Article

Generation of *OH initiated by interaction of Fe2+ and CU+ with dioxygen; comparison with the Fenton chemistry

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Unlabelled: Iron and copper toxicity has been presumed to involve the formation of hydroxyl radical (*OH) from H2O2 in the Fenton reaction. The aim of this study was to verify that Fe2+-O2 and Cu+-O2 chemistry is capable of generating *OH in the quasi physiological environment of Krebs-Henseleit buffer (KH), and to compare the ability of the Fe2+-O2 system and of the Fenton system (Fe2+ + H2O2) to produce *OH. The addition of Fe2+ and Cu+ (0-20 microM) to KH resulted in a concentration-dependent increase in *OH formation, as measured by the salicylate method. While Fe3+ and Cu2+ (0-20 microM) did not result in *OH formation, these ions mediated significant *OH production in the presence of a number of reducing agents. The *OH yield from the reaction mediated by Fe2+ was increased by exogenous Fe3+ and Cu2+ and was prevented by the deoxygenation of the buffer and reduced by superoxide dismutase, catalase, and desferrioxamine. Addition of 1 microM, 5 microM or 10 microM Fe2+ to a range of H2O2 concentrations (the Fenton system) resulted in a H2O2-concentration-dependent rise in *OH formation. For each Fe2+ concentration tested, the *OH yield doubled when the ratio [H2O2]:[Fe2+] was raised from zero to one. In conclusion: (i) Fe2+-O2 and Cu+-O2 chemistry is capable of promoting *OH generation in the environment of oxygenated KH, in the absence of pre-existing superoxide and/or H2O2, and possibly through a mechanism initiated by the metal autoxidation; (ii) The process is enhanced by contaminating Fe3+ and Cu2+; (iii) In the presence of reducing agents also Fe3+ and Cu2+ promote the *OH formation; (iv) Depending on the actual [H2O2]:[Fe2+] ratio, the efficiency of the Fe2+-O2 chemistry to generate *OH is greater than or, at best, equal to that of the Fe2+-driven Fenton reaction.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Fenton reaction is a convenient generator of the hydroxyl radical with known implications in health and disease [1][2][3][4] . The reaction traditionally involves reduction of H 2 O 2 with Fe (II), but can also occur in presence of copper 5 . In view of a very brief half-life of the radical (10 -9 to 10 -10 sec), the methods for its detection are limited and indirect, and include electro chemical detection 3 , electron spin resonance 6 and fluorimetry 7,8 . ...
... Fenton reaction is basically reduction of hydrogen peroxide by iron (II) to form hydroxyl radical and iron (III), the reaction continues owing to regeneration of iron (II) from iron (III) by reducing intermediates/agents in the medium. The reaction occurs even in presence of iron (III) or copper (II) wherein the transition metals are first reduced by hydrogen peroxide or other reducing agents to reduced form 5,16,23 . Dihydroxybenzenes including catechol and its structural isomers have accelerated Fenton reaction 12,17,18 by regenerating reduced iron with potency order as hydroquinone >catechol >resorcinol 12 . ...
... Catechol oxidation was evident only when the three reactants were present together with mean absorbance 0.345 ± 0.001. This validated that copper (II) has acted as catalyst to generate hydroxyl radical like iron [5,32] . ...
Article
Full-text available
A new, simple assay has been optimized to generate and detect hydroxyl radical by Fenton reaction. The assay is based on oxidation of catechol, monitored at 360 nm following incubation at room temperature for ca. 30 minutes, with linearity over 0.25 through 2.5 μmole H2O2 using Fe (II) (0.5 μmole) and acidified catechol (0.5 mg). The Fenton reaction has been characterized by registering: (i) about 13 folds increase in response to H2O2 in presence of iron (II), (ii) inhibition by agents chelating iron and/or neutralizing H2O2 and, (iii) antagonism by established hydroxyl radical scavengers. Hydroxyl radical scavenging potential of the test agents, expressed as μmole scavenged μmole-1 test agent, has been found in the order: quercetin > curcumin> morin > rutin> daflon> diosmin > ascorbic acid > thiourea > DMSO > mannitol > benzoic acid. Citric acid, oxalic acid, tartaric acid, acetic acid and their salts, disodium EDTA, sodium metabislphite, ethanol, methanol and acetone have been evaluated for their influence on the assay when present during or following color development. A comparable Fenton reaction has been also demonstrated while using 1 mg catechol and 10 μmole Cu (II) with linearity over 0.25 through 5.0 μmole H2O2.
... Such an interaction produces a highly reactive iron-oxygen complex, for instance ferryl-or perferryl-complexes (Eqs. 4. and 5), that equals or surpasses the oxidizing potential of the • OH. 8,[20][21][22] Fe ...
... These physiological H 2 O 2 concentrations are insufficient for the initiation of the Fenton reaction 27,28 although the rate constants for the generation of • OH by Fe 2+ -O 2 and Cu + -O 2 complexes are comparable to that of the Fe 2+ -driven Fenton reaction. 21 Although H 2 O 2 is most likely the major promoter of DNA H + damage, the exact nature of Fe 2+ -induced DNA cleavage is still a matter of debate. In order to understand the characteristics of metal ion-induced DNA cleavage, we investigated the effects of pH, buffer components, and radical scavengers on the Fe 2+ -mediated cleavage of pBR322 plasmid and • OH generation reactions in the absence and presence of H 2 O 2 . ...
Article
Full-text available
This work investigated the difference between autoxidation-induced and Fenton-type cleavage of pBR322 plasmid DNA. generation reactions in the absence and presence of under various conditions were also investigated. Although both the autoxidation and Fenton-type reactions showed DNA cleavage and generation, there were significant differences in their efficiencies and reaction rates. The rate and efficiency of the cleavage reaction were higher in the absence of 1.0 mM of than in its presence in 20 mM phosphate buffer. In contrast, the generation reaction was more prominent in the presence of and showed a pH-independent, fast initial reaction rate, but the rate was decreased in the absence of at across the entire tested pH range. Studies using radical scavengers on DNA cleavage and generation reactions in both the absence and presence of confirmed that both reactions spontaneously involved the active oxygen species , , and , indicating that a similar process may participate in both reactions. Based on the above observations, a new mechanism for the autoxidation-induced DNA cleavage reaction is proposed.
... Cu ions can damage cell membranes and affect enzyme functions. The antibacterial properties of Cu are also associated with the formation of reactive oxygen species (ROS) as a result of the classical Fenton reaction [38]. Iron is found in the human body and plays an important role in the functioning of circulatory, respiratory, and immune systems. ...
... Iron is found in the human body and plays an important role in the functioning of circulatory, respiratory, and immune systems. Although Fe does not directly possess bactericidal characteristics, Fe 2+ ions can react with hydrogen peroxide (H 2 O 2 ) to form hydroxyl radicals ( • OH) [38,39]. Fe nanoparticle-decorated TiCaPCON films showed a wide spectrum of antibacterial activity against eight types of different pathogens [40]. ...
Article
Full-text available
Fabrication of bactericidal yet bioactive and biocompatable coatings is still a challenge. Here we report on novel bioactive, bactericidal, antifouling, and cytocompatible TiO2-based multi-element coatings that are effective against multidrug-resistant pathogenes. Bioactive elements (Ca, P, Si, and B) were added from electrolytes during plasma electrolytic oxidation (PEO), after which the coatings were subjected to ion implantation with Fe and Cu ions. Careful selection and optimization of PEO modes allowed obtaining optimal porosity and desired content of bioactive elements. Doping with B or Si improved the proliferation and differentiation of MC3T3-E1 osteoblastic cell. In addition, these materials exhibited good mineralization ability when exposed to simulated body fluid. B- and Si-containing PEO coatings, decorated with Cu nanoparticles, showed good cytocompatibility, strong antibacterial activity against Escherichia coli and Staphylococcus aureus multidrug-resistant strains and completely prevented S. aureus biofilm formation. The B-doped PEO coating also had a pronounced biocidal effect, which may be associated with the boron dissolution and the formation of boron oxide.
... Copper could result in the formation of hydrogen peroxide as an oxidative stress response as it is known to be a pro-oxidant [7,15] which in turn attacks the chemical structure of dyes. The increased decolorization at high copper concentrations could be attributed to intercalation of copper ions with dioxygen [24]. Cultivation conditions (pH, temperature, nutrients, metals,…etc) have a substantial effect on enzyme activity and hence decolourization of dyes from waste water [20,23]. ...
... However, waste water effluent is usually of an alkaline value, and hence, fungal strains capable of decolorizing dyes at wide pH values are desirable for industrial applications. The results obtained show that A. niger could decolorize the effluent at a wide pH values regardless to the laccase activity, therefore, Advances in Environmental Biology, 8(24) December 2014, Pages: [23][24][25][26][27][28] this microorganism is considered of a good potential in the decolorization of dyes in waste water. This also suggests that laccase induction is not the sole explanation to the decolorizing activity of A. flavus. ...
Article
Full-text available
Polyphenol oxidase (laccase) was extracted from the fungus Aspergillus sp. in a low nitrogen/low carbon medium (LN/C) under acidic conditions (pH 4) at room temperature, 30oC. This fungal laccase is known to play a pivotal role in different bioremediation processes. Induction of copper to the medium with after 24 hrs of inoculation induced laccase production. The use of different copper sulfate concentrations induced different protein expressions, 10 μM copper induced 60 KDa fraction which was also present at 50 μM but absent at 100 μM indicating inhibition at high concentrations. The results indicated that enhancing the laccase production would hence increasing the rate of decolonization of colored waste water for re-use in industrial activities but not in potable applications and in non human consumption.
... For instance, polyphenols and vitamins C and E, molecules well-documented for their antioxidant activity, sometimes elicit a pro-oxidant effect [71]. The interaction of polyphenols with transition metal ions leads to a pro-oxidant effect [72][73][74]. Similarly, vitamin E becomes a pro-oxidant at high concentrations [71]. The well-known anti-oxidant vitamin C plays a pro-oxidant role at high concentrations. ...
... Indeed, while vitamin C possesses an anti-oxidative potential at low doses (30-100 mg/kg body weight), it plays a pro-oxidative role at high doses (1000 mg/kg body weight) [75][76][77]. In addition, vitamin C shows a pro-oxidant effect in the presence of iron (Fe 3+ ) or copper (Cu 2+ ) [73,74]. Furthermore, the combination of vitamin C and Trolox (water-soluble analog of vitamin E) may provoke mild oxidative stress [78]. ...
Article
Full-text available
Pancreatic cancer (PC) is the fourth leading cause of all cancer-related deaths. Despite major improvements in treating PC, low survival rate remains a major challenge, indicating the need for alternative approaches, including herbal medicine. Among medicinal plants is Ziziphus nummularia (family Rhamnaceae), which is a thorny shrub rich in bioactive molecules. Leaves of Ziziphus nummularia have been used to treat many pathological conditions, including cancer. However, their effects on human PC are still unknown. Here, we show that the treatment of human pancreatic ductal adenocarcinoma cells (Capan-2) with Ziziphus nummularia ethanolic extract (ZNE) (100–300 μg/mL) attenuated cell proliferation in a time- and concentration-dependent manner. Pretreatment with N-acetylcysteine, an ROS scavenger, attenuated the anti-proliferative effect of ZNE. In addition, ZNE significantly decreased the migratory and invasive capacity of Capan-2 with a concomitant downregulation of integrin α2 and increased cell–cell aggregation. In addition, ZNE inhibited in ovo angiogenesis as well as reduced VEGF and nitric oxide levels. Furthermore, ZNE downregulated the ERK1/2 and NF-κB signaling pathways, which are known to drive tumorigenic and metastatic events. Taken together, our results suggest that ZNE can attenuate the malignant phenotype of Capan-2 by inhibiting hallmarks of PC. Our data also provide evidence for the potential anticancer effect of Ziziphus nummularia, which may represent a new resource of novel anticancer compounds, especially ones that can be utilized for the management of PC.
... 26,27 Cu(I)-O 2 and Fe(II)-O 2 chemistry has been proven to be an efficient way to produce hydroxyl radicals ( • OH) without external H 2 O 2 . 28 Inspired by this research, we have developed a light-up fluorescent assay for GSH based on Cu(I)-O 2 chemistry by using hollow porous copper oxide microspheres (CuO MSs). Terephthalic acid (TPA), which can be oxidized to a highly fluorescent product, hydroxyterephthalate (TPAOH), by the GSH up-regulated formation of • OH, is used as the fluorescent reporter. ...
... This phenomenon is unconventional, however, the fact that antioxidants promote ROS formation in Cu 2+ -accumulation related diseases provides a consistent physical prototype for it. 26,27 During this process, antioxidants reduce the Cu 2+ to Cu + , then promote Cu(I)-O 2 chemistry and the formation of the ROS, including • OH. 28 GSH induced reduction of Cu 2+ in the CuO MSs to Cu + ions was investigated, and under anaerobic conditions the black turbid liquid became clear and a light brown-yellow color (t 1 ), which was attributed to the formation of Cu + , which appeared after the addition of GSH at t 0 . Besides, the morphology changes of the CuO MSs in this process were imaged using SEM, and the collapsed structure and reduced volume also confirmed the degradation of the CuO MSs (Fig. S2, ESI †). ...
Article
Besides the widely concerned role as endogenous antioxidant to scavenge free radicals, glutathione (GSH) can also play the role as prooxidant and promote the CuO-induced formation of hydroxyl radicals to...
