Reactive oxygen species (ROS) mediates the mitochondrial-dependent apoptosis induced by transforming growth factor beta in fetal hepatocytes

Treatment of fetal rat hepatocytes with transforming growth factor beta (TG F-beta) is followed by apoptotic cell death, Analysis of radical oxygen spe cies (ROS) content and mitochondrial transmembrane potential (Delta Psi (m) ), using specific fluorescent probes in FACScan and confocal microscopy, sh owed that TGF-beta mediates ROS production that precedes the loss of Delta Psi (m), the release of cytochrome c, and the activation of caspase 3. TGF- beta induces a decrease in the protein and mRNA levels of bcl-x(L), an anti apoptotic member of the Bcl-2 family. In contrast, there is no change in th e expression and/or translocation of Bax, a proapoptotic member of the same family. EGF maintains Bcl-x(L), preventing Delta Psi (m) collapse and rele ase of cytochrome c, The presence of radical scavengers blocks the decrease in bcl-x(L) levels, Delta Psi (m) collapse, cytochrome c release, and acti vation of caspase 3; in contrast, the presence of glutathione synthesis inh ibitors such as BSO accentuated the effect. The incubation of fetal hepatoc ytes in the presence of ter-butyl-hydroperoxide alone produces a decrease i n bcl-x(L). These results indicate that during the apoptosis mediated by TG F-beta in fetal hepatocytes, ROS may be responsible for the decrease in bcl -x(L) mRNA levels that precedes the loss of Delta Psi (m), the release of c ytochrome c, and the activation of caspase 3, culminating in cell death.