Interleukin-6 produced by enteric neurons regulates the number and phenotype of microbe-responsive regulatory T cells in the gut

T cells regulate intestinal motility and shape enteric neuronal responses to intestinal microbiota

How the gut microbiota and immune system maintain intestinal homeostasis in concert with the enteric nervous system (ENS) remains incompletely understood. To address this gap, we assessed small intestinal transit, enteric neuronal density, enteric neurogenesis, intestinal microbiota, immune cell populations and cytokines in wildtype and T-cell deficient germ-free mice colonized with specific pathogen-free (SPF) microbiota, conventionally raised SPF and segmented filamentous bacteria (SFB)-monocolonized mice. SPF microbiota increased small intestinal transit in a T cell-dependent manner. SPF microbiota increased neuronal density in the myenteric and submucosal plexuses of the ileum and colon, similar to conventionally raised SPF mice, independently of T cells. SFB increased neuronal density in the ileum in a T cell-dependent manner, but independently of T cells in the colon. SPF microbiota stimulated enteric neurogenesis (Sox2 expression in enteric neurons) in the ileum in a T cell-dependent manner, but in the colon this effect was T cell-independent. T cells regulated nestin expression in the ENS. SPF colonization increased Th17 cells, RORγT+ Treg cells, and IL-1β and IL-17A levels in the ileum and colon. By neutralizing IL-1β and IL-17A, we observed that they control microbiota-mediated enteric neurogenesis but were not involved in the regulation of motility. Together, these findings provide new insights into the microbiota-neuroimmune dialog that regulates intestinal physiology.

Microbiota-derived IPA alleviates intestinal mucosal inflammation through upregulating Th1/Th17 cell apoptosis in inflammatory bowel disease

The gut microbiota-derived metabolite indole-3-propionic acid (IPA) plays an important role in maintaining intestinal mucosal homeostasis, while the molecular mechanisms underlying IPA regulation on mucosal CD4+ T cell functions in inflammatory bowel disease (IBD) remain elusive. Here we investigated the roles of IPA in modulating mucosal CD4+ T cells and its therapeutic potential in treatment of human IBD. Leveraging metabolomics and microbial community analyses, we observed that the levels of IPA-producing microbiota (e.g. Peptostreptococcus, Clostridium, and Fournierella) and IPA were decreased, while the IPA-consuming microbiota (e.g. Parabacteroides, Erysipelatoclostridium, and Lachnoclostridium) were increased in the feces of IBD patients than those in healthy donors. Dextran sulfate sodium (DSS)-induced acute colitis and CD45RBhighCD4+ T cell transfer-induced chronic colitis models were then established in mice and treated orally with IPA to study its role in intestinal mucosal inflammation in vivo. We found that oral administration of IPA attenuated mucosal inflammation in both acute and chronic colitis models in mice, as characterized by increased body weight, and reduced levels of pro-inflammatory cytokines (e.g. TNF-α, IFN-γ, and IL-17A) and histological scores in the colon. We further utilized RNA sequencing, molecular docking simulations, and surface plasmon resonance analyses and identified that IPA exerts its biological effects by interacting with heat shock protein 70 (HSP70), leading to inducing Th1/Th17 cell apoptosis. Consistently, ectopic expression of HSP70 in CD4+ T cells conferred resistance to IPA-induced Th1/Th17 cell apoptosis. Therefore, these findings identify a previously unrecognized pathway by which IPA modulates intestinal inflammation and provide a promising avenue for the treatment of IBD.

Gut microbiota in hepatocellular carcinoma immunotherapy: immune microenvironment remodeling and gut microbiota modification

Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality, with limited treatment options at advanced stages. The gut microbiota, a diverse community of microorganisms residing in the gastrointestinal tract, plays a pivotal role in regulating immune responses through the gut-liver axis. Emerging evidence underscores its impact on HCC progression and the efficacy of immunotherapy. This review explores the intricate interactions between gut microbiota and the immune system in HCC, with a focus on key immune cells and pathways involved in tumor immunity. Additionally, it highlights strategies for modulating the gut microbiota - such as fecal microbiota transplantation, dietary interventions, and probiotics - as potential approaches to enhancing immunotherapy outcomes. A deeper understanding of these mechanisms could pave the way for novel therapeutic strategies aimed at improving patient prognosis.

Intestinal IL-17 family orchestrates microbiota-driven histone deacetylation and promotes Treg differentiation to mediate the alleviation of asthma by Ma-Xing-Shi-Gan decoction

BACKGROUND

Gut microbiota imbalance is well-known as one important trigger of allergic asthma. Ma-Xing-Shi-Gan decoction (MXSG) is a traditional Chinese medicine prescription with ideal clinical efficacy on asthma. However, whether and how MXSG exerts its efficacy on asthma through gut microbiota remains unclear.

PURPOSE

To investigate the underlying mechanism of MXSG against asthma using multi-omics technologies.

METHODS

An asthma model was established using 8-week-old C57BL/6 J mice, after which they were daily administrated with high-, medium- and low-dose MXSG for 7 days. Histopathological examinations and flow cytometry were performed to evaluate the effects of MXSG on lung immune injury. Key regulatory pathways were predicted via network pharmacology and verified using 16S rRNA sequencing, metagenomics, metabolomics, and in vivo experiments including the knockout of the targeting gene.

RESULTS

MXSG alleviated asthma symptoms, elevated intestinal microbial diversities, and enriched potential beneficial microbes such as Lactococcus, Lactobacillus, and Limosilactobacillus. Network pharmacology and experimental validation highlighted the IL-17/Treg signaling as crucial for asthma treatment. IL-17 knockout experiments revealed its necessity for Treg differentiation during asthma. Moreover, IL-17-deficient asthmatic mice exhibited lower levels of Lactobacillus and significant changes in microbial genes involving histone deacetylases (HDAC) and short-chain fatty acids (SCFAs). Finally, MXSG significantly boosted SCFA production and reduced HDAC9 expression, which were correlated with Treg cell ratios.

CONCLUSION

Our study delineates a novel mechanism where MXSG synergizes with the IL-17 family to enrich intestinal beneficial microbes (e.g. Lactobacillus) and SCFAs. This inhibits the expression of SCFA-downstream HDAC9 to promote Treg differentiation, and thus potentially alleviates asthma.

Gut neuropeptide involvement in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder affecting over 10 million people. A key pathological feature of PD is the accumulation of misfolded α-synuclein (aSyn) protein in the substantia nigra pars compacta. Aggregation of aSyn can form Lewy bodies that contribute to dopaminergic neuron degeneration and motor symptoms, such as tremor, rigidity, and bradykinesia. Beyond the central nervous system, aSyn aggregates have been detected in the gastrointestinal (GI) tract, suggesting a link between peripheral aSyn and nonmotor PD symptoms. GI symptoms, often preceding motor symptoms by up to 20 years, highlight the bidirectional communication between the central nervous system and the enteric nervous system (gut-brain axis) in PD. Although microbiome alterations and intestinal inflammation have been associated with PD, functional impacts on gut-brain signaling or aSyn aggregation remain unclear. Intestinal neuropeptides are key modulators of gut-brain communication, alter immune response to pathogens and environmental toxins, and may contribute to the function of the luminal gut barrier. Dysregulation of gut neuropeptide signaling, including vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide, ghrelin, cholecystokinin, glucagon-like peptide 1, and substance P, have been associated with pathologic effects of PD in animal models. Despite their potential role in pathogenesis and disease modulation, gut neuropeptide roles in PD are underexplored. This article reviews current knowledge surrounding microbial metabolite and immune influences on gut neuropeptide signaling, aSyn aggregation in the enteric nervous system, and downstream neuroimmune pathway alterations within the context of PD and its mouse models.

