title: NFκB-mediated CXCL1 production in spinal cord astrocytes contributes to the maintenance of bone cancer pain in mice.
abstract: BACKGROUND
  Bone cancer pain (BCP) is one of the most disabling factors in patients suffering from primary bone cancer or bone metastases. Recent studies show several chemokines (for example, CCL2, CXCL10) in the spinal cord are involved in the pathogenesis of BCP. Here we investigated whether and how spinal CXCL1 contributes to BCP.
  
  
  METHODS
  Mouse prostate tumor cell line, RM-1 cells were intramedullary injected into the femur to induce BCP. The mRNA expression of CXCL1 and CXCR2 was detected by quantitative real-time PCR. The protein expression and distribution of CXCL1, NFκB, and CXCR2 was examined by immunofluorescence staining and western blot. The effect of CXCL1 neutralizing antibody, NFκB antagonist, and CXCR2 antagonist on pain hypersensitivity was checked by behavioral testing.
  
  
  RESULTS
  Intramedullary injection of RM-1 cells into the femur induced cortical bone damage and persistent (>21 days) mechanical allodynia and heat hyperalgesia. Tumor cell inoculation also produced CXCL1 upregulation in activated astrocytes in the spinal cord for more than 21 days. Inhibition of CXCL1 by intrathecal administration of CXCL1 neutralizing antibody at 7 days after inoculation attenuated mechanical allodynia and heat hyperalgesia. In cultured astrocytes, TNF-α induced robust CXCL1 expression, which was dose-dependently decreased by NFκB inhibitor. Furthermore, inoculation induced persistent NFκB phosphorylation in spinal astrocytes. Intrathecal injection of NFκB inhibitor attenuated BCP and reduced CXCL1 increase in the spinal cord. Finally, CXCR2, the primary receptor of CXCL1, was upregulated in dorsal horn neurons after inoculation. Inhibition of CXCR2 by its selective antagonist SB225002 attenuated BCP.
  
  
  CONCLUSIONS
  NFκB mediates CXCL1 upregulation in spinal astrocytes in the BCP model. In addition, CXCL1 may be released from astrocytes and act on CXCR2 on neurons in the spinal cord and be involved in the maintenance of BCP. Inhibition of the CXCL1 signaling may provide a new therapy for BCP management.
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
authors.forename: Ming-Di
authors.initials: MD
authors.lastname: Zhu
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Tian
authors.forename: Jin-Hua
authors.initials: JH
authors.lastname: Zhang
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Wu
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, 19 Qixiu Road, Nantong 226001, China. gaoyongjing@hotmail.com.
authors.forename: Yong-Jing
authors.initials: YJ
authors.lastname: Gao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000627:therapeutic use; D001253:Astrocytes / Q000502:physiology*; D001859:Bone Neoplasms / Q000150:complications* / Q000556:secondary; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D054360:Chemokine CXCL1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009368:Neoplasm Transplantation; D009570:Nitriles / Q000494:pharmacology; D010146:Pain / Q000188:drug therapy / Q000209:etiology* / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology; D013116:Spinal Cord / Q000473:pathology*; D013450:Sulfones / Q000494:pharmacology
chemical_list: C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D000906:Antibodies; D054360:Chemokine CXCL1; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D009570:Nitriles; D013450:Sulfones