Electron Spin Resonance Assay Research Articles

Impact of antioxidants on PM2.5 oxidative potential, radical level, and cytotoxicity

Antioxidants are typically seen as agents that mitigate environmental health risks due to their ability to scavenge free radicals. However, our research presents a paradox where these molecules, particularly those within lung fluid, act as prooxidants in the presence of airborne particulate matter (PM2.5), thus enhancing PM2.5 oxidative potential (OP). In our study, we examined a range of antioxidants found in the respiratory system (e.g., vitamin C, glutathione (GSH), and N-acetylcysteine (NAC)), in plasma (vitamin A, vitamin E, and β-carotene), and in food (tert-butylhydroquinone (TBHQ)). We aimed to explore antioxidants' prooxidant and antioxidant interactions with PM2.5 and the resulting OP and cytotoxicity. We employed OH generation assays and electron paramagnetic resonance assays to assess the pro-oxidative and anti-oxidative effects of antioxidants. Additionally, we assessed cytotoxicity interaction using a Chinese hamster ovary cell cytotoxicity assay. Our findings revealed that, in the presence of PM2.5, all antioxidants except vitamin E significantly increased the PM2.5 OP by generating more OH radicals (OH generation rate: 0.16–24.67 pmol·min−1·m−3). However, it's noteworthy that these generated OH radicals were at least partially neutralized by the antioxidants themselves. Among the pro-oxidative antioxidants, vitamin A, β-carotene, and TBHQ showed the least ability to quench these radicals, consistent with their observed impact in enhancing PM2.5 cytotoxicity (PM2.5 LC50 reduced to 91.2 %, 88.8 %, and 75.1 % of PM2.5's original level, respectively). Notably, vitamin A and TBHQ-enhanced PM2.5 OP were strongly associated with the presence of metals and organic compounds, particularly with copper (Cu) contributing significantly (35 %) to TBHQ's pro-oxidative effect. Our study underscores the potential health risks associated with the interaction between antioxidants and ambient pollutants.

Ascorbic Acid Reprograms Epigenome and Epitranscriptome by Reducing Fe(III) in the Catalytic Cycle of Dioxygenases.

Ascorbic acid (ASC) has been reported to stimulate DNA iterative oxidase ten-eleven translocation (TET) enzymes, Jumonji C-domain-containing histone demethylases, and potentially RNA m6A demethylases FTO and ALKBH5 as a cofactor. Although ascorbic acid has been widely investigated in reprogramming DNA and histone methylation status in vitro, in cultured cells and mouse models, its specific role in the catalytic cycle of dioxygenases remains enigmatic. Here, we systematically investigated the stimulation of ASC toward TET2, ALKBH3, histone demethylases, and FTO. We find that ASC reprograms epitranscriptome by erasing the hypermethylated m6A sites in mRNA. Biochemistry and electron spin resonance assays demonstrate that ASC enters the active pocket of dioxygenases and reduces Fe(III), either incorporated upon protein synthesis or generated upon rebounding the hydroxyl radical during oxidation, into Fe(II). Finally, we propose a remedied model for the catalytic cycle of dioxygenases by adding in the essential cofactor, ASC, which refreshes and regenerates inactive dioxygenase through recycling Fe(III) into Fe(II) in a dynamic "hit-and-run" manner.

Therapeutic Potential of Seaweed-Derived Laminaran: Attenuation of Clinical Drug Cytotoxicity and Reactive Oxygen Species Scavenging.

