The Practice of Weight Loss in Combat Sports Athletes: A Systematic Review.

The aim of this systematic review is to comprehensively assess the weight loss (WL) practices in different combat sports (CS). The review protocol was preregistered with PROSPERO [CRD42023487196]. Three databases were searched (Web of Science, EBSCOhost, and PubMed) until 8 December 2023. Eligible studies had to meet five criteria: they must have been (a) written in English, (b) published in a peer-reviewed journal, (c) used a survey design to investigate the WL practices of CS athletes, and (d) reported the WL methods used by athletes using a five-point scale. Twenty-six studies (3994 participants from 14 CS) were included. This review found that (1) WL is highly prevalent in CS athletes; (2) many CS athletes started losing weight for competition as teenagers two to three times a year; (3) CS athletes usually lose <5% body weight in 7-14 days before competition; (4) increasing exercise and gradually dieting are the most commonly used WL methods; and (5) the influence of scientific practitioners on athletes is negligible. The habitual practices of CS athletes may be relatively harmless, but in some special cases, CS athletes also perform extreme WL practices. Scientific practitioners have little influence on their WL practices, which may form a vicious cycle of non-qualified influence.

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.

Kaempferol as an Alternative Cryosupplement for Bovine Spermatozoa: Cytoprotective and Membrane-Stabilizing Effects.

Kaempferol (KAE) is a natural flavonoid with powerful reactive oxygen species (ROS) scavenging properties and beneficial effects on ex vivo sperm functionality. In this paper, we studied the ability of KAE to prevent or ameliorate structural, functional or oxidative damage to frozen-thawed bovine spermatozoa. The analysis focused on conventional sperm quality characteristics prior to or following thermoresistance tests, namely the oxidative profile of semen alongside sperm capacitation patterns, and the levels of key proteins involved in capacitation signaling. Semen samples obtained from 30 stud bulls were frozen in the presence of 12.5, 25 or 50 µM KAE and compared to native ejaculates (negative control-CtrlN) as well as semen samples cryopreserved in the absence of KAE (positive control-CtrlC). A significant post-thermoresistance test maintenance of the sperm motility (p < 0.001), membrane (p < 0.001) and acrosome integrity (p < 0.001), mitochondrial activity (p < 0.001) and DNA integrity (p < 0.001) was observed following supplementation with all KAE doses in comparison to CtrlC. Experimental groups supplemented with all KAE doses presented a significantly lower proportion of prematurely capacitated spermatozoa (p < 0.001) when compared with CtrlC. A significant decrease in the levels of the superoxide radical was recorded following administration of 12.5 (p < 0.05) and 25 µM KAE (p < 0.01). At the same time, supplementation with 25 µM KAE in the cryopreservation medium led to a significant stabilization of the activity of Mg2+-ATPase (p < 0.05) and Na+/K+-ATPase (p < 0.0001) in comparison to CtrlC. Western blot analysis revealed that supplementation with 25 µM KAE in the cryopreservation medium prevented the loss of the protein kinase A (PKA) and protein kinase C (PKC), which are intricately involved in the process of sperm activation. In conclusion, we may speculate that KAE is particularly efficient in the protection of sperm metabolism during the cryopreservation process through its ability to promote energy synthesis while quenching excessive ROS and to protect enzymes involved in the process of sperm capacitation and hyperactivation. These properties may provide supplementary protection to spermatozoa undergoing the freeze-thaw process.

Targeting Tryptophan Catabolism in Ovarian Cancer to Attenuate Macrophage Infiltration and PD-L1 Expression.

