The thioredoxin antioxidant system

Differential responses of a thioredoxin-like protein gene to Vibrio parahaemolyticus challenge in the noble scallop Chlamys nobilis with different total carotenoids content

Being lack of specific immune system, both enzymes and non-enzymatic antioxidants play crucial roles in immune of invertebrates. In the present study, in order to investigate immune roles of enzyme (thioredoxin, TRX) and antioxidants (carotenoids), Golden scallops with golden shell and golden muscle rich in carotenoids content and Brown scallops with brown shell and white muscle less carotenoids content of the noble scallop Chlamys nobilis were challenged by Vibrio parahaemolyticus for 48 h. Firstly, a cDNA of TRX protein gene from the scallop (named as CnTRX) was cloned and characterized. The cDNA contains 1280 bp, consisting of a 5' -UTR of 99 bp, a long 3' -UTR of 860 bp and a 321 bp open reading frame (ORF) encoding 106 amino acids. Phylogenetic analysis showed that CnTRX had a closer evolution relationship with TRX from Chlamys farreri. CnTRX was ubiquitously expressed in all examined tissues including intestine, adductor, mantle, gonad, gill, kidney, hepatopancreas and hemolymph, and the highest expression level was detected in the hemolymph. Next, CnTRX transcripts were significantly up-regulated in V. parahaemolyticus group in comparison with PBS control group. Moreover, CnTRX transcripts were significantly higher in Golden scallops than that of Brown ones at 6 h, 12 h and 24 h with bacteria challenge (P < 0.05). The present result indicates that both CnTRX and carotenoids are important factors involved in the immune defense against bacteria challenge in the noble scallop.

Thioredoxin-1 Overexpression in the Ventromedial Nucleus of the Hypothalamus Preserves the Counterregulatory Response to Hypoglycemia During Type 1 Diabetes in Male Rats

We previously showed that the glutathione precursor, N-acetylcysteine (NAC), prevented hypoglycemia-associated autonomic failure (HAAF) and impaired activation of ventromedial hypothalamus (VMH) glucose-inhibited (GI) neurons by low glucose after recurrent hypoglycemia (RH) in nondiabetic rats. However, NAC does not normalize glucose sensing by VMH GI neurons when RH occurs during diabetes. We hypothesized that recruiting the thioredoxin (Trx) antioxidant defense system would prevent HAAF and normalize glucose sensing after RH in diabetes. To test this hypothesis, we overexpressed Trx-1 (cytosolic form of Trx) in the VMH of rats with streptozotocin (STZ)-induced type 1 diabetes. The counterregulatory response (CRR) to hypoglycemia in vivo and the activation of VMH GI neurons in low glucose using membrane potential sensitive dye in vitro was measured before and after RH. VMH Trx-1 overexpression normalized both the CRR and glucose sensing by VMH GI neurons in STZ rats. VMH Trx-1 overexpression also lowered the insulin requirement to prevent severe hyperglycemia in STZ rats. However, like NAC, VMH Trx-1 overexpression did not prevent HAAF or normalize activation of VMH GI neurons by low glucose in STZ rats after RH. We conclude that preventing HAAF in type 1 diabetes may require the recruitment of both antioxidant systems.

Modulation of thiol-dependent redox system by metal ionsviathioredoxin and glutaredoxin systems

Metal and metalloid ions regulate thioredoxin and glutaredoxin system-mediated biological functions by targeting mammalian thioredoxin reductase and mitochondrial glutaredoxin 2&5.

Opisthorchis viverrini Proteome and Host-Parasite Interactions

The omics technologies have improved our understanding of the molecular events that underpin host-parasite interactions and the pathogenesis of parasitic diseases. In the last decade, proteomics and genomics in particular have been used to characterize the surface and secreted products of the carcinogenic liver fluke Opisthorchis viverrini and revealed important roles for proteins at the host-parasite interface to ensure that the flukes can migrate, feed and reproduce in a hostile environment. This review summarizes the advances made in this area, primarily focusing on discoveries enabled by the publication of the fluke secreted proteomes over the last decade. Protein families that will be covered include proteases, antioxidants, oncogenic proteins and the secretion of exosome-like extracellular vesicles. Roles of these proteins in host-parasite interactions and pathogenesis of fluke-induced hepatobiliary diseases, including cholangiocarcinogenesis, are discussed. Future directions for the application of this knowledge to control infection and disease will also be discussed.

Hypoxia potentiates LPS-induced inflammatory response and increases cell death by promoting NLRP3 inflammasome activation in pancreatic β cells

Hypoxia and islet inflammation are involved in β-cell failure in type 2 diabetes (T2D). Elevated plasma LPS levels have been verified in patients with T2D, and hypoxia occurs in islets of diabetic mice. Activation of inflammasomes in ischemic or hypoxic conditions was identified in various tissues. Here, we investigated whether hypoxia activates the inflammasome in β cells and the possible mechanisms involved. In mouse insulinoma cell line 6 (MIN6), hypoxia (1% O₂) primes the NLRP3 inflammasome along with NF-κB signaling activation. Our results demonstrate that hypoxia can activate the NLRP3 inflammasome in LPS-primed MIN6 to result in initiating the β cell inflammatory response and cell death in vitro. Reactive oxygen species (ROS) and the thioredoxin-interacting protein (TXNIP) are up-regulated in response to hypoxia. Finally, the role of the ROS-TXNIP axis in mediating the activation of the NLRP3 inflammasome and cell death was characterized by pretreating with the ROS scavenger N-acetylcysteine (NAC) and performing TXNIP knockdown experiments in MIN6. Our data indicate for the first time that the inflammasome is involved in the inflammatory response and cell death in hypoxia-induced β cells through the ROS-TXNIP-NLRP3 axis in vitro. This provides new insight into the relationship between hypoxia and inflammation in T2D.

Transcriptional response of Nautella italica R11 towards its macroalgal host uncovers new mechanisms of host-pathogen interaction

Macroalgae (seaweeds) are essential for the functioning of temperate marine ecosystems, but there is increasing evidence to suggest that their survival is under threat from anthropogenic stressors and disease. Nautella italica R11 is recognized as an aetiological agent of bleaching disease in the red alga, Delisea pulchra. Yet, there is a lack of knowledge surrounding the molecular mechanisms involved in this model host-pathogen interaction. Here we report that mutations in the gene encoding for a LuxR-type quorum sensing transcriptional regulator, RaiR, render N. italica R11 avirulent, suggesting this gene is important for regulating the expression of virulence phenotypes. Using an RNA sequencing approach, we observed a strong transcriptional response of N. italica R11 towards the presence of D. pulchra. In particular, genes involved in oxidative stress resistance, carbohydrate and central metabolism were upregulated in the presence of the host, suggesting a role for these functions in the opportunistic pathogenicity of N. italica R11. Furthermore, we show that RaiR regulates a subset of genes in N. italica R11, including those involved in metabolism and the expression of phage-related proteins. The outcome of this research reveals new functions important for virulence of N. italica R11 and contributes to our greater understanding of the complex factors mitigating microbial diseases in macroalgae.

