Characterization of three isoforms of mammalian peroxiredoxin that reduce peroxides in the presence of thioredoxin

Dioscin, a natural steroid saponin, shows remarkable protective effect against acetaminophen-induced liver damage in vitro and in vivo

The aim of the study was to investigate the protective effect of dioscin against APAP-induced hepatotoxicity. In the in vitro tests, HepG2 cells were given APAP pretreatment with or without dioscin. In the in vivo experiments, mice were orally administrated dioscin for five days and then given APAP. Some biochemical and morphology parameters were assayed and the possible mechanism was investigated. Dioscin improved AST release, mitochondrial dysfunction, apoptosis and necrosis of HepG2 cells induced by APAP. Following administration of dioscin, APAP-induced hepatotoxicity in mice was significantly attenuated. Furthermore, the liver cell apoptosis and necrosis, and hepatic mitochondrial edema were also prevented. Fifteen differentially expressed proteins were found by using proteomics, and six of them, Suox, Krt18, Rgn, Prdx1, MDH and PNP were validated. These proteins may be involved in the hepatoprotective effect of dioscin and might cooperate with the levels of Ca(2+) in mitochondria, decreased expression of ATP2A2, and decreased mitochondrial cardiolipin. In addition, dioscin inhibited APAP-induced activation and expression of CYP2E1, up-regulated the expression of Bcl-2 and Bid, and inhibited the expression of Bax, Bak and p53. Dioscin showed a remarkable protective effect against APAP-induced hepatotoxicity by adjusting mitochondrial function. These results indicated that dioscin has the capability on the treatment of liver injury.

Role of sulfiredoxin as a regulator of peroxiredoxin function and regulation of its expression

Peroxiredoxins (Prxs) constitute a family of peroxidases in which cysteine serves as the primary site of oxidation during the reduction of peroxides. Members of the 2-Cys Prx subfamily of Prxs (Prx I to IV in mammals) are inactivated via hyperoxidation of the active-site cysteine to sulfinic acid (Cys-SO(2)H) during catalysis and are reactivated via an ATP-consuming reaction catalyzed by sulfiredoxin (Srx). This reversible hyperoxidation reaction has been proposed to protect H(2)O(2) signaling molecules from premature removal by 2-Cys Prxs or to upregulate the chaperone function of these enzymes. In addition to its sulfinic acid reductase activity, Srx catalyzes the removal of glutathione (deglutathionylation) from modified proteins. The physiological relevance of both the reversible hyperoxidation of 2-Cys Prxs and the deglutathionylation catalyzed by Srx remains unclear. Recent findings have revealed that Srx expression is induced in mammalian cells under a variety of conditions, such as in metabolically stimulated pancreatic β cells, in immunostimulated macrophages, in neuronal cells engaged in synaptic communication, in lung cells exposed to hyperoxia or cigarette smoke, in hepatocytes of ethanol-fed animals, and in several types of cells exposed to chemopreventive agents. Such induction of Srx in mammalian cells is regulated at the transcriptional level, predominantly via activator protein-1 and/or nuclear factor erythroid 2-related factor 2. Srx expression is also regulated at the translational level in Saccharomyces cerevisiae.

Potential relationship among three antioxidant enzymes in eliminating hydrogen peroxide in penaeid shrimp

Antioxidant enzymes, such as glutathione peroxidase (GPx), catalase (CAT), and peroxiredoxin (Prx), are essential components in cells to eliminate excessive reactive oxygen species such as hydrogen peroxide (H(2)O(2)). GPx, CAT, and Prx genes have been reported in penaeid shrimp, and they showed different expression profiles at transcription or protein level when shrimps were challenged by microbes. In order to learn the relationship among the above three genes in their function, GPx, CAT, and Prx transcripts were analyzed, and the variation of GPx and CAT enzyme activity was detected when shrimp was injected with H(2)O(2) or one antioxidant enzyme gene was silenced in shrimp by double-strand RNA injection. The results indicated that there existed some relationships among three antioxidant enzyme genes, CAT, GPx, and Prx in shrimp at transcriptional level. The transcription of CAT and GPx could be directly induced by H(2)O(2) injection, while the transcription of Prx cannot be induced by H(2)O(2). Decreased transcription level of CAT or GPx could lead to increased transcription of the other two genes, which suggested that there existed some compensation among these three antioxidant enzyme genes. These data can help us to understand the roles of antioxidant enzymes in crustacean.

Cell stress proteins in atherothrombosis

Cell stress proteins (CSPs) are a large and heterogenous family of proteins, sharing two main characteristics: their levels and/or location are modified under stress and most of them can exert a chaperon function inside the cells. Nonetheless, they are also involved in the modulation of several mechanisms, both at the intracellular and the extracellular compartments. There are more than 100 proteins belonging to the CSPs family, among them the thioredoxin (TRX) system, which is the focus of the present paper. TRX system is composed of several proteins such as TRX and peroxiredoxin (PRDX), two thiol-containing enzymes that are key players in redox homeostasis due to their ability to scavenge potential harmful reactive oxygen species. In addition to their main role as antioxidants, recent data highlights their function in several processes such as cell signalling, immune inflammatory responses, or apoptosis, all of them key mechanisms involved in atherothrombosis. Moreover, since TRX and PRDX are present in the pathological vascular wall and can be secreted under prooxidative conditions to the circulation, several studies have addressed their role as diagnostic, prognostic, and therapeutic biomarkers of cardiovascular diseases (CVDs).

Cloning and functional characterisation of a peroxiredoxin 1 (NKEF A) cDNA from Atlantic salmon (Salmo salar) and its expression in fish infected with Neoparamoeba perurans

Peroxiredoxin 1 (Prx 1), also known as natural killer enhancing factor A (NKEF A), has been implicated in the immune response of both mammals and fish. Amoebic gill disease (AGD), caused by Neoparamoeba perurans, is a significant problem for the Atlantic salmon (Salmo salar L.) aquaculture industry based in Tasmania, Australia. Here we have cloned and functionally characterized a Prx 1 open reading frame (ORF) from Atlantic salmon liver and shown that Prx 1 gene expression was down-regulated in the gills of Atlantic salmon displaying symptoms of AGD. The Prx 1 ORF encoded all of the residues and motifs characteristic of typical 2-Cys Prx proteins from eukaryotes and the recombinant protein expressed in Escherichia coli catalyzed thioredoxin (Trx)-dependent reduction of H(2)O(2), cumene hydroperoxide (CuOOH) and t-butyl hydroperoxide (t-bOOH) with K(m) values of 122, 77 and 91 μM, respectively, confirming that it was a genuine 2-Cys Prx. The recombinant protein also displayed a double displacement reaction mechanism and a catalytic efficiency (k(cat)/K(m)) with H(2)O(2) of 1.5 × 10(5) M(-1) s(-1) which was consistent with previous reports for the 2-Cys Prx family of proteins. This is the first time that a Prx 1 protein has been functionally characterized from any fish species and it paves the way for further investigation of this important 2-Cys Prx family member in fish.

Redox regulation of mitochondrial function

Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function.

