Desferrioxamine as a lipid chain-breaking antioxidant in sickle erythrocyte membranes

The mechanism of action of desferrioxamine in the inhibition of the catalysis of iron-induced oxidative damage has been ascribed to its ability to chelate available ferric ion (Kb = 10(31)). However, recent work has proposed that the trihydroxamate moiety of desferrioxamine can also be involved in electron transfer reactions involving the superoxide radical, peroxidase/hydrogen peroxide mixtures and ferryl myoglobin radicals. In this study we report evidence for the ability of desferrioxamine to inhibit peroxidative damage to pathological membranes with which non-haem iron is associated through a mechanism of action as a lipid chain breaking antioxidant, independently of its iron chelating properties.

Oxidative stress and tumour cell proliferation

The effects of oxidant stress were studied in immortalised hamster (BHK-21) and rat (208F) cell lines before and after transformation to the malignant state with polyoma virus, or activated H-ras, respectively. Whilst intracellular superoxide production was detectable in both transformed and immortalised cells the rate was somewhat higher in the transformed cells which have lower levels of superoxide dismutase. Because growth of transformed cells was particularly depressed in the presence of MTT, a tetrazolium compound reduced by superoxide, the possible role of active oxygen species in the promotion of cell growth was examined. Low levels of hydrogen peroxide were stimulatory towards both immortalised and transformed cells. In the case of H-ras transformed rat cells, paraquat was also stimulatory provided serum was present in the growth medium. In the absence of serum, paraquat was notably inhibitory but inhibition could be alleviated by addition of low concentrations of alpha-tocopherol (10(-8)M) to the serum-depleted medium. Although depletion of serum from the growth medium also leads to lower cell proliferation, subsequent experiments showed that alpha-tocopherol addition to serum-free medium was sufficient to restimulate growth. In the case of transformed cells, yields of cells were even greater than that encountered in the presence of 10% serum. Thus whilst certain active oxygen species (e.g. hydrogen peroxide) may have a role in promoting the growth of transformed and immortalised cells the necessity for antioxidant protection is important.

The interactions of desferrioxamine and hydroxypyridone compounds with haemoglobin and erythrocytes

The iron chelator desferrioxamine has been applied in many studies of pathological states by several investigators. The resulting decreases in cellular and tissue damage have been interpreted as an indication of the involvement of iron-mediated radical species. Although the nature and location of the iron species have not been identified, the assumption has often been made that desferrioxamine is able to enter cells. This paper reports investigations of the ability of desferrioxamine to cross the erythrocyte membrane in comparison with that of specific hydroxypyridone iron chelators by assessing their interaction with haemoglobin.

The effects of iron-mediated oxidative stress in isolated renal cortical brush border membrane vesicles at normothermic and hypothermic temperatures

Experiments on renal cortical brush border membrane vesicles have been undertaken in order to assess the involvement of iron in oxidative stress at physiological temperatures and under conditions of hypothermia. A decrease in temperature stimulated iron-induced lipid peroxidation. The results are discussed in relation to the role of the oxidation state of the iron and iron(II)/iron(III) ratios in the initiation of peroxidative events.

The suppression of iron release from activated myoglobin by physiological electron donors and by desferrioxamine

Interactions between ferrimyoglobin and hydrogen peroxide have been postulated to lead to the formation of activated ferryl myoglobin. In such systems hydroxyl radical formation has also been demonstrated by its ability to degrade deoxyribose subsequent to the release of iron from the porphyrin ring of the myoglobin. We have investigated the potential for ferrylmyoglobin formation and for iron release from ferrylmyoglobin exposed to hydrogen peroxide; the modulation of the stability of the haem group by membranes and in the presence of desferrioxamine and ascorbate have also been assessed. The results show that iron release from ferrimyoglobin activated by hydrogen peroxide is suppressed in the presence of membranes, apparently by the reduction of the ferryl myoglobin species, and lipid peroxidation occurs. In the presence of desferrioxamine, formation of the ferrylmyoglobin species is suppressed by the electron donating properties of the trihydroxamate moiety, which also functions as a chain-breaking antioxidant when added to peroxidising membranes. The physiological antioxidant ascorbate not only suppresses the formation of the ferryl myoglobin species under the conditions described here, but also reduces the myoglobin iron to the iron II state.

