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Thys L, Meuwissen M, Janssens K, Beysen D. Novel presentation of AADC deficiency as a mild phenotype with exercise-induced dystonic crises: A case report. Heliyon 2024; 10:e23746. [PMID: 38192810 PMCID: PMC10772193 DOI: 10.1016/j.heliyon.2023.e23746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 10/20/2023] [Accepted: 12/12/2023] [Indexed: 01/10/2024] Open
Abstract
Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare autosomal recessive neurometabolic disorder caused by biallelic pathogenic variants in the DDC gene; approximately 140 patients have been described worldwide. AADC deficiency is characterised by a combined deficiency of dopamine, serotonin, adrenaline and noradrenaline causing a highly variable phenotype with developmental delay, early-onset hypotonia, movement disorders and autonomic symptoms. We expand the phenotype of this neurometabolic disorder by reporting on a paediatric patient with a mild phenotype with atypical exercise-induced dystonic crises, a feature that has not been described in AADC deficiency up till now. Additionally, we also present a second patient with typical characteristics and a severe phenotype. The diagnosis in both patients was confirmed by the presence of a homozygous pathogenic variant in the DDC gene and reduced AADC enzyme plasma activity. The use of whole exome sequencing-based strategies has played a crucial role in diagnosing these two patients.
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Affiliation(s)
- Liene Thys
- Department of Paediatric Neurology, Antwerp University Hospital, Edegem, Belgium
| | - Marije Meuwissen
- Department of Medical Genetics, Antwerp University Hospital/University of Antwerp, Edegem, Wilrijk, Belgium
| | - Katrien Janssens
- Department of Medical Genetics, Antwerp University Hospital/University of Antwerp, Edegem, Wilrijk, Belgium
| | - Diane Beysen
- Department of Paediatric Neurology, Antwerp University Hospital, Edegem, Belgium
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2
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Rizzi S, Spagnoli C, Bellini M, Cesaroni CA, Spezia E, Bergonzini P, Caramaschi E, Soliani L, Turco EC, Piccolo B, Demuth L, Cordelli DM, Biasucci G, Frattini D, Fusco C. Aromatic L-Amino-Acid Decarboxylase Deficiency Screening by Analysis of 3-O-Methyldopa in Dried Blood Spots: Results of a Multicentric Study in Neurodevelopmental Disorders. Genes (Basel) 2023; 14:1828. [PMID: 37761968 PMCID: PMC10530573 DOI: 10.3390/genes14091828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 09/15/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
Aromatic L-amino acid decarboxylase deficiency (AADCd) is a rare recessive metabolic disorder caused by pathogenic homozygous or compound heterozygous variants in the dopa decarboxylase (DDC) gene. Adeno-associated viral vector-mediated gene transfer of the human DDC gene injected into the putamen is available. The typical presentation is characterized by early-onset hypotonia, severe developmental delay, movement disorders, and dysautonomia. Recently, mild and even atypical phenotypes have been reported, increasing the diagnostic challenge. The aim of this multicentric study is to identify the prevalence of AADCd in a population of patients with phenotypic clusters characterized by neurodevelopmental disorders (developmental delay/intellectual disability, and/or autism) by 3-O-methyldopa (3-OMD) detection in dried blood spots (DBS). It is essential to identify AADCd promptly, especially within non-typical phenotypic clusters, because better results are obtained when therapy is quickly started in mild-moderate phenotypes. Between 2021 and 2023, 390 patients with non-specific phenotypes possibly associated with AADCd were tested; none resulted in a positive result. This result highlights that the population to be investigated for AADCd should have more defined clinical characteristics: association with common signs (hypotonia) and/or pathognomonic symptoms (oculogyric crisis and dysautonomia). It is necessary to continue to screen selected clusters for reaching diagnosis and improving long-term outcomes through treatment initiation. This underscores the role of newborn screening in identifying AADCd.
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Affiliation(s)
- Susanna Rizzi
- Child Neurology and Psychiatry Unit, Department of Pediatrics, Presidio Ospedaliero Santa Maria Nuova, AUSL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy; (S.R.); (C.A.C.); (D.F.); (C.F.)
| | - Carlotta Spagnoli
- Child Neurology and Psychiatry Unit, Department of Pediatrics, Presidio Ospedaliero Santa Maria Nuova, AUSL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy; (S.R.); (C.A.C.); (D.F.); (C.F.)
| | - Melissa Bellini
- Pediatrics and Neonatology Unit, Maternal and Child Health Department, Guglielmo da Saliceto Hospital, 29121 Piacenza, Italy; (M.B.); (G.B.)
| | - Carlo Alberto Cesaroni
- Child Neurology and Psychiatry Unit, Department of Pediatrics, Presidio Ospedaliero Santa Maria Nuova, AUSL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy; (S.R.); (C.A.C.); (D.F.); (C.F.)
| | - Elisabetta Spezia
- Pediatrics Unit, Department of Pediatrics, Azienda Ospedaliero-Universitaria Policlinico di Modena, 41125 Modena, Italy; (E.S.); (P.B.); (E.C.)
| | - Patrizia Bergonzini
- Pediatrics Unit, Department of Pediatrics, Azienda Ospedaliero-Universitaria Policlinico di Modena, 41125 Modena, Italy; (E.S.); (P.B.); (E.C.)
