Crucial role of peroxiredoxin III in placental antioxidant defense of mice

Regulation of peroxiredoxin-3 gene expression under basal and hyperglycemic conditions: Key roles for transcription factors Sp1, CREB and NF-κB

Peroxiredoxin-3 (Prx-3), a thioredoxin-dependent peroxidase located exclusively in the mitochondrial matrix, catalyses peroxides/peroxinitrites. Altered levels of Prx-3 is associated with diabetic cardiomyopathy (DCM). However, molecular mechanisms of Prx-3 gene regulation remain partially understood. We undertook a systemic analysis of the Prx-3 gene to identify the key motifs and transcriptional regulatory molecules. Transfection of promoter-reporter constructs in the cultured cells identified -191/+20 bp domain as the core promoter region. Stringent in silico analysis of this core promoter revealed putative binding sites for specificity protein 1 (Sp1), cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Interestingly, while co-transfection of the -191/+20 bp construct with Sp1/CREB plasmid diminished Prx3 promoter-reporter activity, mRNA and protein levels, co-transfection with NF-κB expression plasmid augmented the same. Consistently, inhibition of Sp1/CREB/NF-κB expression reversed the promoter-reporter activity, mRNA and protein levels of Prx-3, thereby confirming their regulatory effects. ChIP assays provided evidence for interactions of Sp1/CREB/NF-κB with the Prx-3 promoter. H9c2 cells treated with high glucose as well as streptozotocin (STZ)-treated diabetic rats showed time-dependent reduction in promoter activity, endogenous transcript and protein levels of Prx-3. Augmentation of Sp1/CREB protein levels and their strong binding with Prx-3 promoter are responsible for diminished Prx-3 levels under hyperglycemia. The activation/increase in the NF-κB expression under hyperglycemia was not sufficient to restore the reduction of endogenous Prx-3 levels owing to its weak binding affinity. Taken together, this study elucidates the previously unknown roles of Sp1/CREB/NF-κB in regulating Prx-3 gene expression under hyperglycemic condition.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Decreased Expression of Peroxiredoxin in Patients with Ovarian Endometriosis Cysts

BACKGROUND

Endometriosis (EMT) is a common occurrence in women of reproductive age. Since oxidative stress has been associated with the development and/or progression of the disease, the present study was conducted to detect the expression of peroxiredoxin (PRX) isoforms, including PRX1, PRX2, and PRX3.

METHODS

Fifty-two patients with ovarian endometriosis cysts and 47 controls were included in the study. Serum levels of PRXs were detected by enzyme-linked immunosorbent assay, and the expression of PRX in the endometrium was examined by immunohistochemistry.

RESULTS

Serum PRX1, PRX2, and PRX3 were significantly lower in EMT patients than in controls. The expression of the three isoforms was significantly decreased in ectopic endometrium compared to that in eutopic or control endometrium. There was no difference in PRX expression between eutopic endometrium of EMT patients and control endometrium, and no association was found between serum PRX levels and immunostaining scores.

CONCLUSION

Our results are the first report that PRXs are downregulated in EMT patients, which suggests that PRXs are involved in the oxidative state of the disease.

Knockout Mouse Models for Peroxiredoxins

Peroxiredoxins (PRDXs) are members of a highly conserved peroxidase family and maintain intracellular reactive oxygen species (ROS) homeostasis. The family members are expressed in most organisms and involved in various biological processes, such as cellular protection against ROS, inflammation, carcinogenesis, atherosclerosis, heart diseases, and metabolism. In mammals, six PRDX members have been identified and are subdivided into three subfamilies: typical 2-Cys (PRDX1, PRDX2, PRDX3, and PRDX4), atypical 2-Cys (PRDX5), and 1-Cys (PRDX6) subfamilies. Knockout mouse models of PRDXs have been developed to investigate their in vivo roles. This review presents an overview of the knockout mouse models of PRDXs with emphases on the biological and physiological changes of these model mice.

Plasma level of peroxiredoxin 3 in patients with polycystic ovarian syndrome

BACKGROUND

As a member of peroxiredoxin (PRX) family, PRX3 is predominantly located in mitochondria and plays an important role of free radical scavenging. Since a body of evidence demonstrated the involvement of PRX3 in insulin secretion, insulin sensitivity, and glucose metabolism, the present study was conducted to investigate the role of PRX3 in the pathogenesis of polycystic ovarian syndrome (PCOS) featured in insulin resistance.

METHODS

Enzyme-linked immunosorbent assay was performed to detect plasma PRX3 in PCOS patients and control subjects. Levels of reactive oxygen species (ROS) and oxidized PRXs were detected in mouse islet cells treated with gradient glucose.

RESULTS

We did not find significant difference of fasting plasma PRX3 between PCOS patients and controls. No association was noticed between fasting plasma PRX3 and fasting plasma glucose or insulin. After oral glucose tolerance test (OGTT), PCOS patients showed higher levels of both glucose and insulin as compared to controls. The plasma level of PRX3 was significantly increased at 2 h and began to fall back at 3 h of OGTT. There was a one-hour time lag of peak values between plasma PRX3 and insulin, and the plasma PRX3 at 2 h was positively correlated with the insulin level at 1 h of OGTT of PCOS patients. In addition, the level of ROS was significantly elevated at 1 h and oxidized PRX3 was increased dramatically at 2 h of 16.7mM glucose stimulation in mouse islet cells.

