Abstract
Generally, bacterial infection may occur in parallel with the phase in which pain is felt in the dental pulp and tissue around the root apex. We investigated the influence of neuropeptides on bacterial inflammation. In this study, we investigated the influence of substance P (SP) on the proinflammatory cytokine mRNA expression level in human dental pulp-derived cells (HDPC) stimulated with a bacterial inflammatory agent, LPS. HDPC collected from the first premolar extracted for orthodontic treatment were used. SP alone did not increase the TNF-α mRNA expression level, but SP induced a significant increase the TNF-α mRNA expression in cells stimulated with low-level LPS (1 μg/mL). However, a significant increase was not induced in cells stimulated with high-level LPS (10 μg/mL). The IL-8 mRNA expression level was increased by SP alone, and SP additionally induced a significant increase in cells stimulated with low-level LPS (1 μg/mL). It was suggested that neuropeptide may enhance early or mild bacterial inflammation.
