Amplex Red Research Articles

Hydroxychloroquine Effects on THP-1 Macrophage Cholesterol Handling: Cell Culture Studies Corresponding to the TARGET Cardiovascular Trial.

Background and Objectives: Cardiovascular (CV) risk is elevated in rheumatoid arthritis (RA). RA patient plasma causes pro-atherogenic derangements in cholesterol transport leading to macrophage foam cell formation (FCF). The TARGET randomized clinical trial compares CV benefits of 2 RA drug regimens. Hydoxychloroquine (HCQ) is a key medication used in TARGET. This study examines effects of HCQ on lipid transport to elucidate mechanisms underlying TARGET outcomes and as an indicator of likely HCQ effects on atherosclerosis in RA. Materials and Methods: THP1 human macrophages were exposed to media alone, IFNγ (atherogenic cytokine), HCQ, or HCQ + IFNγ. Cholesterol efflux protein and scavenger receptor mRNA levels were quantified by qRT-PCR and corresponding protein levels were assessed by Western blot. FCF was evaluated via Oil-Red-O and fluorescent-oxidized LDL. Intracellular cholesterol and efflux were quantified with Amplex Red assay. Results: With the exception of a decrease in the efflux protein cholesterol 27-hydroxylase in the presence IFNγ at all HCQ concentrations, no significant effect on gene or protein expression was observed upon macrophage exposure to HCQ and this was reflected in the lack of change in FCF and oxidized LDL uptake. Conclusions: HCQ did not significantly affect THP1 macrophage cholesterol transport. This is consistent with TARGET, which postulates superior effects of anti-TNF agents over sulfasalazine + HCQ.

Caveolin-1 influences mitochondrial plasticity and function in hepatic stellate cell activation.

Caveolin-1 (Cav-1) is an integral membrane protein present in all organelles, responsible for regulating and integrating multiple signals as a platform. Mitochondria are extremely adaptable to external cues in chronic liver diseases, and expression of Cav-1 may affect mitochondrial flexibility in hepatic stellate cells (HSCs) activation. We previously demonstrated that exogenous expression of Cav-1 was sufficient to increase some classical markers of activation in HSCs. Here, we aimed to evaluate the influence of exogenous expression and knockdown of Cav-1 on regulating the mitochondrial plasticity, metabolism, endoplasmic reticulum(ER)-mitochondria distance, and lysosomal activity in HSCs. To characterize the mitochondrial, lysosomal morphology, and ER-mitochondria distance, we perform transmission electron microscopeanalysis. We accessed mitochondria and lysosomal networks and functions through a confocal microscope and flow cytometry. The expression of mitochondrial machinery fusion/fission genes was examined by real-time polymerase chain reaction. Total and mitochondrial cholesterol content was measured using Amplex Red. To define energy metabolism, we used the Oroboros system in the cells. We report that GRX cells with exogenous expression or knockdown of Cav-1 changed mitochondrial morphometric parameters, OXPHOS metabolism, ER-mitochondria distance, lysosomal activity, and may change the activation state of HSC. This study highlights that Cav-1 may modulate mitochondrial function and structural reorganization in HSC activation, being a potential candidate marker for chronic liver diseases and a molecular target for therapeutic intervention.

Activity of AC electrokinetically immobilized horseradish peroxidase.

Dielectrophoresis (DEP) is an AC electrokinetic effect mainly used to manipulate cells. Smaller particles, like virions, antibodies, enzymes, and even dye molecules can be immobilized by DEP as well. In principle, it was shown that enzymes are active after immobilization by DEP, but no quantification of the retained activity was reported so far. In this study, the activity of the enzyme horseradish peroxidase (HRP) is quantified after immobilization by DEP. For this, HRP is immobilized on regular arrays of titanium nitride ring electrodes of 500nm diameter and 20nm widths. The activity of HRP on the electrode chip is measured with a limit of detection of 60fg HRP by observing the enzymatic turnover of Amplex Red and H2 O2 to fluorescent resorufin by fluorescence microscopy. The initial activity of the permanently immobilized HRP equals up to 45% of the activity that can be expected for an ideal monolayer of HRP molecules on all electrodes of the array. Localization of the immobilizate on the electrodes is accomplished by staining with the fluorescent product of the enzyme reaction. The high residual activity of enzymes after AC field induced immobilization shows the method's suitability for biosensing and research applications.

