IDO Activity Research Articles

The kynurenine pathway in HIV, frailty and inflammaging.

Kynurenine (Kyn) is a circulating tryptophan (Trp) catabolite generated by enzymes including IDO1 that are induced by inflammatory cytokines such as interferon-gamma. Kyn levels in circulation increase with age and Kyn is implicated in several age-related disorders including neurodegeneration, osteoporosis, and sarcopenia. Importantly, Kyn increases with progressive disease in HIV patients, and antiretroviral therapy does not normalize IDO1 activity in these subjects. Kyn is now recognized as an endogenous agonist of the aryl hydrocarbon receptor, and AhR activation itself has been found to induce muscle atrophy, increase the activity of bone-resorbing osteoclasts, decrease matrix formation by osteoblasts, and lead to senescence of bone marrow stem cells. Several IDO1 and AhR inhibitors are now in clinical trials as potential cancer therapies. We propose that some of these drugs may be repurposed to improve musculoskeletal health in older adults living with HIV.

L-Kynurenine participates in cancer immune evasion by downregulating hypoxic signaling in T lymphocytes

ABSTRACT Malignant tumors often escape anticancer immune surveillance by suppressing the cytotoxic functions of T lymphocytes. While many of these immune evasion networks include checkpoint proteins, small molecular weight compounds, such as the amino acid L-kynurenine (LKU), could also substantially contribute to the suppression of anti-cancer immunity. However, the biochemical mechanisms underlying the suppressive effects of LKU on T-cells remain unclear. Here, we report for the first time that LKU suppresses T cell function as an aryl hydrocarbon receptor (AhR) ligand. The presence of LKU in T cells is associated with AhR activation, which results in competition between AhR and hypoxia-inducible factor 1 alpha (HIF-1α) for the AhR nuclear translocator, ARNT, leading to T cell exhaustion. The expression of indoleamine 2,3-dioxygenase 1 (IDO1, the enzyme that leads to LKU generation) is induced by the TGF-β-Smad-3 pathway. We also show that IDO-negative cancers utilize an alternative route for LKU production via the endogenous inflammatory mediator, the high mobility group box 1 (HMGB-1)-interferon-gamma (IFN-γ) axis. In addition, other IDO-negative tumors (like T-cell lymphomas) trigger IDO1 activation in eosinophils present in the tumor microenvironment (TME). These mechanisms suppress cytotoxic T cell function, and thus support the tumor immune evasion machinery.

Does smoking influence tryptophan metabolism in periodontal inflammation? A cross-sectional study.

The aim of this study was to identify the effects of smoking and periodontal inflammation on tryptophan-kynurenine metabolism as well as the correlation between these findings and clinical periodontal parameters. It has been shown that the tryptophan amino acid's primary catabolic pathway, the kynurenine pathway (KP), may serve as a key biomarker for periodontal disease. Although there are studies investigating the effect of smoking on KYN-TRP metabolism, the effect of smoking on periodontal disease through KP has not been revealed so far. The salivary and serum samples were gathered from 24 nonsmoker (NS-P) stage III, grade B generalized periodontitis and 22 smoker (S-P) stage III, grade C generalized periodontitis patients, in addition to 24 nonsmoker (NS-C) and 24 smoker (S-C) periodontally healthy control individuals. Saliva and serum IL-6, kynurenine (KYN), and tryptophan (TRP) values, and KYN/TRP ratio were analyzed by liquid chromatography-mass spectrometry. Clinical periodontal measurements were recorded. Salivary TRP values were significantly higher in both periodontitis groups than control groups (p < .05). Salivary KYN values were highest in NS-P group (p < .05). Salivary KYN values did not differ significantly between periodontitis groups (p = .84). Salivary KYN/TRP ratio was significantly lower in NS-P group compared to other groups (p < .001). Serum TRP value is higher in S-P group than other groups; however, significant difference was found in S-C group (p < .05). Serum KYN values were significantly lower in smokers than nonsmokers. Serum KYN/TRP ratio is higher in NS-P group. NS-P group has the highest salivary IL-6 levels, NS-C group has the lowest values (p < .05). Our results point out that smoking exacerbates inflammation in the periodontium and increases TRP destruction and decreases IDO activity by suppressing KP in serum. As a result, kynurenine and its metabolites may be significant biomarkers in the link between smoking and periodontal disease.

Indoleamine 2,3-Dioxygenase 1 Deletion-Mediated Kynurenine Insufficiency Inhibits Pathological Cardiac Hypertrophy.

