Ablation of Shank1 Protects against 6-OHDA-induced Cytotoxicity via PRDX3-mediated Inhibition of ER Stress in SN4741 Cells

BACKGROUND

Postsynaptic density (PSD) is an electron-dense structure that contains various scaffolding and signaling proteins. Shank1 is a master regulator of the synaptic scaffold located at glutamatergic synapses, and has been proposed to be involved in multiple neurological disorders.

METHODS

In this study, we investigated the role of shank1 in an in vitro Parkinson's disease (PD) model mimicked by 6-OHDA treatment in neuronal SN4741 cells. The expression of related molecules was detected by western blot and immunostaining.

RESULTS

We found that 6-OHDA significantly increased the mRNA and protein levels of shank1 in SN4741 cells, but the subcellular distribution was not altered. Knockdown of shank1 via small interfering RNA (siRNA) protected against 6-OHDA treatment, as evidenced by reduced lactate dehydrogenase (LDH) release and decreased apoptosis. The results of RT-PCR and western blot showed that knockdown of shank1 markedly inhibited the activation of endoplasmic reticulum (ER) stress associated factors after 6-OHDA exposure. In addition, the downregulation of shank1 obviously increased the expression of PRDX3, which was accompanied by the preservation of mitochondrial function. Mechanically, downregulation of PRDX3 via siRNA partially prevented the shank1 knockdowninduced protection against 6-OHDA in SN4741 cells.

CONCLUSION

In summary, the present study has provided the first evidence that the knockdown of shank1 protects against 6-OHDA-induced ER stress and mitochondrial dysfunction through activating the PRDX3 pathway.

Pure cerebellar ataxia due to bi-allelic PRDX3 variants including recurring p.Asp202Asn

Bi-allelic variants in peroxiredoxin 3 (PRDX3) have only recently been associated with autosomal recessive spinocerebellar ataxia characterized by early onset slowly progressive cerebellar ataxia, variably associated with hyperkinetic and hypokinetic features, accompanied by cerebellar atrophy and occasional olivary and brainstem involvement. Herein, we describe a further simplex case carrying a reported PRDX3 variant as well as two additional cases with novel variants. We report the first Brazilian patient with SCAR32, replicating the pathogenic status of a known variant. All presented cases from the Brazilian and Indian populations expand the phenotypic spectrum of the disease by displaying prominent neuroradiological findings. SCAR32, although rare, should be included in the differential diagnosis of sporadic or recessive childhood and adolescent-onset pure and complex cerebellar ataxia.

Autoantibodies to Peroxiredoxin I and IV in Patients with Systemic Autoimmune Diseases

Anti-oxidative enzymes protect living bodies from various oxidative stresses. In the systemic autoimmune diseases, autoantibodies to oxidized molecules and to anti-oxidative enzymes have been reported. To promote understanding of the relationships between autoimmunity and oxidative stress, we here investigate whether autoimmunity to the anti-oxidative peroxiredoxin (Prxs) enzymes exists in patients with systemic autoimmune diseases. Specifically, we detected autoantibodies to recombinant Prx I and Prx IV respectively by ELISA and western blotting. Next, clinical parameters were compared between the anti-Prx I or IV-positive and-negative patients. We found that 33% of the 92 patients with autoimmune diseases tested possessed autoantibodies to Prx I (57% in systemic lupus erythematosus (SLE), 19% in rheumatoid arthritis (RA), 5% in Behçet disease, and 46% in primary vasculitis syndrome). In contrast, autoantibodies to Prx IV were detected in only 17% of the same patients. No significant correlation was found between occurrence of the two autoantibodies. Clinically, possession of anti-Prx I autoantibodies correlated with lower serum levels of CH50, C3, and C4. Taken together, our data demonstrate the existence of autoantibodies to Prxs for the first time. The autoantibodies to Prx I may be involved in the pathophysiology of systemic autoimmune diseases such as SLE and vasculitis.

Model for the exceptional reactivity of peroxiredoxins 2 and 3 with hydrogen peroxide: a kinetic and computational study

Peroxiredoxins (Prx) are thiol peroxidases that exhibit exceptionally high reactivity toward peroxides, but the chemical basis for this is not well understood. We present strong experimental evidence that two highly conserved arginine residues play a vital role in this activity of human Prx2 and Prx3. Point mutation of either ArgI or ArgII (in Prx3 Arg-123 and Arg-146, which are ∼3-4 Å or ∼6-7 Å away from the active site peroxidative cysteine (C(p)), respectively) in each case resulted in a 5 orders of magnitude loss in reactivity. A further 2 orders of magnitude decrease in the second-order rate constant was observed for the double arginine mutants of both isoforms, suggesting a cooperative function for these residues. Detailed ab initio theoretical calculations carried out with the high level G4 procedure suggest strong catalytic effects of H-bond-donating functional groups to the C(p) sulfur and the reactive and leaving oxygens of the peroxide in a cooperative manner. Using a guanidinium cation in the calculations to mimic the functional group of arginine, we were able to locate two transition structures that indicate rate enhancements consistent with our experimentally observed rate constants. Our results provide strong evidence for a vital role of ArgI in activating the peroxide that also involves H-bonding to ArgII. This mechanism could explain the exceptional reactivity of peroxiredoxins toward H(2)O(2) and may have wider implications for protein thiol reactivity toward peroxides.

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.

The combination of genetic variations in the PRDX3 gene and dietary fat intake contribute to obesity risk

Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the antioxidant capacity of the cell. This imbalance and an excess of ROS induce tissue/cellular damage, which are implicated in chronic inflammation disorders such as obesity, insulin resistance, and metabolic syndromes. Peroxiredoxins (Prxs) are the most abundant and ancient cellular antioxidant proteins that help to control intracellular peroxide levels and ROS-dependent signaling. Of the six mammalian isoforms, Prx III is specifically localized in mitochondria. In this study, we detected novel associations between genetic variations of the PRDX3 gene and BMI and obesity risk in the general Japanese population. In addition, these associations were observed only in the subjects with high dietary fat intake, but not in the subjects with low dietary fat intake. These findings indicate that the interaction between genetic variations in the PRDX3 gene and dietary fat intake is important for modulation of BMI and obesity risk.

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

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

Loss of manganese superoxide dismutase leads to abnormal growth and signal transduction in mouse embryonic fibroblasts

Manganese superoxide dismutase (MnSOD) in the mitochondria plays an important role in cellular defense against oxidative damage. Homozygous MnSOD knockout (Sod2(-/-)) mice are neonatal lethal, indicating the essential role of MnSOD in early development. To investigate the potential cellular abnormalities underlying the aborted development of Sod2(-/-) mice, we examined the growth of isolated mouse embryonic fibroblasts (MEFs) from Sod2(-/-) mice. We found that the proliferation of Sod2(-/-) MEFs was significantly decreased compared with wild-type MEFs despite the absence of morphological differences. The Sod2(-/-) MEFs produced less cellular ATP, had lower O(2) consumption, generated more superoxide, and expressed less Prdx3 protein. Furthermore, the loss of MnSOD dramatically altered several markers involved in cell proliferation and growth, including decreased growth stimulatory function of mTOR signaling and enhanced growth inhibitory function of GSK-3β signaling. Interestingly, the G-protein-coupled receptor-mediated intracellular Ca(2+) signal transduction was also severely suppressed in Sod2(-/-) MEFs. Finally, the ratio of microtubule-associated protein light chain 3 (LC3)-II/LC3-I, an index of autophagic activity, was increased in Sod2(-/-) MEFs, consistent with a reduction in mTOR signal transduction. These data demonstrate that MnSOD deficiency results in alterations in several key signaling pathways, which may contribute to the lethal phenotype of Sod2(-/-) mice.