| | - Elisa Caramaschi
- Pediatrics Unit, Department of Pediatrics, Azienda Ospedaliero-Universitaria Policlinico di Modena, 41125 Modena, Italy; (E.S.); (P.B.); (E.C.)
| | - Luca Soliani
- U.O.C. Neuropsichiatria dell’età Pediatrica, IRCCS Istituto Delle Scienze Neurologiche di Bologna, 40138 Bologna, Italy; (L.S.); (D.M.C.)
| | - Emanuela Claudia Turco
- Child Neuropsychiatry Unit, Mother and Child Department, University-Hospital of Parma, 43126 Parma, Italy; (E.C.T.); (B.P.)
| | - Benedetta Piccolo
- Child Neuropsychiatry Unit, Mother and Child Department, University-Hospital of Parma, 43126 Parma, Italy; (E.C.T.); (B.P.)
| | - Laura Demuth
- R&D Biochemistry, Centogene GmbH, 18055 Rostock, Germany;
| | - Duccio Maria Cordelli
- U.O.C. Neuropsichiatria dell’età Pediatrica, IRCCS Istituto Delle Scienze Neurologiche di Bologna, 40138 Bologna, Italy; (L.S.); (D.M.C.)
- Dipartimento di Scienze Mediche e Chirurgiche (DIMEC), Alma Mater Studiorum, Università di Bologna, 40138 Bologna, Italy
| | - Giacomo Biasucci
- Pediatrics and Neonatology Unit, Maternal and Child Health Department, Guglielmo da Saliceto Hospital, 29121 Piacenza, Italy; (M.B.); (G.B.)
| | - Daniele Frattini
- Child Neurology and Psychiatry Unit, Department of Pediatrics, Presidio Ospedaliero Santa Maria Nuova, AUSL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy; (S.R.); (C.A.C.); (D.F.); (C.F.)
| | - Carlo Fusco
- Child Neurology and Psychiatry Unit, Department of Pediatrics, Presidio Ospedaliero Santa Maria Nuova, AUSL-IRCCS di Reggio Emilia, 42123 Reggio Emilia, Italy; (S.R.); (C.A.C.); (D.F.); (C.F.)
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3
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Hwu W, Hsu R, Li M, Lee H, Chen H, Lee N, Chien Y. Aromatic l-amino acid decarboxylase deficiency in Taiwan. JIMD Rep 2023; 64:387-392. [PMID: 37701332 PMCID: PMC10494508 DOI: 10.1002/jmd2.12387] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/13/2023] [Accepted: 07/21/2023] [Indexed: 09/14/2023] Open
Abstract
Aromatic l-amino acid decarboxylase (AADC) deficiency is a rare inherited disorder that affects neurotransmitter biosynthesis. A DDC founder mutation c.714 + 4A > T (IVS6 + 4A > T) is prevalent in the Chinese population. This study investigated the epidemiology of AADC deficiency in Taiwan by analyzing data from National Taiwan University Hospital (NTUH), a central institution for diagnosing and treating the disease. From January 2000 to March 2023, 77 patients with AADC deficiency visited NTUH. Among them, eight were international patients seeking a second opinion, and another two had one or both non-Chinese parents; all others were ethnically Chinese. The c.714 + 4A > T mutation accounted for 85% of all mutated alleles, and 94% of patients exhibited a severe phenotype. Of the 77 patients, 31 received gene therapy at a mean age of 3.76 years (1.62-8.49) through clinical trials, and their current ages were significantly older than those of the remaining patients. Although the combined incidence of AADC deficiency in this study (1:66491 for 2004 and later) was lower than that reported in newborn screening (1:31997 to 1:42662), case surges coincided with the launch of clinical trials and the implementation of newborn screening. Currently, many young patients are awaiting for treatment.
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Affiliation(s)
- Wuh‐Liang Hwu
- Department of PediatricsNational Taiwan University HospitalTaipeiTaiwan
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
- Graduate Institute of Integrated MedicineChina Medical UniversityTaichung CityTaiwan
| | - Rai‐Hseng Hsu
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
| | - Mei‐Hsin Li
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
| | - Hui‐Min Lee
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
| | - Hui‐An Chen
- Department of PediatricsNational Taiwan University HospitalTaipeiTaiwan
| | - Ni‐Chung Lee
- Department of PediatricsNational Taiwan University HospitalTaipeiTaiwan
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
| | - Yin‐Hsiu Chien
- Department of PediatricsNational Taiwan University HospitalTaipeiTaiwan
- Department of Medical GeneticsNational Taiwan University HospitalTaipeiTaiwan
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4
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Himmelreich N, Montioli R, Garbade SF, Kopesky J, Elsea SH, Carducci C, Voltattorni CB, Blau N. Spectrum of DDC variants causing aromatic l-amino acid decarboxylase ( AADC) deficiency and pathogenicity interpretation using ACMG-AMP/ACGS recommendations. Mol Genet Metab 2022; 137:359-381. [PMID: 36427457 DOI: 10.1016/j.ymgme.2022.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/25/2022] [Accepted: 11/08/2022] [Indexed: 11/13/2022]
Abstract
Pathogenic variants in dopa decarboxylase (DDC), the gene encoding the aromatic l-amino acid decarboxylase (AADC) enzyme, lead to a severe deficiency of neurotransmitters, resulting in neurological, neuromuscular, and behavioral manifestations clinically characterized by developmental delays, oculogyric crises, dystonia, and severe neurologic dysfunction in infancy. Historically, therapy has been aimed at compensating for neurotransmitter abnormalities, but response to pharmacologic therapy varies, and in most cases, the therapy shows little or no benefit. A novel human DDC gene therapy was recently approved in the European Union that targets the underlying genetic cause of the disorder, providing a new treatment option for patients with AADC deficiency. However, the applicability of human DDC gene therapy depends on the ability of laboratories and clinicians to interpret the results of genetic testing accurately enough to diagnose the patient. An accurate interpretation of genetic variants depends in turn on expert-guided curation of locus-specific databases. The purpose of this research was to identify previously uncharacterized DDC variants that are of pathologic significance in AADC deficiency as well as characterize and curate variants of unknown