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

The present study investigated the presence, possible synthesis and release of catecholamines (CA) by human amniotic epithelial cells (HAEC) using HPLC with electrochemical detection. The presence of CA was indicated by the detection of norepinephrine (NE), dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in extracts of cultured HAEC. Incubation of HAE cells in medium supplemented with 1-tyrosine (CA precursor) and tetrahydrobiopterin (tyrosine hydroxylase cofactor) significantly increased the production of catecholamines, suggesting CA synthesis by HAEC. In contrast, pharmacological inhibition of tyrosine hydroxylase by alpha-methyl-p-tyrosine (MPT) significantly reduced CA production, further confirming CA synthesis by HAEC. Catecholamines were also detected in the cell incubation media, demonstrating the ability of HAEC to spontaneously secrete CA. Moreover, incubation of cells with 50 mM K+ for 10 min increased the amount of CA released into the medium. Additionally, the detection of DOPAC, a primary metabolite of DA, in HAEC strongly indicates that these cells contain DA metabolizing enzymes. The present results suggest that HAEC synthesize and release CA. These cells may be a possible candidate for transplantation therapy of neurodegenerative diseases such as Parkinson's disease and also may serve as a model to study the aspects of catecholaminergic activity.
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PMID:Evidence for synthesis and release of catecholamines by human amniotic epithelial cells. 942 2

Glial cell line-derived neurotrophic factor, the newest member of the transforming growth factor-beta superfamily, has been shown to promote the survival and differentiation of dopaminergic neurons in the ventral mesencephalon. Glial cell line-derived neurotrophic factor has been implicated in both the in vitro and in vivo recovery of mesencephalic dopaminergic cells challenged with the neurotoxins 1-methyl-4-phenylpyridinium and 6-hydroxydopamine. Previous studies have shown increased survival of intrastriatally transplanted dopaminergic cells when followed by infusion of neurotrophic factors such as basic fibroblast growth factor, brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor. However, the effects of glial cell line-derived neurotrophic factor co-administered with dopaminergic cells prior to implantation in the host striatum have not been studied. In the present study, the hypothesis was that treating fetal ventral mesencephalic tissue containing the dopaminergic substantia nigra with glial cell line-derived neurotrophic factor either during storage or at the time of transplantation, would enhance grafted dopaminergic cell survival and functional reinnervation of the host striatum in the unilaterally 6-hydroxydopamine-lesioned rat. To test this hypothesis, two experiments were performed. In the first experimental group (n = 7), fetal ventral mesencephalons from embryonic day 14 rats were maintained in hibernation medium containing glial cell line-derived neurotrophic factor (1 migrogram/ml) at 4 degrees C for six days prior to dissociation and stereotactic implantation into the host striatum: the control group (n = 5) received tissue hibernated without glial cell line-derived neurotrophic factor. The second experimental group (n = 8) received fresh fetal ventral mesencephalic tissue treated with glial cell line-derived neurotrophic factor (0.2 microgram/microliter) while the control group (n = 5) received the fresh graft with no glial cell line-derived neurotrophic factor. Transplantation success was assessed by behavioural analysis (rotometry) and tyrosine hydroxylase immunohistochemistry. Cell counts of tyrosine hydoxylase-stained sections revealed a statistically significant increase in tyrosine hydroxylase-positive neurons in grafts exposed to glial cell line-derived neurotrophic factor during hibernation as compared to control grafts. In addition, there was a statistically significant enhancement of fibre density in the glial cell line-derived neurotrophic factor hibernation graft group as compared to the glial cell line-derived neurotrophic factor fresh graft group. Behavioural analysis three weeks post-grafting exhibited a statistically significant decrease in amphetamine-induced rotations in animals transplanted with glial cell line-derived neurotrophic factor grafts as compared to control grafts. These findings suggest that storing dopaminergic cells in a glial cell line-derived neurotrophic factor-containing medium prior to transplantation increases graft survival, graft derived fibre outgrowth, and behavioural recovery in the adult host. This observation has potential implications for enhancing the efficacy of neural transplantation in the treatment of Parkinson's disease.
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PMID:Glial cell line-derived neurotrophic factor improves intrastriatal graft survival of stored dopaminergic cells. 946 Jul 46

