Biomedical subjects

Shuji Kaneko

Publications and source records attributed to Shuji Kaneko.

30 records · Page 2Linked to original sources

PubMed2003

Serofendic acid prevents acute glutamate neurotoxicity in cultured cortical neurons.

We have previously reported that a novel neuroprotective substance named serofendic acid was purified and isolated from ether extract of fetal calf serum. In the present study, we investigated the effect of serofendic acid on acute neurotoxicity induced by L-glutamate (Glu) using primary cultures of rat cortical neurons. Exposure of cortical cultures to Glu for 1 h caused a marked decrease in cell viability, as determined by trypan blue exclusion. This acute Glu neurotoxicity was prevented by N-methyl-D-aspartate (NMDA) receptor antagonists, extracellular Ca(2+) removal, nitric oxide (NO) synthase inhibitor and NO scavenger. Serofendic acid prevented acute Glu neurotoxicity in a concentration-dependent manner. Acute neurotoxicity was induced by ionomycin, a Ca(2+) ionophore, and S-nitroso-L-cysteine, an NO donor. Serofendic acid also prevented both ionomycin- and S-nitroso-L-cysteine-induced neurotoxicity. Moreover, the protective effect of serofendic acid on acute Glu neurotoxicity was not affected by cycloheximide, a protein synthesis inhibitor, and actinomycin D, an RNA synthesis inhibitor. These results indicate that serofendic acid protects cultured cortical neurons from acute Glu neurotoxicity by reducing the cytotoxic action of NO and de novo protein synthesis is not required for this neuroprotection.

Animals↗

PubMed2003

Nicotinic acetylcholine receptor-mediated neuroprotection by donepezil against glutamate neurotoxicity in rat cortical neurons.

Donepezil is a potent and selective acetylcholinesterase (AChE) inhibitor developed for the treatment of Alzheimer's disease. To elucidate whether donepezil shows neuroprotective action in addition to amelioration of cognitive deficits, we examined the effects of donepezil on glutamate-induced neurotoxicity using primary cultures of rat cortical neurons. A 10-min exposure of cultures to glutamate followed by a 1-h incubation with glutamate-free medium caused a marked loss of viability, as determined by Trypan blue exclusion. Glutamate neurotoxicity was prevented by 24-h pretreatment of donepezil in a concentration-dependent manner. Among AChE inhibitors examined, donepezil and certain AChE inhibitors such as tacrine and galanthamine showed potent neuroprotective action, although physostigmine did not affect glutamate neurotoxicity. Neuroprotective action of donepezil was antagonized by mecamylamine, a nicotinic acetylcholine receptor (nAChR) antagonist, but not by scopolamine, a muscarinic acetylcholine receptor antagonist. Furthermore, both dihydro-beta-erythroidine, an alpha4beta2-neuronal nAChR antagonist, and methyllycaconitine, an alpha7-nAChR antagonist, each also significantly antagonized the effect of donepezil. Next, we examined the effects of donepezil on glutamate-induced apoptosis. Exposure of 100 microM glutamate to cortical neurons for 24 h induced apoptotic neuronal death and nuclear fragmentation. Donepezil for 24 h before and 24 h during glutamate exposure prevented nuclear fragmentation and glutamate-induced apoptosis. These results suggest that donepezil not only protects cortical neurons against glutamate neurotoxicity via alpha4beta2- and alpha7-nAChRs but also prevents apoptotic neuronal death.

Animals↗

PubMed2003

N-Methyl-D-aspartate receptors contribute to the maintenance of dopaminergic neurons in rat midbrain slice cultures.

Excitatory neuronal activity produces beneficial influences on neuronal survival under several circumstances. We show that cultivation of rat midbrain slices in the presence of elevated extracellular Mg(2+) resulted in a marked decrease in the number of dopaminergic neurons. The effect was prominent when Mg(2+) was added to the medium during the first week of cultivation. Chronic treatment with antagonists of N-methyl-D-aspartate receptors such as 2-amino-5-phosphonovaleric acid, MK-801 and ifenprodil also resulted in a marked loss of dopaminergic neurons, whereas nicotinic receptor antagonists showed no effect. The effect of MK-801 was abolished by chronic depolarization by elevated extracellular K(+), or by application of forskolin or dibutyryl cyclic AMP. Thus, tonic activation of N-methyl-D-aspartate receptors driven by neuronal activity may play an important role in the maintenance of dopaminergic neurons.

