Involvement of the Nrf2/HO-1 signaling pathway in sulfuretin-induced protection against amyloid beta25-35 neurotoxicity.

Sulfuretin, one of the major flavonoid glycosides found in the stem bark of Albizzia julibrissin and heartwood of Rhus verniciflua, is a known anti-oxidant. We previously demonstrated that sulfuretin inhibits neuronal death via reactive oxygen species (ROS)-dependent mechanisms in human SH-SY5Y cells, although other relevant mechanisms of action of this compound remain largely uncharacterized. As part of our ongoing exploration of the pharmacological actions of sulfuretin, we studied the neuroprotective effects of sulfuretin against amyloid beta (Aß)-induced neurotoxicity in human SH-SY5Y and primary hippocampal neuron cells and investigated the possible mechanisms involved. Specifically, we found in the present study that sulfuretin significantly attenuates the decrease in cell viability, release of lactate dehydrogenase, and accumulation of ROS associated with Aß25-35-induced neurotoxicity in neuronal cells. Furthermore, sulfuretin stimulated the activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a downstream target of phosphatidylinositol 3-kinases (PI3K)/Akt. We demonstrated that sulfuretin induces the expression of heme oxygenase-1 (HO-1), an anti-oxidant response gene. Notably, we found that the neuroprotective effects of sulfuretin were diminished by an Nrf2 small interfering RNA (siRNA), the HO-1 inhibitor zinc protoporphyrin IX (ZnPP), as well as the PI3K/Akt inhibitor LY294002. Taken together, these results indicated that sulfuretin protects neuronal cells from Aß25-35-induced neurotoxicity through activation of Nrf/HO-1 and PI3K/Akt signaling pathways. Our results also indicate that sulfuretin-induced induction of Nrf2-dependent HO-1 expression via the PI3K/Akt signaling pathway has preventive and/or therapeutic potential for the management of Alzheimer's disease.

Gastrodia Elata Bl Attenuates Cocaine-Induced Conditioned Place Preference and Convulsion, but not Behavioral Sensitization in Mice: Importance of GABA(A) Receptors.

It has been suggested that GABAergic neurotransmission can modulate cocaine dependence and seizure activity. Since Gastrodia elata Bl (GE), an oriental herb agent, has been shown to enhance GABAergic transmission, we examined whether GE affects cocaine-induced seizures, conditioned place preference (CPP), and behavioral sensitization in mice. Treatment with GE (500 or 1000 mg/kg, p.o.) significantly delayed seizure onset time and significantly shortened seizure duration induced by cocaine (90 mg/kg, i.p.). In addition, cocaine (15 mg/kg, i.p.)-induced CPP was significantly attenuated by GE in a dose-dependent manner. However, GE did not significantly alter behavioral sensitization induced by cocaine (15 mg/kg, i.p.). In order to understand whether GABAergic receptors are implicated in GE-mediated pharmacological action in response to cocaine, GABA(A) receptor antagonist bicuculline and GABA(B) receptor antagonist SCH 50911 were employed in the present study. GE-mediated attenuations on the cocaine-induced seizures and CPP were significantly reversed by bicuculline (0.25 or 0.5 mg/kg, i.p.), but not by SCH 50911 (1.5 or 3.0 mg/kg, i.p.). Therefore, our results suggest that GE attenuates cocaine-induced seizures and CPP via, at least in part, GABA(A) receptor activation.

Gastrodia elata bl attenuates methamphetamine-induced dopaminergic toxicity via inhibiting oxidative burdens.

It has been recognized that Gastrodia elata Bl (GE), an oriental herb medicine, ameliorates various neurological disorders, that GE modulates the monoaminergic and GABAergic systems, and that GE possess antioxidant activities. We examined whether GE affects methamphetamine (MA)-induced striatal dopaminergic toxicity in mice. Treatment with MA (7.5 mg/kg, i.p. × 4) resulted in significant decreases in behavioural activity (as shown by locomotor activity and rota rod performance), dopamine level, tyrosine hydroxylase (TH) activity, and TH protein expression (as evaluated by immunocytochemistry and western blot analysis). In addition, MA treatment showed significant increases in lipid peroxidation [as evaluated by 4-hydroxy-2-nonenal (4-HNE) expression and malondialdehyde formation], protein oxidation (as shown by protein carbonyl expression and its formation), and reactive oxygen species (ROS) formation. Treatment with GE significantly attenuates MA-induced behavioural and dopaminergic impairments, and oxidative stresses in a dose-dependent manner. Our results suggest that GE treatment shows anti-dopaminergic effects in response to MA insult via, at least in part, inhibiting oxidative stresses in the striatum of the mice.

