The physiological role of zinc as an antioxidant

Comparative in vitro oxygen radical scavenging ability of zinc methionine and selected zinc salts and antioxidants

1. The concentration-dependent scavenging abilities of zinc DL-methionine, zinc sulfate, zinc gluconate, zinc picolinate and selected free radical scavengers, including superoxide dismutase (SOD), catalase, mannitol, allopurinol and DL-methionine, were examined against biochemically generated superoxide anion, hydroxyl radical and hypochlorite radical plus hypochlorous acid, by chemiluminescence and cytochrome c reduction. 2. Zinc methionine was the most effective of the zinc compounds that were tested. Following incubations with superoxide anion, hydroxyl radical, and hypochlorite radical-generating systems, in the presence of 50 microM zinc DL-methionine approximately 38%, 47% and 28% inhibition in reactive oxygen species generation was observed, respectively, compared to control groups. 3. The protective abilities of various zinc salts, as well as selected free radical scavengers and antioxidants were also assessed on phorbol ester (TPA)-induced lactate dehydrogenase (LDH) release from cultured PC-12 cells. Preincubation showed better protection than coincubation. Approximately 45% and 50% inhibition in TPA-induced LDH leakage was observed following preincubation with 50 microM zinc DL-methionine and 50 microM vitamin E succinate, respectively. Zinc DL-methionine exhibited better protection against LDH leakage than any other zinc salt tested. 4. The results indicate that zinc DL-methionine can attenuate the biochemical consequences of oxygen free radicals, and is comparable to other well-known antioxidants and free radical scavengers in the in vitro system that was employed.

Zinc and DNA fragmentation in keratinocyte apoptosis: its inhibitory effect in UVB irradiated cells

Zinc has been shown to have antioxidant properties and to exhibit inhibitory effects on apoptosis. In this work we investigated the effect of zinc on DNA integrity and on apoptosis of HaCaT keratinocytes. Cells were submitted to zinc deprivation by a diffusible zinc chelator, (N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine) (TPEN) or supplied with zinc chloride and submitted to UVB radiation. After cell exposure to TPEN for 2 h, strand breaks significantly impaired DNA resistance to alkaline denaturation. DNA strand breaks induced by a 6 h TPEN application were significantly prevented if zinc chloride was supplied together with the chelator. TPEN also generated, after 4-6 h of application, cytoplasmic histone-associated DNA fragments (mononucleosomes and oligonucleosomes), features of cell death by apoptosis. Moreover, UVB irradiation led to early DNA strand breaks and to an increase in cytoplasmic nucleosomes which was maximum 10 h after irradiation. These effects were prevented by the supply of zinc chloride (0.1 mM) in the culture medium. These results suggest that zinc ions interfere with the apoptosis process at an early stage, by decreasing DNA damage able to trigger apoptosis.

Vitamin E improves the free radical defense system potential and insulin sensitivity of rats fed high fructose diets

The purpose of this study was to investigate the effects of vitamin E in rats fed a high fructose diet which leads to insulin resistance, on some components of the free radical defense system and on insulin sensitivity. The rats (postweaning, 50 g) were divided into three groups: the control group (C, n = 16), which received a purified diet containing 60 g/100 g carbohydrates, the high fructose-fed group (FT, n = 16),fed a diet in which 56.8% of the carbohydrate as fructose, and a high fructose and vitamin E-fed group (FVE, n = 16), fed the FT diet supplemented with 3.4 g vitamin E/kg diet (vs. 0.17 g/kg in C and FT groups). The duration of the treatment was 6 wk. Insulin sensitivity was determined in half of the rats in each group using the euglycemic hyperinsulinic glucose clamp technique. The remaining rats were investigated for plasma glucose, insulin, triglyceride and fructosamine concentrations and for components of the free radical defense system. The FT group had a significantly lower insulin sensitivity than the C group. Basal glycemia was not different among the groups. In comparison with the C group, the FT group had a greater lipid peroxidation, as indicated by the higher concentrations of plasma thiobarbituric acid reactive substances (TBARS) and blood disulfide glutathione (GSSG) and the lower Cu-Zn superoxide dismutase (Cu-Zn SOD) activity. These markers approached the values of the controls after addition of vitamin E. Moreover, the FVE group had a higher insulin sensitivity than the FT group, but it remained lower than in the C group. These results show that a high fructose diet in rats leads to insulin resistance and a defect in the free radical defense system. Vitamin E supplementation improves insulin sensitivity in fructose-fed rats.

Comparison of Zn and vitamin E for protection against hyperoxia-induced lung damage

The objective of the present study was to demonstrate an antioxidant function for Zn in vivo by comparing the efficacy of Zn or Vitamin E without additional energy intake for protection of Zn-deficient (ZnDF) or energy-restricted (ER) rats from hyperoxia-induced lung damage. Zn (200 mumol ZnCl2/kg b.wt.) or Vitamin E (100 mg alpha-tocopherol/kg b.wt.) was injected IP before exposure to 85% oxygen or air for 5 d. During the exposure period, all injected ZnDF or ER rats were restricted to 5 g Zn-deficient or Zn-adequate diet/day, respectively, the amount of diet consumed by the untreated ZnDF or ER rats. We clearly demonstrated that injection of Zn without additional energy intake can protect ZnDF and ER rats from hyperoxia-induced lung damage assessed by the histopathological scoring system and magnetic resonance imaging (MRI). Vitamin E was not as effective as Zn in either ZnDF or ER rats for preventing hyperoxia-induced lung damage. Zn injection did not exert its antioxidant effect through increased lung CuZn-superoxide dismutase activity or metallothionein. This difference in the effectiveness of Vitamin E and Zn for hyperoxic protection in lung injury may be due to the specificity of antioxidant function, i.e., vitamin E inhibits oxidation of membrane lipids and Zn protects sulfhydryl groups of proteins.

Hepatocytes from metallothionein-I and II knock-out mice are sensitive to cadmium- and tert-butylhydroperoxide-induced cytotoxicity

Metallothionein (MT) has been proposed to play an important role in heavy metal detoxication and in the scavenging of free radicals. Effects of MT on the cytotoxicity of cadmium (Cd), tert-butylhydroperoxide (t-BHP) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined using primary hepatocyte cultures from control (C57BL/6J) and MT-I and II knock-out (MT-null) mice. Compared to control hepatocytes, MT-null hepatocytes had minimal Cd-binding proteins (MT equivalents), but cellular glutathione concentration was similar to the control hepatocytes. MT-null hepatocytes were more sensitive than controls to the cytotoxic effects of Cd (50-300 microM) and t-BHP (125-500 microM), as indicated by the levels of lactate dehydrogenase released into the medium. Cd and t-BHP also produced more lipid peroxidation in MT-null hepatocytes than in control cells, as demonstrated by the abundance of thiobarbituric acid-reactive substances. However, MT-null hepatocytes were equally sensitive as controls to the cytotoxicity of MNNG (0.5-2.0 mM), suggesting that MT does not protect against MNNG-induced cytotoxicity. These results support the hypothesis that constitutive MT levels affect the sensitivity of mammalian cells to Cd and oxidative stress.

