L-carnitine protects neurons from 1-methyl-4-phenylpyridinium-induced neuronal apoptosis in rat forebrain culture.

1-Methyl-4-phenylpyridinium ion (MPP+), an inhibitor of mitochondrial complex I, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with an elevation of intracellular reactive oxygen species (ROS) and apoptosis. L-carnitine plays an integral role in attenuating the brain injury associated with mitochondrial neurodegenerative disorders. The present study investigates the effects of L-carnitine against the toxicity of MPP+ in rat forebrain primary cultures. Cells in culture were treated for 24 h with 100, 250, 500 and 1000 microM MPP+ alone or co-incubated with L-carnitine. MPP+ produced a dose-related increase in DNA fragmentation as measured by cell death ELISA (enzyme-linked immunosorbent assay), an increase in the number of TUNEL (terminal dUTP nick-end labeling)-positive cells and a reduction in the mitochondrial metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). No significant effect was observed with the release of lactate dehydrogenase (LDH), indicating that cell death presumably occurred via apoptotic mechanisms. Co-incubation of MPP+ with L-carnitine significantly reduced MPP+-induced apoptosis. Western blot analyses showed that neurotoxic concentrations of MPP+ decreased the ratio of BCL-X(L) to Bax and decreased the protein levels of polysialic acid neural cell adhesion molecules (PSA-NCAM), a neuron specific marker. L-carnitine blocked these effects of MPP+ suggesting its potential therapeutic utility in degenerative disorders such as Parkinson's disease, Alzheimer's disease, ornithine transcarbamylase deficiency and other mitochondrial diseases.

Selective alterations of transcription factors in MPP+-induced neurotoxicity in PC12 cells.

MPP(+) (1-methyl-4-phenylpyridinium; the active metabolite of the neurotoxin MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine)) depletes dopamine (DA) content and elicits cell death in PC12 cells. However, the mechanism of MPP(+)-induced neurotoxicity is still unclear. In this study, the dose response and time-course of MPP(+)-induced DA depletion and decreased cell viability were determined in nerve growth factor (NGF)-differentiated PC12 cells. The alteration of transcription factors (TFs) induced by MPP(+) from a selected dose level and time point was then evaluated using protein/DNA-binding arrays. K-means clustering analysis identified four patterns of protein/DNA-binding changes. Three of the 28 TFs identified in PC12 cells increased by 100% (p53, PRE, Smad SBE) and 2 decreased by 50% (HSE, RXR(DR1)) of control with MPP(+) treatment. In addition, three TFs decreased within the range of 33-50% (TFIID, E2F1, CREB) and two TFs increased within the range of 50-100% (PAX-5, Stat4). An electrophoretic mobility shift assay (EMSA) was used to confirm the changes of p53 and HSE. The observed changes in TFs correlated with the alterations of DA and cell viability. The data indicates that selective transcription factors are involved in MPP(+)-induced neurotoxicity and it provides mechanistic information that may be applicable to animal studies with MPTP and clinical studies of Parkinson's disease.

Quinolinic acid induces oxidative stress in rat brain synaptosomes.

The oxidative action of quinolinic acid (QUIN), and the protective effects of glutathione (GSH), and 2-amino-5-phosphonovaleric acid (APV), were tested in rat brain synaptosomes, Reactive oxygen species (ROS) formation was quantified after the exposure of synaptosomes to increasing concentrations of QUIN (25-500 microM). The potency of QUIN to induce lipid peroxidation (LP) was tested as a regional index of thiobarbituric acid-reactive substances (TBARS) production, and the antioxidant actions of both GSH (50 microM) and APV (250 microM) on QUIN-induced LP were evaluated in synaptosomes prepared from different brain regions. QUIN induced concentration-dependent increases in ROS formation and TBARS in all regions analyzed, but increased production of fluorescent peroxidized lipids only in the striatum and the hippocampus, whereas both GSH and APV decreased this index. These results suggest that the excitotoxic action of QUIN involves regional selectivity in the oxidative status of brain synaptosomes, and may be prevented by substances exhibiting antagonism at the NMDA receptor.

