Variable overoxidation of peroxiredoxins in human lung cells in severe oxidative stress

NHLRC2 expression is increased in idiopathic pulmonary fibrosis

BACKGROUND

Variants of NHL repeat-containing protein 2 (NHLRC2) have been associated with severe fibrotic interstitial lung disease in early childhood and NHLRC2 has been listed as a differentially expressed gene between rapidly and slowly progressing idiopathic pulmonary fibrosis (IPF) patients. However, its cell type-specific localization in human lung tissue is unknown. The aim of this study was to evaluate NHLRC2 mRNA and protein expression in different cell types of lung tissue samples and to investigate the effect of transforming growth factor (TGF)-β1 exposure on NHLRC2 expression in vitro.

METHODS

The NHLRC2 expression in lung tissue samples was studied by immunohistochemistry (50 IPF, 10 controls) and mRNA in situ hybridization (8 IPF, 3 controls). The immunohistochemical NHLRC2 expression was quantified with image analysis software and associated with the clinical and smoking data of the patients. NHLRC2 expression levels in primary stromal and small airway epithelial cell lines after exposure to TGF-β1 was measured by quantitative reverse transcription polymerase chain reaction and Western blot analysis.

RESULTS

NHLRC2 expression was detected especially in bronchiolar epithelial cells, type II pneumocytes and macrophages in normal lung. In the lungs of IPF patients, NHLRC2 was mainly expressed in hyperplastic alveolar epithelial cells lining fibroblast foci and honeycombs. NHLRC2 expression assessed by image analysis was higher in IPF compared to controls (p < 0.001). Ever-smokers had more prominent NHLRC2 staining than non-smokers (p = 0.037) among IPF patients. TGF-β1 exposure did not influence NHLRC2 levels in lung cell lines.

CONCLUSIONS

NHLRC2 expression was higher in IPF compared to controls being widely expressed in type II pneumocytes, macrophages, bronchiolar epithelium, and hyperplastic alveolar epithelium. Additionally, its expression was not regulated by the exposure to TGF-β1 in vitro. Further studies are needed to clarify the role of NHLRC2 in IPF.

Redox Regulation in Aging Lungs and Therapeutic Implications of Antioxidants in COPD

Mammals, including humans, are aerobic organisms with a mature respiratory system to intake oxygen as a vital source of cellular energy. Despite the essentiality of reactive oxygen species (ROS) as byproducts of aerobic metabolism for cellular homeostasis, excessive ROS contribute to the development of a wide spectrum of pathological conditions, including chronic lung diseases such as COPD. In particular, epithelial cells in the respiratory system are directly exposed to and challenged by exogenous ROS, including ozone and cigarette smoke, which results in detrimental oxidative stress in the lungs. In addition, the dysfunction of redox regulation due to cellular aging accelerates COPD pathogenesis, such as inflammation, protease anti-protease imbalance and cellular apoptosis. Therefore, various drugs targeting oxidative stress-associated pathways, such as thioredoxin and N-acetylcysteine, have been developed for COPD treatment to precisely regulate the redox system. In this review, we present the current understanding of the roles of redox regulation in the respiratory system and COPD pathogenesis. We address the insufficiency of current COPD treatment as antioxidants and discuss future directions in COPD therapeutics targeting oxidative stress while avoiding side effects such as tumorigenesis.

Downregulation of peroxiredoxin II suppresses the proliferation and metastasis of gastric cancer cells

Peroxiredoxin (Prx) II is an imperative member of the superfamily of peroxidases. It serves an essential role in scavenging organic hydroperoxide and H2O2. It is involved in the development of various malignant tumors. In order to investigate the significance of Prx II expressions level in gastric cancer (GC), downregulation of Prx II was performed to investigate its role in the proliferation and migration of gastric adenocarcinoma cells. In GC cells and 45 GC specimens, the mRNA and protein expression levels of Prx II were determined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. The Prx II expression profile in another 116 GC specimens was also detected with immunohistochemistry (IHC). The changes in the proliferation and migration of MKN45 and MGC-803 cells folllowing transfection with small interfering RNA (siRNA) were detected by cell counting kit (CCK)-8, western blot analysis, and Transwell migration and invasion assays. The results revealed that the expression of Prx II in GC tissues and GC cells were significantly upregulated compared with the normal control. There was a significant association between the expression level of Prx II and various factors, including tumor size, histological differentiation, the depth of invasion, the stage of tumor-node-metastasis (TNM) and lymph node metastasis in GC (P<0.05). Survival in patients with higher Prx II expression was significantly decreased compared with those with lower Prx II expression (P<0.01). Prx II, depth of invasion, lymph node metastasis and distant metastasis were identified as independent prognosis factors of GC (P<0.05). Knockdown of Prx II significantly suppressed the proliferation and the migration of GC cells. These experiments revealed that Prx II promotes the development of GC, affecting the survival of patients with GC.

