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Research Interests 【 display / non-display 】

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• Biology and Biochemistry of Reactive Oxygen, Nitrogen, Sulfur species

• Antioxidant system in Plants

• Bioremedation in Subtropical Environment

• Study on the mechanisms of coral bleaching

Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• Pleiotropic Functions of Nitric Oxide Produced by Ascorbate for the Prevention and Mitigation of COVID-19: A Revaluation of Pauling's Vitamin C Therapy.

  Yamasaki H, Imai H, Tanaka A, Otaki JM

  Microorganisms ( Microorganisms )  11 ( 2 ) 397   2023.02 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Linus Pauling, who was awarded the Nobel Prize in Chemistry, suggested that a high dose of vitamin C (L-ascorbic acid) might work as a prevention or treatment for the common cold. Vitamin C therapy was tested in clinical trials, but clear evidence was not found at that time. Although Pauling’s proposal has been strongly criticized for a long time, vitamin C therapy has continued to be tested as a treatment for a variety of diseases, including coronavirus infectious disease 2019 (COVID-19). The pathogen of COVID-19, SARS-CoV-2, belongs to the β-coronavirus lineage, which includes human coronavirus, severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS). This review intends to shed new light on vitamin C antiviral activity that may prevent SARS-CoV-2 infection through the chemical production of nitric oxide (NO). NO is a gaseous free radical that is largely produced by the enzyme NO synthase (NOS) in cells. NO produced by upper epidermal cells contributes to the inactivation of viruses and bacteria contained in air or aerosols. In addition to enzymatic production, NO can be gener-ated by the chemical reduction of inorganic nitrite (NO2−), an alternative mechanism for NO production in living organisms. Dietary vitamin C, largely contained in fruits and vegetables, can reduce the nitrite in saliva to produce NO in the oral cavity when chewing foods. In the stomach, salivary nitrite can also be reduced to NO by vitamin C secreted from the epidermal cells of the stomach. The strong acidic pH of gastric juice facilitates the chemical reduction of salivary nitrite to produce NO. Vitamin C contributes in multiple ways to the host innate immune system as a first-line defense mechanism against pathogens. Highlighting chemical NO production by vitamin C, we suggest that controversies on the therapeutic effects of vitamin C in previous clinical trials may partly be due to less appreciation of the pleiotropic functions of vitamin C as a universal bioreductant.

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• Phytochemical Antioxidants: Past, Present and Future

  Yasuko Sakihama, Hideo Yamasaki

  Antioxidants - Benefits, Sources, Mechanisms of Action ( IntechOpen )    2021.01 [ Peer Review Accepted ]

  Type of publication: Research paper (other science council materials etc.)

  　View Summary

  Most diseases that are difficult to prevent and cure are “syndromes" that are governed by multiple components with complicated interactions. Whatever the cause of such diseases, overproduction of harmful reactive oxygen species (ROS) can often be observed in progression of the disease. Under such conditions, the cells may be challenged by “oxidative stress" due to excessively generated oxidants. Antioxidants can be defined as chemical compounds that scavenge ROS or free radicals over-produced in the cells under oxidative stress conditions. The plant pigments flavonoids and betalains, rich in fruits and vegetables, are reactive not only with ROS but also with reactive nitrogen species (RNS) and possibly with reactive sulfur species (RSS). Here, we provide an overview of updates on the antioxidative functions of the plant pigments along with some prospects for future research on phytochemical antioxidants.

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• Blood nitrate and nitrite modulating nitric oxide bioavailability: Potential therapeutic functions in COVID-19.

  Yamasaki H

  Nitric oxide : biology and chemistry ( Elsevier BV )  103   29 - 30   2020.10 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Most outcomes of COVID-19 are associated with dysfunction of the vascular system, particularly in the lung. Inhalation of nitric oxide (NO) gas is currently being investigated as a treatment for patients with moderate to severe COVID-19. In addition to the expected vasodilation effect, it has been also suggested that NO potentially prevents infection by SARS-CoV-2. Since NO is an unstable radical molecule that is easily oxidized by multiple mechanisms in the human body, it is practically difficult to control its concentration at lesions that need NO. Inorganic nitrate and/or nitrite are known as precursors of NO that can be produced through chemical as well enzymatic reduction. It appears that this NO synthase (NOS)-independent mechanism has been overlooked in the current developing of clinical treatments. Here, I suggest the missing link between nitrate and COVID-19 in terms of hypoxic NO generation.

