574 Opioid System is Prominently Expressed in Inflamed Human Dental Pulp

Thursday, March 22, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Session
M.A. HENRY, S. LUO, M. LI, and K.M. HARGREAVES, Endodontics, University of Texas - San Antonio / Health Science Ctr, San Antonio, TX
The use of the tooth as a model system for studying pain mechanisms is well established.  Pulpitis is typically attributed to inflammatory mechanisms secondary to a bacterial invasion of the pulp.  Bacterial invasion results in immune responses and although the pain-promoting effects of immune cells are well known, other evidence suggests pain relief by the peripheral release of endogenous opioids from immune cells.  Although opioid-containing immune cells have been described in the inflamed rat dental pulp, similar studies in humans are lacking.  Objectives: The aim of this study was to characterize the effect of inflammation on the endogenous opioid system (peptides and receptors) within the human dental pulp.  Methods: Normal and inflamed human dental pulp sections were stained with antibodies against opioid peptides (β-endorphin/met-enkephalin/dynorphin A), or their receptors (mu/delta/kappa) with the indirect immunofluorescence method and evaluated with confocal microscopy.  Expressions were characterized within N52/PGP9.5-identified axons, and the expression of β-endorphin was further characterized within specific immune cells with CD3 (T-lymphocytes), CD14 (monocytes/macrophages), CD23 (B-lymphocytes) and SPM250 (granulocytes) antibodies.  Results: All opioid peptides were minimally expressed within normal specimens, but were prominently expressed within immune cells in inflamed specimens.  Use of immune cell-specific antibodies showed prominent β-endorphin expression within B-lymphocytes and macrophages, less so in T-lymphocytes and rare in granulocytes.  All three opioid-receptors showed minimal expression in normal specimens but with a prominent expression within immune cells and in nerve fibers in inflamed specimens.  Conclusions: Opioid peptides and receptors are highly expressed within the inflamed human dental pulp.  Activation of the endogenous opioid system provides a potent method to modify pulpitis pain severity and may contribute to the varying pain levels experienced in patients with pulpitis.
This abstract is based on research that was funded entirely or partially by an outside source: NIDCR DE015576

Keywords: Immune response, Neuroscience, Opioids, Pain and Pulp
See more of: Neuroscience II
See more of: Neuroscience