The role of intracellular zinc in chromium(VI)-induced oxidative stress, DNA damage and apoptosis

Several studies have demonstrated that zinc is required for the optimal functioning of the skin. Changes in intracellular zinc concentrations have been associated with both improved protection of skin cells against various noxious factors as well as with increased susceptibility to external stress. Still, little is known about the role of intracellular zinc in hexavalent chromium (Cr(VI))-induced skin injury. To address this question, the effects of zinc deficiency or supplementation on Cr(VI)-induced cytotoxicity, oxidative stress, DNA injury and cell death were investigated in human diploid dermal fibroblasts during 48 h. Zinc levels in fibroblasts were manipulated by pretreatment of cells with 100 microM ZnSO4 and 4 or 25 microM zinc chelator TPEN. Cr(VI) (50, 10 and 1 microM) was found to produce time- and dose-dependent cytotoxicity resulting in oxidative stress, suppression of antioxidant systems and activation of p53-dependent apoptosis which is reported for the first time in this model in relation to environmental Cr(VI). Increased intracellular zinc partially attenuated Cr(VI)-induced cytotoxicity, oxidative stress and apoptosis by enhancing cellular antioxidant systems while inhibiting Cr(VI)-dependent apoptosis by preventing the activation of caspase-3. Decreased intracellular zinc enhanced cytotoxic effects of all the tested Cr(VI) concentrations, leading to rapid loss of cell membrane integrity and nuclear dispersion--hallmarks of necrosis. These new findings suggest that Cr(VI) as a model environmental toxin may damage in deeper regions residing skin fibroblasts whose susceptibility to such toxin depends among others on their intracellular Zn levels. Further investigation of the impact of Zn status on skin cells as well as any other cell populations exposed to Cr(VI) or other heavy metals is warranted.     

Sustained delivery of exogenous melatonin influences biomarkers of oxidative stress and total antioxidant capacity in summer-stressed anestrous water buffalo (Bubalus bubalis)

High ambient temperature during summer in tropical and subtropical countries predisposes water buffaloes (Bubalus bubalis) to develop oxidative stress having antigonadotropic and antisteroidogenic actions. Melatonin is a regulator of seasonal reproduction in photoperiodic species and highly effective antioxidant and free radical scavenger. Therefore, a study was designed to evaluate the effect of sustained-release melatonin on biomarkers of oxidative stress i.e., the serum malondialdehyde (MDA) and nitric oxide (NO), and the total antioxidant capacity (TAC). For the study, postpartum buffaloes diagnosed as summer anestrus (absence of overt signs of estrus, concurrent rectal examination, and RIA for serum progesterone) were grouped as treated (single subcutaneous injection of melatonin at 18 mg/50 kg body weight dissolved in sterilized corn oil as vehicle, n = 20) and untreated (subcutaneous sterilized corn oil, n = 8). Blood sampling for estimation of serum TAC and MDA (mmol/L) and NO (μmol/L) was carried out at 4 days of interval from 8 days before treatment till 28 days after treatment or for the ensuing entire cycle length. Results showed serum TAC concentration was higher in the treatment group with a significant (P < 0.05) increasing trend, whereas MDA and NO revealed a significant (P < 0.05) decline. Serum MDA and NO were higher in control compared with those of treatment group. Moreover, buffaloes in the treatment group showed 90% estrus induction with 18.06 ± 1.57 days mean interval from treatment to the onset of estrus. These results report that melatonin has a protective effect by elevating antioxidant status and reducing oxidative stress resulting in the induction of cyclicity in summer-stressed anestrous buffaloes.     

