Generation of reactive oxygen species by Co(II) from H2O2 in the presence of chelators in relation to DNA damage and 2'-deoxyguanosine hydroxylation

Sex-specific and dose-response relationships of urinary cobalt and molybdenum levels with glucose levels and insulin resistance in U.S. adults

Growing studies have linked metal exposure to diabetes risk. However, these studies had inconsistent results. We used a multiple linear regression model to investigate the sex-specific and dose-response associations between urinary metals (cobalt (Co) and molybdenum (Mo)) and diabetes-related indicators (fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), homeostasis model assessment for insulin resistance (HOMA-IR), and insulin) in a cross-sectional study based on the United States National Health and Nutrition Examination Survey. The urinary metal concentrations of 1423 eligible individuals were stratified on the basis of the quartile distribution. Our results showed that the urinary Co level in males at the fourth quartile (Q4) was strongly correlated with increased FPG (β = 0.61, 95% CI: 0.17-1.04), HbA1c (β = 0.31, 95% CI: 0.09-0.54), insulin (β = 8.18, 95% CI: 2.84-13.52), and HOMA-IR (β = 3.42, 95% CI: 1.40-5.44) when compared with first quartile (Q1). High urinary Mo levels (Q4 vs. Q1) were associated with elevated FPG (β = 0.46, 95% CI: 0.17-0.75) and HbA1c (β = 0.27, 95% CI: 0.11-0.42) in the overall population. Positive linear dose-response associations were observed between urinary Co and insulin (P_nonlinear = 0.513) and HOMA-IR (P_nonlinear = 0.736) in males, as well as a positive linear dose-response relationship between urinary Mo and FPG (P_nonlinear = 0.826) and HbA1c (P_nonlinear = 0.376) in the overall population. Significant sex-specific and dose-response relationships were observed between urinary metals (Co and Mo) and diabetes-related indicators, and the potential mechanisms should be further investigated.

Low Toxicity of Metal-Organic Framework MOF-74(Co) Nano-Particles In Vitro and In Vivo

With the rapid development of metal-organic frameworks (MOF), the toxicity and environmental safety of MOF materials should be thoroughly investigated. The behaviors and bio-effects of MOF materials after oral exposure are largely unknown. In this study, we performed a pilot toxicity evaluation of MOF-74(Co) nanoparticles (NPs) both in vitro and in vivo. The cell viability and cell cycle were monitored after LO2 cells were incubated with MOF-74(Co). The Co contents, bodyweight, serum biochemistry, histopathological changes, and oxidative stress parameters were measured after oral exposure to MOF-74(Co) NPs in mice. LO2 cells showed viability loss at 100 mg/L. The cell cycle arrest was more sensitive, which was observed even at 12.5 mg/L. MOF-74(Co) NPs led to a significant accumulation of Co in the liver and kidneys. No bodyweight loss was observed and the serum biochemical index was mainly unchanged. Except for slight inflammation, the histopathological images of the liver and kidneys after oral exposure to MOF-74(Co) NPs were normal compared to the control. Meaningful oxidative stress was found in the liver and kidneys. The results collectively indicated the low toxicity of MOF-74(Co) NPs after oral exposure in mice.

U-shaped association between plasma cobalt levels and type 2 diabetes

AIMS

We aimed to investigate the association of plasma cobalt with newly diagnosed type 2 diabetes (T2D) and further explore the potential interaction effects between cobalt and several redox metals, such as manganese, copper and selenium.

DESIGN

A large case-control study including 4564 subjects was conducted. 2282 cases with newly diagnosed T2D and 2282 controls were matched by sex and age. The concentrations of cobalt and other metals in plasma were detected with inductively coupled plasma mass spectrometry (ICPMS).

RESULTS

The medians of the cobalt concentrations in plasma were 1.68 μg/dL for controls and T2D. There was a U-shaped relation between T2D and plasma cobalt, which was categorized into quartiles. After multivariable adjusted for the confounding factors, the odds ratios (ORs) of T2D across quartiles were 1.22 (95% CI: 1.01, 1.46), 1.12 (95% CI: 0.94, 1.35), 1.00 (reference) and 1.46 (95% CI: 1.22, 1.75), respectively. The association was almost consistent in subgroup analyses. According to the restricted cubic spline analysis, the lowest ORs of T2D was observed at the plasma cobalt of 2.00 μg/dL. There was a significant interaction between plasma cobalt and copper (P < 0.01). The ORs of T2D in those with medium concentration of plasma cobalt and copper was the lowest.

CONCLUSIONS

Higher or lower concentrations of plasma cobalt were related to higher ORs of T2D. The inter-relationship among redox metals in T2D should be further investigated.

