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Walters DC, Brown MN, Schmidt MA, Klein AB, Wellendorph P, Vogel KR, Ainslie GR, Roullet J, Gibson KM. Novel Molecular Markers in Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD), an Orphan Disorder of GABA Metabolism. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.818.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Brown MN, Gibson KM, Schmidt MA, Walters DC, Roullet J. Clinical Efficacy of Glutamine Supplementation in
aldh5a1
KO Mice (
aldh5a1
−/−
)
, a Phenocopy of the GABA Metabolic Disorder Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD). FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.553.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Vogel KR, Ainslie GR, McConnell A, Roullet JB, Gibson KM. Toxicologic/transport properties of NCS-382, a γ-hydroxybutyrate (GHB) receptor ligand, in neuronal and epithelial cells: Therapeutic implications for SSADH deficiency, a GABA metabolic disorder. Toxicol In Vitro 2017; 46:203-212. [PMID: 29031482 DOI: 10.1016/j.tiv.2017.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 09/24/2017] [Accepted: 10/10/2017] [Indexed: 12/16/2022]
Abstract
We report the in vitro assessment of pharmacotoxicity for the high-affinity GHB receptor ligand, NCS-382, using neuronal stem cells derived from mice with a targeted deletion of the aldehyde dehydrogenase 5a1 gene (succinic semialdehyde dehydrogenase(SSADH)-deficient mice). These animals represent a phenocopy of the human disorder of GABA metabolism, SSADH deficiency, that metabolically features accumulation of both GABA and the GABA-analog γ-hydroxybutyric acid in conjunction with a nonspecific neurological phenotype. We demonstrate for the first time using MDCK cells that NCS-382 is actively transported and capable of inhibiting GHB transport. Following these in vitro assays with in vivo studies in aldh5a1-/- mice, we found the ratio of brain/liver GHB to be unaffected by chronic NCS-382 administration (300mg/kg; 7 consecutive days). Employing a variety of cellular parameters (reactive oxygen and superoxide species, ATP production and decay, mitochondrial and lysosomal number, cellular viability and necrosis), we demonstrate that up to 1mM NCS-382 shows minimal evidence of pharmacotoxicity. As well, studies at the molecular level indicate that the effects of NCS-382 at 0.5mM are minimally toxic as evaluated using gene expression assay. The cumulative data provides increasing confidence that NCS-382 could eventually be considered in the therapeutic armament for heritable SSADH deficiency.
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Koenig MK, Hodgeman R, Riviello JJ, Chung W, Bain J, Chiriboga CA, Ichikawa K, Osaka H, Tsuji M, Gibson KM, Bonnen PE, Pearl PL. Phenotype of GABA-transaminase deficiency. Neurology 2017; 88:1919-1924. [PMID: 28411234 DOI: 10.1212/wnl.0000000000003936] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 02/27/2017] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE We report a case series of 10 patients with γ-aminobutyric acid (GABA)-transaminase deficiency including a novel therapeutic trial and an expanded phenotype. METHODS Case ascertainment, literature review, comprehensive evaluations, and long-term treatment with flumazenil. RESULTS All patients presented with neonatal or early infantile-onset encephalopathy; other features were hypotonia, hypersomnolence, epilepsy, choreoathetosis, and accelerated linear growth. EEGs showed burst-suppression, modified hypsarrhythmia, multifocal spikes, and generalized spike-wave. Five of the 10 patients are currently alive with age at last follow-up between 18 months and 9.5 years. Treatment with continuous flumazenil was implemented in 2 patients. One patient, with a milder phenotype, began treatment at age 21 months and has continued for 20 months with improved alertness and less excessive adventitious movements. The second patient had a more severe phenotype and was 7 years of age at initiation of flumazenil, which was not continued. CONCLUSIONS GABA-transaminase deficiency presents with neonatal or infantile-onset encephalopathy including hypersomnolence and choreoathetosis. A widened phenotypic spectrum is reported as opposed to lethality by 2 years of age. The GABA-A benzodiazepine receptor antagonist flumazenil may represent a therapeutic strategy.
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Bi W, Bi Y, Gao X, Li P, Hou S, Zhang Y, Bammert C, Jockusch S, Legalley TD, Michael Gibson K, Bi L. Indole-TEMPO conjugates alleviate ischemia-reperfusion injury via attenuation of oxidative stress and preservation of mitochondrial function. Bioorg Med Chem 2017; 25:2545-2568. [PMID: 28359673 DOI: 10.1016/j.bmc.2017.03.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 03/14/2017] [Accepted: 03/16/2017] [Indexed: 01/13/2023]
Abstract
Mitochondrial oxidative damage contributes to a wide range of pathologies including ischemia/reperfusion injury. Accordingly, protecting mitochondria from oxidative damage should possess therapeutic relevance. In the present study, we have designed and synthesized a series of novel indole-TEMPO conjugates that manifested good anti-inflammatory properties in a murine model of xylene-induced ear edema. We have demonstrated that these compounds can protect cells from simulated ischemia/reperfusion (s-I/R)-induced reactive oxygen species (ROS) overproduction and mitochondrial dysfunction. Furthermore, we have demonstrated that indole-TEMPO conjugates can attenuate organ damage induced in rodents via intestinal I/R injury. We therefore propose that the pharmacological profile and mechanism of action of these indole-TEMPO conjugates involve convergent roles, including the ability to decrease free radical production via lipid peroxidation which couples to an associated decrease in ROS-mediated activation of the inflammatory process. We further hypothesize that the protective effects of indole-TEMPO conjugates partially reside in maintaining optimal mitochondrial function.
