Upregulation Of Indoleamine 2,3-dioxygenase Research Articles

Indoleamine-2,3-dioxygenase (IDO) Mediates the Suppression of T Cells by IFN-γ Primed Mesenchymal Stromal Cells in the Treatment of Psoriasis-Like Inflammation.

Psoriasis is a chronic and incurable skin inflammation driven by an abnormal immune response. Our study aims to investigate the potential of interferon-γ (IFN-γ) primed mesenchymal stem cells (IMSCs) in targeting T cells to attenuate psoriasis-like inflammation, and to elucidate the underlying molecular mechanism involved. Mesenchymal stem cells (MSCs) were isolated from the umbilical cord and identified based on their surface markers. Psoriasis models were established and then treated with IMSCs. Flow cytometry analysis was used to examine cell surface markers and T cell percentages. Indoleamine-2,3-dioxygenase (IDO) was knocked down by small interfering RNA (siRNA) and examined with western blot assay. The proliferative capacity of T cells was assessed using water-soluble tetrazolium salt-1(WST-1). Additionally, an immunohistochemical assay was used to determine epidermal thickness. The psoriasis area and severity index (PASI) scores were also assessed. We observed significant therapeutic efficacy of IMSCs against psoriasis-like inflammation in mice. Treatment with IMSCs resulted in a notable reduction in T cell infiltration within psoriatic lesions. Furthermore, we demonstrated that the therapeutic efficacy was mediated by the upregulation of IDO through IFN-γ stimulation. In vitro, IDO inhibited T cell proliferation, and in vivo, the therapeutic efficacy was eliminated when MSCs were transfected with IDO siRNA. IMSCs can treat psoriasis by suppressing T cell infiltration and the suppression is mediated by IDO.

The role of the kynurenine pathway in cardiovascular disease.

The kynurenine pathway (KP) serves as the primary route for tryptophan metabolism in most mammalian organisms, with its downstream metabolites actively involved in various physiological and pathological processes. Indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) serve as the initial and pivotal enzymes of the KP, with IDO playing important and intricate roles in cardiovascular diseases. Multiple metabolites of KP have been observed to exhibit elevated concentrations in plasma across various cardiovascular diseases, such as atherosclerosis, hypertension, and acute myocardial infarction. Multiple studies have indicated that kynurenine (KYN) may serve as a potential biomarker for several adverse cardiovascular events. Furthermore, Kynurenine and its downstream metabolites have complex roles in inflammation, exhibiting both inhibitory and stimulatory effects on inflammatory responses under different conditions. In atherosclerosis, upregulation of IDO stimulates KYN production, mediating aromatic hydrocarbon receptor (AhR)-induced exacerbation of vascular inflammation and promotion of foam cell formation. Conversely, in arterial calcification, this mediation alleviates osteogenic differentiation of vascular smooth muscle cells. Additionally, in cardiac remodeling, KYN-mediated AhR activation exacerbates pathological left ventricular hypertrophy and fibrosis. Interventions targeting components of the KP, such as IDO inhibitors, 3-hydroxyanthranilic acid, and anthranilic acid, demonstrate cardiovascular protective effects. This review outlines the mechanistic roles of KP in coronary atherosclerosis, arterial calcification, and myocardial diseases, highlighting the potential diagnostic, prognostic, and therapeutic value of KP in cardiovascular diseases, thus providing novel insights for the development and application of related drugs in future research.

Anti-inflammatory Response Induced by Exopolysaccharide of the Probiotic Bacillus subtilis

Abstract Probiotics can lessen the severity of intestinal inflammatory diseases, although the mechanisms by which this occur are poorly understood. We showed that exopolysaccharide (EPS) from the probiotic Bacillus subtilis induces anti-inflammatory macrophages and protects mice from enteric infection and sepsis. Here, we examined the molecular mechanisms by which EPS induces an anti-inflammatory response. In co-cultures of OVA-loaded bone marrow-derived dendritic cells (BMDC) and OT-II T cells, EPS inhibits T cell activation in a TLR4-dependent manner. We hypothesize that EPS engages TLR4 and activates the noncanonical NF-kB signaling pathway, which up-regulates the expression of indoleamine 2,3-dioxygenase (IDO). IDO degrades the essential amino acid tryptophan into kynurenine, which leads to suppression of T-cell activation and induction of tolerance. Western blot analysis of BMDCs treated with EPS showed nuclear translocation of the transcription factor RelB, which is central to the noncanonical pathway and upregulation of IDO. Inhibition of IDO using the inhibitor 1-methyl tryptophan, and ido1−/− BMDCs reverse the effect of EPS. We conclude that EPS inhibition of T cell activation and proliferation is mediated by IDO. We have identified a novel mechanism for immune protection by a probiotic molecule.

