Peroxiredoxin V Contributes to Antioxidant Defense of Lung Epithelial Cells

The synergistic effects of PRDX5 and Nrf2 on lung cancer progression and drug resistance under oxidative stress in the zebrafish models

Previous studies have shown that PRDX5 and Nrf2 are antioxidant proteins related to abnormal reactive oxidative species (ROS). PRDX5 and Nrf2 play a critical role in the progression of inflammations and tumors. The combination of PRDX5 and Nrf2 was examined by Co-immunoprecipitation, western blotting and Immunohistochemistry. H2O2 was applied to affect the production of ROS and induced multi-resistant protein 1 (MRP1) expression in NSCLC cells. The zebrafish models mainly investigated the synergistic effects of PRDX5 and Nrf2 on lung cancer drug resistance under oxidative stress. We showed that PRDX5 and Nrf2 form a complex and significantly increase the NSCLC tissues compared to adjacent tissues. The oxidative stress improved the combination of PRDX5 and Nrf2. We demonstrated that the synergy between PRDX5 and Nrf2 is positively related to the proliferation and drug resistance of NSCLC cells in the zebrafish models. In conclusion, our data indicated that PRDX5 could bind to Nrf2 and has a synergistic effect with Nrf2. Meanwhile, in the zebrafish models, PRDX5 and Nrf2 have significant regulatory impacts on lung cancer progression and drug resistance activities under oxidative stress.

Effects of Antioxidant Gene Overexpression on Stress Resistance and Malignization In Vitro and In Vivo: A Review

Reactive oxygen species (ROS) are normal products of a number of biochemical reactions and are important signaling molecules. However, at the same time, they are toxic to cells and have to be strictly regulated by their antioxidant systems. The etiology and pathogenesis of many diseases are associated with increased ROS levels, and many external stress factors directly or indirectly cause oxidative stress in cells. Within this context, the overexpression of genes encoding the proteins in antioxidant systems seems to have become a viable approach to decrease the oxidative stress caused by pathological conditions and to increase cellular stress resistance. However, such manipulations unavoidably lead to side effects, the most dangerous of which is an increased probability of healthy tissue malignization or increased tumor aggression. The aims of the present review were to collect and systematize the results of studies devoted to the effects resulting from the overexpression of antioxidant system genes on stress resistance and carcinogenesis in vitro and in vivo. In most cases, the overexpression of these genes was shown to increase cell and organism resistances to factors that induce oxidative and genotoxic stress but to also have different effects on cancer initiation and promotion. The last fact greatly limits perspectives of such manipulations in practice. The overexpression of GPX3 and SOD3 encoding secreted proteins seems to be the "safest" among the genes that can increase cell resistance to oxidative stress. High efficiency and safety potential can also be found for SOD2 overexpression in combinations with GPX1 or CAT and for similar combinations that lead to no significant changes in H₂O₂ levels. Accumulation, systematization, and the integral analysis of data on antioxidant gene overexpression effects can help to develop approaches for practical uses in biomedical and agricultural areas. Additionally, a number of factors such as genetic and functional context, cell and tissue type, differences in the function of transcripts of one and the same gene, regulatory interactions, and additional functions should be taken into account.

Molecular cloning, prokaryotic expression and the anti-inflammatory activity of porcine PRDX5

Peroxiredoxin 5 (PRDX5) is the sole member of the atypical 2-Cys subfamily of mammalian PRDXs, a family of thiol-dependent peroxidases. In addition to its antioxidant effect, PRDX5 has been implicated in modulating the inflammatory response. In this study, the full-length cDNA encoding porcine PRDX5 (pPRDX5) was cloned. Subsequently, using porcine alveolar macrophages (PAMs), the target cells of PRRSV infection in vivo, we found that the recombinant pPRDX5 protein inhibited inflammatory responses induced by tumor necrosis factor alpha (TNF-α) or porcine reproductive and respiratory syndrome virus (PRRSV), a virus causing severe interstitial pneumonia in pigs. By contrast, knockdown of endogenous pPRDX5 with specific siRNA enhanced inflammatory responses induced by TNF-α or PRRSV. We also demonstrated that the involvement of pPRDX5 in inflammation regulation depended on its peroxidase activity. Taken together, these results showed that pPRDX5 is an anti-inflammatory molecule, which may play an important immune-regulation role in the pathogenicity of PRRSV.

