Peroxiredoxins, oxidative stress, and cell proliferation

Uterine secretome and its modulation in rat (Rattus norvegicus)

The present study identifies uterine fluid (UF) proteins that display differential abundance during the embryo-permissive phase in nonconception and conception cycles in rats. UF samples were collected from nonpregnant rats in the proestrous (n=17) and metestrous (n=18) phases and also from pregnant (n=17) and pseudopregnant (n=17) rats on day 4 post coitus. UF protein profile in the metestrous phase was compared with that in the proestrous phase. Similarly, UF protein profile of the pregnant rats was compared with that of the pseudopregnant rats. Two-dimensional PAGE, followed by densitometric analysis of the paired protein spots, revealed differential abundance of 44 proteins in the metestrous phase, compared with that in the proestrous phase. Of these, 29 proteins were identified by matrix-assisted laser desorption/ionization time-of-flight or liquid chromatography–tandem mass spectrometry. Functional groups such as proteases, protease inhibitors, and oxidoreductases were enriched in differentially abundant proteins. Total protease activity in UF was found to be significantly (P<0.05; t-test) higher in the proestrous phase, compared with that in the metestrous phase. Furthermore, 41 UF proteins were found to be differentially abundant in pregnant rats, compared with pseudopregnant rats. Of these, 11 proteins could be identified. Immunoblotting analysis confirmed significantly higher (P<0.05; t-test) abundance of β-actin, Rho-specific guanine nucleotide dissociation inhibitor alpha (Rho-GDIα), and peroxiredoxin-2 and -6 in the metestrous phase, compared with that in the proestrous phase. Compared with pseudopregnant rats, pregnant rats had significantly higher (P<0.05; t-test) levels of UF β-actin and Rho-GDIα. Furthermore, these proteins could be detected in the culture supernatants of endometrial epithelial cell lines, thereby providing an evidence of their secretion from endometrial epithelial cells. Data obtained from the study expand our knowledge on the uterine milieu that favours embryo implantation.

Proteomic analysis of novel targets associated with TrkA-mediated tyrosine phosphorylation signaling pathways in SK-N-MC neuroblastoma cells

Tropomyosin-related kinase A (TrkA) is a receptor-type protein tyrosine kinase and exploits pleiotypic roles via nerve growth factor (NGF)-dependent or NGF-independent mechanisms in various cell types. Here, we showed that the inhibition of TrkA activity by GW441756 resulted in the suppression of tyrosine phosphorylation of cellular proteins including extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK). To find novel targets associated with TrkA-mediated tyrosine phosphorylation signaling pathways, we investigated GW441756 effects on TrkA-dependent targets in SK-N-MC neuroblastoma cells by proteomic analysis. The major TrkA-dependent protein spots controlled by GW441756 were determined by PDQuest image analysis, identified by MALDI-TOF MS and MALDI-TOF/TOF MS/MS, and verified by 2DE/Western blot analysis. Thus, we found that most of the identified protein spots were modified forms in a normal condition, and their modifications were regulated by TrkA activity. Especially, our results demonstrated that the modifications of α-tubulin and heterogeneous nuclear ribonucleoproteins C1/C2 (hnRNP C1/C2) were significantly upregulated by TrkA, whereas α-enolase modification was downregulated by TrkA, and it was suppressed by GW441756, indicating that TrkA activity is required for their modifications. Taken together, we suggest here that the major novel TrkA-dependent targets such as α-tubulin, hnRNP C1/C2, and α-enolase could play an essential role in TrkA-mediated tyrosine phosphorylation signaling pathways via regulation of their posttranslational modifications.

Peroxiredoxin overexpression in MCF-7 breast cancer cells and regulation by cell proliferation and oxidative stress

Peroxiredoxins are thiol-specific antioxidant proteins that protect cells from ROS-induced cell death and are elevated in several cancers. We found that five of the six mammalian peroxiredoxins are overexpressed in MCF-7 breast cancer cells at the mRNA and protein levels, compared to noncancerous MCF-10A cells. Inhibition of MCF-7 proliferation reduced the levels of several peroxiredoxins. In contrast, all six proteins were strongly and transiently induced in MCF-7 cells by H₂O₂. These data suggest that coordinate overexpression of peroxiredoxins may be an important cancer cell adaptation, and that these proteins can be regulated by cell proliferation and oxidative stress.

Gene responses in the central nervous system of zebrafish embryos exposed to the neurotoxicant methyl mercury

Methyl mercury (MeHg) is a neurotoxicant with adverse effects on the development of the nervous system from fish to man. Despite a detailed understanding of the molecular mechanisms by which MeHg affects cellular homeostasis, it is still not clear how MeHg causes developmental neurotoxicity. We performed here a genome-wide transcriptional analysis of MeHg-exposed zebrafish embryos and combined this with a whole-mount in situ expression analysis of 88 MeHg-affected genes. The majority of the analyzed genes showed tissue- and region-restricted responses in various organs and tissues. The genes were linked to gene ontology terms like oxidative stress, transport and cell protection. Areas even within the central nervous system (CNS) are affected differently resulting in distinct cellular stress responses. Our study revealed an unexpected heterogeneity in gene responses to MeHg exposure in different tissues and neuronal subregions, even though the known molecular action of MeHg would predict a similar burden of exposed cells. The overall structure of the developing brain of MeHg-exposed embryos appeared normal, suggesting that the mechanism leading to differentiation of the CNS is not overtly affected by exposure to MeHg. We propose that MeHg disturbs the function of the CNS by disturbing the cellular homeostasis. As these cellular stress responses comprise genes that are also involved in normal neuronal activity and learning, MeHg may affect the developing CNS in a subtle manner that manifests itself in behavioral deficits.

Sulfiredoxin-1 protects PC12 cells against oxidative stress induced by hydrogen peroxide

Oxidative stress results in protein oxidation and is implicated in cerebral disease, such as Parkinson's disease, Alzheimer's disease, and ischemic stroke. Sulfiredoxin-1 (Srxn1) is an endogenous antioxidant protein that has neuroprotective effects. The mechanisms of Srxn1 in oxidative stress have not been well studied, however. This study used 180 μM H2 O2 exposure for 24 hr to model oxidative stress. This experimental design allowed us to explore the protective effects and underlying mechanisms of Srxn1 in PC12 cells. To investigate Srxn1's role in oxidative stress protection, transient knockdowns of Srxn1 in PC12 cells were performed prior to treatment with 180 μM H2 O2 for 24 hr. Knockdown of Srxn1 resulted in decreased cell viability and increased cellular damage as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and lactate dehyrogenase analysis, respectively. Intracellular superoxide dismutase and glutathione are important indexes of oxidative stress; these were reduced in Srxn1 knockdown PC12. We further found that the decreased Srxn1 correlated with a reduction in 2-Cys Prdxs activity. Moreover, 2-Cys Prdxs protein levels were increased in the H2 O2 -dosed cells, as measured by RT-PCR and immunoblot analysis. These results suggested that Srxn1 can protect PC12 cells from H2 O2 -induced oxidative stress and are involve in Prdxs activity. Srxn1 play a protective role against oxidative injury and demonstrates potential as a target for neuroprotective intervention in oxidative stress.

