Thiol Group Of Glutathione Research Articles

Identification of naphthalimide-derivatives as novel PBD-targeted polo-like kinase 1 inhibitors with efficacy in drug-resistant lung cancer cells

Targeting polo-box domain (PBD) small molecule for polo-like kinase 1 (PLK1) inhibition is a viable alternative to target kinase domain (KD), which could avoid pan-selectivity and dose-limiting toxicity of ATP-competitive inhibitors. However, their efficacy in these settings is still low and inaccessible to clinical requirement. Herein, we utilized a structure-based high-throughput virtual screen to find novel chemical scaffold capable of inhibiting PLK1 via targeting PBD and identified an initial hit molecule compound 1a. Based on the lead compound 1a, a structural optimization approach was carried out and several series of derivatives with naphthalimide structural motif were synthesized. Compound 4Bb was identified as a new potent PLK1 inhibitor with a KD value of 0.29 μM. 4Bb could target PLK1 PBD to inhibit PLK1 activity and subsequently suppress the interaction of PLK1 with protein regulator of cytokinesis 1 (PRC1), finally leading to mitotic catastrophe in drug-resistant lung cancer cells. Furthermore, 4Bb could undergo nucleophilic substitution with the thiol group of glutathione (GSH) to disturb the redox homeostasis through exhausting GSH. By regulating cell cycle machinery and increasing cellular oxidative stress, 4Bb exhibited potent cytotoxicity to multiple cancer cells and drug-resistant cancer cells. Subcutaneous and oral administration of 4Bb could effectively inhibit the growth of drug-resistant tumors in vivo, doubling the survival time of tumor bearing mice without side effects in normal tissues. Thus, our study offers an orally-available, structurally-novel PLK1 inhibitor for drug-resistant lung cancer therapy.

Dual-function sensor based on NH2-MIL-101(Fe)@Cu/CeO2 nanozyme for colorimetric and fluorescence detection of heavy metals

Heavy metal ions exhibit significant toxicity and pose threats to ecosystems and human health. Therefore, the development of sensitive detection methods is crucial. Nanozyme-based heavy metal sensors have garnered attention, yet existing nanozymes often suffer from low catalytic activity, limited functionality, and unclear mechanisms. To address these issues, this study successfully synthesized an organic-inorganic hybrid nanozyme (NH2-MIL-101(Fe)@Cu/CeO2) using doping and composite techniques, creating a dual-functional sensor. It's worth noting that in NH2-MIL-101(Fe)@Cu/CeO2, copper doping and heterojunction formation may increase oxygen vacancy concentration, promoting electron transfer. Compared to individual components like amino-terephthalic acid iron (III) metal-organic framework (NH2-MIL-101(Fe)) and copper-doped cerium dioxide (Cu/CeO2), this composite material exhibited enhanced peroxidase-like activity (oxidase-like, peroxidase-mimic, catalase-mimic, and superoxide dismutase-mimic). Particularly, NH2-MIL-101(Fe)@Cu/CeO2 displayed outstanding peroxidase-like activity, with Km values of 0.02 mM for TMB and 0.49 mM for H2O2, surpassing most nanozymes, along with high reaction rate (Vmax = 3.82 × 10−5 mM/s). Leveraging NH2-MIL-101(Fe)@Cu/CeO2's peroxidase-like behavior, TMB oxidation turned blue, inhibited by glutathione causing fading. Importantly, Hg2+ complexed with glutathione's thiol group forming GSH-Hg2+, restoring the blue color. Utilizing these properties, a colorimetric sensor for Hg2+ detection was developed. Furthermore, NH2-MIL-101(Fe)@Cu/CeO2 also exhibited remarkable fluorescence performance; Cu2+ binding with amino groups quenched fluorescence. Exploiting this phenomenon, a fluorescent sensor for Cu2+ detection was devised. Results demonstrated this dual-functional sensor's advantages: high sensitivity (LODHg2+ = 0.7 nM, LODCu2+ = 0.1 µM), strong selectivity, wide linear range (0.01 ∼ 4 µM and 8 ∼ 600 µM), and robust stability (90 % activity retained after three cycles).

Catalytic and molecular properties of alkaliphilic and thermotolerant β-etherase from Altererythrobacter sp. B11.

