Vagus nerve stimulation dampens intestinal inflammation in a murine model of experimental food allergy

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

Atopic dermatitis and food allergy: More than sensitization

The increased risk of food allergy in infants with atopic dermatitis (AD) has long been recognized; an epidemiologic phenomenon termed "the atopic march." Current literature supports the hypothesis that food antigen exposure through the disrupted skin barrier in AD leads to food antigen-specific immunoglobulin E production and food sensitization. However, there is growing evidence that inflammation in the skin drives intestinal remodeling via circulating inflammatory signals, microbiome alterations, metabolites, and the nervous system. We explore how this skin-gut axis helps to explain the link between AD and food allergy beyond sensitization.

Minimally invasive vagus nerve stimulation modulates mast cell degranulation via the microbiota-gut-brain axis to ameliorate blood-brain barrier and intestinal barrier damage following ischemic stroke

Mast cells (MCs) play a significant role in various diseases, and their activation and degranulation can trigger inflammatory responses and barrier damage. Several studies have indicated that vagus nerve stimulation (VNS) exerts ameliorates neurological injury, and regulates gut MC degranulation. However, there is limited research on the modulatory effect of VNS on MCs in both the gut and brain in brain ischemia-reperfusion (I/R) injury in this process. We aim to develop a minimally invasive, targeted and convenient VNS approach to assess the impact of VNS and to clarify the relationship between VNS and MCs on the prognosis of acute ischemic stroke. We utilized middle cerebral artery occlusion/reperfusion (MCAO/r) to induce brain I/R injury. After the experiment, the motor function and neurofunctional impairments of the rats were detected, and the gastrointestinal function, blood-brain barrier (BBB) and intestinal barrier damage, and systemic and local inflammation were evaluated by Nissl, TTC staining, Evans blue, immunofluorescence staining, transmission electron microscopy, western blot assays, ELISA, and fecal 16S rRNA sequencing methods. Our research confirmed that our minimally invasive VNS method is a novel approach for stimulating the vagus nerve. VNS alleviated motor deficits and gastrointestinal dysfunction while also suppressing intestinal and neuroinflammation. Additionally, VNS ameliorated gut microbiota dysbiosis in rats. Furthermore, our analysis indicated that VNS reduces chymase secretion by modulating MCs degranulation and improves intestinal and BBB damage. Our results showed that VNS treatment can alleviate the damage of BBB and colonic barrier after cerebral I/R by modulating mast cell degranulation, and alleviates systemic inflammatory responses.

Vagus Nerve Stimulation and Inflammation in Cardiovascular Disease: A State-of-the-Art Review

Vagus nerve stimulation (VNS) has been found to exert anti-inflammatory effects in different clinical settings and has been associated with improvement of clinical outcomes. However, evidence on the mechanistic link between the potential association of inflammatory status with clinical outcomes following VNS is scarce. This review aims to summarize the existing knowledge linking VNS with inflammation and its potential link with major outcomes in cardiovascular diseases, in both preclinical and clinical studies. Existing data show that in the setting of myocardial ischemia and reperfusion, VNS seems to reduce inflammation resulting in reduced infarct size and reduced incidence of ventricular arrhythmias during reperfusion. Furthermore, VNS has a protective role in vascular function following myocardial ischemia and reperfusion. Atrial fibrillation burden has also been reduced by VNS, whereas suppression of inflammation may be a potential mechanism for this effect. In the setting of heart failure, VNS was found to improve systolic function and reverse cardiac remodeling. In summary, existing experimental data show a reduction in inflammatory markers by VNS, which may cause improved clinical outcomes in cardiovascular diseases. However, more data are needed to evaluate the association between the inflammatory status with the clinical outcomes following VNS.

