Faculty Profiles - NAKAMURA Yoshimasa

Papers - NAKAMURA Yoshimasa

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Benzyl isothiocyanate ameliorates lipid accumulation in 3T3-L1 preadipocytes during adipocyte differentiation. Reviewed

Liang Y, Sasaki I, Takeda Y, Zhu B, Munemasa S, Nakamura T, Murata Y, Nakamura Y

Bioscience, biotechnology, and biochemistry 82 ( 12 ) 2130 - 2139 2018.12

Authorship：Last author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Oxford University Press (OUP)

<title>ABSTRACT</title>
Benzyl isothiocyanate (BITC) is an organosulfur compound derived from cruciferous vegetables and papaya seeds. In this study, we investigated the effect of BITC on the lipid accumulation in 3T3-L1 preadipocytes during adipocyte differentiation. The treatment of BITC during the differentiation-inducing stage significantly ameliorated the lipid accumulation, whereas it had no inhibitory effect during the differentiation-maintaining stage. BITC also significantly suppressed the mRNA expression of the adipocyte-specific markers, such as CCAAT/enhancer-binding protein α (C/EBPα), C/EBPβ, C/EBPδ and peroxisome proliferator-activated receptor γ. BITC significantly inhibited the phosphorylation of extracellular signal-regulated kinase phosphorylation, whereas it enhanced that of AMP-activated protein kinase. Furthermore, BITC significantly suppressed the intracellular 2-deoxyglucose uptake as well as glucose transporter 4 expression. These results suggest that inhibition of the adipocyte differentiation and glucose uptake may mainly contribute to the inhibitory effect of BITC on the lipid accumulation in 3T3-L1 preadipocytes.

Abbreviations: PPARγ: peroxisome proliferator-activated receptor γ; CEBP: CCAAT/enhancer-binding protein; GLUT4: glucose transporter 4; AMPK: AMP-activated protein kinase; ERK1/2: extracellular signal-regulated kinase 1/2; MAPK: a mitogen-activated protein kinase; ITCs: isothiocyanates; BITC: benzyl isothiocyanate; FBS: fetal bovine serum; CS: calf serum; AITC: allyl ITC; IBMX: 3-isobutyl-1-methylxanthine; LDH: lactate dehydrogenase; KRH: Krebs-Ringer-Hepes-bicarbonate; 2-DG: 2-deoxy-d-glucose

DOI： 10.1080/09168451.2018.1514247

Oxidative stress involved in textural changes of sea cucumber Stichopus japonicus body wall during low-temperature treatment. Reviewed

Dong X, Qi H, Feng D, He B, Nakamura Y, Yu C, Zhu B

Int. J. Food Prop. 21 ( 1 ) 2646 - 2659 2018.12

Methyl-β-cyclodextrin potentiates the BITC-induced anti-cancer effect through modulation of the Akt phosphorylation in human colorectal cancer cells. Reviewed

Yang Q, Miyagawa M, Liu X, Zhu B, Munemasa S, Nakamura T, Murata Y, Nakamura Y

Bioscience, biotechnology, and biochemistry 82 ( 12 ) 2158 - 2167 2018.12

Authorship：Last author,　Corresponding author Publishing type：Research paper (scientific journal) Publisher：Oxford University Press (OUP)

<title>ABSTRACT</title>
Methyl-β-cyclodextrin (MβCD) is an effective agent for the removal of plasma membrane cholesterol. In this study, we investigated the modulating effects of MβCD on the antiproliferation induced by benzyl isothiocyanate (BITC), an ITC compound mainly derived from papaya seeds. We confirmed that MβCD dose-dependently increased the cholesterol level in the medium, possibly through its removal from the plasma membrane of human colorectal cancer cells. The pretreatment with a non-toxic concentration (2.5 mM) of MβCD significantly enhanced the BITC-induced cytotoxicity and apoptosis induction, which was counteracted by the cholesterol supplementation. Although BITC activated the phosphoinositide 3-kinase (PI3K)/Akt pathway, MβCD dose-dependently inhibited the phosphorylation level of Akt. On the contrary, the treatment of MβCD enhanced the phosphorylation of mitogen activated protein kinases, but did not potentiate their BITC-induced phosphorylation. These results suggested that MβCD might potentiate the BITC-induced anti-cancer by cholesterol depletion and thus inhibition of the PI3K/Akt-dependent survival pathway.

