Cheminformatics analysis of indoleamine and tryptophan 2,3-dioxygenase inhibitors: A descriptor and fingerprint based machine learning approach to disclose selectivity measures.

Indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) are attractive drug targets for cancer immunotherapy. After disappointing results of the epacadostat as a selective IDO inhibitor in phase III clinical trials, there is much interest in the development of the TDO selective inhibitors. In the current study, several data analysis methods and machine learning approaches including logistic regression, Random Forest, XGBoost and Support Vector Machines were used to model a data set of compounds retrieved from ChEMBL. Models based on the Morgan fingerprints revealed notable fragments for the selective inhibition of the IDO, TDO or both. Multiple fragment docking was performed to find the best set of bound fragments and their orientation in the space for efficient linking. Linking the fragments and optimization of the final molecules were accomplished by means of an artificial intelligence generative framework. Finally, selectivity of the optimized molecules was assessed and the top 4 lead molecules were filtered through PAINS, Brenk and NIH filters. Results indicated that phenyloxalamide, fluoroquinoline, and 3-bromo-4-fluroaniline confer selectivity towards the IDO inhibition. Correspondingly, 1-benzyl-1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione was found to be an integral fragment for the selective inhibition of the TDO by constituting a coordination bond with the Fe atom of heme. In addition, furo[2,3-c]pyridine-2,3-diamine was found as a common fragment for inhibition of the both targets and can be used in the design of the dual target inhibitors of the IDO and TDO. The new fragments introduced here can be a useful building blocks for incorporation into the selective TDO or dual IDO/TDO inhibitors.

Kynurenines as a Novel Target for the Treatment of Inflammatory Disorders.

This review discusses the potential of targeting the kynurenine pathway (KP) in the treatment of inflammatory diseases. The KP, responsible for the catabolism of the amino acid tryptophan (TRP), produces metabolites that regulate various physiological processes, including inflammation, cell cycle, and neurotransmission. These metabolites, although necessary to maintain immune balance, may accumulate excessively during inflammation, leading to systemic disorders. Key KP enzymes such as indoleamine 2,3-dioxygenase 1 (IDO1), indoleamine 2,3-dioxygenase 2 (IDO2), tryptophan 2,3-dioxygenase (TDO), and kynurenine 3-monooxygenase (KMO) have been considered promising therapeutic targets. It was highlighted that both inhibition and activation of these enzymes may be beneficial, depending on the specific inflammatory disorder. Several inflammatory conditions, including autoimmune diseases, for which modulation of KP activity holds therapeutic promise, have been described in detail. Preclinical studies suggest that this modulation may be an effective treatment strategy for diseases for which treatment options are currently limited. Taken together, this review highlights the importance of further research on the clinical application of KP enzyme modulation in the development of new therapeutic strategies for inflammatory diseases.

Indoleamine 2,3-Dioxygenase Inhibitor Suppresses Colon Cancer Cell Migration, Invasion, and Epithelial-Mesenchymal Transition.

BACKGROUND/AIM: Indoleamine 2,3-dioxygenase 1 (IDO1) is a key enzyme in tryptophan metabolism and plays an important role in immunosuppression. The effects of IDO1 on tumor invasion and metastasis have been studied in several types of malignancies. However, the role of IDO1 in these steps in colorectal cancer (CRC) has not been elucidated. Therefore, we aimed to investigate the effects of IDO1 on invasion, migration, and epithelial-mesenchymal transition (EMT) in CRC cells. MATERIALS AND METHODS: All experiments were performed using the DLD-1 colon cancer cell line that expresses IDO1. We conducted a scratch wound healing assay and Boyden chamber assay to investigate the impact of IDO1 on DLD-1 cell migration and invasion, respectively, in the presence and absence of the IDO1 inhibitor L-1-methyl-tryptophan (L-1-MT). Additionally, western blotting was performed to analyze alterations in the expression of EMT-related markers caused by L-1-MT. RESULTS: High expression of IDO1 was confirmed in the cytoplasm of DLD-1 by immunofluorescence staining. In the scratch wound healing assay, the invasion ability of DLD-1 cells decreased to 62% after treatment with L-1-MT at 1,000 µM for 24 h. In the Boyden chamber assay, the migration of DLD-1 cells was suppressed by 85% after treatment with L-1-MT at 2,500 µM for 24 h. L-1-MT treatment increased the expression level of E-cadherin and decreased the expression levels of vimentin, Snail, and Slug. CONCLUSION: IDO1 inhibition reduced the invasion and migration ability of IDO1-expressing DLD-1 colon cancer cells, which was accompanied by altered expression of EMT-related proteins. IDO1 could be a potential target for the treatment of advanced CRC.

