Tomohiro Nishimura

Keio University, Edo, Tōkyō, Japan

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Publications (34)80.12 Total impact

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    ABSTRACT: Estriol biosynthesis in human placenta requires uptake of a fetal liver-derived estriol precursor, 16α-hydroxydehydroepiandrosterone sulfate (16α-OH DHEAS), by placental syncytiotrophoblasts at their basal plasma membrane (BM), which faces the fetal circulation. The aim of this work is to identify the transporter(s) mediating 16α-OH DHEAS uptake at the fetal side of syncytiotrophoblasts by using human placental BM-enriched vesicles and to examine the contribution of the putative transporter to estriol synthesis at the cellular level, using choriocarcinoma JEG-3 cells. Organic anion transporter (OAT) 4 and organic anion transporting polypeptide 2B1 proteins were enriched in human placental BM vesicles compared with crude membrane fraction. Uptake of [(3)H]16α-OH DHEAS by BM vesicles was partially inhibited in the absence of sodium, but was significantly increased in the absence of chloride and after preloading glutarate. Uptake of [(3)H]16α-OH DHEAS by BM vesicles was significantly inhibited by OAT4 substrates such as DHEAS, estrone-3-sulfate, and bromosulfophthalein (BSP), but not by cyclosporin A, tetraethylammonium, p-aminohippuric acid, or cimetidine. These characteristics of vesicular [(3)H]16α-OH DHEAS uptake are in good agreement with those of human OAT4-transfected COS-7 cells, as well as forskolin-differentiated JEG-3 cells. Estriol secretion from differentiated JEG-3 cells was detected when the cells were incubated with 16α-OH DHEAS for 8 hrs, but was inhibited in the presence of 50 μ M BSP. Our results indicate that OAT4 at the BM of human placental syncytiotrophoblasts plays a predominant role in uptake of 16α-OH DHEAS for placental estriol synthesis.
    Endocrinology 04/2015; DOI:10.1210/en.2015-1130 · 4.64 Impact Factor
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    ABSTRACT: Mechanisms regulating fetal transfer of olmesartan, an angiotensin-II receptor type 1 antagonist, are important as potential determinants of life-threatening adverse fetal effects. The purpose of this study was to examine the olmesartan transport mechanism through the basal plasma membrane (BM) of human syncytiotrophoblasts forming the placental barrier. Uptake of olmesartan by human placental BM vesicles was potently inhibited by dehydroepiandrosterone sulfate (DHEAS), estrone 3-sulfate, and bromosulfophthalein, which are all typical substrates of organic anion transporter (OAT) 4 localized at the BM of syncytiotrophoblasts, and was increased in the absence of chloride. In tetracycline-inducible OAT4-expressing cells, [(3) H]olmesartan uptake was increased by tetracycline treatment. Olmesartan uptake via OAT4 was concentration dependent with a Km of 20 μM, and was increased in the absence of chloride. [(3) H]Olmesartan efflux via OAT4 was also observed and was trans-stimulated by extracellular chloride and DHEAS. Thus, OAT4 mediates bidirectional transport of olmesartan and appears to regulate fetal transfer of olmesartan at the BM of syncytiotrophoblasts. Efflux transport of olmesartan via OAT4 from syncytiotrophoblasts to the fetal circulation might be facilitated in the presence of an inwardly directed physiological chloride gradient and extracellular DHEAS. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.
