title: Tris-hydroxymethyl-aminomethane enhances capsaicin-induced intracellular Ca(2+) influx through transient receptor potential V1 (TRPV1) channels.
abstract: Non-selective transient receptor potential vanilloid (TRPV) cation channels are activated by various insults, including exposure to heat, acidity, and the compound capsaicin, resulting in sensations of pain in the skin, visceral organs, and oral cavity. Recently, TRPV1 activation was also demonstrated in response to basic pH elicited by ammonia and intracellular alkalization. Tris-hydroxymethyl aminomethane (THAM) is widely used as an alkalizing agent; however, the effects of THAM on TRPV1 channels have not been defined. In this study, we characterized the effects of THAM-induced TRPV1 channel activation in baby hamster kidney cells expressing human TRPV1 (hTRPV1) and the Ca(2+)-sensitive fluorescent sensor GCaMP2 by real-time confocal microscopy. Notably, both capsaicin (1 μM) and pH 6.5 buffer elicited steep increases in the intracellular Ca(2+) concentration ([Ca(2+)]i), while treatment with THAM (pH 8.5) alone had no effect. However, treatment with THAM (pH 8.5) following capsaicin application elicited a profound, long-lasting increase in [Ca(2+)]i that was completely inhibited by the TRPV1 antagonist capsazepine. Taken together, these results suggest that hTRPV1 pre-activation is required to provoke enhanced, THAM-induced [Ca(2+)]i increases, which could be a mechanism underlying pain induced by basic pH.
authors.affiliation: Department of Palliative Medicine, Seirei Sakura Citizen Hospital, Chiba 285-8765, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Murakami
authors.affiliation: Laboratory of Molecular Pathology and Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-8510, Japan; Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Sudo
authors.affiliation: Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Miyano
authors.affiliation: Laboratory of Molecular Pathology and Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba 278-8510, Japan; Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Nishimura
authors.affiliation: Palliative Care Division, National Cancer Center Hospital, Tokyo 104-0045, Japan; Department of Palliative Care, Japanese Red Cross Medical Center, Tokyo 150-8935, Japan.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Matoba
authors.affiliation: Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan; Department of Anesthesia and Intensive Care, National Cancer Center Hospital, Tokyo 104-0045, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Shiraishi
authors.affiliation: Department of Social and Health Management, International University of Health and Welfare, Tochigi 324-8501, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Konno
authors.affiliation: Division of Cancer Pathophysiology, National Cancer Center Research Institute, Tokyo 104-0045, Japan; Division of Supportive Care Research, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, Tokyo 104-0045, Japan; Innovation Center for Supportive, Palliative and Psychosocial Care, National Cancer Center, Tokyo 104-0045, Japan. Electronic address: yuezono@ncc.go.jp.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Uezono
mesh_terms: D000178:Acrylamides / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002478:Cells, Cultured; D006224:Cricetinae; D006863:Hydrogen-Ion Concentration; D010146:Pain / Q000235:genetics; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000178:Acrylamides; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; C445419:tris(hydroxymethyl)-acrylamidomethane; C071423:capsazepine; D002211:Capsaicin; D002118:Calcium
keywords: Calcium signaling; Nociceptive pain; TRPV cation channels; TRPV1 receptor; Tris-hydroxymethyl aminomethane (THAM)