Induction Of IDO Research Articles

Metabolomic Disparities in Intraocular Fluid Across Varied Stages of Cataract Progression: Implications for the Analysis of Cataract Development.

Introduction: The lens's metabolic demands are met through a continuous circulation of aqueous humor, encompassing a spectrum of components such as organic and inorganic ions, carbohydrates, glutathione, urea, amino acids, proteins, oxygen, carbon dioxide, and water. Metabolomics is a pivotal tool, offering an initial insight into the complexities of integrated metabolism. In this investigative study, we systematically scrutinize the composition of intraocular fluid in individuals afflicted with cataracts. Methods: The investigation involved a comprehensive analysis of aqueous humor samples from a cohort comprising 192 patients. These individuals were stratified by utilizing the SPONCS classification system, delineating distinct groups characterized by the hardness of cataracts. The analytical approach employed targeted quantitative metabolite analysis using HILIC-based liquid chromatography coupled with high-resolution mass spectrometric detection. The metabolomics data analysis was performed with MetaboAnalyst 5.0. Results: The results of the enrichment analysis have facilitated the inference that the discerned disparities among groups arise from disruptions in taurine and hypotaurine metabolism, variations in tryptophan metabolism, and modifications in mitochondrial beta-oxidation of short-chain saturated fatty acids and pyrimidine metabolism. Conclusion: A decline in taurine concentration precipitates diminished glutathione activity, prompting an elevated requirement for NAD+ and instigating tryptophan metabolism along the kynurenine pathway. Activation of this pathway is additionally prompted by interferon-gamma and UV radiation, leading to the induction of IDO. Concurrently, heightened mitochondrial beta-oxidation signifies a distinctive scenario in translocating fatty acids into the mitochondria, enhancing energy production.

Mycobacterium leprae induces a tolerogenic profile in monocyte-derived dendritic cells via TLR2 induction of IDO.

The enzyme IDO‐1 is involved in the first stage of tryptophan catabolism and has been described in both microbicidal and tolerogenic microenvironments. Previous data from our group have shown that IDO‐1 is differentially regulated in the distinctive clinical forms of leprosy. The present study aims to investigate the mechanisms associated with IDO‐1 expression and activity in human monocyte‐derived dendritic cells (mDCs) after stimulation with irradiated Mycobacterium leprae and its fractions. M. leprae and its fractions induced the expression and activity of IDO‐1 in human mDCs. Among the stimuli studied, irradiated M. leprae and its membrane fraction (MLMA) induced the production of proinflammatory cytokines TNF and IL‐6 whereas irradiated M. leprae and its cytosol fraction (MLSA) induced an increase in IL‐10. We investigated if TLR2 activation was necessary for IDO‐1 induction in mDCs. We observed that in cultures treated with a neutralizing anti‐TLR2 antibody, there was a decrease in IDO‐1 activity and expression induced by M. leprae and MLMA. The same effect was observed when we used a MyD88 inhibitor. Our data demonstrate that coculture of mDCs with autologous lymphocytes induced an increase in regulatory T (Treg) cell frequency in MLSA‐stimulated cultures, showing that M. leprae constituents may play opposite roles that may possibly be related to the dubious effect of IDO‐1 in the different clinical forms of disease. Our data show that M. leprae and its fractions are able to differentially modulate the activity and functionality of IDO‐1 in mDCs by a pathway that involves TLR2, suggesting that this enzyme may play an important role in leprosy immunopathogenesis.

WITHDRAWN: Immunomodulatory effects of sCD83 via induction of TGF-β1 and IDO: an in vitro and rat orthotopic liver transplantation study

WITHDRAWN: Immunomodulatory effects of sCD83 via induction of TGF-β1 and IDO: an in vitro and rat orthotopic liver transplantation study

The antidepressant effects of GM-CSF are mediated by the reduction of TLR4/NF-\u0138B-induced IDO expression