    Journal of Pharmaceutical Sciences 03/2015; DOI:10.1002/jps.24434 · 3.01 Impact Factor
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    ABSTRACT: Hypotaurine is a precursor of taurine and an antioxidant, and is concentrated in fetal plasma compared to maternal plasma. Hypotaurine is significantly decreased in fetal plasma of ezrin (Vil2) knock-out mice, and fetuses show intrauterine growth retardation. The aim of this study was to characterize the mechanism through which cellular hypotaurine level is maintained in placental trophoblasts, and the effect of hypotaurine on oxidative stress induced by hydrogen peroxide (H2O2). Hypotaurine transfer from extracellular fluid and antioxidant effect of hypotaurine were analyzed in rat placental trophoblast TR-TBT 18d-1 cells. We found that hypotaurine is concentrated into rat placental trophoblast TR-TBT 18d-1 cells, and the level of hypotaurine was markedly reduced by culture in medium supplemented with dialyzed fetal bovine serum (FBS) instead of normal FBS. The hypotaurine level recovered almost completely when hypotaurine was added to the culture medium, indicating that intracellular hypotaurine is predominantly supplied by transport across the plasma membrane from extracellular fluid rather than by biosynthesis. Hypotaurine showed a cytoprotective effect against H2O2-induced oxidative damage in TR-TBT 18d-1 cells. Hypotaurine treatment of TR-TBT 18d-1 cells increased antioxidant capacity against hydroxyl radical and peroxyl radical. The concentration of intracellular hydroxyl radical induced by H2O2 in TR-TBT 18d-1 cells was significantly reduced by hypotaurine treatment. These results indicate that intracellular hypotaurine is mainly supplied to placental trophoblasts by transfer from extracellular fluid across the plasma membrane, and may play a role in cell protection by scavenging reactive oxygen species. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Placenta 03/2015; DOI:10.1016/j.placenta.2015.02.014 · 3.29 Impact Factor
  • Placenta 09/2014; 35(9):A97. DOI:10.1016/j.placenta.2014.06.315 · 3.29 Impact Factor
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    ABSTRACT: Ezrin is a membrane-associated cytoplasmic protein that serves to link cell-membrane proteins with the actin-based cytoskeleton, and also plays a role in regulation of the functional activities of some transmembrane proteins. It is expressed in placental trophoblasts. We hypothesized that placental ezrin is involved in the supply of nutrients from mother to fetus, thereby influencing fetal growth. The aim of this study was firstly to clarify the effect of ezrin on fetal growth and secondly to determine whether knockout of ezrin is associated with decreased concentrations of serum and placental nutrients. Ezrin knockout mice (Ez-/-) were confirmed to exhibit fetal growth retardation. Metabolome analysis of fetal serum and placental extract of ezrin knockout mice by means of capillary electrophoresis-time-of-flight mass spectrometry revealed a markedly decreased concentration of hypotaurine, a precursor of taurine. However, placental levels of cysteine and cysteine sulfinic acid (precursors of hypotaurine) and taurine were not affected. Lack of hypotaurine in Ez-/- mice was confirmed by liquid chromatography with tandem mass spectrometry. Administration of hypotaurine to heterogenous dams significantly decreased the placenta-to-maternal plasma ratio of hypotaurine in wild-type fetuses but only slightly decreased it in ezrin knockout fetuses, indicating that the uptake of hypotaurine from mother to placenta is saturable and that disruption of ezrin impairs the uptake of hypotaurine by placental trophoblasts. These results indicate that ezrin is required for uptake of hypotaurine from maternal serum by placental trophoblasts, and plays an important role in fetal growth.
    PLoS ONE 08/2014; 9(8):e105423. DOI:10.1371/journal.pone.0105423 · 3.53 Impact Factor
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    ABSTRACT: The purpose of this study is to assess the role of the protein kinase A (PKA) in regulating uptake of dehydroepiandrosterone sulfate (DHEAS), an estrogen precursor, by syncytiotrophoblasts. Forskolin, a PKA activator, significantly increased [3H]DHEAS uptake and the mRNA expression levels of organic anion transporter (OAT) 4 and CYP19A1 in choriocarcinoma JEG-3 cells, while other steroid sulfate transporters present in the placenta showed no change in expression level. KT5720, a PKA inhibitor, attenuated these effects of forskolin. Accordingly, the PKA pathway appears to play an important role in estrogen synthesis by cooperatively regulating OAT4 and steroidogenic enzymes in syncytiotrophoblasts.
