Biomedical subjects

M Asanuma

Publications and source records attributed to M Asanuma.

At least 19 recordsLinked to original sources

PubMed2005

Rotenone induces aggregation of gamma-tubulin protein and subsequent disorganization of the centrosome: relevance to formation of inclusion bodies and neurodegeneration.

Neurodegenerative disorders are characterized by progressive loss of specific neurons in the central nervous system. Although they have different etiologies and clinical manifestations, most of them share similar histopathologic characteristics such as the presence of inclusion bodies in both neurons and glial cells, which represent intracellular aggregation of misfolded or aberrant proteins. In Parkinson's disease, formation of inclusion bodies has been associated with the aggresome-related process and consequently with the centrosome. However, the significance of the centrosome in the neurodegenerative process remains obscure. In the present study, the morphological and functional changes in the centrosome induced by rotenone, a common insecticide used to produce experimental Parkinsonism, were examined both in vitro and in vivo. Aggregation of gamma-tubulin protein, which is a component of the centrosome matrix and recently identified in Lewy bodies of Parkinson's disease, was observed in primary cultures of mesencephalic cells treated with rotenone. Rotenone-treated neurons and astrocytes showed enlarged and multiple centrosomes. These centrosomes also displayed multiple aggregates of alpha-synuclein protein. Neurons with disorganized centrosomes exhibited neurite retraction and microtubule destabilization, and astrocytes showed disturbances of mitotic spindles. The Golgi apparatus, which is closely related to the centrosome, was dispersed in both rotenone-treated neuronal cells and the substantia nigra of rotenone-treated rats. Our findings suggested that recruitment of abnormal proteins in the centrosome contributed to the formation of inclusion bodies, and that rotenone markedly affected the structure and function of the centrosome with consequent induction of cytoskeleton disturbances, disassembly of the Golgi apparatus and collapse of neuronal cells.

Animals↗

PubMed2004

Neuroprotective effects of nonsteroidal anti-inflammatory drugs on neurodegenerative diseases.

It is well known that nonsteroidal anti-inflammatory drugs (NSAIDs) possess anti-inflammatory, analgesic and antipyretic properties by inhibiting cyclooxygenase (COX), a prostaglandin-synthesizing enzyme. It has also been revealed that NSAIDs exert inhibitory effects on the generating system of nitric oxide radicals and modulating effects on transcription factors which are related to inflammatory reactions including cytokine expression. Recently, a number of studies have been conducted focusing on the neuroprotective effects of NSAIDs, since it has been reported that inflammatory processes are associated with the pathogenesis of several neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. In the experimental model of Parkinson's disease, NSAIDs have also exerted neuroprotective effects which are based not only on their COX-inhibiting effects but also on other properties: inhibitory effects on nitric oxide synthesis, action as agonists for peroxisome proliferator-activated receptor gamma, and some unknown pharmacological effects. In this article, various pharmacological effects of NSAIDs except their inhibitory action on COX are reviewed, and possible neuroprotective effects of NSAIDs have been discussed on neurodegenerative diseases, especially Parkinson's disease.

Animals↗

PubMed2001

Delta opioid peptide [D-Ala2, D-Leu5]enkephalin causes a near complete blockade of the neuronal damage caused by a single high dose of methamphetamine: examining the role of p53.