Spontaneous and specific chemical cross-linking in live cells to capture and identify protein interactions

Covalently locking interacting proteins in situ is an attractive strategy for addressing the challenge of identifying weak and transient protein interactions, yet it is demanding to execute chemical reactions in live systems in a biocompatible, specific, and autonomous manner. Harnessing proximity-enabled reactivity of an unnatural amino acid incorporated in the bait toward a target residue of unknown proteins, here we genetically encode chemical cross-linkers (GECX) to cross-link interacting proteins spontaneously and selectively in live cells. Obviating an external trigger for reactivity and affording residue specificity, GECX enables the capture of low-affinity protein binding (affibody with Z protein), elusive enzyme-substrate interaction (ubiquitin-conjugating enzyme UBE2D3 with substrate PCNA), and endogenous proteins interacting with thioredoxin in E. coli cells, allowing for mass spectrometric identification of interacting proteins and crosslinking sites. This live cell chemistry-based approach should be valuable for investigating currently intangible protein interactions in vivo for better understanding of biology in physiological settings.

Proteins associate via weak and transient interactions that are challenging to identify in vivo. Here, the authors use a genetically encoded chemical cross-linker to covalently lock interacting proteins in live cells, allowing them to identify the captured proteins by mass spectrometry.

Comparative transcriptome analysis of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) reveals novel insights into heat stress tolerance in insects

BACKGROUND

Heat tolerance is a key parameter that affects insect distribution and abundance. Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is a devastating pest of mulberry in the main mulberry-growing regions and can cause tremendous losses to sericulture by directly feeding on mulberry leaves and transmitting viruses to Bombyx mori. Moreover, G. pyloalis shows a prominent capacity for adaptation to daily and seasonal temperature fluctuations and can survive several hours under high temperature. To date, the molecular mechanism underlying the outstanding adaptability of this pest to high temperature remains unclear.

RESULTS

In this study, we performed comparative transcriptome analyses on G. pyloalis exposed to 25 and 40 °C for 4 h. We obtained 34,034 unigenes and identified 1275 and 1222 genes significantly upregulated or downregulated, respectively, by heat stress. Data from the transcriptome analyses indicated that some processes involved in heat tolerance are conserved, such as high expression of heat shock protein (HSP) genes and partial repression of metabolism progress. In addition, vitamin digestion and absorption pathways and detoxification pathways identified here provided new insights for the investigation of the molecular mechanisms of heat stress tolerance. Furthermore, transcriptome analysis indicated that immune and phosphatidylinositol signaling system have a close relationship with heat tolerance. In addition, the expression patterns of ten randomly selected genes, such as HSP and cytochrome P450, were consistent with the transcriptome results obtained through quantitative real-time PCR.

CONCLUSIONS

Comparisons among transcriptome results revealed the upregulation of HSPs and genes involved in redox homeostasis, detoxication, and immune progress. However, many metabolism progresses, such as glycolysis/gluconeogenesis and fatty acid biosynthesis, were partially repressed. The results reflected that the heat tolerance of G. pyloalis is a fairly complicated process and related to a broad range of physiological regulations. Our study can improve understanding on the mechanisms of insect thermal tolerance.

H2S and polysulfide metabolism: Conventional and unconventional pathways

It is now well established that hydrogen sulfide (H₂S) is an effector of a wide variety of physiological processes. It is also clear that many of the effects of H₂S are mediated through reactions with cysteine sulfur on regulatory proteins and most of these are not mediated directly by H₂S but require prior oxidation of H₂S and the formation of per- and polysulfides (H₂S_n, n = 2-8). Attendant with understanding the regulatory functions of H₂S and H₂S_n is an appreciation of the mechanisms that control, i.e., both increase and decrease, their production and catabolism. Although a number of standard "conventional" pathways have been described and well characterized, novel "unconventional" pathways are continuously being identified. This review summarizes our current knowledge of both the conventional and unconventional.

Characterization of Foodborne Strains of Staphylococcus aureus by Shotgun Proteomics: Functional Networks, Virulence Factors and Species-Specific Peptide Biomarkers

In the present work, we applied a shotgun proteomics approach for the fast and easy characterization of 20 different foodborne strains of Staphylococcus aureus (S. aureus), one of the most recognized foodborne pathogenic bacteria. A total of 644 non-redundant proteins were identified and analyzed via an easy and rapid protein sample preparation procedure. The results allowed the differentiation of several proteome datasets from the different strains (common, accessory, and unique datasets), which were used to determine relevant functional pathways and differentiate the strains into different Euclidean hierarchical clusters. Moreover, a predicted protein-protein interaction network of the foodborne S. aureus strains was created. The whole confidence network contains 77 nodes and 769 interactions. Most of the identified proteins were surface-associated proteins that were related to pathways and networks of energy, lipid metabolism and virulence. Twenty-seven virulence factors were identified, and most of them corresponded to autolysins, N-acetylmuramoyl-L-alanine amidases, phenol-soluble modulins, extracellular fibrinogen-binding proteins and virulence factor EsxA. Potential species-specific peptide biomarkers were screened. Twenty-one species-specific peptide biomarkers, belonging to eight different proteins (nickel-ABC transporter, N-acetylmuramoyl-L-alanine amidase, autolysin, clumping factor A, gram-positive signal peptide YSIRK, cysteine protease/staphopain, transcriptional regulator MarR, and transcriptional regulator Sar-A), were proposed to identify S. aureus. These results constitute the first major dataset of peptides and proteins of foodborne S. aureus strains. This repository may be useful for further studies, for the development of new therapeutic treatments for S. aureus food intoxications and for microbial source-tracking in foodstuffs.