Excessive glutamate transmission in the basal ganglia is a major factor in the neural mechanisms underlying parkinsonian akinesia. Activation of kappa opioid receptors causes a presynaptic reduction in glutamate release. Kappa opioid receptors are concentrated in those regions of the basal ganglia associated with increased glutamate transmission in parkinsonism. In this study, we use the alpha-methyl-p-tyrosine and reserpine-treated rat model of parkinsonism to investigate whether systemic administration of the kappa opioid agonists enadoline (CI-977) and U69,593 can alleviate the symptoms of parkinsonism either alone or in conjunction with dopamine replacement therapy. We report that, when administered alone, both enadoline and U69,593 can increase locomotion in monoamine-depleted rats. No increase in locomotor activity was seen after kappa opioid agonist administration in non-parkinsonian rats. The responses to kappa opioid agonists were blocked by co-administration of either the nonspecific opioid receptor antagonist naloxone or the selective kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI). An important finding is that when enadoline and L-dopa are administered together, their anti-akinetic properties are synergistic. Thus, the doses of enadoline and L-dopa required to alleviate akinesia when administered together are lower than either administered alone. These data illustrate the importance of kappa opioid receptors in the neural mechanisms controlling voluntary movement and suggest that kappa opioid agonists may have a role as adjuncts to dopamine replacement in the management of Parkinson's disease.
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PMID:Kappa-opioid receptor agonists increase locomotor activity in the monoamine-depleted rat model of parkinsonism. 953 34

The trapping of decarboxylation products of radiolabelled dopa analogs in living human brain occurs as a function of the activity of dopa decarboxylase. This enzyme is now understood to regulate, with tyrosine hydroxylase, cerebral dopamine synthesis. Influx into brain of dopa decarboxylase substrates such as 6-[18F]fluorodopa and beta-[11C]dopa measured by positron emission tomography can be analyzed by solution of linear differential equations, assuming irreversible trapping of the decarboxylated products in brain. The isolation of specific physiological steps in the pathway for catecholamine synthesis requires compartmental modelling of the observed dynamic time-activity curves in plasma and in brain. The several approaches to the compartmental modelling of the kinetics of labelled substrates of dopa decarboxylase are now systematically and critically reviewed. Labelled catechols are extensively metabolized by hepatic catechol-O-methyltransferase yielding brain-penetrating metabolites. The assumption of a fixed blood-brain permeability ratio for O-methyl-6-[18F]fluorodopa or O-methyl-beta-[11C]dopa to the parent compounds eliminates several parameters from compartmental models. However, catechol-O-methyltransferase activity within brain remains a possible factor in underestimation of cerebral dopa decarboxylase activity. The O-methylation of labelled catechols is blocked with specific enzyme inhibitors, but dopa decarboxylase substrates derived from m-tyrosine may supplant the catechol tracers. The elimination from brain of decarboxylated tracer metabolites can be neglected without great prejudice to the estimation of dopa decarboxylase activity when tracer circulation is less than 60 minutes. However, elimination of dopamine metabolites from brain occurs at a rate close to that observed previously for metabolites of glucose labelled in the 6-position. This phenomenon can cause systematic underestimation of the rate of dopa decarboxylation in brain. The spillover of radioactivity due to the limited spatial resolution of tomographs also results in underestimation of dopa decarboxylase activity, but correction for partial volume effects is now possible. Estimates of dopa decarboxylase activity in human brain are increased several-fold by this correction. Abnormally low influx of dopa decarboxylase tracers in the basal ganglia is characteristic of Parkinson's disease and other movement disorders. Consistent with postmortem results, the impaired retention of labelled dopa is more pronounced in the putamen than in the caudate nucleus of patients with Parkinson's disease; this heterogeneity persists after correction for spillover. Current in vivo assays of dopa decarboxylase activity fail to discriminate clinically distinct stages in the progression of Parkinson's disease and are, by themselves, insufficient for differential diagnosis of Parkinson's disease and other subcortical movement disorders. However, potential new avenues for therapeutics can be tested by quantifying the rate of metabolism of exogenous dopa in living human brain.
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PMID:Compartmental analysis of dopa decarboxylation in living brain from dynamic positron emission tomograms. 955 74