Effects of High-Grain Diet With Buffering Agent on the Hepatic Metabolism in Lactating Goats

To gain insight on the effects of a high-grain diet with buffering agent on liver metabolism and the changes of plasma biochemical parameters and amino acids in hepatic vein and portal vein, commercial kit and high performance liquid chromatography (HPLC) were applied to determine the concentration of amino acids of hepatic vein and portal vein blood samples, quantitative real-time PCR and comparative proteomic approach was employed to investigate proteins differentially expressed in liver in lactating dairy goats feeding high-grain diet with buffering agent or only high-grain diet. Results showed that feeding high-grain diet with buffering agent to lactating dairy goats could outstanding increase amino acid content of Gln (p < 0.01), and the amino acid contents of Arg and Tyr in BG were significantly higher (p < 0.05) than that in HG. After adding the buffering agent, the metabolism of amino acids in the liver were changed and most of the amino acids were increasingly synthesized and decreasingly consumed in the liver. In addition, 46 differentially expressed protein spots (≥1.5-fold changed) were detected in buffering group vs. control group using 2-DE technique and MALDI-TOF/TOF proteomics analyzer. Of these, 24 proteins showed increased expression and 22 proteins showed decreased expression in the buffer group vs. control group. Data on Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis reveals that the high-grain diet with buffering agent alter the expression of proteins related to amino acids metabolism and glycometabolism. In addition, the results conclude that feeding high-grain diet with buffering agent can strengthen anti-oxidant capacity, stress ability, slow down urea metabolism, and alter amino acid metabolism as well as glycometabolism in the liver through different detection methods including proteomic analysis, real-time PCR analysis and biochemical analysis.

Peroxiredoxin 5 Protects TGF-β Induced Fibrosis by Inhibiting Stat3 Activation in Rat Kidney Interstitial Fibroblast Cells

Renal fibrosis is a common final pathway of end-stage kidney disease which is induced by aberrant accumulation of myofibroblasts. This process is triggered by reactive oxygen species (ROS) and proinflammatory cytokines generated by various source of injured kidney cells. Peroxiredoxin 5 (Prdx5) is a thiol-dependent peroxidase that reduces oxidative stress by catalyzing intramolecular disulfide bonds. Along with its antioxidant effects, expression level of Prdx5 also was involved in inflammatory regulation by immune stimuli. However, the physiological effects and the underlying mechanisms of Prdx5 in renal fibrosis have not been fully characterized. Sprague-Dawley rats were subjected to unilateral ureteral obstruction (UUO) for 1 or 7 days. For the in vitro model, NRK49F cells, a rat kidney interstitial fibroblast cell lines, were treated with transforming growth factor β (TGF-β) for 0, 1, 3, or 5 days. To access the involvement of its peroxidase activity in TGF-β induced renal fibrosis, wild type Prdx5 (WT) and double mutant Prdx5 (DM), converted two active site cysteines at Cys 48 and Cys 152 residue to serine, were transiently expressed in NRK49F cells. The protein expression of Prdx5 was reduced in UUO kidneys. Upregulation of fibrotic markers, such as fibronectin and alpha-smooth muscle actin (α-SMA), declined at 5 days in time point of higher Prdx5 expression in TGF-β treated NRK49F cells. The overexpression of wild type Prdx5 by transient transfection in NRK49F cells attenuated the TGF-β induced upregulation of fibronectin and α-SMA. On the other hand, the transient transfection of double mutant Prdx5 did not prevent the activation of fibrotic markers. Overexpression of Prdx5 also suppressed the TGF-β induced upregulation of Stat3 phosphorylation, while phosphorylation of Smad 2/3 was unchanged. In conclusion, Prdx5 protects TGF-β induced fibrosis in NRK49F cells by modulating Stat3 activation in a peroxidase activity dependent manner.

Peroxiredoxin V selectively regulates IL-6 production by modulating the Jak2-Stat5 pathway

Mammalian peroxiredoxin V (PrdxV) is a multifunctional protein that protects cells from DNA damage and inhibits stress-induced apoptosis. However, PrdxV is also known to be involved in modulating lipopolysaccharide (LPS)-induced host cell signaling, but its precise role is not fully understood. In this study, we used stably transfected RAW264.7 cells and transiently transfected 293-mTLR4-MD2-CD14 cells expressing wild-type (WT) or mutant (C48S) PrdxV to characterize the function and mechanism of action of PrdxV in LPS-induced immune responses. We found that PrdxV selectively reduces production of interleukin 6 (IL-6) by inhibiting activation of signal transducer and activator of transcription 5 (Stat5) through interaction with Jak2. Notably, this activity of PrdxV was dependent on its catalytic Cys48 residue, but not its peroxidase activity. The binding of to Jak2 effectively inhibited Jak2 phosphorylation, but PrdxV did not act as efficiently as SOCS1 (suppressor of cytokine signaling 1). Our results suggest that PrdxV is a key mediator contributing to the regulation of LPS/TLR4-induced immune responses.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