The role of the enteric nervous system in the pathogenesis of Clostridioides difficile infection

Clostridioides difficile is the leading cause of antibiotic-associated diarrhoea worldwide. In the USA, C. difficile infection (CDI) is the eighth leading cause for hospital readmission and seventh for mortality among all gastrointestinal disorders. Gastrointestinal dysmotility and/or diarrhoea occurs after the acute phase of CDI, but persistent gastrointestinal dysfunction post-infection supports contributions of neuroplasticity in the enteric nervous system (ENS), which has a key role in regulating intestinal motility and secretion, in the natural course of CDI. Here, our goal is to provide an up-to-date summary of how the ENS and extrinsic innervation of the gut are affected by CDI and how ENS responses contribute to CDI pathogenesis and outcomes. Enteric neurons and glia are targets of C. difficile toxins in humans and in preclinical model, and changes to the ENS and extrinsic innervation contribute to intestinal inflammation, damage and secretory diarrhoea. These findings suggest possible bidirectional interaction between CDI and the ENS. More studies focusing on understanding how various neurotransmitters and mediators released by the ENS and extrinsic neurons modulate immune responses to CDI could provide insight into novel pharmacological approaches to balance the host response, improve the management of CDI and prevent gastrointestinal dysfunction post-infection.

A transcriptional atlas of gut-innervating neurons reveals activation of interferon signaling and ferroptosis during intestinal inflammation

Enteric infections often cause long-term sequelae, including persistent gastrointestinal symptoms, such as pain, discomfort, or irritable bowel syndrome. The plethora of sensory symptoms indicates that gut-innervating neurons might be directly affected by inflammation. However, sequencing studies of neurons in the gastrointestinal tract are hampered by difficulties in purifying neurons, especially during inflammation. Activating a nuclear GFP tag selectively in neurons enabled sort purification of intrinsic and extrinsic neurons of the gastrointestinal tract in models of intestinal inflammation. Using bulk and single-nucleus RNA sequencing, we mapped the whole transcriptomic landscape and identified a conserved neuronal response to inflammation, which included the interferon signaling and ferroptosis pathway. Deletion of the interferon receptor 1 in neurons regulated ferroptosis, neuronal loss, and consequently gut-transit time. Collectively, this study offers a resource documenting neuronal adaptation to inflammatory conditions and exposes the interferon and ferroptosis pathways as signaling cascades activated in neurons during inflammation.

Neuroimmune interactions: The bridge between inflammatory bowel disease and the gut microbiota

BACKGROUND

The multidimensional regulatory mechanism of the gut-brain-immune axis in the context of inflammatory bowel disease (IBD) has garnered significant attention, particularly regarding how intestinal microbiota finely regulates immune responses through immune cells and sensory neurons.

MAIN BODY

Metabolites produced by intestinal microbiota influence the phenotype switching of immune cells via complex signalling pathways, thereby modulating their anti-inflammatory and pro-inflammatory functions during intestinal inflammation. Furthermore, sensory neurons exhibit heightened sensitivity to microbial-derived signals, which is essential for preserving intestinal balance and controlling pathological inflammation by integrating peripheral environmental signals with local immune responses. The dynamic equilibrium between immune cells and the neuroimmunoregulation mediated by sensory neurons collectively sustains immune homeostasis within the intestine. However, this coordination mechanism is markedly disrupted under the pathological conditions associated with IBD.

CONCLUSION

An in-depth exploration of the interactions among immune cells, gut microbiota and sensory neurons may yield significant insights into the pathological mechanisms underlying IBD and guide the creation of new treatment approaches.

KEY POINTS

The gut microbiota regulates the gut-brain-immune axis, modulating neuroimmune interactions in IBD. Microbiota-derived metabolites influence immune cells, thereby affecting neurons. Neurons secrete mediators, enabling bidirectional neuroimmune communication essential for intestinal homeostasis. Disruptions contribute to IBD, offering therapeutic targets.

Neurons as Immunomodulators: From Rapid Neural Activity to Prolonged Regulation of Cytokines and Microglia

Regulation of the brain's neuroimmune system is central to development, normal function, and disease. Neuronal communication to microglia, the primary immune cells of the brain, is well known to involve purinergic signaling mediated via ATP secretion and the cytokine fractalkine. Recent evidence shows that neurons release multiple cytokines beyond fractalkine, yet these are less studied and poorly understood. In contrast to ATP, cytokines are a class of signaling molecule that are much larger, with longer signaling and farther diffusion. We posit that neuron-expressed cytokines are an essential mechanism of neuron-microglia communication that arises as part of both normal learning and memory and in response to tissue pathology. Thus, neurons are underappreciated immunomodulatory cells that express diverse immunomodulatory signals. While neuronally sourced cytokines have been understudied, new technical advances make this a timely topic. The goal of this review is to define what is known about the cytokines expressed from neurons, how they are regulated, and the effects of these cytokines on microglia. We delineate key knowledge gaps and needs for new tools to define and analyze neuronal roles in immunomodulation. Given that cytokines are central regulators of microglial function, a broad new body of work is required to illuminate functional links between these neuronally expressed cytokines and sustained and transient microglial function.

Vagal pathway activation links chronic stress to decline in intestinal stem cell function

Chronic stress adversely affects intestinal health, but the specific neural pathways linking the brain to intestinal tissue are not fully understood. Here, we show that chronic stress-induced activation of the central amygdala-dorsal motor nucleus of the vagus (CeA-DMV) pathway accelerates premature aging and impairs the stemness of intestinal stem cells (ISCs). This pathway influences ISC function independently of the microbiota, the hypothalamic-pituitary-adrenal (HPA) axis, the immune response, and the sympathetic nervous system (SNS). Under chronic stress, DMV-mediated vagal activation prompts cholinergic enteric neurons to release acetylcholine (ACh), which engages ISCs via the M3 muscarinic acetylcholine receptor (CHRM3). This interaction activates the p38 mitogen-activated protein kinase (MAPK) pathway, triggering growth arrest and mitochondrial fragmentation, thereby accelerating an aging-like decline in ISCs. Together, our findings provide insights into an alternative neural mechanism that links stress to intestinal dysfunction. Strategies targeting the DMV-associated vagal pathway represent potential therapeutic approaches for stress-induced intestinal diseases.

Decoding the neuroimmune axis in colorectal cancer: From neural circuitry to therapeutic innovation

The nervous and immune systems are two major components that maintain body homeostasis, with their functional roles often overlapping significantly. Both systems are capable of identifying, integrating, and organizing responsive reactions to various external stimuli. The gut, referred to as the "second brain" and the largest immune organ in the body, serves as the most frequent focal site for neuroimmune interactions. Colorectal cancer (CRC), as the predominant solid tumor arising in this neuroimmune-rich microenvironment, remains understudied through the lens of neuroimmune regulatory mechanisms. This review systematically synthesizes current evidence to elucidate the neuroimmune axis in CRC pathogenesis, with particular emphasis on neuroimmune crosstalk-mediated remodeling of tumor immunity. We comprehensively catalog the immunomodulatory effects exerted by principal neuroregulatory mediators, categorized as: (1) neurotransmitters (glutamate, glutamine, γ-aminobutyric acid, epinephrine, norepinephrine, dopamine, serotonin, acetylcholine, and gaseous signaling molecules); (2) neuropeptides (substance P, calcitonin gene-related peptide, vasoactive intestinal peptide); and (3) neurotrophic factors. Furthermore, we critically evaluate the translational prospects and therapeutic challenges of targeting neuroimmune pathways and propose strategic priorities and research focuses for advancing the development of neuroimmune interaction-related therapeutic approaches in CRC.

