Novel roles of peroxiredoxins in inflammation, cancer and innate immunity

First report of Peroxiredoxin-5 (PRDX5) in starry flounder (Platichthys stellatus): Molecular features and expression analysis

In this study, the Peroxiredoxin-5 (PRDX5) gene from starry flounder (Platichthys stellatus, PsPRDX5) was identified through next-generation sequencing (NGS) and verified via cloning and sequencing. The predicted amino acid sequence, derived from the cDNA, was confirmed by multiple sequence alignment and phylogenetic analysis, establishing its homology with related sequences. PsPRDX5 mRNA was expressed across all examined tissues in healthy starry flounder, with distinct tissue-specific expression profiles. Following artificial infection with viral hemorrhagic septicemia virus (VHSV) and Streptococcus parauberis PH0710, significant alterations in PsPRDX5 mRNA expression were observed. VHSV infection resulted in a pronounced downregulation of PsPRDX5 in most major tissues, except for a significant upregulation in the intestine at 7 days post-infection. Conversely, infection with S. parauberis PH0710 led to a significant upregulation of PsPRDX5 in nearly all tissues. These results suggest that the differential expression of PsPRDX5 in response to VHSV and S. parauberis PH0710 reflects pathogen-specific immune and antioxidant defense mechanisms, highlighting the role of PsPRDX5 in the immune response of starry flounder to both viral and bacterial infections.

Antioxidant enzyme Prdx1 inhibits osteoclastogenesis via suppressing ROS and NFATc1 signaling pathways

Bone is a dynamic organ which continuously undergoes remodeling throughout one's lifetime. Cellular production of reactive oxygen species (ROS) is essential for regulating bone homeostasis. Osteoclasts, multinucleated giant cells differentiated from macrophage lineage, are responsible for osteolytic bone conditions which are closely linked to ROS signaling pathways. In this study, an anti-ROS enzyme, peroxiredoxin 1 (Prdx1) was found to be expressed both in bone marrow macrophages and osteoclasts. Recombinant Prdx1 protein was found to dose-dependently inhibit ROS production and osteoclast differentiation. Mechanistically, Prdx1 protein also attenuated NFATc1 activation as well as the expression of C-Fos, V-ATPase-d2, Cathepsin K, and Integrin αV. Collectively, Prdx1 is a negative regulator on osteoclast formation via inhibiting RANKL-mediated ROS activity, thus suggesting its potential application for treating osteoclast related disorders.

Nrf2 Plays a Key Role in Erythropoiesis during Aging

Aging is characterized by increased oxidation and reduced efficiency of cytoprotective mechanisms. Nuclear factor erythroid-2-related factor (Nrf2) is a key transcription factor, controlling the expression of multiple antioxidant proteins. Here, we show that Nrf2-/- mice displayed an age-dependent anemia, due to the combined contributions of reduced red cell lifespan and ineffective erythropoiesis, suggesting a role of Nrf2 in erythroid biology during aging. Mechanistically, we found that the expression of antioxidants during aging is mediated by activation of Nrf2 function by peroxiredoxin-2. The absence of Nrf2 resulted in persistent oxidation and overactivation of adaptive systems such as the unfolded protein response (UPR) system and autophagy in Nrf2-/- mouse erythroblasts. As Nrf2 is involved in the expression of autophagy-related proteins such as autophagy-related protein (Atg) 4-5 and p62, we found impairment of late phase of autophagy in Nrf2-/- mouse erythroblasts. The overactivation of the UPR system and impaired autophagy drove apoptosis of Nrf2-/- mouse erythroblasts via caspase-3 activation. As a proof of concept for the role of oxidation, we treated Nrf2-/- mice with astaxanthin, an antioxidant, in the form of poly (lactic-co-glycolic acid) (PLGA)-loaded nanoparticles (ATS-NPs) to improve its bioavailability. ATS-NPs ameliorated the age-dependent anemia and decreased ineffective erythropoiesis in Nrf2-/- mice. In summary, we propose that Nrf2 plays a key role in limiting age-related oxidation, ensuring erythroid maturation and growth during aging.

Paracrine Signaling Mediated by the Cytosolic Tryparedoxin Peroxidase of Trypanosoma cruzi

