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The roles of superoxide radical (O2â¢-) in the domains of physiological, physical, and material chemistry are becoming increasingly recognized. Although extensive efforts have been directed to understand O2â¢- functions in diverse aquatic systems, there is a lack of systematic and in-depth review for its kinetics and mechanisms in various environmental scenarios. This review aims to bridge this gap through discussion of O2â¢- generation pathways under both natural and controlled conditions. The merits and limitations of the generation and detection methods under various conditions are compared, with emphasis on different approaches for the determination of O2â¢--triggered reaction kinetics. We summarize the reaction rate constants of O2â¢- with organic contaminants covering a wide diversity of structures and reactivity. The comparison indicates that O2â¢- exhibits weak reactivity with most contaminants and lacks selectivity towards compounds with different functional groups, except with quinones which exhibit higher reactivity compared to non-quinones. Further, the reaction mechanisms, namely single electron transfer, nucleophilic substitution, hydrogen atom abstraction, and radical-adduct formation, are critically evaluated. Various environmental implications of O2â¢- are highlighted including maintenance of biogeochemical iron cycle, synthesis of nanoparticles for antibacterial purposes, desorption of contaminants from heterogeneous interfaces, and synergetic degradation of contaminants.
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Superóxidos , Superóxidos/química , CinéticaRESUMO
Electron paramagnetic resonance (EPR) spectroscopy and imaging coupled with the use of suitable probes is a promising tool for assessment of the tumor microenvironment (TME). Measurement of multiple TME parameters by EPR is very desirable but challenging. Herein, we designed and synthesized a class of negative-charged trityl quinodimethane MTPs as unimolecular triple-function extracellular probes for redox, pH, and oxygen (O2) levels. Using the deuterated analogue, dMTP5, which has an optimal pKa as well as high sensitivity to bioreduction and O2, we reasonably evaluated pH effects on efflux of reducing agents from HepG2 cells and cellular O2 consumption.
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Oxigênio , Substâncias Redutoras , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Oxigênio/química , Oxirredução , Concentração de Íons de HidrogênioRESUMO
Ultrasound coupled with activated persulfate can synergistically degrade aqueous organic contaminants. Here, in situ electron paramagnetic resonance spin trapping was used to compare radicals produced by ultrasonically activated persulfate (US-PS) and its individual technologies, ultrasound alone (US) and heat-activated persulfate (PS), with respect to temperature. Radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide, DMPO, to form detectable nitroxide adducts. Using initial rates of radical adduct formation, and compared to US and PS, US-PS at 40 and 50 °C resulted in the largest synergistic production of radicals. Radicals generated from US were reasonably consistent from 40 to 70 °C, indicating that temperature had little effect on cavitational bubble collapse over this range. However, synergy indexes calculated from initial rates showed that ultrasonic activation of persulfate at the bubble interface changes with temperature. From these results, we speculate that higher temperatures enhance persulfate uptake into cavitation bubbles via nanodroplet injection. DMPO-OH was the predominant adduct detected for all conditions. However, competition modeling and spin trapping in the presence of nitrobenzene and atrazine probes showed that SO4â¢- predominated. Therefore, the DMPO-OH signal is derived from SO4â¢- trapping with subsequent DMPO-SO4- hydrolysis to DMPO-OH. Spin trapping is effective in quantifying total radical adduct formation but limited in measuring primary radical speciation in this case.