Antiatherogenic properties of zinc: implications in endothelial cell metabolism

Zinc is an essential component of biomembranes and is necessary for maintenance of membrane structure and function. There is evidence that zinc can provide antiatherogenic properties by preventing metabolic physiologic derangements of the vascular endothelium. Because of its antioxidant and membrane-stabilizing properties, zinc appears to be crucial for the protection against cell-destabilizing agents such as polyunsaturated lipids and inflammatory cytokines. Zinc also may be antiatherogenic by interfering with signaling pathways involved in apoptosis. Most importantly, we have evidence that zinc can protect against inflammatory cytokine-mediated activation of oxidative stress-responsive transcription factors, such as nuclear factor kappa B and AP-1. It is very likely that certain lipids and zinc deficiency may potentiate the cytokine-mediated inflammatory response and endothelial cell dysfunction in atherosclerosis. Thus, the antiatherogenic role of zinc appears to be in its ability to inhibit oxidative stress-responsive factors involved in disruption of endothelial integrity and atherosclerosis. We discuss antiatherogenic properties of zinc with a focus on endothelial cell metabolism.

Increased oxidative stress and decreased antioxidant defenses in mucosa of inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation whose cellular components are capable of oxidative respiratory bursts that may result in tissue injury. Mucosal biopsies were analyzed for protein carbonyl content (POPs), DNA oxidation products [8-hydroxy-2'-deoxyguanosine (8-OHdG)], reactive oxygen intermediates (ROIs), trace metals (copper, zinc, and iron) and superoxide dismutase (Cu-Zn SOD). In Crohn's disease biopsies, there was an increase in ROIs, POPs, 8-OHdG, and iron, while decreased copper and Cu-Zn SOD activity were found in inflamed tissues compared to controls. For ulcerative colitis, there was an increase in ROIs, POPs, and iron in inflamed tissue compared to controls, while decreased zinc and copper were observed. An imbalance in the formation of reactive oxygen species and antioxidant micronutrients may be important in the pathogenesis and/or perpetuation of the tissue injury in IBD and may provide a rationale for therapeutic modulation with antioxidants.

Changed serum trace element profile in Down's syndrome

Being cofactors of important antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), which are significantly modified in Down's syndrome (trisomy 21), serum levels of microtrace elements zinc, copper, and selenium and of macroelement magnesium are reported in 16 subjects with Down's syndrome (DS) and their respective well age- and sex-matched controls. Serum zinc and selenium levels were significantly lowered in DS subjects, whereas copper levels were elevated. Consequently, a marked increase (40%) of the copper/zinc ratio in DS persons was observed. There were no differences in serum levels of magnesium between DS and control subjects.

A20 blocks endothelial cell activation through a NF-kappaB-dependent mechanism

The A20 gene product is a novel zinc finger protein originally described as a tumor necrosis factor alpha (TNF)-inducible early response gene in human umbilical vein endothelial cells (HUVEC). Its described function is to block TNF-induced apoptosis in fibroblasts and B lymphocytes, but more recently it has also been shown to play a role in lymphoid cell maturation. The mechanism of action of A20 is unknown. The aim of our study was to assess the effect of A20 upon endothelial cell activation. By transfecting bovine aortic endothelial cells (BAEC) with A20 as well as reporter constructs consisting of the promoters of genes known to be up-regulated during endothelial cell activation, i.e. E-selectin, interleukin (IL)-8, tissue factor (TF), and inhibitor of nuclear factor kappaBalpha (IkappaBalpha), we demonstrate that A20 expression inhibits gene up-regulation associated with TNF, lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate (PMA), and hydrogen peroxide (H2O2)-induced endothelial cell (EC) activation. The mechanism of action of A20 is in part, or totally, due to the blockade of nuclear factor kappaB (NF-kappaB), as shown by its ability to suppress the activity of a NF-kappaB reporter. This effect is specific, as A20 does not block a noninducible, constitutively expressed reporter, Rous sarcoma virus-luciferase (RSV-LUC); nor does it block the c-Tat-inducible, NF-kappaB-independent reporter, human immunodeficiency virus-chloramphenicol acetyltransferase (HIV-CAT). How A20 blocks NF-kappaB is unclear, although we demonstrate that it does not affect p65 (RelA)-mediated gene transactivation. The inhibition of endothelial cell activation by A20 is a novel function for A20.

Metallothionein and zinc as potential antioxidants in radical-induced lipid peroxidation in cultured hepatocytes

Rat hepatocytes were isolated by a two-step collagenase perfusion technique and introduced to the hydroxyl radical (OH)-generating xanthine-xanthine oxidase-iron (X/XO/Fe) system. The amount of thiobarbituric acid reactive substances (TBA) and thiobarbituric acid bound malondialdehyde (TBA-MDA) were assayed in homogenates after different phases of cultivation. The effects on lipid peroxidation of supplemented metallothionein (MT) ranging from 25 to 75 microM and zinc ranging from 14.5 to 77.8 microM, as well as the effect of a Zn-pretreatment for 18 h were investigated. The addition of X/XO/Fe resulted in a 3 to 4-fold increase in the levels of TBA and TBA-MDA. These results show that X/XO/Fe initiated the lipid peroxidation in the hepatocyte cell system. High doses of supplemented MT inhibited the production of TBA and TBA-MDA. Neither Zn nor the Zn-pretreatment, which resulted in an increase of intracellular MT, had any effect on TBA and TBA-MDA levels. This study suggests that MT can act as an antioxidant in high concentrations via the cysteinyl groups of the protein. The postulated protective effects of Zn via its release from the oxidized MT can be ruled out.