Peroxiredoxins are abundant and ubiquitous proteins that participate in different cellular functions, such as oxidant detoxification, protein folding, and intracellular signaling. Under different cellular conditions, peroxiredoxins can be secreted by different parasites, promoting the induction of immune responses in hosts. In this work, we demonstrated that the cytosolic tryparedoxin peroxidase of Trypanosoma cruzi (cTXNPx) is secreted by epimastigotes and trypomastigotes associated with extracellular vesicles and also as a vesicle-free protein. By confocal microscopy, we show that cTXNPx can enter host cells by an active mechanism both through vesicles and as a recombinant protein. Transcriptomic analysis revealed that cTXNPx induces endoplasmic reticulum stress and interleukin-8 expression in epithelial cells. This analysis also suggested alterations in cholesterol metabolism in cTXNPx-treated cells, which was confirmed by immunofluorescence showing the accumulation of LDL and the induction of LDL receptors in both epithelial cells and macrophages. BrdU incorporation assays and qPCR showed that cTXNPx has a mitogenic, proliferative, and proinflammatory effect on these cells in a dose-dependent manner. Importantly, we also demonstrated that cTXNPx acts as a paracrine virulence factor, increasing the susceptibility to infection in cTXNPx-pretreated epithelial cells by approximately 40%. Although the results presented in this work are from in vitro studies and likely underestimate the complexity of parasite-host interactions, our work suggests a relevant role for this protein in establishing infection.

Peroxiredoxins in erythrocytes: far beyond the antioxidant role

The red blood cells (RBCs) are essential to transport oxygen (O2) and nutrients throughout the human body. Changes in the structure or functioning of the erythrocytes can lead to several deficiencies, such as hemolytic anemias, in which an increase in reactive oxidative species generation is involved in the pathophysiological process, playing a significant role in the severity of several clinical manifestations. There are important lines of defense against the damage caused by oxidizing molecules. Among the antioxidant molecules, the enzyme peroxiredoxin (Prx) has the higher decomposition power of hydrogen peroxide, especially in RBCs, standing out because of its abundance. This review aimed to present the recent findings that broke some paradigms regarding the three isoforms of Prxs found in RBC (Prx1, Prx2, and Prx6), showing that in addition to their antioxidant activity, these enzymes may have supplementary roles in transducing peroxide signals, as molecular chaperones, protecting from membrane damage, and maintenance of iron homeostasis, thus contributing to the overall survival of human RBCs, roles that seen to be disrupted in hemolytic anemia conditions.

Depletion of peroxiredoxin II promotes keratinocyte apoptosis and alleviates psoriatic skin lesions via the PI3K/AKT/GSK3β signaling axis

Psoriasis is a chronic, systemic immune-mediated disease caused by abnormal proliferation, decreased apoptosis, and over-differentiation of keratinocytes. The psoriatic skin lesions due to abnormal keratinocytes are closely associated with ROS produced by inflammatory cells. Peroxiredoxin II (Prx II) is an efficient antioxidant enzyme, which were highly expressed in skin tissues of psoriasis patient. However, the detailed mechanical functions of Prx II on psoriatic skin remain to be elucidated. Present study showed that depletion of Prx II results in alleviation of symptoms of IMQ-induced psoriasis in mice, but no significant differences in the amounts of serum inflammatory factors. Prx II-knockdown HaCaT cells were susceptible to H₂O₂-induced apoptosis mediated by Ca²⁺ release from the endoplasmic reticulum through 1,4,5-triphosphate receptors (IP3Rs), the PI3K/AKT pathway and phosphorylated GSK3β (Ser9) were significant downregulated. Additionally, significantly reduced sensitivity of Prx II-knockdown HaCaT cells to apoptosis was evident post NAC, 2-APB, BAPTA-AM, SC79 and LiCl treated. These results suggest that Prx II regulated apoptosis of keratinocytes via the PI3K/AKT/GSK3β signaling axis. Furthermore, treatment with the Prx II inhibitor Conoidin A significantly alleviated psoriatic symptoms in IMQ model mice. These findings have important implications for developing therapeutic strategies through regulate apoptosis of keratinocytes in psoriasis, and Prx II inhibitors may be exploited as a therapeutic drug to alleviate psoriatic symptoms.

Peroxiredoxin 1 of Procambarus clarkii govern immune responses during pathogen infection

Members of the peroxiredoxin family are involved in a wide variety of physiological processes, including the ability to combat the effects of oxidative stress and immune responses, among others. Here, we cloned the cDNA of Procambarus clarkii Peroxiredoxin 1 (designated as PcPrx-1) and investigated its biological role in immune system functions in relation to microbial pathogens. The PcPrx-1 cDNA had 744 base pairs in an open reading frame that encoded 247 amino acid residues and contained a PRX_Typ2cys domain. The analysis of tissue specific expression patterns revealed that PcPrx-1 expression was ubiquitous in all tissues. In addition, the mRNA transcript of PcPrx-1 was found to be highest in the hepatopancreas. There was a significant upregulation of PcPrx-1 gene transcripts after exposure to LPS, PGN, and Poly I:C, but the transcription patterns were different after pathogen challenge. Double-stranded RNA was used to knockdown PcPrx-1, which resulted in a striking change in the expression of all the tested P. clarkii immune-associated genes, including lectin, Toll, cactus, chitinase, phospholipase, and sptzale. On the whole, these results suggest that PcPrx-1 is important to confer innate immunity against pathogens by governing the expression of critical transcripts that encode immune-associated genes.