Abbreviations: CDs: cyclodextrins; MβCD: methyl-β-cyclodextrin; ITCs: isothiocyanates; BITC: benzyl isothiocyanate; PI3K: phosphoinositide 3-kinase; PDK1: phosphoinositide-dependent kinase-1; MAPK: mitogen activated protein kinase; ERK1/2: extracellular signal-regulated kinase1/2; JNK: c-Jun N-terminal kinase; PI: propidium iodide; FBS: fatal bovine serum; TLC: thin-layer chromatography; PBS(-): phosphate-buffered saline without calcium and magnesium; MEK: MAPK/ERK kinase; PIP2: phosphatidylinositol-4,5-bisphosphate; PIP3: phosphatidylinositol-3,4,5-trisphosphate

DOI： 10.1080/09168451.2018.1514249

Lycii fructus extract ameliorates hydrogen peroxide-induced cytotoxicity through indirect antioxidant action. Reviewed

Xu W, Saiki S, Myojin T, Liu Y, Zhu B, Murata Y, Ashida H, Tsunenaga M, Nakamura Y

Bioscience, biotechnology, and biochemistry 82 ( 10 ) 1812 - 1820 2018.10

Guard Cell Salicylic Acid Signaling Is Integrated into Abscisic Acid Signaling via the Ca²⁺/CPK-Dependent Pathway. Reviewed

Prodhan MY, Munemasa S, Nahar MN, Nakamura Y, Murata Y

Plant physiology 178 ( 1 ) 441 - 450 2018.9

Lymphatic metabolites of quercetin after intestinal administration of quercetin-3-glucoside and its aglycone in rats Reviewed

Toshiyuki Nakamura, Chinatsu Kinjo, Yoshimasa Nakamura, Yoji Kato, Miyu Nishikawa, Masahiro Hamada, Noriyuki Nakajima, Shinichi Ikushiro, Kaeko Murota

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS 645 126 - 136 2018.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE INC

Quercetin is a major flavonoid, present as its glycosidic forms in plant foods. In this study, quercetin-3-glucoside (Q3G) was administered intraduodenally to thoracic lymph-cannulated rats, and its lymphatic transport was investigated. The resulting lymphatic and plasma metabolites were identified with LC-MS/MS and compared with those after administration of quercetin aglycone.The total concentration of quercetin metabolites in the lymph was about four times lower than that in the plasma, and quercetin and its methylated form isorhamnetin were detected as their glucuronides, sulfates and diglucuronides both in the lymph and the plasma after Q3G and quercetin administrations. The lymph levels of the glucuronides after Q3G administration were lower than those after quercetin administration, whereas those in the plasma showed the opposite pattern. Both the lymph and plasma levels of the sulfates after Q3G administration were lower than those after quercetin administration. Some of the intestinal metabolites like quercetin monoglucuronides were transported directly into the lymph and the hepatic metabolites like the diglucuronides were eventually transferred from the plasma into the lymph.These results indicate that the absorbed Q3G is partly transported into the intestinal lymph as quercetin metabolites. Deglycosylation in the enterocyte is also suggested to affect the subsequent metabolic pathways.

DOI： 10.1016/j.abb.2018.03.024

Benzyl isothiocyanate attenuates the hydrogen peroxide-induced interleukin-13 expression through glutathione S-transferase P induction in T lymphocytic leukemia cells. Reviewed

Tang Y, Naito S, Abe-Kanoh N, Ogawa S, Yamaguchi S, Zhu B, Murata Y, Nakamura Y

Journal of biochemical and molecular toxicology 32 ( 6 ) e22054 2018.4

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

We investigated the effect of benzyl isothiocyanate (BITC) on the hydrogen peroxide-induced gene expression of a T-helper-2 cytokine, interleukin (IL)-13, in T lymphocytic leukemia Jurkat cells. The 24-h pretreatment of BITC significantly inhibited the IL-13 expression enhanced by hydrogen peroxide. Although the BITC pretreatment did not change the enhanced level of the phosphorylated c-Jun N-terminal kinase (JNK), it significantly inhibited the nuclear translocation of c-Jun induced by hydrogen peroxide. BITC also increased the protein expression of glutathione S-transferase (GST) isozymes, GSTP1/2, as well as the total GST activity. A GSTP1/2 specific inhibitor, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol (NBDHEX), significantly counteracted the inhibitory effect of BITC on the hydrogen peroxide-enhanced IL-13 upregulation as well as the c-Jun nuclear translocation. Taken together, these results suggested that BITC inhibits the oxidative stress-mediated IL-13 mRNA expression, possibly through interference of the c-Jun phosphorylation by GSTP.