significance (VUSs) to further advance the diagnostic accuracy of genetic testing for this condition. DDC variants were identified using existing databases and the literature. The pathogenicity of the variants was classified using modified American College of Medical Genetics and Genomics/Association for Molecular Pathology/Association for Clinical Genomic Science (ACMG-AMP/ACGS) criteria. To improve the current variant interpretation recommendations, in silico variant interpretation tools were combined with structural 3D modeling of protein variants and applied comparative analysis to predict the impact of the variant on protein function. A total of 422 variants were identified (http://biopku.org/home/pnddb.asp). Variants were identified on nearly all introns and exons of the DDC gene, as well as the 3' and 5' untranslated regions. The largest percentage of the identified variants (48%) were classified as missense variants. The molecular effects of these missense variants were then predicted, and the pathogenicity of each was classified using a number of variant effect predictors. Using ACMG-AMP/ACGS criteria, 7% of variants were classified as pathogenic, 32% as likely pathogenic, 58% as VUSs of varying subclassifications, 1% as likely benign, and 1% as benign. For 101 out of 108 reported genotypes, at least one allele was classified as pathogenic or likely pathogenic. In silico variant pathogenicity interpretation tools, combined with structural 3D modeling of variant proteins and applied comparative analysis, have improved the current DDC variant interpretation recommendations, particularly of VUSs.
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Affiliation(s)
- Nastassja Himmelreich
- Dietmar-Hopp Metabolic Center and Centre for Pediatrics and Adolescent Medicine, University Children's Hospital, Heidelberg, Germany
| | - Riccardo Montioli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Sven F Garbade
- Dietmar-Hopp Metabolic Center and Centre for Pediatrics and Adolescent Medicine, University Children's Hospital, Heidelberg, Germany.
| | - Jeffrey Kopesky
- Medical Affairs, PTC Therapeutics, Inc., South Plainfield, NJ, USA.
| | - Sarah H Elsea
- Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Carla Carducci
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
| | - Carla B Voltattorni
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Nenad Blau
- Divisions of Metabolism, University Children's Hospital, Zürich, Switzerland.
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Fang M, Wang X, Jia Z, Qiu Q, Li P, Chen L, Yang H. A Simple and Efficient Method for the Substrate Identification of Amino Acid Decarboxylases. Int J Mol Sci 2022; 23. [PMID: 36498879 DOI: 10.3390/ijms232314551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 11/12/2022] [Accepted: 11/18/2022] [Indexed: 11/24/2022] Open
Abstract
Amino acid decarboxylases convert amino acids into different biogenic amines which regulate diverse biological processes. Therefore, identifying the substrates of amino acid decarboxylases is critical for investigating the function of the decarboxylases, especially for the new genes predicted to be amino acid decarboxylases. In the present work, we have established a simple and efficient method to identify the substrates and enzymatic activity of amino acid decarboxylases based on LC-MS methods. We chose GAD65 and AADC as models to validate our method. GAD65 and AADC were expressed in HEK 293T cells and purified through immunoprecipitation. The purified amino acid decarboxylases were subjected to enzymatic reaction with different substrate mixtures in vitro. LC-MS analysis of the reaction mixture identified depleted or accumulated metabolites, which corresponded to candidate enzyme substrates and products, respectively. Our method successfully identified the substrates and products of known amino acid decarboxylases. In summary, our method can efficiently identify the substrates and products of amino acid decarboxylases, which will facilitate future amino acid decarboxylase studies.
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Gowda VK, Vegda H, Nagarajan BB, Shivappa SK. Clinical Profile and Outcome of Indian Children with Aromatic L-Amino Acid Decarboxylase Deficiency: A primary CSF Neurotransmitter Disorder Mimicking as Dyskinetic Cerebral Palsy. J Pediatr Genet 2020; 10:85-91. [PMID: 33996177 DOI: 10.1055/s-0040-1714690] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/09/2020] [Indexed: 10/23/2022]
Abstract
Aromatic L-amino acid decarboxylase (AADC) deficiency is a disorder of neurotransmitter synthesis. It presents with psychomotor delay, dystonia, oculogyric crisis, and autonomic features. There is paucity of literature on this disorder. Hence, we are reporting this series with an objective to study profile and outcome of Indian children with AADC deficiency. In this retrospective review, all case records of genetically confirmed cases of AADC deficiency at the pediatric neurology department in a tertiary care hospital, from March 2014 to March 2020, were analyzed. The data were extracted in a predesigned proforma and analyzed. Out of seven cases, five were males. Median age of onset of symptoms was 4 months but median age of diagnosis was 12 months. All of them had developmental delay, oculogyric crisis, dystonia, increased sweating, intermittent fever, feeding and sleep disturbance, irritability, failure to thrive, axial hypotonia with dyskinetic quadriparesis, and normal magnetic resonance imaging (MRI) of brain and electroencephalogram (EEG). All of them were treated with pyridoxal 5-phosphate, trihexyphenidyl and pramipexole and six cases, in addition, were given bromocriptine. One case was additionally treated with selegiline. One case showed good improvement, five showed partial improvement, and one case expired. In conclusion, AADC deficiency should be suspected in any child with dyskinetic quadriparesis, oculogyric crisis, autonomic disturbances like increased sweating, intermittent fever, and sleep disturbance with normal neuroimaging.
