Involvement of leptin signaling in the development of cannabinoid CB2 receptor-dependent mirror image pain

Sci Rep. 2018 Jul 17;8(1):10827. doi: 10.1038/s41598-018-28507-6.

Abstract

Neuropathic pain typically appears in a region innervated by an injured or diseased nerve and, in some instances, also on the contralateral side. This so-called mirror image pain is often observed in mice lacking CB2 receptors after sciatic nerve injury, but the underlying mechanisms for this phenotype largely remain unclear. Here we focused on peripheral leptin signaling, which modulates neuropathic pain development and interacts with the endocannabinoid system. Leptin production is induced at the site of nerve injury in CB2-deficient mice (CB2-KO) mice and wild type controls (WT). However, induction of leptin receptor expression was only observed in the injured nerve of CB2-KO mice. This was paralleled by a stimulation of the leptin receptor-downstream STAT3 signaling and an infiltration of F4/80-positive macrophages. Interestingly, an upregulation of leptin receptor expression STAT3 activity and macrophage infiltration was also observed on the non-injured nerve of CB2-KO mice thus reflecting the mirror image pain in CB2-KO animals. Importantly, perineurally-administered leptin-neutralizing antibodies reduced mechanical hyperalgesia, blocked mirror image pain and inhibited the recruitment of F4/80-positive macrophages. These results identify peripheral leptin signaling as an important modulator of CB2 signaling in neuropathic pain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Neutralizing / administration & dosage
  • Hyperalgesia / drug therapy
  • Leptin / immunology
  • Leptin / metabolism*
  • Macrophages / cytology
  • Macrophages / immunology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neuralgia / drug therapy
  • Neuralgia / etiology
  • Neuralgia / pathology*
  • Peripheral Nerve Injuries / complications
  • Peripheral Nerve Injuries / pathology
  • Receptor, Cannabinoid, CB2 / genetics
  • Receptor, Cannabinoid, CB2 / metabolism*
  • Receptors, Leptin / metabolism
  • STAT3 Transcription Factor / metabolism
  • Sciatic Nerve / metabolism
  • Signal Transduction
  • Up-Regulation

Substances

  • Antibodies, Neutralizing
  • Leptin
  • Receptor, Cannabinoid, CB2
  • Receptors, Leptin
  • STAT3 Transcription Factor