High-grade serous carcinoma (HGSC) of the fallopian tube, ovary, and peritoneum is the most common type of ovarian cancer and is predicted to be immunogenic because the presence of tumor-infiltrating lymphocytes conveys a better prognosis. However, the efficacy of immunotherapies has been limited because of the immune-suppressed tumor microenvironment (TME). Tumor metabolism and immune-suppressive metabolites directly affect immune cell function through the depletion of nutrients and activation of immune-suppressive transcriptional programs. Tryptophan (TRP) catabolism is a contributor to HGSC disease progression. Two structurally distinct rate-limiting TRP catabolizing enzymes, indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2), evolved separately to catabolize TRP. IDO1/TDO2 are aberrantly expressed in carcinomas and metabolize TRP into the immune-suppressive metabolite kynurenine (KYN), which can engage the aryl hydrocarbon receptor to drive immunosuppressive transcriptional programs. To date, IDO inhibitors tested in clinical trials have had limited efficacy, but those inhibitors did not target TDO2, and we find that HGSC cell lines and clinical outcomes are more dependent on TDO2 than IDO1. To identify inflammatory HGSC cancers with poor prognosis, we stratified patient ascites samples by IL6 status, which correlates with poor prognosis. Metabolomics revealed that IL6-high patient samples had enriched KYN. TDO2 knockdown significantly inhibited HGSC growth and TRP catabolism. The orally available dual IDO1/TDO2 inhibitor, AT-0174, significantly inhibited tumor progression, reduced tumor-associated macrophages, and reduced expression of immune-suppressive proteins on immune and tumor cells. These studies demonstrate the importance of TDO2 and the therapeutic potential of AT-0174 to overcome an immune-suppressed TME. SIGNIFICANCE: Developing strategies to improve response to chemotherapy is essential to extending disease-free intervals for patients with HGSC of the fallopian tube, ovary, and peritoneum. In this article, we demonstrate that targeting TRP catabolism, particularly with dual inhibition of TDO2 and IDO1, attenuates the immune-suppressive microenvironment and, when combined with chemotherapy, extends survival compared with chemotherapy alone.

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.

Potential of Targeting TDO2 as the Lung Adenocarcinoma Treatment.

Tryptophan catabolism plays an important role in the metabolic reconnection in cancer cells to support special demands of tumor initiation and progression. The catabolic product of the tryptophan pathway, kynurenine, has the capability of suppressing the immune reactions of tumor cells. In this study, we conducted internal and external cohort studies to reveal the importance of tryptophan 2,3-dioxygenase (TDO) for lung adenocarcinoma (LUAD). Our study further demonstrated that the TDO2 expression was associated with the proliferation, survival, and invasion of LUAD cells, and targeting TDO2 for LUAD tumors could be a potential therapeutic strategy.

TDO2-overexpressed Dendritic Cells Possess Tolerogenicity and Ameliorate Collagen-induced Arthritis by Modulating the Th17/Regulatory T Cell Balance.

Tolerogenic dendritic cells are promising for restoring immune homeostasis and may be an alternative therapy for autoimmune diseases such as rheumatoid arthritis. The kynurenine pathway is a vital mechanism that induces tolerance in dendritic cells (DCs). Tryptophan 2,3-dioxygenase (TDO2) is an important rate-limiting enzyme in the kynurenine pathway and participates in immune regulation. However, the role of TDO2 in shaping the tolerogenic phenotypes of DCs remains unclear. In this study, we investigated the effects and mechanisms of TDO2-overexpressed DCs in regulating the T cell balance both in vivo and in vitro. TDO2-overexpressed DC2.4 and TDO2-/- mouse bone marrow-derived DCs (BMDCs) were generated to verify the role of TDO2 in DC maturation and functionality. TDO2 overexpression in BMDCs via PGE2 treatment exhibited an immature phenotype and tolerogenic state, whereas TDO2-/- BMDCs exhibited a mature phenotype and a proinflammatory state. Furthermore, transplant of TDO2-overexpressed BMDCs alleviated collagen-induced arthritis severity in mice, which was correlated with a reduction in Th17 populations and an increase in regulatory T cells. Collectively, these results indicate that TDO2 plays an important role in the tolerogenic phenotype and may be a promising target for the generation tolerogenic DCs for rheumatoid arthritis treatment.

Serum indoleamine 2, 3-dioxygenase and tryptophan-2, 3-dioxygenase: potential biomarkers for the diagnosis of major depressive disorder.

