Effects of proinflammatory cytokines on the expression of mineralization markers and heme oxygenase-1 in human pulp cells

The roles of IL-1 alpha and TNF-alpha in early pulp inflammation were investigated by determining the alkaline phosphatase (ALP) activity, the osteonectin (ON), osteocalcin (OC), bone sialoprotein (BSP), and heme oxygenase-1 (HO-1) expression using an immunoblot method. Primary cultured dental pulp cells were treated with IL-1 alpha, TNF-alpha, or both for 3, 7, and 14 days. The pulp cells treated with IL-1 alpha for 3 days showed elevated ALP activity and increased ON, OC, and HO-1 expression, whereas TNF-alpha treatment did not increase the ALP activity and no BSP was expressed until day 14. The pulp cells treated with both IL-1 alpha and TNF-alpha for 3 days showed increased HO-1 expression compared with that of the control. These data suggest that IL-1 alpha and TNF-alpha produced in the early inflammatory reaction have different functions in human pulp cells. IL-1 alpha induces ALP, ON, and OC in tooth mineralization and it may play a role in the cytoprotection of pulp cells via HO-1 expression, while long-term treatment of TNF-alpha may inhibit the tooth mineralization.