Huntington's Disease Reviews: 2001
Backman, L. and L. Farde (2001). "Dopamine and cognitive functioning: brain imaging findings in Huntington's disease and normal aging." Scand J Psychol 42(3): 287-96.
Recent brain imaging studies in Huntington's disease (HD) and normal aging suggest a relationship between central dopaminergic neurotransmission and cognitive performance. Results demonstrate substantial losses in dopamine (DA) function in both HD and aging. Moreover, HD patients and older adults show deficits across multiple cognitive domains, including episodic memory, speed of processing, and executive functioning. Although few studies are available at present, there is converging evidence that multiple measures of pre- and postsynaptic DA biochemistry are (a) highly interrelated, and (b) strongly associated with the cognitive deficits that accompany HD and aging. There is also emerging evidence that DA neurotransmission influences cognitive performance independent of HD or age. In general, the research reviewed in this article indicates that the nigrostriatal DA system is an important component of a frontostriatal circuitry that is critically involved in cognitive functioning.
Banaclocha, M. M. (2001). "Therapeutic potential of N-acetylcysteine in age-related mitochondrial neurodegenerative diseases." Med Hypotheses 56(4): 472-7.
Increasing lines of evidence suggest a key role for mitochondrial damage in neurodegenerative diseases. Brain aging, Parkinson's disease, Alzheimer's disease, Huntington's disease and Friedreich's ataxia have been associated with several mitochondrial alterations including impaired oxidative phosphorylation. Mitochondrial impairment can decrease cellular bioenergetic capacity, which will then increase the generation of reactive oxygen species resulting in oxidative damage and programmed cell death. This paper reviews the mechanisms of N-acetylcysteine action at the cellular level, and the possible usefulness of this antioxidant for the treatment of age-associated neurodegenerative diseases. First, this thiol can act as a precursor for glutathione synthesis as well as a stimulator of the cytosolic enzymes involved in glutathione regeneration. Second, N-acetylcysteine can act by direct reaction between its reducing thiol group and reactive oxygen species. Third, it has been shown that N-acetylcysteine can prevent programmed cell death in cultured neuronal cells. And finally, N-acetylcysteine also increases mitochondrial complex I and IV specific activities both in vitro and in vivo in synaptic mitochondrial preparations from aged mice. In view of the above, and because of the ease of its administration and lack of toxicity in humans, the potential usefulness of N-acetylcysteine in the treatment of age-associated mitochondrial neurodegenerative diseases deserves investigation.
Becker, G. and D. Berg (2001). "Neuroimaging in basal ganglia disorders: perspectives for transcranial ultrasound." Mov Disord 16(1): 23-32.
Transcranial sonography is a new diagnostic tool, allowing not only the evaluation of cerebral arteries but also the two-dimensional display of the brain parenchyma. In this review we will summarize basics of the application, the ultrasound anatomy of the brain and sonographic findings in some movement disorders. While in normal adults basal ganglia nuclei are hypoechogenic, they are hyperechogenic in certain basal ganglia disorders. In Parkinson's disease, for example, the substantia nigra can be depicted as a distinctly echogenic area. An elevated echogenicity of the lentiform nuclei was noticed in patients with primary adult-onset dystonia. In both disorders the altered echogenicity may arise from higher heavy metal tissue content (i.e. iron in Parkinson's disease and copper in primary dystonia). Our findings converge to the hypothesis that transcranial ultrasound sensitively detects pathological metal accumulation not identified by other neuroimaging techniques (CT and MRI) and therefore provides new insights in the diagnosis of basal ganglia disorders. The implications of these findings for the understanding of the pathogenesis and its usefulness for the early diagnosis of movement disorders are outlined.
Bowater, R. P. and R. D. Wells (2001). "The intrinsically unstable life of DNA triplet repeats associated with human hereditary disorders." Prog Nucleic Acid Res Mol Biol 66: 159-202.
Expansions of specific DNA triplet repeats are the cause of an increasing number of hereditary neurological disorders in humans. In some diseases, such as Huntington's and several spinocerebellar ataxias, the repetitive DNA sequences are translated into long tracts of the same amino acid (usually glutamine), which alters interactions with cellular constituents and leads to the development of disease. For other disorders, including common genetic disorders such as myotonic dystrophy and fragile X syndrome, the DNA repeat is located in noncoding regions of transcribed sequences and disease is probably caused by altered gene expression. In studies in lower organisms, mammalian cells, and transgenic mice, high frequencies of length changes (increases and decreases) occur in long DNA triplet repeats. These observations are similar to other types of repetitive DNA sequences, which also undergo frequent length changes at genomic loci. A variety of processes acting on DNA influence the genetic stability of DNA triplet repeats, including replication, recombination, repair, and transcription. It is not yet known how these different multienzyme systems interact to produce the genetic mutation of expanded repeats. In vitro studies have identified that DNA triplet repeats can adopt several unusual DNA structures, including hairpins, triplexes, quadruplexes, slipped structures, and highly flexible and writhed helices. The formation of stable unusual structures within the cell is likely to disturb DNA metabolism and be a critical intermediate in the molecular mechanism(s) leading to genetic instabilities of DNA repeats and, hence, to disease pathogenesis.
Burson, C. M. and K. R. Markey (2001). "Genetic counseling issues in predictive genetic testing for familial adult-onset neurologic diseases." Semin Pediatr Neurol 8(3): 177-86.
Genetic counseling is important in any genetic testing situation in order to address the various issues related to obtaining a genetic diagnosis. Presymptomatic testing for adult-onset neurodegenerative disease, in particular, presents a complex counseling scenario. It is imperative to discuss the potential impact of test results on patients' family dynamics, insurability and employability, family planning, and future health in addition to ascertaining a complete understanding of recurrence, inheritance, and testing parameters. The Huntington disease presymptomatic testing protocol is well-defined and has been used for more than 10 years. These guidelines, which protect both patient and provider, can now be applied to other diseases as further presymptomatic testing capabilities are realized.
Butterfield, D. A., B. J. Howard, et al. (2001). "Brain oxidative stress in animal models of accelerated aging and the age-related neurodegenerative disorders, Alzheimer's disease and Huntington's disease." Curr Med Chem 8(7): 815-28.
Oxidative stress in brain is emerging as a potential causal factor in aging and age-related neurodegenerative disorders. Brain tissue from living patients is difficult to acquire; hence, animal models of aging and age-related neurodegenerative disorders, though not perfect models, have provided tissue to study the role of oxidative stress in these disorders. In this review, the central role of oxidative damage in brain in models of accelerated aging (progeria and Werner's syndrome) and the age-related neurodegenerative disorders, Alzheimer's disease and Huntington's disease, will be presented and evaluated. To the extent that the animal models faithfully mirror their respective disorders, and based on the totality of the studies, it is apparent that oxidative stress, the excess of free radicals over the means of scavenging these harmful agents, may play critical roles in the molecular basis of accelerated aging, Alzheimer's disease, and Huntington's disease.
Butterfield, D. A. and J. Kanski (2001). "Brain protein oxidation in age-related neurodegenerative disorders that are associated with aggregated proteins." Mech Ageing Dev 122(9): 945-62.
Protein oxidation, one of a number of brain biomarkers of oxidative stress, is increased in several age-related neurodegenerative disorders or animal models thereof, including Alzheimer's disease, Huntington's disease, prion disorders, such as Creutzfeld-Jakob disease, and alpha-synuclein disorders, such as Parkinson's disease and frontotemporal dementia. Each of these neurodegenerative disorders is associated with aggregated proteins in brain. However, the relationship among protein oxidation, protein aggregation, and neurodegeneration remain unclear. The current rapid progress in elucidation of mechanisms of protein oxidation in neuronal loss should provide further insight into the importance of free radical oxidative stress in these neurodegenerative disorders.
Calabrese, V., G. Scapagnini, et al. (2001). "Mitochondrial involvement in brain function and dysfunction: relevance to aging, neurodegenerative disorders and longevity." Neurochem Res 26(6): 739-64.
It is becoming increasingly evident that the mitochondrial genome may play a key role in neurodegenerative diseases. Mitochondrial dysfunction is characteristic of several neurodegenerative disorders, and evidence for mitochondria being a site of damage in neurodegenerative disorders is partially based on decreases in respiratory chain complex activities in Parkinson's disease, Alzheimer's disease, and Huntington's disease. Such defects in respiratory complex activities, possibly associated with oxidant/antioxidant balance perturbation, are thought to underlie defects in energy metabolism and induce cellular degeneration. Efficient functioning of maintenance and repair process seems to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, which are composed of genes termed vitagenes. A promising approach for the identification of critical gerontogenic processes is represented by the hormesis-like positive effect of stress. In the present review, we discuss the role of energy thresholds in brain mitochondria and their implications in neurodegeneration. We then review the evidence for the role of oxidative stress in modulating the effects of mitochondrial DNA mutations on brain age-related disorders and also discuss new approaches for investigating the mechanisms of lifetime survival and longevity.
Cattaneo, E., D. Rigamonti, et al. (2001). "Loss of normal huntingtin function: new developments in Huntington's disease research." Trends Neurosci 24(3): 182-8.
