Tryptophan Metabolism in Obesity: The Indoleamine 2,3-Dioxygenase-1 Activity and Therapeutic Options.

Obesity activates both innate and adaptive immune responses in adipose tissue. Adipose tissue macrophages are functional antigen-presenting cells that promote the proliferation of interferon-gamma (IFN-γ)-producing cluster of differentiation (CD)4+ T cells in adipose tissue of obese subjects. The increased formation of neopterin and degradation of tryptophan may result in decreased T-cell responsiveness and lead to immunodeficiency. The activity of inducible indoleamine 2,3-dioxygenase-1 (IDO1) plays a major role in pro-inflammatory, IFN-γ-dominated settings. The expression of several kynurenine pathway enzyme genes is significantly increased in obesity. IDO1 in obesity shifts tryptophan metabolism from serotonin and melatonin synthesis to the formation of kynurenines and increases the ratio of kynurenine to tryptophan as well as with neopterin production. Reduction in serotonin (5-hydroxytryptamine; 5-HT) production provokes satiety dysregulation that leads to increased caloric uptake and obesity. According to the monoamine-deficiency hypothesis, a deficiency of cerebral serotonin is involved in neuropsychiatric symptomatology of depression, mania, and psychosis. Indeed, bipolar disorder (BD) and related cognitive deficits are accompanied by a higher prevalence of overweight and obesity. Furthermore, the accumulation of amyloid-ß in Alzheimer's disease brains has several toxic effects as well as IDO induction. Hence, abdominal obesity is associated with vascular endothelial dysfunction. kynurenines and their ratios are prognostic parameters in coronary artery disease. Increased kynurenine/tryptophan ratio correlates with increased intima-media thickness and represents advanced atherosclerosis. However, after bariatric surgery, weight reduction does not lead to the normalization of IDO1 activity and atherosclerosis. IDO1 is involved in the mechanisms of immune tolerance and in the concept of tumor immuno-editing process in cancer development. Serum IDO1 activity is still used as a parameter in cancer development and growth. IDO-producing tumors show a high total IDO immunostaining score, and thus, using IDO inhibitors, such as Epacadostat, Navoximod, and L isomer of 1-methyl-tryptophan, seems an important modality for cancer treatment. There is an inverse correlation between serum folate concentration and body mass index, thus folate deficiency leads to hyperhomocysteinemia-induced oxidative stress. Immune checkpoint blockade targeting cytotoxic T-lymphocyte-associated protein-4 synergizes with imatinib, which is an inhibitor of mitochondrial folate-mediated one-carbon (1C) metabolism. Antitumor effects of imatinib are enhanced by increasing T-cell effector function in the presence of IDO inhibition. Combining IDO targeting with chemotherapy, radiotherapy and/or immunotherapy, may be an effective tool against a wide range of malignancies. However, there are some controversial results regarding the efficacy of IDO1 inhibitors in cancer treatment.

Prognostic relevance of high expression of kynurenine pathway markers in glioblastoma.

Glioblastoma (GBM) continues to exhibit a discouraging survival rate despite extensive research into new treatments. One factor contributing to its poor prognosis is the tumor's immunosuppressive microenvironment, in which the kynurenine pathway (KP) plays a significant role. This study aimed to explore how KP impacts the survival of newly diagnosed GBM patients. We examined tissue samples from 108 GBM patients to assess the expression levels of key KP markers-tryptophan 2,3-dioxygenase (TDO2), indoleamine 2,3-dioxygenase (IDO1/2), and the aryl hydrocarbon receptor (AhR). Using immunohistochemistry and QuPath software, three tumor cores were analyzed per patient to evaluate KP marker expression. Kaplan-Meier survival analysis and stepwise multivariate Cox regression were used to determine the effect of these markers on patient survival. Results showed that patients with high expression of TDO2, IDO1/2, and AhR had significantly shorter survival times. This finding held true even when controlling for other known prognostic variables, with a hazard ratio of 3.393 for IDO1, 2.775 for IDO2, 1.891 for TDO2, and 1.902 for AhR. We suggest that KP markers could serve as useful tools for patient stratification, potentially guiding future immunomodulating trials and personalized treatment approaches for GBM patients.

AT-0174, a novel dual IDO1/TDO2 enzyme inhibitor, synergises with temozolomide to improve survival in an orthotopic mouse model of glioblastoma.

