The role of G-protein receptor 84 in experimental neuropathic pain

Louise S C Nicol, John M. Dawes, Federica La Russa, Athanasios Didangelos, Anna K. Clark, Clive Gentry, John Grist, John B. Davies, Marzia Malcangio, Stephen B. McMahon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)
189 Downloads (Pure)

Abstract

G-protein receptor 84 (GPR84) is an orphan receptor that is induced markedly in monocytes/macrophages and microglia during inflammation, but its pathophysiological function is unknown. Here, we investigate the role of GPR84 in a murine model of traumatic nerve injury. Naive GPR84 knock-out (KO) mice exhibited normal behavioral responses to acute noxious stimuli, but subsequent to partial sciatic nerve ligation (PNL), KOs did not develop mechanical or thermal hypersensitivity, in contrast to wild-type (WT) littermates. Nerve injury increased ionized calcium binding adapter molecule 1 (Iba1) and phosphorylated p38 MAPK immunoreactivity in the dorsal horn and Iba1 and cluster of differentiation 45 expression in the sciatic nerve, with no difference between genotypes. PCR array analysis revealed that Gpr84 expression was upregulated in the spinal cord and sciatic nerve of WT mice. In addition, the expression of arginase-1, a marker for anti-inflammatory macrophages, was upregulated in KO sciatic nerve. Based on this evidence, we investigated whether peripheral macrophages behave differently in the absence of GPR84. We found that lipopolysaccharide-stimulated KO macrophages exhibited attenuated expression of several proinflammatory mediators, including IL-1β, IL-6, and TNF-α. Forskolin-stimulated KO macrophages also showed greater cAMP induction, a second messenger associated with immunosuppression. In summary, our results demonstrate that GPR84 is a proinflammatory receptor that contributes to nociceptive signaling via the modulation of macrophages, whereas in its absence the response of these cells to an inflammatory insult is impaired.

Original languageEnglish
Pages (from-to)8959-8969
Number of pages11
JournalJournal of Neuroscience
Volume35
Issue number23
DOIs
Publication statusPublished - 10 Jun 2015

Keywords

  • Cytokine
  • G-protein linked receptors
  • Inflammation
  • Macrophage
  • Microglia
  • Neuropathic pain

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