Synthesis of Pt Nanoparticles Encapsulated inside Dendrimers As Tunable Oxidase Mimics for Turn-on Fluorescent Sensing of Oxygen

Here, we present the controllable synthesis of dendrimer-encapsulated Pt nanoparticles (Pt DENs) utilizing repetitively coupled chemical reduction and galvanic exchange reactions. This facile method allowed controllable synthesis of the Pt DENs with fair homogeneity in size and composition. In particular, in contrast to the conventional dendrimer-templating methods, the proposed synthesis method allowed substantial increase in the applicable number of Pt atoms up to 1320 in Pt DENs without being limited by the fixed number of complexation sites for the Pt2+ precursor ions in dendrimers. We also present a detailed investigation on the oxidase-mimetic activity of the Pt DENs for catalytic oxidation of Amplex Red to resorufin with O2. Importantly, after clarifying intrinsic oxidase-mimetic activity of the Pt DENs, we disclosed that the Pt DENs’ oxidase-mimetic activity was tailorable for the oxidation of Amplex Red to resorufin especially with fine-tuning of the Pt2+/dendrimer ratios by using the proposed synthesis method.

Measuring peroxidasin activity in live cells using bromide addition for signal amplification

Peroxidasin (PXDN) is involved in the crosslinking of collagen IV, a major constituent of basement membranes. Disruption of basement membrane integrity as observed in genetic alterations of collagen IV or PXDN can result in developmental defects and diverse pathologies. Hence, the study of PXDN activity in (patho)physiological contexts is highly relevant. So far, measurements of PXDN activity have been reported from purified proteins, cell lysates and de-cellularized extracellular matrix. Here, for the first time we report the measurement of PXDN activity in live cells using the Amplex Red assay with a signal amplifying modification. We observe that bromide addition enhances the obtained signal, most likely due to formation of HOBr. Abrogation of signal amplification by the HOBr scavenger carnosine supports this hypothesis. Both, pharmacological inhibition as well as complementary genetic approaches confirm that the obtained signal is indeed related to PXDN activity. We validate the modified assay by investigating the effect of Brefeldin A, to inhibit the secretory pathway and thus the access of PXDN to the extracellular Amplex Red dye. Our method opens up new possibilities to investigate the activity of PXDN in (patho)physiological contexts.

Uric Acid Reacts with Peroxidasin, Decreases Collagen IV Crosslink, Impairs Human Endothelial Cell Migration and Adhesion.

Uric acid is considered the main substrate for peroxidases in plasma. The oxidation of uric acid by human peroxidases generates urate free radical and urate hydroperoxide, which might affect endothelial function and explain, at least in part, the harmful effects of uric acid on the vascular system. Peroxidasin (PXDN), the most recent heme-peroxidase described in humans, catalyzes the formation of hypobromous acid, which mediates collagen IV crosslinks in the extracellular matrix. This enzyme has gained increasing scientific interest since it is associated with cardiovascular disease, cancer, and renal fibrosis. The main objective here was to investigate whether uric acid would react with PXDN and compromise the function of the enzyme in human endothelial cells. Urate decreased Amplex Red oxidation and brominating activity in the extracellular matrix (ECM) from HEK293/PXDN overexpressing cells and in the secretome of HUVECs. Parallelly, urate was oxidized to 5-hydroxyisourate. It also decreased collagen IV crosslink in isolated ECM from PFHR9 cells. Urate, the PXDN inhibitor phloroglucinol, and the PXDN knockdown impaired migration and adhesion of HUVECs. These results demonstrated that uric acid can affect extracellular matrix formation by competing for PXDN. The oxidation of uric acid by PXDN is likely a relevant mechanism in the endothelial dysfunction related to this metabolite.

Improvement of 2,2'-Azobis(2-Methylpropionamidine) Dihydrochloride-Induced Hepatic Redox Imbalance in Swiss Mice and HepG2 Cells by Rutin.

Redox imbalance can lead to irreversible damages to biological functions. In this context, rutin stands out for its antioxidant potential. The objective of this study was to evaluate the acute and chronic effect of rutin on the hepatic redox imbalance. The study was performed according to three different protocols. First, healthy male Swiss mice were divided into two groups: control and rutin, the second of which received chronic oral supplementation of rutin (10 mg/kg). The second involved evaluation of the generation of reactive oxygen species (ROS) by HepG2 cells, incubated or not with rutin (20 and 40 μg/mL) for 3 h. The final protocol involved assessment of the acute effect of rutin (10 mg/kg) in mice with oxidative stress induced by 2,2'-azobis(2-methylpropionamidine) dihydrochloride (ABAP). After the in vivo treatments, the livers were collected to analyze the oxidative damage by thiol, and the antioxidant defense by catalase, superoxide dismutase, and glutathione peroxidase. In the HepG2 cells, the following probes were employed to assess the ROS production: dichlorofluorescein, MitoSOX, dihydroethidium, and Amplex Red. Rutin administered chronically improved the antioxidant defense in healthy animals, and when administered acutely both inhibited the increased production of ROS in HepG2 cells and improved the redox imbalance parameters in mice with induced oxidative stress. This study suggests rutin as a protective agent for restoration of hepatic redox homeostasis in redox injury induced by ABAP in Swiss mice and HelpG2 cells.

