L-DOPA exacerbates amphetamine-induced dopamine depletion

Metabolic engineering of Escherichia coli for the production of an antifouling agent zosteric acid

Zosteric acid (ZA) is a Zostera species-derived, sulfated phenolic acid compound with antifouling activity and has gained much attention due to its nontoxic and biodegradable characteristics. However, the yield of Zostera species available for ZA extraction is limited by natural factors, such as season, latitude, light, and temperature. Here we report the development of metabolically engineered Escherichia coli strains capable of producing ZA from glucose and glycerol. First, intracellular availability of the sulfur donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS) was enhanced by knocking out the cysH gene responsible for PAPS consumption and overexpressing the genes required for PAPS biosynthesis. Co-overexpression of the genes encoding tyrosine ammonia-lyase, sulfotransferase 1A1, ATP sulfurylase, and adenosine 5'-phosphosulfate kinase constructed ZA producing strain with enhanced PAPS supply. Second, the feedback-resistant forms of aroG and tyrA genes (encoding 3-deoxy-d-arabinoheptulosonate 7-phosphate synthase and chorismate mutase, respectively) were overexpressed to relieve the feedback regulation of L-tyrosine biosynthesis. Third, the pykA gene involved in phosphoenolpyruvate-consuming reaction, the regulator gene tyrR, the competing pathway gene pheA, and the ptsHIcrr genes essential for the PEP:carbohydrate phosphotransferase system were deleted. Moreover, all genes involved in the shikimate pathway and the talA, tktA, and tktB genes in the pentose phosphate pathway were examined for ZA production. The PTS-independent glucose uptake system, the expression vector system, and the carbon source were also optimized. As a result, the best-performing strain successfully produced 1.52 g L^-1 ZA and 1.30 g L^-1p-hydroxycinnamic acid from glucose and glycerol in a 700 mL fed-batch bioreactor.

Design, synthesis and evaluation of a boronic acid based artificial receptor for (L)-DOPA in aqueous media

Design and synthesis of a boronic acid based artificial receptor which selectively and effectively bound to a neurotransmitter, l-DOPA (), in aqueous media. In addition, the synthetic receptor was found to effectively inhibit the DDC (l-DOPA decarboxylase) enzymatic reaction under physiological conditions.

Voluntary exercise and tail shock have differential effects on amphetamine-induced dopaminergic toxicity in adult BALB/c mice

Exercise exerts neuroprotective effects and facilitates neural recovery in animal models of Parkinson's disease. In the present studies, effects of exercise on amphetamine-induced dopaminergic toxicity were assessed in mice housed individually either with or without access to run wheels. Mice in run wheel cages ran approximately 20 000 revolutions/day (over 10 km/day). Some mice received amphetamine (18.5 mg/kg x 4 injections) whereas controls received saline. Amphetamine caused a 90% dopamine depletion in mice housed either with or without run wheels. A precipitous drop was seen in run wheel activity following amphetamine, lasting at least 7 days. A significant decrease in food intake, water intake and body weight also occurred. The opportunity to exercise did not facilitate behavioral or neurochemical recovery at 1, 2 or 3 days, or 2 weeks after injections. Therefore, shock stress, a component of some forced exercise studies, was evaluated to determine whether stress without exercise provided neuroprotection against amphetamine. Results indicate that shock stress exerted neuroprotective effects, reducing the amphetamine-induced dopamine depletion. It is concluded that voluntary running does not afford either behavioral or neuroprotection nor facilitate recovery from amphetamine-induced dopaminergic toxicity; rather, elevated glucocorticoid levels following shock stress were associated with a reduction in the dopamine depletion.

Shock stress protects mice against amphetamine-induced dopaminergic toxicity

The effect of tail shock (ten, 2.0 mA/0.15 s shocks) on amphetamine-induced dopaminergic toxicity in adult, male BALB/c mice was assessed. Fifteen minutes following a single shock session, mice received amphetamine (50-mg/kg) or saline as follows: Shock/Saline; NoShock/Saline; Shock/Amphetamine; No Shock/Amphetamine. Amphetamine caused a 60% dopamine depletion in the No Shock/Amphetamine group. Tail shock provided neuroprotection against amphetamine-induced dopamine depletion, an effect likely related to the stress response.

Risperidone reduction of amphetamine-induced self-injurious behavior in mice

The behavioral and neurochemical effects of high doses of amphetamine administered to BALB/c mice were examined in the presence and absence of co-administered haloperidol (a D2 antagonist), SCH 23390 (a D1 antagonist) and risperidone (a mixed 5-HT2/D2 antagonist). It was observed that mice displayed a dose-dependent increase in stereotypic behavior, oral dyskinesia, and self-injurious behavior (SIB) in response to amphetamine treatment. Furthermore, agents that blocked the SIB reversed the amphetamine-induced release of serotonin. This effect was unrelated to hyperthermia or non-specific sedation (as assessed by measurement of motor activity). These data are interpreted in the context of the underlying basis of murine SIB involving both dopaminergic and serotonergic activation and demonstrate the efficacy of risperidone in treating these behaviors.

