SYNOPSIS
It is important to investigate the influence of neuropeptides on pulpitis and apical periodontitis to understand the pathogenic mechanism of these inflammations at the cellular level. Evaluating the effects of neuropeptides on cells is also useful for establishing, new treatments to prevent the spread of inflammation. Then, neuropeptide is related to these mechanisms of tissue regeneration. The present study investigated the influence of stimulating human dental pulp cells (HDPC) and human periodontal ligament fibroblasts (HPdLF) with neuropeptides alone on the expression of proinflammatory cytokine mRNA.
HDPC collected from the extracted first premolar for orthodontic treatment and commercially available healthy HPdLF were used for the study. Substance P (SP) and calcitonin gene-related peptide (CGRP) were used as neuropeptides. The mRNA expression of the proinflammatory cytokines IL-1b, IL-6, IL-8, and TNF-a were quantified at 6 and 24 hours.
Significant mRNA expression of only IL-8 among the proinflammatory cytokines was observed 6 hours after stimulation with both SP and CGRP in HDPC (P < 0.05). In HPdLF, significant IL-8 mRNA expression was observed after SP stimulation alone. Although a significant increase in IL-8 mRNA expression was observed in both cells by SP+CGRP stimulation (P < 0.05), there was no synergetic effect. The IL-8 mRNA expression level was significantly higher in HDPC than HPdLF both when the cells were stimulated with SP and when they were stimulated with CGRP. These results suggest that local neutrophil infiltration is induced by IL-8 expression, and that HDPC is more sensitive than HPdLF to neuropeptides when pulp and periodontal membrane cells were stimulated with neuropeptides alone.

Key words: human dental pulp cell (HDPC), human periodontal ligament fibroblast (HPdLF), substance P (SP), carcitonin gene-related peptide (CGRP), PCR