3-hydroxyanthranilic Acid Research Articles

Determination of 3-hydroxyanthranilic acid in the sweat of healthy older adults

3-Hydroxyanthranillic acid (3HAA) is one of the key metabolites from the tryptophan (TRP) metabolism pathway and is associated with aging, age-associated diseases, and healthy lifespan extension. This study aims to detect 3HAA in the sweat of healthy older adults using simple, high-performance liquid chromatography (HPLC) method. Chromatographic separation using 20 mmol/L sodium acetate, 3 mmol/L zinc acetate, and 7% (v/v) acetonitrile as mobile phase is possible to simultaneous detect 3HAA, KYN, and TRP with UV and fluorescence detection, respectively, under 6 min. This method demonstrated excellent linearity with coefficient of determination (r2) greater than 0.998 for all analytes. The linear range were 0.05–6 µg/mL for TRP, 0.1–6 µg/mL for KYN and 0.2–6 µg/mL for 3HAA. Percentage recoveries from spiked in human sweat ranged from 90 ± 7–101 ± 3 for TRP, 86 ± 1–92 ± 3 for KYN, and 96 ± 1–103 ± 4 for 3HAA. The precision (%RSD) of repeatability and reproducibility is less than 3% and 6%, respectively. This method was used in a cross-sectional study with 81 participants aged 50–79 years, selected randomly from a local primary healthcare hospital’s sampling frame. A detectable amount of 3HAA was observed in all sweat samples, marking the first report of 3HAA presence in human sweat. Additionally, the results revealed that the 3HAA sweat levels increased with age analyzed in three different age groups ranging from 50–59, 60–69, and 70–79. These findings enhance our understanding of sweat profiles and their correlation with aging, potentially further improving early diagnosis, disease monitoring, and development of customized treatment programs for older adults.

Usefulness of the 3-hydroxykynurenine/kynurenic acid ratio as a diagnostic biomarker for diffuse larger B-cell lymphoma.

Reports have shown that the kynurenine pathway, one of the pathways by which tryptophan is metabolized, is activated in patients with diffuse large B-cell lymphoma (DLBCL). Activation of the kynurenine pathway triggers the production of various metabolites, such as kynurenine (Kyn), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilic acid (3-HAA), kynurenic acid (KA) and anthranilic acid (AA), which contribute to immune tolerance. The current study aimed to investigate the changes in metabolites of kynurenine pathway in DLBCL patients and evaluate their performance predicting DLBCL. Changes in metabolites of kynurenine pathway were examined using high-performance liquid chromatography in 35 DLBCL patients (age 61.2 ± 13.5 years) and 44 healthy controls (age 58.5 ± 12.5 years). DLBCL patients had significantly higher levels of 3-HK, AA, and 3-HAA but lower levels of Tryptophan (Trp) and KA compared to healthy controls. Given that the ratio of each metabolite represents the change in the Kyn pathway, the 3-HK/KA ratio was examined. Notably, DLBCL patients had a significantly higher 3-HK/KA ratio compared to healthy controls. In DLBCL, the area under the receiver operative characteristic (ROC) curve for 3-HK/KA (0.999) was higher than that for lactate dehydrogenase (0.885) and comparable to that for soluble interleukin-2 receptor (sIL-2R) (0.997). Based on ROC curve analysis, the 3-HK/KA ratio was found to be useful biomarker for the diagnosis of DLBCL. Our results suggest that the 3-HK/KA ratio is a clinically useful biomarker of DLBCL. Moreover, its combination with existing markers, such as sIL-2R, can improve its effectiveness of diagnosing DLBCL.

