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Biomedical subjects

S Nagayama

Publications and source records attributed to S Nagayama.

At least 19 recordsLinked to original sources
PubMed2001

Carbenoxolone, a new inducer of heat shock protein 70.

Heat shock protein 70 (Hsp70) is capable of protecting cells, tissues, organs, and animals from a subsequent, normally lethal heating, as well as from numerous disease states. Therefore, it would be of great therapeutic benefit to discover compounds that are clinically safe yet able to induce Hsp70 in patients. Carbenoxolone, an antiulcer drug, protects gastric mucosal cells against irritants in vivo and in vitro. We assessed here whether carbenoxolone induces Hsp70 expression in human cell lines. We found that carbenoxolone increased the expression of Hsp70 protein and mRNA, and Hsp70 promoter activity.

Anti-Ulcer Agents↗
PubMed2001

Reversal of LRP-associated drug resistance in colon carcinoma SW-620 cells.

Resistance to multiple drugs is mediated by lung resistance-related protein (LRP) as well as P-glycoprotein (P-gp) and multidrug resistance protein (MRP). The levels of expression of LRP mRNA and LRP in a human colon carcinoma cell line, SW-620, were increased by the differentiation-inducing agent, sodium butyrate (NaB). Treatment of SW-620 cells with NaB for 2 weeks conferred resistance to adriamycin (ADM) and VP-16. The resistance was almost completely reversed by PAK-104P, a pyridine analog, but not by cepharanthine. ADM accumulated mainly in the nuclei of SW-620 cells not treated with NaB and in the cytoplasm of SW-620 cells treated with NaB. When the NaB-treated SW-620 cells were incubated with ADM in the presence of PAK-104P, the accumulation of ADM in nuclei was substantially increased. Isolated nuclei from untreated cells accumulated more ADM than nuclei from NaB-treated cells. Efflux of ADM from the nuclei isolated from NaB-treated cells was enhanced. PAK-104P and an antibody against LRP increased the accumulation of ADM in the isolated nuclei from NaB-treated cells, and inhibited the enhanced efflux of ADM from the nuclei. These findings suggest that at least in part, PAK-104P reverses LRP-mediated drug resistance by inhibiting the efflux of ADM from nuclei. PAK-104P may be useful for reversing MDR in tumors that overexpress LRP.

Alkaloids↗
PubMed2001

Involvement of microsomal cytochrome P450 and cytosolic thymidine phosphorylase in 5-fluorouracil formation from tegafur in human liver.

Recently, we have reported that tegafur, an anticancer agent, is biotransformed into active drug 5-fluorouracil (5-FU) by cytochromes P450 1A2, 2A6, and 2C8 in human liver microsomes (T. Komatsu et al., Drug Metab. Dispos, 28: 1457-1463, 2000). Because the conversion of tegafur into 5-FU has also been reported to be catalyzed by cytosolic thymidine phosphorylase (dThdPase), the involvement of human liver microsomes and cytosol and individual differences in 5-FU formation from tegafur were investigated. In 14 human samples, the mean rates of 5-FU formation in liver microsomes were 5-fold and 2-fold higher than those in liver cytosol at substrate concentrations of 100 microM and 1 mM tegafur, respectively. In the presence of 5-chloro-2,4-dihydroxypyridine, a dihydropyrimidine dehydrogenase inhibitor, the rates of 5-FU formation by the combination of liver microsomes and cytosol showed 5- and 3-fold interindividual differences at 100 microM and 1 mM tegafur, respectively. Kinetic analysis of human liver cytosolic 5-FU formation indicated an apparent higher Km value (16 +/- 4 mM) than that of liver microsomes (1.8 +/- 0.3 mM) with similar Vmax values. Human liver cytosolic 5-FU formation was confirmed to be catalyzed by dThdPase with correlation and chemical inhibition studies. These results suggested that 5-FU formation from tegafur in human liver was mainly catalyzed by microsomal P450 at low concentrations of tegafur, but the contribution of cytosolic 5-FU formation by dThdPase would be important at high concentrations.

Antimetabolites, Antineoplastic↗
PubMed2001

Effects of 5-fluorouracil on the drug-metabolizing enzymes of the small intestine and the consequent drug interaction with nifedipine in rats.