Peroxiredoxin V: A candidate breast tumor marker of population specificity

Breast and cervical cancers account for approximately 50% of all types of cancer in Sudanese women. In a previous preliminary proteomic study aimed to identify proteins that were differentially expressed between tumors and control tissues (n=24), we identified peroxiredoxin V (PrdxV) as a candidate tumor marker. Peroxiredoxins (Prdxs) are a family of multifunctional proteins that are involved in the cell protection against oxidative stress, modulation of intracellular signaling, and regulation of cell proliferation. Knockout animal models suggest that the regulation of these proteins may be a novel target for therapeutic interventions. A total of 91 tumors and 79 normal breast tissues obtained from a panel of 106 Sudanese breast cancer patients, as well as 31 paired tissue samples (tumors and controls) from Chinese cancer patients were included in this study. Tissue sections were examined using immunohistochemistry (IHC) for PrdxI, V and VI antibodies. The PrdxV mRNA pattern of expression was also investigated using in situ hybridization (ISH). The overall expression of the same Prdx family members was also examined in a panel of Chinese breast carcinoma and control samples. Statistical comparisons were performed between Prxds antibodies, and between available demographic and pathological parameters. The studied Prdxs were found to be overexpressed in both Sudanese and Chinese breast cancer and control samples. PrdxV was the only member of the Prdxs family to be significantly down-regulated in Sudanese tumor samples, with only a few cases being immunoreactive for PrdxV (11%). Significant elevation was demonstrated between tumors and controls at both the protein (using IHC) (P=0.000) and mRNA (using ISH) (P= 0.044) levels. However, the finding was more apparent and statistically significant at the protein level, suggesting the presence of post-translational modification. These findings suggest that PrdxV is a tumor marker of population specificity. However, more studies are needed to investigate the applicability of PrdxV as a marker in Sudanese breast cancer patients and its potential implications in therapy.

Miiuy croaker (Miichthys miiuy) Peroxiredoxin2: molecular characterization, genomic structure and immune response against bacterial infection

Peroxiredoxin2 (Prx2) protein is an important member in cellular antioxidant protein superfamily. Prx2 exists widely in prokaryotes and eukaryotes, it not only plays a part in eliminate reactive oxygen, but also takes effect in many other metabolic activities, such as stimulate epithelial cell proliferation, participate in the signal transduction in cells and so on. After molecular cloning we got that the complete cDNA sequence of Prx2 consists 882 bp, including a 5'-UTR of 46 bp, an open reading frame (ORF) of 591 bp, and a 3'-UTR of 245 bp. The complete gene of miiuy croaker Prx2 has 5 exons and 4 introns. The deduced 197 amino acid residues of miiuy croaker Prx2 consists a Val-Cys-Pro (VCP) motifs. In order to better elucidate the immune mechanisms of the Prx2 in the lower vertebrates, we conducted a research about the Prx2 gene of miiuy croaker and its expression pattern after bacterial infection. Real-time PCR (RT-PCR) results showed that expression of Prx2 was up-regulated in kidney, liver and spleen under infection with Vibrio anguillarum, and expressed level differently in ten different uninjected tissues. Our results suggested that Prx2 might be involved in immune defence in miiuy croaker.

Proteomics in HepG2 hepatocarcinoma cells with stably silenced expression of PRDX1

Peroxiredoxin 1 (PRDX1) is a member of the peroxiredoxin family. Aberrant expression of PRDX1 has been described in various cancers. We investigated the significance of this up-regulation in non-challenged hepatocellularcarcinoma (HCC) cells by establishing a HepG2 cell line stably expressing a Prdx1 shRNA. Prdx1 silencing reversed, at least partially, the tumoural phenotype of HepG2 cells, resulting in morphological changes, delayed cell growth, down-regulation of transcripts for AFP, osteopontin and β-catenin and decreased γ-glutamyl transpeptidase activity, and oppositely up-regulation of transcripts for E-cadherin and proapoptotic proteins (BAX, CASP3) and increased alkaline phosphatase and CASP3 activities. Proteomic profiling identified 16 spots differentially expressed in Prdx1-silenced cells. Most of the variations involved the down-regulation of proteins with pivotal roles in cell proliferation and differentiation, in agreement with the observed phenotypic changes. We also investigated the effect of Prdx1 silencing on thiol protein oxidation. Proteins prone to reversible cysteine oxidation play major physiological functions. Notably, the down-regulation and altered redox status of key enzymes of carbohydrate and amino acid metabolism suggested a disturbance of the Warburg effect and glutamine utilization, two major pathways in the proliferation of tumour cells. Overall, these observations suggest that PRDX1 acts as a pro-cancer protein in HCC HepG2 cells.

Mitochondrial thiols in the regulation of cell death pathways

SIGNIFICANCE

Regulation of mitochondrial H(2)O(2) homeostasis and its involvement in the regulation of redox-sensitive signaling and transcriptional pathways is the consequence of the concerted activities of the mitochondrial energy- and redox systems.

RECENT ADVANCES

The energy component of this mitochondrial energy-redox axis entails the formation of reducing equivalents and their flow through the respiratory chain with the consequent electron leak to generate [Formula: see text] and H(2)O(2). The mitochondrial redox component entails the thiol-based antioxidant system, largely accounted for by glutathione- and thioredoxin-based systems that support the activities of glutathione peroxidases, peroxiredoxins, and methionine sulfoxide reductase. The ultimate reductant for these systems is NADPH: mitochondrial sources of NADPH are the nicotinamide nucleotide transhydrogenase, isocitrate dehydrogenase-2, and malic enzyme. NADPH also supports the glutaredoxin activity that regulates the extent of S-glutathionylation of mitochondrial proteins in response to altered redox status.

CRITICAL ISSUES

The integrated network of these mitochondrial thiols constitute a regulatory device involved in the maintenance of steady-state levels of H(2)O(2), mitochondrial and cellular redox and metabolic homeostasis, as well as the modulation of cytosolic redox-sensitive signaling; disturbances of this regulatory device affects transcription, growth, and ultimately influences cell survival/death.

FUTURE DIRECTIONS

The modulation of key mitochondrial thiol proteins, which participate in redox signaling, maintenance of the bioenergetic machinery, oxidative stress responses, and cell death programming, provides a pivotal direction in developing new therapies towards the prevention and treatment of several diseases.

Elucidation of allosteric inhibition mechanism of 2-Cys human peroxiredoxin by molecular modeling

We used molecular dynamics (MD) simulations and protein docking to elucidate the mechanism of allosteric inhibition of the human form of peroxiredoxin (Prx), 2-Cys proliferation associated gene (PAG). Beginning by using the rat form of Prx, 2-Cys heme-binding protein as a template, we used homology modeling to find the structure of human 2-Cys PAG, which is in dimeric form. Molecular dynamics simulations showed that the structure of the reduced form of the 2-Cys PAG dimer fluctuates as the two monomers drift away and approach each other. We then used SiteMap to search for binding sites on the surface of this dimer. A binding site between the two monomers was found, and virtual screening with docking was performed to identify a ligand binding to this site. Subsequent MD simulation revealed that with this ligand in the binding site, the dimer structure of 2-Cys PAG becomes stabilized such that two cysteine residues from two monomers, which are partners of a disulfide bond of the oxidized form, remain separated. This mechanism can be used as an allosteric inhibition of Prx as a hydrogen peroxide reducer, the role of which has been studied as an anticancer drug target.

