Figure 7. AMPK, LKB1, p53, p21, and p16 protein expression after H₂O₂ exposure for 1 and 16 hr.

Keratinocytes were treated with the indicated concentration of H₂O₂ and harvested after 1 hr (a–f) or16 hr (g.) for western blotting (a,b). AMPK activity, assessed by its phosphorylation at Thr172 and that of its substrate ACC Ser79, was increased only at the high (250 µM) concentration of H₂O₂(c). Phosphorylation of LKB1 (Ser431), an upstream kinase of AMPK, was slightly decreased by 50 µM H₂O₂ and increased by 250 µM H₂O₂ (d, e). p53 expression and phosphorylation were increased by 50 and 100 µM H₂O₂ and were variably affected by 250 µM H₂O₂ (f). Activation (phosphorylation) of p38-MAPK was only observed with 250 µM H₂O₂. g. Incubation with H₂O₂ (50 µM) for 16 h induced the cyclin-dependent kinase inhibitor, p21^CIP1 but not p16 ^INK. (n = 3–6, * p<0.05, ** p<0.01).