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Professor Akira Tsuji: Scientist, Educator, and Leader
COMMENTARY Professor Akira Tsuji: Scientist, Educator, and Leader TETSUYA TERASAKI,1 YUICHI SUGIYAMA,2 LESLIE Z. BENET3 1
Department of Biochemical Pharmacology and Therapeutics, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan 2 Department of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 3
Department of Bioengineering and Therapeutic Sciences, Schools of Pharmacy and Medicine, University of California, San Francisco, California 94103-0912 Received 5 May 2011; accepted 6 May 2011 Published online 31 May 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jps.22638
INTRODUCTION This issue of the Journal of Pharmaceutical Science is specially dedicated to honor Emeritus Professor Akira Tsuji following his retirement from Kanazawa University, to celebrate his enormous contributions to research and education in the field of pharmaceutical science, and it is a great privilege to have this opportunity to write a commentary on his achievements and successes. Dr. Tsuji served for 42 years at Kanazawa University and retired on March 31, 2010. During his 28 years as a full professor, Akira Tsuji was a thoughtful mentor to his many students, who altogether received 92 Bachelor’s, 85 Master’s, and 28 PhD degrees under his guidance. He greatly inspired both his students and his collaborators, many of whom went on to make important contributions in many fields, including academia, industry, government, hospital medicine, and pharmacy. Those who know Professor Tsuji will be aware of his strong passion for research and education and his warm and unforgettable personality. In this Commentary, we are proud to catalogue his many and significant achievements.
KANAZAWA CITY AS THE CRADLE Akira Tsuji was born in Kanazawa city, Japan, in 1942 and was accepted as a student by the Faculty of Pharmaceutical Science, Kanazawa University, in 1962. As we introduce Dr. Tsuji, we cannot forget the Correspondence to: Tetsuya Terasaki (Telephone: +81-22795-6831; Fax: +81-22-795-6886; E-mail: [email protected]. tohoku.ac.jp) Journal of Pharmaceutical Sciences, Vol. 100, 3541–3546 (2011) © 2011 Wiley-Liss, Inc. and the American Pharmacists Association
Professor Akira Tsuji
place where he lives and has worked. Kanazawa city, which has a population of 462,000, is not only well known as a tourist city, but is also a home of 12 universities. It was established more than 400 years ago by Toshiie Maeda (1539–1599), the lord of Kaga (the old name of Ishikawa prefecture), who was an eminent daimyo during the Azuchimomoyama period. Lord Maeda was one of the leading generals of Oda Nobunaga, who initiated the unification of Japan; he also made great efforts to educate the people, helping Kanazawa to prosper as a city of traditional arts and craft, as it still is today. Kanazawa is called “little Kyoto” and attracts visitors from all over the world. It is noteworthy that the Faculty of Pharmaceutical Sciences of Kanazawa University has the longest history of any Faculty of Pharmaceutical Sciences in Japan. It was established in July 1867 by the 14th
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lord, Yoshiyasu Maeda, who founded a pharmacy in a public hospital to provide practical service and education, including lectures on galenics (now pharmaceutics), chemistry, and botany. When Akira Tsuji studied there as a junior student, the main campus of Kanazawa University was located within the beautiful castle wall, only 10 min walk from his house, which is in the central district of Samurai houses. As a junior student, he also showed great talent for music and was a member of an amateur band.
ONCE-IN-A-LIFETIME OPPORTUNITY When Akira Tsuji became a senior student, he encountered Professor Tsukinaka Yamana (who died in 2009) and found him an inspiring mentor. Tsukinaka Yamana had graduated from the Faculty of Pharmaceutical Sciences, University of Tokyo, and had published an interesting paper entitled “Studies on nonfermentative constituents of starch sugar. II. A method of estimation of 6-alpha-glucosylglucogen and gentiobiose formed from glucose” in 1950, in Japanese; this was the first paper reporting the results of chemical kinetics.1 Coincidentally, Professor Takeru Higuchi, the father of modern day pharmaceutics in the United States, also published a paper entitled “The kinetics of the hydrolysis of procaine” in the same year.2 Akira Tsuji enjoyed both mathematics and physical chemistry, and thanks to the inspiring lectures of Professor Yamana, he became very interested in the study of chemical kinetics as a basis for understanding drug stability in solution.
MOVING FROM PHYSICAL PHARMACY TO BIOPHARMACY Akira Tsuji published his first paper on the stability of benzothiadiazines,3 and after receiving his Master’s degree in 1968, he was immediately appointed a Research Associate in the laboratory of Professor Yamana at Kanazawa University. In a series of studies, he worked to clarify the mechanisms of intramolecular hydrolysis and chose to apply his research background to elucidate the degradation mechanism of beta-lactam antibiotics in aqueous solution. He was successful in this endeavor,4,5 and received his PhD degree from the University of Tokyo in 1976. The title of his thesis was “Chemical kinetic study on stability of beta-lactam antibiotics in aqueous solution.” In the same year, he became an associate professor of Kanazawa University. Tetsuya Terasaki, a coauthor of this Commentary, started his undergraduate research in the laboratory of Professor Yamana and Associate Professor Tsuji in that year. Terasaki clearly remembers that on the day he started his research, Dr. Tsuji proposed a quite new research project, changing his research focus from chemical kinetics to pharmacokinetics. This typified Professor JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
Tsuji, who always showed a farseeing intelligence in proposing new research projects and always asked his students and colleagues what they thought essential and original, resulting in truly innovative research projects. He felt that it was important to challenge difficult problems, and he thought that if they could be solved, the solution provided an unforgettable feeling of achievement. It was, therefore, natural and innovative of Professor Tsuji to begin studies of the small intestinal absorption mechanism of betalactam antibiotics, and he introduced the “permeability clearance concept” for analysis of the absorption rate of beta-lactam antibiotics from the small intestine, thereby separating the degradation rate from the apparent elimination rate in the perfusate of the small intestinal lumen.6 He noted that the absorption rate is dependent on the perfusate volume in the small intestinal lumen, whereas the degradation rate in the solution is independent of the volume. After only 4 years, in 1980, he was appointed full professor.
UNFORGETTABLE TIME WITH FAMILY IN SAN FRANCISCO, CALIFORNIA, AND BUFFALO, NEW YORK Akira Tsuji married Yoko Sumi on March 9, 1969, and has three daughters, Megumi, Izumi, and Machiko, as well as three granddaughters and one grandson. Although he has spent most of his life in research and education, he is also devoted to his family. As he was appointed full professor at a young age of 38, it was difficult then to find enough time to spend with his family. Fortunately, he had the opportunity to take a sabbatical as a visiting professor in the United States, supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT, Japan. He stayed at the laboratory of Professor Leslie Benet, School of Pharmacy, University of California, in San Francisco (also a coauthor of this Commentary) during the spring of 1988. He also had an opportunity to work in the laboratory of Professor Jerome J. Schentag, Millard Fillmore Hospital and School of Pharmacy, State University of New York, in Buffalo during the summer of 1988. His wife and daughters also stayed with him during that period. There is no doubt that he and his family enjoyed their life in San Francisco and Buffalo very much and have many unforgettable memories of those days. His experiences at these laboratories in San Francisco and Buffalo greatly affected not only his life, but also his ideas about research and education.
