Regulation of protein function by S-glutathiolation in response to oxidative and nitrosative stress

The garlic compound ajoene covalently binds vimentin, disrupts the vimentin network and exerts anti-metastatic activity in cancer cells

BACKGROUND

Garlic has been used for centuries for its flavour and health promoting properties that include protection against cancer. The vinyl disulfide-sulfoxide ajoene is one of the phytochemicals found in crushed cloves, hypothesised to act by S-thiolating reactive cysteines in target proteins.

METHODS

Using our fluorescently labelled ajoene analogue called dansyl-ajoene, ajoene's protein targets in MDA-MB-231 breast cancer cells were tagged and separated by 2D electrophoresis. A predominant band was identified by MALDI-TOF MS/MS to be vimentin. Target validation experiments were performed using pure recombinant vimentin protein. Computational modelling of vimentin bound to ajoene was performed using Schrödinger and pKa calculations by Epik software. Cytotoxicity of ajoene in MDA-MB-231 and HeLa cells was measured by the MTT assay. The vimentin filament network was visualised in ajoene-treated and non-treated cells by immunofluorescence and vimentin protein expression was determined by immunoblot. The invasion and migration activity was measured by wound healing and transwell assays using wildtype cells and cells in which the vimentin protein had been transiently knocked down by siRNA or overexpressed.

RESULTS

The dominant protein tagged by dansyl-ajoene was identified to be the 57 kDa protein vimentin. The vimentin target was validated to reveal that ajoene and dansyl-ajoene covalently bind to recombinant vimentin via a disulfide linkage at Cys-328. Computational modelling showed Cys-328 to be exposed at the termini of the vimentin tetramer. Treatment of MDA-MB-231 or HeLa cells with a non-cytotoxic concentration of ajoene caused the vimentin filament network to condense; and to increase vimentin protein expression. Ajoene inhibited the invasion and migration of both cancer cell lines which was found to be dependent on the presence of vimentin. Vimentin overexpression caused cells to become more migratory, an effect that was completely rescued by ajoene.

CONCLUSIONS

The garlic-derived phytochemical ajoene targets and covalently modifies vimentin in cancer cells by S-thiolating Cys-328. This interaction results in the disruption of the vimentin filament network and contributes to the anti-metastatic activity of ajoene in cancer cells.

The glutathione system and the related thiol network in Caenorhabditis elegans

Advances in the field of redox biology have contributed to the understanding of the complexity of the thiol-based system in mediating signal transduction. The redox environment is the overall spatiotemporal balance of oxidation-reduction systems within the integrated compartments of the cell, tissues and whole organisms. The ratio of the reduced to disulfide glutathione redox couple (GSH:GSSG) is a key indicator of the redox environment and its associated cellular health. The reaction mechanisms of glutathione-dependent and related thiol-based enzymes play a fundamental role in the function of GSH as a redox regulator. Glutathione homeostasis is maintained by the balance of GSH synthesis (de novo and salvage pathways) and its utilization through its detoxification, thiol signalling, and antioxidant defence functions via GSH-dependent enzymes and free radical scavenging. As such, GSH acts in concert with the entire redox network to maintain reducing conditions in the cell. Caenorhabditis elegans offers a simple model to facilitate further understanding at the multicellular level of the physiological functions of GSH and the GSH-dependent redox network. This review discusses the C. elegans studies that have investigated glutathione and related systems of the redox network including; orthologs to the protein-encoding genes of GSH synthesis; glutathione peroxidases; glutathione-S-transferases; and the glutaredoxin, thioredoxin and peroxiredoxin systems.

BODIPY-Based Fluorescent Probe for Dual-Channel Detection of Nitric Oxide and Glutathione: Visualization of Cross-Talk in Living Cells

Nitric oxide (NO) and glutathione (GSH) have interplaying roles in oxidant-antioxidant balance. In this work, we developed the first example of a single fluorescent probe that displayed a turn-on fluorescence response toward NO and GSH from dual emission channels. The probe was synthesized by introducing 4-amino-3-(methylamino)-phenol to a BODIPY scaffold. Specifically, the NO-mediated transformation of diamine into a triazole triggered the fluorescence in the green channel, and the GSH-induced S_NAr substitution reaction led to the red-shifted emission in the red channel. The probe was successfully applied to detect the exogenous and endogenous NO and GSH in macrophage cells. More importantly, the probe revealed that NO induced by interferon-γ (IFN-γ), lipopolysaccharide (LPS), and l-arginine (l-Arg) could also elicit the augmentation of intracellular GSH. We anticipate the probe would hold great potential for investigating the redox balance in biological processes.

Multifunctional PLGA-based nanoparticles as a controlled release drug delivery system for antioxidant and anticoagulant therapy

Background

Ischemia/reperfusion (I/R) injury causes the generation of many ROS such as H₂O₂ and leads to vascular thrombosis, which causes tissue damage.

Purpose

In this investigation, poly (lactideco-glycolide) (PLGA)-based nanoparticles are used for their anticoagulant and antioxidant properties in vascular therapy.

Methods

Both heparin and glutathione are entrapped on PLGA-stearylamine nanoparticles by layer-by-layer interactions.

Results

The drug release rate is successfully controlled with only 10.3% of the heparin released after 96 hours. An H₂O₂-responsive platform is also developed by combining silk fibroin and horse peroxidase to detect H₂O₂ in this drug delivery system. Besides, hyaluronic acid was decorated on the surface of nanoparticles to target the human bone marrow mesenchymal stem cells (hBMSCs) for cell therapy. The results of an in vitro study indicate that the nanoparticles could be taken up by hBMSCs within 2 hours and exocytosis occurred 6 hours after cellular uptake.

Conclusion

We propose that the multifunctional nanoparticles that are formed herein can be effectively delivered to the site of an I/R injury via the hBMSC homing effect. The proposed approach can potentially be used to treat vascular diseases, providing a platform for hBMSCs for the controlled delivery of a wide range of drugs.

Annexin A2 extracellular translocation and virus interaction: A potential target for antivirus-drug discovery

Annexin A2 is a membrane scaffolding and binding protein, which mediated various cellular events. Its functions are generally affected by cellular localization. In the cytoplasm, they interacted with different phospholipid membranes in Ca²⁺ -dependent manner and play vital roles including actin binding, remodeling and dynamics, cytoskeletal rearrangement, and lipid-raft microdomain formation. However, upon cell exposure to certain stimuli, annexin A2 translocates to the external leaflets of the plasma membrane where annexin A2 was recently reported to serve as a virus receptor, play an important role in the formation of virus replication complex, or implicated in virus assembly and budding. Here, we review some of annexin A2 roles in virus infections and the potentiality of targeting annexin A2 in the design of novel and promising antivirus agent that may have a broader consequence in virus therapy.

