Apoptosis and redox homostasis: on a possible mechanism of action of Bcl-2

We discuss the involvement of several mammalian redox systems in the regula tion of apoptosis. We focus especially on the role that mitochondria and th e still ill-characterized plasma membrane NADH-oxidoreductase system play i n apoptosis. The latter system was shown to respond to downregulation of mi tochondrial function; inhibition of either system induces apoptosis. Apopto sis induced by inhibitors of the oxidase involves both Bcl-2 and calcineuri n, two proteins recently shown to be capable of forming a tight complex. We suggest that Bcl-2 acts as an antioxidant, but in an electron sense rather than in an oxygen sense.