BackgroundIndoleamine 2, 3-dioxygenase 1 (IDO) is responsible for the progression of the kynurenine pathway. This pathway has been implicated in the pathophysiology of inflammation-induced depression in which conventional antidepressants are not effective. It has been reported that granulocyte-macrophage stimulating factor (GM-CSF) could interfere with the induction of IDO in septic patients. We hypothesized that GM-CSF could exert antidepressant effects through IDO downregulation in a model for acute inflammation-induced depression.MethodsTo produce the model, lipopolysaccharide (LPS) (0.83 mg/kg) was administered intraperitoneally to mice. It has been well documented that LPS mediates IDO overexpression through TLR4/NF-ĸB signaling. In the treatment group, mice received GM-CSF (30 μg/kg, i.p.) thirty minutes prior to LPS injection. A validated selective serotonin reuptake inhibitor, fluoxetine (30 mg/kg i.p.), was also administered to an experimental group 30 min prior to LPS. Depressive-like behaviors were evaluated based on the duration of immobility in the forced swim test. To confirm that GM-CSF interferes with IDO induction in LPS treated mice, real-time PCR was used to quantify IDO mRNA expression. Furthermore, in order to study whether GM-CSF inhibits the TLR4/NF-ĸB signaling pathway, we measured levels ofpNF-ĸB and TLR4 by western blotting.ResultsGM-CSF demonstrated significant antidepressant activity in the presence of LPS on immobility (p < .001) and latency (p = .010) times in the forced swim test. In contrast, fluoxetine did not show any antidepressant activity on either immobility (p = .918) or latency (p = .566) times. Furthermore, GM-CSF inhibited the increase in IDO mRNA (p = .032) and protein (p = .016) expression as a result of LPS administration. A similar trend was observed for TLR4 (p = .042) and pNF-ĸB (p = .026) expression as both proteins showed reduced expression levels in the GM-CSF-pretreated group compared to the untreated (LPS) group.ConclusionOur results propose a promising antidepressant effect for GM-CSF possibly through the downregulation of IDO expression. This remedying effect of GM-CSF could be attributed to decreased amounts of TLR4 and active NF-ĸB in the treated mice.

Helicase-Driven Activation of NFκB-COX2 Pathway Mediates the Immunosuppressive Component of dsRNA-Driven Inflammation in the Human Tumor Microenvironment.

Presence of cytotoxic CD8+ T cells (CTL) in tumor microenvironments (TME) is critical for the effectiveness of immune therapies and patients' outcome, whereas regulatory T(reg) cells promote cancer progression. Immune adjuvants, including double-stranded (ds)RNAs, which signal via Toll-like receptor-3 (TLR3) and helicase (RIG-I/MDA5) pathways, all induce intratumoral production of CTL-attractants, but also Treg attractants and suppressive factors, raising the question of whether induction of these opposing groups of immune mediators can be separated. Here, we use human tumor explant cultures and cell culture models to show that the (ds) RNA Sendai Virus (SeV), poly-I:C, and rintatolimod (poly-I:C12U) all activate the TLR3 pathway involving TRAF3 and IRF3, and induce IFNα, ISG-60, and CXCL10 to promote CTL chemotaxis to ex vivo-treated tumors. However, in contrast with SeV and poly I:C, rintatolimod did not activate the MAVS/helicase pathway, thus avoiding NFκB- and TNFα-dependent induction of COX2, COX2/PGE2-dependent induction of IDO, IL10, CCL22, and CXCL12, and eliminating Treg attraction. Induction of CTL-attractants by either poly I:C or rintatolimod was further enhanced by exogenous IFNα (enhancer of TLR3 expression), whereas COX2 inhibition enhanced the response to poly-I:C only. Our data identify the helicase/NFκB/TNFα/COX2 axis as the key suppressive pathway of dsRNA signaling in human TME and suggest that selective targeting of TLR3 or elimination of NFκB/TNFα/COX2-driven suppression may allow for selective enhancement of type-1 immunity.Significance: This study characterizes two different poly-I:C-induced signaling pathways in their induction of immunostimulatory and suppressive factors and suggests improved ways to reprogram the TME to enhance the antitumor efficacy of immunotherapies. Cancer Res; 78(15); 4292-302. ©2018 AACR.

Antiviral Effect of IDO in Mouse Fibroblast Cells During Influenza Virus Infection.

