Seasonal variability of oxidative stress markers in city bus drivers. Part I. Oxidative damage to DNA

We investigated the seasonal variability of 8-oxodeoxyguanosine (8-oxodG), a marker of oxidative damage to DNA, in urine of 50 bus drivers and 50 controls in Prague, Czech Republic, in three seasons with different levels of air pollution: winter 2005, summer 2006 and winter 2006. The exposure to environmental pollutants (carcinogenic polycyclic aromatic hydrocarbons, c-PAHs, particulate matter (PM), and volatile organic compounds (VOC)) was monitored by personal and/or stationary monitors. For the analysis of 8-oxodG levels, the ELISA technique was used. Bus drivers were exposed to significantly higher levels of c-PAHs in winter 2006, while in the other two seasons the exposure of controls was unexpectedly higher than that of bus drivers. We did not see any difference in VOC exposure between both groups in summer 2006 and in winter 2006; VOC were not monitored in winter 2005. 8-OxodG levels were higher in bus drivers than in controls in all seasons. The median levels of 8-oxodG (nmol/mmol creatinine) in bus drivers vs. controls were as follows: winter 2005: 7.79 vs. 6.12 (p=0.01); summer 2006: 6.91 vs. 5.11 (p<0.01); winter 2006: 5.73 vs. 3.94 (p<0.001). Multivariate logistic regression analysis identified PM2.5 and PM10 levels, measured by stationary monitors during a 3-day period before urine collection, as the only factors significantly affecting 8-oxodG levels, while the levels of c-PAHs had no significant influence.     

Oxidative and nitrosative stress in ammonia neurotoxicity

Increased ammonia accumulation in the brain due to liver dysfunction is a major contributor to the pathogenesis of hepatic encephalopathy (HE). Fatal outcome of rapidly progressing (acute) HE is mainly related to cytotoxic brain edema associated with astrocytic swelling. An increase of brain ammonia in experimental animals or treatment of cultured astrocytes with ammonia generates reactive oxygen and nitrogen species in the target tissues, leading to oxidative/nitrosative stress (ONS). In cultured astrocytes, ammonia-induced ONS is invariably associated with the increase of the astrocytic cell volume. Interrelated mechanisms underlying this response include increased nitric oxide (NO) synthesis which is partly coupled to the activation of NMDA receptors and increased generation of reactive oxygen species by NADPH oxidase. ONS and astrocytic swelling are further augmented by excessive synthesis of glutamine (Gln) which impairs mitochondrial function following its accumulation in there and degradation back to ammonia (“the Trojan horse” hypothesis). Ammonia also induces ONS in other cell types of the CNS: neurons, microglia and the brain capillary endothelial cells (BCEC). ONS in microglia contributes to the central inflammatory response, while its metabolic and pathophysiological consequences in the BCEC evolve to the vasogenic brain edema associated with HE. Ammonia-induced ONS results in the oxidation of mRNA and nitration/nitrosylation of proteins which impact intracellular metabolism and potentiate the neurotoxic effects. Simultaneously, ammonia facilitates the antioxidant response of the brain, by activating astrocytic transport and export of glutathione, in this way increasing the availability of precursors of neuronal glutathione synthesis.     

Oxidative and nitrosative stress in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder marked by movement impairment caused by a selective degeneration of dopaminergic neurons. The mechanism for dopaminergic neuronal degeneration in PD is not completely clear, but it is believed that oxidative and nitrosative stress plays an important role during the pathogenesis of PD. This notion is supported by various studies that several indices of oxidative and nitrosative stress are increased in PD patients. In recent years, different pathways that are known to be important for neuronal survival have been shown to be affected by oxidative and nitrosative stress. Apart from the well-known oxidative free radicals induced protein nitration, lipid peroxidation and DNA damage, increasing evidence also suggests that some neuroprotective pathways can be affected by nitric oxide through S-nitrosylation. In addition, the selective dopaminergic neurodegeneration suggests that generation of oxidative stress associated with the metabolism of dopamine is an important contributor. Thorough understanding of how oxidative stress can contribute to the pathogenesis of PD will help formulate potential therapy for the treatment of this neurodegenerative disorder in the future.     