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• D-Cysteine-Induced Rapid Root Abscission in the Water Fern Azolla Pinnata: Implications for the Linkage between D-Amino Acid and Reactive Sulfur Species (RSS) in Plant Environmental Responses.

  Yamasaki H, Ogura MP, Kingjoe KA, Cohen MF

  Antioxidants ( Antioxidants )  8 ( 9 )   2019.09 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) have been proposed as universal signaling molecules in plant stress responses. There are a growing number of studies suggesting that hydrogen sulfide (H#D2#DRS) or Reactive Sulfur Species (RSS) are also involved in plant abiotic as well as biotic stress responses. However, it is still a matter of debate as to how plants utilize those RSS in their signaling cascades. Here, we demonstrate that d-cysteine is a novel candidate for bridging our gap in understanding. In the genus of the tiny water-floating fern #IAzolla#IR, a rapid root abscission occurs in response to a wide variety of environmental stimuli as well as chemical inducers. We tested five H#D2#DRS chemical donors, Na#D2#DRS, GYY4137, 5a, 8l, and 8o, and found that 5a showed a significant abscission activity. Root abscission also occurred with the polysulfides Na#D2#DRS#D2#DR, Na#D2#DRS#D3#DR, and Na#D2#DRS#D4#DR. Rapid root abscission comparable to other known chemical inducers was observed in the presence of d-cysteine, whereasLl-cysteine showed no effect. We suggest that D-cysteine is a physiologically relevant substrate to induce root abscission in the water fern #IAzolla#IR.

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• Dynamics of nitrite content in fresh spinach leaves: evidence for nitrite formation caused by microbial nitrate reductase activity

  Naoko S Watanabe, Hideo Yamasaki

  Journal of Nutrition & Food Sciences   7   1 - 7   2017.02 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Nitrite (NO#D2#DR#U-#UR) contained in dietary foods has long been recognized for its toxicity as the causative agent of methemoglobinemia and also as a source of mutagenic nitrosamines. Because of these potential toxicities, nitrite as well as nitrate contained in foods and drinks are strictly limited by regulations in many countries. Recent studies have offered us to update our recognition of nitrite; nitrite is an important precursor for nitric oxide (NO) that is required for fundamental physiological activities including vasorelaxation. Although it is well established that green vegetables contain high amounts of nitrate, there has been controversy regarding the source of nitrite accumulation in fresh green vegetables. In this study, we investigated the dynamics of nitrite and nitrate contents in spinach leaf extracts to verify the mechanisms of nitrite formation. The time course of nitrite production in leaf extracts showed a reciprocal relationship with nitrate degradation, suggesting a conversion from nitrate to nitrite. The reaction strongly depended on temperature and it was suppressed at a low temperature. Sodium tungstate, a nitrate reductase enzyme inhibitor, was effective to suppress the conversion. Pre-sterilization by autoclaving or filter sterilization completely prevented the formation of nitrite as well as degradation of nitrate. We suggest that previous reports of nitrite accumulation can be attributed to microbial nitrate reductase activities that occur during the degradation spinach leaves.

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Books 【 display / non-display 】

Books 【 display / non-display 】

• Antioxidants - Benefits, Sources, Mechanisms of Action

  Sakihama Y, Yamasaki H ( Part: Allotment Writing ,  Phytochemical Antioxidants: Past, Present and Future )

  IntechOpen  2021.01

• Plant organ abscission: from models to crops

  Michael F Cohen, Sushma Gurung, Giovanni Birarda, Hoi-Ying N Holman, Hideo Yamasaki ( Part: Multiple Authorship ,  Bimodal effect of hydrogen peroxide and oxidative events in nitrite-induced rapid root abscission by the water fern Azolla pinnata )

  Frontiers in Plant Science  2017

• Oxidative stress in applied basic research and clinical practice: studies on pediatric disorders

  Yamasaki H, Watanabe NS, Fukuto J, Cohen MF ( Part: Multiple Authorship ,  Nitrite-dependent nitric oxide production pathway: diversity of NO production systems, )

  Springer  2014

• New trends in Okinawan academia 4

  Oshiro S, Oshiro H, Oyakawa K, Yamasaki H, Kawamoto Y, Kina I ( Part: Joint Editing and Writing )

  Okinawa Times  2012.03

• Annual Plant Reviews Volume 42, Nitrogen Metabolism plants in the Post-Genomic Era

  Yamasaki H, Itoh RD, Bouchard JN, Dghim AA, Hossain KK, Gurung, S, Cohen MF ( Part: Multiple Authorship ,  Nitric oxide synthase-like activities in plants )

