The effects of levodopa therapy in patients with Parkinson's disease I. Clinical response

Eighty-eight patients with Parkinson''s disease were treated with levodopa. A group of elderly patients 65 years and older was compared with a second group under the age of 65, and it was found that generally the younger patients could be treated with greater success than the older ones. Most of the elderly could not tolerate the large doses required to produce optimal physical recovery. Severity of complications forced discontinuance of treatment in a larger percentage of elderly patients. The rate of complications was about equal in the two groups, except the incidence of confusion, which was significantly higher in the elderly. Of the two deaths that occurred, both were in the older group. Results of treatment were better in patients whose families gave positive support.     

Comparison of therapeutic effects and mortality data of levodopa and levodopa combined with selegiline in patients with early,mild Parkinson's disease. Parkinson's Disease Research Group of the United Kingdom.

OBJECTIVE: To compare effectiveness of levodopa and levodopa combined with selegiline in treating early, mild Parkinson''s disease. DESIGN: Open, long term, prospective randomised trial. SETTING: 93 hospitals throughout United Kingdom. SUBJECTS: 520 patients with early Parkinson''s disease who were not receiving dopaminergic treatment. INTERVENTIONS: Treatment with levodopa and dopa decarboxylase inhibitor (arm 1) or levodopa and decarboxylase inhibitor in combination with selegiline (arm 2). MAIN OUTCOME MEASURES: Assessments of serial disability, frequency and severity of adverse events, and deaths from all causes. RESULTS: After average of 5-6 years'' follow up, mortality ratio in arm 2 compared with arm 1 was 1.57 (95% confidence interval 1.09 to 2.30), and difference in survival between the two arms was significant (log rank test, P = 0.015). Hazard ratio adjusted for age and sex was 1.49 (1.02 to 2.16), and after adjustment for other baseline factors it increased to 1.57 (1.07 to 2.31). Patients in arm 1 had slightly worse disability scores than those in arm 2, but differences were not significant. Functionally disabling peak dose dyskinesias and on/off fluctuations were more frequent in arm 2 than arm 1. During the trial the dose of levodopa required to produce optimum motor control steadily increased in arm 1 (median daily dose 375 mg at 1 year and 625 mg at 4 years), but median dose in arm 2 did not change (375 mg). CONCLUSIONS: Levodopa in combination with selegiline seemed to confer no clinical benefit over levodopa alone in treating early, mild Parkinson''s disease. Moreover mortality was significantly higher with combination treatment, casting doubts on its chronic use in Parkinson''s disease.     

Effects of levodopa therapy in Parkinson's disease II. Measurement of behavioural changes

Forty-seven patients with Parkinson''s disease were evaluated prior to and during levodopa treatment (at five weeks and at six months), to obtain quantitative measures of the effects of the disease and of levodopa on a variety of cognitive and psychomotor functions, by means of psychological tests and special apparatus. Analysis of the findings in relation to a comparable control group shows that before treatment patients had impaired performance of all motor tasks, but no differences in cognitive functioning were found. Most motor functions had improved after five weeks on levodopa and this improvement was maintained at the six-month follow-up, but cognitive functions remained largely unchanged. The relationship between patients'' age, disability, duration of illness and drug tolerance is also discussed in relation to the functions measured.     

Comparison of endothelial progenitor cells in Parkinson's disease patients treated with levodopa and levodopa/COMT inhibitor

Background

Levodopa treatment in Parkinson''s disease (PD) increases in serum homocysteine levels due to its metabolism via catechol O-methyltransferase. Endothelial progenitor cells (EPCs) have the capacity to differentiate into mature endothelial cells and are markers for endothelial functions and cardiovascular risks. Along with traditional vascular risk factors, hyperhomocysteinemia is known to decrease the level of EPCs. In the present study, we hypothesized that that levodopa-induced hyperhomocysteinemia leads to a change in EPC levels.

