Intestinal Intraepithelial Lymphocytes Research Articles

The silent threat: Nanopolystyrene and chrysene pollutants disrupt the intestinal mucosal barrier, new insights from juvenile Siniperca chuatsi

The intestinal mucosal barrier—comprising microbial, mechanical, chemical, and immunological barriers—is critical to protection against pathogens and maintenance of host health; however, it remains unclear whether it is affected by environmental contaminants. Therefore, the present study assessed whether exposure to ambient concentrations of nanopolystyrene (NP) and chrysene (CHR)—two ubiquitous environmental pollutants in the aquatic environment—affect the intestinal mucosal barrier in juvenile Siniperca chuatsi. After exposure for 21 days, S. chuatsi exhibited intestinal oxidative stress and imbalance of intestinal microbial homeostasis. NP and/or CHR exposure also disrupted the intestinal mechanical barrier, as evidenced by the altered intestinal epithelial cell morphology, disrupted structure of intercellular tight junctions, and decreased expression of tight junction proteins. Damage to the intestinal chemical barrier manifested as thinning of the mucus layer owing to the loss and damage of goblet cells. Furthermore, the intestinal immunological barrier was impaired as indicated by the loss of intestinal intraepithelial lymphocytes and increase in pro-inflammatory cytokines, chemokines, and immunoglobulins. These findings collectively suggest that the intestinal mucosal barrier was damaged. This study is, to the best of our knowledge, the first to report that exposure to NP and/or CHR at environmentally relevant concentrations disrupts the intestinal mucosal barrier in organisms and highlight the significance of nanoplastic/CHR pollution for intestinal health.

Intraepithelial Lymphocytes of the Intestine.

The intestinal epithelium, which segregates the highly stimulatory lumen from the underlying tissue, harbors one of the largest lymphocyte populations in the body, intestinal intraepithelial lymphocytes (IELs). IELs must balance tolerance, resistance, and tissue protection to maintain epithelial homeostasis and barrier integrity. This review discusses the ontogeny, environmental imprinting, Tcell receptor (TCR) repertoire, and function of intestinal IELs. Despite distinct developmental pathways, IEL subsets share core traits including an epithelium-adapted profile, innate-like properties, cytotoxic potential, and limited TCR diversity. IELs also receive important developmental and functional cues through interactions with epithelial cells, microbiota, and dietary components. The restricted TCR diversity of IELs suggests that a limited set of intestinal antigens drives IEL responses, with potential functional consequences. Finally, IELs play a key role in promoting homeostatic immunity and epithelial barrier integrity but can become pathogenic upon dysregulation. Therefore, IELs represent intriguing but underexamined therapeutic targets for inflammatory diseases and cancer. Expected final online publication date for the Annual Review of Immunology, Volume 42 is April 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Single cell analysis revealed that two distinct, unique CD4+ T cell subsets were increased in the small intestinal intraepithelial lymphocytes of aged mice.

Recent advances in research suggest that aging has a controllable chronic inflammatory disease aspect. Aging systemic T cells, which secrete pro-inflammatory factors, affect surrounding somatic cells, and accelerate the aging process through chronic inflammation, have attracted attention as potential therapeutic targets in aging. On the other hand, there are few reports on the aging of the intestinal immune system, which differs from the systemic immune system in many ways. In the current study, we investigated the age-related changes in the intestinal immune system, particularly in T cells. The most significant changes were observed in the CD4+ T cells in the small intestinal IEL, with a marked increase in this fraction in old mice and reduced expression of CD27 and CD28, which are characteristic of aging systemic T cells. The proliferative capacity of aging IEL CD4+ T cells was significantly more reduced than that of aging systemic T cells. Transcriptome analysis showed that the expression of inflammatory cytokines was not upregulated, whereas Cd8α, NK receptors, and Granzymes were upregulated in aging IEL CD4+ T cells. Functional analysis showed that aging IEL T cells had a higher cytotoxic function against intestinal tumor organoids in vitro than young IEL T cells. scRNAseq revealed that splenic T cells show a transition from naïve to memory T cells, whereas intestinal T cells show the emergence of a CD8αα+CD4+ T cell fraction in aged mice, which is rarely seen in young cells. Further analysis of the aging IEL CD4+ T cells showed that two unique subsets are increased that are distinct from the systemic CD4+ T cells. Subset 1 has a pro-inflammatory component, with expression of IFNγ and upregulation of NFkB signaling pathways. Subset 2 does not express IFNγ, but upregulates inhibitory molecules and nIEL markers. Expression of granzymes and Cd8a was common to both. These fractions were in opposite positions in the clustering by UMAP and had different TCR repertoires. They may be involved in the suppression of intestinal aging and longevity through anti-tumor immunity, elimination of senescent cells and stressed cells in the aging environment. This finding could be a breakthrough in aging research.