Methamphetamine-sensitized mice are accompanied by memory impairment and reduction of N-methyl-d-aspartate receptor ligand binding in the prefrontal cortex and hippocampus.

The aim of the present study was to investigate a causal relationship between low-dose methamphetamine-induced (METH; 2 mg/kg, i.p. once every other day for 7 days) behavioral sensitization and memory function. We first investigated the spatial working memory (short-term memory) and long-term memory in mice behaviorally sensitized by repeated METH treatments. We also assessed changes in NMDA receptor binding in METH-treated mice. Acute METH administration induces hyperlocomotion but do not induce memory impairment of changes in NMDA receptor binding. However, repeated METH treatment in mice produced behavioral sensitization and showed memory impairment and a decrease in NMDA receptor binding in the prefrontal cortex, as well as in the CA1, CA2, and CA3 regions of the hippocampus. These results suggest that repeated METH-induced behavioral sensitization may be accompanied by memory impairment, characterized by decreased NMDA receptor binding in the prefrontal cortex and hippocampus. Our study shows clearly that repeated but not acute low dose METH treatment induces memory impairment in mice and the possible mechanism involves reduction of NMDA receptor binding in specific brain regions associated with learning and memory.

Effects of capsazepine, a transient receptor potential vanilloid type 1 antagonist, on morphine-induced antinociception, tolerance, and dependence in mice.

BACKGROUND: Repeated morphine treatment has been shown to induce transient receptor potential vanilloid type 1 (TRPV1) expression in the spinal cord, dorsal root ganglion (DRG), and sciatic nerve of a rat model. Increased TRPV1 expression may therefore play a role in morphine tolerance. In this study, we evaluated the hypothesis that blockage of TRPV1 may be useful as an adjunctive pain management therapy. We investigated whether blockage of TRPV1 by capsazepine, a TRPV1 antagonist, affected antinociception, development of tolerance, and physical dependence on morphine in mice. METHODS: Institute of Cancer Research mice were pretreated with capsazepine and post-treated with morphine acutely and repeatedly. Antinociception and its tolerance were assessed using the hot-plate test. Morphine dependence was examined through the manifestation of withdrawal symptoms induced by naloxone in morphine-dependent mice. RESULTS: Acute capsazepine treatment (5 mg kg⁻¹, i.p.) potentiated the antinociceptive effects of morphine, as measured by the hot-plate test. Repeated co-treatment of capsazepine (2.5 mg kg⁻¹ i.p.) with morphine attenuated the development of tolerance to the antinociceptive effect of morphine. The development of morphine dependence was also reduced by capsazepine (1.25 or 2.5 mg kg⁻¹ i.p.). CONCLUSIONS: Our results suggest that TRPV1 antagonists can be used adjunctively to morphine treatment because they strengthen morphine antinociception and prevent the development of tolerance, and also physical dependence, on morphine.

Blockade of M1 muscarinic acetylcholine receptors modulates the methamphetamine-induced psychomotor stimulant effect.

Muscarinic acetylcholine receptors (M1-M5) regulate many key functions of the CNS and peripheral nervous system. In the present study, the role of M1 muscarinic receptors (M1R) in the psychomotor stimulant and sensitizing properties of methamphetamine (METH) is investigated using molecular, neurochemical, and behavioral approaches. Acute and repeated treatment with METH increased M1R mRNA expression in the frontal cortex and the CA2 region of the hippocampus. Repeated treatment with METH also increased M1R mRNA expression in the dentate gyrus. Dicyclomine, an M1R antagonist, did not affect the psychomotor effect of METH, but it attenuated METH-induced increases in the dopamine (DA) efflux in the nucleus accumbens (NAc). Dicyclomine enhanced the psychomotor effect of METH after repeated treatment with METH and 8.0 mg/kg of dicyclomine, and also augmented the increase in the NAc DA overflow evoked by repeated METH treatment. These results suggest that M1R plays a role in the METH-induced psychomotor stimulant effect by changing the release of DA in the NAc of mice.