Silencing the Peroxiredoxin III gene inhibits cell proliferation in breast cancer

Peroxiredoxin III (Prx III), an antioxidant protein found in mitochondria, plays an essential role in mitochondrial homeostasis. Aberrant expression of Prx III has been implicated in the tumorigenesis of various cancers. In this study, we evaluated the expression of Prx III in breast cancer tissues and elucidated its role in cell proliferation, a hallmark of cancer. Breast tissue microarrays comprising 106 breast cancer sections were stained with Prx III antibody using immunohistochemisty and correlated with proliferating cell nuclear antigen (PCNA) immunostaining. To validate the role of Prx III in cell proliferation, expression of Prx III was analyzed at the mRNA and protein levels by real-time RT-PCR, Western blotting and immunofluorescence in vitro. siRNA mediated silencing of Prx III in MDA-MB-231 breast cancer cells was performed and the effect on the cell cycle was examined. Prx III expression in patient tissue microarray samples was found to be positively associated with PCNA immunostaining, a proliferative marker. Prx III was expressed in both MCF-7 and MDA-MB-231 breast cancer cell lines and transient transfection with siPrx III in MDA-MB-231 cells induced inhibition of cell proliferation and cell cycle arrest. The data suggests that Prx III has a significant role in cell cycle regulation and could be a potential proliferation marker in breast cancer.

Expression of human peroxiredoxin isoforms in response to cervical carcinogenesis

Despite considerable progress in understanding the function of peroxiredoxin (Prx) in cancer, its expression patterns have not been extensively studied in response to cervical carcinogenesis. We evaluated the expression of Prx isoforms in normal tissue, cervical intraepithelial neoplasia (CIN1, CIN2, and CIN3), and cervical cancer. We found strong pattern of increased Prx II and III immunostaining with increasing severity of the lesion. No difference in staining intensity by grade of lesion was observed for Prx I, and IV. Therefore, we conclude that Prx II and III are upregulated in response to the development of cervical cancer.

Reduction of mitochondrial H2O2 by overexpressing peroxiredoxin 3 improves glucose tolerance in mice

H(2)O(2) is a major reactive oxygen species produced by mitochondria that is implicated to be important in aging and pathogenesis of diseases such as diabetes; however, the cellular and physiological roles of mitochondrial H(2)O(2) remain poorly understood. Peroxiredoxin 3 (Prdx3/Prx3) is a thioredoxin peroxidase localized in mitochondria. To understand the cellular and physiological roles of mitochondrial H(2)O(2) in aging and pathogenesis of age-associated diseases, we generated transgenic mice overexpressing Prdx3 (Tg(PRDX3) mice). Tg(PRDX3) mice overexpress Prdx3 in a broad range of tissues, and the Prdx3 overexpression occurs exclusively in the mitochondria. As a result of increased Prdx3 expression, mitochondria from Tg(PRDX3) mice produce significantly reduced amount of H(2)O(2), and cells from Tg(PRDX3) mice have increased resistance to stress-induced cell death and apoptosis. Interestingly, Tg(PRDX3) mice show improved glucose homeostasis, as evidenced by their reduced levels of blood glucose and increased glucose clearance. Tg(PRDX3) mice are also protected against hyperglycemia and glucose intolerance induced by high-fat diet feeding. Our results further show that the inhibition of GSK3 may play a role in mediating the improved glucose tolerance phenotype in Tg(PRDX3) mice. Thus, our results indicate that reduction of mitochondrial H(2)O(2) by overexpressing Prdx3 improves glucose tolerance.

The thioredoxin reductase inhibitor auranofin triggers apoptosis through a Bax/Bak-dependent process that involves peroxiredoxin 3 oxidation

Thioredoxin reductase (TrxR) is a key selenoprotein antioxidant enzyme and a potential target for anti-cancer drugs. One potent inhibitor of TrxR is the gold (I) compound auranofin, which can trigger mitochondrial-dependent apoptosis pathways. The exact mechanism of apoptosis induction by auranofin is not yet clear, but there are indications that mitochondrial oxidative stress is a central event. We assessed the redox state of the peroxiredoxins (Prxs) in Jurkat T-lymphoma cells treated with auranofin, and found that mitochondrial Prx3 was considerably more sensitive to oxidation than the cytosolic Prx1 and 2, indicating selective mitochondrial stress. Prx3 oxidation was detected at apoptotic doses of auranofin in several cell types, and occurred before other mitochondrial events including cytochrome c release and mitochondrial depolarisation. Auranofin was also able to sensitise U937 cells to TNF-alpha-mediated apoptosis. Auranofin-induced apoptosis was effectively blocked by the overexpression of Bcl-2, and Bax/Bak deficient mouse embryonic fibroblasts were also resistant to apoptosis, indicating a central role for the pro-apoptotic proteins of this family in auranofin-triggered apoptosis. Auranofin exposure inhibited the proliferation of apoptosis-resistant cells, and at higher doses of auranofin could cause cell death through necrosis. We conclude that auranofin induces apoptosis in cells through a Bax/Bak-dependent mechanism associated with selective disruption of mitochondrial redox homeostasis in conjunction with oxidation of Prx3.

Mitochondrial peroxiredoxin 3 is rapidly oxidized in cells treated with isothiocyanates

Isothiocyanates are phytochemicals with anti-cancer properties that include the ability to trigger apoptosis. A substantial body of evidence suggests that reaction of the electrophilic isothiocyanate moiety with cysteine residues in cellular proteins and glutathione accounts for their biological activity. In this study we investigated the effect of several different isothiocyanates on the redox states of the cysteine-dependent peroxiredoxins (Prx) in Jurkat T lymphoma cells, and compared this to known effects on the selenoprotein thioredoxin reductase, glutathione reductase and intracellular GSH levels. Interestingly, oxidation of mitochondrial Prx3 could be detected as early as 5 min after exposure of cells to phenethyl isothiocyanate, with complete oxidation occurring at doses that only had small inhibitory effects on total cellular thioredoxin reductase and glutathione reductase activities. Peroxiredoxin oxidation was specific to the mitochondrial isoform with cytoplasmic Prx1 and Prx2 maintained in their reduced forms at all analyzed time points and concentrations of isothiocyanate. Phenethyl isothiocyanate could react with purified Prx3 directly, but it did not oxidize Prx3 or promote its oxidation by hydrogen peroxide. A selection of aromatic and alkyl isothiocyanates were tested and while all lowered cellular GSH levels, only the isothiocyanates that caused Prx3 oxidation were able to trigger cell death. We propose that pro-apoptotic isothiocyanates selectively disrupt mitochondrial redox homeostasis, as indicated by Prx3 oxidation, and that this contributes to their pro-apoptotic activity.

Oxidation of mitochondrial peroxiredoxin 3 during the initiation of receptor-mediated apoptosis

It is hypothesized that activation of death receptors disrupts the redox homeostasis of cells and that this contributes to the induction of apoptosis. The redox status of the peroxiredoxins, which are extremely sensitive to increases in H2O2 and disruption of the thioredoxin system, were monitored in Jurkat T lymphoma cells undergoing Fas-mediated apoptosis. The only detectable change during the early stages of apoptosis was oxidation of mitochondrial peroxiredoxin 3. Increased H2O2 triggers peroxiredoxin overoxidation to a sulphinic acid; however during apoptosis peroxiredoxin 3 was captured as a disulfide, suggesting impairment of the thioredoxin system responsible for maintaining peroxiredoxin 3 in its reduced form. Peroxiredoxin 3 oxidation was an early event, occurring within the same timeframe as increased mitochondrial oxidant production, caspase activation and cytochrome c release. It preceded other major apoptotic events including mitochondrial permeability transition and phosphatidylserine exposure, and glutathione depletion, global thiol protein oxidation and protein carbonylation. Peroxiredoxin 3 oxidation was also observed in U937 cells stimulated with TNF-alpha. We hypothesize that the selective oxidation of peroxiredoxin 3 leads to an increase in mitochondrial H2O2 and that this may influence the progression of apoptosis.

