Protease-activated receptor 2 sensitizes the transient receptor potential vanilloid 4 ion channel to cause mechanical hyperalgesia in mice.
Exacerbated sensitivity to mechanical stimuli that are normally innocuous or mildly painful (mechanical allodynia and hyperalgesia) occurs during inflammation and underlies painful diseases. Proteases that are generated during inflammation and disease cleave protease-activated receptor 2 (PAR2) on afferent nerves to cause mechanical hyperalgesia in the skin and intestine by unknown mechanisms. We hypothesized that PAR2-mediated mechanical hyperalgesia requires sensitization of the ion channel transient receptor potential vanilloid 4 (TRPV4). Immunoreactive TRPV4 was coexpressed by rat dorsal root ganglia (DRG) neurons with PAR2, substance P (SP) and calcitonin gene-related peptide (CGRP), mediators of pain transmission. In PAR2-expressing cell lines that either naturally expressed TRPV4 (bronchial epithelial cells) or that were transfected to express TRPV4 (HEK cells), pretreatment with a PAR2 agonist enhanced Ca2+ and current responses to the TRPV4 agonists phorbol ester 4alpha-phorbol 12,13-didecanoate (4alphaPDD) and hypotonic solutions. PAR2-agonist similarly sensitized TRPV4 Ca2+ signals and currents in DRG neurons. Antagonists of phospholipase Cbeta and protein kinases A, C and D inhibited PAR2-induced sensitization of TRPV4 Ca2+ signals and currents. 4alphaPDD and hypotonic solutions stimulated SP and CGRP release from dorsal horn of rat spinal cord, and pretreatment with PAR2 agonist sensitized TRPV4-dependent peptide release. Intraplantar injection of PAR2 agonist caused mechanical hyperalgesia in mice and sensitized pain responses to the TRPV4 agonists 4alphaPDD and hypotonic solutions. Deletion of TRPV4 prevented PAR2 agonist-induced mechanical hyperalgesia and sensitization. This novel mechanism, by which PAR2 activates a second messenger to sensitize TRPV4-dependent release of nociceptive peptides and induce mechanical hyperalgesia, may underlie inflammatory hyperalgesia in diseases where proteases are activated and released.
Grant
Andrew D
AD
Department of Surgery, UCSF, 513 Parnassus Ave., Room S1268, San Francisco, CA 94143-0660, USA.
Cottrell
Graeme S
GS
Amadesi
Silvia
S
Trevisani
Marcello
M
Nicoletti
Paola
P
Materazzi
Serena
S
Altier
Christophe
C
Cenac
Nicolas
N
Zamponi
Gerald W
GW
Bautista-Cruz
Francisco
F
Lopez
Carlos Barajas
CB
Joseph
Elizabeth K
EK
Levine
Jon D
JD
Liedtke
Wolfgang
W
Vanner
Stephen
S
Vergnolle
Nathalie
N
Geppetti
Pierangelo
P
Bunnett
Nigel W
NW
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism; D006801:Humans; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D010455:Peptides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*
D010455:Peptides; D044464:Receptor, PAR-2; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C486576:Trpv4 protein, mouse; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide