Figure 5.

Opposing effects of retinoic acid (RA) on tumour necrosis factor-α (TNF-α) and interferon (IFN) -induced STAT-1 protein expression. THP-1 cells were pretreated with or without RA (10⁻⁸ m) for 16 hr and then treated with TNF-α (5 ng/ml) and/or IFN-γ (2·5 U/ml) for 24 and 48 hr in the presence and absence of fresh RA. Cells were harvested and Western blotting was performed to detect STAT-1 protein. The upper panels are Western blot analyses showing STAT-1 protein accumulation 24 and 48 hr after cytokine stimulation and Ponceau S staining of the membranes. The lower panels are the corresponding graphs showing the relative induction of STAT-1 protein (mean ±SD of two independent experiments).