title: 3-Iodothyronamine increases transient receptor potential melastatin channel 8 (TRPM8) activity in immortalized human corneal epithelial cells.
abstract: 3-Iodothyronamine (3T1AM) is an endogenous thyroid hormone metabolite that interacts with the human trace amine-associated receptor 1 (hTAAR1), a G-protein-coupled receptor, to induce numerous physiological responses including dose-dependent body temperature lowering in rodents. 3T1AM also directly activates cold-sensitive transient receptor potential melastatin 8 (TRPM8) channels in human conjunctival epithelial cells (HCjEC) at constant temperature as well as reducing rises in IL-6 release induced by transient receptor potential vanilloid 1 (TRPV1) activation by capsaicin (CAP). Here, we describe that 3T1AM-induced TRPM8 activation suppresses through crosstalk TRPV1 activation in immortalized human corneal epithelial cells (HCEC). RT-PCR and immunofluorescent staining identified TRPM8 gene and protein expression. Increases in Ca(2+) influx induced by the TRPM8 agonists either 3T1AM (0.1-10 μM), menthol (500 μM), icilin (15-60 μM) or temperature lowering (either <17°C or >17°C) were all blocked by 10-20 μM BCTC, a mixed TRPV1/TRPM8 antagonist. BCTC blocked 3T1AM-induced recombinant TRPM8 activation of Ca(2+) transients in an osteosarcoma heterologous expression system. The effects of BCTC in HCEC were attributable to selective TRPM8 inhibition since whole-cell patch-clamp currents underlying Ca(2+) rises induced by 20 μM CAP were BCTC insensitive. On the other hand, Ca(2+) transients induced by activating TRPV1 with either CAP or a hyperosmolar medium were suppressed during exposure to either 1 μM 3T1AM or 15 μM icilin. All of these modulatory effects on intracellular Ca(2+) regulation induced by the aforementioned agents were attributable to changes in underlying inward and outward current. Taken together, TRPM8 activation by 3T1AM markedly attenuates and even eliminates hyperosmolar and CAP induced TRPV1 activation through crosstalk.
authors.affiliation: Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Lucius
authors.affiliation: Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Noushafarin
authors.initials: N
authors.lastname: Khajavi
authors.affiliation: School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325027, PR China.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Reinach
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Köhrle
authors.affiliation: Gastroenterology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Priyavathi
authors.initials: P
authors.lastname: Dhandapani
authors.affiliation: Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Huimann
authors.affiliation: Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Ljubojevic
authors.affiliation: Gastroenterology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Grötzinger
authors.affiliation: Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: stefan.mergler@charite.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Mergler
mesh_terms: D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D011719:Pyrazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D013970:Thyronines / Q000494:pharmacology*
chemical_list: C487948:3-iodothyronamine; D015850:Interleukin-6; C475772:N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carboxamide; D011719:Pyrazines; D011725:Pyridines; D011744:Pyrimidinones; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D013970:Thyronines; C490483:icilin; D002211:Capsaicin; D002118:Calcium
keywords: Calcium; Dry eye disease; Human corneal epithelium; Intracellular Ca(2+); Planar patch-clamp technique; Thyronamine; Transient receptor potential melastatin 8 channel