title: Pharmacological blockade of TRPM8 ion channels alters cold and cold pain responses in mice.
abstract: TRPM8 (Transient Receptor Potential Melastatin-8) is a cold- and menthol-gated ion channel necessary for the detection of cold temperatures in the mammalian peripheral nervous system. Functioning TRPM8 channels are required for behavioral responses to innocuous cool, noxious cold, injury-evoked cold hypersensitivity, cooling-mediated analgesia, and thermoregulation. Because of these various roles, the ability to pharmacologically manipulate TRPM8 function to alter the excitability of cold-sensing neurons may have broad impact clinically. Here we examined a novel compound, PBMC (1-phenylethyl-4-(benzyloxy)-3-methoxybenzyl(2-aminoethyl)carbamate) which robustly and selectively inhibited TRPM8 channels in vitro with sub-nanomolar affinity, as determined by calcium microfluorimetry and electrophysiology. The actions of PBMC were selective for TRPM8, with no functional effects observed for the sensory ion channels TRPV1 and TRPA1. PBMC altered TRPM8 gating by shifting the voltage-dependence of menthol-evoked currents towards positive membrane potentials. When administered systemically to mice, PBMC treatment produced a dose-dependent hypothermia in wildtype animals while TRPM8-knockout mice remained unaffected. This hypothermic response was reduced at lower doses, whereas responses to evaporative cooling were still significantly attenuated. Lastly, systemic PBMC also diminished cold hypersensitivity in inflammatory and nerve-injury pain models, but was ineffective against oxaliplatin-induced neuropathic cold hypersensitivity, despite our findings that TRPM8 is required for the cold-related symptoms of this pathology. Thus PBMC is an attractive compound that serves as a template for the formulation of highly specific and potent TRPM8 antagonists that will have utility both in vitro and in vivo.
authors: Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America.
authors: Wendy M
authors: WM
authors: Knowlton
authors: Richard L
authors: RL
authors: Daniels
authors: Radhika
authors: R
authors: Palkar
authors: Daniel D
authors: DD
authors: McCoy
authors: David D
authors: DD
authors: McKemy
mesh_terms: D000700:Analgesics / Q000627:therapeutic use*; D000818:Animals; D003592:Cytophotometry; D004594:Electrophysiology; D051379:Mice; D009944:Organoplatinum Compounds / Q000627:therapeutic use; D000077150:Oxaliplatin; D000074025:TRPA1 Cation Channel; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism; D013697:Thermosensing / Q000187:drug effects*; D050051:Transient Receptor Potential Channels / Q000378:metabolism
chemical_list: D000700:Analgesics; D009944:Organoplatinum Compounds; D000074025:TRPA1 Cation Channel; D050053:TRPM Cation Channels; C492297:TRPM8 protein, mouse; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; D000077150:Oxaliplatin