Faculty Profiles - NAKAMURA Yoshimasa

Papers - NAKAMURA Yoshimasa

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Proline and glyclinebetaine induce antioxidant defense gene expression and suppress cell death in cultured tobacco cells under salt stress Reviewed

Nasrin Akhter Banu, Anamul Hoque, Megumi Watanabe-Sugimoto, Ken Matsuoka, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshlyuki Murata

JOURNAL OF PLANT PHYSIOLOGY 166 ( 2 ) 146 - 156 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER GMBH, URBAN & FISCHER VERLAG

Salt stress causes oxidative damage and cell death in plants. Plants accumulate proline and glycinebetaine (betaine) to mitigate detrimental effects of salt stress. The aim of this study was to investigate the protective effects of proline and betaine on cell death in NaCl-unadapted tobacco (Nicotiana tabacum) Bright Yellow-2 suspension-cultured cells subjected to salt stress. Salt stress increased reactive oxygen species (ROS) accumulation, lipid peroxidation, nuclear deformation and degradation, chromatin condensation, apoptosis-tike cell death and ATP contents. Neither proline nor betaine affected apoptosis-like cell death and G, phase population, and increased ATP contents in the 200 mM NaCl-stressed cells. However, both of them effectively decreased ROS accumulation and lipid peroxidation, and suppressed nuclear deformation and chromatin condensation induced by severe salt stress. Evans Blue staining experiment showed that both proline and betaine significantly suppressed increment of membrane permeability induced by 200 mM NaCl. Furthermore, among the ROS scavenging antioxidant defense genes studied here, mRNA levels of salicylic acid-binding (SAbind) catalase (CAT) and lignin-forming peroxidase (POX) were found to be increased by proline and betaine under salt stress. It is concluded that both proline and betaine provide a protection against NaCl-induced cell death via decreasing level of ROS accumulation and lipid peroxidation as well as improvement of membrane integrity. (C) 2008 Elsevier GmbH. ALL rights reserved.

DOI： 10.1016/j.jplph.2008.03.002

Nitric oxide functions in both methyl jasmonate signaling and abscisic acid signaling in Arabidopsis guard cells Reviewed

Naoki Saito, Yoshimasa Nakamura, Izumi C. Mori, Yoshiyuki Murata

Plant Signaling and Behavior 4 ( 2 ) 119 - 120 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：Landes Bioscience

Intracellular components in methyl jasmonate (MeJA) signaling remain largely unknown, to compare those in well-understood abscisic acid (ABA) signaling. We have reported that nitric oxide (NO) is a signaling component in MeJA-induced stomatal closure, as well as ABA-induced stomatal closure in the previous study. To gain further information about the role of NO in the guard cell signaling, NO production was examined in an ABA- and MeJA-insensitive Arabidopsis mutant, rcn1. Neither MeJA nor ABA induced NO production in rcn1 guard cells. Our data suggest that NO functions downstream of the branch point of MeJA and ABA signaling in Arabidopsis guard cells. ©2009 Landes Bioscience.

DOI： 10.4161/psb.4.2.7537

Chemoprevention by Isothiocyanates: Molecular Basis of Apoptosis Induction Invited Reviewed

Yoshimasa Nakamura

FOOD FACTORS FOR HEALTH PROMOTION 61 170 - 181 2009

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：KARGER

An important and promising group of compounds that have a cancer-chemopreventive property are organosulfur compounds, such as isothiocyanates (ITCs). Various ITCs are effective chemoprotective agents against chemical carcinogenesis in experimental animals. Several epidemiological studies also indicated that the dietary consumption of ITCs or ITC-containing foods inversely correlates with the risk of developing lung, breast, and colon cancers, providing evidence that they have a potential to prevent cancer in humans. Mechanistically, ITCs are capable of inhibiting both the formation and development of a cancer cell through multiple pathways; i.e. the inhibition of carcinogen-activating cytochrome P450 mono-oxygenases, induction of carcinogen-detoxifying phase 2 enzymes, induction of apoptosis, and inhibition of cell cycle progression. We have clarified the molecular mechanisms underlying the relationship between cell cycle regulation and apoptosis induced by benzyl ITC (BITC), a major ITC compound isolated from papaya (Corica papaya) fruit. We identified phosphorylated Bcl-2 as a key molecule linking p38 MAPK-dependent cell cycle regulation with the c-Jun N-terminal kinase activation by BITC. We also established that BITC exerts the cytotoxic effect more preferentially in the proliferating cells than in the quiescent cells. Furthermore, p53 was found to be a potential negative regulator of apoptosis induction by BITC in normal epithelial cells through inhibition of cell cycle progression at the G(0)/G(1) phase. In contrast, treatment with an excessive concentration of BITC resulted in necrotic cell death in an ATP-dependent manner. This review addresses the biological impact of cell death induction by BITC as well as other ITCs and the involved molecules regulating signal pathways. Copyright (C) 2009 S. Karger AG, Basel

