Biomedical subjects

M Naoi

Publications and source records attributed to M Naoi.

At least 55 records · Page 3Linked to original sources

PubMed1998

Structural significance of azaheterocyclic amines related to Parkinson's disease for dopamine transporter.

We have evaluated the neuronal uptake of 12 neutral and quaternary azaheterocyclic amines that are possible candidates for idiopathic Parkinson's disease via dopamine transporter of striatal synaptosomes. The double-reciprocal plots for dopamine transporter obtained from Wistar rat and C57BL/6 mouse synaptosomes with N-methyl-4-phenylpyridinium cation (MPP+) as a substrate were identical to each other. Neutral beta-carbolines and tetrahydroisoquinolines were unfavorable substrates for dopamine transporter. The quarternization of these compounds strikingly increased the affinity for dopamine transporter with 2-10 times greater Km and 10 times smaller Vmax values than MPP+. Although catechol tetrahydroisoquinolines were weak substrates, their quarternization reduced their original properties as substrates for dopamine transporter. These results provide both topographic and electrogenic information of azaheterocyclic amines for the dopamine transporter-mediated influx. The intramolecular distance between the N-atom and the centroid of the benzene ring could be an important factor for the recognition of binding site of dopamine transporter, and an adequate net charge similar to dopamine would be further required for translocation into the cells.

1-Methyl-4-phenylpyridinium↗

PubMed1998

Novel assay for glutathione reductase activity by high-performance liquid chromatography with electrochemical detection.

A new method was devised for the direct measurement of glutathione reductase activity in crude tissue samples using high-performance liquid chromatography and electrochemical detection with a mercury/gold electrode. This assay depends on the high sensitivity of the electrode to detect SH groups produced from a substrate, oxidized glutathione, the interference of which can be excluded by setting the oxidation voltage as low as 100 mV. The sensitivity was high enough to detect the activity in crude samples containing less than 1 microg of protein. This method proved to be sensitive and simple for the measurement of this biologically important reductant activity without the need for a further purification procedure.

Animals↗

PubMed1998

(R)salsolinol N-methyltransferase activity increases in parkinsonian lymphocytes.

Recently, an endogenous catechol isoquinoline, 1(R),2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [N-methyl(R)salsolinol], was proved to be a neurotoxin specific for dopamine neurons by in vivo and in vitro experiments. This N-methyl(R)salsolinol was found to increase significantly in the cerebrospinal fluid of untreated parkinsonian patients, suggesting its possible involvement in the pathogenesis of Parkinson's disease. To clarify the mechanism of the increase, the activity of enzymes related to the metabolism of the neurotoxin was examined in lymphocytes prepared from parkinsonian patients and controls. In patients with Parkinson's disease, the activity of a neutral N-methyltransferase, measured by using (R)salsolinol as a substrate, was found to increase significantly (100.2 +/- 81.8 pmol/min/mg of protein) in comparison with that in controls (18.9 +/- 15.0 pmol/min/mg of protein). The distribution of the activity was bimodal in the parkinsonian patients, whereas it was singular in controls. The activity of other related enzymes, an alkaline N-methyltransferase and N-methyl(R)salsolinol oxidase, in parkinsonian lymphocytes was the same as in controls. Increase of the neutral N-methyltransferase may be an endogenous factor in the pathogenesis of Parkinson's disease.

Aged↗

PubMed1998

Oxidation of N-methyl(R)salsolinol: involvement to neurotoxicity and neuroprotection by endogenous catechol isoquinolines.

1(R), 2(N)-Dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, N-methyl(R)salsolinol, is a potent dopaminergic neurotoxin to induce parkinsonism in rats. The cytotoxicity of N-methyl(R)salsolinol proved to be ascribed to its oxidation into cytotoxic 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion with generation of hydroxyl radical. The isoquinolinium ion caused massive necrosis in the striatum, whereas N-methyl(R)salsolinol depleted selectively dopaminergic neurons in the substantia nigra without necrotic tissue reaction. N-Methyl(R)salsolinol induced DNA damage to human neuroblastoma SH-SY5Y cells, which could be prevented by anti-oxidants and cycloheximide. These results suggest that oxidative stress through oxidation of N-methyl(R)salsolinol induces apoptotic cell death. On the other hand, (R)salsolinol proved to scavenge hydroxyl radical produced by oxidation of dopamine. The neurotoxicity and neuroprotection of catechol isoquinolines may be ascribed to their oxidation and scavenging of radicals.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1998

Generation of reactive oxygen species accounts for cytotoxicity of an endogenous dopaminergic neurotoxin, (R)-N-methylsalsolinol, to differentiated dopaminergic SH-SY5Y cells.

The mechanism of the cytotoxicity of endogenous dopamine-derived (R)-1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-N-methylsalsolinol] to differentiated human dopaminergic neuroblastoma SH-SY5Y cells was studied using a reduction-oxidation indicator, Alamar Blue. N-Methylsalsolinol and its oxidation product, 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion, were found to inhibit oxidative phosphorylation, as shown by the Redox capacity. Antioxidants, such as reduced glutathione, catalase, Tris and n-propyl gallate, reduced the cytotoxicity of N-methylsalsolinol, suggesting that hydroxyl radical was the major reactive oxygen species for the cytotoxicity. Deprenyl also protected the cells from the decrease of the Redox capavity by N-methylsalsolinol. However, antioxidants did not protect the cells from the cytotoxicity of the catechol isoquinolinium ion. The results suggest that oxidative stress induced by hydroxyl radical may be involved in the cell death of dopaminergic neurons by N-methylsalsolinol.

Cell Differentiation↗

PubMed1998

Effects of various tetrahydroisoquinoline derivatives on mitochondrial respiration and the electron transfer complexes.

We report effect of various tetrahydroisoquinoline derivatives on mitochondrial respiration and the electron transfer complexes. Generally these compounds were potent inhibitors of NADH-linked mitochondrial state 3 respiration and complex I. Presence of a phenyl group at the C1 position or oxidation of N-methylated isoquinones into N-methylisoquinolinium ion augmented the potency to inhibit mitochondrial respiration and complex I. Many of these compounds have been identified in human brains. In view of the mitochondrial and oxidative stress hypothesis, our results suggest involvement of these neurotoxins as potential causes of mitochondrial failure in Parkinson's disease.

Animals↗

PubMed1998

Oxidation of 1-amino-4-phenyl-1,2,3,6-tetrahydropyridine, a 1-amino analog of MPTP, by type A and B monoamine oxidase.

A 1-amino analog of MPTP, 1(N)-amino-4-phenyl-1,2,3,6-tetrahydropyridine, was synthesized and the oxidation was examined using human synaptosomal mitochondria as sources of type A and B monoamine oxidase. An oxidation product, 1-amino-4-phenylpyridinium ion, was quantified by high-performance liquid chromatography-fluorometric detection. The amino analog was a substrate of both type A and B monoamine oxidase and the oxidation depended linearly on the enzyme amount and the reaction time with an optimal pH around 7.5. After the systemic injection of the amino analog in C57/black mice for one week, 1-amino-4-phenylpyridinium ion was detected in the brain. 1(N)-Amino-4-phenyl-1,2,3,6-tetrahydropyridine was proved to be cytotoxic to pheochromocytoma PC12 cells, and it may be a new neurotoxin bioactivated through the oxidation by type A and B monoamine oxidase.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1998

Effects of endurance physical training on hydroxyl radical generation in rat tissues.

