Glutathione Peroxidase-like Activity Research Articles

ZIF-67 as a Template Generating and Tuning "Raisin Pudding"-Type Nanozymes with Multiple Enzyme-like Activities: Toward Online Electrochemical Detection of 3,4-Dihydroxyphenylacetic Acid in Living Brains.

Due to its unique structure and high porosity, metal-organic frameworks (MOFs) can act not only as nanozyme materials but also as carriers to encapsulate natural enzymes and thus have received extensive attention in recent years. However, a few research studies have been conducted to investigate MOF as a template to generate and tune nanozymes in the structure and performance. In this work, the "raisin pudding"-type ZIF-67/Cu0.76Co2.24O4 nanospheres (ZIF-67/Cu0.76Co2.24O4 NSs) were obtained by rationally regulating the weight ratio of ZIF-67 and Cu(NO3)2 in the synthesis process. Here, ZIF-67 not only acts as a template but also provides a cobalt source for the synthesis of cobalt copper oxide on the surface of ZIF-67/Cu0.76Co2.24O4 NSs with multiple enzyme-like activities. The ZIF-67/Cu0.76Co2.24O4 NSs can mimic four kinds of enzymes with peroxidase-like, glutathione peroxidase-like, superoxide dismutase-like, and laccase-like activities. Based on its laccase-like activity, an online electrochemical system for continuous monitoring of 3,4-dihydroxyphenylacetic acid with good linearity in the range of 0.5-20 μM and a detection limit of 0.15 μM was established. Furthermore, the alteration of DOPAC in the brain microdialysate before and after ischemia of the rats' brain was also successfully recorded. This work not only raises a new idea for the synthesis of nanozyme materials with multiple enzyme activities but also provides a new solution for the detection of neurotransmitters in living brains.

Age-Related Effects of Orthovanadate Nanoparticles Involve Activation of GSH-Dependent Antioxidant System in Liver Mitochondria.

Vanadium is an important ultra-trace element nowadays attracting attention with particular emphasis on medical application. But the therapeutic application of vanadium-based drugs is still questionable and restricted due to some toxic side effects. It was found that unique redox properties of vanadium in nanoform provided antioxidant activity and prevented oxidative disturbance in cells in vitro. Though, on the organism level, ambiguous effects of vanadium-based nanoparticles were observed. In this study, the age-related features of prooxidant/antioxidant balance in blood serum and liver mitochondrial and postmitochondrial fractions of 3 and 18-month-old Wistar male rats treated with orthovanadate nanoparticles (GdVO4/Eu3+, 8 × 25nm) within 2months have been investigated. Prooxidant potential-related indexes were the content of lipid hydroperoxides as well as aconitase activity. Activity of glutathione peroxidase, glutathione-S-transferase, glutaredoxin, glutathione reductase, glucose-6-phosphate dehydrogenase, and NADPH-dependent isocitrate dehydrogenase designated the tissue antioxidant potential. Based on the obtained values, the integral index of the prooxidant/antioxidant balance-the reliability coefficient (Kr) has been calculated. The data show that due to activation some chain links of GSH-dependent antioxidant system, GdVO4/Eu3+ nanoparticles increase the reliability of the prooxidant-antioxidant balance in tissues and especially in the liver mitochondria of old animals (Kr in mitochondria of young rats was 2.94, and in mitochondria of old ones-9.83 conventional units). Detected in vitro glutathione peroxidase-like activity of the GdVO4/Eu3+ nanoparticles is supposed to be among factors increasing the reliability of the system. So, for the first time, the beneficial effect of the long-term orthovanadate nanoparticle consumption in old males has been discovered.

