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Nagarajan S, Prabu R, Parachuri N, Thulasidas M. Electroretinogram as a Screening Tool to Assess Vigabatrin-Induced Retinal Toxicity in Children With Infantile Spasms. J Pediatr Ophthalmol Strabismus 2024; 61:273-278. [PMID: 38482803 DOI: 10.3928/01913913-20240215-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
PURPOSE To assess the utility of electroretinogram (ERG) as a screening tool for vigabatrin-induced retinal toxicity in children with infantile spasms. METHODS This was an observational cohort study including children with infantile spasms receiving treatment with vigabatrin. A 30-Hz flicker potential ERG, using the RETeval system (LKC Technologies), was done at baseline before starting vigabatrin at 6 months and 1 year. The amplitudes were recorded. RESULTS Eleven children were included in the study. The most common etiologic factor for infantile spasms was tuberous sclerosis (36.4%) followed by West syndrome (27.3%). The mean age of the children was 7.14 ± 2.9 months, with a range of 3 to 16 months. The mean difference in amplitude was 3.21 ± 2.45 and 5.72 ± 4.18 µV at 6 and 12 months follow-up, respectively (P < .001). Eight of the 11 children (72.7%) showed vigabatrin-induced retinal toxicity, and all 8 children were receiving vigabatrin for more than 6 months. CONCLUSIONS ERG can be used for vigabatrin-induced retinal toxicity monitoring in children with infantile spasms. Vigabatrin-induced retinal toxicity is related to the duration of treatment rather than cumulative dosage. [J Pediatr Ophthalmol Strabismus. 2024;61(4):273-278.].
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Colmers PLW, Arshad MN, Mukherjee J, Lin S, Ng SFJ, Sarmiere P, Davies PA, Moss SJ. Sustained Inhibition of GABA-AT by OV329 Enhances Neuronal Inhibition and Prevents Development of Benzodiazepine Refractory Seizures. eNeuro 2024; 11:ENEURO.0137-24.2024. [PMID: 38937107 PMCID: PMC11236575 DOI: 10.1523/eneuro.0137-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 06/18/2024] [Accepted: 06/24/2024] [Indexed: 06/29/2024] Open
Abstract
γ-Aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the adult brain which mediates its rapid effects on neuronal excitability via ionotropic GABAA receptors. GABA levels in the brain are critically dependent upon GABA-aminotransferase (GABA-AT) which promotes its degradation. Vigabatrin, a low-affinity GABA-AT inhibitor, exhibits anticonvulsant efficacy, but its use is limited due to cumulative ocular toxicity. OV329 is a rationally designed, next-generation GABA-AT inhibitor with enhanced potency. We demonstrate that sustained exposure to OV329 in mice reduces GABA-AT activity and subsequently elevates GABA levels in the brain. Parallel increases in the efficacy of GABAergic inhibition were evident, together with elevations in electroencephalographic delta power. Consistent with this, OV329 exposure reduced the severity of status epilepticus and the development of benzodiazepine refractory seizures. Thus, OV329 may be of utility in treating seizure disorders and associated pathologies that result from neuronal hyperexcitability.
