1
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Clària J, Moreau R, Fenaille F, Amorós A, Junot C, Gronbaek H, Coenraad MJ, Pruvost A, Ghettas A, Chu-Van E, López-Vicario C, Oettl K, Caraceni P, Alessandria C, Trebicka J, Pavesi M, Deulofeu C, Albillos A, Gustot T, Welzel TM, Fernández J, Stauber RE, Saliba F, Butin N, Colsch B, Moreno C, Durand F, Nevens F, Bañares R, Benten D, Ginès P, Gerbes A, Jalan R, Angeli P, Bernardi M, Arroyo V. Orchestration of Tryptophan-Kynurenine Pathway, Acute Decompensation, and Acute-on-Chronic Liver Failure in Cirrhosis. Hepatology 2019; 69:1686-1701. [PMID: 30521097 DOI: 10.1002/hep.30363] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 10/22/2018] [Indexed: 12/12/2022]
Abstract
Systemic inflammation (SI) is involved in the pathogenesis of acute decompensation (AD) and acute-on-chronic liver failure (ACLF) in cirrhosis. In other diseases, SI activates tryptophan (Trp) degradation through the kynurenine pathway (KP), giving rise to metabolites that contribute to multiorgan/system damage and immunosuppression. In the current study, we aimed to characterize the KP in patients with cirrhosis, in whom this pathway is poorly known. The serum levels of Trp, key KP metabolites (kynurenine and kynurenic and quinolinic acids), and cytokines (SI markers) were measured at enrollment in 40 healthy subjects, 39 patients with compensated cirrhosis, 342 with AD (no ACLF) and 180 with ACLF, and repeated in 258 patients during the 28-day follow-up. Urine KP metabolites were measured in 50 patients with ACLF. Serum KP activity was normal in compensated cirrhosis, increased in AD and further increased in ACLF, in parallel with SI; it was remarkably higher in ACLF with kidney failure than in ACLF without kidney failure in the absence of differences in urine KP activity and fractional excretion of KP metabolites. The short-term course of AD and ACLF (worsening, improvement, stable) correlated closely with follow-up changes in serum KP activity. Among patients with AD at enrollment, those with the highest baseline KP activity developed ACLF during follow-up. Among patients who had ACLF at enrollment, those with immune suppression and the highest KP activity, both at baseline, developed nosocomial infections during follow-up. Finally, higher baseline KP activity independently predicted mortality in patients with AD and ACLF. Conclusion: Features of KP activation appear in patients with AD, culminate in patients with ACLF, and may be involved in the pathogenesis of ACLF, clinical course, and mortality.
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Affiliation(s)
- Joan Clària
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain.,Hospital Clínic, IDIBAPS and CIBERehd, Barcelona, Spain
| | - Richard Moreau
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain.,Inserm, Centre de Recherche sur l'Inflammation, Université Paris Diderot-Paris, Département Hospitalo-Universitaire UNITY; Service d'Hépatologie, Hôpital Beaujon, Assistance Publique-Hôpitaux de Paris; Laboratoire d'Excellence Inflamex, ComUE Sorbonne Paris Cité, Paris, France
| | - François Fenaille
- CEA, INRA, Université Paris Saclay, Laboratoire d'Etude du Métabolisme des Médicaments, MetaboHUB-Paris, Gif-Sur-Yvette, France
| | - Alex Amorós
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain
| | - Christophe Junot
- CEA, INRA, Université Paris Saclay, Laboratoire d'Etude du Métabolisme des Médicaments, MetaboHUB-Paris, Gif-Sur-Yvette, France
| | - Henning Gronbaek
- Department of Hepatology & Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
| | - Minneke J Coenraad
- Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, the Netherlands
| | - Alain Pruvost
- CEA, INRA Université Paris Saclay, Service de Pharmacologie et Immunoanalyse, Plateforme SMArt-MS, Gif-sur-Yvette, France
| | - Aurélie Ghettas
- CEA, INRA Université Paris Saclay, Service de Pharmacologie et Immunoanalyse, Plateforme SMArt-MS, Gif-sur-Yvette, France
| | - Emeline Chu-Van
- CEA, INRA, Université Paris Saclay, Laboratoire d'Etude du Métabolisme des Médicaments, MetaboHUB-Paris, Gif-Sur-Yvette, France
| | | | - Karl Oettl
- Medical University of Graz, Graz, Austria
| | - Paolo Caraceni
- Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy
| | - Carlo Alessandria
- Division of Gastroenterology and Hepatology, San Giovanni Battista Hospital, Torino, Italy
| | - Jonel Trebicka
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain.,Department of Internal Medicine I, University of Bonn, Bonn, Germany.,J.W. Goethe University Hospital, Frankfurt, Germany
| | - Marco Pavesi
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain
| | - Carme Deulofeu
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain
| | | | - Thierry Gustot
- CUB Hopital Erasme, Université Libre de Bruxelles, Brussels, Belgium
| | | | - Javier Fernández
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain.,Hospital Clínic, IDIBAPS and CIBERehd, Barcelona, Spain
| | | | - Faouzi Saliba
- Hôpital Paul Brousse, Université Paris-Sud, Villejuif, France
| | - Noémie Butin
- CEA, INRA, Université Paris Saclay, Laboratoire d'Etude du Métabolisme des Médicaments, MetaboHUB-Paris, Gif-Sur-Yvette, France
| | - Benoit Colsch
- CEA, INRA, Université Paris Saclay, Laboratoire d'Etude du Métabolisme des Médicaments, MetaboHUB-Paris, Gif-Sur-Yvette, France
| | - Christophe Moreno
- CUB Hopital Erasme, Université Libre de Bruxelles, Brussels, Belgium
| | - François Durand
- Inserm, Centre de Recherche sur l'Inflammation, Université Paris Diderot-Paris, Département Hospitalo-Universitaire UNITY; Service d'Hépatologie, Hôpital Beaujon, Assistance Publique-Hôpitaux de Paris; Laboratoire d'Excellence Inflamex, ComUE Sorbonne Paris Cité, Paris, France
| | | | - Rafael Bañares
- Facultad de Medicina, Universidad Complutense, Madrid, Spain
| | | | - Pere Ginès
- Hospital Clínic, IDIBAPS and CIBERehd, Barcelona, Spain
| | - Alexander Gerbes
- Department of Medicine II, University Hospital LMU Munich, Liver Center Munich, Munich, Germany
| | - Rajiv Jalan
- Liver Failure Group, Institute for Liver Disease Health, University College London, Royal Free Hospital, London, United Kingdom
| | - Paolo Angeli
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain.,Unit of Internal Medicine and Hepatology, Department of Medicine, DIMED, University of Padova, Padoa, Italy
| | - Mauro Bernardi
- Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy
| | - Vicente Arroyo
- European Foundation for the Study of Chronic Liver Failure Consortium and Grifols Chair, Barcelona, Spain
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2
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Hyperammonemia in review: pathophysiology, diagnosis, and treatment. Pediatr Nephrol 2012; 27:207-22. [PMID: 21431427 DOI: 10.1007/s00467-011-1838-5] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 01/09/2011] [Accepted: 01/12/2011] [Indexed: 12/31/2022]
Abstract
Ammonia is an important source of nitrogen and is required for amino acid synthesis. It is also necessary for normal acid-base balance. When present in high concentrations, ammonia is toxic. Endogenous ammonia intoxication can occur when there is impaired capacity of the body to excrete nitrogenous waste, as seen with congenital enzymatic deficiencies. A variety of environmental causes and medications may also lead to ammonia toxicity. Hyperammonemia refers to a clinical condition associated with elevated ammonia levels manifested by a variety of symptoms and signs, including significant central nervous system (CNS) abnormalities. Appropriate and timely management requires a solid understanding of the fundamental pathophysiology, differential diagnosis, and treatment approaches available. The following review discusses the etiology, pathogenesis, differential diagnosis, and treatment of hyperammonemia.
