Th17 Cell Effector Function Research Articles

Qingchang suppository ameliorates mucosal inflammation in ulcerative colitis by inhibiting the differentiation and effector functions of Th1 and Th17 cells

Ethnopharmacological relevanceQing Chang Suppository (QCS), a traditional Chinese medicine formula, has been shown to effectively alleviate mucosal inflammation in patients with ulcerative colitis (UC). While the mechanism of QCS appears to be related to the regulation of CD4+T cell subset responses, direct evidence demonstrating that QCS inhibits Th1 and Th17 cell activation in UC (particularly based on human data) remains lacking. Additionally, the precise mechanisms through which QCS affects these cells have yet to be fully elucidated. Aim of studyThis study aimed to investigate the effects of QCS on Th1 and Th17 cell responses in UC and to explore the underlying mechanisms. Materials and methodsTwenty-eight patients with mild-to-moderate UC were recruited and treated with QCS for 12 weeks. Symptoms were assessed every two weeks, with sigmoidoscopies performed at baseline and at week 12. Intestinal mucosal biopsies and peripheral blood (PB) were collected at these time points. At the end of the trial, patients were categorized into responder and non-responder groups based on a modified Mayo disease activity index score. Healthy controls (HCs) were defined as subjects without IBD or colorectal carcinoma but with colon polyps. The frequencies of IFN-γ+CD4+T cells and IL-17A+CD4+T cells in PB and colonic mucosa were measured using flow cytometry. The expression levels and localization of T-bet, RORγT, IFN-γ, TNF-α, and IL-17A were determined via immunofluorescence, and JNK signaling activation was assessed through immunoblotting and immunohistochemistry. All parameters were compared across the three groups. ResultsAt week 12, responders showed a significant reduction in colonic mucosal inflammation compared to baseline, accompanied by decreased frequencies of IFN-γ+CD4+T and IL-17A+CD4+ T cells in both PB and the colonic epithelial layer. Notably, Th1 and Th17 cell activity around intestinal epithelial cells (IECs) was nearly undetectable, as evidenced by the diminished expression of T-bet, RORγT, IFN-γ, TNF-α, and IL-17A. Additionally, JNK phosphorylation in these cells was significantly reduced. In contrast, non-responders exhibited no meaningful improvement; colonic pathology remained unchanged, and elevated levels of IFN-γ+CD4+T and IL-17A+CD 4+T cells persisted in both the PB and colonic epithelial layer. The presence of Th1 and Th17 cells and their associated cytokines around IECs remained substantial, and there was no significant change in JNK activation. ConclusionQCS attenuates mucosal inflammation in UC patients by inhibiting the differentiation and effector functions of Th1 and Th17 cells, primarily through the regulation of the JNK signaling pathway.

Integrin α3 promotes TH17 cell polarization and extravasation during autoimmune neuroinflammation.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) caused by CNS-infiltrating leukocytes, including TH17 cells that are critical mediators of disease pathogenesis. Although targeting leukocyte trafficking is effective in treating autoimmunity, there are currently no therapeutic interventions that specifically block encephalitogenic TH17 cell migration. Here, we report integrin α3 as a TH17 cell-selective determinant of pathogenicity in experimental autoimmune encephalomyelitis. CNS-infiltrating TH17 cells express high integrin α3, and its deletion in CD4+ T cells or Il17a fate-mapped cells attenuated disease severity. Mechanistically, integrin α3 enhanced the immunological synapse formation to promote the polarization and proliferation of TH17 cells. Moreover, the transmigration of TH17 cells into the CNS was dependent on integrin α3, and integrin α3 deficiency enhanced the retention of CD4+ T cells in the perivascular space of the blood-brain barrier. Integrin α3-dependent interactions continuously maintain TH17 cell identity and effector function. The requirement of integrin α3 in TH17 cell pathogenicity suggests integrin α3 as a therapeutic target for MS treatment.

