Lymphocyte DNA damage and oxidative stress in patients with iron deficiency anemia

Oxidant stress has been shown to play an important role in the pathogenesis of iron deficiency anemia. The aim of this study was to investigate the association between lymphocyte DNA damage, total antioxidant capacity and the degree of anemia in patients with iron deficiency anemia. Twenty-two female with iron deficiency anemia and 22 healthy females were enrolled in the study. Peripheral DNA damage was assessed using alkaline comet assay and plasma total antioxidant capacity was determined using an automated measurement method. Lymphocyte DNA damage of patients with iron deficiency anemia was significantly higher than controls (p<0.05), while total antioxidant capacity was significantly lower (p<0.001). While there was a positive correlation between total antioxidant capacity and hemoglobin levels (r=0.706, p<0.001), both total antioxidant capacity and hemoglobin levels were negatively correlated with DNA damage (r=-0.330, p<0.05 and r=-0.323, p<0.05, respectively). In conclusion, both oxidative stress and DNA damage are increased in IDA patients. Increased oxidative stress seems as an important factor that inducing DNA damage in those IDA patients. The relationships of oxidative stress and DNA damage with the severity of anemia suggest that both oxidative stress and DNA damage may, in part, have a role in the pathogenesis of IDA.     

Iron and oxidative stress in bacteria

The appearance of oxygen on earth led to two major problems: the production of potentially deleterious reactive oxygen species and a drastic decrease in iron availability. In addition, iron, in its reduced form, potentiates oxygen toxicity by converting, via the Fenton reaction, the less reactive hydrogen peroxide to the more reactive oxygen species, hydroxyl radical and ferryl iron. Conversely superoxide, by releasing iron from iron-containing molecules, favors the Fenton reaction. It has been assumed that the strict regulation of iron assimilation prevents an excess of free intracellular iron that could lead to oxidative stress. Studies in bacteria supporting that view are reviewed. While genetic studies correlate oxidative stress with increase of intracellular free iron, there are only few and sometimes contradictory studies on direct measurements of free intracellular metal. Despite this weakness, the strict regulation of iron metabolism, and its coupling with regulation of defenses against oxidative stress, as well as the role played by iron in regulatory protein in sensing redox change, appear as essential factors for life in the presence of oxygen.     

Mechanisms of homocysteine-induced oxidative stress

Hyperhomocysteinemia decreases vascular reactivity and is associated with cardiovascular morbidity and mortality. However, pathogenic mechanisms that increase oxidative stress by homocysteine (Hcy) are unsubstantiated. The aim of this study was to examine the molecular mechanism by which Hcy triggers oxidative stress and reduces bioavailability of nitric oxide (NO) in cardiac microvascular endothelial cells (MVEC). MVEC were cultured for 0-24 h with 0-100 microM Hcy. Differential expression of protease-activated receptors (PARs), thioredoxin, NADPH oxidase, endothelial NO synthase, inducible NO synthase, neuronal NO synthase, and dimethylarginine-dimethylaminohydrolase (DDAH) were measured by real-time quantitative RT-PCR. Reactive oxygen species were measured by using a fluorescent probe, 2',7'-dichlorofluorescein diacetate. Levels of asymmetric dimethylarginine (ADMA) were measured by ELISA and NO levels by the Griess method in the cultured MVEC. There were no alterations in the basal NO levels with 0-100 microM Hcy and 0-24 h of treatment. However, Hcy significantly induced inducible NO synthase and decreased endothelial NO synthase without altering neuronal NO synthase levels. There was significant accumulation of ADMA, in part because of reduced DDAH expression by Hcy in MVEC. Nitrotyrosine expression was increased significantly by Hcy. The results suggest that Hcy activates PAR-4, which induces production of reactive oxygen species by increasing NADPH oxidase and decreasing thioredoxin expression and reduces NO bioavailability in cultured MVEC by 1) increasing NO2-tyrosine formation and 2) accumulating ADMA by decreasing DDAH expression.     

The oxidative stress of zinc deficiency

Zinc is an essential catalytic and structural cofactor for many enzymes and other proteins. While Zn2+ is not redox active under physiological conditions, it has been known for many years that zinc deficiency causes increased oxidative stress and, consequently, increased oxidative damage to DNA, proteins, and lipids. These results have indicated that zinc plays an indirect antioxidant role and that dietary inadequacy may contribute to human diseases such as cancer. Recent studies are helping to identify the primary sources of oxidative stress in low zinc. In addition, through studies of the model eukaryotic cell, Saccharomyces cerevisiae, we are now beginning to understand the strategies cells use to limit this stress and reduce its damage.     