BACKGROUND: Glioblastoma is an aggressive brain cancer, usually of unknown etiology, and with a very poor prognosis. Survival from diagnosis averages only 3 months if left untreated and this only increases to 12-15 months upon treatment. Treatment options are currently limited and typically comprise radiotherapy plus a course of the DNA-alkylating chemotherapeutic temozolomide. Unfortunately, the disease invariably relapses after several months of treatment with temozolomide, due to the development of resistance to the drug. Increased local tryptophan metabolism is a feature of many solid malignant tumours through increased expression of tryptophan metabolising enzymes. Glioblastomas are notable for featuring increased expression of the tryptophan catabolizing enzymes indole-2,3-dioxygenase-1 (IDO1), and especially tryptophan-2,3-dioxygenase-2 (TDO2). Increased IDO1 and TDO2 activity is known to suppress the cytotoxic T cell response to tumour cells, and this has led to the proposal that the IDO1 and TDO2 enzymes represent promising immuno-oncology targets. In addition to immune modulation, however, recent studies have also identified the activity of these enzymes is important in the development of resistance to chemotherapeutic agents. METHODS: In the current study, the efficacy of a novel dual inhibitor of IDO1 and TDO2, AT-0174, was assessed in an orthotopic mouse model of glioblastoma. C57BL/6J mice were stereotaxically implanted with GL261(luc2) cells into the striatum and then administered either vehicle control, temozolomide (8 mg/kg IP; five 8-day cycles of treatment every 2 days), AT-0174 (120 mg/kg/day PO) or both temozolomide + AT-0174, all given from day 7 after implantation. RESULTS: Temozolomide decreased tumour growth and improved median survival but increased the infiltration of CD4+ Tregs. AT-0174 had no significant effect on tumour growth or survival when given alone, but provided clear synergy in combination with temozolomide, further decreasing tumour growth and significantly improving survival, as well as elevating CD8+ T cell expression and decreasing CD4+ Treg infiltration. CONCLUSION: AT-0174 exhibited an ideal profile for adjunct treatment of glioblastomas with the first-line chemotherapeutic drug temozolomide to prevent development of CD4+ Treg-mediated chemoresistance.

DEC-DRR: deep ensemble of classification model for diabetic retinopathy recognition.

Most diabetes patients are liable to have diabetic retinopathy (DR); however, the majority of them might not be even aware of the ailment. Therefore, early detection and treatment of DR are necessary to prevent vision loss. But, avoiding DR is not a simple process. An ophthalmologist can typically identify DR through an optical evaluation of the fundus and through the evaluation of color pictures. However, due to the increased count of DR patients, this could not be possible as it consumes more time. To rectify this problem, a novel deep ensemble-based DR classification technique is developed in this work. Initially, a Wiener filter (WF) is applied for preprocessing the image. Then, the enhanced U-Net-based segmentation process is done. Subsequent to the segmentation process, features are extracted that include statistical features, inferior superior nasal temporal (ISNT), cup to disc ratio (CDR), and improved LGBP as well. Further, deep ensemble classifiers (DEC) like CNN, Bi-GRU, and DMN are used to recognize the disease. The outcomes from DMN, CNN, and Bi-GRU are then subjected to improved SLF. Additionally, the weights of DMN, CNN, and Bi-GRU are adjusted via pelican updated Tasmanian devil optimization (PU-TDO). Finally, outputs on DR (microaneurysms, hemorrhages, hard exudates, and soft exudates) are obtained. The performance of DEC + PU-TDO for diabetic retinopathy is computed over extant models with regard to different measures for four datasets. The results on accuracy using the DEC + PU-TDO scheme for the IDRID dataset is maximum around 0.975 at 90th LP while other models have less accuracy. The FPR of DEC + PU-TDO is less around 0.039 at the 90th LP for the SUSTech-SYSU dataset, while other extant models have maximum FPR.

A Review of the Evidence for Tryptophan and the Kynurenine Pathway as a Regulator of Stem Cell Niches in Health and Disease.