While upregulation of 2,3-dioxygenase (IDO) accompanied by degradation of tryptophan along the kynurenine pathway have been reported to exert antimicrobial effects against a wide range of infectious agents, its role in the replication of influenza A virus remains uncertain. We performed experiments using influenza A/WSN/33 virus infection of mouse fibroblast cell-line (NIH-3T3) to study the effects of IDO on viral replication. Influenza infection resulted in prominent elevations of transcripts encoding IDO, interferon (IFN)-β, and segment 8 of the virus in NIH-3T3 cells. Introduction of siRNA targeted against IDO followed by infection resulted in further increased levels of viral RNA without altering IFN-β expression. Inhibition of IDO during the infection also resulted in reduction of virus-driven upregulation of 3-hydroxyanthranilate 3,4-dioxygenase (HAAO), but not kynurenine 3-monooxygenase (KMO), which are enzymes downstream in the kynurenine pathway. Thus, induction of IDO appears to contribute to limiting replication of the WSN/33 strain of influenza A virus in murine NIH-3T3 cells.

Mesenchymal Stromal Cell Growth and Glycocalyx Morphology are Regulated by Media Glucose Levels and Hypoxia

Physiological conditions such as hypoxia and/or chemical environments such as glucose levels in the media function as key regulators of cell behavior. Mesenchymal stromal cells (MSCs) are unique cells which have played an important role in many regenerative medicine technologies. They are characterized by a multi‐lineage potential, ability to self‐renew and immunomodulatory properties. The microenvironment of stem cells may play a crucial role in maintaining their stemness and regenerative potential, and the cellular glycocalyx may be an important cell based regulator within this microenvironment. Hyaluronan (HA), a non‐sulfonated linear glycosaminoglycan found in the glycocalyx of MSCs and other cell types has been implicated in regulation of various physiological processes including inflammation, tissue regeneration, cell proliferation and migration.Here we investigated the effect of hypoxic environments (1% O2 or 5% O2) as well as different glucose concentrations in minimal media on MSC identity, viability and potency as well as production of HA levels in the glycocalyx.MSCs were derived from bone marrow and maintained in different oxygen conditions (1% O2, 5% O2 or room air (~21% O2)). Additionally, bone marrow derived MSCs were also grown in alpha minimal essential media (αMEM) containing either low (1 mg/mL) or high (4.5 mg/mL) levels of glucose. Cell viability was measured microscopically using Trypan blue dye exclusion as well by flow cytometry with annexin V and propidium iodide staining. MSCs were characterized for identity through flow cytometry and potency through the induction of IDO by IFN‐gamma. HA levels were detected with biotin‐conjugated HA binding protein (HABP) followed by FITC‐conjugated streptavidin.Significantly higher numbers of MSCs were derived from bone marrow in 5% O2 (21067 ±1579 cells/cm2) when compared to 1% (14000 ± 5327 cells/cm2) or 21% O2 (10721 ± 3782 cells/cm2). Additionally, cells grown in 5% O2 had significantly lower doubling times of 42.5 ± 3.8 h in passage 1 in comparison to 52.8 ± 4.9 h for cells grown in 21% O2. However, no significant differences in cell morphology, cell identity and cell viability were observed between cells grown in 1%, 5% or 21% O2.Cells grown in high glucose media resulted in significantly enhanced cell yields (39333 ± 6839 cells/cm2) in comparison to those cultured in low glucose media (13111 ± 1736 cells/cm2). MSCs also displayed large intricate networks of high molecular weight (HMW) HA in the glycocalyx as shown by HABP binding and fluorescence microscopy. In comparison, MSCs grown in low glucose media displayed disperse networks of HA. Additionally, there was a 3‐fold increase observed in levels of HA when MSCs were cultured in high glucose media versus cells grown in low glucose media. MSCs in high glucose also displayed enhanced levels of CD44, one of the receptors of HA. Finally, Hyaluronidase treated cells grown in high glucose media displayed a lack of network formation of high molecular HA in the glycocalyx and a 2‐fold decrease in cell yield.These results suggest that the physiological and chemical environment of MSCs can play an important role in their growth characteristics. The balance between HMW and LMW HA as observed through the presence or absence of intricate networks of HA as a part of the cellular glycocalyx could be a significant factor regulating MSC growth and potency.

