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Bregalda A, Carducci C, Pascucci T, Ambrogini P, Sartini S, Pierigè F, di Carlo E, Fiori E, Ielpo D, Pagliarini M, Leuzzi V, Magnani M, Rossi L. New findings about neuropathological outcomes in the PKU mouse throughout lifespan. Mol Genet Metab 2024; 143:108543. [PMID: 39047302 DOI: 10.1016/j.ymgme.2024.108543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 07/17/2024] [Accepted: 07/17/2024] [Indexed: 07/27/2024]
Abstract
Phenylketonuria (PKU, OMIM 261600) is a genetic disorder caused by a deficiency of the hepatic enzyme phenylalanine hydroxylase (PAH). If left untreated, PKU leads to systemic phenylalanine (Phe) accumulation, which can result in irreversible brain damage and intellectual disabilities. In the last 60 years, early and strict dietary restriction of phenylalanine (Phe) intake proved to prevent the severe clinical phenotype of untreated PKU. While the specific mechanisms through which phenylalanine causes brain damage are still poorly understood, preclinical models have been deeply explored to characterize the neurotoxic effect of Phe on neurodevelopmental processes. At the same time, that on the aging brain still needs to be explored. In the brain of untreated PAHEnu2(-/-) mouse, we previously reported a reduction of myelin basic protein (MBP) during postnatal development up to 60 PND. Later in the diseased mouse's life, a spontaneous and persistent restoration of MBP was detected. In this present longitudinal study, ranging from 14 to 540 post-natal days (PND) of untreated PAHEnu2(-/-) mice, we further investigated: a) the long-life consistency of two Phe-related brain metabolic alterations, such as large neutral amino acids (LNAA) and biogenic amine neurotransmitters' depletion; b) the outcome of locomotor functions during the same life span; c) the integrity of myelin as assessed ex vivo by central (hippocampus) and peripheral (extensor digitorum longus-sciatic nerve) action potential conduction velocities. In contrast with the results of other studies, brain Leu, Ile, and Val concentrations were not significantly altered in the brain PAHEnu2(-/-) mouse. On the other hand, 3-O-Methyldopa (3-OMD, a biomarker of L-DOPA), serotonin, and its associated metabolites were reduced throughout most of the considered time points, with consistent reductions observed prevalently from 14 to 60 PND. Normal saltatory conduction was restored after 60 PND and remained normal at the last examination at 360 PND, resulting nonetheless in a persistent locomotor impairment throughout a lifetime. These new findings contribute to laying the foundations for the preclinical characterization of aging in PKU, confirming neurotransmitter defects as consistent metabolic traits. LNAAs have a minor role, if any, in brain damage pathogenesis. Transient myelin synthesis failure may impact brain connectivity during postnatal development but not nervous signal conduction.
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Affiliation(s)
- Alessandro Bregalda
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy; Pathology Unit, Centro di Riferimento Oncologico di Aviano (C.R.O.) IRCCS, via Franco Gallini 2, 33081 Aviano (PN), Italy.
| | - Claudia Carducci
- Department of Experimental Medicine, Sapienza University, viale del Policlinico 155, 00161 Rome, Italy
| | - Tiziana Pascucci
- Fondazione Santa Lucia IRCCS, via Del Fosso di Fiorano, 64, 00143 Rome, Italy; Department of Psychology and Centro "Daniel Bovet", Sapienza University, via dei Marsi 78, 00185 Rome, Italy
| | - Patrizia Ambrogini
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy
| | - Stefano Sartini
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy
| | - Francesca Pierigè
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy
| | - Emanuele di Carlo
- Department of Experimental Medicine, Sapienza University, viale del Policlinico 155, 00161 Rome, Italy
| | - Elena Fiori
- Fondazione Santa Lucia IRCCS, via Del Fosso di Fiorano, 64, 00143 Rome, Italy; Technopole Foundation, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Donald Ielpo
- Fondazione Santa Lucia IRCCS, via Del Fosso di Fiorano, 64, 00143 Rome, Italy; Department of Psychology and Centro "Daniel Bovet", Sapienza University, via dei Marsi 78, 00185 Rome, Italy
| | - Marica Pagliarini
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy
| | - Vincenzo Leuzzi
- Department of Human Neuroscience, Sapienza University, via dei Sabelli 108, 00185 Rome, Italy
| | - Mauro Magnani
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy; EryDel SpA, via Antonio Meucci 3, 20091 Bresso (MI), Italy
| | - Luigia Rossi
- Department of Biomolecular Sciences, University of Urbino "Carlo Bo", via Ca' Le Suore 2, 61029 Urbino (PU), Italy; EryDel SpA, via Antonio Meucci 3, 20091 Bresso (MI), Italy
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Kuila S, Dey S, Singh P, Shrivastava A, Nanda J. Phenylalanine-based fibrillar systems. Chem Commun (Camb) 2023; 59:14509-14523. [PMID: 37987167 DOI: 10.1039/d3cc04138g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Phenylketonuria (PKU) is an inborn metabolic disorder characterized by excess accumulation of phenylalanine (Phe) and its fibril formation, resulting in progressive intellectual disability. Several research groups have approached from various directions to understand the formation of toxic amyloid fibrils from the essential amino acid Phe. Different parameters like the nature of the solvent, pH, Phe concentration, temperature, etc. influence the fibril formation kinetics. In this article, we have summarized all major findings regarding the formation of Phe-based fibrils in aqueous and organic media and discussed how non-covalent interactions are involved in the self-assembly process using spectroscopic and microscopic techniques. The toxicity of Phe-based fibrils is compared with other neurodegenerative peptides. It is noted that the Phe-based fibrils can also induce various globular proteins into toxic fibrils. Later, we discuss the different approaches to inhibit fibril formation and reduce its toxicity. The presence of polyphenolic compounds, drugs, amino acids, nanoparticles, metal ions, crown ethers, and others showed a remarkable inhibitory effect on fibril formation. To the best of our knowledge, this is the first-ever etymological analysis of the Phe-fibrillar system and its inhibition to create a strong database against PKU.
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Affiliation(s)
- Soumen Kuila
- Department of Chemistry, University of North Bengal, Raja Rammohanpur, Siliguri 734013, West Bengal, India.
| | - Sukantha Dey
- Department of Chemistry, University of North Bengal, Raja Rammohanpur, Siliguri 734013, West Bengal, India.
| | - Pijush Singh
- Department of Chemistry, University of North Bengal, Raja Rammohanpur, Siliguri 734013, West Bengal, India.
- Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India
| | - Akash Shrivastava
- Department of Chemistry, University of North Bengal, Raja Rammohanpur, Siliguri 734013, West Bengal, India.
| | - Jayanta Nanda
- Department of Chemistry, University of North Bengal, Raja Rammohanpur, Siliguri 734013, West Bengal, India.
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Cornelissen F, Markert G, Deutsch G, Antonara M, Faaij N, Bartelink I, Noske D, Vandertop WP, Bender A, Westerman BA. Explaining Blood-Brain Barrier Permeability of Small Molecules by Integrated Analysis of Different Transport Mechanisms. J Med Chem 2023; 66:7253-7267. [PMID: 37217193 PMCID: PMC10259449 DOI: 10.1021/acs.jmedchem.2c01824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Indexed: 05/24/2023]
Abstract
The blood-brain barrier (BBB) represents a major obstacle to delivering drugs to the central nervous system (CNS), resulting in the lack of effective treatment for many CNS diseases including brain cancer. To accelerate CNS drug development, computational prediction models could save the time and effort needed for experimental evaluation. Here, we studied BBB permeability focusing on active transport (influx and efflux) as well as passive diffusion using previously published and self-curated data sets. We created prediction models based on physicochemical properties, molecular substructures, or their combination to understand which mechanisms contribute to BBB permeability. Our results show that features that predicted passive diffusion over membranes overlap with features that explain endothelial permeation of approved CNS-active drugs. We also identified physical properties and molecular substructures that positively or negatively predicted BBB transport. These findings provide guidance toward identifying BBB-permeable compounds by optimally matching physicochemical and molecular properties to BBB transport mechanisms.
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Affiliation(s)
- Fleur
M.G. Cornelissen
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
| | - Greta Markert
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K.
| | - Ghislaine Deutsch
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K.
| | - Maria Antonara
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K.
| | - Noa Faaij
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
| | - Imke Bartelink
- Department
of Pharmacy, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
| | - David Noske
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
| | - W. Peter Vandertop
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
| | - Andreas Bender
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K.
| | - Bart A. Westerman
- Department
of Neurosurgery, Amsterdam UMC, location VUMC, Cancer Center, Amsterdam 1105, AZ, the Netherlands
- Window
Consortium (www.window-consortium.org)
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Cognitive Functioning in Adults with Phenylketonuria in a Cohort of Spanish Patients. Behav Neurol 2023; 2023:9681740. [PMID: 36815863 PMCID: PMC9931468 DOI: 10.1155/2023/9681740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 02/10/2023] Open
Abstract
The early introduction of a low phenylalanine (Phe) diet has been demonstrated to be the most successful treatment in subjects with phenylketonuria (PKU), especially for preventing severe cognitive and neurological damages. However, it still concerns that even if treated in the first months of life with supplements and following a diet, they can show slight scores below people without PKU in neuropsychological assignments. We investigated 20 adults with classical PKU aged 19-48 years (mean age 29 years) and 20 heathy controls matched by age, gender, and years of education. Patients and controls were assessed with an extended neuropsychological battery, as well as psychological aspects and quality of life, also the last Phe level result was obtained. Results showed that the most affected cognitive domains are processing speed, executive functioning, memory, and also theory of mind, but very well-preserved verbal fluency, language, and visuospatial functioning. In quality of life, some significant results were seen specially in anxiety of Phe levels, anxiety of Phe levels during pregnancy, guilt if poor adherence to supplements, and if dietary protein restriction not followed. No significant results were obtained for the psychological variables. In conclusion, it has been shown that a combination of a low Phe diet, supplement intake, and keeping Phe levels in a low range seems appropriate to have the most normal and alike cognitive performance to persons without PKU.
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Pardridge WM. A Historical Review of Brain Drug Delivery. Pharmaceutics 2022; 14:1283. [PMID: 35745855 PMCID: PMC9229021 DOI: 10.3390/pharmaceutics14061283] [Citation(s) in RCA: 63] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/01/2022] [Accepted: 06/07/2022] [Indexed: 12/13/2022] Open
Abstract
The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.
