Thiol Redox Regulation Research Articles

Thiamine disulfide derivatives in thiol redox regulation: Role of thioredoxin and glutathione systems

Thiamine disulfide derivatives in thiol redox regulation: Role of thioredoxin and glutathione systems

Redox regulation in chloroplast thylakoid lumen: The pmf changes everything, again.

Photosynthesis is the foundation of life on Earth. However, if not well regulated, it can also generate excessive reactive oxygen species (ROS), which can cause photodamage. Regulation of photosynthesis is highly dynamic, responding to both environmental and metabolic cues, and occurs at many levels, from light capture to energy storage and metabolic processes. One general mechanism of regulation involves the reversible oxidation and reduction of protein thiol groups, which can affect the activity of enzymes and the stability of proteins. Such redox regulation has been well studied in stromal enzymes, but more recently, evidence has emerged of redox control of thylakoid lumenal enzymes. This review/hypothesis paper summarizes the latest research and discusses several open questions and challenges to achieving effective redox control in the lumen, focusing on the distinct environments and regulatory components of the thylakoid lumen, including the need to transport electrons across the thylakoid membrane, the effects of pH changes by the proton motive force (pmf) in the stromal and lumenal compartments, and the observed differences in redox states. These constraints suggest that activated oxygen species are likely to be major regulatory contributors to lumenal thiol redox regulation, with key components and processes yet to be discovered.

Genome-wide analysis and transcriptional regulation of the typical and atypical thioredoxins in Arabidopsis thaliana.

Thioredoxins (TRXs), a large subclass of ubiquitous oxidoreductases, are involved in thiol redox regulation. Here, we performed a comprehensive analysis of TRXs in the Arabidopsis thaliana genome, revealing 41 genes encoding 18 typical and 23 atypical TRXs, and 6 genes encoding thioredoxin reductases (TRs). The high number of atypical TRXs indicates special functions in plants that mostly await elucidation. We identified an atypical class of thioredoxins called TRX-c in the genomes of photosynthetic eukaryotes. Localized to the chloroplast, TRX-c displays atypical CPLC, CHLC and CNLC motifs in the active sites. In silico analysis of the transcriptional regulations of TRXs revealed high expression of TRX-c in leaves and strong regulation under cold, osmotic, salinity and metal ion stresses.

Current Trends and Future Perspectives of Hydrogen Sulfide Donors

ABSTRACT: Hydrogen sulfide (H2S) gas is included to be the most critical endogenous gasotransmitters that has several pathophysiological effects in many human cells and organ tissues. The synthesis of endogenous H2S in cells via several pathways. Variant biological effects of H2S including ion channel regulation, redox regulation of protein, thiols, polysulfides, thiosulfate/sulfite, and anti-oxidant activities affecting many cellular and molecular reactions. Therefore, it is essential to review H2S chemical biology, methods of detection of H2S release and its effects on pathological and physiological functions along with their therapeutic uses, including cardiovascular protective activities, anti-inflammatory and anti-tumor activities of the H2S donors.

Chlamydomonas as a model for reactive oxygen species signaling and thiol redox regulation in the green lineage.

One-sentence summary: Advances in proteomic and transcriptomic studies have made Chlamydomonas a powerful research model in redox and reactive oxygen species regulation with unique and overlapping mechanisms with plants.

Thiol Redox Regulation of Plant β-Carbonic Anhydrase.

β-carbonic anhydrases (βCA) accelerate the equilibrium formation between CO2 and carbonate. Two plant βCA isoforms are targeted to the chloroplast and represent abundant proteins in the range of >1% of chloroplast protein. While their function in gas exchange and photosynthesis is well-characterized in carbon concentrating mechanisms of cyanobacteria and plants with C4-photosynthesis, their function in plants with C3-photosynthesis is less clear. The presence of conserved and surface-exposed cysteinyl residues in the βCA-structure urged to the question whether βCA is subject to redox regulation. Activity measurements revealed reductive activation of βCA1, whereas oxidized βCA1 was inactive. Mutation of cysteinyl residues decreased βCA1 activity, in particular C280S, C167S, C230S, and C257S. High concentrations of dithiothreitol or low amounts of reduced thioredoxins (TRXs) activated oxidized βCA1. TRX-y1 and TRX-y2 most efficiently activated βCA1, followed by TRX-f1 and f2 and NADPH-dependent TRX reductase C (NTRC). High light irradiation did not enhance βCA activity in wildtype Arabidopsis, but surprisingly in βca1 knockout plants, indicating light-dependent regulation. The results assign a role of βCA within the thiol redox regulatory network of the chloroplast.

