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Biomedical subjects

Anthony H V Schapira

Publications and source records attributed to Anthony H V Schapira.

At least 19 recordsLinked to original sources
PubMed2006

Mitochondrial disease.

Defects of mitochondrial metabolism cause a wide range of human diseases that include examples from all medical subspecialties. This review updates the topic of mitochondrial diseases by reviewing the most important recent advances in this area. The factors influencing inheritance, maintenance and replication of mtDNA are reviewed and the genotype-phenotype of mtDNA disorders has been expanded, with new insights into epidemiology, pathogenesis and its role in ageing. Recently identified nuclear gene mutations of mitochondrial proteins include mutations of frataxin causing Friedreich's ataxia, PINK1, DJ1 causing Parkinson's disease and POLG causing infantile mtDNA depletion syndrome, ophthalmoplegia, parkinsonism, male subfertility and, in a transgenic mouse model, premature senescence. Mitochondrial defects in neurodegenerative diseases include Parkinson's, Alzheimer's and Huntington's disease. Improved understanding of mtDNA inheritance and mutation penetrance patterns, and novel techniques for mtDNA modification offer significant prospects for more accurate genetic counselling and effective future therapies.

Animals↗
PubMed2006

Etiology of Parkinson's disease.

The etiology of Parkinson's disease (PD) has long been thought to involve both genetic and environmental factors, but until recently there has been no direct evidence to support either one as a causative factor. However, in the past 8 years six different genes have been identified as causing familial PD. Together, they support the notion that common pathogenetic mechanisms exist across the etiologic spectrum of PD. Specifically, mutations in alpha-synuclein, parkin, UCHL1, DJ1, PINK1, and LRRK2 cause PD, with a Mendelian pattern of inheritance. DJ1 and PINK1 are mitochondrial proteins and overexpression of alpha-synuclein and parkin induce mitochondrial defects. These same proteins are involved in the response to oxidative stress and affect proteasomal function. In contrast, few environmental factors have been characterized. Nevertheless, those toxins that have been demonstrated to have the ability to cause nigrostriatal cell death appear to interact by interfering with mitochondrial function, inducing oxidative stress, and modifying proteasomal function. Therefore, common themes are beginning to emerge in the etiopathogenesis of PD. This bodes well for research focused on the development of treatments that will modify the course of PD.

Brain↗
PubMed2006

Proteasomal inhibition causes loss of nigral tyrosine hydroxylase neurons.

Dysfunction of the ubiquitin-proteasomal system (UPS) has been implicated in the pathogenesis of Parkinson's disease. The systemic administration of UPS inhibitors has been reported to induce nigrostriatal cell death and model Parkinson's disease pathology in rodents. We administered a synthetic, specific UPS inhibitor (PSI) subcutaneously to rats and quantified substantia nigral tyrosine hydroxylase-positive dopaminergic neurons by stereology. PSI caused a 15% decrease in UPS activity at 2 weeks and a 42% reduction in substantia nigra pars compacta tyrosine hydroxylase-positive neurons at 8 weeks. Systemic inhibition of the UPS warrants further evaluation as a means to model Parkinson's disease.

Animals↗
PubMed2006

International multicenter pilot study of the first comprehensive self-completed nonmotor symptoms questionnaire for Parkinson's disease: the NMSQuest study.

Nonmotor symptoms (NMS) of Parkinson's disease (PD) are not well recognized in clinical practice, either in primary or in secondary care, and are frequently missed during routine consultations. There is no single instrument (questionnaire or scale) that enables a comprehensive assessment of the range of NMS in PD both for the identification of problems and for the measurement of outcome. Against this background, a multidisciplinary group of experts, including patient group representatives, has developed an NMS screening questionnaire comprising 30 items. This instrument does not provide an overall score of disability and is not a graded or rating instrument. Instead, it is a screening tool designed to draw attention to the presence of NMS and initiate further investigation. In this article, we present the results from an international pilot study assessing feasibility, validity, and acceptability of a nonmotor questionnaire (NMSQuest). Data from 123 PD patients and 96 controls were analyzed. NMS were highly significantly more prevalent in PD compared to controls (PD NMS, median = 9.0, mean = 9.5 vs. control NMS, median = 5.5, mean = 4.0; Mann-Whitney, Kruskal-Wallis, and t test, P < 0.0001), with PD patients reporting at least 10 different NMS on average per patient. In PD, NMS were highly significantly more prevalent across all disease stages and the number of symptoms correlated significantly with advancing disease and duration of disease. Furthermore, frequently, problems such as diplopia, dribbling, apathy, blues, taste and smell problems were never previously disclosed to the health professionals.