β-glucan has been shown to be effective for several diseases such as immune regulation and blood pressure suppression. Seaweed contains a β-1,3/1,6-glucan called laminaran. The present commercial source of β-glucan is black yeast; however, a fermentation process using organic carbon substrates makes production unsustainable, whereas macroalgae provide a sustainable alternative with the use of CO2 and seawater as growth substrates. However, bioactivity studies on laminaran are limited. We aimed to evaluate whether laminaran can scavenge reactive oxygen species (ROS) and attenuate cytotoxicity caused by clinical drugs such as indomethacin (Ind) and dabigatran (Dab). Electron spin resonance assay revealed that laminaran scavenged singlet oxygen (1O2) and superoxide anions (O2•-) directly but did not scavenge hydroxyl radicals (•OH). Mitochondrial ROS detection dye showed that laminaran scavenged mitochondrial O2•- produced upon administration of Ind or Dab. Moreover, significant reductions in •OH and peroxynitrate (ONOO-) levels were observed. Since •OH and ONOO- are generated from O2•- in the cells, laminaran could indirectly suppress the generation of •OH and ONOO- via the removal of O2•-. Both Ind and Dab induce cell injury via ROS production. Laminaran attenuated the cytotoxicity derived from these drugs and may represent a functional food with anti-aging and disease prevention properties.

RENEB Inter-Laboratory Comparison 2021: Inter-Assay Comparison of Eight Dosimetry Assays.

Tools for radiation exposure reconstruction are required to support the medical management of radiation victims in radiological or nuclear incidents. Different biological and physical dosimetry assays can be used for various exposure scenarios to estimate the dose of ionizing radiation a person has absorbed. Regular validation of the techniques through inter-laboratory comparisons (ILC) is essential to guarantee high quality results. In the current RENEB inter-laboratory comparison, the performance quality of established cytogenetic assays [dicentric chromosome assay (DCA), cytokinesis-block micronucleus assay (CBMN), stable chromosomal translocation assay (FISH) and premature chromosome condensation assay (PCC)] was tested in comparison to molecular biological assays [gamma-H2AX foci (gH2AX), gene expression (GE)] and physical dosimetry-based assays [electron paramagnetic resonance (EPR), optically or thermally stimulated luminescence (LUM)]. Three blinded coded samples (e.g., blood, enamel or mobiles) were exposed to 0, 1.2 or 3.5 Gy X-ray reference doses (240 kVp, 1 Gy/min). These doses roughly correspond to clinically relevant groups of unexposed to low exposed (0-1 Gy), moderately exposed (1-2 Gy, no severe acute health effects expected) and highly exposed individuals (>2 Gy, requiring early intensive medical care). In the frame of the current RENEB inter-laboratory comparison, samples were sent to 86 specialized teams in 46 organizations from 27 nations for dose estimation and identification of three clinically relevant groups. The time for sending early crude reports and more precise reports was documented for each laboratory and assay where possible. The quality of dose estimates was analyzed with three different levels of granularity, 1. by calculating the frequency of correctly reported clinically relevant dose categories, 2. by determining the number of dose estimates within the uncertainty intervals recommended for triage dosimetry (±0.5 Gy or ±1.0 Gy for doses <2.5 Gy or >2.5 Gy), and 3. by calculating the absolute difference (AD) of estimated doses relative to the reference doses. In total, 554 dose estimates were submitted within the 6-week period given before the exercise was closed. For samples processed with the highest priority, earliest dose estimates/categories were reported within 5-10 h of receipt for GE, gH2AX, LUM, EPR, 2-3 days for DCA, CBMN and within 6-7 days for the FISH assay. For the unirradiated control sample, the categorization in the correct clinically relevant group (0-1 Gy) as well as the allocation to the triage uncertainty interval was, with the exception of a few outliers, successfully performed for all assays. For the 3.5 Gy sample the percentage of correct classifications to the clinically relevant group (≥2 Gy) was between 89-100% for all assays, with the exception of gH2AX. For the 1.2 Gy sample, an exact allocation to the clinically relevant group was more difficult and 0-50% or 0-48% of the estimates were wrongly classified into the lowest or highest dose categories, respectively. For the irradiated samples, the correct allocation to the triage uncertainty intervals varied considerably between assays for the 1.2 Gy (29-76%) and 3.5 Gy (17-100%) samples. While a systematic shift towards higher doses was observed for the cytogenetic-based assays, extreme outliers exceeding the reference doses 2-6 fold were observed for EPR, FISH and GE assays. These outliers were related to a particular material examined (tooth enamel for EPR assay, reported as kerma in enamel, but when converted into the proper quantity, i.e. to kerma in air, expected dose estimates could be recalculated in most cases), the level of experience of the teams (FISH) and methodological uncertainties (GE). This was the first RENEB ILC where everything, from blood sampling to irradiation and shipment of the samples, was organized and realized at the same institution, for several biological and physical retrospective dosimetry assays. Almost all assays appeared comparably applicable for the identification of unexposed and highly exposed individuals and the allocation of medical relevant groups, with the latter requiring medical support for the acute radiation scenario simulated in this exercise. However, extreme outliers or a systematic shift of dose estimates have been observed for some assays. Possible reasons will be discussed in the assay specific papers of this special issue. In summary, this ILC clearly demonstrates the need to conduct regular exercises to identify research needs, but also to identify technical problems and to optimize the design of future ILCs.