Neuroprotective Effects of Thymoquinone in Acrylamide-Induced Peripheral Nervous System Toxicity Through MAPKinase and Apoptosis Pathways in Rat

Acrylamide (ACR) is extensively used in industrial areas and has been demonstrated to induce neurotoxicity via oxidative stress and apoptosis. In this study, we assessed the probable protective effects of thymoquinone (TQ), an active constituent of Nigella sativa, against ACR-induced neurotoxicity. ACR (50 mg/kg, i.p., for 11 days) and TQ (2.5, 5 and 10 mg/kg, i.p., for 11 days) were administered to rats. On 12th day, gait score was examined and rats were sacrificed. Malondialdehyde (MDA) and reduced glutathione (GSH) contents were determined in sciatic nerve. Furthermore, western blotting was conducted. The exposure of rats to ACR caused severe gait disabilities. The MDA and GSH contents were increased and decreased, respectively. ACR decreased P-ERK/ERK ratio and myelin basic protein (MBP) content, but significantly increased P-JNK/JNK, P-P38/P38, Bax/Bcl-2 ratios and caspase 3 and 9 levels. Concurrently administration of TQ (5 and 10 mg/kg) with ACR, prevented gait abnormalities and meaningfully reduced MDA and elevated the GSH contents. Furthermore, TQ (5 mg/kg) elevated the P-ERK/ERK ratio and MBP content while reduced the P-JNK/JNK, P-P38/P38 ratios and apoptotic markers. MAP kinase and apoptosis signaling pathways were involved in ACR-induced neurotoxicity in rat sciatic nerve and TQ significantly reduced ACR neurotoxicity. TQ afforded neuroprotection, in part, due to its anti-oxidative stress and anti-apoptotic mechanisms.

Reversible S-glutathionylation of human 6-pyruvoyl tetrahydropterin synthase protects its enzymatic activity

6-Pyruvoyl tetrahydropterin synthase (PTS) converts 7,8-dihydroneopterin triphosphate into 6-pyruvoyltetrahydropterin and is a critical enzyme for the de novo synthesis of tetrahydrobiopterin, an essential cofactor for aromatic amino acid hydroxylases and nitric-oxide synthases. Neopterin derived from 7,8-dihydroneopterin triphosphate is secreted by monocytes/macrophages, and is a well-known biomarker for cellular immunity. Because PTS activity in the cell can be a determinant of neopterin production, here we used recombinant human PTS protein to investigate how its activity is regulated, especially depending on redox conditions. Human PTS has two cysteines: Cys-43 at the catalytic site and Cys-10 at the N terminus. PTS can be oxidized and consequently inactivated by H₂O₂ treatment, oxidized GSH, or S-nitrosoglutathione, and determining the oxidized modifications of PTS induced by each oxidant by MALDI-TOF MS, we show that PTS is S-glutathionylated in the presence of GSH and H₂O₂ S-Glutathionylation at Cys-43 protected PTS from H₂O₂-induced irreversible sulfinylation and sulfonylation. We also found that PTS expressed in HeLa and THP-1 cells is reversibly modified under oxidative stress conditions. Our findings suggest that PTS activity and S-glutathionylation is regulated by the cellular redox environment and that reversible S-glutathionylation protects PTS against oxidative stress.

KRIT1 Loss-Of-Function Associated with Cerebral Cavernous Malformation Disease Leads to Enhanced S-Glutathionylation of Distinct Structural and Regulatory Proteins

Loss-of-function mutations in the KRIT1 gene are associated with the pathogenesis of cerebral cavernous malformations (CCMs), a major cerebrovascular disease still awaiting therapies. Accumulating evidence demonstrates that KRIT1 plays an important role in major redox-sensitive mechanisms, including transcriptional pathways and autophagy, which play major roles in cellular homeostasis and defense against oxidative stress, raising the possibility that KRIT1 loss has pleiotropic effects on multiple redox-sensitive systems. Using previously established cellular models, we found that KRIT1 loss-of-function affects the glutathione (GSH) redox system, causing a significant decrease in total GSH levels and increase in oxidized glutathione disulfide (GSSG), with a consequent deficit in the GSH/GSSG redox ratio and GSH-mediated antioxidant capacity. Redox proteomic analyses showed that these effects are associated with increased S-glutathionylation of distinct proteins involved in adaptive responses to oxidative stress, including redox-sensitive chaperonins, metabolic enzymes, and cytoskeletal proteins, suggesting a novel molecular signature of KRIT1 loss-of-function. Besides providing further insights into the emerging pleiotropic functions of KRIT1, these findings point definitively to KRIT1 as a major player in redox biology, shedding new light on the mechanistic relationship between KRIT1 loss-of-function and enhanced cell sensitivity to oxidative stress, which may eventually lead to cellular dysfunctions and CCM disease pathogenesis.

Changes in lecithin: cholesterol acyltransferase, cholesteryl ester transfer protein and paraoxonase-1 activities in patients with colorectal cancer

BACKGROUND

Previous studies revealed decreased level of high-density lipoprotein cholesterol (HDLC) as important factor for development of colorectal cancer (CRC). Quantity and structure of HDL particles depend on activities of lipid transfer proteins lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP), but this topic is largely unexplored in CRC. The main objective of this study was to investigate activities of LCAT and CETP in patients with CRC. Additionally, we analyzed activity of paraoxonase-1 (PON-1), as a main carrier of HDL-antioxidant function.

MATERIALS AND METHODS

Ninety-nine CRC patients and 101 healthy individuals were included. LCAT and CETP activities were assessed by measuring rates of formation and transfer of cholesteryl esters. PON-1 paraoxonase and arylesterase activities were measured.

RESULTS

Lower levels of HDL-C (p < .001) were observed in cohort of patients, alongside with decreased LCAT (p < .050) and increased CETP activity (p < .050). Both PON-1 activities were diminished in CRC (p < .050 and p < .001 respectively). Univariate logistic regression singled out HDL-C level (OR = 0.218, p < .001), CETP activity (OR = 1.010, p < .01) and mass (OR = 0.994, p < .001) as possible markers of elevated CRC risk. CETP mass maintained its predictive significance when adjusted for traditional risk factors and level of oxidative stress (OR = 0.993, p < .001; OR = 0.982, p < .050, respectively).

CONCLUSION

Our results demonstrated increased CETP and decreased LCAT and PON-1 activities in CRC patients. In preliminary analysis CETP mass was identified as potential significant predictor of CRC development, suggesting that alterations in HDL-C levels, alongside with changes in HDL structure might have a role in carcinogenesis.

Thioredoxin and glutaredoxin regulate metabolism through different multiplex thiol switches

The aim of the present study was to define the role of Trx and Grx on metabolic thiol redox regulation and identify their protein and metabolite targets. The hepatocarcinoma-derived HepG2 cell line under both normal and oxidative/nitrosative conditions by overexpression of NO synthase (NOS3) was used as experimental model. Grx1 or Trx1 silencing caused conspicuous changes in the redox proteome reflected by significant changes in the reduced/oxidized ratios of specific Cys's including several glycolytic enzymes. Cys⁹¹ of peroxiredoxin-6 (PRDX6) and Cys¹⁵³ of phosphoglycerate mutase-1 (PGAM1), that are known to be involved in progression of tumor growth, are reported here for the first time as specific targets of Grx1. A group of proteins increased their Cys_RED/Cys_OX ratio upon Trx1 and/or Grx1 silencing, including caspase-3 Cys¹⁶³, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) Cys²⁴⁷ and triose-phosphate isomerase (TPI) Cys²⁵⁵ likely by enhancement of NOS3 auto-oxidation. The activities of several glycolytic enzymes were also significantly affected. Glycolysis metabolic flux increased upon Trx1 silencing, whereas silencing of Grx1 had the opposite effect. Diversion of metabolic fluxes toward synthesis of fatty acids and phospholipids was observed in siRNA-Grx1 treated cells, while siRNA-Trx1 treated cells showed elevated levels of various sphingomyelins and ceramides and signs of increased protein degradation. Glutathione synthesis was stimulated by both treatments. These data indicate that Trx and Grx have both, common and specific protein Cys redox targets and that down regulation of either redoxin has markedly different metabolic outcomes. They reflect the delicate sensitivity of redox equilibrium to changes in any of the elements involved and the difficulty of forecasting metabolic responses to redox environmental changes.

