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Takemi Yoshida

Publications and source records attributed to Takemi Yoshida.

At least 19 recordsLinked to original sources
PubMed2007

A physiological role of AMP-activated protein kinase in phenobarbital-mediated constitutive androstane receptor activation and CYP2B induction.

CAR (constitutive androstane receptor) is a nuclear receptor that regulates the transcription of target genes, including CYP (cytochrome P450) 2B and 3A. The transactivation by CAR is regulated by its subcellular localization; however, the mechanism that governs nuclear translocation has yet to be clarified. It has been reported recently that AMPK (AMP-activated protein kinase) is involved in phenobarbital-mediated CYP2B induction in a particular culture system. We therefore investigated in vivo whether AMPK is involved in the activation of CAR-dependent gene expression. Immunoblot analysis using an antibody which recognizes Thr-172-phosphorylated AMPKalpha1/2 revealed phenobarbital-induced AMPK activation in rat and mouse livers as well. Phenobarbital, however, failed to increase the liver phospho-AMPK level of tumour-bearing rats in which CAR nuclear translocation had been impaired. In in vivo reporter gene assays employing PBREM (phenobarbital-responsive enhancer module) from CYP2B1, an AMPK inhibitor 8-bromo-AMP abolished phenobarbital-induced transactivation. In addition, Cyp2b10 gene expression was attenuated by 8-bromo-AMP. Forced expression of a dominant-negative mutant and the wild-type of AMPKalpha2 in the mouse liver suppressed and further enhanced phenobarbital-induced PBREM-reporter activity respectively. Moreover, the AMPK activator AICAR (5-amino-4-imidazolecarboxamide riboside) induced PBREM transactivation and an accumulation of CAR in the nuclear fraction of the mouse liver. However, AICAR and metformin, another AMPK activator, failed to induce hepatic CYP2B in mice and rats. These observations suggest that AMPK is at least partly involved in phenobarbital-originated signalling, but the kinase activation by itself is not sufficient for CYP2B induction in vivo.

AMP-Activated Protein Kinases↗
PubMed2006

The neuroprotective effect of heme oxygenase (HO) on oxidative stress in HO-1 siRNA-transfected HT22 cells.

To investigate the role of heme oxygenase (HO) isozymes, we used siRNA technology to suppress HO-1 expression. HO-1 siRNA-transfected HT22 cells were vulnerable to hydrogen peroxide- and 4-hydroxynonenal-induced cytotoxicity. Biliverdin and bilirubin, degradative products of heme catalyzed by HO, protected HT22 cells from the insult of these oxidative stressors. These results suggest that inducible HO-1 plays a protective role against oxidative stress in HT22 cells.

Aldehydes↗
PubMed2006

Heme oxygenase-1 gene expression in human alveolar epithelial cells (A549) following exposure to whole cigarette smoke on a direct in vitro exposure system.

Many in vitro studies have employed cigarette smoke condensates or soluble smoke components to investigate the biological effects of cigarette smoke. However, neither of these methods evaluates the biological effects of fresh whole cigarette smoke. It is most desirable to conduct in vitro biological studies under conditions which accommodate the dynamic physicochemical character of fresh cigarette smoke. Previously we reported the development of a whole smoke exposure system to assess the biological effects of mainstream cigarette smoke. The exposure system design was based on a combination of the sedimentation procedure and the CULTEX cultivation technique, which includes a systemized air/liquid interface methodology and exposes the cells to fresh smoke at every puff. The aim of this study was to adopt the other biological endpoint to our whole smoke exposure system. We focused on heme oxygenase (HO)-1 mRNA gene expression, an enzyme which has recently been shown to be highly responsible for oxidative stress. In the present study, a dose-response relationship between the HO-1 mRNA expression based on the reverse transcription real-time PCR method and total exposure to cigarette smoke was observed. When a Cambridge filter pad was placed between the cigarette and exposure module, to ensure the cells were only exposed to the gas/vapor phase, the latter, as well as the whole smoke, induced HO-1 mRNA dose dependently. For the next step, acetate plain and charcoal filters with the same pressure drop were prepared to assess the potential ability of charcoal filters with regard to the vapor phase performance. The results revealed reduced HO-1 mRNA gene expression when a charcoal filter was used. Direct whole smoke exposure is a significant approach and may reflect the conditions of exposure essentially resulting from direct contact between cells and a dynamic mixture of gaseous and particulate constituents. We were able to adopt a gene expression assay for oxidative stress to the whole smoke exposure system, following the adaptation of cytotoxicity assays. This system, which includes several advantages involving the post-exposure washing of cells, by adding the exchanging medium and assuring the exposure of the particulate phase through the sedimentation method, may have potential for further investigations into the molecular basis of smoking-related lung disease.

