A microbially produced AhR ligand promotes a Tph1-driven tolerogenic program in multiple sclerosis

Multiple sclerosis is a debilitating autoimmune disease, characterized by chronic inflammation of the central nervous system. While the significance of the gut microbiome on multiple sclerosis pathogenesis is established, the underlining mechanisms are unknown. We found that serum levels of the microbial postbiotic tryptophan metabolite indole-3-carboxaldehyde (3-IAld) inversely correlated with disease duration in multiple sclerosis patients. Much like the host-derived tryptophan derivative L-Kynurenine, 3-IAld would bind and activate the Aryl hydrocarbon Receptor (AhR), which, in turn, controls endogenous tryptophan catabolic pathways. As a result, in peripheral lymph nodes, microbial 3-IAld, affected mast-cell tryptophan metabolism, forcing mast cells to produce serotonin via Tph1. We thus propose a protective role for AhR-mast-cell activation driven by the microbiome, whereby natural metabolites or postbiotics will have a physiological role in immune homeostasis and may act as therapeutic targets in autoimmune diseases.

A back-door insights into the modulation of Src kinase activity by the polyamine spermidine

Src is a protein tyrosine kinase commonly activated downstream of transmembrane receptors and plays key roles in cell growth, migration and survival signaling pathways. In conventional dendritic cells (cDCs), Src is involved in the activation of the non-enzymatic functions of indoleamine 2,3-dioxygenase 1 (IDO1), an immunoregulatory molecule endowed with both catalytic activity and signal transducing properties. Prompted by the discovery that the metabolite spermidine confers a tolerogenic phenotype on cDCs that is dependent on both the expression of IDO1 and the activity of Src kinase, we here investigated the spermidine mode of action. We found that spermidine directly binds Src in a previously unknown allosteric site located on the backside of the SH2 domain and thus acts as a positive allosteric modulator of the enzyme. Besides confirming that Src phosphorylates IDO1, here we showed that spermidine promotes the protein-protein interaction of Src with IDO1. Overall, this study may pave the way toward the design of allosteric modulators able to switch on/off the Src-mediated pathways, including those involving the immunoregulatory protein IDO1.

A tryptophan metabolite prevents depletion of circulating endothelial progenitor cells in systemic low-grade inflammation

Background

Chronic systemic inflammation reduces the bioavailability of circulating endothelial progenitor cells (EPCs). Indoleamine 2,3-dioxygenase 1 (IDO1), a key enzyme of immune tolerance catalyzing the initial step of tryptophan degradation along the so-called l-kynurenine (l-kyn) pathway, that is induced by inflammatory stimuli and exerts anti-inflammatory effects. A specific relationship between IDO1 activity and circulating EPC numbers has not yet been investigated.

Methods

In this study, circulating EPCs were examined in mice treated with low doses of lipopolysaccharide (LPS) to mimic low-grade inflammation. Moreover, the association between IDO1 activity and circulating EPCs was studied in a cohort of 277 patients with variable systemic low-grade inflammation.

Results

Repeated low doses of LPS caused a decrease in circulating EPCs and l-kyn supplementation, mimicking IDO1 activation, significantly increased EPC numbers under homeostatic conditions preventing EPC decline in low-grade endotoxemia. Accordingly, in patients with variable systemic low-grade inflammation, there was a significant interaction between IDO1 activity and high-sensitivity C-reactive protein (hs-CRP) in predicting circulating EPCs, with high hs-CRP associated with significantly lower EPCs at low IDO1 activity but not at high IDO1 activity.

Interpretation

Overall, these findings demonstrate that systemic low-grade inflammation reduces circulating EPCs. However, high IDO1 activity and l-kyn supplementation limit circulating EPC loss in low-grade inflammation.