ENTHUSIASTIC MENTOR OF WOMEN SCIENTISTS AND FOREIGN STUDENTS Dr. Tsuji has been a dedicated mentor of women scientists and foreign students since he started his academic career. Ms. Etsuko Miyamoto and DOI 10.1002/jps
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Ms. Emi Nakashima were his outstanding colleagues during the change of his research direction from physical pharmacy to pharmacokinetics. Ms. Etsuko Miyamoto received her PhD degree in 1980 and is currently a professor at Hokuriku University. Ms. Emi Nakashima received her PhD degree in 1983 and is currently a professor at Keio University. Dr. Nakashima also had the opportunity to work in the laboratory of Leslie Benet as a visiting associate professor. Ms. Young-Sook Kang was the first foreign PhD student of Professor Tsuji, who received her PhD degree in 1990; she is currently a professor at Sookmyung Women’s University, College of Pharmacy, Seoul, in Korea. Mr. Matheus Timbul Simanjuntak was the second foreign PhD student, and he received his PhD degree in 1991; he is currently a professor at University Sumatera Utara, Medan, Indonesia.
CONTINUOUS CUTTING EDGE RESEARCH Tetsuya Terasaki was appointed as a Research Associate in Akira Tsuji’s laboratory immediately after receiving his PhD degree from the University of Tokyo in 1982. In 1979, Akira Tsuji had published his first paper regarding the physiologically based pharmacokinetics (PB-PK) of beta-lactam antibiotics.7 On the basis of this early study, he constructed an advanced PB-PK model, that is, the extracellular fluid (ECF) distribution model, to describe the tissue distribution mechanism of beta-lactam antibiotics in the body.8 He also applied the ECF distribution model for the analysis of interspecies differences and age dependency of the pharmacokinetics of beta-lactam antibiotics. Moreover, he and Professor Fujio Ichimura (deceased 2001), Hospital Pharmacy, Kanazawa University, applied the model to humans, especially obese children, collaborating with Leslie Benet and Emi Nakashima.9 He modified the ECF distribution model for the analysis of insulin transfer to the liver,10 collaborating with Hitoshi Sato, who is currently a professor at Showa University. In 1991, he also introduced brain microdialysis technology to demonstrate that peptide drugs permeate across the blood– brain barrier (BBB) by measuring the peptide drug concentration in the dialysate,11 collaborating with Yoshiharu Deguchi, who is currently a professor at Teikyo University.
TWENTY YEARS TO ANSWER A RESEARCH QUESTION From the middle of the 1980s, Akira Tsuji started to focus on membrane transport research. Akira Tsuji performed several research projects on the membrane transport mechanism of beta-lactam antibiotics. He obtained a beta-lactam antibiotic transporter complementary DNA by using a Xenopus oocyte expression DOI 10.1002/jps
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cloning system in 1993,12 whereas Dr. Matthias Hediger discovered a proton-coupled oligopeptide transporter in rabbit small intestine in 1994,13 collaborating with Drs. Yoshikatsu Kanai, Vadivel Ganapathy, and Frederick H. Leibach. Akira Tsuji collaborated with Professor Eiji Takeda and Dr. Kenichi Miyamoto, who is currently a professor at Tokushima University, to determine the sequence and tissue distribution of rat oligopeptide transporter in 1996.14 Akira Tsuji was very pleased to complete this research project, having spent nearly 20 years to find the transporter protein since his first publication in 1977.15 An important collaborator with Professor Tsuji is Dr. Ikumi Tamai, who began working with Dr. Tsuji in 1982, the year he received his BS in Pharmacy from Kanazawa University, and continued to publish ground breaking studies on membrane transporters with Professor Tsuji, as will be detailed in the next section of this Commentary, through 2002. Dr. Ikumi Tamai was appointed a Professor at Kanazawa University following Professor Tsuji’s retirement.
NO BOUNDARIES FOR RESEARCH Although Akira Tsuji was extremely busy as a scientist, he also spent time on informal round-table discussions of many subjects, including philosophy, science, history, culture, tradition, and etiquette, with his students and colleagues, accompanying Japanese food and sake. One day, Tetsuya Terasaki asked him the question, “What is the ultimate goal of research?” He answered, “First, we have to carefully consider the essential factors for performing truly original research and for developing interdisciplinary research fields, then perhaps we will be able to find an answer to your question.” Akira Tsuji expanded his research to clarify the role of efflux transporters in normal tissues, aiming at understanding drug distribution and elimination in the body in addition to their role in drug resistance in cancer patients. Employing primary-cultured bovine brain capillary endothelial cells, he demonstrated that P-glycoprotein (P-gp) acts as an efflux transporter at the BBB in 1992.16 It was not by chance that he found that the BBB’s role as a functional barrier involves efflux transporters. He had already completed related research, for example, showing that Escherichia coli acquires a drug-resistant character by increasing the efflux transport in the presence of beta-lactam antibiotics,17 and showing that the brain distribution of quinolone antibiotics is significantly restricted as compared with that of peripheral organs.18 In 1994, he succeeded in demonstrating that BBB P-gp acts as an efflux transporter to reduce the in vivo brain distribution of cyclosporin A by means of transient adenosine triphosphate depletion studies in rats.19 In the same year, Dr. Alfred Schinkel JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
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published the first paper describing the mdr1a knockout mouse.20 Among many outstanding works, an important finding was that benzoic acid is transported by Caco-2 cells in a pH-dependent manner,21 which is apparently consistent with the prediction of the pH partition hypothesis. He also clarified the structure– activity relationship of the monocarboxylic acid transporter in Caco-2 cells,22 collaborating with Takuo Ogihara, who is currently a professor at Takasaki University of Health and Welfare. He received the 1996 AAPS Meritorious Manuscript Award from American Association of Pharmaceutical Scientists for his paper.21 Among more than 300 publications, there is no doubt that Akira Tsuji’s breakthrough research is a series of studies focusing on the organic cation transporter (OCTN). Akira Tsuji cloned organic cation transporters OCTN1 (SLC22A4)23 and OCTN2 (SLC22A5)24 (his most highly cited publication) and clarified that OCTN2 transports L-carnitine in a sodium ion-dependent manner. He proved that hereditary systemic carnitine deficiency (SCD) observed in the juvenile visceral steatosis mouse is caused by genetic mutation (L352R) of Octn2 protein. More importantly, he proved that human primary SCD is caused by mutations in the gene encoding OCTN2,25 collaborating with Dr. Gozo Tsujimoto, who is currently a professor at Kyoto University. Recently, Akira Tsuji and Yukio Kato, who is currently a professor at Kanazawa University, using originally established gene-knockout mice found that OCTN1 transports ergothioneine, a naturally occurring potent antioxidant, and thereby plays a key role in the maintenance of systemic and intestinal exposure to ergothioneine.26 Recently, Akira Tsuji also extended his research to analyze the effect of transporter protein complex formation. He found that PDZ adaptor protein PDZK2 stimulates the transport activity of OCTN2 by modulating cell-surface expression,27 and a mutation of adaptor protein PDZK1 affects the transport activity of OCTNs and peptide transporter 2 (PEPT2).28 He also found that Pept1 and Sglt1 proteins are metabolized in the lysosomes of small intestinal epithelial cells in the Rab8−/– mouse, resulting in the loss of small intestinal absorption of di- or tripeptides and glucose,29 collaborating with Professor Akihiro Harada, Gunma University. This work is an important contribution to the research on microvilli inclusion disease.