Phenylpropanone monomers, including guaiacyl hydroxypropanone, are important precursors for the synthesis of various chemicals. The monomers are obtained in a three-step cascade reaction catalyzed by a group of enzymes in the β-etherase system that cleaves the β-O-4 bond, the major bond in lignin. In this study, one of the β-etherase of the glutathione-S-transferase superfamily, AbLigF2, was discovered in genus Altererythrobacter, and the recombinant etherase was characterized. The enzyme showed maximal activity at 45°C, maintained 30% of its activity after 2h at 50°C, and was the most thermostable among the previously reported enzymes. Moreover, N13, S14, and S115, located near the thiol group of glutathione, had a significant effect on the maximum reaction rate of enzyme activity. This study suggests that AbLigF2 has the potential to serve as a thermostable enzyme for lignin utilization and provides insights into its catalytic mechanism.

Functional significance of serine 13 in the active site of glutathione S-transferase F3 from Oryza sativa

Plant glutathione S-transferase (GST, EC 2.5.1.18) is an enzyme that detoxifies various electrophilic compounds including herbicides and organic pollutants by catalyzing the formation of conjugates with reduced glutathione (GSH). Although the structure and function of the GST subunits in rice, an important food in Asia, are not well understood, they are crucial for herbicide development. To investigate the role of active site residues in rice Phi-class GSTF3 (OsGSTF3), evolutionarily conserved serine residues were replaced with alanine using site-directed mutagenesis to obtain the mutants S13A, S38A, S69A, and S169A. These four mutants were expressed in Escherichia coli and purified to electrophoretic homogeneity using immobilized GSH affinity chromatography. Mutation of Ser13 to Ala resulted in substantial reductions in specific activities and kcat/Km values for the GSH-[1-chloro-2,4-dinitrobenzene (CDNB)] conjugation reaction. In contrast, mutations of Ser38, Ser69, and Ser169 to Ala had little effect on the activities and kinetic parameters. Additionally, the mutation of Ser13 to Ala significantly affected the KmGSH and I50 values of S-hexylglutathione and S-(2,4-dinitrophenyl)glutathione, which compete with GSH and the product of GSH-CDNB conjugation, respectively. A pH-log (kcat/KmCDNB) plot was used to estimate the pKa value of GSH in the enzyme-GSH complex of the wild-type enzyme, which was approximately 6.9. However, the pKa value of GSH in the enzyme-GSH complex of the S13A mutant was approximately 8.7, which was about 1.8 pK units higher than that of the wild-type enzyme. OsGSTF3 was also crystallized for crystallographic study, and the structure analyses revealed that Ser13 is located in the active site and that its side chain is in close proximity to the thiol group of glutathione bound in the enzyme. Based on these substitution effects on kinetic parameters, the dependence of kinetic parameters on the pH and 3-dimensional structure, it was suggested that Ser13 in rice OsGSTF3 is the residue responsible for catalytic activity by lowering the pKa of GSH in the enzyme-GSH complex and enhancing the nucleophilicity of the GSH thiol in the active site.

Peptide Cysteine Thiols Act as Photostabilizer of Avobenzone through Stabilizing the Transition State of Keto-Enol Tautomerization.

Photostabilizers have been used to impart stability to an FDA-approved chemical UV-A filter avobenzone against the UV-A radiations and sunlight. The thiol group of glutathione plays a critical role in imparting the photostabilization activity of glutathione on avobenzone. The current report aims to evaluate the photostabilization activity of multiple thiols containing cysteine peptides on avobenzone. Cysteine-tripeptide and cysteine-pentapeptide were chemically synthesized and characterized using mass spectrometry. Synthetic peptides were assessed for their photostabilization activity on the enolic-form of the avobenzone under natural sunlight using UV spectroscopy in both protic and aprotic solvents. Unlike glutathione, which has pronounced activity in protic solvents, cysteine-pentapeptide exhibits similar photoprotection activity in both protic and aprotic solvents. Computational calculations using DFT suggest that peptide cysteine thiols may assist in the reversal of the photoketonization process of avobenzone thereby exhibiting the photoprotection activity to the enolic-form of avobenzone. Peptide cysteine thiols lower the activation energy barrier of keto-to-enol tautomerization of avobenzone by 30 kcal mol-1 by assisting the proton shuttle through a six-membered transition state. The current report emphasizes the applications of peptide thiols in cosmetics and may help in the development of peptides as aesthetic medicines.