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Affiliation(s)
- Phillip L W Colmers
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Muhammad Nauman Arshad
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | | | | | - Shu Fun Josephine Ng
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | | | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1 6BT, United Kingdom
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Zheng Q, He S, Xu SL, Ma MD, Fan M, Ge JF. Pharmacokinetics and tissue distribution of vigabatrin enantiomers in rats. Saudi Pharm J 2024; 32:101934. [PMID: 38223203 PMCID: PMC10787297 DOI: 10.1016/j.jsps.2023.101934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 12/21/2023] [Indexed: 01/16/2024] Open
Abstract
Purpose To investigate the pharmacokinetics and tissue distribution of VGB racemate and its single enantiomers, and explore the potential of clinic development for single enantiomer S-VGB. Methods In the pharmacokinetics study, male Sprague-Dawley rats were gavaged with VGB racemate or its single enantiomers dosing 50, 100 or 200 mg/kg, and the blood samples were collected during 12 h at regular intervals. In the experiment of tissue distribution, VGB and its single enantiomers were administered intravenously dosing 200 mg/kg, and the tissues including heart, liver, spleen, lung and kidney, eyes, hippocampus, and prefrontal cortex were separated at different times. The concentrations of R-VGB and S-VGB in the plasma and tissues were measured using HPLC. Results Both S-VGB and R-VGB could be detected in the plasma of rats administered with VGB racemate, reaching Cmax at approximately 0.5 h with t1/2 2-3 h. There was no significant pharmacokinetic difference between the two enantiomers when VGB racemate was given 200 mg/kg and 100 mg/kg. However, when given at the dose of 50 mg/kg, S-VGB presented a shorter t1/2 and a higher Cl/F than R-VGB, indicating a faster metabolism of S-VGB. Furthermore, when single enantiomer was administered respectively, S-VGB presented a slower metabolism than R-VGB, as indicated by a longer t1/2 and MRT but a lower Cmax. Moreover, compared with the VGB racemate, the single enantiomers S-VGB and R-VGB had shorter t1/2 and MRT, higher Cmax and AUC/D, and lower Vz/F and Cl/F, indicating the stronger oral absorption and faster metabolism of single enantiomer. In addition, regardless of VGB racemate administration or single enantiomer administration, S-VGB and R-VGB had similar characteristics in tissue distribution, and the content of S-VGB in hippocampus, prefrontal cortex and liver was much higher than that of R-VGB. Conclusions Although there is no transformation between S-VGB and R-VGB in vivo, those two enantiomers display certain disparities in the pharmacokinetics and tissue distribution, and interact with each other. These findings might be a possible interpretation for the pharmacological and toxic effects of VGB and a potential direction for the development and optimization of the single enantiomer S-VGB.
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Affiliation(s)
- Qiang Zheng
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Shuai He
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Song-Lin Xu
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Meng-Die Ma
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Min Fan
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
| | - Jin-Fang Ge
- School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, PR China
- Anhui Provincial Laboratory of Inflammatory and Immune Disease, Anhui Institute of Innovative Drugs, Hefei, Anhui 230032, PR China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, Anhui 230032, PR China
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Rasmussen AD, Truchot N, Dyssegaard A, Fant P. Retinal and Systemic Toxicity of Vigabatrin Is Driven by the S-Enantiomer in the Long Evans Rat. Toxicol Pathol 2023; 51:126-134. [PMID: 37401471 DOI: 10.1177/01926233231179147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023]
Abstract
In this study, we assessed the toxicity and toxicokinetics of racemic vigabatrin and its S- and R-enantiomers (vigabatrin consists of 50:50% of the two enantiomers) by administering doses of the three test articles to male Long Evans rats via oral gavage. The animals were housed under high-intensity light conditions and the study consisted of an escalating dose phase and a 21-day fixed-dose phase. Systemic toxicity of vigabatrin appears to be due to the Vig-S-enantiomer only, as increasing doses of Vig-S or Vig-RS caused body weight loss, decreased food consumption, and affected activity. Administration of the Vig-R-enantiomer did not cause any such effects. Systemic exposure to R- and S-enantiomers was approximately linear with dose. Compared to administration of the racemate, there appeared to be a tendency for animals to take up higher amounts of Vig-R and lower amounts of Vig-S when administered as enantiomer. Bilateral retinal atrophy was observed in the fixed-dose phase in rats receiving Vig-S (either alone or as part of Vig-RS) and was characterized by irregular thinning and disorganization of the outer nuclear layer and thinning of the photoreceptor layer. The administration of the R-enantiomer alone did not cause any microscopic retinal change.
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Affiliation(s)
| | - Nathalie Truchot
- Charles River Laboratories France Safety Assessment, Saint-Germain-Nuelles, France
| | | | - Pierluigi Fant
- Charles River Laboratories France Safety Assessment, Saint-Germain-Nuelles, France
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Use of Visual Electrophysiology to Monitor Retinal and Optic Nerve Toxicity of Medications. Biomolecules 2022; 12:biom12101390. [PMID: 36291599 PMCID: PMC9599231 DOI: 10.3390/biom12101390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/26/2022] [Accepted: 09/26/2022] [Indexed: 12/03/2022] Open
Abstract
It is important for clinicians to consider exposure to toxic substances and nutritional deficiencies when diagnosing and managing cases of vision loss. In these cases, physiologic damage can alter the function of key components of the visual pathway before morphologic changes can be detected by traditional imaging methods. Electrophysiologic tests can aid in the early detection of such functional changes to visual pathway components, including the retina or optic nerve. This review provides an overview of various electrophysiologic techniques, including multifocal electroretinogram (mfERG), full-field ERG (ffERG), electrooculogram (EOG), pattern electroretinogram (PERG), and visual evoked potential (VEP) in monitoring the retinal and optic nerve toxicities of alcohol, amiodarone, cefuroxime, cisplatin, deferoxamine, digoxin, ethambutol, hydroxychloroquine, isotretinoin, ocular siderosis, pentosane, PDE5 inhibitors, phenothiazines (chlorpromazine and thioridazine), quinine, tamoxifen, topiramate, vigabatrin, and vitamin A deficiency.