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Óxidos N-Cíclicos , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Radicais Livres , Cinética , Marcadores de Spin , Detecção de Spin/métodos , TemperaturaRESUMO
Animal data indicate that ketogenic diets are associated with improved mitochondrial function, but human data are lacking. We aimed to characterize skeletal muscle mitochondrial changes in response to a ketogenic diet combined with exercise training in healthy individuals. Twenty-nine physically active adults completed a 12-wk supervised exercise program after self-selection into a ketogenic diet (KD, n = 15) group or maintenance of their habitual mixed diet (MD, n = 14). Measures of metabolic health and muscle biopsies (vastus lateralis) were obtained before and after the intervention. Mitochondria were isolated from muscle and studied after exposure to carbohydrate (pyruvate), fat (palmitoyl-l-carnitine), and ketone (ß-hydroxybutyrate+acetoacetate) substrates. Compared with MD, the KD resulted in increased whole body resting fat oxidation (P < 0.001) and decreased fasting insulin (P = 0.019), insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR), P = 0.022], and visceral fat (P < 0.001). The KD altered mitochondrial function as evidenced by increases in mitochondrial respiratory control ratio (19%, P = 0.009), ATP production (36%, P = 0.028), and ATP/H2O2 (36%, P = 0.033) with the fat-based substrate. ATP production with the ketone-based substrate was four to eight times lower than with other substrates, indicating minimal oxidation. The KD resulted in a small decrease in muscle glycogen (14%, P = 0.035) and an increase in muscle triglyceride (81%, P = 0.006). These results expand our understanding of human adaptation to a ketogenic diet combined with exercise. In conjunction with weight loss, we observed altered skeletal muscle mitochondrial function and efficiency, an effect that may contribute to the therapeutic use of ketogenic diets in various clinical conditions, especially those associated with insulin resistance.
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Dieta Cetogênica , Exercício Físico/fisiologia , Mitocôndrias Musculares/fisiologia , Músculo Esquelético/metabolismo , Adaptação Fisiológica/efeitos dos fármacos , Adaptação Fisiológica/fisiologia , Adulto , Gorduras na Dieta/farmacologia , Metabolismo Energético/efeitos dos fármacos , Metabolismo Energético/fisiologia , Humanos , Insulina/metabolismo , Resistência à Insulina/fisiologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Masculino , Mitocôndrias Musculares/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/ultraestrutura , OxirreduçãoRESUMO
Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20 kHz; 250 W) to activated persulfate over a range of bulk temperatures (20-60 °C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS). At 20 °C, observed US-PS rate constants strongly correlated with Wilke-Chang diffusion coefficients. This correlation indicates PAH molecules diffuse to the bubble-water interface prior to reaction with sulfate radicals (SO4-) generated at the interface. At higher temperatures, observed US-PS rate constants appear to be a more complicated function of temperature and diffusion coefficients. Synergy indexes for PAHs with fast diffusion coefficients were greatest at 20 °C. Fluoranthene, the largest and most hydrophobic PAH, had a maximum synergy index at 30 °C; it benefited from additional thermal persulfate activation in bulk solution. Fluoranthene synergy indexes, however, decreased above 30 °C and became antagonistic at 60 °C. Electron paramagnetic resonance (EPR) spin trapping was used to quantify hydroxyl radical (OH) produced from acoustic cavitation in the absence of persulfate. These data showed consistent OH production from 20 to 60 °C, indicating PAH antagonisms at 60 °C were not due to lower bubble collapse temperatures. Instead, the results suggest that PAH antagonisms are caused by increased radical-radical recombination as bulk temperature increases. In effort to develop an efficient, combined remediation technology, this work suggests bulk temperatures between 20 and 40 °C maximize US-PS synergisms.
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New derivatives of α-phenyl-N-tert-butyl nitrone (PBN) bearing a hydroxyl, an acetate, or an acetamide substituent on the N-tert-butyl moiety and para-substituted phenyl or naphthlyl moieties were synthesized. Their ability to trap hydroxymethyl radical was evaluated by electron paramagnetic resonance spectroscopy. The presence of two electron-withdrawing substituents on both sides of the nitronyl function improves the spin-trapping properties, with 4-HOOC-PBN-CH2OAc and 4-HOOC-PBN-CH2NHAc being â¼4× more reactive than PBN. The electrochemical properties of the derivatives were further investigated by cyclic voltammetry and showed that the redox potentials of the nitrones are largely influenced by the nature of the substituents both on the aromatic ring and on the N-tert-butyl function. The acetamide derivatives PBN-CH2NHAc, 4-AcNHCH2-PBN-CH2NHAc, and 4-MeO-PBN-CH2NHAc were the easiest to oxidize. A computational approach was used to rationalize the effect of functionalization on the free energies of nitrone reactivity with hydroxymethyl radical as well as on the electron affinity and ionization potential. Finally, the neuroprotection of the derivatives was evaluated in an in vitro model of cellular injury on cortical neurons. Five derivatives showed good protection at very low concentrations (0.1-10 µM), with PBN-CH2NHAc and 4-HOOC-PBN being the two most promising agents.