Impaired Kynurenine Pathway in Inflammatory Bowel Disease

Background/Objectives: Inflammatory bowel diseases primarily encompass Crohn’s disease and ulcerative colitis. Insufficient levels of tryptophan cause an imbalance in the gut microbiota, leading to inflammation in the gastrointestinal tract. The main catabolic pathway of tryptophan is the kynurenine pathway. Our study aims to evaluate serum tryptophan, the kynurenine pathway, and oxidative stress parameters, including total oxidant status and total antioxidant capacity, in patients with Crohn’s disease and ulcerative colitis. Methods: The study included 80 follow-up patients in remission diagnosed with Crohn’s disease and ulcerative colitis who attended the Gastroenterology Outpatient Clinic, as well as 78 healthy controls. Serum tryptophan, kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and kynurenic acid levels were measured with liquid chromatography and tandem mass spectrometry (LC-MS/MS). All statistical analysis was performed using R version 4.2.1. Statistical Language. Results: Serum tryptophan, 3-hydroxyanthranilic acid, and total antioxidant capacity were lower in patients with ulcerative colitis and Crohn’s disease compared to those in the control group. The serum total oxidant status in the control group was significantly lower than in patients with Crohn’s disease and ulcerative colitis. Conclusions: The results of our research indicate that tryptophan and kynurenine pathway metabolites could potentially contribute to the pathogenesis of inflammatory bowel diseases.

Transcriptomic and Metabolomic Analyses Reveal the Attenuating Role of Cordycepin and Cordyceps militaris Extract on Acute Liver Injury Induced by LPS in Piglets.

Cordyceps militaris extract (CME) contains many bioactive compounds, mainly cordycepin (CPN). This study aimed to investigate the possible mechanisms underlying the amelioration of LPS-induced acute liver injury in piglets by CME or CPN supplementation using multi-omics analysis. Twenty-four weaned piglets were randomly distributed into 4 groups (n = 6): the control and LPS groups were fed basal diets; the CPN + LPS (CPN-LPS) and CME + LPS (CME-LPS) groups were fed the basal diets supplemented with CME or CPN. The results showed that CPN or CME supplementation significantly decreased the C-reactive protein level (p < 0.05) and improved liver tissue pathology to prevent acute liver injury after LPS treatment. Compared with LPS, the transcriptomic analysis indicated that CPN supplementation significantly downregulated cell adhesion molecules, while CME supplementation significantly downregulated inflammatory mediator regulation of TRP channels, complement and coagulation cascades and cytokine-cytokine receptor interaction. The metabolomic results showed that CPN or CME supplementation significantly reduced disease biomarker of bicyclo-prostaglandin E2, and increased levels of deoxyinosine and 3-hydroxyanthranilic acid (p < 0.05). The combined transcriptome and metabolome helped identify two metabolites PC 34:2 and PC 36:0, which may be associated with the restoration of liver cell morphology. In conclusion, CPN and CME could attenuate LPS-induced acute liver injury by regulating immune-related genes and metabolites. This study elucidates the potential protective mechanism of CPN or CME supplementation against acute liver injury.

Untargeted Metabolomics and Quantitative Analysis of Tryptophan Metabolites in Myalgic Encephalomyelitis Patients and Healthy Volunteers: A Comparative Study Using High-Resolution Mass Spectrometry.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, complex illness characterized by severe and often disabling physical and mental fatigue. So far, scientists have not been able to fully pinpoint the biological cause of the illness and yet it affects millions of people worldwide. To gain a better understanding of ME/CFS, we compared the metabolic networks in the plasma of 38 ME/CFS patients to those of 24 healthy control participants. This involved an untargeted metabolomics approach in addition to the measurement of targeted substances including tryptophan and its metabolites, as well as tyrosine, phenylalanine, B vitamins, and hypoxanthine using liquid chromatography coupled to mass spectrometry. We observed significant alterations in several metabolic pathways, including the vitamin B3, arginine-proline, and aspartate-asparagine pathways, in the untargeted analysis. The targeted analysis revealed changes in the levels of 3-hydroxyanthranilic acid, 3-hydroxykynurenine, hypoxanthine, and phenylalanine in ME/CFS patients compared to the control group. These findings suggest potential alterations in immune system response and oxidative stress in ME/CFS patients.

