MPTP toxicity causes vocal, auditory, orientation and movement defects in the echolocation bat.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can damage dopaminergic neurons in the substantia nigra in many mammals with biochemical and cellular changes that are relatively similar to those observed in Parkinson's disease. Our study examined whether MPTP-treated echolocation bats can cause changes in bat echolocation system. By considering ultrasound spectrums, auditory brainstem-evoked potentials and flight trajectories of normal bats, we observed that the vocal, auditory, orientation and movement functions of MPTP-treated bats were significantly impaired, and they exhibited various symptoms resembling those in patients with Parkinson's disease. Our immunohistochemistry and western blot analyses further indicated that expression of vocal-related FOXP2 in the superior colliculus, auditory-related otoferlin in the inferior colliculus, dopamine synthesis-related aromatic l-amino acid decarboxylase in the substantia nigra and dopamine receptor in the striatum was significantly decreased. Furthermore, protein expression related to inflammation, oxidative stress and apoptosis in the substantia nigra was significantly increased in MPTP-treated bats. These results indicate that inflammation, oxidative stress and apoptosis may be instrumental in dopaminergic neurodegeneration in the substantia nigra. The vocal, auditory and orientation and movement dysfunctions of MPTP-treated bats are relatively consistent with symptoms of Parkinson's disease.

Bioavailability and Neuroprotectivity of 3-(3, 4-dimethoxy phenyl)-1-4 (methoxy phenyl) prop-2-en-1-one against Schizophrenia: an in silico approach.

Schizophrenia is a major debilitating disorder worldwide. Schizophrenia is a result of multi-gene mutation and psycho-social factors. Mutated amino acid sequences in genes of DOPA such as TH, DDC, DBH, VMAT2, and NMDA (SET-1) have been implicated as major factors causing schizophrenia. In addition mutations in genes other than the DOPA genes such as RGS4, NRG1, COMT, AKT1 and DTNBP1 (SET 2) have also been implicated in the pathogenesis of schizophrenia. Several medicinal herbs and their bioactive constituents have been reported to be involved in ameliorating different neurological disorders including schizophrenia. The present study is mainly focused to study the effect of bioactive compound isolated from the celastrus panuculatus on DOPA and other related genes of schizophrenia using in silico approach. Moledular docking study was carriedout aginast all the selected targets with the lingds i.e. compound and clozapine using the autodock vina 4.0 module implemented in Pyrx 2010.12. The 3 D structures of genes of intrest were retrieved from the protein data bank (PDB). The bioavailability and pharmacological properties of the ligands were determined using OSIRIS server. The novelty of the compound was determined based on fitness, docking and bioavailability score. From the results it is observed that, the compoud has exhibited best dock score against all the selected targets than the clozapie except DBH and VMAT2 in SET-1 targets of DOPA genes. Where as the compound has shown best pharmacokinetic and biologicl property score than the clozapine. Hence, the compound can be considered for further in vitro and in vivo studies to determine the therapeutic efficacy and drug candidacy of the compound in future.

Induction of dopamine biosynthesis by l-DOPA in PC12 cells: implications of L-DOPA influx and cyclic AMP.

The effects of 3,4-dihydroxyphenylalanine (l-DOPA) on dopamine biosynthesis and cytotoxicity were investigated in PC12 cells. l-DOPA treatment (20-200 microM) increased the levels of dopamine by 226%-504% after 3-6 h of treatment and enhanced the activities of tyrosine hydroxylase (TH) and aromatic l-amino acid decarboxylase (AADC). l-DOPA (20-200 muM) treatment led to a 562%-937% increase in l-DOPA influx at 1 h, which inhibited the activity of TH, but not AADC, during the same period. The extracellular releases of dopamine were also increased by 231%-570% after treatment with 20 and 200 microM l-DOPA for 0.5-3 h. l-DOPA at a concentration of 100-200 microM, but not 20 microM, exerted apoptotic cytotoxicity towards PC12 cells for 24-48 h. l-DOPA (20-200 microM) increased the intracellular cyclic AMP levels by 318%-557% after 0.5-1 h in a concentration-dependent manner. However, the elevated cyclic AMP levels by l-DOPA could not protect against l-DOPA (100-200 microM)-induced cytotoxicity after 24-48 h. In addition, l-DOPA (20-200 microM)-induced increases in cyclic AMP and dopamine were significantly reduced by treatment with SCH23390 (dopamine D(1) receptor antagonist). The increased levels of dopamine by l-DOPA were also reduced by H89 (protein kinase A, PKA, inhibitor) and GF109203X (protein kinase C inhibitor); however, the reduction by GF109203X was not significant. l-DOPA at 20-200 microM stimulated the phosphorylation of PKA and cyclic AMP-response element binding protein and induced the biosynthesis of the TH protein. These results indicate that 20-200 microM l-DOPA induces dopamine biosynthesis by two pathways. One pathway involves l-DOPA directly entering the cells to convert dopamine through AADC activity (l-DOPA decarboxylation). The other pathway involves l-DOPA and/or released dopamine activating TH to enhance dopamine biosynthesis by the dopamine D(1) receptor-cyclic AMP-PKA signaling system (dopamine biosynthesis by TH).

