Oxygen: How Do We Stand It?

The electronic structure of ground state oxygen, which is essential for the life of all aerobic organisms, makes it potentially dangerous for those organisms. Atmospheric oxygen contains two unpaired electrons with parallel spin states, which predisposes it to reduction by a univalent pathway. As a consequence, normal aerobic metabolism generates dangerous reactive intermediates of the reduction of O₂. These include superoxide radical (O₂^–), hydrogen peroxide (H₂O₂), and hydroxyl radical (HO). These reactive oxygen species and others that they can engender can damage all cellular macromolecules and unless opposed by cellular defenses, would make aerobic life impossible. Such defenses include superoxide dismutases, catalases, and peroxidases, enzymes that decrease the concentration of the reactive oxygen species that are their substrates, and others that repair or recycle oxidatively damaged macromolecules. Any factor that stimulates reactive oxygen species production or suppresses the antioxidant systems would inevitably cause cell damage. The role of such oxidative damage in various diseases is well documented. In vivo detection of O^2– and other reactive oxygen species is however hampered by the lack of easy, specific, and sensitive analytical methods. Potential artifacts and limitations of the most common detection methods currently in use are briefly discussed.Key Words: Reactive oxygen species, Superoxide, Singlet oxygen, Hydrogen peroxide, Nitric oxide, Free radical, Oxidative stress, Superoxide dismutase, Superoxide assay     

肝癌患者血清及组织中ROS、T-SOD、MnSOD水平的测定

目的　研究原发性肝癌患者血清及组织内活性氧类物质 (ROS)、总超氧化物歧化酶 (T SOD)、锰超氧化物歧化酶 (MnSOD)水平。方法　选择 2 0例原发性肝癌组织和癌旁组织及对应血清。采用Fenton反应测定血清中ROS ,组织内ROS测定采用流式细胞技术。患者血清及组织匀浆内T SOD、MnSOD采用黄嘌呤氧化酶法测定。结果　原发性肝癌患者血清和组织内ROS水平明显高于正常对照 (P <0 .0 1) ,肿瘤患者血清中T SOD和MnSOD水平低于正常对照 (P <0 .0 1) ,血清中ROS与MnSOD呈明显负相关 (r =- 0 .92 4 ) ,癌组织内T SOD和MnSOD水平明显高于癌旁组织 (P <0 .0 1)。结论　ROS可能参与肝癌的发生 ,MnSOD在消除ROS阻止肝癌发生中可能发挥重要作用。血清中ROS、MnSOD与组织ROS、MnSOD之间可能有重新分配的过程。     

Mitochondrial complex I deficiency leads to increased production of superoxide radicals and induction of superoxide dismutase.

Mitochondria were isolated from skin fibroblast cultures derived from healthy individuals (controls) and from a group patients with complex I (NADH-CoQ reductase) deficiency of the mitochondrial respiratory chain. The complex I deficient patients included those with fatal infantile lactic acidosis (FILA), cardiomyopathy with cataracts (CC), hepatopathy with tubulopathy (HT), Leigh's disease (LD), cataracts and developmental delay (CD), and lactic acidemia in the neonatal period followed by mild symptoms (MS). Production of superoxide radicals, on addition of NADH, were measured using the luminometric probe lucigenin with isolated fibroblast mitochondrial membranes. Superoxide production rates were highest with CD and decreased in the order CD >> MS > LD > control > HT > FILA = CC. The quantity of Mn-superoxide dismutase (MnSOD), as measured by ELISA techniques, however, was highest in CC and FILA and lowest in CD. Plots of MnSOD quantity versus superoxide production showed an inverse relationship for most conditions with complex I deficiency. We hypothesize that oxygen radical production is increased when complex I activity is compromised. However, the observed superoxide production rates are modulated by the variant induction of MnSOD which decreases the rates, sometimes below those seen in control fibroblast mitochondria. In turn, we show that the variant induction of MnSOD is most likely a function of the change in the redox state of the cell experienced rather than a result of the complex I defect per se.     