Pyruvate dehydrogenase fuels a critical citrate pool that is essential for Th17 cell effector functions

Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in T helper 17 (Th17) cells still remains to be studied. Here, we show that PDH is essential for the generation of a glucose-derived citrate pool needed for Th17 cell proliferation, survival, and effector function. Invivo, mice harboring a Tcell-specific deletion of PDH are less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increases glutaminolysis, glycolysis, and lipid uptake in a mammalian target of rapamycin (mTOR)-dependent manner. However, cellular citrate remains critically low in mutant Th17 cells, which interferes with oxidative phosphorylation (OXPHOS), lipid synthesis, and histone acetylation, crucial for transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restores their metabolism and function, identifying a metabolic feedback loop within the central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.

Deciphering the mechanism of Tinospora cordifolia extract on Th17 cells through in-depth transcriptomic profiling and in silico analysis.

Naive CD4+ T cells differentiate into effector (Th1, Th2, Th17) cells and immunosuppressive (Treg) cells upon antigenic stimulation in the presence of a specific cytokine milieu. The T cell in vitro culture system provides a very efficient model to study compounds' therapeutic activity and mechanism of action. Tinospora cordifolia (Willd.) Hook.f. & Thomson (Family. Menispermaceae) is one of the widely used drugs in Ayurveda (ancient Indian system of medicine) for various ailments such as inflammatory conditions, autoimmune disorders, and cancer as well as for promoting general health. In vitro and in vivo studies on immune cells comprising dendritic cells, macrophages, and B cells suggest its immune-modulating abilities. However, to date, the effect of T. cordifolia on individual purified and polarized T cell subsets has not been studied. Studying drug effects on T cell subsets is needed to understand their immunomodulatory mechanism and to develop treatments for diseases linked with T cell abnormalities. In this study, we examined the immunomodulatory activity of T. cordifolia on primary CD4+ T cells, i.e., Th1, Th17, and iTreg cells. An aqueous extract of T. cordifolia was non-cytotoxic at concentrations below 1500µg/ml and moderately inhibited the proliferation of naive CD4+ T cells stimulated with anti-CD3ε and anti-CD28 for 96h. T. cordifolia treatment of naive CD4+ T cells differentiated under Th17-polarizing conditions exhibited reduced frequency of IL-17 producing cells with inhibition of differentiation and proliferation. For the first time, in-depth genome-wide expression profiling of T. cordifolia treated naive CD4+ T cells, polarized to Th17 cells, suggests the broad-spectrum activity of T. cordifolia. It shows inhibition of the cytokine-receptor signaling pathway, majorly via the JAK-STAT signaling pathway, subsequently causing inhibition of Th17 cell differentiation, proliferation, and effector function. Additionally, the molecular docking studies of the 69 metabolites of T. cordifolia further substantiate the inhibitory activity of T. cordifolia via the cytokine-receptor signaling pathway. Furthermore, in vitro polarized Th1 and iTreg cells treated with T. cordifolia extract also showed reduced IFN-γ production and FoxP3 expression, respectively. This study provides insight into the plausible mechanism/s of anti-inflammatory activity of T. cordifolia involving T cells, mainly effective in Th17-associated autoimmune and inflammatory diseases.

Intracellular Ca2+ Signaling and Calcium Release-Activated Calcium Modulator ORAI1 Are Associated With CD4+ T Lymphocytes in Dairy Cows.

