Direct detection of reactive oxygen species ex vivo

Reactive oxygen species function as signaling molecules in controlling plant development and hormonal responses

Reactive oxygen species (ROS) serve as second messengers in plant signaling pathways to remodel plant growth and development. New insights into how enzymatic ROS-producing machinery is regulated by hormones or localized during development have provided a framework for understanding the mechanisms that control ROS accumulation patterns. Signaling-mediated increases in ROS can then modulate the activity of proteins through reversible oxidative modification of specific cysteine residues. Plants also control the synthesis of antioxidants, including plant-specialized metabolites, to further define when, where, and how much ROS accumulate. The availability of sophisticated imaging capabilities, combined with a growing tool kit of ROS detection technologies, particularly genetically encoded biosensors, sets the stage for improved understanding of ROS as signaling molecules.

Overview of oxidative stress findings in hepatic encephalopathy: From cellular and ammonium-based animal models to human data

Oxidative stress is a natural phenomenon in the body. Under physiological conditions intracellular reactive oxygen species (ROS) are normal components of signal transduction cascades, and their levels are maintained by a complex antioxidants systems participating in the in-vivo redox homeostasis. Increased oxidative stress is present in several chronic diseases and interferes with phagocytic and nervous cell functions, causing an up-regulation of cytokines and inflammation. Hepatic encephalopathy (HE) occurs in both acute liver failure (ALF) and chronic liver disease. Increased blood and brain ammonium has been considered as an important factor in pathogenesis of HE and has been associated with inflammation, neurotoxicity, and oxidative stress. The relationship between ROS and the pathophysiology of HE is still poorly understood. Therefore, sensing ROS production for a better understanding of the relationship between oxidative stress and functional outcome in HE pathophysiology is critical for determining the disease mechanisms, as well as to improve the management of patients. This review is emphasizing the important role of oxidative stress in HE development and documents the changes occurring as a consequence of oxidative stress augmentation based on cellular and ammonium-based animal models to human data.

Detection of Vascular Reactive Oxygen Species in Experimental Atherosclerosis by High-Resolution Near-Infrared Fluorescence Imaging Using VCAM-1-Targeted Liposomes Entrapping a Fluorogenic Redox-Sensitive Probe

Excessive production of reactive oxygen species (ROS) and the ensuing oxidative stress are instrumental in all phases of atherosclerosis. Despite the major achievements in understanding the regulatory pathways and molecular sources of ROS in the vasculature, the specific detection and quantification of ROS in experimental models of disease remain a challenge. We aimed to develop a reliable and straightforward imaging procedure to interrogate the ROS overproduction in the vasculature and in various organs/tissues in atherosclerosis. To this purpose, the cell-impermeant ROS Brite™ 700 (RB700) probe that produces bright near-infrared fluorescence upon ROS oxidation was encapsulated into VCAM-1-targeted, sterically stabilized liposomes (VLp). Cultured human endothelial cells (EC) and macrophages (Mac) were used for in vitro experiments. C57BL6/J and ApoE-/- mice were randomized to receive normal or high-fat, cholesterol-rich diet for 10 or 32 weeks. The mice received a retroorbital injection with fluorescent tagged VLp incorporating RB700 (VLp-RB700). After two hours, the specific signals of the oxidized RB700 and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (NBD-DSPE), inserted into liposome bilayers, were measured ex vivo in the mouse aorta and various organs by high-resolution fluorescent imaging. VLp-RB700 was efficiently taken up by cultured human EC and Mac, as confirmed by fluorescence microscopy and spectrofluorimetry. After systemic administration in atherosclerotic ApoE-/- mice, VLp-RB700 were efficiently concentrated at the sites of aortic lesions, as indicated by the augmented NBD fluorescence. Significant increases in oxidized RB700 signal were detected in the aorta and in the liver and kidney of atherosclerotic ApoE-/- mice. RB700 encapsulation into sterically stabilized VCAM-1-sensitive Lp could be a novel strategy for the qualitative and quantitative detection of ROS in the vasculature and various organs and tissues in animal models of disease. The accurate and precise detection of ROS in experimental models of disease could ease the translation of the results to human pathologies.