Immunohistochemical Detection of Indoleamine 2,3-Dioxygenase in Spontaneous Mammary Carcinomas of 96 Pet Rabbits.

For mammary carcinomas in pet rabbits, prognostic biomarkers are poorly defined, and treatment is limited to surgical excision. Additional treatment options are needed for rabbit patients for which surgery is not a suitable option. In human breast cancer, the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) represents a prognostic biomarker and possible therapeutic target. This retrospective immunohistochemical study examined IDO1 in 96 pet rabbit mammary carcinomas with known mitotic count, hormone receptor status, and percentage of stromal tumor infiltrating lymphocytes (TILs). Tumors were obtained from 96 pet rabbits with an average of 5.5 years. All rabbits with reported sex (n = 88) were female or female-spayed. Of the carcinomas, 94% expressed IDO1, and 86% had sparse TILs consistent with cold tumors. Statistically significant correlations existed between a higher percentage of IDO1-positive tumor cells, lower mitotic counts, and increased estrogen receptor expression. The threshold for significance was IDO1 staining in >10% of tumor cells. These results lead to the assumption that IDO1 expression contributes to tumorigenesis and may represent a prognostic biomarker and possible therapeutic target also in pet rabbit mammary carcinomas. They also support the value of rabbits for breast cancer research.

Interstitial Foci Expression of Indoleamine 2,3-Dioxygenase 1: A Potential Biomarker for Kidney Transplant Rejection.

(1) Background: Kidney transplantation is the best therapy for patients with end-stage renal disease, but the risk of rejection complicates it. Indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme involved in immune response modulation, has been suggested to play a role in transplant immunological injury. The aim of the study was to explore the expression of IDO1 in the interstitial foci of transplanted kidneys and its potential association with rejection episodes. (2) Methods: This retrospective study analysed kidney transplant biopsies from 121 patients, focusing on IDO1 expression in interstitial foci. Immunohistochemistry was used to detect IDO1, and patients were categorised based on IDO1 presence (IDO1-IF positive or negative). The incidence of rejection was compared between these groups. (3) Results: Patients with IDO1 expression in interstitial foci (IDO1-IF(+)) exhibited higher incidences of rejection 46/80 (57.5%) vs. 10/41 (24.34%) patients compared to IDO1-IF(-) patients, which was statistically significant with p = 0.0005. The analysis of antibody-mediated rejection showed that IDO1-IF(+) patients developed AMR at 12/80 (15%), while only 1 IDO1-IF(-) negative patient did (2,44%), with p = 0.035. T-cell-mediated rejection was also more common in IDO1-IF(+) patients 43/80 (53.75%) than in IDO1-IF(-) patients 7/41 (17.07%), with p = 0.0001. (4) Conclusions: IDO1 expression in interstitial foci of renal transplant biopsies is associated with a higher incidence of rejection, suggesting that IDO1 could serve as a potential biomarker for transplant rejection. These findings highlight the importance of IDO1 in immune regulation and its potential utility in improving the management of kidney transplant recipients.

IDO1 Inhibitor RY103 Suppresses Trp-GCN2-Mediated Angiogenesis and Counters Immunosuppression in Glioblastoma.