2-Amino-5-phosphonovalerate↗

PubMed2003

Neuroprotective effects of alpha-tocopherol on oxidative stress in rat striatal cultures.

Oxidative stress caused by an increase in free radicals plays an important role in neuronal death. We investigated the effects of alpha-tocopherol on oxidative stress-induced cytotoxicity using primary cultures of rat striatal neurons. alpha-Tocopherol at concentrations of 1-10 microM significantly prevented cytotoxicity induced by superoxide radical (O(2(-)) donor, 1,1'-dimethyl-4,4'-bipyridium dichloride (paraquat). In contrast, alpha-tocopherol did not affect the cytotoxicity of hydrogen peroxide (H(2)O(2)), which enhances hydroxyl radical (.OH) formation by metal-catalyzed Fenton reactions. alpha-Tocopherol significantly inhibited the cytotoxicity of nitric oxide (NO) donors, S-nitrosocysteine and 3-morpholinosydnonimine (SIN-1). alpha-Tocopherol showed potent protection against cytotoxicity induced by L-buthionine-[S,R]-sulfoximine (BSO), which causes depletion of intracellular glutathione. Moreover, alpha-tocopherol afforded a moderate but significant inhibition of cytotoxicity induced by a non-specific protein kinase inhibitor, staurosporine, which is known to induce apoptosis in many types of cells including neurons. These results suggest that alpha-tocopherol protects striatal neurons by the reduction of oxidative stress, presumably by decreasing intracellular O(2)(-) levels, and at least partly by the inhibition of apoptosis.

Animals↗

PubMed2003

Lipopolysaccharide-induced dopaminergic cell death in rat midbrain slice cultures: role of inducible nitric oxide synthase and protection by indomethacin.

Glial cell activation associated with inflammatory reaction may contribute to pathogenic processes of neurodegenerative disorders, through production of several cytotoxic molecules. We investigated the consequences of glial activation by interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS) in rat midbrain slice cultures. Application of IFN-gamma followed by LPS caused dopaminergic cell death and accompanying increases in nitrite production and lactate dehydrogenase release. Aminoguanidine, an inhibitor of inducible nitric oxide synthase (iNOS), or SB203580, an inhibitor of p38 mitogen-activated protein kinase, prevented dopaminergic cell loss as well as nitrite production. SB203580 also suppressed expression of iNOS and cyclooxygenase-2 (COX-2) induced by IFN-gamma/LPS. A COX inhibitor indomethacin protected dopaminergic neurons from IFN-gamma/LPS-induced injury, whereas selective COX-2 inhibitors such as NS-398 and nimesulide did not. Notably, indomethacin was able to attenuate neurotoxicity of a nitric oxide (NO) donor. Neutralizing antibodies against tumour necrosis factor-alpha and interleukin-1beta did not inhibit dopaminergic cell death caused by IFN-gamma/LPS, although combined application of these antibodies blocked lactate dehydrogenase release and decrease in the number of non-dopaminergic neurons. These results indicate that iNOS-derived NO plays a crucial role in IFN-gamma/LPS-induced dopaminergic cell death, and that indomethacin exerts protective effect by mechanisms probably related to NO neurotoxicity rather than through COX inhibition.

Animals↗

PubMed2003

Alternative splicing of Cav2 genes and their functional significance.

Alternative splicing is one of the most pharmacologically and physiologically significant mechanisms for the functional diversity of the mammalian genomes. Here I review recent results on the diversity of the Ca(v)2 subclass of voltage-dependent Ca(2+) channel gene in neurons. Although the entire picture of alternative splicing is not yet understood, emerging evidences suggest the Ca(v)2 isoforms permit optimization of Ca(2+) signaling in different regions of the brain with specific pharmacological ligands.

