ABSTRACT
BackgroundPyridoxine-dependent epilepsy (PDE-ALDH7A1) is an inborn error of lysine catabolism that presents with refractory epilepsy in newborns. Biallelic ALDH7A1 variants lead to deficiency of α-aminoadipic semialdehyde dehydrogenase/antiquitin, resulting in accumulation of piperideine-6-carboxylate (P6C), and secondary deficiency of the important cofactor pyridoxal-5'-phosphate (PLP, active vitamin B6) through its complexation with P6C. Vitamin B6 supplementation resolves epilepsy in patients, but intellectual disability may still develop. Early diagnosis and treatment, preferably based on newborn screening, could optimize long-term clinical outcome. However, no suitable PDE-ALDH7A1 newborn screening biomarkers are currently available.MethodsWe combined the innovative analytical methods untargeted metabolomics and infrared ion spectroscopy to discover and identify biomarkers in plasma that would allow for PDE-ALDH7A1 diagnosis in newborn screening.ResultsWe identified 2S,6S-/2S,6R-oxopropylpiperidine-2-carboxylic acid (2-OPP) as a PDE-ALDH7A1 biomarker, and confirmed 6-oxopiperidine-2-carboxylic acid (6-oxoPIP) as a biomarker. The suitability of 2-OPP as a potential PDE-ALDH7A1 newborn screening biomarker in dried bloodspots was shown. Additionally, we found that 2-OPP accumulates in brain tissue of patients and Aldh7a1-knockout mice, and induced epilepsy-like behavior in a zebrafish model system.ConclusionThis study has opened the way to newborn screening for PDE-ALDH7A1. We speculate that 2-OPP may contribute to ongoing neurotoxicity, also in treated PDE-ALDH7A1 patients. As 2-OPP formation appears to increase upon ketosis, we emphasize the importance of avoiding catabolism in PDE-ALDH7A1 patients.FundingSociety for Inborn Errors of Metabolism for Netherlands and Belgium (ESN), United for Metabolic Diseases (UMD), Stofwisselkracht, Radboud University, Canadian Institutes of Health Research, Dutch Research Council (NWO), and the European Research Council (ERC).
Subject(s)
Epilepsy/metabolism , Metabolomics , Pipecolic Acids/metabolism , Aldehyde Dehydrogenase/deficiency , Aldehyde Dehydrogenase/metabolism , Animals , Biomarkers/metabolism , Child , Epilepsy/genetics , Female , Humans , Mice , Mice, Knockout , Spectrophotometry, Infrared , Zebrafish/genetics , Zebrafish/metabolismABSTRACT
JMJD2A, a 2-oxoglutarate dependent N(epsilon)-methyl lysine histone demethylase, is inhibited by disruption of its Zn-binding site by Zn-ejecting compounds including disulfiram and ebselen; this observation may enable the development of inhibitors selective for this subfamily of 2OG dependent oxygenases that do not rely on binding to the highly-conserved Fe(ii)-containing active site.
Subject(s)
Jumonji Domain-Containing Histone Demethylases/metabolism , Zinc/chemistry , Azoles/chemistry , Binding Sites , Catalytic Domain , Crystallography, X-Ray , Disulfiram/chemistry , Isoindoles , Jumonji Domain-Containing Histone Demethylases/antagonists & inhibitors , Organoselenium Compounds/chemistry , Selenium/chemistry , Spectrometry, Mass, Electrospray IonizationABSTRACT
The hypoxic response in humans is regulated by the hypoxia-inducible transcription factor system; inhibition of hypoxia-inducible factor (HIF) activity has potential for the treatment of cancer. Chetomin, a member of the epidithiodiketopiperazine (ETP) family of natural products, inhibits the interaction between HIF-alpha and the transcriptional coactivator p300. Structure-activity studies employing both natural and synthetic ETP derivatives reveal that only the structurally unique ETP core is required and sufficient to block the interaction of HIF-1alpha and p300. In support of both cell-based and animal work showing that the cytotoxic effect of ETPs is reduced by the addition of Zn(2+) through an unknown mechanism, our mechanistic studies reveal that ETPs react with p300, causing zinc ion ejection. Cell studies with both natural and synthetic ETPs demonstrated a decrease in vascular endothelial growth factor and antiproliferative effects that were abrogated by zinc supplementation. The results have implications for the design of selective ETPs and for the interaction of ETPs with other zinc ion-binding protein targets involved in gene expression.