Evaluation of radical scavenging properties of shikonin

With the aim of developing effective anti-inflammatory drugs, we have been investigating the biochemical effects of shikonin of “Shikon” roots, which is a naphthoquinone with anti-inflammatory and antioxidative properties. Shikonin scavenged reactive oxygen species like hydroxyl radical, superoxide anion (O₂^•−) and singlet oxygen in previous studies, but its reactivity with reactive oxygen species is not completely understood, and comparison with standard antioxidants is lacking. This study aimed elucidation of the reactivity of shikonin with nitric oxide radical and reactive oxygen species such as alkyl-oxy radical and O₂^•−. By using electron paramagnetic resonance spectrometry, shikonin was found unable of reacting with nitric oxide radical in a competition assay with oxyhemoglobin. However, shikonin scavenged alkyl-oxy radical from 2,2''-azobis(2-aminopropane) dihydrochloride with oxygen radical absorbance capacity, ORAC of 0.25 relative to Trolox, and showed a strong O₂^•−-scavenging ability (42-fold of Trolox; estimated reaction rate constant: 1.7 × 10⁵ M⁻¹s⁻¹) in electron paramagnetic resonance assays with CYPMPO as spin trap. Concerning another source of O₂^•−, the phagocyte NADPH oxidase (Nox2), shikonin inhibited the Nox2 activity by impairing catalysis when added before enzyme activation (IC₅₀: 1.1 µM; NADPH oxidation assay). However, shikonin did not affect the preactivated Nox2 activity, although having potential to scavenge produced O₂^•−. In conclusion, shikonin scavenged O₂^•− and alkyl-oxy radical, but not nitric oxide radical.     

Rifampin Induces Hydroxyl Radical Formation in Mycobacterium tuberculosis

The antituberculosis (anti-TB) drug rifampin (RIF) binds to the beta subunit of the RNA polymerase (RpoB) of Mycobacterium tuberculosis, but the bactericidal responses triggered after target interaction are not known. To evaluate whether RIF induced an oxidative burst, lysates of RIF-treated M. tuberculosis were tested for determination of reactive oxygen species (ROS) by the electron paramagnetic resonance (EPR) technique using 1-hydroxy-3-carboxy-pyrrolidine (CPH) and 5,5-dimethyl-1-pyrrolidine-N-oxide (DMPO) as spin traps. M. tuberculosis killing by RIF stimulated an increase in the rate of formation of the CPH radical (CP·). Lysate pretreatment with the O₂·⁻ and ·OH scavengers superoxide dismutase (SOD) and thiourea (THIO), respectively, or with the metal chelator diethylene triamine pentaacetic acid (DTPA) inhibited CP· formation, arguing in favor of a metal-catalyzed ROS response. Formation of CP· did not increase following treatment of RIF-resistant strains with RIF, indicating that the ROS were induced after RpoB binding. To identify the ROS formed, lysates of RIF-treated bacilli were incubated with DMPO, a spin trap specific for ·OH and O₂·⁻, with or without pretreatment with SOD, catalase, THIO, or DTPA. Superoxide dismutase, catalase, and THIO decreased formation of the DMPO-OH adduct, and SOD plus DTPA completely suppressed it, suggesting that RIF activated metal-dependent O₂·⁻-mediated mechanisms producing ·OH inside tubercle bacilli. The finding that the metal chelator DTPA reduced the bactericidal activity of RIF supported the possibility that ·OH was generated through these mechanisms and that it participated at least in part in M. tuberculosis killing by the drug.     