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

AIMS

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

RESULTS

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

INNOVATION

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

CONCLUSION

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

Peroxiredoxin 5: structure, mechanism, and function of the mammalian atypical 2-Cys peroxiredoxin

Peroxiredoxin 5 (PRDX5) was the last member to be identified among the six mammalian peroxiredoxins. It is also the unique atypical 2-Cys peroxiredoxin in mammals. Like the other five members, PRDX5 is widely expressed in tissues but differs by its surprisingly large subcellular distribution. In human cells, it has been shown that PRDX5 can be addressed to mitochondria, peroxisomes, the cytosol, and the nucleus. PRDX5 is a peroxidase that can use cytosolic or mitochondrial thioredoxins to reduce alkyl hydroperoxides or peroxynitrite with high rate constants in the 10(6) to 10(7) M(-1)s(-1) range, whereas its reaction with hydrogen peroxide is more modest, in the 10(5) M(-1)s(-1) range. PRDX5 crystal structures confirmed the proposed enzymatic mechanisms based on biochemical data but revealed also some specific unexpected structural features. So far, PRDX5 has been viewed mainly as a cytoprotective antioxidant enzyme acting against endogenous or exogenous peroxide attacks rather than as a redox sensor. Accordingly, overexpression of the enzyme in different subcellular compartments protects cells against death caused by nitro-oxidative stresses, whereas gene silencing makes them more vulnerable. Thus, more than 10 years after its molecular cloning, mammalian PRDX5 appears to be a unique peroxiredoxin exhibiting specific functional and structural features.

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.

Proteomic analysis of protein expression affected by peroxiredoxin V knock-down in hypoxic kidney

Peroxiredoxin V, an atypical thioredoxin peroxidase, is widely expressed in mammalian tissues. In addition, Prdx V is localized in mitochondria, peroxisome, cytosol, and the nucleus. Prdx V has been reported to protect a wide range of cellular environments as an antioxidant enzyme, and its dysfunctions may be implicated in several diseases, such as cancer, inflammation, and neurodegenerative disease. Identification and relative quantification of proteins affected by Prdx V may help identify novel signaling mechanisms that are important for oxidative stress response. However, the role of Prdx V in the modulation of hypoxia-related cellular response is not studied yet. To examine the function of endogenous Prdx V in hypoxic condition in vivo, we generated a transgenic mouse model with Prdx V siRNA expression controlled by U6 promoter. Of many tissues, the knockdown of Prdx V expression was displayed in the kidney, lung, and liver but not the spleen and skin. We conducted on the basis of nano-UPLC-MS(E) proteomic study to identify the Prdx V-affected protein networks in hypoxic kidneys. In this study, we identified protein networks associated with oxidative stress, fatty acid metabolism, and mitochondrial dysfunction. Our results indicated that Prdx V affected to regulation of kidney homeostasis under hypoxia stress.

Extracellular proteomes of M-CSF (CSF-1) and GM-CSF-dependent macrophages

Macrophage colony-stimulating factor (M-CSF) (also known as CSF-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have distinct effects on macrophage lineage populations, which are likely to be contributing to their functional heterogeneity. A comparative proteomic analysis of proteins released into culture media from such populations after M-CSF and GM-CSF exposure was carried out. Adherent macrophage populations, termed bone marrow-derived macrophage (BMM) and GM-BMM, were generated after treatment of murine bone marrow precursors with M-CSF and GM-CSF, respectively. Proteins in 16-h serum-free conditioned media (CM) were identified by two-dimensional gel electrophoresis and mass spectrometry. Respective protein profiles from BMM and GM-BMM CM were distinct and there was the suggestion of a switch from primarily signal peptide-driven secretion to non-classical secretion pathways from BMM to GM-BMM. Extracellular expression of cathepsins (lysosomal proteases) and their inhibitors seems to be a characteristic difference between these macrophage cell types with higher levels usually observed in BMM-CM. Furthermore, we have identified a number of proteins in BMM-CM and GM-BMM-CM that could be involved in various tissue regeneration and inflammatory (immune) processes, respectively. The uncharacterized protein C19orf10, a protein found at high levels in the synovial fluid of arthritis patients, was also differentially regulated; its extracellular levels were upregulated in the presence of GM-CSF.