5-Fluorouracil (5-FU) is a widely used antineoplastic agent. 5-FU therapy often causes gastrointestinal toxicity, which is suppressed by concomitant administration of potassium oxonate (Oxo). Here, we investigated the effect of 5-FU on the small-intestinal drug-metabolizing enzymes, which play important roles in the first-pass metabolism of drugs, in rats, by enzyme measurements and immunoblot analyses. During repeated administration of a combination of 1-(2-tetrahydrofuryl)-5-fluorouracil, an oral 5-FU-derivative drug, and 5-chloro-2,4-dihydroxypyridine (FCD), an inhibitor of 5-FU degradation, the activities of 7-ethoxyresorufin-O-deethylase, testosterone 6beta-hydroxylase, 4-methylumbelliferone UDP-glucuronyltransferase, and 1-chloro-2,4-dinitrobenzene glutathione S-transferase decreased significantly on day 4, and the activity of NADPH-cytochrome P450 (CYP) reductase decreased significantly on day 7. These effects were found to be attributable to a reduction in the enzyme protein contents in the small-intestinal mucosa. The enzymatic alterations significantly increased the plasma concentrations of orally administered nifedipine, which was prevented by concomitant administration of Oxo with FCD. However, consecutive administration of FCD for 4 days did not cause any alterations in the activity of the hepatic CYP isozyme-supported testosterone hydroxylase. These results suggest that continuous exposure to 5-FU leads to a decrease in the activities of drug-metabolizing enzymes in the intestinal mucosa by decreasing their enzyme protein contents, and increases the plasma concentrations of orally administered nifedipine, and that the sensitivity of these enzymes to the drug is greater than that of the enzymes of the liver. These effects were prevented by concomitant administration of Oxo.

Administration, Oral↗
PubMed2000

A novel classification of Lewis acids on the basis of activity and selectivity.

Group 3-15 metal chlorides (Lewis acids) were classified on the basis of activity and aldehyde- and aldimine-selectivity in an addition reaction of a silyl enol ether. Based on the experimental results, metal chlorides (Lewis acids) were classified as follows: A, active; B, weak; C, inactive for the activation of the aldehyde and/or aldimines. Groups A and B were further divided into A-1 or B-1 (aldehyde-selective), A-2 or B-2 (aldimine-selective), and A-3 or B-3 (neutral). The final classification is as follows: A-1, BCl3, AlCl3, TiCl4, GaCl3, ZrCl4, SnCl4, SbCl5, SbCl3, HfCl4, ReCl5; A-2, ScCl3, FeCl3, InCl3, BiCl3; A-3, NbCl5, MoCl3. MoCl5, SnCl2, TaCl5, WCl5. WCl6, ReCl3, TlCl3; B-1, none; B-2, SiCl4, FeCl2, CoCl2, CuCl, CuCl2, GeCl4, YCl3, OsCl3, PtCl2; B-3, ZnCl2, RuCl3; C, VCl3, CrCl3, MnCl2, NiCl2, RhCl3, PdCl2, AgCl, CdCl2, IrCl3, AuCl, HgCl2, HgCl, PbCl2. This classification has revealed several new fundamental aspects of elements (metal chlorides) as Lewis acids.

Acids↗
PubMed2000

Spinocerebellar ataxia type 6 mutation alters P-type calcium channel function.

Abnormal CAG repeat expansion in the alpha1A voltage-dependent calcium channel gene is associated with spinocerebellar ataxia type 6, an autosomal dominant cerebellar ataxia with a predominant loss of the Purkinje cell. A reverse transcriptase-polymerase chain reaction analysis of mRNA from mouse Purkinje cells revealed a predominant expression of the alpha1A channel lacking an asparagine-proline (NP) stretch in the domain IV (alpha1A(-NP)). Human alpha1A channels carrying various polyglutamine length with or without NP were expressed in HEK293 cells, and channel properties were compared using a whole-cell voltage clamp technique. alpha1A(-NP), corresponding to P-type channel, with 24 and 28 polyglutamines found in patients showed the voltage dependence of inactivation shifting negatively by 6 and 11 mV, respectively, from the 13 polyglutamine control. Contrarily, the alpha1A channel with NP (alpha1A(+NP)), corresponding to Q-type channel, with 28 polyglutamines exhibited a positive shift of 5 mV. These results suggest that altered function of alpha1A(-NP) may contribute to degeneration of Purkinje cells, which express predominantly alpha1A(-NP), due to the reduced Ca(2+) influx resulting from the negative shift of voltage-dependent inactivation. On the other hand, other types of neurons, expressing both alpha1A(-NP) and alpha1A(+NP), may survive because the positive shift of voltage-dependent inactivation of alpha1A(+NP) compensates Ca(2+) influx.

Animals↗
PubMed2000

Reduction of 5-fluorouracil (5-FU) gastrointestinal (GI) toxicity resulting from the protection of thymidylate synthase (TS) in GI tissue by repeated simultaneous administration of potassium oxonate (Oxo) in rats.