Identification of astrocyte regulators by nucleic acid cytometry

Multiple sclerosis is a chronic inflammatory disease of the central nervous system1. Astrocytes are heterogeneous glial cells that are resident in the central nervous system and participate in the pathogenesis of multiple sclerosis and its model experimental autoimmune encephalomyelitis2,3. However, few unique surface markers are available for the isolation of astrocyte subsets, preventing their analysis and the identification of candidate therapeutic targets; these limitations are further amplified by the rarity of pathogenic astrocytes. Here, to address these challenges, we developed focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), a high-throughput microfluidic cytometry method that combines encapsulation of cells in droplets, PCR-based detection of target nucleic acids and droplet sorting to enable in-depth transcriptomic analyses of cells of interest at single-cell resolution. We applied FIND-seq to study the regulation of astrocytes characterized by the splicing-driven activation of the transcription factor XBP1, which promotes disease pathology in multiple sclerosis and experimental autoimmune encephalomyelitis4. Using FIND-seq in combination with conditional-knockout mice, in vivo CRISPR-Cas9-driven genetic perturbation studies and bulk and single-cell RNA sequencing analyses of samples from mouse experimental autoimmune encephalomyelitis and humans with multiple sclerosis, we identified a new role for the nuclear receptor NR3C2 and its corepressor NCOR2 in limiting XBP1-driven pathogenic astrocyte responses. In summary, we used FIND-seq to identify a therapeutically targetable mechanism that limits XBP1-driven pathogenic astrocyte responses. FIND-seq enables the investigation of previously inaccessible cells, including rare cell subsets defined by unique gene expression signatures or other nucleic acid markers.

Endotoxin-Tolerance Mimicking to Study TLR in Promotion of Tolerogenic DCs and Tr1 Cells

Dendritic cells (DCs) are key regulators of immunogenic and tolerogenic immune responses. Both these immune responses require DCs respectively to activate effector T cells or to induce their anergy and T regulatory activity. Modifications of DCs in the laboratory and several pharmacological agents can enhance and stabilize their tolerogenic properties. Recent evidences demonstrate that activation of specific toll-like receptors (TLRs) can be involved in induction of DCs with tolerogenic properties able to initiate T regulatory cell responses.In the present chapter, we show a detail protocol to obtain in vitro regulatory conventional DCs (cDCs) in response to repeated exposure to lipopolysaccharide (LPS), a ligand of TLR4, by mimicking the mechanism of endotoxin tolerance. Subsequently, the protective effect of cDCs' conditionate with LPS will be describe in in vivo inflammatory model of endotoxemia. Finally, we illustrate the method to study the ability of LPS-conditionate cDCs to promote T regulatory cells in ex vivo system.

Indoleamine 2,3-dioxygenase 1 activation in mature cDC1 promotes tolerogenic education of inflammatory cDC2 via metabolic communication

Conventional dendritic cells (cDCs), cDC1 and cDC2, act both to initiate immunity and maintain self-tolerance. The tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) is used by cDCs in maintaining tolerance, but its role in different subsets remains unclear. At homeostasis, only mature CCR7⁺ cDC1 expressed IDO1 that was dependent on IRF8. Lipopolysaccharide treatment induced maturation and IDO1-dependent tolerogenic activity in isolated immature cDC1, but not isolated cDC2. However, both human and mouse cDC2 could induce IDO1 and acquire tolerogenic function when co-cultured with mature cDC1 through the action of cDC1-derived l-kynurenine. Accordingly, cDC1-specific inactivation of IDO1 in vivo exacerbated disease in experimental autoimmune encephalomyelitis. This study identifies a previously unrecognized metabolic communication in which IDO1-expressing cDC1 cells extend their immunoregulatory capacity to the cDC2 subset through their production of tryptophan metabolite l-kynurenine. This metabolic axis represents a potential therapeutic target in treating autoimmune demyelinating diseases.

Effectiveness and safety of 1L PEG-ASC preparation for colonoscopy in patients with inflammatory bowel diseases

INTRODUCTION

The effectiveness of bowel cleansing is a key element for high-quality colonoscopy. Recently, a 1 L polyethylene glycol plus ascorbate (PEG-ASC) solution has been introduced, but effectiveness and safety of this preparation have not been assessed in IBD patients. This study aims to evaluate effectiveness and safety of 1 L PEG-ASC solution in patients with IBD compared to controls.

METHODS

We retrospectively analysed prospectively collected data on a cohort of 411 patients performing a colonoscopy after preparation with 1 L PEG-ASC, consecutively enrolled in 5 Italian centres.

RESULTS

Overall, 185/411 (45%) were patients with IBD and 226/411 (55%) served as controls. A significantly higher cleansing success was achieved in IBD patients (92.9% vs 85.4%, p = 0.02). The multiple regression model showed that presence of IBD (OR=2.514, 95%CI=1.165-5.426; P = 0.019), lower age (OR=0.981, 95%CI=0.967-0.996; P = 0.014), split preparation (OR=2.430, 95%CI=1.076-5.492; P = 0.033), absence of diabetes (OR=2.848, 95%CI=1.228-6.605; P = 0.015), and of chronic constipation (OR=3.350, 95%CI=1.429-7.852; P = 0.005), were independently associated with cleansing success. The number of treatment-emergent adverse events (TEAEs) (51 vs 62%, p = 0.821), and of patients with TEAEs (22.2% vs 21.2%, p = 0.821), were similar in IBD patients and in controls, respectively.

