Indoleamine 2,3-dioxygenase (IDO) is essential for dendritic cell activation and chemotactic responsiveness to chemokines

Indoleamine 2, 3-dioxygenase (IDO) is a rate-limiting enzyme for the tryptophan catabolism. In human and murine cells, IDO inhibits antigen-specific T cell proliferation in vitro and suppresses T cell responses to fetal alloantigens during murine pregnancy. In mice, IDO expression is an inducible feature of specific subsets of dendritic cells (DCs), and is important for T cell regulatory properties. However, the effect of IDO and tryptophan deprivation on DC func- tions remains unknown. We report here that when tryptophan utilization was prevented by a pharmacological inhibitor of IDO, 1-methyl tryptophan (1MT), DC activation induced by pathogenic stimulus lipopolysaccharide (LPS) or inflam- matory cytokine TNF-α was inhibited both phenotypically and functionally. Such an effect was less remarkable when DC was stimulated by a physiological stimulus, CD40 ligand. Tryptophan deprivation during DC activation also regu- lated the expression of CCR5 and CXCR4, as well as DC responsiveness to chemokines. These results suggest that tryptophan usage in the microenvironment is essential for DC maturation, and may also play a role in the regulation of DC migratory behaviors.

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

Tumor cells induce an immunosuppressive microen-vironment 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 immuno-suppression 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.

Inhibition of allogeneic T-cell response by Kupffer cells expressing indoleamine 2,3-dioxygenase

AIM:To explore the possibility and mechanism of inhibiting allogeneic T-cell responses by Kupffer cells (KC)pretreated with interferon-γ(IFN-γ)in vitro. METHODS:The expressions of indoleamine 2,3-dioxygenase(IDO)mRNA and FasL mRNA in KC pretreated with IFN-γwere studied with real-time polymerase chain reaction(PCR).The catabolism of tryptophan by IDO from KC was analyzed by high performance liquid chromatography.Allogeneic T-cell response was used to confirm the inhibition of KC in vitro.The proliferation of lymphocytes was detected using[ 3 H]thymidine incorporation.Cell cycle and lymphocyte apoptosis were evaluated by flow cytometric assay. RESULTS:Real-time PCR revealed IDO mRNA and FasL mRNA expressions in KC pretreated with IFN-γ,and IDO catabolic effect was confirmed by a decrease in tryptophan and increase in kynurenine concentration. KC expressing IDO and FasL in BABL/c mice acquired the ability to suppress the proliferation of T-cells from C57BL/6,which could be blocked by addition of 1-methyl-tryptophan and anti-FasL antibody.KC expressing IDO could induce allogeneic T-cell apoptosisCONCLUSION:In addition to Fas/FasL pathway,IDO may be another mechanism for KC to induce immune tolerance.

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 IDOdependent 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.

Expression of indoleamine 2,3-dioxygenase in a murine model of Aspergillus fumigatus keratitis

AIM： To observe the presence and expression of indoleamine 2,3-dioxygenase（IDO） during the corneal immunity to Aspergillus fumigatus（A. fumigatus） in the murine models.·METHODS： The murine model of fungal keratitis was established by smearing with colonies of A. fumigatus after scraping central epithelium of cornea and covering with contact lenses in C57BL/6 mice. The mice were randomly divided into control group, sham group and A.fumigatus keratitis group. The cornea was monitored daily using a slit lamp and recorded disease score after infection. Corneal lesion was detected by immunofluorescence staining. IDO m RNA and protein were also detected by quantitative reverse transcription-polymerase chain reaction（q RT-PCR） and Western blot.· RESULTS： The disease score and slit lamp photography indicated that disease severity was consistent with corneal inflammation in the murine models, and the disease scores in A. fumigatus keratitis group were obviously higher than those in the sham group. By immunofluorescence staining, IDO was mainly localized in corneal epithelium and stroma in the murine corneal tissues with A. fumigatus keratitis. Compared with the sham group, IDO m RNA expression was significantly enhanced in corneal epithelium infected by A. fumigatus. Furthermore, IDO protein expression detected by Western blot was in accord with transcript levels of IDO m RNA measured by q RT-PCR. IDO protein expression was enhanced after A. fumigatus infection compared with the sham group.·CONCLUSION： IDO is detected in corneal epithelium and stroma locally, which indicates IDO takes part in the pathogenesis of A. fumigatus keratitis and plays a key role in immune regulation at the early stage.