... It is important to note here that Cu is one of the elements that present in cigarette smoke, and therefore, this is may be the main reason of its high level that detected in serum of smokers. In fact, Cu is a redox-active transition metal that can participate in single electron reactions and catalyze the formation of free radicals, especially the undesirable OH radicals [31]. Hence, any increase in its levels, as a result of smoking, will lead to increase the formation of toxic free radicals, which in turn lead to increase the risk of lung cancer. ...
Article
Full-text available
Lung cancer is one of the most common leading causes of cancer mortality around the world. Many efforts have been made recently to use element contents in human body to aid for diagnosing various diseases including cancer. Accordingly, this study aimed to investigate the serum contents of elements Cr, Cu, Mn, Ni, Zn, Mg, and Fe of lung cancer patients and compared them with those found in smokers and non-smoking controls using atomic absorption spectrophotometry technique. The results obtained showed that there were significantly lower levels of Zn, Fe, and Mg (p<0.001) in patients and smokers than in non-smokers. The Zn and Mg levels of patients were significantly lower than in smokers. The serum levels of Cu, Mn, Ni, and Cr were significantly higher (p<0.001) in lung cancer patients than in smokers and controls. In addition, it was found out that the Cu/Zn ratio was significantly higher in patients and smokers than those of controls. The results suggest that adequate intake of Zn and Mg may have a protective role in the occurrence of lung cancer, while the high levels of Cu, Mn, Ni, and Cr may cause a threat of lung cancer. It is also possible to conclude that exposure to cigarette smoke leads to impair oxidant defense system. The data suggest that Cu/Zn ratio could be of great value in diagnosis and evaluating the lung cancer. In addition, it is possible to rely on trace elements to give indications to warn, especially the smokers, of the risk of lung cancer.
... As described in Section 2.1, the cellular ROS were increased when DpdtpA was exposed to the CT26 cells. It was conceivable that the intracellular ROS at least partially were generated from lysosomes due to occurrence of ferritinophagy that may trigger Fenton-like reaction [37]. To test the speculation, the lysosomal membrane of permeability (LMP) was determined as described previously [38]. ...
Article
Full-text available
Epithelial-mesenchymal transition (EMT) contributes to metastasis and drug resistance; inhibition of EMT may attenuate metastasis and drug resistance. It has been demonstrated that ferritinophagy involves the process of many diseases; however, the relationship between EMT and ferritinophagy was not fully established. Some iron chelators show the ability to inhibit EMT, but whether ferritinophagy plays a role in EMT is largely unknown. To this end, we investigated the effect of a novel iron chelator, DpdtpA (2,2 ′ -di-pyridylketone dithiocarbamate propionic acid), on EMT in the CT26 cell line. The DpdtpA displayed excellent antitumor ( IC50=1.5±0.2 μM ), leading to ROS production and apoptosis occurrence. Moreover, the ROS production correlated with ferritin degradation. The upregulation of LC3-II and NCOA4 from immunofluorescence and Western blotting analysis revealed that the occurrence of ferritinophagy contributed to ROS production. Furthermore, DpdtpA could induce an alteration both in morphology and in epithelial-mesenchymal markers, displaying significant EMT inhibition. The correlation analysis revealed that DpdtpA-induced ferritinophagy contributed to the EMT inhibition, implying that NCOA4 involved EMT process, which was firstly reported. To reinforce this concept, the ferritinophagic flux (NCOA4/ferritin) in either treated by TGF- β 1 or combined with DpdtpA was determined. The results indicated that activating ferritinophagic flux would enhance ROS production which accordingly suppressed EMT or implementing the EMT suppression seemed to be through “fighting fire with fire” strategy. Taken together, our data demonstrated that ferritinophagic flux was a dominating driving force in EMT proceeding, and the new finding definitely will enrich our knowledge of ferritinophagy in EMT process.
... A cursory assessment of the specificity, dose-dependence, pH-dependence, and kinetics of the NOx-producing reactions of L-NAME and NaAscH or H 2 O 2 was also performed ( Supplementary Fig. 9). Of note, NOx production from L-NAME in PBS was 5 to 10 fold greater than in HEPES buffer ( Supplementary Fig. 9D), possibly because of the catalysis of iron autoxidation by PBS during incubation [29]. ...
Article
Full-text available
L-NG-Nitro arginine methyl ester (L-NAME) has been widely applied for several decades in both basic and clinical research as an antagonist of nitric oxide synthase (NOS). Herein, we show that L-NAME slowly releases NO from its guanidino nitro group. Daily pretreatment of rats with L-NAME potentiated mesenteric vasodilation induced by nitrodilators such as nitroglycerin, but not by NO. Release of NO also occurred with the NOS-inactive enantiomer D-NAME, but not with L-arginine or another NOS inhibitor L-NMMA, consistent with the presence or absence of a nitro group in their structure and their nitrodilator-potentiating effects. Metabolic conversion of the nitro group to NO-related breakdown products was confirmed using isotopically-labeled L-NAME. Consistent with Fenton chemistry, transition metals and reactive oxygen species accelerated the release of NO from L-NAME. Both NO production from L-NAME and its nitrodilator-potentiating effects were augmented under inflammation. NO release by L-NAME can confound its intended NOS-inhibiting effects, possibly by contributing to a putative intracellular NO store in the vasculature. Keywords: L-NAME, Nitrodilator, L-arginine analogues, Fenton chemistry, Preformed intracellular NO store
... Evidence suggests that Cu 2þ and Cu þ may also play this role in the body.- [60] OH Á is the most reactive of all the ROS as there is no enzymatic system to defend living organisms against it. In a cellular system, OH Á will bind a proton most likely by abstracting one from a substrate. ...
Article
We describe the newest approach to photodynamic therapy (PDT) using metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). PDT’s characteristic method of treating cancer noninvasive and selective has garnered much attention. It is in this perspective that research to develop new materials capable of exploiting PDT’s chemical, physical, and biological characteristics in the form of improved photosensitizers (PS) must be understood. PDT has entered the realm of nanotechnology as researchers seek to overcome various challenges that are hindering its effectiveness. Crystal engineering of porous materials, which are more functional than small molecules, is being explored to invent and utilize existing platforms for the use in PDT. MOFs are at the forefront of these investigations and the anti-tumor ability of well-designed nano-MOFs (nMOFs) has recently been reported. In addition to these structures, in this Critical Review we will also discuss the possibility of using COF for future use PDT.
... The OH was produced in situ using Fenton ferrous salt (Fe 2þ ) reagents [45,46], which promoted cross-linking for photo-SPIE-NIA. Others transition metals, like Cu 2þ , were also adopted to generate radicals through Fentonlike chemistry [45,47]. A new SPIE-IA procedure (SPIE-Rad) was developed using the free radical species produced by the Fentonlike reactions. ...
Article
This review focuses on novel, highly-sensitive, non-competitive immunochemical designs for detection of small molecule compounds (SMCs). According to immunochemistry theory, a common and apt protocol for SMCs is the competitive assay. However, it suffers several technical disadvantages due to the single recognition epitope. For higher sensitivity investigations, lots of novel non-competitive designs were reported and discussed for detection of SMCs in recent decades. The proposed non-competitive designs were summarized into six modes in this work. Based on the non-competitive designs, SMCs were monitored with higher sensitivity and stability than previously, and across a broader linear detection range. These new technologies and the challenges encountered in development are discussed, in order to highlight the future prospects of each protocol. We aim to guide the choice of different detection methods and inspire new ideas for SMCs.
... Iron also has an important role in the formation of reactive oxygen species (ROS), including hydroxyl radical, superoxide radical, and hydrogen peroxide, which are toxic and cause profound damage to DNA, proteins, and lipids. [3][4][5] Since Iron has an important role in ROS generation and the human body has no mechanism for iron removal, iron accumulation in the body causes devastating damage to biological pathways and critical organs such as the heart, liver, bone marrow, and pancreas. Therefore, the chance of progression toward diseases such as diabetes, heart failure, atherosclerosis, and metabolic syndrome increases in patients with thalassaemia. ...
Article
Full-text available
BACKGROUND Thalassaemia is a hereditary disorder and has an economic burden on patients and the government. The most prevalent complication in these patients is iron overload which is followed by cardiomyopathy. Digoxin is considered as a treatment against heart failure in thalassaemia. The present study evaluated the effect of two digoxin concentrations on iron content and antioxidative defense in cardiac tissue of iron-overloaded rats. METHODS The study was conducted on 48 rats which were divided into 6 groups. Group 1 was the control group and did not receive any treatment and group 2 was the iron overload group. In addition groups 3 and 4 were the digoxin control groups which received 1 and 5 mg/kg/day of digoxin, respectively. Groups 5 and 6 received 1 and 5 mg/kg/day of digoxin plus iron-dextran, respectively. After 1 month, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant status (TAS) were assessed in cardiac tissues. RESULTS Co-administration of iron-dextran and digoxin (1 and 5 mg/kg/day) significantly increased SOD and TAS levels (P < 0.0010) and reduced MDA (P < 0.0010) in heart tissue compared to control and iron overload groups. GPX levels significantly reduced in groups 5 and 6 (iron + digoxin 1 (P < 0.0500) and iron + digoxin 5) (P < 0.0010) compared to the iron control group. CONCLUSION Digoxin remarkably facilitates iron uptake by cardiomyocytes by affecting other channels such as L-type and T-type Ca2+ channels (LTCC and TTCC). Digoxin administration in the iron-overloaded rat model deteriorated antioxidative parameters and increased iron entry into heart tissue at higher doses. Therefore, in patients with beta thalassaemia major, digoxin must be administered with great care and serum iron and ferritin must be regularly monitored.
... However, cadmium had lethal impact on plant material. Obtained results present that copper and iron were able not only to direct production of reactive forms of oxygen through the Fenton or the Haber-Weiss reaction (URBAŃSKI, BERĘSEWICZ 2000), but also through oxidative burst. This fact was also confirmed for copper by RAEYMAEKERS et al. (2003). ...
Research
Full-text available
In this work the reaction of Nicotiana tabacum cv. Bright Yellow 2 cells on the presence of 500 μM zinc, 500 μM cadmium, 10 μM copper and 5 μM iron was studied. It was confirmed that all tested heavy metals induced in tobacco cell suspension culture early stress response manifested by increased production of hydrogen peroxide. The highest level of hydrogen peroxide was marked in samples containing cadmium ions. This metal was also the most toxic for tested plant material. Less toxic were ions of copper and zinc. Iron ions gave the weakest stress response (probably because of the plant cell peroxidase inhibition).
... For example, Fe 2+ easily reacts with H 2 O 2 to form hydroxyl radicals ( • OH) through the classic homogeneous Fenton reaction. 66,67 Different reactions of oxidative radical generation by iron oxide NPs in the biological environment were considered by Wang 68 and Rtimi 69 under sunlight irradiation. The combination of oxidized Fe NPs and TiO 2 could promote intensive ROS generation under UV or visible light absorption. ...
... The choice of salt of copper but no iron is due to several factors: (1) low reaction rate constant between the Fe 2+ and the H 2 O 2 (76 × M −1 s −1 ) requires a 10-24-h incubation and (2) unstable Fe 2+ determines ex tempore immediate use. On the contrary, the reaction rate constant of ROS production by reacting Cu 2+ with H 2 O 2 is much higher (4.7 × 10 3 × M −1 s −1 ), and the solution is stable and may be reused (Urbanski and Beresewicz 2000). Surface fluorescence was measured at room temperature using a microplate reader (Tecan, Austria) at the λexc = 380 nm and the λem = 460 nm. ...
Article
Full-text available
The rapid development of nanotechnology raises questions assessment of their impact on living objects. In the present study, we evaluated the impact of nanoparticle (NP) CuO at concentrations ranging from 0.8 to 63.5 g/l in the test on wheat seedlings Triticum vulgare during 1–72 h. In the viability test (WST-test), cells were isolated from the roots of seedlings T. vulgare, 12 h not observed increase reductase activity after 24 h decreased rate of not more than 19% compared with the control. The number of dead cells in seedlings of T. vulgaris after exposure with CuO nanoparticles to the test with Evans blue increased by 5–15% compared to control. We observed that a significant increase in copper revenues leaves 4.5–8.9 times more in relation to the control and the roots—in 5–9.7 times. During the determined amount of active oxygen species, a significant proportional increase in the total pool of reactive oxygen species (ROS) in roots increased to 27.6% after exposure to NP CuO compared with the control. It is shown that in the introduction in medium, the NP CuO in the doses ranging from 3.2 to 63.5 g/l leads to DNA fragmentation and increases the fragments less than 3000 bp on 51.4–62.8%. The totality of our results influences nanoforms of copper oxide on the amount of ROS, and the viability of the genomic component of the cells shows different mechanisms of damage in the activation of a metabolic reaction, to determine the concentration of nano-CuO.
... This is clear when comparing the addition of either copper or iron to HSA or IgG. Both metals induced protein carbonylation consistent with their participation in Fenton-type reactions that produce hydroxyl radicals (51). However, addition of copper resulted in a much higher degree of protein destabilization and aggregation (indicated by * in Fig. 6). ...