The gut-organ axis: Clinical aspects and immune mechanisms

The gut-brain axis exemplifies the bidirectional connection between the intestines and the brain, as evidenced by the impact of severe stress on gastrointestinal symptoms including abdominal pain and diarrhea, and conversely, the influence of abdominal discomfort on mood. Clinical observations support the notion of the gut-brain connection, including an increased prevalence of inflammatory bowel disease (IBD) in patients with depression and anxiety, as well as the association of changes in the gut microbiota with neurological disorders such as multiple sclerosis, Parkinson's disease, stroke and Alzheimer's disease. The gut and brain communicate via complex mechanisms involving inflammatory cytokines, immune cells, autonomic nerves, and gut microbiota, which contribute to the pathogenesis in certain gut and brain diseases. Two primary pathways mediate the bidirectional information exchange between the intestinal tract and the brain: signal transduction through bloodstream factors, such as bacterial metabolites and inflammatory cytokines, and neural pathways, such as neurotransmitters and inflammatory cytokines within the autonomic nervous system through the interaction between the nerve cells and beyond. In recent years, the basic mechanisms of the pathophysiology of the gut-brain axis have been gradually elucidated. Beyond the gut-brain interaction, emerging evidence suggests the influence of the gut extends to other organs, such as the liver and lungs, through intricate inter-organ communication pathways. An increasing number of reports on this clinical and basic cross-organ interactions underscore the potential for better understanding and novel therapeutic strategies targeting inter-organs networks. Further clarification of interactions between multiorgans premises transformative insights into cross-organ therapeutic strategies.

Neuroimmune Circuits in Allergic Diseases

Communication between the nervous and immune systems is evolutionarily conserved. From primitive eukaryotes to higher mammals, neuroimmune communication utilizes multiple complex and complementary mechanisms to trigger effective but balanced responses to environmental dangers such as allergens and tissue damage. These responses result from a tight integration of the nervous and immune systems, and accumulating evidence suggests that this bidirectional communication is crucial in modulating the initiation and development of allergic inflammation. In this review, we discuss the basic mechanisms of neuroimmune communication, with a focus on the recent advances underlying the importance of such communication in the allergic immune response. We examine neuronal sensing of allergens, how neuropeptides and neurotransmitters regulate allergic immune cell functions, and how inflammatory factors derived from immune cells coordinate complex peripheral and central nervous system responses. Furthermore, we highlight how fundamental aspects of host biology, from aging to circadian rhythm, might affect these pathways. Appreciating neuroimmune communications as an evolutionarily conserved and functionally integrated system that is fundamentally involved in type 2 immunity will provide new insights into allergic inflammation and reveal exciting opportunities for the management of acute and chronic allergic diseases.

Enteric GABAergic neuron-derived γ-aminobutyric acid initiates expression of Igfbp7 to sustain ILC3 homeostasis

Neuronal signals have emerged as critical factors that regulate group 3 innate lymphoid cell (ILC3) response and tissue homeostasis, but the molecular mechanisms underlying this regulation remain largely elusive. Here, we identified that the enteric GABAergic neuron-derived neurotransmitter γ-aminobutyric acid (GABA) inhibited proliferation and IL-17A production in ILC3s in a manner dependent on the GABA receptors Gabbr1 and Gabbr2. Conditional deletion of Gabbr1 or ablation of GABAergic neurons caused increased IL-17A production and aggravated colitis. Mechanistically, GABA suppressed the expression of the LIP isoform of the transcription factor C/EBP-β in ILC3s, which repressed the transcription of Igfbp7, which encodes the secreted factor Igfbp7. Autocrine Igfbp7 signaling through the receptor Igf1R inhibited ILC3 proliferation and IL-17A production. Suppression of signaling through the GABA-C/EBP-β-IGFBP7 pathway highly correlated with severity of intestinal inflammation in patients with inflammatory bowel disease (IBD). Collectively, our findings describe an important molecular mechanism underlying the maintenance of gut immune homeostasis.

Escherichia Abundance and Metabolism Align with Vitiligo Disease Activity

Vitiligo is a cutaneous autoimmune disorder characterized by progressive depigmentation due to melanocyte destruction by cytotoxic T cells. Genetic factors predispose patients to the disease and are supported by environmental factors that often initiate new disease episodes. We investigated whether disease outcomes were partially defined by pathogenic microbes that drive nutrient deficiency and inflammation. Our study presents the results of research on the diet and gut microbiome composition of patients with vitiligo and healthy controls from Kazakhstan and the United States. Dietary nutrient intake was assessed using the National Institutes of Health-generated Diet History Questionnaire. Patients with active vitiligo exhibit a limited intake of specific fatty acids, amino acids, fiber, and zinc. Disease activity was further characterized by the abundance of Odoribacter and Escherichia in the gut. Metabolic pathway analysis supported the role of the Escherichia genus in disease activity by limiting energy metabolism and amino acid biosynthetic pathways. Disease activity also aligned with elevated circulating pro-inflammatory cytokines. These findings suggest that nutritional limitations are not compensated by metabolites from the gut microbiome in active disease, potentially leaving room for inflammation and exacerbating vitiligo. The intricate relationship among diet, gut microbiome composition, and disease progression in vitiligo highlights potential avenues for targeted interventions to reduce autoimmune activity and improve patient outcomes.

Nerve-racking worms

The enteric nervous system is a key regulator of inflammation, crosstalking directly with the immune system at the mucosal surfaces of the gastrointestinal tract. In this issue of Immunity, Wang and colleagues demonstrate that intrinsic enteric neurons (iENs) sense interleukin (IL)-13 to restrain group 2 innate lymphoid cell (ILC2) activity during helminth infection, uncovering a novel neuro-immune-regulatory circuit.

The Acute Effects of a Fast-Food Meal Versus a Mediterranean Food Meal on the Autonomic Nervous System, Lung Function, and Airway Inflammation: A Randomized Crossover Trial

BACKGROUND/OBJECTIVES

This study aimed to assess the acute effects of two isoenergetic but micronutrient-diverse meals-a Mediterranean-like meal (MdM) and a fast food-like meal (FFM)-on the autonomic nervous system (ANS), lung function, and airway inflammation response.

METHODS

Forty-six participants were enrolled in a randomized crossover clinical trial, consuming two isoenergetic meals: FFM (burger, fries, and sugar-sweetened drink) and MdM (vegetable soup, whole-wheat pasta, salad, olive oil, sardines, fruit, and water). Pupillometry assessed parasympathetic (MaxD, MinD, Con, ACV, MCV) and sympathetic (ADV, T75) nervous system outcomes. Lung function and airway inflammation were measured before and after each meal through spirometry and fractional exhaled nitric oxide (FeNO), respectively.

RESULTS

Mixed-effects model analysis showed that the MdM was associated with a hegemony of parasympathetic responses, with a significant increase of MaxD associated with a faster constriction velocity (ACV and MCV); on the other side, the FFM was associated with changes in the sympathetic response, showing a quicker redilation velocity (a decrease in T75). After adjusting for confounders, the mixed-effects models revealed that the FFM significantly decreased T75. Regarding lung function, a meal negatively impacted FVC (ae = -0.079, p < 0.001) and FEV1 (ae = -0.04, p = 0.017); however, FeNO increased, although after adjusting, no difference between meals was seen.

CONCLUSIONS

Our study showed that the FFM counteracted the parasympathetic activity of a meal, while a meal, irrespective of the type, decreased lung function and increased airway inflammation.