Aged↗
PubMed2006

Coordinating outcomes measurement in ataxia research: do some widely used generic rating scales tick the boxes?

The objective of this study was to examine the psychometric properties of four widely used generic health status measures in Friedreich's ataxia (FA), to determine their suitability as outcome measures. Fifty-six people with genetically confirmed FA completed the Barthel Index (BI), General Health Questionnaire (GHQ-12), EuroQol (EQ-5D), and Medical Outcomes Study 36-item Short Form Health Survey (SF-36) by means of postal survey. Six psychometric properties (data quality, scaling assumptions, acceptability, reliability, validity, and responsiveness) were examined. The response rate was 97%. In general, the psychometric properties of the four measures satisfied recommended criteria. However, closer examination highlighted limitations restricting their use for treatment trials. For example, the BI had high levels of missing data, EQ-5D had poor discriminant ability, and five SF-36 scales had high floor and/or ceiling effects. Most scale scores did not span the entire scale range, had means that differed notably from the scale mid-point, and had wide confidence intervals. Effect sizes (ES) were small for all four measures raising questions about their ability to detect clinically significant change. Results highlight the potential limitations of these four scales for evaluating health outcomes in FA and suggest the need for new disease-specific patient-based measures of its impact.

Activities of Daily Living↗
PubMed2006

Non-motor symptoms of Parkinson's disease: diagnosis and management.

The clinical diagnosis of Parkinson's disease rests on the identification of the characteristics related to dopamine deficiency that are a consequence of degeneration of the substantia nigra pars compacta. However, non-dopaminergic and non-motor symptoms are sometimes present before diagnosis and almost inevitably emerge with disease progression. Indeed, non-motor symptoms dominate the clinical picture of advanced Parkinson's disease and contribute to severe disability, impaired quality of life, and shortened life expectancy. By contrast with the dopaminergic symptoms of the disease, for which treatment is available, non-motor symptoms are often poorly recognised and inadequately treated. However, attention is now being focused on the recognition and quantitation of non-motor symptoms, which will form the basis of improved treatments. Some non-motor symptoms, including depression, constipation, pain, genitourinary problems, and sleep disorders, can be improved with available treatments. Other non-motor symptoms can be more refractory and need the introduction of novel non-dopaminergic drugs. Inevitably, the development of treatments that can slow or prevent the progression of Parkinson's disease and its multicentric neurodegeneration provides the best hope of curing non-motor symptoms.

Autonomic Nervous System Diseases↗
PubMed2006

TCH346 as a neuroprotective drug in Parkinson's disease: a double-blind, randomised, controlled trial.

BACKGROUND: There is an important unmet medical need in Parkinson's disease for a neuroprotective treatment that slows or stops disease progression. TCH346 is a potent anti-apoptotic drug that protects against loss of dopaminergic neurons in laboratory models. Our aim was to assess TCH346 as a neuroprotective drug in patients with Parkinson's disease. METHODS: Patients presenting at 45 international movement disorder clinics with early untreated Parkinson's disease were assessed as part of this parallel-group, double-blind, randomised controlled trial. 301 eligible patients were randomly assigned 12-18 months' treatment with TCH346 at a daily dose of 0.5 mg (n=78), 2.5 mg (n=79), or 10 mg (n=73), or placebo (n=71), followed by a 4 week washout period. The primary outcome measure was time to development of a disability requiring dopaminergic treatment. Secondary outcome measures were the annual rate of change in the unified Parkinson's disease rating scale (UPDRS) and the PDQ-39, a measure of quality of life. Analyses were by intention-to-treat. This study is pending registration with . FINDINGS: 255 patients completed the study. TCH346 did not differ from placebo for any of the study outcomes. Treatment was needed in 26 (34%) patients in the TCH346 0.5 mg group, 30 (38%) in the TCH346 2.5 mg group, 24 (33%) in the TCH346 10 mg group, and 23 (32%) in the placebo group. There were no significant differences between groups. There were no differences between groups in the annual change in the UPDRS or PDQ-39 either. Few patients withdrew because of adverse events and none was judged to be related to the study intervention. INTERPRETATION: TCH346 did not show evidence of a neuroprotective effect. The discrepancy between the preclinical promise of TCH346 and the clinical outcome could have arisen because of the use of laboratory models that do not accurately reflect the pathogenesis of Parkinson's disease, the doses of study drug used, insensitive clinical endpoints, and the patient population selected for study.