OBJECTIVE: The objective of this study was to observe the changes in the levels of indoleamine 2, 3-dioxygenase (IDO) and tryptophan-2, 3-dioxygenase (TDO) in patients with major depressive disorder (MDD) and investigate their potential role as novel biomarkers for diagnosing MDD. METHODS: A total of 55 MDD patients and 55 healthy controls (HC) were enrolled in the study. The severity of MDD was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24) before and after treatment. The serum concentrations of IDO and TDO were measured at baseline and after treatment. The correlations between the serum levels of IDO and TDO and HAMD-24 scores were evaluated using Pearson's correlation test. Receiver operating characteristic (ROC) curve analysis was used to evaluate the area under the curve (AUC) of serum levels of IDO and TDO for discriminating MDD patients from HC. RESULTS: The serum IDO and TDO concentrations were significantly higher in patients with MDD at baseline than in healthy controls, and decreased significantly after 2 weeks or 1 month of treatment. The levels of IDO and TDO were significantly positively correlated with HAMD-24 scores. Furthermore, the AUC values for IDO and TDO were 0.999 and 0.966, respectively. CONCLUSION: The study suggests that serum IDO and TDO may serve as novel biomarkers for diagnosing MDD. These findings may lead to a better understanding of the pathogenesis of MDD and the development of new therapeutic targets.

Characterization and RNA interference-mediated silencing of tryptophan 2,3-dioxygenase gene in Carpophilus hemipterus (L.) (Coleoptera: Nitidulidae).

Dried fruit beetle, Carpophilus hemipterus (Linnaeus, 1758) (Coleoptera: Nitidulidae), is a serious pest of ripened fresh fruit in the orchard and dried fruit in postprocessing storage. Despite the economic impact and widespread distribution of C. hemipterus, there is a lack of functional genomics research seeking to elucidate features of molecular physiology for improved pest management. Here, we report the characterization of the gene named Vermilion in C. hemipterus (ChVer) that encodes for tryptophan 2,3-dioxygenase. The Vermilion is frequently used as a visual marker for genomics approaches as tryptophan 2,3-dioxygenase is involved in the biosynthesis of eye coloration pigments in insects. We identified 1628 bp long full-length transcript of ChVer from transcriptomic database of C. hemipterus. The expression analysis among adult body parts revealed peak ChVer expression in head compared to thorax and abdomen, which is consistent with its role. Among the C. hemipterus developmental stages, peak ChVer expression was observed in first instar larva, second instar larva, and adult male stages, whereas the lowest levels of expression were seen in third instar larva, prepupa, and pupa. The nanoinjection of ChVer double-stranded RNA in larval C. hemipterus resulted in a significant reduction in ChVer transcript levels as well as caused a loss of eye color, that is, the white-eyed phenotype in adults. Characterization of visually traceable marker gene and robust RNA interference response seen in this study will enable genomics research is this important pest.

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.

Tryptophan metabolism enzymes are potential targets in ovarian clear cell carcinoma.

AIM: As the second most prevalent subtype of epithelial ovarian cancers, ovarian clear cell carcinoma (OCCC) is known for its chemoresistance to conventional platinum-based therapy. In this work, we examined the tryptophan (Trp) metabolism enzymes' differential expression in patients with OCCC to assess the potential for personalised treatment. METHODS: A total of 127 OCCC tissues were used to construct tissue microarrays, and immunohistochemistry (IHC) staining of the Trp enzymes IDO1, IDO2, TDO2 and IL4I1 was performed. The correlations between Trp enzyme expression and clinical characteristics were analysed. RESULTS: Positive IDO1, IDO2, TDO2 and IL4I1 staining was identified in 26.8%, 94.5%, 75.6% and 82.7% of OCCC respectively. IDO1-positive samples were more common in the chemoresistant group than in the platinum-sensitive group (46.7% vs. 19.8%). Moreover, positive expression of IDO1, TDO2 and IL4I1 was related to advanced stage, metastasis, bilateral tumours, endometriosis and tumour rupture (p < 0.05) respectively. Univariate analysis revealed a significant association between bilateral tumours, lymph node metastasis, advanced stage, distant metastasis and aberrant cytology with a poor prognosis for OCCC, while the absence of residual tumour was correlated with a favourable outcome (p < 0.05). However, only bilateral tumours and lymph node metastases were related to a poor prognosis after multivariate analysis. CONCLUSION: This is the first study to investigate the expression of the Trp enzymes IDO1, IDO2, TDO2 and IL4I1 in OCCC tissues. IDO2, TDO2 and IL4I1 were detected in the majority of OCCC. Clinical traits were correlated with IDO1, IDO2, TDO2 and IL4I1 expression. IDO1 may be used as a therapeutic target given the large percentage of chemoresistant cases with IDO1 expression. These results will aid the development of personalised therapies for OCCC.

