Isothiocyanates from Wasabia japonica Activate Transient Receptor Potential Ankyrin 1 Channel

Methylsulfinyl)hexyl isothiocyanate (6-MSITC) and 6-(methylthio)hexyl isothiocyanate (6-MTITC) have low pungency and are responsible for the fresh flavor of wasabi (Wasabia japonica (Miq) Matsumura). In this study, we found that these two isothiocyanates activate transient receptor potential ankyrin 1 (TRPA1), and 6-MSITC activates transient receptor potential vanilloid 1 (TRPV1), but not other transient receptor potential channels expressed in sensory neurons. Both 6-MSITC and 6-MTITCinduced intracellular Ca 2+ increases in human embryonic kidney-derived 293 cells expressing mouse TRPA1 (mTRPA1) as measured by Ca 2+ imaging. In whole-cell patch-clamp recordings, 6-MSITC and 6-MTITC dose-dependently activated both mTRPA1 (EC50 = 147 ± 26 µ M for 6-MSITC and 30 ± 3 µ M for 6-MTITC) and human TRPA1 (hTRPA1; EC50 = 39 ± 4 µ M for 6-MSITC and 34 ± 3 µ M for 6-MTITC). In addition, TRPA1 N-terminal cysteines, which are reported to be important for channel activation by electrophilic ligands, were involved in 6-MSITC- and 6-MTITC-evoked TRPA1 activation. These isothio- cyanates also activated endogenous TRPA1 expressed in mouse dorsal root ganglion neurons and intraplantar injection of 10-30 mM 6-MSITC-evoked pain-r elated behaviors in mice. These results indicate the following: 1) 6-MSITC and 6-MTITC activate both mTRPA1 and hTRPA1; 2) 6-MSITC activates mTRPV1; and 3) the pharmacological functions of these isothiocy- anates could be derived from TRPA1 activation.