Extracellular ATP-mediated signaling for survival in hyperoxia-induced oxidative stress

Respiratory failure is a serious consequence of lung cell injury caused by treatment with high inhaled oxygen concentrations. Human lung microvascular endothelial cells (HLMVEC) are a principal target of hyperoxic injury (hyperoxia). Cell stress can cause release of ATP, and this extracellular nucleotide can activate purinoreceptors and mediate responses essential for survival. In this investigation, exposure of endothelial cells to an oxidative stress, hyperoxia, caused rapid but transient ATP release (20.03 +/- 2.00 nm/10(6) cells in 95% O(2) versus 0.08 +/- 0.01 nm/10(6) cells in 21% O2 at 30 min) into the extracellular milieu without a concomitant change in intracellular ATP. Endogenously produced extracellular ATP-enhanced mTOR-dependent uptake of glucose (3467 +/- 102 cpm/mg protein in 95% oxygen versus 2100 +/- 112 cpm/mg protein in control). Extracellular addition of ATP-activated important cell survival proteins like PI 3-kinase and extracellular-regulated kinase (ERK-1/2). These events were mediated primarily by P2Y receptors, specifically the P2Y2 and/or P2Y6 subclass of receptors. Extracellular ATP was required for the survival of HLMVEC in hyperoxia (55 +/- 10% surviving cells with extracellular ATP scavengers [apyrase + adenosine deaminase] versus 95 +/- 12% surviving cells without ATP scavengers at 4 d of hyperoxia). Incubation with ATP scavengers abolished ATP-dependent ERK phosphorylation stimulated by hyperoxia. Further, ERK activation also was found to be important for cell survival in hyperoxia, as treatment with PD98059 enhanced hyperoxia-mediated cell death. These findings demonstrate that ATP release and subsequent ATP-mediated signaling events are vital for survival of HLMVEC in hyperoxia.     

Magnesium deficiency increases oxidative stress in rats

Magnesium deficiency has been implicated in the development of atherosclerosis and late diabetic complications, diseases often associated with increased oxidative stress. Present study was carried out to examine the effect of magnesium deficiency on oxidative stress and total radical trapping antioxidant parameter (calculated) in rats and correlate it with the development of free radical mediated diseases. Male Wistar rats were divided into two groups and pair fed for six weeks with low magnesium diet (70 mg/kg) and control diet (990 mg/kg) prepared synthetically. Deionized water was given ad libitum. Low magnesium diet caused a significant decrease in plasma and red blood cell magnesium levels. A marked increase in plasma malondialdehyde and corresponding decrease in total radical trapping antioxidant parameters (calculated) were observed in the low magnesium diet group than control group. The level of plasma glucose increased moderately in the low magnesium diet group. Hypertriglyceridemia and significantly decreased plasma HDL (high density lipoprotein)-cholesterol levels were observed in the low magnesium diet group. The results clearly demonstrate that magnesium deficiency is associated with increased oxidative stress through reduction in plasma antioxidants and increased lipid peroxidation suggesting that the increased oxidative stress may be due to increased susceptibility of body organs to free radical injury.     

Mechanisms of siderophore iron transport in enteric bacteria.

Uptake of 55Fe- and 3H-labeled siderophores and their chronic analogues have been studied in Salmonella typhimurium LT-2 and Escherichia coli K-12. In S. typhimurium LT-2, at least two different mechanisms for siderophore iron transport may be operative. Uptake of 55Fe- and 3H-labeled ferrichrome and kinetically inert lambda-cis-chromic [3H]deferriferrichrome by the S. typhimurium LT-2 enb7 mutant, which is defective in the production of its native siderophore, enterobactin, appears to occur by two concurrent mechanisms. The first mechanism is postulated to involve either rapid uptake of iron released from the ferric complex by cellular reduction without penetration of the complex or ligand or dissociation of the complex and simultaneous uptake of both ligand and iron coupled with simultaneous expulsion of the ligand. The second mechanism appears to consist of slower uptake of the intact ferric complex.     