PURPOSE: An important cytotoxic effect of 5-fluorouracil (5-FU) is the inactivation of thymidylate synthase (TS) (EC 2.1.1.45) activity by the formation of a ternary complex consisting of covalently bound 5-fluorodeoxyuridine 5'-monophosphate (FdUMP), TS and 5,10-methylenetetrahydrofolate (CH2FH4). The gastrointestinal (GI) toxicity of 5-FU is also caused by its phosphorylation in the GI tract. Potassium oxonate (O(XO)) competitively inhibits pyrimidine phosphoribosyltransferase (EC 2.4.2.10), which converts 5-FU to 5-fluorouridine 5'-monophosphate (FUMP) in vitro. In this study the benefits of combining Oxo and tegafur (FT), which is a masked compound of 5-FU, in reducing the GI toxicity of 5-FU and in protecting the activity of TS in the normal GI tissues were evaluated. METHODS: We administered orally a preparation of 1 M FT and 0.4 M 5-chloro-2,4-dihydroxypyridine (CDHP) with or without 1 M O(XO) (called S-1 and FT + CDHP, respectively) or vehicle only (control) to rats for ten consecutive days and compared the toxicity, the histopathological findings and the free TS activity in the GI tissues of the treated rats. RESULTS: During the experimental periods, the signs of toxicity, such as a decrease in body weight, diarrhea and death, were only observed in the rats treated with FT + CDHP. The histopathological findings in the ileum and colon samples from rats treated consecutively with S-1 on day 1, day 4, day 7 and day 10 were less frequent and more mild than in the samples from rats treated with FT + CDHP. Furthermore, the free TS activities in the ileum samples of rats given S-1 and FT + CDHP were significantly decreased compared with the activity in samples from the control rats throughout the experimental periods. The free TS activities in GI tissues of rats treated with S-1 were higher than the TS activities in tissues from rats treated with FT + CDHP daily from day 4 to day 10, although activities in S-1-treated rat were decreased to almost same low levels as in FT + CDHP-treated rats on day 1. CONCLUSIONS: Our results suggest that repeated simultaneous administration of Oxo and FT can effectively protect the activity of TS by decreasing FdUMP via FUMP from 5-FU in GI tissue, and may lead to a reduction in GI toxicity.

Animals↗
PubMed2000

Cramping pain and prolonged elevation of serum creatine kinase levels in a patient with Guillain-Barré syndrome following Campylobacter jejuni enteritis.

We describe a patient with Guillain-Barré syndrome (GBS) following Campylobacter jejuni enteritis, accompanied with severe cramping pain and a marked increase in serum creatine kinase (CK) levels. Both conditions became evident three weeks after the onset of GBS and continued for longer than one month. In this patient, it is possible that rapid extensive denervation due to severe axonal degeneration of motor nerve terminals might have caused hyperexcitability in regional muscles, leading to recurrent muscle cramps and persistent release of muscular CK.

Adult↗
PubMed2000

A Novel Polymer-Supported Scandium Catalyst Which Shows High Activity in Water.

Lewis acids in water on a polymer support (1) have been used, for the first time, as a catalyst. The organic solvent-free catalytic activity, first tested with allylation reactions with tetraallyltin, extended to other Lewis acid catalyzed reactions with a range of carbonyl compounds to afford the corresponding alcohol; reactions of aromatic, aliphatic, heterocyclic aldehydes and even ketones proceeded smoothly. Catalyst recovery was quantitative after simple filtration.

Journal Article↗
PubMed2000

[Comparison of pharmacokinetics of 5-FU and alpha-fluoro-beta-alanine, a metabolite of 5-FU, in plasma after administration of UFT, tegafur, 5-FU or doxifluridine to rats].

Toxic effects (neurotoxicity and cardiotoxicity) of 5-FU and its derivatives have been reported by many investigators. These toxicities are considered to be caused by the inhibition of the TCA cycle by alpha-fluoro-beta-alanine (FBAL), a metabolite of 5-FU, and later metabolites. In this study, we focused on FBAL as an index of the above toxicities. We compared the concentrations of 5-FU and FBAL in plasma after administration of UFT, tegafur (FT), 5-FU or doxifluridine (5'-DFUR) to rats (75 mumol/kg) in order to evaluate which compound has the better balance of efficacy and toxicity. UFT exhibited the lowest FBAL concentration in plasma followed by FT, 5'-DFUR and 5-FU. The ratio of FBAL to 5-FU in Cmax and AUC after dosing of UFT was the lowest among these four test compounds. These data indicate that the lowest ratio of FBAL to 5-FU resulted from the inhibitory effect of uracil, a component of UFT, on the metabolism of 5-FU. In conclusion, the present results suggest that UFT has a better balance of efficacy and toxicity than FT, 5-FU and 5'-DFUR.