Lymphocytes from rheumatoid arthritis patients have elevated levels of intracellular peroxiredoxin 2, and a greater frequency of cells with exofacial peroxiredoxin 2, compared with healthy human lymphocytes

Peroxiredoxin 2 has immune regulatory functions, but its expression in human peripheral blood lymphocytes and levels in extracellular fluid in healthy subjects and rheumatoid arthritis patients are poorly described. In the present study, the median intracellular peroxiredoxin 2 protein content of lymphocytes from rheumatoid arthritis patients was more than two-fold higher compared with healthy subjects’ lymphocytes. Intracellular peroxiredoxin 3 levels were similar in healthy and rheumatoid arthritis lymphocytes. Flow cytometry detected peroxiredoxin 2 on the surface of ca. 8% of T cells and ca. 56% of B cells (median % values) of all subjects analyzed. Exofacial thioredoxin-1 was also observed. In the total lymphocyte population from rheumatoid arthritis patients, few cells (median, 6%) displayed surface peroxiredoxin 2. In contrast, a significantly increased proportion of interleukin-17^+ve lymphocytes were exofacially peroxiredoxin 2^+ve (median, 39%). Prdx2 was also detected in human extracellular fluids. We suggest that crucial inflammatory cell subsets, i.e. interleukin-17^+ve T cells, exhibit increased exofacial redox-regulating enzymes and that peroxiredoxin 2 may be involved in the persistence of pro-inflammatory cells in chronic inflammation.

Glutathione synthesis and its role in redox signaling

Glutathione (GSH) is the most abundant antioxidant and a major detoxification agent in cells. It is synthesized through two-enzyme reaction catalyzed by glutamate cysteine ligase and glutathione synthetase, and its level is well regulated in response to redox change. Accumulating evidence suggests that GSH may play important roles in cell signaling. This review will focus on the biosynthesis of GSH, the reaction of S-glutathionylation (the conjugation of GSH with thiol residue on proteins), GSNO, and their roles in redox signaling.

Protein glutathionylation in the regulation of peroxiredoxins: a family of thiol-specific peroxidases that function as antioxidants, molecular chaperones, and signal modulators

SIGNIFICANCE

Reversible protein glutathionylation plays an important role in cellular regulation, signaling transduction, and antioxidant defense. This redox-sensitive mechanism is involved in regulating the functions of peroxiredoxins (Prxs), a family of ubiquitously expressed thiol-specific peroxidase enzymes. Glutathionylation of certain Prxs at their active-site cysteines not only provides reducing equivalents to support their peroxidase activity but also protects Prxs from irreversible hyperoxidation. Typical 2-Cys Prx also functions as a molecular chaperone when it exists as a decamer and/or higher molecular weight complexes. The hyperoxidized sulfinic derivative of 2-Cys Prx is reactivated by sulfiredoxin (Srx). In this review, the roles of glutathionylation in the regulation of Prxs are discussed with respect to their molecular structure and functions as antioxidants, molecular chaperones, and signal modulators.

RECENT ADVANCES

Recent findings reveal that glutathionylation regulates the quaternary structure of Prx. Glutathionylation of Prx I at Cys(83) converts the decameric Prx to its dimers with the loss of chaperone activity. The findings that dimer/oligomer structure specific Prx I binding proteins, e.g., phosphatase and tensin homolog (PTEN) and mammalian Ste20-like kinase-1 (MST1), regulate cell cycle and apoptosis, respectively, suggest a possible link between glutathionylation and those signaling pathways.

CRITICAL ISSUES

Knowing how glutathionylation affects the interaction between Prx I and its nearly 20 known interacting proteins, e.g., PTEN and MST1 kinase, would reveal new insights on the physiological functions of Prx.

FUTURE DIRECTIONS

In vitro studies reveal that Prx oligomerization is linked to its functional changes. However, in vivo dynamics, including the effect by glutathionylation, and its physiological significance remain to be investigated.

Characterization of a putative thioredoxin peroxidase prx1 of Candida albicans

In this study, we characterized a putative peroxidase Prx1 of Candida albicans by: 1) demonstrating the thioredoxin-linked peroxidase activity with purified proteins, 2) examining the sensitivity to several oxidants and the accumulation of intracellular reactive oxygen species with a null mutant (prx1Δ), a mutant (C69S) with a point mutation at Cys69, and a revertant, and 3) subcelluar localization. Enzymatic assays showed that Prx1 is a thioredoxin-linked peroxidase which reduces both hydrogen peroxide (H(2)O(2)) and tert-butyl hydroperoxide (t-BOOH). Compared with two other strong H(2)O(2) scavenger mutants for TSA1 and CAT1, prx1Δ and C69S were less sensitive to H(2)O(2), menadione and diamide at all concentrations tested, but were more sensitive to low concentration of t-BOOH. Intracellular reactive oxygen species accumulated in prx1Δ and C69S cells treated with t-BOOH but not H(2)O(2). These results suggest that peroxidase activity of Prx1 is specified to t-BOOH in cells. In both biochemical and physiological cases, the evolutionarily conserved Cys69 was found to be essential for the function. Immunocytochemical staining revealed Prx1 is localized in the cytosol of yeast cells, but is translocated to the nucleus during the hyphal transition, though the significances of this observation are unclear. Our data suggest that PRX1 has a thioredoxin peroxidase activity reducing both t-BOOH and H(2)O(2), but its cellular function is specified to t-BOOH.

Expression of peroxiredoxin 1, 2, and 6 in the rat brain during perinatal development and in response to dexamethasone

Peroxiredoxins (Prdx), a family of antioxidant proteins, have important defensive roles in the degenerative brain diseases and neuronal cell death in adult subjects. However, little is known in the neonatal brain. Here, we studied the developmental expression of Prdxs and their response to dexamethasone in the perinatal rat brain. Prdx 1 expression increased during late gestations and peaked at postnatal-day 1, when its expression gradually decreased. Prdx 2 expression remained largely unchanged. Prdx 6 expression continually increased as growing. Using immunohistochemistry, each Prdx showed a strong expression in the cerebral cortex and hippocampus. Prdx 1 was strongly expressed in the corpus callosum. The dexamethasone injection increased the expression of Prdx 6. In conclusion, we reveal for the first time that Prdx 1, 2 and 6 are found in abundance in the perinatal rat brain and are differentially expressed during development. The expression of Prdx 6 was affected by dexamethasone treatment.

Intracellular GSH and ascorbate inhibit radical-induced protein chain peroxidation in HL-60 cells

The results of this study suggest that the well-documented loss of GSH and ascorbate in organisms under oxidative stress may be mainly due to their reactions with protein radicals and/or peroxides. Protein hydroperoxides were generated in HL-60 cells exposed to radiation-generated hydroxyl radicals. We found for the first time evidence of chain peroxidation of the proteins in cells, with each hydroxyl radical leading to the formation of about 10 hydroperoxides. Protein peroxidation showed a lag, probably due to the endogenous antioxidant enzymes, with simultaneous loss of the intracellular GSH. Enhancement of the GSH levels by N-acetylcysteine decreased the formation of hydroperoxides, while treatment with l-buthionine sulfoximine had the opposite effect. The effect of variation of GSH levels on the formation of the peroxidized proteins is explained primarily by reduction of the protein hydroperoxides by GSH. Loading of the cells with ascorbate resulted in reduction of the amounts of protein hydroperoxides generated by the radiation, which was proportional to the intracellular ascorbate concentration. In contrast to the GSH, inhibition of protein hydroperoxide formation in the presence of the high (mM) intracellular ascorbate levels achieved was mainly due to the direct scavenging of hydroxyl radicals by the vitamin.

