Indoleamine 2,3-dioxygenase-1, a Novel Therapeutic Target for Post-Vascular Injury Thrombosis in CKD.

BACKGROUND: CKD, characterized by retained uremic solutes, is a strong and independent risk factor for thrombosis after vascular procedures . Urem ic solutes such as indoxyl sulfate (IS) and kynurenine (Kyn) mediate prothrombotic effect through tissue factor (TF). IS and Kyn biogenesis depends on multiple enzymes, with therapeutic implications unexplored. We examined the role of indoleamine 2,3-dioxygenase-1 (IDO-1), a rate-limiting enzyme of kynurenine biogenesis, in CKD-associated thrombosis after vascular injury. METHODS: IDO-1 expression in mice and human vessels was examined. IDO-1-/- mice, IDO-1 inhibitors, an adenine-induced CKD, and carotid artery injury models were used. RESULTS: Both global IDO-1-/- CKD mice and IDO-1 inhibitor in wild-type CKD mice showed reduced blood Kyn levels, TF expression in their arteries, and thrombogenicity compared with respective controls. Several advanced IDO-1 inhibitors downregulated TF expression in primary human aortic vascular smooth muscle cells specifically in response to uremic serum. Further mechanistic probing of arteries from an IS-specific mouse model, and CKD mice, showed upregulation of IDO-1 protein, which was due to inhibition of its polyubiquitination and degradation by IS in vascular smooth muscle cells. In two cohorts of patients with advanced CKD, blood IDO-1 activity was significantly higher in sera of study participants who subsequently developed thrombosis after endovascular interventions or vascular surgery. CONCLUSION: Leveraging genetic and pharmacologic manipulation in experimental models and data from human studies implicate IS as an inducer of IDO-1 and a perpetuator of the thrombotic milieu and supports IDO-1 as an antithrombotic target in CKD.

Indoleamine 2,3 dioxygenase (IDO) level as a marker for significant coronary artery disease.

BACKGROUND: Indoleamine 2,3 dioxygenase (IDO), the rate-limiting enzyme in the kynurenine (Kyn) pathway of tryptophan (Trp) degradation, is modulated by inflammation, and is regarded as a key molecule driving immunotolerance and immunosuppressive mechanisms. Little is known about IDO activity in patients with active coronary artery disease (CAD). METHODS: We prospectively enrolled patients who were scheduled to undergo coronary angiography. Measurement of IDO, high-sensitivity troponin T (hs-TnT), and high-sensitivity C-reactive protein (hs-CRP) levels was performed at baseline, and IDO activity was monitored at the 6-month follow-up. RESULTS: Three hundred and five patients were enrolled. Ninety-eight patients (32.1%) presented with recent acute coronary syndrome (ACS). Significant difference in IDO, kynurenine, and hs-TnT between patients with and without significant CAD was observed. Baseline IDO activity, kynurenine level, and hs-TnT level were all significantly higher in significant CAD patients with 3-vessel, 2-vessel, and 1-vessel involvement than in those with insignificant CAD [(0.17, 0.13, and 0.16 vs. 0.03, respectively; p = 0.003), (5.89, 4.58, and 5.24 vs. 2.74 µM/g, respectively; p = 0.011), and (18.27, 12.22, and 12.86 vs. 10.89 mg/dL, respectively; p < 0.001)]. One-year mortality was 3.9%. When we compared between patients who survived and patients who died, we found a significantly lower prevalence of left main (LM) disease by coronary angiogram (6.1% vs. 33.3%, p = 0.007), and also a trend toward higher baseline kynurenine (5.07 vs. 0.79 µM/g, p = 0.082) and higher IDO (0.15 vs. 0.02, p = 0.081) in patients who survived. CONCLUSION: Immunometabolic response mediated via IDO function was enhanced in patients with CAD, and correlated with the extent and severity of disease. Patients with LM disease had higher 1-year mortality. Lower level of IDO, as suggested by inadequate IDO response, demonstrated a trend toward predicting 1-year mortality. Trial registration TCTR Trial registration number TCTR20200626001. Date of registration 26 June 2020. "Retrospectively registered".

Alterations of serum levels of plasminogen, TNF-α, and IDO in granulomatosis with polyangiitis patients.