CONCLUSION

It seems that PRX3 does not show its antioxidant function under baseline conditions. Instead, PRX3 responds to oxidative stress induced by rapid increase of insulin and glucose in patients with PCOS.

Epigenetic Regulation of the Nitric Oxide Pathway, 17-α Hydroxyprogesterone Caproate, and Recurrent Preterm Birth

OBJECTIVE

We sought to evaluate nitric oxide pathway placental gene expression and the epigenome (CpG methylation) among women receiving 17-α hydroxyprogesterone caproate (17-OHPC) with and without recurrent preterm birth (PTB).

STUDY DESIGN

This was a case-control study. We prospectively recruited women with ≥ 1 prior singleton spontaneous PTB <34 weeks receiving 17-OHPC. DNA and RNA were isolated from placentas. RNA abundance (gene expression) and the methylome were analyzed for 84 genes in nitric oxide pathways. Women with recurrent PTB <34 weeks (cases) were compared with those delivering at term (controls). Statistical analysis included multivariable models with Bonferroni's corrected p-values.

RESULTS

In this study, 17 women met inclusion criteria; 7 preterm cases (delivered at 22.6 ± 2.9 weeks) and 10 term controls (delivered at 38.5 ± 0.8 weeks). Groups had similar PTB history, race/ethnicity, and socioeconomic risk factors for PTB. Twenty-seven nitric oxide genes displayed differential expression (p < 0.05 and q < 0.10) when comparing placentas from preterm cases and term controls; all were downregulated in preterm cases. Eight hundred sixty corresponding CpG sites were differentially methylated between the preterm cases and term controls (Bonferroni's p-value <0.05).

CONCLUSION

CpG methylation and gene expression patterns in nitric oxide pathway genes differ among placentas from recurrent PTB compared with term birth following 17-OHPC exposure.

New Challenges to Study Heterogeneity in Cancer Redox Metabolism

Reactive oxygen species (ROS) are important pathophysiological molecules involved in vital cellular processes. They are extremely harmful at high concentrations because they promote the generation of radicals and the oxidation of lipids, proteins, and nucleic acids, which can result in apoptosis. An imbalance of ROS and a disturbance of redox homeostasis are now recognized as a hallmark of complex diseases. Considering that ROS levels are significantly increased in cancer cells due to mitochondrial dysfunction, ROS metabolism has been targeted for the development of efficient treatment strategies, and antioxidants are used as potential chemotherapeutic drugs. However, initial ROS-focused clinical trials in which antioxidants were supplemented to patients provided inconsistent results, i.e., improved treatment or increased malignancy. These different outcomes may result from the highly heterogeneous redox responses of tumors in different patients. Hence, population-based treatment strategies are unsuitable and patient-tailored therapeutic approaches are required for the effective treatment of patients. Moreover, due to the crosstalk between ROS, reducing equivalents [e.g., NAD(P)H] and central metabolism, which is heterogeneous in cancer, finding the best therapeutic target requires the consideration of system-wide approaches that are capable of capturing the complex alterations observed in all of the associated pathways. Systems biology and engineering approaches may be employed to overcome these challenges, together with tools developed in personalized medicine. However, ROS- and redox-based therapies have yet to be addressed by these methodologies in the context of disease treatment. Here, we review the role of ROS and their coupled redox partners in tumorigenesis. Specifically, we highlight some of the challenges in understanding the role of hydrogen peroxide (H₂O₂), one of the most important ROS in pathophysiology in the progression of cancer. We also discuss its interplay with antioxidant defenses, such as the coupled peroxiredoxin/thioredoxin and glutathione/glutathione peroxidase systems, and its reducing equivalent metabolism. Finally, we highlight the need for system-level and patient-tailored approaches to clarify the roles of these systems and identify therapeutic targets through the use of the tools developed in personalized medicine.

Downregulation of peroxiredoxin-3 by hydrophobic bile acid induces mitochondrial dysfunction and cellular senescence in human trophoblasts

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific disorder characterised by raised bile acids in foetal-maternal circulation, which threatens perinatal health. During the progression of ICP, the effect of oxidative stress is underscored. Peroxiredoxin-3 (PRDX3) is a mitochondrial antioxidant enzyme that is crucial to balance intracellular oxidative stress. However, the role of PRDX3 in placental trophoblast cells under ICP is not fully understood. We demonstrated that the level of PRDX3 was downregulated in ICP placentas as well as bile acids–treated trophoblast cells and villous explant in vitro. Toxic levels of bile acids and PRDX3 knockdown induced oxidative stress and mitochondrial dysfunction in trophoblast cells. Moreover, silencing of PRDX3 in trophoblast cell line HTR8/SVneo induced growth arrest and cellular senescence via activation of p38-mitogen-activated protein kinase (MAPK) and induction of p21^WAF1/CIP and p16^INK4A. Additionally, enhanced cellular senescence, determined by senescence-associated beta-galactosidase staining, was obviously attenuated by p38-MAPK inhibitor SB203580. Our data determined that exposure to bile acid decreased PRDX3 level in human trophoblasts. PRDX3 protected trophoblast cells against mitochondrial dysfunction and cellular senescence induced by oxidative stress. Our results suggest that decreased PRDX3 by excessive bile acids in trophoblasts plays a critical role in the pathogenesis and progression of ICP.