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3
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Gommeren K, Claeys S, De Rooster H, Hamaide A, Daminet S. Outcome from status epilepticus after portosystemic shunt attenuation in 3 dogs treated with propofol and phenobarbital. J Vet Emerg Crit Care (San Antonio) 2010; 20:346-51. [DOI: 10.1111/j.1476-4431.2010.00537.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Braissant O. Current concepts in the pathogenesis of urea cycle disorders. Mol Genet Metab 2010; 100 Suppl 1:S3-S12. [PMID: 20227314 DOI: 10.1016/j.ymgme.2010.02.010] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Accepted: 02/08/2010] [Indexed: 12/14/2022]
Abstract
The common feature of urea cycle diseases (UCD) is a defect in ammonium elimination in liver, leading to hyperammonemia. This excess of circulating ammonium eventually reaches the central nervous system, where the main toxic effects of ammonium occur. These are reversible or irreversible, depending on the age of onset as well as the duration and the level of ammonium exposure. The brain is much more susceptible to the deleterious effects of ammonium during development than in adulthood, and surviving UCD patients may develop cortical and basal ganglia hypodensities, cortical atrophy, white matter atrophy or hypomyelination and ventricular dilatation. While for a long time, the mechanisms leading to these irreversible effects of ammonium exposure on the brain remained poorly understood, these last few years have brought new data showing in particular that ammonium exposure alters several amino acid pathways and neurotransmitter systems, cerebral energy, nitric oxide synthesis, axonal and dendritic growth, signal transduction pathways, as well as K(+) and water channels. All these effects of ammonium on CNS may eventually lead to energy deficit, oxidative stress and cell death. Recent work also proposed neuroprotective strategies, such as the use of NMDA receptor antagonists, nitric oxide inhibitors, creatine and acetyl-l-carnitine, to counteract the toxic effects of ammonium. Better understanding the pathophysiology of ammonium toxicity to the brain under UCD will allow the development of new strategies for neuroprotection.
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Affiliation(s)
- Olivier Braissant
- Inborn Errors of Metabolism, Clinical Chemistry Laboratory, Centre Hospitalier Universitaire Vaudois and University of Lausanne, CI 02/33, Lausanne, Switzerland.
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5
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Cagnon L, Braissant O. Hyperammonemia-induced toxicity for the developing central nervous system. ACTA ACUST UNITED AC 2007; 56:183-97. [PMID: 17881060 DOI: 10.1016/j.brainresrev.2007.06.026] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 06/15/2007] [Accepted: 06/15/2007] [Indexed: 12/12/2022]
Abstract
In pediatric patients, hyperammonemia can be caused by various acquired or inherited disorders such as urea cycle deficiencies or organic acidemias. The brain is much more susceptible to the deleterious effects of ammonium during development than in adulthood. Hyperammonemia can provoke irreversible damages to the developing central nervous system that lead to cortical atrophy, ventricular enlargement and demyelination, responsible for cognitive impairment, seizures and cerebral palsy. Until recently, the mechanisms leading to these irreversible cerebral damages were poorly understood. Using experimental models allowing the analysis of the neurotoxic effects of ammonium on the developing brain, these last years have seen the emergence of new clues showing that ammonium exposure alters several amino acid pathways and neurotransmitter systems, as well as cerebral energy metabolism, nitric oxide synthesis, oxidative stress, mitochondrial permeability transition and signal transduction pathways. Those alterations may explain neuronal loss and impairment of axonal and dendritic growth observed in the different models of congenital hyperammonemia. Some neuroprotective strategies such as the potential use of NMDA receptor antagonists, nitric oxide inhibitors, creatine and acetyl-l-carnitine have been suggested to counteract these toxic effects. Unraveling the molecular mechanisms involved in the chain of events leading to neuronal dysfunction under hyperammonemia may be useful to develop new potential strategies for neuroprotection.
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Affiliation(s)
- Laurène Cagnon
- Clinical Chemistry Laboratory, Centre Hospitalier Universitaire Vaudois and University of Lausanne, CI 02/33, Avenue Pierre-Decker 2, CH-1011 Lausanne, Switzerland
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6
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Thakur V, Rupar CA, Ramsay DA, Singh R, Fraser DD. Fatal cerebral edema from late-onset ornithine transcarbamylase deficiency in a juvenile male patient receiving valproic acid. Pediatr Crit Care Med 2006; 7:273-6. [PMID: 16575347 DOI: 10.1097/01.pcc.0000216682.56067.23] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The aims of this report are to 1) present a rare case of fatal cerebral edema associated with late-onset ornithine transcarbamylase (OTC) deficiency in a juvenile male patient receiving valproic acid and 2) review the neuropathologic changes associated with the hyperammonemia. DESIGN Case report. SETTING A community hospital and a tertiary pediatric critical care unit. INTERVENTIONS Carbohydrate administration, intravenous nitrogen excretion cocktail, and high-flux hemodialysis. MEASUREMENTS AND MAIN RESULTS Despite aggressive therapy for presumed late-onset OTC deficiency, the patient rapidly developed fatal cerebral edema with tonsillar herniation. A liver biopsy confirmed OTC deficiency with approximately 3% of residual hepatic enzyme activity. Chromosomal analysis showed a normal male karyotype. A thorough molecular analysis of the coding region in the OTC gene Xp21.1 was completed, but mutations were not identified, suggesting an upstream or downstream abnormality. Severe brain swelling was evident on neuropathology, and histopathology showed Alzheimer type II astrocytes, neuronal cytoplasmic changes, and hypertrophy and eosinophilia of the small arterial walls. CONCLUSIONS OTC deficiency is the most common urea cycle defect causing hyperammonemia. Late-onset presentations of OTC are infrequent, primarily affecting female patients. We present a rare case of a late-onset OTC deficiency in a juvenile male patient receiving valproic acid therapy who developed fatal cerebral edema. Valproic acid exacerbates acute elevations in ammonia and may contribute synergistically with ammonia to cerebral mitochondrial dysfunction.