Mast cells link immune sensing to antigen-avoidance behaviour

The physiological functions of mast cells remain largely an enigma. In the context of barrier damage, mast cells are integrated in type 2 immunity and, together with immunoglobulin E (IgE), promote allergic diseases. Allergic symptoms may, however, facilitate expulsion of allergens, toxins and parasites and trigger future antigen avoidance1-3. Here, we show that antigen-specific avoidance behaviour in inbred mice4,5 is critically dependent on mast cells; hence, we identify the immunological sensor cell linking antigen recognition to avoidance behaviour. Avoidance prevented antigen-driven adaptive, innate and mucosal immune activation and inflammation in the stomach and small intestine. Avoidance was IgE dependent, promoted by Th2 cytokines in the immunization phase and by IgE in the execution phase. Mucosal mast cells lining the stomach and small intestine rapidly sensed antigen ingestion. We interrogated potential signalling routes between mast cells and the brain using mutant mice, pharmacological inhibition, neural activity recordings and vagotomy. Inhibition of leukotriene synthesis impaired avoidance, but overall no single pathway interruption completely abrogated avoidance, indicating complex regulation. Collectively, the stage for antigen avoidance is set when adaptive immunity equips mast cells with IgE as a telltale of past immune responses. On subsequent antigen ingestion, mast cells signal termination of antigen intake. Prevention of immunopathology-causing, continuous and futile responses against per se innocuous antigens or of repeated ingestion of toxins through mast-cell-mediated antigen-avoidance behaviour may be an important arm of immunity.

Recent advances in cellular and molecular mechanisms of IgE-mediated food allergy

Food allergy is a public health issue the prevalence of which is steadily increasing. New discoveries have contributed to the understanding of the molecular and cellular mechanisms that lead to IgE-mediated food allergy. Novel scientific findings have defined roles for specific cell types, such as T follicular helper cells, in induction of high-affinity IgE by B cells. Also, not only mast cells and basophils contribute to food anaphylaxis, but also other cell types, such as neutrophils and macrophages. Elucidation of mechanisms involved in sensitization to food allergens through organs including the skin is key to deepening our understanding of the "dual exposure" hypothesis, which suggests that allergic sensitization is mainly acquired through inflamed skin while the oral route induces tolerance. This review considers the latest scientific knowledge about the molecular and cellular mechanisms of IgE-mediated food allergy. It reveals crucial components involved in the sensitization and elicitation phases and emerging approaches in anaphylaxis pathophysiology.

Vagus innervation in the gastrointestinal tumor: Current understanding and challenges

The vagus nerve (VN) is the main parasympathetic nerve of the autonomic nervous system. It is widely distributed in the gastrointestinal tract and maintains gastrointestinal homeostasis with the sympathetic nerve under physiological conditions. The VN communicates with various components of the tumor microenvironment to positively and dynamically affect the progression of gastrointestinal tumors (GITs). The intervention in vagus innervation delays GIT progression. Developments in adeno-associated virus vectors, nanotechnology, and in vivo neurobiological techniques have enabled the creation of precisely regulated "tumor neurotherapies". Furthermore, the combination of neurobiological techniques and single cell sequencing may reveal more insights into VN and GIT. The present review aimed to summarize the mechanisms of communication between the VN and the gastrointestinal TME and to explore the potential and challenges of VN-based tumor neurotherapy in GITs.

Neuroimmune regulation in Hirschsprung's disease associated enterocolitis

Neuroimmune pathways are important part of the regulation of inflammatory response. Nerve cells regulate the functions of various immune cells through neurotransmitters, and then participate in the inflammatory immune response. Hirschsprung's disease (HD) is a congenital abnormal development of intestinal neurons, and Hirschsprung-associated enterocolitis (HAEC) is a common complication, which seriously affects the quality of life and even endangers the lives of children. Neuroimmune regulation mediates the occurrence and development of enteritis, which is an important mechanism. However, there is a lack of review on the role of Neuroimmune regulation in enterocolitis associated with Hirschsprung's disease. Therefore, this paper summarizes the characteristics of the interaction between intestinal nerve cells and immune cells, reviews the neuroimmune regulation mechanism of Hirschsprung's disease associated enterocolitis (HAEC), and looks forward to the potential clinical application value.