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Affiliation(s)
- William M Pardridge
- Department of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
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Nandi S, Ghosh B, Ghosh M, Layek S, Nandi PK, Sarkar N. Phenylalanine Interacts with Oleic Acid-Based Vesicle Membrane. Understanding the Molecular Role of Fibril-Vesicle Interaction under the Context of Phenylketonuria. J Phys Chem B 2021; 125:9776-9793. [PMID: 34420302 DOI: 10.1021/acs.jpcb.1c05592] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present contribution, on the basis of a spectroscopic and microscopic investigation, the characterization and photophysics of various assemblies of oleic acid/oleate solution at three pH values, namely, 8.28, 9.72, and 11.77, were explored. The variation in the dynamic response of aqua molecules in and around the assemblies has been interrogated by a picoseconds solvation dynamics experiment using a time-correlated single-photon counting setup employing coumarin-153 as a probe. On the one hand, the time-resolved fluorescence anisotropy measurement along with the fluorescence correlation spectroscopy experiment was executed to extract information regarding the comparison of the extent of the internal restricted confinement of these assemblies. On the other hand, an effort to investigate the cross-interaction between the self-assembled architectures of l-phenylalanine (l-Phe), responsible for phenylketonuria (PKU) disorder, and the oleic acid at the vesicle-forming pH established that the l-Phe fibrillar morphologies strongly alter the dynamic properties of the vesicle membrane formed by the oleic acid. Specifically, the interaction of the l-Phe assemblies with the oleic acid vesicle membrane is found to introduce the flexibility of the vesicle membrane and alter the hydration properties of the membrane. To track the fibril-induced alterations of the oleic acid vesicle properties, various spectroscopic and microscopic investigations were performed. The mutual reconciliation of the experimental outputs, therefore, portrays the state of the art, which accounts for the fibril-induced alterations of the properties of the oleic acid vesicle membrane, the mimicking setup of the cellular membrane, thereby informing us that alterations of such a property of the membrane should be taken into active consideration during the rational development of therapeutic modulators against disorders like PKU.
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Affiliation(s)
- Sourav Nandi
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Biswajoy Ghosh
- School of Medical Science and Technology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Meghna Ghosh
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Souvik Layek
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Pratyush Kiran Nandi
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Nilmoni Sarkar
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
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Abstract
Phenylketonuria (PKU; also known as phenylalanine hydroxylase (PAH) deficiency) is an autosomal recessive disorder of phenylalanine metabolism, in which especially high phenylalanine concentrations cause brain dysfunction. If untreated, this brain dysfunction results in severe intellectual disability, epilepsy and behavioural problems. The prevalence varies worldwide, with an average of about 1:10,000 newborns. Early diagnosis is based on newborn screening, and if treatment is started early and continued, intelligence is within normal limits with, on average, some suboptimal neurocognitive function. Dietary restriction of phenylalanine has been the mainstay of treatment for over 60 years and has been highly successful, although outcomes are still suboptimal and patients can find the treatment difficult to adhere to. Pharmacological treatments are available, such as tetrahydrobiopterin, which is effective in only a minority of patients (usually those with milder PKU), and pegylated phenylalanine ammonia lyase, which requires daily subcutaneous injections and causes adverse immune responses. Given the drawbacks of these approaches, other treatments are in development, such as mRNA and gene therapy. Even though PAH deficiency is the most common defect of amino acid metabolism in humans, brain dysfunction in individuals with PKU is still not well understood and further research is needed to facilitate development of pathophysiology-driven treatments.
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Affiliation(s)
- Francjan J van Spronsen
- Beatrix Children's Hospital, University Medical Centre Groningen, University of Groningen, Groningen, Netherlands.
| | - Nenad Blau
- University Children's Hospital in Zurich, Zurich, Switzerland
| | - Cary Harding
- Department of Molecular and Medical Genetics and Department of Pediatrics, Oregon Health & Science University, Oregon, USA
| | | | - Nicola Longo
- Department of Pediatrics, University of Utah, Salt Lake City, Utah, USA
| | - Annet M Bosch
- University of Amsterdam, Department of Pediatrics, Division of Metabolic Disorders, Emma Children's Hospital, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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Pardridge WM. The Isolated Brain Microvessel: A Versatile Experimental Model of the Blood-Brain Barrier. Front Physiol 2020; 11:398. [PMID: 32457645 PMCID: PMC7221163 DOI: 10.3389/fphys.2020.00398] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 04/02/2020] [Indexed: 12/12/2022] Open
Abstract
A versatile experimental model for the investigation of the blood-brain barrier (BBB), including the neuro-vascular unit, is the isolated brain microvessel preparation. Brain microvessels are primarily comprised of endothelial cells, but also include pericytes, pre-capillary arteriolar smooth muscle cells, astrocyte foot processes, and occasional nerve endings. These microvessels can be isolated from brain with a 3 h procedure, and the microvessels are free of brain parenchyma. Brain microvessels have been isolated from fresh animal brain, fresh human brain obtained at neurosurgery, as well as fresh or frozen autopsy human brain. Brain microvessels are the starting point for isolation of brain microvessel RNA, which then enables the production of BBB cDNA libraries and a genomics analysis of the brain microvasculature. Brain microvessels, combined with quantitative targeted absolute proteomics, allow for the quantitation of specific transporters or receptors expressed at the brain microvasculature. Brain microvessels, combined with specific antibodies and immune labeling of isolated capillaries, allow for the cellular location of proteins expressed within the neuro-vascular unit. Isolated brain microvessels can be used as an “in vitro” preparation of the BBB for the study of the kinetic parameters of BBB carrier-mediated transport (CMT) systems, or for the determination of dissociation constants of peptide binding to BBB receptor-mediated transport (RMT) systems expressed at either the animal or the human BBB. This review will discuss how the isolated brain microvessel model system has advanced our understanding of the organization and functional properties of the BBB, and highlight recent renewed interest in this 50 year old model of the BBB.
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Affiliation(s)
- William M Pardridge
- Department of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Nandi S, Pyne A, Ghosh M, Banerjee P, Ghosh B, Sarkar N. Antagonist Effects of l-Phenylalanine and the Enantiomeric Mixture Containing d-Phenylalanine on Phospholipid Vesicle Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:2459-2473. [PMID: 32073868 DOI: 10.1021/acs.langmuir.9b03543] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One of the congenital flaws of metabolism, phenylketonuria (PKU), is known to be related to the self-assembly of toxic fibrillar aggregates of phenylalanine (Phe) in blood at elevated concentrations. Our experimental findings using l-phenylalanine (l-Phe) at millimolar concentration suggest the formation of fibrillar morphologies in the dry phase, which in the solution phase interact strongly with the model membrane composed of 1,2-diacyl-sn-glycero-phosphocholine (LAPC) lipid, thereby decreasing the rigidity (or increasing the fluidity) of the membrane. The hydrophobic interaction, in addition to the electrostatic attraction of Phe with the model membrane, is found to be responsible for such phenomena. On the contrary, various microscopic observations reveal that such fibrillar morphologies of l-Phe are severely ruptured in the presence of its enantiomer d-phenylalanine (d-Phe), thereby converting the fibrillar morphologies into crushed flakes. Various biophysical studies, including the solvation dynamics experiment, suggest that this l-Phe in the presence of d-Phe, when interacting with the same model membrane, now reverts the rigidity of the membrane, i.e., increases the rigidity of the membrane, which was lost due to interaction with l-Phe exclusively. Fluorescence anisotropy measurements also support this reverse rigid character of the membrane in the presence of an enantiomeric mixture of amino acids. A comprehensive understanding of the interaction of Phe with the model membrane is further pursued at the single-molecular fluorescence detection level using fluorescence correlation spectroscopy (FCS) experiments. Therefore, our experimental conclusion interprets a linear correlation between increased permeability and enhanced fluidity of the membrane in the presence of l-Phe and certifies d-Phe as a therapeutic modulator of l-Phe fibrillar morphologies. Further, the study proposes that the rigidity of the membrane lost due to interaction with l-Phe was reinstated-in fact, increased-in the presence of the enantiomeric mixture containing both d- and l-Phe.
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Abstract
Aspartame is a synthetic dipeptide artificial sweetener, frequently used in foods, medications, and beverages, notably carbonated and powdered soft drinks. Since 1981, when aspartame was first approved by the US Food and Drug Administration, researchers have debated both its recommended safe dosage (40 mg/kg/d) and its general safety to organ systems. This review examines papers published between 2000 and 2016 on both the safe dosage and higher-than-recommended dosages and presents a concise synthesis of current trends. Data on the safe aspartame dosage are controversial, and the literature suggests there are potential side effects associated with aspartame consumption. Since aspartame consumption is on the rise, the safety of this sweetener should be revisited. Most of the literature available on the safety of aspartame is included in this review. Safety studies are based primarily on animal models, as data from human studies are limited. The existing animal studies and the limited human studies suggest that aspartame and its metabolites, whether consumed in quantities significantly higher than the recommended safe dosage or within recommended safe levels, may disrupt the oxidant/antioxidant balance, induce oxidative stress, and damage cell membrane integrity, potentially affecting a variety of cells and tissues and causing a deregulation of cellular function, ultimately leading to systemic inflammation.
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Affiliation(s)
- Arbind Kumar Choudhary
- Department of Physiology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Etheresia Pretorius
- Department of Physiological Sciences, Faculty of Health Sciences, Stellenbosch University, Stellenbosch, South Africa
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Winn SR, Scherer T, Thöny B, Ying M, Martinez A, Weber S, Raber J, Harding CO. Blood phenylalanine reduction corrects CNS dopamine and serotonin deficiencies and partially improves behavioral performance in adult phenylketonuric mice. Mol Genet Metab 2018; 123:6-20. [PMID: 29331172 PMCID: PMC5786171 DOI: 10.1016/j.ymgme.2017.10.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/17/2017] [Accepted: 10/17/2017] [Indexed: 01/12/2023]
Abstract
Central nervous system (CNS) deficiencies of the monoamine neurotransmitters dopamine and serotonin have been implicated in the pathophysiology of neuropsychiatric dysfunction in human phenylketonuria (PKU). In this study, we confirmed the occurrence of brain dopamine and serotonin deficiencies in association with severe behavioral alterations and cognitive impairments in hyperphenylalaninemic C57BL/6-Pahenu2/enu2 mice, a model of human PKU. Phenylalanine-reducing treatments, including either dietary phenylalanine restriction or liver-directed gene therapy, initiated during adulthood were associated with increased brain monoamine content along with improvements in nesting behavior but without a change in the severe cognitive deficits exhibited by these mice. At euthanasia, there was in Pahenu2/enu2 brain a significant reduction in the protein abundance and maximally stimulated activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase 2 (TPH2), the rate limiting enzymes catalyzing neuronal dopamine and serotonin synthesis respectively, in comparison to levels seen in wild type brain. Phenylalanine-reducing treatments initiated during adulthood did not affect brain TH or TPH2 content or maximal activity. Despite this apparent fixed deficit in striatal TH and TPH2 activities, initiation of phenylalanine-reducing treatments yielded substantial correction of brain monoamine neurotransmitter content, suggesting that phenylalanine-mediated competitive inhibition of already constitutively reduced TH and TPH2 activities is the primary cause of brain monoamine deficiency in Pahenu2 mouse brain. We propose that CNS monoamine deficiency may be the cause of the partially reversible adverse behavioral effects associated with chronic HPA in Pahenu2 mice, but that phenylalanine-reducing treatments initiated during adulthood are unable to correct the neuropathology and attendant cognitive deficits that develop during juvenile life in late-treated Pahenu2/enu2 mice.