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Biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), coexist in biological systems with diverse biological roles. Thus, analytical techniques that can detect, quantify, and distinguish between multiple biothiols are desirable but challenging. Herein, we demonstrate the simultaneous detection and quantitation of multiple biothiols, including up to three different biothiols in a single sample, using electron paramagnetic resonance (EPR) spectroscopy and a trityl-radical-based probe (MTST). We term this technique EPR thiol-trapping. MTST could trap thiols through its methanethiosulfonate group to form the corresponding disulfide conjugate with an EPR spectrum characteristic of the trapped thiol. MTST was used to investigate effects of l-buthionine sulfoximine (BSO) and pyrrolidine dithiocarbamate (PDTC) on the efflux of GSH and Cys from HepG2 cells.
Assuntos
Técnicas Biossensoriais/métodos , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Mesilatos/química , Compostos de Sulfidrila/química , HumanosRESUMO
Membranous organelles are major endogenous sources of reactive oxygen and nitrogen species. When present at high levels, these species can cause macromolecular damage and disease. To better detect and scavenge free radical forms of the reactive species at their sources, we investigated whether nitrone spin traps could be selectively targeted to intracellular membranes using a bioorthogonal imaging approach. Electron paramagnetic resonance imaging demonstrated that the novel cyclic nitrone 5-dodecylcarbamoyl-5-N-dodecylacetamide-1-pyroline-N-oxide (diC12PO) could be used to target the nitrone moiety to liposomes composed of phosphatidyl choline. To test localization with authentic membranes in living cells, fluorophores were introduced via strain-promoted alkyne-nitrone cycloaddition (SPANC). Two fluorophore-conjugated alkynes were investigated: hexynamide-fluoresceine (HYA-FL) and dibenzylcyclooctyne-PEG4-5/6-sulforhodamine B (DBCO-Rhod). Computational and mass spectrometry experiments confirmed the cycloadduct formation of DBCO-Rhod (but not HYA-FL) with diC12PO in cell-free solution. Confocal microscopy of bovine aortic endothelial cells treated sequentially with diC12PO and DBCO-Rhod demonstrated clear localization of fluorescence with intracellular membranes. These results indicate that targeting of nitrone spin traps to cellular membranes is feasible, and that a bioorthogonal approach can aid the interrogation of their intracellular compartmentalization properties.
Assuntos
Acetamidas/química , Teoria da Densidade Funcional , Fluorescência , Imagem Óptica , Acetamidas/síntese química , Animais , Bovinos , Células Cultivadas , Espectroscopia de Ressonância de Spin Eletrônica , Estrutura MolecularRESUMO
Postprandial hyperglycemia (PPH) transiently impairs vascular endothelial function (VEF) in an oxidative stress-dependent manner by decreasing nitric oxide (NOâ¢) bioavailability. Dairy milk and its proteins attenuate PPH, but whether this improves VEF is unknown. We hypothesized that dairy milk, mediated by its whey and/or casein proteins, improves VEF by attenuating PPH-induced oxidative stress that otherwise decreases NO⢠bioavailability. A randomized, cross-over trial was conducted in adults with prediabetes (n=23) who ingested glucose (75 g, GLU) alone or with 473 mL of non-fat dairy milk (MILK) or isonitrogenous (16.5 g) amounts of whey (WHEY) or casein (CASEIN) in 473 mL of water. Prior to and at 30 min intervals for 180 min postprandially, we assessed brachial artery flow-mediated dilation (FMD) and measured biomarkers of glycemic control, oxidative stress, and NO⢠homeostasis. FMDAUC decreased to the greatest extent during GLU, which was similarly improved in dairy trials. Compared with GLU, AUCs for glucose, malondialdehyde, F2-isoprostanes, methylglyoxal, and endothelin-1 were similarly lower in dairy trials. Plasma arginine and NO⢠metabolites were greater but methylated arginine metabolites were lower in dairy trials compared with GLU. Postprandial insulin, lipids, and tetrahydrobiopterin redox status did not differ among trials. Thus, dairy milk, mediated by its whey and casein proteins, attenuates PPH-mediated impairments in VEF by limiting oxidative stress. This improves NO⢠bioavailability to the vascular endothelium by increasing arginine availability and limiting competitive inhibition on NO⢠biosynthesis by asymmetric dimethylarginine. These findings support observational studies that dairy milk lowers cardiovascular disease risk.