A DNA-based fluorescent probe maps NOS3 activity with subcellular spatial resolution

Nitric oxide synthase 3 (NOS3) produces the gasotransmitter nitric oxide (NO), which drives critical cellular signaling pathways by S-nitrosylating target proteins. Endogenous NOS3 resides at two distinct subcellular locations: the plasma membrane and the trans-Golgi network (TGN). However, NO generation arising from the activities of both these pools of NOS3 and its relative contribution to physiology or disease is not yet resolvable. We describe a fluorescent DNA-based probe technology, NOckout, that can be targeted either to the plasma membrane or the TGN, where it can quantitatively map the activities of endogenous NOS3 at these locations in live cells. We found that, although NOS3 at the Golgi is tenfold less active than at the plasma membrane, its activity is essential for the structural integrity of the Golgi. The newfound ability to spatially map NOS3 activity provides a platform to discover selective regulators of the distinct pools of NOS3.

Ischemia/Reperfusion Injury in the Aged Liver: The Importance of the Sinusoidal Endothelium in Developing Therapeutic Strategies for the Elderly

The liver endothelium plays a key role in the progression and resolution of liver diseases in young and adult individuals. However, its role in older people remains unknown. We have herein evaluated the importance of the sinusoidal endothelium in the pathophysiology of acute liver injury, and investigated the applicability of simvastatin, in aged animals. Eighteen-months-old male Wistar rats underwent 60 minutes of partial warm ischemia followed by 2 hours of reperfusion (WIR). A group of aged rats received simvastatin for 3 days before WIR. Endothelial phenotype, parenchymal injury, oxidative and nitrosative stress, and fenestrae dynamics were analyzed. The effects of WIR and simvastatin were investigated in primary LSEC from aged animals. The results of this study demonstrated that WIR significantly damages the liver endothelium and its effects are markedly worse in old animals. WIR-aged livers exhibited reduced vasodilation and sinusoidal capillarization, associated with liver damage and cellular stress. Simvastatin prevented the detrimental effects of WIR in aged livers. In conclusion, the liver sinusoidal endothelium of old animals is highly vulnerable to acute insult, thus targeted protection is especially relevant in preventing liver damage. Simvastatin represents a useful therapeutic strategy in aging.

Bioluminescence Detection of Superoxide Anion Using Aequorin

Although the superoxide anion (O2-·) is generated during normal cellular respiration and has fundamental roles in a wide range of cellular processes, such as cell proliferation, migration, apoptosis, and homeostasis, its dysregulation is associated with a variety of diseases. Regarding these prominent roles in biological systems, the development of accurate methods for quantification of superoxide anion has attracted tremendous research attention. Here, we evaluated aequorin, a calcium-dependent photoprotein, as a potential bioluminescent reporter protein of superoxide anion. The mechanism is based on the measurement of aequorin bioluminescence, where the lower the concentration of coelenterazine under the oxidation of superoxide anion, the lower the amount aequorin regeneration, leading to a decrease in bioluminescence. The bioluminescence intensity of aequorin was proportional to the concentration of superoxide anion in the range from 4 to 40 000 pM with a detection limit (S/N = 3) of 1.2 pM, which was 5000-fold lower than those of the chemiluminescence methods. The proposed method exhibited high sensitivity and has been successfully applied to the determination of superoxide anion in the plant cell samples. The results could suggest a photoprotein-based bioluminescence system as a highly sensitive, specific, and simple bioluminescent probe for in vitro detection of superoxide anion.

Antioxidant Enzyme-Mimetic Activity and Neuroprotective Effects of Cerium Oxide Nanoparticles Stabilized with Various Ratios of Citric Acid and EDTA