Indoleamine 2,3-dioxygenase adjusts neutrophils recruitment and chemotaxis in Aspergillus fumigatus keratitis

AIM: To explore the effect of indoleamine 2,3-dioxygenase(IDO) on recruitment and chemotaxis function of neutrophils in Aspergillus fumigatus(A.fumigatus) keratitis.METHODS: C57BL/6 mice models of A.fumigatus keratitis were established by inoculating hyphae of A.fumigatus evenly on the corneas.The clinical scores and inflammatory cytokines expression were measured respectively on the 1^(st), 3^(th), 5^(th) day after infection.The 1-MT(1 mg/m L) was administered by gavage to exert an inhibitory effect on IDO during infection.The mice were divided into control group, 1-MT group, A.fumigatus(A.F.) group, and 1-MT+A.F.groups.The corneas were monitored by slit lamp microscopy, and recorded disease scores in 3 d after infection.Myeloperoxidase(MPO) assay was done to evaluate the neutrophils infiltration.Immunofluorescence staining was used to detect the recruitment of neutrophils in murine corneas.The m RNA of inflammatory cytokines was measured with reverse transcription-polymerase chain reaction(RT-PCR).RESULTS: The corneal inflammation and the clinical score reached the peak on the 3;day after the corneal infection.The m RNA of inflammatory cytokines of the A.F.group reached the highest on the 3;day after the infection accordingly.Meanwhile, the results of slit light photography indicated that inhibitors of IDO made inflammation more serious contrasted with the A.F.group on the 3;day.Besides, imunofluorescence staining and MPO indicated that 1-MT enhanced the recruitment, infiltration and chemotaxis of neutrophils obviously in contrast to the A.F.group.RT-PCR indicated that 1-MT increased the expression of CXCL-1, ICAM-1, IL-1β, and IL-8 significantly.CONCLUSION: IDO participates in the pathogenesis of A.fumigatus keratitis and plays an important role in inducing immune protection by inhibiting neutrophils-related inflammatory reaction and suppressing recruitment and chemotaxis of the neutrophils.

Mesenchymal-epithelial Transition Factor Regulates Monocyte Function during Mycobacterial Infection via Indoleamine 2,3-dioxygenase

Objective Mycobacterium tuberculosis(Mtb),the causative agent of tuberculosis(TB),causes an estimated 1.6 million human deaths annually,but the pathogenesis of TB remains unclear.Immunity plays a critical role in the onset and outcome of TB.This study aimed to uncover the roles of innate and adaptive immunity in TB.Methods The gene expression profiles generated by RNA sequencing from human peripheral blood mononuclear cells(PBMCs)stimulated with or without Mtb strain H37Rv antigens were analyzed.A total of 973 differentially expressed mRNAs were identified.Results The differentially expressed genes were enriched in innate immunity signaling functions.The mesenchymal-epithelial transition factor(MET)gene was significantly upregulated in CD14^(+)monocytes.A MET inhibitor improved the uptake of the BCG strain by monocytes and macrophages as well as inhibited the expression of indoleamine 2,3-dioxygenase(IDO).The expression of IDO was increased in PBMCs stimulated with Mtb antigens,and the IDO inhibitor promoted the expression of CD40,CD83,and CD86.Conclusion Our results might provide clues regarding the immunomodulatory mechanisms used by Mtb to evade the host defense system.