Identification of vitamin D sensitive pathways during lung development

BACKGROUND

We have previously shown that vitamin D deficiency has a detrimental impact on lung development. In this study, we aimed to identify the mechanisms linking vitamin D with lung development using a mouse model of dietary manipulation.

METHODS

Female offspring were euthanized at different time-points; embryonic day (E)14.5, E17.5 or postnatal day (P)7. Lung tissue was collected for mass spectrometry-based proteomic analysis. Label-free quantitation was used to identify the differentially expressed proteins and ELISA confirmed the expression of selected proteins. Lungs from separate groups of mice were fixed and processed for stereological assessment of lung structure.

RESULTS

No differences in protein expression between vitamin D deficient and replete mice were detected at E14.5 and E17.5, whereas 66 proteins were differentially expressed in P7 lungs. The expression of pulmonary surfactant-associated protein B (SP-B) and peroxiredoxin 5 (PRDX5) were reduced in P7 lungs of vitamin D deficient mice, while the production of collagen type Ι alpha 1 (COL1A1) was higher in lungs of vitamin D deficient mice. There were no differences in lung volume, parenchymal volume, volume of airspaces or surface area of airspaces between vitamin D deficient and vitamin D replete mice across three time-points.

CONCLUSIONS

The difference in protein expression during the early postnatal time-point suggests that vitamin D deficiency may induce alterations of lung structure and function in later life during alveolarization stage through impaired pulmonary surfactant production and anti-oxidative stress ability as well as enhanced collagen synthesis. These data provided a plausible mechanism linking maternal vitamin D deficiency with altered postnatal lung function.

MicroRNA-26a-5p and microRNA-23b-3p up-regulate peroxiredoxin III in acute myeloid leukemia

MicroRNAs (miRNAs) are small RNAs that regulate target gene expression. Using microarray-based miRNA expression profiling, we compared the miRNA expression in granulocytes from four patients with acute myeloid leukemia and four healthy controls. Thirty-four miRNAs were found to be differentially expressed, including 20 miRNAs that were up-regulated and 14 miRNAs that were down-regulated. The expression of selected miRNAs (miR-26a-5p and miR-23b-3p) was independently validated in 20 patients and 12 healthy controls. Notably, we demonstrated that peroxiredoxin III (PrxIII) is a common direct target of both miR-26a-5p and miR-23b-3p. Furthermore, these results indicate that the two decreased miRNAs could scavenge cellular reactive oxygen species (ROS) by targeting the PrxIII gene. These findings are discussed with regard to the known function of PrxIII as a ROS scavenger and the high endogenous ROS levels required for hematopoietic stem cell differentiation. These findings may potentially offer insights into the pathological relationships between miR-26a-5p, miR-23b-3p and leukemogenesis.

Keratinocyte growth factor and glucocorticoid induction of human peroxiredoxin 6 gene expression occur by independent mechanisms that are synergistic

AIMS

Peroxiredoxin 6 (Prdx6), a 1-cys Prdx has both peroxidase and phospholipase A2 activities, protecting against oxidative stress and regulating pulmonary surfactant phospholipid metabolism. This study determined the mechanism by which keratinocyte growth factor (KGF) and the glucocorticoid analogue, dexamethasone (Dex), induce increased Prdx6 expression.

RESULTS

Transcriptional activation by KGF in both A549 lung adenocarcinoma cells and rat lung alveolar epithelial type II (ATII) cells utilizes an antioxidant response element (ARE), located between 357 and 349 nucleotides before the PRDX6 translational start, that is also necessary for upregulation of the human PRDX6 promoter in response to oxidative stress. Activation is mediated by binding of the transcription factor, Nrf2, to the ARE as shown by experiments using siRNA against Nrf2 and by transfecting ATII cells isolated from lungs of Nrf2 null mice. KGF triggers the migration of Nrf2 from cytoplasm to nucleus where it binds to the PRDX6 promoter as shown by chromatin immunoprecipitation assays. Activation of transcription by Dex occurs through a glucocorticoid response element located about 750 nucleotides upstream of the PRDX6 translational start.

INNOVATION

This study demonstrates that KGF can activate an ARE in a promoter without reactive oxygen species involvement and that KGF and Dex can synergistically activate the PRDX6 promoter and protect cells from oxidative stress.