Transplacental pharmacokinetics of cocaine and benzoylecgonine in plasma and hair of rhesus monkeys.

There is large variability in the rate and extent of fetal damage from cocaine in humans; however, the sources of such variability are not presently known. In order to study the relationship between maternal cocaine pharmacokinetics at the end of pregnancy and maternal or infant cocaine and benzoylecgonine hair concentrations at birth, ten rhesus monkeys were administered cocaine intramuscularly throughout pregnancy. Cocaine and benzoylecgonine hair concentrations were determined at birth and correlated with maternal pharmacokinetics during pregnancy. There were no correlations between either maternal cocaine Cmax or AUC0-infinity and maternal and infant hair cocaine or benzoylecgonine concentrations. There were no significant correlations between maternal hair benzoylecgonine concentrations and either maternal benzoylecgonine AUC0-120 (r = 0.60; P = 0.07) or benzoylecgonine Cmax (r = 0.60; P = 0.07). No correlations existed between infant hair benzoylecgonine concentrations and either maternal benzoylecgonine AUC0-120 (r = 0.30; P = 0.40) or benzoylecgonine Cmax (r = 0.30; P = 0.40). Also, no correlation was found between maternal cocaine dose and maternal or infant cocaine and benzoylecgonine hair concentrations. In comparison to toxicants such as nicotine and carbon monoxide for which there is a good correlation between maternal systemic exposure and neonatal concentrations, the lack of a similar relationship for cocaine is consistent with the role of the placenta in contributing to the variability in the amounts of cocaine reaching the fetus and hence, potentially to the risk of adverse fetal outcome.

Mercuric chloride-induced reactive oxygen species and its effect on antioxidant enzymes in different regions of rat brain.

The present study was undertaken to determine if in vitro exposure to mercuric chloride produces reactive oxygen species (ROS) in the synaptosomes prepared from various regions of rat brain. The effects of in vivo exposure to mercury on antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in different regions of rat brain were also investigated. Adult male Sprague-Dawley (CD) rats were dosed with 0, 1, 2.0 or 4.0 mg HgCl2/kg body weight, for 7 days. One week after the last dose, animals were sacrificed by decapitation, their brains were removed and dissected and frozen in dry ice prior to measuring the activities of these enzymes. The results demonstrated that in vitro exposure to mercury produced a concentration-dependent increase of ROS in different regions of the rat brain. In vivo exposure to mercury produced a significant decrease of total SOD, Cu, Zn-SOD and Mn-SOD activities in the cerebellum of rats treated with different doses of mercury. SOD activity did not vary significantly in cerebral cortex and brain stem. GPx activity declined in a dose-dependent manner in the cerebellum with a significant reduction in animals receiving the 4 mg HgCl2/kg body weight. The activity of GPx increased in the brain stem while unchanged in the cerebral cortex. The results demonstrate that inorganic mercury decreased SOD activity significantly in the cerebellum while GPx activity was affected in both cerebellum and brain stem. Therefore, it can be concluded that oxidative stress may contribute to the development of neurodegenerative disorders caused by mercury intoxication.

The effect of chronic cocaine exposure throughout pregnancy on maternal and infant outcomes in the rhesus monkey.

To explore the effects of gestational cocaine exposure in a nonhuman primate model, pregnant rhesus monkeys were either treated (N = 10) with escalating doses of cocaine up to 7.5 mg/kg (IM), three times per day, 5 consecutive days per week, prior to conception and throughout gestation, or were not treated (N = 10) with cocaine at all. Substantial levels of both cocaine and its major metabolite, benzoylecgonine, were observed in samples of hair taken at birth from mothers and infants of the cocaine-treated group. Despite these differences in cocaine exposure, the experimental groups did not differ significantly with respect to maternal outcome, as measured by body weight again during pregnancy and length of pregnancy. On the other hand, the experimental groups did differ significantly with respect to infant outcome, as measured at birth by body weight, overall length, and crown circumference, all of which were decreased in the cocaine-treated group. A variety of reflexes tested at birth were normal in the cocaine-treated group. It was concluded that, in a rhesus monkey model, chronic cocaine exposure throughout pregnancy had no significant effect on maternal outcome, but did significantly affect infant outcome as assessed in this investigation.

