Ischemic injuries are associated with several pathological conditions, including stroke and myocardial infarction. Several studies have indicated extensive apoptotic cell death in the infarcted area as well as in the penumbra region of the infarcted tissue. Studies with transgenic animals suggest that the mitochondrion-mediated apoptosis pathway is involved in ischemia-related cell death. This pathway is triggered by activation of pro-apoptotic Bcl-2 family members such as Bax. Here, we have identified and synthesized two low molecular weight compounds that block Bax channel activity. The Bax channel inhibitors prevented cytochrome c release from mitochondria, inhibited the decrease in the mitochondrial membrane potential, and protected cells against apoptosis. The Bax channel inhibitors did not affect the conformational activation of Bax or its translocation and insertion into the mitochondrial membrane in cells undergoing apoptosis. Furthermore, the compounds protected neurons in an animal model of global brain ischemia. The protective effect in the animal model correlated with decreased cytochrome c release in the infarcted area. This is the first demonstration that Bax channel activity is required in apoptosis.Apoptosis is a conserved cell death mechanism essential for normal development and tissue homeostasis in multicellular organisms. Although apoptosis presumably participates in the development of all cell lineages, aberrations in the expression of pro-or anti-apoptotic proteins have been implicated in the initiation of a variety of human diseases, including arteriosclerosis, heart failure, infertility, autoimmunity, immunodeficiency, and cancer, in addition to diseases affecting the nervous system such as neurodegeneration and ischemia (1-3). Several intracellular apoptosis signaling pathways have been identified, including the death receptor pathway and the mitochondrial pathway (4 -6). The induction of apoptosis ultimately converges upon the activation of cysteine proteases of the caspase family. The Bcl-2 family proteins are located upstream at organelle membranes and control the activation of downstream caspases, representing a critical proximal intracellular checkpoint in the mitochondrial apoptosis pathway. The Bcl-2 family is composed of pro-and anti-apoptotic members. Anti-apoptotic Bcl-2 family members display sequence homology in four ␣-helical domains called BH1-BH4.3 Pro-apoptotic Bcl-2 members can be further subdivided into more fully conserved, "multidomain" members with homology in the BH1-BH3 domains (e.g. Bax and Bak) or the "BH3-only" members (e.g. Bid, Bad, and Bim). Genetic and biochemical analyses indicate that the multidomain proteins Bax and Bak function as the essential gateway to the intrinsic cell death pathway operating at the mitochondria. The upstream BH3-only members respond to particular apoptotic signals and subsequently, either directly or indirectly, trigger the conformational activation of Bax and/or Bak. Overexpression of the anti-apoptotic protein Bcl-2 or deletion o...

Recent evidence suggests that activation of the c-Jun NH 2