Activity and protein level of CuZnSOD and MnSOD in benign and malignant liver tumors

OBJECTIVES: Superoxide dismutase (SOD) is a key antioxidant enzyme, responsible for scavenging of superoxide anion - a precursor of all reactive oxygen species (ROS). ROS are implicated in many pathologies, particularly in tumor disease. The aim of our work was to evaluate SOD isoforms' activity and protein level changes in liver tumors. DESIGN AND METHODS: Materials were obtained from patients with liver tumors and with liver cirrhosis diagnosed by routine histopathological examination. Activity and protein level of SOD were determined by means of the Beauchamp and Fridovich assay and by Western blot analysis. RESULTS: Decreased activity of CuZnSOD and MnSOD and distinct differences in SOD isoforms' protein expression in liver cirrhosis were found. Results also showed higher protein level and activity of SOD isoforms in liver malignant tumors than in benign ones. CONCLUSIONS: Malignant tumors have a better antioxidant system than benign ones. Moreover, weakening of antioxidant mechanisms and accumulation of oxidative damage in cirrhotic liver could initiate liver carcinogenesis.     

Modulation of skin tumorigenesis by SOD.

Generation of reactive oxygen species (ROS) has been implicated in the development of cancer. Groundwork establishing mitochondria as a critical source of ROS generation and the role of manganese superoxide dismutase (MnSOD) in preventing mitochondria-mediated cell death have been well established. In a seemingly contradictory role, it also is well documented that increased MnSOD expression suppresses the carcinogenesis effect of ROS. Our recent studies demonstrated that overexpression of MnSOD reduced tumor incidence in the two-stage 7,12-dimethylbenz(a)-anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) skin carcinogenesis model. However, reduction of MnSOD by heterozygous knockout of the MnSOD gene (Sod 2+/-) did not lead to an increase in tumor incidence. Thus, how modulation of mitochondrial ROS levels alter the outcome of developing cancer is unclear. This review will provide background information on the sequence of ROS-mediated events in the mitochondria and evidence that suggests that the antioxidant and tumor suppressor functions of MnSOD are indeed inter-related. It also will offer insights into the mechanisms by which MnSOD modulates the outcome of early stage skin carcinogenesis.     

Silica modification of titania nanoparticles enhances photocatalytic production of reactive oxygen species without increasing toxicity potential in vitro

Titania (TiO₂) nanoparticles were surface modified using silica and citrate to implement a ‘safe-by-design’ approach for managing potential toxicity of titania nanoparticles by controlling surface redox reactivity. DLS and zeta-potential analyses confirmed the surface modification, and electron microscopy and surface area measurements demonstrated nanoscale dimensions of the particles. Electron paramagnetic resonance (EPR) was used to determine the exogenous generation of reactive oxygen species (ROS). All the produced spray dried nanotitania lowered levels of ROS when compared to the corresponding dispersed nanotitania, suggesting that the spray drying process is an appropriate design strategy for the control of nano TiO₂ ROS reactivity. The modification of nanotitania with silica and with citrate resulted in increased levels of ROS generation in exogenous measurements, including photoexcitation for 60 minutes. The dichlorodihydrofluorescein (DCFH) assay of dose-dependent production of oxidative stress, generated by pristine and modified nanotitania in macrophages and alveolar epithelial cells, found no significant change in toxicity originating from the generation of reactive oxygen species. Our findings show that there is no direct correlation between the photocatalytic activity of nanotitania and its oxidative stress-mediated potential toxicity, and it is possible to improve the former, for example adding silica as a modifying agent, without altering the cell redox equilibrium.

Titania (TiO₂) nanoparticles were surface modified using silica and citrate to implement a ‘safe-by-design’ approach for managing potential toxicity of titania nanoparticles by controlling surface redox reactivity.     