Interaction between childhood trauma experience and TPH2 rs7305115 gene polymorphism in brain gray matter volume.

BACKGROUND: Childhood trauma is one of the most extensively studied and well-supported environmental risk factors for the development of mental health problems. The human tryptophan hydroxylase 2 (TPH2) gene is one of the most promising candidate genes in numerous psychiatric disorders. However, it is now widely acknowledged that neither genetic variation nor environmental exposure alone can fully explain all the phenotypic variance observed in psychiatric disorders. Therefore, it is necessary to consider the interaction between the two factors in psychiatric research. METHODS: We enrolled a sizable nonclinical cohort of 786 young, healthy adults who underwent structural MRI scans and completed genotyping, the Childhood Trauma Questionnaire (CTQ) and behavioural scores. We identified the interaction between childhood trauma and the TPH2 rs7305115 gene polymorphism in the gray matter volume (GMV) of specific brain subregions and the behaviour in our sample using a multiple linear regression framework. We utilized mediation effect analysis to identify environment /gene-brain-behaviour relationships. RESULTS: We found that childhood trauma and TPH2 rs7305115 interacted in both behaviour and the GMV of brain subregions. Our findings indicated that the GMV of the right posterior parietal thalamus served as a significant mediator supporting relationship between childhood trauma (measured by CTQ score) and anxiety scores in our study population, and the process was partly modulated by the TPH2 rs7305115 gene polymorphism. Moreover, we found only a main effect of childhood trauma in the GMV of the right parahippocampal gyrus area, supporting the relationship between childhood trauma and anxiety scores as a significant mediator. CONCLUSIONS: Our findings suggest that early-life trauma may have a specific and long-term structural effect on brain GMV, potentially leading to altered cognitive and emotional processes involving the parahippocampal gyrus and thalamus that may also be modulated by the TPH2 gene polymorphism. This finding highlights the importance of considering genetic factors when examining the impact of early-life experiences on brain structure and function. Gene‒environment studies can be regarded as a powerful objective supplement for targeted therapy, early diagnosis and treatment evaluation in the future.

Identification of tryptophan metabolism- and immune-related genes signature and prediction of immune infiltration landscape in bladder urothelial carcinoma.

Introduction: Tryptophan metabolism is indirectly involved in immune tolerance and promotes response to anticancer drugs. However, the mechanisms underlying tryptophan metabolism and immune landscape in bladder urothelial carcinoma (BLCA) are not fully understood. Methods: A BLCA dataset containing 406 tumor samples with clinical survival information and 19 normal samples were obtained from the Cancer Genome Atlas database. The validation set, GSE32894, contained 223 BLCA tumor samples with survival information, and the single-cell dataset, GSE135337, included seven BLCA tumor samples; both were obtained from the gene expression omnibus database. Univariate and multivariate Cox regression analyses were conducted to evaluate clinical parameters and risk scores. Immune infiltration and checkpoint analyses were performed to explore the immune landscape of BLCA. Single-cell analysis was conducted to further identify the roles of model genes in BLCA. Finally, NAMPT expression in BLCA and adjacent tissues was detected using RT-qPCR, CCK-8 and Transwell assays were conducted to determine the role of NAMPT in BLCA cells. Results: Six crossover genes (TDO2, ACAT1, IDO1, KMO, KYNU, and NAMPT) were identified by overlap analysis of tryptophan metabolism-related genes, immune-related genes, and differentially expressed genes (DEGs). Three biomarkers, NAMPT, IDO1, and ACAT1, were identified using Cox regression analysis. Accordingly, a tryptophan metabolism- and immune-related gene risk model was constructed, and the patients were divided into high- and low-risk groups. There were significant differences in the clinical parameters, prognosis, immune infiltration, and immunotherapy response between the risk groups. RT-qPCR revealed that NAMPT was upregulated in BLCA samples. Knocking down NAMPT significantly inhibited BLCA cell proliferation, migration, and invasion. Discussion: In our study, we constructed a tryptophan metabolism- and immune-related gene risk model based on three biomarkers, namely NAMPT, IDO1, and ACAT1, that were significantly associated with the progression and immune landscape of BLCA. The risk model could effectively predict patient prognosis and immunotherapy response and can guide individualized immunotherapy.

