Biomedical subjects

Chihiro Tohda

Publications and source records attributed to Chihiro Tohda.

17 recordsLinked to original sources

PubMed2006

Protective effect of grape seed polyphenols against high glucose-induced oxidative stress.

We aimed to clarify whether grape seed polyphenols (GSPs) are candidates therapeutic agents against diabetes mellitus, and to determine what degree of GSP oligomerization has the most potent efficacy. We studied the protective effects of various molecular weight GSPs (monomer, oligomer, polymer, and oligonol) on high glucose-induced cytotoxicity. In the present study, a high concentration of glucose (30 mM) induced cytotoxicity and oxidative stress (reactive oxygen species and nitric oxide) in cultured LLC-PK1 cells, but treatment with GSPs, especially oligomer GSPs, had potent protective effects against high glucose-induced oxidative stress. In addition, high glucose induced nuclear translocation of nuclear factor-kappa B, and increased expression of cyclooxygenase-2, inducible nitric oxide synthase, and bax, but GSP treatment inhibited them. These results indicate that GSPs have protective effects against high glucose-induced cytotoxicity, and among them, oligomer GSPs have more potent effects than other GSPs (monomer, polymer, and oligonol) on high glucose-induced renal cell damage.

Animals↗

PubMed2006

Comparison of Anti-inflammatory Activities of Six Curcuma Rhizomes: A Possible Curcuminoid-independent Pathway Mediated by Curcuma phaeocaulis Extract.

We aimed to compare the anti-inflammatory activities of six species of Curcuma drugs using adjuvant arthritis model mice. When orally administered 1 day before the injection of adjuvant, the methanol extract of Curcuma phaeocaulis significantly inhibited paw swelling and the serum haptoglobin concentration in adjuvant arthritis mice. Also when orally administered 1 day after the injection of adjuvant, the methanol extract of Curcuma phaeocaulis significantly inhibited paw swelling. Other Curcuma species (Curcuma longa, Curcuma wenyujin, Curcuma kwangsiensis, Curcuma zedoaria and Curcuma aromatica) had no significant inhibitory effects on adjuvant-induced paw swelling. Cyclooxygenase (COX)-2 activity was significantly inhibited by the methanol extract of C. phaeocaulis. Curcuminoids' (curcumin, bis-demethoxycurcumin and demethoxycurcumin) were rich in C. longa, but less in C. phaeocaulis and C. aromatica, not in C. wenyujin, C. kwangsiensis and C. zedoaria, suggesting that curcuminoids' contents do not relate to inhibition of arthritis swelling. Therefore, C. phaeocaulis may be a useful drug among Curcuma species for acute inflammation, and the active constituents of C. phaeocaulis are not curcuminoids.

Journal Article↗

PubMed2006

Metabolite 1 of protopanaxadiol-type saponins, an axonal regenerative factor, stimulates teneurin-2 linked by PI3-kinase cascade.

We previously showed that 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol (M1), a metabolite of protopanaxadiol-type ginseng saponins by intestinal bacteria had axonal extension activity in degenerated neurons, and improved memory disorder and synaptic loss induced by an active fragment of amyloid beta, Abeta(25-35). It is unknown how M1 shows these effects in neurons. To clarify the signal transduction mechanism of M1-induced axonal extension, phosphorylated proteins by M1 stimulation were identified because most cellular signal pathways are regulated by phosphorylation/dephosphorylation. The combination of immunoprecipitation and MALDI-TOF-MS revealed that teneurin-2 and mPar3 were specifically phosphorylated by M1 stimulation. Because mPar3 is known as an axonal specifying molecule and to be regulated by phosphatidylinositol 3-kinase (PI3-kinase), the involvement of teneurin-2 and PI3-kinase in the M1 signal was studied. In teneurin-2-deficient cortical neurons, M1-induced axonal extension and PI3-kinase activation were significantly inhibited. In addition, treatment with PI3-kinase inhibitor also reduced M1-induced axonal extension. These results suggest that M1 induces axonal outgrowth through the teneurin-2-PI3-kinase cascade.

Amyloid beta-Peptides↗

PubMed2006

Withanoside IV and its active metabolite, sominone, attenuate Abeta(25-35)-induced neurodegeneration.

