Iron is the intracellular metal involved in the production of DNA damage by oxygen radicals

Tremendous Fidelity of Vitamin D3 in Age-related Neurological Disorders

Vitamin D3 (VD) is a secosteroid hormone and shows a pleiotropic effect in brain-related disorders where it regulates redox imbalance, inflammation, apoptosis, energy production, and growth factor synthesis. Vitamin D3's active metabolic form, 1,25-dihydroxy Vitamin D3 (1,25(OH)2D3 or calcitriol), is a known regulator of several genes involved in neuroplasticity, neuroprotection, neurotropism, and neuroinflammation. Multiple studies suggest that VD deficiency can be proposed as a risk factor for the development of several age-related neurological disorders. The evidence for low serum levels of 25-hydroxy Vitamin D3 (25(OH)D3 or calcidiol), the major circulating form of VD, is associated with an increased risk of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), dementia, and cognitive impairment. Despite decades of evidence on low VD association with neurological disorders, the precise molecular mechanism behind its beneficial effect remains controversial. Here, we will be delving into the neurobiological importance of VD and discuss its benefits in different neuropsychiatric disorders. The focus will be on AD, PD, and HD as they share some common clinical, pathological, and epidemiological features. The central focus will be on the different attributes of VD in the aspect of its anti-oxidative, anti-inflammatory, anti-apoptotic, anti-cholinesterase activity, and psychotropic effect in different neurodegenerative diseases.

Genotoxic and mutagenic evaluation in Eisenia foetida annelids exposed to iron ore tailings from the region of Brumadinho, MG, Brazil

Soils that have a disproportion of metallic elements due to anthropic activities endanger the terrestrial fauna. This study evaluated whether earthworms (Eisenia foetida) exposed to ore tailings from Brumadinho region presented a higher frequency of genotoxic and mutagenic damages than annelids from a reference area (control). The animals were exposed to substrates containing 0%, 25%, 50%, 75%, and 100% iron mining waste. The results indicated increased DNA damage (p < 0.05), detected by the comet assay at 25% and 50%. There was a three-fold increase in micronuclei in animals on the substrates with the highest concentrations (75% and 100%) [F = 3.095; p = 0.02]. The earthworms lost weight as the percentage of mining waste increased. We concluded that E. foetida presented DNA damage in the contaminated soils of Brumadinho. However, more research is fundamental, once the environmental disaster in Brumadinho was one of the biggest mining catastrophe in Brazil.

Vitamin D suppresses ferroptosis and protects against neonatal hypoxic-ischemic encephalopathy by activating the Nrf2/HO-1 pathway

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is a major cause of neonatal death, and vitamin D (VD) is a neuroprotection nutrition whose deficiency is associated with its risk. However, the mechanism of VD involved in neonatal HIE is not well known.

METHODS

In this experiment a hypoxic-ischemic brain damage (HIBD) model was established by using the Rice-Vannucci method, rats were intraperitoneally injected with 0.1 µg/kg VD every day for two weeks. The brain damage and mitochondria injury were examined by hematoxylin-eosin (HE) staining and transmission electron microscope (TEM), respectively. The oxidation response and inflammatory factors were determined by enzyme-linked immunosorbent assay (ELISA), and the cell viability was determined by Cell Counting Kit-8 (CCK-8). mRNA and protein expression were detected by quantitative real real-time PCR (qRT-PCR), Western blot, and immunofluorescence.

RESULTS

The results showed VD effectively ameliorated brain histologic damage and mitochondria injury induced by hypoxic ischemia (HI). VD elevated the expression of Nrf2 and HO-1, which resulted in increased levels of GPX4, superoxide dismutase (SOD), and glutathione (GSH) and reduced content of malondialdehyde (MDA) and reactive oxygen species (ROS), resulting in decreased ferroptosis in HI-treated rats. Moreover, VD reduced the secretion of inflammatory factors, tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β.

CONCLUSIONS

VD suppresses ferroptosis through activation of the Nrf2/HO-1 signaling pathway and exerts a protective role in neonatal HIE.

Ferroin in dyes degradation by Fenton-like process: a chemical waste recycling perspective

Published literature describes the formation of the Fe (II)-phenanthroline complex (ferroin) as a stop way for Fenton processes, reducing radical yield. By contrast, this study presents evidence that ferroin can be activated by UVA in mildly acidic media in a photo-Fenton-like process. Because ferroin is the main waste from total iron determination in environmental samples, a recycling approach is suggested. Based on the best practices of waste management planning, an application of the proposed method for treating another chemical waste is presented. Titrimetric ammonia determination waste containing 2.67 mg L^-1 methyl red azo dye and 1.33 mg L^-1 methylene blue was degraded using the optimized experimental conditions: pH = 5.2-5.4; [H₂O₂] = 310 mg L^-1; [ferroin] = 1.4 mg L^-1; temperature = 36 ± 1 °C; reaction time = 165 min under UVA irradiation. Attenuation of most intense spectroscopic bands for the dyes achieved 94% (510 nm) and 96% (665 nm) reduction for methyl red and methylene blue, respectively, with degradation of ferroin itself. The present work brings empirical evidence that is possible to recycle ferroin as photo-Fenton-like process catalyst, as well as determine the best conditions for providing less acidic treated effluents with negligible suspended solid concentration, better than that obtained from classical photo-Fenton processes.