Validation studies on the 5-hydroxy-L-[beta-11C]-tryptophan/PET method for probing the decarboxylase step in serotonin synthesis.

The two-tissue compartment model, including irreversible trapping in the second compartment (2TCM) is used to describe the kinetics of 5-Hydroxy-L-[beta-(11)C]-tryptophan ([(11)C]HTP), a radioligand used in positron emission tomography (PET) for probing the second enzymatic step in the biosynthesis of serotonin. In this study, we examined the capacity of the model to track pharmacological changes in this biological process. We also investigated the potential loss of [(11)C]HTP-derived radioactivity during a PET study, since loss should be negligible not to alter quantification. Six rhesus monkeys were investigated using bolus [(11)C]HTP/PET methodology before and after pharmacological intervention. The second enzymatic step in serotonin synthesis was inhibited using the aromatic L-amino acid decarboxylase inhibitor NSD1015 (10 mg/kg). The extent of [(11)C]-derived radioactivity loss from the brain was studied by inhibition of the enzyme responsible for formation of the tissue metabolite, monoamine oxidase A, using clorgyline (2 mg/kg). After NSD1015, the uptake of [(11)C]HTP-derived radioactivity was increased in all the investigated brain regions, while the parameter used to reflect decarboxylase activity, the net accumulation rate constant (K(acc)), was decreased by 37% in the striatum, compared with baseline. Pretreatment with clorgyline did not change the brain uptake of [(11)C]HTP-derived radioactivity or K(acc). This study demonstrates that the 2TCM for [(11)C]HTP/PET is able to detect changes occurring during alteration of the biological process (i.e., the conversion of HTP to serotonin). Elimination of the radiotracer metabolite [(11)C]HIAA from the brain may be considered negligible if the PET study is limited to 60 min.

Levodopa-responsive aromatic L-amino acid decarboxylase deficiency.

We report three siblings, who were treated empirically with levodopa combined with carbidopa. There was an immediate therapeutic response. Biochemical investigation surprisingly showed the clinical phenotype to be caused by aromatic L-amino acid decarboxylase deficiency. Molecular characterization showed a homozygous point mutation (c.387 G-->A) in exon 3. Kinetic studies showed the mutation to decrease the binding affinity for the substrate. This, combined with structural modeling suggesting alteration of active site configuration, provided an explanation for the therapeutic response to levodopa.

Increased tryptophan decarboxylase and monoamine oxidase activities induce Sekiguchi lesion formation in rice infected with Magnaporthe grisea.

