Kynurenine pathway metabolism following prenatal KMO inhibition and in Mecp2+/− mice, using liquid chromatography-tandem mass spectrometry

Abstract

To quantify the full range of tryptophan metabolites along the kynurenine pathway, a liquid chromatography – tandem mass spectrometry method was developed and used to analyse brain extracts of rodents treated with the kynurenine-3-mono-oxygenase (KMO) inhibitor Ro61-8048 during pregnancy. There were significant increases in the levels of kynurenine, kynurenic acid, anthranilic acid and 3-hydroxy-kynurenine (3-HK) in the maternal brain after 5 h but not 24 h, while the embryos exhibited high levels of kynurenine, kynurenic acid and anthranilic acid after 5 h which were maintained at 24 h post-treatment. At 24 h there was also a strong trend to an increase in quinolinic acid levels (P = 0.055). No significant changes were observed in any of the other kynurenine metabolites. The results confirm the marked increase in the accumulation of some neuroactive kynurenines when KMO is inhibited, and re-emphasise the potential importance of changes in anthranilic acid. The prolonged duration of metabolite accumulation in the embryo brains indicates a trapping of compounds within the embryonic CNS independently of maternal levels. When brains were examined from young mice heterozygous for the meCP2 gene – a potential model for Rett syndrome - no differences were noted from control mice, suggesting that the proposed roles for kynurenines in autism spectrum disorder are not relevant to Rett syndrome, supporting its recognition as a distinct, independent, condition.

Kynurenine Pathway Activation in Human African Trypanosomiasis

“…We were unable to measure the terminal metabolites—xanthurenic acid, quinolinic acid, and picolinic acid—that have previously been detected by this tandem mass spectrometry method in brain samples [ 19 ]. CSF levels of xanthurenic acid were <0.5 nmol/L, and accurate quantification would require the concentration of larger sample volumes prior to analysis..…”

“…Tandem mass spectrometry parameters were as follows: curtain gas, 45; CAD gas, medium; ion source voltage, −4500 V; gas temperature, 400°C; gas 1, 30; and gas 2, 30. Full details of mass spectrometry conditions are described by Forrest et al [ 19 ].…”

Galantamine-Memantine Combination and Kynurenine Pathway Enzyme Inhibitors in the Treatment of Neuropsychiatric Disorders

“…In addition, this KMO inhibitor also managed to increase 3-HK and QUIN levels in the rat striatum moderately [97]. Ro61-8048 is another experimental inhibitor of KMO that has been shown to substantially increase KYNA levels in the brain by more than 10-fold [98][99][100]. Another KMO inhibitor, meta-nitrobenzoyl alanine, has been studied widely [101,102] and is associated with markedly elevated levels of KYNA in the rat brain (nearly 5 times more than the baseline).…”

Quantitative proteomic analysis shows alterations in patient Rett syndrome iPSC cultures at early neuronal progenitor stages

“…Although RTT is more often classified as a neurodevelopmental disorder, recent studies in cytokine release also suggest involvement of the immune system [49]. A previous study demonstrated that during early brain formation disturbances in the metabolism produces changes in the morphological and biochemical development of the brains [50]. Another study further observed that models with synaptic defects during development fail to couple to metabolic pathways [51].…”