DOI： 10.1159/000212749

(-)-Epigallocatechin-3-gallate Potentiates the Cytotoxicity Induced by Benzyl Isothiocyanate and Hydrogen Peroxide in Human Jurkat T Lymphocytes Reviewed

Haitao Wu, Tomoko Yokoyama, Beiwei Zhu, Yasuaki Shimoishi, Yoshiyuki Murata, Yoshimasa Nakamura

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 72 ( 11 ) 3034 - 3037 2008.11

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

(-)-Epigallocatechin-3-gallate (EGCG)-induced apoptosis was along both the extracellular signal-regulated protein kinase (ERK) and c-jun N-terminal kinase (JNK) pathways in Jurkat cells. Co-treatment with EGCG potentiated the cytotoxicity induced by benzyl isothiocyanate (BITC) and H2O2, both being inhibited by ERK and JNK inhibitors. These results suggest the significant role of mitogen-activated protein kinase (MAPK) signaling in the apoptosis induction regulated by EGCG alone and in combination.

DOI： 10.1271/bbb.80422

Effect of Dimethyl Sulfides on the Induction of Apoptosis in Human Leukemia Jurkat Cells and HL-60 Cells Reviewed

Gongliang Zhang, Haitao Wu, Beiwei Zhu, Yasuaki Shimoishi, Yoshimasa Nakamura, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 72 ( 11 ) 2966 - 2972 2008.11

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

Organosulfur compounds have been established to possess anticancer effects. To provide a better understanding of the biological function of dimethyl sulfides, dimethyl monosulfide (Me2S), dimethyl disulfide (Me2S2), dimethyl trisulfide (Me2S3) and dimethyl tetrasulfide (Me2S4) were used as experimental materials to investigate their effects on apoptosis induction in human leukemia Jurkat cells and HL-60 cells. Treatment with 20 Km dimethyl sulfides for 24 h decreased the viability of both cells. The cell viability-reducing effect of these sulfides was in the following order: Me2S4 approximate to Me2S3 > Me2S2 approximate to Me2S for Jurkat cells and Me2S4 > Me2S3 > Me2S2 approximate to Me2S for HL-60 cells. Me2S3 and Me2S4 significantly induced DNA fragmentation and caspase-3 activation. The addition of GSH or NAC completely suppressed the sulfide-induced apoptosis. Our results indicate that dimethyl sulfides with a larger number of sulfur atoms more strongly induced apoptosis in both human leukemia cells via ROS production and caspase-3 activation.

DOI： 10.1271/bbb.80453

Deficient Glutathione in Guard Cells Facilitates Abscisic Acid-Induced Stomatal Closure but Does Not Affect Light-Induced Stomatal Opening Reviewed

Md. Sarwar Jahan, Ken'ichi Ogawa, Yoshimasa Nakamura, Yasuaki Shimoishi, Izumi C. Mori, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 72 ( 10 ) 2795 - 2798 2008.10

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

We investigated the role of glutathione (GSH) in stomatal movements using a GSH deficient mutant, chlorinal-1 (ch1-1). Guard cells of ch1-1 mutants accumulated less GSH than wild types did. Light induced stomatal opening in ch1-1 and wild-type plants. Abscisic acid (ABA) induced stomatal closure in ch1-1 mutants more than wild types without enhanced reactive oxygen species (ROS) production. Therefore, GSH functioned downstream of ROS production in the ABA signaling cascade.

