CRP-induced RANKL expression and production in peripheral blood monocytes. (A) After peripheral blood CD14+ monocytes were cultured with 0 to 1.0 μg/mL of CRP for 72 h, the expression of RANKL mRNA was determined using real-time PCR. The expression of RANKL mRNA increased in a dose-dependent manner with a maximal effect at 1.0 μg/mL of CRP. (B) In monocytes cultured with CRP, the production of RANKL was measured using sandwich ELISA. CRP also increased RANKL production of cultured monocytes in a dose-dependent manner. (C) After peripheral blood CD14+ monocytes were cultured with CRP for 72 h, the concentrations of IL-1β, TNF-α, and IL-6 in culture media were determined using sandwich ELISA. CRP does not stimulate monocytes to produce IL-1β, IL-6, or TNF-α. The data represents the mean ± SEM for three independent experiments; *
P <0.05, **
P <0.01. CRP, C-reactive protein; ELISA, enzyme-linked immunosorbent assay; IL, interleukin; RANKL, receptor activator of nuclear factor kappa-B ligand; SEM, standard error of the mean; TNF, tumor necrosis factor.