Mitochondrial structure and function in the untreated Jackson toxic milk (tx-j) mouse, a model for Wilson disease

Structural changes in hepatocellular mitochondria are characteristic of Wilson disease (WD). Features include variability in size and shape, increased density of matrix, discreet inclusions, and cystic dilatation of the cristae. We examined the functional basis for these mitochondrial changes in the toxic milk (tx-j) mouse model for WD. Its normal syngeic strain, C3H, served as control. Hepatic histology was near-normal in tx-j mice at 3-4-months-old and showed mild inflammation and steatosis at 6-months-old. Transmission electron microscopy showed typical mitochondrial abnormalities, specifically cystic dilatation of tips of cristae, in 3, 4, and 6-month-old tx-j mice and none in normal 3-month-old C3H mice. Citrate synthase (CS) activity was initially lower in tx-j mice than age-matched controls but increased over the first 6 months such that it was significantly greater at 5 and 6-months-old (p<0.003). No evidence for hepatic mtDNA depletion was found by long-PCR analysis. NB-PAGE showed preservation of all complexes in the oxidative-phosphorylation chain except complex IV which declined markedly from 5-months-old onwards. Hepatic complex IV activity was significantly decreased in 5-month-old tx-j mice (p<0.04). Expression of mitochondrial transfer factor A (TFAM) mRNA declined progressively in 6-8-month-old tx-j mice; immunodetectable protein levels declined in parallel. Expression of mtSSB mRNA was uniformly low in tx-j mice from 1-8-months-old. Levels of two mitochondrial antioxidant proteins capable of binding copper, thioredoxin-2 and peroxiredoxin-3, rose over the first 6 months of life. Mitochondrial changes occur early in WD and reflect complex, probably oxidative, injury.

The use of isobaric tag peptide labeling (iTRAQ) and mass spectrometry to examine rare, primitive hematopoietic cells from patients with chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a hematopoietic stem cell disease, associated with a t(9, 22) chromosomal translocation leading to formation of the BCR/ABL chimeric protein, which has an intrinsic tyrosine kinase activity. Recently, the BCR/ABL tyrosine kinase inhibitor imatinib mesylate (imatinib) has been successfully used clinically, although, disease relapse can still occur. The precise detail of the mechanism by which CML cells respond to imatinib is still unclear. We therefore systematically examined the effects of imatinib on the primitive CML cell proteome, having first established that the drug inhibits proliferation and induces increased apoptosis and differentiation. To define imatinib-induced effects on the CML proteome, we employed isobaric tag peptide labeling (iTRAQ) coupled to two-dimensional liquid chromatography/tandem mass spectrometry. Given the limited clinical material available, the isobaric tag approach identified a large population of proteins and provided relative quantification on four samples at once. Novel consequences of the action of imatinib were identified using this mass spectrometric approach. DEAD-box protein 3, heat shock protein 105 kDa, and peroxiredoxin-3 were identified as potential protein markers for response to imatinib.

Localization and H2O2-specific induction of PRDX3 in the eye lens

PURPOSE

Peroxiredoxin III (PRDX3) is a mitochondrial peroxidase that defends cells against oxidative damage and therefore could play a role in cataract formation. To establish a possible role for PRDX3 in lens function, PRDX3 was localized to specific human lens sub-regions and the levels of PRDX3 in human lens cells and rat lenses exposed to exogenously-added oxidative stress determined.

METHODS

PRDX3 levels were monitored by RT-PCR, western analysis, and immunofluorescence. PRDX3 levels in human lens epithelial cells and whole rat lenses exposed to H2O2, TBHP, and heat-treatment were also examined relative to untreated controls by RT-PCR and western analysis.

RESULTS

Significant levels of PRDX3 mRNA and protein were detected in human lens epithelia and fiber cells. PRDX3 was localized to the mitochondria in human lens epithelial cells. PRDX3 was highly induced in human lens epithelial cells by as little as 2 microM H2O2 and by 50 microM H2O2 in cultured rat lenses. Induction of PRDX3 was specific for H2O2 in cultured lens cells since sub-lethal levels of TBHP or heat-shock did not result in detectable increases in the level of PRDX3.

CONCLUSIONS

These data demonstrate that PRDX3 is present throughout the lens and localized to the mitochondria in lens epithelial cells. PRDX3 was specifically induced by low levels of H2O2 in human lens epithelial cells and rat lenses suggesting that induction of PRDX3 is an acute response of the lens to increased H2O2 levels. These data provide evidence for an important role for PRDX3 in lens H2O2-detoxification, mitochondrial maintenance, and possibly cataract formation.

Immunohistochemical localization of 2-Cys peroxiredoxins in human ciliary body

2-Cys peroxiredoxins (PRDX) are novel antioxidant enzymes that eliminate the hydrogen peroxide in cells to protect the cellular components from reactive oxygen species. To evaluate whether 2-Cys PRDX family plays a role in human ciliary body, the expression of PRDX I, II and III on normal human ciliary body was investigated. Three normal human ciliary body tissues obtained from three donor eyeballs were examined by an immunohistochemistry using light microscopy and fluorescent microscopy with antibodies directed against the PRDX I, II and III. In the normal human ciliary body, PRDX I, II and III were immunolocalized to the non-pigmented epithelial cells and ciliary muscle fibers. It suggests that 2-Cys PRDXs may have physiological functions to protect cells in human ciliary body.

The role of peroxiredoxin III on late stage of proerythrocyte differentiation

Peroxiredoxin III (Prdx III), the mitochondrial peroxidase, was preferentially expressed in murine erythroleukemia (MEL) cells. However, the mechanisms by which Prdx III regulates erythroid differentiation are unknown. In this study, K562 cells were differentiated by Ara-C treatment, and Prdx III was dramatically increased until day 5. We also investigated Prdx III expression pattern on in vitro erythropoiesis of human CD34(+) cells. When human CD34(+) cells became proerythrocyte on day 7, Prdx III was diminished, and then augmented on day 12. We established the stable sublines of Prdx III overexpression (O/E), and dominant-negative (D/N). The intracellular ROS level of Prdx III O/E cell line was lower than D/N stable cell lines. Moreover, Prdx III O/E cell line was placed in G1-arrest, but not D/N cell lines. Finally, the expression level of beta-globin and GATA-1 was dramatically increased in Prdx III O/E cell line.

Proteomic analysis defines altered cellular redox pathways and advanced glycation end-product metabolism in glomeruli of db/db diabetic mice

To attain a profile of protein expression during diabetes, we applied proteomic analysis to glomeruli of 160-day-old db/db diabetic and db/m nondiabetic mice. Glomerular proteins were extracted and separated by two-dimensional gel electrophoresis to construct a proteome map. Matrix-assisted laser desorption and ionization-time of flight mass spectrometry and peptide mass fingerprinting were used to identify 190 proteins. Of 105 analyzed spots, expression of 40 proteins, including the antioxidative enzymes peroxiredoxin 1 and 3, glutathione peroxidase 1, and SOD-1, was increased with diabetes, suggesting an adaptive response to oxidative stress associated with this diabetic model. However, activity of glutathione peroxidase and SOD was unaltered in glomeruli of diabetic mice. Expression of glyoxalase I was increased in glomeruli of diabetic mice. Because the cofactor for glyoxalase I, glutathione, is decreased in renal cortex of db/db mice, renal cortical glyoxalase I activity was measured in vitro with fixed amounts of exogenous glutathione. Glyoxalase I activity was decreased in renal cortex of db/db mice. These data indicate that diabetes-induced decreases in glyoxalase I activity are likely to be due to glutathione-dependent and -independent mechanisms and that increased expression of glyoxalase I may represent an insufficient adaptive response to increased methylglyoxal formation.