Distribution of 2,4-dichlorophenoxyacetic acid (2,4-D) in maternal and fetal rabbits.

The distribution of 2,4-dichlorophenoxyacetic acid (2,4-D) was examined in maternal and fetal rabbits. Pregnant New Zealand rabbits (28-30 d gestational age) were anesthetized with ketamine/xylazine and the femoral vein and artery were catheterized for compound administration and sampling. Dams received iv [14C]2,4-D (12.5 microCi/kg) with unlabeled sodium 2,4-D (1, 10, or 40 mg/kg) in saline. Blood and tissue were collected up to 2 h after dosing. Fetal to maternal plasma AUC ratios were 0.09, 0.07, and 0.16 after the 1, 10, or 40 mg/kg dose, respectively. Extraplasma AUCs were greatest in maternal kidney and uterus and lowest in maternal and fetal brain. A greater than fourfold elevation in fetal AUC was found when the dose was increased from 10 to 40 mg/kg, suggesting saturation of maternal plasma binding of 2,4-D. Although the in vitro fetal brain tissue to incubation media ratio was unity (1.03 +/- 0.1, mean +/- SD), fetal brain AUCs were 10% or less of the fetal plasma AUCs, indicating the brain barrier system to 2,4-D is functioning in the late-gestation fetal rabbit. However, its development may not be complete due to the higher brain tissue to plasma ratios in the fetus compared to the dam.

Manganese-induced reactive oxygen species: comparison between Mn+2 and Mn+3.

Manganese (Mn) is an essential element, the deficiency or excess of which is known to cause neurotoxicity in experimental animals and man. The mechanism of action of Mn neurotoxicity is still unclear. The present study was designed to evaluate whether in vitro or in vivo exposure to Mn produced reactive oxygen species (ROS). We also sought to determine if a single injection of Mn produces changes in monoamines concentration in different regions of rat brain. Adult Sprague-Dawley rats were dosed with 0, 50 or 100 mg/kg, ip with either MnCl2 (Mn+2) or MnOAc (Mn+3) and were sacrificed 1 h after the dose was administered. Brains were quickly removed and dissected for neurochemical analysis. ROS were measured by a molecular probe, 2',7'-dichlorofluorescein diacetate (DCFH-DA), and monoamines and their metabolites were measured by HPLC/EC. In vitro exposure to MnCl2 (1-1000 microM) produced dose-dependent increases of ROS in striatum whereas MnOAc produced similar increases at much lower concentrations (1-100 microM). In vivo exposure to MnOAc (Mn+3) produced significant increases of ROS in caudate nucleus and hippocampus, whereas MnCl2 (Mn+2) produced significant effects only in hippocampus. Concentrations of dopamine, serotonin and their metabolites (DOPAC, HVA and 5-HIAA) were not altered with acute injections of either MnCl2 or MnOAc. These data suggest that both divalent and trivalent manganese induce ROS, however, Mn+3 is an order of magnitude more potent than Mn+2.

Pharmacokinetics of cocaine in pregnant and nonpregnant rhesus monkeys.

To determine pharmacokinetic parameters for cocaine in rhesus monkey plasma, samples were taken over several hours after i.m. administration of cocaine plus a tritiated cocaine tracer. Cocaine and its metabolites, benzoylecgonine and norcocaine, were isolated via HPLC and quantitated using liquid scintillation spectrometry. Pregnant subjects were dosed with cocaine at 0.3 (n = 3) or 1.0 (n = 3) mg/kg, whereas nonpregnant female subjects were dosed with 1.0 mg/kg (n = 3). For the pregnant subjects, pharmacokinetic studies were conducted on about gestational day 125 and areas under the concentration versus time curve (AUCs, ng/mL x h) were 64 +/- 26 (+/- SEM) and 143 +/- 12; half-lives (t1/2s, h) were 1.9 +/- 0.6 and 1.1 +/- 0.1 after 0.3 and 1.0 mg/kg i.m., respectively. For nonpregnant subjects dosed acutely with 1.0 mg/kg, the AUC was 262 +/- 63 and the t1/2 was 1.4 +/- 0.3. There appear to be few differences in the pharmacokinetic parameters of cocaine and benzoylecgonine between pregnant and nonpregnant monkeys in this study.