The evolution and putative function of phosducin-like proteins in the malaria parasite Plasmodium

Ubiquitous to the proteomes of all living species is the presence of proteins containing the thioredoxin (Trx)-domain. The best characterized Trx-domain containing proteins include the enzymes involved in cellular redox metabolism facilitated by their cysteine-containing active site. But not all members of the Trx-fold superfamily exhibit this catalytic motif, e.g., the phosducin-like (PhLP) family of proteins. Genome sequencing efforts have uncovered new Trx-domain containing proteins, and their redox activity and cellular functions have yet to be determined. The genome of the malaria parasite Plasmodium contains multiple thioredoxins and thioredoxin-like proteins which are of considerable interest given their role in the parasite's antioxidant defense. While adaptations within the Trx-domain have been studied, primarily with respect to redox active structures, PhLP proteins have not been examined. Using the uncharacterized phosducin-like protein from Plasmodium berghei PhLP-1, we investigated the evolution of PhLP proteins across all branches of the tree of life. As a result of our analysis, we have discovered the presence of two additional PhLP proteins in Plasmodium, PhLP-2 and PhLP-3. Sequence homology with annotated PhLP proteins in other species confirms that the Plasmodium PhLP-2 and PhLP-3 belong to the PhLP family of proteins. Furthermore, as a result of our analysis we hypothesize that the PhLP-2 thioredoxin was lost over time given its absence from higher-order eukaryotes. Probing deeper into the putative function of these proteins, inspection of the active sites indicate that PbPhLP-1 and PbPhLP-2 may be redox active while PbPhLP-3 is very likely not. The results of this phylogenetic study provide insight into the emergence of this family of Trx-domain containing proteins.

Pathological conditions involving extracellular hemoglobin: molecular mechanisms, clinical significance, and novel therapeutic opportunities for α(1)-microglobulin

Hemoglobin (Hb) is the major oxygen (O(2))-carrying system of the blood but has many potentially dangerous side effects due to oxidation and reduction reactions of the heme-bound iron and O(2). Extracellular Hb, resulting from hemolysis or exogenous infusion, is shown to be an important pathogenic factor in a growing number of diseases. This review briefly outlines the oxidative/reductive toxic reactions of Hb and its metabolites. It also describes physiological protection mechanisms that have evolved against extracellular Hb, with a focus on the most recently discovered: the heme- and radical-binding protein α(1)-microglobulin (A1M). This protein is found in all vertebrates, including man, and operates by rapidly clearing cytosols and extravascular fluids of heme groups and free radicals released from Hb. Five groups of pathological conditions with high concentrations of extracellular Hb are described: hemolytic anemias and transfusion reactions, the pregnancy complication pre-eclampsia, cerebral intraventricular hemorrhage of premature infants, chronic inflammatory leg ulcers, and infusion of Hb-based O(2) carriers as blood substitutes. Finally, possible treatments of these conditions are discussed, giving a special attention to the described protective effects of A1M.

Biochemical characterization of human peroxiredoxin 2, an antioxidative protein

Human peroxiredoxin 2 (Prx2), which is abundant in erythrocytes, has been shown to play a key role in protecting erythrocytes against oxidative stress by scavenging reactive oxygen species as well as participating in cell signal transduction. Here, human Prx2 gene was successfully cloned into Escherichia coli BL21 (DE3) for Prx2 expression. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis suggested that the recombinant protein was expressed mainly in a soluble form. The recombinant protein was purified by one-step Ni-nitrilotriacetic acid chelating affinity chromatography to a purity of up to 91.5%. The peroxidase activity of Prx2 to scavenge H(2)O(2) was determined by a ferrithiocyanate assay. The ability of Prx2 to protect plasmid DNA was tested by using a mixed-function oxidation system, and results showed that Prx2 could prevent DNA from undergoing oxidative stress. Ultraviolet (UV)-induced cell apoptosis assay demonstrated that Prx2 is also able to protect NIH/3T3 cells from UV-induced damage, suggesting its possible applications in cosmetics and other areas.

Proteome profiling of tolbutamide-treated rat primary hepatocytes using nano LC-MS/MS and label-free protein quantitation

Tolbutamide is used as a first line oral antihyperglycemic drug for type 2 diabetes. One side effect of this drug, hepatotoxicity, is well recognized; however, the precise mechanisms underlying tolbutamide-induced hepatotoxicity remain unclear. In this respect, proteomics techniques were used to gain further insight into the mechanistic processes of the hepatotoxicity induced by this drug. In this study, we aimed to identify molecular pathways based on proteins responding to cellular toxicity in tolbutamide-treated primary hepatocytes, using nano UPLC-MS/MS analysis. Rat primary hepatocytes were treated with an IC(20) concentration for 24 h to study the hepatotoxic effects of tolbutamide. For high-throughput label-free quantitation, tryptic-digested peptides of proteins from cell lysates were analyzed using LC-MS/MS and quantitated using the IDEAL-Q software, in which several parameters, such as assisted sequence, elution time, and mass-to-charge ratio were included. We quantified a total of 330 distinct proteins from the tolbutamide-treated hepatocytes and identified 55 upregulated and 82 downregulated proteins with expression changes. Among these differentially expressed proteins, we focused mainly on the 18 upregulated proteins belonging to xenobiotic cytochrome P450 (CYP), drug metabolism/detoxification, oxidative stress/antioxidant response, and cell damage pathway. CYP2D1, CYP2C11, UDP-glucuronosyltransferase 2B (UGT2B), superoxide dismutase 2 (SOD2), 60 kDa heat shock protein (HSPD1), heat shock protein 90 (HSP90), and catalase (CAT) were confirmed by Western blot analysis. In addition, various xenobiotic CYP proteins upregulated in the tolbutamide-treated group, CYP2D1, CYP2C13, and CYP2C11 were confirmed by reverse transcriptase-PCR analysis. Our results offer important new insights into the molecular mechanisms of tolbutamide-induced hepatotoxicity.

Proteomic study on usnic-acid-induced hepatotoxicity in rats

Usnic acid, a lichen metabolite, is used as a dietary supplement for weight loss. However, clinical studies have shown that usnic acid causes hepatotoxicity. The present study aims to investigate the mechanism of usnic acid hepatotoxicity in vivo. Two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to analyze the expression profiles of differentially regulated and expressed proteins in rat liver after usnic acid administration. The results reveal the differential expression of 10 proteins in usnic-acid-treated rats compared to the normal controls. These proteins are associated with oxidative stress, lipid metabolism, and several other molecular pathways. The endoplasmic reticulum and mitochondria may be the primary targets of usnic-acid-induced hepatotoxicity.

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.

Apnea stimulates the adaptive response to oxidative stress in elephant seal pups

Extended breath-hold (apnea) bouts are routine during diving and sleeping in seals. These apneas result in oxygen store depletion and blood flow redistribution towards obligatory oxygen-dependent tissues, exposing seals to critical levels of ischemia and hypoxemia. The subsequent reperfusion/reoxygenation has the potential to increase oxidant production and thus oxidative stress. The contributions of extended apnea to oxidative stress in adapted mammals are not well defined. To address the hypothesis that apnea in seals is not associated with increased oxidative damage, blood samples were collected from northern elephant seal pups (N=6) during eupnea, rest- and voluntary submersion-associated apneas, and post-apnea (recovery). Plasma 4-hydroxynonenal (HNE), 8-isoprostanes (8-isoPGF(2α)), nitrotyrosine (NT), protein carbonyls, xanthine and hypoxanthine (HX) levels, along with xanthine oxidase (XO) activity, were measured. Protein content of XO, superoxide dismutase 1 (Cu,ZnSOD), catalase and myoglobin (Mb), as well as the nuclear content of hypoxia inducible factor 1α (HIF-1α) and NF-E2-related factor 2 (Nrf2), were measured in muscle biopsies collected before and after the breath-hold trials. HNE, 8-iso PGF(2α), NT and protein carbonyl levels did not change among eupnea, apnea or recovery. XO activity and HX and xanthine concentrations were increased at the end of the apneas and during recovery. Muscle protein content of XO, CuZnSOD, catalase, Mb, HIF-1α and Nrf2 increased 25-70% after apnea. Results suggest that rather than inducing the damaging effects of hypoxemia and ischemia/reperfusion that have been reported in non-diving mammals, apnea in seals stimulates the oxidative stress and hypoxic hormetic responses, allowing these mammals to cope with the potentially detrimental effects associated with this condition.