Ion channel regulation of gut immunity

Mounting evidence indicates that gastrointestinal (GI) homeostasis hinges on communications among many cellular networks including the intestinal epithelium, the immune system, and both intrinsic and extrinsic nerves innervating the gut. The GI tract, especially the colon, is the home base for gut microbiome which dynamically regulates immune function. The gut's immune system also provides an effective defense against harmful pathogens entering the GI tract while maintaining immune homeostasis to avoid exaggerated immune reaction to innocuous food and commensal antigens which are important causes of inflammatory disorders such as coeliac disease and inflammatory bowel diseases (IBD). Various ion channels have been detected in multiple cell types throughout the GI tract. By regulating membrane properties and intracellular biochemical signaling, ion channels play a critical role in synchronized signaling among diverse cellular components in the gut that orchestrates the GI immune response. This work focuses on the role of ion channels in immune cells, non-immune resident cells, and neuroimmune interactions in the gut at the steady state and pathological conditions. Understanding the cellular and molecular basis of ion channel signaling in these immune-related pathways and initial testing of pharmacological intervention will facilitate the development of ion channel-based therapeutic approaches for the treatment of intestinal inflammation.

Dual effects of supplemental oxygen on pulmonary infection, inflammatory lung injury, and neuromodulation in aging and COVID-19

Clinical studies have shown a significant positive correlation between age and the likelihood of being infected with SARS-CoV-2. This increased susceptibility is positively correlated with chronic inflammation and compromised neurocognitive functions. Postmortem analyses suggest that acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), with systemic and lung hyperinflammation, can cause significant morbidity and mortality in COVID-19 patients. Supraphysiological supplemental oxygen, also known as hyperoxia, is commonly used to treat decreased blood oxygen saturation in COVID-19 patients. However, prolonged exposure to hyperoxia alone can cause oxygen toxicity, due to an excessive increase in the levels of reactive oxygen species (ROS), which can overwhelm the cellular antioxidant capacity. Subsequently, this causes oxidative cellular damage and increased levels of aging biomarkers, such as telomere shortening and inflammaging. The oxidative stress in the lungs and brain can compromise innate immunity, resulting in an increased susceptibility to secondary lung infections, impaired neurocognitive functions, and dysregulated hyperinflammation, which can lead to ALI/ARDS, and even death. Studies indicate that lung inflammation is regulated by the central nervous system, notably, the cholinergic anti-inflammatory pathway (CAIP), which is innervated by the vagus nerve and α7 nicotinic acetylcholine receptors (α7nAChRs) on lung cells, particularly lung macrophages. The activation of α7nAChRs attenuates oxygen toxicity in the lungs and improves clinical outcomes by restoring hyperoxia-compromised innate immunity. Mechanistically, α7nAChR agonist (e.g., GAT 107 and GTS-21) can regulate redox signaling by 1) activating Nrf2, a master regulator of the antioxidant response and a cytoprotective defense system, which can decrease cellular damage caused by ROS and 2) inhibiting the activation of the NF-κB-mediated inflammatory response. Notably, GTS-21 has been shown to be safe and it improves neurocognitive functions in humans. Therefore, targeting the α7nAChR may represent a viable therapeutic approach for attenuating dysregulated hyperinflammation-mediated ARDS and sepsis in COVID-19 patients receiving prolonged oxygen therapy.

Enteric nervous system and intestinal epithelial regulation of the gut-brain axis

The gut-brain axis describes a bidirectional interplay within the enteric environment between the intestinal epithelium, the mucosal immune system, and the microbiota with the enteric nervous system. This interplay provides a link between exogenous environmental stimuli such as nutrient sensing, and nervous system function, as well as a mechanism of feedback from cortical and sensory centers of the brain to enteric activities. The intestinal epithelium is one of the human body's largest sources of hormones and neurotransmitters, which have critical effects on neuronal function. The influence of the gut microbiota on these processes appears to be profound; yet to date, it has been insufficiently explored. Disruption of the intestinal microbiota is linked not only to diseases in the gut but also to brain symptomatology, including neurodegenerative and behavioral disorders (Parkinson disease, Alzheimer disease, autism, and anxiety and/or depression). In this review we discuss the cellular wiring of the gut-brain axis, with a particular focus on the epithelial and neuronal interaction, the evidence that has led to our current understanding of the intestinal role in neurologic function, and future directions of research to unravel this important interaction in both health and allergic disease.