NLRP3 Inflammasome Is Critical for Lipopolysaccharide‐Induced Depressive‐Like Behaviors

Cerebral inflammation is considered to contribute to the pathogenesis of depressive disorders, but the molecular target to intervene inflammation‐mediated depressive symptoms is still poorly elucidated. Recent studies intriguingly proposed the implication of NLRP3 inflammasome signaling in the depressive‐like disorders, although the molecular basis by which NLRP3 inflammasome activation contributes to depression is unclear. In this study, we examined lipopolysaccharide (LPS)‐induced depressive‐like behaviors in wild‐type and Nlrp3‐deficient mice. The levels of proinflammatory cytokines in the brain homogenate were not significantly different between wild‐type and Nlrp3‐deficient mice after LPS administration. However, significant reduction of active caspase‐1 was observed in the hippocampus of Nlrp3‐deficient mice brain compared to wild‐type mice. Of interest, LPS administration to mice caused a cerebral induction of Ido mRNA in a NLRP3‐dependent manner. Supporting this data, NLRP3 inflammasome‐activating stimulations, but not interleukin‐1β treatment, triggered a significant induction of IDO in mixed glial cells. Collectively, our findings suggest that IDO is a potential downstream mediator of the NLRP3 inflammasome in the progression of depressive‐like behaviors.Support or Funding InformationThis work was supported by the Bio &amp; Medical Technology Development Program of the NRF funded by the Korean government, (2015M3A9B6073856)

Soluble CD83 Inhibits T Cell Activation by Binding to the TLR4/MD-2 Complex on CD14+ Monocytes.

The transmembrane protein CD83, expressed on APCs, B cells, and T cells, can be expressed as a soluble form generated by alternative splice variants and/or by shedding. Soluble CD83 (sCD83) was shown to be involved in negatively regulating the immune response. sCD83 inhibits T cell proliferation in vitro, supports allograft survival in vivo, prevents corneal transplant rejection, and attenuates the progression and severity of autoimmune diseases and experimental colitis. Although sCD83 binds to human PBMCs, the specific molecules that bind sCD83 have not been identified. In this article, we identify myeloid differentiation factor-2 (MD-2), the coreceptor within the TLR4/MD-2 receptor complex, as the high-affinity sCD83 binding partner. TLR4/MD-2 mediates proinflammatory signal delivery following recognition of bacterial LPSs. However, altering TLR4 signaling can attenuate the proinflammatory cascade, leading to LPS tolerance. Our data show that binding of sCD83 to MD-2 alters this signaling cascade by rapidly degrading IL-1R-associated kinase-1, leading to induction of the anti-inflammatory mediators IDO, IL-10, and PGE2 in a COX-2-dependent manner. sCD83 inhibited T cell proliferation, blocked IL-2 secretion, and rendered T cells unresponsive to further downstream differentiation signals mediated by IL-2. Therefore, we propose the tolerogenic mechanism of action of sCD83 to be dependent on initial interaction with APCs, altering early cytokine signal pathways and leading to T cell unresponsiveness.

Activated STING enhances Tregs infiltration in the HPV-related carcinogenesis of tongue squamous cells via the c-jun/CCL22 signal

The negative role of the activated stimulator of IFN genes (STING) has been uncovered in autoinflammatory disease and cancer. However, the role of STING in virus-related carcinogenesis is not well known. Herein, HPV+ tongue squamous cell carcinoma (TSCC) (n=25) and HPV− TSCC samples (n=25) were randomly collected and were verified by in situ hybridization (ISH) and p16 immunohistochemistry (IHC) to assess the expression and activated status of STING through IHC. The results showed that the expression of STING was up-regulated during the development of TSCC. Interestingly, although the expression of STING showed no difference between HPV+/− TSCC samples, the activated status of STING with dark staining around the nucleus was observed in HPV+ TSCC samples. The role of activated STING was analyzed in three cell lines by siRNA and indicated that activated STING had no impact on cell viability or apoptosis but promoted the induction of several immunosuppressive cytokines, e.g., IL-10, IDO and CCL22, which facilitated the infiltration of regulatory T cells (Tregs). Moreover, increased infiltration of Foxp3+ Tregs along with increased expression of CCL22 was confirmed in HPV+ TSCC samples. An inhibitor of the MAPK/AP-1 pathway (U0126) and the silencing of c-jun significantly suppressed CCL22 induction and the recruitment of Tregs by activated STING. Furthermore, down-regulated miR-27 was verified in independent fresh TSCC samples (n=50) and eight cell lines, which enhanced STING activation and led to increased CCL22 expression for Tregs recruitment in the TSCC microenvironment. Therefore, our findings provided distinct insight into the side effects of activated STING in HPV-related carcinogenesis.