Glioma is characterized by strong immunosuppression and excessive angiogenesis. Based on existing reports, it can be speculated that the resistance to anti-angiogenic drug vascular endothelial growth factor A (VEGFA) antibody correlates to the induction of novel immune checkpoint indoleamine 2,3-dioxygenase 1 (IDO1), while IDO1 has also been suggested to be related to tumor angiogenesis. Herein, we aim to clarify the potential role of IDO1 in glioma angiogenesis and the mechanism behind it. Bioinformatic analyses showed that the expressions of IDO1 and angiogenesis markers VEGFA and CD34 were positively correlated and increased with pathological grade in glioma. IDO1-overexpression-derived-tryptophan depletion activated the general control nonderepressible 2 (GCN2) pathway and upregulated VEGFA in glioma cells. The tube formation ability of angiogenesis model cells could be inhibited by IDO1 inhibitors and influenced by the activity and expression of IDO1 in condition medium. A significant increase in serum VEGFA concentration and tumor CD34 expression was observed in IDO1-overexpressing GL261 subcutaneous glioma-bearing mice. IDO1 inhibitor RY103 showed positive anti-tumor efficacy, including the anti-angiogenesis effect and upregulation of natural killer cells in GL261 glioma-bearing mice. As expected, the combination of RY103 and anti-angiogenesis agent sunitinib was proved to be a better therapeutic strategy than either monotherapy.

Association of Indoleamine 2,3-Dioxygenase (IDO) Activity with Outcome after Cardiac Surgery in Adult Patients.

Indoleamine 2,3-deoxygenase (IDO) plays an important role in the catabolism of the amino acid tryptophan. Tryptophan and its metabolites are key immune modulators. Increased IDO activity has been observed in various diseases and is associated with worse clinical outcomes. However, comprehensive research regarding its role in cardiac surgery remains limited. Therefore, we aimed to investigate perioperative changes in IDO activity and pathway metabolites, along with their impact on clinical outcomes in adult patients undergoing cardiac surgery. As an observational cohort study conducted at the Inselspital in Bern from January to December 2019, we retrospectively analyzed the data of prospectively collected biobank samples of patients undergoing cardiac surgery with the use of cardiopulmonary bypass. IDO pathway metabolite analysis was conducted by mass spectrometry. Perioperative dynamics were descriptively assessed and associated with pre-defined clinical outcome measures (30-day mortality, 1-year mortality, incidence of stroke and myocardial infarction, and length of hospital stay) through a multi-step exploratory regression analysis. A cohort of 192 adult patients undergoing cardiac surgery with the use of cardiopulmonary bypass were included (median age 67.0, IQR 60.0-73.0, 75.5% male). A significant perioperative decrease in the kynurenine/tryptophan (Kyn/Trp) ratio (-2.298, 95% CI -4.028 to -596, p = 0.009) and significant perioperative dynamics in the associated metabolites was observed. No association of perioperative changes in IDO activity and pathway metabolites with clinical outcomes was found. A significant decrease in the Kyn/Trp ratio among adult patients undergoing cardiac surgery indicates a perioperative downregulation of IDO, which stands in contrast to other pro-inflammatory conditions. Further studies are needed to investigate IDO in the setting of perioperative immunomodulation, which is a key driver of postoperative complications in cardiac surgery patients.

Light-Triggered PROTAC Nanoassemblies for Photodynamic IDO Proteolysis in Cancer Immunotherapy.

