Microbial Sensing by Intestinal Myeloid Cells Controls Carcinogenesis and Epithelial Differentiation

Unraveling cysteinyl leukotrienes and their receptors in inflammation through the brain-gut-lung axis

Cysteinyl leukotrienes (CysLTs), as potent lipid inflammatory mediators, play a pivotal role in systemic multi-organ inflammation and inter-organ communication through interactions with their receptors (CysLTRs). However, However, the function of CysLT3R is unclear and lacks a network of cross-organ metabolite interactions, and the clinical use of leukotriene receptor antagonists (LTRAs) has certain limitations. This review systematically synthesizes existing evidence and proposes future directions by clarifying receptor subtype specificity, optimizing targeted therapies, exploring CysLTs' applications in neuroimmunology, and elucidating the dual roles of CysLTs in chronic inflammation. It is indicated that CysLTs activate eosinophils, mast cells, and airway tuft cells, driving type 2 immune responses and mucus secretion in the lungs, thereby exacerbating respiratory diseases such as asthma. In the nervous system, CysLTs aggravate neurodegenerative disorders like cerebral ischemia and Alzheimer's disease by disrupting the blood-brain barrier, promoting glial activation, and inducing neuronal damage. In the gut, CysLTs regulate anti-helminth immunity via the tuft cell-ILC2 pathway and collaborate with prostaglandin D2 (PGD2) to modulate bile excretion and mucosal protection. Furthermore, CysLTs mediate communication through the gut-lung and gut-brain axes via metabolites such as succinate, contributing to cross-organ inflammatory regulation. In conclusion, this review highlights the complex roles of CysLTs in chronic inflammation, providing a theoretical foundation for precise intervention in multi-organ inflammatory diseases, which provides a theoretical framework for precision interventions in multi-organ inflammatory diseases and inspires interdisciplinary breakthroughs.

Crosstalk between gut microbiota and gut resident macrophages in inflammatory bowel disease

Macrophages residing in the gut maintain gut homeostasis by orchestrating patho-gens and innocuous antigens. A disturbance in macrophages leads to gut inflamma-tion, causing conditions such as inflammatory bowel disease (IBD). Macrophages ex-hibit remarkable plasticity, as they are sensitive to various signals in the tissue micro-environment. During the recent decades, gut microbiota has been highlighted refer-ring to their critical roles in immunity response. Microbiome-derived metabolites and products can interact with macrophages to participate in the progression of IBD. In this review, we describe recent findings in this field and provide an overview of the current understanding of microbiota-macrophages interactions in IBD, which may lead to the development of new targets and treatment options for patients with IBD.

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Crosstalk between epithelium, myeloid and innate lymphoid cells during gut homeostasis and disease

The gut epithelium not only provides a physical barrier to separate a noxious outside from a sterile inside but also allows for highly regulated interactions between bacteria and their products, and components of the immune system. Homeostatic maintenance of an intact epithelial barrier is paramount to health, requiring an intricately regulated and highly adaptive response of various cells of the immune system. Prolonged homeostatic imbalance can result in chronic inflammation, tumorigenesis and inefficient antitumor immune control. Here we provide an update on the role of innate lymphoid cells, macrophages and dendritic cells, which collectively play a critical role in epithelial barrier maintenance and provide an important linkage between the classical innate and adaptive arm of the immune system. These interactions modify the capacity of the gut epithelium to undergo continuous renewal, safeguard against tumor formation and provide feedback to the gut microbiome, which acts as a seminal contributor to cellular homeostasis of the gut.

Interactions between intestinal morphology, digestion, inflammatory responses, and gut microbiota of juvenile channel catfish elicited by dietary enzymatic rice protein

