Examination of the Signal Transduction Pathways Leading to Upregulation of Tissue Type Plasminogen Activator by Interleukin-1α in Human Pulp Cells

Tissue type plasminigen activator (t-PA) is one of the important proteolysis factors in the pathogenesis of pulpal inflammation. However, the mechanisms and signal transduction pathways involved in the production of t-PA in human pulp cells are not fully understood. The purpose of this study was to investigate the t-PA activity in human pulp cells stimulated with various pharmacological agents. IL-1α was used to evaluate t-PA activity in human pulp cells using casein zymography and enzyme-linked immunosorbent assay (ELISA). Furthermore, to search possible signal transduction pathways, p38 inhibitor SB203580, MEK inhibitor U0126, and phosphatidylinositaol 3-kinase (PI3K) inhibitor LY294002 were added to test how they modulated the t-PA activity. The main casein secreted by human pulp cells migrated at 70 kDa and represented t-PA. Secretion of t-PA was found to be stimulated with IL-1α during 2 day cultured period (p < 0.05). From the results of casein zymography and ELISA, SB203580, U0126, and LY294002 significantly reduced the IL-1α-stimulated t-PA production, respectively (p < 0.05). Our findings demonstrated that IL-1α enhance t-PA production in human pulp cells, and the signal transduction pathways p38, MEK, and PI3K are involved in the inhibition of t-PA. SB203580, U0126, and LY294002 suppress t-PA activity and may also have important implication for pharmacological intervention.