Neuro-allergology: Mast cell-nerve cross-talk

Mast cells (MCs) are derived from hematopoietic stem cells in the bone marrow, and their maturation is regulated by the tissue environment, such as the skin, lung and gut, leading to host defense. Peripheral nerve fibers located in various tissues are involved in diverse physiological and pathological processes. Anatomical relationships between MCs and nerve fibers were reported to have been observed in various organs. Moreover, MCs are positive for a large number of receptors for classical neurotransmitters (e.g., acetylcholine and corticotropin-releasing hormone) and neuropeptides (e.g., substance P, calcitonin gene-related peptides and hemokinin), and MC's functions are regulated by those nerve-derived factors. Also, histamine and proteases produced and released by MCs modulate nerve fiber functions. This functional cross-talk between MCs and nerve fibers can play physiological and pathological roles. MCs are key effector cells of allergic inflammation, such as atopic dermatitis, airway inflammation and food allergy. Here, we summarize and discuss the molecular mechanisms underlying the functional and anatomical cross-talk between MCs and nerve fibers in allergic inflamed tissues.

Dysfunction of the Autonomic Nervous System and its Role in the Pathogenesis of Septic Critical Illness (Review)

Dysfunction of the autonomic nervous system (ANS) of the brain in sepsis can cause severe systemic inflammation and even death. Numerous data confirmed the role of ANS dysfunction in the occurrence, course, and outcome of systemic sepsis. The parasympathetic part of the ANS modifies the inflammation through cholinergic receptors of internal organs, macrophages, and lymphocytes (the cholinergic anti-inflammatory pathway). The sympathetic part of ANS controls the activity of macrophages and lymphocytes by influencing β2-adrenergic receptors, causing the activation of intracellular genes encoding the synthesis of cytokines (anti-inflammatory beta2-adrenergic receptor interleukin-10 pathway, β2AR–IL-10). The interaction of ANS with infectious agents and the immune system ensures the maintenance of homeostasis or the appearance of a critical generalized infection. During inflammation, the ANS participates in the inflammatory response by releasing sympathetic or parasympathetic neurotransmitters and neuropeptides. It is extremely important to determine the functional state of the ANS in critical conditions, since both cholinergic and sympathomimetic agents can act as either anti- or pro-inflammatory stimuli.

Probiotic Interventions Alleviate Food Allergy Symptoms Correlated With Cesarean Section: A Murine Model

Delivery by cesarean section (CS) is linked to an increased incidence of food allergies in children and affects early gut microbiota colonization. Furthermore, emerging evidence has connected disordered intestinal microbiota to food allergies. Here, we investigated the impact of CS on a rat model for food allergy to ovalbumin (OVA). Rats delivered by CS were found to be more responsive to OVA sensitization than vaginally born ones, displaying a greater reduction in rectal temperature upon challenge, worse diarrhea, and higher levels of OVA-specific antibodies and histamine. 16S rRNA sequencing of feces revealed reduced levels of Lactobacillus and Bifidobacterium in the CS rats. Preventative supplementation with a probiotic combination containing Lactobacillus and Bifidobacterium could protect CS rats against an allergic response to OVA, indicating that the microbiota dysbiosis contributes to CS-related response. Additionally, probiotic intervention early in life might help to rebuild aberrant Th2 responses and tight junction proteins, both of which have been linked to CS-related high allergic reactions. Taken together, this study shows that disordered intestinal microbiota plays an essential role in the pathogenesis of food allergy mediated by CS. More importantly, interventions that modulate the microbiota composition in early life are therapeutically relevant for CS-related food allergies.

