Chemiluminescent detection of oxidants in vascular tissue. Lucigenin but not coelenterazine enhances superoxide formation

Finely-Tuning Chemiluminescent Color of CdTe Nanocrystals and Its Application for Near-Infrared Semi-Automatic Immunoassay

Chemiluminescence (CL), especially commercialized CL immunoassay (CLIA), is normally performed within the eye-visible region of the spectrum by exploiting the electronic-transition-related emission of the molecule luminophore. Herein, dual-stabilizers-capped CdTe nanocrystals (NCs) is employed as a model of nanoparticulated luminophore to finely tune the CL color with superior color purity. Initialized by oxidizing the CdTe NCs with potassium periodate (KIO4), intermediates of the reactive oxygen species (ROS) tend to charge CdTe NCs in both series-connection and parallel-connection routes and dominate the charge-transfer CL of CdTe NCs. The CdTe NCs/KIO4 system can exhibit color-tunable CL with the maximum emission wavelength shifted from 694 nm to 801 nm, and the red-shift span is over 100 nm. Both PL and CL of each of the CdTe NCs are bandgap-engineered; the change in the NCs surface state via CL reaction enables CL of each of the CdTe NCs to be red-shifted for ∼20 nm to PL, while the change in the NCs surface state via labeling CdTe NCs to secondary-antibody (Ab2) enables CL of the CdTe NCs-Ab2 conjugates to be red-shifted for another ∼20 nm to bare CdTe NCs. The CL of CdTe753-Ab2/KIO4 is ∼791 nm, which can perform near-infrared CL immunoassay and semi-automatically determined procalcitonin (PCT) on commercialized in vitro diagnosis (IVD) instruments.

Enhanced Photon Emission of Chemiluminescent Luminophore for Ultra-Fast and Semi-Automatic Immunoassay toward Single Molecule Detection

Optical single molecule detection is normally achieved via amplifying the total emission of photons of luminophores and is strongly anticipated to extend the commercialized application of chemiluminescence (CL). To overcome the limited CL photons of molecule luminophores, herein, a nanocrystal (NC) luminophore self-amplified strategy is proposed to repetitively excite CL luminophores for amplifying the total CL photons per luminophore, which can be exploited to perform CL immunoassays (CLIAs) toward single molecule detection via employing KMnO₄ as the CL triggering agent and the dual-stabilizer-capped CdTe NCs as the CL luminophore. KMnO₄ can oxidize the S element from each stabilizer of mercaptopropionic acid (MPA) and release enough energy to excite the CdTe core for flash CL. The substantial MPA around each CdTe core enables every CdTe luminophore to be repetitively excited and give off amplified total CL photons in a self-enhanced way. The CL of CdTe NCs/KMnO₄ can release all photons rapidly, and the collection of all these photons can be utilized to determine the model analyte of thyroid-stimulating hormone antigen (TSH) with a limit of detection of 5 ag/mL (S/N = 3), which is corresponding to about 2-4 TSH molecules in a 20 μL sample. The whole immunologic operating process can be terminated within 6 min. This strategy of repetitively breaking the CL reaction involving chemical bonds within one luminophore is promising for semi-automatic as well as fully automatic single molecule detection and extends the commercialized application of CL immunodiagnosis.

Vascular redox signaling, eNOS uncoupling and endothelial dysfunction in the setting of transportation noise exposure or chronic treatment with organic nitrates

SIGNIFICANCE

Cardiovascular disease and drug-induced health side effects are frequently associated with - or even caused by - an imbalance between the concentrations of reactive oxygen and nitrogen species (RONS) and antioxidants respectively determining the metabolism of these harmful oxidants.

RECENT ADVANCES

According to the "kindling radical" hypothesis, initial formation of RONS may further trigger the additional activation of RONS formation under certain pathological conditions. The present review will specifically focus on a dysfunctional, uncoupled endothelial nitric oxide synthase (eNOS) caused by RONS in the setting of transportation noise exposure or chronic treatment with organic nitrates, especially nitroglycerin. We will further describe the various "redox switches" that are proposed to be involved in the uncoupling process of eNOS.

CRITICAL ISSUES

In particular, the oxidative depletion of tetrahydrobiopterin (BH4), and S-glutathionylation of the eNOS reductase domain will be highlighted as major pathways for eNOS uncoupling upon noise exposure or nitroglycerin treatment. In addition, oxidative disruption of the eNOS dimer, inhibitory phosphorylation of eNOS at threonine or tyrosine residues, redox-triggered accumulation of asymmetric dimethylarginine (ADMA) and L-arginine deficiency will be discussed as alternative mechanisms of eNOS uncoupling.

FUTURE DIRECTIONS

The clinical consequences of eNOS dysfunction due to uncoupling on cardiovascular disease will be summarized also providing a template for future clinical studies on endothelial dysfunction caused by pharmacological or environmental risk factors.

Ultrasensitive and real-time optical detection of cellular oxidative stress using graphene-covered tunable plasmonic interfaces

Reactive oxygen species (ROS) regulate various physiological and pathological conditions in cells by interacting with signaling molecules and inducing oxidative stress. Therefore, sensitive monitoring of ROS levels in living cells is important to track cellular state and study the complex role of ROS in the development of various pathologies. Herein, we present an optically tunable plasmonic interface covered with graphene to monitor cellular ROS levels with superior sensitivity and cellular comfortability. As a sensing principle, we employed plasmon resonance energy transfer (PRET)-based spectral quenching dips modulated by redox-active cytochrome c for real-time monitoring. By transferring graphene layers to plasmonic nanoparticles immobilized on a glass substrate, the scattering profiles of the nanoprobes were adjusted in terms of the position, width, and intensity of the peaks to determine the optimal conditions for measuring the PRET signal. Using the optimized graphene-covered plasmonic nanoprobe, we obtained calibration curves over a wide concentration range from femtomoles to millimoles for hydrogen peroxide based on the change in the PRET signal. Before monitoring cellular ROS, we confirmed that a high density of cells adhered well to the graphene-covered plasmonic interface by observing immunofluorescence images of the cytoskeleton of the immobilized cells. Finally, we monitored the real-time ROS generated by the cells under oxidative stress conditions by directly measuring the spectral changes of the probes around the cells. We believe that the proposed graphene-covered tunable plasmonic interface has versatile applicability for investigating cellular stress and disease progression by monitoring ROS levels under various cellular conditions.