Myricetin inhibits interferon-γ-induced programmed death ligand-1 and indoleamine 2,3-dioxygenase 1 expression in lung cancer cells

OBJECTIVE Programmed death ligand-1(PD-L1)and indoleamine 2,3-dioxygenase 1(IDO1)are immune checkpoints which can be induced by interferon-γ(IFN-γ)in the tumor microenvironment,leading to immune escape of tumors.Myricetin(MY)is a flavonoid distributed in many edible and medicinal plants.The aim of this study is to clarify the effect and the mechanism of MY on inhibiting IFN-γ-induced PD-L1 and IDO1 in lung cancer cells.METHODS Expressions of PD-L1 and major histocompatibility complex-I(MHC-I)were evaluated by flow cytometry and Western blotting,and the expression of IDO1 was measured by Western blotting.qRT-PCR was used to detect their mRNA levels.The function of T cells was evaluated using a co-culture system consist of lung cancer cells and the Jurkat-PD-1 T cell line that overexpressing PD-1.Molecular docking analysis,Western blotting and immunofluorescence were used for mechanism study.RESULTS MY potently inhibited IFN-γ-induced PD-L1 and IDO1 expression in human lung cancer cells,while didn't show obvious effect on the expression of MHC-I.In addition,MY restored the survival,proliferation,CD69 expression and interleukin-2(IL-2)secretion of Jurkat-PD-1 T cells suppressed by IFN-γ-treated lung cancer cells in the co-culture system.Mechanistically,IFN-γup-regulated PD-L1 and IDO1 at the transcriptional level through the JAK-STAT-IRF1 axis,which was targeted and inhibited by MY.CONCLUSION Our research revealed a new insight into the anti-tumor effects of MY which inhibited IFN-γ-induced PD-L1 and IDO1 expression,supporting the potential of MY in anti-tumor immunotherapy.

Molecular Cloning and Characterization of Porcine Indoleamine 2,3-Dioxygenase and Its Expression in Various Tissues

In order to confirm the existence of indoleamine 2,3-dioxygenase(IDO) gene in swine,and to clone the novel gene followed by the molecule structure properties and expression pattern analysis,the porcine mRNA sequences homologous to human IDO were obtained from GenBank database by bioinformatics method.By using RT-PCR,the IDO gene was cloned from porcine endothelial cell line and the accuracy of the nucleic acid sequence was confirmed,and the expression pattern of the gene was detected.The three-dimensional structure model of porcine IDO was built referring to the tertiary structure of human IDO using biological sequence analysis software and database.The results showed that the porcine IDO was identified by sequencing.The nucleotide sequences were confirmed as a novel gene after submitted to Genbank.Porcine IDO was expressed in the lung,thymus,epididymis and anterior chamber with a basic level,however in peripheral blood mononuclear cells(PBMCs) the IDO gene was highly expressed.The three-dimensional structure model of porcine IDO was similar to that of human IDO.It was suggested that identification of the structure information of porcine IDO is essential to further investigate the immunologic function of the gene.Study of IDO on NK cells-mediated xenograft rejection will be a novel therapeutic target for the development of xenotransplantation.

Relationship of Abortion and the Expression of Indoleamine 2,3- dioxygenase (IDO) in Villus and Syncytiotrophoblasts

Objective To study the relationship of abortion and the expression of indoleamine 2, 3- dioxygenase （IDO） in villus and syncytiotrophoblast in vitro. Methods RT-PCR was applied to analyze the mRNA transcription of lDO in villus of normal pregnancy and inevitable abortion and JAR cells as well. Immunohistochemistry was applied to analyze the expression of IDO protein in villus. Western blot was applied to determinate the expression of IDO protein on cultured syncytiotrophoblast. Highperformance liquid chromatography was applied to determinate whether there was kynurenine in cell culture medium of syncytiotrophoblast. Results The expression of IDO mRNA and protein in villus of inevitable abortion was lower than that of normal pregnancy; IDO mRNA did not express in JAR cells. IDO protein expressed on cultured syncytiotrophoblast, and there was kynurenine in cell culture medium of syncytiotrophoblast. Conclusion Appropriate expression of IDO in villus is necessary.for maintenance of normal pregnancy and an active IDO protein expresses in syncytiotrophoblast.

