Kynurenine 3-monooxygenase Research Articles

Breast cancer metastasis progression is associated with elevated activity of kynurenine monooxygenase and kynureninase

Breast cancer metastasis progression is associated with elevated activity of kynurenine monooxygenase and kynureninase

Gene expression of kynurenine pathway enzymes in depression and following electroconvulsive therapy.

This study aimed to investigate changes in mRNA expression of the kynurenine pathway (KP) enzymes tryptophan 2, 3-dioxygenase (TDO), indoleamine 2, 3-dioxygenase 1 and 2 (IDO1, IDO2), kynurenine aminotransferase 1 and 2 (KAT1, KAT2), kynurenine monooxygenase (KMO) and kynureninase (KYNU) in medicated patients with depression (n = 74) compared to age- and sex-matched healthy controls (n = 55) and in patients with depression after electroconvulsive therapy (ECT). Associations with mood score (24-item Hamilton Depression Rating Scale, HAM-D24), plasma KP metabolites and selected glucocorticoid and inflammatory immune markers known to regulate KP enzyme expression were also explored. HAM-D24 was used to evaluate depression severity. Whole blood mRNA expression was assessed using quantitative real-time polymerase chain reaction. KAT1, KYNU and IDO2 were significantly reduced in patient samples compared to control samples, though results did not survive statistical adjustment for covariates or multiple comparisons. ECT did not alter KP enzyme mRNA expression. Changes in IDO1 and KMO and change in HAM-D24 score post-ECT were negatively correlated in subgroups of patients with unipolar depression (IDO1 only), psychotic depression and ECT responders and remitters. Further exploratory correlative analyses revealed altered association patterns between KP enzyme expression, KP metabolites, NR3C1 and IL-6 in depressed patients pre- and post-ECT. Further studies are warranted to determine if KP measures have sufficient sensitivity, specificity and predictive value to be integrated into stress and immune associated biomarker panels to aid patient stratification at diagnosis and in predicting treatment response to antidepressant therapy.

Mechanism of Treadmill Exercise Combined with Rich Environmental Stimulation to Improve Depression in Post-stroke Depression Model Rats.

Post-stroke depression (PSD) is a common complication, occurring in approximately one-third of these patients. The neurological symptoms of PSD affect patients' daily life and subsequent recovery. Analyzing the pathogenesis of post-stroke depression from a psychological perspective, it was found that PSD patients often feel despair and anxiety, and it is crucial to explore non-pharmacological ways to improve post-stroke depressive symptoms. A combination of exercise and rich environmental stimulation (RES) has been found effective in improving post-stroke depressive symptoms. Therefore, this study aimed to explore the effects of exercise and rich environmental stimulation on PSD in rats and their potential underlying mechanisms and to provide a theoretical basis for managing PSD. The PSD rat model was constructed, and the depression-like behaviors of rats in each group were evaluated using the open field test (OFT), sucrose preference test (SPT), and forced swimming test (FST). Moreover, changes in the morphological behavior of rat hippocampus were observed using hematoxylin-eosin (HE) staining and Nissl staining. The expression levels of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) in hippocampus tissues were assessed using enzyme linked immunosorbent assay (ELISA), and the levels of tryptophan-related proteins were determined employing western blot analysis. Additionally, a kynurenine-3-monooxygenase (KMO) inhibitor was administered to the combined stimulation group, and the levels of tryptophan (TRP), 5-HT, kynurenine (KYN), 3-hydroxy-kynurenine (3-HK), and quinolinic acid (QA) were evaluated using liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS). Treadmill exercise combined with rich environmental stimulation significantly reduced the immobility time in the FST (p < 0.01), increased the exploratory behavior in the OFT (p < 0.05), and increased the sucrose water consumption in the SPT (p < 0.01), indicating that the depression-like behavior was improved. Treadmill exercise combined with rich environmental stimulation also improved the shape of the damaged hippocampus and increased the number of neurons in the hippocampus. Additionally, treadmill exercise combined with rich environmental stimulation significantly increased the levels of 5-HT and NE in hippocampus tissues (p < 0.01) and decreased KMO protein level (p < 0.01). In the KMO inhibitor group, the neural function was efficiently restored, the levels of 3-HK, QA, and KMO in the hippocampus were substantially reduced (p < 0.01), and the expression level of 5-HT was increased (p < 0.01). Exercise stimulation combined with enriched environmental stimuli alleviates post-stroke depression in rats, and the underlying mechanisms may be related to TRP/KYN/3-HK/QA excitotoxicity pathways and increased 5-hydroxytryptamine levels.