Immunosuppressive Pathways Are Activated by the Immune System

Abstract CD8+ T cells are required for induction of IDO and PD-L1 and recruitment of Treg cells to tumors.

Aryl hydrocarbon receptor signaling regulates NF-κB RelB activation during dendritic-cell differentiation.

How the aryl hydrocarbon receptor (AhR) regulates dendritic-cell (DC) differentiation is unknown. We show that activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) caused enhanced differentiation from immature DCs (IDCs) to mature DCs (MDCs) in the bone-marrow-derived DCs (BMDC) from B6 wild-type mice but not in the BMDCs from AhR-null mice as indicated by the expression of CD11c and class II major histocompatibility complex (MHC). Enhanced maturation of BMDCs was associated with elevated levels of CD86 and an increased AhR-dependent nuclear accumulation of nuclear factor-kappa-light-chain enhancer of activated B cell (NF-κB) member RelB in BMDCs. The expression of interleukin (IL) 10 and chemokine DC-CK1 was suppressed, whereas that of CXCL2, CXCL3 and IL-22 was significantly increased in AhR-activated BMDCs. Furthermore, TCDD induced expression of the regulatory enzymes indoleamine 2,3-dioxygenase (IDO1) and indoleamine 2,3-dioxygenase-like 1 (IDO2). Increased expression of IDO2 was associated with coexpression of the cell-surface marker CCR6. Interestingly, mRNA expression of the chemokine receptor CCR6 was drastically decreased in AhR-null IDCs and MDCs. Overall, these data demonstrate that AhR modifies the maturation of BMDCs associated with the induction of the regulatory enzyme IDO and altered expression of cytokine, chemokines and DC-specific surface markers and receptors.

The α7β0 Isoform of the Complement Regulator C4b-Binding Protein Induces a Semimature, Anti-Inflammatory State in Dendritic Cells

The classical pathway complement regulator C4b-binding protein (C4BP) is composed of two polypeptides (α- and β-chains), which form three plasma oligomers with different subunit compositions (α7β1, α7β0, and α6β1). We show in this article that the C4BP α7β0 isoform (hereafter called C4BP[β(-)] [C4BP lacking the β-chain]), overexpressed under acute-phase conditions, induces a semimature, tolerogenic state on human monocyte-derived dendritic cells (DCs) activated by a proinflammatory stimulus. C4BP isoforms containing β-chain (α7β1 and α6β1; C4BP[β(+)]) neither interfered with the normal maturation of DCs nor competed with C4BP(β(-)) activity on these cells. Immature DCs (iDCs) treated with C4BP(β(-)) retained high endocytic activity, but, upon LPS treatment, they did not upregulate surface expression of CD83, CD80, and CD86. Transcriptional profiling of these semimature DCs revealed that treatment with C4BP(β(-)) prevented the induction of IDO and BIC-1, whereas TGF-β1 expression was maintained to the level of iDCs. C4BP(β(-))-treated DCs were also unable to release proinflammatory Th1 cytokines (IL-12, TNF-α, IFN-γ, IL-6, IL-8) and, conversely, increased IL-10 secretion. They prevented surface CCR7 overexpression and, accordingly, displayed reduced chemotaxis, being morphologically indistinguishable from iDCs. Moreover, C4BP(β(-))-treated DCs failed to enhance allogeneic T cell proliferation, impairing IFN-γ production in these cells and, conversely, promoting CD4(+)CD127(low/neg)CD25(high)Foxp3(+) T cells. Deletion mutant analysis revealed that the complement control protein-6 domain of the α-chain is necessary for the tolerogenic activity of C4BP(β(-)). Our data demonstrate a novel anti-inflammatory and immunomodulatory function of the complement regulator C4BP, suggesting a relevant role of the acute-phase C4BP(β(-)) isoform in a number of pathophysiological conditions and potential applications in autoimmunity and transplantation.