Activation of mucosal insulin receptor exacerbates intestinal inflammation by promoting tissue resident memory T cells differentiation through EZH2

BackgroundInflammatory Bowel Diseases (IBD), an autoimmune disease characterised by abnormal intestinal immunity, are related to vital morbidity around the world. However, therapeutic agents for IBD have not achieved desired benefit. Exploring new therapeutic targets for IBD, especially based on its abnormally intestinal immunity, could alleviate the flare-up and worsening of IBD. Tissue resident memory T cells (TRM) are core of multiple autoimmune diseases, including IBD. However, the mechanism of TRM differentiation remains to be investigated.MethodsThe alterations in mRNA and lncRNA profile of intestinal intraepithelial lymphocytes (IELs), the largest component of intestinal TRM, were analyzed in DSS-induced chronic colitis. Based on it, we examined the function of rectal insulin instillation in a dextran sodium sulfate (DSS) induced chronic colitis. Furthermore, we investigated the downstream-target of the insulin pathway—EZH2 and the crucial role of EZH2 in intestinal tissue resident memory T cell differentiation by utilizing EZH2fl/flCD4cre mice.ResultsInsulin receptor (INSR) expression was found to be significantly reduced. Activation of mucosal insulin pathway by rectal insulin instillation exacerbated colitis by disrupting IELs subgroups and up-regulating TNF-ɑ and IL-17 expression. Rectal insulin instillation promoted EZH2 expression and EZH2 inhibition alleviated chronic colitis. EZH2fl/flCD4cre mice restored the normal IEL subgroups and suppressed TNF-ɑ and IL-17 expression, exhibiting alleviated colitis. IELs from EZH2fl/flCD4cre mice exhibit significant changes in TRM related phenotype. CD4+TRM was significantly increased in chronic colitis and decreased in EZH2fl/flCD4cre mice.ConclusionInsulin receptor of intestinal mucosal T-cells could promote intestinal TRM differentiation via EZH2. Our discoveries suggest that therapies targeting colonic INSR and EZH2 could be potential treatment for IBD based on its regulatory effects on TRM. Insulin receptor inhibitors rather than insulin should be applied during colitis-active phase. In addition, EZH2 shows to be a downstream signal of the insulin pathway and EZH2 inhibitor could alleviating intestinal inflammation. However, the critical role of EZH2 in TRM differentiation restricts the anti-tumor effects of EZH2 inhibitor in vivo.

Effects of Huangqi Gancao Decoction on intestinal immunity and microbiota in immunocompromised mice models.

The classical medicinal formula Huangqi Gancao Decoction (HQGCD), originating from the medical book" Yi Lin Gai Cuo". Up to now, the studies focusing on the immunoenhancement effects of HQGCD are few, and the actionpathway is not yet clear. In this study, SPF male KM mice were utilized as a model for immunosuppression. Comprehensive observations were made regarding the general behavior and condition of the mice, in addition to monitoring fluctuations in body weight and food intake. The blood routine index was measured, and morphological changes in the ileum and colon tissues were examined. The level of secretory immunoglobulin A (sIgA), superoxide dismutase (SOD), and malondialdehyde (MDA) in ileum and colon tissues were quantified. Additionally, the bone marrow total DNA index was assessed. Flow cytometry analyzed the proportions of CD3⁺, CD4⁺, CD8⁺, and CD4+CD8+ double-positive (DP) T lymphocytes in small intestinal intraepithelial lymphocytes (IELs). Lastly, the composition and diversity of the cecal microbiota were evaluated using 16S rDNA sequencing technology. After HQGCD intervention, there were no significant changes in the mice's feed intake and body weight. However, the tissue structures of the ileum and colon showed recovery. In the blood routine index, there was an increase in the total white blood cell count, lymphocyte count, red blood cell count, hematocrit, and hemoglobin content. Additionally, the bone marrow total DNA index was elevated. Level of SOD and sIgA in ileum and colon tissues increased, while the level of MDA decreased. The proportions of CD3⁺ and CD4⁺ T lymphocytes within IELs increased, along with an increase in DP T lymphocytes in IELs (DP IELs), whereas the proportion of CD8⁺ T lymphocytes decreased. The cecal microbiota underwent changes, with an increase in the variety and number of beneficial microbiota. HQGCD could restore the intestinal immune function of immunocompromised mice, and had a certain positive effect on cecal microbiota.

Dual regulation effect and mechanism of human myeloid-derived suppressor cells on anticolorectal cancer cells activity of Vγ9Vδ2 T cells.

Myeloid-derived suppressor cells (MDSC) are a group of immature inhibitory cells of bone marrow origin. Human γδ T cells (mainly Vγ9Vδ2 T cells) have emerged as dominant candidates for cancer immunotherapy because of their unique recognition pattern and broad killing activity against tumor cells. Intestinal mucosal intraepithelial lymphocytes are almost exclusively γδ T cells, so it plays an important role in inhibiting the development of colorectal cancer. In this study, we investigated the effects and molecular mechanism of human MDSC on anticolorectal cancer cells activity of Vγ9Vδ2 T cells. Our results suggested that MDSC can reduce the NKG2D expression of Vγ9Vδ2 T cells through direct cell-cell contact, which is associated with membrane-type transforming growth factor-β. In contrast, MDSC can increase Vγ9Vδ2 T cells activation and production of IFN-γ, perforin, Granzyme B through direct cell-cell contact. This may be related to the upregulation of T-bet in Vγ9Vδ2 T cells by MDSC. However, MDSC had a dominant negative regulatory effect on the anticolorectal cancer cells activity of Vγ9Vδ2 T cells. Our study provides a theoretical basis for the immune regulatory function of human MDSC on γδ T cells. This will be conducive to the clinical development of a new antitumor therapy strategy.

Commensal bacteria maintain a Qa-1b-restricted unconventional CD8+ T population in gut epithelium.

Intestinal intraepithelial lymphocytes (IELs) are characterized by an unusual phenotype and developmental pathway, yet their specific ligands and functions remain largely unknown. Here by analysis of QFL T cells, a population of CD8+ T cells critical for monitoring the MHC I antigen processing pathway, we established that unconventional Qa-1b-restricted CD8+ T cells are abundant in intestinal epithelium. We found that QFL T cells showed a Qa-1b-dependent unconventional phenotype in the spleen and small intestine of naïve wild-type mice. The splenic QFL T cells showed innate-like functionality exemplified by rapid response to cytokines or antigens, while the gut population was refractory to stimuli. Microbiota was required for the maintenance, but not the initial gut homing of QFL T cells. Moreover, monocolonization with Pediococcus pentosaceus, which expresses a peptide that cross-activated QFL T cells, was sufficient to maintain QFL T cells in the intestine. Thus, microbiota is critical for shaping the Qa-1b-restricted IEL landscape.