Administration, Oral↗
PubMed2000

[Multiple exostoses].

Multiple exostoses is a hereditary disease characterized by multiple osteocartilagenous tumors, of which the histological structures are similar to those of normal epiphyses. Genetic linkage has identified three different loci for this disease: EXT1 on 8q, EXT2 on 11p, and EXT3 on 19p. The EXT1 and EXT2 genes were recently isolated and mutation analyses have been performed in a number of patients with different ethnic backgrounds. The data indicate that mutations of these genes occurred in broad regions of each gene, and the loss-of-function mutations were predominant, although there were some missense mutations that may create functionally defective protein. Tumor cells were shown to be homozygous for the mutant allele, which is consistent with the concept of these genes as tumor suppressor genes. Recent progress for the functional analyses has disclosed that these genes encode the protein with glycosyltransferase activity and regulate the diffusion of Hedgehog protein, which is the key molecule for the skeletal development. Further analyses of these genes may provide us with the knowledge for the development of epiphyses, and may open the new research field for the regeneration of epiphyses.

Epiphyses↗
PubMed2000

Tissue distribution and biotransformation of potassium oxonate after oral administration of a novel antitumor agent (drug combination of tegafur, 5-chloro-2,4-dihydroxypyridine, and potassium oxonate) to rats.

S-1, a new oral 5-fluorouracil (5-FU)-derivative antitumor agent, is composed of tegafur, 5-chloro-2,4-dihydropyridine, and potassium oxonate (Oxo). Oxo, which inhibits the phosphorylation of 5-FU, is added to reduce the gastrointestinal (GI) toxicity of the agent. In this study, we investigated the tissue distribution and the metabolic fate of Oxo in rats after oral administration of S-1. Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU, but little distributed to other tissues, including tumorous ones in which 5-FU was observed after oral administration of S-1. Plasma concentration-time profiles of Oxo and its metabolites after i.v. and oral administration of S-1 revealed that Oxo was mainly converted to cyanuric acid in the GI tract. Furthermore, the analysis of drug-related radioactivity in GI contents and in vitro studies suggested that Oxo was converted to cyanuric acid by two routes, the first being direct conversion by the gut flora in the cecum, and the second, conversion by xanthine oxidase or perhaps by aldehyde oxidase after degradation to 5-azauracil (5-AZU) by the gastric acid. These results indicate that, although a part of the administered Oxo was degraded in the GI tract, Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU and that little was distributed to other tissues, including tumors. We conclude that this is the reason why Oxo suppresses the GI toxicity of 5-FU without affecting its antitumor activity.

Administration, Oral↗
PubMed2000

Bioactivation of tegafur to 5-fluorouracil is catalyzed by cytochrome P-450 2A6 in human liver microsomes in vitro.

Tegafur is a prodrug of 5-fluorouracil (5-FU) consisting of a new class of oral chemotherapeutic agents, tegafur/uracil and S-1, which are classified as dihydropyrimidine dehydrogenase inhibitory fluoropyrimidines. It is bioactivated to 5-FU via 5'-hydroxylation mediated by cytochrome P-450 (CYP). However, which isoform(s) of CYP is responsible for the bioactivation process of tegafur remains unclear. The purpose of the present study was to identify the human CYP isoform(s) involved in the metabolic activation of tegafur using human liver microsomes and cDNA-expressed human CYPs. The formation of 5-FU from tegafur in human liver microsomes showed biphase kinetics with Km and Vmax values for the high-affinity component of 0.43 +/- 0.05 mM and 4.02 +/- 1.70 nmol/mg/min (mean +/- SD, n = 4), respectively. In the correlation study using a panel of 10 human liver microsomes, the formation of 5-FU from tegafur showed a significant correlation (r = 0.98; P < 0.001) with coumarin 7-hydroxylation, a marker activity of CYP2A6. In addition, a specific substrate of CYP2A6 and anti-CYP2A6 antibody inhibited the formation of 5-FU by 90% in human liver microsomes. Moreover, cDNA-expressed CYP2A6 showed the highest activity for the formation of 5-FU among 10 cDNA-expressed CYPs, with a Km value similar to that found for the high-affinity component in human liver microsomes. These findings clearly suggest that CYP2A6 is a principal enzyme responsible for the bioactivation process of tegafur in human liver microsomes. However, to what extent the bioactivation of tegafur by CYP2A6 accounts for the formation of 5-FU in vivo remains unclear, because the formation of 5-FU from tegafur is also catalyzed by the soluble fraction of a 100,000 x g supernatant and also derived from spontaneous degradation of tegafur.