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Affiliation(s)
- Varsha Thakur
- Department of Paediatrics, Children's Hospital of Western Ontario, London, Ontario, Canada
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7
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Mueller D, Shamblott MJ, Fox HE, Gearhart JD, Martin LJ. Transplanted human embryonic germ cell-derived neural stem cells replace neurons and oligodendrocytes in the forebrain of neonatal mice with excitotoxic brain damage. J Neurosci Res 2005; 82:592-608. [PMID: 16247803 DOI: 10.1002/jnr.20673] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Stem cell therapy is a hope for the treatment of some childhood neurological disorders. We examined whether human neural stem cells (hNSCs) replace lost cells in a newborn mouse model of brain damage. Excitotoxic lesions were made in neonatal mouse forebrain with the N-methyl-D-aspartate (NMDA) receptor agonist quinolinic acid (QA). QA induced apoptosis in neocortex, hippocampus, striatum, white matter, and subventricular zone. This degeneration was associated with production of cleaved caspase-3. Cells immunopositive for inducible nitric oxide synthase were present in damaged white matter and subventricular zone. Three days after injury, mice received brain parenchymal or intraventricular injections of hNSCs derived from embryonic germ (EG) cells. Human cells were prelabeled in vitro with DiD for in vivo tracking. The locations of hNSCs within the mouse brain were determined through DiD fluorescence and immunodetection of human-specific nestin and nuclear antigen 7 days after transplantation. hNSCs survived transplantation into the lesioned mouse brain, as evidenced by human cell markers and DiD fluorescence. The cells migrated away from the injection site and were found at sites of injury within the striatum, hippocampus, thalamus, and white matter tracts and at remote locations in the brain. Subsets of grafted cells expressed neuronal and glial cell markers. hNSCs restored partially the complement of striatal neurons in brain-damaged mice. We conclude that human EG cell-derived NSCs can engraft successfully into injured newborn brain, where they can survive and disseminate into the lesioned areas, differentiate into neuronal and glial cells, and replace lost neurons. (c) 2005 Wiley-Liss, Inc.
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Affiliation(s)
- Dawn Mueller
- Department of Gynecology and Obstetrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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8
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Berger RP, Heyes MP, Wisniewski SR, Adelson PD, Thomas N, Kochanek PM. Assessment of the Macrophage Marker Quinolinic Acid in Cerebrospinal Fluid after Pediatric Traumatic Brain Injury: Insight into the Timing and Severity of Injury in Child Abuse. J Neurotrauma 2004; 21:1123-30. [PMID: 15453983 DOI: 10.1089/neu.2004.21.1123] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This study measured quinolinic acid (QUIN), a macrophage-microglia derived neurotoxin, in the cerebrospinal fluid (CSF) of children after non-inflicted and inflicted traumatic brain injury (nTBI, iTBI), and correlated QUIN concentrations with age, mechanism of injury (nTBi vs. iTBI), Glasgow Coma Scale (GCS) score and 6-month Glasgow Outcome Score. One hundred fifty-two CSF samples were collected from 51 children with severe TBI (GCS < or = 8). CSF was collected at the time an intraventricular catheter was placed and daily thereafter. QUIN concentration was measured by gas chromatography-mass spectroscopy. Patients ranged in age from 2 months to 16 years. Eleven children (22%) had iTBI. Initial and peak CSF QUIN concentrations were higher in patients with iTBI versus nTBI after adjusting for time after injury and GCS. Despite the lack of a history of trauma in 82% of children with iTBI, 100% had a peak QUIN concentration of >100 nM. There was a significant increase in the CSF concentrations of QUIN following severe nTBI and iTBI in children. Higher initial and peak QUIN concentrations after iTBI may be due to severity of injury, young age, and/or delay in seeking medical care, which allows for increased secondary injury.
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Affiliation(s)
- Rachel Pardes Berger
- Department of Pediatrics, Children's Hospital of Pittsburgh, 3705 Fifth Avenue, Pittsburgh, PA 15213, USA.
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9
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Gropman AL, Batshaw ML. Cognitive outcome in urea cycle disorders. Mol Genet Metab 2004; 81 Suppl 1:S58-62. [PMID: 15050975 DOI: 10.1016/j.ymgme.2003.11.016] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2003] [Revised: 08/03/2003] [Accepted: 11/17/2003] [Indexed: 11/30/2022]
Abstract
Despite treatment, cognitive and motor deficits are common in individuals with inherited urea cycle disorders. However, the extent to which the deficits involve specific cognitive or sensorimotor domains is unknown. Furthermore, little is known about the neurochemical basis of cognitive impairment in these disorders. This paper reviews studies of cognitive and motor dysfunction in urea cycle disorders, and discusses potential venues for investigation of the underlying neural basis that may elucidate these defects. Such methods of investigation may serve as a model for studying the relationship between genes, biochemical markers, brain function, and behavior in other metabolic diseases.
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Affiliation(s)
- Andrea L Gropman
- Children's Research Institute, Children's National Medical Center, Department of Pediatrics, George Washington University School of Medicine and Health Sciences, Washington, DC 20010-2916, USA
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10
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Abstract
The symptoms and signs of ornithine transcarbamylase deficiency are discussed. When the condition occurs among males in the neonatal period it is likely to be lethal. Pathological findings are non-specific. The diagnosis should be considered if coma with cerebral oedema and respiratory alkalosis occurs for no obvious reason. When hyperammonaemia is found, enzyme assay on a liver biopsy should be considered. A useful clue in an asymptomatic patient is a voluntary adoption of a vegetarian diet. Provocative tests, such as the allopurinol test can be used, but the method most frequently applied is mutation analysis. In the case of prenatal diagnosis this is possible on a chorionic villus sample. The prognosis of ornithine transcarbamylase deficiency is better for those with an onset after infancy, but morbidity from brain damage does not appear to be linked to the number of episodes of hyperammonaemia that have occurred. The syndrome results from a deficiency of the mitochondrial enzyme ornithine transcarbamylase which catalyses the conversion of ornithine and carbamoyl phosphate to citrulline. The gene responsible for this enzyme is located on Xp21.1, and is expressed in the liver and gut. Mutations can be divided into two groups: those with neonatal onset with all enzyme activity abolished, and those with later onset with partial and varying enzyme deficiency. There can be a variety of precipitating causes, for example sodium valproate. Treatment can be given with a low protein diet, and with alternate pathway drugs such as sodium benzoate and phenylbutyrate. Liver transplant can be considered when symptoms are life-threatening, although there may be severe complications.Gene replacement therapy is the hope of the future.
