Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Deferoxamine”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed2002

Acquisition, storage and release of iron by cultured human hepatoma cells.

BACKGROUND/AIMS: The recovery from iron overload is hampered by the limited number of pathways and therapeutic agents available for the augmentation of iron secretion/excretion. The present study was aimed to investigate the process of iron storage and release by cultured human hepatoma cells, the role of transferrin receptors and ferritin in this process as well as the effect of iron chelators. METHODS: We followed the acquisition, storage and release of iron by cultured cells HepG2 and Hep3B by biochemical means and electron microscopy. RESULTS: The uptake of iron from diferric transferrin (Trf) was extremely low, while iron as ferric-ammonium-citrate (FAC) was taken up readily, especially by Hep3B cells. Up to 80% of the iron taken up by hepatoma cells was released to the medium. The rate of spontaneous iron release depended on the extent of iron loading. ApoTrf and deferoxamine facilitated release after 1- and 7-day iron-exposure. Up to a third of the radio-iron released from the cells was associated with ferritin. The release of ferritin-iron was not enhanced by either deferoxamine or Trf. CONCLUSIONS: Ferritin-iron release appeared to be an important mechanism of iron discarding in cultured human hepatoma cells, independent of the activity of chelating agents.

Apoproteins↗
PubMed1986

Brain iron delocalization and lipid peroxidation following cardiac arrest.

Brain injury after cardiac arrest and resuscitation may occur, in part, by oxygen radical mechanisms. The availability of a transition metal, such as iron, is essential for in vitro initiation of this type of reaction. The brain has significant stores of iron bound in large proteins. We conducted this study to determine whether iron availability is enhanced in the canine brain following resuscitation from 15 minutes of cardiac arrest, and whether this iron is associated with the appearance of products of radical-mediated lipid peroxidation (LP) after two hours of reperfusion. Examination of the data by the method of multivariate analysis revealed significant increases in the low molecular weight species (LMWS) iron (300% of nonischemic controls, P less than .01), malondialdehyde (MDA), a lipid peroxidation degradation product (145% of nonischemic controls, P less than .01), and conjugated dienes (CD) (204% of nonischemic controls, P = .07). Therapy with deferoxamine (50 mg/kg IV immediately post resuscitation) produced a reduction in MDA and CD to levels statistically indistinguishable from nonischemic controls. We conclude that brain tissue iron is delocalized from normal storage forms to a LMWS pool after two hours of reperfusion following resuscitation from a 15-minute cardiac arrest, and that this is associated with increased products of LP. The increase in LP products is blocked by treatment with deferoxamine.

Analysis of Variance↗
PubMed1987

Iron overload and mobilization in long-term hemodialysis patients.

Iron overload from repeated transfusions of RBCs in long-term hemodialysis patients is a problem of increasing clinical significance. We report on the prevalence of and diagnostic criteria for identification of hemodialysis patients with iron overload. In 150 unselected hemodialysis patients, 62 (41%) had ferritin levels greater than 2,000 ng/mL (normal = 10 to 360 ng/mL). In 16 of these patients, accurate transfusion histories were obtained and ferritin levels correlated with calculated transfusional iron burden (r = 0.553, P less than .05). These patients could be divided into two distinct groups on the basis of their response to a single dose (2 g, IV) of deferoxamine: "high" responders had twice the level of feroxamine (the chelated product of deferoxamine and iron) of the "low" responders (P less than .001). High responders also had significantly higher prevalence of the "hemochromatosis" alleles A3, B7, and B14 than a large group of dialysis patients awaiting transplantation (71% v 37%, P less than .001). In two patients with iron overload and clinically significant bone disease, bone histology revealed prominent iron staining at the calcification front. We conclude that transfusional iron overload is a significant clinical problem in long-term hemodialysis patients, that may also be associated with bone pathology.

Adult↗
PubMed1989

Plasma aluminum levels (unstimulated and stimulated): clinical and biochemical findings in 185 patients undergoing chronic hemodialysis for 4 to 95 months.