    Placenta 08/2014; 35(8). DOI:10.1016/j.placenta.2014.06.003 · 3.29 Impact Factor
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    ABSTRACT: Betaine uptake is induced by hypertonic stress in a placental trophoblast cell line, and involvement of amino acid transport system A was proposed. Here, we aimed to identify the subtype(s) of system A that mediates hypertonicity-induced betaine uptake. Measurement of [(14)C]betaine uptake by HEK293 cells transiently transfected with human or rat SNAT1, SNAT2 and SNAT4 revealed that only human and rat SNAT2 have betaine uptake activity. The Michaelis constants (Km) of betaine uptake by human and rat SNAT2 were estimated to be 5.3mM and 4.6mM, respectively. Betaine exclusively inhibited the uptake activity of SNAT2 among the rat system A subtypes. We found that rat SNAT1, SNAT2 and SNAT4 were expressed at the mRNA level under isotonic conditions, while expression of SNAT2 and SNAT4 was induced by hypertonicity in TR-TBT 18d-1 cells. Western blot analyses revealed that SNAT2 expression on plasma membrane of TR-TBT 18d-1 cells was more potently induced by hypertonicity than that in total cell lysate. Immunocytochemistry confirmed that the induction of SNAT2 expression in TR-TBT 18d-1 cells exposed to hypertonic conditions and indicated that SNAT2 was localized on the plasma membrane in these cells. Our results indicate that SNAT2 transports betaine, and that tonicity-sensitive SNAT2 expression may be involved in regulation of betaine concentration in placental trophoblasts.
    Biochimica et Biophysica Acta 01/2014; 1838(5). DOI:10.1016/j.bbamem.2014.01.004 · 4.66 Impact Factor
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    ABSTRACT: Endothelial progenitor cells (EPC) can differentiate into both endothelial cells and contractile smooth muscle cells (SMC). Previously we reported that TR-BME2 cells, a model for EPC, developed contractile SMC-like characteristics in culture medium deprived of endothelial cell growth factors (ECGF). The aim of the present study was to clarify the effect of one of these factors, basic fibroblast growth factor (bFGF) on differentiation of EPC. First it was confirmed that bFGF receptor (FGFR-1) mRNA is expressed in TR-BME2 cultured in both ECGF-rich and ECGF-deprived medium. When TR-BME2 cells were cultured in ECGF-deprived medium, they differentiated into contractile SMC. Expression of an undifferentiated state marker, CD133, and proliferation of TR-BME2 were both reduced by ECGF deprivation, but these changes were diminished in the presence of bFGF. mRNA expression of smooth muscle α-actin (SMA) and smooth muscle protein 22 (SM22), which are contractile SMC markers, was induced by deprivation of ECGF and the induction was suppressed by bFGF. In vascular endothelial cell growth factor (VEGF)-induced tube formation assay, TR-BME2 cells formed tube structures in the presence of bFGF, but not in its absence. Our results indicate that bFGF is essential for the maintenance of EPC phenotype, serving to suppress differentiation to contractile SMC.