Physical exercise is known to increase oxygen consumption to compensate for enhanced ATP consumption and thus to induce oxidative stress in tissues. Our previous data indicate that training significantly increased the hydroxyl radical level in rat tissues after physical exercise, but reduced the basal level in aged rats. This result suggests the paradoxical effect of physical training, which may be to increase or scavenge reactive oxygen species (ROS) generated by physical exercise. In this paper, the effects of training on the levels of hydroxyl radicals and the anti-oxidative glutathione system, were examined in rats. After 3 weeks' training, rats were sacrificed at rest or after treadmill running, and the levels of hydroxyl radicals trapped with salicylic acid, reduced (GSH); and oxidized glutathione (GSSG) in tissues were quantified by high-performance liquid chromatography-electrochemical detection (HPLC-ECD). Endurance training reduced the basal level of hydroxyl radicals significantly in plasma and soleus muscle. In liver and brain a similar tendency was observed, but the difference was not statistically significant. In liver the basal level of GSH increased significantly after training. Slower training with longer duration reduced the basal levels of hydroxyl radical in plasma more markedly than more intense training. These results suggest that endurance exercise can increase the anti-oxidative capacity in rats.

Animals↗

PubMed1998

Cytotoxicity of 1-amino-4-phenyl-1,2,3,6-tetrahydropyridine and 1-amino-4-phenylpyridinium ion, 1-amino analogues of MPTP and MPP+, to clonal pheochromocytoma PC12 cells.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces parkinsonism in humans after its oxidation into 1-methyl-4-phenylpyridinium ion (MPP+) by type B monoamine oxidase. The 1-amino analogues of MPTP and MPP+, 1-amino-4-phenyl-1,2,3, 6-tetrahydropyridine (APTP) and 1-amino-4-phenylpyridinium ion (APP+), were synthesized, and their cytotoxicity to clonal pheochromocytoma PC12 cells was examined using a tetrazolium formazan assay. After incubation for 48 and 72 h, both APP+ and APTP were found to be cytotoxic to PC12 cells, whereas with the N-methyl analogues, only MPP+, but not MPTP, was cytotoxic. The cytotoxicity of APTP increased with incubation time and equaled that of MPP+ after 72 h. It was found that APTP was oxidized to APP+ by type A monoamine oxidase in PC12 cells, suggesting that APP+ itself may damage the cells. In addition to APTP and APP+, N-amino analogues of N-methylisoquinolines and related derivatives were also synthesized and examined for their cytotoxicity to PC12 cells.

1-Methyl-4-phenylpyridinium↗

PubMed1998

(-)-Deprenyl protects human dopaminergic neuroblastoma SH-SY5Y cells from apoptosis induced by peroxynitrite and nitric oxide.

In Parkinson's disease the cell death of dopamine neurons has been proposed to be mediated by an apoptotic death process, in which nitric oxide may be involved. This article reports the induction of apoptosis by nitric oxide and peroxynitrite in human dopaminergic neuroblastoma SH-SY5Y cells and the antiapoptotic activity of (-)-deprenyl. After the cells were treated with a nitric oxide donor, NOR-4, or a peroxynitrite donor, SIN-1, DNA damage was quantitatively studied using a single-cell gel electrophoresis (comet) assay. NOR-4 and SIN-1 induced DNA damage dose-dependently. Cycloheximide and alkaline treatment of the cells prevented the DNA damage, indicating that the damage is apoptotic and that it depends on the intracellular signal transduction. Superoxide dismutase and the antioxidants reduced glutathione and alpha-tocopherol protected the cells from the DNA damage. (-)-Deprenyl protected the cells from the DNA damage induced by nitric oxide or peroxynitrite almost completely. The protection by (-)-deprenyl was significant even after it was washed from the cells, indicating that (-)-deprenyl may activate the intracellular system against apoptosis. These results suggest that (-)-deprenyl or related compounds may be neuroprotective to dopamine neurons through its antiapoptotic activity.

Antiparkinson Agents↗

PubMed1998

Seroprevalence of Bartonella henselae and Toxoplasma gondii infections among pet cats in Kanagawa and Saitama Prefectures.