Stimulatory effect of oral administration of green tea and caffeine on locomotor activity in SKH-1 mice

Administration of green tea or caffeine was shown previously to inhibit ultraviolet B light-induced carcinogenesis in SKH-1 mice, and this effect was associated with a reduction in dermal fat. In the present study, oral administration of 0.6% green tea (6 mg tea solids/ml) or 0.04% caffeine (0.4 mg/ml; equivalent to the amount of caffeine in 0.6% green tea) as the sole source of drinking fluid to SKH-1 mice for 15 weeks increased total 24 hr locomotor activity by 47 and 24%, respectively (p<0.0001). Oral administration of 0.6% decaffeinated green tea (6 mg tea solids/ml) for 15 weeks increased locomotor activity by 9% (p<0.05). The small increase in locomotor activity observed in mice treated with decaffeinated green tea may have resulted from the small amounts of caffeine still remaining in decaffeinated green tea solutions (0.047 mg/ml). The stimulatory effects of orally administered green tea and caffeine on locomotor activity were paralleled by a 38 and 23% increase, respectively, in the dermal muscle layer thickness. In addition, treatment of the mice with 0.6% green tea or 0.04% caffeine for 15 weeks decreased the weight of the parametrial fat pad by 29 and 43%, respectively, and the thickness of the dermal fat layer was decreased by 51 and 47%, respectively. These results indicate that oral administration of green tea or caffeine to SKH-1 mice increases locomotor activity and muscle mass and decreases fat stores. The stimulatory effect of green tea and caffeine administration on locomotor activity described here may contribute to the effects of green tea and caffeine to decrease fat stores and to inhibit carcinogenesis induced by UVB in SKH-1 mice.

Current research on methamphetamine-induced neurotoxicity: animal models of monoamine disruption

Methamphetamine (METH)-induced neurotoxicity is characterized by a long-lasting depletion of striatal dopamine (DA) and serotonin as well as damage to striatal dopaminergic and serotonergic nerve terminals. Several hypotheses regarding the mechanism underlying METH-induced neurotoxicity have been proposed. In particular, it is thought that endogenous DA in the striatum may play an important role in mediating METH-induced neuronal damage. This hypothesis is based on the observation of free radical formation and oxidative stress produced by auto-oxidation of DA consequent to its displacement from synaptic vesicles to cytoplasm. In addition, METH-induced neurotoxicity may be linked to the glutamate and nitric oxide systems within the striatum. Moreover, using knockout mice lacking the DA transporter, the vesicular monoamine transporter 2, c-fos, or nitric oxide synthetase, it was determined that these factors may be connected in some way to METH-induced neurotoxicity. Finally a role for apoptosis in METH-induced neurotoxicity has also been established including evidence of protection of bcl-2, expression of p53 protein, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), activity of caspase-3. The neuronal damage induced by METH may reflect neurological disorders such as autism and Parkinson's disease.

Methamphetamine-induced striatal dopamine release, behavior changes and neurotoxicity in BALB/c mice

The behaviors associated with the neurotoxic effects of methamphetamine were evaluated in BALB/c mice. Hyperthermia and behavioral observations were measured 60 min after each subcutaneous injection of methamphetamine (4x4 or 8 mg/kg) or saline, each given 2 h apart. The behavioral observations included stereotyped behaviors, incidence of hemorrhage in breast, salivation and self-injurious behavior (SIB). Repeated administration of methamphetamine produced these behavioral changes and hyperthermia, but resulted in hypothermia by the final injection (8 mg/kg). In addition, the methamphetamine treatment induced a long-lasting dopamine depletion of similar magnitude in the 4 and 8 mg/kg-treated animals. In a time course study striatal monoamine levels were measured 60 min after each injection of these doses. The first and second injections of methamphetamine (8 mg/kg) produced a drastic increase in striatal 3-methoxytyramine; this failed to occur after the third or fourth injection of the same dose. In contrast, 4 mg/kg of methamphetamine also produced an increase in 3-methoxytyramine after the second and third injections of the drug and, in this case, these were maintained for the duration of the treatment. Striatal 3, 4-dihydroxyphenylacetic acid levels also drastically decreased following both doses of methamphetamine, suggesting inhibition of monoamine oxidase in striatum. Moreover, a single injection of methamphetamine increased striatal 2,3-dihydroxybenzoic acid formation. These results suggest that the incidence of hyperthermia, SIB and striatal dopamine neurotoxicity are closely linked to striatal dopamine release and inhibition of monoamine oxidase produced by methamphetamine in BALB/c mice.

Neurotoxic effects of amphetamine plus L-DOPA

1. Male Swiss Webster mice were administered a series of amphetamine injections preceded by either saline or L-DOPA. 2. This injection regimen was performed for either one, two or three consecutive weeks and neurotoxic effects of the drugs were determined one week later. 3. Amphetamine treatment for two weeks produced a greater striata-dopaminergic lesion that treatment for only one week. Three weeks of treatment did not exacerbate the lesion, indicating that the damage had reached maximal levels. 4. L-DOPA pretreatment did not significantly alter any of the toxic effects of the amphetamine. Therefore, some dopaminergic neurons may be resistant to the toxic effects of amphetamine.