DOI： 10.1002/jbt.22054

Phenethyl isothiocyanate activates leptin signaling and decreases food intake. Reviewed International journal

Miho Yagi, Yukiko Nakatsuji, Ayumi Maeda, Hiroki Ota, Ryosuke Kamikubo, Noriyuki Miyoshi, Yoshimasa Nakamura, Mitsugu Akagawa

PloS one 13 ( 11 ) e0206748 2018

Language：English Publishing type：Research paper (scientific journal)

Obesity, a principal risk factor for the development of diabetes mellitus, heart disease, and hypertension, is a growing and serious health problem all over the world. Leptin is a weight-reducing hormone produced by adipose tissue, which decreases food intake via hypothalamic leptin receptors (Ob-Rb) and the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway. Protein tyrosine phosphatase 1B (PTP1B) negatively regulates leptin signaling by dephosphorylating JAK2, and the increased activity of PTP1B is implicated in the pathogenesis of obesity. Hence, inhibition of PTP1B may help prevent and reduce obesity. In this study, we revealed that phenethyl isothiocyanate (PEITC), a naturally occurring isothiocyanate in certain cruciferous vegetables, potently inhibits recombinant PTP1B by binding to the reactive cysteinyl thiol. Moreover, we found that PEITC causes the ligand-independent phosphorylation of Ob-Rb, JAK2, and STAT3 by inhibiting cellular PTP1B in differentiated human SH-SY5Y neuronal cells. PEITC treatment also induced nuclear accumulation of phosphorylated STAT3, resulting in enhanced anorexigenic POMC expression and suppressed orexigenic NPY/AGRP expression. We demonstrated that oral administration of PEITC to mice significantly reduces food intake, and stimulates hypothalamic leptin signaling. Our results suggest that PEITC might help prevent and improve obesity.

DOI： 10.1371/journal.pone.0206748

(-)-Epigallocatechin-3-gallate inhibits human angiotensin-converting enzyme activity through an autoxidation-dependent mechanism Reviewed

Zhe Liu, Sayaka Nakashima, Toshiyuki Nakamura, Shintaro Munemasa, Yoshiyuki Murata, Yoshimasa Nakamura

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY 31 ( 9 ) 2017.9

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

We investigated the molecular mechanisms involved in the angiotensin-converting enzyme (ACE) inhibition by (-)-epigallocatechin-3-gallate (EGCg), a major tea catechin. EGCg inhibited both the ACE activity in the lysate of human colorectal cancer cells and human recombinant ACE (rh-ACE) in a dose-dependent manner. Co-incubation with zinc sulfate showed no influence on the rh-ACE inhibition by EGCg, whereas it completely counteracted the inhibitory effect of ethylenediaminetetraacetic acid, a chelating-type ACE inhibitor. Although hydrogen peroxide was produced by the autoxidation of EGCg, hydrogen peroxide itself had little effect on the ACE activity. Conversely, the co-incubation of EGCg with borate or ascorbic acid significantly diminished the EGCg inhibition. A redox-cycling staining experiment revealed that rh-ACE was covalently modified by EGCg. A Lineweaver-Burk plot analysis indicated that EGCg inhibited the ACE activity in a non-competitive manner. These results suggested that EGCg might allosterically inhibit the ACE activity through oxidative conversion into an electrophilic quinone.

DOI： 10.1002/jbt.21932

Inhibition of phosphatidylinositide 3-kinase ameliorates antiproliferation by benzyl isothiocyanate in human colon cancer cells Reviewed

Xiaoyang Liu, Chiaki Takano, Tomomi Shimizu, Shintaro Yokobe, Naomi Abe-Kanoh, Beiwei Zhu, Toshiyuki Nakamura, Shintaro Munemasa, Yoshiyuki Murata, Yoshimasa Nakamura

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 491 ( 1 ) 209 - 216 2017.9

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

In the present study, we clarified the role of phosphatidylinositide 3-kinase (PI3K) in antiproliferation induced by benzyl isothiocyanate (BITC) in human colorectal cancer cells. BITC simultaneously activated the PI3K/Akt/forkhead box 0 (FoxO) pathway, whereas it significantly inhibited the proliferation in human colorectal cancer cells. Inhibitory experiments using a PI3K selective inhibitor, LY294002 or NVP-BEZ235, significantly enhanced the BITC-induced antiproliferation and apoptotic cell population with the attenuation of the BITC-induced activation of the PI3K/Akt/FoxO survival pathway. Furthermore, BITC enhanced the insulin-activated PI3K/Akt/FoxO pathway, possibly through its inhibition of the protein tyrosine phosphatase 1B enzymatic activity. Taken together, these results suggested that the PI3K/Akt/FoxO pathway negatively regulates the BITC-induced antiproliferation in human colorectal cancer cells. (C) 2017 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2017.07.078