Air Pollutants↗
PubMed2006

Lipopolysaccharide-induced microglial activation induces learning and memory deficits without neuronal cell death in rats.

We used lipopolysaccharide (LPS) to activate microglia that play an important role in the brain immune system. LPS injected into the rat hippocampus CA1 region activated microglial cells resulting in an increased production of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha in the hippocampus during the initial stage of treatment. Immunostaining for IL-1beta was increased at 6 hr after LPS injection. IL-1beta-immunopositive cells were co-localized with immunostaining for CD11b. Subacute treatment with LPS by the same route for 5 days caused long-term activation of microglia and induced learning and memory deficits in animals when examined with a step-through passive avoidance test, but histochemical analysis showed that neuronal cell death was not observed under these experimental conditions. The increased expression of the heme oxygenase-1 (HO-1) gene, an oxidative stress maker, was observed. However, the genetic expression of brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, decreased during the course of LPS treatment. We found decreases in [3H]MK801 binding in the hippocampus CA1 region by LPS-treatment for 5 days. The data shows that glutamatergic transmission was attenuated in the LPS-treated rats. These results suggest that long-term activation of microglia induced by LPS results in a decrease of glutamatergic transmission that leads to learning and memory deficits without neuronal cell death. The physiologic significance of these findings is discussed.

Animals↗
PubMed2006

Analysis of the expression of heme oxygenase-1 gene in human alveolar epithelial cells exposed to cigarette smoke condensate.

Airway epithelium is exposed to inhaled exogenous sources. Injury of the alveolar epithelium by cigarette smoking is presumed to be an important process in the pathogenesis of smoking-related pulmonary diseases. Current mechanistic assays that measure the toxicity of cigarette smoke focus on carcinogenesis. However, there is a need to design assays relevant to other disease processes. Oxidative stress is implicated in the pathogenesis of many respiratory diseases including chronic obstructive pulmonary disease. Therefore, we evaluated whether in vitro studies of cigarette smoking are appropriate to examine HO-1 mRNA expression. The human lung epithelial cell line A549 was exposed to the particulate fraction of cigarette smoke (Cigarette Smoke Condensate; CSC) and examined for the induction of HO-1 mRNA. HO-1 gene expression by CSC is increased dose-dependently. In comparison of the induction of HO-1 mRNA by CSC prepared from flue-cured or Burley tobacco, CSC from flue-cured tobacco seems to tend to induce an mRNA of HO-1 higher than CSC from Burley tobacco. The adaptation of HO-1 mRNA expression assay as a biologically relevant indicator of cigarette smoke-induced stress may be exemplified in this study whereby CSC derived from cigarette smoke positively correlated with an increase in HO-1 expression and the difference of the type of tobacco can be detected.

Auranofin↗
PubMed2006

[DLST as a method for detecting TS-1-induced allergy].

Drug-induced allergic adverse events including rash, interstitial pneumonia and hepatic injury are often observed in a few patients treated with anticancer drugs that are 5-FU derivatives, including TS-1. In patients suspected to be liable to develop allergic reactions, the drug-induced lymphocyte stimulation test (DLST), based on the (3)H-thymidine incorporation ratio into the DNA of lymphocytes derived from the patients, is generally employed to identify drugs that could induce allergy. In this case report, we conducted the DLST on 20 healthy volunteers without TS-1 treatment in order to obtain reference data on the evaluation of TS-1-induced allergy. Even though all 20 volunteers were healthy, there were 6 positive responses to the DLST. In view of the positive response to TS-1 in healthy volunteers undergoing the DLST, it is suggested that the DLST could show a false positive response through an intracellular function that accelerates incorporation of thymidine in the lymphocytes by the salvage pathway after inhibition of DNA de novo synthesis caused by 5-FU derivative anticancer, including TS-1. Therefore, such a positive response to the drugs is considered, in fact, to be false-positive in the DLST. In view of the occurrence of false-positive results, the possibility of drug-induced allergy in patients receiving TS-1 should be carefully evaluated using a combination of other clinical examinations.

Adult↗
PubMed2005

5Alpha-bile alcohols function as farnesoid X receptor antagonists.