A Focused Review of Neural Recording and Stimulation Techniques With Immune-Modulatory Targets

The complex interactions established between the nervous and immune systems have been investigated for a long time. With the advent of small and portable devices to record and stimulate nerve activity, researchers from many fields began to be interested in how nervous activity can elicit immune responses and whether this activity can be manipulated to trigger specific immune responses. Pioneering works demonstrated the existence of a cholinergic inflammatory reflex, capable of controlling the systemic inflammatory response through a vagus nerve-mediated modulation of the spleen. This work inspired many different areas of technological and conceptual advancement, which are here reviewed to provide a concise reference for the main works expanding the knowledge on vagus nerve immune-modulatory capabilities. In these works the enabling technologies of peripheral nervous activity recordings were implemented and embody the current efforts aimed at controlling neural activity with modulating functions in immune response, both in experimental and clinical contexts.

Bidirectional communication between neural and immune systems

The immune and nervous systems share many features, including receptor and ligand expression, enabling efficient communication between the two. Accumulating evidence suggests that the communication is bidirectional, with the neural system regulating immune cell functions and vice versa. Steroid hormones from the hypothalamus-pituitary-adrenal gland axis are examples of systemic regulators for this communication. Neural reflexes describe regional regulation mechanisms that are a historically new concept that helps to explain how the neural and body systems including immune system communicate. Several recently identified neural reflexes, including the inflammatory reflex and gateway reflex, significantly impact the activation status of the immune system and are associated with inflammatory diseases and disorders. Either pro-inflammatory or anti-inflammatory effects can be elicited by these neural reflexes. On the other hand, the activities of immune cells during inflammation, for example the secretion of inflammatory mediators, can affect the functions of neuronal systems via neural reflexes and modulate biological outputs via specific neural pathways. In this review article, we discuss recent advances in the understanding of bidirectional neuro-immune interactions, with a particular focus on neural reflexes.

Vagus Nerve Stimulation Promotes Epithelial Proliferation and Controls Colon Monocyte Infiltration During DSS-Induced Colitis

Background: We previously showed increased susceptibility to dextran sulfate sodium (DSS)-induced colitis in vagotomized mice. Here, we evaluated whether vagus nerve stimulation (VNS) is able to reduce the severity of DSS colitis and aimed to unravel the mechanism involved.

Methods: Colitis was induced in wild type mice by 2.5% DSS administration in drinking water for 5 days. VNS (5 Hz, 1 ms, 1 mA) was applied 1 day prior to and after 4 days of DSS administration to evaluate changes in epithelial integrity and inflammatory response, respectively. Epithelial integrity was assessed using TUNEL and Ki67 staining. Monocytes, immature and mature macrophages were sorted from colonic samples and gene expression levels of pro-inflammatory cytokines were studied.

Results: VNS applied prior to DSS administration (i.e., prophylactic VNS) reduced disease activity index (VNS 0.8 ± 0.6 vs. sham 2.8 ± 0.7, p < 0.001, n = 5) and tended to improve histology score. Prophylactic VNS significantly increased epithelial cell proliferation and diminished apoptosis compared to sham stimulation. VNS applied at day 4 during DSS administration (i.e., therapeutic VNS) decreased the influx of monocytes, monocyte-derived macrophages and neutrophils, and significantly reduced pro-inflammatory cytokine expression (i.e., Tnfα and Cxcl1) in immature macrophages compared to sham stimulation.

Conclusions: A single period of VNS applied prior to DSS exposure reduced DSS-induced colitis by an improvement in epithelial integrity. On the other hand, VNS applied during the inflammatory phase of DSS colitis reduced cytokine expression in immature macrophages. Our data further underscores the potential of VNS as novel therapeutic approach for inflammatory bowel diseases.