Aberrant amino acid metabolism is implicated in cardiac hypertrophy, while the involvement of tryptophan metabolism in pathological cardiac hypertrophy remains elusive. Herein, we aimed to investigate the effect and potential mechanism of IDO1 (indoleamine 2,3-dioxygenase) and its metabolite kynurenine (Kyn) on pathological cardiac hypertrophy. Transverse aortic constriction was performed to induce cardiac hypertrophy in IDO1-knockout (KO) mice and AAV9-cTNT-shIDO1 mice. Liquid chromatography-mass spectrometry was used to detect the metabolites of tryptophan-Kyn pathway. Chromatin immunoprecipitation assay and dual luciferase assay were used to validate the binding of protein and DNA. IDO1 expression was upregulated in both human and murine hypertrophic myocardium, alongside with increased IDO1 activity and Kyn content in transverse aortic constriction-induced mice's hearts using liquid chromatography-mass spectrometry analysis. Myocardial remodeling and heart function were significantly improved in transverse aortic constriction-induced IDO1-KO mice, but were greatly exacerbated with subcutaneous Kyn administration. IDO1 inhibition or Kyn addition confirmed the alleviation or aggravation of hypertrophy in cardiomyocyte treated with isoprenaline, respectively. Mechanistically, IDO1 and metabolite Kyn contributed to pathological hypertrophy via the AhR (aryl hydrocarbon receptor)-GATA4 (GATA binding protein 4) axis. This study demonstrated that IDO1 deficiency and consequent Kyn insufficiency can protect against pathological cardiac hypertrophy by decreasing GATA4 expression in an AhR-dependent manner.

NLG-919 combined with cisplatin to enhance inhibitory effect on cell migration and invasion via IDO1-Kyn-AhR pathway in human nasopharyngeal carcinoma cell.

As a common aggressive head and neck cancer, nasopharyngeal carcinoma (NPC) received cisplatin treatment as a first-line chemotherapy. Platinum-induced resistance is a major limitation of current treatment strategy in the advanced NPC. Increased indoleamine 2,3-dioxygenase (IDO1) activities are found in cisplatin-resistant NPC cells versus cisplatin-sensitive NPC cells. As an IDO1 immunosuppressant, NLG-919 has entered clinical phase I to treat advanced solid tumors. To reverse cisplatin resistance, we investigated the combinatory application of cisplatin and NLG-919 in NPC treatment. In vitro biological studies on cisplatin-resistant and cisplatin-sensitive NPC cells were taken to imply that the combination of NLG-919 and cisplatin got a stronger impact on the induction of cell apoptosis and the inhibition of cell migration, exploring superior effect of antitumor over single drug. We proved that the mechanism of the combined therapy could inhibit the activity of IDO1, blocking amino acid tryptophan conversion to kynurenine through the kynurenine pathway, which further inhibited the aryl hydrocarbon receptor expression. Our study underscored the combination of cisplatin and NLG-919 as a potent therapeutic way for the reversal of cisplatin resistance.

Indoleamine 2,3-Dioxygenase (IDO) Activity: A Perspective Biomarker for Laboratory Determination in Tumor Immunotherapy.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a heme enzyme involved in catalyzing the conversion of tryptophan (Trp) into kynurenine (Kyn) at the first rate-limiting step in the kynurenine pathway of L-tryptophan metabolism. It has been found to be involved in several biological functions such as aging, immune microorganism, neurodegenerative and infectious diseases, and cancer. IDO1 plays an important role in immune tolerance by depleting tryptophan in the tumor microenvironment and inhibiting the proliferation of effector T cells, which makes it an important emerging biomarker for cancer immunotherapy. Therefore, the research and development of IDO1 inhibitors are of great importance for tumor therapy. Of interest, IDO activity assays are of great value in the screening and evaluation of inhibitors. Herein, we mainly review the biological functions of IDO1, immune regulation, key signaling molecules in the response pathway, and the development of IDO1 inhibitors in clinical trials. Furthermore, this review provides a comprehensive overview and, in particular, a discussion of currently available IDO activity assays for use in the evaluation of IDO inhibitors in human blood. We believe that the IDO activity is a promising biomarker for the immune escape and laboratory evaluation of tumor immunotherapy.

The antioxidant/anti-inflammatory protective effects of rutin against ethanol-induced testicular perturbation in rats: Involvement of the immunosuppressive indoleamine 2,3-dioxygenase.

