PNAs breach the blood-brain barrier?
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
M J During
Publications and source records attributed to M J During.
Environmental enrichment inhibits spontaneous apoptosis, prevents seizures and is neuroprotective.
The mammalian brain has a high degree of plasticity, with dentate granule cell neurogenesis and glial proliferation stimulated by an enriched environment combining both complex inanimate and social stimulation. Moreover, rodents exposed to an enriched environment both before and after a cerebral insult show improved cognitive performance. One of the most robust associations of environmental enrichment is improved learning and memory in the Morris water maze, a spatial task that mainly involves the hippocampus. Furthermore, clinical evidence showing an association between higher educational attainment and reduced risk of Alzheimer and Parkinson-related dementia indicates that a stimulating environment has positive effects on cerebral health that may provide some resilience to cerebral insults. Here we show that in addition to its effects on neurogenesis, an enriched environment reduces spontaneous apoptotic cell death in the rat hippocampus by 45%. Moreover, these environmental conditions protect against kainate-induced seizures and excitotoxic injury. The enriched environment induces expression of glial-derived neurotrophic factor and brain-derived neurotrophic factor and increases phosphorylation of the transcription factor cyclic-AMP response element binding protein, indicating that the influence of the environment on spontaneous apoptosis and cerebral resistance to insults may be mediated through transcription factor activation and induction of growth factor expression.
Animals↗
CREB phosphorylation promotes nerve cell survival.
The cyclic AMP-responsive element binding protein (CREB) is a posttranslationally activated transcription factor that has been implicated in numerous brain functions including cell survival. In this study we investigated whether CREB overexpression using transient transfection of a pAAV/CMV-CREB plasmid altered neuronal cells' susceptibility to apoptosis. We found that elevated CREB protein inhibited apoptosis induced by okadaic acid. At least part of this effect is critically dependent on prolonged Ser133 phosphorylation, as a directed mutation at this site decreased CREB-induced protection. These results suggest that CREB is a survival factor for neuronal cells and that treatments aimed at augmenting CREB phosphorylation in the brain may be neuroprotective.
Animals↗
Global CNS gene transfer for a childhood neurogenetic enzyme deficiency: Canavan disease.
The neurogenetic prototypic disease on which we chose to test our gene therapy strategy is Canavan disease (CD). CD is an autosomal recessive leukodystrophy associated with spongiform degeneration of the brain. At present the disease is uniformly fatal in affected probands. CD is characterized by mutations in the aspartoacylase (ASPA) gene, resulting in loss of enzyme activity. In this review, recent evidence is summarized on the etiology and possible treatments for CD. In particular, we discuss two gene delivery systems representing recent advances in both viral and liposome technology: a novel cationic liposome-polymer-DNA (LPD) complex, DCChol/DOPE-protamine, as well as recombinant adeno-associated virus (AAV) vectors.
Acetates↗
Modulation of rat rotational behavior by direct gene transfer of constitutively active protein kinase C into nigrostriatal neurons.
The modulation of motor behavior by protein kinase C (PKC) signaling pathways in nigrostriatal neurons was examined by using a genetic intervention approach. Herpes simplex virus type 1 (HSV-1) vectors that encode a catalytic domain of rat PKCbetaII (PkcDelta) were developed. PkcDelta exhibited a constitutively active protein kinase activity with a substrate specificity similar to that of rat brain PKC. As demonstrated in cultured sympathetic neurons, PkcDelta caused a long-lasting, activation-dependent increase in neurotransmitter release. In the rat brain, microinjection of HSV-1 vectors that contain the tyrosine hydroxylase promoter targeted expression to dopaminergic nigrostriatal neurons. Expression of pkcDelta in a small percentage of nigrostriatal neurons (approximately 0.1-2%) was sufficient to produce a long-term (>/=1 month) change in apomorphine-induced rotational behavior. Nigrostriatal neurons were the only catecholaminergic neurons that contained PkcDelta, and the amount of rotational behavior was correlated with the number of affected nigrostriatal neurons. The change in apomorphine-induced rotational behavior was blocked by a dopamine receptor antagonist (fluphenazine). D2-like dopamine receptor density was increased in those regions of the striatum innervated by the affected nigrostriatal neurons. Therefore, this strategy enabled the demonstration that a PKC pathway or PKC pathways in nigrostriatal neurons modulate apomorphine-induced rotational behavior, and altered dopaminergic transmission from nigrostriatal neurons appears to be the affected neuronal physiology responsible for the change in rotational behavior.
