Astrocyte elevated gene-1 participates in the production of pro-inflammatory cytokines in dental pulp cells via NF-κB signalling pathway.

AIM: To identify the role of astrocyte elevated gene-1 (AEG-1) and the mechanism underlying the inflammatory response in dental pulp cells.

METHODOLOGY: Astrocyte elevated gene-1 expression was detected at different stages of pulpitis in a rat model using immunohistochemistry. RT-qPCR and Western blot were used to assess AEG-1 expression in human dental pulp cells stimulated by lipopolysaccharide (LPS). The LPS-induced expression of inflammatory cytokine genes was quantified by RT-qPCR in cells transfected with AEG-1 or negative control (NC) siRNA. Immunofluorescence and Western blot were utilized to evaluate the activation of NF-κB signalling in AEG-1 knockdown cells. AEG-1 expression was also investigated by Western blot in dental pulp cells pre-treated with inhibitors of NF-κB and PI-3K signalling before the addition of LPS. Data were analysed statistically using one-way anova.

RESULTS: The exposure of dental pulp tissue to LPS resulted in acute inflammation with necrosis and AEG-1 expression in the pulp tissue beneath the perforation. In LPS-stimulated dental pulp cells, AEG-1 mRNA and protein were significantly up-regulated (P < 0 .05) in a time- and dose-dependent manner. In AEG-1 knockdown cells, the synthesis of IL-1, IL-6 and TNF-α mRNA was suppressed significantly (P < 0.05) upon LPS induction. AEG-1 knockdown also inhibited nuclear translocation of p65. Suppression of NF-κB and PI-3K abrogated the LPS-induced up-regulation of AEG-1.

CONCLUSION: Astrocyte elevated gene-1 participated in inflammatory cytokine synthesis via NF-κB signalling in the dental pulp. Both NF-κB and PI-3K signalling are involved in LPS-induced AEG-1 expression in dental pulp cells.