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Trx1 and Grx1 Cys redox targets are abundant among Glycolytic enzymes.

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PRDX6-Cys⁹¹ and PGAM-Cys¹⁵³ are specific targets of Grx1.

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Down regulation of thioredoxin and glutaredoxin have different metabolic outcomes.

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Glutathione synthesis and membrane lipid composition are sensitive to Trx1 and Grx1 down regulation.

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Redoxins down regulation also induce target Cys reductive changes under NOS3 overexpression.

Trigonelline therapy confers neuroprotection by reduced glutathione mediated myeloperoxidase expression in animal model of ischemic stroke

AIM

Stroke is devastating with a limited choice of intervention. Many pharmacological entities are available but none of them have evolved successfully in counteracting the multifaceted molecular alterations following stroke. Myeloperoxidase (MPO) has been reported to play an important role in neuroinflammation following neurodegenerative diseases. Therefore, using it as a therapeutic target may be a strategy to confer neuroprotection in stroke. Trigonelline (TG), a plant alkaloid has shown neuroprotective effects in the past. Here we explore its neuroprotective effects and its role in glutathione mediated MPO inhibition in ischemic stroke.

METHODS

An in silico study was performed to confirm effective TG and MPO interaction. An in vitro evaluation of toxicity with biochemical estimations was performed. Further, in vivo studies were undertaken where rats were treated with 25, 50 and 100 mg/kg TG or standard MPO inhibiting drug4‑Aminobenzoic hydrazide (4‑ABH) at 60 min prior, post immediate and an hour post 90 min of middle cerebral artery occlusion (MCAo) followed by 24 h reperfusion. Rats were evaluated for neurodeficit and motor function tests. Brains were further harvested for infarct size evaluation, biochemical analysis, and western blot experiments.

KEY FINDINGS

TG at 100 mg/kg dose i.p. administered immediately post ischemia confers neuroprotection by reducing cerebral infarct with improvement in motor and neurodeficit scores. Furthermore, elevated nitrite and MDA levels were also found to be reduced in brain regions in the treated group. TG also potentiated intrinsic antioxidant status and markedly inhibited reduced glutathione mediated myeloperoxidase expression in the cortical brain region.

SIGNIFICANCE

TG confers neuroprotection by reduced glutathione mediated myeloperoxidase inhibition in ischemic stroke.

Targeting redox regulation to treat substance use disorder using N‐acetylcysteine

Substance use disorder (SUD) is a chronic relapsing disorder characterized by transitioning from acute drug reward to compulsive drug use. Despite the heavy personal and societal burden of SUDs, current treatments are limited and unsatisfactory. For this reason, a deeper understanding of the mechanisms underlying addiction is required. Altered redox status, primarily due to drug-induced increases in dopamine metabolism, is a unifying feature of abused substances. In recent years, knowledge of the effects of oxidative stress in the nervous system has evolved from strictly neurotoxic to include a more nuanced role in redox-sensitive signaling. More specifically, S-glutathionylation, a redox-sensitive post-translational modification, has been suggested to influence the response to drugs of abuse. In this review we will examine the evidence for redox-mediating drugs as therapeutic tools focusing on N-acetylcysteine as a treatment for cocaine addiction. We will conclude by suggesting future research directions that may further advance this field.

Apolipoprotein E favours the blunting by high-fat diet of prostacyclin receptor activation in the mouse aorta

BACKGROUND AND PURPOSE

NO-mediated, endothelium-dependent relaxations of isolated arteries are blunted by ageing and high-fat diets, as well as by apolipoprotein E deletion. The present study was designed to test the hypothesis that apolipoprotein E deletion impairs endothelium-dependent responses to prostacyclin (IP) receptor activation.

EXPERIMENTAL APPROACH

Five-week-old ApoE^+/+ and ApoE^-/- mice were fed normal chow or high-fat diet for 29 weeks. The aortae were isolated for the measurements of isometric tension in Halpern-Mulvany myographs. Levels of proteins were assessed by Western blotting and immunofluorescence, and cyclic nucleotide levels by elisa.

KEY RESULTS

The IP receptor agonist, iloprost, induced endothelium-, NO-synthase- and IP-dependent relaxations in aortae of young ApoE^+/+ mice. High-fat diet favoured activation of thromboxane receptors by iloprost, causing contraction. Apolipoprotein E was present in aortae of ApoE^+/+ mice, especially in endothelium. Its presence was augmented by high-fat diet. Its deletion potentiated iloprost-induced relaxations in aortae of young mice and prevented the blunting of this response by high-fat diet. Levels of cAMP were higher, but those of cGMP were lower in the aorta of ApoE^-/- than in ApoE^+/+ mice of the same age. The levels of IP receptor protein were not different between ApoE^+/+ and ApoE^-/- mice.

CONCLUSIONS AND IMPLICATIONS

Iloprost induced an endothelium-dependent relaxation in the aorta of young healthy mice which involved both the cGMP and cAMP pathways. This response was blunted by prolonged exposure to a high-fat diet. Apolipoprotein E deletion potentiated relaxations to IP receptor activation, independently of age and diet.

Reactive oxygen species and protein modifications in spermatozoa

Cellular response to reactive oxygen species (ROS) includes both reversible redox signaling and irreversible nonenzymatic reactions which depend on the nature and concentration of the ROS involved. Changes in thiol/disulfide pairs affect protein conformation, enzymatic activity, ligand binding, and protein-protein interactions. During spermatogenesis and epididymal maturation, there are ROS-dependent modifications of the sperm chromatin and flagellar proteins.The spermatozoon is regulated by redox mechanisms to acquire fertilizing ability. For this purpose, controlled amounts of ROS are necessary to assure sperm activation (motility and capacitation). Modifications of the thiol groups redox status of sperm proteins are needed for spermatozoon to achieve fertilizing ability. However, when ROS are produced at high concentrations, the established oxidative stress promotes pathological changes affecting sperm function and leading to infertility. Sperm proteins are sensitive to high levels of ROS and suffer modifications that impact on motility, capacitation, and the ability of the spermatozoon to recognize and bind to the zona pellucida and damage of sperm DNA. Thiol oxidation, tyrosine nitration, and S-glutathionylation are highlighted in this review as significant redox-dependent protein modifications associated with impairment of sperm function and alteration of paternal genome leading to infertility. Peroxiredoxins, the primary antioxidant protection in spermatozoa, are affected by most of the protein modifications described in this review. They play a significant role in both physiological and pathological processes in mammalian spermatozoa.