Animals↗
Towards gene therapy for the central nervous system.
Gene therapy has generated enormous scientific, medical and public interest over the last decade. Clinical trials involving approximately 2000 patients worldwide have targeted simple genetic diseases such as cystic fibrosis, muscular dystrophy, adenosine deaminase deficiency, Gaucher's disease and familial hypercholesterolemia, as well as complex acquired diseases such as cancer and AIDS. The central nervous system is a new and particularly exciting target for gene therapy because its unique properties prevent the successful treatment of many neurological disorders by conventional means. This review discusses the potential applications of in vivo gene therapy to neurological disorders that have the greatest potential for genetic treatments.
Central Nervous System Diseases↗
Peroral gene therapy of lactose intolerance using an adeno-associated virus vector.
Gene therapy is usually reserved for severe and medically refractory disorders because of the toxicity, potential long-term risks and invasiveness of most gene transfer protocols. Here we show that an orally administered adeno-associated viral vector leads to persistent expression of a beta-galactosidase transgene in both gut epithelial and lamina propria cells, and that this approach results in long-term phenotypic recovery in an animal model of lactose intolerance. A gene 'pill' associated with highly efficient and stable gene expression might be a practical and cost-effective strategy for even relatively mild disorders, such as lactase deficiency.
Administration, Oral↗
In vivo expression of therapeutic human genes for dopamine production in the caudates of MPTP-treated monkeys using an AAV vector.
An adeno-associated virus (AAV) vector, expressing genes for human tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC), demonstrated significantly increased production of dopamine in 293 (human embryonic kidney) cells. This bicistronic vector was used to transduce striatal cells of six asymptomatic but dopamine-depleted monkeys which had been treated with the neurotoxin MPTP. Striatal cells were immunoreactive for the vector-encoded TH after stereotactic injection for periods up to 134 days, with biochemical effects consistent with dopamine biosynthetic enzyme expression. A subsequent experiment was carried out in six more severely depleted and parkinsonian monkeys. Several TH/aadc-treated monkeys showed elevated levels of dopamine near injection tracts after 2.5 months. Two monkeys that received a beta-galactosidase expressing vector showed no change in striatal dopamine. Behavioral changes could not be statistically related to the vector treatment groups. Toxicity was limited to transient fever in several animals and severe hyperactivity in one animal in the first days after injection with no associated histological evidence of inflammation. This study shows the successful transfection of primate neurons over a period up to 2.5 months with suggestive evidence of biochemical phenotypic effects and without significant toxicity. While supporting the idea of an in vivo gene therapy for Parkinson's disease, more consistent and longer lasting biochemical and behavioral effects will be necessary to establish the feasibility of this appraoch in a primate model of parkinsonism.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
Prospects for gene therapy in pediatric neurosurgery.
Gene therapy represents a powerful tool for both the study and potential treatment of pediatric neurological diseases. The majority of strategies for brain gene therapy have focused upon the use of modified viruses as vehicles for efficient delivery of genes into cells of the central nervous system. Retroviruses were originally the most popular vehicles for gene transfer outside the brain; however, these only function in actively dividing cells and have thus been limited to developmental neurobiology and treatment of brain tumors. Viruses with DNA-based genomes can transfer genes to both dividing and nondividing cells such as neurons, and these include adenovirus, adeno-associated virus and herpes simplex virus. Each system has special features, and the choice of vehicle may be based upon a variety of factors including toxicity or immunogenicity of the vector in vivo, size of the gene which can be inserted, titer of virus which can be obtained and technical difficulty in generating reagent grade viruses. Pediatric patients present unique opportunities for gene therapy, and inherited genetic defects and brain tumors are among the pediatric disorders which would most benefit from this new field. Preclinical studies using each of these systems in a variety of models of pediatric CNS disease have proven promising. Several ongoing studies have been initiated for treatment of pediatric brain tumors, and a protocol for treatment of an inherited neurological defect has recently achieved approval for initial clinical trials. Continued advances in gene therapy technology and delivery systems combined with the explosion of available genetic information should make gene therapy an increasingly important tool for the future of pediatric neurosurgery.
