The Putative Cannabinoid Receptor GPR55 Plays a Role in Mechanical Hyperalgesia Associated With Inflammatory and Neuropathic Pain

Pain. 2008 Sep 30;139(1):225-36. doi: 10.1016/j.pain.2008.04.006. Epub 2008 May 27.

Abstract

It has been postulated that the G protein-coupled receptor, GPR55, is a third cannabinoid receptor. Given that the ligands at the CB(1) and CB(2) receptors are effective analgesic and anti-inflammatory agents, the role of GPR55 in hyperalgesia associated with inflammatory and neuropathic pain has been investigated. As there are no well-validated GPR55 tool compounds, a GPR55 knockout (GPR55(-/-)) mouse line was generated and fully backcrossed onto the C57BL/6 strain. General phenotypic analysis of GPR55(-/-) mice revealed no obvious primary differences, compared with wild-type (GPR55(+/+)) littermates. GPR55(-/-) mice were then tested in the models of adjuvant-induced inflammation and partial nerve ligation. Following intraplantar administration of Freund's complete adjuvant (FCA), inflammatory mechanical hyperalgesia was completely absent in GPR55(-/-) mice up to 14 days post-injection. Cytokine profiling experiments showed that at 14 days post-FCA injection there were increased levels of IL-4, IL-10, IFN gamma and GM-CSF in paws from the FCA-injected GPR55(-/-) mice when compared with the FCA-injected GPR55(+/+) mice. This suggests that GPR55 signalling can influence the regulation of certain cytokines and this may contribute to the lack of inflammatory mechanical hyperalgesia in the GPR55(-/-) mice. In the model of neuropathic hypersensitivity, GPR55(-/-) mice also failed to develop mechanical hyperalgesia up to 28 days post-ligation. These data clearly suggest that the manipulation of GPR55 may have therapeutic potential in the treatment of both inflammatory and neuropathic pain.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Female
  • Hyperalgesia / genetics
  • Hyperalgesia / metabolism*
  • Inflammation / genetics
  • Inflammation / metabolism
  • Inflammation / physiopathology
  • Inflammation Mediators / metabolism
  • Inflammation Mediators / physiology*
  • Ligation
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Molecular Sequence Data
  • Neuralgia / genetics
  • Neuralgia / metabolism*
  • Pain Measurement / methods
  • Physical Stimulation / methods
  • Receptors, Cannabinoid / deficiency
  • Receptors, Cannabinoid / genetics
  • Receptors, Cannabinoid / physiology*

Substances

  • GPR55 protein, mouse
  • Inflammation Mediators
  • Receptors, Cannabinoid