Endothelin potentiates TRPV1 via ETA receptor-mediated activation of protein kinase C.
BACKGROUND
Endothelin-1 (ET-1) both stimulates nociceptors and sensitizes them to noxious stimuli, an effect probably mediated by the ETA receptor (ETAR) expressed in sensory neurons. The cellular mechanisms of this ET-1-mediated effect are only poorly understood. TRPV1, the heat-, pH- and capsaicin-sensitive cation channel already known to be modulated by a number of cellular mediators released in response to noxious stimuli and during inflammation, is a potential target for the action of ET-1.


RESULTS
We studied the effects of ET-1 on TRPV1 in sensory neurons from the dorsal root ganglion (DRG) and in HEK293 cells coexpressing TRPV1 and the ETAR. Specific 125I-ET-1 binding sites (817 +/- 92 fmol/mg) were detected in membrane preparations of DRG with an ETAR/ETBR ratio of 60:40. In an immunofluorescence analysis, coexpression of TRPV1 and the ETAR was found in a subpopulation of primary sensory neurons. ET-1 strongly potentiated capsaicin-induced TRPV1 currents in some neurons, and in HEK293 cells co-expressing TRPV1 and the ETAR. Weaker potentiation was observed in HEK293 cells coexpressing TRPV1 and the ETBR. ETAR activation also increased responses to low pH and heat. In HEK293 cells, strong potentiation of TRPV1 like that induced by ET-1 via the ETAR could be induced by PKC activation, but not with activators of the adenylyl cyclase or the PKA pathway. Furthermore, inhibition of PKC with bisindolylmaleimide X (BIM X) or mutation of the PKC phosphorylation site S800 completely prevented ETAR-mediated potentiation.


CONCLUSIONS
We conclude that ET-1 potentiates TRPV1 by a PKC-dependent mechanism and that this could play a major role in the algogenic and hyperalgesic effects of ET-1 described in previous studies.
Plant
Tim D
TD
Institut für Pharmakologie und Toxikologie, FB-Medizin, Philipps-Universität Marburg, Karl-von-Frisch-Str, 1, 35032 Marburg, Germany. plant@staff.uni-marburg.de
Zöllner
Christian
C
Kepura
Frauke
F
Mousa
Shaaban S
SS
Eichhorst
Jenny
J
Schaefer
Michael
M
Furkert
Jens
J
Stein
Christoph
C
Oksche
Alexander
A
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009154:Mutation; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D019332:Endothelin-1; D007295:Inositol Phosphates; D044022:Receptor, Endothelin A; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D005576:Colforsin; D000242:Cyclic AMP; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002211:Capsaicin