THE SEPARATION OF FERRITIN AND HAEMOSIDERIN FOR STUDIES IN THE METABOLISM OF IRON

Protective activity of purpurin against d-galactosamine and lipopolysaccharide-induced hepatorenal injury by upregulation of heme oxygenase-1 in the RBC degradation cycle

Acute liver failure, associated with oxidative stress and sustained inflammation is the major clinical manifestation of liver diseases with a high mortality rate due to limited therapeutic options. Purpurin is a bioactive compound of Rubia cordifolia that has been used in textile staining, as a food additive, and as a treatment of multiple chronic and metabolic diseases associated with inflammation and oxidative stress. The present work aimed to investigate the protective efficacy of purpurin against hepatorenal damage. Thirty-six female albino rats were equally assigned into six groups. Purpurin was administered orally once a day for 6 days at doses of 05, 10, and 20 mg/kg, respectively. Intraperitoneal injection of lipopolysaccharide (50 μg/kg) was administered to the animals on 6th day evening, 1 h after d-galactosamine (300 mg/kg) administration to induce hepatorenal injury. The results revealed that purpurin alleviated alterations in serological and hematological parameters as well as restored histoarchitectural and cellular integrity of the liver and kidney. Purpurin restored superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, and glutathione content in hepatorenal tissues. Accompanied by the diminution of increased bilirubin and biliverdin, purpurin also diminished total cholesterol, triglyceride, and lipid peroxidation in hepatorenal tissues. Purpurin markedly attenuated the elevation of CYP2E1, restored glutathione-S-transferase, and prevented DNA damage in hepatorenal tissues. Purpurin reduced iron overload by reducing heme depletion and recycling of ferritin and hemosiderin. It also reinforced biliverdin reductase, heme oxygenase-1 to employ hepatorenal protection by regulating antioxidant enzymes and other pathways that produced NADPH. Thus, it may be concluded that purpurin has protective potential against acute hepatorenal injury.

Study on iron availability from prepared soybean sprouts using an iron-deficient rat model

During soya seeds germination in FeSO(4) solutions their phytoferritin content is multiplied. Prepared soybean sprouts have been proposed as a safe and easily available source of iron supplementation. The preparation was compared with FeSO(4) and ferritin isolates, using rats with induced iron deficiency anaemia. After the end of the 2-week supplementation experiment, it was observed that no statistically significant differences in haemoglobin concentration, mean corpuscular volume, mean corpuscular haemoglobin, and mean corpuscular haemoglobin concentration existed between those animals supplemented with sprouts enriched in ferritin, ferritin isolate and FeSO(4) and healthy animals forming the control group. Moreover, the examined preparation had a beneficial influence on the recreation of ferritin reserves in both the liver and the blood serum, and also did not induce negative alterations in general growth parameters of animals. Use of an easily obtainable ferritin iron source may be a profitable alternative in supplementation due to its wide availability and food preservative properties.

Denatured H-ferritin subunit is a major constituent of haemosiderin in the liver of patients with iron overload

BACKGROUND AND AIMS

Iron is stored in hepatocytes in the form of ferritin and haemosiderin. There is a marked increase in iron rich haemosiderin in iron overloaded livers, and ferric iron in amounts exceeding the ferritin and haemosiderin binding capacity may promote free radical generation, causing cellular damage. The aim of this study was to characterise hepatic haemosiderin using four antibodies specific for either native or denatured H/L-ferritin subunits.

METHODS

Ferritin and haemosiderin were prepared from the livers of three patients with post-transfusional iron overload. The assembled ferritin molecules were analysed by non-denaturing polyacrylamide gel electrophoresis (PAGE)-immunoblotting. Ferritin subunits in the haemosiderin fraction were assessed by denaturing sodium dodecyl sulphate (SDS)-PAGE-immunoblotting. Distribution of native and denatured ferritin subunits in hepatocytes was examined by immunogold electron microscopy.

RESULTS

Non-denaturing PAGE-immunoblot analyses showed that the assembled liver ferritins were recognised by the antibodies for native ferritins and not by those for the denatured subunits. Both SDS-PAGE-immunoblot and immunogold electron microscopic analyses disclosed that haemosiderin of iron overloaded liver reacted predominantly to the monoclonal antibody for the denatured H-ferritin subunit, to a lesser degree to that for denatured L-ferritin, and very weakly, if any, with antibodies for native H-ferritin or L-ferritin.

CONCLUSIONS

These results suggest that in iron overloaded liver, haemosiderin consists predominantly of denatured H-ferritin subunits.