Effects of Oxaliplatin Treatment on the Myenteric Plexus Innervation and Glia in the Murine Distal Colon

Oxaliplatin (platinum-based chemotherapeutic agent) is a first-line treatment of colorectal malignancies; its use associates with peripheral neuropathies and gastrointestinal side effects. These gastrointestinal dysfunctions might be due to toxic effects of oxaliplatin on the intestinal innervation and glia. Male Balb/c mice received intraperitoneal injections of sterile water or oxaliplatin (3 mg/kg/d) triweekly for 2 weeks. Colon tissues were collected for immunohistochemical assessment at day 14. The density of sensory, adrenergic, and cholinergic nerve fibers labeled with calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH), and vesicular acetylcholine transporter (VAChT), respectively, was assessed within the myenteric plexus of the distal colon. The number and proportion of excitatory neurons immunoreactive (IR) against choline acetyltransferase (ChAT) were counted, and the density of glial subpopulations was determined by using antibodies specific for glial fibrillary acidic protein (GFAP) and s100β protein. Oxaliplatin treatment induced significant reduction of sensory and adrenergic innervations, as well as the total number and proportion of ChAT-IR neurons, and GFAP-IR glia, but increased s100β expression within the myenteric plexus of the distal colon. Treatment with oxaliplatin significantly alters nerve fibers and glial cells in the colonic myenteric plexus, which could contribute to long-term gastrointestinal side effects following chemotherapeutic treatment.

Glutathionylation: a regulatory role of glutathione in physiological processes

Glutathione (γ-glutamyl-cysteinyl-glycine) is an intracellular thiol molecule and a potent antioxidant that participates in the toxic metabolism phase II biotransformation of xenobiotics. It can bind to a variety of proteins in a process known as glutathionylation. Protein glutathionylation is now recognised as one of important posttranslational regulatory mechanisms in cell and tissue physiology. Direct and indirect regulatory roles in physiological processes include glutathionylation of major transcriptional factors, eicosanoids, cytokines, and nitric oxide (NO). This review looks into these regulatory mechanisms through examples of glutathione regulation in apoptosis, vascularisation, metabolic processes, mitochondrial integrity, immune system, and neural physiology. The focus is on the physiological roles of glutathione beyond biotransformational metabolism.

Positive Regulation of Interleukin-1β Bioactivity by Physiological ROS-Mediated Cysteine S-Glutathionylation

Reactive oxygen species (ROS)-induced cysteine S-glutathionylation is an important posttranslational modification (PTM) that controls a wide range of intracellular protein activities. However, whether physiological ROS can modulate the function of extracellular components via S-glutathionylation is unknown. Using a screening approach, we identified ROS-mediated cysteine S-glutathionylation on several extracellular cytokines. Glutathionylation of the highly conserved Cys-188 in IL-1β positively regulates its bioactivity by preventing its ROS-induced irreversible oxidation, including sulfinic acid and sulfonic acid formation. We show this mechanism protects IL-1β from deactivation by ROS in an in vivo system of irradiation-induced bone marrow (BM) injury. Glutaredoxin 1 (Grx1), an enzyme that catalyzes deglutathionylation, was present and active in the extracellular space in serum and the BM, physiologically regulating IL-1β glutathionylation and bioactivity. Collectively, we identify cysteine S-glutathionylation as a cytokine regulatory mechanism that could be a therapeutic target in the treatment of various infectious and inflammatory diseases.

Small-molecule inhibition of STAT3 in radioresistant head and neck squamous cell carcinoma

While STAT3 has been validated as a target for treatment of many cancers, including head and neck squamous cell carcinoma (HNSCC), a STAT3 inhibitor is yet to enter the clinic. We used the scaffold of C188, a small-molecule STAT3 inhibitor previously identified by us, in a hit-to-lead program to identify C188-9. C188-9 binds to STAT3 with high affinity and represents a substantial improvement over C188 in its ability to inhibit STAT3 binding to its pY-peptide ligand, to inhibit cytokine-stimulated pSTAT3, to reduce constitutive pSTAT3 activity in multiple HNSCC cell lines, and to inhibit anchorage dependent and independent growth of these cells. In addition, treatment of nude mice bearing xenografts of UM-SCC-17B, a radioresistant HNSCC line, with C188-9, but not C188, prevented tumor xenograft growth. C188-9 treatment modulated many STAT3-regulated genes involved in oncogenesis and radioresistance, as well as radioresistance genes regulated by STAT1, due to its potent activity against STAT1, in addition to STAT3. C188-9 was well tolerated in mice, showed good oral bioavailability, and was concentrated in tumors. Thus, C188-9, either alone or in combination with radiotherapy, has potential for use in treating HNSCC tumors that demonstrate increased STAT3 and/or STAT1 activation.

Applications of Reactive Cysteine Profiling

Cysteine thiols are involved in a diverse set of biological transformations, including nucleophilic and redox catalysis, metal coordination and formation of both dynamic and structural disulfides. Often posttranslationally modified, cysteines are also frequently alkylated by electrophilic compounds, including electrophilic metabolites, drugs, and natural products, and are attractive sites for covalent probe and drug development. Quantitative proteomics combined with activity-based protein profiling has been applied to annotate cysteine reactivity, susceptibility to posttranslational modifications, and accessibility to chemical probes, uncovering thousands of functional and small-molecule targetable cysteines across a diverse set of proteins, proteome-wide in an unbiased manner. Reactive cysteines have been targeted by high-throughput screening and fragment-based ligand discovery efforts. New cysteine-reactive electrophiles and compound libraries have been synthesized to enable inhibitor discovery broadly and to minimize nonspecific toxicity and off-target activity of compounds. With the recent blockbuster success of several covalent inhibitors, and the development of new chemical proteomic strategies to broadly identify reactive, ligandable and posttranslationally modified cysteines, cysteine profiling is poised to enable the development of new potent and selective chemical probes and even, in some cases, new drugs.

Protein S-glutathionylation induced by hypoxia increases hypoxia-inducible factor-1α in human colon cancer cells

Hypoxia is a common characteristic of many types of solid tumors. Intratumoral hypoxia selects for tumor cells that survive in a low oxygen environment, undergo epithelial-mesenchymal transition, are more motile and invasive, and show gene expression changes driven by hypoxia-inducible factor-1α (HIF-1α) activation. Therefore, targeting HIF-1α is an attractive strategy for disrupting multiple pathways crucial for tumor growth. In the present study, we demonstrated that hypoxia increases the S-glutathionylation of HIF-1α and its protein levels in colon cancer cells. This effect is significantly prevented by decreasing oxidized glutathione as well as glutathione depletion, indicating that S-glutathionylation and the formation of protein-glutathione mixed disulfides is related to HIF-1α protein levels. Moreover, colon cancer cells expressing glutaredoxin 1 are resistant to inducing HIF-1α and expressing hypoxia-responsive genes under hypoxic conditions. Therefore, S-glutathionylation of HIF-1α induced by tumor hypoxia may be a novel therapeutic target for the development of new drugs.

Reactive nitrogen species (RNS)-resistant microbes: adaptation and medical implications

Nitrosative stress results from an increase in reactive nitrogen species (RNS) within the cell. Though the RNS - nitric oxide (·NO) and peroxynitrite (ONOO-) - play pivotal physiological roles, at elevated concentrations, these moieties can be poisonous to both prokaryotic and eukaryotic cells alike due to their capacity to disrupt a variety of essential biological processes. Numerous microbes are known to adapt to nitrosative stress by elaborating intricate strategies aimed at neutralizing RNS. In this review, we will discuss both the enzymatic systems dedicated to the elimination of RNS as well as the metabolic networks that are tailored to generate RNS-detoxifying metabolites - α-keto-acids. The latter has been demonstrated to nullify RNS via non-enzymatic decarboxylation resulting in the production of a carboxylic acid, many of which are potent signaling molecules. Furthermore, as aerobic energy production is severely impeded during nitrosative stress, alternative ATP-generating modules will be explored. To that end, a holistic understanding of the molecular adaptation to nitrosative stress, reinforces the notion that neutralization of toxicants necessitates significant metabolic reconfiguration to facilitate cell survival. As the alarming rise in antimicrobial resistant pathogens continues unabated, this review will also discuss the potential for developing therapies that target the alternative ATP-generating machinery of bacteria.

