The apoptotic regulatory protein ARC (apoptosis repressor with caspase recruitment domain) prevents oxidant stress-mediated cell death by preserving mitochondrial function

ARC is an apoptotic regulatory protein expressed almost exclusively in myog enic cells. It contains a caspase recruitment domain (CARD) through which i t has been shown to block the activation of some initiator caspases. Becaus e ARC also blocks caspase-independent events associated with apoptosis, suc h as hypoxia-induced cytochrome c release, we examined its role in cell dea th triggered by exposure to hydrogen peroxide (H2O2) in the myogenic cell l ine, H9c2. Cell death in this model was caspase-independent and characteriz ed by dose-dependent reduction in ARC expression accompanied by disruption of the mitochondrial membrane potential (Delta psi (m)) and loss of plasma membrane integrity, typical of necrotic cell death. Ectopic expression of A RC prevented both H2O2-induced mitochondrial dysfunction and cell death wit hout affecting the stress kinase response, suggesting that ARCs protective effects were downstream of early signaling events and not due to quenching of H2O2. ARC was also effective in blocking H2O2-induced loss of membrane i ntegrity and/or disruption of Delta psi (m) in two human cell lines in whic h it is not normally expressed. These results demonstrate that, in addition to its ability to block caspase-dependent and -independent events in apopt osis, ARC also prevents necrosis-like cell death via the preservation of mi tochondrial function.