While proteolysis-targeting chimeras (PROTACs) hold great potential for persistently reprogramming the immunosuppressive tumor microenvironment via targeted protein degradation, precisely activating them in tumor tissues and preventing uncontrolled proteolysis at off-target sites remain challenging. Herein, a light-triggered PROTAC nanoassembly (LPN) for photodynamic indoleamine 2,3-dioxygenase (IDO) proteolysis is reported. The LPN is derived from the self-assembly of prodrug conjugates, which comprise a PROTAC, cathepsin B-specific cleavable peptide linker, and photosensitizer, without any additional carrier materials. In colon tumor models, intravenously injected LPNs initially silence the activity of PROTACs and accumulate significantly in targeted tumor tissues due to an enhanced permeability and retention effect. Subsequently, the cancer biomarker cathepsin B begins to trigger the release of active PROTACs from the LPNs through enzymatic cleavage of the linkers. Upon light irradiation, tumor cells undergo immunogenic cell death induced by photodynamic therapy to promote the activation of effector T cells, while the continuous IDO degradation of PROTAC simultaneously blocks tryptophan metabolite-regulated regulatory-T-cell-mediated immunosuppression. Such LPN-mediated combinatorial photodynamic IDO proteolysis effectively inhibits tumor growth, metastasis, and recurrence. Collectively, this study presents a promising nanomedicine, designed to synergize PROTACs with other immunotherapeutic modalities, for more effective and safer cancer immunotherapy.

Kynurenine acts as a signaling molecule to attenuate pulmonary fibrosis by enhancing the AHR-PTEN axis.

INTRODUCTION: Pulmonary fibrosis (PF) is a fatal fibrotic lung disease without any options to halt disease progression. Feasible evidence suggests that aberrant metabolism of amino acids may play a role in the pathoetiology of PF. However, the exact impact of kynurenine (Kyn), a metabolite derived from tryptophan (Trp) on PF is yet to be addressed. OBJECTIVES: This study aims to elucidate the role of kynurenine in both the onset and advancement of PF. METHODS: Liquid chromatography-tandem mass spectrometry was employed to assess Kyn levels in patients with idiopathic PF and PF associated with Sjögren's syndrome. Additionally, a mouse model of PF induced by bleomycin was utilized to study the impact of Kyn administration. Furthermore, cell models treated with TGF-ß1 were used to explore the mechanism by which Kyn inhibits fibroblast functions. RESULTS: We demonstrated that high levels of Kyn are a clinical feature in both idiopathic PF patients and primary Sjögren syndrome associated PF patients. Further studies illustrated that Kyn served as a braking molecule to suppress fibroblast functionality, thereby protecting mice from bleomycin-induced lung fibrosis. The protective effects depend on AHR, in which Kyn induces AHR nuclear translocation, where it upregulates PTEN expression to blunt TGF-ß mediated AKT/mTOR signaling in fibroblasts. However, in fibrotic microenviroment, the expression of AHR is repressed by methyl-CpG-binding domain 2 (MBD2), a reader interpreting the effect of DNA methylation, which results in a significantly reduced sensitivity of Kyn to fibroblasts. Therefore, exogenous administration of Kyn substantially reversed established PF. CONCLUSION: Our studies not only highlighted a critical role of Trp metabolism in PF pathogenesis, but also provided compelling evidence suggesting that Kyn could serve as a promising metabolite against PF.

Reprogrammed IDO-Induced Immunosuppressive Microenvironment Synergizes with Immunogenic Magnetothermodynamics for Improved Cancer Therapy.

Indoleamine 2,3-dioxygenase (IDO), highly expressed in hepatocellular carcinoma (HCC), plays a pivotal role in creating an immune-suppressive tumor microenvironment. Inhibiting IDO activity has emerged as a promising immunotherapeutic strategy; however, the delivery of IDO inhibitors to the tumor site is constrained, limiting their therapeutic efficacy. In this study, we developed a magnetic vortex nanodelivery system for the targeted delivery of the IDO inhibitor NLG919, integrated with magnetic hyperthermia therapy to reverse the immune-suppressive microenvironment of liver cancer and inhibit tumor growth. This system comprises thermoresponsive polyethylenimine-coated ferrimagnetic vortex-domain iron oxide nanorings (PI-FVIOs) loaded with NLG919 (NLG919/PI-FVIOs). Under thermal effects, NLG919 can be precisely released from the delivery system, counteracting IDO-mediated immune suppression and synergizing with NLG919/PI-FVIOs-mediated magnetothermodynamic (MTD) therapy-induced immunogenic cell death (ICD), resulting in effective HCC suppression. In vivo studies demonstrate that this combination therapy significantly inhibits tumor growth and metastasis by enhancing the accumulation of cytotoxic T lymphocytes and suppressing regulatory T cells within the tumor. Overall, our findings reveal that NLG919/PI-FVIOs can induce a potent antitumor immune response by disrupting the IDO pathway and activating the ICD, offering a promising therapeutic avenue for HCC treatment.