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Affiliation(s)
- Vykuntaraju K Gowda
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
| | - Hemadri Vegda
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
| | - Balamurugan B Nagarajan
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
| | - Sanjay K Shivappa
- Department of Pediatric Neurology, Indira Gandhi Institute of Child Health, Bengaluru, Karnataka, India
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Xu Z, Zou C, Guo M, Bian H, Zhao W, Wang J. Metastasis-associated protein 1 (MTA1) regulates the catecholamine production homeostasis via transcriptional repression of aromatic l-amino acid decarboxylase ( Aadc) in the interstitial cells of Cajal of mouse prostate. Biochem Biophys Res Commun 2020; 528:732-739. [PMID: 32522342 DOI: 10.1016/j.bbrc.2020.05.125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 05/17/2020] [Indexed: 12/30/2022]
Abstract
Based on the lately identified role for the interstitial cells of Cajal (ICCs) of mouse prostate in catecholamine production, as well as the well-established role for the master coregulator metastasis-associated protein 1 (MTA1) in inflammation, we probed into the functional link between aberrant MTA1 expression and pathogenesis of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) using both a MTA1-/- mouse model of experimental autoimmune prostatitis (EAP) and an in vitro chronic prostatitis model in cultured murine ICCs. EAP-induced MTA1 expression was enriched in ICCs of mouse prostate. EAP resulted in a higher increase in the pelvic pain response in MTA1-/- mice compared to WT mice. Consistently, the ICCs from MTA1-/- mice produced higher levels of catecholamines upon induction of in vitro chronic prostatitis. Mechanistically, MTA1 could directly suppress the transcription of Aadc, a rate-limiting enzyme during catecholamine synthesis, in a HDAC2-depdendent manner. Importantly, treatment with AADC inhibitor NSD-1015 significantly ameliorated EAP-elicited pain response and catecholamine overactivity in MTA1-/- mice. Taken together, our findings reveal an inherent regulatory role of the MTA1/AADC pathway in the maintenance of catecholamine production homeostasis in prostate ICCs, and also point to a potential use of HDAC inhibitors and/or AADC inhibitors to treat CP/CPPS.
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Affiliation(s)
- Zhibin Xu
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China
| | - Chunbo Zou
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China
| | - MaoMao Guo
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China
| | - Hao Bian
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China
| | - Wenchao Zhao
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China
| | - Jiangping Wang
- Department of Urology, Taizhou People's Hospital, Taizhou, 225300, Jiangsu Province, PR China.
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Pineda-Cirera L, Cabana-Domínguez J, Benetó N, Diez H, Arenas C, Cormand B, Fernàndez-Castillo N. DDC expression is not regulated by NFAT5 (TonEBP) in dopaminergic neural cell lines. Gene 2020; 742:144569. [PMID: 32165301 DOI: 10.1016/j.gene.2020.144569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 01/21/2020] [Accepted: 03/08/2020] [Indexed: 11/30/2022]
Abstract
The nuclear factor of activated T-cells 5 (NFAT5), also known as tonicity-responsive enhancer-binding protein (TonEBP), is a transcription factor that regulates osmoadaptive response in multiple tissues and is highly expressed in the developing central nervous system. A former study reported that NFAT5 activation through hypertonic stress increases the expression of the dopa decarboxylase enzyme (DDC), also known as aromatic-l-amino-acid decarboxylase (AADC), in human renal proximal tubule cells, leading to an increase of dopamine synthesis. In a previous study, we identified NFAT5 as a candidate gene for cocaine dependence, a complex psychiatric disorder in which dopaminergic neurotransmission plays an important role. Therefore, to test the hypothesis that NFAT5 may also affect dopamine levels in the nervous system through the regulation of DDC expression, we examined this regulation using two neural dopaminergic cell lines, SH-SY5Y and PC12. The effect of NFAT5 on the expression of the neuronal isoform of DDC was evaluated by qRT-PCR. Upon hypertonic stress, NFAT5 was activated and accumulated into the nuclei and, subsequently, the expression of NFAT5 and its known targets sodium/myo-inositol cotransporter 1 (SMIT) and sodium chloride/taurine cotransporter (TAUT) increased, as expected. However, the expression of DDC decreased. When silencing the expression of NFAT5 with a specific shRNA we observed that the downregulation of DDC is independent from NFAT5 in both cell lines and is due to hypertonic stress. In conclusion, NFAT5 does not regulate the expression of the neuronal isoform of DDC in neural dopaminergic cell lines and, consequently, it does not modulate dopamine synthesis through DDC.