the Study of Xenobiotics (JSSX) Scientific Achievement Award in 1999, the Pharmaceutical Society of Japan (PSJ) Scientific Achievement Award in 2002, the Academy of Pharmaceutical Science and Technology, Japan (APSTJ) Scientific Achievement Award in 2005 and the Asian–Pacific International Society for the Study of Xenobiotics (ISSX) Scientific Achievement Award in 2005. He was also nominated as a 0.5% Top Scientist in all research fields throughout the world in 2004, based on the total number of citations of his publications. In 2010, he received the Pharmaceutical Sciences World Congress Research Achievement Award. He served as the President (2004–2005) and Vice President (2002–2003) of JSSX, and on the Council of the ISSX (2004–2008), JSSX (2002–2008), APSTJ (2004–2008), and PSJ (2003–2004). He was made a fellow of the AAPS in 1997 and a fellow of the JSSX in 2008. He served as Cochair of the 2nd World Conference on Drug Absorption, Transport and Delivery in Hawaii in 2003 and as Chair of the 4th World Conference on Drug Absorption, Transport and Delivery in Kanazawa in 2007. He served as the Editor for Japan of the Journal of Pharmacy and Pharmacology (1997–2000), the Editor for Japan and the Far East of Biopharmaceutics and Drug Disposition (1997–2007) and Associate Editor of the Journal of Pharmaceutical Sciences (2002–2008).
AWARDS AND HONORS, AND CONTRIBUTIONS TO SCIENTIFIC SOCIETIES
MASTER OF THE ART OF LIVING
Akira Tsuji has published over 300 peer-reviewed original research articles and 25 review articles and book chapters. He received the Japanese Society for JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
CONTRIBUTION TO KANAZAWA UNIVERSITY: THE DESIGN OF THE NEW CAMPUS AND EDUCATION OF PRACTICAL PHARMACY Akira Tsuji served as the Dean of the Faculty of Pharmaceutical Sciences, Kanazawa University, from 2000 to 2003, and also as the Dean of the Graduate School of Natural Science and Technology, Kanazawa University, from 2005 to 2006. His significant contributions to the university include serving as the Chair of the committee of new campus design for the new campus building of the Graduate School of Natural Science and Technology in Kakuma town. The buildings and design have been praised by the MEXT as an excellent and flexible university campus for the 21st century. In 2003, he also contributed to the establishment of a community pharmacy where the members of the university faculty staff, including his student Ryo Matsushita who is now a professor at Kanazawa University, teaches practical dispensing to the undergraduate students.
Professor Tsuji is loved and admired by many friends and scientists, young and old because he enjoys not only science, but also life. He understands well that life is full of its ups and downs, and continues his DOI 10.1002/jps
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positive attitude to try to enjoy life even when he sees some difficulties, which strongly influences his students, friends and acquaintances. He makes it a point to share his conviviality with his friends and students over good food and drink, and states that it really is fun to devote himself to science as well as enjoy life. And he is an expert both in science and enjoyment of life as shown in the following remembrance of the Commentary coauthor Yuichi Sugiyama. At the banquet of a scientific meeting, there was a competition for predicting the quality of five very good brands of “Sake” (Japanese wine) in terms of price. Amongst the many competitors, Dr. Tsuji was the only one to predict the ranking of the five different “Sake” with perfect accuracy. He is indeed the best sommelier. The following saying is quoted from the most influential classics of Zen literature, The Blue Cliff Record—Every day is a good day to be alive, whether the sun’s shining or not. And Professor Tsuji truly is the Master of the art of living, who has and continues to put this saying into practice.
CONCLUSION Akira Tsuji has contributed significantly to the progress of pharmaceutical science in various areas from physical pharmacy to biopharmacy, and from membrane transport biochemistry to pathophysiology. His research has covered a wide range of topics, and it includes important discoveries relating to the mechanisms of diseases. He has also made great contributions as an educator and leader. We are honored and pleased to have the opportunity to write this Commentary and express our appreciation for his many contributions and his friendship and guidance to us over many years. Now, in his retirement, we wish him good health and a wonderful time with his family and friends.