Ultrasmall copper nanoclusters with multi-enzyme activities

Reactive oxygen species (ROS) as a key messenger of signal transduction mediate physiological activities, however, oxidative stress produced by excessive ROS can cause the destruction of cell homeostasis, which will result in a series of diseases. Therefore, effective control of ROS level is critical to the homeostasis of the cell. Here, we reported that glutathione (GSH)-stabilized copper nanoclusters (CuNCs) with about 9 Cu atoms can functionally mimic three major antioxidant enzymes, namely catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD). The rate of H₂O₂ decomposition was calculated to be ∼0.23 mg L⁻¹ s⁻¹ when the concentration of CuNCs was 100 μg mL⁻¹. The SOD-like activity by catalyzing the disproportionation of superoxide to H₂O₂ and O₂ reached 25.6 U mg⁻¹ when the effective inhibition rate was ∼55.4%. Intracellular ROS scavenging studies further identified that CuNCs can obviously protect cells from oxidative stress and the cell viability recovered to above 90%. Hence, we expect that ultrasmall CuNCs will provide good therapeutic potential in the future treatment of ROS-related diseases.

Ultrasmall copper nanoclusters (CuNCs) can functionally mimic three major antioxidant enzymes, showing impressive intracellular ROS scavenging abilities.     

Photodynamic and Sonodynamic Treatment by Phthalocyanine on Cancer Cell Lines

Photodynamic therapy is a modality of treatment for tumors. The photochemical interactions of sensitizer, light and molecular oxygen produce reactive oxygen species (ROS) such as singlet oxygen, peroxide, hydroxyl radical and superoxide ion. The tumor is destroyed either by the formation of highly reactive singlet oxygen (type II mechanism) or by the formation of radical products (type 1 mechanism) generated in an energy transfer reaction. The resulting damage to organelles within malignant cells leads to tumor ablation. The cellular effects include membrane damage, mitochondrial damage and DNA damage. A new treatment modality called sonodynamic therapy has been developed, in which the ultrasound–induced cytotoxicity of sonochemical sensitizers inhibits tumor growth. In this study, the promising new generation of sensitizers – phthalocyanines – were used to induce the photodamage. In addition, we applied an ultrasound treatment to support the photodynamic effect. We report on the production of ROS in G361 melanoma cells. Light-emitting diodes were used to evoke the photodynamic effect. Changes in cells were evaluated using fluorescence microscope and atomic force microscopy. The quantitative ROS production changes in relation to sensitizer concentration, irradiation doses and ultrasound intensity were proved by a fluororeader. Our results showed the highest generation of ROS within G361 melanoma cells was achieved at an irradiation dose of 15 Jcm^-2 followed by ultrasound treatment at intensity of 2 Wcm^-2 and frequency of 1 MHz in the presence of 100 μM chloroaluminum phthalocyanine disulfonate (ClAlPcS₂). These results suggest that ClAlPcS₂ is a potential photosensitizer and sonosensitizer for sonodynamic or photodynamic treatment of cancer. (E-mail: kol@tunw.upol.cz)     

Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor. However, the characterization of surface defects is very complex and a deeper understanding of them remains a great challenge. In this work, a series of nano-TiO₂ was synthesized and their optical properties due to surface defects were studied. The results showed that the surface oxygen vacancies on nano-TiO₂ can induce chemiluminescence (CL) by luminol. The greater the number of surface oxygen vacancies, the stronger the luminescence signal, and the greater the production of reactive oxygen species. Further studies revealed that the CL intensity was positively correlated with the oxygen vacancy content on the surface of nano-TiO₂. Moreover, there was also a clear correlation between the oxygen vacancies and photogenerated superoxide radicals (O₂˙⁻) on nano-TiO₂ suspensions. Therefore, a simple and rapid CL method was developed for evaluating the oxygen vacancy content and their implied ability to photogenerate O₂˙⁻ on nano-TiO₂ and has great potential in distinguishing surface oxygen vacancies and judging photocatalytic performance in oxides.

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor.     

