Figure 4. UV-induced MMP-1 expression is mediated by ERK and JNK activation but not by p38 activation in HaCaT cells.

(A) Cells were serum-starved for 24 hr, irradiated with UV light (55 mJ/cm²) and harvested at the indicated times. Total cell lysates were prepared and subjected to Western blotting using specific antibodies. The bands are representative of results from three independent experiments. (B) HaCaT cells were pretreated with U0126(U) [ERK (MEK1) inhibitor; 10 µM], SP600125(SP) [JNK inhibitor; 10 µM], and SB203580(SB) [p38 inhibitor; 10 µM] for 1 hr, and then irradiated with UV. Irradiated cells were cultured for 48 hr and MMP-1 expression was determined by Western blotting. All experiments were performed in triplicate. Values shown are means ± SEM (n = 4), * p<0.05 versus the control, ^# p<0.05 versus UV-irradiated cells.