The nutritional status of dairy cows and the metabolism of specific nutrients are critical regulators of immune cell function. Around the time of parturition, mobilization of body lipid and muscle helps compensate for the decrease in nutrient intake and the increased requirements of the mammary gland for lactation. An end-result of these processes is the marked increase in circulating concentrations of fatty acids (FA), which are a major risk factor for immune dysfunction. In food animal species such as dairy cows, any disturbance in nutritional or immunological homeostasis leads to deleterious feedback loops that can further risk health, efficiency of nutrient use, and compromise availability of safe and nutritious dairy foods for humans. Despite substantial progress with respect to regulation of innate immunity, such knowledge for adaptive immunity is scarce. To help bridge this gap in knowledge, we sought to study the role of calcium release-activated calcium modulator ORAI1 activation in T cells systemic immune function in vivo. CD4+ T cells were isolated from peripheral blood of dairy cows diagnosed as healthy or with ketosis, a common metabolic disorder of FA metabolism. Results revealed that levels of intracellular Ca2+ and reactive oxygen species (ROS) along with the abundance of store-operated Ca2+ entry (SOCE) moiety increased during ketosis. Further, plasma concentrations of inflammatory cytokines were elevated, the balance of Th17/Treg cells was disrupted, mitochondrial function impaired, and the abundance of mitophagy-related proteins in CD4+ T cells altered during ketosis. Molecular characterization of the direct effects of FA was evaluated in CD4+ T cells isolated from the spleen of 1-day-old calves. Enhanced supply of FA increased intracellular Ca2+ and ROS concentrations, upregulated the abundance of proteins associated with mitochondrial dynamics and ORAI1. Intermediates of mitophagy accumulated and the balance of Th17/Treg cells also was affected by the supply of FA. These negative effects were attenuated by silencing or inhibition of ORAI1 in CD4+ T cells. Together, data indicated that physiological states that lead to increases in systemic concentrations of FA could impact adaptive immunity negatively through ORAI1 regulated intracellular Ca2+, ROS balance, and increased effector functions of Th17 cells.

The glucose transporter GLUT3 controls T helper 17 cell responses through glycolytic-epigenetic reprogramming

Metabolic reprogramming is a hallmark of activated Tcells. The switch from oxidative phosphorylation to aerobic glycolysis provides energy and intermediary metabolites for the biosynthesis of macromolecules to support clonal expansion and effector function. Here, we show that glycolytic reprogramming additionally controls inflammatory gene expression via epigenetic remodeling. We found that the glucose transporter GLUT3 is essential for the effector functions of Th17 cells in models of autoimmune colitis and encephalomyelitis. At the molecular level, we show that GLUT3-dependent glucose uptake controls a metabolic-transcriptional circuit that regulates the pathogenicity of Th17 cells. Metabolomic, epigenetic, and transcriptomic analyses linked GLUT3 to mitochondrial glucose oxidation and ACLY-dependent acetyl-CoA generation as a rate-limiting step in the epigenetic regulation of inflammatory gene expression. Our findings are also important from a translational perspective because inhibiting GLUT3-dependent acetyl-CoA generation is a promising metabolic checkpoint to mitigate Th17-cell-mediated inflammatory diseases.

Pharmacological Inhibition of Glutaminase 1 Normalized the Metabolic State and CD4+ T Cell Response in Sjogren's Syndrome.

Previous studies have shown that abnormal metabolic reprogramming in CD4+ T cells could explain the occurrence of several autoimmune disorders, including Sjogren's syndrome (SS). However, therapeutic targets of the abnormal metabolism of CD4+ T cells remain to be explored. Here, we report that glutaminase 1 (Gls1), a pivotal factor in glutaminolysis, might be involved in the pathogenesis of SS. The expression of Gls1 was upregulated in infiltrated labial CD4+ T cells and circulating CD4+ T cells of SS patients. Inhibiting Gls1 with BPTES significantly abolished the proliferation rate, as indicated by EdU, CFSE, and Western blot analyses. Additionally, BPTES downregulated the extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) values of activated CD4+ T cells from SS mice. In vivo, we injected different doses of BPTES into SS-like NOD/Ltj mice and found that 10 mg/kg BPTES significantly restored the salivary flow rate. Histological and qRT–PCR analyses showed that this concentration of BPTES attenuated lymphocytic infiltration and the numbers of PCNA-positive cells and CD4+ T cells. The proportions of IFNγ-producing cells and IL-17A-producing cells and the expression of several proinflammatory cytokines, including IFNγ and IL-17A, were also affected in the salivary glands of SS-like mice. Cytokine production in circulating serum was analyzed and showed that BPTES downregulated the effector functions of Th17 cells and Th1 cells. Collectively, these results indicate a positive relationship between Gls1 and SS development. Pharmacological inhibition of Gls1 with BPTES could normalize the effector functions of CD4+ T cells and effectively attenuate the symptoms of SS.

