Antioxidant activity of Vitamin-C in iron-overloaded human plasma
Berger T.M.; Polidori M.C.; Dabbagh A.; Evans P.J.; Halliwell B.; Morrow J.D.; Roberts II L.J.; Frei B.
B. Frei, Whitaker Cardiovascular Inst., Boston University School of Medicine, 80 East Concord St., Boston, MA 02118 USA
Journal of Biological Chemistry (USA), 1997, 272/25 (15656-15660)
Vitamin-C (ascorbic acid, AA) can act as an antioxidant or a pro- oxidant in vitro, depending on the absence or the presence, respectively, of redox-active metal ions. Some adults with iron-overload and some premature infants have potentially redox-active, bleomycin-detectable iron (BDI) in their plasma. Thus, it has been hypothesized that the combination of AA and BDI causes oxidative damage in vivo. We found that plasma of preterm infants contains high levels of AA and F2-isoprostanes, stable lipid peroxidation end products. However, F2-isoprostane levels were not different between those infants with BDI (138 plus or minus 51 pg/ml, n = 19) and those without (126 plus or minus 41 pg/ml, n = 10), and the same was true for protein carbonyls, a marker of protein oxidation (0.77 plus or minus 0.31 and 0.68 plus or minus 0.13 nmol/mg protein, respectively). Incubation of BDI-containing plasma from preterm infants did not result in detectable lipid hydroperoxide formation (less than or equal to10 nM cholesteryl ester hydroperoxides) as long as AA concentrations remained high. Furthermore, when excess iron was added to adult plasma, BDI became detectable, and endogenous AA was rapidly oxidized. Despite this apparent interaction between excess iron and endogenous AA, there was no detectable lipid peroxidation as long as AA was present at >10% of its initial concentration. Finally, when iron was added to plasma devoid of AA, lipid hydroperoxides were formed immediately, whereas endogenous and exogenous AA delayed the onset of iron-induced lipid peroxidation in a dose-dependent manner. These findings demonstrate that in iron-overloaded plasma, AA acts an antioxidant toward lipids. Furthermore, our data do not support the hypothesis that the combination of high plasma concentrations of AA and BDI, or BDI alone, causes oxidative damage to lipids and proteins in vivo.
Effect of vitamin E supplementation on hepatic fibrogenesis in chronic dietary iron overload
Brown K.E.; Poulos J.E.; Li L.; Soweid A.M.; Ramm G.A.; O'Neill R.; Britton R.S.; Bacon B.R.
B.R. Bacon, Div. of Gastroenterology/Hepatology, Dept. of Internal Medicine, Saint Louis Univ. Hlth. Sci. Center, 3635 Vista Ave., St. Louis, MO 63110-0250 USA
American Journal of Physiology - Gastrointestinal and Liver Physiology (USA), 1997, 272/1 35-1 (G116-G123)
It has been suggested that lipid peroxidation plays an important role in hepatic fibrogenesis resulting from chronic iron overload. Vitamin E is an important lipid-soluble antioxidant that has been shown to be decreased in patients with hereditary hemochromatosis and in experimental iron overload. The aim of this study was to determine the effects of vitamin E supplementation on hepatic lipid peroxidation and fibrogenesis in an animal model of chronic iron overload. Rats were fed the following diets for 4, 8, or 14 mo: standard laboratory diet (control), diet with supplemental vitamin E (200 IU/kg, control + E), diet with carbonyl iron (Fe), and diet with carbonyl iron supplemented with vitamin E (200 IU/kg, Fe + E). Iron loading resulted in significant decreases in hepatic and plasma vitamin E levels at all time points, which were overcome by vitamin E supplementation. Thiobarbituric acid-reactive substances (an index of lipid peroxidation) were increased three- to fivefold in the iron-loaded livers; supplementation with vitamin E reduced these levels by at least 50% at all time points. Hepatic hydroxyproline levels were increased twofold by iron loading. Vitamin E did not affect hydroxyproline content at 4 or 8 mo but caused an 18% reduction at 14 mo in iron-loaded livers. At 8 and 14 mo, vitamin E decreased the number of alpha-smooth muscle actin-positive stellate cells in iron-loaded livers. These results demonstrate a dissociation between lipid peroxidation and collagen production and suggest that the profibrogenic action of iron in this model is mediated through effects which cannot be completely suppressed by vitamin E.