Genotoxicity of 11 heavy metals detected as food contaminants in two human cell lines

Heavy metals, such as arsenic (As), antimony (Sb), barium (Ba), cadmium (Cd), cobalt (Co), germanium (Ge), lead (Pb), nickel (Ni), tellurium (Te), and vanadium (V) are widely distributed in the environment and in the food chain. Human exposure to heavy metals through water and food has been reported by different international agencies. Although some of these heavy metals are essential elements for human growth and development, they may also be toxic at low concentrations due to indirect mechanisms. In this study, the genotoxic and cytotoxic properties of 15 different oxidation statuses of 11 different heavy metals were investigated using high-throughput screening (γH2AX assay) in two human cell lines (HepG2 and LS-174T) representative of target organs (liver and colon) for food contaminants. Base on their lowest observed adverse effect concentration, the genotoxic potency of each heavy metal in each cell line was ranked in decreasing order, NaAsO₂  > CdCl₂  > PbCl₂ (only in LS-174T cells) > As₂ O₅  > SbCl₃  > K₂ TeO₃  > As₂ O₃ . No significant genotoxicity was observed with the other heavy metals tested. Cell viability data indicate that several heavy metals (As, Cd, Co, Ni, Sb, and Te) induce cytotoxicity at high concentrations, whereas an increase in the number of cells was observed for lead concentrations >100 µM in both cell lines tested, suggesting that lead stimulates cell growth. All these results highlight the possible human health hazards associated with the presence of heavy metals present in food. Environ. Mol. Mutagen. 59:202-210, 2018. © 2017 Wiley Periodicals, Inc.

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.

Recent aspects of uranium toxicology in medical geology

Uranium (U) is a chemo-toxic, radiotoxic and even a carcinogenic element. Due to its radioactivity, the effects of U on humans health have been extensively investigated. Prolonged U exposure may cause kidney disease and cancer. The geological distribution of U radionuclides is still a great concern for human health. Uranium in groundwater, frequently used as drinking water, and general environmental pollution with U raise concerns about the potential public health problem in several areas of Asia. The particular paleo-geological hallmark of India and other Southern Asiatic regions enhances the risk of U pollution in rural and urban communities. This paper highlights different health and environmental aspects of U as well as uptake and intake. It discusses levels of U in soil and water and the related health issues. Also described are different issues of U pollution, such as U and fertilizers, occupational exposure in miners, use and hazards of U in weapons (depleted U), U and plutonium as catalysts in the reaction between DNA and H₂O_2, and recycling of U from groundwater to surface soils in irrigation. For use in medical geology and U research, large databases and data warehouses are currently available in Europe and the United States.

Novel complexes of Co(III) and Ni(II) containing peptide ligands: synthesis, DNA binding and photonuclease activity

The new cobalt(III) and nickel(II) complexes of the type [M(L)2(H2O)2](n)(+) (where M = Co(III) or Ni(II) ion, n = 3 for Co and 2 for Ni, L = peptides Fmoc. Ala-val-OH (F-AVOH), Fmoc-Phe-Leu-Ome (F-PLOMe) and Z-Ala-Phe-CONH2 (Z-APCONH2)) were synthesized and structurally characterized by FTIR, (1)H NMR, elemental analysis and electronic spectral data. An octahedral geometry has been proposed for all the synthesized Co(III) and Ni(II) metal complexes. The binding property of the complexes with CT-DNA was studied by absorption spectral analysis, followed by viscosity measurement and thermal denaturation studies. Detailed analysis revealed that the metal complexes intercalates into the DNA base stack as intercalator. The photo induced cleavage studies shows that the complexes possess photonuclease property against pUC19 DNA under UV-Visible irradiation.

Antiproliferative and apoptosis-induction studies of a metallosurfactant in human breast cancer cell MCF-7

The cytotoxic potential of the surfactant–cobalt(iii) complex (metallosurfactant) cis-[Co(trien)(C₁₄H₂₉NH₂)Cl](ClO₄)₂ was tested on an MCF-7 breast cancer cell.

Trace elements and carcinogenicity: a subject in review

Cancer is known to be a multi-step process, which involves different stages including initiation, promotion, progression and metastasis. Chemical carcinogens including most trace elements can change any of these processes to induce their carcinogenic effects. Various studies confirm that cancer arises from the accumulation of irreversible DNA damage, which results from multiple mutations in critical genes in the body organ. Chemical carcinogens most often directly or after xenobiotic metabolism, act as genotoxic causes to induce DNA damage. Genotoxic carcinogen refers to a group of chemicals capable of producing cancer by directly altering the genetic material of target cells. Other carcinogens are however classified as non-genotoxic, which represents chemicals that are capable of producing cancer by some secondary mechanism not related to direct gene damage. They act as tumor promoters, endocrine-modifiers, receptor mediators, immunosuppressant, or inducers of tissue-specific toxicity and inflammatory responses. The diversity of modes of action, of non-genotoxic carcinogens, the tissue and species specificity and the absence of genotoxicity makes it extremely hard to predict their carcinogenic potential. The roles of trace metals (some of which are either genotoxic or non-genotoxic) in cancer development and inhibition have a complex character and have raised many questions because of their essential and toxic effects on people's health. Trace metals such as cadmium, nickel, arsenic, beryllium and chromium (VI) have been recognized as human or animal carcinogens by International Agency for Research on Cancer (IARC). The Carcinogenic capability of these metals depends mainly on factors such as oxidation states and chemical structures. The oxidative concept in metal carcinogenesis proposes that complexes formed by these metals, in vivo, in the vicinity of DNA, catalyze redox reactions, which in turn oxidize DNA. The most significant effect of reactive oxygen species in the carcinogenesis progression is DNA damage, which results in DNA lesions like strand breaks and the sister-chromatid exchange. This article reviews the carcinogenicity of various trace elements.

