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Biomedical subjects

C Warren Olanow

Publications and source records attributed to C Warren Olanow.

At least 55 records · Page 3Linked to original sources
PubMed2004

Unilateral stimulation of the subthalamic nucleus in Parkinson disease: a double-blind 12-month evaluation study.

OBJECT: Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been established as an effective treatment for Parkinson disease (PD). Nevertheless, bilateral surgical procedures can be associated with frequent and severe complications. The aim in the present study was to assess the safety and efficacy of unilateral STN stimulation, and the need for a second procedure. METHODS: Twelve patients with PD underwent unilateral DBS of the STN and were followed up for 12 months. Patients were assessed at baseline and at each visit in a double-blind fashion by analyzing the Unified PD Rating Scale (UPDRS), ambulation speed, and home diaries. Levodopa-off/stimulation-on UPDRS motor scores were improved by 26 +/- 8% (p < 0.05, mean +/- standard deviation [SD]) compared with the baseline levodopa-off score; there was a 50% improvement in contralateral features, a 17% improvement ipsilaterally, and a 36% improvement in axial features. The mean ambulation speed increased by 83 +/- 44% (p < 0.01, mean +/- SD). The medication-on time with dyskinesias was significantly reduced (p < 0.01) and the daily levodopa dose was reduced by 19 +/- 6% (p < 0.05, mean +/- SD). There were no clinically significant side effects. CONCLUSIONS: Unilateral DBS of the STN is safe and well tolerated, and may provide sufficient benefit so that additional surgery is not required.

Adult↗
PubMed2003

Activation of phosphoinositide 3-kinase by D2 receptor prevents apoptosis in dopaminergic cell lines.

Whereas dopamine agonists are known to provide symptomatic benefits for Parkinson's disease, recent clinical trials suggest that they might also be neuroprotective. Laboratory studies demonstrate that dopamine agonists can provide neuroprotective effects in a number of model systems, but the role of receptor-mediated signalling in these effects is controversial. We find that dopamine agonists have robust, concentration-dependent anti-apoptotic activity in PC12 cells that stably express human D(2L) receptors from cell death due to H(2)O(2) or trophic withdrawal and that the protective effects are abolished in the presence of D(2)-receptor antagonists. D(2) agonists are also neuroprotective in the nigral dopamine cell line SN4741, which express endogenous D(2) receptors, whereas no anti-apoptotic activity is observed in native PC12 cells, which do not express detectable D(2) receptors. Notably, the agonists studied differ in their relative efficacy to mediate anti-apoptotic effects and in their capacity to stimulate [(35)S]guanosine 5'-[gamma-thio]triphosphate ([(35)S]GTP[S]) binding, an indicator of G-protein activation. Studies with inhibitors of phosphoinositide 3-kinase (PI 3-kinase), extracellular-signal-regulated kinase or p38 mitogen-activated protein kinase indicate that the PI 3-kinase pathway is required for D(2) receptor-mediated cell survival. These studies indicate that certain dopamine agonists can complex with D(2) receptors to preferentially transactivate neuroprotective signalling pathways and to mediate increased cell survival.

1-Phosphatidylinositol 4-Kinase↗
PubMed2003

Neuroprotection in Parkinson's disease: clinical trials.