Sekiguchi lesion (sl)-mutant rice infected with Magnaporthe grisea showed increased light-dependent tryptophan decarboxylase (TDC) and monoamine oxidase (MAO) activities. TDC and MAO activities were observed before the penetration of M. grisea to rice cells and maintained high levels even after Sekiguchi lesion formation. Light-dependent expression of TDC gene was observed in leaves inoculated with M. grisea before Sekiguchi lesion formation. Spore germination fluid (SGF) of M. grisea also induced Sekiguchi lesion formation accompanied by increased enzymes activities and tryptamine accumulation. Sekiguchi lesion was also induced by treatments with tryptamine and beta-phenylethylamine, which are substrates for MAO, but was not induced by non-substrates such as indole-3-propionic acid, (+/-)-phenylethylamine and tryptophan under light. Light-dependent induction of Sekiguchi lesion by tryptamine was significantly inhibited in the presence of MAO inhibitors, metalaxyl and semicarbazide, and H2O2-scavengers, ascorbic acid and catalase. H2O2 in M. grisea-infected leaves with and without Sekiguchi lesions was demonstrated directly in situ by strong 3,3'-diaminobenzidine (DAB) staining. On the other hand, H2O2 induced Sekiguchi lesions on leaves of cv. Sekiguchi-asahi under light, but not in darkness. This difference was associated with the decrease of catalase activity in infected leaves under light and the absence of decrease in darkness. We hypothesize that the H2O2-induced breakdown of cellular organelles such as chloroplasts and mitochondria in mesophyll cells may cause high TDC and MAO activities and the development of Sekiguchi lesion, and that the sl gene products in wild-type rice may function as a suppressor of organelle breakdown caused by chemical or environmental stress.

Norepinephrine precursor therapy in neurogenic orthostatic hypotension.

BACKGROUND: In patients with neurogenic orthostatic hypotension (NOH), the availability of the sympathetic neurotransmitter norepinephrine (NE) in the synaptic cleft is insufficient to maintain blood pressure while in the standing posture. METHODS AND RESULTS: We determined the effect of oral administration of the synthetic amino acid L-threo-3,4-dihydroxyphenylserine (L-DOPS), which is decarboxylated to NE by the enzyme L-aromatic amino acid decarboxylase (L-AADC) in neural and nonneural tissue, on blood pressure and orthostatic tolerance in 19 patients with severe NOH (8 with pure autonomic failure and 11 with multiple-system atrophy). A single-blind dose-titration study determined the most appropriate dose for each patient. Patients were then enrolled in a double-blind, placebo-controlled, crossover trial. L-DOPS significantly raised mean blood pressure both supine (from 101+/-4 to 141+/-5 mm Hg) and standing (from 60+/-4 to 100+/-6 mm Hg) for several hours and improved orthostatic tolerance in all patients. After L-DOPS, blood pressure increases were closely associated with increases in plasma NE levels. Oral administration of carbidopa, which inhibits L-AADC outside the blood-brain barrier, blunted both the increase in plasma NE and the pressor response to L-DOPS in all patients CONCLUSIONS: Acute administration of L-DOPS increases blood pressure and improves orthostatic tolerance in patients with NOH. The pressor effect results from conversion of L-DOPS to NE outside the central nervous system.

Aromatic L-amino acid decarboxylase deficiency with hyperdopaminuria. Clinical and laboratory findings in response to different therapies.

Aromatic L-amino acid decarboxylase (AADC - E.C. 4.1.1.28) converts L-dopa to dopamine and 5-hydroxytryptophan to serotonin. Inherited deficiency of this enzyme leads to decreased brain levels of these neurotransmitters. Clinically this results in the development of a progressive neurometabolic disorder characterized by severe hypotonia, dystonic and choreoathetoid movements, oculogyric crises, and hypothermia from infancy. Here we describe the clinical, biochemical and molecular details of two affected brothers, one of whom, despite the lack of AADC, presented with hyperdopaminuria. In addition, we detail his reactions to treatment with dopaminergic agonists, monoamine oxidase inhibitors and pyridoxine.

6-(18)F-DOPA PET study in patients with schizophrenia. Positron emission tomography.

Presynaptic dopamine metabolism was studied in a group of patients with schizophrenia and in an age- and gender-matched normal control group using 6-[(18)F]fluoro-L-DOPA ((18)F-DOPA) and positron emission tomography (PET). Nineteen patients, nine drug-free, 10 on neuroleptics, and 13 normal control subjects underwent PET scans using (18)F-DOPA. The neuroleptic-treated patients were taking typical neuroleptics (N=4) or the atypical neuroleptic, clozapine (N=6). The ratio of specific/non-specific activity was calculated for eight cortical and subcortical regions of interest. Medication-free patients had a significant reduction in (18)F-DOPA uptake in the ventral striatum (P=0.04) and significantly increased uptake in the posterior cingulate (P=0.02) compared with normal control subjects. The 18F-DOPA PET technique proved to be useful and sensitive in detecting changes in dopamine metabolism in patients with schizophrenia in vivo. The results of this study provide evidence of an aberrant dopamine system in schizophrenia.