Proteomics Reveal Enhanced Oxidative Stress Responses and Metabolic Adaptation in Acidithiobacillus ferrooxidans Biofilm Cells on Pyrite.

Reactive oxygen species (ROS) cause oxidative stress and growth inhibition by inactivation of essential enzymes, DNA and lipid damage in microbial cells. Acid mine drainage (AMD) ecosystems are characterized by low pH values, enhanced levels of metal ions and low species abundance. Furthermore, metal sulfides, such as pyrite and chalcopyrite, generate extracellular ROS upon exposure to acidic water. Consequently, oxidative stress management is especially important in acidophilic leaching microorganisms present in industrial biomining operations, especially when forming biofilms on metal sulfides. Several adaptive mechanisms have been described, but the molecular repertoire of responses upon exposure to pyrite and the presence of ROS are not thoroughly understood in acidophiles. In this study the impact of the addition of H2O2 on iron oxidation activity in Acidithiobacillus ferrooxidans DSM 14882T was investigated. Iron(II)- or sulfur-grown cells showed a higher sensitivity toward H2O2 than pyrite-grown ones. In order to elucidate which molecular responses may be involved, we used shot-gun proteomics and compared proteomes of cells grown with iron(II)-ions against biofilm cells, grown for 5 days in presence of pyrite as sole energy source. In total 1157 proteins were identified. 213 and 207 ones were found to have increased levels in iron(II) ion-grown or pyrite-biofilm cells, respectively. Proteins associated with inorganic sulfur compound (ISC) oxidation were among the latter. In total, 80 proteins involved in ROS degradation, thiol redox regulation, macromolecule repair mechanisms, biosynthesis of antioxidants, as well as metal and oxygen homeostasis were found. 42 of these proteins had no significant changes in abundance, while 30 proteins had increased levels in pyrite-biofilm cells. New insights in ROS mitigation strategies, such as importance of globins for oxygen homeostasis and prevention of unspecific reactions of free oxygen that generate ROS are presented for A. ferrooxidans biofilm cells. Furthermore, proteomic analyses provide insights in adaptations of carbon fixation and oxidative phosphorylation pathways under these two growth conditions.

Thiol redox-regulation for efficient adjustment of sulfur metabolism in acclimation to abiotic stress.

Sulfur assimilation and sulfur metabolism are tightly controlled at the transcriptional, post-transcriptional, and post-translational levels in order to meet the demand for reduced sulfur in growth and metabolism. These regulatory mechanisms coordinate the cellular sulfhydryl supply with carbon and nitrogen assimilation in particular. Redox homeostasis is an important cellular parameter intimately connected to sulfur by means of multiple thiol modifications. Post-translational thiol modifications such as disulfide formation, sulfenylation, S-nitrosylation, persulfidation, and S-glutathionylation allow for versatile switching and adjustment of protein functions. This review focuses on redox-regulation of enzymes involved in the sulfur assimilation pathway, namely adenosine 5´-phosphosulfate reductase (APR), adenosine 5´-phosphosulfate kinase (APSK), and γ-glutamylcysteine ligase (GCL). The activity of these enzymes is adjusted at the transcriptional and post-translational level depending on physiological requirements and the state of the redox and reactive oxygen species network, which are tightly linked to abiotic stress conditions. Hormone-dependent fine-tuning contributes to regulation of sulfur assimilation. Thus, the link between oxylipin signalling and sulfur assimilation has been substantiated by identification of the so-called COPS module in the chloroplast with its components cyclophilin 20-3, O-acetylserine thiol lyase, 2-cysteine peroxiredoxin, and serine acetyl transferase. We now have a detailed understanding of how regulation enables the fine-tuning of sulfur assimilation under both normal and abiotic stress conditions.

Thiol-Redox Regulation in Lung Development and Vascular Remodeling.