Transplacental pharmacokinetics and maternal/fetal plasma concentrations of cocaine in pregnant macaques near term.

The transplacental pharmacokinetics of cocaine were studied in three pregnant rhesus monkeys (Macaca mulatta) at 150-154 days of pregnancy (term approximately 165 days). Animals were dosed intramuscularly with cocaine hydrochloride at 1 mg/kg, supplemented with a tritiated cocaine tracer. Plasma cocaine and its metabolite benzoylecgonine levels were determined after separation by HPLC and subsequent quantification by liquid scintillation spectrometry. Cocaine levels peaked in maternal blood within 10-20 min after dosing, and cocaine was detected in fetal blood within 5 min, reaching peak concentrations within 30-120 min. Mean maternal elimination half-lives (t1/2) for cocaine and benzoylecgonine were 1.2 +/- 0.5 hr and 12.4 +/- 6.6 hr (+/- SEM), respectively; fetal half-lives were 0.5 +/- 0.2 and 7.7 +/- 3.0 hr. Mean maternal residence times were 1.9 +/- 0.5 and 17.0 +/- 9.1 hr for cocaine and benzoylecgonine, respectively; fetal values were 2.1 +/- 0.2 and 11.6 +/- 3.5 hr. Total areas under the concentration versus time curves (AUCs) for cocaine and benzoylecgonine in maternal plasma were 360 +/- 38 and 585 +/- 260 (ng/ml) hr, respectively; fetal values were 104 +/- 29 and 262 +/- 61 (ng/ml) hr. Based on AUC comparisons for cocaine, fetal exposures are thus approximately one-third of maternal exposures, demonstrating that substantial exposure to cocaine does occur in utero.

Metabolism of methapyrilene by Fischer-344 rat and B6C3F1 mouse hepatocytes.

1. Suspension cultures of freshly isolated F344 rat and B6C3F1 mouse hepatocytes were compared for their ability to transform various concentrations of methapyrilene (MP). 2. MP metabolites were isolated and purified by h.p.l.c., and were identified by comparing their chromatographic and mass spectral properties with those of authentic standards. 3. Both rat and mouse hepatocytes transformed MP to tentatively identified 2-thiophenecarboxylic acid (I), and definitively identified mono-N-desmethyl methapyrilene glucuronide (II), methapyrilene glucuronide (III), methapyrilene N-oxide (V), and mono-N-desmethyl methapyrilene (VII).

Behavioral and neurochemical effects of prenatal methylenedioxymethamphetamine (MDMA) exposure in rats.

MDMA is a hallucinogenic drug that is used by the general public as a recreational drug of abuse. The neurobehavioral consequences of prenatal MDMA exposure are unknown. Groups of pregnant rats were gavaged with 0, 2.5, or 10 mg/kg MDMA during gestation on alternate gestational days 6-18. Gestational duration, litter size, neonatal birth weights and physical appearance at birth were unaffected by MDMA treatments. Pregnancy weight gain was significantly reduced by MDMA treatment. Progeny growth, maturational parameters (eye opening and incisor eruption times), surface righting reflex, swimming performance, forelimb grip strength, milk-induced behaviors, passive avoidance behavior, figure-8 maze activity over 48 hours, the density of brain serotonin (5-HT) uptake sites, and brain 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels were unaffected by MDMA treatments. Olfactory discrimination on postnatal days (PND) 9-11 was enhanced in both male and female MDMA-treated progeny, while negative geotaxis (PND 7-10) was delayed in female pups. In contrast to progeny, MDMA caused dose-dependent decreases in 5-HT and 5-HIAA levels in discrete brain areas of the dam. It is concluded that prenatal exposure to MDMA at the levels used here produces only subtle behavioral alterations in developing rats. The dam is more at risk for MDMA-induced 5-HT depletion than is the conceptus.