Activation of 5-HT1A Receptors Normalizes the Overexpression of Presynaptic 5-HT1A Receptors and Alleviates Diabetic Neuropathic Pain.

Neuropathic pain is a well-documented phenomenon in experimental and clinical diabetes; however, current treatment is unsatisfactory. Serotoninergic-containing neurons are key components of the descending autoinhibitory pathway, and a decrease in their activity may contribute at least in part to diabetic neuropathic pain (DNP). A streptozotocin (STZ)-treated rat was used as a model for type 1 diabetes mellitus (T1DM). Pain transmission was evaluated using well-established nociceptive-based techniques, including the Hargreaves apparatus, cold plate and dynamic plantar aesthesiometer. Using qRT-PCR, Western blotting, immunohistochemistry, and HPLC-based techniques, we also measured in the central nervous system and peripheral nervous system of diabetic animals the expression and localization of 5-HT1A receptors (5-HT1AR), levels of key enzymes involved in the synthesis and degradation of tryptophan and 5-HT, including tryptophan hydroxylase-2 (Tph-2), tryptophan 2,3-dioxygenase (Tdo), indoleamine 2,3-dioxygenase 1 (Ido1) and Ido2. Moreover, spinal concentrations of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA, a metabolite of 5-HT) and quinolinic acid (QA, a metabolite of tryptophan) were also quantified. Diabetic rats developed thermal hyperalgesia and cold/mechanical allodynia, and these behavioral abnormalities appear to be associated with the upregulation in the levels of expression of critical molecules related to the serotoninergic nervous system, including presynaptic 5-HT1AR and the enzymes Tph-2, Tdo, Ido1 and Ido2. Interestingly, the level of postsynaptic 5-HT1AR remains unaltered in STZ-induced T1DM. Chronic treatment of diabetic animals with 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT), a selective 5-HT1AR agonist, downregulated the upregulation of neuronal presynaptic 5-HT1AR, increased spinal release of 5-HT (↑ 5-HIAA/5-HT) and reduced the concentration of QA, decreased mRNA expression of Tdo, Ido1 and Ido2, arrested neuronal degeneration and ameliorated pain-related behavior as exemplified by thermal hyperalgesia and cold/mechanical allodynia. These data show that 8-OH-DPAT alleviates DNP and other components of the serotoninergic system, including the ratio of 5-HIAA/5-HT and 5-HT1AR, and could be a useful therapeutic agent for managing DNP.

MED12 mutation activates the tryptophan/kynurenine/AHR pathway to promote growth of uterine leiomyomas.

Uterine leiomyomas cause heavy menstrual bleeding, anemia, and pregnancy loss in millions of women worldwide. Driver mutations in the transcriptional mediator complex subunit 12 (MED12) gene in uterine myometrial cells initiate 70% of leiomyomas that grow in a progesterone-dependent manner. We showed a distinct chromatin occupancy landscape of MED12 in mutant MED12 (mut-MED12) versus WT-MED12 leiomyomas. Integration of cistromic and transcriptomics data identified tryptophan 2,3-dioxygenase (TDO2) as the top mut-MED12 target gene that was significantly upregulated in mut-MED12 leiomyomas when compared with adjacent myometrium and WT-MED12 leiomyomas. TDO2 catalyzes the conversion of tryptophan to kynurenine, an aryl hydrocarbon receptor (AHR) ligand that we confirmed to be significantly elevated in mut-MED12 leiomyomas. Treatment of primary mut-MED12 leiomyoma cells with tryptophan or kynurenine stimulated AHR nuclear translocation, increased proliferation, inhibited apoptosis, and induced AHR-target gene expression, whereas blocking the TDO2/kynurenine/AHR pathway by siRNA or pharmacological treatment abolished these effects. Progesterone receptors regulated the expression of AHR and its target genes. In vivo, TDO2 expression positively correlated with the expression of genes crucial for leiomyoma growth. In summary, activation of the TDO2/kynurenine/AHR pathway selectively in mut-MED12 leiomyomas promoted tumor growth and may inform the future development of targeted treatments and precision medicine.