Plasma aluminum levels (unstimulated and stimulated by deferoxamine infusion), along with signs and symptoms associated with aluminum overload, were evaluated in 185 patients (97 men, 88 women; mean age, 58 +/- 8 years) who had been undergoing dialysis for 4 to 95 months and who were still receiving treatment in 1985 at a free-standing dialysis facility which has always used water purified by reverse osmosis. Monthly water aluminum levels never exceeded 15 micrograms/L; therefore, the major source of aluminum in these patients was oral phosphate binders. Unstimulated plasma aluminum levels ranged from 7 to 392 micrograms/L, averaged 81.5 +/- 56.4, and did not correlate with the duration of dialysis (r = 0.07; P greater than 0.31) or frequency of symptoms. Stimulated plasma aluminum levels increased in a linear fashion (r = 0.57; P less than 0.0001) with time on dialysis; however, there was no statistical association between the stimulated aluminum levels and a variety of nonspecific musculoskeletal or CNS symptoms, evidence of hyperparathyroidism, hematocrit, or calcium or phosphorus levels. These findings suggest that total body aluminum, as reflected in deferoxamine-stimulated serum aluminum levels, increases as a function of time undergoing dialysis.

Aluminum↗
PubMed2001

3,4-Dichlorophenylhydroxylamine cytotoxicity in renal cortical slices from Fischer 344 rats.

3,4-Dichlorophenylhydroxylamine (3,4-CPHA) is the N-hydroxyl metabolite of 3,4-dichloroaniline. 3,4-Dichloroaniline is a breakdown product of the herbicide Propanil. Previous work has shown that 3,4-dichloroaniline is acutely toxic to the kidney and bladder. The purpose of this study was to examine the in vitro toxicity of 3,4-dichlorophenylhydroxylamine. Renal cortical slices were prepared from male Fischer 344 rats (190-250 g) and were incubated with 0-0.5 mM 3,4-CPHA for 30-120 min under oxygen and constant shaking. 3,4-CPHA produced a concentration and time dependent alteration in lactate dehydrogenase (LDH) leakage, organic ion accumulation and pyruvate stimulated gluconeogenesis. Glutathione levels were diminished within 60 min below control values by 0.1 and 0.5 mM 3,4-CPHA. A 30 min pretreatment with 0.1 mM deferoxamine did not alter 3,4-CPHA toxicity. Alterations in pyruvate stimulated gluconeogenesis and LDH leakage were comparable between vehicle and deferoxamine pretreated tissues. Other studies examined the effect of (1 mM) glutathione, 2 mM ascorbic acid and 1 mM dithiothreitol (DTT) on toxicity. Pretreatment for 30 min with vehicle or 1 mM DTT induced comparable changes in LDH leakage and pyruvate stimulated gluconeogenesis. Pretreatment for 30 min with 1 mM glutathione or 2 mM ascorbic acid reduced 3,4-CPHA toxicity. LDH leakage was not elevated as markedly in renal slices pretreated with glutathione relative to slices pretreated with vehicle. These results indicate that 3,4-CPHA toxicity is through an iron independent mechanism. 3,4-CPHA cytotoxicity was reduced by pretreatment with glutathione or ascorbic acid suggesting formation of a reactive intermediate.

Analysis of Variance↗
PubMed2003

Protection of cells from menadione-induced apoptosis by inhibition of lipid peroxidation.

Menadione is a commonly used compound that causes oxidative stress. We investigated the influence of lipid peroxidation on the apoptotic response of mouse myogenic C2C12 cells following menadione-induced oxidative stress. The presence of hypodiploid cells and phosphatidylserine translocation were assayed to detect apoptotic cells. Menadione at 10-40 micro M induced cell apoptosis. Menadione at dose of 80 micro M induced both apoptosis and necrosis. At a 160 micro M dosage, menadione induced cell necrosis. Caspase 3 activation is required for menadione-induced apoptosis. Incubation of cells with 40 micro M menadione resulted in the depletion of cellular glutathione and increased lipid peroxidation. Pre-treatment of cells with cysteine suppressed the menadione-induced apoptosis and prevented changes in reactive oxygen species levels, glutathione levels and lipid peroxidation. Pre-treatment of cells with deferoxamine mesylate, an iron chelator, also reduced both menadione-induced apoptosis and lipid peroxidation. However, this did not prevent menadione-induced glutathione depletion. Thus, the inhibition of lipid peroxidation by deferoxamine mesylate prevented apoptosis even though cellular glutathione remained depleted. Our data suggest that menadione-induced apoptosis is directly linked to iron-dependent lipid peroxidation.