Review of 10 years of research on breast cancer patients: Focus on indoleamine 2,3-dioxygenase.

Therapeutic manipulation of the immune system in cancer has been an extensive area of research in the field of oncoimmunology. Immunosuppression regulates antitumour immune responses. An immunosuppressive enzyme, indoleamine 2,3-dioxygenase (IDO) mediates tumour immune escape in various malignancies including breast cancer. IDO upregulation in breast cancer cells may lead to the recruitment of regulatory T (T-regs) cells into the tumour microenvironment, thus inhibiting local immune responses and promoting metastasis. Immunosuppression induced by myeloid derived suppressor cells activated in an IDO-dependent manner may enhance the possibility of immune evasion in breast cancer. IDO overexpression has independent prognostic significance in a subtype of breast cancer of emerging interest, basal-like breast carcinoma. IDO inhibitors as adjuvant therapeutic agents may have clinical implications in breast cancer. This review proposes future prospects of IDO not only as a therapeutic target but also as a valuable prognostic marker for breast cancer.

Tolerance Induction by Exopolysaccharide from the Probiotic Bacillus subtilis

Abstract Intestinal microbiota can lessen the severity of inflammatory diseases, although the mechanisms by which this occur are poorly understood. We showed that exopolysaccharide (EPS) from the probiotic Bacillus subtilis induces anti-inflammatory macrophages and protects mice from enteric infection and sepsis. Here, we examined the molecular mechanisms by which EPS induces an anti-inflammatory response. In co-cultures of OVA-loaded bone marrow-derived dendritic cells (BMDC) and OT-II T cells, EPS inhibits T cell activation in a TLR4-dependent manner. We hypothesize that EPS engages TLR4 and activates the noncanonical NF-kB signaling pathway, which up-regulates the expression of indoleamine 2,3-dioxygenase (IDO). IDO degrades the essential amino acid tryptophan into kynurenine. The subsequent tryptophan depletion and kynurenine formation leads to suppression of T-cell activation and induction of tolerance. Western blot analysis of BMDC treated with EPS showed nuclear translocation of the transcriptional factor RelB, which is central to the noncanonical pathway, and upregulation of IDO. Inhibition of IDO using the inhibitor, 1-methyl tryptophan and deletion of IDO in BMDCs reverses the effect of EPS. We conclude that EPS inhibition of T cell activation and proliferation is mediated by IDO.

Blockade of AIM2 inflammasome or α1-AR ameliorates IL-1β release and macrophage-mediated immunosuppression induced by CAR-T treatment

BackgroundInterleukin (IL) 1 released from monocytes/macrophages is one of the critical determinants in mediating the adverse events of chimeric antigen receptor T cell (CAR-T) therapy, including cytokine release syndrome and...

Indoleamine 2,3-Dioxygenase Mediates Survival of Chronic Lymphocytic Leukemia B Cells through Aryl Hydrocarbon Receptor By Inducing Mcl1

