Tissue monocytes/macrophages in inflammation: hyperalgesia versus opioid-mediated peripheral antinociception

Title

Tissue monocytes/macrophages in inflammation: hyperalgesia versus opioid-mediated peripheral antinociception

Creator

Brack A; Labuz D; Schiltz A; Rittner HL; Machelska H; Schafer M; Reszka R; Stein C

Publisher

Anesthesiology

Date

2004

Subject

Male; Analgesics; Animals; Rats; Biomarkers of Pain; Injections; Pain Measurement/drug effects; Freund's Adjuvant; Wistar; Flow Cytometry; Foot/pathology; Opioid/administration & dosage/pharmacology; Clodronic Acid/pharmacokinetics/pharmacology; Fentanyl/administration & dosage/pharmacology; Heat; Hyperalgesia/chemically induced/pathology/psychology; Inflammation/chemically induced/pathology; Liposomes; Macrophages/pathology; Monocytes/pathology; Non-Narcotic/pharmacokinetics/pharmacology; Pressure

Description

BACKGROUND: Opioid-containing leukocytes migrate to peripheral sites of inflammation. On exposure to stress, opioid peptides are released, bind to opioid receptors on peripheral sensory neurons, and induce endogenous antinociception. In later stages of Freund's complete adjuvant-induced local inflammation, monocytes/macrophages are a major opioid-containing leukocyte subpopulation, but these cells also produce proalgesic cytokines. In this study, the role of tissue monocytes/macrophages in hyperalgesia and in peripheral opioid-mediated antinociception was investigated. METHODS: After intraplantar injection of Freund's adjuvant, leukocyte subpopulations and opioid-containing leukocytes were analyzed by flow cytometry in the inflamed paw in the presence or absence of monocyte/macrophage depletion by intraplantar injection of clodronate-containing liposomes (phosphate-buffered saline and empty liposomes served as controls). Paw volume was measured with a plethysmometer. Hyperalgesia was determined by measuring heat-induced paw withdrawal latency and paw pressure threshold. Paw pressure threshold was also measured after swim stress and injection of fentanyl. RESULTS: At 48 and 96 h of inflammation, it was found that (1). monocytes/macrophages were the largest leukocyte subpopulation (> 55% of all leukocytes) and the predominant producers of opioid peptides (71-77% of all opioid-containing leukocytes in the paw), (2). clodronate-containing liposomes depleted monocytes/macrophages by 30-35% (P 0.05), and (4) opioid-containing leukocytes and swim stress but not fentanyl-induced antinociception were significantly decreased by clodronate-containing liposomes (P 0.05, all by t test; opioid-containing cells and swim stress-induced increase of paw pressure threshold were reduced by 35-42% and 20%, respectively). CONCLUSION: Partial depletion of tissue monocytes/macrophages impairs peripheral endogenous opioid-mediated antinociception without affecting hyperalgesia.
2004

Rights

Article information provided for research and reference use only. PedPalASCNET does not hold any rights over the resource listed here. All rights are retained by the journal listed under publisher and/or the creator(s).

Type

Journal Article

Citation List Month

Backlog

Pages

204-211

Issue

1

Volume

101

Citation

Brack A; Labuz D; Schiltz A; Rittner HL; Machelska H; Schafer M; Reszka R; Stein C, “Tissue monocytes/macrophages in inflammation: hyperalgesia versus opioid-mediated peripheral antinociception,” Pediatric Palliative Care Library, accessed May 22, 2022, https://pedpalascnetlibrary.omeka.net/items/show/12841.

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