Mitochondrial thioredoxin-2/peroxiredoxin-3 system functions in parallel with mitochondrial GSH system in protection against oxidative stress

A dominant-negative, active-site mutant (C93S-Trx2) of mitochondrial thioredoxin-2 (Trx2) was expressed in cells to study the function of the thioredoxin system in protection against mitochondrial oxidative stress. C93S-Trx2 was detected as a disulfide with mitochondrial peroxiredoxin-3 (Prx3) but not peroxiredoxin-5 (Prx5). C93S-Trx2 enhanced sensitivity to cell death induced by tert-butylhydroperoxide or by tumor necrosis factor-alpha (TNF-alpha). In cells treated with buthionine sulfoximine (BSO) to deplete glutathione (GSH), endogenous Trx2 was oxidized, C93S-Trx2 potentiated toxicity, and overexpression of Trx2 protected against toxicity. Thus, the results show that Trx2 interacts with Prx3 in vivo and that the Trx2/Prx3 system functions in parallel with the GSH system to protect mitochondria from oxidative stress. The additive protection by Trx2 and GSH shows that Trx2 and GSH systems are both functionally important at low oxidative stress conditions.

Role of manganese superoxide dismutase on growth and invasive properties of human estrogen-independent breast cancer cells

Manganese superoxide dismutase (MnSOD) is known to play a role in cancer. MnSOD exerts a tumor suppressive effect in estrogen-dependent human breast cancer cells. In the present study we investigated the in vitro role of MnSOD in the growth of some aggressive and highly metastatic estrogen-independent breast cancer cells, i.e., MDA-MB231 and SKBR3 cells. We show that estrogen-independent cells expressed a significantly higher basal MnSOD level compared to estrogen-dependent human breast cancer cell lines (MCF-7 and T47D). For MDA-MB231 cells, the high-MnSOD level was accompanied by an overproduction of intracellular hydrogen peroxide (H2O2) and by a low expression of the major H2O2-detoxifying enzymes, catalase, and peroxiredoxin 3, compared to MCF-7 cells. Suppression of MnSOD expression by antisense RNA was associated with a decrease of H2O2 content and caused a stimulation of growth with a reduced cell doubling time but induced a decrease of colony formation. Furthermore, treatment of MDA-MB231 cells with H2O2 scavengers markedly reduced tumor cell growth and colony formation. In addition, MnSOD suppression or treatment with H2O2 scavengers reduced the invasive properties of MDA-MB231 cells up to 43%, with a concomitant decrease of metalloproteinase-9 activity. We conclude that MnSOD plays a role in regulating tumor cell growth and invasive properties of estrogen-independent metastatic breast cancer cells. These action are mediated by MnSOD-dependent H2O2 production. In addition, these results suggest that MnSOD up-regulation may be one mechanism that contributes to the development of metastatic breast cancers.

Increased susceptibility of MER5 (peroxiredoxin III) knockout mice to LPS-induced oxidative stress

MER5 (also called peroxiredoxin III, PrxIII) is a member of peroxiredoxin family that has antioxidant activity. The present study was performed to investigate its in vivo function using MER5 knockout mice. MER5 knockout mice were born in normal frequency and could grow to maturity, but we found that intracellular ROS levels are significantly higher in the macrophages of the knockout mice. We examined roles of MER5 function for the oxidative stress responses by intratracheal inoculation of lipopolysaccharide (LPS) to the mice. Lung inflammation such as inflammatory cell infiltration and airway wall thickening was more severely detected in the knockout mice. At the same time, oxidative damage on DNA and proteins was more strongly detected in lung tissues of the knockout mice, including 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation and protein carbonylation. The degrees of lung inflammation and oxidative damage were positively related with LPS doses. Our results indicate that MER5 knockout mice accumulated higher intracellular ROS levels, which cause LPS-induced lung injury more severely, and thus, suggested that MER5 acts as an important scavenger of reactive oxygen species (ROS) under oxidative stress.

Cardiotrophin-1 is an essential factor in the natural defense of the liver against apoptosis

We previously reported that exogenous cardiotrophin-1 (CT-1), a member of the IL-6 family of cytokines, exerts hepatoprotective effects. Because CT-1 is expressed in the normal liver, we hypothesized that this cytokine may constitute an endogenous defense of the liver against proapoptotic stimuli. Here, we found that CT-1-/- mice died faster than wild-type animals after challenge with a lethal dose of the Fas agonist Jo-2. At sublethal doses of Jo-2, all wild-type mice survived whereas CT-1-/- animals developed extensive hepatocyte apoptosis with 50% mortality at 24 hours. Pretreatment with CT-1 improved survival and reduced injury in both CT-1-/- and wild-type animals. Upon Fas ligation the activation of STAT-3, a molecule that defends the liver against apoptosis, was lower in CT-1-/- mice than in wild-type animals despite similar IL-6 up-regulation in the 2 groups. Analysis of liver transcriptome in CT-1-/- and wild-type mice showed that 9 genes reported to be associated with cell survival/death functions were differentially expressed in the 2 groups. Four of these genes [IGFBP1, peroxiredoxin3, TNFR1, and calpastatin (endogenous inhibitor of calpain)] could be validated by real-time PCR. All of them were down-regulated in CT-1-/- mice and were modulated by CT-1 administration. Treatment of CT-1-/- animals with the calpain inhibitor MDL28170 afforded significant protection against Fas-induced liver injury.

CONCLUSION

CT-1-/- mice are highly sensitive to Fas-mediated apoptosis due in part to deficient STAT-3 activation and inadequate control of calpain activity during the apoptotic process. Our data show that CT-1 is a natural defense of the liver against apoptosis. This cytokine may have therapeutic potential.

Behavioural and expressional phenotyping of nitric oxide synthase-I knockdown animals

The gaseous messenger nitric oxide (NO) has been implicated in a wide range of behaviors, including aggression, anxiety, depression, and cognitive functioning. To further elucidate the physiological role of NO and its down-stream mechanisms, we conducted behavioral and expressional phenotyping of mice lacking the neuronal isoform of nitric oxide synthase (NOS-I), the major source of NO in the central nervous system. No differences were observed in activity-related parameters; in contrast to the a priori hypothesis, derived from pharmacological treatments, depression-related tests (Forced Swim Test, Learned Helplessness) also yielded no significantly different results. A subtle anxiolytic phenotype however was present, with knockdown mice displaying a higher open arm time as compared to their respective wildtypes, yet all other investigated anxiety-related parameters were unchanged. The most prominent feature however was gender-independent cognitive impairment in spatial learning and memory, as assessed by the Water Maze test and an automatized holeboard paradigm. No significant dysregulation of monoamine transporters was evidenced by qRT PCR. To further examine the underlying molecular mechanisms, the transcriptome of knockdown animals was thus examined in the hippocampus, striatum and cerebellum by microarray analysis. A set of >120 differentially expressed genes was identified, whereat the hippocampus and the striatum showed similar expressional profiles as compared to the cerebellum in hierarchical clustering. Among the most significantly up-regulated genes were Peroxiredoxon 3, Atonal homologue 1, Kcnj1, Kcnj8, CCAAT/enhancer binding protein (C/EBP), alpha, 3 genes involved in GABA(B) signalling and, intriguingly, the glucocorticoid receptor GR. While GABAergic genes might underlie reduced anxiety, dysregulation of the glucocorticoid receptor can well contribute to a blunted stress response as found in NOS1 knockdown mice. Furthermore, by CREB inhibition, glucocorticoid receptor upregulation could at least partially explain cognitive deficits in these animals. Taken together, NOS1 knockdown mice display a characteristic behavioural profile consisting of reduced anxiety and impaired learning and memory, paralleled by differential expression of the glucocorticoid receptor and GABAergic genes. Further research has to assess the value of these mice as animal models e.g. for Alzheimer's disease or attention deficit disorder, in order to clarify a possible pathophysiological role of NO therein.

