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 major neuropathology of Parkinson's disease (PD) is the degeneration of nigrostriatal dopamine (DA), resulting in a deficiency of DA, and of the enzyme tyrosine hydroxylase (TH), which catalyzes the synthesis of L-dopa. The symptomatic treatment of PD consists of replenishing DA by administering L-dopa, which is enzymatically converted to DA in the striatum. The increase of TH activity by modification of the enzyme leads to an increased synthesis of striatal L-dopa, and thereby replenishes the missing DA more efficiently. The activity of TH is increased by protein kinase-dependent phosphorylation of the enzyme or by inhibition of dephosphorylation with specific phosphatase inhibitors. Thus, modification of TH results in an activated form of the enzyme, which might provide a basis for developing new strategies in the treatment of PD. The extraneuronal enzyme, catechol-O-methyl transferase (COMT), inactivates catecholamines by O-methylation, and its inhibition leads to increased levels of striatal DA. The availability of selective and nontoxic COMT inhibitors makes it possible to assess their therapeutic role in treatment of PD. The intraneuronal enzymes, monoamine oxidase (MAO)-A and MAO-B, inactivate catecholamines and other biogenic amines, such as serotonin, by deamination. Inhibition of these enzyme activities leads to increased levels of striatal DA. The irreversible MAO-B inhibitor selegiline was shown to exert antiparkinsonian activity, especially in the early stages of parkinsonism. Selegiline also prevents the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism in MPTP-treated mice and monkeys. Its role in the prevention of the disease is under investigation in several clinical centers.
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PMID:The role of the regulatory enzymes of catecholamine synthesis in Parkinson's disease. 834 92

The present study was performed to determine the effect of a nearly complete nigrostriatal dopaminergic denervation on DARPP-32 levels in the striatum from animals and parkinsonian patients. DARPP-32 levels were estimated by in vitro phosphorylation in the presence of cAMP, or after inactivation of endogenous kinases and phosphatases, in the presence of the catalytic subunit of cAMP-dependent protein kinase. Intranigral 6-hydroxydopamine (6-OHDA) infusion in rats, or peripheral administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to common marmosets, did not change striatal DARPP-32 levels. Postmortem studies, carried out on brains obtained shortly after death, from patients with Parkinson disease, or from patients with progressive supranuclear palsy, showed that the levels of striatal DARPP-32 were not different from controls. These results indicate that dopaminergic striatal denervation did not modify the amount of DARPP-32 in the striatum, suggesting that the expression of DARPP-32, a protein which mediates some of the effects of dopamine in striatal neurons, is independent from the dopaminergic innervation.
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PMID:Lack of change in striatal DARPP-32 levels following nigrostriatal dopaminergic lesions in animals and in parkinsonian syndromes in man. 210 23

Tyrosine hydroxylase (TH) activity of human postmortem brain tissues from controls and patients with Parkinson's disease (PD) was examined in the presence of Fe2+ and phosphorylation agents, such as cyclic AMP, exogenous protein kinase, calcium plus calmodulin (Ca2+-CaM), and ATP. TH activity from parkinsonian tissue was increased by 48% with statistical significance in the presence of exogenous protein kinase. Cyclic AMP alone had no effect, whereas Ca2+-CaM increased the activity by only 10%. The presence of acetylcholine resulted in a slight decrease in enzyme activity. Human TH was stimulated 13.17-fold in the presence of 1 mM Fe2+. For iron dependence, no significant differences could be shown for the Km values of TH in striata of PD, while the activity of TH was half of that of controls. Here stimulation with 1 mM Fe2+ raised the activity of TH 11-fold. Stimulation of rat, gerbil, pig, and human caudate nucleus TH with Fe2+ shows remarkable species differences. In particular, the sensitivity of human TH to stimulating processes is noteworthy. H2O2 decreases TH activity only at high concentrations. Species differences are noted for the combined incubation of Fe2+ and H2O2. In the gerbil caudate nucleus, H2O2 does not prevent the stimulating properties of Fe2+, while the pig shows a dose-dependent decline of TH activity. In conclusion, there are no significant changes in the stimulating properties of human caudate nucleus TH activity with Fe2+ in PD, while such differences are noted by using exogenous protein kinase. Furthermore, experimental evidence shows that TH activity declines at high concentrations of H2O2 only. Potentiation of this effect by Fe2+ seems to be species-dependent.
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PMID:Tyrosine hydroxylase activity in caudate nucleus from Parkinson's disease: effects of iron and phosphorylating agents. 289 84