Mechanisms and regulation of iron and heme utilization in Gram-negative bacteria

Iron and heme are essential nutrients for most pathogenic microorganisms and play a pivotal role in microbial pathogenesis. To survive within the iron-limited environment of the host, bacteria utilize iron-siderophore complexes, iron-binding proteins (transferrin, lactoferrin), free heme and heme bound to hemoproteins (hemoglobin, haptoglobin, hemopexin). A mechanism of iron and heme transport depends on the structures of Gram-negative bacterial membranes. Siderophores, hemophores and outer membrane receptors take part in iron or heme binding. The transport of these ligands across the outer membrane involves outer membrane receptors. The energy for this transport is delivered from the inner membrane by a TonB-ExbB-ExbD complex. The transport across the cytoplasmic membrane involves periplasmic and inner membrane proteins comprising the ABC systems, which utilize the energy derived from ATP hydrolysis. The major regulatory role in iron homeostasis plays a Fur-Fe2+ repressor.     

Effects of iron deficiency and iron overload on angiogenesis and oxidative stress-a potential dual role for iron in breast cancer

Estrogen alone cannot explain the differences in breast cancer (BC) recurrence and incidence rates in pre- and postmenopausal women. In this study, we have tested a hypothesis that, in addition to estrogen, both iron deficiency due to menstruation and iron accumulation as a result of menstrual stop play important roles in menopause-related BC outcomes. We first tested this hypothesis in cell culture models mimicking the high-estrogen and low-iron premenopausal condition or the low-estrogen and high-iron postmenopausal condition. Subsequently, we examined this hypothesis in mice that were fed iron-deficient and iron-overloaded diets. We show that estrogen only slightly up-regulates vascular endothelial growth factor (VEGF), an angiogenic factor known to be important in BC recurrence. It is, rather, iron deficiency that significantly promotes VEGF by stabilizing hypoxia-inducible factor-1α. Conversely, high iron levels increase oxidative stress and sustain mitogen-activated protein kinase activation, which are mechanisms of known significance in BC development. Taken together, our results suggest, for the first time, that an iron-deficiency-mediated proangiogenic environment could contribute to the high recurrence of BC in young patients, and iron-accumulation-associated pro-oxidant conditions could lead to the high incidence of BC in older women.     

A virus capsid‐like nanocompartment that stores iron and protects bacteria from oxidative stress

Living cells compartmentalize materials and enzymatic reactions to increase metabolic efficiency. While eukaryotes use membrane‐bound organelles, bacteria and archaea rely primarily on protein‐bound nanocompartments. Encapsulins constitute a class of nanocompartments widespread in bacteria and archaea whose functions have hitherto been unclear. Here, we characterize the encapsulin nanocompartment from Myxococcus xanthus, which consists of a shell protein (EncA, 32.5 kDa) and three internal proteins (EncB, 17 kDa; EncC, 13 kDa; EncD, 11 kDa). Using cryo‐electron microscopy, we determined that EncA self‐assembles into an icosahedral shell 32 nm in diameter (26 nm internal diameter), built from 180 subunits with the fold first observed in bacteriophage HK97 capsid. The internal proteins, of which EncB and EncC have ferritin‐like domains, attach to its inner surface. Native nanocompartments have dense iron‐rich cores. Functionally, they resemble ferritins, cage‐like iron storage proteins, but with a massively greater capacity (~30,000 iron atoms versus ~3,000 in ferritin). Physiological data reveal that few nanocompartments are assembled during vegetative growth, but they increase fivefold upon starvation, protecting cells from oxidative stress through iron sequestration.     

The iron cycle and oxidative stress in the lung

Iron is critical for many aspects of cellular function, but it can also generate reactive oxygen species that can damage biological macromolecules. To limit oxidative stress, iron acquisition and its distribution must be tightly regulated. In the lungs, which are continuously exposed to the atmosphere, the risk of oxidative damage is particularly high because of the high oxygen concentration and the presence of significant amounts of catalytically active iron in atmospheric particulates. An effective system of metal detoxification must exist to minimize the associated generation of oxidative stress in the lungs. Here we summarize the evidence that a number of specific proteins that control iron uptake in the gastrointestinal tract are also employed in the lung to transport iron into epithelial cells and sequester it in a catalytically inactive form in ferritin. Furthermore, these and other proteins facilitate ferritin release from lung cells to the epithelial and bronchial lining fluids for clearance by the mucociliary system or to the reticuloendothelial system for long-term storage of iron. These pathways seem to be the primary mechanism for control of oxidative stress presented by iron in the respiratory tract.     

