JNK inhibitor curcumin, but not ERK- or p38-specific inhibitors, abrogates uPA induction by MNNG.
C2C12 cells were pretreated for 30 minutes with 30 μmol/L curcumin, 50 μmol/L PD98059, or 10 μmol/L SB203580 before stimulation with 70 μmol/L MNNG. Curcumin inhibits uPA mRNA induction by MNNG. Northern blot analysis of 20 μg of total RNA from C2C12 cells stimulated or not for 2 hours with MNNG. Cell pretreatments (curcumin, SB203580, and PD98059), and DNA probes (uPA and GAPDH) used for hybridization, are indicated in the Figure. (B) Curcumin inhibits uPA transcriptional induction by MNNG. C2C12 cell lines expressing different uPA promoter-luciferase contructs were pretreated for 30 minutes with 50 mmol/L PD98059, 10 μmol/L SB203580, and 30 μmol/L curcumin, before an 8-hour stimulation with 70 μmol/L MNNG. Only results obtained with the C2C12 cell line containing p-8.2-Luc are shown. Reporter activities correspond to the mean of 5 independent luciferase measurements. Luciferase activity is expressed relative to the activity found in untreated cells, which was given a value of 1. (C) Curcumin inhibits AP1-binding to the uPA-enhancer element. Electrophoretic mobility shift assays were performed with 5 μg of nuclear extracts from unstimulated or 2-hour MNNG-stimulated C2C12 cells (pretreated or not for 30 minutes with 30 μmol/L curcumin) and with32P-labeled uPA-AP1B site.
