calcimycin and phenylhydrazine

Oxidant-induced damage has been proposed to be the underlying mechanism for loss of membrane phospholipid asymmetry in the erythrocyte membrane. In sickle cell disease, thalassemia, and diabetes as well as in senescent erythrocytes, an apparent correlation between oxidative damage and loss of phosphatidylserine asymmetry has been reported. In the present study, erythrocytes were subjected to various levels of oxidative stress and/or sulfhydryl modifying agents. The transmembrane location of phosphatidylserine (PS) was assessed by FITC-conjugated annexin V labeling and the PS-dependent prothrombinase assay. Transbilayer movement of spin-labeled PS was used to determine aminophospholipid translocase activity. Our data show that cells did not expose PS as the result of oxidative stress induced by phenylhydrazine, hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, or sulfhydryl modification by N-ethylmaleimide (NEM) and diamide, even under conditions that led to severe cellular damage and impairment of aminophospholipid translocase activity. In contrast, the increase of intracellular calcium induced by treatment with calcium and ionophore A23187 leads to a rapid scrambling of the lipid bilayer and the exposure of PS, which can be exacerbated by the inhibition of aminophospholipid translocase activity. Oxidation of the cells with hydrogen peroxide or phenylhydrazine did not affect A23187-induced uptake of calcium, but partly inhibited calcium-induced membrane scrambling. In conclusion, oxidative damage of erythrocytes does not induce exposure of phosphatidylserine on the membrane surface, but can interfere with both aminophospholipid translocase activity and calcium-induced randomization of membrane phospholipids.

Topics: Aniline Compounds; Annexin A5; Calcimycin; Calcium; Erythrocyte Deformability; Erythrocyte Membrane; Ethylmaleimide; Flow Cytometry; Fluorescein-5-isothiocyanate; Fluorescent Dyes; Humans; Hydrogen Peroxide; Membrane Lipids; Oxidative Stress; Phenylhydrazines; Phosphatidylserines; Phospholipids; Sulfhydryl Reagents; Thromboplastin; Xanthenes

Studies were carried out to characterize further the cytoplasmic ATP- and ubiquitin-independent proteolytic system in red blood cells that degrades hemoglobin damaged by exposure to oxidants (Fagan, J. M., Waxman, L., and Goldberg, A. L. (1986) J. Biol. Chem. 261, 5705-5713). Several proteases were ruled out as having a major role in the degradation of oxidant-treated hemoglobin (Ox-Hb). Acid hydrolases are not active in this process since the degradation of Ox-Hb has a pH optimum between 6 and 8. The calpains are also not involved since inhibitors of cysteine proteases (leupeptin and trans-epoxysuccinyl-L-leucylamido-(3-methyl)butane) did not diminish the increased proteolysis in intact erythrocytes treated with oxidants or in lysates to which Ox-Hb was added. The degradation of Ox-Hb was unaffected by inhibitors of serine and aspartic proteases. Removal of the high M(r) multicatalytic proteinase by immunoprecipitation also did not significantly affect the degradation of Ox-Hb in erythrocyte lysates. The degradation of Ox-Hb was sensitive to metal chelators and sulfhydryl-modifying reagents but not to specific inhibitors of known metalloproteases. Insulin, which is rapidly degraded in lysates, completely blocked the degradation of Ox-Hb. Insulin- and Ox-Hb-hydrolyzing activity was also inhibited following immunoprecipitation of the 100-kDa metalloinsulinase. The metalloinsulinase, which is inhibited by sulfhydryl-modifying reagents and which requires divalent metals, may therefore participate in the degradation of hemoglobin damaged by oxidants in erythrocytes.

Topics: Adenosine Triphosphate; Animals; Azides; Calcimycin; Cations, Divalent; Cysteine Proteinase Inhibitors; Edetic Acid; Electrophoresis, Polyacrylamide Gel; Erythrocytes; Hemoglobins; Hydrogen Peroxide; Ionomycin; Kinetics; Leucine; Male; Oxidants; Phenylhydrazines; Pyrimidinones; Rabbits; Rats

Reticulocytes from various species (rat, mouse, rhesus monkey) obtained by phenylhydrazine treatment of the animals metabolized polyenoic fatty acids via a lipoxygenase pathway. Linoleic acid was converted to 13-hydro(pero)xy-9,11(Z,E)octadecadienoic acid [13-H(P)ODE] and 9-hydro(pero)xy-10,12(E,Z)octadecadienoic acid [9-H(P)ODE], whereas arachidonic acid was oxygenated to 15-hydroxy-5,8,11,13(Z,Z,Z,E)eicosatetraenoic acid (15-HETE) as shown by straight-phase high-pressure liquid chromatography (SP-HPLC). Addition of calcium and ionophore A 23,187 strongly enhanced the formation of lipoxygenase products, whereas 5,8,11,14eicosatetraenoic acid (ETYA) completely inhibited their formation. Estimates of the specific radioactivities of the lipoxygenase products indicate differences in the metabolization of externally added and endogenously released polyenoic fatty acids. These results strongly suggest that lipoxygenases generally occur in immature red blood cells.

Topics: 5,8,11,14-Eicosatetraynoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Calcimycin; Chromatography, High Pressure Liquid; Hydroxyeicosatetraenoic Acids; Linoleic Acid; Linoleic Acids; Lipoxygenase; Lipoxygenase Inhibitors; Macaca; Mice; Phenylhydrazines; Rats; Reticulocytes; Species Specificity