CONCLUSION

These two different activators work through different DNA elements. Their combined effect on transcription of the reporter gene is synergistic; however, at the protein level, the combined effect is additive and protects cells from oxidative damage.

Glutathione redox control of asthma: from molecular mechanisms to therapeutic opportunities

Asthma is a chronic inflammatory disorder of the airways associated with airway hyper-responsiveness and airflow limitation in response to specific triggers. Whereas inflammation is important for tissue regeneration and wound healing, the profound and sustained inflammatory response associated with asthma may result in airway remodeling that involves smooth muscle hypertrophy, epithelial goblet-cell hyperplasia, and permanent deposition of airway extracellular matrix proteins. Although the specific mechanisms responsible for asthma are still being unraveled, free radicals such as reactive oxygen species and reactive nitrogen species are important mediators of airway tissue damage that are increased in subjects with asthma. There is also a growing body of literature implicating disturbances in oxidation/reduction (redox) reactions and impaired antioxidant defenses as a risk factor for asthma development and asthma severity. Ultimately, these redox-related perturbations result in a vicious cycle of airway inflammation and injury that is not always amenable to current asthma therapy, particularly in cases of severe asthma. This review will discuss disruptions of redox signaling and control in asthma with a focus on the thiol, glutathione, and reduced (thiol) form (GSH). First, GSH synthesis, GSH distribution, and GSH function and homeostasis are discussed. We then review the literature related to GSH redox balance in health and asthma, with an emphasis on human studies. Finally, therapeutic opportunities to restore the GSH redox balance in subjects with asthma are discussed.

Profiling the erythrocyte membrane proteome isolated from patients diagnosed with chronic obstructive pulmonary disease

Structural and metabolic alterations in erythrocytes play an important role in the pathophysiology of Chronic Obstructive Pulmonary Disease (COPD). Whether these dysfunctions are related to the modulation of erythrocyte membrane proteins in patients diagnosed with COPD remains to be determined. Herein, a comparative proteomic profiling of the erythrocyte membrane fraction isolated from peripheral blood of smokers diagnosed with COPD and smokers with no COPD was performed using differential (16)O/(18)O stable isotope labeling. A total of 219 proteins were quantified as being significantly differentially expressed within the erythrocyte membrane proteomes of smokers with COPD and healthy smokers. Functional pathway analysis showed that the most enriched biofunctions were related to cell-to-cell signaling and interaction, hematological system development, immune response, oxidative stress and cytoskeleton. Chorein (VPS13A), a cytoskeleton related protein whose defects had been associated with the presence of cell membrane deformation of circulating erythrocytes was found to be down-regulated in the membrane fraction of erythrocytes obtained from COPD patients. Methemoglobin reductase (CYB5R3) was also found to be underexpressed in these cells, suggesting that COPD patients may be at higher risk for developing methemoglobinemia. This article is part of a Special Issue entitled: Integrated omics.

Molecular Cloning and Sequence Analysis of Peroxiredoxin cDNA from American White Shrimp (Litopenaeus vannamei)

Peroxiredoxin (Prx) is an antioxidant protein, which protects organisms against various oxidative stresses. In this study, we isolated Peroxiredoxin cDNA from the muscle tissues of American white shrimp, Litopenaeus vannamei, using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The full-length cDNA consists of 962-bp, which includes a 49-bp 5′-untranslated region (UTR), a 316-bp 3′-untranslated region, and a 597-bp open reading frame (ORF) encoding 198 amino acids. The signal peptide sequence was not found in this cDNA. We aligned the deduced amino acid sequence with the known amino acid sequences of Fenneropenaeus indicus, Fenneropenaeus chinensis, Marsupenaeus japonicus, Scylla serrata, Drosophila melanogaster, Bos taurus, Branchiostoma belcheri, Anoplopoma fimbria, and Rattus norvegicus, and the sequence similarities scores were found to be 97%, 96%, 95%, 83%, 72%, 70%, 80%, 81%, and 75%, respectively. We also found 2-cysteine (Cys) residues in this peroxiredoxin sequence. The RT-PCR analysis revealed that the peroxiredoxin mRNA was expressed in the gills, hepatopancreas, muscles, intestine, and hemocytes. Studies using this newly cloned peroxiredoxin gene from Litopenaeus vannamei will add to the existing knowledge base on the physiological role of peroxiredoxin in shrimp species.