Current status and future directions in food protein-induced enterocolitis syndrome: An NIAID workshop report of the June 22, 2022, virtual meeting

Food protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated gastrointestinal food allergy characterized by delayed, protracted vomiting and accompanied by lethargy and pallor, usually 1 to 4 hours after ingesting the food allergen. The pathophysiology of FPIES remains unknown, and currently there are no diagnostic biomarkers available to assess disease activity or its resolution. Over the last 2 decades, FPIES has become increasingly recognized in both pediatric and adult patients. Forty years after the initial FPIES description, the first FPIES code appeared in the International Classification of Diseases, Tenth Revision (ICD-10), and the first international consensus guidelines for the diagnosis and management of FPIES were published. On June 22, 2022, the National Institute of Allergy and Infectious Diseases (NIAID) held its first virtual multidisciplinary workshop on FPIES. Various clinical and translational aspects of FPIES as well as important areas of unmet needs were discussed as priorities for future research during this 2-day virtual workshop. Our report provides a summary of content of the workshop, including updated literature on the topic areas, and also provides critical commentary on the state of FPIES.

Neuro-immune cell interactions in the regulation of intestinal immune homeostasis

PURPOSE OF REVIEW

Bidirectional regulation between neurons and immune cells in the intestine governs essential physiological processes, including digestion, metabolism and motility, while also controlling intestinal inflammation and maintaining tissue homeostasis. This review covers recent advances and future research challenges focused on the regulatory molecules and potential therapeutic targets in neuron-immune interactions within the intestine.

RECENT FINDINGS

Recently identified molecular and cellular pathways have been shown to regulate neuron-immune cell cross talk in the context of maintaining tissue homeostasis, modulating inflammation, and promoting intestinal repair. Additionally, behaviors governed by the central nervous system, including feeding and stress responses, can play key roles in regulating intestinal immunity and inflammation.

SUMMARY

This review emphasizes recent progress in understanding the complex interplay between the nervous system and intestinal immune system and outlines future research directions. These advances have the potential to lead to innovative therapies targeting gastrointestinal disorders including inflammatory bowel diseases, allergic responses and cancer.

Early subclinical stages of the inflammatory bowel diseases: insights from human and animal studies

The inflammatory bowel diseases (IBD) occur in genetically susceptible individuals that mount inappropriate immune responses to their microbiota leading to chronic intestinal inflammation. The natural history of IBD progression begins with early subclinical stages of disease that occur before clinical diagnosis. Improved understanding of those early subclinical stages could lead to new or improved strategies for IBD diagnosis, prognostication, or prevention. Here, we review our current understanding of the early subclinical stages of IBD in humans including studies from first-degree relatives of patients with IBD and members of the general population who go on to develop IBD. We also discuss representative mouse models of IBD that can be used to investigate disease dynamics and host-microbiota relationships during these early stages. In particular, we underscore how mouse models of IBD that develop disease later in life with variable penetrance may present valuable opportunities to discern early subclinical mechanisms of disease before histological inflammation and other severe symptoms become apparent.

Investigating tributyltin's toxic effects: Intestinal barrier and neuroenteric disruption in rat's jejunum

The expansion of economic activities in coastal areas has significantly increased chemical contamination, leading to major environmental challenges. Contaminants enter the human body through the food chain, particularly via seafood and water consumption, triggering biomagnification and bioaccumulation processes. The gastrointestinal tract (GIT) acts as a selective barrier, protecting against chemical pollutants and maintaining homeostasis through a complex network of cells and immune responses. This study assessed impact of tributyltin (TBT), a highly toxic organometallic compound used in antifouling coatings for ships, on the GIT and myenteric neural plasticity in young rats. TBT exposure leads to histopathological changes, including epithelial detachment and inflammatory foci, especially at lower environmental doses. The study found that TBT causes significant reductions in villi height, increases in goblet cells and intraepithelial lymphocytes, and disrupts the myenteric plexus, with higher densities of extraganglionic neurons in exposed animals.

The role of reactive enteric glia-macrophage interactions in acute and chronic inflammation

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.

Development of a non-invasive bioassay for adiponectin target engagement in mice

Adiponectin-based therapeutic strategies are promising for managing metabolic diseases and reducing inflammation, prompting the development of adiponectin receptor agonists. However, monitoring their pharmacodynamic actions in clinical applications is challenging. This study aimed to identify peripheral biomarkers to monitor adiponectin actions using ALY688, an adiponectin receptor agonist peptide. RNA sequencing analysis of whole blood identified a cluster of genes that were significantly increased in the ALY688-treated group compared to the control. This gene cluster was validated by qPCR and further confirmed in human peripheral blood mononuclear cells treated with ALY688 ex vivo. We also confirmed a functional outcome of ALY688 action in mice as our study also demonstrated the anti-inflammatory effect of ALY688 in a sublethal LPS mouse model. In summary, a newly identified gene cluster signature is suitable for assessing the pharmacodynamic action of adiponectin or its mimetics in blood samples.

Neuroimmune Crossroads: The Interplay of the Enteric Nervous System and Intestinal Macrophages in Gut Homeostasis and Disease

A defining unique characteristic of the gut immune system is its ability to respond effectively to foreign pathogens while mitigating unnecessary inflammation. Intestinal macrophages serve as the cornerstone of this balancing act, acting uniquely as both the sword and shield in the gut microenvironment. The GI tract is densely innervated by the enteric nervous system (ENS), the intrinsic nervous system of the gut. Recent advances in sequencing technology have increasingly suggested neuroimmune crosstalk as a critical component for homeostasis both within the gut and in other tissues. Here, we systematically review the ENS-macrophage axis. We focus on the pertinent molecules produced by the ENS, spotlight the mechanistic contributions of intestinal macrophages to gut homeostasis and inflammation, and discuss both existing and potential strategies that intestinal macrophages use to integrate signals from the ENS. This review aims to elucidate the complex molecular basis governing ENS-macrophage signaling, highlighting their cooperative roles in sustaining intestinal health and immune equilibrium.

Coinhibitory Molecule VISTA Play an Important Negative Regulatory Role in the Immunopathology of Bronchial Asthma

Objective

To investigate the significance of VISTA in bronchial asthma and its impact on the disease.

Methods

Human peripheral blood of asthma children was gathered. The expression concentrations of VISTA, IL-4, IL-6, CD25, CD40L, and PD-L2 in peripheral blood plasma were detected by ELISA. We established the mouse model of asthma and intervened with agonistic anti-VISTA mAb (4C11) and VISTA fusion protein. ELISA, flow cytometry, and Western blotting were performed to detect the expression levels of Th1, Th2, and Th17 cell subsets and related characteristic cytokines, as well as the protein levels of MAPKs, NF-κB, and TRAF6 in lung tissues. In addition, the infiltration of eosinophils and inflammatory cells, airway mucus secretion, and VISTA protein expression in lung histopathological sections of different groups of mice were analyzed.

Results

The concentration of VISTA in human asthma group decreased significantly (p < 0.05); A positive correlation was observed between VISTA and CD40L. The intervention of 4C11 mAb and fusion protein respectively during the induction period increase the differentiation of Th1 cells and the secretion of IFN-γ, and inhibit the differentiation of Th2 and Th17 cells, as well as the secretion of IL-4, IL-5, IL-13 and IL-17, partially reduce the pathological changes of asthma in mouse lungs and correct the progress of asthma. The MAPK, NF-κB, and TRAF6 protein levels were the middle range in the 4C11 mAb and fusion protein groups (p < 0.05).