Effects of probiotic Bacillus as a substitute for antibiotics on antioxidant capacity and intestinal autophagy of piglets

The objective of this study was to evaluate effects of probiotic Bacillus amyloliquefaciens (Ba) as a substitute for antibiotics on growth performance, antioxidant ability and intestinal autophagy of piglets. Ninety piglets were divided into three groups: G1 (containing 150 mg/Kg aureomycin in the diet); G2 (containing 75 mg/Kg aureomycin and 1 × 10⁸ cfu/Kg Ba in the diet); G3 (containing 2 × 10⁸ cfu/Kg Ba in the diet without any antibiotics). Each treatment had three replications of ten pigs per pen. Results showed that Ba replacement significantly increased the daily weight gain of piglets. Moreover, improved antioxidant status in serum and jejunum was noted in Ba-fed groups as compared with aureomycin group. Increased gene expression of antioxidant enzymes and elevated nuclear factor erythroid 2 related factor 2 (Nrf2) in jejunum was also observed in Ba-fed groups. Besides, Ba replacement significantly decreased jejunal c-Jun N-terminal kinase (JNK) phosphorylation compared with antibiotic group. Western blotting results also revealed that replacing all antibiotics with Ba initiated autophagy in the jejunum as evidenced by increased microtubule-associated protein 1 light chain 3 II (LC3-II) abundance. Taken together, these results indicate that replacing aureomycin with Ba can improve growth performance and antioxidant status of piglets via increasing antioxidant capacity and intestinal autophagy, suggesting a good potential for Ba as an alternative to antibiotics in feed.

Partial purification and characterization of glutathione S-transferase from the somatic tissue of Gastrothylax crumenifer (Trematoda: Digenea)

AIM

Aim of the present study was to carry out the partial purification and biochemical characterization of glutathione S-transferase (GST) from the somatic tissue of ruminal amphistome parasite, Gastrothylax crumenifer (Gc) infecting Indian water buffalo (Bubalus bubalis).

MATERIALS AND METHODS

The crude somatic homogenate of Gc was subjected to progressive ammonium sulfate precipitation followed by size exclusion chromatography in a Sephacryl S 100-HR column. The partially purified GST was assayed spectrophotometrically, and the corresponding enzyme activity was also recorded in polyacrylamide gel. GST isolated from the amphistome parasite was also exposed to variable changes in temperature and the pH gradient of the assay mixture.

RESULTS

The precipitated amphistome GST molecules showed maximum activity in the sixth elution fraction. The GST subunit appeared as a single band in the reducing polyacrylamide gel electrophoresis with an apparent molecular weight of 26 kDa. The GST proteins were found to be fairly stable up to 37°C, beyond this the activity got heavily impaired. Further, the GST obtained showed a pH optima of 7.5.

CONCLUSION

Present findings showed that GST from Gc could be conveniently purified using gel filtration chromatography. The purified enzyme showed maximum stability and activity at 4°C.

Continuous feeding of spent ammonium sulphite liquor improves the production and saccharification performance of cellulase by Penicillium oxalicum

Spent ammonium sulphite liquor (SASL) is the main effluent from the ammonium sulphite pulping process, and contains amounts of lignocellulosic oligomers, monosaccharides and ammonium salts. The effect of continuous SASL-feeding on cellulase production by Penicillium oxalicum was studied. With a rate-varying feeding strategy, the maximal filter paper enzyme (FPase) activity reached 17.66U/mL at 144h, and the specific FPase activity increased from 1.74U/mg (without SASL) to 2.40U/mg. Accordingly, the glucan hydrolysis conversion of delignified corn cob residue by the enzymes from continuous SASL-feeding fermentation was significantly higher than that without SASL at equal protein loadings. Comparative proteomic analysis demonstrated that the proteins involved in lignocellulose degradation were specifically up-regulated in the crude cellulase with SASL-feeding. The obtained crude enzyme was efficient in the hydrolysis of pulping products, with a glucan conversion of 81.87% achieved after 72h saccharification of ammonium sulphite pulp.

The lipid peroxidation product 4-hydroxy-2-nonenal induces tissue factor decryption via ROS generation and the thioredoxin system

Many pathophysiologic agents transform cryptic tissue factor (TF) on cells to prothrombotic TF, and one such stimulus is 4-hydroxy-2-nonenal (HNE), the most abundant aldehyde produced by the oxidation of ω-6 polyunsaturated fatty acids. HNE was shown to induce reactive oxygen species (ROS) generation and p38 MAPK activation, but the link between them and their role in TF decryption are unclear. The present study was carried out to elucidate potential mechanisms involved in HNE-induced TF decryption in monocytic cells. The data presented herein show that mitochondria are the primary source for HNE-induced ROS generation. The inhibition of mitochondrial electron transport chain complex III and V blocked HNE-induced ROS generation, but not p38 MAPK activation. These inhibitors reduced phosphatidylserine (PS) externalization and TF decryption significantly, but not completely. HNE treatment inhibited the activities of thioredoxin reductase (TrxR) and thioredoxin (Trx), independent of ROS. Inhibition of the TrxR/Trx system by HNE or pharmacological inhibitors induced p38 MAPK activation, PS externalization, and TF decryption. Additional studies revealed that the inhibition of TrxR/Trx led to activation of apoptosis signal-regulating kinase (ASK-1) and mitogen-activated protein kinase kinase 3/6. Inhibition of ASK-1 expression by small interfering RNA or its activity by pharmacological inhibitors diminished HNE-induced TF decryption. Overall, our data suggest that HNE induces TF decryption by 2 distinctive pathways. One is ROS dependent but independent of p38 MAPK activation, and the other is via TrxR/Trx and is p38 MAPK activation dependent. However, both mechanisms result in the enhancement of PS at the outer leaflet that is responsible for TF decryption.

Targeting the Thioredoxin Reductase-Thioredoxin System from Staphylococcus aureus by Silver Ions

The thioredoxin system, which is composed of NADPH, thioredoxin reductase (TrxR), and thioredoxin (Trx), is one of the major disulfide reductase systems used by bacteria against oxidative stress. In particular, this reductase system is crucial for the survival of the pathogenic bacterium Staphylococcus aureus, which lacks a natural glutathione/glutaredoxin (Grx) system. Although silver ions and silver-containing materials have been used as antibacterial agents for centuries, the antibacterial mechanism of silver is not well-understood. Herein, we demonstrate that silver ions bind to the active sites of S. aureus TrxR and Trx with dissociation constants of 1.4 ± 0.1 μM and 15.0 ± 5.0 μM and stoichiometries of 1 and 2 Ag⁺ ions per protein, respectively. Importantly, silver ion binding leads to oligomerization and functional disruption of TrxR as well as Trx. Silver also depleted intracellular thiol levels in S. aureus, disrupting bacterial thiol-redox homeostasis. Our study provides new insights into the antibacterial mechanism of silver ions. Moreover, the Trx and TrxR system might serve as a feasible target for the design of antibacterial drugs.