Defective mitochondrial peroxiredoxin-3 results in sensitivity to oxidative stress in Fanconi anemia

Cells from patients with Fanconi anemia (FA), an inherited disorder that includes bone marrow failure and cancer predisposition, have increased sensitivity to oxidative stress through an unknown mechanism. We demonstrate that the FA group G (FANCG) protein is found in mitochondria. Wild-type but not G546R mutant FANCG physically interacts with the mitochondrial peroxidase peroxiredoxin-3 (PRDX3). PRDX3 is deregulated in FA cells, including cleavage by a calpainlike cysteine protease and mislocalization. FA-G cells demonstrate distorted mitochondrial structures, and mitochondrial extracts have a sevenfold decrease in thioredoxin-dependent peroxidase activity. Transient overexpression of PRDX3 suppresses the sensitivity of FA-G cells to H₂O₂, and decreased PRDX3 expression increases sensitivity to mitomycin C. Cells from the FA-A and -C subtypes also have PRDX3 cleavage and decreased peroxidase activity. This study demonstrates a role for the FA proteins in mitochondria witsh sensitivity to oxidative stress resulting from diminished peroxidase activity. These defects may lead to apoptosis and the accumulation of oxidative DNA damage in bone marrow precursors.

Impairment of mitochondrial anti-oxidant defence in SOD1-related motor neuron injury and amelioration by ebselen

There is now compelling evidence of mitochondrial dysfunction in motor neuron disease (MND), but the molecular basis of these abnormalities is unknown. It is also unclear whether the observed mitochondrial dysfunction plays a central role in disease pathogenesis, and if so, whether its amelioration might present therapeutic opportunities. We adopted a candidate generation approach using proteomics to screen for changes in mitochondrial protein expression in a well-validated cell-culture model of superoxide dismutase 1 (SOD1) related familial MND (fMND). Changed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy. Protein candidates included apoptotic regulators, anti-oxidants and components of the electron transport chain. Confirmatory Western blotting was performed, and validated protein expression changes were further investigated. Peroxiredoxin 3 (Prx3), a mitochondrial thioredoxin-dependent hydroperoxidase, is downregulated in the presence of mutant SOD1 in both our cell-culture model and in the spinal cord mitochondria of mutant SOD1 transgenic mice. We confirm the expression of Prx3 within the mitochondria of spinal motor neurons in mouse and humans by immunohistochemistry. Using quantitative real-time PCR (Q-PCR), we show that Prx3 is also downregulated in spinal motor neurons from patients with both sporadic (sMND) and SOD1-related fMND. In a disease characterized by oxidative stress, this represents a potentially important deficit in mitochondrial anti-oxidant defence. Recent evidence suggests that oxidative stress from aberrant copper chemistry may not play a major part in the pathogenesis of SOD1-related fMND. From the results of this study we propose disruption of mitochondrial anti-oxidant defence as an alternative mechanism whereby mutant SOD1 may generate oxidative stress within motor neurons. We further demonstrate that ebselen, an anti-oxidant drug already safely used in human studies and that acts as a Prx mimic, is able to ameliorate the toxicity of mutant SOD1 in our cell-culture model. We conclude by showing that ebselen is capable of inducing transcription of the anti-oxidant response element (ARE) and postulate that ebselen may act both by the transcriptional upregulation of anti-oxidant proteins, and directly as an anti-oxidant in its own right.

Overexpression of mitochondrial peroxiredoxin-3 prevents left ventricular remodeling and failure after myocardial infarction in mice

BACKGROUND

Mitochondrial oxidative stress and damage play major roles in the development and progression of left ventricular (LV) remodeling and failure after myocardial infarction (MI). We hypothesized that overexpression of the mitochondrial antioxidant, peroxiredoxin-3 (Prx-3), could attenuate this deleterious process.

METHODS AND RESULTS

We created MI in 12- to 16-week-old, male Prx-3-transgenic mice (TG+MI, n=37) and nontransgenic wild-type mice (WT+MI, n=39) by ligating the left coronary artery. Prx-3 protein levels were 1.8 times higher in the hearts from TG than WT mice, with no significant changes in other antioxidant enzymes. At 4 weeks after MI, LV thiobarbituric acid-reactive substances in the mitochondria were significantly lower in TG+MI than in WT+MI mice (mean+/-SEM, 1.5+/-0.2 vs 2.2+/-0.2 nmol/mg protein; n=8 each, P<0.05). LV cavity dilatation and dysfunction were attenuated in TG+MI compared with WT+MI mice, with no significant differences in infarct size (56+/-1% vs 55+/-1%; n=6 each, P=NS) and aortic pressure between groups. Mean LV end-diastolic pressures and lung weights in TG+MI mice were also larger than those in WT+sham-operated mice but smaller than those in WT+MI mice. Improvement in LV function in TG+MI mice was accompanied by a decrease in myocyte hypertrophy, interstitial fibrosis, and apoptosis in the noninfarcted LV. Mitochondrial DNA copy number and complex enzyme activities were significantly decreased in WT+MI mice, and this decrease was also ameliorated in TG+MI mice.

CONCLUSIONS

Overexpression of Prx-3 inhibited LV remodeling and failure after MI. Therapies designed to interfere with mitochondrial oxidative stress including the antioxidant Prx-3 might be beneficial in preventing cardiac failure.

Sex-based molecular profiling of hepatitis C virus-related hepatocellular carcinoma

It has been suggested that sex affects not only the incidence of hepatocellular carcinoma (HCC) but also the outcome after treatment. However, no sex-specific therapeutic targets for HCC have been identified. Identification of sex-specific genes will allow for the development of more personalized therapies. To this end, we investigated the expression of approximately 6000 genes in 50 samples of hepatitis C virus (HCV)-related HCC by oligonucleotide microarray. Our supervised learning method and subsequent random permutation test identified 27 genes that were differentially expressed in samples from male (n=34) and female (n=16) patients. Our gene selection was validated by a false discovery rate of only 0.5%. For the 27 genes, expression levels of 12 were higher and expression levels of 15 were lower in HCC samples from men than in HCC samples from women. For the cell proliferation-related genes identified, expression levels of PRDX1 were relatively high in HCC samples from men, and expression levels of PRDX3 were relatively high in HCC samples from women. The DNA microarray data for PRDX1 and PRDX3 were reproduced by reverse transcription-PCR analysis. Our results suggest that these 27 genes may serve as molecular targets or markers for sex-specific treatment of HCV-related HCC. Further studies are needed to elucidate their possible roles in male and female patients with HCV-related HCC.

RPK118, a PX domain-containing protein, interacts with peroxiredoxin-3 through pseudo-kinase domains

RPK118 is a sphingosine kinase-1-binding protein that has been implicated in sphingosine 1 phosphate-mediated signaling. It contains a PX (phox homology) domain and two pseudo-kinase domains, and co-localizes with sphingosine kinase-1 on early endosomes. In this study we identified a novel RPK118-binding protein, PRDX3 (peroxiredoxin-3), by yeast two-hybrid screening. The interaction between these proteins was confirmed by pull-down assays and co-immunoprecipitation experiments. Deletion studies showed that RPK118 interacted with PRDX3 through its pseudokinase domains, and with early endosomes through its PX domain. Double immunofluorescence experiments demonstrated that PRDX3 co-localized with RPK118 on early endosomes in COS7 cells. PRDX3 is a member of the antioxidant family of proteins synthesized in the cytoplasm and functioning in mitochondria. Our findings indicate that RPK118 is a PRDX3-binding protein that may be involved in transporting PRDX3 from the cytoplasm to its mitochondrial site of function or to other membrane structures via endosome trafficking.