REFERENCES 1. Yamana T. 1950. Studies on nonfermentive constituents of starch sugar. II. A method of estimation of 6-alphaglucosylglucogen and gentiobiose formed from glucose (in Japanese). Yakugaku Zasshi 70:641–643. 2. Higuchi T, Havinga A, Busse LW. 1950. The kinetics of the hydrolysis of procaine. J Am Pharm Assoc Am Pharm Assoc 39:405–410. 3. Yamana T, Mizukami Y, Tsuji A. 1967. Studies on the stability of drugs. 18. Stability of benzothiadiazines. (9). The optimum for the formation of the intermediate in the degradation of chlorothiazide in aqueous alkali (in Japanese). Yakugaku Zasshi 87:1447–1450. 4. Yamana T, Tsuji A, Mizukami Y. 1974. Kinetic approach to the development in beta-lactam antibiotics. I. Comparative stability of semisynthetic penicllins and 6-aminopenicillanic acid in aqueous solution. Chem Pharm Bull 22:1186–1197. 5. Yamana T, Tsuji A. 1976. Comparative stability of cephalosporins in aqueous solution: Kinetics and mechanisms of degradation. J Pharm Sci 65:1563–1574. DOI 10.1002/jps
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6. Tsuji A, Miyamoto E, Kagami I, Sakaguchi H, Yamana T. 1978. GI absorption of $-lactam antibiotics I: Kinetic assessment of competing absorption and degradation in GI tract. J Pharm Sci 67:1701–1704. 7. Tsuji A, Miyamoto E, Terasaki T, Yamana T. 1979. Physiological pharmacokinetics of $-lactam antibiotics: Penicillin V distribution and elimination after intravenous administration in rats. J Pharm Pharmacol 31:116–119. 8. Tsuji A, Yoshikawa T, Nishide K, Minami H, Kimura M, Nakashima E, Terasaki T, Miyamoto E, Nightingale CH, Yamana T. 1983. Physiologically based pharmacokinetic model for $-lactam antibiotics I: Tissue distribution and elimination in rats. J Pharm Sci 72:1239–1252. 9. Koshida R, Nakashima E, Taniguchi N, Tsuji A, Benet LZ, Ichimura F. 1989. Prediction of distribution volumes of cefazolin and tobramycin in obese children based physiological pharmacokinetic concepts. Pharm Res 6:486–491. 10. Sato H, Terasaki T, Okumura K, Tsuji A. 1991. Effect of receptor up-regulation on insulin pharmacokinetics in streptozotocin-treated diabetic rats. .Pharm Res 8:563– 569. 11. Terasaki T, Deguchi Y, Sato T, Hirai K, Tsuji A. 1991. In vivo transport of a dynorphin-like analgesic peptide, E-2078, through the blood–brain barrier: An application of brain microdialysis. Pharm Res 8:815–820. 12. Terasaki T, Kadowaki A, Higashida H, Nakayama K, Tamai I, Tsuji A. 1993. Expression of the Na+ dependent uridine transport system of rabbit small intestine: Studies with mRNAinjected Xenopus laevis oocytes. Biol Pharm Bull 16:493–496. 13. Fei YJ, Kanai Y, Nussberger S, Ganapathy V, Leibach FH, Romero MF, Singh SK, Boron WF, Hediger MA. 1994. Expression cloning of a mammalian proton-coupled oligopeptide transporter. Nature 368(6471):563–566. 14. Miyamoto K, Shiraga T, Morita K, Yamamoto H, Haga H, Taketani Y, Tamai I, Sai Y, Tsuji A, Takeda E. 1996. Sequence, tissue distribution, and developmental changes in rat intestinal oligopeptide transporter. Biochim Biophys Acta 1305:34–38. 15. Tsuji A, Nakashima E, Kagami I, Honjo N, Yamana T. 1977. Effect of dose-concentration on the absorption of amoxicillin and ampicillin from the rat intestine. J Pharm Pharmacol 29:707–708. 16. Tsuji A, Terasaki T, Takabatake Y, Tenda Y, Tamai I, Yamashima T, Moritani S, Tsuruo T, Yamashita J. 1992. P-glycoprotein as the drug efflux pump in primary cultured bovine brain capillary endothelial cells. Life Sci 51:1427–1437. 17. Tsuji A, Hamano S, Asano T, Nakashima E, Yamana T, Mitsuhashi S. 1984. Microbial kinetics of $-lactam antibiotics against Escherichia coli. J Pharm Sci 73:1418–1422. 18. Okezaki E, Terasaki T, Nakamura M, Nagata O, Kato H, Tsuji A. 1988. Structure-tissue distribution relationship based on physiological pharmacokinetics for NY-198, a new antimicrobial agent, and the related pyridonecarboxylic acids. Drug Metab Dispos 16:865–874. 19. Sakata A, Tamai I, Kawazu K, Deguchi Y, Ohnishi T, Saheki A, Tsuji A. 1994. In vivo evidence for ATP-dependent P-glycoprotein mediated transport of cyclosporin A at the blood–brain barrier. Biochem Pharmacol 48:1989–1992. 20. Schinkel AH, Smit JJ, van Tellingen O, Beijnen JH, Wagenaar E, van Deemter L, Mol CA, Van Der Valk MA, Robanus-Maandag EC, te Riele HP, Berns AJM, Borst P. 1994. Disruption of the mouse mdr1a P-glycoprotein gene leads to a deficiency in the blood–brain barrier and to increased sensitivity to drugs. Cell 77:491–502. 21. Tsuji A, Takanaga H, Tamai I, Terasaki T. 1994. Transcellular transport of benzoic acid across Caco-2 cells by a pH-dependent and carrier-mediated transport mechanism. Pharm Res 11:30–37. JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
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22. Ogihara T, Tamai I, Tsuji A. 1999. Structural characterization of substrates for the anion exchange transporter in Caco-2 cells. J Pharm Sci 88:1217–1221. 23. Tamai I, Yabuuchi H, Nezu J, Sai Y, Oku A, Shimane M, Tsuji A. 1997. Cloning and characterization of a novel human pH-dependent organic cation transporter, OCTN1. FEBS Lett 419:107–111. 24. Tamai I, Ohashi R, Nezu J, Yabuuchi H, Oku A, Shimane M, Sai Y, Tsuji A. 1998. Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. J Biol Chem 273:20378–20382. 25. Nezu J, Tamai I, Oku A, Ohashi R, Yabuuchi H, Hashimoto N, Nikaido H, Sai Y, Koizumi A, Shoji Y, Takada G, Matsuishi T, Yoshino M, Kato H, Ohura T, Tsujimoto G, Hayakawa J, Shimane M, Tsuji A. 1999. Primary systemic carnitine deficiency is caused by mutations in a gene encoding sodium ion-dependent carnitine transporter. Nat Genet 21:91–94.
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26. Kato Y, Kubo Y, Iwata D, Kato S, Sudo T, Sugiura T, Kagaya T, Wakayama T, Hirayama A, Sugimoto M, Sugihara K, Kaneko S, Soga T, Asano M, Tomita M, Matsui T, Wada M, Tsuji A. 2010. Gene knockout and metabolome analysis of carnitine/ organic cation transporter OCTN1. Pharm Res 27:832–840. 27. Watanabe C, Kato Y, Sugiura T, Wakayama T, Iseki S, Tsuji A. 2006. PDZ adaptor protein PDZK2 stimulates transport activity of organic cation/carnitine transporter OCTN2 by modulating cell-surface expression. Drug Metab Dispos 34:1927– 1934. 28. Sugiura T, Kato Y, Kubo Y, Tsuji A. 2006. Mutation in an adaptor protein PDZK1 affects transport activity of organic cation transporter OCTNs and oligopeptide transporter PEPT2. Drug Metab Pharmacokinet 21:375–383. 29. Sato T, Mushiake S, Kato Y, Sato K, Sato M, Takeda N, Ozono K, Miki K, Kubo Y, Tsuji A, Harada R, Harada A. 2007. The Rab8 GTPase regulates apical protein localization in intestinal cells. Nature 448(7151):366–369.