Article
Full-text available
Purpose: Ascorbic acid has been considered as a potential radical scavenging excipient for pharmaceutical formulations. However, under certain circumstances, ascorbic acid can generate reactive oxygen species via redox cycling. The objective of this study was to investigate ascorbic acid-induced oxidative carbonylation of therapeutic proteins and correlate the increase in carbonylation with protein aggregation. Methods: An optimized ELISA for quantifying carbonyl levels was used to compare the oxidizing potentials of ascorbic acid and hydrogen peroxide by testing four pharmaceutically-relevant proteins (human serum albumin, immunoglobulin G, granulocyte-colony stimulating factor and calcitonin). Several transition metals at micromolar concentrations were evaluated for their ability to enhance ascorbic acid-induced protein carbonylation. Protein aggregation under oxidative conditions, with or without free radical scavengers, was measured by aggregate binding fluorescent dye and confirmed by microfluidic imaging. Results: Addition of ascorbic acid alone resulted in higher increases in carbonylation than addition of hydrogen peroxide. The presence of trace amounts (>75 ppb) of copper enhanced oxidative effects of ascorbic acid, whereas other tested metals did not comparably promote oxidation. During oxidation, protein destabilization indicated by loss of the full-length protein, positively correlated with the increase in protein aggregation. However, levels of aggregation did not always correlate with the levels of protein carbonylation. At comparable carbonylation levels, addition of copper produced greater protein destabilization and aggregation than addition of iron. Conclusions: The results strongly suggest that ascorbic acid with traces of metals, especially copper, can promote therapeutic protein carbonylation and potentially aggregation. At similar carbonylation levels, some oxidative conditions may lead to greater protein destabilization than others.
... No non-stoichiometric copper phases or covellite was found, as was proposed in the literature for the oxidative leaching of chalcopyrite[15,16], which, from 3 g pure chalcopyrite with particle size of 165 m in 357 mL of solution at 40 @BULLET C, Oxidants: 0.2 M CuSO4 and 0.035 g/min O3.may be suggesting that the methanol prevents the formation of these phases. On one hand, alcohols possess the ability to stabilize the cuprous ion[9,17], while on the other, cuprous ions coordinate highly oxidizing radicals[18], which can react with iron as well as with copper. In this manner, chalcopyrite can be dissolved with little or no refractory intermediates. ...
Article
Chalcopyrite dissolution under environmental conditions has been one of the major challenges facing researchers. The current processes for obtaining copper have pollution issues, which will severely limit their application as environmental controls become stricter. Faced with this problem, a number of eco-friendlier methods, such as GALVANOX and HydroCopper (Outokumpu), have been proposed, although they have not been industrialized, mainly due to their high operating costs. The authors previously proposed an alternative system to leach chalcopyrite, which is based on the use of aqueous polar organic solutions. In the process, copper extraction increases in mixtures of acetone or ethylene glycol with aqueous sulfuric acid solutions. The drawback is the large concentration of oxidizing agents needed to obtain high percentages of chalcopyrite dissolution, which can make the process lose viability. In this investigation, the effect of acetic acid, formic acid, methanol and ethanol, whose chemical characteristics are similar to those previously proposed, were evaluated by cyclic voltammetry. It was found that in the presence of these organic solvents, higher electrochemical responses were obtained compared with those found with sulfuric acid alone, a similar behavior to that obtained with acetone. Leaching experiments results coincided with the corresponding findings of the electrochemical study and X-ray diffraction results provided evidence to support the proposed reactions.
... In this aspect, in the presence of catalytic iron and copper ions, . ascorbate, despite of its antioxidant capability, may produce OH .owing to its metal reducing capability which is similar to O 2 [ 22 ] generation together with H O while ascorbate (0.2-4 mM) may take 2 2 .part as a cellular reducer to exchange O in Heber-Weiss reaction. ...
... H 2 O 2 is a potent oxidative agent that can generate highly reactive hydroxyl radicals in the presence of metal cations via the Fenton reaction (Emerit et. al, 2001;Urbañski and Berêsewicz, 2000). Such imbalance in the production of large amounts of reactive oxygen free radicals has harmful effects on the different cellular macromolecules including DNA, proteins, lipids and carbohydrates (Sies, 1993). ...
Article
Full-text available
Abstract The main objective of this project is to study the possible association between anti-oxidant/redox status and DNA instability in Down syndrome. The activities of 5 antioxidant enzymes were studied in 19 Down syndrome (DS) cases and in age- and sex-matched normal controls. Sister Chromatid Exchanges (SCE) were measured in lymphocyte cultures derived from all DS and control subjects. All DS and control individuals had normal hematological parameters, but the proliferation and mitotic indices were significantly lower in the DS- than in the controls-derived lymphocyte cultures, while the average generation time was higher than that in the controls. The specific activity of superoxide dismutase in the DS individuals was 40% higher than that in the controls, while the specific activity of glutathione S-transferase in the DS group was significantly lower than that in the controls (P ≤ 0.05). Catalase and glutathione peroxides’ activities were not different between the two groups (P > 0.05). SCE rate in the DS derived cultures was significantly higher (P < 0.001) than that of the controls. DS individuals have a higher oxidative stress, higher superoxide dismutase activities and higher rates of SCE in their derived lymphocyte cultures compared to those of the controls. We claim that such differences may have resulted from the over expression of superoxide dismutase gene, leading to imbalanced cellular antioxidant mechanisms and, consequently, resulted in a high concentration of free radicals that destabilized the DNA as expressed by the high rate of SCE. Key Words: Down syndrome, Antioxidant enzymes, Catalase, Glutathione peroxidase, Glutathione S- transferase, Oxidative stress, Sister chromatid exchanges (SCE). * Corresponding author. e-mail: may@yu.edu.jo ; maysadiq333@yahoo.com. 1. Introduction Trisomy 21, known as Down Syndrome (DS), is one of the most common human chromosomal disorders in live born children (1 in 800–1000) (Capone, 2004), leading to the characteristic phenotypes of DS individuals, which include a constant common feature of early mental decline and premature aging. DS affected individuals may also suffer from developmental abnormalities, specific cardiac and gastrointestinal congenital malformations, thyroid dysfunction and increased risk for various types of leukemia (Antonarakis and Epstein, 2006; Roizen and Patterson, 2003; Shaw et. al, 2006). The characteristic phenotypes of DS were suggested to be the ultimate results of the triplication of the Down Syndrome Critical Region (DSCR) 21q22.1 - 21q22.3 (Vesa et. al, 2005), which includes the gene coding for the enzyme, copper zinc superoxide dismutase (SOD1), implicated in the conversion of the harmful superoxide anion radical (O2 .-) to molecular oxygen (O2) and hydrogen peroxide (H2O2) (Gardiner and Davisson
... Rather, radical-mediated footprinting is an established methodology for evaluating protein structure via solvent accessible reactivity, 37 as well as for mapping protein-protein and protein-DNA interactions. [38][39][40][41][42][43][44][45][46][47] Generation of ROS by reaction with redox active Fe, Cu, and Mncomplexes 38,[48][49][50][51][52][53][54][55][56][57][58] in the presence of reductant leads to controlled backbone or side chain attack which can be used to evaluate regions of macromolecular interface. While ribose ring radical strand breaks in DNA are generally due to H-atom abstraction from relatively weak tertiary C-H bonds 38 that are statistically plentiful and readily accessible, 59 H-atom abstraction from proteins is more complex. ...
Article
Full-text available
Current approaches toward modulation of metal-induced Aβ aggregation pathways involve the development of small molecules that bind metal ions, such as Cu(II) and Zn(II), and interact with Aβ. For this effort, we present the enediyne-containing ligand (Z)-N,N′-bis[1-pyridin-2-yl-meth(E)-ylidene]oct-4-ene-2,6-diyne-1,8-diamine (PyED), which upon chelation of Cu(II) and Zn(II) undergoes Bergman-cyclization to yield diradical formation. The ability of this chelation-triggered diradical to modulate Aβ aggregation is evaluated relative to the non-radical generating control pyridine-2-ylmethyl-(2-{[(pyridine-2-ylmethylene)-amino]-methyl}-benzyl)-amine (PyBD). Variable-pH, ligand UV-vis titrations reveal pKa = 3.81(2) for PyBD, indicating it exists mainly in the neutral form at experimental pH. Lipinski's rule parameters and evaluation of blood–brain barrier (BBB) penetration potential by the PAMPA–BBB assay suggest that PyED may be CNS+ and penetrate the BBB. Both PyED and PyBD bind Zn(II) and Cu(II) as illustrated by bathochromic shifts of their UV-vis features. Speciation diagrams indicate that Cu(II)–PyBD is the major species at pH 6.6 with a nanomolar Kd, suggesting the ligand may be capable of interacting with Cu(II)–Aβ species. In the presence of Aβ40/42 under hyperthermic conditions (43 °C), the radical-generating PyED demonstrates markedly enhanced activity (2–24 h) toward the modulation of Aβ species as determined by gel electrophoresis. Correspondingly, transmission electron microscopy images of these samples show distinct morphological changes to the fibril structure that are most prominent for Cu(II)–Aβ cases. The loss of CO2 from the metal binding region of Aβ in MALDI-TOF mass spectra further suggests that metal–ligand–Aβ interaction with subsequent radical formation may play a role in the aggregation pathway modulation.
... Similar to iron, copper (Cu) ions are also capable of catalyzing Fenton like reactions [124]. However, reaction kinetics by Cu is more sensitive to pH of the reaction solution, copper ion concentration and presence of substrate. ...
Article
Inorganic nanostructures have emerged as potential nanoplatforms for cancer therapy and imaging. The clinical translation of mesoporous silica nanoparticles after iron nanoparticles have led to growing interest in these nanoplatforms. The present review presents copper sulphide based nanostructures as a versatile platform for multimodal therapy and imaging of cancer. This review gives a detailed description of various synthesis methods of copper sulphide nanostructures and also discusses the various factors which can help in modulating the morphology of copper sulphide based nanostructures. The article further sheds light on the unique thermal, electronic and optical properties of these nanostructures which holds potential for biomedical applications. The role of copper sulphide nanostructures in serving as therapeutic platforms for cancer therapy has been explained along with alternative therapeutic approaches apart from chemotherapy for cancer including photothermal therapy, photodynamic therapy, radiotherapy and gene therapy. The review also inculcates the potential of copper sulphide nanoplatforms for multimodal imaging ability including MRI, radio-imaging, fluorescence imaging and photoacoustic imaging. The theranostic nanoplatform based on copper sulphide nanostructures have also been overviewed. The role of copper sulphide nanostructures in receptor targeted therapy of cancer has also been discussed in brief for better understanding of its role in targeted cancer therapy. The article gives insight about the toxicological issue associated with cooper sulphide nanoparticles and also provides regarding the recent advancements in copper sulphide nanostructures including nano-heterostructures and metal organic frameworks for future biomedical application.
... 4) [37]. OH· can also be initially generated by interaction of Fe 2+ and Cu + with oxygen (O 2 ) [38]. ...
Article
Full-text available
Chemical coprecipitation technique is proven to be a beneficial method to prepare uniformly mixed catalyst metal and Kraft lignin precursors. Coprecipitation is a simple, yet very complex process which is highly sensitive to the reaction conditions, particularly temperature. In an exothermic coprecipitation process, the reaction rate can become uncontrollable over certain temperatures which could lead to a thermal runaway reaction. In this work, metal-lignin nanocomposites were synthesized by coprecipitation of metal (M) salts and Kraft lignin. Kraft lignin and metal salts were dissolved in organic solvents and DI water, respectively, to make lignin solution/suspension and metal salt aqueous solution. The aqueous solutions of metal salts were then added to the lignin solutions/suspensions and mixed well, resulting in chelation of transition metal ions to the functional groups of lignin chains and co-precipitation of metal-lignin composites from the solvents. To develop a safe process for producing M-lignin composites in a large volume, potential reactions, exothermic or endothermic processes, hazards gases, and volatiles were evaluated during the coprecipitation process. The effects of transition metal type, solvent selection, concentration of metal salts, and initial solution temperature on the interactions between metal ions and Kraft lignin, metal uniformity in the lignin matrix, and morphology of the metal-lignin composites were investigated during the coprecipitation process. Cu, Mo, Ni, and Fe were investigated as the transition metals for the metal-lignin composites. Fenton or Fenton-like reactions were discovered to occur during the Fe- and Cu-lignin coprecipitation process and tremendous heat evolved, which lead to the overshoot of the reaction system temperature in a very short time (i.e. a few seconds). Significant amounts of CO2 and toxic NO2 gasses were released during the coprecipitation process when Fenton or Fenton-like reactions occurred. No interaction or a very weak interaction occurred between lignin and Mo(VI) ions when mixing both solutions. Ni ions were coordinated strongly to oxygen-containing functional groups in lignin, but no Fenton or Fenton-like reaction was detected during Ni-lignin coprecipitation. Fenton reaction or Fenton-like reaction occurred when tetrahydrofuran (THF) and acetone were used to dissolve Kraft lignin, and the reaction became highly fierce and unmanageable with increasing of iron content in the composite. The reaction initialization time was shortened with increase of initial solution temperature and thermal runaway reaction might occur if the initial mixing temperature reached 60 °C or above.
... Since copper is an essential trace element presenting toxic properties when in excess, organisms developed sophisticated mechanisms to provide the micronutrient to biological processes while preventing Cu 1+ toxicity. This includes the increase in the production of toxic hydroxyl radicals, damaging DNA and proteins (Urbanski and Berêsewicz, 2000;García-Santamarina and Thiele, 2015). Mechanisms that allow copper homeostasis at an appropriate concentration operates at several levels. ...