CONCLUSIONS

Results from this study support the effectiveness and safety of 1 L PEG-ASC solution in IBD patients, which may improve the definition of endoscopic outcomes both in Crohn's disease and ulcerative colitis.

Tryptophan Metabolites at the Crossroad of Immune-Cell Interaction via the Aryl Hydrocarbon Receptor: Implications for Tumor Immunotherapy

The Aryl hydrocarbon receptor (AhR) is a critical regulator of both innate and adaptive immune responses, with potent immunomodulatory effects that makes this receptor an attractive molecular target for novel therapeutics. Accumulating evidence indicates that diverse—both host’s and microbial—tryptophan metabolites profoundly regulate the immune system in the host via AhR, promoting either tolerance or immunity, largely as a function of the qualitative and quantitative nature of the metabolites being contributed by either source. Additional findings indicate that host and microbiota-derived tryptophan metabolic pathways can influence the outcome of immune responses to tumors. Here, we review recent studies on the role and modalities of AhR activation by various ligands, derived from either host-cell or microbial-cell tryptophan metabolic pathways, in the regulation of immune responses. Moreover, we highlight potential implications of those ligands and pathways in tumor immunotherapy, with particular relevance to checkpoint-blockade immune intervention strategies.

Gut-licensed IFNγ+ NK cells drive LAMP1+TRAIL+ anti-inflammatory astrocytes

Astrocytes are glial cells that are abundant in the central nervous system (CNS) and that have important homeostatic and disease-promoting functions1. However, little is known about the homeostatic anti-inflammatory activities of astrocytes and their regulation. Here, using high-throughput flow cytometry screening, single-cell RNA sequencing and CRISPR-Cas9-based cell-specific in vivo genetic perturbations in mice, we identify a subset of astrocytes that expresses the lysosomal protein LAMP12 and the death receptor ligand TRAIL3. LAMP1+TRAIL+ astrocytes limit inflammation in the CNS by inducing T cell apoptosis through TRAIL-DR5 signalling. In homeostatic conditions, the expression of TRAIL in astrocytes is driven by interferon-γ (IFNγ) produced by meningeal natural killer (NK) cells, in which IFNγ expression is modulated by the gut microbiome. TRAIL expression in astrocytes is repressed by molecules produced by T cells and microglia in the context of inflammation. Altogether, we show that LAMP1+TRAIL+ astrocytes limit CNS inflammation by inducing T cell apoptosis, and that this astrocyte subset is maintained by meningeal IFNγ+ NK cells that are licensed by the microbiome.

Pharmacologic Induction of Endotoxin Tolerance in Dendritic Cells by L-Kynurenine

Endotoxin tolerance aims at opposing hyperinflammatory responses to lipopolysaccharide (LPS) exposure. The aryl hydrocarbon receptor (AhR) participates in protection against LPS-mediated tissue damage, as it plays a necessary role in restraining the proinflammatory action of IL-1β and TNF-α while fostering the expression of protective TGF-β. TGF-β, in turn, promotes durable expression of the immune regulatory enzyme indoleamine 2,3-dioxygenase 1 (IDO1). IDO1 degrades L-tryptophan to L-kynurenine-an activating ligand for AhR-thus establishing a feed-forward loop. In this study, we further demonstrate that L-kynurenine also promotes the dissociation of the Src kinase-AhR cytosolic complex, leading to the activation of both genomic and non-genomic events in conventional dendritic cells (cDCs) primed with LPS. Specifically, the Src kinase, by phosphorylating the downstream target IDO1, triggers IDO1's signaling ability, which results in enhanced production of TGF-β, an event key to establishing full endotoxin tolerance. We demonstrated that exogenous L-kynurenine can substitute for the effects of continued or repeated LPS exposure and that the AhR-Src-IDO1 axis represents a critical step for the transition from endotoxin susceptibility to tolerance. Moreover, much like fully endotoxin-tolerant dendritic cells (DCs) (i.e., treated twice with LPS in vitro), DCs-treated once with LPS in vitro and then with kynurenine-confer resistance on naïve recipients to an otherwise lethal LPS challenge. This may have clinical implications under conditions in which pharmacologically induced onset of endotoxin tolerance is a therapeutically desirable event.