Adult↗
PubMed2006

Novel pharmacological targets for the treatment of Parkinson's disease.

Dopamine deficiency, caused by the degeneration of nigrostriatal dopaminergic neurons, is the cause of the major clinical motor symptoms of Parkinson's disease. These symptoms can be treated successfully with a range of drugs that include levodopa, inhibitors of the enzymatic breakdown of levodopa and dopamine agonists delivered by oral, subcutaneous, transcutaneous, intravenous or intra-duodenal routes. However, Parkinson's disease involves degeneration of non-dopaminergic neurons and the treatment of the resulting predominantly non-motor features remains a challenge. This review describes the important recent advances that underlie the development of novel dopaminergic and non-dopaminergic drugs for Parkinson's disease, and also for the motor complications that arise from the use of existing therapies.

Adenosine A2 Receptor Antagonists↗
PubMed2005

Isolation of transcriptomal changes attributable to LHON mutations and the cybridization process.

Leber's hereditary optic neuropathy (LHON) is thought to be the most common disease resulting from mitochondrial DNA (mtDNA) point mutations, and transmitochondrial cytoplasmic hybrid (cybrid) cell lines are the most frequently used model for understanding the pathogenesis of mitochondrial disorders. We have used oligonucleotide microarrays and a novel study design based on shared transcripts to allocate transcriptomal changes into rho-zero-dependent, cybridization-dependent and LHON-dependent categories in these cells. The analysis indicates that the rho-zero process has the largest transcriptomal impact, followed by the cybridization process, and finally the LHON mutations. The transcriptomal impacts of the rho-zero and cybridization processes preferentially and significantly affect the mitochondrial compartment, causing upregulation of many transcripts involved in oxidative phosphorylation, presumably in response to the mtDNA depletion that occurs at the rho-zero step. Nine LHON-specific transcriptional alterations were shared among osteosarcoma cybrids and lymphoblasts bearing LHON mutations. Notably, the aldose reductase transcript was overexpressed in LHON cybrids and lymphoblasts. Aldose reductase is also overexpressed in diabetic retinopathy, leading to optic nerve and retinal complications. The LHON-specific increase in transcript level was confirmed by quantitative reverse transcription-polymerase chain reaction (RT-PCR), and a western blot confirmed a higher level of aldose reductase in mutant mitochondria. One product of aldose reductase is sorbitol, which has been linked to osmotic stress, oxidative stress and optic neuropathy, and sorbitol levels were increased in LHON cybrids. If these results are confirmed in patient tissues, aldose reductase inhibitors could have some therapeutic value for LHON.

Aldehyde Reductase↗
PubMed2005

Antioxidant treatment of patients with Friedreich ataxia: four-year follow-up.

BACKGROUND: Decreased mitochondrial respiratory chain function and increased oxidative stress have been implicated in the pathogenesis of Friedreich ataxia (FRDA), raising the possibility that energy enhancement and antioxidant therapies may be an effective treatment. OBJECTIVE: To evaluate the long-term efficacy of a combined antioxidant and mitochondrial enhancement therapy on the bioenergetics and clinical course of FRDA. DESIGN: Open-labeled pilot trial over 47 months.Patients Seventy-seven patients with clinical and genetically defined FRDA. Intervention A combined coenzyme Q(10) (400 mg/d) and vitamin E (2100 IU/d) therapy of 10 patients with FRDA over 47 months. MAIN OUTCOME MEASURES: Clinical assessment using echocardiography and the International Cooperative Ataxia Rating Scale and cardiac and skeletal muscle bioenergetics as assessed using phosphorus P 31 magnetic resonance spectroscopy. RESULTS: There was a significant improvement in cardiac and skeletal muscle bioenergetics that was maintained throughout the 47 months of therapy. Echocardiographic data revealed significantly increased fractional shortening at the 35- and 47-month time points. Comparison with cross-sectional data from 77 patients with FRDA indicated the changes in total International Cooperative Ataxia Rating Scale and kinetic scores over the trial period were better than predicted for 7 patients, but the posture and gait and hand dexterity scores progressed as predicted. CONCLUSION: This therapy resulted in sustained improvement in mitochondrial energy synthesis that was associated with a slowing of the progression of certain clinical features and a significant improvement in cardiac function.

