Figure 10.

LPS-dependent cytokine production is mediated by X-box–binding protein-1 mRNA splicing (XBP-1s). Macrophage-like differentiated THP-1 cultures stably expressing a control pQCXIN vector, a pQCXIN vector containing a dominant negative XBP-1 (DN-XBP-1), or a pQCXIN vector containing XBP-1s were stimulated for 6 hours with vehicle or 100 ng/ml LPS from Pseudomonas aeruginosa. The levels of XBP-1s (A), tumor necrosis factor (TNF)-α (B), and IL-6 (C) mRNA were analyzed by quantitative reverse transcriptase polymerase chain reaction and expressed as fold change relative to 18S mRNA. TNF-α (D) and IL-6 (E) protein secretion into the culture media was determined by ELISA. The y-axis uses a logarithmic scale for TNF-α and IL-6 mRNA and protein secretion. Data are from six independent experiments and represent mean ± SD. One-way analysis of variance was used for the statistical analysis. *P < 0.05, **P < 0.01, and ***P < 0.001 spliced XBP-1 or DN-XBP-1 expressing cells versus control cells. ND = not detected. The fold changes of TNF-α mRNA in dTHP-1 cells expressing control, DN-XBP, and XBP-1s and exposed to vehicle are 0.7 ± 0.5, 0.3 ± 0.1, and 1 ± 0.5, respectively. The fold changes of IL-6 mRNA in dTHP-1 cells expressing control and DN-XBP-1 and exposed to vehicle are 0.8 ± 0.5 and 0.3 ± 0.15, respectively.