An Antifungal Polycyclic Tetramate Macrolactam, Heat-Stable Antifungal Factor (HSAF), Is a Novel Oxidative Stress Modulator in Lysobacter enzymogenes

Polycyclic tetramate macrolactams (PoTeMs) are a fast-growing family of antibiotic natural products found in phylogenetically diverse microorganisms. Surprisingly, none of the PoTeMs have been investigated for potential physiological functions in their producers. Here, we used heat-stable antifungal factor (HSAF), an antifungal PoTeM from Lysobacter enzymogenes, as a model to show that PoTeMs form complexes with iron ions, with an association constant (K_a ) of 2.71 × 10⁶ M^-1 The in vivo and in vitro data showed formation of 2:1 and 3:1 complexes between HSAF and iron ions, which were confirmed by molecular mechanical and quantum mechanical calculations. HSAF protected DNA from degradation in high concentrations of iron and H₂O₂ or under UV radiation. HSAF mutants of L. enzymogenes barely survived under oxidative stress and exhibited markedly increased production of reactive oxygen species (ROS). Exogenous addition of HSAF into the mutants significantly prevented ROS production and restored normal growth in the mutants under the oxidative stress. The results reveal that the function of HSAF is to protect the producer microorganism from oxidative damage rather than as an iron-acquisition siderophore. The characteristic structure of PoTeMs, a 2,4-pyrrolidinedione-embedded macrolactam, may represent a new iron-chelating scaffold of microbial metabolites. The study demonstrated a previously unrecognized strategy for microorganisms to modulate oxidative damage to the cells.IMPORTANCE PoTeMs are a family of structurally distinct metabolites that have been found in a large number of bacteria. Although PoTeMs exhibit diverse therapeutic properties, the physiological function of PoTeMs in the producer microorganisms had not been investigated. HSAF from Lysobacter enzymogenes is an antifungal PoTeM that has been subjected to extensive studies for mechanisms of biosynthesis, regulation, and antifungal activity. Using HSAF as a model system, we here showed that the characteristic structure of PoTeMs, a 2,4-pyrrolidinedione-embedded macrolactam, may represent a new iron-chelating scaffold of microbial metabolites. In L. enzymogenes, HSAF functions as a small-molecule modulator for oxidative damage caused by iron, H₂O₂, and UV light. Together, the study demonstrated a previously unrecognized strategy for microorganisms to modulate oxidative damage to the cells. HSAF represents the first member of the fast-growing PoTeM family of microbial metabolites whose potential biological function has been studied.

Mitochondrial reactive oxygen species and heme, non-heme iron metabolism

Mitochondria are one of the most important organelles for eukaryotes, including humans, to produce energy. In the energy-producing process, mitochondria constantly generate reactive oxygen species as a by-product of electrons leaking out from the electron transport chain react with oxygen. The active oxygen, in turn, plays pivotal roles in mediating several signalings, including those that are implicated in the development of some diseases such as neurodegenerative disease, cardiovascular disease, and carcinogenesis. This signaling, derived from mitochondrial reactive oxygen species, also affects intracellular iron homeostasis by regulating the expression of transporters. Heme iron is incorporated into cells through HCP1, and non-heme iron is transported by DMT1 in absorptive cells. Intracellular iron is exported by ferroportin and bound with transferrin. In most types of cell including erythrocyte, transferrin-bound iron is incorporated through transferrin-transferrin receptor system. We previously reported that the expression of HCP1 and DMT1 was upregulated in cancer cells and that overexpression of manganese superoxide dismutase, which is a mitochondrial-specific superoxide dismutase, downregulated the expression. These findings indicate that mitochondrial reactive oxygen species is associated with iron-related oxidative reactions. Recently, a mitochondria-specific iron transporter, mitoferrin, was identified, and the relationships among mitochondria, iron transportation, and diseases have been increasingly clarified.

Bioactive Polyphenols and Neuromodulation: Molecular Mechanisms in Neurodegeneration

The interest in dietary polyphenols in recent years has greatly increased due to their antioxidant bioactivity with preventive properties against chronic diseases. Polyphenols, by modulating different cellular functions, play an important role in neuroprotection and are able to neutralize the effects of oxidative stress, inflammation, and apoptosis. Interestingly, all these mechanisms are involved in neurodegeneration. Although polyphenols display differences in their effectiveness due to interindividual variability, recent studies indicated that bioactive polyphenols in food and beverages promote health and prevent age-related cognitive decline. Polyphenols have a poor bioavailability and their digestion by gut microbiota produces active metabolites. In fact, dietary bioactive polyphenols need to be modified by microbiota present in the intestine before being absorbed, and to exert health preventive effects by interacting with cellular signalling pathways. This literature review includes an evaluation of the literature in English up to December 2019 in PubMed and Web of Science databases. A total of 307 studies, consisting of research reports, review articles and articles were examined and 146 were included. The review highlights the role of bioactive polyphenols in neurodegeneration, with a particular emphasis on the cellular and molecular mechanisms that are modulated by polyphenols involved in protection from oxidative stress and apoptosis prevention.

