Figure 3.

MAP kinase activation by oxidative stress. (a) JNK activation by H₂O₂. (Top) Time course of JNK activation by H₂O₂ in ESCM. Wild-type ESCM were treated with 1 mM H₂O₂ for 0–60 min. (Middle and Bottom) Dose-response of JNK activation by H₂O₂ in wild-type and MEKK1−/− ESCM (15-min treatment). The data represent the average fold of the controls from three independent experiments (mean ± SEM). * and #, P < 0.05 vs. each corresponding control. (b) p38 activation by H₂O₂. (Top) Phosphorylation of p38 in wild-type ESCM incubated with 1 mM H₂O₂ for various periods of time. (Middle) Dose response of p38 phosphorylation by H₂O₂ in wild-type and MEKK1−/− ESCM. (Bottom) Activation of p38 in wild-type and MEKK1−/−ESCM treated with 1 mM H₂O₂ for 10 min. (c) ERK activation by H₂O₂. (Top) Phosphorylation of ERK in wild-type ESCM incubated with 1 mM H₂O₂ for various periods of time. (Middle) Dose response of ERK phosphorylation by H₂O₂ in wild-type and MEKK1−/− ESCM. (Bottom) Activation of ERK2 in wild-type and MEKK1−/− ESCM treated with 1 mM H₂O₂ for 10 min. (d) JNK activation by hypoxia/reoxygenation. Wild-type and MEKK1−/− ESCM were subjected to a hypoxic atmosphere by immediately replacing the medium with the hypoxic medium. Cells were incubated in a hypoxic condition for 10 min (Hypoxia-1) or 60 min (Hypoxia-2). After 60-min treatment of cells in hypoxia, cells were reoxygenated by immediately replacing the hypoxic medium with a normoxic medium and incubated in a normoxic condition for an additional 15 min. The data in the graph represent the average percentage of the controls from three independent experiments (mean ± SEM). * and #, P < 0.05 vs. each corresponding control.