Evaluation of biotargeting and ecotoxicity of Co²⁺-containing nanoscale polymeric complex by applying multi-marker approach in bivalve mollusk Anodonta cygnea

Cobalt (Co(2+)) is present in many nanoscaled materials created for various applications. The key goal of our study was to develop sensitive approaches for assessing the bio-risks associated with using novel Co(2+)-containing nanoscaled polymeric complex (Co-NC). Freshwater bivalve mollusk Anodonta cygnea (Unionidae) was subjected to 14 d action of the developed Co-NC, as well as of Co(2+) applied in the corresponding concentration (50 μg L(-1)) or polymeric substance (PS). All experimental groups under study have demonstrated signs of toxic targeting, notably changes in DNA characteristics, oxidative stress (with particularities in each exposed group) and activation of anaerobiosis (Co(2+) and Co-NC). However, the group exposed to Co-NC showed some advantages that can be related to the activation of metallothionein (MT) function (increase in the level of MT-related SH-groups (MT-SH)): low level of oxyradical formation, no increase in protein carbonylation and vitellogenin-like proteins concentration unlike in Co(2+) and PS exposed groups. On the other hand, Co(2+) increased metal (Co, Cu, Zn and Cd) binding to MT (MT-Me) without changes in MT-SH level jointly with activation of oxyradical formation and apoptosis and decreasing of lysosomal membrane stability. PS per se initiated unbalanced changes in activities of the biotransformation enzymes ethoxyresorufin-O-deethylase and glutathione-S-transferase. Thus, Co(2+) complexing with the developed PS prevented bio-toxic effects of free Co(2+) ions and PS per se, at least in the studied hydrobiont. The MT-SH was the main distinguishing index of Co-NC group selected by classification and regression tree analysis.

Genotoxicity evaluation of nanomaterials: dna damage, micronuclei, and 8-hydroxy-2-deoxyguanosine induced by magnetic doped CdSe quantum dots in male mice

Quantum dots (QDs) are a novel class of inorganic fluorophores which are gaining widespread recognition as a result of their exceptional photophysical properties and their applications as a biomarker and in molecular biomedical imaging. The aim of this study was to evaluate the in vivo genotoxicity in mice exposed to CdSe quantum dots of average size 5.0 ± 0.2 nm and CdSe doped with 1% cobalt ions of similar size. The quantum dots are surface modified using mercaptoacetic acid (MAA) in order to be biocompatible and water-soluble. The MAA-QDs were given to the mice orally at doses of 500, 1000, and 2000 mg/kg by weight of MAA-QDs. Bone marrow and liver samples were collected after two and seven days of treatment. The results indicated that after two days of treatment, the high dose of doped MAA-QDs was significantly able to induce DNA damage, formation of micronuclei (MNs), and generation of DNA adduct (8-hydroxy-2-deoxyguanosine, 8-OHdG). However, increasing DNA damage and the frequency of MNs formation as well as the generation of DNA adducts were observed with both the undoped MAA-QDs (2000 mg/kg) and doped MAA-QDs (1000 and 2000 mg/kg) after seven days of treatment. The results of our study indicate that exposure to high doses of pure MAA-QDs or MAA-QDs doped with cobalt has the potential to cause indirect in vivo genetic damage, which may be attributed to free radical-induced oxidative stress in mice.

Advances in metal-induced oxidative stress and human disease

Detailed studies in the past two decades have shown that redox active metals like iron (Fe), copper (Cu), chromium (Cr), cobalt (Co) and other metals undergo redox cycling reactions and possess the ability to produce reactive radicals such as superoxide anion radical and nitric oxide in biological systems. Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others. The underlying mechanism of action for all these metals involves formation of the superoxide radical, hydroxyl radical (mainly via Fenton reaction) and other ROS, finally producing mutagenic and carcinogenic malondialdehyde (MDA), 4-hydroxynonenal (HNE) and other exocyclic DNA adducts. On the other hand, the redox inactive metals, such as cadmium (Cd), arsenic (As) and lead (Pb) show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione. Interestingly, for arsenic an alternative mechanism of action based on the formation of hydrogen peroxide under physiological conditions has been proposed. A special position among metals is occupied by the redox inert metal zinc (Zn). Zn is an essential component of numerous proteins involved in the defense against oxidative stress. It has been shown, that depletion of Zn may enhance DNA damage via impairments of DNA repair mechanisms. In addition, Zn has an impact on the immune system and possesses neuroprotective properties. The mechanism of metal-induced formation of free radicals is tightly influenced by the action of cellular antioxidants. Many low-molecular weight antioxidants (ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), glutathione (GSH), carotenoids, flavonoids, and other antioxidants) are capable of chelating metal ions reducing thus their catalytic activity to form ROS. A novel therapeutic approach to suppress oxidative stress is based on the development of dual function antioxidants comprising not only chelating, but also scavenging components. Parodoxically, two major antioxidant enzymes, superoxide dismutase (SOD) and catalase contain as an integral part of their active sites metal ions to battle against toxic effects of metal-induced free radicals. The aim of this review is to provide an overview of redox and non-redox metal-induced formation of free radicals and the role of oxidative stress in toxic action of metals.

