(a) Cell-free medium was conditioned by treatment with He-GIW. Cells were then treated by conditioned medium immediately, or 1 h, 2 h, or 3 h after He-GIW conditioning. (b) Cell medium was renewed before, concomitantly with, or 30 min or 1 h after He-GIW treatment. (c) Cells were treated with He-GIW alone or in presence of NAC or 10% FCS. Cell medium was renewed 1h after treatment (Triggering phase only in black) or not (Full exposure in white). (d) Cells were treated with He-GIW, and 10% FCS or NAC were added immediately, 1 h, 2h, or 3h after treatment. In every experiment, the percentage of DiOC6 negative cells was assayed 6 h after cell treatment. Note that death can be inhibited even if cells have been exposed to the 1h triggering phase. Error bars represent S.E.M. of three independent experiments. p<0.05 (*), p<0.01 (**) and p<0.001 (***).