Animals↗
PubMed1999

Generation of active oxygen species from advanced glycation end-products (AGEs) during ultraviolet light A (UVA) irradiation and a possible mechanism for cell damaging.

Advanced glycation end-products (AGEs) have been reported to be accumulated in dermal skin. However, the role of AGEs in the photoaging of human skin remains unknown, and for this reason, we have examined the interaction between AGEs and ultraviolet A light (UVA) from both the chemical and biological aspects. Previously, we reported that exposing human dermal fibroblasts to UVA in the presence of AGEs that were prepared with bovine serum albumin (BSA) decreased the cell viability due to superoxide anion radical s (.O2(-)) and hydroxyl radicals (.OH) generated by AGEs under UVA irradiation, and active oxygen species are detected with ESR spin-trapping. To identify the active oxygen species in detail and to clarify the cell damaging mechanism, we performed several experiments and the following results were obtained. (1) In ESR spin-trapping, by addition of dimethyl sulfoxide and superoxide dismutase, ESR signals due to .O2(-) -derived DMPO-OOH and .OH-derived DMPO-OH adducts, respectively, were detectable. (2) UVA-irradiated AGEs elevated the lipid peroxide levels in both fibroblasts and liposomes. But the peroxidation in liposomes was inhibited by addition of deferoxamine. (3) Survival of fibroblasts exposed to UVA in the presence of AGEs was elevated by addition of deferoxamine. And finally, (4) survival of fibroblasts was found to be regulated by the level of H2O2. On the basis of these results, we propose a possible mechanism in which AGEs under UVA irradiation generate active oxygen species involving .O2(-), H2O2, and .OH, and the .OH species plays a harmful role in promoting cell damage.

Cell Survival↗
PubMed1998

Increasing vulnerability of astrocytes to oxidative injury with age despite constant antioxidant defenses.

This paper investigates the vulnerability of astrocytes to oxidative injury as a function of age in culture in mice. Primary murine cortical astrocyte cultures of different ages were exposed to H2O2, combined oxygen-glucose deprivation or glucose deprivation. Astrocytes became more vulnerable to damage from each injury paradigm with age, showing transitions between 15 and 22 days. Both the antioxidant glutathione and superoxide dismutase activity increased after 30 days in culture, while catalase activity did not change up to 34 days. When the decrease in glutathione with injury was measured, young cells showed no change with H2O2 and decreases of < 20% after oxygen-glucose deprivation or glucose deprivation, while older cultures lost > 50% of their glutathione with the same insults. Since iron can be a catalyst for hydroxyl radical formation, we stained cultures and found both iron staining and ferritin immunoreactivity increased with age. Increased iron correlated with protection by deferoxamine against H2O2 injury. The three injury paradigms each had a unique pattern of protection by antioxidants. Dimethylthiourea, a hydrophilic antioxidant, protected from all three insults. Trolox, a lipophilic antioxidant, protected older astrocytes from oxygen-glucose deprivation and glucose deprivation. Deferoxamine provided near complete protection from H2O2, partial protection from oxygen-glucose deprivation and no protection from glucose deprivation. As evidence of increasing oxidative stress, lipid peroxidation resulting from oxygen-glucose deprivation increased with age, assessed with cis-parinaric acid. The increasing sensitivity of ageing astrocytes to oxidative injury occurs while antioxidant defenses are maintained. Increased sensitivity to H2O2 or oxygen-glucose deprivation correlates with iron accumulation.

Aging↗
PubMed1997

Dopamine neurotoxicity in cortical neurons.