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Affiliation(s)
- Shelley R Winn
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Tanja Scherer
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Beat Thöny
- Department of Pediatrics, University of Zurich, Steinweissstrasse 75, Zurich CH-8032, Switzerland
| | - Ming Ying
- Department of Biomedicine, KG Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway
| | - Aurora Martinez
- Department of Biomedicine, KG Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway
| | - Sydney Weber
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Jacob Raber
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA; Department of Neurology, Division of Neuroscience, ONPRC, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA; Department of Radiation Medicine, Division of Neuroscience, ONPRC, Oregon Health & Science University, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA
| | - Cary O Harding
- Department of Medical and Molecular Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR 97239, USA.
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Didycz B, Bik-Multanowski M. Blood phenylalanine instability strongly correlates with anxiety in phenylketonuria. Mol Genet Metab Rep 2017; 14:80-82. [PMID: 29326880 PMCID: PMC5758931 DOI: 10.1016/j.ymgmr.2017.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/07/2017] [Accepted: 12/07/2017] [Indexed: 01/11/2023] Open
Abstract
We assessed the relationship between anxiety and long-term metabolic control in adolescents with phenylketonuria (PKU). We used a standardized psychological test to measure anxiety level and analyzed lifelong blood phenylalanine stability in a selected group of 25 PKU teenagers with treatment adherence problems. We demonstrated significant correlations of anxiety with variability of blood phenylalanine concentrations and with severity of hyperphenylalaninemia. Avoiding blood phenylalanine fluctuations in childhood can probably reduce anxiety in PKU adolescents.
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Affiliation(s)
- Bozena Didycz
- Department of Medical Genetics, Jagiellonian University Medical College, Krakow, Poland
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Intrinsic property of phenylalanine to trigger protein aggregation and hemolysis has a direct relevance to phenylketonuria. Sci Rep 2017; 7:11146. [PMID: 28894147 PMCID: PMC5593866 DOI: 10.1038/s41598-017-10911-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/15/2017] [Indexed: 01/31/2023] Open
Abstract
Excess accumulation of phenylalanine is the characteristic of untreated Phenylketonuria (PKU), a well-known genetic abnormality, which triggers several neurological, physical and developmental severities. However, the fundamental mechanism behind the origin of such diverse health problems, particularly the issue of how they are related to the build-up of phenylalanine molecules in the body, is largely unknown. Here, we show cross-seeding ability of phenylalanine fibrils that can effectively initiate an aggregation process in proteins under physiological conditions, converting native protein structures to β-sheet assembly. The resultant fibrils were found to cause severe hemolysis, yielding a plethora of deformed erythrocytes that is highly relevant to phenylketonuria. Unique arrangement of zwitterionic phenylalanine molecules in their amyloid-like higher order entities is predicted to promote both hydrophobic and electrostatic interaction, sufficient enough to trap proteins and to preferentially interact with the membrane components of RBCs. Since the prevalence of hemolysis and amyloid related psychoneurological severities are mostly observed in PKU patients, we propose that the inherent property of phenylalanine fibrils to trigger hemolysis and to induce protein aggregation may have direct relevance to the disease mechanism of PKU.
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Varatharaj A, Galea I. The blood-brain barrier in systemic inflammation. Brain Behav Immun 2017; 60:1-12. [PMID: 26995317 DOI: 10.1016/j.bbi.2016.03.010] [Citation(s) in RCA: 681] [Impact Index Per Article: 97.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/06/2016] [Accepted: 03/15/2016] [Indexed: 12/22/2022] Open
Abstract
The blood-brain barrier (BBB) plays a key role in maintaining the specialized microenvironment of the central nervous system (CNS), and enabling communication with the systemic compartment. BBB changes occur in several CNS pathologies. Here, we review disruptive and non-disruptive BBB changes in systemic infections and other forms of systemic inflammation, and how these changes may affect CNS function in health and disease. We first describe the structure and function of the BBB, and outline the techniques used to study the BBB in vitro, and in animal and human settings. We then summarise the evidence from a range of models linking BBB changes with systemic inflammation, and the underlying mechanisms. The clinical relevance of these BBB changes during systemic inflammation are discussed in the context of clinically-apparent syndromes such as sickness behaviour, delirium, and septic encephalopathy, as well as neurological conditions such as Alzheimer's disease and multiple sclerosis. We review emerging evidence for two novel concepts: (1) a heightened sensitivity of the diseased, versus healthy, BBB to systemic inflammation, and (2) the contribution of BBB changes induced by systemic inflammation to progression of the primary disease process.
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Affiliation(s)
- Aravinthan Varatharaj
- Clinical Neurosciences, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Mailpoint 806, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, United Kingdom.
| | - Ian Galea
- Clinical Neurosciences, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Mailpoint 806, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, United Kingdom.
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Concolino D, Mascaro I, Moricca MT, Bonapace G, Matalon K, Trapasso J, Radhakrishnan G, Ferrara C, Matalon R, Strisciuglio P. Long-term treatment of phenylketonuria with a new medical food containing large neutral amino acids. Eur J Clin Nutr 2017; 71:51-55. [PMID: 27623981 PMCID: PMC5222990 DOI: 10.1038/ejcn.2016.166] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 07/08/2016] [Accepted: 07/31/2016] [Indexed: 11/12/2022]
Abstract
BACKGROUND/OBJECTIVES Phenylketonuria (PKU) is an autosomal recessive disease caused by deficient activity of phenylalanine hydroxylase. A low phenylalanine (Phe) diet is used to treat PKU. The diet is very restrictive, and dietary adherence tends to decrease as patients get older. Methods to improve dietary adherence and blood Phe control are continuously under investigation. SUBJECTS/METHODS A new formula Phe-neutral amino acid (PheLNAA) has been tested in this study with the purpose of improving the compliance and lowering blood phenylalanine. The formula has been tested for nitrogen balance, and it is nutritionally complete. It is fortified with more nutritional additives that can be deficient in the PKU diet, such as B12, Biotin, DHA, Lutein and increased levels of large neutral amino acids to help lower blood Phe. The new formula has been tested on 12 patients with a loading test of 4 weeks. RESULTS Fifty-eight percent of patients had a significant decline in blood Phe concentration from baseline throughout the study. The PheLNAA was well tolerated with excellent compliance and without illnesses during the study. CONCLUSIONS In conclusion, the new formula is suitable for life-long treatment of PKU, and it offers the PKU clinic a new choice for treatment.
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Affiliation(s)
- D Concolino
- Department of Medical and Surgical Science, Pediatrics Unit, University 'Magna Graecia', Catanzaro, Italy
| | - I Mascaro
- Department of Medical and Surgical Science, Pediatrics Unit, University 'Magna Graecia', Catanzaro, Italy
| | - M T Moricca
- Department of Medical and Surgical Science, Pediatrics Unit, University 'Magna Graecia', Catanzaro, Italy
| | - G Bonapace
- Department of Medical and Surgical Science, Pediatrics Unit, University 'Magna Graecia', Catanzaro, Italy
| | - K Matalon
- Department of Health and Human Performance, University of Houston, Houston, TX, USA
| | - J Trapasso
- Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA
| | - G Radhakrishnan
- Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA
| | - C Ferrara
- Department of Public Health and Infectious Diseases, Sapienza University, Rome, Italy
| | - R Matalon
- Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA
| | - P Strisciuglio
- Department of Translational medical Science, Section of Pediatrics, Federico II University, Naples, Italy
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Bongiovanni R, Mchaourab AS, McClellan F, Elsworth J, Double M, Jaskiw GE. Large neutral amino acids levels in primate cerebrospinal fluid do not confirm competitive transport under baseline conditions. Brain Res 2016; 1648:372-379. [DOI: 10.1016/j.brainres.2016.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/08/2016] [Accepted: 08/09/2016] [Indexed: 01/27/2023]
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Schuck PF, Malgarin F, Cararo JH, Cardoso F, Streck EL, Ferreira GC. Phenylketonuria Pathophysiology: on the Role of Metabolic Alterations. Aging Dis 2015; 6:390-9. [PMID: 26425393 DOI: 10.14336/ad.2015.0827] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 08/27/2015] [Indexed: 11/01/2022] Open
Abstract
Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism caused by the deficiency of phenylalanine hydroxylase. This deficiency leads to the accumulation of Phe and its metabolites in tissues and body fluids of PKU patients. The main signs and symptoms are found in the brain but the pathophysiology of this disease is not well understood. In this context, metabolic alterations such as oxidative stress, mitochondrial dysfunction, and impaired protein and neurotransmitters synthesis have been described both in animal models and patients. This review aims to discuss the main metabolic disturbances reported in PKU and relate them with the pathophysiology of this disease. The elucidation of the pathophysiology of brain damage found in PKU patients will help to develop better therapeutic strategies to improve quality of life of patients affected by this condition.
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Affiliation(s)
- Patrícia Fernanda Schuck
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Fernanda Malgarin
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - José Henrique Cararo
- 1 Laboratório de Erros Inatos do Metabolismo, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Fabiola Cardoso
- 2 Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Emilio Luiz Streck
- 3 Laboratório de Bioenergética, Unidade Acadêmica de Ciências da Saúde, Universidade do Extremo Sul Catarinense, Criciúma, SC, Brazil
| | - Gustavo Costa Ferreira
- 2 Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Harding CO, Winn SR, Gibson KM, Arning E, Bottiglieri T, Grompe M. Pharmacologic inhibition of L-tyrosine degradation ameliorates cerebral dopamine deficiency in murine phenylketonuria (PKU). J Inherit Metab Dis 2014; 37:735-43. [PMID: 24487571 PMCID: PMC4119869 DOI: 10.1007/s10545-013-9675-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 12/18/2013] [Accepted: 12/30/2013] [Indexed: 12/22/2022]
Abstract
Monoamine neurotransmitter deficiency has been implicated in the etiology of neuropsychiatric symptoms associated with chronic hyperphenylalaninemia in phenylketonuria (PKU). Two proposed explanations for neurotransmitter deficiency in PKU include first, that chronically elevated blood L-phenylalanine (Phe) inhibits the transport of L-tyrosine (Tyr) and L-tryptophan (Trp), the substrates for dopamine and serotonin synthesis respectively, into brain. In the second hypothesis, elevated Phe competitively inhibits brain tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) activities, the rate limiting steps in dopamine and serotonin synthesis. Dietary supplementation with large neutral amino acids (LNAA) including Tyr and Trp has been recommended for individuals with chronically elevated blood Phe in an attempt to restore amino acid and monoamine homeostasis in brain. As a potential alternative treatment approach, we demonstrate that pharmacologic inhibition of Tyr degradation through oral administration of nitisinone (NTBC) yielded sustained increases in blood and brain Tyr, decreased blood and brain Phe, and consequently increased dopamine synthesis in a murine model of PKU. Our results suggest that Phe-mediated inhibition of TH activity is the likely mechanism of impaired dopamine synthesis in PKU. Pharmacologic inhibition of Tyr degradation may be a promising adjunct therapy for CNS monoamine neurotransmitter deficiency in hyperphenylalaninemic individuals with PKU.