Endogenous formaldehyde scavenges cellular glutathione resulting in redox disruption and cytotoxicity

Formaldehyde (FA) is a ubiquitous endogenous and environmental metabolite that is thought to exert cytotoxicity through DNA and DNA-protein crosslinking, likely contributing to the onset of the human DNA repair condition Fanconi Anaemia. Mutations in the genes coding for FA detoxifying enzymes underlie a human inherited bone marrow failure syndrome (IBMFS), even in the presence of functional DNA repair, raising the question of whether FA causes relevant cellular damage beyond genotoxicity. Here, we report that FA triggers cellular redox imbalance in human cells and in Caenorhabditis elegans. Mechanistically, FA reacts with the redox-active thiol group of glutathione (GSH), altering the GSH:GSSG ratio and causing oxidative stress. FA cytotoxicity is prevented by the enzyme alcohol dehydrogenase 5 (ADH5/GSNOR), which metabolizes FA-GSH products, lastly yielding reduced GSH. Furthermore, we show that GSH synthesis protects human cells from FA, indicating an active role of GSH in preventing FA toxicity. These findings might be relevant for patients carrying mutations in FA-detoxification systems and could suggest therapeutic benefits from thiol-rich antioxidants like N-acetyl-L-cysteine.

Allicin, an Antioxidant and Neuroprotective Agent, Ameliorates Cognitive Impairment.

Allicin (diallylthiosulfinate) is a defense molecule produced by cellular contents of garlic (Allium sativum L.). On tissue damage, the non-proteinogenic amino acid alliin (S-allylcysteine sulfoxide) is converted to allicin in an enzyme-mediated process catalysed by alliinase. Allicin is hydrophobic in nature, can efficiently cross the cellular membranes and behaves as a reactive sulfur species (RSS) inside the cells. It is physiologically active molecule with the ability to oxidise the thiol groups of glutathione and between cysteine residues in proteins. Allicin has shown anticancer, antimicrobial, antioxidant properties and also serves as an efficient therapeutic agent against cardiovascular diseases. In this context, the present review describes allicin as an antioxidant, and neuroprotective molecule that can ameliorate the cognitive abilities in case of neurodegenerative and neuropsychological disorders. As an antioxidant, allicin fights the reactive oxygen species (ROS) by downregulation of NOX (NADPH oxidizing) enzymes, it can directly interact to reduce the cellular levels of different types of ROS produced by a variety of peroxidases. Most of the neuroprotective actions of allicin are mediated via redox-dependent pathways. Allicin inhibits neuroinflammation by suppressing the ROS production, inhibition of TLR4/MyD88/NF-κB, P38 and JNK pathways. As an inhibitor of cholinesterase and (AChE) and butyrylcholinesterase (BuChE) it can be applied to manage the Alzheimer’s disease, helps to maintain the balance of neurotransmitters in case of autism spectrum disorder (ASD) and attention deficit hyperactive syndrome (ADHD). In case of acute traumatic spinal cord injury (SCI) allicin protects neuron damage by regulating inflammation, apoptosis and promoting the expression levels of Nrf2 (nuclear factor erythroid 2-related factor 2). Metal induced neurodegeneration can also be attenuated and cognitive abilities of patients suffering from neurological diseases can be ameliorates by allicin administration.

CdSe/ZnS quantum dots capped with oleic acid and L-glutathione: Structural properties and application in detection of Hg2+