Assuntos
Endotélio Vascular/efeitos dos fármacos , Hiperglicemia/dietoterapia , Proteínas do Leite/farmacologia , Estado Pré-Diabético/dietoterapia , Adulto , Arginina/sangue , Disponibilidade Biológica , Endotelina-1/sangue , Endotélio Vascular/fisiopatologia , Feminino , Humanos , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Óxido Nítrico/metabolismo , Óxido Nítrico/farmacocinética , Estresse Oxidativo/efeitos dos fármacos , Estado Pré-Diabético/fisiopatologia , Soro do LeiteRESUMO
Postprandial hyperglycemia (PPH) transiently impairs vascular endothelial function (VEF) in an oxidative-stress-dependent manner by decreasing nitric oxide (NOâ¢) bioavailability. Dairy milk, regardless of fat content, attenuates PPH, but whether this improves VEF by limiting oxidative stress responses that otherwise decrease NO⢠bioavailability is not known. We hypothesized that nonfat and full-fat dairy milk would similarly improve VEF by attenuating PPH-induced oxidative stress that otherwise decreases NO⢠biosynthesis and bioavailability. A randomized, crossover trial was conducted in adults with prediabetes (n=22) who ingested glucose (75 g) dissolved in 473 ml of water (GLU), or glucose with an equal volume of nonfat dairy milk (NFM) or full-fat dairy milk (FFM). Prior to and at 30-min intervals for 180 min postprandially, we assessed brachial artery flow-mediated dilation (FMD) and measured circulating biomarkers of glycemic control, oxidative stress and NO⢠homeostasis. AUC0-180 min for FMD and NO⢠metabolites was lowest in GLU but relatively greater in NFM and FFM. Compared with GLU, AUCs for glucose, malondialdehyde, F2-isoprostanes and endothelin-1 were similarly lower in dairy trials. Milk-mediated vasoprotection was accompanied by greater levels of plasma arginine and lower levels of asymmetric dimethylarginine and symmetric dimethylarginine. Postprandial insulin, lipids and tetrahydrobiopterin redox status did not differ among trials. Thus, dairy milk, regardless of its fat content, attenuates PPH-mediated impairments in VEF by limiting oxidative stress. This improves NO⢠bioavailability to the vascular endothelium by increasing arginine availability and limiting competitive inhibition on NO⢠biosynthesis by asymmetric dimethylarginine.