Seroprevalence of Bartonella henselae and Toxoplasma gondii was investigated among 471 pet cats obtained from seven private animal hospitals in Kanagawa and Saitama Prefectures during the period from May 1994 to June 1995. 'Furthermore, 67 randomly selected from the 471 serum samples were examined for the feline immunodeficiency virus (FIV) antibody and feline leukemia virus (FeLV) antigen. The antibody to B. henselae was examined by an indirect immunofluorescent antibody test. T. gondii, FIV and FeLV infections in cats were detected with respective commercial kits. Of the cat serum samples tested, 43 (9.1%) were found to be seropositive for B. henselae and 41 (8.7%) for T. gondii. The B. henselae-positive rate (12.9%) of male cats was significantly higher than that (5.2%) of female cats. On the other hand, T. gondii-positive rate was 9.1% in male and 8.7% in female cats and there was no significant difference in the positivity between sexes. The positive rate in each hospital varied from 0 to 19.5% for B. henselae and 4.9 to 18.8% for T. gondii. The ages of B. henselae- and T. gondii-positive cats were distributed from < 1-year-old to 14-year-old and the seropositivity increased with age of cats. Of the 67 cat serum samples, 16 and 6 cases were positive for FIV and FeLV, respectively. There was no relationship between these viral and B. henselae infections in cats.

Animals↗

PubMed1997

Preparation of (R)-N-methylsalsolinol via reversed-phase high-performance liquid chromatography using beta-cyclodextrin as a mobile-phase additive.

A new preparation method was devised using beta-cyclodextrin as a mobile-phase additive in a reversed-phase high-performance liquid chromatography system. Preparative separation of the biologically active (R)-enantiomer was achieved from racemic N-methylsalsolinol. Beta-cyclodextrin was removed completely in good yield by acid extraction and solid-phase extraction. By a slight modification, this method will be applicable to the isolation of various types of biologically important enantiomers.

Chromatography, High Pressure Liquid↗

PubMed1997

A neutral N-methyltransferase activity in the striatum determines the level of an endogenous MPP+-like neurotoxin, 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion, in the substantia nigra of human brains.

An endogenous MPTP-like dopaminergic neurotoxin, N-methyl(R)salsolinol, increases in the parkinsonian cerebrospinal fluid and accumulates in the human nigro-striatum. An N-methyltransferase specific for (R)salsolinol was found in human brain with optimal pH at 7.0 and 8.5. The correlation of the enzyme activity with the level of N-methyl(R)salsolinol and its oxidation product, 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion was examined in the brain regions. Neutral N-methyltransferase activity in the striatum was found to correlate with the level of the endogenous MPP+-like isoquinolinium ion in the substantia nigra (P < 0.001). Considering that this neutral N-methyltransferase activity increases in parkinsonian lymphocytes, the enzyme may be an endogenous factor in the pathogenesis of Parkinson's disease.

Caudate Nucleus↗

PubMed1997

A neurotoxin N-methyl(R)salsolinol induces apoptotic cell death in differentiated human dopaminergic neuroblastoma SH-SY5Y cells.

In retinoic acid-differentiated SH-SY5Y cells an endogenous neurotoxin N-methyl(R)salsolinol induced apoptotic cell death. Using a single cell gel electrophoresis (comet) assay, DNA damage was quantitatively measured, and it was found to depend on the concentration of N-methyl(R)salsolinol and the incubation time up to 6 h. The differentiated cells were more sensitive to N-methyl(R)salsolinol than the undifferentiated cells. Radical scavengers protected the cells from DNA damage, indicating oxidative stress is involved in the apoptotic cell process. These results suggest that apoptosis induced by endogenous neurotoxins might be the mechanism of the cell death of dopamine neurons in Parkinson's disease.

Apoptosis↗

PubMed1997

Assay for the (R)- and (S)-enantiomers of salsolinols in biological samples and foods with ion-pair high-performance liquid chromatography using beta-cyclodextrin as a chiral mobile phase additive.