Dopamine (DA), at concentrations greater than 100 microM, has previously been demonstrated to be toxic to mesencephalic, striatal and dorsal root ganglion cell cultures. Pharmacological experiments suggest that DA also may play a role in the cortical neurotoxicity caused by systemic administration of N-methyl-D-aspartate receptor antagonists such as phencyclidine and MK-801. In this study, the potential toxicity of DA in primary cortical cell cultures was determined in vitro. Using calcein and ethidium homodimer fluorescence as a marker for live and dead cells, respectively, we observed that a 24 h treatment with 10-100 microM DA produced a concentration-dependent increase in the number of ethidium homodimer-labelled cells. The cell death induced by 10 microM DA was dramatically reduced by co-administration of either superoxide dismutase and catalase or deferoxamine mesylate, an iron chelator. To verify this observation, the effects of 10 microM DA on the release of cytoplasmic lactate dehydrogenase (LDH) was measured. DA increased LDH release in a manner that was inhibited by both superoxide dismutase/catalase and deferoxamine. Nomifensine potentiated the effect of DA on LDH release, suggesting a protective role for DA uptake in this system. On the other hand, neither D1 nor D2 antagonists were able to prevent DA-induced LDH release. These data suggest that relatively low concentrations of DA can be injurious to cortical neurons through a mechanism that likely involves DA autooxidation and the formation of reactive oxygen species such as superoxide anion and hydroxyl radical. This mechanism may be important in the toxic effects of psychomotor stimulants such as amphetamine. However, the failure of DA receptor antagonists to affect DA-induced injury argues that the effect of DA on cortical neurons in culture does not model the toxic effect of phencyclidine and MK-801 observed in vivo.

Animals↗
PubMed2001

Ischemia-reperfusion injury of the cochlea: effects of an iron chelator and nitric oxide synthase inhibitors.

Release of free iron from cellular stores and activation of nitric oxide synthase (NOS) has been implicated in a wide variety of cochlear injuries. In order to evaluate the effects of deferoxamine (a iron chelator), 3-bromo-7-nitroindazole (a relatively selective neuronal NOS (nNOS) inhibitor) or aminoguanidine (a relatively selective inducible NOS (iNOS) inhibitor) on the post-ischemic cochlear dysfunction, albino guinea pigs were subjected to 30 min ischemia, and the threshold shifts of the compound action potential (CAP) from pre-ischemic values were compared with those of control animals 4 h after the onset of reperfusion. A statistically significant reduction in the post-ischemic CAP threshold shift was observed in the animals treated with deferoxamine or 3-bromo-7-nitroindazole. However, aminoguanidine did not affect the post-ischemic CAP threshold shift. These results suggest that free iron and nNOS play deleterious roles in the cochlear injury induced by transient ischemia.

Action Potentials↗
PubMed1998

Mechanism of brain protection by nitroxide radicals in experimental model of closed-head injury.

Reactive oxygen-derived species were previously implicated in mediation of post-traumatic brain damage; however, the efficacy of traditional antioxidants in preventing/reversing the damage is sometimes limited. The present work focused on the mechanisms underlying the neuroprotective activity of cell permeable, nontoxic, antioxidants, namely stable nitroxide radicals in an experimental model of rat closed-head injury. Brain damage was induced by the weight-drop method and the clinical status was evaluated according to a neurological severity score at 1 h and 24 h, where the difference between these scores reflects the extent of recovery. The metal chelator deferoxamine as well as three nitroxide derivatives, differing in hydrophilicity and charge, and one hydroxylamine (a reduced nitroxide) facilitated the clinical recovery and decreased the brain edema. The nitroxides, but neither the hydroxylamine nor deferoxamine, protected the integrity of the blood-brain barrier. Superoxide dismutase also improved the clinical recovery but did not affect brain edema or the blood-brain barrier. The results suggest that by switching back and forth between themselves, the nitroxide and hydroxylamine act catalytically as self-replenishing antioxidants, and protect brain tissue by terminating radical-chain reactions, oxidizing deleterious metal ions, and by removal of intracellular superoxide.

Animals↗
PubMed2002

Prevention of the areca nut extract-induced unscheduled DNA synthesis of gingival keratinocytes by vitamin C and thiol compounds.

