Inhibitory Effect Of Superoxide Dismutase Research Articles

Inhibitory effects of superoxide dismutase 3 on IgE production in B cells

Immunoglobulin E (IgE) functions as a first-line defense against parasitic infections. However, aberrant production of IgE is known to be associated with various life-threatening allergic diseases. Superoxide dismutase 3 (SOD3) has been found to suppress IgE in various allergic diseases such as allergic conjunctivitis, ovalbumin-induced allergic asthma, and dust mite-induced atopic dermatitis-like skin inflammation. However, the role of SOD3 in the regulation of IgE production in B cells remains elusive. In this study, we investigated the effect of SOD3 on LPS/IL-4 and anti-CD40/IL-4-mediated secretion of IgE in murine B cells. Our data showed that SOD3 can suppress both LPS/IL-4 and antiCD40/IL-7-induced IgE secretion in B cells isolated from both wild-type (SOD3+/+) and SOD3 knock-out (SOD3−/−) mice. Interestingly, B cells isolated from SOD3−/− mice showed higher secretion of IgE, whereas, the use of DETCA, a known inhibitor of SOD3 activity, reversed the inhibitory effect of SOD3 on IgE production. Similarly, SOD3 was found to reduce the proliferation, IgE isotype switch, ROS level, and CCL17 and CCL22 productions in B cells. Furthermore, SOD3 was found to suppress both LPS/IL-4 and anti-CD40/IL-4-mediated activation of downstream signaling such as JAK1/JAK3, STAT6, NF-κB, p38, and JNK in B cells. Taken together, our data showed that SOD3 can be used as an alternative therapy to restrict IgE-mediated allergic diseases.

Comparative Study of Antioxidant and Pro-Oxidant Properties of Homoleptic and Heteroleptic Copper Complexes with Amino Acids, Dipeptides and 1,10-Phenanthroline: The Quest for Antitumor Compounds.

In a search for new antitumoral agents, a series of homoleptic copper(II) complexes with amino acids and dipeptides, as well as heteroleptic complexes containing both dipeptides and 1,10-phenanthroline, were studied. Furthermore, a single-crystal structure containing alanyl-leucinato ([Cu3(AlaLeu)3(H2O)3(CO3)]·PF6·H2O), which is the first homotrinuclear carbonato-bridged copper(II) complex with a dipeptide moiety, is presented. To assess possible antitumor action mechanisms, we focused on the comparative analysis of pro- and antioxidant behaviors. Pro-oxidant activity, in which the reactive oxygen species (ROS) formed by the reaction of the complexes with H2O2 produce oxidative damage to 2-deoxy-d-ribose, was evaluated using the TBARS method. Additionally, the antioxidant action was quantified through the superoxide dismutase (SOD)-like activity, using a protocol based on the inhibitory effect of SOD on the reduction of nitrobluetetrazolium (NBT) by the superoxide anion generated by the xanthine/xanthine oxidase system. Our findings show that Cu–amino acid complexes are strong ROS producers and moderate SOD mimics. Conversely, Cu–dipeptide–phen complexes are good SOD mimics but poor ROS producers. The activity of Cu–dipeptide complexes was strongly dependent on the dipeptide. A DFT computational analysis revealed that complexes with high SOD-like activity tend to display a large dipole moment and condensed-to-copper charge, softness and LUMO contribution. Moreover, good ROS producers have higher global hardness and copper electrophilicity, lower copper softness and flexible and freely accessible coordination polyhedra.

Inhibitory effects of superoxide dismutase 3 on Propionibacterium acnes-induced skin inflammation