Ironing the mitochondria: Relevance to its dynamics

The mitochondrion is "jack of many trades and master of one". Despite being a master in energy generation, it plays a significant role in other cellular processes, including calcium homeostasis, cell death, and iron metabolism. Since mitochondria employ the majority of cellular iron, it plays a central role in the iron homeostasis. Iron could be a major regulator of mitochondrial dynamics as the excess of iron leads to oxidative stress, which causes a disturbance in mitochondrial dynamics. Remarkably, abnormal iron accumulation has been observed in the brain regions of the neurodegenerative disorders patients. These neurodegenerative disorders are also often associated with the abnormal mitochondrial dynamics. Here in this article, we will mainly discuss the studies focused on unravelling the role of iron in mitochondrial dynamics.

Oxidation Chemistry of DNA and p53 Tumor Suppressor Gene

The chemistry of DNA and its repair selectivity control the influence of genomic oxidative stress on the development of serious disorders such as cancer and heart diseases. DNA is oxidized by endogenous reactive oxygen species (ROS) in vivo or in vitro as a result of high energy radiation, non-radiative metabolic processes, and other consequences of oxidative stress. Some oxidations of DNA and tumor suppressor gene p53 are thought to be mutagenic when not repaired. For example, site-specific oxidations of p53 tumor suppressor gene may lead to cancer-related mutations at the oxidation site codon. This review summarizes the research on the primary products of the most easily oxidized nucleobase guanine (G) when different oxidation methods are used. Guanine is by far the most oxidized DNA base. The primary initial oxidation product of guanine for most, but not all, pathways is 8-oxoguanine (8-oxoG). With an oxidation potential much lower than G, 8-oxoG is readily susceptible to further oxidation, and the products often depend on the oxidants. Specific products may control the types of subsequent mutations, but mediated by gene repair success. Site-specific oxidations of p53 tumor suppressor gene have been reported at known mutation hot spots, and the codon sites also depend on the type of oxidants. Modern methodologies using LC-MS/MS for codon specific detection and identification of oxidation sites are summarized. Future work aimed at understanding DNA oxidation in nucleosomes and interactions between DNA damage and repair is needed to provide a better picture of how cancer-related mutations arise.

Reactive Oxygen Species Generation in Human Cells by a Novel Magnetic Resonance Imaging Contrast Agent

The novel positive-contrast magnetic resonance imaging (MRI) marker C4 consists of an aqueous solution of cobalt chloride (CoCl₂) complexed with the chelator N-acetylcysteine (NAC). We evaluated whether the presence of C4 or its components would produce reactive oxygen species (ROS, including hydroxyl, peroxyl, or other reactive oxygen species) in cultured cells. Human cancer or normal cells were incubated with 1% (w/v) CoCl₂·6H₂O or 2% NAC or a combination of both (1% CoCl₂·6H₂O : 2% NAC in an aqueous solution, abbreviated as Co : NAC) in the presence or absence of H₂O₂. Intracellular ROS levels were measured and quantified by change in relative fluorescence units. Student's t-tests were used. In all cell lines exposed to 1000 μM H₂O₂, the Co : NAC led to ≥94.7% suppression of ROS at 5 minutes and completely suppressed ROS at 60 and 90 minutes; NAC suppressed ROS by ≥76.6% at 5 minutes and by ≥94.5% at 90 minutes; and CoCl₂·6H₂O suppressed ROS by ≥37.2% at 30 minutes and by ≥48.6% at 90 minutes. These results demonstrate that neither Co : NAC nor its components generated ROS; rather, they suppressed ROS production in cultured cells, suggesting that C4 would not enhance ROS production in clinical use.

Crucial role of chelatable iron in silver nanoparticles induced DNA damage and cytotoxicity

Damage to mitochondria and subsequent ROS leakage is a commonly accepted mechanism of nanoparticle toxicity. However, malfunction of mitochondria results in generation of superoxide anion radical (O₂^•-), which due to the relatively low chemical reactivity is rather unlikely to cause harmful effects triggered by nanoparticles. We show that treatment of HepG2 cells with silver nanoparticles (AgNPs) resulted in generation of H₂O₂ instead of O₂^•-, as measured by ROS specific mitochondrial probes. Moreover, addition of a selective iron chelator diminished AgNPs toxicity. Altogether these results suggest that O₂^•- generated during NPs induced mitochondrial collapse is rapidly dismutated to H₂O₂, which in the presence of iron ions undergoes a Fenton reaction to produce an extremely reactive hydroxyl radical (^•OH). Clarification of the mechanism of NPs-dependent generation of ^•OH and demonstration of the crucial role of iron ions in NPs toxicity will facilitate our understanding of NPs toxicity and the design of safe nanomaterials.

•

Superoxide radical is the main product generated by nanosilver exposed mitochondria.

•

Iron chelation prevent the cell from nanosilver induced DNA damage.

•

Iron chelation diminish nanosilver cytotoxicity.