Iron in liver diseases other than hemochromatosis
Bonkovsky H.L.; Banner B.F.; Lambrecht R.W.; Rubin R.B.
Div. of Digestive Disease/Nutrition, Univ. of Massachusetts Med. Center, 55 Lake Avenue, North, Worcester, MA 01655 USA
Seminars in Liver Disease (USA), 1996, 16/1 (65-82)
There is growing evidence that normal or only mildly increased amounts of iron in the liver can be damaging, particularly when they are combined with other hepatotoxic factors such as alcohol, porphyrogenic drugs, or chronic viral hepatitis. Iron enhances the pathogenicity of microorganisms, adversely affects the function of macrophages and lymphocytes, and enhances fibrogenic pathways, all of which may increase hepatic injury due to iron itself or to iron and other factors. Iron may also be a co-carcinogen or promoter of hepatocellular carcinoma, even in patients without HC or cirrhosis. Based on this and other evidence, we hope that the era of indiscriminate iron supplementation will come to an end. Bloodletting, a therapy much in vogue 2 centuries ago, is deservedly enjoying a renaissance, based on our current understanding of the toxic effects of iron and the benefits of its depletion.
Div. of Gastroenterology/Hepatology, Department of Internal Medicine, Saint Louis Univ. School of Medicine, 3635 Vista Ave., St. Louis, MO 63110-0250 USA
Seminars in Liver Disease (USA), 1996, 16/1 (3-12)
Figure 3 summarizes several proposed mechanisms of iron- or copper- induced hepatotoxicity. It has long been suspected that free radicals may play a role in iron- and copper-induced cell toxicity because of the powerful prooxidant action of iron and copper salts in vitro. In the presence of available cellular reductants, iron or copper in low molecular weight forms may play a catalytic role in the initiation of free radical reactions. The resulting oxyradicals have the potential to damage cellular lipids, nucleic acids, proteins, and carbohydrates, resulting in wide-ranging impairment in cellular function and integrity. However, cells are endowed with cytoprotective mechanisms (antioxidants, scavenging enzymes, repair processes) that act to counteract the effects of free radical production. Thus, the net effect of metal-induced free radicals on cellular function will depend on the balance between radical production and the cytoprotective systems. As a result, there may be a rate of free radical production that must be exceeded before cellular injury occurs. Evidence has now accumulated that iron or copper overload in experimental animals can result in oxidative damage to lipids in vivo, once the concentration of the metal exceeds a threshold level. In the liver, this lipid peroxidation is associated with impairment of membrane dependent functions of mitochondria (oxidative metabolism) and lysosomes (membrane integrity, fluidity, pH). Although these findings do not prove causality, it seems likely that lipid peroxidation is involved, since similar functional defects are produced by metal-induced lipid peroxidation in these organelles in vitro. Both iron and copper overload impair hepatic mitochondrial respiration, primarily through a decrease in cytochrome c oxidase activity. In iron overload, hepatocellular calcium homeostasis may be impaired through damage to mitochondrial and microsomal calcium sequestration. DNA has also been reported to he a target of metal-induced damage in the liver; this may have consequences as regards malignant transformation. The levels of some antioxidants in the liver are decreased in rats with iron or copper overload, which is also suggestive of ongoing oxidative stress. Reduced cellular ATP levels, lysosomal fragility, impaired cellular calcium homeostasis, and damage to DNA may all contribute to hepatocellular injury in iron and copper overload. There are few data addressing the key issue of whether tree radical production is increased in patients with iron or copper overload. Patients with hereditary hemochromatosis have elevated plasma levels of TBA-reactants and increased hepatic levels of MDA-protein and HNE-protein adducts, indicative of lipid peroxidation. Mitochondria isolated from the livers of Wilson disease patients have evidence of lipid peroxidation, and some patients with Wilson disease have decreased hepatic and plasma levels of vitamin E. Additional investigation will be required to fully assess oxidant stress and its potential pathophysiologic role in patients with iron or copper overload.