Hematopoietic Stem Cell Regeneration Enhanced by Ectopic Expression of ROS-detoxifying Enzymes in Transplant Mice

High levels of reactive oxygen species (ROS) can exhaust hematopoietic stem cells (HSCs). Thus, maintaining a low state of redox in HSCs by modulating ROS-detoxifying enzymes may augment the regeneration potential of HSCs. Our results show that basal expression of manganese superoxide dismutase (MnSOD) and catalase were at low levels in long-term and short-term repopulating HSCs, and administration of a MnSOD plasmid and lipofectin complex (MnSOD-PL) conferred radiation protection on irradiated recipient mice. To assess the intrinsic role of elevated MnSOD or catalase in HSCs and hematopoietic progenitor cells, the MnSOD or catalase gene was overexpressed in mouse hematopoietic cells via retroviral transduction. The impact of MnSOD and catalase on hematopoietic progenitor cells was mild, as measured by colony-forming units (CFUs). However, overexpressed catalase had a significant beneficial effect on long-term engraftment of transplanted HSCs, and this effect was further enhanced after an insult of low-dose γ-irradiation in the transplant mice. In contrast, overexpressed MnSOD exhibited an insignificant effect on long-term engraftment of transplanted HSCs, but had a significant beneficial effect after an insult of sublethal irradiation. Taken together, these results demonstrate that HSC function can be enhanced by ectopic expression of ROS-detoxifying enzymes, especially after radiation exposure in vivo.     

Deficiency of Lung Antioxidants in Idiopathic Pulmonary Arterial Hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is associated with lower levels of the pulmonary vasodilator nitric oxide (NO) and its biochemical reaction products (nitrite [NO₂ ⁻], nitrate [NO₃ ⁻]), in part, due to the reduction in pulmonary endothelial NO synthesis. However, NO levels are also determined by consumptive reactions, such as with superoxide to form peroxynitrite, which subsequently may generate stable products of nitrotyrosine (Tyr‐NO₂) and/or NO₃ ⁻. In this context, superoxide dismutase (SOD) preserves NO in vivo by scavenging superoxide and preventing the consumptive reactions. Here, we hypothesized that reactive oxygen species (ROS) consumption of NO may contribute to the low NO level and development of pulmonary hypertension. To test this, nitrotyrosine and antioxidants glutathione (GSH), glutathione peroxidase (GPx), catalase, and SOD were evaluated in IPAH patients and healthy controls. SOD and GPx activities were decreased in IPAH lungs (all p < 0.05), while catalase and GSH activities were similar among the groups (all p > 0.2). SOD activity was directly related to exhaled NO (eNO) (R ²= 0.72, p= 0.002), and inversely related to bronchoalveolar lavage (BAL) NO₃ ⁻ (R ²=–0.73, p= 0.04). Pulmonary artery pressure (PAP) could be predicted by a regression model incorporating SOD, GPx, and NO₃ values (R ²= 0.96, p= 0.01). These findings suggest that SOD and GPx are associated with alterations in NO and PAP in IPAH.     

On a heavy path – determining cold plasma-derived short-lived species chemistry using isotopic labelling

Cold atmospheric plasmas (CAPs) are promising medical tools and are currently applied in dermatology and epithelial cancers. While understanding of the biomedical effects is already substantial, knowledge on the contribution of individual ROS and RNS and the mode of activation of biochemical pathways is insufficient. Especially the formation and transport of short-lived reactive species in liquids remain elusive, a situation shared with other approaches involving redox processes such as photodynamic therapy. Here, the contribution of plasma-generated reactive oxygen species (ROS) in plasma liquid chemistry was determined by labeling these via admixing heavy oxygen ¹⁸O₂ to the feed gas or by using heavy water H₂¹⁸O as a solvent for the bait molecule. The inclusion of heavy or light oxygen atoms by the labeled ROS into the different cysteine products was determined by mass spectrometry. While products like cysteine sulfonic acid incorporated nearly exclusively gas phase-derived oxygen species (atomic oxygen and/or singlet oxygen), a significant contribution of liquid phase-derived species (OH radicals) was observed for cysteine-S-sulfonate. The role, origin, and reaction mechanisms of short-lived species, namely hydroxyl radicals, singlet oxygen, and atomic oxygen, are discussed. Interactions of these species both with the target cysteine molecule as well as the interphase and the liquid bulk are taken into consideration to shed light onto several reaction pathways resulting in observed isotopic oxygen incorporation. These studies give valuable insight into underlying plasma–liquid interaction processes and are a first step to understand these interaction processes between the gas and liquid phase on a molecular level.