Stem cells are ubiquitously found in various tissues and organs in the body, and underpin the body's ability to repair itself following injury or disease initiation, though repair can sometimes be compromised. Understanding how stem cells are produced, and functional signaling systems between different niches is critical to understanding the potential use of stem cells in regenerative medicine. In this context, this review considers kynurenine pathway (KP) metabolism in multipotent adult progenitor cells, embryonic, haematopoietic, neural, cancer, cardiac and induced pluripotent stem cells, endothelial progenitor cells, and mesenchymal stromal cells. The KP is the major enzymatic pathway for sequentially catabolising the essential amino acid tryptophan (TRP), resulting in key metabolites including kynurenine, kynurenic acid, and quinolinic acid (QUIN). QUIN metabolism transitions into the adjoining de novo pathway for nicotinamide adenine dinucleotide (NAD) production, a critical cofactor in many fundamental cellular biochemical pathways. How stem cells uptake and utilise TRP varies between different species and stem cell types, because of their expression of transporters and responses to inflammatory cytokines. Several KP metabolites are physiologically active, with either beneficial or detrimental outcomes, and evidence of this is presented relating to several stem cell types, which is important as they may exert a significant impact on surrounding differentiated cells, particularly if they metabolise or secrete metabolites differently. Interferon-gamma (IFN-γ) in mesenchymal stromal cells, for instance, highly upregulates rate-limiting enzyme indoleamine-2,3-dioxygenase (IDO-1), initiating TRP depletion and production of metabolites including kynurenine/kynurenic acid, known agonists of the Aryl hydrocarbon receptor (AhR) transcription factor. AhR transcriptionally regulates an immunosuppressive phenotype, making them attractive for regenerative therapy. We also draw attention to important gaps in knowledge for future studies, which will underpin future application for stem cell-based cellular therapies or optimising drugs which can modulate the KP in innate stem cell populations, for disease treatment.

Amelioration of Neurochemical Alteration and Memory and Depressive Behavior in Sepsis by Allopurinol, a Tryptophan 2,3-Dioxygenase Inhibitor.

BACKGROUND: In response to inflammation and other stressors, tryptophan is catalyzed by Tryptophan 2,3-Dioxygenase (TDO), which leads to activation of the kynurenine pathway. Sepsis is a serious condition in which the body responds improperly to an infection, and the brain is the inflammation target in this condition. OBJECTIVE: This study aimed to determine if the induction of TDO contributes to the permeability of the Blood-Brain Barrier (BBB), mortality, neuroinflammation, oxidative stress, and mitochondrial dysfunction, besides long-term behavioral alterations in a preclinical model of sepsis. METHODS: Male Wistar rats with two months of age were submitted to the sepsis model using Cecal Ligation and Perforation (CLP). The rats received allopurinol (Allo, 20 mg/kg, gavage), a TDO inhibitor, or a vehicle once a day for seven days. RESULTS: Sepsis induction increased BBB permeability, IL-6 level, neutrophil infiltrate, nitric oxide formation, and oxidative stress, resulting in energy impairment in 24h after CLP and Allo administration restored these parameters. Regarding memory, Allo restored short-term memory impairment and decreased depressive behavior. However, no change in survival rate was verified. CONCLUSION: In summary, TDO inhibition effectively prevented depressive behavior and memory impairment 10 days after CLP by reducing acute BBB permeability, neuroinflammation, oxidative stress, and mitochondrial alteration.

IoT-based external attacks aware secure healthcare framework using blockchain and SB-RNN-NVS-FU techniques.

BACKGROUND: In recent times, there has been widespread deployment of Internet of Things (IoT) applications, particularly in the healthcare sector, where computations involving user-specific data are carried out on cloud servers. However, the network nodes in IoT healthcare are vulnerable to an increased level of security threats. OBJECTIVE: This paper introduces a secure Electronic Health Record (EHR) framework with a focus on IoT. METHODS: Initially, the IoT sensor nodes are designated as registered patients and undergo initialization. Subsequently, a trust evaluation is conducted, and the clustering of trusted nodes is achieved through the application of Tasmanian Devil Optimization (STD-TDO) utilizing the Student's T-Distribution. Utilizing the Transposition Cipher-Squared random number generator-based-Elliptic Curve Cryptography (TCS-ECC), the clustered nodes encrypt four types of sensed patient data. The resulting encrypted data undergoes hashing and is subsequently added to the blockchain. This configuration functions as a network, actively monitored to detect any external attacks. To accomplish this, a feature reputation score is calculated for the network's features. This score is then input into the Swish Beta activated-Recurrent Neural Network (SB-RNN) model to classify potential attacks. The latest transactions on the blockchain are scrutinized using the Neutrosophic Vague Set Fuzzy (NVS-Fu) algorithm to identify any double-spending attacks on non-compromised nodes. Finally, genuine nodes are granted permission to decrypt medical records. RESULTS: In the experimental analysis, the performance of the proposed methods was compared to existing models. The results demonstrated that the suggested approach significantly increased the security level to 98%, reduced attack detection time to 1300 ms, and maximized accuracy to 98%. Furthermore, a comprehensive comparative analysis affirmed the reliability of the proposed model across all metrics. CONCLUSION: The proposed healthcare framework's efficiency is proved by the experimental evaluation.

