Thiol Oxidation Research Articles

Antenatal creatine supplementation reduces persistent fetal lung inflammation and oxidative stress in an ovine model of chorioamnionitis.

Chorioamnionitis is a common antecedent of preterm birth and induces inflammation and oxidative stress in the fetal lungs. Reducing inflammation and oxidative stress in the fetal lungs may improve respiratory outcomes in preterm infants. Creatine is an organic acid with known anti-inflammatory and antioxidant properties. The objective of the study was to evaluate the efficacy of direct fetal creatine supplementation to reduce inflammation and oxidative stress in fetal lungs arising from an in utero proinflammatory stimulus. Fetal lambs (n = 51) were instrumented at 90 days gestation to receive a continuous infusion of creatine monohydrate (6 mg·kg-1·h-1) or saline for 17 days. Maternal chorioamnionitis was induced with intra-amniotic lipopolysaccharide (LPS; 1 mg, O55:H6) or saline 7 days before delivery at 110 days gestation. Tissue creatine content was assessed with capillary electrophoresis, and inflammatory markers were analyzed with Luminex Magpix and immunohistochemistry. Oxidative stress was measured as the level of protein thiol oxidation. The effects of LPS and creatine were analyzed using a two-way ANOVA. Fetal creatine supplementation increased lung creatine content by 149% (PCr<0.0001) and had no adverse effects on lung morphology. LPS-exposed groups showed increased levels of interleukin-8 in the bronchoalveolar lavage (PLPS<0.0001) and increased levels of CD45+ leukocytes (PLPS<0.0001) and MPO+ (PLPS<0.0001) cells in the lung parenchyma. Creatine supplementation significantly reduced the levels of CD45+ (PCr=0.045) and MPO+ cells (PCr=0.012) in the lungs and reduced thiol oxidation in plasma (PCr<0.01) and lung tissue (PCr=0.02). In conclusion, fetal creatine supplementation reduced markers of inflammation and oxidative stress in the fetal lungs arising from chorioamnionitis.NEW & NOTEWORTHY We evaluated the effect of antenatal creatine supplementation to reduce pulmonary inflammation and oxidative stress in the fetal lamb lungs arising from lipopolysaccharide (LPS)-induced chorioamnionitis. Fetal creatine supplementation increased lung creatine content and had no adverse effects on systemic fetal physiology and overall lung architecture. Importantly, fetuses that received creatine had significantly lower levels of inflammation and oxidative stress in the lungs, suggesting an anti-inflammatory and antioxidant benefit of creatine.

Innovative Application of Polyether Amine as a Recyclable Catalyst in Aerobic Thiophenol Oxidation

Polyether amines are versatile compounds characterized by a flexible structure, consisting of polyoxypropylene and polyoxyethylene as the backbone, with amine groups at each end. They have widespread applications in various industrial processes and daily life. Despite their versatility, the utilization of polyether amines as base catalysts is rare. In this study, one kind of three-arm polyether amine 1 was employed as an environmentally friendly, cost-effective catalyst for the aerobic oxidation of thiophenols, leading to the synthesis of disulfides. The oxidative coupling of thiols serves as a fundamental pathway for the production of disulfides, which are vital in both chemical and biological processes. In contrast to known methods for thiol oxidation, this polyether amine-based catalytic process eliminates the need for expensive stoichiometric oxidants and minimizes the formation of over-oxidized by-products. Using a mere 0.5 mol % of the polyether amine 1 as the catalyst, a remarkable &gt; 96% yield was achieved for all 16 tested substrates, encompassing a diverse range of functional groups, under the catalytic aerobic oxidation conditions. Furthermore, it is noteworthy that over 90% of the polyether amine catalyst can be efficiently recovered for reuse without loss of activity, making this a sustainable and cost-effective catalytic approach.

Enzymatically Triggered Peptide-Lipid Conjugation of Designed Membrane Active Peptides for Controlled Liposomal Release.