DOI： 10.1271/bbb.80407

Roles of RCN1, regulatory a subunit of protein phosphatase 2A, in methyl jasmonate signaling and signal crosstalk between methyl jasmonate and abscisic acid Reviewed

Naoki Saito, Shintaro Munemasa, Yoshimasa Nakamura, Yasuaki Shimoishi, Izumi C. Mori, Yoshiyuki Murata

PLANT AND CELL PHYSIOLOGY 49 ( 9 ) 1396 - 1401 2008.9

Language：English Publishing type：Research paper (scientific journal) Publisher：OXFORD UNIV PRESS

Methyl jasmonate (MeJA) as well as abscisic acid (ABA) induces stomatal closure with their signal crosstalk. We investigated the function of a regulatory A subunit of protein phosphatase 2A, RCN1, in MeJA signaling. Both MeJA and ABA failed to induce stomatal closure in Arabidopsis rcn1 knockout mutants unlike in wild-type plants. Neither MeJA nor ABA induced reactive oxygen species (ROS) production and suppressed inward-rectifying potassium channel activities in rcn1 mutants but not in wild-type plants. These results suggest that RCN1 functions upstream of ROS production and downstream of the branch point of MeJA signaling and ABA signaling in Arabidopsis guard cells.

DOI： 10.1093/pcp/pcn106

Structure-dependent photodegradation of carotenoids accelerated by dimethyl tetrasulfide under UVA irradiation Reviewed

Gongliang Zhang, Beiwei Zhu, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 72 ( 8 ) 2176 - 2183 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

Carotenoids are used in wide-ranging food applications, but they are susceptible to degradation by many factors including light. We examined the photodegradation of five kinds of carotenoids and three kinds of anthocyanins to clarify which structures of pigments were favorable to accelerated degradation by sulfides under UVA irradiation. Under UVA irradiation, crocetin and crocin were decomposed more rapidly in the presence of dimethyl tetrasulfide than in the absence of the sulfide, but not as rapidly as beta-carotene, zeaxanthin and beta-cryptoxanthin were. However, cyanidin was decomposed more slowly in the presence of sulfide than in the absence of sulfide. Moreover, the photodegradation of kuromanin and keracyanin was not affected by the addition of a sulfide. We also examined the mechanism for this accelerated degradation. Normal hexane was more favorable to the photodegradation of beta-carotene than methanol and ethanol. The accelerated degradation was inhibited by free radical scavengers, but enhanced by the addition of deuterium oxide. These results suggest that conjugated double bonds were favorable to the accelerated photodegradation by sulfide and that this reaction was mediated by free radicals.

DOI： 10.1271/bbb.80251

Galloylated catechins as potent inhibitors of hypochlorous acid-induced DNA damage Reviewed

Yoshichika Kawai, Yuri Matsui, Hajime Kondo, Hiroshi Morinaga, Koji Uchida, Noriyuki Miyoshi, Yoshimasa Nakamura, Toshihiko Osawa

CHEMICAL RESEARCH IN TOXICOLOGY 21 ( 7 ) 1407 - 1414 2008.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Hypochlorous acid (HOC1), a strong oxidant derived from myeloperoxidase in neutrophils and macrophages, can chlorinate DNA bases at the site of inflammation. Because little is known about the protective role of natural antioxidants, such as polyphenols, for the myeloperoxidase-derived DNA damage, we screened the inhibitory effects of various phenolic antioxidants on the chlorination of the 2'-deoxycytidine residue by HOC1 in vitro and found that green tea catechins, especially (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg), significantly inhibited the chlorination. These catechins also reduced nucleoside- and taurine-chloramines, which can induce secondary oxidative damage, into their native forms. Mass spectrometric and nuclear magnetic resonance analyses showed that ECg and EGCg can effectively scavenge HOC1 and/or chloramine species resulting in the formation of mono-and dichlorinated ECg and EGCg. Using the HL-60 human leukemia cell line, it was found that ECg could efficiently accumulate in the cells. Immunocytometric analyses using antihalogenated 2'-deoxycytidine antibody showed that pretreatment of cells with ECg inhibited the HOC1-induced immunofluorescence. In addition, the chlorinated ECg derivatives were detected in the HOC1-treated HL-60 cells. These results showed that green tea catechins, especially 3-galloylated catechins, may be the plausible candidate for the prevention of inflammation-derived DNA damage and perhaps carcinogenesis.