Copper-thioguanine metallodrug with self-reinforcing circular catalysis for activatable MRI imaging and amplifying specificity of cancer therapy

For chemotherapy, drug delivery systems often suffer from the inefficient drug loading capability, which usually cause systems toxicity and extra burden to excrete carrier itself. Moreover, the cancer therapeutic efficacy is also greatly limited by the specificity of tumor microenvironment for reactive oxygen species (ROS) based cancer therapeutic strategy (e.g., chemodynamic therapy). Herein, we have developed metal-drug coordination nanoplatform that can not only be responsive to tumor microenvironment but also modulate it, so as to achieve efficient treatment of cancer. Excitingly, by employing small molecule drug (6-thioguanine) as ligand copper ions, we achieve a high drug loading rate (60.1%) and 100% of utilization of metal-drug coordination nanoplatform (Cu-TG). Interestingly, Cu-TG possessed high-efficiently horseradish peroxidase-like, glutathione peroxidase-like and catalase-like activity. Under the tumor microenvironment, Cu-TG exhibited the self-reinforcing circular catalysis that is able to amplify the cellular oxidative stress, inducing notable cancer cellular apoptosis. Moreover, Cu-TG could be activated with glutathione (GSH) and facilitated for GSH triggered 6-TG release, higher selective therapeutic effect toward cancer cells, and GSH activated T1 weight-magnetic resonance imaging. Based on the above properties, Cu-TG exhibited magnetic resonance imaging (MRI) guiding, efficient and synergistic combination of chemodynamic and chemotherapy with self-reinforcing therapeutic outcomes in vivo.

Cu∥-loaded polydopamine coatings with in situ nitric oxide generation function for improved hemocompatibility.

NO is the earliest discovered gas signal molecule which is produced by normal healthy endothelial cells, and it has many functions, such as maintaining cardiovascular homeostasis, regulating vasodilation, inhibiting intimal hyperplasia and preventing atherosclerosis in the blood system. Insufficient NO release is often observed in the pathological environment, for instance atherosclerosis. It was discovered that NO could be released from the human endogenous NO donor by many compounds, and these methods can be used for the treatment of certain diseases in the blood system. In this work, a series of copper-loaded polydopamine (PDA) coatings were produced through self-polymerization time for 24, 48 and 72 h. The chemical composition and structure, coating thickness and hydrophilicity of the different copper-loaded PDA coatings surfaces were characterized by phenol hydroxyl quantitative, X-ray photoelectron spectroscopy, ellipsometry atomic force microscopy and water contact angles. The results indicate that the thickness and the surface phenolic hydroxyl density of the PDA coatings increased with the polymerization time.This copper-loaded coating has glutathione peroxidase-like activity, and it has the capability of catalyzing NO releasing from GSNO. The surface of the coating showed desirable hemocompatibility, the adhesion and activation of platelets were inhibited on the copper-loaded coatings. At the same time, the formation of the thrombosis was also suppressed. These copper-loaded PDA coatings could provide a promising platform for the development of blood contact materials.

Endothelium-Mimicking Multifunctional Coating Modified Cardiovascular Stents via a Stepwise Metal-Catechol-(Amine) Surface Engineering Strategy.

Stenting is currently the major therapeutic treatment for cardiovascular diseases. However, the nonbiogenic metal stents are inclined to trigger a cascade of cellular and molecular events including inflammatory response, thrombogenic reactions, smooth muscle cell hyperproliferation accompanied by the delayed arterial healing, and poor reendothelialization, thus leading to restenosis along with late stent thrombosis. To address prevalence critical problems, we present an endothelium-mimicking coating capable of rapid regeneration of a competently functioning new endothelial layer on stents through a stepwise metal (copper)-catechol-(amine) (MCA) surface chemistry strategy, leading to combinatorial endothelium-like functions with glutathione peroxidase-like catalytic activity and surface heparinization. Apart from the stable nitric oxide (NO) generating rate at the physiological level (2.2 × 10−10 mol/cm2/min lasting for 60 days), this proposed strategy could also generate abundant amine groups for allowing a high heparin conjugation efficacy up to ∼1 μg/cm2, which is considerably higher than most of the conventional heparinized surfaces. The resultant coating could create an ideal microenvironment for bringing in enhanced anti-thrombogenicity, anti-inflammation, anti-proliferation of smooth muscle cells, re-endothelialization by regulating relevant gene expressions, hence preventing restenosis in vivo. We envision that the stepwise MCA coating strategy would facilitate the surface endothelium-mimicking engineering of vascular stents and be therefore helpful in the clinic to reduce complications associated with stenosis.