The immunoreactivity of cortical and brainstem-type Lewy bodies has been investigates with antibodies to the cyclin-dependent kinase 5 (cdk5), to the extracellular regulated kinase 1 (ERK-1), and to the cdc2p34 kinase and with antibodies specific for phosphorylation epitopes typical of paired helical filament-tau (PHF-tau). Both cortical and brainstem-type Lewy bodies in diffuse Lewy body disease and brainstem-type Lewy bodies in Parkinson's disease were found to be immunoreactive for cdk5 but not for cdc2p34 or ERK-1 or with the PHF-tau antibodies. Double immunolabeling showed that cdk5-positive Lewy bodies were also ubiquitin immunoreactive and that cdk5 antibodies labeled as many Lewy bodies as ubiquitin antibodies in adequately fixed tissue. The cdk5 immunoreactivity of Lewy bodies was abolished by preabsorption of the antibody with a cdk5 peptide. The antibodies to cdk5 labeled a single 33-kd species on Western blots of human brain homogenates, with a similar intensity in control, diffuse Lewy body disease, and Alzheimer's disease, and this cdk5 species was found mainly in the particulate fraction of brain homogenates. This observation suggests that cdk5 might be a protein kinase involved in the phosphorylation of a molecular component of Lewy bodies, for example, neurofilament proteins known to be present in these inclusions.
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PMID:Cortical and brainstem-type Lewy bodies are immunoreactive for the cyclin-dependent kinase 5. 748 9

Midbrain dopaminergic neurons, whose loss in adults results in Parkinson's disease, can be specified during embryonic development by a contact-dependent signal from floor plate cells. Here we show that the amino-terminal product of Sonic hedgehog autoproteolysis (SHH-N), an inductive signal expressed by floor plate cells, can induce dopaminergic neurons in vitro. We show further that manipulations to increase the activity of cyclic AMP-dependent protein kinase A, which is known to antagonize hedgehog signaling, can block dopaminergic neuron induction by floor plate cells. Our results and those of other studies indicate that SHH-N can function in a dose-dependent manner to induce different cell types within the neural tube. Our results also provide the basis for a potential cell transplantation therapy for Parkinson's disease.
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PMID:Induction of midbrain dopaminergic neurons by Sonic hedgehog. 761 28

The aim of this study was to achieve a better understanding of the integration in striatal medium-sized spiny neurons (MSNs) of converging signals from glutamatergic and dopaminergic afferents. The review of the literature in the first section shows that these two types of afferents not only contact the same striatal cell type, but that individual MSNs receive both a corticostriatal and a dopaminergic terminal. The most common sites of convergence are dendritic shafts and spines of MSNs with a distance between the terminals of less than 1-2 microns. The second section focuses on synaptic transmission and second messenger activation. Glutamate, the candidate transmitter of corticostriatal terminals, via different types of glutamate receptors can evoke an increase in intracellular free calcium concentrations. The net effect of dopamine in the striatum is a stimulation of adenylate cyclase activity leading to an increase in cAMP. The subsequent sections present information on calcium- and cAMP-sensitive biochemical pathways and review the regional and subcellular distribution of the components in the striatum. The specific biochemical reaction steps were formalized as simplified equilibrium equations. Parameter values of the model were chosen from published experimental data. Major results of this analysis are: at intracellular free calcium concentrations below 1 microM the stimulation of adenylate cyclase by calcium and dopamine is at least additive in the steady state. Free calcium concentrations exceeding 1 microM inhibit adenylate cyclase, which is not overcome by dopaminergic stimulation. The kinases and phosphatases studied can be divided in those that are almost exclusively calcium-sensitive (PP2B and CaMPK), and others that are modulated by both calcium and dopamine (PKA and PP1). Maximal threonine-phosphorylation of the phosphoprotein DARPP requires optimal concentrations of calcium (about 0.3 microM) and dopamine (above 5 microM). It seems favourable if the glutamate signal precedes phasic dopamine release by approximately 100 msec. The phosphorylation of MAP2 is under essentially calcium-dependent control of at least five kinases and phosphatases, which differentially affect its heterogeneous phosphorylation sites. Therefore, MAP2 could respond specifically to the spatio-temporal characteristics of different intracellular calcium fluxes. The quantitative description of the calcium- and dopamine-dependent regulation of DARPP and MAP2 provides insights into the crosstalk between glutamatergic and dopaminergic signals in striatal MSNs. Such insights constitute an important step towards a better understanding of the links between biochemical pathways, physiological processes, and behavioural consequences connected with striatal function. The relevance to long-term potentiation, reinforcement learning, and Parkinson's disease is discussed.
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PMID:Postsynaptic integration of glutamatergic and dopaminergic signals in the striatum. 783 76

