Control of inflammatory pain by chemokine-mediated recruitment of opioid-containing polymorphonuclear cells

Control of inflammatory pain by chemokine-mediated recruitment of opioid-containing polymorphonuclear cells

Brack A; Rittner HL; Machelska H; Leder K; Mousa SA; Schafer M; Stein C

Pain

2004

Male; Pain Measurement; Analysis of Variance; Animals; Rats; Non-U.S. Gov't; Research Support; Comparative Study; Dose-Response Relationship; Drug; Receptors; Naloxone/pharmacology; Freund's Adjuvant; Wistar; Flow Cytometry/methods; Antibodies/pharmacology; Cell Count/methods; Cell Movement/physiology; Chemokines; Chemokines/immunology/physiology; Corticotropin-Releasing Hormone/therapeutic use; CXC/immunology/metabolism; Drug Administration Routes; Enzyme-Linked Immunosorbent Assay/methods; Gene Expression Regulation/physiology; Immunohistochemistry/methods; Intercellular Signaling Peptides and Proteins/immunology/metabolism; Interleukin-8B/metabolism; Narcotics/metabolism; Neurogenic Inflammation/chemically induced/complications/therapy; Neutrophils/metabolism; Pain Threshold/drug effects; Pain/etiology/therapy

Opioid-containing leukocytes can counteract inflammatory hyperalgesia. Under stress or after local injection of corticotropin releasing factor (CRF), opioid peptides are released from leukocytes, bind to opioid receptors on peripheral sensory neurons and mediate antinociception. Since polymorphonuclear cells (PMN) are the predominant opioid-containing leukocyte subpopulation in early inflammation, we hypothesized that PMN and their recruitment by chemokines are important for peripheral opioid-mediated antinociception at this stage. Rats were intraplantarly injected with complete Freund's adjuvant (CFA). Using flow cytometry, immunohistochemistry, and ELISA, leukocyte subpopulations, chemokine receptor (CXCR2) expression on opioid-containing leukocytes and the CXCR2 ligands keratinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant-2 (CINC-2) were quantified. Paw pressure threshold (PPT) was determined before and after intraplantar and subcutaneous injection of CRF with or without naloxone. PMN depletion was achieved by intravenous injection of an antiserum. Chemokines were blocked by intraplantar injection of anti-MIP-2 and/or anti-KC antiserum. We found that at 2 h post CFA (i) intraplantar but not subcutaneous injection of CRF produced dose-dependent and naloxone-reversible antinociception (P0.05, ANOVA). In summary, in early inflammation peripheral opioid-mediated antinociception is critically dependent on PMN and their recruitment by CXCR2 chemokines.

2004

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