Biomedical subjects

Jeffrey S Friedman

Publications and source records attributed to Jeffrey S Friedman.

4 recordsLinked to original sources

PubMed2005

A method for rapid mouse siderocyte enrichment.

OBJECTIVE: Iron overload is a key contributor to the pathogenesis of multiple disorders including the sideroblastic anemias. The specific iron compounds present in tissues or cells that are the target of iron deposition remain poorly understood, but there is evidence that some forms are magnetically active. We have developed a simple and specific method to purify iron-overloaded red blood cells using magnetic affinity columns. Here we describe this method and characterize purified Sod2-deficient siderocytes. MATERIALS AND METHODS: RBC derived from mice transplanted with Sod2-deficient hematopoietic stem cells served as a source of iron-laden cells. Purification was based upon the observation that iron deposits in Sod2-deficient cells are "magnetically susceptible" and allow for retention of iron-laden cells in a strong magnetic field. Peripheral blood from Sod2-deficient chimeric mice was passed through magnetic separation columns; iron-overloaded cells were eluted and characterized by flow cytometry, Western blot, and microscopy. RESULTS: We were able to purify 2.8% of the total red cells as iron-laden siderocytes. The magnetically purified Sod2-deficient cells were predominantly identified as reticulocytes. They had numerous siderotic granules, produced enhanced levels of reactive oxygen species, and showed increased protein oxidative damage, mitochondrial enrichment, and mitochondrial hyperpolarization. CONCLUSIONS: Our method can be used to purify iron-laden cells as well as iron-associated subcellular fractions prepared from iron-loaded tissues, allowing elucidation of the structure, location, and protein composition of such iron deposits. This data will help develop our understanding of the pathogenesis of SA and other disorders characterized by iron overload.

Anemia, Sideroblastic↗

PubMed2004

Ticking fast or ticking slow, through Shc must you go?

Circumstantial evidence places the p66 isoform of the adapter protein Shc in a position to mediate the accelerated aging phenotype displayed by mice expressing shortened forms of the tumor suppressor protein p53. We present a model in which p66(shc) may be responsible for integrating signals from the p53 pathway with signals from the insulin-like growth factor-1/Daf pathway in mammals. A full understanding of how interactions between p53 and p66(shc) affect longevity will require the production of animals with mutations in the genes encoding both proteins.

Adaptor Proteins, Signal Transducing↗

PubMed2004

SOD2-deficiency anemia: protein oxidation and altered protein expression reveal targets of damage, stress response, and antioxidant responsiveness.

SOD2 is an antioxidant protein that protects cells against mitochondrial superoxide. Hematopoietic stem cells (HSCs) lacking SOD2 are capable of rescuing lethally irradiated hosts, but reconstituted animals display a persistent hemolytic anemia characterized by increased oxidative damage to red cells, with morphologic similarity to human "sideroblastic" anemia. We report further characterization of this novel SOD2-deficiency anemia. Electron micrographs of SOD2-deficient reticulocytes reveal striking mitochondrial proliferation and mitochondrial membrane thickening. Peripheral blood smears show abundant iron-stainable granules in mature red cells (siderocytes). Fluorescence-activated cell sorting (FACS) analysis of cells labeled with oxidation-sensitive dyes demonstrates enhanced production of superoxide and hydrogen peroxide by SOD2-deficient cells. Oxidative damage to proteins is increased in SOD2-deficient cells, with much of the damage affecting membrane/insoluble proteins. Red cell proteome analysis demonstrates that several proteins involved in folding/chaperone function, redox regulation, adenosine triphosphate (ATP) synthesis, and red cell metabolism show altered expression in SOD2-deficient cells. This data, combined with information on how protein expression levels change upon antioxidant therapy, will aid in identification of proteins that are sensitive to oxidative damage in this model, and by extension, may have a role in the regulation of red cell lifespan in other hemolytic disorders.

Adenosine Triphosphate↗

PubMedDate not supplied

SOD2-deficiency sideroblastic anemia and red blood cell oxidative stress.

Iron overload is a feature of an array of human disorders such as sideroblastic anemias, a heterogeneous group of erythropoietic disorders without identified cause in most cases. However, sideroblastic anemias appear to result from a disturbance at the interface between mitochondrial function and iron metabolism. A defining feature is excessive iron deposition within mitochondria of developing red cells, the consequences of which are an increase in cellular free radicals production, increased damage to proteins, and reduced cell survival. Because of its mitochondrial location, superoxide dismutase (SOD2) is the principal defense against the toxicity of superoxide anions generated by the oxidative phosphorylation. We have used hematopoietic stem cell transplantation to study blood cells lacking SOD2. We became interested in the role SOD2 plays in the metabolism of superoxide anions during erythroid development, as anemia is the major phenotype in transplanted animals. Our exploration of this model suggests that oxidative stress-and in particular, mitochondrial- derived oxidants-plays an important role in the pathogenesis of the human disorder, sideroblastic anemia. Here we review the relation between mitochondrial dysfunction and sideroblastic anemia, describe several methods for assessing oxidative damage to mature or developing red cells, present data on, and discuss the potential of antioxidant therapy for this disorder.

Anemia, Sideroblastic↗