Metabolism of hydrogen sulfide (H2S) and Production of Reactive Sulfur Species (RSS) by superoxide dismutase

Reactive sulfur species (RSS) such as H₂S, HS^•, H₂S_n, (n = 2–7) and HS₂^•- are chemically similar to H₂O and the reactive oxygen species (ROS) HO^•, H₂O₂, O₂^•- and act on common biological effectors. RSS were present in evolution long before ROS, and because both are metabolized by catalase it has been suggested that “antioxidant” enzymes originally evolved to regulate RSS and may continue to do so today. Here we examined RSS metabolism by Cu/Zn superoxide dismutase (SOD) using amperometric electrodes for dissolved H₂S, a polysulfide-specific fluorescent probe (SSP4), and mass spectrometry to identify specific polysulfides (H₂S₂-H₂S₅). H₂S was concentration- and oxygen-dependently oxidized by 1 μM SOD to polysulfides (mainly H₂S₂, and to a lesser extent H₂S₃ and H₂S₅) with an EC₅₀ of approximately 380 μM H₂S. H₂S concentrations > 750 μM inhibited SOD oxidation (IC₅₀ = 1.25 mM) with complete inhibition when H₂S > 1.75 mM. Polysulfides were not metabolized by SOD. SOD oxidation preferred dissolved H₂S over hydrosulfide anion (HS^-), whereas HS^- inhibited polysulfide production. In hypoxia, other possible electron donors such as nitrate, nitrite, sulfite, sulfate, thiosulfate and metabisulfite were ineffective. Manganese SOD also catalyzed H₂S oxidation to form polysulfides, but did not metabolize polysulfides indicating common attributes of these SODs. These experiments suggest that, unlike the well-known SOD-mediated dismutation of two O₂^•- to form H₂O₂ and O_2^, SOD catalyzes a reaction using H₂S and O₂ to form persulfide. These can then combine in various ways to form polysulfides and sulfur oxides. It is also possible that H₂S (or polysulfides) interact/react with SOD cysteines to affect catalytic activity or to directly contribute to sulfide metabolism. Our studies suggest that H₂S metabolism by SOD may have been an ancient mechanism to detoxify sulfide or to regulate RSS and along with catalase may continue to do so in contemporary organisms.

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Polysulfides are reactive sulfide species (RSS) and are similar to reactive oxygen species (ROS).

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RSS may be the antecedent of redox regulatory and stress-related modalities.

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RSS likely persist in modern-day organisms and are regulated by SOD.

Metabolic shift at the class level sheds light on adaptation of methanogens to oxidative environments

Methanogens have long been considered strictly anaerobic and oxygen-sensitive microorganisms, but their ability to survive oxygen stress has also been documented. Indeed, methanogens have been found in oxidative environments, and antioxidant genes have been detected in their genomes. How methanogens adapt to oxidative environments, however, remain poorly understood. Here, we systematically predicted and annotated antioxidant features from representative genomes across six well-established methanogen orders. Based on functional gene content involved in production of reactive oxygen species, Hierarchical Clustering analyses grouped methanogens into two distinct clusters, corresponding to the Class I and II methanogens, respectively. Comparative genomics suggested a systematic shift in metabolisms across the two classes, resulting in an enrichment of antioxidant features in the Class II. Moreover, meta-analysis of 16 S rRNA gene sequences obtained from EnvDB indicated that members of Class II were more frequently recovered from microaerophilic and even oxic environments than the Class I members. Phylogenomic analysis suggested that the Class I and II methanogens might have evolved before and around the Great Oxygenation Event, respectively. The enrichment of antioxidant features in the Class II methanogens may have played a key role in the adaption of this group to oxidative environments today and historically.

Synthesis of naphthazarin derivatives and identification of novel thioredoxin reductase inhibitor as potential anticancer agent

Mammalian thioredoxin reductase (TrxR) enzymes play a crucial role in regulating multiple redox-based signaling pathways and have attracted increasing attention as promising anticancer drug targets. We report here the synthesis of a panel of naphthazarin derivatives and discovery of 2-methyl-5,8-dihydroxy-1,4-naphthoquinone (3, 2-methylnaphthazarin) as a potent cytotoxic agent with a submicromolar half maximal inhibitory concentration to the human promyelocytic leukemia HL-60 cells. Mechanism studies reveal that the compound selectively inhibits TrxR to induce oxidative stress-mediated apoptosis of HL-60 cells. Knockdown of TrxR sensitizes the cells to 3 insults, while overexpression of the functional enzyme confers resistance to the compound treatment, underpinning the physiological significance of targeting TrxR by 3. Clarification of the interaction of compound 3 with TrxR unveils a mechanism underlying the cellular action of the compound, and sheds light in considering development of the compound as a potential cancer chemotherapeutic agent.

Proteomics of Staphylococcus aureus biofilm matrix in a rat model of orthopedic implant-associated infection

The matrix proteins of Staphylococcus aureus biofilm have not been well defined. Previous efforts to identify these proteins were performed using in vitro systems. Here we use a proteomic approach to identify biofilm matrix proteins directly from infected bone implants using a rat model of orthopedic implant-associated S. aureus infection. Despite heavy presence of host proteins, a total of 28 and 105 S. aureus proteins were identified during acute infection and chronic infection, respectively. Our results show that biofilm matrix contains mostly intracellular cytoplasmic proteins and, to a much less extent, extracellular and cell surface-associated proteins. Significantly, leukocidins were identified in the biofilm matrix during chronic infection, suggesting S. aureus is actively attacking the host immune system even though they are protected within the biofilm. The presence of two surface-associated proteins, Ebh and SasF, in the infected bone tissue during acute infection was confirmed by immunohistochemistry. In addition, a large number of host proteins were found differentially expressed in response to S. aureus biofilm formed on bone implants.

Oxidative Stress in Human Atherothrombosis: Sources, Markers and Therapeutic Targets

Atherothrombosis remains one of the main causes of morbidity and mortality worldwide. The underlying pathology is a chronic pathological vascular remodeling of the arterial wall involving several pathways, including oxidative stress. Cellular and animal studies have provided compelling evidence of the direct role of oxidative stress in atherothrombosis, but such a relationship is not clearly established in humans and, to date, clinical trials on the possible beneficial effects of antioxidant therapy have provided equivocal results. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is one of the main sources of reactive oxygen species (ROS) in human atherothrombosis. Moreover, leukocyte-derived myeloperoxidase (MPO) and red blood cell-derived iron could be involved in the oxidative modification of lipids/lipoproteins (LDL/HDL) in the arterial wall. Interestingly, oxidized lipoproteins, and antioxidants, have been analyzed as potential markers of oxidative stress in the plasma of patients with atherothrombosis. In this review, we will revise sources of ROS, focusing on NADPH oxidase, but also on MPO and iron. We will also discuss the impact of these oxidative systems on LDL and HDL, as well as the value of these modified lipoproteins as circulating markers of oxidative stress in atherothrombosis. We will finish by reviewing some antioxidant systems and compounds as therapeutic strategies to prevent pathological vascular remodeling.