Modulation of Aromatic Amino Acid Metabolism by Indigenous Non-Saccharomyces Yeasts in Croatian Maraština Wines.

This study aimed to provide novel information on the impact of indigenous non-Saccharomyces yeasts, including Metschnikowia chrysoperlae, Metschnikowia sinensis/shanxiensis, Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum, Hanseniaspora guilliermondii, and Pichia kluyveri, on metabolites related to the metabolism of tryptophan, phenylalanine, and tyrosine. The experiment included two fermentation practices: monoculture and sequential fermentation with commercial Saccharomyces cerevisiae, using sterile Maraština grape juice. A targeted approach through ultrahigh-resolution liquid chromatography associated with mass spectrometry was used to quantify 38 metabolites. All the indigenous yeasts demonstrated better consumption of tryptophan in monoculture than in interaction with S. cerevisiae. M. sinensis/shanxiensis was the only producer of indole-3-carboxylic acid, while its ethyl ester was detected in monoculture fermentation with H. guilliermondii. H. guilliermondii consumed the most phenylalanine among the other isolates. 5-hydroxy-L-tryptophan was detected in fermentations with M. pulcherrima and M. sinensis/shanxiensis. M. pulcherrima significantly increased tryptophol content and utilised tyrosine in monoculture fermentations. Sequential fermentation with M. sinensis/shanxiensis and S. cerevisiae produced higher amounts of N-acetyl derivatives of tryptophan and phenylalanine, while H. guilliermondii-S. cerevisiae fermentation resulted in wines with the highest concentrations of L-kynurenine and 3-hydroxyanthranilic acid. P. kluyveri produced the highest concentration of N-acetyl-L-tyrosine in monoculture fermentations. These findings highlight the different yeast metabolic pathways.

Abstract P141: Salt tips the balance of tryptophan metabolism between host and gut microbiota in a sex specific manner

Introduction: Tryptophan (Trp) diet attenuates hypertension in male Dahl salt sensitive (S) rats with unknown mechanisms. Kynurenine (a vasodilator) and serotonin (mixed effects on blood pressure) are host-derived Trp metabolites while indole is produced exclusively by the gut microbiota. We have previously shown that the gut microbiota of male, but not female, S rats is susceptible to salt, causing a higher indole level that elevated blood pressure. In this study, we reported the sex differences in all Trp metabolites with a focus on the impact of salt and the mechanisms by which female gut microbiota is more resilient. Methodology: S rats of both sexes (10–13-week-old, n = 4-7/group) were maintained on either a low-salt (0.3 % NaCl, LS) or high-salt (2 % NaCl, HS) diet for 3 weeks. Trp metabolites were analyzed in serum and cecum by LC-MS/MS. To investigate if estrogen shape gut microbiota, gonadectomy was performed on 7-week-old Spontaneously Hypertensive Rats (SHR) of both sexes (n=5/group). β-estradiol (2.8 mg/kg) was administered subcutaneously for 12 weeks before fecal 16S rRNA gene sequencing. Results: Females had elevated levels of kynurenine (Kyn) compared to male S rats on both LS (5.5 ± 1.4 vs. 2.1 ± 0.5 µM; P &lt;0.05) and HS (7 ± 1.3 vs. 4.2 ± 1 µM; P &lt;0.05). Kyn metabolites including kynurenic acid, 3-hydroxykynurenine, 3-hydroxyanthranilic acid were elevated in the serum of females compared with males, and HS amplified this difference (all P &lt;0.05). Further, HS significantly decreased the serum serotonin levels in both sexes ( P &lt;0.01 in females, P &lt;0.0001 in males). Intriguingly, HS increased cecal indole levels in male ( P &lt;0.05), but not in female rats. Microbiota analysis of gonadectomized (GDX) SHR rats revealed (1) Significant differences in β-diversity between intact vs. GDX rats ( P &lt;0.01), and between GDX male vs. female rats ( P =0.01); (2) Estrogen supplementation eliminates the gut microbiota differences between GDX females and males ( P =0.18). Conclusion: We demonstrated sex differences in Trp metabolism in response to high salt. Further, estrogen masked the microbial differences between GDX male and female SHR rats. In summary, salt led to an elevated Trp-Kyn metabolism in female host, and an enhanced Trp-indole metabolism in male gut microbiota, which could be due to the estrogen’s effect on shaping gut microbiota. Thus, the Trp metabolism in salt-sensitive hypertension is regulated in a sex-specific manner.