BACKGROUND: Granulomatosis with polyangiitis (GPA) is a representative of vasculitides associated with anti-neutrophil cytoplasmic autoantibodies. "Classical" antibodies directed against proteinase 3 are involved in the pathogenesis and are part of the GPA diagnosis at the same time. Along with them, however, antibodies against Lysosomal-Associated Membrane Protein-2 (LAMP-2) and antibodies directed against plasminogen have been described in GPA.Objectives and methodology: We performed a cross-sectional study enrolling 34 patients diagnosed with GPA. Our study was aimed at looking for correlations between serum levels of LAMP-2 and plasminogen and the clinical manifestations of the GPA. Furthermore, we examined serum levels of tumor necrosis factor-alpha (TNF-α) and its associated indoleamine-pyrrole 2,3-dioxygenase (IDO), as well as we looked for a correlation between these cytokines and the clinical manifestations of GPA. RESULTS: The results showed that in GPA, serum plasminogen levels were negatively associated with renal involvement (receiver operating characteristic (ROC) area under the curve (AUC) of 0.78) (95% CI 0.53-0.91), p = 0.035, and the extent of proteinuria, Spearman's Rho = -0.4, p = 0.015. Increased levels of TNF-α and IDO correlated with disease activity, Spearman's Rho =0.62, p = 0.001 and Spearman's Rho = 0.4, p = 0.022, respectively, whereas only TNF-α was increased in severe forms of GPA with lung involvement (ROC AUC of 0.8) (95% CI 0.66-0.94), p = 0.005. CONCLUSIONS: In this study, we demonstrate the alteration of soluble factors, which play an important role in the pathogenesis of GPA and their relationship with the clinical manifestations of the disease. Our main results confirm the associations of increased secretory TNF-α and some clinical manifestations, and we describe for the first time decreased serum plasminogen levels and their association with renal involvement.

Prognostic value of indoleamine 2,3 dioxygenase in patients with higher-risk myelodysplastic syndromes treated with azacytidine.

Hypomethylating agents (HMAs) are widely used in patients with higher-risk myelodysplastic syndromes (MDS) not eligible for stem cell transplantation; however, the response rate is <50%. Reliable predictors of response are still missing, and it is a major challenge to develop new treatment strategies. One current approach is the combination of azacytidine (AZA) with checkpoint inhibitors; however, the potential benefit of targeting the immunomodulator indoleamine-2,3-dioxygenase (IDO-1) has not yet been evaluated. We observed moderate to strong IDO-1 expression in 37% of patients with high-risk MDS. IDO-1 positivity was predictive of treatment failure and shorter overall survival. Moreover, IDO-1 positivity correlated inversely with the number of infiltrating CD8+ T cells, and IDO-1+ patients failed to show an increase in CD8+ T cells under AZA treatment. In vitro experiments confirmed tryptophan catabolism and depletion of CD8+ T cells in IDO-1+ MDS, suggesting that IDO-1 expression induces an immunosuppressive microenvironment in MDS, thereby leading to treatment failure under AZA treatment. In conclusion, IDO-1 is expressed in more than one-third of patients with higher-risk MDS, and is predictive of treatment failure and shorter overall survival. Therefore, IDO-1 is emerging as a promising predictor and therapeutic target, especially for combination therapies with HMAs or checkpoint inhibitors.

1-Methyl-D-tryptophan activates aryl hydrocarbon receptor, a pathway associated with bladder cancer progression.

BACKGROUND: Indoleamine 2, 3-dioxygenase-1 (IDO1) is a promising target for immunotherapy in bladder cancer (BC). IDO1 breaks-down tryptophan to generate kynurenine derivatives, which may activate the aryl hydrocarbon receptor (AHR). AHR is an important target for carcinogens, but its association with BC progression was unknown. Two IDO1 inhibitors used in clinical trials are 1-methyl-D-tryptophan (MT) and INCB240360. Because MT is an aromatic hydrocarbon, it may be a ligand for AHR. We hypothesized that AHR could be associated with BC progression and that MT could activate AHR in BC. METHODS: BC patients (n = 165) were selected from the Gene Expression Omnibus database. A cut-off point for relative expression of AHR and cytochrome 450 enzymes (CYP1A1, CYP1A2, and CYP1B1; markers of AHR activation) was determined to compare with the grade, stage, and tumor progression. For in vitro experiments, RT4 (grade 1) and T24 (grade 3) BC cells were incubated with MT and INCB240360 to evaluate the expression of AHR and CYP1A1. RESULTS: AHR activation was associated with grade, stage, and progression of BC. T24 cells express more CYP1A1 than RT4 cells. Although IDO1 expression and kynurenine production are elevated in T24 cells concomitantly to CYP1A1 expression, IDO1 inhibitors were not able to decrease CYP1A1 expression, in contrast, MT significantly increased it in both cell lines. CONCLUSION: In conclusion, it is rational to inhibit IDO1 in BC, among other factors because it contributes to AHR activation. However, MT needs to be carefully evaluated for BC because it is an AHR pathway agonist independently of its effects on IDO1.

