Oxysterol Sensing through the Receptor GPR183 Promotes the Lymphoid-Tissue-Inducing Function of Innate Lymphoid Cells and Colonic Inflammation

There's no place like home: How local tissue microenvironments shape the function of innate lymphoid cells

Innate lymphoid cells (ILC) have emerged as critical immune effectors with key roles in orchestrating the wider immune response. While ILC are relatively rare cells they are found enriched within discrete microenvironments, predominantly within barrier tissues. An emerging body of evidence implicates complex and multi-layered interactions between cell types, tissue structure and the external environment as key determinants of ILC function within these niches. In this review we will discuss the specific components that constitute ILC-associated microenvironments and consider how they act to determine health and disease. The development of holistic, integrated models of ILC function within complex tissue environments will inform new understanding of the contextual cues and mechanisms that determine the protective versus disease-causing roles of this immune cell family.

High Expression of GPR183 Predicts Poor Survival in Cytogenetically Normal Acute Myeloid Leukemia

Acute myeloid leukemia (AML) with a normal karyotype (CN-AML) constitutes approximately 50% of all AML cases, presenting significant prognostic variability, and highlighting the urgent need for the identification of novel molecular biomarkers. In this study, we systematically assessed GPR183 expression levels using qRT-PCR in our clinical follow-up study which included 283 CN-AML patients. Using Kaplan-Meier analysis, we found that patients with high GPR183 expression levels exhibited significantly worse overall survival (OS) (P = 0.046) and event-free survival (EFS) (P = 0.030) compared to those with low GPR183 expression. Comprehensive univariate and multivariate Cox regression analyses confirmed that GPR183 expression is a prognostic factor for OS and EFS (P < 0.05). To further validate these findings, we analyzed an independent cohort of 104 CN-AML patients from the GSE71014 dataset, corroborating our primary results, and indicating that high GPR183 expression is associated with poorer survival outcomes. Additionally, RNA-seq data from the GSE71014 dataset were analyzed by Gene Set Enrichment Analysis (GSEA). The results suggested that GPR183 may influence disease progression through the activation of the "TNFa Signaling Via NF-κB" pathway. Collectively, these findings suggested that GPR183 could serve as a valuable prognostic biomarker in CN-AML, offering insights into the underlying mechanisms of disease progression.

Immune crosstalk between respiratory and intestinal mucosal tissues in respiratory infections

Mucosal tissues, including those in the respiratory and gastrointestinal tracts, are critical barrier surfaces for pathogen invasion. Infections at these sites not only trigger local immune response, but also recruit immune cells from other tissues. Emerging evidence in the mouse models and human samples indicates that the immune crosstalk between the lung and gut critically impacts and determines the course of respiratory disease. Here we summarize the current knowledge of the immune crosstalk between the respiratory and gastrointestinal tracts, and discuss how immune cells are recruited and migrate between these tissues during respiratory infections. We also discuss how commensal bacteria contribute to these processes.

Cholesterol sensing and metabolic adaptation in tissue immunity

Cholesterol metabolites, particularly oxidized forms known as oxysterols, play crucial roles in modulating immune and metabolic processes across various tissues. Concentrations of local cholesterol and its metabolites influence tissue-specific immune responses by shaping the metabolic and spatial organization of immune cells in barrier organs like the small intestine (SI) and lungs. We explore recent molecular and cellular evidence supporting the metabolic adaptation of innate and adaptive immune cells in the SI and lung, driven by cholesterol and cholesterol metabolites. Further research should unravel the detailed molecular mechanisms and spatiotemporal adaptations involving cholesterol metabolites in distinct mucosal tissues in homeostasis or infection. We posit that pharmacological interventions targeting the generation or sensing of cholesterol metabolites might be leveraged to enhance long-term immune protection in mucosal tissues or prevent autoinflammatory states.

Sexual Dimorphism in the Immunometabolic Role of Gpr183 in Mice

Context

Excessive eating and intake of a Western diet negatively affect the intestinal immune system, resulting in compromised glucose homeostasis and lower gut bacterial diversity. The G protein-coupled receptor GPR183 regulates immune cell migration and intestinal immune response and has been associated with tuberculosis, type 1 diabetes, and inflammatory bowel diseases.

Objective

We hypothesized that with these implications, GPR183 has an important immunometabolic role and investigated this using a global Gpr183 knockout mouse model.

Methods

Wild-type (WT) and Gpr183-deficient (Gpr183-/-) mice were fed a high-fat, high-sucrose diet (HFSD) for 15 weeks. We investigated changes in weight, body composition, fecal immunoglobulin A (IgA) levels, fecal microbiome, and glucose tolerance before and after the diet. Macrophage infiltration into visceral fat was determined by flow cytometry, and hepatic gene expression was measured.

Results

A sexual dimorphism was discovered, whereby female Gpr183-/- mice showed adverse metabolic outcomes compared to WT counterparts with inferior glucose tolerance, lower fecal IgA levels, and increased macrophage infiltration in visceral fat. In contrast, male Gpr183-/- mice had significantly lower fasting blood glucose after diet than male WT mice. Liver gene expression showed reduced inflammation and macrophage markers in Gpr183-/- livers, regardless of sex, while the pancreatic islet area did not differ between the groups. No conclusive differences were found after microbiome sequencing.

Conclusion

Gpr183 maintains metabolic homeostasis in female but not in male mice independent of diet. If confirmed in humans, future therapy targeting GPR183 should consider this sexual dimorphism.

Oxysterols contribute to immune cell recruitment in SLE skin lesions

BACKGROUND

Abnormal oxysterol metabolism has been observed in the peripheral blood of SLE patients, but its role in systemic lupus erythematosus (SLE) skin lesions remains unclear.

METHODS

Targeted oxidized lipid metabolomics analysis using liquid chromatography-mass spectrometry (LC-MS) was performed to quantify oxysterols in SLE skin lesions. Immunohistochemical staining and single-cell sequencing data analysis confirmed the upregulation of oxysterol-encoding enzymes CH25H and CYP7B1. The impact on fibroblast-mediated PBMCs chemotaxis was assessed using a transwell chamber.

RESULTS

We identified aberrant oxidized cholesterol metabolism in SLE skin lesions, characterized by elevated levels of 7-ketocholesterol, 5α-6α-cholestane-3β,5α,6β-triol, and so on. Fibroblasts were the primary cells expressing oxysterol-encoding genes, with CH25H and CYP7B1 expression upregulated via the IL-1β-mediated p38 MAPK and NFκB pathways. Notably, IL-1β-stimulated fibroblasts demonstrated enhanced PBMCs recruitment, which was attenuated by a GPR183 inhibitor.

CONCLUSION

Our findings reveal a potential mechanism by which fibroblasts contribute to immune cell recruitment in SLE skin lesions by expression of CH25H and CYP7B1. This study underscores the significance of oxysterol metabolism in SLE skin lesion pathogenesis and highlights potential therapeutic targets for SLE skin lesion treatment.

Screening and identification of key biomarkers associated with endometriosis using bioinformatics and next-generation sequencing data analysis

Background

Endometriosis is a common cause of endometrial-type mucosa outside the uterine cavity with symptoms such as painful periods, chronic pelvic pain, pain with intercourse and infertility. However, the early diagnosis of endometriosis is still restricted. The purpose of this investigation is to identify and validate the key biomarkers of endometriosis.