    Biological & Pharmaceutical Bulletin 01/2014; 37(4):688-93. DOI:10.1248/bpb.b13-00841 · 1.78 Impact Factor
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    ABSTRACT: It is important to address the tissue permeability of drugs, particularly in tissues that have a blood-tissue barrier, in terms of both lipophilicity and the contribution of transporters. Here, we employed umbilical perfusion in rats to evaluate in vivo fetal-to-maternal transfer clearances of various xenobiotics. We measured fetal-to-maternal clearance (CLfm ) of 23 compounds, which have a broad range of lipophilicity. Drugs for which CLfm was more than 300 µL/(mL min) belonged exclusively to Biopharmaceutical Drug Disposition Classification System (BDDCS) class 1 (highly permeable) and those for which CLfm was less than 50 µL/(mL min) belonged exclusively to BDDCS class 3 (poorly permeable). For most drugs, CLfm values were broadly consistent with lipophilicity. However, CLfm of digoxin was saturable and was inhibited by verapamil, suggesting that P-glycoprotein (P-gp)-mediated efflux has a substantially effect on measured clearance. CLfm of mitoxantrone continued to increase slightly at high concentrations of mitoxantrone, but placental-to-maternal clearance of mitoxantrone was saturable, implying that Bcrp1 contributes to mitoxantrone efflux across the placenta. Thus, we measured CLfm by umbilical perfusion and examined the relationship between CLfm and lipophilicity of xenobiotics. Fetal-to-maternal transport clearances measured in this study will be helpful to understand the characteristics of the blood-placental barrier. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
    Journal of Pharmaceutical Sciences 09/2013; 102(9). DOI:10.1002/jps.23551 · 3.01 Impact Factor
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    ABSTRACT: Substrate-induced upregulation of ATP-binding cassette subfamily G member 2 (ABCG2) has been well studied in cancer cells, but it is also important to understand whether ABCG2 is upregulated by its substrates in tissues in which it is constitutively expressed. In the present study, we aimed to clarify the regulatory mechanism of Abcg2 expression by its substrate, mitoxantrone, in placental cells. Abcg2 mRNA expression in rat placental TR-TBT 18d-1 cells treated with 10 μM mitoxantrone for 24 h was increased, compared with that in nontreated cells, whereas 10 μM pheophorbide-a had no effect. Methylated CpG level in the promoter region of the Abcg2 gene was low and was not altered by mitoxantrone. On the contrary, mitoxantrone markedly increased the expression of estrogen receptor (ER) α and progesterone receptor (PR) B. Fulvestrant, an ER antagonist, attenuated the mitoxantrone-induced increase of Abcg2 mRNA expression, whereas mifepristone, a PR antagonist, had little effect. 17β-estradiol, an ER ligand, positively regulated the mitoxantrone-induced increase of Abcg2 expression. DNA demethylation by 5-aza-2-deoxycytidine treatment increased ERα expression, but mitoxantrone failed to facilitate the demethylation of ERα promoter in TR-TBT 18d-1 cells. In conclusion, Abcg2 expression is induced by mitoxantrone via the induction of ERα in TR-TBT 18d-1 cells. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
    Journal of Pharmaceutical Sciences 09/2013; 102(9). DOI:10.1002/jps.23549 · 3.01 Impact Factor
  • Placenta 09/2013; 34(9):A46. DOI:10.1016/j.placenta.2013.06.139 · 3.29 Impact Factor
  • Masatoshi Tomi, Kenji Oda, Tomohiro Nishimura, Emi Nakashima
    Placenta 09/2013; 34(9):A95. DOI:10.1016/j.placenta.2013.06.281 · 3.29 Impact Factor
  • Placenta 09/2013; 34(9):A46. DOI:10.1016/j.placenta.2013.06.140 · 3.29 Impact Factor
  • Placenta 09/2013; 34(9):A94. DOI:10.1016/j.placenta.2013.06.279 · 3.29 Impact Factor
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    ABSTRACT: The purpose of this study was to clarify the transport characteristics of nucleosides in rat placenta and the changes of functional expression of nucleoside transporters in rat placenta with experimental diabetes mellitus. Placental uptake clearances of [(3)H]adenosine and [(3)H]zidovudine from maternal blood was much higher than that of [(14)C]mannitol. Xenopus oocytes injected with rat ENT1 and ENT2 cRNA took up [(3)H]adenosine with K(m) values of 6.1 and 26 µM, respectively. [(3)H]Adenosine transport by rat placental brush-border membrane vesicles (BBMV) was saturable and was inhibited by nitrobenzylthioinosine (NBMPR), a specific ENT inhibitor, in a manner consistent with involvement of both rat ENT1 and ENT2. [(3)H]Didanosine was modestly taken up by placenta, and the inhibitory effect of 100 µM NBMPR on [(3)H]ddI uptake by BBMV suggested a role of ENT2-mediated transport. Expression of ENT1, ENT2, ENT3, CNT2, and CNT3 mRNAs was detected in placenta of control and streptozotocin (STZ)-induced diabetic pregnant rats, and CNT2 (SLC28A2) expression was significantly increased in STZ-induced diabetic rats. Consistently, Na(+)-dependent adenosine uptake by BBMV from STZ-induced diabetic pregnant rats was higher than that from control rats. These results suggest the involvement of placental ENT2 as well as ENT1 in nucleoside uptake from maternal blood, and the induction of CNT2 in experimental diabetes mellitus.