There are about 600 million betel quid (BQ) chewers in the world. BQ chewing is the major risk factor of oral cancer in India, Taiwan, South Africa and numerous other countries. Areca nut (AN) extract, the main component of BQ, exerts cytotoxicity and genotoxicity to several types of cells. In the present study, AN extract induced the unscheduled DNA synthesis (UDS) of gingival keratinocytes (GK). Vitamin C, at concentration of 50 and 200 microg/ml prevented the AN-induced UDS by 41 and 56%, respectively. Glutathione (GSH, 1-3 mM) and N-acetyl-L-cysteine (NAC, 1-3 mM) also protected the AN-induced UDS by 89-100 and 76-90%. These preventive effects were not due to cytotoxicity as analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Deferoxamine (20 and 30 mM), an iron chelator and a free radical scavenger, also prevented AN extract induced UDS of GK by 30-55%. On the contrary, banthocuproine (50-200 microM, a copper chelator) and 1,10-phenanthroline (50, 100 microM, a lipid permeable iron chelator), lacked preventive effects. Specific reactive oxygen species scavengers such as dimethyl-sulfoxide (2%), mannitol (10-20 mM), dimethylthiourea (10-20 mM), pyruvate (10 mM), catalase (200 and 400 U/ml), and superoxide dismutase (50 and 200 U/ml) also lacked these preventive effects. Moreover, higher concentrations of H(2)O(2) (0.5-1 mM) inhibited the basal levels of UDS by 19-37%. Interestingly, NAC, GSH, Vitamin C and deferoxamine cannot prevent the AN-induced morphological changes of GK at similar concentrations. These results reveal that AN extract-induced UDS of GK is associated with free radical reactions. Possibly different ingredients of AN is responsible for genotoxicity and cytotoxicity. Vitamin C, GSH and NAC may be potentially used in the future for chemoprevention of BQ chewing related oral mucosal lesions.

Antioxidants↗
PubMed1998

Direct evidence of caeruloplasmin antioxidant properties.

The chain-breaking antioxidant potential of caeruloplasmin and bovine serum albumin (BSA) has been investigated in comparison with other well-established antioxidants. Their Oxygen Radical Absorbing Capacity (ORAC), was measured by using beta-phycocyanin (beta-PC) as a fluorescent indicator protein, 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) as a peroxyl radical generator and the water soluble vitamin E analogue, Trolox, as a reference standard. The relative peroxyl absorbing capacities/mole for Trolox, caeruloplasmin, heat-denatured caeruloplasmin (hCP), catalase, bovine serum albumin (BSA), superoxide dismutase (SOD), and deferoxamine were 1; 2.6; 3.3; 3.7; 1.2; 0.1; 0.2, respectively. Caeruloplasmin was far more effective as a peroxyl radical scavenger than SOD, deferoxamine and BSA, but slightly less effective than catalase. The peroxyl radical absorbing capacity of caeruloplasmin was enhanced by heat-denaturation of the protein. Electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trap, was applied in order to measure the scavenger abilities of caeruloplasmin on superoxide radical and hydroxyl radical production and the concentration required to inhibit by 50% oxygen free radical formation (IC50) was determined. The IC50 values of caeruloplasmin, hCP, and BSA for the superoxide radical were 12, 2, 260 microM and for the hydroxyl radical 15, 2, 200 microM. These results show that caeruloplasmin is an effective chain-breaking antioxidant for a variety of radicals, independently of its catalytic ferroxidase activity.

Antioxidants↗
PubMed1996

Myoglobin inhibits proliferation of cultured human proximal tubular (HK-2) cells.

