Fig. 4.

Induction of HO-1 by PPARγ ligands is upstream of AP-1 induction. A: primary lung fibroblasts were pretreated with the AP-1 inhibitor SP600125 (0.1 mM) and then treated with CDDO (1 μM), 15d-PGJ₂ (5 μM), or rosiglitazone (20 μM) for 24 h. HO-1 expression was evaluated by Western blot. RE, relative expression of HO-1 normalized to GAPDH with untreated cells = 1. Results shown are representative of 2 independent experiments. B: primary human lung fibroblasts were cotransfected with an AP-1 reporter construct and a β-galactosidase control construct and then treated with CDDO (1 μM), 15d-PGJ₂ (5 μM), or rosiglitazone (20 μM) with or without 5 mM NAC. After 24 h, luciferase activity was determined and normalized to β-galactosidase activity. Results shown are representative of 2 independent experiments, each performed on triplicate cultures. *Significant increase compared with untreated; †significant decrease compared with CDDO alone, P < 0.05 (ANOVA).