The role of peroxidases in the pathogenesis of atherosclerosis

Reactive oxygen species (ROS), which include superoxide anions and peroxides, induce oxidative stress, contributing to the initiation and progression of cardiovascular diseases involving atherosclerosis. The endogenous and exogenous factors hypercholesterolemia, hyperglycemia, hypertension, and shear stress induce various enzyme systems such as nicotinamide adenine dinucleotide (phosphate) oxidase, xanthine oxidase, and lipoxygenase in vascular and immune cells, which generate ROS. Besides inducing oxidative stress, ROS mediate signaling pathways involved in monocyte adhesion and infiltration, platelet activation, and smooth muscle cell migration. A number of antioxidant enzymes (e.g., superoxide dismutases, catalase, glutathione peroxidases, and peroxiredoxins) regulate ROS in vascular and immune cells. Atherosclerosis results from a local imbalance between ROS production and these antioxidant enzymes. In this review, we will discuss 1) oxidative stress and atherosclerosis, 2) ROS-dependent atherogenic signaling in endothelial cells, macrophages, and vascular smooth muscle cells, 3) roles of peroxidases in atherosclerosis, and 4) antioxidant drugs and therapeutic perspectives.

Thioredoxin 1-mediated post-translational modifications: reduction, transnitrosylation, denitrosylation, and related proteomics methodologies

Despite the significance of redox post-translational modifications (PTMs) in regulating diverse signal transduction pathways, the enzymatic systems that catalyze reversible and specific oxidative or reductive modifications have yet to be firmly established. Thioredoxin 1 (Trx1) is a conserved antioxidant protein that is well known for its disulfide reductase activity. Interestingly, Trx1 is also able to transnitrosylate or denitrosylate (defined as processes to transfer or remove a nitric oxide entity to/from substrates) specific proteins. An intricate redox regulatory mechanism has recently been uncovered that accounts for the ability of Trx1 to catalyze these different redox PTMs. In this review, we will summarize the available evidence in support of Trx1 as a specific disulfide reductase, and denitrosylation and transnitrosylation agent, as well as the biological significance of the diverse array of Trx1-regulated pathways and processes under different physiological contexts. The dramatic progress in redox proteomics techniques has enabled the identification of an increasing number of proteins, including peroxiredoxin 1, whose disulfide bond formation and nitrosylation status are regulated by Trx1. This review will also summarize the advancements of redox proteomics techniques for the identification of the protein targets of Trx1-mediated PTMs. Collectively, these studies have shed light on the mechanisms that regulate Trx1-mediated reduction, transnitrosylation, and denitrosylation of specific target proteins, solidifying the role of Trx1 as a master regulator of redox signal transduction.

Mitochondrial peroxiredoxin III is a potential target for cancer therapy

Mitochondria are involved either directly or indirectly in oncogenesis and the alteration of metabolism in cancer cells. Cancer cells contain large numbers of abnormal mitochondria and produce large amounts of reactive oxygen species (ROS). Oxidative stress is caused by an imbalance between the production of ROS and the antioxidant capacity of the cell. Several cancer therapies, such as chemotherapeutic drugs and radiation, disrupt mitochondrial homeostasis and release cytochrome c, leading to apoptosome formation, which activates the intrinsic pathway. This is modulated by the extent of mitochondrial oxidative stress. The peroxiredoxin (Prx) system is a cellular defense system against oxidative stress, and mitochondria in cancer cells are known to contain high levels of Prx III. Here, we review accumulating evidence suggesting that mitochondrial oxidative stress is involved in cancer, and discuss the role of the mitochondrial Prx III antioxidant system as a potential target for cancer therapy. We hope that this review will provide the basis for new strategic approaches in the development of effective cancer treatments.

Systemic remodeling of the redox regulatory network due to RNAi perturbations of glutaredoxin 1, thioredoxin 1, and glucose-6-phosphate dehydrogenase

BACKGROUND

Cellular clearance of reactive oxygen species is dependent on a network of tightly coupled redox enzymes; this network rapidly adapts to oxidative conditions such as aging, viral entry, or inflammation. Current widespread use of shRNA as a means to perturb specific redox couples may be misinterpreted if the targeted effects are not monitored in the context of potential global remodeling of the redox enzyme network.

RESULTS

Stable cell lines containing shRNA targets for glutaredoxin 1, thioredoxin 1, or glucose-6-phosphate dehydrogenase were generated in order to examine the changes in expression associated with altering cytosolic redox couples. A qRT PCR array revealed systemic off-target effects of altered antioxidant capacity and reactive oxygen species formation. Empty lentiviral particles generated numerous enzyme expression changes in comparison to uninfected cells, indicating an alteration in antioxidant capacity irrespective of a shRNA target. Of the three redox couples perturbed, glutaredoxin 1, attenuation produced the most numerous off-target effects with 10/28 genes assayed showing statistically significant changes. A multivariate analysis extracted strong co-variance between glutaredoxin 1 and peroxiredoxin 2 which was subsequently experimentally verified. Computational modeling of the peroxide clearance dynamics associated with the remodeling of the redox network indicated that the compromised antioxidant capacity compared across the knockdown cell lines was unequally affected by the changes in expression of off-target proteins.

CONCLUSIONS

Our results suggest that targeted reduction of redox enzyme expression leads to widespread changes in off-target protein expression, changes that are well-insulated between sub-cellular compartments, but compensatory in both the production of and protection against intracellular reactive oxygen species. Our observations suggest that the use of lentivirus can in itself have off-target effects on dynamic responses to oxidative stress due to the changes in species concentrations.

Engineering of 2-Cys peroxiredoxin for enhanced stress-tolerance

A typical 2-cysteine peroxiredoxin (2-Cys Prx)-like protein (PpPrx) that alternatively acts as a peroxidase or a molecular chaperone in Pseudomonas putida KT2440 was previously characterized. The dual functions of PpPrx are regulated by the existence of an additional Cys(112) between the active Cys(51) and Cys(171) residues. In the present study, additional Cys residues (Cys(31), Cys(112), and Cys(192)) were added to PpPrx variants to improve their enzymatic function. The optimal position of the additional Cys residues for the dual functionality was assessed. The peroxidase activities of the S31C and Y192C mutants were increased 3- to 4-fold compared to the wild-type, while the chaperone activity was maintained at > 66% of PpPrx. To investigate whether optimization of the dual functions could enhance stress-tolerance in vivo, a complementation study was performed. The S31C and Y192C mutants showed a much greater tolerance than other variants under a complex condition of heat and oxidative stresses. The optimized dual functions of PpPrx could be adapted for use in bioengineering systems and industries, such as to develop organisms that are more resistant to extreme environments.