DOI： 10.1021/tx800069e

Proline and glycinebetaine enhance antioxidant defense and methylglyoxal detoxification systems and reduce NaCl-induced damage in cultured tobacco cells Reviewed

Md. Anamul Hoque, Mst. Nasrin Akhter Banu, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshiyuki Murata

JOURNAL OF PLANT PHYSIOLOGY 165 ( 8 ) 813 - 824 2008

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER GMBH, URBAN & FISCHER VERLAG

Salt stress impairs reactive oxygen species (ROS) and methylglyoxal (MG) detoxification systems, and causes oxidative damage to plants. Up-regulation of the antioxidant and glyoxalase systems provides protection against NaCl-induced oxidative damage in plants. Thiol-disulfide contents, glutathione content and its associated enzyme activities involved in the antioxidant defense and glyoxalase systems, and protein carbonylation in tobacco Bright Yellow-2 cells grown in suspension culture were investigated to assess the protection offered by proline and glycinebetaine against salt stress. Salt stress increased protein carbonylation, contents of thiol, disulfide, reduced (GSH) and oxidized (GSSG) forms of glutathione, and the activity of glutathione-S-transferase and glyoxalase II enzymes, but decreased redox state of both thiol-disulfide and glutathione, and the activity of glutathione peroxidase and glyoxalase I enzymes involved in the ROS and MG detoxification systems. Exogenous application of proline or glycinebetaine resulted in a reduction of protein carbonylation, and in an increase in glutathione redox state and activity of glutathione peroxidase, glutathione-S-transferase and glyoxalase I under salt stress. Neither proline noi glycinebetaine, however, had any direct protective effect on NaCl-induced GSII-associated enzyme activities. The present study, therefore, suggests that both proline and glycinebetaine provide a protective action against NaCl-induced oxidative damage by reducing protein carbonylation, and enhancing antioxidant defense and MG detoxification systems. (C) 2007 Elsevier GmbH. All rights reserved.

DOI： 10.1016/j.jplph.2007.07.013

Exogenous proline and glycinebetaine increase NaCl-induced a scorbate-glutathione cycle enzyme activities, and proline improves salt tolerance more than glycinebetaine in tobacco Bright Yellow-2 suspension-cu ltured cells Reviewed

Md. Anamul Hoque, Mst. Nasrin Akhter Banu, Eiji Okuma, Yoshiyuki Murata

JOURNAL OF PLANT PHYSIOLOGY 164 ( 11 ) 1457 - 1468 2007.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER GMBH, URBAN & FISCHER VERLAG

Up-regulation of the antioxidant system provides protection against NaCl-induced oxidative damage in plants. Antioxidants and activity of enzymes involved in the ascorbate-glutathione (ASC-GSH) cycle in tobacco Bright Yellow-2 (BY-2) were investigated to assess the antioxidant protection offered by exogenous proline and glycinebetaine (betaine from now on) against salt stress using cells grown in suspension culture. Reduced ascorbate (ASC) was detected in BY-2 cells but dehydroascorbate (DHA) was not. Large quantities of a reduced form of glutathione (GSH) and smaller quantities of an oxidized form of glutathione (GSSG) were detected in BY-2 cells. Salt stress significantly reduced the contents of ASC and GSH as well. as activities of ASC-GSH cycle enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR). Exogenous proline or betaine increased the activities of all enzymes except MDHAR involved in NaCl-induced ASC-GSH cycle. Levels of ASC and GSH in BY-2 cells under salt stress were lower in the presence of proline or betaine than in the absence of proline or betaine whereas there was no difference in redox status. Proline proved more effective than betaine in maintaining the activity of enzymes involved in NaCl-induced ASC-GSH cycle. Neither proline nor betaine had any direct protective effect on NaCl-induced enzyme activity involved in the antioxidant system; however, both improved salt tolerance by increasing enzyme activity. The present study, together with our earlier findings [Hoque MA, Okuma E, Banu MNA, Nakamura Y, Shimoishi Y, Murata Y. Exogenous proline mitigates the detrimental effects of salt stress more than exogenous betaine by increasing antioxidant enzyme activities. J Plant Physiol 2006;164:553-61.], suggests that proline offered greater protection against salt stress than betaine did because proline was more effective in increasing the activity of enzymes involved in the antioxidant system. (C) 2006 Elsevier GmbH. All rights reserved.

