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Toshihiko Kasahara

Publications and source records attributed to Toshihiko Kasahara.

14 recordsLinked to original sources
PubMed2006

DNA damage and altered gene expression of enzymes for metabolism and DNA repair by tamoxifen and toremifene in the female rat liver.

Effects of hepatocarcinogenic TAM and non-hepatocarcinogenic TOR on the formation of hepatic DNA adducts and on the gene expression of hepatic drug-metabolizing enzymes and DNA repair enzymes/proteins were comparatively examined in female Sprague-Dawley rats treated with TAM (20 or 40 mg/kg/day, i.g.) or TOR (40 mg/kg/day, i.g.) for 1, 2 or 8 weeks. Hepatic TAM-DNA adducts were formed even after 1 week of treatment with TAM at either dose, and the adduct levels increased in a dose- and treatment period-dependent manner, whereas no DNA adducts were detected in any of the TOR-treated rats. Conversely, TAM and TOR showed almost the same capacity for increasing the gene expression of drug-metabolizing enzymes responsible for metabolic activation and detoxification, at least up to the 2-week treatment mark. Accordingly, differences in DNA adduct formation between TAM- and TOR-treated rats would not be primarily dependent on the capacity for inducing hepatic drug-metabolizing enzymes. In addition, a drastic increase in the gene expression of cytochrome P4503A2 (CYP3A2), an activation enzyme of TAM, by the 8-week treatment with TAM might have contributed to the increased formation of DNA adducts. Gene expressions of DNA repair enzymes/proteins responsible for a nucleotide excision repair system were not significantly changed in any of the rats treated with either drug. The present findings suggest that the difference between TAM and TOR in hepatocarcinogenic potency is dependent on the capacity to form DNA adducts rather than modulating the expression of drug-metabolizing enzymes and DNA repair enzymes/proteins.

Animals↗
PubMed2006

Gene expression profile in liver of differing ages of rats after single oral administration of acetaminophen.

In order to verify the influence of the rat age on hepatotoxicity, male Sprague-Dawley rats of 6 (young) and 12 (adult) weeks of age were orally administered acetaminophen (APAP), isoniazid (INH), or carbon tetrachloride (CCl4). Liver samples were obtained in a time-course manner, and changes in gene expression examined by an Affymetrix GeneChip. APAP caused more prominent hepatic injury with respect to pathology and blood biochemistry in adults than in young rats, whereas no obvious age-related differences were observed in INH- or CCl4-treated rats. Comparing gene expression in control rats, CYP3A13 was higher and GSTY2c was lower in adults, suggesting that production of the active metabolite of APAP is higher and its detoxification is lower in adults. The total amount of glutathione and total SH in rat liver was found to be higher in adult rats whereas the extent of its reduction by APAP was larger in adults. A detailed analysis of genes showing age-related differences revealed that some of them were different not in their extent but in their time course, i.e., the stress responses occurred earlier in the young than in the adult, resulting in a difference at 24 hr after dosing. These results suggest that the age-related difference in toxicity would be attributed to a higher expression of CYP3A13, producing the active metabolite of APAP as well as the lower expression of the detoxification enzyme, GSTY2c, in adult rats. Furthermore, these differences affect the time course of APAP toxicity. The present study clearly depicts the advantage of the multi-time, multi-dose protocol employed in our project for analyzing the mechanism of toxicity by gene expression profiling.

Acetaminophen↗
PubMed2006

Evaluation of methods for duration of preservation of RNA quality in rat liver used for transcriptome analysis.

In The Toxicogenomics Project, about 150 chemicals are administered to rats, and gene expression in the liver analyzed by Affymetrix GeneChip and stored in the database. As the quality of RNA greatly influences the accuracy of gene expression data, conditions of the storage of the sample are very important. Recently, an RNA stabilization solution, RNAlater, has become commercially available. In this study, the new storage method was compared with the traditional storage method (stored in freezer or liquid nitrogen) under various conditions by looking at the degradation of RNA assessed by its total yield, OD260/280 ratio, 28S/18S ratio, and quantity of beta-actin. It was confirmed that RNAlater preserved the liver tissue sample by maintaining the quality of RNA for one year (in liquid N(2) or -80 degrees C), for 3 days (4 degrees C), or for 2 hr (room temperature) without degradation of RNA. Quality of RNA samples dissolved in buffer RLT and stored at -20 degrees C tended to decrease, but samples stored at -80 degrees C were almost equivalent to those stored in liquid nitrogen. In conclusion, we recommend the following procedure for preservation of liver tissue for extraction of RNA: 1) tissues removed should be put into chilled RNAlater as soon as possible; 2) samples in RNAlater must be stored overnight or longer at 4 degrees C and can be left for as long as 2 weeks without freezing; 3) samples in RNAlater can be stored for at least one year under less than -20 degrees C and 4) samples dissolved in buffer RLT can be preserved at least for one year under -80 degrees C.