Commensal bacteria maintain a Qa-1b-restricted unconventional CD8+ T population in gut epithelium

Intestinal intraepithelial lymphocytes (IELs) are characterized by an unusual phenotype and developmental pathway, yet their specific ligands and functions remain largely unknown. Here by analysis of QFL T cells, a population of CD8+ T cells critical for monitoring the MHC I antigen processing pathway, we established that unconventional Qa-1b-restricted CD8+ T cells are abundant in intestinal epithelium. We found that QFL T cells showed a Qa-1b-dependent unconventional phenotype in the spleen and small intestine of naïve wild-type mice. The splenic QFL T cells showed innate-like functionality exemplified by rapid response to cytokines or antigens, while the gut population was refractory to stimuli. Microbiota was required for the maintenance, but not the initial gut homing of QFL T cells. Moreover, monocolonization with Pediococcus pentosaceus, which expresses a peptide that cross-activated QFL T cells, was sufficient to maintain QFL T cells in the intestine. Thus, microbiota is critical for shaping the Qa-1b-restricted IEL landscape.

The transcription factor Aiolos restrains the activation of intestinal intraepithelial lymphocytes.

Intestinal intraepithelial lymphocytes (IELs) exhibit prompt innate-like responses to microenvironmental cues and require strict control of effector functions. Here we showed that Aiolos, an Ikaros zinc-finger family member encoded by Ikzf3, acted as a regulator of IEL activation. Ikzf3-/- CD8αα+ IELs had elevated expression of NK receptors, cytotoxic enzymes, cytokines and chemokines. Single-cell RNA sequencing of Ikzf3-/- and Ikzf3+/+ IELs showed an amplified effector machinery in Ikzf3-/- CD8αα+ IELs compared to Ikzf3+/+ counterparts. Ikzf3-/- CD8αα+ IELs had increased responsiveness to interleukin-15, which explained a substantial part, but not all, of the observed phenotypes. Aiolos binding sites were close to those for the transcription factors STAT5 and RUNX, which promote interleukin-15 signaling and cytolytic programs, and Ikzf3 deficiency partially increased chromatin accessibility and histone acetylation in these regions. Ikzf3 deficiency in mice enhanced susceptibility to colitis, underscoring the relevance of Aiolos in regulating the effector function in IELs.

Novel T cell/organoid culture system allows ex vivo modeling of intestinal graft-versus-host disease.

Acute graft-versus-host disease (GvHD) remains the biggest clinical challenge and prognosis-determining complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Donor T cells are acceptedly key mediators of alloreactivity against host tissues and here especially the gut. In support of previous studies, we found that the intestinal intra-epithelial lymphocyte (IEL) compartment was dynamically regulated in the course of MHC class I full mismatch allo-HSCT. However, while intestinal epithelial cell (IEC) damage endangers the integrity of the intestinal barrier and is a core signature of intestinal GvHD, the question whether and to what degree IELs are contributing to IEC dysregulation is poorly understood. To study lymphoepithelial interaction, we employed a novel ex vivo T cell/organoid co-culture model system. Here, allogeneic intra-epithelial T cells were superior in inducing IEC death compared to syngeneic IEL and allogeneic non-IEL T cells. The ability to induce IEC death was predominately confined to TCRβ+ T cells and was executed in a largely IFNγ-dependent manner. Alloreactivity required a diverse T cell receptor (TCR) repertoire since IELs genetically modified to express a TCR restricted to a single, non-endogenous antigen failed to mediate IEC pathology. Interestingly, minor histocompatibility antigen (miHA) mismatch was sufficient to elicit IEL-driven IEC damage. Finally, advanced live cell imaging analyses uncovered that alloreactive IELs patrolled smaller areas within intestinal organoids compared to syngeneic controls, indicating their unique migratory properties within allogeneic IECs. Together, we provide here experimental evidence for the utility of a co-culture system to model the cellular and molecular characteristics of the crosstalk between IELs and IEC in an allogeneic setting ex vivo. In the light of the emerging concept of dysregulated immune-epithelial homeostasis as a core aspect of intestinal GvHD, this approach represents a novel experimental system to e.g. screen therapeutic strategies for their potential to normalize T cell/IEC- interaction. Hence, analyses in pre-clinical in vivo allo-HSCT model systems may be restricted to hereby positively selected, promising approaches.