Cold atmospheric plasmas (CAPs) are promising medical tools producing short-lived reactive species.     

Antioxidant and anti-aging potential of a peptide formulation (Gal2–Pep) conjugated with gallic acid

Skin is highly vulnerable to premature aging due to external stress, therefore, in this study, a peptide formulation, (galloyl)₂–KTPPTTP (Gal₂–Pep) was synthesized by combining TPPTTP peptide, and gallic acid (GA). All peptides were synthesized on 2-chlorotrityl chloride resin using solid-phase peptide synthesis (SPPS), and analyzed on an electrospray ionization (ESI)/quadrupole-time-of-flight (Q-TOF) tandem mass spectroscopy (MS) system. Initially, Gal₂–Pep showed no toxicity below the concentration 100 μM with cell survival rate of 88% for keratinocytes and fibroblasts. The reactive oxygen species (ROS) scavenging activity of Gal₂–Pep was more stable compared to GA alone; and after four weeks at room temperature, its ROS scavenging activity remained higher than 50%. Moreover, the peptide formulation, Gal₂–Pep also exhibited elastase inhibitory effect in CCD-1064Sk fibroblast cells. Based on the results of RT-qPCR, it was proved in this study that Gal₂–Pep increased the expression of PGC-1α to prevent oxidative stress, and validated its potential as an anti-aging agent through increasing the expression of type I collagen and by decreasing the expression of matrix metalloproteinase-1 (MMP1). The findings obtained reinforce the suggestion that the peptide formulation synthesized in this study could be used as a natural antioxidant and anti-aging agent for its cosmetic applications.

Skin is highly vulnerable to premature aging due to external stress, therefore, in this study, a peptide formulation, (galloyl)₂–KTPPTTP (Gal₂–Pep) was synthesized by combining TPPTTP peptide, and gallic acid (GA).     

Disruption of skeletal myocytes initiates superoxide release: contribution of NADPH oxidase

Generation of reactive oxygen species (ROS) as an early local reaction to muscle crush injury has frequently been predicted. However, although it is known that severe inflammatory reactions occurring after major muscle trauma originate mainly from early local incidents within the injured tissue, no detailed studies exist on the local generation of ROS in response to myocyte destruction thus far. Therefore, in this study, ROS formation after lethal mechanical damage was examined using a model of scraping injury to cultured C2C12 skeletal myocytes and superoxide detection by lucigenin chemiluminescence, nitrotetrazolium blue chloride reduction, or electron spin resonance spectroscopy. Mechanical rupture of myocytes resulted in an immediate release of superoxide from the damaged cells that could be substantially blocked by the superoxide scavengers superoxide dismutase (51%), tiron (95%), and MAMA/NO (93%) and by hypoxia (83% inhibition). Superoxide generation was primarily confined to the myocytes' membrane fraction and 7- to 8-fold enhanced by the addition of NADH or NADPH. The NADPH-enhanced superoxide generation could largely be diminished by the NAD(P)H oxidase inhibitors diphenyleneiodonium and apocynin in cell lysates (97% and 35% inhibition, respectively) and in isolated membrane fractions (61% and 63% inhibition). We thus conclude that immediately after myocyte damage, large amounts of superoxide are formed that predominantly originate from membrane-bound electron-transferring enzymes, especially NAD(P)H oxidase. This suggests a decisive role of ROS in the pathogenesis of tissue trauma, with superoxide being an initiator of the signaling mechanism from injured myocytes to the surrounding tissue and, potentially, to the whole body.     