Unexpected Photocatalytic Degeneration of NAD + for Inducing Apoptosis of Hypoxia Cancer Cells

Unexpected Photocatalytic Degeneration of NAD ⁺ for Inducing Apoptosis of Hypoxia Cancer Cells

Highly Efficient Degradation of Tetracycline Hydrochloride in Water by Oxygenation of Carboxymethyl Cellulose-Stabilized FeS Nanofluids.

The transformation of organic pollutants by stabilized nano-FeS in oxic conditions is far less understood than in anoxic states. Herein, carboxymethyl cellulose-stabilized FeS (CMC-FeS) nanofluids are prepared at a CMC-to-FeS mass ratio of 1/2 and their performance of tetracycline hydrochloride (TC) degradation under oxic conditions was investigated. Here, we showed that TC could be efficiently removed by oxygenation of CMC-FeS nanofluids at neutral initial pH. We found that CMC-FeS dosages as low as 15 mg/L can achieve the TC removal efficiency as high as 99.1% at an initial TC concentration of 50 mg/L. Oxidative degradation plays a predominated role in TC removal (accounting for 58.0%), adsorption has the second importance (accounting for 37.0%), and reduction has minor impact (accounting for 4.1%) toward TC removal. Electron spin resonance assays, fluorescent detection using coumarin as a probe, and radical scavenging experiments confirm that hydroxy radicals (•OH), both in free and surface-bound forms, contribute to oxidation of TC. Humic acids brought detrimental effects on TC removal and therefore should be biologically degraded in advance. This work offers a facile and cost-effective solution to decontaminate TC in natural and engineered water bodies.

Soybean processing wastes and their potential in the generation of high value added products

Soybean and its derivatives are rich sources of nutrients and bioactive compounds with antioxidant properties, however, the wastes with high nutritional value are discarded by the industry. This study aimed to evaluate centesimal composition, microbial safety and antioxidant activity of soybean processing wastes (okara and okara flour) and soymilk. High fiber, carbohydrate, energy and lipids contents were found. Antioxidant activity by spectrophotometric and Electron Paramagnetic Resonance assays showed values for soybean (72.4% and 83.5%), okara (9.6% and 7.7%), okara flour (30.7% and 11.5%) and soymilk (28.4% and 36.5%). The total phenolic content was an average of 3.33 mg of gallic acid equivalent.g−1. Infrared spectra revealed no significant changes in the absorption bands, guaranteeing non-alteration in the compounds composition after processing. Microbiological assays indicated that soybean derivatives are safe for consumption. These results reinforce that these wastes contain bioactive compounds of interest with great potential to generate high value added products.

Antioxidant Efficacy of Natural Ubiquinol Compared to Synthetic References – In Vitro Study