Targeting Aging with Functional Food: Pasta with Opuntia Single-Arm Pilot Study

Interventions to extend life span represent the new perspective in aging investigation. Healthy dietary habits are important modifiable factors that can favor a healthy aging phenotype. Many studies have demonstrated benefits for metabolic syndrome and type 2 diabetes mellitus resulting from the traditional Mediterranean foods. Opuntia Ficus Indica (OFI), widespread in the Mediterranean basin, belongs to the Cactaceae family. It is known for its antioxidant and anti-inflammatory properties. Moreover, products containing extracts from OFI fruits or cladodes have been used to control obesity and other metabolic parameters, such as glycemia and lipid profile. The aim of this study was to analyze the antioxidant and anti-inflammatory effect of pasta with 3% of OFI cladode extracts added to show its beneficial effect in human health. We performed a single arm longitudinal intervention study in 42 healthy volunteers, administrating 500 g/week of this functional pasta for 30 days. Our pasta had antioxidant and anti-inflammatory properties with putative effect on the aging process and related metabolic diseases. We also demonstrated a hypoglycemic effect. The results are preliminary, but it is possible to speculate that our pasta could be considered an effective food for the prevention of age-related metabolic disorders.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Kynurenic Acid Prevents Cytoskeletal Disorganization Induced by Quinolinic Acid in Mixed Cultures of Rat Striatum

Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan known to modulate a number of mechanisms involved in neural dysfunction. Although its activity in the brain has been widely studied, the effect of KYNA counteracting the actions of quinolinic acid (QUIN) remains unknown. The present study aims at describing the ability of 100 μM KYNA preventing cytoskeletal disruption provoked by QUIN in astrocyte/neuron/microglia mixed culture. KYNA totally preserved cytoskeletal organization, cell morphology, and redox imbalance in mixed cultures exposed to QUIN. However, KYNA partially prevented morphological alteration in isolated primary astrocytes and failed to protect the morphological alterations of neurons caused by QUIN exposure. Moreover, KYNA prevented QUIN-induced microglial activation and upregulation of ionized calcium-binding adapter molecule 1 (Iba-1) and partially preserved tumor necrosis factor-α (TNF-α) level in mixed cultures. TNF-α level was also partially preserved in astrocytes. In addition to the mechanisms dependent on redox imbalance and microglial activation, KYNA prevented downregulation of connexin-43 and the loss of functionality of gap junctions (GJs), preserving cell-cell contact, cytoskeletal organization, and cell morphology in QUIN-treated cells. Furthermore, the toxicity of QUIN targeting the cytoskeleton of mixed cultures was not prevented by the N-methyl-D-aspartate (NMDA) antagonist MK-801. We suggest that KYNA protects the integrity of the cytoskeleton of mixed cultures by complex mechanisms including modulating microglial activation preventing oxidative imbalance and misregulated GJs leading to disrupted cytoskeleton in QUIN-treated cells. This study contributed to elucidate the molecular basis of KYNA protection against QUIN toxicity.

Ultraviolet A-induced oxidation in cornea: Characterization of the early oxidation-related events

Exposure to sunlight ultraviolet-A (UVA), the main component of solar UV reaching the eyes, is suspected to play an important part in the onset of ocular pathologies. UVA primary biological deleterious effects arise from the photo-induction of oxidative stress in cells. However, the molecular bases linking UVA-induced oxidation to UVA toxicity in eyes remain poorly understood, especially with regards to the cornea. To shed some light on this issue, we have investigated the susceptibility and response potential of the different corneal cellular layers (epithelium, stroma and endothelium) to UVA-induced oxidation. We have monitored UVA-induced immediate effects on cellular redox balance, on mitochondrial membrane potential, on 8-Hydroxy-2'-deoxyguanosine (8-OHdG) accumulation in cellular DNA and on S-glutathionylated proteins (PSSG) levels along whole rabbit corneas. Higher redox imbalance was observed in the posterior part of the cornea following irradiation. Conversely, UVA-altered mitochondrial membrane potentials were observed only in anterior portions of the cornea. UVA-induced 8-OHdG were found in nuclear DNA of epithelia, while they were found in both nuclear and mitochondrial DNA in stromal and endothelial cells. Finally, significantly higher levels of cytosolic PSSG were measured in epithelia and endothelia immediately after UVA exposure, but not in stromas. Taken together, our findings indicate that while corneal epithelial cells are subjected to important modifications in response to UVA exposure, they efficiently limit the early manifestations of UVA-induced toxicity. On the other hand, the corneal endothelium is more susceptible to UVA-induced oxidation-related toxicity.

The role of S-nitrosoglutathione reductase (GSNOR) in human disease and therapy

S-nitrosoglutathione reductase (GSNOR), or ADH5, is an enzyme in the alcohol dehydrogenase (ADH) family. It is unique when compared to other ADH enzymes in that primary short-chain alcohols are not its principle substrate. GSNOR metabolizes S-nitrosoglutathione (GSNO), S-hydroxymethylglutathione (the spontaneous adduct of formaldehyde and glutathione), and some alcohols. GSNOR modulates reactive nitric oxide (•NO) availability in the cell by catalyzing the breakdown of GSNO, and indirectly regulates S-nitrosothiols (RSNOs) through GSNO-mediated protein S-nitrosation. The dysregulation of GSNOR can significantly alter cellular homeostasis, leading to disease. GSNOR plays an important regulatory role in smooth muscle relaxation, immune function, inflammation, neuronal development and cancer progression, among many other processes. In recent years, the therapeutic inhibition of GSNOR has been investigated to treat asthma, cystic fibrosis and interstitial lung disease (ILD). The direct action of •NO on cellular pathways, as well as the important regulatory role of protein S-nitrosation, is closely tied to GSNOR regulation and defines this enzyme as an important therapeutic target.

Redox regulation of ischemic limb neovascularization - What we have learned from animal studies

Mouse hindlimb ischemia has been widely used as a model to study peripheral artery disease. Genetic modulation of the enzymatic source of oxidants or components of the antioxidant system reveal that physiological levels of oxidants are essential to promote the process of arteriogenesis and angiogenesis after femoral artery occlusion, although mice with diabetes or atherosclerosis may have higher deleterious levels of oxidants. Therefore, fine control of oxidants is required to stimulate vascularization in the limb muscle. Oxidants transduce cellular signaling through oxidative modifications of redox sensitive cysteine thiols. Of particular importance, the reversible modification with abundant glutathione, called S-glutathionylation (or GSH adducts), is relatively stable and alters protein function including signaling, transcription, and cytoskeletal arrangement. Glutaredoxin-1 (Glrx) is an enzyme which catalyzes reversal of GSH adducts, and does not scavenge oxidants itself. Glrx may control redox signaling under fluctuation of oxidants levels. In ischemic muscle increased GSH adducts through Glrx deletion improves in vivo limb revascularization, indicating endogenous Glrx has anti-angiogenic roles. In accordance, Glrx overexpression attenuates VEGF signaling in vitro and ischemic vascularization in vivo. There are several Glrx targets including HIF-1α which may contribute to inhibition of vascularization by reducing GSH adducts. These animal studies provide a caution that excess antioxidants may be counter-productive for treatment of ischemic limbs, and highlights Glrx as a potential therapeutic target to improve ischemic limb vascularization.

