Role of substance P and calcitonin gene-related peptide in the regulation of interleukin-8 and monocyte chemotactic protein-1 expression in human dental pulp

AIM: To determine whether leucocyte infiltration during neurogenic inflammation in the pulp is regulated by neuropeptides via inducing the release of proinflammatory chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) from human dental pulp. METHODOLOGY: Cultured primary pulp cells and pulp tissue explants were stimulated with substance P (SP) and/or calcitonin gene-related peptide (CGRP). IL-8 or MCP-1, secreted from cultured cells or produced in pulp explants, was analysed by enzyme-linked immunosorbent assay. RESULTS: Substance P induced IL-8 secretion from cultured pulp cells (approximately threefold increase over control, P < 0.05) and from pulp tissue explants (two- to three fold). SP only minimally to moderately induced MCP-1 (approximately two fold) in cultured pulp cells. While MCP-1 induction in cultured pulp cells was detected after 24 h of SP stimulation, no induction was observed in pulp tissue. CGRP did not induce IL-8, but moderately increased MCP-1 production (approximately three fold) in cultured pulp cells. There was no synergistic induction of MCP-1 by SP plus CGRP stimulation of pulp cells. CONCLUSIONS: Substance P is a stronger inducer of IL-8 production in dental pulp than CGRP. IL-8 is more strongly induced than MCP-1 by SP, suggesting a more important role for IL-8 than MCP-1 in leucocyte infiltration during neurogenic inflammation in dental pulp.