In vitro antioxidant activity of Moringa oleifera lam. Leaf after Monascus purpureus fermentation and chemical component changes by untargeted metabolomics

This study aims to explore the enhancement effect of semi-solid fermentation of Monascus purpureus on the antioxidant properties of Moringa oleifera Lam. leaf (MOLL), as well as to analyze the potential antioxidant substances and their production mechanisms. In this study, the antioxidant activity of MOLL fermented with Monascus purpureus was evaluated in vitro. To gain further insight, we employed untargeted metabolomics to analyze the differentially abundant metabolites, and 30 key differentially expressed metabolites were identified. Notably, 15 of these metabolites were positively correlated with free radical scavenging activity. By utilizing a combination of KEGG topological and enrichment analyses, tryptophan metabolism was identified as a crucial pathway. Interestingly, Monascus purpureus fermentation significantly enhanced the conversion of tryptophan into metabolites with antioxidant properties, such as melatonin, kynurenine, and 3-hydroxyanthranilic acid, suggesting that fermentation with Monascus purpureus is a promising approach for enhancing the antioxidant properties of MOLL.

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.

Preliminary studies on changes in the amount of tryptophan metabolites in human glioma tissues

BackgroundWe have developed and validated methods for the determination of three major tryptophan metabolites metabolized by the kynurenine pathway, namely kynurenine (KYN), 3-hydroxykynurenine (3-HK), and 3-hydroxyanthranilic acid (3-HAA). KYN and 3-HK were determined using RP-HPLC-UV, and 3-HAA using RP-HPLC-FL. We then developed a comparative method based on CE-UV. The developed methods were validated and 36 samples of human brain glioma tissue homogenates were assayed in all 4 grades of malignancy, and the concentration levels of assayed metabolites were compared with available clinical data. ResultsEach of the methods is characterized by high precision, accuracy and repeatability, and the determined LOQ values indicate the possibility of performing quantitative analysis on the available samples of human glioma tumors (36 samples in grades G1–G4). The concentration values of selected metabolites obtained using HPLC methods were subjected to statistical analysis and preliminary clinical data processing. We found statistically significant differences in the concentrations of KYN, 3-HK and 3-HAA between the various grades of the disease, and characterized these differences more precisely by means of the Dunn–Bonferroni post hoc test. We did not find that the patient's environment or habits significantly affected the metabolites concentration of the study samples population. In addition, we showed a high positive correlation between KYN, 3-HK and 3-HAA, which appears to be a characteristic that describes metabolic changes of Trp in relation to KYN, 3-HK and 3-HAA, and indicates potential diagnostic value. SignificanceThe preliminary studies carried out contribute new knowledge on the molecular basis of human brain glioma. They also provide valuable information useful for the development of glioma diagnostics, differentiation of disease grades and assessment of the patient's condition. The obtained relationships between metabolite concentrations and the grade of malignancy of the disease and correlations between metabolite concentrations constitute the basis for further broader biochemical and clinical analysis.

Substrate-Based Ligand Design for Phenazine Biosynthesis Enzyme PhzF.