Methods

Next-generation sequencing dataset GSE243039 was obtained from the Gene Expression Omnibus database, and differentially expressed genes (DEGs) between endometriosis and normal control samples were identified. After screening of DEGs, gene ontology (GO) and REACTOME pathway enrichment analyses were performed. Furthermore, a protein–protein interaction (PPI) network was constructed and modules were analyzed using the Human Integrated Protein–Protein Interaction rEference database and Cytoscape software, and hub genes were identified. Subsequently, a network between miRNAs and hub genes, and network between TFs and hub genes were constructed using the miRNet and NetworkAnalyst tool, and possible key miRNAs and TFs were predicted. Finally, receiver operating characteristic curve analysis was used to validate the hub genes.

Results

A total of 958 DEGs, including 479 upregulated genes and 479 downregulated genes, were screened between endometriosis and normal control samples. GO and REACTOME pathway enrichment analyses of the 958 DEGs showed that they were mainly involved in multicellular organismal process, developmental process, signaling by GPCR and muscle contraction. Further analysis of the PPI network and modules identified 10 hub genes, including vcam1, snca, prkcb, adrb2, foxq1, mdfi, actbl2, prkd1, dapk1 and actc1. Possible target miRNAs, including hsa-mir-3143 and hsa-mir-2110, and target TFs, including tcf3 (transcription factor 3) and clock (clock circadian regulator), were predicted by constructing a miRNA-hub gene regulatory network and TF-hub gene regulatory network.

Conclusions

This investigation used bioinformatics techniques to explore the potential and novel biomarkers. These biomarkers might provide new ideas and methods for the early diagnosis, treatment and monitoring of endometriosis.

GPCRs: emerging targets for novel T cell immune checkpoint therapy

Although immune checkpoint blockade (ICB) has become the mainstay of treatment for advanced solid organ malignancies, success in revitalizing the host anticancer immune response remains limited. G-protein coupled receptors (GPCRs) are a broad family of cell-surface proteins that have been regarded as main players in regulating the immune system, namely by mediating the activity of T lymphocytes. Among the most novel immunoregulatory GPCRs include GPR171, lysophosphatidic acid receptors (LPARs), GPR68, cannabinoid receptor 2 (CB2), and prostaglandin E receptors, many of which have shown promise in mediating antitumor response via activation of cytotoxic T cells, inhibiting immunosuppressive lymphocytes, and facilitating immune cell infiltration within the tumor microenvironment across multiple types of cancers. This paper reviews our current understanding of some of the most novel GPCRs-their expression patterns, evolving roles within the immune system and cancer, potential therapeutic applications, and perspective for future investigation.

Oxysterol Sensing Through GPR183 Triggers Endothelial Senescence in Hypertension

BACKGROUND

Despite endothelial dysfunction being an initial step in the development of hypertension and associated cardiovascular/renal injuries, effective therapeutic strategies to prevent endothelial dysfunction are still lacking. GPR183 (G protein-coupled receptor 183), a recently identified G protein-coupled receptor for oxysterols and hydroxylated metabolites of cholesterol, has pleiotropic roles in lipid metabolism and immune responses. However, the role of GPR183 in the regulation of endothelial function remains unknown.

METHODS

Endothelial-specific GPR183 knockout mice were generated and used to examine the role of GPR183 in endothelial senescence by establishing 2 independent hypertension models: desoxycorticosterone acetate/salt-induced and Ang II (angiotensin II)-induced hypertensive mice. Echocardiography, transmission electron microscopy, blood pressure measurement, vasorelaxation response experiments, flow cytometry analysis, and chromatin immunoprecipitation analysis were performed in this study.

RESULTS

Endothelial GPR183 was significantly induced in hypertensive mice, which was further confirmed in renal biopsies from subjects with hypertensive nephropathy. Endothelial-specific deficiency of GPR183 markedly alleviated cardiovascular and renal injuries in hypertensive mice. Moreover, we found that GPR183 regulated endothelial senescence in both hypertensive mice and aged mice. Mechanistically, GPR183 disrupted circadian signaling by inhibiting PER1 (period circadian regulator 1) expression, thereby facilitating endothelial senescence and dysfunction through the cAMP (cyclic adenosine monophosphate)/PKA (protein kinase A)/CREB (cAMP-response element binding protein) signaling pathway. Importantly, pharmacological inhibition of the oxysterol-GPR183 axis by NIBR189 or clotrimazole ameliorated endothelial senescence and cardiovascular/renal injuries in hypertensive mice.

CONCLUSIONS

This study discovers a previously unrecognized role of GPR183 in promoting endothelial senescence. Pharmacological targeting of GPR183 may be an innovative therapeutic strategy for hypertension and its associated complications.

Single-cell transcriptome sequencing reveals altered peripheral blood immune cells in patients with severe tuberculosis

Tuberculosis is a serious global health burden, resulting in millions of deaths each year. Several circulating cell subsets in the peripheral blood are known to modulate the host immune response to Mycobacterium tuberculosis (Mtb) infection in different ways. However, the characteristics and functions of these subsets to varying stages of tuberculosis infection have not been well elucidated. Peripheral blood immune cells (PBICs) were isolated from healthy donors (HD group), individuals with mild tuberculosis (MI group), and individuals with severe tuberculosis (SE group). CD4+ naive T cells and CD8+ T cells were decreased in the SE and MI groups, while CD14+ monocytes were increased in the SE group. Further analysis revealed increased activated CD4+ T cells, transitional CD8+ T cells, memory-like NK cells, and IGHG3highTTNhighFCRL5high B cells were increased in all patients with tuberculosis (SE and MI group). In contrast, Th17 cells, cytotoxic NK cells, and cytotoxic CD4+ T cells were decreased. Moreover, the increase of CD14+CD16+ monocytes correlated with severe tuberculosis, and the GBP5highRSAD2high neutrophils were unique to patients with severe tuberculosis. Cellular communication analysis revealed that CD8+ T cells exhibited the highest incoming interaction strength in the SE group. The increased CD8+ T cell incoming interactions are associated with the MHC-I and LCK pathways, with HLA-(A-E)-CD8A, HLA-(A-E)-CD8B, and LCK-(CD8A+CD8B) being ligand-receptor pairs. Patients with tuberculosis, especially severe tuberculosis, have profound changes in peripheral blood immune cell profiles. CD8+ T cells showed the highest incoming interaction strength in patients with severe tuberculosis, with the main signals being MHC-I and LCK pathways.