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Nutt JG, Curtze C, Hiller A, Anderson S, Larson PS, Van Laar AD, Richardson RM, Thompson ME, Sedkov A, Leinonen M, Ravina B, Bankiewicz KS, Christine CW. Aromatic L-Amino Acid Decarboxylase Gene Therapy Enhances Levodopa Response in Parkinson's Disease. Mov Disord 2020; 35:851-858. [PMID: 32149427 PMCID: PMC7318280 DOI: 10.1002/mds.27993] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/15/2020] [Accepted: 01/24/2020] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND As Parkinson's disease progresses, levodopa treatment loses efficacy, partly through the loss of the endogenous dopamine-synthesizing enzyme L-amino acid decarboxylase (AADC). In the phase I PD-1101 study, putaminal administration of VY-AADC01, an investigational adeno-associated virus serotype-2 vector for delivery of the AADC gene in patients with advanced Parkinson's disease, was well tolerated, improved motor function, and reduced antiparkinsonian medication requirements. OBJECTIVES This substudy aimed to determine whether the timing and magnitude of motor response to intravenous levodopa changed in PD-1101 patients after VY-AADC01 administration. METHODS Participants received 2-hour threshold (0.6 mg/kg/h) and suprathreshold (1.2 mg/kg/h) levodopa infusions on each of 2 days, both before and approximately 6 months after VY-AADC01. Infusion order was randomized and double blinded. Unified Parkinson's Disease Rating Scale motor scores, finger-tapping speeds, and dyskinesia rating scores were assessed every 30 minutes for 1 hour before and ≥3 hours after start of levodopa infusion. RESULTS Of 15 PD-1101 patients, 13 participated in the substudy. Unified Parkinson's Disease Rating Scale motor score area under the curve responses to threshold and suprathreshold levodopa infusions increased by 168% and 67%, respectively, after VY-AADC01; finger-tapping speeds improved by 162% and 113%, and dyskinesia scores increased by 208% and 72%, respectively, after VY-AADC01. Adverse events (mild/moderate severity) were reported in 5 participants during levodopa infusions pre-VY-AADC01 and 2 participants post-VY-AADC01 administration. CONCLUSIONS VY-AADC01 improved motor responses to intravenous levodopa given under controlled conditions. These data and findings from the parent study support further clinical development of AADC gene therapy for people with Parkinson's disease. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- John G Nutt
- Department of Neurology, Oregon Health & Science University, Portland, Oregon, USA
| | - Carolin Curtze
- Department of Biomechanics, University of Nebraska at Omaha, Omaha, Nebraska, USA
| | - Amie Hiller
- Department of Neurology, Oregon Health & Science University, Portland, Oregon, USA
| | - Shannon Anderson
- Department of Neurology, Oregon Health & Science University, Portland, Oregon, USA
| | - Paul S Larson
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, USA
| | - Amber D Van Laar
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - R Mark Richardson
- Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Marin E Thompson
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, USA
| | | | | | - Bernard Ravina
- Voyager Therapeutics, Inc., Cambridge, Massachusetts, USA
| | - Krystof S Bankiewicz
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California, USA.,Department of Neurology, University of California San Francisco, San Francisco, California, USA.,Department of Neurological Surgery, The Ohio State University, Columbus, Ohio, USA
| | - Chadwick W Christine
- Department of Neurology, University of California San Francisco, San Francisco, California, USA
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10
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Dai L, Ding C, Fang F. A novel DDC gene deletion mutation in two Chinese mainland siblings with aromatic l-amino acid decarboxylase deficiency. Brain Dev 2019; 41:205-209. [PMID: 30144970 DOI: 10.1016/j.braindev.2018.08.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 08/07/2018] [Accepted: 08/08/2018] [Indexed: 12/23/2022]
Abstract
BACKGROUND Aromatic l-amino acid decarboxylase (AADC) deficiency (OMIM #608643) is a rare and severe disorder of biogenic amine synthesis caused by mutations in the DDC gene. The phenomenology of the movement disorder includes intermittent oculogyric crises and limb dystonia, generalized athetosis, and impaired voluntary movement. OBJECTIVE To identify clinical manifestations and DDC gene mutations in two Chinese mainland children who are siblings with AADC deficiency. METHODS We used targeted next-generation sequencing and quantitative polymerase chain reaction (qPCR) to reveal DDC mutations in these children. RESULTS Two DDC gene mutations were found: one missense mutation, c.1040G > A (p.Arg347Gln), is a reported mutation derived from the mother; the other mutation, a whole-exon 11 and 12 deletion, is a novel mutation derived from the father. The index patient and her brother both had poor sucking power and feeding difficulty at birth and episodes of oculogyric crises, truncal hypotonia, limb hypertonia, sleep disturbances, irritability, and motor delay. The siblings both died at 1 year and 10 months due to asphyxia and pneumonia during gaze and hypertonia episodes. CONCLUSION This study identified a novel DDC gene deletion mutation in two siblings with AADC deficiency disease in the Chinese mainland population.
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Affiliation(s)
- Lifang Dai
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, 100045, China
| | - Changhong Ding
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, 100045, China.
| | - Fang Fang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, 100045, China.