Possibilities for controlling the release of pharmaceuticals from liposomal drug delivery systems can enhance their efficacy and reduce their side effects. Membrane-active peptides (MAPs) can be tailored to promote liposomal release when conjugated to lipid head groups using thiol-maleimide chemistry. However, the rapid oxidation of thiols hampers the optimization of such conjugation-dependent release strategies. Here, we demonstrate a de novo designed MAP modified with an enzyme-labile Cys-protection group (phenylacetamidomethyl (Phacm)) that prevents oxidation and facilitates in situ peptide lipidation. Before deprotection, the peptide lacks a defined secondary structure and does not interact with maleimide-functionalized vesicles. After deprotection of Cys using penicillin G acylase (PGA), the peptide adopts an α-helical conformation and triggers rapid release of vesicle content. Both the peptide and PGA concentrations significantly influence the conjugation process and, consequently, the release kinetics. At a PGA concentration of 5 μM the conjugation and release kinetics closely mirror those of fully reduced, unprotected peptides. We anticipate that these findings will enable further refinement of MAP conjugation and release processes, facilitating the development of sophisticated bioresponsive MAP-based liposomal drug delivery systems.

Selenium catalysis enables negative feedback organic oscillators.

The construction of materials regulated by chemical reaction networks requires regulatory motifs that can be stacked together into systems with desired properties. Multiple autocatalytic reactions producing thiols are known. However, negative feedback loop motifs are unavailable for thiol chemistry. Here, we develop a negative feedback loop based on the selenocarbonates. In this system, thiols induce the release of aromatic selenols that catalyze the oxidation of thiols by organic peroxides. This negative feedback loop has two important features. First, catalytic oxidation of thiols follows Michaelis-Menten-like kinetics, thus increasing nonlinearity for the negative feedback. Second, the strength of the negative feedback can be tuned by varying substituents in selenocarbonates. When combined with the autocatalytic production of thiols in a flow reactor, this negative feedback loop induces sustained oscillations. The availability of this negative feedback motif enables the future construction of oscillatory, homeostatic, adaptive, and other regulatory circuits in life-inspired systems and materials.

Redox proteomics in melanoma cells: An optimized protocol

Cancer development and progression are intimately related with post-translational protein modifications, e.g., highly reactive thiol moiety of cysteines enables structural rearrangements resulting in redox biological switches. In this context, redox proteomics techniques, such as 2D redox DIGE, biotin switch assay and OxIcat are fundamental tools to identify and quantify redox-sensitive proteins and to understand redox mechanisms behind thiol modifications. Given the great variability in redox proteomics protocols, problems including decreased resolution of peptides and low protein amounts even after enrichment steps may occur. Considering the biological importance of thiol's oxidation in melanoma, we adapted the biotin-switch assay technique for melanoma cells in order to overcome the limitations and improve coverage of detected proteins.

A Conformational-Dependent Interdomain Redox Relay at the Core of Protein Disulfide Isomerase Activity.

Aims: Protein disulfide isomerases (PDIs) are a family of chaperones resident in the endoplasmic reticulum (ER). In addition to holdase function, some members catalyze disulfide bond formation and isomerization, a crucial step for native folding and prevention of aggregation of misfolded proteins. PDIs are characterized by an arrangement of thioredoxin-like domains, with the canonical protein disulfide isomerase A1 (PDIA1) organized as four thioredoxin-like domains forming a horseshoe with two active sites, a and a', at the extremities. We aimed to clarify important aspects underlying the catalytic cycle of PDIA1 in the context of the full pathways of oxidative protein folding operating in the ER. Results: Using two fluorescent redox sensors, redox green fluorescent protein 2 (roGFP2) and HyPer (circularly permutated yellow fluorescent protein containing the regulatory domain of the H2O2-sensing protein OxyR), either unfolded or native, as client substrates, we identified the N-terminal a active site of PDIA1 as the main oxidant of thiols. From there, electrons can flow to the C-terminal a' active site, with the redox-dependent conformational flexibility of PDIA1 allowing the formation of an interdomain disulfide bond. The a' active site then acts as a crossing point to redirect electrons to ER downstream oxidases or back to client proteins to reduce scrambled disulfide bonds. Innovation and Conclusions: The two active sites of PDIA1 work cooperatively as an interdomain redox relay mechanism that explains PDIA1 oxidative activity to form native disulfides and PDIA1 reductase activity to resolve scrambled disulfides. This mechanism suggests a new rationale for shutting down oxidative protein folding under ER redox imbalance. Whether it applies to physiological substrates in cells remains to be shown.