Cerium oxide (CeO2) nanoparticles (CeNPs) are potent antioxidants that are being explored as potential therapies for diseases in which oxidative stress plays an important pathological role. However, both beneficial and toxic effects of CeNPs have been reported, and the method of synthesis as well as physico-chemical, biological, and environmental factors can impact the ultimate biological effects of CeNPs. In the present study, we explored the effect of different ratios of citric acid (CA) and EDTA (CA/EDTA), which are used as stabilizers during synthesis of CeNPs, on the antioxidant enzyme-mimetic and biological activity of the CeNPs. We separated the CeNPs into supernatant and pellet fractions and used commercially available enzymatic assays to measure the catalase-, superoxide dismutase (SOD)-, and oxidase-mimetic activity of each fraction. We tested the effects of these CeNPs in a mouse hippocampal brain slice model of ischemia to induce oxidative stress where the fluorescence indicator SYTOX green was used to assess cell death. Our results demonstrate that CeNPs stabilized with various ratios of CA/EDTA display different enzyme-mimetic activities. CeNPs with intermediate CA/EDTA stabilization ratios demonstrated greater neuroprotection in ischemic mouse brain slices, and the neuroprotective activity resides in the pellet fraction of the CeNPs. The neuroprotective effects of CeNPs stabilized with equal proportions of CA/EDTA (50/50) were also demonstrated in two other models of ischemia/reperfusion in mice and rats. Thus, CeNPs merit further development as a neuroprotective therapy for use in diseases associated with oxidative stress in the nervous system.

Towards sustainable diagnostics: replacing unstable H2O2 by photoactive TiO2 in testing systems for visible and tangible diagnostics for use by blind people

Blind and color blind people cannot use colorimetric diagnostics; the problem is especially severe in rural areas where high temperatures and the absence of electricity challenge modern diagnostics. Here we propose to replace the unstable component of a diagnostic test, H2O2, with stable TiO2. Under UV irradiation, TiO2 forms reactive oxygen species that initiate polymerization of acrylamide causing liquid-to-gel transition in an analyte-dependent manner. We demonstrate that specific DNA sequences can be detected using this approach. This development may enable the detection of biological molecules by users with limited resources, for example in developing countries or for travelers in remote areas.

Concentration effects of the UV filter oxybenzone in Cyperus alternifolius: assessment of tolerance by stress-related response

Phytoremediation has been proposed to reduce the load of the sunscreen oxybenzone (OBZ) in the aquatic environment. Despite the proven removal efficiency of this compound, little is known about its influence, particularly oxidative stress on plants. In this study, a short-term incubation of macrophytic Cyperus alternifolius was performed to prove the plant's ability to withstand the stress. Detached shoots were immersed in medium spiked with different concentrations of OBZ (50, 100, and 500 μM) for 2, 4, and 7 days, respectively. Increased formation of O₂^- and H₂O₂ in Cyperus treated with OBZ was characterized by intense colorization following histochemical staining. Alterations of enzyme activities involved in the antioxidative defense system indicate an adaptive response of C. alternifolius to this xenobiotic stress. Quantification of lipid peroxidation reveals that no significant membrane damage occurred during incubation with OBZ. Overall, 50 μM OBZ (tenfold higher than the amount frequently detected in the environment) exhibited low toxic effects. Accordingly, this pilot study provides information on the potential use of Cyperus to remove emerging sunscreen contaminants from water bodies.

Use and Evaluation of Newly Synthesized Fluorescence Probes to Detect Generated OH• Radicals in Fibroblast Cells

Reactive oxygen species (ROS) are pro-oxidant molecules synthesized in body with various functions and are essential for life. Increasing in reactive oxygen species or decreasing in antioxidants level cause oxidative stress which is very harmful. OH• radical is one of ROS's, with tendency to bind to lipids, DNA and proteins which cause irreversible damage in cells. The most devastating consequences related to excess OH• radicals occur via direct binding to nucleic acids and proteins. Quantification of this high reactive radical with short life time is difficult. Electron Spin Resonance, Fluorescence, and Luminescence Spectroscopy are commonly used to determine the level of ROS. Fluorescence Probes have higher specificity and sensitivity with their excellent sensors to detect ROS's compare to the other methods. Also, there are different probes specifically designed for each radical. The purpose of this study was to identify the probe better suiting for detection of OH• radical levels. The two most recommended fluorescence probes, 2-[6-(4 V-Hydroxy) phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (HPF) and coumarin-3-carboxylic acid (3-CCA) to determine OH• radical levels were compared. Following the formation of OH• radical with Fenton reaction, HPF and 3-CCA probes were added to cells and spectrofluorometric measurements were performed in their respective wavelengths. The mean amplitude of fluorescence for HPF was 32.72 ± 2.37 F.I (n = 40) and for 3-CCA was 52.11 ± 0.5 F.I (n = 40). This difference was statistically significant. 3-CCA also demonstrated more stable measurements at different days compered to HPF.