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Affiliation(s)
- Cary O Harding
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Mailstop L-103, 3181 Sam Jackson Park Rd., Portland, OR, 97239, USA,
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Vogel KR, Arning E, Wasek BL, McPherson S, Bottiglieri T, Gibson KM. Brain-blood amino acid correlates following protein restriction in murine maple syrup urine disease. Orphanet J Rare Dis 2014; 9:73. [PMID: 24886632 PMCID: PMC4022424 DOI: 10.1186/1750-1172-9-73] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 04/25/2014] [Indexed: 12/19/2022] Open
Abstract
Background Conventional therapy for patients with maple syrup urine disease (MSUD) entails restriction of protein intake to maintain acceptable levels of the branched chain amino acid, leucine (LEU), monitored in blood. However, no data exists on the correlation between brain and blood LEU with protein restriction, and whether correction in blood is reflected in brain. Methods To address this question, we fed intermediate MSUD mice diets of 19% (standard) and 6% protein, with collection of sera (SE), striata (STR), cerebellum (CE) and cortex (CTX) for quantitative amino acid analyses. Results LEU and valine (VAL) levels in all brain regions improved on average 28% when shifting from 19% to 6% protein, whereas the same improvements in SE were on average 60%. Isoleucine (ILE) in brain regions did not improve, while the SE level improved 24% with low-protein consumption. Blood-branched chain amino acids (LEU, ILE, and VAL in sera (SE)) were 362-434 μM, consistent with human values considered within control. Nonetheless, numerous amino acids in brain regions remained abnormal despite protein restriction, including glutamine (GLN), aspartate (ASP), glutamate (GLU), gamma-aminobutyric acid (GABA), asparagine (ASN), citrulline (CIT) and serine (SER). To assess the specificity of these anomalies, we piloted preliminary studies in hyperphenylalaninemic mice, modeling another large neutral aminoacidopathy. Employing an identical dietary regimen, we found remarkably consistent abnormalities in GLN, ASP, and GLU. Conclusions Our results suggest that blood amino acid analysis may be a poor surrogate for assessing the outcomes of protein restriction in the large neutral amino acidopathies, and further indicate that chronic neurotransmitter disruptions (GLU, GABA, ASP) may contribute to long-term neurocognitive dysfunction in these disorders.
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Affiliation(s)
| | | | | | | | | | - K Michael Gibson
- Experimental and Systems Pharmacology, College of Pharmacy, Washington State University, 412 E, Spokane Falls Blvd,, Pharmaceutical and Biomedical Sciences Building, Room 347, P,O, Box 1495, 99210-1495 Spokane, WA, USA.
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20
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Neurocognitive evidence for revision of treatment targets and guidelines for phenylketonuria. J Pediatr 2014; 164:895-899.e2. [PMID: 24485821 DOI: 10.1016/j.jpeds.2013.12.015] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 11/14/2013] [Accepted: 12/11/2013] [Indexed: 11/22/2022]
Abstract
OBJECTIVES To compare the neurocognitive outcomes of patients with phenylketonuria (PKU) to determine whether decreasing phenylalanine (Phe) levels to <240 is preferable to the use of 360 μmol/L as an upper-target Phe level. An additional aim was to establish the influence of biochemical indices other than Phe on neurocognitive outcomes. STUDY DESIGN Patients with PKU (n = 63; mean age 10.8 ± 2.3 years) and healthy controls (n = 73; mean age 10.9 ± 2.2 years) performed computerized tasks measuring neurocognitive functions (inhibitory control, cognitive flexibility, and motor control). Lifetime and concurrent blood Phe levels, Phe-to-tyrosine ratio (Phe:Tyr), and Phe variations were examined in relation to neurocognitive outcomes using nonparametric tests and regression analyses. RESULTS Patients with PKU with Phe levels ≤240 μmol/L and healthy controls performed equally well. Patients with Phe levels between 240 and 360 μmol/L and ≥360 μmol/L performed more poorly than did controls across tasks. Patients with Phe levels ≤240 μmol/L performed significantly better than patients with levels between 240 and 360 μmol/L on tasks measuring inhibitory control and cognitive flexibility. Absolute Phe levels and Phe variation were the best predictors of motor control, whereas Phe:Tyr were the best predictors of inhibitory control. CONCLUSIONS The results of this study suggest that upper Phe targets should be lowered to optimize neurocognitive outcomes. Moreover, Phe variation and Phe:Tyr appear to be of additional value in treatment monitoring.
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Vogel KR, Arning E, Wasek BL, Bottiglieri T, Gibson KM. Non-physiological amino acid (NPAA) therapy targeting brain phenylalanine reduction: pilot studies in PAHENU2 mice. J Inherit Metab Dis 2013; 36:513-23. [PMID: 22976763 PMCID: PMC3654543 DOI: 10.1007/s10545-012-9524-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/11/2012] [Accepted: 07/19/2012] [Indexed: 11/26/2022]
Abstract
Transport of large neutral amino acids (LNAA) across the blood brain barrier (BBB) is facilitated by the L-type amino acid transporter, LAT1. Peripheral accumulation of one LNAA (e.g., phenylalanine (phe) in PKU) is predicted to increase uptake of the offending amino acid to the detriment of others, resulting in disruption of brain amino acid homeostasis. We hypothesized that selected non-physiological amino acids (NPAAs) such as DL-norleucine (NL), 2-aminonorbornane (NB; 2-aminobicyclo-(2,1,1)-heptane-2-carboxylic acid), 2-aminoisobutyrate (AIB), and N-methyl-aminoisobutyrate (MAIB), acting as competitive inhibitors of various brain amino acid transporters, could reduce brain phe in Pah (enu2) mice, a relevant murine model of PKU. Oral feeding of 5 % NL, 5 % AIB, 0.5 % NB and 3 % MAIB reduced brain phe by 56 % (p < 0.01), -1 % (p = NS), 27 % (p < 0.05) and 14 % (p < 0.01), respectively, compared to untreated subjects. Significant effects on other LNAAs (tyrosine, methionine, branched chain amino acids) were also observed, however, with MAIB displaying the mildest effects. Of interest, MAIB represents an inhibitor of the system A (alanine) transporter that primarily traffics small amino acids and not LNAAs. Our studies represent the first in vivo use of these NPAAs in Pah (enu2) mice, and provide proof-of-principle for their further preclinical development, with the long-term objective of identifying NPAA combinations and concentrations that selectively restrict brain phe transport while minimally impacting other LNAAs and downstream intermediates.
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Affiliation(s)
- Kara R. Vogel
- Section of Clinical Pharmacology, College of Pharmacy, Washington State University, Spokane, WA USA
| | - Erland Arning
- Institute of Metabolic Disease, Baylor Research Institute, Baylor University Medical Center, Dallas, TX USA
| | - Brandi L. Wasek
- Institute of Metabolic Disease, Baylor Research Institute, Baylor University Medical Center, Dallas, TX USA
| | - Teodoro Bottiglieri
- Institute of Metabolic Disease, Baylor Research Institute, Baylor University Medical Center, Dallas, TX USA
| | - K. Michael Gibson
- Section of Clinical Pharmacology, College of Pharmacy, Washington State University, Spokane, WA USA
- Correspondence: Section of Clinical Pharmacology, College of Pharmacy, Washington State University, 313 Wegner Hall, PO Box 646510, Pullman WA 99164-6510; phone 509-335-4754; fax 509-335-5902;
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22
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Deo AK, Theil FP, Nicolas JM. Confounding Parameters in Preclinical Assessment of Blood–Brain Barrier Permeation: An Overview With Emphasis on Species Differences and Effect of Disease States. Mol Pharm 2013; 10:1581-95. [DOI: 10.1021/mp300570z] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Anand K. Deo
- UCB Pharma S.A., Chemin du Foriest, B-1420 Braine-l’Alleud,
Belgium
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23
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Phenylalanine assembly into toxic fibrils suggests amyloid etiology in phenylketonuria. Nat Chem Biol 2012; 8:701-6. [DOI: 10.1038/nchembio.1002] [Citation(s) in RCA: 294] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 05/07/2012] [Indexed: 11/08/2022]
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Kyono K, Takashima T, Katayama Y, Kawasaki T, Zochi R, Gouda M, Kuwahara Y, Takahashi K, Wada Y, Onoe H, Watanabe Y. Use of [18F]FDOPA-PET for in vivo evaluation of dopaminergic dysfunction in unilaterally 6-OHDA-lesioned rats. EJNMMI Res 2011; 1:25. [PMID: 22214344 PMCID: PMC3251329 DOI: 10.1186/2191-219x-1-25] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 11/10/2011] [Indexed: 11/22/2022] Open
Abstract
Background We evaluated the utility of L-3,4-dihydroxy-6-[18F]fluoro-phenylalanine ([18F]FDOPA) positron emission tomography (PET) as a method for assessing the severity of dopaminergic dysfunction in unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats by comparing it with quantitative biochemical, immunohistochemical, and behavioral measurements. Methods Different doses of 6-OHDA (0, 7, 14, and 28 μg) were unilaterally injected into the right striatum of male Sprague-Dawley rats. Dopaminergic functional activity in the striatum was assessed by [18F]FDOPA-PET, measurement of striatal dopamine (DA) and DA metabolite levels, tyrosine hydroxylase (TH) immunostaining, and methamphetamine-induced rotational testing. Results Accumulation of [18F]FDOPA in the bilateral striatum was observed in rats pretreated with both aromatic L-amino acid decarboxylase and catechol-O-methyltransferase (COMT) inhibitors. Unilateral intrastriatal injection of 6-OHDA produced a significant site-specific reduction in [18F]FDOPA accumulation. The topological distribution pattern of [18F]FDOPA accumulation in the ipsilateral striatum agreed well with the pattern in TH-stained corresponding sections. A significant positive relationship was found between Patlak plot Ki values and striatal levels of DA and its metabolites (r = 0.958). A significant negative correlation was found between both Ki values (r = -0.639) and levels of DA and its metabolites (r = -0.719) and the number of methamphetamine-induced rotations. Conclusions Ki values determined using [18F]FDOPA-PET correlated significantly with the severity of dopaminergic dysfunction. [18F]FDOPA-PET makes it possible to perform longitudinal evaluation of dopaminergic function in 6-OHDA-lesioned rats, which is useful in the development of new drugs and therapies for Parkinson's disease (PD).