Integrating network pharmacology and bioinformatics to explore the mechanism of Xiaojian Zhongtang in treating major depressive disorder: An observational study.

Major depressive disorder (MDD) is a common mental illness. The traditional Chinese medicine compound Xiaojian Zhongtang (XJZT) has a good therapeutic effect on MDD, but the specific mechanism is not clear. The aim of this study is to explore the molecular mechanism of XJZT in the treatment of MDD through network pharmacology and bioinformatics. The traditional Chinese medicine system pharmacology database was used to screen the chemical components and targets of XJZT, while the online Mendelian inheritance in man, DisGeNET, Genecards, and therapeutic target database databases were used to collect MDD targets and identify the intersection targets of XJZT and MDD. A "drugs-components-targets" network was constructed using the Cytoscape platform, and the STRING was used for protein-protein interaction analysis of intersecting targets. Gene Ontology and Kyoto encyclopedia of genes and genomes analysis of intersecting targets was performed using the DAVID database. Obtain serum and brain transcriptome datasets of MDD from the gene expression omnibus database, and perform differentially expressed genes, weighted gene co-expression network analysis, gene set enrichment analysis, and receiver operating characteristic analysis. A total of 127 chemical components and 767 targets were obtained from XJZT, among which quercetin, kaempferol, and maltose are the core chemical components, and 1728 MDD targets were screened out, with 77 intersecting targets between XJZT and MDD. These targets mainly involve AGE-RAGE signaling pathway in diabetic complexes, epidermal growth factor receptor tyrosine kinase inhibitor resistance, and HIF-1 signaling pathway, and these core targets have strong binding activity with core components. In addition, 1166 differentially expressed genes were identified in the MDD serum transcriptome dataset, and weighted gene co-expression network analysis identified the most relevant gene modules (1269 genes), among which RAC-alpha serine/threonine-protein kinase (AKT1), D(4) dopamine receptor (DRD4), and kynurenine 3-monooxygenase (KMO) were target genes for the treatment of MDD with XJZT, these 3 genes are mainly related to the ubiquitin-mediated proteolysis, arachidonic acid (AA) metabolism, and Huntington disease pathways, and the expression of AKT1, DRD4, and KMO was also found in the MDD brain transcriptome dataset, which is significantly correlated with the occurrence of MDD. We have identified 3 key targets for XJZT treatment of MDD, including AKT1, KMO, and DRD4, and they can be regulated by the key components of XJZT, including quercetin, maltose, and kaempferol. This provides valuable insights for the early clinical diagnosis and development of therapeutic drugs for MDD.

Ameliorative effect of diclofenac in rotenone corneal kindling model of drug-resistant epilepsy: Edge of dual COX and KMO inhibition

Epilepsy affects millions of people worldwide, about one-third patients with epilepsy exhibits resistance to available antiseizures medications, known as drug-resistant epilepsy (DRE). Mitochondrial dysfunction has been implicated as a hallmark in drug-resistant epilepsy via activation of microglial kynurenine 3-monooxygenase (KMO) and cyclooxygenase (COX) enzymes, leading to neuroinflammation and oxidative stress. Diclofenac, an equipotent non selective cyclooxygenase inhibitor, has inhibitory action on KMO enzyme and has also shown anti-inflammatory and antioxidant properties in animal models of epilepsy. These properties make it a suitable candidate for amelioration of DRE. However, its potential in drug-resistant epilepsy remained unexplored till date. In this study, dose dependent effect of diclofenac (5 mg/kg, 10 mg/kg, 20 mg/kg) has been explored in rotenone corneal kindling model of mitochondrial DRE. The results of our study revealed the induction of drug resistance to antiseizure medications and induced kynurenine 3-monooxygenase activity in rotenone corneal kindled epileptic mice in comparison to naive mice. Treatment of rotenone corneal kindled epileptic mice with diclofenac resulted in a significant decrease in drug resistance to antiseizure medications as evident by a reduction in seizure score in the treatment groups as compared to control group, in post-treatment resistance validation. The kynurenine 3-monooxygenase inhibitory activity (as evidenced by decreased levels of neurotoxic quinolinic acid) and the antioxidant effect (as evident by significantly reduced oxidative stress) in the diclofenac treated groups, emerged as a major contributor for its ameliorative action. Findings of this study suggests, diclofenac can be used as an adjunct therapy in amelioration of drug-resistant epilepsy.