A Study of the Wound Healing Mechanism of a Traditional Chinese Medicine, Angelica sinensis, Using a Proteomic Approach

Angelica sinensis (AS) is a traditional Chinese herbal medicine that has been formulated clinically to treat various form of skin trauma and to help wound healing. However, the mechanism by which it works remains a mystery. In this study we have established a new platform to evaluate the pharmacological effects of total AS herbal extracts as well as its major active component, ferulic acid (FA), using proteomic and biochemical analysis. Cytotoxic and proliferation-promoting concentrations of AS ethanol extracts (AS extract) and FA were tested, and then the cell extracts were subject to 2D PAGE analysis. We found 51 differentially expressed protein spots, and these were identified by mass spectrometry. Furthermore, biomolecular assays, involving collagen secretion, migration, and ROS measurements, gave results that are consistent with the proteomic analysis. In this work, we have demonstrated a whole range of pharmacological effects associated with Angelica sinensis that might be beneficial when developing a wound healing pharmaceutical formulation for the herbal medicine.

Differential expression and function of peroxiredoxin 1 and peroxiredoxin 6 in cancerous MCF-7 and noncancerous MCF-10A breast epithelial cells

Peroxiredoxins are thiol-specific antioxidant proteins whose expression is elevated in several cancers. We compared the expression and function of Prdx1 and Prdx6 between the MCF-7 mammary adenocarcinoma cell line and the noncancerous MCF-10A cell line. We found elevated Prdx1 expression in MCF-7 cells and comparable expression of Prdx6. Suppression of Prdx1 and/or Prdx6 resulted in a modest increase in peroxide-induced cytotoxicity of MCF-7 cells, and a dramatic increase in MCF-10A cytotoxicity with and without hydrogen peroxide treatment. Our data confirm a cytoprotective role for peroxiredoxins and suggest a synergistic role for Prdx1 and Prdx6 in MCF-10A cells.

Sub-proteomic study on macrophage response to Candida albicans unravels new proteins involved in the host defense against the fungus

In previous proteomic studies on the response of murine macrophages against Candida albicans, many differentially expressed proteins involved in processes like inflammation, cytoskeletal rearrangement, stress response and metabolism were identified. In order to look for proteins important for the macrophage response, but in a lower concentration in the cell, 3 sub-cellular extracts were analyzed: cytosol, organelle/membrane and nucleus enriched fractions from RAW 264.7 macrophages exposed or not to C. albicans SC5314 for 3 h. The samples were studied using DIGE technology, and 17 new differentially expressed proteins were identified. This sub-cellular fractionation permitted the identification of 2 mitochondrion proteins, a membrane receptor, Galectin-3, and some ER related proteins, that are not easily detected in total cell extracts. Besides, the study of different fractions allowed us to detect, not only total increase in Galectin-3 protein amount, but its distinct allocation along the interaction. The identified proteins are involved in the pro-inflammatory and oxidative responses, immune response, unfolded protein response and apoptosis. Some of these processes increase the host response and others could be the effect of C. albicans resistance to phagocytosis. Thus, the sub-proteomic approach has been a very useful tool to identify new proteins involved in macrophage-fungus interaction. This article is part of a Special Issue entitled: Translational Proteomics.

Peroxiredoxin-2 upregulated by NF-κB attenuates oxidative stress during the differentiation of muscle-derived C2C12 cells

AIM

Many studies have reported that the generation of reactive oxygen species (ROS) increases during the differentiation of muscle-derived C2C12 cells. Peroxiredoxin-2 (Prx-2) is an abundant mammalian enzyme that protects against oxidative stress. However, the role of Prx-2 in muscle differentiation has not been investigated.

RESULTS

In this study, we demonstrated that Prx-2 expression increases during muscle differentiation and regeneration in response to exogenous H(2)O(2). This increase occurs only in myoblast cell lines because no increase in Prx-2 expression was observed in the NIH3T3, MEF, Chang, or HEK293 cell lines. The antioxidants, N-acetyl L-cysteine (NAC) and 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron), both suppressed myogenesis and Prx-2 expression. Moreover, Prx-2 was upregulated at the transcriptional level by NF-κB during the differentiation of muscle-derived C2C12 cells. We also found that inhibition of phosphatidylinositol 3-kinase (PI3K) blocks NF-κB activation and suppresses Prx-2 expression. Interestingly, Prx-2 knockdown increased the expression levels of other antioxidant enzymes, including all of the other Prx family member, thioredoxin-1 (Trx-1) and catalase, but also enhanced the accumulation of endogenous ROS during muscle differentiation.

INNOVATION

In this study, we demonstrated for the first time that Prx-2 is unregulated during the muscle differentiation and regeneration.

CONCLUSION

Prx-2 is upregulated via the PI3K/NF-κB pathway and attenuates oxidative stress during muscle differentiation and regeneration.

The response to heat shock and oxidative stress in Saccharomyces cerevisiae

A common need for microbial cells is the ability to respond to potentially toxic environmental insults. Here we review the progress in understanding the response of the yeast Saccharomyces cerevisiae to two important environmental stresses: heat shock and oxidative stress. Both of these stresses are fundamental challenges that microbes of all types will experience. The study of these environmental stress responses in S. cerevisiae has illuminated many of the features now viewed as central to our understanding of eukaryotic cell biology. Transcriptional activation plays an important role in driving the multifaceted reaction to elevated temperature and levels of reactive oxygen species. Advances provided by the development of whole genome analyses have led to an appreciation of the global reorganization of gene expression and its integration between different stress regimens. While the precise nature of the signal eliciting the heat shock response remains elusive, recent progress in the understanding of induction of the oxidative stress response is summarized here. Although these stress conditions represent ancient challenges to S. cerevisiae and other microbes, much remains to be learned about the mechanisms dedicated to dealing with these environmental parameters.

Downregulation of PRDX1 by promoter hypermethylation is frequent in 1p/19q-deleted oligodendroglial tumours and increases radio- and chemosensitivity of Hs683 glioma cells in vitro

Deletions of chromosomal arms 1p and 19q are frequent in oligodendroglial tumours and linked to radio- and chemotherapy response as well as longer survival. The molecular mechanisms underlying this clinically important association are as yet unknown. Here, we studied the peroxiredoxin 1 (PRDX1) gene at 1p34.1 for promoter methylation and expression in primary gliomas and investigated its role in radio- and chemosensitivity of glioma cells in vitro. In total, we screened primary glioma tissues from 93 patients for methylation of the 5'-CpG island of PRDX1 by sodium bisulfite sequencing. PRDX1 mRNA and protein expression levels were determined in subsets of the tumours by quantitative PCR and western blot analysis, respectively. PRDX1 hypermethylation and reduced expression were frequently detected in oligodendroglial tumours and secondary glioblastomas, but not in primary glioblastomas. In oligodendroglial tumours, both PRDX1 hypermethylation and reduced mRNA expression were significantly associated with 1p/19q-deletion. Stable knockdown of PRDX1 by lentiviral transduction of short-hairpin (sh)RNA constructs significantly increased apoptosis and reduced cell viability of Hs683 glioma cells exposed to ionizing irradiation or temozolomide in vitro. Taken together, our findings indicate that epigenetic silencing of PRDX1 is frequent in 1p/19q-deleted oligodendroglial tumours and likely contributes to radio- and chemosensitivity of these tumours.