Liver tryptophan 2,3-dioxygenase: a determinant of anxiety-like behaviour - studies with chronic nicotine administration in rats.

Deletion of the tryptophan 2,3-dioxygenase ( TDO2 ) gene induces an anxiolytic-like behaviour in mice and TDO inhibition by allopurinol elicits an antidepressant-like effect in rats exposed to restraint stress. Chronic nicotine administration inhibits TDO activity, enhances brain serotonin synthesis and exerts anxiolytic- and antidepressant-like effects in rodent models. There is a strong association between anxiety, depression and tobacco use, which is stronger in women than in men. The present study aimed to examine the relationship between behavioural measures of anxiety and depression with liver TDO activity, brain tryptophan concentration and serotonin synthesis in rats treated chronically with nicotine. Behavioural measures included the elevated plus maze (EPM), open field (OFT) and forced swim (FST) tests. Biochemical measures included TDO activity, serum corticosterone and brain Trp, 5-HT and 5-HIAA concentrations. Anxiolytic-like and antidepressant-like effects of chronic nicotine were confirmed in association with TDO inhibition and elevation of brain Trp and 5-HT. Sex differences in behaviour were independent of the biochemical changes. At baseline, female rats performed better than males in OFT and FST. Nicotine was less anxiolytic in females in the open arm test. Nicotine treatment did not elicit different responses between sexes in the FST. Our findings support the notion that liver TDO activity exhibits a strong association with behavioural measures of anxiety and depression in experimental models, but provide little evidence for sex differences in behavioural response to nicotine. The TDO-anxiety link may be underpinned by kynurenine metabolites as well as serotonin.

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.

Identification of paeoniflorin from Paeonia lactiflora pall. As an inhibitor of tryptophan 2,3-dioxygenase and assessment of its pharmacological effects on depressive mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The radix of Paeonia lactiflora Pall. (PaeR) is a traditional Chinese medicine (TCM) clinically used for treating depression. Although it has been established that PaeR can protect the liver and alleviate depressive-like behaviors, its bioactive chemicals and antidepressant mechanism remain unclear. Our pilot study showed that PaeR reduced the expression of the L-tryptophan- catabolizing enzyme tryptophan 2,3-dioxygenase (TDO) in the livers of stress-induced depression-like mice. AIM OF THE STUDY: This study aimed to screen potential TDO inhibitors from PaeR and investigate the potential therapeutic use of TDO inhibition for treating depression. MATERIALS AND METHODS: Molecular docking, magnetic ligand fishing, and secrete-pair dual luminescence assay were conducted for in vitro ligand discovery and high-throughput screening of TDO inhibitors. Stable TDO overexpression was achieved in HepG2 cell lines to evaluate the TDO inhibitory activities of drugs in vitro by RT-PCR and Western blot analyses of TDO at mRNA and protein levels. In vivo validation of TDO inhibitory potency and evaluation of TDO inhibition as a potential therapeutic strategy for major depressive disorder (MDD) were performed using mice subjected to "3 + 1″ combined stresses for at least 30 days to induce depression-like behaviors. A well-known TDO inhibitor, LM10, was evaluated in parallel. RESULTS: The PaeR extract significantly ameliorated depressive-like behaviors of stressed mice, attributed to inhibition of TDO expression and tryptophan modulation metabolism. After a comprehensive analysis of molecular docking, ligand fishing, and luciferase assay, paeoniflorin was screened as a TDO inhibitor from the PaeR extract. This compound, structurally different from LM10, potently inhibited human and mouse TDO in cell- and animal-based assays. The effects of TDO inhibitors on MDD symptoms were evaluated in a stress-induced depression-like mouse model. In mice, both inhibitors had beneficial effects on stress-induced depressive-like behavioral despair and unhealthy physical status. Moreover, both inhibitors increased the liver serotonin/tryptophan ratio and decreased the kynurenine/tryptophan ratio after oral administration, demonstrating in vivo inhibition of TDO activity. Our data substantiated the potential of TDO inhibition as a therapeutic strategy to improve behavioral activity and decrease despair symptoms in major depressive disorder. CONCLUSIONS: This study introduced a hitherto undocumented comprehensive screening strategy to identify TDO inhibitors in PaeR extract. Our findings also highlighted the potential of PaeR as a source of antidepressant constituents and pinpointed the inhibition of TDO as a promising therapeutic approach for managing major depressive disorder.