OLFM4 modulates intestinal inflammation by promoting IL-22+ILC3 in the gut

Group 3 innate lymphoid cells (ILC3s) play key roles in intestinal inflammation. Olfactomedin 4 (OLFM4) is highly expressed in the colon and has a potential role in dextran sodium sulfate-induced colitis. However, the detailed mechanisms underlying the effects of OLFM4 on ILC3-mediated colitis remain unclear. In this study, we identify OLFM4 as a positive regulator of IL-22+ILC3. OLFM4 expression in colonic ILC3s increases substantially during intestinal inflammation in humans and mice. Compared to littermate controls, OLFM4-deficient (OLFM4-/-) mice are more susceptible to bacterial infection and display greater resistance to anti-CD40 induced innate colitis, together with impaired IL-22 production by ILC3, and ILC3s from OLFM4-/-mice are defective in pathogen resistance. Besides, mice with OLFM4 deficiency in the RORγt compartment exhibit the same trend as in OLFM4-/-mice, including colonic inflammation and IL-22 production. Mechanistically, the decrease in IL-22+ILC3 caused by OLFM4 deficiency involves the apoptosis signal-regulating kinase 1 (ASK1)- p38 MAPK signaling-dependent downregulation of RAR-related orphan receptor gamma (RORγt) protein. The OLFM4-metadherin (MTDH) complex upregulates p38/RORγt signaling, which is necessary for IL-22+ILC3 activation. The findings indicate that OLFM4 is a novel regulator of IL-22+ILC3 and essential for modulating intestinal inflammation and tissue homeostasis.

Group 3 innate lymphoid cells in intestinal health and disease

The gastrointestinal tract is an immunologically rich organ, containing complex cell networks and dense lymphoid structures that safeguard this large absorptive barrier from pathogens, contribute to tissue physiology and support mucosal healing. Simultaneously, the immune system must remain tolerant to innocuous dietary antigens and trillions of normally beneficial microorganisms colonizing the intestine. Indeed, a dysfunctional immune response in the intestine underlies the pathogenesis of numerous local and systemic diseases, including inflammatory bowel disease, food allergy, chronic enteric infections or cancers. Here, we discuss group 3 innate lymphoid cells (ILC3s), which have emerged as orchestrators of tissue physiology, immunity, inflammation, tolerance and malignancy in the gastrointestinal tract. ILC3s are abundant in the developing and healthy intestine but their numbers or function are altered during chronic disease and cancer. The latest studies provide new insights into the mechanisms by which ILC3s fundamentally shape intestinal homeostasis or disease pathophysiology, and often this functional dichotomy depends on context and complex interactions with other cell types or microorganisms. Finally, we consider how this knowledge could be harnessed to improve current treatments or provoke new opportunities for therapeutic intervention to promote gut health.

Crosstalk between CD8+ T cells and mesenchymal stromal cells in intestine homeostasis and immunity

The intestine represents the most complex cellular network in the whole body. It is constantly faced with multiple types of immunostimulatory agents encompassing from food antigen, gut microbiome, metabolic waste products, and dead cell debris. Within the intestine, most T cells are found in three primary compartments: the organized gut-associated lymphoid tissue, the lamina propria, and the epithelium. The well-orchestrated epithelial-immune-microbial interaction is critically important for the precise immune response. The main role of intestinal mesenchymal stromal cells is to support a structural framework within the gut wall. However, recent evidence from stromal cell studies indicates that they also possess significant immunomodulatory functions, such as maintaining intestinal tolerance via the expression of PDL1/2 and MHC-II molecules, and promoting the development of CD103+ dendritic cells, and IgA+ plasma cells, thereby enhancing intestinal homeostasis. In this review, we will summarize the current understanding of CD8+ T cells and stromal cells alongside the intestinal tract and discuss the reciprocal interactions between T subsets and mesenchymal stromal cell populations. We will focus on how the tissue residency, migration, and function of CD8+ T cells could be potentially regulated by mesenchymal stromal cell populations and explore the molecular mediators, such as TGF-β, IL-33, and MHC-II molecules that might influence these processes. Finally, we discuss the potential pathophysiological impact of such interaction in intestine hemostasis as well as diseases of inflammation, infection, and malignancies.

Early life microbiome influences on development of the mucosal innate immune system

The gut microbiota is well known to possess immunomodulatory capacities, influencing a multitude of cellular signalling pathways to maintain host homeostasis. Although the formation of the immune system initiates before birth in a sterile environment, an emerging body of literature indicates that the neonatal immune system is influenced by a first wave of external stimuli that includes signals from the maternal microbiota. A second wave of stimulus begins after birth and must be tightly regulated during the neonatal period when colonization of the host occurs concomitantly with the maturation of the immune system, requiring a fine adjustment between establishing tolerance towards the commensal microbiota and preserving inflammatory responses against pathogenic invaders. Besides integrating cues from commensal microbes, the neonatal immune system must also regulate responses triggered by other environmental signals, such as dietary antigens, which become more complex with the introduction of solid food during the weaning period. This "window of opportunity" in early life is thought to be crucial for the proper development of the immune system, setting the tone of subsequent immune responses in adulthood and modulating the risk of developing chronic and metabolic inflammatory diseases. Here we review the importance of host-microbiota interactions for the development and maturation of the immune system, particularly in the early-life period, highlighting the known mechanisms involved in such communication. This discussion is focused on recent data demonstrating microbiota-mediated education of innate immune cells and its role in the development of lymphoid tissues.

Group 3 innate lymphoid cells: A trained Gutkeeper

Group 3 innate lymphoid cells (ILC3s) are tissue-resident immune lymphocytes that critically regulate intestinal homeostasis, organogenesis, and immunity. ILC3s possess the capacity to "sense" the inflammatory environment within tissues, especially in the context of pathogen challenges that imprints durable non-antigen-specific changes in ILC3 function. As such, ILC3s become a new actor in the emerging field of trained innate immunity. Here, we summarize recent discoveries regarding ILC3 responses to bacterial challenges and the role these encounters play in triggering trained innate immunity. We further discuss how signaling events throughout ILC3 ontogeny potentially control the development and function of trained ILC3s. Finally, we highlight the open questions surrounding ILC3 "training" the answers to which may reveal new insights into innate immunity. Understanding the fundamental concepts behind trained innate immunity could potentially lead to the development of new strategies for improving immunity-based modulation therapies for inflammation, infectious diseases, and cancer.

Navigating the metabolic maze: anomalies in fatty acid and cholesterol processes in Alzheimer's astrocytes

Alzheimer's disease (AD) is the most common cause of dementia, and its underlying mechanisms have been a subject of great interest. The mainstream theory of AD pathology suggests that the disease is primarily associated with tau protein and amyloid-beta (Aβ). However, an increasing body of research has revealed that abnormalities in lipid metabolism may be an important event throughout the pathophysiology of AD. Astrocytes, as important members of the lipid metabolism network in the brain, play a significant role in this event. The study of abnormal lipid metabolism in astrocytes provides a new perspective for understanding the pathogenesis of AD. This review focuses on the abnormal metabolism of fatty acids (FAs) and cholesterol in astrocytes in AD, and discusses it from three perspectives: lipid uptake, intracellular breakdown or synthesis metabolism, and efflux transport. We found that, despite the accumulation of their own fatty acids, astrocytes cannot efficiently uptake fatty acids from neurons, leading to fatty acid accumulation within neurons and resulting in lipotoxicity. In terms of cholesterol metabolism, astrocytes exhibit a decrease in endogenous synthesis due to the accumulation of exogenous cholesterol. Through a thorough investigation of these metabolic abnormalities, we can provide new insights for future therapeutic strategies by literature review to navigate this complex metabolic maze and bring hope to patients with Alzheimer's disease.