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Vogel KR, Arning E, Bottiglieri T, Gibson KM. Multicompartment analysis of protein-restricted phenylketonuric mice reveals amino acid imbalances in brain. J Inherit Metab Dis 2017; 40:227-235. [PMID: 27761676 DOI: 10.1007/s10545-016-9984-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 09/12/2016] [Accepted: 09/18/2016] [Indexed: 02/05/2023]
Abstract
BACKGROUND The mainstay of therapy for phenylketonuria (PKU) remains dietary protein restriction. Developmental and neurocognitive outcomes for patients, however, remain suboptimal. We tested the hypothesis that mice with PKU receiving protein-restricted diets would reveal disruptions of brain amino acids that shed light on these neurocognitive deficits. METHOD Phenylalanine hydroxylase-deficient (PKU) mice and parallel controls (both wild-type and heterozygous) were fed custom diets containing 18, 6, and 4 % protein for 3 weeks, after which tissues (brain, liver, sera) were collected for amino acid analysis profiling. RESULTS Phenylalanine (phe) was increased in all tissues (p < 0.0001) of PKU mice and improved with protein restriction. In sera, decreased tyrosine (p < 0.01) was corrected (defined as not significantly different from the level in control mice receiving 18 % chow) with protein restriction, whereas protein restriction significantly increased many other amino acids. A similar trend for increased amino acid levels with protein restriction was also observed in liver. In brain, the effects of protein restriction on large neutral amino acids (LNAAs) were variable, with some deficit correction (threonine, methionine, glutamine) and no correction of tyrosine under any dietary paradigm. Protein restriction (4 % diet) in PKU mice significantly decreased lysine, arginine, taurine, glutamate, asparagine, and serine which had been comparable to control mice under 18 % protein intake. CONCLUSION Depletion of taurine, glutamate, and serine in the brain of PKU mice with dietary protein restriction may provide new insight into neurocognitive deficits of PKU.
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Johansen SS, Wang X, Sejer Pedersen D, Pearl PL, Roullet JB, Ainslie GR, Vogel KR, Gibson KM. Gamma-Hydroxybutyrate (GHB) Content in Hair Samples Correlates Negatively with Age in Succinic Semialdehyde Dehydrogenase Deficiency. JIMD Rep 2017; 36:93-98. [PMID: 28213850 DOI: 10.1007/8904_2017_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/02/2017] [Accepted: 01/05/2017] [Indexed: 12/13/2022] Open
Abstract
Gamma-hydroxybutyrate (GHB) is a drug of abuse, an approved therapeutic for narcolepsy, an agent employed for facilitation of sexual assault, as well as a biomarker of succinic semialdehyde dehydrogenase deficiency (SSADHD). Our laboratory seeks to identify surrogate biomarkers in SSADHD that can shed light on the developmental course of this neurometabolic disease. Since GHB may be quantified in hair as a potential surrogate to identify victims of drug-related assault, we have opted to examine its level in SSADHD. We quantified GHB in hair derived from ten patients with SSADHD, and documented a significant negative age correlation. These findings are consistent with recent results in patient biological fluids, including plasma and red blood cells. These findings may provide additional insight into the developmental course of SSADHD (Jansen et al., J Inherit Metab Dis 39:795-800, 2016).
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Vogel KR, Ainslie GR, Pearl PL, Gibson KM. Aberrant mTOR signaling and disrupted autophagy: The missing link in potential vigabatrin-associated ocular toxicity? Clin Pharmacol Ther 2017; 101:458-461. [PMID: 27864823 DOI: 10.1002/cpt.581] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/07/2016] [Accepted: 11/15/2016] [Indexed: 12/31/2022]
Abstract
Vigabatrin (VGB; γ-vinylGABA) is a unique antiepileptic directly elevating CNS GABA via inactivation of the GABA metabolic enzyme GABA-transaminase. VGB is effective in treating infantile spasms, a rare seizure disorder associated with significant morbidity. The potential for unexplained bilateral constriction of the visual field associated with VGB intervention can severely limit its temporal utility. Removal of this potential adverse effect with adjuvant intervention(s) would represent a significant advance in epilepsy therapeutics.