Significance: Redox homeostasis is finely tuned and governed by distinct intracellular mechanisms. The dysregulation of this either by external or internal events is a fundamental pathophysiologic base for many pulmonary diseases. Recent Advances: Based on recent discoveries, it is increasingly clear that cellular redox state and oxidation of signaling molecules are critical modulators of lung disease and represent a final common pathway that leads to poor respiratory outcomes. Critical Issues: Based on the wide variety of stimuli that alter specific redox signaling pathways, improved understanding of the disease and patient-specific alterations are needed for the development of therapeutic targets. Further Directions: For the full comprehension of redox signaling in pulmonary disease, it is essential to recognize the role of reactive oxygen intermediates in modulating biological responses. This review summarizes current knowledge of redox signaling in pulmonary development and pulmonary vascular disease.

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 CysRED/CysOX 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.

Thiol Based Redox Signaling in Plant Nucleus.

Reactive oxygen species (ROS) are well-described by-products of cellular metabolic activities, acting as signaling molecules and regulating the redox state of proteins. Solvent exposed thiol residues like cysteines are particularly sensitive to oxidation and their redox state affects structural and biochemical capacities of many proteins. While thiol redox regulation has been largely studied in several cell compartments like in the plant chloroplast, little is known about redox sensitive proteins in the nucleus. Recent works have revealed that proteins with oxidizable thiols are important for the regulation of many nuclear functions, including gene expression, transcription, epigenetics, and chromatin remodeling. Moreover, thiol reducing molecules like glutathione and specific isoforms of thiols reductases, thioredoxins and glutaredoxins were found in different nuclear subcompartments, further supporting that thiol-dependent systems are active in the nucleus. This mini-review aims to discuss recent progress in plant thiol redox field, taking examples of redox regulated nuclear proteins and focusing on major thiol redox systems acting in the nucleus.

P-78 - Role of thiol redox regulation in the mitochondrial signaling network

Reactive oxygen species (ROS) are not only damaging molecules but are also involved in redox signaling events. In mitochondria, thiol redox state is finely tuned mainly by the thioredoxin and the glutathione systems. Cyclophilin D (CypD), a key regulator of mitochondrial permeability transition, was recently shown to be subjected to redox regulation. In particular, CypD was recognized to directly interact with thioredoxin 2 and peroxiredoxin 3 of the thioredoxin system. In addition, the CypD prolyl cis-trans isomerase activity was shown to depend on its redox state with a higher catalytic efficiency in its reduced status. An important player in mitochondrial thiol redox regulation is glutaredoxin 2 (Grx2). This enzyme normally resides in the mitochondrial matrix as an inactive dimer coordinating a [2Fe-2S]2+ cluster. However, oxidative stress induction can trigger protein monomerization and activation. In this context, it has been observed that Grx2 is extremely active as a disulfide reductase in conditions of glutathione depletion and thioredoxin system inhibition. Thus, Grx2 seems very efficient in the recovery of a proper redox balance. In conclusion, thiol redox regulation, by tuning the activity of specific enzymes, has a key role in mitochondrial signaling pathways.

Protein S-Bacillithiolation Functions in Thiol Protection and Redox Regulation of the Glyceraldehyde-3-Phosphate Dehydrogenase Gap in Staphylococcus aureus Under Hypochlorite Stress.