Iron overload and the predisposition of cells to antioxidant consumption and peroxidative damage

We have investigated the effects of iron overload in vivo on the tocopherol levels and the extent of lipid peroxidation in rat liver microsomes and their response to subsequent oxidative stress in vitro. The results demonstrate a direct correlation between consumption of antioxidant defences and the induction and extent of malondialdehyde production in microsomes prepared from iron-loaded rats. The data are consistent with the requirement for iron (II)/iron (III) ratios in lipid peroxidation in control microsomes.

Free radicals and the regulation of mammalian cell proliferation

The question of whether free radicals or free radical-related species play a role in the modulation of mammalian cell proliferation is examined. Although a positive role for free radicals as specific components of mitogenic pathways is not apparent it is clear that certain free radical-derived species can have a significant modulatory influence on components of major growth signal transduction mechanisms. Free radical-derived species are also involved in the production of prostaglandins which themselves can modulate cell growth. Free radicals themselves appear to have a down regulatory effect on cell proliferation inasmuch as protection from oxidative stress enhances cell proliferation. On the other hand, in certain cases low levels of active oxygen species can enhance cell proliferation.

Heinz bodies do not modify the membrane characteristics of common marmoset (Callithrix jacchus) erythrocytes

The possibility was examined that the membrane function of erythrocytes obtained from healthy common marmosets (Callithrix jacchus) was modified by the presence in the cells of Heinz bodies. No significant differences were found in erythrocyte endogenous free malonyl dialdehyde (MDA) or reduced glutathione (GSH) between normal human erythrocytes and marmoset erythrocytes containing Heinz bodies. Membrane fluorescent chromolipids, surface charge and thiol levels were similar in both species but average membrane bulk lipid fluidity was slightly elevated in the marmosets. It was concluded that, in contrast to the situation in human erythrocytes, the presence of Heinz bodies in red cells of marmosets does not adversely affect the properties of the membrane.

The elliptocyte: a study of the relationship between cell shape and membrane structure using the camelid erythrocyte as a model

1. The elliptocytic shape of the camelid erythrocyte is very stable and has a high resistance to modification by drugs and treatment which alter the shape of the discocytic erythrocytes of scimitar-horned oryx and man. 2. Differences in the erythrocyte membrane proteins have been found which indicate that proteins play an important role in stabilisation of the camelid elliptocyte. 3. The organisation of the cytoskeletal network in camelid elliptocytes differs from that established for human discocytes.

Cell proliferation and oxidative stress

Antioxidants such as mannitol, butylated hydroxytoluene and alpha-tocopherol enhance the growth of polyoma virus transformed and non-transformed BHK-21 cells. In the case of mannitol this is observed even in the absence of added calf serum. In part these effects may operate to protect cellular growth control mechanisms. On the other hand oxidants such as H2O2 and t-butyl hydroperoxide can inhibit growth and overall cellular protein synthesis, through mechanisms that are likely to involve radicals. In the case of H2O2 the inhibitory effects can nevertheless be reduced by 'prestressing' the cells with mild heat or with H2O2 itself. Paradoxically very low concentrations (10(-8) M) of H2O2 or t-butyl hydroperoxide can actually stimulate cell growth, even in the absence of serum. These stimulatory effects however do not appear to involve radicals as they are enhanced by inclusion of mannitol or DMSO in the medium.

Iron-mediated oxidative stress in erythrocytes

Erythrocytes subjected extracellularly to iron-mediated oxidant stress undergo haemoglobin oxidation and membrane damage, which can be modulated by maintaining the energy requirements of the cells. The results presented here suggest that a balance exists between the oxidation state of the haemoglobin and the oxidative deterioration of the membrane lipids, which is dependent on the metabolic state of the erythrocytes. These findings have important implications for thalassaemic erythrocytes that may be exposed to excess plasma iron levels, in which excessive membrane-bound iron in the form of haemichromes is a characteristic feature and in which cellular ATP levels are lowered.