The delta opioid peptide [D-Ala2, D-Leu5]enkephalin (DADLE) has been reported to block the neurotoxicity induced by multiple administrations of a moderate dose of methamphetamine (METH). We examined in this study if DADLE might block the neurotoxicity caused by a single high dose of METH in CD-1 mice. The levels of dopamine transporter (DAT), tyrosine hydroxylase (TH), major biogenic amines including DA, 5-hydroxytryptamine (5-HT), and their metabolites were examined. In addition, since the tumor suppressor p53 has been implicated in the neurotoxicity of METH, this study also examined the levels of p53 mRNA and protein affected by METH and DADLE. METH (25 mg/kg, i.p.) caused significant losses of DAT, TH, DA, 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-HT in the striatum within 72 h. The administration of a single dose of DADLE (20 mg/kg, i.p., 30 min before METH) caused a complete blockade of all losses induced by METH except for that of the DA content (a approximately 50% blockade). DADLE did not affect the changes of rectal temperature induced by the administration of the high dose of METH. METH increased p53 mRNA in the striatum and the hippocampus of CD-1 mouse. DADLE abolished the p53 mRNA increase caused by METH. METH tended to increase the p53 protein level at earlier time points. However, METH significantly decreased the p53 protein level by about 30% at the 72-h time point. DADLE blocked both the increase of p53 mRNA and the decrease of p53 protein caused by METH. These results demonstrate a neuroprotective effect of DADLE against the neuronal damage and the alteration of p53 gene expression caused by a single high dose of METH. The results also indicate an apparent discordance between the protein level of p53 and the neurotoxicity caused by a high dose of METH. Synapse 39:305-312, 2001. Published 2001 Wiley-Liss, Inc.

Animals↗

PubMed2001

Progressive cortical atrophy after forebrain ischemia in diabetic rats.

The morphological changes in the brain of diabetic rats were examined up to 8 weeks after transient forebrain ischemia produced by transient occlusion of both carotid arteries. Using histochemistry, we also examined the extent and rate of development of atrophic changes in the brain, appearance of astrocytes, activated microglia, and glucose transporter 1 (GLUT1) in streptozotocin-treated rat brains after forebrain ischemia. Atrophic changes appeared in the hippocampus in both non-diabetic-- and diabetic--ischemic groups 4 weeks after ischemia. In diabetic--ischemic rats, the atrophic changes were more severe and progressed more rapidly in the hippocampus, and were also observed in the frontal, temporal and parietal cortices, but not in any cortical areas of the non-diabetic--ischemic rats and non-ischemic--diabetic rats. We observed reduced density of GLUT1 in all cortical regions and hippocampus in ischemic-diabetic rats at 4--8 weeks, when the number of activated microglias and astroglias increased in all cortical regions. Although severe atrophic changes were observed in the gray matter, no serious injury was noted in the white matter in the diabetic-ischemic group. Our results indicate that brain ischemia in the presence of diabetes causes more severe late-onset damage culminating in brain atrophy, compared with non-diabetics.

Animals↗

PubMed2001

Molecular mechanism in activation of glutathione system by ropinirole, a selective dopamine D2 agonist.

We have previously reported that ropinirole, a non-ergot dopamine agonist, has neuroprotective effects against 6-hydroxydopamine in mice based on in vivo antioxidant properties such as the glutathione (GSH)-activating effect. In the present study, we determined that the effects of ropinirole on the level of expression of GSH-related enzyme mRNA, these enzymes were shown to regulate GSH contents in the brain. This study focused on the mechanism of GSH enhancement by ropinirole. Striatal GSH contents were significantly increased by 7-day daily administration of ropinirole. Furthermore, the expression levels of gamma-glutamylcysteine synthetase (gamma-GCS), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) mRNA increased following daily injections of ropinirole for 7 days. In addition, ropinirole treatment for 7 days suppressed auto-oxidation in mouse striatal homogenates, in contrast to the vehicle treatment. In conclusion, ropinirole was able to suppress auto-oxidation, most probably by increasing GSH levels due to an increase of GSH synthesis. In addition, it is likely that auto-oxidation was also suppressed by the activation of GSH-regulating enzymes such as GPx, GR, and GST in the mouse striatum. Thus, our results indicate that the GSH-activating effect of ropinirole may render this dopamine agonist beneficial as a neuroprotective drug.

Animals↗

PubMed2001

Neuroprotective effects of non-steroidal anti-inflammatory drugs by direct scavenging of nitric oxide radicals.