P106 ENZYMES INVOLVED IN THE CATABOLISM OF TRYPTOPHAN IN THE PROGNOSIS OF BLADDER CANCER

Bladder cancer (BC) ranks third among the most common carcinomas in Brazil. Tumor immunology opens up perspectives for treatment, where the enzyme indoleamine 2,3-dioxygenase-1 (IDO1) stands out for degrading the amino acid tryptophan, initiating a cascade that culminates in the generation of catabolites (derived from kynurenine). These catabolites, in different associations, determine degrees of local immunosuppression. These catabolites are generated by other enzymes that have not yet been studied in BC. We analyzed the expression of enzymes involved in tryptophan catabolism in order to correlate them with the stage, recurrence, and progression of BC. Analysis of published microarray databases was performed using the NCBI (National Center of Biotechnology Information) and accessed through GEO Datasets (Gene Expression Omnibus). The descriptor “Bladder cancer” was used. Series that provided analysis of normal bladder tissue (Normal) versus BC, including cases of non-muscle invasive BC (CBNMI) and muscle invasive BC (CBMI), recurrence and progression. Statistical analysis was performed using the GEO2R and ROC curve was used. The transcripts were: Tryptophan 2,3-dioxygenase (TDO2), Indoleamine 2,3-dioxygenase (IDO1), Kynurenine Formamidase (AFMID), Kynureninase (KNYU), Kynurenine-oxoglutarate-transaminase 1 (KYAT1), and Kynurenine Monooxygenase (KMU). GSE13507 series was selected, with ten Normal samples and 165 BC samples, including 104 CBNMI and 61 CBMI cases. CBNMI was predicted by KYNU, AFMID, and KYAT1 (AUC of 0.625, 0.589, and 0.638, respectively; p&lt;0.05), while for CBMI were, IDO1, TDO2, and KMO (AUC of 0.662, 0.633, and 0.601, respectively; p&lt;0.05). No enzyme was found to be important in predicting progression; however, the IDO1 enzyme was predictive of recurrence (AUC of 0.366; p&lt;0.05). A relationship between the two IDO1/KYNU was established, which improved the prediction of stage for CBNMI (AUC of 0.733, p&lt;0.05), non-progression (AUC of 0.619, p&lt;0.05), and non-recurrence (AUC of 0.626, p&lt;0.05). The expression of enzymes involved in tryptophan catabolism may aid in the prognosis of BC. It is likely that these enzymes are involved in tumor immunomodulation, which will be explored in future studies.

Alterations in the Blood Kynurenine Pathway Following Long-Term PM2.5 and PM10 Exposure: A Cross-Sectional Study.

Human exposure to PM2.5 and PM10 has been linked to respiratory and cardiovascular diseases through inflammation activation. The kynurenine pathway is associated with inflammation, and it is necessary to investigate the effects of long-term PM2.5 and PM10 exposure on this pathway. This study aimed to conduct a cross-sectional analysis of long-term PM2.5 and PM10 exposure's impact on the kynurenine pathway using proton NMR spectroscopy (1H-NMR). The participants were divided into a low-PM-exposure group (LG; n = 98), and a high-PM-exposure group (HG; n = 92). The metabolites of tryptophan were determined in blood by 1H-NMR. Serotonin, cinnabarinic acid, xanthurenic acid, 5-hydroxytryptophan, indoleacetic acid, tryptamine, melatonin, L-tryptophan, 5-hydroxy-L-tryptophol, indoxyl, 2-aminobenzoic acid, 5-HTOL, hydroxykynurenine, L-3-hydroxykynurenine, N-formyl kynurenine, 3-hydroxy anthranilic acid, kynurenic acid, and picolinic acid significantly increased (p < 0.05) in the HG group. Conversely, NAD and quinolinic acid significantly decreased in the HG group compared to the LG group. The enzyme activities of indoleamine 2,3-dioxygenase and formamidase significantly decreased, while kynureninase and kynurenine monooxygenase significantly increased. The kynurenine pathway is linked to inflammation and non-communicable diseases. Disruption of the kynurenine pathway from particulate matter might promote diseases. Reducing exposure to the particulate matter is crucial for preventing adverse health effects.

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.

Inhibition of Indoleamine 2,3-Dioxygenase Exerts Antidepressant-like Effects through Distinct Pathways in Prelimbic and Infralimbic Cortices in Rats under Intracerebroventricular Injection with Streptozotocin.

