Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

From 1983, when dopaminergic structures were visualized for the first time in the human brain by positron emission tomography (PET) and onwards about 120 PET studies on Parkinsons disease have been listed in MEDLINE. With 18F-fluorodopa presynaptic dopamine insufficiency can be demonstrated in PD. By using 11C-nomifensine the dopamine reuptake sites can be visualized with PET. These results indicate that the striatal dopaminergic terminals are relatively preserved in PD as compared to the extreme reductions of dopamine in this region post mortem. Radiolabelled D2-agonists indicate a slight increase in these binding sites in de novo PD and no marked reduction in more advanced disease. 11C-selegiline have been used to demonstrate the intracerebral MAO-B inhibition by therapeutic doses of this drug. 11C-L-dopa and PET have demonstrat the rapid striatal decarboxylation of therapeutic doses of L-dopa also in advanced PD and a rough estimate of the striatal dopamine concentration inducing an "on-response" has been obtained. These contributions of PET to PD research are discussed in the article.
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PMID:What has PET told us about Parkinson's disease? 180 35

Four aspects about monoamine oxidase (MAO; E.C. 1.4.3.4) are of obvious interest in relation to Parkinson's disease and its treatment with the irreversible and selective MAO-B inhibitor L-deprenyl and are discussed in this review: 1) To what extent the two forms of MAO are of importance for the deamination of dopamine and to what degree MAO localised inside and outside of dopaminergic nerve terminals contributes 2) The kinetics of the MAO-protein, i.e. the rate of recovery of MAO after irreversible inhibition. 3) To what extent MAO may be changed as a consequence of the pathophysiological processes. 4) To what extent MAO may be involved as a force in the pathophysiological processes.
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PMID:Monoamine oxidase, dopamine and Parkinson's disease. 180 38

Systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) gives rise to motor deficits in humans and other primates which closely resemble those seen in patients with Parkinson's disease. These deficits are associated with a relatively selective loss of cells in the pars compacta of the substantia nigra and severe reductions in the concentrations of dopamine, noradrenaline and serotonin in the striatum. Similarly, in mice of various different strains the administration of MPTP also induces a marked loss of dopaminergic cells with severe depletion of biogenic amines, but higher doses of MPTP are required to produce these effects in mice than in primates. This review summarises advances made in understanding the biochemical events which underlie the remarkable neurotoxic action of MPTP. Major steps in the expression of neurotoxicity involve the conversion of MPTP to the toxic agent 1-methyl-4-phenylpyridinium ion (MPP+) by type B monoamine oxidase (MAO-B) in the glia, specific uptake of MPP+ into the nigro-striatal dopaminergic neurones, the intraneuronal accumulation of MPP+, and the neurotoxic action of MPP+. This is exerted mainly through the inhibition of the enzymes of the respiratory chain (Complex I), the disturbance of Ca2+ homeostasis, and possibly by the formation of free radicals. The relevance of the MPTP model to idiopathic Parkinson's disease is discussed.
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PMID:MPTP mechanisms of neurotoxicity and their implications for Parkinson's disease. 181 82

We treated 20 early Parkinson's disease subjects with the dopamine agonist lisuride in combination with the MAO-B inhibitor selegiline (L-deprenyl). We started with lisuride alone for one month, then we added selegiline versus placebo to lisuride in double-blind conditions for 3 months; finally all patients received lisuride and selegiline for another 3 months. Lisuride alone (1.43 +/- 0.10 mg) significantly improved PD. When selegiline (10 mg/day) was added in the double-blind phase the mean lisuride dosage could be reduced by 22.8% without deterioration of the clinical effects, and the same occurred in the former placebo group when selegiline was added. The combination of both drugs was well tolerated. These data are of interest for the interpretation of the effects of selegiline.
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PMID:Lisuride plus selegiline in the treatment of early Parkinson's disease. 190 85

(-)-Deprenyl has been increasingly used in recent years as an adjuvant with levodopa and a decarboxylase inhibitor in the treatment of Parkinson's disease. The inhibition of dopa decarboxylase and monoamine oxidase B resulting from this combination suggests that there may be a counter-regulatory increase in the activity of the third main enzyme in the catabolism of levodopa, i.e. catecholamine-O-methyl transferase (COMT). The current study on 36 patients with Parkinson's disease under long-term treatment with levodopa/dopadecarboxylase inhibitor showed, however, that the erythrocyte-COMT was unaffected by additional (-)-deprenyl medication. The patients in this study received levodopa and benserazide either with (-)-deprenyl (n = 21) or without (-)-deprenyl (n = 15). When allowance was made for the different genotypes, COMTLL, COMTLH, and COMTHH, there were no differences in the enzyme activities between the two treatment groups and the untreated controls (n = 26). On the basis of these results, consideration is given to the conditions in which COMT inhibitors are likely to be of value in the treatment of Parkinson's disease.
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PMID:(-)-Deprenyl treatment of patients with Parkinson's disease does not affect erythrocyte catechol-O-methyl transferase activity. 195 92