The Relevance of Mammalian Peroxiredoxins to the Gametogenesis, Embryogenesis, and Pregnancy Outcomes

Peroxiredoxin (PRX) defines a family that provides antioxidant defense in different cell types by removing reactive oxygen species (ROS) through conserved active cysteines, with the support of other types of antioxidants such as thioredoxin, glutaredoxin, and glutathione peroxidase. By regulation of intracellular ROS levels, the mammalian PRXs influence a variety of reproductive processes including gamete maturation, fertilization, and embryo development. Experimental mice lacking PRXs developed normally, but some showed accelerated decrease in fertility with aging, suggesting that deficiency of PRXs did not have lethal consequences for reproduction. The aim of this review is to summarize the role of mammalian PRXs in the reproductive performance.

Plekhs1 and Prdx3 are candidate genes responsible for mild hyperglycemia associated with obesity in a new animal model of F344-fa-nidd6 rat

Type 2 diabetes is a polygenic disease and characterized by hyperglycemia and insulin resistance, and it is strongly associated with obesity. However, the mechanism by which obesity contributes to onset of type 2 diabetes is not well understood. We generated rat strains with a hyperglycemic quantitative trait locus (QTL) derived from the Otsuka Long-Evans Tokushima Fatty rat and a fa/fa (Lepr^–/–) locus derived from the Zucker Fatty rat. Phenotypes for plasma glucose, and insulin levels were measured, and RNA and protein levels were determined using reverse transcription quantitative PCR and Western blot analyses, respectively. Compared with the obese control strain F344-fa (Lepr^–/–), plasma glucose levels of the obese F344-fa-nidd6 (Lepr^–/– and Nidd6/of) significantly increased, and plasma insulin levels significantly decreased. These phenotypes were not observed in the lean strains, suggesting that the Nidd6/of locus harbors a diabetogenic gene associated with obesity. We measured the expression of 41 genes in the Nidd6/of QTL region of each strain and found that the mRNA expression levels of the two genes significantly differed between the obese strains. The two genes, pleckstrin homology domain-containing, family S member 1 (Plechs1) and peroxiredoxin III (Prdx3), were differentially expressed only in the obese rats, suggesting that these two genes are involved in the mild elevation of blood glucose levels and insulin resistance in obesity.

Featured Article: Accelerated decline of physical strength in peroxiredoxin-3 knockout mice

As a member of peroxiredoxin family, peroxiredoxin-3 plays a major role in the control of mitochondrial level of reactive oxygen species. During the breeding of experimental mice, we noticed that the peroxiredoxin-3 knockout mice were listless with aging. In the present study, we compared the swimming exercise performance and oxidative status between peroxiredoxin-3 knockout mice (n = 15) and wild-type littermates (n = 15). At the age of 10 months, the physical strength of peroxiredoxin-3 knockout mice was much lower than the wild-type littermates. Increased oxidative damage and decreased mitochondrial DNA copy number of the animal skeletal muscles were observed in peroxiredoxin-3 knockout mice as compared to that in the wild-type littermates. In addition, we found increased apoptotic cells in the brains of peroxiredoxin-3 knockout mice. Our results suggest that the deficiency of peroxiredoxin-3 induces accelerated oxidative stress and mitochondrial impairment, resulting in the decrease of energy supply and cellular activities. Peroxiredoxin-3 might be involved in the inhibition of aging process.

Interplay between oxidant species and energy metabolism

It has long been recognized that energy metabolism is linked to the production of reactive oxygen species (ROS) and critical enzymes allied to metabolic pathways can be affected by redox reactions. This interplay between energy metabolism and ROS becomes most apparent during the aging process and in the onset and progression of many age-related diseases (i.e. diabetes, metabolic syndrome, atherosclerosis, neurodegenerative diseases). As such, the capacity to identify metabolic pathways involved in ROS formation, as well as specific targets and oxidative modifications is crucial to our understanding of the molecular basis of age-related diseases and for the design of novel therapeutic strategies.

Herein we review oxidant formation associated with the cell's energetic metabolism, key antioxidants involved in ROS detoxification, and the principal targets of oxidant species in metabolic routes and discuss their relevance in cell signaling and age-related diseases.

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Energy metabolism is both a source and target of oxidant species.

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Reactive oxygen species are formed in redox reactions in catabolic pathways.

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Sensitive targets of oxidant species regulate the flux of metabolic pathways.

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Metabolic pathways and antioxidant systems are regulated coordinately.