Bioelectronics in the brain-gut axis: focus on inflammatory bowel disease (IBD)

Accumulating evidence shows that intestinal homeostasis is mediated by cross-talk between the nervous system, enteric neurons and immune cells, together forming specialized neuroimmune units at distinct anatomical locations within the gut. In this review, we will particularly discuss how the intrinsic and extrinsic neuronal circuitry regulates macrophage function and phenotype in the gut during homeostasis and aberrant inflammation, such as observed in inflammatory bowel disease (IBD). Furthermore, we will provide an overview of basic and translational IBD research using these neuronal circuits as a novel therapeutic tool. Finally, we will highlight the different challenges ahead to make bioelectronic neuromodulation a standard treatment for intestinal immune-mediated diseases.

Intestinal Mucosal Barrier Is Regulated by Intestinal Tract Neuro-Immune Interplay

Inflammatory bowel disease, irritable bowel syndrome and severe central nervous system injury can lead to intestinal mucosal barrier damage, which can cause endotoxin/enterobacteria translocation to induce infection and is closely related to the progression of metabolic diseases, cardiovascular and cerebrovascular diseases, tumors and other diseases. Hence, repairing the intestinal barrier represents a potential therapeutic target for many diseases. Enteral afferent nerves, efferent nerves and the intrinsic enteric nervous system (ENS) play key roles in regulating intestinal physiological homeostasis and coping with acute stress. Furthermore, innervation actively regulates immunity and induces inherent and adaptive immune responses through complex processes, such as secreting neurotransmitters or hormones and regulating their corresponding receptors. In addition, intestinal microorganisms and their metabolites play a regulatory role in the intestinal mucosal barrier. This paper primarily discusses the interactions between norepinephrine and β-adrenergic receptors, cholinergic anti-inflammatory pathways, nociceptive receptors, complex ENS networks, gut microbes and various immune cells with their secreted cytokines to summarize the key roles in regulating intestinal inflammation and improving mucosal barrier function.

Bidirectional sensory neuron-immune interactions: a new vision in the understanding of allergic inflammation

Peripheral neurons (including sensory neurons) are ubiquitously distributed in all tissues, particularly at the interface with the environment. The primary function of sensory neurons is the transmission of sensations of temperature, pain and itch to elicit appropriate behavioral responses. More recently, sensory neurons have emerged as potent regulators of type 2 immune responses and allergic inflammation. There is increasing evidence showing that neurons can express receptors previously thought to be restricted to the immune compartment. In addition, certain subtypes of immune cells (e.g. mast cells, ILC2s or macrophages) also express specific neuroreceptors that provide them with the capacity to integrate neuron-derived signals and modulate their activation status during the development of allergic inflammation.

Lack of Mucosal Cholinergic Innervation Is Associated With Increased Risk of Enterocolitis in Hirschsprung's Disease

BACKGROUND & AIMS

Hirschsprung's disease (HSCR) is a congenital intestinal motility disorder defined by the absence of enteric neuronal cells (ganglia) in the distal gut. The development of HSCR-associated enterocolitis remains a life-threatening complication. Absence of enteric ganglia implicates innervation of acetylcholine-secreting (cholinergic) nerve fibers. Cholinergic signals have been reported to control excessive inflammation, but the impact on HSCR-associated enterocolitis is unknown.

METHODS

We enrolled 44 HSCR patients in a prospective multicenter study and grouped them according to their degree of colonic mucosal acetylcholinesterase-positive innervation into low-fiber and high-fiber patient groups. The fiber phenotype was correlated with the tissue cytokine profile as well as immune cell frequencies using Luminex analysis and fluorescence-activated cell sorting analysis of colonic tissue and immune cells. Using confocal immunofluorescence microscopy, macrophages were identified in close proximity to nerve fibers and characterized by RNA-seq analysis. Microbial dysbiosis was analyzed in colonic tissue using 16S-rDNA gene sequencing. Finally, the fiber phenotype was correlated with postoperative enterocolitis manifestation.