NOX activation in reactive astrocytes regulates astrocytic LCN2 expression and neurodegeneration

Reactive astrocytes (RA) secrete lipocalin-2 (LCN2) glycoprotein that regulates diverse cellular processes including cell death/survival, inflammation, iron delivery and cell differentiation. Elevated levels of LCN2 are considered as a biomarker of brain injury, however, the underlying regulatory mechanisms of its expression and release are not well understood. In this study, we investigated the role of astrocytic Na+/H+ exchanger 1 (NHE1) in regulating reactive astrocyte LCN2 secretion and neurodegeneration after stroke. Astrocyte specific deletion of Nhe1 in Gfap-CreER+/-;Nhe1f/f mice reduced astrogliosis and astrocytic LCN2 and GFAP expression, which was associated with reduced loss of NeuN+ and GRP78+ neurons in stroke brains. In vitro ischemia in astrocyte cultures triggered a significant increase of secreted LCN2 in astrocytic exosomes, which caused neuronal cell death and neurodegeneration. Inhibition of NHE1 activity during in vitro ischemia with its potent inhibitor HOE642 significantly reduced astrocytic LCN2+ exosome secretion. In elucidating the cellular mechanisms, we found that stroke triggered activation of NADPH oxidase (NOX)-NF-κB signaling and ROS-mediated LCN2 expression. Inhibition of astrocytic NHE1 activity attenuated NOX signaling and LCN2-mediated neuronal apoptosis and neurite degeneration. Our findings demonstrate for the first time that RA use NOX signaling to stimulate LCN2 expression and secretion. Blocking astrocytic NHE1 activity is beneficial to reduce LCN2-mediated neurotoxicity after stroke.

Photolon Nanoporous Photoactive Material with Antibacterial Activity and Label-Free Noncontact Method for Free Radical Detection

The worldwide increase in bacterial resistance and healthcare-associated bacterial infections pose a serious threat to human health. The antimicrobial photodynamic method reveals the opportunity for a new therapeutic approach that is based on the limited delivery of photosensitizer from the material surface. Nanoporous inorganic–organic composites were obtained by entrapment of photosensitizer Photolon in polysiloxanes that was prepared by the sol–gel method. The material was characterized by its porosity, optical properties (fluorescence and absorbance), and laser-induced antimicrobial activity against Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The permanent encapsulation of Photolon in the silica coating and the antimicrobial efficiency was confirmed by confocal microscope and digital holotomography. The generation of free radicals from nanoporous surfaces was proved by scanning Kelvin probe microscopy. For the first time, it was confirmed that Kelvin probe microscopy can be a label-free, noncontact alternative to other conventional methods based on fluorescence or chemiluminescence probes, etc. It was confirmed that the proposed photoactive coating enables the antibacterial photodynamic effect based on free radicals released from the surface of the coating. The highest bactericidal efficiency of the proposed coating was 87.16%. This coating can selectively limit the multiplication of bacterial cells, while protecting the environment and reducing the risk of surface contamination.

Non-invasive and accurate readout of superoxide anion in biological systems by near-infrared light

Infectious and inflammatory diseases involve superoxide anion (O₂^•-) production. Real-time and non-invasive evaluation of O₂^•- in intact biological systems has been a significant challenge in biology and medicine. Here, I report that an advanced near-infrared chemiluminescent probe, MCLA-800, enables reliable non-invasive optical readout of O₂^•-ex vivo and in vivo. MCLA-800 allowed highly selective and sensitive monitoring of O₂^•- in undiluted human whole blood ex vivo. For the first time, the use of MCLA-800 revealed two reproducible types of O₂^•- production in response to stimulation by unopsonized zymosan particles of Saccharomyces cerevisiae, that is, slow response (S-type) and fast response (F-type), specific to each individual. O₂^•- production was synchronized with myeloperoxidase (MPO) activation in the former type but not in the latter. Moreover, as new findings, MCLA-800 chemiluminescence demonstrated that the chemiluminescence intensity-time properties of formyl-methionyl-leucyl-phenylalanine (fMLP)- or phorbol 12-myristate 13-acetate (PMA)-induced O₂^•- production and MPO activity were independent of S- and F-type zymosan-induced MCLA-800 chemiluminescence whole blood and that PMA-induced MPO activation synchronized with PMA-induced O₂^•- production in S- and F-type zymosan-induced MCLA-800 chemiluminescence whole blood, but fMLP-induced MPO activation did not synchronize with fMLP-induced O₂^•- production in both of S- and F-type blood. Furthermore, MCLA-800 spatiotemporally allowed non-invasive and clear in vivo imaging of O₂^•- in animal models of acute dermatitis and focal arthritis. Therefore, MCLA-800 could be possibly applied in various advanced diagnostic techniques.

Nanoceria potently reduce superoxide fluxes from mitochondrial electron transport chain and plasma membrane NADPH oxidase in human macrophages

Cerium oxide nanoparticles, also known as nanoceria, possess antioxidative and anti-inflammatory activities in animal models of inflammatory disorders, such as sepsis. However, it remains unclear how nanoceria affect cellular superoxide fluxes in macrophages, a critical type of cells involved in inflammatory disorders. Using human ML-1 cell-derived macrophages, we showed that nanoceria at 1-100 μg/ml potently reduced superoxide flux from the mitochondrial electron transport chain (METC) in a concentration-dependent manner. The inhibitory effects of nanoceria were also shown in succinate-driven mitochondria isolated from the macrophages. Furthermore, nanoceria markedly mitigated the total intracellular superoxide flux in the macrophages. These data suggest that nanoceria could readily cross the plasma membrane and enter the mitochondrial compartment, reducing intracellular superoxide fluxes in unstimulated macrophages. In macrophages undergoing respiratory burst, nanoceria also strongly reduced superoxide flux from the activated macrophage plasma membrane NADPH oxidase (NOX) in a concentration-dependent manner. Token together, the results of the present study demonstrate that nanoceria can effectively diminish superoxide fluxes from both METC and NOX in human macrophages, which may have important implications for nanoceria-mediated protection against inflammatory disease processes.

Comprehensive Review of Methodology to Detect Reactive Oxygen Species (ROS) in Mammalian Species and Establish Its Relationship with Antioxidants and Cancer

Evidence suggests that reactive oxygen species (ROS) mediate tissue homeostasis, cellular signaling, differentiation, and survival. ROS and antioxidants exert both beneficial and harmful effects on cancer. ROS at different concentrations exhibit different functions. This creates necessity to understand the relation between ROS, antioxidants, and cancer, and methods for detection of ROS. This review highlights various sources and types of ROS, their tumorigenic and tumor prevention effects; types of antioxidants, their tumorigenic and tumor prevention effects; and abnormal ROS detoxification in cancer; and methods to measure ROS. We conclude that improving genetic screening methods and bringing higher clarity in determination of enzymatic pathways and scale-up in cancer models profiling, using omics technology, would support in-depth understanding of antioxidant pathways and ROS complexities. Although numerous methods for ROS detection are developing very rapidly, yet further modifications are required to minimize the limitations associated with currently available methods.

Approaches for Reactive Oxygen Species and Oxidative Stress Quantification in Epilepsy

Oxidative stress (OS) and excessive reactive oxygen species (ROS) production have been implicated in many neurological pathologies, including acute seizures and epilepsy. Seizure-induced damage has been demonstrated both in vitro and in several in vivo seizure and epilepsy models by direct determination of ROS, and by measuring indirect markers of OS. In this manuscript, we review the current reliable methods for quantifying ROS-related and OS-related markers in pre-clinical and clinical epilepsy studies. We first provide pieces of evidence for the involvement of different sources of ROS in epilepsy. We then discuss general methods and assays used for the ROS measurements, mainly superoxide anion, hydrogen peroxide, peroxynitrite, and hydroxyl radical in in vitro and in vivo studies. In addition, we discuss the role of these ROS and markers of oxidative injury in acute seizures and epilepsy pre-clinical studies. The indirect detection of secondary products of ROS such as measurements of DNA damage, lipid peroxidation, and protein oxidation will also be discussed. This review also discusses reliable methods for the assessment of ROS, OS markers, and their by-products in epilepsy clinical studies.

Dynamic regulation of NADPH oxidase 5 by intracellular heme levels and cellular chaperones

NADPH oxidase 5 (NOX5) is a transmembrane signaling enzyme that produces superoxide in response to elevated cytosolic calcium. In addition to its association with numerous human diseases, NOX5 has recently been discovered to play crucial roles in the immune response and cardiovascular system. Details of NOX5 maturation, and specifically its response to changes in intracellular heme levels have remained unclear. Here we establish an experimental system in mammalian cells that allows us to probe the influence of heme availability on ROS production by NOX5. We identified a mode of dynamic regulatory control over NOX5 activity through modulation of its heme saturation and oligomeric state by intracellular heme levels and Hsp90 binding. This regulatory mechanism allows for fine-tuning and reversible modulation of NOX5 activity in response to stimuli.

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.

CD40L controls obesity-associated vascular inflammation, oxidative stress, and endothelial dysfunction in high fat diet-treated and db/db mice

Aims

CD40 ligand (CD40L) signaling controls vascular oxidative stress and related dysfunction in angiotensin-II-induced arterial hypertension by regulating vascular immune cell recruitment and platelet activation. Here we investigated the role of CD40L in experimental hyperlipidemia.

Methods and results

Male wild type and CD40L-/- mice (C57BL/6 background) were subjected to high fat diet for sixteen weeks. Weight, cholesterol, HDL, and LDL levels, endothelial function (isometric tension recording), oxidative stress (NADPH oxidase expression, dihydroethidium fluorescence) and inflammatory parameters (inducible nitric oxide synthase, interleukin-6 expression) were assessed. CD40L expression, weight, leptin and lipids were increased, and endothelial dysfunction, oxidative stress and inflammation were more pronounced in wild type mice on a high fat diet, all of which was almost normalized by CD40L deficiency. Similar results were obtained in diabetic db/db mice with CD40/TRAF6 inhibitor (6877002) therapy. In a small human study higher serum sCD40L levels and an inflammatory phenotype were detected in the blood and Aorta ascendens of obese patients (body mass index > 35) that underwent by-pass surgery.

Conclusion

CD40L controls obesity-associated vascular inflammation, oxidative stress and endothelial dysfunction in mice and potentially humans. Thus, CD40L represents a therapeutic target in lipid metabolic disorders which is a leading cause in cardiovascular disease.

Chemical Probes for Redox Signaling and Oxidative Stress

SIGNIFICANCE

Cellular reactive oxygen species (ROS) mediate redox signaling cascades that are critical to numerous physiological and pathological processes. Analytical methods to monitor cellular ROS levels and proteomic platforms to identify oxidative post-translational modifications (PTMs) of proteins are critical to understanding the triggers and consequences of redox signaling. Recent Advances: The prevalence and significance of redox signaling has recently been illuminated through the use of chemical probes that allow for sensitive detection of cellular ROS levels and proteomic dissection of oxidative PTMs directly in living cells.

CRITICAL ISSUES

In this review, we provide a comprehensive overview of chemical probes that are available for monitoring ROS and oxidative PTMs, and we highlight the advantages and limitations of these methods.

FUTURE DIRECTIONS

Despite significant advances in chemical probes, the low levels of cellular ROS and low stoichiometry of oxidative PTMs present challenges for accurately measuring the extent and dynamics of ROS generation and redox signaling. Further improvements in sensitivity and ability to spatially and temporally control readouts are essential to fully illuminate cellular redox signaling.