Article
Full-text available
Copper is an essential micronutrient for the performance of important biochemical processes such as respiration detoxification, and uptake of metals like iron. Studies have shown that copper deprivation is a strategy used by the host against pathogenic fungi such as Cryptoccocus neoformans and Candida albicans during growth and development of infections in the lungs and kidneys. Although there are some studies, little is known about the impact of copper deprivation in members of the Paracoccidioides genus. Therefore, using isobaric tag labeling (iTRAQ)-Based proteomic approach and LC-MS/MS, we analyzed the impact of in vitro copper deprivation in the metabolism of Paracoccidioides brasiliensis. One hundred and sixty-four (164) differentially abundant proteins were identified when yeast cells were deprived of copper, which affected cellular respiration and detoxification processes. Changes in cellular metabolism such as increased beta oxidation and cell wall remodeling were described.
... However, the group with Fe/Cu ratio of 0, consisting of the only Cu, produced weak fluorescence, indicating low conversion efficiency from H 2 O 2 to ROS. The result indicated that the combination of Fe with Cu in the oxide form could enhance the catalytic ability to generate ROS [63][64][65]. The optimal Fe/Cu ratio of 2 was shown to have reached the highest conversion rate. ...
Article
Full-text available
In this work we developed methylene blue-immobilized copper-iron nanoparticles (MB-CuFe NPs) through a facile one-step hydrothermal reaction to achieve a better phototherapeutic effect. The Fe/Cu ratio of the CuFe NPs was controllable by merely changing the loading amount of iron precursor concentration. The CuFe NPs could serve as a Fenton catalyst to convert hydrogen peroxide (H2O2) into reactive oxygen species (ROS), while the superparamagnetic properties also suggest magnetic resonance imaging (MRI) potential. Furthermore, the Food and Drug Administration (FDA)-approved MB photosensitizer could strongly adsorb onto the surface of CuFe NPs to facilitate the drug delivery into cells and improve the photodynamic therapy at 660 nm via significant generation of singlet oxygen species, leading to enhanced cancer cell-damaging efficacy. An MTT (thiazolyl blue tetrazolium bromide) assay proved the low cytotoxicity of the CuFe NPs to cervical cancer cells (HeLa cells), namely above 80% at 25 ppm of the sample dose. A slight dissolution of Cu and Fe ions from the CuFe NPs in an acidic environment was obtained, providing direct evidence for CuFe NPs being degradable without the risk of long-term retention in the body. Moreover, the tremendous photo-to-thermal conversion of CuFe NPs was examined, which might be combined with photodynamic therapy (PDT) for promising development in the depletion of cancer cells after a single pulse of deep-red light irradiation at high laser power.
... The pro-oxidant effect of vitamin C also occurs when it is combined with iron where it reduces Fe 3+ to Fe 2+ or when it is combined with copper and reduces Cu 2+ to Cu + . This process is accompanied by increased hydrogen peroxide (H 2 O 2 ) production, and consequently, the formation of hydroxyl radical (OH · ) [153,155,156]. As iron and copper act as enzyme cofactors that are essential for cellular life, they might participate in the autooxidation of vitamin C. Hence, vitamin C might provoke mild oxidative stress when there is a high level of iron in the body due to its prooxidative properties [151,154,157,158]. ...
Article
Full-text available
Oxidative stress occurs when there is an imbalance between the production of free radicals and the detoxification of these reactive products. Regular exercise greatly increases the production of free radicals in humans, while excessive exercise could lead to cellular and tissue damage. This paper presents a review of studies focusing on exercise-induced oxidative stress, sufficient intensity of aerobic or anaerobic exercises, and how exercise volume and duration could increase free radicals in humans. Furthermore, this review examines the effects of chronic or acute vitamin C supplementation in minimising oxidative stress during exercise. In this regard, vitamin C is commonly consumed as an antioxidant supplement by endurance athletes to minimise exercise-induced oxidative stress, augment recovery and improve performance. However, there is still a lack of evidence regarding the antioxidant effects of vitamin C supplements during exercise. Based on the review, it could be concluded healthy, physically active individuals might not require regular intakes of non-physiological dosages of vitamin C. On the other hand, studies found that regular exercise could lead to higher antioxidant production that could be beneficial in mitigating oxidative stress and improving individuals’ health.
... Copper is known to be a pro-oxidant, its addition to the fungal cultivation media and its interaction with the fungal cells results in the formation of hydrogen peroxide as an oxidative stress response (Palansiami and Lakshmanan 2010). Copper ions were reported to interact with dioxygen in the medium in a Fenton-like reaction (Urbanski and Berjesewicz 2000), its presence may have contributed to increasing the attack to the dye molecules present in the effluent. Copper is an important component of laccase active site could enhance laccase activity under certain conditions, it is also an important metal that acts as a catalytic oxidant, Copper-dioxygen complexes have been suggested to play important roles in a number of catalytic oxidation reactions, it is the major component protein involved in dioxygen metabolism and a main contributor to several physiological functions such as dioxygen carriers, oxidases, oxygenases and superoxide dismutases, it is therefore considered plausible to consider copper dioxygen adducts as the main key reaction intermediates in enzymatic reactions (Akyilmaz et al., 2010). ...
Article
Full-text available
Aspergillus flavus was isolated from soil and exhibited laccase activity under both constitutive and copper induced conditions. Spiking the medium with 1 mM copper sulfate resulted in an increase in the activity which reached 51.84 U/ml. a distinctive protein band was detected at 60 kDa. The extracellular enzyme was purified 81 fold using gel filtration chromatography and resulted in two different laccase fractions L1 and L2, the latter had a higher enzymatic activity which reached 79.57 U/ml and specific activity of 64.17 U/μg protein. The analysis of the spectrum of the L2 fraction showed a shoulder at 330 nm which is characteristic for T2/T3 copper centers; both copper and zinc were detected suggesting that this is an unconventional white laccase. Primers of laccase gene were designed and synthesized to recover specific gene from A. flavus. Sequence analysis indicated putative laccase (Genbank ID: JF683612) at the amino acid level suggesting a close identity to laccases from other genera containing the copper binding site. Decolorization of textile waste water under different conditions showed possible application in bioremediation within a short period of time. The effect of copper on A. flavus was concentration dependent.
... 37 Copper is a redox-active transition metal that can participate in single electron reactions and catalyze formation of free radicals, including the undesirable hydroxyl radicals. 38 So, any increase in its levels will lead to increase formation of toxic free radicals, which in turn lead to increase the risk of asthma. ...
Article
Full-text available
Introduction: Asthma is a chronic inflammatory disease of the airways characterized by recurrent respiratory symptoms of dyspnea, wheezing, chest tightness, and cough. Aim: This study aims to investigate the concentrations of Cu, Zn, Mg, Mn, Fe, Cr, Ni, and Al in the serum of asthmatic patients. Materials and methods: An atomic absorption technique was used to determine the levels of trace elements. The study included sixty asthmatic patients and ninety healthy individuals as control group their ages ranging from 20 to 45 years. Results: We found a significant increase of the levels of copper, iron, and aluminum by 20%, 54%, and 47% ( p <0.01), respectively, in the asthmatic patients as compared with the controls. On the other hand, in comparison with the controls, the levels of zinc, magnesium, manganese, and nickel were found to be significantly decreased ( p <0.01) by 24%, 16%, 53%, and 81%, respectively, in the asthmatic patient group. Moreover, chromium level showed non-significant differences ( p >0.05) between patients and control group. Conclusions: The increased level of Cu and Fe may reflect their potential role in the pathogenesis of asthma. Furthermore, the serum iron levels tend to be increased as a result of the inflammatory process that occurs in asthma. Low levels of Zn, Mg, and Mn may contribute to allergic diseases due to their role in the synthesis of certain antioxidants or to their effect on the immune system.
... Copper's potential to act as a catalyst for the production of free radicals is well documented. Many in vitro studies have shown that copper (Cu 2+ ) has been found to be a significantly more redox active metal than iron (Fe 3+ ) in various applications [223]. Mild to severe copper deficiencies result in reduced IL-2 production and decreased T cell proliferation, resulting in lymphopenia, making copper an essential component for the maintenance of a healthy immune system [212]. ...
Article
Full-text available
Food components have long been recognized to play a fundamental role in the growth and development of the human body, conferring protective functionalities against foreign matter that can be severe public health problems. Micronutrients such as vitamins and minerals are essential to the human body, and individuals must meet their daily requirements through dietary sources. Micronutrients act as immunomodulators and protect the host immune response, thus preventing immune evasion by pathogenic organisms. Several experimental investigations have been undertaken to appraise the immunomodulatory functions of vitamins and minerals. Based on these experimental findings, this review describes the immune-boosting functionalities of micronutrients and the mechanisms of action through which these functions are mediated. Deficiencies of vitamins and minerals in plasma concentrations can lead to a reduction in the performance of the immune system functioning, representing a key contributor to unfavorable immunological states. This review provides a descriptive overview of the characteristics of the immune system and the utilization of micronutrients (vitamins and minerals) in preventative strategies designed to reduce morbidity and mortality among patients suffering from immune invasions or autoimmune disorders.
... Copper is known to be a pro-oxidant, its addition to the fungal cultivation media and its interaction with the fungal cells results in the formation of hydrogen peroxide as an oxidative stress response (Palansiami and Lakshmanan 2010). Copper ions were reported to interact with dioxygen in the medium in a Fenton-like reaction (Urbanski and Berjesewicz 2000), its presence may have contributed to increasing the attack to the dye molecules present in the effluent. Copper is an important component of laccase active site could enhance laccase activity under certain conditions, it is also an important metal that acts as a catalytic oxidant, Copper-dioxygen complexes have been suggested to play important roles in a number of catalytic oxidation reactions, it is the major component protein involved in dioxygen metabolism and a main contributor to several physiological functions such as dioxygen carriers, oxidases, oxygenases and superoxide dismutases, it is therefore considered plausible to consider copper dioxygen adducts as the main key reaction intermediates in enzymatic reactions (Akyilmaz et al., 2010). ...
Article
Full-text available
Aspergillus flavus was isolated from soil and exhibited laccase activity under both constitutive and copper induced conditions. Spiking the medium with 1 mM copper sulfate resulted in an increase in the activity which reached 51.84 U/mL, a distinctive protein band was detected at 60 kDa. The extracellular enzyme was purified 81 fold using gel filtration chromatography and resulted in two different laccase fractions L1 and L2, the latter had a higher enzymatic activity which reached 79.57 U/mL and specific activity of 64.17 U/μg protein. The analysis of the spectrum of the L2 fraction showed a shoulder at 330 nm which is characteristic for T2/T3 copper centers; both copper and zinc were detected suggesting that this is an unconventional white laccase. Primers of laccase gene were designed and synthesized to recover specific gene from A. flavus . Sequence analysis indicated putative laccase (Genbank ID: JF683612) at the amino acid level suggesting a close identity to laccases from other genera containing the copper binding site. Decolorization of textile waste water under different conditions showed possible application in bioremediation within a short period of time. The effect of copper on A. flavus was concentration dependent.
Article
Industrial and agricultural wastes are the main source of copper accumulation in the soil. Copper is an essential micronutrient for plants, required for their growth, and participates in oxidation-reduction reactions. However, copper becomes a toxic metal when it is in tissues at concentrations higher than those needed for plant growth (>30mg·kg-1). Copper promotes the generation of reactive oxygen species (ROS), in enzymatic and non-enzymatic form (through the Fenton reaction), which may cause oxidation of proteins and lipids, alter membrane integrity, photosynthesis and growth, and induce cell death. Among the biochemical mechanisms that are induced in response to the oxidative damage caused by copper is the in crease in the activities of antioxidant enzymes such as catalase, superoxide dismutase, glutathione reductase, ascorbate and guaiacol peroxidases. Some studies indicate that antioxidant secondary metabolites such as phenolic acids, polyamines and flavonols could also be involved in counteracting the oxidative damage generated by copper. Due to the relevance of the damage that causes in plants the exposure to toxic levels of copper, in this article we review the studies performed from 2000 to 2012, showing the biochemical and physiological processes affected in plants by the oxidative stress induced by the metal and the antioxidant mechanisms that participate in the defense to copper excess.
Article
Fenton reaction and iron autoxidation have been debated for the major process in ROS mediated DNA cleavage. We compared both processes on iron oxidation, DNA cleavage, and cyclic voltammetric experiment at different pHs. Both oxidation reactions were preferred at basic pH condition, unlike DNA cleavage. This indicates that iron oxidation and the following steps probably occur separately. The ROS generated from autoxidation seems to be superoxide radical since sod exerted the best inhibition on DNA cleavage when H2O2 was absent. In comparison of cyclic voltammograms of Fe2+ in NaCl solution and phosphate buffer, DNA addition to phosphate buffer induced significant change in the redox cycle Of iron, indicating that iron may bind DNA as a complex with phosphate. Different pulse voltammogram in the presence of ctDNA suggest that iron ions are recyclable at acidic pH, whereas they may form an electrically stable complex with DNA at high pH condition.