The application of intracerebroventricular injection of streptozotocin (ICV-STZ) is considered a useful animal model to mimic the onset and progression of sporadic Alzheimer's disease (sAD). In rodents, on day 7 of the experiment, the animals exhibit depression-like behaviors. Indoleamine 2,3-dioxygenase (IDO), a rate-limiting enzyme catalyzing the conversion of tryptophan (Trp) to kynurenine (Kyn), is closely related to depression and AD. The present study aimed to investigate the pathophysiological mechanisms of preliminary depression-like behaviors in ICV-STZ rats in two distinct cerebral regions of the medial prefrontal cortex, the prelimbic cortex (PrL) and infralimbic cortex (IL), both presumably involved in AD progression in this model, with a focus on IDO-related Kyn pathways. The results showed an increased Kyn/Trp ratio in both the PrL and IL of ICV-STZ rats, but, intriguingly, abnormalities in downstream metabolic pathways were different, being associated with distinct biological effects. In the PrL, the neuroprotective branch of the Kyn pathway was attenuated, as evidenced by a decrease in the kynurenic acid (KA) level and Kyn aminotransferase II (KAT II) expression, accompanied by astrocyte alterations, such as the decrease in glial fibrillary acidic protein (GFAP)-positive cells and increase in morphological damage. In the IL, the neurotoxicogenic branch of the Kyn pathway was enhanced, as evidenced by an increase in the 3-hydroxy-kynurenine (3-HK) level and kynurenine 3-monooxygenase (KMO) expression paralleled by the overactivation of microglia, reflected by an increase in ionized calcium-binding adaptor molecule 1 (Iba1)-positive cells and cytokines with morphological alterations. Synaptic plasticity was attenuated in both subregions. Additionally, microinjection of the selective IDO inhibitor 1-Methyl-DL-tryptophan (1-MT) in the PrL or IL alleviated depression-like behaviors by reversing these different abnormalities in the PrL and IL. These results suggest that the antidepressant-like effects linked to Trp metabolism changes induced by 1-MT in the PrL and IL occur through different pathways, specifically by enhancing the neuroprotective branch in the PrL and attenuating the neurotoxicogenic branch in the IL, involving distinct glial cells.

Direct parental CRISPR gene editing in the predatory bug Orius strigicollis, a biocontrol agent against small arthropods.

The predatory flower bug Orius strigicollis serves as a valuable biocontrol agent against small arthropods; however, its effectiveness can vary, especially when population establishment fails due to low prey/pest densities. A promising approach to improve the efficacy of O. strigicollis as a biocontrol agent is through gene editing. However, as females lay their eggs in plant tissue, the conventional embryo injection approach is challenging in this species. In this study, we aimed to develop an efficient and practical gene editing technique for O. strigicollis using direct parental CRISPR (DIPA-CRISPR). Female bugs at various postemergence stages received Cas9 ribonucleoprotein injections, with subsequent genotyping of their offspring (G0) using PCR and a heteroduplex mobility assay. We targeted the kynurenine 3-monooxygenase gene (cinnabar), pivotal for insect ommochrome pigment biosynthesis. Through experimental optimization, we achieved a peak gene editing efficiency of 52%, i.e., 52% of G0 progeny carried gene-edited alleles when injecting 1 day postemergence. Notably, some gene-edited G0 adults exhibited a red-eye mosaic phenotype, in contrast to the black-eyed wild type. Crossing experiments confirmed the heritability of the introduced mutations in the subsequent generation (G1), enabling the establishment of a cinnabar-knockout line with bright red eyes. We demonstrate that our DIPA-CRISPR gene editing method tailored for O. strigicollis is efficient and practical. Our findings highlight the potency of DIPA-CRISPR as a tool for O. strigicollis genetic engineering and suggest broader applications for enhancing other biocontrol agents. © 2024 Society of Chemical Industry.

DFT modeling of water-assisted hydrogen peroxide formation from a C(4a)-(hydro)peroxyflavin.

