Figure 4. H₂O₂ induced p21^Cip1 accumulation is mediated by JNK and ERK activations

A: HLE B-3 cells were treated for 30 min with specific kinases inhibitors before treatment with 200 μM H₂O₂. The kinase inhibitors used were 20 μM SB203580 (SB), 20 μM SP600125 (SP), 1 μM Wortmanin (W), 20 μM U0126 (U), and 10 μM GF109203X (GF) which inhibit p38, JNK, PI-3 kinase, MEK, and PKC, respectively. p21^Cip1 and actin levels were measured after 16 h of H₂O₂ treatment. B: HLE B-3 cells were stimulated with 200 μM of H₂O₂ for the indicated time period. After lysis, 10 μg (for ERK) or 30 μg (for JNK) of total proteins were loaded on 10% PAGE gel. Phosphorylated (p-ERK and p-JNK) or nonphosphorylated levels of JNK and ERK were measured by western blot analysis using specific antibodies. C: FACS analysis showed that SP600125 and U0126 blocked G₂/M phase arrest caused by H₂O₂. The data shown are representative of two to three independent experiments.