This study investigated the influence of rutin against EtOH-induced testicular impairment in rats and the involvement of the indole-aminergic pathway. Four groups of eight rats each were orally exposed to drinking water (Group 1), EtOH (5 g/kg bwt, Group 2), R (5 g/kg bwt, Group 3), and EtOH + R (5 g/kg bwt + 50 mg/kg bwt, Group 4) via gavage for 15 days. Results showed that exposure to EtOH significantly (p < 0.0001) reduced the testicular antioxidant system and increased lipid peroxidation (LPO) relative to control. We observed a significant (p < 0.0001) increase in the inflammatory biomarkers, with attendant disruption in the testicular histological structure and concomitant elevation in the activities of indoleamine 2,3-dioxygenase (IDO), in comparison with control and no noticeable effects in tryptophan 2,3-dioxygenase (TDO) activity across the groups. Rutin-only exposed group did not show any alteration in the measured parameters when compared with the control. Rutin co-exposure augmented the antioxidant system, prevented histological damage, reduced LPO and inflammation, and thus, lowered EtOH-mediated increase in IDO activity, compared with control. Overall, these findings reveal the involvement of the indole-aminergic pathway in rutin's protective influence against EtOH-induced testicular impairment in rats.

Accelerated kynurenine pathway downregulates immune activation in patients with axial spondyloarthritis

Various studies reported that the kynurenine (Kyn) pathway plays a pivotal role in regulating the balance between activation and inhibition of the immune system. Proinflammatory cytokines can accelerate the Kyn pathway by altering indoleamine (2, 3)- dioxygenase (IDO) allosteric enzyme activity. Excessive cytokine release and immune system activation have essential roles in the pathogenesis of axial spondyloarthritis (axSpA). We aimed to investigate the relationship of the Kyn pathway with proinflammatory cytokines and with the severity of the disease in patients with axSpA.The study included 104 patients with axSpA and 54 healthy volunteers. The severity of the disease was determined by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). The Kyn pathway was evaluated by IDO activity calculated with Kyn/Tryptophan (Trp) ratio. Plasma Trp and Kyn concentrations were measured with tandem mass spectrometry. Serum IL 17/23 and IFN-γ concentrations were measured with ELISA. These groups were compared in terms of IDO, IL-17, IL-23, IFN-γ, and BASDAI.Plasma IDO activity was significantly increased, however, serum IL-17, IL-23, and IFN-γ levels were significantly decreased in patients compared to healthy volunteers. While IFN-γ was positively correlated with the severity of the disease (p = 0.02), it also had a significant inverse correlation with IDO activity (p < 0.001). However, these correlations are weak.As a result of this study, the Kyn pathway is accelerated and proinflammatory cytokine levels are decreased in patients with axSpA. All of these results with an indirect weak negative association between high IDO and low disease activity suggest that an accelerated Kyn pathway may limit the immune system activation in axSpA disease.

Regulation of IDO2 by the Aryl Hydrocarbon Receptor (AhR) in Breast Cancer.

Indoleamine 2,3-dioxygenase 2 (IDO2) is a tryptophan-catabolizing enzyme and a homolog of IDO1 with a distinct expression pattern compared with IDO1. In dendritic cells (DCs), IDO activity and the resulting changes in tryptophan level regulate T-cell differentiation and promote immune tolerance. Recent studies indicate that IDO2 exerts an additional, non-enzymatic function and pro-inflammatory activity, which may play an important role in diseases such as autoimmunity and cancer. Here, we investigated the impact of aryl hydrocarbon receptor (AhR) activation by endogenous compounds and environmental pollutants on the expression of IDO2. Treatment with AhR ligands induced IDO2 in MCF-7 wildtype cells but not in CRISPR-cas9 AhR-knockout MCF-7 cells. Promoter analysis with IDO2 reporter constructs revealed that the AhR-dependent induction of IDO2 involves a short-tandem repeat containing four core sequences of a xenobiotic response element (XRE) upstream of the start site of the human ido2 gene. The analysis of breast cancer datasets revealed that IDO2 expression increased in breast cancer compared with normal samples. Our findings suggest that the AhR-mediated expression of IDO2 in breast cancer could contribute to a pro-tumorigenic microenvironment in breast cancer.