Actins↗
PubMed2005

Effect of the difference in vehicles on gene expression in the rat liver--analysis of the control data in the Toxicogenomics Project Database.

The Toxicogenomics Project is a 5-year collaborative project by the Japanese government and pharmaceutical companies in 2002. Its aim is to construct a large-scale toxicology database of 150 compounds orally administered to rats. The test consists of a single administration test (3, 6, 9 and 24 h) and a repeated administration test (3, 7, 14 and 28 days), and the conventional toxicology data together with the gene expression data in liver as analyzed by using Affymetrix GeneChip are being accumulated. In the project, either methylcellulose or corn oil is employed as vehicle. We examined whether the vehicle itself affects the analysis of gene expression and found that corn oil alone affected the food consumption and biochemical parameters mainly related to lipid metabolism, and this accompanied typical changes in the gene expression. Most of the genes modulated by corn oil were related to cholesterol or fatty acid metabolism (e.g., CYP7A1, CYP8B1, 3-hydroxy-3-methylglutaryl-Coenzyme A reductase, squalene epoxidase, angiopoietin-like protein 4, fatty acid synthase, fatty acid binding proteins), suggesting that the response was physiologic to the oil intake. Many of the lipid-related genes showed circadian rhythm within a day, but the expression pattern of general clock genes (e.g., period 2, arylhydrocarbon nuclear receptor translocator-like, D site albumin promoter binding protein) were unaffected by corn oil, suggesting that the effects are specific for lipid metabolism. These results would be useful for usage of the database especially when drugs with different vehicle control are compared.

Animals↗
PubMed2005

Establishment of an in vitro high-throughput screening assay for detecting phospholipidosis-inducing potential.

Excessive accumulation of phospholipids results in phospholipidosis (PL), which may interfere with cellular functions, leading to acute or chronic disease or even death. Electron-microscopic detection of cytoplasmic lamellar bodies is often used as a diagnostic criterion of PL, but a faster, more convenient procedure is required for high-throughput assay of the PL-inducing potential of candidate drugs. We have developed a 96-well microplate cell-culture method for detecting PL, using a phosphatidylcholine-conjugated dye (NBD-PC) and a fluoro-microplate reader. The fluorescence intensity due to NBD-PC was normalized to that of Hoechst33342, used as an indicator of cell number, to obtain the amount of NBD-PC taken up per living cell. To select a suitable cell type, we examined the PL-detection sensitivity of five cell lines, as well as human and rat primary hepatocyte cultures, with five cationic amphiphilic drugs (CAD) as PL inducers and a negative control compound. The cell lines CHO-K1 and CHL/IU gave the best results. The NBD-PC uptake per CHO-K1 cell showed a high correlation with the pathological score of PL for 24 compounds, including PL-positive and negative compounds. This high-throughput screening assay for PL-inducing potential (HTS-PL assay) offers high sensitivity and accuracy, and it allows simultaneous determination of cytotoxicity.

4-Chloro-7-nitrobenzofurazan↗
PubMed2005

Left atrial thrombosis associated with antipsychotic drugs.

The authors report a case of a 36-year-old shizophrenic patient with left atrial thrombosis. There have been small number of case reports of antipsychotic drugs-associated thromboembolic events. All of them are venous ones. This paper describes the first case of atrial thrombosis associated with antipsychotic drugs.

Adult↗
PubMed2005

Presenile dementia mimicking Pick's disease: an autopsy case of localized amygdala degeneration with character change and emotional disorder.

This report concerns an autopsy case showing localized amygdala degeneration. The patient was a Japanese single woman without hereditary burden who was 58 years old at the time of death. At the age of 55 years, the patient began to feel anxiety, agitation and depressive in mood. At age 58 years, she developed marked character changes and emotional disorders, although disorientation and memory disturbance were slight. We suspected her disease was a variant of presenile dementia, especially Pick's disease, and some neuroradiological examinations disclosed bilateral temporal involvements. We could not make a definitive diagnosis from the clinical findings. She choked to death 3 years after the disease onset. From the neuropathological examinations, the known neurodegenerative diseases causing dementia, including Pick's disease, were excluded and we diagnosed our case as having localized amygdala degeneration. Localized amygdala degeneration itself is very rare. Moreover, in this case, the amygdala degeneration was presumed to be idiopathic, without any apparent cause. To our knowledge, this is the first case of idiopathic localized amygdala degeneration. This case indicates that localized amygdala degeneration can cause presenile dementia, and that character changes and emotional disorders are predominant over memory disturbance and/or disorientation.