Article
Calcium channel blockers represent a group of therapeutically important compounds that have found an application in treatment of systemic vascular resistance and arterial pressure, eventually angina pectoris. We studied possibility of application of a BY-2 cell model to evaluate the potential of newly prepared potential calcium channel blockers. In the preliminary experiment, toxicity of studied compounds was determined. In the next experiment, we evaluated possible protective effect of studied compounds on programmed cell death induced by hydrogen peroxide on the BY-2 cells. Calcium channel blocker lanthanum ions and imidazole, inhibitor of NAD(P)H oxidase (EC 1.6.3.1) that prevents reactive oxygen species formation and programmed cell death, were used as reference compounds to compare the effect of studied compounds. We studied changes in the cell viability and growth as well as markers of cell proliferation, levels of intracellular free calcium ions, reactive oxygen species, lipid peroxidation, and markers of programmed cell death, mitochondrial membrane potential and caspase-like activity. Late signs of programmed cell death (changes in nuclear architecture) were also evaluated. Our experiments revealed protective potential of studied compounds against programmed cell death induced by hydrogen peroxide and possibility of application of the BY-2 cell culture to evaluate pharmacological effects of studied compounds in preliminary tests.
Article
Full-text available
The main objective of this project is to study the possible association between anti-oxidant/redox status and DNA instability in Down syndrome. The activities of 5 antioxidant enzymes were studied in 19 Down syndrome (DS) cases and in age- and sex-matched normal controls. Sister Chromatid Exchanges (SCE) were measured in lymphocyte cultures derived from all DS and control subjects. All DS and control individuals had normal hematological parameters, but the proliferation and mitotic indices were significantly lower in the DS- than in the controls-derived lymphocyte cultures, while the average generation time was higher than that in the controls. The specific activity of superoxide dismutase in the DS individuals was 40% higher than that in the controls, while the specific activity of glutathione S-transferase in the DS group was significantly lower than that in the controls (P = 0.05). Catalase and glutathione peroxides' activities were not different between the two groups (P > 0.05). SCE rate in the DS derived cultures was significantly higher (P < 0.001) than that of the controls. DS individuals have a higher oxidative stress, higher superoxide dismutase activities and higher rates of SCE in their derived lymphocyte cultures compared to those of the controls. We claim that such differences may have resulted from the over expression of superoxide dismutase gene, leading to imbalanced cellular antioxidant mechanisms and, consequently, resulted in a high concentration of free radicals that destabilized the DNA as expressed by the high rate of SCE.
Article
Redox transition metals have been implicated as crucial players in pathogenesis of neurodegenerative diseases. Intracellular signaling mechanism(s) responsible for oxidative stress and death in single-cell model exposed to metals has not yet been fully elucidated. The objective of the study was to determine the mechanism by which metals induced apoptosis in human peripheral blood lymphocytes (PBL).MethodsPBL were exposed to 50, 100, 250, 500, and 1,000 μM (Fe2+), (Mn2+), (Cu2+), and (Zn2+)-(SO4). Apoptotic/necrotic morphology was assessed with acridine orange/ethidium bromide staining. Further evaluations comprised production of H2O2, generation of hydroxyl radical (·OH), disruption of mitochondrial transmembrane potential (ΔΨm), caspase-3 activation, and activation of NF-κB and p53 transcriptional factors.ResultsMorphologic analysis showed that 500 μM provoked maximal percentage of apoptosis (22–30% AO/EB) and minimal necrosis (3–7%), whereas low concentrations were innocuous but 1,000 μM induced mainly necrosis (>40% AO/EB). Metals generated both H2O2 and (·OH) by Fenton reaction. Hydroxyl scavengers protected PBL from metal-induced apoptosis. All metals induced mitochondrial depolarization (17–62% nonfluorescent cells) and activated caspase-3 concomitantly with apoptotic morphology (25–32% AO/EB) at 24 h, and neither NF-κB nor p53 transcription factor showed activation.Conclusions This study provides evidence that redox-active (Fe2+), (Mn2+), (Cu2+), and (Zn2+) ion-induced apoptosis in PBL by (H2O2)/(·OH) generation, resulting in mitochondria depolarization, caspase-3 activation, and nuclear fragmentation independent of NF-κB and p53 transcription factors activation. Our data highlight the potential use of lymphocytes as a model to screen antioxidant strategies designed to remove H2O2/·OH associated with metal-catalyzed reactions in neurodegenerative disorders.
Article
This study constructs a novel strategy for the activation of molecular oxygen over naturally abundant tenorite (CuO) complexed with ascorbic acid (AA). According to the results of ATR-FTIR characterization and DFT calculation, AA forms inner-sphere complexes with copper on the CuO surface (Cu(II)) in a monodentate mononuclear configuration, reduces Cu(II) to Cu(I), and complexes the latter species to efficiently activate molecular oxygen for the in situ production of H2O2 and subsequently generate reactive oxidants for the degradation of organic compounds. The multiple evidence of oxidant scavenging tests, EPR spectroscopy, molecular probe experiments, and XPS and XANES analyses collectively suggest that the dominant reactive oxidant is the surface-bound high-valent copper species (Cu(III)) rather than •OH. Compared with •OH, Cu(III) possesses the different oxidation behaviors for bisphenol A and benzoic acid and is less reactive toward alcohols and compounds with strongly electron-withdrawing groups and heterocyclic rings. The CuO/AA system exhibits stable performance that is only marginally affected by the water matrix and shows high durability in repetition tests. Thus, this work describes a promising strategy for the oxidation of organic contaminants via the activation of molecular oxygen and provides insights into the properties and identifications of the Cu(III) species.
Thesis
The rise of nanotechnology industries has led to the design and production of new nano-scaled materials such as quantum dots, nano-metals, carbon nanotubes, fullerenes and a myriad of functionalised derivatives. Extensive work concerning well characterised pathogenic fibres has led to the development of a fibre paradigm that suggests respirable fibres vary in their ability to cause disease based on length and pulmonary bio-persistence. Induction of oxidative stress is also a central plank of the mechanism used to explain inflammatory, fibrotic and carcinogenic effects of fibres. The toxicity of different particle types has consistently been shown to depend upon particle size and surface area, reactive surface molecular groups, metal content, organic content and the presence of endotoxins. A growing body of work has begun to examine the potential pathogenicity of carbon nanotubes to the pulmonary system as a consequence of superficial similarities to known pathogenic particle and fibres. The aim of this thesis was to investigate the potential toxicity of two commercially manufactured multi-walled carbon nanotubes (MWCNT) compared to a panel of low and high toxicity particles and fibres. The pro-inflammatory nature of MWCNT was examined in vitro and in vivo to determine the effects they may exert in the pulmonary system. In aqueous solutions of phosphate buffered saline, saline and cell culture medium (with or without foetal calf serum supplementation) MWCNT were found to exist as tight aggregates even after sonication. Analysis of metal content of MWCNT by ICP-AES revealed the presence of a low percentage of non extractable residual iron. From analysis of MWCNT by electron spin resonance (ESR) the CNT were found to be ready producers of a free radical species, despite this MWCNT were not able to cleave plasmid DNA. Upon incubation with the alveolar epithelial cell line A549 MWCNTs did not cause noticeable toxicity but did dose dependently deplete total glutathione levels. No increase in production of the pro-inflammatory cytokine IL-8 could be detected at the level of protein or at the level of mRNA. Analysis of the levels (protein and mRNA) of the pro-fibrotic mediator TGF-β did not indicate induction of a fibrotic response to MWCNT. Neither were MWCNTs found to consistently activate the pro-inflammatory associated transcription factor nuclear factor kappa B (NF-κB). Upon instillation into the peritoneal cavity of mice MWCNT failed to induce a pro-inflammatory response in contrast to long amosite asbestos that induced an extensive inflammatory reaction. Analysis of the diaphragms of exposed animals revealed the induction by MWCNT of an apparent foreign body type reaction. Overall with limited processing and dispersion MWCNT were morphologically more akin to particles than fibres. Although apparently able to spontaneously generate ROS in aqueous solution this did not translate into a capacity to cause toxicity or a capacity to induce inflammation either in vitro or in vivo.
Article
Full-text available
With the inclusion of engineered nanomaterials in industrial processes and consumer products, wastewater treatment plants (WWTPs) could serve as a major sink for these emerging contaminants. Previous research has demonstrated that nanomaterials are potentially toxic to microbial communities utilized in biological wastewater treatment (BWT). Copper-based nanoparticles (CuNPs) are of particular interest based on their increasing use in wood treatment, paints, household products, coatings, and byproducts of semiconductor manufacturing. A critical step in BWT is nutrient removal through nitrification. This study examined the potential toxicity of uncoated and polyvinylpyrrolidone (PVP) coated CuO, and Cu2O nanoparticles, as well as Cu ions to microbial communities responsible for nitrification in BWT. Inhibition was inferred from changes to the specific oxygen uptake rate (sOUR) in the absence and presence of Cu ions and CuNPs. X-ray Absorption Fine Structure spectroscopy, with Linear Combination Fitting (LCF), was utilized to track changes to Cu speciation throughout exposure. Results indicate that the dissolution of Cu ions from CuNPs drive microbial inhibition. The presence of a PVP coating on CuNPs has little effect on inhibition. LCF analysis of the biomass combined with metal partitioning analysis supports the current hypothesis that Cu-induced cytotoxicity is primarily caused by reactive oxygen species formed from ionic Cu in solution via catalytic reaction intermediated by reduced Cu(I) species.
Article
Full-text available
This paper compares the DNA interactions of a bis 9‐aminomethylanthracene dye (2) vs. a mono‐anthracene (4) under high ionic strength conditions similar to those in the cell nucleus (∼150 mM NaCl and 260 mM KCl). The chloride salts triggered an enhancement in anthracene‐sensitized DNA photocleavage, where bis‐anthracene 2 exhibited superior DNA binding affinity, faster reaction kinetics, and higher levels of DNA damage at low‐ to sub‐micro molar dye concentrations (350 nm hν, pH 7.0). While spectroscopic and viscometric data suggested that the chloride salts reduced DNA intercalation in favor of a non‐intercalative binding mode in which 2 and 4 were better able to generate hydroxyl radicals, there was evidence of persistent intercalation of the second anthracene ring of 2. We propose that such an interaction anchored the bis‐anthracene to DNA under the high ionic strength conditions, increasing its binding affinity and photocleaving capabilities relative to the mono analog (4).
Article
Copper is an essential metal for homeostasis and the functioning of living organisms. We investigated the effects of a high copper concentration on the myocardial mechanics, investigating the reactive oxygen species (ROS) mediated effects. The developed force of papillary muscles was reduced after acute exposure to a high copper concentration and was prevented by co-incubation with tempol, DMSO and catalase. The reuptake of calcium by the sarcoplasmic reticulum was reduced by copper and restored by tempol. The contractile response to Ca2+ was reduced and reversed by antioxidants. The response to the β-adrenergic agonist decreased after exposure to copper and was restored by tempol and catalase. In addition, the in situ detection showed increased O2·- and OH·. Contractions dependent on the sarcolemmal Ca2+ influx were impaired by copper and restored by antioxidants. Myosin-ATPase activity decreased significantly after copper exposure. In conclusion, a high copper concentration can acutely impair myocardial excitation-contraction coupling, reduce the capacity to generate force, reduce the Ca2+ inflow and its reuptake, and reduce myosin-ATPase activity, and these effects are mediated by the local production of O2·-, OH· and H2O2. These toxicity effects of copper overload suggest that copper is a risk factor for cardiovascular disease.
Article
Percutaneous devices—indwelling catheters—related infections are serious clinical incidents. It is accordingly necessary to develop anti-infective coating materials suitable for the devices for long-term effectiveness. In our research group, highly dispersible and crystalline hydroxyapatite (HAp) nanoparticles doped with metallic or halogen ions possessing antibacterial activities have been developed. In this study, antibacterial, dispersible, and crystalline zinc (Zn)-doped hydroxyapatite [Zn(15)-HAp] nanoparticles substituted with 13.5% Zn content [Zn/(Zn + Ca) × 100] were prepared by a wet chemical method using an anti-sintering agent through calcination. Antibacterial activities of Zn(15)-HAp nanoparticles were evaluated using Escherichia coli ( E. coli) and Staphylococcus aureus. The survival rates of the bacteria on Zn(15)-HAp nanoparticles were significantly lower than that on normal HAp (nHAp) coated surfaces, while no influences were observed on proliferation of L929 cells. Even after soaking Zn(15)-HAp nanoparticles in PBS for 2 weeks, the antibacterial activities against E. coli were maintained at a similar level to a 20 min soaking. The bacterial death was related to not only ion-exchange phenomenon between Zn and magnesium ions but also accumulation of reactive oxygen species (ROS) in the cells. Allergic-like reactions—anaphylactoid reactions—might not readily occur with Zn(15)-HAp nanoparticles because the amounts of histamine released from HMC-1 cells co-cultured with nanoparticles were not significantly different to that of nHAp, but were statistically much lower than that of chlorhexidine.