Propionibacterium acnes is a well-known commensal bacterium that plays an important role in the pathogenesis of acne and chronic inflammatory skin disease. In this study, we investigated the effect of superoxide dismutase 3 (SOD3) on P. acnes- or peptidoglycan (PGN)-induced inflammation in vitro and in vivo. Our data demonstrated that SOD3 suppressed toll-like receptor-2 (TLR-2) expression in P. acnes- or PGN-treated keratinocytes and sebocytes. Moreover, we found that SOD3 suppressed the expressions of phosphorylated nuclear factor-κB (NF-κB) and p38 in P. acnes- or PGN-treated cells. SOD3 also exhibited an anti-inflammatory role by reducing the expression of inflammasome-related proteins (NLRP3, ASC, caspase-1) and inhibiting the expression of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interleukin-8. In addition, SOD3 reduced lipid accumulation and expression of lipogenic regulators in P. acnes-treated sebocytes. Recombinant SOD3-treated wild-type mice and SOD3 transgenic mice, which were subcutaneously infected with P. acnes, showed tolerance to inflammation through reducing inflammatory cell infiltration in skin, ear thickness, and expression of inflammatory mediators. Our result showed that SOD3 could suppress the inflammation through inhibition of TLR2/p38/NF-κB axis and NLRP3 inflammasome activation. Therefore, SOD3 could be a promising candidate for treatment of P. acnes-mediated skin inflammation.

Augmented inhibitory effect of superoxide dismutase on superoxide anion release from macrophages by chemical modification with polysaccharide and attenuation effects on radiation-induced inflammatory cytokine expression in vitro

To improve the ability of superoxide dismutase (SOD) to suppress reactive oxygen species (ROS)-mediated injury, chemically modified derivatives of SOD with N,N,N-trimethyl chitosan chloride (TMC) and heparin, cationized SOD (TMC-SOD), and anionized SOD (heparin-SOD) were designed and prepared. In this study, the inhibitory effect of TMC-SOD and heparin-SOD on superoxide anion release from macrophages was studied in vitro. Both TMC-SOD and heparin-SOD exhibited excellent inhibitory effects on superoxide anion release from macrophages, and the effects of TMC-SOD surpassed those of native SOD and heparin-SOD. The effects of TMC-SOD and heparin-SOD on inflammatory cytokine expression in vitro were also evaluated. The results showed that both TMC-SOD and heparin-SOD could significantly lower the levels of transforming growth factor-β1 (TGF-β1) and interleukine-1β (IL-1β) expressed by irradiated 3T3 fibroblasts. These results demonstrated that cationic polysaccharide or anionic polysaccharide SOD derivatives might be useful in the prevention and treatment of ROS-mediated inflammatory diseases. This study also demonstrated that chemical modification of SOD, especially cationization, greatly enhanced SOD’s intracellular delivery and, consequently, produced a significant protective effect against ROS-mediated injury.

Effect of Superoxide Dismutase on Bleomycin-Induced Dermal Sclerosis: Implications for the Treatment of Systemic Sclerosis

Bleomycin has a chemical toxicity capable of inducing superoxide radicals, which are suggested to play an important part in bleomycin-induced pulmonary fibrosis. We have recently established a mouse model for scleroderma induced by repeated local injections of bleomycin. In this study, we examined the inhibitory effect of superoxide dismutase on the development of dermal sclerosis induced by bleomycin using this mouse model. PC-superoxide dismutase, which is a lecithinized superoxide dismutase with high tissue accumulation and long half-life in blood, was administered (3000 U per kg; dissolved in 5% mannitol) 3 h before the injection of bleomycin in C3H mice for 3 wk. Systemic PC-superoxide dismutase markedly inhibited the development of dermal sclerosis, which was also accompanied by a decrease in the number of infiltrating mast cells and eosinophils. Furthermore, the hydroxyproline content in the skin was significantly reduced, as compared with mice treated with bleomycin only or bleomycin and 5% mannitol. In a separate experiment, after the development of dermal sclerosis following treatment with bleomycin for 3 wk, PC-superoxide dismutase was administered for 2 wk. Histologic examination again revealed a reduction of dermal sclerosis, followed by a significant associate in the number of both mast cells and eosinophils. The hydroxyproline content in the skin was not significantly decreased, however, even after injections of high amounts of PC-superoxide dismutase (30,000 U per kg). These results support the involvement of oxygen free radicals in bleomycin-induced dermal sclerosis, and also indicate that administration of superoxide dismutase may be effective in the therapeutic approach in systemic sclerosis.