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Affiliation(s)
- Kiyoshi Kyono
- RIKEN Center for Molecular Imaging Science, Hyogo, Japan.
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25
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Johansson J, Landgren M, Fernell E, Vumma R, Åhlin A, Bjerkenstedt L, Venizelos N. Altered tryptophan and alanine transport in fibroblasts from boys with attention-deficit/hyperactivity disorder (ADHD): an in vitro study. Behav Brain Funct 2011; 7:40. [PMID: 21942982 PMCID: PMC3191351 DOI: 10.1186/1744-9081-7-40] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/24/2011] [Indexed: 12/11/2022] Open
Abstract
Background The catecholaminergic and serotonergic neurotransmitter systems are implicated in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). The amino acid tyrosine is the precursor for synthesis of the catecholamines dopamine and norepinephrine, while tryptophan is the precursor of serotonin. A disturbed transport of tyrosine, as well as other amino acids, has been found in a number of other psychiatric disorders, such as schizophrenia, bipolar disorder and autism, when using the fibroblast cell model. Hence, the aim of this study was to explore whether children with ADHD may have disturbed amino acid transport. Methods Fibroblast cells were cultured from skin biopsies obtained from 14 boys diagnosed with ADHD and from 13 matching boys without a diagnosis of a developmental disorder. Transport of the amino acids tyrosine, tryptophan and alanine across the cell membrane was measured by the cluster tray method. The kinetic parameters, maximal transport capacity (Vmax) and affinity constant (Km) were determined. Any difference between the two groups was analyzed by Student's unpaired t-test or the Mann Whitney U test. Results The ADHD group had significantly decreased Vmax (p = 0.039) and Km (increased affinity) (p = 0.010) of tryptophan transport in comparison to controls. They also had a significantly higher Vmaxof alanine transport (p = 0.031), but the Km of alanine transport did not differ significantly. There were no significant differences in any of the kinetic parameters regarding tyrosine transport in fibroblasts for the ADHD group. Conclusions Tryptophan uses the same transport systems in both fibroblasts and at the blood brain barrier (BBB). Hence, a decreased transport capacity of tryptophan implies that less tryptophan is being transported across the BBB in the ADHD group. This could lead to deficient serotonin access in the brain that might cause disturbances in both the serotonergic and the catecholaminergic neurotransmitter systems, since these systems are highly interconnected. The physiological importance of an elevated transport capacity of alanine to the brain is not known to date.
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Affiliation(s)
- Jessica Johansson
- Department of Clinical Medicine, School of Health and Medical Sciences, Örebro University, 701 82 Örebro, Sweden
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De K, Chandra S, Ganguly S, Sarkar B, Misra M. Synthesis and radiobiological evaluation of a new 99mTc-labeled small peptide: 99mTc-YGGSLAK as imaging agent. J Labelled Comp Radiopharm 2011. [DOI: 10.1002/jlcr.1883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Vumma R, Johansson J, Lewander T, Venizelos N. Tryptophan transport in human fibroblast cells-a functional characterization. Int J Tryptophan Res 2011; 4:19-27. [PMID: 22084600 PMCID: PMC3195221 DOI: 10.4137/ijtr.s6913] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
There are indications that serotonergic neurotransmission is disturbed in several psychiatric disorders. One explanation may be disturbed transport of tryptophan (precursor for serotonin synthesis) across cell membranes. Human fibroblast cells offer an advantageous model to study the transport of amino acids across cell membranes, since they are easy to propagate and the environmental factors can be controlled. The aim of this study was to functionally characterize tryptophan transport and to identify the main transporters of tryptophan in fibroblast cell lines from healthy controls. Tryptophan kinetic parameters (Vmax and Km) at low and high concentrations were measured in fibroblasts using the cluster tray method. Uptake of 3H (5)-L-tryptophan at different concentrations in the presence and absence of excess concentrations of inhibitors or combinations of inhibitors of amino acid transporters were also measured. Tryptophan transport at high concentration (0.5 mM) had low affinity and high Vmax and the LAT1 isoform of system-L was responsible for approximately 40% of the total uptake of tryptophan. In comparison, tryptophan transport at low concentration (50 nM) had higher affinity, lower Vmax and approximately 80% of tryptophan uptake was transported by system-L with LAT1 as the major isoform. The uptake of tryptophan at the low concentration was mainly sodium (Na+) dependent, while uptake at high substrate concentration was mainly Na+ independent. A series of different transporter inhibitors had varying inhibitory effects on tryptophan uptake. This study indicates that tryptophan is transported by multiple transporters that are active at different substrate concentrations in human fibroblast cells. The tryptophan transport trough system-L was mainly facilitated by the LAT1 isoform, at both low and high substrate concentrations of tryptophan.
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Affiliation(s)
- Ravi Vumma
- School of Health and Medical Sciences, Department of Clinical Medicine, Örebro University, SE-701 82 Örebro, Sweden
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Uchida Y, Ohtsuki S, Katsukura Y, Ikeda C, Suzuki T, Kamiie J, Terasaki T. Quantitative targeted absolute proteomics of human blood-brain barrier transporters and receptors. J Neurochem 2011; 117:333-45. [PMID: 21291474 DOI: 10.1111/j.1471-4159.2011.07208.x] [Citation(s) in RCA: 579] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We have obtained, for the first time, a quantitative protein expression profile of membrane transporters and receptors in human brain microvessels, that is, the blood-brain barrier (BBB). Brain microvessels were isolated from brain cortexes of seven males (16-77 years old) and protein expression of 114 membrane proteins was determined by means of a liquid chromatography-tandem mass spectrometric quantification method using recently established in-silico peptide selection criteria. Among drug transporters, breast cancer resistance protein showed the most abundant protein expression (8.14 fmol/μg protein), and its expression level was 1.85-fold greater in humans than in mice. By contrast, the expression level of P-glycoprotein in humans (6.06 fmol/μg protein) was 2.33-fold smaller than that of mdr1a in mice. The organic anion transporters reported in rodent BBB, that is, multidrug resistance-associated protein, organic anion transporter and organic anion-transporting polypeptide family members, were under limit of quantification in humans, except multidrug resistance-associated protein 4 (0.195 fmol/μg protein). Among detected transporters and receptors for endogenous substances, the glucose transporter 1 level was similar to that of mouse, while the L-type amino acid transporter 1 level was fivefold smaller than that of mouse. These findings should be useful for understanding human BBB function and its differences from that in mouse.
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Affiliation(s)
- Yasuo Uchida
- Graduate School of Pharmaceutical Sciences, Tohoku University, Japan
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Chandra S, De K, Ganguly S, Sarkar B, Misra M. Synthesis, radiolabeling and biological evaluation of a neutral tripeptide and its derivatives for potential nuclear medicine applications. Peptides 2009; 30:2399-408. [PMID: 19712720 DOI: 10.1016/j.peptides.2009.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 08/14/2009] [Accepted: 08/14/2009] [Indexed: 11/20/2022]
Abstract
Peptides are important regulators of growth and cellular functions not only in normal tissue but also in tumors. So they are becoming radioligands of increasing interest in nuclear oncology for targeted tumor diagnosis and therapy. So development of new peptide radiopharmaceuticals is becoming one of the most important areas in nuclear medicine research. A small tripeptide derivative NH(2)PhePheCys was synthesized by Fmoc solid phase peptide synthesis using an automated synthesizer. The oxidized form, i.e. NH(2)PhePheCysCysPhePheNH(2,) was also prepared by iodine oxidation method from NH(2)PhePheCys(ACM). The ligands were analyzed by HPLC and mass spectroscopy. They were radiolabeled with (99m)Tc using SnCl(2). In vitro analytical studies and biological characterizations were performed using the peptide radiopharmaceuticals. Images taken under gamma camera showed very high uptake in the liver, lung and spleen. Significant uptake was also observed in bone marrow and brain for (99m)Tc-NH(2)PhePheCys. Metabolites were produced in vivo when the radiopharmaceuticals were injected intravenously and were identified from rat brain and liver homogenate studies. Clearance through kidney did not show any evidence of breaking of the labeled compounds and formation of free (99m)Tc. Radiopharmaceuticals prepared using tripeptide and hexapeptide ligands were transported into the brain through blood brain barrier depending on the size and sequence characteristics. Using this property of peptide new derivatives can be prepared to develop (99m)Tc radiopharmaceuticals for imaging normal brain tissues as well as for diagnosing various brain disorders.
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Affiliation(s)
- Susmita Chandra
- Indian Institute of Chemical Biology, 4 Raja SC Mullick Road, Kolkata-32, West Bengal 700032, India.
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30
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Persson ML, Johansson J, Vumma R, Raita J, Bjerkenstedt L, Wiesel FA, Venizelos N. Aberrant amino acid transport in fibroblasts from patients with bipolar disorder. Neurosci Lett 2009; 457:49-52. [PMID: 19429160 DOI: 10.1016/j.neulet.2009.03.095] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 03/25/2009] [Accepted: 03/25/2009] [Indexed: 10/21/2022]
Abstract
Aberrant tyrosine transport is a repeated finding in fibroblasts from schizophrenic patients. The transport aberration could lead to disturbances in the dopaminergic and noradrenergic neurotransmitter systems. Tyrosine and tryptophan are the precursors of the neurotransmitters dopamine and serotonin. Disturbed dopaminergic, noradrenergic and serotoninergic systems are implicated as causes of bipolar disorder. Hence, the aim of this study was to explore whether patients with bipolar disorder have an aberrant transport of tyrosine and/or tryptophan. Fibroblast cell lines from patients with bipolar type-1 disorder (n=10) and healthy controls (n=10) were included in this study. All patients fulfilled the DSM-IV diagnostic criteria. The transport of amino acids across the cell membranes was measured by the cluster tray method. The kinetic parameters, maximal transport velocity (V(max)) and affinity constant (K(m)) were determined. A significantly lower V(max) for tyrosine (p=0.027) was found in patients with bipolar type-1 disorder in comparison to healthy controls. No significant differences in K(m) for tyrosine and in the kinetic parameters of tryptophan between patients with bipolar type-1 disorder and healthy controls were observed. The decreased tyrosine transport (low V(max)) found in this study may indicate less access of dopamine in the brain, resulting in disturbed dopaminergic and/or noradrenergic neurotransmission, that secondarily could lead to disturbances in other central neurotransmitter systems, such as the serotoninergic system. However, as sample size was small in this study and an age difference between patients and controls existed, the present findings should be considered as pilot data. Further studies with larger sample number are needed to elucidate the transport aberration and the significance of these findings.