DOI 10.1002/jps
Department of Biochemical Pharmacology and Therapeutics, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan 2 Department of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 3
Department of Bioengineering and Therapeutic Sciences, Schools of Pharmacy and Medicine, University of California, San Francisco, California 94103-0912 Received 5 May 2011; accepted 6 May 2011 Published online 31 May 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jps.22638
INTRODUCTION This issue of the Journal of Pharmaceutical Science is specially dedicated to honor Emeritus Professor Akira Tsuji following his retirement from Kanazawa University, to celebrate his enormous contributions to research and education in the field of pharmaceutical science, and it is a great privilege to have this opportunity to write a commentary on his achievements and successes. Dr. Tsuji served for 42 years at Kanazawa University and retired on March 31, 2010. During his 28 years as a full professor, Akira Tsuji was a thoughtful mentor to his many students, who altogether received 92 Bachelor’s, 85 Master’s, and 28 PhD degrees under his guidance. He greatly inspired both his students and his collaborators, many of whom went on to make important contributions in many fields, including academia, industry, government, hospital medicine, and pharmacy. Those who know Professor Tsuji will be aware of his strong passion for research and education and his warm and unforgettable personality. In this Commentary, we are proud to catalogue his many and significant achievements.
KANAZAWA CITY AS THE CRADLE Akira Tsuji was born in Kanazawa city, Japan, in 1942 and was accepted as a student by the Faculty of Pharmaceutical Science, Kanazawa University, in 1962. As we introduce Dr. Tsuji, we cannot forget the Correspondence to: Tetsuya Terasaki (Telephone: +81-22795-6831; Fax: +81-22-795-6886; E-mail: [email protected]. tohoku.ac.jp) Journal of Pharmaceutical Sciences, Vol. 100, 3541–3546 (2011) © 2011 Wiley-Liss, Inc. and the American Pharmacists Association
Professor Akira Tsuji
place where he lives and has worked. Kanazawa city, which has a population of 462,000, is not only well known as a tourist city, but is also a home of 12 universities. It was established more than 400 years ago by Toshiie Maeda (1539–1599), the lord of Kaga (the old name of Ishikawa prefecture), who was an eminent daimyo during the Azuchimomoyama period. Lord Maeda was one of the leading generals of Oda Nobunaga, who initiated the unification of Japan; he also made great efforts to educate the people, helping Kanazawa to prosper as a city of traditional arts and craft, as it still is today. Kanazawa is called “little Kyoto” and attracts visitors from all over the world. It is noteworthy that the Faculty of Pharmaceutical Sciences of Kanazawa University has the longest history of any Faculty of Pharmaceutical Sciences in Japan. It was established in July 1867 by the 14th
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lord, Yoshiyasu Maeda, who founded a pharmacy in a public hospital to provide practical service and education, including lectures on galenics (now pharmaceutics), chemistry, and botany. When Akira Tsuji studied there as a junior student, the main campus of Kanazawa University was located within the beautiful castle wall, only 10 min walk from his house, which is in the central district of Samurai houses. As a junior student, he also showed great talent for music and was a member of an amateur band.
ONCE-IN-A-LIFETIME OPPORTUNITY When Akira Tsuji became a senior student, he encountered Professor Tsukinaka Yamana (who died in 2009) and found him an inspiring mentor. Tsukinaka Yamana had graduated from the Faculty of Pharmaceutical Sciences, University of Tokyo, and had published an interesting paper entitled “Studies on nonfermentative constituents of starch sugar. II. A method of estimation of 6-alpha-glucosylglucogen and gentiobiose formed from glucose” in 1950, in Japanese; this was the first paper reporting the results of chemical kinetics.1 Coincidentally, Professor Takeru Higuchi, the father of modern day pharmaceutics in the United States, also published a paper entitled “The kinetics of the hydrolysis of procaine” in the same year.2 Akira Tsuji enjoyed both mathematics and physical chemistry, and thanks to the inspiring lectures of Professor Yamana, he became very interested in the study of chemical kinetics as a basis for understanding drug stability in solution.
MOVING FROM PHYSICAL PHARMACY TO BIOPHARMACY Akira Tsuji published his first paper on the stability of benzothiadiazines,3 and after receiving his Master’s degree in 1968, he was immediately appointed a Research Associate in the laboratory of Professor Yamana at Kanazawa University. In a series of studies, he worked to clarify the mechanisms of intramolecular hydrolysis and chose to apply his research background to elucidate the degradation mechanism of beta-lactam antibiotics in aqueous solution. He was successful in this endeavor,4,5 and received his PhD degree from the University of Tokyo in 1976. The title of his thesis was “Chemical kinetic study on stability of beta-lactam antibiotics in aqueous solution.” In the same year, he became an associate professor of Kanazawa University. Tetsuya Terasaki, a coauthor of this Commentary, started his undergraduate research in the laboratory of Professor Yamana and Associate Professor Tsuji in that year. Terasaki clearly remembers that on the day he started his research, Dr. Tsuji proposed a quite new research project, changing his research focus from chemical kinetics to pharmacokinetics. This typified Professor JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
Tsuji, who always showed a farseeing intelligence in proposing new research projects and always asked his students and colleagues what they thought essential and original, resulting in truly innovative research projects. He felt that it was important to challenge difficult problems, and he thought that if they could be solved, the solution provided an unforgettable feeling of achievement. It was, therefore, natural and innovative of Professor Tsuji to begin studies of the small intestinal absorption mechanism of betalactam antibiotics, and he introduced the “permeability clearance concept” for analysis of the absorption rate of beta-lactam antibiotics from the small intestine, thereby separating the degradation rate from the apparent elimination rate in the perfusate of the small intestinal lumen.6 He noted that the absorption rate is dependent on the perfusate volume in the small intestinal lumen, whereas the degradation rate in the solution is independent of the volume. After only 4 years, in 1980, he was appointed full professor.
UNFORGETTABLE TIME WITH FAMILY IN SAN FRANCISCO, CALIFORNIA, AND BUFFALO, NEW YORK Akira Tsuji married Yoko Sumi on March 9, 1969, and has three daughters, Megumi, Izumi, and Machiko, as well as three granddaughters and one grandson. Although he has spent most of his life in research and education, he is also devoted to his family. As he was appointed full professor at a young age of 38, it was difficult then to find enough time to spend with his family. Fortunately, he had the opportunity to take a sabbatical as a visiting professor in the United States, supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT, Japan. He stayed at the laboratory of Professor Leslie Benet, School of Pharmacy, University of California, in San Francisco (also a coauthor of this Commentary) during the spring of 1988. He also had an opportunity to work in the laboratory of Professor Jerome J. Schentag, Millard Fillmore Hospital and School of Pharmacy, State University of New York, in Buffalo during the summer of 1988. His wife and daughters also stayed with him during that period. There is no doubt that he and his family enjoyed their life in San Francisco and Buffalo very much and have many unforgettable memories of those days. His experiences at these laboratories in San Francisco and Buffalo greatly affected not only his life, but also his ideas about research and education.