Advances in our understanding of the cause and pathogenesis of Parkinson's disease (PD) have permitted the rational selection of putative neuroprotective agents for study in PD. However, the list of agents that might provide neuroprotective effects derived from laboratory studies is daunting, and we face the challenge of determining which agents to bring to the clinic and how to find the resources (patients and funds) to properly study so many promising therapeutic opportunities.1 Appropriate outcome variables that are not confounded by any symptomatic effect of the drug and are acceptable to clinicians and regulatory authorities also remain to be defined. The first clinical trials designed to test the capacity of putative neuroprotective agents to alter the natural history of PD have now been performed and illustrate some of these problems. The DATATOP (Deprenyl and Tocopherol Antioxidant Therapy of PD) study used the time to reach a disease milestone in untreated PD patients (ie, need for levodopa) as the primary end point. However, interpretation of results was confounded by the drug's symptomatic effect. The SINDEPAR (Sinemet-Deprenyl-Parlodel) study used the change in motor score between initial visit and final visit after washout of all study medications as the primary end point. However, here too there were concerns about confounding symptomatic effects, because antiparkinsonian medications have now been shown to have a long duration response that can persist for weeks and perhaps even months after withdrawal. More recent studies have used surrogate markers of the integrity of nigrostriatal function such as striatal uptake of fluorodopa on positron emission tomography (PET) or beta-CIT-on single-photon emission computerized tomography (SPECT) as primary outcome measures. However, it has not yet been confirmed that striatal uptake of these isotopes does in fact correlate with the remaining number of dopamine neurons or terminals, and the possibility of a confounding pharmacological effect has not yet been completely excluded. To date, no drug has been established to have a neuroprotective effect in PD, and none has been approved for a neuroprotective indication. Furthermore, regulatory agencies have not yet agreed that any of the outcome measures currently used will be acceptable for approval of a new drug. Resolution of these issues is of critical importance to convince pharmaceutical companies to expend the hundreds of millions of dollars necessary to bring a new drug to market. Drugs that already have been approved in PD for their symptomatic effects, such as dopamine agonists or propargylamines (eg, selegiline), offer the best opportunity for establishing that a drug is neuroprotective in PD in the immediate future, but herein also lies the difficulty of establishing that any benefits observed are not solely because of the drug's symptomatic properties. Currently, this will most likely entail demonstrating that the drug provides benefit for PD patients for both imaging and clinical markers of disease progression.

Clinical Trials as Topic↗
PubMed2003

Proteolytic stress: a unifying concept for the etiopathogenesis of Parkinson's disease.

The etiopathogenesis of Parkinson's disease (PD) has been elusive. Recently, several lines of evidence have converged to suggest that defects in the ubiquitin-proteasome system and proteolytic stress underlie nigral pathology in both familial and sporadic forms of the illness. In support of this concept, mutations in alpha-synuclein that cause the protein to misfold and resist proteasomal degradation cause familial PD. Similarly, mutations in two enzymes involved in the normal function of the ubiquitin-proteasome system, parkin and ubiquitin C-terminal hydrolase L1, are also associated with hereditary PD. Furthermore, structural and function defects in 26/20S proteasomes with accumulation and aggregation of potentially cytotoxic abnormal proteins have been identified in the substantia nigra pars compacta of patients with sporadic PD. Thus, a defect in protein handling appears to be a common factor in sporadic and the various familial forms of PD. This hypothesis may also account for the vulnerability of the substantia nigra pars compacta in PD, why the disorder is age related, and the nature of the Lewy body. It has also facilitated the development of experimental models that recapitulate the behavioral and pathological features of PD, and hopefully will lead to the development of novel neuroprotective therapies for the disorder.

Cysteine Endopeptidases↗
PubMed2003

A double-blind controlled trial of bilateral fetal nigral transplantation in Parkinson's disease.

Thirty-four patients with advanced Parkinson's disease participated in a prospective 24-month double-blind, placebo-controlled trial of fetal nigral transplantation. Patients were randomized to receive bilateral transplantation with one or four donors per side or a placebo procedure. The primary end point was change between baseline and final visits in motor component of the Unified Parkinson's Disease Rating Scale in the practically defined off state. There was no significant overall treatment effect (p = 0.244). Patients in the placebo and one-donor groups deteriorated by 9.4 +/- 4.25 and 3.5 +/- 4.23 points, respectively, whereas those in the four-donor group improved by 0.72 +/- 4.05 points. Pairwise comparisons were not significant, although the four-donor versus placebo groups yielded a p value of 0.096. Stratification based on disease severity showed a treatment effect in milder patients (p = 0.006). Striatal fluorodopa uptake was significantly increased after transplantation in both groups and robust survival of dopamine neurons was observed at postmortem examination. Fifty-six percent of transplanted patients developed dyskinesia that persisted after overnight withdrawal of dopaminergic medication ("off"-medication dyskinesia). Fetal nigral transplantation currently cannot be recommended as a therapy for PD based on these results.

Adult↗
PubMed2003

Sleepiness in Parkinson's disease: a controlled study.