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Domouky AM, Samy WM, Rashad WA. Therapeutic effect of the mesenchymal stem cells on vigabatrin-induced retinopathy in adult male albino rat. Anat Cell Biol 2022; 55:217-228. [PMID: 35773221 PMCID: PMC9256488 DOI: 10.5115/acb.22.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 02/25/2022] [Accepted: 03/06/2022] [Indexed: 12/02/2022] Open
Abstract
Vigabatrin (VGB) is an effective antiepileptic drug used mainly to treat infantile spasms and refractory complex partial seizures. However, using VGB was restricted as it was known to cause retinal toxicity that appears as a severe peripheral visual field defect. Accordingly, this study was conducted to examine the histopathological and biochemical effects of VGB on the retina in adult male albino rats and assess the possible therapeutic role of mesenchymal stem cells (MSCs) against this potential toxicity. The rats were divided into three groups (control group, VGB group, and VGB/MSCs group), one week after 65 days of VGB treatment ±MSCs. The right eyeballs were prepared for histological and immunohistochemical examination, whereas the left eyeballs were prepared for real-time polymerase chain reaction analysis. Our results demonstrated that MSCs ameliorated retinal pathological changes and downregulated the expression of glial fibrillary acidic protein, vascular endothelial growth factor, and synaptophysin after VGB administration suggesting MSCs function and vascular modulating effect. Moreover, MSCs regulate retinal tissue gene expression of BAX, Bcl-2, BDNF, NGF, synapsin, interleukin (IL)-6, IL-1β, and occludin suggesting MSCs antiapoptotic and immunomodulating effect. In conclusion, MSCs administration could be a suitable therapeutic line to ameliorate VGB-induced retinopathy.
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Affiliation(s)
- Ayat Mahmoud Domouky
- Department of Human Anatomy & Embryology, Faculty of Medicine, Zagazig University, Zagazig, Zagazig, Egypt
| | - Walaa M Samy
- Department of Medical Biochemistry, Faculty of Medicine, Zagazig University, Zagazig, Egypt
| | - Walaa A Rashad
- Department of Human Anatomy & Embryology, Faculty of Medicine, Zagazig University, Zagazig, Zagazig, Egypt
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Walters D, Vogel KR, Brown M, Shi X, Roullet JB, Gibson KM. Transcriptome analysis in mice treated with vigabatrin identifies dysregulation of genes associated with retinal signaling circuitry. Epilepsy Res 2020; 166:106395. [PMID: 32679486 DOI: 10.1016/j.eplepsyres.2020.106395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/02/2020] [Accepted: 06/09/2020] [Indexed: 10/24/2022]
Abstract
Vigabatrin (VGB; γ-vinyl-GABA) is an antiepileptic drug that elevates CNS GABA via irreversible inactivation of the GABA catabolic enzyme GABA-transaminase. VGB's clinical utility, however, can be curtailed by peripheral visual field constriction (pVFC) and thinning of the retinal nerve fiber layer (RNFL). Earlier studies from our laboratory revealed disruptions of autophagy by VGB. Here, we tested the hypothesis that VGB administration to animals would reveal alterations of gene expression in VGB-treated retina that associated with autophagy. VGB (140 mg/kg/d; subcutaneous minipump) was continuously administered to mice (n = 6 each VGB/vehicle) for 12 days, after which animals were euthanized. Retina was isolated for transcriptome (RNAseq) analysis and further validation using qRT-PCR and immunohistochemistry (IHC). For 112 differentially expressed retinal genes (RNAseq), two databases (Gene Ontology; Kyoto Encyclopedia of Genes and Genomes) were used to identify genes associated with visual function. Twenty four genes were subjected to qRT-PCR validation, and five (Gb5, Bdnf, Cplx9, Crh, Sox9) revealed significant dysregulation. IHC of fixed retinas verified significant down-regulation of Gb5 in photoreceptor cells. All of these genes have been previously shown to play a role in retinal function/circuitry signaling. Minimal impact of VGB on retinal autophagic gene expression was observed. This is the first transcriptome analysis of retinal gene expression associated with VGB intake, highlighting potential novel molecular targets potentially related to VGB's well known ocular toxicity.