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11
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Holt DE, Washabau RJ, Djali S, Dayrell-Hart B, Drobatz KJ, Heyes MP, Robinson MB. Cerebrospinal fluid glutamine, tryptophan, and tryptophan metabolite concentrations in dogs with portosystemic shunts. Am J Vet Res 2002; 63:1167-71. [PMID: 12171172 DOI: 10.2460/ajvr.2002.63.1167] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine whether glutamine (GLN), tryptophan (TRP), and tryptophan metabolite concentrations are higher in cerebralspinal fluid (CSF) dogs with naturally occurring portosystemic shunts (PSS), compared with control dogs. ANIMALS 11 dogs with confirmed PSS and 12 control dogs fed low- and high-protein diets. PROCEDURE Cerebrospinal fluid and blood samples were collected from all dogs. Serum and CSF concentrations of GLN, alanine, serine, TRP, 5-hydroxyindoleacetic acid (5-HIAA), and quinolinic acid (QUIN) were measured. RESULTS Cerebrospinal fluid concentrations of GLN, TRP, and 5-HIAA were significantly higher in PSS dogs, compared with control dogs fed high- or low-protein diets. Cerebrospinal fluid QUIN concentration was significantly higher in PSS dogs, compared with control dogs fed the low-protein diet. Serum QUIN concentration was significantly lower in PSS dogs, compared with control dogs fed either high- or low-protein diets. CONCLUSIONS AND CLINICAL RELEVANCE An increase in CNS GLN concentration is associated with high CSF concentrations of TRP and TRP metabolites in dogs with PSS. High CSF 5-HIAA concentrations indicate an increased flux of TRP through the CNS serotonin metabolic pathway, whereas high CSF QUIN concentrations indicate an increased metabolism of TRP through the indolamine-2,3-dioxygenase pathway. The high CSF QUIN concentrations in the face of low serum QUIN concentrations in dogs with PSS indicates that QUIN production from TRP is occurring in the CNS. High concentrations of QUIN and other TRP metabolites in the CNS may contribute to neurologic abnormalities found in dogs with PSS and hepatic encephalopathy.
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Affiliation(s)
- David E Holt
- Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA
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12
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Abstract
Hyperammonemia is mainly found in hepatic encephalopathy and in genetic defects of the urea cycle or other pathways of the intermediary metabolism. Clinically a difference has to be made between chronic moderate hyperammonemia and acutely increased concentrations. Pathogenetic mechanisms of ammonia toxicity to the brain are partly unraveled. In some animal models confounding variables, such as the reduced intake of food and amino acid imbalance due to liver insufficiency, do not allow to establish unequivocal causal relationships between the ammonia concentration and measured effects. In chronic moderate hyperammonemia an increased flux through the serotonin pathway is a key factor. It is caused by an increased transport of large neutral amino acids (including tryptophan) through the blood-brain barrier, accentuated by the imbalance of plasma amino acids in hepatic insufficiency. It is stimulated by D- or L-glutamine. Evidence is presented showing that a functioning gamma-glutamyl cycle (glutathione formation) is a prerequisite. In acute hyperammonemia involvement of NMDA receptors, glutamate, NO and cGMP plays an additional role. In hyperammonemic crises the increased cerebral blood flow leads to brain edema; factors discussed here are increased osmolytes in astrocytes and serotoninergic activity. Recent data indicate that axonal development is affected by ammonia and can be normalized in vitro by creatine supplementation in developing mixed brain cell aggregate cultures, thus reviving the old hypothesis of the impact of hyperammonemia on energy metabolism in the developing brain that could cause mental retardation.
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Affiliation(s)
- Claude Bachmann
- Laboratoire Central de Chimie Clinique, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
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13
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Yamanouchi H, Yokoo H, Yuhara Y, Maruyama KI, Sasaki A, Hirato J, Nakazato Y. An autopsy case of ornithine transcarbamylase deficiency. Brain Dev 2002; 24:91-4. [PMID: 11891099 DOI: 10.1016/s0387-7604(01)00408-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We present an autopsy case of ornithine transcarbamylase (OTC) deficiency with grumose degeneration in the dentate nucleus of the cerebellum. The patient had intractable neonatal convulsions and hyperammonemia from the 3rd day after birth. Diagnosis of OTC deficiency was made based on null activity of the enzyme and four-base deletions in exon 9 of the OTC gene. Death was due to sepsis as well as disseminated intravascular coagulation at 1 year and 2 months of age. Neuropathology showed multiple cystic changes and ulegyria in the bilateral frontal and parietal lobes. Multiple cysts were associated with the region, which was infiltrated with macrophages surrounded by astroglia showing palisading pattern. Ferrugination was marked in the thalamus and severe neuronal loss with astrogliotic change in the CA1-2 area of the hippocampus. Grumose degeneration was noted in the dentate nucleus of the cerebellum. This is the first report of grumose degeneration in OTC deficiency.
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Affiliation(s)
- Hideo Yamanouchi
- Pediatric Neurology Group, Department of Pediatrics, Dokkyo University School of Medicine, 880 Kitakobayashi, Mibu, Shimotsuga, Tochigi 321-0293, Japan.
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14
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de Jonge WJ, Marescau B, D'Hooge R, De Deyn PP, Hallemeesch MM, Deutz NE, Ruijter JM, Lamers WH. Overexpression of arginase alters circulating and tissue amino acids and guanidino compounds and affects neuromotor behavior in mice. J Nutr 2001; 131:2732-40. [PMID: 11584097 DOI: 10.1093/jn/131.10.2732] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Arginine is an intermediate of the ornithine cycle and serves as a precursor for the synthesis of nitric oxide, creatine, agmatine and proteins. It is considered to be a conditionally essential amino acid because endogenous synthesis only barely meets daily requirements. In rapidly growing suckling neonates, endogenous arginine biosynthesis is crucial to compensate for the insufficient supply of arginine via the milk. Evidence is accumulating that the intestine rather than the kidney plays a major role in arginine synthesis in this period. Accordingly, ectopic expression of hepatic arginase in murine enterocytes by genetic modification induces a selective arginine deficiency. The ensuing phenotype, whose severity correlates with the level of transgene expression in the enterocytes, could be reversed with arginine supplementation. We analyzed the effect of arginine deficiency on guanidine metabolism and neuromotor behavior. Arginine-deficient transgenic mice continued to suffer from an arginine deficiency after the arginine biosynthetic enzymes had disappeared from the enterocytes. Postweaning catch-up growth in arginine-deficient mice was characterized by increased levels of all measured amino acids except arginine. Furthermore, plasma total amino acid concentration, including arginine, was significantly lower in adult male than in adult female transgenic mice. Decreases in the concentration of plasma and tissue arginine led to significant decreases in most metabolites of arginine. However, the accumulation of the toxic guanidino compounds, guanidinosuccinic acid and methylguanidine, corresponded inversely with circulating arginine concentration, possibly reflecting a higher oxidative stress under hypoargininemic conditions. In addition, hypoargininemia was associated with disturbed neuromotor behavior, although brain levels of toxic guanidino compounds and ammonia were normal.