Forkhead box P3 and indoleamine 2,3-dioxygenase co-expression in Pakistani triple negative breast cancer patients

BACKGROUND Forkhead box P3(FOXP3)is a specific marker for immunosuppressive regulatory T(T-reg)cells.T-regs and an immunosuppressive enzyme,indoleamine 2,3-dioxygenase(IDO),are associated with advanced disease in cancer.AIM To evaluate the co-expression of FOXP3 and IDO in triple negative breast cancer(TNBC)with respect to hormone-positive breast cancer patients from Pakistan.METHODS Immunohistochemistry was performed to analyze the expression of FOXP3,IDO,estrogen receptor,progesterone receptor,and human epidermal growth factor receptor on tissues of breast cancer patients(n=100):Hormone-positive breast cancer(n=51)and TNBC(n=49).A total of 100 patients were characterized as FOXP3 negative vs positive and further categorized based on low,medium,and high IDO expression score.Univariate and multivariate logistic regression models were used.RESULTS Out of 100 breast tumors,25%expressed FOXP3 positive T-regs.A significant coexpression of FOXP3 and IDO was observed among patients with TNBC(P=0.01)compared to those with hormone-positive breast cancer.Two variables were identified as significant independent risk factors for FOXP3 positive:IDO expression high(adjusted odds ratio(AOR)5.90;95%confidence interval(CI):1.22-28.64;P=0.03)and TNBC(AOR 2.80;95%CI:0.96-7.95;P=0.05).CONCLUSION Our data showed that FOXP3 positive cells might be associated with high expression of IDO in TNBC patients.FOXP3 and IDO co-expression may also suggest its involvement in disease,and evaluation of FOXP3 and IDO expression in TNBC patients may offer a new therapeutic option.

T-cell proliferation is inhibited by the induction of indoleamine 2,3-dioxygenase in spleen-derived dendritic cells in rat

Background Increasing evidence suggests that, by the production of indoleamine 2, 3-dioxygenase （IDO）, dendritic cells （DC） may reduce the activity of T lymphocytes and inhibit T lymphocyte proliferation-induced immune tolerance.One promising way is inspired by increasing IDO expression in DG cells for immune tolerance after transplantation. The aim of this work was to examine the effect of interferon-y （IFN-γ） on the expression of IDO by DC.Methods Spleen-derived rat DCs were cultured and induced by cytokines, and the expression of OX62 and surface molecules CD80 and CD86 were measured with flow cytometry. After the DCs were induced by IFN-γ at different concentrations （0, 100, 300, 500 U/ml）, the expression levels of IDO mRNA were measured with real-time PCR, and the expression levels of IDO protein in DCs were measured with Western blotting. The allogeneic mixed lymphocyte reaction （MLR） was used to test the effects of DCs incubated with different concentrations of IFN-γ on allogeneic T lymphocyte proliferation.Results Under the microscope, the DCs induced by IFN-γ showed a typical dendritic morphology. The expression rate of OX62 was above 80% and the positive expression rates of CD80 and CD86 were both about 80%. The expressions of IDO mRNA and IDO protein increased gradually with the increase of IFN-γ concentration, showing statistical significance in the differences between the groups （P 〈0.05）. Compared with the control DC, the DC incubated with IFN-γ had a notable decrease in allostimulatory activity （P 〈0.05）. With the increasing IFN-γ concentration, the T lymphocyte proliferation decreased, and the difference between the groups was also statistically significant （P 〈0.05）.Conclusions The highly purified spleen derived rat DCs can be successfully acquired through the improved adhesion in-vitro method. IFN-γ can induce increased expression of IDO in spleen-derived rat DCs and reduce the spleen DCs＇ capacity to stimulate the proliferation of allogeneic T cells.

Indoleamine 2,3-dioxygenase in tumor induced tolerance

Objective To review the recent studies about the role of indoleamine 2,3-dioxygenase （IDO） in tumor induced tolerance. Data sources Published articles （1978-2009） on IDO and tumor induced tolerance were selected from Medline. Study selection Articles selected were relevant to development of IDO in tumor induced tolerance. Of all originally identified articles, 50 specially addressed the stated purpose. Results Recent work has revealed IDO at high levels in tumors and in tumor-draining lymph nodes and a close relationship between IDO activity and the regulatory T cells. Conclusion Up-regulation of IDO is proven to be a mechanism of acquired tolerance in tumors, in which the closely coupled positive feedback system between IDO and reclulatorv T cells may be considered to play an important role.