Discovery of a Highly Potent Oxysterol Receptor GPR183 Antagonist Bearing the Benzo[d]thiazole Structural Motif for the Treatment of Inflammatory Bowel Disease (IBD)

Accumulating evidence has demonstrated a critical pathological role of oxysterol receptor GPR183 in various inflammatory and autoimmune diseases, including inflammatory bowel disease (IBD). However, the currently reported GPR183 antagonists are very limited and not qualified for in vivo studies due to their inferior druglike properties. Herein, we conducted a structural elaboration focusing on improving its PK and safety profile based on a reference antagonist NIBR189. Of note, compound 33, bearing an aminobenzothiazole motif, exhibited reduced hERG inhibition, improved PK properties, and robust antagonistic activity (IC50 = 0.82 nM) with high selectivity against GPR183. Moreover, compound 33 displayed strong in vitro antimigration and anti-inflammatory activity in monocytes. Oral administration of compound 33 effectively improved the pathological symptoms of DSS-induced experimental colitis. All of these findings demonstrate that compound 33 is a novel and promising GPR183 antagonist suitable for further investigation to treat IBD.

A conserved transcriptional program for MAIT cells across mammalian evolution

Mucosal-associated invariant T (MAIT) cells harbor evolutionarily conserved TCRs, suggesting important functions. As human and mouse MAIT functional programs appear distinct, the evolutionarily conserved MAIT functional features remain unidentified. Using species-specific tetramers coupled to single-cell RNA sequencing, we characterized MAIT cell development in six species spanning 110 million years of evolution. Cross-species analyses revealed conserved transcriptional events underlying MAIT cell maturation, marked by ZBTB16 induction in all species. MAIT cells in human, sheep, cattle, and opossum acquired a shared type-1/17 transcriptional program, reflecting ancestral features. This program was also acquired by human iNKT cells, indicating common differentiation for innate-like T cells. Distinct type-1 and type-17 MAIT subsets developed in rodents, including pet mice and genetically diverse mouse strains. However, MAIT cells further matured in mouse intestines to acquire a remarkably conserved program characterized by concomitant expression of type-1, type-17, cytotoxicity, and tissue-repair genes. Altogether, the study provides a unifying view of the transcriptional features of innate-like T cells across evolution.

Therapeutic Applications of Oxysterols and Derivatives in Age-Related Diseases, Infectious and Inflammatory Diseases, and Cancers

Oxysterols, resulting from the oxidation of cholesterol, are formed either by autoxidation, enzymatically, or by both processes. These molecules, which are provided in more or less important quantities depending on the type of diet, are also formed in the body and their presence is associated with a normal physiological activity. Their increase and decrease at the cellular level and in biological fluids can have significant consequences on health due or not to the interaction of some of these molecules with different types of receptors but also because oxysterols are involved in the regulation of RedOx balance, cytokinic and non-cytokinic inflammation, lipid metabolism, and induction of cell death. Currently, various pathologies such as age-related diseases, inflammatory and infectious diseases, and several cancers are associated with abnormal levels of oxysterols. Due to the important biological activities of oxysterols, their interaction with several receptors and their very likely implications in several diseases, this review focuses on these molecules and on oxysterol derivatives, which are often more efficient, in a therapeutic context. Currently, several oxysterol derivatives are developed and are attracting a lot of interest.

Implication of Oxysterols and Phytosterols in Aging and Human Diseases

Cholesterol is easily oxidized and can be transformed into numerous oxidation products, among which oxysterols. Phytosterols are plant sterols related to cholesterol. Both oxysterols and phytosterols can have an impact on human health and diseases.Cholesterol is a member of the sterol family that plays essential roles in biological processes, including cell membrane stability and myelin formation. Cholesterol can be metabolized into several molecules including bile acids, hormones, and oxysterols. On the other hand, phytosterols are plant-derived compounds structurally related to cholesterol, which can also have an impact on human health. Here, we review the current knowledge about the role of oxysterols and phytosterols on human health and focus on the impact of their pathways on diseases of the central nervous system (CNS), autoimmune diseases, including inflammatory bowel diseases (IBD), vascular diseases, and cancer in both experimental models and human studies. We will first discuss the implications of oxysterols and then of phytosterols in different human diseases.

Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3

Innate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.

ILC3: a case of conflicted identity

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

Bcl-2 supports survival and metabolic fitness of quiescent tissue-resident ILC3

Group 3 innate lymphoid cells (ILC3) are potent effector cells with critical roles in enforcing immunity, barrier integrity and tissue homeostasis along the gastrointestinal tract. ILC3 are considered primarily tissue-resident cells, seeding the gastrointestinal tract during embryonic stages and early life. However, the mechanisms through which mature ILC3 are maintained within adult tissues are poorly understood. Here, we report that lymphoid tissue-inducer-like (LTi-like) ILC3 exhibit minimal turnover in the healthy adult intestinal tract, persist for extended periods of time, and display a quiescent phenotype. Strikingly, during enteric bacterial infection LTi-like ILC3 also exhibit negligible hematopoietic replenishment and remain non-proliferative, despite robustly producing cytokines. Survival of LTi-like ILC3 was found to be dependent upon the balance between the metabolic activity required to drive effector function and anti-apoptotic programs. Notably, the pro-survival protein B-cell lymphoma-2 (Bcl-2) was required for the survival of LTi-like ILC3 ex vivo but was rendered partially dispensable if mitochondrial respiration was inhibited. Together we demonstrate LTi-like ILC3 are a tissue-resident, quiescent population that persist independently of hematopoietic replenishment to survive within the intestinal microenvironment.

Cholesterol-autoxidation metabolites in host defense against infectious diseases

Cholesterol plays essential roles in biological processes, including cell membrane stability and myelin formation. Cholesterol can be metabolized to oxysterols by enzymatic or nonenzymatic ways. Nonenzymatic cholesterol metabolites, also called cholesterol-autoxidation metabolites, are formed dependent on the oxidation of reactive oxygen species (ROS) such as OH• or reactive nitrogen species, such as ONOO- . Cholesterol-autoxidation metabolites are abundantly produced in diseases such as inflammatory bowel disease and atherosclerosis, which are associated with oxidative stress. Recent studies have shown that cholesterol-autoxidation metabolites can further regulate the immune system. Here, we review the literature and summarize how cholesterol-autoxidation metabolites, such as 25-hydroxycholesterol (25-OHC), 7α/β-OHC, and 7-ketocholesterol, deal with the occurrence and development of infectious diseases through pattern recognition receptors, inflammasomes, ROS production, nuclear receptors, G-protein-coupled receptor 183, and lipid availability. In addition, we include the research regarding the roles of these metabolites in COVID-19 infection and discuss our viewpoints on the future research directions.

The Oxysterol Receptor EBI2 Links Innate and Adaptive Immunity to Limit IFN Response and Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with abnormal activation of the immune system. Recent attention is increasing about how aberrant lipid and cholesterol metabolism is linked together with type I interferon (IFN-I) signaling in the regulation of the pathogenesis of SLE. Here, a metabonomic analysis is performed and increased plasma concentrations of oxysterols, especially 7α, 25-dihydroxycholesterol (7α, 25-OHC), are identified in SLE patients. The authors find that 7α, 25-OHC binding to its receptor Epstein-Barr virus-induced gene 2 (EBI2) in macrophages can suppress STAT activation and the production of IFN-β, chemokines, and cytokines. Importantly, monocytes/macrophages from SLE patients and mice show significantly reduced EBI2 expression, which can be triggered by IFN-γ produced in activated T cells. Previous findings suggest that EBI2 enhances immune cell migration. Opposite to this effect, the authors demonstrate that EBI2-deficient macrophages produce higher levels of chemokines and cytokines, which recruits and activates myeloid cells,T and B lymphocytes to exacerbate tetramethylpentadecane-induced SLE. Together, via sensing the oxysterol 7α, 25-OHC, EBI2 in macrophages can modulate innate and adaptive immune responses, which may be used as a potential diagnostic marker and therapeutic target for SLE.