DOI： 10.1016/j.jplph.2006.10.004

Dietary flavonoid apigenin is a potential inducer of intracellular oxidative stress: The role in the interruptive apoptotic signal Reviewed

Noriyuki Miyoshi, Kisa Naniwa, Takayo Yamada, Toshihiko Osawa, Yoshimasa Nakamura

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 466 ( 2 ) 274 - 282 2007.10

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE INC

Apigenin is a representative dietary flavone (2-phenyl-4H-1-benzopyran-4-one) inhibiting cancer cell growth both in cell culture systems and in vivo. The prooxidant potential of apigenin was confirmed by the observations using flowcytometric and irnmunoblotting techniques that the intracellular accumulations of reactive oxygen species (ROS) and protein carbonyls were detected in the cells treated, with apigenin in a dose-dependent manner. Conversely, chrysin (5,7-dihydroxyflavone) did not show any prooxidant effect. A structure-activity relationship data thus indicated that a 4'-monohydroxyl group, which can be oxidized to semiquinone radical but not up to quinone-like metabolite, is essential for prooxidant effect. When HL-60 cells were treated with not only a heme synthesis inhibitor succinyl acetone (SA) but also myeloperoxidase (MPO) inhibitors, the ROS level enhanced by apigenin was significantly reduced. The gathered data suggested that peroxidase-catalyzed production of apigenin B-ring phenoxyl radicals might be responsible for the prooxidant effect. This is supported by the observation that MPO is able to catalyze production of apigenin phenoxyl radicals, detected by an electron spin resonance-spin trapping technique. We also reveal that both SA and a-tocopherol enhance cellular susceptibility to apoptosis-inducing stimuli by apigenin. In conclusion, the prooxidant effect of apigenin is likely to oxidize a variety of thiols through the formation of phenoxyl radicals and thus seems to play a significant role in the abortive apoptotic pathway switching to necrotic cell death. (c) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.abb.2007.07.026

Exogenous proline mitigates the detrimental effects of salt stress more than exogenous betaine by increasing antioxidant enzyme activities Reviewed

Md. Anamul Hoque, Eiji Okuma, Mst. Nasrin Akhter Banu, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshiyuki Murata

JOURNAL OF PLANT PHYSIOLOGY 164 ( 5 ) 553 - 561 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER GMBH, URBAN & FISCHER VERLAG

Proline and betaine accumulate in plant cells under environmental stresses including stress. Here, we investigated effects of proline and betaine on the growth and activities of antioxidant enzymes in tobacco Bright Yellow-2 (BY-2) culture cells in suspension under salt stress. Both proline and betaine mitigated the inhibition of growth of BY-2 cells under salt stress and the mitigating effect of proline was more than that of betaine. Salt stress significantly decreased the activities of superoxide dismutase (SOD), catalase and peroxidase in BY-2 cells. Exogenous application of proline or betaine alleviated the reduction in catalase and peroxidase activities but not SOD activity under salt stress. In addition, proline was found to be effective in alleviating the inhibition of salt stress-induced catalase and peroxidase activities in BY-2 cells. Neither proline nor betaine directly scavenged superoxide (02) or hydrogen peroxide (H2O2). It is concluded that exogenous proline mitigates the detrimental effects of salt stress more than exogenous betaine because of its superior ability to increase the activities of antioxidant enzymes. (C) 2006 Elsevier GmbH. All rights reserved.

DOI： 10.1016/j.jplph.2006.03.010

Detection of modified tyrosines as an inflammation marker in a photo-aged skin model Reviewed

Yukiko Ishitsuka, Fumio Maniwa, Chiharu Koide, Natsuko Douzaki, Yoji Kato, Yoshimasa Nakamura, Toshihiko Osawa

PHOTOCHEMISTRY AND PHOTOBIOLOGY 83 ( 3 ) 698 - 705 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SOC PHOTOBIOLOGY

Reactive nitrogen species, produced during the process of inflammation induced by various factors including UV radiation, modify amino acids in crucial proteins. It is assumed that skin tissue is more likely to be modified, as it is located at the outer layer of a body that is exposed to UV radiation on a daily basis. To investigate the influence of the modified tyrosine on UV-exposed skin, we detected the nitrotyrosine or halogenated tyrosine and dityrosine in photo-aged model mice. The back skin of mice was exposed to a dose of 10 J cm(-2) day(-1) every day for 15 weeks. Samples exhibiting typical symptoms of photo aging were provided to the immunofluorescence study. The quantification of modified proteins was accomplished through a chemical analytical method known as HPLC-tandem mass spectrometry. Analysis of the irradiated skin samples showed that all modified tyrosine except nitrotyrosine demonstrated statistically significant increases. The molecular weights of major modified proteins, confirmed as 25-50 kDa, were measured using Western blot analysis with an anti-nitrotyrosine antibody. Furthermore, the immunofluorescence study verified that the localization of myeloperoxidase conformed to that of nitrotyrosine. This result suggests that the modified tyrosine was produced during the process of inflammation by UV irradiation. In this study, we used a low dose of UV irradiation to which we are exposed in daily life. Our results suggest that UV exposure in daily life may induce the production of modified tyrosines and skin aging.