Cullin 4B protein ubiquitin ligase targets peroxiredoxin III for degradation

Cullin 4B (CUL4B) is a scaffold protein that assembles cullin-RING ubiquitin ligase (E3) complexes. Recent studies have revealed that germ-line mutations in CUL4B can cause mental retardation, short stature, and many other abnormalities in humans. Identifying specific CUL4B substrates will help to better understand the physiological functions of CUL4B. Here, we report the identification of peroxiredoxin III (PrxIII) as a novel substrate of the CUL4B ubiquitin ligase complex. Two-dimensional gel electrophoresis coupled with mass spectrometry showed that PrxIII was among the proteins up-regulated in cells after RNAi-mediated CUL4B depletion. The impaired degradation of PrxIII observed in CUL4B knockdown cells was confirmed by Western blot. We further demonstrated that DDB1 and ROC1 in the DDB1-CUL4B-ROC1 complex are also indispensable for the proteolysis of PrxIII. In addition, the degradation of PrxIII is independent of CUL4A, a cullin family member closely related to CUL4B. In vitro and in vivo ubiquitination assays revealed that CUL4B promoted the polyubiquitination of PrxIII. Furthermore, we observed a significant decrease in cellular reactive oxygen species (ROS) production in CUL4B-silenced cells, which was associated with increased resistance to hypoxia and H(2)O(2)-induced apoptosis. These findings are discussed with regard to the known function of PrxIII as a ROS scavenger and the high endogenous ROS levels required for neural stem cell proliferation. Together, our study has identified a specific target substrate of CUL4B ubiquitin ligase that may have significant implications for the pathogenesis observed in patients with mutations in CUL4B.

Protein Signatures in Human MDA-MB-231 Breast Cancer Cells Indicating a More Invasive Phenotype Following Knockdown of Human Endometase/Matrilysin-2 by siRNA

Human matrix metalloproteinase-26 (MMP-26/endometase/matrilysin-2) is a putative biomarker for carcinomas of breast, prostate, and other cancers of epithelial origin. MMP-26 expression was silenced using small interfering RNA (siRNA) in the human breast cancer cell line MDA-MB-231. Immunological and proteomics approaches, including two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry, were employed to identify differential protein expression in MMP-26 knockdown cells. A comparison of the protein expression profiles of control and MMP-26 knockdown cells revealed nine differentially regulated proteins. Five of the proteins (heat shock protein 90, glucose-regulated protein 78 (GRP78), annexin V, tropomyosin, and peroxiredoxin II) were up-regulated, while alpha-tubulin, cystatin SA-III, breast cancer metastasis suppressor 1 (BRMS1) and beta-actin were down-regulated. This decrease of BRMS1 expression is concomitant with an increase of invasion through matrix-coated membranes. These results suggest an important role for MMP-26 in the regulation of proteins involved in invasive and metastatic breast cancers.

Peroxiredoxin 6 differentially regulates acute and chronic cigarette smoke&#x2013;mediated lung inflammatory response and injury

Peroxiredoxin 6 (Prdx6) exerts its protective role through peroxidase activity against H₂O₂ and phospholipid hydroperoxides. We hypothesized that targeted disruption of Prdx6 would lead to enhanced susceptibility to cigarette smoke (CS)-mediated lung inflammation and/or emphysema in mouse lung. Prdx6 null (Prdx6⁻/⁻mice exposed to acute CS showed no significant increase of inflammatory cell influx or any alterations in lung levels of proinflammatory cytokines compared to wild-type (WT) mice. Lung levels of antioxidant enzymes were significantly increased in acute CS-exposed Prdx6⁻/⁻ compared to WT mice. Overexpressing (Prdx6⁻/⁻) mice exposed to acute CS showed significant decrease in lung antioxidant enzymes associated with increased inflammatory response compared to CS-exposed WT mice or air-exposed Prdx6⁻/⁻ mice. However, chronic 6 months of CS exposure resulted in increased lung inflammatory response, mean linear intercept (Lm), and alteration in lung mechanical properties in Prdx6⁻/⁻ when compared to WT mice exposed to CS. These data show that targeted disruption of Prdx6 does not lead to increased lung inflammatory response but is associated with increased antioxidants, suggesting a critical role of lung Prdx6 and several compensatory mechanisms during acute CS-induced adaptive response, whereas this protection is lost in chronic CS exposure leading to emphysema.