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Chien YH, Chen PW, Lee NC, Hsieh WS, Chiu PC, Hwu WL, Tsai FJ, Lin SP, Chu SY, Jong YJ, Chao MC. 3-O-methyldopa levels in newborns: Result of newborn screening for aromatic l-amino-acid decarboxylase deficiency. Mol Genet Metab 2016; 118:259-63. [PMID: 27216367 DOI: 10.1016/j.ymgme.2016.05.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/14/2016] [Accepted: 05/14/2016] [Indexed: 11/16/2022]
Abstract
BACKGROUND The diagnosis of aromatic l-amino-acid decarboxylase (AADC) deficiency is often delayed because a cerebrospinal fluid analysis is required to detect a neurotransmitter deficiency. We here demonstrated that an elevated concentration of l-dopa metabolite 3-O-methyldopa (3-OMD) in dried blood spots could be integrated into newborn screening program to precisely predict AADC deficiency. METHODS After obtaining parental consent, an additional spot was punched from newborn filter paper, eluted, cleaned, and analyzed by tandem mass spectrometry. Newborns with a 3-OMD concentration exceeding 500ng/mL were referred for confirmatory testing. RESULTS From September 2013 to December 2015, 127,987 newborns were screened for AADC deficiency. The mean 3-OMD concentration in these newborns was 88.08ng/mL (SD=27.74ng/mL). Four newborns exhibited an elevated 3-OMD concentration (range, 939-3241ng/mL). All four newborns were confirmed to carry two pathologic DDC mutations, indicating an incidence of AADC deficiency of 1:32,000. During the follow-up period, three patients developed typical symptoms of AADC deficiency. Among 16 newborns with mildly elevated 3-OMD levels, six were heterozygous for the DDC IVS6+4A>T mutation. CONCLUSION Newborn screening of AADC deficiency was achieved with a 100% positive-predictive rate. An association for gestational age could be further elucidated.
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Affiliation(s)
- Yin-Hsiu Chien
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Pin-Wen Chen
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan
| | - Ni-Chung Lee
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wu-Shiun Hsieh
- Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Pao-Chin Chiu
- Department of Pediatrics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Wuh-Liang Hwu
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan; Department of Pediatrics, National Taiwan University College of Medicine, Taipei, Taiwan.
| | - Fuu-Jen Tsai
- Department of Pediatrics, China Medical University Hospital, Taichung, Taiwan
| | - Shuan-Pei Lin
- Department of Pediatrics, Mackay Memorial Hospital, Taipei, Taiwan
| | - Shao-Yin Chu
- Department of Pediatrics, Buddhist Tzu-Chi General Hospital, Taiwan
| | - Yuh-Jyh Jong
- Department of Pediatrics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Mei-Chyn Chao
- Department of Pediatrics, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
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Wienecke J, Ren LQ, Hultborn H, Chen M, Møller M, Zhang Y, Zhang M. Spinal cord injury enables aromatic L-amino acid decarboxylase cells to synthesize monoamines. J Neurosci 2014; 34:11984-2000. [PMID: 25186745 DOI: 10.1523/JNEUROSCI.3838-13.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Serotonin (5-HT), an important modulator of both sensory and motor functions in the mammalian spinal cord, originates mainly in the raphe nuclei of the brainstem. However, following complete transection of the spinal cord, small amounts of 5-HT remain detectable below the lesion. It has been suggested, but not proven, that this residual 5-HT is produced by intraspinal 5-HT neurons. Here, we show by immunohistochemical techniques that cells containing the enzyme aromatic l-amino acid decarboxylase (AADC) occur not only near the central canal, as reported by others, but also in the intermediate zone and dorsal horn of the spinal gray matter. We show that, following complete transection of the rat spinal cord at S2 level, AADC cells distal to the lesion acquire the ability to produce 5-HT from its immediate precursor, 5-hydroxytryptophan. Our results indicate that this phenotypic change in spinal AADC cells is initiated by the loss of descending 5-HT projections due to spinal cord injury (SCI). By in vivo and in vitro electrophysiology, we show that 5-HT produced by AADC cells increases the excitability of spinal motoneurons. The phenotypic change in AADC cells appears to result from a loss of inhibition by descending 5-HT neurons and to be mediated by 5-HT1B receptors expressed by AADC cells. These findings indicate that AADC cells are a potential source of 5-HT at spinal levels below an SCI. The production of 5-HT by AADC cells, together with an upregulation of 5-HT2 receptors, offers a partial explanation of hyperreflexia below a chronic SCI.
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Alfadhel M, Kattan R. Aromatic amino Acid decarboxylase deficiency not responding to pyridoxine and bromocriptine therapy: case report and review of response to treatment. J Cent Nerv Syst Dis 2014; 6:1-5. [PMID: 24453523 PMCID: PMC3891626 DOI: 10.4137/jcnsd.s12938] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 12/03/2013] [Accepted: 12/11/2013] [Indexed: 11/05/2022] Open
Abstract
Aromatic L-amino acid decarboxylase (AADC) deficiency (MIM #608643) is an autosomal recessive inborn error of monoamines. It is caused by a mutation in the DDC gene that leads to a deficiency in the AADC enzyme. The clinical features of this condition include a combination of dopamine, noradrenaline, and serotonin deficiencies, and a patient may present with hypotonia, oculogyric crises, sweating, hypersalivation, autonomic dysfunction, and progressive encephalopathy with severe developmental delay. We report the case of an 8-month-old boy who presented with the abovementioned symptoms and who was diagnosed with AADC deficiency based on clinical, biochemical, and molecular investigations. Treatment with bromocriptine and pyridoxine showed no improvement. These data support the findings observed among previously reported cohorts that showed poor response of this disease to current regimens. Alternative therapies are needed to ameliorate the clinical complications associated with this disorder.