Biomimetic Hydrogel-Mediated Mechano-Immunometabolic Therapy for Inhibition of ccRCC Recurrence After Surgery.

The unique physical tumor microenvironment (TME) and aberrant immune metabolic status are two obstacles that must be overcome in cancer immunotherapy to improve clinical outcomes. Here, an in situ mechano-immunometabolic therapy involving the injection of a biomimetic hydrogel is presented with sequential release of the anti-fibrotic agent pirfenidone, which softens the stiff extracellular matrix, and small interfering RNA IDO1, which disrupts kynurenine-mediated immunosuppressive metabolic pathways, together with the multi-kinase inhibitor sorafenib, which induces immunogenic cell death. This combination synergistically augmented tumor immunogenicity and induced anti-tumor immunity. In mouse models of clear cell renal cell carcinoma, a single-dose peritumoral injection of a biomimetic hydrogel facilitated the perioperative TME toward a more immunostimulatory landscape, which prevented tumor relapse post-surgery and prolonged mouse survival. Additionally, the systemic anti-tumor surveillance effect induced by local treatment decreased lung metastasis by inhibiting epithelial-mesenchymal transition conversion. The versatile localized mechano-immunometabolic therapy can serve as a universal strategy for conferring efficient tumoricidal immunity in "cold" tumor postoperative interventions.

Taking advantage of the interaction between the sulfoxide and heme cofactor to develop indoleamine 2, 3-dioxygenase 1 inhibitors.

Taking advantage of key interactions between sulfoxide and heme cofactor, we used the sulfoxide as the anchor functional group to develop two series of indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitors: 2-benzylsulfinylbenzoxazoles (series 1) and 2-phenylsulfinylbenzoxazoles (series 2). In vitro enzymatic screening shows that both series can inhibit the activity of IDO1 in low micromolar (series 1) or nanomolar (series 2) levels. They also show inhibitory selectivity between IDO1 and tryptophan 2, 3-dioxygenase 2. Interestingly, although series 1 is less potent IDO1 inhibitors of these two series, it exhibited stronger inhibitory activity toward kynurenine production in interferon-γ stimulated BxPC-3 cells. Enzyme kinetics and binding studies demonstrated that 2-sulfinylbenzoxazoles are non-competitive inhibitors of tryptophan, and they interact with the ferrous form of heme. These results demonstrated 2-sulfinylbenzoxazoles as type II IDO1 inhibitors. Furthermore, molecular docking studies supports the sulfoxide being of the key functional group that interacts with the heme cofactor. Compound 22 (series 1) can inhibit NO production in a concentration dependent manner in lipopolysaccharides (LPS) stimulated RAW264.7 cells, and can relieve pulmonary edema and lung injury in LPS induced mouse acute lung injury models.

Design, synthesis and biological evaluation of novel quinazoline derivatives as immune checkpoint inhibitors.

In this work, we report 14 novel quinazoline derivatives as immune checkpoint inhibitors, IDO1 and PD-L1. The antitumor screening of synthesized compounds on ovarian cancer cells indicated that compound V-d and V-l showed the most activity with IC50 values of about 5 µM. Intriguingly, compound V-d emerges as a stand out, triggering cell death through caspase-dependent and caspase-independent manners. More importantly, V-d presents its ability to hinder tumor sphere formation and re-sensitized cisplatin-resistant A2780 cells to cisplatin treatment. These findings suggest that compound V-d emerges as a promising lead candidate for the future development of immuno anticancer agents.