•

Nanosilver toxicity depends on Fenton reaction involving superoxide-derived H₂O₂.

Vitamin D and Its Role in Neonatal Hypoxic-Ischemic Brain Injury

Emerging evidence has demonstrated that vitamin D plays an important role in many adult neurologic disorders, but is also critical in neuronal development and pruning in the neonatal and pediatric populations. Neonates are at a particularly high risk of vitamin D deficiency, in part due to the high prevalence of maternal deficiency during pregnancy. Several preclinical studies have demonstrated that infants born to vitamin D-deficient mothers are at a high risk of developing neonatal brain injury, and recent clinical studies have shown that neonates with hypoxic-ischemic encephalopathy (HIE) tend to be vitamin D-deficient. There are limited data, however, on whether additional prenatal or postnatal supplementation may alter the prevalence or severity of neonatal HIE. This review examines the current data supporting the neuroprotective role of vitamin D, with a focus on how these findings may be translated to neonates with HIE.

DNA agarose gel electrophoresis for antioxidant analysis: Development of a quantitative approach for phenolic extracts

Most of the fast in vitro assays proposed to determine the antioxidant capacity of a compound/extract lack either biological context or employ complex protocols. Therefore, the present work proposes the improvement of an agarose gel DNA electrophoresis in order to allow for a quantitative estimation of the antioxidant capacity of pure phenolic compounds as well as of a phenolic rich extract, while also considering their possible pro-oxidant effects. The result obtained demonstrated that the proposed method allowed for the evaluation of the protection of DNA oxidation [in the presence of hydrogen peroxide (H₂O₂) and an H₂O₂/iron (III) chloride (FeCl₃) systems] as well as for the observation of pro-oxidant activities, with the measurements registering interclass correlation coefficients above 0.9. Moreover, this method allowed for the characterization of the antioxidant capacity of a blueberry extract while demonstrating that it had no perceived pro-oxidant effect.

Geno- and cytotoxicity induced on Cyprinus carpio by aluminum, iron, mercury and mixture thereof

Metals such as Al, Fe and Hg are used in diverse anthropogenic activities. Their presence in water bodies is due mainly to domestic, agricultural and industrial wastewater discharges and constitutes a hazard for the organisms inhabiting these environments. The present study aimed to evaluate geno- and cytotoxicity induced by Al, Fe, Hg and the mixture of these metals on blood of the common carp Cyprinus carpio. Specimens were exposed to the permissible limits in water for human use and consumption according to the pertinent official Mexican norm [official Mexican norm NOM-127-SSA1-1994] Al (0.2mgL^-1), Fe (0.3mgL^-1), Hg (0.001mgL^-1) and their mixture for 12, 24, 48, 72 and 96h. Biomarkers of genotoxicity (comet assay and micronucleus test) and cytotoxicity (caspase-3 activity and TUNEL assay) were evaluated. Significant increases relative to the control group (p<0.05) were observed in all biomarkers at all exposure times in all test systems; however, damage was greater when the metals were present as a mixture. Furthermore, correlations between metal concentrations and biomarkers of geno- and cytotoxicity were found only at certain exposure times. In conclusion, Al, Fe, Hg and the mixture of these metals induce geno- and cytotoxicity on blood of C. carpio.

Does any drug to treat cancer target mTOR and iron hemostasis in neurodegenerative disorders?

The prevalence of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease are increased by age. Alleviation of their symptoms and protection of normal neurons against degeneration are the main aspects of the research to establish novel therapeutic strategies. Iron as the one of most important cation not only play important role in the structure of electron transport chain proteins but also has pivotal duties in cellular activities. But disruption in iron hemostasis can make it toxin to neurons which causes lipid peroxidation, DNA damage and etc. In patients with Alzheimer and Parkinson misbalancing in iron homeostasis accelerate neurodegeneration and cause neuroinflmmation. mTOR as the common signaling pathway between cancer and neurodegenerative disorders controls iron uptake and it is in active form in both diseases. Anti-cancer drugs which target mTOR causes iron deficiency and dual effects of mTOR inhibitors can candidate them as a therapeutic strategy to alleviate neurodegeneration/inflammation because of iron overloading.

A Potential Alternative against Neurodegenerative Diseases: Phytodrugs

Neurodegenerative diseases (ND) primarily affect the neurons in the human brain secondary to oxidative stress and neuroinflammation. ND are more common and have a disproportionate impact on countries with longer life expectancies and represent the fourth highest source of overall disease burden in the high-income countries. A large majority of the medicinal plant compounds, such as polyphenols, alkaloids, and terpenes, have therapeutic properties. Polyphenols are the most common active compounds in herbs and vegetables consumed by man. The biological bioactivity of polyphenols against neurodegeneration is mainly due to its antioxidant, anti-inflammatory, and antiamyloidogenic effects. Multiple scientific studies support the use of herbal medicine in the treatment of ND; however, relevant aspects are still pending to explore such as metabolic analysis, pharmacokinetics, and brain bioavailability.

Synthesis, characterization, DFT calculations, and electrochemical comparison of novel iron(ii) complexes with thione and selone ligands

Characterization of Fe(ii)–thone and –selone complexes revealed that these ligands oxidize before Fe(ii), suggesting an iron-binding mechanism for similar antioxidants.

