Kynurenine 3-monooxygenase Research Articles

Oxidative and Excitatory Neurotoxic Stresses in CRISPR/Cas9-Induced Kynurenine Aminotransferase Knockout Mice: A Novel Model for Despair-Based Depression and Post-Traumatic Stress Disorder.

Memory and emotion are especially vulnerable to psychiatric disorders such as post-traumatic stress disorder (PTSD), which is linked to disruptions in serotonin (5-HT) metabolism. Over 90% of the 5-HT precursor tryptophan (Trp) is metabolized via the Trp-kynurenine (KYN) metabolic pathway, which generates a variety of bioactive molecules. Dysregulation of KYN metabolism, particularly low levels of kynurenic acid (KYNA), appears to be linked to neuropsychiatric disorders. The majority of KYNA is produced by the aadat (kat2) gene-encoded mitochondrial kynurenine aminotransferase (KAT) isotype 2. Little is known about the consequences of deleting the KYN enzyme gene. In CRISPR/Cas9-induced aadat knockout (kat2-/-) mice, we examined the effects on emotion, memory, motor function, Trp and its metabolite levels, enzyme activities in the plasma and urine of 8-week-old males compared to wild-type mice. Transgenic mice showed more depressive-like behaviors in the forced swim test, but not in the tail suspension, anxiety, or memory tests. They also had fewer center field and corner entries, shorter walking distances, and fewer jumping counts in the open field test. Plasma metabolite levels are generally consistent with those of urine: antioxidant KYNs, 5-hydroxyindoleacetic acid, and indole-3-acetic acid levels were lower; enzyme activities in KATs, kynureninase, and monoamine oxidase/aldehyde dehydrogenase were lower, but kynurenine 3-monooxygenase was higher; and oxidative stress and excitotoxicity indices were higher. Transgenic mice displayed depression-like behavior in a learned helplessness model, emotional indifference, and motor deficits, coupled with a decrease in KYNA, a shift of Trp metabolism toward the KYN-3-hydroxykynurenine pathway, and a partial decrease in the gut microbial Trp-indole pathway metabolite. This is the first evidence that deleting the aadat gene induces depression-like behaviors uniquely linked to experiences of despair, which appear to be associated with excitatory neurotoxic and oxidative stresses. This may lead to the development of a double-hit preclinical model in despair-based depression, a better understanding of these complex conditions, and more effective therapeutic strategies by elucidating the relationship between Trp metabolism and PTSD pathogenesis.

Constitutive loss of kynurenine-3-monooxygenase changes circulating kynurenine metabolites without affecting systemic energy metabolism.

Kynurenic acid (KYNA) and quinolinic acid (QUIN) are metabolites of the kynurenine pathway of tryptophan degradation with opposing biological activities in the central nervous system. In the periphery, KYNA is known to positively affect metabolic health, whereas the effects of QUIN remain less explored. Interestingly, metabolic stressors, including exercise and obesity, differentially change the balance between circulating KYNA and QUIN. Here, we hypothesized that chronically elevated levels of circulating KYNA and reduced levels of QUIN would manifest as differences in whole-body energy metabolism. To test this, we used a mouse model lacking the enzyme kynurenine 3-monooxygenase (KMO), thus shunting kynurenine away from QUIN synthesis and towards KYNA production. KMO-deficient and wild-type littermate male and female mice were evaluated under chow and high-fat diets. Comprehensive kynurenine pathway metabolite profiling in plasma showed that the loss of KMO elicits robust changes in circulating levels of kynurenine metabolites. This included a 45-fold increase in kynurenine, a 26-fold increase in KYNA, and a 99% decrease in QUIN levels, depending on the diet. However, despite these changes, loss of KMO did not significantly impact whole-body energy metabolism or change the transcriptomic profile of subcutaneous adipose tissue on either diet. With KMO inhibitors being considered as therapeutic candidates for various disorders, this work shows that chronic systemic KMO inhibition does not have widespread metabolic effects. Our data also indicates that the beneficial effects of KYNA on metabolism may depend on its acute, intermittent elevation in circulation, akin to transient exercise-induced signals that mediate improved metabolic health.

3-Hydroxyanthranic acid inhibits growth of oral squamous carcinoma cells through growth arrest and DNA damage inducible alpha.