Seasonal variability of oxidative stress markers in city bus drivers. Part II. Oxidative damage to lipids and proteins

The aim of the present study was to investigate the seasonal variability of markers of oxidative damage to lipids (15-F2t-isoprostane, 15-F2t-IsoP) and proteins (protein carbonyl levels) in 50 bus drivers and 50 controls from Prague, Czech Republic, and to identify factors affecting oxidative stress markers. The samples were collected in three seasons with different levels of air pollution. The exposure to environmental pollutants (carcinogenic polycyclic aromatic hydrocarbons, c-PAHs, particulate matter, PM2.5 and PM10, and volatile organic compounds, VOC) was monitored by personal and/or stationary monitors. For the analysis of both markers, ELISA techniques were used. The median levels of individual markers in bus drivers versus controls were as follows: 15-F2t-IsoP (nmol/mmol creatinine): winter 2005, 0.81 versus 0.68 (p<0.01); summer 2006, 0.62 versus 0.60 (p=0.90); winter 2006, 0.76 versus 0.51 (p<0.001); carbonyl levels (nmol/ml plasma): winter 2005, 14.1 versus 12.9 (p=0.001); summer 2006, 17.5 versus 16.6 (p=0.26); winter 2006, 13.5 versus 11.7 (p<0.001). Multivariate logistic regression identified PM levels measured by stationary monitors over a period 25-27 days before urine collection as a factor positively associated with lipid peroxidation, while protein oxidation levels correlated negatively with both c-PAHs and PM levels. In conclusion, markers of oxidative damage to lipids and proteins were increased in bus drivers in winter seasons, but not in summer. Lipid peroxidation was positively correlated with c-PAHs and PM exposure; protein oxidation correlated negatively and was highest in summer suggesting another factor(s) affecting protein carbonyl levels.     

Oxidative and nitrosative stress in Staphylococcus aureus biofilm

Diverse chemical and physical agents can alter cellular functions associated with oxidative metabolism, thus stimulating the production of reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI) in planktonic bacterial physiology. However, more research is necessary to determine the precise role of cellular stress in biofilm. The present study was designed to address the issues of Staphylococcus aureus biofilm formation with respect to the generation of oxidative and nitrosative stress. We studied three pathogenic S. aureus clinical strains and an ATCC strain exposed to a different range of culture conditions (time, temperature, pH, reduction and atmospheric conditions) using quantitative methods of biofilm detection. We observed that cellular stress could be produced inside biofilms, thereby affecting their growth, resulting in an increase of ROS and RNI production, and a decrease of the extracellular matrix under unfavorable conditions. These radical oxidizers could then accumulate in an extracellular medium and thus affect the matrix. These results contribute to a better understanding of the processes that enable adherent biofilms to grow on inert surfaces and lead to an improved knowledge of ROS and RNI regulation, which may help to clarify the relevance of biofilm formation in medical devices.     