Two structures of CdSe/ZnS quantum dots (QDs), with different solubility properties, were prepared, characterized, and applied as fluorescent-based probes to detect Hg2+ ions. From oleic acid-capped CdSe/ZnS QDs (CdSe/ZnS/OA), glutathione-capped CdSe/ZnS QDs (CdSe/ZnS/GSH) were obtained by a ligand exchange reaction upon microwave radiation. X-ray diffraction (XRD), Fourier-Transform Infrared (FT-IR), and X-ray Photoelectron Spectroscopy (XPS) were employed to determine crystallinity, structural characteristics, and chemical composition according to the capping agent. Synthesis methodology produced nanocrystals with cubic zinc blende structure. The coordination mode between the carboxylate group of oleic acid (OA) and the thiol group of glutathione (GSH), and the Zn2+ ions of QDs surface was discussed. Ultraviolet-visible (UV–Vis) spectroscopy and photoluminescence (PL) measurements characterized the optical properties of QDs. The replacement of OA by GSH ligands on QDs surface produced a red-shift of the first absorption maximum and the emission band. Photoluminiscence quantum yield (PL QY) improved from 20% (for CdSe/ZnS/OA) to 26% (for CdSe/ZnS/GSH). The fluorescence (FL) quenching of Hg2+ induction was studied considering the solubility properties of the two structures of QDs. Measurements for hydrophobic CdSe/ZnS/OA QDs were realized in a heterogeneous medium composed of toluene and water. While for CdSe/ZnS/GSH, experiments were carried out in an aqueous solution. Hg2+ ions quenched 100% fluorescence of both structures of QDs, displaying high selectivity, rapid response time. The limit of detection (LOD) for CdSe/ZnS/OA was 74.8 nM and for CdSe/ZnS/GSH was 54.8 nM. Results indicate that the two CdSe/ZnS core/shell QDs are candidates for Hg2+ and other metal ions sensing.

Tumor Microenvironment Modulation Platform Based on Composite Biodegradable Bismuth-Manganese Radiosensitizer for Inhibiting Radioresistant Hypoxic Tumors.

Solid tumors possess a unique internal environment with high-level thiols (mainly glutathione), over-expressed H2 O2 , and low oxygen partial pressure, which severely restrict the radiotherapy (RT) efficacy. To overcome the imperfections of RT alone, there is vital to design a multifunctional radiosensitizer that simultaneously achieves multimodal therapy and tumor microenvironment (TME) regulation. Bismuth (Bi)-based nanospheres are wrapped in the MnO2 layer to form core-shell-structured radiosensitizer (Bi@Mn) that can effectively load docetaxel (DTX). The solubility of Bi@Mn-DTX is further improved via folic acid-modified amphiphilic polyethylene glycol (PFA). Bi@Mn-DTX-PFA can specifically respond to the TME to realize multimodal therapy. Primarily, the outer MnO2 layer responds with H2 O2 and glutathione to release oxygen and generate •OH, thereby alleviating hypoxia and achieving chemodynamic therapy (CDT). Afterward, the strong coordination between Bi3+ and deprotonated thiol groups in glutathione allows the mesoporous Bi-containing core bonding with glutathione to form a water-soluble complex. These actions conduce Bi@Mn-DTX-PFA degradation, further releasing DTX to implement chemotherapy (CHT). In addition, the degradation in vivo and tumor enrichment of Bi@Mn-PFA are explored via T1 -weighted magnetic resonance and computed tomography imaging. The biodegradable composite Bi@Mn-DTX-PFA can simultaneously modulate the TME and achieve multimodal treatment (RT/CDT/CHT) for hypoxic tumors.

Environmentally friendly recycling system for epoxy resin with dynamic covalent bonding

ABSTRACT Recycling of epoxy resin and its composites is extremely difficult due to its thermoset nature. In this study, we proposed the environmentally-friendly recycling system of epoxy resin with dynamic covalent bonding in the assistance of cysteine-containing tripeptide, so-called glutathione. The glutathione attached on the epoxy resin and resulted in the cleavage of dynamic disulfide bonds of epoxy resin through thiol-disulfide exchange reaction between the thiol group of glutathione and disulfide bonding of epoxy resin, followed by the scission of epoxy networks. Therefore, the degraded epoxy residue was dissolved into chloroform. Finally, this resulting product could be reused as reagent for preparation the new epoxy materials with approximately 90% of initial mechanical strength via regeneration of disulfide bonding through heating. This work demonstrated the different aspect to understand the decomposition and recycling of thermosetting networks and the wide application under more environmentally friendly condition.