Introduction: Chronic lymphocytic leukemia (CLL) is a dynamic disease in which monoclonal B cells proliferate within the pseudo-follicular centers in lymphoid organs and then they accumulate due to an intrinsic defect of apoptosis. Leukemic cells are considered as "addicted to the host" since extrinsic signals from the microenvironment strongly influence the establishment of a progressive immunosuppression for malignant cell growth and survival. The cytoplasmic enzyme indoleamine 2,3-dioxygenase (IDO) mediates the conversion of the essential amino acid tryptophan (Trp) into metabolic byproducts such as kynurenine (Kyn). Kyn and other secondary metabolites are endogenous activators of the aryl hydrocarbon receptor (AHR), a ligand-controlled transcription factor that mediates cellular responses to toxins or endogenous ligands. The IDO-Kyn-AHR axis plays important roles in carcinogenesis and cancer progression. The mechanisms that promote inflammation around tumor tissues and determine immune tolerance consist in Trp depletion, which induces T cell apoptosis, and in Kyn-mediated AHR activation that inhibits effector T cells and promotes regulatory T cells differentiation. IDO protein is expressed in human hematologic malignancies and its level is correlated with a poor prognosis and chemoresistance. The IDO activity, measured as the Kyn/Trp ratio, was reported to be increased in CLL cases comparing to normal controls. Aim: We wondered to characterize the expression of IDO and AHR in CLL patients and to dissect the biological function of the IDO-Kyn-AHR axis. Methods: Gene transcription and protein expression were evaluated by real time PCR and western blot. Enzymatic activity was assessed through ELISA. Survival was measured with PI/annexin V assay. Overexpression and silencing of target genes was obtained by nucleofection. Results: Firstly, we observed that CLL cells expressed both IDO and AHR at variable levels. Moreover, we found that several microenvironmental signals such as IFNγ, LPS, anti-IgM, CpG oligo DNA, CD40L and TNFα were able to up-regulate IDO and AHR mRNA and protein. To characterize the pathways able to mediate IDO expression, we stimulated CLL cells with IFNγ and CD40L. Using ruxolitinib, an inhibitor of JAK-STAT pathway, we found that IFNγ induced IDO through STAT1 signaling. Again, CD40L stimulation determined IDO overexpression through the non-canonical NF-kB pathway, as assessed by treating cells with NF-κB inducing kinase inhibitor, NIK SMI1. We also confirmed that IFNγ-treated CLL cells were able to produce a functional IDO enzyme by measuring Kyn production and Trp consumption by ELISA. The strong increase in the Kyn/Trp ratio induced by IFNγ was significantly reduced by ruxolitinib treatment. To verify if Kyn produced by CLL cells could act through an autocrine loop on AHR, leukemic cells were treated with Kyn. We observed that Kyn mediated AHR translocation from the cytoplasm to the nuclei, inducing its activation as assessed by up-regulation of CYP1A1, a known AHR target gene. Of interest, we found that Kyn treatment improved CLL cells survival. Analyzing the anti-apoptotic proteins of the Bcl2 family after Kyn treatment, we found the induction of Mcl1, that was affected by adding CH-223191, an antagonist of AHR. Moreover, we transfected CLL cells with an IDO vector. The up-regulation of IDO increased CLL cells survival through the induction of Mcl1. Accordingly, when CLL cells were silenced for AHR, we observed a reduction of their survival. Conclusion: Our data demonstrate the constitutive expression of IDO and AHR in CLL cells. Furthermore, the tumor microenvironment promotes the induction of IDO and AHR through a complex signaling crosstalk with leukemic cells. Our findings underline that IDO-Kyn-AHR axis is active in CLL cells and promotes Mcl1 expression, sustaining the survival of CLL cells. Disclosures Luppi: Gilead Sci: Consultancy, Speakers Bureau; MSD: Consultancy; Sanofi: Consultancy; Abbvie: Consultancy; Daiichi-Sankyo: Consultancy; Novartis: Consultancy, Speakers Bureau. Marasca:Gilead Sci: Honoraria, Research Funding; Roche: Consultancy, Honoraria; Shire: Consultancy, Honoraria; Janssen: Honoraria, Research Funding; Abbvie: Consultancy, Honoraria.

Abstract A46: Upregulation of IDO in bacterial vaginosis: Role in HPV coinfection