The reduction of fishmeal in aquafeeds has been the concern of researchers. Replacing fishmeal with plant proteins affects intestinal function and inflammation, but the interaction between the intestinal responses and gut microbiota remains unclear. In this study, juvenile channel catfish (Ictalurus punctatus) was fed with four diets in which enzymatic rice protein (RP) replaced fishmeal at levels of 0 (FM), 2.5% (RP2.5), 5.0% (RP5.0), and 7.5% (RP7.5) for 8 weeks to solve the problem mentioned above. Quantification of intestinal morphology showed that 2.5% or 5.0% RP significantly increased villus length and goblet cell number, accompanied by higher activities of intestinal trypsin, alkaline phosphatase (AKP), and Na⁺/K⁺-ATPase (NKA) in RP2.5 group (P < 0.05). In contrast, 7.5% RP slightly damaged the intestinal mucosa and significantly reduced the activities of amylase, AKP, and NKA, as well as decreased serum complement 4 (C4) and immunoglobulin M (IgM). Noteworthy, RT-qPCR showed that 2.5% RP significantly down-regulated intestinal mRNA expression level of il8, while up-regulated mif, tlr4, tlr7, tgfβ3, and cldn2. In contrast, 7.5% RP up-regulated the mRNA expression levels of il1β, il8, and mif, while down-regulated cldn3d. Analysis of gut microbiota showed that 2.5% RP increased the relative abundance of Bacteroidetes and significantly activated potential functions of gut microbiota involved in carbohydrate metabolism. The 7.5% RP increased the diversity of the gut microbiota, accompanied by a significant increase in the relative abundance of conditionally pathogenic bacteria such as Vibrio, Serratia, and Aeromonas (classified as Proteobacteria). Notably, Vibrio was the biomarker species with the greatest difference between the FM and RP7.5 groups (genus level). Correlation analysis indicated that Vibrio may affect immunity through the C4 pathway and further lead to gut inflammation and digestive impairment. Taken above, these results indicated that RP could affect intestinal morphology, digestion, and inflammation, and interact with the composition and potential function of gut microbiota. The low RP supplement (2.5%) improved intestinal morphology and digestion, while high supplement (7.5%) disrupted gut microbiota homeostasis, resulting in damage to intestinal mucosa and inflammatory response.

Macrophage orchestration of epithelial and stromal cell homeostasis in the intestine

The intestinal tract is a complex ecosystem where numerous cell types of epithelial, immune, neuronal, and endothelial origin coexist in an intertwined, highly organized manner. The functional equilibrium of the intestine relies heavily on the proper crosstalk and cooperation among each cell population. Furthermore, macrophages are versatile, innate immune cells that participate widely in the modulation of inflammation and tissue remodeling. Emerging evidence suggest that macrophages are central in orchestrating tissue homeostasis. Herein, we describe how macrophages interact with epithelial cells, neurons, and other types of mesenchymal cells under the context of intestinal inflammation, followed by the therapeutic implications of cellular crosstalk pertaining to the treatment of inflammatory bowel disease.

Single-cell atlas of the aging mouse colon

We performed massive single-cell sequencing in the aging mouse colonic epithelium and immune cells. We identified novel compartment-specific markers as well as dramatic aging-associated changes in cell composition and signaling pathways, including a shift from absorptive to secretory epithelial cells, depletion of naive lymphocytes, and induction of eIF2 signaling. Colon cancer is one of the leading causes of death within the western world, incidence of which increases with age. The colonic epithelium is a rapidly renewing tissue, tasked with water and nutrient absorption, as well as hosting intestinal microbes. The colonic submucosa is populated with immune cells interacting with and regulating the epithelial cells. However, it is unknown whether compartment-specific changes occur during aging and what impact this would cause. We show that both epithelial and immune cells differ significantly between colonic compartments and experience significant age-related changes in mice. We found a shift in the absorptive-secretory cell balance, possibly linked to age-associated intestinal disturbances, such as malabsorption. We demonstrate marked changes in aging immune cells: population shifts and interactions with epithelial cells, linking cytokines (Ifn-γ, Il1B) with the aging of colonic epithelium. Our results provide new insights into the normal and age-associated states of the colon.