IDO1 promotes CSFV replication by mediating tryptophan metabolism to inhibit NF-κB signaling.

Tryptophan metabolism plays a crucial role in facilitating various cellular processes essential for maintaining normal cellular function. Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the conversion of tryptophan (Trp) into kynurenine (Kyn), thereby initiating the degradation of Trp. The resulting Kyn metabolites have been implicated in the modulation of immune responses. Currently, the role of IDO1-mediated tryptophan metabolism in the process of viral infection remains relatively unknown. In this study, we discovered that classical swine fever virus (CSFV) infection of PK-15 cells can induce the expression of IDO1, thereby promoting tryptophan metabolism. IDO1 can negatively regulate the NF-κB signaling by mediating tryptophan metabolism, thereby facilitating CSFV replication. We found that silencing the IDO1 gene enhances the expression of IFN-α, IFN-ß, and IL-6 by activating the NF-κB signaling pathway. Furthermore, our observations indicate that both silencing the IDO1 gene and administering exogenous tryptophan can inhibit CSFV replication by counteracting the cellular autophagy induced by Rapamycin. This study reveals a novel mechanism of IDO1-mediated tryptophan metabolism in CSFV infection, providing new insights and a theoretical basis for the treatment and control of CSFV.IMPORTANCEIt is well known that due to the widespread use of vaccines, the prevalence of classical swine fever (CSF) is shifting towards atypical and invisible infections. CSF can disrupt host metabolism, leading to persistent immune suppression in the host and causing significant harm when co-infected with other diseases. Changes in the host's metabolic profiles, such as increased catabolic metabolism of amino acids and the production of immunoregulatory metabolites and their derivatives, can also influence virus replication. Mammals utilize various pathways to modulate immune responses through amino acid utilization, including increased catabolic metabolism of amino acids and the production of immunoregulatory metabolites and their derivatives, thereby limiting viral replication. Therefore, this study proposes that targeting the modulation of tryptophan metabolism may represent an effective approach to control the progression of CSF.

Tryptophan deficiency induced by indoleamine 2,3-dioxygenase 1 results in glucose transporter 1-dependent promotion of aerobic glycolysis in pancreatic cancer.

Indoleamine 2,3-dioxygenase 1 (IDO1), the key enzyme in the catabolism of the essential amino acid tryptophan (Trp) through kynurenine pathway, induces immune tolerance and is considered as a critical immune checkpoint, but its impacts as a metabolism enzyme on glucose and lipid metabolism are overlooked. We aim to clarify the potential role of IDO1 in aerobic glycolysis in pancreatic cancer (PC). Analysis of database revealed the positive correlation in PC between the expressions of IDO1 and genes encoding important glycolytic enzyme hexokinase 2 (HK2), pyruvate kinase (PK), lactate dehydrogenase A (LDHA) and glucose transporter 1 (GLUT1). It was found that IDO1 could modulate glycolysis and glucose uptake in PC cells, Trp deficiency caused by IDO1 overexpression enhanced glucose uptake by stimulating GLUT1 translocation to the plasma membrane of PC cells. Besides, Trp deficiency caused by IDO1 overexpression suppressed the apoptosis of PC cells via promoting glycolysis, which reveals the presence of IDO1-glycolysis-apoptosis axis in PC. IDO1 inhibitors could inhibit glycolysis, promote apoptosis, and exhibit robust therapeutic efficacy when combined with GLUT1 inhibitor in PC mice. Our study reveals the function of IDO1 in the glucose metabolism of PC and provides new insights into the therapeutic strategy for PC.

VEEV TC-83 Triggers Dysregulation of the Tryptophan-Kynurenine Pathway in the Central Nervous System That Correlates with Cognitive Impairment in Tg2576 Mice.