Molecular characterization, immune and xenobiotic responses of glutathione S-transferase omega 1 from the big-belly seahorse: Novel insights into antiviral defense

Glutathione S-transferases (GSTs) are important enzymes involved in phase II detoxification and function by conjugating with the thiol group of glutathione. In this study, we isolated an omega class GST from the big-belly seahorse (Hippocampus abdominalis; HaGSTO1) to study the putative xenobiotic responses and defense ability against viral and bacterial infections in this animal. The isolated HaGSTO1 gene, with a cording sequence of 720 bp, encodes a peptide of 239 amino acids. The predicted molecular mass and theoretical isoelectric point of HaGSTO1 was 27.47 kDa and 8.13, respectively. In-silico analysis of HaGSTO1 revealed a characteristic N-terminal thioredoxin-like domain and a C-terminal domain. Unlike other GSTs, the C-terminal of HaGSTO1 reached up to the N-terminal, and the N-terminal functional group was cysteine rather than tyrosine or serine, as observed in other GSTs. Phylogenetic analysis showed the evolutionary proximity of HaGSTO1 with other identified vertebrate and invertebrate GST orthologs. For the first time, we demonstrated the viral defense capability of HaGSTO1 against viral hemorrhagic septicemia virus (VHSV) infection. All six nucleoproteins of VHSV were significantly downregulated in HaGSTO1-overexpressing FHM cells at 24 h after infection compared with those in the control. Moreover, arsenic toxicity was significantly reduced in HaGSTO1-overexpressing FHM cells, and cell viability increased. Real-time polymerase chain reaction analysis showed that HaGSTO1 transcripts were highly expressed in the pouch and gill when compared with those in other tissues. Blood HaGSTO1 transcripts were significantly upregulated after Edwardsiella tarda, Streptococcus iniae, lipopolysaccharide, and polyinosinic:polycytidylic acid challenge experiments. Collectively, these findings suggest the involvement of HaGSTO1 in the host defense mechanism of seahorses.

Unveiling the Synergistic Role of Oxygen Functional Groups in the Graphene-Mediated Oxidation of Glutathione.

This is the first report of an atomic-scale direct oxidation mechanism of the thiol group in glutathione (GSH) by epoxides on graphene oxide (GO) at room temperature. The proposed reaction mechanism is determined using a coupled experimental and computational approach; active sites for the reaction are determined through examination of GO surface chemistry changes before and after exposure to GSH, and density functional theory (DFT) calculations determine the reaction barriers for the possible GO-GSH reaction schemes. The findings build on the previously established catalytic mechanism of GSH oxidation by graphenic nanocarbon surfaces and importantly identify the direct reaction mechanism which becomes important in low-oxygen environments. Experimental results suggest epoxides as the active sites for the reaction with GSH, which we confirm using DFT calculations of reaction barriers and further identify a synergism between the adjacent epoxide and hydroxyl groups on the GO surface. The direct oxidation mechanism at specific oxygen sites offers insight into controlling GO chemical reactivity through surface chemistry manipulations. This insight is critical for furthering our understanding of GO oxidative stress pathways in cytotoxicity as well as for providing rational material design for GO applications that can leverage this reaction.

Smart phone assisted quinoline-hemicyanine based fluorescent probe for the selective detection of glutathione and the application in living cells.

Quinoline appended hemicyanine 6MIM with strong ICT character was successfully synthesized through simple condensation reaction of 6-methoxy-2-chloro-3-formyl quinoline with 2-benzothiazolinium iodide. The photophysical characteristics of synthesized probe revealed that it would selectively detect glutathione (GSH) when it compared with different amino acids including biothiols and the detection limit is found to be 100nM. The turn off sensor is due to thiol-halogen SNAr nucleophilic substitution between 6MIM and thiol group in glutathione. More importantly, the biosensor 6MIM was effectively applied in the fluorescence bioimaging of GSH in living cells with low cell toxicity. The colorimetric detectable color change of 6MIM-GSH has been effectively integrated with smartphone assisted RGB color value application with lowest detection value of 120nM.