Thioredoxin 1 overexpression extends mainly the earlier part of life span in mice

We examined the effects of increased levels of thioredoxin 1 (Trx1) on resistance to oxidative stress and aging in transgenic mice overexpressing Trx1 [Tg(TRX1)(+/0)]. The Tg(TRX1)(+/0) mice showed significantly higher Trx1 protein levels in all the tissues examined compared with the wild-type littermates. Oxidative damage to proteins and levels of lipid peroxidation were significantly lower in the livers of Tg(TRX1)(+/0) mice compared with wild-type littermates. The survival study demonstrated that male Tg(TRX1)(+/0) mice significantly extended the earlier part of life span compared with wild-type littermates, but no significant life extension was observed in females. Neither male nor female Tg(TRX1)(+/0) mice showed changes in maximum life span. Our findings suggested that the increased levels of Trx1 in the Tg(TRX1)(+/0) mice were correlated to increased resistance to oxidative stress, which could be beneficial in the earlier part of life span but not the maximum life span in the C57BL/6 mice.

Peroxiredoxin 2 deficiency exacerbates atherosclerosis in apolipoprotein E-deficient mice

RATIONALE

Peroxiredoxin 2 (Prdx2), a thiol-specific peroxidase, has been reported to regulate proinflammatory responses, vascular remodeling, and global oxidative stress.

OBJECTIVE

Although Prdx2 has been proposed to retard atherosclerosis development, no direct evidence and mechanisms have been reported.

METHODS AND RESULTS

We show that Prdx2 is highly expressed in endothelial and immune cells in atherosclerotic lesions and blocked the increase of endogenous H(2)O(2) by atherogenic stimulation. Deficiency of Prdx2 in apolipoprotein E-deficient (ApoE(-/-)) mice accelerated plaque formation with enhanced activation of p65, c-Jun, JNKs, and p38 mitogen-activated protein kinase; and these proatherogenic effects of Prdx2 deficiency were rescued by administration of the antioxidant ebselen. In bone marrow transplantation experiments, we found that Prdx2 has a major role in inhibiting atherogenic responses in both vascular and immune cells. Prdx2 deficiency resulted in increased expression of vascular adhesion molecule-1, intercellular adhesion molecule-1, and monocyte chemotactic protein-1, which led to increased immune cell adhesion and infiltration into the aortic intima. Compared with deficiency of glutathione peroxidase 1 or catalase, Prdx2 deficiency showed a severe predisposition to develop atherosclerosis.

CONCLUSIONS

Prdx2 is a specific peroxidase that inhibits atherogenic responses in vascular and inflammatory cells, and specific activation of Prdx2 may be an effective means of antiatherogenic therapy.

Multiple functions of peroxiredoxins: peroxidases, sensors and regulators of the intracellular messenger H₂O₂, and protein chaperones

Peroxiredoxins (Prxs) are a family of peroxidases that reduce peroxides, with a conserved cysteine residue (the peroxidatic Cys) serving as the site of oxidation by peroxides. Peroxides oxidize the peroxidatic Cys-SH to Cys-SOH, which then reacts with another cysteine residue (typically the resolving Cys [C(R)]) to form a disulfide that is subsequently reduced by an appropriate electron donor. On the basis of the location or absence of the C(R), Prxs are classified into 2-Cys, atypical 2-Cys, and 1-Cys Prx subfamilies. In addition to their peroxidase activity, members of the 2-Cys Prx subfamily appear to serve as peroxide sensors for other proteins and as molecular chaperones. During catalysis, the peroxidatic Cys-SOH of 2-Cys Prxs is occasionally further oxidized to Cys-SO(2)H before disulfide formation, resulting in inactivation of peroxidase activity. This hyperoxidation, which is reversed by the ATP-dependent enzyme sulfiredoxin, modulates the sensor and chaperone functions of 2-Cys Prxs. The peroxidase activity of 2-Cys Prxs is extensively regulated via tyrosine and threonine phosphorylation, which allows modulation of the local concentration of the intracellular messenger H(2)O(2). Finally, 2-Cys Prxs interact with a variety of proteins, with such interaction having been shown to modulate the function of the binding partners in a reciprocal manner.

Molecular characterization and expression analysis of six peroxiredoxin paralogous genes in gilthead sea bream (Sparus aurata): insights from fish exposed to dietary, pathogen and confinement stressors

The aim of this work was to underline the physiological role of the antioxidant peroxiredoxin (PRDX) family in gilthead sea bream (Sparus aurata L.), a perciform fish extensively cultured in the Mediterranean area. First, extensive BLAST searches were done on the gilthead sea bream cDNA database of the AQUAMAX European Project (www.sigenae.org/iats), and six contigs were unequivocally identified as PRDX1-6 after sequence completion by RT-PCR. The phylogenetic analysis evidenced three major clades corresponding to PRDX1-4 (true 2-Cyst PRDX subclass), PRDX5 (atypical 2-Cys PRDX subclass) and PRDX6 (1-Cys PRDX subclass) that reflected the present hierarchy of vertebrates. However, the PRDX2 branch of modern fish including gilthead sea bream was related to the monophyletic PRDX1 node rather than to PRDX2 cluster of mammals and primitive fish, which probably denotes the acquisition of novel functions through vertebrate evolution. Transcriptional studies by means of quantitative real-time PCR evidenced a ubiquitous PRDX gene expression that was tissue specific for each PRDX isoform. In a second set of transcriptional studies, liver and head kidney were chosen as target tissues in fish challenged with i) the intestinal parasite Enteromyxum leei, ii) a plant oil (VO) diet with deficiencies in essential fatty acids and iii) prolonged exposure to high-rearing densities. These studies showed that PRDX genes were highly and mostly constitutively expressed in the liver and were not affected by dietary intervention or high density. In contrast, head kidney was highly sensitive to the different experimental challenges: significantly lower values were found for PRDX5 in the three trials, for PRDX6 in parasitized and high density fish and for PRDX1 in parasitized and VO fish. PRDX2, 3 and 5 were decreased only in VO, high density and parasitized animals, respectively. These findings would highlight the role of PRDXs as integrative and highly predictive biomarkers of health and welfare in fish and gilthead sea bream in particular.

Endothelin-1 overexpression restores diastolic function in eNOS knockout mice

BACKGROUND

The cardiac nitric oxide and endothelin-1 (ET-1) systems are closely linked and play a critical role in cardiac physiology. The balance between both systems is often disturbed in cardiovascular diseases. To define the cardiac effect of excessive ET-1 in a status of nitric oxide deficiency, we compared left ventricular function and morphology in wild-type mice, ET-1 transgenic (ET(+/+)) mice, endothelial nitric oxide synthase knockout (eNOS(-/-)) mice, and ET(+/+)eNOS(-/-) mice.