The enzyme toxicity and genotoxicity of chlorpyrifos and its toxic metabolite TCP to zebrafish Danio rerio

Chlorpyrifos is a broad-spectrum organophosphorus insecticide (O,O-diethyl -O-3,5,6-trichloro-2-pyridyl phosphorothioate) that is used in numerous agricultural and urban pest controls. The primary metabolite of chlorpyrifos is 3,5,6-trichloro pyridine-2-phenol (TCP). Because of its strong water solubility and mobility, this harmful metabolite exists in the environment in a large amount. Although TCP has potentially harmful effects on organisms in the environment, few studies have addressed TCP pollution. Therefore, this study was undertaken to investigate the effect of chlorpyrifos and TCP on the microsomal cytochrome P450 content in the liver, on the activity of NADPH-P450 reductase and antioxidative enzymes [catalase (CAT) and superoxide dismutase (SOD)], and on reactive oxygen species (ROS) generation and DNA damage in zebrafish. Male and female zebrafish were separated and exposed to a control solution and three concentrations of chlorpyrifos (0.01, 0.1, 1 mg L(-1)) and TCP (0.01, 0.1, 0.5 mg L(-1)), respectively, sampled after 5, 10, 15, 20 and 25 days. The results indicated that the P450 content and the NADPH-P450 reductase and antioxidative enzyme (CAT and SOD) activities could be induced by chlorpyrifos and TCP. DNA damage of zebrafish was enhanced with increasing chlorpyrifos and TCP concentrations. Meanwhile, chlorpyrifos and TCP induced a significant increase of ROS generation in the zebrafish hepatopancreas. In conclusion, this study proved that chlorpyrifos (0.01-1 mg L(-1)) and TCP (0.01-0.5 mg L(-1)) are both highly toxic to zebrafish.

Changes in markers of oxidative stress and DNA damage in human visceral adipose tissue from subjects with obesity and type 2 diabetes

AIMS

In the past 30 years, prevalence of obesity has almost trebled resulting in an increased incidence of type 2 diabetes mellitus and other co-morbidities. Visceral adipose tissue is believed to play a vital role, but underlying mechanisms remain unclear. Our aim was to investigate changes in markers of oxidative damage in human visceral adipose tissue to determine levels of oxidative burden that may be attributed to obesity and/or diabetes.

METHODS

Visceral adipose tissue samples from 61 subjects undergoing abdominal surgery grouped as lean, obese and obese with type 2 diabetes mellitus, were examined using 3 different markers of oxidative stress. Malondialdehyde (MDA) concentration was measured as a marker of lipid peroxidation, telomere length and Comet assay as markers of oxidative DNA damage.

RESULTS

No significant difference in MDA concentration, telomere length and DNA damage was observed between groups, although longer telomere lengths were seen in the obese with diabetes group compared to the obese group (P<0.05). Lower MDA concentration and longer telomere length were seen in subjects with diabetes compared to those without (P<0.05). DNA damage, analysed via Comet assay, was significantly lower in subjects with diabetes compared to those without (P<0.05).

CONCLUSION

A paradoxical decrease in oxidative stress and DNA damage was observed in samples from subjects with type 2 diabetes mellitus. Further work is required to investigate this further, however this phenomenon may be due to an up regulation of antioxidant defences in adipose tissue.