Augmented inhibitory effect of superoxide dismutase on superoxide anion release from macrophages by direct cationization

Superoxide dismutase (SOD) was modified into cationized form (Cat-SOD) in order to enhance its pharmacological efficacy based on an electrostatic interaction. The inhibitory effect of Cat-SOD on superoxide anion release from inflammatory macrophages and its cellular interaction were studied in vitro. Cat-SOD exhibited an excellent inhibitory effect on superoxide anion release from the macrophages, and this effect surpassed those of native SOD and SOD modified with mannose (Man-SOD) which is taken up via mannose receptor-mediated endocytosis by macrophages. In the presence of colchicine, a microtubule-disruptive agent, the inhibitory effect of Cat-SOD was slightly impaired, whereas the effect of Man-SOD completely disappeared. The intracellular localization of fluorescein isothiocyanate-labeled SOD, Cat-SOD and Man-SOD observed by confocal laser microscopy supported the difference in their abilities to eliminate superoxide anions. The different sensitivities of Cat-SOD and Man-SOD to colchicine were also confirmed by the confocal laser microscopic images, suggesting their distinct intracellular trafficking pathways in the macrophages. In conclusion, Cat-SOD is desirable for its pharmacological activity, which is probably the result of its ability to be delivered to the vicinity of NADPH-oxidase which locates in the cell membrane and generates superoxide anions.

Involvement of both protein kinase C and G proteins in superoxide production after IgE triggering in guinea pig eosinophils

ABSTRACT To study the function and mechanism of eosinophils via the low affinity IgE receptor (FceRII), we examined the production of 0 2 metabolites by measuring the luminol-dependent chemiluminescence (LDCL) response and the generation of cysteinyl leukotrienes. Eosinophils obtained from guinea pig peritoneal fluid sensitized with horse serum were purified. Luminol-dependent chemiluminescence was induced by stimulation with monoclonal anti-CD23 antibody, but not by mouse serum (controls). The mean (±SEM) value of LDCL was 20.6±1.3X10 3 c.p.m. This reaction consisted of an initial rapid phase and a propagation phase and ended within lOmin. Guinea pig eosinophils were histochemically stained with monoclonal anti-CD23 antibody. The major product generated in the LDCL response was superoxide, as determined by the measurement of superoxide by cytochrome c reduction and the complete inhibitory effect of superoxide dismutase on the LDCL response. Pretreatment with either pertussis toxin or cholera toxin inhibited the LDCL reaction. Depletion of bivalent ions by EDTA inhibited this response and the protein kinase C inhibitor D-sphingosin inhibited both 1-oleoyl-2-acetyl-glycerol-induced and FcϵRII-mediated LDCL. These findings suggest that the NADPH-protein kinase C pathway may be involved in the FceRII-mediated LDCL response in guinea pig eosinophils.

Inhibitory effects of superoxide dismutase and cyclic guanosine 3',5'- monophosphate on estrogen production in cultured rat granulosa cells

Inhibitory effects of superoxide dismutase and cyclic guanosine 3',5'- monophosphate on estrogen production in cultured rat granulosa cells

Inhibitory effects of superoxide dismutase and cyclic guanosine 3',5'-monophosphate on estrogen production in cultured rat granulosa cells.