Effect of antioxidants on the genotoxicity of phenethyl isothiocyanate

Isothiocyanates are plant-derived compounds that may be beneficial in the prevention of certain chronic diseases. Yet, by stimulating the production of reactive oxygen species (ROS), isothiocyanates can be genotoxic. Whether antioxidants influence isothiocyanate-induced genotoxicity is unclear, but this situation was clarified appreciably herein. In HCT116 cells, phenethyl isothiocyanate (PEITC) increased ROS production, which was inhibited by N-acetylcysteine (NAC) and deferoxamine (DFO) but not by ascorbic acid (ASC) and trolox (TRX) that were found to be more potent radical scavengers. Surprisingly, ASC and TRX each intensified the DNA damage that was caused by PEITC, but neither ASC nor TRX by themselves caused any DNA damage. In contrast, NAC and DFO each not only attenuated PEITC-induced DNA damage but also attenuated the antioxidant-intensified, PEITC-induced DNA damage. To determine if the DNA damage could be related to possible changes in the major antioxidant defence system, glutathione (GSH) was investigated. PEITC lowered GSH levels, which was prevented by NAC, whereas ASC, TRX and DFO neither inhibited nor enhanced the GSH-lowering effect of PEITC. The GSH synthesis inhibitor, buthionine sulphoxime, intensified PEITC-induced DNA damage, although by itself buthionine sulphoxime did not directly cause DNA damage. The principal findings suggest that ASC and TRX make PEITC more genotoxic, which might be exploited in killing cancer cells as one approach in killing cancer cells is to extensively damage their DNA so as to initiate apoptosis.

Mitochondrial iron homeostasis and its dysfunctions in neurodegenerative disorders

Synthesis of the iron-containing prosthetic groups-heme and iron-sulfur clusters-occurs in mitochondria. The mitochondrion is also an important producer of reactive oxygen species (ROS), which are derived from electrons leaking from the electron transport chain. The coexistence of both ROS and iron in the secluded space of the mitochondrion makes this organelle particularly prone to oxidative damage. Here, we review the elements that configure mitochondrial iron homeostasis and discuss the principles of iron-mediated ROS generation in mitochondria. We also review the evidence for mitochondrial dysfunction and iron accumulation in Alzheimer's disease, Huntington Disease, Friedreich's ataxia, and in particular Parkinson's disease. We postulate that a positive feedback loop of mitochondrial dysfunction, iron accumulation, and ROS production accounts for the process of cell death in various neurodegenerative diseases in which these features are present.

Iron, oxidative stress and gestational diabetes

Both iron deficiency and hyperglycemia are highly prevalent globally for pregnant women. Iron supplementation is recommended during pregnancy to control iron deficiency. The purposes of the review are to assess the oxidative effects of iron supplementation and the potential relationship between iron nutrition and gestational diabetes. High doses of iron (~relative to 60 mg or more daily for adult humans) can induce lipid peroxidation in vitro and in animal studies. Pharmaceutical doses of iron supplements (e.g., 10× RDA or more for oral supplements or direct iron supplementation via injection or addition to the cell culture medium) for a short or long duration will induce DNA damage. Higher heme-iron intake or iron status measured by various biomarkers, especially serum ferritin, might contribute to greater risk of gestational diabetes, which may be mediated by iron oxidative stress though lipid oxidation and/or DNA damage. However, information is lacking about the effect of low dose iron supplementation (≤60 mg daily) on lipid peroxidation, DNA damage and gestational diabetes. Randomized trials of low-dose iron supplementation (≤60 mg daily) for pregnant women are warranted to test the relationship between iron oxidative stress and insulin resistance/gestational diabetes, especially for iron-replete women.

The interplay between iron accumulation, mitochondrial dysfunction, and inflammation during the execution step of neurodegenerative disorders

A growing set of observations points to mitochondrial dysfunction, iron accumulation, oxidative damage and chronic inflammation as common pathognomonic signs of a number of neurodegenerative diseases that includes Alzheimer’s disease, Huntington disease, amyotrophic lateral sclerosis, Friedrich’s ataxia and Parkinson’s disease. Particularly relevant for neurodegenerative processes is the relationship between mitochondria and iron. The mitochondrion upholds the synthesis of iron–sulfur clusters and heme, the most abundant iron-containing prosthetic groups in a large variety of proteins, so a fraction of incoming iron must go through this organelle before reaching its final destination. In turn, the mitochondrial respiratory chain is the source of reactive oxygen species (ROS) derived from leaks in the electron transport chain. The co-existence of both iron and ROS in the secluded space of the mitochondrion makes this organelle particularly prone to hydroxyl radical-mediated damage. In addition, a connection between the loss of iron homeostasis and inflammation is starting to emerge; thus, inflammatory cytokines like TNF-alpha and IL-6 induce the synthesis of the divalent metal transporter 1 and promote iron accumulation in neurons and microglia. Here, we review the recent literature on mitochondrial iron homeostasis and the role of inflammation on mitochondria dysfunction and iron accumulation on the neurodegenerative process that lead to cell death in Parkinson’s disease. We also put forward the hypothesis that mitochondrial dysfunction, iron accumulation and inflammation are part of a synergistic self-feeding cycle that ends in apoptotic cell death, once the antioxidant cellular defense systems are finally overwhelmed.