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Affiliation(s)
- M L Persson
- Stockholm County Council, Center for Dependency Disorder, Karolinska University Hospital Huddinge, Stockholm, Sweden
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31
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Grimes MA, Cameron JL, Fernstrom JD. Cerebrospinal fluid concentrations of large neutral and basic amino acids in Macaca mulatta: diurnal variations and responses to chronic changes in dietary protein intake. Metabolism 2009; 58:129-40. [PMID: 19059540 DOI: 10.1016/j.metabol.2008.08.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2008] [Accepted: 08/13/2008] [Indexed: 11/17/2022]
Abstract
In rats, dietary protein intake influences brain concentrations of tryptophan, tyrosine, and other large neutral amino acids (LNAAs) and the neurotransmitters to which they are linked. Few experiments have examined these dietary protein-amino acid relationships in nonhuman primates, in relation to time of day or dietary protein content. We therefore examined the effect in monkeys of changes in chronic protein intake on 24-hour plasma and cerebrospinal fluid (CSF) concentrations of LNAAs (tyrosine, phenylalanine, branched-chain amino acids) and basic amino acids. Juvenile male monkeys (Macaca mulatta) consumed for sequential 4-week periods diets differing in protein content (approximately 23% --> approximately 16% --> approximately 10% --> approximately 6% protein [percentage of energy]). The daily ration was presented as a morning meal of fruit and an afternoon meal of fruit and a commercial diet to mimic feeding patterns in the wild. During week 4 on each diet, blood and CSF were sampled repeatedly over a 48-hour period via indwelling catheters. Plasma and CSF LNAA concentrations varied markedly with time of day and dietary protein content, showing up to 4-fold variations. Diurnal variations in plasma and CSF basic amino acids were smaller in magnitude and generally not strongly linked to dietary protein content. A measure of the competitive transport of LNAAs across the blood-brain barrier, calculated using plasma concentrations of the LNAAs and their blood-brain barrier kinetic constants, predicted the observed CSF concentration of each LNAA examined remarkably well, except for phenylalanine. Based on observations in rats, the variations in the CSF concentrations of the LNAAs in monkeys may be large enough to influence metabolic and signaling pathways in brain to which they have been linked.
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Affiliation(s)
- Michael A Grimes
- Department of Anthropology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Landvogt C, Mengel E, Bartenstein P, Buchholz HG, Schreckenberger M, Siessmeier T, Scheurich A, Feldmann R, Weglage J, Cumming P, Zepp F, Ullrich K. Reduced cerebral fluoro-L-dopamine uptake in adult patients suffering from phenylketonuria. J Cereb Blood Flow Metab 2008; 28:824-31. [PMID: 17971791 DOI: 10.1038/sj.jcbfm.9600571] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Deficiency of phenylalanine hydroxylase activity in phenylketonuria (PKU) causes an excess of phenylalanine (Phe) throughout the body, predicting impaired synthesis of catecholamines in the brain. To test this hypothesis, we used positron emission tomography (PET) to measure the utilization of 6-[18F]fluoro-L-DOPA [corrected] (FDOPA) in the brain of adult patients suffering from PKU and in healthy controls. Dynamic 2-h long FDOPA emission recordings were obtained in seven adult PKU patients (five females, two males; age: 21 to 27 years) with elevated serum Phe levels, but lacking neurologic deficits. Seven age-matched, healthy volunteers were imaged under identical conditions. The utilization of FDOPA in striatum was calculated by linear graphical analysis (k3S, min(-1)), with cerebellum serving as a nonbinding reference region. The time to peak activity in all brain time-radioactivity curves was substantially delayed in the PKU patients relative to the control group. The mean magnitude of k3S in the striatum of the PKU patients (0.0052+/-0.0004 min(-1)) was significantly lower than in the control group (0.0088+/-0.0009 min(-1)) (P<0.001). There was no significant correlation between individual serum Phe levels and k3S. The unidirectional clearance of FDOPA to brain was impaired in adult patients suffering from PKU, presumably reflecting the competitive inhibition of the large neutral amino acid carrier by Phe. Assuming this competition to be spatially uniform, the relationship between striatum and cerebellum time-activity curves additionally suggests inhibition of DOPA efflux, possibly also due to competition from Phe. The linear graphical analysis shows reduced k3S in striatum, indicating reduced DOPA decarboxylase activity.
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Vumma R, Wiesel FA, Flyckt L, Bjerkenstedt L, Venizelos N. Functional characterization of tyrosine transport in fibroblast cells from healthy controls. Neurosci Lett 2008; 434:56-60. [PMID: 18262359 DOI: 10.1016/j.neulet.2008.01.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 12/20/2007] [Accepted: 01/13/2008] [Indexed: 10/22/2022]
Abstract
Human fibroblast cells are an advantageous model to study the transport of amino acids across cell membranes, since one can control the environmental factors. A major problem in all earlier studies is the lack of precise and detailed knowledge regarding the expression and functionality of tyrosine transporters in human fibroblasts. This motivated us to perform a systematic functional characterization of the tyrosine transport in fibroblast cells with respect to the isoforms of system-L (LAT1, LAT2, LAT3, LAT4), which is the major transporter of tyrosine. Ten (n=10) fibroblast cell lines from healthy volunteers were included in the study. Uptake of L-[U-14C] tyrosine in fibroblasts was measured using the cluster tray method in the presence and absence of excess concentrations of various combinations of inhibitors. This study demonstrated that LAT1 is involved in 90% of total uptake of tyrosine and also around 51% of alanine. Not more than 10% can be accounted for by LAT2, LAT3 and LAT4 isoforms. LAT2 seems to be functionally weak in uptake of tyrosine while LAT3 and LAT4 contributed around 7%. 10% could be contributed by system-A (ATA2 isoform). Alanine consequently inhibited the tyrosine transport by up to 60%. Tyrosine transport through the LAT1 isoform has a higher affinity compared to system-L. In conclusion, the LAT1 isoform is the major transporter of tyrosine in human fibroblast cells. Competition between tyrosine and alanine for transport is shown to exist, probably between LAT1 and LAT2 isoforms. This study established fibroblast cells as a suitable experimental model for studying amino acid transport defects in humans.
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Affiliation(s)
- Ravi Vumma
- Department of Clinical Medicine, Biomedicine, Orebro University, SE-701 82 Orebro, Sweden
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Moyle JJ, Fox AM, Bynevelt M, Arthur M, Burnett JR. A neuropsychological profile of off-diet adults with phenylketonuria. J Clin Exp Neuropsychol 2007; 29:436-41. [PMID: 17497567 DOI: 10.1080/13803390600745829] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The metabolic disorder phenylketonuria (PKU) is treated early by a low-phenylalanine diet. While this prevents global cognitive impairment, some patients still experience cognitive and neurophysiological abnormalities. Neuropsychological testing of early treated, currently off-diet, PKU patients attending an adult PKU clinic showed a reduction in the Perceptual Organization Index (POI), Processing Speed Index (PSI) from the Wechsler Adult Intelligence Scale Third Edition (WAIS-III), and Part A of the Trail Making Test for the PKU group relative to controls. Taken together, these results supported a profile of reduced information-processing speed.
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Affiliation(s)
- J J Moyle
- School of Psychology, The University of Western Australia, Perth, WA, Australia.
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35
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Stanila A, Marcu A, Rusu D, Rusu M, David L. Spectroscopic studies of some copper(II) complexes with amino acids. J Mol Struct 2007. [DOI: 10.1016/j.molstruc.2006.11.048] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
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36
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Matalon R, Michals-Matalon K, Bhatia G, Burlina AB, Burlina AP, Braga C, Fiori L, Giovannini M, Grechanina E, Novikov P, Grady J, Tyring SK, Guttler F. Double blind placebo control trial of large neutral amino acids in treatment of PKU: effect on blood phenylalanine. J Inherit Metab Dis 2007; 30:153-8. [PMID: 17334706 DOI: 10.1007/s10545-007-0556-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 01/30/2007] [Accepted: 01/31/2007] [Indexed: 11/28/2022]
Abstract
Large neutral amino acids (LNAA) have been used on a limited number of patients with phenylketonuria (PKU) with the purpose of decreasing the influx of phenylalanine (Phe) to the brain. In an open-label study using LNAA, a surprising decline of blood Phe concentration was found in patients with PKU in metabolic treatment centres in Russia, the Ukraine, and the United States. To validate the data obtained from this trial, a short-term double-blind placebo control study was done using LNAA in patients with PKU, with the participation of three additional metabolic centres--Milan, Padua and Rio de Janeiro. The results of the short trial showed significant lowering of blood Phe concentration by an average of 39% from baseline. The data from the double-blind placebo control are encouraging, establishing proof of principle of the role of orally administered LNAA in lowering blood Phe concentrations in patients with PKU. Long-term studies will be needed to validate the acceptability, efficacy and safety of such treatment.
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Affiliation(s)
- R Matalon
- Department of Pediatrics, University of Texas Medical Branch, Children's Hospital, Galveston, Texas, USA.
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37
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Matalon R, Michals-Matalon K, Bhatia G, Grechanina E, Novikov P, McDonald JD, Grady J, Tyring SK, Guttler F. Large neutral amino acids in the treatment of phenylketonuria (PKU). J Inherit Metab Dis 2006; 29:732-8. [PMID: 16988900 DOI: 10.1007/s10545-006-0395-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 07/18/2006] [Accepted: 08/01/2006] [Indexed: 11/27/2022]
Abstract
Large neutral amino acids (LNAAs) have been used on a limited number of patients with phenylketonuria (PKU) with the purpose of decreasing the influx of phenylalanine (Phe) to the brain. In earlier studies on mice with PKU (ENU(2)/ENU(2)), LNAAs were given and a surprising decline in blood Phe concentrations was observed. The formula used in the mouse experiment (PreKUnil) lacked lysine. Therefore, a new formulation of LNAAs (NeoPhe) was developed, introducing changes in the concentration of some amino acids and adding lysine, so that such a mixture could be used in humans. The new formula was found to be effective in reducing blood Phe concentration in mice by about 50% of the elevated levels. Patients with PKU were given LNAAs and blood Phe concentrations were determined in an open-label study. Three centers--in Russia, the Ukraine and the USA--took part in the study. NeoPhe was given at 0.5 g/kg per day in three divided doses to eight subjects with PKU and at 1.0 g/kg per day to three patients, for one week. The NeoPhe resulted in decrease of elevated blood Phe by 50% in both groups. The preliminary data from this study are encouraging and a double blind placebo-controlled trial will be required to show long-term efficacy and tolerance of LNAAs in the treatment of PKU.