AbstractThere are many studies dealing with the oxidized form (Ubiquinone) of coenzyme Q10, but only a little of its reduced form (Ubiquinol). Two yeast‐based Ubiquinols (UQH2_S, Sigma‐Aldrich; UQH2_K, Kaneka) were investigated for in vitro antioxidant efficacy compared to synthetic antioxidants. The antioxidant efficacy of UQH2_S and UQH2_K by the 2,2‐diphenyl‐1‐picrylhydrazyl’ (DPPH) assay as well as by the 2,2’‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic) acid’ (ABTS) assay was almost identical (IC50DPPH/ABTS 0.387/0.226–0.219 mM, respectively). The values were higher (p&lt;0.05) than that of α‐tocopherol, Gallic acid, Butylhydroxyanisole, Butylhydroxytoluene. Ferric Reducing Antioxidant Power’ values for Ubiquinols (0.05–0.3 mM) were higher (p&lt;0.05) than for the other antioxidants, except Gallic acid. According to the Electron paramagnetic resonance assay, the antioxidant activity of α‐tocopherol/UQH2_S mixture was higher compared to the individual antioxidant only in specific combinations.

The first copper(I) complex of anthrahydrazone with potential ROS scavenging activity showed significant in vitro anticancer activity by inducing apoptosis and autophagy

Based on the anticancer pharmacophore of anthrahydrazone and quinoline, a new quinolylanthrahydrazone ligand, 9-AQH (anthracene-9-quinolylhydrazone), was synthesized to further afford four metal complexes, [CoII(9-AQH)(NO3)2(H2O)] (1), [NiII(9-AQH)2(H2O)2]·2NO3 (2), [CuI(9-AQH)2]·NO3 (3), [ZnII(9-AQH)2(NO3)]·NO3 (4), determined by X-ray single crystal diffraction analysis. The reaction of Cu(NO3)2 with 9-AQH formed the stable and repeatable copper(I) complex 3. In vitro screening demonstrated only 3 showed significant and broad-spectrum anticancer activity, indicating that Cu(I) played a key role in exerting the anticancer activity. In solution, Cu(I) was not naturally oxidized to Cu(II) suggested by 1H-NMR (Nuclear Magnetic Resonance) and EPR (Electron Paramagnetic Resonance) analysis. The presence of 3 could also catalyze the H2O2 system to give hydroxyl free radicals, suggested by further EPR and electrophoresis assay. At the cellular level, although no obvious Cu(II) signals were detected and the total ROS (Reactive Oxygen Species) scavenging in the tumor cells treated with 3, the potential redox property between Cu(I)/Cu(II), as a key role, should not be denied for the significant anticancer activity of 3, considering the much complicated circumstance and other reductive substances in cells. The anticancer mechanism of 3 on the most sensitive MGC-803 cells pointed to significant cell apoptosis through mitochondrial pathway, rather than cell cycle arrest. While the autophagy observed in tumor cells treated by 3 suggested its complicated anticancer mechanism, and whether there was an intrinsic correlation still needed to be further investigated.

Antioxidant effects of gallic acid alkyl esters of various chain lengths in oyster during frying process

SummaryThe antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate, ethyl gallate, propyl gallate, butyl gallate (GA‐C4), octyl gallate, lauryl gallate, hexadecyl gallate and octadecyl gallate in frying oil (soybean oil) and oyster during frying were investigated. Rancimat induction period (RIP) assay indicated GA and its alkyl esters effectively improved the oxidative stability of soybean oil according to the ‘polar paradox’; that is, the antioxidant effects of the polyphenols decreased in lipid system with the increasing of hydrophobicity. Results also indicated that GA and its alkyl esters all effectively retarded lipid oxidation in oyster tissue according to parameters including RIP, peroxide value and electron spin resonance assays. Moreover, the antioxidant efficiency in oyster increased with the alkyl chain length until GA‐C4, and thereafter, the antioxidant effects decreased, similar to the ‘cut‐off effect’. This study provides basic data for improving the oxidative stability of seafood during frying.