Retinal cholinergic and dopaminergic deficits of aged rats are improved following treatment with GM1 ganglioside.

Selected cholinergic and dopaminergic markers were compared in the retina of aged (20-22-months-old) and young (3-months-old) rats before and after treatment with GM1 ganglioside. The dopaminergic markers, tyrosine hydroxylase, aromatic L-amino acid decarboxylase, dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid were comparable in the young and aged animals and GM1 treatment did not alter them. In contrast, mazindol binding, a marker for the dopamine transporter, was diminished in the aged retina and treatment with GM1 restored binding to values found in the young animals. The cholinergic markers choline acetyltransferase and hemicholinium-3 binding, a marker for the high-affinity choline transport, were depressed in aged rats and GM1 corrected the deficits.

Opposite effects of glutamate antagonists and antiparkinsonian drugs on the activities of DOPA decarboxylase and 5-HTP decarboxylase in the rat brain.

This study measured the activities of L-DOPA and 5-HTP decarboxylase (DDC and 5-HTPDC) in the substantia nigra and corpus striatum of reserpine-treated rats. Acute injection of the NMDA receptor antagonists CGP 40116 (5 mg/kg) and HA 966 (5 mg/kg), and to a lesser extent eliprodil (10 mg/kg), greatly elevated DDC in both structures, whilst having no effect on (nigra) or inhibiting (striatum) 5-HTPDC. L-DOPA (25 mg/kg) on its own inhibited both enzymes in either brain region. The weak NMDA receptor-channel blockers (and antiparkinsonian drugs) budipine (10 mg/kg), memantine (40 mg/kg) and amantadine (40 mg/kg) strongly increased DDC, whilst not affecting or decreasing 5-HTPDC activity in nigra and striatum. The L-DOPA-induced suppression of DDC was mostly reversed by all three antiparkinsonian drugs, whilst L-DOPA-induced inhibition of 5-HTPDC was only reversed by CGP 40116 (striatum only). It is concluded that glutamate exerts a differential physiological influence on the biosynthesis of dopamine and 5-HT in the brain, by tonically suppressing DDC and tonically stimulating 5-HTPDC. The L-DOPA-induced reduction in DDC may help to explain the eventual loss of efficacy of L-DOPA therapy in parkinsonian patients. It is suggested, however, that it may be possible to extend the lifetime of L-DOPA therapy with drugs which potentiate the activity of DDC, such as budipine and the 1-aminoadamantanes.

The O-methylated derivative of L-DOPA, 3-O-methyl-L-DOPA, fails to inhibit neuronal and non-neuronal aromatic L-amino acid decarboxylase.

The present study examined whether the O-methylated derivative of L-DOPA, 3-O-methyl-L-DOPA (3-OM-L-DOPA), inhibits neuronal (brain) and non-neuronal (liver and kidney) aromatic L-amino acid decarboxylase (AADC) activity. The incubation of brain, liver and kidney homogenates with 3-OM-L-DOPA (5 mM) did not result in the formation of 3-methoxytyramine, the compound expected to result from the decarboxylation of 3-OM-L-DOPA. Incubation of tissue homogenates with L-DOPA resulted in a concentration-dependent formation of dopamine, revealing K(m) values (in mM) of similar magnitude for brain (0.8), liver (1.6) and kidney (1.0). Both benserazide and L-5-hydroxytryptophan (L-5-HTP) were found to produce concentration dependent decreases in AADC activity with K(i) values in the microM range. By contrast, 3-OM-L95% reduction) in liver and kidney AADC activity accompanied by a marked decrease (49% reduction) in brain AADC activity. By contrast, the administration of 30 mg/kg (p.o.) 3-OM-L-DOPA, which generates levels in brain, liver and kidney six-fold those in L-DOPA-treated rats, was found to change neither neuronal nor non-neuronal AADC activity. In conclusion, 3-OM-L-DOPA fails to interact with neuronal and non-neuronal AADC, either as substrate or inhibitor.

SCH 23390 enhances exogenous L-DOPA decarboxylation in nigrostriatal neurons.