Plasma Indoleamine 2,3-Dioxygenase Activity Is Associated With the Size of the Human Immunodeficiency Virus Reservoir in Patients Receiving Antiretroviral Therapy.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) is an immunoregulatory enzyme that metabolizes tryptophan to immunosuppressive kynurenines. We investigated whether IDO activity is associated with the size of HIV reservoir. METHODS: Total human immunodeficiency virus (HIV) DNA in peripheral blood mononuclear cells (PBMCs) from 127 HIV-infected patients receiving antiretroviral therapy (ART) was quantified. Tryptophan and kynurenine concentrations, as well as microbial translocation markers, were measured in plasma samples. T-cell activation and exhaustion in PBMCs were assessed by flow cytometry. RESULTS: Elevated IDO activity prior to ART correlated with on-ART HIV DNA (r = 0.35, P = .004), but was not associated with pre-ART HIV DNA. A median duration of 15 months of ART significantly decreased IDO activity; however, these levels were still higher than those observed in HIV-uninfected controls. Among treated participants, IDO activity positively correlated with their concurrent HIV DNA (r = 0.36, P < .0001). Multivariate model showed an independent association of pre-ART CD4/CD8 ratio (adjusted odds ratio [aOR], 0.75 per 0.1 increase [95% confidence interval {CI}, .62-.91]) and on-ART IDO activity (aOR, 1.09 per nM/µM increase [95% CI, 1.04-1.14]) with higher levels of HIV DNA on-ART. A lack of association of the microbial translocation markers was observed with the size of HIV reservoir. HIV DNA positively correlated with the proportions of activated CD4 T and CD8 T cells and exhausted CD4 T cells. CONCLUSIONS: We observed a positive correlation between IDO activity and total HIV DNA in blood, highlighting the important role of immunometabolic aberrations in HIV persistence.

The role of IDO, IL-10, and TGF-ß in the HCV-associated chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma.

Indoleamine-2,3-dioxygenase (IDO) is an enzyme that catalyzes tryptophan to kynurenine and studies have revealed that IDO play a vital role in regulation of liver immunity and inflammation activities. This study investigated the association between plasma IDO and disease severity and the possible marker role of IDO in the inflammatory process of hepatitis C. In this study, 80 individuals with HCV infection were retrospectively selected. Plasma levels of IDO, IL-10, and TGF-ß were assayed by ELISA. Clinical characteristics of patients, including the levels of ALT, AST, and total bilirubin (TBil) were collected from clinical databases. HCV-related liver cirrhosis (HC-Cirr) and HCV-related Hepatocellular carcinoma (HCV-HCC) had significantly high plasma levels of IDO compared to other patient groups and healthy controls. Plasma IL-10 level were significantly greater in all chronic liver disease groups and with respect to TGF-ß, the level was high in all the selected patients with HCV infection compare with controls. Moreover, HCV-HCC patients showed highest values for both IL-10 and TGF-ß, with significant difference compared with other groups. In addition, plasma IDO was positively correlated with TGF-ß among all patients with HCV infection (r = 0.4509, P < 0.0001), with IL-10 in CHC patients (r = 0.4787, P = 0.0047), with TBil in HCV-Cirr patients (r = 0.4671; P = 0.0093). High level of IDO and TGF-ß is associated with hepatocyte necrosis and intrahepatic inflammation, and may be used as an index of disease progression for patients with chronic HCV infection.

Phenotypically resembling myeloid derived suppressor cells are increased in children with HIV and exposed/infected with Mycobacterium tuberculosis.