Peroxiredoxins, a novel target in cancer radiotherapy

Reactive oxygen species (ROS) are toxic at high levels in the mammalian cells. Mammalian cells have developed many enzymatic and nonenzymatic antioxidative systems in various cellular compartments to maintain an appropriate level of ROS and regulate their action. Peroxiredoxins (Prxs), a family of peroxidase that reduced intracellular peroxides (one type of ROS) with the thioredoxin system as the electron donor, were highly expressed in various cellular compartments. In this minireview, we discussed the regulation of Prxs expression in cancer cell and its relationship with ionizing radiation. As Prxs could be induced by radiation and its expression status could determine the radiosensitivity of cancer cells, Prxs might be a potential target for radiotherapy in cancer.

Peptides with dual binding specificity for HLA-A2 and HLA-E are encoded by alternatively spliced isoforms of the antioxidant enzyme peroxiredoxin 5

Peptides with dual binding specificity for classical HLA class I and non-classical HLA-E molecules have been identified in virus-encoded proteins, but not in cellular proteins from normal or neoplastic cells. Expression screening of a melanoma cDNA library with a CTL clone recognizing an HLA-A2-restricted tumor-specific epitope encoded by mutant peroxiredoxin 5 (Prdx5), a stress-inducible peroxidase, led to the identification of two alternatively spliced isoforms of the same gene. These isoforms, which lack the catalytic cysteine fundamental for enzymatic activity, showed widespread expression in neoplastic and normal tissues but were unstable at the protein level, being detectable, following transient transfection, only after lactacystin treatment to inhibit proteasomal degradation. Isoform-specific sequences which formed, respectively, as result of exon 1 splicing to either exon 3 or 4, encoded two distinct nonapeptides (AMAPIKTHL and AMAPIKVRL, not present in the full-length protein) with anchor residues for HLA-A2 and HLA-E molecules and able to stabilize HLA-A2 and HLA-E cell surface expression. HLA-E+ targets, loaded with these peptides, were not recognized by NK cells expressing CD94/NKG2A inhibitory or CD94/NKG2C activatory receptors. However, both peptides were recognized, although with low avidity, by HLA-E-restricted CD8+ CTL. The nonapeptide AMAPIKVRL was used to elicit HLA-A2-restricted CTL clones that killed peptide-pulsed lymphoblastoid cell lines and melanoma cells expressing the corresponding Prdx5 isoform. Our results suggest that alternatively spliced isoforms of Prdx5, through the generation of HLA-E- and HLA-A2-restricted peptides may be part of immune-mediated stress response contributing to the detection and elimination of damaged normal or neoplastic cells.

Increased p53 level, Bax/Bcl-x(L) ratio, and TRAIL receptor expression in human emphysema

RATIONALE

Emphysema is mainly known for the complex inflammatory processes associated with its development. In addition to lung inflammation, it is now accepted that increased alveolar cell apoptosis is also part of emphysema pathophysiology. However, little is known about the mechanisms involved in alveolar apoptosis. We postulate that oxidative stress and proinflammatory cytokines could lead to p53 accumulation, Bax/Bcl-x(L) ratio elevation, and higher tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor levels in the emphysematous lung.

OBJECTIVES

To evaluate the expression of p53, Bax, Bcl-x(L), TRAIL, and TRAIL receptors in lung parenchyma from nonemphysematous nonsmokers and smokers and emphysematous smokers and ex-smokers and to determine whether H2O2 and/or TNF can modulate the expression of these apoptotic proteins.

METHODS

p53, Bax, Bcl-x(L), and TRAIL receptor protein levels in lung parenchyma were measured by Western blot, and TRAIL mRNA levels were measured by real-time polymerase chain reaction. Changes in TRAIL receptor, Bax, Bcl-x(L), and p53 protein levels after in vitro H2O2 and/or TNF stimulation of A549 cells were also assessed by Western blot.

MEASUREMENTS AND MAIN RESULTS

The p53 protein levels, the Bax/Bcl-x(L) ratio, and TRAIL receptors 1, 2, and 3 protein levels were significantly higher in subjects with emphysema. Moreover, they were also increased after H2O2 and TNF treatments of A549 cells.

CONCLUSIONS

These findings suggest that oxidative stress and proinflammatory cytokines may be involved in the elevation of p53 levels, the Bax/Bcl-x(L) ratio, and TRAIL receptor levels, new mechanisms that may be implicated in the increased alveolar cell apoptosis that occurs in emphysema.