Exogenous L-DOPA enhances dopamine metabolism in the intact and denervated striatum, and is the treatment of choice for Parkinsonism. Aromatic L-amino acid decarboxylase (AAAD) converts L-DOPA to dopamine. Blockade of dopamine D1-like receptors increases the activity of AAAD in both intact and denervated striatum. A single dose of SCH 23390, a dopamine D1-like receptor antagonist, increases the activity of AAAD in the striatum and midbrain and induces small changes in dopamine metabolism. When L-DOPA is administered after SCH 23390, there is a significant increase in the formation of 3,4-dihydroxyphenylacetic acid and dopamine turnover in striatum and midbrain compared to L-DOPA alone, suggesting further enhancement of dopamine metabolism. When the studies are repeated in the MPTP mouse model of Parkinson's disease, there is significantly more dopamine metabolism in the striatum of lesioned mice pretreated with SCH 23390 than in a comparison group treated with L-DOPA alone. These studies suggest that it may be possible to enhance the conversion of L-DOPA to dopamine in Parkinson's disease patients by administering substances that augment brain AAAD.

Direct fluorometry of phase-extracted tryptamine-based fast quantitative assay of L-tryptophan decarboxylase from Catharanthus roseus leaf.

An assay for the enzyme L-tryptophan decarboxylase (TDC; EC 4.1.1.28) is described. It is based on direct fluorometry of the enzymatic reaction product (tryptamine) selectively recovered in ethyl acetate from the reaction mixture. Catalytically formed tryptamine from tryptophan in the incubation mixture is selectively (free from tryptophan) physically separated as ethyl acetate solution under basic (pH > or = 11) conditions and subjected to direct fluorescence measurement in the organic solvent using a spectrofluorometer with excitation and emission wavelengths of 280 and 350 nm, respectively. Tryptamine production rate was quantitated from the luminescence response curve of tryptamine drawn under similar extraction and measurement conditions. Luminescence calibration curves were drawn for tryptamine in aqueous (water or buffer system) as well as in organic solvent as recovered from the varied aqueous solution conditions including those similar to the enzyme incubation mixture. The luminescence calibration graphs were linear for at least 0.5 to 10 microM tryptamine. The examination of interassay variations and the comparative magnitude of fluorescence response allowed to infer that a satisfactory and sufficient sample luminescence response was retained under the varied conditions including those akin to the enzymatic assay mixture, allowing adaptation of the fluorometry for the TDC activity quantitation. The assay was found to follow the proportionality principle of product formation with respect to catalytic reaction time as well as protein concentration in the assay mixture using Catharanthus roseus leaf crude homogenate as well as the enzyme preparation at different states of purity. The rate of tryptamine formation under the catalytic conditions was linear for at least 1 h at 30 degrees C. Though the assay has been demonstrated to use the C. roseus leaf as the enzyme source, it should be equally applicable to other plant and nonplant sources. The merits and precautions of the protocol have been discussed.

Tyrosine hydroxylase and aromatic L-amino acid decarboxylase in mesencephalic cultures after MPP+: the consequences of treatment with GM1 ganglioside.

Rat embryonic mesencephalic cultures were treated with the dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP+), and GM1 ganglioside added after the toxin. Twelve days after a 24-h exposure to MPP+, there was a significant decrement in tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AAAD) activities. In addition, TH mRNA was decreased, whereas AAAD mRNA was no different from control cultures. Adding GM1 to control unlesioned cultures had no effect on TH activity or mRNA. In contrast, GM1 modestly increased both the activity and mRNA for AAAD. In the MPP+-treated cultures, GM1 induced a partial recovery of TH and AAAD activity and increased mRNA for both above unlesioned control levels. Our studies demonstrate that GM1 upregulates the synthetic enzymes for dopamine in MPP+-lesioned embryonic mesencephalic cultures, and suggest that TH and AAAD respond differentially to the neurotoxin insult.

Dizocilpine enhances striatal tyrosine hydroxylase and aromatic L-amino acid decarboxylase activity.