Improving the oxidative stability of flaxseed oil with composite antioxidants comprising gallic acid alkyl ester with appropriate chain length

A gallic acid (GA) alkyl ester exerting the best antioxidant effect in flaxseed oil was identified from ten GA alkyl esters with various chain lengths, which was used in combination with other antioxidants including antioxidant of bamboo leaves, ascorbyl palmitate, butylated hydroxytoluene, phytic acid, phospholipid, rosemary extract, tocopherol, tea polyphenols, and tea polyphenol palmitate (TPP) to improve oxidative stability of flaxseed oil. Rancimat induction period, peroxide value, thiobarbituric acid-reactive substances, and electron paramagnetic resonance assays indicate that myristyl gallate (GA-C14) was the best GA ester. The flaxseed oil containing GA-C14 and TPP demonstrated the best oxidative stability among all the composite antioxidants. Through optimizing the mixture ratio, the flaxseed oil containing 34.4 mg/kg GA-C14 and 480 mg/kg TPP showed the best oxidative stability. Its shelf life was predicted by an accelerated shelf life testing using the Arrhenius model, which was prolonged 4.83-fold compared to the control sample under 25 °C.

Rapid thermal surface engineering of g-C3N4 for efficient hydrogen evolution

Graphite carbon nitride (g-C3N4) is a fascinating 2D photocatalyst, but preparing ultrathin g-C3N4 with outstanding surface properties by a green and facile method is still a tremendous challenge. In this research, g-C3N4 nanosheets were modified through H2O2-assisted rapid thermal surface treatment. The rapid decomposition of H2O2 molecules on the surface greatly optimized the surface properties of the catalyst. Thus, the modified g-C3N4 nanosheets had more interfacial active sites and broader visible light absorption and showed the largest hydrogen evolution rate of 894.9 μmol g−1 h−1. Photoluminescence and electron spin resonance (ESR) assays showed that the modified photocatalyst accelerated charge transfer and thereby attained higher photocatalytic H2 generation efficiency. This research offers a new strategy to develop g-C3N4-based 2D photocatalysts for H2 preparation.

Metal-Free Electro-Activated Sulfite Process for As(III) Oxidation in Water Using Graphite Electrodes

Transition-metal-activated sulfite [S(IV)] processes for water decontamination have recently received intense attention in the field of decontamination by advanced oxidation processes (AOPs). However, the drawback with respect to the secondary metal sludge contamination involved in various AOPs has been argued often. In this work, we developed a novel electro-sulfite (ES) process using stable and low-cost graphite electrodes to address that concern. Arsenite [As(III)] was used as the target compound for removal by the ES process because of its wide presence and high toxicity. Parameters, including cell voltage, S(IV) concentration, solution pH, and water matrix, and the mechanisms for reactions on anode and cathode were investigated in electrolytic cells containing one or two compartments, respectively. The results show that the ES process using 1 mM S(IV) and 2 V cell voltage oxidizes 5 μM As(III) at a rate of 0.127 min-1, which is 15-fold higher than mere electrolysis without S(IV) addition (0.008 min-1) at pH 7. Further studies using radical scavengers and electron spin resonance assays demonstrated that oxysulfur radicals (i.e., SO5•- and SO4•-) and HO• are responsible for As(III) oxidation in the ES process. However, HO2• produced via the oxygen reduction reaction in the EO process plays a major role in As(III) oxidation, which explains the lower reaction rate in the absence of S(IV). The effectiveness of the ES process was moreover evidenced by 60-82% As(III) oxidation in field water within 40 min. Overall, this work realizes the metal-free activation of S(IV) and significantly leverages the S(IV)-based water treatment technologies.

Nanomaterial categorization by surface reactivity: A case study comparing 35 materials with four different test methods

Nanomaterials (NMs) can be manufactured in plenty of variants differing in their physicochemical properties. Functional assays can be highly useful to cope with the enormous variability by supporting prioritization and categorization. Oxidative potential (OP) seems to be in particular important in this context and different assays are available. However, their reliability and predictivity are not well-characterized.This study compares four different test methods for measuring NM OP. Reactive oxygen species (ROS) generation was measured on a set of 35 different materials, all extensively characterized with respect to physicochemical properties and most of them with respect to toxicity. Different acellular assays were applied, namely electron spin resonance (ESR) spectroscopy using CPH spin probe and DMPO spin trap, and the ferric reduction ability of serum (FRAS) assay. In addition, protein carbonylation as a marker for oxidative protein damage was analyzed in NRK-52E cells. All assays were assessed individually for their predictivity compared to established toxicological endpoints. We also aimed to identify the optimal assay combination using multivariate logistic regression and other statistical measures.BET surface area-based doses were more suitable to relate surface reactivity to toxicity. In addition, normalization to the deposited dose was advantageous for cellular assays as it improved the predictivity for in vitro as well as in vivo toxicity. The carbonylation assay, potentially in combination with ESR (DMPO spin trap) or FRAS assay, led to the best predictive performance.In summary, we propose a testing strategy for NM OP and demonstrated the applicability in an extended case study on 35 materials. This work is an important contribution towards reliable grouping and testing strategies for NMs.