The cofactor of a class A monooxygenase is reduced at an external location of the enzyme and is subsequently pulled back into the active site after the reduction. This observation brings the question; is there any defense mechanism of the active site of a monooxygenase against the formation of the harmful hydrogen peroxide from the reactive C(4a)-(hydro)peroxide intermediate? In this study, the barrier energies of one to three water molecule-mediated uncoupling reaction mechanisms in water exposed reaction conditions were determined. These were found to be facile barriers. Secondly, uncoupling was modeled in the active site of kynurenine 3-monooxygenase complex which was represented with 258 atoms utilizing cluster approach. Comparison of the barrier energy of the cluster model to the models that represent the water exposed conditions revealed that the enzyme does not have an inhibitory reaction site architecture as the compared barrier energies are roughly the same. The main defense mechanism of KMO against the formation of the hydrogen peroxide is deduced to be the insulation, and without this insulation, the monooxygenation would not take place as the barrier height of the hydrogen peroxide formation within the active site is almost half of that of the monooxygenation.

Tryptophan Promotes the Production of Xanthophyll Compounds in Yellow Abdominal Fat through HAAO.

Abdominal fat, which in the past was often regarded as waste and discarded, has in recent years been used as a fat source to produce meat by-products. Yellow abdominal fat has higher economic value. Therefore, improving the color of abdominal fat plays an important role in improving the appearance of meat products. This study aimed to identify the contributors and the regulatory network involved in the formation of yellow and white color in abdominal fat. We found that four xanthophyll compounds were significantly different in yellow and white abdominal fat chicken, including zeaxanthin, lutein, canthaxanthin, and β-cryptoxanthin. There were 551 different and 8 common metabolites significantly correlated with these 4 xanthophyll compounds. Similarly, a total of 54 common genes were identified in 4 common related pathways (Complement and coagulation cascades, Metabolic pathways, PPAR signaling pathway, Carbon metabolism) of the 8 common metabolites. The high expression of HAAO in the yellow abdominal fat group leads to the degradation of tryptophan and its intermediate 5-hydroxyindole, and subsequently to the formation of the four xanthophyll compounds. This process is also regulated by tyrosine, kynurenine 3-monooxygenase (KMO), homogentisate 1, 2-dioxygenase (HGD), etc. Together, these findings show the effect of tryptophan on abdominal fat color, as well as a negative regulatory effect of HAAO and 5-hydroxyindole on the production of xanthophyll compounds involved in abdominal fat coloration.

Unraveling the nexus of NAD+ metabolism and diabetic kidney disease: insights from murine models and human data.

Nicotinamide adenine dinucleotide (NAD+) is a critical coenzyme involved in kidney disease, yet its regulation in diabetic kidney disease (DKD) remains inadequately understood. Therefore, we investigated the changes of NAD+ levels in DKD and the underlying mechanism. Alternations of NAD+ levels and its biosynthesis enzymes were detected in kidneys from streptozotocin-induced diabetic mouse model by real-time PCR and immunoblot. The distribution of NAD+ de novo synthetic enzymes was explored via immunohistochemical study. NAD+ de novo synthetic metabolite was measured by LC-MS. Human data from NephroSeq were analyzed to verify our findings. The study showed that NAD+ levels were decreased in diabetic kidneys. Both mRNA and protein levels of kynurenine 3-monooxygenase (KMO) in NAD+ de novo synthesis pathway were decreased, while NAD+ synthetic enzymes in salvage pathway and NAD+ consuming enzymes remained unchanged. Further analysis of human data suggested KMO, primarily expressed in the proximal tubules shown by our immunohistochemical staining, was consistently downregulated in human diabetic kidneys. Our study demonstrated KMO of NAD+ de novo synthesis pathway was decreased in diabetic kidney and might be responsible for NAD+ reduction in diabetic kidneys, offering valuable insights into complex regulatory mechanisms of NAD+ in DKD.

Identification of potent inhibitors of kynurenine-3-monooxygenase from natural products: In silico and in vitro approaches

Existing inhibitors of kynurenine-3-monooxygenase (KMO) have side effects and poorly cross the blood-brain barrier. Therefore, the discovery of new molecules targeting KMO isnecessary.This study aims to develop a novel therapeutic drug targeting KMO using computational methods and experimental validation of natural compounds.The results of our study show that the top four compounds, namely, 3′-Hydroxy-alpha-naphthoflavone exhibited the best docking scores with KMO (−10.0 kcal/mol), followed by 3′-Hydroxy-ss-naphthoflavone (−9.9 kcal/mol), genkwanin (−9.2 kcal/mol) and apigenin(-9.1 kcal/mol) respectively. Molecular dynamics was used to assess the stability of the primary target, KMO, and inhibitor complexes. We found stable interactions of 3′-Hydroxy-ss-naphthoflavone and apigenin with KMO up to 100 ns. Further, kinetic measurements showed that 3′-Hydroxy-alpha-naphthoflavone and 3′-Hydroxy-ss-naphthoflavone induce competitive inhibition with a good IC50 activity (15.85 ± 0.98 μM and 18.71 ± 0.78, respectively), while Genkwanin and Apigenin exhibit non-competitive inhibition mechanism (21.61 ± 0.97 μM and 24.14 ± 1.00 μM, respectively).Drug-likeness features and ADME analysis features also showed that the top four compounds could be used as potential candidates to replace the synthetic KMO inhibitor drugs with known side effects and poor brain-blood barrier penetration.