Targeting of neuroblastoma cells through Kynurenine-AHR pathway inhibition.

Neuroblastoma poses significant challenges in clinical management. Despite its relatively low incidence, this malignancy contributes disproportionately to cancer-related childhood mortality. Tailoring treatments based on risk stratification, including MYCN oncogene amplification, remains crucial, yet high-risk cases often confront therapeutic resistance and relapse. Here, we explore the aryl hydrocarbon receptor (AHR), a versatile transcription factor implicated in diverse physiological functions such as xenobiotic response, immune modulation, and cell growth. Despite its varying roles in malignancies, AHR's involvement in neuroblastoma remains elusive. Our study investigates the interplay between AHR and its ligand kynurenine (Kyn) in neuroblastoma cells. Kyn is generated from tryptophan (Trp) by the activity of the enzymes indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO2). We found that neuroblastoma cells displayed sensitivity to the TDO2 inhibitor 680C91, exposing potential vulnerabilities. Furthermore, combining TDO2 inhibition with retinoic acid or irinotecan (two chemotherapeutic agents used to treat neuroblastoma patients) revealed synergistic effects in select cell lines. Importantly, clinical correlation analysis using patient data established a link between elevated expression of Kyn-AHR pathway genes and adverse prognosis, particularly in older children. These findings underscore the significance of the Kyn-AHR pathway in neuroblastoma progression, emphasizing its potential role as a therapeutic target.

TDO2 promotes bladder cancer progression via AhR-mediated SPARC/FILIP1L signaling.

The enzyme tryptophan 2,3-dioxygenase (TDO2) has been implicated in the dysregulation across a variety of human cancers. Despite this association, the implications of TDO2 in the progression of bladder cancer have eluded thorough understanding. In this study, we demonstrate that TDO2 expression is notably elevated in bladder cancer tissues and serves as an unfavorable prognostic factor for overall survival. Through a series of biological functional assays, we have determined that TDO2 essentially enhances cell proliferation, metastatic potential, and imparts a decreased sensitivity to the chemotherapeutic agent cisplatin. Our mechanistic investigations reveal that TDO2 augments aryl hydrocarbon receptor (AhR) signaling pathways and subsequently upregulates the expression of SPARC and FILIP1L. Importantly, we have identified a positive correlation between TDO2 levels and the basal/squamous subtype of bladder cancer, and we provide evidence to suggest that TDO2 expression is modulated by the tumor suppressors RB1 and TP53. From a therapeutic perspective, we demonstrate that the targeted inhibition of TDO2 with the molecular inhibitor 680C91 markedly attenuates tumor growth and metastasis while concurrently enhancing the efficacy of cisplatin. These findings open a new therapeutic avenue for the management of bladder cancer.

Discovery of novel IDO1/TDO2 dual inhibitors: a consensus Virtual screening approach with molecular dynamics simulations, and binding free energy analysis.

The pursuit of effective cancer immunotherapy drugs remains challenging, with overexpression of indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2) allowing cancer cells to evade immune attacks. While several IDO1 inhibitors have undergone clinical testing, only three dual IDO1/TDO2 inhibitors have reached human trials. Hence, this study focuses on identifying novel IDO1/TDO2 dual inhibitors through consensus structure-based virtual screening (SBVS). ZINC15 natural products library was refined based on molecular descriptors, and the selected compounds were docked to the holo form IDO1 and TDO2 using two different software programs and ranked according to their consensus docking scores. The top-scoring compounds underwent in silico evaluations for pharmacokinetics, toxicity, CYP3A4 affinity, molecular dynamics (MD) simulations, and MM-GBSA binding free energy calculations. Five compounds (ZINC00000079405/10, ZINC00004028612/11, ZINC00013380497/12, ZINC00014613023/13, and ZINC00103579819/14) were identified as potential IDO1/TDO2 dual inhibitors due to their high consensus docking scores, key residue interactions with the enzymes, favorable pharmacokinetics, and avoidance of CYP3A4 binding. MD simulations of the top three hits with IDO1 indicated conformational changes and compactness, while MM-GBSA analysis revealed strong binding free energy for compounds 10 (ΔG: -20.13 kcal/mol) and 11 (ΔG: -16.22 kcal/mol). These virtual hits signify a promising initial step in identifying candidates as supplementary therapeutics to immune checkpoint inhibitors in cancer treatment. Their potential to deliver potent dual inhibition of IDO1/TDO2, along with safety and favorable pharmacokinetics, makes them compelling. Validation through in vitro and in vivo assays should be conducted to confirm their activity, selectivity, and preclinical potential as holo IDO1/TDO2 dual inhibitors.Communicated by Ramaswamy H. Sarma.