The farnesoid X receptor (FXR) is a bile acid/alcohol-activated nuclear receptor that regulates lipid homeostasis. Unlike other steroid receptors, FXR binds bile acids in an orientation that allows the steroid nucleus A ring to face helix 12 in the receptor, a crucial domain for coactivator-recruitment. Because most naturally occurring bile acids and alcohols contain a cis-oriented A ring, which is distinct from that of other steroids and cholesterol metabolites, we investigated the role of this 5beta-configuration in FXR activation. The results showed that the 5beta-(A/B cis) bile alcohols 5beta-cyprinol and bufol are potent FXR agonists, whereas their 5alpha-(A/B trans) counterparts antagonize FXR transactivation and target gene expression. Both isomers bound to FXR, but their ability to induce coactivator-recruitment and thereby induce transactivation differed. These findings suggest a critical role for the A-ring orientation of bile salts in agonist/antagonist function.

Cell Line, Tumor↗
PubMed2005

Impaired nuclear translocation of CAR in hepatic preneoplastic lesions: association with an attenuated CYP2B induction by phenobarbital.

Phenobarbital (PB) induction of CYP2B, a representative target gene of constitutive androstane receptor (CAR), has been observed to be attenuated in preneoplastic lesions of rat liver; however, molecular basis for this attenuation is poorly understood. In this report, we provide evidence indicating that the CAR expressed in the hepatic preneoplastic lesions of rats and mice was resistant to nuclear translocation and transactivation of the PB-responsive enhancer module upon PB treatment. These observations suggest that the attenuation of the induction of CYP2B by PB in hepatic preneoplastic lesions is evidently a consequence of impaired nuclear translocation of CAR.

Active Transport, Cell Nucleus↗
PubMed2005

Redox regulation of the transcriptional repressor Bach1.

Bach1 is a transcriptional repressor of heme oxygenase-1, one of the most inducible phase 2 proteins. Bach1 binds in conjunction with a small Maf protein to tandem repeats of the antioxidant response element (ARE) and quenches the target gene expression. On the other hand, the transactivator Nrf2 binds and up-regulates the ARE-governed gene expression. By using a sulfhydryl oxidizing agent, diamide, here we provide evidence which indicates that the Bach1 function is regulated by the redox state. Diamide showed restricted Nrf2 nuclear translocation and ARE-driven reporter activity but reversed the ARE transcriptional activity suppressed by ectopically expressed Bach1. Substitution of the conserved cysteine residue in the DNA binding domain of Bach1 to serine (C574S mutant) caused a refractory response to the diamide-mediated reactivation of the Bach1-suppressed reporter activity. Moreover, diamide induced cytoplasmic translocation of the GFP-Bach1 fusion protein but failed to translocate the fusion protein consisting of the C574S mutant. These data suggest that redox regulation of Bach1 is an alternative mechanism to induce multiple ARE-governed genes.

Animals↗
PubMed2005

Tissue- and dose-dependent alteration of stress-inducible proteins by beta2-adrenoceptor agonist, salbutamol, in rats.

The effects of selective beta(2)-adrenoceptor agonists on proinflammatory cytokines and the expression of stress-inducible proteins have not yet been clarified. We investigated the effect of a higher dose (60 mg/kg intravenously) of salbutamol, a selective beta(2)-adrenoceptor agonist, on the induction of interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)-alpha in plasma and the expression of protein and mRNA of metallothioein-1 (MT-1), heme oxygenase-1 (HO-1) and inducible nitric oxide synthase (iNOS) in heart, lung, liver and spleen in rats. The plasma IL-6 concentration was significantly increased after administration with a maximum increase at 3 hr in a dose-dependent manner, but IL-1beta and TNF-alpha concentrations were not changed. MT-1 mRNA increased in heart, lung and liver, but not in spleen, and MT-1 protein increased in endocardium, fibroblasts of lung and periportal regions in liver. HO-1 mRNA was not changed in lung, decreased at 3 hr in liver and spleen, and increased at 6 hr in liver. Contrary to liver, HO-1 mRNA in the heart increased at 3 hr and decreased at 6 hr. HO-1 protein increased in cardiomyocytes and centrilobular regions in the liver. iNOS mRNA increased in lung, liver and spleen, but decreased in the heart, and iNOS protein increased in alveolar type II cells and hepatocytes, and decreased in necrotic cardiomyocytes. In contrast, a lower dose (6 mg/kg intravenously) of salbutamol suppressed lipopolysaccharide-induced HO-1 and iNOS mRNA. We conclude that salbutamol tissue- and dose-dependently alters the expression of stress-inducible proteins.