ENTHUSIASTIC MENTOR OF WOMEN SCIENTISTS AND FOREIGN STUDENTS Dr. Tsuji has been a dedicated mentor of women scientists and foreign students since he started his academic career. Ms. Etsuko Miyamoto and DOI 10.1002/jps
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Ms. Emi Nakashima were his outstanding colleagues during the change of his research direction from physical pharmacy to pharmacokinetics. Ms. Etsuko Miyamoto received her PhD degree in 1980 and is currently a professor at Hokuriku University. Ms. Emi Nakashima received her PhD degree in 1983 and is currently a professor at Keio University. Dr. Nakashima also had the opportunity to work in the laboratory of Leslie Benet as a visiting associate professor. Ms. Young-Sook Kang was the first foreign PhD student of Professor Tsuji, who received her PhD degree in 1990; she is currently a professor at Sookmyung Women’s University, College of Pharmacy, Seoul, in Korea. Mr. Matheus Timbul Simanjuntak was the second foreign PhD student, and he received his PhD degree in 1991; he is currently a professor at University Sumatera Utara, Medan, Indonesia.
CONTINUOUS CUTTING EDGE RESEARCH Tetsuya Terasaki was appointed as a Research Associate in Akira Tsuji’s laboratory immediately after receiving his PhD degree from the University of Tokyo in 1982. In 1979, Akira Tsuji had published his first paper regarding the physiologically based pharmacokinetics (PB-PK) of beta-lactam antibiotics.7 On the basis of this early study, he constructed an advanced PB-PK model, that is, the extracellular fluid (ECF) distribution model, to describe the tissue distribution mechanism of beta-lactam antibiotics in the body.8 He also applied the ECF distribution model for the analysis of interspecies differences and age dependency of the pharmacokinetics of beta-lactam antibiotics. Moreover, he and Professor Fujio Ichimura (deceased 2001), Hospital Pharmacy, Kanazawa University, applied the model to humans, especially obese children, collaborating with Leslie Benet and Emi Nakashima.9 He modified the ECF distribution model for the analysis of insulin transfer to the liver,10 collaborating with Hitoshi Sato, who is currently a professor at Showa University. In 1991, he also introduced brain microdialysis technology to demonstrate that peptide drugs permeate across the blood– brain barrier (BBB) by measuring the peptide drug concentration in the dialysate,11 collaborating with Yoshiharu Deguchi, who is currently a professor at Teikyo University.
TWENTY YEARS TO ANSWER A RESEARCH QUESTION From the middle of the 1980s, Akira Tsuji started to focus on membrane transport research. Akira Tsuji performed several research projects on the membrane transport mechanism of beta-lactam antibiotics. He obtained a beta-lactam antibiotic transporter complementary DNA by using a Xenopus oocyte expression DOI 10.1002/jps
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cloning system in 1993,12 whereas Dr. Matthias Hediger discovered a proton-coupled oligopeptide transporter in rabbit small intestine in 1994,13 collaborating with Drs. Yoshikatsu Kanai, Vadivel Ganapathy, and Frederick H. Leibach. Akira Tsuji collaborated with Professor Eiji Takeda and Dr. Kenichi Miyamoto, who is currently a professor at Tokushima University, to determine the sequence and tissue distribution of rat oligopeptide transporter in 1996.14 Akira Tsuji was very pleased to complete this research project, having spent nearly 20 years to find the transporter protein since his first publication in 1977.15 An important collaborator with Professor Tsuji is Dr. Ikumi Tamai, who began working with Dr. Tsuji in 1982, the year he received his BS in Pharmacy from Kanazawa University, and continued to publish ground breaking studies on membrane transporters with Professor Tsuji, as will be detailed in the next section of this Commentary, through 2002. Dr. Ikumi Tamai was appointed a Professor at Kanazawa University following Professor Tsuji’s retirement.
NO BOUNDARIES FOR RESEARCH Although Akira Tsuji was extremely busy as a scientist, he also spent time on informal round-table discussions of many subjects, including philosophy, science, history, culture, tradition, and etiquette, with his students and colleagues, accompanying Japanese food and sake. One day, Tetsuya Terasaki asked him the question, “What is the ultimate goal of research?” He answered, “First, we have to carefully consider the essential factors for performing truly original research and for developing interdisciplinary research fields, then perhaps we will be able to find an answer to your question.” Akira Tsuji expanded his research to clarify the role of efflux transporters in normal tissues, aiming at understanding drug distribution and elimination in the body in addition to their role in drug resistance in cancer patients. Employing primary-cultured bovine brain capillary endothelial cells, he demonstrated that P-glycoprotein (P-gp) acts as an efflux transporter at the BBB in 1992.16 It was not by chance that he found that the BBB’s role as a functional barrier involves efflux transporters. He had already completed related research, for example, showing that Escherichia coli acquires a drug-resistant character by increasing the efflux transport in the presence of beta-lactam antibiotics,17 and showing that the brain distribution of quinolone antibiotics is significantly restricted as compared with that of peripheral organs.18 In 1994, he succeeded in demonstrating that BBB P-gp acts as an efflux transporter to reduce the in vivo brain distribution of cyclosporin A by means of transient adenosine triphosphate depletion studies in rats.19 In the same year, Dr. Alfred Schinkel JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
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published the first paper describing the mdr1a knockout mouse.20 Among many outstanding works, an important finding was that benzoic acid is transported by Caco-2 cells in a pH-dependent manner,21 which is apparently consistent with the prediction of the pH partition hypothesis. He also clarified the structure– activity relationship of the monocarboxylic acid transporter in Caco-2 cells,22 collaborating with Takuo Ogihara, who is currently a professor at Takasaki University of Health and Welfare. He received the 1996 AAPS Meritorious Manuscript Award from American Association of Pharmaceutical Scientists for his paper.21 Among more than 300 publications, there is no doubt that Akira Tsuji’s breakthrough research is a series of studies focusing on the organic cation transporter (OCTN). Akira Tsuji cloned organic cation transporters OCTN1 (SLC22A4)23 and OCTN2 (SLC22A5)24 (his most highly cited publication) and clarified that OCTN2 transports L-carnitine in a sodium ion-dependent manner. He proved that hereditary systemic carnitine deficiency (SCD) observed in the juvenile visceral steatosis mouse is caused by genetic mutation (L352R) of Octn2 protein. More importantly, he proved that human primary SCD is caused by mutations in the gene encoding OCTN2,25 collaborating with Dr. Gozo Tsujimoto, who is currently a professor at Kyoto University. Recently, Akira Tsuji and Yukio Kato, who is currently a professor at Kanazawa University, using originally established gene-knockout mice found that OCTN1 transports ergothioneine, a naturally occurring potent antioxidant, and thereby plays a key role in the maintenance of systemic and intestinal exposure to ergothioneine.26 Recently, Akira Tsuji also extended his research to analyze the effect of transporter protein complex formation. He found that PDZ adaptor protein PDZK2 stimulates the transport activity of OCTN2 by modulating cell-surface expression,27 and a mutation of adaptor protein PDZK1 affects the transport activity of OCTNs and peptide transporter 2 (PEPT2).28 He also found that Pept1 and Sglt1 proteins are metabolized in the lysosomes of small intestinal epithelial cells in the Rab8−/– mouse, resulting in the loss of small intestinal absorption of di- or tripeptides and glucose,29 collaborating with Professor Akihiro Harada, Gunma University. This work is an important contribution to the research on microvilli inclusion disease.