    Drug Metabolism and Pharmacokinetics 02/2012; 27(4). DOI:10.2133/dmpk.DMPK-11-RG-103 · 2.86 Impact Factor
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    ABSTRACT: The purpose of this research was to noninvasively evaluate the influence of aromatherapy on work performance in 14 healthy young adults. Participants in a room filled with the fragrance of lavender completed a self-reported questionnaire and multi-dimensional fatigue inventory-20 (MFI-20). Further, as an objective measure, blood flow in the inferior frontal cortex was evaluated via near-infrared spectroscopy (NIRS) as a parameter of working memory capacity. Compared to the control stage (no aromatherapy), exposure to aromatherapy achieved a significant reduction in general and mental fatigue according to MFI-20. Self-reported questionnaires also indicated improvement, but the differences were not statistically significant. NIRS measurement during the task performance of an N-back program indicated that regional blood flow in the inferior frontal cortex was significantly increased through exposure to aromatherapy, compared to without. The prefrontal area in the brain is involved in working memory, attention concentration and judgment. These results suggest that lavender may improve both cognitive ability and mood. A larger study with more aroma oils seems warranted.
    01/2012; 38(4):265-271. DOI:10.5649/jjphcs.38.265
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    Masatoshi Tomi, Tomohiro Nishimura, Emi Nakashima
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    ABSTRACT: Administration of antiviral drugs to pregnant women with influenza, human immunodeficiency virus (HIV), and herpes simplex virus (HSV) infections is widely accepted as an effective treatment to safeguard the health of the mother and fetus. This review deals with the transfer of antiviral drugs to the fetus across the placental barrier, which is formed by an epithelial layer of syncytiotrophoblasts. First, the structure, function, and developmental change of the placenta and the placental barrier are briefly presented. We then review the transplacental permeability of antiviral drugs, such as oseltamivir for influenza, antiretrovirals (e.g., zidovudine, didanosine, and saquinavir) for HIV, and acyclovir for HSV, focusing on the involvement of ATP-binding cassette, organic anion/cation, and nucleoside transporters. The increasing evidence that is becoming available about transport mechanisms operating at the placental barrier is expected to be useful in the development of techniques to control fetal and placental transfer of antiviral drugs, and thereby to obtain maximum therapeutic benefit while minimizing potential fetal toxicity.
    Journal of Pharmaceutical Sciences 09/2011; 100(9):3708-18. DOI:10.1002/jps.22642 · 3.01 Impact Factor
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    ABSTRACT: A possible approach to improve antiretroviral therapy with nucleoside reverse transcriptase inhibitors is to enhance inhibitor delivery to CD4-positive T cells. We previously showed that dehydroepiandrosterone sulfate (DHEAS) enhances zidovudine (AZT) transfer into syncytiotrophoblast. Here, we investigated whether DHEAS also enhances AZT transfer into a cellular model of human T lymphocytes, and whether AZT is taken up by a specific transport system. The effects of DHEAS and related compounds on the uptake of [(3) H]AZT and other nucleosides by Molt-4 cells (a model of human CD4-positive T cells) were measured. [(3) H]AZT uptake by Molt-4 cells was nitrobenzylthioinosine insensitive and pH dependent, and the uptake was significantly inhibited by 1 mM ethylisopropylamiloride. [(3) H]AZT uptake by Molt-4 cells was increased in the presence of DHEAS, whereas uptake of other nucleosides was reduced. Kinetic study revealed that the maximum uptake velocity (up to 30 min) was increased in the presence of DHEAS. The structural requirements for AZT uptake-enhancing activity were studied using structural analogues of DHEAS. Estrone-3-sulfate and 16α-hydroxy DHEAS also enhanced AZT uptake into Molt-4 cells. The use of uptake enhancers may be a good strategy to improve the efficacy of antiretroviral therapy.