Huntington's disease is characterized by a loss of brain striatal neurons that occurs as a consequence of an expansion of a CAG repeat in the huntingtin protein. The resulting extended polyglutamine stretch confers a deleterious gain-of-function to the protein. Analysis of the mutant protein has attracted most of the research activity in the field, however re-examination of earlier data and new results on the beneficial functions of normal huntingtin indicate that loss of the normal protein function might actually equally contribute to the pathology. Thus, complete elucidation of the physiological role(s) of huntingtin and its mode of action are essential and could lead to new therapeutic approaches.
Chaudhuri, K. R. (2001). "Autonomic dysfunction in movement disorders." Curr Opin Neurol 14(4): 505-11.
Dysfunction of the autonomic nervous system is an under-recognised but important aspect of the aetiological and clinical manifestation of primary degenerative dysautonomias such as multiple system atrophy (MSA) and Parkinson's disease (PD). Although the clinical presentation of dysautonomia in these two disorders may overlap, yet pathological and in vivo imaging studies suggest considerable differences. Functional imaging studies suggest that selective cardiac sympathetic denervation may occur early in PD but not in other parkinsonian syndromes. The clinical implication of this apparently disease specific peripheral dysautonomia is unknown and would be the subject of much interest in future years. Dysautonomia in degenerative disorders also affect respiration, genitourinary function and sleep. Sleep related disorders such as rapid eye movement behaviour disorder and urinary voiding dysfunction appear to precede the development of PD related symptoms while patients with sporadic ataxia have been shown to progress to develop MSA. Dysautonomia has also been recognised in other movement disorders, examples being the combination of dystonia and complex regional pain syndrome with elevated HLA-DR13 and late onset Huntington's disease presenting with dominant parkinsonism and minimal chorea. These studies have helped progress in various diagnostic and management parameters in relation to autonomic dysfunction and movement disorders.
Chiurazzi, P. and G. Neri (2001). "Pharmacological reactivation of inactive genes: the fragile X experience." Brain Res Bull 56(3-4): 383-7.
The present review on the pharmacological reactivation of inactive genes focuses on our experience with the fragile X syndrome. The fragile X syndrome of mental retardation is the prototype of a series of inherited neurological disorders caused by abnormal expansion of repeated trinucleotide sequences embedded in various genes. In a number of these disorders, such as Huntington disease and several forms of spinocerebellar ataxias, the expanded CAG repeat is translated, resulting in a polyglutamine-containing protein that indirectly causes neurodegeneration. On the contrary, in the fragile X syndrome, the expanded CGG repeat is contained in the regulatory region of the FMR1 gene and causes transcriptional inactivation. The mutation spares the coding region of the FMR1 gene, which potentially would allow synthesis of a normal protein if transcription could be restored. This prompted us to try and reactivate the gene function with different pharmacological regimens. We discuss our successful results with DNA demethylating and histone hyperacetylating drugs and their implications for future treatments of the fragile X syndrome.
Clostre, F. (2001). "[Mitochondria: recent pathophysiological discoveries and new therapeutic perspectives]." Ann Pharm Fr 59(1): 3-21.
Until about a decade ago, few researchers in clinical or evolutionary biology paid much attention to mitochondria. But over the years, as technological advances in molecular biology made nuclear functions more accessible to them, interest in mitochondria began to revive. First, geneticists started tracing certain rare inherited disorders to mutations in the mitochondria's circular genome. More recently, other researchers have speculated that mitochondria might contribute to aging, either by releasing tissue-damaging reactive oxygen molecules or by impairing and depriving the cell of the energy it needs to function. One the most important recent developments has been the recognition that mitochondria play a central role in the regulation of programmed cell death, or apoptosis. Now, we know that mitochondria play a decisive role in life-death decisions for the cell and may choose between the apoptotic and necrotic pathways. Mitochondria can trigger cell death in a number of ways: by disrupting electron transport and energy metabolism, by activating the mitochondrial permeability transition, by releasing and/or activating proteins that mediate apoptosis. Any or all of these mechanisms may help to explain how mitochondrial defects contribute to the pathogenesis of neuronal death or dysfunction in ischemia/reperfusion injury as well as in human degenerative diseases including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. This has opened up new avenues for understanding the pathogenesis of neurodegeneration and may lead to new and more effective therapeutic approaches to these diseases.
Cunningham, D. A., C. Herring, et al. (2001). "Analysis of patients treated with living pig tissue for evidence of infection by porcine endogenous retroviruses." Trends Cardiovasc Med 11(5): 190-6.
The use of pigs as a source of cells and organs for transplantation has the potential to reduce the current chronic shortage of organs for the treatment of many end-stage diseases. The risk of transmission of infectious agents across the species barrier (zoonoses) has to be assessed. Many such agents can be eliminated from the pig herd. However, porcine endogenous retroviruses, which are carried within the pig genome, are not easily eliminated. They can infect primary and immortalized human cells in vitro, but to date no evidence for in vivo infection has been found in retrospective studies of humans exposed to viable porcine cells. Small-scale clinical trials using porcine cells for the treatment of Parkinson's and Huntington's disease are currently in progress. The prospective monitoring of these patients in conjunction with further research into the biology of this virus will help address safety issues.
Davies, S. and D. B. Ramsden (2001). "Huntington's disease." Mol Pathol 54(6): 409-13.
The most recent findings in the elucidation of the molecular pathology of Huntington's disease are reviewed. Particular interest has been paid to the role of huntingtin and its associated proteins in excitotoxicity mediated via NMDA and kainate receptors.
Davis, K. M. and J. Y. Wu (2001). "Role of glutamatergic and GABAergic systems in alcoholism." J Biomed Sci 8(1): 7-19.
The pharmacological effects of ethanol are complex and widespread without a well-defined target. Since glutamatergic and GABAergic innervation are both dense and diffuse and account for more than 80% of the neuronal circuitry in the human brain, alterations in glutamatergic and GABAergic function could affect the function of all neurotransmitter systems. Here, we review recent progress in glutamatergic and GABAergic systems with a special focus on their roles in alcohol dependence and alcohol withdrawal-induced seizures. In particular, NMDA-receptors appear to play a central role in alcohol dependence and alcohol-induced neurological disorders. Hence, NMDA receptor antagonists may have multiple functions in treating alcoholism and other addictions and they may become important therapeutics for numerous disorders including epilepsy, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's chorea, anxiety, neurotoxicity, ischemic stroke, and chronic pain. One of the new family of NMDA receptor antagonists, such as DETC-MESO, which regulate the redox site of NMDA receptors, may prove to be the drug of choice for treating alcoholism as well as many neurological diseases.
Deckel, A. W. (2001). "Nitric oxide and nitric oxide synthase in Huntington's disease." J Neurosci Res 64(2): 99-107.
Nitric oxide (NO) is a biologically active inorganic molecule produced when the semiessential amino acid l-arginine is converted to l-citrulline and NO via the enzyme nitric oxide synthase (NOS). NO is known to be involved in the regulation of many physiological processes, such as control of blood flow, platelet adhesion, endocrine function, neurotransmission, neuromodulation, and inflammation, to name only a few. During neuropathological conditions, the production of NO can be either protective or toxic, dependent on the stage of the disease, the isoforms of NOS involved, and the initial pathological event. This paper reviews the properties of NO and NOS and the pathophysiology of Huntington's disease (HD). It discusses ways in which NO and NOS may interact with the protein product of HD and reviews data implicating NOS in the neuropathology of HD. This is followed by a synthesis of current information regarding how NO/NOS may contribute to HD-related pathology and identification of areas for potential future research.
Emerich, D. F. (2001). "Neuroprotective possibilities for Huntington's disease." Expert Opin Biol Ther 1(3): 467-79.
Huntington's disease (HD) is a devastating genetic disorder. Despite the absence of effective therapy, there has been an explosion in interest for developing treatment strategies aimed at lessening or preventing the neuronal death that occurs in this disease. In large part, the renewed interest in neuroprotective strategies has been spurred by our increasing understanding of the genetic and molecular events that drive the underlying neuropathology of HD. This escalating understanding of the biological underpinnings of HD is derived from several convergent sources represented by investigators with clinical, genetic, molecular, physiological and neurobehavioural backgrounds. The diversity of data being generated has, in turn, produced a unique time in HD research where an impressive number of potential therapeutics are coming to the forefront. This review outlines several of these possibilities including the use of intracerebrally delivered neurotrophic factors, pharmacologically altering cellular energy production, the use of antiglutamatergic drugs, the use of caspase inhibitors and inhibitors of protein aggregation. This review also touches on the interesting possibility of whether or not the neurodegeneration in HD is at least partially reversible in nature. All of these possibilities are highlighted in the context that HD is a neurodegenerative disorder in which genetic detection provides a clear and unequivocal opportunity for neuroprotection.
Emerich, D. F. and H. C. Salzberg (2001). "Update on immunoisolation cell therapy for CNS diseases." Cell Transplant 10(1): 3-24.