Pulsatilla chinensis saponins ameliorated murine depression by inhibiting intestinal inflammation mediated IDO1 overexpression and rebalancing tryptophan metabolism

BackgroundCurrent antidepressant therapy remains unsatisfactory due to the complex pathogenesis. Emerging evidence suggested that depression is associated with inflammatory bowel disease (IBD), intestinal inflammation is an increasingly accepted factor that influences depression, but the mechanism is unclear. PurposeIn the current study, we determined whether Pulsatilla chinensis saponins (PRS), a phytomedicine from Pulsatilla chinensis (Bunge) Regel with excellent anti-IBD effect, could improve the depression. Furthermore, we investigated the mechanisms to explore the relationship between IBD and depression and provide new source for the urgent development of antidepressants from phytomedicine. MethodsThe antidepressant activity of PRS was accessed by behavioral test and multichannel technology in depression mice induced by Chronic Unpredictable Mild Stress (CUMS). 16S rDNA-based microbiota and RNA-seq in colon was used to explore potential intestinal metabolism affected by PRS. To illustrate the underlying mechanisms of anti-depression effect of PRS, targeted metabolomics, ELISA assay, immunofluorescence staining, Western Blot, and qPCR were carried out. ResultsThe results clarified that CUMS induced depression with tryptophan (Trp) metabolism and intestinal inflammation. PRS effectively suppressed the depression and acted as a regulator of Trp/kynurenine (Kyn) metabolic and intestinal inflammation confirmed by analysis of microflora and colon RNA. Meanwhile PRS reduced interferon gamma (IFN-γ), inhibited JAK1-STAT1 phosphorylation, decreased IDO1 levels to protect against the overactivity of Trp/kyn path, suggesting that IFN-γ activated IDO1 probably a significant target for PRS to exert anti-depression effects. To further confirm the mechanism, this research expressed that PRS improved IDO1 activity and depressive behavior in mice with IFN-γ-induced depression. Furthermore, the therapeutic effect of 1-methyl-tryptophan (1-MT) well known as an IDO1 inhibitor in depression and clinically used anti-UC drug Mesalazine (MS) was demonstrated to confirm the potential mechanism. ConclusionThe study is the first to reveal the antidepressant effect of PRS and further demonstrate its potential therapeutic targets. In addition, it also clarifies that the Trp/kyn pathway is the crosstalk between IBD and depression and provides new choice for depression treatment. And it also provides an important basis for the follow-up development and exploration of anti-intestinal antidepressants.

Abstract 2805: Pharmacogenomic platform using patient-derived cells to delineate tumor heterogeneity and therapeutic response of refractory lung cancer

Abstract A pharmacogenomic platform using patient-derived cells (PDCs) was established to identify the underlying resistance mechanisms and tailored treatment for advanced or refractory lung cancer patients. Drug sensitivity screening was acquired from short-term PDC culture and multi-omics datasets were acquired from lung cancer PDCs (n = 199). Integrative analysis was performed to explore susceptible drug candidates from genetic variants, gene expression, and clinical profiles. To demonstrate PDC heterogeneity and its therapeutic response, cellular subpopulation was identified from single cell transcriptome from the patients (n = 8) harboring EGFR mutations with poor response to EGFR-TKIs. Mutation and gene expression profile of our PDC samples conserved with lung cancer tissue. Poor survival mutations were observed in KRAS, PDGFA, KEAP1, and MET. EGFR rare variants facilitated fast progression as well as poor susceptibility in EGFR-TKIs. PDC therapeutic subtypes classified patients into five groups: (1) epithelial-to-mesenchymal transition (EMT)-like (30.6 %), (2) EGFR-dominant (21.4 %), (3) stemness (19.4 %), (4) angiogenesis (17.3 %), and (5) inflammatory (11.2 %). The subtypes implicated in distinct pathway regulation activation, variant enrichment, pathologic type, and survival as well as therapeutic candidates. Meanwhile, single cell transcriptome uncovered IDO1 and MET activation of EGFR-TKI resistance cancer cells. Stromal cell clusters exhibited the variety according to combinatorial immunotherapy response. While VEGFA+, and TOP2A+ clusters exhibited well response to angiogenesis and DNA damage target drug combinations of patients, CALB2+ cluster was clearly abundant to non-responder patients. We could detect angiogenesis (dasatinib) and DNA damage (irinotecan) drug candidates according to stromal clusters’ scoring from bulk PDC samples. Our PDC platform recapitulated the molecular characteristics of solid lung tumor tissues including tumor microenvironment. Uncovered molecular mechanism implied drug candidates. Citation Format: Charny Park, Sehwa Hong, Mihwa Hwang, Youngjoo Lee, Bo Ram Song, Eun Hye Kang, Hanna Sim, Beung-Chul Ahn, Kum Hui Hwang, Namhee Yu, Sunshin Kim, Ji-Youn Han. Pharmacogenomic platform using patient-derived cells to delineate tumor heterogeneity and therapeutic response of refractory lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2805.