Peroxiredoxin 2 inhibits granulosa cell apoptosis during follicle atresia through the NFKB pathway in mice

Peroxiredoxin 2 (PRDX2) has been known to act as an antioxidant enzyme whose main function is H(2)O(2) reduction in cells. We aimed to study the expression patterns of PRDX2 in mouse ovaries and explore the function of this protein in apoptosis of granulosa cells (GCs). We found that the expression of the PRDX2 protein in atretic follicle GCs was markedly higher than in healthy follicle GCs. In vitro, the transfection of siRNA targeting the Prdx2 gene inhibited the proliferation and induced the apoptosis of primary cultured GCs. Furthermore, suppression of PRDX2 resulted in the augmentation of endogenous H(2)O(2), and the ability to eliminate the exogenous H(2)O(2) was attenuated. The expression of PRDX2 and nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB), whose activity was inhibited by binding to IKB, increased in GCs treated with various concentrations of H(2)O(2) for 30 min. However, no significant change in cytoplasmic IKB expression was observed. At 2 h after treatment with H(2)O(2), nuclear NFKB expression level was reduced, cytoplasmic IKB expression was increased, and PRDX2 expression was unchanged. Silencing of the Prdx2 gene caused early changes in NFKB and IKB expression in the primary cultured GCs compared to that in control cells. Taken together, these data suggest that PRDX2 plays an important role in inhibiting apoptosis in GCs and that PRDX2 actions may be related to the expression of NFKB and IKB.

Hemoglobin α and β are ubiquitous in the human lung, decline in idiopathic pulmonary fibrosis but not in COPD

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) are disorders of the lung parenchyma. They share the common denominators of a progressive nature and poor prognosis. The goal was to use non-biased proteomics to discover new markers for these diseases.

METHODS

Proteomics of fibrotic vs. control lung tissue suggested decreased levels of several spots in the lung specimens of IPF patients, which were identified as Hemoglobin (Hb) α and β monomers and Hbα complexes. The Hbα and β monomers and complexes were investigated in more detail in normal lung and lung specimens of patients with IPF and COPD by immunohistochemistry, morphometry and mass spectrometry (MS).

RESULTS

Both Hb monomers, in normal lung, were expressed especially in the alveolar epithelium. Levels of Hbα and β monomers and complexes were reduced/lost in IPF but not in the COPD lungs when compared to control lung. MS-analyses revealed Hbα modification at cysteine105 (Cysα105), preventing formation of the Hbα complexes in the IPF lungs. Hbα and Hbβ were expressed as complexes and monomers in the lung tissues, but were secreted into the bronchoalveolar lavage fluid and/or induced sputum supernatants as complexes corresponding to the molecular weight of the Hb tetramer.

CONCLUSIONS

The abundant expression of the oxygen carrier molecule Hb in the normal lung epithelium and its decline in IPF lung are new findings. The loss of Hb complex formation in IPF warrants further studies and may be considered as a disease-specific modification.

Mitochondrial peroxiredoxin 3 is more resilient to hyperoxidation than cytoplasmic peroxiredoxins

The Prxs (peroxiredoxins) are a family of cysteine-dependent peroxidases that decompose hydrogen peroxide. Prxs become hyperoxidized when a sulfenic acid formed during the catalytic cycle reacts with hydrogen peroxide. In the present study, Western blot methodology was developed to quantify hyperoxidation of individual 2-Cys Prxs in cells. It revealed that Prx 1 and 2 were hyperoxidized at lower doses of hydrogen peroxide than would be predicted from in vitro data, suggesting intracellular factors that promote hyperoxidation. In contrast, mitochondrial Prx 3 was considerably more resistant to hyperoxidation. The concentration of Prx 3 was estimated at 125 microM in the mitochondrial matrix of Jurkat T-lymphoma cells. Although the local cellular environment could influence susceptibility, purified Prx 3 was also more resistant to hyperoxidation, suggesting that despite having C-terminal motifs similar to sensitive eukaryote Prxs, other structural features must contribute to the innate resilience of Prx 3 to hyperoxidation.

Oxidant stress stimulates expression of the human peroxiredoxin 6 gene by a transcriptional mechanism involving an antioxidant response element