•

Mouse colon shows compartment-specific transcriptional and population differences

•

Old animal colon switches to a pro-inflammatory state

•

Changes in epithelium linked to changes in tissue-resident immune cells

Tuft cells are key mediators of interkingdom interactions at mucosal barrier surfaces

Although tuft cells were discovered over 60 years ago, their functions have long been enigmatic, especially in human health. Nonetheless, tuft cells have recently emerged as key orchestrators of the host response to diverse microbial infections in the gut and airway. While tuft cells are epithelial in origin, they exhibit functions akin to immune cells and mediate important interkingdom interactions between the host and helminths, protists, viruses, and bacteria. With broad intra- and intertissue heterogeneity, tuft cells sense and respond to microbes with exquisite specificity. Tuft cells can recognize helminth and protist infection, driving a type 2 immune response to promote parasite expulsion. Tuft cells also serve as the primary physiologic target of persistent murine norovirus (MNV) and promote immune evasion. Recently, tuft cells were also shown to be infected by rotavirus. Other viral infections, such as influenza A virus, can induce tuft cell–dependent tissue repair. In the context of coinfection, tuft cells promote neurotropic flavivirus replication by dampening antiviral adaptive immune responses. Commensal and pathogenic bacteria can regulate tuft cell abundance and function and, in turn, tuft cells are implicated in modulating bacterial infiltration and mucosal barrier integrity. However, the contribution of tuft cells to microbial sensing in humans and their resulting effector responses are poorly characterized. Herein, we aim to provide a comprehensive overview of microbial activation of tuft cells with an emphasis on tuft cell heterogeneity and differences between mouse and human tuft cell biology as it pertains to human health and disease.

Enteric Tuft Cells in Host-Parasite Interactions

Enteric tuft cells are chemosensory epithelial cells gaining attention in the field of host-parasite interactions. Expressing a repertoire of chemosensing receptors and mediators, these cells have the potential to detect lumen-dwelling helminth and protozoan parasites and coordinate epithelial, immune, and neuronal cell defenses against them. This review highlights the versatility of enteric tuft cells and sub-types thereof, showcasing nuances of tuft cell responses to different parasites, with a focus on helminths reflecting the current state of the field. The role of enteric tuft cells in irritable bowel syndrome, inflammatory bowel disease and intestinal viral infection is assessed in the context of concomitant infection with parasites. Finally, the review presents pertinent questions germane to understanding the enteric tuft cell and its role in enteric parasitic infections. There is much to be done to fully elucidate the response of this intriguing cell type to parasitic-infection and there is negligible data on the biology of the human enteric tuft cell—a glaring gap in knowledge that must be filled.

Tuft cells in the pathogenesis of chronic rhinosinusitis with nasal polyps and asthma

OBJECTIVE

To review the latest discoveries regarding the role of tuft cells in the pathogenesis of chronic rhinosinusitis (CRS) with nasal polyposis and asthma.

DATA SOURCES

Reviews and primary research manuscripts were identified from PubMed, Google, and bioRxiv using the search words airway epithelium, nasal polyposis, CRS or asthma and chemoreceptor cell, solitary chemosensory cell, brush cell, microvillus cell, and tuft cell.

STUDY SELECTIONS

Studies were selected on the basis of novelty and likely relevance to the functions of tuft cells in chronic inflammatory diseases in the upper and lower airways.

RESULTS

Tuft cells coordinate a variety of immune responses throughout the body. After the activation of bitter-taste receptors, tuft cells coordinate the secretion of antimicrobial products by adjacent epithelial cells and initiate the calcium-dependent release of acetylcholine resulting in neurogenic inflammation, including mast cell degranulation and plasma extravasation. Tuft cells are also the dominant source of interleukin-25 and a significant source of cysteinyl leukotrienes that play a role in initiating inflammatory processes in the airway. Tuft cells have also been found to seem de novo in the distal airway after a viral infection, implicating these cells in dysplastic remodeling in the distal lung in the pathogenesis of asthma.

CONCLUSION

Tuft cells bridge innate and adaptive immunes responses and play an upstream role in initiating type 2 inflammation in the upper and possibly the lower airway. The role of tuft cells in respiratory pathophysiology must be further investigated, because tuft cells are putative high-value therapeutic targets for novel therapeutics in CRS with nasal polyps and asthma.

Paneth cell-derived growth factors support tumorigenesis in the small intestine

Paneth cells, known for their production of antimicrobial peptides and growth factors in the gut epithelium, are found to play a key role in intestinal tumor formation through secretion of Wnt3.