RESULTS

The presence of mucosal nerve fiber innervation correlated with reduced T-helper 17 cytokines and cell frequencies. In high-fiber tissue, macrophages co-localized with nerve fibers and expressed significantly less interleukin 23 than macrophages from low-fiber tissue. HSCR patients lacking mucosal nerve fibers showed microbial dysbiosis and had a higher incidence of postoperative enterocolitis.

CONCLUSIONS

The mucosal fiber phenotype might serve as a prognostic marker for enterocolitis development in HSCR patients and may offer an approach to personalized patient care and new therapeutic options.

Anatomical variation and distribution of the vagus nerve in the esophageal hiatus: a cross-sectional study of post-mortem cases in Uganda

PURPOSE

Vagus nerve injuries during gastroesophageal surgery may cause significant symptoms due to loss of vagal anti-inflammatory and neuromodulator function. Many previous studies have shown high anatomical variability of the vagus nerve at the esophageal hiatus, but information on its variability in Uganda specifically and Africa in general is scanty. This study provides a reliable and detailed description of the anatomical variation and distribution of the vagus nerve in the esophageal hiatus region of post-mortem cases in Uganda.

METHODS

This was an analytical cross-sectional survey of 67 unclaimed post-mortem cases. Data collection used a pretested data collection form. Data were entered into Epi-Info version 6.0 data base then exported into STATA software 13.0 for analysis.

RESULTS

The pattern of the anterior vagal trunk structures at the esophageal hiatus was: single trunk [65.7%]; biplexus [20.9%]; triplexus [8.9%] and double-but-not-connected trunks [4.5%]. The pattern of the posterior trunk structures were: single trunk [85.1%]; biplexus 10.4% and triplexus [4.5%]. There was no statistically significant gender difference in the pattern of vagal fibres. There was no major differences in the pattern from comparable British studies.

CONCLUSION

The study confirmed high variability in the distribution of the vagus nerve at the esophageal hiatus, unrelated to gender differences. Surgeons must consider and identify variants of vagal innervation when carrying out surgery at the gastroesophageal junction to avoid accidental vagal injuries. Published surgical techniques for preserving vagal function are valid in Uganda.

The intestinal neuro-immune axis: crosstalk between neurons, immune cells, and microbes

The gastrointestinal tract is densely innervated by a complex network of neurons that coordinate critical physiological functions. Here, we summarize recent studies investigating the crosstalk between gut-innervating neurons, resident immune cells, and epithelial cells at homeostasis and during infection, food allergy, and inflammatory bowel disease. We introduce the neuroanatomy of the gastrointestinal tract, detailing gut-extrinsic neuron populations from the spinal cord and brain stem, and neurons of the intrinsic enteric nervous system. We highlight the roles these neurons play in regulating the functions of innate immune cells, adaptive immune cells, and intestinal epithelial cells. We discuss the consequences of such signaling for mucosal immunity. Finally, we discuss how the intestinal microbiota is integrated into the neuro-immune axis by tuning neuronal and immune interactions. Understanding the molecular events governing the intestinal neuro-immune signaling axes will enhance our knowledge of physiology and may provide novel therapeutic targets to treat inflammatory diseases.

Highlights and recent developments in allergic diseases in EAACI journals (2019)

The European Academy of Allergy and Clinical Immunology (EAACI) owns three journals: Allergy, Pediatric Allergy and Immunology and Clinical and Translational Allergy. One of the major goals of EAACI is to support health promotion in which prevention of allergy and asthma plays a critical role and to disseminate the knowledge of allergy to all stakeholders including the EAACI junior members. There was substantial progress in 2019 in the identification of basic mechanisms of allergic and respiratory disease and the translation of these mechanisms into clinics. Better understanding of molecular and cellular mechanisms, efforts for the development of biomarkers for disease prediction, novel prevention and intervention studies, elucidation of mechanisms of multimorbidities, entrance of new drugs in the clinics as well as recently completed phase three clinical studies and publication of a large number of allergen immunotherapy studies and meta-analyses have been the highlights of the last year.