METHODS AND RESULTS

eNOS(-/-) and ET(+/+)eNOS(-/-) mice developed high blood pressure compared with wild-type and ET(+/+) mice. Left ventricular catheterization showed that eNOS(-/-) mice, but not ET(+/+)eNOS(-/-) , developed diastolic dysfunction characterized by increased end-diastolic pressure and relaxation constant tau. To elucidate the causal molecular mechanisms driving the rescue of diastolic function in ET(+/+)eNOS(-/-) mice, the cardiac proteome was analyzed. Two-dimensional gel electrophoresis coupled to mass spectrometry offers an appropriate hypothesis-free approach. ET-1 overexpression on an eNOS(-/-) background led to an elevated abundance and change in posttranslational state of antioxidant enzymes (e.g., peroxiredoxin-6, glutathione S-transferase mu 2, and heat shock protein beta 7). In contrast to ET(+/+)eNOS(-/-) mice, eNOS(-/-) mice showed an elevated abundance of proteins responsible for sarcomere disassembly (e.g., cofilin-1 and cofilin-2). In ET(+/+)eNOS(-/-) mice, glycolysis was favored at the expense of fatty acid oxidation.

CONCLUSION

eNOS(-/-) mice developed diastolic dysfunction; this was rescued by ET-1 transgenic overexpression. This study furthermore suggests that cardiac ET-1 overexpression in case of eNOS deficiency causes specifically the regulation of proteins playing a role in oxidative stress, myocytes contractility, and energy metabolism.

The protective effect of ENA Actimineral resource A on CCl4-induced liver injury in rats

ENA Actimineral Resource A (ENA-A) is alkaline water that is composed of refined edible cuttlefish bone and two different species of seaweed, Phymatolithon calcareum and Lithothamnion corallioides. In the present study, ENA-A was investigated as an antioxidant to protect against CCl(4)-induced oxidative stress and hepatotoxicity in rats. Liver injury was induced by either subacute or chronic CCl(4) administration, and the rats had free access to tap water mixed with 0% (control group) or 10% (v/v) ENA-A for 5 or 8 weeks. The results of histological examination and measurement of antioxidant activity showed that the reactive oxygen species production, lipid peroxidation, induction of CYP2E1 were decreased and the antioxidant activity, including glutathione and catalase production, was increased in the ENA-A groups as compared with the control group. On 2-DE gel analysis of the proteomes, 13 differentially expressed proteins were obtained in the ENA-A groups as compared with the control group. Antioxidant proteins, including glutathione S-transferase, kelch-like ECH-associated protein 1, and peroxiredoxin 1, were increased with hepatocyte nuclear factor 3-beta and serum albumin precursor, and kininogen precursor decreased more in the ENA-A groups than compared to the control group. In conclusion, our results suggest that ENA-A does indeed have some protective capabilities against CCl(4)-induced liver injury through its antioxidant function.

Molecular cloning and characterization of a thioredoxin peroxidase gene from Apis cerana cerana

Thioredoxin peroxidases (Tpxs) play important roles in protecting organisms against the toxicity of reactive oxygen species (ROS) and regulating intracellular signal transduction. In the present study, we cloned the full cDNA of Tpx1 encoding a 195-amino acid protein from Apis cerana cerana (Acc). Based on the genomic DNA sequence, a 1442-bp 5'-flanking region was obtained, and the putative transcription factor binding sites were predicted. Quantitative PCR analysis showed that AccTpx1 was highly expressed in thorax and that the AccTpx1 transcript reached its highest level in two-week-old adult worker honeybees. Moreover, expression of the AccTpx1 transcript was increased by various abiotic stresses, such as ultraviolet light, HgCl(2) , and insecticide treatments. In addition, the recombinant AccTpx1 protein exhibited antioxidant activity; it removed hydrogen peroxide and protected DNA. These results suggest that AccTpx1 plays an important role in protecting honeybees from oxidative injury and may act in extending the lifespan of them.

In situ kinetic trapping reveals a fingerprint of reversible protein thiol oxidation in the mitochondrial matrix

Reactive oxygen species (ROS) are released at the mitochondrial inner membrane by the electron transport chain (ETC). Increasing evidence suggests that mitochondrial H2O2 acts as a signaling molecule and participates in the (feedback) regulation of mitochondrial activity and turnover. It seems likely that key mitochondrial components contain redox-sensitive thiols that help to adapt protein function to changes in electron flow. However, the identity of most redox-regulated mitochondrial proteins remains to be defined. Thioredoxin 2 (Trx2) is the major protein-thiol-reducing oxidoreductase in the mitochondrial matrix. We used in situ mechanism-based kinetic trapping to identify disulfide-exchange interactions of Trx2 within functional mitochondria of intact cells. Mass spectrometry successfully identified known and suspected Trx2 target proteins and, in addition, revealed a set of new candidate target proteins. Our results suggest that the mitochondrial protein biosynthesis machinery is a major target of ETC-derived ROS. In particular, we identified mitochondrial methionyl-tRNA synthetase (mtMetRS) as one of the most prominent Trx2 target proteins. We show that an increase in ETC-derived oxidants leads to an increase in mtMetRS oxidation in intact cells. In conclusion, we find that in situ kinetic trapping provides starting points for future functional studies of intramitochondrial redox regulation.

Upregulation of peroxiredeoxin III in the hippocampus of acute immobilization stress model rats and the Foxo3a-dependent expression in PC12 cells

Stress induces structural plasticity in neurons of the adult central nervous system (CNS) and alters the levels of cellular production of reactive oxygen species (ROS), and these changes might involve modifications of the antioxidant defense system. This study investigated whether acute stress altered the expression pattern of peroxiredoxin (Prx) III, which is an antioxidant enzyme that controls cytokine-induced peroxide levels. Prx III immunoreactivity was upregulated in the pyramidal neurons of the hippocampus and in the motor neurons of the spinal cord in an acute immobilization stress (AIS) model. In addition, we tested whether the transcription factor Foxo3a was necessary for the expression of Prx III. The depletion of Foxo3a led to a marked reduction of Prx III and a compensatory enhancement of mitochondrial superoxide dismutase (Mn-SOD) in PC12 cells. The results of this study suggest that Foxo3a mediates the neuronal levels of expression of Prx III and the levels of expression of Mn-SOD in mitochondria. These mechanisms may play an important role in neuroprotection against oxidative stress. Furthermore, Prx III upregulation might be an useful approach for the management of stress.

Glutathionylation of peroxiredoxin I induces decamer to dimers dissociation with concomitant loss of chaperone activity

Reversible protein glutathionylation, a redox-sensitive regulatory mechanism, plays a key role in cellular regulation and cell signaling. Peroxiredoxins (Prxs), a family of peroxidases that is involved in removing H(2)O(2) and organic hydroperoxides, are known to undergo a functional change from peroxidase to molecular chaperone upon overoxidation of its catalytic cysteine. The functional change is caused by a structural change from low molecular weight oligomers to high molecular weight complexes that possess molecular chaperone activity. We reported earlier that Prx I can be glutathionylated at three of its cysteine residues, Cys52, -83, and -173 [Park et al. (2009) J. Biol. Chem., 284, 23364]. In this study, using analytical ultracentrifugation analysis, we reveal that glutathionylation of Prx I, WT, or its C52S/C173S double mutant shifted its oligomeric status from decamers to a population consisting mainly of dimers. Cys83 is localized at the putative dimer-dimer interface, implying that the redox status of Cys83 may play an important role in stabilizing the oligomeric state of Prx I. Studies with the Prx I (C83S) mutant show that while Cys83 is not essential for the formation of high molecular weight complexes, it affects the dimer-decamer equilibrium. Glutathionylation of the C83S mutant leads to accumulation of dimers and monomers. In addition, glutathionylation of Prx I, both the WT and C52S/C173S mutants, greatly reduces their molecular chaperone activity in protecting citrate synthase from thermally induced aggregation. Together, these results reveal that glutathionylation of Prx I promotes changes in its quaternary structure from decamers to smaller oligomers and concomitantly inactivates its molecular chaperone function.