Mechanistic Study of the Phytocompound, 2- β -D-Glucopyranosyloxy-1-hydroxytrideca-5,7,9,11-tetrayne in Human T-Cell Acute Lymphocytic Leukemia Cells by Using Combined Differential Proteomics and Bioinformatics Approaches

Bidens pilosa, a medicinal herb worldwide, is rich in bioactive polyynes. In this study, by using high resolution 2-dimensional gel electrophoresis coupled with mass spectrometry analysis, as many as 2000 protein spots could be detected and those whose expression was specifically up- or downregulated in Jurkat T cells responsive to the treatment with 2-β-D-glucopyranosyloxy-1-hydroxytrideca-5,7,9,11-tetrayne (GHTT) can be identified. GHTT treatment can upregulate thirteen proteins involved in signal transduction, detoxification, metabolism, energy pathways, and channel transport in Jurkat cells. Nine proteins, that is, thioredoxin-like proteins, BH3 interacting domain death agonist (BID protein involving apoptosis), methylcrotonoyl-CoA carboxylase beta chain, and NADH-ubiquinone oxidoreductase, were downregulated in GHTT-treated Jurkat cells. Further, bioinformatics tool, Ingenuity software, was used to predict signaling pathways based on the data obtained from the differential proteomics approach. Two matched pathways, relevant to mitochondrial dysfunction and apoptosis, in Jurkat cells were inferred from the proteomics data. Biochemical analysis further verified both pathways involving GHTT in Jurkat cells. These findings do not merely prove the feasibility of combining proteomics and bioinformatics methods to identify cellular proteins as key players in response to the phytocompound in Jurkat cells but also establish the pathways of the proteins as the potential therapeutic targets of leukemia.

Agonist of farnesoid X receptor protects against bile acid induced damage and oxidative stress in mouse placenta--a study on maternal cholestasis model

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific disorder, which is characterized by raised serum bile acid level and potential adverse fetal outcome. Farnesoid X receptor (FXR), also known as a bile acid receptor, was found to be expressed in placenta with low level. Whether activation of FXR by specific agonists could regulate the pathogenesis of ICP is still unclear.

METHODS

A model of maternal cholestasis was induced by administration of 17α-ethynylestradiol (E2) in pregnant mice for 6 days. We explored the regulatory effect of WAY-362450 (W450), a highly selective and potent FXR agonist on placenta.

RESULTS

In this study, we demonstrated that administration of E2 increased bile acid levels in mouse serum, liver and amniotic fluid. Bile acid levels were significantly decreased after W450 treatment. W450 protected against the impairment of placentas induced by E2, including severe intracellular edema and apoptosis of trophoblasts. Moreover, W450 significantly induced the expressions of FXR target bile acid transport gene ATP-binding cassette, sub-family B (MDR/TAP), member 11 (Abcb11;Bsep) in placenta. W450 could also attenuate placental oxidative stress and increase the expressions of antioxidant enzymes Prdx1 and Prdx3.

DISCUSSION AND CONCLUSION

In conclusion, our data demonstrated that FXR agonist W450 modulated bile acid balance and protected against placental oxidative stress. Thus, our results support that potent FXR agonists might represent promising drugs for the treatment of ICP.

Preoxiredoxin family members (Prx3 and Prx4) and pregnancy disorder (recurrent pregnancy loss)

Placenta is a pregnancy unique tissue, and proper formation of placenta is a key phenomenal step for success of a pregnancy. Peroxiredoxins (Prxs) are a family of antioxidant proteins. This family is composed of six members, among which Peroxiredoxin 3 (Prx3) and Peroxiredoxin 4 (Prx4) are expressed by cytotrophoblast cells and play an important role in the implantation and a normal placentation through their antioxidant activities. Although the presence of autoantibody against several peroxiredoxin family members was reported before, there was no report regarding the presence of antibodies against Prx3 or Prx4 in human pregnancy miscarriage. So for the first time we hypothesize and indicate that uncontrolled oxidative stress, due to anti-peroxiredoxins antibodies, may affect the proper formation of the placenta and lead to placentation-related pregnancy disorders such as miscarriage. Our results indicate that two placental proteins, Prx3 and Prx4, may act as new placental immune targets. Considering the role of antioxidant defense in the protection of placenta from oxidative stress, production of antibodies against peroxiredoxins 3 and 4 may introduce a new autoimmune hypothesis for miscarriages, which is needed to be tested in the future works.

Tuning of peroxiredoxin catalysis for various physiological roles

Peroxiredoxins (Prxs) make up an ancient family of enzymes that are the predominant peroxidases for nearly all organisms and play essential roles in reducing hydrogen peroxide, organic hydroperoxides, and peroxynitrite. Even between distantly related organisms, the core protein fold and key catalytic residues related to its cysteine-based catalytic mechanism have been retained. Given that these enzymes appeared early in biology, Prxs have experienced more than 1 billion years of optimization for specific ecological niches. Although their basic enzymatic function remains the same, Prxs have diversified and are involved in roles such as protecting DNA against mutation, defending pathogens against host immune responses, suppressing tumor formation, and--for eukaryotes--helping regulate peroxide signaling via hyperoxidation of their catalytic Cys residues. Here, we review the current understanding of the physiological roles of Prxs by analyzing knockout and knockdown studies from ∼25 different species. We also review what is known about the structural basis for the sensitivity of some eukaryotic Prxs to inactivation by hyperoxidation. In considering the physiological relevance of hyperoxidation, we explore the distribution across species of sulfiredoxin (Srx), the enzyme responsible for rescuing hyperoxidized Prxs. We unexpectedly find that among eukaryotes appearing to have a "sensitive" Prx isoform, some do not contain Srx. Also, as Prxs are suggested to be promising targets for drug design, we discuss the rationale behind recently proposed strategies for their selective inhibition.

