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

<p>(<b>A</b>) 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>B</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), * <i>p</i><0.05 versus the control, ^#<i>p</i><0.05 versus UV-irradiated cells.