DOI： 10.1562/2006-07-24-RA-978

The coronatine-insensitive 1 mutation reveals the hormonal signaling interaction between abscisic acid and methyl jasmonate in arabidopsis guard cells. Specific impairment of ion channel activation and second messenger production Reviewed

Shintaro Munemasa, Kenji Oda, Megumi Watanabe-Sugimoto, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshiyuki Murata

PLANT PHYSIOLOGY 143 ( 3 ) 1398 - 1407 2007.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SOC PLANT BIOLOGISTS

Methyl jasmonate (MeJA) elicits stomatal closing similar to abscisic acid (ABA), but whether the two compounds use similar or different signaling mechanisms in guard cells remains to be clarified. We investigated the effects of MeJA and ABA on second messenger production and ion channel activation in guard cells of wild-type Arabidopsis ( Arabidopsis thaliana) and MeJA-insensitive coronatine-insensitive 1 (coi1) mutants. The coi1 mutation impaired MeJA-induced stomatal closing but not ABA-induced stomatal closing. MeJA as well as ABA induced production of reactive oxygen species (ROS) and nitric oxide (NO) in wild-type guard cells, whereas MeJA did not induce production of ROS and NO in coi1 guard cells. The experiments using an inhibitor and scavengers demonstrated that both ROS and NO are involved in MeJA-induced stomatal closing as well as ABA-induced stomatal closing. Not only ABA but also MeJA activated slow anion channels and Ca2+ permeable cation channels in the plasma membrane of wild-type guard cell protoplasts. However, in coi1 guard cell protoplasts, MeJA did not elicit either slow anion currents or Ca2+ permeable cation currents, but ABA activated both types of ion channels. Furthermore, to elucidate signaling interaction between ABA and MeJA in guard cells, we examined MeJA signaling in ABA-insensitive mutant ABA-insensitive 2 (abi2-1), whose ABA signal transduction cascade has some disruption downstream of ROS production and NO production. MeJA also did not induce stomatal closing but stimulated production of ROS and NO in abi2-1. These results suggest that MeJA triggers stomatal closing via a receptor distinct from the ABA receptor and that the coi1 mutation disrupts MeJA signaling upstream of the blanch point of ABA signaling and MeJA signaling in Arabidopsis guard cells.

DOI： 10.1104/pp.106.091298

Expression and Ca2+ dependency of plasma membrane K+ channels of tobacco suspension cells adapted to salt stress Reviewed

Naoki Kasukabe, Megumi Watanabe-Sugimoto, Ken Matsuoka, Eiji Okuma, Ichiro Obi, Yoshimasa Nakamura, Yasuaki Shimoishi, Yoshiyuki Murata, Tadaaki Kakutani

PLANT AND CELL PHYSIOLOGY 47 ( 12 ) 1674 - 1677 2006.12

Language：English Publishing type：Research paper (scientific journal) Publisher：OXFORD UNIV PRESS

The expression of plasma membrane K+ channels of NaCl-adapted tobacco suspension cells and effects of extracellular Ca2+ on plasma membrane K+ channels were investigated. Reverse transcription-PCR (RT-PCR) analysis showed that expression of TORK1, which encodes a K+ channel, was much lower in NaCl-adapted cells than in NaCl-unadapted cells. The magnitude of the outward K+ currents of NaCl-adapted as well as NaCl-unadapted cells decreased with increasing extracellular Ca2+ but there is no significant difference in Ca2+ dependency of the K+ current. These analyses suggest that reduction of the number of K+ channels might cause NaCl adaptation of cells through the decrease of outward K+ currents.