Delivery of potentially therapeutic drugs to the brain is hindered by the blood-brain barrier (BBB), which restricts the diffusion of drugs from the vasculature to the brain parenchyma. One means of overcoming the BBB is with cellular implants that produce and deliver therapeutic molecules. Polymer encapsulation, or immunoisolation, provides a means of overcoming the BBB to deliver therapeutic molecules directly into the CNS region of interest. Immunoisolation is based on the observation that xenogeneic cells can be protected from host rejection by encapsulating, or surrounding, them within an immunoisolatory, semipermeable membrane. Cells can be enclosed within a selective, semipermeable membrane barrier that admits oxygen and required nutrients and releases bioactive cell secretions, but restricts passage of larger cytotoxic agents from the host immune defense system. The selective membrane eliminates the need for chronic immunosuppression of the host and allows the implanted cells to be obtained from nonhuman sources. In this review, cell immunoisolation for treating CNS diseases is updated from considerations of device configurations, membrane manufacturing and characterization in preclinical models of Alzheimer's and Huntington's disease.
Fehder, W. P. and S. D. Douglas (2001). "Interactions between the nervous and immune systems." Semin Clin Neuropsychiatry 6(4): 229-40.
Substantial morphologic and functional evidence exists that supports the reciprocal interactions that occur between the nervous and immune systems. The nervous and immune systems have been increasingly found to use a common chemical language in the form of neuropeptides, cytokines, and hormones. Sophisticated immunologic techniques such as the identification and detection of immune cell surface markers enable researchers to determine the origin and activity of diverse cells in the blood and central nervous system. These techniques have elucidated the activity of immune cells in the central nervous system (CNS) that was previously thought to be privileged from immune surveillance in the presence of an intact blood brain barrier. Immune cells in the CNS play a central role in several degenerative diseases such as Alzheimer's disease, Huntington's disease, Multiple sclerosis, AIDS dementia complex, and nerve destruction associated with trauma. Immune cells also play a role in demyelinating peripheral nerve disorders. Cytokines and neuropeptides secreted by peripheral immune cells have profound effects on behavior that is mediated by the CNS. The close integration between immune and nervous system responses is being increasingly recognized in physiologic and pathologic conditions.
Fischbeck, K. H. (2001). "Polyglutamine expansion neurodegenerative disease." Brain Res Bull 56(3-4): 161-3.
Kennedy's disease was the first of eight neurodegenerative disorders found to be caused by expanded polyglutamine repeats. Each of these disorders is likely caused by a toxic gain of function in the disease gene product, often associated with inclusions of mutant protein in susceptible neurons. The mechanism of toxicity may involve sequestration and depletion of a polyglutamine-containing protein that is important to neuronal survival, such as CREB-binding protein. Recent insights into the biochemistry and cellular pathology of the polyglutamine expansion neurodegenerative diseases provide the opportunity for systematic drug screens and a rational approach to effective therapy.
Gamboa, J., F. J. Jimenez-Jimenez, et al. (2001). "[Voice disorders caused by neurological diseases]." Rev Neurol 33(2): 153-68.
OBJECTIVE: To review voice disorders in neurological diseases, with special emphasis to acoustic analysis. DEVELOPMENT: In the first part of this article we describe data regarding neural control of voice, physiology of phonation, and examination of the patient with voice disturbances, including the use of voice laboratory, acoustic analysis fundamentals, phonetometric measures and aerodynamic measures. In the second part, we review the voice disturbances associated to neurological diseases, emphasizing into movement disorders (specially Parkinson s disease, essential tremor, and spasmodic dysphonia). CONCLUSIONS: A number of neurological diseases causing alterations of corticospinal pathway, cerebellum, basal ganglia and upper and/or lower motoneurons can induce voice disturbances. Voice examination using ear, nose & throat examination, endoscopy and videorecording of laryngeal movements, acoustic analysis, elecroglottography, laryngeal electromyography, and aerodynamic measures, could be useful in the clinical examination of some neurological diseases.
Gilbert, P., S. Self, et al. (2001). "Sieve analysis: methods for assessing from vaccine trial data how vaccine efficacy varies with genotypic and phenotypic pathogen variation." J Clin Epidemiol 54(1): 68-85.
A key component in the evaluation of efficacy of a vaccine to protect against disease caused by an antigenically diverse infectious pathogen in a preventative vaccine trial is assessing how vaccine-induced protection depends on genotypic and phenotypic variations of the exposing pathogen. This assessment is made by comparing pathogen isolates between infected vaccinated subjects and infected unvaccinated subjects. A survey of efficacy trial reports reveals a lack of systematic, quantitative investigation in this question. Analysis tools for testing if vaccine protection against disease is superior against some pathogen strains, and for estimating the magnitude of this differential vaccine protection, are described. The broad applicability of the methods is illustrated through analysis of isolates taken from persons infected while participating in vaccine trails for cholera, HIV-1, hepatitis B, rotavirus, and pneumococcus. These analyses reveal intriguing trends for Genentech's monovalent rgp120 HIV-1 vaccine, for two whole-killed-cell oral cholera vaccines, and for other vaccines.
Gimenez y Ribotta, M. (2001). "Gene therapy strategies in neurodegenerative diseases." Histol Histopathol 16(3): 883-93.
Treatment of neurodegenerative diseases by classical pharmacotherapy is restricted by blood-brain barrier which prevents access to the brain of potentially therapeutic molecules. Recent progress in the knowledge of pathophysiological molecular processes, and in the development of molecular biotechnology have opened the way to new therapeutic interventions for these disorders. This chapter reviews the most recent gene therapy strategies using experimental models for neurodegenerative diseases.
Gjedde, A. (2001). "[Receptor mapping in living human beings by means of positron emission tomography]." Ugeskr Laeger 163(38): 5199-205.
PET can map neurotransmitter synthesis, storage, release, binding to receptors, and re-uptake in the brain with tracer concentrations in the picomolar or nanomolar range. Tracers are analogues of naturally occurring precursors or ligands, or are drugs, which bind with varying degrees of specificity to receptor subtypes in the brain. Tracers have been synthesised for many transmitter systems, but dopaminergic and serotonergic neurotransmissions are the main foci of current efforts to selectively trace synthesis, storage, re-uptake, or post-synaptic binding of neurotransmitters. Common measures of the tracer uptake and binding include precursor clearance (k3), a measure of transmitter synthesis and trapping, and binding potential (pB), a measure of the receptor binding per unit of unbound tracer, and hence a measure of the release of the endogenous transmitter, or the occupancy of a drug. Dopamine tracers are used in diseases of the basal ganglia, whereas serotonin, benzodiazepine, and opiate tracers are used in lesions of the cerebral cortex. PET has revealed loss of dopaminergic terminals and dopamine synthetic capacity in Parkinson's disease, MPTP intoxication, and Lesch-Nyhan's syndrome; release of dopamine after administration of cocaine and amphetamine, and in motor activity and cognition; increased synaptic dopamine and release of dopamine, and the 70-90% neuroleptic occupancy of dopamine receptors in the striatum, in patients with schizophrenia; loss of muscarinic and nicotinergic receptors in Alzheimer's disease, and benzodiazepine and opiate receptors in stroke, epilepsy, and Huntington's chorea; altered opiate receptors in chronic pain and drug abuse; and release of opiates in analgesia; but changes in serotonin synthesis, transport, and binding in affective or psychotic disorders remain elusive.
Glass, M. (2001). "The role of cannabinoids in neurodegenerative diseases." Prog Neuropsychopharmacol Biol Psychiatry 25(4): 743-65.
An understanding of the actions of Cannabis (Marijuana) has evolved from folklore to science over the previous hundred years. This progression was spurred by the discovery of an endogenous cannabinoid system consisting of two receptors and two endogenous ligands. This system appears to be intricately involved in normal physiology, specifically in the control of movement, formation of memories and appetite control. As we are developing an increased understanding of the physiological role of endocannabinoids it is becoming clear that they may be involved in the pathology of several neurological diseases. Furthermore an array of potential therapeutic targets is being determined--including specific cannabinoid agonists and antagonists as well as compounds that interrupt the synthesis, uptake or metabolism of the endocannabinoids. This article reviews the recent progress in understanding the contribution of endocannabinoids to the pathology and therapy of Huntington's disease. Parkinson's disease, schizophrenia and tremor.
Glosser, G. (2001). "Neurobehavioral aspects of movement disorders." Neurol Clin 19(3): 535-51, v.
Cognitive, behavioral, affective, and psychiatric symptoms occur in almost all movement disorders. Diagnosis and management of movement disorders depends critically on an understanding of these neurobehavioral symptoms. This article reviews the neurobehavioral aspects of two representative movement disorders; Parkinson's disease and Huntington's disease.
Goossens, D., J. Del-Favero, et al. (2001). "Trinucleotide repeat expansions: do they contribute to bipolar disorder?" Brain Res Bull 56(3-4): 243-57.
It has long been known that bipolar disorder has a true but complex genetic background. Reports on genetic anticipation in bipolar disorder opened the way to a new approach for genetic studies. Indeed, anticipation, a decreasing age at onset, and/or increasing disease severity in successive generations, were recently explained by an expansion of trinucleotide repeats in monogenic diseases like Huntington's disease and Fragile X syndrome. The involvement of trinucleotide repeat expansions in bipolar disorder received even more support when studies reported association of large CAG/CTG repeats with bipolar disorder. Even though a large number of studies have been conducted, this association is still unexplained. Here, we review the studies investigating the trinucleotide repeat expansion hypothesis in bipolar disorder. Studies on anticipation, on association of anonymous large CAG/CTG repeats and on specific trinucleotide repeats are critically analysed and discussed, showing a field with precipitate conclusions or inconclusive results. The analysis suggests that there are indications, though disputable, supporting the trinucleotide repeat expansion hypothesis in bipolar disorder, but no conclusive evidence has been hitherto provided.