Impact of antioxidants on the ability of phenolic phytochemicals to kill HCT116 colon cancer cells

Certain phenolic phytochemicals can kill cancer cells. Possible interference from antioxidants is a concern, and this issue has not been studied appreciably. Therefore, the effect of ascorbate and N-acetylcysteine on the ability of epigallocatechin gallate (EGCG) and curcumin to kill HCT116 colon cancer cells was examined. EGCG and curcumin each caused DNA damage in the cells. The DNA-damaging ability of EGCG, but not curcumin, was hindered by either ascorbate or NAC, which was also shown in HT29 and SW480 colon cancer cells. Also, iron chelators (deferoxamine and 2,2'-dipyridyl) inhibited the ability of EGCG, but not curcumin, to cause damage to the DNA in HCT116 cells. Interestingly, curcumin, but not EGCG, increased the expression of growth arrest and DNA damage-inducible gene 153 and also heme oxygenase-1, and this stress gene upregulation by curcumin was antioxidant-insensitive. With prolonged incubation of HCT116 cells with either EGCG or curcumin, cell shrinkage, membrane blebbing, apoptotic bodies, and chromatin condensation/fragmentation were observed. These morphological changes were not apparent in EGCG-treated cells that had been pretreated with either ascorbate or NAC. However, the ascorbate and NAC pretreatments did not prevent the occurrence of the morphological changes in curcumin-treated cells. Thus, these findings suggest that ascorbate and NAC interfere with the ability of EGCG, but not curcumin, to kill HCT116 cells. This basic knowledge may help to better plan and optimize strategies for chemoprevention or chemotherapy.

Novel chelators for cancer treatment: where are we now?

SIGNIFICANCE

Under normal circumstances, cellular iron levels are tightly regulated due to the potential toxic effects of this metal ion. There is evidence that tumors possess altered iron homeostasis, which is mediated by the perturbed expression of iron-related proteins, for example, transferrin receptor 1, ferritin and ferroportin 1. The de-regulation of iron homeostasis in cancer cells reveals a particular vulnerability to iron-depletion using iron chelators. In this review, we examine the absorption of iron from the gut; its transport, metabolism, and homeostasis in mammals; and the molecular pathways involved. Additionally, evidence for alterations in iron processing in cancer are described along with the perturbations in other biologically important transition metal ions, for example, copper(II) and zinc(II). These changes can be therapeutically manipulated by the use of novel chelators that have recently been shown to be highly effective in terms of inhibiting tumor growth.

RECENT ADVANCES

Such chelators include those of the thiosemicarbazone class that were originally thought to target only ribonucleotide reductase, but are now known to have multiple effects, including the generation of cytotoxic radicals.

CRITICAL ISSUES

Several chelators have shown marked anti-tumor activity in vivo against a variety of solid tumors. An important aspect is the toxicology and the efficacy of these agents in clinical trials.

FUTURE DIRECTIONS

As part of the process of the clinical assessment of the new chelators, an extensive toxicological assessment in multiple animal models is essential for designing appropriate dosing protocols in humans.

Antioxidant Activity of Porcelainberry (Ampelopsis brevipedunculata(Maxim.) Trautv.)

The stem and root of Porcelainberry (Ampelopsis brevipedunculata (Maxim.) Trautv.) (AB) was traditionally used as an anti-inflammatory, diuretic and anti-hepatotoxic agent in folk medicine. In this study, cell-free and cell culture systems were employed to investigate the antioxidant activity of the methanol extract of AB (MEAB). The cell-free system showed that the MEAB exhibited dose-dependent antioxidant activities against linoleic acid peroxidation and plasmid DNA oxidation. We also demonstrated that the MEAB possessed strong reducing power and scavenging effects of hydroxyl radicals and DPPH free radicals.

The harmful effects of reactive oxygen metabolites on HepG2 cells and the possible antioxidant effects of the MEAB were also investigated. Pretreatment or cotreatment of HepG2 cells with the MEAB could significantly protect cells from H 2 O 2-induced oxidative stress. This implies that the antioxidant effects in cell culture may result from the direct interaction between the MEAB and exogenous oxidant sources, as these occur in cell free systems, as well as from the induction of cellular stress gene expression. The antioxidant activity of the MEAB may partially explain its anti-inflammatory and anti-hepatotoxic effects.

Antioxidant Activity of Methanol Extract of the Lotus Leaf (Nelumbo nucifera Gertn.)