SMALL-SCALE ISOLATION OF FERRITIN FOR THE ASSAY OF THE INCORPORATION OF 14C-LABELLED AMINO ACIDS

1. A new procedure is described for the isolation of pure ferritin from small amounts of tissue. After the removal of most of the tissue proteins by heat coagulation, the ferritin fraction was chromatographed successively on CM-cellulose and Sephadex G-200. 2. The isolated ferritin appeared to be free from other proteins, as judged by its sedimentation pattern in the ultracentrifuge, by electrophoresis on polyacrylamide gel and by immunoelectrophoresis. 3. After the injection of [(14)C]leucine into a series of rats, the specific activity of liver ferritin isolated by the new procedure bore a constant relationship to that of liver ferritin separated by antigen-antibody precipitation. The procedure can thus be used to obtain ferritin of suitable purity for studies of amino acid incorporation. 4. The new procedure can be used to measure the total ferritin protein content of a tissue. It is not possible to use ultraviolet absorption for the measurement of ferritin protein because of considerable interference from the iron that it contains.

Hepatic iron deprivation prevents spontaneous development of fulminant hepatitis and liver cancer in Long-Evans Cinnamon rats

Several clinical studies have suggested that excess hepatic iron accumulation is a progressive factor in some liver diseases including chronic viral hepatitis and hemochromatosis. However, it is not known whether iron-induced hepatotoxicity may be directly involved in hepatitis, cirrhosis, and liver cancer. The Long-Evans Cinnamon (LEC) rat, which accumulates excess copper in the liver as in patients with Wilson's disease, is of a mutant strain displaying spontaneous hemolysis, hepatitis, and liver cancer. We found previously that LEC rats harbored an additional abnormality: accumulation of as much iron as copper in the liver. In the present study, we compared the occurrence of hepatitis and liver cancer in LEC rats fed an iron-deficient diet (ID) with those in rats fed a regular diet (RD). The RD group showed rapid increments of hepatic iron concentrations as the result of hemolysis, characteristics of fulminant hepatitis showing apoptosis, and a 53% mortality rate. However, no rats in the ID group died of fulminant hepatitis. Hepatic iron, especially "free" iron concentration and the extent of hepatic fibrosis in the ID group were far less than those of the RD group. At week 65, all rats in the RD group developed liver cancer, whereas none did in the ID group. These results suggest that the accumulation of iron, possibly by virtue of synergistic radical formation with copper, plays an essential role in the development of fulminant hepatitis, hepatic fibrosis, and subsequent hepatocarcinogenesis in LEC rats.

Iron accumulation in tissues of magnesium-deficient rats with dietary iron overload

The mineral imbalances in magnesium-deficient rats with dietary iron overload were studied. Forty-four male Wistar rats were divided into six groups and fed six diets, two by three, fully crossed: magnesium adequate or deficient, and iron deficient, adequate, or excess. The concentrations of iron, magnesium, calcium, and phosphorus in tissues of the rats were measured. The results were as follows: (1) The excess iron intake reinforced the iron accumulation in liver and spleen of magnesium deficient rats; (2) The saturation of iron binding capacity was enormously elevated in the magnesium deficient rats fed excess iron; and (3) Dietary iron deprivation diminished the degree of calcium deposition in kidney of magnesium deficient rats. These results suggest that magnesium-deprived rats have abnormal iron metabolism losing homeostatic regulation of plasma iron, and magnesium deficient rats with dietary iron overload may be used as an experimental hemochromatosis model.

Determination of nonheme iron using inductively coupled plasma-atomic emission spectrometry

A technique for the rapid and accurate estimation of nonheme iron using inductively coupled plasma-atomic emission spectrometry is described. Yttrium was used as an internal standard. An external calibration method was used. The standards were prepared in a matrix composed of 2.5N HCl in 10% (w/v) trichloroacetic acid. The supernatant and coagulum fractions of liver nonheme iron were separated by the method of Drysdale and Ramsay with minor modification. The data determined by this procedure was compared and found to be agreement with data determined by the method of Hallgren. To evaluate the iron status of rats, hemoglobin and liver nonheme iron were determined. Hemoglobin and all of the nonheme iron fractions of the rats fed an iron-deficient diet were significantly lower than those of the rats fed an iron-sufficient diet. The blood content in the liver was estimated to be 80 microL/g from the blood iron concentration, and the difference between total and nonheme iron concentration in liver.