Indoleamine dioxygenase and tryptophan dioxygenase activities are regulated through control of cell heme allocation by nitric oxide.

Indoleamine-2, 3-dioxygenase (IDO1) and Tryptophan-2, 3-dioxygenase (TDO) catalyze the conversion of L-tryptophan to N-formyl-kynurenine and thus play primary roles in metabolism, inflammation, and tumor immune surveillance. Because their activities depend on their heme contents, which vary in biological settings and go up or down in a dynamic manner, we studied how their heme levels may be impacted by nitric oxide (NO) in mammalian cells. We utilized cells expressing TDO or IDO1 either naturally or via transfection and determined their activities, heme contents, and expression levels as a function of NO exposure. We found NO has a bimodal effect: a narrow range of low NO exposure promoted cells to allocate heme into the heme-free TDO and IDO1 populations and consequently boosted their heme contents and activities 4- to 6-fold, while beyond this range the NO exposure transitioned to have a negative impact on their heme contents and activities. NO did not alter dioxygenase protein expression levels, and its bimodal impact was observed when NO was released by a chemical donor or was generated naturally by immune-stimulated macrophage cells. NO-driven heme allocations to IDO1 and TDO required participation of a GAPDH-heme complex and for IDO1 required chaperone Hsp90 activity. Thus, cells can up- or downregulate their IDO1 and TDO activities through a bimodal control of heme allocation by NO. This mechanism has important biomedical implications and helps explain why the IDO1 and TDO activities in animals go up and down in response to immune stimulation.

Serotonergic modulation of normal and abnormal brain dynamics: The genetic influence of the TPH2 G-703T genotype and DNA methylation on wavelet variance in children and adolescents with and without ADHD.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that often persists into adulthood. Core symptoms of ADHD, such as impulsivity, are caused by an interaction of genetic and environmental factors. Epigenetic modifications of DNA, such as DNA methylation, are thought to mediate the interplay of these factors. Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme in brain serotonin synthesis. The TPH2 gene has frequently been investigated in relation to ADHD, e.g., showing that TPH2 G-703T (rs4570625) polymorphism influences response control and prefrontal signaling in ADHD patients. In this (epi)genetic imaging study we examined 144 children and adolescents (74 patients, 14 females) using fMRI at rest and during performing a waiting impulsivity (WI) paradigm. Both, TPH2 G-703T (rs4570625) genotype and DNA methylation in the 5' untranslated region (5'UTR) of TPH2 were associated with wavelet variance in fronto-parietal regions and behavioral performance, taking TPH2 genotype into account. In detail, comparisons between genotypes of patients and controls revealed highest wavelet variance and longest reaction times in patients carrying the T allele [indicative for a gene-dosage effect, i.e., the WI phenotype is a direct result of the cumulative effect of ADHD and TPH2 variation]. Regressions revealed a significant effect on one specific DNA methylation site in ADHD patients but not controls, in terms of a significant prediction of wavelet variance in fronto-parietal regions as well as premature responses. By the example of the TPH2 G-703T (rs4570625) polymorphism, we provide insight into how interactive genetic and DNA methylation affect the ADHD and/or impulsive endophenotype.