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Affiliation(s)
- W J de Jonge
- Department of Anatomy & Embryology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
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15
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Abstract
In just under 20 years the kynurenine family of compounds has developed from a group of obscure metabolites of the essential amino acid tryptophan into a source of intensive research, with postulated roles for quinolinic acid in neurodegenerative disorders, most especially the AIDS-dementia complex and Huntington's disease. One of the kynurenines, kynurenic acid, has become a standard tool for use in the identification of glutamate-releasing synapses, and has been used as the parent for several groups of compounds now being developed as drugs for the treatment of epilepsy and stroke. The kynurenines represent a major success in translating a basic discovery into a source of clinical understanding and therapeutic application, with around 3000 papers published on quinolinic acid or kynurenic acid since the discovery of their effects in 1981 and 1982. This review concentrates on some of the recent work most directly relevant to the understanding and applications of kynurenines in medicine.
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Affiliation(s)
- T W Stone
- Institute of Biomedical and Life Sciences, University West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK.
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Abstract
In most tissues, including brain, a major proportion of the tryptophan which is not used for protein synthesis is metabolised along the kynurenine pathway. Long regarded as the route by which many mammals generate adequate amounts of the essential co-factor nicotinamide adenine dinucleotide, two components of the pathway are now known to have marked effects on neurones. Quinolinic acid is an agonist at the N-methyl-D-aspartate sensitive subtype of glutamate receptors in the brain, while kynurenic acid is an antagonist and, thus, a potential neuroprotectant. A third kynurenine, 3-hydroxykynurenine, is involved in the generation of free radicals which can also damage neurones. Quinolinic acid is increasingly implicated in neurodegenerative disorders, most especially the AIDS-dementia complex and Huntington's disease, while kynurenic acid has become a standard for the identification of glutamate-releasing synapses, and has been used as the parent for several groups of compounds now being developed as drugs for the treatment of epilepsy and stroke.
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Affiliation(s)
- T W Stone
- Institute of Biomedical & Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK.
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Bengtsson F. Brain tryptophan/serotonin perturbations in metabolic encephalopathy and the hazards involved in the use of psychoactive drugs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 467:139-54. [PMID: 10721051 DOI: 10.1007/978-1-4615-4709-9_20] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Several combined pathogenetic factors such as hyperammonemia, different brain tryptophan metabolic disturbances and serotonin physiological/pharmacological alterations not yet defined in all details, will often give rise to the clinical neuropsychiatric condition known as hepatic encephalopathy (HE). Indeed, to this the probable exposure to novel potent CNS-monoamine acting drugs today may put such patients at certain risk for other pharmacodynamic (PD) responses than usually are expected from these "safe" drugs. Moreover, with a compromised liver function in HE, also pharmacokinetic (PK) features for the drugs are likely changed in these patients. Thus, the ultimate clinical outcome by this probable but unknown PD/PK-deviation for such psychoactive drugs when given to HE-patients needs further clarification. Accordingly, delineation of both PD- and PK-effects in experimental HE should shed light on this issue of relevance for monoamine-active drug safety as well as on some further details in the complex tryptophan/monoamine-related pathophysiology that comes into play in HE.
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Affiliation(s)
- F Bengtsson
- Department of Psychiatry, University Hospital, Linköping, Sweden.
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Butterworth RF. Evidence for forebrain cholinergic neuronal loss in congenital ornithine transcarbamylase deficiency. Metab Brain Dis 2000; 15:83-91. [PMID: 10885542 DOI: 10.1007/bf02680015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Congenital ornithine transcarbamylase (OTC) deficiency in humans results in failure to thrive, hypotonia, seizures and mental retardation. Neuropathologic evaluation reveals significant cerebral cortical atrophy, delayed myelination and Alzheimer type II astrocytosis. Using an animal model of congenital OTC deficiency, the sparse fur (spf) mouse, studies reveal convincing evidence of a loss of forebrain cholinergic neurons in this condition. Evidence includes (i) reduced activities of the cholinergic nerve terminal enzyme choline acetyltransferase (ChAT), (ii) a 25% loss of ChAT immunostaining, (iii) reduced high affinity transport of [3H]choline by cortical synaptosomes and (iv) a selective reduction in densities of presynaptic muscarinic M2 binding sites, in spf mouse brain compared to controls. A partial correction of the cholinergic deficit was observed following treatment with acetyl-L-carnitine. Possible mechanisms responsible for cholinergic neuronal loss in congenital OTC deficiency include decreased synthesis of the ChAT substrate acetyl CoA, impaired cerebral energy metabolism and NMDA receptor-mediated excitotoxicity. Loss of forebrain cholinergic neurons is consistent with the severe cognitive impairment characteristic of congenital OTC deficiency.
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Affiliation(s)
- R F Butterworth
- Neuroscience Research Unit, CHUM/Hôpital Saint-Luc, Montreal, Quebec, Canada.
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Heldmann E, Holt DE, Brockman DJ, Brown DC, Perkowski SZ. Use of propofol to manage seizure activity after surgical treatment of portosystemic shunts. J Small Anim Pract 1999; 40:590-4. [PMID: 10664958 DOI: 10.1111/j.1748-5827.1999.tb03029.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The anaesthetic agent propofol has anticonvulsant properties and has been used in the treatment of refractory status epilepticus in human medicine. This report describes the use of propofol in four cats and one dog with naturally occurring seizures following surgical attenuation of single extrahepatic portosystemic shunts. Two of the animals had seizures that were unresponsive to other anticonvulsants. Subanaesthetic doses of intravenous propofol (1.0 to 3.5 mg/kg boluses and 0.01 to 0.25 mg/kg/minute continuous rate infusions) were used to control the seizures in all animals. However, a good neurological outcome was achieved in only two of the five cases, which is similar to the situation in previous reports.