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Summary Highly crystalline and emissive carbon dots (CDs) are firstly synthesized via an ionothermal method in organic solvents. In contrast to well-established approaches, ZnCl2 is utilized as the pyrolysis-promoting agent to prepare emissive CDs with tunable wavelengths, directly by carbonization from different O and N precursors under a mild reaction condition at 210°C. More than 50% synthetic yield and 39% photoluminescent quantum yield (blue CD) are obtained. XAFS measurements, in conjunction with TEM, HAADF-STEM, UPS, and ESR analyses, allow us to obtain energy diagram configuration and confirm the luminescent nature of these hard-core structured CDs. Importantly, the resulting CDs exhibit excellent capability to photogenerate superoxide radical anion (O2⋅–), which can be exemplified by both photodynamic therapy and photooxidative cyclization synthesis of tetrahydroquinolines. Representative pharmaceutical mifepristone can be derivatized in 90% yield within 10 min of irradiation of the CDs in an elegant flow reactor.

Structural Analysis of the Stratum Corneum using EPR and EPR Imaging with Stable Spin Probes.

X-band (9.4 GHz) electron paramagnetic resonance (EPR) and electron paramagnetic resonance imaging (EPRI) were used for elucidating structural aspects of the stratum corneum (SC). We found that psoriasis vulgaris (PV)-SC has a less-ordered structure than that of the control SC, indicating the abnormal architecture of PV-SC. Different spectra were observed for the PV-SC. The three-line spectral pattern suggests that the 5-doxylstearic acid (5-DSA) is mobile or less rigid in the SC. The simulated order parameter (S0) value obtained for 5-DSA in the SC was approximately 0.20. The statistical analysis suggests that the value of the PV-SC is significantly smaller than that of the control (p < 0.01). Thus, we suggest that this EPR assay is of great use for evaluating SC function. In addition, the EPRI of various SC samples provides a useful image concerning SC status. A strong red image was observed for the PV skin. No red lesion region was observed in the control. The EPR images differentiated various sizes and number distribution concerning the disordered states in the SC.

Theoretical and experimental investigation of the antioxidative activity of monascin.

Monascin, a specific type of monascus pigments, exhibits many bioactivities. In this study, the antioxidative activity of monascin was investigated by theoretical and experimental methods. First, the antioxidant potential of six monascus pigments was predicted by density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP/6-31+G (d, p) level, and monascus yellow pigments were predicted to have strong antioxidant capacity, as they can transfer hydrogen to free radicals and accept electrons from radicals. Then, the free radical-scavenging capacity of monascin for 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, and hydroxyl radicals was experimentally validated by electron spin resonance (ESR) measurement. Monascin exhibited a quenching effect on DPPH, superoxide, and hydroxyl radicals in a dose-dependent manner. Specifically, the scavenging activity of monascin for DPPH, superoxide, and hydroxyl radicals was 97.5%, 59.5%, and 68.6%, respectively, when 0.1 mg mL-1 monascin was present. Our study provides theoretical evidence for the strong antioxidative activity of monascin and offers a simple and reliable strategy to determine the antioxidative activity.