Antioxidant capacity develops with maturation in the deep-diving hooded seal

Maturation in hooded seals is characterized by the rapid development of their physiological diving capacity and is accompanied by increases in oxidant production but not oxidative damage. To test the hypothesis that the antioxidant system of hooded seals develops as they transition from a terrestrial to an aquatic environment, we obtained the complete cDNA sequence that encodes the NF-E2-related factor 2 (Nrf2), a central regulator of the antioxidant response, and compared Nrf2 mRNA and protein expression levels in muscle samples from neonate, weaned pups and adult hooded seals, along with glutathione (GSH) levels and the activity/protein content of the antioxidant enzymes catalase, glutathione peroxidase (GPx), peroxyredoxin VI (PrxVI), thioredoxin 1 (Trx1), thioredoxin reductase (TrxR), glutaredoxin 1 (Glrx1), glutathione disulphide reductase, glutathione S-transferase and glutamate-cysteine ligase. The Nrf2 of the hooded seal is 1822 bp long and encodes a protein of 606 amino acids with a leucine zipper domain and Keap1-mediated proteosomal degradation residues, which are key for Nrf2 function and regulation. Although neither Nrf2 mRNA nor Nrf2 nuclear protein content are higher in adults than in pups, GSH levels along with GPx, PrxVI, Trx1, TrxR and Glrx1 activity/protein content increase with maturation, suggesting that the potential for peroxide removal increases with development in hooded seals, and that these enzymes contribute to the regulation of the intracellular redox state and the prevention of oxidative damage in these deep-diving mammals.

In-depth identification of pathways related to cisplatin-induced hepatotoxicity through an integrative method based on an informatics-assisted label-free protein quantitation and microarray gene expression approach

Cisplatin is used widely for treatment of a variety of cancer diseases. Recently, however, the use of cisplatin is restricted because of its adverse effects such as hepatotoxicity. There is no study with current proteomics technology to evaluate cisplatin-induced hepatotoxicity, even if some studies have reported on the hepatotoxicity. In this study, proteomic as well as genomic analyses have been used for identification of proteins and genes that respond to cisplatin treatment in rat primary hepatocytes. To investigate the hepatotoxic effects of cisplatin, rat primary hepatocytes were treated with an IC(20) concentration for 24 h. From proteomic analysis based on label-free quantitation strategy, cisplatin induced 76 up-regulated and 19 down-regulated proteins among 325 distinct proteins. In the mRNA level, genomic analysis revealed 72 up-regulated and 385 down-regulated genes in the cisplatin-treated group. Based on these two analyses, 19 pathways were commonly altered, whereas seven pathways were identified only by proteomic analysis, and 19 pathways were identified only by genomic analysis. Overall, this study explained the mechanism of cisplatin-induced hepatotoxicity with two points of view: well known pathways including drug metabolism, fatty acid metabolism, and glycolysis/TCA cycle and little known pathways including urea cycle and inflammation metabolism, for hepatotoxicity of other toxic agents. Up-regulated proteins detected by proteomic analysis in the cisplatin-treated group: FBP1 (fructose 1,6-bisphosphatase 1), FASN (fatty acid synthase), CAT (catalase), PRDX1 (peroxiredoxin-1), HSPD1 (60-kDa heat shock protein), MDH2 (malate dehydrogenase 2), and ARG1 (arginase 1), and also down-regulated proteins in the cisplatin-treated group: TPM1 (tropomyosin 1), TPM3 (tropomyosin 3), and CTSB (cathepsin B), were confirmed by Western blot analysis. In addition, up-regulated mRNAs detected by microarray analysis in the cisplatin-treated group: GSTA2, GSTT2, YC2, TXNRD1, CYP2E1, CYP2C13, CYP2D1, ALDH17, ARG1, ARG2, and IL-6, and also down-regulated mRNAs: CYP2C12, CYP26B1, TPM1, and TPM3, were confirmed by RT-PCR analysis. In case of PRDX1, FASN, and ARG1, they were further confirmed by immunofluorescence analysis. Through the integrated proteomic and genomic approaches, the present study provides the first pathway map related to cisplatin-induced hepatotoxicity, which may provide new insight into the mechanism of hepatotoxicity.

Basic principles and emerging concepts in the redox control of transcription factors

Convincing concepts of redox control of gene transcription have been worked out for prokaryotes and lower eukaryotes, whereas the knowledge on complex mammalian systems still resembles a patchwork of poorly connected findings. The article, therefore, reviews principles of redox regulation with special emphasis on chemical feasibility, kinetic requirements, specificity, and physiological context, taking well investigated mammalian transcription factor systems, nuclear transcription factor of bone marrow-derived lymphocytes (NF-κB), and kelch-like ECH-associated protein-1 (Keap1)/Nrf2, as paradigms. Major conclusions are that (i) direct signaling by free radicals is restricted to O(2)•- and •NO and can be excluded for fast reacting radicals such as •OH, •OR, or Cl•; (ii) oxidant signals are H(2)O(2), enzymatically generated lipid hydroperoxides, and peroxynitrite; (iii) free radical damage is sensed via generation of Michael acceptors; (iv) protein thiol oxidation/alkylation is the prominent mechanism to modulate function; (v) redox sensors must be thiol peroxidases by themselves or proteins with similarly reactive cysteine or selenocysteine (Sec) residues to kinetically compete with glutathione peroxidase (GPx)- and peroxiredoxin (Prx)-type peroxidases or glutathione-S-transferases, respectively, a postulate that still has to be verified for putative mammalian sensors. S-transferases and Prxs are considered for system complementation. The impact of NF-κB and Nrf2 on hormesis, management of inflammatory diseases, and cancer prevention is critically discussed.

Dual neuroprotective pathways of a pro-electrophilic compound via HSF-1-activated heat-shock proteins and Nrf2-activated phase 2 antioxidant response enzymes

Activation of the Keap1/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway and consequent induction of phase 2 antioxidant enzymes is known to afford neuroprotection. Here, we present a series of novel electrophilic compounds that protect neurons via this pathway. Natural products, such as carnosic acid (CA), are present in high amounts in the herbs rosemary and sage as ortho-dihydroquinones, and have attracted particular attention because they are converted by oxidative stress to their active form (ortho-quinone species) that stimulate the Keap1/Nrf2 transcriptional pathway. Once activated, this pathway leads to the production of a series of antioxidant phase 2 enzymes. Thus, such dihydroquinones function as redox-activated 'pro-electrophiles'. Here, we explored the concept that related para-dihydroquinones represent even more effective bioactive pro-electrophiles for the induction of phase 2 enzymes without producing toxic side effects. We synthesized several novel para-hydroquinone-type pro-electrophilic compounds (designated D1 and D2) to analyze their protective mechanism. DNA microarray, PCR, and western blot analyses showed that compound D1 induced expression of heat-shock proteins (HSPs), including HSP70, HSP27, and DnaJ, in addition to phase 2 enzymes such as hemeoxygenase-1 (HO-1), NADP(H) quinine-oxidoreductase1, and the Na(+)-independent cystine/glutamate exchanger (xCT). Treatment with D1 resulted in activation of Nrf2 and heat-shock transcription factor-1 (HSF-1) transcriptional elements, thus inducing phase 2 enzymes and HSPs, respectively. In this manner, D1 protected neuronal cells from both oxidative and endoplasmic reticulum (ER)-related stress. Additionally, D1 suppressed induction of 78 kDa glucose-regulated protein (GRP78), an ER chaperone protein, and inhibited hyperoxidation of peroxiredoxin 2 (PRX2), a molecule that is in its reduced state can protect from oxidative stress. These results suggest that D1 is a novel pro-electrophilic compound that activates both the Nrf2 and HSF-1 pathways, and may thus offer protection from oxidative and ER stress.