Adenoviridae↗
Novel methods for studying new antiepileptic drug pharmacology.
A number of new antiepileptic drugs act by indirect mechanisms and thus produce effects that may not best be measured by traditional blood studies of the drugs and their metabolites. Study of the indirect action of these drugs on GABA-mediated inhibition by microdialysis and nuclear MR spectroscopy has proved more relevant. These new investigative techniques may also prove valuable as compounds affecting glutamate or other excitatory neurotransmitters are developed.
Animals↗
Targets for gene therapy of Parkinson's disease: growth factors, signal transduction, and promoters.
Parkinson's disease gene therapy is in its infancy. All studies to date have been in experimental animals and there are no clinical protocols currently approved. Several non-human primate studies however, have been completed and preliminary data appear promising. When dealing with a complex acquired disorder of unknown etiology, gene therapy is likely to provide symptomatic and palliative relief at best and will not be curative. However, if the gene therapy approach has advantages in terms of the risk/benefit ratio, cost and efficacy over current treatments, then it should be brought to clinical trial. This article discusses some future directions and areas of intense investigation at present. The advances in the field over the past five years have been tremendous and it appears possible that before the year 2000, clinical gene therapy trials in Parkinson's disease will be ongoing.
Animals↗
Adenovirus vector-mediated gene transfer into human epileptogenic brain slices: prospects for gene therapy in epilepsy.
As a first step in the development of a gene therapy approach to epilepsy, we evaluated the ability of adenovirus vectors to direct the transfer into and expression of a marker gene in human brain slices obtained from patients undergoing surgery for medically intractable epilepsy. Following injection of adenovirus vectors containing the Escherichia coli lacZ gene into hippocampal and cortical brain slices, lacZ mRNA, beta-galactosidase protein, and enzymatic activity were detected, confirming successful gene transfer, transcription, and translation into a functional protein. Transfected cells were predominantly glial, with some neurons expressing beta-galactosidase as well. These results support the potential of adenovirus vectors to transfer genetic information into human epileptogenic brain, resulting in expression of the gene into a functional protein. These findings also have implications for the development of gene therapy approaches to certain seizure disorders. A number of potential therapeutic approaches are discussed, including the elevation of inhibitory neurotransmitter or neuropeptide levels, expression or modulation of postsynaptic receptors, and manipulation of signal transduction systems.
Adenoviruses, Human↗
Direct gene transfer into human epileptogenic hippocampal tissue with an adeno-associated virus vector: implications for a gene therapy approach to epilepsy.
PURPOSE: Virus vectors capable of transferring genetic information into human cells provide hope for improved therapy in several neurological diseases, including epilepsy. We evaluated the ability of an adeno-associated virus (AAV) vector to transfer and cause expression of a lacZ marker gene in brain slices obtained from patients undergoing temporal lobectomy for control of medically intractable seizures. METHODS: Human brain slices were injected with an AAV vector (AAVlacZ) encoding Escherichia coli beta-galactosidase and incubated for as long as 24 h. The presence of lacZ mRNA. beta-galactosidase protein and enzymatic activity were assayed by reverse transcriptase polymerase chain reaction (rtPCR), immunocytochemistry, and the X-Gal technique, respectively. RESULTS: AAVlacZ directed the expression in human epileptogenic brain of E. coli beta-galactosidase that had functional activity. Expression was observed in < or =5 h and was sustained for as long as the slices were viable. Morphological analysis indicated that neurons were preferentially transfected, and there was no evidence of cytotoxicity. CONCLUSIONS: Our results confirm the feasibility of using AAV vectors to transfer genes into the human CNS and in particular, into neurons. Replacement of the lacZ gene with a functional gene modulating hippocampal neuronal physiology, might allow a localized genetic intervention for focal seizures based on the stereotaxic or endovascular delivery of such a vector system into the appropriate brain region.
Dependovirus↗
Gene trial in New Zealand.
Explore the source record for details and available documents.
Canavan Disease↗
Prospects for gene therapy in Parkinson's disease.