Metal dyshomeostasis and oxidative stress in Alzheimer’s disease

Alzheimer’s disease is the leading cause of dementia in the elderly and is defined by two pathological hallmarks; the accumulation of aggregated amyloid beta and excessively phosphorylated Tau proteins. The etiology of Alzheimer’s disease progression is still debated, however, increased oxidative stress is an early and sustained event that underlies much of the neurotoxicity and consequent neuronal loss. Amyloid beta is a metal binding protein and copper, zinc and iron promote amyloid beta oligomer formation. Additionally, copper and iron are redox active and can generate reactive oxygen species via Fenton (and Fenton-like chemistry) and the Haber–Weiss reaction. Copper, zinc and iron are naturally abundant in the brain but Alzheimer’s disease brain contains elevated concentrations of these metals in areas of amyloid plaque pathology. Amyloid beta can become pro-oxidant and when complexed to copper or iron it can generate hydrogen peroxide. Accumulating evidence suggests that copper, zinc, and iron homeostasis may become perturbed in Alzheimer’s disease and could underlie an increased oxidative stress burden. In this review we discuss oxidative/nitrosative stress in Alzheimer’s disease with a focus on the role that metals play in this process. Recent studies have started to elucidate molecular links with oxidative/nitrosative stress and Alzheimer’s disease. Finally, we discuss metal binding compounds that are designed to cross the blood brain barrier and restore metal homeostasis as potential Alzheimer’s disease therapeutics.     

The complex interplay of iron metabolism,reactive oxygen species,and reactive nitrogen species: Insights into the potential of various iron therapies to induce oxidative and nitrosative stress

Production of minute concentrations of superoxide (O₂⁻) and nitrogen monoxide (nitric oxide, NO) plays important roles in several aspects of cellular signaling and metabolic regulation. However, in an inflammatory environment, the concentrations of these radicals can drastically increase and the antioxidant defenses may become overwhelmed. Thus, biological damage may occur owing to redox imbalance—a condition called oxidative and/or nitrosative stress. A complex interplay exists between iron metabolism, O₂⁻, hydrogen peroxide (H₂O₂), and NO. Iron is involved in both the formation and the scavenging of these species. Iron deficiency (anemia) (ID(A)) is associated with oxidative stress, but its role in the induction of nitrosative stress is largely unclear. Moreover, oral as well as intravenous (iv) iron preparations used for the treatment of ID(A) may also induce oxidative and/or nitrosative stress. Oral administration of ferrous salts may lead to high transferrin saturation levels and, thus, formation of non-transferrin-bound iron, a potentially toxic form of iron with a propensity to induce oxidative stress. One of the factors that determine the likelihood of oxidative and nitrosative stress induced upon administration of an iv iron complex is the amount of labile (or weakly-bound) iron present in the complex. Stable dextran-based iron complexes used for iv therapy, although they contain only negligible amounts of labile iron, can induce oxidative and/or nitrosative stress through so far unknown mechanisms. In this review, after summarizing the main features of iron metabolism and its complex interplay with O₂⁻, H₂O₂, NO, and other more reactive compounds derived from these species, the potential of various iron therapies to induce oxidative and nitrosative stress is discussed and possible underlying mechanisms are proposed. Understanding the mechanisms, by which various iron formulations may induce oxidative and nitrosative stress, will help us develop better tolerated and more efficient therapies for various dysfunctions of iron metabolism.     

NO对镉胁迫下小麦根系生长发育的生理影响

为了探究外源物一氧化氮（NO）供体硝普钠（sodium nitroprusside,SNP）对Cd²⁺胁迫下小麦根系生长发育和活性氧代谢的影响,以小麦（Triticum aestivum L.）为材料,研究10 mmol/L CdCl₂胁迫下,30 μmol/L硝普钠（含一氧化氮NO）对小麦根系生长发育和活性氧代谢的影响。结果显示,外施SNP后,Cd²⁺胁迫下的小麦根长度、鲜重与干重较单独镉胁迫处理分别上升了48.0%、107.7%和87.3%,根系超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）的活性分别上升了28.5%、7.4%、19.2%和9.8%,根中超氧自由基（O₂^.-）和过氧化氢（H₂O₂）的含量分别降低了80.5％和47.0％;同时外施SNP,使镉胁迫下小麦根中的可溶性糖含量和脯氨酸含量分别上升了24.7％和22.1%;使根中丙二醛（MDA）含量降低了30.2％;使根系活力上升了15.3%。因此,外源NO在一定程度上可以显著提高小麦根的抗氧化能力,增强小麦的抗逆性,缓解镉对小麦根系的毒害,进而促进小麦幼苗根系的生长发育。     