Untargeted metabolomics yields insight into extramammary Paget's disease mechanisms.

Background: Extramammary Paget's disease (EMPD) is a rare cutaneous malignancy, commonly affecting the external genitalia and perianal area of the elderly with unclear pathogenesis. Metabolomics provides a novel perspective for uncovering the metabolic mechanisms of a verity of cancers. Materials and methods: Here, we explored the metabolome of EMPD using an untargeted strategy. In order to further investigate the potential relationship between metabolites and gene expression, we re-analyzed the gene expression microarray data (GSE117285) using differential expression analysis and functional enrichment analyses. Results: Results showed that a total of 896 metabolites were identified and 87 metabolites including 37 upregulated and 50 downregulated significantly in EMPD were sought out. In the following feature selection analyses, four metabolites, namely, cyclopentyl fentanyl-d5, LPI 17:0, guanosine-3',5'-cyclic monophosphate, kynurenine (KYN, high in EMPD) were identified by both random forest and support vector machine analyses. We then identified 1,079 dysfunctional genes: 646 upregulated and 433 downregulated in EMPD. Specifically, the tryptophan-degrading enzyme including indoleamine-2,3-dioxygenase-1 (IDO1) and tryptophan 2,3-dioxygenase (TDO2) were also increased. Generally, cancers exhibit a high expression of IDO1 and TDO2 to catabolize tryptophan, generating abundant KYN. Moreover, we also noticed the abnormal activation of sustaining proliferative signaling in EMPD. Conclusion: In conclusion, this study was the first to reveal the metabolome profile of EMPD. Our results demonstrate that IDO1/TDO2-initialized KYN metabolic pathway may play a vital role in the development and progression of EMPD, which may serve as a potential therapeutic target for treating EMPD.

Angucyclinones with IDO and TDO inhibitory activities isolated from the actinomycetes Umezawaea beigongshangensis.

Four previously undescribed angucyclinones umezawaones A-D (1-4) were isolated from the liquid cultures of Umezawaea beigongshangensis. Their structures were determined by spectroscopic analyses, single crystal X-ray diffraction, quantum chemical 13C NMR and electronic circular dichroism calculations. All compounds displayed strong inhibitory activities against indoleamine 2,3-dioxygenase and tryptophan-2,3-dioxygenase in enzymatic assay, especially compound 2.

Therapeutic effects of in vivo administration of an inhibitor of tryptophan 2,3-dioxygenase (680c91) for the treatment of fibroids: a preclinical study.

