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.

Autolytic enzymes are responsible for increased melanization of carbon stressed Aspergillus nidulans cultures.

Melanization of carbon stressed Aspergillus nidulans cultures were studied. Melanin production showed strong positive correlation with the activity of the secreted chitinase and ß-1,3-glucanase. Deletion of either chiB encoding an autolytic endochitinase or engA encoding an autolytic ß-1,3-endoglucanase, or both, almost completely prevented melanization of carbon stressed cultures. In contrast, addition of Trichoderma lyticase to cultures induced melanin production. Synthetic melanin could efficiently inhibit the purified ChiB chitinase activity. It could also efficiently decrease the intensity of hyphal fragmentation and pellet disorganization in Trichoderma lyticase treated cultures. Glyphosate, an inhibitor of L-3,4-dihydroxyphenylalanine-type melanin synthesis, could prevent melanization of carbon-starved cultures and enhanced pellet disorganization, while pyroquilon, a 1,8-dihydroxynaphthalene-type melanin synthesis inhibitor, enhanced melanization, and prevented pellet disorganization. We concluded that cell wall stress induced by autolytic cell wall hydrolases was responsible for melanization of carbon-starved cultures. The produced melanin can shield the living cells but may not inhibit the degradation and reutilization of cell wall materials of dead hyphae. Controlling the activity of autolytic hydrolase production can be an efficient approach to prevent unwanted melanization in the fermentation industry, while applying melanin synthesis inhibitors can decrease the resistance of pathogenic fungi against the chitinases produced by the host organism.

Inhibition of lentil copper/TPQ amine oxidase by the mechanism-based inhibitor derived from tyramine.

Copper amine oxidase from lentil (Lens esculenta) seedlings was shown to catalyze the oxidative deamination of tyramine and three similar aromatic monoamines, benzylamine, phenylethylamine and 4-methoxyphenylethylamine. Tyramine, an important plant intermediate, was found to be both a substrate and an irreversible inhibitor of the enzyme whereas the other amines were not inhibitory. In the course of tyramine oxidation the enzyme gradually became inactivated with the concomitant appearance of a new absorption at 560 nm due to the formation of a stable adduct. Inactivation took place only in the presence of oxygen and was probably due to the reaction of the enzyme with the oxidation product of tyramine, p-hydroxyphenylacetaldehyde. The kinetic data obtained in this study indicate that tyramine represents a new interesting type of physiological mechanism-based inhibitor for plant copper amine oxidases.

Is DOPA a neurotransmitter?

Historically, 3,4-dihydroxyphenylalanine (DOPA) has been considered to be an inert amino acid that alleviates the symptoms of Parkinson's disease by its conversion to dopamine via the enzyme aromatic L-amino acid decarboxylase. In contrast to this generally accepted idea, we propose that DOPA itself is a neurotransmitter and/or neuromodulator in addition to being a precursor of dopamine. Several criteria such as synthesis, metabolism, active transport, existence, physiological release, competitive antagonism and physiological or pharmacological responses must be satisfied before a compound is accepted as a neurotransmitter. Recent evidence suggests that DOPA fulfills these criteria in its involvement in baroreflex neurotransmission.

DOPA cyclohexyl ester, a competitive DOPA antagonist, protects glutamate release and resultant delayed neuron death by transient ischemia in hippocampus CA1 of conscious rats.

In rat striata, DOPA released is a causal factor for glutamate release and resultant delayed neuron death by four-vessel occlusion. Nanomolar DOPA cyclohexyl ester (CHE), a potent and relatively stable competitive DOPA antagonist, protects these events. We tried to clarify whether DOPA CHE protects these events in hippocampal CA1 pyramidal cell layers most vulnerable against ischemia. Five to 10 min ischemia caused slight to mild glutamate release in 10 min samples during microdialysis and mild to severe neuron death 96 h after reperfusion. DOPA and dopamine were under assay limit in this design, but were basally detected by 20 min sampling and released by 20 min ischemia. In 10 min samples, intrahippocampal perfusion of 100 nM DOPA CHE 10 min before ischemia for 70 min did not inhibit glutamate release by 10 min ischemia, while it abolished glutamate release and protected delayed neuron death by 5 min ischemia. DOPA CHE is neuroprotective under a mild ischemic condition in rat hippocampus CA1.

[A DOPA antagonist, DOPA cyclohexyl ester inhibits transient brain ischemia-induced release of glutamate and delayed neuronal cell death in striatal and hippocampal region of in vivo rats].