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Affiliation(s)
- Dana Walters
- Department of Pharmacotherapy, Washington State University College of Pharmacy and Pharmaceutical Sciences, Spokane, WA, USA.
| | - Kara R Vogel
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
| | - Madalyn Brown
- Department of Pharmacotherapy, Washington State University College of Pharmacy and Pharmaceutical Sciences, Spokane, WA, USA.
| | - Xutong Shi
- Department of Pharmacotherapy, Washington State University College of Pharmacy and Pharmaceutical Sciences, Spokane, WA, USA.
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, Washington State University College of Pharmacy and Pharmaceutical Sciences, Spokane, WA, USA.
| | - K Michael Gibson
- Department of Pharmacotherapy, Washington State University College of Pharmacy and Pharmaceutical Sciences, Spokane, WA, USA.
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Zhang E, Ryu J, Levi SR, Oh JK, Hsu CW, Cui X, Lee TT, Wang NK, Lima de Carvalho JR, Tsang SH. PKM2 ablation enhanced retinal function and survival in a preclinical model of retinitis pigmentosa. Mamm Genome 2020; 31:77-85. [PMID: 32342224 DOI: 10.1007/s00335-020-09837-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 04/08/2020] [Indexed: 12/13/2022]
Abstract
Retinitis pigmentosa (RP) is a neurodegenerative disorder that causes irreversible vision loss in over 1.5 million individuals world-wide. The genetic heterogeneity of RP necessitates a broad therapy that is able to provide treatment in a gene- and mutation- non-specific manner. In this study, we identify the therapeutic benefits of metabolic reprogramming by targeting pyruvate kinase M2 (PKM2) in a Pde6β preclinical model of RP. The genetic contributions of PKM2 inhibition in retinal degeneration were evaluated through histology and electroretinogram (ERG) followed by a statistical analysis using a linear regression model. Notably, PKM2 ablation resulted in thicker retinal layers in Pde6β-mutated mice as compared to the controls, suggesting greater photoreceptor survival. Consistent with these anatomical findings, ERG analyses revealed that the maximum b-wave is on average greater in Pkm2 knockout mice than in mice with intact Pkm2, indicating enhanced photoreceptor function. These rescue phenotypes from Pkm2 ablation in a preclinical model of RP indicate that a metabolome reprogramming may be useful in treating RP.
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Affiliation(s)
- Ethan Zhang
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
| | - Joseph Ryu
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
| | - Sarah R Levi
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
| | - Jin Kyun Oh
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
- State University of New York At Downstate Medical Center, Brooklyn, NY, USA
| | - Chun Wei Hsu
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
| | - Xuan Cui
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
- The College of Optometry, Tianjin Medical University Eye Hospital, Tianjin Medical University Eye Institute, Tianjin, China
| | - Ting-Ting Lee
- Department of Genetics, Stanford University, Stanford, CA, USA
| | - Nan-Kai Wang
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan
| | - Jose Ronaldo Lima de Carvalho
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
- Department of Ophthalmology, Empresa Brasileira de Servicos Hospitalares (EBSERH) - Hospital das Clinicas de Pernambuco (HCPE), Federal University of Pernambuco (UFPE), Recife, Brazil
- Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Stephen H Tsang
- Jonas Children's Vision Care and Bernard & Shirlee Brown Glaucoma Laboratory, Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA.
- Department of Pathology & Cell Biology, Institute of Human Nutrition, and Columbia Stem Cell Initiative, Columbia University, New York, NY, USA.