Non-anemic iron deficiency,oral iron supplementation,and oxidative damage in college-aged females

Oxidative damage, as indicated by protein carbonyl and lipid hydroperoxide concentrations, was assessed in the plasma of college-aged females with adequate iron status and with non-anemic iron deficiency before and after eight weeks of iron supplementation. At baseline, the mean serum ferritin, iron, transferrin saturation, and total iron binding capacity of the iron deficient group (n = 13) was significantly different from the iron adequate controls (n = 24). Mean plasma lipid hydroperoxide and protein carbonyl concentrations did not differ between groups at baseline. Following eight weeks of iron supplementation, the mean serum ferritin, iron, and transferrin saturation significantly increased and the total iron binding capacity significantly decreased in the iron deficient group. No significant differences in plasma lipid hydroperoxide or protein carbonyl concentrations were found between groups at the end of the study period. When plasma lipid hydroperoxide and protein carbonyl concentrations of subjects within groups were compared at the start versus at the end of the study, no significant differences were found for either group. Neither non-anemic iron deficiency nor its treatment with oral iron supplements is associated with oxidative damage in the plasma of college-aged females.     

Activation of Nrf2/Keap1 signaling and autophagy induction against oxidative stress in heart in iron deficiency

We investigated the effects of dietary iron deficiency on the redox system in the heart. Dietary iron deficiency increased heart weight and accumulation of carbonylated proteins. However, expression levels of heme oxygenase-1 and LC3-II, an antioxidant enzyme and an autophagic marker, respectively, in iron-deficient mice were upregulated compared to the control group, resulting in a surrogate phenomenon against oxidative stress.     

Iron homeostasis and management of oxidative stress response in bacteria

Iron is both an essential nutrient for the growth of microorganisms, as well as a dangerous metal due to its capacity to generate reactive oxygen species (ROS) via the Fenton reaction. For these reasons, bacteria must tightly control the uptake and storage of iron in a manner that restricts the build-up of ROS. Therefore, it is not surprising to find that the control of iron homeostasis and responses to oxidative stress are coordinated. The mechanisms concerned with these processes, and the interactions involved, are the subject of this review.     

Ozone-induced oxidative stress: Mechanisms of action and reaction

In this review we explore several models which might explain ozone (O₃)-induced injury to plant foliage. Ozone enters the cell through the wall and plasma membrane where active oxygen species are generated. If the concentration of O₃ is very high, unregulated cell death will occur. Alternatively, the active oxygen species, or succeeding reaction products, may serve as elicitors of regulated plant responses. These regulated responses include the induction of ethylene which could serve as a primary signal for—or a facilitator of—subsequent responses. The role of regulated suppression of photosynthetic genes and induction of chitinases and β-1,3-glucanase in programmed cell death is explored. Induction of antioxidants, enzymes of lignification and glutathione- S -transferase are discussed in the context of O₃-induced cell repair or cell protection. A second model is postulated to explain induction of accelerated foliar senescence by low levels of O₃. The notion that O₃-induced elicitation of responses in the nucleus might lead to increased oxidative stress in the chloroplast is considered as a mechanism for accelerating the rate of degradation of ribulose-1,5-bisphosphate car-boxylase/oxygenase (Rubisco). The mechanisms by which O₃ induces loss of Rubisco, and the relationship to accelerated foliar senescence are discussed.     

Protein mistranslation protects bacteria against oxidative stress

Accurate flow of genetic information from DNA to protein requires faithful translation. An increased level of translational errors (mistranslation) has therefore been widely considered harmful to cells. Here we demonstrate that surprisingly, moderate levels of mistranslation indeed increase tolerance to oxidative stress in Escherichia coli. Our RNA sequencing analyses revealed that two antioxidant genes katE and osmC, both controlled by the general stress response activator RpoS, were upregulated by a ribosomal error-prone mutation. Mistranslation-induced tolerance to hydrogen peroxide required rpoS, katE and osmC. We further show that both translational and post-translational regulation of RpoS contribute to peroxide tolerance in the error-prone strain, and a small RNA DsrA, which controls translation of RpoS, is critical for the improved tolerance to oxidative stress through mistranslation. Our work thus challenges the prevailing view that mistranslation is always detrimental, and provides a mechanism by which mistranslation benefits bacteria under stress conditions.