FIGURE 1.

Carbon monoxide confers protection against apoptosis. Primary cultures of astrocytes cultured in 24-well plates were pretreated with 50 μm CO for 3 h, following apoptosis induction by 18-h exposure to the thiol cross-linker diamide (Dia; 0–250 μm) (A and B) and to the pro-oxidant t-BHP (0–280 μm) (C and D). The apoptotic hallmarks were assessed by flow cytometry. In A and C, the percentage of cells presenting high mitochondrial potential, detected by DiOC₆(3), is expressed. In B and D, the percentage of cells containing intact plasma membrane (viable cells) is presented, assessed with PI fluorochrome. All values are mean ± S.D. (error bars), n = 4. *, p < 0.05 compared with control and CO-treated cells for each concentration of diamide (A and B); #, p < 0.05 compared with control and CO-treated cells for each concentration of t-BHP (C and D). E, immunodetection of caspase-3 activation by its cleavage into 12-kDa fractions. The first lane corresponds to astrocytes treated with diamide at 200 μm (18 h); the second lane shows astrocytes pretreated with 50 μm CO (3 h), followed by diamide induction of apoptosis; and the third lane shows control astrocytes.