The specific role of 3-hydroxyanthranilic acid(3-HAA) in oral squamous cell carcinoma (OSCC) remains unclear. This study investigated the roles of 3-HAA in OSCC and the underlying mechanism. The effects of 3-HAA on OSCC were examined using CCK-8, colony formation, EdU incorporation assays and xenograft mouse model. The underlying mechanisms were investigated with RNA-seq, apoptosis array and cell cycle array. Short hairpin RNAs (shRNAs) were used to knockdown the expression of growth arrest and DNA damage inducible alpha (GADD45A) in OSCC cells. CCK-8 and xenograft mouse model were employed to elucidate the role of GADD45A. The binding sites between GADD45A and Yin Yang 1(YY1) were determined using luciferase reporter assay. 3-HAA was selectively down-regulated in OSCC patients and the decreasing level intensified with pathological progression. Higher expression of kynurenine 3-monooxygenase (KMO) and kynureninase (KYNU), which can increase the content of 3-HAA, was associated with poorer prognosis of OSCC patients. Exogenous 3-HAA hampered growth of OSCC cells both in vitro and in vivo. 3-HAA induced growth arrest, G2/M-phase arrest, and apoptosis of OSCC cells. RNA-seq indicated that 3-HAA significantly increased GADD45A expression. 3-HAA promoted transcription of GADD45A by transcription factor YY1. Knockdown of GADD45A significantly reversed 3-HAA-induced growth inhibition of OSCC cells in vivo and in vitro. 3-HAA induced apoptosis and cell cycle arrest of OSCC cells via GADD45A, indicating that 3-HAA and GADD45A are potential therapeutic targets for OSCC.

In-Silico and In-Vivo Characterization of Anti-Neuro inflammatory potential of Tetrahydrocoptisine by using LPS-Induced model in mice

Neuroinflammation can be directly linked to the imbalance in the Kynurenine-tryptophan Pathway (KP) metabolism. Under inflammatory circumstances, the KP is activated, resulting in a rise in the KP metabolite L-kynurenine (KYN) in the peripheral and central nervous systems (CNS). Increased amounts of KYN in the brain may lead to neurotoxic KYN metabolites, mostly due to breakdown by Kynurenine-3-monooxygenase (KMO). Tetrahydrocoptisine (also known as stylopine) is an alkaloid isolated from Corydalis impatiens. Molecular docking with specific proteins involved in the Neuroinflammation mechanism was studied. LPS-induced neuroinflammation to mice. After 7 days of acclimatization, the animals in groups II, III, and IV were given 5 mg/kg i.p. of the endotoxin LPS. Groups III and IV were subsequently given daily intraperitoneal doses of 18.4 mg/kg and 36.8 mg/kg of our test medication Tetrahydrocoptisine, while group II was used as a disease control. On the 15th day, all groups were assessed neuro-behaviorally. On the 16th day, the mice were slaughtered for histopathology, lipid peroxidation, and nitrite studies. The neurobehavioural assessment involving elevated plus-maze, sucrose preference test, line crossing, and actophotometer revealed that the test drug is capable of decreasing LPS-induced anxiety, depression, and anhedonia at both low and high doses respectively. The histopathological analysis indicated that the neurodegeneration is attenuated at high doses of Tetrahydrocoptisine. A test drug demonstrated potency in inhibiting Kynurenine monooxygenase (KMO) expression in the brain, leading to reduced levels of nitric oxide and lipid peroxidation compared to a control group.

Chronic stress induces behavioural changes through increased kynurenic acid by downregulation of kynurenine-3-monooxygenase with microglial decline.

Alterations in tryptophan-kynurenine (TRP-KYN) pathway are implicated in major depressive disorder (MDD). α7 nicotinic acetylcholine (α7nACh) receptor regulates the hypothalamic-pituitary-adrenal (HPA) axis. We have shown that deficiency of kynurenine 3-monooxygenase (KMO) induces depression-like behaviour via kynurenic acid (KYNA; α7nACh antagonist). In this study, we investigated the involvement of the TRP-KYN pathway in stress-induced behavioural changes and the regulation of the HPA axis. Mice were exposed to chronic unpredictable mild stress (CUMS) and subjected to behavioural tests. We measured TRP-KYN metabolites and the expression of their enzymes in the hippocampus. KMO heterozygous mice were used to investigate stress vulnerability. We also evaluated the effect of nicotine (s.c.) on CUMS-induced behavioural changes and an increase in serum corticosterone (CORT) concentration. CUMS decreased social interaction time but increased immobility time under tail suspension associated with increased serum corticosterone concentration. CUMS increased KYNA levels via KMO suppression with microglial decline in the hippocampus. Kmo+/- mice were vulnerable to stress: they exhibited social impairment and increased serum corticosterone concentration even after short-term CUMS. Nicotine attenuated CUMS-induced behavioural changes and increased serum corticosterone concentration by inhibiting the increase in corticotropin-releasing hormone. Methyllycaconitine (α7nACh antagonist) inhibited the attenuating effect of nicotine. CUMS-induced behavioural changes and the HPA axis dysregulation could be induced by the increased levels of KYNA via KMO suppression. KYNA plays an important role in the pathophysiology of MDD as an α7nACh antagonist. Therefore, α7nACh receptor is an attractive therapeutic target for MDD.