Expression and Prognostic Value of Indoleamine 2,3-dioxygenase in Pancreatic Cancer

Background： Indoleamine 2,3-dioxygenase （IDO）, an enzyme for tryptophan metabolism through the kynurenine pathway, exhibits an immunosuppressive effect and induces immune tolerance in tumor cells. The effects of IDO on pancreatic cancer are poorly understood. This study aimed to investigate the expression and prognostic significance of IDO in pancreatic cancer. Methods： We evaluated the protein expression of IDO in PANC-1, CFPAC-I, and BxPC-3 cell lines with or without 48 11 treatment by 500 U/ml interferon-,/（IFN-y）. We performed immunollistochemical staining and Western blot analysis lbr IDO expression in both pancreatic cancer and normal pancreas tissues obtained from Chinese PLA General Hospital from July 2012 to December 2013. Survival analysis was performed to correlate IDO expression and histopathologic parameters with overall survival. The Kaplan-Meier method and Cox proportional hazards regression model were conducted. Results＂ PANC-I, CFPAC-I, and BxPC-3 cell lines expressed IDO at the protein level, and the relative expression amount increased after stimulation with 500 U/ml IFN-y. Immunohistochemical analysis results revealed that high IDO expression was observed in 59% of pancreatic adenocarcinoma tissues. Compared with normal pancreatic tissues, pancreatic adenocarcinoma showed significantly higher IDO expression levels, especially among patients with high tumor node metastasis （TNM） stages （X2= 4.550, P = 0.030）, poor histological differentiation （X2=5.690, P = 0.017）, and lymph node metastasis （X2=4.340 P = 0.037）. Kaplan-Meier survival curves showed that high 1DO expression was correlated with low survival rates （hazard ratio [HR] = 0.49 P = 0.009）. Multivariate analysis using Cox proportional hazards model indicated that lymph node metastasis （HR = 0.35 P= 0.010） and IDO expression （HR = 0.42 P = 0.020） were two independent prognostic predictors of pancreatic adenocarcinoma. Conclusions： The study confirmed that high IDO expression in pancreatic adenocarcinoma was related to poor prognosis of patients. These findings provided evidence that IDO was involved in pancreatic adenocarcinoma progression and might serve as a relevant therapeutic target.

AncPhore: A versatile tool for anchor pharmacophore steered drug discovery with applications in discovery of new inhibitors targeting metallo-β-lactamases and indoleamine/tryptophan 2,3-dioxygenases

We herein describe AncPhore,a versatile tool for drug discovery,which is characterized by pharmacophore feature analysis and anchor pharmacophore(i.e.,most important pharmacophore features)steered molecular fitting and virtual screening.Comparative analyses of numerous protein-ligand complexes using AncPhore revealed that anchor pharmacophore features are biologically important,commonly associated with protein conservative characteristics,and have significant contributions to the binding affinity.Performance evaluation of AncPhore showed that it had substantially improved prediction ability on different types of target proteins including metalloenzymes by considering the specific contributions and diversity of anchor pharmacophore features.To demonstrate the practicability of AncPhore,we screened commercially available chemical compounds and discovered a set of structurally diverse inhibitors for clinically relevant metallo-β-lactamases(MBLs);of them,4 and 6 manifested potent inhibitory activity to VIM-2,NDM-1 and IMP-1 MBLs.Crystallographic analyses of VIM-2:4 complex revealed the precise inhibition mode of 4 with VIM-2,highly consistent with the defined anchor pharmacophore features.Besides,we also identified new hit compounds by using AncPhore for indoleamine/tryptophan 2,3-dioxygenases(IDO/TDO),another class of clinically relevant metalloenzymes.This work reveals anchor pharmacophore as a valuable concept for target-centered drug discovery and illustrates the potential of AncPhore to efficiently identify new inhibitors for different types of protein targets.