Comparative study of the formation of oxidative damage marker 8-hydroxy-2′-deoxyguanosine (8-OHdG) adduct from the nucleoside 2′-deoxyguanosine by transition metals and suspensions of particulate matter in relation to metal content and redox reactivity

An association between exposure to ambient particulate matter (PM) and increased incidence of mortality and morbidity due to lung cancer and cardiovascular diseases has been demonstrated by recent epidemiological studies. Reactive oxygen species (ROS), especially hydroxyl radicals, generated by PM, have been suggested by many studies as an important factor in the oxidative damage of DNA by PM. The purpose of this study was to characterize quantitatively hydroxyl radical generation by various transition metals in the presence of H2O2 in aqueous buffer solution (pH 7.4) and hydroxylation of 2'-deoxyguanosine (dG) to 8-hydroxy-2'-deoxyguanosine (8-OHdG) under similar conditions. The order of metals' redox reactivity and hydroxyl radical production was Fe(II), V(IV), Cu(I), Cr(III), Ni(II), Co(II), Pb(II), Cd(II). Then, we investigated the generation of hydroxyl radicals in the presence of H2O2 by various airborne PM samples, such as total suspended particulate (TSP), PM10, PM2.5 (PM with aerodynamic diameter 10 and 2.5 microm), diesel exhaust particles (DEP), gasoline exhaust particles (GEP) and woodsmoke soot under the same conditions. When suspensions of PMs were incubated with H2O2 and dG at pH 7.4, all particles induced hydroxylation of dG and formation of 8-OHdG in a dose-dependent increase. Our findings demonstrated that PM's hydroxyl radical (HO radical) generating ability and subsequent dG hydroxylation is associated with the concentration of water-soluble metals, especially Fe and V and other redox or ionizable transition metals and not their total metal content, or insoluble metal oxides, via a Fenton-driven reaction of H2O2 with metals. Additionally, we observed, by Electron paramagnetic resonance (EPR), that PM suspensions in the presence of H2O2 generated radical species with dG, which were spin-trapped by 2-methyl-2-nitroso-propane (MNP).

Investigation of the Molecular Nature of Low-molecular-mass Cobalt(II) Ions in Isolated Osteoarthritic Knee-joint Synovial Fluid

High field 1H NMR spectroscopy demonstrated that addition of Co(II) ions to osteoarthritic knee-joint synovial fluid (SF) resulted in its complexation by a range of biomolecules, the relative efficacies of these complexants/chelators being citrate >> histidine - threonine >> glycine - glutamate - glutamine - phenylalanine tyrosine > formate > lactate >> alanine > valine > acetate > pyruvate > creatinine, this order reflecting the ability of these ligands to compete for the available Co(II) in terms of (1) thermodynamic equilibrium constants for the formation of their complexes and (2) their SF concentrations. Since many of these SF Co(II) complexants (e.g. histidinate) serve as powerful *OH scavengers, the results acquired indicate that any of this radical generated from the Co(II) source in such complexes via Fenton or pseudo-Fenton reaction systems will be "site-specifically" scavenged. The significance of these observations with regard to cobalt toxicity and the in vivo corrosion of cobalt-containing metal alloy joint prostheses (e.g. CoCr alloys) is discussed.

8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis

There is extensive experimental evidence that oxidative damage permanently occurs to lipids of cellular membranes, proteins, and DNA. In nuclear and mitochondrial DNA, 8-hydroxy-2' -deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2' -deoxyguanosine (8-oxodG) is one of the predominant forms of free radical-induced oxidative lesions, and has therefore been widely used as a biomarker for oxidative stress and carcinogenesis. Studies showed that urinary 8-OHdG is a good biomarker for risk assessment of various cancers and degenerative diseases. The most widely used method of quantitative analysis is high-performance liquid chromatography (HPLC) with electrochemical detection (EC), gas chromatography-mass spectrometry (GC-MS), and HPLC tandem mass spectrometry. In order to resolve the methodological problems encountered in measuring quantitatively 8-OHdG, the European Standards Committee for Oxidative DNA Damage was set up in 1997 to resolve the artifactual oxidation problems during the procedures of isolation and purification of oxidative DNA products. The biomarker 8-OHdG or 8-oxodG has been a pivotal marker for measuring the effect of endogenous oxidative damage to DNA and as a factor of initiation and promotion of carcinogenesis. The biomarker has been used to estimate the DNA damage in humans after exposure to cancer-causing agents, such as tobacco smoke, asbestos fibers, heavy metals, and polycyclic aromatic hydrocarbons. In recent years, 8-OHdG has been used widely in many studies not only as a biomarker for the measurement of endogenous oxidative DNA damage but also as a risk factor for many diseases including cancer.

