Repression of ferritin expression increases the labile iron pool, oxidative stress, and short-term growth of human erythroleukemia cells

Abstract

The role of ferritin expression on the labile iron pool of cells and its implications for the control of cell proliferation were assessed. Antisense oligodeoxynucleotides were used as tools for modulating the expression of heavy and light ferritin subunits of K562 cells. mRNA and protein levels of each subunit were markedly reduced by 2-day treatment with antisense probes against the respective subunit. Although the combined action of antisense probes against both subunits reduced their protein expression, antisense repression of one subunit led to an increased protein expression of the other. Antisense treatment led to a rise in the steady-state labile iron pool, a rise in the production of reactive oxygen species after pro-oxidative challenges and in protein oxidation, and the down-regulation of transferrin receptors. When compared to the repression of individual subunits, corepression of each subunit evoked a more than additive increase in the labile iron pool and the extent of protein oxidation. These treatments had no detectable effects on the long-term growth of cells.

Cell sensitivity to oxidative stress is influenced by ferritin autophagy

“…It has been shown previously that downregulation of H-ferritin by siRNA or overexpression of a mutated H-ferritin chain results in an increase of the labile iron pool and sensitization of cells to oxidative stress [91][92][93]. The same was found following overexpression of mutated L-ferritin variants [94].…”

Reduction of Fe(III) Ions Complexed to Physiological Ligands by Lipoyl Dehydrogenase and Other Flavoenzymes in Vitro

“…5A and Table I), an increase of the intracellular concentration of metabolically active Fe(III) should decisively enhance the level/production of Fe(II), thereby initiating/enhancing radical-mediated damaging processes. The concentration of intracellular iron in transit is generally reported to be in the low M range (1,2,6,9,14,15). We found that in liver cells iron in transit is distributed over several subcellular compartments at concentrations ranging from 6 to 7 M in the cytosol and from 9 to 12 M in mitochondria (78,85).…”

“…This cytotoxicity is mainly related to the fact that it catalyzes the formation of hydroxyl radicals ( ⅐ OH) from hydrogen peroxide (H 2 O 2 , Reaction 1 (11,12)) or forms high valent iron-oxygen (ferryl) species (13 Whereas H 2 O 2 reacts only slowly with most biomolecules, the hydroxyl radical and the high valent iron-oxygen species, which may also be generated from molecular oxygen in competition with the classical Fenton reaction, react rapidly, often close to diffusion control, with virtually all biological molecules (12). Consequently, such reactive oxygen species-mediated, irondependent injurious processes are considered to be crucial pathogenetic factors for numerous diseases (5,6,10,14,15). At least a small fraction of the iron in transit must exist within the ferrous (Fe(II) oxidation state, which is the basis for the numerous metabolic functions of iron (e.g.…”

The role of endocytic pathways in cellular uptake of plasma non-transferrin iron

“…Chronic exposure of cells in vitro to artificial iron complexes that presumably mimic NTBI (usually ferric citrate) [10][11][12]28,29 has been shown to generate cellular iron overload as indicated by increased ferritin levels, ROS generation, protein and DNA oxidation, and other indicators of cell damage. [30][31][32] However, the relevance of such models to cell iron overload in vivo is open to question because of various factors associated with the presence of NTBI in plasma: i) the association/complexation of NTBI with various acids and plasma proteins; 28 ii) the changes in chemical composition of NTBI with changing iron concentrations 12 and plasma oxidation; 29,30 and iii) the changes in NTBI properties due to fluctuations in plasma component composition. Adsorption of NTBI to macromolecular plasma components, such as albumin, 28,29 may restrict its access to iron reductases and divalent ion transporters at the cell surface due to steric hindrance.…”