Dizocilpine administration enhances dopamine metabolism in the rat striatum, nucleus accumbens, olfactory tubercle, and prefrontal cortex. Concomitant with increased metabolism is enhanced tyrosine hydroxylase and aromatic L-amino acid decarboxylase activities in the striatum and increased mRNA for the two enzymes in the midbrain. Activation of dopaminergic neurons may, in part, explain increased locomotor activity in normal animals and the ability of dizocilpine to potentiate the antiparkinsonian action of L-3,4-dihydroxyphenylalanine in an animal model.

The effects of monoamine oxidase B inhibition on dopamine metabolism in rats with nigro-striatal lesions.

The purpose of this study was to examine whether monoamine oxidase type B (MAO-B) has a role in striatal dopamine metabolism in animals with a unilateral lesion of the medial forebrain bundle, and whether 2-phenylethylamine (PE) could have a role in amplification of dopamine (DA) responses in DA depleted striatum. Inhibition of MAO-B did not alter DA metabolism in lesioned striata. PE accumulation decreased with loss of DA as long as there was no DA dysfunction. In lesioned striata with dysfunction of DA transmission at the synaptic level, PE accumulation increased, suggesting a compensatory increase in PE synthesis. This increase in PE levels does not appear to be mediated by an increase in the total striatal aromatic L-amino acid decarboxylase (AADC) activity. We conclude that inhibition of MAO-B has no effect on DA metabolism in the hemi-parkinsonian rat striatum and that PE could be involved in the antiparkinsonian action of MAO-B inhibitors.

Rat liver aromatic L-amino acid decarboxylase: spectroscopic and kinetic analysis of the coenzyme and reaction intermediates.

The physiochemical properties of the coenzyme in rat liver aromatic L-amino acid decarboxylase (AADC) expressed in Escherichia coli have been studied by spectroscopic analysis of the enzyme, its reaction intermediates, and its complexes with substrate analogs. The enzyme, having one pyridoxal 5'-phosphate (PLP) per subunit, shows a prominent absorption maximum at 335 nm and a weaker one at 425 nm. The spectrum did not essentially change in the pH range of 6.0-8.0. When the coenzyme was excited at 335 nm, it emitted fluorescence primarily at 520 nm. The structure for the absorption at 335 nm was ascribed to the enolimine form of the PLP-lysine Schiff base. On the reaction of AADC with L-3,4-dihydroxyphenylalanine (L-dopa), the absorption of PLP showed biphasic changes before reaching a steady-state. Results of both pre-steady-state and steady-state kinetic analyses were consistent with the model that the reaction proceeds as shown in the equation: E + S<==>X1<==>X2-->E + P. The rate constant was determined for each step, and the Km value for L-dopa was obtained as 0.086 mM. The absorption spectra of the two intermediates, X1 and X2, were postulated from the calculation of the absorption changes during the first and the second steps of the reaction in which X1 and X2 showed an absorption maximum at 425 and 380 nm, respectively, with a concomitant decrease in absorbance at 335 nm. These predicted absorption spectra of X1 and X2 showed striking resemblances to those of AADC complexed with dihydroxyphenylacetic acid (DOPAc) and L-dopa methyl ester (DopaOMe), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of different body allowances of aldosterone on serotonin and cAMP metabolism in the tissues of rats with a disordered trophic function of the nervous system]. / Vliianie raznoi obespechenosti organizma alsoteronom na obmen serotonina i tsAMF v tkaniakh krys pri narushenii troficheskoi funktsii nervnoi sistemy.

Effect of aldosterone on the content of serotonin, cAMP, and the activity of 5-hydroxytryptophane decarboxylase was studied in different rat tissues (hypothalamus, kidneys, tibial muscles) in norm and following the lesion of sciatic nerve in nonadrenalectomized and adrenalectomized animals, that is in conditions of severe deficiency of endogenous aldosterone. In nonadrenalectomized rats, exogenous aldosterone exerted either very little effect or no effect on the tissues metabolism of serotonin and cAMP. Aldosterone induced changes in the content of considered substances against the background of adrenalectomy in animals with intact sciatic nerve. These changes were observed usually only in hypothalamus and kidneys and reached their peak 60 or 90 min following the aldosterone administration. The changes in serotonin and cAMP tissues metabolism under the chronic stimulation of nervous system periphery with aldosterone may be an additional factor which enables further aggravation of trophic state of tissues and organs and alteration of their sensitivity to hormones, in particular, aldosterone.