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Affiliation(s)
- E Heldmann
- Department of Clinical Studies, University of Pennsylvania School of Veterinary Medicine, Philadelphia 19104, USA
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Rao KV, Qureshi IA. Reduction in the MK-801 binding sites of the NMDA sub-type of glutamate receptor in a mouse model of congenital hyperammonemia: prevention by acetyl-L-carnitine. Neuropharmacology 1999; 38:383-94. [PMID: 10219976 DOI: 10.1016/s0028-3908(98)00160-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Our earlier studies on the pharmacotherapeutic effects of acetyl-L-carnitine (ALCAR), in sparse-fur (spf) mutant mice with X linked ornithine transcarbamylase deficiency, have shown a restoration of cerebral ATP, depleted by congenital hyperammonemia and hyperglutaminemia. The reduced cortical glutamate and increased quinolinate may cause a down-regulation of the N-methyl-D-aspartate (NMDA) receptors, observed by us in adult spf mice. We have now studied the kinetics of [3H]-MK-801 binding to NMDA receptors in spf mice of different ages to see the effect of chronic hyperammonemia on the glutamate neurotransmission. We have also studied the Ca2+-dependent and independent (4-aminopyridine (AP) and veratridine-mediated) release of glutamate and the uptake of [3H]-glutamate in synaptosomes isolated from mutant spf mice and normal CD-1 controls. All these studies were done with and without ALCAR treatment (4 mmol/kg wt i.p. daily for 2 weeks), to see if its effect on ATP repletion could correct the glutamate neurotransmitter abnormalities. Our results indicate a normal MK-801 binding in 12-day-old spf mice but a significant reduction immediately after weaning (21 day), continuing into the adult stage. The Ca2+-independent release of endogenous glutamate from synaptosomes was significantly elevated at 35 days, while the uptake of glutamate into synaptosomes was significantly reduced in spf mice. ALCAR treatment significantly enhanced the MK-801 binding, neutralized the increased glutamate release and restored the glutamate uptake into synaptosomes of spf mice. These studies point out that: (a) the developmental abnormalities of the NMDA sub-type of glutamate receptor in spf mice could be due to the effect of sustained hyperammonemia, causing a persistent release of excess glutamate and inhibition of the ATP-dependent glutamate transport, (b) the modulatory effects of ALCAR on the NMDA binding sites could be through a repletion of ATP, required by the transporters to efficiently remove extracellular glutamate.
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Affiliation(s)
- K V Rao
- Division of Medical Genetics, Sainte-Justine Hospital, Montreal, Que, Canada
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Hopkins KJ, Oster-Granite ML. Characterization of N-methyl-d-aspartate receptors in the hyperammonemic sparse fur mouse. Brain Res 1998; 797:209-17. [PMID: 9666130 DOI: 10.1016/s0006-8993(98)00362-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The N-methyl-d-aspartate (NMDA) receptor, a glutamate receptor subtype, is a ligand-gated ion channel. Overstimulation of NMDA receptors may increase intracellular Ca2+ concentrations to lethal levels in neurodegenerative disorders affecting the basal ganglia. Such excitotoxicity may also contribute to the loss of medium spiny neurons in the striata of the hyperammonemic sparse fur (spf/Y) mouse, a model of the X-linked disorder of the urea cycle, ornithine carbamoyltransferase deficiency (OCTD). Levels of quinolinic acid (QA), a potent NMDA agonist, are elevated in the brains of spf/Y mice. Further, direct injection of QA into the striatum produces selective degeneration of medium spiny neurons. Microglia, an endogenous source of QA in the brain, are abundant in spf/Y mice during the period of neuronal degeneration. The location and density of NMDA receptors was visualized by gold labelled immunocytochemistry with a polyclonal antibody to the NMDAR1 receptor subtype and their distribution quantified. A 58% reduction was found in the median density value in the layer V pyramidal neurons in fronto-parietal cortex (p<0.001), but no significant change was observed in the striatum. NMDA receptor binding was examined using [3H]dizocilpine ([3H]MK-801). Receptor density (Bmax) in the striata of clinically stable spf/Y mice and +/Y littermates was unchanged, but was decreased 15% (p<0.01) in the fronto-parietal cortices in clinically stable spf/Y mice compared with +/Y littermate controls.
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Affiliation(s)
- K J Hopkins
- Department of Environmental Toxicology, University of California, Riverside, CA 92521, USA. ucracl.ucr.edu
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22
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Stastný F, Dvoráková L, Lisý V. Biochemical characteristics of gamma-glutamyl transpeptidase in capillaries from entorhinohippocampal complex of quinolinate-lesioned rat brain. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1997; 32:143-61. [PMID: 9437664 DOI: 10.1007/bf02815173] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Quinolinic acid (QUIN) is an endogenous excitotoxic agonist of the N-methyl-D-aspartate (NMDA) type of glutamate receptor, which causes slowly progressing degeneration of vulnerable neurons in some brain regions. Using changes in the activity of membrane-bound gamma-glutamyl transpeptidase (GGT) as a marker of cell damage, we found a significant decrease of this enzyme activity, which was preferentially located in the ipsilateral hippocampal formation and entorhinal cortex, 4 d after the unilateral intracerebroventricular (icv) injection of 0.5 mumol QUIN. The dose of QUIN divided into two half-doses injected bilaterally led to a symmetrical decline of GGT activity in hippocampal areas. The lesion was characterized by a suppression of GGT activity in hippocampal and entorhinal capillaries, corresponding to 60 and 81% of their initial value, respectively, but no significant changes were ascertained in synaptosomal membranes. The changes in the activity of capillary GGT were associated with the decrease of apparent maximal velocity Vmaxapp, whereas apparent Michaelis constant K(m)app (0.69-0.79 mM) remained unaffected. In the nonlesioned brain, concanavalin A (Con A) affinity chromatography revealed five glycoforms of synaptosomal GGT in contrast to only one found in hippocampal and entorhinal capillaries. The results document that neither the saccharide moiety of GGT nor the value of enzyme K(m)app is significantly affected by the QUIN-induced lesion of the rat brain. However, the suppression of GGT activity, which is accompanied by a decrease in the value of Vmaxapp in brain microvessels, may suggest dysfunction of the blood-brain barrier (BBB) in the QUIN-injured rat brain.
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Affiliation(s)
- F Stastný
- Department of Molecular Neurobiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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23
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Dobbie MS, Surtees RA. Concentrations of quinolinic acid in cerebrospinal fluid measured by gas chromatography and electron-impact ionisation mass spectrometry. Age-related changes in a paediatric reference population. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1997; 696:53-8. [PMID: 9300908 DOI: 10.1016/s0378-4347(97)00221-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A simple method for the determination of the excitotoxin, quinolinic acid (QUIN) in cerebrospinal fluid (CSF) is described. QUIN, in lyophilized samples, was silylated by N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide in a single-step reaction at 65 to 70 degrees C to form a di-tert.-butyldimethylsilyl ester. Neither pre-purification of QUIN from CSF nor post-derivatisation sample clean-up was required. The derivatives were analysed by gas chromatography-electron impact mass spectrometry resulting in a prominent and characteristic [M-57]+ fragment ion which was used for quantitation. 2,6-Pyridine dicarboxylic acid, a structural analog of QUIN, was used as the internal standard. The detection limits for injected standards are in the femtomole range. CSF QUIN was found to be age-related and three preliminary reference ranges for CSF QUIN were found: 0 to 1 years, 31 +/- 15 nM QUIN (mean +/- standard deviation): 1.1 to 3 years, 26 +/- 15 nM; 3.1 to 14 years, 14 +/- 9 nM.
