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Comparative study of iron mobilization from haemosiderin, ferritin and iron(III) precipitates by chelators.

ABSTRACT: The heteroaromatic chelators 1,2-dimethyl-3-hydroxypyrid-4-one, maltol, mimosine and 2,4-dihydroxypyridine-N-oxide, have been shown to mobilize iron from human spleen haemosiderin, ferritin and also from iron(III) precipitates, all containing equal amounts of iron, at physiological pH. In the case of almost every chelator, the least-solubilized polynuclear iron form was ferritin, whereas haemosiderin was more soluble and the iron(III) precipitate the most soluble of all. Most of the chelators were more efficient than desferrioxamine at releasing iron from ferritin, but less efficient in the removal of iron from the other two polynuclear iron forms. It is suggested that the chelator differences in iron mobilization may be related to variations in the chelator molecular structure, the protein structure, iron forms and in the mechanism of iron release.

SUBMITTER: Kontoghiorghes GJ

PROVIDER: S-EPMC1147528 | biostudies-other | 1987 Jan

REPOSITORIES: biostudies-other

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Iron release from haemosiderin and ferritin by therapeutic and physiological chelators.

Project description:Iron release from both human and horse spleen haemosiderin to desferrioxamine was substantially less than that released from ferritin samples. This finding contradicts a previous report [Kontoghiorges, Chambers & Hoffbrand (1987) Biochem. J. 241, 87-92]. Differences in phosphate content of cores and in core size between haemosiderin and ferritin did not account for the different iron-release rates. Iron released to acetate was found to stimulate lipid peroxidation in liposomes, whereas that released to stronger chelators such as citrate and desferal did not. Absorption spectra and gel-filtration studies suggest that the acetate-solubilized iron was in the form of low-molecular-mass (less than 5 kDa) ferrihydrite fragments.

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Iron precipitates

Project description:Iron precipitates Raw sequence reads

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Ferroportin-mediated mobilization of ferritin iron precedes ferritin degradation by the proteasome.

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The role of iron in ferritin- and haemosiderin-mediated lipid peroxidation in liposomes.

Project description:Ferritin and haemosiderin were shown, by the measurement of malondialdehyde production and loss of polyunsaturated fatty acids, to stimulate lipid peroxidation in liposomes. At pH 7.4 ascorbate was additionally required to achieve peroxidation; however, peroxidation occurred at pH 4.5 in the presence of iron-proteins alone. The damage was completely inhibited by the incorporation of chain-breaking antioxidants (alpha-tocopherol and butylated hydroxytoluene) into the liposomes. Metal chelators (desferrioxamine and EDTA) also completely inhibited lipid peroxidation. These and further results indicate that, at pH 4.5, even in the absence of a reducing agent, iron is released from haemosiderin and can mediate oxidative damage to a lipid membrane.

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Siderosomal ferritin. The missing link between ferritin and haemosiderin?

Project description:A minor electrophoretically fast component was found in ferritin from iron-loaded rat liver in addition to a major electrophoretically slow ferritin similar to that observed in control rats. The electrophoretically fast ferritin showed immunological identity with the slow component, but on electrophoresis in SDS it gave a peptide of 17.3 kDa, in contrast with the electrophoretically slow ferritin, which gave a major band corresponding to the L-subunit (20.7 kDa). Thus the electrophoretically fast ferritin resembles that reported by Massover [(1985) Biochim. Biophys. Acta 829, 377-386] in livers of mice with short-term parenteral iron overload. The electrophoretically fast ferritin had a lower iron content (2000 Fe atoms/molecule) than the electrophoretically slow ferritin (3000 Fe atoms/molecule). Removal and re-incorporation of iron was possible without effect on the electrophoretic mobility of either ferritin species. On subcellular fractionation the electrophoretically fast ferritin was enriched in pellet fractions and was the sole soluble ferritin isolated from iron-laden secondary lysosomes (siderosomes). The amount and relative proportion of the electrophoretically fast species increased with iron loading. Haemosiderin isolated from siderosomes was found to contain a peptide reactive to anti-ferritin serum and corresponding to the 17.3 kDa peptide of the electrophoretically fast ferritin species. Unlike the electrophoretically slow ferritin, the electrophoretically fast ferritin did not become significantly radioactive in a 1 h biosynthetic labelling experiment. We conclude that the minor ferritin is not, as has been suggested for mouse liver ferritin, 'a completely new species of smaller holoferritin that represents a shift in the ferritin phenotype' in response to siderosis, but a precursor of haemosiderin, in agreement with the proposal by Richter [(1984) Lab. Invest. 50, 26-35] concerning siderosomal ferritin.

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