Hedera, P. (2001). "Ethical principles and pitfalls of genetic testing for dementia." J Geriatr Psychiatry Neurol 14(4): 213-21.
Progress in the genetics of dementing disorders and the availability of clinical tests for practicing physicians increase the need for a better understanding of multifaceted issues associated with genetic testing. The genetics of dementia is complex, and genetic testing is fraught with many ethical concerns. Genetic testing can be considered for patients with a family history suggestive of a single gene disorder as a cause of dementia. Testing of affected patients should be accompanied by competent genetic counseling that focuses on probabilistic implications for at-risk first-degree relatives. Predictive testing of at-risk asymptomatic patients should be modeled after presymptomatic testing for Huntington's disease. Testing using susceptibility genes has only a limited diagnostic value at present because potential improvement in diagnostic accuracy does not justify potentially negative consequences for first-degree relatives. Predictive testing of unaffected subjects using susceptibility genes is currently not recommended because individual risk cannot be quantified and there are no therapeutic interventions for dementia in presymptomatic patients.
Ho, L. W., J. Carmichael, et al. (2001). "The molecular biology of Huntington's disease." Psychol Med 31(1): 3-14.
BACKGROUND: Huntington's disease (HD) is a fatal neurodegenerative disorder with an autosomal dominant mode of inheritance. It leads to progressive dementia, psychiatric symptoms and an incapacitating choreiform movement disorder, culminating in premature death. HD is caused by an increased CAG repeat number in a gene coding for a protein with unknown function, called huntingtin. The trinucleotide CAG codes for the amino acid glutamine and the expanded CAG repeats are translated into a series of uninterrupted glutamine residues (a polyglutamine tract). METHODS: This review describes the epidemiology, clinical symptomatology, neuropathological features and genetics of HD. The main aim is to examine important findings from animal and cellular models and evaluate how they have enriched our understanding of the pathogenesis of HD and other diseases caused by expanded polyglutamine tracts. RESULTS: Selective death of striatal and cortical neurons occurs. It is likely that the HD mutation confers a deleterious gain of function on the protein. Neuronal intranuclear inclusions containing huntingtin and ubiquitin develop in patients and transgenic mouse models of HD. Other proposed mechanisms contributing to neuropathology include excitotoxicity, oxidative stress, impaired energy metabolism, abnormal protein interactions and apoptosis. CONCLUSIONS: Although many interesting findings have accumulated from studies of HD and other polyglutamine diseases, there remain many unresolved issues pertaining to the exact roles of intranuclear inclusions and protein aggregates, the mechanisms of selective neuronal death and delayed onset of illness. Further knowledge in these areas will inspire the development of novel therapeutic strategies.
Hsu, Y. Y., A. T. Du, et al. (2001). "Magnetic resonance imaging and magnetic resonance spectroscopy in dementias." J Geriatr Psychiatry Neurol 14(3): 145-66.
This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect.
Hu, F. B. and W. C. Willett (2001). "Diet and coronary heart disease: findings from the Nurses' Health Study and Health Professionals' Follow-up Study." J Nutr Health Aging 5(3): 132-8.
In the last decade, our understanding of the nutrients and foods most likely to promote cardiac health has improved substantially, owing in part to the data from several large and carefully conducted prospective cohort studies, including the Nurses' Health Study (NHS) and Health Professionals' Follow-up Study (HPFS). Using more refined dietary assessment tools and multiple measurements, the NHS and HPFS have provided a wealth of information not only on major types of fat and different classes of fatty acids, but also other aspects of diet, including antioxidants, folate, fiber, dietary glycemic load, and overall dietary patterns. These studies, along with metabolic, clinical and other epidemiological studies, have provided strong evidence for a major role of dietary modification in the prevention of coronary heart disease (CHD).
Hughes, R. E. and J. M. Olson (2001). "Therapeutic opportunities in polyglutamine disease." Nat Med 7(4): 419-23.
Polyglutamine diseases comprise a class of familial neurodegenerative disorders caused by expression of proteins containing expanded polyglutamine tracts. Great progress has been made in elucidating the molecular mechanisms contributing to polyglutamine pathology, and in identifying potential drug targets. Although much remains to be learned, these advances provide an opportunity for rational approaches to target-based drug discovery.
Ishiguro, H., H. Sawada, et al. (2001). "[Huntington's disease model mouse and neuronal cell death]." No To Shinkei 53(9): 829-37.
Joel, D. (2001). "Open interconnected model of basal ganglia-thalamocortical circuitry and its relevance to the clinical syndrome of Huntington's disease." Mov Disord 16(3): 407-23.
The early stages of Huntington's disease (HD) present with motor, cognitive, and emotional symptoms. Correspondingly, current models implicate dysfunction of the motor, associative, and limbic basal ganglia-thalamocortical circuits. Available data, however, indicate that in the early stages of the disease, striatal damage is mainly restricted to the associative striatum. Based on an open interconnected model of basal ganglia-thalamocortical organization, we provide a detailed account of the mechanisms by which associative striatal pathology may lead to the complex pattern of motor, cognitive, and emotional symptoms of early HD. According to this account, the degeneration of a direct and several indirect pathways arising from the associative striatum leads to impaired functioning of: (1) the motor circuit, resulting in chorea and bradykinesia, (2) the associative circuit, resulting in abnormal eye movements, "frontal-like" cognitive deficits and "cognitive disinhibition," and (3) the limbic circuit, resulting in affective and psychiatric symptoms. When relevant, this analysis is aided by comparing the symptomatology of HD patients to that of patients with mild to moderate Parkinson's disease, since in the latter there is similar dysfunction of direct pathways but opposite dysfunction of indirect pathways. Finally, we suggest a potential novel treatment of HD and provide supportive evidence from a rat model of the disease.
Kagan, B. L., Y. Hirakura, et al. (2001). "The channel hypothesis of Huntington's disease." Brain Res Bull 56(3-4): 281-4.
Extended tracts of polyglutamine (PG) have been implicated in the pathogenicity of the mutant protein huntingtin and have been shown to form ion channels in planar lipid bilayers. These lines of evidence suggest that huntingtin and other PG mutant proteins may damage cells via a channel mechanism. This mechanism could cause damage to the plasma membrane by running down ionic gradients, discharging membrane potential; or allowing influx of toxic ions such as Ca(2+). PG damage to intracellular membranes such as the lysosomal membrane or the mitochondrial membrane could also injure cells via leakage of toxic enzymes or triggering of apoptosis. The channel mechanism is well-established for microbial toxins, and the existence of at least six other "amyloid" channels relevant to diseases such as Alzheimer's and Creutzfeld-Jakob, suggests that this may be a widespread pathogenic mechanism.
Kato, R. (2001). "[Huntington disease]." Ryoikibetsu Shokogun Shirizu(33): 823-4.
Kimura, N., R. Sugihara, et al. (2001). "[A case of neuro-Behcet's disease presenting with chorea]." Rinsho Shinkeigaku 41(1): 45-9.
A 46-year-old man was admitted to our hospital because of emotional instability and involuntary movement of the right upper limb. Neurological examination revealed inability to concentrate, emotional incontinence, recent memory disturbance, chorea of bilateral upper limbs and neck, and bilateral pyramidal signs. Brain MRI showed atrophy of bilateral caudate nucleus and diffuse abnormal intensity area with low intensity on T1-weighted images and high intensity on T2-weighted images in cerebral white matter around the lateral ventricles. Huntington's disease was suspected at first, but it was ruled out by DNA analysis. After admission, oral and genital aphthae developed and the CSF examination showed pleocytosis (273 leukocytes/mm3; 39 polymorphonuclear leukocytes and 234 lymphocytes), so we diagnosed this case as neuro-Behcet's disease. Although basal ganglia is occasionally involved in neuro-Behcet's disease, chorea is rare. Neuro-Behcet's disease should be considered as a cause of chorea.
Lashwood, A. and F. Flinter (2001). "Clinical and counselling implications of preimplantation genetic diagnosis for Huntington's disease in the UK." Hum Fertil (Camb) 4(4): 235-8.
