The upregulation of receptor activator NF-kB ligand expression by interleukin-1α and Porphyromonas endodontalis in human osteoblastic cells

Chen S-C, Huang F-M, Lee S-S, Li, M-Z, Chang Y-C. The upregulation of receptor activator NF-kB ligand expression by interleukin-1α and Porphyromonas endodontalis in human osteoblastic cells. International Endodontic Journal, 42, 375-380, 2009.AbstractAim To investigate the receptor activator of nuclear factor-kappa B (NF-kB) ligand (RANKL) in osteoblastic cells stimulated with inflammatory mediators. Methodology The expression of RANKL in human osteoblastic cell line U2OS stimulated by pro-inflammatory cytokine interleukin (IL)-1α and black-pigmented bacteria Porphyromonas endodontalis was investigated by Western blot and enzyme-linked immunosorbent assay (ELISA). The significance of the results obtained from control and treated groups was statistically analysed by the paired Student's t-test. Results IL-1α was found to upregulate RANKL production in U2OS cells (P < 0.05). Investigations of the time dependence of RANKL expression in IL-1α-treated cells revealed a rapid accumulation of RANKL protein after 1 h of exposure; it remained elevated throughout the 24-h incubation period shown by Western blot and ELISA. In addition, P. endodontalis also increased RANKL expression in U2OS cells after 4-h incubation period demonstrated by Western blot and ELISA (P < 0.05). Conclusions IL-1α and P. endodontalis may be involved in developing apical periodontitis through the stimulation of RANKL production.