Considerable interindividual variation in the pharmacokinetics of tolperisone HCl.

OBJECTIVE: The aim of this study was to determine the pharmacokinetic profiles of oral tolperisone hydrochloride in healthy volunteers. METHODS: After the oral administration of tolperisone hydrochloride, the plasma concentrations of tolperisone were measured in 15 healthy male Korean volunteers. The tolperisone concentration was determined using high-performance liquid chromatography with a C18 reverse-phase column. RESULTS: Very large interindividual differences in the AUC and Cmax were detected after oral tolperisone HCl. The AUC0-infinity, varied from 125.9-1,241.3 ng/ml x h, and the Cmax varied from 64.2 and 784.9 ng/ml. The tmax of tolperisone was 0.90 +/- 0.31 h and the mean half-life was 1.00 +/- 0.28 h. CONCLUSION: These results suggest that the pharmacological effect of oral tolperisone HCl varies between individuals, and the oral tolperisone HCl dose might need to be individualized.

Inhibitory effects of berberine against morphine-induced locomotor sensitization and analgesic tolerance in mice.

We previously reported that a methanolic extract of Coptis japonica, which is a well-known traditional oriental medicine, inhibits morphine-induced conditioned place preference (CPP) in mice. Berberine is a major component of Coptis japonica extract, and it has been established that the adverse effects of morphine on the brain involve dopamine (DA) receptors. However, to our knowledge, no study has investigated the inhibitory effects of berberine on morphine-induced locomotor sensitization and analgesic tolerance in mice. Here, we investigated the effects of berberine on morphine-induced locomotor sensitization and on the development of analgesic tolerance. Furthermore, we examined the effects of berberine treatment on N-methyl-D-aspartate (NMDA) receptor channel activity expressed in Xenopus laevis oocytes. Berberine was found to completely block both morphine-induced locomotor sensitization and analgesic tolerance, and reduce D(1) and NMDA receptor bindings in the cortex. Moreover, berberine markedly inhibited NMDA current in Xenopus laevis oocytes expressing NMDA receptor subunits. Our results suggest that the inhibitory effects of berberine on morphine-induced locomotor sensitization and analgesic tolerance are closely related to the modulation of D1 and NMDA receptors, and that berberine should be viewed as a potential novel means of attenuating morphine-induced sensitization and analgesic tolerance.

Inhibitory effects of MK-801 on contextual sensitization to climbing behavior and on development of tolerance to hypothermia induced by a single high dose of apomorphine.

A single high dose of apomorphine (10 mg x kg(-1)) produced not only contextual sensitization to and conditioning of climbing behavior, but also context-independent tolerance to hypothermia. MK-801 (0.15 and 0.3 mg x kg(-1)) inhibited contextual sensitization to and conditioning of climbing behavior. Development of tolerance to hypothermia was also inhibited by MK-801. Dopamine D1 antagonist, SCH23390 (0.5 mg x kg(-1)), but not D2 antagonist, sulpiride, inhibited sensitization to and conditioning of climbing behavior. D2 antagonist, sulpiride (50 mg x kg(-1)), but not D1 antagonist, SCH23390, inhibited development of tolerance to hypothermia. These results suggest that MK-801 inhibited contextual sensitization to climbing behavior and development of tolerance to hypothermia through glutamatergic modulation of dopaminergic functions at dopamine receptors.

Lack of mu-opioid receptor leads to an increase in the NMDA receptor subunit mRNA expression and NMDA-induced convulsion.

