1,721,017 research outputs found
Iron, Oxidative Damage and Ferroptosis in Rhabdomyosarcoma.
No full textRecent data have indicated a fundamental role of iron in mediating a non-apoptotic and non-necrotic oxidative form of programmed cell death termed ferroptosis that requires abundant cytosolic free labile iron to promote membrane lipid peroxidation. Different scavenger molecules and detoxifying enzymes, such as glutathione (GSH) and glutathione peroxidase 4 (GPX4), have been shown to overwhelm or exacerbate ferroptosis depending on their expression magnitude. Ferroptosis is emerging as a potential weapon against tumor growth since it has been shown to potentiate cell death in some malignancies. However, this mechanism has been poorly studied in Rhabdomyosarcoma (RMS), a myogenic tumor affecting childhood and adolescence. One of the main drivers of RMS genesis is the Retrovirus Associated DNA Sequences/Extracellular signal Regulated Kinases (RAS/ERK)signaling pathway, the deliberate activation of which correlates with tumor aggressiveness and oxidative stress levels. Since recent studies have indicated that treatment with oxidative inducers can significantly halt RMS tumor progression, in this review we covered different aspects, ranging from iron metabolism in carcinogenesis and tumor growth, to mechanisms of iron-mediated cell death, to highlight the potential role of ferroptosis in counteracting RMS growth
Inhibition of glutathione peroxidase 4 primes mouse C2C12 myoblasts and rhabdomyosarcoma cell lines to ferroptosis
Full text linkFerroptosis is a recently discovered form of cell death causally linked to the ability of iron to induce oxidative damage by peroxidation of polyunsaturated fatty acids (PUFAs). Misregulated ferroptosis has been implicated in a number of pathological processes and there is a growing interest in the pre-clinical use of ferroptosis inducers against tumors. Cells to prevent ferroptosis mostly engage in the activity of glutathione peroxidase 4 (GPx4), a selenoenzyme that uses glutathione for neutralizing lipid hydroperoxides. Two major ferroptosis inducers mediating GPx4 inhibition have been identified, namely Erastin (eradicator of RAS and ST-expressing cells) and RSL3 (RAS selective Lethal 3). In this work we have investigated their effect on mouse skeletal C2C12 myoblasts and cell lines of rhabdomyosarcoma (RMS), the most frequent soft-tissue tumor affecting children and adolescents. As evaluated by using specific fluorescent probes, treatment with Erastin or RSL3 agents resulted in a marked production of both cytoplasmic/mitochondrial ROS and lipid ROS, which correlated in a dose-dependent manner with a decreased cell viability, as evaluated by means of Neutral Red assays after 48 hours. In Erastin-treated cell lines ferroptosis was enhanced in the presence of iron supplementation (through ferric ammonium citrate), while it was prevented by pre-treatment with agents sequestering iron (bathophenanthrolinedisulfonic acid), antioxidant scavengers (glutathione and N-acetylcysteine) and lipid ROS scavengers (ferrostatin-1). We observed Erastin to be more effective to promote ferroptosis in the cell lines showing a higher proliferation rate. Indeed, inhibition of ERK signaling, as observed during differentiation or upon pharmacological treatment with PD090859 agent, prevented ferroptosis in Erastin-treated human RMS embryonal RD and C2C12 cell lines. Furthermore, we found Erastin and RSL3 to be more effective in inducing ferroptosis in RD subclones characterized by higher ERK1/2 phosphorylation and proliferation rate. Taken together, our data suggest that iron metabolism could play a key role in the cell fate of muscle cells; in addition, the use of ferroptotic inducers could offer a novel alternative to improve the efficacy of conventional antineoplastic cocktails utilized against RMS
The importance of eukaryotic ferritins in iron handling and cytoprotection
No full textFerritins, the main intracellular iron storage proteins, have been
studied for over 60years, mainly focusing on the mammalian
ones.Thisallowedtheelucidationofthestructureoftheseproteins
and the mechanisms regulating their iron incorporation and
mineralization.However,ferritinispresentinmost,althoughnot
all, eukaryotic cells, comprising monocellular and multicellular
