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Title: Hydrogen peroxide and arginine in the life and death of leukaemic cells
Author: Brown, R. D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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The proliferation and/or survival of a variety of cells are dependent on cellular hydrogen peroxide (H2O2) production. We tested whether this was true of leukaemic cells, using cell lines derived from leukaemic patients (CEM, 697, Mn-60 and Tanoue). Addition of as little as 5 μM H2O2 to leukaemic cells inhibited proliferation and induced death. Addition of N-acetylcysteine to remove endogenous H2O2 stimulated survival and proliferation, suggesting that basal levels of H2O2 promoted cell death. The glutathione peroxidase mimetic, ebselen, killed the cells by a novel, rapid form of death, preceded by cell blebbing, and was prevented by N-acetylcysteine; suggesting toxicity is not due to ebselen’s antioxidant activity. Ascorbic acid, even at 100 μM, induced death through H2O2 production. Addition of catalase inhibited the proliferation of all four cell lines, and induced death in two. However, this turned out to be due to an arginase contamination of the catalase, not due to catalyse’s antioxidant activity. Thus H2O2 does not promote the proliferation and survival of leukaemic cells, rather the opposite. The results suggest the use of H2O2-producing ascorbate as a potential treatment for leukaemia. Pure arginase inhibited the proliferation and survival of leukaemic cells, an effect that was reversed at low arginase levels by the addition of L-arginine. Cell death (but not cytostasis) was also prevented by adding citrulline but not ornithine, suggesting these cells lack the mitochondrial part of the urea cycle for L-arginine synthesis. Arginase treatment induced more death than arginine-free medium, suggesting that arginase can draw out and breakdown intra-cellular L-arginine. The arginase-induced death was apoptotic, as it was accompanied by caspase activation and was inhibited by caspase inhibitors. Arginase-induced death occurs through cell signalling that results in apoptosis, possibly involving PKC, and apparently not involving previously known amino acid-deprivation responses. Arginase could be used as a treatment for some types of leukaemia.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available