Modulation of exudate inflammation parameters in rat carrageenan-induced granuloma by modification of exudate iron levels

We have used the carrageenan-induced pouch-granuloma in rats to investigate how changes in low-molecular-mass iron chelate levels in the exudate, induced by iron loading (iron-dextran) or chelation (desferrioxamine) influence cellular and systemic inflammatory parameters. In the iron-treated group we observed a rapid decrease in the number of leukocytes and exudate volume; there was also an increase in ferritin iron and low-molecular-mass iron chelates, and on the eighth day a systemic response. In the desferrioxamine-treated group we detected a decrease in low-molecular-mass iron chelates, ferritin iron, and an increase in the number of leukocytes. We describe the protective effects of desferrioxamine against the deleterious effects of ferrous iron and relate this to its chelating and scavenging activity. The results suggest that the levels of low-molecular-mass iron chelates modulate the inflammatory response, possibly through their contribution to the oxygen free radical generation, which is responsible for the cell membrane damage and subsequently its death. The modulatory action of iron-dextran and desferrioxamine support our hypothesis.

Iron storage in Saccharomyces cerevisiae

A ferritin-like molecule was purified from iron-loaded cells of Saccharomyces cerevisiae, but its iron content was very low and was not representative of the cellular iron content. A study of the intracellular distribution of iron has shown that the vacuoles are involved in the storage of iron in the yeast cell. Moreover, it seems that this vacuolar iron can be further utilised by the cells for iron-requiring processes such as mitochondriogenesis.

Influence of laying on iron metabolism in quail

Haematological and iron content values for liver, spleen, intestines, blood, ovary and eggs were determined in female quails, from the prelaying state to full laying. A drop in hematocrit, haemoglobin and in the liver stores occurred at the onset of laying (48 to 51 d of age), but these values recovered after 5 to 10 d. The iron lost in eggs (0.3 mg Fe/egg) was responsible for this. An active homeostatic control must be necessary to supply adequate iron for both eggs and blood formation. Quails fed on an iron-deficient diet distributed iron preferentially to the haematopoietic processes, at the expense of the iron content of the eggs and a subsequent reduction of viability.

The influence of riboflavin deficiency on absorption and liver storage of iron in the growing rat

1. Iron absorption was measured in weanling riboflavin-deficient (RD) rats or weight-matched (WM) controls fed on appropriate diets for 7 weeks. Concentrations of radio-Fe (59Fe) in plasma were monitored every 30 min for 4 h following intragastric administration. 2. Total Fe absorption in RD rats was significantly lower than that in WM controls, and the tissues of the stomach and small intestine of RD rats retained significantly (P less than 0.001) more 59Fe by comparison with WM groups. 3. In a separate experiment, ferritin-Fe concentrations were measured in the livers of four groups of rats (ad lib. (C), pair-fed (PF) and WM controls and RD) at day 0, and subsequently at days 14, 21, 28, 35 and 49. 4. Liver ferritin-Fe concentration was significantly lower (P less than 0.05) in RD rats than in all other controls after 3 weeks on the respective diets and remained lower for the remainder of the experiment.

Functional studies on rat-liver isoferritins

Rat-liver and horse-spleen isoferritins were obtained by preparative isoelectric focussing and several of these were fractionated further by sucrose density gradient centrifugation. H- and L-subunit compositions were also measured. Isoferritins were found to have neither a fixed iron content nor a unique subunit composition. In both species within a single isoferritin a small increase in the percentage of H subunit paralleled increasing iron content. Although in horse-spleen ferritin a similar correlation was found over the isoferritin profile as a whole, this was not generally true of rat-liver isoferritins, since iron distributions varied with the iron status of the animals. Rates of iron incorporation into isoapoferritins were measured in vitro and the distribution of 59Fe among rat liver isoferritins was measured at various times after injection of 59Fe. The data do not support the proposal that, in rat liver, L-rich isoferritins are the preferred iron-storage form.

Iron mobilization in estrogenized male quail

A single diethylstilbestrol (DES) injection (5 mg DES/100 g body wt) was administrated to several lots (three specimens each) of adult male quail (Coturnix coturnix japonica). The birds were sacrificed 24, 48, 72 and 96 hr after the DES injection. A significant increase in liver weight and a clear drop in the hemoglobin concentration were observed after 24 hr. Later, a progressive rise was observed in plasma iron, total iron binding capacity, plasma copper and the phosphoprotein (vitellogenin), which reached highest values after 96 hr. In the liver, the iron showed an initial increase (24 hr), due to a rise in non-ferritin iron followed by a progressive decrease. Ferritin iron increased slowly but was significantly higher after 96 hr. This experimental model on male quail suggests an estrogen response in birds that could be more general and uniform than in mammals.