Superoxide dismutases (SOD) modulate oxygen free radical metabolism and influence second messenger signaling in a variety of cell types. We have investigated the influence and possible mechanisms of action of SOD on aromatase activity in cultured rat granulosa cells. Although treatment of granulosa cells with FSH (0.3-30 ng/ml) resulted in a dose-dependent stimulation of estrogen levels, cotreatment of cells with SOD (10(-6) M) significantly attenuated estrogen production at the highest doses of FSH. The effects of SOD were dose dependent between 10(-7)-10(-5) M, with increasing amounts of SOD causing decreasing concentrations of estrogen. Cotreatment of cells with catalase (1500 U/ml) failed to prevent the inhibitory influence of SOD on estrogen production, indicating that the effects of SOD were not due to accumulation of hydrogen peroxide. Although incubation with either forskolin or (Bu)2cAMP alone stimulated estrogen production from granulosa cells, cotreatment with SOD significantly attenuated estrogen levels, indicating that SOD can inhibit aromatase activity at one or more post-FSH receptor sites. Treatment of cells with SOD, FSH, or forskolin resulted in small, but significant, increase in cGMP concentrations. In contrast, cotreatment of cells with FSH plus SOD as well as forskolin plus SOD had a marked synergistic effect on cGMP content, increasing cGMP levels over 100-fold. Incubation of granulosa cells with (Bu)2cGMP (2 mM) significantly decreased FSH-induced estrogen levels in a dose-dependent manner (0.25-2 mM). In addition, (Bu)2cGMP attenuated both forskolin- and (Bu)2cAMP-induced estrogen production. In contrast to the effects of (Bu)2cGMP and SOD on estradiol levels, these agents had no significant effect on progesterone production by cultured granulosa cells. These results demonstrate attenuated induction of aromatase activity by FSH in cultured rat granulosa cells cotreated with SOD, suggesting a potential modulatory role of this antioxidant on granulosa cell functions. The findings that SOD and activators of the cAMP-dependent signaling pathway synergistically increase the levels of the second messenger cGMP and that (Bu)2cGMP treatment attenuates FSH-, forskolin-, and cAMP-induced aromatase activity suggest a potential mechanism of SOD action and demonstrate the antagonist action of cGMP on cAMP-mediated estrogen production.

Effects of Superoxide Dismutase and Catalase during Reduction of Adrenochrome by DT-Diaphorase and NADPH-Cytochrome P450 Reductase

NADPH-cytochrome P450 reductase and DT-diaphorase catalyze the one- and two-electron reduction of adrenochrome to its o-semiquinone and o-hydroquinone, respectively. Under aerobic conditions both adrenochrome o-semiquinone and o-hydroquinone proved to be unstable, undergoing autoxidation with concomitant oxygen consumption and continuous NADPH and NADH oxidation. Molecular oxygen was found to play a predominant role in autoxidation of o-semiquinone during reduction of adrenochrome catalyzed by NADPH-cytochrome P450 reductase. In addition, molecular oxygen, in the presence of manganese, was found to be responsible for the majority of autoxidation of o-semiquinone. However, the role of superoxide radicals in the autoxidation of leucoadrenochrome during the reduction of adrenochrome by DT-diaphorase was found to be predominant. Catalase differed significantly with respect to NADPH and NADH oxidation during reduction of adrenochrome catalyzed by NADPH-cytochrome P450 reductase and DT-diaphorase, Catalase increased NADPH oxidation slightly, while NADH oxidation was inhibited during reduction of adrenochrome by NADPH cytochrome P450 reductase and DT-diaphorase, respectively, The presence of manganese in the incubation mixture was found to increase the prooxidant role of catalase on autoxidation during one-electron reduction of aminochrome catalyzed by NADPH cytochrome P450 reductase. A marked difference in the inhibitory effect of superoxide dismutase on oxygen consumption during adrenochrome reduction catalyzed by NADPH-cytochrome P450 reductase and DT-diaphorase was also observed, A possible mechanism for reduction of adrenochrome by NADPH-cytochrome P450 reductase and DT-diaphorase and a role for superoxide dismutase and catalase are proposed.

Activated microglia cause superoxide-mediated release of iron from ferritin

Ferritin contains the greatest part of the iron found in the brain, and the release of iron stores from ferritin has an essential role in iron-dependent lipid peroxidation. We examined the effect of cultured microglia on iron mobilization from ferritin. Microglia stimulated by phorbol myristate acetate caused the release of iron from ferritin, which was detected by monitoring iron-ferrozine complex formation. This iron mobilization was mediated by microglial superoxide production, as evidence by the significant inhibitory effect of superoxide dismutase. The role of superoxide was also supported by the close correspondence of cumulative microglial superoxide production, as demonstrated by the MCLA ( Cypridina luciferin analogue)-dependent chemiluminescence assay, to the time course of iron release from ferritin. Iron release induced by activated microglia may be partly responsible for the oxidative damage that is thought to occur in Parkinson's disease and other neurodegenerative disorders.