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Walters DC, Arning E, Bottiglieri T, Jansen EEW, Salomons GS, Brown MN, Schmidt MA, Ainslie GR, Roullet JB, Gibson KM. Metabolomic analyses of vigabatrin (VGB)-treated mice: GABA-transaminase inhibition significantly alters amino acid profiles in murine neural and non-neural tissues. Neurochem Int 2019; 125:151-162. [PMID: 30822440 DOI: 10.1016/j.neuint.2019.02.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/19/2019] [Accepted: 02/20/2019] [Indexed: 11/18/2022]
Abstract
The anticonvulsant vigabatrin (VGB; SabrilR) irreversibly inhibits GABA transaminase to increase neural GABA, yet its mechanism of retinal toxicity remains unclear. VGB is suggested to alter several amino acids, including homocarnosine, β-alanine, ornithine, glycine, taurine, and 2-aminoadipic acid (AADA), the latter a homologue of glutamic acid. Here, we evaluate the effect of VGB on amino acid concentrations in mice, employing a continuous VGB infusion (subcutaneously implanted osmotic minipumps), dose-escalation paradigm (35-140 mg/kg/d, 12 days), and amino acid quantitation in eye, visual and prefrontal cortex, total brain, liver and plasma. We hypothesized that continuous VGB dosing would reveal numerous hitherto undescribed amino acid disturbances. Consistent amino acid elevations across tissues included GABA, β-alanine, carnosine, ornithine and AADA, as well as neuroactive aspartic and glutamic acids, serine and glycine. Maximal increase of AADA in eye occurred at 35 mg/kg/d (41 ± 2 nmol/g (n = 21, vehicle) to 60 ± 8.5 (n = 8)), and at 70 mg/kg/d for brain (97 ± 6 (n = 21) to 145 ± 6 (n = 6)), visual cortex (128 ± 6 to 215 ± 19) and prefrontal cortex (124 ± 11 to 200 ± 13; mean ± SEM; p < 0.05), the first demonstration of tissue AADA accumulation with VGB in mammal. VGB effects on basic amino acids, including guanidino-species, suggested the capacity of VGB to alter urea cycle function and nitrogen disposal. The known toxicity of AADA in retinal glial cells highlights new avenues for assessing VGB retinal toxicity and other off-target effects.
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Affiliation(s)
- Dana C Walters
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Erland Arning
- Baylor Scott & White Research Institute, Institute of Metabolic Disease, Dallas, TX, USA
| | - Teodoro Bottiglieri
- Baylor Scott & White Research Institute, Institute of Metabolic Disease, Dallas, TX, USA
| | - Erwin E W Jansen
- Metabolic Laboratory, Department of Clinical Chemistry, Amsterdam University Medical Center, the Netherlands
| | - Gajja S Salomons
- Metabolic Laboratory, Department of Clinical Chemistry, Amsterdam University Medical Center, the Netherlands
| | - Madalyn N Brown
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Michelle A Schmidt
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Garrett R Ainslie
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA.
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Walters DC, Jansen EEW, Ainslie GR, Salomons GS, Brown MN, Schmidt MA, Roullet J, Gibson KM. Preclinical tissue distribution and metabolic correlations of vigabatrin, an antiepileptic drug associated with potential use-limiting visual field defects. Pharmacol Res Perspect 2019; 7:e00456. [PMID: 30631446 PMCID: PMC6321982 DOI: 10.1002/prp2.456] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/06/2018] [Accepted: 12/07/2018] [Indexed: 01/30/2023] Open
Abstract
Vigabatrin (VGB; (S)-(+)/(R)-(-) 4-aminohex-5-enoic acid), an antiepileptic irreversibly inactivating GABA transaminase (GABA-T), manifests use-limiting ocular toxicity. Hypothesizing that the active S enantiomer of VGB would preferentially accumulate in eye and visual cortex (VC) as one potential mechanism for ocular toxicity, we infused racemic VGB into mice via subcutaneous minipump at 35, 70, and 140 mg/kg/d (n = 6-8 animals/dose) for 12 days. VGB enantiomers, total GABA and β-alanine (BALA), 4-guanidinobutyrate (4-GBA), and creatine were quantified by mass spectrometry in eye, brain, liver, prefrontal cortex (PFC), and VC. Plasma VGB concentrations increased linearly by dose (3 ± 0.76 (35 mg/kg/d); 15.1 ± 1.4 (70 mg/kg/d); 34.6 ± 3.2 μmol/L (140 mg/kg/d); mean ± SEM) with an S/R ratio of 0.74 ± 0.02 (n = 14). Steady state S/R ratios (35, 70 mg/kg/d doses) were highest in eye (5.5 ± 0.2; P < 0.0001), followed by VC (3.9 ± 0.4), PFC (3.6 ± 0.3), liver (2.9 ± 0.1), and brain (1.5 ± 0.1; n = 13-14 each). Total VGB content of eye exceeded that of brain, PFC and VC at all doses. High-dose VGB diminished endogenous metabolite production, especially in PFC and VC. GABA significantly increased in all tissues (all doses) except brain; BALA increases were confined to liver and VC; and 4-GBA was prominently increased in brain, PFC and VC (and eye at high dose). Linear correlations between enantiomers and GABA were observed in all tissues, but only in PFC/VC for BALA, 4-GBA, and creatine. Preferential accumulation of the VGB S isomer in eye and VC may provide new insight into VGB ocular toxicity.