A novel form of the human manganese superoxide dismutase protects rat and human livers undergoing ischaemia and reperfusion injury

Hepatic microcirculatory dysfunction due to cold storage and warm reperfusion (CS+WR) injury during liver transplantation is partly mediated by oxidative stress and may lead to graft dysfunction. This is especially relevant when steatotic donors are considered. Using primary cultured liver sinusoidal endothelial cells (LSECs), liver grafts from healthy and steatotic rats, and human liver samples, we aimed to characterize the effects of a new recombinant form of human manganese superoxide dismutase (rMnSOD) on hepatic CS+WR injury. After CS+WR, the liver endothelium exhibited accumulation of superoxide anion (O2-) and diminished levels of nitric oxide (NO); these detrimental effects were prevented by rMnSOD. CS+WR control and steatotic rat livers exhibited markedly deteriorated microcirculation and acute endothelial dysfunction, together with liver damage, inflammation, oxidative stress, and low NO. rMnSOD markedly blunted oxidative stress, which was associated with a global improvement in liver damage and microcirculatory derangements. The addition of rMnSOD to CS solution maintained its antioxidant capability, protecting rat and human liver tissues. In conclusion, rMnSOD represents a new and highly effective therapy to significantly upgrade liver procurement for transplantation.

Oxidant mechanisms in childhood obesity: the link between inflammation and oxidative stress

Evidence of obesity-induced oxidative stress in adults has emerged in the past several years, and similar evidence has been demonstrated in children more recently. The reactive species of oxygen or nitrogen can chemically alter all major classes of biomolecules by modifying their structure and function. Organisms have developed mechanisms to protect biomolecules from the deleterious effects of free radicals. These include the enzymes superoxide dismutase, catalase, and glutathione peroxidase, as well as water and lipid-soluble antioxidants, such as glutathione, ascorbate (vitamin C), α-tocopherol (vitamin E), and β-carotene. Obesity creates oxidant conditions that favor the development of comorbid diseases. Energy imbalances lead to the storage of excess energy in adipocytes, resulting in both hypertrophy and hyperplasia. These processes are associated with abnormalities of adipocyte function, particularly mitochondrial stress and disrupted endoplasmic reticulum function. In this sense, oxidative stress can also be induced by adipocyte associated inflammatory macrophages. There is a close link among obesity, a state of chronic low-level inflammation, and oxidative stress. In addition, the dysregulation of adipocytokines, which are secreted by adipose tissue and promoted by oxidative stress, act synergistically in obesity-related metabolic abnormalities. Adipocytokines link the local and systemic inflammation responses in the context of obesity. It is thought that the evaluation of oxidative status may allow for the identification of patients at an increased risk of complications. Decreasing the levels of chronic inflammation and oxidative stress in childhood may decrease cardiovascular morbidity and mortality in adulthood.

Involvement of oxidative stress in age-related bone loss

BACKGROUND

Age-related bone loss is a primary factor in osteoporosis and osteoporotic fractures in the elderly. Although oxidative stress was reported to play an important role in aging and postmenopausal bone loss, data on relating oxidative stress to age-related bone loss were scanty. This study aimed to investigate whether oxidative stress is involved in age-related bone loss.

MATERIALS AND METHODS

Young, adult, and old male Wistar rats were used in this study. Each group consisted of 26 animals. Oxidative stress parameters, such as advanced oxidation protein products (AOPP), malondialdehyde (MDA), and superoxide dismutase (SOD), were measured in the plasma and right femur homogenates. Bone mineral density (BMD) of left femurs and histomorphometry of tibias were investigated.

RESULTS

In the plasma and femurs, the levels of AOPP and MDA were increased and the SOD activity was decreased with aging. Femur BMD decreased significantly in old rats. Bone histomorphometry indicated decreases in cancellous bone volume, trabecular thickness, percent labeled perimeter, mineral apposition rate, and bone formation rate with aging. The AOPP levels in plasma and femur, and MDA levels in the plasma were negatively correlated with the femur BMD. The SOD activity in plasma and femur was positively correlated with the femur BMD.

CONCLUSIONS

Increase of oxidative stress and bone loss appear with aging. Oxidative stress is involved in age-related bone loss and might play an important role in the pathology of age-related bone loss.