Sudden-onset sleep episodes while driving have been reported in Parkinson's disease (PD) patients, and termed sleep attacks because they were reported to be irresistible and to occur without warning. We postulate that these episodes are due to excessive daytime sleepiness secondary to the high frequency of sleep disorders in PD patients and the sedative effects of dopaminergic medications. We assessed the frequency and relationship between excess daytime sleepiness and sleep episodes while driving (SE) in patients with PD. We evaluated 101 consecutive PD patients presenting to the Movement Disorder Center at the Mount Sinai School of Medicine using a questionnaire that incorporated a subjective estimate of sleepiness, the Epworth Sleepiness Scale (ESS) and information on disease severity and dopaminergic medications. One hundred age-matched respondents without PD served as a control population. Excess daytime sleepiness was reported in 76% of PD patients compared to 47% of controls (P < 0.05). The mean ESS scores for PD patients was 9.1 +/- 6.1 versus 5.7 +/- 4.4 in controls (P < 0.001). ESS scores > or =10 were observed in 40.6% of PD patients compared to 19% of controls (P < 0.01) and 24% of PD patients had scores > or =15, compared to 5% of controls (P < 0.001). Sleep episodes while driving were experienced by 20.8% of PD drivers compared to 6% of control drivers (P < 0.05). The mean daily levodopa (L-dopa) dose equivalent was 1,142 +/- 858 mg in PD drivers who experienced a SE while driving compared to 626 +/- 667 mg in those who had not (P < 0.05). Similarly, ESS was significantly greater in drivers with a SE than in those without (11.6 +/- 6.4 vs. 8.4 +/- 4.1; P < 0.05). Logistic regression analysis demonstrated that ESS and mean daily L-dopa dose equivalents were predictors of sleep episodes while driving, whereas age, gender, disease severity, and individual dopaminergic agents were not. These findings support the notion that sleep episodes while driving in PD patients are related to excess daytime sleepiness and dopaminergic load. Physicians should advise and treat patients accordingly.

Adult↗
PubMed2003

Altered proteasomal function in sporadic Parkinson's disease.

Parkinson's disease (PD) is characterized pathologically by preferential degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNc). Nigral cell death is accompanied by the accumulation of a wide range of poorly degraded proteins and the formation of proteinaceous inclusions (Lewy bodies) in dopaminergic neurons. Mutations in the genes encoding alpha-synuclein and two enzymes of the ubiquitin-proteasome system, parkin and ubiquitin C-terminal hydrolase L1, are associated with neurodegeneration in some familial forms of PD. We now show that, in comparison to age-matched controls, alpha-subunits (but not beta-subunits) of 26/20S proteasomes are lost within dopaminergic neurons and 20S proteasomal enzymatic activities are impaired in the SNc in sporadic PD. In addition, while the levels of the PA700 proteasome activator are reduced in the SNc in PD, PA700 expression is increased in other brain regions such as the frontal cortex and striatum. We also found that levels of the PA28 proteasome activator are very low to almost undetectable in the SNc compared to other brain areas in both normal and PD subjects. These findings suggest that failure of the ubiquitin-proteasome system to adequately clear unwanted proteins may underlie vulnerability and degeneration of the SNc in both sporadic and familial PD.

Aged↗
PubMed2003

Assessment of sleepiness and unintended sleep in Parkinson's disease patients taking dopamine agonists.

OBJECTIVE: We sought to determine if patients with Parkinson's disease (PD), taking dopamine agonists (DAs) and reporting unintended sleep episodes (SEs), exhibit physiologically defined daytime sleepiness and can thus be differentiated from those taking DAs but not reporting SEs. METHODS: Twenty-four patients with abnormal Epworth Sleepiness Scale scores of >10 who were taking DAs were enrolled into one of two groups: those with SEs (SE+, n=16) and those without (SE-, n=8). Three consecutive days of testing included two nights of polysomnography followed by the Multiple Sleep Latency Test (MSLT). RESULTS: Overall frequency of pathological sleepiness (MSLT <5 min) was 42% (10/24). Mean levels of sleepiness, frequencies of pathological sleepiness, and naps with stage 2 or REM-sleep were similar between SE+ and SE- groups. Sleep tendency was similar in patients prescribed pergolide, ropinirole, and pramipexole combined with levodopa. Polysomnography testing revealed no significant differences between the groups in total sleep time, sleep efficiency, sleep architecture, or presence of restless legs syndrome or periodic leg movements. There was no relation between degree of nocturnal sleep disturbance and level of daytime sleepiness. CONCLUSIONS: The results of this study suggest SEs in PD patients occur upon a background of excessive daytime sleepiness and are unrelated to nocturnal sleep or use of a specific DA.