Recently, it has been reported that inflammatory processes are associated with the pathophysiology of Alzheimer's disease and that treatment of non-steroidal anti-inflammatory drugs reduce the risk for Alzheimer's disease. In the present study, we examined nitric oxide radical quenching activity of non-steroidal anti-inflammatory drugs and steroidal drugs using our established direct in vitro nitric oxide radical detecting system by electron spin resonance spectrometry. The non-steroidal anti-inflammatory drugs, aspirin, mefenamic acid, indomethacin and ketoprofen directly and dose-dependently scavenged generated nitric oxide radicals. In experiments of nitric oxide radical donor, NOC18-induced neuronal damage, these four non-steroidal drugs significantly prevented the NOC18-induced reduction of cell viability and apoptotic nuclear changes in neuronal cells without affecting the induction of inducible nitric oxide synthase-like immunoreactivity. However, ibuprofen, naproxen or steroidal drugs, which had less or no scavenging effects in vitro, showed almost no protective effects against NOC18-induced cell toxicity. These results suggest that the protective effects of the former four non-steroidal anti-inflammatory drugs against apoptosis might be mainly due to their direct nitric oxide radical scavenging activities in neuronal cells. These direct NO. quenching activities represent novel effects of non-steroidal anti-inflammatory drugs. Our findings identified novel pharmacological mechanisms of these drugs to exert not only their anti-inflammatory, analgesic, antipyretic activities but also neuroprotective activities against neurodegeneration.

Alzheimer Disease↗

PubMed2001

Localization, regulation, and function of metallothionein-III/growth inhibitory factor in the brain.

The metallothionein (MT) family is a class of low molecular, intracellular, and cysteine-rich proteins with a high affinity for metals. Although the first of these proteins was discovered nearly 40 years ago, their functional significance remains obscure. Four major isoforms (MT-I, MT-II, MT-III, and MT-IV) have been identified in mammals. MT-I and MT-II are ubiquitously expressed in various organs including the brain, while expression of MT-III and MT-IV is restricted in specific organs. MT-III was detected predominantly in the brain, and characterized as a central nervous system-specific isomer. The role of MTs in the central nervous system has become an intense focus of scientific research. An isomer of MTs, MT-III, of particular interest, was originally discovered as a growth inhibitory factor, and has been found to be markedly reduced in the brain of patients with Alzheimer's disease and several other neurodegenerative diseases. MT-III fulfills unique biological roles in homeostasis of the central nervous system and in the etiology of neuropathological disorders.

Alzheimer Disease↗

PubMed2000

Expression of metallothionein-III mRNA and its regulation by levodopa in the basal ganglia of hemi-parkinsonian rats.

In the brain, metallothionein (MT)-III exhibits a free radical scavenging activity. Here we examined the expression of MT-III mRNA in the basal ganglia of 6-hydroxydopamine (6-OHDA)-lesioned hemi-parkinsonian rats and its regulation by levodopa. The level of MT-III mRNA was significantly decreased in the striatum of 6-OHDA-lesioned side. Levodopa treatment significantly increased the expression of striatal MT-III mRNA in the non-lesioned side, but showed no significant effect in the 6-OHDA-lesioned side. These results suggest that the regulation of MT-III mRNA may be related to the progressive degeneration in parkinsonism.

Animals↗

PubMed2000

Direct interactions of methamphetamine with the nucleus.

Possible direct effects of methamphetamine (METH) on transcription factors AP-1 and cAMP response element-binding protein (CREB) in the nucleus were assessed by electrophoretic mobility-shift assay. In vitro addition of METH to nuclear extract from brain tissue increased DNA-binding activities of both transcription factors. In addition, injections of METH to mice induced increases in the binding of AP-1 and CREB, which were depleted by preincubating the nuclear extract with anti-METH antibody. We also examined the cellular distribution of METH in mesencephalic neuronal cells using an immunofluorescence experiment with anti-METH antibody. METH-like immunoreactivity was seen to accumulate in the cytosol 4-6 h after the METH treatment. Furthermore, METH-positive signals were also observed in the nuclei of the METH-treated cells. The present study is the first demonstration that METH can have direct effects on DNA-binding protein complex by redistributing not only in the cytosol but also into the nucleus.

