title: Transient receptor potential channel TRPM8 agonists stimulate calcium influx and neurotensin secretion in neuroendocrine tumor cells.
abstract: TRPM8 is a member of the melastatin-type transient receptor potential ion channel family. Activation by cold or by agonists (menthol, icilin) induces a transient rise in intracellular free calcium concentration ([Ca(2+)](i)). Our previous study demonstrated that Ca(2+)-permeable cation channels play a role in IGF-1-induced secretion of chromogranin A in human neuroendocrine tumor (NET) cell line BON [Mergler et al.: Neuroendocrinology 2006;82:87-102]. Here, we extend our earlier study by investigating the expression of TRPM8 and characterizing its impact on [Ca(2+)](i) and the secretion of neurotensin (NT). We identified TRPM8 expression in NET BON cells by RT-PCR, Western blotting and immunofluorescence staining. Icilin increased [Ca(2+)](i) in TRPM8-transfected human embryonic kidney cells (HEK293) but not in mock-transfected cells. Icilin and menthol induced Ca(2+) transients in BON cells as well as in primary NET cell cultures of two different pancreatic NETs as detected by single cell fluorescence imaging. Icilin increased non-selective cation channel currents in BON cells as detected by patch-clamp recordings. This activation was associated with increased NT secretion. Taken together, this study demonstrates for the first time the expression TRPM8 in NET cells and its role in regulating [Ca(2+)](i) and NT secretion. The regulation of NT secretion in NETs by TRPM8 may have a potential clinical implication in diagnosis or therapy.
authors.affiliation: Department of Internal Medicine, Division of Hepatology and Gastroenterology, Charité - Universitatsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany. stefan.mergler@charite.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Mergler
authors.forename: Mathias Z
authors.initials: MZ
authors.lastname: Strowski
authors.forename: Simone
authors.initials: S
authors.lastname: Kaiser
authors.forename: Thomas
authors.initials: T
authors.lastname: Plath
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Giesecke
authors.forename: Marleen
authors.initials: M
authors.lastname: Neumann
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosokawa
authors.forename: Shigeo
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Jan
authors.initials: J
authors.lastname: Langrehr
authors.forename: Peter
authors.initials: P
authors.lastname: Neuhaus
authors.forename: Ursula
authors.initials: U
authors.lastname: Plöckinger
authors.forename: Bertram
authors.initials: B
authors.lastname: Wiedenmann
authors.forename: Carsten
authors.initials: C
authors.lastname: Grötzinger
mesh_terms: D002118:Calcium / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008610:Menthol / Q000494:pharmacology*; D008954:Models, Biological; D018358:Neuroendocrine Tumors / Q000473:pathology*; D009496:Neurotensin / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D011744:Pyrimidinones / Q000494:pharmacology*; D050053:TRPM Cation Channels / Q000819:agonists* / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D011744:Pyrimidinones; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D008610:Menthol; D009496:Neurotensin; C490483:icilin; D002118:Calcium