We have previously obtained evidence that DOPA is probably involved in an upstream process of mechanisms for in vivo neuronal cell death in striatum. We attempted to clarify whether or not this is also the case in hippocampal region of conscious Wistar rats. Four vessels were occluded for 5 min during microdialysis of hippocampus. DOPA, dopamine and glutamate (Glu) in perfusates collected every 10 min were measured by HPLC-ECD and spectrophotometer. Delayed neuronal cell death in hippocampus was evaluated 96 hr after ischemia. Five-min transient brain ischemia induced Glu release, with the peak being 2.5-fold of a basal release at the fraction immediately after ischemia. The release of DOPA and dopamine was not consistently detectable, but an increase was sometimes observed during and after ischemia. Delayed neuronal cell death was slight to moderate with 5-min ischemia. Intrastriatal perfusion of DOPA cyclohexyl ester (DOPA CHE) at 100 nM, a novel stable potent competitive DOPA antagonist, almost completely inhibited the ischemia-induced glutamate release, and protected hippocampal neurons from delayed cell death. Endogenously released DOPA itself seems to act on its recognition site and to behave as a causal and/or deteriorating factor on glutamate release and resultant delayed neuronal cell death by transient ischemia in rats.

Deficiency of renal dopaminergic-dependent natriuretic response to acute sodium load in black salt-sensitive subjects in contrast to salt-resistant subjects.

OBJECTIVE: To evaluate the involvement of the renal dopaminergic system in the natriuretic responses to acute saline load in salt-resistant (SR) and salt-sensitive (SS) black normotensive (NT) and hypertensive (HT) subjects. DESIGN AND METHODS: We studied the relationship between the urinary excretion of dopa, dopamine (DA) and its metabolite DOPAC and the natriuretic responses to acute volume expansion (2 l NaCl 0.9% over 2 h) in 20 black NT subjects (12 SR and 8 SS) and 19 black HT subjects (10 SS and 9 SR). Subjects received a low salt (LS) diet (40 mmol sodium/day) for 1 week and a high salt (HS) diet (300 mmol sodium/day) for 1 week; the sequence of the dietary regimens was randomized. Comparisons were made between the results before the saline infusion (baseline) and the results 2 h after the infusion. RESULTS: In all the groups saline infusion induced significant increases in urinary volume (ml/4 h) of two- to three-fold and in urinary sodium excretion (mmol/4 h) of three- to ten-fold; these increases were significantly greater during the HS diet than during the LS diet. Saline infusion significantly increased the mean arterial pressure (MAP) by 5 mmHg in HT-SS subjects and by 4-5 mmHg in NT-SS subjects, but the MAP did not changed in the NT-SR and HT-SR groups. Under the LS diet, saline infusion changed the DA excretion (in nmol/4 h) by -49+/-89 in HT-SS subjects, by 17+/-52 in NT-SS subjects, by 235+/-72 in HT-SR subjects and by 220+/-86 in NT-SR subjects (P < 0.05 between SR and SS subjects). The saline infusion-induced changes in DA excretion correlated significantly with the increases in urinary sodium excretion (r = 0.71, P < 0.01) in the NT-SR and HT-SR subjects under the LS diet, but not in the SR groups on the HS diet nor in the SS groups (HT and NT) on either diet. Saline infusion significantly reduced the DA/dopa ratio in SS (NT and HT) but not SR (NT and HT) subjects, whereas the DA/DOPAC (dihydroxyphenylacetic acid) ratios were similar in all the groups. CONCLUSIONS: The urinary dopaminergic system may participate in the natriuretic responses to acute sodium load only in SR subjects (NT and HT) and only under LS diets, but not in SS subjects (NT and HT). This strongly suggests that black NT- and HT-SS subjects have an underlying impairment in the activity of the renal dopaminergic system which may be associated with a reduced decarboxylation of dopa into DA.

Peroxynitrite-mediated inhibition of DOPA synthesis in PC12 cells.

Experimental evidence has implicated oxidative stress in the development of Parkinson's disease, amyotrophic lateral sclerosis, and other degenerative neuronal disorders. Recently, peroxynitrite, which is formed by the nearly diffusion-limited reaction of nitric oxide with superoxide, has been suggested to be a mediator of oxidant-induced cellular injury. The potential role of peroxynitrite in the pathology associated with Parkinson's disease was evaluated by examining its effect on DOPA synthesis in PC12 pheochromocytoma cells. Peroxynitrite was generated from the compound 3-morpholinosydnonimine (SIN-1), which releases superoxide and nitric oxide simultaneously. Exposure of PC12 cells to peroxynitrite for 60 min greatly diminished their ability to synthesize DOPA without apparent cell death. The inhibition was due neither to the formation of free nitrotyrosine nor the oxidation of DOPA by peroxynitrite. The inhibition in DOPA synthesis by SIN-1 was abolished when superoxide was scavenged by the addition of superoxide dismutase. These data indicated that neither nitric oxide nor hydrogen peroxide generated by the dismutation of superoxide is responsible for the SIN-1-mediated inhibition of DOPA production. The inhibition of DOPA synthesis at high concentration of SIN-1 persisted even after removal of SIN-1. The inactivation of the tyrosine hydroxylase may be responsible for the significant decline in DOPA formation by peroxynitrite. Inactivation of tyrosine hydroxylase may be part of the initial insult in oxidative damage that eventually leads to cell death.