Indoleamine-2,3-dioxygenase activity in experimental human endotoxemia

BackgroundExcessive tryptophan metabolism to kynurenine by the rate-limiting enzyme endothelial indoleamine 2,3-dioxygenase 1 (IDO) controls arterial vessel relaxation and causes hypotension in murine endotoxemia. However, its relevance in human endotoxemia has not been investigated so far. We thus aimed to study changes in blood pressure in parallel with tryptophan and kynurenine levels during experimental endotoxemia in humans.FindingsSix healthy male volunteers were given E. coli lipopolysaccharide (LPS; 4 ng/kg) as a 1-min intravenous infusion. They had levels of soluble E-Selectin and soluble vascular cell adhesion molecule-1 as well as IDO activity assessed as the kynurenine-to-tryptophan plasma ratio by liquid chromatography-tandem mass spectrometry at various time points during a 24 h time course. During endotoxemia, IDO activity significantly increased, reaching peak levels at 8 h after LPS infusion (44.0 ± 15.2 vs. 29.4 ± 6.8 at baseline, P<0.0001). IDO activity correlated inversely with the development of hypotension as shown by random effects linear regression models. Finally, IDO activity exhibited a kinetic profile similar to that of soluble endothelial-specific adhesion molecules.ConclusionsLPS is a triggering factor for the induction of IDO in men. Our findings strongly support the concept that the induction of IDO in the vascular endothelium contributes to hypotension in human sepsis.

A GpC-Rich Oligonucleotide Acts on Plasmacytoid Dendritic Cells To Promote Immune Suppression

Short synthetic oligodeoxynucleotides (ODNs) rich in CpG or GpG motifs have been considered as potential modulators of immunity in clinical settings. In this study, we show that a synthetic GpC-ODN conferred highly suppressive activity on mouse splenic plasmacytoid dendritic cells, demonstrable in vivo in a skin test assay. The underlying mechanism involved signaling by noncanonical NF-κB family members and TGF-β-dependent expression of the immunoregulatory enzyme IDO. Unlike CpG-ODNs, the effects of GpC-ODN required TLR7/TRIF-mediated but not TLR9/MyD88-mediated events, as do sensing of viral ssRNA and the drug imiquimod. Induction of IDO by a GpC-containing ODN could also be demonstrated in human dendritic cells, allowing those cells to assist FOXP3+ T cell generation in vitro. Among potentially therapeutic ODNs, this study identifies GpC-rich sequences as novel activators of TLR7-mediated, IDO-dependent regulatory responses.

Immunotherapy with Costimulatory Dendritic Cells To Control Autoimmune Inflammation

Costimulation-deficient dendritic cells (DCs) prevent autoimmune disease in mouse models. However, autoimmune-prone mice and humans fail to control expansion of peripheral autoreactive effector memory T cells (T(EMs)), which resist immunoregulation by costimulation-deficient DCs. In contrast, activation of DC costimulation may be coupled with regulatory capacity. To test whether costimulatory DCs control T(EMs) and attenuate established autoimmune disease, we used RelB-deficient mice, which have multiorgan inflammation, expanded peripheral autoreactive T(EMs), and dysfunctional Foxp3(+) regulatory T cells (Tregs) cells and conventional DCs. T(EMs) were regulated by Foxp3(+) Tregs when costimulated by CD3/CD28-coated beads or wild-type DCs but not DCs deficient in RelB or CD80/CD86. After transfer, RelB and CD80/CD86-sufficient DCs restored tolerance and achieved a long-term cure of autoimmune disease through costimulation of T(EM) and Foxp3(+) Treg IFN-γ production, as well as induction of IDO by host APCs. IDO was required for regulation of T(EMs) and suppression of organ inflammation. Our data challenge the paradigm that costimulation-deficient DCs are required to regulate established autoimmune disease to avoid T(EM) activation and demonstrate cooperative cross-talk between costimulatory DCs, IFN-γ, and IDO-dependent immune regulation. IFN-γ and IDO activity may be good surrogate biomarkers measured against clinical efficacy in trials of autoimmune disease immunoregulation.

Cutting Edge: Negative Regulation of Dendritic Cells through Acetylation of the Nonhistone Protein STAT-3

Histone deacetylase (HDAC) inhibition modulates dendritic cell (DC) functions and regulates experimental graft-vs-host disease and other immune-mediated diseases. The mechanisms by which HDAC inhibition modulates immune responses remain largely unknown. STAT-3 is a transcription factor shown to negatively regulate DC functions. In this study we report that HDAC inhibition acetylates and activates STAT-3, which regulates DCs by promoting the transcription of IDO. These findings demonstrate a novel functional role for posttranslational modification of STAT-3 through acetylation and provide mechanistic insights into HDAC inhibition-mediated immunoregulation by induction of IDO.