Hepatocyte proliferative activity in chronic liver damage as assessed by the monoclonal antibody MIB1 Ki67 in archival material: The role of etiology, disease activity, iron, and lipid peroxidation
Farinati F.; Cardin R.; D'Errico A.; De Maria N.; Naccarato R.; Cecchetto A.; Grigioni W.
CMAD, Istituto di Medicina Interna, Policlinico Universitario, Via Giustiniani 2, 35128 Padova Italy
Hepatology (USA), 1996, 23/6 (1468-1475)
Hepatitis B virus (HBV)- and hepatitis C virus (HCV)related liver damage is linked to an increased risk of hepatocellular carcinoma, but the mechanisms underlying hepatitis C viral activity are not known. We therefore compared hepatocellular proliferative activity in chronic C virus-related hepatitis and in liver damage of other etiology. Hepatocyte proliferation rate was investigated in 56 patients with chronic hepatitis using the Ki67 MIB1 monoclonal antibody in archival material. According to etiology, the patients were subgrouped as follows: HCV (34), HBV (11), Alcohol (4), HCV + Alcohol (4), and Hemochromatosis (3). Proliferation rate was correlated with age, sex, etiology, disease activity, liver iron storage, free-radical production, and glutathione levels by regression and discriminant analysis. HCV-positive patients had significantly more MIB1-positive hepatocytes in the periportal area (P < .011) and in the low-proliferating perivenular area (zones 2 and 3) (P < .05). The number of MIB1-positive cells correlated directly with alanine transaminase (ALT) levels, Knodell index (KI), and, inversely, with iron saturation. By stepwise discriminant analysis, ALT levels and etiology were identified as single independent variables. These data suggest that HCV infection induces increased and abnormal hepatocyte proliferation, which might be related to the increased risk of hepatocellular carcinoma in patients with HCV-related liver damage.
Hepatic iron deposition in human disease and animal models
Halliday J.W.; Searle J.
Liver Unit, Queensland Institute Med Research, Royal Brisbane Hospital, 300 Herston Road, Herston, Brisbane, QLD 4029 Australia
BioMetals (United Kingdom), 1996, 9/2 (205-209)
Iron deposition occurs in parenchymal cells of the liver in two major defects in human subjects (i) in primary iron overload (genetic haemochromatosis) and (ii) secondary to anaemias in which erythropolesis is increased (thalassaemia). Transfusional iron overload results in excessive storage primarily in cells of the reticule endothelial system. The storage patterns in these situations are quite characteristic. Excessive iron storage, particularly in parenchymal cells eventually results in fibrosis and cirrhosis. There is no animal model or iron overload which completely mimics genetics haemochromatosis but dietary iron loading with carbonyl iron or ferrocene does produce excessive parenchymal iron stores in the rat. Such models have been used to study iron toxicity and the action of iron chelators in the effective removal of excessive iron stores.
Long-term intraperitoneal deferoxamine for hemochromatosis
Swartz R.D.; Legault D.J.
Michigan University Medical Center, 3914 TC-Box 0364, Ann Arbor, MI 48109-0364 USA
American Journal of Medicine (USA), 1996, 100/3 (308-312)
Intraperitoneal deferoxamine is a well-established treatment for aluminum accumulation syndrome in patients with end-stage renal disease receiving peritoneal dialysis, but the use of intraperitoneal deferoxamine has not been described outside of the setting of chronic renal failure. We present here a case of secondary hemochromatosis, complicated by cirrhosis and cardiomyopathy, in which a chronic peritoneal dialysis catheter was used both to treat ascites and to deliver parenteral deferoxamine for iron overload. Daily urinary iron excretion was similar to that achieved when using standard routes of deferoxamine administration. Over a 2-year period, reversal of both the biochemical indicators and the clinical manifestations of iron overload was accomplished.