Influence of ozone on traffic-related particulate matter on the generation of hydroxyl radicals through a heterogeneous synergistic effect

Epidemiologic studies suggest that ozone (O(3)) and airborne particulate matter (PM) can interact causing acute respiratory inflammation and other respiratory diseases. Recent studies investigated the hypothesis that the effects of air pollution caused by O(3) and PM are larger than the effect of these two pollutants individually. We investigated the hypothesis that ozone and traffic-related PM (PM(10) and PM(2.5), diesel and gasoline exhaust particles) interact synergistically to produce increasing amounts of highly reactive hydroxyl radicals (HO) in a heterogeneous aqueous mixture at physiological pH. Electron paramagnetic resonance (EPR) and spin trapping were used for the measurements. Results showed that HO radicals are generated by the catalytic action of PM surface area with ozone and that EPR peak intensities are two to three times higher compared to PM samples without ozone. Incubation of the nucleoside 2'-deoxyguanosine (dG) in aqueous mixtures of ozone and PM at pH 7.4 resulted in the hydroxylation at C(8) position of dG. The formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) showed a 2-2.5-fold increase over control (PM without O(3)). These results suggest that PM and O(3) act synergistically generating a sustained production of reactive HO radicals. Partitioning of O(3) into the particle phase depends on the concentration, hygroscopicity and particle size.

Effect of selected alcohol dehydrogenase inhibitors on human hepatic lactate dehydrogenase activity - an in vitro study

Metabolic acidosis severely complicates methanol and ethylene glycol intoxications. Acidosis is caused by acid metabolites and can be intensified by lactate elevation. Lactate concentration depends on the NADH(2)/NAD ratio. Lactate dehydrogenase (LDH, E.C.1.1.1.27.) supplies more lactate when the level of NADH(2) is elevated. The aim of the study was to evaluate the effect of alcohol dehydrogenase (ADH) inhibitors and substrates: cimetidine, EDTA, 4-methylpyrazole (4-MP), Ukrain and ethanol on LDH activity. The activity of LDH was determined spectrophotometrically in human liver homogenates incubated with cimetidine, EDTA, 4-MP and Ukrain at concentrations of 2 x 10(-6), 10(-5) and 5 x 10(-5) m as well as ethanol at concentrations of 12.50, 25.00, 50.00 mm. The LDH activity was significantly increased by 10(-5) and 5 x 10(-5) m concentrations of cimetidine and 4-MP, and by all concentrations of ethanol. The most effective change of LDH activity of about 26% (P<0.01) was observed at the highest concentration of ethanol. Ukrain inhibited LDH activity at both concentrations, i.e. 10(-5) and 5 x 10(-5) m (P<0.05). However, EDTA did not significantly influence LDH activity. The data showed that ethanol and 4-MP, the main antidotes in methanol or ethylene glycol poisoning, may increase liver LDH activity - an undesirable effect during the therapy of patients intoxicated with these alcohols. On the other hand, the decrease of LDH activity in the presence of Ukrain is a promising finding but definitely requires further investigation.

Inactivation of herpes simplex type 1 gene vector on immobilized metal affinity chromatography: oxidative damage by hydroxyl free radicals and its prevention

Metal catalyzed oxidation (MCO), which typically involves oxygen free radical generation, is an important pathway that leads to the deterioration of many biological molecules in solution. The occurrence of MCO in immobilized metal affinity chromatography (IMAC) systems and its potential for inactivating biological products has not been well recognized. In this study, we report the inactivation of herpes simplex virus type 1 (HSV-1) gene therapy vector on immobilized cobalt affinity chromatography. We observed that purification of KgBHAT, an HSV-1 mutant bearing cobalt affinity tags (HAT) on the surface, on an IDA-Co2+ column using crude supernatant as starting material resulted in signification loss in virus infectivity (<5% recovery). Electron spin resonance (ESR) revealed that the virus inactivation was caused by hydroxyl free radicals generated from the interactions between cellular impurities and the metal ions on the column. Inclusion of 20 mM ascorbate, a free radical scavenger, in the chromatography mobile phase effectively scavenged the hydroxyl radicals and dramatically augmented the infectivity recovery to 70%. This finding is the first demonstration of oxygen free radical-mediated biological inactivation in an actual IMAC purification and the way on how to effectively prevent it.

Presence of imidazole in loading buffer prevents formation of free radical in immobilized metal affinity chromatography and dramatically improves the recovery of herpes simplex virus type 1 gene therapy vectors

We have recently shown that immobilized metal affinity chromatography (IMAC) is an effective technique for purification of herpes simplex virus type 1 (HSV-1) gene vector engineered to display cobalt affinity tag on the envelope. However, the tagged HSV-1 viruses were severely inactivated by oxidative hydroxyl free radicals when crude HSV-1 supernatant was applied on an immobilized cobalt column and eluted by a low pH buffer. Furthermore, we have reported that virus inactivation could be prevented by inclusion of high concentration of ascorbate in chromatographic mobile phase. In this paper we report that when elution of bound virus was attempted by inclusion of imidazole in elution buffer, rather than lowering the pH of elution buffer, similar inactivation was also observed. The results also demonstrated that virus inactivation was dramatically reduced by inclusion of 20mM imidazole in the loading buffer. Electron spin resonance (ESR) experiments suggest that imidazole prevents hydroxyl free radical generation from the cobalt complexes. This is the first report describing the role of imidazole in preventing free radical formation in an IMAC column. From a practical stand point, our results imply that inclusion of appropriate amount of imidazole in the loading buffer is an effective strategy for improving the recovery yield of active products and for enhancing product quality during IMAC purification.