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Vogel KR, Ainslie GR, Roullet JB, McConnell A, Gibson KM. In vitro toxicological evaluation of NCS-382, a high-affinity antagonist of γ-hydroxybutyrate (GHB) binding. Toxicol In Vitro 2017; 40:196-202. [PMID: 28119166 DOI: 10.1016/j.tiv.2017.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Revised: 01/16/2017] [Accepted: 01/19/2017] [Indexed: 12/17/2022]
Abstract
γ-Hydroxybutyric acid (GHB), a minor metabolite of the inhibitory neurotransmitter GABA, can accumulate to significant concentrations in the heritable disorder of GABA degradation, succinic semialdehyde dehydrogenase (SSADH) deficiency (SSADHD). Moreover, GHB may be employed in therapeutic settings (treatment of narcolepsy), as well as instances of illicit activity, including acquaintance sexual assault and the induction of euphoria. High-affinity binding sites for GHB in the brain have been identified, although the absolute identity of these receptors remains unclear. Pharmacological antagonism of GHB binding may have multiple instances of therapeutic relevance. The high affinity GHB receptor antagonist, NCS-382 (6,7,8,9-tetrahydro-5-hydroxy-5H-benzo-cyclohept-6-ylideneacetic acid) has not been piloted in humans. To address the potential clinical utility of NCS-382, we have piloted initial studies of its toxicology in HepG2 and primary hepatocyte cells. At high dose (0.5mM), NCS-382 showed no capacity for inhibition of microsomal CYPs (CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4) and minimal potential for activation of xenobiotic nuclear receptors. Additional cellular integrity and functional assays (viability, oxidative stress, apoptosis, ATP production) revealed little evidence for cytotoxicity, and a low degree of dysregulation of >370 genes actively engaged in the mediation of cellular toxicity. In vitro testing indicates a low probability of cellular toxicity associated with NCS-382.
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Vogel KR, Ainslie GR, Schmidt MA, Wisor JP, Gibson KM. mTOR Inhibition Mitigates Molecular and Biochemical Alterations of Vigabatrin-Induced Visual Field Toxicity in Mice. Pediatr Neurol 2017; 66:44-52.e1. [PMID: 27816307 PMCID: PMC5866057 DOI: 10.1016/j.pediatrneurol.2016.09.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 09/21/2016] [Accepted: 09/25/2016] [Indexed: 01/01/2023]
Abstract
BACKGROUND Gamma-vinyl-γ-aminobutyric acid (GABA) (vigabatrin) is an antiepileptic drug and irreversible GABA transaminase inhibitor associated with visual field impairment, which limits its clinical utility. We sought to relate altered visual evoked potentials associated with vigabatrin intake to transcriptional changes in the mechanistic target of rapamycin (mTOR) pathway and GABA receptors to expose further mechanisms of vigabatrin-induced visual field loss. METHODS Vigabatrin was administered to mice via an osmotic pump for two weeks to increase GABA levels. Visual evoked potentials were examined, eye samples were collected, and gene expression was measured by quantitative reverse transcription-polymerase chain reaction. Similarly, human retinal pigment epithelial cells (ARPE19) were exposed to vigabatrin and treated with mTOR inhibitors for mTOR pathway analysis and to assess alterations in organelle accumulation by microscopy. RESULTS Dysregulated expression of transcripts in the mTOR pathway, GABAA/B receptors, metabotropic glutamate (Glu) receptors 1/6, and GABA/glutamate transporters in the eye were found in association with visual evoked potential changes during vigabatrin administration. Rrag genes were upregulated in both mouse eye and ARPE19 cells. Immunoblot of whole eye revealed greater than three fold upregulation of a 200 kDa band when immunoblotted for ras-related guanosine triphosphate binding D. Microscopy of ARPE19 cells revealed selective reversal of vigabatrin-induced organelle accumulation by autophagy-inducing drugs, notably Torin 2. Changes in the mTOR pathway gene expression, including Rrag genes, were corrected by Torin 2 in ARPE19 cells. CONCLUSIONS Our studies, indicating GABA-associated augmentation of RRAG and mTOR signaling, support further preclinical evaluation of mTOR inhibitors as a therapeutic strategy to potentially mitigate vigabatrin-induced ocular toxicity.
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Vogel KR, Ainslie GR, Jansen EEW, Salomons GS, Gibson KM. Therapeutic relevance of mTOR inhibition in murine succinate semialdehyde dehydrogenase deficiency (SSADHD), a disorder of GABA metabolism. Biochim Biophys Acta Mol Basis Dis 2017; 1863:33-42. [PMID: 27760377 PMCID: PMC5154833 DOI: 10.1016/j.bbadis.2016.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 08/24/2016] [Accepted: 10/13/2016] [Indexed: 02/06/2023]
Abstract
Aldehyde dehydrogenase 5a1-deficient (aldh5a1-/-) mice, the murine orthologue of human succinic semialdehyde dehydrogenase deficiency (SSADHD), manifest increased GABA (4-aminobutyric acid) that disrupts autophagy, increases mitochondria number, and induces oxidative stress, all mitigated with the mTOR (mechanistic target of rapamycin) inhibitor rapamycin [1]. Because GABA regulates mTOR, we tested the hypothesis that aldh5a1-/- mice would show altered levels of mRNA for genes associated with mTOR signaling and oxidative stress that could be mitigated by inhibiting mTOR. We observed that multiple metabolites associated with GABA metabolism (γ-hydroxybutyrate, succinic semialdehyde, D-2-hydroxyglutarate, 4,5-dihydrohexanoate) and oxidative stress were significantly increased in multiple tissues derived from aldh5a1-/- mice. These metabolic perturbations were associated with decreased levels of reduced glutathione (GSH) in brain and liver of aldh5a1-/- mice, as well as increased levels of adducts of the lipid peroxidation by-product, 4-hydroxy-2-nonenal (4-HNE). Decreased liver mRNA levels for multiple genes associated with mTOR signaling and oxidative stress parameters were detected in aldh5a1-/- mice, and several were significantly improved with the administration of mTOR inhibitors (Torin 1/Torin 2). Western blot analysis of selected proteins corresponding to oxidative stress transcripts (glutathione transferase, superoxide dismutase, peroxiredoxin 1) confirmed gene expression findings. Our data provide additional preclinical evidence for the potential therapeutic efficacy of mTOR inhibitors in SSADHD.