Alternative Splicing↗

PubMed2002

Antagonism of NMDA receptors by sigma receptor ligands attenuates chemical ischemia-induced neuronal death in vitro.

We investigated the effects of sigma receptor ligands on neuronal death induced by chemical ischemia using primary cultures of rat cerebral cortical neurons. The induction of chemical ischemia by sodium azide and 2-deoxy-D-glucose led to delayed neuronal death in a time- and concentration-dependent manner, as determined by trypan blue exclusion. The neurotoxicity was inhibited by N-methyl-D-aspartate (NMDA) receptor antagonists, indicating the involvement of glutamate. The sigma receptor ligands (+)-N-allylnormetazocine ((+)-SKF10,047) and haloperidol, but not carbetapentane and R(+)-3-(3-hydroxyphenyl)-N-propylpiperidine ((+)-3-PPP), prevented chemical ischemia-induced neurotoxicity in a concentration-dependent manner. The protective effects of (+)-SKF10,047 and haloperidol were not affected by the sigma receptor antagonists. (+)-SKF10,047 and haloperidol, but not carbetapentane and (+)-3PPP, inhibited the glutamate-induced increase in intracellular Ca(2+), and the inhibitory effects were not attenuated by sigma receptor antagonists. These results suggest that direct interaction with NMDA receptors but not sigma receptors is crucial to the neuroprotective effects of sigma receptor ligands with affinity for NMDA receptors.

2-Amino-5-phosphonovalerate↗

PubMed2002

Regulation of N-methyl-D-aspartate cytotoxicity by neuroactive steroids in rat cortical neurons.

We investigated the effects of neuroactive steroids on N-methyl-D-aspartate (NMDA) cytotoxicity in cultured rat cortical neurons. 3alpha-hydroxy-5beta-pregnan-20-one sulfate (3alpha5betaS) attenuated, whereas pregnenolone sulfate and pregnenolone hemisuccinate exacerbated, NMDA neurotoxicity in cortical slice cultures. These actions of steroids were not affected by inhibition of protein synthesis, by blockade of GABA(A) receptors, or by blockade of sigma receptors. In addition, the actions of steroids were not affected by manipulation of cyclic AMP levels or protein kinase C activity. We found that 3alpha5betaS attenuated and pregnenolone hemisuccinate augmented NMDA-induced currents in cortical neurons, whereas pregnenolone sulfate exerted no significant effect. Fluorometric measurements revealed that 3alpha5betaS attenuated and pregnenolone hemisuccinate augmented glutamate-induced increase in intracellular Ca(2+). Pregnenolone sulfate slowed the decay of Ca(2+) increase induced by glutamate, without significant effect on the peak amplitude of Ca(2+) increase. These results indicate that neuroactive steroids affect NMDA cytotoxicity by modulation of Ca(2+) influx through NMDA receptor-associated channels.

Action Potentials↗

PubMed2002

Possible coupling of prostaglandin E receptor EP(1) to TRP5 expressed in Xenopus laevis oocytes.

We previously reported that the prostaglandin E(2) (PGE(2)) receptor subtype EP(1) is coupled to intracellular Ca(2+) mobilization in CHO cells, which is dependent on extracellular Ca(2+) in a pertussis toxin-insensitive manner [H. Katoh, et al., Biochim. Biophys. Acta 1244 (1995) 41-48]. However, it remains unknown about the signal transduction involved in this response. To investigate the mechanism regulating Ca(2+) mobilization mediated by EP(1) receptors in detail, we performed a series of experiments using the Xenopus laevis oocyte expression system and found that endogenous G(q) and/or G(11), and not G(i1) is involved in the Ca(2+) mobilization induced by PGE(2). We further investigated the receptor-activated Ca(2+) channel (RACC)-related response by introducing mRNA for mouse transient receptor potential 5 (TRP5), a possible candidate for the RACC, and found effective coupling between them. These results suggest that the EP(1) receptors induce Ca(2+) mobilization via G(q) and/or G(11) and Ca(2+) influx via TRP.