Following nephrotoxic injury, renal repair is dependent on tubular regeneration. In the case of myoglobinuric acute renal failure (ARF), persistence of myoglobin within tubular cells, or sublethal injury sustained at the height of exposure to it, might retard this process. To test this hypothesis, a human proximal tubular cell line (HK-2) was cultured for 24 hours in the absence or presence of clinically relevant myoglobin concentrations (0.5, 1, 2, 4 mg/ml). Immediately following myoglobin removal, lethal cell injury (vital dye uptake), lipid peroxidation, and DNA damage (alkaline unwinding assay) were assessed. The extent of cell proliferation was estimated over the next four days by a tetrazolium based (MTT) assay and by determining total intracellular LDH. Myoglobin's effects on protein and DNA synthesis were also assessed (35S-methionine and bromodeoxyuridine incorporation, respectively). Myoglobin induced dose-dependent lipid peroxidation (malondialdehyde generation) and cell death (up to 80% vital dye uptake with the 4 mg/ml challenge). Although 1 mg/ml myoglobin caused no cell death, it induced nearly complete growth arrest. This lasted for approximately three days following myoglobin removal from the media. Neither of two control proteins (albumin; lysozyme) nor a second nephrotoxin (gentamicin; 1 mg/ml) reproduced this effect. The 1 mg/ml myoglobin challenge caused an 80 to 90% depression in protein and DNA synthesis. It also induced significant DNA damage, as assessed by the alkaline unwinding assay (P < 0.01). Iron chelation therapy (deferoxamine) mitigated myoglobin-induced cell killing. However, its addition following myoglobin loading worsened HK-2 outgrowth by exerting a direct anti-proliferative effect. These results indicate that: (1) sublethal myoglobin toxicity can induce transient proximal tubular cell growth arrest, potentially slowing recovery from ARF; (2) this effect correlates with, and could result from, heme-induced DNA damage and a blockade in DNA/protein synthesis; and (3) deferoxamine can inhibit proximal tubular cell proliferation. This possibility needs to be considered in designing clinical trials with DFO for myohemoglobinuric ARF.

Acute Kidney Injury↗
PubMed1998

In vitro and in vivo evidence suggesting a role for iron in cisplatin-induced nephrotoxicity.

Cisplatin is a widely used antineoplastic agent that has nephrotoxicity as a major side effect. The underlying mechanism of this nephrotoxicity is still not well known. Iron has been implicated to play an important role in several models of tissue injury, presumably through the generation of hydroxyl radicals via the Haber-Weiss reaction or other highly toxic free radicals. In the present study we examined the catalytic iron content and the effect of iron chelators in an in vitro model of cisplatin-induced cytotoxicity in LLC-PK1 cells (renal tubular epithelial cells) and in an in vivo model of cisplatin-induced acute renal failure in rats. Exposure of LLC-PK1 cells to cisplatin resulted in a significant increase in bleomycin-detectable iron (iron capable of catalyzing free radical reactions) released into the medium. Concurrent incubation of LLC-PK1 cells with iron chelators including deferoxamine and 1,10-phenanthroline significantly attenuated cisplatin-induced cytotoxicity as measured by lactate dehydrogenase (LDH) release. Bleomycin-detectable iron content was also markedly increased in the kidney of rats treated with cisplatin. Similarly, administration of deferoxamine in rats provided marked functional (as measured by blood urea nitrogen and creatinine) and histological protection against cisplatin-induced acute renal failure. In a separate study, we examined the role of hydroxyl radical in cisplatin-induced nephrotoxicity. Incubation of LLC-PK1 cells with cisplatin caused an increase in hydroxyl radical formation. Hydroxyl radical scavengers, dimethyl sulfoxide, mannitol and benzoic acid, significantly reduced cisplatin-induced cytotoxicity and, treatment with dimethyl sulfoxide or dimethylthiourea provided significant protection against cisplatin-induced acute renal failure. Taken together, our data strongly support a critical role for iron in mediating tissue injury via hydroxyl radical (or a similar oxidant) in this model of nephrotoxicity.

Acute Kidney Injury↗
PubMed2003

Transcriptional effects of hypoxia on fusiogenic syncytin and its receptor ASCT2 in human cytotrophoblast BeWo cells and in ex vivo perfused placental cotyledons.