Amperometric determination of superoxide anions generated from phytoplankton Chattonella antiqua

Superoxide anions (0;) now attract much attention in many fields of biology since it is realized that superoxide anions are produced in significant quantities in various parts of biological systems from micro-organisms to mammals [ 11. However, in most cases the biological significance and mechanism of the generation of 0; are not yet understood. Chattonellu antiqua is a highly toxic phytoplankton which is harmful to ‘fish, especially in fish farms. On the basis of morphological and histochemical observations of the cells, it is proposed that 0; might be involved in the toxic mechanism responsible for mortality in fish exposed to a large population of C. antiqua [2-61. The inhibitory effects of superoxide dismutase (SOD) on the ability of C. antiqua to reduce ferricytochrome c to ferrrocytochrome c support this assumption [51. This communication provides direct evidence, obtained electrochemically, for the generation of 0; by C. antiqua. In a previous paper we demonstrated that the electrochemical detection of 0; generated from a single stimulated neutrophil (human and porcine) could be achieved using a microelectrode technique in which a single cell was brought into contact with a working electrode of size similar to that of the cell [71. We have used this technique, with a slight modification, for C. antiqua since the size and the nature of the cell are rather different from those of neutrophils. C. antiqua was obtained from the Akashio Research Institute of Kagawa Prefecture, and cultured in an Erd-Schreiber Modified (ESM) medium of pH 8.2 with constant illumination at around 23°C. Cultures contained ca. 1 X lo5 cells/ml after l-2 weeks under these conditions. Figure 1 shows photomicrographs of C. antiqua cells. When motile, they are spindle shaped and propel themselves by the

The influence of medium components on Cu 2+-dependent oxidation of low-density lipoproteins and its sensitivity to superoxide dismutase

The extent of in vitro Cu 2+-dependent oxidation of low-density lipoproteins (LDL) has been reported to vary widely depending upon reaction conditions. In this study, the effect of proteins and amino acids on Cu 2+-induced LDL oxidation was examined. Treatment of LDL with 5 μM CuSO 4 for 18 h in either phosphate-buffered saline (PBS) or Ham's F-10 medium resulted in extensive oxidation as determined by the content of thiobarbituric acid reactive substances (TBARS) and by increased lipoprotein electronegativity. In PBS, oxidation was entirely blocked by histidine and the tripeptide, gly-his-lys (GHK). Oxidation was also prevented by bovine serum albumin, but superoxide dismutase (SOD) provided only 20% protection. Both proteins bound similar amounts of Cu 2+, but albumin appeared to be a more effective peroxyl radical trap as evidenced by its ability to prevent LDL oxidation induced by 2,2′-azo-bis(2-amidinopropane hydrochloride). In F-10 medium, SOD had marked inhibitory effects, in contrast to PBS. The addition of disulfides to PBS markedly enhanced the ability of SOD to inhibit oxidation. These results indicate that medium components which affect Cu 2+ availability influence LDL oxidation and suggest that albumin is ideally suited as a plasma antioxidant to prevent oxidative modification of LDL. Furthermore, in certain instances, the inhibitory effects of SOD may be attributable to effects such as Cu 2+ binding rather than dismutation of superoxide.

Horseradish peroxidase-catalyzed aerobic oxidation of indole-3-acetic acid: II. Oxygen uptake and chemiexcitation

Light emission from the horseradish peroxidase-catalyzed aerobic or anaerobic oxidation of indole-3-acetic acid has been investigated under opposite extreme conditions of enzyme/substrate ratio. The O 2-dependent chemiluminescent processes represent a minor part of the total oxygen consumption. Superoxide is involved in chemiexcitation as is evident from the observed inhibitory effect of superoxide dismutase. At high enzyme/substrate ratio, only a part of the emission is dependent on superoxide ion; at low ratio the dependence is extensive. At high ratio, some of the emission is independent of superoxide and O 2. The identical quenching effects of d-and l-tryptophan are consistent with the formation of the quenching species only in bulk solution. The similarity of the emission spectra under extreme conditions indicates that the same main emitters are formed. This is also supported by the effect of quenchers. Possibly some of the emitters originate in the oxidative cleavage of the 2,3-double bond of the indole ring.