Comparative study of ferritins from dove Columba oena and chicken Gallus domesticus livers

A comparative study of ferritin from the liver of doves and chicken has been carried out. In both cases, the molecular weight, the number of iron atoms bounded to the protein and composition of amino acids were determined. The ferritins were isolated by the Luxton method. The identification of both proteins was carried out by acrylamide gel electrophoresis. Ferritin from the dove showed two bands while that from the chicken only one.

Isolation and characterization of Phycomyces blakesleeanus ferritin

Ferritin was isolated from the fungus Phycomyces blakesleeanus and compared biochemically and immunologically with horse spleen ferritin. Phycomyces and horse spleen ferritins were shown to exhibit similar electrophoretic patterns on polyacrylamide gels. Both preparations yielded an identical single band on sodium dodecyl sulfate-containing polyacrylamide gels. Tryptic digests of Phycomyces ferritin yielded 17 ninhydrin-positive spots as compared to 26 for horse spleen ferritin tryptic digests. Phycomyces ferritin was immunologically unrelated to horse spleen ferritin.

Studies on the concentration and intracellular localization of iron proteins in liver biopsy specimens from patients with iron overload with special reference to their role in lysosomal disruption

Liver biopsies were collected from control subjects and patients with iron overload due to either primary or secondary haemochromatosis. They were analysed for iron proteins by cation exchange chromatography and flameless atomic absorption spectrophotometry. In control tissue the transferrin fraction contains 25%, ferritin 50% and haemprotein and haemosiderin 10--15% each, of the total iron. In iron overloaded tissue the ferritin and haemosiderin iron increases approximately 10- and 100-fold, respectively, compared with control tissue. There was a close positive correlation between enhanced lysosomal fragility as determined by measurements of latent N-acetyl-beta-glucosaminidase and haemosiderin content of the tissue; it is suggested that the haemosiderin is responsible for the lysosomal disruption and hence the tissue damage in iron overload. Studies were performed on the intracellular localization of ferritin and of total iron in biopsy extracts from control subjects and from patients with iron overload. In control tissue, ferritin contains most of the iron and is apparently free in the cytosol. In iron overload, ferritin is the major iron protein in the post-nuclear supernatant sedimenting into the gradient as the free protein. There are, however, significant amounts of immunoreactive ferritin deeper in the gradients but this cannot be assigned to any particular subcellular organelle. The extreme fragility of lysosomes in iron overloaded human tissue makes isolation of these organelles for detailed biochemical analysis extremely difficult.

Separation and assay of iron proteins in needle biopsy specimens of human liver

A micro method has been developed for the separation of the principal classes of iron proteins in needle biopsy specimens of human liver. The iron content of the fractions was determined by automated flameless atomic absorption spectrophotometry in a one step procedure. The levels of total iron, transferrin-, ferritin-, haemprotein- and haemosiderin-iron are reported for control tissue.

Lysosomal disruption in the pathogenesis of hepatic damage in primary and secondary haemochromatosis

The disruption of lysosomes with release of their content of lytic enzymes was an early concept for the possible role of these organelles in the pathogenesis of tissue damage. Many examples are known of primary lysosomal storage diseases due to a congenital deficiency of certain acid hydrolases. It is suggested that iron overload due to either primary haemochromatosis or transfusional siderosis is a form of acquired secondary lysosomal storage disease. Subcellular fractionation experiments and electron microscopic studies have shown that liver tissue from patients with iron overload has iron-laden lysosomes. Similar results have been found in iron-overloaded rats. In patients, but not in experimental animals, enzymic analyses have shown increased activities of acid hydrolases and strikingly enhanced lysosomal fragility in liver homogenates. When it has been possible to deplete the patients of the excessive iron, these parameters have returned to normal. The possible mechanisms by which the iron compounds disrupt lysosomes, including distension with ferritin or haemosiderin or free-radical-mediated membrane damage, will be discussed.

On the quantitative determination of liver ferritin in the rat

The measurement of liver ferritin is usually performed after homogenization of liver, heating the homogenate and centrifugation. Because ferritin is stable to 80 degrees this protein and its iron are recovered in the supernatant. We found that this procedure resulted in losses of ferritin so we developed a method to measure ferritin protein in the unheated homogenate. Total liver ferritin iron could be calculated with use of the ferritin protein and ferritin iron values as measured in the supernatant after heating the liver homogenate.