Conclusion

The findings suggest VISTA may play a negative regulatory role in the occurrence and development of bronchial asthma.

Pathogenic mechanisms in the evolution of food allergy

The early development of the neonatal immune system is profoundly influenced by exposure to dietary and microbial antigens, which shapes mucosal tolerance. Successful oral tolerance induction is crucially dependent on microbially imprinted immune cells, most notably the RORγt+ regulatory T (Treg) and antigen presenting cells and is essential for preventing food allergy (FA). The development of FA can be envisioned to result from disruptions at key checkpoints (CKPTs) that govern oral tolerance induction. These include gut epithelial sensory and effector circuits that when dysregulated promote pro-allergic gut dysbiosis. They also include microbially imprinted immune regulatory circuits that are disrupted by dysbiosis and pro-allergic immune responses unleashed by the dysregulation of the aforementioned cascades. Understanding these checkpoints is essential for developing therapeutic strategies to restore immune homeostasis in FA.

Ageing-related bone and immunity changes: insights into the complex interplay between the skeleton and the immune system

Ageing as a natural irreversible process inherently results in the functional deterioration of numerous organ systems and tissues, including the skeletal and immune systems. Recent studies have elucidated the intricate bidirectional interactions between these two systems. In this review, we provide a comprehensive synthesis of molecular mechanisms of cell ageing. We further discuss how age-related skeletal changes influence the immune system and the consequent impact of immune system alterations on the skeletal system. Finally, we highlight the clinical implications of these findings and propose potential strategies to promote healthy ageing and reduce pathologic deterioration of both the skeletal and immune systems.

A chemogenetic screen reveals that Trpv1-expressing neurons control regulatory T cells in the gut

Neuroimmune cross-talk participates in intestinal tissue homeostasis and host defense. However, the matrix of interactions between arrays of molecularly defined neuron subsets and of immunocyte lineages remains unclear. We used a chemogenetic approach to activate eight distinct neuronal subsets, assessing effects by deep immunophenotyping, microbiome profiling, and immunocyte transcriptomics in intestinal organs. Distinct immune perturbations followed neuronal activation: Nitrergic neurons regulated T helper 17 (TH17)-like cells, and cholinergic neurons regulated neutrophils. Nociceptor neurons, expressing Trpv1, elicited the broadest immunomodulation, inducing changes in innate lymphocytes, macrophages, and RORγ+ regulatory T (Treg) cells. Neuroanatomical, genetic, and pharmacological follow-up showed that Trpv1+ neurons in dorsal root ganglia decreased Treg cell numbers via the neuropeptide calcitonin gene-related peptide (CGRP). Given the role of these neurons in nociception, these data potentially link pain signaling with gut Treg cell function.

Systematic Insights into the Relationship between the Microbiota-Gut-Brain Axis and Stroke with the Focus on Tryptophan Metabolism

Stroke, as a serious cerebral vascular disease with high incidence and high rates of disability and mortality, has limited therapeutic options due to the narrow time window. Compelling evidence has highlighted the significance of the gut microbiota and gut-brain axis as critical regulatory factors affecting stroke. Along the microbiota-gut-brain axis, tryptophan metabolism further acquires increasing attention for its intimate association with central nervous system diseases. For the purpose of exploring the potential role of tryptophan metabolism in stroke and providing systematic insights into the intricate connection of the microbiota-gut-brain axis with the pathological procedure of stroke, this review first summarized the practical relationship between microbiota and stroke by compiling the latest case-control research. Then, the microbiota-gut-brain axis, as well as its interaction with stroke, were comprehensively elucidated on the basis of the basic anatomical structure and physiological function. Based on the crosstalk of microbiota-gut-brain, we further focused on the tryptophan metabolism from the three major metabolic pathways, namely, the kynurenine pathway, serotonin pathway, and microbial pathway, within the axis. Moreover, the effects of tryptophan metabolism on stroke were appreciated and elaborated here, which is scarcely found in other reviews. Hopefully, the systematic illustration of the mechanisms and pathways along the microbiota-gut-brain axis will inspire more translational research from metabolic perspectives, along with more attention paid to tryptophan metabolism as a promising pharmaceutical target in order to reduce the risk of stroke, mitigate the stroke progression, and ameliorate the stroke prognosis.

Stability and plasticity of regulatory T cells in health and disease

The mechanisms that negatively regulate inflammation upon a pathogenic stimulus are crucial for the maintenance of tissue integrity and organ function. T regulatory cells are one of the main drivers in controlling inflammation. The ability of T regulatory cells to adapt to different inflammatory cues and suppress inflammation is one of the relevant features of T regulatory cells. During this process, T regulatory cells express different transcription factors associated with their counterparts, Th helper cells, including Tbx21, GATA-3, Bcl6, and Rorc. The acquisition of this transcription factor helps the T regulatory cells to suppress and migrate to the different inflamed tissues. Additionally, the T regulatory cells have different mechanisms that preserve stability while acquiring a particular T regulatory cell subtype. This review focuses on describing T regulatory cell subtypes and the mechanisms that maintain their identity in health and diseases.

Azathioprine promotes intestinal epithelial cell differentiation into Paneth cells and alleviates ileal Crohn's disease severity

Paneth cells (PCs), a subset of intestinal epithelial cells (IECs) found at the base of small intestinal crypts, play an essential role in maintaining intestinal homeostasis. Altered PCs function is associated with diverse intestinal pathologies, including ileal Crohn's disease (CD). CD patients with ileal involvement have been previously demonstrated to display impairment in PCs and decreased levels of anti-microbial peptides. Although the immunosuppressive drug Azathioprine (AZA) is widely used in CD therapy, the impact of AZA on IEC differentiation remains largely elusive. In the present study, we hypothesized that the orally administered drug AZA also exerts its effect through modulation of the intestinal epithelium and specifically via modulation of PC function. AZA-treated CD patients exhibited an ileal upregulation of AMPs on both mRNA and protein levels compared to non-AZA treated patients. Upon in vitro AZA stimulation, intestinal epithelial cell line MODE-K exhibited heightened expression levels of PC marker in concert with diminished cell proliferation but boosted mitochondrial OXPHOS activity. Moreover, differentiation of IECs, including PCs differentiation, was boosted in AZA-treated murine small intestinal organoids and was associated with decreased D-glucose consumption and decreased growth rates. Of note, AZA treatment strongly decreased Lgr5 mRNA expression as well as Ki67 positive cells. Further, AZA restored dysregulated PCs associated with mitochondrial dysfunction. AZA-dependent inhibition of IEC proliferation is accompanied by boosted mitochondria function and IEC differentiation into PC.

Immunological regulation of skeletal muscle adaptation to exercise

Exercise has long been acknowledged for its powerful disease-preventing, health-promoting effects. However, the cellular and molecular mechanisms responsible for the beneficial effects of exercise are not fully understood. Inflammation is a component of the stress response to exercise. Recent work has revealed that such inflammation is not merely a symptom of exertion; rather, it is a key regulator of exercise adaptations, particularly in skeletal muscle. The purpose of this piece is to provide a conceptual framework that we hope will integrate exercise immunology with exercise physiology, muscle biology, and cellular immunology. We start with an overview of early studies in the field of exercise immunology, followed by an exploration of the importance of stromal cells and immunocytes in the maintenance of muscle homeostasis based on studies of experimental muscle injury. Subsequently, we discuss recent advances in our understanding of the functions and physiological relevance of the immune system in exercised muscle. Finally, we highlight a potential immunological basis for the benefits of exercise in musculoskeletal diseases and aging.