Affective Symptoms↗
PubMed2005

Characterization of structural and catalytic differences in rat intestinal alkaline phosphatase isozymes.

To understand the differences between the rat intestinal alkaline phosphatase isozymes rIAP-I and rIAP-II, we constructed structural models based on the previously determined crystal structure for human placental alkaline phosphatase (hPLAP). Our models of rIAP-I and rIAP-II displayed a typical alpha/beta topology, but the crown domain of rIAP-I contained an additional beta-sheet, while the embracing arm region of rIAP-II lacked the alpha-helix, when each model was compared to hPLAP. The representations of surface potential in the rIAPs were predominantly positive at the base of the active site. The coordinated metal at the active site was predicted to be a zinc triad in rIAP-I, whereas the typical combination of two zinc atoms and one magnesium atom was proposed for rIAP-II. Using metal-depleted extracts from rat duodenum or jejunum and hPLAP, we performed enzyme assays under restricted metal conditions. With the duodenal and jejunal extract, but not with hPLAP, enzyme activity was restored by the addition of zinc, whereas in nonchelated extracts, the addition of zinc inhibited duodenal IAP and hPLAP, but not jejunal IAP. Western blotting revealed that nearly all of the rIAP in the jejunum extracts was rIAP-I, whereas in duodenum the percentage of rIAP-I (55%) correlated with the degree of AP activation (60% relative to that seen with jejunal extracts). These data are consistent with the presence of a triad of zinc atoms at the active site of rIAP-I, but not rIAP-II or hPLAP. Although no differences in amino acid alignment in the vicinity of metal-binding site 3 were predicted between the rIAPs and hPLAP, the His153 residue of both rIAPs was closer to the metal position than that in hPLAP. Between the rIAPs, a difference was observed at amino acid position 317 that is indirectly related to the coordination of the metal at metal-binding site 3 and water molecules. These findings suggest that the side-chain position of His153, and the alignment of Q317, might be the major determinants for activation of the zinc triad in rIAP-I.

Alkaline Phosphatase↗
PubMed2003

The gene expression of hepatic proteins responsible for DNA repair and cell proliferation in tamoxifen-induced hepatocarcinogenesis.

Altered gene expression of the DNA repair- and cell proliferation-associated proteins/enzymes was examined during the process of tamoxifen-induced hepatocarcinogenesis in female Sprague-Dawley rats. When rats were treated by gavage with a single dose of tamoxifen (20 mg/kg body weight) or with the same dose given at 24-h intervals for 2, 12 or 52 weeks, no histopathological change was observed in the liver after 2 weeks. Pathologically altered cell foci and placental form of glutathione-S-transferase (GST-P)-positive foci were observed in the liver after 12 weeks of treatment. Treatment for 52 weeks resulted in the formation of liver hyperplastic nodules that strongly expressed GST-P. During the process of carcinogenesis, changes in hepatic gene expression of DNA repair proteins/enzymes (XPA and XPC, xeroderma pigmentosum complementation groups A and C, respectively; APE, apurinic/apyrimidinic endonuclease) and of cell proliferation-associated proteins (c-myc; PCNA, proliferating cell nuclear antigen; cyclin D1, cyclin B, and p34cdc2) were examined by RT-PCR. The gene expression of XPA and APE was increased by the tamoxifen treatment for 2 or 12 weeks, but no increase was observed after the 52-week treatment. In addition, no significant change in XPC gene expression occurred at any period examined. The gene expression of c-myc, PCNA, and cyclin D1 was increased in a time-dependent fashion up to 12 weeks of treatment, and this increase was maintained up to 52 weeks of treatment. The gene expression of cyclin B and p34cdc2 was increased after the 1-day treatment, reverted to the control level at 2 and 12 weeks of treatment, and was remarkably increased after the 52-week treatment. In the present study, we demonstrate the altered gene expression of various proteins/enzymes involved in DNA repair, cell growth and the cell cycle during the process of tamoxifen-induced hepatocarcinogenesis. We discuss the relationship between the altered gene expression and hepatocarcinogenesis.

Animals↗
PubMed2003

Long-term administration of highly purified eicosapentaenoic acid ethyl ester improves blood coagulation abnormalities and dysfunction of vascular endothelial cells in Otsuka Long-Evans Tokushima fatty rats.