Tumor-infiltrating gamma delta T-cells reveal exhausted subsets with remarkable heterogeneity in colorectal cancer.

The γδT-cells recognize infected or transformed cells. However, unlike αβT-cells, γδT-cells are innate-like immune cells, with no major histocompatibility complex restriction requirements. γδT-cells are the main population of intestinal intraepithelial lymphocytes (IELs) and are associated with the antitumor immune response, particularly in colorectal cancer (CRC). Although CD8+ T-cells exhibit dysfunction and even exhaustion in the tumor microenvironment (TME), which contributes to tumor immune escape, whether the same applies to tumor-infiltrating (TI)-γδT-cells is not completely understood. Here, we sought to investigate the expression pattern of inhibitory receptors and functional state of TI-γδT-cells, and reveal the features of exhausted TI-γδT-cells in the CRC TME. We demonstrated that TI-γδT-cells exhibited exhaustion phenotypes and displayed more severe functional exhaustion than TI-CD8+ T-cells or NK-cells in the TME of CRC. In addition, scRNA-seq analysis of TI-γδT-cells revealed three exhausted subsets with remarkable heterogeneity. The presence of three heterogeneous exhausted γδT-cell (Tex) populations, including Texprog , Textran and Texterm were further confirmed by flow cytometry, on the basis of PD-1 and TIM-3 expression. Finally, we revealed that c-Maf not only contributed to γδT-cell exhaustion via upregulation of inhibitory receptors, but also involved in the exhaustion of CD8+ T and NK-cells. c-Maf may also be an important contributor to γδT-cell exhaustion in CRC patients. These findings indicated that TI-γδT-cells exhibit phenotypic and functional exhaustion in the CRC TME. The revealed features of exhausted TI-γδT-cells may provide help for understanding the mechanisms and the association of γδT-cell exhaustion with tumor development and pathogenesis.

Interleukin-7 and interleukin-15 as prognostic biomarkers in sepsis and septic shock: Correlation with inflammatory markers and mortality

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection and a syndrome shaped by pathogen and host factors evolving over time. During sepsis, the absolute number of lymphocytes decreases. CD4+ and CD8+ T cells, B cells, and NK cells are reduced. Lymphocytes are an essential element of the body's defence against pathogens. Interleukin 7 has strong anti-apoptotic properties and induces the proliferation of CD4+ and CD8+ T lymphocytes. IL-15 prompts the generation of mature NK cells in the bone marrow, plays an important role in the generation, cytotoxicity, and survival of CD8+ T lymphocytes, and is essential for the survival of natural killer T (NKT) and intestinal intraepithelial lymphocytes (IELs). The study highlights the importance of monitoring IL-7 levels in patients with sepsis and septic shock, as low levels of this cytokine were associated with an increased risk of mortality. Physicians should consider using IL-7 levels as a biomarker to identify patients who are at higher risk of mortality and may require more aggressive treatment.