Repression of the mitochondrial peroxiredoxin antioxidant system does not shorten life span but causes reduced fitness in Caenorhabditis elegans

The mitochondrial free radical theory of aging proposes that aging is a consequence of progressive mitochondrial dysfunction caused by lifelong accumulation of oxidative damage. Aging is therefore expected to accelerate if the rate of this oxidative damage accumulation increases. Studies attempting to test this prediction through modulation of oxidative damage by altering antioxidant defenses have reported conflicting results. Here we investigated the effects of repressing prdx-3, responsible for the detoxification of mitochondrial hydrogen peroxide, in developmentally normal wild-type Caenorhabditis elegans. We report that life span and levels of oxidative protein damage were not altered when prdx-3 was repressed in adult nematodes. We further found evidence that mitochondrial uncoupling increased in response to repression of prdx-3. Nevertheless repression of prdx-3 led to reductions in steady-state levels of ATP, motility, and brood size, indicating the importance of this enzyme to normal life in C. elegans.

Prx I suppresses K-ras-driven lung tumorigenesis by opposing redox-sensitive ERK/cyclin D1 pathway

AIMS

Coupled responses of mutated K-ras and oxidative stress are often an important etiological factor in non-small-cell lung cancer (NSCLC). However, relatively few studies have examined the control mechanism of oxidative stress in oncogenic K-ras-driven NSCLC progression. Here, we studied whether the redox signaling pathway governed by peroxiredoxin I (Prx I) is involved in K-ras(G12D)-mediated lung adenocarcinogenesis.

RESULTS

Using human-lung adenocarcinoma tissues and lung-specific K-ras(G12D)-transgenic mice, we found that Prx I was significantly up-regulated in the tumor regions via activation of nuclear erythroid 2-related factor 2 (Nrf2) transcription. Interestingly, the increased reactive oxygen species (ROS) by null mutation of Prx I greatly promoted K-ras(G12D)-driven lung tumorigenesis in number and size, which appeared to require the activation of the ROS-dependent extracellular signal-regulated kinase (ERK)/cyclin D1 pathway.

INNOVATION

Taken together, these results suggest that Prx I functions as an Nrf2-dependently inducible tumor suppressant in K-ras-driven lung adenocarcinogenesis by opposing ROS/ERK/cyclin D1 pathway activation.

CONCLUSION

These findings provide a better understanding of oxidative stress-mediated lung tumorigenesis.

Anti-apoptotic role of peroxiredoxin III in cervical cancer cells

As a member of peroxiredoxin (Prx) family, PrxIII is predominantly located in mitochondria and plays an important role as a scavenger of reactive oxygen species (ROS). Since previous reports demonstrated over-expression of PrxIII in cervical cancer, we conducted the present study to investigate the significance of PrxIII in cervical cancer development and/or progression.

Cervical cancer cells were cultured from tissues derived from cervical cancer patients. After successful knockdown of PrxIII expression by small interfering RNA, we evaluated ROS level, viable cell number, and apoptosis of cervical cancer cells along with the culture time.

The production of ROS was increased in cervical cancer cells as compared with normal cervical epithelia. Knockdown of PrxIII expression induced up-regulation of other Prx members including PrxI, PrxII, and PrxV. ROS level was higher in down-regulated cervical cancer cells than in controls and the difference was increasing with culture time. We also observed increased apoptosis and decreased viable cell number in down-regulated cervical cancer cells.

Our results suggest that PrxIII is an indispensable ROS scavenger, which protects tumor cells against oxidative damage and subsequent apoptosis.

Peroxiredoxin 3 is a novel marker for cell proliferation in cervical cancer

Although peroxiredoxin 3 (Prx3) has been reported to be involved in cervical cancer (CC) carcinogenesis, the significance of Prx3 in CC progression remains unclear. The present study was conducted to investigate the expression features of Prx3 to better understand the mechanism of tumor growth and invasion. Sixty-eight patients with invasive squamous cervical cancer were included in the present study. The status of human papillomavirus (HPV) infection was detected by hybridization and quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemistry was performed on paraffin-embedded sections using monoclonal antibodies against Prx3 and Ki67. All samples were positive for high-risk HPV, among which fifty-six samples were positive for HPV16, seven for HPV18 and five for HPV33. The expression of HPV16 E6/E7 was significantly higher in cancer areas compared to the adjacent normal epithelial tissuses. The positive cells for Prx3 and Ki67 were significantly higher in cancer cells compared to normal epitheliums and the staining pattern of Prx3 was consistent with that of Ki67 (Pearson's correlation coefficient was 0.801, P= 0.000). The upregulation of Prx3 might be a protective response to oxidative stress in the cancer microenvironment. The expression consistency of Prx3 and Ki67 suggests Prx3 to be a potential marker for cell proliferation of CC.

Presence of autoantibody against two placental proteins, peroxiredoxin 3 and peroxiredoxin 4, in sera of recurrent pregnancy loss patients

PROBLEM

Recurrent pregnancy loss (RPL) is defined as two or more consecutive abortion before the 20th week of gestation. Autoimmune diseases increase the risk and accounts for at least 20% of RPL. Placenta is a pregnancy unique tissue, and proper formation of placenta is key phenomenal for success of a pregnancy. The aim of this study was to investigate the placental proteins that may act as antibody targets in RPL patients.