The clinical efficacy of dopamine (DA) replacement therapy for patients with Parkinson's disease (PD) depends on the preservation of postsynaptic DA receptors and their intracellular signalling mechanisms in the striatum long after degeneration of the nigrostriatal DA pathway. DA activates adenylyl cyclase (AC) and phospholipase C (PLC) via the D1 receptor, and inhibits through the D2 receptor, thereby regulating the production of intracellular second messengers, cyclic adenosine 3',5'-monophosphate (cAMP), 1,2-diacylglycerol (DAG) and Ca2+. Recent advances in molecular biology have made it possible to monitor the intracellular signal transduction cascade following receptor activation by various transmitters. The authors review the literature addressing this issue, summarized as follows: (1) striatal D1 and D2 receptor densities remain constant, at least in treated and non-demented patients; (2) DA-sensitive AC activity appears to be increased in the putamen of treated patients, although this remains to be confirmed; (3) levels of cAMP-dependent protein kinase (PKA) are normal in non-demented patients, consistent with unchanged levels of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of M(r) 32,000); (4) levels of Ca2+/phospholipid-dependent protein kinase (PKC) and of inositol 1,4,5-trisphosphate (InsP3) receptor also remain unchanged in non-demented patients; (5) the above three second messenger sites as well as densities of D1 and D2 receptors are decreased in the striatum of demented PD patients (PDD). We tentatively conclude that postreceptor signalling function is intact in the striatum of non-demented PD patients and that there is a clear difference between non-demented patients and PDD, i.e. striatal dopaminoceptive neurons are affected in PDD.
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PMID:Transmembrane signalling systems in the brain of patients with Parkinson's disease. 795 88

The neuropathology of Parkinson's disease is characterized by the degeneration of dopaminergic neurons in the substantia nigra. We have recently shown that the activation of protein kinase A improves the survival of dopaminergic neurons in culture and, furthermore, protects them from the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium ion (MPP+) in vitro. We have now analysed the potential of phosphodiesterase inhibitors to increase cAMP levels in dopaminergic neurons, to improve their survival in culture and to protect them from the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in vivo. Increasing intracellular cAMP with phosphodiesterase type IV-specific inhibitors enhanced the survival of dopaminergic neurons in culture. Inhibitors of other phosphodiesterase types were not active. In vivo, phosphodiesterase type IV inhibitors reduced the MPTP-induced dopamine depletion in the striatum of C57BL/6 mice. Furthermore, the loss of tyrosine hydroxylase-immunopositive neurons in the substantia nigra of these animals was diminished. After Nissl staining, a similar reduction of the MPTP-induced loss of neurons was observed in the substantia nigra. The protective effect of protein kinase A activation did not appear to be due to the blocking of MPP+ uptake into dopaminergic neurons. This was not decreased after treatment with forskolin or 8-(4-chlorophenylthio)-cAMP. Thus, protein kinase A regulates the survival and differentiation of dopaminergic substantia nigra neurons in vivo, implicating a therapeutic potential for substances which regulate cAMP turnover in these neurons.
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PMID:Inhibitors of type IV phosphodiesterases reduce the toxicity of MPTP in substantia nigra neurons in vivo. 884 48

Chronically administered levodopa, the standard treatment for Parkinson's disease, is ultimately associated with disabling alterations in motor response. To evaluate the possible contribution of striatal cAMP-dependent protein kinase A (PKA) signaling pathways to these response modifications, the acute effects of a PKA inhibitor, Rp-cAMPS, on motor response changes attending chronic, twice-daily administration of levodopa were measured in 6-hydroxydopamine lesioned hemi-parkinsonian rats. A single intrastriatal injection of Rp-cAMPS (2.5 or 25 microg) attenuated both the shortened duration and augmented intensity of levodopa-induced turning in a dose dependent manner. Rp-cAMPS completely normalized motor responses to a dopamine D1 agonist (SKF 38392), but had no effect on those to a dopamine D2 agonist (quinpirole). These results suggest that D1 receptor-mediated PKA activation may contribute to the development of the altered motor responses associated with chronic levodopa treatment.
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PMID:Protein kinase A inhibitor attenuates levodopa-induced motor response alterations in the hemi-parkinsonian rat. 919 74

Cell adhesion molecules play a central role in neural development and are also critically involved in axonal regeneration and synaptic plasticity in the adult nervous system. We investigated whether the neural cell adhesion molecule L1 was capable of stimulating survival and differentiation in the mid-brain dopaminergic neurons which degenerate in Parkinson's disease. Monoclonal L1 antibodies, known to enhance neurite outgrowth, were substrate-coated or added at the time of plating to medium of cultures containing mid-brain dopaminergic neurons from 14-day-old fetal rats. Tritiated dopamine uptake per well and the number of tyrosine hydroxylase-immunopositive neurons increased in a dose-dependent manner with increasing concentrations of L1 antibody, suggesting that L1 acts directly or indirectly as a growth factor for dopaminergic neurons. A monoclonal L1 antibody not enhancing neurite outgrowth was ineffective. The growth-promoting effects of L1 antibodies on dopaminergic neurons in culture did not appear to be mediated by the cAMP-activated protein kinase A pathway, since combined treatment with a phosphodiesterase inhibitor had only additive effects on the L1-induced increase of dopamine uptake, and in addition, antibodies against L1 failed to protect cultures of dopaminergic neurons against the neurotoxin MPP+, whereas pretreatment with forskolin and phosphodiesterase type-IV inhibitors was strongly protective.
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PMID:L1 neural cell adhesion molecule is a survival factor for fetal dopaminergic neurons. 967 69


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