Levels of Methionine Enkephalin and Substance P are Elevated in Inflamed Human Tooth Pulp

Abstract

Purpose of the study: Endogenous opioid peptides such as methionine enkephalin (ME) and neuropeptides such as substance P (SP) are involved in modulating pain sensitive neurons. Recent studies have used human peripheral tissue such as dental pulp to investigate the effects whether inflammation and decay affect neuropeptide levels, this study investigates whether ME and SP levels are altered in inflamed human tooth pulp. Methods: After Ethics Committee approval, ME and SP were extracted in 250 µl of 0.5M acetic acid from the tooth pulp of 8 patients: 4 with healthy pulps and 4 with inflamed pulps. We used liquid chromatography and mass spectrometry (LC–MS) to detect changes in peptide concentration in the extracts. Peptide levels were compared to standard curves for each peptide, each sample was run in triplicate. Results: Both ME (1.20 ng/µl) and SP (1.86 ng/µl) were present in healthy pulp, and the levels of both peptides were significantly increased in inflamed tissue (4.37 ng/µl) for ME and 6.90 ng/µl for SP (P = 0.029 and P < 0.001 for ME and SP respectively). [Figure 1][1] illustrates the changes in peptide levels in inflammation compared to a healthy status. ![Figure 1][2] Figure 1 Graph shows the concentration of ME and SP in both experimental groups (n = 8). *Significant difference compared inflamed with control group (P = 0.029 for ME and P < 0.001 for SP). Conclusions: Inflammation in teeth can lead to severe pain in patients. We have, for the first time, identified an elevation of an endogenous opioid in inflamed human teeth, providing further evidence for endogenous analgesic mechanisms that may be therapeutically manipulated. [1]: #F1 [2]: pending:yes