Estradiol regulates the thioredoxin antioxidant system in the mouse uterus

The rodent uterus responds to acute estradiol (E2) treatment with a series of well characterized physiological responses. In a recent screen for genes involved in this response, we found that several genes in the thioredoxin (Txn) pathway were rapidly modified after E2 treatment in the mouse uterus. Txn is a 12-kDa protein with multiple roles in the cell, including protection against oxidative stress and apoptosis, regulation of transcription factor activity, and regulation of cellular proliferation. Txn in combination with Txn reductase (Txnrd) and Txn-interacting protein (Txnip) constitute the mammalian Txn pathway. This pathway exists in multiple locations in the cell, including the cytosol and mitochondria. To analyze the levels of Txn, Txnrd, and Txnip in the uterus, we treated ovariectomized adult mice with a time course of E2 and analyzed mRNA levels by real-time PCR. E2 rapidly decreased the expression of Txnip, but increased the levels of cytosolic Txn1 and Txnrd1 as well as mitochondrial Txn2. Using the ER antagonist, ICI 182,780, and mice lacking functional estrogen receptor alpha (ERalpha), we demonstrate that these E2-mediated changes require ERalpha, but not ERbeta. The repression of Txnip by E2 was also demonstrated in vitro in MCF-7 human breast cancer cells. This repression was blocked by treatment with the histone deacetylase inhibitor, trichostatin A, suggesting that repression by E2 may involve regulation of histone acetylation. We conclude that the rapid E2-mediated activation of the Txn pathway is an important step in the response of the mammalian uterus to estrogen.

Peroxiredoxin III, a mitochondrion-specific peroxidase, regulates apoptotic signaling by mitochondria

Various proapoptotic stimuli increase the production of superoxide and H(2)O(2) by mitochondria. Whereas superoxide impairs mitochondrial function and is removed by Mn(2+)-dependent superoxide dismutase, the role and metabolism of mitochondrial H(2)O(2) during apoptosis have remained unclear. The effects on apoptotic signaling of depletion of peroxiredoxin (Prx) III, a mitochondrion-specific H(2)O(2)-scavenging enzyme, have now been investigated by RNA interference in HeLa cells. Depletion of Prx III resulted in increased intracellular levels of H(2)O(2) and sensitized cells to induction of apoptosis by staurosporine or TNF-alpha. The rates of mitochondrial membrane potential collapse, cytochrome c release, and caspase activation were increased in Prx III-depleted cells, and these effects were reversed by ectopic expression of Prx III or mitochondrion-targeted catalase. Depletion of Prx III also exacerbated damage to mitochondrial macromolecules induced by the proapoptotic stimuli. Our results suggest that Prx III is a critical regulator of the abundance of mitochondrial H(2)O(2), which itself promotes apoptosis in cooperation with other mediators of apoptotic signaling.

Construction of eukaryotic expression plasmid of human PRX3 and its expression in HEK-293FT cells

To construct the eukaryotic expression plasmid of human PRX3 and measure its expression in the HEK-293FT cells, the full-length coding region of human PRX3 was cloned by PCR and inserted into the eukaryotic expression vector pcDNA4-Xpress (A). HEK-293FT cells were transiently transfected with the recombinant plasmid. Western blot and immuofluorescence were used to detect the expression of the fusion protein. In the experiment, restriction analysis identified the construction of the recombinant plasmid and the inserted sequence was identical with that published on GenBank. Western blot and immunofluorescence confirmed the expression of the recombinant protein in transfected HEK-293FT cells. It was concluded that the eukaryotic expression plasmid of human PRX3 was constructed successfully and the recombinant could be expressed efficiently in HEK-293FT cells, which provides a sound basis for the further study on human PRX3.

Multiple organ pathology, metabolic abnormalities and impaired homeostasis of reactive oxygen species in Epas1-/- mice

Hypoxia-inducible factor (HIF) transcription factors respond to multiple environmental stressors, including hypoxia and hypoglycemia. We report that mice lacking the HIF family member HIF-2alpha (encoded by Epas1) have a syndrome of multiple-organ pathology, biochemical abnormalities and altered gene expression patterns. Histological and ultrastructural analyses showed retinopathy, hepatic steatosis, cardiac hypertrophy, skeletal myopathy, hypocellular bone marrow, azoospermia and mitochondrial abnormalities in these mice. Serum and urine metabolite studies showed hypoglycemia, lactic acidosis, altered Krebs cycle function and dysregulated fatty acid oxidation. Biochemical assays showed enhanced generation of reactive oxygen species (ROS), whereas molecular analyses indicated reduced expression of genes encoding the primary antioxidant enzymes (AOEs). Transfection analyses showed that HIF-2alpha could efficiently transactivate the promoters of the primary AOEs. Prenatal or postnatal treatment of Epas1-/- mice with a superoxide dismutase (SOD) mimetic reversed several aspects of the null phenotype. We propose a rheostat role for HIF-2alpha that allows for the maintenance of ROS as well as mitochondrial homeostasis.

Mitochondrial peroxiredoxin-3 protects hippocampal neurons from excitotoxic injury in vivo

Mitochondria are involved in excitotoxic damage of nerve cells. Following the breakdown of the calcium-buffering ability of mitochondria, mitochondrial calcium overload induces reactive oxygen species (ROS) bursts that produce free radicals and open permeability transition pores, ultimately leading to neuronal cell death. In the present study, we focused on a mitochondrial antioxidant protein, peroxiredoxin-3 (Prx-3), to investigate the mechanism by which toxic properties of ROS were up-regulated in mitochondria of damaged nerve cells. Immunohistochemical analysis revealed that Prx-3 protein exists in mitochondria of rat hippocampus, whereas we found a significant decrease in Prx-3 mRNA and protein levels associated with an increase in nitrated proteins in the rat hippocampus injured by microinjection of ibotenic acid. Furthermore, in vivo adenoviral gene transfer of Prx-3 completely inhibited protein nitration and markedly reduced gliosis, a post-neuronal cell death event. Since mitochondrial Prx-3 seems to be neuroprotective against oxidative insults, our findings suggest that Prx-3 up-regulation might be a useful novel approach for the management of neurodegenerative diseases.

Increased expression of mitochondrial peroxiredoxin-3 (thioredoxin peroxidase-2) protects cancer cells against hypoxia and drug-induced hydrogen peroxide-dependent apoptosis

Peroxiredoxin-3 (Prdx3) is a mitochondrial member of the antioxidant family of thioredoxin peroxidases that uses mitochondrial thioredoxin-2 (Trx2) as a source of reducing equivalents to scavenge hydrogen peroxide (H(2)O(2)). Low levels of H(2)O(2) produced by the mitochondria regulate physiological processes, including cell proliferation, while high levels of H(2)O(2) are toxic to the cell and cause apoptosis. WEHI7.2 thymoma cells with stable overexpression of Prdx3 displayed decreased levels of cellular H(2)O(2) and decreased cell proliferation without a change in basal levels of apoptosis. Prdx3-transfected cells showed a marked resistance to hypoxia-induced H(2)O(2) formation and apoptosis. Prdx3 overexpression also protected the cells against apoptosis caused by H(2)O(2), t-butylhydroperoxide, and the anticancer drug imexon, but not by dexamethasone. Thus, mitochondrial Prdx3 is an important cellular antioxidant that regulates physiological levels of H(2)O(2), leading to decreased cell growth while protecting cells from the apoptosis-inducing effects of high levels of H(2)O(2).