Article
As an important reactive oxygen species (ROS) with selective oxidation, singlet oxygen (1O2) has wide application prospects in biology and the environment. However, the mechanism of 1O2 formation, especially the conversion of superoxide radicals (•O2-) to 1O2, has been a great controversy. This process is often disturbed by hydroxyl radicals (•OH). Here, we develop a molybdenum cocatalytic Fenton system, which can realize the transformation from •O2- to 1O2 on the premise of minimizing •OH. The Mo0 exposed on the surface of molybdenum powder can significantly improve the Fe3+/Fe2+ cycling efficiency and weaken the production of •OH, leading to the generation of •O2-. Meanwhile, the exposed Mo6+ can realize the transformation of •O2- to 1O2. The molybdenum cocatalytic effect makes the conventional Fenton reaction have high oxidation activity for the remediation of organic pollutants and prompt the inactivation of Staphylococcus aureus, as well as the adsorption and reduction of heavy metal ions (Cu2+, Ni2+ and Cr6+). Compared with iron powder, molybdenum powder is more likely to promote the conversion from Fe3+ to Fe2+ during the Fenton reaction, resulting in a higher Fe2+/Fe3+ ratio and better activity regarding the remediation of organics. Our findings clarify the transformation mechanism from •O2- to 1O2 during the Fenton-like reaction and provide a promising REDOX Fenton-like system for water treatment.
Article
Heme oxygenase-1(HO-1) is a stress-inducible enzyme that mediates antioxidative and cytoprotective effects to maintain cellular redox homeostasis. In the present study, the full sequence of HO-1 was cloned from golden pompano, Trachinotus ovatus, by RT-PCR and RACE-PCR. The full cDNA sequence of HO-1 was 1349 bp in length which comprised of a 726 bp open reading frame (ORF) preceded by 262 bp 5′-untranslated region (UTR), and followed a 360 bp 3′UTR, encoding 241 amino acid residues. Phylogenetic analysis revealed that HO-1 showed highest similarity to that of Takifugu rubripes. Tissue distribution analysis showed that the expression level of HO-1 was relatively high in heart, liver and spleen. A trial was conducted to investigate the response of Nrf2/HO-1 signaling pathway to oxidative stress induced by copper. The results showed that mRNA expression of NF-E2-related nuclear factor2 (Nrf2), Kelch-like-ECH-associated protein1 (keap1), superoxide dismutase (SOD), catalase (CAT), HO-1, NAD(P)H quinone oxidoreductase 1 (NQO1) and GSH-PX all significantly increased in copper treated group than that in the control group. This work provides new insight into the molecular mechanism underlying the Nrf2/HO-1 pathway in oxidative response in T. ovatus.
Article
Full-text available
This review article is focused on the impact of antioxidants and prooxidants on health with emphasis on the type of antioxidants that should be taken. Medical researchers suggest that diet may be the solution for the control of chronic diseases such as cardiovascular complications, hypertension, diabetes mellitus, and different cancers. In this survey, we found scientific evidence that the use of antioxidants should be limited only to the cases where oxidative stress has been identified. This is often the case of specific population groups such as postmenopausal women, the elderly, infants, workers exposed to environmental pollutants, and the obese. Before starting any supplementation, it is necessary to measure oxidative stress and to identify and eliminate the possible sources of free radicals and thus increased oxidative stress.
Article
Full-text available
Fungal laccase is a robust enzyme with broad specificity and applicability in industrial processes. The successful use of enzymes requires large scale production within a short time. As laccase production is highly dependent on medium components and cultural conditions, the optimization of the same is essential for enhancement of its production efficiency. The objectives of present study were to screen litter dwelling fungi for their laccase production and optimize the culture conditions for hyper-production of laccase. A total of 58 fungal isolates were procured from 25 litter samples of plant origin collected from the Western Ghats of Karnataka, India. Among these, five including Mucor circinelloides GL1, Fusarium oxysporum GL2, F. oxysporum GL3, F. verticillioides GL5 and Ceriporiopsis sp. PA1 were selected for optimization studies based on their laccase producing ability. Maximum production was noticed in the optimized culture media and conditions compared to minimal media. Enhanced laccase production was observed by incubating them in optimized media at 28 °C for 8 days at 150 rpm. The laccase enzyme was purified from M. circinelloides GL1 using series of purification steps. The purified enzyme was a monomeric protein band with an apparent molecular weight of about 40 kDa. The present study reported that an indigenous litter dwelling fungus M. circinelloides GL1 found to be efficacious laccase producer in comparison to other isolates tested in this study. Therefore, it can further be utilized as a better biocatalyst in pertinent biotechnological applications.
Article
Soil is a living heterogeneous body mass consists of solid, water, gases, organic, inorganic matters and organisms and acts upon as a source and sink of any contaminant. Nanotechnology is a diversified, dynamic and transformative technology, which stimulates the scientific innovation for the betterment of different sectors of the society which produces large number of nanocontaminants. Nanocontaminants in the soil are a major concern because of their toxicities with subsequent threat to soil, environment and human community. These contaminants may badly influence soil ecology, crop production, or product quality, ground water purity and human health. Moreover, the safety protocol for the specific nanocontaminants is yet to be developed to protect our environment and ecology. Of late many research experiments were conducted to investigate and comprehend the outcome, lethal dose and behaviour of nanocontaminants and consequently to extend this knowledge for development of bio-safety protocol to handle the nanocontaminants in the coming decade. Research initiatives are focused on to understand the impacts of manufactured nanoparticles on human being, soil and formulate combat mechanisms to mitigate the adverse consequences of nanocontaminants on human health and soil quality. While this attempt signifies an exclusive chance for soil scientists to investigate these highly potential technologies, it also emphasizes on foremost challenges to a field of research that has great scope to predict the consequences of nanocontaminants on the soil ecology and animal health. Currently nanocontaminants draw the major world research attention and need more endeavours to entirely assess their impacts. This review documented an outline of impacts of nanocontaminants in soil, which highlights the understanding of major interactive effects of nanocontaminants on soil organisms, plants, and human. This article also provides highlights of the challenges that soil researchers and policy makers face when developing risk assessment tool for nanocontaminants in soil and subsequently for human being.Graphic abstract
Article
Developing more soluble and stable nanoformulation for the potent anticancer complex of copper diethyldithiocarbamate (CD) is extremely desired. Herein, for the first time, CD nanoparticles (NPs) were formulated by chelating diethyldithiocarbamate to bacterially and green chemically prepared copper oxide NPs (Bio CO NPs and Chemo CO NPs, respectively). Chemo CO NPs were produced in simpler and less time-consuming manner with higher NPs homogeneity. These CO NPs were identified, by X-ray diffractometer, as CuO and Cu2O, respectively. The nanoformulated CD complexes (Bio CD NPs and Chemo CD NPs) which have nanosizes (215.7 nm and 148.1 nm, respectively) with negative zeta potentials (∼-20 mv), exhibited not only high serum stability and solubility but also a potent anticancer effect. More importantly, Chemo CD NPs outperformed Bio CD NPs in the terms of synergistic anticancer index, apoptosis induction (>81% and <54%, respectively) and anti-migration efficacy (≥80% and <71%, respectively). This could be attributed to smaller nanosize and Cu2O of Chemo CD NPs causing higher cellular uptake with stronger inhibition of aldehyde dehydrogenase 1A1 and more free radical generation in Chemo CD NPs-treated cancer cells than Bio CD NPs. This distinct anticancer efficacy of novel Chemo CD NPs deserves further investigation using animal models.
Article
This review paper is focused on the detailed consideration of the structure, properties and reactions of H2O2. The paper highlights the importance of revealing these processes’ mechanisms, since they have been insufficiently studied so far, or the related data have a fragmentary and incomplete character. A special attention is given to catalytic oxidation reactions, formation and properties of intermediates, their role in the natural environment.
Article
Recent reviews evidence that the naturally occurring compounds containing the chromone skeleton exhibit antiradical activities, providing protection against oxidative stress. The antioxidant activities of 13 new synthesized chromonyl-2,4-thiazolidinediones, chromonyl-2,4-imidazolidinediones and chromonyl-2-thioxoimidzolidine-4-ones were evaluated using in vitro antioxidant assays, including superoxide anion radical (O2-•), hydroxyl radical (HO•), 2,2-diphenyl-1-picryl-hydrazyl free radical (DPPH(•) ) scavenging capacity and total antioxidant capacity ferric ion reducing activity. Superoxide anion radical was produced using potassium superoxide/18-crown-6-ether dissolved in dimethylsulfoxide, and the Fenton-like reaction (Fe(II) + H2 O2 ) was a generator of hydroxyl radicals. Chemiluminescence, spectrophotometry, electron paramagnetic resonance (EPR) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin trap were the measurement techniques. The results showed that the majority of the chromone derivatives tested showed a strong scavenging effect towards free radicals, similar to the chemiluminescence reaction with superoxide anion radical with a high activity, inhibition of the DMPO-OOH radical EPR signal (24-58%), the DMPO-OH radical EPR signal (4-75%) and DPPH radical EPR signal (6-100%) at 1 mmol/L. Several of the examined compounds exhibited the high reduction potentials. The results obtained show that the new synthesized chromone derivatives may directly scavenger reactive oxygen species and thus may play a protective role against oxidative damage. Copyright © 2014 John Wiley & Sons, Ltd.
Article
Full-text available
Little is known about changes in the amount of iron in the intracellular low molecular weight pool, which catalyzes the Fenton reactions during reperfusion after ischemia. In this study a new approach is presented to measure low molecular weight iron and it is applied to normal hearts during ischemia and to iron-loaded hearts during anoxia and reoxygenation. The results of this study show that (a) during ischemia in normal hearts a progressive 30-fold increase occurs in low molecular weight iron after 45 min of ischemia, whereas (b) during 45 min of anoxic perfusion the low molecular weight iron does not increase. This means that the reductive release from the storage protein ferritin is greatly enhanced by the acidification that occurs during ischemia. (c) Anoxic perfusion of iron-loaded hearts does increase low molecular weight iron and there is a further increase upon reoxygenation, which is prevented by (+)-cyanidanol-3. Based on these findings it is concluded that oxygen deprivation enhances the susceptibility of rat hearts to oxygen radicals by increasing the amount of catalytic, ferrous iron in the low molecular weight pool.
Article
Full-text available
The reaction between hydrogen peroxide and ferrous EDTA generates an oxidizing intermediate (I1) which is not the hydroxyl radical. It oxidizes ferrocytochrome c and also reacts with hydrogen peroxide (k5 = 3.2 X 10(3) M-1 S-1) to form a second oxidizing transient (I2). I1 is not scavenged by t-butyl alcohol whereas I2 is. I1 is found to be significantly less reactive than the hydroxyl radical toward benzoate ion, t-butyl alcohol, acetate ion, arginine, and serine, but is scavenged by compounds with readily oxidizable functional groups such as ethanol and isopropyl alcohol. This indicates that I1 does not undergo the characteristic reactions of the hydroxyl radical but shows a pattern of reactivity more associated with a metal ion oxidant like a ferryl (FeO2+)-EDTA complex.
Article
Full-text available
The application of kinetic probes that allow one to determine relative reactivities of biologically relevant substrates with oxidizing intermediates in the Fenton reagent (H2O2 plus Fe2+ in acidic aqueous solution) is described. These results lead to the conclusion that there are two key intermediates with very different reactivity patterns. One (X) is proposed to be an iron complex formed via direct reaction of H2O2 with Fe2+, which reacts with N-nitrosodimethylamine to generate a strong transient absorption at 450 nm. This provides a sensitive spectrophotometric probe of the competitive reactivities toward X of biologically relevant substrates such as nucleic acid components and amino acids. The second intermediate (Y) is probed by its oxidation of the Ru(bpy)2+3 ion (bpy = 2,2'-bipyridine) to a product with an absorption band centered at 500 nm. In the absence of other substrates, Ru(bpy)2+3 is oxidized at rates independent of the Ru concentration, but the product yield is diminished by competing reactions with substrates that can intercept X. Competition studies demonstrate reactivity patterns for X and Y that are clearly distinct from the pattern predicted for the hydroxyl radical, the intermediate commonly invoked in discussions of Fenton oxidations. These data require reevaluation of the mechanisms by which the Fenton reagent oxidizes biological substrates.
Article
Full-text available
In our search to establish a reference .OH production system with respect to which the reactivity of copper(II) complexes could then be tested, the influence of free Cu2+ ions on the Cu+/H2O2 reaction has been investigated. This influence depends on the CCu2+/CCu+ ratio. At low Cu2+ concentrations, .OH damage to various detector molecules decreases with increasing Cu2+ concentrations until CCu2+/CCu+ reaches unity. Above this value, .OH damage increases sharply until CCu2+/CCu+ becomes equal to 5 with salicylate and 2 with deoxyribose, ratios for which the protective effect of Cu2+ cancels. Finally, at higher concentrations, Cu2+ ions logically add their own .OH production to that normally expected from Cu+ ions. The possible origin of this unprecedented alternate effect has been discussed. The possible influence of Cu+ ions on the generation of .OH radicals by water gamma radiolysis has also been tested and, as already established for Cu2+ in a previous work, shown to be nonexistent. This definitely confirms that either form of ionised copper cannot scavenge .OH radicals in the absence of a ligand.