Peroxiredoxin 6 (Prdx6) is a unique antioxidant enzyme that can reduce phospholipid and other hydroperoxides. A549 cells, a human lung-derived cell line, express both Prdx6 and Nrf2, a transcription factor that binds to antioxidant-response elements (AREs) and promotes expression of antioxidant genes. Treatment of A549 cells with 500 microM H(2)O(2) increased Prdx6 mRNA levels 2.5-fold, whereas treatment with 400 microM H(2)O(2) or 200 microM tert-butylhydroquinone (t-BHQ) triggered a corresponding 2.5-fold increase in reporter gene activity in A549 cells transfected with the pSEAP2:Basic vector (BD Bioscience), containing 1524 nucleotides of the human Prdx6 promoter region. Deletion of a consensus ARE sequence present between positions 357 and 349 before the start of transcription led to a striking decrease in both basal and H(2)O(2)- or t-BHQ-induced activation in A549 cells and H(2)O(2)-induced activation in primary rat alveolar type II cells. Cotransfection with Nrf2 stimulated the Prdx6 promoter in an ARE-dependent manner, whereas it was negatively regulated by Nrf3. siRNA targeting Nrf2 down-regulated reporter gene expression, whereas siRNA targeting the Nrf2 repressor, Keap1, up-regulated it. Binding of Nrf2 to the ARE sequence in chromatin was confirmed by PCR after chromatin immunoprecipitation. These data demonstrate that the ARE within the Prdx6 promoter is a key regulator of basal transcription of the Prdx6 gene and of its inducibility under conditions of oxidative stress.

In vitro allergen challenge of peripheral blood induces differential gene expression in mononuclear cells of asthmatic patients: inhibition of cytosolic phospholipase A2alpha overcomes the asthma-associated response

BACKGROUND

Existing treatments for asthma are not effective in all patients and disease exacerbations are common, highlighting the need for increased understanding of disease mechanisms and novel treatment strategies. The leukotriene pathway including the enzyme responsible for arachidonic acid release from cellular phospholipids, cPLA(2)alpha, is a major contributor to asthmatic responses and an attractive target in asthma therapies.

OBJECTIVE

The study reported here investigates (a) the differential effects of in vitro exposure of peripheral blood mononuclear cells (PBMCs) to allergen between asthma and healthy subjects, and (b) the contribution of cPLA(2)alpha to these differences in gene expression.

METHODS

In vitro responses of asthma (N=26) and healthy (N=11) subject PBMC samples to allergen stimulation in the presence and absence of cPLA(2)alpha inhibition or 5-lipoxygenase inhibition were compared at the gene expression level using oligonucleotide arrays and at the protein level using ELISA.

RESULTS

Subject samples within both asthma and healthy groups showed allergen-dependent cytokine production and allergen-dependent gene expression changes, although transcriptional profiling identified 153 genes that were modulated significantly differently by allergen between asthma and healthy subjects. Among these were genes previously associated with asthma, but the majority (about 80%) have not previously been associated with asthma.

CONCLUSIONS

Transcriptional profiling elucidated novel gene expression differences between the asthmatic and healthy subject samples. Although 5-lipoxygenase inhibition did not significantly affect allergen-modulated gene expression, the inhibition of cPLA(2)alpha activity affected many of the allergen-dependent, asthma-associated gene expression changes.

Peroxiredoxin II expression and its association with oxidative stress and cell proliferation in human idiopathic pulmonary fibrosis

Oxidant burden has been suggested to be a contributor to the pathogenesis of idiopathic pulmonary fibrosis (IPF). The study focused on peroxiredoxin (Prx) II, an antioxidant that has been associated with platelet-derived growth factor (PDGF) signaling and consequent cell proliferation. Localization and expression of Prx II, PDGF receptors (PDGFRalpha, PDGFRbeta), Ki67, and nitrotyrosine were assessed in control (n=10) and IPF/usual interstitial pneumonia (UIP) (n=10) lung biopsies by immunohistochemistry and morphometry. Prx II oxidation was determined by standard and non-reducing Western blots, two-dimensional gel electrophoresis, and mass spectrometry. Prx II localized in the IPF/UIP epithelium and alveolar macrophages. Prx II-positive area in the fibroblastic foci (FF) was smaller than in other parenchymal areas (p=0.03) or in the hyperplastic epithelium (p=0.01). There was no major Prx II oxidation in IPF/UIP compared with the normal lung. The FF showed only minor immunoreactivity to the PDGFRs; Ki67, a marker of cell proliferation; and nitrotyrosine, a marker of oxidative/nitrosative stress. The results suggest that Prx II oxidation does not relate to the pathogenesis of IPF/UIP and that Prx II, PDGFRs, and proliferating cells colocalize in the IPF/UIP lung. Unexpectedly, FF represented areas of low cell proliferation.

Does the oxidative stress in chronic obstructive pulmonary disease cause thioredoxin/peroxiredoxin oxidation?

The thioredoxin/peroxiredoxin system comprises a redox-regulated antioxidant family in human lung; its significance, regulation, or oxidation has not been evaluated in smoking-related lung diseases. Here, we present the expression of the thioredoxin/peroxiredoxin system in lung biopsies from normal lung (n = 14), smokers (n = 21), and patients with chronic obstructive pulmonary disease (COPD, n = 38), and assess the possible inactivation/oxidation of this system by nonreducing Western blotting, two-dimensional gel electrophoresis, and mass spectrometry. Our study shows that the thiol status of the Trx/Prx-system can be modulated in vitro, but it appears to have high resistance against the oxidative stress in COPD.