Up-regulation of indoleamine 2,3-dioxygenase 1(IDO1)expression and catalytic activity is associated with immunosuppression and poor prognosis in penile squamous cell carcinoma patients

Background: Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan (Trp)catabolism have been demonstrated to play an important role in tumor immunosuppression. This study examined the expression and catalytic activity of IDO1 in penilesquamous cell carcinoma (PSCC) and explored their clinical significance.Methods: IDO1 expression level, serum concentrations of Trp and kynurenine (Kyn)were examined in 114 PSCC patients by immunohistonchemistry and solid-phaseextraction-liquid chromatography-tandem mass spectrometry. The survival was analyzed using Kaplan-Meier method and the log-rank test. Hazard ratio of death was analyzed via univariate and multivariate Cox regression. Immune cell types were definedby principal component analysis. The correlativity was assessed by Pearson’s correlation analysis.Results: The expression level of IDO1 in PSCC cells was positively correlatedwith serum Kyn concentration and Kyn/Trp radio (KTR;both P < 0.001) but negatively correlated with serum Trp concentration (P = 0.001). Additionally, IDO1 upregulation in cancer cells and the increase of serum KTR were significantly associated with advanced N stage (both P < 0.001) and high pathologic grade (P = 0.008and 0.032, respectively). High expression level of IDO1 in cancer cells and serumKTR were associated with short disease-specific survival (both P < 0.001). However, besides N stage (hazard radio [HR], 6.926;95% confidence interval [CI],2.458-19.068;P < 0.001) and pathologic grade (HR, 2.194;95% CI, 1.021-4.529;P = 0.038), only serum KTR (HR, 2.780;95% CI, 1.066-7.215;P = 0.036) was anindependent predictor for PSCC prognosis. IDO1 expression was positively correlated with the expression of interferon-𝛾 (IFN𝛾, P < 0.001) and immunosuppressivemarkers (programmed cell death protein 1, cytotoxic T-lymphocyte-associated protein 4 and programmed death-ligand 1 and 2;all P < 0.05), and the infiltration ofimmune cells (including cytotoxic T lymphocytes, regulatory T lymphocytes, tumorassociated macrophages, and myeloid-derived suppressor cells;all P < 0.001) inPSCC tissues. Furthermore, the expression of IDO1 was induced by IFN𝛾 in a dosedependent manner in PSCC cells.Conclusions: IFN𝛾-induced IDO1 plays a crucial role in immunoediting andimmunosuppression in PSCC. Additionally, serum KTR, an indicator of IDO1catabolic activity, can be utilized as an independent prognostic factor for PSCC.

Indoleamine 2,3-dioxygenase and regulatory dendritic cells contribute to the allograft protection induced by infusion of donor-specific splenic stromal cells

It has been reported that splenic stromal cells(SSCs)are capable of directly supporting the development of CD11c ^(lo)CD45RB^(+) IL-10-producing dendritic cells(DCs)from lineage-negative c-kit^(+) progenitor cells in the absence of exogenous cytokines.In vitro,DCs that differentiate on stromal cells suppress mixed leukocyte reaction responses and induce primary alloreactive CD4^(+) T cells to differentiate into IL-10-producing Tr1 cells.However,the precise mechanisms by which these SSCs exert their regulatory functions in vivo remain undefined.Furthermore,their possible contribution to the development of allograft transplantation tolerance has yet to be examined.Here,we have used both murine skin and cardiac allograft transplantation models to explore whether in vivo alloresponses can be regulated by infusion with donor-derived SSCs and to investigate the possible mechanisms by which SSCs exert regulatory effects to prevent allograft rejection.We show that intravenous SSC infusion prolonged murine skin allograft survival.The prolonged graft survival is associated with augmentation of the generation of regulatory DC subsets and CD4^(+) CD25^(+) Foxp3^(+) regulatory T cells(Tregs),as well as upregulation of the production of suppressive cytokines IL-10 and transforming growth factor(TGF)-b.Moreover,we found that indoleamine 2,3-dioxygenase and SSC-derived regulatory DCs contribute to allograft protection by infusion of donor-specific SSCs.Our data suggest that donor-derived SSCs could be used as a therapeutic target to promote transplantation tolerance.

