3-Hydroxyanthranilic acid Administration Did Not Prevent Age Related Bone Loss

Aging is associated with accumulation of various tryptophan degradation products that may having either bone anabolic or catabolic effects. In epidemiologic studies, elevated levels of 3-hydroxyanthranilic acid (3-HAA) are associated with a higher bone mineral density (BMD). We have previously shown that the C57BL/6 mouse loses bone mass with age. Thus, we hypothesized that administering 3-HAA via a daily intraperitoneal (IP) injection would result in preserved or increased BMD. In an IACUC-approved protocol, we injected 26-month-old C57BL/6 mice with either a low dose (0.5 mg) or high dose (5 mg) of 3-HAA IP five days a week for eight weeks. At the end of this time mice were sacrificed and body composition and bone mineral density measured by DigiMus. BMD was significantly lower in the high dose 3-HAA group: 0.0570 + 0.004 vs 0.0473 + 0.006 vs 0.0432 + 0.0075 gm/cm2, (means+SD, Control vs 0.5 mg 3HAA vs 5 mg 3HAA, p=0.004, 0 vs 5.0 mg, n=6-9/group). 3-HAA had no significant impact on body composition (lean body mass: 86.7 + 1.7% vs 86.2 + 2.7% vs 86.1 + 2.0%, Control vs 0.5 mg vs 5.0 mg 3-HAA, p=ns; and fat mass 12.6 + 2.0% vs 13.8 + 2.7% vs 13.9 + 2.0% vs 0.2%, Control vs 0.5 vs 5 mg 3-HAA, p=ns). Thus, 3-HAA did not prevent bone loss in older mice but instead significantly worsened bone loss. 3-HAA is known to have both pro- and anti- oxidant effects depending on the environment. These data would suggest that at the higher concentrations 3-HAA is acting predominantly as a pro-oxidant molecule accelerating age-related bone loss.

Targeting kynurenine metabolism to reduce inflammation and enhance stress response during aging

Aberrant kynurenine pathway metabolism is increasingly linked to aging and age-associated disease. Kynurenine metabolic activity increases with age and becomes dysregulated during various forms of age-associated pathology in humans. By manipulating one or more kynurenine pathway enzymes and metabolites, we have extended lifespan up to 40% in Caenorhabditis elegans. In particular, elevating physiological levels of the kynurenine pathway metabolite 3-hydroxyanthranilic acid (3HAA) by directly supplementing 3HAA or inhibiting the enzyme 3HAA dioxygenase (HAAO) extends C. elegans lifespan by ~30%. 3HAA delivered chronically in chow similarly extends lifespan in aged C57BL/6 mice. In ongoing work, we are investigating the mechanisms underlying the benefits of multiple kynurenine pathway interventions using tools in C. elegans, mice, and human cell culture. We have preliminary evidence for activation of broad-spectrum cellular stress response, enhanced immune function, and reduced inflammation. Among other roles, the kynurenine pathway is the sole metabolic route for de novo synthesis of nicotinamide adenine dinucleotide (NAD+) from tryptophan in Eukaryotic cells. We are examining the regulatory interaction between kynurenine metabolism and the two NAD+ recycling pathways, Salvage and Preiss-Handler, both as potential mechanistic mediators and as possible parallel targets for combined interventions with synergistic benefits in aging. We are further evaluating the impact of these interventions in several models of specific age-associated diseases, including sepsis, chronic inflammation, stroke, Alzheimer’s disease, and cancer. Finally, we are developing pharmaceutical strategies to replicate key genetic and metabolic interventions within the kynurenine pathway that can be readily translated into clinical applications.