METHOD OF STUDY

Total placental proteins were extracted and separated using 2D-PAGE technique. Separated protein spots were transferred on PVDF membrane and blotted with sera from 20 RPL patients and compared with the protein spots that membrane blotted with sera from 20 normal women. Differentially blotted spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry mass spectrometry technique. The results of the mass analysis also were confirmed by western blot using mAb and reverse transcriptase polymerase chain reaction technique.

RESULTS

The results indicated that RPL women may produce antibody against Peroxiredoxin 3 (Prx3) and Peroxiredoxin 4 (Prx4).

CONCLUSION

Our results indicate that two placental proteins, Prx3 and Prx4, may act as new placental immune targets. Considering the role of antioxidant defense in the protection of placenta from oxidative stress, production of antibodies against peroxiredoxins 3 and 4 may introduce a new autoimmune hypothesis in RPL, which is needed to be tested in the future works.

Quantitative proteomic analysis of pregnancy-related proteins from peripheral blood mononuclear cells during pregnancy in pigs

Information obtained from peripheral blood could help us understand the underlying mechanisms in autoimmune diseases, cancer, pregnancy, and other conditions. In this paper, we present the protein map of porcine peripheral blood mononuclear cells (PBMC) to better understand the molecular expression changes that occur during pregnancy using proteomic analysis. We detected 94 differentially expressed proteins in pregnant vs. non-pregnant (NP) pigs, and a representative set of the proteins was subjected to LC-MS/MS analysis. Furthermore, the identified proteins were categorized according to their biological process and molecular function. By classifying the proteins according to their functions, a large number of differentially regulated proteins involved in anti-oxidant, detoxification and stress response pathways were found, including peroxiredoxin (PRX) 1, 2, and 6, glutathione-S-transferase (GST), annexin A2, and A6, and heat shock protein 27 (HSP 27) during pregnancy (pregnancy d of E40, embryonic day 40; E70, embryonic day 70; and E93, embryonic day 93) compared with non-pregnancy. In this study, a proteomic approach utilizing 2-DE and LC-MS/MS was applied to evaluate specific molecular expression changes during pregnancy compared with non-pregnancy. Together, these data offer new information about the proteome map and factors that are differentially regulated during maintenance of normal pregnancy.

Peroxiredoxin 3 is a key molecule regulating adipocyte oxidative stress, mitochondrial biogenesis, and adipokine expression

AIMS

Increased oxidative stress and mitochondrial dysfunction in obese adipocytes contribute to adipokine dysregulation, inflammation, and insulin resistance.

RESULTS

Through an advanced proteomic analysis, we found that peroxiredoxin 3 (Prx3), a thioredoxin-dependent mitochondrial peroxidase, is highly expressed in 3T3-L1 adipocytes compared to preadipocytes. Interestingly, in obese db/db mice and human subjects, adipose Prx3 levels were significantly decreased, indicating its association with obesity. We therefore employed Prx3 knockout (KO) mice and transfected 3T3-L1 cells to examine the role of endogenous Prx3 in adipocyte metabolism. Prx3 KO mice had increased fat mass compared to wild-type due to adipocyte hypertrophy. Increased adipogenic transcription factors and lipogenic gene expression during differentiation of adipose tissue-derived stem cells from Prx3-deficient mice confirmed that these adipocytes are likely to accumulate fat. Mitochondrial protein carbonylation in Prx3 KO adipose tissue and mitochondrial superoxide level in Prx3 knockdown 3T3-L1 cells were increased showing aberrant regulation of oxidative stress. Proteomic analysis and gene expression analysis of Prx3 KO mice adipocytes also showed defect in mitochondria biogenesis along with enzymes involved in glucose/lipid metabolism and oxidative phosphorylation. In addition, expression level of adiponectin was downregulated and plasminogen activator inhibitor-1 was upregulated in Prx3 KO adipocytes. Impaired glucose tolerance and insulin resistance further implied metabolic dysregulation in Prx3 KO mice.

INNOVATION AND CONCLUSION

These data suggest that endogenous Prx3 may play an essential role in maintaining normal characteristics of adipocytes and that defect in Prx3 alters mitochondrial redox state and function, and adipokine expression in adipocytes leading to metabolic alteration.

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.

Oxidative stress and diabetes: what can we learn about insulin resistance from antioxidant mutant mouse models?

The development of metabolic dysfunctions like diabetes and insulin resistance in mammals is regulated by a myriad of factors. Oxidative stress seems to play a central role in this process as recent evidence shows a general increase in oxidative damage and a decrease in oxidative defense associated with several metabolic diseases. These changes in oxidative stress can be directly correlated with increased fat accumulation, obesity, and consumption of high-calorie/high-fat diets. Modulation of oxidant protection through either genetic mutation or treatment with antioxidants can significantly alter oxidative stress resistance and accumulation of oxidative damage in laboratory rodents. Antioxidant mutant mice have previously been utilized to examine the role of oxidative stress in other disease models, but have been relatively unexplored as models to study the regulation of glucose metabolism. In this review, we will discuss the evidence for oxidative stress as a primary mechanism linking obesity and metabolic disorders and whether alteration of antioxidant status in laboratory rodents can significantly alter the development of insulin resistance or diabetes.

