Interleukin-1beta Inhibits alkaline phosphatase of pulp cells via cyclooxygenase activation

Interleukin-1beta (IL-1beta) is an important proinflammatory cytokine to mediate pulpal inflammation via activation of monocytes, macrophages and neutrophils. Objectives: The purpose of this study was to determine if IL-1beta may down-regulate alkaline phosphatase (ALP) activity of cultured human dental pulp (HDP) cells via activation of cyclooxygenase (COX). Methods: HDP cells were cultured from healthy pulp tissue of human first premolars or third molars. The cells were exposed to IL-1beta in the presence or absence of aspirin, a COX inhibitor. ALP staining and quantitative ALP activity assay were used to evaluate the differentiation status of the pulp cells. Reverse transcription- polymerase chain reaction (RT-PCR) was used to determine the ALP mRNA expression in the HDP cells. Differences between the aspirin-treated and untreated groups were statistically analyzed by one-way analyses of variance (ANOVA) and post-hoc Tukey tests. Results: We found that IL-1beta (0.1-5 ng/ml) suppressed the ALP enzyme activity and mRNA expression in HDP cells. Treatment of pulp cells with aspirin (100 and 200 uM) effectively attenuated the inhibitory effect of IL-1beta on ALP activity and ALP mRNA expression. Conclusion: These results demonstrate that IL-1beta suppresses the ALP of human dental pulp cells and may involve in the pathogenesis of pulp inflammation via impairment of pulpal differentiation. This event is associated with activation of COX by IL-1beta.