Effects of Proinflammatory Cytokines on the Expression of Mineralization Markers and Heme Oxygenase-1 in Human Pulp Cells

The roles of IL-1α and TNF-α 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-1α, TNF-α, or both for 3, 7, and 14 days. The pulp cells treated with IL-1α for 3 days showed elevated ALP activity and increased ON, OC, and HO-1 expression, whereas TNF-α treatment did not increase the ALP activity and no BSP was expressed until day 14. The pulp cells treated with both IL-1α and TNF-α for 3 days showed increased HO-1 expression compared with that of the control. These data suggest that IL-1α and TNF-α produced in the early inflammatory reaction have different functions in human pulp cells. IL-1α 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-α may inhibit the tooth mineralization.