The present study investigated in situ hybridization of N-methyl-D-aspartate (NMDA) receptor (NR) subunit mRNA and convulsion induced by intracerebroventricular injection of NMDA, in order to examine changes in NMDA receptor function in mu-opioid receptor gene knockout mice. Levels of NR1 and NR2A subunit mRNA were significantly increased in the parietal cortex (8.4 and 10.6%, respectively) and hypothalamus (8.7 and 15.2%, respectively) in mu-opioid receptor knockout mice. Levels of NR2B subunit mRNA were noted to be increased in the parietal cortex (9.1%), thalamus (7.7%), and hypothalamus (10.4%) in mu-opioid receptor knockout mice. The ED(50) for NMDA-induced convulsion in wild-type mice was 0.20 microg/10 microl/mouse. The ED(50) in mu-opioid receptor knockout mice was 0.14 microg/10 microl/mouse. There is a significant difference in the potency ratio of wild-type mice versus knockout mice (potency ratio: 1.44, P < 0.05). These results indicate that mu-opioid receptor knockout mice are more sensitive to NMDA-induced convulsion. Therefore, these results suggest that absence of mu-opioid receptor gene is accompanied by changes in the NMDA receptor system which can modulate the synaptic excitability in the process such as convulsion or epilepsy.

Differential effects of morphine, DPDPE, and U-50488 on apomorphine-induced climbing behavior in mu-opioid receptor knockout mice.

The present study examined the hypothesis whether the opioid receptors (mu, delta, and kappa) contribute to a behavioral dopaminergic activation produced by dopamine receptor agonist, apomorphine, by comparing responses in wild type and mu-opioid receptor knockout mice. The data suggest that expression of mu-opioid receptors plays an important role in the enhancement of climbing behavior induced by apomorphine. Compared to wild type mice, a response in the dopaminergic behavior by treatment with delta-receptor agonist, DPDPE, is more sensitive to the mice lacking mu-opioid receptor. Treatment with kappa-receptor agonist, U-50488, is potentiated the apomorphine-induced climbing behavior in wild type and mu-opioid receptor knockout mice. These responses may be independent of that through mu-opioid receptors. Therefore, the our results show that dopaminergic activation measured by climbing behavior in mu-opioid receptors knockout mice are differently regulated by mu-, delta-, and kappa-opioid receptor agonists.

Effects of morphine on pentobarbital-induced responses in mu-opioid receptor knockout mice.

Effects of morphine on the potentiation of pentobarbital-induced responses were investigated using mu-opioid receptor knockout mice. The duration of loss of righting reflex, hypothermia, and loss of motor coordination induced by pentobarbital were measured after pretreatment with either morphine or saline. Morphine pretreatment failed to show potentiation of both pentobarbital-induced loss of righting reflex and hypothermia in mu-opioid receptor knockout mice, while it significantly potentiated these responses in the wild-type controls. For motor incoordination test, morphine potentiated pentobarbital-induced motor incoordination in the wild-type mice. However, morphine may have opposite effects in the mu-opioid receptor knockout mice. These results demonstrate that synergism between morphine and pentobarbital is not detected in mu-opioid receptor knockout mice and that potentiation of pentobarbital-induced loss of righting reflex and hypothermia by morphine is mediated through mu-opioid receptor. It was interesting to note that pentobarbital-induced decrease in body temperature was less severe in mu-opioid receptor knockout mice than in wild-type mice.

Inhibition of baclofen on morphine-induced hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity.

The effects of baclofen on the development of reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine were examined in mice. A single administration of morphine induced hyperactivity and the morphine-induced hyperactivity was inhibited dose dependently by the administration of a GABA(B)receptor agonist, baclofen (1.25, 2.5 and 5 mg kg(-1), i.p.). Daily repeated administration of morphine developed reverse tolerance to the hyperactivity of morphine. The concomitant administration of baclofen inhibited the morphine-induced hyperactivity and the baclofen administration prior to and during the chronic administration of morphine in mice inhibited the development of reverse tolerance to the hyperactivity of morphine (10 mg kg(-1), s.c.). Postsynaptic dopamine receptor supersensitivity was also developed in reverse-tolerant mice that had received the same morphine. The development of postsynaptic dopamine receptor supersensitivity was evidenced by the enhanced ambulatory activity of apomorphine (2 mg kg(-1), s.c.). Baclofen also inhibited the development of postsynaptic dopamine receptor supersensitivity induced by the chronic administration of morphine. These results suggest that the hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine may be modulated via the activation of GABA(B)receptors induced by baclofen.