Effect of selected alcohol dehydrogenase inhibitors on the human heart lactate dehydrogenase activity--an in vitro study

Metabolic acidosis complicates methanol, ethylene glycol and other alcohol intoxications. It is caused firstly by acid metabolites and secondly by the lactate elevation. The aim of the study was to evaluate the effect of alcohol dehydrogenase (ADH; EC 1.1.1.1) inhibitors and substrates: 4-methylpyrazole (4-MP), cimetidine, EDTA, ethanol and methanol on lactate dehydrogenase (LDH; EC 1.1.1.27) activity. The activity of LDH was determined spectrophotometrically in in vitro human heart homogenates with the mentioned compounds at 0.01, 0.1, 1.0 mM concentrations of 4-MP, cimetidine, EDTA, and 12.5, 25.0, 50.0 mM of ethanol and methanol. The LDH activity was significantly inhibited by 0.1 mM (p<0.05) and 1.0 mM (p<0.01) 4-MP and 1.00 mM EDTA (p<0.05). Higher LDH activity vs. control was observed in the samples incubated with all studied ethanol and methanol concentrations but these differences were not statistically significant. Thus, 4-MP was found to be the most effective inhibitor of LDH of all compounds tested. Therefore, such effect of 4-MP seems to be an additional advantage in methanol and ethylene glycol intoxications.

Peroxynitrite Modulates Release of Inflammatory Mediators from Guinea Pig Lung Mast Cells Activated by Antigen-Antibody Reaction

BACKGROUND

Peroxynitrite (ONOO-), the product of the reaction between the superoxide anion (*O2-) and nitric oxide (NO), is produced during inflammatory disease and may be a major cytotoxic agent. No reports are available as to whether ONOO- generates or modulates inflammatory mediator release from activated guinea pig lung mast cells. In this study, we explored the modulatory role of intracellular ONOO- on inflammatory mediator release (histamine and leukotrienes) from activated mast cells.

METHODS

Guinea pig lung mast cells were purified by the enzyme digestion, and by using the rough and discontinuous Percoll density gradients. Mast cells were sensitized with IgG1 (anti-ovalbumin) antibody and challenged with ovalbumin (OVA). The intracellular ROS formation was determined by following the oxidative production of 2', 7'-dichlorofluorescein diacetate (DCFH-DA), dihydrorhodamine 123 (DHR), and anti-nitrotyrosine antibody immunofluorescence. Histamine was assayed using a fluorometric analyzer, leukotrienes by radioimmunoassay, intracellular Ca2+ levels by confocal scanning microscopy, and PLA(2) activity using prelabeling of [3H]arachidonic acid.

RESULTS

ROS detected by DCFH-DA weakly increased in mast cells activated with OVA (1.0 g/ml), and the ROS so generated was inhibited by ebselen (50 microM). However, the ROS detected by DHR increased 3-fold under the same conditions. Peroxynitrite scavengers sL-MT, DMTU, and inhibitor FeTPPS inhibited ROS formation but the NADPH oxidase inhibitor diphenyleneiodonium (DPI) only partially inhibited this formation. Dimethyl thiourea (DMTU) and seleno-L-methionine (sL-MT) inhibited the tyrosine nitration of cytosolic proteins, the release of histamine and leukotrienes, Ca2+ influx, and the PLA(2) activity evoked by mast cell activation.

CONCLUSION

The data obtained suggests that the ROS generated by the antigen/antibody reaction activated mast cells is ONOO-, and that this modulates the release of inflammatory mediators via Ca2+ -dependent PLA(2) activity.

Human skeletal muscle lactate dehydrogenase activity in the presence of some alcohol dehydrogenase inhibitors

Methanol, ethylene glycol and other alcohol intoxications are complicated by severe acidosis which could be caused by formation of metabolic acids and additionally lactic acid production. An increasing nicotinamide adenine dinucleotide reduced/nicotinamide adenine dinucleotide oxidized (NADH/NAD) ratio during alcohol biotransformation is responsible for the induction of lactic acidosis. The main purpose of the present paper was to evaluate the effect of 4-methylpyrazole, cimetidine, ethylenediaminetetraacetic acid disodium salt, ethanol and methanol on lactate dehydrogenase (E.C. 1.1.1.27) activity and to discuss this issue. The activity of the enzyme was determined spectrophotometrically, in vitro using human enzyme skeletal muscle homogenates. 4-Methylpyrazole, cimetidine and ethylenediaminetetraacetic acid disodium salt at concentrations 0.01, 0.1, 1.0 mM and 12.5, 25.0, 50.0 mM of ethanol and methanol were studied. Our results showed that cimetidine increased lactate dehydrogenase activity as compared to the control at all tested concentrations. Such activity was noted for 4-methylpyrazole at 0.1 mM and higher concentration. By contrast, no significant effect on lactate dehydrogenase activity in the presence of ethylenediaminetetraacetic acid disodium salt, methanol and ethanol was observed.