Oxidative and nitrosative stress in the maintenance of myocardial function

Reactive oxygen species (ROS) are generated by several different cellular sources, and their accumulation within the myocardium is widely considered to cause harmful oxidative stress. On the other hand, their role as second messengers has gradually emerged. The equilibrium of the nitroso/redox balance between reactive nitrogen species and ROS is crucial for the health of cardiomyocytes. This review provides a comprehensive overview of sources of oxidative stress in cardiac myocytes and describes the role of the nitroso/redox balance in cardiac pathophysiology. Although the exact mechanism of ROS production by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox's) is not completely understood, Nox2 and Nox4 have particularly important roles within the myocardium. Increasing evidence suggests that Nox2 produces superoxide and Nox4 generates only hydrogen peroxide. We also discuss the key role of nitric oxide synthases (NOSs) in the maintenance of the nitroso/redox balance: uncoupled endothelial NOS has been suggested to shift from nitric oxide to ROS production, contributing to increased oxidative stress within the myocardium. Furthermore, we highlight the importance of sequentially targeting and/or regulating the specific sources of oxidative and nitrosative stress to prevent and/or reverse myocardial dysfunction. Inhibition of NADPH oxidase-dependent ROS is considered to be a potential strategy for treatment of cardiomyopathy. Neither in vivo nor clinical data are available for NADPH oxidase inhibitors. Specifically targeting the mitochondria with the antioxidant MitoQ would be a very promising translation approach, because it could prevent mitochondrial permeability transition pore opening when ROS are produced during heart reperfusion. Enhancing NO signaling could also be a promising therapeutic approach against myocardial dysfunction.     

Oxidative and nitrosative events in asthma

Asthma affects over 15 million individuals in the United States, with over 1.5 million emergency room visits, 500,000 hospitalizations, and 5500 deaths each year, many of which are children. Airway inflammation is the proximate cause of the recurrent episodes of airflow limitation in asthma. Research applying molecular biology, chemistry, and cell biology to human asthma and model systems of asthma over the last decade has revealed that numerous biologically active proinflammatory mediators lead to increased production of reactive oxygen species (ROS) and the gaseous molecule nitric oxide (NO). Persistently increased ROS and NO in asthma lead to reactive nitrogen species (RNS) formation and subsequent oxidation and nitration of proteins, which may cause alterations in protein function that are biologically relevant to airway injury/inflammation. Eosinophil peroxidase and myeloperoxidase, leukocyte-derived enzymes, amplify oxidative events and are another enzymatic source of NO-derived oxidants and nitrotyrosine formation in asthma. Concomitant with increased generation of oxidative and nitrosative molecules in asthma, loss of protective antioxidant defense, specifically superoxide dismutase (SOD), contributes to the overall toxic environment of the asthmatic airway. This review discusses the rapidly accruing data linking oxidative and nitrosative events as critical participants in the acute and chronic inflammation of asthmatic airways.     

Oxidative and nitrative stress markers in glaucoma

Glaucoma is a progressive optic neuropathy and is the leading cause of blindness in the United States and other industrialized countries. Elevated pressure in the eye is a risk factor for glaucoma and indeed experimental studies of induced pressure elevation in nonhuman primate's results in typical glaucomatous optic nerve damage. However, normal intraocular pressure can also lead to loss of vision in glaucoma. Although the initiating causes leading to glaucoma are unknown, oxidative and nitrative stress appears to play a role in the progressive neuronal death that is characteristic of glaucomatous optic nerve damage. Increased markers of oxidative stress that have been reported in glaucoma include protein nitrotyrosine, carbonyls in proteins, lipid oxidation products and oxidized DNA bases. Studies have also highlighted the role of nitric oxide in glaucoma by reporting the presence of inducible nitric oxide synthase in the iris-ciliary body, retina and in the glaucomatous optic nerve head of experimental rat models. This review discusses the role of reactive oxygen and nitrogen species in the pathogenesis of glaucoma and examines the relevance of antioxidants in neurodegeneration associated with the disease. It is concluded that oxidative and nitrative stress have a pathogenic role in glaucoma.     

