The antinociceptive effects of JWH-015 in chronic inflammatory pain are produced by nitric oxide-cGMP-PKG-KATP pathway activation mediated by opioids.
BACKGROUND
Cannabinoid 2 receptor (CB2R) agonists attenuate inflammatory pain but the precise mechanism implicated in these effects is not completely elucidated. We investigated if the peripheral nitric oxide-cGMP-protein kinase G (PKG)-ATP-sensitive K(+) (KATP) channels signaling pathway triggered by the neuronal nitric oxide synthase (NOS1) and modulated by opioids, participates in the local antinociceptive effects produced by a CB2R agonist (JWH-015) during chronic inflammatory pain.


RESULTS
In wild type (WT) and NOS1 knockout (NOS1-KO) mice, at 10 days after the subplantar administration of complete Freund's adjuvant (CFA), we evaluated the antiallodynic (von Frey filaments) and antihyperalgesic (plantar test) effects produced by the subplantar administration of JWH-015 and the reversion of their effects by the local co-administration with CB2R (AM630), peripheral opioid receptor (naloxone methiodide, NX-ME) or CB1R (AM251) antagonists. Expression of CB2R and NOS1 as well as the antinociceptive effects produced by a high dose of JWH-015 combined with different doses of selective L-guanylate cyclase (ODQ) or PKG (Rp-8-pCPT-cGMPs) inhibitors or a KATP channel blocker (glibenclamide), were also assessed. Results show that the local administration of JWH-015 dose-dependently inhibited the mechanical and thermal hypersensitivity induced by CFA which effects were completely reversed by the local co-administration of AM630 or NX-ME, but not AM251. Inflammatory pain increased the paw expression of CB2R and the dorsal root ganglia transcription of NOS1. Moreover, the antinociceptive effects of JWH-015 were absent in NOS1-KO mice and diminished by their co-administration with ODQ, Rp-8-pCPT-cGMPs or glibenclamide.


CONCLUSIONS
These data indicate that the peripheral antinociceptive effects of JWH-015 during chronic inflammatory pain are mainly produced by the local activation of the nitric oxide-cGMP-PKG-KATP signaling pathway, triggered by NOS1 and mediated by endogenous opioids. These findings suggest that the activation of this pathway might be an interesting therapeutic target for the treatment of chronic inflammatory pain with cannabinoids.
Grup de Neurofarmacologia Molecular, Institut de Recerca de l'Hospital de la Sta Creu i Sant Pau and Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain.
Roger
R
Negrete
Arnau
A
Hervera
Sergi
S
Leánez
Jesús M
JM
Martín-Campos
Olga
O
Pol
D000700:Analgesics / Q000627:therapeutic use*; D000701:Analgesics, Opioid / Q000378:metabolism*; D000818:Animals; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism; D005905:Glyburide / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology / Q000627:therapeutic use*; D054086:KATP Channels / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009270:Naloxone / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D010146:Pain / Q000188:drug therapy* / Q000276:immunology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D043882:Receptors, Cannabinoid / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013873:Thionucleotides
C090860:8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphorothioate; D000700:Analgesics; D000701:Analgesics, Opioid; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D007211:Indoles; D054086:KATP Channels; D010880:Piperidines; D011720:Pyrazoles; D000644:Quaternary Ammonium Compounds; D043882:Receptors, Cannabinoid; D013873:Thionucleotides; D009569:Nitric Oxide; D009270:Naloxone; C103505:AM 251; C041269:N-methylnaloxone; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; D006152:Cyclic GMP; D005905:Glyburide; C094023:iodopravadoline; C402944:JHW 015