title: Contribution of transient receptor potential vanilloid subfamily 1 to endothelin-1-induced thermal hyperalgesia.
abstract: Endothelin-1 (ET-1) plays an important role in peripheral pain processing. However, the mechanisms of the nociceptive action of ET-1 have not been fully elucidated. In this study, we investigated the contribution of transient receptor potential vanilloid subfamily 1 (TRPV1) to ET-1-induced thermal hyperalgesia. Intraplantar ET-1-induced thermal hyperalgesia was examined by assessing the paw withdrawal latency to noxious heat stimuli. In electrophysiological study, whole-cell patch-clamp recordings were performed to investigate the interaction of ET-1 and TRPV1 using human embryonic kidney 293 (HEK293) cells expressing endothelin type A receptor (ET(A)) and TRPV1. Intraplantar ET-1 (3, 10 and 30 pmol) produced thermal hyperalgesia in a dose-dependent manner. Thermal hyperalgesia was attenuated by the inhibition of ET(A) and protein kinase C (PKC) but not that of ET(B). ET-1-induced thermal hyperalgesia was significantly attenuated in TRPV1-deficient mice compared with that in wild-type mice. In voltage-clamp experiments, 10 nM capsaicin evoked small inward currents in HEK293 cells expressing TRPV1 and ET(A). In the presence of ET-1, capsaicin produced much larger current responses (P<0.05). Mutation at PKC-specific TRPV1 phosphorylation sites (S800A/S502A) and PKC inhibitors inhibited the potentiating effect of ET-1. In addition, ET-1 decreased the temperature threshold for TRPV1 activation in a PKC-dependent manner (from 41.0+/-0.4 degrees C to 32.6+/-0.6 degrees C). In addition, Western blot analysis was also performed to confirm ET-1-induced phosphorylation of TRPV1. Incubation of ET-1 and intraplantar ET-1 evoked phosphorylation of TRPV1 in HEK293 cells expressing TRPV1 and ET(A) and the skin, respectively. These results suggest that the sensitization of TRPV1 activity through an ET(A)-PKC pathway contributes to ET-1-induced thermal hyperalgesia.
authors.affiliation: Department of Anesthesiology, Sapporo Medical University School of Medicine, South 1, West 16, Chuo-ku, Sapporo, 060-8543, Japan. kawamata@sapmed.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kawamata
authors.forename: W
authors.initials: W
authors.lastname: Ji
authors.forename: J
authors.initials: J
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Niiyama
authors.forename: S
authors.initials: S
authors.lastname: Furuse
authors.forename: A
authors.initials: A
authors.lastname: Namiki
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D015153:Blotting, Western; D002211:Capsaicin / Q000494:pharmacology; D002460:Cell Line; D004594:Electrophysiology; D019332:Endothelin-1 / Q000633:toxicity*; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced* / Q000503:physiopathology* / Q000523:psychology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011930:Reaction Time; D044022:Receptor, Endothelin A / Q000187:drug effects; D050916:TRPV Cation Channels / Q000502:physiology*
chemical_list: D019332:Endothelin-1; D044022:Receptor, Endothelin A; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D011493:Protein Kinase C; D002211:Capsaicin