Challenges in IBD Research 2024: Preclinical Human IBD Mechanisms

Preclinical human inflammatory bowel disease (IBD) mechanisms is one of 5 focus areas of the Challenges in IBD Research 2024 document, which also includes environmental triggers, novel technologies, precision medicine, and pragmatic clinical research. Herein, we provide a comprehensive overview of current gaps in inflammatory bowel diseases research that relate to preclinical research and deliver actionable approaches to address them with a focus on how these gaps can lead to advancements in IBD interception, remission, and restoration. The document is the result of multidisciplinary input from scientists, clinicians, patients, and funders and represents a valuable resource for patient-centric research prioritization. This preclinical human IBD mechanisms section identifies major research gaps whose investigation will elucidate pathways and mechanisms that can be targeted to address unmet medical needs in IBD. Research gaps were identified in the following areas: genetics, risk alleles, and epigenetics; the microbiome; cell states and interactions; barrier function; IBD complications (specifically fibrosis and stricturing); and extraintestinal manifestations. To address these gaps, we share specific opportunities for investigation for basic and translational scientists and identify priority actions.

Critical role of the gut microbiota in immune responses and cancer immunotherapy

The gut microbiota plays a critical role in the progression of human diseases, especially cancer. In recent decades, there has been accumulating evidence of the connections between the gut microbiota and cancer immunotherapy. Therefore, understanding the functional role of the gut microbiota in regulating immune responses to cancer immunotherapy is crucial for developing precision medicine. In this review, we extract insights from state-of-the-art research to decipher the complicated crosstalk among the gut microbiota, the systemic immune system, and immunotherapy in the context of cancer. Additionally, as the gut microbiota can account for immune-related adverse events, we discuss potential interventions to minimize these adverse effects and discuss the clinical application of five microbiota-targeted strategies that precisely increase the efficacy of cancer immunotherapy. Finally, as the gut microbiota holds promising potential as a target for precision cancer immunotherapeutics, we summarize current challenges and provide a general outlook on future directions in this field.

The Imperative for Innovative Enteric Nervous System-Intestinal Organoid Co-Culture Models: Transforming GI Disease Modeling and Treatment

This review addresses the need for innovative co-culture systems integrating the enteric nervous system (ENS) with intestinal organoids. The breakthroughs achieved through these techniques will pave the way for a transformative era in gastrointestinal (GI) disease modeling and treatment strategies. This review serves as an introduction to the companion protocol paper featured in this journal. The protocol outlines the isolation and co-culture of myenteric and submucosal neurons with small intestinal organoids. This review provides an overview of the intestinal organoid culture field to establish a solid foundation for effective protocol application. Remarkably, the ENS surpasses the number of neurons in the spinal cord. Referred to as the "second brain", the ENS orchestrates pivotal roles in GI functions, including motility, blood flow, and secretion. The ENS is organized into myenteric and submucosal plexuses. These plexuses house diverse subtypes of neurons. Due to its proximity to the gut musculature and its cell type complexity, there are methodological intricacies in studying the ENS. Diverse approaches such as primary cell cultures, three-dimensional (3D) neurospheres, and induced ENS cells offer diverse insights into the multifaceted functionality of the ENS. The ENS exhibits dynamic interactions with the intestinal epithelium, the muscle layer, and the immune system, influencing epithelial physiology, motility, immune responses, and the microbiome. Neurotransmitters, including acetylcholine (ACh), serotonin (5-HT), and vasoactive intestinal peptide (VIP), play pivotal roles in these intricate interactions. Understanding these dynamics is imperative, as the ENS is implicated in various diseases, ranging from neuropathies to GI disorders and neurodegenerative diseases. The emergence of organoid technology presents an unprecedented opportunity to study ENS interactions within the complex milieu of the small and large intestines. This manuscript underscores the urgent need for standardized protocols and advanced techniques to unravel the complexities of the ENS and its dynamic relationship with the gut ecosystem. The insights gleaned from such endeavors hold the potential to revolutionize GI disease modeling and treatment paradigms.

Piezo1-Mediated Neurogenic Inflammatory Cascade Exacerbates Ventricular Remodeling After Myocardial Infarction

BACKGROUND

Heart failure is associated with a high rate of mortality and morbidity, and ventricular remodeling invariably precedes heart failure. Ventricular remodeling is fundamentally driven by mechanotransduction that is regulated by both the nervous system and the immune system. However, it remains unknown which key molecular factors govern the neuro/immune/cardio axis that underlies mechanotransduction during ventricular remodeling. Here, we investigated whether the mechanosensitive Piezo cation channel-mediated neurogenic inflammatory cascade underlies ventricular remodeling-related mechanotransduction.

METHODS

By ligating the left coronary artery of rats to establish an in vivo model of chronic myocardial infarction (MI), lentivirus-mediated thoracic dorsal root ganglion (TDRG)-specific Piezo1 knockdown rats and adeno-associated virus-PHP.S-mediated TDRG neuron-specific Piezo1 knockout mice were used to investigate whether Piezo1 in the TDRG plays a functional role during ventricular remodeling. Subsequently, neutralizing antibody-mediated TDRG IL-6 (interleukin-6) inhibition rats and adeno-associated virus-PHP.S-mediated TDRG neuron-specific IL-6 knockdown mice were used to determine the mechanism underlying neurogenic inflammation. Primary TDRG neurons were used to evaluate Piezo1 function in vitro.

RESULTS

Expression of Piezo1 and IL-6 was increased, and these factors were functionally activated in TDRG neurons at 4 weeks after MI. Both knockdown of TDRG-specific Piezo1 and deletion of TDRG neuron-specific Piezo1 lessened the severity of ventricular remodeling at 4 weeks after MI and decreased the level of IL-6 in the TDRG or heart. Furthermore, inhibition of TDRG IL-6 or knockdown of TDRG neuron-specific IL-6 also ameliorated ventricular remodeling and suppressed the IL-6 cascade in the heart, whereas the Piezo1 level in the TDRG was not affected. In addition, enhanced Piezo1 function, as reflected by abundant calcium influx induced by Yoda1 (a selective agonist of Piezo1), led to increased release of IL-6 from TDRG neurons in mice 4 weeks after MI.

CONCLUSIONS

Our findings point to a critical role for Piezo1 in ventricular remodeling at 4 weeks after MI and reveal a neurogenic inflammatory cascade as a previously unknown facet of the neuronal immune signaling axis underlying mechanotransduction.

Navigating the blurred path of mixed neuroimmune signaling

Evolution has created complex mechanisms to sense environmental danger and protect tissues, with the nervous and immune systems playing pivotal roles. These systems work together, coordinating local and systemic reflexes to restore homeostasis in response to tissue injury and infection. By sharing receptors and ligands, they influence the pathogenesis of various diseases. Recently, a less-explored aspect of neuroimmune communication has emerged: the release of neuropeptides from immune cells and cytokines/chemokines from sensory neurons. This article reviews evidence of this unique neuroimmune interplay and its impact on the development of allergy, inflammation, itch, and pain. We highlight the effects of this neuroimmune signaling on vital processes such as host defense, tissue repair, and inflammation resolution, providing avenues for exploration of the underlying mechanisms and therapeutic potential of this signaling.