[Zinc--update of an essential trace element]

Since the recognition of zinc as an essential trace element in man and animals there has been a remarkable progress in our knowledge of the role of zinc in nutritional physiology, biology and medicine during the last few decades. Highlights in zinc research, mechanisms and homeostatic regulation of zinc absorption, sources of zinc intake, dietary factors and mineral interactions affecting zinc bioavailability are reviewed in the present paper. This is followed by an overview of the biochemical functions of zinc in enzymes, gene expression, endocrinology, immunology and oxidative stress. General signs and metabolic consequences of zinc deficiency as well as excessive intake and toxicity of zinc are summarized. Furthermore, national and international dietary zinc recommendations and different methods to determine the zinc status are discussed.

Zinc transport in mammalian cells

The importance of zinc in cell physiology is related mainly to its intracellular involvement in enzyme catalysis, protein structure, protein-protein interactions, and protein-oligonucleotide interactions. The mechanisms by which Zn2+ enters mammalian cells have been studied in a variety of cell systems. A review of this literature indicates that, in all cells, Zn2+ interacts with extracellular binding sites, which are likely to include binding sites involved in the subsequent translocation of this ion to the cell interior. Inside the cell, Zn2+ binds to cytosolic and organelle binding sites or is taken up by intracellular organelles. Despite these general conclusions, the mechanisms of the different transport and binding steps are, for most cell types, only partially solved. This review critically discusses the literature on mammalian Zn2+ transport and outlines some critical points for future research of the mechanisms of transport of this ion.

Plasma copper and lipid peroxidation in cigarette smokers

Plasma levels of copper and lipid peroxidation were evaluated in 14 smokers as compared to 14 nonsmokers. Plasma copper concentrations were higher in smokers than in nonsmokers (122.5 +/- 19.15 vs. 101.5 +/- 16.2 micrograms/dl, P < .01). Plasma lipoperoxidation, evaluated as fluorescent damage products of lipid peroxidation (FDPL), also was higher in smokers than in nonsmokers (20.35 +/- 2.6 vs. 17.1 +/- 2.95 units of relative fluorescence/ml, P < .01). A significant and positive correlation between the number of cigarettes smoked, expressed as pack years, and the levels of either FDPL (r = .61, P < .025) or copper (r = .55, P < .05) was found. Moreover, a significant and positive relationship between copper and FDPL values was observed in smokers (r = .64; P < .025), but not in nonsmokers. These data indicate that cigarette smoke-related plasma oxidant load may be partly due to enhanced levels of the prooxidant metal cooper, potentially suggesting the supplementation of specific antioxidants (e.g., zinc) to counteract cigarette smoke-induced oxidative stress in smokers.

Zinc supplementation enhances the effectiveness of St. Thomas' Hospital No. 2 cardioplegic solution in an in vitro model of hypothermic cardiac arrest

The present study was done to assess the effectiveness of a zinc-supplemented cardioplegic solution in an in vitro model of hypothermic arrest. Isolated hearts were perfused in the nonworking mode. All hearts were subjected to 2 hours of hypothermic arrest, at 10 degrees C, followed by 60 minutes of recovery. In protocol 1, arrest was initiated with infusion of cardioplegic solution with or without 30 mumol/l zinc for 5 minutes, which was then reinfused for 5 minutes every 15 minutes during arrest. In protocol 2, arrest was initiated with infusion of cardioplegic solution with or without 40 mumol/L zinc for 10 minutes. Cardioplegic solution (without zinc) was then reinfused for 5 minutes before the hearts were rewarmed. In protocol 1 hearts, peak postischemic left ventricular developed systolic pressure was 106 +/- 5 mm Hg and 80 +/- 3 mm Hg in zinc-treated versus control hearts, respectively (p < 0.05 by repeated-measures analysis of variance). In protocol 2 hearts, recovery of postischemic left ventricular developed systolic pressure peaked at 74 +/- 4 mm Hg and 46 +/- 8 mm Hg in zinc-treated and control hearts, respectively (p 0.05, repeated-measures analysis of variance). Similar effects were observed for the left ventricular rate of relaxation (p < 0.05, repeated-measures analysis of variance). Except for some minor effects, lactate dehydrogenase release was not affected by zinc supplementation. The present study demonstrates that zinc supplementation further enhances the normally observed preservation of postarrest cardiac function and suggests possible clinical utility for this metal as an additive to standard crystalloid cardioplegic solutions.

Influence of zinc on selected cellular functions of cultured human retinal pigment epithelium

Zinc is a necessary micronutrient, usually abundant in human RPE. Our study was undertaken to determine the effects of short-term, zinc deficiency on human retinal pigment epithelium (RPE) using a culture model of fetal human RPE cells. Human fetal RPE cells were isolated and cultured in Coon's modified Ham's F-12 medium. For zinc depletion studies, cells were cultured for 1 week in Chelex-treated Dulbecco's modified Eagle's medium containing low (0.25 microM) or physiologic (11 microM) total zinc concentrations as determined by flame atomic absorption spectroscopy. Protein synthesis was determined by incorporation of 35S-cysteine/methionine and labeled proteins analysed by polyacrylamide gel electrophoresis. Several cell parameters and enzymes were significantly reduced below control when cultured in low zinc: zinc content (40%), proliferation (63%), protein/well (50%), catalase activity (68%), alkaline phosphatase activity (61%), alpha-mannosidase activity (68%), and metallothionein (82%). No statistically significant decline was seen in acid phosphatase activity, superoxide dismutase activity, glutathione peroxidase activity and dexamethasone induction of metallothionein. Zinc repletion (100 microM, 1 h) increased catalase and alpha-mannosidase activities from 32% and 33% of control to 75% and 73%, respectively. Cycloheximide did not inhibit this short-term zinc-induced repletion of catalase or alpha-mannosidase. Protein synthesis in low zinc medium was depressed, but not significantly, as shown by incorporation of radiolabeled 35S-cysteine/methionine into newly synthesized proteins. The effects of zinc deficiency in cultured human RPE are selective. Adequate intracellular zinc was required for maximal activity of some enzymes. The dependence of catalase activity on zinc was not predicted and may help explain the observed decline in catalase activity seen with age in RPE. Our model of zinc deficiency should prove useful in elucidating the complex effects of zinc deficiency and repletion in human RPE.