Review on the relationship between nicotinic acetylcholine receptors and dopaminergic neurotransmission in the central nervous system--dopa is an endogenous neuroactive substance.

L-3,4-Dihydroxyphenylalanine (DOPA) is believed to be an inert precursor for dopamine (DA). Contrary, transmitter-like endogenous DOPA is released from in vitro and in vivo striata: DOPA is released by neuronal activities under physiological conditions from striata of conscious rats. Furthermore, exogenous nanomolar DOPA itself produces an in vitro presynaptic response to facilitate the catecholamine release. An in vivo postsynaptic depressor response is elicited by DOPA microinjected into the nucleus tractus solitarii. These responses are antagonized by L-DOPA methyl ester, a competitive DOPA antagonist. In striata, DOPA is an endogenous potentiator for presynaptic beta-adrenoceptors to facilitate the DA release and also probably for postsynaptic D2-receptors to increase locomotor activities. Nicotine releases DA and transmitter-like DOPA in vitro and in vivo striata. Nicotine (0.1-1.0 mg/kg, sc) dose-dependently increases locomotor activities. This increase is stereoselective and mecamylamine (1.0 mg/kg, sc)-sensitive but not antagonized by L-DOPA methyl ester (200 micrograms, ivt). Then, a selective low ip dose of alpha-methyl-p-tyrosine (alpha-MPT) to inhibit the basal release of DOPA without decreasing the basal release of DA was explored in vivo striata: it was 3 mg/kg. Pretreatment with this dose did inhibit the nicotine-induced increases in locomotor activities. This result suggests that endogenously released DOPA is in part relevant to nicotine-induced behavior in rats.

Brain-derived neurotrophic factor selectively rescues mesencephalic dopaminergic neurons from 2,4,5-trihydroxyphenylalanine-induced injury.

Brain-derived neurotrophic factor (BDNF) supports the survival of sensory neurons as well as retinal ganglion cells, basal forebrain cholinergic neurons, and mesencephalic dopaminergic neurons in vitro. Here we examined the ability of BDNF to confer protection on cultured dopaminergic neurons against the neurotoxic effects of 6-hydroxyDOPA (TOPA or 2,4,5-trihydroxyphenylalanine), a metabolite of the dopamine pathway suggested to participate in the pathology of Parkinson's disease. Cells prepared from embryonic day 14-15 rat mesencephalon were maintained with 10-50 ng/ml BDNF for 7 days prior to addition of TOPA (10-30 microM) for 24 hr. In BDNF-treated cultures, the extensive loss (> 90%) of tyrosine hydroxylase immunopositive cells was virtually (< 10%) eliminated, while the equally drastic loss (> 90%) of the overall cell population was limited to only a 25-30% recovery. Furthermore, the monosialoganglioside GM1 (1-10 microM), although inactive alone, acted synergistically with subthreshold amounts of BDNF to rescue tyrosine hydroxylase-positive cells against TOPA neurotoxicity. These results add impetus to exploring the therapeutic potential of gangliosides and BDNF in Parkinson's disease.

Glutathione prevents 2,4,5-trihydroxyphenylalanine excitotoxicity by maintaining it in a reduced, non-active form.

2,4,5-Trihydroxyphenylalanine (TOPA) in aqueous solution has been shown to form an non-N-methyl-D-aspartate (non-NMDA) agonist and neurotoxin, TOPA quinone. We examined whether the endogenous chemical reductant glutathione (GSH) could abolish the agonist properties of TOPA and block its excitotoxicity in rat cortical neurons in culture by preventing the formation of TOPA quinone. The oxidative formation of TOPA quinone from TOPA (30-500 microM) at pH 7.2 was measured spectrophotometrically. Using glutathione (0.05-3 mM) as the reducing agent, we found that the optimal [GSH]:[TOPA] ratio which significantly retarded TOPA quinone formation was 10:1. Thus, 3 mM GSH prevented whole-cell currents induced by a solution of 300 microM TOPA but did not affect currents elicited by 300 microM kainate. In addition, 2 mM GSH protected neurons from the toxic effects of 200 microM TOPA, but was not effective against 200 microM NMDA. These results suggest that the presence of endogenous reductants may limit the toxicity of TOPA.

