Free radical activity of industrial fibers: role of iron in oxidative stress and activation of transcription factors (original) (raw)
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Iron inhibits the nitric oxide synthesis elicited by asbestos in murine macrophages
Free Radical Biology and Medicine, 2001
Crocidolite fibers stimulated nitric oxide synthase (NOS) activity and expression in glial and alveolar murine macrophages: this effect was inhibited by iron supplementation and enhanced by iron chelation. We suggest that in these cells crocidolite stimulates NOS expression by decreasing the iron bioavailability and activating an iron-sensitive transcription factor.
Role of Iron in Asbestos-Body-Induced Oxidant Radical Generation
Journal of Toxicology and Environmental Health, Part A, 1999
Asbestos bodies (AB) were harvested from human lung tissue digests and isolated from uncoated asbestos fibers. Samples containing 1000 AB were added to a reactive solution to investigate the ability of AB to oxidize deoxy-D-ribose and generate reactive oxygen species (ROS) in the presence of ascorbate and hydrogen peroxide as determined by formation of thiobarbituric acid (TBA)-reactive products. Three types of asbestos fibers were tested for comparison, since they are known to be able to produce ROS. The absorbance values measured with 1000 AB were significantly higher than those observed with 1000 fibers of the three types of asbestos. Since in our reaction system the only source of transition metals was the iron-rich AB, data suggest iron derived from the ferritin coating of AB was involved in oxidant generation. Addition of iron to AB enhanced TBA-reactive product formation, while chelation of Fe with deferoxamine reduced this reaction. Hydroxyl radical scavengers 1,3-dimethyl-2-thiourea (DMTU) and mannitol (MN) also effectively blocked TBA-reactive product generation. Data indicate the importance of Fe in ABinduced oxidant damage. With the addition of polymorphonuclear leukocytes (PMN) to AB, incubation in the reactive solution gave very high amounts of TBA-reactive products, but using a reactive solution devoid of ascorbate, very low amounts of TBA-reactive products were generated. In the latter condition, the superoxide of cell membranes probably reduced and removed iron from AB-coating ferritin, but less effectively than ascorbate. Further after the possible reoxidation of Fe 2+ , Fe 3+ could be coordinated by lactoferrin. Since such availability of reductant is never approached in living systems, the iron in the AB coating is unlikely to function as a catalyst of Fenton-type reactions in vivo.
Toxicological Sciences, 2019
Asbestos is the main causative agent of malignant pleural mesothelioma. The variety known as crocidolite (blue asbestos) owns the highest pathogenic potential, due to the dimensions of its fibers as well as to its content of iron. The latter can in fact react with macrophage-derived hydrogen peroxide in the so called Fenton reaction, giving rise to highly reactive and mutagenic hydroxyl radical. On the other hand, hydroxyl radical can as well originate after thiol-dependent reduction of iron, a process capable of starting its redox cycling. Previous studies showed that glutathione (GSH) is one such thiol, and that cellular gamma-glutamyltransferase (GGT) can efficiently potentiate GSH-dependent iron redox cycling and consequent oxidative stress. As GGT is expressed in macrophages and is released upon their activation, the present study was aimed at verifying the hypothesis that GSH/GGT-dependent redox reactions may participate in the oxidative stress following the activation of macr...