The effect of zinc supplementation on plasma lipids and low-density lipoprotein oxidation in males

Recent studies in animals and in vitro support the hypothesis that zinc, an essential micronutrient, possesses antioxidant properties. The aims of this study were to determine whether zinc provides antioxidant protection in humans by decreasing low-density lipoprotein (LDL) oxidizability and to determine the effect of zinc supplementation on plasma lipid and its distribution among lipoproteins. Ten healthy male volunteers were recruited to participate in a randomized crossover trial. Subjects were asked to consume 50 mg zinc as 220 mg zinc sulphate (equivalent to 4 x recommended dietary intake, or RDI) daily for 4 weeks, followed by placebo, and vice versa. Venous blood samples were collected at 2-week intervals for the determination of plasma lipids and the in vitro oxidizability of LDL in the presence of copper ions. No changes in the oxidizability of LDL or the plasma concentrations of total cholesterol, high-density lipoprotein (HDL) cholesterol and its subfractions, LDL cholesterol, or triacylglycerol were observed following zinc supplementation compared to placebo. Plasma zinc concentrations were increased significantly, indicating that the lack of effect was not due to poor compliance. The antioxidant effect of zinc in relation to LDL was not demonstrated in humans at this dose, and higher doses are unlikely to be effective given the adverse interaction with copper metabolism and the potential decrease in the activity of superoxide dismutase, a free radical quenching enzyme. The findings of this study suggest that zinc provides little, if any, antioxidant protection against LDL oxidation in humans.

Selenium status, plasma zinc, copper, and magnesium in vegetarians

Plasma zinc (Zn), copper (Cu), and magnesium (Mg) concentrations, copper/zinc ratio, and selenium (Se) status were studied in 44 vegetarians (22 males and 22 females) and their age- and sex-matched nonvegetarians in the Bratislava region (Slovakia). Vegetarians had statistically significant lower levels of plasma Zn and Cu than nonvegetarians, which may be the result of lower bioavailability of Zn and Cu from this type of diet. No differences in plasma Mg levels were found between vegetarians and nonvegetarians. Se status, as expressed by plasma and erythrocyte concentrations and plasma and erythrocyte glutathione peroxidase activities (GPx), was significantly lower in vegetarians when compared to nonvegetarians. In the series as a whole, there were significantly higher correlations between plasma and erythrocyte Se concentrations and between plasma and erythrocyte GPx activities. Significant positive correlations were also found between plasma Se concentrations and erythrocyte GPx activities, and between erythrocyte Se concentrations and erythrocyte GPx activities. A vegetarian diet does not provide a sufficient supply of essential antioxidant trace elements, like Zn, Cu, and especially Se. Se supplementation should be recommended to this risk group of the population.

The effect of zinc on bacterial phagocytosis, killing and cytoprotection in human polymorphonuclear leucocytes

An in vitro study examining the effects of zinc treatment on human PMN cell phagocytosis and killing of Staphylococcus aureus and Staphylococcus epidermidis and the cytoprotection of zinc against staphylococcal toxins. Phagocytosis was studied by transmission electron microscopy using different microbiological techniques, one of which was designed to follow the kinetics of bacterial killing. No effect was found on phagocytosis and bacterial killing. The cytotoxic effects of a crude toxin and an alpha-toxin extracted from Staphylococcus aureus preparations were studied on human PMN cells using the standard 51Cr release assay. Both toxins induced a dose-dependent leakage of 51Cr, indicating cell membrane damage. These results were confirmed by electron microscopy during the phagocytosis of S. aureus, where severe PMN cellular degeneration was observed. The addition of zinc to PMN cells strongly inhibited the release of 51Cr. In conclusion, our results show that zinc in higher than physiological concentrations does not inhibit PMN cell functions such as phagocytosis and intracellular killing of S. aureus and S. epidermidis. The addition of zinc may be beneficial in certain clinical situations, such as wound healing, zinc deficiency and infections involving toxin-producing bacteria, e.g. S. aureus.

Zinc inhibition of electron transfer: mechanism of beta receptor inhibition?

Zinc has been shown to inhibit β-receptor activation of adenylate cyclase at a post receptor site. We have postulated that the β-receptor is one of several receptors activated by reduction, followed by transmembrane elector transfer accelerated by GTP. GTP accelerates electron transfer in a model system and this accelerated electron transfer is inhibited by zinc. This could explain the mechanism of the post receptor inhibition by zinc of the adenylate cyclase stimulation which follows β-receptor activation.

Metallothionein/disulfide interactions, oxidative stress, and the mobilization of cellular zinc

Glutathione disulfide, the major cellular disulfide, releases zinc from metallothionein (MT) [W. Maret (1994) Oxidative metal release from metallothionein via zinc-thiol/disulfide interchange, Proc. natn. Acad. Sci. U.S.A. 91, 237-241]. Here, the interaction of rabbit liver MT-II with other selected biological disulfides (coenzyme A/glutathione mixed disulfide, coenzyme A disulfide, and cystamine) was investigated by measuring concomitant release of radioactive 65-zinc from MT. These disulfides react more rapidly than glutathione disulfide, thus underscoring the reactivity of zinc sulfur bonds in the clusters of MT and the importance of the MT/disulfide interaction as a chemical mechanism for mobilizing zinc from a thermodynamically stable zinc complex. Two implications of these in vitro findings are discussed. (i) Apparently, in the case of zinc which is redox inert, Nature has availed itself of the redox activity of the cysteine ligand to mobilize the metal, and, presumably to permit redox-control of cellular zinc distribution. The mobilization of zinc from MT suggests a possible function of MT as a physiological zinc donor. (ii) A shift of the glutathione redox balance under conditions of oxidative stress will accelerate metal release from MT. Such a disturbance of metal metabolism has important consequences for the progression of diseases such as Alzheimer's and Parkinson's disease where oxidative stress occurs in affected brain tissue.

Inhibition of the oxidative modification of LDL by nitecapone

We studied in vitro the ability of nitecapone, 3-[(3,4-dihydroxy-5-nitrophenyl)methylene]-2,4-pentanedione, a novel water-soluble compound with antioxidative properties, to inhibit the LDL oxidation promoted by copper ions, the aqueous free radical generator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH), and mouse peritoneal macrophages. In these three oxidation systems, the extent of LDL oxidation was determined by measuring the formation of conjugated dienes, the formation of thiobarbituric acid-reactive substances, the change in the electrophoretic mobility of LDL, and the uptake of LDL by macrophages. When LDL oxidation was promoted by copper ions, the reaction was found to be inhibited by nitecapone added in a three- to five-molar excess of the concentration of copper ions. The mechanism by which nitecapone exerted its antioxidative effect in copper-mediated LDL oxidation depended on binding and redox inactivation of the copper ions. Moreover, nitecapone released LDL-bound copper ions and so rendered the LDL particles more resistant to oxidation. In contrast to a water-soluble alpha-tocopherol analogue that was rapidly consumed during the oxidative process, nitecapone retained its inhibitory effect for at least 2 days. Using immobilized metal ion affinity chromatography, we showed that nitecapone binds both copper and iron ions, whereas its affinity for zinc ions is low. Nitecapone also inhibited LDL oxidation in the free radical-mediated oxidation system (AAPH). In this system, nitecapone showed synergistic antioxidative action with ascorbic acid. Finally, nitecapone inhibited macrophage-mediated LDL oxidation. Accordingly, nitecapone appears to have a unique antioxidative profile in that it both selectively chelates pro-oxidative transition metals and scavenges free radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired function of postoperative macrophages from zinc-deficient rats decreases collagen contraction. Brief report

