial cells are emerging as critical players in the regulation of intestinal motility, secretion, epithelial barrier function, and gut homeostasis in health and disease. Enteric glia react to intestinal inflammation by converting to a 'reactive glial phenotype' and enteric gliosis, contributing to neuroinflammation, enteric neuropathy, bowel motor dysfunction and dysmotility, diarrhea or constipation, 'leaky gut', and visceral pain. The focus of the minireview is on the impact of inflammation on enteric glia reactivity in response to diverse insults such as intestinal surgery, ischemia, infections (C. difficile infection, HIV-Tat-induced diarrhea, endotoxemia and paralytic ileus), GI diseases (inflammatory bowel diseases, diverticular disease, necrotizing enterocolitis, colorectal cancer) and functional GI disorders (postoperative ileus, chronic intestinal pseudo-obstruction, constipation, irritable bowel syndrome). Significant progress has been made in recent years on molecular pathogenic mechanisms of glial reactivity and enteric gliosis, resulting in enteric neuropathy, disruption of motility, diarrhea, visceral hypersensitivity and abdominal pain. There is a growing number of glial molecular targets with therapeutic implications that includes receptors for interleukin-1 (IL-1R), purines (P2X2R, A2BR), PPARα, lysophosphatidic acid (LPAR1), Toll-like receptor 4 (TLR4R), estrogen-β receptor (ERβ) adrenergic α-2 (α-2R) and endothelin B (ETBR), connexin-43 / Colony-stimulating factor 1 signaling (Cx43/CSF1) and the S100β/RAGE signaling pathway. These exciting new developments are the subject of the minireview. Some of the findings in pre-clinical models may be translatable to humans, raising the possibility of designing future clinical trials to test therapeutic application(s). Overall, research on enteric glia has resulted in significant advances in our understanding of GI pathophysiology.

Enteric glial cells represent the enteric population of peripheral glia. According to their 'glial' nature, their principal function is to support enteric neurons in both structural and functional ways. Mounting evidence however demonstrates that enteric glial cells crucially contribute to the majority of enteric nervous system functions, thus acting as pivotal players in the maintenance of gut homeostasis. Various types of enteric glia are present within the gut wall, creating an intricate interaction network with other gastrointestinal cell types. Their distribution throughout the different layers of the gut wall translates in characteristic phenotypes that are tailored to the local tissue requirements of the digestive tract. This heterogeneity is assumed to be mirrored by functional specialization, but the extensive plasticity and versatility of enteric glial cells complicates a one on one phenotype/function definition. Moreover, the relative contribution of niche-specific signals versus lineage determinants for driving enteric glial heterogeneity is still uncertain. In this review we focus on the current understanding of phenotypic and functional enteric glial cell heterogeneity, from a microenvironmental and developmental perspective.

The enteric nervous system is a dense network of enteric neurons and glia housed in the gastrointestinal tract. This system is responsible for performing several functions that enable digestion as well as maintaining gut homeostasis through diverse signaling processes including those that arise from interactions with the immune system. Bidirectional communication between enteric neurons and enteric glia has gained increased attention for playing essential roles in enteric nervous system function. Neuronal mediators such as neurotransmitters stimulate enteric glia and subsequent gliotransmission processes refine neuronal signaling during intestinal motor control. In this mini-review, we present and discuss the basis of intercellular signaling between neurons and glia in the enteric nervous system and the relevance of these interactions to gut function.

The enteric nervous system (ENS) is one of the important systems that regulate gastrointestinal function. The ENS is made up of enteric glial cells (EGCs) and neurons. For a long time, it was believed that the function of EGCs was only to give structural support to neurons. However, recent evidence indicates EGCs are involved in most gut functions, including the development and plasticity of the ENS, epithelial barrier, and motility. However, it remains unclear whether EGCs have the potential to modify colonic motility following irritable bowel syndrome (IBS) with predominant diarrhea (IBS-D). This study aimed to investigate changes in EGCs during IBS-D and assessed the effects of manipulating EGCs. An IBS-D rat model was constructed using acetic acid and restraint stress, and DL-fluorocitric acid (FC), an inhibitor of EGCs, was administered. The changes in EGCs and colonic motility were studied by employing techniques comprising morphological, molecular biological and functional experiments. The results showed significant activation of EGCs in the myenteric plexus (MP) of the IBS-D-induced rat colon with accelerated colonic motility. FC significantly reduced the activation of EGCs and colonic motility caused by acetic acid and restraint stress. Hypercontraction of the colon caused by IBS-D may be associated with activation of EGCs in the MP of the colon and this was prevented by FC. Therefore, regulating colon hypercontraction through interference with the activation of EGCs has significant prospects for clinical application to alleviate diarrhea in patients with IBS-D.

The gastrointestinal tract has the important task of absorbing nutrients, a complex process that requires an intact barrier allowing the passage of nutrients but that simultaneously protects the host against invading microorganisms. To maintain and regulate intestinal homeostasis, the gut is equipped with one of the largest populations of macrophages in the body. Here, we will discuss our current understanding of intestinal macrophage heterogeneity and describe their main functions in the different anatomical niches of the gut during steady state. In addition, their role in inflammatory conditions such as infection, inflammatory bowel disease, and postoperative ileus are discussed, highlighting the roles of macrophages in immune defense. To conclude, we describe the interaction between macrophages and the enteric nervous system during development and adulthood and highlight their contribution to neurodegeneration in the context of aging and diabetes.

Muscularis Externa Macrophages (ME-Macs) and enteric glial cells (EGCs) are closely associated cell types in the bowel wall, and important interactions are thought to occur between them during intestinal inflammation. They are involved in developing postoperative ileus (POI), an acute, surgery-induced inflammatory disorder triggered by IL-1 receptor type I (IL1R1)-signaling. In this study, we demonstrate that IL1R1-signaling in murine and human EGCs induces a reactive state, named enteric gliosis, characterized by a strong induction of distinct chemokines, cytokines, and the colony-stimulating factors 1 and 3. Ribosomal tagging revealed enteric gliosis as an early part of POI pathogenesis, and mice with an EGC-restricted IL1R1-deficiency failed to develop postoperative enteric gliosis, showed diminished immune cell infiltration, and were protected from POI. Furthermore, the IL1R1-deficiency in EGCs altered the surgery-induced glial activation state and reduced phagocytosis in macrophages, as well as their migration and accumulation around enteric ganglia. In patients, bowel surgery also induced IL-1-signaling, key molecules of enteric gliosis, and macrophage activation. Together, our data show that IL1R1-signaling triggers enteric gliosis, which results in ME-Mac activation and the development of POI. Intervention in this pathway might be a useful prophylactic strategy in preventing such motility disorders and gut inflammation.