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Attri SV, Singhi P, Wiwattanadittakul N, Goswami JN, Sankhyan N, Salomons GS, Roullett JB, Hodgeman R, Parviz M, Gibson KM, Pearl PL. Incidence and Geographic Distribution of Succinic Semialdehyde Dehydrogenase (SSADH) Deficiency. JIMD Rep 2016; 34:111-115. [PMID: 27815844 DOI: 10.1007/8904_2016_14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 09/12/2016] [Accepted: 09/14/2016] [Indexed: 02/17/2023] Open
Abstract
The incidence of succinic semialdehyde dehydrogenase (SSADH) deficiency, an autosomal recessive inherited disorder of GABA degradation, is unknown. Upon a recent diagnosis of a new family of affected fraternal twins from the Punjabi ethnic group of India, case ascertainment from the literature and our database was done to determine the number of confirmed cases along with their geographic distribution. The probands presented with global developmental delay, infantile onset epilepsy, and a persistent neurodevelopmental disorder upon diagnosis at 10 years of age with intellectual disability, expressive aphasia, and behavioral problems most prominent for hyperactivity. Gamma-hydroxybutyric aciduria and homozygous ALDH5A1 c.608C>T; p.Pro203Leu mutations were confirmed. Identification of all available individual cases with clinical details available including geographic or ethnic origin revealed 182 patients from 40 countries, with the largest number of patients reported from the USA (24%), Turkey (10%), China (7%), Saudi Arabia (6%), and Germany (5%). This study provides an accounting of all published cases of confirmed SSADH deficiency and provides data useful in planning further studies of this rare inborn error of metabolism.
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Vogel KR, Ainslie GR, Gibson KM. mTOR inhibitors rescue premature lethality and attenuate dysregulation of GABAergic/glutamatergic transcription in murine succinate semialdehyde dehydrogenase deficiency (SSADHD), a disorder of GABA metabolism. J Inherit Metab Dis 2016; 39:877-886. [PMID: 27518770 PMCID: PMC5114712 DOI: 10.1007/s10545-016-9959-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/15/2016] [Accepted: 06/21/2016] [Indexed: 02/07/2023]
Abstract
Recent studies have identified a role for supraphysiological gamma-aminobutyric acid (GABA) in the regulation of mechanistic target of rapamycin (mTOR), a protein kinase with pleiotropic roles in cellular development and homeostasis, including integration of growth factors and nutrient sensing and synaptic input in neurons (Lakhani et al. 2014; Vogel et al. 2015). Aldehyde dehydrogenase 5a1-deficient (aldh5a1 -/- ) mice, the murine orthologue of human succinic semialdehyde dehydrogenase deficiency (SSADHD), manifest increased GABA that disrupts mitophagy and increases mitochondria number with enhanced oxidant stress. Treatment with the mTOR inhibitor, rapamycin, significantly attenuates these GABA-related anomalies. We extend those studies through characterization of additional rapamycin analog (rapalog) agents including temsirolimus, dual mTOR inhibitors [Torin 1 and 2 (Tor 1/ Tor 2), Ku-0063794, and XL-765], as well as mTOR-independent autophagy inducers [trehalose, tat-Beclin 1, tacrolimus (FK-506), and NF-449) in aldh5a1 -/- mice. Rapamycin, Tor 1, and Tor 2 rescued these mice from premature lethality associated with status epilepticus. XL-765 extended lifespan significantly and induced weight gain in aldh5a1 -/- mice; untreated aldh5a1 -/- mice failed to increase body mass. Expression profiling of animals rescued with Tor 1/Tor 2 and XL-765 revealed multiple instances of pharmacological compensation and/or correction of GABAergic and glutamatergic receptors, GABA/glutamate transporters, and GABA/glutamate-associated proteins, with Tor 2 and XL-765 showing optimal outcomes. Our studies lay the groundwork for further evaluation of mTOR inhibitors in aldh5a1 -/- mice, with therapeutic ramifications for heritable disorders of GABA and glutamate neurotransmission.
