YY162 prevents ADHD-like behavioral side effects and cytotoxicity induced by Aroclor1254 via interactive signaling between antioxidant potential, BDNF/TrkB, DAT and NET.

Methylphenidate (MP) has become the primary drug of choice for treatment of attention-deficit/hyperactivity disorder (ADHD). However, its psychotropic effects severely hamper long-term clinical use. We evaluated the effects of YY162, which consists of terpenoid-strengthened Ginkgo biloba and ginsenoside Rg3, on the ADHD-like condition induced by Aroclor1254, because both components have been suggested to modulate oxidative stress, dopaminergic neurotransmission, and brain-derived neurotrophic factor (BDNF) signaling, which may be critical targets for understanding the pathogenesis of ADHD. YY162 attenuated the increase in reactive oxygen species (ROS) and decrease in BDNF levels induced by Aroclor1254 in SH-SY5Y neuroblastoma cells. YY162 significantly attenuated Aroclor1254-induced ADHD-like behavior and oxidative stress in ICR mice. Furthermore, YY162 attenuated reductions in p-TrkB, BDNF, dopamine transporter (DAT) and norepinephrine transporter (NET) expression. These attenuating effects of YY162 were comparable to those of MP. Importantly, K252a, a TrkB antagonist, counteracted the protective effects of YY162. Our results suggest that YY162 possesses significant protective activities against ADHD-like conditions with negligible behavioral side effects, and that interactive signaling between antioxidant potential and BDNF/TrkB receptor for the positive modulation of the DAT and NET is important for YY162-mediated neuroprotective activity.

Role of microsomal epoxide hydrolase in methamphetamine-induced drug dependence in mice.

Microsomal epoxide hydrolase (mEH) and cytochrome P-450 (CYP) ensure the rapid detoxification of epoxides generated during the oxidative metabolism of xenobiotics. Although CYP has been demonstrated to modulate methamphetamine (METH)-induced behavioral effects, little is known about the role of the mEH gene on these effects. We examined the role of mEH gene expression in METH-induced conditioned place preference and behavioral sensitization by using mEH(-/-) and wild-type (WT) mice. Extracellular dopamine (DA) levels and DA uptake into synaptosomes were assessed by using an in vivo microdialysis and [(3)H]DA uptake assay. We applied double-label immunocytochemistry to characterize mEH-positive cellular types. METH-induced behavioral responses paralleled striatal c-Fos-like immunoreactivity. METH treatment resulted in increased extracellular DA levels in the nucleus accumbens but decreased synaptosomal DA uptake in the striatum. These behavioral and neurochemical changes were more pronounced in the mEH(-/-) mice than in WT mice. In WT mice, mEH-like immunoreactivity was expressed in astrocytes labeled by GFAP or S100B after METH treatment. The results suggest that epoxide intermediates mediate METH drug dependence and that astrocytic reactions of mEH protein are important in the endogenous modulation in response to METH drug dependence.

Growth hormone-releaser diet attenuates beta-amyloid(1-42)-induced cognitive impairment via stimulation of the insulin-like growth factor (IGF)-1 receptor in mice.

We previously demonstrated that the growth hormone (GH)-releaser diet ameliorated beta-amyloid (A beta) (1-42)-induced memory impairment, but the underlying mechanism remained to be characterized. We show here that the GH-releaser diet significantly attenuated A beta(1-42)-induced impairment in context-dependent conditioned fear, with a reduction in GH levels and changes in hippocampal acetylcholine, acetylcholinesterase, choline acetyltransferase, insulin-like growth factor (IGF)-1, and IGF-1-receptor activity in mice. JB-1, an IGF-1-receptor antagonist, significantly blocked GH-releaser diet-mediated pharmacological actions. Our results suggest that the GH-releaser diet prevents A beta(1-42)-induced cognitive deficits via stimulation of the hippocampal IGF-1 receptor.

Ginsenosides attenuate kainic acid-induced synaptosomal oxidative stress via stimulation of adenosine A(2A) receptors in rat hippocampus.