Huntington's disease is an autosomal dominant neurodegenerative disorder that usually occurs in adult life. Individuals at risk can have a gene test before the onset of symptoms, and prenatal diagnosis is available. Preimplantation genetic diagnosis (PGD) for Huntington's disease is now available for couples in whom one partner has the gene for Huntington's disease. A licence to practise PGD is required from the Human Fertilisation and Embryology Authority, and there are several complex issues relating to PGD for Huntington's disease that require consideration. The partner of the Huntington's disease gene carrier should have a presymptomatic test to ensure accuracy in a PGD cycle. There should be a delay between blood sampling and testing for Huntington's disease to allow time for reflection and withdrawal from testing. All PGD treatment has an associated risk of misdiagnosis. If confirmatory prenatal testing is not undertaken after a successful PGD cycle, no confirmation of diagnosis will be obtained at birth. Guidelines indicate that individuals who are at risk cannot be tested before 18 years. There is concern over the ability of a child or adolescent to make an informed choice about testing before this age. Confirmatory testing at birth after PGD would be in direct contravention of these guidelines. In the UK, the law requires consideration of the welfare of children born after assisted conception treatment. Presenting symptoms of Huntington's disease may affect the parenting abilities of an affected individual. There is a need for an assessment of a patient's current Huntington's disease status and their planned provision of care of children if Huntington's disease affects parenting. It has been necessary to create a detailed working protocol for the management of PGD for Huntington's disease to address these issues.
Lindquist, S., S. Krobitsch, et al. (2001). "Investigating protein conformation-based inheritance and disease in yeast." Philos Trans R Soc Lond B Biol Sci 356(1406): 169-76.
Our work supports the hypothesis that a protein can serve as an element of genetic inheritance. This protein-only mechanism of inheritance is propagated in much the same way as hypothesized for the transmission of the protein-only infectious agent in the spongiform encephalopathies; hence these protein factors have been called yeast prions. Our work has focused on [PSI(+)], a dominant cytoplasmically inherited factor that alters translational fidelity.This change in translation is produced by a self-perpetuating change in the conformation of the translation-termination factor, Sup35. Most recently, we have determined that new elements of genetic inheritance can be created by deliberate genetic engineering, opening prospects for new methods of manipulating heredity. We have also uncovered evidence that other previously unknown elements of protein-based inheritance are encoded in the yeast genome. Finally, we have begun to use yeast as a model system for studying human protein folding diseases, such as Huntington's disease. Proteins responsible for some of these diseases have properties uncannily similar to those that produce protein-based mechanisms of inheritance.
Link, C. D. (2001). "Transgenic invertebrate models of age-associated neurodegenerative diseases." Mech Ageing Dev 122(14): 1639-49.
Transgenic Drosophila melanogaster and Caenorhabditis elegans strains have been engineered to express human proteins associated with neurodegenerative diseases. These model systems include transgenic animals expressing beta-amyloid peptide (Alzheimer's disease), polyglutamine repeat proteins (Huntington's disease, Spinocerebellar ataxia), and alpha-synuclein (Parkinson's disease). In most of these invertebrate models, some aspects of the human diseases are reproduced. Although expression of all these proteins in transgenic mice has been instructive, the invertebrate models offer experimental advantages (e.g. forward genetic screens) that can potentially address some of the outstanding questions regarding the cellular processes underlying these diseases. This review considers what has been learned from these invertebrate models, and speculates what further insight may be gained from them.
Lovell-Badge, R. (2001). "The future for stem cell research." Nature 414(6859): 88-91.
Stem cells have offered much hope by promising to greatly extend the numbers and range of patients who could benefit from transplants, and to provide cell replacement therapy to treat debilitating diseases such as diabetes, Parkinson's and Huntington's disease. The issue of stem cell research is politically charged, prompting biologists to begin engaging in ethical debates, and generating in the general public an unusually high level of interest in this aspect of biology. But excitement notwithstanding, there is a long way to go in basic research before new therapies will be established, and now the pressure is on for scientists and clinicians to deliver.
Maat-Kievit, J. A., M. Losekoot, et al. (2001). "[From gene to disease; HD gene and Huntington disease]." Ned Tijdschr Geneeskd 145(44): 2120-3.
Huntington's disease (HD) is a late onset, incurable, autosomal dominantly-inherited, progressive neuropsychiatric disease, characterised by chorea, changes in personality, mood and behaviour, and dementia. Huntington's disease is a clinical diagnosis. The advent of DNA diagnosis has made predictive, prenatal and preimplantation testing possible for at-risk persons or asymptomatic carriers. The prevalence is estimated to be 3-10/100,000 among individuals of European descent; HD is less common in other ethnic groups. Huntington's disease is caused by an expanded trinucleotide CAG repeat in the HD gene on chromosome 4. The gene encodes for the protein huntingtin, with an as yet unknown function. The mutated huntingtin has an elongated stretch of glutamines which leads to a gain of function such as overactivity, excitotoxicity, or to interactions with other proteins.
Mak, W. and S. L. Ho (2001). "The impact of molecular biology on clinical neurology." Hong Kong Med J 7(1): 40-9.
Advances in molecular biology have increased our understanding of both inherited and sporadic forms of neurological disease. In this review, the impact of these advances is discussed in relation to specific neurological conditions. These include the hereditary neuropathies and ataxias, Huntington's disease, and the muscular dystrophies, as well as Alzheimer's disease, Parkinson's disease, and motor neuron disease. Genetic channelopathies, such as familial hemiplegic migraine, are also described. Although knowledge in this area overall is still relatively scant, current advances in molecular biology have helped in the reclassification of some neurological disorders, thereby providing a further step towards the development of rational therapies to treat these conditions.
Martin-Rendon, E., M. Azzouz, et al. (2001). "Lentiviral vectors for the treatment of neurodegenerative diseases." Curr Opin Mol Ther 3(5): 476-81.
A number of potential gene therapy applications in the adult nervous system include neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. During the last five years, lentiviral vectors have developed into extremely efficient gene transfer vehicles to the nervous system, revealing a wide range of possibilities for the treatment or such disorders. This review describes the most important and recent advances in the development of lentiviral vectors as well as the demonstration of proof-of-principle in animal models of human neurodegenerative diseases.
Mazurova, Y. (2001). "New therapeutic approaches for the treatment of Huntington's disease." Acta Medica (Hradec Kralove) 44(4): 119-23.
The use of transplantation (TR) of fetal neural tissue as a therapeutic method started much later in patients suffering from Huntington's disease (HD) than in those with Parkinson's disease. The clinical trial, following a wide range of animal experiments (neurotoxic models and newly also transgenic mice), includes about 30 HD patients until now. Because of limited use of the human fetal tissue by ethical and technical concerns, there is necessity to search for the alternative sources for neural grafting. The first attempt with xenotransplantation (in 12 HD patients) and with TR of encapsulated genetically modified cells (in 6 HD patients) was performed, but no appreciable improvement of status in any of those patients was noted. Since no effective pharmacological treatment of HD is available, the TR of fetal neural tissue is now the only therapeutic approach which provides a reduction of symptoms in most of grafted patients. The possibilities are enormous offered by neural stem cells, optionally by embryonic stem cells, which could be expanded in cultures, cloned or genetically modified and then grafted into the patient's brain. On the other hand, the neural progenitor and stem cells, normally present within the subependymal layer of the lateral brain ventricles also in adulthood, might be induced to become an endogenous source of glia and neurons participating in the brain's repair.
McEwan, I. J. (2001). "Structural and functional alterations in the androgen receptor in spinal bulbar muscular atrophy." Biochem Soc Trans 29(Pt 2): 222-7.
The androgen receptor is a member of the nuclear receptor superfamily, and regulates gene expression in response to the steroid hormones testosterone and dihydrotestosterone. Mutations in the receptor have been correlated with a diverse range of clinical conditions, including androgen insensitivity, prostate cancer and spinal bulbar muscular atrophy, a neuromuscular degenerative condition. The latter is caused by expansion of a polyglutamine repeat within the N-terminal domain of the receptor. Thus the androgen receptor is one of a growing number of neurodegenerative disease-associated proteins, including huntingtin (Huntington's disease), ataxin-1 (spinocerebellar ataxia, type 1) and ataxin-3 (spinocerebellar ataxia, type 3), which show expansion of CAG triplet repeats. Although widely studied, the functions of huntingtin, ataxin-1 and ataxin-3 remain unknown. The androgen receptor, which has a well-recognized function in gene regulation, provides a unique opportunity to investigate the functional significance of poly(amino acid) repeats in normal and disease states.
Meiser, B. and S. Dunn (2001). "Psychological effect of genetic testing for Huntington's disease: an update of the literature." West J Med 174(5): 336-40.
Naarding, P., H. P. Kremer, et al. (2001). "Huntington's disease: a review of the literature on prevalence and treatment of neuropsychiatric phenomena." Eur Psychiatry 16(8): 439-45.
A review was made of the literature on Huntington's disease, including the clinical neurology, recent advances in pathophysiology and genetic mechanisms and psychopathology. It can be concluded that research on the latter is scarce, although the subject is relevant because of the co-occurrence of psychiatric, neurological and genetic phenomena, which may lead to novel concepts in the understanding of brain function. So far, attempts to provide a comprehensive and pragmatic description of the psychopathology of Huntington's disease have been disappointing, probably due to the limitations of the DSM classification system in this disorder. Future research should focus not only on this classification system, but also on neuropsychological functioning, because of the degenerative nature of the disease. Systematic and controlled studies should be performed on the treatment of psychiatric abnormalities in Huntington's disease before any conclusions can be drawn.
Nance, M. A. and R. H. Myers (2001). "Juvenile onset Huntington's disease--clinical and research perspectives." Ment Retard Dev Disabil Res Rev 7(3): 153-7.