Cannabidiol disrupts tryptophan metabolism in the human term placenta

The increasing use of cannabis during pregnancy raises concerns about its impact on fetal development. While cannabidiol (CBD) shows therapeutic promise, its effects during pregnancy remain uncertain. We investigated CBD's influence on tryptophan (TRP) metabolism in the human placenta. TRP is an essential amino acid that is metabolized via the serotonin and kynurenine (KYN) pathways, which are critical for fetal neurodevelopment. We used human term villous placental explants, an advanced ex vivo model, to study CBD's impact on key TRP metabolic enzymes. In addition, vesicles isolated from the microvillous membrane (MVM) of the human placenta were used to assess CBD’s effect on placental serotonin uptake. Explants were exposed to CBD at therapeutic (0.1, 1, 2.5 μg/ml) and non-therapeutic (20 and 40 μg/ml) concentrations to determine its effects on the gene and protein expression of key enzymes in TRP metabolism and metabolite release. CBD upregulated TRP hydroxylase (TPH) and downregulated monoamine oxidase (MAO-A), resulting in reduced levels of 5-hydroxyindoleacetic acid (HIAA). It also downregulated serotonin transporter expression and inhibited serotonin transport across the MVM by up to 60% while simultaneously enhancing TRP metabolism via the kynurenine pathway by upregulating indoleamine-pyrrole 2,3-dioxygenase (IDO-1). Among kynurenine pathway enzymes, kynurenine 3 monooxygenase (KMO) was upregulated while kynurenine aminotransferase 1 (KAT-1) was downregulated; the former is associated with neurotoxic metabolite production, while the latter is linked to reduced neuroprotective metabolite levels. Overall, these results indicate that CBD modulates TRP catabolism in the human placenta, potentially disrupting the tightly regulated homeostasis of the serotonin and KYN pathways.

Kynurenine 3-monooxygenase limits de novo NAD+ synthesis through dietary tryptophan in renal proximal tubule epithelial cell models.

Nicotinamide adenine dinucleotide (NAD+) is a pivotal coenzyme, essential for cellular reactions, metabolism, and mitochondrial function. Depletion of kidney NAD+ levels and reduced de novo NAD+ synthesis through the tryptophan-kynurenine pathway are linked to acute kidney injury (AKI), whereas augmenting NAD+ shows promise in reducing AKI. We investigated de novo NAD+ biosynthesis using in vitro, ex vivo, and in vivo models to understand its role in AKI. Two-dimensional (2-D) cultures of human primary renal proximal tubule epithelial cells (RPTECs) and HK-2 cells showed limited de novo NAD+ synthesis, likely due to low pathway enzyme gene expression. Using three-dimensional (3-D) spheroid culture model improved the expression of tubular-specific markers and enzymes involved in de novo NAD+ synthesis. However, de novo NAD+ synthesis remained elusive in the 3-D spheroid culture, regardless of injury conditions. Further investigation revealed that 3-D cultured cells could not metabolize tryptophan (Trp) beyond kynurenine (KYN). Intriguingly, supplementation of 3-hydroxyanthranilic acid into RPTEC spheroids was readily incorporated into NAD+. In a human precision-cut kidney slice (PCKS) ex vivo model, de novo NAD+ synthesis was limited due to substantially downregulated kynurenine 3-monooxygenase (KMO), which is responsible for KYN to 3-hydroxykynurenine conversion. KMO overexpression in RPTEC 3-D spheroids successfully reinstated de novo NAD+ synthesis from Trp. In addition, in vivo study demonstrated that de novo NAD+ synthesis is intact in the kidney of the healthy adult mice. Our findings highlight disrupted tryptophan-kynurenine NAD+ synthesis in in vitro cellular models and an ex vivo kidney model, primarily attributed to KMO downregulation.NEW & NOTEWORTHY Nicotinamide adenine dinucleotide (NAD+) is essential in regulating mitochondrial function. Reduced NAD+ synthesis through the de novo pathway is associated with acute kidney injury (AKI). Our study reveals a disruption in de novo NAD+ synthesis in proximal tubular models, but not in vivo, attributed to downregulation of enzyme kynurenine 3-monooxygenase (KMO). These findings highlight a crucial role of KMO in governing de novo NAD+ biosynthesis within the kidney, shedding light on potential AKI interventions.