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Affiliation(s)
- Dana C. Walters
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
| | - Erwin E. W. Jansen
- Metabolic LaboratoryDepartment of Clinical ChemistryAmsterdam University Medical CenterAmsterdamThe Netherlands
| | - Garrett R. Ainslie
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
| | - Gajja S. Salomons
- Metabolic LaboratoryDepartment of Clinical ChemistryAmsterdam University Medical CenterAmsterdamThe Netherlands
| | - Madalyn N. Brown
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
| | - Michelle A. Schmidt
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
| | - Jean‐Baptiste Roullet
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
| | - K. M. Gibson
- Department of PharmacotherapyCollege of Pharmacy and Pharmaceutical SciencesWashington State UniversitySpokaneWashington
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VIGABATRIN TOXICITY IN INFANCY IS ASSOCIATED WITH RETINAL DEFECT IN ADOLESCENCE: A Prospective Observational Study. Retina 2017; 37:858-866. [PMID: 27552291 DOI: 10.1097/iae.0000000000001246] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose was to determine whether vigabatrin (VGB) (Sabril)-attributed retinal toxicity defined by electroretinogram in early childhood is associated with visual system defect in adolescents after discontinuation of VGB. METHODS This prospective cross-sectional study included 24 children previously treated with VGB and monitored in early childhood by electroretinogram for VGB-attributed retinal defects. Ten had been diagnosed with VGB-attributed retinal defect (Group I) and 14 had no VGB-attributed retinal defect (Group II). Outcome measures were extent of monocular visual fields using Goldmann kinetic perimetry and RNFL thickness at the optic nerve head, using optical coherence tomography. RESULTS Of those able to complete testing (6 eyes Group I and 16 eyes Group II), Goldmann results revealed results of visual field loss in Group I and not in Group II. The optical coherence tomography results demonstrated attenuation of the RNFL in all 6 eyes of Group I participants and in only 1 eye of 10 Group II participants. Optical coherence tomography data were nonoverlapping between Group 1 and Group II eyes. CONCLUSION The VGB-attributed retinal toxicity identified by means of electroretinogram in infancy was associated with visual field loss and RNFL attenuation of the retinal nerve when tested in adolescence.
