Figure 3.

Inhibition of LDL-IC-stimulated MMP-1 expression by PD98059 and actinomycin D. (a) U937 cells were incubated for 24 hr with 150 µg/ml of LDL-IC in the presence of increasing concentrations of PD98059 as indicated. After incubation, the conditioned medium was subjected to ELISA to quantify secreted MMP-1. Dimethyl sulphoxide, a vehicle for PD98059, was 0·1% of the medium volume and has been shown to have no effect on MMP-1 secretion.⁸ Data presented are the mean ± SEM of three different experiments run in duplicate. (b) U937 cells were preincubated in medium with actinomycin D (5 µg/ml) for 30 min The cells were then incubated with 150 µg/ml of LDL-IC for 24 hr. After the incubation, total RNA was isolated for Northern blot analysis of MMP-1 mRNA as described in Materials and Methods. (c) control; IC, LDL-IC; Act, actinomycin D.