Animals↗

PubMed2000

Antioxidants protect against dopamine-induced metallothionein-III (GIF) mRNA expression in mouse glial cell line (VR-2g).

Metallothionein (MT)-III, originally discovered as a growth inhibitory factor (GIF), is a brain specific isomer of MTs and is markedly reduced in the brain of patients with Alzheimer's disease (AD) or other neurodegenerative diseases. We analyzed the level and regulation of mRNA expression of MT-III in immortalized fetal mouse brain glial cells (VR-2g) by reverse transcriptase-polymerase chain reaction (RT-PCR). We have recently reported that dopamine (DA) increases the expression of MT-III mRNA in vitro. In this study, we investigated the mechanism of such increase by examining the effects of DA agonists (SKF38393 or bromocriptine) and DA antagonists (SCH23390 or sulpiride) on the expression of MT-III mRNA. MT-III mRNA did not change by either agonist and DA-increased MT-III mRNA was not inhibited by either antagonist. These results suggested that the induction of MT-III mRNA by DA was not mediated by stimulation of DA receptors. On the other hand, DA-induced MT-III mRNA expression was strongly inhibited by the addition of antioxidants (glutathione, vitamin E or ascorbic acid), indicating that DA-enhanced MT-III mRNA was mediated by reactive oxygen species. Our results suggest that oxidative stress may be one of the principle factors that modulate MT-III mRNA expression.

Adrenergic Agents↗

PubMed2000

Protective effect of oren-gedoku-to against induction of neuronal death by transient cerebral ischemia in the C57BL/6 mouse.

We examined the neuroprotective effects of oren-gedoku-to (TJ15), a herbal medicine, after transient forebrain ischemia. Transient forebrain ischemia was induced by occlusion of both common carotid arteries for 15 min in C57BL/6 mice treated with TJ15. In the control ischemic group without TJ15 treatment, histologic examination of brain tissue collected seven days after reperfusion showed death of pyramidal cells in CA2-3 area of the hippocampus, unilaterally or bilaterally. In mice treated with oral TJ15 (845 mg/kg/day) for five weeks, the frequency of ischemic neuronal death was significantly lower. Immunohistochemistry for Cu/Zn-superoxide dismutase (Cu/Zn-SOD) showed strongly reactive astrocytes in the hippocampus of ischemic mice treated with TJ15. Damage to nerve cells by free radicals plays an important role in the induction of neuronal death by ischemia-reperfusion injury. Our results suggest that TJ15 protects against ischemic neuronal death by increasing the expression of Cu/Zn-SOD and suggest that oren-gedoku-to reduces the exposure of hippocampal neurons to oxidative stress.

Animals↗

PubMed2000

Bromocriptine markedly suppresses levodopa-induced abnormal increase of dopamine turnover in the parkinsonian striatum.

Bromocriptine, a dopamine agonist, is commonly used in combination with levodopa for the treatment of Parkinson's disease (PD). To investigate the theoretical basis of such combination therapy, we examined the effects of bromocriptine administered alone or in combination with levodopa on dopamine turnover in the striatum of hemi-parkinsonism rats. The parkinsonian striatum showed a 3.4-fold increase of dopamine turnover relative to the control striatum, as often observed in the brain of PD patients. A 7-day course of levodopa therapy markedly increased dopamine turnover in the parkinsonian striatum (53-fold of control level) than in the control striatum (5-fold of the control level). However, bromocriptine specifically and markedly suppressed the levodopa-induced abnormal activation of dopamine turnover in the parkinsonian striatum. Our findings explain the pharmacological basis for the introduction of bromocriptine during long-term levodopa therapy.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2000

Inhibition of tyrosinase reduces cell viability in catecholaminergic neuronal cells.