Evaluating the Risk of Tumors Diseases Based on Measurement of Urinary and Serumal Antioxidants Using the New Agar Diffusion Methods

Objectives. To discuss the characteristics of the amount of urinary total antioxidants in tumor diseases and the possibility of utilizing the changing regulation of urinary antioxidants to diagnose tumor diseases. Method. Urine and serum specimens from 130 healthy people were used to investigate the variation of antioxidant capacity against age. Urine and serum specimens from 44 unselected patients with tumors and 44 healthy people with same age background were used to explore the significance of urinary antioxidant capacity in clinic to diagnose tumor diseases. Potassium permanganate agar method and iodine starch method were used to determine the amount of total antioxidants. Results. In healthy people, more antioxidants in urine were measured in older people, while the results were opposite in serum. More antioxidants were found in urine of tumor patients than in healthy people with same age-range. Conclusions. According to the results of 130 measurements, the amount of antioxidants in urine varies by age. By using agar methods to measure antioxidants, the effect of age is required to be considered. Antioxidants levels from tumor patients were significantly higher than healthy individuals in urine. The combination of urine and serum to determine total antioxidants can better diagnose tumor diseases based on iodine starch method, with area under the receiver operating characteristics curve at 0.787.

S-nitrosylation and S-glutathionylation of Cys134 on troponin I have opposing competitive actions on Ca2+ sensitivity in rat fast-twitch muscle fibers

Nitric oxide is generated in skeletal muscle with activity and decreases Ca2+ sensitivity of the contractile apparatus, putatively by S-nitrosylation of an unidentified protein. We investigated the mechanistic basis of this effect and its relationship to the oxidation-induced increase in Ca2+ sensitivity in mammalian fast-twitch (FT) fibers mediated by S-glutathionylation of Cys134 on fast troponin I (TnIf). Force-[Ca2+] characteristics of the contractile apparatus in mechanically skinned fibers were assessed by direct activation with heavily Ca2+-buffered solutions. Treatment with S-nitrosylating agents, S-nitrosoglutathione (GSNO) or S-nitroso- N-acetyl-penicillamine (SNAP), decreased pCa50 ( = −log10 [Ca2+] at half-maximal activation) by ~−0.07 pCa units in rat and human FT fibers without affecting maximum force, but had no effect on rat and human slow-twitch fibers or toad or chicken FT fibers, which all lack Cys134. The Ca2+ sensitivity decrease was 1) fully reversed with dithiothreitol or reduced glutathione, 2) at least partially reversed with ascorbate, indicative of involvement of S-nitrosylation, and 3) irreversibly blocked by low concentration of the alkylating agent, N-ethylmaleimide (NEM). The biotin-switch assay showed that both GSNO and SNAP treatments caused S-nitrosylation of TnIf. S-glutathionylation pretreatment blocked the effects of S-nitrosylation on Ca2+ sensitivity, and vice-versa. S-nitrosylation pretreatment prevented NEM from irreversibly blocking S-glutathionylation of TnIf and its effects on Ca2+ sensitivity, and likewise S-glutathionylation pretreatment prevented NEM block of S-nitrosylation. Following substitution of TnIf into rat slow-twitch fibers, S-nitrosylation treatment caused decreased Ca2+ sensitivity. These findings demonstrate that S-nitrosylation and S-glutathionylation exert opposing effects on Ca2+ sensitivity in mammalian FT muscle fibers, mediated by competitive actions on Cys134 of TnIf.

Post-translational Modifications in Regulation of Chloroplast Function: Recent Advances

Post-translational modifications (PTMs) of proteins enable fast modulation of protein function in response to metabolic and environmental changes. Phosphorylation is known to play a major role in regulating distribution of light energy between the Photosystems (PS) I and II (state transitions) and in PSII repair cycle. In addition, thioredoxin-mediated redox regulation of Calvin cycle enzymes has been shown to determine the efficiency of carbon assimilation. Besides these well characterized modifications, recent methodological progress has enabled identification of numerous other types of PTMs in various plant compartments, including chloroplasts. To date, at least N-terminal and Lys acetylation, Lys methylation, Tyr nitration and S-nitrosylation, glutathionylation, sumoylation and glycosylation of chloroplast proteins have been described. These modifications impact DNA replication, control transcriptional efficiency, regulate translational machinery and affect metabolic activities within the chloroplast. Moreover, light reactions of photosynthesis as well as carbon assimilation are regulated at multiple levels by a number of PTMs. It is likely that future studies will reveal new metabolic pathways to be regulated by PTMs as well as detailed molecular mechanisms of PTM-mediated regulation.

Post-translational modifications of Medicago truncatula glutathione peroxidase 1 induced by nitric oxide

Plant glutathione peroxidases (Gpx) catalyse the reduction of various peroxides, such as hydrogen peroxide (H₂O₂), phospholipid hydroperoxides and peroxynitrite, but at the expense of thioredoxins rather than glutathione. A main function of plant Gpxs is the protection of biological membranes by scavenging phospholipid hydroperoxides, but some Gpxs have also been associated with H₂O₂ sensing and redox signal transduction. Nitric oxide (NO) is not only known to induce the expression of Gpx family members, but also to inhibit Gpx activity, presumably through the S-nitrosylation of conserved cysteine residues. In the present study, the effects of NO-donors on both the activity and S-nitrosylation state of purified Medicago truncatula Gpx1 were analyzed using biochemical assay measurements and a biotin-switch/mass spectrometry approach. MtGpx1 activity was only moderately inhibited by the NO-donors diethylamine-NONOate and S-nitrosoglutathione, and the inhibition may be reversed by DTT. The three conserved Cys of MtGpx1 were found to be modified through S-nitrosylation and S-glutathionylation, although to different extents, by diethylamine-NONOate and S-nitrosoglutathione, or by a combination of diethylamine-NONOate and reduced glutathione. The regulation of MtGpx1 and its possible involvement in the signaling process is discussed in the light of these results.

Glutathionylation of Pea Chloroplast 2-Cys Prx and Mitochondrial Prx IIF Affects Their Structure and Peroxidase Activity and Sulfiredoxin Deglutathionylates Only the 2-Cys Prx

Together with thioredoxins (Trxs), plant peroxiredoxins (Prxs), and sulfiredoxins (Srxs) are involved in antioxidant defense and redox signaling, while their regulation by post-translational modifications (PTMs) is increasingly regarded as a key component for the transduction of the bioactivity of reactive oxygen and nitrogen species. Among these PTMs, S-glutathionylation is considered a protective mechanism against overoxidation, it also modulates protein activity and allows signaling. This study explores the glutathionylation of recombinant chloroplastic 2-Cys Prx and mitochondrial Prx IIF from Pisum sativum. Glutathionylation of the decameric form of 2-Cys Prx produced a change in the elution volume after FPLC chromatography and converted it to its dimeric glutathionylated form, while Prx IIF in its reduced dimeric form was glutathionylated without changing its oligomeric state. Mass spectrometry demonstrated that oxidized glutathione (GSSG) can glutathionylate resolving cysteine (Cys¹⁷⁴), but not the peroxidatic equivalent (Cys⁵²), in 2-Cys Prx. In contrast, GSSG was able to glutathionylate both peroxidatic (Cys⁵⁹) and resolving (Cys⁸⁴) cysteine in Prx IIF. Glutathionylation was seen to be dependent on the GSH/GSSG ratio, although the exact effect on the 2-Cys Prx and Prx IIF proteins differed. However, the glutathionylation provoked a similar decrease in the peroxidase activity of both peroxiredoxins. Despite growing evidence of the importance of post-translational modifications, little is known about the enzymatic systems that specifically regulate the reversal of this modification. In the present work, sulfiredoxin from P. sativum was seen to be able to deglutathionylate pea 2-Cys Prx but not pea Prx IIF. Redox changes during plant development and the response to stress influence glutathionylation/deglutathionylation processes, which may represent an important event through the modulation of peroxiredoxin and sulfiredoxin proteins.

