Toll-like receptor 4-mediated inflammation triggered by extracellular IFI16 is enhanced by lipopolysaccharide binding
Fig 4
Weak TLR4-activating LPS variants and the TLR4 antagonist LPS-RS do not potentiate IFI16 proinflammatory activity.
(A) qRT-PCR analysis of IL-6, IL-8 and TNF-α mRNA expression levels in 786-O or THP-1 cells stimulated for 24 h with or without IFI16 (25 μg/ml), LPS from E. coli F583 (LPS-F583, 10 ng/ml) or LPS from R. sphaeroides (LPS-RS, 10 ng/ml), MPLA (10 ng/ml), DPLA (10 ng/ml) or in the presence of one of the following complexes: IFI16/LPS-F583, IFI16/LPS-RS, IFI16/MPLA or IFI16/DPLA. Values are normalized to GAPDH mRNA and plotted as fold induction over mock-treated cells. qRT-PCR data are presented as mean values of biological triplicates. Error bars indicate SD, and the P values refer to comparisons between IFI16 vs. IFI16/LPS or IFI16/lipid A complex-treated cells (*P < 0.05, **P < 0.01, ***P < 0.001; two-way ANOVA followed by Dunnett’s test). (B) Protein concentration of IL-6, IL-8 and TNF-α evaluated by ELISA in supernatants derived from 786-O or THP-1 cells stimulated for 24 h as described in the legend to panel A. Data are expressed as mean values ± SD of three independent experiments (*P < 0.05, **P < 0.01, ***P < 0.001; ns, not significant; two-way ANOVA followed by Dunnett’s test). The P values are relative to comparisons between IFI16- and IFI16/LPS- or IFI16/lipid A-treated cells.