Quantitative determination of trace levels of hydrogen peroxide in crospovidone and a pharmaceutical product using high performance liquid chromatography with coulometric detection

A reliable and reproducible high performance liquid chromatography method with coulometric detection was developed and validated for the quantitative determination of trace-levels of hydrogen peroxide in crospovidone, a pharmaceutical excipient, and a capsule pharmaceutical product. The method conditions included: a reproducible extraction procedure to provide a concentrated extract, aqueous extraction solvent; a simple HPLC mobile phase (aqueous 50 mM ammonium acetate) compatible with the coulometric detection; a reserve-phase HPLC column that did not collapse under 100% aqueous mobile phase conditions providing sufficient retention and separation of hydrogen peroxide from interferences; and a coulometric detector with a multi-electrode array providing sensitive and selective detection. The method validation results, including those for specificity, linearity, accuracy, precision, and recovery, were acceptable for the determination of trace levels of hydrogen peroxide. The method was shown to be linear over the range of 0.6-4.5 ppm (microg/g) and 6-90 ppm (microg/g) for the pharmaceutical product and crospovidone, respectively. The described method was applied to the determination of trace levels of hydrogen peroxide in different batches of crospovidone and the corresponding pharmaceutical product batches manufactured from these batches of this excipient.

Antioxidant Protective Mechanisms against Reactive Oxygen Species (ROS) Generated by Mitochondrial P450 Systems in Steroidogenic Cells

Mitochondrial P450 type enzymes catalyze central steps in steroid biosynthesis, including cholesterol conversion to pregnenolone, 11beta and 18 hydroxylation in glucocorticoid and mineralocorticoid synthesis, C-27 hydroxylation of bile acids, and 1alpha and 24 hydroxylation of 25-OH-vitamin D. These monooxygenase reactions depend on electron transfer from NADPH via FAD adrenodoxin reductase and 2Fe-2S adrenodoxin. These systems can function as a futile NADPH oxidase, oxidizing NADPH in absence of substrate, and leak electrons via adrenodoxin and P450 to O(2), producing superoxide and other reactive oxygen species (ROS). The degree of uncoupling depends on the P450 and steroid substrate. Studies with purified proteins and overexpression in cultured cells show consistently that adrenodoxin, but not reductase, is responsible for ROS production that can lead to apoptosis. In the ovary and corpus luteum, antioxidant enzyme activities superoxide dismutase, catalase, and glutathione peroxidase parallel steroidogenesis. Antioxidant beta-carotene, alpha-tocopherol, and ascorbate can protect against oxidative damages of P450 systems. In testis Leydig cells, steroidogenesis is associated with aging of the steroidogenic capacity.

Increased oxidative stress in cirrhotic rat livers: A potential mechanism contributing to reduced nitric oxide bioavailability

In cirrhotic livers, decreased nitric oxide (NO) bioavailability is a major factor increasing intrahepatic vascular tone. In several vascular disorders, an increase in superoxide (O(2) (-)) has been shown to contribute to reduced NO bioavailability through its reaction with NO to form peroxynitrite. This study was aimed to test the hypothesis that, in cirrhotic livers, increased O(2) (-), by reacting with NO, reduces NO bioavailability. In control and cirrhotic rat livers, NO bioavailability was evaluated by the measurement of cyclic guanosine monophosphate in liver tissue and by 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM-DA) fluorescence in isolated sinusoidal endothelial cells (SEC); the O(2) (-) content was determined by dihydroethidium staining in fresh liver sections. In addition, the role of endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), and cyclooxygenase (COX) as possible sources of O(2) (-) and the role of superoxide dismutase (SOD) enzymatic activity as an O(2) (-) scavenger were determined in liver homogenates. Protein-nitrotyrosination, a marker of the NO-O(2) (-) reaction, was evaluated in liver homogenates. Furthermore, in control SEC and bovine aortic endothelial cells, NO modulation by O(2) (-) was evaluated. Cirrhotic livers exhibited increased O(2) (-) levels. This was due, at least in part, to increased production by COX and XO but not eNOS and to reduced scavenging by SOD. Increased O(2) (-) was associated with a significant reduction in NO bioavailability and increased nitrotyrosinated proteins. In endothelial cells, an inverse relationship between O(2) (-) levels and NO bioavailability was observed.

CONCLUSION

Our data show that oxidative stress may contribute to reduced NO bioavailability in cirrhotic livers, supporting the evaluation of O(2) (-) reduction as a potential mechanism to restore NO content.