206-OR: A Human Gut Commensal, Parabacteroides distasonis, Stimulates an Inflammatory Response Specific to the Pancreas but Not to the Intestines, and Induces Type 1 Diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by the destruction of pancreatic β-cells, resulting in insulin deficiency and hyperglycemia. Previous studies have shown that the gut microbiome is associated with the development and incidence of diabetes, however, the main trigger of T1D is unknown. Insulin protein epitopes are the primary targets of the T-cells, stimulating an autoimmune response against β-cells. We previously identified and characterized a bacterial peptide mimic of insulin B-chain 9-23 epitope (insB:9-23) in P. distasonis, a human gut commensal. This bacterial mimic, hprt4-18, is identified in the N-terminal of the hypoxanthine-guanine phosphoribosyltransferase protein. It activates both human T-cell clones and nonobese diabetic (NOD) mice T-cell hybridomas specific to insB:9-23. Reanalysis of DIABIMMUNE data confirms that exposure to hprt-4:18 in the first three years of life increases the risk of seropositivity. The colonization of female NOD mice's gut microbiome with P. distasonis accelerated the infiltration of T-cells into the islets and increased the incidence of T1D. In addition, P. distasonis colonization increased splenic CD4+ and CD8+ T-cells and decreased FoxP3+ Treg cells. Because the first interaction between the host immune system and gut microbes occurs in the intestines, we determined the direct effects of P. distasonis colonization on intestinal intraepithelial lymphocyte (IELs) composition. Notably, P. distasonis colonization decreased CD4+, CD4+ CD62L+ (Naïve), CD8+CD44+ (Effector), CD4+CD44+CD62L+ (Central) T-cell and B-cell populations. Taken together, these results support our molecular mimicry mechanism hypothesis as P. distasonis decrease inflammation in the intestines, however, induce an autoimmune response specific to pancreatic β-cells resulting in accelerated diabetes incidence in female NOD mice. Disclosure K.Girdhar: None. A.Raisingani: None. E.Altindis: None. Funding JDRF T1D (5112731); Mathers Foundation

TGF-β controls development of TCRγδ+CD8αα+ intestinal intraepithelial lymphocytes

γδ intestinal intraepithelial lymphocytes (IELs) constitute the majority of IELs with unique CD8αα+ homodimers that are distinct from γδT cells in other tissues. However, it remains largely unclear how those cells develop. Here we show that transforming growth factor beta (TGF-β) signaling controls the development of TCRγδ+CD8αα+ IELs. Deletion of TGF-β receptors or Smad3 and Smad2 in bone marrow stem cells caused a deficiency of TCRγδ+CD8αα+ IELs in mixed bone marrow chimeric mice. Mechanistically, TGF-β is required for the development of TCRγδ+CD8αα+ IELs thymic precursors (CD44–CD25– γδ thymocytes). In addition, TGF-β signaling induced CD8α in thymic γδT cells and maintained CD8α expression and survival in TCRγδ+CD8αα+ IELs. Moreover, TGF-β also indirectly controls TCRγδ+CD8αα+ IELs by modulating the function of intestinal epithelial cells (IECs). Importantly, TGF-β signaling in TCRγδ+CD8αα+ IELs safeguarded the integrity of the intestinal barrier in dextran sulfate sodium (DSS)-induced colitis.

The role of intestinal intraepithelial lymphocytes in resistance against coccidiosis in chickens

Abstract Coccidiosis is a critical enteric disease that costs more than $14.5 billion in annual cost to world poultry industry. It is caused by different Eimeriaspecies that invade and replicate within the intestinal epithelium in a site-specific manner. The Eimeriainfection induces local intestinal damage, reduces feed consumption, feed utilization, and growth performance, and increasing mortality rate. With the recent antibiotic ban including anticoccidial drugs in chicken production, the live vaccination become widely used to control coccidiosis. However, the live vaccines are expensive, require time to circulate in the host to induce a protective immunity, and process a high-risk factor for necrotic enteritis caused by clostridium perfringens. Therefore, there is a high demand for development of safe, protective, and inexpensive vaccines against coccidiosis which require better understanding of host immune responses to Eimeria parasites. The aim of this study is to elucidate the protective role of intestinal intraepithelial lymphocytes (IELs) during the Eimeriainfection. At 3 week of age, SPF white-leghorn chicks were divided into 3 groups. Each group (n=50) was orally inoculated with 20,000 oocytes of Eimeria (E) acervuline or E. maxima, or mock-inoculated with PBS. At 2 day post-infection (dpi), 7 dpi and 14 dpi, the frequency and the number of small intestinal IEL populations were determined by a flow cytometry. Eimeriainfection induced the number of TCRγδ +, TCRβ +, TCR neg, TCRβ +CD4 +, TCRβ +CD4 +CD8α +, TCRβ +CD8αβ +, TCRβ +CD8αα +, and iCD8α IELs compared to the control group at 14 dpi. However, there was no difference among groups at 2 and 7 dpi. More experiments are underway to determine the effector and function of each subset of IELs. Startup funding, The OSU