OBJECTIVE: Fibroids are characterized by marked overexpression of tryptophan 2,3 dioxygenase (TDO2). The objective of this study was to determine the effectiveness of in vivo administration of an inhibitor of TDO2 (680C91) on fibroid size and gene expression. DESIGN: Animal and ex vivo human study. SETTING: Academic Research Institution. SUBJECTS: Severe combined immunodeficiency mice bearing human fibroid xenografts treated with vehicle and TDO2 inhibitor. INTERVENTION: Daily intraperitoneal administration of 680C91 or vehicle for 2 months and in vitro studies with fibroid explants. MAIN OUTCOME MEASURES: Tumor weight and gene expression profile of xenografts and in vitro mechanistic experiments using fibroid explants. RESULTS: Compound 680C91 was well-tolerated with no effects on blood chemistry and body weight. Treatment of mice with 680C91 resulted in 30% reduction in the weight of fibroid xenografts after 2 months of treatment and as expected lower levels of kynurenine, the byproduct of tryptophan degradation and an endogenous ligand of aryl hydrocarbon receptor (AhR) in the xenografts. The expression of cytochrome P450 family 1 subfamily B member 1 (CYP1B1), transforming growth factor ß3 (TGF-ß3), fibronectin (FN1), cyclin-dependent kinase 2 (CDK2), E2F transcription factor 1 (E2F1), interleukin 8 (IL-8) and secreted protein acidic and cysteine rich (SPARC) mRNA were lower in the xenografts of mice treated with 680C91 compared with vehicle controls. Similarly, the protein abundance of collagen, FN1, CYP1B1, and SPARC were lower in the xenografts of 680C9- treated mice compared with vehicle controls. Immunohistochemical analysis of xenografts indicated decreased expression of collagen, Ki67 and E2F1 but no significant changes in cleaved caspase 3 expression in mice treated with 680C91. The levels of kynurenine in the xenografts showed a direct correlation with the tumor weight and FN1 levels. In vitro studies with fibroid explants showed a significant induction of CYP1B1, TGF-ß3, FN1, CDK2, E2F1, IL8, and SPARC mRNA by tryptophan, which could be blocked by cotreatment with 680C91 and the AhR antagonist CH-223191. CONCLUSION: The results indicate that correction of aberrant tryptophan catabolism in fibroids could be an effective treatment through its effect to reduce cell proliferation and extracellular matrix accumulation.

TDO2 deficiency attenuates the hepatic lipid deposition and liver fibrosis in mice with diet-induced non-alcoholic fatty liver disease.

Purpose: Non-alcoholic fatty liver disease (NAFLD) represents an increasingly prevalent set of liver diseases. Tryptophan 2,3-dioxygenase 2 (TDO2) is the major enzyme of tryptophan catabolism and is abnormally expressed in liver cancer, but the function of TDO2 in NAFLD remains unclear. The current study was designed to probe into the effect and mechanism of TDO2 on NAFLD. Methods: C57BL/6 mice and TDO2-knockout (KO) mice were fed with a high-fat diet for 16 weeks to construct the NAFLD model in vivo; primary hepatocytes isolated from TDO2-KO mice were exposed to palmitate (PA) to establish the NAFLD model in vitro. The expression of TDO2 was determined using Western blot. The function and mechanism of TDO2 were evaluated by enzyme-linked immunosorbent assay, hematoxylin-eosin staining, Oil Red O staining, immunohistochemical assay, and Western blot. Results: The expression of TDO2 in the liver tissue of NAFLD mice was more than three times that in the control group. Functionally, TDO2 knockout reduced hepatic lipid deposition and liver fibrosis in NAFLD mice in vivo and primary hepatocytes induced by 200 µM PA in vitro. Mechanistically, the loss of TDO2 restrained hepatic lipid deposition and expression levels of fibrosis-related markers in PA-treated primary hepatocytes, and these trends were partially reversed by 10 ng/ml receptor activator of the nuclear factor kappa-B ligand (RANKL, an activator of the NF-κB pathway). Conclusion: Knocking out TDO2 repressed hepatic lipid deposition and liver fibrosis in mice with NAFLD, and reduced hepatic lipid deposition and expressions of fibrosis-related markers in PA-treated primary hepatocytes by inactivating the NF-κB pathway.

Suppression of Kynurenine 3-Monooxygenase as a Treatment for Triple-negative Breast Carcinoma.

Kynurenine 3-monooxygenase (KMO), a key enzyme within the kynurenine (KYN) pathway of tryptophan (TRY) metabolism, enables the excess production of toxic metabolites (such as 3-hydroxykynurenine, xanthurenic acid, 3-hydroxyanthranilic acid and quinolinic acid), and modulates the balance between these toxic molecules and the protective metabolite, kynurenic acid (KYNA). Despite its importance, KMO suppression as a treatment for cancer has not been fully explored. Instead, researchers have focused on prevention of KYN pathway activity by inhibition of enzymes indoleamine 2,3-dioxygenase (IDO1 and IDO2) or tryptophan 2,3-dioxygenase (TDO, also known as TDO2). However, studies using IDO/TDO inhibitors against cancer have not yet shown that this type of treatment can be successful. We argue that KMO suppression can be an effective strategy for treatment of cancer by 1) decreasing toxic metabolites within the KYN pathway and 2) increasing levels of KYNA, which has important protective and anticancer properties. This strategy may be beneficial in the treatment of aggressive breast cancer, particularly in patients with triple-negative breast cancer. A major challenge to this strategy, when searching for an effective treatment for tumors, especially tumors like breast carcinoma that often metastasize to the brain, is finding KMO inhibitors that adequately cross the blood-brain barrier.