Sexual dimorphisms in renal mitochondrial bioenergetics

BackgroundStudies have shown that men have higher incidences of end‐stage renal disease than women at every point across the lifespan. Animal models for various renal diseases have similar occurrence with males being affected more frequently. Recent efforts have been heavily focused on delineating the mechanisms behind these sex‐based differences from various angles, with the mitochondria being highlighted as a target for sex difference‐related renal pathologies. The goal of this study is to investigate the sexual dimorphisms of renal mitochondria and their dependency on renal hemodynamics before disease onset.MethodsMitochondria were isolated from PBS‐flushed kidneys of Sprague Dawley male (SDM) and female (SDF) rats at 11 weeks of age using differential centrifugation. Renal cortex (SDMC vs SDFC) and medulla (SDMMvs SDFM) were separated for individual measurements. Mitochondrial membrane potential and hydrogen peroxide production were measured in spectrofluorimetry using the fluorescent dyes TMRM and Amplex Red, respectively. A portion of mitochondria were submitted to a histology core for electron microscopy. Additionally, mitochondrial oxygen consumption rate (OCR) was also assessed using Seahorse assay. Lipid peroxide radical formation was detected using electron paramagnetic resonance (EPR) with in vivo spin trapping. As a measure of renal function, GFR was assessed using FITC‐Inulin in conscious animals.ResultsElectron microscopy revealed similar yield of mainly round‐shaped isolated mitochondria with retained cristae and membrane structures in all groups. SDFM showed a higher membrane potential than SDMM (238.1±12.4 vs 162.0±8.8 au, p<0.001; respectively). Both SDFC and SDFM had higher hydrogen peroxide production in comparison to their male counterparts (cortex: 99443.7±3061.7 vs 69943.4±1708.6 au/protein, p<0.001; respectively. medulla: 113366.7±5430.7 vs 60613±2297.1 au/protein, p<0.001; respectively). Overall female mitochondria exhibited decreases in their basal, ATP‐linked, leaked OCRs as well as spare capacity compared to males (spare capacity: cortex: 5.9±0.6 vs 14.3±1.3, p<0.001; respectively. medulla: 4.9±0.6 vs 11.6±0.7 pmol/min/protein, p<0.001; respectively). EPR showed similar lipid peroxide radical levels in both sexes and sections of kidney. In the next part of the study, we explored if renal mitochondrial bioenergetics correlated with the GFR of the animal. Our data show the following GFR values for male and female rats as normalized to two kidney weights (2KW) and 2KW/ total body weight (2KW/TBW), respectively: 1.4±0.2 vs 0.8±0.1 mL/min/2KW, p=0.1416 and 0.5±0.1 vs 0.2±0.02 mL/min/2KW/TBW, p=0.0143. We did not observe any correlation between mitochondrial membrane potential and ROS production (measured in the isolated renal cortical mitochondria) with GFR in male or female rats (n= 5 in each group).ConclusionsOverall, we show here that female renal mitochondria exhibit lower oxygen consumption, higher ROS emission, and membrane potential vs males; however, lipid peroxidation is similar. Currently, we do not see a correlation between mitochondrial bioenergetics and GFR. More studies designed with higher statistical power are required to further elucidate the relationship between renal blood flow and mitochondrial bioenergetics.