Comparison between the cervical and abdominal vagus nerves in mice, pigs, and humans

BACKGROUND

Vagus nerve (VN) stimulation is currently evaluated as a novel approach to treat immune-mediated disorders. The optimal stimulation parameters, however, largely depend on the VN composition potentially impacting on its clinical translation. Hence, we evaluated whether morphological differences exist between the cervical and abdominal VNs across different species.

MATERIALS AND METHODS

The cervical and abdominal VNs of mouse, pig, and humans were stained for major basic protein and neurofilament F to identify the percentage and size of myelinated and non-myelinated fibers.

RESULTS

The percentage of myelinated fibers was comparable between species, but was higher in the cervical VN compared with the abdominal VN. The cervical VN contained 54 ± 4%, 47 ± 7%, and 54 ± 7% myelinated fibers in mouse, pig, and humans, respectively. The myelinated fibers consisted of small-diameter (mouse: 71%, pig: 80%, and humans: 63%), medium-diameter (mouse: 21%, pig: 18%, and humans: 33%), and large-diameter fibers (mouse: 7%, pig: 2%, and humans: 4%). The abdominal VN predominantly contained unmyelinated fibers (mouse: 93%, pig: 90%, and humans: 94%). The myelinated fibers mainly consisted of small-diameter fibers (mouse: 99%, pig: 85%, and humans: 74%) and fewer medium-diameter (mouse: 1%, pig: 13%, and humans: 23%) and large-diameter fibers (mouse: 0%, pig: 2%, and humans: 3%).

CONCLUSION

The VN composition was largely similar with respect to myelinated and unmyelinated fibers in the species studied. Human and porcine VNs had a comparable diameter and similar amounts of fibrous tissue and contained multiple fascicles, implying that the porcine VN may be suitable to optimize stimulation parameters for clinical trials.

Gut macrophages: key players in intestinal immunity and tissue physiology

The mammalian gastrointestinal tract harbors a large reservoir of tissue macrophages, which, in concert with other immune cells, help to maintain a delicate balance between tolerance to commensal microbes and food antigens, and resistance to potentially harmful microbes or toxins. Beyond their roles in resistance and tolerance, recent studies have uncovered novel roles played by tissue-resident, including intestinal-resident macrophages in organ physiology. Here, we will discuss recent advances in the understanding of the origin, phenotype and function of macrophages residing in the different layers of the intestine during homeostasis and under pathological conditions.

Vagus nerve stimulation dampens intestinal inflammation in a murine model of experimental food allergy

Background

The vagus nerve has emerged as an important modulator of the intestinal immune system. Its anti‐inflammatory properties have been previously shown in innate and Th1/Th17 predominant inflammatory models. To what extent the vagus nerve is of importance in Th2 inflammatory responses like food allergy is still unclear. In this study, we therefore aimed to investigate the effect of vagotomy (VGX) and vagus nerve stimulation (VNS), on the development and severity of experimental food allergy.

Methods

Balb/C mice were first sensitized with ovalbumin (OVA) in the presence of alum. Prior to oral challenges with OVA, mice were subjected to VGX or VNS. Disease severity was determined by assessing severity and onset of diarrhoea, OVA‐specific antibody production, mast cell number and activity, inflammatory gene expression in duodenal tissue and lamina propria immune cells by flow cytometry analysis.

Results

When compared to control mice, VGX did not significantly affect the development and severity of the disease in our model of food allergy. VNS, on the other hand, resulted in a significant amelioration of the different inflammatory parameters assessed. This effect was independent of α7nAChR and is possibly mediated through the dampening of mast cells and increased phagocytosis of OVA by CX3CR1^hi macrophages.

Conclusions

These results underscore the anti‐inflammatory properties of the vagus nerve and the potential of neuro‐immune interactions in the intestine. Further insight into the underlying mechanisms could ultimately lead to novel therapeutic approaches in the treatment of not only food allergy but also other immune‐mediated diseases.