Fig. 4

Effect of NAC and z-DEVED-fmk on the β-carotene-induced alterations of intracellular ROS levels, caspase-3 activity, Ku70/80 levels, and Ku-DNA-binding activity in AGS cells. The cells were pretreated with NAC (2 mM) or z-DEVED-fmk (5 μM) for 2 h and then cultured with β-carotene (100 μM) for 30 min a and 12 h (b–d). a Intracellular ROS levels were assessed by measuring DCF fluorescence. The relative fluorescence intensity of cells treated without β-carotene (none) was set at 100 %. The results are expressed as the mean ± SEM of four separate experiments. *p < 0.05 versus cells treated without β-carotene (none); +p < 0.05 versus cells treated with β-carotene alone (control). b Caspase-3 activity was determined by measuring the cleavage of the fluorescent peptide substrate DEVDAFC. Caspase-3 activity in cells treated without β-carotene (none) was set at 100 %. The results are expressed as the mean ± SEM of four separate experiments. *p < 0.05 versus cells treated without β-carotene (none); +p < 0.05 versus cells treated with β-carotene alone (control). c The levels of Ku70 and Ku80 in total cell lysates were determined with Western blot analysis. Actin served as a loading control. d Ku-DNA-binding activity in nuclear extracts was determined with EMSA. None, cells treated without β-carotene; control, cells treated with β-carotene alone