Huntington's disease (HD) is an inherited neurodegenerative disorder. The mutation which causes the disease is an expansion in the number of repetitions of three nucleotides, C, A, and G in exon 1 of the huntingtin gene. The gene normally has 15 to 30 repeats and an expansion to 40 or more is associated with HD. HD usually has a mid-life onset, but a juvenile form, defined by onset of symptoms before the age of 21 years, is present in about 7% of HD cases. Juvenile HD is characterized by (1) transmission from an HD affected father, (2) an unusually large repeat size, usually of 60 or more units, and (3) unique clinical features, including rigidity and seizure disorder. Although juvenile onset is associated with a more severe neuropathological involvement, the neuropathological characteristics of juvenile HD are similar to those seen in the adult form in that the striatum bears the brunt of the illness. Clumps of protein, termed inclusion bodies, which stain positive for huntingtin and ubiquitin, are found primarily in the nucleus but also in the cytoplasm and axons in HD neurons. Research suggests that these inclusion bodies sequester a deleterious protein fragment and prolong cell life during the degenerative process of the disease.
Orr, H. T. (2001). "Beyond the Qs in the polyglutamine diseases." Genes Dev 15(8): 925-32.
Orth, M. and A. H. Schapira (2001). "Mitochondria and degenerative disorders." Am J Med Genet 106(1): 27-36.
In mammalian cells, mitochondria provide energy from aerobic metabolism. They play an important regulatory role in apoptosis, produce and detoxify free radicals, and serve as a cellular calcium buffer. Neurodegenerative disorders involving mitochondria can be divided into those caused by oxidative phosphorylation (OXPHOS) abnormalities either due to mitochondrial DNA (mtDNA) abnormalities, e.g., chronic external ophthalmoplegia, or due to nuclear mutations of OXPHOS proteins, e.g., complex I and II associated with Leigh syndrome. There are diseases caused by nuclear genes encoding non-OXPHOS mitochondrial proteins, such as frataxin in Friedreich ataxia (which is likely to play an important role in mitochondrial-cytosolic iron cycling), paraplegin (possibly a mitochondrial ATP-dependent zinc metalloprotease of the AAA-ATPases in hereditary spastic paraparesis), and possibly Wilson disease protein (an abnormal copper transporting ATP-dependent P-type ATPase associated with Wilson disease). Huntingon disease is an example of diseases with OXPHOS defects associated with mutations of nuclear genes encoding non-mitochondrial proteins such as huntingtin. There are also disorders with evidence of mitochondrial involvement that cannot as yet be assigned. These include Parkinson disease (where a complex I defect is described and free radicals are generated from dopamine metabolism), amyotrophic lateral sclerosis, and Alzheimer disease, where there is evidence to suggest mitochondrial involvement perhaps secondary to other abnormalities.
Palmer, G. C. (2001). "Neuroprotection by NMDA receptor antagonists in a variety of neuropathologies." Curr Drug Targets 2(3): 241-71.
Because of adverse reactions, early efforts to introduce high affinity competitive or use-dependent NMDA receptor antagonists into patients suffering from stroke, head trauma or epilepsy met with failure. Later it was discovered that both low affinity use-dependent NMDA receptor antagonists and compounds with selective affinity for the NR2B receptor subunit met the criteria for safe administration into patients. Furthermore, these low affinity antagonists exhibit significant mechanistic differences from their higher affinity counterparts. Success of the latter is attested to the ability of the following low affinity compounds to be marketed: 1) Cough suppressant-dextromethorphan (available for decades); 2) Parkinson's disease--amantadine, memantine and budipine; 3) Dementia--memantine; and 4) Epilepsy--felbamate. Moreover, Phase III clinical trials are ongoing with remacemide for epilepsy and Huntington's disease and head trauma for HU-211. A host of compounds are or were under evaluation for the possible treatment of stroke, head trauma, hyperalgesia and various neurodegenerative disorders. Despite the fact that other drugs with associated NMDA receptor mechanisms have reached clinical status, this review focuses only on those competitive and use-dependent NMDA receptor antagonists that reached clinical trails. The ensuing discussions link the in vivo pharmacological investigations that led to the success/mistakes/ failures for eventual testing of promising compounds in the clinic.
Persky, A. M. and G. A. Brazeau (2001). "Clinical pharmacology of the dietary supplement creatine monohydrate." Pharmacol Rev 53(2): 161-76.
Creatine is a dietary supplement purported to improve exercise performance and increase fat-free mass. Recent research on creatine has demonstrated positive therapeutic results in various clinical applications. The purpose of this review is to focus on the clinical pharmacology and therapeutic application of creatine supplementation. Creatine is a naturally occurring compound obtained in humans from endogenous production and consumption through the diet. When supplemented with exogenous creatine, intramuscular and cerebral stores of creatine and its phosphorylated form, phosphocreatine, become elevated. The increase of these stores can offer therapeutic benefits by preventing ATP depletion, stimulating protein synthesis or reducing protein degradation, and stabilizing biological membranes. Evidence from the exercise literature has shown athletes benefit from supplementation by increasing muscular force and power, reducing fatigue in repeated bout activities, and increasing muscle mass. These benefits have been applied to disease models of Huntington's, Parkinson's, Duchenne muscular dystrophy, and applied clinically in patients with gyrate atrophy, various neuromuscular disorders, McArdle's disease, and congestive heart failure. This review covers the basics of creatine synthesis and transport, proposed mechanisms of action, pharmacokinetics of exogenous creatine administration, creatine use in disease models, side effects associated with use, and issues on product quality.
Petersen, A., O. Hansson, et al. (2001). "[Huntington disease--yet another mad protein?]." Lakartidningen 98(50): 5756-8, 5761.
Huntington's disease is an autosomal dominant neurodegenerative disorder caused by an expanded CAG repeat. It is characterized by motor and cognitive disturbances, as well as cellular dysfunction and loss in the basal ganglia and the cerebral cortex. The mutant protein huntingtin aggregates in cells. The toxicity of mutant huntingtin, or the loss of its normal function, causes disruption of cellular functions such as protein and calcium metabolism, transmitter release, mitochondria and gene transcription. Recent findings in basic research open up new possibilities for novel therapies.
Piccioni, F., S. Simeoni, et al. (2001). "Polyglutamine tract expansion of the androgen receptor in a motoneuronal model of spinal and bulbar muscular atrophy." Brain Res Bull 56(3-4): 215-20.
Spinobulbar muscular atrophy (SBMA) is a late-onset disorder characterized by progressive muscle loss, degeneration of motoneurons in the spinal cord and brainstem, and partial androgen insensitivity. SBMA is directly correlated with the expansion of CAG repeats encoding a polyglutamine tract (polyQ) of extended length. The identification of polyQ expansion in SBMA led to the discovery of an entire class of neurodegenerative disorders. In fact, at least eight different diseases, including Huntington's disease, share a common molecular mechanism involving an expansion of a polyQ tract within different proteins. The elongated polyQ tract causes a toxic gain of function in the mutant protein and is associated with the formation of intracellular aggregates, whose pathogenetic role has not been fully established yet. Our observations in a motoneuron cell line (NSC34), indicate that the expression of the androgen receptor (AR) carrying the elongated polyQ tract (AR-Q48) has a toxic effect in aggregate-independent manner. In fact, in basal condition, AR-Q48 shows a cytoplasmic diffuse distribution, yet it reduces the viability of transfected NSC34. In contrast, testosterone treatment, while inducing aggregation of the mutant AR, also increases cell viability. Aggregates in NSC34 are localized mainly in the perinuclear region and occasionally in the neuropil, whereas no nuclear aggregate has ever been found. Further observations of the minor subset of cells showing neuropil aggregates, reveal an alteration of the neurite morphology, suggesting a different role of the two types of cytoplasmic aggregates.
Pisani, A., P. Bonsi, et al. (2001). "Role of tonically-active neurons in the control of striatal function: cellular mechanisms and behavioral correlates." Prog Neuropsychopharmacol Biol Psychiatry 25(1): 211-30.
1. The striatum is primarily involved in motor planning and motor learning. Human diseases involving its complex circuitry lead to movement disorders such as Parkinson's disease (PD) and Huntington's disease (HD). Moreover the striatum has been involved in processes linked to reward, cognition and drug addiction. 2. The high content of acetylcholine (ACh) found in the striatum is due to the presence of cholinergic interneurons. The intrinsic electrical and synaptic properties of these interneurons have been recently characterized. However, their functional significance is far from being fully elucidated. 3. In vivo electrophysiological experiments from behaving monkeys have identified these cholinergic interneurons as "Tonically Active Neurons" (TANs). They are activated by presentation of sensory stimuli of behavioral significance or linked to reward. 4. Experimental evidence showed that integrity of the nigrostriatal dopaminergic system is essential for TANs to express learned activity. 5. PD is known to be due to the loss of the nigrostriatal dopaminergic pathway and the ensuing imbalance between the content of dopamine and acetylcholine in the striatum. This evidence supports the hypothesis that cholinergic interneurons, or TANs, play a key role in the modulation of striatal function.
Redondo-Verge, L. (2001). "[Cognitive deterioration in Huntington disease]." Rev Neurol 32(1): 82-5.