OBJECTIVE: The purpose of this study was to test the hypothesis that hypoxia down-regulates placental syncytin, which could play a role in altered placentogenesis; we investigated the influence of hypoxia on syncytin and its receptor ASCT2 gene expression in BeWo cells and in ex vivo perfused human cotyledons. STUDY DESIGN: BeWo cells were incubated with deferoxamine or cobalt chloride under normoxia and hypoxia. Additionally, a model of dually ex vivo perfused cotyledons was applied. Under hypoxic and cobalt chloride stimuli syncytin, ASCT2, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-actin, and beta(2)-microglobulin (beta(2)-MG) messenger RNAs were analyzed with the use of real-time polymerase chain reaction. RESULTS: Hypoxia, deferoxamine, and cobalt chloride markedly decreased syncytin messenger RNA in BeWo cells, whereas ASCT2 messenger RNA was not altered significantly. In isolated perfused cotyledons, hypoxia also reduced syncytin (P<.05) but not ASCT2 messenger RNA. CONCLUSION: Our data provide first evidence that syncytin gene expression is down-regulated by hypoxia, which strengthens the hypothesis that syncytin is reduced in disturbed pregnancies in the course of placental hypoxia.

Amino Acid Transport System ASC↗
PubMed1987

Translation of ferritin light and heavy subunit mRNAs is regulated by intracellular chelatable iron levels in rat hepatoma cells.

Acute administration of iron to rats has been previously shown to induce liver ferritin synthesis by increasing the translation of inactive cytoplasmic ferritin mRNAs for both heavy (H) and light (L) subunits by mobilizing them onto polyribosomes. In this report rat hepatoma cells in culture are used to explore the relationship of this response to intracellular iron levels. After adding iron as ferric ammonium citrate to the medium, latent ferritin H- and L-mRNAs were extensively transferred to polyribosomes, accompanied by increased uptake of [35S]methionine into ferritin protein. Because total cellular levels of L- and H-mRNA were not significantly changed by exposure to iron, the increased ferritin mRNAs on polyribosomes most probably come from an inactive cytoplasmic pool, consistent with the inability of actinomycin-D and of cordycepin to inhibit iron-induced ferritin synthesis. When deferoxamine mesylate, an intracellular iron chelator, was added after the addition of iron to the medium, ferritin mRNA on the polyribosomes was reduced, while the free messenger pool increased, and ferritin synthesis diminished. In contrast, the extracellular iron chelator diethylenetriaminepentaacetic acid failed to inhibit the induction of ferritin protein synthesis. Addition of iron in the form of hemin also caused translocation of mRNA to polyribosomes, a response that could be similarly quenched by deferoxamine. Because hemin does not release chelatable iron extracellularly, we conclude that the level of chelatable iron within the cell has a regulatory role in ferritin synthesis through redistribution of the messenger RNAs between the free mRNA pool and the polyribosomes.

Animals↗
PubMed2003

Regulation of c-myc gene by nitric oxide via inactivating NF-kappa B complex in P19 mouse embryonal carcinoma cells.

Nitric oxide (NO) may regulate gene expression by directly modifying redox state-sensitive residues of transcription factors. Here we show that the NO donor, sodium nitroprusside (SNP), rapidly represses c-myc gene transcription in a protein synthesis-independent manner in P19 embryonal carcinoma cells by inactivation of NF-kappa B. SNP treatment reduces the DNA binding ability of the constitutively active NF-kappa B heterodimer, p65/p50, and its consequent transactivation of the c-myc promoter. Repression can be blocked by the peroxynitrite scavenger, deferoxamine, but not by dithiothreitol, which triggers reduction of S-nitrosylated residues. In HEK293 cells, where tumor necrosis factor-alpha can activate NF-kappa B, SNP likewise suppresses the binding of the active NF-kappa B complex, restoring the binding of the repressive p50/p50 homodimer complex. This effect of SNP in HEK293 cells is also blocked by deferoxamine. Chromatin immunoprecipitation analysis of SNP-treated P19 cells reveals reduced association of p65, but not of p50, with the promoter region of the endogenous c-myc gene. SNP-induced p65 dissociation was associated with the recruitment of histone deacetylase 1 and 2 to the endogenous c-myc gene promoter and the subsequent deacetylation of its chromatin histone. This study is the first to demonstrate that NO modulates the transcriptional activity of the c-myc gene promoter by dissociating the active form of NF-kappa B and replacing it with a repressive NF-kappa B complex, correlated with the recruitment of gene-silencing histone deacetylases. In light of findings that NF-kappa B stimulates Myc oncoprotein expression in cancers, our findings suggest that NO should be investigated as a prospective therapeutic cancer agent.

Animals↗