Combating Age-Associated Immune Decline Using Kynurenine Pathway Interventions

Select kynurenine pathway interventions extend lifespan in invertebrate models and are of interest in treating age-associated diseases. Kynurenine pathway activity is responsive to inflammatory signaling, and we are evaluating the potential for these interventions to increase pathogen resistance and curtail age-associated immune decline in Caenorhabditis elegans and mammals. The kynurenine pathway facilitates the catabolism of tryptophan to nicotinamide adenine dinucleotide (NAD). Our lab has found that supplementing the kynurenine metabolite 3-hydroxyanthranilic acid (3HAA) or inhibiting the enzyme 3HAA dioxygenase (HAAO) extends lifespan in C. elegans. 3HAA has demonstrated pro/anti-inflammatory properties in mammals, suggesting a potential role in immune function. C. elegans have a primitive immune system that lacks an adaptive element, but it recapitulates aspects of innate immune signaling and pathogen response. I hypothesize kynurenine pathway interventions that impact C. elegans’ lifespan similarly improve pathogen resistance and immunity. Interventions within the kynurenine pathway are capable of differentially impacting pathogenesis and lifespan of C. elegans challenged with Psuedomonas aeruginosa. C. elegans subjected to select lifespan-extending kynurenine pathway interventions fared better when challenged with P. aeruginosa at older ages. Additionally, fluorescent infection tracking has displayed decreased infection rates in worms with elevated 3HAA. Our data suggests pro-immune activity is facilitated by 3HAA acting downstream of the dbl-1 pathway in addition to directly inhibiting bacterial growth. Our goal is to discover the mechanism(s) through which the kynurenine pathway interacts with immune function in animals and identify potential targets for clinical therapy in aging populations.

Serum profiles of tryptophan-kynurenine pathway metabolites in psoriasis

Aim: Chronic inflammation is closely associated with tryptophan (TRP)-kynurenine (KYN) metabolic pathway. However, TRP-KYN pathway has not been fully elucidated in psoriasis, a systemic inflammatory disease with skin lesions and extracutaneous manifestations. Herein, we studied comprehensively serum profiles of TRP-KYN pathway metabolites in psoriatic patients (PSOs) to clarify the involvement of this pathway in the pathophysiology of psoriasis and to evaluate serum biomarkers reflecting systemic inflammation in PSOs. Methods: The concentrations of main TRP metabolites, TRP, KYN, 3-hydroxykynurenine (3HK), kynurenic acid (KYNA), 3-hydroxyanthranilic acid (3HAA), and anthranilic acid (AA), were determined by high-performance liquid chromatography in the sera from 65 PSOs and 35 healthy controls (HCs). The levels of these metabolites and the ratios of metabolites were compared between these subjects. The correlations between these values and the psoriasis area severity index (PASI) scores were analyzed. Skin samples from PSOs and HCs were subjected to immunohistochemical staining for kynureninase. Cytokine concentrations were comprehensively measured in the same samples and the correlations between the cytokine levels and TRP-KYN pathway metabolite levels were examined. Results: Serum TRP, KYN, and KYNA concentrations were lower and the 3HAA concentrations were higher in PSOs than in HCs. The ratios of 3HK/KYN, 3HAA/3HK, and 3HK/AA were higher in PSOs than in HCs. The AA levels and the ratio of AA/KYN were weakly positively correlated, and TRP, KYNA, and 3HK levels and the ratios of KYNA/KYN and 3HAA/AA were weakly negatively correlated with the PASI scores. The AA, KYN, and KYNA levels were positively correlated with the interferon gamma-induced protein 10 (IP-10) concentrations. Kynureninase expression was enhanced in the epidermis, both involved and uninvolved skin. Conclusions: Serum profiles of TRP-KYN pathway metabolites differed between PSOs and HCs. TRP-KYN pathway-associated processes, including kynureninase activation, may be involved in the pathogenesis of psoriasis, and thus serve as targets for psoriasis therapy.

Kynurenine derivative 3-HAA is an agonist ligand for transcription factor YY1

The 3-hydroxyanthranilic acid (3-HAA), a derivative of kynurenine, was reported to suppress tumor growth. However, the function of 3-HAA largely remains unclear. Here, we report that 3-hydroxyanthranilic acid (3-HAA) is lower in tumor cells, while adding exogenous 3-HAA induces apoptosis in hepatocellular carcinoma by binding YY1. This 3-HAA binding of YY1 leads to phosphorylation of YY1 at the Thr 398 by PKCζ, concomitantly enhances YY1 chromatin binding activity to increase expression of target genes. These findings demonstrate that 3-HAA is a ligand of YY1, suggesting it is a promising therapeutic candidate for HCC.