A chromatographic procedure was devised for the quantitative determination of the enantiomers of salsolinol and N-methylsalsolinol, which are biologically important alkaloids. The enantiomers of salsolinol and N-methylsalsolinol were completely separated using beta-cyclodextrin in a reversed-phase ion-pair system. The HPLC method was sensitive enough to detect the isoquinolines at a concentration less than 0.1 pmol per injection. The presence of (R)- and (S)-salsolinol was confirmed in fermented foods and beverages, while N-methylsalsolinol was not detected. On the other hand, the (R)-enantiomers of both salsolinol and N-methylsalsolinol were found to predominate in the human brain.

Beverages↗

PubMed1997

A dopaminergic neurotoxin, 1(R), 2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, N-methyl(R)salsolinol, and its oxidation product, 1,2(N)-dimethyl-6,7-dihydroxyisoquinolinium ion, accumulate in the nigro-striatal system of the human brain.

N-Methyl(R)salsolinol was found to be an endogenous dopaminergic neurotoxin inducing parkinsonism in rodents and to increase in the cerebrospinal fluid of parkinsonian patients. The amounts of N-methyl(R)salsolinol and related compounds in the human brain regions were quantitatively analyzed. Only the (R)-enantiomer of salsolinol derivatives were detected, which suggests their enzymatic synthesis in situ. In the nigro-striatal system, the concentration of N-methyl(+)salsolinol was higher than in the frontal cortex, and its oxidized catechol isoquinolinium ion was detected only in the substantia nigra significantly. The accumulation of these neurotoxins in the nigro-striatal region might account for selective cell death of dopamine neurons in the substantia nigra of Parkinson's disease.

Chromatography, High Pressure Liquid↗

PubMed1997

N-methyl-(R)salsolinol as a dopaminergic neurotoxin: from an animal model to an early marker of Parkinson's disease.

A dopamine-derived 1(R), 2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydrosioquinoline [N-methyl-(R)salsolinol] was found to occur enantioselectively in human brain. This isoquinoline induced parkinsonism in rat after injection in the striatum, and the behavioral, biochemical and pathological changes were very similar to those in Parkinson's disease. N-Methyl-(R)salsolinol depleted dopamine neurons in the rat substantia nigra without necrotic tissue reaction, which may be due to the apoptotic death process, as proved by its induction of DNA damage in dopaminergic neuroblastoma SH-SY5Y cells. N-Methyl-(R)salsolinol was found to increase significantly in the cerebrospinal fluid of parkinsonian patients. All these results suggest that N-methyl-(R)salsolinol may be an endogenous neurotoxin to cause Parkinson's disease and the enzymes involved in its biosynthesis and catabolism may be endogenous factors in the pathogenesis of this disease.

Animals↗

PubMed1997

Cytotoxicity of endogenous isoquinolines to human dopaminergic neuroblastoma SH-SY5Y cells.

Endogenous isoquinolines with and without catechol structure have been proposed to be neurotoxins specific for dopamine neurons. In this paper they were examined for the cytotoxicity of human dopaminergic neuroblastoma SH-SY5Y cells. The cytotoxicity was quantitatively determined using Alamar Blue assay, by which the reduction-oxidation potency in the living cells can be measured spectrometrically. 1,2-Dimethyl-6,7-dihydroxyisoquinolinium ion [1,2-DMDHIQ+], an oxidation product of a parkinsonism-inducing isoquinoline, 1(R),2(N)-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahroisoquinoline [N-methyl-(R)salsolinol, NM(R)Sal] was found to be the most potent toxin among isoquinolines examined. In general, catechol isoquinolines were more toxic than isoquinolines without catechol structure. With and without catechol structure, the oxidized isoquinolinium ion having methyl groups at C-1 and N-2 positions proved to be more cytotoxic than the simple isoquinolines. The involvement of 1,2-DMDHIQ+ to the neurotoxicity of NM(R)Sal was suggested and discussed.

Cell Survival↗