Adolescent↗
PubMed2005

Severe impairment of complex I-driven adenosine triphosphate synthesis in leber hereditary optic neuropathy cybrids.

BACKGROUND: Leber hereditary optic neuropathy (LHON) is a maternally inherited form of central vision loss associated with mitochondrial DNA point mutations that affect the ND subunits of complex I. OBJECTIVE: To elucidate the bioenergetic consequences of complex I dysfunction in LHON. DESIGN: The biochemical phenotypes of LHON mutations have been investigated using the transmitochondrial cytoplasmic hybrid (cybrid) cell model derived from the osteocarcoma parental cell line 143B.TK-. SETTING: Research laboratories at neuroscience and biochemistry departments at the University of Bologna, Scientific Institute "E. Medea," and University of College Medical School. PARTICIPANTS: Fibroblast cell lines were obtained from patients affected with LHON, as defined by the presence of 1 pathogenic mutation, and from healthy volunteers as controls to construct cybrid cell lines. MAIN OUTCOME MEASURES: Complex I (glutamate-malate)- and complex II (succinate)-dependent adenosine triphosphate (ATP) synthesis, their respective respiratory rates, and total cellular ATP content were investigated using digitonin permeabilized cybrid cells. Multiple cybrid cell lines were constructed, introducing into osteosarcoma-derived rho(0) cells either wild-type or LHON mutant mitochondria carrying each of the 3 common mutations at positions 11778/ND4, 3460/ND1, and 14484/ND6. RESULTS: All 3 LHON mutations impaired ATP synthesis and the respiratory control ratio driven by complex I substrates. In contrast, succinate-driven ATP synthesis, respiration rates, and respiratory control ratios were not affected. However, the defective ATP synthesis with complex I substrates did not result in reduced ATP cellular content, indicating a compensatory mechanism. CONCLUSIONS: The LHON pathogenic mutations profoundly impair complex I-dependent synthesis of ATP, providing a common biochemical feature that may play a major role in LHON pathogenesis. Stratification of the results by mutation suggests that the 11778/ND4 mutation may induce an uncoupling of cybrid respiration, whereas the other 2 mutations impair the oxygen consumption rate.

Adenosine Triphosphate↗
PubMed2005

International Cooperative Ataxia Rating Scale (ICARS): appropriate for studies of Friedreich's ataxia?

Clinicians require scientifically rigorous, clinically meaningful rating scales to evaluate the health impact of disease and treatment that cannot be measured using conventional laboratory instruments. This study evaluated the psychometric properties of the International Cooperative Ataxia Rating Scale (ICARS), a commonly used clinician-rated measure, in Friedreich's ataxia (FRDA). People with confirmed FRDA were assessed by using the ICARS. Two assumptions of its measurement model were tested: the legitimacy of reporting ICARS scores in FRDA, and the acceptability, reliability, and validity of total and subscale scores. Seventy-seven people with FRDA were assessed. The ICARS total score effectively satisfied all psychometric criteria tested. The posture and gait disturbances subscale also performed well. The other three subscales did not pass standard criteria for tests of scaling assumptions, reliability, and validity. This small study recommends only the use of the ICARS total score as a measure of FRDA. However, the extent to which this score quantifies the true extent of FRDA remains uncertain as our validity testing was limited, partly by the lack of appropriate validating measures. Further validity testing, and examination of responsiveness, is required before the ICARS can be recommended as an outcome measure for treatment trials of FDRA.

Adolescent↗
PubMed2005

Assessment of the significance of mitochondrial DNA damage by chemotherapeutic agents.