Increased disease susceptibility during early life has been linked to immune immaturity, regulatory T-cell/TH2 immune biasing and hyporesponsiveness. The contribution of myeloid derived suppressor cells (MDSCs) remains uninvestigated. Here, we assessed peripheral MDSC in HIV-infected and -uninfected children with tuberculosis (TB) disease before, during and after TB treatment, along with matched household contacts (HHCs), HIV-exposed, -infected and -uninfected children without recent TB exposure. Serum analytes and enzymes associated with MDSC accumulation/activation/function were measured by colorimetric- and fluorescence arrays. Peripheral frequencies of cells phenotypically resembling MDSCs were significantly increased in HIV-exposed uninfected (HEU) and M.tb-infected children, but peaked in children with TB disease and remained high following treatment. MDSC in HIV-infected (HI) children were similar to unexposed uninfected controls; however, HAART-mediated MDSC restoration to control levels could not be disregarded. Increased MDSC frequencies in HHC coincided with enhanced indoleamine-pyrrole-2,3-dioxygenase (IDO), whereas increased MDSC in TB cases were linked to heightened IDO and arginase-1. Increased MDSC were paralleled by reduced plasma IP-10 and thrombospondin-2 levels in HEU and significantly increased plasma IL-6 in HI HHC. Current investigations into MDSC-targeted treatment strategies, together with functional analyses of MDSCs, could endorse these cells as novel innate immune regulatory mechanism of infant HIV/TB susceptibility.

Immunobiochemical pathways of neopterin formation and tryptophan breakdown via indoleamine 2,3-dioxygenase correlate with circulating tumor cells in ovarian cancer patients- A study of the OVCAD consortium.

OBJECTIVE: Circulating tumor cells (CTCs) may represent a chronic stimulus for the immune system. In the present study we investigated the potential association of CTCs, the immune activation marker neopterin, and the ratio of kynurenine to tryptophan (Kyn/Trp) as a measure for tryptophan breakdown. METHODS: Neopterin, tryptophan and kynurenine levels were measured in plasma samples from patients with benign gynecological diseases (n=65) and with primary advanced epithelial ovarian cancer (EOC) at diagnosis (n=216) and six months after adjuvant platinum-based chemotherapy (n=45) by an enzyme-linked immunosorbent assay and high performance liquid chromatography. The presence of CTCs had been assessed in a previous study by qPCR-based analysis of CTC-related transcripts in the blood. The respective plasma levels in EOC and benign samples were compared using a two-tailed Chi2 or Fisher's exact test. The associations of the analytes and Kyn/Trp with clinicopathological parameters, platinum-sensitivity, and the presence of CTC-related transcripts were assessed using a two-sided t-test. Associations with patient outcome were evaluated using Cox regression analysis. RESULTS: In EOC, elevated Kyn/Trp and neopterin levels were associated with advanced disease, peritoneal carcinomatosis, ascites, sub-optimal debulking, poor response to therapy and worse outcome. Likewise, neopterin and Kyn/Trp were elevated in CTC-positive patients, both at diagnosis and at follow-up in platinum-sensitive disease. CONCLUSIONS: We observed concomitant alterations of CTCs and immune system related biomarkers suggesting that immune responses along with increase of neopterin and Kyn/Trp concentrations are not necessarily only located at the site of the tumor, but may also go on in the circulation.

Pilot Study of the Tart Cherry Juice for the Treatment of Insomnia and Investigation of Mechanisms.

BACKGROUND: Insomnia is common in the elderly and is associated with chronic disease, but use of hypnotics increases the incidence of falls. Montmorency tart cherry juice has improved insomnia by self-report questionnaire. STUDY QUESTION: Is insomnia confirmed by polysomnography and is tryptophan availability a potential mechanism for treating insomnia? STUDY DESIGN: A placebo-controlled balanced crossover study with subjects older than 50 years and insomnia were randomized to placebo (2 weeks) or cherry juice (2 weeks) (240 mL 2 times/d) separated by a 2-week washout. MEASURES AND OUTCOMES: Sleep was evaluated by polysomnography and 5 validated questionnaires. Serum indoleamine 2,3-dioxygenase (IDO), the kynurenine-to-tryptophan ratio, and prostaglandin E2 were measured. In vitro, Caco-2 cells were stimulated with interferon-gamma, and the ability of cherry juice procyanidin to inhibit IDO which degrades tryptophan and stimulates inflammation was measured. The content of procyanidin B-2 and other major anthocyanins in cherry juice were determined. RESULTS: Eleven subjects were randomized; 3 with sleep apnea were excluded and referred. The 8 completers with insomnia increased sleep time by 84 minutes on polysomnography (P = 0.0182) and sleep efficiency increased on the Pittsburgh Sleep Quality Index (P = 0.03). Other questionnaires showed no significant differences. The serum kynurenine-to-tryptophan ratio decreased, as did the level of prostaglandin E2 (both P < 0.05). In vitro, cherry juice procyanidin B-2 dose-dependently inhibited IDO. CONCLUSIONS: Cherry juice increased sleep time and sleep efficiency. Cherry juice procyanidin B-2 inhibited IDO, increased tryptophan availability, reduced inflammation, and may be partially responsible for improvement in insomnia.