Abstract Introduction: Bacterial vaginosis, a modification of the vaginal microbiota, is positively associated with the acquisition of certain genital infections, including cervical human papillomavirus (HPV) infection. In turn, HPV infection is the chief etiologic agent in the development of cervical cancer. Although HPV infection is widely prevalent, only few infected women will develop cervical cancer, suggesting that environmental or host factors contribute to malignancy. In this study, we are interested in identifying if the enzyme indoleamine-2,3-dioxygenase (IDO) has a role in the mechanism by which BV contributes to HPV infection and cervical lesion. IDO catalyzes the oxidation of the essential amino acid tryptophan (Trp) to kynurenine. IDO expression is induced by IFN-gamma and has been linked to T-cell immunosuppression and immune tolerance. IDO also plays an important role in host–pathogen interactions during viral and bacterial infections and on immune-escape of cancer cells. Methods: This cross-sectional study included 296 women attending the Women's Hospital - CAISM/UNICAMP. The case group was composed of women who had a confirmed histologic diagnosis of cervical intraepithelial neoplasia (CIN) grade 1, 2, or 3 or squamous cell carcinoma (SCC). The control group was composed of women who presented at least two previous normal Pap smears. The levels of IDO expression were analyzed by immunocytochemistry in liquid-based cytology samples from 196 women. Score 1 and 2 (0 to 50% of DAB stained squamous cells) were considered as mild expression and Score 3 and 4 (51 to 100% of DAB stained squamous cells) were considered as strong expression. Immunocytochemical analysis considered both atypical and typical squamous in the counting. The Gram-stained slides were analyzed by Nugent criteria. We used the Linear Array Genotyping HPV kit for detection of 37 types of low- and high-risk HPVs. Multiplex PCR was performed for the diagnosis of Chlamydia trachomatis (Ct), Neisseria gonorrhoeae (Ng), and Trichomonas vaginalis. Study variables were evaluated by odds ratio (OR) with a 95% confidence interval (CI) and Qui-square test and significance level was defined at 5%. Results: BV was positively associated with genital infection by HPV (p = 0.02), Trichomonas vaginalis (p=0.001) and endocervicitis by Ct and Ng (p= 0.000003). We found a higher frequency of strong expression of IDO (74%, 31/42) in women with BV when compared with women without BV (44%, 60/137 and p= 0.0007). Although the expression of IDO was slightly greater for HPV infection associated with BV (62%, 15/24), and women with CIN1 and CIN3 had a slightly higher frequency of IDO expression, these associations were not statistically significant. No correlation was found for IDO and CIN2, CIN3, or SCC. Conclusion: Here we show that IDO is upregulated in BV but is not associated with the severity of cervical lesion. We also found that BV is positively associated with genital infection by HPV. We suggest that upregulation of IDO in BV could be one of the cofactors that lead to an increased risk of HPV coinfection, whose importance is attenuated during cervical lesion progression. Ongoing studies are focused on the analysis of IDO expression, specifically in the atypical cells of cervical lesions. Citation Format: Paloma Almeida Venancio, Silvya Stuchi Maria-Engler, Marcia Edilaine Lopes Consolaro, Luisa Lina Villa, Sophie Françoise Derchain, Ana Campa, Michelle Garcia Discacciati. Upregulation of IDO in bacterial vaginosis: Role in HPV coinfection [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A46.

Cathepsin C Aggravates Neuroinflammation Involved in Disturbances of Behaviour and Neurochemistry in Acute and Chronic Stress-Induced Murine Model of Depression.

Major depression has been interpreted as an inflammatory disease characterized by cell-mediated immune activation, which is generally triggered by various stresses. Microglia has been thought to be the cellular link between inflammation and depression-like behavioural alterations. The expression of cathepsin C (Cat C), a lysosomal proteinase, is predominantly induced in microglia in neuroinflammation. However, little is known about the role of Cat C in pathophysiology of depression. In the present study, Cat C transgenic mice and wild type mice were subjected to an intraperitoneal injection of LPS (0.5mg/kg) and 6-week unpredictable chronic mild stress (UCMS) exposure to establish acute and chronic stress-induced depression model. We examined and compared the behavioural and proinflammatory cytokine alterations in serum and depression-targeted brain areas of Cat C differentially expressed mice in stress, as well as indoleamine 2,3-dioxygenase (IDO) and 5-hydroxytryptamine (5HT) levels in brain. The results showed that Cat C overexpression (Cat C OE) promoted peripheral and central inflammatory response with significantly increased TNFα, IL-1β and IL-6 in serum, hippocampus and prefrontal cortex, and resultant upregulation of IDO and downregulation of 5HT expression in brain, and thereby aggravated depression-like behaviours accessed by open field test, forced swim test and tail suspension test. In contrast, Cat C knockdown (Cat C KD) partially prevented inflammation, which may help alleviate the symptoms of depression in mice. To the best of our knowledge, we are the first to demonstrate that Cat C aggravates neuroinflammation involved in disturbances of behaviour and neurochemistry in acute and chronic stress-induced murine model of depression.

Pathogenic role for the kynurenine pathway in maternal immune activation-induced autism-like behavior in mice