MAFG-driven astrocytes promote CNS inflammation

Multiple sclerosis is a chronic inflammatory disease of the CNS1. Astrocytes contribute to the pathogenesis of multiple sclerosis2, but little is known about the heterogeneity of astrocytes and its regulation. Here we report the analysis of astrocytes in multiple sclerosis and its preclinical model experimental autoimmune encephalomyelitis (EAE) by single-cell RNA sequencing in combination with cell-specific Ribotag RNA profiling, assay for transposase-accessible chromatin with sequencing (ATAC-seq), chromatin immunoprecipitation with sequencing (ChIP-seq), genome-wide analysis of DNA methylation and in vivo CRISPR-Cas9-based genetic perturbations. We identified astrocytes in EAE and multiple sclerosis that were characterized by decreased expression of NRF2 and increased expression of MAFG, which cooperates with MAT2α to promote DNA methylation and represses antioxidant and anti-inflammatory transcriptional programs. Granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling in astrocytes drives the expression of MAFG and MAT2α and pro-inflammatory transcriptional modules, contributing to CNS pathology in EAE and, potentially, multiple sclerosis. Our results identify candidate therapeutic targets in multiple sclerosis.

Engagement of Nuclear Coactivator 7 by 3-Hydroxyanthranilic Acid Enhances Activation of Aryl Hydrocarbon Receptor in Immunoregulatory Dendritic Cells

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the first step in the kynurenine pathway of tryptophan (Trp) degradation that produces several biologically active Trp metabolites. L-kynurenine (Kyn), the first byproduct by IDO1, promotes immunoregulatory effects via activation of the Aryl hydrocarbon Receptor (AhR) in dendritic cells (DCs) and T lymphocytes. We here identified the nuclear coactivator 7 (NCOA7) as a molecular target of 3-hydroxyanthranilic acid (3-HAA), a Trp metabolite produced downstream of Kyn along the kynurenine pathway. In cells overexpressing NCOA7 and AhR, the presence of 3-HAA increased the association of the two molecules and enhanced Kyn-driven, AhR-dependent gene transcription. Physiologically, conventional (cDCs) but not plasmacytoid DCs or other immune cells expressed high levels of NCOA7. In cocultures of CD4⁺ T cells with cDCs, the co-addition of Kyn and 3-HAA significantly increased the induction of Foxp3⁺ regulatory T cells and the production of immunosuppressive transforming growth factor β in an NCOA7-dependent fashion. Thus, the co-presence of NCOA7 and the Trp metabolite 3-HAA can selectively enhance the activation of ubiquitary AhR in cDCs and consequent immunoregulatory effects. Because NCOA7 is often overexpressed and/or mutated in tumor microenvironments, our current data may provide evidence for a new immune check-point mechanism based on Trp metabolism and AhR.

A novel kynurenine-dependent circuit in DC1 promote IDO1 expression in DC2 leading to experimental autoimmune encephalomyelitis suppression

Classical dendritic cells (cDCs) are professional antigen-presenting cells that play a key role in shaping appropriate immune responses. DCs are a potent T cell activators but they are also involved in maintaining immune homeostasis and self-tolerance. DCs can be classified into three major types: pDC, DC1 and DC2. One mechanism by which DCs regulate tolerance involves indoleamine 2,3-dioxygenase 1 (IDO1) a tryptophan (Trp) metabolizing enzyme. In this study, we analyzed the ability of L-Kyn to induce tolerogenic IDO1 pathway in different DCs subsets in vitro and in vivo model of experimental autoimmune encephalomyelitis (EAE). We show that inflammatory stimuli, like LPS, was able to induce IDO1 only in DC1, but not in DC2 or pDC, when DCs were treated as isolated cultures. In contrast, when LPS was added to cultures containing all three DC subsets, LPS could also induce IDO1 expression in DC2, which acquired tolerogenic function. Induction of IDO1 in DC2 involved a novel DC1-DC2 communication pathway mediated by a Kyn-AhR-RelB axis. Kynurenine produced by DC1 activates AhR in DC2 inducing IDO1 in a RelB-dependent manner. In vitro L-Kyn treatment impaired DC2 T cells priming ability causing suppression of MOG-specific reactivity with an increment of Foxp3+ CD4+ T cells. In vivo, oral administration of L-Kyn induces functional Treg cells that suppress EAE and this effect is completely abrogated in Ahrflox/floxCD11C Cre+ mice. These data suggest that in specific microenvironments, small numbers of IDO1-expressing DC1 may spread tolerogenic activity to DC2 cells through a kynurenine-AhR axis and L-Kyn could constituting a unique endogenous molecule for therapeutic immunomodulation of inflammatory and autoimmune diseases.