Aims: Bacillithiol (BSH) is the major low-molecular-weight thiol of the human pathogen Staphylococcus aureus. In this study, we used OxICAT and Voronoi redox treemaps to quantify hypochlorite-sensitive protein thiols in S. aureus USA300 and analyzed the role of BSH in protein S-bacillithiolation.Results: The OxICAT analyses enabled the quantification of 228 Cys residues in the redox proteome of S. aureus USA300. Hypochlorite stress resulted in >10% increased oxidation of 58 Cys residues (25.4%) in the thiol redox proteome. Among the highly oxidized sodium hypochlorite (NaOCl)-sensitive proteins are five S-bacillithiolated proteins (Gap, AldA, GuaB, RpmJ, and PpaC). The glyceraldehyde-3-phosphate (G3P) dehydrogenase Gap represents the most abundant S-bacillithiolated protein contributing 4% to the total Cys proteome. The active site Cys151 of Gap was very sensitive to overoxidation and irreversible inactivation by hydrogen peroxide (H2O2) or NaOCl in vitro. Treatment with H2O2 or NaOCl in the presence of BSH resulted in reversible Gap inactivation due to S-bacillithiolation, which could be regenerated by the bacilliredoxin Brx (SAUSA300_1321) in vitro. Molecular docking was used to model the S-bacillithiolated Gap active site, suggesting that formation of the BSH mixed disulfide does not require major structural changes.Conclusion and Innovation: Using OxICAT analyses, we identified 58 novel NaOCl-sensitive proteins in the pathogen S. aureus that could play protective roles against the host immune defense and include the glycolytic Gap as major target for S-bacillithiolation. S-bacillithiolation of Gap did not require structural changes, but efficiently functions in redox regulation and protection of the active site against irreversible overoxidation in S. aureus. Antioxid. Redox Signal. 28, 410–430.

Mapping the phenotypic repertoire of the cytoplasmic 2-Cys peroxiredoxin – Thioredoxin system. 1. Understanding commonalities and differences among cell types

The system (PTTRS) formed by typical 2-Cys peroxiredoxins (Prx), thioredoxin (Trx), Trx reductase (TrxR), and sulfiredoxin (Srx) is central in antioxidant protection and redox signaling in the cytoplasm of eukaryotic cells. Understanding how the PTTRS integrates these functions requires tracing phenotypes to molecular properties, which is non-trivial. Here we analyze this problem based on a model that captures the PTTRS’ conserved features. We have mapped the conditions that generate each distinct response to H2O2 supply rates (vsup), and estimated the parameters for thirteen human cell types and for Saccharomyces cerevisiae. The resulting composition-to-phenotype map yielded the following experimentally testable predictions. The PTTRS permits many distinct responses including ultra-sensitivity and hysteresis. However, nearly all tumor cell lines showed a similar response characterized by limited Trx-S- depletion and a substantial but self-limited gradual accumulation of hyperoxidized Prx at high vsup. This similarity ensues from strong correlations between the TrxR, Srx and Prx activities over cell lines, which contribute to maintain the Prx-SS reduction capacity in slight excess over the maximal steady state Prx-SS production. In turn, in erythrocytes, hepatocytes and HepG2 cells high vsup depletes Trx-S- and oxidizes Prx mainly to Prx-SS. In all nucleated human cells the Prx-SS reduction capacity defined a threshold separating two different regimes. At sub-threshold vsup the cytoplasmic H2O2 concentration is determined by Prx, nM-range and spatially localized, whereas at supra-threshold vsup it is determined by much less active alternative sinks and μM-range throughout the cytoplasm. The yeast shows a distinct response where the Prx Tsa1 accumulates in sulfenate form at high vsup. This is mainly due to an exceptional stability of Tsa1's sulfenate. The implications of these findings for thiol redox regulation and cell physiology are discussed. All estimates were thoroughly documented and provided, together with analytical approximations for system properties, as a resource for quantitative redox biology.

Evaluation of Efficacy and Toxicity of Exfoliated Silicate Nanoclays as a Feed Additive for Fumonisin Detoxification.

The efficacy of nanosilicate clay platelets (NSCP), exfoliated silicates from natural montmorillonites, as a feed additive for ameliorating fumonisin B1 (FB1) toxicosis was evaluated. Toxicological mechanisms by NSCP were examined through proteomic and biochemical analyses. Dietary supplementation with NSCP at a low level of 40 mg/kg of feed improved growth performances in chickens with respect to FB1 toxicosis. Other issues of ameliorated symptoms including serum and/or hepatic aspartate aminotransferase activity, oxidative stress indicators, and sphinganine/sphingosine ratio, a hallmark of FB1 toxicosis, were considered. Chickens with NSCP inclusion alone at 1000 mg/kg of feed exhibited no changes in hepatic histology, oxidative status, and serum parameters and even had a higher feed intake. Proteomic analysis with liver tissues identified 45 distinct proteins differentially affected by FB1 and/or NSCP, in which proteins involved in thiol metabolism and redox regulation, glycolysis, carcinogenesis, and detoxification by glutathione S-transferase were promoted by FB1, whereas NSCP caused differential changes of protein abundances related to methionine/cysteine and choline/glycine interconversion for glutathione synthesis, redox regulation by peroxiredoxin, toxin/metabolite delivery by albumin, glycolysis, tricarboxylic acid cycle, adenosine triphosphate (ATP) synthesis, and chaperon escort for endoplasmic reticulum stress relief. Functional analyses confirmed the enhancement of hepatic metabolic processes for ATP and NAD(P)H production to meet the need for detoxification, antioxidative defense, and toxin/metabolite clearance by FB1 or NSCP ingestion. On the basis of the amelioration of FB1 toxicosis, global profile of hepatic protein expressions, and validated toxicological mechanisms, NSCP were concluded as a safe and effective agent for FB1 detoxification.