Zinc deficiency impairs connective tissue contraction in the perforated rat mesentery model. Since the rat mesentery is almost avascular, free peritoneal macrophages are important for mesenteric repair. Impairment of contraction may thus be caused either by a direct effect of zinc deficiency on tissue cells or by hampered macrophage function. To further elucidate the role of macrophages in tissue contraction, we studied their effect on lattice contraction. A number of typical functions of macrophages in zinc deficiency were also investigated. Lattice contraction was significantly impaired by conditioned medium from zinc-deficient macrophages. Zinc deficiency did not influence peripheral blood leukocyte number, but postoperatively the number of peritoneal macrophages increased on days 7 and 10. A significant release of lysosomal enzymes from macrophages was recorded during phagocytosis, whilst no difference was observed between controls and zinc-deficient macrophages. Superoxide anion generation during phagocytosis was not significantly increased in zinc deficiency. Conditioned medium from zinc-deficient macrophages was shown to impair lattice contraction in vitro and the results are compatible with impaired macrophage function as a cause of decreased connective tissue contraction in vivo.

Effects of zinc on copper-induced and spontaneous lipid peroxidation

Zinc (Zn) is an essential nonredox metal that has been regarded as having antioxidant properties. Some epidemiological indications and therapeutic results point to a role of Zn in restricting the development and the progression of some diseases. Redox-active metals like iron and copper are involved in oxidative injury mechanisms, and a decrease in the Zn:Cu ratio may be associated with certain pathologies. We studied the effect of Zn on the copper-induced lipid peroxidation in diluted human plasma. Lipid peroxidation was evaluated by measuring the formation of conjugated dienes and of thiobarbituric acid reactive products. We found that 20 microM Zn reduced the 125-microM copper-dependent formation of conjugated dienes by 27% and of thiobarbituric acid reactive products by 49%, during a 3-h incubation period. The inhibition of lipid peroxidation by 125 microM Zn is almost total in the same conditions. The time-course study of the inhibitory effect of 125 microM Zn showed that it lasted for 7 h, which was the maximum incubation period tested. We also found that Zn had an inhibitory effect on the spontaneous lipid peroxidation in rat brain whole homogenates. Our results support the antioxidant properties of Zn, which may be potentially relevant to the protection of human plasma constituents, competing with the transition metals for redox reactions.

Zinc deficiency does not enhance LDL uptake by P 388 D1 macrophages in vitro

The aim of the study was to investigate the effect of zinc depletion on the susceptibility of Wistar rat low-density lipoproteins (LDL) to peroxidation and their uptake by macrophages, before and after in vitro oxidation. The rats were fed for 7 wk a Zn-adequate diet (100 ppm) ad libitum (AL), a Zn-deficient diet (0.2 ppm) ad libitum (ZD), or a Zn-adequate diet according to the pair-feeding method (PF). Zinc status was determined and, for each group, blood was pooled, and LDS were isolated and labeled with 125Iodine. An aliquot of each LDL sample was oxidized using FeII 10 microM/ascorbate 250 microM. Oxidized and nonoxidized (native) LDL were incubated with P 388 D1 macrophages, and their rates of uptake and degradation by macrophages were measured. Before oxidation, LDL uptake and degradation were not modified by the diet, suggesting that Zn deficiency did not modify rat LDL in vivo. After oxidation, both LDL uptake and degradation were significantly enhanced in the three groups. Nevertheless, we did not observe a significant effect of Zn deficiency. This observation suggests that, in our experimental conditions, Zn deficiency did not modify LDL catabolism.

Zinc prevents the structural and functional properties of free radical treated-insulin

We have previously reported that zinc deficiency could increase in vivo lipid peroxidation and decrease rat insulin sensitivity. In the present paper, we address the hypothesis of the role of zinc on insulin molecule in relation to free radical damage. From native recombinant human insulin, we prepared a zinc-depleted insulin. Both preparations were subjected to controlled free radical attack by incubation in the presence of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH). To obtain minimally oxidized insulin, the oxidation process was monitored by measuring the intrinsic fluorescence of the insulin preparations. For 2.5 mM of AAPH, the autofluorescence of zinc-depleted insulin markedly decreased as compared to that of native insulin. These data are in favor of conformational changes of the insulin molecule which were further studied by quenching of fluorescence by means of potassium iodide. Using the euglycaemic hyperinsulinic glucose clamp technique in rats, the in vivo activities of the different insulin preparations, showed that oxidized zinc-depleted insulin had a marked reduced activity as compared to oxidized native insulin. From our results, we suggest that structural modification of the insulin molecule took place after zinc depletion and free radical treatment. Moreover, zinc depletion appeared to increase the susceptibility of insulin to free radicals.

Urinary zinc excretion and acute phase response in cancer patients

We investigated urinary zinc and serum levels of C-reactive protein, alpha-1 acid glycoprotein, haptoglobin, transferrin and prealbumin in 55 patients with solid tumors and 20 controls. Urinary zinc, serum C-reactive protein, alpha-1 acid glycoprotein and haptoglobin were significantly higher, and serum prealbumin was significantly lower in cancer patients. A significant positive correlation between urinary zinc and C-reactive protein, alpha-1 acid glycoprotein and haptoglobin, as well as a negative correlation with transferrin and prealbumin were observed. Hyperzincuria in cancer patients appears to be linked to the acute phase response. Our data provide further evidence implicating systemic inflammatory response in increased urinary zinc excretion.