Treatment with ginsenosides attenuated KA-induced seizures and oxidative stress in the synaptosome, and reduced synaptic vesicles at the presynaptic terminals dose-dependently. The adenosine A(2A) receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl) xanthine reversed the ginsenoside-mediated pharmacological actions. Neither the adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine nor the adenosine A(2B) receptor antagonist alloxazine affected the ginsenoside-mediated pharmacological actions. Our results suggest that ginsenosides block KA-induced synaptosomal oxidative stress, associated with hippocampal degeneration, through activation of adenosine A(2A) receptors.

Kainate-induced mitochondrial oxidative stress contributes to hippocampal degeneration in senescence-accelerated mice.

We have demonstrated that kainate (KA) induces a reduction in mitochondrial Mn-superoxide dismutase (Mn-SOD) expression in the rat hippocampus and that KA-induced oxidative damage is more prominent in senile-prone (SAM-P8) than senile-resistant (SAM-R1) mice. To extend this, we examined whether KA seizure sensitivity contributed to mitochondrial degeneration in these mouse strains. KA-induced seizure susceptibility in SAM-P8 mice paralleled prominent increases in lipid peroxidation and protein oxidation and was accompanied by significant impairment in glutathione homeostasis in the hippocampus. These findings were more pronounced in the mitochondrial fraction than in the hippocampal homogenate. Consistently, KA-induced decreases in Mn-SOD protein expression, mitochondrial transmembrane potential, and uncoupling protein (UCP)-2 expression were more prominent in SAM-P8 than SAM-R1 mice. Marked release of cytochrome c from mitochondria into the cytosol and a higher level of caspase-3 cleavage were observed in KA-treated SAM-P8 mice. Additionally, electron microscopic evaluation indicated that KA-induced increases in mitochondrial damage and lipofuscin-like substances were more pronounced in SAM-P8 than SAM-R1 animals. These results suggest that KA-mediated mitochondrial oxidative stress contributed to hippocampal degeneration in the senile-prone mouse.

Role of glutathione peroxidase in the ontogeny of hippocampal oxidative stress and kainate seizure sensitivity in the genetically epilepsy-prone rats.

Oxidative stress may contribute to epileptogenicity in genetic models of epilepsy. To address this, we examined the enzymatic activity of cytosolic Cu/Zn superoxide dismutase (SOD-1), mitochondrial Mn superoxide dismutase (SOD-2), and glutathione peroxidase (GPx) in the developing hippocampus of genetically epilepsy-prone rats (GEPR-9s). We also measured changes in the GSH/GSSG ratio, lipid peroxidation, and protein oxidation at post-natal days (PD) 7, 30, and 90, respectively. Compared with control Sprague-Dawley (SD) rats, GEPR-9s showed similar SOD-1 and SOD-2 activity but lower GPx activity. Epilepsy-prone rats also showed lower GSH/GSSG ratios than controls, and more lipid peroxidation (as measured by malondialdehyde levels) and protein oxidation (as measured by carbonyl levels). Treatment with kainic acid (KA) resulted in more pronounced seizures, less GPx activity, and lower GSH/GSSG ratios in GEPR-9s than in controls, but KA did not significantly affect SOD-1 or SOD-2 activity, suggesting that GEPR-9s do not compensate for reduced GPx activity by increasing SOD. Moreover, KA treatment resulted in significantly a lower GSH/GSSG ratio and GPx-like immunoreactivity and higher malondialdehyde and carbonyl levels in GEPR-9s than in controls. These findings were more evident in GEPR-9s at PD 90 than at PD 30, indicating that oxidative stress is age-dependent. Double-labeling immunocytochemical analysis demonstrated co-localization of GPx-immunoreactive glia-like cells and reactive astrocytes, as labeled by glial fibrillary acidic protein (GFAP). This suggests that mobilization of astroglial cells for synthesis of GPx protein is a response to KA insult, intended to decrease the neurotoxicity induced by peroxides. These responses were more pronounced in control SD rats than in GEPR-9s. Our results suggest that impairment of the GPx (including glutathione)-mediated antioxidant system contributed to epileptogenesis in GEPR-9s.

Dextromethorphan attenuates trimethyltin-induced neurotoxicity via sigma1 receptor activation in rats.