the Study of Xenobiotics (JSSX) Scientific Achievement Award in 1999, the Pharmaceutical Society of Japan (PSJ) Scientific Achievement Award in 2002, the Academy of Pharmaceutical Science and Technology, Japan (APSTJ) Scientific Achievement Award in 2005 and the Asian–Pacific International Society for the Study of Xenobiotics (ISSX) Scientific Achievement Award in 2005. He was also nominated as a 0.5% Top Scientist in all research fields throughout the world in 2004, based on the total number of citations of his publications. In 2010, he received the Pharmaceutical Sciences World Congress Research Achievement Award. He served as the President (2004–2005) and Vice President (2002–2003) of JSSX, and on the Council of the ISSX (2004–2008), JSSX (2002–2008), APSTJ (2004–2008), and PSJ (2003–2004). He was made a fellow of the AAPS in 1997 and a fellow of the JSSX in 2008. He served as Cochair of the 2nd World Conference on Drug Absorption, Transport and Delivery in Hawaii in 2003 and as Chair of the 4th World Conference on Drug Absorption, Transport and Delivery in Kanazawa in 2007. He served as the Editor for Japan of the Journal of Pharmacy and Pharmacology (1997–2000), the Editor for Japan and the Far East of Biopharmaceutics and Drug Disposition (1997–2007) and Associate Editor of the Journal of Pharmaceutical Sciences (2002–2008).
AWARDS AND HONORS, AND CONTRIBUTIONS TO SCIENTIFIC SOCIETIES
MASTER OF THE ART OF LIVING
Akira Tsuji has published over 300 peer-reviewed original research articles and 25 review articles and book chapters. He received the Japanese Society for JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
CONTRIBUTION TO KANAZAWA UNIVERSITY: THE DESIGN OF THE NEW CAMPUS AND EDUCATION OF PRACTICAL PHARMACY Akira Tsuji served as the Dean of the Faculty of Pharmaceutical Sciences, Kanazawa University, from 2000 to 2003, and also as the Dean of the Graduate School of Natural Science and Technology, Kanazawa University, from 2005 to 2006. His significant contributions to the university include serving as the Chair of the committee of new campus design for the new campus building of the Graduate School of Natural Science and Technology in Kakuma town. The buildings and design have been praised by the MEXT as an excellent and flexible university campus for the 21st century. In 2003, he also contributed to the establishment of a community pharmacy where the members of the university faculty staff, including his student Ryo Matsushita who is now a professor at Kanazawa University, teaches practical dispensing to the undergraduate students.
Professor Tsuji is loved and admired by many friends and scientists, young and old because he enjoys not only science, but also life. He understands well that life is full of its ups and downs, and continues his DOI 10.1002/jps
PROFESSOR AKIRA TSUJI
positive attitude to try to enjoy life even when he sees some difficulties, which strongly influences his students, friends and acquaintances. He makes it a point to share his conviviality with his friends and students over good food and drink, and states that it really is fun to devote himself to science as well as enjoy life. And he is an expert both in science and enjoyment of life as shown in the following remembrance of the Commentary coauthor Yuichi Sugiyama. At the banquet of a scientific meeting, there was a competition for predicting the quality of five very good brands of “Sake” (Japanese wine) in terms of price. Amongst the many competitors, Dr. Tsuji was the only one to predict the ranking of the five different “Sake” with perfect accuracy. He is indeed the best sommelier. The following saying is quoted from the most influential classics of Zen literature, The Blue Cliff Record—Every day is a good day to be alive, whether the sun’s shining or not. And Professor Tsuji truly is the Master of the art of living, who has and continues to put this saying into practice.
CONCLUSION Akira Tsuji has contributed significantly to the progress of pharmaceutical science in various areas from physical pharmacy to biopharmacy, and from membrane transport biochemistry to pathophysiology. His research has covered a wide range of topics, and it includes important discoveries relating to the mechanisms of diseases. He has also made great contributions as an educator and leader. We are honored and pleased to have the opportunity to write this Commentary and express our appreciation for his many contributions and his friendship and guidance to us over many years. Now, in his retirement, we wish him good health and a wonderful time with his family and friends.