CELL-AUTONOMOUS HEDGEHOG SIGNALING CONTROLS TH17 DIFFERENTIATION TO DRIVE INTESTINAL INFLAMMATION AND IS A DRUGGABLE TARGET FOR THE TREATMENT OF INFLAMMATORY BOWEL DISEASE

Abstract BACKGROUND T helper 17 (Th17) cells play a key role in barrier protection in the gastrointestinal tract but are also key pathological drivers of Inflammatory Bowel Disease (IBD). Although a number of key transcription factors governing Th17 differentiation have been identified, the intracellular signaling pathways regulating Th17 differentiation are poorly understood. Given the highly druggable nature of many intracellular signaling pathways, understanding the signaling pathways involved in Th17 differentiation holds great promise to identify novel drug targets for the treatment of IBD. Hedgehog (Hh) signaling controls cell-fate choices in numerous tissue compartments and is targetable by highly selective, clinically-approved small molecule inhibitors. However the role of Hh signaling in Th17 differentiation and effector function is unstudied. METHODS We generated two conditional knockout mouse models targeting Hh signaling components Smo and Ihh to study Th17 differentiation and effector function in vitro and in vivo in murine T cell adoptive transfer colitis. We supplement this with the use of two small-molecule Smo antagonists for both in vitro and in vivo studies of Th17 function. To underscore the translational relevance of our findings, we have conducted bioinformatic analyses of published gene expression datasets of human rectal biopsies from two large independent cohorts of Ulcerative Colitis patients and healthy controls as well as from sorted human effector T cells from blood and lamina propria of healthy individuals. RESULTS We find that intracellular Hh signaling, independently of extracellular Hh ligands, selectively drives differentiation and effector function of Th17 cells but not of other T helper cell lineages. Using two models of intestinal inflammation, we demonstrate that inhibition of the Hh pathway with either the clinically-approved small molecule inhibitor vismodegib or genetic ablation of Ihh in CD4+ T cells profoundly diminishes disease severity and Th17-induced pathology in the intestine. Our bioinformatic analyses show that Hh component expression levels are upregulated in human ulcerative colitis patient samples and are closely correlated with expression of Th17 markers/cytokines. Mechanistically we show that the T-cell-intrinsic Indian Hedgehog (Ihh) ligand signals via the signal transducer Smoothened to activate both canonical and non-canonical Hh pathways, through the Gli3 transcription factor and AMPK phosphorylation, respectively. CONCLUSIONS We uncover Hh signaling as a novel pathway controlling Th17 differentiation and pathogenicity in IBD with Gli3 acting as a newly-identified crucial regulatory transcription factor. Our work paves the way for the use of Hh inhibitors for the treatment of IBD.

DOP48 Hedgehog signalling controls Th17 differentiation to drive intestinal inflammation and is a druggable target for the treatment of IBD

Abstract Background T helper 17 (Th17) cells play an important role in barrier protection in the gastrointestinal tract but are also key pathological drivers of Inflammatory Bowel Disease (IBD). Although a number of transcription factors governing Th17 differentiation have been identified, the intracellular signalling pathways regulating Th17 differentiation are poorly understood. Hedgehog (Hh) signalling controls cell-fate choices in numerous tissue compartments and is targetable by highly selective, clinically-approved small molecule inhibitors. However the role of Hh signalling in Th17 differentiation and effector function is unstudied. Methods We generated two conditional knockout mouse models targeting Hh signalling components Smo and Ihh to study Th17 differentiation in vitro by flow cytometry and gene expression analysis. For in vivo studies, T cell adoptive transfer colitis was performed using donor Ihh knockout T cells or heterozygote controls. Histological analysis, mouse weight, colon length/weight measurements, and flow cytometric analysis was performed. We supplement this with the use of two small-molecule Smo antagonists for in vitro and in vivo studies of Th17 function. To underscore the translational relevance of our findings, we conducted bioinformatic analyses of published gene expression datasets of human rectal biopsies from two large independent cohorts of Ulcerative Colitis patients and healthy controls. Results We find that intracellular Hh signalling, independently of extracellular Hh ligands, selectively drives differentiation and effector function of Th17 cells but not of other T helper cell lineages. We demonstrate in vivo that inhibition of the Hh pathway with either the clinically-approved small molecule inhibitor vismodegib or genetic ablation of Ihh in CD4+ T cells results in a significant decrease in histological and clinical readouts of disease severity as well as a significant reduction in IL-17a+ Th17 cells. Our bioinformatic analyses show that Hh component expression levels are upregulated in human Ulcerative Colitis patient samples and are closely correlated with expression of Th17 markers. Mechanistically we show that the T-cell-intrinsic Indian Hedgehog (Ihh) ligand signals via the signal transducer Smoothened to activate both canonical and non-canonical Hh pathways, through the Gli3 transcription factor and AMPK phosphorylation, respectively. Conclusion We uncover Hh signalling as a novel pathway controlling Th17 differentiation and pathogenicity in IBD with Gli3 acting as a newly-identified crucial regulatory transcription factor. Our work paves the way for the use of Hh inhibitors for the treatment of IBD.

