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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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Affiliation(s)
- K R Vogel
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA
| | - G R Ainslie
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA
| | - E E W Jansen
- Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Neuroscience Campus, Amsterdam, The Netherlands
| | - G S Salomons
- Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center, Neuroscience Campus, Amsterdam, The Netherlands
| | - K M Gibson
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA.
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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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Affiliation(s)
- Kara R Vogel
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Pharmaceutical and Basic Sciences Building Room 347, 412 E. Spokane Falls Blvd, Spokane, WA, 99202, USA.
| | - Garrett R Ainslie
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Pharmaceutical and Basic Sciences Building Room 347, 412 E. Spokane Falls Blvd, Spokane, WA, 99202, USA
| | - K Michael Gibson
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Pharmaceutical and Basic Sciences Building Room 347, 412 E. Spokane Falls Blvd, Spokane, WA, 99202, USA
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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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Affiliation(s)
- P Malaspina
- Department of Biology, University "Tor Vergata", Rome, Italy
| | - J-B Roullet
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA
| | - P L Pearl
- Department of Neurology, Boston Children's Hospital, Boston, MA, USA
| | - G R Ainslie
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA
| | - K R Vogel
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA
| | - K M Gibson
- Division of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, Spokane, WA, USA.
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Vanadia E, Gibson KM, Pearl PL, Trapolino E, Mangano S, Vanadia F. Therapeutic efficacy of magnesium valproate in succinic semialdehyde dehydrogenase deficiency. JIMD Rep 2012; 8:133-7. [PMID: 23430529 DOI: 10.1007/8904_2012_170] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 07/18/2012] [Accepted: 07/24/2012] [Indexed: 12/26/2022] Open
Abstract
Succinic semialdehyde dehydrogenase deficiency (SSADHD), a disorder of γ-aminobutyric acid (GABA) metabolism, manifests typically as a nonprogressive neurodevelopmental disorder with cognitive deficiency, neuropsychiatric morbidity and epilepsy. Therapy targets symptomatic seizures and neurobehavioral disturbances. We report an adolescent female with SSADHD whose unresponsiveness to a broad spectrum of antiepileptics was circumvented with magnesium valproate (MgVPA). Epilepsy remains well controlled in our patient, with concomitant improvements in behavioral symptoms and an absence of adverse symptoms. MgVPA intervention may have utility in SSADHD.
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Affiliation(s)
- Elena Vanadia
- Department of Child and Adolescent Neuropsychiatry, University of Palermo, Palermo, Italy,
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Absalom N, Eghorn LF, Villumsen IS, Karim N, Bay T, Olsen JV, Knudsen GM, Bräuner-Osborne H, Frølund B, Clausen RP, Chebib M, Wellendorph P. α4βδ GABA(A) receptors are high-affinity targets for γ-hydroxybutyric acid (GHB). Proc Natl Acad Sci U S A 2012; 109:13404-9. [PMID: 22753476 PMCID: PMC3421209 DOI: 10.1073/pnas.1204376109] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
γ-Hydroxybutyric acid (GHB) binding to brain-specific high-affinity sites is well-established and proposed to explain both physiological and pharmacological actions. However, the mechanistic links between these lines of data are unknown. To identify molecular targets for specific GHB high-affinity binding, we undertook photolinking studies combined with proteomic analyses and identified several GABA(A) receptor subunits as possible candidates. A subsequent functional screening of various recombinant GABA(A) receptors in Xenopus laevis oocytes using the two-electrode voltage clamp technique showed GHB to be a partial agonist at αβδ- but not αβγ-receptors, proving that the δ-subunit is essential for potency and efficacy. GHB showed preference for α4 over α(1,2,6)-subunits and preferably activated α4β1δ (EC(50) = 140 nM) over α4β(2/3)δ (EC(50) = 8.41/1.03 mM). Introduction of a mutation, α4F71L, in α4β1(δ)-receptors completely abolished GHB but not GABA function, indicating nonidentical binding sites. Radioligand binding studies using the specific GHB radioligand [(3)H](E,RS)-(6,7,8,9-tetrahydro-5-hydroxy-5H-benzocyclohept-6-ylidene)acetic acid showed a 39% reduction (P = 0.0056) in the number of binding sites in α4 KO brain tissue compared with WT controls, corroborating the direct involvement of the α4-subunit in high-affinity GHB binding. Our data link specific GHB forebrain binding sites with α4-containing GABA(A) receptors and postulate a role for extrasynaptic α4δ-containing GABA(A) receptors in GHB pharmacology and physiology. This finding will aid in elucidating the molecular mechanisms behind the proposed function of GHB as a neurotransmitter and its unique therapeutic effects in narcolepsy and alcoholism.