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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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Affiliation(s)
- Kara R Vogel
- Section of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University Spokane, Washington
| | - Garrett R Ainslie
- Section of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University Spokane, Washington
| | - Erwin E W Jansen
- Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center Neuroscience Campus, Amsterdam, The Netherlands
| | - Gajja S Salomons
- Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center Neuroscience Campus, Amsterdam, The Netherlands
| | - K Michael Gibson
- Section of Experimental and Systems Pharmacology, College of Pharmacy, Washington State University Spokane, Washington
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Rimkus CDM, Andrade CS, Leite CDC, McKinney AM, Lucato LT. Toxic leukoencephalopathies, including drug, medication, environmental, and radiation-induced encephalopathic syndromes. Semin Ultrasound CT MR 2014; 35:97-117. [PMID: 24745887 DOI: 10.1053/j.sult.2013.09.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Toxic leukoencephalopathies can be secondary to the exposure to a wide variety of exogenous agents, including cranial irradiation, chemotherapy, antiepileptic agents, drugs of abuse, and environmental toxins. There is no typical clinical picture, and patients can present with a wide array of signs and symptoms. Involvement of white matter is a key finding in this scenario, although in some circumstances other high metabolic areas of the central nervous system can also be affected. Magnetic resonance (MR) imaging usually discloses bilateral and symmetric white matter areas of hyperintense signal on T2-weighted and fluid-attenuated inversion recovery images, and signs of restricted diffusion are associated in the acute stage. In most cases, the changes are reversible, especially with prompt recognition of the disease and discontinuation of the noxious agent. Either the MR or clinical features may be similar to several nontoxic entities, such as demyelinating diseases, leukodystrophies, hepatic encephalopathy, vascular disease, hypoxic-ischemic states, and others. A high index of suspicion should be maintained whenever a patient presents recent onset of neurologic deficit, searching the risk of exposure to a neurotoxic agent. Getting to know the most frequent MR appearances and mechanisms of action of causative agents may help to make an early diagnosis and begin therapy, improving outcome. In this review, some of the most important causes of leukoencephalopathies are presented; as well as other 2 related conditions: strokelike migraine attacks after radiation therapy syndrome and reversible splenial lesions.
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Affiliation(s)
| | - Celi Santos Andrade
- Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Claudia da Costa Leite
- Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Alexander M McKinney
- Department of Radiology/Neuroradiology, University of Minnesota and Hennepin County Medical Centers, Minneapolis, MN
| | - Leandro Tavares Lucato
- Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
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The effects of taurine on vigabatrin, high light intensity and mydriasis induced retinal toxicity in the pigmented rat. ACTA ACUST UNITED AC 2014; 67:13-20. [PMID: 25446799 DOI: 10.1016/j.etp.2014.09.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 08/05/2014] [Accepted: 09/24/2014] [Indexed: 11/22/2022]
Abstract
The overall purpose of this study was to establish a model that may be used for examining the effect of Vigabatrin-induced retinal toxicity in pigmented rats, and subsequently examine the possible effects of taurine on the retinal toxicity. In the first part of the study, pigmented Long Evans rats were subjected to combinations of induced mydriasis, low/high light intensities (40/2000 lx) and oral administration of near-MTD (Maximum Tolerated Dose) doses (200 mg/kg/day) of Vigabatrin for up to 6 weeks. The combination of mydriasis and high light intensity applied to Long Evans rats resulted in retinal damage that was increased by the administration of Vigabatrin. In the second part of the study Long Evans rats were subjected to combinations of induced mydriasis and high/low light intensity (40/2000 lx) while being orally administered low (30 mg/kg/day) or high (200 mg/kg/day) doses of Vigabatrin for up to 6 weeks. In addition, selected groups of animals were administered taurine via the drinking water (20 mg/ml), resulting in systemic taurine concentrations of approximately threefold the endogenous concentration. The combined results of the studies demonstrate that retinal damage can be induced in pigmented animals when combining mydriasis and high light intensity. Retinal damage was functionally evaluated by electroretinography (ERG), then confirmed by histopathology. While depending on mydriasis and high light intensity, administration of Vigabatrin increased the retinal toxicity and resulted in the formation of rosette-like structures in the retina in a dose-related manner. Administration of taurine did not alleviate the Vigabatrin-induced retinal toxicity, as demonstrated either functionally by ERG or morphologically, although systemic concentrations of 3-fold the endogenous levels were reached, and it was thus not possible to demonstrate a protective effect of taurine in these pigmented animals.