Prenatal inflammation is a risk factor for neurodevelopmental disorders. In rodent models, maternal immune activation (MIA) causes phenotypes in offspring that resemble many of the features of these human disorders, but the pathogenic mechanisms remain unclear. Immune activation upregulates the tryptophan metabolizing enzyme indoleamine 2,3-dioxygenase (IDO) which mediates many of the behavioral consequences of inflammation in adults, and experimentally increasing kynurenine levels of pregnant dams causes developmental consequences in the offspring. Therefore, we hypothesized that MIA-induced upregulation of IDO during gestation is a pathogenic mechanism by which fetal neurodevelopment is disrupted and autism-like phenotypes develop. Pregnant female IDO-/- mice or control C57BL/6J mice were administered 20 kg/mg polyinosinic:polycytidylic acid (poly I:C) or saline i.p. on gestational day 12.5. At various ages, autism-like behaviors were measured. Repetitive self-grooming behavior was significantly increased in WT-MIA male offspring compared to WT-saline controls. Self- grooming behavior in IDO-/- mice was not affected by MIA. MIA reduced preference for social novelty, measured in the 3-chamber test, in male offspring independent of IDO, while it increased social novelty preference in WT female mice. In mice with targeted deletion of kynurenine monooxygensase (KMO), endogenous kynurenine levels are markedly increased, and offspring of KMO KO dams exhibit several autism-like behaviors. Our data suggest that IDO may play an important pathogenic role in the development of specific autism-like behaviors caused by MIA.

Human regulatory macrophages are potent in suppression of the xenoimmune response via indoleamine-2,3-dioxygenase-involved mechanism(s).

For xenotransplantation to truly succeed, we must develop immunomodulatory strategies to suppress the xenoimmune response but by minimizing immunosuppression over the long term. Regulatory macrophages (Mreg) have been shown to suppress polyclonal T-cell proliferation in vitro and prolong allograft survival in vivo. However, the question of whether they are capable of suppressing xenoimmune responses remains unknown. This study assessed the potential of human Mreg to be used as an effective immunomodulatory method in xenotransplantation. CD14+ monocytes selected from human peripheral blood mononuclear cells (PBMC) were cultured with macrophage colony-stimulating factor (M-CSF) for 7days with IFN-γ added at day 6 for Mreg induction. Mreg phenotyping was performed by flow cytometric analysis, and the in vitro suppressive function was assessed by mixed lymphocyte reaction (MLR) using irradiated pig PBMC as the xenogeneic stimulator cells, human PBMC as responder cells, and autologous Mreg as suppressor cells. To assess mRNA expression of Mreg functional molecules indoleamine-2,3-dioxygenase (IDO), IL-10, inducible nitric oxide synthase (iNOS) and TGF-β were measured by real-time PCR. Supernatants were collected from the MLR cultures for IDO activity assay by high-performance liquid chromatography (HPLC). The effects of the IDO inhibitor 1-D/L-methyl-tryptophan (1-MT), iNOS inhibitor NG -monomethyl-l-arginine (L-NMMA), and anti-IFN-γ or anti-TGF-β monoclonal antibody (mAb) treatment on Mreg suppressive capacity were tested from the supernatants of the MLR assays. We demonstrated that induced Mreg with a phenotype of CD14low CD16-/low CD80low CD83-/low CD86+/hi HLA-DR+/hi were capable of suppressing proliferating human PBMC, CD4+, and CD8+ T cells, even at a higher responder:Mreg ratio of 32:1 in a pig-human xenogeneic MLR. The strong suppressive potency of Mreg was further correlated with their upregulated IDO expression and activity. The IDO upregulation of Mreg was associated with an increased production of IFN-γ, an IDO stimulator, by xenoreactive responder cells in the xenogeneic MLR. While no effect on Mreg suppressive potency was detected by addition of the iNOS inhibitor L-NMMA or anti-TGF-β mAb into the MLR assays, inhibition of IDO activity by neutralizing IFN-γ or by IDO inhibitor 1-MT substantially impaired the capacity of Mreg to suppress the xenogeneic response, indicating the importance of upregulated IDO activity in Mreg-mediated suppression of the xenogeneic response in vitro. This study demonstrates that human Mreg are capable of suppressing the xenoimmune response in vitro via IDO-involved mechanism(s), suggesting their potential role as an effective immunomodulatory tool in xenotransplantation.

AhR mediates an anti-inflammatory feedback mechanism in human Langerhans cells involving FcεRI and IDO.

Aryl hydrocarbon receptor (AhR), an important regulator of immune responses, is activated by UVB irradiation in the skin. Langerhans cells (LC) in the epidermis of patients with atopic dermatitis (AD) carry the high-affinity receptor for IgE, FcεRI, and are crucially involved in the pathogenesis of AD by inducing inflammatory responses and regulating tolerogenic processes. We investigated AhR and AhR repressor (AhRR) expression and functional consequences of AhR activation in human ex vivo skin cells and in in vitro-generated LC. Epidermal cells from healthy skin were analyzed for their expression of AhR and AhRR. LC generated from CD34+ hematopoietic stem cells (CD34LC) were treated with the UV photoproduct and AhR ligand 6-formylindolo[3,2-b]carbazole (FICZ). Cell surface receptors, transcription factors, and the tolerogenic tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) were analyzed using flow cytometry and quantitative PCR. Epidermal LC and CD34LC express AhR and AhRR. AhR was also found in keratinocytes, which lack AhRR. AhR activation of LC by FICZ caused downregulation of FcεRI in CD34LC without affecting their maturation. AhR-mediated regulation of FcεRI did not involve any known transcription factors related to this receptor. Furthermore, we could show upregulation of IDO mediated by AhR engagement. Our study shows that AhR activation by FICZ reduces FcεRI and upregulates IDO expression in LC. This AhR-mediated anti-inflammatory feedback mechanism may dampen the allergen-induced inflammation in AD.