Murine macrophages response to iron
Journal of Proteomics, 2012
Macrophages play a critical role at the crossroad between iron metabolism and immunity, being able to store and recycle iron derived from the phagocytosis of senescent erythrocytes. The way by which macrophages manage non-heme iron at physiological concentration is still not fully understood. We investigated protein changes in mouse bone marrow macrophages incubated with ferric ammonium citrate (FAC 10 μM iron). Differentially expressed spots were identified by nano RP-HPLC-ESI-MS/MS. Transcriptomic, metabolomics and western immunoblotting analyses complemented the proteomic approach. Pattern analysis was also used for identifying networks of proteins involved in iron homeostasis. FAC treatment resulted in higher abundance of several proteins including ferritins, cytoskeleton related proteins, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) at the membrane level, vimentin, arginase, galectin-3 and macrophage migration inhibitory factor (MIF). Interestingly, GAPDH has been recently proposed to act as an alternative transferrin receptor for iron acquisition through internalization of the GAPDHtransferrin complex into the early endosomes. FAC treatment also induced the up-regulation of oxidative stress-related proteins (PRDX), which was further confirmed at the metabolic level (increase in GSSG, 8-isoprostane and pentose phosphate pathway intermediates) through mass spectrometry-based targeted metabolomics approaches. This study represents an example of the potential usefulness of "integarated omics" in the field of iron biology, especially for the elucidation of the molecular mechanisms controlling iron homeostasis in normal and disease conditions. This article is part of a Special Issue entitled: Integrated omics.
2010
Alveolar macrophages have been implicated in the pathogenesis of a number of acute and chronic lung disorders. We have previously shown that normal human alveolar macrophages exhibit decreased DNA binding activity of the transcription factor, AP-1, compared with monocytes. Furthermore, this decrease in AP-1 DNA binding appears to be due to a decrease in the redox active protein, redox factor (Ref)-1. Ref-1 is an important redox regulator of a number of transcription factors, including NF-B and AP-1. In this study we evaluated the role of asbestos, a prototypic model of chronic fibrotic lung disease, in Ref-1 expression and activity. We found that incubation with low concentrations of crocidolite asbestos (0.5-1.25 g/cm 2) resulted in an increase in nuclear Ref-1 protein after 5 min, with a persistent elevation in protein up to 24 h. Additionally, an increase in nuclear Ref-1 could be induced by treating the cells with an oxidant-generating stimulus (iron loading plus PMA) and inhibited by diphenyleneiodonium chloride, an inhibitor of NADPH oxidase. The asbestos-induced accumulation of nuclear Ref-1 was associated with an increase in AP-1 DNA binding activity. These findings suggest that an exposure associated with fibrotic lung disease, i.e., asbestos, modulates accumulation of nuclear Ref-1 in macrophages, and that this effect is mediated by an oxidant stimulus.
The Journal of Immunology, 2002
Alveolar macrophages have been implicated in the pathogenesis of a number of acute and chronic lung disorders. We have previously shown that normal human alveolar macrophages exhibit decreased DNA binding activity of the transcription factor, AP-1, compared with monocytes. Furthermore, this decrease in AP-1 DNA binding appears to be due to a decrease in the redox active protein, redox factor (Ref)-1. Ref-1 is an important redox regulator of a number of transcription factors, including NF-B and AP-1. In this study we evaluated the role of asbestos, a prototypic model of chronic fibrotic lung disease, in Ref-1 expression and activity. We found that incubation with low concentrations of crocidolite asbestos (0.5-1.25 g/cm 2) resulted in an increase in nuclear Ref-1 protein after 5 min, with a persistent elevation in protein up to 24 h. Additionally, an increase in nuclear Ref-1 could be induced by treating the cells with an oxidant-generating stimulus (iron loading plus PMA) and inhibited by diphenyleneiodonium chloride, an inhibitor of NADPH oxidase. The asbestos-induced accumulation of nuclear Ref-1 was associated with an increase in AP-1 DNA binding activity. These findings suggest that an exposure associated with fibrotic lung disease, i.e., asbestos, modulates accumulation of nuclear Ref-1 in macrophages, and that this effect is mediated by an oxidant stimulus.