Enhancement of mitochondrial oxidative stress and up-regulation of antioxidant protein peroxiredoxin III/SP-22 in the mitochondria of human pre-eclamptic placentae

A growing body of evidence indicates that the pathogenesis of pre-eclampsia is closely associated with oxidative stress occurring in mitochondria. In the present study, we evaluated the degree of mitochondrial lipid peroxidation by assessing the accumulation of 4-hydroxy-2-nonenal (HNE)-modified proteins and examined the expression of mitochondrial antioxidant protein peroxiredoxin III/SP-22 in normal and pre-eclamptic human placentae. The accumulation of HNE-modified proteins increased to a greater extent in both the mitochondria and cytosol of pre-eclamptic placentae than in those of normal placentae. Moreover, the accumulation of HNE-modified proteins was much more evident in the mitochondria than in the cytosol, indicating that lipid peroxidation occurred mainly in the mitochondria of pre-eclamptic placentae. The mRNA expression of peroxiredoxin III/SP-22 was increased about 2-fold in pre-eclamptic placentae compared to normal placentae. The protein levels of peroxiredoxin III/SP-22 were approximately 4-fold higher in pre-eclamptic placentae than in normal placentae. Immunohistochemistry of placental tissues showed that the levels of peroxiredoxin III/SP-22 protein were increased in the trophoblasts of floating villi, stromal cells of stem villi, and decidual cells in pre-eclamptic placentae. These results indicate that peroxiredoxin III/SP-22 plays a crucial role in the protection of placental function from oxidative stress occurring in mitochondria of pre-eclamptic placentae.

Peroxiredoxin II is essential for sustaining life span of erythrocytes in mice

Peroxiredoxins (Prxs) are a family of antioxidant proteins that reduce peroxide levels by using reducing agents such as thioredoxin. These proteins were characterized to have a number of cellular functions, including cell proliferation and differentiation and protection of specific proteins from oxidative damage. However, the physiological roles of the peroxiredoxins have not been determined. To clarify the physiological relevance of this protein type, we generated a mouse model deficient in Prx II, which is abundantly expressed in all types of cells. The Prx II-/- mice were healthy in appearance and fertile. However, they had splenomegaly caused by the congestion of red pulp with hemosiderin accumulation. Heinz bodies were detected in their peripheral blood, and morphologically abnormal cells were elevated in the dense red blood cell (RBC) fractions, which contained markedly higher levels of reactive oxygen species (ROS). The Prx II-/- mice had significantly decreased hematocrit levels, but increased reticulocyte counts and erythropoietin levels, indicative of a compensatory action to maintain hematologic homeostasis in the mice. In addition, a labeling experiment with the thiol-modifying reagent biotinylated iodoacetamide (BIAM) in Prx II-/- mice revealed that a variety of RBC proteins were highly oxidized. Our results suggest that Prx II-/- mice have hemolytic anemia and that Prx II plays a major role in protecting RBCs from oxidative stress in mice.

Identification of galectin I and thioredoxin peroxidase II as two arsenic-binding proteins in Chinese hamster ovary cells

In this study, we report the identification of two arsenic-binding proteins from Chinese hamster ovary (CHO) cells. The crude extract derived from CHO and SA7 (arsenic-resistant CHO cells) was applied to a phenylarsine oxide-agarose affinity column, and after extensive washing, the absorbed proteins were eluted with buffers containing 20 mM 2-mercaptoethanol (2-ME) or dithiothreitol (DTT). Three differentially expressed proteins, galectin 1 (Gal-1; in the 2-ME-eluted fraction from CHO cells), glutathione S-transferase P-form (GST-P) and thioredoxin peroxidase II (TPX-II), respectively in the 2-ME- and DTT-eluted fractions from SA7 cells, were identified by partial amino acid sequence analysis after separation by SDS/PAGE. The GST-P protein has been previously shown to facilitate the excretion of sodium arsenite [As(III)] from SA7 cells. TPX II was detected predominately in SA7 cells [routinely cultured in As(III)-containing medium], but not in CHO or SA7N (a revertant of SA7 cells cultured in regular medium) cells. In contrast, Gal-1 was specifically identified in CHO and SA7N cells, but not in SA7 cells. The preferential expression of Gal-1 in CHO cells and TPX-II in SA7 cells was further illustrated by quantitative PCR analysis. The binding of Gal-1 and TPX-II with As(III) was further verified by both co-immunoprecipitation and co-elution of Gal-1 and TPX-II with As(III). It is suggested that Gal-1 and TPX-II are two proteins that serve as high-affinity binding sites for As(III) and thus both may be involved in the biological action of As(III).

Cyclic GMP-dependent protein kinase regulates the expression of thioredoxin and thioredoxin peroxidase-1 during hormesis in response to oxidative stress-induced apoptosis

Human neuroblastoma cells, SH-SY5Y, contain relatively low levels of thioredoxin (Trx); thus, they serve favorably as a model for studying oxidative stress-induced apoptosis (Andoh, T., Chock, P. B., and Chiueh, C. C. (2001) J. Biol. Chem. 277, 9655-9660). When these neurotrophic cells were subjected to nonlethal 2-h serum deprivation, their neuronal nitric oxide synthase and Trx were up-regulated, and the cells became more tolerant of oxidative stress, indicating that NO may protect cells from serum deprivation-induced apoptosis. Here, the mechanism by which NO exerts its protective effects was investigated. Our results reveal that in SH-SY5Y cells, NO inhibits apoptosis through its ability to activate guanylate cyclase, which in turn activates the cGMP-dependent protein kinase (PKG). The activated PKG is required to protect cells from lipid peroxidation and apoptosis, to inhibit caspase-9 and caspase-3 activation, and to elevate the levels of Trx peroxidase-1 and Trx, which subsequently induces the expression of Bcl-2. Furthermore, active PKG promotes the elevation of c-Jun, phosphorylated MAPK/ERK1/2, and c-Myc, consistent with the notion that PKG enhances the expression of Trx through its c-Myc-, AP-1-, and PEA3-binding motifs. Elevation of Trx and Trx peroxidase-1 and Mn(II)-superoxide dismutase would reduce H(2)O(2) and O(2)(), respectively. Thus, the cytoprotective effect of NO in SH-SY5Y cells appears to proceed via the PKG-mediated pathway, and S-nitrosylation of caspases plays a minimal role.

Mixed lineage kinase LZK and antioxidant protein-1 activate NF-kappaB synergistically

Leucine zipper-bearing kinase (LZK) is a novel member of the mixed lineage kinase (MLK) family [Sakuma, H., Ikeda, A., Oka, S., Kozutsumi, Y., Zanetta, J. P., and Kawasaki, T. (1997) J. Biol. Chem.272, 28622-28629]. We have previously shown that LZK activates the c-Jun-NH2 terminal kinase (JNK) pathway, but not the extracellular signal-related kinase (ERK) pathway, by acting as a mitogen-activated protein kinase kinase kinase (MAPKKK) [Ikeda, A., Hasegawa, K., Masaki, M., Moriguchi, T., Nishida, E., Kozutsumi, Y., Oka, S., and Kawasaki, T. (2001) J. Biochem.130, 773-781]. However, the mode of activation of LZK remains largely unknown. By means of a yeast two-hybrid screening system, we have identified a molecule localized to mitochondria, antioxidant protein-1 (AOP-1), that binds to LZK and which acts as a modulator of LZK activity. Recently, several MAPKKKs involved in the JNK pathway, such as MEKK1, TAK1 and MLK3, were shown, using over-expression assay systems, to activate a transcription factor, NF-kappaB, through activation of the IKK complex. Using similar assay systems, we demonstrated that LZK activated NF-kappaB-dependent transcription through IKK activation only weakly, but this was reproducible, and that AOP-1 enhanced the LZK-induced NF-kappaB activation. We also provided evidence that LZK was associated directly with the IKK complex through the kinase domain, and that AOP-1 was recruited to the IKK complex through the binding to LZK.