OBJECTIVES: To review, summarize and update data on the pattern of cognitive deterioration in Huntington's disease (HD). DEVELOPMENT: HD represents a paradigm of frontostriatal dementia in which cognitive deterioration affects three large domains: memory, executive and visual-spatial functions. Episodic explicit memory deficit mainly affects the processes of information recovery, whilst changes in implicit memory are impaired in learning procedures but not in priming. Executive dysfunction constitutes an essential characteristic, affecting the working memory, attention, sequencing and planning. Complex visual-spatial functions are severely affected and this may affect recognition of complex figures and facial gestures. Some of these mental changes may be detected during preclinical stages. At the present time, since it is possible to make a definite genetic diagnosis and there is neuropathological data on HD, this condition is considered to be an excellent clinical model for the study of the cognitive functions carried out by the cortico-striatal circuits. CONCLUSIONS: Using a multidisciplinary approach a cognitive model has been established in which the corpus striatum is considered to be the basic structure for selection of information which will generate the appropriate response, both motor and behavioral, for the context involved. Loss of this capacity leads to mental rigidity and perseveration in conduct, which are typical of the cognitive disorders of HD.
Rideout, H. J. and L. Stefanis (2001). "Caspase inhibition: a potential therapeutic strategy in neurological diseases." Histol Histopathol 16(3): 895-908.
Caspases are intracellular proteases that participate in apoptotic pathways in mammalian cells, including neurons. Here we review evidence that caspase inhibition, through pharmacological or molecular means, may inhibit neuronal cell death in a number of in vitro and in vivo models of neurological disease. It has recently become clear that, at least in most cell culture models, caspase inhibition offers only transient protection, and that a caspase-independent death eventually occurs. This may be due to irreversible caspase-independent alterations at the level of the mitochondria. Despite concerns that targeting caspases alone may prove insufficient to truly reverse the effects of various death stimuli, in vivo studies indicate that caspase inhibition promotes survival and functional outcome in a variety of neurological disease models. In addition, studies of human post-mortem material suggest that caspases are activated in certain human neurological diseases. Caspase inhibition may therefore provide a novel strategy for the treatment of such disorders. Caspases, through the generation of toxic fragments of critical protein substrates, may also be involved in earlier steps of neuronal dysfunction, such as protein aggregation in Huntington's and Alzheimer's disease, and therefore caspase inhibition may be of additional value in the treatment of these particular disorders.
Roig, C. (2001). "[Saccadic eye movements in extrapyramidal disorders and particularly in Huntington's disease]." Neurologia 16(2): 57-62.
Sawa, A. (2001). "Mechanisms for neuronal cell death and dysfunction in Huntington's disease: pathological cross-talk between the nucleus and the mitochondria?" J Mol Med 79(7): 375-81.
Huntington's disease (HD) is a hereditary neurodegenerative condition caused by a characteristic mutation in the huntingtin (htt) gene. This gene was identified in 1993. Both the mitochondria and the nucleus play an important role in HD pathology. However, the precise molecular mechanisms remain unclear. A key strategy for understanding HD pathology is to identify signaling cascades initiated by mutant Htt that lead to neuronal cell death and dysfunction. Apoptotic stress induces greater mitochondrial depolarization in HD lymphoblasts than in control subjects. This leads to overactivation of caspase-3, which is capable of cleaving htt. Truncated forms of Htt, which are similar to the caspase-cleaved products in size, exist in the nucleus of HD patient and animal model brains. We hypothesize that caspases, which are activated by mitochondrial depolarization, play a role in producing truncated forms of Htt, which accumulate in the nucleus. Truncated forms of mutant Htt that accumulate in the nucleus are toxic to cells. There is growing evidence that truncated forms of mutant Htt in the nucleus influence gene transcription by binding to proteins such as CREB binding protein (CBP) response element binding protein binding protein, N-COR, glyceraldehyde-3-phosphate dehydrogenase, and p53. p53 regulates the transcription of various mitochondrial proteins which may underlie the mitochondrial abnormalities, especially the vulnerability to mitochondrial depolarization, seen in HD tissues. Taken together, we hypothesize a noxious signaling cascade between the mitochondria and the nucleus, initiated by mutant Htt, which may underlie HD pathology.
Sayre, L. M., M. A. Smith, et al. (2001). "Chemistry and biochemistry of oxidative stress in neurodegenerative disease." Curr Med Chem 8(7): 721-38.
The age-related neurodegenerative diseases exemplified by Alzheimer&hyp;s disease (AD), Lewy body diseases such as Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington&hyp;s disease are characterized by the deposition of abnormal forms of specific proteins in the brain. Although several factors appear to underlie the pathological depositions, the cause of neuronal death in each disease appears to be multifactorial. In this regard, evidence in each case for a role of oxidative stress is provided by the finding that the pathological deposits are immunoreactive to antibodies recognizing protein side-chains modified either directly by reactive oxygen or nitrogen species, or by products of lipid peroxidation or glycoxidation. Although the source(s) of increased oxidative damage are not entirely clear, the findings of increased localization of redox-active transition metals in the brain regions most affected is consistent with their contribution to oxidative stress. It is tempting to speculate that free radical oxygen chemistry plays a pathogenetic role in all these neurodegenerative conditions, though it is as yet undetermined what types of oxidative damage occur early in pathogenesis, and what types are secondary manifestations of dying neurons. Delineation of the profile of oxidative damage in each disease will provide clues to how the specific neuronal populations are differentially affected by the individual disease conditions.
Sieradzan, K. A. and D. M. Mann (2001). "The selective vulnerability of nerve cells in Huntington's disease." Neuropathol Appl Neurobiol 27(1): 1-21.
It is now more than 7 years since the genetic mutation causing Huntington's disease (HD) was first identified. Unstable CAG expansion in the IT15 gene, responsible for disease, is translated into an abnormally long polyglutamine (polyQ) tract near the N-terminus of the huntingtin protein. The presence of expanded polyQ in the mutant protein leads to its abnormal proteolytic cleavage with liberation of toxic N-terminal fragments that tend to aggregate, probably first in the cytoplasm. Subsequent nuclear translocation of the cleaved mutant huntingtin is associated with formation of intranuclear protein aggregates and neurotoxicity, probably involving apoptotic cascades. These processes, which can be experimentally modelled in cultured neuronal and non-neuronal cells, seem to underlie neurodegeneration in HD, and also other polyQ disorders, such as dentatorubro-pallidoluysian degeneration, spinal and bulbar muscular atrophy and the spinocerebellar ataxias. They do not, however, explain why within the corpus striatum and cerebral cortex certain nerve cells are susceptible to disease and others are not. In the human HD brain, vulnerable pyramidal neurones within the deeper layers of the cerebral cortex frequently contain large intranuclear inclusions composed of N-terminal fragments of huntingtin. Such inclusions are, however, rare within neurones of the striatum, even in the medium spiny neurones preferentially lost from this region. While inclusions per se do not seem to be neurotoxic, they may provide a surrogate marker of molecular pathology. Recent studies indicate that the nuclear accumulation of mutant huntingtin interferes with transcriptional events. Of particular importance may be the effect on the genes encoding neurotransmitter receptor proteins, especially those involved with glutamatergic neurotransmission. Such changes may trigger or facilitate a low-grade, chronic excitotoxicity of the glutamatergic cortical projection neurones on their target cells in the striatum, already partly compromised by the toxic effects of the HD mutation. This combination of insults, for anatomical reasons experienced predominantly by striatal projection neurones, would eventually cause their selective demise.
Silkis, I. (2001). "The cortico-basal ganglia-thalamocortical circuit with synaptic plasticity. II. Mechanism of synergistic modulation of thalamic activity via the direct and indirect pathways through the basal ganglia." Biosystems 59(1): 7-14.
A possible mechanism underlying the modulatory role of dopamine, adenosine and acetylcholine in the modification of corticostriatal synapses, subsequent changes in signal transduction through the "direct" and "indirect" pathways in the basal ganglia and variations in thalamic and neocortical cell activity is proposed. According to this mechanism, simultaneous activation of dopamine D1/D2 receptors as well as inactivation of adenosine A1/A(2A) receptors or muscarinic M4/M1 receptors on striatonigral/striatopallidal inhibitory cells can promote the induction of long-term potentiation/depression in the efficacy of excitatory cortical inputs to these cells. Subsequently augmented inhibition of the activity of inhibitory neurons of the output nuclei of the basal ganglia through the "direct" pathway together with reduced disinhibition of these nuclei through the "indirect" pathway synergistically increase thalamic and neocortical cell firing. The proposed mechanism can underlie such well known effects as "excitatory" and "inhibitory" influence of dopamine on striatonigral and striatopallidal cells, respectively; the opposite action of dopamine and adenosine on these cells; antiparkinsonic effects of dopamine receptor agonists and adenosine or acetylcholine muscarinic receptor antagonists.
Sil'kis, I. G. (2001). "[Mechanisms of effects of adenosine and dopamine on modification of synapses in striato-nigral and striato-pallidal neurons]." Ross Fiziol Zh Im I M Sechenova 87(2): 155-69.