Effects of heme oxygenase system on the cyclooxygenase in the primary cultured hypothalamic cells.

Endogenous carbon monoxide (CO) shares with nitric oxide (NO) a role as a putative neural messenger in the brain. Both gases are believed to modulate CNS function via an increase in cytoplasmic cGMP concentrations secondary to the activation of soluble guanylate cyclase (sGC). Recently CO and NO were proposed as a possible mediator of febrile response in hypothalamus. NO has been reported to activate both the constitutive and inducible isoform of the cyclooxygenase (COX). Thus, we investigated whether CO arising from heme catabolism by heme oxygenase (HO) is involved in the febrile response via the activation of COX in the hypothalamus. PGE2 which is a final mediator of febrile response released from primary cultured hypothalamic cells was taken as a marker of COX activity. PGE2 concentration was measured with EIA kits. Exogenous CO (CO-saturated medium) and hemin (a substrate and potent inducer of HO) evoked an increase in PGE2 release from hypothalamic cells, and these effects were blocked by methylene blue (an inhibitor of sGC). And membrane permeable cGMP analogue, dibutyryl-cGMP elicited significant increases in PGE2 release. These results suggest that there may be a functional link between HO and COX enzymatic activities. The gaseous product of hemin through the HO pathway, CO, might play a role through the modulation of the COX activity in the hypothalamus.

NMDA-type glutamatergic modulation in dopaminergic activation measured by apomorphine-induced cage climbing behaviors.

The present study examined the hypothesis that NMDA, AMPA/Kainate, and metabotropic (mGlu) glutamate receptors contribute to a behavioral stimulation induced by activation of dopamine receptors by comparing responses in apomorphine-induced cage climbing behaviors in mice. MK-801, CNQX, and MCPG were served as the NMDA receptor, AMPA/Kainate receptor, and mGlu receptor antagonist, respectively, to elucidate the glutamatergic modulation in apomorphine-induced dopaminergic activation in mice. Drugs were administered intracerebroventricularly (i.c.v.) into the mouse brain 15 min before the apomorphine treatment (2 mg/kg, s.c.). I.c.v. injection of MK-801 inhibited the apomorphine-induced cage climbing behavior dose-dependently. However, treatments with CNQX and MCPG did not any significant change in apomorphine-induced cage climbing behavior in mice. These results suggest that stimulation of NMDA type of glutamate receptors could contribute to the dopaminergic stimulation, but not AMPA/Kainate and mGlu type glutamate receptors.

Effects of acetylbergenin against D -galactosamine-induced hepatotoxicity in rats.

The hepatoprotective effects of acetylbergenin were examined against D -galactosamine (GalN)-induced liver damage in rats, compared with that of bergenin reported previously. Acetylbergenin was synthesized from acetylation of bergenin, isolated from Mallotus japonicus, to increase lipophilic and physiological activities. Acetylbergenin was administered orally once daily for 7 days and then GalN (400 mg kg(-1), i.p.) was injected at 24 h and 96 h after the final administration of acetylbergenin. Acetylbergenin reduced the elevated serum enzyme activities of alanine/aspartate aminotransferase, sorbitol dehydrogenase and gamma -glutamyltransferase and the formation of hepatic malondialdehyde induced by GalN. Acetylbergenin also significantly restored towards normalization the decreased levels of glutathione and the decreased activities of glutathione S-transferase and glutathione reductase induced by GalN. Therefore, these results suggest that acetylbergenin has hepatoprotective effects against GalN-induced hepatotoxicity by inhibiting lipid peroxidation and maintaining an adequate level of GSH for the detoxification of xenobiotics as underlying hepatoprotective mechanisms. In addition, lipophilic acetylbergenin showed more activity in the hepatoprotection than that of the much less lipophilic bergenin reported previously.

Regulation of c-fos gene expression by lipopolysaccharide and cycloheximide in C6 rat glioma cells.