A Multifunctional Cascade Bioreactor Based on Hollow‐Structured Cu2MoS4 for Synergetic Cancer Chemo‐Dynamic Therapy/Starvation Therapy/Phototherapy/Immunotherapy with Remarkably Enhanced Efficacy

The unique tumor microenvironment (TME) facilitates cancer proliferation and metastasis, and it is hard to cure cancer completely via monotherapy. Herein, a multifunctional cascade bioreactor based on hollow mesoporous Cu2 MoS4 (CMS) loaded with glucose oxidase (GOx) is constructed for synergetic cancer therapy by chemo-dynamic therapy (CDT)/starvation therapy/phototherapy/immunotherapy. The CMS harboring multivalent elements (Cu1+/2+ , Mo4+/6+ ) exhibit Fenton-like, glutathione (GSH) peroxidase-like and catalase-like activity. Once internalized into the tumor, CMS could generate ·OH for CDT via Fenton-like reaction and deplete overexpressed GSH in TME to alleviate antioxidant capability of the tumors. Moreover, under hypoxia TME, the catalase-like CMS could react with endogenous H2 O2 to generate O2 for activating the catalyzed oxidation of glucose by GOx for starvation therapy accompanied with the regeneration of H2 O2 . The regenerated H2 O2 can devote to Fenton-like reaction for realizing GOx-catalysis-enhanced CDT. Meanwhile, the CMS under 1064 nm laser irradiation shows remarkable tumor-killing ability by phototherapy due to its excellent photothermal conversion efficiency (η = 63.3%) and cytotoxic superoxide anion (·O2 - ) generation performance. More importantly, the PEGylated CMS@GOx-based synergistic therapy combined with checkpoint blockade therapy could elicit robust immune responses for both effectively ablating primary tumors and inhibiting cancer metastasis.

Copper-Driven Deselenization: A Strategy for Selective Conversion of Copper Ion to Nanozyme and Its Implication for Copper-Related Disorders.

Synthetic organic molecules, which can selectively convert excess intracellular copper (Cu) ions to nanozymes with an ability to protect cells from oxidative stress, are highly significant in developing therapeutic agents against Cu-related disorder like Wilson's disease. Here, we report 1,3-bis(2-hydroxyethyl)-1 H-benzoimidazole-2-selenone (1), which shows a remarkable ability to remove Cu ion from glutathione, a major cytosolic Cu-binding ligand, and thereafter converts it into copper selenide (CuSe) nanozyme that exhibits remarkable glutathione peroxidase-like activity, at cellular level of H2O2 concentration, with excellent cytoprotective effect against oxidative stress in hepatocyte. Cu-driven deselenization of 1, under physiologically relevant conditions, occurred in two steps. The activation of C═Se bond by metal ion is the crucial first step, followed by cleavage of the metal-activated C═Se bond, initiated by the OH group of N-(CH2)2OH substituent through neighboring group participation (deselenization step), resulted in the controlled synthesis of various types of Cu2-xSe nanocrystals (NCs) (nanodisks, nanocubes, and nanosheets) and tetragonal Cu3Se2 NCs, depending upon the oxidation state of the Cu ion used to activate the C═Se bond. Deselenization of 1 is highly metal-selective. Except Cu, other essential metal ions, including Mn2+, Fe2+, Co2+, Ni2+, or Zn2+, failed to produce metal selenide under identical reaction conditions. Moreover, no significant change in the expression level of Cu-metabolism-related genes, including metallothioneines MT1A, is observed in liver cells co-treated with Cu and 1, as opposed to the large increase in the concentrations of these genes observed in cells treated with Cu alone, suggesting the participation of 1 in Cu homeostasis in hepatocyte.

Fe-N/C single-atom catalysts exhibiting multienzyme activity and ROS scavenging ability in cells.

Fe-N/C single atom catalysts (SACs) exhibit peroxidase-like, oxidase-like, catalase-like, and glutathione peroxidase-like activity. Fe-N/C SACs are successfully applied to control the intracellular H2O2 level. This study not only explores the types of SACs mimicking enzymes but also provides opportunities for SACs in biomedical and other bioengineering applications.

Cyclic telluride reagents with remarkable glutathione peroxidase-like activity for purification-free synthesis of highly pure organodisulfides

Cyclic tellurides enable rapid and quantitative oxidation of various organothiols through a GPx-like catalytic cycle in a biphasic microflow system.

Design, synthesis, and biological evaluation of histone deacetylase inhibitors possessing glutathione peroxidase-like and antioxidant activities against Alzheimer's disease.