Role of testosterone in the regulation of tuberoinfundibular dopaminergic neurons in the male rat.

The effects of testosterone on the tuberoinfundibular dopamine (DA) neuronal activity was examined by determining the rate of DA synthesis-accumulation of 3,4-dihydroxyphenylalanine (DOPA) after administration of a decarboxylase inhibitor and the concentration of a DA metabolite,--3,4-dihydroxyphenylacetic acid (DOPAC)--in the median eminence in the male rat. Within 1 week after orchidectomy, there was an increase in the accumulation of DOPA and the concentration of DOPAC in the median eminence, but there was no change in the concentration of DA. Conversely, 1 day after testosterone administration to orchidectomized rats, the elevated DOPAC concentrations in the median eminence returned to levels comparable to those in gonadally intact rats. Neither orchidectomy nor testosterone replacement had any effect on plasma prolactin concentrations, but inhibition of prolactin secretion following administration of the DA agonist bromocriptine blocked the increase in DOPA accumulation in the median eminence of orchidectomized rats; this latter effect was reversed by intracerebroventricular administration of prolactin. On the other hand, intracerebroventricular injection of prolactin caused a similar increase in the accumulation of DOPA in the median eminence of gonadally intact, orchidectomized, and testosterone-treated orchidectomized rats. Immobilization stress decreased the accumulation of DOPA and the concentration of DOPAC in the median eminence of orchidectomized rats, but had no effect in intact or testosterone-treated orchidectomized rats. These results indicate that testosterone inhibits the basal activity of tuberoinfundibular DA neurons and blocks the inhibitory effects of physical restraint on these neurons, but does not alter the ability of these neurons to respond to delayed activation by prolactin.

Postinjection L-phenylalanine increases basal ganglia contrast in PET scans of 6-18F-DOPA.

The sensitivity of 18F-DOPA positron emission tomography for imaging presynaptic dopamine systems is limited by the amount of specific-to-nonspecific accumulation of radioactivity in brain. In rhesus monkeys, we have been able to increase this ratio by taking advantage of the lag time between 18F-DOPA injection and the formation of its main metabolite, the amino acid 18F-fluoromethoxydopa, the entrance of which into brain is responsible for most of the brain's nonspecific radioactivity. By infusing an unlabeled amino acid, L-phenylalanine, starting 15 min after 18F-DOPA administration, we preferentially blocked the accumulation of 18F-fluoromethoxydopa by preventing its entrance into brain through competition at the large neutral amino acid transport system of the blood-brain barrier. This method appears as reliable as the original and more sensitive, as demonstrated by the comparison of normal and MPTP-treated animals under both conditions.

The oxyradical-scavenging activity of azelaic acid in biological systems.

We have previously shown that azelaic acid, a C9 dicarboxylic acid, as disodium salt (C(9)2Na) is capable of inhibiting significantly the hydroxylation of aromatic compounds and the peroxidation of arachidonic acid due to reactive hydroxyl radicals (HO.). In this paper we have investigated the ability of C(9)2Na to inhibit the oxyradical induced toxicity towards two tumoral cell lines (Raji and IRE1) and normal human fibroblasts (HF). Oxyradicals were generated either by the addition of polyphenols to the medium, or by direct irradiation of phosphate buffered-saline in which cells were incubated from 15 min prior to incubation in normal medium. The effects of C(9)2Na were compared with those obtained by mannitol (MAN), superoxide dismutase (SOD) and catalase (CAT). C(9)2Na, MAN, SOD and CAT significantly decreased the polyphenol toxicity towards cell lines cultured up to 24 h. After 48 h of incubation the above compounds lost the capability of protecting cells from polyphenol toxicity. This suggests that the toxic role of oxyradicals (O2-., H2O2, HO.) persists for about 24 h and, subsequently other toxic mechanisms must be involved, which are not affected by oxyradical scavengers. SOD and CAT did not show any protective effect on UV induced cytotoxicity, while both C(9)2Na and MAN were capable of reducing significantly the UV damage towards cell lines, even after 48 h incubation. This can be explained by the fact that UV cytotoxicity depends mainly on the generation of HO., that can be "scavenged" by C(9)2Na or MAN, but not by SOD or CAT. C(9)2Na and MAN were not significantly degraded in the period during which they afford protection against HO..