Cancer cell membrane–encapsulated biomimetic nanoparticles for tumor immuno-photothermal therapy

Immune checkpoint blockade is one of the most promising approaches in cancer immunotherapy, but patient response rates are low due to low tumor immunogenicity. Herein, we proposed a biomimetic nanoparticle loaded with indocyanine green (ICG) and NLG919 (an effective IDO-1 enzyme inhibitor), which can enhance the immunogenicity of tumor through photothermal and increase the infiltration of cytotoxic T lymphocytes in tumor, thus enhancing the immunotherapy response. In a 4T1 bilateral tumor model, CFIN targeted to the tumor site, which mediated the superior photothermal effect and eliminated the primary tumor. More importantly, high temperature improved the immunogenicity of tumors and created a favorable niche for tumor-infiltrating lymphocytes (TILs) recruitment. At the same time, NLG919 was released to inhibit the activity of IDO-1 and prevented the degradation of tryptophan, thus reversing the microenvironment of immunosuppressed tumors and producing strong prevention of distant metastasis of tumors. Therefore, CFIN combines the advantages of photothermal therapy and immunotherapy to activate mature dendritic cells, initiate cytotoxic T lymphocytes, trigger the body’s innate and adaptive immune responses, eliminate primary tumors, and inhibit distal tumor growth. More importantly, CFIN can be used as a nanovaccine to provide long-term immune memory effect immunity and prevent tumor recurrence. This strategy provides a simple but promising approach for treating metastatic cancer and preventing tumors.

A chemokine network of T cell exhaustion and metabolic reprogramming in renal cell carcinoma.

Renal cell carcinoma (RCC) is frequently infiltrated by immune cells, a process which is governed by chemokines. CD8+T cells in the RCC tumor microenvironment (TME) may be exhausted which most likely influence therapy response and survival. The aim of this study was to evaluate chemokine-driven T cell recruitment, T cell exhaustion in the RCC TME, as well as metabolic processes leading to their functional anergy in RCC. Eight publicly available bulk RCC transcriptome collectives (n=1819) and a single cell RNAseq dataset (n=12) were analyzed. Immunodeconvolution, semi-supervised clustering, gene set variation analysis and Monte Carlo-based modeling of metabolic reaction activity were employed. Among 28 chemokine genes available, CXCL9/10/11/CXCR3, CXCL13/CXCR5 and XCL1/XCR1 mRNA expression were significantly increased in RCC compared to normal kidney tissue and also strongly associated with tumor-infiltrating effector memory and central memory CD8+ T cells in all investigated collectives. M1 TAMs, T cells, NK cells as well as tumor cells were identified as the major sources of these chemokines, whereas T cells, B cells and dendritic cells were found to predominantly express the cognate receptors. The cluster of RCCs characterized by high chemokine expression and high CD8+ T cell infiltration displayed a strong activation of IFN/JAK/STAT signaling with elevated expression of multiple T cell exhaustion-associated transcripts. Chemokinehigh RCCs were characterized by metabolic reprogramming, in particular by downregulated OXPHOS and increased IDO1-mediated tryptophan degradation. None of the investigated chemokine genes was significantly associated with survival or response to immunotherapy. We propose a chemokine network that mediates CD8+ T cell recruitment and identify T cell exhaustion, altered energy metabolism and high IDO1 activity as key mechanisms of their suppression. Concomitant targeting of exhaustion pathways and metabolism may pose an effective approach to RCC therapy.

Mapping the immune landscape in small cell lung cancer by analysing expression of immuno-modulators in tissue biopsies and paired blood samples