Assuntos
Endotélio Vascular/fisiopatologia , Hiperglicemia/prevenção & controle , Leite , Estado Pré-Diabético/dietoterapia , Adulto , Animais , Disponibilidade Biológica , Artéria Braquial/fisiologia , Artéria Braquial/fisiopatologia , Espessura Intima-Media Carotídea , Feminino , Glicolipídeos , Glicoproteínas , Humanos , Hiperglicemia/fisiopatologia , Insulina/sangue , Gotículas Lipídicas , Lipídeos/sangue , Masculino , Leite/química , Óxido Nítrico/metabolismo , Óxido Nítrico/farmacocinética , Estresse Oxidativo , Estado Pré-Diabético/fisiopatologiaRESUMO
Replacing a portion of a glucose challenge with whole eggs (EGG) or egg whites (WHITE) was shown to protect against glucose-induced impairments in vascular function. We hypothesised in the present study that previously observed vasoprotection following co-ingestion of EGG or WHITE with glucose was attributed to limiting postprandial hyperglycaemia-induced oxidative stress that improves NOâ bioavailability. Prediabetic men completed a randomised, cross-over study in which they ingested isoenergetic meals containing 100 g glucose (GLU), or 75 g glucose with 1·5 EGG, seven WHITE or two egg yolks (YOLK). At 30 min intervals for 3 h, we assessed plasma NOâ metabolites, the lipid peroxidation biomarker malondialdehyde, antioxidants, arginine and its methylated metabolites (asymmetric dimethylarginine and symmetric dimethylarginine), tetrahydrobiopterin redox status, vasoconstrictors and inflammatory markers. Compared with GLU, malondialdehyde was lower and NOâ metabolites were greater in EGG and WHITE, but YOLK was not different from GLU. Malondialdehyde was inversely correlated with NOâ metabolites and vascular function, whereas NOâ metabolites were positively correlated with vascular function. Compared with GLU, arginine was greater, but asymmetric and symmetric dimethylarginine and angiotensin-II were lower in all egg-based meals. Antioxidants, tetrahydrobiopterin redox status and inflammatory markers did not differ among treatments. Thus, while each egg-based meal improved arginine metabolism, only EGG and WHITE limited lipid peroxidation. This suggests that vasoprotection mediated by EGG and WHITE likely occurs in an NOâ-dependent manner by improving arginine metabolism and attenuating oxidative stress that otherwise limit NOâ biosynthesis and bioavailability to the vascular endothelium.
Assuntos
Arginina/metabolismo , Clara de Ovo , Ovos , Glucose/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Estado Pré-Diabético , Adulto , Arginina/sangue , Estudos Cross-Over , Dieta , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/fisiologia , Humanos , Hiperglicemia , Masculino , Refeições , Pessoa de Meia-IdadeRESUMO
Impaired mitochondrial function often results in excessive production of reactive oxygen species (ROS) and is involved in the etiology of many chronic diseases, including cardiovascular disease, diabetes, neurodegenerative disorders, and cancer. Moderate levels of mitochondrial ROS, however, can protect against chronic disease by inducing upregulation of mitochondrial capacity and endogenous antioxidant defense. This phenomenon, referred to as mitohormesis, is induced through increased reliance on mitochondrial respiration, which can occur through diet or exercise. Nutritional ketosis is a safe and physiological metabolic state induced through a ketogenic diet low in carbohydrate and moderate in protein. Such a diet increases reliance on mitochondrial respiration and may, therefore, induce mitohormesis. Furthermore, the ketone ß-hydroxybutyrate (BHB), which is elevated during nutritional ketosis to levels no greater than those resulting from fasting, acts as a signaling molecule in addition to its traditionally known role as an energy substrate. BHB signaling induces adaptations similar to mitohormesis, thereby expanding the potential benefit of nutritional ketosis beyond carbohydrate restriction. This review describes the evidence supporting enhancement of mitochondrial function and endogenous antioxidant defense in response to nutritional ketosis, as well as the potential mechanisms leading to these adaptations.
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EPR spectroscopy, coupled with the use of tetrathiatriarylmethyl (TAM) radicals, has been a reliable method to detect the superoxide radical (O2.- ). However, the specificity and biocompatibility of TAM radicals need to be further improved. Although derivatization may overcome the drawbacks of current TAM radicals, esterification or amidation through the carboxylic groups greatly changes their redox properties and makes them inert to O2.- . Herein, the synthesis of a perthiatriarylmethyl (PST) radical and its dendritic derivatives, PST-TA and PST-NA, in which PST is covalently linked with dendrons containing three (TA) and nine (NA) carboxylic acids, respectively. The results show that PST rapidly reacts with O2.- to yield a unique quinone methide product. Dendritic modification of PST slightly decreases the reactivities of PST-TA and PST-NA, but notably increases their biostability toward various oxidoreductants. The detection limit of PST-NA to O2.- was estimated to be 2.1â nm min-1 over 60â min of detection. Importantly, PST-NA shows threefold higher sensitivity to O2.- in the presence and absence of ascorbic acid than that of the classic spin-trapping technique. In addition, the application of PST-NA to detect extracellular O2.- generation in stimulated RAW 264.7 macrophages was also explored. This study demonstrates that PST-NA has great potential for specific detection and quantitation of O2.- in extracellular sites.