Circadian Rhythm↗
PubMed2003

Levodopa is toxic to dopamine neurons in an in vitro but not an in vivo model of oxidative stress.

Levodopa is the "gold standard" for the symptomatic treatment of Parkinson's disease (PD). There is a theoretical concern, however, that levodopa might accelerate the rate of nigral degeneration, because it undergoes oxidative metabolism and is toxic to cultured dopaminergic neurons. Most in vivo studies do not show evidence of levodopa toxicity; levodopa is not toxic to normal rodents, nonhuman primates, or humans and is not toxic to dopamine neurons in dopamine-lesioned rodents or nonhuman primates in most studies. However, the potential for levodopa to be toxic in vivo has not been tested under conditions of oxidative stress such as exist in PD. To assess whether levodopa is toxic under these circumstances, we have examined the effects of levodopa on dopamine neurons in mesencephalic cultures and rat pups in which glutathione synthesis has been inhibited by L-buthionine sulfoximine. Levodopa toxicity to cultured dopaminergic neurons was enhanced by glutathione depletion and diminished by antioxidants. In contrast, treatment of neonatal rats with levodopa, administered either alone or in combination with glutathione depletion, did not cause damage to the dopamine neurons of the substantia nigra or changes in striatal levels of dopamine and its metabolites. This study provides further evidence to support the notion that although levodopa can be toxic to dopamine neurons in vitro, it is not likely to be toxic to dopamine neurons in vivo and specifically in conditions such as PD.

Animals↗
PubMed2002

Proteasome inhibition causes nigral degeneration with inclusion bodies in rats.

Structural and functional defects in 26/20S proteasomes occur in the substantia nigra pars compacta and may underlie protein accumulation, Lewy body formation and dopaminergic neuronal death in Parkinson's disease. We therefore determined the pathogenicity of proteasomal impairment following stereotaxic unilateral infusion of lactacystin, a selective proteasome inhibitor, into the substantia nigra pars compacta of rats. These animals became progressively bradykinetic, adopted a stooped posture and displayed contralateral head tilting. Administration of apomorphine to lactacystin-treated rats reversed behavioral abnormalities and induced contralateral rotations. Lactacystin caused dose-dependent degeneration of dopaminergic cell bodies and processes with the cytoplasmic accumulation and aggregation of alpha-synuclein to form inclusion bodies. These findings support the notion that failure of the ubiquitin-proteasome system to degrade and clear unwanted proteins is an important etiopathogenic factor in Parkinson's disease.

Acetylcysteine↗
PubMed2002

Selective loss of 20S proteasome alpha-subunits in the substantia nigra pars compacta in Parkinson's disease.

The proteolytic activities of 26/20S proteasomes are impaired in the substantia nigra pars compacta (SNc) in sporadic Parkinson's disease (PD). In the present study, we examined the structural integrity of the proteasome by determining the levels of the beta- and alpha-subunits which together normally constitute the catalytic core of 26/20S proteasomes. Western blot analyzes and immunohistochemical staining revealed a major and selective loss of alpha-subunits in dopaminergic neurons of the SNc but not in other brain regions in sporadic PD. This defect is known to cause the proteasome to become unstable and prevents its assembly with resultant impairment of enzymatic activity. Thus, structural and function defects in 26/20S proteasomes may underlie protein accumulation, formation of proteinaceous Lewy bodies and dopaminergic neuronal death in the SNc in sporadic PD.

Aged↗
PubMed2002

The role of dopamine agonists in the treatment of early Parkinson's disease.