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Triphenylamine and its derivatives (TPAs) are promising for the photocatalytic oxidative coupling of thiols to disulfides, but suffer from the easy polymerization and difficult separation. In this paper, by immobilizing the TPAs into MOF with photoredox inert Sr nodes, the photo‐generated electrons were successfully controlled to transfer from the excited TPAs to O2, and finally realize the heterogeneous catalytic oxidation of thiols to disulfides. More details are discussed in the article by Zhang et al. on page 1093—1099.image

Pathological Impact of Redox Post-Translational Modifications.

Oxidative stress is involved in the development of several pathologies. The different reactive oxygen species (ROS) produced during oxidative stress are at the origin of redox post-translational modifications (PTMs) on proteins and impact nucleic acids and lipids. This review provides an overview of recent data on cysteine and methionine oxidation and protein carbonylation following oxidative stress in a pathological context. Oxidation, like nitration, is a selective process and not all proteins are impacted. It depends on multiple factors, including amino acid environment, accessibility, and physical and chemical properties, as well as protein structures. Thiols can undergo reversible oxidations and others that are irreversible. On the contrary, carbonylation represents irreversible PTM. To date, hundreds of proteins were shown to be modified by ROS and reactive nitrogen species (RNS). We reviewed recent advances in the impact of redox-induced PTMs on protein functions and activity, as well as its involvement in disease development or treatment. These data show a complex situation of the involvement of redox PTM on the function of targeted proteins. Many proteins can have their activity decreased by the oxidation of cysteine thiols or methionine S-methyl thioethers, while for other proteins, this oxidation will be activating. This complexity of redox PTM regulation suggests that a global antioxidant therapeutic approach, as often proposed, is unlikely to be effective. However, the specificity of the effect obtained by targeting a cysteine or methionine residue to be able to inactivate or activate a particular protein represents a major interest if it is possible to consider this targeting from a therapeutic point of view with our current pharmacological tools. Antioxid. Redox Signal. 41, 152-180.

Specificity and dynamics of H2O2 detoxification by the cytosolic redox regulatory network as revealed by in vitro reconstitution

The thiol redox state is a decisive functional characteristic of proteins in cell biology. Plasmatic cell compartments maintain a thiol-based redox regulatory network linked to the glutathione/glutathione disulfide couple (GSH/GSSG) and the NAD(P)H system. The basic network constituents are known and in vivo cell imaging with gene-encoded probes have revealed insight into the dynamics of the [GSH]2/[GSSG] redox potential, cellular H2O2 and NAD(P)H+H+ amounts in dependence on metabolic and environmental cues. Less understood is the contribution and interaction of the network components, also because of compensatory reactions in genetic approaches. Reconstituting the cytosolic network of Arabidopsis thaliana in vitro from fifteen recombinant proteins at in vivo concentrations, namely glutathione peroxidase-like (GPXL), peroxiredoxins (PRX), glutaredoxins (GRX), thioredoxins, NADPH-dependent thioredoxin reductase A and glutathione reductase and applying Grx1-roGFP2 or roGFP2-Orp1 as dynamic sensors, allowed for monitoring the response to a single H2O2 pulse. The major change in thiol oxidation as quantified by mass spectrometry-based proteomics occurred in relevant peptides of GPXL, and to a lesser extent of PRX, while other Cys-containing peptides only showed small changes in their redox state and protection. Titration of ascorbate peroxidase (APX) into the system together with dehydroascorbate reductase lowered the oxidation of the fluorescent sensors in the network but was unable to suppress it. The results demonstrate the power of the network to detoxify H2O2, the partially independent branches of electron flow with significance for specific cell signaling and the importance of APX to modulate the signaling without suppressing it and shifting the burden to glutathione oxidation.