A novel method for isolation and flow cytometry analysis of intraepithelial lymphocytes from colon biopsies

Investigating the immune responses of the intestine in response to different insults is predominantly limited to indirect methods such as circulating markers of intestinal health or gene expression from dissections. We describe here a validated protocol for the isolation and subsequent flow cytometry analysis of intestinal intraepithelial lymphocytes (IEL) from colonic biopsy samples. Colon biopsy samples were collected with endoscopy forceps from Holstein dairy bull calves at d 2, 28, and 42 of life. The biopsies were put into an isolation solution of Hanks' balanced salt solution, and fetal bovine serum followed by digestion solution. The solution was filtered and the flow-through, containing IEL, was stained with fluorescent antibodies for flow cytometry analysis. Density gradient separation of the isolate yielded higher viability and cleaner samples for flow cytometry analysis. Anti-bovine γ chain of the T cell receptor was used to identify populations of gamma delta (γδ) T cells via flow cytometry. In addition, γδ T cell subsets were identified using an anti-bovine antibody against the coreceptor workshop cluster 1. This method allowed for the precise identification of lymphocyte populations and evaluation of the proportion of different subsets of γδ T cells from intestinal IEL over time. The technique described here will allow the research community to characterize intestinal immune function over time and improve our understanding of how different management and nutritional strategies affect intestinal health.

Metformin alleviates liver fibrosis in mice by enriching Lactobacillus sp. MF-1 in the gut microbiota

BackgroundLiver fibrosis is associated with gut dysbiosis. Metformin administration has emerged as a promising method for the treatment of organ fibrosis. We aimed to investigate whether metformin ameliorates liver fibrosis by enhancing the gut microbiota in mice with carbon tetrachloride (CCl4)-induced liver fibrosis and the underlying mechanism. Materials and methodsA liver fibrosis mouse model was established, and the therapeutic effects of metformin were observed. We administered antibiotic treatment and performed fecal microbiota transplantation (FMT), and 16S rRNA-based microbiome analysis to evaluate the effects of the gut microbiome on metformin-treated liver fibrosis. We isolated the bacterial strain preferably enriched by metformin and assessed its antifibrotic effects. ResultsMetformin treatment repaired the gut integrity of the CCl4-treated mice. It reduced the number of bacteria in colon tissues and reduced the portal vein lipopolysaccharide (LPS) levels. The FMT performed on the metformin-treated CCl4 mice alleviated their liver fibrosis and reduced their portal vein LPS levels. The markedly changed gut microbiota was screened out from the feces and named Lactobacillus sp. MF-1 (L. sp. MF-1). In the CCl4-treated mice, daily gavage of L. sp. MF-1 maintained gut integrity, inhibited bacterial translocation, and reduced liver fibrosis. Mechanistically, metformin or L. sp. MF-1 inhibited the apoptosis of intestinal epithelial cells and restored CD3+ intestinal intraepithelial lymphocytes in the ileum and CD4+Foxp3+ lamina propria lymphocytes in the colon. ConclusionsMetformin and its enriched L. sp. MF-1 can reinforce the intestinal barrier to alleviate liver fibrosis by restoring immune function.

Intestinal cell type-specific communication networks underlie homeostasis and response to Western diet.