Biological markers of oxidative stress induced by ethanol and iron overload in rat.
Wisniewska-Knypl JM; Wronska-Nofer T
Department of Toxicological Biochemistry, Nofer Institute of Occupational Medicine, Lodz, Poland.
Int J Occup Med Environ Health (Poland) 1994, 7 (4) p355-63
Studies on rats treated for 15 months with ethanol (10%, w/v, solution in drinking water) revealed that the stimulation of hepatic cytochrome P-450 monooxygenases activity was accompanied by enhanced microsomal malondialdehyde formation, a lipid peroxidation index and a decreased level of the antioxidant, alpha-tocopherol. The other components of the prooxidant/antioxidant system, diene conjugates and catalase, glutathione peroxidase and superoxide dismutase activities were unaffected. Oxidative stress in blood was shown by a significant decrease in the alpha-tocopherol level whereas lipid peroxidation and antioxidant enzyme activity remained unchanged. The prooxidative effect of ethanol was catalytically promoted by an iron overload (Fe-saccharate, 100 mg Fe3+/kg body wt. intraperitoneally, 2, 5 and 7 day before test) to simulate the effect of alcoholic hemochromatosis. Thus, the level of malondialdehyde and alpha-tocopherol in the serum may be recommended as biological markers of ethanol-provoked oxidative stress, which is especially useful in the evaluation of the combined effect of ethanol and other chemicals that affect the redistribution of active iron complexes.
Antioxidant status and lipid peroxidation in hereditary haemochromatosis.
Young IS; Trouton TG; Torney JJ; McMaster D; Callender ME; Trimble ER
Department of Clinical Biochemistry, Queen's University of Belfast, UK.
Free Radic Biol Med (United States) Mar 1994, 16 (3) p393-7
Hereditary haemochromatosis is characterised by iron overload that may lead to tissue damage. Free iron is a potent promoter of hydroxyl radical formation that can cause increased lipid peroxidation and depletion of chain-breaking antioxidants. We have therefore assessed lipid peroxidation and antioxidant status in 15 subjects with hereditary haemochromatosis and age/sex matched controls. Subjects with haemochromatosis had increased serum iron (24.8 (19.1-30.5) vs. 17.8 (16.1-19.5) mumol/l, p = 0.021) and % saturation (51.8 (42.0-61.6) vs. 38.1 (32.8-44.0), p = 0.025). Thiobarbituric acid reactive substances (TBARS), a marker of lipid peroxidation, were increased in haemochromatosis (0.59 (0.48-0.70) vs. 0.46 (0.21-0.71) mumol/l, p = 0.045), and there were decreased levels of the chain-breaking antioxidants alpha-tocopherol (5.91 (5.17-6.60) vs. 7.24 (6.49-7.80) mumol/mmol cholesterol, p = 0.001), ascorbate (51.3 (33.7-69.0) vs. 89.1 (65.3-112.9), p = 0.013), and retinol (1.78 (1.46-2.10) vs. 2.46 (2.22-2.70) mumol/l, p = 0.001). Patients with hereditary haemochromatosis have reduced levels of antioxidant vitamins, and nutritional antioxidant supplementation may represent a novel approach to preventing tissue damage. However, the use of Vitamin-C may be deleterious in this setting as ascorbate can have prooxidant effects in the presence of iron overload.
Iron storage, lipid peroxidation and glutathione turnover in chronic anti-HCV positive hepatitis.
Farinati F, Cardin R, De Maria N, Della Libera G, Marafin C, Lecis E, Burra P, Floreani A, Cecchetto A, Naccarato R
Cattedra Malattie Apparato Digerente, Universita di Padova, Italy.