(+)-sulpiride antagonises the renal effects of gamma-L-glutamyl-L-dopa in man.

1. gamma-L-glutamyl-L-dopa (gludopa) was given by intravenous infusion to six healthy salt-replete men on two occasions, with and without pretreatment with (+)-sulpiride. 2. Gludopa increased sodium excretion, glomerular filtration rate and effective renal plasma flow whilst decreasing plasma renin activity. 3. (+)-sulpiride had no significant effect on baseline natriuresis, renal haemodynamics or plasma renin activity, but significantly attenuated the rise in sodium excretion, glomerular filtration rate and effective renal plasma flow produced by gludopa. 4. (+)-sulpiride abolished the acute fall in plasma renin activity seen with gludopa. 5. (+)-sulpiride raised serum prolactin concentration but did not affect the ris in urine dopamine excretion rate caused by gludopa. 6. Gludopa exerts its renal effects by stimulating specific dopamine receptors which are principally of the DA1 subtype.

Domperidone treatment in man inhibits the fall in plasma renin activity induced by intravenous gamma-L-glutamyl-L-dopa.

The dopamine pro-drug gamma-L-glutamyl-L-dopa (gludopa) was administered intravenously to six normal subjects at a dose of 12.5 micrograms min-1 kg-1, either with or without the dopamine antagonist domperidone. A control was provided by the intravenous infusion of domperidone and saline on a separate occasion. Intravenous gludopa produced a significant natriuresis, whether administered alone or in combination with domperidone. After gludopa infusion, there was a significant fall in plasma renin activity, an effect which was attenuated significantly by concomitant treatment with domperidone. These observations suggest that blockade of renal DA2 dopamine receptors has little or no effect on gludopa-induced natriuresis, but that at least part of the dopaminergic inhibition of renin release is mediated by renal DA2 receptors.

Presynaptic inhibition of dopamine synthesis in rat striatum: effects of chronic dopamine depletion and receptor blockade.

These studies assessed the effects of dopamine (DA) depletion and receptor blockade on presynaptic inhibition of DA synthesis in the rat striatum. Chronic reserpine administration significantly decreased striatal DA levels but did not affect in vivo tyrosine hydroxylase activity, as determined by following dihydroxyphenylalanine (DOPA) accumulations. Both reserpine and haloperidol increased the sensitivity of presynaptic striatal DA response as determined by the ability of apomorphine (APO) to inhibit DOPA accumulation in NSD-1015-treated rats. The effect of concurrent administration of reserpine plus haloperidol on presynaptic response was additive. Additivity occurred at doses of reserpine and haloperidol which induced maximum sensitivity when administered singularly. The data suggest that increases in sensitivity of presynaptic DA response following DA depletion and receptor blockade are mediated by separate regulatory mechanisms.

The effect of cysteine on oxidation of tyrosine, dopa, and cysteinyldopas.

The influence of cysteine on the oxidation of tyrosine, dopa, and monocysteinyldopas by mushroom tyrosinase was reexamined. During oxidation of tyrosine in the presence of cysteine the concentration of dopa increased slowly, whereas the concentration of cysteinyldopas increased more rapidly. When the concentration of cysteine decreased the cysteinyldopas were rapidly consumed and dopa concentrations increased sharply. Experiments on the oxidation of dopa by tyrosinase in the presence of cysteine showed that this thiol does not inhibit the oxidation. Dopa concentrations decreased more rapidly in the presence of cysteine because cysteine addition to dopaquinone prevented reformation of dopa from dopaquinone. Both 2-S-cysteinyldopa and 5-S-cysteinyldopa are substrates for tyrosinase. The oxidation of cysteinyldopas was inhibited at high cysteine concentrations. The greater part of 2,5-S,S-dicysteinyldopa formed during the oxidation of monocysteinyldopas in the presence of cysteine is derived from 5-S-cysteinyldopa, which is a better substrate for tyrosinase than 2-S-cysteinyldopa. The fact that cysteine binds more rapidly to 5-S-cysteinyldopaquinone than to 2-S-cysteinyldopaquinone further stresses the importance of 5-S-cysteinyldopa in the formation of 2,5-S,S-dicysteinyldopa. Oxidation of dopa in the presence of cysteine and glutathione or methionine showed that glutathione is added to dopaquinone but less rapidly than cysteine. Methionine showed insignificant addition to dopaquinone. When dopa or 5-OH-dopa is added to an incubate of cysteinyldopa and tyrosinase the oxidation of cysteinyldopa is accelerated owing to oxidation of cysteinyldopa by dopaquinone or 5-OH-dopaquinone.