Nitric oxide and cardiobiology-methods for intact hearts and isolated myocytes

The cross talk between reactive oxygen species (ROS) and reactive nitrogen species (RNS) plays a pivotal role in the regulation of myocardial and vascular function. Both nitric oxide and redox-based signaling involve the posttranslational modification of proteins through S-nitrosylation and oxidation of specific cysteine residues. Disruption of this cross talk between ROS and RNS contributes to the pathogenesis of heart failure. Therefore, the elucidation of these complex chemical interactions may improve our understanding of cardiovascular pathophysiology. This chapter discusses the significant role of spatial confinement of nitric oxide synthases, NADPH oxidase, and xanthine oxidoreductase in the regulation of myocardial excitation-contraction coupling. This chapter describes techniques for assessing oxidative and nitrosative stress. A variety of assays have been developed that quantify S-nitrosylated proteins. Among them, the biotin-switch method directly evaluates endogenously nitrosylated proteins in a reproducible way. Identification of the biotinylated or S-nitrosylated proteins subjected to the biotin-switch assay are described and evaluated with a one-dimensional gel (Western blot) or with the newly developed two-dimensional fluorescence difference gel electrophoresis proteomic analysis. Quantifying the number of free thiols with the monobromobimane assay in a protein of interest allows estimation of cysteine oxidation and, in turn, the state of nitroso-redox balance of effector molecules. In summary, this chapter reviews the biochemical methods that assess the impact of nitroso/redox signaling in the cardiovascular system.

Transmission of oxLDL-derived lipid peroxide radicals into membranes of vascular cells is the main inducer of oxLDL-mediated oxidative stress

Oxidatively modified LDL is generally accepted to be an important elicitor of pro-mitotic, pro-inflammatory, and atherogenic effects in vascular cells. The uptake of oxLDL and concomitant activation of the O(2)*-producing NAD(P)H oxidase and/or oxLDL as a self-contained emitter of O(2)* are believed to trigger these malfunctions. The following observations allowed reinvestigating the mode of oxLDL-induced stress: (1) we observed that artery smooth muscle primary cells internalize fluorescently labelled oxidized or acetylated LDL considerably less efficient than endothelial cells. (2) Both types of cells, however, displayed an oxLDL concentration dependent level of oxidative stress as monitored by the oxidation of carboxy-H2DCFDA to fluorescent carboxy-DCF. A dose dependent decrease of dihydroethidine oxidation to oxyethidine implied an oxLDL-induced depletion of the cellular energy pool. The release of O(2)* by exogenous oxLDL, as postulated above, did not sufficiently explain intracellular stress because the fluorescence was only marginally blocked by antioxidative enzymes (SOD, catalase) or substances (L-NAME, DMSO, DMHP, DMTU). We were able to reveal a third mode of oxLDL-induced stress by showing with the help of a fluorescent, oxidizable lipid analogue (BODIPY 581/591 C(11)) that oxLDL-derived lipid peroxides and radicals migrate into cellular membranes giving rise to a chronic inoculation of the vascular cells with oxidative chain reactions. The novel data may help to design adequate therapeutic strategies against oxLDL-induced cardiovascular diseases.

The aging kidney: role of endothelial oxidative stress and inflammation

The population in the Western world is aging. In 1996 those aged 60 years and over formed 21% of the EU population, by 2022 this proportion will have risen to 27%. Based on current trends a third of the EU population could be 60 years of age and over by the age 2050. Epidemiological studies suggest that even in the absence of other risk factors (e.g. diabetes, hypertension, hypercholesterolemia), advanced age itself significantly increases cardiovascular morbidity by promoting the development of atherosclerosis and by impairing normal cellular functions. One of the most prominent organs affected by aging is the kidney. There is evidence that age-associated phenotypic changes may be an important cause of renal failure. We propose that vascular oxidative stress and inflammation are generalized phenomena during senescence, which importantly contribute to the morphological and functional changes in the aging kidney. The present review focuses on some of the mechanisms by which advanced age may promote vascular oxidative and nitrosative stress and the possible downstream mechanisms by which reactive oxygen and nitrogen species may impair vascular and renal function in aging.