3-HAA Metabolic Pathway Regulates HCC Growth

Background Kynurenine, a metabolite of tryptophan, promotes immune tolerance in development and tumor evasion by binding to the aryl hydrocarbon receptor (AHR). However, the kynurenine catabolic enzyme IDO1 inhibitors fail in clinical trials. Methods The LC-MS/MS and GC-MS/MS were performed to measure the concentration of tryptophan metabolites. The PCX model, PDX model, and transposon liver cancer models were used to evaluate the effects of 3-HAA, DUSP6, and YY1 on HCC tumor formation and/or tumor growth. Results 3-hydroxyanthranilic acid (3-HAA) induced HCC apoptosis and reduced xenografted tumor growth, the survival of the transposon HCC mice, and synergized with IDO1 inhibitor on HCC growth in vivo. Overexpression of 3-HAA synthesis enzyme KMO suppressed tumor formation and tumor growth by increasing endogenous 3-HAA while adding exogenous 3-HAA also inhibited tumor growth. Notably, 3-HAA was lower in tumor cells due to the downregulation of its synthetic enzyme KMO/KYNU and/or upregulation of its catalytic enzyme HAAO. The mechanistic investigation demonstrated that 3-HAA induced dual-specificity phosphatase 6 (DUSP6) transcription. DUSP6 overexpression induced apoptosis of hepatocellular carcinoma (HCC) cells and suppressed the HCC growth in vitro and in vivo. DUSP6 knockdown abolished 3-HAA-induced apoptosis and restores tumor growth. Conclusions These findings demonstrate that 3-HAA metabolic pathway regulates HCC cell growth, suggesting it is a promising therapeutic candidate for HCC.

Associations between plasma kynurenines and cognitive function in individuals with normal glucose metabolism, prediabetes and type 2 diabetes: the Maastricht Study

Aims/hypothesis Studies investigating associations between kynurenines and cognitive function have generally been small, restricted to clinical samples or have found inconsistent results, and associations in the general adult population, and in individuals with type 2 diabetes in particular, are not clear. Therefore, the aim of the present study was to investigate cross-sectional associations between plasma kynurenines and cognitive function in a cohort of middle-aged participants with normal glucose metabolism, prediabetes (defined as impaired fasting glucose and/or impaired glucose tolerance) and type 2 diabetes. Methods Plasma kynurenines were quantified in 2358 participants aged 61 ± 8 years. Cross-sectional associations of kynurenines with cognitive impairment and cognitive domain scores were investigated using logistic, multiple linear and restricted cubic spline regression analyses adjusted for several confounders. Results Effect modification by glucose metabolism status was found for several associations with cognitive impairment, hence analyses were stratified. In individuals with prediabetes, 3-hydroxykynurenine (OR per SD 0.59 [95% CI 0.37, 0.94]) and 3-hydroxyanthranilic acid (0.67 [0.47, 0.96]) were associated with lower odds of cognitive impairment after full adjustment. In individuals with type 2 diabetes, kynurenine (0.80 [0.66, 0.98]), 3-hydroxykynurenine (0.82 [0.68, 0.99]), kynurenic acid (0.81 [0.68, 0.96]), xanthurenic acid (0.73 [0.61, 0.87]) and 3-hydroxyanthranilic acid (0.73 [0.60, 0.87]) were all associated with lower odds of cognitive impairment. Kynurenic acid (β per SD 0.07 [95% CI 0.02, 0.13]) and xanthurenic acid (0.06 [0.01, 0.11]) were also associated with better executive function/attention. No associations were observed in individuals with normal glucose metabolism. Conclusions/interpretation Several kynurenines were cross-sectionally associated with lower odds of cognitive impairment and better cognitive functioning in type 2 diabetes, while less widespread associations were seen in prediabetes. Low levels of kynurenines might be involved in the pathway of type 2 diabetes and cognitive decline but this needs further studies. Graphical abstract

SYNTHESIS OF NEW QUINAZOLINONE-BASED CONJUGATES AND IN VITRO CYTOTOXIC EVALUATION

A series of new quinazolione derivatives containing a conjugate sytem 13 a-l were synthesized via a three step-procedure. The first step is the condensation of 5-hydroxyanthranilic acid (10) at 160oC for 2 h to afford the intermediate 11 in high yield. This intermediate was then reacted with n-butylamin in acetic acid at 160oC for 14 h to give 12 in 92%. Finally, the reaction of 12 with different aldehydes in acetic acid at 140oC for 14h furnished new conjugates 13a-l in 62-81%. The bioassay results showed that several compounds displayed cytotoxic effect against two cell lines including HepG-2 and SKLu-1 in which 13h exhibited the strongest cytotoxic effect against SKLu-1 with IC50 value of 5.05 µg/mL.