REFERENCES 1. Yamana T. 1950. Studies on nonfermentive constituents of starch sugar. II. A method of estimation of 6-alphaglucosylglucogen and gentiobiose formed from glucose (in Japanese). Yakugaku Zasshi 70:641–643. 2. Higuchi T, Havinga A, Busse LW. 1950. The kinetics of the hydrolysis of procaine. J Am Pharm Assoc Am Pharm Assoc 39:405–410. 3. Yamana T, Mizukami Y, Tsuji A. 1967. Studies on the stability of drugs. 18. Stability of benzothiadiazines. (9). The optimum for the formation of the intermediate in the degradation of chlorothiazide in aqueous alkali (in Japanese). Yakugaku Zasshi 87:1447–1450. 4. Yamana T, Tsuji A, Mizukami Y. 1974. Kinetic approach to the development in beta-lactam antibiotics. I. Comparative stability of semisynthetic penicllins and 6-aminopenicillanic acid in aqueous solution. Chem Pharm Bull 22:1186–1197. 5. Yamana T, Tsuji A. 1976. Comparative stability of cephalosporins in aqueous solution: Kinetics and mechanisms of degradation. J Pharm Sci 65:1563–1574. DOI 10.1002/jps
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6. Tsuji A, Miyamoto E, Kagami I, Sakaguchi H, Yamana T. 1978. GI absorption of $-lactam antibiotics I: Kinetic assessment of competing absorption and degradation in GI tract. J Pharm Sci 67:1701–1704. 7. Tsuji A, Miyamoto E, Terasaki T, Yamana T. 1979. Physiological pharmacokinetics of $-lactam antibiotics: Penicillin V distribution and elimination after intravenous administration in rats. J Pharm Pharmacol 31:116–119. 8. Tsuji A, Yoshikawa T, Nishide K, Minami H, Kimura M, Nakashima E, Terasaki T, Miyamoto E, Nightingale CH, Yamana T. 1983. Physiologically based pharmacokinetic model for $-lactam antibiotics I: Tissue distribution and elimination in rats. J Pharm Sci 72:1239–1252. 9. Koshida R, Nakashima E, Taniguchi N, Tsuji A, Benet LZ, Ichimura F. 1989. Prediction of distribution volumes of cefazolin and tobramycin in obese children based physiological pharmacokinetic concepts. Pharm Res 6:486–491. 10. Sato H, Terasaki T, Okumura K, Tsuji A. 1991. Effect of receptor up-regulation on insulin pharmacokinetics in streptozotocin-treated diabetic rats. .Pharm Res 8:563– 569. 11. Terasaki T, Deguchi Y, Sato T, Hirai K, Tsuji A. 1991. In vivo transport of a dynorphin-like analgesic peptide, E-2078, through the blood–brain barrier: An application of brain microdialysis. Pharm Res 8:815–820. 12. Terasaki T, Kadowaki A, Higashida H, Nakayama K, Tamai I, Tsuji A. 1993. Expression of the Na+ dependent uridine transport system of rabbit small intestine: Studies with mRNAinjected Xenopus laevis oocytes. Biol Pharm Bull 16:493–496. 13. Fei YJ, Kanai Y, Nussberger S, Ganapathy V, Leibach FH, Romero MF, Singh SK, Boron WF, Hediger MA. 1994. Expression cloning of a mammalian proton-coupled oligopeptide transporter. Nature 368(6471):563–566. 14. Miyamoto K, Shiraga T, Morita K, Yamamoto H, Haga H, Taketani Y, Tamai I, Sai Y, Tsuji A, Takeda E. 1996. Sequence, tissue distribution, and developmental changes in rat intestinal oligopeptide transporter. Biochim Biophys Acta 1305:34–38. 15. Tsuji A, Nakashima E, Kagami I, Honjo N, Yamana T. 1977. Effect of dose-concentration on the absorption of amoxicillin and ampicillin from the rat intestine. J Pharm Pharmacol 29:707–708. 16. Tsuji A, Terasaki T, Takabatake Y, Tenda Y, Tamai I, Yamashima T, Moritani S, Tsuruo T, Yamashita J. 1992. P-glycoprotein as the drug efflux pump in primary cultured bovine brain capillary endothelial cells. Life Sci 51:1427–1437. 17. Tsuji A, Hamano S, Asano T, Nakashima E, Yamana T, Mitsuhashi S. 1984. Microbial kinetics of $-lactam antibiotics against Escherichia coli. J Pharm Sci 73:1418–1422. 18. Okezaki E, Terasaki T, Nakamura M, Nagata O, Kato H, Tsuji A. 1988. Structure-tissue distribution relationship based on physiological pharmacokinetics for NY-198, a new antimicrobial agent, and the related pyridonecarboxylic acids. Drug Metab Dispos 16:865–874. 19. Sakata A, Tamai I, Kawazu K, Deguchi Y, Ohnishi T, Saheki A, Tsuji A. 1994. In vivo evidence for ATP-dependent P-glycoprotein mediated transport of cyclosporin A at the blood–brain barrier. Biochem Pharmacol 48:1989–1992. 20. Schinkel AH, Smit JJ, van Tellingen O, Beijnen JH, Wagenaar E, van Deemter L, Mol CA, Van Der Valk MA, Robanus-Maandag EC, te Riele HP, Berns AJM, Borst P. 1994. Disruption of the mouse mdr1a P-glycoprotein gene leads to a deficiency in the blood–brain barrier and to increased sensitivity to drugs. Cell 77:491–502. 21. Tsuji A, Takanaga H, Tamai I, Terasaki T. 1994. Transcellular transport of benzoic acid across Caco-2 cells by a pH-dependent and carrier-mediated transport mechanism. Pharm Res 11:30–37. JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 100, NO. 9, SEPTEMBER 2011
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22. Ogihara T, Tamai I, Tsuji A. 1999. Structural characterization of substrates for the anion exchange transporter in Caco-2 cells. J Pharm Sci 88:1217–1221. 23. Tamai I, Yabuuchi H, Nezu J, Sai Y, Oku A, Shimane M, Tsuji A. 1997. Cloning and characterization of a novel human pH-dependent organic cation transporter, OCTN1. FEBS Lett 419:107–111. 24. Tamai I, Ohashi R, Nezu J, Yabuuchi H, Oku A, Shimane M, Sai Y, Tsuji A. 1998. Molecular and functional identification of sodium ion-dependent, high affinity human carnitine transporter OCTN2. J Biol Chem 273:20378–20382. 25. Nezu J, Tamai I, Oku A, Ohashi R, Yabuuchi H, Hashimoto N, Nikaido H, Sai Y, Koizumi A, Shoji Y, Takada G, Matsuishi T, Yoshino M, Kato H, Ohura T, Tsujimoto G, Hayakawa J, Shimane M, Tsuji A. 1999. Primary systemic carnitine deficiency is caused by mutations in a gene encoding sodium ion-dependent carnitine transporter. Nat Genet 21:91–94.
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26. Kato Y, Kubo Y, Iwata D, Kato S, Sudo T, Sugiura T, Kagaya T, Wakayama T, Hirayama A, Sugimoto M, Sugihara K, Kaneko S, Soga T, Asano M, Tomita M, Matsui T, Wada M, Tsuji A. 2010. Gene knockout and metabolome analysis of carnitine/ organic cation transporter OCTN1. Pharm Res 27:832–840. 27. Watanabe C, Kato Y, Sugiura T, Wakayama T, Iseki S, Tsuji A. 2006. PDZ adaptor protein PDZK2 stimulates transport activity of organic cation/carnitine transporter OCTN2 by modulating cell-surface expression. Drug Metab Dispos 34:1927– 1934. 28. Sugiura T, Kato Y, Kubo Y, Tsuji A. 2006. Mutation in an adaptor protein PDZK1 affects transport activity of organic cation transporter OCTNs and oligopeptide transporter PEPT2. Drug Metab Pharmacokinet 21:375–383. 29. Sato T, Mushiake S, Kato Y, Sato K, Sato M, Takeda N, Ozono K, Miki K, Kubo Y, Tsuji A, Harada R, Harada A. 2007. The Rab8 GTPase regulates apical protein localization in intestinal cells. Nature 448(7151):366–369.
DOI 10.1002/jps