Antiproliferative and apoptotic interaction between azathioprine and N-acetylcysteine in acute lymphoblastic leukemia Jurkat cells

Abstract T cell acute lymphoblastic leukaemia is a type of cancer that develops from lymphoid progenitors, and chemotherapy is corner stone of the treatment. Thiopurine drugs, consisting of 6-mercaptopurine, 6-thioguanine, and azathioprine (Aza), can effectively treat this disease. To be activated, Aza must first be biotransformed to 6-mercaptopurine by thiol groups in glutathione. However, glutathione is decreased in cancer cells due to high levels of reactive oxygen species (ROS). N-acetylcysteine could provide thiol groups for glutathione synthesis to biotransform Aza. Using flow cytometry, the ability of N-acetylcysteine to increase the antiproliferative and apoptotic effects of Aza without increasing ROS was tested in Jurkat cells. Individually, Aza 1.0 and 2.0 μM, as well as N- acetylcysteine 3.0 mM, induced apoptosis and cell cycle arrest. Together, Aza + N-acetylcysteine significantly reduced proliferation compared to that obtained with the individual drugs. Combination of N-acetylcysteine 3.0 mM with Aza 1.0 μM was as effective at inducing apoptosis as Aza 2.0 μM alone. The combination of N-acetylcysteine 3.0 mM + Aza 1.0 μM increased cell cycle arrest at the G2/M phase. We found that Aza 1.0 or 2.0 μM induced a significant increase in ROS compared to that in untreated cells, while N-acetylcysteine 3.0 mM and N-acetylcysteine 3.0 mM + Aza 1.0 μM kept ROS at control levels; the latter drugpairing represents a favourable combination to reduce oxidative stress in the presence of Aza. In conclusion, N-acetylcysteine augments antiproliferative and apoptotic effects of Aza without increasing ROS in vitro.

Molecular characterization and functional analysis of glutathione S-transferase kappa 1 (GSTκ1) from the big belly seahorse (Hippocampus abdominalis): Elucidation of its involvement in innate immune responses

Glutathione S-transferases (GSTs) are essential enzymes for the bioactivation of xenobiotics through the conjugation of the thiol group of glutathione (GSH). In this study, a kappa class of GST was identified from the big belly seahorse (Hippocampus abdominalis) (HaGSTκ1) and its biochemical and functional properties were analyzed. HaGSTκ1 has 231 amino acids encoded by a 696 bp open reading frame (ORF). The protein has a predicted molecular mass of 26.04 kDa and theoretical isoelectric point (pI) of 8.28. It comprised a thioredoxin domain, disulfide bond formation protein A (DsbA) general fold, and Ser15 catalytic site as well as GSH-binding and polypeptide-binding sites. Phylogenetic analysis revealed that HaGSTκ1 is closely clustered with the kappa class of GSTs from teleost fishes. The recombinant (rHaGSTκ1) protein exhibited activity toward 1-chloro-2,4-dinitrobenzene (CDNB), 4-nitrobenzyl (4-NBC), and 4-nitrophenethyl bromide (4-NPB) but not 1,2-dichloro-4-nitrobenzene (DCNB). The optimum pH and temperature were 8 and 30 °C, respectively, for the catalysis of CDNB and the universal substrate of GSTs. The rHaGSTκ1 activity was efficiently inhibited in the presence of Cibacron blue (CB) as compared with hematin. Most prominent expression of HaGSTκ1 was observed in the liver and kidney among the fourteen different tissues of normal seahorse. After challenge with lipopolysaccharide (LPS), polyinosinic-polycytidylic (poly I:C), gram-negative Edwardsiella tarda, and gram-positive Streptococcus iniae, HaGSTκ1 expression was significantly modulated in the liver and blood tissues. Altogether, our study proposes the plausible important role of HaGSTκ1 in innate immunity and detoxification of harmful xenobiotics.

Glutathione as a photo-stabilizer of avobenzone: an evaluation under glass-filtered sunlight using UV-spectroscopy.

Avobenzone is the most widely used UVA filter in sunscreen lotion and it is prone to degradation in the presence of sunlight/UV radiation. To overcome the photo-instability of avobenzone, various photostabilizers have been used as additives, including antioxidants such as vitamin C, vitamin E, and ubiquinone. In the present study, the well known antioxidant, glutathione, was evaluated for protecting avobenzone from photodegradation in the presence of glass-filtered sunlight. The features of glutathione as a skin whitener and a radical scavenger in cells have prompted the assessment of the photostabilzing activity of glutathione on avobenzone. Glutathione significantly attenuated the glass-filtered sunlight-induced degradation of avobenzone at equimolar or higher ratios of glutathione and avobenzone. Mutational studies have been undertaken to investigate the role of the thiol group and the isopeptide bond of glutathione on its photoprotection activity towards avobenzone. The thiol group of glutathione plays a vital role in exhibiting the photoprotection activity, which was further supported by the studies on photodegradation of avobonzone in the presence of β-mercaptoethanol. The dual role of glutathione as a skin whitening agent and a photostabilizer of avobenzone may be useful for the development of multipurpose cosmetic lotions.