A simple sensor based on 1,8-naphthalimide with large Stokes shift for detection of hypochlorous acid in living cells

Hypochlorous acid (HOCl), one of the most reactive and deleterious reactive oxygen species (ROS), plays a vital role in many pathological and physiological processes. However, as a result of the highly reactive and diffusible nature of HOCl, its uncontrolled production may lead to an adverse effect on host physiology. Because of its biological importance, many efforts have been focused on developing selective fluorescent probes to image HOCl. However, it is still challenging to design a fluorescent probe with exclusive selectivity towards HOCl. In this study, a novel fluorescent probe for HOCl, Probe 1 was rationally designed based on 1,8-naphthalimide. As the concentration of HOCl increased, the fluorescence intensity of the probe gradually decreased, and the solution color changed from yellow-green to colorless, indicating this is a “naked-eye sensor”. Probe 1 has a large Stokes shift (120 nm), which can effectively avoid fluorescence self-absorption. In addition, Probe 1 shows excellent selectivity to HOCl among different ions including common ROS, high sensitivity, fast response (<2 min), high fluorescence quantum yield (Φ = 0.93) and low detection limit (0.237 μM). Finally, the imaging results in HeLa cells showed that the probe could be used for the detection of exogenous and endogenous HOCl, and proved the potential of the probe as a biosensor for the detection of HOCl.

Probe 1 shows excellent selectivity to HOCl among different ions including common ROS, high sensitivity, high fluorescence quantum yield (Φ = 0.93), low detection limit (0.237 μM) and successfully used for the detection of HOCl in cells.     

Rational design of a selective and sensitive “turn-on” fluorescent probe for monitoring and imaging hydrogen peroxide in living cells

As one type of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) plays a key role in regulating a variety of cellular functions. Herein, a fluorescent probe N-Py-BO was well designed and synthesized and its ability for detecting H₂O₂ by fluorescence intensity was evaluated. In the design, the arylboronate ester group was acted as a reaction site for H₂O₂. Upon reaction with H₂O₂ under physiological conditions, the boronate moiety in the probe was oxidized, followed by detachment from the probe and as a result, a “turn-on” fluorescence response for H₂O₂ was acquired. Due to the D–A structure formation between N,N′-dimethylaminobenzene and the –CN group and the linkage by thiophene and C C bonds to increase the conjugate length, this probe showed a remarkable red shift of emission wavelength (650 nm) as well as a large Stokes shift (214 nm). An excellent linear relation with concentrations of H₂O₂ ranging from 2.0 to 200 μM and a good selectivity over other biological species were obtained. Importantly, taking advantage of the low toxicity and good biocompatibility, the developed probe was successfully applied to monitoring and imaging H₂O₂ and its level fluctuation in living cells, which provided a powerful tool for evaluation of cellular oxidative stress and understanding the pathophysiological process of H₂O₂-related diseases.

A fluorescent probe N-Py-BO was well designed and synthesized and its ability for detecting H₂O₂ by fluorescence intensity was evaluated.     

S-nitrosylation: integrator of cardiovascular performance and oxygen delivery

Delivery of oxygen to tissues is the primary function of the cardiovascular system. NO, a gasotransmitter that signals predominantly through protein S-nitrosylation to form S-nitrosothiols (SNOs) in target proteins, operates coordinately with oxygen in mammalian cellular systems. From this perspective, SNO-based signaling may have evolved as a major transducer of the cellular oxygen-sensing machinery that underlies global cardiovascular function. Here we review mechanisms that regulate S-nitrosylation in the context of its essential role in “systems-level” control of oxygen sensing, delivery, and utilization in the cardiovascular system, and we highlight examples of aberrant S-nitrosylation that may lead to altered oxygen homeostasis in cardiovascular diseases. Thus, through a bird’s-eye view of S-nitrosylation in the cardiovascular system, we provide a conceptual framework that may be broadly applicable to the functioning of other cellular systems and physiological processes and that illuminates new therapeutic promise in cardiovascular medicine.