Redox Signaling Mediated by Thioredoxin and Glutathione Systems in the Central Nervous System

SIGNIFICANCE

The thioredoxin (Trx) and glutathione (GSH) systems play important roles in maintaining the redox balance in the brain, a tissue that is prone to oxidative stress due to its high-energy demand. These two disulfide reductase systems are active in various areas of the brain and are considered to be critical antioxidant systems in the central nervous system (CNS). Various neuronal disorders have been characterized to have imbalanced redox homeostasis. Recent Advances: In addition to their detrimental effects, recent studies have highlighted that reactive oxygen species/reactive nitrogen species (ROS/RNS) act as critical signaling molecules by modifying thiols in proteins. The Trx and GSH systems, which reversibly regulate thiol modifications, regulate redox signaling involved in various biological events in the CNS.

CRITICAL ISSUES

In this review, we focus on the following: (i) how ROS/RNS are produced and mediate signaling in CNS; (ii) how Trx and GSH systems regulate redox signaling by catalyzing reversible thiol modifications; (iii) how dysfunction of the Trx and GSH systems causes alterations of cellular redox signaling in human neuronal diseases; and (iv) the effects of certain small molecules that target thiol-based signaling pathways in the CNS.

FUTURE DIRECTIONS

Further study on the roles of thiol-dependent redox systems in the CNS will improve our understanding of the pathogenesis of many human neuronal disorders and also help to develop novel protective and therapeutic strategies against neuronal diseases. Antioxid. Redox Signal. 27, 989-1010.

G6PD plays a neuroprotective role in brain ischemia through promoting pentose phosphate pathway

TIGAR-regulated pentose phosphate pathway (PPP) plays a critical role in the neuronal survival during cerebral ischemia/reperfusion. Glucose-6-phosphate dehydrogenase (G6PD) is a rate-limiting enzyme in PPP and thus, we hypothesized that it plays an essential role in anti-oxidative defense through producing NADPH. The present study investigated the regulation and the role of G6PD in ischemia/reperfusion-induced neuronal injury with in vivo and in vitro models of ischemic stroke. The results showed that the levels of G6PD mRNA and protein were increased after ischemia/reperfusion. In vivo, lentivirus-mediated G6PD overexpression in mice markedly reduced neuronal damage after ischemia/reperfusion insult, while lentivirus-mediated G6PD knockdown exacerbated it. In vitro, overexpression of G6PD in cultured primary neurons decreased neuronal injury under oxygen and glucose deprivation/reoxygenation (OGD/R) condition, whereas knockdown of G6PD aggravated it. Overexpression of G6PD increased levels of NADPH and reduced form of glutathione (rGSH), and ameliorated ROS-induced macromolecular damage. On the contrary, knockdown of G6PD executed the opposite effects in mice and in primary neurons. Supplementation of exogenous NADPH alleviated the detrimental effects of G6PD knockdown, whereas further enhanced the beneficial effects of G6PD overexpression in ischemic injury. Therefore, our results suggest that G6PD protects ischemic brain injury through increasing PPP. Thus G6PD may be considered as potential therapeutic target for treatment of ischemic brain injury.

Progress in understanding the molecular oxygen paradox - function of mitochondrial reactive oxygen species in cell signaling

The molecular oxygen (O2) paradox was coined to describe its essential nature and toxicity. The latter characteristic of O2 is associated with the formation of reactive oxygen species (ROS), which can damage structures vital for cellular function. Mammals are equipped with antioxidant systems to fend off the potentially damaging effects of ROS. However, under certain circumstances antioxidant systems can become overwhelmed leading to oxidative stress and damage. Over the past few decades, it has become evident that ROS, specifically H2O2, are integral signaling molecules complicating the previous logos that oxyradicals were unfortunate by-products of oxygen metabolism that indiscriminately damage cell structures. To avoid its potential toxicity whilst taking advantage of its signaling properties, it is vital for mitochondria to control ROS production and degradation. H2O2 elimination pathways are well characterized in mitochondria. However, less is known about how H2O2 production is controlled. The present review examines the importance of mitochondrial H2O2 in controlling various cellular programs and emerging evidence for how production is regulated. Recently published studies showing how mitochondrial H2O2 can be used as a secondary messenger will be discussed in detail. This will be followed with a description of how mitochondria use S-glutathionylation to control H2O2 production.

Potential anti-cancer activity of 7-O-pentyl quercetin: Efficient, membrane-targeted kinase inhibition and pro-oxidant effect

Quercetin is a redox-active plant-derived flavonoid with potential anticancer effects, stemming largely from its interaction with a number of proteins, and in particular from inhibition of pro-life kinases. To improve efficacy, we reasoned that a local increase in concentration of the compound at the level of cell membranes would result in a more efficient interaction with membrane-associated signaling kinases. We report here the synthesis of all five isomeric quercetin derivatives in which an n-pentyl group was linked via an ether bond to each hydroxyl of the flavonoid kernel. This strategy proved effective in directing quercetin to cellular membranes, and revealed a remarkable dependence of the derivatives' bioactivity on the specific site of functionalization. The isomer bearing the pentyl group in position 7, Q-7P, turned out to be the most effective and promising derivative, selectively inducing apoptosis in tumoral and fast-growing cells, while sparing slow-growing, non-tumoral ones. Cytotoxicity for tumoral cells was strongly enhanced compared to quercetin itself. Q-7P induced massive ROS production, which however accounted only partially for cell death. Alterations in the levels of various signaling phospho-proteins were observed in a proteomics screen. An important contribution seems to come from inhibition of the PI3K/Akt pathway. This work opens new perspectives in developing membrane-associating, polyphenol-based anticancer agents.