Th17 cells: from gut homeostasis to CNS pathogenesis

Th17 cells play crucial roles in host-microbe interactions, but can also promote chronic inflammation and tissue pathology. Factors influencing Th17 cell heterogeneity and effector functions in different inflammatory contexts remain unclear. Schnell et al. demonstrate that intestinal Th17 cells form a reservoir from which pathogenic Th17 cells can be elicited during severe tissue inflammation.

Interactome Networks of FOSL1 and FOSL2 in Human Th17 Cells.

Dysregulated function of Th17 cells has implications in immunodeficiencies and autoimmune disorders. Th17 cell differentiation is orchestrated by a complex network of transcription factors, including several members of the activator protein (AP-1) family. Among the latter, FOSL1 and FOSL2 modulate the effector functions of Th17 cells. However, the molecular mechanisms underlying these effects are unclear, owing to the poorly characterized protein interaction networks of FOSL factors. Here, we establish the first interactomes of FOSL1 and FOSL2 in human Th17 cells, using affinity purification–mass spectrometry analysis. In addition to the known JUN proteins, we identified several novel binding partners of FOSL1 and FOSL2. Gene ontology analysis found a significant fraction of these interactors to be associated with RNA-binding activity, which suggests new mechanistic links. Intriguingly, 29 proteins were found to share interactions with FOSL1 and FOSL2, and these included key regulators of Th17 fate. We further validated the binding partners identified in this study by using parallel reaction monitoring targeted mass spectrometry and other methods. Our study provides key insights into the interaction-based signaling mechanisms of FOSL proteins that potentially govern Th17 cell differentiation and associated pathologies.

Effector functions of Th17 cells are regulated by IL-35 and TGF-β in visceral leishmaniasis.

Visceral leishmaniasis (VL) is a debilitating human pathogenesis in which the body's immune functions are severely compromised. Various subsets of T cells, including Th17 cells are important regulators of immune responses observed in various pathologies. The role of Th17 cells and its correlation with immuno-regulatory cytokines are however not well understood in human VL. Herein we studied how IL-17 is associated with the progression of Leishmania donovani infection using murine model of VL. We found induction of a strong IL-17 response at the early phase of infection which progressively reduced to basal level during chronic VL. The mechanistic study of this behavior was found to be linked with the role of regulatory T cells (CD4+ CD25+ T cells) that suppresses the proliferation of the Th17 cell population. Moreover, TGF-β and IL-35 derived from CD4+ CD25+ T cells are the key mediators for the downregulation of IL-17 during chronic VL. Thus, this study points to an antagonistic effect of Tregs and Th17 cells that can be used for designing better therapeutic and preventive strategies against leishmaniasis.

Metabolic rewiring: a new master of Th17 cell plasticity and heterogeneity.