Verification of radiodynamic therapy by medical linear accelerator using a mouse melanoma tumor model

Combined treatment with 5-aminolevulinic acid (5-ALA) and X-rays improves tumor suppression in vivo. This is because the accumulated protoporphyrin IX from 5-ALA enhances the generation of ROS by the X-ray irradiation. In the present study, a high-energy medical linear accelerator was used instead of a non-medical low energy X-ray irradiator, which had been previously used. Tumor-bearing mice implanted with B16-BL6 melanoma cells were treated with fractionated doses of irradiation (in total, 20 or 30 Gy), using two types of X-ray irradiator after 5-ALA administration. Suppression of tumor growth was enhanced with X-ray irradiation in combination with 5-ALA treatment compared with X-ray treatment alone, using both medical and non-medical X-ray irradiators. 5-ALA has been used clinically for photodynamic therapy. Thus, “radiodynamic therapy”, using radiation from medical linacs as a physical driving force, rather than the light used in photodynamic therapy, may have potential clinical applications.

Taking up the cudgels for the traditional reactive oxygen and nitrogen species detection assays and their use in the cardiovascular system

Reactive oxygen and nitrogen species (RONS such as H2O2, nitric oxide) confer redox regulation of essential cellular functions (e.g. differentiation, proliferation, migration, apoptosis), initiate and catalyze adaptive stress responses. In contrast, excessive formation of RONS caused by impaired break-down by cellular antioxidant systems and/or insufficient repair of the resulting oxidative damage of biomolecules may lead to appreciable impairment of cellular function and in the worst case to cell death, organ dysfunction and severe disease phenotypes of the entire organism. Therefore, the knowledge of the severity of oxidative stress and tissue specific localization is of great biological and clinical importance. However, at this level of investigation quantitative information may be enough. For the development of specific drugs, the cellular and subcellular localization of the sources of RONS or even the nature of the reactive species may be of great importance, and accordingly, more qualitative information is required. These two different philosophies currently compete with each other and their different needs (also reflected by different detection assays) often lead to controversial discussions within the redox research community. With the present review we want to shed some light on these different philosophies and needs (based on our personal views), but also to defend some of the traditional assays for the detection of RONS that work very well in our hands and to provide some guidelines how to use and interpret the results of these assays. We will also provide an overview on the "new assays" with a brief discussion on their strengths but also weaknesses and limitations.

Thiophene bridged hydrocyanine – a new fluorogenic ROS probe

In this report, we present a new hydrocyanine analog, termed as thiophene-bridged hydrocyanine (TBHC), which has its double bonds replaced with a bisthiophene, is 8.06-fold more stable to auto-oxidation than hydro-Cy5 and significantly better in cell culture.

Theoretical modulation of singlet/triplet chemiexcitation of chemiluminescent imidazopyrazinone dioxetanone via C8-substitution

DFT analysis of the thermolysis of C₈-substituted imidazopyrazinone dioxetanone allows the rational tuning of the activation barrier and singlet/triplet chemiexcitation.

Multimodality Imaging of Cancer Superoxide Anion Using the Small Molecule Coelenterazine

PURPOSE

We evaluated the small molecule coelenterazine as a potential reporter of cancer-associated superoxide anion in cell culture and in mice.

PROCEDURES

The superoxide anion concentrations of various cancer cell lines were quantified by coelenterazine chemiluminescence in vitro. Coelenteramide fluorescence was detected via flow cytometry and fluorescent microscopy. Coelenterazine was used for the in vivo detection of cancer-associated superoxide anion using the 4T1 breast adenocarcinoma mouse model.

RESULTS

Various cell lines in culture demonstrated different superoxide anion concentrations, with a signal range of 3.15 ± 0.06 to 11.80 ± 0.24 times that of background. In addition to chemiluminescent detection of coelenterazine, we demonstrated fluorescent detection of coelenteramide within the cytoplasm of cells. 4T1 murine mammary adenocarcinoma tumors in mice demonstrated significantly higher 2.13 ± 0.19-fold coelenterazine-based chemiluminescence than that of surrounding normal tissues.

CONCLUSIONS

Collectively, our results indicate that coelenterazine can be used to assay superoxide anion concentrations in cultured cancer cells and in tumors growing in mice.

Threshold levels of extracellular l-arginine that trigger NOS-mediated ROS/RNS production in cardiac ventricular myocytes

l-Arginine (L-Arg) is the substrate for nitric oxide synthase (NOS) to produce nitric oxide (NO), a signaling molecule that is key in cardiovascular physiology and pathology. In cardiac myocytes, L-Arg is incorporated from the circulation through the functioning of system-y⁺ cationic amino acid transporters. Depletion of L-Arg leads to NOS uncoupling, with O₂ rather than L-Arg as the terminal electron acceptor, resulting in superoxide formation. The reactive oxygen species (ROS) superoxide (O₂˙^-), combined with NO, may lead to the production of the reactive nitrogen species (RNS) peroxynitrite (ONOO^-), which is recognized as a major contributor to myocardial depression. In this study we aimed to determine the levels of external L-Arg that trigger ROS/RNS production in cardiac myocytes. To this goal, we used a two-step experimental design in which acutely isolated cardiomyocytes were loaded with the dye coelenterazine that greatly increases its fluorescence quantum yield in the presence of ONOO^- and O₂˙^- Cells were then exposed to different concentrations of extracellular L-Arg and changes in fluorescence were followed spectrofluorometrically. It was found that below a threshold value of ~100 µM, decreasing concentrations of L-Arg progressively increased ONOO^-/ O₂˙^--induced fluorescence, an effect that was not mimicked by d-arginine or l-lysine and was fully blocked by the NOS inhibitor l-NAME. These results can be explained by NOS aberrant enzymatic activity and provide an estimate for the levels of circulating L-Arg below which ROS/RNS-mediated harmful effects arise in cardiac muscle.

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.

Endothelial Cell Seeding onto Various Biomaterials Causes Superoxide-induced Cell Death

The seeding and/or in-growth of endothelial cells on a number of blood-contacting implants are a concern for both biomaterials and tissue engineering. While endothelialization has been viewed positively, owing to their ability to regulate both smooth muscle and blood, there is evidence which suggests that endothelial cells on a nonoptimized surface may be counterproductive. The present study describes the experimentation designed to elucidate the effect of culture substrate on intracellular superoxide (SO) levels, a marker for endothelial cell dysfunction. The adaptation of the use of dihydroethidium under physiologically relevant shearing conditions is also reported.