Prolonged fasting increases glutathione biosynthesis in postweaned northern elephant seals

Northern elephant seals experience prolonged periods of absolute food and water deprivation (fasting) while breeding, molting or weaning. The postweaning fast in elephant seals is characterized by increases in the renin-angiotensin system, expression of the oxidant-producing protein Nox4, and NADPH oxidase activity; however, these increases are not correlated with increased oxidative damage or inflammation. Glutathione (GSH) is a potent reductant and a cofactor for glutathione peroxidases (GPx), glutathione-S transferases (GST) and 1-cys peroxiredoxin (PrxVI) and thus contributes to the removal of hydroperoxides, preventing oxidative damage. The effects of prolonged food deprivation on the GSH system are not well described in mammals. To test our hypothesis that GSH biosynthesis increases with fasting in postweaned elephant seals, we measured circulating and muscle GSH content at the early and late phases of the postweaning fast in elephant seals along with the activity/protein content of glutamate-cysteine ligase [GCL; catalytic (GCLc) and modulatory (GCLm) subunits], γ-glutamyl transpeptidase (GGT), glutathione disulphide reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), GST and PrxVI, as well as plasma changes in γ-glutamyl amino acids, glutamate and glutamine. GSH increased two- to four-fold with fasting along with a 40-50% increase in the content of GCLm and GCLc, a 75% increase in GGT activity, a two- to 2.5-fold increase in GR, G6PDH and GST activities and a 30% increase in PrxVI content. Plasma γ-glutamyl glutamine, γ-glutamyl isoleucine and γ-glutamyl methionine also increased with fasting whereas glutamate and glutamine decreased. Results indicate that GSH biosynthesis increases with fasting and that GSH contributes to counteracting hydroperoxide production, preventing oxidative damage in fasting seals.

Stage-related alterations in renal cell carcinoma--comprehensive quantitative analysis by 2D-DIGE and protein network analysis

Renal cell carcinoma accounts for about 3% of adult malignancies and 85% of neoplasms arising from the kidney. To identify potential progression markers for kidney cancer we examined non-neoplastic and neoplastic kidney tissue from three groups of patients, which represent different tumor stages (pT1, pT2, pT3) by a fluorescence two-dimensional difference gel electrophoresis (2D-DIGE) approach combined with MALDI-ToF-MS/MS. Delta2D software package was used for gel image based quantification and statistical analysis. Thereby, a comprehensive Principal Component Analysis (PCA) could be performed and allowed a robust quality control of the experiment as well as a classification of the analyzed samples, which correlated with the predicted stages from the pathological examination. Additionally for selected candidate proteins we detected a correlation to the tumor grading as revealed by immunohistochemistry. On the 2D protein map 176 spots out of 989 were detected as at least 2-fold differentially expressed. These spots were analyzed by MALDI-ToF-MS/MS and 187 different proteins were identified. The functional clustering of the identified proteins revealed ten groups. Within these groups we found 86 enzymes, 63 proteins of unknown function, 14 transporter, 8 peptidases and 7 kinases. From the systems biology approach we could map many of these proteins in major pathways involved in remodelling of cytoskeleton, mitochondrial dysfunctions and changes in lipid metabolism. Due to complexity of the highly interconnected pathway network, further expression and functional validation of these proteins might provide new insights in kidney cancer progression to design novel diagnostic and therapeutic strategies.

Nitric oxide activates an Nrf2/sulfiredoxin antioxidant pathway in macrophages

Peroxiredoxins (Prx's) are a family of peroxidases that maintain thiol homeostasis by catalyzing the reduction of organic hydroperoxides, H₂O₂, and peroxynitrite. Under conditions of oxidative stress, eukaryotic Prx's can be inactivated by the substrate-dependent oxidation of the catalytic cysteine to sulfinic acid, which may regulate the intracellular messenger function of H₂O₂. A small redox protein, sulfiredoxin (Srx), conserved only in eukaryotes, has been shown to reduce sulfinylated 2-Cys Prx's, adding to the complexity of the H₂O₂ signaling network. In this study, we addressed the regulation of Srx expression in immunostimulated primary macrophages that produce both reactive oxygen species (ROS) and nitric oxide (NO(•)). We present genetic evidence that NO-mediated Srx up-regulation is mediated by the transcription factor nuclear factor erythroid 2-related factor (Nrf2). We also show that the NO(•)/Srx pathway inhibits generation of ROS. These results reveal a link between innate immunity and H₂O₂ signaling. We propose that an NO(•)/Nrf2/Srx pathway participates in the maintenance of redox homeostasis in cytokine-activated macrophages and other inflammatory settings.

Deficiency of Prdx6 in lens epithelial cells induces ER stress response-mediated impaired homeostasis and apoptosis

The multifunctional cytoprotective protein peroxiredoxin 6 (Prdx6) maintains cellular homeostasis and membrane integrity by regulating expression of intracellular reactive oxygen species (ROS) and phospholipid turnover. Using cells derived from targeted inactivation of Prdx6 gene or its depletion by RNA interference or aging, we showed that Prdx6 deficiency in cells evoked unfolded protein response (UPR), evidenced by increased expression or activation of proapoptotic factors, CHOP, ATF4, PERK, IRE-α and eIF2-α and by increased caspases 3 and 12 processing. Those cells displayed enhanced and sustained expression of endoplasmic reticulum (ER) stress-related chaperon proteins, Bip/glucose-regulated protein 78, calnexin, and calreticulin. Under cellular stress induced by hypoxia (1% O(2) or CoCl(2) treatment) or tunicamycin, Prdx6-deficient cells exhibited aberrant activation of ER stress-responsive genes/protein with higher expression of ROS, and died with apoptosis. Wild-type cells exposed to tunicamycin or hypoxia remained relatively insensitive with lower expression of ROS and ER-responsive genes than did Prdx6-deficient cells, but upregulation of ER stress responsive proteins or chaperones mimicked the UPR response of Prdx6-deficient or aging cells. Expression of Prdx6 blocked ER stress-induced deleterious signaling by optimizing physiologically aberrant expression of ER stress responsive genes/proteins in Prdx6-deficient cells or cells facing stressors, and rescued the cells from apoptosis. These findings demonstrate that impaired homeostasis and progression of pathogenesis in Prdx6-deficient lens epithelial cells or in aging cells should be blocked by a supply of Prdx6. The results provide a new molecular basis for understanding the etiology of several age-associated degenerative disorders, and potentially for developing antioxidant Prdx6-based therapeutics.

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.

Differential expression of peroxiredoxins in prostate cancer: consistent upregulation of PRDX3 and PRDX4

BACKGROUND

The peroxiredoxins (PRDXs) are emerging as regulators of antioxidant defense, apoptosis, and therapy resistance in cancer. Because their significance in prostate cancer (PCa) is unclear, we investigated their expression and clinical associations in PCa.

METHODS

Transcript expression of PRDX1-6 in PCa was evaluated in cancer gene microarray datasets, whereas protein expression was evaluated by immunoblotting in prostate cell lines, and by immunohistochemistry (IHC) in prostate tissue microarrays (TMAs) containing tumor (n = 80) and control (n = 17) tissues. PRDX3 was also analyzed in TMAs containing PCa tissues from African-American and Caucasian patients (n = 150 per group). PRDX expression was correlated with patients' clinicopathologic characteristics.