At the present, medication of dementia is limited to symptomatic treatments such as the use of cholinesterase inhibitors. To cure dementia completely, that is regaining neuronal function, reconstruction of neuronal networks is necessary. Therefore, we have been exploring antidementia drugs based on reconstructing neuronal networks in the damaged brain and found that withanoside IV (a constituent of Ashwagandha; the root of Withania somnifera) induced neurite outgrowth in cultured rat cortical neurons. Oral administration of withanoside IV (10 micromol/kg/day) significantly improved memory deficits in Abeta(25-35)-injected (25 nmol, i.c.v.) mice and prevented loss of axons, dendrites, and synapses. Sominone, an aglycone of withanoside IV, was identified as the main metabolite after oral administration of withanoside IV. Sominone (1 microM) induced axonal and dendritic regeneration and synaptic reconstruction significantly in cultured rat cortical neurons damaged by 10 microM Abeta(25-35). These data suggest that orally administrated withanoside IV may ameliorate neuronal dysfunction in Alzheimer's disease and that the active principle after metabolism is sominone.

Amyloid beta-Peptides↗

PubMed2006

Characterization of anti-neurodegenerative effects of Polygala tenuifolia in Abeta(25-35)-treated cortical neurons.

Although Polygala tenuifolia WILLD (PT) was classically mentioned as an anti-dementia drug in Chinese and Japanese traditional medicine, basic research showed only enhancement of the cholinergic function. In Alzheimer's disease, neuritic atrophy and synaptic loss occur prior to neuronal death event, and may be the first trigger of the memory impairment. Therefore, we studied effects of Polygala tenuifolia WILLD (PT) on Abeta(25-35)-induced neuronal damage using rat cortical neurons for characterization of activities of PT under Abeta-induced neuronal damage. Treatment with the water extract of PT enhanced axonal length dose-dependently after Abeta(25-35)-induced axonal atrophy. However, dendritic atrophy and synaptic loss induced by Abeta(25-35) were not recovered by treatment with PT extract. In contrast, Abeta(25-35)-induced cell damage was completely inhibited by PT extract. By characterization of PT effects on neuronal morphological plasticity and cell damage, usefulness as well as an insufficiency of PT as an anti-dementia drug was clarified.

Amyloid beta-Peptides↗

PubMed2005

Neuritic regeneration and synaptic reconstruction induced by withanolide A.

We investigated whether withanolide A (WL-A), isolated from the Indian herbal drug Ashwagandha (root of Withania somnifera), could regenerate neurites and reconstruct synapses in severely damaged neurons. We also investigated the effect of WL-A on memory-deficient mice showing neuronal atrophy and synaptic loss in the brain. Axons, dendrites, presynapses, and postsynapses were visualized by immunostaining for phosphorylated neurofilament-H (NF-H), microtubule-associated protein 2 (MAP2), synaptophysin, and postsynaptic density-95 (PSD-95), respectively. Treatment with A beta(25-35) (10 microM) induced axonal and dendritic atrophy, and pre- and postsynaptic loss in cultured rat cortical neurons. Subsequent treatment with WL-A (1 microM) induced significant regeneration of both axons and dendrites, in addition to the reconstruction of pre- and postsynapses in the neurons. WL-A (10 micromol kg(-1) day(-1), for 13 days, p.o.) recovered A beta(25-35)-induced memory deficit in mice. At that time, the decline of axons, dendrites, and synapses in the cerebral cortex and hippocampus was almost recovered. WL-A is therefore an important candidate for the therapeutic treatment of neurodegenerative diseases, as it is able to reconstruct neuronal networks.

Animals↗

PubMed2005

Search for natural products related to regeneration of the neuronal network.

The reconstruction of neuronal networks in the damaged brain is necessary for the therapeutic treatment of neurodegenerative diseases. We have screened the neurite outgrowth activity of herbal drugs, and identified several active constituents. In each compound, neurite outgrowth activity was investigated under amyloid-beta-induced neuritic atrophy. Most of the compounds with neurite regenerative activity also demonstrated memory improvement activity in Alzheimer's disease-model mice. Protopanaxadiol-type saponins in Ginseng drugs and their metabolite, M1 (20-O-beta-D-glucopyranosyl-(20S)-protopanaxadiol), showed potent regeneration activity for axons and synapses, and amelioration of memory impairment. Withanolide derivatives (withanolide A, withanoside IV, and withanoside VI) isolated from the Indian herbal drug Ashwagandha, also showed neurite extension in normal and damaged cortical neurons. Trigonelline, a constituent of coffee beans, demonstrated the regeneration of dendrites and axons, in addition to memory improvement.