Whole-genome resequencing identifies candidate genes and SNPs in genomic regions associated with shell color selection in the Pacific oyster, Crassostrea gigas

The various shell colors of bivalves not only result in a better visual perception but also show great commercial value as a highly potential breeding trait. Four shell color strains of Pacific oyster (Crassostrea gigas) characterized by black (SB), white (SW), gold (SG), and orange (SO) were bred purposefully for more than ten generations. In this study, whole-genome resequencing was performed on 20 oysters from each of the four strains, and a total of 14.67 million single nucleotide polymorphisms (SNPs) were obtained after stringent filtering, with an average sequencing depth of >10×. The population structure analysis provided support for the subdivision of all samples into four major genetic clusters corresponding to shell color phenotypes, indicating a high level of genomic differentiation driven by artificial selection. Then, a composite measure of fixation index (FST) and cross-population composite likelihood ratio (XP-CLR) allowed us to identify 336 to 414 candidate divergent regions (CDRs) in pairwise comparisons of different shell colors, with a total of 480 to 614 corresponding genes distributed. Of particular interest were tyrosinase (TYR) and perilipin2 (PLIN2) occurring with extremely high frequency, which participates in shell color determination by regulating melanin production and carotenoid metabolism, respectively. In addition, two genes, namely porphobilinogen deaminase (PBGD) and hephaestin (HEPH), may have a potential function in the accumulation of specific porphyrin in orange shells, while the kynurenine 3-monooxygenase (KMO) gene, known to be involved in ommochrome biosynthesis, may contribute to the darker coloration in black shells. Further, a total of 304 SNPs were extracted from the exons of candidate genes mentioned above, of which 25 loci had highly significant differences among populations (p-value ≤0.01). After Sanger sequencing in another population, 14 SNPs were successfully validated as specific loci closely linked to different shell colors of black, white, gold, and orange, respectively. All in all, the results of this study shed light on the molecular basis of pigmentation and facilitate the selective breeding of C. gigas with desired phenotypic color.

Chronic Ethanol Intake Impairs Niacin Nutritional Status in Mice.

Niacin is involved in many biological reactions relating energy metabolism, redox reactions, DNA repair and longevity. Since niacin deficiency has been reported in alcoholic patients, and niacin coenzyme NAD is used as substrate to dehydrogenate ethanol in the liver, ethanol consumption can be a factor to impair niacin nutritional status. We have recently established the niacin insufficient model mice using kynurenine 3-monooxygenase knock out (KMO-/-) mice with niacin-limited diet, which lack the de novo NAD synthesis pathway from tryptophan. To evaluate the effects of chronic ethanol intake on niacin nutritional status, 4 wk old KMO-/- mice were fed 4 or 30 mg/kg nicotinic acid containing diets with or without 15% ethanol for 35 d. The mice fed 4 mg/kg nicotinic acid diet with ethanol showed lower body weight gain and niacin nutritional markers such as liver and blood NAD, and urine nicotinamide metabolites than the mice without ethanol. These animals did not show any difference in the NAD synthesis, NAD salvage and nicotinamide catabolic pathways. Chronic ethanol intake failed to affect any indices in the mice fed the 30 mg/kg nicotinic acid diet. When the diet was exchanged the 4 mg/kg for 30 mg/kg nicotinic acid diet to the mice showed chronic ethanol-induced growth retardation, their body weight rapidly increased. These results show that chronic ethanol intake impairs niacin nutritional status in the niacin insufficient mice, and enough niacin intake can prevent this impairment. Our findings also suggest that chronic ethanol intake increases niacin requirement by increase of NAD consumption.