The biosynthesis of dopamine (DA) in catecholaminergic neurons is regulated by tyrosine hydroxylase, which converts tyrosine into 3, 4-dihydroxyphenylalanine (L-DOPA). In melanocytes, tyrosinase catalyzes both the hydroxylation of tyrosine and the consequent oxidation of L-DOPA to form melanin. Although it has been demonstrated that tyrosinase is also expressed in the brain, the physiological role of tyrosinase in the brain is still obscure. In this study, to investigate the role of tyrosinase in catecholaminergic neuronal cells, we examined the effects of tyrosinase inhibition on the viability of CATH.a and SH-SY5Y cells using tyrosinase inhibitors-specifically, phenylthiourea (PTU) and 5-hydroxyindole (5-HI)-and the transfection of antisense tyrosinase cDNA. Both inhibitors significantly reduced the cell viability of CATH.a cells in a dose-dependent manner. PTU also specifically enhanced DA-induced cell death, but 5-HI did not. This discrepancy in cell death is probably due to the inhibitors' different mechanism of action: 5-HI inhibits the hydroxylation of tyrosine as a competitor for the substrate to induce cell death that may be due to depletion of DA, whereas PTU mainly inhibits the enzymatic oxidation of L-DOPA and DA rather than tyrosine hydroxylation to increase consequently autooxidation of DA. Indeed, the intracellular DA content in CATH.a cells was enhanced by PTU exposure. In contrast, PTU showed no enhancing effects on DA-induced cell death of SH-SY5Y cells, which express little tyrosinase. Furthermore, transfection with antisense tyrosinase cDNA into CATH.a cells dramatically reduced cell viability and significantly enhanced DA-induced cell death. These results suggest that tyrosinase controls the intracellular DA content by biosynthesis or enzymatic oxidation of DA, and the dysfunction of this activity induces cell death by elevation of intracellular DA level and consequent gradual autooxidation of DA to generate reactive oxygen species.

Animals↗

PubMed2000

Immunophilin ligands prevent H2O2-induced apoptotic cell death by increasing glutathione levels in neuro 2A neuroblastoma cells.

We examined the effects of FK506 and its non-immunosuppressive derivative, GPI1046, on H2O2-induced reduction of cell viability and apoptotic cell death in Neuro 2A cells. Our results suggest that the protective properties of GPI1046 against H2O2-induced reduction of cell viability are equipotent with those of FK506 and may be mediated by increased intracellular concentrations of glutathione (GSH). In addition, both FK506 and GPI1046 prevented apoptotic cell death in Neuro 2A cells, although the antiapoptotic effect of FK506 was somewhat stronger than that of GPI1046. These findings suggest that non-immunosuppressive immunophilin ligands such as GPI1046 might be potentially useful in treatment of neurodegenerative diseases without serious side effects such as immune deficiency.

Animals↗

PubMed1999

Early treatment with cyclosporin A ameliorates the reduction of muscarinic acetylcholine receptors in gerbil hippocampus after transient forebrain ischemia.

Recent evidence has suggested that cyclosporin A (CsA), an immunosuppressive agent, has neuroprotective properties. However, its mechanisms associated with this activity remain unclear. We have previously shown that post-ischemic administration of CsA daily for 14 days prevented the decrease of muscarinic acetylcholine receptor binding in the hippocampus in the gerbil model of 5-min transient forebrain ischemia. In the present study, CsA (5 mg/kg, subcutaneously) was administered to each animal just after, 2 and 6 h after ischemia so as not to exert its immunosuppressive effect. Initial CsA treatment significantly restored the declined muscarinic acetylcholine receptor binding of the hippocampus 14 days after ischemia similar to the previous report. However, CsA did not alter reactive changes of astrocytes and microglia in the CA1 area of the hippocampus, which had been suppressed by daily administration. These results indicate that CsA could positively modulate the hippocampal acetylcholine neurotransmission system broken down through the ischemia-induced pyramidal cell death and its action mechanism may have no relation to the immunosuppressive properties.

Animals↗

PubMed1999

Bifemelane hydrochloride protects against cytotoxicity of hydrogen peroxide on cultured rat neuroblastoma cell line.