RESULTS

Analysis of PRDX expression in cancer microarray datasets revealed consistent upregulation (tumor vs. normal) of PRDX3 and 4. All PRDXs exhibited elevated protein expression in PCa cell lines, compared with non-tumor cells. IHC revealed significant overexpression of PRDX3 and 4 in PCa, associated with age, increased prostate specific antigen (PSA), tumor stage, or Gleason score. High PRDX3 staining was associated with early age and elevated Gleason score at time of radical prostatectomy in African-American but not in Caucasian patients with PCa. PSA recurrence free survival in patients with low PRDX3 tumor expression was significantly longer in Caucasians compared to African-Americans, but no difference was detected for high expression.

CONCLUSIONS

PRDXs exhibit differential expression in prostate tumors, with PRDX3 and 4 consistently upregulated. Their role in PCa development, and their potential as biological determinants of PCa health disparities and novel therapeutic targets, deserve further investigation.

2D-DIGE proteomic analysis of changes in estrogen/progesterone-induced rat breast hyperplasia upon treatment with the Mongolian remedy RuXian-I

RuXian-I has traditionally been used as a remedy for breast hyperplasia in the Inner Mongolia Autonomous Region of China. As a first step toward the investigation of biomarkers associated with RuXian-I treatment, a proteome-wide analysis of rat breast tissue was conducted. First, rat breast hyperplasia was induced by injection of estradiol and progesterone. After treatment with RuXian-I, there is a marked decrease in the hyperplasia, as can be shown by decreases in the nipple diameter and the pathological changes in breast. Subsequently, we used an approach that integrates size-based 2D-DIGE, MALDI-TOF/TOF-MS, and bioinformatics to analyze data from the control group, the model group and the RuXian-I treatment group. Using this approach, seventeen affected proteins were identified. Among these, 15 (including annexin A1, annexin A2, superoxide dismutase [Mn], peroxiredoxin-1, translationally-controlled tumor protein and α B-crystallin) were significantly up-regulated in the model group and down-regulated upon treatment with RuXian-I, and two (Tpil protein and myosin-4) have the opposite change trend. The expression of annexin A1 was confirmed using immunohistochemistry. The expression of superoxide dismutase (SOD) activity was confirmed biochemically. These results indicated that RuXian-I treats rat breast hyperplasia through regulation of cell cycle, immune system, metabolic, signal transduction, etc. The differential expressions of these proteins (annexin A1, superoxide dismutase [Mn], alpha B-crystallins and translationally controlled tumor protein, among others) were associated with occurrence and metastasis of breast cancer. These findings might provide not only far-reaching valuable insights into the mechanism of RuXian-I action, but also leads for prognosis and diagnosis of breast hyperplasia and breast cancer.

Expression of peroxiredoxin I regulated by gonadotropins in the rat ovary

Objective

Peroxiredoxins (Prxs) play an important role in regulating cellular differentiation and proliferation in several types of mammalian cells. This report examined the expression of Prx isotype I in the rat ovary after hormone treatment.

Methods

Immature rats were injected with 10 IU of pregnant mare's serum gonadotropin (PMSG) to induce the growth of multiple preovulatory follicles and 10 IU of human chorionic gonadotropin (hCG) to induce ovulation. Immature rats were also treated with diethylstilbestrol (DES), an estrogen analogue, to induce the growth of multiple immature follicles. Northern blot analysis was performed to detect gene expression. Cell-type specific localization of Prx I mRNA were detected by in situ hybridization analysis.

Results

During follicle development, ovarian Prx I gene expression was detected in 3-day-old rats and had increased in 21-day-old rats. The levels of Prx I mRNA slightly declined one to two days following treatment with DES. A gradual increase in Prx I gene expression was observed in ovaries obtained from PMSG-treated immature rats. Furthermore, hCG treatment of PMSG-primed rats resulted in a gradual stimulation of Prx I mRNA levels by 24 hours (2.1-fold increase) following treatment, which remained high until 72 hours following treatment. In situ hybridization analysis revealed the expression of the Prx I gene in the granulosa cells of PMSG-primed ovaries and in the corpora lutea of ovaries stimulated with hCG for 72 hours.

Conclusion

These results demonstrate the gonadotropin and granulosa cell-specific stimulation of Prx I gene expression, suggesting its role as a local regulator of follicle development.

Identification of clinically relevant protein targets in prostate cancer with 2D-DIGE coupled mass spectrometry and systems biology network platform

Prostate cancer (PCa) is the most common type of cancer found in men and among the leading causes of cancer death in the western world. In the present study, we compared the individual protein expression patterns from histologically characterized PCa and the surrounding benign tissue obtained by manual micro dissection using highly sensitive two-dimensional differential gel electrophoresis (2D-DIGE) coupled with mass spectrometry. Proteomic data revealed 118 protein spots to be differentially expressed in cancer (n = 24) compared to benign (n = 21) prostate tissue. These spots were analysed by MALDI-TOF-MS/MS and 79 different proteins were identified. Using principal component analysis we could clearly separate tumor and normal tissue and two distinct tumor groups based on the protein expression pattern. By using a systems biology approach, we could map many of these proteins both into major pathways involved in PCa progression as well as into a group of potential diagnostic and/or prognostic markers. Due to complexity of the highly interconnected shortest pathway network, the functional sub networks revealed some of the potential candidate biomarker proteins for further validation. By using a systems biology approach, our study revealed novel proteins and molecular networks with altered expression in PCa. Further functional validation of individual proteins is ongoing and might provide new insights in PCa progression potentially leading to the design of novel diagnostic and therapeutic strategies.

Actinobacterial peroxidases: an unexplored resource for biocatalysis

Peroxidases are redox enzymes that can be found in all forms of life where they play diverse roles. It is therefore not surprising that they can also be applied in a wide range of industrial applications. Peroxidases have been extensively studied with particular emphasis on those isolated from fungi and plants. In general, peroxidases can be grouped into haem-containing and non-haem-containing peroxidases, each containing protein families that share sequence similarity. The order Actinomycetales comprises a large group of bacteria that are often exploited for their diverse metabolic capabilities, and with recent increases in the number of sequenced genomes, it has become clear that this metabolically diverse group of organisms also represents a large resource for redox enzymes. It is therefore surprising that, to date, no review article has been written on the wide range of peroxidases found within the actinobacteria. In this review article, we focus on the different types of peroxidases found in actinobacteria, their natural role in these organisms and how they compare with the more well-described peroxidases. Finally, we also focus on work remaining to be done in this research field in order for peroxidases from actinobacteria to be applied in industrial processes.

Influence of iNOS and COX on peroxiredoxin gene expression in primary macrophages

Peroxiredoxins (Prxs) are a family of multifunctional antioxidant thiol-dependent peroxidases. This study aimed to examine the regulatory mechanisms of Prx gene expression in murine bone marrow-derived macrophages (BMMs) using standardized serum-free conditions. Stimulation with LPS and IFNγ increased mRNA levels of Prx 1, 2, 4, 5, and 6 in BMMs of both C57BL/6 and BALB/c mice, with Prx 1, 2, 4, and 6 more strongly induced in C57BL/6 BMMs. Further investigations on signaling pathways in C57BL/6 BMMs demonstrated that up-regulation of Prx 5 and 6 by LPS and IFNγ was associated with the activation of multiple protein kinases, most notably JAK2, PI3K, and p38 MAPK. Our experiments also revealed a contribution of inducible NO synthase-derived nitric oxide to the increase in Prx 1, 2, 4, and 6 mRNA expression, whereas NADPH oxidase-derived superoxide was not involved. Furthermore, we could show that LPS- and IFNγ-induced gene expression of Prx 6 was also regulated in an NO-independent manner by cyclooxygenases and prostaglandin E(2). Taken together our results indicate a possible role for Prxs in defense mechanisms of activated macrophages against oxidative stress during inflammation or infection.