Neurodegenerative diseases are chronic conditions affecting the central nervous system (CNS). Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid beta in the limbic and cortical brain regions. AD is presumed to result from genetic abnormalities or environmental factors, including viral infections, which may have deleterious, long-term effects. In this study, we demonstrate that the Venezuelan equine encephalitis virus (VEEV) commonly induces neurodegeneration and long-term neurological or cognitive sequelae. Notably, the effects of VEEV infection can persistently influence gene expression in the mouse brain, suggesting a potential link between the observed neurodegenerative outcomes and long-term alterations in gene expression. Additionally, we show that alphavirus encephalitis exacerbates the neuropathological profile of AD through crosstalk between inflammatory and kynurenine pathways, generating a range of metabolites with potent effects. Using a mouse model for ß-amyloidosis, Tg2576 mice, we found that cognitive deficits and brain pathology were more severe in Tg2576 mice infected with VEEV TC-83 compared to mock-infected controls. Thus, during immune activation, the kynurenine pathway plays a more active role in the VEEV TC-83-infected cells, leading to increases in the abundance of transcripts related to the kynurenine pathway of tryptophan metabolism. This pathway generates several metabolites with potent effects on neurotransmitter systems as well as on inflammation, as observed in VEEV TC-83-infected animals.

Exploring a repurposed candidate with dual hIDO1/hTDO2 inhibitory potential for anticancer efficacy identified through pharmacophore-based virtual screening and in vitro evaluation.

Discovering effective anti-cancer agents poses a formidable challenge given the limited efficacy of current therapeutic modalities against various cancer types due to intrinsic resistance mechanisms. Cancer immunochemotherapy is an alternative strategy for breast cancer treatment and overcoming cancer resistance. Human Indoleamine 2,3-dioxygenase (hIDO1) and human Tryptophan 2,3-dioxygenase 2 (hTDO2) play pivotal roles in tryptophan metabolism, leading to the generation of kynurenine and other bioactive metabolites. This process facilitates the de novo synthesis of Nicotinamide Dinucleotide (NAD), promoting cancer resistance. This study identified a new dual hIDO1/hTDO2 inhibitor using a drug repurposing strategy of FDA-approved drugs. Herein, we delineate the development of a ligand-based pharmacophore model based on a training set of 12 compounds with reported hIDO1/hTDO2 inhibitory activity. We conducted a pharmacophore search followed by high-throughput virtual screening of 2568 FDA-approved drugs against both enzymes, resulting in ten hits, four of them with high potential of dual inhibitory activity. For further in silico and in vitro biological investigation, the anti-hypercholesterolemic drug Pitavastatin deemed the drug of choice in this study. Molecular dynamics (MD) simulations demonstrated that Pitavastatin forms stable complexes with both hIDO1 and hTDO2 receptors, providing a structural basis for its potential therapeutic efficacy. At nanomolar (nM) concentration, it exhibited remarkable in vitro enzyme inhibitory activity against both examined enzymes. Additionally, Pitavastatin demonstrated potent cytotoxic activity against BT-549, MCF-7, and HepG2 cell lines (IC50 = 16.82, 9.52, and 1.84 µM, respectively). Its anticancer activity was primarily due to the induction of G1/S phase arrest as discovered through cell cycle analysis of HepG2 cancer cells. Ultimately, treating HepG2 cancer cells with Pitavastatin affected significant activation of caspase-3 accompanied by down-regulation of cellular apoptotic biomarkers such as IDO, TDO, STAT3, P21, P27, IL-6, and AhR.

Indoleamine 2,3-dioxygenase (IDO1) - Can dendritic cells and monocytes expressing this moonlight enzyme change the phase of Parkinson's Disease?