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Affiliation(s)
- M S Dobbie
- Division of Biochemistry and Genetics, Institute of Child Health (UCLMS), London, UK
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24
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Bengtsson F, Bergqvist PB, Apelqvist G. Brain tryptophan perturbation in hepatic encephalopathy: implications for effects by neuropsychoactive drugs in clinical practice. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 420:1-33. [PMID: 9286423 DOI: 10.1007/978-1-4615-5945-0_1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- F Bengtsson
- Department of Clinical Pharmacology, Lund University Hospital, Sweden
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25
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Qureshi IA, Rao KV. Sparse-fur (spf) mouse as a model of hyperammonemia: alterations in the neurotransmitter systems. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 420:143-58. [PMID: 9286431 DOI: 10.1007/978-1-4615-5945-0_9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- I A Qureshi
- Division of Medical Genetics, Hôpital Sainte-Justine Montréal, Québec, Canada
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26
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Ratnakumari L, Qureshi IA, Butterworth RF. Central muscarinic cholinergic M1 and M2 receptor changes in congenital ornithine transcarbamylase deficiency. Pediatr Res 1996; 40:25-8. [PMID: 8798241 DOI: 10.1203/00006450-199607000-00005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Congenital ornithine transcarbamylase (OTC) deficiency results in neuropathologic damage to the cerebral cortex, basal ganglia, and thalamus. However, the precise nature of the cell loss, as well as the pathophysiologic mechanisms responsible for it, have not been fully elucidated. In the present study, densities of the M1 and M2 subclasses of muscarinic cholinergic binding sites were assessed using quantitative receptor autoradiography in the brains of sparse-fur (spf) mice with congenital OTC deficiency and in age-matched CD-1 controls. Densities of binding sites for the muscarinic M1 subtype ligand [3H]pirenzepine were reduced by 24-54% (p < 0.01) in frontal cortex, caudate/ putamen, and hippocampal CA1 and CA2 areas. Since muscarinic M1 sites are localized presynaptically, their selective loss, together with a previous report of reduced activities of the presynaptic cholinergic enzyme choline acetyltransferase, confirms that loss of cholinergic neurons is an important feature of congenital OTC deficiency. Densities of binding sites for the predominantly postsynaptic muscarinic M2 subtype ligand 3H-AFDX 384 were increased by up to 60% (p < 0.01) in cerebral cortex, hippocampus, globus pallidus, as well as thalamic and hypothalamic structures of OTC-deficient mice. Increased M2 sites in the cerebral cortex, hippocampus, and thalamus are most likely the result of up-regulation of these sites after the loss of the presynaptic neuron. These findings support the presence of a central muscarinic cholinergic lesion in congenital OTC deficiency.
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Affiliation(s)
- L Ratnakumari
- Department of Medical Genetics, Hôpital Sainte-Justine, Montreal, Quebec, Canada
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27
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Colombo JP, Bachmann C, Cervantes H, Kokorovic M, Perritaz R. Tyrosine uptake and regional brain monoamine metabolites in a rat model resembling congenital hyperammonemia. Pediatr Res 1996; 39:1036-40. [PMID: 8725266 DOI: 10.1203/00006450-199606000-00017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hyperammonemia found in congenital disorders has a toxic effect on the central nervous system. Disturbances of brain neurotransmitter metabolism have been proposed, such as an increased transport of tryptophan into the brain and an increased flux through the serotonin pathway. Results concerning the catecholamine pathway are, however, contradictory. We therefore studied whether hyperammonermia increases brain uptake of the neurotransmitter precursor amino acid tyrosine and whether these changes affect the concentration of neurotransmitters and their metabolites in different brain areas (frontal cortex, caudatus-putamen, thalamus, hypothalamus, hippocampus/substantia nigra, brainstem) of rats made hyperammonemic with urease. The brain uptake of tyrosine was measured in the forebrain, brainstem, and cerebellum. The brain areas were analyzed for dopamine, 3,4-hydroxyphenylacetic acid; homovanillic acid, norepinephrine, and vanillylmandelic acid. The brain uptake index of tyrosine was increased in the forebrain and brainstem of the hyperammonemic rats with concomitantly elevated concentrations in the forebrain of tyrosine, phenylalanine, and tryptophan. The homovanillic acid content was significantly increased in the hypothalamus, hippocampus/substantia nigra and brainstem. The concentrations of norepinephrine, dopamine, and 3, 4-hydroxyphenylacetic acid were not significantly changed. Vanillylmandellic acid was decreased in the caudatus-putamen, thalamus, and hypothalamus. The data indicate an undisturbed neurotransmitter synthesis and, taken with the augmented tyrosine uptake at the blood-brain barrier, an increased flux through the dopamine pathway. These changes observed in the hyperammonemic animal model could contribute to the understanding of the pathogenic mechanisms and offer an explanation for the neuropsychiatric disturbances observed in children with congenital hyperammonemia.
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Affiliation(s)
- J P Colombo
- Department of Clinical Chemistry, University of Berne, Switzerland
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28
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Robinson MB, Hopkins K, Batshaw ML, McLaughlin BA, Heyes MP, Oster-Granite ML. Evidence of excitotoxicity in the brain of the ornithine carbamoyltransferase deficient sparse fur mouse. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1995; 90:35-44. [PMID: 8777776 DOI: 10.1016/0165-3806(96)83484-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ornithine carbamoyltransferase deficiency (OCTD) is the most common inborn error of urea synthesis. An X-linked disorder, OCTD males commonly present with hyperammonemic coma in the newborn period. There is a high rate of mortality and morbidity, with most survivors sustaining severe brain damage and resultant developmental disabilities. Although ammonia is presumed to be the principal neurotoxin, there is evidence that other neurochemical alterations may also be involved. The OCTD sparse fur (spf/Y) mouse has proven to be a useful model of this disease with similar metabolic and neurochemical alterations to those found in the human disease. In this study, the levels of the tryptophan derived excitotoxin quinolinic acid were examined in the brains of spf/Y mice. In addition, the neuropathology was examined using both light and electron microscopic approaches. Consistent with reports in children with urea cycle disorders, the levels of tryptophan and quinolinic acid were increased two-fold in various brain regions of the spf/Y mouse. Quinolinic acid, an agonist at the N-methyl-D-aspartate (NMDA) receptors, is known to produce selective cell loss in the striatum. We found a significant loss of medium spiny neurons and increased numbers of reactive oligodendroglia and microglia in the striatum of spf/Y mice. These neurochemical and neuropathological observations are consistent with an excitotoxic influence on brain injury in OCTD. It leads us to suggest that administration of NMDA receptor antagonists may ameliorate brain damage in children with inborn errors of urea synthesis.