Methylglyoxal induces inhibition of growth, accumulation of anthocyanin, and activation of glyoxalase I and II in Arabidopsis thaliana Reviewed

Tahsina Sharmin Hoque, Misugi Uraji, Md Anamul Hoque, Yoshimasa Nakamura, Yoshiyuki Murata

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY 31 ( 7 ) 2017.7

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

Methylglyoxal (MG) is a highly reactive stress-related -ketoaldehyde and a physiological metabolite of glycolysis, which is accumulated in ample amount under stressful conditions. In the present study, the effect of different doses of MG on growth, anthocyanin production, MG contents, and activities of two types of glyoxalases (glyoxalase I and glyoxalase II) were examined in Arabidopsis seedlings. MG at 0.1 mM dose did not affect seedling growth, anthocyanin accumulation, MG contents, or activities of glyoxalases, whereas MG at 0.5 mM and 1 mM inhibited seedling growth and induced anthocyanin accumulation, MG accumulation, and glyoxalase (both I and II) activation. Therefore, MG can reduce plant growth as a toxic molecule and can stimulate stress responses as a signal molecule under stress conditions.

DOI： 10.1002/jbt.21901

Cytotoxic and cytoprotective effects of tryptamine-4,5-dione on neuronal cells: a double-edged sword Reviewed

Naoko Suga, Akira Murakami, Yoshimasa Nakamura, Akari Ishisaka, Noritoshi Kitamoto, Mikiko Ito, Yoji Kato

FREE RADICAL RESEARCH 51 ( 5 ) 545 - 553 2017

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

Serotonin (5-hydroxytryptamine) is a putative substrate for myeloperoxidase, which may convert it into the reactive quinone tryptamine-4,5-dione (TD). In this study, we found that the viability of human SH-SY5Y neuroblastoma cells treated with 25 mu M TD was increased to approximately 117%. On the other hand, the cell viability was significantly decreased by exposure to TD (150-200 mu M), with an increase in intracellular reactive oxygen species (ROS). Interestingly, pretreatment of SH-SY5Y cells with 100 mu M TD prevented cell death and suppressed intracellular ROS generation evoked by the addition of hydrogen peroxide (H2O2). Expression of the phase-II antioxidant enzyme NAD(P)H: quinone oxidoreductase 1 and haem oxygenase 1 were upregulated by TD at a concentration of 50-100 mu M. Nuclear factor erythroid 2-related factor 2 (Nrf2), the regulator of these enzyme, was translocated from the cytosol to the nucleus by 100 mu M TD. In summary, moderate concentrations of TD may increase the self-defence capacity of neuronal cells against oxidative stress.

DOI： 10.1080/10715762.2017.1331038

Inhibition of phosphatidylinositide 3-kinase impairs the benzyl isothiocyanate-induced accumulation of autophagic molecules and Nrf2 in human colon cancer cells Reviewed

Xiaoyang Liu, Naomi Abe-Kanoh, Yujia Liu, Beiwei Zhu, Shintaro Munemasa, Toshiyuki Nakamura, Yoshiyuki Murata, Yoshimasa Nakamura

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 81 ( 11 ) 2212 - 2215 2017

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

The regulating role of phosphatidylinositide 3-kinase (PI3K) in benzyl isothiocyanate (BITC)-induced Nrf2 activation, contributing to the inducible expression of cytoprotective genes, was investigated. BITC significantly enhanced the accumulation of Nrf2 as well as autophagic molecules in human colorectal cancer HCT-116 cells. Experiments using a PI3K-specific inhibitor suggested that PI3K plays the key role in the non-canonical Nrf2 activation by BITC.