Parkinson's Disease (PD) is the second most common neurodegenerative disease where central and peripheral immune dysfunctions have been pointed out as a critical component of susceptibility and progression of this disease. Dendritic cells (DCs) and monocytes are key players in promoting immune response regulation and can induce the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) under pro-inflammatory environments. This enzyme with catalytic and signaling activity supports the axis IDO1-KYN-aryl hydrocarbon receptor (AhR), promoting disease-specific immunomodulatory effects. IDO1 is a rate-limiting enzyme of the kynurenine pathway (KP) that begins tryptophan (Trp) catabolism across this pathway. The immune functions of the pathway, which are extensively described in cancer, have been forgotten so far in neurodegenerative diseases, where a chronic inflammatory environment underlines the progression of the disease. Despite dysfunctions of KP have been described in PD, these are mainly associated with neurotoxic functions. With this review, we aim to focus on the immune properties of IDO1+DCs and IDO1+monocytes as a possible strategy to balance the pro-inflammatory profile described in PD. We also highlight the importance of exploring the role of dopaminergic therapeutics in IDO1 modulation to possibly optimize current PD therapeutic strategies.

Derangements of immunological proteins in HIV-associated diffuse large B-cell lymphoma: the frequency and prognostic impact.

Introduction: Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy of B-cells frequently encountered among people living with HIV. Immunological abnormalities are common in immunocompetent individuals with DLBCL, and are often associated with poorer outcomes. Currently, data on derangements of immunological proteins, such as cytokines and acute phase reactants, and their impact on outcomes in HIV-associated DLBCL (HIV-DLBCL) is lacking. This study assessed the levels and prognostic relevance of interleukin (IL)-6, IL-10 and Transforming Growth Factor Beta (TGFß), the acute phase proteins C-reactive protein (CRP) and ferritin; serum free light chains (SFLC) (elevation of which reflects a prolonged pro-inflammatory state); and the activity of the immunosuppressive enzyme Indoleamine 2,3-dioxygenase (IDO)in South African patients with DLBCL. Methods: Seventy-six patients with incident DLBCL were enrolled, and peripheral blood IL-6, IL-10, TGFß, SFLC and IDO-activity measured in selected patients. Additional clinical and laboratory findings (including ferritin and CRP) were recorded from the hospital records. Results: Sixty-one (80.3%) of the included patients were people living with HIV (median CD4-count = 148 cells/ul), and survival rates were poor (12-month survival rate 30.0%). The majority of the immunological proteins, except for TGFß and ferritin, were significantly higher among the people living with HIV. Elevation of IL-6, SFLC and IDO-activity were not associated with survival in HIV-DLBCL, while raised IL-10, CRP, ferritin and TGFß were. On multivariate analysis, immunological proteins associated with survival independently from the International Prognostic Index (IPI) included TGFß, ferritin and IL-10. Conclusion: Derangements of immunological proteins are common in HIV-DLBCL, and have a differential association with survival compared to that reported elsewhere. Elevation of TGFß, IL-10 and ferritin were associated with survival independently from the IPI. In view of the poor survival rates in this cohort, investigation of the directed targeting of these cytokines would be of interest in our setting.

The Role of the Placental Enzyme Indoleamine 2,3-Dioxygenase in Normal and Abnormal Human Pregnancy.

The biologically significant phenomenon that the fetus can survive immune attacks from the mother has been demonstrated in mammals. The survival mechanism depends on the fetus and placenta actively defending themselves against attacks by maternal T cells, achieved through the localized depletion of the amino acid L-tryptophan by an enzyme called indoleamine 2,3-dioxygenase. These findings were entirely unexpected and pose important questions regarding diseases related to human pregnancy and their prevention during human pregnancy. Specifically, the role of this mechanism, as discovered in mice, in humans remains unknown, as does the extent to which impaired activation of this process contributes to major clinical diseases in humans. We have, thus, elucidated several key aspects of this enzyme expressed in the human placenta both in normal and abnormal human pregnancy. The questions addressed in this brief review are as follows: (1) localization and characteristics of human placental indoleamine 2,3-dioxygenas; (2) overall tryptophan catabolism in human pregnancy and a comparison of indoleamine 2,3-dioxygenase expression levels between normal and pre-eclamptic pregnancy; (3) controlling trophoblast invasion by indoleamine 2,3-dioxygenase and its relation to the pathogenesis of placenta accrete spectrum.