We showed that dextromethorphan (DM) provides neuroprotective/anticonvulsant effects and that DM and its major metabolite, dextrorphan, have a high-affinity for sigma(1) receptors, but a low affinity for sigma(2) receptors. In addition, we found that DM has a higher affinity than DX for sigma(1) sites, whereas DX has a higher affinity than DM for PCP sites. We extend our earlier findings by showing that DM attenuated trimethyltin (TMT)-induced neurotoxicity (convulsions, hippocampal degeneration and spatial memory impairment) in rats. This attenuation was reversed by the sigma(1) receptor antagonist BD 1047, but not by the sigma(2) receptor antagonist ifenprodil. DM attenuates TMT-induced reduction in the sigma(1) receptor-like immunoreactivity of the rat hippocampus, this attenuation was blocked by the treatment with BD 1047, but not by ifenprodil. These results suggest that DM prevents TMT-induced neurotoxicity, at least in part, via sigma(1) receptor stimulation.

Effects of dextrorotatory morphinans on brain Na+ channels expressed in Xenopus oocytes.

We previously demonstrated that dextromethorphan (DM; 3-methoxy-17-methylmorphinan) analogs have neuroprotective effects. Here, we investigated the effects of DM, three of its analogs (DF, 3-methyl-17-methylmorphinan; AM, 3-allyloxy-17-methoxymorphian; and CM, 3-cyclopropyl-17-methoxymorphinan) and one of its metabolites (HM; 3-methoxymorphinan), on Na(+) channel activity. We used the two-microelectrode voltage-clamp technique to test the effects of DM, DF, AM, CM and HM on Na(+) currents (I(Na)) in Xenopus oocytes expressing cRNAs encoding rat brain Nav1.2 alpha and beta1 or beta2 subunits. In oocytes expressing Na(+) channels, DM, DF, AM and CM, but not HM, induced tonic and use-dependent inhibitions of peak I(Na) following low- and high-frequency stimulations. The order of potency for the inhibition of peak I(Na) was AM-CM > DM=DF. The DM, DF, AM and CM-induced tonic inhibitions of peak I(Na) were voltage-dependent, dose-dependent and reversible. The IC(50) values for DM, DF, AM and CM were 116.7+/-14.9, 175.8+/-16.9, 38.6+/-15.5, and 42.5+/-8.5 microM, respectively. DM and its analogs did not affect the steady-state activation and inactivation voltages. AM and CM, but not DM and DF, inhibited the plateau I(Na) more effectively than the peak I(Na) in oocytes expressing inactivation-deficient I1485Q-F1486Q-M1487Q (IFMQ3) mutant channels; the IC(50) values for AM and CM in this system were 8.4+/-1.3 and 8.7+/-1.3 microM, respectively, for the plateau I(Na) and 43.7+/-5.9 and 32.6+/-7.8 microM, respectively, for the peak I(Na). These results collectively indicate that DM and its analogs could be novel Na(+) channel blockers acting on the resting and open states of brain Na(+) channels.

Repeated intracerebroventricular infusion of nicotine prevents kainate-induced neurotoxicity by activating the alpha7 nicotinic acetylcholine receptor.

We examined whether (-)-nicotine infusion can affect kainic acid (KA)-induced neurotoxicity in rats. Although treatment with a single nicotine infusion (0.5 or 1.0 microg/side, i.c.v.) failed to attenuate KA-induced neurotoxicity, repeated nicotine infusions (1.0 microg/side/day for 10 days) attenuated the seizures, the severe loss of cells in hippocampal regions CA1 and CA3, the increase in activator protein (AP)-1 DNA binding activity, and mortality after KA administration. alpha-Bungarotoxin and mecamylamine blocked the neuroprotective effects of nicotine. These results suggest that repeated nicotine treatment provides alpha7 nicotinic acetylcholine receptor-mediated neuroprotection against KA toxicity.

Growth hormone releaser attenuates beta-amyloid (1 - 42)-induced memory impairment in mice.

Accumulating evidence indicates that growth hormone (GH) might be effective at preventing the development of Alzheimer's disease. However, exogenous GH treatment has exhibited side effects for clinical application; thus supplementation with amino acids to promote the release of GH could be a possible alternative treatment. In this study, mice that were fed with a diet of GH-releasing supplements had significantly attenuated memory impairments and hippocampal changes in the acetylcholinesterase activity and acetylcholine level induced by amyloid beta protein (Abeta) (1 - 42). Our results suggest that the use of GH-releasing supplement exerts beneficial effects on the memory impairment induced by Abeta (1 - 42).