Small cell lung carcinomas (SCLC) are aggressive tumors with high propensity to metastasize. Recent NCCN guidelines have incorporated immunotherapy in extensive stage SCLC. Limited benefit in few patients compounded by side effects of unwonted immune-checkpoint-inhibitor (ICPI) usage necessitates identification of potential biomarkers predicting response to ICPIs. Attempting this, we analysed expression of various immunoregulatory molecules in tissue biopsies and paired blood samples of SCLC patients. In 40 cases, immunohistochemistry for expression of immune inhibitory receptors CTLA-4, PD-L1 and IDO1 was performed. Matched blood samples were quantified for IFN-γ, IL-2, TNF-α and sCTLA-4 levels using immunoassay and additionally for IDO1 activity (Kynurenine/Tryptophan ratio) using LC–MS. Immunopositivity for PD-L1, IDO1 and CTLA-4 was identified in 9.3%, 6.2% and 71.8% cases, respectively. Concentration of serum IFN-γ (p-value < 0.001), TNF-α (p-value = 0.025) and s-CTLA4 (p-value = 0.08) were higher in SCLC patients while IL-2 was lower (p-value = 0.003) as compared to healthy controls. IDO1 activity was significantly elevated in SCLC cohort (p-value = 0.007). We proffer that SCLC patients show immune suppressive milieu in their peripheral circulation. Analysis of CTLA4 immunohistochemical expression along with s-CTLA4 levels appears prospective as biomarkers for predicting responsiveness to ICPIs. Additionally, evaluation of IDO1 appears cogent both as prognostic marker and potential therapeutic target as well.

IDO1 Activity Predicts Lung Toxicity in Patients with Unresectable Stage III NSCLC and Chemoradiotherapy.

Indoleamine 2,3-dioxygenase 1 (IDO1) acts as the key rate-limiting enzyme that converts tryptophan (Trp) to kynurenine (Kyn). Its activity was primarily induced by interferon-γ (IFN-γ), which was reported to play a role in the development of acute radiation-induced pneumonitis. In this study, we aimed to investigate the correlation between IDO1 activity and radiation-induced lung toxicity (RILT) in stage III nonsmall cell lung cancer (NSCLC) patients who were treated with chemoradiotherapy (CRT). Systemic IDO1 activity was reflected by Kyn : Trp ratio. Plasma levels of Kyn and Trp in 113 stage III NSCLC patients were measured by high-performance liquid chromatography (HPLC) before the initiation of radiotherapy. Dynamic change of IDO1 activity was followed in 23 patients before, during, and after radiotherapy. We also used RNA sequencing (RNA-seq) data from the Cancer Genome Atlas Program (TCGA) database and performed gene set enrichment analysis (GSEA) to explore how IDO1 was involved in the development of RILT. 9.7% (11/113) of the whole group developed G3+ (greater than or equal to Grade 3) RILT. Preradiation IDO1 activity was significantly higher in patients who developed G3 + RILT than in nonG3 + RILT patients. (P = 0.029, AUC = 0.70). Univariate and multivariate analyses showed that high IDO1 activity was independently associated with the risk of G3 + RILT (P = 0.034). A predictive model combining both IDO1 activity and FEV1 was established for severe RILT and displayed a moderate predictive value (AUC = 0.83, P < 0.001). The incidence of G3 + RILT was 2.6% (1/38) in patients with an IDO activity ≤0.069 and FEV1 > 59.4%, and 50.0% (6/12) in those with an IDO activity >0.069 and FEV1 ≤ 59.4%. Of 23 patients with dynamic tracking, the IDO1 activity of postradiation was significantly lower than midradiation (P = 0.021), though no significant differences among the three time points were observed (P = 0.070). Bioinformatic analysis using RNA-seq data from 1014 NSCLC patients revealed that IDO mainly functioned in the inflammatory response instead of the late fibrosis process in NSCLC patients. High baseline IDO1 activity combined with unfavorable baseline FEV1 was predictive of severe RILT in unresectable stage III NSCLC patients. IDO1 might play a role in the acute inflammatory response. Finding effective interventions to alleviate RILT using IDO inhibitors is warranted in the future.

Rutin co-treatment prevented cognitive impairment/depression-like behavior and decreased IDO activation following 35 days of ethanol administration in male Wistar rats.

Alcohol (ethanol) is among the most popularly consumed beverages globally. Ethanol was earlier demonstrated to elicit cognitive impairment and depressive-like effects in both human and animal studies. Rutin (R) is known for its antioxidant, anti-inflammatory, immunomodulatory, and anti-depressive properties, among others. Herein, we investigate the impact of rutin on ethanol-induced cognitive impairment and depressive-like effects in rats and the involvement of the indoleaminergic pathway. Three groups of eight rats each were orally exposed to drinking water (group 1), ethanol (5g/kg body weight)-group 2 (via oral gavage), and ethanol+R (5g/kg body weight+50mg/kg body weight)-group 3 (via oral gavage) for 35 days. Results showed that exposure to ethanol significantly (p<0.0001) reduced spontaneous alternation in the Y-maze and increased immobility time in the tail suspension test (TST), which indicates cognitive impairment and depressive-like behavior in rats. We observed increased IDO activity/expression, and inflammatory responses, with attendant disruption in antioxidant systems and concomitant elevation in malondialdehyde (MDA) levels in the cerebral cortex and hippocampus. Following rutin co-exposure, an ethanol-mediated increase in indoleamine 2,3-dioxygenase [IDO] activity/expression and decrease in antioxidant enzymes, in addition to an increase in markers of inflammatory response and MDA production, was significantly (p<0.0001) prevented compared with controls. Additionally, altered behavioral indices were prevented by rutin co-exposure. Taken together, these findings reveal the involvement of the indoleaminergic pathway in rutin preventive influence against ethanol-induced cognitive impairment and depressive-like behavior in rats.