Role of NF-κB transcriptional factor activation during chronic fluoride intoxication in development of oxidative-nitrosative stress in rat’s gastric mucosa

Fluoride compounds are known as hazardous environmental pollutants that can enter the body with drinking water. Chronic exposure to fluoride leads to development of oxidative stress and can lead to activation of nuclear factor κB (NF-κB). The aim of this work is to clarify the role of NF-kB activation in production of reactive nitrogen and oxygen species, activity of antioxidant enzymes and intensity of lipid peroxidation (LPO) in gastric mucosa of rats during chronic fluoride intoxication.Materials and methodsWe carried out the study on 18 mature male rats of the Wistar line. The animals were divided into 3 groups: control animals (6), group of chronic fluoride intoxication (6), and animals (6), which received the NF-κB inhibitor, namely ammonium pyrrolidine dithiocarbamate (PDTC) in a dose of 76 mg / kg (iNF-κB group) during modeling of chronic fluoride intoxication. To assess the development of oxidative stress we studied superoxide production (O₂^-), activity of superoxide dismutase (SOD), catalase (CAT) and concentration of free malondialdehyde (MDA). We also assessed NO production and concentration of its metabolites (peroxynitrite, nitrosilated thiol groups, nitrites).ResultsChronic fluoride intoxication leads to NO hyperproduction with subsequent increase in concentration of its later metabolites (peroxynitrite, nitrosilated thiol groups, nitrites). Production of O₂^- increases, SOD activity decreases, CAT activity increases and MDA concentration also increases. Inhibition of NF-kB activation by PDTC normalizes the parameters studied.ConclusionsActivation of NF-κB during chronic fluoride intoxication leads to the development of hyperproduction of NO and development of oxidative-nitrosative stress.     

铅胁迫下三叶鬼针草内源一氧化氮的生成及其对氧化损伤的缓解效应

对不同浓度铅(Pb)胁迫下三叶鬼针草(Bidens pilosa L.)叶、茎和根中内源一氧化氮(NO)和活性氧(ROS)的生成机制及根系活力的变化,内源NO对Pb胁迫下三叶鬼针草幼苗氧化损伤的缓解效应进行了研究。结果显示,在0~1000 mg/L范围内,随着Pb浓度的增加,叶片中NO含量呈升高趋势,根中NO含量呈先升高后降低的趋势,但仍高于对照,Pb浓度在0~400 mg/L范围内,茎中NO含量与对照持平,Pb浓度大于600 mg/L时,茎中NO含量低于对照;600 mg/L Pb处理能显著增强叶、茎和根中一氧化氮合成酶(NOS)和硝酸还原酶(NR)活性,显著增加叶和茎中亚硝酸根离子(NO_2~-)和类胡萝卜素(Car)含量,NOS、NR、NO_2~-和Car均能促进叶片中内源NO的生成,NOS是根中内源NO生成的主要途径。Pb胁迫使超氧阴离子(O_2~(·-))产生速率、过氧化氢(H_2O_2)含量、丙二醛(MDA)含量和相对电导率(REC)显著升高,从而造成幼苗严重的膜脂过氧化损伤,而胁迫诱发产生的NO能降低根中ROS的产生,促进幼苗根系活力,进而缓解胁迫造成的膜脂过氧化损伤。     

Zinc deficiency differentially affects redox homeostasis of rice genotypes contrasting in ascorbate level