The present study describes a standardized method for the use of dihydroethidium as a marker for intracellular oxidative stress under physiologic shear. Levels of hydrogen peroxide (oxidative stress producing agent) are optimized to a minimum of 60 μM (under static conditions) to allow for the detection of SO within the free radical scavenging environment. A flow rate of 24.4 mL/min is applied and found to produce physiologically relevant shear stress (8.2 dynes/cm2) within the system under study. Dihydroethidium is a useful marker for assessing intracellular oxidative stress in studies that require shear.

Chemiluminescence Imaging of Superoxide Anion Detects Beta-Cell Function and Mass

Superoxide anion is produced during normal cellular respiration and plays key roles in cellular physiology with its dysregulation being associated with a variety of diseases. Superoxide anion is a short-lived molecule and, therefore, its homeostatic regulation and role in biology and disease requires dynamic quantification with fine temporal resolution. Here we validated coelenterazine as a reporter of intracellular superoxide anion concentration and used it as a dynamic measure both in vitro and in vivo. Chemiluminescence was dependent upon superoxide anion levels, including those produced during cellular respiration, and concentrations varied both kinetically and temporally in response to physiologically relevant fluctuations in glucose levels. In vivo imaging with coelenterazine revealed that beta cells of the pancreas have increased levels of superoxide anion, which acted as a measure of beta-cell function and mass and could predict the susceptibility of mice to diabetes mellitus. Glucose response and regulation are key elements of cellular physiology and organismal biology, and superoxide anion appears to play a fundamental and dynamic role in both of these processes.

Using glow stick chemistry for biological imaging

PURPOSE

This study describes an imaging strategy based on glow stick chemistry to non-invasively image oxidative stress and reactive oxygen species (ROS) production in living animals.

PROCEDURES

Upon stimulation, phagocytes produce toxic levels of ROS to kill engulfed microorganisms. The mitochondrial respiratory chain continually generates low levels of superoxide (O2·(-)) that serve as a source for generation of downstream ROS, which function as regulatory signaling intermediaries. A ROS-reacting substrate, 2-methyl-6-[4-methoxyphenyl]-3,7-dihydroimidazo[1,2-a]pyrazin-3-one hydrochloride, was used as the chemical energy donor for generating energy transfer luminescence in phagosomes and mitochondria.

RESULTS

Using targeted photoluminescent dyes with specific subcellular localization that serve as chemical energy recipients, our imaging data demonstrate proof-of-concept for using glow stick chemistry to visualize ROS production associated with phagocytosis and mitochondrial respiration in living mice.

CONCLUSIONS

Glow stick imaging is a complementary hybrid of chemiluminescence and photoluminescence imaging, capable of generating red or far-red emission for deep tissue imaging.

Mechanism of alcohol-enhanced lucigenin chemiluminescence in alkaline solution

The chemiluminescence (CL) of lucigenin (Luc(2+)) can be enhanced by different alcohols in alkaline solution. The effect of different fatty alcohols on the CL of lucigenin was related to the carbon chain length and the number of hydroxyl groups. Glycerol provides the greatest enhancement. UV/Vis absorption spectra and fluorescence spectra showed that N-methylacridone (NMA) was produced in the CL reaction in the presence of different alcohols. The peak of the CL spectrum was located at 470 nm in all cases, indicating that the luminophore was always the excited-state NMA. The quenching of lucigenin CL by superoxide dismutase (SOD) and the electron spin resonance (ESR) results with the spin trap of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrated that superoxide anions (O2 (•-)) were generated from dissolved oxygen in the CL reaction and that glycerol and dihydroxyacetone (DHA) can promote O2 (•-) production by the reduction of dissolved oxygen in alkaline solution. It was assumed that the enhancement provided by different alcohols was related to the solvent effect and reducing capacity. Glycerol and DHA can also reduce Luc(2+) into lucigenin cation radicals (Luc(•+) ), which react with O2 (•-) to produce CL, and glycerol can slowly transform into DHA, which is oxidized quickly in alkaline solution.

Site-2 protease responds to oxidative stress and regulates oxidative injury in mammalian cells

Site-2 protease (S2P) is a membrane-embedded protease that site-specifically cleaves intramembrane transcription factors, a necessary step for their maturation. S2P is well known to regulate cholesterol biosynthesis and endoplasmic reticulum stress in mammalian cells. In this study, we hypothesized that S2P could be responsible for the regulation of cellular oxidative injury under oxidative stress. Wild type Chinese hamster ovary (WT CHO) cells and their mutant M19 cells with defective S2P gene were exposed to different oxidative stress conditions. Results showed that oxidative stress significantly up-regulated S2P expression in WT CHO cells. Notably, M19 cells had remarkably higher level of superoxide and elevated rates of cell death than WT CHO cells. The vulnerability to oxidative stress was reversed by the transfection of S2P gene but not rescued by exogenous supplement of cholesterol, oleate, and mevalonate, indicating that lack of S2P gene leads cells to be more vulnerable to oxidative stress. Furthermore, compared with WT CHO cells, M19 cells had higher nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and lower paraoxonase-2 expression. Taken together, these results suggest that S2P can be a protease responding to oxidative stress and has the function of regulating cellular oxidative injury.

In vivo imaging of inflammatory phagocytes

Inflammation contributes to the pathophysiology of many diseases. In this report, we present noninvasive bioluminescence imaging methods that distinguish acute and chronic inflammation in mouse models. Systemic delivery of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils, whose myeloperoxidase (MPO) activity is required for luminol bioluminescence. In contrast, bioluminescence from injection of lucigenin (bis-N-methylacridinium nitrate) closely correlates with late phase and chronic inflammation. Lucigenin bioluminescence is independent of MPO and, instead, requires phagocyte NADPH oxidase (Phox) activity in macrophages. We are able to visualize tissue inflammation resulting from wound healing, bacterial infection, foreign substance implantation, and antitumor immune responses. Given the central role of inflammation in a variety of disorders, we believe these noninvasive imaging methods can help dissect the differential roles of neutrophils and macrophages in a variety of pathological conditions.