Posterior tibial slope correlated with metaphyseal inclination more than metaphyseal height.

BACKGROUND: Excessive posterior tibial slope (PTS) is an independent risk factor for anterior cruciate ligament reconstruction (ACLR) failure, but it remains unclear how PTS relates to other proximal tibial morphologic parameters. The purpose of this study was to analyse sagittal tibial metaphysis morphology, and to calculate the correlation coefficients of PTS with anatomical features. METHODS: The authors retrospectively reviewed lateral radiographs of 350 patients that were scheduled to receive primary ACLR to digitize 15 landmarks on the patella, femur, fibula, and tibia, and measure PTS, patellar height, as well as metaphysis height and inclination. Pearson correlation coefficients (r) were computed to assess the linear relationship of PTS with other parameters. RESULTS: The PTS was 9.8 ± 3.1° (mid-shaft axis), anterior metaphyseal height and inclination was 30.9 ± 4.6 mm and 33.9 ± 7.2°, and posterior metaphyseal height and inclination was 16.1 ± 4.0 mm and 22.0 ± 5.8°. PTS had a low correlation with anterior (r, 0.225) and posterior metaphyseal heights (r, -0.183). PTS had moderate correlations with anterior (r, 0.385) and posterior metaphysis inclination (r, 0.417). CONCLUSION: PTS has a low correlation with anterior metaphyseal height, but a moderate correlation with anterior and posterior metaphyseal inclination. The moderate correlation between PTS and metaphysis inclination sheds light on the origin of the deformity, and knees with higher PTS are therefore likely to have metaphyses with greater posterior inclinations. The clinical relevance of these findings is that tibial deflexion osteotomy techniques should attempt to address the underlying deformity of excessive PTS by adjusting metaphyseal inclination rather than making diaphyseal resections.

Preclinical PK investigation of a novel IDO1/TDO dual inhibitor-SHR9146 in mouse plasma and tissues by LC-MS/MS.

Purpose: The aim of the present study was to establish a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of SHR9146, a novel IDO1/TDO dual inhibitor, in mouse plasma and tissues, and to apply it to investigate the preclinical plasma pharmacokinetics and tissue distribution of SHR9146 in mice. Methods: Samples were spiked with deuterated SHR9146-d4 as an internal standard and pretreated by protein-precipitation extraction with methanol. Chromatographic separation was performed on a Venusil ABS C18 column (150 × 4.6 mm, 5 µm) by isocratic elution with 10 mM ammonium acetate buffer containing 0.1% formic acid solution and methanol as mobile phases. MS detection was conducted in positive electrospray ionization with multiple reaction monitoring at m/z 444.1/229.4 for SHR9146 and m/z 448.4/229.2 for the internal standard. Results: The method showed good linearity in the calibration range from 0.05 to 50.0 µg/mL. Precisions (intra- and inter-run) were in the range from 0.5% to 5.1%, and accuracies (RE) were between -3.0% and 4.4% for all the concentration levels. SHR9146 was stable in all the tested bio-samples with recoveries >90%. Pharmacokinetic parameters were obtained by non-compartmental analysis. SHR9146 has a half-life of 0.713 h when IV-injected, with CL 12 mL/min/kg and Vd 0.666 L/kg. After oral dosing from 20 to 80 mg/kg, Cmax (range from 8.751 to 12.893 µg/mL) and AUC0-t (range from 15.606 to 69.971 µg·h/mL) of SHR9146 showed dose proportionality. Other post-oral pharmacokinetic parameters in plasma were as follows (n=6): Tmax 0.79 ± 0.36 h, t1/2 1.586 ± 0.853 h, CL 19.8 ± 0.9 mL/min/kg, Vd 3.427± 1.617 L/kg, and absolute bioavailability of 54.2% ± 12.6% (range from 40.2% to 64.7%). In addition, SHR9146 was found to be absorbed rapidly and distributed widely and mainly in the stomach, adrenal gland, liver, and lung. Conclusion: The method was simple, sensitive, accurate, and specific and was successfully applied for the preclinical pharmacokinetic and tissue distribution study of SHR9146 in mice. The results showed that SHR9146 had dose-independent kinetics in mice via oral administration and was absorbed rapidly and distributed widely. The study provides a good basis for further drug development assessment.