Thrombin-induced kynurenine 3-monooxygenase causes variations in the kynurenine pathway, leading to neurological deficits in a murine intracerebral hemorrhage model

Thrombin-induced kynurenine 3-monooxygenase causes variations in the kynurenine pathway, leading to neurological deficits in a murine intracerebral hemorrhage model

Vision guides the twilight search for oviposition sites of the Asian tiger mosquito, Aedes albopictus.

Oviposition site selection is an important component of vector mosquito reproductive biology. The Asian Tiger mosquito, Aedes albopictus, is a major and important vector of arboviruses including Dengue. Previous studies documented the preference of gravid females for small, dark-colored water containers as oviposition sites, which they sought during the twilight period (dusk) of their locomotor activity. Vision plays an important role in this behavior, and factors such as the shape, size, and color of the container, light intensity, polarization, spectrum, and other visual cues guide the search for suitable oviposition sites, but the mechanistic factors driving this behavior are unclear. We blindfolded adult female compound eyes and observed the effects of a lack of vision on the ability to discriminate and utilize preferred oviposition sites. Furthermore, the transcriptomes of blindfolded mosquitoes were screened to identify genes with vision-sensitive expression profiles and gene-editing was used to create non-functional mutations in two of them, rhodopsin-like (mutation designated 'rho-l△807') and kynurenine hydroxylase (mutation designated 'khw'). Behavioral tests of both mutant and control strains revealed that the rho-l△807 mutant mosquitoes had a significant decrease in their ability to search for preferred oviposition sites that correlated with a reduced ability to recognize long-wavelength red light. The khw mutant mosquitoes also had a reduced ability to identify preferred oviposition sites that correlated with reductions in their ability to respond to variations in daily brightness and their ability to discriminate among different color options of the containers and background monochromatic light. This study underscores the importance of visual cues in the oviposition site selection behavior of adult female Ae. albopictus. We demonstrate that wild-type rho-l and kh gene products play a crucial role in this behavior, as mutants exhibit altered sensitivity or recognition of light intensity and substrate colors.

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

Metastasis remains the major cause of death in breast cancer (BrCa) and lacks specific treatment strategies. The kynurenine pathway (KP) has been suggested as a key mechanism facilitating progression of BrCa. While KP activity has been explored in primary BrCa, its role in metastasis remains unclear. To better understand this, we examined changes in the KP of BrCa with no metastasis compared to BCa that produced local or distant metastases. Given that the cancer cell secretome plays a role in metastasis, we also investigated the relationship between changes in KP activity and serum proteins of patients with local or distant metastases. To investigate changes in the KP in BrCa, with and without metastasis, we quantified KP metabolites in blood sera collected from patients with stage 1 BrCa (n = 34), BrCa with local metastases (n = 46), BrCa with distant metastases (n = 20) and healthy controls (n = 39). The serum protein profile of the BrCa patients with local or distant metastasis was determined before correlation analyses were carried out to examine the relationship between changes in the KP and cancer serum proteins using SPSS. We found that the KP was elevated in BrCa patients with local and distant metastasis compared to healthy controls and stage 1 BrCa patients. The activity of kynurenine monooxygenase (KMO) and kynureninase (KYNU) A was positively associated with disease stage and was higher compared to healthy controls. Proteome analysis in patients with local or distant metastasis revealed the dysregulation of 14 proteins, 9 of which were up-regulated and 5 down-regulated at the distant metastasis stage. Importantly, three of these proteins have not been previously linked to BrCa metastasis. In the correlation studies between the KP profile, cancer serum proteins and metastasis status, KYNU A had the greatest number of significant associations with cancer serum protein, followed by KMO. Our findings reveal that the KP was regulated differently at various stages of BrCa and was more dysregulated in patients with local or distant metastasis. These KP activity changes showed a significant association with cancer serum proteins in BrCa patients with local or distant metastasis, highlighting the potential role of KP in BrCa metastasis.

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.