Animals↗

PubMed2002

Adenosine 5'-triphosphate inhibits slow depolarization induced by repetitive dorsal root stimulation via P2Y purinoceptors in substantia gelatinosa neurons of the adult rat spinal cord slices with the dorsal root attached.

We previously reported that slow depolarization of substantia gelatinosa neurons is evoked by repetitive stimulation of C-fibers of dorsal root in adult rat spinal cord transverse slices with the dorsal root attached, which was considered to be an event relevant to spinal nociception. In the present study, we investigated the effects of adenosine 5'-triphosphate (ATP) and its analogs on the slow depolarization. ATP (10-100 microM) significantly inhibited the amplitude of slow depolarization in a concentration-dependent manner. The inhibitory effect of ATP was not reversed by suramin, an antagonist for some P2-purinoceptors, and was mimicked by a P2Y selective agonist uridine 5'-triphosphate, but not a P2X selective agonist alpha,beta-methylene ATP. These results suggest that ATP inhibits the slow depolarization of substantia gelatinosa neurons relevant to nociceptive transmission in the spinal dorsal horn, via suramin-insensitive P2Y purinoceptors.

Action Potentials↗

PubMed2002

Isolation of a diterpenoid substance with potent neuroprotective activity from fetal calf serum.

Excess activation of glutamate receptors and production of free radicals including nitric oxide may result in severe and irreversible damage to the mammalian central nervous system (CNS), but endogenous defense systems that protect neurons from these insults are poorly understood. Here, we purified and isolated a neuroprotective substance, which has been named "serofendic acid," from a lipophilic fraction of FCS based on the ability to protect rat primary cortical neurons against nitric oxide cytotoxicity. Mass spectrometry and NMR spectroscopy revealed the chemical structure of serofendic acid (15-hydroxy-17-methylsulfinylatisan-19-oic acid) as a sulfur-containing atisane-type diterpenoid, which is unique among known endogenous substances. Synthetic serofendic acid exhibited potent protective actions on cortical neurons against cytotoxicity of a nitric oxide donor as well as of glutamate, although it did not show appreciable influences on glutamate receptor-mediated responses in these neurons. Electron spin resonance analysis demonstrated that serofendic acid had no direct scavenging activity on nitric oxide radicals but was capable of inhibiting the generation of hydroxyl radical, a presumed "executor" radical in the nitric oxide-mediated neurotoxic cascade. These findings suggest that serofendic acid is a low-molecular-weight bioactive factor that promotes survival of CNS neurons, probably through the attenuation of free radical-mediated insults.

Animals↗

PubMed2002

Identification and characterization of novel human Ca(v)2.2 (alpha 1B) calcium channel variants lacking the synaptic protein interaction site.

The physical interaction between the presynaptic vesicle release complex and the large cytoplasmic region linking domains II and III of N-type (Ca(v)2.2) calcium channel alpha(1)B subunits is considered to be of fundamental importance for efficient neurotransmission. By PCR analysis of human brain cDNA libraries and IMR32 cell mRNA, we have isolated novel N-type channel variants, termed Ca(v)2.2-Delta1 and Delta2, which lack large parts of the domain II-III linker region, including the synaptic protein interaction site. They appear to be widely expressed across the human CNS as indicated by RNase protection assays. When expressed in tsA-201 cells, both novel variants formed barium-permeable channels with voltage dependences and kinetics for activation that were similar to those observed with the full-length channel. All three channel types exhibited the hallmarks of prepulse facilitation, which interestingly occurred independently of G-protein betagamma subunits. By contrast, the voltage dependence of steady-state inactivation seen with both Delta1 and Delta2 channels was shifted toward more depolarized potentials, and recovery from inactivation of Delta1 and Delta2 channels occurred more rapidly than that of the full-length channel. Moreover, the Delta1 channel was dramatically less sensitive to both omega-conotoxin MVIIA and GVIA than either the Delta2 variant or the full-length construct. Finally, the domain II-III linker region of neither variant was able to effectively bind syntaxin in vitro. These results suggest that the structure of the II-III linker region is an important determinant of N-type channel function and pharmacology. The lack of syntaxin binding hints at a unique physiological function of these channels.

Alternative Splicing↗