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Jansen EE, Vogel KR, Salomons GS, Pearl PL, Roullet JB, Gibson KM. Correlation of blood biomarkers with age informs pathomechanisms in succinic semialdehyde dehydrogenase deficiency (SSADHD), a disorder of GABA metabolism. J Inherit Metab Dis 2016; 39:795-800. [PMID: 27686230 PMCID: PMC5115636 DOI: 10.1007/s10545-016-9980-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 08/30/2016] [Accepted: 09/12/2016] [Indexed: 12/23/2022]
Abstract
We hypothesized that blood levels of γ-aminobutyric acid (GABA) and γ-hydroxybutyric acid (GHB), biomarkers of succinic semialdehyde dehydrogenase deficiency (SSADHD), would correlate with age. GABA and GHB were quantified in plasma and red blood cells (RBCs) from 18 patients (age range 5-41 years; median 8). Both metabolites negatively correlated with age (P < 0.05). Plasma and RBC GHB declined with age, reaching a nadir and approximate steady state by 10 years. Declining plasma GABA achieved this approximate steady state at 30-40 years of age. These biomarker relationships may reflect further GABA- and GHB-ergic neurotransmission imbalances that correlate with the onset of adolescent/adulthood neuropsychiatric morbidity and epilepsy in SSADHD.
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Ainslie GR, Gibson KM, Vogel KR. A pharmacokinetic evaluation and metabolite identification of the GHB receptor antagonist NCS-382 in mouse informs novel therapeutic strategies for the treatment of GHB intoxication. Pharmacol Res Perspect 2016; 4:e00265. [PMID: 27891231 PMCID: PMC5115179 DOI: 10.1002/prp2.265] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 08/09/2016] [Accepted: 08/12/2016] [Indexed: 02/01/2023] Open
Abstract
Gamma‐aminobutyric acid (GABA) is an endogenous inhibitory neurotransmitter and precursor of gamma‐hydroxybutyric acid (GHB). NCS‐382 (6,7,8,9‐tetrahydro‐5‐hydroxy‐5H‐benzo‐cyclohept‐6‐ylideneacetic acid), a known GHB receptor antagonist, has shown significant efficacy in a murine model of succinic semialdehyde dehydrogenase deficiency (SSADHD), a heritable neurological disorder featuring chronic elevation of GHB that blocks the final step of GABA degradation. NCS‐382 exposures and elimination pathways remain unknown; therefore, the goal of the present work was to obtain in vivo pharmacokinetic data in a murine model and to identify the NCS‐382 metabolites formed by mouse and human. NCS‐382 single‐dose mouse pharmacokinetics were established following an intraperitoneal injection (100, 300, and 500 mg/kg body weight) and metabolite identification was conducted using HPLC‐MS/MS. Kinetic enzyme assays employed mouse and human liver microsomes. Upon gaining an understanding of the NCS‐382 clearance mechanisms, a chemical inhibitor was used to increase NCS‐382 brain exposure in a pharmacokinetic/pharmacodynamic study. Two major metabolic pathways of NCS‐382 were identified as dehydrogenation and glucuronidation. The Km for the dehydrogenation pathway was determined in mouse (Km = 29.5 ± 10.0 μmol/L) and human (Km = 12.7 ± 4.8 μmol/L) liver microsomes. Comparable parameters for glucuronidation were >100 μmol/L in both species. Inhibition of NCS‐382 glucuronidation, in vivo, by diclofenac resulted in increased NCS‐382 brain concentrations and protective effects in gamma‐butyrolactone‐treated mice. These initial evaluations of NCS‐382 pharmacokinetics and metabolism inform the development of NCS‐382 as a potential therapy for conditions of GHB elevation (including acute intoxication & SSADHD).
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Wernli C, Finochiaro S, Volken C, Andresen-Streichert H, Buettler A, Gygax D, Salomons GS, Jansen EE, Ainslie GR, Vogel KR, Gibson KM. Targeted screening of succinic semialdehyde dehydrogenase deficiency (SSADHD) employing an enzymatic assay for γ-hydroxybutyric acid (GHB) in biofluids. Mol Genet Metab Rep 2016. [PMID: 28649510 PMCID: PMC5470939 DOI: 10.1016/j.ymgmr.2016.07.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
HYPOTHESIS An enzymatic assay for quantification of γ-hydroxybutyric acid (GHB) in biofluids can be employed for targeted screening of succinic semialdehyde dehydrogenase deficiency (SSADHD) in selected populations. RATIONALE We used a two-tiered study approach, in which the first study (proof of concept) examined 7 urine samples derived from patients with SSADHD and 5 controls, and the second study (feasibility study) examined a broader sample population of patients and controls, including plasma. OBJECTIVE Split samples of urine and plasma (anonymized) were evaluated by enzymatic assay, gas chromatography alone (proof of concept) and gas chromatography-mass spectrometry, and the results compared. METHOD Multiple detection methods have been developed to detect GHB. We evaluated an enzymatic assay which employs recombinant GHB dehydrogenase coupled to NADH production, the latter quantified on a Cobas Integra 400 Plus. Results: In our proof of concept study, we analyzed 12 urine samples (5 controls, 7 SSADHD), and in the feasibility study we evaluated 33 urine samples (23 controls, 10 SSADHD) and 31 plasma samples (14 controls, 17 SSADHD). The enzymatic assay carried out on a routine clinical chemistry analyzer was robust, revealing excellent agreement with instrumental methods in urine (GC-FID: r = 0.997, p ≤ 0.001; GC-MS: r = 0.99, p ≤ 0.001); however, the assay slightly over-estimated GHB levels in plasma, especially those in which GHB levels were low. Conversely, correlations for the enzymatic assay with comparator methods for higher plasma GHB levels were excellent (GC-MS; r = 0.993, p ≤ 0.001). CONCLUSION We have evaluated the capacity of this enzymatic assay to identify patients with SSADHD via quantitation of GHB. The data suggests that the enzymatic assay may be a suitable screening method to detect SSADHD in selected populations using urine. In addition, the assay can be used in basic research the elucidate the mechanism of the underlying disease or monitor GHB- levels for the evaluation of drug candidates. SYNOPSIS An enzymatic assay for GHB in biofluids was evaluated as a screening method for SSADHD and found to be reliable in urine, but in need of refinement for application to plasma.