On the basis of earlier suggested unitary mechanism of synaptic plasticity opposite effects of adenosine and dopamine on the cAMP concentration in striatal spinal cells can emphasize the well known antagonistic interactions between A2A and D2 receptors on striatopallidal cells and between A1 and D1 receptors on striatonigral cells. This is due to that both the dopamine agonist and adenosine antagonist must promote the induction of long-term potentiation/depression of efficacy of excitatory cortical inputs to striatopallidal/striatonigral cells. This modification must lead to synergistic disinhibition of thalamic cells via "direct" and "indirect" pathways through basal ganglia and subsequent strengthening of motor activity.
Sobue, G. (2001). "[Molecular pathogenesis of motor neuron diseases]." Nihon Shinkei Seishin Yakurigaku Zasshi 21(1): 21-25.
Spinal and bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS) are representative motor neuron diseases in which selective neuronal degeneration occurs. In this paper, some molecular aspects are discussed related to the pathogenesis of the neuronal degeneration. SBMA is a an X-linked neurodegenerative disease caused by the expansion of a CAG repeat in the first exon of the androgen receptor (AR) gene. To date, eight CAG repeat diseases have been identified, including spinal and bulbar muscular atrophy (SBMA), Huntington's disease (HD), dentatorubralpallidoluysian atrophy (DRPLA), and five spinocerebellar ataxias (SCAs 1, 2, 3, 6, 7). These disorders very likely share a common pathogenesis caused by the gain of a toxic function associated with the expanded polyglutamine tract. Several mechanisms have been postulated as a pathogenic process for neurodegeneration caused by the expanded polyglutamine tract. In SBMA, nuclear inclusions (NIs) containing mutant AR protein have been observed in regions of SBMA central nervous system susceptible to degenerations. Transcriptional factors or their cofactors, such as CREB or creb-binding protein (CBP) sequestrated in NIs, may alter the major intracellular transcriptional signal transduction and ultimately may result in neuronal degeneration. The components in the ubiquitin-proteasome pathway also colocalized in NIs and contribute to the path-ogenesis of SBMA. We generated two types of transgenic mice expressing 239Q under the control of human AR promoter and full-size AR containing 97Q. Marked neurological symptoms and extensive nuclear inclusions were observed in both transgenic lines, but there was no neuronal cell death, suggesting that major neurological phenotype was due to neuronal dysfunction instead of neuronal cell death. As for the therapeutic strategies, the overexpression of Hsp70 and Hsp40 chaperones acted together to protect a cultured neuronal cell model of SBMA from inclusion formation and cell death by mutant AR with expanded polyglutamine tract. In regard to ALS, we are screening the gene expression profiles of the motor neurons from the human ALS and SOD transgenic mouse spinal cord. Motor neurons were microdissected from the spinal cord samples by a lazer-captured microdissection system. Gene expression profiles were screened by cDNA microarray and molecular indexing. Several new molecules were cloned and characterized for their function and relation to neuronal cell dysfunction. Some molecules characterized in this procedure were briefly described.
Squitieri, F., M. Cannella, et al. (2001). "Onset and pre-onset studies to define the Huntington's disease natural history." Brain Res Bull 56(3-4): 233-8.
Huntington's disease's (HD) clinical history has not been defined yet. However, many aspects of the most confusing clinical stages, i.e., the first and last disease phases, including the symptom progression and the disease duration, have been better approached after discovery of the responsible gene. The existence of accurate genetic tests, available for affected and pre-symptomatic subjects (i.e., mutation carriers) and the possibility to study transgenic in vivo models, are actually helping us to understand some of the aspects of HD clinical presentation. HD may present with motor symptoms other than chorea, the psychiatric manifestations may represent part of the clinical picture and cognitive deterioration may occur very early in the disease and depend on early cortical involvement. Pre-onset studies are of crucial importance in understanding the temporal sequence of the clinical events. This is also very important for future therapeutic strategies in those diseases initiating late in the life, such as HD.
Stone, T. W. (2001). "Kynurenines in the CNS: from endogenous obscurity to therapeutic importance." Prog Neurobiol 64(2): 185-218.
In just under 20 years the kynurenine family of compounds has developed from a group of obscure metabolites of the essential amino acid tryptophan into a source of intensive research, with postulated roles for quinolinic acid in neurodegenerative disorders, most especially the AIDS-dementia complex and Huntington's disease. One of the kynurenines, kynurenic acid, has become a standard tool for use in the identification of glutamate-releasing synapses, and has been used as the parent for several groups of compounds now being developed as drugs for the treatment of epilepsy and stroke. The kynurenines represent a major success in translating a basic discovery into a source of clinical understanding and therapeutic application, with around 3000 papers published on quinolinic acid or kynurenic acid since the discovery of their effects in 1981 and 1982. This review concentrates on some of the recent work most directly relevant to the understanding and applications of kynurenines in medicine.
Stone, T. W. (2001). "Endogenous neurotoxins from tryptophan." Toxicon 39(1): 61-73.
In most tissues, including brain, a major proportion of the tryptophan which is not used for protein synthesis is metabolised along the kynurenine pathway. Long regarded as the route by which many mammals generate adequate amounts of the essential co-factor nicotinamide adenine dinucleotide, two components of the pathway are now known to have marked effects on neurones. Quinolinic acid is an agonist at the N-methyl-D-aspartate sensitive subtype of glutamate receptors in the brain, while kynurenic acid is an antagonist and, thus, a potential neuroprotectant. A third kynurenine, 3-hydroxykynurenine, is involved in the generation of free radicals which can also damage neurones. Quinolinic acid is increasingly implicated in neurodegenerative disorders, most especially the AIDS-dementia complex and Huntington's disease, while kynurenic acid has become a standard for the identification of glutamate-releasing synapses, and has been used as the parent for several groups of compounds now being developed as drugs for the treatment of epilepsy and stroke.
Sudarsky, L. (2001). "Neurologic disorders of gait." Curr Neurol Neurosci Rep 1(4): 350-6.
Gait disorders are important because of their prevalence, particularly among the elderly, and the associated risk of falls and injury. Neural networks that organize locomotion and maintain balance are briefly reviewed. Gait disorders can be classified based on observational features or by etiology. Several common disorders are discussed in more detail. Recent progress includes use of botulinum toxin for spastic gait in cerebral palsy, neurosurgical treatment of Parkinson's disease, and newer rehabilitation approaches to gait and balance training.
Tarnopolsky, M. A. and M. F. Beal (2001). "Potential for creatine and other therapies targeting cellular energy dysfunction in neurological disorders." Ann Neurol 49(5): 561-74.
Substantial evidence indicates that bioenergetic dysfunction plays either a primary or secondary role in the pathophysiology of cell death in neurodegenerative and neuromuscular disorders, and even in normal aging. Agents that ameliorate bioenergetic defects may therefore be useful in therapy. Creatine, which increases muscle and brain phosphocreatine concentrations, and may inhibit the activation of the mitochondrial permeability transition, protects against neuronal degeneration in transgenic murine models of amyotrophic lateral sclerosis and Huntington's disease and in chemically mediated neurotoxicity. Initial studies of creatine use in humans appear promising; however, further long-term, well-designed trials are needed. Coenzyme Q10, Gingko biloba, nicotinamide, riboflavin, carnitine, lipoic acid, and dichloroacetate are other agents which may have beneficial effects on energy metabolism, but the preclinical and clinical evidence for efficacy in neurological diseases remains limited. These compounds are widely used as dietary supplements; however, they must be subjected to rigorous evaluation through randomized, double-blinded trials to establish efficacy, cost-effectiveness and safety in neurological disorders.
Tsuda, T., Y. Onodera, et al. (2001). "[Molecular and clinical features of SCA 7]." No To Shinkei 53(1): 25-33.
Turner, C. and A. H. Schapira (2001). "Mitochondrial dysfunction in neurodegenerative disorders and ageing." Adv Exp Med Biol 487: 229-51.
Violante, V., A. Luongo, et al. (2001). "Transglutaminase-dependent formation of protein aggregates as possible biochemical mechanism for polyglutamine diseases." Brain Res Bull 56(3-4): 169-72.
Transglutaminases (Enzyme Commission 126.96.36.199) are a large family of enzymes that show the common capacity to catalyze cross-linking of protein substrates. Some members of this family of enzymes are also capable of catalyzing other reactions important for the cell life. The distribution and the role of these enzymes have been widely studied in numerous cell types and tissues, but only recently their expression and functions started to be investigated in the central nervous system. One of the main biochemical properties of the transglutaminase enzymes is to form large protein aggregates that are insoluble in all known protein detergents, such as urea, guanidinium, and sodium dodecyl sulfate. Recently, the transglutaminase activity has been hypothesized to be involved in the pathogenetic mechanisms responsible for the formation of cellular inclusions present in Huntington disease and in all the other polyglutamine (polyQ) diseases hitherto identified, such as spinobulbar muscular atrophy or Kennedy disease, spinocerebellar ataxias (SCA-1, SCA-2, SCA-3 or Machado-Joseph disease, SCA-6 and SCA-7) and dentatorubropallidoluysian atrophy. In this review we describe the biochemical properties of the transglutaminase enzymes and some recent findings about the physiopathological roles played by these enzymes in the central nervous system.