Figure 4.

Rac1 in involved in doxorubicin-stimulated DDR. (a) H9c2 cells were pre-treated with lovastatin (Lova) (20 μM), geranylgeranyl transferase inhibitor (GGTI) (20 μM) or farnesyl transferase inhibitor (FTI) (2 μM) for 16 h. Pre-treatment with Clostridium difficile toxin BF (TcdBF) (1 μg/ml) or Clostridium sordellii lethal toxin (TcsL) (10 μg/ml) was carried out for 2 h. Afterwards, doxorubicin (1 μM) was added and H2AX phosphorylation (γH2AX) was analyzed 1 h later by western blot. The histogram shows quantitative data (mean±S.D.) which were obtained from three independent experiments. Relative γH2AX level in untreated cells (Con) was set to 1.0. ^*P≤0.05, significantly different from Doxo-treated cells. (b) H9c2 cells were pre-treated with the Rac1-GEF inhibitor NSC23766 (100 μM, 3 h) before doxorubicin exposure (1 μM). H2AX phosphorylation was assayed 1 h later. (c) After 1 h pre-treatment with p38 kinase inhibitor SB203580 (p38i) (10 μM) or JNK inhibitor (JNKi) (10 μM), doxorubicin (1 μM) was added. After further incubation period of 1 h, phosphorlyation of H2AX was analyzed by western blot. The histogram shows quantitative data (mean±S.D.) obtained from four independent experiments. Relative γH2AX level in untreated cells (Con) was set to 1.0. ^*P≤0.05, significantly different from Doxo-treated cells