Indoleamine 2,3-Dioxygenase in Endometriosis

Endometriosis(EMS)is a chronic inflammatory and estrogen-dependent gynecological disease characterized by the presence of endometrial tissue outside the uterine cavity.Although it is a benign disease,EMS is tumor-like in several aspects,which include unrestrained growth,decreased apoptosis,and aggressive invasion.EMS involves endocrine disorders and immunological factors.Indoleamine 2,3-dioxygenase(IDO)is an intracellular enzyme that catalyzes the initial and rate-limiting step of the metabolism of tryptophan.IDO is a potential candidate facilitating EMS development.Increased IDO expression in both eutopic and ectopic endometria of women with EMS is biologically important in aspects,which include regulation of endometrial stromal cell function and modulation of adjacent local immunocytes to generate a supportive microenvironment.In turn,the expression of IDO can be regulated by the complex endocrine-immune microenvironment networks in endometrial lesions.Here,we systematically review the roles of IDO in EMS to explore its pathological implications and treatment potential.

Kynurenine pathway of tryptophan metabolism in pathophysiology and therapy of major depressive disorder

Serotonin deficiency in major depressive disorder(MDD)has formed the basis of antidepressant drug development and was originally attributed to induction of the major tryptophan(Trp)-degrading enzyme,liver Trp 2,3-dioxygenase(TDO),by cortisol,leading to decreased Trp availability to the brain for serotonin synthesis.Subsequently,the serotonin deficiency was proposed to involve induction of the extrahepatic Trp-degrading enzyme indoleamine 2,3-dioxygenase(IDO)by proinflammatory cytokines,with inflammation being the underlying cause.Recent evidence,however,challenges this latter concept,as not all MDD patients are immune-activated and,when present,inflammation is mild and/or transient.A wide range of antidepressant drugs inhibit the activity of liver TDO and bind specifically to the enzyme,but not to IDO.IDO induction is not a major event in MDD,but,when it occurs,its metabolic consequences may be masked and overridden by upregulation of kynurenine monooxygenase(KMO),the gateway to production of modulators of immune and neuronal functions.KMO appears to be activated in MDD by certain proinflammatory cytokines and antidepressants with anti-inflammatory properties may block this activation.We demonstrate the ability of the antidepressant ketamine to dock(bind)to KMO.The pathophysiology of MDD may be underpinned by both the serotonin deficiency and glutamatergic activation mediated respectively by TDO induction and N-methyl-D-aspartate receptor activation.Inhibition of TDO and KMO should be the focus of MDD pharmacotherapy.

Immunotherapy and immunoescape in colorectal cancer

Immunotherapy encompasses a variety of interventions and techniques with the common goal of eliciting tumor cell destructive immune responses. Colorectal carcinoma often presents as metastatic disease that impedes curative surgery. Novel strategies such as active immunization with dendritic cells (DCs), gene transfer of cytokines into tumor cells or administration of immunostimulatory monoclonal antibodies (such as anti-CD137 or anti-CTLA-4) have been assessed in preclinical studies and are at an early clinical development stage. Importantly, there is accumulating evidence that chemotherapy and immunotherapy can be combined in the treatment of some cases with colorectal cancer, with synergistic potentiation as a result of antigens cross-presented by dendritic cells and/or elimination of competitor or suppressive T lymphocyte populations (regulatory T-cells). However, genetic and epigenetic unstable carcinoma cells frequently evolve mechanisms of immunoevasion that are the result of either loss of antigen presentation, or an active expression of immunosuppressive substances. Some of these actively immunosuppressive mechanisms are inducible by cytokines that signify the arrival of an effector immune response. For example, induction of 2, 3 indoleamine dioxygenase (IDO) by IFNγ in colorectal carcinoma cells. Combinational and balanced strategies fostering antigen presentation, T-cell costimulation and interference with immune regulatory mechanisms will probably take the stage in translational research in the treatment of colorectal carcinoma.