Alzheimer Disease↗

PubMed2005

Influence of amla (Emblica officinalis Gaertn.) on hypercholesterolemia and lipid peroxidation in cholesterol-fed rats.

The effects of amla on low-density lipoprotein (LDL) oxidation and cholesterol levels were investigated in vitro and in vivo using Cu(2+)-induced LDL oxidation and cholesterol-fed rats. SunAmla and ethyl acetate (EtOAc) extract of amla significantly inhibited thiobarbituric acid (TBA)-reactive substance level in the Cu(2+)-induced LDL oxidation and the effects were stronger than those of probucol. In addition, the administration of SunAmla (at a dose of 20 or 40 mg/kg body weight/d) or EtOAc extract of amla (at a dose of 10 or 20 mg/kg body weight/d) for 20 d to rats fed 1% cholesterol diet significantly reduced total, free and LDL-cholesterol levels in a dose-dependent manner, and EtOAc extract of amla exhibited more potent serum cholesterol-lowering effect than SunAmla in the same amount. Furthermore, the oxidized LDL level in serum was markedly elevated in cholesterol-fed control rats as compared with normal rats, while it was significantly decreased by the administration of SunAmla or EtOAc extract of amla. Moreover, the serum TBA-reactive substance level was also significantly decreased after oral administration of SunAmla or EtOAc extract of amla. These results suggest that amla may be effective for hypercholesterolemia and prevention of atherosclerosis.

Animals↗

PubMed2004

Abeta(25-35)-induced memory impairment, axonal atrophy, and synaptic loss are ameliorated by M1, A metabolite of protopanaxadiol-type saponins.

We previously screened neurite outgrowth activities of several Ginseng drugs in human neuroblastoma, and demonstrated that protopanaxadiol (ppd)-type saponins were active constituents. Since ppd-type saponins are known to be completely metabolized to 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol (M1) by intestinal bacteria when taken orally, M1 and ginsenoside Rb1, as a representative of ppd-type saponins, were examined for cognitive disorder. In a mouse model of Alzheimer's disease (AD) by Abeta(25-35) i.c.v. injection, impaired spatial memory was recovered by p.o. administration of ginsenoside Rb1 or M1. Although the expression levels of phosphorylated NF-H and synaptophysin were reduced in the cerebral cortex and the hippocampus of Abeta(25-35)-injected mice, their levels in ginsenoside Rb1- and M1-treated mice were almost completely recovered up to control levels. Potencies of the effects were not different between ginsenoside Rb1 and M1 when given orally, suggesting that most of the ginsenoside Rb1 may be metabolized to M1, and M1 is an active principal of ppd-type saponins for the memory improvement. In cultured rat cortical neurons, M1 showed extension activity of axons, but not dendrites. The axon-specific outgrowth was seen even when neuritic atrophy had already progressed in response to administration of Abeta(25-35) as well as in the normal condition. These results suggest that M1 has axonal extension activity in degenerated neurons, and improve memory disorder and synaptic loss induced by Abeta(25-35). M1 was shown to be effective in vitro and in vivo, indicating that Ginseng drugs containing ppd-type saponins may reactivate neuronal function in AD by p.o. administration.

Amyloid beta-Peptides↗

PubMed2003

Repair of amyloid beta(25-35)-induced memory impairment and synaptic loss by a Kampo formula, Zokumei-to.