Rapid fluorescent visualization of multiple NAD(P)H oxidoreductases in homogenate, permeabilized cells, and tissue slices

Intracellular NAD(P)H oxidoreductases are a class of diverse enzymes that are the key players in a number of vital processes. The method we present and validate here is based on the ability of many NAD(P)H oxidoreductases to reduce the superoxide probe lucigenin, which is structurally similar to flavins, to its highly fluorescent water-insoluble derivative dimethylbiacridene. Two modifications of the method are proposed: (i) an express method for tissue homogenate and permeabilized cells in suspensions and (ii) a standard procedure for cells in culture and acute thin tissue slices. The method allows one to assess, visualize, and localize, using fluorescent markers of cellular compartments, multiple NADH and NADPH oxidoreductase activities. The application of selective inhibitors (e.g., VAS2870, a NOX2 inhibitor; plumbagin, a NOX4 inhibitor) allows one to distinguish and compare specific NAD(P)H oxidoreductase activities in cells and tissues and to attribute them to known enzymes. The method is simple, rapid, and flexible. It can be easily adapted to a variety of tasks. It will be useful for investigations of the role of various NAD(P)H oxidoreductases in a number of physiological and pathophysiological processes.

Detection of superoxide anion and hydrogen peroxide production by cellular NADPH oxidases

BACKGROUND

The recent recognition that isoforms of the cellular NADPH-dependent oxidases, collectively known as the NOX protein family, participate in a wide range of physiologic and pathophysiologic processes in both the animal and plant kingdoms has stimulated interest in the identification, localization, and quantitation of their products in biological settings. Although several tools for measuring oxidants released extracellularly are available, the specificity and selectivity of the methods for reliable analysis of intracellular oxidants have not matched the enthusiasm for studying NOX proteins.

SCOPE OF REVIEW

Focusing exclusively on superoxide anion and hydrogen peroxide produced by NOX proteins, this review describes the ideal probe for analysis of O2(-) and H2O2 generated extracellularly and intracellularly by NOX proteins. An overview of the components, organization, and topology of NOX proteins provides a rationale for applying specific probes for use and a context in which to interpret results and thereby construct plausible models linking NOX-derived oxidants to biological responses. The merits and shortcomings of methods currently in use to assess NOX activity are highlighted, and those assays that provide quantitation of superoxide or H2O2 are contrasted with those intended to examine spatial and temporal aspects of NOX activity.

MAJOR CONCLUSIONS

Although interest in measuring the extracellular and intracellular products of the NOX protein family is great, robust analytical probes are limited.

GENERAL SIGNIFICANCE

The widespread involvement of NOX proteins in many biological processes requires rigorous approaches to the detection, localization, and quantitation of the oxidants produced. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.

AVE3085 protects coronary endothelium from the impairment of asymmetric dimethylarginine by activation and recoupling of eNOS

PURPOSE

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of eNOS and it is recognized as a risk factor for endothelial dysfunction in cardiovascular diseases. We investigated the effect of AVE3085, a newly developed transcription enhancer of eNOS, on ADMA-induced endothelial dysfunction in coronary arteries with underlying mechanisms explored.

METHODS

Porcine coronary small arteries (diameter 600-800 μm) were studied in a myograph for endothelium-dependent relaxation to bradykinin and endothelium-independent relaxation to sodium nitroprusside. Protein expressions of eNOS and phosphorylated-eNOS (p-eNOS(Ser1177) and p-eNOS(Thr495)), and nitrotyrosine formation were determined by Western blot. NO release was directly measured with a NO microsensor. Productions of O(2) (.-) and peroxynitrite (ONOO(-)) were determined by lucigenin- and luminol- enhanced chemiluminescence respectively.

RESULTS

Exposure to ADMA significantly decreased the bradykinin-induced vasorelaxation and reduced the protein expression of p-eNOS(Ser1177) whereas increased the expression of p-eNOS(Thr495) and nitrotyrosine. Pre-incubation with AVE3085 restored the bradykinin-induced relaxation, reversed the decrease of p-eNOS(Ser1177), and lowered the level of p-eNOS(Thr495) and nitrotyrosine. NO release in response to bradykinin was significantly reduced by ADMA and such reduction was restored by AVE3085. AVE3085 also prevented the elevation of O (2) (.-) and ONOO(-) levels in coronary arteries exposed to ADMA.

CONCLUSIONS

AVE3085 prevents ADMA-induced endothelial dysfunction in coronary arteries. The protective effect of AVE3085 may be attributed to increased NO production resulting from enhanced eNOS activation, and decreased oxidative stress that involves inhibition of O (2) (.-) generation by eNOS recoupling. The present study suggested the therapeutic potential of AVE3085 in endothelial dysfunction in cardiovascular disorders.

Peroxynitrite formation in nitric oxide-exposed submitochondrial particles: detection, oxidative damage and catalytic removal by Mn-porphyrins

Peroxynitrite (ONOO(-)) formation in mitochondria may be favored due to the constant supply of superoxide radical (O(2)(∙-)) by the electron transport chain plus the facile diffusion of nitric oxide ((∙)NO) to this organelle. Herein, a model system of submitochondrial particles (SMP) in the presence of succinate plus the respiratory inhibitor antimycin A (to increase O(2)(∙-) rates) and the (∙)NO-donor NOC-7 was studied to directly establish and quantitate peroxynitrite by a multiplicity of methods including chemiluminescence, fluorescence and immunochemical analysis. While all the tested probes revealed peroxynitrite at near stoichiometric levels with respect to its precursor radicals, coumarin boronic acid (a probe that directly reacts with peroxynitrite) had the more straightforward oxidation profile from O(2)(∙-)-forming SMP as a function of the (∙)NO flux. Interestingly, immunospintrapping studies verified protein radical generation in SMP by peroxynitrite. Substrate-supplemented SMP also reduced Mn(III)porphyrins (MnP) to Mn(II)P under physiologically-relevant oxygen levels (3-30 μM); then, Mn(II)P were capable to reduce peroxynitrite and protect SMP from the inhibition of complex I-dependent oxygen consumption and protein radical formation and nitration of membranes. The data directly support the formation of peroxynitrite in mitochondria and demonstrate that MnP can undergo a catalytic redox cycle to neutralize peroxynitrite-dependent mitochondrial oxidative damage.