Statins regulates inflammatory macrophage phenotype through the activation of AhR

Statins are 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase competitive inhibitors, that lower blood cholesterol, but also exert potent anti-inflammatory effects. The xenobiotic receptor, aryl hydrocarbon receptor (AhR), plays crucial role in the control of inflammatory responses. Evidences suggest that selected statins promote the transcription of the main AhR target gene, cytochrome P450 family 1 (Cyp1a1). Macrophages are essential components of innate and adaptive immunity, characterized by AhR expression and activity. Based on these evidences, we investigated potential AhR-mediated immune regulatory properties of statins in Bone Marrow Derived Macrophages (BMDM).

We found that BMDM activation with the pro-inflammatory cytokine TNFa induced the inflammatory marker, inducible nitric oxide synthase (iNOS), which was completely prevented in BMDMs treated with TNFa in combination with specific statins, namely, atorvastatin and rosuvastatin. We confirmed high AhR expression in BMDM that was increased upon treatment with TNFa. We investigated the ability of different statins to activate AhR using a luciferase reporter assay cell lines and in BMDCs. We found that selected statins, such as atorvastatin and rosuvastatin, activated AhR in a dose dependent manner, an activation prevented in cells expressing selected AhR mutants. Notably, AhR deficient BMDMs, expressed undetectable levels of the main statin target protein HMG-CoA, which was instead highly expressed in wild type BMDMs.

These data demonstrate that natural or synthetic statins can play regulatory roles in macrophages. Moreover, our results suggest a potential involvement of AhR in statin-mediated anti-inflammatory effects in macrophages.

Small molecule modulators of prion protein (PrpC) in Dendritic cells regulate inflammatory responses in a model of Multiple Sclerosis

Experimental autoimmune encephalomyelitis (EAE) is the most commonly used experimental model for human multiple sclerosis, an autoimmune disease driven by differentiated Th1 and Th17 cells, and inflammatory dendritic cells (DCs). Recent data show that EAE is worsened in mice lacking PrPC protein and disease exacerbation has been attributed to T cells, which would differentiate into more aggressive effectors, when deprived of PrPC.

Novel compounds, modulating PrPC activity, have been recently developed, although not tested in EAE models yet. Interestingly, by specific gene array studies, we found that PrPC was highly expressed in DCs and differentially expressed among selected DC subsets. Moreover, by using a series of computational, and biochemical assays we identified novel small molecules, able to modulate PrPC function in specific cell lines overexpressing PrPC. By employing such tools, we studied the impact of PrPC modulation in promoting regulatory DC subsets. To this aim, DCs were treated either with novel PrPC modulators or a reference PrPC binding molecule Fe (III)-TMPyP. Then, they were co-cultured with sorted naïve CD4+ T cells in vitro. Notably, we found a significant expansion of FOXP3+CD4+ T regulatory (Treg) cells in cultures containing DC subsets, which were pre-treated with the specific PrPC modulators. Moreover, in a EAE model, we showed that systemic administration of such PrPC regulators, resulted in significant reduction of disease severity, compared to untreated controls. Overall, our results suggest that PrPC modulation in selected DC subsets may represent a novel means to restrain inflammatory T cell effectors, resulting in reduced inflammation, demyelination, and axonal injury in a model of EAE.

The engagement of the aryl hydrocarbon receptor by tryptophan derivatives can prevent the development of anti-FVIII antibodies in an experimental model of hemophilia A

Patients affected by haemophilia A require treatment with factor VIII (FVIII) protein. The most relevant complication is the development of neutralizing FVIII-specific antibodies or “inihibitors”. We reported that the inhibitor-positive status was associated with reduced activity of the immune-regulatory enzyme indoleamine 2,3-dioxygenase 1 (IDO1), that promotes regulatory effects via the production of tryptophan catabolites, known as kynurenines. Some of those tryptophan derivatives are endogenous ligands for the Aryl hydrocarbon receptor (AhR). In this study we tested the potential of tryptophan-related AhR ligands for inhibiting the development of anti-FVIII antibodies in hemophilic (F8 KO) mice. To this aim, F8 KO mice were treated with recombinant human FVIII (rhFVIII) alone or in combination with selected AhR ligands once weekly for four weeks. Antibody titers were tested by specific ELISA and Bethesda test. All mice treated with rhFVIII developed high-titer anti-FVIII antibodies after 4 weeks of treatment. Administration of a specific tryptophan metabolite prevented the generation of anti-FVIII antibodies in almost 80% of F8 KO mice. The protective effect of these AhR ligands was negated by co-administration of the AhR antagonist CH-223191 or in AhR KO mice. Similar results were obtained by administration of engineered gold nanoparticles loaded with the same tryptophan metabolite and rhFVIII. These results suggest that the engagement of AhR, by specific tryptophan derivatives, may be a possible new strategy to control the immune response to rhFVIII. Our findings might lead to the development of novel immunomodulatory interventions for preventing or eradicating inhibitors in hemophilia A patients.