DOI： 10.1080/09168451.2017.1374830

3,4-Dihydroxyphenylacetic acid is a potential aldehyde dehydrogenase inducer in murine hepatoma Hepa1c1c7 cells Reviewed

Yujia Liu, Ayuki Kurita, Sayaka Nakashima, Beiwei Zhu, Shintaro Munemasa, Toshiyuki Nakamura, Yoshiyuki Murata, Yoshimasa Nakamura

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 81 ( 10 ) 1978 - 1983 2017

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

3,4-Dihydroxyphenylacetic acid (DOPAC) is one of the major colonic microflora-produced catabolites of quercetin glycosides, such as quercetin 4-glucoside derived from onion. Here, we investigated whether DOPAC modulates the aldehyde dehydrogenase (ALDH) activity and protects the cells from the acetaldehyde-induced cytotoxicity in vitro. DOPAC was shown to enhance not only the total ALDH activity, but also the gene expression of ALDH1A1, ALDH2 and ALDH3A1 in a concentration-dependent manner. DOPAC simultaneously stimulated the nuclear translocation of NFE2-related factor 2 and aryl hydrocarbon receptor. The pretreatment of DOPAC completely protected the cells from the acetaldehyde-induced cytotoxicity. The present study suggested that DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.

DOI： 10.1080/09168451.2017.1361809

MPK9 and MPK12 function in SA-induced stomatal closure in Arabidopsis thaliana Reviewed

Md. Atiqur Rahman Khokon, Mohammad Abdus Salam, Fabien Jammes, Wenxiu Ye, Mohammad Anowar Hossain, Eiji Okuma, Yoshimasa Nakamura, Izumi C. Mori, June M. Kwak, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 81 ( 7 ) 1394 - 1400 2017

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

Salicylic acid (SA) induces stomatal closure sharing several components with abscisic acid (ABA) and methyl jasmonate (MeJA) signaling. We have previously shown that two guard cell-preferential mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate ABA signaling and MeJA signaling in Arabidopsis thaliana. In this study, we examined whether these two MAPKs are involved in SA-induced stomatal closure using genetic mutants and a pharmacological, MAPKK inhibitor. Salicylic acid induced stomatal closure in mpk9 and mpk12 single mutants but not in mpk9 mpk12 double mutants. The MAPKK inhibitor PD98059 inhibited SA-induced stomatal closure in wild-type plants. Salicylic acid induced extracellular reactive oxygen species (ROS) production, intracellular ROS accumulation, and cytosolic alkalization in the mpk9, mpk12, and mpk9 mpk12 mutants. Moreover, SA-activated S-type anion channels in guard cells of wild-type plants but not in guard cells of mpk9 mpk12 double mutants. These results imply that MPK9 and MPK12 are positive regulators of SA signaling in Arabidopsis guard cells.

DOI： 10.1080/09168451.2017.1308244

Exogenous proline enhances the sensitivity of Tobacco BY-2 cells to arsenate Reviewed

Mst Nur-E-Nazmun Nahar, Mohammad Muzahidul Islam, Md. Anamul Hoque, Anna Yonezawa, Md. Yeasin Prodhan, Toshiyuki Nakamura, Yoshimasa Nakamura, Shintaro Munemasa, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 81 ( 9 ) 1726 - 1731 2017

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

Arsenic causes physiological and structural disorders in plants. Proline is accumulated as a compatible solute in plants under various stress conditions and mitigates stresses. Here, we investigated the effects of exogenous proline on tobacco Bright Yellow-2 (BY-2) cultured cells under AsO4- stress. Arsenate did not inhibit BY-2 cell growth at 40 and 50 mu M but did it at 60 mu M. Proline at 0.5 to 10 mM did not affect the cell growth but delayed it at 20 mM. At 40 mu M AsO4-, neither 0.5 mM nor 1 mM proline affected the cell growth but 10 mM proline inhibited it. In the presence of AsO4-, 10 mM proline increased the number of Evans Blue-stained (dead) cells and decreased the number of total cells. Together, our results suggest that exogenous proline does not alleviate arsenate toxicity but enhances the sensitivity of BY-2 cells to arsenate.

DOI： 10.1080/09168451.2017.1340088

Chitosan signaling in guard cells requires endogenous salicylic acid Reviewed

Md. Yeasin Prodhan, Mohammad Issak, Toshiyuki Nakamura, Shintaro Munemasa, Yoshimasa Nakamura, Yoshiyuki Murata

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 81 ( 8 ) 1536 - 1541 2017

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

An elicitor chitosan (CHT) induces stomatal closure but the mechanism remains to be clarified. A phytohormone salicylic acid (SA) is crucial for elicitor-induced defense signaling in plants. Here we investigated whether endogenous SA is required for CHT signaling in guard cells. In the SA-deficient nahG mutant, treatment of CHT did not induce either apoplastic reactive oxygen species (ROS) production or stomatal closure but co-treatment of CHT and SA induced both apoplastic ROS production and stomatal closure, indicating the involvement of endogenous SA in CHT-induced apoplastic ROS production and CHT-induced stomatal closure. Furthermore, CHT induced transient cytosolic free calcium concentration increments in the nahG mutant in the presence of exogenous SA but not in the absence of exogenous SA. These results provide evidence that endogenous SA is a crucial element in CHT-induced stomatal closure.