A series of hybrids containing the pharmacophores of the histone deacetylase (HDAC) inhibitor, SAHA, and the antioxidant ebselen were designed and synthesized as multi-target-directed ligands against Alzheimer's disease. An in vitro assay indicated that some of these molecules exhibit potent HDAC inhibitory activity and ebselen-related pharmacological effects. Specifically, the optimal compound 7f was found to be a potent HDAC inhibitor (IC50 = 0.037 μM), possessing rapid hydrogen peroxide scavenging activity and glutathione peroxidase-like activity (ν0 = 150.0 μM min-1) and good free oxygen radical absorbance capacity (value of ORAC: 2.2). Furthermore, compound 7f showed significant protective effects against damage induced by H2O2 and the ability to prevent ROS accumulation in PC12 cells.

Hydrophobicity and glutathione peroxidase-like activity of substituted salicyloyl-5-seleninic acids: Re-investigations on aromatic selenium compounds based on their hydrophobicity

Previously we have shown that some of 5-selenized salicylic acid derivatives exhibit glutathione peroxidase (GPx)-like activities higher than or equal to ebselen [Yu et al., Chem. Eur. J., 2008, 14, 7066; Org. Biomol. Chem., 2010, 8, 828]. For understanding the absence of GPx-like activity of the homologue of 5-seleninic anhydride of salicyloylglycine with a loger side chain, we have further synthesized 19 new derivatives (5-seleninic acids of methyl or phenyl salicylates, N-salicyloyl ω-carboxyalkylamines or N-salicyloyl alkyl/phenyl amines, and some of their diselenides). Some of the 5-seleninic acids which carry long side chains or cyclohexyl group have exerted no GPx–like activity, irrespective of whether they are derived from ω-carboxyalkylamines or simple alkylamines. Such lacks of GPx-like activity let us quantitatively relate the GPx-like activities of the congeners of the above 3 series with their hydrophobicity (ClogP), which showed satisfactory correlations in each series. The molecular hydrophobicity was then extensively applied to diverse known aromatic selenium GPx mimics including diaryl diselenides and ebselen derivatives to explain their GPx-like activities in comparably quantitative mode, which could be helpful in designing new improved GPx mimic analogues in each series.

Chalcogen-containing phenolics as antiproliferative agents.

The increasing number of cancer cases has stimulated researchers to seek for novel approaches. We have combined two bioactive moieties: a polyphenolic scaffold and an organoselenium motif. Four different families (isothiocyanates/thioureas, and their selenium isosters) derived from dopamine, (±)-norepinephrine and R-epinephrine were accessed. Heterocumulenes derived from dopamine and β-O-methylnoradrenaline were strong antiproliferative agents (GI50<10μM). Selenoureas derived from β-O-methylnoradrenaline bearing electron-withdrawing groups (halogen, -NO2, -Ph) on the phenyl ring, were also strong antiproliferative agents, besides exhibiting good antiradical and glutathione peroxidase-like activities. Up to a 14-fold increased activity was achieved compared with classical chemotherapeutic agents, exhibiting also different mechanisms of action (cell cycle assays). Redox analysis on HeLa cells suggested an increase of ROS levels after the incubation period. the combination of organoselenium and phenolic moieties might provide valuable lead compounds with relevant antiproliferative properties.

Glutathione Peroxidase-Like Activity of Amino-Substituted Water-Soluble Cyclic Selenides: A Shift of the Major Catalytic Cycle in Methanol.

We previously reported that water-soluble cyclic selenides can mimic the antioxidative function of glutathione peroxidase (GPx) in water through a simple catalytic cycle, in which the selenide (>Se) is oxidized by H2O2 to the selenoxide (>Se=O) and the selenoxide is reduced by a thiol back to the selenide. In methanol, however, the GPx-like activity could not be explained by this simple scenario. To look into the reasons for the unusual behaviors in methanol, monoamino-substituted cyclic selenides with a variable ring size were synthesized, and the intermediates of the catalytic cycle were characterized by means of 77Se-NMR and LC–MS spectroscopies. In water, it was confirmed that the selenide and the selenoxide mainly contribute to the antioxidative function, though a slight contribution from the dihydroxy selenane (>Se(OH)2) was also suggested. In methanol, on the other hand, other active species, such as hydroxyselenonium (>Se+–OH) and hydroxy perhydroxy selenane (>Se(OH)(OOH)), could be generated to build another catalytic cycle. This over-oxidation would be more feasible for amino-substituted cyclic selenides, probably because the ammonium (NH3+) group would transfer a proton to the selenoxide moiety to produce a hydroxyselenonium species in the absence of an additional proton source. Thus, a shift of the major catalytic cycle in methanol would make the GPx-like antioxidative function of selenides perplexing.