A Theoretical Study on the Antioxidant Activity of Piceatannol and Isorhapontigenin Scavenging Nitric Oxide and Nitrogen Dioxide Radicals

The antioxidant activity of naturally occurring stilbene compounds piceatannol (PIC) and isorhapontigenin (ISO) scavenging two free radicals (NO and NO₂) were studied using density functional theory (DFT) method. Four reaction mechanisms have been considered: hydrogen atom transfer (HAT), radical adduct formation (RAF), single electron transfer (SET), and sequential proton loss electron transfer (SPLET). The reaction channels in water solution were traced independently, and the respective thermodynamic and kinetic parameters were obtained. We found PIC and ISO scavenge NO mainly through RAF mechanism, and scavenge NO₂ through HAT mechanism. The capacity of PIC scavenging NO₂ is much higher than ISO, but the reactivity of scavenging NO is lower than ISO.

Structure-Activity Relationships ofN-Cinnamoyl and Hydroxycinnamoyl Amides onα-Glucosidase Inhibition

Currently, there is an increasing interest towardsα-glucosidase inhibition of various diseases including diabetes mellitus type 2, cancer, HIV, and B- and C-type viral hepatitis. Cinnamic acid derivatives have been shown to be potentially valuable as a new group ofα-glucosidase inhibitors. Therefore, herein, theα-glucosidase inhibitory activity oftrans-N-cinnamoyl and hydroxycinnamoyl amides was studied in vitro. Results revealed that the tested hydroxycinnamoyl amides (1–16) inhibiteda-glucosidase with IC50s ranging between 0.76 and 355.1 μg/ml. Compounds1,2,5,6,9,14, and15showed significant inhibition of yeastα-glucosidase, being even more potent ones than the used positive inhibitor acarbose (IC50=2.50±0.21 μg/ml).

Non-linear impact of glutathione depletion on C. elegans life span and stress resistance

The redox environment in cells and organisms is set by low-molecular mass and protein-bound thiols, with glutathione (GSH) representing a major intracellular redox buffer. Subtle thiol oxidation elicits signal transduction processes and adaptive responses to cope with stressors, whereas highly oxidizing conditions may provoke cell death. We here tested how thiol depletion affects life span, stress resistance and stress signaling in the model organism Caenorhabditis elegans. Diethyl maleate (DEM), an α,β-unsaturated carbonyl compound that conjugates to GSH and other thiols, decreased C. elegans life span at a concentration of 1mM. In contrast, low and moderate doses of DEM (10-100µM) increased mean and maximum life span and improved resistance against oxidative stress. DEM-induced life span extension was not detectable in worms deficient in either the FoxO orthologue, DAF-16, or the Nrf2 orthologue, SKN-1, pointing to a collaborative role of the two transcription factors in life span extension induced by thiol depletion. Cytoprotective target genes of DAF-16 and SKN-1 were upregulated after at least 3 days of exposure to 100µM DEM, but not 1mM DEM, whereas only 1mM DEM caused upregulation of egl-1, a gene controlled by a p53-orthologue, CEP-1. In order to test whether depletion of GSH may elicit effects similar to DEM, we suppressed GSH biosynthesis in worms by attenuating γ-glutamylcysteine synthetase (gcs-1) expression through RNAi. The decline in GSH levels elicited by gcs-1 knockdown starting at young adult stage did not impair viability, but increased both stress resistance and life expectancy of the worms. In contrast, gcs-1 knockdown commencing right after hatching impaired nematode stress resistance and rendered young adult worms prone to vulval ruptures during egg-laying. Thus, modest decrease in GSH levels in young adult worms may promote stress resistance and life span, whereas depletion of GSH is detrimental to freshly hatched and developing worms.

Cataract induction by administration of nitroglycerin in cardiac patients through imbalance in redox status

Purpose

The objective of this study was to evaluate the role of nitroglycerin in the pathogenesis of cataract.

Design

Prospective study.

Patient and methods

This study was performed in adults from tertiary Saudi Arabian hospitals (34 males and 26 females in each group, aged from 40 to 60 years), who were divided into four groups with an equal number of subjects (control group, cardiac group, idiopathic cataract group, and a group of cardiac patients using nitroglycerin and with cataracts). Fasting glucose concentrations, blood glycated hemoglobin levels, lipid profiles, and levels of nitrite, conjugated dienes (CD), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and reduced glutathione (GSH) were determined.

Results

Treatment of cardiac patients with nitroglycerin produced an imbalance in their systemic redox status, leading to the development of cataracts, which was reflected by a significant increase in the levels of nitrite, CD, and TBARS and a significant decrease in SOD activity and GSH, compared with idiopathic cataract patients. The results of correlation studies and multiple regression analysis revealed a significant positive correlation between different biochemical parameters (GSH, SOD, TBARS, CD, and nitrite) in the blood and lens in both idiopathic cataract patients and cardiac patients treated with nitroglycerin.

Conclusion

The study points to the relative and predictive effects of nitric oxide derived from nitroglycerin in the development of cataract in the presence of the oxidative stress induced by nitroglycerin treatment.

Selective Gas-Phase Ion/Ion Reactions: Enabling Disulfide Mapping via Oxidation and Cleavage of Disulfide Bonds in Intermolecularly-Linked Polypeptide Ions

The selective gas-phase oxidation of disulfide bonds to their thiosulfinate form using ion/ion reactions and subsequent cleavage is demonstrated here. Oxidizing reagent anions are observed to attach to all polypeptides, regardless of amino acid composition. Direct proton transfer yielding a charge-reduced peptide is also frequently observed. Activation of the ion/ion complex between an oxidizing reagent anion and a disulfide-containing peptide cation results in oxygen transfer from the reagent anion to the peptide cation to form the [M+H+O](+) species. This thiosulfinate derivative can undergo one of several rearrangements that result in cleavage of the disulfide bond. Species containing an intermolecular disulfide bond undergo separation of the two chains upon activation. Further activation can be used to generate more sequence information from each chain. These oxidation ion/ion reactions have been used to illustrate the identification of S-glutathionylated and S-cysteinylated peptides, in which low molecular weight thiols are attached to cysteine residues in peptides via disulfide bonds. The oxidation chemistry effectively labels peptide ions with readily oxidized groups, such as disulfide bonds. This enables a screening approach for the identification of disulfide-linked peptides in a disulfide mapping application involving enzymatic digestion. The mixtures of ions generated by tryptic and peptic digestions of lysozyme and insulin, respectively, without prior separation or isolation were subjected both to oxidation and proton transfer ion/ion chemistry to illustrate the identification of peptides in the mixtures with readily oxidized groups.