Atorvastatin Modulates the Function and Trafficking of Dopamine Transporters

IntroductionDopaminergic signaling is involved in learning, memory, reward, movement, and emotion. The dopamine transporter (DAT) is the primary mechanism for terminating this signaling via DA uptake. A few lines of evidence indicate that DAT function is regulated by membrane cholesterol. Cholesterol is a critical component of plasma membranes and plays an essential role in regulating membrane fluidity, protein compartmentalization, and function. Statins are cholesterol‐lowering medications that have been linked to mild cognitive impairment. The goal of this project was to examine the effects of atorvastatin‐mediated reductions in cholesterol content on DAT function and trafficking.MethodsCultured cells & cholesterol measurement: HA‐tagged human DAT (hDAT) was stably expressed in neuroblastoma 2a (N2A) cells using G418 as selection. Cells were treated with atorvastatin (0.1, 0.3, 1.0, or 10 μM) and membrane cholesterol content was measured using Amplex Red.[3H]DA Uptake: After 24hr atorvastatin or vehicle treatment, cells were incubated with 15 nM [3H]DA in the presence of various concentrations of non‐labeled DA and [3H]DA uptake was measured to determine Vmax and Km.Cocaine inhibition of DA uptake & cholesterol replenishment: Cells were treated for 24hr with atorvastatin (1 μM) or vehicle and incubated with 15 nM [3H]DA and increasing concentrations of cocaine (100 nM‐10 μM). To determine if there was a causal effect of reduced cholesterol content and cocaine inhibition of DA uptake, atorvastatin‐treated cells were replenished with water soluble cholesterol (~40 mg per gram solid; MβCD) prior to cocaine inhibition.Amphetamine‐induced, DAT‐mediated DA efflux: Cells treated for 24hrs with either atorvastatin (1 μM) or vehicle were preloaded with 30 nM of [3H]DA. Then, cells were incubated with amphetamine (1 or 10 μM). AMPH‐induced DA efflux was determined by measuring DA content in the medium across time.Surface DAT Biotinylation: Basal surface levels of DAT in atorvastatin and vehicle treated cells, as well as DA‐induced DAT internalization, were measured by surface biotinylation using membrane non‐permeable sulfo‐NHS‐SS biotin.ImmunocytochemistryWe measured levels of F‐actin and G‐actin to determine the effects of atorvastatin treatment on actin dynamics using immunocytochemistry.ResultsWe found that atorvastatin dose dependently reduced membrane cholesterol content. This reduction was accompanied by decreases in the maximal rate of DA uptake and by decreases in the potency of cocaine to inhibit [3H]DA uptake. In contrast, atorvastatin treatment did not significantly alter AMPH‐induced DA efflux. Importantly, the reduced ability of cocaine to inhibit DA uptake was reversed by replenishing cholesterol in atorvastatin‐treated cells, suggesting a direct causal effect of reduced cholesterol content and cocaine inhibition. Lastly, we found that atorvastatin disrupted actin dynamics and abolished DA‐induced DAT internalization. The present study provides evidence for the first time that atorvastatin dysregulates DAT function and trafficking. Furthermore, this dysregulation may be associated with the cognitive deficits observed in patients receiving atorvastatin treatment.

Targeting p21‐highly‐expressing Senescent Cells Enhances Skeletal Muscle Function through Mitochondrial Function and Reactive Oxygen Species

BACKGROUNDThe accumulation of senescent cells is a hallmark of aging in the skeletal muscle which causes reactive oxygen species (ROS) and mitochondrial dysfunction. p21 is one of the major regulators and most recognized cellular markers for senescent cells. Recent evidence demonstrated that clearance of p21high cells enhances muscle function including grip strength, hanging endurance, and maximal walking speed in mice. However, it is still unclear how the muscle performance enhances through the clearance of p21high cells. One of the potential mechanisms is mitochondrial function and/or mitochondria‐derived ROS. Therefore, this study investigated the linkage between mitochondria and p21high cells in aging or high fat diet‐induced muscle dysfunction.METHODSFive p21‐Cre/+; +/+ (P) and p21‐Cre/+; DTA/+ (PD) obese mice fed by high fat diet were administrated with tamoxifen for twice. Five P lean mice fed by normal chow were adopted as normal control. We previously demonstrated that p21high cells accumulate in obese P mice, and can be eliminated in obese PD mice by tamoxifen treatment. Mitochondrial respiration was measured, by high‐resolution respirometry, in permeabilized muscle fibers from the soleus muscle. Mitochondria‐derive ROS production was determined using Amplex Red assays. One‐way ANOVAs with Bonferroni post‐hoc were used to determine differences between groups (P < 0.05).RESULTSReductions in complex I + II state 3 respiration were observed in p21‐Cre mice with high fat diet but the clearance of p21high cells using tamoxifen enhanced complex I + II state 3 respiration (Lean P: 35.2 ± 3.13 pmol·s‐1·mg‐1; Obese P: 17.45 ± 2.85 pmol·s‐1·mg‐1; Obese PD: 30.04 ± 3.19 pmol·s‐1·mg‐1; P < 0.05). State 4 respiration did not differ between groups (P > 0.05). Respiratory Control Ratio (RCR), defined as respiration in state 3 divided by respiration in state 4, significantly decreased in high fat diet group but clearing p21high cells restored respiratory function (Lean P: 4.20 ± 1.18; Obese P: 2.21 ± 1.11; Obese PD: 3.85 ± 1.60; P<0.05). Also, high fat diet increased mitochondrial ROS production, but tamoxifen treatment attenuated ROS production (Lean P: 10.16 ± 0.41 pmol·s‐1·mg‐1; Obese P: 26.83 ± 0.54 pmol·s‐1·mg‐1; Obese PD: 12.23 ± 0.54 pmol·s‐1·mg‐1; P<0.05).CONCLUSIONThese results demonstrated that p21high cells may play a causal role in mitochondrial dysfunction and ROS emission in the skeletal muscle with obesity and other chronic diseases. Therefore, targeting p21high cells may enhance muscle performance through decreasing mitochondria‐derived ROS and enhancing mitochondrial function.