Binding Mode and Structure-Activity Relationships of ITE as an Aryl Hydrocarbon Receptor (AhR) Agonist

Discovered as a modulator of the toxic response to environmental pollutants, aryl hydrocarbon receptor (AhR) has recently gained attention for its involvement in various physiological and pathological pathways. AhR is a ligand-dependent transcription factor activated by a large array of chemical compounds, which include metabolites of l-tryptophan (l-Trp) catabolism as endogenous ligands of the receptor. Among these, 2-(1'H-indole-3'-carbonyl)thiazole-4-carboxylic acid methyl ester (ITE) has attracted interest in the scientific community, being endowed with nontoxic, immunomodulatory, and anticancer AhR-mediated functions. So far, no information about the binding mode and interactions of ITE with AhR is available. In this study, we used docking and molecular dynamics to propose a putative binding mode of ITE into the ligand binding pocket of AhR. Mutagenesis studies were then instrumental in validating the proposed binding mode, identifying His 285 and Tyr 316 as important key residues for ligand-dependent receptor activation. Finally, a set of ITE analogues was synthesized and tested to further probe molecular interactions of ITE to AhR and characterize the relevance of specific functional groups in the chemical structure for receptor activity.

IDO1 activity in selected immune cells controls antibody responses

Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme involved in the initial step of tryptophan degradation along the kynurenine pathway. It has immunosuppressive effects, linked to enzymic and non-enzymic regulatory functions. IDO1 is also crucial for sustaining the function of T regulatory cells (Treg), which are involved in the establishment of peripheral tolerance.

We recently found that defective IDO1 induction is associated to anti-FVIII antibody production in patients with severe Hemophilia A1. In hemophilic mice, CpG- rich oligodeoxynucleotides (CpG-ODN) administration induced IDO1 expression in dendritic cells (DCs) that control FVIII antibody response.

Recently we discovered that CpG-ODN selectively induced IDO1 in a subset of conventional DCs (cDCs). IDO1 was found to be highly expressed in gut CD11C+CD103+ DCs, which are required for establishment of oral tolerance2. Based on these data we analyzed the impact of IDO1 deficiency in controlling antibody responses, in two different experimental models (FVIII and ovalbumin, OVA, immunization). Interestingly, IDO1 deficiency resulted in a significant increase of FVIII-specific antibody production relative to wild type controls. Similarly, IDO KO mice showed a significant immunoglobulin production in a model of OVA-induced oral tolerance.

These data suggest the regulatory role of IDO1 in controlling antibody responses to self and non-self antigens.

Aryl hydrocarbon receptor: a novel target for the anti-inflammatory activity of statin therapy

Statin therapy is associated with an attenuation of the systemic inflammatory response. Aryl hydrocarbon receptor (AhR) is believed to play an active role in the control of inflammation. Specific statins promote the transcription of Cyp1a1, which induction involves AhR activation1. We investigated whether AhR might be involved in the anti-inflammatory effect of statins treatment.

We performed luciferase assay to test the ability of murine hepatocytes overexpressing AhR and the xenobiotic responsive elements (XRE) and the ability of murine embryonic fibroblast AhR KO, transfected with different mutants of AhR to activate receptor in response to statins. Lipopolysaccharide (LPS)-treated RAW 264.7 macrophage cells were tested for the expression of AhR and for pro-inflammatory/anti-inflammatory response to different statins. Activated AhR WT and KO macrophages were tested for the expression of M1 and M2 markers and for pro-inflammatory/anti-inflammatory cytokines production. Luciferase assays showed that atorvastatin and pravastatin activated AhR, but no AhR mutants. LPS treatment of RAW 264.7 cell line induced AhR. Exposure of RAW 264.7 to both pravastatin and atorvastatin concomitantly to LPS reduced IL-6 production and increased IL-10 secretion. Atorvastatin and pravastatin potentiated arginase expression and anti-inflammatory response in activated macrophages in AhR dependent manner.