Research progress on the mechanism of cholesterol-25-hydroxylase in intestinal immunity

Inflammatory bowel disease (IBD), a general term encompassing Crohn's disease (CD) and ulcerative colitis (UC), and other conditions, is a chronic and relapsing autoimmune disease that can occur in any part of the digestive tract. While the cause of IBD remains unclear, it is acknowledged that the disease has much to do with the dysregulation of intestinal immunity. In the intestinal immune regulatory system, Cholesterol-25-hydroxylase (CH25H) plays an important role in regulating the function of immune cells and lipid metabolism through catalyzing the oxidation of cholesterol into 25-hydroxycholesterol (25-HC). Specifically, CH25H focuses its mechanism of regulating the inflammatory response, signal transduction and cell migration on various types of immune cells by binding to relevant receptors, and the mechanism of regulating lipid metabolism and immune cell function via the transcription factor Sterol Regulator-Binding Protein. Based on this foundation, this article will review the function of CH25H in intestinal immunity, aiming to provide evidence for supporting the discovery of early diagnostic and treatment targets for IBD.

Immunomodulatory effects of inulin and its intestinal metabolites

"Dietary fiber" (DF) refers to a type of carbohydrate that cannot be digested fully. DF is not an essential nutrient, but it plays an important part in enhancing digestive capacity and maintaining intestinal health. Therefore, DF supplementation in the daily diet is highly recommended. Inulin is a soluble DF, and commonly added to foods. Recently, several studies have found that dietary supplementation of inulin can improve metabolic function and regulate intestinal immunity. Inulin is fermented in the colon by the gut microbiota and a series of metabolites is generated. Among these metabolites, short-chain fatty acids provide energy to intestinal epithelial cells and participate in regulating the differentiation of immune cells. Inulin and its intestinal metabolites contribute to host immunity. This review summarizes the effect of inulin and its metabolites on intestinal immunity, and the underlying mechanisms of inulin in preventing diseases such as type 2 diabetes mellitus, inflammatory bowel disease, chronic kidney disease, and certain cancer types.

Emerging roles of host and microbial bioactive lipids in inflammatory bowel diseases

The intestinal tract harbors diverse microorganisms, host- and microbiota-derived metabolites, and potentially harmful dietary antigens. The epithelial barrier separates the mucosa, where diverse immune cells exist, from the lumen to avoid excessive immune reactions against microbes and dietary antigens. Inflammatory bowel disease (IBD), such as ulcerative colitis and Crohn's disease, is characterized by a chronic and relapsing disorder of the gastrointestinal tract. Although the precise etiology of IBD is still largely unknown, accumulating evidence suggests that IBD is multifactorial, involving host genetics and microbiota. Alterations in the metabolomic profiles and microbial community are features of IBD. Advances in mass spectrometry-based lipidomic technologies enable the identification of changes in the composition of intestinal lipid species in IBD. Because lipids have a wide range of functions, including signal transduction and cell membrane formation, the dysregulation of lipid metabolism drastically affects the physiology of the host and microorganisms. Therefore, a better understanding of the intimate interactions of intestinal lipids with host cells that are implicated in the pathogenesis of intestinal inflammation might aid in the identification of novel biomarkers and therapeutic targets for IBD. This review summarizes the current knowledge on the mechanisms by which host and microbial lipids control and maintain intestinal health and diseases.

Single-cell RNA sequencing of human lung innate lymphoid cells in the vascular and tissue niche reveals molecular features of tissue adaptation

Innate lymphoid cells (ILCs) are sentinels of healthy organ function, yet it is unknown how ILCs adapt to distinct anatomical niches within tissues. Here, we used a unique humanized mouse model, MISTRG mice transplanted with human hematopoietic stem and progenitor cells (HSPCs), to define the gene signatures of human ILCs in the vascular versus the tissue (extravascular) compartment of the lung. Single-cell RNA sequencing in combination with intravascular cell labeling demonstrated that heterogeneous populations of human ILCs and natural killer (NK) cells occupied the vascular and tissue niches in the lung of HSPC-engrafted MISTRG mice. Moreover, we discovered that niche-specific cues shape the molecular programs of human ILCs in the distinct sub-anatomical compartments of the lung. Specifically, extravasation of ILCs into the lung tissue was associated with the upregulation of genes involved in the acquisition of tissue residency, cell positioning within the lung, sensing of tissue-derived signals, cellular stress responses, nutrient uptake, and interaction with other tissue-resident immune cells. We also defined a core tissue signature shared between human ILCs and NK cells in the extravascular space of the lung, consistent with imprinting by signals from the local microenvironment. The molecular characterization of human ILCs and NK cells in the vascular and tissue niches of the lung provides new knowledge on the mechanisms of ILC tissue adaptation and represents a resource for further studies.

Regulation of systemic metabolism by tissue-resident immune cell circuits

Recent studies have demonstrated that tissue homeostasis and metabolic function are dependent on distinct tissue-resident immune cells that form functional cell circuits with structural cells. Within these cell circuits, immune cells integrate cues from dietary contents and commensal microbes in addition to endocrine and neuronal signals present in the tissue microenvironment to regulate structural cell metabolism. These tissue-resident immune circuits can become dysregulated during inflammation and dietary overnutrition, contributing to metabolic diseases. Here, we review the evidence describing key cellular networks within and between the liver, gastrointestinal tract, and adipose tissue that control systemic metabolism and how these cell circuits become dysregulated during certain metabolic diseases. We also identify open questions in the field that have the potential to enhance our understanding of metabolic health and disease.

Crosstalk between the gut microbiota and innate lymphoid cells in intestinal mucosal immunity

The human gastrointestinal mucosa is colonized by thousands of microorganisms, which participate in a variety of physiological functions. Intestinal dysbiosis is closely associated with the pathogenesis of several human diseases. Innate lymphoid cells (ILCs), which include NK cells, ILC1s, ILC2s, ILC3s and LTi cells, are a type of innate immune cells. They are enriched in the mucosal tissues of the body, and have recently received extensive attention. The gut microbiota and its metabolites play important roles in various intestinal mucosal diseases, such as inflammatory bowel disease (IBD), allergic disease, and cancer. Therefore, studies on ILCs and their interaction with the gut microbiota have great clinical significance owing to their potential for identifying pharmacotherapy targets for multiple related diseases. This review expounds on the progress in research on ILCs differentiation and development, the biological functions of the intestinal microbiota, and its interaction with ILCs in disease conditions in order to provide novel ideas for disease treatment in the future.

