The Neural Cell Adhesion Molecule Antibody Blocks Cold Water Swim Stress-Induced Analgesia and Cell Adhesion Between Lymphocytes and Cultured Dorsal Root Ganglion Neurons

Abstract

In Brief BACKGROUND: Opioid-containing immune cells migrate in a site-directed manner into inflamed tissue and adhere to sensory nerve fibers. These cells release opioid peptides in close proximity to these fibers, thereby avoiding localized degradation by peptidases, and delivering opioid peptides proximal to opioid receptors to provide antinociception. METHODS: The effects of the anti–neural-cell-adhesion molecule (anti-NCAM) were assessed on cold water swim stress-induced antinociception in Wistar rats with Freund’s adjuvant-induced inflammation of one hindpaw. Algesiometry was assessed for both thermal and mechanical stimuli. Cell adhesion experiments examining the effects of β-endorphin and antibodies to NCAM and intercellular cell adhesion molecule-1 and were performed on cultured dorsal root ganglion neurons and isolated lymphocytes. Lymphocyte binding was determined by fluorescence using calcein AM loaded into freshly isolated lymphocytes. RESULTS: The direct adhesion between lymphocytes and cultured sensory neurons was inhibited by anti-NCAM. This adhesion was also demonstrated to be opioid dependent, with lymphocyte adhesion to cultured sensory neurons reduced in the presence of 1 μM β-endorphin, which was reversed by 100 μM naloxone. Moreover, anti-NCAM blocked cold-water-swim-induced analgesia in inflamed paws both to thermal and mechanical stimuli. However, anti-NCAM did not affect fentanyl-induced antinociception. CONCLUSIONS: This study provides insight into the role of cell adhesion molecules in lymphocyte adhesion to sensory neurons and a link to immune-derived antinociception. IMPLICATIONS: The immune system not only contributes to inflammation, it also provides localized analgesia. The means by which this analgesia is provided within inflamed tissue is not fully understood. These studies demonstrate evidence for the direct adhesion between neurons and immune cells in vitro and the role this adhesion may have in immune-derived analgesia. This has implications on new therapeutics that might enhance this binding interaction to improve analgesic effects.