Effects of mild zinc deficiency, plus or minus an acute-phase response, on galactosamine-induced hepatitis in rats

Zn deficiency is hypothesized to produce poor resistance to injury involving oxidative stress. This could occur by impairing Zn antioxidant function(s) or by indirectly limiting adaptive protective mechanisms such as a rise in acute-phase proteins. The present study examined rats fed diets adequate or moderately low in Zn (4 or 25 micrograms/g diet) for 9 d. The lower intake produced a mild Zn deficiency based on body weight, plasma Zn and plasma alkaline phosphatase (EC 3.1.3.1) activity. Galactosamine injection, an oxidative stress, produced much more liver injury in the mildly Zn-deficient rats. However, injury was strongly inhibited in rats from each dietary group by an acute-phase response due to turpentine-induced leg inflammation. Mild Zn deficiency did not prevent a rise in levels of the acute-phase protein caeruloplasmin (EC 1.16.3.1), but did limit the usual inflammation-induced rise in hepatic levels of metallothionein, a Zn protein with possible antioxidant function. In conclusion, high degrees of galactosamine-induced hepatitis were associated with mild Zn deficiency, but the liver injury was blocked by prior stimulation of an acute-phase response, regardless of Zn status.

Effects of chronic caffeine feeding on the activities of oxygen free radical defense enzymes in the growing rat heart and liver

The purpose of the present study was to determine the relationship between concentration of Zn, Cu and Fe, and the catalase, glutathione peroxidase and superoxide dismutase activities in the heart and liver of newborn rats whose dams were fed a diet supplemented with caffeine. Heart Zn levels of the 22- and 30-day-old rats of the caffeine group showed a decrease, whereas liver Zn levels showed an increase compared to the control. Cu levels in the liver at day 22 in the caffeine group were less than in the control. Cu- and Zn-containing superoxide dismutase activities showed an increase in the hearts of the caffeine group compared to the control. The activity of catalase and glutathione peroxidase showed no difference in the heart and liver between the groups. The present study suggests the possible involvement of superoxide dismutase enzyme in the impairment of heart formation as a result of chronic caffeine intake in the early growing period.

The oxidation of low density lipoprotein by cells or iron is inhibited by zinc

We have examined the effect of zinc ions on low density lipoprotein (LDL) oxidation by macrophages, endothelial cells and iron ions in terms of the increased uptake of the LDL by macrophages. Zinc ions inhibited LDL modification by both cell types (which is dependent on the presence of iron ions in the culture medium) and by iron ions alone. As oxidised LDL is believed to be involved in atherogenesis, this raises the possibility that zinc may be an endogenous protective factor against atherosclerosis.

Hypochlorous acid-induced zinc release from thiolate bonds: a potential protective mechanism towards biomolecules oxidant damage during inflammation

It has been proposed that metalloprotein zinc mobilization mediated by hypochlorous acid (HOCl) may induce cell injury (see H. Fliss and M. Ménard (1991), Archives of Biochemistry and Biophysics, 287, 175-179). In the present paper, we have demonstrated using a dimercaptopropanol-zinc complex that, once released from thiolate bonds by HOCl, zinc can exert a significant antioxidant effect on both linolenic acid and deoxyribose oxidation induced by iron. In these experimental conditions, however, the antagonism towards deoxyribose oxidation is notably less than that towards linolenic acid peroxidation, thus suggesting a more specific inhibitory effect of zinc on iron-mediated oxidant damage when polyunsaturated fatty acids represent the oxidizable substrate. The antioxidant effects of zinc are strictly related to the "free" form; indeed, the dimercaptopropanol-zinc complex per se is stimulatory even on biomolecules oxidant damage, apparently as a result of the prooxidant prooxidant interaction of the thiol compound with iron. In light of these results, it may be proposed that the zinc released from thiolate bonds by HOCl could specifically limit tissue oxidative burden in pathological conditions involving neutrophil accumulation and activation, such as inflammation and ischemia-reperfusion.

Reactive oxygen species produced in metal-catalyzed oxidation of bis(trifluoromethyl)disulfide and protection by ZE

Bis(trifluoromethyl)disulfide (TFD), used as an industrial fumigant, was found to generate a thiyl free radical as seen by EPR/spin trapping. Oxygen appears to be an absolute requirement for radical production. The results obtained in this investigation implicate the production of thiyl and reactive oxygen species (ROS), superoxide radical anion and hydroxyl radicals, during TFD autoxidation. The rate of production of these free radical intermediates was found to increase in the presence of iron(III) and copper(II). In addition, the metal ion chelator DETAPAC and ROS scavengers ethanol, mannitol, and PEG-SOD/catalase were found to inhibit free radical production. Reactive oxygen species were not formed when a high-potency zinc plus antioxidant, ZE caps, was present. These results provide support for the pro-oxidation of TFD and a protective role for zinc.

Effects of mild zinc deficiency, plus or minus acute phase response, on CCl4 hepatotoxicity

Low zinc (Zn) intake could be expected to compromise resistance to oxidative stress, even when accompanied by a normally protective acute phase response pretreatment. Mildly Zn deficient rats showed very high degrees of CCl4-induced hepatic cell membrane injury as assessed by serum sorbitol dehydrogenase activities. Rats pair-fed adequate Zn also showed above normal degrees of injury, but much less than rats fed low Zn. An acute phase response, elicited by leg inflammation, strongly protected rats consuming adequate Zn, either ad libitum or pair-fed, against the CCl4-induced rise in sorbitol dehydrogenase. However, the effect was partially absent in rats fed low Zn. Zinc intake had no effect on CCl4-produced microsomal injury, assessed by glucose-6-phosphatase activities. Rats fed low Zn showed normal hepatic levels of metallothionein, a Zn protein with proposed antioxidant functions, but did not show the rise in metallothionein levels normally associated with acute phase response. In summary, mild Zn deficiency caused poor resistance to CCl4-induced plasma membrane injury and partially negated acute phase response protective effects. Metallothionein was not involved in the former effect, but may have contributed to the latter.

Nutrition, endothelial cell metabolism, and atherosclerosis

The vascular endothelium that forms an interface between the blood and the surrounding tissues is continuously exposed to both physiologic and pathophysiologic stimuli. These stimuli are often mediated by nutrients that can contribute to the overall function of the endothelial cell in the regulation of vascular tone, coagulation and fibrinolysis, cellular growth and differentiation, and immune and inflammatory responses. Therefore, nutrient-mediated functional changes of the endothelium and the underlying tissues may be significantly involved in the atherosclerotic disease process. There is evidence that individual nutrients or nutrient derivatives may either provoke or prevent metabolic and physiologic perturbations of the vascular endothelium. Preservation of nutrients that exhibit antiatherogenic properties may, therefore, be a critical issue in the preparation and processing of foods. This review focuses on selected nutrients as they affect endothelial cell metabolism and their possible implications in atherosclerosis.