J Hepatol 1995 Apr;22(4):449-56
BACKGROUND/AIMS: Little is known about the pathogenesis of liver damage related to hepatitis C virus. The presence of steatosis or increased ferritin levels, and preliminary data on the relevance of iron as a prognostic factor prompted us to ascertain whether hepatitis C virus-related liver damage might be mediated by iron accumulation.
METHODS: We evaluated the degree of hepatic inflammation and steatosis, serum ferritin, transferrin saturation and iron levels, tissue iron concentrations and iron index, liver glutathione and malondialdehyde in 33 males and 20 females with chronic hepatitis C virus- or hepatitis B virus-related hepatitis (42 + 11). We also considered six patients with both alcohol abuse and hepatitis C virus, four males with chronic alcoholic liver disease and four males with genetic hemochromatosis, giving a total of 67. All diagnoses were histologically confirmed. Patients with cirrhosis were excluded.
RESULTS: Our data show that: 1. Steatosis is more frequent in hepatitis C virus and hepatitis C virus+alcohol abuse patients; 2. In males, serum ferritin and tissue iron are significantly higher in hepatitis C virus- than in hepatitis B virus-positive patients (p < 0.01 and 0.05); transferrin saturation is higher (p < 0.05) in hepatitis C virus-positive than in hepatitis B virus-positive patients only when males and females are considered together; 3. Serum ferritin and transferrin saturation only correlate with liver iron (r = 0.833 and r = 0.695, respectively, p = 0.00001); tissue iron is significantly higher in hepatitis C virus- than in hepatitis B virus-positive patients (p < 0.05); 4. In patients with chronic hepatitis, serum ferritin is a better marker of liver iron storage than transferrin saturation, both in males and in females; 5. Hepatitis C virus-positive patients have higher malondialdehyde levels and activation of turnover of glutathione, probably in response to free-radical-mediated liver damage. Females have lower liver iron levels but similar trends.
CONCLUSIONS: These findings suggest that hepatitis C virus-related liver damage is characterized by increased iron storage (possibly induced by the virus) which elicits a free-radical-mediated peroxidation, with consequent steatosis and activation of glutathione turnover.
Induction of oxidative single- and double-strand breaks in DNA by ferric citrate.
Toyokuni S; Sagripanti JL
Molecular Biology Branch, Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD 20857.
Free Radic Biol Med (United States) Aug 1993, 15 (2) p117-23
The relative risk of primary hepatocellular carcinoma in genetic hemochromatosis (GH) is estimated at over 200 times as that of control populations. Recently, ferric ion chelated to citrate (Fe-citrate) was identified as the major non-transferrin-bound iron in the serum of GH patients. We investigated whether low concentration of Fe-citrate plus reductant could damage supercoiled plasmid DNA under physiological pH and ionic strength. Incubation of Fe-citrate with either H2O2, L-ascorbate, or L-cysteine induced single- and double-strand breaks in supercoiled plasmid pZ189 in a concentration- and time-dependent fashion. DNA strand breaks produced by Fe-citrate plus H2O2 increased at reduced pH (< or = 6.9). Catalase and free radical scavengers inhibited the DNA breakage produced by Fe-citrate in combination with each reductant, suggesting that H2O2 and finally .OH are responsible DNA damaging species. The catalytic ability of Fe-citrate to induce DNA strand breaks, particularly double-strand breaks (DSBs), may contribute to the carcinogenic processes observed in GH.
A unique rodent model for both the cardiotoxic and hepatotoxic effects of prolonged iron overload.
Carthew P, Dorman BM, Edwards RE, Francis JE, Smith AG
MRC Toxicology Unit, University of Leicester, United Kingdom.
Lab Invest 1993 Aug;69(2):217-22
BACKGROUND: Hemochromatosis is a disease of excessive iron storage leading to tissue damage and fibrosis. Both genetic hemochromatosis, which can affect 1 in 500 of some populations, and the form of this disease which occurs as a secondary consequence of the hemoglobinopathy, homozygous beta-thalassemia, with 40 million carriers worldwide, have a common pathology. The cardiotoxicity and hepatotoxicity, which occurs with this disease, have never been produced experimentally in other species.