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Sulfate radical anion (SO4â¢-) and hydroxyl radical (OH) based advanced oxidation technologies has been extensively used for removal of aromatic contaminants (ACs) in waters. In this study, we investigated the Gibbs free energy (ΔGSET∘) of the single electron transfer (SET) reactions for 76 ACs with SO4â¢- and OH, respectively. The result reveals that SO4â¢- possesses greater propensity to react with ACs through the SET channel than OH. We hypothesized that the electron distribution within the molecule plays an essential role in determining the ΔGSET∘ and subsequent SET reactions. To test the hypothesis, a quantitative structure-activity relationship (QSAR) model was developed for predicting ΔGSET∘ using the highest occupied molecular orbital energies (EHOMO), a measure of electron distribution and donating ability. The standardized QSAR models are reported to be ΔG°SET=-0.97×EHOMO - 181 and ΔG°SET=-0.97×EHOMO - 164 for SO4â¢- and OH, respectively. The models were internally and externally validated to ensure robustness and predictability, and the application domain and limitations were discussed. The single-descriptor based models account for 95% of the variability for SO4â¢- and OH. These results provide the mechanistic insight into the SET reaction pathway of radical and non-radical bimolecular reactions, and have important applications for radical based oxidation technologies to remove target ACs in different waters.
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Tetrathiatriaylmethyl (trityl) radicals have found wide biomedical applications as magnetic resonance probes. Trityl radicals and their derivatives are generally stable toward biological reducing agents such as glutathione (GSH) and ascorbate. We demonstrate that the triester (ET-03) and triamide (AT-03) derivatives of the Finland trityl radical exhibit unique reduction by thiols such as GSH and cysteine (Cys) to generate the corresponding trityl carbanions as evidenced by the loss of EPR signal and appearance of characteristic UV-vis absorbance at 644 nm under anaerobic conditions. The trityl carbanions can be quickly converted back to the original trityl radicals by oxygen (O2) in air, thus rendering the reaction between the trityl derivative and biothiol undetectable under aerobic conditions. The reduction product of O2 by the trityl carbanions was shown to be superoxide radical (O2â¢-) by EPR spin-trapping. Kinetic studies showed that the reaction rate constants (k) depend on the types of both trityl radicals and thiols with the order of kET-03/Cys (0.336 M-1 s-1) > kET-03/GSH (0.070 M-1 s-1) > kAT-03/Cys (0.032 M-1 s-1) > kAT-03/GSH (0.027 M-1 s-1). The reactivity of trityl radicals with thiols is closely related to the para-substituents of trityl radicals as well as the pKa of the thiols and is further reflected by the rate of O2â¢- production and consumptions of O2 and thiols. This novel reaction represents a new metabolic process of trityl derivatives and should be considered in the design and application of new trityl radical probes.