Horseradish peroxidase-catalyzed aerobic oxidation and peroxidation of indole-3-acetic acid: I. Optical spectra

A study of the indole-3-acetate reaction with horseradish peroxidase, in the absence or presence of hydrogen peroxide, has been performed, employing rapid scan and conventional spectrophotometry. We present here the first clear spectral evidence, obtained on the millisecond time scale, indicating that at pH 5.0 and for high [enzyme/ substrate] ratios peroxidase compound III is formed. Most, if not all, of the compound III is formed by oxygenation of the ferrous peroxidase. There is an inhibitory effect of superoxide dismutase and histidine on compound III formation which indicates the involvement of the active oxygen species superoxide and singlet oxygen. It is concluded that the oxidation of indole-3-acetate by horseradish peroxidase at pH 5.0 proceeds through compound III formation to the catalytically inactive forms P-670 and P-630. A reaction path in which the enzyme is directly reduced by indole-3-acetate might be involved as an initiation step. Rapid scan spectral data, which indicate differences in the formation and decay of enzyme intermediate compounds at pH 7.0, in comparison with those observed at pH 5.0, are also presented. At pH 7.0 compound II is a key intermediate in oxidation-peroxidation of substrate. Mechanisms of reactions consistent with the experimental data are proposed and discussed.

Generation of Semiquinone and Oxygen Radicals by the Reaction of Menadione with Reduced Glutathione at Various pH.

Semiquinone radicals of menadione were generated during the reaction of menadione with reduced glutathione (GSH), dependent upon the pH. Under aerobic conditions, cytochrome c was reduced during the reaction, and superoxide dismutase (SOD) inhibited the cytochrome c reduction. The inhibitory effect of SOD was greater at a high pH than at a low pH. In the presence of Fe3+ or ethylenediaminetetraacetic acid (EDTA)-Fe3+, deoxyribose was degraded during the reaction of menadione with GSH, dependent upon the pH. Greater amounts of deoxyribose were degraded at a low pH than at a high pH. The reduction of Fe3+ of EDTA-Fe3+ also depended on the pH, and SOD strongly inhibited the Fe3+ reduction, indicating that Fe3+ or Fe3+-EDTA was reduced by superoxide. SOD, catalase, mennitol and benzoate inhibited the deoxyribose degradation at various pH values. These results indicate that the menadione semiquinone radical is readily formed at an alkali pH but a hydroxyl radical is predominantly produced near a neutral pH. A hydroxyl radical may be generated via an iron-catalyzed Haber-Weiss reaction.

Peroxidase-promoted oxidation and peroxidation of the serotonergic neurotoxin 5,7-dihydroxytryptamine. A new pathway for its metabolic degradation.

Spectral data provide the first evidence that lactoperoxidase, a model enzyme for most mammalian peroxidases, catalyzed the one-electron oxidation and/or peroxidation of 5,7-dihydroxytryptamine. This process correlates with the production of superoxide radicals as is evident from the observed inhibitory effect of superoxide dismutase on product formation. 5,7-Dihydroxytryptamine is a classical peroxidase-oxidase substrate acting as a one-electron donor for enzyme compounds I, II and III. The one-electron peroxidatic oxidation of this serotonergic neurotoxin, responsible for the selective degeneration of central (5-hydroxytryptamine) neurons, is a fast process requiring measurement on the ms time scale. Attention is drawn to the biochemical and toxicological implications, because this fast reaction results in formation of known cell damaging species: free radicals, superoxide radicals and quinoidal products probably involved in the toxic action of 5,7-dihydroxytryptamine.