Although Zokumei-to (ZMT), a Kampo formula, has been used for postapopletic sequelae such as paralysis and logopathy, only few studies of this drug have been carried out. We hypothesized that ZMT may affect neuronal plasticity and investigated whether or not this drug is capable of improving learning impairment and synaptic loss observed in patients with Alzheimer's disease (AD). Amyloid beta(25-35) [Abeta(25-35)] (4.7 nmol) was intracerebroventricularly injected into ddY mice (male, 6 weeks old). Fourteen days after the injection, mice were given ZMT extract (500 mg/kg/day) per os for 15 days. In a memory acquisition test, the Abeta(25-35)-injected mice required more time to master this task than did mice in the saline- or reverse peptide Abeta(35-25)-treated groups. ZMT-treated mice shortened escape latencies during trial days 3-5, but not significantly. Three days after the last drug treatment, a retention test was performed. Following ZMT, the number of crossings over a platform was significantly decreased in Abeta(25-35)-injected mice compared with those in the control groups. However, ZMT-treated mice showed complete recovery of this number. Although Abeta(25-35) injection decreased synaptophysin expression in the cerebral cortex and the hippocampus, ZMT treatment significantly increased the level of expression of synaptophysin up to the control level. Donepezil hydrochloride (DNP, 0.5 mg/kg/day, p.o.) clinically used for AD had no effect on memory retention and synaptophysin levels. Abeta(25-35)-induced neuronal loss was not observed in any region of the brain. The present results suggest that memory impairment and synaptic loss in AD patients may be improved by treatment with ZMT, even after such impairment has already progressed.

Alzheimer Disease↗

PubMed2003

Comprehensive identifying method for localized mRNAs in single neuronal axons.

Evidence indicating the presence of axonal mRNA in mammalian neurons has been limited to cytoskeletal components such as beta-actin, tau, and beta-tublin, and is still a subject of controversial debate. A new strategy is needed to prove that axonal transport of mRNAs is a general phenomenon, and to determine the purpose of this transport. I have therefore established a method to comprehensively identify axonal mRNAs. Single axonal terminals of cultured cerebral cortical neurons were aspirated, and total RNA was prepared and served for RT-PCR using a tagged random primer. Nine kinds of mRNA (Axomer-1 to -9) were shown to be expressed in an axonal domain, none with any homology with any functionally known sequences. These results suggest that quite a few mRNAs transported in axons may exist in the central nervous system of mammals, or at least of rats. This method appears to be useful to identify mRNAs in axons inclusively, sequence-independently, and even at low expression levels.

Animals↗

PubMed2003

Effects of curcuma drugs on vasomotion in isolated rat aorta.

The effectiveness of Curcuma drugs against "Oketsu" and the differences in their efficacy were evaluated by examining their vasomotional effects as one index. Since nitric oxide (NO) is the relaxation factor of vascular smooth muscle and also an inhibitor of platelet aggregation in blood vessels, substances showing NO-dependent relaxation are thought to be effective in improving Oketsu. In this study, five Curcuma drugs derived from Curcuma longa, C. kwangsiensis, C. phaeocaulis, C. wenyujin, and C. zedoaria were used. Methanol extracts exhibited intense effects on relaxation in rings precontracted by prostaglandin F(2alpha) (PGF(2alpha)) despite pretreatment with and without N(G)-nitro-l-arginine methyl ester (L-NAME) as an inhibitor of NO synthesis. The maximal activities were approximately 80% at 10(-3) g/ml. From these methanol extracts, curcumin and eight sesquiterpenes were isolated. Since all these compounds showed NO-independent relaxation effects with almost the same intensities, the relaxation effects of Curcuma drugs can be estimated by the total amounts of curcumin and sesquiterpenes. Polysaccharides, the main constituents of methanol-insoluble compounds of water extracts, in contrast, showed contraction effects; only polysaccharides in C. zedoaria showed NO-dependent relaxation as well as contraction. All water extracts showed relaxation effects as sum of the methanol-soluble compounds-induced relaxation and polysaccharides-induced contraction. Therefore, all Curcuma drugs tested in the present study can be effective for vasodilation. Moreover, the drug derived from C. zedoaria has potential to cure Oketsu with its various acting points.

Animals↗

PubMed2002

Axon- or dendrite-predominant outgrowth induced by constituents from Ashwagandha.