Oxidative stress-dependent oligomeric status of erythrocyte peroxiredoxin II (PrxII) during storage under standard blood banking conditions

Although biochemical properties of 2-Cys peroxiredoxins have been extensively studied in various cell lines and organisms, redox-induced structural transitions of peroxiredoxin II (PrxII) in human erythrocytes certainly warrant further investigation. In this work, cytosol and membrane ghosts of both fresh erythrocytes (cells obtained just after blood collection) and 28-day stored erythrocytes were analyzed by proteomics tools. We demonstrated that in fresh red blood cells PrxII exhibits four different oligomeric states in cytosol, whereas no PrxII complexes are in the membrane. The highest molecular weight PrxII protein complex (440 kDa) was proven to derive from the association between tetrameric catalase (CAT, 232 kDa) and decameric PrxII, whereas oligomers at 140, 100 and 67 kDa resulted to be homo-polymeric complexes composed of variable copies of PrxII monomeric subunits. Interestingly, the 440 kDa complex contained both reduced and oxidized (disulphide-linked dimers) PrxII decamers. Upon oxidative stress (28-day storage), the PrxII oligomers at 100 kDa in the cytosol disappeared and the CAT-PrxII hetero-oligomeric complex at 440 kDa is converted to a higher molecular weight structure (480 kDa) due to the presence therein of cross-linked species of PrxII and hemoglobin. More interestingly, oxidized red cell membranes contained the CAT-PrxII complex detected in 0-day cytosol as a consequence of protein recruitments induced by oxidative stress, however it showed a greater percentage of PrxII dimers. Finally, since the adoption of distinct PrxII structures is known to be closely related to different functions, peroxidase activity assays were performed demonstrating a positive reaction for oligomers at 440 kDa (both in cytosol and membrane compartment) and at 140 kDa. Our results contribute to clarify structural and functional switching of peroxiredoxin II in erythrocytes, thus possibly opening new scenarios in the biological roles played by this protein in defense mechanisms against oxidative stress, especially with the reference to red cell storage lesions.

Mitochondrial ROS generation and its regulation: mechanisms involved in H(2)O(2) signaling

Mitochondria are the main source of reactive oxygen species in the cell. These reactive oxygen species have long been known as being involved in oxidative stress. This is a review of the mechanisms involved in reactive oxygen species generation by the respiratory chain and some of the dehydrogenases and the control by thermodynamic and kinetic constraints. Mitochondrial ROS produced at the level of the bc1 complex as well at the level of complex I are discussed. It was recognized more than a decade ago that they can also function as signaling molecules. This signaling role will be developed both in terms of mechanism and in terms of mitochondrial ROS signaling. The notion that hydrogen peroxide acts not only as a damaging oxidant but also as a signaling molecule was proposed more than a decade ago. Hydrogen peroxide signaling can be either direct (oxidation of its target) or indirect (involving peroxiredoxins, for example). The consequences of ROS signaling on crucial biologic processes such as cell proliferation and differentiation are discussed.

Different consequences of reactions with hydrogen peroxide and t-butyl hydroperoxide in the hyperoxidative inactivation of rat peroxiredoxin-4

Eukaryotic typical 2-Cys type peroxiredoxin (Prx) is inactivated by hyperoxidation of the peroxidatic cysteine to a sulphinic acid in a catalytic cycle-dependent manner. This inactivation process has been well documented for cytosolic isoforms of Prx. However, such a hyperoxidative inactivation has not fully been investigated in Prx-4, a secretable endoplasmic reticulum-resident isoform, in spite of being a typical 2-Cys type, and details of this process are reported herein. As has been observed in many peroxiredoxins, the peroxidase activity of Prx-4 was almost completely inhibited in the reaction with t-butyl hydroperoxide. On the other hand, when H(2)O(2) was used as the substrate, the peroxidase activity significantly remained after oxidative damage. In spite of these different consequences, mass spectrometric analyses indicated that both reactions resulted in the same oxidative damage, i.e. sulphinic acid formation at the peroxidatic cysteine, suggesting that another cysteine in the active site confers the peroxidase activity. As suggested by the analyses using cysteine-substituted mutants sulphinic acid formation at the peroxidatic cysteine may play a role in the development of the possible alternative mechanism, thereby sustaining the peroxidase activity that prefers H(2)O(2).

Both thioredoxin 2 and glutaredoxin 2 contribute to the reduction of the mitochondrial 2-Cys peroxiredoxin Prx3

The proteins from the thioredoxin family are crucial actors in redox signaling and the cellular response to oxidative stress. The major intracellular source for oxygen radicals are the components of the respiratory chain in mitochondria. Here, we show that the mitochondrial 2-Cys peroxiredoxin (Prx3) is not only substrate for thioredoxin 2 (Trx2), but can also be reduced by glutaredoxin 2 (Grx2) via the dithiol reaction mechanism. Grx2 reduces Prx3 exhibiting catalytic constants (K(m), 23.8 μmol·liter(-1); V(max), 1.2 μmol·(mg·min)(-1)) similar to Trx2 (K(m), 11.2 μmol·liter(-1); V(max), 1.1 μmol·(mg·min)(-1)). The reduction of the catalytic disulfide of the atypical 2-Cys Prx5 is limited to the Trx system. Silencing the expression of either Trx2 or Grx2 in HeLa cells using specific siRNAs did not change the monomer:dimer ratio of Prx3 detected by a specific 2-Cys Prx redox blot. Only combined silencing of the expression of both proteins led to an accumulation of oxidized protein. We further demonstrate that the distribution of Prx3 in different mouse tissues is either linked to the distribution of Trx2 or Grx2. These results introduce Grx2 as a novel electron donor for Prx3, providing further insights into pivotal cellular redox signaling mechanisms.

Mitochondrial peroxiredoxins are critical for the maintenance of redox state and the survival of adult Drosophila

Drosophila mitochondria contain two peroxidases, peroxiredoxin 3 (dPrx3) and peroxiredoxin 5 (dPrx5), which together constitute the sole known intramitochondrial mechanism for the catalytic removal of hydrogen and organic peroxides. dPrx3 exists exclusively within mitochondria, whereas dPrx5 is also present in some other intracellular compartments. Levels of these two peroxiredoxins were genetically manipulated, singly and together, in D. melanogaster, for the purpose of understanding their respective functions. Underexpression of dPrx3 by 90-95% had no discernable effect on life span under normal or oxidative stress conditions; the dPrx5 null flies were previously reported to exhibit a 10% shortening of mean life span and an increase in sensitivity to oxidative stress. Flies underexpressing both dPrx3 and dPrx5 showed an 80% decrease in life span, a severe disruption in thiol homeostasis, and a massive induction of apoptosis in the muscle and digestive system tissues. The early mortality in flies underexpressing both peroxiredoxins was partially offset by overexpression of thioredoxin reductase but not mitochondrion-targeted catalase. These results suggest that mitochondrial peroxiredoxins confer specific protection for thioredoxin/glutathione systems, play a critical role in the maintenance of global thiol homeostasis, and prevent the age-associated apoptosis and premature death.