The phenazine pyocyanin is an important virulence factor of the pathogen Pseudomonas aeruginosa, which is on the WHO list of antibiotic resistant "priority pathogens". In this study the isomerase PhzF, a key bacterial enzyme of the pyocyanin biosynthetic pathway, was investigated as a pathoblocker target. The aim of the pathoblocker strategy is to reduce the virulence of the pathogen without killing it, thus preventing the rapid development of resistance. Based on crystal structures of PhzF, derivatives of the inhibitor 3-hydroxyanthranilic acid were designed. Co-crystal structures of the synthesized derivatives with PhzF revealed spacial limitations of the binding pocket of PhzF in the closed conformation. In contrast, ligands aligned to the open conformation of PhzF provided more room for structural modifications. The intrinsic fluorescence of small 3-hydroxyanthranilic acid derivatives enabled direct affinity determinations using FRET assays. The analysis of structure-activity relationships showed that the carboxylic acid moiety is essential for binding to the target enzyme. The results of this study provide fundamental structural insights that will be useful for the design of PhzF-inhibitors.

Discovery of Novel Ortho-Aminophenol Derivatives Targeting Lipid Peroxidation with Potent Antiferroptotic Activities.

The concept of ferroptosis inhibition has gained growing recognition as a promising therapeutic strategy for addressing a wide range of diseases. Here, we present the discovery of four series of ortho-aminophenol derivatives as potential ferroptosis inhibitors beginning with the endogenous substance 3-hydroxyanthranilic acid (3-HA) by employing quantum chemistry techniques, in vitro and in vivo assays. Our findings reveal that these ortho-aminophenol derivatives exhibit unique intra-H bond interactions, compelling ortho-amines to achieve enhanced alignment with the aromatic π-system, thereby expanding their activity. Notably, compounds from all four series display remarkable activity against RSL3-induced ferroptosis, showcasing an activity 100 times more than that of 3-HA. Furthermore, these compounds also demonstrate robust in vivo efficacy in protecting mice from kidney ischemia-reperfusion injury and acetaminophen-induced hepatotoxicity. In summary, we provide four distinct series of active scaffolds that significantly expand the chemical space of ferroptosis inhibitors, serving as valuable insights for future structural modifications.

Eight-day fasting modulates serum kynurenines in healthy men at rest and after exercise.

Tryptophan's (Trp) metabolites are undervalued markers of human health. Their serum concentrations are modified by physical exercise and other factors, among which fasting has a well-documented role. Although this mechanism is hardly explored, thus, the study aimed to determine the effect of the 8-day fasting period and the impact of such a procedure on a single bout of an endurance exercise on the concentration of kynurenine pathway (KP) metabolites. 10 participants fasted for 8 days, and 10 as a control group participated in the study. The exercise was performed at baseline after an overnight fast and repeated post 8 days. The 8 days of fasting increased the resting 3-hydroxy-L-kynurenine (3HK), picolinic acid (PA), kynurenic acid (KYNA), and xanthurenic acid (XA) serum concentration. Also elevated phenylalanine (Phe) and tyrosine (Tyr) levels were recorded, suggesting expanded proteolysis of muscle proteins. In turn, physical activity caused a decrease in the concentration of 3-hydroxyanthranilic acid (3HAA) and PA after fasting. The obtained results were not recorded in controls. The results of this study show that the health-promoting effects of fasting are associated with changes in the KYN pathway. The increase in the concentration of PA and XA metabolites following fasting is capable of penetrating the blood-brain barrier, and KYNA, which initiates several beneficial changes, supports this assumption.

The role of the kynurenine pathway in cardiovascular disease.

The kynurenine pathway (KP) serves as the primary route for tryptophan metabolism in most mammalian organisms, with its downstream metabolites actively involved in various physiological and pathological processes. Indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) serve as the initial and pivotal enzymes of the KP, with IDO playing important and intricate roles in cardiovascular diseases. Multiple metabolites of KP have been observed to exhibit elevated concentrations in plasma across various cardiovascular diseases, such as atherosclerosis, hypertension, and acute myocardial infarction. Multiple studies have indicated that kynurenine (KYN) may serve as a potential biomarker for several adverse cardiovascular events. Furthermore, Kynurenine and its downstream metabolites have complex roles in inflammation, exhibiting both inhibitory and stimulatory effects on inflammatory responses under different conditions. In atherosclerosis, upregulation of IDO stimulates KYN production, mediating aromatic hydrocarbon receptor (AhR)-induced exacerbation of vascular inflammation and promotion of foam cell formation. Conversely, in arterial calcification, this mediation alleviates osteogenic differentiation of vascular smooth muscle cells. Additionally, in cardiac remodeling, KYN-mediated AhR activation exacerbates pathological left ventricular hypertrophy and fibrosis. Interventions targeting components of the KP, such as IDO inhibitors, 3-hydroxyanthranilic acid, and anthranilic acid, demonstrate cardiovascular protective effects. This review outlines the mechanistic roles of KP in coronary atherosclerosis, arterial calcification, and myocardial diseases, highlighting the potential diagnostic, prognostic, and therapeutic value of KP in cardiovascular diseases, thus providing novel insights for the development and application of related drugs in future research.