Urinary 8-hydroxydeoxyguanosine and sister chromatid exchanges in patients with total hip replacements

Ion release from metal implants has been suspected to increase the risk of genotoxic effects in patients wearing orthopedic metal devices. In this study we used urinary 8-hydroxydeoxyguanosine (8-OHdG) as marker of oxidative DNA damage and the frequency of sister chromatid exchanges in lymphocytes to test a possible relationship between the concentrations of chromium or cobalt and the induction of cytogenetic modifications in 46 patients with total hip replacements. A broad range of individual levels of metals has been observed in these patients: chromium in blood, 1.59-14.11 microg/L; chromium in urine, 0.79-93.80 microg/24 h; cobalt in blood, 0.77-37.80 microg/L; cobalt in urine, 2.59-166.94 microg/24 h. By linear regression analysis, no significant correlation between urinary 8OHdG or sister chromatid exchange (SCE) and the concentrations of metals was found. However, cobalt in blood as well as 8-OHdG in urine were higher in patients with implants 3-4 yr old as compared to patients with implants 1-2 yr old. Smoking significantly increased the frequency of SCE. Our data do not indicate a dependence of 8-OHdG in urine or SCE on the levels of chromium or cobalt in patients with total hip replacements.

The role of metals in site-specific DNA damage with reference to carcinogenesis

We reviewed the mechanism of oxidative DNA damage with reference to metal carcinogenesis and metal-mediated chemical carcinogenesis. On the basis of the finding that chromium (VI) induced oxidative DNA damage in the presence of hydrogen peroxide (H2O2), we proposed the hypothesis that endogenous reactive oxygen species play a role in metal carcinogenesis. Since then, we have reported that various metal compounds, such as cobalt, nickel, and ferric nitrilotriacetate, directly cause site-specific DNA damage in the presence of H2O2. We also found that carcinogenic metals could cause DNA damage through indirect mechanisms. Certain nickel compounds induced oxidative DNA damage in rat lungs through inflammation. Endogenous metals, copper and iron, catalyzed ROS generation from various organic carcinogens, resulting in oxidative DNA damage. Polynuclear compounds, such as 4-aminobiphenyl and heterocyclic amines, appear to induce cancer mainly through DNA adduct formation, although their N-hydroxy and nitroso metabolites can also cause oxidative DNA damage. On the other hand, mononuclear compounds, such as benzene metabolites, caffeic acid, and o-toluidine, should express their carcionogenicity through oxidative DNA damage. Metabolites of certain carcinogens efficiently caused oxidative DNA damage by forming NADH-dependent redox cycles. These findings suggest that metal-mediated oxidative DNA damage plays important roles in chemical carcinogenesis.

Update on the genotoxicity and carcinogenicity of cobalt compounds

OBJECTIVE

To integrate recent understandings of the mechanisms of genotoxicity and carcinogenicity of the different cobalt compounds.

METHOD

A narrative review of the studies published since the last IARC assessment in 1991 (genotoxicity, experimental carcinogenesis, and epidemiology).

RESULTS

Two different mechanisms of genotoxicity, DNA breakage induced by cobalt metal and especially hard metal particles, and inhibition of DNA repair by cobalt (II) ions contribute to the carcinogenic potential of cobalt compounds. There is evidence that soluble cobalt (II) cations exert a genotoxic and carcinogenic activity in vitro and in vivo in experimental systems but evidence in humans is lacking. Experimental data indicate some evidence of a genotoxic potential for cobalt metal in vitro in human lymphocytes but there is no evidence available of a carcinogenic potential. There is evidence that hard metal particles exert a genotoxic and carcinogenic activity in vitro and in human studies, respectively. There is insufficient information for cobalt oxides and other compounds.

CONCLUSION

Although many areas of uncertainty remain, an assessment of the carcinogenicity of cobalt and its compounds requires a clear distinction between the different compounds of the element and needs to take into account the different mechanisms involved.

The role of hydroxyl radical as a messenger in Cr(VI)-induced p53 activation

The present study investigates whether reactive oxygen species (ROS) are involved in p53 activation, and if they are, which species is responsible for the activation. Our hypothesis is that hydroxyl radical (.OH) functions as a messenger for the activation of this tumor suppressor protein. Human lung epithelial cells (A549) were used to test this hypothesis. Cr(VI) was employed as the source of ROS due to its ability to generate a whole spectrum of ROS inside the cell. Cr(VI) is able to activate p53 by increasing the protein levels and enhancing both the DNA binding activity and transactivation ability of the protein. Increased cellular levels of superoxide radicals (O(2)(-).), hydrogen peroxide (H(2)O(2)), and.OH radicals were detected on the addition of Cr(VI) to the cells. Superoxide dismutase, by enhancing the production of H(2)O(2) from O(2)(-). radicals, increased p53 activity. Catalase, an H(2)O(2) scavenger, eliminated.OH radical generation and inhibited p53 activation. Sodium formate and aspirin,.OH radical scavengers, also suppressed p53 activation. Deferoxamine, a metal chelator, inhibited p53 activation by chelating Cr(V) to make it incapable of generating radicals from H(2)O(2). NADPH, which accelerated the one-electron reduction of Cr(VI) to Cr(V) and increased.OH radical generation, dramatically enhanced p53 activation. Thus.OH radical generated from Cr(VI) reduction in A549 cells is responsible for Cr(VI)-induced p53 activation.