Antifungal organoselenium compound loaded nanoemulsions stabilized by bifunctional cationic surfactants

Over last few decades, organoselenium compounds have been extensively studied in organic and medicinal chemistry. Ebselen (2-phenylbenzisoselenazol-3(2H)-one, BSe) and its analogues have emerged as potential pharmaceuticals and promising catalysts of various oxidation reactions and potential pharmaceuticals. For instance, their biological interest relies on their antioxidant, anti-inflammatory and glutathione peroxidase-like activities as well as antimicrobial, antiviral and chemopreventive effects. One of the major obstacles for their practical use is poor water solubility. For this purpose the potential of dicephalic cationic surfactants, N,N-bis[3,3′-(trimethylammonio)propyl]alkylamide dichlorides, to form physically stable nanoemulsion-based drug carriers in the presence of a variety of oils (oleic acid, Capmul MCM and PG-8) and the organoselenium-derived cargo was explored. Nanoemulsions were characterized by visual and microscopic observations, as well as dynamic light scattering (DLS) measurements of particle size and distributions. Results of transmission electron microscopy (TEM) and DLS showed that nearly spherical droplets of very similar size were obtained, with oleic acid bringing best properties. Time-depended size (DH) and ξ-potential measurements, dispersion stability test and kinetic stability studies with multiple light scattering (MLS) technique proved high colloid stability of the fabricated systems. Positively charged nanoemulsions with high ξ-potential values up to 87mV showed no significant evolution in backscattering profiles. The nanoemulsions were evaluated for antimicrobial efficacy towards Candida albicans and its biofilm. Strong antifungal activity was observed, with deleterious morphological changes in cellular structures and yeasts cell surface alterations. In conclusion, the designed oil-in-water nanoemulsion-based carriers, stabilized by dicephalic cationic surfactants can comprise a promising delivery system for poorly water soluble organoselenium derivatives of efficient antimicrobial activities.

Evaluation of the toxicity of α-(phenylselanyl) acetophenone in mice

Selenium is an essential micronutrient with several biological roles in the human body, but supra nutritional consumption can cause toxic effects. The potential deleterious effects of organoselenium compounds are controversial. The compound α-(phenylselanyl) acetophenone (PSAP) exhibits antioxidant, antidepressant-like and glutathione peroxidase-like activity, which makes important the elucidation of any toxic effects. Hence, the present study aims to investigate the in vitro toxicity of PSAP in Chinese Hamster ovary cells (through MTT assay) and analyse its genotoxicity using the comet assay in mice leukocytes after acute or chronic treatments, alongside with biochemical analyses. Our results demonstrate that the oral administration of PSAP in acute (1, 5, 10, 50, 200 mg/kg) and chronic (1, 10, 50, 200 mg/kg) doses did not cause genotoxicity. The compound presented cytotoxic effect in the MTT assay just at 500 μM after 24 h of administration and at 250 and 500 μM after 48 and 72 h of administration. According to biochemical analysis, PSAP presented a minor toxic effect by altering δ-ALA-D activity in liver and catalase activity in kidney at the highest tested concentration. Taking together, these data indicate that PSAP has low toxic effects after chronic administration in mice.

Synthesis, Structure and Antioxidant Activity of Cyclohexene-Fused Selenuranes and Related Derivatives.

Synthesis, structure and antioxidant activity of new cyclohexene-fused spiroselenuranes and a spirotellurane is reported. Oxidation reactions of bis(o-formylcyclohex-1-ene)selenide/bis(2-hydroxymethylcyclohex-1-ene)selenide provide the corresponding spiroselenuranes. The glutathione peroxidase-like activity of the newly synthesized compounds has been evaluated.

Introduction of a catalytic triad increases the glutathione peroxidase-like activity of diaryl diselenides.