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Affiliation(s)
- Majid Alfadhel
- Division of Genetics, Department of Pediatrics, King Saud bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Rana Kattan
- Division of General Pediatrics, Department of Pediatrics, King Saud bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Riyadh, Saudi Arabia
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Zhang MZ, Wang Y, Yao B, Gewin L, Wei S, Capdevila JH, Harris RC. Role of epoxyeicosatrienoic acids (EETs) in mediation of dopamine's effects in the kidney. Am J Physiol Renal Physiol 2013; 305:F1680-6. [PMID: 24154693 DOI: 10.1152/ajprenal.00409.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We have recently demonstrated that intrarenal dopamine plays an important role in preventing the development of systemic hypertension. Similarly, renal cytochrome P-450 (CYP)-epoxygenase-derived arachidonic acid metabolites, epoxyeicosatrienoic acids (EETs), also are antihypertensive through inhibiting sodium reabsorption and vasodilation. The potential interaction between renal dopamine and epoxygenase systems was investigated. Catechol-O-methyl-transferase (COMT)(-/-) mice with increased intrarenal dopamine levels and proximal tubule deletion of aromatic amino acid decarboxylase (ptAADC(-/-)) mice with renal dopamine deficiency were treated with a low-salt diet or high-salt diet for 2 wk. Wild-type or Cyp2c44(-/-) mice were treated with gludopa, which selectively increased renal dopamine levels. In low salt-treated mice, urinary EET levels were related to renal dopamine levels, being highest in COMT(-/-) mice and lowest in ptAADC(-/-) mice. In high salt-treated mice, total EET and individual EET levels in both the kidney and urine were also highest in COMT(-/-) mice and lowest in ptAADC(-/-) mice. Selective increases in renal dopamine in response to gludopa administration led to marked increases in both total and all individual EET levels in the kidney without any changes in blood levels. qRT-PCR and immunoblotting indicated that gludopa increased renal Cyp2c44 mRNA and protein levels. Gludopa induced marked increases in urine volume and urinary sodium excretion in wild-type mice. In contrast, gludopa did not induce significant increases in urine volume or urinary sodium excretion in Cyp2c44(-/-) mice. These studies demonstrate that renal EET levels are maintained by intrarenal dopamine, and Cyp2c44-derived EETs play an important role in intrarenal dopamine-induced natriuresis and diuresis.
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Affiliation(s)
- Ming-Zhi Zhang
- Div. of Nephrology, C3121 MCN, Vanderbilt Univ. School of Medicine and Nashville Veterans Affairs Hospital, Nashville, TN 37232.
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Bonifácio MJ, Sutcliffe JS, Torrão L, Wright LC, Soares-da-Silva P. Brain and peripheral pharmacokinetics of levodopa in the cynomolgus monkey following administration of opicapone, a third generation nitrocatechol COMT inhibitor. Neuropharmacology 2013; 77:334-41. [PMID: 24148813 DOI: 10.1016/j.neuropharm.2013.10.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/22/2013] [Accepted: 10/08/2013] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The present study aimed at evaluating the effect of opicapone, a third generation nitrocatechol catechol-O-methyltransferase (COMT) inhibitor, on the systemic and central bioavailability of 3,4-dihydroxy-l-phenylalanine (levodopa) and related metabolites in the cynomolgus monkey. METHODS Four monkeys, implanted with guiding cannulas for microdialysis probes, in the substantia nigra, dorsal striatum and prefrontal cortex, were randomized in two groups that received, in a crossover design, vehicle or 100 mg/kg opicapone for 14 days. Twenty-three hours after last administration of vehicle or opicapone, animals were challenged with levodopa/benserazide (12/3 mg/kg). Extracellular dialysate and blood samples were collected over 360 min (at 30 min intervals) for the assays of catecholamine and COMT activity. RESULTS Opicapone increased levodopa systemic exposure by 2-fold not changing Cmax values and reduced both 3-O-methyldopa (3-OMD) exposure and Cmax values by 5-fold. These changes were accompanied by ∼76-84% reduction in erythrocyte COMT activity. In dorsal striatum and substantia nigra, opicapone increased levodopa exposure by 1.7- and 1.4-fold, respectively, reducing 3-OMD exposure by 5- and 7-fold respectively. DOPAC exposure was increased by 4-fold in the substantia nigra. In the prefrontal cortex, opicapone increased levodopa exposure and reduced 3-OMD levels by 2.3- and 2.4-fold, respectively. CONCLUSIONS Opicapone behaved as long-acting COMT inhibitor that markedly increased systemic and central levodopa bioavailability. Opicapone is a strong candidate to fill the unmet need for COMT inhibitors that lead to more sustained levodopa levels in Parkinson's disease patients.