IRF4-mediated Treg phenotype switching can aggravate hyperoxia-induced alveolar epithelial cell injury

Bronchopulmonary dysplasia (BPD) is characterized by alveolar dysplasia, and evidence indicates that interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various inflammatory lung diseases. Nonetheless, the significance and mechanism of IRF4 in BPD remain unelucidated. Consequently, we established a mouse model of BPD through hyperoxia exposure, and ELISA was employed to measure interleukin-17 A (IL-17 A) and interleukin-6 (IL-6) expression levels in lung tissues. Western blotting was adopted to determine the expression of IRF4, surfactant protein C (SP-C), and podoplanin (T1α) in lung tissues. Flow cytometry was utilized for analyzing the percentages of FOXP3+ regulatory T cells (Tregs) and FOXP3+RORγt+ Tregs in CD4+ T cells in lung tissues to clarify the underlying mechanism. Our findings revealed that BPD mice exhibited disordered lung tissue structure, elevated IRF4 expression, decreased SP-C and T1α expression, increased IL-17 A and IL-6 levels, reduced proportion of FOXP3+ Tregs, and increased proportion of FOXP3+RORγt+ Tregs. For the purpose of further elucidating the effect of IRF4 on Treg phenotype switching induced by hyperoxia in lung tissues, we exposed neonatal mice with IRF4 knockout to hyperoxia. These mice exhibited regular lung tissue structure, increased proportion of FOXP3+ Tregs, reduced proportion of FOXP3+RORγt+ Tregs, elevated SP-C and T1α expression, and decreased IL-17 A and IL-6 levels. In conclusion, our findings demonstrate that IRF4-mediated Treg phenotype switching in lung tissues exacerbates alveolar epithelial cell injury under hyperoxia exposure.

Interplay between Microbiota and γδ T Cells: Insights into Immune Homeostasis and Neuro-Immune Interactions

The gastrointestinal (GI) tract of multicellular organisms, especially mammals, harbors a symbiotic commensal microbiota with diverse microorganisms including bacteria, fungi, viruses, and other microbial and eukaryotic species. This microbiota exerts an important role on intestinal function and contributes to host health. The microbiota, while benefiting from a nourishing environment, is involved in the development, metabolism and immunity of the host, contributing to the maintenance of homeostasis in the GI tract. The immune system orchestrates the maintenance of key features of host-microbe symbiosis via a unique immunological network that populates the intestinal wall with different immune cell populations. Intestinal epithelium contains lymphocytes in the intraepithelial (IEL) space between the tight junctions and the basal membrane of the gut epithelium. IELs are mostly CD8+ T cells, with the great majority of them expressing the CD8αα homodimer, and the γδ T cell receptor (TCR) instead of the αβ TCR expressed on conventional T cells. γδ T cells play a significant role in immune surveillance and tissue maintenance. This review provides an overview of how the microbiota regulates γδ T cells and the influence of microbiota-derived metabolites on γδ T cell responses, highlighting their impact on immune homeostasis. It also discusses intestinal neuro-immune regulation and how γδ T cells possess the ability to interact with both the microbiota and brain.

Role reversals: non-canonical roles for immune and non-immune cells in the gut

The intestine is home to an intertwined network of epithelial, immune, and neuronal cells as well as the microbiome, with implications for immunity, systemic metabolism, and behavior. While the complexity of this microenvironment has long since been acknowledged, recent technological advances have propelled our understanding to an unprecedented level. Notably, the microbiota and non-immune or structural cells have emerged as important conductors of intestinal immunity, and by contrast, cells of both the innate and adaptive immune systems have demonstrated non-canonical roles in tissue repair and metabolism. This review highlights recent works in the following two streams: non-immune cells of the intestine performing immunological functions; and traditional immune cells exhibiting non-immune functions in the gut.

The crosstalk between enteric nervous system and immune system in intestinal development, homeostasis and diseases

The gut is the largest digestive and absorptive organ, which is essential for induction of mucosal and systemic immune responses, and maintenance of metabolic-immune homeostasis. The intestinal components contain the epithelium, stromal cells, immune cells, and enteric nervous system (ENS), as well as the outers, such as gut microbiota, metabolites, and nutrients. The dyshomeostasis of intestinal microenvironment induces abnormal intestinal development and functions, even colon diseases including dysplasia, inflammation and tumor. Several recent studies have identified that ENS plays a crucial role in maintaining the immune homeostasis of gastrointestinal (GI) microenvironment. The crosstalk between ENS and immune cells, mainly macrophages, T cells, and innate lymphoid cells (ILCs), has been found to exert important regulatory roles in intestinal tissue programming, homeostasis, function, and inflammation. In this review, we mainly summarize the critical roles of the interactions between ENS and immune cells in intestinal homeostasis during intestinal development and diseases progression, to provide theoretical bases and ideas for the exploration of immunotherapy for gastrointestinal diseases with the ENS as potential novel targets.

Homeostatic, repertoire and transcriptional relationships between colon T regulatory cell subsets

Foxp3+ regulatory T cells (Tregs) in the colon are key to promoting peaceful coexistence with symbiotic microbes. Differentiated in either thymic or peripheral locations, and modulated by microbes and other cellular influencers, colonic Treg subsets have been identified through key transcription factors (TFs; Helios, Rorγ, Gata3, and cMaf), but their interrelationships are unclear. Applying a multimodal array of immunologic, genomic, and microbiological assays, we find more overlap than expected between populations. The key TFs (Rorγ, Helios, Gata3, and cMaf) play different roles, some essential for subset identity, others driving functional gene signatures. Functional divergence was clearest under challenge. Single-cell genomics revealed a spectrum of phenotypes between the Helios+ and Rorγ+ poles, different Treg-inducing bacteria inducing the same Treg phenotypes to varying degrees, not distinct populations. TCR repertoires in monocolonized mice revealed that Helios+ and Rorγ+ Tregs are related and cannot be uniquely equated to tTreg and pTreg. Comparison of spleen and colon repertoires revealed that 2 to 5% of clonotypes are shared between the locations. We propose that rather than the origin of their differentiation, tissue-specific cues dictate the spectrum of colonic Treg phenotypes.

Breast cancer stem cells generate immune-suppressive T regulatory cells by secreting TGFβ to evade immune-elimination

Cancer stem cells (CSCs), being the primary contributors in tumor initiation, metastasis, and relapse, ought to have seminal roles in evasion of immune surveillance. Tumor-promoting CD4+CD25+FOXP3+ T-regulatory cells (Tregs) have been described to abolish host defense mechanisms by impeding the activities of other immune cells including effector T cells. However, whether CSCs can convert effector T cells to immune-suppressive Treg subset, and if yes, the mechanism underlying CSC-induced Treg generation, are limitedly studied. In this regard, we observed a positive correlation between breast CSC and Treg signature markers in both in-silico and immunohistochemical analyses. Mirroring the conditions during tumor initiation, low number of CSCs could successfully generate CD4+CD25+FOXP3+ Treg cells from infiltrating CD4+ T lymphocytes in a contact-independent manner. Suppressing the proliferation potential as well as IFNγ production capacity of effector T cells, these Treg cells might be inhibiting antitumor immunity, thereby hindering immune-elimination of CSCs during tumor initiation. Furthermore, unlike non-stem cancer cells (NSCCs), CSCs escaped doxorubicin-induced apoptosis, thus constituting major surviving population after three rounds of chemotherapy. These drug-survived CSCs were also able to generate CD4+CD25+FOXP3+ Treg cells. Our search for the underlying mechanism further unveiled the role of CSC-shed immune-suppressive cytokine TGFβ, which was further increased by chemotherapy, in generating tumor Treg cells. In conclusion, during initiation as well as after chemotherapy, when NSCCs are not present in the tumor microenvironment, CSCs, albeit present in low numbers, generate immunosuppressive CD4+CD25+FOXP3+ Treg cells in a contact-independent manner by shedding high levels of immune-suppressive Treg-polarizing cytokine TGFβ, thus escaping immune-elimination and initiating the tumor or causing tumor relapse.