Oxidative stress as a mediator of apoptosis

Many agents which induce apoptosis are either oxidants or stimulators of cellular oxidative metabolism. Conversely, many inhibitors of apoptosis have antioxidant activities or enhance cellular antioxidant defenses. Mammalian cells exist in a state of oxidative siege in which survival requires an appropriate balance of oxidants and antioxidants. Thomas Buttke and Paul Sandstrom suggest that eukaryotic cells may benefit from this perilous existence by invoking oxidative stress as a common mediator of apoptosis.

Effect of CH3HgCl and several transition metals on the dopamine neuronal carrier; peculiar behaviour of Zn2+

CH3Hg+ and metal ions inhibited the specific binding of (1-[2-(diphenylmethoxy)ethyl]-4-(3-phenyl-2-[1-3H]propenyl) piperazine) ([3H]GBR 12783) to the dopamine neuronal carrier present in membranes from rat striatum with a general rank order of potency CH3Hg+ > Cu2+ > Cd2+ > Zn2+ > Ni2+ = Mn2+ = Co2+, suggesting that -SH groups are chiefly involved in this inhibition. Five millimolar dithiothreitol reversed the rather stable block of the specific binding produced by Cd2+ or Zn2+. An increase in the concentration of Na+, or addition of either K+ or Ca2+ reduced the inhibitory effects of metal cations, except Cu2+. Zn2+ (3 microM) reduced the inhibitory potency of Cd2+ on the binding but was ineffective against CH3Hg+ and Cu2+. Zn2+ at 0.3 to 10 microM significantly enhanced the specific binding of [3H]GBR 12783 and [3H]cocaine by 42 to 146%. Zn2+ (3 microM) increased the affinity of all pure uptake inhibitors tested and of the majority of the substrates for the [3H]GBR 12783 binding site. Dissociation experiments revealed that Zn2+ both inhibited and enhanced the [3H]GBR 12783 binding by recognizing amino acids located close to or in the radioligand binding site. Micromolar concentrations of Zn2+ noncompetitively blocked the [3H]dopamine uptake but they did not modify the block of the transport provoked by pure uptake inhibitors. These findings suggest that Na+, K+, Ca2+ and metal ions could recognize some -SH groups located in the [3H]GBR 12783 binding site; low concentrations of Zn2+ could allow a protection of these -SH groups.

Isolation of V79 fibroblast cell lines containing elevated metallothionein levels that have increased resistance to the cytotoxic effects of ultraviolet-A radiation

Isolated clones of V79 Chinese hamster lung fibroblasts, selected for resistance against cadmium toxicity, were exposed to monochromatic 365 nm ultraviolet-A (UVA; 320 nm to visible light) radiation and examined for cell survival. All three of the Cd-resistant V79 clones (V79Cd) tested exhibited significant increases in survival after irradiation compared with control cultures similar to the increased survival observed in Zn acetate-induced V79 cells. Dose-modifying factors calculated for these survival experiments were all approximately 1.5. When characterized for steady-state levels of metallothionein (MT) mRNA and associated Cd-binding activity, all of the Cd-resistant V79Cd clones demonstrated elevated constitutive levels of both, implicating MT as the mechanism responsible for the observed cellular resistance to Cd and also to 365 nm UVA radiation. However, whereas levels of intracellular MT protein correlated with differences in survival against Cd, MT intracellular levels did not correlate well with protection against 365 nm UVA. Increased cell survival after exposure to 365 nm UVA radiation mediated by MT appeared to reach a threshold level and MT only provided a limited degree of protection. Since UVA radiation is known to cause cell death mediated through the intracellular generation of reactive oxygen species (ROS), these results suggest that the role of MT in ameliorating cellular photooxidative damage produced by UVA is by reducing intracellular ROS.

A pulse radiolytic study on the reaction of hydroxyl and superoxide radicals with yeast Cu(I)-thionein

In a pulse radiolytic study employing aqueous intact yeast copper(I)-thionein at pH 7 it was shown that both superoxide and hydroxyl radicals efficiently react with this Cu(I)- and thiolate-rich protein. The reaction constant of hydroxyl radicals with Cu(I)-thionein was determined by competition kinetics and was 2.2 x 10(11) M-1 s-1 at a rate close to a diffusion-controlled limit. The reaction of Cu(I)-thionein with superoxide was also successful and proceeded at a rate of 7.5 x 10(6) M-1 s-1. According to chiroptical and luminescence emission measurements minor oxidation of the copper(I)-thiolate oligonuclear binding centres was observed, leading to the release of some Cu(II). It is important to realise the dual reactivity of this yeast Cu(I)-thiolate protein in controlling copper transport and storage as well as its distinct role in the scavenging of free radicals.

Reversal of selenium and zinc deficiencies in chronic hemodialysis patients by intravenous sodium selenite and zinc gluconate supplementation. Time-course of glutathione peroxidase repletion and lipid peroxidation decrease

In six chronic dialyzed uremic patients, an intravenous sodium selenite (Se 50 micrograms during 5 wk and then 100 micrograms) and zinc gluconate (Zn 5 mg) supplementation was performed during 20 wk at each dialysis session three times weekly. Before supplementation, plasma Se and Zn, plasma and erythrocytes (RBC) antioxidant metallo-enzymes glutathione peroxidase (GPX), and superoxide dismutase (SOD) were significantly decreased, whereas lipid peroxidation (as thiobarbituric acid reactants TBARs) was increased. To obtain a significative change in plasma selenium, we had to use an Se dose of 100 micrograms/dialysis session. Then, treatment-increased plasma Se (from 0.58 +/- 0.09 to 0.89 +/- 0.16 mumol/L) led to a repletion of RBC-GPX (from 29.6 +/- 6 to 43 +/- 5.8 U/g Hb) and increased plasma GPX levels (from 62 +/- 13 to 151 +/- 43 U/L). Plasma Zn and RBC-SOD did not vary significantly. The change of TBARs was not observed between wk 1 and 4. They decreased significantly between wk 4 (4.80 +/- 0.21 mumol/L) and wk 20 (4.16 +/- 0.26 mumol/L). We noted a low correlation between TBARs and plasma GPX. A strong correlation was observed between Se and plasma GPX. The reversal of Se deficiencies should reduce oxidative damage observed in these patients.

