title: Activation of spinal MrgC-Gi-NR2B-nNOS signaling pathway by Mas oncogene-related gene C receptor agonist bovine adrenal medulla 8-22 attenuates bone cancer pain in mice.
abstract: OBJECTIVE
  In the present study, we investigate the effects of Mas oncogene-related gene (Mrg) C receptors (MrgC) on the expression and activation of spinal Gi protein, N-methyl-D-aspartate receptor subunit 2B (NR2B), and neuronal nitric oxide synthase (nNOS) in mouse model of bone cancer pain.
  
  
  METHODS
  The number of spontaneous foot lift (NSF) and paw withdrawal mechanical threshold (PWMT) were measured after inoculation of tumor cells and intrathecal injection of MrgC agonist bovine adrenal medulla 8-22 (BAM8-22) or MrgC antagonist anti-MrgC for 14 days after operation. Expression of spinal MrgC, Gi protein, NR2B and nNOS and their phosphorylated forms after inoculation was examined by immunohistochemistry and Western blotting. Double labeling was used to identify the co-localization of NR2B or nNOS with MrgC in spinal cord dorsal horn (SCDH) neurons. The effects of intrathecal injection of BAM8-22 or anti-MrgC on nociceptive behaviors and the corresponding expression of spinal MrgC, Gi protein, NR2B and nNOS were also investigated.
  
  
  RESULTS
  The expression of spinal MrgC, Gi protein, NR2B, and nNOS was higher in tumor-bearing mice in comparison to sham mice or normal mice. Intrathecal injection of MrgC agonist BAM8-22 significantly alleviated bone cancer pain, up-regulated MrgC and Gi protein expression, and down-regulated the expression of spinal p-NR2B, t-nNOS and p-nNOS in SCDH on day 14 after operation, whereas administration of anti-MrgC produced the opposite effect. Meanwhile, MrgC-like immunoreactivity (IR) co-localizes with NR2B-IR or nNOS-IR in SCDH neurons.
  
  
  CONCLUSIONS
  The present study demonstrates that MrgC-activated spinal Gi-NR2B-nNOS signaling pathway plays important roles in the development of bone cancer pain. These findings may provide a novel strategy for the treatment of bone cancer pain.
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Yu'e
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Juan
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Yishan
authors.initials: Y
authors.lastname: Lei
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Cui'e
authors.initials: C
authors.lastname: Lu
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Bailing
authors.initials: B
authors.lastname: Hou
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Zhengliang
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University Nanjing 210008, P. R. China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Gu
keywords: BAM8-22; Gi protein; MrgC; NR2B; anti-MrgC; bone cancer pain; nNOS