Mesenchymal stem cells attenuate liver fibrosis by suppressing Th17 cells - an experimental study.

This study investigates molecular and cellular mechanisms involved in mesenchymal stem cell (MSC)-mediated modulation of IL-17 signaling during liver fibrosis. Mice received CCl4 (1 µl/g intraperitoneally) twice/week for 1 month. MSCs (1 × 106 ), or MSC-conditioned medium (MSC-CM), were intravenously injected 24 h after CCl4 and on every 7th day. Liver fibrosis was determined by macroscopic examination, histological analysis, Sirius red staining, and RT-PCR. Serum levels of cytokines, indoleamine 2,3-dioxygenase (IDO), and kynurenine were determined by ELISA. Flow cytometry was performed to identify liver-infiltrated cells. In vitro, CD4+ T cells were stimulated and cultured with MSCs. 1-methyltryptophan was used for inhibition of IDO. MSCs significantly attenuated CCl4 -induced liver fibrosis by decreasing serum levels of inflammatory IL-17, increasing immunosuppressive IL-10, IDO, and kynurenine, reducing number of IL-17 producing Th17 cells, and increasing percentage of CD4+ IL-10+ T cells. Injection of MSC-CM resulted with attenuated fibrosis accompanied with the reduced number of Th17 cells in the liver and decreased serum levels of IL-17. MSC-CM promoted expansion of CD4+ FoxP3+ IL-10+ T regulatory cells and suppressed proliferation of Th17 cells. This phenomenon was completely abrogated in the presence of IDO inhibitor. MSCs, in IDO-dependent manner, suppress liver Th17 cells which lead to the attenuation of liver fibrosis.

[Value of indoleamine 2,3-dioxygenase in diagnosis of systemic inflammatory response syndrome after cardiopulmonary bypass in children with congenital heart disease].

OBJECTIVE: To study the value of indoleamine 2,3-dioxygenase (IDO) in the early diagnosis of systemic inflammatory response syndrome (SIRS) after cardiopulmonary bypass in children with congenital heart disease. METHODS: A total of 90 children with congenital heart disease who underwent cardiopumonary bypass surgery between May 2012 and January 2016 were enrolled. According to the prsence or absence of SIRS after surgery, they were divided into SIRS group (n=43) and control group (n=47). Peripheral blood samples were collected before surgery, during surgery, and after surgery. Serum levels of IDO, C-reactive protein (CRP), and interleukin-6 (IL-6) were measured and compared between the two groups. The receiver operating characteristic (ROC) curve was used to evaluate their diagnostic efficiency. RESULTS: Compared with the control group, the SIRS group had higher serum CRP levels at 72 hours after surgery, higher IL-6 levels during surgery and at 72 hours after surgery, and higher IDO levels at 24 and 72 hours after surgery. IDO had a certain value in the diagnosis of SIRS at 24 hours after surgery with an area under the ROC curve (AUC) of 0.793, a specificity of 100%, and a sensitivity of 58.14%. CRP, IL-6, and IDO had a certain value in the diagnosis of SIRS at 72 hours after surgery. IDO had the highest diagnostic efficiency with an AUC of 0.927, a specificity of 95.74%, and a sensitivity of 76.74% at 72 hours after surgery. CONCLUSIONS: IL-6, CRP, and IDO have a certain value in the diagnosis of SIRS after surgery for congenital heart disease, and IDO has a higher diagnostic efficiency. IDO can predict the development of SIRS in children after surgery for congenital heart disease earlier.

Plasma Indoleamine 2, 3-Dioxygenase, a Biomarker for Tuberculosis in Human Immunodeficiency Virus-Infected Patients.