Analysis of kinetics of dihydroethidium fluorescence with superoxide using xanthine oxidase and hypoxanthine assay

Superoxide (O(2) (-)) is an important reactive oxygen species (ROS), and has an essential role in physiology and pathophysiology. An accurate detection of O(2) (-) is needed to better understand numerous vascular pathologies. In this study, we performed a mechanistic study by using the xanthine oxidase (XOD)/hypoxanthine (HX) assay for O(2) (-) generation and a O(2) (-) sensitive fluorescent dye dihydroethidium (DHE) for O(2) (-) measurement. To quantify O(2) (-) and DHE interactions, we measured fluorescence using a microplate reader. We conducted a detailed reaction kinetic analysis for DHE-O(2) (-) interaction to understand the effect of O(2) (-) self-dismutation and to quantify DHE-O(2) (-) reaction rate. Fluorescence of DHE and 2-hydroethidium (EOH), a product of DHE and O(2) (-) interaction, were dependent on reaction conditions. Kinetic analysis resulted in a reaction rate constant of 2.169 ± 0.059 × 10(3) M(-1) s(-1) for DHE-O(2) (-) reaction that is ~100× slower than the reported value of 2.6 ± 0.6 × 10(5) M(-1) s(-1). In addition, the O(2) (-) self-dismutation has significant effect on DHE-O(2) (-) interaction. A slower reaction rate of DHE with O(2) (-) is more reasonable for O(2) (-) measurements. In this manner, the DHE is not competing with superoxide dismutase and NO for O(2) (-). Results suggest that an accurate measurement of O(2) (-) production rate may be difficult due to competitive interference for many factors; however O(2) (-) concentration may be quantified.

The effect of reactive oxygen species on whole blood aggregation and the endothelial cell-platelet interaction in patients with coronary heart disease

Background

The effect of reactive oxygen species (ROS) on platelet function in coronary heart disease (CHD) is complex and poorly defined. Platelet aggregation studies in healthy volunteers have demonstrated contrasting results when platelets are exposed to ROS. We investigated the effect of ROS on whole blood aggregation (WBA) and the endothelial cell-platelet interaction in patients with CHD.

Methods and Results

ROS generated by xanthine and xanthine oxidase caused a concentration-dependent inhibition of WBA in blood from healthy donors and patients with CHD. In patients with CHD, 100 μM xanthine and 100 mU/ml xanthine oxidase inhibited WBA in response to 3 μg/ml collagen by 28.9% (95% CI 15.9%-41.8%, p < 0.001) and in response to 5 μM ADP by 36.0% (95% CI 9.6%-62.4%, p = 0.005). Using nitrotyrosine expression, platelets isolated from patients with CHD were found to be susceptible to peroxynitrite damage. The addition of 1 × 10⁵ cultured endothelial cells inhibited WBA in response to 3 μg/ml collagen by 31.2% (95% CI 12.2%-50.2%, p < 0.05) and in response to 5 μM ADP by 31.6% (95% CI 2.5-60.7%, p < 0.05). Addition of xanthine and xanthine oxidase did not alter this effect, however pre-treatment of endothelial cells with a nitric oxide synthase inhibitor (L-NAME) partly reversed the inhibition.

Conclusion

ROS inhibit WBA in blood from patients with CHD. Whilst endothelial cells also inhibit WBA, the effect is attenuated by L-NAME, suggesting that nitric oxide is likely to remain an important protective mechanism against thrombosis in CHD.

Differential effects of NADPH oxidase and xanthine oxidase inhibition on sympathetic reinnervation in postinfarct rat hearts

Superoxide has been shown to play a major role in ventricular remodeling and arrhythmias after myocardial infarction. However, the source of increased myocardial superoxide production and the role of superoxide in sympathetic innervation remain to be further characterized. Male Wistar rats, after coronary artery ligation, were randomized to vehicle, allopurinol, or apocynin for 4weeks. To determine the role of peroxynitrite in sympathetic reinnervation, we also used 3-morpholinosydnonimine (a peroxynitrite generator). The postinfarction period was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine, xanthine oxidase activity, NADPH oxidase activity, and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle-treated infarcted rats compared with sham. Sympathetic hyperinnervation was blunted after administration of allopurinol. Arrhythmic scores in the allopurinol-treated infarcted rats were significantly lower than those in vehicle. For similar levels of ventricular remodeling, apocynin had no beneficial effects on oxidative stress, sympathetic hyperinnervation, or arrhythmia vulnerability. Allopurinol-treated hearts had significantly decreased nerve growth factor expression, which was substantially increased after coadministration of 3-morpholinosydnonimine. These results indicate that xanthine oxidase but not NADPH oxidase largely mediates superoxide production after myocardial infarction. Xanthine oxidase inhibition ameliorates sympathetic innervation and arrhythmias possibly via inhibition of the peroxynitrite-mediated nerve growth factor pathway.

Molecular imaging of pulmonary disease in vivo

Characterization and noninvasive measurement of molecular pathways and biochemistry in living cells, animal models, and humans at the cellular and molecular level is now possible using remote imaging detectors. Positron and single photon emission tomography scanners, highly sensitive cameras for bioluminescence and fluorescence imaging, as well as high-magnetic-field magnetic resonance imaging scanners, can be used to study such diverse processes as signal transduction, receptor density and function, host response to pathogens, cell trafficking, and gene transfer. In many cases, images from more than one modality can be fused, allowing structure-function and multifunction relationships to be studied on a tissue-restricted or regional basis. "Molecular imaging" holds enormous potential for elucidating the molecular mechanisms of pulmonary disease and therapeutic response in intact animal models and humans.

Line and birth season effects on plasma testosterone and oxidative stress parameters in testis of maturing rabbits

Oxidative stress plays a key role in the male reproductive function. Differences between rabbit breeds have been found for testis size, seminiferous tubule diameter, number and size of interstitial and germ cells, etc. Traits related to the redox system could also be affected by genetic factors. It is likely that differences between breeds for these traits would lead to differences in reproductive maturation and fertility. We have investigated in the present paper the age-related changes of the plasma testosterone (TST) concentration, superoxide anion (O(2)(-)) radical formation, superoxide dismutase (SOD) activity, catalase (CAT) activity and thiobarbituric acid-reactive substances (TBARs) level in testis of rabbits in two breeds selected for different aptitudes (Caldes for growth rate and Prat for litter size). The effect of birth season for these traits was also assessed. Major changes in parameters related to oxidative stress were observed at an early age and most probably can be explained by the concomitant changes in testicular structure and function. Both lines showed similar developmental profiles and levels for all the variables studied. There was no interaction between line and birth season, consequently environmental conditions affected both lines in the same manner. Significant differences between males born in different seasons were found for O(2)(-) (4.84+/-0.19RLU/mg tissuemin versus 5.67+/-0.19RLU/mg tissuemin), SOD (6.12+/-0.11U/mg protein versus 7.09+/-0.11U/mg protein) and CAT (0.058+/-0.002K/mg protein versus 0.040+/-0.002K/mg protein). Future studies should take into account differences between seasons for a more precise analysis.