The dual-targeted plant sulfiredoxin retroreduces the sulfinic form of atypical mitochondrial peroxiredoxin

Sulfiredoxin (Srx) couples the energy of ATP hydrolysis to the energetically unfavorable process of reducing the inactive sulfinic form of 2-cysteine peroxiredoxins (Prxs) to regenerate its active form. In plants, Srx as well as typical 2-cysteine Prx have been considered as enzymes with exclusive chloroplast localization. This work explores the subcellular localization of Srx in pea (Pisum sativum) and Arabidopsis (Arabidopsis thaliana). Immunocytochemistry, analysis of protein extracts from isolated intact organelles, and cell-free posttranslational import assays demonstrated that plant Srx also localizes to the mitochondrion in addition to plastids. The dual localization was in line with the prediction of a signal peptide for dual targeting. Activity tests and microcalorimetric data proved the interaction between Srx and its mitochondrial targets Prx IIF and thioredoxin. Srx catalyzed the retroreduction of the inactive sulfinic form of atypical Prx IIF using thioredoxin as reducing agent. Arabidopsis Srx also reduced overoxidized human Prx V. These results suggest that plant Srx could play a crucial role in the regulation of Prx IIF activity by controlling the regeneration of its overoxidized form in mitochondria, which are sites of efficient reactive oxygen species production in plants.

Role of peroxiredoxin III in the pathogenesis of pre-eclampsia as evidenced in mice

As a member of peroxiredoxin (Prx) family, PrxIII has been demonstrated to play an important role in scavenging intracellular reactive oxygen species (ROS). Since PrxIII knockout mice exhibited oxidative stress in placentas resembling pathophysiologic changes in placentas of human pre-eclampsia, we measured blood pressure through the carotid artery and detected oxidative status by western blotting in pregnant mice. We did not notice hypertension in pregnant PrxIII knockout mice as compared with wild-type littermates, although endothelin-1 was overexpressed in PrxIII-deficient placentas. Our results indicate that PrxIII is not involved in pre-eclamptic development. Instead, PrxIII is an indispensable antioxidant in placentas where oxidative stress exists.

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.

Glutathione peroxidase 1 deficiency attenuates allergen-induced airway inflammation by suppressing Th2 and Th17 cell development

Engagement of T cell receptor (TCR) triggers signaling pathways that mediate activation, proliferation, and differentiation of T lymphocytes. Such signaling events are mediated by reactive oxygen species (ROS), including hydrogen peroxide and lipid peroxides, both of which are reduced by glutathione peroxidase 1 (GPx1). We have now examined the role of GPx1 in the activation, differentiation, and functions of CD4(+) T helper (Th) cells. TCR stimulation increased the intracellular ROS concentration in Th cells in a time-dependent manner, and such TCR-induced ROS generation was found to promote cell proliferation. GPx1-deficient Th cells produced higher levels of intracellular ROS and interleukin-2 than wild-type Th cells and proliferated at a faster rate than did wild-type cells. Moreover, differentiation of GPx1-deficient Th cells was biased toward Th1, and Th17 cell development was also impeded by GPx1 depletion. Consistent with these findings, GPx1-null mice were protected from the development of ovalbumin-induced allergic asthma. Eosinophil infiltration, goblet cell hyperplasia, collagen deposition, and airway hyperresponsiveness were thus all attenuated in the lungs of GPx1-null mice. These data indicate that GPx1-dependent control of intracellular ROS accumulation is important not only for regulation of Th cell proliferation but for modulation of differentiation into Th1, Th2, and Th17 cells.

Mitochondrial peroxiredoxin involvement in antioxidant defence and redox signalling

Prxs (peroxiredoxins) are a family of proteins that are extremely effective at scavenging peroxides. The Prxs exhibit a number of intriguing properties that distinguish them from conventional antioxidants, including a susceptibility to inactivation by hyperoxidation in the presence of excess peroxide and the ability to form complex oligomeric structures. These properties, combined with a high cellular abundance and reactivity with hydrogen peroxide, have led to speculation that the Prxs function as redox sensors that transmit signals as part of the cellular response to oxidative stress. Multicellular organisms express several different Prxs that can be categorized by their subcellular distribution. In mammals, Prx 3 and Prx 5 are targeted to the mitochondrial matrix. Mitochondria are a major source of hydrogen peroxide, and this oxidant is implicated in the damage associated with aging and a number of pathologies. Hydrogen peroxide can also act as a second messenger, and is linked with signalling events in mitochondria, including the induction of apoptosis. A simple kinetic competition analysis estimates that Prx 3 will be the target for up to 90% of hydrogen peroxide generated in the matrix. Therefore, mitochondrial Prxs have the potential to play a major role in mitochondrial redox signalling, but the extent of this role and the mechanisms involved are currently unclear.