The pathways which are activated following damage to nuclear DNA in cancer cells are well understood. There is evidence that treatment with several chemotherapeutic agents may result in damage to mitochondrial DNA. This study investigated the contribution of mitochondrial DNA to cytotoxicity of DNA-interactive agents. To understand the significance of drug interactions with mitochondrial DNA, we investigated A549 non-small cell lung cancer cell lines and their rho0 derivatives in which mitochondrial DNA has been eradicated. The parental cell line showed increased sensitivity to the anthracycline daunorubicin when compared with the A549 rho0 line. In addition, the A549 rho0 line was resistant to the rhodacyanine derivative, MKT-077, which has been shown to interact with mitochondrial DNA. Southern blotting demonstrated that MKT-077 mediated damage to mitochondrial but not nuclear DNA. Restoration of mitochondrial DNA by formation of cybrids restored sensitivity to these agents. The mitochondrial DNA damage, following treatment of A549 rho0 cells with MKT-077, resulted in G2 arrest which was not mediated by expression of p53. Mitochondrial DNA is a critical target for MKT-077 and daunorubicin, and is a potential target for novel chemotherapeutic agents.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2004

Analysis of the trinucleotide CAG repeat from the DNA polymerase gamma gene (POLG) in patients with Parkinson's disease.

The human gene for the catalytic subunit of the mitochondrial DNA (mtDNA) polymerase (POLG) contains a trinucleotide CAG repeat encoding a polyglutamine tract near the amino-terminus of the protein. Expansions of similar polyglutamine-encoding CAG microsatellite repeats in other genes are known to cause neurodegenerative disorders. As mitochondrial dysfunction has been implicated in the aetiology of Parkinson's disease, we determined the POLG CAG repeat length in DNA samples extracted from 22 idiopathic Parkinson's disease patients and 31 control subjects. The distribution of the POLG CAG repeat length in the control samples matched the distribution reported for control samples by others. Comparison between the CAG repeat length distribution of control and Parkinson's disease samples revealed no evidence of either germ line or somatic POLG CAG repeat instability in Parkinson's disease patients. Our results rule out POLG CAG repeat instability as a common pathogenic mechanism in idiopathic Parkinson's disease.

Adult↗
PubMed2004

Leber hereditary optic neuropathy mtDNA mutations disrupt glutamate transport in cybrid cell lines.

Leber hereditary optic neuropathy (LHON) is a maternally inherited form of retinal ganglion cell degeneration leading to optic atrophy which is caused by point mutations in the mitochondrial genome (mtDNA). Three pathogenic mutations (positions 11778/ND4, 3460/ND1 and 14484/ND6) account for the majority of LHON cases and they affect genes that encode for different subunits of mitochondrial complex I. Excitotoxic injury to retinal ganglion cells and the optic nerve has been previously hypothesized, especially given the high susceptibility of this neural cell type to glutamate toxicity. Osteosarcoma-derived cytoplasmic hybrids (cybrids) generated from six unrelated LHON patients, two cell lines for each pathogenic mutation, were compared with cybrids obtained from three healthy controls. Molecular and biochemical analyses showed that excitatory amino acid transporter 1 (EAAT1)/GLAST is the most active glutamate transporter in this cellular model. The glutamate uptake maximal velocity was significantly reduced in all LHON cybrids compared with control cybrids. This reduction was correlated in a mutation-specific fashion with the degree of mitochondrial production of reactive oxygen species, which is enhanced in LHON cybrids. Our findings support the hypothesis that the genetically determined mitochondrial dysfunction in LHON patients leads to impaired activity of the EAAT1 glutamate transporter. This observation is particularly relevant since EAAT1 is the major means of glutamate removal in the inner retina and this prevents retinal ganglion cells being damaged as a result of excitotoxicity.

Amino Acid Transport System X-AG↗
PubMed2004

Neuroprotection in Parkinson disease: mysteries, myths, and misconceptions.

Parkinson disease is an age-related neurodegenerative disease that affects approximately 1 million persons in the United States. Current therapies provide effective control of symptoms, particularly in the early stages of the disease, but most patients develop motor complications with long-term treatment, and features develop such as postural instability, falling, and dementia that are not adequately controlled with existing medications. Accordingly, neuroprotective therapy that might slow, stop, or reverse disease progression is urgently needed. While many agents appear to be promising based on laboratory studies, selecting clinical end points for clinical trials that are not confounded by symptomatic effects of the study intervention has been difficult. More recently, neuroimaging end points have been used as biomarkers of disease progression, but again there are concerns that they may be influenced by regulatory effects of the drugs used. We review clinical trials aimed at detecting neuroprotection in Parkinson disease and address the controversies surrounding the interpretation of these studies.

Antioxidants↗