Levodopa is the gold standard for the symptomatic treatment of Parkinson's disease (PD). However, chronic treatment is associated with development of motor complications in the majority of patients. Recent laboratory studies suggest that pulsatile administration of a short-acting agent, such as levodopa, contributes to the development of these problems and that they might be mitigated through the use of longer-acting dopamine agonists. Placebo-controlled clinical trials have shown that dopamine agonists have anti-parkinsonian effects in patients with early PD. More importantly, four different prospective double-blind studies have demonstrated that initiating symptomatic therapy with a dopamine agonist is associated with a significantly reduced risk for development of motor complications than is initial treatment with a dopamine agonist. Furthermore, several lines of laboratory research suggest that dopamine agonists might protect dopaminergic neurons in PD and retard the rate of disease progression. Double-blind trials using clinical and imaging end points are now testing this hypothesis and the results should soon be available. On the basis of this evidence, a rational approach to the treatment of PD patients who are not elderly or cognitively impaired is to initiate therapy with a dopamine agonist and supplement with levodopa when dopamine agonist monotherapy can no longer provide satisfactory clinical control.

Animals↗
PubMed2002

Impact of sustained deprenyl (selegiline) in levodopa-treated Parkinson's disease: a randomized placebo-controlled extension of the deprenyl and tocopherol antioxidative therapy of parkinsonism trial.

Deprenyl (selegiline) delays the need for levodopa therapy in patients with early Parkinson's disease, but the long-term benefits of this treatment remain unclear. During 1987 to 1988, 800 patients with early Parkinson's disease were randomized in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism trial to receive deprenyl, tocopherol, combined treatments, or a placebo and were then placed on active deprenyl (10mg/day). A second, independent randomization was carried out in early 1993 for 368 subjects who by that time had required levodopa and who had consented to continuing the deprenyl treatment (D subjects) or changing to a matching placebo (P subjects) under double-blind conditions. The first development of wearing off, dyskinesias, or on-off motor fluctuations was the prespecified primary outcome measure. During the average 2-year follow-up, there were no differences between the treatment groups with respect to the primary outcome measure (hazard ratio, 0.87; 95% confidence interval, 0.63, 1.19; p = 0.38), withdrawal from the study, death, or adverse events. Although 34% of D subjects developed dyskinesias and only 19% of P subjects did (p = 0.006), only 16% of D subjects developed freezing of gait but 29% of P subjects did (p = 0.0003). Decline in motor performance was less in D subjects than P subjects. Levodopa-treated Parkinson's disease patients who had been treated with deprenyl for up to 7 years, compared with patients who were changed to a placebo after about 5 years, experienced slower motor decline and were more likely to develop dyskinesias but less likely to develop freezing of gait.

Aged↗
PubMed2002

Aggresome-related biogenesis of Lewy bodies.

Neurodegenerative disorders such as Parkinson's disease (PD) and 'dementia with Lewy bodies' (DLB) are characterized pathologically by selective neuronal death and the appearance of intracytoplasmic protein aggregates (Lewy bodies). The process by which these inclusions are formed and their role in the neurodegenerative process remain elusive. In this study, we demonstrate a close relationship between Lewy bodies and aggresomes, which are cytoplasmic inclusions formed at the centrosome as a cytoprotective response to sequester and degrade excess levels of potentially toxic abnormal proteins within cells. We show that the centrosome/aggresome-related proteins gamma-tubulin and pericentrin display an aggresome-like distribution in Lewy bodies in PD and DLB. Lewy bodies also sequester the ubiquitin-activating enzyme (E1), the proteasome activators PA700 and PA28, and HSP70, all of which are recruited to aggresomes for enhanced proteolysis. Using novel antibodies that are specific and highly sensitive to ubiquitin-protein conjugates, we revealed the presence of numerous discrete ubiquitinated protein aggregates in neuronal soma and processes in PD and DLB. These aggregates appear to be being transported from peripheral sites to the centrosome where they are sequestered to form Lewy bodies in neurons. Finally, we have shown that inhibition of proteasomal function or generation of misfolded proteins cause the formation of aggresome/Lewy body-like inclusions and cytotoxicity in dopaminergic neurons in culture. These observations suggest that Lewy body formation may be an aggresome-related event in response to increasing levels of abnormal proteins in neurons. This phenomenon is consistent with growing evidence that altered protein handling underlies the etiopathogenesis of PD and related disorders.

Acetylcysteine↗