In vitro stimulation of apoferritin synthesis by iron

The apparent induction of apoferritin synthesis by iron has been examined in cell-free systems from rat and rabbit liver. Both systems allowed the complete synthesis de novo of apoferritin isolated by chromatographic or immunological means. Addition of iron at levels of 0.2--1 mM specifically stimulated incorporation of radioactive amino acids into apoferritin purified after classical heat extraction. The effect was also observed when iron was added at the end of the incubation period in the absence of continuing protein synthesis. Further, iron addition had no effect on the amount of newly synthesised apoferritin subunits as estimated by direct immunological precipitation from the reaction mixture. These results suggest that iron acts at some stage subsequent to translation in stimulating apoferritin biosynthesis.

Heterogeneity in tissue ferritins displayed by gel electrofocusing

1. Horse spleen ferritin and human liver ferritin were examined by gel electrofocusing under conditions that demonstrated equilibrium focusing. Both ferritins were resolved into multiple isoferritins. Both families of isoferritins were separable from one another. 2. Horse spleen ferritin was also resolved into five components by ion-exchange chromatography on DEAE-Sephadex A-50. Each of the major chromatographic fractions contained only a few of the isoferritins seen on gel electrofocusing. Each chromatographic fraction corresponded to different portions of the isoferritin profile. 3. These results indicate that the heterogeneity seen in many ferritins by gel electrofocusing represents structural heterogeneity in the ferritin population as isolated from the tissues.

Iron metabolism in the veal calf. 2. Iron requirements and the effect of copper supplementation

1. The iron requirements of eighteen Ayrshire bull calves reared on fat-supplemented skim milk for 14 weeks fromc.16 d of age have been studied. There was a highly significant relationship between dietary Fe intake (10, 40 and 100 mg/kg dry diet) and blood haemoglobin concentration, packed cell volume and plasma Fe concentration.

2. A microcytic normochromic anaemia developed in the calves given a diet containing 10 mg Fe/kg diet, but not in the other calves.

3. Plasma Fe concentrations increased to > 5 μg Fe/ml in calves receiving 100 mg Fe/kg diet but there were no effects of Fe treatment on plasma Fe-binding capacity, which rose from 4·9 to 8·4 μg Fe/ml during the experiment. Saturation of plasma transferrin was only 3% in the Fe-deficient calves.

4. There were some significant effects of Fe treatment on tissue concentrations of Fe and cytochromec.

5. Dietary supplementation with 5 mg copper/kg dry diet had little effect on the growth or haematological status of the calves, although there were significant Cu × Fe interactions for mean corpuscular haemoglobin and mean corpuscular volume. There was no evidence of Cu deficiency in the calves, as measured by blood and liver Cu concentrations and by ceruloplasmin and cytochrome oxidase activities.

Iron metabolism in the veal calf. The availability of different iron compounds

1. The haematological status of Ayrshire bull calves reared on fat-supplemented skim milk from about 17 d of age has been examined. The calves were moderately anaemic after an 11-week experiment and it was shown that their performance was related to their blood haemoglobin concentration.

2. The relative availabilities of iron from FeSO4, ferric citrate, ferric-ethylenediaminetetra-acetate and iron phytate were compared at a supplementary dietary concentration of 30 μg Fe/g. No significant differences were noted between the three soluble Fe sources but the Fe of the insoluble iron phytate was less available.

3. The decreases in blood haemoglobin concentrations in all calves were greatest in the early weeks of the experiment. In calves given supplementary Fe, however, there was generally an improvement in haematological status after 6 weeks. Plasma Fe concentrations fell to 0·20 μg/ml in the most deficient animals. Total Fe binding capacities averaged about 10 μg Fe/ml in the later stages of the experiment.

4. Some of the calves were copper-deficient, and in some animals the effects of dietary Cu supplementation on both Cu and Fe metabolism were studied. About 50% of the supplementary Cu was retained in the livers of the calves.

5. A dietary intake of 40 μg Fe/g milk powder appears to be sufficient to prevent all but a very mild anaemia, provided the Fe is presented in soluble form.

Effect of actinomycin D, cycloheximide, and acute blood loss of ferritin synthesis in rat liver

1. The mechanism of the stimulation of ferritin synthesis by iron in vivo has been studied in rat liver. Ferritin synthesis and turnover was measured by [(14)C]leucine incorporation. 2. Actinomycin D had no inhibitory effect, after administration of iron, on [(14)C]leucine incorporation into ferritin but appeared to augment the effect of iron on ferritin synthesis. 3. Cycloheximide completely abolished the stimulation by iron of [(14)C]leucine into ferritin and was subsequently utilized to show that iron acts in vivo by translational induction of apoferritin synthesis, rather than by stabilization of apoferritin or its precursors. 4. This conclusion was confirmed by showing that 2 days after acute bleeding, when iron was in the process of being removed from hepatic ferritin stores, ferritin synthesis was decreased whereas breakdown rates were unchanged.