Hourglass, a rapid analysis framework for heterogeneous bioimaging data, identifies sex disparity in IL-6/STAT3-associated immune phenotypes in pancreatic cancer

Integration and mining of bioimaging data remains a challenge and lags behind the rapidly expanding digital pathology field. We introduce Hourglass, an open-access analytical framework that streamlines biology-driven visualization, interrogation, and statistical assessment of multiparametric datasets. Cognizant of tissue and clinical heterogeneity, Hourglass systematically organizes observations across spatial and global levels and within patient subgroups. Applied to an extensive bioimaging dataset, Hourglass promptly consolidated a breadth of known interleukin-6 (IL-6) functions via its downstream effector STAT3 and uncovered a so-far unknown sexual dimorphism in the IL-6/STAT3-linked intratumoral T-cell response in human pancreatic cancer. As an R package and cross-platform application, Hourglass facilitates knowledge extraction from multi-layered bioimaging datasets for users with or without computational proficiency and provides unique and widely accessible analytical means to harness insights hidden within heterogeneous tissues at the sample and patient level. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Human HLA prolongs the host inflammatory response in Streptococcus suis serotype 2 infection compared to mouse H2 molecules

Streptococcus suis (S. suis) is widely acknowledged as a significant zoonotic pathogen in Southeast Asia and China, which has led to a substantial number of fatalities in both swine and humans. Despite the prevalent use of mice as the primary animal model to study S. suis pathogenesis, the substantial differences in the major histocompatibility complex (MHC) between humans and mice underscore the ongoing exploration for a more suitable and effective animal model. In this study, humanized transgenic HLA-A11/DR1 genotypes mice were used to evaluate the differences between humanized HLA and murine H2 in S. suis infection. Following intravenous administration of S. suis suspensions, we investigated bacterial load, cytokine profiles, pathological alterations, and immune cell recruitment in both Wild-type (WT) and humanized mice across different post-infection time points. Relative to WT mice, humanized mice exhibited heightened pro-inflammatory cytokines, exacerbated tissue damage, increased granulocyte recruitment with impaired resolution, notably more pronounced during the late infection stage. Additionally, our examination of bacterial clearance rates suggests that HLA-A11/DR1 primarily influences cell recruitment and mitochondrial reactive oxygen species (ROS) production, which affects the bacterial killing capacity of macrophages in the late stage of infection. The reduced IL-10 production and lower levels of regulatory T cells in humanized mice could underlie their compromised resolution ability. Intervention with IL-10 promotes bacterial clearance and inflammatory regression in the late stages of infection in transgenic mice. Our findings underscore the heightened sensitivity of HLA-A11/DR1 mice with impaired resolution to S. suis infection, effectively mirroring the immune response seen in humans during infection. The humanized HLA-A11/DR1 mice could serve as an optimal animal model for investigating the pathogenic and therapeutic mechanisms associated with sepsis and other infectious diseases.

Enteric neuro-immune interactions in intestinal health and disease

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.

The role of cellular and molecular neuroimmune crosstalk in gut immunity

The gastrointestinal tract is densely innervated by the peripheral nervous system and populated by the immune system. These two systems critically coordinate the sensations of and adaptations to dietary, microbial, and damaging stimuli from the external and internal microenvironment during tissue homeostasis and inflammation. The brain receives and integrates ascending sensory signals from the gut and transduces descending signals back to the gut via autonomic neurons. Neurons regulate intestinal immune responses through the action of local axon reflexes or through neuronal circuits via the gut-brain axis. This neuroimmune crosstalk is critical for gut homeostatic maintenance and disease resolution. In this review, we discuss the roles of distinct types of gut-innervating neurons in the modulation of intestinal mucosal immunity. We will focus on the molecular mechanisms governing how different immune cells respond to neural signals in host defense and inflammation. We also discuss the therapeutic potential of strategies targeting neuroimmune crosstalk for intestinal diseases.

Regulatory T cells in the face of the intestinal microbiota

Regulatory T cells (Treg cells) are key players in ensuring a peaceful coexistence with microorganisms and food antigens at intestinal borders. Startling new information has appeared in recent years on their diversity, the importance of the transcription factor FOXP3, how T cell receptors influence their fate and the unexpected and varied cellular partners that influence Treg cell homeostatic setpoints. We also revisit some tenets, maintained by the echo chambers of Reviews, that rest on uncertain foundations or are a subject of debate.

Intestinal factors promoting the development of RORγt+ cells and oral tolerance

The gastrointestinal tract has to harmonize the two seemingly opposite functions of fulfilling nutritional needs and avoiding the entry of pathogens, toxins and agents that can cause physical damage. This balance requires a constant adjustment of absorptive and defending functions by sensing environmental changes or noxious substances and initiating adaptive or protective mechanisms against them through a complex network of receptors integrated with the central nervous system that communicate with cells of the innate and adaptive immune system. Effective homeostatic processes at barrier sites take the responsibility for oral tolerance, which protects from adverse reactions to food that cause allergic diseases. During a very specific time interval in early life, the establishment of a stable microbiota in the large intestine is sufficient to prevent pathological events in adulthood towards a much larger bacterial community and provide tolerance towards diverse food antigens encountered later in life. The beneficial effects of the microbiome are mainly exerted by innate and adaptive cells that express the transcription factor RORγt, in whose generation, mediated by different bacterial metabolites, retinoic acid signalling plays a predominant role. In addition, recent investigations indicate that food antigens also contribute, analogously to microbial-derived signals, to educating innate immune cells and instructing the development and function of RORγt+ cells in the small intestine, complementing and expanding the tolerogenic effect of the microbiome in the colon. This review addresses the mechanisms through which microbiota-produced metabolites and dietary antigens maintain intestinal homeostasis, highlighting the complementarity and redundancy between their functions.

Vancomycin-induced gut microbial dysbiosis alters enteric neuron-macrophage interactions during a critical period of postnatal development

Vancomycin is a broad-spectrum antibiotic widely used in cases of suspected sepsis in premature neonates. While appropriate and potentially lifesaving in this setting, early-life antibiotic exposure alters the developing microbiome and is associated with an increased risk of deadly complications, including late-onset sepsis (LOS) and necrotizing enterocolitis (NEC). Recent studies show that neonatal vancomycin treatment disrupts postnatal enteric nervous system (ENS) development in mouse pups, which is in part dependent upon neuroimmune interactions. This suggests that early-life antibiotic exposure could disrupt these interactions in the neonatal gut. Notably, a subset of tissue-resident intestinal macrophages, muscularis macrophages, has been identified as important contributors to the development of postnatal ENS. We hypothesized that vancomycin-induced neonatal dysbiosis impacts postnatal ENS development through its effects on macrophages. Using a mouse model, we found that exposure to vancomycin in the first 10 days of life, but not in adult mice, resulted in an expansion of pro-inflammatory colonic macrophages by increasing the recruitment of bone-marrow-derived macrophages. Single-cell RNA sequencing of neonatal colonic macrophages revealed that early-life vancomycin exposure was associated with an increase in immature and inflammatory macrophages, consistent with an influx of circulating monocytes differentiating into macrophages. Lineage tracing confirmed that vancomycin significantly increased the non-yolk-sac-derived macrophage population. Consistent with these results, early-life vancomycin exposure did not expand the colonic macrophage population nor decrease enteric neuron density in CCR2-deficient mice. Collectively, these findings demonstrate that early-life vancomycin exposure alters macrophage number and phenotypes in distinct ways compared with vancomycin exposure in adult mice and results in altered ENS development.