Inhibition of STAT-mediated cytokine responses to chemically-induced colitis prevents inflammation-associated neurobehavioral impairments.

Depression can be associated with chronic systemic inflammation, and production of peripheral proinflammatory cytokines and upregulation of the kynurenine pathway have been implicated in pathogenesis of depression. However, the mechanistic bases for these comorbidities are not yet well understood. As tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), which convert tryptophan to kynurenine, are rate-limiting enzymes of the kynurenine pathway, we screened TDO or IDO inhibitors for effects on the production of proinflammatory cytokines in a mouse macrophage cell line. The TDO inhibitor 680C91 attenuated LPS-induced pro-inflammatory cytokines including IL-1ß and IL-6. Surprisingly, this effect was TDO-independent, as it occurred even in peritoneal macrophages from TDO knockout mice. Instead, the anti-inflammatory effects of 680C91 were mediated through the suppression of signal transducer and activator of transcription(STAT) signaling. Furthermore, 680C91 suppressed production of proinflammatory cytokines and STAT signaling in an animal model of inflammatory bowel disease. Specifically, 680C91 effectively attenuated acute phase colon cytokine responses in male mice subjected to dextran sulfate sodium (DSS)-induced colitis. Interestingly, this treatment also prevented the development of anxiodepressive-like neurobehaviors in DSS-treated mice during the recovery phase. The ability of 680C91 to prevent anxiodepressive-like behavior in response to chemically-induced colitis appeared to be due to rescue of attenuated dopamine responses in the nucleus accumbens. Thus, inhibition of STAT-mediated, but TDO-independent proinflammatory cytokines in macrophages can prevent inflammation-associated anxiety and depression. Identification of molecular mechanisms involved may facilitate the development of new treatments for gastrointestinal-neuropsychiatric comorbidity.

Identification and characterization of tryptophan-kynurenine pathway-related genes involving lamprey (Lampetra japonica) innate immunity.

The tryptophan-kynurenine (TRP-KYN) pathway is involved in several biological functions, including immunosuppression, inflammatory response, and tumor suppression. Six TRP-KYN pathway-related genes, tryptophan 2,3-dioxygenase (TDO), indoleamine 2,3-dioxygenase 2 (IDO2), aminoadipate aminotransferase (AADAT), glutamate oxaloacetate transaminase 2 (GOT2), kynurenine monooxygenase (KMO), and kynureninase (KYNU) have been identified and cloned from the jawless vertebrate lamprey (Lampetra japonica) to gain insights into their evolution and characterization. Expression distribution showed that the key gene Lj-TDO was highly expressed in the oral gland. Real-time quantitative PCR showed that TRP-KYN pathway-related genes were significantly overexpressed after multi-stimulation. RNA interference showed that Lj-IDO2 knockdown regulated the expression of inflammatory factors. In conclusion, our study successfully clarified the ancestral features and functions of the TRP-KYN pathway, while providing valuable insights into the involvement of this pathway in the immune responses of a jawless vertebrate.

Discovery and biological evaluation of a new type of dual inhibitors of indoleamine 2,3-dioxygenase 1 and tryptophan 2,3-dioxygenase from ethnomedicinal plant Dactylicapnos scandens.

The root of Dactylicapnos scandens (D.Don.) Hutch (Papaveraceae), one of the most famous ethno-medicinal plants from the Bai communities in P. R. China, is used to treat various inflammations and tumours. Bioassay-guided phytochemical research on D. scandens followed by semi-synthesis led to a series of undescribed tetrahydroisoquinoline alkaloids with dual inhibitory activities against indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO). The previously undescribed dark-green alkaloid dactycapnine A exhibited the best dual inhibitor effects among the identified compounds. Structure-activity relationship analysis revealed the importance of the base skeleton with a hyperconjugation system. The performed semi-synthesis further yielded bioactive dimeric and trimeric compounds with hyperconjugated systems. Performed STD NMR experiments disclosed direct interactions between dactycapnine A and IDO1/TDO. Inhibition kinetics indicated dactycapnine A as a mixed-type dual inhibitor. These findings provided a possible explanation for the anticancer properties of the ethno-medicinal plant species D. scandens.