Advances in bioluminescence imaging of live animal models

Many of the obligate steps of physiology and disease are dynamic in time and space, and thus, end-point assays do not always provide a full understanding of these processes. Comprehensive understanding of the functional complexity of protein interactions and cell trafficking requires mapping of cellular and molecular function within complex systems over biologically relevant time scales. New approaches to bioluminescence imaging of cell migration, signaling pathways, drug action, and interacting protein partners in vivo allow the study of biology and disease within the context of living animals.

NADPH oxidase contributes to coronary endothelial dysfunction in the failing heart

Increased reactive oxygen species (ROS) produced by the failing heart can react with nitric oxide (NO), thereby decreasing NO bioavailability. This study tested the hypothesis that increased ROS generation contributes to coronary endothelial dysfunction in the failing heart. Congestive heart failure (CHF) was produced in six dogs by ventricular pacing at 240 beats/min for 4 wk. Studies were performed at rest and during treadmill exercise under control conditions and after treatment with the NADPH oxidase inhibitor and antioxidant apocynin (4 mg/kg iv). Apocynin caused no significant changes in heart rate, aortic pressure, left ventricular (LV) systolic pressure, LV end-diastolic pressure, or maximum rate of LV pressure increase at rest or during exercise in normal or CHF dogs. Apocynin caused no change in coronary blood flow (CBF) in normal dogs but increased CBF at rest and during exercise in animals with CHF (P < 0.05). Intracoronary ACh caused dose-dependent increases of CBF that were blunted in CHF. Apocynin had no effect on the response to ACh in normal dogs but augmented the response to ACh in CHF dogs (P < 0.05). The oxidative stress markers nitrotyrosine and 4-hydroxy-2-nonenal were significantly greater in failing than in normal myocardium. Furthermore, coelenterazine chemiluminescence for O(2)(-) was more than twice normal in failing myocardium, and this difference was abolished by apocynin. Western blot analysis of myocardial lysates demonstrated that the p47(phox) and p22(phox) subunits of NADPH were significantly increased in the failing hearts, while real-time PCR demonstrated that Nox2 mRNA was significantly increased. The data indicate that increased ROS generation in the failing heart is associated with coronary endothelial dysfunction and suggest that NADPH oxidase may contribute to this abnormality.

Antioxidant effects of green tea and its polyphenols on bladder cells

Genitourinary tract inflammation/ailments affect the quality of life and health of a large segment of society. In recent years, studies have demonstrated strong antioxidant effects of green tea and its associated polyphenols in inflammatory states. This in vitro study examined the antioxidant capabilities (and putative mechanisms of action) of green tea extract (GTE), polyphenon-60 (PP-60, 60% pure polyphenols), (-)-epicatechin-3-gallate (ECG) and (-)-epigallocatechin-3-gallate (EGCG) in normal/malignant human bladder cells following catechin treatment+/-1 mM H2O2 (oxidative agent). Cell viability, apoptosis and reactive oxygen species (ROS) formation were evaluated. Our results showed that H2O2 exposure significantly reduced normal (UROtsa) and high-grade (TCCSUP, T24) bladder cancer (BlCa) cell viability compared with control-treated cells (p<0.001). No affect on low-grade RT4 and SW780 BlCa cell viability was observed with exposure to H2O2. Compared to H2O2-treated UROtsa, treatment with PP-60, ECG and EGCG in the presence of H2O2 significantly improved UROtsa viability (p<0.01), with strongest effects evoked by ECG. Additionally, though not as effective as in UROtsa cells, viability of both high-grade TCCSUP and T24 BlCa cells, in comparison to H2O2-treated cells, was significantly improved (p<0.01) by treatment with PP-60, ECG, and EGCG in the presence of H2O2. Overall, our findings demonstrate that urothelium cell death via H2O2-induced oxidative stress is mediated, in part, through superoxide (O2-.;), and potentially, direct H2O2 mechanisms, suggesting that green tea polyphenols can protect against oxidative stress/damage and bladder cell death.

Detection of protein-protein interactions in live cells and animals with split firefly luciferase protein fragment complementation

Protein fragment complementation has emerged as a powerful tool for measuring protein-protein interactions in the context of live cells. The adaptation of this strategy for use with firefly luciferase now allows for the non-invasive, quantitative, real-time readout of protein interactions in lysates, live cells, and whole animals. Bioluminescence provides a robust imaging modality due to its extremely low background signal and large dynamic range. The split luciferase fusion constructs described here are inducible by addition of ligands, small molecules or drugs, in this example, rapamycin, and have been shown to work in vivo.

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.

Detection and measurement of reactive oxygen intermediates in mitochondria and cells

Reactive oxygen intermediates (ROIs) play a key role in a number of human diseases either by inducing cell death, cellular proliferation, or by acting as mediators in cellular signaling. Therefore, their measurement in vivo and in cell culture is desirable but technically difficult and often troublesome. To address some of the key methodological issues in examining the formation of ROI in cells and mitochondria, this chapter discusses the following: (a) the cellular sources of ROI and their enzymatic removal, (b) common methods used to determine cellular and mitochondrial ROI such as chemiluminescence, electron paramagnetic resonance spectroscopy, fluorescence, and enzymatic techniques, and (c) some common problems associated with these assays and the interpretation of data. We also provide some simple protocols for the estimation of ROI production in cells and mitochondria, and when measuring ROI in cells and mitochondria, we emphasize the need for thorough understanding of results obtained and their interpretation.