Adrenergic beta-2 Receptor Agonists↗
PubMed2004

Involvement of interleukin-6 and tumor necrosis factor alpha in CYP3A11 and 2C29 down-regulation by Bacillus Calmette-Guerin and lipopolysaccharide in mouse liver.

Bacillus Calmette-Guérin (BCG) and lipopolysaccharide (LPS) are well known potent activators of the cell-mediated immune system and thus lead to the decreases in cytochrome P450 (P450). In this study we used interleukin (IL)-1alpha/beta, IL-6, or tumor necrosis factor alpha (TNFalpha) knockout (KO) mice to investigate how each cytokine is involved in P450 down-regulation, especially CYP3A11 and 2C29. BCG (40 mg/kg) was found to reduce both CYP3A11 and 2C29 mRNAs at 24 h after treatment in IL-1alpha/beta KO mice in a manner similar to that seen in wild-type mice. CYP3A11 mRNA, but not CYP2C29 mRNA, was significantly decreased by BCG treatment in the TNFalpha KO mice, although the decrease was less than that of wild-type or IL-1alpha/beta KO mice. In contrast, BCG showed no significant effect on CYP3A11 and 2C29 mRNAs in IL-6 KO mice. On the other hand, LPS was able to decrease CYP3A11 and 2C29 mRNA levels in all of the cytokine KO mice and markedly increased systemic levels of TNFalpha; BCG (40 mg/kg) lacked such activity. The present study has shown that IL-6 and TNFalpha are likely to be major factors involved in the down-regulation of CYP3A11 and 2C29 mRNAs in mice. In addition, there exist differences in the amount and/or kind of cytokines released by BCG or LPS, the latter being more potent than the former. This will be a possible reason for differential capability of P450 down-regulation between BCG and LPS.

Animals↗
PubMed2004

Quantitative estimation of myocardial fibrosis based on receptor occupancy for beta2-adrenergic receptor agonists in rats.

To develop beta2-adrenergic receptor (AR) agonists with higher selectivity, it is essential to evaluate the cardiac side effects which are the most serious side effects of this class of drugs. We studied receptor occupancy of beta1-ARs in rats as a possible cause for the side effect of beta2-AR agonists, namely myocardial fibrosis. Myocardial fibrosis in rats was observed on Day 7 after the administration of salbutamol and terbutaline, both of which are selective beta2-AR agonists, at higher dose levels. To evaluate receptor occupancy, plasma concentrations of (R)-salbutamol and (R)-terbutaline, plasma protein binding and the EC50 for chronotropic effects in rats were determined. Based on the plasma concentrations, the plasma protein binding and EC50, receptor occupancy-time profiles were constructed. The relationship between the receptor occupancy-time profile under the curve, the AUCphi, and the degree of myocardial fibrosis was evaluated with a multiple correlation analysis. Myocardial fibrosis was significantly correlated (r2 > 0.78) to the AUCphi with the threshold above approximately 50%, but not to plasma concentrations. These results indicate that the receptor occupancy theory is also useful for the evaluation of the chronotropic side effects of beta2-AR agonists.

Adrenergic beta-Agonists↗
PubMed2004

Nrf2-dependent gene expressions: a molecular toxicological aspect.

Although NF-E2 related factor 2 (Nrf2) was found to be a transcriptional regulator that controls an expression of the beta-globin gene, the notion is now widely accepted that this transfactor serves as a master regulator for the gene expression of a battery of proteins acting on anti-oxidative stress and detoxification of electrophiles. The function of Nrf2 that bears transcriptional activation depends solely on its nuclear localization, which is regulated by interaction with the cytosolic anchor protein Keap1 and its own turnover rate. In the present mini-review, we focus on the regulation of Nrf2 function and discuss the physiological and toxicological aspects of this transcriptional factor.

Animals↗
PubMed2003

Role of c-Myc in nitric oxide-mediated suppression of cytochrome P450 3A4.

Cytochrome P450 (CYP) 3A4, which is abundant in human liver and small intestine and participates in the metabolism of various drugs and xenochemicals, is known to be induced by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in the colon carcinoma cell line Caco-2 cells. Nitric oxide (NO) is able to inhibit CYP3A4 expression and catalytic activity. In this study, we investigated the mechanism of suppression by NO of 1,25(OH)2D3-induced CYP3A4 expression in Caco-2 cells. Caco-2 cells were exposed for 36 h to 400 nM 1,25(OH)2D3, and the induction of CYP3A4 mRNA expression was detected by real-time PCR. Because c-Myc regulates the expression of several genes, we examined its effect on the CYP3A4 expression induced by 1,25(OH)2D3. The expression of c-myc mRNA was increased in the early stage but decreased 36 h after the treatment of Caco-2 cells with 1,25(OH)2D3. The NO donor NOR-4 suppressed CYP3A4 expression induced by 1,25(OH)2D3 in Caco-2 cells in contrast, it significantly induced c-myc gene expression. Treatment of Caco-2 cells with the c-myc antisense oligonucleotide reversed the inhibitory effect of NOR-4 on CYP3A4 expression induced by 1,25(OH)2D3. These results suggest that the suppression of 1,25(OH)2D3-induced CYP3A4 expression by NO is due to c-myc expression.