Superoxide Dismutase as an Inhibitor of Erythroid Progenitor Cell Cyclinga

C57Bl/6 (B6) mice and mice of a congeneic strain, B6S, differ in the proportions of erythroid progenitor cells (BFU-E) typically seen in DNA synthesis in in vivo cell suicide assays, and bone marrow supernatants (MS) prepared from B6 mice can inhibit BFU-E cycling in vitro. Using in vitro BFU-E DNA synthesis assays and a model system of BFU-E in culture (DA-1 cells) as screening methods for the detection of inhibitors of BFU-E cycling, we have purified the protein that is apparently responsible for the inhibitory effects of MS on progenitor cells and that is also an antagonist of the stimulatory effects of interleukin-3 (IL-3) on DA-1 cell proliferation in culture. We have identified this protein as the Cu,Zn-containing form of the antioxidant enzyme superoxide dismutase (SOD), which is normally present in large amounts in erythrocytes. MS from B6S mice does not inhibit BFU-E DNA synthesis. However, measurements of SOD activity showed no differences between B6 and B6S mice; thus the difference between the effects of B6S-MS and B6-MS is not due to differences in the levels of SOD present. The inhibitory effects of SOD on BFU-E in vitro are opposed by the stimulatory effects of IL-3 in a dose-dependent manner, and similar interactions between stimulatory and inhibitory factors also appear to determine the effects of mouse-derived preparations on erythroid cells. If the interactions seen in vitro are applicable to the state in vivo, SOD may be a constitutive inhibitor of erythroid progenitor cell cycling in mice, acting in opposition to stimulatory factors whose expression varies in response to genetic and physiological influences.

Superoxide Dismutase Specifically Inhibits Erythroid Cell DNA Synthesis and Proliferation

The antioxidant enzyme superoxide dismutase (SOD) was previously shown to inhibit both the proliferation of murine erythroid DA-1 cells growing in the presence of Interleukin-3 (IL-3) and the DNA synthesis of marrow erythroid progenitor cells (BFU-E) in vitro. We show here that the inhibition of marrow cell DNA synthesis by SOD is specific for BFU-E and erythroid precursors (CFU-E), with other myeloid progenitors (CFU-GM) and stem cells (CFU-S) being unaffected, and IL-3 blocks the inhibitory effects of SOD on BFU-E in a dose-dependent manner. Extending earlier observations on the effects of SOD on cell proliferation, it was found that SOD was capable of inhibiting DA-1 cell proliferation supported by either IL-3 or erythropoietin (epo), but had no effect on IL-3 dependent FDCP-1 cells, nor on epo-dependent HCD-57 cells. Of several murine erythroleukemia cell lines tested, only those transformed with Friend SFFVa virus were inhibited by SOD, while those transformed with Friend SFFVp or MuLV virus were not affected. These results show that the effects of SOD are not antagonistic to particular growth factors but rather the inhibition is specific for erythroid cells, and cells of the proper stage can be inhibited even if they have been transformed to factor independence.

The role of myeloperoxidase in the oxidation of biologically active polyhydroxyphenols (substituted catechols)

The reaction of myeloperoxidase with biologically active polyhydroxyphenols (substituted catechols): catecholamine, norepinephrine and 2,4,5-trihydroxyphenylalanine [Phe(OH)3] were investigated by using the ESR spin-stabilization technique and rapid-scan spectrophometry in the millisecond time scale. The results presented here indicate that dihydroxyphenols and trihydroxyphenols are substrates in the myeloperoxidase reaction. The data of ESR and rapid-scan optical investigation of the myleoperoxidase reaction with the dihydroxyphenols catecholamine and norepinephrine clearly indicate a normal peroxidase-type pathway of catecholamine degradation. The first evidence of o-semiquinone radical formation as a product of the enzymatic oxidation of catecholamine by myeloperoxidase is reported. The results obtained by rapid-scan spectrophotometric investigation of enzyme intermediate formation and decay showed qualitative agreement with the spin-stabilization studies. The first results on the reaction of myeloperoxidase with the trihydroxyphenol Phe(OH)3 presented here, indicate that it plays a role as an electron donor for myeloperoxidase I, but we were unable to obtain evidence that a normal peroxidase cycle is occurring. The inhibitory effect of superoxide dismutase on product formation was evident and indicate the involvement of superoxide radicals in the process. Attention is drawn to the biochemical and toxicological implications of these and other related studies of substituted catechol peroxidation by mammalian peroxidases.