Mangiferin prevents corticosterone-induced behavioural deficits via alleviation of oxido-nitrosative stress and down-regulation of indoleamine 2,3-dioxygenase (IDO) activity

Background: In recent years, a substantial amount of experimental studies have demonstrated that exogenous administration of corticosterone causes anxiety and depressive-like behaviour in rodents which involves hypothalamic-pituitary-adrenal axis dysregulation. Our present study aimed to explore the neuroprotective potential of mangiferin against corticosterone-induced anxiety and depressive-like behaviour.Methods: Corticosterone (40 mg/kg; subcutaneously) was administered once daily in swiss albino mice for 21 days. Mice were treated simultaneously with mangiferin (40 mg/kg; p.o.), 30 min prior to the corticosterone injection.Results: Chronic administration of corticosterone caused anxiety and depressive-like behaviour in mice which was significantly alleviated by mangiferin treatment. Biochemical analysis revealed that mangiferin treatment significantly attenuated corticosterone-induced oxido-nitrosative stress and neuroinflammation in the hippocampus region. Furthermore, concomitant treatment with mangiferin significantly enhanced the hippocampal brain-derived neurotrophic factor (BDNF) level and decreased the serum corticosterone level in the corticosterone-treated animals. Western blotting analysis revealed that corticosterone administration significantly up-regulated the indoleamine 2,3-dioxygenase (IDO) protein expression level in the hippocampus which was significantly reduced by mangiferin treatment.Conclusion: Taken together, our results suggest that mangiferin exerts anti-anxiety and antidepressant effect in corticosterone-treated rats, which is probably mediated through up-regulation of BDNF level along with inhibition of oxido-nitrosative stress, neuroinflammation and IDO up-regulation in the hippocampus region.

Modulation of human umbilical cord‐derived mesenchymal stromal cells immunophenotype through cellular priming

The in vitro immunomodulation effects of bone marrow‐derived mesenchymal stromal cells (BM‐MSCs) can be drastically altered by stimulation of toll‐like receptor (TLR) 3 and 4 into diametrically different immunomodulatory phenotypes similar to activated macrophage type 1 (M1) and macrophage type 2 (M2) polarization. BM‐MSCs activated by TLR4 ligand lipopolysaccharide (LPS) display an enhanced pro‐inflammatory phenotype (MSC1). In contrast, BM‐MSCs stimulated by Poly I:C, a TLR3 ligand that simulates a viral infection, display an anti‐inflammatory phenotype, called MSC2. This phenomenon has been termed “MSC priming”. The objective of this study was to determine whether human umbilical cord‐derived (HUC) MSCs display enhanced immune suppression after MSC1 versus MSC2 priming. Four different media conditions: 1) the TLR4 ligand LPS, 2) the TLR3 ligand Poly I:C, 3) interferon gamma (IFN‐γ) which upregulates TLR4 receptors and 4) human platelet lysate (HPL) versus control (multipotent adult progenitor cell (MAPC) medium. Five independent MSC lines were tested. Immune properties were assayed by examining the cell's suppression on the proliferation of stimulated murine splenocytes and 2) cytokine production: PGE2 and indoleamine 2,3‐dioxygenase (IDO) via ELISA. Cells cultured in IFN‐γ, LPS and Poly I:C media showed significant upregulation of IDO compared to MAPC medium. The expression of PGE2 was not significantly altered. Compared with MAPC medium, HPL medium inhibited the immunosuppressive effects of MSCs. In contrast, IFN‐γ and MAPC medium had the greatest immunosuppressive effects. Umbilical cord‐derived MSCs did not undergo MSC1 priming by TLR3 ligand stimulation like bone marrow‐derived MSCs.

Indoleamine 2,3-dioxygenase: As a potential prognostic marker and immunotherapeutic target for hepatocellular carcinoma.