DOI： 10.1093/pcp/pcl030

A novel labdane-type trialdehyde from Myoga (Zingiber mioga Roscoe) that potently inhibits human platelet aggregation and human 5-lipoxygenase Reviewed

Masako Abe, Yoshio Ozawa, Yasushi Uda, Yasujiro Morimitsu, Yoshimasa Nakamura, Toshihiko Osawa

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 70 ( 10 ) 2494 - 2500 2006.10

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

We screened myoga extracts for inhibitors of human platelet aggregation and human 5-lipoxygenase. We identified a novel labdane type of diterpene, together with three known diterpenes (miogadial and galanals A and B) from the flower buds of myoga. Spectroscopic data indicated the structure of the new compound to be 12(E)-labdene-15,16,(8 beta)17-trial (miogatrial). Miogatrial and miogadial were potent inhibitors of human platelet aggregation and human 5-lipoxygenase (5-LOX). The sesquiterpene, polygodial, also exhibited strong inhibitory activity against human platelet aggregation and 5-LOX. On the other hand, galanals A and B did not have inhibitory activity in either experimental system. It thus appears that a 3-formyl-3-butenal structure was essential for the potent inhibition of human platelet aggregation and human 5-LOX.

DOI： 10.1271/bbb.60226

Cell death induction by isothiocyanates and their underlying molecular mechanisms Invited Reviewed

Yoshimasa Nakamura, Noriyuki Miyoshi

BIOFACTORS 26 ( 2 ) 123 - 134 2006

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IOS PRESS

An important and promising group of compounds that have a chemopreventive property are organosulfur compounds, such as isothiocyanates (ITCs). In recent years, it has been shown that ITCs induce apoptosis in various cancer cell lines and experimental rodents. During the course of apoptosis induction by ITC, multiple signal-transduction pathways and apoptosis intermediates are modulated. We have also clarified the molecular mechanism underlying the relationship between cell cycle arrest and apoptosis induced by benzyl isothiocyanate ( BITC), a major ITC compound isolated from papaya. The exposure of cells to BITC resulted in the inhibition of the G(2)/M progression that coincided with not only the up-regulated expression of the G(2)/M cell cycle arrest-regulating genes but also the apoptosis induction. The experiment using the phase-specific synchronized cells demonstrated that the G(2)/M phase-arrested cells are more sensitive to undergoing apoptotic stimulation by BITC than the cells in other phases. We identified the phosphorylated Bcl-2 as a key molecule linking the p38 MAPK-dependent cell cycle arrest with the JNK activation by BITC. We also found that BITC induced the cytotoxic effect more preferentially in the proliferating normal human colon epithelial cells than in the quiescent cells. Conversely, treatment with an excessive concentration of BITC resulted in necrotic cell death without DNA ladder formation. This review addresses the biological impact of cell death induction by BITC as well as other ITCs and the involved signal transduction pathways.

DOI： 10.1002/biof.5520260203

Dietary isothiocyanates modify mitochondrial functions through their electrophilic reaction Reviewed

M Kawakami, N Harada, M Hiratsuka, K Kawai, Y Nakamura

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 69 ( 12 ) 2439 - 2444 2005.12

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

We found that both benzyl isothiocyanate (ITC) and phenyl ITC inhibited respiration in the mitochondria in an electrophilic reaction-dependent manner. ITG induced mitochondrial swelling and cytochrome c release were prevented by cyclosporin A, indicating that they are mediated through the ITC moiety-dependent reaction to critical thiol groups for the opening of membrane permeability transition-dependent pores.

DOI： 10.1271/bbb.69.2439

A fermented grain food product extract ameliorates tumor promoter-induced skin oxidative stress Reviewed

Y Nakamura, T Osawa

FOOD SCIENCE AND TECHNOLOGY RESEARCH 11 ( 4 ) 373 - 375 2005.12

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：KARGER

We demonstrated that a dietary supplement, Antioxidant Biofactor (AOB (R)), a fermented grain food, inhibits phorbol ester (TPA)-induced inflammatory responses. Pretreatment of mouse skin with ethyl acetate extract of AOB (0.5 mg) significantly attenuated the hydrogen peroxide level in mouse skin without inhibition of edema formation. Also, exposure of AOB extract to differentiated HL-60 cells resulted in dose-dependent inhibition of TPA-induced superoxide generation, which was stronger than those of the raw materials of AOB. Our results suggest that AOB is effective for prevention of skin oxidative stress.

DOI： 10.3136/fstr.11.373

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