An exploratory study on the effect of kynurenine metabolites on sEnd-2 endothelioma cells.

Cancer is the second leading cause of mortality worldwide. The development of anticancer therapy plays a crucial role in mitigating tumour progression and metastasis. Epithelioid hemangioendothelioma is a very rare cancer, however, with a high systemic involvement. Kynurenine metabolites which includel-kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid have been shown to inhibit T-cell proliferation resulting in a decrease in cell growth of natural killercells and T cells. Furthermore, metabolites such as l-kynurenine have been shown to inhibit proliferation of melanoma cells in vitro. Considering these metabolite properties, the present study aimed to explore the in vitro effects of l-kynurenine, quinolinic acid and kynurenic acid on endothelioma sEnd-2 cells and on endothelial (EA. hy926 cells) (control cell line). The in vitro effect at 24, 48, and 72 h exposure to a range of 1-4 mM of the respective kynurenine metabolites on the two cell lines in terms of cell morphology, cell cycle progression and induction of apoptosis was assessed. The half inhibitory concentration (IC50), as determined using nonlinear regression, for l-kynurenine, quinolinic acid and kynurenic acid was 9.17, 15.56, and 535.40 mM, respectively. Optical transmitted light differential interference contrast and hematoxylin and eosin staining revealed cells blocked in metaphase, formation of apoptotic bodies and compromised cell density in l-kynurenine-treated cells. A statistically significant increase in the number of cells present in the sub-G1 phase was observed in l-kynurenine-treated sample. To our knowledge, this was the first in vitro study conducted to investigate the mechanism of action of kynurenine metabolites on endothelioma sEnd-2 cells. It can be concluded that l-kynurenine exerts an antiproliferative effect on the endothelioma sEnd-2 cell line by decreasing cell growth and proliferation as well as a metaphase block. These hallmarks suggest cell death via apoptosis. Further research will be conducted on l-kynurenine to assess the effect on cell adhesion in vitro and in vivo as cell-cell adhesion has been shown to increase metastasis to distant organs therefore, the inhibition of adhesion may lead to a decrease in metastasis.

Electro-oxidation of synthetic lignin with different mediators for the laccase mediator system (3-hydroxyanthranilic acid, 4-hydroxybenzoic acid, phenol red)

Three mediators for the laccase mediator system, 3-hydroxyanthranilic acid (3-HAA), 4-hydroxybenzoic acid (HBA), and phenol red (PR) were investigated as mediators in an electrolytic mediator system (EMS) for the degradation of guaiacyl synthetic lignin (G-DHP). All the electron-oxidations of G-DHP with 3-HAA, HBA and PR in the absence of 2,6-lutidine proceeded to give the electrolysis residues in moderate yields. The significant β-β and β-5 linkage loss was found in all the electrolysis residues, especially the residue in the electro-oxidation with PR was significant. The addition of 2,6-lutidine as a base increased the yields of the electrolysis residues and influenced the relative ratio of β-O-4, β-5 and β-β linkages to some extent, that is, increase of β-O-4 linkage loss and decrease of β-β linkages loss (in the electro-oxidation with 3-HAA), increase of β-O-4 linkage loss (in that with 3-HBA), increase of β-5 linkages loss (in that with PR at 0.35 V) and decrease of β-O-4 and β-β linkages loss (in that with PR at 0.70 V). Thus, the base such as 2,6-lutidine was also one of the critical factors for reaction efficiency and reaction selectivity in the EMS. Consequently,3-HAA, HBA, and PR could be used as mediators in EMS for lignin degradation, especially 3-HAA is the most preferable because of the low applied potential.