Peroxiredoxin II restrains DNA damage-induced death in cancer cells by positively regulating JNK-dependent DNA repair

The 2-Cys peroxiredoxins (Prx) belong to a family of antioxidant enzymes that detoxify reactive oxygen and nitrogen species and are distributed throughout the intracellular and extracellular compartments. However, the presence and role of 2-Cys Prxs in the nucleus have not been studied. This study demonstrates that the PrxII located in the nucleus protects cancer cells from DNA damage-induced cell death. Although the two cytosolic 2-Cys Prxs, PrxI and PrxII, were found in the nucleus, only PrxII knockdown selectively and markedly increased cell death in the cancer cells treated with DNA-damaging agents. The increased death was completely reverted by the nuclearly targeted expression of PrxII in an activity-independent manner. Furthermore, the antioxidant butylated hydroxyanisole did not influence the etoposide-induced cell death. Mechanistically, the knockdown of Prx II expression impaired the DNA repair process by reducing the activation of the JNK/c-Jun pathway. These results suggest that PrxII is likely to be attributed to a tumor survival factor positively regulating JNK-dependent DNA repair with its inhibition possibly sensitizing cancer cells to chemotherapeutic agents.

Overoxidation of 2-Cys peroxiredoxin in prokaryotes: cyanobacterial 2-Cys peroxiredoxins sensitive to oxidative stress

In eukaryotic organisms, hydrogen peroxide has a dual effect; it is potentially toxic for the cell but also has an important signaling activity. According to the previously proposed floodgate hypothesis, the signaling activity of hydrogen peroxide in eukaryotes requires a transient increase in its concentration, which is due to the inactivation by overoxidation of 2-Cys peroxiredoxin (2-Cys Prx). Sensitivity to overoxidation depends on the structural GGLG and YF motifs present in eukaryotic 2-Cys Prxs and is believed to be absent from prokaryotic enzymes, thus representing a paradoxical gain of function exclusive to eukaryotic organisms. Here we show that 2-Cys Prxs from several prokaryotic organisms, including cyanobacteria, contain the GG(L/V/I)G and YF motifs characteristic of sensitive enzymes. In search of the existence of overoxidation-sensitive 2-Cys Prxs in prokaryotes, we have analyzed the sensitivity to overoxidation of 2-Cys Prxs from two cyanobacterial strains, Anabaena sp. PCC7120 and Synechocystis sp. PCC6803. In vitro analysis of wild type and mutant variants of the Anabaena 2-Cys Prx showed that this enzyme is overoxidized at the peroxidatic cysteine residue, thus constituting an exception among prokaryotes. Moreover, the 2-Cys Prx from Anabaena is readily and reversibly overoxidized in vivo in response to high light and hydrogen peroxide, showing higher sensitivity to overoxidation than the Synechocystis enzyme. These cyanobacterial strains have different strategies to cope with hydrogen peroxide. While Synechocystis has low content of less sensitive 2-Cys Prx and high catalase activity, Anabaena contains abundant and sensitive 2-Cys Prx, but low catalase activity, which is remarkably similar to the chloroplast system.

A model of redox kinetics implicates the thiol proteome in cellular hydrogen peroxide responses

Hydrogen peroxide is appreciated as a cellular signaling molecule with second-messenger properties, yet the mechanisms by which the cell protects against intracellular H(2)O(2) accumulation are not fully understood. We introduce a network model of H(2)O(2) clearance that includes the pseudo-enzymatic oxidative turnover of protein thiols, the enzymatic actions of catalase, glutathione peroxidase, peroxiredoxin, and glutaredoxin, and the redox reactions of thioredoxin and glutathione. Simulations reproduced experimental observations of the rapid and transient oxidation of glutathione and the rapid, sustained oxidation of thioredoxin on exposure to extracellular H(2)O(2). The model correctly predicted early oxidation profiles for the glutathione and thioredoxin redox couples across a range of initial extracellular [H(2)O(2)] and highlights the importance of cytoplasmic membrane permeability to the cellular defense against exogenous sources of H(2)O(2). The protein oxidation profile predicted by the model suggests that approximately 10% of intracellular protein thiols react with hydrogen peroxide at substantial rates, with a majority of these proteins forming protein disulfides as opposed to protein S-glutathionylated adducts. A steady-state flux analysis predicted an unequal distribution of the intracellular anti-oxidative burden between thioredoxin-dependent and glutathione-dependent antioxidant pathways, with the former contributing the majority of the cellular antioxidant defense due to peroxiredoxins and protein disulfides.

Conformational and oligomeric effects on the cysteine pK(a) of tryparedoxin peroxidase

Typical 2-Cys peroxiredoxins (Prxs) are peroxidases which regulate cell signaling pathways, apoptosis, and differentiation. These enzymes are obligate homodimers, and can form decamers in solution. During catalysis, Prxs exhibit cysteine-dependent reactivity which requires the deprotonation of the peroxidatic cysteine (C(p)) supported by a lowered pK(a) in the initial step. We present the results of molecular dynamics simulations combined with pKa calculations on the monomeric, dimeric and decameric forms of one typical 2-Cys Prx, the tryparedoxin peroxidase from Trypanosoma cruzi (PDB id, 1uul). The calculations indicate that C(p) (C52) pK(a) values are highly affected by oligomeric state; an unshifted C(p) pK(a) (approximately 8.3, comparable to the pK(a) of isolated cysteine) is calculated for the monomer. In the dimers, starting with essentially identical structures, the C(p)s evolve dynamically asymmetric pK(a)s during the simulations; one subunit's C(p) pK(a) is shifted downward at a time, while the other is unshifted. However, when averaged over time, or multiple simulations, the two subunits within a dimer exhibit the same C(p), showing no preference for a lowered pK(a) in either subunit. Two conserved pathways that communicate the asymmetric pK(a)s between C(p)s of different subunits can be identified. In the decamer, all the C(p) pK(a)s are shifted downward, with slight asymmetry in the dimers which form the decamers. Structural analyses implicate oligomerization effects as responsible for these oligomeric state-dependent C(p) pK(a) shifts. The intra-dimer and the inter-dimer subunit contacts in the decamer restrict the conformations of the side chains of several residues (T49, T54 and E55) calculated to be key in shifting the C(p) pK(a). In addition, the backbone fluctuations of a few residues (M46, D47 and F48) result in a different electrostatic environment for the C(p) in dimers relative to the monomers. These side chain and backbone interactions which contribute to pK(a) modulation indicate the importance of oligomerization to the function of the typical 2-Cys Prxs.