Zinc (Zn) deficiency is an important mineral disorder affecting rice production, and is associated with the formation of oxidative stress in plant tissue. In this study we investigated processes of oxidative stress formation as affected by ascorbate (AsA) in two pairs of contrasting rice genotypes: (i) two indica lines differing in field tolerance to Zn deficiency and AsA metabolism, i.e. RIL46 (tolerant) and IR74 (sensitive); (ii) the japonica wild-type Nipponbare (tolerant) and the AsA deficient TOS17 mutant line ND6172 (sensitive) having a 20–30% lower AsA level due to the knockout of an AsA biosynthetic gene (OsGME1). Plants were grown hydroponically under +Zn and −Zn conditions for 21 days and samples were investigated after 7, 14, and 21 days of treatment. Tissue Zn concentrations below 20 mg kg⁻¹ in the −Zn treatment induced the formation of visible symptoms of Zn deficiency from day 14 in all genotypes, but especially in the sensitive IR74. Significant increases in lipid peroxidation were observed in the leaves of the sensitive genotypes IR74 and ND6172, and in the roots of IR74, but not in the tolerant genotypes. At day 21, the tolerant genotypes RIL46 and Nipponbare had significantly higher AsA levels in both shoots and roots compared to the sensitive lines. Consistently, higher levels of hydrogen peroxide formation in leaves and roots of the sensitive genotypes were detected using staining methods. Differences in foliar hydrogen peroxide formation between IR74 and RIL46 became apparent on day 7 and between ND6172 and Nipponbare on day 14. Similarly, genotypic differences in hydrogen peroxide formation in the roots were seen on day 21. In conclusion, our data demonstrate that Zn deficiency leads to a redox imbalance in roots and shoots prior to the occurrence of visible symptoms, and that the antioxidant AsA plays an important role in maintaining the redox homeostasis under Zn deficiency.     

New aspects of adipogenesis: Radicals and oxidative stress

Preadipocytes are multipotent adipogenic precursor cells that can be isolated from mature adipose tissue. They have been receiving increasing attention in the context of obesity, type 2 diabetes, and other nutrition-associated diseases. Understanding the physiological and pathophysiological processes in fat neo-formation, energy homeostasis, and adipose tissue physiology is the basis for research on metabolic diseases and the respective pharmaceutical intervention. While the hormonal influence on intracellular signaling in adipogenesis has been intensively investigated, the effects of free radical formation and oxidative stress have just started to gain scientific attention. This review summarizes the present knowledge on the main molecular pathways in preadipocyte maturation and focuses on recent findings indicating that besides hormonal stimuli reactive oxygen species (ROS) and free radicals may also interact with preadipocyte differentiation.     

Significance of phenols in cadmium and nickel uptake

The effects of 2-aminoindane-2-phosphonic acid (AIP), a potent phenylalanine ammonia-lyase (PAL) inhibitor, on the accumulation of cadmium and nickel in chamomile (Matricaria chamomilla) were examined in this study. In vitro assay of AIP effect showed a 90% reduction in PAL activity. In plants cultured for 7 days in Cd or Ni solutions with AIP, PAL activity was higher in both shoots and roots (in comparison with metals without AIP), and was correlated with changes in free phenylalanine content. Individual amino acids were both positively and negatively affected by AIP, with the accumulation of tyrosine and proline showing increases in some variants. Contents of soluble phenols and flavonoids were not considerably affected, while amounts of coumarin-related compounds, cell wall-bound phenols and phenolic acids were substantially reduced in AIP-treated variants. Lignin accumulation decreased in controls and increased in Cd variants in response to AIP. Shoot Cd content was depleted, but shoot Ni was elevated by AIP. Total root content of Cd and Ni decreased in +AIP variants. AIP also caused more expressive changes in hydrogen peroxide and superoxide content in Cd than in Ni variants. Our results indicate that phenols have important roles in the uptake of Cd and Ni. The present findings are discussed in the context of available data regarding AIP's effect on phenols.     

Oxidized LDLs affect nitric oxide and radical generation in brain endothelial cells

There is an increase in the generation of reactive oxygen species and nitric oxide in the cerebral microcirculation in Alzheimer's disease. The factors that cause this increase in oxidative stress have not been identified. Increasing evidence suggests that there are common mechanisms in atherosclerosis and Alzheimer's disease. The objective of this study was to determine the effects of oxidized low density lipoproteins (LDLs) on brain endothelial cells. Cultured rat brain endothelial cells were treated with either native LDL (10 microg/ml) or LDL oxidized in vitro using 4-hydroxy-2-nonenal (HNE-LDL) (10 microg/ml), for 24h. The results showed that HNE-LDL significantly increased production of nitric oxide (p<0.01), decreased membrane fluidity (p<0.05), and increased reactive oxygen species generation (p<0.01). These data demonstrate that oxidized LDLs affect nitric oxide and radical generation in brain endothelial cells and could contribute to cerebrovascular dysfunction in Alzheimer's disease.     