Oxidative stress has been proposed as a pathogenetic mechanism in Parkinson's disease (PD). One mechanism of oxidative cellular injury is the nitration of protein tyrosine residues, mediated by peroxynitrite, a reaction product of nitric oxide and superoxide radicals. We demonstrate here the presence of nitrotyrosine immunoreactivity in Lewy bodies within melanized neurons and in amorphous deposits associated with intact and degenerating neurons. The core of the Lewy body was frequently intensely immunolabeled, while the rim was lightly labeled or unlabeled. This likely reflects the fact that tyrosine residues of neurofilament proteins are primarily localized to Lewy body cores, and suggests that nitrotyrosine is present in neurofilament protein itself. Although these observations are as yet unable to provide a definitive link between oxidative stress and neuronal dysfunction, they demonstrate that oxidative stress has occurred within the vulnerable neurons of PD, leaving a permanent marker of oxidative modification of neuronal proteins within the target cells of neurodegeneration. In addition, these observations provide a potential link between excitotoxicity and oxidative stress within the vulnerable neurons of PD and represent a pathogenetic mechanism in common with the 2 other major age-related neurodegenerative diseases, Alzheimer disease and amyotrophic lateral sclerosis.
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PMID:Protein nitration in Parkinson's disease. 960 Feb 27

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces an experimental model of Parkinson's disease (PD). It replicates most of the clinical features of PD as well as the main biochemical and pathologic hallmarks of the disease. Although the MPTP model departs from PD in several aspects, it is thought that important insights into the neurodegenerative process of PD may be obtained by elucidating the molecular mechanism of MPTP. In this article, we summarize the different steps of the complex metabolic pathway of MPTP and show how they may be implicated in predisposing individuals to PD. We also outline findings pertinent to the mode of action of MPTP including overproduction of free radicals, implication of nitric oxide, nitration of tyrosine, impairment of mitochondrial respiration, and occurrence of apoptosis. All of these factors may participate in the cascade of deleterious events that ultimately lead to the death of dopaminergic neurons after MPTP administration. Because of the similarity between PD and the MPTP model, we are speculating that a similar scenario may underlie the neurodegenerative process in PD.
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PMID:Mechanisms of MPTP toxicity. 961 16

We have previously demonstrated that fetal nigral grafts can survive, reinnervate the striatum, and mediate clinically relevant recovery in a patient with Parkinson's disease (PD). Most previous autopsy cases have failed to identify meaningful numbers of viable grafted cells suggesting that differences in critical transplant variables determine graft viability. The present study evaluated the structural and functional correlates of fetal nigral transplantation in a second PD patient who received fetal nigral grafts according to our previously published transplant protocol. A 61-year-old woman with severe PD received bilateral fetal nigral grafts to the postcommissural putamen from seven donor fetuses (four right side and three left side) aged 6.5-9 weeks postconception. This patient died 19 months after surgery from a cause unrelated to the transplant surgery. Her postoperative clinical course was characterized by improved motor and activities of daily living scores during "off time," reduced "off time," and increased "on" time without dyskinesia. Positron emission tomography (PET) scans revealed a bilateral and progressive increase in fluorodopa (FD) uptake within the grafted putamen. Postmortem examination of the right hemisphere revealed large oval-shaped grafts containing more than 138,000 tyrosine-hydroxylase-immunoreactive (TH-ir) neurons. Grafted cells formed a seamless border with the host and provided dense TH-ir innervation to 78% of the host postcommissural putamen. Graft-mediated sprouting of host fibers was not observed. These data provide essential confirmation that, under appropriate transplant conditions, grafted nigral neurons can survive, reinnervate the host striatum, and provide clinical benefit to PD patients. These findings also support the concept that improved motor function and striatal FD uptake on PET after nigral grafting in PD are the result of the viability of grafted neurons and graft-derived reinnervation of the host striatum.
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PMID:Fetal nigral grafts survive and mediate clinical benefit in a patient with Parkinson's disease. 961 26