Yeast mitochondrial glutathione is an essential antioxidant with mitochondrial thioredoxin providing a back-up system

Glutathione is an abundant, low-molecular-weight tripeptide whose biological importance is dependent upon its redox-active free sulphydryl moiety. Its role as the main determinant of thiol-redox control has been challenged such that it has been proposed to play a crucial role in iron–sulphur clusters maturation, and only a minor role in thiol redox regulation, predominantly as a back-up system for the cytoplasmic thioredoxin system. Here, we have tested the importance of mitochondrial glutathione in thiol-redox regulation. Glutathione reductase (Glr1) is an oxidoreductase which converts oxidized glutathione to its reduced form. Yeast Glr1 localizes to both the cytosol and mitochondria and we have used a Glr1M1L mutant that is constitutively localized to the cytosol to test the requirement for mitochondrial Glr1. We show that the loss of mitochondrial Glr1 specifically accounts for oxidant sensitivity of a glr1 mutant. Loss of mitochondrial Glr1 does not influence iron–sulphur cluster maturation and we have used targeted roGFP2 fluorescent probes to show that oxidant sensitivity is linked to an altered redox environment. Our data indicate mitochondrial glutathione is crucial for mitochondrial thiol-redox regulation, and the mitochondrial thioredoxin system provides a back-up system, but cannot bear the redox load of the mitochondria on its own.

Imbalance in Protein Thiol Redox Regulation and Cancer-Preventive Efficacy of Selenium.

Although several experimental studies showed cancer-preventive efficacy of supplemental dietary selenium, human clinical trials questioned this efficacy. Identifying its molecular targets and mechanism is important in understanding this discrepancy. Methylselenol, the active metabolite of selenium, reacts with lipid hydroperoxides bound to protein kinase C (PKC) and is oxidized to methylseleninic acid (MSA). This locally generated MSA selectively inactivates PKC by oxidizing its critical cysteine sulfhydryls. The peroxidatic redox cycle occurring in this process may explain how extremely low concentrations of selenium catalytically modify specific membrane-bound proteins compartmentally separated from glutathione and selectively induce cytotoxicity in promoting cells. Mammalian thioredoxin reductase (TR) is itself a selenoenzyme with a catalytic selenocysteine residue. Together with thioredoxin (Trx), it catalyzes reduction of selenite and selenocystine by NADPH generating selenide which in the presence of oxygen redox cycles producing reactive oxygen species. Trx binds with high affinity to PKC and reverses PKC inactivation. Therefore, established tumor cells overexpressing TR and Trx may escape the cancer-preventive actions of selenium. This suggests that in some cases, certain selenoproteins may counteract selenometabolite actions. Lower concentrations of selenium readily inactivate antiapoptotic PKC isoenzymes e and a which have a cluster of vicinal thiols, thereby inducing apoptosis. Higher concentrations of selenium also inactivate proapoptotic enzymes such as proteolytically activated PKCd fragment, holo-PKCz, caspase-3, and c-Jun N-terminal kinase, which all have a limited number of critical cysteine residues and make tumor cells resistant to selenium-induced apoptosis. This may explain the intriguing U-shaped curve that is seen with dietary selenium intake and the extent of cancer prevention.