BACKGROUND: There is no biomarker for diagnosing active tuberculosis in patients with human immunodeficiency virus (HIV) infection. Indoleamine 2, 3-dioxygenase (IDO) is an immunoregulatory enzyme that breaks down tryptophan (Trp) to metabolites known as kynurenines (Kyns). We investigated whether IDO activity, as measured by the ratio of Kyn to Trp, could be used to diagnose or predict active tuberculosis disease in HIV-infected adults. METHODS: Kyn and Trp concentrations were measured using ultraperformance liquid chromatography mass spectrometry in plasma samples from 32 HIV-infected patients in whom active tuberculosis developed and who were followed up prospectively. We compared to 70 HIV-infected control subjects from the same cohort in whom tuberculosis did not develop, matched by age, sex, and CD4 cell count, and 37 unmatched HIV-infected patients with a diagnosis of pneumonia. Clinical parameters, including body mass index, CD4 cell count, HIV load, and C-reactive protein levels were analyzed. RESULTS: At the time of tuberculosis diagnosis, IDO activity was significantly higher in patients with tuberculosis than in controls (P < .001). Six months before tuberculosis diagnosis, IDO activity was significantly higher in all patients who later developed tuberculosis (P < .001) than controls. After 6 months of tuberculosis treatment, IDO activity in patients with tuberculosis declined to levels similar to those in controls. IDO activity was 4-fold higher in patients with tuberculosis than in those with pneumonia, and could be used to distinguish them. With a receiver operating characteristic curve, IDO activity had a sensitivity of 97%, a specificity of 99%, and positive and negative predictive values of 89% and 100% for detecting active tuberculosis disease. CONCLUSION: Plasma IDO activity is suitable as a biomarker of active tuberculosis in HIV-positive patients.

Increased Activity of the Immunoregulatory Enzyme Indoleamine-2,3-Dioxygenase with Consecutive Tryptophan Depletion Predicts Death in Patients with Neuroendocrine Neoplasia.

BACKGROUND/AIMS: Data from a considerable number of malignancies demonstrate that depletion of the essential amino acid tryptophan via induction of the immunoregulatory enzyme indoleamine-2,3-dioxygenase (IDO) serves as an important tumour escape strategy and is of prognostic importance. Here we investigate the predictive value of the activity of IDO as well as levels of tryptophan and respective downstream catabolites in a large cohort of patients with neuroendocrine neoplasms (NEN). METHODS: 142 consecutive Caucasian patients (62 male, aged 60.3 ± 11.9 years) with histologically confirmed NEN were systematically analysed in a retrospective blinded end point analysis. Patients were followed up for a mean period of about 3.9 ± 1.9 years. Clinical outcome, levels of established biomarkers, and tryptophan degradation markers (assessed using tandem mass spectrometry) including estimated IDO activity were recorded. Cox proportional hazards regression models were performed for the assessment of prognostic power. RESULTS: We found that baseline tryptophan levels were significantly lower and IDO activity was significantly increased in non-survivors. The risk for death inclined stepwise and was highest in patients in the upper tertile of IDO activity. Cox proportional regression models identified IDO activity as an independent predictor of death. CONCLUSIONS: In this retrospective analysis, we observed that baseline activity of the immunoregulatory enzyme IDO was significantly increased in non-survivors. IDO activity was identified as an independent predictor of death in this cohort of NEN patients. Whether IDO activity or tryptophan depletion serves to guide future therapeutic interventions in NEN remains to be established.

Indoleamine 2,3 dioxygenase as a prognostic and follow-up marker in melanoma. A comparative study with LDH and S100B.

BACKGROUND: To date, lactate dehydrogenase (LDH) and S100B remain the most useful biomarkers for follow-up of melanoma patients. In recent years, indoleamine 2,3-dioxygenase (IDO), an immunosuppressive enzyme, has been proposed as a new potential tumour biomarker for melanoma. However, further studies are needed to confirm the usefulness of IDO expression as an independent prognostic factor. OBJECTIVE: To explore the potential association between serum IDO levels and melanoma stage at diagnosis and recurrence, and to compare the results to those obtained with LDH and S100B. In addition, we also investigated a possible cut off for IDO level as a prognostic factor for overall survival. METHODS: IDO, LDH and S100B levels were measured in serum samples of 186 patients in all melanoma stages at diagnosis and twice a year thereafter. A cut-off point for IDO levels was calculated using receiver operating characteristic curves to explore the association between these levels and the likelihood of lymphatic spread. Survival curves were estimated for patient groups stratified by IDO level (higher or lower than the cut off), using the Kaplan-Meier method. RESULTS: At diagnosis, serum IDO levels were significantly higher in stages IB, II, III and IV, whereas S100B levels were significantly higher in stages III and IV, and LDH levels were only higher in stage IV. In relapsed patients, significant increases were found in levels of all three markers. Finally, overall survival was significantly longer in patients with IDO levels below a cut off of 1.65 µM at diagnosis than in those with higher levels (91.3 vs. 71.0% at 36 months). CONCLUSION: In melanoma patients, serum IDO levels are significantly associated with disease stage, relapses and overall survival. These results indicate IDO could be a useful serum prognostic marker for melanoma.