Graphene oxide quantum dots (GOQDs) induce behavioral disorders via the disturbance of kynurenine pathway in zebrafish larvae

The emergence of graphene quantum dots (GQDs) expands the use of graphene derivatives in nanomedicine for its direct therapeutic applications in treating neurodegeneration, inflammation, metabolic dysfunction, and among others. Nevertheless, the biosafety assessment of GQDs remains deficient mostly because of the diverse surface characteristics of the nanoparticles. Our prior work demonstrated that GQDs can induce strong thigmotactic effects in zebrafish larvae over a wide range of concentrations, yet the underlying metabolic mechanisms remain largely unknown. In this study, we conducted a further exploration about graphene oxide quantum dots (GOQDs) for its potential neurotoxic effect on the behaviors of zebrafish larvae by combining neurotransmitter-targeted metabolomics with locomotion analysis. After continuous exposure to a concentration gradient of GOQDs (12.5 - 25 – 50 – 100 - 200 μg/mL) for 7 days, the thigmotactic activities of zebrafish larvae were observed across all exposure concentrations relative to the control group, while the basal locomotor activities, including distance moved and average velocity, were significantly changed by low concentrations of GOQDs. Targeted metabolomics was performed using zebrafish larvae at 7 days post-fertilization (dpf) that were exposed to 12.5 and 200 μg/mL, both of which were found to perturb the kynurenine pathway by regulating the levels of kynurenine, 3-hydroxyanthranilic acid (3-HAA), and quinolinic acid (QA). Furthermore, the thigmotaxis of larval fish induced by GOQDs during exposure could be counteracted by supplementing Ro-61-8048, an agonist acting on kynurenine 3-monooxygenase (KMO). In conclusion, our study establishes the involvement of the kynurenine pathway in GOQDs-induced thigmotaxis, which is independent of the transcriptional modulation of glutamate receptor families.

Construction and validation of a joint diagnosis model based on random forest and artificial intelligence network for hepatitis B-related hepatocellular carcinoma.

Hepatitis B virus (HBV) is the dominant pathogenic factor of hepatocellular carcinoma (HCC) in Asia and Africa. Early identification and clinical diagnosis are crucial for HBV-related HCC. Random forest (RF) and artificial neural network (ANN) were an innovative and highly effective supervised machine learning (ML) algorithm for the early diagnosis and screening of HBV-related HCC. This study aims to identify significant biomarkers and develop a novel genetic model for the efficient diagnosis of HBV-related HCC. Gene Expression Omnibus (GEO) Series (GSE)19665, GSE55092, and GSE121248 were used to identify significant differentially expressed genes (DEGs). The enrichment analysis was performed on Metascape online tool. The RF algorithm and ANN were used to select the potential predictive gene panels and construct an HBV-related HCC diagnostic model. Subsequently, GSE17548, GSE104310, GSE44074, and GSE136247 were used to test the accuracy of the ANN model. Finally, the CIBERSORT algorithm was used to assess the abundance of immune infiltrates in all samples. First, 116 genes were identified as DEGs, and the DEGs were particularly enriched in cellular hormone metabolic process, monocarboxylic acid metabolic process, NABA extracellular matrix (ECM) AFFILIATED steroid metabolic process and metabolism of bile acid and bile salt. DNA topoisomerase II alpha (TOP2A), C-type lectin domain family 1 member B (CLEC1B), BUB1 mitotic checkpoint serine/threonine kinase B (BUB1B), ficolin 2 (FCN2), C-X-C motif chemokine ligand 14 (CXCL14), cyclase associated actin cytoskeleton regulatory protein 2 (CAP2), ficolin 3 (FCN3), kynurenine 3-monooxygenase (KMO) and cadherin related family member 2 (CDHR2) were available to develop an HBV-related HCC diagnostic model. After validation, the diagnostic model showed high sensitivity (88.5%, 90%, 88.5%, 76.5%) and specificity (100%, 81.8%, 89.5%, 72.2%), and the areas under the receiver operating characteristic (ROC) curves showed excellent efficiency (1, 0.927, 0.921, 0.833). Finally, the percentage of infiltrating immune cell types [B cells naïve, B cells memory, plasma cells, T cells CD8, T cells CD4 memory resting, T cells regulatory (Tregs), T cells gamma delta, natural killer (NK) cells resting, NK cells activated, Macrophages M0, Dendritic cells activated, Mast cells activated] for hepatitis B-related HCC were significantly different from that of non-cancerous liver tissue with HBV. A novel early diagnostic model of HBV-related HCC was established, and the model showed better efficiency in distinguishing HBV-related HCC from other non-cancerous with HBV individuals.