The small intestine plays a key role in immunity and mediates inflammatory responses to high fat diets. We have used single-cell RNA-sequencing (scRNA-seq) and statistical modeling to examine gaps in our understanding of the dynamic properties of intestinal cells and underlying cellular mechanisms. Our scRNA-seq and flow cytometry studies of different layers of intestinal cells revealed new cell subsets and modeled developmental trajectories of intestinal intraepithelial lymphocytes, lamina propria lymphocytes, conventional dendritic cells, and enterocytes. As compared to chow-fed mice, a high-fat high-sucrose (HFHS) "Western" diet resulted in the accumulation of specific immune cell populations and marked changes to enterocytes nutrient absorption function. Utilizing ligand-receptor analysis, we profiled high-resolution intestine interaction networks across all immune cell and epithelial structural cell types in mice fed chow or HFHS diets. These results revealed novel interactions and communication hubs among intestinal cells, and their potential roles in local as well as systemic inflammation.

Repression of the aryl-hydrocarbon receptor prevents oxidative stress and ferroptosis of intestinal intraepithelial lymphocytes

The aryl-hydrocarbon receptor (AHR) is a ligand-activated transcription factor that buoys intestinal immune responses. AHR induces its own negative regulator, the AHR repressor (AHRR). Here, we show that AHRR is vital to sustaining intestinal intraepithelial lymphocytes (IELs). AHRR deficiency reduced IEL representation in a cell-intrinsic fashion. Single-cell RNA sequencing revealed an oxidative stress profile in Ahrr-/- IELs. AHRR deficiency unleashed AHR-induced expression of CYP1A1, a monooxygenase that generates reactive oxygen species, increasing redox imbalance, lipid peroxidation, and ferroptosis in Ahrr-/- IELs. Dietary supplementation with selenium or vitamin E to restore redox homeostasis rescued Ahrr-/- IELs. Loss of IELs in Ahrr-/- mice caused susceptibility to Clostridium difficile infection and dextran sodium-sulfate-induced colitis. Inflamed tissue of inflammatory bowel disease patients showed reduced Ahrr expression that may contribute to disease. We conclude that AHR signaling must be tightly regulated to prevent oxidative stress and ferroptosis of IELs and to preserve intestinal immune responses.

Dysregulation of CD177+ neutrophils on intraepithelial lymphocytes exacerbates gut inflammation via decreasing microbiota-derived DMF

ABSTRACT Neutrophils synergize with intestinal resident intraepithelial lymphocytes (IELs) to serve as the first-line defense and maintain intestinal homeostasis. However, the underlying mechanisms whereby neutrophils regulate IELs to inhibit intestinal inflammation are still not completely understood. Here, we found that depletion of neutrophils (especially CD177+ subset) caused expansion of colitogenic TCRγδ+CD8αα+ IELs, increased intestinal inflammation, and dysbiosis after dextran sulfate sodium exposure or Citrobacter rodentium infection in mice. scRNA-seq analysis revealed a pyroptosis-related gene signature and hyperresponsiveness to microbiota in TCRγδ+CD8αα+ IELs from colitic Cd177 −/− mice. Microbiota-derived fumarate and its derivative dimethyl fumarate (DMF), as well as fumarate-producing microbiotas, decreased in the feces of colitic Cd177 −/− mice. Elimination of dysbiosis by antibiotics treatment or co-housing procedure and DMF supplementation restrained TCRγδ+CD8αα+ IEL activation. Consistently, DMF significantly alleviated intestinal mucosal inflammation in mice through restricting gasdermin D (GSDMD)-induced pyroptosis of TCRγδ+CD8αα+ IELs. Therefore, our data reveal that neutrophils inhibit intestinal inflammation by promoting microbiota-derived DMF to regulate TCRγδ+CD8αα+ IEL activation in a GSDMD-mediated pyroptosis-dependent manner, and that DMF may serve as a therapeutic target for the management of intestinal inflammation.