invertebratesandvertebrates.Theaimofthisreviewistoprovide
anupdateonthegeneralpropertiesofferritinsthatarecommonto
variouseukaryoticphyla(exceptplants),andtogiveanoverview
on the structure, function and regulation of ferritins. An update
on the animal models that were used to characterize H, L and
mitochondrialferritinsisalsoprovided.Thedatashowthatferritin
structure is highly conserved among different phyla. It exerts an
important cytoprotective function against oxidative damage and
playsaroleininnateimmunity,whereitalsocontributestoprevent
parenchymal tissue from the cytotoxicity of pro-inflammatory
agonists released by the activation of the immune response
activation. Less clear are the properties of the secretory ferritins
expressed by insects and molluscs, which may be important for
understanding the role played by ferritin in mammals
Ferritin, cellular iron storage and regulation
No full textFerritin is considered the major iron storage protein which maintains a large iron core in its cavity and has ferroxidase activity. There are many types of ferritin particularly in prokaryotes that include the canonical 24-mer FTN molecules, the heme-containing BFR, the smaller 12-mer DPS and the newly recognized EncFtn of encapsulin that forms a very large iron storage compartment. Recent studies show that ferritin function is more dynamic than previous depicted and new mechanisms of ferritin iron recycling are emerging. They participate to the regulation of cellular iron homeostasis as those of ferritin biosynthesis, cooperating also with the iron-dependent mechanism of cellular iron secretion. Some of these basic processes are in common between unicellular and animal cells, and this review aims at discussing the findings on the connections between iron storage, cellular iron regulation and ferritin iron recycling that have been explored in unicellular organisms and in animals. © 2017 IUBMB Life, 2017
Hepcidin antagonists for potential treatments of disorders with hepcidin excess
No full textThe discovery of hepcidin clarified the basic mechanism of the control of systemic iron homeostasis. Hepcidin is mainly produced by the liver as a propeptide and processed by furin into the mature active peptide. Hepcidin binds ferroportin, the only cellular iron exporter, causing the internalization and degradation of both. Thus hepcidin blocks iron export from the key cells for dietary iron absorption (enterocytes), recycling of hemoglobin iron (the macrophages) and the release of storage iron from hepatocytes, resulting in the reduction of systemic iron availability. The BMP/HJV/SMAD pathway is the major regulator of hepcidin expression that responds to iron status. Also inflammation stimulates hepcidin via the IL6/STAT3 pathway with a support of an active BMP/HJV/SMAD pathway. In some pathological conditions hepcidin level is inadequately elevated and reduces iron availability in the body, resulting in anemia. These conditions occur in the genetic iron refractory iron deficiency anemia and the common anemia of chronic disease (ACD) or anemia of inflammation. Currently, there is no definite treatment for ACD. Erythropoiesis-stimulating agents and intravenous iron have been proposed in some cases but they are scarcely effective and may have adverse effects. Alternative approaches aimed to a pharmacological control of hepcidin expression have been attempted, targeting different regulatory steps. They include hepcidin sequestering agents (antibodies, anticalins, and aptamers), inhibitors of BMP/SMAD or of IL6/STAT3 pathway or of hepcidin transduction (siRNA/shRNA) or ferroportin stabilizers. In this review we summarized the biochemical interactions of the proteins involved in the BMP/HJV/SMAD pathway and its natural inhibitors, the murine and rat models with high hepcidin levels currently available and finally the progresses in the development of hepcidin antagonists, with particular attention to the role of heparins and heparin sulfate proteoglycans in hepcidin expression and modulation of the BMP6/SMAD pathway
Non-Anticoagulant Heparins Are Hepcidin Antagonists for the Treatment of Anemia