Tumor cells induce an immunosuppressive microenvironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma (HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immunosuppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.

The safety of autologous and metabolically fit bone marrow mesenchymal stromal cells in medically refractory Crohn's disease – a phase 1 trial with three doses

Mesenchymal stromal cells ability to reset immune functionalities may be useful in Crohn's disease. To perform a first-in-human phase 1 safety clinical trial of metabolically fit autologous bone marrow-derived mesenchymal stromal cells in 12 subjects with Crohn's disease utilising three doses. Autologous mesenchymal stromal cells were derived from marrow aspirate and propagated for 2-3 weeks with fibrinogen depleted human platelet lysate and subsequently administered to subjects without interval cryobanking. Twelve subjects received a single mesenchymal stromal cell intravenous infusion of 2, 5 or 10 million cells/kg BW(n = 4/group). Infused mesenchymal stromal cells were analysed for cell surface marker expression, IDO(indoleamine 2,3-dioxygenase) upregulation by IFNγ stimulation, and inhibition of third party peripheral blood mononuclear cell proliferation in vitro. The primary end point measured was safety and tolerability; clinical response was assessed as a secondary endpoint. All patients tolerated the mesenchymal stromal cell infusion well and no dose limiting toxicity was seen. Seven patients had serious adverse events of which five were hospitalisations for Crohn's disease flare. Two of these serious adverse events were possibly related to the mesenchymal stromal cells infusion. Five subjects showed clinical response 2 weeks after the infusion. Mesenchymal stromal cell phenotype, cytokine responsiveness, and peripheral blood mononuclear cell proliferation blockade were not different among the patients. Single infusion of fresh autologous bone marrow mesenchymal stromal cells propagated ex vivo using human platelet lysate-supplemented media was safe and feasible at intravenous doses of up to 10 million cells/kg BW in patients with Crohn's disease.

Indoleamine 2,3-dioxygenase: First evidence of expression in rainbow trout (Oncorhynchus mykiss)

The role of enzymes as active antimicrobial agents of the innate immunity in teleost fish is proposed in diverse works. Secretion of Indoleamine 2,3-dioxygenase (IDO) has been described in higher vertebrates; it degrades l-tryptophan in extracellular environments associated mainly with mucosal organs. The effect of IDO on decreasing amino acid concentration may inhibit the growth of potential pathogens. In fish the study of this molecule is still. Here we report the identification of an Onchorhyncus mykiss IDO homologue (OmIDO). IDO was cloned, sequenced, and the primary structure shows conservation of key functional sites. The constitutive expression is altered when the fish is challenged with LPS as a pathogen-associated molecular pattern (PAMPs). Up-regulation of IDO was shown preferentially in the fish’s mucosal cells. In order to obtain evidence of a possible regulation mechanism, an in vitro cell model was used for to show that OmIDO is induced by rIFN. These study has identified a Indoleamine 2,3-dyoxigenase in O. mykiss will contribute to expands our knowledge of the function this protein in fish immune response. These findings allow to propose the use of OmIDO as a molecular indicator of strength of the animal’s immune response and wellbeing.

Indoleamine 2,3-Dioxygenase Is Involved in the Inflammation Response of Corneal Epithelial Cells to Aspergillus fumigatus Infections.

Indoleamine 2,3-dioxygenase (IDO), which is mainly expressed in activated dendritic cells, is known as a regulator of immune responses. However, the role of IDO in immune responses against fungal corneal infection has not been investigated. To evaluate the regulatory mechanisms of IDO in fungal inflammation, we resorted to human corneal epithelial cells (HCECs), known as the first barrier of cornea against pathogenic microorganisms. We found that IDO was significantly up-regulated in corneal epithelium infected with Aspergillus fumigatus (A. fumigatus) and HCECs incubated with spores of A. fumigatus. Furthermore, IDO inhibitor (1-methyltryptophan, 1-MT) enhanced inflammatory cytokines IL-1β and IL-6 expression which were up-regulated by A. fumigatus spores infection. Dectin-1, as one of the important C-type lectin receptors, can identify β-glucan, and mediate fungal innate immune responses. In the present study, pre-treatment with curdlan, a Dectin-1 agonist, further enhanced IDO expression compared with A. fumigatus stimulation. While laminarin, the Dectin-1 specific inhibitor, partially inhibited IDO expression stimulated by A. fumigatus. Further studies demonstrated inhibition of IDO activity amplified the expressions of inflammatory cytokines IL-1β and IL-6 induced by activation of Dectin-1. These results suggested that IDO was involved in the immune responses of fungal keratitis. The activation of Dectin-1 may contribute to A. fumigatus spores-induced up-regulation of IDO.