Article
Full-text available
Direct evidence for substantial mobilization of copper in the coronary flow immediately following prolonged, but not short, cardiac ischemia is presented. In the first coronary flow fraction (CFF) of reperfusion (0.15 ml), after 35 min of ischemia, the level of copper (as well as of iron) was 8- to 9-fold higher than the preischemic value. The levels in subsequent CFFs decreased and reached the preischemic value, indicating that both metals appear in a burst at the resumption of coronary flow. When the first CFF was used in a reaction mixture containing ascorbate and salicylate, the latter underwent chemical hydroxylation and was converted to its dihydroxybenzoate derivatives. Likewise, this CFF promoted the ascorbate-driven DNA degradation. Subsequent 150 CFFs were serially collected and demonstrated low activities. Following 18 min of ischemia, the copper level in the first CFF of reperfusion was only 15% over the preischemic value. In contrast, the mobilization of iron into coronary flow was significant but markedly lower than after 35 min. The levels of copper and the redox activity of the first CFF correlated well with the degree of loss of cardiac function, after 18 and 35 min of ischemia, respectively. After 18 min of ischemia, cardiac function was about 50% and the damage is considered reversible, whereas after 35 min the functional loss exceeded 80% and is considered irreversible. These results are in accord with the causative role that copper and iron can play in heart injury following ischemia, by virtue of their capacity to catalyze the production of hydroxyl radicals, and could lead to the development of new modalities for intervention in tissue injury.
Article
Full-text available
Vitamin C is marketed as a dietary supplement, partly because of its `antioxidant' properties. However, we report here that vitamin C administered as a dietary supplement to healthy humans exhibits a pro-oxidant, as well as an antioxidant, effect in vivo.
Article
The effects of co-supplementing healthy volunteers with iron (14 mg/day ferrous sulphate) and vitamin C (either 60 mg/day or 260 mg/day as ascorbic acid) on levels of oxidative DNA damage in white blood cells were studied. The subjects were divided into two groups: one group of 20 volunteers with a higher mean initial level of plasma vitamin C (71.9 ± 14.0 μmol/l) and a second group of 18 volunteers with a lower mean level (50.4 ± 25.8 μmol/l). In the first group there was a significant rise in several oxidative DNA base damage products and in total oxidative DNA damage in DNA extracted from white blood cells, but not in 8-hydroxyguanine, after 6 weeks of supplementation. However, after 12 weeks levels returned approximately to normal. In the group with the lower initial level of plasma ascorbate, presupplemental levels of oxidative DNA damage were higher and decreased on supplementation with iron and ascorbate. Since oxidative DNA damage has been suggested as a risk factor for the development of cancer, the implications of increased levels in well-nourished subjects after iron/ascobate supplementation are disturbing in view of the frequent use of dietary supplements containing both iron salts and ascorbate.
Article
We investigated changes in pH1 during ischaemia-reperfusion of isolated rat hearts using phosphorus nuclear magnetic resonance spectroscopy (31P NMR). Hearts were separated into three groups according to the perfusion buffer: bicarbonate-buffered Krebs solution, HEPES-buffered Krebs solution, or bicarbonate-buffered Krebs solution plus 10−6m 5-(N-ethyl-N-isopropyl) amiloride (EIPA).In HEPES buffer and in bicarbonate buffer plus EIPA, pH at the end of 30 min of ischaemia and pH oscillations observed during early reperfusion were lower than in bicarbonate buffer. Thus, the presence of two pH regulation mechanisms (Na+-H+ antiport and Na+-HCO3− symport) was confirmed in the isolated rat heart, while in HEPES buffer, pH was regulated by Na+-H+ antiport, and in bicarbonate buffer plus EIPA, by Na+-HCO3− symport.When cardiac contraction was inhibited by 10 mm 2,3-butanedione 2-monoxime (BDM), we observed, in all cases, a less pronounced decrease in pHi at the end of ischaemia, and in pHi oscillations at the onset of reperfusion. These effects were similar to those observed with 150 × 10−8m verapamil and might thus be related to a decrease in intracellular calcium. However, with BDM, a greater reduction in the pH recovery rate was observed only in HEPES buffer, suggesting a possible phosphatase-like effect affecting the Na+-H+ exchange. Whatever the buffer used, the protective effect of BDM was reflected by an increase in the rate pressure product, which was not observed with verapamil.
Article
The rate of oxidation of Fe(II) by atmospheric oxygen at pH 7.0 is significantly enhanced by low molecular weight Fe(III)-complexing agents in the order EDTA ≈ nitrilotriacetate > citrate > phosphate > oxalate. This simple effect of Fe(III) binding probably accounts for the “ferroxidase” activity exhibited by transferrin and ferritin.
Article
In 1969, McCully made the clinical observation linking elevated plasma homocyst(e)ine concentrations with vascular disease.1 He reported autopsy evidence of extensive arterial thrombosis and atherosclerosis in two children with elevated plasma homocyst(e)ine concentrations and homocystinuria. On the basis of this observation, he proposed that elevated plasma homocyst(e)ine (hyperhomocyst(e)inemia) can cause atherosclerotic vascular disease. The term “homocyst(e)ine” is used to define the combined pool of homocysteine, homocystine, mixed disulfides involving homocysteine, and homocysteine thiolactone found in the plasma of patients with hyperhomocyst(e)inemia. Subsequent investigations have confirmed McCully's hypothesis, and it has recently become clear that hyperhomocyst(e)inemia is an independent risk factor . . .
Article
Mechanisms of iron-catalyzed lipid peroxidation depend on the presence or absence of preformed lipid hydroperoxides (LOOH). Preformed LOOH are decomposed by Fe(II) to highly reactive lipid alkoxyl radicals, which in turn promote the formation of new LOOH. However, in the absence of LOOH, both Fe2+ and Fe3+ must be available to initiate lipid peroxidation, with optimum activity occurring as the Fe2+/Fe3+ ratio approaches unity. The simultaneous availability of Fe2+ and Fe3+ can be achieved by oxidizing some Fe2+ with hydrogen peroxide or with chelators that favor autoxidation of Fe2+ by molecular oxygen. Alternatively, one can use Fe3+ and reductants like superoxide, ascorbate or thiols. In either case excess Fe2+ oxidation or Fe3+ reduction will inhibit lipid peroxidation by converting all the iron to the Fe3+ or Fe2+ form, respectively. Superoxide dismutase and catalase can affect lipid peroxidation by affecting iron reduction/oxidation and the formation of a (1:1) Fe2+/Fe3+ ratio. Hydroxyl radical scavengers can also increase or decrease lipid peroxidation by affecting the redox cycling of iron.
Article
Reperfusion of acutely ischemic myocardium is associated with various distinctive pathophysiologic derangements, which are collectively referred to as reperfusion injury. Among these, three have been attributed to oxygen radicals: a) arrhythmias, b) transient mechanical dysfunction ("stunning"), and c) cell death. a) Reperfusion-induced arrhythmias. Although the precise mechanism for reperfusion arrhythmias remains to be determined, considerable evidence suggests that oxygen radicals play an important pathogenetic role in these rhythm disturbances. b) Transient mechanical dysfunction ("myocardial stunning"). Studies suggest that this abnormality is caused by events occurring in the initial seconds of reperfusion, and therefore represents a manifestation of sublethal, reversible reperfusion injury. Although our understanding of the mechanism of myocardial stunning is still fragmentary, there is overwhelming evidence for a pathogenetic role of oxygen radicals. c) Cell death. The evidence that reperfusion causes extension of the infarct produced by the antecedent ischemia is highly controversial. Although several studies have reported reduction of infarct size with antioxidants applied at the time of reperfusion, numerous other investigations have failed to reproduce these results. At present, there is no obvious explanation for this discrepancy. What is clear is that short-term administration of antioxidants at the time of reperfusion will not produce sustained limitation of infarct size. However, the possibility that long-term administration of antioxidants will produce sustained limitation of infarct size merits further consideration. In conclusion, there is strong evidence that the generation of oxygen radicals upon reperfusion plays an important pathogenetic role in two manifestations of reperfusion injury, namely, arrhythmias and stunning. Intense controversy persists regarding whether oxygen radicals contribute to extending cell death upon reperfusion and whether reperfusion in itself causes cell death. On the basis of the evidence available at this time, oxygen radicals appear to be important in the genesis of relatively mild, sublethal forms of myocellular damage, but their role in the genesis of lethal myocellular injury remains to be established.
Article
Publisher Summary This chapter discusses the role of free radicals and catalytic metal ions in human disease. The importance of transition metal ions in mediating oxidant damage naturally leads to the question as to what forms of such ions might be available to catalyze radical reactions in vivo . The chapter discusses the metabolism of transition metals, such as iron and copper. It also discusses the chelation therapy that is an approach to site-specific antioxidant protection. The detection and measurement of lipid peroxidation is the evidence most frequently cited to support the involvement of free radical reactions in toxicology and in human disease. A wide range of techniques is available to measure the rate of this process, but none is applicable to all circumstances. The two most popular are the measurement of diene conjugation and the thiobarbituric acid (TBA) test, but they are both subject to pitfalls, especially when applied to human samples. The chapter also discusses the essential principles of the peroxidation process. When discussing lipid peroxidation, it is essential to use clear terminology for the sequence of events involved; an imprecise use of terms such as initiation has caused considerable confusion in the literature. In a completely peroxide-free lipid system, first chain initiation of a peroxidation sequence in a membrane or polyunsaturated fatty acid refers to the attack of any species that has sufficient reactivity to abstract a hydrogen atom from a methylene group.
Article
Superoxide (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (.OH) produced from the "autoxidation" of biomolecules, such as ascorbate, catecholamines, or thiols, have been implicated in numerous toxicities. However, the direct reaction of dioxygen with the vast majority of biomolecules, including those listed above, is spin forbidden, a condition which imposes a severe kinetic limitation on this reaction pathway. Therefore, an alternate mechanism must be invoked to explain the "autoxidations" reactions frequently reported. Transition metals are efficient catalysts of redox reactions and their reactions with dioxygen are not spin restricted. Therefore it is likely that the "autoxidation" observed for many biomolecules is, in fact, metal catalyzed. In this paper we discuss: 1) the quantum mechanic, thermodynamic, and kinetic aspects of the reactions of dioxygen with biomolecules; 2) the involvement of transition metals in biomolecule oxidation; and 3) the biological implications of metal catalyzed oxidations. We hypothesize that true autoxidation of biomolecules does not occur in biological systems, instead the "autoxidation" of biomolecules is the result of transition metals bound by the biomolecules.
Article
A method for the determination of desferrioxamine-available iron in tissue fractions is described which involves incubation with desferrioxamine, extraction of desferrioxamine and its iron-bound form, ferrioxamine, and quantitation of these two forms of the drug by reversed-phase hplc analysis. Chelatable iron levels in the 1-10 microMolar region could be accurately and reproducibly measured using this technique. The desferrioxamine-available iron levels in both the cortex and medulla of rabbit kidneys were significantly elevated (up to 2-fold) after the organs had been subjected to 2 hours warm ischaemia or 24 hours cold storage at 0 degrees C in hypertonic citrate solution. There was no change in the total iron content of the tissues under these circumstances and thus a redistribution of intracellular iron to more available pools had presumably taken place as a result of ischaemia. This redistribution of iron may be an important factor in the initiation of peroxidative damage to cell membranes upon reperfusion of the organ with oxygen.
Article
Protein exposed to glucose is cleaved, undergoes conformational change and develops fluorescent adducts ('glycofluorophores'). These changes are presumed to result from the covalent attachment of glucose to amino groups. We have demonstrated, however, that the fragmentation and conformational changes observed are dependent upon hydroxyl radicals produced by glucose autoxidation, or some closely related process, and that antioxidants dissociate structural damage caused by the exposure of glucose to protein from the incorporation of monosaccharide into protein. We have also provided further evidence that glycofluorophore formation is dependent upon metal-catalysed oxidative processes associated with ketoaldehyde formation. If experimental glycation is an adequate model of tissue damage occurring in diabetes mellitus, then these studies indicate a therapeutic role for antioxidants.
Article
The iron chelator desferal is a powerful inhibitor of lipid peroxidation and of hydroxyl radical formation dependent on the presence of iron salts. Desferal also reacts with superoxide radical with a second-order rate constant approximately equal to 3 X 10(2) M-1 s-1 at pH 10.2 and approximately 9 X 10(2) M-1 s-1 at physiological pH. It is concluded that this slow reaction of desferal with O2- is unlikely to influence the interpretation of experiments in which the chelator is used. The ability of desferal to react with hydroxyl radical (k2 approximately 10(10) M-1 s-1) is a far more likely source of error in the interpretation of results using this chelating agent.
Article
Assays for brain tissue malondialdehyde (MDA) and low molecular weight chelated (LMWC) iron were used to examine samples of the cerebral cortex obtained from dogs 2 h after resuscitation from a 15-min cardiac arrest. The effect of post-resuscitation treatment with lidoflazine and/or desferrioxamine was similarly examined. Non-ischemic brain samples had LMWC iron levels (in nmol/100 mg tissue) of 12.32 + 2.60 and MDA levels (in nmol/100 mg tissue) of 8.46 + 1.35. Animals subjected to cardiac arrest and resuscitation and standard intensive care (SIC) had LMWC iron levels of 37.04 + 4.58 (p less than .01 against non-ischemic controls) and MDA levels of 12.24 + 1.9 (p less than .05 against non-ischemic controls). All treatment interventions significantly reduced the LMWC iron (p less than .05), but only treatment with desferrioxamine alone significantly reduced MDA (p less than .05), although a trend toward reduction of the MDA was also evident in animals treated with both desferrioxamine and lidoflazine. LMWC iron levels are increased in the post-ischemic brain, and this increase may be related to lipid peroxidation in the brain following resuscitation from cardiac arrest. These changes are probably pathologic and are amenable to pharmacologic intervention.
