Activation of TRPA1 channels by the fatty acid amide hydrolase inhibitor 3'-carbamoylbiphenyl-3-yl cyclohexylcarbamate (URB597).
As a member of the transient receptor potential (TRP) ion channel superfamily, the ligand-gated ion channel TRPA1 has been implicated in nociceptive function and pain states. The endogenous ligands that activate TRPA1 remain unknown. However, various agonists have been identified, including environmental irritants (e.g., acrolein) and ingredients of pungent natural products [e.g., allyl isothiocyanate (ITC), cinnamaldehyde, allicin, and gingerol]. In general, these agents are either highly reactive, nonselective, or not potent or efficacious, significantly limiting their utilities in the study of TRPA1 channel properties and biological functions. In a search for novel TRPA1 agonists, we identified 3'-carbamoylbiphenyl-3-yl cyclohexylcarbamate (URB597), a potent and systemically active inhibitor of fatty acid amide hydrolase (FAAH). This enzyme is responsible for anandamide degradation and therefore has been pursued as an antinociceptive and antiepileptic drug target. Using Ca(2+) influx assays and patch-clamp techniques, we demonstrated that URB597 could activate heterologously expressed human and rat TRPA1 channels, whereas two other FAAH inhibitors (i.e., URB532 and Compound 7) had no effect. When applied to inside-out membrane patches expressing rat TRPA1, URB597 elicited single-channel activities with a unitary conductance of 40 pS. Furthermore, URB597 activated TRPA1 channels endogenously expressed in a population of rat dorsal root ganglion neurons that also responded to ITC. In contrast to its effect on TRPA1, URB597 inhibited TRPM8 and had no effects on TRPV1 or TRPV4. Thus, we conclude that URB597 is a novel agonist of TRPA1 and probably activates the channel through a direct gating mechanism.
Niforatos
Wende
W
Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064-6125, USA.
Zhang
Xu-Feng
XF
Lake
Marc R
MR
Walter
Karl A
KA
Neelands
Torben
T
Holzman
Thomas F
TF
Scott
Victoria E
VE
Faltynek
Connie R
CR
Moreland
Robert B
RB
Chen
Jun
J
D000581:Amidohydrolases / Q000037:antagonists & inhibitors*; D000818:Animals; D017487:Ankyrins; D001549:Benzamides / Q000737:chemistry / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism*; D002219:Carbamates / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism; D014162:Transfection; D050051:Transient Receptor Potential Channels / Q000378:metabolism*; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D017487:Ankyrins; D001549:Benzamides; D015220:Calcium Channels; D002219:Carbamates; D009419:Nerve Tissue Proteins; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels; D050916:TRPV Cation Channels; D050051:Transient Receptor Potential Channels; D000099252:Fatty Acid Amide Hydrolases; C473350:TRPA1 protein, human; C425966:TRPM8 protein, human; C494482:TRPV1 protein, human; C416986:TRPV4 protein, human; C480976:Trpa1 protein, rat; C500528:cyclohexyl carbamic acid 3'-carbamoylbiphenyl-3-yl ester