Altered collagen homeostasis in human aortic smooth muscle cells (HAoSMCs) induced by aldosterone

The importance of aldosterone for cardiovascular diseases is well established. Most of the adverse effects seem to originate from its ability to produce vascular injury, including fibrosis. It is currently under debate whether aldosterone per se is able to induce fibrosis or whether it acts as a cofactor under pathological conditions. We tested whether aldosterone per se and in the presence of reactive oxygen stress (H(2)O(2)) enhances collagen abundance in human aortic smooth muscle cell (HAoSMC) media in primary culture and, if so, by which means. Collagen abundance, as well as epidermal growth factor receptor (EGFR) expression and ERK1/2 phosphorylation, was investigated by ELISA and Western blot. Collagenase activity and H(2)O(2) formation were determined by fluorometry and luminometry. Aldosterone alone did not affect collagen abundance but potentiated the stimulatory effect of low concentrations of H(2)O(2) (1-10 micromol/l). This effect disappeared when shedding of membrane-bound EGFR ligands was prevented by GM6001. EGFR expression and cellular EGF responsiveness were enhanced by aldosterone. Inhibition of the EGFR kinase (tyrphostin AG1478) prevented the increase of collagen. The increase in collagen abundance was prevented by blockade of the mineralocorticoid receptor (MR) and could be reproduced by MR transfection into Chinese hamster ovary cells. We conclude that aldosterone sensitizes HAoSMC for H(2)O(2)-induced increase of collagen abundance at least in part by enhanced EGFR expression.

Noxa1 is a central component of the smooth muscle NADPH oxidase in mice

NADPH oxidase is the most important source of oxygen-derived radicals (ROS) in the vascular wall. In vascular smooth muscle cells (VSMC), NADPH oxidase is characterized by the expression of the membrane subunit Nox1, which is activated by cytoplasmic proteins binding to its activation domain. We set out to identify the cytoplasmic protein involved in NADPH oxidase activation in mouse VSMC. Western blot analysis revealed that human endothelial cells and leukocytes but not VSMC from the aorta of the rat and the mouse express the classic NADPH oxidase activator p67phox. In mouse VSMC, however, the p67phox homologue Noxa1 was detected. Using antibodies generated against mouse Noxa1, the protein was observed in the cytosolic fraction of mouse VSMC with a molecular weight of about 51 kDa. Immunohistochemistry revealed that Noxa1 is expressed in the smooth muscle layer but not in endothelium or the adventitia of the mouse carotid artery. Fluorescent fusion proteins of Noxa1 were observed to be expressed in the cytoplasm of VSMC and coexpression of the NADPH oxidase organizer Noxo1 targeted the complex to membrane. An antisense plasmid of Noxa1 attenuated the endogenous Noxa1 protein expression in VSMC. This plasmid attenuated the ROS formation in mouse VSMC as detected using L012 chemiluminescence and prevented the agonist-induced ROS production in response to basic fibroblast growth factor and epidermal growth factor. In conclusion, these data indicate that Noxa1 replaces p67phox in VSMC and plays a central role in the activation of the NADPH oxidase in the vascular wall.

Expression and regulation of antioxidant enzymes in the developing limb support a function of ROS in interdigital cell death

Vertebrate limb development is a well-studied model of apoptosis; however, little is known about the intracellular molecules involved in activating the cell death machinery. We have shown that high levels of reactive oxygen species (ROS) are present in the interdigital 'necrotic' tissue of mouse autopod, and that antioxidants can reduce cell death. Here, we determined the expression pattern of several antioxidant enzymes in order to establish their role in defining the areas with high ROS levels. We found that the genes encoding the superoxide dismutases and catalase are expressed in autopod, but they are downregulated in the interdigital regions at the time ROS levels increased and cell death was first detected. The possible role of superoxide and/or peroxide in activating cell death is supported by the protective effect of a superoxide dismutase/catalase mimetic. Interestingly, we found that peroxidase activity and glutathione peroxidase-4 gene (Gpx4) expression were restricted to the non-apoptotic tissue (e.g., digits) of the developing autopod. Induction of cell death with retinoic acid caused an increase in ROS and decrease in peroxidase activity. Even more inhibition of glutathione peroxidase activity leads to cell death in the digits, suggesting that a decrease in antioxidant activity, likely due to Gpx4, caused an increase in ROS levels, thus triggering apoptosis.