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Tsang SH, Chan L, Tsai YT, Wu WH, Hsu CW, Yang J, Tosi J, Wert KJ, Davis RJ, Mahajan VB. Silencing of tuberin enhances photoreceptor survival and function in a preclinical model of retinitis pigmentosa (an american ophthalmological society thesis). TRANSACTIONS OF THE AMERICAN OPHTHALMOLOGICAL SOCIETY 2014; 112:103-115. [PMID: 25646031 PMCID: PMC4311672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
PURPOSE To assess the functional consequences of silencing of tuberin, an inhibitor of the mTOR signaling pathway, in a preclinical model of retinitis pigmentosa (RP) in order to test the hypothesis that insufficient induction of the protein kinase B (PKB)-regulated tuberin/mTOR self-survival pathway initiates apoptosis. METHODS In an unbiased genome-scale approach, kinase peptide substrate arrays were used to analyze self-survival pathways at the onset of photoreceptor degeneration. The mutant Pde6b(H620Q)/Pde6b(H620Q) at P14 and P18 photoreceptor outer segment (OS) lysates were labeled with P-ATP and hybridized to an array of 1,164 different synthetic peptide substrates. At this stage, OS of Pde6b(H620Q)/Pde6b(H620Q) rods are morphologically normal. In vitro kinase assays and immunohistochemistry were used to validate phosphorylation. Short hairpin RNA (shRNA) gene silencing was used to validate tuberin's role in regulating survival. RESULTS At the onset of degeneration, 162 peptides were differentially phosphorylated. Protein kinases A, G, C (AGC kinases), and B exhibited increased activity in both peptide array and in vitro kinase assays. Immunohistochemical data confirmed altered phosphorylation patterns for phosphoinositide-dependent kinase-1 (PDK1), ribosomal protein S6 (RPS6), and tuberin. Tuberin gene silencing rescued photoreceptors from degeneration. CONCLUSIONS Phosphorylation of tuberin and RPS6 is due to the upregulated activity of PKB. PKB/tuberin cell growth/survival signaling is activated before the onset of degeneration. Substrates of the AGC kinases in the PKB/tuberin pathway are phosphorylated to promote cell survival. Knockdown of tuberin, the inhibitor of the mTOR pathway, increased photoreceptor survival and function in a preclinical model of RP.
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Affiliation(s)
- Stephen H Tsang
- Institute of Human Nutrition, Department of Pathology and Cell Biology and the Department of Ophthalmology, Columbia University, New York, New York
| | - Lawrence Chan
- Department of Ophthalmology, Columbia University, New York, New York
| | - Yi-Ting Tsai
- Department of Ophthalmology, Columbia University, New York, New York
| | - Wen-Hsuan Wu
- Department of Ophthalmology, Columbia University, New York, New York
| | - Chun-Wei Hsu
- Department of Ophthalmology, Columbia University, New York, New York
| | - Jin Yang
- Department of Ophthalmology, Columbia University, New York, New York; and Tianjin Medical University Eye Hospital, Tianjin, China
| | - Joaquin Tosi
- Department of Ophthalmology, Columbia University, New York, New York; and Kresge Eye Institute, Wayne State University, Detroit, Michigan
| | - Katherine J Wert
- Department of Ophthalmology, Columbia University, New York, New York; and Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Richard J Davis
- Department of Ophthalmology, Columbia University, New York, New York; and Neural Stem Cell Institute, Rensselaer, New York
| | - Vinit B Mahajan
- Omics Lab, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa
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Barrett D, Yang J, Sujirakul T, Tsang SH. Vigabatrin Retinal Toxicity First Detected with Electroretinographic Changes: A Case Report. ACTA ACUST UNITED AC 2014; 5. [PMID: 26295007 DOI: 10.4172/2155-9570.1000363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vigabatrin is an effective antiepileptic drug (AED) typically used in the treatment of refractory partial seizures and infantile spasms. Its use, however, is limited due to the concern of retinal toxicity and subsequent visual field defects. Herewith in we describe a case of vigabatrin toxicity that illustrates electroretinographic (ERG) changes occur before imaging and visual field deterioration. Decrease in maximal ERG b: a ratio was observed before thinning of the retinal nerve fiber layer (RNFL) on optical coherence tomography (OCT).
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Affiliation(s)
- Dianne Barrett
- College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA
| | - Jin Yang
- Edward S. Harkness Eye Institute, Columbia University, New York, NY 10032, USA
| | - Tharikarn Sujirakul
- Edward S. Harkness Eye Institute, Columbia University, New York, NY 10032, USA
| | - Stephen H Tsang
- Edward S. Harkness Eye Institute, Columbia University, New York, NY 10032, USA ; Bernard & Shirlee Brown Glaucoma Laboratory, Departments of Ophthalmology, Pathology & Cell Biology, Columbia University, New York, NY 10032, USA ; New York-Presbyterian Hospital/Columbia University Medical Center, New York, NY 10032, USA
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