Interferon-gamma Mediated Metabolic Pathways in Hospitalized Patients During Acute and Reconvalescent COVID-19.

Fatigue, sleep disturbance, and neurological symptoms during and after COVID-19 are common and might be associated with inflammation-induced changes in tryptophan (Trp) and phenylalanine (Phe) metabolism. This pilot study investigated interferon gamma inducible biochemical pathways (namely Trp catabolism, neopterin, tyrosine [Tyr], and nitrite formation) during acute COVID-19 and reconvalescence. Thirty one patients with moderate to severe COVID-19 admitted to the University Hospital of Innsbruck in early 2020 (March-May) were followed up. Neurotransmitter precursors Trp, Phe, Tyr as well as kynurenine (Kyn), neopterin, nitrite, and routine laboratory parameters were analyzed during acute infection and at a follow-up (FU) 60 days thereafter. Clinical symptoms of patients (neurological symptoms, fatigue, sleep disturbance) were recorded and associations with concentrations of laboratory parameters investigated. Almost half of the patients suffered from neurological symptoms (48.4%), the majority of patients experienced sleep difficulties (56.7%) during acute COVID-19. Fatigue was present in nearly all patients. C-reactive protein (CRP), interleukin-6 (IL-6), neopterin, Kyn, Phe concentrations were significantly increased, and Trp levels depleted during acute COVID-19. Patients with sleep impairment and neurological symptoms during acute illness presented with increased CRP and IL-6 concentrations, Trp levels were lower in patients with sleep disturbance. In general, inflammatory markers declined during reconvalescence. A high percentage of patients suffered from persistent symptoms at FU (neurological symptoms: 17.2%, fatigue: 51.7%, sleeping disturbance: 34.5%) and had higher CRP concentrations. Nitrite and Phe levels were lower in patients with sleeping difficulties at FU and Kyn/Trp ratio, as indicator of IDO activity, was significantly lower in patients with neurological symptoms compared to patients without them at FU. In summary, inflammation induced alterations of amino acid metabolism might be related to acute and persisting symptoms of COVID-19.

Role of 5-HT1A-mediated upregulation of brain indoleamine 2,3 dioxygenase 1 in the reduced antidepressant and antihyperalgesic effects of fluoxetine during maintenance treatment.

The reduced antidepressant and antihyperalgesic effects of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine during maintenance treatment has been reported, but little is known about the molecular mechanism of this phenomenon. In three comorbid pain and depression animal models (genetic predisposition, chronic social stress, arthritis), we showed that the fluoxetine's antidepressant and antihyperalgesic effects were reduced during the maintenance treatment. Fluoxetine exposure induced upregulation of the 5-hydroxytryptamine 1A (5-HT1A) auto-receptor and indoleamine 2,3 dioxygenase 1 (IDO1, a rate-limiting enzyme of tryptophan metabolism) in the brainstem dorsal raphe nucleus (DRN), which shifted the tryptophan metabolism away from the 5-HT biosynthesis. Mechanistically, IDO1 upregulation was downstream to fluoxetine-induced 5-HT1A receptor expression because 1) antagonism of the 5-HT1A receptor with WAY100635 or 5-HT1A receptor knockout blocked the IDO1 upregulation, and 2) inhibition of IDO1 activity did not block the 5-HT1A receptor upregulation following fluoxetine exposure. Importantly, inhibition of either the 5-HT1A receptor or IDO1 activity sustained the fluoxetine's antidepressant and antihyperalgesic effects, indicating that 5-HT1A-mediated IDO1 upregulation in the brainstem DRN contributed to the reduced antidepressant and antihyperalgesic effects of fluoxetine. These results suggest a new strategy to improving the therapeutic efficacy of SSRI during maintenance treatment.