The decrement in dopamine levels exceeds the loss of dopaminergic neurons in Parkinson's disease (PD) patients and experimental models of PD. This discrepancy is poorly understood and may represent an important event in the pathogenesis of PD. Herein, we report that the rate-limiting enzyme in dopamine synthesis, tyrosine hydroxylase (TH), is a selective target for nitration following exposure of PC12 cells to either peroxynitrite or 1-methyl-4-phenylpyridiniun ion (MPP+). Nitration of TH also occurs in mouse striatum after MPTP administration. Nitration of tyrosine residues in TH results in loss of enzymatic activity. In the mouse striatum, tyrosine nitration-mediated loss in TH activity parallels the decline in dopamine levels whereas the levels of TH protein remain unchanged for the first 6 hr post MPTP injection. Striatal TH was not nitrated in mice overexpressing copper/zinc superoxide dismutase after MPTP administration, supporting a critical role for superoxide in TH tyrosine nitration. These results indicate that tyrosine nitration-induced TH inactivation and consequently dopamine synthesis failure, represents an early and thus far unidentified biochemical event in MPTP neurotoxic process. The resemblance of the MPTP model with PD suggests that a similar phenomenon may occur in PD, influencing the severity of parkisonian symptoms.
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PMID:Inactivation of tyrosine hydroxylase by nitration following exposure to peroxynitrite and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). 963 6

Since binding sites for morphine, nicotine and strychnine exist in the brain, it is possible that they may have some role in neuronal function. The presence/variation in the levels of these alkaloids in the brain of rats fed tryptophan and tyrosine, and in the serum of patients with some neurodegenerative and psychiatric disorders were studied. Brain of rats loaded with tyrosine (500 mg/kg b wt X 14 days) showed increased amounts of morphine, while that from animals loaded with tryptophan (in the same dose) showed presence of strychnine and increased amounts of nicotine. Strychnine is being reported in mammalian brain for the first time. Serum of patients with epilepsy, Parkinson's disease (PD) and manic depressive psychosis (MDP) was also examined for the presence of these alkaloids. Serum of control subjects did not show the presence of any of these alkaloids, while that of all 3 patients groups contained strychnine. Morphine was present only in the serum of patients of MDP. Nicotine was present in trace amounts in the serum of all these patients. Presence of these alkaloids in the serum of patients of neurodegenerative and psychiatric disorders is being reported for the first time, to the best of our knowledge.
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PMID:Endogenous alkaloids in the brain of rats loaded with tyrosine/tryptophan & in the serum of patients of neurodegenerative & psychiatric disorders. 967 Jun 21

In this study, we investigated the presence, possible synthesis, and release of catecholamines (CA) by monkey amniotic epithelial cells (MAEC) using different methods. Immunocytochemical techniques demonstrated the presence of tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), dopamine-beta-hydroxylase (DBH), and dopamine (DA) immunoreactivities, suggesting the capability of these cells to synthesize CA. Further evidence from high performance liquid chromatography (HPLC) studies indicated the presence of norepinephrine (NE), DA, and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the cell extracts of cultured MAEC. Incubation of MAEC for various time intervals in medium supplemented with L-tyrosine and tetrahydrobiopterin significantly increased the production of CA, thus confirming active synthesis of CA by MAEC and that increasing the incubation time increases this synthesis. In contrast, pharmacological inhibition of TH by alpha-methyl-p-tyrosine significantly reduced CA production, further confirming CA synthesis by MAEC. Catecholamines were also detected in the cell incubation media, suggesting the ability of MAEC to spontaneously secrete CA. Moreover, depolarization with high concentration of K+ increased the amount of CA released into the incubation media. Additionally, the detection of DOPAC, a primary metabolite of DA, in MAEC strongly indicates that these cells contain DA metabolizing enzymes. These results demonstrate the presence of CA in MAEC and that these cells can synthesize and release CA. Further extensive studies are needed to fully explore MAEC so that it may serve as a model to study the aspects of catecholaminergic activity in primate cells and may be a possible candidate for allotransplantation therapy of monkey model of Parkinson's disease.
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PMID:Synthesis and release of catecholamines by cultured monkey amniotic epithelial cells. 967 Sep 97


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