Oxidative stress in fetal lambs exposed to intra-amniotic endotoxin in a chorioamnionitis model

Chorioamnionitis is a risk factor for the development of bronchopulmonary dysplasia. Endotoxin-induced oxidative stress to the fetus in the uniquely hypoxic intrauterine environment has not been reported. Using a model of chorioamnionitis, we measured markers of pulmonary and systemic oxidant exposures in fetal lambs at 124 d gestation (term = 150 d) exposed to 10 mg intra-amniotic endotoxin 2 d (n = 6) or 7 d (n = 6) before delivery, or saline as controls (n = 9). The 7 d endotoxin-exposed animals had 3-fold higher protein carbonyls (0.66 +/- 0.46 versus 0.23 +/- 0.14 nmol/mg protein) and 10-fold greater myeloperoxidase activity (2.38 +/- 1.87 versus 0.27 +/- 0.18 nM) in the bronchoalveolar lavage fluid (BALF), suggestive of neutrophil-derived oxidant activity. However, in the lung tissue, protein carbonyls, superoxide dismutase, and peroxiredoxin 1 were not different between groups. The expression of peroxiredoxin 1 was prominent, primarily in the peri-bronchiolar epithelium. Notably, evidence of oxidant exposure was minimal at 2 d when BALF inflammatory cells, lung IL-1beta, and IL-8 were highest. Intra-amniotic endotoxin induced systemic oxidative stress as plasma protein carbonyl was elevated at 7 d (0.14 +/- 0.04 nmol/mg protein; p = 0.005). Surfactant protein A and B mRNAs were highest at 2 d, suggesting that oxidative stress did not contribute to the lung maturation response. A modest lung oxidative stress in chorioamnionitis could contribute to bronchopulmonary dysplasia.

Role of the Nrf2-antioxidant system in cytotoxicity mediated by anticancer cisplatin: implication to cancer cell resistance

The treatment of alkylating cytotoxic drug cisplatin is often limited by high incidence rate of resistance. In the present study, the potential involvement of the transcription factor Nrf2 in determination of cisplatin cytotoxicity has been investigated. Nrf2-deficient murine embryonic fibroblasts showed increased cell death, cytotoxicity, and apoptosis in response to cisplatin treatment compared to wild-type cells. Cisplatin-resistant human ovarian cancer SK-OV cells, which are retaining 25-fold higher levels of GSH than murine fibroblasts, could be sensitized by inhibition of Nrf2. Transfection with Nrf2 siRNA into SK-OV cells resulted in severe degree of GSH depletion and exacerbated cytotoxicity following cisplatin treatment compared to scrambled RNA control. In conclusion, we propose that the Nrf2 pathway, which plays a protective role in normal cells, can be a potential target to control cancer cell resistance to oxidants, cytotoxic chemicals, and radiation.

Migrating leukocytes are the source of peroxiredoxin V during inflammation in the airways

Background

We characterized changes in expression of the antioxidant protein Peroxiredoxin V (PRXV) during airway inflammation.

Methods

Studies in anesthetized rats and mice; PRXV expression determined by Western blot analyses and immunohistochemistry; PRXV m-RNA expression determined by Taq-Man RT-PCR.

Results

Bacterial lung inflammation did not change expression of PRXV in murine epithelia but produced massive influx of leukocytes highly expressing PRXV. Endotoxin and f-MLP induced leukocyte migration in rat trachea but did not change mRNA levels and PRXV protein expression in tracheal epithelial cells. In primary airway cell culture (cow), alveolar epithelial cells A549, or co-culture of A549 with murine macrophages RAW264.7, exposure to live bacteria increased expression of PRXV, which required serum. PRXV was secreted in vitro by epithelial and immune cells.

Conclusion

Inflammation increased expression of PRXV in airways by at least 2 mechanisms: cell population shift by massive influx of leukocytes expressing PRXV, and moderate post-transcriptional up-regulation of PRXV in epithelial cells.