Abstract 2353: Noncanonical NF-κB activation mediates STAT3-stimulated IDO up-regulation in myeloid-derived suppressor cells in breast cancer

Abstract Immunotherapy for cancer treatment is achieved through the activation of competent immune effector cells and the inhibition of immunosuppressive cells, such as myeloid-derived suppressor cells (MDSCs). While MDSCs have been shown to contribute to breast cancer development, the mechanism underlying MDSCs-mediated immunosuppression is unclear. We have identified a poorly differentiated MDSC subset in breast cancer suppressing T-cell function through signal transducer and activator of transcription (STAT) 3-dependent indoleamine 2,3 dioxygenase (IDO) up-regulation. Here we investigated the mechanisms underlying aberrant expression of IDO in MDSCs. MDSCs were induced by co-culturing human CD33+ myeloid progenitors with MDA-MB-231 breast cancer cells. Increased STAT3 activation in MDSCs was correlated with activation of the noncanonical nuclear factor-κB (NF-κB) pathway, including increased NF-κB-inducing kinase (NIK) protein level, phosphorylation of cytoplasmic inhibitor of NF-κB kinase (IKK) α and p100, and RelB-p52 nuclear translocation. Blocking STAT3 activation with the small molecule inhibitor JSI-124 significantly inhibited the accumulation of NIK and IDO expression in MDSCs. Knock-down of NIK in MDSCs suppressed IDO expression, but not STAT3 activation. RelB-p52 dimers were found to directly bind to the IDO promoter, leading to IDO expression in MDSCs. IL-6 was found to stimulate STAT3-dependent, NF-κB-mediated IDO up-regulation in MDSCs. Furthermore, significant positive correlation between the numbers of pSTAT3+ MDSCs, IDO+ MDSCs, and NIK+ MDSCs was observed in human breast cancers. These results demonstrate a STAT3-NF-κB-IDO pathway in breast cancer-derived MDSCs, which provides insight into understanding immunosuppressive mechanisms of MDSCs in breast cancer. Citation Format: Jinpu Yu, Yue Wang, Hui Li, Xiubao Ren. Noncanonical NF-κB activation mediates STAT3-stimulated IDO up-regulation in myeloid-derived suppressor cells in breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2353. doi:10.1158/1538-7445.AM2015-2353

TNFα mediates stress-induced depression by upregulating indoleamine 2,3-dioxygenase in a mouse model of unpredictable chronic mild stress.

Depression is often preceded by exposure to stressful life events. Chronic stress causes perturbations in the immune system, and up-regulates production of proinflammatory cytokines, which has been proposed to be associated with the pathogenesis of clinical depression. However, the potential mechanisms by which stress-induced proinflammatory cytokines lead to the development of depression are not well understood. Here, we sought to screen the main proinflammatory cytokines and the potential mechanisms linking inflammation to depression-like behavior during unpredictable, chronic, mild stress (UCMS), in vivo. Mice were allocated into four groups in each separate experiment: saline-control, saline-UCMS, drug-control and drug-UCMS. Development of depression-like behavior was reflected as a reduction in sucrose preference, and increased immobility in both the forced swim and tail suspension tests. The following drugs were administered intraperitoneally: the pan-anti-inflammatory tetracycline derivative, minocycline (30 mg/kg, daily), the tumor necrosis factor (TNF)α monoclonal antibody, infliximab (10 mg/kg, twice weekly), and the indoleamine 2, 3-dioxygenase (IDO) inhibitor, 1-methyltryptophan (1-MT, 10 mg/mouse, daily). Plasma TNFα, IL-1β and IL-18 increased significantly after the four-week UCMS exposure. Pretreatment of mice with minocycline completely blocked any upregulation. Concurrent with development of depression-like behaviors, the concentration of TNFα in plasma and the cerebral cortex increased remarkably. The tryptophan-degrading enzyme IDO was up-regulated in the cortex following UCMS exposure. Treatment of mice with minocycline, infliximab or 1-MT prevented the development of depression-like behaviors. Furthermore, blockade of TNFα inhibited expression of IDO and protected cortical neurons from UCMS-induced damage. These results suggest that TNFα plays a critical role in mediating UCMS-induced depression through up-regulation of IDO and subsequent damage of cortical neurons.