Analysis of the Interactions Between Thioredoxin and 20 Selenoproteins in Chicken

Thioredoxin (Trx) is a small molecular protein with complicated functions in a number of processes, including inflammation, apoptosis, embryogenesis, cardiovascular disease, and redox regulation. Some selenoproteins, such as glutathione peroxidase (Gpx), iodothyronine deiodinase (Dio), and thioredoxin reductase (TR), are involved in redox regulation. However, whether there are interactions between Trx and selenoproteins is still not known. In the present paper, we used a Modeller, Hex 8.0.0, and the KFC2 Server to predict the interactions between Trx and selenoproteins. We used the Modeller to predict the target protein in objective format and assess the accuracy of the results. Molecular interaction studies with Trx and selenoproteins were performed using the molecular docking tools in Hex 8.0.0. Next, we used the KFC2 Server to further test the protein binding sites. In addition to the selenoprotein physiological functions, we also explored potential relationships between Trx and selenoproteins beyond all the results we got. The results demonstrate that Trx has the potential to interact with 19 selenoproteins, including iodothyronine deiodinase 1 (Dio1), iodothyronine deiodinase 3 (Dio3), glutathione peroxidase 1 (Gpx1), glutathione peroxidase 2 (Gpx2), glutathione peroxidase 3 (Gpx3), glutathione peroxidase 4 (Gpx4), selenoprotein H (SelH), selenoprotein I (SelI), selenoprotein M (SelM), selenoprotein N (SelN), selenoprotein T (SelT), selenoprotein U (SelU), selenoprotein W (SelW), selenoprotein 15 (Sep15), methionine sulfoxide reductase B (Sepx1), selenophosphate synthetase 1 (SPS1), TR1, TR2, and TR3, among which TR1, TR2, TR3, SPS1, Sep15, SelN, SelM, SelI, Gpx2, Gpx3, Gpx4, and Dio3 exhibited intense correlations with Trx. However, additional experiments are needed to verify them.

Impaired cross-talk between the thioredoxin and glutathione systems is related to ASK-1 mediated apoptosis in neuronal cells exposed to mercury

Mercury (Hg) compounds target both cysteine (Cys) and selenocysteine (Sec) residues in peptides and proteins. Thus, the components of the two major cellular antioxidant systems - glutathione (GSH) and thioredoxin (Trx) systems - are likely targets for mercurials. Hg exposure results in GSH depletion and Trx and thioredoxin reductase (TrxR) are prime targets for mercury. These systems have a wide-range of common functions and interaction between their components has been reported. However, toxic effects over both systems are normally treated as isolated events. To study how the interaction between the glutathione and thioredoxin systems is affected by Hg, human neuroblastoma (SH-SY5Y) cells were exposed to 1 and 5μM of inorganic mercury (Hg2+), methylmercury (MeHg) or ethylmercury (EtHg) and examined for TrxR, GSH and Grx levels and activities, as well as for Trx redox state. Phosphorylation of apoptosis signalling kinase 1 (ASK1), caspase-3 activity and the number of apoptotic cells were evaluated to investigate the induction of Trx-mediated apoptotic cell death. Additionally, primary cerebellar neurons from mice depleted of mitochondrial Grx2 (mGrx2D) were used to examine the link between Grx activity and Trx function. Results showed that Trx was affected at higher exposure levels than TrxR, especially for EtHg. GSH levels were only significantly affected by exposure to a high concentration of EtHg. Depletion of GSH with buthionine sulfoximine (BSO) severely increased Trx oxidation by Hg. Notably, EtHg-induced oxidation of Trx was significantly enhanced in primary neurons of mGrx2D mice. Our results suggest that GSH/Grx acts as backups for TrxR in neuronal cells to maintain Trx turnover during Hg exposure, thus linking different mechanisms of molecular and cellular toxicity. Finally, Trx oxidation by Hg compounds was associated to apoptotic hallmarks, including increased ASK-1 phosphorylation, caspase-3 activation and increased number of apoptotic cells.

Mitochondrial matrix pH as a decisive factor in neurometabolic imaging

Alterations of cellular bioenergetics are a common feature in most neurodegenerative disorders. However, there is a selective vulnerability of different brain regions, cell types, and even mitochondrial populations to these metabolic disturbances. Thus, the aim of our study was to establish and validate an in vivo metabolic imaging technique to screen for mitochondrial function on the subcellular level. Based on nicotinamide adenine dinucleotide (phosphate) fluorescence lifetime imaging microscopy [NAD(P)H FLIM], we performed a quantitative correlation to high-resolution respirometry. Thereby, we revealed mitochondrial matrix pH as a decisive factor in imaging NAD(P)H redox state. By combining both parameters, we illustrate a quantitative, high-resolution assessment of mitochondrial function in metabolically modified cells as well as in an amyloid precursor protein-overexpressing model of Alzheimer's disease. Our metabolic imaging technique provides the basis for dissecting mitochondrial deficits not only in a range of neurodegenerative diseases, shedding light onto bioenergetic failures of cells remaining in their metabolic microenvironment.

Innate immune evasion strategies against Cryptococcal meningitis caused by Cryptococcus neoformans

As an infectious fungus that affects the respiratory tract, Cryptococcus neoformans (C. neoformans) commonly causes asymptomatic pulmonary infection. C. neoformans may target the brain instead of the lungs and cross the blood-brain barrier (BBB) in the early phase of infection; however, this is dependent on successful evasion of the host innate immune system. During the initial stage of fungal infection, a complex network of innate immune factors are activated. C. neoformans utilizes a number of strategies to overcome the anti-fungal mechanisms of the host innate immune system and cross the BBB. In the present review, the defensive mechanisms of C. neoformans against the innate immune system and its ability to cross the BBB were discussed, with an emphasis on recent insights into the activities of anti-phagocytotic and anti-oxidative factors in C. neoformans.

Immunization with alkyl hydroperoxide reductase subunit C reduces Fusobacterium nucleatum load in the intestinal tract

Fusobacterium nucleatum (Fn) is an important tumour-associated bacterium in colorectal cancer (CRC). The antioxidant protein alkyl hydroperoxide reductase subunit C (AhpC) can induce strong antibacterial immune response during various pathogen infections. Our study aimed to evaluate the efficacy of Fn-AhpC as a candidate vaccine. In this work, by western blot analysis, we showed that Fn-AhpC recombinant protein could be recognized specifically by antibodies present in the sera of CRC patients; using the mouse Fn-infection model, we observed that systemic prophylactic immunization with AhpC/alum conferred significant protection against infection in 77.3% of mice. In addition, we measured the anti-AhpC antibody level in the sera of CRC patients and found that there was no obvious increase of anti-AhpC antibodies in the early-stage CRC group. Furthermore, we treated Fn with the sera from both immunized mice and CRC patients and found that sera with high anti-AhpC antibodies titre could inhibit Fn growth. In conclusion, our findings support the use of AhpC as a potential vaccine candidate against inhabitation or infection of Fn in the intestinal tract, which could provide a practical strategy for the prevention of CRC associated with Fn infection.