[Clinical Evaluation of Indoleamine 2, 3-Dioxygenase in the Serum of Patients with Locally Advanced Breast Cancer during Mohs Paste Treatment].

Locally advanced breast cancer lesions often compromise patients' quality of life(QOL). Mohs paste is a histopathological fixative with zinc chloride as the main ingredient. It is applied when performing chemosurgery for skin tumors. In recent years, this paste has reportedly been very effective for the control of various symptoms of skin metastases in inoperable advanced cancers, such as pungent odor and hemorrhage, in the field of palliative care. We evaluated the clinical significance of indoleamine 2, 3-dioxygenase(IDO)in the serum of patients with locally advanced breast cancer during Mohs paste treatment. IDO activity was measured by the tryptophan(Trp)/kynurenine(Kyn)ratio. Trp and Kyn levels were measured using high performance liquid chromatography(HPLC). We collected serum samples from 3 locally advanced breast cancer cases: once in the pre-treatment phase, 2 times in the post-treatment phase, and 5 times in the post-treatment phase. Then, we measured the Trp/Kyn ratio and CRP in these samples during Mohs paste treatment. There were no significant differences in serum Trp/ Kyn ratios between the phases, but serum CRP values decreased after Mohs paste treatment. These results suggest that Mohs paste treatment for locally advanced breast cancer lesions may be useful in enhancing patients' QOL without immunosuppression.

Decreased tryptophan and increased kynurenine levels in mastocytosis associated with digestive symptoms.

The main metabolism pathway of tryptophan is protein formation, but it can also be metabolized into serotonin and kynurenine. Indoleamine 2,3-dioxygenase (IDO) is the enzyme that catalyzes the degradation of tryptophan into kynurenine. Mastocytosis is a heterogeneous disease characterized by mast cell accumulation in various tissues with 57% of patients having gastrointestinal involvement. We studied tryptophan metabolism in mastocytosis patients displaying or not gastrointestinal features and healthy subjects (n = 26 in each group). Mastocytosis patients with digestive symptoms displayed significantly increased kynurenine level and IDO activity as compared to healthy controls and mastocytosis patients without digestive symptoms. This could be linked to mast cell-mediated digestive inflammation among patients with mastocytosis. This work is the first focusing on kynurenine pathway in a mast cell disease and could help to understand the pathogenesis of digestive features in mastocytosis as well as in other mast cell-mediated diseases.

Low indoleamine 2,3-dioxygenase activity in persistent food allergy in children.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO), which degrades tryptophan (Trp) to kynurenine (Kyn), has been demonstrated to contribute to modulation of allergic responses. However, the role of IDO in food allergy has not yet been elucidated. METHODS: Serum Trp and Kyn concentrations were analyzed by high-pressure liquid chromatography. Expression of IDO gene was measured by real-time PCR. The levels of interleukin (IL)-4, IL-10, and interferon (IFN)-γ in cell culture supernatants were measured by ELISA. RESULTS: Kyn/Trp (IDO activity) was significantly lower in subjects with food allergy (n = 100) than in aged-matched healthy controls (n = 112) (P = 0.004). Kyn/Trp was decreased from healthy through completely tolerant, partially tolerant, and reactive ones [LN transformation (mean ± SEM) healthy: 3.9 ± 0.02 µM/mM; completely tolerant: 3.83 ± 0.04; partially tolerant: 3.8 ± 0.06; reactive: 3.7 ± 0.04] (P = 0.008). The frequency of genetic polymorphisms of IDO did not reveal a significant association with Trp, Kyn, and Kyn/Trp in healthy and food-allergic cases. Culture of PBMC experiments yielded that IDO mRNA expression was not different between tolerant and reactive groups. IL-4 synthesis when stimulated with casein increased significantly in subjects who are reactive and tolerant to foods (P = 0.042, P = 0.006, respectively). Increase in IL-10 synthesis was observed only in children tolerant to milk, but not in reactive ones. IFN-γ synthesis, when stimulated with IL-2 and ß-lactoglobulin in cell culture, was significantly higher in subjects tolerant to milk than in the reactive ones (P = 0.005 and P = 0.029, respectively). CONCLUSION: Our results imply the probability of involvement of IDO in development of tolerance process, and we presume that high IDO activity is associated with nonresponsiveness to food allergens despite allergen sensitization.