Paneth cells (PCs) are small intestinal epithelial cells that secrete antimicrobial peptides and growth factors, such as Wnt ligands. Intriguingly, the context in which PC-derived Wnt secretion is relevant in vivo remains unknown as intestinal epithelial ablation of Wnt does not affect homeostatic proliferation or restitution after irradiation injury. Considering the importance of growth factors in tumor development, we explored here the role of PCs in intestinal carcinogenesis using a genetic model of PC depletion through conditional expression of diphtheria toxin-α subunit. PC depletion in Apc^Min mice impaired adenoma development in the small intestine and led to decreased Wnt3 expression in small bowel adenomas. To determine if PC-derived Wnt3 was required for adenoma development, we examined tumor formation after PC-specific ablation of Wnt3. We found that this was sufficient to decrease small intestinal adenoma formation; moreover, organoids derived from these tumors displayed slower growth capacity. Overall, we report that PC-derived Wnt3 is required to sustain early tumorigenesis in the small bowel and identify a clear role for PC-derived Wnt production in intestinal pathology.

The relationship between intestinal goblet cells and the immune response

Goblet cells (GCs) are single-cell glands that produce and secrete mucin. Mucin forms a mucus layer, which can separate the materials in cavities from the intestinal epithelium and prevent the invasion of pathogenic microorganisms in various ways. GCs can also participate in the immune response through nonspecific endocytosis and goblet cell-associated antigen passages (GAPs). GCs endocytose soluble substances from the lumen and transmit antigens to the underlying antigen-presenting cells (APCs). A variety of immuno-regulatory factors can promote the differentiation, maturation of GCs, and the secretion of mucin. The mucin secreted by GCs forms a mucus layer, which plays an important role in resisting the invasion of foreign bacteria and intestinal inherent microorganisms, regulating the immune performance of the body. Therefore, the present study mainly reviews the barrier function of the mucus layer, the mucus secreted by goblet cells, the protective effect against pathogenic bacteria, the delivery of luminal substances through GAPs and the relationship between GCs and the immune response.

Regulation of immune responses by tuft cells

Tuft cells are rare, secretory epithelial cells that generated scant immunological interest until contemporaneous reports in 2016 linked tuft cells with type 2 immunity in the small intestine. Tuft cells have the capacity to produce an unusual spectrum of biological effector molecules, including IL-25, eicosanoids implicated in allergy (such as cysteinyl leukotrienes and prostaglandin D₂) and the neurotransmitter acetylcholine. In most cases, the extracellular signals controlling tuft cell effector function are unknown, but signal transduction is thought to proceed via canonical, G protein-coupled receptor-dependent pathways involving components of the signalling pathway used by type II taste bud cells to sense sweet, bitter and umami compounds. Tuft cells are ideally positioned as chemosensory sentinels that can detect and relay information from diverse luminal substances via what appear to be stereotyped outputs to initiate both positive and aversive responses through populations of immune and neuronal cells. Despite recent insights, numerous questions remain regarding tuft cell lineage, diversity and effector mechanisms and how tuft cells interface with the immunological niche in the tissues where they reside.

Clostridium ramosum regulates enterochromaffin cell development and serotonin release

Peripheral serotonin (5-hydroxytryptamine: 5-HT) synthesized in the intestine by enterochromaffin cells (ECs), plays an important role in the regulation of peristaltic of the gut, epithelial secretion and promotes the development and maintenance of the enteric neurons. Recent studies showed that the indigenous gut microbiota modulates 5-HT signalling and that ECs use sensory receptors to detect dietary and microbiota-derived signals from the lumen to subsequently transduce the information to the nervous system. We hypothesized that Clostridium ramosum by increasing gut 5-HT availability consequently contributes to high-fat diet-induced obesity. Using germ-free mice and mice monoassociated with C. ramosum, intestinal cell lines and mouse organoids, we demonstrated that bacterial cell components stimulate host 5-HT secretion and program the differentiation of colonic intestinal stem progenitors toward the secretory 5-HT-producing lineage. An elevated 5-HT level regulates the expression of major proteins involved in intestinal fatty acid absorption in vitro, suggesting that the presence of C. ramosum in the gut promotes 5-HT secretion and thereby could facilitates intestinal lipid absorption and the development of obesity.