Oxidative stress markers in patients with post-traumatic stress disorder

Recent study data support the role of oxidative stress in diverse psychiatric disorders. Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants and/or a depletion of antioxidants. There are numerous studies that indicate that free radicals (FRs) damage neurons, and then play an important role in the pathophysiology of schizophrenia and depression. Active oxygen can cause considerable damage and disrupt the important physiological functions of proteins, lipids, enzymes and DNA. The aim of our study was to investigate the possible differences in the concentration of tromboxane B2, 8-OHdG and protein carbonyls, as significant markers of oxidative damage, and urate, albumin and total protein concentrations as antioxidative molecules in PTSD patients in comparison to the healthy control group. The study included 74 male participants who were active soldiers in the Croatian armed forces from 1991 to 1995. 46 subjects with chronic and current PTSD were recruited from the Department of Psychiatry of Dubrava University Hospital during 2010, 28 healthy subjects were recruited in the same period during the regular medical examination at the Dubrava University Hospital. Study results have shown that there is no statistically significant difference in urinary concentrations of 8-OHdG, serum thromboxane B2, and serum urates between two studied groups. Statistically significant difference of the protein carbonyl concentrations was examined. Concentrations were significantly lower in the PTSD group than in the control group. The clinical significance of these results was examined using ROC analysis. The obtained ROC curves did not separate the groups in a satisfactory manner.     

Oxidative stress markers during a course of hyperthyroidism

INTRODUCTION: Previous studies have shown the presence of oxidative stress in hyperthyroid patients. The aim of this study was to evaluate the influence of hyperthyroidism on lipid peroxidation, plasma lipoprotein oxidation and antioxidant status. We have estimated the clinical utility of the biochemical parameters analysed as markers of oxidative stress in hyperthyroidism. MATERIAL AND METHODS: Twenty five patients with overt hyperthyroidism because of Graves' disease or toxic multinodular goitre and 20 healthy subjects were included in the study. Lipid peroxidation was evaluated by measurement of peroxides and malondialdehyde with 4-hydroxynonenal (MDA + 4-HNE) concentrations. Autoantibodies against oxidised LDL (anti-oxLDL) were assayed as a marker of lipoprotein oxidation. Changes in the antioxidant defence system were estimated by measurement of total antioxidant status in serum (TAS) and erythrocyte superoxide dismutase activity (SOD). RESULTS: A significant increase in serum concentration of peroxides and MDA + 4-HNE was observed in patients with hyperthyroidism. However, no difference was found in anti-oxLDL concentration and antioxidant status parameters (TAS, SOD) between the control group and the patient group. CONCLUSIONS: Our results indicate an intensification of the oxidative processes caused by an excess of thyroid hormones, which is not accompanied by a response from the antioxidant system. Elevated concentrations of lipid peroxidation products in serum, both peroxides and malondialdehyde with 4-hydroxynonenal, may be useful as markers of oxidative stress during the course of hyperthyroidism.     

Nitric oxide and nitrosative stress tolerance in yeast

The opportunistic human fungal pathogen Candida albicans encounters diverse environmental stresses when it is in contact with its host. When colonizing and invading human tissues, C. albicans is exposed to ROS (reactive oxygen species) and RNIs (reactive nitrogen intermediates). ROS and RNIs are generated in the first line of host defence by phagocytic cells such as macrophages and neutrophils. In order to escape these host-induced oxidative and nitrosative stresses, C. albicans has developed various detoxification mechanisms. One such mechanism is the detoxification of NO (nitric oxide) to nitrate by the flavohaemoglobin enzyme CaYhb1. Members of the haemoglobin superfamily are highly conserved and are found in archaea, eukaryotes and bacteria. Flavohaemoglobins have a dioxygenase activity [NOD (NO dioxygenase domain)] and contain three domains: a globin domain, an FAD-binding domain and an NAD(P)-binding domain. In the present paper, we examine the nitrosative stress response in three fungal models: the pathogenic yeast C. albicans, the benign budding yeast Saccharomyces cerevisiae and the benign fission yeast Schizosaccharomyces pombe. We compare their enzymatic and non-enzymatic NO and RNI detoxification mechanisms and summarize fungal responses to nitrosative stress.     