Development and butyrylcholinesterase/monoamine oxidase inhibition potential of PVA-Berberis lycium nanofibers

Abstract The aim of this study was to evaluate the potential inhibitory effect of montmorillonite (MMT)-reinforced, glutaraldehyde-crosslinked PVA (polyvinyl alcohol) nanofibers loaded with root extract of Berberis lycium on monoamine oxidase A and B (MAO A and B) and butyrylcholinesterase (BChE) by using slightly modified Ellman’s test and Amplex Red monoamine oxidase assay, respectively. Enzyme inhibition studies of extract-loaded nanofibers showed significant inhibitory potential against MAO A, B, and BChE. There was an increase in enzyme inhibition with an increased extract concentration loaded to nanofibers. The fibers were characterized by TGA (thermal gravimetric analysis), SEM (scanning electron microscopy), XRD (X-ray diffractometry), and FTIR (Fourier-transform infra-red) spectroscopy to investigate thermal stability, morphology, structural changes, and functional groups in the nanofibers, respectively. SEM results of fabricated nanofibers reflected the beadless and smooth morphology of nanofibers with the porous structure. The contact angle measurements of fabricated nanofibers showed suitable hydrophilicity of nanofibers. The nanofibers loaded with the root extract of Berberis lycium have been found to be potent inhibitors of MAO A, B, and the BChE enzyme.

Chronic Lactate Exposure Decreases Mitochondrial Function by Inhibition of Fatty Acid Uptake and Cardiolipin Alterations in Neonatal Rat Cardiomyocytes.

IntroductionLactate is an important signaling molecule with autocrine, paracrine and endocrine properties involved in multiple biological processes including regulation of gene expression and metabolism. Levels of lactate are increased chronically in diseases associated with cardiometabolic disease such as heart failure, type 2 diabetes, and cancer. Using neonatal ventricular myocytes, we tested the hypothesis that chronic lactate exposure could decrease the activity of cardiac mitochondria that could lead to metabolic inflexibility in the heart and other tissues.MethodsNeonatal rat ventricular myocytes (NRVMs) were treated for 48 h with 5, 10, or 20 mM lactate and CPT I and II activities were tested using radiolabelled assays. The molecular species profile of the major mitochondrial phospholipid, cardiolipin, was determined using electrospray ionization mass spectrometry along with reactive oxygen species (ROS) levels measured by Amplex Red and mitochondrial oxygen consumption using the Seahorse analyzer.ResultsCPT I activity trended downward (p = 0.07) and CPT II activity significantly decreased with lactate exposure (p < 0.001). Cardiolipin molecular species containing four 18 carbon chains (72 carbons total) increased with lactate exposure, but species of other sizes decreased significantly. Furthermore, ROS production was strongly enhanced with lactate (p < 0.001) and mitochondrial ATP production and maximal respiration were both significantly down regulated with lactate exposure (p < 0.05 and p < 0.01 respectively).ConclusionsChronic lactate exposure in cardiomyocytes leads to a decrease in fatty acid transport, alterations of cardiolipin remodeling, increases in ROS production and decreases in mitochondrial oxygen consumption that could have implications for both metabolic health and flexibility. The possibility that both intra-, or extracellular lactate levels play roles in cardiometabolic disease, heart failure, and other forms of metabolic inflexibility needs to be assessed in vivo.

An improved Amplex Red‐based fluorometric assay of phenol oxidases and peroxidases activity: A case study on Haplic Chernozem