Early response of glutathione- and thioredoxin-dependent antioxidant defense systems to Tl(I)- and Tl(III)-mediated oxidative stress in adherent pheochromocytoma (PC12adh) cells

Thallium (Tl) is a toxic heavy metal that causes oxidative stress both in vitro and in vivo. In this work, we evaluated the production of oxygen (ROS)- and nitrogen (RNS)-reactive species in adherent PC12 (PC12adh) cells exposed for 0.5-6 h to Tl(I) or Tl(III) (10-100 µM). In this system, Tl(I) induced mostly H₂O₂ generation while Tl(III) induced H₂O₂ and ONOO^·- generation. Both cations enhanced iNOS expression and activity, and decreased CuZnSOD expression but without affecting its activity. Tl(I) increased MnSOD expression and activity but Tl(III) decreased them. NADPH oxidase (NOX) activity remained unaffected throughout the period assessed. Oxidant levels returned to baseline values after 6 h of incubation, suggesting a response of the antioxidant defense system to the oxidative insult imposed by the cations. Tl also affected the glutathione-dependent system: while Tl(III) increased glutathione peroxidase (GPx) expression and activity, Tl(I) and Tl(III) decreased glutathione reductase (GR) expression. However, GR activity was mildly enhanced by Tl(III). Finally, thioredoxin-dependent system was evaluated. Only Tl(I) increased 2-Cys peroxiredoxins (2-Cys Prx) expression, although both cations increased their activity. Tl(I) increased cytosolic thioredoxin reductase (TrxR1) and decreased mitochondrial (TrxR2) expression. Tl(III) had a biphasic effect on TrxR1 expression and slightly increased TrxR2 expression. Despite of this, both cations increased total TrxR activity. Obtained results suggest that in Tl(I)-exposed PC12adh cells, there is an early response to oxidative stress mainly by GSH-dependent system while in Tl(III)-treated cells both GSH- and Trx-dependent systems are involved.

Monitoring thioredoxin redox with a genetically encoded red fluorescent biosensor

Thioredoxin (Trx) is one of the two major thiol antioxidants, playing essential roles in redox homeostasis and signaling. Despite its importance, there is a lack of methods for monitoring Trx redox dynamics in live cells, hindering a better understanding of physiological and pathological roles of the Trx redox system. In this work, we developed the first genetically encoded fluorescent biosensor for Trx redox by engineering a redox relay between the active-site cysteines of human Trx1 and rxRFP1, a redox-sensitive red fluorescent protein. We used the resultant biosensor-TrxRFP1-to selectively monitor perturbations of Trx redox in various mammalian cell lines. We subcellularly localized TrxRFP1 to image compartmentalized Trx redox changes. We further combined TrxRFP1 with a green fluorescent Grx1-roGFP2 biosensor to simultaneously monitor Trx and glutathione redox dynamics in live cells in response to chemical and physiologically relevant stimuli.

Targeting the Thioredoxin System for Cancer Therapy

Thioredoxin (Trx) and thioredoxin reductase (TrxR) are essential components of the Trx system which plays pivotal roles in regulating multiple cellular redox signaling pathways. In recent years TrxR/Trx have been increasingly recognized as an important modulator of tumor development, and hence targeting TrxR/Trx is a promising strategy for cancer treatment. In this review we first discuss the structural details of TrxR, the functions of the Trx system, and the rational of targeting TrxR/Trx for cancer treatment. We also highlight small-molecule TrxR/Trx inhibitors that have potential anticancer activity and review their mechanisms of action. Finally, we examine the challenges of developing TrxR/Trx inhibitors as anticancer agents and perspectives for selectively targeting TrxR/Trx.

A Reexamination of Thioredoxin Reductase from Thermoplasma acidophilum, a Thermoacidophilic Euryarchaeon, Identifies It as an NADH-Dependent Enzyme

Flavin-containing Trx reductase (TrxR) of Thermoplasma acidophilum (Ta), a thermoacidophilic facultative anaerobic archaeon, lacks the structural features for the binding of 2'-phosphate of nicotinamide adenine dinucleotide phosphate (NADPH), and this feature has justified the observed lack of activity with NADPH; NADH has also been reported to be ineffective. Our recent phylogenetic analysis identified Ta-TrxR as closely related to the NADH-dependent enzymes of Thermotoga maritima and Desulfovibrio vulgaris, both being anaerobic bacteria. This observation instigated a reexamination of the activity of the enzyme, which showed that Ta-TrxR is NADH dependent; the apparent K_m for NADH was 3.1 μM, a physiologically relevant value. This finding is consistent with the observation that NADH:TrxR has thus far been found primarily in anaerobic bacteria and archaea.

New tricks for an old dog: Brf2-dependent RNA Polymerase III transcription in oxidative stress and cancer

Here, we discuss the role of Brf2, an RNA Polymerase III core transcription factor, as a master switch of the oxidative stress response. We highlight the interplay of Brf2 with the Nrf2/Keap1 pathway, as well as the role of Brf2 in cancer and other possible regulations.

6-Methoxyethylamino-numonafide inhibits hepatocellular carcinoma xenograft growth as a single agent and in combination with sorafenib

Hepatocellular carcinoma (HCC) is the third leading form of cancer worldwide, and its incidence is increasing rapidly in the United States, tripling over the past 3 decades. The current chemotherapeutic strategies against localized and metastatic HCC are ineffective. Here we report that 6-methoxyethylamino-numonafide (MEAN) is a potent growth inhibitor of murine xenografts of 2 human HCC cell lines. At the same dose and with the same treatment strategies, MEAN was more efficacious in inhibiting tumor growth in mice than sorafenib, the only approved drug for HCC. Treatment by MEAN at an effective dose for 6 wk was well tolerated by animals. Combined therapy using both sorafenib and MEAN enhanced tumor growth inhibition over monotherapy with either agent. Additional experiments revealed that MEAN inhibited tumor growth through mechanisms distinct from those of either its parent compound, amonafide, or sorafenib. MEAN suppressed C-MYC expression and increased expression of several tumor suppressor genes, including Src homology region 2 domain-containing phosphatase-1 (SHP-1) and TXNIP (thioredoxin-interacting protein). As an encouraging feature for envisioned clinical application, the IC₅₀ of MEAN was not significantly changed in several drug-resistant cell lines with activated P-glycoprotein drug efflux pumps compared to drug-sensitive parent cells, demonstrating the ability of MEAN to be effective in cells resistant to existing chemotherapy regimens. MEAN is a promising candidate for clinical development as a single-agent therapy or in combination with sorafenib for the management of HCC.-Liu, Y., Lou, G., Norton, J. T., Wang, C., Kandela, I., Tang, S., Shank, N. I., Gupta, P., Huang, M., Avram, M. J., Green, R., Mazar, A., Appella, D., Chen, Z., Huang, S. 6-Methoxyethylamino-numonafide inhibits hepatocellular carcinoma xenograft growth as a single agent and in combination with sorafenib.