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Affiliation(s)
- Nathan Absalom
- Faculty of Pharmacy A15, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Laura F. Eghorn
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Inge S. Villumsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Nasiara Karim
- Faculty of Pharmacy A15, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Tina Bay
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jesper V. Olsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark; and
| | - Gitte M. Knudsen
- Neurobiology Research Unit and Center for Integrated Molecular Brain Imaging (Cimbi), Rigshospitalet and University of Copenhagen, 2100 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rasmus P. Clausen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mary Chebib
- Faculty of Pharmacy A15, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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Kim KJ, Pearl PL, Jensen K, Snead OC, Malaspina P, Jakobs C, Gibson KM. Succinic semialdehyde dehydrogenase: biochemical-molecular-clinical disease mechanisms, redox regulation, and functional significance. Antioxid Redox Signal 2011; 15:691-718. [PMID: 20973619 PMCID: PMC3125545 DOI: 10.1089/ars.2010.3470] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Succinic semialdehyde dehydrogenase (SSADH; aldehyde dehydrogenase 5a1, ALDH5A1; E.C. 1.2.1.24; OMIM 610045, 271980) deficiency is a rare heritable disorder that disrupts the metabolism of the inhibitory neurotransmitter 4-aminobutyric acid (GABA). Identified in conjunction with increased urinary excretion of the GABA analog gamma-hydroxybutyric acid (GHB), numerous patients have been identified worldwide and the autosomal-recessive disorder has been modeled in mice. The phenotype is one of nonprogressive neurological dysfunction in which seizures may be prominently displayed. The murine model is a reasonable phenocopy of the human disorder, yet the severity of the seizure disorder in the mouse exceeds that observed in SSADH-deficient patients. Abnormalities in GABAergic and GHBergic neurotransmission, documented in patients and mice, form a component of disease pathophysiology, although numerous other disturbances (metabolite accumulations, myelin abnormalities, oxidant stress, neurosteroid depletion, altered bioenergetics, etc.) are also likely to be involved in developing the disease phenotype. Most recently, the demonstration of a redox control system in the SSADH protein active site has provided new insights into the regulation of SSADH by the cellular oxidation/reduction potential. The current review summarizes some 30 years of research on this protein and disease, addressing pathological mechanisms in human and mouse at the protein, metabolic, molecular, and whole-animal level.
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Affiliation(s)
- Kyung-Jin Kim
- Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Republic of Korea
| | - Phillip L. Pearl
- Department of Neurology, Children's National Medical Center, Washington, District of Columbia
| | - Kimmo Jensen
- Synaptic Physiology Laboratory, Department of Physiology and Biophysics, Aarhus University, Aarhus, Denmark
- Center for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - O. Carter Snead
- Department of Neurology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | | | - Cornelis Jakobs
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
| | - K. Michael Gibson
- Department of Biological Sciences, Michigan Technological University, Houghton, Michigan
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Errington AC, Gibson KM, Crunelli V, Cope DW. Aberrant GABA(A) receptor-mediated inhibition in cortico-thalamic networks of succinic semialdehyde dehydrogenase deficient mice. PLoS One 2011; 6:e19021. [PMID: 21526163 PMCID: PMC3079762 DOI: 10.1371/journal.pone.0019021] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 03/14/2011] [Indexed: 01/19/2023] Open
Abstract
Aberrant γ-aminobutyric acid type A (GABAA) receptor-mediated inhibition in cortico-thalamic networks remains an attractive mechanism for typical absence seizure genesis. Using the whole-cell patch clamp technique we examined ‘phasic’ and ‘tonic’ GABAA inhibition in thalamocortical neurons of somatosensory (ventrobasal, VB) thalamus, nucleus reticularis thalami (NRT) neurons, and layer 5/6 pyramidal neurons of the somatosensory (barrel) cortex of succinic semialdehyde dehydrogenase (SSADH) knock-out (SSADH−/−) mice that replicate human SSADH deficiency and exhibit typical absence seizures. We found increased sIPSC frequency in both VB and NRT neurons and larger sIPSC amplitude in VB neurons of SSADH−/− mice compared to wild-type animals, demonstrating an increase in total phasic inhibition in thalamus of SSADH−/− mice. mIPSCs in both VB and NRT neurons were no different between genotypes, although there remained a trend toward more events in SSADH−/− mice. In cortical layer 5/6 pyramidal neurons, sIPSCs were fewer but larger in SSADH−/− mice, a feature retained by mIPSCs. Tonic currents were larger in both thalamocortical neurons and layer 5/6 pyramidal neurons from SSADH−/− mice compared to WTs. These data show that enhanced, rather than compromised, GABAA receptor-mediated inhibition occurs in cortico-thalamic networks of SSADH−/− mice. In agreement with previous studies, GABAA receptor-mediated inhibitory gain-of-function may be a common feature in models of typical absence seizures, and could be of pathological importance in patients with SSADH deficiency.
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Affiliation(s)
- Adam C Errington
- School of Biosciences, Cardiff University, Cardiff, United Kingdom.
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