Systemic oxidative stress in children and teenagers with Down syndrome

Aims

The aim of this study was to evaluate the antioxidant status and oxidative stress biomarkers in the blood of children and teenagers with Down syndrome.

Main methods

The analysis of enzymatic antioxidant defenses, such as the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione transferase (GST), non-enzymatic antioxidants, such as levels of reduced glutathione (GSH), uric acid (UA) and vitamin E, as well as oxidative damage indicators, such as protein carbonyls (PC) levels and lipoperoxidation (TBARS), of DS individuals (n = 20) compared to healthy controls (n = 18). Except the vitamin E was measured by HPLC, all other markers were measured spectrophotometrically.

Key Findings

Antioxidant enzymes analysis showed significant increases in the SOD (47.2%), CAT (24.7%) and GR (49.6%) activities in DS subjects. No significant difference in GPx activity was detected while GST activity (61.2%) was decreased, and both responses may be consequence of the depletion of GSH (24.9%) levels. There were no significant differences in TBARS levels, while PC levels showed decreased (31.7%) levels compared to healthy controls, which may be related to the increase (16.1%) found in serum UA. Levels of vitamin E showed no significant differences between DS individuals compared to controls.

Significance

The results revealed a systemic pro-oxidant status in DS individuals, evidenced by the increased activity of some important antioxidant enzymes, together with decreased GSH levels in whole blood and elevated UA levels in plasma, probably as an antioxidant compensation related to the redox imbalance in DS individuals.     

Oxidative stress and antioxidant defense responses of Etroplus suratensis to acute temperature fluctuations

Fishes are always exposed to various environmental stresses and the chances of succumbing to such stresses are of great physiological concern. Any change in temperature from the ambient condition can induce various metabolic and physiological changes in the body. The present study evaluates the effects of temperature induced stress on the antioxidant profile of Etroplus suratensis such as superoxide dismutase, catalase, glutathione peroxidase and lipid peroxidation. Fishes of same size were kept in a thermostatized bath at three different temperature regimes viz 16 °C, 27 °C (ambient temperature) and 38 °C for 72 h. These temperatures were selected based on the CT Max (Critical Thermal Maximum) and CT Min (Critical Thermal Minimum) exhibited by E. suratensis. Superoxide dismutase and catalase activity was found maximum in brain and muscle respectively during the 48th hour of exposure in fishes kept at 38 °C. At 16 °C the antioxidant response of glutathione peroxidase was maximum in muscles, whereas the lipid peroxidation rate was found to be high in gills compared to other tissues. The profound increase in the levels of oxidative stress related biomarkers indicate that the thermal stressors severely affected oxidative state of E. suratensis by the second day of experiment. Such down-regulation of redox state accompanied with the induction of oxidative stress cascade may lead to physiological damage in various tissues in fishes, in vivo. However current data indicate that a transition to low and high temperature environment from ambient condition severely affected the levels and profile of the antioxidant markers overtime in E. suratensis.     

A polyphenolic flavonoid glabridin: Oxidative stress response in multidrug-resistant Staphylococcus aureus

Glabridin a polyphenolic flavonoid from Glycyrrhiza glabra is known to possess several therapeutic properties. In the present study, we report for the first time the in vitro antibacterial activity (MIC values ranging from 3.12 to 25 μg/mL) of glabridin against multidrug-resistant clinical isolates of S. aureus by inducing oxidative stress. Increased levels of H₂O₂ and NO were observed in a dose-dependent manner after treatment of glabridin that further affected macromolecules such as DNA, lipids, and proteins. Surprisingly, glabridin was found to possess antioxidant properties when used at lower concentrations using three different methods including DPPH, FRAP, and SOD assays. These observations were further validated through the expression analysis of oxidative stress-responsive genes using qRT-PCR wherein glabridin was observed to up- and down-regulate these genes at lower and higher concentrations, respectively. In in vitro combination experiments, glabridin was found to reduce the MIC of different antibiotics such as norfloxacin, oxacillin, and vancomycin by up to 4-fold, while the MIC of glabridin itself was found to be reduced by up to 8-fold in the presence of antibiotics. A synergistic interaction was observed between norfloxacin and glabridin when used in combination against multidrug-resistant clinical isolate SA 4627 of Staphylococcus aureus at much lower concentrations, indicating the suitability of glabridin in combination therapy.     