We investigated the effect of highly purified eicosapentaenoic acid ethyl ester (EPA-E) on blood coagulation abnormalities and dysfunction of vascular endothelial cells in spontaneously diabetic Otsuka Long-Evans Tokushima Fatty rats. The animals were treated with either EPA-E or lard at a daily dose of 0.3 g/kg/day for 52 weeks by gavage, and their coagulation/fibrinolytic parameters, platelet aggregation, and functions of the vascular endothelial cells were examined. EPA-E significantly improved coagulation-related parameters including prothrombin time, activated partial thromboplastin time, fibrinogen level, and activities of factor II, V, VII, VIII, IX, X, XI, and XII, and antithrombin III, and fibrinolysis-related parameters including plasminogen, tissue-type plasminogen activator, alpha(2)-plasmin inhibitor, and plasminogen activator inhibitor. It also suppressed ADP- or collagen-induced platelet aggregation and the cholesterol/phospholipid molar ratio in platelet membranes at a dose of 0.3 g/kg. In addition, it significantly increased the migration activity of vascular endothelial cells, and decreased the binding of vascular endothelial cells to vascular endothelial growth factor. In contrast, lard had no effect on hypercoagulation, hypofibrinolysis, and platelet hyperaggregation but significantly aggravated the dysfunction of vascular endothelial cells. These data demonstrate that EPA-E beneficially altered certain factors known to promote thrombosis and atherosclerosis in this animal model.

Animals↗
PubMed2003

[Somatization disorder].

Explore the source record for details and available documents.

Diagnostic and Statistical Manual of Mental Disord↗
PubMed2002

Heat shock induces intestinal-type alkaline phosphatase in rat IEC-18 cells.

We demonstrate a previously unknown regulation for intestinal-type alkaline phosphatase (IAP) as a heat shock protein (HSP). Heat shock to rat intestinal epithelial cells (IEC)-18 at 43 degrees C induced the expression of IAP-I and HSP72 mRNAs time dependently (<60 min) but did not induce expression of IAP-II, tissue nonspecific-type alkaline phosphatase (TNAP), or HSP90 as determined by the RT-PCR method. To confirm the identity of the IAP-I gene, we sequenced the amplification product of IAP-I and found the gene to have 99% homology with the sequence of the IAP-I gene in rat intestine. Under the subculture conditions used, no IAP protein was detected in IEC-18 cells, but it became detectable as a 62-kDa band on a Western blot after heat shock. IAP-I was also induced by sodium arsenite, which generates reactive oxygen species and is an inducer of members of the HSP family. Glutathione suppressed activating protein-1 and cAMP response element-binding protein activation caused by heat shock but did not suppress the expression of IAP-I. These results suggest that cellular stress induces the elevation of IAP-I mRNA and protein synthesis. IAP-I may play an important role as a dephosphorylating enzyme under stress conditions.

Alkaline Phosphatase↗
PubMed2002

Change in the gene expression of hepatic tamoxifen-metabolizing enzymes during the process of tamoxifen-induced hepatocarcinogenesis in female rats.

Altered gene expression of the enzymes responsible for tamoxifen metabolism during the process of tamoxifen-induced hepatocarcinogenesis in female Sprague-Dawley rats was examined by the RT-PCR method. Treatment of rats with tamoxifen (20 mg/kg body/day) for 52 weeks, but not the 1 day, 2 or 12 week treatments, resulted in the formation of the liver hyperplastic nodules. The gene expression of CYP3A subfamily enzymes, especially CYP3A1, responsible for not only detoxification (N-demethylation) but also activation (alpha-hydroxylation) of tamoxifen, was increased by the tamoxifen treatments for 2 and 12 weeks, whereas after the 52 week treatment, the expression in the induced nodules returned to the control level. The gene expression of SULT2A subfamily sulfotransferases, especially HSTa, responsible for metabolic activation of alpha-hydroxytamoxifen was decreased to a level <20% of the control in the nodules, although no significant change in the expression was observed in the liver of rats treated with tamoxifen for 1 day, 2 or 12 weeks. On the other hand, the gene expression of CYP3A2 and flavin-containing monooxygenase 1 (FMO1), responsible for the N-demethylation and N-oxidation, respectively, of tamoxifen was increased in a time-dependent fashion up to the 52 week treatment. Although the gene expression of UDP-glucuronosyltransferase(s), which might be responsible for detoxification of tamoxifen, was also increased by the tamoxifen treatment for 2 or 12 weeks, it decreased to the control level in the nodules after the 52 week treatment. The present findings demonstrate that in the early stage of the formation of the liver hyperplastic nodules by tamoxifen, the genes of the enzymes responsible for not only detoxification but also activation of tamoxifen were activated, whereas in the later stage (in the nodules), the genes of the detoxification enzymes, CYP3A2 and FMO1, remained active, but those of the activation enzymes such as CYP3A1 and HSTa were suppressed.

Animals↗