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Key Words
- CV, coefficient of variation
- Enzymatic enzyme assay
- GABA, gamma-aminobutyric acid
- GC-FID, gas chromatography-flame ionization detector
- GC–MS, gas chromatography–mass spectrometry
- GHB, gamma-hydroxybutyrate (also γ-hydroxybutyric acid)
- GHBDH, GHB-dehydrogenase
- IDM, isotope dilution method
- LLOQ, lower limit of quantification
- LOD, limit of detection
- NADH, nicotinamide adenine dinucleotide, reduced form
- SSADHD, succinic semialdehyde dehydrogenase deficiency
- Succinic semialdehyde dehydrogenase
- Succinic semialdehyde dehydrogenase deficiency
- r, correlation coefficient (Pearson)
- γ-hydroxybutyric acid
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Schreiber JM, Pearl PL, Dustin I, Wiggs E, Barrios E, Wassermann EM, Gibson KM, Theodore WH. Biomarkers in a Taurine Trial for Succinic Semialdehyde Dehydrogenase Deficiency. JIMD Rep 2016; 30:81-87. [PMID: 27338723 DOI: 10.1007/8904_2015_524] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/10/2015] [Accepted: 11/26/2015] [Indexed: 02/17/2023] Open
Abstract
AIM We tested the hypothesis that patients with succinic semialdehyde dehydrogenase (SSADH) deficiency on taurine would have decreased cortical excitability as measured by transcranial magnetic stimulation (TMS) and improved cognition, due to taurine's partial GABA(A and B) receptor agonist effects and rescue in the null mouse model from status epilepticus and premature lethality. METHOD Biomarkers including neuropsychological testing, TMS, and CSF metabolites were studied in a cohort of patients on and off three months' taurine treatment. RESULTS Seven patients (5M/2F; age range 12-33 years) were enrolled in this open-label crossover study. Baseline average full-scale IQ (FSIQ) was 44.1 (range 34-55). Of six who returned at 6-month follow-up, five completed cognitive testing (3M/2F) on therapy; average FSIQ = 43.4 (range 33-51). CSF biomarkers (n = 4 subjects) revealed elevation in taurine levels but no change in free or total GABA. Baseline cortical excitability measured with TMS agreed with previous findings in this population, with a short cortical silent period and lack of long-interval intracortical inhibition. Patients on taurine showed a decrease in cortical silent period and short-interval intracortical inhibition compared to their off taurine study. INTERPRETATION TMS demonstrated decreased inhibition in patients on taurine, in contrast to the study hypothesis, but consistent with its failure to produce clinical or cognitive improvement. TMS may be a useful biomarker for therapy in pediatric neurotransmitter disorders.
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Malaspina P, Roullet JB, Pearl PL, Ainslie GR, Vogel KR, Gibson KM. Succinic semialdehyde dehydrogenase deficiency (SSADHD): Pathophysiological complexity and multifactorial trait associations in a rare monogenic disorder of GABA metabolism. Neurochem Int 2016; 99:72-84. [PMID: 27311541 DOI: 10.1016/j.neuint.2016.06.009] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 12/21/2022]
Abstract
Discovered some 35 years ago, succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a rare, autosomal recessively-inherited defect in the second step of the GABA degradative pathway. Some 200 patients have been reported, with broad phenotypic and genotypic heterogeneity. SSADHD represents an unusual neurometabolic disorder in which two neuromodulatory agents, GABA (and the GABA analogue, 4-hydroxybutyrate), accumulate to supraphysiological levels. The unexpected occurrence of epilepsy in several patients is counterintuitive in view of the hyperGABAergic state, in which sedation might be expected. However, the epileptic status of some patients is most likely represented by broader imbalances of GABAergic and glutamatergic neurotransmission. Cumulative research encompassing decades of basic and clinical study of SSADHD reveal a monogenic disease with broad pathophysiological and clinical phenotypes. Numerous metabolic perturbations unmasked in SSADHD include alterations in oxidative stress parameters, dysregulation of autophagy and mitophagy, dysregulation of both inhibitory and excitatory neurotransmitters and gene expression, and unique subsets of SNP alterations of the SSADH gene (so-called ALDH5A1, or aldehyde dehydrogenase 5A1 gene) on the 6p22 chromosomal arm. While seemingly difficult to collate and interpret, these anomalies have continued to open novel pathways for pharmacotherapeutic considerations. Here, we present an update on selected aspects of SSADHD, the ALDH5A1 gene, and future avenues for research on this rare disorder of GABA metabolism.