Inactivation of <Emphasis Type=Italic>Escherichia coli</Emphasis> and coliform bacteria in traditional brass and earthernware water storage vessels

The detection and enumeration of indicator bacteria such as Escherichia coli is used to assess the extent of faecal contamination of drinking water. On the basis of this approach, the effectiveness of storing water contaminated with faecal indicator bacteria in brass or earthern vessels (mutkas) of the type used in rural India have been investigated. Suspensions of bacteria in sterile distilled water were maintained for up to 48 h in each vessel and enumerated by surface plate counts on nutrient agar (non-selective) and several selective coliform media at 37 °C either under standard aerobic conditions, or under conditions designed to neutralise reactive oxygen species (ROS), e.g. using an anaerobic cabinet to prepare plates of pre-reduced growth medium or by inclusion of sodium pyruvate in the growth medium, with incubation of aerobically-prepared plates in an anaerobic jar. The counts obtained for E. coli decreased on short-term storage in a brass mutka; counts for selective media were lower than for equivalent counts for non-selective medium, with ROS-neutralised conditions giving consistently higher counts than aerobic incubation. However, after 48 h, no bacteria were cultivable under any conditions. Similar results were obtained using water from environmental sources in the Panjab, and from rural households where brass and earthern mutkas are used for storage of drinking water, with enumeration on selective coliform media (presumptive total coliforms). In all cases results indicated that, while storage of water in a brass mutka can inactivate E. coli and coliforms over a 48 h period, standard aerobic plate counting using selective media may not be fully effective in enumerating sub-lethally damaged bacteria.     

氧化应激与幽门螺杆菌感染相关性胃炎

幽门螺杆菌(Helicobacter pylori,H.pylori)是一种选择性定植于胃上皮细胞的革兰氏阴性菌,是一种广泛传染的病原菌,也是诱导产生慢性胃炎的主要因素之一。近年来研究表明幽门螺杆菌感染诱导机体产生氧化应激反应,并通过各种逃逸机制避免被杀灭。幽门螺杆菌能不断刺激中性粒细胞和巨噬细胞表达活性氧和活性氮,导致体内活性氧和活性氮的过度积累,致使细胞的凋亡和胃粘膜损伤的加剧,这是导致胃炎发生及加重的重要因素。本文对幽门螺杆感染引起氧化应激反应的研究进展作简要综述。     

Promoted proliferation of an SOD-deficient mutant of Escherichia coli under oxidative stress induced by photoexcited TiO2

An SOD null mutant of Escherichia coli (IM303) and its wild-type strain (MM294) were cultivated with or without sublethal oxidative stress generated from photoexcited TiO2. Concerning maximum specific growth rate of the cells, mum, measured under various conditions, the mum value of IM303 cells increased notably in the presence of TiO2 illuminated with light (I = 12.5 W m(-2)), being about two times higher than that of the cells grown in the absence of TiO2 and light. The mum value of IM303 cells under the oxidative condition restored to a level comparable to that of wild-type MM294 cells, which coincided with the finding that the content of reactive oxygen species lowered in IM303 cells under the oxidative stress. Colony isolation was conducted to obtain the cells prevailing in the early culture phase of IM303 cells in the presence of TiO2 and light. It was found that the isolates exhibited the outgrowing properties with the increased mum values under both the conditions with and without TiO2 and light. It was also indicated that in the culture of typically selected isolate, the cells started to grow with a relatively short lag in a threonine-minus medium.