Overexpression of mitochondrial thioredoxin reductase and peroxiredoxin III in hepatocellular carcinomas

Thioredoxin reductase 2 (TrxR2), thioredoxin II (Trx II) and peroxiredoxin III (Prx III) are specifically localized in mitochondria and believed to play important roles in the regulation of cellular redox status by serving as a primary line of defense against H2O2 produced during respiration. Substantial evidence indicates that the alteration of cellular redox status is a critical factor involved in cell growth and death and results in tumorigenesis. We therefore investigated the expression of TrxR2 and Prx III in 58 paraffin-embedded hepatocellular carcinoma tissues by immunohistochemistry. The labeling indices of TrxR2 and Prx III were significantly higher in tumor tissues than in the corresponding adjacent normal tissues. In 39 (67.2%) out of 58 samples, the levels of TrxR2 expression were higher in tumor tissues than in corresponding adjacent normal tissues, while 11 samples (19.0%) showed lower expression in tumor tissues. Prx III expression was increased in tumor tissues of 23 samples (39.7%) compared to adjacent normal tissues and were decreased in 18 samples (31.0%). These results suggest that alterations in cellular redox status by enhanced expression of TrxR2 and/or Prx III might be associated with the formation and development of hepatocellular carcinomas.

[The BCL-xL and ACR-1 genes promote differentiation and reduce apoptosis in muscle fibers of mdx mice]

The effects of the human BCL-xL and ACR-1 genes on dystrophin expression in cross-striated muscle fibers (CSMF) and on CSMF viability were studied in mdx mice after ballistic cotransfection with the human dystrophin minigene. In control mice, the proportion of dystrophin-positive (D(+)) and dying CSMF were 2.1 +/- 0.1 and 2.1 +/- 0.3%, respectively. Introduction of the dystrophin minigene (20 micrograms of the pSG5dys plasmid) increased the proportions of D(+) and dying CSMF to 5.6 +/- 1.4% and 4.5 +/- 0.9%, respectively. When pSG5dys was introduced along with the pSFFV-Neo plasmid carrying the BCL-xL gene (10 micrograms of each plasmid per shot), the death of CSMF decreased to 3.7 +/- 1% and the proportion of D(+) CSMF significantly (P < 0.05) increased to 12.2 +/- 2.2%. Contransfection with the dystrophin minigene and the BCL-xL gene at 20 micrograms of each plasmid per shot did not stimulate generation of D(+) CSMF, but did reduce the CSMF death to 1.5 +/- 0.3%. Introduction of pSG5dys along with the pRc-CMV-10.1 plasmid containing the ACR-1 gene (10 micrograms of each plasmid per shot) reduced the proportion of D(+) CSMF to 1.1 +/- 0.5% and significantly reduced the proportion of dying CSMF to 0.9 +/- 0.3% as compared with the proportions observed in intact mice or in mice subjected to transfection with pSG5dys. Introduction of the pSG5dys plasmid substantially reduced the proportion of CSMF with peripheral nuclei, suggesting disturbed CSMF differentiation. After cotransfection with the human-dystrophin minigene, the BCL-xL and ACR-1 genes did not affect the extent of CSMF differentiation as compared with that observed in the case of the dystrophin minigene alone. Thus, ballistic transfection of mdx mice with the human dystrophin gene used along with the BCL-xL or ACR-1 gene was shown to suppress the death of muscle fibers and to expedite dystrophin synthesis and cell differentiation.

Molecular and enzymatic characterisation of Schistosoma mansoni thioredoxin

Defense against oxidative damage can be mediated through glutathione and/or thioredoxin utilising systems. Here, we report the identification and characterisation of a thioredoxin from Schistosoma mansoni. The predicted protein has similarity to previously characterised thioredoxins including conservation of the redox active site. Recombinant six-histidine tagged schistosome thioredoxin had insulin reduction activity and supported the enzymatic function of thioredoxin reductase and thioredoxin peroxidase. By Western blotting, all mammalian stages of the schistosome lifecycle expresses thioredoxin. Thioredoxin is present in egg secretory products and antibodies against the recombinant protein produce the circumoval precipitin reaction. This is the first identification of defined antigen producing this reaction. Furthermore, thioredoxin is a novel egg immunogen as it elicits an antibody response in schistosome-infected mice. The most significant IgG production against thioredoxin occurs after parasite oviposition commences. These observations suggest that thioredoxin participates in processes vital to the parasite and may facilitate the passage and survival of eggs across inflamed host tissues.

DNA microarray reveals increased expression of thioredoxin peroxidase in thioredoxin-1 transfected cells and its functional consequences

The mammalian thioredoxins are a family of small redox proteins that undergo NADPH dependent reduction by thioredoxin reductase. Reduced thioredoxins reduce oxidized cysteine groups on proteins including transcription factors to increase their binding to DNA, and is a source of reducing equivalents for enzymes such as thioredoxin peroxidase which removes H2O2 and alkyl peroxides. Thioredoxin-1 is over expressed in many human tumors where it is associated with aggressive tumor growth, inhibited apoptosis and decreased patient survival. Transfection of cells with thioredoxin-1 has been shown to increase cell growth and inhibit apoptosis. We have used DNA micro array to investigate the effects of thioredoxin-1 transfection on the expression of a panel of 520 redox, apoptosis and cell growth related genes in MCF-7 human breast cancer cells. One of the genes whose expression was increased as a result of thioredoxin-1 over expression was thioredoxin peroxidase-2. This increase was confirmed by Northern blotting. Transfection of mouse WEHI7.2 thymoma cells with human thioredoxin peroxidase-2 was found to protect the cells from apoptosis induced by H2O2 but not from apoptosis induced by dexamethasone, doxorubicin or etoposide. Thus, increased thioredoxin peroxidase-2 expression does not explain the widespread antiapoptotic effects of thioredoxin-1.

Proteomics analysis of cellular response to oxidative stress. Evidence for in vivo overoxidation of peroxiredoxins at their active site

The proteomics analysis reported here shows that a major cellular response to oxidative stress is the modification of several peroxiredoxins. An acidic form of the peroxiredoxins appeared to be systematically increased under oxidative stress conditions. Peroxiredoxins are enzymes catalyzing the destruction of peroxides. In doing so, a reactive cysteine in the peroxiredoxin active site is weakly oxidized (disulfide or sulfenic acid) by the destroyed peroxides. Cellular thiols (e.g. thioredoxin) are used to regenerate the peroxiredoxins to their active state. Tandem mass spectrometry was carried out to characterize the modified form of the protein produced in vivo by oxidative stress. The cysteine present in the active site was shown to be oxidized into cysteic acid, leading to an inactivated form of peroxiredoxin. This strongly suggested that peroxiredoxins behave as a dam upon oxidative stress, being both important peroxide-destroying enzymes and peroxide targets. Results obtained in a primary culture of Leydig cells challenged with tumor necrosis factor alpha suggested that this oxidized/native balance of peroxiredoxin 2 may play an active role in resistance or susceptibility to tumor necrosis factor alpha-induced apoptosis.

The c-Myc target gene PRDX3 is required for mitochondrial homeostasis and neoplastic transformation

Deregulated expression of the c-Myc transcription factor is found in a wide variety of human tumors. Because of this significant role in oncogenesis, considerable effort has been devoted to elucidating the molecular program initiated by deregulated c-myc expression. The primary transforming activity of Myc is thought to arise through transcriptional regulation of numerous target genes. Thus far, Myc target genes involved in mitochondrial function have not been characterized in depth. Here, we describe a nuclear c-Myc target gene, PRDX3, which encodes a mitochondrial protein of the peroxiredoxin gene family. Expression of PRDX3 is induced by the mycER system and is reduced in c-myc(-/-) cells. Chromatin immunoprecipitation analysis spanning the entire PRDX3 genomic sequence reveals that Myc binds preferentially to a 930-bp region surrounding exon 1. We show that PRDX3 is required for Myc-mediated proliferation, transformation, and apoptosis after glucose withdrawal. Results using mitochondria-specific fluorescent probes demonstrate that PRDX3 is essential for maintaining mitochondrial mass and membrane potential in transformed rat and human cells. These data provide evidence that PRDX3 is a c-Myc target gene that is required to maintain normal mitochondrial function.