Gut-liver axis: barriers and functional circuits

The gut and the liver are characterized by mutual interactions between both organs, the microbiome, diet and other environmental factors. The sum of these interactions is conceptualized as the gut-liver axis. In this Review we discuss the gut-liver axis, concentrating on the barriers formed by the enterohepatic tissues to restrict gut-derived microorganisms, microbial stimuli and dietary constituents. In addition, we discuss the establishment of barriers in the gut and liver during development and their cooperative function in the adult host. We detail the interplay between microbial and dietary metabolites, the intestinal epithelium, vascular endothelium, the immune system and the various host soluble factors, and how this interplay establishes a homeostatic balance in the healthy gut and liver. Finally, we highlight how this balance is disrupted in diseases of the gut and liver, outline the existing therapeutics and describe the cutting-edge discoveries that could lead to the development of novel treatment approaches.

Controversial role of ILC3s in intestinal diseases: A novelty perspective on immunotherapy

ILC3s have been identified as crucial immune regulators that play a role in maintaining host homeostasis and modulating the antitumor response. Emerging evidence supports the idea that LTi cells play an important role in initiating lymphoid tissue development, while other ILC3s can promote host defense and orchestrate adaptive immunity, mainly through the secretion of specific cytokines and crosstalk with other immune cells or tissues. Additionally, dysregulation of ILC3-mediated overexpression of cytokines, changes in subset abundance, and conversion toward other ILC subsets are closely linked with the occurrence of tumors and inflammatory diseases. Regulation of ILC3 cytokines, ILC conversion and LTi-induced TLSs may be a novel strategy for treating tumors and intestinal or extraintestinal inflammatory diseases. Herein, we discuss the development of ILCs, the biology of ILC3s, ILC plasticity, the correlation of ILC3s and adaptive immunity, crosstalk with the intestinal microenvironment, controversial roles of ILC3s in intestinal diseases and potential applications for treatment.

Embryonic type 3 innate lymphoid cells sense maternal dietary cholesterol to control local Peyer's patch development

Lymphoid tissue inducer (LTi) cells develop during intrauterine life and rely on developmental programs to initiate the organogenesis of secondary lymphoid organs (SLOs). This evolutionary conserved process endows the fetus with the ability to orchestrate the immune response after birth and to react to the triggers present in the environment. While it is established that LTi function can be shaped by maternal-derived cues and is critical to prepare the neonate with a functional scaffold to mount immune response, the cellular mechanisms that control anatomically distinct SLO organogenesis remain unclear. We discovered that LTi cells forming Peyer's patches, gut-specific SLOs, require the coordinated action of two migratory G protein coupled receptors (GPCR) GPR183 and CCR6. These two GPCRs are uniformly expressed on LTi cells across SLOs, but their deficiency specifically impacts Peyer's patch formation, even when restricted to fetal window. The unique CCR6 ligand is CCL20, while the ligand for GPR183 is the cholesterol metabolite 7α,25-Dihydroxycholesterol (7α,25-HC), whose production is controlled by the enzyme cholesterol 25-hydroxylase (CH25H). We identified a fetal stromal cell subset that expresses CH25H and attracts LTi cells in the nascent Peyer's patch anlagen. GPR183 ligand concentration can be modulated by the cholesterol content in the maternal diet and impacts LTi cell maturation in vitro and in vivo, highlighting a link between maternal nutrients and intestinal SLO organogenesis. Our findings revealed that in the fetal intestine, cholesterol metabolite sensing by GPR183 in LTi cells for Peyer's patch formation is dominant in the duodenum, the site of cholesterol absorption in the adult. This anatomic requirement suggests that embryonic, long-lived non-hematopoietic cells might exploit adult metabolic functions to ensure highly specialized SLO development in utero.

Skin γδ T cell inflammatory responses are hardwired in the thymus by oxysterol sensing via GPR183 and calibrated by dietary cholesterol

Dietary components and metabolites have a profound impact on immunity and inflammation. Here, we investigated how sensing of cholesterol metabolite oxysterols by γδ T cells impacts their tissue residency and function. We show that dermal IL-17-producing γδ T (Tγδ17) cells essential for skin-barrier homeostasis require oxysterols sensing through G protein receptor 183 (GPR183) for their development and inflammatory responses. Single-cell transcriptomics and murine reporter strains revealed that GPR183 on developing γδ thymocytes is needed for their maturation by sensing medullary thymic epithelial-cell-derived oxysterols. In the skin, basal keratinocytes expressing the oxysterol enzyme cholesterol 25-hydroxylase (CH25H) maintain dermal Tγδ17 cells. Diet-driven increases in oxysterols exacerbate Tγδ17-cell-mediated psoriatic inflammation, dependent on GPR183 on γδ T cells. Hence, cholesterol-derived oxysterols control spatially distinct but biologically linked processes of thymic education and peripheral function of dermal T cells, implicating diet as a focal parameter of dermal Tγδ17 cells.

Endothelial cell-derived oxysterol ablation attenuates experimental autoimmune encephalomyelitis

The vasculature is a key regulator of leukocyte trafficking into the central nervous system (CNS) during inflammatory diseases including multiple sclerosis (MS). However, the impact of endothelial-derived factors on CNS immune responses remains unknown. Bioactive lipids, in particular oxysterols downstream of Cholesterol-25-hydroxylase (Ch25h), promote neuroinflammation but their functions in the CNS are not well-understood. Using floxed-reporter Ch25h knock-in mice, we trace Ch25h expression to CNS endothelial cells (ECs) and myeloid cells and demonstrate that Ch25h ablation specifically from ECs attenuates experimental autoimmune encephalomyelitis (EAE). Mechanistically, inflamed Ch25h-deficient CNS ECs display altered lipid metabolism favoring polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) expansion, which suppresses encephalitogenic T lymphocyte proliferation. Additionally, endothelial Ch25h-deficiency combined with immature neutrophil mobilization into the blood circulation nearly completely protects mice from EAE. Our findings reveal a central role for CNS endothelial Ch25h in promoting neuroinflammation by inhibiting the expansion of immunosuppressive myeloid cell populations.

GPR183 antagonism reduces macrophage infiltration in influenza and SARS-CoV-2 infection

RATIONALE

Severe viral respiratory infections are often characterised by extensive myeloid cell infiltration and activation and persistent lung tissue injury. However, the immunological mechanisms driving excessive inflammation in the lung remain poorly understood.

OBJECTIVES

To identify the mechanisms that drive immune cell recruitment in the lung during viral respiratory infections and identify novel drug targets to reduce inflammation and disease severity.

METHODS

Preclinical murine models of influenza A virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

RESULTS

Oxidised cholesterols and the oxysterol-sensing receptor GPR183 were identified as drivers of monocyte/macrophage infiltration to the lung during influenza A virus (IAV) and SARS-CoV-2 infection. Both IAV and SARS-CoV-2 infection upregulated the enzymes cholesterol 25-hydroxylase (CH25H) and cytochrome P450 family 7 subfamily member B1 (CYP7B1) in the lung, resulting in local production of the oxidised cholesterols 25-hydroxycholesterol (25-OHC) and 7α,25-dihydroxycholesterol (7α,25-OHC). Loss-of-function mutation of Gpr183 or treatment with a GPR183 antagonist reduced macrophage infiltration and inflammatory cytokine production in the lungs of IAV- or SARS-CoV-2-infected mice. The GPR183 antagonist significantly attenuated the severity of SARS-CoV-2 infection and viral loads. Analysis of single-cell RNA-sequencing data on bronchoalveolar lavage samples from healthy controls and COVID-19 patients with moderate and severe disease revealed that CH25H, CYP7B1 and GPR183 are significantly upregulated in macrophages during COVID-19.

CONCLUSION

This study demonstrates that oxysterols drive inflammation in the lung via GPR183 and provides the first preclinical evidence for the therapeutic benefit of targeting GPR183 during severe viral respiratory infections.

An epithelial cell-derived metabolite tunes immunoglobulin A secretion by gut-resident plasma cells

Immunoglobulin A (IgA) secretion by plasma cells, terminally differentiated B cells residing in the intestinal lamina propria, assures microbiome homeostasis and protects the host against enteric infections. Exposure to diet-derived and commensal-derived signals provides immune cells with organizing cues that instruct their effector function and dynamically shape intestinal immune responses at the mucosal barrier. Recent data have described metabolic and microbial inputs controlling T cell and innate lymphoid cell activation in the gut; however, whether IgA-secreting lamina propria plasma cells are tuned by local stimuli is completely unknown. Although antibody secretion is considered to be imprinted during B cell differentiation and therefore largely unaffected by environmental changes, a rapid modulation of IgA levels in response to intestinal fluctuations might be beneficial to the host. In the present study, we showed that dietary cholesterol absorption and commensal recognition by duodenal intestinal epithelial cells lead to the production of oxysterols, evolutionarily conserved lipids with immunomodulatory functions. Using conditional cholesterol 25-hydroxylase deleter mouse line we demonstrated that 7α,25-dihydroxycholesterol from epithelial cells is critical to restrain IgA secretion against commensal- and pathogen-derived antigens in the gut. Intestinal plasma cells sense oxysterols via the chemoattractant receptor GPR183 and couple their tissue positioning with IgA secretion. Our findings revealed a new mechanism linking dietary cholesterol and humoral immune responses centered around plasma cell localization for efficient mucosal protection.

Novel evaluation indicators of MOG35∼55 induced experimental autoimmune encephalomyelitis in C57BL/6J mice

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS), characterized by demyelinating neuropathy. Despite a long period of research on the immune mechanisms involved in CNS diseases, the etiology of MS remains unknown. MS may present with different clinical and pathological manifestations due to the involvement of different pathogenic processes, including balance and mobility disorders, psychiatric abnormalities, and intestinal dysfunction. We used an animal model of MS, experimental autoimmune encephalomyelitis (EAE), to assess clinical symptoms of MS with the aim of creating new indicators for the assessment of EAE. Our results show that EAE mice develop severe bone loss, anxiety-like moods, and intestinal inflammation in addition to clinical phenomena such as inflammatory infiltration and demyelination of the spinal cord. Our new indicators aim to provide a more comprehensive assessment of MS to avoid the pitfalls of a single intervention and also to provide a more systematic assessment of the effectiveness of drugs used to treat MS.

Metagenomic and single-cell RNA-Seq survey of the Helicobacter pylori-infected stomach in asymptomatic individuals

Helicobacter pylori colonization of the gastric niche can persist for years in asymptomatic individuals. To deeply characterize the host-microbiota environment in H. pylori-infected (HPI) stomachs, we collected human gastric tissues and performed metagenomic sequencing, single-cell RNA-Seq (scRNA-Seq), flow cytometry, and fluorescent microscopy. HPI asymptomatic individuals had dramatic changes in the composition of gastric microbiome and immune cells compared with noninfected individuals. Metagenomic analysis uncovered pathway alterations related to metabolism and immune response. scRNA-Seq and flow cytometry data revealed that, in contrast to murine stomachs, ILC2s are virtually absent in the human gastric mucosa, whereas ILC3s are the dominant population. Specifically, proportion of NKp44+ ILC3s out of total ILCs were highly increased in the gastric mucosa of asymptomatic HPI individuals, and correlated with the abundance of selected microbial taxa. In addition, CD11c+ myeloid cells and activated CD4+ T cells and B cells were expanded in HPI individuals. B cells of HPI individuals acquired an activated phenotype and progressed into a highly proliferating germinal-center stage and plasmablast maturation, which correlated with the presence of tertiary lymphoid structures within the gastric lamina propria. Our study provides a comprehensive atlas of the gastric mucosa-associated microbiome and immune cell landscape when comparing asymptomatic HPI and uninfected individuals.

Stromal regulation of the intestinal barrier

The intestinal barrier is a complex structure that allows the absorption of nutrients while ensuring protection against intestinal pathogens and balanced immunity. The development and maintenance of a functional intestinal barrier is a multifactorial process that is only partially understood. Here we review novel findings on the emerging role of mesenchymal cells in this process using insights gained from lineage tracing approaches, Cre-based gene deletion, and single-cell transcriptomics. The current evidence points toward a key organizer role for distinct mesenchymal lineages in intestinal development and homeostasis, regulating both epithelial and immune components of the intestinal barrier. We further discuss recent findings on functional mesenchymal heterogeneity and implications for intestinal regeneration and inflammatory intestinal pathologies.

T cell-derived interleukin-22 drives the expression of CD155 by cancer cells to suppress NK cell function and promote metastasis

Although T cells can exert potent anti-tumor immunity, a subset of T helper (Th) cells producing interleukin-22 (IL-22) in breast and lung tumors is linked to dismal patient outcome. Here, we examined the mechanisms whereby these T cells contribute to disease. In murine models of lung and breast cancer, constitutional and T cell-specific deletion of Il22 reduced metastases without affecting primary tumor growth. Deletion of the IL-22 receptor on cancer cells decreases metastasis to a degree similar to that seen in IL-22-deficient mice. IL-22 induced high expression of CD155, which bound to the activating receptor CD226 on NK cells. Excessive activation led to decreased amounts of CD226 and functionally impaired NK cells, which elevated the metastatic burden. IL-22 signaling was also associated with CD155 expression in human datasets and with poor patient outcomes. Taken together, our findings reveal an immunosuppressive circuit activated by T cell-derived IL-22 that promotes lung metastasis.

Implication of Oxysterols in Infectious and Non-Communicable Inflammatory Diseases

Oxysterols, derived from cholesterol oxidation, are formed either by autoxidation, via enzymes, or by both processes [...].

Pathogenic role of 25-hydroxycholesterol in cancer development and progression

Cholesterol is an essential lipid that serves several important functions, including maintaining the homeostasis of cells, acting as a precursor to bile acid and steroid hormones and preserving the stability of membrane lipid rafts. 25-hydroxycholesterol (25-HC) is a cholesterol derivative that may be formed from cholesterol. 25-HC is a crucial component in various biological activities, including cholesterol metabolism. In recent years, growing evidence has shown that 25-HC performs a critical function in the etiology of cancer, infectious diseases and autoimmune disorders. This review will summarize the latest findings regarding 25-HC, including its biogenesis, immunomodulatory properties and role in innate/adaptive immunity, inflammation and the development of various types of cancer.

