cytochrome-c-t and Anemia--Aplastic

Using genetically modified mouse models, we report here that p53 upregulated modulator of apoptosis (Puma) and Bcl-2 interacting mediator of cell death (Bim), two pro-apoptotic members of the B-cell lymphoma protein-2 (Bcl-2) family of proteins, cooperate in causing bone marrow and gastrointestinal tract toxicity in response to chemo and radiation therapy. Deletion of both Puma and Bim provides long-term survival without evidence of increased tumor susceptibility following a lethal challenge of carboplatin and ionizing radiation. Consistent with these in vivo findings, studies of primary mast cells demonstrated that the loss of Puma and Bim confers complete protection from cytokine starvation and DNA damage, similar to that observed for Bax/Bak double knockout cells. Biochemical analyses demonstrated an essential role for either Puma or Bim to activate Bax, thereby leading to mitochondrial outer membrane permeability, cytochrome c release and apoptosis. Treatment of cytokine-deprived cells with ABT-737, a BH3 mimetic, demonstrated that Puma is sufficient to activate Bax even in the absence of all other known direct activators, including Bim, Bid and p53. Collectively, our results identify Puma and Bim as key mediators of DNA damage-induced bone marrow failure and provide mechanistic insight into how BH3-only proteins trigger cell death.

Topics: Anemia, Aplastic; Animals; Apoptosis; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; Bcl-2-Like Protein 11; Biphenyl Compounds; Bone Marrow Diseases; Bone Marrow Failure Disorders; Cell Survival; Cytochromes c; DNA Damage; Gene Deletion; Hemoglobinuria, Paroxysmal; Mast Cells; Membrane Proteins; Mice; Mice, Knockout; Mitochondrial Membranes; Nitrophenols; Permeability; Piperazines; Proto-Oncogene Proteins; Sulfonamides; Tumor Suppressor Protein p53; Tumor Suppressor Proteins

Aplastic anaemia (AA) is a disease characterised by bone marrow hypocellularity and peripheral blood pancytopenia. AA is also associated with mitochondrial aberrations. The present study was undertaken primarily to test the hypothesis that a nutrient mixture could affect the nutritional rehabilitation of mitochondrial aberrations in AA mice. BALB/c AA mice were induced by a combination of hypodermic injections of acetylphenylhydrazine (100 mg/kg), X-rays (2·0 Gy) and intraperitoneal injections of cyclophosphamide (80 mg/kg). We treated these mice with nutrient mixture-supplemented diets in a dose-dependent manner (1445·55, 963·7, 674·59 mg/kg per d), and the effects of the nutrient mixture for mitochondrial rehabilitation were analysed in AA mice. Transmission electron microscopy showed that mitochondrial ultrastructural abnormalities in bone marrow cells, splenocytes and hepatocytes of the nutrient mixture groups were restored markedly, compared with the AA group. Mitochondrial membrane potentials of the nutrient mixture groups were increased remarkably. Western blot analysis also revealed that the nutrient mixture significantly inhibited cytochrome c release of mitochondria in the AA group. Furthermore, the mitochondrial DNA content of the nutrient mixture groups was also increased. Our data suggest that the nutrient mixture may promote the rehabilitation of mitochondrial aberrations, and consequently protects against mitochondrial dysfunction in AA mice.

Topics: Anemia, Aplastic; Animals; Blood Cell Count; Bone Marrow Cells; Cells, Cultured; Cytochromes c; Cytosol; Disease Models, Animal; DNA, Mitochondrial; Hemoglobins; Hepatocytes; Male; Membrane Potential, Mitochondrial; Mice; Mice, Inbred BALB C; Microscopy, Electron, Transmission; Mitochondria; Mitochondrial Diseases; Nutritional Support; Random Allocation; Spleen