Proteomic analysis of pulmonary sclerosing hemangioma

Sclerosing hemangioma (SH) is a rare benign pulmonary tumor derived from the primitive respiratory epithelium. However, the pathogenesis of SH has not yet been clear. Surfactant protein, thyroid transcription factor-1, epithelial membrane antigen, cytokeratin, and vimentin have been identified in SH by immunohistochemistry and electron microscopy. To identify proteins specifically regulated in SH, 2-D PAGE was performed using SH and paired normal tissues. Ten selected differentially expressed protein spots were identified by PMF, MALDI-TOF-MS, and database searching. Apolipoprotein A-1, antizyme inhibitor, heat shock 27-kDa protein 1, and antioxidant proteins, such as peroxiredoxin II (Prx II) and GST, were identified among the down-regulated proteins in SH. Western blot and immunohistochemistry confirmed reduced expressions of Prx II and GST in SH versus normal lung tissue. This study is the first report on the reduced expressions of Prx II and GST in SH.

Oxidative/nitrosative stress and peroxiredoxin 2 are associated with grade and prognosis of human renal carcinoma

Peroxiredoxins (Prxs) 1-6 were assessed in 138 renal cell carcinomas (RCC) using immunohistochemistry and selected samples by Western blotting analysis. Oxidative/nitrosative damage was evaluated using nitrotyrosine immunoreactivity. The expressions of Prxs were correlated with tumor grade and survival and nitrotyrosine reactivity. Non-malignant kidney tubular cells showed positivity with variable intensity for all six Prxs. In RCCs, most cases were positive for Prxs 1 and 2, while only 15-20% of tumors showed expression for Prxs 3 and 4. Prx 2 was associated with tumors of a lower grade (p=0.009) and with a lower frequency of distant metastases (p=0.046). Patients with tumors expressing Prx2 had better prognosis (p=0.027). Instead, nitrotyrosine was significantly associated with high grade tumors (p=0.001). Compared with the non-malignant kidney tubular cells, low Prx expression in the tumor cells can make them more susceptible to oxidative damage. Prx 2 was more abundantly expressed in low grade tumors, suggesting that this protein could play a role in preventing the development of oxidative damage, which in turn can lead to the activation of pathways leading to aggressive tumors.

Oxidant and antioxidant balance in the airways and airway diseases

Although oxygen is a prerequisite to life, at concentrations beyond the physiological limits it may be hazardous to the cells. Since the lungs are directly exposed to very high amounts of oxygen, it is imperative for the organ to possess defences against possible oxidative challenge. The lungs are therefore endowed with an armamentarium of a battery of endogenous agents called antioxidants. The antioxidant species help the lungs ward off the deleterious consequences of a wide variety of oxidants/reactive oxygen species such as superoxide anion, hydroxyl radical, hypohalite radical, hydrogen peroxide and reactive nitrogen species such as nitric oxide, peroxynitrite, nitrite produced endogenously and sometimes accessed through exposure to the environment. The major non-enzymatic antioxidants of the lungs are glutathione, vitamins C and E, beta-carotene, uric acid and the enzymatic antioxidants are superoxide dismutases, catalase and peroxidases. These antioxidants are the first lines of defence against the oxidants and usually act at a gross level. Recent insights into cellular redox chemistry have revealed the presence of certain specialized proteins such as peroxiredoxins, thioredoxins, glutaredoxins, heme oxygenases and reductases, which are involved in cellular adaptation and protection against an oxidative assault. These molecules usually exert their action at a more subtle level of cellular signaling processes. Aberrations in oxidant: antioxidant balance can lead to a variety of airway diseases, such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis which is the topic of discussion in this review.

T lymphocytes and dendritic cells are activated by the deletion of peroxiredoxin II (Prx II) gene

Peroxiredoxin II (Prx II) is a member of antioxidant enzyme family and it plays a protective role against oxidative damage. Constitutive production of endogenous reactive oxygen species was detected in spleen and bone marrow cells lacking Prx II. Here, we investigated the role of Prx II in immune responses. The total number of splenocytes (especially, the population of S-phase cells and CD3(+) T cells) was significantly higher in Prx II(-/-) mice than in wild type. Number of peripheral blood mononuclear cells (PBMCs) in Prx II(-/-) mice was also higher than wild type. Differentiation of Prx II(-/-) mouse bone marrow cells into CD11c-positive dendritic cells was greater than that of wild type. Transplantation of Prx II(-/-) bone marrow cells into wild type mice increased PBMCs in blood and bone marrow-derived dendritic cells. Prx II deletion enhances concanavalin A (ConA)-induced splenocyte proliferation and mixed lymphocyte reaction (MLR) activity of bone marrow-derived CD11c-positive dendritic cells to stimulate recipient splenocytes. Collectively, these data suggest that Prx II inhibits the immune cell responsiveness, which may be regulated by scavenging the low amount of reactive oxygen species (ROS).