Peroxiredoxins from the plant parasitic root-knot nematode, Meloidogyne incognita, are required for successful development within the host

Root-knot nematodes, Meloidogyne spp., are sedentary biotrophic parasites which are able to infest > 2000 plant species. After root invasion they settle sedentarily inside the vascular cylinder and maintain a compatible interaction for up to 8 weeks. Plant cells respond to pathogen attacks by producing reactive oxygen species (ROS). These ROS, in particular hydroperoxides, are important regulators of host-parasite interactions and partly govern the success or failure of disease. ROS producing and ROS scavenging enzymes from both the pathogen and the host finely tune the redox state at the host-pathogen interface. We have analysed the gene structure and organization of peroxiredoxins (prx) in Meloidogyne incognita and analysed their role in the establishment of the nematode in its host. Meloidogyne incognita has seven prx genes that can be grouped with other nematode prx into three clades. Clade B prx genes are more actively transcribed in parasitic stages compared with free-living pre-parasitic juveniles. We confirmed in vitro the activity of one of these, Mi-prx2.1, on hydrogen peroxide and butylhydroperoxide. We showed by ultrastructural immunocytochemistry the expression of clade B PRX proteins in the hypodermis and pseudocoelum beneath the tissues directly in contact with the environment, both in free-living and parasitic stages. Finally, knock-down of clade B prx genes led to a significant reduction in the ability of the nematodes to complete their life cycle in the host. The expression of clade B PRX proteins in the tissues in close contact with plant cells during parasitism and the impaired development of nematodes inside the host after clade B prx knock-down suggest an important role for these genes during infection.

B- to plasma-cell terminal differentiation entails oxidative stress and profound reshaping of the antioxidant responses

Limited amounts of reactive oxygen species are necessary for cell survival and signaling, but their excess causes oxidative stress. H(2)O(2) and other reactive oxygen species are formed as byproducts of several metabolic pathways, possibly including oxidative protein folding in the endoplasmic reticulum. B- to plasma-cell differentiation is characterized by a massive expansion of the endoplasmic reticulum, finalized to sustain abundant immunoglobulin (Ig) synthesis and secretion. The increased production of disulfide-rich Ig might cause oxidative stress that could serve signaling roles in the differentiation and lifespan control of antibody-secreting cells. Here we show that terminal B-cell differentiation entails redox stress, NF-E2-related factor-2 (Nrf2) activation, and reshaping of the antioxidant responses. However, plasma-cell differentiation was not dramatically impaired in peroxiredoxin (Prx)1-, 2-, 3-, and 4-, glutathione peroxidase 1-, and Nrf2-knockout splenocytes, suggesting redundancy and robustness in antioxidant systems. Endoplasmic reticulum (ER)-resident Prx4 increases dramatically during differentiation. In its absence, IgM secretion was not significantly affected, but more high-molecular-weight covalent complexes accumulated intracellularly. Our results suggest that the early intracellular production of H(2)O(2) facilitates B-cell proliferation and reveal a role for the Nrf2 pathway in the differentiation and function of IgM-secreting cells.

Hydrogen peroxide modifies human sperm peroxiredoxins in a dose-dependent manner

Low levels of reactive oxygen species (ROS) modulate signaling pathways required for human sperm activation, but high levels impair sperm function, leading to infertility. Peroxiredoxins (PRDXs) are enzymes with a dual role as ROS scavengers and modulators of ROS-dependent signaling. The present study aimed to characterize PRDXs in human spermatozoa and possible modifications resulting from hydrogen peroxide (H(2)O(2)). We found PRDX1, PRDX4, PRDX5, and PRDX6 in both seminal plasma and spermatozoa. Using immunocytochemistry, we demonstrated that these PRDXs are differentially localized in the head, acrosome, mitochondrial sheath, and flagellum. These observations were confirmed by immunoblotting using cytosolic, Triton-soluble and -insoluble, and head and flagella sperm fractions. PRDXs are dose-dependently modified by H(2)O(2), as seen by the formation of disulfide bridges and high-molecular-mass complexes. This first study, to our knowledge, on PRDXs in human spermatozoa indicates that PRDX1, PRDX4, PRDX5, and PRDX6 are modified when spermatozoa are challenged with H(2)O(2). This suggests that PRDXs may protect these cells at high levels of H(2)O(2) but could also control H(2)O(2) levels within different cell compartments so that normal sperm activation can occur.

Discovery of novel bladder cancer biomarkers by comparative urine proteomics using iTRAQ technology

A urine sample preparation workflow for the iTRAQ (isobaric tag for relative and absolute quantitation) technique was established. The reproducibility of this platform was evaluated and applied to discover proteins with differential levels between pooled urine samples from nontumor controls and three bladder cancer patient subgroups with different grades/stages (a total of 14 controls and 23 cancer cases in two multiplex iTRAQ runs). Combining the results of two independent clinical sample sets, a total of 638 urine proteins were identified. Among them, 55 proteins consistently showed >2-fold differences in both sample sets. Western blot analyses of individual urine samples confirmed that the levels of apolipoprotein A-I (APOA1), apolipoprotein A-II, heparin cofactor 2 precursor and peroxiredoxin-2 were significantly elevated in bladder cancer urine specimens (n = 25-74). Finally, we quantified APOA1 in a number of urine samples using a commercial ELISA and confirmed again its potential value for diagnosis (n = 126, 94.6% sensitivity and 92.0% specificity at a cutoff value of 11.16 ng/mL) and early detection (n = 71, 83.8% sensitivity and 94.0% specificity). Collectively, our results provide the first iTRAQ-based quantitative profile of bladder cancer urine proteins and represent a valuable resource for the discovery of bladder cancer markers.

Redox regulation of lipopolysaccharide-mediated sulfiredoxin induction, which depends on both AP-1 and Nrf2

Sulfiredoxin (Srx) is an enzyme that catalyzes the reduction of cysteine sulfinic acid of hyperoxidized peroxiredoxins and exerts a protective antioxidant role. Here we investigated the regulatory mechanism of Srx induction by lipopolysaccharide (LPS) in mouse macrophages. LPS up-regulated Srx expression on the transcriptional level. The promoter region of the Srx gene contained putative NF-κB and AP-1 (activator protein-1) sites, and the proximal site of three AP-1 sites was embedded within the antioxidant response element (ARE), a cis-acting element for Nrf2 (nuclear factor erythroid 2-related factor). Mutational analysis of the Srx promoter revealed that Srx induction is dependent on AP-1 sites and ARE but not on NF-κB sites. Consistently, both transcription factors, AP-1 and Nrf2, were required for LPS-mediated Srx induction, as revealed by chromatin immunoprecipitation using antibodies specific for c-Jun and c-Fos and little Srx induction in Nrf2-null bone marrow-derived macrophages. Among mitogen-activated protein kinases that mediate the signal transduction by LPS, JNK played a major role in Srx induction. Moreover, chemical antioxidants, such as N-acetylcysteine and butylated hydroxyanisole, and the NADPH oxidase inhibitor diphenyleneiodonium inhibited Srx induction as well as generation of reactive oxygen species, both of which were also suppressed in Nox2 (NADPH oxidase 2)-deficient bone marrow-derived macrophages. These results suggest that LPS-mediated Srx induction is dependent on both AP-1 and Nrf2, which is regulated by Nox2-derived reactive oxygen species.