Numerous advances in in vivo and ex vivo gene-therapy approaches to Parkinson's disease offer promise for direct clinical trials in patients in the next several years. These systems are predicated on introducing gene that encode enzymes responsible for dopamine biosynthesis or neurotrophic factors that may delay nigrostriatal degeneration or facilitate regeneration. We review the current status of experimental approaches to gene therapy for Parkinson's disease. Comparative advantages and disadvantages of each system are enumerated, and preclinical trials of some of the systems are evaluated. Although the specific in vivo or ex vivo methods used for gene transfer into the brain are likely to be supplanted by newer technology over the next decade, the principles and approaches developed in current studies likely will remain the same.
Adenoviridae↗
Accumulation of cytotoxins during the development of seizures and edema after hypoxic-ischemic injury in late gestation fetal sheep.
Several hours after an hypoxic-ischemic injury to the developing brain, hyperemia, then seizures, edema, and infarction can develop. The roles of nitric oxide (NO) synthesis and excitotoxin accumulation during these later phases of injury are not known. The time course of extracellular levels of amino acids within the parasagittal parietal cortex were measured with microdialysis during and for 3 d after 30 min of cerebral ischemia in nine chronically instrumented near-term fetal sheep (119-133 d). Cortical electroencephalographic (EEG) activity and extracellular space (ECS) were quantified simultaneously with real-time spectral analysis and cortical impedance measurements, respectively. Amino acid concentrations were measured using HPLC. During ischemia, citrulline (by-product of NO synthesis), glutamate, glycine, and gamma-aminobutyric acid (GABA) concentrations rose to 147 +/- 18%, 180 +/- 20%, 290 +/- 50% and 4800 +/- 1300% of baseline respectively (p < 0.05). The excitotoxic index ([glutamate] x [glycine]/[GABA]) decreased to 15 +/- 8%. Upon reperfusion, the cytotoxic edema and amino acid accumulation largely resolved within 1 h, and the EEG was depressed. Citrulline began to rise again by 4 h (p < 0.05), reaching a maximum (273 +/- 21%) at 32 +/- 2 h. Seizure activity developed at 7 +/- 2 h, and impedance plus the excitotoxic index then rose progressively and peaked at 32 +/- 2 h (480 +/- 170%). At 72 h, there was severe neuronal loss and laminar necrosis within the parasagittal cortex. These data suggest that, several hours after a severe hypoxicischemic injury, NO synthesis increased, then seizures arose, and edema developed concomitantly with the accumulation of excitotoxins.
Animals↗
Transfection of human lactotroph adenoma cells with an adenovirus vector expressing tyrosine hydroxylase decreases prolactin release.
Pituitary adenomas are common intracranial neoplasms, for which surgery and radiation are usually not curative. In attempting to develop gene therapy as a better approach to treating pituitary adenomas, we chose lactotroph adenomas as a model. The rationale for the use of this model is based on the observation that dopamine agonists decrease prolactin secretion by lactotroph adenomas, and also decrease their size. We transfected primary cultures of human lactotroph adenoma cells with an adenovirus vector containing a cDNA which encodes a human tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine. Transfection induced expression of tyrosine hydroxylase and increased production of dopamine, resulting in the predicted biologic effect of decreased prolactin secretion. These results demonstrate the potential for gene therapy of lactotroph adenomas and perhaps other pituitary adenomas, which are less amenable to pharmacologic treatment than lactotroph adenomas.
Adenoma↗
Hippocampal GABA transporter function in temporal-lobe epilepsy.
Electrophysiological studies of human temporal-lobe epilepsy suggest that a loss of hippocampal GABA-mediated inhibition may underlie the neuronal hyperexcitability. However, GABA (gamma-aminobutyric acid)-containing cells are preserved and GABA receptors are maintained in the surviving hippocampal neurons. Diminished GABA release may therefore mediate the loss of inhibition. Here we show that, in the human brain, potassium-stimulated release of GABA was increased, and glutamate-induced, calcium-independent release of GABA was markedly decreased, in epileptogenic hippocampi, in contrast with contralateral, non-epileptogenic hippocampi. The glutamate-induced GABA release in vivo was transporter-mediated in rats. Furthermore, in amygdala-kindled rats, a model for human epilepsy, a decrease in glutamate-induced GABA release was associated with a 48% decrease in the number of GABA transporters. These data suggest that temporal-lobe epilepsy is characterized in part by a loss of glutamate-stimulated GABA release that is secondary to a reduction in the number of GABA transporters.
Amygdala↗