3-Hydroxyanthranilic Acid Delays Paralysis in Caenorhabditis elegans Models of Amyloid-Beta and Polyglutamine Proteotoxicity.

Age is the primary risk factor for neurodegenerative diseases such as Alzheimer's and Huntington's disease. Alzheimer's disease is the most common form of dementia and a leading cause of death in the elderly population of the United States. No effective treatments for these diseases currently exist. Identifying effective treatments for Alzheimer's, Huntington's, and other neurodegenerative diseases is a major current focus of national scientific resources, and there is a critical need for novel therapeutic strategies. Here, we investigate the potential for targeting the kynurenine pathway metabolite 3-hydroxyanthranilic acid (3HAA) using Caenorhabditis elegans expressing amyloid-beta or a polyglutamine peptide in body wall muscle, modeling the proteotoxicity in Alzheimer's and Huntington's disease, respectively. We show that knocking down the enzyme that degrades 3HAA, 3HAA dioxygenase (HAAO), delays the age-associated paralysis in both models. This effect on paralysis was independent of the protein aggregation in the polyglutamine model. We also show that the mechanism of protection against proteotoxicity from HAAO knockdown is mimicked by 3HAA supplementation, supporting elevated 3HAA as the mediating event linking HAAO knockdown to delayed paralysis. This work demonstrates the potential for 3HAA as a targeted therapeutic in neurodegenerative disease, though the mechanism is yet to be explored.

The Mediating Role of Kynurenine Pathway Metabolites on the Relationship Between Inflammation and Muscle Mass in Oldest-Old Men.

Tryptophan (TRP) metabolites along the kynurenine (KYN) pathway (KP) have been found to influence muscle. Proinflammatory cytokines are known to stimulate the degradation of TRP down the KP. Given that both inflammation and KP metabolites have been connected with loss of muscle, we assessed the potential mediating role of KP metabolites on inflammation and muscle mass in older men. Five hundred and five men (85.0 ± 4.2 years) from the Osteoporotic Fractures in Men cohort study with measured D3-creatine dilution (D3Cr) muscle mass, KP metabolites, and inflammation markers (C-reactive protein [CRP], alpha-1-acid glycoprotein [AGP] and a subsample [n = 305] with interleukin [IL-6, IL-1β, IL-17A] and tumor necrosis factor-α [TNF-α]) were included in the analysis. KP metabolites and inflammatory markers were measured using liquid chromatography-tandem mass spectrometry and immunoassays, respectively. 23%-92% of the inverse relationship between inflammatory markers and D3Cr muscle mass was mediated by KP metabolites (indirect effect p < .05). 3-hydroxyanthranilic acid (3-HAA), quinolinic acid (QA), TRP, xanthurenic acid (XA), KYN/TRP, 3-hydroxykynurenine (3-HK)/3-HAA, QA/3-HAA, and nicotinamide (NAM)/QA mediated the AGP relationship. 3-HAA, QA, KYN/TRP, 3-HK/XA, HKr ratio, 3-HK/3-HAA, QA/3-HAA, and NAM/QA mediated the CRP. KYN/TRP, 3-HK/XA, and NAM/QA explained the relationship for IL-6 and 3-HK/XA and QA/3-HAA for TNF-α. No mediation effect was observed for the other cytokines (indirect effect p > .05). KP metabolites, particularly higher ratios of KYN/TRP, 3-HK/XA, 3-HK/3-HAA, QA/3-HAA, and a lower ratio of NAM/QA, mediated the relationship between inflammation and low muscle mass. Our preliminary cross-sectional data suggest that interventions to alter D3Cr muscle mass may focus on KP metabolites rather than inflammation per se.