Vertebrate-specific glutaredoxin is essential for brain development

Cellular functions and survival are dependent on a tightly controlled redox potential. Currently, an increasing amount of data supports the concept of local changes in the redox environment and specific redox signaling events controlling cell function. Specific protein thiol groups are the major targets of redox signaling and regulation. Thioredoxins and glutaredoxins catalyze reversible thiol-disulfide exchange reactions and are primary regulators of the protein thiol redox state. Here, we demonstrate that embryonic brain development depends on the enzymatic activity of glutaredoxin 2. Zebrafish with silenced expression of glutaredoxin 2 lost virtually all types of neurons by apoptotic cell death and the ability to develop an axonal scaffold. As demonstrated in zebrafish and in a human cellular model for neuronal differentiation, glutaredoxin 2 controls axonal outgrowth via thiol redox regulation of collapsin response mediator protein 2, a central component of the semaphorin pathway. This study provides an example of a specific thiol redox regulation essential for vertebrate embryonic development.

Desiccation tolerant plants as model systems to study redox regulation of protein thiols

While the majority of plants and animals succumb to water loss, desiccation tolerant organisms can lose almost all of their intracellular water and revive upon rehydration. Only about 300 ‘resurrection’ angiosperms and very few animals are desiccation tolerant. By contrast, many bryophytes and most lichens are desiccation tolerant and so are the seeds and pollen grains of most flowering plants. The current literature reveals that the extreme fluctuations in water content experienced by desiccation tolerant organisms are accompanied by equally extreme changes in cellular redox state. Strongly oxidizing conditions upon desiccation can cause irreversible oxidation of free cysteine residues of proteins, which can change protein structure and function, and contribute to protein denaturation. It appears likely that reversible formation of disulphide bonds, in particular through protein glutathionylation, contributes to the set of protection mechanisms that confer desiccation tolerance. Upon rehydration, de-glutathionylation can be catalyzed by glutaredoxins (GRXs) and protein disulphide bonds can be reduced through NADPH-dependent thioredoxins (TRXs). Due to their ability to survive severe oxidative stress, desiccation tolerant plants and seeds are excellent models to study protein redox regulation, which may provide tools for enhancing tolerance to drought and more generally, to oxidative stress, in crops.

Abstract 430: Serpin-A1 and A3 as potential pharmacodynamic biomarkers for NOV-002, a redox-modulating anti-cancer agent

Abstract NOV-002 is a formulation of disodium glutathione disulfide (GSSG) that is in Phase III clinical trials for the treatment of advanced non-small cell lung cancer and other oncology indications in combination with standard chemotherapeutic regimens. In addition to increased efficacy compared to chemotherapy alone (survival, tumor growth), NOV-002 has been shown to mitigate chemotherapy-induced hematological suppression. In animal studies it was found that, when administered after chemotherapy, NOV-002 stimulated proliferation of bone marrow progenitor cells and normalized peripheral blood levels of leukocytes and platelets. NOV-002's pharmacokinetic properties demonstrate first order absorption / elimination with a plasma half-life of ∼13 mins. The redox regulation of protein thiols persist in plasma for ∼4 hours. Using mass spectrometry, we identified that Serpin-A1 and -A3 were S-glutathionylated following NOV-002 administration to mice. Serpin-A1 and -A3 were also glutathionylated in a dose- and time- dependent S-glutathionylation following NOV-002 treatment of mouse or human plasma in vitro. There is evidence that members of the Serpin protein family can influence myeloproliferation and hematopoetic progenitor cell mobilization (Winkler et al., 2005; van Pel et al., 2006). Specifically, down regulation of serpins has been demonstrated in bone marrow during progenitor cell mobilization (van Pel et al., 2006), and this influences the marrow microenvironment and migratory behavior of hematopoetic precursor cells. Furthermore, glutathionylation of Serpins has been shown to inhibit their activity (Taygi et al., 1991 and 1992). Since our data shows that Serpins A1 and A3 are S-glutathionylated in plasma following NOV-002 treatment, there may be a mechanistic link between this effect and its in vivo myeloproliferative actions. Moreover, liberation of serpins into the peripheral circulation may also provide an indication that proteolytic pathways have been activated. Since the plasma half-life of S-glutathionylated proteins is ∼4 hours (Townsend et al., 2006), it may be possible to identify and develop these post-translationally modified blood proteins as pharmacodynamic biomarkers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 430.