Article
Evidence is presented for a sensitive method useful for the detection of hydroxyl free radical generation in various systems. The methodology employs high pressure liquid chromatography with electrochemical detection (LCED) for the quantification and identification of the hydroxylation products from the reaction of OH with both phenol and salicylate. A detection limit of less than 1 pmol for the hydroxylation products has been achieved with electrochemical detector responses linear over at least three orders of magnitude. Detection and quantitation of the hydroxylation products obtained and formed during OH generation from biologically meaningful systems have been demonstrated. The three systems utilized were ADP/FE(II)/H2O/, hypoxanthine/xanthine oxidase plus chelated iron, and UV photolysis of H2O2.
Article
The hypothesis that oxygen-derived free radicals play an important role in myocardial ischemic and reperfusion injury has received a lot of support. In the presence of catalytic amounts of transition metals such as iron, superoxide anions, and hydrogen peroxide can be transformed into a highly reactive hydroxyl radical .OH (Haber-Weiss reaction). In view of this, we have undertaken this study to investigate whether iron is involved in the reperfusion syndrome and therefore could aggravate free radicals injury. Coronary effluent iron concentrations and cardiac cytosolic iron levels were evaluated in rat hearts subjected to an ischemia/reperfusion sequences. In the case of total ischemia, iron concentration in coronary effluents peaked immediately in the first sample collected upon reperfusion. However, in the case of partial ischemia, iron concentration in coronary effluents peaked rather exclusively during ischemia period. Cardiac cytosolic iron level augmented significantly after 30 min of total ischemia and non significantly in the other ischemia protocols compared to perfused control hearts. It also appears that the iron released is not protein-bound, and could therefore have a marked catalytic activity. The results of the present study suggest that in the oxygen paradox, iron plays an important role in inducing alterations during reoxygenation.
Article
The oxidation of Fe2+ was investigated by electron paramagnetic resonance (EPR) spin trapping techniques with N-t-butyl-alpha-phenylnitrone (PBN) and dimethyl sulfoxide. Under pure oxygen, the spin adduct PBN/.OCH3 was rapidly generated by the addition of Fe2+ (0.2-1.2 mM) into phosphate buffer containing ethylenediaminetetraacetate (EDTA), dimethyl sulfoxide and PBN at pH 7.4, but it decayed. The decay process of PBN/.OCH3 consists of two components. The fast decay was dependent on Fe2+ concentration. Another was due to destruction of the spin adduct by superoxide anion (.O2-), because superoxide dismutase (SOD) markedly prevented the decay. Catalase decreased the yield of PBN/.OCH3. When Fe(3+)-EDTA and ascorbate were used instead of Fe(2+)-EDTA, similar phenomena were detected. These results demonstrate that Fe2+ reacts with O2 to generate .O2-, then H2O2, which produces .CH3 by the reaction with Fe2+ and dimethyl sulfoxide. The .OCH3 radical results from the reaction between .CH3 and O2. The adduct PBN/.OCH3 decays by the reaction with Fe2+ and .O2-.
Article
We examined the effect of iron (II) on the generation of hydroxyl radicals (.OH) in the extracellular fluid of rat myocardium. Salicylic acid in Ringer's solution (0.5 nmole x microliter(-1) x min(-1)) was directly infused through a microdialysis probe to detect the generation of OH as reflected by the formation of dihydroxybenzoic acid (DHBA) in the myocardium. Iron clearly produced a dose-dependent increase in .OH formation. A positive linear correlation between iron (II) and the formation of 2,3-DHBA (R2 = 0.970) or 2.5-DHBA (R2 = 0.983) was observed. However, when desferrioxamine (DES) was infused through a dialysis probe, a marked increase in DHBA formation was obtained. The present results suggest that iron (III) may reduce .OH formation by the Fenton reaction.
Article
Superoxide promotes hydroxyl-radical formation and consequent DNA damage in cells of all types. The long-standing hypothesis that it primarily does so by delivering electrons to adventitious iron on DNA was refuted by recent studies in Escherichia coli. Alternative proposals have suggested that superoxide may accelerate oxidative DNA damage by leaching iron from storage proteins or enzymic [4Fe-4S] clusters. The released iron might then deposit on the surface of the DNA, where it could catalyze the formation of DNA oxidants using other electron donors. The latter model is affirmed by the experiments described here. Whole-cell electron paramagnetic resonance demonstrated that the level of loose iron in superoxide-stressed cells greatly exceeds that of unstressed cells. Bacterial iron storage proteins were not the major source for free iron, since superoxide also increased iron levels in mutants lacking these iron storage proteins. However, overproduction of an enzyme containing a labile [4Fe-4S] cluster dramatically increased the free iron content of cells when they were growing in air. The rates of spontaneous mutagenesis and DNA damage from exogenous H2O2 increased commensurately. It is striking that both growth defects and DNA damage caused by superoxide ensue from its ability to damage a subset of iron-sulfur clusters.
Article
There is considerable dispute about whether the hydroxylating ability of peroxynitrite (ONOO-)- derived species involves hydroxyl radicals (OH.). This was investigated by using salicylate and phenylalanine, attack of OH. upon which leads to the formation of 2,3- and 2,5-dihydroxybenzoates, and o- m- and p- tyrosines respectively. On addition of ONOO- to salicylate, characteristic products of hydroxylation (and nitration) were observed in decreasing amounts with rise in pH, although added products of hydroxylation of salicylate were not recovered quantitatively at pH 8.5, suggesting further oxidation of these products and underestimating of hydroxylation at alkaline pH. Hydroxylation products decreased in the presence of several OH. scavengers, especially formate, to extents similar to those obtained when hydroxylation was achieved by a mixture of iron salts, H2O2 and ascorbate. However, OH. scavengers also inhibited formation of salicylate nitration products. Ortho, p- and m-tyrosines as well as nitration products were also observed when ONOO- was added to phenylalanine. The amount of these products again decreased at high pH and were decreased by addition of OH. scavengers. We conclude that although comparison with Fenton systems suggests OH. formation, simple homolytic fission of peroxynitrous acid (ONOOH) to OH. and NO2. would not explain why OH. scavengers inhibit formation of nitration products.
Article
The reaction of Fe2+ with molecular oxygen (autoxidation) was investigated in 20 mM phosphate buffer (pH 7.4) at 37 degrees C using a fluorescent OH probe, coumarin-3-carboxylic acid. The autoxidation of unchelated Fe2+ produces OH radicals. Polyphosphatic chelators (pyrophosphate and tri- and tetrapoly phosphate) enhanced the generation of radicals. This effect was explained by an alteration of the reaction mechanism. The two-electron reduction of the oxygen molecule and the generation of hydrogen peroxide intermediates are the major reactions during Fe2+ autoxidation. The polyphosphatic complexes of ferrous ion reduce molecular oxygen and reactive oxygen intermediates by a one-electron mechanism. The chelation of ferrous ion increases the generation of the superoxide radical and production of OH during ferrous ion autoxidation and in the Fenton reaction. The results consider the ferrous ion-polyphosphate system as a convenient model for the generation of hydroxyl radical in biological systems.
Article
A sensitive electrochemical detection system was employed together with a specific salicylate hydroxylation assay to comparatively assess the effects of various substances on the iron-mediated generation of the hydroxyl radical (.OH). Hydroxyl radical production was found to be enhanced significantly by reduced glutathione, cysteine, ascorbic acid, and selected catechols, but not by mannitol, melatonin or tyramine. The data showed that over the range of concentrations examined, the augmented effects were linearly proportional to the amount of added reductant for a given amount of iron in the system. The pro-oxidant activity of thiols and ascorbate reduced and recycled iron providing both hydrogen peroxide (H2O2) and catalytic ferrous ions for augmented .OH production by the Fenton reaction. The enhanced production of .OH by catechols resulted from their oxidation either by molecular oxygen or ferric ions, with the accompanying formation of semiquinones, superoxide anion and H2O2. These data caution against therapeutic applications of thiols and ascorbate for ameliorating oxy-radical-induced tissue damage in environments where free redox-active metal ions may be present to function both as foci for site-specific peroxidative activity, and as catalysts to promote the pro-oxidant properties of certain endogenous reductants, thereby elevating rather than diminishing .OH levels.
Article
The kinetics of the production of hydroxyl radicals during the autoxidation of ferrous ion complexes at pH 7.4 was investigated using the fluorescent probe coumarin-3-carboxylic acid. Polyphosphates (tri- and tetrapolyphosphate and their adenosine derivatives), citrate, and acetic derivatives of ethyleneamine ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), ethylenediamine-(N,N')-diacetic acid (EDDA) and nitrilotriacetic acid (NTA) were used as iron chelators. Production of hydroxyl radical in these chemical systems was compared with that by radiation to determine the equivalent doses of radiation that produced equal amounts of .OH. The amount of .OH formed during ferrous ion autoxidation is determined by the concentration of the complex, its structure and the radical scavenging by the chelator molecule. Production of .OH for homologous ethylenamine acetates increases with increased complex stability: NTA < EDDA < TTHA < EDTA < DTPA. The radiation dose equivalence for 0.1 mM complexes increased from 5 Gy for NTA to 25 Gy for DTPA. The radiation dose equivalence for polyphosphates was 15 Gy for tripolyphosphate and 32 Gy for tetrapolyphosphate. The dose equivalences for adenosine phosphates are lower, 5 Gy for ATP and 10 Gy for adenosine tetraphosphate, due to intramolecular .OH scavenging. The rate of generation of .OH shows an inverse correlation with the charge of the ferrous ion complex, varying from 2 cGy/s for DTPA to 1.2 Gy/s for EDTA. The data presented indicate the usefulness of autoxidation of ferrous ion complexes for generation of .OH in chemical systems. The ability to control the amount and the rate of production of .OH may prove useful for examining the cytotoxic effects of .OH generated in biological systems.
Article
Iron can be a detrimental catalyst in biological free radical oxidations. Because of the high physiological ratio of [O2]/[H2O2] (> or = 10(3)), we hypothesize that the Fenton reaction with pre-existing H2O2 is only a minor initiator of free radical oxidations and that the major initiators of biological free radical oxidations are the oxidizing species formed by the reaction of Fe2+ with dioxygen. We have employed electron paramagnetic resonance spin trapping to examine this hypothesis. Free radical oxidation of: 1) chemical (ethanol, dimethyl sulfoxide); 2) biochemical (glucose, glyceraldehyde); and 3) cellular (L1210 murine leukemia cells) targets were examined when subjected to an aerobic Fenton (Fe2+ + H2O2 + O2) or an aerobic (Fe2+ + O2) system. As anticipated, the Fenton reaction initiates radical formation in all the above targets. Without pre-existing H2O2, however, Fe2+ and O2 also induce substantial target radical formation. Under various experimental ratios of [O2]/[H2O2] (1-100 with [O2] approximately 250 microM), we compared the radical yield from the Fenton reaction vs. the radical yield from Fe2+ + O2 reactions. When [O2]/[H2O2] < 10, the Fenton reaction dominates target molecule radical formation; however, production of target-molecule radicals via the Fenton reaction is minor when [O2]/[H2O2] > or = 100. Interestingly, when L1210 cells are the oxidation targets, Fe2+ + O2 is observed to be responsible for formation of nearly all of the cell-derived radicals detected, no matter the ratio of [O2]/[H2O2]. Our data demonstrate that when [O2]/[H2O2] > or = 100, Fe2+ + O2 chemistry is an important route to initiation of detrimental biological free radical oxidations.
Article
Transient ischemia has been shown to impair endothelium-dependent, but not endothelium-independent, coronary vasodilation, indicating selective endothelial dysfunction. Here a hypothesis was tested that agonist mediated activation of protein kinase C (PKC) and the related overproduction of the oxidative species contribute to the mechanism of the endothelial dysfunction. Perfused guinea-pig hearts were subjected either to 30 min global ischemia/30 min reperfusion or to 30 min aerobic perfusion with a PKC activator, phorbol ester (1 n M, PMA). Coronary flow responses to a bolus of acetylcholine (ACh) and sodium nitroprusside (SNP) were used as measures of endothelium-dependent and endothelium-independent vascular function, respectively. Salicylate hydroxylation was used as the assay for the myocardial hydroxyl radical (.OH) formation. Both ischemia/reperfusion and PMA impaired the ACh response and augmented the myocardial.OH production. The effect of ischemia/reperfusion on the ACh response: (i) was fully prevented by a PKC inhibitor, chelerythrine (2microM) and a mixed endothelin blocker, bosentan (20microM); (ii) was partially prevented by an endothelin converting-enzyme inhibitor, phosphoramidon (40microM), and superoxide dismutase (150-500 U/ml, SOD) and (iii) was affected neither by catalase (600 U/ml) nor by losartan (20microM) and captopril (250microM), nor by prazosin (10microM). SOD, but not bosentan, partially prevented the effect of PMA on the ACh response. None of the interventions studied affected the SNP response. The reperfusion-induced.OH release was attenuated by chelerythrine and bosentan, was not affected by prazosin and was increased by SOD. These results implicate the following sequence of events in the mechanism of the post-ischemic endothelial dysfunction: ischemia/reperfusion, endothelin-induced PKC activation, increased production of superoxide and/or some of its toxic metabolite, damage to the endothelium and endothelial dysfunction. The results argue against the contribution of angiotensin II, adrenergicalpha(1)-receptors and kinins in the mechanism of the post-ischemic endothelial dysfunction in guinea-pig hearts.