The combination of Butyricicoccus pullicaecorum and 3-hydroxyanthranilic acid prevents postmenopausal osteoporosis by modulating gut microbiota and Th17/Treg

BackgroundPostmenopausal osteoporosis (PMO) is a chronic condition characterized by decreased bone strength. This study aims to investigate the effects and mechanisms of the combination of Butyricicoccus pullicaecorum (Bp) and 3-hydroxyanthranilic acid (3-HAA) on PMO.MethodsThe effects of Bp and 3-HAA on PMO were evaluated in ovariectomized (OVX) rats by assessing stereological parameters, femur microstructure, and autophagy levels. The T helper (Th) 17/Regulatory T (Treg) cells of rats were detected using flow cytometric analysis. Furthermore, the impact of Bp and 3-HAA on the gut microbiota of rats was assessed using 16S rRNA gene sequencing. The correlation between the gut microbiota of rats and Th17/Treg immune factors, as well as femoral stereo parameters, was separately assessed using Spearman rank correlation analysis.ResultsBp and 3-HAA treatments protected OVX rats by promoting osteogenesis and inhibiting autophagy. Compared to the Sham group, OVX rats showed an increase in Th17 cells and a decrease in Treg cells. Bp and 3-HAA reversed these changes. Enterorhabdus and Pseudomonas were significantly enriched in OVX rats. Bp and 3-HAA regulated the gut microbiota of OVX rats, enriching pathways related to nutrient metabolism and immune function. There was a correlation between the gut microbiota and the Th17/Treg, as well as femoral stereo parameters. The concurrent administration of Bp and 3-HAA medication facilitated the enrichment of gut microbiota associated with the improvement of PMO.ConclusionThe combination therapy of Bp and 3-HAA can prevent PMO by modulating the gut microbiota and restoring Th17/Treg immune homeostasis.

The In Vitro Effect of Kynurenine Metabolites on Cell morphology, Cell cycle progression and the Induction of Apoptosis in Tumour Endothelioma Cells

Background: Cancer is one of the leading causes of death worldwide. The development of anticancer therapies plays a crucial role in mitigating tumour progression and metastasis. Kynurenine metabolites which include L-kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid have been shown to inhibit T-cell proliferation resulting in a decrease in cell growth of natural killer (NK) cells and T cells. Research showed that L-kynurenine inhibits proliferation of melanoma cells in vitro. Methods: The present study aimed to explore the in vitro influence of L-kynurenine, quinolinic acid and kynurenic acid on endothelioma sEnd-2 cells at concentration ranges of 1 mM – 4 mM for 24 h, 48 h and 72 h on cell morphology, cell cycle progression and induction of apoptosis. Results and Discussion: The half inhibitory concentration (IC50), as determined using GraphPad Prism, for L-kynurenine, quinolinic acid and kynurenic acid was 10.77 mM, 14.78 mM and 535.40 mM respectively. Optical transmitted light differential interference contrast and hematoxylin and eosin staining revealed the presence of cells blocked in metaphase, formation of apoptotic bodies and compromised cell density in L-kynurenine- and quinolinic acid- treated cells. A statistically significant increase in the number of cells present in the sub-G1 phase was observed in L-kynurenine-treated samples. Conclusion: It can be concluded that L-kynurenine exerts an antiproliferative effect on the sEnd-2 cell line by a decrease in cell growth and proliferation and metaphase block. These hallmarks suggest cell death via apoptosis. Further research will be conducted on L-kynurenine to assess the effect on cell adhesion in vitro and in vivo. This research was supported by the following grants: The Research Development Programme at the University of Pretoria awarded to Dr YN Hlophe; National Research Foundation awarded to Dr YN Hlophe (A1F4685 &amp; N1F580); The University Capacity Development Programme (UCDP) awarded to Ms Tatchum (A1D783 &amp; N1F120). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.