AbstractThe initial steps of complex organic matter degradation in soil comprise several oxidative processes catalysed by phenol oxidases and peroxidases. Commonly, their activity is determined by colorimetric approaches based on a range of substrates, making comparison between studies difficult. To improve this shortcoming, we conducted a calibration procedure for assessing phenol oxidase and peroxidase activities in soils by a sensitive fluorometric assay. This assay is based on the colourless and non‐fluorescent Amplex Red® reagent as a substrate, which forms a fluorescent product, resorufin, upon oxidation. Commercially available resorufin was used as a standard for calibration. We applied Michaelis–Menten kinetics to determine functional traits of phenol oxidases and peroxidases in a case study on Haplic Chernozem from different land‐use and climate treatments of a field experiment. The kinetic parameters, limit of detection and limit of quantification demonstrated a high sensitivity of the fluorometric assay to differences caused by these treatments. For the total oxidative enzymes, the catalytic efficiency (Kcat, calculated as Vmax/Km) was 30% higher in the cropland compared with the pasture plot. However, compared with soil samples collected from ambient climatic conditions, Kcat of total oxidoreductases was 60% lower in cropland exposed to elevated air temperature and drought. The phenol oxidase activity was substantially higher than peroxidase activity in cropland land use. However, higher Kcat of peroxidase than phenol oxidase resulted in 60% faster substrate turnover under both climatic conditions. In our case study, the Amplex Red‐based assay enabled rapid and high‐throughput analyses of phenol oxidase and peroxidase activity in soil. The sensitivity of this assay for soil enzymology applications needs further testing for a larger range of soils and environmental conditions.Highlights A novel fluorometric assay of phenol oxidase and peroxidase activity in soil is proposed Resorufin fits very well for calibration simplifying the comparisons between studies Phenol oxidase and peroxidase displayed apparent Michaelis–Menten kinetics Amplex Red was sensitive for land‐use and climate treatments on Haplic Chernozem

Protective Effects of Alternanthera sessilis Ethanolic Extract against TNF-α or H2O2-Induced Endothelial Activation in Human Aortic Endothelial Cells.

Activation of the endothelium has been shown to contribute to the early stage of vascular diseases such as atherosclerosis and hypertension. In endothelial activation, excess reactive oxygen species (ROS) production and increased expression of cell adhesion molecules cause an increase in vascular permeability. Alternanthera sessilis (L.) R. Br. is an edible traditional herbal plant, which has previously been shown to possess antioxidant and anti-inflammatory effects. However, the effect of A. sessilis on the activation of human aortic endothelial cells (HAECs) remains unknown. This study aimed to investigate the effects of A. sessilis on endothelial permeability, vascular cell adhesion-1 (VCAM-1) expression, production of ROS and hydrogen peroxide (H2O2), and superoxide dismutase (SOD) and catalase (CAT) activities. The viability of HAECs was first determined using the MTT viability assay. The effect of A. sessilis on endothelial permeability was examined using the FITC-dextran permeability assay. Besides, enzyme-linked immunosorbent assay (ELISA) was done to assess soluble VCAM-1 (sVCAM-1) expression. The production of ROS and H2O2 was studied using 2′,7′-dichlorodihydrofluorescein diacetate (H2-DCFDA) and Amplex Red fluorescent dyes, respectively. SOD and CAT activities were also measured using commercial kits. Our results showed that 25–200 μg/mL of A. sessilis ethanolic extract did not cause significant death in HAECs. A. sessilis at 200 μg/mL significantly inhibited TNF-α-induced hyperpermeability of HAECs. However, A. sessilis did not reduce increased VCAM-1 expression induced by TNF-α. A. sessilis also significantly reduced TNF-α-induced increased ROS production, but not H2O2 production. Furthermore, 100 μM of H2O2 decreased both SOD and CAT activities in HAECs at 2 h. A. sessilis ethanolic extract dramatically increased both reduced SOD and CAT activities caused by H2O2. The liquid chromatography-mass spectrometry (LC-MS) analysis of A. sessilis ethanolic extract demonstrated the presence of arachidonic acid, azadirachtin, astaxanthin, flavanole base + 3O, 2Prenyl, and vicenin 2, while the gas chromatography-mass spectrometry (GC-MS) analysis showed that the extract contains 1,3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one, 3-deoxy-d-mannoic lactone, 4-pyrrolidinobenzaldehyde, and n-hexadecanoic acid. In conclusion, our findings suggest that A. sessilis ethanolic extract protects against endothelial hyperpermeability and oxidative stress elicited by pro-inflammatory or prooxidant stimulus. This study reveals a therapeutic potential of A. sessilis in preventing endothelial activation, which is a key event in early atherosclerosis.

A Novel Enzyme-Free Ratiometric Fluorescence Immunoassay Based on Silver Nanoparticles for the Detection of Dibutyl Phthalate from Environmental Waters.