These data show that atorvastatin and pravastatin activate AhR, attenuate the inflammatory response induced by LPS and promote M2 phenotype in AhR dependent manner. AhR might represent a mediator of the anti-inflammatory effects of statin treatment.

Protective role of conventional dendritic cells in experimental model of sepsis

Sepsis is a serious medical condition caused by an overwhelming immune response to infection and is a major challenge in the intensive care unit, where it’s one of the leading causes of death. Dendritic cells (DCs), acting as sentinels, constantly sense and respond to environmental stimuli. During the progression of sepsis, DCs have been reported to take part in the aberrant immune response and be necessary for survival. Recently, we demonstrated that activation of Aryl Hydrocarbon receptor (AhR), by tryptophan metabolites in DCs, represents a protective mechanism in an experimental animal model of Lipopolysaccharide (LPS)-induced septic shock. Based on these results we examined the role of DCs subsets in sepsis. To determine whether DCs are required for protection against LPS sterile septic shock we used Zbtb46DTR mouse model. We found that Zbtb46DTR chimeras treated with diphtheria toxin are unable to survive after sub-lethal LPS challenge compared to wild-type mice reconstituted with wild-type bone marrow. In addition, naive mice intravenously transferred with LPS-treated DCs survived to a lethal LPS challenge. Notably, we found that mice lacking of CD24+ DCs are extremely susceptible to LPS. Moreover, LPS selectively induces indoleamine-2,3-dioxygenase 1 (IDO1) in bone marrow-derived CD24+. Our data demonstrate for the first time that DCs and specifically CD24+ DCs, play a critical role in sepsis protection.

Deciphering Interleukin 4-induced gene-1 as novel immune regulatory pathway in dendritic cell subsets

Interleukin 4-induced gene-1 (IL4i1) is as L-phenylalanine oxidase initially described as an early IL-4-inducible gene in B cells [1]. Herein, we analyzed IL4I1 expression in different DC subsets and investigated the possible role of IL4I1 in T-cell regulation. By using a novel and highly specific antibody, reactive to mouse IL4I1, developed in our laboratory, we found that IL4i1 could be induced by IL-4 or CpG olognucleotides (CpGODN) only in classical DCs (cDC). IL4i1 induction, by IL-4 was prevented in cDCs isolated from AhR−/− mice. Moreover, IL-4–treated cDCs cultured with CD4+T cells favored the expansion of FoxP3+ CD4+ T cells (Treg) compared to untreated cDCs. This effect was abrogated in the presence of a small interfering RNA (siRNA) targeting IL4i1 but not by a control siRNA. Notably, IL-4-induced IL4i1 expression in cDCs required aryl hydrocarbon receptor (AhR) in these cells. IL4I1-mediated oxidative deamination of phenylalanine produces H2O2 and phenylpyruvate (PP). Recently we found that PP is a novel ligand of AhR. Phenylpyruvate administration in vivo significantly reduced disease severity in a murine model of multiple sclerosis, such effect was prevented in AhR−/− mice. Overall, these results point IL4i1 as a key enzyme in the regulation of immune responses.

CpG type-A induction of an early protective environment in experimental multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory, demyelinating disease of the CNS that mimics human multiple sclerosis (MS), and it is thought to be driven by Th1 and Th17 myelin-reactive cells. Although adaptive immununity is clearly pivotal in the pathogenesis of EAE – with an essential role of CD4+ T cells – little is known of early, innate responses in this experimental setting. CpG-rich oligodeoxynucleotides (ODNs), typically found in microbial genomes, are potent activators of TLR9 in plasmacytoid dendritic cells (pDCs). In this study, we compared the effects of two types of CpG, namely, type A and type B, on EAE. We found that treatment with CpG type-A ODN (CpG-A) – known to induce high amounts of IFN-α in pDCs – significantly reduced disease severity in EAE, relative to controls (12.63 ± 1.86 vs. 23.49 ± 1.46, respectively; p = 0.001). Treatment also delayed onset of neurological deficits and reduced spinal cord demyelination, while increasing the percentage of splenic regulatory (Foxp3+CD4+) T cells. CpG-A likewise reduced the levels of IL-17 and IFN-γ in the CNS. Mechanistic insight into those events showed that CpG-A promoted a regulatory phenotype in pDCs. Moreover, adoptive transfer of pDCs isolated from CpG-A–treated mice inhibited CNS inflammation and induced disease remission in acute-phase EAE. Our data thus identify a link between TLR9 activation by specific ligands and the induction of tolerance via innate immunity mechanisms.