  Wiley-Blackwell Publishing  2011

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Other Papers 【 display / non-display 】

Other Papers 【 display / non-display 】

• Pleiotropic roles of vitamin C in prevention of COVID-19: How to prevent oral infection of the novel coronavirus

  Hideo Yamasaki

    59 ( 4 ) 165 - 167   2021.04  [Refereed]

   

• Nitrate Paradox in Human Health: Research History of the Reductive Pathway for NO Production

  Hideo Yamasaki

  KASEAA   57 ( 11 ) 686 - 688   2019.11  [Refereed]

   

• Comment 1

  Hideo Yamasaki

  Journal of Tourism Sciences   8   59 - 60   2017.07

   

  DOI

• Nitric oxide research, a key to integrate life and environmental sciences

  Hideo Yamasaki

  Proceedings of US Japan Society for the Promotion of Science Alumni Association ( US JSPS Alumni Association )    14 - 15   2011.03

   

• Long-term effect of eutrophication on the growth and photosynthesis of the reef-building corals stylophora pistillata and Acropora spp.

  Yuen, TS, Yamazaki SS, Nakamura T, Yamasaki H

  琉球大学21世紀COEプログラム「サンゴ礁島嶼系の生物多様性の総合解析」報告書 ( 琉球大学21世紀COEプログラム )    2008.03

   

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Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Escaping troubled waters: An animal-like stimulus-response behavior in a model plant

  Michael F Cohen, Hideo Yamasaki

  The 12th International NO Conference  2022.10  -  2022.11 

• Yin-Yang of bioactive gaseous molecules: Bridging the gap between Western science and traditional Eastern philosophies

  Hideo Yamasaki

  Special Lecture  (Chinese Culture University, Taiwan)  2018.05  -  2018.05 

• ONS biology for bridging the gaps

  Hideo Yamasaki

  9th International Conference on the Biology, Chemistry, and Therapeutic Applications of Nitric Oxide  (Sendai International Center, Sendai, Japan)  2016.05  -  2016.05 

• Nitric oxide research in living organisms

  Hideo Yamasaki

  Special Lecture  (Chinese Culture University, Taiwan)  2014.11  -  2014.11 

• Nitrite as a crossroad of multidisciplines: its past, present and future

  Hideo Yamasaki

  The International Symposium on Food, Nutrition and Vascular Function 2013  ( Tokushima, Japan)  2013.12  -  2013.12 

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Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2019.04  -  2022.03 

  Investigator(s): Hideo Yamasaki 

  Direct: 3,300,000 (YEN)  Overheads: 990,000 (YEN)  Total: 4,290,000 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2015.04  -  2018.03 

  Investigator(s): Hideo Yamasaki 

  Direct: 13,000,000 (YEN)  Overheads: 3,900,000 (YEN)  Total: 16,900,000 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2015.04  -  2018.03 

  Direct: 13,000,000 (YEN)  Overheads: 16,900,000 (YEN)  Total: 3,900,000 (YEN)

• Grant-in-Aid for Scientific Research(B)

  Project Year: 2011.04  -  2014.03 

  Investigator(s): Hideo Yamasaki 

  Direct: 9,700,000 (YEN)  Overheads: 2,910,000 (YEN)  Total: 12,610,000 (YEN)

• Grant-in-Aid for JSPS Fellows

  Project Year: 2007.04  -  2010.03 

  Investigator(s): Takashi Nakamura 

  Direct: 3,300,000 (YEN)  Total: 3,300,000 (YEN)

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Social Activity 【 display / non-display 】

Social Activity 【 display / non-display 】

• 2015.07

  -

  2017.03

• 2015.07

  -

  2017.03

• 2014.11

  　

  　

• 2014.08

  　

  　

• 2012.09

  -

  2015.03

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Media Coverage 【 display / non-display 】

Media Coverage 【 display / non-display 】

• 沖縄県自然環境再生指針検討委員会 委員長

  沖縄県  2014.7

Academic Activities 【 display / non-display 】

Academic Activities 【 display / non-display 】

• 日本NO学会 

  2016.6

  　

  　

• 沖縄科学技術大学院大学(OIST) 

  2014.11

  　

  　

• 沖縄県 

  2014.8

  　

  　

• 日本植物学会 

  2013.1

  -

  2018.12

  種別： Academic society, research group, etc. 

• 沖縄県産業振興公社 

  2012.5

  -

  2013.3

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