In this study, hydrogen peroxide ( H 2 O 2)-mediated Caco-2 cytotoxicity was employed to investigate the potential antioxidant activity of the methanol extract from the lotus leaf (Nelumbo nucifera Gertn.). A dose-dependent protective effect against reactive oxygen species (ROS)-induced cytotoxicity was observed when Caco-2 cells were treated with 10 mM H 2 O 2 in combination with the methanol extract of the lotus leaf (0.1–0.3 mg/ml). However, no significant effect was found when co-treating Caco-2 cells with 10 mM H 2 O 2 and α-tocopherol. In vitro assay revealed that the extract exhibited scavenging activities on free radicals and hydroxyl radicals, and metal binding ability as well as reducing power, which may explain in part the mechanism behind the extract's ability to protect cells from oxidative damage. In addition, the extract also exhibited concentration-dependent antioxidant activities against hemoglobin-induced linoleic acid peroxidation and Fenton reaction-mediated plasmid DNA oxidation.

Iron and vascular calcification. Is there a link?

Iron deficiency is frequently seen in patients with end-stage renal disease, particularly in those treated by dialysis, this is because of an impairment in gastrointestinal absorption and ongoing blood losses or alternatively, due to an impaired capacity to mobilize iron from its stores, called functional iron deficiency. Therefore, these patients may require intravenous iron to sustain adequate treatment with erythropoietin-stimulating agents. Aside from this, they are also prone to vascular calcification, which has been reported a major contributing factor in the development of cardiovascular disease and the increased mortality associated herewith. Several factors and mechanisms underlying the development of vascular calcification in chronic kidney diseased patients have been put forward during recent years. In view of the ability of iron to exert direct toxic effects and to induce oxidative stress on the one hand versus its essential role in various cellular processes on the other hand, the possible role of iron in the development of vascular calcification should be considered.

Antioxidant activity of sulfur and selenium: a review of reactive oxygen species scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms

It is well known that oxidation caused by reactive oxygen species (ROS) is a major cause of cellular damage and death and has been implicated in cancer, neurodegenerative, and cardiovascular diseases. Small-molecule antioxidants containing sulfur and selenium can ameliorate oxidative damage, and cells employ multiple antioxidant mechanisms to prevent this cellular damage. However, current research has focused mainly on clinical, epidemiological, and in vivo studies with little emphasis on the antioxidant mechanisms responsible for observed sulfur and selenium antioxidant activities. In addition, the antioxidant properties of sulfur compounds are commonly compared to selenium antioxidant properties; however, sulfur and selenium antioxidant activities can be quite distinct, with each utilizing different antioxidant mechanisms to prevent oxidative cellular damage. In the present review, we discuss the antioxidant activities of sulfur and selenium compounds, focusing on several antioxidant mechanisms, including ROS scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms. Findings of several recent clinical, epidemiological, and in vivo studies highlight the need for future studies that specifically focus on the chemical mechanisms of sulfur and selenium antioxidant behavior.

Clustered DNA lesion sites as a source of mutations during human colorectal tumourigenesis

The role of gene mutations in tumourigenesis is well understood, however, the mechanism(s) by which they arise are less clear. Indeed, the common assumption that tumourigenic mutations are the result of DNA replication errors is apparently contradicted by the very low division frequency of the cells from which tumours are thought to arise (i.e. deep stem cells). As a potential solution to this paradox, we tested a model whereby clustered DNA lesion sites (CLS) (where several lesions occur within a few base pairs of each other on opposing strands) could give rise to mutations in quiescent cells. We used statistical analyses to search for sets of dinucleotide sequences (designated target sequences) that are present at and in close proximity to mutation sites in four genes associated with human colorectal tumourigenesis (adenomatosis polyposis coli (APC), v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphoinositide-3-kinase, catalytic, alpha polypeptide (PIK3CA), and tumour protein p53 (TP53)). The dinucleotides CG, AC-GT, TG, and GC were identified as target sequences in at least three of the genes analysed. Consistent with their designation as target sequences, these dinucleotides have all been identified as high probability sites of oxidative damage formation in in vitro studies. Our results strongly suggest a statistical association between the presence of multiple, clustered target sequences and mutational events. We propose that CLS are a major source of mutations during human tumourigenesis.

Oxidative stress and aging: the potential role of iron

According to the free radical theory of aging proposed by Denham Harman more than 50 years ago, oxidatively modified cellular components accumulate continuously in the cells during the organism's lifespan leading to progressive decline of cellular functions. Since then, it has been shown that proteins, lipids, nucleic acids and other cell components undergo reversible and/or irreversible oxidative modifications during aging. Moreover, oxidized cell components can undergo further oxidative modifications leading to formation of products that cell degradation systems are incapable of removing. Accumulation of such non-degradable aggregates further inhibits the functionality of degradation systems, thus aggravating the effects and leading to a vicious cycle. In this presentation, we propose that the availability of intracellular iron in its redox active form (labile iron) represents the main catalyst that mediates extensive oxidative modifications of cellular components and ultimately leads to their accumulation and consequent cellular dysfunction. It is tempting to speculate that regulated restriction of labile iron may have positive effects on health in general and aging in particular.