Oxidative stress and heat shock protein induction in human cells

Agents which induce heat shock protein synthesis in cultured monolayers of Hela cells such as hyperthermia, ethanol and sodium arsenite can also cause increases in the levels of lipid peroxidation as determined by the formation of TBA-products. The heat induced increases may be diminished by addition to the medium of mannitol or EGTA. These compounds are known to depress heat shock protein synthesis. Following hyperthermia there is also a decrease in protein synthesis. In vitro studies indicate possible damage to ribosomes, and since the heat induced loss of protein synthetic capacity can be increased by superoxide dismutase inhibitors, and prevented by mannitol, such effects may be linked to the increases observed in lipid peroxidation. It is suggested that a connection exists between lipid peroxidation and heat shock protein gene activation.

Modulation of iron-mediated oxidant damage in erythrocytes by cellular energy levels

In this work we have investigated the effects of iron-induced oxidative stress on erythrocytes and their membranes, the importance of haemoglobin oxidation and of the maintenance of the metabolic properties of the cells. The results show that by maintaining the energy requirements of the erythrocyte, methaemoglobin production is minimised under conditions of iron-stress. However, in this situation, the membranes of the erythrocytes become more susceptible to the oxidative damage and increased lipid peroxidation ensues.

Role of membrane-bound haemoglobin products in oxidative damage in sickle cell membranes

Even though the development of the membrane abnormalities in sickle cell erythrocytes is due to the presence of a mutant gene product, sickle cell anaemia is in a sense a membrane disease. In particular, the presence of iron-containing breakdown products of haemoglobin in the sickle cell membranes provides a source of continued oxidative damage. An understanding of the primary causes of these membrane abnormalities may be useful in the development of effective therapies.

Sickle cell membranes and oxidative damage

Sickle erythrocytes and their membranes are susceptible to endogenous free-radical-mediated oxidative damage which correlates with the proportion of irreversibly sickled cells. The suppression of incubation-induced oxidative stress by antioxidants, free radical scavengers and an iron chelator suggest that oxidation products of membrane-bound haemoglobin contribute towards the pathology of the disease.

Susceptibility of tamarin (Saguinus labiatus) red blood cell membrane lipids to oxidative stress: implications for wasting marmoset syndrome

Captive Callitrichids frequently suffer a fatal wasting disease, wasting marmoset syndrome (WMS), of unexplained cause. This paper describes studies on the erythrocytes from animals in a breeding colony of tamarins (Saguinus labiatus), in which deaths from anaemia and wasting were occurring, to seek evidence for biochemical changes which could lead to oxidative damage and premature cell lysis. In only one animal of 33 studied did the red blood cell lipids show an increased susceptibility to oxidative damage. This animal, with some degree of certainty, could be diagnosed as having WMS. It was concluded that evidence for a primary deficiency of antioxidants as a cause of unexplained deaths, or WMS, in the colony could not at present be substantiated.

t-butyl hydroperoxide-induced perturbations of human erythrocytes as a model for oxidant stress

Erythrocytes were incubated with t-butyl hydroperoxide in the presence and absence of hemoglobin as a model system for oxidative stress and the alterations in the structure and integrity of the membranes were investigated. The results showed that in the presence of hemoglobin a significant modification in the membrane surface charge was induced but no such alteration was observed in peroxidized hemoglobin-free membranes. As increased hemoglobin oxidation occurred in the erythrocytes, membrane lipid peroxidation diminished, suggesting a protective role for methemoglobin in t-butyl hydroperoxide-induced lipid peroxidation. Electrophoresis on polyacrylamide gels showed modification of the cytoplasmic protein region but no high molecular weight aggregates formed at the concentrations of the hydroperoxide used in this work. The results suggest that the t-butyl hydroperoxide/normal erythrocyte system seems to be an instructive model for membrane perturbations characteristic of oxidative disorders.

Oxidative effects of iron on erythrocytes

In this work we have investigated the effects of iron-induced free radical formation in normal human erythrocytes in vitro, as a model system for studying iron damage, and in erythrocytes from patients with beta-thalassaemia major. The resulting oxidative effects were measured in terms of methaemoglobin formation and reduced glutathione loss. The effects of desferrioxamine, an iron-chelating agent, were also investigated. The results show that the increased methaemoglobin formation after iron-induced oxidative stress is consistent with a decline in the intracellular glutathione levels and that this process is inhibited by desferrioxamine. Similar treatment of red cell haemolysates produces less methaemoglobin. This suggests that, on exposure of intact erythrocytes to iron-induced free radical effects, the red cell membrane exacerbates the breakdown of the antioxidant defences of the cell and the oxidation of haemoglobin.