EXPERIMENTAL DESIGN: Using a regimen of iron dextran administered subcutaneously to gerbils on a weekly basis for 7 weeks, we have produced severe hemosiderosis, especially of the liver and heart. By examining gerbils at 1, 2 and 3 months after the final iron injections we followed the subsequent development of hemochromatosis in the hearts and livers of iron overloaded animals.
RESULTS: Hemochromatosis of the liver was evident as a scarring fibrosis in all cases between 1 and 3 months after iron dextran administration to gerbils. The iron burden in the cardiac myocytes of gerbils gradually increased between 1 and 3 months, resulting in hemochromatosis of the heart 2 and 3 months after the final iron dextran injections.
CONCLUSIONS: Repeated parenteral injections of iron dextran to gerbils resulted in hemochromatosis affecting the liver and heart with a pathology which is the same as occurs in the end-stage disease in man. This model will allow the detailed study of the mechanism of iron induced, free radical tissue damage, which is thought to be the cause of these lesions and will also be useful in the evaluation of iron chelating therapies to determine whether the hepatic and cardiac pathology of iron overload can be modulated over a long period.
Biochemical and biophysical investigations of the ferrocene-iron-loaded rat. An animal model of primary haemochromatosis.
Ward RJ; Florence AL; Baldwin D; Abiaka C; Roland F; Ramsey MH; Dickson DP; Peters TJ; Crichton RR
Department of Clinical Biochemistry, King's College School of Medicine and Dentistry, London, England.
Eur J Biochem (Germany) Dec 5 1991, 202 (2) p405-10
Male Wistar rats fed with ferrocene had high hepatic iron loading (7.24 +/- 1.97 mg Fe/g tissue) after 6 weeks, principally located in lysosomes, which was comparable to the levels and distribution determined in human haemochromatosis. The two iron-storage proteins, ferritin and haemosiderin were isolated from the livers of the ferrocene-loaded rats and their iron cores were investigated by Mossbauer spectroscopy and inductively coupled plasma-emission spectrometry. Ferrihydrite was the predominant form of iron present in both ferritin and haemosiderin, while haemosiderin contained higher amounts of phosphorus, magnesium, calcium and barium, then either normal or ferrocene-loaded ferritin. Free-radical-mediated damage in the iron-loaded livers was inferred by the significant depletion of alpha-tocopherol in both the livers and subcellular hepatic lysosomal fraction, which inversely correlated with the increasing iron content (r = -0.61; P less than 0.05) and was associated with increased fragility of the lysosomal membranes.
Antioxidant and iron-chelating activities of the flavonoids catechin, quercetin and diosmetin on iron-loaded rat hepatocyte cultures
Morel I, Lescoat G, Cogrel P, Sergent O, Pasdeloup N, Brissot P, Cillard P, Cillard J
Laboratoire de Biologie Cellulaire et Vegetale, UFR des Sciences Pharmaceutiques, Rennes, France.
Biochem Pharmacol 1993 Jan 7;45(1):13-9
The cytoprotective effect of three flavonoids, catechin, quercetin and diosmetin, was investigated on iron-loaded hepatocyte cultures, considering two parameters: the prevention of iron-increased lipid peroxidation and the inhibition of intracellular enzyme release. These two criteria of cytoprotection allowed the calculation of mean inhibitory concentrations (IC50) which revealed that the effectiveness of these flavonoids could be classified as follows: catechin>quercetin>diosmetin. These IC50 values have been related to structural characteristics of the flavonoids tested. Moreover, the investigation of the capacity of these flavonoids to remove iron from iron-loaded hepatocytes revealed a good relationship between this iron-chelating ability and the cytoprotective effect. The cytoprotective activity of catechin, quercetin and diosmetin could thus be ascribed to their widely known antiradical property but also to their iron-chelating effectiveness. These findings increase further the prospects for the development and clinical application of these potent antioxidants.