Induction of IDO by Bacille Calmette-Guérin Is Responsible for Development of Murine Depressive-Like Behavior

Chronic inflammation activates the tryptophan-degrading enzyme IDO, which is well known to impair T cell proliferation. We have previously established that bacille Calmette-Guérin (BCG), an attenuated form of Mycobacterium bovis, is associated with persistent activation of IDO in the brain and chronic depressive-like behavior, but a causative role has not been established. In these experiments we used both pharmacologic and genetic approaches to test the hypothesis that IDO activation is responsible for the development of chronic depression that follows BCG infection. BCG induced TNF-alpha, IFN-gamma, and IDO mRNA steady-state transcripts in the brain as well as the enzyme 3-hydroxyanthranilic acid oxygenase (3-HAO) that lies downstream of IDO and generates the neuroactive metabolite, quinolinic acid. Behaviors characteristic of depression were apparent 1 wk after BCG infection. Pretreatment with the competitive IDO inhibitor 1-methyltryptophan fully blocked BCG-induced depressive-like behaviors. Importantly, IDO-deficient mice were completely resistant to BCG-induced depressive-like behavior but responded normally to BCG induction of proinflammatory cytokines. These results are the first to prove that the BCG-induced persistent activation of IDO is accompanied by the induction of 3-hydroxyanthranilic acid oxygenase and that IDO is required as an initial step for the subsequent development of chronic depressive-like behavior.

Activation of the innate immune receptor, TLR3, promotes a pro-implantation phenotype in human endometrial cells in-vitro

OBJECTIVE: In ruminant species, a unique type I interferon (IFN), Interferon-τ, is exclusively secreted by the blastocyst and is required for successful pregnancy. Although there is no pregnancy-specific IFN in humans, endometrial IFN expression may be stimulated by Toll-like receptor 3 (TLR3) ligation. We have previously demonstrated cyclic expression of human endometrial epithelial TLR3, with highest expression during mid- and late secretory phases, suggesting a possible role of TLR3 in embryo implantation. The aim of this study is to determine the effects of TLR3 ligation on expression of implantation-associated genes. DESIGN: Laboratory study. MATERIALS AND METHODS: RL95-2 endometrial epithelial cell line and primary cultures of mid-secretory endometrial epithelial cells were treated in triplicate with 5μg/ml of TLR3 ligand, polyinosinic-polycytidylic acid (PolyI:C), a negative control (PolydI:dC), or carrier for 2, 8, 16, and 24 hours. Relative changes in mRNA expression were measured using Taqman® real time RT-PCR (ddCT method) normalized to constitutive genes GAPDH and PPIA in RL95-2 and primary cells, respectively. PolyI:C effects in RL95-2 cells are completely dependent on TLR3. RESULTS: The table shows the peak change in mRNA expression for each gene studied. Treatment with negative controls, polydI:dC or carrier had no effects. Gene names follow standard HUGO nomenclature with common abbreviations noted. Although LIF and CD55 were not induced in primary cells, baseline expression of each was very high in control cells. Also, IP-10 (CXCL10) induction has been shown previously in response to polyI:C. CONCLUSIONS: TLR3 ligation, known to mediate inflammatory responses to viral products, may also be important in promoting embryo implantation, via induction of IDO, COX-2, RANTES, and IP-10. Further studies are ongoing to investigate the role of TLR3 in embryo implantation. Additionally, this is the first evidence of IFNε expression by human endometrium.Table 1Changes in Gene Expression with TLR3 LigationPeak Increase in Expression (fold change; hours)GeneFunctionRL95-2 CellsPrimary CellsINDO (IDO)Fetal Immunotolerance78x; 8h9x; 8hPTGS2 (COX2)Implantation defect in KO Mice6x; 8h10x; 2hCCL5 (RANTES)Embryo Invasion1900x; 24h86x; 8hLIFEmbryo Attachment50x; 8hNo ChangeCD55 (DAF)Prevents Complement Attack4x; 2hNo ChangeISG15Induced at Implantation Sites23x; 8h7x; 8hIFNB1 (IFNβ)Unknown3700x; 2h120x; 2hIFNE1 (IFNε)UnknownNo ChangeNo Change Open table in a new tab

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