Antimetabolites, Antineoplastic↗
PubMed1999

Developmental changes in distribution of death-associated protein kinase mRNAs.

Death-associated protein kinase (DAP-kinase) is Ca(2+)/calmodulin-dependent serine/threonine kinase that contains ankyrin repeats and the death domain. It has been isolated as a positive mediator of interferon-gamma-induced apoptotic cell death of HeLa cells. In order to reveal the physiological role of DAP-kinase, the tissue distribution and developmental changes in mRNA expression of DAP-kinase were investigated by Northern blot and in situ hybridization analyses. DAP-kinase mRNA was predominantly expressed in brain and lung. In brain, DAP-kinase mRNA had already appeared at embryonic day 13 (E13) and was, thereafter, detected throughout the entire embryonic period. High levels of expression were detected in proliferative and postmitotic regions within cerebral cortex, hippocampus, and cerebellar Purkinje cells. These findings suggest that DAP-kinase may play an important role in neurogenesis where a physiological type of cell death takes place. The overall expression of DAP-kinase mRNA in the brain gradually declined at postnatal stages, and the expression became restricted to hippocampus, in which different expression patterns were observed among rostral, central, and caudal coronal sections, suggesting that DAP-kinase may be implicated in some neuronal functions. Furthermore, it was found that the expression of DAP-kinase mRNA was increased prior to a certain cell death induced by transient forebrain ischemia, indicating a possible relationship between DAP-kinase and neuronal cell death.

Animals↗
PubMed1999

Multidrug resistance and the lung resistance-related protein in human colon carcinoma SW-620 cells.

BACKGROUND: Lung resistance-related protein (LRP), the major vault protein in humans, is sometimes overexpressed in multidrug-resistant cells. Because cells transfected with the LRP gene did not express the multidrug-resistant phenotype, we investigated whether LRP is involved in multidrug resistance. METHODS: SW-620 cells, a human colon carcinoma cell line, alone or transfected with an expression vector carrying a LRP-specific ribozyme or with an empty vector, were treated with sodium butyrate to induce differentiation. Expression of P-glycoprotein, multidrug resistance protein, and LRP in the cells was examined by northern and western blotting, and the efflux of doxorubicin in the cells or isolated nuclei was examined by fluorescence microscopy. RESULTS: A 2-week treatment with sodium butyrate induced LRP and conferred resistance to doxorubicin, vincristine, etoposide, gramicidin D, and paclitaxel (Taxol) in SW-620 cells. Insertion of either of two LRP-specific ribozymes into SW-620 cells inhibited these activities. Levels of drugs accumulating in the cells were not decreased by sodium butyrate, suggesting that the adenosine triphosphate-binding cassette transporter is not involved in sodium butyrate-induced multidrug resistance. Doxorubicin was mainly located in the nuclei of untreated cells and in the cytoplasm of sodium butyrate-treated cells. Isolated nuclei from untreated cells or sodium butyrate-treated cells incubated with anti-LRP polyclonal antibodies contained more doxorubicin than the nuclei of sodium butyrate-treated cells alone. Efflux of doxorubicin was greater from the nuclei of sodium butyrate-treated cells than the nuclei of untreated cells or of sodium butyrate-treated cells transfected with a LRP-specific ribozyme and was inhibited by an anti-LRP polyclonal antibody. CONCLUSIONS: LRP is involved in resistance to doxorubicin, vincristine, etoposide, paclitaxel, and gramicidin D and has an important role in the transport of doxorubicin from the nucleus to the cytoplasm.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Characterization of CFTR expression in a human pulmonary mucoepidermoid carcinoma cell line, NCI-H292 cells.

The NCI-H292 cell, a human pulmonary mucoepidermoid carcinoma cell line, is commonly used for studying bacterial and viral infections of airway epithelial cells. Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) is the main cause of fetal lung infection in cystic fibrosis patients. In this study, we examined CFTR expression in NCI-H292 cells to determine whether NCI-H292 cells possess sufficient, normally functioning CFTR. The results of RT-PCR and Northern blotting analysis indicated that the CFTR gene expression level was much lower in NCI-H292 cells than in T84 cells. However, Western blotting analysis showed that protein expression in NCI-H292 cells was comparable to that in T84 cells. Furthermore, whole-cell and cell-attached patch clamp electrophysiological techniques indicated that the Cl- current induced by intracellular cAMP elevation in NCI-H292 cells was comparable to that in T84 cells. These findings suggest that NCI-H292 cells with a low level of CFTR gene expression possess enough functional CFTR to show a physiological response.

Base Sequence↗