T helper type 17 (Th17) cells are characterized by inherent plasticity and heterogeneity displaying both pathogenic and tissue-protective functions. Emerging evidence has illuminated a pivotal role for metabolic reprogramming in shaping Th17 cell fate determination. Metabolic responses are regulated by a constellation of factors and environmental triggers, including cytokines, nutrients, oxygen levels, and metabolites. Dysregulation of metabolic pathways not only influences Th17 cell plasticity and effector function but also affects the outcome of Th17-linked autoimmune, inflammatory, and antitumor responses. Understanding the molecular mechanisms underpinning metabolic reprogramming can allow the enhancement of protective Th17 cell-mediated responses during infections and cancer, concomitant with the suppression of detrimental Th17 processes during autoimmune and inflammatory diseases. In the present review, we describe major metabolic pathways underlying the differentiation of Th17 cells and their crosstalk with intracellular signaling mediators, we discuss how metabolic reprogramming affects Th17 cell plasticity and functions, and, finally, we outline current advances in the exploitation of metabolic checkpoints for the development of novel therapeutic interventions for the management of tissue inflammation, autoimmune disorders, and cancer.

Regulatory T cells suppress Th17 cell Ca2+ signaling in the spinal cord during murine autoimmune neuroinflammation.

T lymphocyte motility and interaction dynamics with other immune cells are vital determinants of immune responses. Regulatory T (Treg) cells prevent autoimmune disorders by suppressing excessive lymphocyte activity, but how interstitial motility patterns of Treg cells limit neuroinflammation is not well understood. We used two-photon microscopy to elucidate the spatial organization, motility characteristics, and interactions of endogenous Treg and Th17 cells together with antigen-presenting cells (APCs) within the spinal cord leptomeninges in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Th17 cells arrive before the onset of clinical symptoms, distribute uniformly during the peak, and decline in numbers during later stages of EAE. In contrast, Treg cells arrive after Th17 cells and persist during the chronic phase. Th17 cells meander widely, interact with APCs, and exhibit cytosolic Ca2+ transients and elevated basal Ca2+ levels before the arrival of Treg cells. In contrast, Treg cells adopt a confined, repetitive-scanning motility while contacting APCs. These locally confined but highly motile Treg cells limit Th17 cells from accessing APCs and suppress Th17 cell Ca2+ signaling by a mechanism that is upstream of store-operated Ca2+ entry. Finally, Treg cell depletion increases APC numbers in the spinal cord and exaggerates ongoing neuroinflammation. Our results point to fundamental differences in motility characteristics between Th17 and Treg cells in the inflamed spinal cord and reveal three potential cellular mechanisms by which Treg cells regulate Th17 cell effector functions: reduction of APC density, limiting access of Th17 cells to APCs, and suppression of Th17 Ca2+ signaling.

NK cell receptor NKG2D enforces proinflammatory features and pathogenicity of Th1 and Th17 cells.

NKG2D is a danger sensor expressed on different subsets of innate and adaptive lymphocytes. Despite its established role as a potent activator of the immune system, NKG2D-driven regulation of CD4+ T helper (Th) cell-mediated immunity remains unclear. In this study, we demonstrate that NKG2D modulates Th1 and proinflammatory T-bet+ Th17 cell effector functions in vitro and in vivo. In particular, NKG2D promotes higher production of proinflammatory cytokines by Th1 and T-bet+ Th17 cells and reinforces their transcription of type 1 signature genes, including Tbx21. Conditional deletion of NKG2D in T cells impairs the ability of antigen-specific CD4+ T cells to promote inflammation in vivo during antigen-induced arthritis and experimental autoimmune encephalomyelitis, indicating that NKG2D is an important target for the amelioration of Th1- and Th17-mediated chronic inflammatory diseases.

Histone H3K27me3 demethylases regulate human Th17 cell development and effector functions by impacting on metabolism

T helper (Th) cells are CD4+ effector T cells that play a critical role in immunity by shaping the inflammatory cytokine environment in a variety of physiological and pathological situations. Using a combined chemico-genetic approach, we identify histone H3K27 demethylases KDM6A and KDM6B as central regulators of human Th subsets. The prototypic KDM6 inhibitor GSK-J4 increases genome-wide levels of the repressive H3K27me3 chromatin mark and leads to suppression of the key transcription factor RORγt during Th17 differentiation. In mature Th17 cells, GSK-J4 induces an altered transcriptional program with a profound metabolic reprogramming and concomitant suppression of IL-17 cytokine levels and reduced proliferation. Single-cell analysis reveals a specific shift from highly inflammatory cell subsets toward a resting state upon demethylase inhibition. The root cause of the observed antiinflammatory phenotype in stimulated Th17 cells is reduced expression of key metabolic transcription factors, such as PPRC1. Overall, this leads to reduced mitochondrial biogenesis, resulting in a metabolic switch with concomitant antiinflammatory effects. These data are consistent with an effect of GSK-J4 on Th17 T cell differentiation pathways directly related to proliferation and include regulation of effector cytokine profiles. This suggests that inhibiting KDM6 demethylases may be an effective, even in the short term, therapeutic target for autoimmune diseases, including ankylosing spondylitis.