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Rodan LH, Gibson KM, Pearl PL. Clinical Use of CSF Neurotransmitters. Pediatr Neurol 2015; 53:277-86. [PMID: 26194033 DOI: 10.1016/j.pediatrneurol.2015.04.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 04/04/2015] [Accepted: 04/06/2015] [Indexed: 11/18/2022]
Abstract
BACKGROUND Cerebrospinal fluid neurotransmitter collection, analysis, and follow-up are integral to the diagnosis and management of multiple inborn metabolic errors, some of which require prompt identification and intervention to improve outcome. Cerebrospinal fluid pterins and monoamine metabolites are diagnostic in a range of primary neurotransmitter disorders, including disorders of biogenic amine synthesis, metabolism, and transport. RELEVANT DISORDERS Recently described mutations of the human dopamine transporter are associated with an elevated cerebrospinal fluid homovanillic acid:hydroxyindoleacetic acid ratio. Disorders of pyridoxine metabolism are also detectable via cerebrospinal fluid quantification of bioamines, amino acids, and pyridoxal-5-phosphate levels. Cerebrospinal fluid amino acids are diagnostic in disorders of gamma aminobutyric acid, glycine, and serine metabolism. A wide range of acquired and genetic disorders has also been associated with secondary alterations in cerebrospinal fluid levels of monoamine metabolites, glycine, and neopterin. CONCLUSIONS Lumbar puncture is required to detect abnormal cerebrospinal fluid metabolites in a significant proportion of these disorders, including treatable entities such as dopa-responsive deficiencies of guanosine-5'-triphosphate cyclohydrolase I (Segawa disease), sepiapterin reductase, and tyrosine hydroxylase.
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Lapalme-Remis S, Lewis EC, De Meulemeester C, Chakraborty P, Gibson KM, Torres C, Guberman A, Salomons GS, Jakobs C, Ali-Ridha A, Parviz M, Pearl PL. Natural history of succinic semialdehyde dehydrogenase deficiency through adulthood. Neurology 2015; 85:861-5. [PMID: 26268900 DOI: 10.1212/wnl.0000000000001906] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 03/20/2015] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE The natural history of succinic semialdehyde dehydrogenase (SSADH) deficiency in adulthood is unknown; we elucidate the clinical manifestations of the disease later in life. METHODS A 63-year-old man with long-standing intellectual disability was diagnosed with SSADH deficiency following hospitalization for progressive decline, escalating seizures, and prolonged periods of altered consciousness. We present a detailed review of his clinical course and reviewed our SSADH deficiency database adult cohort to derive natural history information. RESULTS Of 95 patients in the database for whom age at diagnosis is recorded, there are 40 individuals currently aged 18 years or older. Only 3 patients were diagnosed after age 18 years. Of 25 adults for whom data are available after age 18, 60% have a history of epilepsy. Predominant seizure types are generalized tonic-clonic, absence, and myoclonic. EEGs showed background slowing or generalized epileptiform discharges in two-thirds of adults for whom EEG data were collected. History of psychiatric symptoms was prominent, with frequent anxiety, sleep disturbances, and obsessive-compulsive disorder. CONCLUSIONS We identified patients older than 18 years with SSADH deficiency in our database following identification and review of a patient diagnosed in the seventh decade of life. The illness had a progressive course with escalating seizures in the index case, with fatality at age 63. Diagnosis in adulthood is rare. Epilepsy is more common in the adult than the pediatric SSADH deficiency cohort; neuropsychiatric morbidity remains prominent.
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Parviz M, Vogel K, Gibson KM, Pearl PL. Disorders of GABA metabolism: SSADH and GABA-transaminase deficiencies. JOURNAL OF PEDIATRIC EPILEPSY 2015; 3:217-227. [PMID: 25485164 DOI: 10.3233/pep-14097] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Clinical disorders known to affect inherited gamma-amino butyric acid (GABA) metabolism are autosomal recessively inherited succinic semialdehyde dehydrogenase and GABA-transaminase deficiency. The clinical presentation of succinic semialdehyde dehydrogenase deficiency includes intellectual disability, ataxia, obsessive-compulsive disorder and epilepsy with a nonprogressive course in typical cases, although a progressive form in early childhood as well as deterioration in adulthood with worsening epilepsy are reported. GABA-transaminase deficiency is associated with a severe neonatal-infantile epileptic encephalopathy.
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Yapici NB, Mandalapu S, Gibson KM, Bi L. Targeted fluorescent probes for detection of oxidative stress in the mitochondria. Bioorg Med Chem Lett 2015; 25:3476-80. [PMID: 26189896 DOI: 10.1016/j.bmcl.2015.07.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/30/2015] [Accepted: 07/02/2015] [Indexed: 10/23/2022]
Abstract
Mitochondrial oxidative stress has been implicated in aging, neurodegenerative diseases, diabetes, stroke, ischemia/reperfusion injury, age-related macular degeneration (AMD) and cancer. Recently, we developed two new mitochondria-targeting fluorescent probes, MitoProbes I/II, which specifically localize in mitochondria and employed both in vivo and in vitro for detection of mitochondrial oxidative stress. Here, we report the design and synthesis of these agents, as well as their utility for real-time imaging of mitochondrial oxidative stress in cells.