Comparative kinetics of oxidation and GPx-like activity of 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane and 2,6-Dimethoxy-9-selenabicyclo[3.3.1]nonane

The first representative of a new class of organoselenium bicyclic compounds, 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane, was prepared by the iodine-mediated reaction of elemental selenium and 1,3-cyclooctadiene. Comparative kinetics of the oxidation of 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane 1 and its isomer 2,6-dimethoxy-9-selenabicyclo[3.3.1]nonane 2 were studied by 1H NMR spectroscopy and found to be dozens of times faster for the former. The catalytic activity of 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane 9-oxide formed in situ from 1 and simulating the GPx-like activity in oxidation of thiols by H2O2 in MeOH, is shown to be higher than that of the isomeric 2,6-dimethoxy-9-selenabicyclo[3.3.1]nonane 9-oxide.

A Comprehensive Review on Potential Molecular Drug Targets for the Management of Alzheimer's Disease.

Alzheimer's disease (AD) is an onset and incurable neurodegenerative disorder that has been linked to various genetic, environmental, and lifestyle factors. Recent research has revealed several potential targets for drug development, such as the prevention of Aβ production and removal, prevention of tau hyperphosphorylation, and keeping neurons alive. Drugs that target numerous ADrelated variables have been developed, and early results are encouraging. This review provides a concise map of the different receptor signaling pathways associated with Alzheimer's Disease, as well as insight into drug design based on these pathways. It discusses the molecular mechanisms of AD pathogenesis, such as oxidative stress, aging, Aβ turnover, thiol groups, and mitochondrial activities, and their role in the disease. It also reviews the potential drug targets, in vivo active agents, and docking studies done in AD and provides prospects for future drug development. This review intends to provide more clarity on the molecular processes that occur in Alzheimer's patient's brains, which can be of use in diagnosing and preventing the condition.

The role of GAPDH in the selective toxicity of CNP in melanoma cells.

Malignant melanoma is the most aggressive form of skin cancer with a rather poor prognosis. Standard chemotherapy often results in severe side effects on normal (healthy) cells finally being difficult to tolerate for the patients. Shown by us earlier, cerium oxide nanoparticles (CNP, nanoceria) selectively killed A375 melanoma cells while not being cytotoxic at identical concentrations on non-cancerous cells. In conclusion, the redox-active CNP exhibited both prooxidative as well as antioxidative properties. In that context, CNP induced mitochondrial dysfunction in the studied melanoma cells via generation of reactive oxygene species (primarily hydrogen peroxide (H2O2)), but that does not account for 100% of the toxicity. Cancer cells often show an increased glycolytic rate (Warburg effect), therefore we focused on CNP mediated changes of the glucose metabolism. It has been shown before that glyceraldehyde 3-phosphate dehydrogenase (GAPDH) activity is regulated via oxidation of a cysteine in the active center of the enzyme with a subsequent loss of activity. Upon CNP treatment, formation of cellular lactate and GAPDH activity were significantly lowered. The treatment of melanoma cells and melanocytes with the GAPDH inhibitor heptelidic acid (HA) decreased viability to a much higher extent in the cancer cells than in the studied normal (healthy) cells, highlighting and supporting the important role of GAPDH in cancer cells. We identified glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as a target protein for CNP mediated thiol oxidation.

Glutathione Protects other Cellular Thiols against Oxidation by CuII-Dp44mT.