The effect of lipopolysaccharide (LPS) on the expression of immediate early genes, such as c-fos and c-jun, was examined in C6 rat glioma cells. LPS (1 microg/ml) alone did not affect c-fos mRNA level. LPS, however, transiently increased c-jun mRNA level. Cycloheximide (CHX, 20 microM), a protein synthesis inhibitor, alone caused increases of c-fos and c-jun mRNA levels. LPS showed a potentiating effect in the regulation of c-fos mRNA level, whereas LPS showed an additive action for the regulation of CHX-induced c-jun mRNA expression. To determine if CREB and mitogen-activated protein kinases (MAPKs) are involved in the regulation of c-fos mRNA expression by LPS and CHX, Western blot was carried out using the phosphorylated form of antibodies against ERK, JNK, p38, and CREB. LPS transiently increased the phosphorylation of p38-MAPK and CREB. In addition, LPS alone elevated phosphorylation of ERK (p44/p42) MAPK in a time-dependent manner. Furthermore, LPS plus CHX enhanced phosphorylation of ERK, p38, and CREB in a synergistic manner. Our results suggest that the phosphorylation of ERK, p38, and CREB may be involved in the regulation of synergistic c-fos mRNA expression induced by LPS plus CHX in C6 rat glioma cells.

N-Methyl-D-aspartate receptor antagonists enhance the head-twitch response, a 5-hydroxytryptamine2 receptor-mediated behaviour, in reserpine-treated mice.

In this study, N-methyl-D-aspartate (NMDA)-receptor antagonists enhanced the head-twitch response induced by 5-hydroxytryptamine (5-HT) in reserpine-treated mice. To minimize the risk of any indirect involvement of NMDA-receptor antagonists (D(-)-2-amino-5-phosphonopentanoic acid (AP-5), D(-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP), (+)-5-methyl-10,11-dihydroxy-5H-dibenzo-[a,d]-cyclohepten-5,10-imi ne (MK-801), ketamine, dextrorphan and dextromethorphan) with 5-HT neurones, vesicle stores of monoamines, especially 5-HT, were depleted with reserpine. In addition, the enhancement of 5-HT-induced head-twitch response was inhibited by apomorphine and NMDA as well as ritanserin in reserpine-treated mice. These results support our previous conclusion that NMDA receptors play important roles in the glutamatergic modulation of 5-HTergic function at the postsynaptic 5-HT2 receptors in mice.

An autoradiographic study of [3H]AMPA receptor binding and in situ hybridization of AMPA sensitive glutamate receptor A (GluR-A) subunits following morphine withdrawal in the rat brain.

Chronic treatment with opioids is well known to result in the development of physical dependence. More recently, glutamatergic mechanisms have been implicated in expression of the withdrawal syndrome from opioids. To better examine glutamatergic involvement, an autoradiographic study of [3H]AMPA receptor binding and an assessment of in situ hybridization of AMPA sensitive glutamate receptor A (GluR-A) subunits in the rat brain were each performed 7 h after withdrawal from morphine infusion. Animals were rendered dependent by intracerebroventricular (i.c.v.) infusion of morphine (26 nmol/microl/h) via osmotic minipumps for 3 days. Brain sections of 14-microm thickness were incubated with 15 nM [3H]AMPA for quantitation of binding to the AMPA receptor. The probe for in situ hybridization was labeled at its 3' end using terminal deoxynucleotidyl transferase and [35S]dATP. The highest degree of [3H]AMPA binding was shown in the hippocampus. The extent of [3H]AMPA binding was increased significantly in the cortex areas (18-21%), caudate-putamen (20%), and hippocampus (7-9%) of rats following withdrawal from morphine. The highest levels of mRNA for GluR-A, flop and flip subunits, were found in the dentate gyrus and in the CA3 region of the hippocampus, respectively. The levels of mRNA for the flop form of GluR-A were decreased in the CA3 of hippocampus (8%) of the rat brain. The levels of mRNA for the flip form of GluR-A were increased in the parietal cortex (7%) and the entorhinal cortex (8%). Increases in the binding of [3H]AMPA to its receptor may play an important role during withdrawal from morphine dependence.