Reactive oxygen species (ROS)-mediated diseased states are of major concern in modern day life. Under oxidative stress conditions, the cellular antioxidants deplete, leading to several biological disorders. Small molecule mimics of different antioxidant enzymes are found to be useful in supplementing the biological systems to detoxify ROS. In this study, we have synthesized a series of amine or amide-based diselenides containing an additional amino group as glutathione peroxidase (GPx) mimetics. These diselenides act as a catalytic triad model of the native GPx featuring two basic amino groups near the selenium centre. A comparison of the catalytic activities reveals that the additional amino group increases the activity significantly in the presence of aromatic thiols. Deprotonation of thiol by an additional amine either stabilizes the selenolate intermediate or facilitates the nucleophilic attack of thiol in other intermediates. The (77)Se NMR experiments and DFT calculations show that the amino group does not have any significant effect on the catalytic intermediates. Although the amino moiety increases the nucleophilicity of the thiol, it does not prevent the thiol exchange reactions that take place in the selenenyl sulfide intermediates.

Effects of methoxy substituents on the glutathione peroxidase-like activity of cyclic seleninate esters.

Cyclic seleninate esters function as mimetics of the antioxidant enzyme glutathione peroxidase and catalyze the reduction of hydrogen peroxide with a stoichiometric thiol. While a single electron-donating methoxy substituent para to the selenium atom enhances the catalytic activity, m-methoxy groups have little effect and o-methoxy substituents suppress activity. The effects of multiple methoxy groups are not cumulative. This behavior can be rationalized by opposing mesomeric and steric effects. Oxidation of the product disulfide via its thiolsulfinate was also observed.

Pyridoxine-derived organoselenium compounds with glutathione peroxidase-like and chain-breaking antioxidant activity.

One of the vitamin B6 vitamers, pyridoxine, was modified to incorporate selenium in various oxidation states in place of the methyl group in position 2. Such compounds were conveniently accessed by treatment of bis-4,5-(carboethoxy)-2-iodo-3-pyridinol with disodium diselenide and LiAlH4 -reduction. After work-up, selone 7 was isolated in good yield as an air-stable crystalline material. Hydrogen bonding to the neighboring hydroxyl group, as revealed by the short intramolecular Se⋅⋅⋅H distance in the crystal structure is likely to provide extra stabilization to the compound. Computational studies showed that selone 7 is more stable than the corresponding selenol tautomer by 12.2 kcal mol(-1) . Hydrogen peroxide oxidation of the selone 7 afforded diselenide 12, and, on further oxidation, seleninic acid 13. Treatment of the seleninic acid with thiophenol provided an isolable selenosulfide 14. The glutathione peroxidase-like properties of the pyridoxine-derived compounds were assessed by using the coupled reductase method. Seleninic acid 13 was found to be twofold more active than ebselen. The chain-breaking capacity of the pyridoxine compounds were studied in a water/chlorobenzene membrane model containing linoleic acid as an oxidizable substrate and N-acetylcysteine as a thiol reducing agent. Diselenide 15 could match α-tocopherol when it comes to reactivity towards peroxyl radicals and inhibition time.

Synthesis and Evaluation of Multi-Target-Directed Ligands against Alzheimer’s Disease Based on the Fusion of Donepezil and Ebselen

A novel series of compounds obtained by fusing the cholinesterase inhibitor donepezil and the antioxidant ebselen were designed as multi-target-directed ligands against Alzheimer's disease. An in vitro assay showed that some of these molecules did not exhibit highly potent cholinesterase inhibitory activity but did have various other ebselen-related pharmacological effects. Among the molecules, compound 7d, one of the most potent acetylcholinesterase inhibitors (IC50 values of 0.042 μM for Electrophorus electricus acetylcholinesterase and 0.097 μM for human acetylcholinesterase), was found to be a strong butyrylcholinesterase inhibitor (IC50 = 1.586 μM), to possess rapid H2O2 and peroxynitrite scavenging activity and glutathione peroxidase-like activity (ν0 = 123.5 μM min(-1)), and to be a substrate of mammalian TrxR. A toxicity test in mice showed no acute toxicity at doses of up to 2000 mg/kg. According to an in vitro blood-brain barrier model, 7d is able to penetrate the central nervous system.