Genetic engineering of Pseudomonas chlororaphis Lzh-T5 to enhance production of trans-2,3-dihydro-3-hydroxyanthranilic acid

Trans-2,3-dihydro-3-hydroxyanthranilic acid (DHHA) is a cyclic β-amino acid used for the synthesis of non-natural peptides and chiral materials. And it is an intermediate product of phenazine production in Pseudomonas spp. Lzh-T5 is a P. chlororaphis strain isolated from tomato rhizosphere found in China. It can synthesize three antifungal phenazine compounds. Disruption the phzF gene of P. chlororaphis Lzh-T5 results in DHHA accumulation. Several strategies were used to improve production of DHHA: enhancing the shikimate pathway by overexpression, knocking out negative regulatory genes, and adding metal ions to the medium. In this study, three regulatory genes (psrA, pykF, and rpeA) were disrupted in the genome of P. chlororaphis Lzh-T5, yielding 5.52 g/L of DHHA. When six key genes selected from the shikimate, pentose phosphate, and gluconeogenesis pathways were overexpressed, the yield of DHHA increased to 7.89 g/L. Lastly, a different concentration of Fe3+ was added to the medium for DHHA fermentation. This genetically engineered strain increased the DHHA production to 10.45 g/L. According to our result, P. chlororaphis Lzh-T5 could be modified as a microbial factory to produce DHHA. This study laid a good foundation for the future industrial production and application of DHHA.

Establishment of an Early Diagnosis Model of Colon Cancerous Bowel Obstruction Based on 1HNMR

Objective To prospectively establish an early diagnosis model of acute colon cancerous bowel obstruction by applying nuclear magnetic resonance hydrogen spectroscopy(1H-NMR) technology based metabolomics methods, combined with machine learning. Methods In this study, serum samples of 71 patients with acute bowel obstruction requiring emergency surgery who were admitted to the Emergency Department of Sichuan Provincial People's Hospital from December 2018 to November 2020 were collected within 2 hours after admission, and NMR spectroscopy data was taken after pretreatment. After postoperative pathological confirmation, they were divided into colon cancerous bowel obstruction (CBO) group and adhesive bowel obstruction (ABO) control group. Used MestReNova software to extract the two sets of spectra bins, and used the MetaboAnalyst5.0 website to perform partial least square discrimination (PLS-DA), combining the human metabolome database (HMDB) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to find possible different Metabolites and related metabolic pathways. Results 22 patients were classified as CBO group and 30 were classified as ABO control group. Compared with ABO group, the level of Xanthurenic acid, 3-Hydroxyanthranilic acid, Gentisic acid, Salicyluric acid, Ferulic acid, Kynuric acid, CDP, Mandelic acid, NADPH, FAD, Phenylpyruvate, Allyl isothiocyanate, and Vanillylmandelic acid increased in the CBO group; while the lecel of L-Tryptophan and Bilirubin decreased (all P < 0.05). There were significant differences between two groups in the tryptophan metabolism, tyrosine metabolism, glutathione metabolism, phenylalanine metabolism and synthesis pathways of phenylalanine, tyrosine and tryptophan (all P < 0.05). Tryptophan metabolism pathway had the greatest impact (Impact = 0.19). The early diagnosis model of colon cancerous bowel was established based on the levels of six metabolites: Xanthurenic acid, 3-Hydroxyanthranilic acid, Gentisic acid, Salicylic acid, Ferulic acid and Kynuric acid (R2 = 0.995, Q2 = 0.931, RMSE = 0.239, AUC = 0.962). Conclusion This study firstly used serum to determine the difference in metabolome between patients with colon cancerous bowel obstruction and those with adhesive bowel obstruction. The study found that the metabolic information carried by the serum was sufficient to discriminate the two groups of patients and provided the theoretical supporting for the future using of the more convenient sample for the differential diagnosis of patients with colon cancerous bowel obstruction. Quantitative experiments on a large number of samples were still needed in the future.