Serum indoleamine 2,3 dioxygenase and tryptophan and kynurenine ratio using the UPLC-MS/MS method, in patients undergoing peritoneal dialysis, hemodialysis, and kidney transplantation.

BACKGROUND: The level and activity of indoleamine 2,3-dioxygenase (IDO) and the concentrations of L-tryptophan and its metabolite L-kynurenine were determined in association with various renal diseases. However, there have been no data regarding these parameters in patients on peritoneal dialysis compared to those undergoing hemodialysis or kidney transplantation. METHODS: This study investigated the level and activity of IDO and determined oxidative balance by calculating the total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI). We enrolled 60 kidney disease patients, including 20 on peritoneal dialysis (PD group), 19 on hemodialysis (HD group), and 21 with kidney transplantation (KT group), as well as 21 control group. RESULTS: IDO levels were increased in the PD, HD, and KT groups compared to the control group. The concentration of kynurenine was significantly increased in the PD group compared to the other groups (p < 0.01). The kynurenine/tryptophan ratio was increased in the PD group compared to the other groups (all p < 0.01). TAS levels in the PD and HD groups were significantly decreased compared to the control group (both p < 0.05). TAS levels in the PD group were significantly decreased compared to the KT group. TOS levels in the PD group were higher than in the HD and KT groups. CONCLUSION: The results showed that IDO levels were increased in peritoneal dialysis and hemodialysis patients and in renal transplant recipients, while oxidative stress was found to be related to IDO activity and was most increased in the patients on peritoneal dialysis.

The kynurenine pathway activities in a sub-Saharan HIV/AIDS population.

BACKGROUND: Tryptophan is an essential amino acid for the synthesis of proteins and important metabolites such as serotonin, melatonin, tryptamine and niacin. After protein synthesis, more than 90 % of tryptophan catabolism occurs along the kynurenine pathway. The inflammation-inducible enzyme indoleamine 2,3 dioxygenase (IDO) is responsible for the first rate-limiting step in the kynurenine pathway, i.e., oxidation of tryptophan to kynurenine. Excessive IDO activity in conditions such as HIV/AIDS may lead to tryptophan depletion and accumulation of metabolites downstream from kynurenine. Little is known about the kynurenine pathway of HIV/AIDS patients in sub-Saharan regions. This study, in a low income sub-Saharan HIV/AIDS population, examined the effects of activities in the kynurenine pathway on plasma levels of tryptophan, kynurenine and the neurotoxin quinolinic acid, and on de novo synthesis of nicotinamide. METHODS: Plasma samples were obtained from a cohort of 105 HIV patients and 60 controls. Kynurenine pathway metabolites were analysed using gas chromatography - mass spectrometry. ELISA and flow cytometry were used to assess plasma inflammatory markers. RESULTS: IDO activity, depletion of tryptophan, as well as accumulation of kynurenine and the neurotoxin quinolinic acid, were not only significantly greater in the patients than in the controls, but also markedly greater than in HIV/AIDS patients from developed countries. Tryptophan levels were 12.3 % higher, kynurenine levels 16.2 % lower, quinolinic acid levels 43.2 % lower and nicotinamide levels 27,2 % lower in patients on antiretroviral treatment than in antiretroviral-naïve patients. Patients' kynurenine pathway metabolites correlated with the levels of inflammatory markers, including that of the major IDO-inducer, interferon-gamma. Indications are that the rate of de novo synthesis of nicotinamide in the kynurenine pathway correlates with increases in quinolinic acid levels up to a point where saturation of the enzyme quinolinate phosphoribosyl transferase occurs. CONCLUSIONS: Higher levels of inflammatory activity in this low income sub-Saharan HIV/AIDS population than in patients from developed countries lead to greater tryptophan depletion and greater accumulation of metabolites downstream from tryptophan with quinolinic acid levels often reaching levels associated with the development of HIV/AIDS-associated neurocognitive dysfunction. De novo synthesis of nicotinamide from quinolinic acid contributes to the maintenance of nicotinamide, and by implication NAD levels, in HIV/AIDS patients from low income populations. Antiretroviral treatment partially corrects disturbances in the kynurenine pathway.