Methodology/Principal Findings

We prospectively enrolled PD patients who had been prescribed either levodopa/carbidopa (PD-L group, n = 28) or levodopa/carbidopa/COMT inhibitor (PD-LC group, n = 25) for more than 1 year. The number of circulating EPCs was measured by flow cytometry using dual staining of anti-CD34 and anti-KDR antibodies. The EPCs were divided into tertiles based on their distributions and a logistic regression analysis was used to estimate independent predictors of the highest tertile of EPCs. The number of endothelial progenitor cells was significantly decreased in PD-L patients (118±99/mL) compared with either PD-LC patients (269±258/mL, p = 0.007) or controls (206±204/mL, p = 0.012). The level of homocysteine was significantly increased in PD-L patients (14.9±5.3 µmol/L) compared with either PD-LC patients (11.9±3.0 µmol/L, p = 0.028) or controls (11.1±2.5 µmol/L, p = 0.012). The level of homocysteine was negatively correlated with endothelial progenitor cell levels (r = −0.252, p = 0.028) and was an independent predictor of the highest tertile of endothelial progenitor cell levels (OR; 0.749 [95% CI: 0.584–0.961]).

Conclusions/Significance

These data indicate that a higher consumption of EPC for restoration of endothelial damage may be associated with chronic levodopa treatment in PD patients.     

Modulation of habit formation by levodopa in Parkinson's disease

Dopamine promotes the execution of positively reinforced actions, but its role for the formation of behaviour when feedback is unavailable remains open. To study this issue, the performance of treated/untreated patients with Parkinson's disease and controls was analysed in an implicit learning task, hypothesising dopamine-dependent adherence to hidden task rules. Sixteen patients on/off levodopa and fourteen healthy subjects engaged in a Go/NoGo paradigm comprising four equiprobable stimuli. One of the stimuli was defined as target which was first consistently preceded by one of the three non-target stimuli (conditioning), whereas this coupling was dissolved thereafter (deconditioning). Two task versions were presented: in a 'Go version', only the target cue required the execution of a button press, whereas non-target stimuli were not instructive of a response; in a 'NoGo version', only the target cue demanded the inhibition of the button press which was demanded upon any non-target stimulus. Levodopa influenced in which task version errors grew from conditioning to deconditioning: in unmedicated patients just as controls errors only rose in the NoGo version with an increase of incorrect responses to target cues. Contrarily, in medicated patients errors went up only in the Go version with an increase of response omissions to target cues. The error increases during deconditioning can be understood as a perpetuation of reaction tendencies acquired during conditioning. The levodopa-mediated modulation of this carry-over effect suggests that dopamine supports habit conditioning under the task demand of response execution, but dampens it when inhibition is required. However, other than in reinforcement learning, supporting dopaminergic actions referred to the most frequent, i. e., non-target behaviour. Since this is passive whenever selective actions are executed against an inactive background, dopaminergic treatment could in according scenarios contribute to passive behaviour in patients with Parkinson's disease.     

Comparisons of therapeutic effects of levodopa,levodopa and selegiline,and bromocriptine in patients with early,mild Parkinson's disease: three year interim report. Parkinson's Disease Research Group in the United Kingdom.

OBJECTIVE--To determine the optimum treatment for early Parkinson''s disease. DESIGN--An open, long term, prospective randomised trial conducted by the Parkinson''s Disease Research Group of the United Kingdom. SETTING--93 hospitals throughout the United Kingdom. SUBJECTS--782 patients with early Parkinson''s disease who were not receiving dopaminergic treatment. INTERVENTIONS--Patients allocated to treatment with levodopa/dopa decarboxylase inhibitor alone (arm 1), levodopa/decarboxylase inhibitor/selegiline in combination (arm 2), or bromocriptine (arm 3). MAIN OUTCOME MEASURES--Disability assessment as judged by improvement on Hoehn and Yahr, modified Webster, and North Western University disability scales. Adverse event profile and mortality ratios. RESULTS--Interim results indicate that all three treatment regimens led to improvement in baseline disabilities after 12 months'' treatment and that deterioration in control was apparent by three years. No significant differences were found between the results of treatment in arm 1 and arm 2, but both were significantly more effective than bromocriptine (arm 3) and had fewer early adverse reactions. The adjusted difference (95% confidence interval) in Webster rating for arm 3 v 1 was 0.93 points (0.27 to 1.50; p = 0.0058) and for arm 3 v 2 was 1.25 points (0.61 to 1.89; p = 0.0002). The incidence of dyskinesias and motor oscillations, however, was significantly lower in arm 3 (2% and 5%, respectively) than in arm 1 (27% and 33%, respectively) and arm 2 (34% and 35%, respectively). CONCLUSIONS--As there were no marked differences in functional improvement between the three groups the choice of treatment in the early stages of Parkinson''s disease may not be critical.     