No full textThe peptide hormone hepcidin is a key controller of systemic iron homeostasis, and its expression in the liver is mainly regulated by bone morphogenetic proteins (BMPs), which are heparin binding proteins. In fact, heparins are strong suppressors of hepcidin expression in hepatic cell lines that act by inhibiting the phosphorylation of SMAD1/5/8 proteins elicited by the BMPs. The inhibitory effect of heparins has been demonstrated in cells and in mice, where subcutaneous injections of non-anticoagulant heparins inhibited liver hepcidin expression and increased iron bioavailability. The chemical characteristics for high anti-hepcidin activity in vitro and in vivo include the 2O-and 6O-sulfation and a molecular weight above 7 kDa. The most potent heparins have been found to be the super-sulfated ones, active in hepcidin suppression with a molecular weight as low as 4 kDa. Moreover, the alteration of endogenous heparan sulfates has been found to cause a reduction in hepcidin expression in vitro and in vivo, indicating that heparins act by interfering with the interaction between BMPs and components of the complex involved in the activation of the BMP/SMAD1/5/8 pathway. This review summarizes recent findings on the anti-hepcidin activity of heparins and their possible use for the treatment of anemia caused by hepcidin excess, including the anemia of chronic diseases
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Pantothenate kinase-2 (Pank2) silencing causes cell growth reduction, cell-specific ferroportin upregulation and iron deregulation
No full textPantothenate kinase 2 (Pank2) is a mitochondrial enzyme that catalyses the first regulatory step of Coenzyme A synthesis and that is responsible for a genetic movement disorder named Pank-associated neurodegeneration (PKAN). This is characterized by abnormal iron accumulation in the brain, particularly in the globus pallidus. We downregulated Pank2 in some cell lines by using specific siRNAs to study its effect on iron homeostasis. In HeLa cells this caused a reduction of cell proliferation and of aconitase activity, signs of cytosolic iron deficiency without mitochondrial iron deposition, and a 12-fold induction of ferroportin mRNA. Pank2 silencing caused a strong induction of ferroportin mRNA also in hepatoma HepG2, a modest one in neuroblastoma SH-SY5Y and none in glioma U373 cells. A reduction of cell growth was observed in all these cell types. The strong Pank2-mediated alteration of ferroportin expression in some cell types might alter iron transfer to the brain and be connected with brain iron accumulation. (C) 2010 Elsevier Inc. All rights reserved
Iron release from ferritin by flavin nucleotides.
No full textExtensive in-vitro studies have focused on elucidating the mechanism of iron uptake and mineral core formation in ferritin. However, despite a plethora of studies attempting to characterize iron release under different experimental conditions, the in-vivo mobilization of iron from ferritin remains poorly understood. Several iron-reductive mobilization pathways have been proposed including, among others, flavin mononucleotides, ascorbate, glutathione, dithionite, and polyphenols. Here, we investigate the kinetics of iron release from ferritin by reduced flavin nucleotide, FMNH2, and discuss the physiological significance of this process in-vivo.
METHODS:
Iron release from horse spleen ferritin and recombinant human heteropolymer ferritin was followed by the change in optical density of the Fe(II)-bipyridine complex using a Cary 50 Bio UV-Vis spectrophotometer. Oxygen consumption curves were followed on a MI 730 Clark oxygen microelectrode.
RESULTS:
The reductive mobilization of iron from ferritin by the nonenzymatic FMN/NAD(P)H system is extremely slow in the presence of oxygen and might involve superoxide radicals, but not FMNH2. Under anaerobic conditions, a very rapid phase of iron mobilization by FMNH2 was observed.
CONCLUSIONS:
Under normoxic conditions, FMNH2 alone might not be a physiologically significant contributor to iron release from ferritin.
GENERAL SIGNIFICANCE:
There is no consensus on which iron release pathway is predominantly responsible for iron mobilization from ferritin under cellular conditions. While reduced flavin mononucleotide (FMNH2) is one likely candidate for in-vivo ferritin iron removal, its significance is confounded by the rapid oxidation of the latter by molecular oxygen
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