A novel ratiometric fluorescent immunoassay was developed based on silver nanoparticles (AgNPs) for the sensitive determination of dibutyl phthalate (DBP). In the detection system, AgNPs were labeled on the secondary antibody (AgNPs@Ab2) for signal amplification, which aimed to regulate the H2O2 concentrations. When AgNPs-Ab2 and antigen–primary antibody (Ab1) were linked by specific recognition, the blue fluorescence of Scopoletin (SC) could be effectively quenched by the H2O2 added while the red fluorescence of Amplex Red (AR) was generated. Under the optimized conditions, the calculated detection of limit (LOD, 90% inhibition) reached 0.86 ng/mL with a wide linear range of 2.31–66.84 ng/mL, which was approximately eleven times lower than that by HRP-based traditional ELISA with the same antibody. Meanwhile, it could improve the inherent built-in rectification to the environment by the combination of the dual-output ratiometric fluorescence assays with ELISA, which also enhanced the accuracy and precision (recoveries, 87.20–106.62%; CV, 2.57–6.54%), indicating it can be applied to investigate the concentration of DBP in water samples.

Soil oxidoreductase zymography: Visualizing spatial distributions of peroxidase and phenol oxidase activities at the root-soil interface

Decomposition of organic material in the rhizosphere – the most dynamic microbial habitat in soil – involves arrays of oxidoreductase and hydrolytic enzymes. Spatial distributions of various hydrolytic activities in soil have already been explored by zymographic techniques. However, the distribution of oxidative activity in the rhizosphere remains to be studied. Thus, we extended a Time-Lapse Zymography technique, using Amplex Red® reagent, to visualize and quantify distributions of phenol oxidase and peroxidase activities in the rhizosphere of Zea mays L. growing in a Haplic Phaeozem and the non-rhizospheric soil. The gross oxidative activity was greatest at the root surfaces, and fell to background soil levels 1.26 and 0.73 mm from seminal (>1 mm diameter) and lateral (<0.5 mm diameter) roots, respectively. The rhizosphere extent relative to the root radius was 59% broader around lateral than around seminal roots. The greatest activities, up to 30 nmol cm−2 min−1, were peroxidase-dominated and closely associated with roots. The results confirm the utility of the approach for studying spatio-temporal distributions of oxidative activities in soil. However, actual activity of oxidoreductases in the field will be strongly controlled by fluctuating environmental conditions such as soil aeration and the gradient of reactive oxygen species, which need to be considered especially in anoxic soils.

EPITHELIAL DUOX2 ACTIVATION INCREASES GUT PERMEABILITY AND BACTERIAL TRANSLOCATION THAT IS RESCUED WITH BUTYRATE SUPPLEMENTATION

Abstract BACKGROUND Inflammatory bowel diseases (IBD) are chronic pathologies characterized by dysbiosis, defects in epithelial barrier function, and increased redox stress. Dysbiosis in IBD involves an expansion of Proteobacteria and a reduction of Firmicutes, which produce metabolites important in maintaining gut homeostasis. The epithelial NADPH oxidase dual oxidase 2 (DUOX2) catalyzes the production of hydrogen peroxide (H2O2) and is the only gene consistently altered in IBD patients in association with dysbiosis and before the onset of disease. However, the functional consequence of DUOX2 activation in IBD is not understood. Using models of dysbiosis leading to DUOX2 activation, we aimed to dissect the contribution of DUOX2 activity to the defects in epithelial barrier function observed in IBD. METHODS villin-TLR4 (vTLR4) mice, which express a constitutively active form of TLR4 in colonic epithelial cells (CECs) and have increased activation of DUOX2, vTLR4-DUOX2-KO mice, and their wild-type (WT) littermates were euthanized. Livers were collected for permeability assessment by bacterial translocation. Colonic tissue was collected for RNA-sequencing and isolation of CECs for gene expression determinations by qPCR. Separately, vTLR4 mice and littermates were treated with butyrate in drinking water. Tissue was harvested for the same determinations and for measurement of epithelial H2O2 production via Amplex Red. Colonoids from WT mice were treated with butyrate and stimulated with IFNγ or heat-killed adherent invasive Escherichia coli. H2O2 production and gene expression of Duox2 were determined. RESULTS RNA-sequencing revealed that abrogation of DUOX2 activity downregulated cytokine-mediated signaling and cytokine production pathways, including tumor necrosis factors and key chemotactic proteins such as CXCL1 and CXCL2. Similarly, expression of Tnfa, Cxcl1, and Cxcl2 was significantly downregulated to WT levels in vTLR4-DUOX2-KO mice. vTLR4 mice had increased bacterial translocation, which was rescued by deletion of DUOX2. Butyrate treatment inhibited epithelial H2O2 response to stimuli in vitro, which was accompanied by a reduction in Duox2 transcripts. In vivo, butyrate treatment of vTLR4 mice significantly reduced epithelial production of H2O2, bacterial translocation to the liver, and led to a downregulation of Tnfa, Cxcl1, and Cxcl2 transcripts. CONCLUSIONS Chronic DUOX2 activity leads to defects in epithelial barrier function resulting in increased bacterial translocation. This leads to an increase in proinflammatory cytokines and chemokines. The microbial metabolite butyrate blocked DUOX2 activity, rescuing intestinal permeability and reducing bacterial translocation and inflammatory cytokine gene expression. We posit that therapies aimed at controlling DUOX2 activity through microbiome or metabolome-targeted approaches may be beneficial in IBD.