P: 71 Faecal Cytokine Profiling Provides Novel Insights Into Intestinal Barrier Disruption and Bacterial Translocation in Acute Decompensation of Cirrhosis

BACKGROUND: Intestinal dysbiosis with gut barrier impairment (GBI) and bacterial translocation (BT) are recognised as central features of acutely decompensated cirrhosis (AD) and propagating hepatic encephalopathy (HE). Gut mucosal function is technically challenging to investigate, with a difficulty in obtaining representative tissue in cirrhotics and a paucity of non-invasive techniques. A novel assay we developed was to quantify faecal cytokines (FC) as surrogate makers of intestinal inflammation, compared to GBI markers and systemic cytokines. METHODS: Protein was extracted from faeces of patients with stable cirrhosis (SC; n = 16), AD (n = 48), and healthy participants (HC; n = 31). A multiplex panel of 13 cytokines were quantified by electrochemiluminescence or ELISA in paired faecal lysates and plasma. Intestinal epithelium-associated fatty acid binding protein 2 (FABP2) and intestinal-microbiota metabolite D-lactate, as markers of intestinal barrier disruption, were quantified by ELISA and colorimetric enzymatic assay, respectively. RESULTS: Median ages and MELD scores of AD vs SC patients were 61 (53–68) vs 55 (44–59) years and 18 (13–26) vs 8 (7.0–8.5), respectively. Male gender predominated (AD: 65%; SC: 75%) The causes of cirrhosis were alcohol, NAFLD and treated hepatitis C. Median venous ammonia levels were significantly higher in AD vs SC (51 [38–74] vs 36 [26–59], P = 0.027). Faecal IL-1β, IFN-γ, TNF-α, IL-21, IL-17A/F and IL-22 were significantly different in AD vs SC on univariate comparison (q < 0.01 all comparisons). Along with IL-1β, faecal IL-23 was significantly elevated in AD vs HC (P = 0.0007), important in promoting deleterious Th17 cell effector function. Faecal FABP2 and D-lactate (P < 0.0001 for both) and plasma FABP2 and D-lactate (P = 0.0004; P = 0.011) were significantly elevated in AD vs SC and AD vs HC, respectively, consistent with GBI. FABP2 was the faecal marker that correlated most strongly with disease scores (Spearman's rho: Child-Pugh 0.466, P < 0.0001; MELD 0.488, P < 0.0001). With the exception of IL-8, IL-12 & IL-23, faecal cytokines and D-lactate were more discriminant than circulating equivalent molecules in discriminating AD from SC by Principal Component Analysis (Figure 1). CONCLUSIONS: FC profiling represents a novel targeted approach to localised measurement of the intestinal cytokine milieu in cirrhosis, and in conjunction with D-lactate, demonstrates that progression to AD from SC may be a intestinally initiated and mediated process. The AD gut micro-environment may skew T cell priming away from restorative Tregs and towards inflammatory Th1/Th17 profiles, promoting epithelial barrier damage and preventing repair. These data provide insights into intestinal mucosal injury and GBI, as a novel pathobiology in AD and HE.