Delayed effects of transcriptional responses in Mycobacterium tuberculosis exposed to nitric oxide suggest other mechanisms involved in survival

Mycobacterium tuberculosis has succeeded as a human pathogen for tens of thousands of years thanks to its ability to resist and adapt to the adverse conditions it encounters upon infection. Bacterial adaptation to stress is commonly viewed in the context of transcriptional regulation, with the implicit expectation that an initial transcriptomic response is tightly coupled to an ensuing proteomic response. However, after challenging M. tuberculosis with nitric oxide we found that the rapid transcriptional responses, detectable within minutes of nitric oxide exposure, typically took several hours to manifest on the protein level. Furthermore, early proteomic responses were dominated by the degradation of a set of proteins, specifically those containing damaged iron-sulphur clusters. Overall, our findings are consistent with transcriptional responses participating mostly in late-stage recovery rather than in generating an immediate resistance to nitric oxide stress, suggesting that survival of M. tuberculosis under acute stress is contingent on mechanisms other than transcriptional regulation. These findings provide a revised molecular understanding of an important human pathogen.

Differential expression of disulfide reductase enzymes in a free-living platyhelminth (Dugesia dorotocephala)

A search of the disulfide reductase activities expressed in the adult stage of the free-living platyhelminth Dugesia dorotocephala was carried out. Using GSSG or DTNB as substrates, it was possible to obtain a purified fraction containing both GSSG and DTNB reductase activities. Through the purification procedure, both disulfide reductase activities were obtained in the same chromatographic peak. By mass spectrometry analysis of peptide fragments obtained after tryptic digestion of the purified fraction, the presence of glutathione reductase (GR), thioredoxin-glutathione reductase (TGR), and a putative thioredoxin reductase (TrxR) was detected. Using the gold compound auranofin to selectively inhibit the GSSG reductase activity of TGR, it was found that barely 5% of the total GR activity in the D. dorotocephala extract can be assigned to GR. Such strategy did allow us to determine the kinetic parameters for both GR and TGR. Although It was not possible to discriminate DTNB reductase activity due to TrxR from that of TGR, a chromatofocusing experiment with a D. dorotocephala extract resulted in the obtention of a minor protein fraction enriched in TrxR, strongly suggesting its presence as a functional protein. Thus, unlike its parasitic counterparts, in the free-living platyhelminth lineage the three disulfide reductases are present as functional proteins, albeit TGR is still the major disulfide reductase involved in the reduction of both Trx and GSSG. This fact suggests the development of TGR in parasitic flatworms was not linked to a parasitic mode of life.

The Deep Thioredoxome in Chlamydomonas reinhardtii: New Insights into Redox Regulation

Thiol-based redox post-translational modifications have emerged as important mechanisms of signaling and regulation in all organisms, and thioredoxin plays a key role by controlling the thiol-disulfide status of target proteins. Recent redox proteomic studies revealed hundreds of proteins regulated by glutathionylation and nitrosylation in the unicellular green alga Chlamydomonas reinhardtii, while much less is known about the thioredoxin interactome in this organism. By combining qualitative and quantitative proteomic analyses, we have comprehensively investigated the Chlamydomonas thioredoxome and 1188 targets have been identified. They participate in a wide range of metabolic pathways and cellular processes. This study broadens not only the redox regulation to new enzymes involved in well-known thioredoxin-regulated metabolic pathways but also sheds light on cellular processes for which data supporting redox regulation are scarce (aromatic amino acid biosynthesis, nuclear transport, etc). Moreover, we characterized 1052 thioredoxin-dependent regulatory sites and showed that these data constitute a valuable resource for future functional studies in Chlamydomonas. By comparing this thioredoxome with proteomic data for glutathionylation and nitrosylation at the protein and cysteine levels, this work confirms the existence of a complex redox regulation network in Chlamydomonas and provides evidence of a tremendous selectivity of redox post-translational modifications for specific cysteine residues.

Oxidative stress, metabolomics profiling, and mechanism of local anesthetic induced cell death in yeast

The World Health Organization designates lidocaine as an essential medicine in healthcare, greatly increasing the probability of human exposure. Its use has been associated with ROS generation and neurotoxicity. Physiological and metabolomic alterations, and genetics leading to the clinically observed adverse effects have not been temporally characterized. To study alterations that may lead to these undesirable effects, Saccharomyces cerevisiae grown on aerobic carbon sources to stationary phase was assessed over 6h. Exposure of an LC50 dose of lidocaine, increased mitochondrial depolarization and ROS/RNS generation assessed using JC-1, ROS/RNS specific probes, and FACS. Intracellular calcium also increased, assessed by ICP-MS. Measurement of the relative ATP and ADP concentrations indicates an initial 3-fold depletion of ATP suggesting an alteration in the ATP:ADP ratio. At the 6h time point the lidocaine exposed population contained ATP concentrations roughly 85% that of the negative control suggesting the surviving population adapted its metabolic pathways to, at least partially restore cellular bioenergetics. Metabolite analysis indicates an increase of intermediates in the pentose phosphate pathway, the preparatory phase of glycolysis, and NADPH. Oxidative stress produced by lidocaine exposure targets aconitase decreasing its activity with an observed decrease in isocitrate and an increase citrate. Similarly, increases in α-ketoglutarate, malate, and oxaloacetate imply activation of anaplerotic reactions. Antioxidant molecule glutathione and its precursor amino acids, cysteine and glutamate were greatly increased at later time points. Phosphatidylserine externalization suggestive of early phase apoptosis was also observed. Genetic studies using metacaspase null strains showed resistance to lidocaine induced cell death. These data suggest lidocaine induces perpetual mitochondrial depolarization, ROS/RNS generation along with increased glutathione to combat the oxidative cellular environment, glycolytic to PPP cycling of carbon generating NADPH, obstruction of carbon flow through the TCA cycle, decreased ATP generation, and metacaspase dependent apoptotic cell death.