A rare case of sigmoid colon obstruction in patient with ulcerative colitis: role of transabdominal ultrasound-guided biopsy

INTRODUCTION

Endometriosis is a common chronic gynaecological disease affecting 10 % of women of reproductive age. Of these 5-12 % may present bowel endometriosis that may be asymptomatic or associated with aspecific symptoms even bowel obstruction.

CASE PRESENTATION

The case of a 41-year-old woman with history of ulcerative colitis, previous diagnosis of ovarian endometriosis, recurrent abdominal pain not related to the menstrual cycle, with abdominal pain and obstinate constipation for 2 weeks was referred. The patient underwent colonoscopy, transabdominal ultrasound and ultrasound-guided fine-needle biopsy to have a diagnosis.

DISCUSSION

Endometriosis should be considered in the differential diagnosis of every woman of childbearing age who presents with gastrointestinal or abdominal symptoms. As demonstrated in our case and by the burgeoning literature in this field, we believe that the role of transabdominal ultrasound should be reconsidered in the management of abdominal diseases because this examination associated with ultrasound-guided fine-needle biopsy allows, in expert hands, to obtain adequate histological samples avoiding patients to undergo more invasive tests to get a diagnosis.

Italian familial defective apolipoprotein B patients share a unique haplotype with other Caucasian patients

Familial defective apolipoprotein (apo) B-100 together with familial hypercholesterolemia are the two common genetic conditions that cause hypercholesterolemia. Familial defective apolipoprotein B-100 is due to mutations around codon 3500 of the apo B gene. The most-characterized mutation is a G>A transition at nucleotide 10,708 that results in the substitution of arginine by glutamine at codon 3500 (Apo B Arg3500Gln). Two other mutations are caused by a C>T transition, one at nucleotide 10,800 (Apo B Arg3531Cys) and the other at nucleotide 10,707 (apo B Arg3500Trp). In the present study we describe three new Italian cases of familial defective apolipoprotein B-100 (Apo B Arg3500Gln), one from the Liguria region and two from Sicily, and the haplotype of the apo B gene co-segregating with the mutation. By screening two groups of probands, clinically diagnosed as having Familial Hypercholesterolemia (700 from mainland Italy and 305 from Sicily), the prevalence of familial defective apolipoprotein B-100 due to Arg3500Gln was found to be very low (0.28% and 0.65%, respectively). The Arg3531Cys mutation was not detected in any proband. In the three new families with Arg3500Gln mutation in the present study and in one previously described in Italy, the mutation was associated with a unique apo B haplotype, which is consistent with data previously reported for Caucasian patients [XbaI-, MspI+, EcoRI-, presence of the 5' signal peptide insertion (Ins) allele, and the 49-repeat allele of the 3'-VNTR].

Carotid atherosclerosis in hypercholesterolemic patients: relationship with cardiovascular events

BACKGROUND AND AIM

Extracranial cerebrovascular atherosclerosis is a common feature of hypercholesterolemia and carotid lesions are good predictors of cardiovascular events in the general population. Factors associated with the carotid damage of hypercholesterolemic patients and their relationships with the occurrence of clinical events are investigated in this study.

METHODS AND RESULTS

One hundred and seventeen cardiovascular event-free hypercholesterolemic subjects underwent a complete clinical examination to look for additional risk factors. A blood sample was collected for lipoprotein determination and an ultrasound high resolution B-mode imaging examination of the common carotid arteries was performed. Patients were treated according to the current guidelines during a 4-yr follow-up and all major cardiovascular events were recorded. The prevalence of subjects with increased intima-media thickness and plaque was 21.4% and 29.9% respectively, higher than in normolipidemic controls. Carotid lesions were significantly related to age, hypertension and LDL-cholesterol and HDL-cholesterol levels. The relative risk of developing a major clinical event was 3.92 (95% CI 1.54-9.95, p < 0.004) among categories of carotid status. At multivariate analysis, cardiovascular events were independently related to the diagnosis of familial hypercolesterolemia (FH), baseline carotid score and mean levels of LDL-cholesterol and HDL-cholesterol during the follow-up.

CONCLUSIONS

Common risk factors cooperate with plasma lipoprotein levels in increasing the frequency of carotid lesions of hypercholesterolemic patients. Since such lesions are useful predictors of clinical events, B-mode ultrasound evaluation of the carotids should be routinely included in the management of these patients.