Animals↗
PubMed2003

Atypical protein kinase C mediates activation of NF-E2-related factor 2 in response to oxidative stress.

Transcription factor NF-E2-related factor 2 (Nrf2) regulates the induction of antioxidative proteins, including heme oxygenase-1 (HO-1). Nrf2 is sequestered in the cytoplasm by Keap1 under unstimulated conditions but translocates into the nucleus and transactivates the antioxidant responsive element (ARE) upon exposure to oxidative insults. It has recently been demonstrated that in vitro phosphorylation of Nrf2 on Ser40 by protein kinase C (PKC) facilitates the dissociation of Nrf2 from the Keap1 complex (Huang HC, Nguyen T, and Pickett CB. J Biol Chem 277: 42769-42774, 2002). The present study was designed to examine whether PKC is involved in oxidative stress-mediated nuclear translocation of Nrf2 in vivo and, if so, which PKC isoforms are involved. Induction of HO-1 gene expression by phorone, a glutathione depletor, and 4-hydroxy-2,3-nonenal (4-HNE), an end product of lipid peroxidation, was suppressed by a specific PKC inhibitor, Ro-31-8220, at concentrations that inhibit all isoforms in WI-38 cells. The induction of HO-1 was not affected by prolonged exposure of the cells to 12-O-tetradecanoylphorbol-13 acetate (TPA), suggesting that TPA-insensitive atypical PKC (aPKC) isoforms are involved. An immunocomplex kinase assay revealed that phorone and 4-HNE increased aPKCiota activity. In COS-7 cells, 4-HNE induced nuclear translocation of the Nrf2-green fluorescent protein (GFP) fusion protein, but not the Nrf2(S40A)-GFP mutant. In the absence of oxidative insults, the Nrf2(S40E)-GFP mutant was distributed in the nucleus. The Nrf2-GFP accumulation in the nucleus was induced by coexpression of aPKCiota, but not by a kinase inactive mutant aPKCiota(K274W). The activity of an ARE-driven reporter was increased by coexpression of aPKCiota, and this effect was eliminated by Ro-31-8220 in HepG2 cells. The reporter activity induced by 4-HNE was inhibited by coexpression of aPKCiota(K274W). These results suggest that phosphorylation of Nrf2 Ser40 by aPKC(s) is involved in the nuclear translocation and ARE transactivation of Nrf2 by oxidative stress.

Active Transport, Cell Nucleus↗
PubMed2003

GABAergic modulation of hippocampal glutamatergic neurons: an in vivo microdialysis study.

We have demonstrated the effects of activation of presynaptic gamma-aminobutyric acid (GABA) receptors on glutamate release using in vivo brain microdialysis. A dialysis probe inserted into the hippocampus CA2 area of freely moving rats was perfused with Ringers solution containing 100 mM potassium chloride (KCl) or 0.05 mM veratridine for 20 min. Extracellular concentrations of amino acids were monitored by measuring their levels in dialysates by high performance liquid chromatography (HPLC) fluorometry. Perfusion with depolarizing agents, such as KCl or veratridine, increased extracellular glutamate levels in the hippocampus. Pretreatment with 1 mM GABA, before perfusion with depolarizing agents, significantly suppressed the depolarizing agent-induced increase in glutamate levels. The GABA(B) receptor agonist baclofen (1 mM) also significantly inhibited the depolarizing agent-induced increase in glutamate levels, whereas the GABA(A) receptor agonist, muscimol, had no affect. Similarly, baclofen (0.5 mM) decreased the KCl (13.5 mM)-induced 45Ca(2+) influx into cortical synaptosomes to 57% of the level induced in the absence of baclofen. On the other hands, GABA did not affect the increases in glycine and taurine level by depolarizing agents. These results suggest that GABA modulates depolarization-evoked glutamate release in the hippocampus by inhibiting Ca(2+) entry into neurons, an effect mediated by presynaptic GABA(B) receptors.

Animals↗