Efficacy of combined therapy with amantadine, oseltamivir, and ribavirin in vivo against susceptible and amantadine-resistant influenza A viruses

The limited efficacy of existing antiviral therapies for influenza--coupled with widespread baseline antiviral resistance--highlights the urgent need for more effective therapy. We describe a triple combination antiviral drug (TCAD) regimen composed of amantadine, oseltamivir, and ribavirin that is highly efficacious at reducing mortality and weight loss in mouse models of influenza infection. TCAD therapy was superior to dual and single drug regimens in mice infected with drug-susceptible, low pathogenic A/H5N1 (A/Duck/MN/1525/81) and amantadine-resistant 2009 A/H1N1 influenza (A/California/04/09). Treatment with TCAD afforded >90% survival in mice infected with both viruses, whereas treatment with dual and single drug regimens resulted in 0% to 60% survival. Importantly, amantadine had no activity as monotherapy against the amantadine-resistant virus, but demonstrated dose-dependent protection in combination with oseltamivir and ribavirin, indicative that amantadine's activity had been restored in the context of TCAD therapy. Furthermore, TCAD therapy provided survival benefit when treatment was delayed until 72 hours post-infection, whereas oseltamivir monotherapy was not protective after 24 hours post-infection. These findings demonstrate in vivo efficacy of TCAD therapy and confirm previous reports of the synergy and broad spectrum activity of TCAD therapy against susceptible and resistant influenza strains in vitro.     

Gene therapy for Parkinson's disease

Gene therapy is a potentially powerful approach to the treatment of neurological diseases. The discovery of neurotrophic factors inhibiting neurodegenerative processes and neurotransmitter-synthesizing enzymes provides the basis for current gene therapy strategies for Parkinson's disease. Genes can be transferred by viral or nonviral vectors. Of the various possible vectors, recombinant retroviruses are the most efficient for genetic modification of cells in vitro that can thereafter be used for transplantation (ex vivo gene therapy approach). Recently, in vivo gene transfer to the brain has been developed using adenovirus vectors. One of the advantages of recombinant adenovirus is that it can transduced both quiescent and actively dividing cells, thereby allowing both direct in vivo gene transfer and ex vivo gene transfer to neural cells. Probably because the brain is partially protected from the immune system, the expression of adenoviral vectors persists for several months with little inflammation. Novel therapeutic tools, such as vectors for gene therapy have to be evaluated in terms of efficacy and safety for future clinical trials. These vectors still need to be improved to allow long-term and possibly regulatable expression of the transgene.     

Gene therapy for Parkinson's disease

Parkinson's disease (PD) is a debilitating neurodegenerative disorder arising from loss of dopaminergic neurons in the substantia nigra pars compacta and subsequent depletion of striatal dopamine levels, which results in distressing motor symptoms. The current standard pharmacological treatment for PD is direct replacement of dopamine by treatment with its precursor, levodopa (L-dopa). However, this does not significantly alter disease progression and might contribute to the ongoing pathology. Several features of PD make this disease one of the most promising targets for clinical gene therapy of any neurological disease. The confinement of the major pathology to a compact, localised neuronal population and the anatomy of the basal ganglia circuitry mean that global gene transfer is not required and there are well-defined sites for gene transfer. The multifactorial aetiology of idiopathic PD means that it is unlikely any single gene will cure the disease, and as a result at least three separate gene-transfer strategies are currently being pursued: transfer of genes for enzymes involved in dopamine production; transfer of genes for growth factors involved in dopaminergic cell survival and regeneration; and transfer of genes to reset neuronal circuitry by switching cellular phenotype. The merits of these strategies are discussed here, along with remaining hurdles that might impede transfer of gene therapy technology to the clinic as a treatment for PD.     