Single-Molecule Nanocatalysis Reveals the Kinetics of the Synergistic Effect Based on Single-AuAg Bimetal Nanocatalysts.

Decades of extensive research efforts by scientists in the field of catalysis and nanomaterials have led to a large number of excellent bimetallic nanocatalysts. However, in many cases, the mechanism of the synergistic effect in bimetal catalyst-catalyzed reactions has been systematically neglected due to technical limitations. Herein, we use single-molecule fluorescence microscopy (SMFM) to reveal the mechanism of the synergy of the Au and Ag bimetal catalyst. Compared with that of the Ag nanocatalyst, the incorporation of Au changes the reaction pathway of Amplex Red and H2O2 from a noncompetitive to a competitive reaction mechanism, showing much higher catalytic efficiency. Additionally, the incorporation also inhibits the spontaneous surface reconstruction and facilitates the reaction-induced surface restructuring of the nanocatalyst, resulting in the enhancement of stability and reactivity. These findings provide useful insights into tailoring the reactivity of metal catalysts. This work also confirms the power of SMFM in revealing the origin of the catalytic activity of composite catalysts.

An Optical Sensing Platform for Beta-Glucosidase Activity Using Protein-Inorganic Hybrid Nanoflowers.

In this work, a convenient and dual-signal readout optical sensing platform for the sensitively and selectively determination of beta-glucosidase (β-Glu) activity was reported using protein-inorganic hybrid nanoflowers [BSA-Cu3(PO4)2·3H2O] possessing peroxidase-mimicking activity. The nanoflowers (NFs) were facilely synthesized through a self-assembled synthesis strategy at room temperature. The as-prepared NFs could catalytically convert the colorless and non-fluorescent Amplex Red into colored and highly fluorescent resorufin in the presence of hydrogen peroxide via electron transfer process. β-Glu could hydrolyze cyanogenic glycoside, using amygdalin (Amy) as a model, into cyanide ions (CN-), which can subsequently efficiently suppress the catalytic activity of NFs, accompanied with the fluorescence decrease and the color fading. The concentration of CN- was controlled by β-Glu-triggered enzymatic reaction of Amy. Thus, a sensing system was established for fluorescent and visual determination of β-Glu activity. Under the optimum conditions, the present fluorescent and visual bimodal sensing platform exhibited good sensitivity for β-Glu activity assay with a detection limit of 0.33 U·L-1. The sensing platform was further applied to determinate β-Glu in real samples and satisfactory results were attained. Additionally, the optical sensing system can potentially be a promising candidate for β-Glu inhibitors screening.

Quantitative analysis of vitamin D using m/MALDI-TOF mass spectrometry based on a parylene matrix chip

Vitamin D deficiency is associated with various disorders and is diagnosed based on the concentration of 25-hydroxy vitamin D3 (25(OH)D3) in serum. The parylene matrix chip was fabricated to reduce the matrix background noise, and the homogenous distribution of the matrix was retained for the quantitative analysis of 25(OH)D3. The Amplex Red assay was performed to confirm that the sample-matrix mixing zone of the parylene matrix chip was formed below the surface of the parylene-N film. The homogeneous distribution of the matrix was verified from the fluorescence image. For effective analysis using a parylene matrix chip, 25(OH)D3 was modified through the nucleophilic addition of betaine aldehyde (BA) to form a hemiacetal salt. Such modified 25(OH)D3 with a positive charge from BA could be effectively analyzed using MALDI-TOF mass spectrometry. Serum 25(OH)D3 was extracted by liquid–liquid extraction (LLE) and quantified using MALDI-TOF mass spectrometry based on the parylene matrix chip. The intensity of the mass peak of 25(OH)D3 was linearly correlated (r2 = 0.992) with the concentration of 25(OH)D3 spiked in serum, and the LOD was 0.0056 pmol/μL. Energy drinks and vitamin D3 tablets were also employed for the real sample analysis. Finally, the results of the chemiluminescence binding assay and MALDI-TOF mass spectrometry were statistically analyzed to determine the applicability of the method using the Bland–Altman test and Passing–Bablok regression.