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Pearl PL, Parviz M, Vogel K, Schreiber J, Theodore WH, Gibson KM. Inherited disorders of gamma-aminobutyric acid metabolism and advances in ALDH5A1 mutation identification. Dev Med Child Neurol 2015; 57:611-617. [PMID: 25558043 PMCID: PMC4485983 DOI: 10.1111/dmcn.12668] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/30/2014] [Indexed: 02/01/2023]
Abstract
Inherited disorders of gamma-aminobutyric acid (GABA) metabolism include succinic semialdehyde dehydrogenase (SSADH) and gamma-aminobutyric acid transaminase (GABA-T) deficiencies. The clinical features, pathophysiology, diagnosis, and management of both, and an updated list of mutations in the ALDH5A1 gene, which cause SSADH deficiency, are discussed. A database of 112 individuals (71 children and adolescents, and 41 adults) indicates that developmental delay and hypotonia are the most common symptoms arising from SSADH deficiency. Furthermore, epilepsy is present in two-thirds of SSADH-deficient individuals by adulthood. Research with murine genetic models and human participants, using [11 C] flumazenil positron emission tomography (FMZ-PET) and transcranial magnetic stimulation, have led to therapeutic trials, and the identification of additional disruptions to GABA metabolism. Suggestions for new therapies have arisen from findings of GABAergic effects on autophagy, with enhanced activation of the mammalian target of rapamycin (mTOR) pathway. Details of known pathogenic mutations in the ALDH5A1 gene, three of which have not previously been reported, are summarized here. Investigations into disorders of GABA metabolism provide fundamental insights into the mechanisms underlying epilepsy, and support the importance of developing biomarkers and clinical trials. Comprehensive definition of phenotypes arising as a result of deficiencies in both SSADH and GABA-T may increase our understanding of the neurophysiological consequences of a hyper-GABAergic state.
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Vogel KR, Ainslie GR, Phillips B, Arning E, Bottiglieri T, Shen DD, Gibson KM. Physiological Competition of Brain Phenylalanine Accretion: Initial Pharmacokinetic Analyses of Aminoisobutyric and Methylaminoisobutyric Acids in Pahenu2-/- Mice. Mol Genet Metab Rep 2015; 3:80-87. [PMID: 26120559 PMCID: PMC4478616 DOI: 10.1016/j.ymgmr.2015.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Objective Initial studies on the use of non-physiological amino acids (NPAAs) to block the accretion of Phe in the brain of Pahenu2 −/− mice revealed that 2-aminoisobutyrate (AIB) and N-methyl-2-aminoisobutyrate (MAIB) were promising lead compounds whose pharmacokinetic parameters warranted investigation. Methods Control and Pahenu2 −/− mice received intraperitoneal NPAA treatments as test compounds (150, 300 and 500 mg/kg, 1 or 7 days) followed by collection of sera, liver and brain. LC–MS analysis was developed to quantify both AIB and MAIB in all matrices, and pharmacokinetic parameters for distribution, partitioning, accumulation and MAIB demethylation were determined. Results MAIB was partially converted to AIB in vivo. AIB and MAIB partitioned similarly from sera to the brain and liver, with an approximate 10-fold higher accumulation in the liver compared to the brain. In comparison to MAIB, AIB accumulated to approximately 3 to 7-fold higher concentration in the brain. Analysis of the brain and liver revealed a trend toward decreased Phe with increased MAIB serum concentration. Conclusions Our data support further pharmacokinetic characterization of MAIB and AIB in preparation for additional preclinical safety, toxicity and tolerability studies of both AIB and MAIB.
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Vogel KR, Ainslie GR, Jansen EEW, Salomons GS, Gibson KM. Torin 1 partially corrects vigabatrin-induced mitochondrial increase in mouse. Ann Clin Transl Neurol 2015; 2:699-706. [PMID: 26125044 PMCID: PMC4479529 DOI: 10.1002/acn3.200] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 03/09/2015] [Accepted: 03/11/2015] [Indexed: 12/30/2022] Open
Abstract
Recent findings in mice with targeted deletion of the GABA-metabolic enzyme succinic semialdehyde dehydrogenase revealed a new role for supraphysiological GABA (4-aminobutyric acid) in the activation of the mechanistic target of rapamycin (mTOR) that results in disruption of endogenous mitophagy. Employing biochemical and electron microscopic methodology, we examined the hypothesis that similar outcomes would be observed during intervention with vigabatrin, whose antiepileptic capacity hinges on central nervous system GABA elevation. Vigabatrin intervention was associated with significantly enhanced mitochondrial numbers and areas in normal mice that could be selectively normalized with the rapalog and mechanistic target of rapamycin inhibitor, Torin 1. Moreover, short-term administration of vigabatrin induced apoptosis and enhanced phosphorylation of mechanistic target of rapamycin Ser 2448 in liver. Our results provide new insight into adverse outcomes associated with vigabatrin intervention, and the first evidence that its administration is associated with increased mitochondrial number in central and peripheral tissues that may associate with mechanistic target of rapamycin function and enhanced cell death.
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