    Journal of Pharmaceutical Sciences 09/2011; 100(9):3959-67. DOI:10.1002/jps.22624 · 3.01 Impact Factor
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    ABSTRACT: Recent studies indicate that various members of the organic anion transporting polypeptide (OATP) family are expressed on apical membranes of the small intestine. In the present study, we investigated possible interaction of Oatp with the PDZ protein PDZK1 in mouse small intestine, using [³H]estrone-3-sulfate (E3S) as a typical substrate. After intraduodenal administration, the level of [³H]E3S appearing in the portal vein of pdzk1 gene knockout (pdzk1(-/-)) mice was much lower than that in wild-type mice. Lower intestinal absorption of [³H]E3S in pdzk1(-/-) mice was confirmed in Ussing-type chamber experiments, which showed smaller uptake of [³H]E3S from the apical side in intestinal tissues of pdzk1(-/-) mice compared with wild-type mice. The kinetics and inhibition profile of [³H]E3S uptake in the Ussing-type chamber were similar to those in HEK293 cells stably expressing Oatp1a5, suggesting involvement of Oatp1a5 in [³H]E3S uptake. Immunoreactivity to anti-Oatp1a antibody was colocalized with PDZK1 in the small intestine of wild-type mice, whereas apical localization of Oatp1a protein was reduced in pdzk1(-/-) mice. An immunoprecipitation study revealed physical interaction of PDZK1 with Oatp1a. Thus, PDZK1 appears to act as an adaptor for Oatp1a. This is the first demonstration of a regulatory protein directly interacting with small-intestinal OATP.
    Drug Metabolism and Pharmacokinetics 11/2010; 25(6):588-98. DOI:10.2133/dmpk.DMPK-10-RG-074 · 2.86 Impact Factor
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    ABSTRACT: The aim of the present study was to characterize the mechanism of erythromycin transport at the blood-placenta barrier, using TR-TBT 18d-1 cells as a model of rat syncytiotrophoblasts. [(14)C]Erythromycin was taken up by TR-TBT 18d-1 cells with a Michaelis constant of 466 microM. Although the uptake was not dependent on extracellular Na(+) or Cl(-), it was increased at weakly alkaline pH. Significant overshoot of [(14)C]erythromycin uptake by placental brush-border membrane vesicles was observed in the presence of an outwardly directed proton gradient. These results indicate that erythromycin is transferred by the H(+)-coupled transport system in syncytiotrophoblasts. To address the physiological transport of erythromycin in rat placenta, fetal-to-maternal transport clearance was estimated by means of the single placental perfusion technique. Clearance of [(14)C]erythromycin was higher than that of [(14)C]inulin, a paracellular pathway marker, and was decreased by the addition of 5 mM erythromycin, indicating that saturable efflux system from fetus to mother is involved. The effect of various transporter inhibitors on [(14)C]erythromycin efflux from TR-TBT 18d-1 cells was evaluated. cyclosporin A, fumitremorgin C, and probenecid had no effect, whereas ethylisopropylamiloride, a specific inhibitor of Na(+)/H(+) exchangers (NHEs), was significantly inhibitory. These results suggest that erythromycin efflux transport at the rat blood-placenta barrier is mediated by an erythromycin/H(+) antiport system, driven by H(+) supplied by NHEs.
    Drug metabolism and disposition: the biological fate of chemicals 09/2010; 38(9):1576-81. DOI:10.1124/dmd.110.033266 · 3.33 Impact Factor

Publication Stats

88 Citations
80.12 Total Impact Points

Institutions

  • 2008–2015
    • Keio University
      • Faculty of Pharmacy
      Edo, Tōkyō, Japan
  • 2014
    • Teikyo Heisei University
      Edo, Tōkyō, Japan
  • 2004–2007
    • Kanazawa University
      • Graduate School of Natural Science and Technology
      Kanazawa-shi, Ishikawa-ken, Japan