Knockdown of the type 3 iodothyronine deiodinase (D3) interacting protein peroxiredoxin 3 decreases D3-mediated deiodination in intact cells

The type 3 iodothyronine deiodinase (D3) is the primary deiodinase that inactivates thyroid hormone. Immunoprecipitation of D3, followed by fluorescent two-dimensional difference gel electrophoresis and mass spectrometry, identified peroxiredoxin 3 (Prx3) as a D3-associated protein. This interaction was confirmed using reverse coimmunoprecipitation, in which pull-down of Prx3 resulted in D3 isolation, and by fluorescence resonance energy transfer between cyan fluorescent protein-D3 and yellow fluorescent protein-Prx3. Prx3 overexpression did not change D3 activity in transfected HEK 293 cells; however, Prx3 knockdown resulted in a 50% decrease in D3-mediated whole-cell deiodination. Notably, D3 activity of cell lysates with dithiothreitol as an exogenous reducing factor and D3 protein levels were not decreased with Prx3 knockdown, indicating that the observed reduction in whole-cell deiodination was not simply due to a decrease in D3 enzyme levels. Prx3 knockdown did not change D3's affinity for T3 because saturation of D3-mediated whole-cell deiodination occurred between 20 and 200 nm T3 both with and without Prx3. Furthermore, the decrease in D3 activity in whole cells was not attributable to nonspecific oxidative stress because pretreatment with the antioxidant N-acetyl cysteine did not reverse the effects of Prx3 knockdown. Thioredoxin, the cofactor needed for Prx3 regeneration, supported D3 microsomal activity; however, Prx3 knockdown did not change D3 activity in this system. In conclusion, knockdown of Prx3 decreases D3 activity in whole cells, whereas absolute levels of D3 are unchanged, consistent with Prx3 playing a rate-limiting role in the regeneration of the D3 enzyme.

Peroxiredoxin 5 confers protection against oxidative stress and apoptosis and also promotes longevity in Drosophila

Peroxiredoxin 5 is a distinct isoform of the peroxiredoxin gene family. The antioxidative and anti-apoptotic functions of peroxiredoxin 5 have been extensively demonstrated in cell culture experiments. In the present paper, we provide the first functional analysis of peroxiredoxin 5 in a multicellular organism, Drosophila melanogaster. Similar to its mammalian, yeast or human counterparts, dPrx5 (Drosophila peroxiredoxin 5) is expressed in several cellular compartments, including the cytosol, nucleus and the mitochondrion. Global overexpression of dPrx5 in flies increased resistance to oxidative stress and extended their life span by up to 30% under normal conditions. The dprx5(-/-) null flies were comparatively more susceptible to oxidative stress, had higher incidence of apoptosis, and a shortened life span. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) analysis revealed that the dprx5(-/-) null mutant had discernible tissue-specific apoptotic patterns, similar to those observed in control flies exposed to paraquat. In addition, apoptosis was particularly notable in oenocytes. During development the dPrx5 levels co-varied with ecdysone pulses, suggesting inter-relationship between ecdystreroids and dPrx5 expression. The importance of dPrx5 for development was further underscored by the embryonic lethal phenotype of progeny derived from the dprx5(-/-) null mutant. Results from the present study suggest that the antioxidant and anti-apoptotic activities of dPrx5 play a critical role in development and aging of the fly.

Sulfiredoxin Translocation into Mitochondria Plays a Crucial Role in Reducing Hyperoxidized Peroxiredoxin III

The mitochondria are the major intracellular source of reactive oxygen species (ROS), which are generated during cellular respiration. The role of peroxiredoxin (Prx) III, a 2-Cys Prx family member, in the scavenging of mitochondrial H(2)O(2) has recently been emphasized. While eliminating H(2)O(2), Prx can become overoxidized and inactivated by modifying the active cysteine into cysteine sulfinic acid (Cys-SO(2)H). When 2-Cys Prxs are inactivated in vitro, sulfiredoxin (Srx) reduces the cysteine sulfinic acid to cysteines. However, whereas Srx is localized in the cytoplasm, Prx III is present exclusively in the mitochondria. Although Srx reduces sulfinic Prx III in vitro, it remains unclear whether the reduction of Prx III in cells is actually mediated by Srx. Our gain- and loss-of-function experiments show that Srx is responsible for reducing not only sulfinic cytosolic Prxs (I and II) but also sulfinic mitochondrial Prx III. We further demonstrate that Srx translocates from the cytosol to mitochondria in response to oxidative stress. Overexpression of mitochondrion-targeted Srx promotes the regeneration of sulfinic Prx III and results in cellular resistance to apoptosis, with enhanced elimination of mitochondrial H(2)O(2) and decreased rates of mitochondrial membrane potential collapse. These results indicate that Srx plays a crucial role in the reactivation of sulfinic mitochondrial Prx III and that its mitochondrial translocation is critical in maintaining the balance between mitochondrial H(2)O(2) production and elimination.

Peroxiredoxin III-deficiency sensitizes macrophages to oxidative stress

As a mitochondrial scavenger of reactive oxygen species (ROS), peroxiredoxin III (PrxIII) plays an important role in regulating intracellular ROS level. We previously found that PrxIII knockout (PrxIII(-/-)) mice were more sensitive than wild-type (PrxIII(+/+)) controls to intratracheal inoculation of lipopolysaccharide (LPS), but the precise mechanism remained to be obscure. In the present study, we detected the levels of ROS and tumour necrosis factor alpha (TNF-alpha) in mouse bone-marrow-derived macrophages. LPS stimulation induced transient increase of ROS production and augmentation of TNF-alpha accumulation in PrxIII(-/-) macrophages. In addition, we observed reduced viability and increased apoptosis in PrxIII(-/-) macrophages exposed to LPS. Our results provide direct evidence that PrxIII is necessary for macrophages to protect against LPS-induced oxidative stress.