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Affiliation(s)
- R Matalon
- Department of Pediatrics, University of Texas Medical Branch, Childrens Hospital, Galveston, Texas, USA.
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Hörster F, Schwab MA, Sauer SW, Pietz J, Hoffmann GF, Okun JG, Kölker S, Kins S. Phenylalanine reduces synaptic density in mixed cortical cultures from mice. Pediatr Res 2006; 59:544-8. [PMID: 16549526 DOI: 10.1203/01.pdr.0000203091.45988.8d] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Classical phenylketonuria (PKU) is caused by deficiency of phenylalanine hydroxylase, resulting in an accumulation of its upstream metabolite phenylalanine in brain tissue and cerebrospinal fluid of PKU patients. PKU is neuropathologically characterized by reduced dendritic arborization, loss of synapses, and neurodegeneration. We investigated whether increased concentrations of phenylalanine cause reduced synaptic density and alter dendritic branching. We treated primary cortical neurons differentiated for 21 d in vitro with 5 mM phenylalanine in the presence of all essential amino acids. Immunocytochemical analysis of 12 and 21 d in vitro primary neurons revealed no changes of dendritic morphology or neuronal viability but a significant difference in synaptic density, suggesting that elevated concentrations of extracellular phenylalanine cause an impairment of synaptogenesis. Although impairment of cerebral energy metabolism has been identified as an important pathophysiological principal in many diseases, respiratory chain function has not been extensively studied in PKU before. We investigated whether phenylalanine inhibits respiratory chain complexes I-V. In vitro analysis revealed no inhibitory effect of phenylalanine on complexes I-V, but an inhibition of pyruvate kinase, a key enzyme of glycolysis, catalyzing the formation of pyruvate. Pyruvate kinase is part of the enzyme assay to investigate enzyme activity of mitochondrial complex V and it remains to be elucidated whether this finding is relevant in vivo. In conclusion, elevated concentrations of phenylalanine might be involved in mechanisms underlying impaired synaptogenesis in PKU, supporting the common therapeutic strategy to reduce phenylalanine concentrations in the brain to prevent neurodegeneration.
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Affiliation(s)
- Friederike Hörster
- Department of General Pediatrics, University of Children's Hospital, Heidelberg, Germany.
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Terasaki T, Ohtsuki S. Brain-to-blood transporters for endogenous substrates and xenobiotics at the blood-brain barrier: an overview of biology and methodology. NeuroRx 2005; 2:63-72. [PMID: 15717058 PMCID: PMC539321 DOI: 10.1602/neurorx.2.1.63] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the past decade, research into P-glycoprotein involving the blood-brain barrier (BBB) has seen a shift in the concept of the BBB as a structural barrier to that of a functional barrier for xenobiotics and changed simultaneously the strategy for the discovery and development of drugs acting in the CNS. As far as making advances in neurotherapeutics are concerned, the brain-to-blood transport function at the BBB will be one of the most important issues. Knowing the limitations of the in vivo and in vitro methods for BBB efflux research, it is essential to adopt a multidisciplinary approach in investigating the true physiological role of the BBB. Among several methods, the Brain Efflux Index method and the use of conditionally immortalized brain capillary endothelial cell lines, established from transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen gene, are likely to be very useful tools for the BBB efflux transport research. According to our recent findings using these methods, several transporters in the brain capillary endothelial cells appear to play an important role in reducing the brain level of hydrophilic endogenous substrates produced either in the brain or peripheral organs, e.g., neurotransmitters, neuromodulators, metabolites of neurotransmitters, and uremic toxins. It has been reported also that large hydrophilic molecules, such as IgG, apo-transferrin, and amyloid-beta peptide, are susceptible to brain-to-blood efflux transport. In the light of the latest findings, we have formed the hypothesis that the BBB acts as a CNS detoxifying system for both endogenous substrates and xenobiotics in the brain. A fuller understanding of the physiological role of BBB efflux transporters will provide rational insights to assist in the development of safer neurotherapeutics.
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Affiliation(s)
- Tetsuya Terasaki
- New Industry Creation Hatchery Center and Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
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Terasaki T, Ohtsuki S. Brain-to-blood transporters for endogenous substrates and xenobiotics at the blood-brain barrier: An overview of biology and methodology. Neurotherapeutics 2005. [DOI: 10.1007/bf03206643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Abstract
Phenylketonuria is caused by specific mutations in the phenylalanine hydroxylase gene and is characterized by elevated blood phenylalanine levels, hypomyelination in forebrain structures, reduced dopamine levels, and cognitive difficulties. To determine whether brain tyrosine levels and/or myelination play a role in the up-regulation of dopamine, phenylketonuric mice were placed on a low phenylalanine diet for 4 weeks and as blood phenylalanine levels dropped to normal, the relationships between phenylalanine, tyrosine, dopamine, myelin proteins, and axonal proteins in frontal cortex and striatum were determined using gas chromatography mass spectrometry, histology, and western blotting techniques. Blood phenylalanine rapidly decreased from an eight-fold elevation to near control levels, and blood tyrosine gradually rose from about 50% to near normal values. In frontal cortex and striatum, phenylalanine levels dropped to 2- and 1.5-fold elevations above control, respectively, and tyrosine levels increased but remained less than 70% of control in both structures. In frontal cortex, increases in dopamine and myelin basic protein occurred in a similar biphasic pattern, reaching near normal levels by week 4. In striatum, dopamine and MBP dramatically increased to near normal levels in the first week. Myelination was confirmed histologically and by western blot quantification of phosphorylated neurofilaments. In summary, our results showed: (i) an increase in dopamine despite low brain tyrosine levels and (ii) similar recovery patterns for myelination and dopamine. Since myelin/axonal interactions trigger signaling pathways that result in axonal maturation, we speculate that this interaction also may trigger signals that up-regulate neurotransmitter synthesis.
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Affiliation(s)
- Bernadin Joseph
- Department of Neurology, The University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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42
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Abstract
The availability of amino acids in the brain is regulated by the blood-brain barrier (BBB) large neutral amino acid transporter type 1 (LAT1) isoform, which is characterized by a high affinity (low Km) for substrate large neutral amino acids. The hypothesis that brain amino acid transport activity can be altered with single nucleotide polymorphisms was tested in the present studies with site-directed mutagenesis of the BBB LAT1. The rabbit has a high Km LAT1 large neutral amino acid transporter, as compared to the low Km neutral amino acid transporter at the human or rat BBB. The rabbit LAT1 was cloned from a rabbit brain capillary cDNA library. Alignment of the amino acid sequences of rabbit, human, and rat LAT1 revealed two radical amino acid residues that differ in the rabbit relative to the rat or human LAT1. The G219D mutation had a modest effect on the Km and Vmax of tryptophan transport via cloned rabbit LAT1 in frog oocytes, but the W234L variant reduced the Km by 64% and the Vmax by 96%. Conversely, LAT1 transport of either tryptophan or phenylalanine was nearly normalized when the double mutation W234L/G219D variant was produced. These studies show that marked changes in the affinity and capacity of the LAT1 are caused by single nucleotide polymorphisms and that phenotype can be restored with a double mutation.
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Affiliation(s)
- Ruben J Boado
- Department of Medicine, UCLA School of Medicine, Los Angeles, California 90024, USA.
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Mann GE, Yudilevich DL, Sobrevia L. Regulation of amino acid and glucose transporters in endothelial and smooth muscle cells. Physiol Rev 2003; 83:183-252. [PMID: 12506130 DOI: 10.1152/physrev.00022.2002] [Citation(s) in RCA: 319] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
While transport processes for amino acids and glucose have long been known to be expressed in the luminal and abluminal membranes of the endothelium comprising the blood-brain and blood-retinal barriers, it is only within the last decades that endothelial and smooth muscle cells derived from peripheral vascular beds have been recognized to rapidly transport and metabolize these nutrients. This review focuses principally on the mechanisms regulating amino acid and glucose transporters in vascular endothelial cells, although we also summarize recent advances in the understanding of the mechanisms controlling membrane transport activity and expression in vascular smooth muscle cells. We compare the specificity, ionic dependence, and kinetic properties of amino acid and glucose transport systems identified in endothelial cells derived from cerebral, retinal, and peripheral vascular beds and review the regulation of transport by vasoactive agonists, nitric oxide (NO), substrate deprivation, hypoxia, hyperglycemia, diabetes, insulin, steroid hormones, and development. In view of the importance of NO as a modulator of vascular tone under basal conditions and in disease and chronic inflammation, we critically review the evidence that transport of L-arginine and glucose in endothelial and smooth muscle cells is modulated by bacterial endotoxin, proinflammatory cytokines, and atherogenic lipids. The recent colocalization of the cationic amino acid transporter CAT-1 (system y(+)), nitric oxide synthase (eNOS), and caveolin-1 in endothelial plasmalemmal caveolae provides a novel mechanism for the regulation of NO production by L-arginine delivery and circulating hormones such insulin and 17beta-estradiol.
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Affiliation(s)
- Giovanni E Mann
- Centre for Cardiovascular Biology and Medicine, Guy's, King's, and St. Thomas' School of Biomedical Sciences, King's College London, London, United Kingdom.
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Pietz J, Lutz T, Zwygart K, Hoffmann GF, Ebinger F, Boesch C, Kreis R. Phenylalanine can be detected in brain tissue of healthy subjects by 1H magnetic resonance spectroscopy. J Inherit Metab Dis 2003; 26:683-92. [PMID: 14707517 DOI: 10.1023/b:boli.0000005648.75276.71] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Transport of phenylalanine (Phe) and the other large neutral amino acids across the blood-brain barrier plays a crucial role in the pathogenesis of phenylketonuria (PKU). Thus, investigation of Phe transport kinetics by means of proton magnetic resonance spectroscopy (1H MRS) became an important research area in the mid 1990s. As 1H MRS measurements of brain phenylalanine are restricted to tissue concentrations above 100-150 micromol/kg wet weight, this approach was possible only in PKU patients, and comparison with healthy controls was not achieved. Using standardized single-dose oral Phe loading in three healthy subjects, it was shown that Phe values increase steeply, peak at about 1 h post load, and decrease thereafter. In a single case study, repetitive Phe loading was then performed to achieve a plateau of high blood Phe concentrations for several hours. It was demonstrated that detection and monitoring of brain Phe concentrations is feasible by means of 1H MRS. This approach constitutes a prerequisite for describing carrier kinetics in health.