Porphyrin Containing Polymersomes with Enhanced ROS Generation Efficiency: In Vitro Evaluation

Porphyrins are molecules possessing unique photophysical properties making them suitable for application in photodynamic therapy. The incorporation of porphyrins into natural or synthetic nano-assemblies such as polymersomes is a strategy to improve and prolong their therapeutic capacities and to overcome their limitations as therapeutic and diagnostic agents. Here, 5,10,15,20-tetrakis(1-(6-ethoxy-6-oxohexyl)-4-pyridin-1-io)-21H,23H-porphyrin tetrabromide porphyrin is inserted into polymersomes in order to demonstrate that the encapsulation enhances its ability to generate highly reactive singlet oxygen (1 O2 ) upon irradiation in vitro. The photoactivation of the free and polymersome-encapsulated porphyrin is evaluated by electron spin resonance and cell viability assays on three different mammalian cell lines. The results indicate that by encapsulating the porphyrin, a controlled ROS delivery within the cells is achieved, at the same time avoiding side effects such as dark toxicity, non-specific porphyrin release and over time decreased activity in vitro. This work focuses on showing a not-toxic model system for modern therapeutic nanomedicine, which works under mild irradiation and dosage conditions.

Cyclophilin A Protects Cardiomyocytes against Hypoxia/Reoxygenation-Induced Apoptosis via the AKT/Nox2 Pathway.

Hypoxia/reoxygenation (H/R) accelerates the process of cardiomyocyte apoptosis during ischemia-reperfusion. Excessive reactive oxygen species (ROS) are a critical driver of oxidative stress injury. Cyclophilin A (CyPA) is a major ROS-induced factor in atherosclerosis. There is a positive feedback mechanism between CyPA and ROS, which enables the oxidative stress response to continue and expand. However, it is unclear whether this positive feedback mechanism exists in cardiomyocytes. Through western blotting and flow cytometric assays and TUNEL assay, we found that CyPA inhibited the apoptosis of H9c2 cardiomyocytes under H/R conditions. By dihydroethidium (DHE) staining and electron spin resonance (ESR) assays, we demonstrated that CyPA reduced ROS production and suppressed O2− production dependent on reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. By western blotting, we showed that CyPA inhibited the expression of NADPH oxidase 2 (Nox2) protein by the AKT pathway. Through confocal microscopy assay, we found that CyPA reduced the expression of Nox2 membrane-bound subunits. The current study shows that a positive feedback mechanism does not exist in H9c2 cardiomyoblasts. CyPA protects H9c2 cardiomyoblasts against H/R-induced apoptosis via the AKT/Nox2 pathway. This could be a potential target for ischemia-reperfusion injury therapy.

Enhancement of visible-light-driven photocatalytic activity of carbon plane/g-C3N4/TiO2 nanocomposite by improving heterojunction contact

Effective interface contact between components in heterojunction is crucial to realize high photocatalytic performance of photocatalyst. In this paper, the improvement of heterojunction contact by forming new ternary heterostructure via calcining the mixture of tetracycline and melamine to obtain the graphene-like carbon plane grafted g-C3N4 and then coupling it with TiO2 is reported. The unique carbon plane, which is anchored into g-C3N4 basal domains, acts as a significant role to achieve the sufficient ternary heterojunction contact in the novel carbon plane/g-C3N4/TiO2 nanostructure system. Under visible-light irradiation, the new ternary nanocomposite exhibits excellent photocatalytic activity for efficient removal of aqueous organic contaminants: methylene blue (98.6%), tetracycline (94.0%), and norfloxacin (95.3%), with the corresponding degradation rate constants of 0.0441, 0.0302, and 0.0125 min−1, respectively, which are 54.1, 9.8, and 9.4 times higher than that of the pure g-C3N4. The mechanism study indicates that the excellent photocatalytic activity is attributed to the effective heterojunction, which can successfully extend visible-light absorption, promote charge separation efficiency, and suppress recombination of the photocatalytic electron-hole pairs. Moreover, the electron spin resonance (ESR) assay and radical scavenger experiments demonstrate that the photogenerated holes (h+), superoxide anion radicals (O2−), and hydroxyl radical (OH) play vital roles in photocatalytic degradation process. Importantly, this work may open up novel insights into the design of ternary heterostructure with highly efficacious photocatalytic performance, which suggests attractive applications in environment protection.