Cu-thiosemicarbazones have been intensively investigated for their application in cancer therapy or as antimicrobials. Copper(II)-di-2-pyridylketone-4,4-dimethyl-thiosemicarbazone (CuII-Dp44mT) showed anticancer activity in the submicromolar concentration range in cell culture. The interaction of CuII-Dp44mT with thiols leading to their depletion or inhibition was proposed to be involved in this activity. Indeed, CuII-Dp44mT can catalyze the oxidation of thiols although with slow kinetics. The present work aims to obtain insights into the catalytic activity and selectivity of CuII-Dp44mT toward the oxidation of different biologically relevant thiols. Reduced glutathione (GSH), L-cysteine (Cys), N-acetylcysteine (NAC), D-penicillamine (D-Pen), and the two model proteins glutaredoxin (Grx) and thioredoxin (Trx) were investigated. CuII-Dp44mT catalyzed the oxidation of these thiols with different kinetics, with rates in the following order D-Pen>Cys≫NAC>GSH and Trx>Grx. CuII-Dp44mT was more efficient than CuII chloride for the oxidation of NAC and GSH, but not D-Pen and Cys. In mixtures of biologically relevant concentrations of GSH and either Cys, Trx, or Grx, the oxidation kinetics and spectral properties were similar to that of GSH alone, indicating that the interaction of these thiols with CuII-Dp44mT is dominated by GSH. Hence GSH could protect other thiols against potential deleterious oxidation by CuII-Dp44mT.

Ageing-dependent thiol oxidation reveals early oxidation of proteins with core proteostasis functions.

Oxidative post-translational modifications of protein thiols are well recognized as a readily occurring alteration of proteins, which can modify their function and thus control cellular processes. The development of techniques enabling the site-specific assessment of protein thiol oxidation on a proteome-wide scale significantly expanded the number of known oxidation-sensitive protein thiols. However, lacking behind are large-scale data on the redox state of proteins during ageing, a physiological process accompanied by increased levels of endogenous oxidants. Here, we present the landscape of protein thiol oxidation in chronologically aged wild-type Saccharomyces cerevisiae in a time-dependent manner. Our data determine early-oxidation targets in key biological processes governing the de novo production of proteins, protein folding, and degradation, and indicate a hierarchy of cellular responses affected by a reversible redox modification. Comparison with existing datasets in yeast, nematode, fruit fly, and mouse reveals the evolutionary conservation of these oxidation targets. To facilitate accessibility, we integrated the cross-species comparison into the newly developed OxiAge Database.

Immobilizing Triphenylamine with Photoredox Inert Sr2+ Forming Sr‐MOF with Controlled Electron Migration for Photocatalytic Oxidation of Thiols to Disulfides

Comprehensive SummaryThe photocatalytic oxidative coupling of thiols is one of the most popular methods to synthesize the disulfides. Triphenylamine and its derivatives (TPAs) are promising for the above reaction, but suffer from the easy polymerization and difficult separation. To overcome these obstacles while controlling the photogenerated electrons transfer directly to target substrates, herein, we constructed one TPA‐based metal‐organic framework (MOF), (Me2NH2)[Sr(TCBPA)]·DMA·3H2O (1), by direct self‐assembly of tris(4′‐carboxybiphenyl)amine (H3TCBPA) and photoredox inert strontium ion (Sr2+). DFT calculations revealed that the valence band maximum (VBM) and the conduction band minimum (CBM) are mainly located on TCBPA3–, successfully inhibiting the undesirable electron migration to metal nodes. Experimental results indicated that 1 displays superior performance than homogeneous H3TCBPA, which may result from the abundant π···π and C—H···π interactions between the well‐arranged TCBPA3– and the build‐in electric field between the anionic framework and the Me2NH2+. This work highlights that immobilizing TPAs into MOFs is one promising approach to designing heterogeneous photocatalysts for the synthesis of disulfides by oxidative coupling of thiols.

Using the heme peroxidase APEX2 to probe intracellular H2O2 flux and diffusion

Currently available genetically encoded H2O2 probes report on the thiol redox state of the probe, which means that they reflect the balance between probe thiol oxidation and reduction. Here we introduce the use of the engineered heme peroxidase APEX2 as a thiol-independent chemogenetic H2O2 probe that directly and irreversibly converts H2O2 molecules into either fluorescent or luminescent signals. We demonstrate sensitivity, specificity, and the ability to quantitate endogenous H2O2 turnover. We show how the probe can be used to detect changes in endogenous H2O2 generation and to assess the roles and relative contributions of endogenous H2O2 scavengers. Furthermore, APEX2 can be used to study H2O2 diffusion inside the cytosol. Finally, APEX2 reveals the impact of commonly used alkylating agents and cell lysis protocols on cellular H2O2 generation.