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Oxigênio/química , Compostos de Sulfidrila/química , Superóxidos/química , Compostos de Tritil/química , Ácido Ascórbico/química , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Glutationa/química , Cinética , Oxirredução , Espectrofotometria Ultravioleta , Compostos de Tritil/síntese químicaRESUMO
Ultrasound (US) was shown to activate persulfate (PS) providing an alternative activation method to base or heat as an in situ chemical oxidation (ISCO) method. The kinetics and mechanism of ultrasonic activation of PS were examined in aqueous solution using an in situ electron paramagnetic resonance (EPR) spin trapping technique and radical trapping with probe compounds. Using the spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), hydroxyl radical (â¢OH) and sulfate radical anion (SO4â¢-) were measured from ultrasonic activation of persulfate (US-PS). The yield of â¢OH was up to 1 order of magnitude greater than that of SO4â¢-. The comparatively high â¢OH yield was attributed to the hydrolysis of SO4â¢- in the warm interfacial region of cavitation bubbles formed from US. Using steady-state approximations, the dissociation rate of PS in cavitating bubble systems was determined to be 3 orders of magnitude greater than control experiments without sonication at ambient temperature. From calculations of the interfacial volume surrounding cavitation bubbles and using the Arrhenius equation, an effective mean temperature of 340 K at the bubble-water interface was estimated. Comparative studies using the probe compounds tert-butyl alcohol and nitrobenzene verified the bubble-water interface as the location for PS activation by high temperature with â¢OH contributing a minor role in activating PS to SO4â¢-. The mechanisms unveiled in this study provide a basis for optimizing US-PS as an ISCO technology.
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Espectroscopia de Ressonância de Spin Eletrônica , Detecção de Spin , Óxidos N-Cíclicos/química , Radicais Livres , Radical Hidroxila , Cinética , Marcadores de Spin , terc-Butil ÁlcoolRESUMO
Tetrathiatriarylmethyl (TAM, trityl) radicals have attracted considerable attention as spin probes for biological electron paramagnetic resonance (EPR) spectroscopy and imaging owing to their sharp EPR singlet signals and high biostability. However, their in vivo applications were limited by the short blood circulation lifetimes and strong binding with albumins. Our previous results showed that PEGylation is a feasible method to overcome the issues facing in vivo applications of TAM radicals. In the present study, we synthesized a series of new PEGylated TAM radicals (TTP1, TPP2, TNP1, TNP2, d-TNP1, and d-TNP3) containing various lengths and numbers of mPEG chains. Our results found that the pattern of PEGylation exerts an important effect on physicochemical properties of the resulting TAM radicals. Dendritic PEGylated TAM radicals, TNP1 and TNP2, have higher water solubility and lower susceptibility for self-aggregation than their linear analogues TPP1 and TPP2. Furthermore, dendritic PEGylated TAM radicals exhibit extremely high stability toward various biological oxidoreductants as well as in rat whole blood, liver homogenate, and following in vivo intravenous administration in mice. Importantly, the deuterated derivatives, especially d-TNP3, exhibit excellent properties including the sharp and O2-sensitive EPR singlet signal, good biocompatibility, and prolonged kinetics with half-life time of ≥10 h in mice. These PEGylated TAM radicals should be suitable for a wide range of applications in in vivo EPR spectroscopy and imaging.
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Polietilenoglicóis/química , Compostos de Tritil/síntese química , Radicais Livres/síntese química , Radicais Livres/química , Estrutura Molecular , Compostos de Tritil/químicaRESUMO
The addition of antibacterial functionality to dental resins presents an opportunity to extend their useful lifetime by reducing secondary caries caused by bacterial recolonization. In this study, the potential efficacy of nitrogen-doped titanium dioxide nanoparticles for this purpose was determined. Nitrogen doping was carried out to extend the ultraviolet absorbance into longer wavelength blue light for increased biocompatibility. Titanium dioxide nanoparticles (approximately 20-30 nm) were synthesized with and without nitrogen doping using a sol-gel method. Ultraviolet-Visible spectroscopy indicated a band of trap states, with increasing blue light absorbance as the concentration of the nitrogen dopant increased. Electron paramagnetic resonance measurements indicated the formation of superoxide and hydroxyl radicals upon particle exposure to visible light and oxygen. The particles were significantly toxic to Escherichia coli in a dose-dependent manner after a 1-hour exposure to a blue light source (480 nm). Intracellular reactive oxygen species assay demonstrated that the particles caused a stress response in human gingival epithelial cells when exposed to 1 hour of blue light, though this did not result in detectable release of cytokines. No decrease in cell viability was observed by water-soluble tetrazolium dye assay. The results show that nitrogen-doped titanium dioxide nanoparticles have antibacterial activity when exposed to blue light, and are biocompatible at these concentrations.