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Affiliation(s)
- M B Robinson
- Children's Seashore House, Department of Pediatrics, University of Pennsylvania, School of Medicine, Philadelphia, USA
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29
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Heyes MP, Saito K, Milstien S, Schiff SJ. Quinolinic acid in tumors, hemorrhage and bacterial infections of the central nervous system in children. J Neurol Sci 1995; 133:112-8. [PMID: 8583213 DOI: 10.1016/0022-510x(95)00164-w] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A potential mechanism that may contribute to neurological deficits following central nervous system infection in children was investigated. Quinolinic acid (QUIN) is a neurotoxic metabolite of the kynurenine pathway that accumulates within the central nervous system following immune activation. The present study determined whether the levels of QUIN are increased in the cerebrospinal fluid of children with infections of the CNS, hydrocephalus, tumors or hemorrhage. Extremely high QUIN concentrations were found in patients with bacterial infections or the CNS, despite treatment with antimicrobial agents. CSF QUIN levels were also elevated to a lesser degree in patients with hydrocephalus or tumors. CSF L-kynurenine levels increased in parallel to the accumulations in QUIN, which is consistent with increased activity of the first enzyme of the kynurenine pathway, indoleamine-2,3-dioxygenase. The CSF levels of neopterin, a marker of immune and macrophage activation, were also increase in patients with infections. The cytokines tumor necrosis factor-alpha and interleukin-6 were also detected in some patients' samples, and were highest in patients with infection. These results suggest that QUIN is a sensitive marker of the presence of immune activation within the CNS. Further studies of QUIN as a potential contributor to neurologic dysfunction and neurodegeneration in children with CNS inflammation are warranted.
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Affiliation(s)
- M P Heyes
- Section on Analytical Biochemistry, National Institute of Mental Health, Bethesda, MD 20892, USA
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31
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Trescher WH, McDonald JW, Johnston MV. Quinolinate-induced injury is enhanced in developing rat brain. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1994; 83:224-32. [PMID: 7697883 DOI: 10.1016/0165-3806(94)00141-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Quinolinate, a metabolite of tryptophan in the kynurenine pathway, has been hypothesized to play a role in neuronal injury through activation of the N-methyl-D-aspartate (NMDA) receptor. We evaluated the ontogeny and neuroprotective pharmacology of quinolinate-induced injury in the immature rat brain. Unilateral striatal microinjections of quinolinate (150 nmol/0.5 microliter) were performed at seven ages between postnatal day (PND) 1 and 90. Injury was assessed by comparing the cross-sectional areas of the cerebral hemispheres ipsilateral and contralateral to the injection site in Nissl-stained coronal sections. The susceptibility to quinolinate-induced injury was enhanced in the immature brain with peak toxicity at PND 7 when the ipsilateral cerebral hemisphere was reduced by 16.1 +/- 3.2%. In a dose-response comparison with NMDA-induced injury at PND 7, quinolinate injury was directly related to the dose injected (r2 = 0.73, P < 0.0001), but the neurotoxicity of quinolinate was 20-times less potent than NMDA. In the PND 7 rat brain, quinolinate-induced injury was completely blocked by MK-801 (1 mg/kg, i.p.) and CGS-19755 (10 mg/kg). Dextromethorphan (20 mg/kg) and dextrorphan (20 mg/kg) were partially protective. Ifenprodil, carbamazepine, and nifedipine did not significantly protect against quinolinate-induced injury. Finally, pretreatment with MK-801 (1 mg/kg) 24 h before intracerebral injection of quinolinate resulted in greater injury compared to controls. The findings indicate that quinolinate-induced injury is enhanced in the immature brain in a pattern that is similar to NMDA-induced injury.
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Affiliation(s)
- W H Trescher
- Department of Neurology, Johns Hopkins University, Baltimore, MD
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Ratnakumari L, Qureshi IA, Butterworth RF. Evidence for cholinergic neuronal loss in brain in congenital ornithine transcarbamylase deficiency. Neurosci Lett 1994; 178:63-5. [PMID: 7816342 DOI: 10.1016/0304-3940(94)90290-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Congenital ornithine transcarbamylase (OTC) deficiency in humans is associated with seizures and mental retardation. As part of a series of studies to delineate the neurochemical features of OTC deficiency, activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), respectively, were measured in brain regions of the congenitally hyperammonemic sparse-fur (spf) mouse, a mutant with an X-linked inherited defect of OTC. ChAT activities were reduced by 63% (P < 0.01) in cerebral cortex of spf mice compared with CD-1/Y controls. Activities of the GABA nerve terminal marker enzyme, glutamic acid decarboxylase, on the other hand, were within normal limits. Using an immunohistochemical technique with a monoclonal antibody to ChAT, a significant loss of ChAT-positive neurons was observed throughout the cerebral cortex, septal area and diagonal band of spf mice. These results suggest that a loss of forebrain cholinergic neurons is a feature of congenital OTC deficiency in these mutants. Possible pathogenetic mechanisms responsible for the cholinergic neuronal loss in congenital OTC deficiency include neurotoxic effects of ammonia and accumulation of quinolinic acid.
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Affiliation(s)
- L Ratnakumari
- Department of Medical Genetics, Hôpital Ste-Justine, Montreal, Que., Canada
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Abstract
Inborn errors of urea synthesis can present in the newborn period as a catastrophic illness or later in childhood or adulthood with an indolent course punctuated by hyperammonemic episodes. Because symptoms mimic other neuropsychiatric disorders, it is common for there to be a delay in diagnosis, often with dire consequences. Diagnosis relies on the combination of clinical suspicion and the measurement of ammonium, lactate, and amino acids in plasma and organic acids and orotic acid in urine. Treatment involves nitrogen restriction combined with the stimulation of alternate pathways of waste nitrogen excretion. More recently liver transplantation has been performed as enzyme replacement therapy. The outcome is poor in children who survive prolonged neonatal hyperammonemic coma, with most manifesting developmental disabilities. The etiology of neuronal injury in this disorder is unclear but may involve some combination of ammonia/amino acid accumulation, neurotransmitter alterations, and excitotoxic injury. Gene therapy holds the promise of improved treatment in the future.
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