Potential therapeutic benefits of strategies directed to mitochondria

The mitochondrion is the most important organelle in determining continued cell survival and cell death. Mitochondrial dysfunction leads to many human maladies, including cardiovascular diseases, neurodegenerative disease, and cancer. These mitochondria-related pathologies range from early infancy to senescence. The central premise of this review is that if mitochondrial abnormalities contribute to the pathological state, alleviating the mitochondrial dysfunction would contribute to attenuating the severity or progression of the disease. Therefore, this review will examine the role of mitochondria in the etiology and progression of several diseases and explore potential therapeutic benefits of targeting mitochondria in mitigating the disease processes. Indeed, recent advances in mitochondrial biology have led to selective targeting of drugs designed to modulate and manipulate mitochondrial function and genomics for therapeutic benefit. These approaches to treat mitochondrial dysfunction rationally could lead to selective protection of cells in different tissues and various disease states. However, most of these approaches are in their infancy.

Oxidative stress in mouse liver caused by dietary amino acid deprivation: protective effect of methionine

The aim of this work was to evaluate the effects of a diet depleted of amino acids (protein-free diet, or PFD), as well as the supplementation with methionine (PFD+Met), on the antioxidant status of the female mouse liver. With this purpose, cytosolic protein spots from two-dimensional non-equilibrium pH gel electrophoresis were identified by several procedures, such as mass spectrometry, Western blot, gel matching and enzymatic activity. PFD decreased the contents of catalase (CAT), peroxiredoxin I (Prx-I), and glutathione peroxidase (GPx) by 67%, 37% and 45%, respectively. Gene expression analyses showed that PFD caused a decrease in CAT (-20%) and GPx (-30%) mRNA levels but did not change that of Prx-I. It was also found that, when compared to a normal diet, PFD increased the liver contents of both reactive oxygen species (+50%) and oxidized protein (+88%) and decreased that of glutathione (-45%). Supplementation of PFD with Met prevented these latter effects to varying degrees, whereas CAT, Prx-I and GPx mRNA levels resulted unmodified. Present results suggest that dietary amino acid deprivation deranges the liver antioxidant defences, and this can be, in part, overcome by supplementation with Met.

Peroxiredoxin IV regulates pro-inflammatory responses in large yellow croaker (Pseudosciaena crocea) and protects against bacterial challenge

In this study, we applied a comparative proteomic approach to the analysis of differentially expressed proteins in the spleens of large yellow croaker following treatment with an inactivated trivalent bacterial vaccine. Twenty-four altered proteins were identified by MALDI-TOF or MALDI-TOF-TOF, including immune-related proteins, antioxidant proteins, signal transducers, protein biosynthesis and catabolism modulators, and carbonic anhydrases. Three Prx family members, namely, Prx I, Prx II, and Prx IV, were upregulated after treatment with the vaccine, indicating potentially important roles for these antioxidant proteins in the antibacterial immune response. Large yellow croaker Prx IV (LycPrxIV), which has thiol-dependent peroxidase activity, was constitutively expressed in all tissues examined. Immunoelectron microscopy showed that LycPrxIV was primarily localized to the rER or peroxisome in spleen cells of healthy fish, and its synthesis on the rER increased following treatment with bacterial vaccine. Suppression of LycPrxIV by siRNA resulted in an increase in NF-kappaB activity in spleen tissues, while in vivo administration of recombinant LycPrxIV (rLycPrxIV) caused a decrease in NF-kappaB activity, indicating that LycPrxIV negatively regulates NF-kappaB activation. Likewise, siRNA-mediated knockdown of LycPrxIV increased the expression of TNF-alpha and CC chemokine, and downregulated the expression of IL-10. However, injection of fish with rLycPrxIV induced the opposite expression pattern of these cytokines, suggesting a role for LycPrxIV in regulating pro-inflammatory responses. Bacterial challenge experiments showed that suppression of LycPrxIV expression by siRNA significantly increased fish mortality as compared to controls, whereas rLycPrxIV provided a protective effect. Together, our data suggest that LycPrxIV may regulate pro-inflammatory responses to protect large yellow croaker from bacterial challenge, revealing a novel antibacterial mechanism in fish.

Thioredoxin 1 downregulates MCP-1 secretion and expression in human endothelial cells by suppressing nuclear translocation of activator protein 1 and redox factor-1

To know whether thioredoxin 1 (Trx1) works for an antioxidant defense mechanism in atherosclerosis, the effect of Trx1 on the release of monocyte chemoattractant protein-1 (MCP-1), a potent chemoattractant for recruitment and accumulation of monocytes/macrophages in the intima of artery vessel, was investigated in human endothelial-like EA.hy 926 cells. It was found that overexpression of Trx1 suppressed, whereas knockdown of endogenous Trx1 enhanced, oxidized low-density lipoprotein (oxLDL)-stimulated MCP-1 release and expression in the cells. It was also observed that overexpression of Trx1 suppressed, whereas depletion of endogenous Trx1 greatly promoted, nuclear translocation of c-Jun and the redox factor-1 (Ref-1). Electrophoretic mobility shift assay showed significantly reduced DNA-binding activity of activator protein-1 (AP-1) in Trx1-overexpressing cells but apparently enhanced DNA binding activity of AP-1 in Trx1-knockdown cells, indicating that nuclear Ref-1 rather than Trx1 itself finally dominates the regulation of AP-1 activity, although Trx1 is considered to upregulate AP-1 activity. It was also observed that Trx1 depressed intracellular generation of reactive oxygen species (ROS). Diphenyleneiodonium (DPI), the inhibitor of NADPH oxidase, suppressed MCP-1 secretion, whereas transient expression of Nox1 enhanced transcription of MCP-1 in endothelial cells. Assays with AP-1 and MCP-1 luciferase reporters further demonstrated that transient expression of Trx1 significantly depressed the transcriptional activity of c-Jun/c-Fos and consequent MCP-1 transcription. This study suggests that Trx1 inherently suppresses MCP-1 expression in vascular endothelium and may prevent atherosclerosis by depressing MCP-1 release. Besides the suppression of intracellular ROS generation, the inhibition of nuclear translocation of AP-1 and Ref-1 are mainly responsible for the downregulation of MCP-1 by Trx1.

Thioredoxin and Cancer: A Role for Thioredoxin in all States of Tumor Oxygenation

Thioredoxin is a small redox-regulating protein, which plays crucial roles in maintaining cellular redox homeostasis and cell survival and is highly expressed in many cancers. The tumor environment is usually under either oxidative or hypoxic stress and both stresses are known up-regulators of thioredoxin expression. These environments exist in tumors because their abnormal vascular networks result in an unstable oxygen delivery. Therefore, the oxygenation patterns in human tumors are complex, leading to hypoxia/re-oxygenation cycling. During carcinogenesis, tumor cells often become more resistant to hypoxia or oxidative stress-induced cell death and most studies on tumor oxygenation have focused on these two tumor environments. However, recent investigations suggest that the hypoxic cycling occurring within tumors plays a larger role in the contribution to tumor cell survival than either oxidative stress or hypoxia alone. Thioredoxin is known to have important roles in both these cellular responses and several studies implicate thioredoxin as a contributor to cancer progression. However, only a few studies exist that investigate the regulation of thioredoxin in the hypoxic and cycling hypoxic response in cancers. This review focuses on the role of thioredoxin in the various states of tumor oxygenation.