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Antibacterianos/química , Nanopartículas/química , Nitrogênio/química , Resinas Sintéticas/química , Titânio/química , Catálise , Sobrevivência Celular , Espectroscopia de Ressonância de Spin Eletrônica , Células Epiteliais/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Gengiva/efeitos dos fármacos , Humanos , Radical Hidroxila/química , Luz , Microscopia Confocal , Microscopia Eletrônica de Transmissão , Dióxido de Nitrogênio/química , Estresse Oxidativo , Tamanho da Partícula , Espécies Reativas de Oxigênio/química , Difração de Raios XRESUMO
Hyperglycemia has been implicated in the development of endothelial dysfunction through heightened ROS production. Since nitrones reverse endothelial nitric oxide synthase (eNOS) dysfunction, increase antioxidant enzyme activity, and suppress pro-apoptotic signaling pathway and mitochondrial dysfunction from ROS-induced toxicity, the objective of this study was to determine whether nitrone spin traps DMPO, PBN and PBN-LA were effective at duplicating these effects and improving glucose uptake in an in vitro model of hyperglycemia-induced dysfunction using bovine aortic endothelial cells (BAEC). BAEC were cultured in DMEM medium with low (5.5mM glucose, LG) or high glucose (50mM, HG) for 14 days to model in vivo hyperglycemia as experienced in humans with metabolic disease. Improvements in cell viability, intracellular oxidative stress, NO and tetrahydrobiopterin (BH4)â levels, mitochondrial membrane potential, glucose transport, and activity of antioxidant enzymes were measured from single treatment of BAEC with nitrones for 24h after hyperglycemia. Chronic hyperglycemia significantly increased intracellular ROS by 50%, decreased cell viability by 25%, reduced NO bioavailability by 50%, and decreased (BH4) levels by 15% thereby decreasing NO production. Intracellular glucose transport and superoxide dismutase (SOD) activity were also decreased by 50% and 25% respectively. Nitrone (PBN and DMPO, 50 µM) treatment of BAEC grown in hyperglycemic conditions resulted in the normalization of outcome measures except for SOD and catalase activities. Our findings demonstrate that the nitrones reverse the deleterious effects of hyperglycemia in BAEC. We believe that in vivo testing of these nitrone compounds in models of cardiometabolic disease is warranted.
Assuntos
Aorta/efeitos dos fármacos , Células Endoteliais/efeitos dos fármacos , Endotélio Vascular/efeitos dos fármacos , Hiperglicemia/fisiopatologia , Óxidos de Nitrogênio/farmacologia , Animais , Antioxidantes/metabolismo , Aorta/metabolismo , Aorta/fisiopatologia , Bovinos , Técnicas de Cultura de Células , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Células Endoteliais/metabolismo , Endotélio Vascular/metabolismo , Endotélio Vascular/fisiopatologia , Hiperglicemia/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo III/metabolismo , Óxidos de Nitrogênio/toxicidade , Espécies Reativas de Oxigênio/metabolismoRESUMO
INTRODUCTION: We tested how a treadmill exercise program influences oxygen consumption, oxidative stress, and exercise capacity in the mdx mouse, a model of Duchenne muscular dystrophy. METHODS: At age 4 weeks mdx mice were subjected to 4 weeks of twice-weekly treadmill exercise. Sedentary mdx and wild-type mice served as controls. Oxygen consumption, time to exhaustion, oxidative stress, and myofiber damage were assessed. RESULTS: At age 4 weeks, there was a significant difference in exercise capacity between mdx and wild-type mice. After exercise, mdx mice had lower basal oxygen consumption and exercise capacity, but similar maximal oxygen consumption. Skeletal muscle from these mice displayed increased oxidative stress. Collagen deposition was higher in exercised versus sedentary mice. CONCLUSIONS: Exercised mdx mice exhibit increased oxidative stress, as well as deficits in exercise capacity, baseline oxygen consumption, and increased myofiber fibrosis. Muscle Nerve 54: 110-117, 2016.