Identification, cellular localization, and cDNA cloning of MAO subtypes A and B have increased the insight into the pharmacology of these enzymes, whose primary functions are intra- and extraneuronal inactivation of neurotransmitter (dopamine, noradrenaline and serotonin) and other biogenic amines. In addition, MAO oxidizes the inert uncharacteristic tertiary amine, MPTP, to the parkinson inducing dopaminergic neurotoxin, MPP+, and the novel secondary amine anticonvulsant milacemide to the inhibitory amino acid neurotransmitter, glycine. These recent developments have provided new therapeutic perspectives for the management of Parkinson's disease and seizure disorders via the use of selective inhibitors and amino acid amine prodrug substrates of MAO-B.
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PMID:New directions in monoamine oxidase A and B selective inhibitors and substrates. 198 26

The cause of Parkinson's Disease remains unknown although environmental toxin/s and ageing are likely to play a significant role. Experimental 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine induced parkinsonism can be prevented by monoamine oxidase B inhibitors. Monoamine oxidase B inhibitors have been shown to delay disease progression in early Parkinson's Disease and improve mortality. Symptomatic therapy remains the cornerstone of drug treatment, and should include levodopa replacement with concomitant dopamine agonist therapy in order to achieve maximum efficacy, and reduce side effects. Complicated Parkinson's Disease could be managed by better delivery systems like slow release preparations and parenteral infusions. Brain tissue transplants may offer hope of restoring the damaged nigrostriatal system.
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PMID:Drug treatment of Parkinson's disease: current concepts. 202 54

Acetyl-levo-carnitine (ALC) protects against 1-methyl, 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced toxicity in the nonhuman primate. ALC pretreated monkeys do not show signs of parkinsonism or electroretinographic changes typical of dopaminergic deficiency when given MPTP. In addition, pilot neurochemical and morphological data confirm a partial protection effect. While MAO-B inhibitors, like L-Deprenyl, are thought to protect dopaminergic neurons from MPTP-induced cell death by preventing the conversion of MPTP to its toxic metabolite MPP+, ALC is not known to have MAO-B affinity. Converging evidence suggests that ALC may affect directly mitochondrial respiration, which is known to be the target of MPP+ and affected in human neurodegenerative diseases, including Parkinson's disease. The results of this study point to new therapeutic avenues for the treatment of these nosologic entities.
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PMID:Acetyl-levo-carnitine protects against MPTP-induced parkinsonism in primates. 206 31

MDL 72.974A [(E) 4-fluoro-beta-fluorethylene benzene butanamine] has been shown in animal studies, both in vitro and in vivo, to be a potent, selective, enzyme-activated irreversible inhibitor of MAO-B (Zreika et al., 1989). This compound is under clinical development for the treatment of Parkinson's disease. In this double blind, randomized, placebo-controlled normal volunteer study the tolerability, effects on platelet MAO-B activity and associated pharmacokinetics of increasing single oral doses of MDL 72.974A (0.1-12 mg) were assessed. MDL 72.974A was extremely well tolerated and no treatment-related changes in vital signs or the adjectival check-list (EWL-N) occurred. The compound caused significant dose-dependent inhibition of platelet MAO-B activity at all dose levels with a return to baseline values by day 14. The mean (+/- S.D.) elimination half-life of parent compound was 51 +/- 26 min and mean (+/- S.D.) urinary excretion was 0.54 +/- 0.26% of the administered dose. These results, long action on platelet MAO-B and short elimination half-life, demonstrate MDL 72.974A to be a potent, irreversible inhibitor of MAO-B in man.
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PMID:A double-blind, placebo-controlled study of the tolerability and effects on platelet MAO-B activity of single oral doses of MDL 72.974A in normal volunteers. 208 92

Recent evidence suggests that iron accumulates in substantia nigra pars compacta of patients with Parkinson's disease (PD). This finding is compatible with changes in the respiratory chain activity, increase of malondialdehyde concentration (a measure of lipid peroxidation), decrease of enzyme activity of enzymes involved in detoxication of hydrogen peroxide and oxygen radical species, increased MAO-B-activity in this brain area etc. All these data suggest that oxidative stress may play a certain role in the pathobiochemistry of PD. In addition to the description of the neuroprotective mechanism of the MAO-B-inhibitor L-deprenyl a new aspect focuses the role of the endogenous MAO-B substrates "polyamines" which occur both in neurons and glia. A further aspect of this review deals with the role of calcium as cellular toxin. Although of major importance it is not decided yet whether these biochemical changes are primary or secondary importance to the pathogenesis of PD.
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PMID:The role of monoamine oxidase, iron-melanin interaction, and intracellular calcium in Parkinson's disease. 208 94


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