Epithelial retinoic acid receptor β regulates serum amyloid A expression and vitamin A-dependent intestinal immunity

Vitamin A is a dietary component that is essential for the development of intestinal immunity. Vitamin A is absorbed and converted to its bioactive derivatives retinol and retinoic acid by the intestinal epithelium, yet little is known about how epithelial cells regulate vitamin A-dependent intestinal immunity. Here we show that epithelial cell expression of the transcription factor retinoic acid receptor β (RARβ) is essential for vitamin A-dependent intestinal immunity. Epithelial RARβ activated vitamin A-dependent expression of serum amyloid A (SAA) proteins by binding directly to Saa promoters. In accordance with the known role of SAAs in regulating Th17 cell effector function, epithelial RARβ promoted IL-17 production by intestinal Th17 cells. More broadly, epithelial RARβ was required for the development of key vitamin A-dependent adaptive immune responses, including CD4+ T-cell homing to the intestine and the development of IgA-producing intestinal B cells. Our findings provide insight into how the intestinal epithelium senses dietary vitamin A status to regulate adaptive immunity, and highlight the role of epithelial cells in regulating intestinal immunity in response to diet.

Expression and function of IL-1 receptor type 2 (IL-1RII) regulating human Th17 responses

Abstract Th17 cells are a unique subset of proinflammatory cells conferring protection against extracellular bacteria and fungi, but have been also implicated in the pathogenesis of many autoimmune diseases. IL-1β is critical for the differentiation, expansion, in vivo survival, and effector function of Th17 cells. Among components of IL-1 receptor (IL-1R), decoy IL-1RII is a negative regulator of functional IL-1RI-mediated IL-1β signaling. Given its preferential expression on Treg cells, IL-1RII has been suggested to play a role for controlling the Th17 and Treg balance. However, little is known about a molecular mechanism underlying IL-1RII expression and its contribution to modulation of Th17 responses. Here, we found that IL-1RI and IL-1RII expression were rapidly induced by memory CD4+ T cells after stimulation with TCR alone. Cyclosporin A reduced IL-1RII expression, whereas an augmented FOXP3 was associated with enhanced IL-1RII expression. This finding was corroborated by in vitro assays using NFAT inhibitor, dNP2-VIVIT and an inhibitor of FOXP3/NFAT1 interaction, peptide FOXP3 393–403. Moreover, reporter assay suggests that NFAT/FOXP3 binding sites in IL-1RII promoter are critical for its transcription. At day 2 post-stimulation, there were three distinct subsets; IL-1RI+IL-1RII−, IL-1RI+IL-1RII+, and IL- 1RI−IL-1RII− CD4+ T cells, having unique features including cytokine production profile, the expression of Tregassociated genes, and responsiveness to IL-1β, suggesting a pivotal regulatory role of IL-1RII for human Th17 responses. Our findings will be beneficial to understanding a modulatory mechanism on Th17 response and IL- 1β-mediated IL-1R signaling contributing to pathogenesis of autoimmune diseases.

Egr2 deficiency significantly impairs the development of pathogenic TH17 cells

Abstract TH17 cells have critical functions in host defense at mucosal barriers, but they can also be the key drivers of immunopathology. Since their discovery, multiple transcription factor networks have been described that direct Th17 lineage commitment; however, molecular switches that control the development of “pathogenic” versus “non-pathogenic” TH17 cells remain largely unknown. In this study, we have identified the transcription factor Egr2 as a critical regulator of the TH17 pathogenic program. When ectopically expressed under TH17-polarizing conditions, Egr2 significantly enhanced the expression of TH17 signature genes in a RORγt-dependent manner. Although Egr2-deficient CD4+ T cells could be polarized in vitro into TH17 cells, these cells lacked the pathogenic potential in a TH17-dependent disease model, experimental autoimmune encephalomyelitis (EAE). In both active EAE and passive EAE, Egr2-deficeint TH17 cells failed to induce neuroinflammatory response in the CNS. Analysis of CNS infiltrates revealed reduced accumulation of IL-17A-producing CD4+ T cells and impaired recruitment of monocytes and myeloid dendritic cells in mice with T cell-specific loss of Egr2. Most importantly, transcriptional analysis of ex vivo isolated Egr2-deficient CD4+ T cells revealed that Egr2 controlled the expression of pathogenicity-associated genes in TH17 cells in the CNS. We further show that Egr2 deficiency did not affect the effector function of protective TH17 cells at mucosal barriers in Citrobacter rodentium and Candida albicans infections, suggesting that Egr2 is an attractive candidate for the therapeutic targeting of pathogenic TH17 cells while preserving tissue-protective functions of TH17 cells at barrier sites.