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Affiliation(s)
- M J Bonifácio
- Department of Research & Development, BIAL, 4745-457 São Mamede do Coronado, Portugal
| | - J S Sutcliffe
- Maccine Pte Ltd., 10 Science Park Road, #01-05 The Alpha, Singapore Science Park II, Singapore
| | - L Torrão
- Department of Research & Development, BIAL, 4745-457 São Mamede do Coronado, Portugal
| | - L C Wright
- Department of Research & Development, BIAL, 4745-457 São Mamede do Coronado, Portugal
| | - P Soares-da-Silva
- Department of Research & Development, BIAL, 4745-457 São Mamede do Coronado, Portugal; Department of Pharmacology & Therapeutics, Faculty of Medicine, University Porto, Porto, Portugal.
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Trillo L, Das D, Hsieh W, Medina B, Moghadam S, Lin B, Dang V, Sanchez MM, De Miguel Z, Ashford JW, Salehi A. Ascending monoaminergic systems alterations in Alzheimer's disease. translating basic science into clinical care. Neurosci Biobehav Rev 2013; 37:1363-79. [PMID: 23707776 DOI: 10.1016/j.neubiorev.2013.05.008] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 05/13/2013] [Accepted: 05/16/2013] [Indexed: 01/23/2023]
Abstract
Extensive neuropathological studies have established a compelling link between abnormalities in structure and function of subcortical monoaminergic (MA-ergic) systems and the pathophysiology of Alzheimer's disease (AD). The main cell populations of these systems including the locus coeruleus, the raphe nuclei, and the tuberomamillary nucleus undergo significant degeneration in AD, thereby depriving the hippocampal and cortical neurons from their critical modulatory influence. These studies have been complemented by genome wide association studies linking polymorphisms in key genes involved in the MA-ergic systems and particular behavioral abnormalities in AD. Importantly, several recent studies have shown that improvement of the MA-ergic systems can both restore cognitive function and reduce AD-related pathology in animal models of neurodegeneration. This review aims to explore the link between abnormalities in the MA-ergic systems and AD symptomatology as well as the therapeutic strategies targeting these systems. Furthermore, we will examine possible mechanisms behind basic vulnerability of MA-ergic neurons in AD.
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Affiliation(s)
- Ludwig Trillo
- Department of Physiology, School of Medicine, National University of San Agustin, Arequipa, Peru
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Lammel S, Lim BK, Malenka RC. Reward and aversion in a heterogeneous midbrain dopamine system. Neuropharmacology 2013; 76 Pt B:351-9. [PMID: 23578393 DOI: 10.1016/j.neuropharm.2013.03.019] [Citation(s) in RCA: 512] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 03/11/2013] [Accepted: 03/26/2013] [Indexed: 01/14/2023]
Abstract
The ventral tegmental area (VTA) is a heterogeneous brain structure that serves a central role in motivation and reward processing. Abnormalities in the function of VTA dopamine (DA) neurons and the targets they influence are implicated in several prominent neuropsychiatric disorders including addiction and depression. Recent studies suggest that the midbrain DA system is composed of anatomically and functionally heterogeneous DA subpopulations with different axonal projections. These findings may explain a number of previously confusing observations that suggested a role for DA in processing both rewarding as well as aversive events. Here we will focus on recent advances in understanding the neural circuits mediating reward and aversion in the VTA and how stress as well as drugs of abuse, in particular cocaine, alter circuit function within a heterogeneous midbrain DA system. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- Stephan Lammel
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305, USA
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Guatteo E, Yee A, McKearney J, Cucchiaroni ML, Armogida M, Berretta N, Mercuri NB, Lipski J. Dual effects of L-DOPA on nigral dopaminergic neurons. Exp Neurol 2013; 247:582-94. [PMID: 23481547 DOI: 10.1016/j.expneurol.2013.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 02/05/2013] [Indexed: 11/29/2022]
Abstract
L-DOPA (Levodopa) remains the gold standard for the treatment of motor symptoms of Parkinson's disease (PD), despite indications that the drug may have detrimental effects in cell culture. Classically, l-DOPA increases the production of dopamine (DA) in nigral dopaminergic neurons, while paradoxically inhibiting the firing of these neurons due to activation of D2 autoreceptors by extracellularly released DA. Using a combination of electrophysiology and calcium microfluorometry in brain slices, we have identified a novel effect of L-DOPA on dopaminergic neurons when D2 receptors were blocked. Under these conditions, L-DOPA (0.03-3 mM) evoked an excitatory effect consisting of two components. The 'early' component observed during and immediately after application of the drug, was associated with increased firing, membrane depolarization and inward current. This excitatory response was strongly attenuated by CNQX (10 μM), pointing to the involvement of TOPA quinone, an auto-oxidation product of L-DOPA and a potent activator of AMPA/kainate receptors. The 'late' phase of excitation persisted >30 min after brief L-DOPA application and was not mediated by ionotropic glutamate receptors, nor by D1, α1-adrenergic, mGluR1 or GABAB receptors. It was eliminated by carbidopa, demonstrating its dependence on conversion of L-DOPA to DA. Exogenous DA (50 μM) also evoked a glutamate-receptor independent increase in firing and an inward current when D2 receptors were blocked. In voltage-clamped neurons, both L-DOPA and DA produced a long-lasting increase in [Ca(2+)]i which was unaffected by block of ionotropic glutamate receptors. These results demonstrate that L-DOPA has dual, inhibitory and excitatory, effects on nigral dopaminergic neurons, and suggest that the excitation and calcium rise may have long-lasting consequences for the activity and survival of these neurons when the expression or function of D2 receptors is impaired.
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