Levodopa combined with peripheral decarboxylase inhibition in Parkinson's disease

The authors report their experience, over a 26-month period, in the management of 60 parkinsonian patients with the combination of levodopa and an inhibitor of peripheral dopa-decarboxylase, Ro 4-4602. This approach to Parkinson''s disease is useful, safe, and at least as effective as levodopa alone. To date there have been no recognizable toxic effects attributable to Ro 4-4602. This agent appears to prolong the duration of action of levodopa, smoothing out its therapeutic effects. The percentage of patients obtaining a very good and excellent response is slightly increased. There is a possible diminution in the late-occurring bradykinetic and hypotonic freezing episodes. Nausea and cardiac arrhythmias are lessened, as are the incidence and severity of hypotension. Abnormal involuntary movements remain the limiting adverse side effect.     

Cell replacement therapy for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder in which the degeneration of dopaminergic neurons projecting from the substantia nigra to the striatum is a key pathological feature of the disease. Although pharmacological dopamine replacement is generally very effective in early disease, it is only a symptomatic therapy and can have significant side effects with long term use. One of the key strategies in a more restorative approach to PD therapy involves replacement of this degenerating nigro-striatal dopaminergic network with cells and several possible cell sources are being explored. While much experience and some success have been gained with fetal ventral mesencephalic (FVM) tissue transplants, the rapidly advancing stem cell field is providing attractive alternative options which circumvent many of the ethical and practical problems inherent in trials with FVM tissue. Of these embryonic stem cells and induced pluripotent stem cells seem the most promising. However further development and optimisation of the safety and efficacy of the techniques involved in generating and manipulating these, as well as other, cell sources will be essential before any further clinical trials are carried out.     

Gene therapy approaches for Parkinson's disease

Proteome analysis is usually performed by separating complex cellular protein extracts by two-dimensional-electrophoresis followed by protein identification using mass spectrometry. In this way proteins are compared from normal and diseased tissue in order to detect disease related protein changes. In a strict sense, however, this procedure cannot be called proteome analysis: the tools of proteomics are used just to detect some interesting proteins which are then investigated by protein chemistry as usual. Real proteome research would be studying the cellular proteome as a whole, its composition, organization and its kind of action. At present however, we have no idea how a proteome works as a whole; we have not even a theory about that. If we would know how the proteome of a cell type is arranged, we probably would alter our strategy to detect and analyze disease-related proteins. I will present a theory of proteomics and show some results from our laboratory which support this theory. The results come from investigations of the mouse brain proteome and include mouse models for neurodegenerative diseases.     

Neuroprotective and neurotoxic roles of levodopa (L-DOPA) in neurodegenerative disorders relating to Parkinson's disease

Summary.  Despite its being the most efficacious drug for symptom reversal in Parkinson's disease (PD), there is concern that chronic levodopa (L-DOPA) treatment may be detrimental. In this paper we review the potential for L-DOPA to 1) autoxidize from a catechol to a quinone, and 2) generate other reactive oxygen species (ROS). Overt toxicity and neuroprotective effects of L-DOPA, both in vivo and in vitro, are described in the context of whether L-DOPA may accelerate or delay progression of human Parkinson's disease. Received June 29, 2001 Accepted August 6, 2001 Published online June 3, 2002     

Effect of levodopa on interleukin-15 and RANTES circulating levels in patients affected by Parkinson's disease

Parkinson's disease (PD) is an extra-pyramidal neurodegenerative disorder, in which alterations of the immune system are involved. Interleukin (IL)-15 stimulates cellular immune response and induces growth and differentiation of various immune cells. RANTES, promoting leukocyte infiltration to sites of inflammation, mediates the trafficking and homing of immune cells. To clarify the potential effect of levodopa on the immunological network of PD, we analyzed IL-15 and RANTES serum levels in PD patients, treated or not with levodopa, and in healthy donors. Levodopa-treated patients showed significantly higher IL-15 and RANTES circulating levels with respect to healthy controls and higher, although not significantly, levels with respect to untreated patients. So, we hypothesize that the immunological alterations found in PD may be linked, at least in part, to levodopa therapy.