Cancer Research, 2006
Hypoxia-inducible factor (HIF) is a transcription factor with major roles in many cellular and systemic responses to hypoxia. Activation of HIF pathways under hypoxia is mediated by suppression of the Fe 2+ -and O 2 -dependent HIF hydroxylase enzymes that normally inactivate HIFA subunits. Mechanisms underlying induction of HIF in normoxic conditions are less clearly understood. In human cancers, infiltrating macrophages show up-regulation of HIF and it has recently been shown that normoxic expression of HIF-1A is essential for macrophage function. Here, we report studies of HIF-1A induction following phorbol-12-myristate 13-acetate (PMA)-induced differentiation of monocytic U937 and THP1 cells. HIF-1A was markedly up-regulated under normoxia in this setting and this involved failure of HIF-1A prolyl hydroxylation despite the presence of O 2 . Fluorescence measurements showed that differentiation was associated with marked reduction of the labile iron pool. Both the reduction in labile iron pool and the up-regulation of HIF-1A were suppressed by RNA interference-mediated downregulation of the iron transporter natural resistanceassociated macrophage protein 1. Up-regulation of HIF-1A following PMA-induced differentiation was also abolished by addition of Fe 2+ or ascorbate. These results indicate that physiologic changes in macrophage iron metabolism have an important effect on HIF hydroxylase pathways and suggest means by which the system could be manipulated for therapeutic benefit. (Cancer Res 2006; 66(5): 2600-7) Downloaded from . Effect of ascorbate on cellular iron uptake and release. For iron uptake assays, PMA-treated U937 cells were loaded with either (A) 59 Fe-Tf [8 Ag/mL (106 nmol/L)] or (C ) 175 nmol/L 59 Fe-NTA in the presence of 25 or 250 Amol/L ascorbate or 500 nmol/L cold holo-Tf (X). Points, mean from three independent experiments; experiments; bars, SD. Cold holo-Tf significantly inhibited Tf-dependent iron uptake to 44% of the control level (P < 0.001). For iron release assays, PMA-treated U937 cells loaded for 48 hours with (B ) 59 Fe-Tf or (D ) 59 Fe-NTA were washed with PBS and incubated in serum-free RPMI 1640 supplemented with 25 to 250 Amol/L ascorbate. Points, mean from three independent experiments; bars, SD.
Iron regulates nitric oxide synthase activity by controlling nuclear transcription
Journal of Experimental Medicine, 1994
Recently, it was reported that nitric oxide (NO) directly controls intracellular iron metabolism by activating iron regulatory protein (IRP), a cytoplasmic protein that regulates ferritin translation. To determine whether intracellular iron levels themselves affect NO synthase (NOS), we studied the effect of iron on cytokine-inducible NOS activity and mRNA expression in the murine macrophage cell line J774A.1. We show here that NOS activity is decreased by about 50% in homogenates obtained from cells treated with interferon 3' plus lipopolysaccharide (IFN-3~/LPS) in the presence of 50 ~M ferric iron [Fe(3 +)] as compared with extracts from cells treated with IFN-3~/LPS alone. Conversely, addition of the iron chelator desferrioxamine (100 #M) at the time of stimulation with IFN-3,/LPS increases NOS activity up to 2.5-fold in J774 cells. These effects of changing the cellular iron state cannot be attributed to a general alteration of the IFN-3~/LPS signal, since IFN-3,/LPS-mediated major histocompatibility complex class II antigen expression is unaffected. Furthermore, neither was the intracellular availability of the NOS cofactor tetrahydrobiopterin altered by treatment with Fe(3 +) or desferrioxamine, nor do these compounds interfere with the activity of the hemoprotein NOS in vitro. We demonstrate that the mRNA levels for NOS are profoundly increased by treatment with desferrioxamine and reduced by Fe(3 +). The half-life of NOS mP, NA appeared not to be significantly altered by administration of ferric ion, and NOS mP, NA stability was only slightly prolonged by desferrioxamine treatment. Nuclear run-off experiments demonstrate that nuclear transcription of cytokine-inducible NOS mP, NA is strongly increased by desferrioxamine whereas it is decreased by Fe(3 +). Thus, this transcriptional response appears to account quantitatively for the changes in enzyme activity. Our results suggest the existence of a regulatory loop between iron metabolism and the NO/NOS pathway.