We previously reported that the methanol extract of Ashwagandha (roots of Dunal) induced dendrite extension in a human neuroblastoma cell line. In this study, we found that six of the 18 compounds isolated from the methanol extract enhanced neurite outgrowth in human neuroblastoma SH-SY5Y cells. Double immunostaining was performed in rat cortical neurons using antibodies to phosphorylated NF-H as an axonal marker, and to MAP2 as a dendritic marker. In withanolide A-treated cells, the length of NF-H-positive processes was significantly increased compared with vehicle-treated cells, whereas, the length of MAP2-positive processes was increased by withanosides IV and VI. These results suggest that axons are predominantly extended by withanolide A, and dendrites by withanosides IV and VI.

Animals↗

PubMed2002

Dammarane-type triterpene saponins from Panax japonicus.

Six new dammarane-type saponins (1-6), together with 11 known saponins (7-17), were isolated from Ye-Sanchi, the underground part of Panax japonicus collected in the South of Yunnan Province, China. Their structures were elucidated by chemical and spectroscopic means.

China↗

PubMed2002

Dammarane-type Saponins from Panax japonicus and their neurite outgrowth activity in SK-N-SH cells.

Four new dammarane-type saponins (1-4), named yesanchinosides G-J, together with nine ginsenosides (5-13) were isolated from Ye-Sanchi, the underground part of Panax japonicus collected in the south of Yunnan Province, China. Their structures were elucidated on the basis of spectroscopic and chemical methods. Ginsenosides Rb(1) and Rb(3) and notoginsenosides R(4) (6) and Fa (7) showed significant neurite outgrowth enhancing activities in human neuroblastoma SK-N-SH cells.

Drugs, Chinese Herbal↗

PubMed2002

Withanolide derivatives from the roots of Withania somnifera and their neurite outgrowth activities.

Five new withanolide derivatives (1, 9-12) were isolated from the roots of Withania somnifera together with fourteen known compounds (2-8, 13-19). On the basis of spectroscopic and physiochemical evidence, compounds 1 and 9-12 were determined to be (20S,22R)-3 alpha,6 alpha-epoxy-4 beta,5 beta,27-trihydroxy-1-oxowitha-24-enolide (1), 27-O-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranoside (withanoside VIII, 9), 27-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranosyl (1-->6)-beta-D-glucopyranoside (withanoside IX, 10), 27-O-beta-D-glucopyranosylpubesenolide 3-O-beta-D-glucopyranoside (withanoside X, 11), and (20R,22R)-1 alpha,3 beta,20,27-tetrahydroxywitha-5,24-dienolide 3-O-beta-D-glucopyranoside (withanoside XI, 12). Of the isolated compounds, 1, withanolide A (2), (20S,22R)-4 beta,5 beta,6 alpha,27-tetrahydroxy-1-oxowitha-2,24-dienolide (6), withanoside IV (14), withanoside VI (15) and coagulin Q (16) showed significant neurite outgrowth activity at a concentration of 1 microM on a human neuroblastoma SH-SY5Y cell line.

Disaccharides↗

PubMed2002

Axonal and dendritic extension by protopanaxadiol-type saponins from ginseng drugs in SK-N-SH cells.

Extension of axons and dendrites in neurons may compensate for and repair damaged neuronal networks in the dementia brain. To find out drugs capable of regenerating the neuronal network, we focused on several herbal drugs belonging to the genus Panax, kinds of Ginseng, and investigated neurite outgrowth activity of their extracts and compounds. We found that the methanol extracts of Ginseng (root of P. ginseng), Notoginseng (root of P. notoginseng) and Ye-Sanchi in Chinese (rhizome of a relative to P. vietnamensis) increased neurite outgrowth in SK-N-SH cells. The protopanaxadiol-type saponins, ginsenosides Rb(1) and Rb(3), and notoginsenosides R(4) and Fa isolated from Ye-Sanchi extract extended neurites, while protopanaxatriol-, ocotillol- and oleanane-type saponins had no effect on the neurite outgrowth. The percentage of cells with multipolar neurites and number of varicosities were intensely high in cells treated with the methanol extract of Ye-Sanchi as well as ginsenosides Rb(1) and Rb(3), and notoginsenosides R(4) and Fa. Both phosphorylated NF-H-expressing neurites and MAP2-expressing ones were extended by treatment with those saponins and the extract. Especially, longer neurites were mainly positive for phosphorylated NF-H. These results suggest that protopanaxadiol-type saponins enhance axonal and dendritic formation activity.

Axons↗