Identification of key genes and their association with immune infiltration in adipose tissue of obese patients: a bioinformatic analysis

Immune cell-mediated adipose tissue (AT) inflammation contributes to obesity-related metabolic disorders, but the precise underlying mechanisms remain largely elusive. In this study, we used the R software to screen key differentially expressed genes (DEGs) in AT from lean and obese individuals and conducted function enrichment analysis. We then analysed their PPI network by using the STRING database. Hub genes were screened by cytohubba plugin. Subsequently, CIBERSORTx was used to predict the proportion of immune cells in AT from lean and obese subjects. Finally, the correlation between hub genes and immune cell proportions was analysed. These studies identified 290 DEGs in the AT between lean and obese subjects. Among them, IL6, CCL19, CXCL8, CXCL12, CCL2, CCL3, CCL4, CXCL2, IL1B, and CXCL1 were proved to be hub genes in regulating the protein-protein interaction (PPI) network. We also found that CXCL8 is positively correlated with resting NK cells, monocytes, activated mast cells, and eosinophils, but negatively correlated with CD8⁺ T cells and activated NK cells in obese individuals. Taken together, our study identified key genes in AT that are correlated with immune cell infiltration, uncovering potential new targets for the prevention and treatment of obesity and its related complications via regulating the immune microenvironment.

Macrophages in health and disease

The heterogeneity of tissue macrophages, in health and in disease, has become increasingly transparent over the last decade. But with the plethora of data comes a natural need for organization and the design of a conceptual framework for how we can better understand the origins and functions of different macrophages. We propose that the ontogeny of a macrophage-beyond its fundamental derivation as either embryonically or bone marrow-derived, but rather inclusive of the course of its differentiation, amidst steady-state cues, disease-associated signals, and time-constitutes a critical piece of information about its contribution to homeostasis or the progression of disease.

Immune niches orchestrated by intestinal mesenchymal stromal cells lining the crypt-villus

The mammalian intestine is an organ that can be spatially defined by two axes: longitudinal and vertical. Such anatomical structure ensures the maintenance of a relatively immuno-quiescent and proliferation-promoting crypt for intestinal stem cell differentiation while actively warding off the invading intestinal microbes at the villus tip during digestion and nutrient absorption. Such behavior is achieved by the fine coordination among intestinal epithelial cells, intestinal mesenchymal stromal cells and tissue-resident immune cells like myeloid cells and lymphocytes. Among these cell types resided in the colon, intestinal mesenchymal stromal cells are considered to be the essential link between epithelium, vasculature, neuronal system, and hematopoietic compartment. Recent advancement of single cell and spatial transcriptomics has enabled us to characterize the spatial and functional heterogeneity of intestinal mesenchymal stromal cells. These studies reveal distinctive intestinal mesenchymal stromal cells localized in different regions of the intestine with diverse functions including but not limited to providing cytokines and growth factors essential for different immune cells and epithelial cells which predict niche formation for immune function from the villus tip to the crypt bottom. In this review, we aim to provide an overall view of the heterogeneity of intestinal mesenchymal stromal cells, the spatial distribution of these cells along with their interaction with immune cells and the potential regulatory cytokine profile of these cell types. Summarization of such information may enrich our current understanding of the immuno-regulatory functions of the newly identified mesenchymal stromal cell subsets beyond their epithelial regulatory function.

CD4+-mediated colitis in mice is independent of the GPR183 and GPR18 pathways

Colitis is characterized by an exacerbated intestinal immune response, but the genetic and other mechanisms regulating immune activation remain incompletely understood. In order to identify new pathways leading to colitis, we sought to identify genes with increased expression in the colons of patients that also are near loci identified by genome wide association studies (GWAS) associated with IBD risk. One such SNP, rs9557195 was of particular interest because it is within an intron of G-protein-coupled receptor (GPR) 183, known to be important for lymphocyte migration. Furthermore, this SNP is in close proximity to the gene encoding another G-protein coupled receptor, GPR18. Analyzing publicly available datasets, we found transcripts of GPR183 and GPR18 to be increased in colon biopsies from ulcerative colitis and Crohn's disease patients, and GPR183 was even more increased in patients resistant to TNF treatment. Expression of both genes also was increased in mouse models of colitis. Therefore, our aim was to understand if increased expression of these GPRs in the intestine is related to disease severity in colitis models. Here we investigated the role of these receptors in the T cell transfer model and the dextran sulfate sodium model. In the T cell transfer model, GPR183 expression on donor T cells, as well as on other cell types in the Rag-/- recipients, was not essential for severe colitis induction. Furthermore, deficiency in Rag-/- mice for the enzyme that synthesizes a cholesterol metabolite that is a major ligand for GPR183 also did not affect disease. Similarly, lack of GPR18 expression in T cells or other cell types did not affect colitis pathogenesis in the T cell transfer or in the dextran sulfate sodium model. Therefore, despite increased expression of transcripts for these genes in the intestine during inflammation in humans and mice, they are not required for disease severity in mouse models of colitis induced by chemical injury or T cell cytokines, perhaps due to redundancy in mechanisms important for homing and survival of lymphocytes to the inflamed intestine.

Consequences and mechanisms of myelin debris uptake and processing by cells in the central nervous system

Central nervous system (CNS) disorders and trauma involving changes to the neuronal myelin sheath have long been a topic of great interest. One common pathological change in these diseases is the generation of myelin debris resulting from the breakdown of the myelin sheath. Myelin debris contains many inflammatory and neurotoxic factors that inhibit remyelination and make its clearance a prerequisite for healing in CNS disorders. Many professional and semiprofessional phagocytes participate in the clearance of myelin debris in the CNS. These cells use various mechanisms for the uptake of myelin debris, and each cell type produces its own unique set of pathologic consequences resulting from the debris uptake. Examining these cells' phagocytosis of myelin debris will contribute to a more complete understanding of CNS disease pathogenesis and help us conceptualize how the necessary clearance of myelin debris must be balanced with the detrimental consequences brought about by its clearance.

Identification of macrophage correlated biomarkers to predict the prognosis in patients with intrahepatic cholangiocarcinoma

Background

It has been shown that tumor-associated immune cells, particularly macrophages, play a fundamental role in the development and treatment response of intrahepatic cholangiocarcinoma (ICC). However, little is known about macrophages at the single cellular level of ICC patients.

Methods

ScRNA-seq from Zhang et al. was used in the present study to identify the genes differentially expressed in ICCs. Furthermore, transcriptomic data from TCGA datasets, IHC and flowcytometry from our cohort were used to confirm the findings. Kaplan-Meier and TIDE scores were also used for prognostic analysis and ICB responses.

Results

A significant number of macrophages were found in ICCs as compared to adjacent tissues. We then extracted, processed, and classified the macrophages from the ICCs and adjacent tissues into 12 clusters. Significantly, the macrophages from the ICC exhibited an immunosuppressed state in terms of both signature gene expression and functional enrichment. Furthermore, our results indicate that, of the 10 selective tumor-promoting genes of macrophages, only MMP19 and SIRPα can predict ICB responses in ICCs. Although a higher expression of MMP19 and SIRPα predict a poor prognosis for ICCs without immunotherapy after surgery, patients with high SIRPα expression were more sensitive to immunotherapy, whereas those with high MMP19 expression were not sensitive to immunotherapy. To define the mechanisms, we found that SIRPα^hi ICCs exhibited an increased enrichment KEGG pathway of leukocyte transendothelial migration and neutrophil extracellular trap formation. The increased immune cell infiltration will increase sensitivity to immunotherapy.

Conclusion

Collectively, macrophages are critical to the immune status of ICCs, and MMP19 and SIRPα can predict prognosis and ICB responses for ICCs.