Selective local PMN recruitment by CXCL1 or CXCL2/3 injection does not cause inflammatory pain

J Leukoc Biol. 2006 May;79(5):1022-32. doi: 10.1189/jlb.0805452. Epub 2006 Mar 7.

Abstract

Polymorphonuclear cells (PMN) are recruited in early inflammation and are believed to contribute to inflammatory pain. However, studies demonstrating a hyperalgesic role of PMN did not examine selective PMN recruitment or did not document effective PMN recruitment. We hypothesized that hyperalgesia does not develop after chemokine-induced PMN selective recruitment and is independent of PMN infiltration in complete Freund's adjuvant (CFA)-induced, local inflammation. PMN were recruited by intraplantar injection of CXC chemokine ligand 1 (CXCL1; keratinocyte-derived chemokine), CXCL2/3 (macrophage inflammatory protein-2), or CFA, with or without preceding systemic PMN depletion. Chemokine inoculation resulted in dose (0-30 microg)- and time (0-12 h)-dependent, selective recruitment of PMN as quantified by flow cytometry. CXCL2/3, but not CXCL1, was less effective at high doses, probably as a result of significant down-regulation of CXC chemokine receptor 2 expression on blood PMN. Neither chemokine caused mechanical or thermal hyperalgesia as determined by the Randall-Selitto and Hargreaves test, respectively, despite comparable expression of activation markers (i.e., CD11b, CD18, and L-selectin) on infiltrating PMN. In contrast, CFA injection induced hyperalgesia, independent of PMN recruitment. c-Fos mRNA and immunoreactivity in the spinal cord were increased significantly after inoculation of CFA-independent of PMN-migration but not of CXCL2/3. Measurement of potential hyperalgesic mediators showed that hyperalgesia correlated with local prostaglandin E2 (PGE2) but not with interleukin-1beta production. In summary, hyperalgesia, local PGE2 production, and spinal c-Fos expression occur after CFA-induced inflammation but not after CXCL1- or CXCL2/3-induced, selective PMN recruitment. Thus, PMN seem to be less important in inflammatory hyperalgesia than previously thought.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Surface / immunology
  • Biomarkers / metabolism
  • Chemokine CXCL1
  • Chemokine CXCL2
  • Chemokines, CXC / immunology*
  • Chemokines, CXC / pharmacology
  • Chemotaxis, Leukocyte / drug effects
  • Chemotaxis, Leukocyte / immunology*
  • Cytokines / metabolism
  • Dinoprostone / metabolism
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Down-Regulation / drug effects
  • Down-Regulation / immunology
  • Freund's Adjuvant / pharmacology
  • Hyperalgesia / chemically induced
  • Hyperalgesia / immunology
  • Hyperalgesia / physiopathology
  • Inflammation / chemically induced
  • Inflammation / immunology*
  • Inflammation / physiopathology
  • Male
  • Neutrophils / drug effects
  • Neutrophils / immunology*
  • Pain / chemically induced
  • Pain / immunology*
  • Pain / physiopathology
  • Pain Measurement
  • Posterior Horn Cells / metabolism
  • Proto-Oncogene Proteins c-fos / genetics
  • Rats
  • Rats, Wistar
  • Time Factors
  • Up-Regulation / drug effects
  • Up-Regulation / immunology

Substances

  • Antigens, Surface
  • Biomarkers
  • Chemokine CXCL1
  • Chemokine CXCL2
  • Chemokines, CXC
  • Cxcl1 protein, rat
  • Cxcl2 protein, rat
  • Cytokines
  • Proto-Oncogene Proteins c-fos
  • Freund's Adjuvant
  • Dinoprostone