Tryptophan Metabolism 'Hub' Gene Expression Associates with Increased Inflammation and Severe Disease Outcomes in COVID-19 Infection and Inflammatory Bowel Disease.

The epithelial barrier's primary role is to protect against entry of foreign and pathogenic elements. Both COVID-19 and Inflammatory Bowel Disease (IBD) show commonalities in symptoms and treatment with sensitization of the epithelial barrier inviting an immune response. In this study we use a multi-omics strategy to identify a common signature of immune disease that may be able to predict for more severe patient outcomes. Global proteomic approaches were applied to transcriptome and proteome. Further semi- and relative- quantitative targeted mass spectrometry methods were developed to substantiate the proteomic and metabolomics changes in nasal swabs from healthy, COVID-19 (24 h and 3 weeks post infection); serums from Crohn's disease patients (scored for epithelial leak), terminal ileum tissue biopsies (patient matched inflamed and non-inflamed regions, and controls). We found that the tryptophan/kynurenine metabolism pathway is a 'hub' regulator of canonical and non-canonical transcription, macrophage release of cytokines and significant changes in the immune and metabolic status with increasing severity and disease course. Significantly modified pathways include stress response regulator EIF2 signaling (p = 1 × 10-3); energy metabolism, KYNU (p = 4 × 10-4), WARS (p = 1 × 10-7); inflammation, and IDO activity (p = 1 × 10-6). Heightened levels of PARP1, WARS and KYNU are predictive at the acute stage of infection for resilience, while in contrast, levels remained high and are predictive of persistent and more severe outcomes in COVID disease. Generation of a targeted marker profile showed these changes in immune disease underlay resolution of epithelial barrier function and have the potential to define disease trajectory and more severe patient outcomes.

Triple blockade of Ido-1, PD-L1 and MEK as a potential therapeutic strategy in NSCLC

BackgroundDespite the recent progress in the treatment and outcome of Non Small Cell Lung Cancer (NSCLC), immunotherapy has still significant limitations reporting a significant proportion of patients not benefiting from therapy, even in patients with high PD-L1 expression. We have previously demonstrated that the combined inhibition of MEK and PD-L1 in NSCLC patients derived three dimensional cultures exerted significant synergistic effect in terms of immune-dependent cancer cell death. However, subsequent experiments analyzing the expression of Indoleamine 2,3-dioxygenase-1 (Ido-1) gene expression demonstrated that Ido-1 resulted unaffected by the MEK inhibition and even increased after the combined inhibition of MEK and PD-L1 thus representing a potential escape mechanism to this combination.MethodsWe analyzed transcriptomic profile of NSCLC lung adenocarcinoma cohort of TCGA (The Cancer Genome Atlas), stratifying tumors based on EMT (Epithelial mesenchymal Transition) score; in parallel, we investigated the activation of Ido-1 pathway and modulation of immune cytokines productions both in NSCLC cells lines, in peripheral blood mononuclear cells (PBMCs) and in ex-vivo NSCLC spheroids induced by triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor.ResultsIn NSCLC lung adenocarcinoma patient cohort (from TCGA) Ido-1 gene expression was significantly higher in samples classified as mesenchymal according EMT score. Similarly, on a selected panel of NSCLC cell lines higher expression of MEK and Ido-1 related genes was detected in cells with mesenchymal phenotype according EMT score, thus suggesting a potential correlation of co-activation of these two pathways in the context of EMT, with cancer cells sustaining an immune-suppressive microenvironment. While exerting an antitumor activity, the dual blockade of MEK and PD-L1 enhances the secretion of pro-inflammatory cytokines (IFNγ, TNFα, IL-12 and IL-6) and, consequently, the expression of new immune checkpoints such as Ido-1. The triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor demonstrated significant antiproliferative and proapoptotic activity on ex-vivo NSCLC samples; at the same time the triple combination kept increased the levels of pro-inflammatory cytokines produced by both PBMCs and tumor spheroids in order to sustain the immune response and simultaneously decreased the expression of other checkpoint (such as CTLA-4, Ido-1 and TIM-3) thus promoting an immune-reactive and inflamed micro-environment.ConclusionsWe show that Ido-1 activation is a possible escape mechanism to immune-mediated cell death induced by combination of PD-L1 and MEK inhibitors: also, we show that triple combination of anti-PD-L1, anti-MEK and anti-Ido-1 drugs may overcome this negative feedback and restore anti-tumor immune response in NSCLC patients’ derived three dimensional cultures.