Metal-catalyzed oxidation of the Werner syndrome protein causes loss of catalytic activities and impaired protein-protein interactions

Metal-catalyzed oxidation reactions target amino acids in the metal binding pocket of proteins. Such oxidation reactions generally result in either preferential degradation of the protein or accumulation of a catalytically inactive pool of protein with age. Consistently, levels of oxidized proteins have been shown to increase with age. The segmental, progeroid disorder Werner syndrome results from loss of the Werner syndrome protein (WRN). WRN is a member of the RecQ family of DNA helicases and possesses exonuclease and ATP-dependent helicase activities. Furthermore, each of the helicase and exonuclease domains of WRN contains a metal binding pocket. In this report we examined for metal-catalyzed oxidation of WRN in the presence of iron or copper. We found that WRN was oxidized in vitro by iron but not by copper. Iron-mediated oxidation resulted in the inhibition of both WRN helicase and exonuclease activities. Oxidation of WRN also inhibited binding to several known protein partners. In addition, we did not observe degradation of oxidized WRN by the 20 S proteasome in vitro. Finally, exposure of cells to hydrogen peroxide resulted in oxidation of WRN in vivo. Therefore, our results demonstrate that WRN undergoes metal-catalyzed oxidation in the presence of iron, and iron-mediated oxidation of WRN likely results in the accumulation of a catalytically inactive form of the protein, which may contribute to age-related phenotypes.

Effects of inorganic selenium compounds on oxidative DNA damage

Exposure of Escherichia coli or mammalian cells to H2O2 results in cell death due to iron-mediated DNA damage. Since selenium compounds have been examined for their ability to act as antioxidants to neutralize radical species, and inorganic selenium compounds are used to supplement protein mixes, infant formula, and animal feed, determining the effect of these compounds on DNA damage under conditions of oxidative stress is crucial. In the presence of Fe(II) and H2O2, the effects of Na2SeO4, Na2SeO3, SeO2 (0.5-5000 microM), and Na2Se (0.5-200 microM) on DNA damage were quantified using gel electrophoresis. Both Na2SeO4 and Na2Se have no effect on DNA damage, whereas SeO2 inhibits DNA damage and Na2SeO3 shows antioxidant or pro-oxidant activity depending on H2O2 concentration. Similar electrophoresis experiments with [Fe(EDTA)](2-) (400 microM) and Na2SeO3 or SeO2 show that metal coordination by the selenium compound is required for antioxidant activity. In light of these results, Na2SeO4 may be safer than Na2SeO3 for nutritional supplements.

Ultra high frequency-electromagnetic field irradiation during pregnancy leads to an increase in erythrocytes micronuclei incidence in rat offspring

Mobile telephones and their base stations are an important ultra high frequency-electromagnetic field (UHF-EMF) source and their utilization is increasing all over the world. Epidemiological studies suggested that low energy UHF-EMF emitted from a cellular telephone may cause biological effects, such as DNA damage and changes on oxidative metabolism. An in vivo mammalian cytogenetic test, the micronucleus (MN) assay, was used to investigate the occurrence of chromosomal damage in erythrocytes from rat offspring exposed to a non-thermal UHF-EMF from a cellular phone during their embryogenesis; the irradiated group showed a significant increase in MN occurrence. In order to investigate if UHF-EMF could also alter oxidative parameters in the peripheral blood and in the liver - an important hematopoietic tissue in rat embryos and newborns - we also measured the activity of antioxidant enzymes, quantified total sulfhydryl content, protein carbonyl groups, thiobarbituric acid-reactive species and total non-enzymatic antioxidant defense. No significant differences were found in any oxidative parameter of offspring blood and liver. The average number of pups in each litter has also not been significantly altered. Our results suggest that, under our experimental conditions, UHF-EMF is able to induce a genotoxic response in hematopoietic tissue during the embryogenesis through an unknown mechanism.

Comparative corrosion study of "Ni-free" austenitic stainless steels in view of medical applications

The role of nickel in the biological response to alloys used in medical devices is of immense significance with regard to toxicology and biological performance. There is now a tendency to take nickel out of alloys for medical applications. However, this needs careful evaluation since no compromise is acceptable with regard to mechanical properties, corrosion resistance or any other harmful consequences due to the nickel substitution. This paper analyses the corrosion behaviour and cations released for five austenitic steels, nominally "nickel-free". The analysis of electrochemical parameters, open circuit potential, polarisation resistance, Tafel slopes, corrosion current, breakdown potential, potentiodynamic polarisation curves, and coulometric analysis by zone, reveal that the new austenitic steels, nominally "nickel-free", do not behave in the same way. In the family of steels studied, quite a large dispersion is noted in the corrosion behaviour. With regard to the crevice corrosion behaviour, the steel grades studied can be classified into three groups, with crevice potentials of 600-650mV; 350-450mV and 100-150mV. The release of 18 cations (Al, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, P, Pb, Sn, Sr, Ti, and V) was studied by extraction tests in artificial sweat and bone plasma fluid. The extraction tests reveal that the "nickel-free" steels indeed release only faint traces of nickel. Yet many other elements, some of them potentially harmful, are released in significant amounts. Generally, the amount of cations released is substantially higher in the artificial sweat solution than in the bone plasma.

Interaction of stannous chloride leads to alteration in DNA, triphosphate nucleotides and isolated bases

Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with SnCl2 and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry. Data showed that more than 40% of the initial SnCl2 concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed lesions.