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Affiliation(s)
- J Pietz
- Department of Pediatric Neurology, University of Heidelberg, Germany.
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45
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Umeki N, Fukasawa Y, Ohtsuki S, Hori S, Watanabe Y, Kohno Y, Terasaki T. mRNA Expression and Amino Acid Transport Characteristics of Cultured Human Brain Microvascular Endothelial Cells (hBME). Drug Metab Pharmacokinet 2002; 17:367-73. [PMID: 15618688 DOI: 10.2133/dmpk.17.367] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An in vitro cell culture system for estimating the human blood-brain barrier (BBB) permeability of drugs is required for the development of drugs with effects on the central nervous system. In this study, cultured human brain microvascular endothelial cells (hBME) were characterized. hBME cells exhibited concentration-dependent uptake of L-Leu, L-Glu and L-Lys with K(m) values of 51.1+/-23.1 microM, 163.3+/-79.8 microM and 72.4+/-56.6 microM, respectively. The cellular accumulation of rhodamine123 in hBME cells was unaffected by P-glycoprotein (P-gp) substrates (cyclosporin A, quinidine and verapamil), while the accumulation in human P-gp-overexpressing cells was significantly increased in the presence of these P-gp substrates. RT-PCR revealed that hBME cells expressed large neutral amino acid transporter 1 (LAT1) and its associated molecule (4F2hc), excitatory amino acid transporter 3 (EAAT3), cationic amino acid transporter 1 (CAT1), glucose transporter 1 (GLUT1), monocarboxylic acid transporter 1 (MCT1) and multidrug resistance-associated protein 1 (MRP1). However, no expression of multidrug resistance protein 1 (MDR1) was detected. The results suggest that these amino acid transporters are functionally expressed at the human BBB, and that hBME cells retain the in vivo BBB transport functions and expression characteristics. Consequently, hBME cells should be a useful tool for studies of the human BBB.
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Affiliation(s)
- Nobuo Umeki
- Pharmaceutical Laboratory, Taisho Pharmaceutical Co., Ltd., Saitama, Japan
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Kalsner LR, Rohr FJ, Strauss KA, Korson MS, Levy HL. Tyrosine supplementation in phenylketonuria: diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids. J Pediatr 2001; 139:421-7. [PMID: 11562623 DOI: 10.1067/mpd.2001.117576] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
UNLABELLED Tyrosine supplementation has not consistently been found to improve neuropsychologic function in phenylketonuria (PKU), possibly because of failure to achieve adequate levels of tyrosine in the brain. OBJECTIVES To evaluate blood levels achieved after tyrosine supplementation in treated PKU and calculate brain influxes of tyrosine and other large neutral amino acids before and with tyrosine supplementation. STUDY DESIGN Ten subjects with PKU receiving a phenylalanine-restricted diet were studied over 48 hours; each received tyrosine supplementation (300 mg/kg) on day 2. Plasma phenylalanine and tyrosine were measured every 2 hours, and all free amino acids were measured every 6 hours. Brain influxes of tyrosine and other large neutral amino acids were calculated. RESULTS Plasma tyrosine levels were low normal at baseline. With supplementation there was a substantial but unsustained rise in plasma tyrosine. Calculated brain influx of tyrosine was 27% +/- 19% of normal before supplementation, increasing to 90% +/- 58% of normal with supplementation. Nevertheless, calculated influx remained less than 70% of normal at 50% of the time points. The calculated brain influxes of all other large neutral amino acids except tryptophan were 20% to 40% of normal before and with tyrosine supplementation. CONCLUSIONS Tyrosine supplementation in the diet for PKU produces marked but nonsustained increases in plasma tyrosine levels, with calculated brain influx that often remains suboptimal. This could explain the lack of consistent neuropsychologic benefit with tyrosine supplementation.
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Affiliation(s)
- L R Kalsner
- Division of Genetics and Department of Neurology, Children's Hospital, Boston, Massachusetts, USA
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Duelli R, Enerson BE, Gerhart DZ, Drewes LR. Expression of large amino acid transporter LAT1 in rat brain endothelium. J Cereb Blood Flow Metab 2000; 20:1557-62. [PMID: 11083230 DOI: 10.1097/00004647-200011000-00005] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The expression of the large amino acid transporter, LAT1, was investigated in brain of adult Long-Evans rats. The LAT1 transcript was readily detected in brain microvessels and choroid plexus by reverse transcription polymerase chain reaction analysis using three different gene specific primer pairs. A polyclonal affinity purified antibody against the N-terminus of LAT1 was generated in chickens and used in immunoblot and immunocytochemical analyses of brain tissue sections of adult rats. On immunoblots, the antibody detected a peptide-inhibitable 45 kDa band in a rat brain microvessel membrane preparation. It also identified the same protein band in membrane preparations of different brain structures, as well as in heart and testis, whereas the protein was absent or only faintly detectable in muscle, kidney, and liver. In brain sections, the antibody intensely labeled the luminal and abluminal membranes of brain microvessel endothelial cells in all brain areas examined including cerebral cortex, cerebellum, hippocampus, and in gray and white matter regions. These results suggest that LAT1 is involved in transcellular transport and may play an important role in large, neutral amino acid transfer across the blood-brain barrier.
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Affiliation(s)
- R Duelli
- Department of Biochemistry and Molecular Biology, University of Minnesota, Duluth 55812, USA
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Reymond F, Chopineaux-Courtois V, Steyaert G, Bouchard G, Carrupt PA, Testa B, Girault HH. Ionic partition diagrams of ionisable drugs: pH-lipophilicity profiles, transfer mechanisms and charge effects on solvation. J Electroanal Chem (Lausanne) 1999. [DOI: 10.1016/s0022-0728(98)00418-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Möller HE, Weglage J, Wiedermann D, Ullrich K. Blood-brain barrier phenylalanine transport and individual vulnerability in phenylketonuria. J Cereb Blood Flow Metab 1998; 18:1184-91. [PMID: 9809507 DOI: 10.1097/00004647-199811000-00004] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In vivo nuclear magnetic resonance spectroscopy can be used to measure intracerebral phenylalanine (Phe) concentrations in patients with phenylketonuria (PKU). Stationary levels, obtained under free nutrition, as well as time courses after an oral Phe load (100 mg/kg) were investigated in 11 PKU patients and were correlated with the individual clinical outcome. At blood levels around 1.2 mmol/L, brain Phe was 0.41 to 0.73 mmol/L in clinically "typical" patients, but less than 0.15 mmol/L in three untreated, normally intelligent, adult women. Kinetic investigations revealed higher transport Michaelis constants and lower ratios of the brain influx and consumption rates in these women than in the "typical" control patients (Kt,app = 0.45 to 1.10 mmol/L versus 0.10 mmol/L; T(max)/v(met) = 2.55 to 3.19 versus 7.8 to 14.0). Such variations seem to be major causative factors for the individual vulnerability to PKU.
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Affiliation(s)
- H E Möller
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA
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Breimer DD. [Transport of drugs across the blood-brain barrier]. VERHANDELINGEN - KONINKLIJKE ACADEMIE VOOR GENEESKUNDE VAN BELGIE 1998; 60:47-60; discussion 60-1. [PMID: 9646722 DOI: 10.1007/978-1-4757-0286-6_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The blood-brain barrier prevents an indifferent medicine existing in the blood to enter also in the brain. This barrier has got an anatomical base: it is first consisting in a cerebrovascular layer of endothelial capillary vessels of the peripheral tissue. It is moreover covered by outgrowths of the flial cells, which are called astrocytes. There are, for that reason, important limits to a size of molecules which can reach the cerebral tissue through a paracellular way (through what is called in English "tight-junctions"). Most medicines must use the transcellular way. Lipophily is necessary to follow that way. Year after year, it appeared, thanks to a comparative study of the substances, that there exists--grosso modo--a positive correlation between the lipophilic level and the permeation-level of a substance in the cerebral tissue. There are, however, several exceptions: it is so that hydrophilic substances, possessing an important nourishing function (such as glucosis, amino-acids) seem to penetrate much more easily than we could expect when we consider their physicochemical characteristics. This is the result of the fact that there exist specifical transport-mechanisms for these substances at the level of the endothelial cell-membranes, allowing the penetration of such substances. There exist, on the contrary, lipophilic components that penetrate the cerebral tissue much less strongly than we should expect. This happens because there also exist pumping-mechanisms at the level of the hemato-encephalic barrier. The concerning substance, which was recently discovered is the "glycoprotein P", which is also responsible for the "multi-drug-resistance" and for the resistance of tumors to cytostatics. This phenomenon relies on a very efficient pumping of substances which have penetrated cells in which this protein expressed itself in the membranous structure. In order to obtain a better understanding of the function of the hemato-encephalic barrier, comprising the transport of medicines, it is most important to have reliable experimental models. It is to that aim that, during former years, the technique of cultivating endothelial cerebrovascular cells was developed. These cells are isolated from brains of calves or rats and, subsequently, cultivated on a laboratory medium; about a week later, they have grown a single and confluent layer. This layer represents a kint of "hemato-encephalic barrier" in vitro, which allows us to study the transfer of substances through the layer and thus also the details concerning the transport mechanisms, as well as the factors influencing the permeability of the cells-layer (for instance the inflammatory stimuli). Concerning the "in vivo" research, the technique of intracerebral microdialysis in lab-animals proved to be very promising. In order to effect this microdialysis, a semipermeable microcannula is introduced in the brain tissue, across which an iso-osmotic liquid is being injected continuously. The substances staying in the interstitial liquid of the cerebral tissue will diffuse under the influence of a concentration gradient, into the dialysing liquid and they will also be ready to be analysed. Thanks to this technique, it is possible to follow, in the same animal, the evolution of the concentration in the brain of a substance which has, for instance been injected in a peripheral region. In this way, we obtain, indirectly and in vivo, informations about the functioning-process of the "hemato-encephalic barrier". We can, moreover, effect measures on a specific spot, for instance in tumoral brain tissue: this allows us to study the influence of specific transport-mechanisms. These rather recent techniques, as well in vitro as in vivo, will allow us, in consequence, to increase, during the next years, our understanding of the way the hemato-encephalic barrier functions as to the transfer of medicines towards the central nervous system. This understanding may lead us to new strategies allowing
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Affiliation(s)
- D D Breimer
- Leiden/Amsterdam Center for Drug Research, Sectie Farmacologie, R.U.L., Leiden, Nederland
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