An apoptotic model for nitrosative stress

Nitric oxide overproduction has been implicated in the pathogenesis of many disorders, including artherosclerosis, neurodegenerative diseases, inflammatory and autoimmune diseases, and cancer. The common view holds that nitric oxide-induced cellular injury is caused by oxidative stress. This theory predicts that interactions between reactive nitrogen species and reactive oxygen species produce powerful oxidants that initiate cell death programs. Cytokine-treated murine macrophages are the prototype of this form of cellular injury. Here we report that generation of reactive nitrogen species upon lipopolysacharide/interferon-gamma stimulation of RAW 264.7 cells is largely divorced from production of reactive oxygen species, and that oxidative stress is not principally responsible for cell death (in this model). Rather, the death program is induced mainly by a nitrosative challenge, characterized by the accrual of nitrosylated proteins without a major alteration in cellular redox state. Moreover, interactions between reactive oxygen and nitrogen species may alter the balance between pathways that yield nitrite and nitrate, without impacting the level of S-nitrosylation or extent of cell death. Our results thus (1) provide new insights into NO-related metabolic pathways, (2) demonstrate that apoptotic injury can be caused by nitrosative mechanisms, and (3) establish a model for nitrosative stress in mammalian cells.     

Sleep and sleepiness among Brazilian shift-working bus drivers

The aim of this study was to evaluate daytime and nighttime sleep, as well as daytime and nighttime sleepiness of professional shift-working bus drivers. Thirty-two licensed bus drivers were assessed by nocturnal and diurnal polysomnography (PSG) recording and multiple sleep latency testing (MSLT) sessions. Sleep length was shorter and sleep efficiency reduced during daytime sleep compared with nighttime sleep. Thirty-eight percent of the drivers had indices of obstructive apnea and hypopnea syndrome (>5/h sleep) during nighttime and daytime sleep; more drivers snored during daytime than nighttime sleep (50% vs. 35%, p < 0.05), and 38% of the drivers evidenced periodic leg movements. The MSLT revealed that 42 and 38% of the bus drivers met the criteria for sleepiness when the test was conducted during the day and night, respectively. The daytime as compared to nighttime sleep of shift-working bus drivers was shorter and more fragmented and was associated in many with evidence of excessive sleepiness. Respiratory disorder was a common finding among the professional shift-working bus drivers. All these sleep deficiencies may adversely affect on the job driving performance.     

Regulation of apoptosis by nitrosative stress

Nitrosative stress can prevent or induce apoptosis. It occurs via S-nitrosylation by the interaction of nitric oxide (NO) with the biological thiols of proteins. Cellular redox potential and non-heme iron content determine S-nitrosylation. Apoptotic cell death is inhibited by S-nitrosylation of the redox-sensitive thiol in the catalytic site of caspase family proteases, which play an essential role in the apoptotic signal cascade. Nitrosative stress can also promote apoptosis by the activation of mitochondrial apoptotic pathways, such as the release of cytochrome c, an apoptosis-inducing factor, and endonuclease G from mitochondria, as well as the suppression of NF-kB activity. In this article we reviewed the mechanisms whereby S-nitrosylation and nitrosative stress regulate the apoptotic signal cascade.     

Regulation of cell cycle and stress responses under nitrosative stress in Schizosaccharomyces pombe

Nitric oxide (NO) acts as a signaling molecule in numerous physiological processes but excess production generates nitrosative stress in cells. The exact protective mechanism used by cells to combat nitrosative stress is unclear. In this study, the fission yeast Schizosaccharomyces pombe has been used as a model system to explore cell cycle regulation and stress responses under nitrosative stress. Exposure to an NO donor results in mitotic delay in cells through G2/M checkpoint activation and initiates rereplication. Western blot analysis of phosphorylated Cdc2 revealed that the G2/M block in the cell cycle was due to retention of its inactive phosphorylated form. Interestingly, nitrosative stress results in inactivation of Cdc25 through S-nitrosylation that actually leads to cell cycle delay. From differential display analysis, we identified plo1, spn4, and rga5, three cell cycle-related genes found to be differentially expressed under nitrosative stress. Exposure to nitrosative stress also results in abnormal septation and cytokinesis in S. pombe. In summary we propose a novel molecular mechanism of cell cycle control under nitrosative stress based on our experimental results and bioinformatics analysis.