title: Etodolac activates and desensitizes transient receptor potential ankyrin 1.
abstract: The transient receptor potential ankyrin 1 (TRPA1) channel is well known as a sensor to environmental irritant compounds, cold, and endogenous proalgesic agents. TRPA1 is expressed on sensory neurons and is involved in pain modulation. Etodolac is a cyclooxygenase (COX)-2 inhibitor that belongs to the class of nonsteroidal anti-inflammatory drugs (NSAIDs). A recent study indicates that etodolac inhibits allyl isothiocyanate (AITC)-induced calcium influx in heterologous HEK293 cells and sensory neurons. To examine whether and how etodolac modulates the TRPA1 channels, we applied etodolac to TRPA1-transfected HEK293 cells or rat dorsal root ganglion (DRG) neurons and recorded the currents using the whole-cell patch clamp technique. We found that etodolac at higher doses could activate and then desensitize TRPA1 channels in heterologous expressing HEK293 cells as well as in DRG neurons. The etodolac-induced currents were significantly attenuated in cysteine residues mutated human TRPA1-transfected HEK293 cells. Interestingly, application of etodolac at drug plasma levels in clinical usage did not induce significant TRPA1 currents but reduced the subsequent AITC-induced currents to 25% in HEK293 cells expressing TRPA1. Moreover, no modulatory effect of etodolac on TRPA1 was detected in the cysteine mutant cells. These data indicate a novel mechanism of the anti-inflammatory and analgesic clinical effects of etodolac, which may be involved with its direct activation and the subsequent desensitization of TRPA1 through the covalent modification of cysteine residues.
authors.affiliation: State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China; Department of Pharmacy, School of Pharmacy, Hyogo University of Health Sciences, Kobe, Hyogo, Japan; Department of Anatomy and Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan; Traditional Medicine Research Center, Chinese Medicine Confucius Institute at Hyogo College of Medicine, Kobe, Hyogo, Japan.
authors.forename: Shenglan
authors.initials: S
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Dai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kogure
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Wensheng
authors.initials: W
authors.lastname: Zhang
authors.forename: Koichi
authors.initials: K
authors.lastname: Noguchi
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D017308:Etodolac / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D009419:Nerve Tissue Proteins / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074025:TRPA1 Cation Channel; D014162:Transfection; D050051:Transient Receptor Potential Channels / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D015220:Calcium Channels; D009419:Nerve Tissue Proteins; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; D017308:Etodolac
keywords: NSAIDs; desensitization; pain