MOF-Enabled Electrochemical Sensor for Rapid and Robust Sensing of V-Series Nerve Agents at Low Concentrations.

Among nerve agents, V-series nerve agents are some of the most toxic, making low-concentration detection critical for the protection of individuals, populations, and strategic resources. Electrochemical sensors are ideally suited for the real-time and in-field sensing of these agents. While V-series nerve agents are inherently nonelectroactive, they can be hydrolyzed to electroactive products compatible with electrochemical sensing. Zr(IV) MOFs are next-generation nanoporous materials that have been shown to rapidly catalyze the hydrolysis of nerve agents. This work makes use of these nanomaterials to develop, for the first time, an MOF-enabled electrochemical sensor for V-series nerve agents. Our work demonstrates that the VX thiol hydrolysis product can be electrochemically detected at low concentrations using commercially available gold electrodes. We demonstrate that low-concentration thiol oxidation is an irreversible reaction that is dependent on both mass transport and adsorption. Demeton-S-methylsulfon, a VX simulant, is used to demonstrate the full range of sensor operation that includes hydrolysis and electrochemical detection. We demonstrate that MOF-808 rapidly, selectively, and completely hydrolyzes demeton-S-methylsulfon to less-hazardous dimethyl phosphate and 2-ethylsulfonylethanethiol. Low-concentration measurements of 2-ethylsulfonylethanethiol are performed by using electrochemical techniques. This sensor has a limit of detection of 30 nM or 7.87 μg/L for 2-ethylsulfonylethanethiol, which is near the nerve agent exposure limit for water samples established by the United States military. Our work demonstrates the feasibility of rapid, robust electrochemical sensing of V-series nerve agents at low concentrations for in-field applications.

Investigation of antimicrobial activity of Ultraviolet B radiation and its potential to generate fructose-mediated reactive oxygen species in coconut water

We evaluated the potential antimicrobial activity and inactivation kinetics, photo-reactivation potential and ability to generate reactive oxygen species (ROS) and consequent ascorbic acid degradation in fructose enriched coconut water. UV-B caused 4.5 ± 0.19 log inactivation in E. coli K12 at 0.45 J/cm2 and inactivation kinetics followed Weibull model, compared to log-linear 4 ± 0.05 log reduction at 0.2 J/cm2 dose of UV-C. A lower extent of UV-A (360 nm) induced photo-reactivation was observed in UV-B treated samples compared to UV-C. UV-B mediated microbial inactivation was largely caused by DNA damage and impaired metabolic activity of E. coli. UV-B treatment did not cause membrane damage, or thiol oxidation. Compared to UV-C, UV-B produced lower concentration of ROS from fructose. At a dose required for 4 log reduction of E. coli K12 by UV-B, only 8% ascorbic acid degraded. These results show that UV-B is an attractive alternative to UV-C treatment. Industrial relevanceUV-C irradiation is a cost-effective measure to ensure food safety. However, for fructose-rich products fruit juices, UV-C exposure to photo-sensitive compounds like fructose generates reactive oxygen species that can deteriorate the quality of fructose-rich products. In this context, UV-B provides comparable, albeit slower, antimicrobial effect but provokes milder fructose mediated oxidative stress than UV-C. This study highlights the potential for using UV-B as an alternative to UV-C light treatment for liquid foods.

Triphenylamine-Based Ordered Mesoporous Polymer as a Metal-Free Photocatalyst for Oxidation of Thiols to Disulfide

Triphenylamine-Based Ordered Mesoporous Polymer as a Metal-Free Photocatalyst for Oxidation of Thiols to Disulfide

Sustainable synthesis of thiosulfonates and disulfides by molybdenum-catalyzed selective oxidation of thiols

We report a polyoxomolybdate ([N(n-Bu)4]4Mo8O26) for the selective oxidation of thiols to thiosulfonates and disulfides with H2O2 and air as the oxidant, respectively.