Protective effect of selenium and zinc on UV-A damage in human skin fibroblasts

Ultraviolet A radiation participates in cytotoxicity and carcinogenesis of the skin by a mechanism involving the generation of reactive oxygen species. Endogenous antiradical defense systems utilize metalloenzymes including Se-dependent glutathione peroxidase and Cu and Zn superoxide dismutase. The aim of the present work was to determine the protective effect of two trace elements, Se and Zn, on cultured human diploid fibroblasts exposed to UV-A radiation (broad-spectrum source with a maximum intensity at 375 nm). Selenium in the culture medium (0.1 mg/L) in the form of sodium selenite increased the synthesis and activity of glutathione peroxidase by 60.5% in the absence of exposure to UV-A radiation and by 35% after irradiation with 5 J/cm2 (P = 0.043). The presence of this element significantly increased the survival of UV-A-irradiated fibroblasts (P < 0.0001). This confirms the essential role of Se in the detoxifying activity of the enzyme. In addition, thiobarbituric acid-reacting substances (TBAR), which are lipid peroxidation markers, decreased in the presence of exogenous Se: -19% and -22% without irradiation and after irradiation with 5 J/cm2 (P = 0.056). When Zn was added at the dose of 6.5 mg/L as ZnCl2, fibroblasts subjected to oxidizing stress induced by UV-A were protected from cytotoxicity (P < 0.0001). The TBAR production decreased significantly: -33% without irradiation and -34% after irradiation with 5 J/cm2 (P = 0.008). Superoxide dismutase activity, however, decreased after supplementing with Zn: -26% without irradiation and -20% after UV-A irradiation (P = 0.017). The antioxidant properties of Zn are thus apparently independent of superoxide dismutase activity.

Changes of the Cu and Zn contents in lung and liver in intestinal ischemic reperfusion and general ischemic reperfusion in rabbits

The changes of pulmonary and liver Cu-Zn contents were determined and evaluated in intestinal ischemic reperfusion (IIR) and general ischemic reperfusion (GIR) of rabbits. The contents of pulmonary Zn and liver Cu were found to be lower, and Cu/Zn ratio increased in lung tissue and decreased in liver tissue in IIR. The contents of pulmonary Zn were increased, and the contents of liver Cu were decreased; Cu/Zn ratio also decreased in both tissues in GIR. Pulmonary Cu and liver Zn contents were not changed in IIR and GIR. These results showed that lower or higher Zn in lung tissue and lower Cu in liver tissue were related to the acute tissue injury during IIR and GIR, suggesting that regulating the state of pulmonary Zn and liver Cu should be attempted during the prevention and treatment of both ischemic reperfusions.

Effect of zinc deficiency on lipid peroxidation status and infarct size in rat hearts

The objective of this study was to investigate the effect of dietary zinc on endogenous production of lipid peroxides, and on myocardial infarct size in rats. Male rats were fed a zinc-deficient diet containing 4 ppm zinc, or a standard diet containing 60 ppm zinc. After 3 weeks of diet, half of the animals underwent occlusion of the left coronary artery. The remaining animals underwent sham operation without occlusion. Forty-eight hours later, the hearts were sampled and lipid peroxide levels and infarct size were evaluated. Coronary occlusion was associated with an increase in cardiac lipid peroxide levels which were more pronounced in the zinc deficient group. However, infarct size appeared to be independent from zinc deficiency, despite the free radical-mediated lipid peroxide augmentation reported here. The pharmacological limitation of infarct size in rats with permanent coronary occlusion is discussed.

Effect of zinc supplementation on resistance of cultured human skin fibroblasts toward oxidant stress

In purified system zinc has been shown to have an antioxidant role. Its effects on the resistance of cultured cells towards oxidative stress in vitro were examined. Diploid human skin fibroblasts were grown for 21 d in culture media (RPMI 1640 containing 15% fetal calf serum) added with different zinc (Zn) concentrations (100, 125, and 150 microM as Zinc chlorur ZnCl2). In comparison, cell controls were grown in standard culture media (6.5 microM Zn). The intracellular zinc levels of treated fibroblasts increased from 3- to 7-fold (2330 +/- 120 ng/mg protein in 150-microM Zn-treated cells versus 331 +/- 21 ng/mg protein in control cells). The intracellular copper increased 3- fold whereas the iron content slightly but not significantly decreased. The index of basal lipid peroxidation measured as thiobarbituric acid reactants (TBARs) of zinc-supplemented cells was lower than that of non zinc supplemented controls (0.89 mumol/g protein in 150 microM Zn-treated cells versus 1.59 mumol/g protein in controls). At these high doses of zinc, fibroblasts expressed lower antioxidant metalloenzymes activities. Diminished TBARs in Zn treated cells tends to support that Zn acts protectively against free radical mediated damage. However when the cells were challenged with extracellular oxidant stresses mediated by hypoxanthine/xanthine oxidase or hydrogen peroxide (H2O2), an increased toxicity in Zn-supplemented cells was observed. When we applied an intracellular oxidative stress as UV-B or UV-A radiation, Zn-treated fibroblasts were more resistant than cells grown in normal medium. If Zn has shown antioxidant effect in some in vitro or in vivo systems our observations clearly demonstrate that this role is not mediated by antioxidant metalloenzymes.

Lipid peroxides and antioxidant defenses in accelerated transplantation-associated coronary arteriosclerosis

Accelerated coronary artery disease develops in most if not all heart transplant recipients within the first year after transplantation. Increased lipid peroxidation seems to be involved in atherogenesis. In these patients we have investigated whether there is an association between lipid peroxidation, reduced antioxidant defenses, and some conventional coronary risk factors. Lipid peroxides, lipids, uric acid, albumin, antioxidant enzymes and their cofactors (the trace elements selenium, iron, copper, and zinc) have been determined in heart transplant recipients compared with nonrecipients with coronary artery disease. Lipid peroxides (p = 0.002) and uric acid (p = 0.01) were higher and zinc (p = 0.001) was lower in heart transplant recipients. Thirteen of 30 transplant recipients compared with one of 30 nonrecipients (p < 0.001) had very low (less than 10 mumol/L) zinc levels. Antioxidant enzymes and other trace elements were not significantly different. In univariate regression analysis, zinc correlated positively with albumin (p = 0.02) and negatively with lipid peroxides (p < 0.05). Uricemia had a strongly positive correlation with hydroperoxides (r = 0.45; p = 0.0001). In stepwise multivariate regression analysis, lipids, uricemia, creatinine, and zinc were significant (p < or = 0.004) predictors of the lipid peroxide level. Cyclosporine and corticosteroid dosages were significant (p = 0.01) determinants of zinc concentration in the transplant recipients. Although a causal relationship between increased lipid peroxidation and accelerated arteriosclerosis is not definitely demonstrated, the results of this analysis suggest new insights into conventional coronary disease risk factors and possible therapeutic interventions; further controlled trials are needed.