Hydrogen Peroxide Bleaching of Amaranth Catalysed by Nickel(II) Nitrilotriacetic Acid

The complex of NiII with nitrilotriacetic acid (NTA) (but not other aminocarboxylate complexes) autocatalyses the hydrogen peroxide bleaching of amaranth, although the reaction is inhibited by the absence of light or presence of alcohol, suggesting a radical-based mechanism.

Cobalt-mediated generation of reactive oxygen species and its possible mechanism

Electron spin resonance spin trapping was utilized to investigate free radical generation from cobalt (Co) mediated reactions using 5,5-dimethyl-1-pyrroline (DMPO) as a spin trap. A mixture of Co with water in the presence of DMPO generated 5,5-dimethylpyrroline-(2)-oxy(1) DMPOX, indicating the production of strong oxidants. Addition of superoxide dismutase (SOD) to the mixture produced hydroxyl radical (.OH). Catalase eliminated the generation of this radical and metal chelators, such as desferoxamine, diethylenetriaminepentaacetic acid or 1,10-phenanthroline, decreased it. Addition of Fe(II) resulted in a several fold increase in the .OH generation. UV and O2 consumption measurements showed that the reaction of Co with water consumed molecular oxygen and generated Co(II). Since reaction of Co(II) with H2O2 did not generate any significant amount of .OH radicals, a Co(I) mediated Fenton-like reaction [Co(I) + H2O2-->Co(II) + .OH + OH-] seems responsible for .OH generation. H2O2 is produced from O2.- via dismutation, O2.- is produced by one-electron reduction of molecular oxygen catalyzed by Co. Chelation of Co(II) by biological chelators, such as glutathione or beta-ananyl-3-methyl-L-histidine alters, its oxidation-reduction potential and makes Co(II) capable of generating .OH via a Co(II)-mediated Fenton-like reaction [Co(II) + H2O2-->Co(III) + .OH + OH-]. Thus, the reaction of Co with water, especially in the presence of biological chelators, glutathione, glycylglycylhistidine and beta-ananyl-3-methyl-L-histidine, is capable of generating a whole spectrum of reactive oxygen species, which may be responsible for Co-induced cell injury.

Reactive oxygen species-induced DNA damage and its modification: a chemical investigation

The main purpose of this study was to determine whether well-known reactive oxygen species (ROS)-generating agents can induce DNA damage in a simple chemical system with or without Fenton reaction components (iron and reducing agents), and to explore whether antioxidants which normally exist in the cellular environment can modify such damage, i.e. to determine chemical reactions of relevance to biological systems. A neutral electrophoresis technique was used to investigate DNA double stranded breaks (DSBs) caused by chemical treatments of lambda-DNA in eppendorf tubes by various ROS-generating compounds and the degree of DNA damage was categorised by analysis of enhanced digital images. Double strand breaks were induced by hydroquinone (HQ), benzoquinone (BQ), benzenetriol (BT), hydrogen peroxide (H2O2), bleomycin (BLM) and sodium ascorbate (Vit C). DNA damage was modulated by various agents including catalase (CAT), superoxide dismutase (SOD), desferoxamine mesylate (DFO), ferrous chloride (FeCl2), reduced glutathione (GSH), trolox, silymarin and myricetin. Individual chemicals (except BLM) at the concentration of 1 mM did not induce large numbers of DSBs without iron [Fe(II) or Fe(III) at 25 microM]. GSH enhanced the damaging effect of HQ, BT and Vit C, did not alter the non-damaging effect of H2O2, but had a small protective effect on BLM. When compared with the non-enzyme protein, bovine serum albumin (BSA), SOD had a protective effect against BT, H2O2 and BLM; in the presence of GSH, SOD diminished the effect of HQ, BQ and Vit C but enhanced the effect of BT, H2O2 and BLM. With both GSH and Fe and compared with BSA, SOD enhanced the effect of HQ, BQ and BLM, ameliorated the effect of H2O2, and did not affect the others. CAT showed a protective effect for almost all examined compounds, but had little effect on BLM. With GSH alone, DFO enhanced the effect of HQ, BQ, H2O2 and ameliorated the effect of BT, BLM and Vit C and trolox was largely protective. With GSH and Fe, DFO was protective for all compounds except doxorubicin (Dox), trolox was protective for all compounds except Dox and BLM, silymarin was protective except that it had little effect on BLM and Dox, but myricetin did not show any protective effect. In conclusion, the results from the present study have further highlighted the adverse potential of reducing agents and redox cycling agents, and also the need for a cautious view of antioxidants.