Dapsone and Nitroso Dapsone Activation of Naı̈ve T-Cells from Healthy Donors.

Dapsone (DDS) causes hypersensitivity reactions in 0.5-3.6% of patients. Although clinical diagnosis is indicative of a hypersensitivity reaction, studies have not been performed to define whether dapsone or a metabolite activates specific T-cells. Thus, the aims of this study were to explore the immunogenicity DDS and nitroso DDS (DDS-NO) using peripheral blood mononuclear cells from healthy donors and splenocytes from mice and generate human T-cell clones to characterize mechanisms of T-cell activation. DDS-NO was synthesized from DDS-hydroxylamine and shown to bind to the thiol group of glutathione and human and mouse albumin through sulfonamide and N-hydroxyl sulphonamide adducts. Naïve T-cell priming to DDS and DDS-NO was successful in three human donors. DDS-specific CD4+ T-cell clones were stimulated to proliferate in response to drug via a MHC class II restricted direct binding interaction. Cross reactivity with DDS-NO, DDS-analogues, and sulfonamides was not observed. DDS-NO clones were CD4+ and CD8+, MHC class II and I restricted, respectively, and activated via a pathway dependent on covalent binding and antigen processing. DDS and DDS-NO-specific clones secreted a mixture of Th1 and Th2 cytokines, but not granzyme-B. Splenocytes from mice immunized with DDS-NO were stimulated to proliferate in vitro with the nitroso metabolite, but not DDS. In contrast, immunization with DDS did not activate T-cells. These data show that DDS- and DDS-NO-specific T-cell responses are readily detectable.

The extreme hyper-reactivity of selected cysteines drives hierarchical disulfide bond formation in serum albumin.

After mild reduction of serum albumin, seven among the 34 cysteines forming the disulfide network displayed a surprising hyper-reactivity. Compared to the thiol group of glutathione, the average reactivity of these cysteines towards disulfides and thiol reagents was more than 100 times higher. Using mass spectrometry and kinetic data, we identified all these unusual residues, with Cys75, Cys123 and Cys264 showing the highest reactivity. This effect was mainly due to a low pKa of the sulfhydryl groups and may explain the very fast formation of early disulfides in the nascent protein suggesting the existence of a hierarchical propensity to form such covalent links in selected regions during oxidative folding. An identical pattern of hyper-reactive cysteines was found in albumins from six different mammals. This hyper-reactivity is much higher than the one found in other proteins containing multiple cysteines only devoted to structural disulfide bonds. It is possible that such hyper-reactive cysteines could also be present in other proteins, although their existence has been completely ignored so far.

Glutathione Bioresponsive Cyclodextrin Nanosponges.

Invited for this month's cover is Prof. Francesco Trotta's group from the University of Torino, Italy. The cover picture shows the chemical structure of a glutathione-responsive β-cyclodextrin nanosponge, bearing disulfide bridges and loaded with anticancer doxorubicin (red and white pills). Glutathione thiol groups are able to reduce the nanosponge disulfide moieties. The cleavage of the disulfide bridges allows a targeted release of anticancer drugs into glutathione-rich chemoresistant tumor cells. Read the full text of the article at 10.1002/cplu.201500531.

An Improved Process for Preparation of S-Acetyl-l-glutathione

An efficient one-step synthesis of S-acetyl-l-glutathione has been developed in a DMF–TFA mixed solvent with CoCl2 as catalyst. This process not only has the advantages of selective acylation of the glutathione thiol group without involving the free amino but also highlights recycling of the relatively costly solvent TFA, which improves the yield to 91% and quality to 99.7%. The reaction is cost-effective, efficient, and easy to scale-up.