DOI： 10.1080/09168451.2017.1332979

Reactive Carbonyl Species Mediate ABA Signaling in Guard Cells Reviewed

Md. Moshiul Islam, Wenxiu Ye, Daiki Matsushima, Shintaro Munemasa, Eiji Okuma, Yoshimasa Nakamura, Md. Sanaullah Biswas, Jun'ichi Mano, Yoshiyuki Murata

PLANT AND CELL PHYSIOLOGY 57 ( 12 ) 2552 - 2563 2016.12

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

Drought is responsible for a massive reduction in crop yields. In response to drought, plants synthesize the hormone ABA, which induces stomatal closure, thus reducing water loss. In guard cells, ABA triggers production of reactive oxygen species (ROS), which is mediated by NAD(P) H oxidases. The production of ROS is a key factor for ABA-induced stomatal closure, but it remains to be clarified how the production of ROS is transduced into downstream signaling components in guard cells. We investigated roles of reactive carbonyl species (RCS) in ABA-induced stomatal closure using transgenic tobacco (Nicotiana tabacum) overexpressing Arabidopsis 2-alkenal reductase (AER-OE), which scavenges RCS. ABA and hydrogen peroxide (H2O2) induced accumulation of RCS including acrolein and 4-hydroxy-(E)-2-nonenal in wild-type tobacco but not in AER-OE. Stomatal closure and RCS accumulation in response to ABA and H2O2 were inhibited in AER-OE unlike in the wild type, while ABA-induced H2O2 production in guard cells was observed in AER-OE as well as in the wild type. Moreover, ABA inhibited inward-rectifying K+ channels in wild-type guard cells but not in AER-OE guard cells. These results suggest that RCS is involved in ABAinduced stomatal closure and functions downstream of H2O2 production in the ABA signaling pathway in guard cells.

DOI： 10.1093/pcp/pcw166

Galloylated Catechins as Potent Inhibitors of Angiotensin Converting Enzyme Reviewed

Zhe Liu, Toshiyuki Nakamura, Shintaro Munemasa, Yoshiyuki Murata, Yoshimasa Nakamura

FOOD SCIENCE AND TECHNOLOGY RESEARCH 22 ( 6 ) 847 - 851 2016.11

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

In the present study, we investigated the inhibitory effects of four tea catechins, including (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg), on angiotensin converting enzyme (ACE) activity in vitro. Each catechin treatment significantly reduced the ACE activity with the order of potency being EGCg > ECg > EGC = EC. The addition of 1 mM borate significantly recovered the reduced ACE activities by tea catechins, suggesting that hydroxyl groups at the B-ring or at a galloyl moiety play an important role in the ACE-inhibitory mechanism. The covalent modification of ACE by tea catechins was also observed by a redox-cycling staining experiment. A Lineweaver-Burk plot indicated that EGC and ECg were noncompetitive inhibitors. The galloylated catechins might more potently inhibit ACE activity in an allosteric manner through the interaction of the galloyl moiety with the non-catalytic site of ACE.

DOI： 10.3136/fstr.22.847

A novel tag-free probe for targeting molecules interacting with a flavonoid catabolite Reviewed

Sayaka Nakashima, Zhe Liu, Yuya Yamaguchi, Shunya Saiki, Shintaro Munemasa, Toshiyuki Nakamura, Yoshiyuki Murata, Yoshimasa Nakamura

Biochemistry and Biophysics Reports 7 240 - 245 2016.9

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.

3,4-Dihydroxyphenylacetic acid (DOPAC) is one of the colonic microflora-produced catabolites of quercetin 4'-glucoside (Q4'G). Although the interaction of DOPAC with cellular proteins might be involved in its biological activity, the actual proteins have not yet been identified. In this study, we developed a novel tag-free DOPAC probe to label the targeted proteins by the copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) and verified its efficacy. Various labeled proteins were detected by the DOPAC probe with the azide labeled biotin and a horseradish peroxidase (HRP)-streptavidin complex. Furthermore, a pulldown assay identified Keap1 and aryl hydrocarbon receptor (AhR) as the target proteins for the phase 2 enzyme up-regulation.

DOI： 10.1016/j.bbrep.2016.06.020

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