title: Auto-oxidation products of epigallocatechin gallate activate TRPA1 and TRPV1 in sensory neurons.
abstract: The sensation of astringency is elicited by catechins and their polymers in wine and tea. It has been considered that catechins in green tea are unstable and auto-oxidized to induce more astringent taste. Here, we examined how mammalian transient receptor potential V1 (TRPV1) and TRPA1, which are nociceptive sensors, are activated by green tea catechins during the auto-oxidation process. Neither TRPV1 nor TRPA1 could be activated by any of the freshly prepared catechin. When one of the major catechin, epigallocatechin gallate (EGCG), was preincubated for 3h in Hank's balanced salt solution, it significantly activated both TRP channels expressed in HEK293 cells. Even after incubation, other catechins showed much less effects. Results suggest that only oxidative products of EGCG activate both TRPV1 and TRPA1. Dorsal root ganglion (DRG) sensory neurons were also activated by the incubated EGCG through TRPV1 and TRPA1 channels. Liquid chromatography-mass spectrometry revealed that theasinensins A and D are formed during incubation of EGCG. We found that purified theasinensin A activates both TRPV1 and TRPA1, and that it stimulates DRG neurons through TRPV1 and TRPA1 channels. Results suggested a possibility that TRPV1 and TRPA1 channels are involved in the sense of astringent taste of green tea.
authors.affiliation: Department of Animal Bio-Science, Faculty of Bio-Science, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama-shi, Shiga 526-0829, Japan.
authors.forename: Mako
authors.initials: M
authors.lastname: Kurogi
authors.affiliation: Department of Bio-Science, Faculty of Bio-Science, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama-shi, Shiga 526-0829, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Department of Physiology, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Nagatomo
authors.affiliation: Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Nishigohnaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan and Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan.
authors.forename: Michihiro
authors.initials: M
authors.lastname: Tateyama
authors.affiliation: Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Nishigohnaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan and Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0155, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: Department of Animal Bio-Science, Faculty of Bio-Science, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama-shi, Shiga 526-0829, Japan, o_saito@nagahama-i-bio.ac.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Saitoh
mesh_terms: D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology; D002478:Cells, Cultured; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D019281:Dimerization; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D010084:Oxidation-Reduction; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011984:Sensory Receptor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012911:Snakes; D021241:Spectrometry, Mass, Electrospray Ionization; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D050916:TRPV Cation Channels; D050051:Transient Receptor Potential Channels; D002392:Catechin; C045651:epigallocatechin gallate
keywords: astringency; catechin; taste; theasinensin A