Free radicals are involved in neuronal damage. Bifemelane hydrochloride has been reported to protect neural tissues against ischemic damage and age-related neurodegeneration. We examined the protective effects of bifemelane HCl and the relation between its effectiveness and free radical formation in hydrogen peroxide (H2O2)-induced cytotoxicity using cultured rat neuroblastoma cell line (B50). Cytotoxicity was examined by using the lactate dehydrogenase (LDH) assay and cell viability by the WST-1 assay. H2O2 reduced the survival of B50 cells in a dose-dependent manner, and treatment of these cells with 75 microM or 100 microM H2O2 reduced their viability by 50% relative to the control group. B50 cells were treated with 5 or 10 microM bifemelane for 2 days followed by treatment with 75 microM or 100 microM H2O2. H2O2 cytotoxicity was reduced by pretreatment with bifemelane. We also examined the effect of bifemelane on lipid peroxide formation in B50 cells using thiobarbituric acid reactive substances assay. Pretreatment of B50 cells with 10 microM bifemelane for 2 days reduced lipid peroxide formation to approximately 54% of the control group. Our results suggest that bifemelane hydrochloride provides a protective effect against H2O2 cytotoxicity partly due to its anti-oxidative properties.

Animals↗

PubMed1999

Nitric oxide modulates muscarinic acetylcholine receptor binding in the cerebral cortex of gerbils.

To determine whether nitric oxide (NO) acts as a modulator of muscarinic acetylcholine receptor (mACh-R) function, we performed a radioligand receptor assay using [3H]quinuclidinyl benzylate ([3H]QNB), the NO radical (NO*) donor 3-(2-Hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamin e (NOC7) and a gerbil brain cortical membrane preparation. NOC7 (at 10 microM, 100 microM or 1 mM concentrations) significantly reduced the [3H]QNB binding Kd values (from 0.196 +/- 0.009 nM in the control, to 0.151 +/- 0.013, 0.144 +/- 0.012 and 0.153 +/- 0.007 nM respectively). NOC7 did not alter the displacement curves of atropine or carbachol. Reduction of SH groups with dithiothreitol, in the presence of the NO donor, significantly increased [3H]QNB binding affinity whereas alkylation by N-ethylmaleimide markedly decreased it. The observed enhancing effect on mACh-R binding affinity for [3H]QNB, may reflect conformational changes in the receptors mediated by the NO generated, and these changes might be explained by NO reactions with such groups through conditions supporting redox reactions intrinsic to the NO molecule, similar to those occurring in redox regulatory sites reported for other neurotransmitter pathways in the CNS.

Animals↗

PubMed1999

Glial cells protect neurons against oxidative stress via transcriptional up-regulation of the glutathione synthesis.

We examined the effects of oxidative stress on rat cultured mesencephalic neurons and glial cells. Glial cells were more resistant to 6-hydroxydopamine (6-OHDA) and H2O2 toxicity than neurons. In glial cells, incubation with 6-OHDA and H2O2 induced a significant increase in the expression of gamma-glutamylcysteine synthetase (the rate-limiting enzyme in glutathione synthesis) mRNA, which correlated well with increased TPA-response element (TRE)-binding activity. Furthermore, a subsequent elevation in cellular total glutathione content was also observed. In neurons, both agents decreased TRE-binding activity, and these cells failed to up-regulate the glutathione synthesis. We also examined the mechanisms of the neuroprotective effects of glial cells using a glia conditioned medium. Neurons maintained in glia conditioned medium up-regulated the level of TRE-binding activity, gamma-glutamylcysteine synthetase mRNA expression, and total glutathione content in response to 6-OHDA or H2O2, and became more resistant to both agents than cells maintained in a normal medium. Neurons maintained in normal medium failed to up-regulate the glutathione synthesis. Our results suggest that transcriptional up-regulation of glutathione synthesis in glial cell appears to mediate brain glial cell resistance against oxidative stress, and that glial cells protect neurons via transcriptional up-regulation of the antioxidant system.

Animals↗