"Oxygen Sensing" by Na,K-ATPase: These Miraculous Thiols

Control over the Na,K-ATPase function plays a central role in adaptation of the organisms to hypoxic and anoxic conditions. As the enzyme itself does not possess O2 binding sites its "oxygen-sensitivity" is mediated by a variety of redox-sensitive modifications including S-glutathionylation, S-nitrosylation, and redox-sensitive phosphorylation. This is an overview of the current knowledge on the plethora of molecular mechanisms tuning the activity of the ATP-consuming Na,K-ATPase to the cellular metabolic activity. Recent findings suggest that oxygen-derived free radicals and H2O2, NO, and oxidized glutathione are the signaling messengers that make the Na,K-ATPase "oxygen-sensitive." This very ancient signaling pathway targeting thiols of all three subunits of the Na,K-ATPase as well as redox-sensitive kinases sustains the enzyme activity at the "optimal" level avoiding terminal ATP depletion and maintaining the transmembrane ion gradients in cells of anoxia-tolerant species. We acknowledge the complexity of the underlying processes as we characterize the sources of reactive oxygen and nitrogen species production in hypoxic cells, and identify their targets, the reactive thiol groups which, upon modification, impact the enzyme activity. Structured accordingly, this review presents a summary on (i) the sources of free radical production in hypoxic cells, (ii) localization of regulatory thiols within the Na,K-ATPase and the role reversible thiol modifications play in responses of the enzyme to a variety of stimuli (hypoxia, receptors' activation) (iii) redox-sensitive regulatory phosphorylation, and (iv) the role of fine modulation of the Na,K-ATPase function in survival success under hypoxic conditions. The co-authors attempted to cover all the contradictions and standing hypotheses in the field and propose the possible future developments in this dynamic area of research, the importance of which is hard to overestimate. Better understanding of the processes underlying successful adaptation strategies will make it possible to harness them and use for treatment of patients with stroke and myocardial infarction, sleep apnoea and high altitude pulmonary oedema, and those undergoing surgical interventions associated with the interruption of blood perfusion.

Glutathione adducts induced by ischemia and deletion of glutaredoxin-1 stabilize HIF-1α and improve limb revascularization

Reactive oxygen species (ROS) are increased in ischemic tissues and necessary for revascularization; however, the mechanism remains unclear. Exposure of cysteine residues to ROS in the presence of glutathione (GSH) generates GSH-protein adducts that are specifically reversed by the cytosolic thioltransferase, glutaredoxin-1 (Glrx). Here, we show that a key angiogenic transcriptional factor hypoxia-inducible factor (HIF)-1α is stabilized by GSH adducts, and the genetic deletion of Glrx improves ischemic revascularization. In mouse muscle C2C12 cells, HIF-1α protein levels are increased by increasing GSH adducts with cell-permeable oxidized GSH (GSSG-ethyl ester) or 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanyl thiocarbonylamino) phenylthiocarbamoylsulfanyl] propionic acid (2-AAPA), an inhibitor of glutathione reductase. A biotin switch assay shows that GSSG-ester-induced HIF-1α contains reversibly modified thiols, and MS confirms GSH adducts on Cys(520) (mouse Cys(533)). In addition, an HIF-1α Cys(520) serine mutant is resistant to 2-AAPA-induced HIF-1α stabilization. Furthermore, Glrx overexpression prevents HIF-1α stabilization, whereas Glrx ablation by siRNA increases HIF-1α protein and expression of downstream angiogenic genes. Blood flow recovery after femoral artery ligation is significantly improved in Glrx KO mice, associated with increased levels of GSH-protein adducts, capillary density, vascular endothelial growth factor (VEGF)-A, and HIF-1α in the ischemic muscles. Therefore, Glrx ablation stabilizes HIF-1α by increasing GSH adducts on Cys(520) promoting in vivo HIF-1α stabilization, VEGF-A production, and revascularization in the ischemic muscles.

Redox Regulation of Ischemic Angiogenesis - Another Aspect of Reactive Oxygen Species

Antioxidants are expected to improve cardiovascular disease (CVD) by eliminating oxidative stress, but clinical trials have not shown promising results in chronic CVD. Animal studies have revealed that reactive oxygen species (ROS) exacerbate acute CVDs in which high levels of ROS are observed. However, ROS are also necessary for angiogenesis after ischemia, because ROS not only damage cells but also stimulate the cell signaling required for angiogenesis. ROS affect signaling by protein modifications, especially of cysteine amino acid thiols. Although there are several cysteine modifications, S-glutathionylation (GSH adducts; -SSG), a reversible cysteine modification by glutathione (GSH), plays an important role in angiogenic signal transduction by ROS. Glutaredoxin-1 (Glrx) is an enzyme that specifically removes GSH adducts in vivo. Overexpression of Glrx inhibits, whereas deletion of Glrx improves revascularization after mouse hindlimb ischemia. These studies indicate that increased levels of GSH adducts in ischemic muscle are beneficial in promoting angiogenesis. The underlying mechanism can be explained by multiple targets of S-gluathionylation, which mediate the angiogenic effects in ischemia. Increments in the master angiogenic transcriptional factor, HIF-1α, reduction of the anti-angiogenic factor sFlt1, activation of the endoplasmic reticulum Ca(2+)pump, SERCA, and inhibition of phosphatases may occur as a consequence of enhanced S-glutathionylation in ischemic tissue. In summary, inducing S-glutathionylation by inhibiting Glrx may be a therapeutic strategy to improve ischemic angiogenesis in CVD. (Circ J 2016; 80: 1278-1284).

The N-Terminus of the Floral Arabidopsis TGA Transcription Factor PERIANTHIA Mediates Redox-Sensitive DNA-Binding

The Arabidopsis TGA transcription factor (TF) PERIANTHIA (PAN) regulates the formation of the floral organ primordia as revealed by the pan mutant forming an abnormal pentamerous arrangement of the outer three floral whorls. The Arabidopsis TGA bZIP TF family comprises 10 members, of which PAN and TGA9/10 control flower developmental processes and TGA1/2/5/6 participate in stress-responses. For the TGA1 protein it was shown that several cysteines can be redox-dependently modified. TGA proteins interact in the nucleus with land plant-specific glutaredoxins, which may alter their activities posttranslationally. Here, we investigated the DNA-binding of PAN to the AAGAAT motif under different redox-conditions. The AAGAAT motif is localized in the second intron of the floral homeotic regulator AGAMOUS (AG), which controls stamen and carpel development as well as floral determinacy. Whereas PAN protein binds to this regulatory cis-element under reducing conditions, the interaction is strongly reduced under oxidizing conditions in EMSA studies. The redox-sensitive DNA-binding is mediated via a special PAN N-terminus, which is not present in other Arabidopsis TGA TFs and comprises five cysteines. Two N-terminal PAN cysteines, Cys68 and Cys87, were shown to form a disulfide bridge and Cys340, localized in a C-terminal putative transactivation domain, can be S-glutathionylated. Comparative land plant analyses revealed that the AAGAAT motif exists in asterid and rosid plant species. TGA TFs with N-terminal extensions of variable length were identified in all analyzed seed plants. However, a PAN-like N-terminus exists only in the rosids and exclusively Brassicaceae homologs comprise four to five of the PAN N-terminal cysteines. Redox-dependent modifications of TGA cysteines are known to regulate the activity of stress-related TGA TFs. Here, we show that the N-terminal PAN cysteines participate in a redox-dependent control of the PAN interaction with a highly conserved regulatory AG cis-element, emphasizing the importance of redox-modifications in the regulation of flower developmental processes.