Molecular cloning and functional characterization of peroxiredoxin 4 (prx 4) in freshwater crayfish, Procambarus clarkii

Peroxiredoxin (Prx), which is a newly discovered member of the antioxidant protein family, performs important biological functions in intracellular signal transduction. In the present study, a peroxiredoxin 4 gene was cloned from crayfish for the first time and named Pc-prx 4. According to the amino acid sequence signature, Pc-Prx 4 was identified as the typical 2-Cys Prx molecule, which possessed two conserved cysteines (Cys98 and Cys219). Time-course expression patterns post V. harveyi infection revealed that Pc-prx 4 was likely related to crayfish innate immune defense responses. In particular, the highest fold upregulation of the Pc-prx 4 mRNA transcript reached approximately 170 post V. harveyi infection in the crayfish hepatopancreas. The results of the mixed functional oxidase assay showed that rPc-Prx 4^△ could resist the damaging effect of reactive oxygen species generated from the thiol/Fe³⁺/O₂^- reaction system to some extent. In addition, the results of the RNAi assay revealed that the crayfish survival rate was obviously increased post injection of V. harveyi when Pc-prx 4 was knocked down. Further study revealed that both hemolymph melanization and PO activity were strengthened to different degrees in the RNAi assay. Therefore, we speculated that the increase in the crayfish survival rate was likely due to the increase in hemolymph melanization. The obviously reinforced hemolymph melanization was directly caused by the upregulation of hemolymph PO activity, which was induced by the knockdown of Pc-prx 4. However, further studies are still indispensable for illuminating the molecular mechanism of Pc-prx 4 in the crayfish innate immune defense system.

Apoptotic responses stimulated by the trichloroethylene metabolite S-(1,2-dichlorovinyl)-L-cysteine depend on cell differentiation state in BeWo human trophoblast cells

During pregnancy, the placental villous cytotrophoblasts differentiate via cell fusion and multinucleation to create syncytiotrophoblasts, a cell type at the maternal-fetal interface. Apoptosis of syncytiotrophoblasts is associated with adverse pregnancy outcomes. The human trophoblast BeWo cell line has been used as an in vitro model for this differentiation process, also known as syncytialization. In the current study, we exposed unsyncytialized BeWo cells, BeWo cells undergoing syncytialization, and syncytialized BeWo cells to S-(1,2-dichlorovinyl)-L-cysteine (DCVC), a metabolite of the industrial chemical trichloroethylene (TCE). DCVC exposure at 50 μM for 48 h decreased cell viability, increased cytotoxicity, increased caspase 3/7 activity, and increased nuclear condensation or fragmentation in BeWo cells regardless of their differentiation status. Investigating mechanisms of apoptosis, DCVC increased H2O2 abundance and decreased PRDX2 mRNA in all three BeWo cell models. DCVC decreased tumor necrosis factor-receptor 1 (TNF-R1) concentration in media and decreased NFKB1 and PRDX1 mRNA expression in syncytialized BeWo cells only. DCVC decreased BCL2 mRNA expression in syncytializing BeWo cells and in syncytialized BeWo cells only. Decreased LGALS3 mRNA was seen in unsyncytialized BeWo cells only. Together, these data suggest roles for oxidative stress and pro-inflammatory mechanisms underlying apoptosis in BeWo cells with differences depending on differentiation state.

Molecular characterization, immune expression, and functional delineation of peroxiredoxin 1 in Epinephelus akaara

Peroxiredoxin 1 is a member of the typical 2-Cys peroxiredoxin family, which serves diverse functions in gene expression, immune and inflammatory responses, and tumor progression. In this study, we aimed to analyze the structural, functional, and immunomodulatory properties of peroxiredoxin 1 from Epinephelus akaara (EaPrx1). The open reading frame of EaPrx1 is 597 base pairs in length, encoding 198 amino acids, with a molecular weight of approximately 22 kDa. The in silico analysis revealed that EaPrx1 shares a conserved thioredoxin fold and signature motifs that are critical for its catalytic activity and oligomerization. Further, EaPrx1 is closely related to Epinephelus lanceolatus Prx1 and clustered in the Fishes group of the vertebrate clade, revealing that EaPrx1 was conserved throughout evolution. In terms of tissue distribution, a high level of EaPrx1 expression was observed in the spleen, brain, and blood tissues. Likewise, in immune challenge experiments, significant transcriptional modulations of EaPrx1 upon lipopolysaccharide, polyinosinic:polycytidylic acid, and nervous necrosis virus injections were noted at different time points, indicating the immunological role of EaPrx1 against pathogenic infections. In the functional analysis, rEaPrx1 exhibited substantial DNA protection, insulin disulfide reduction, and tissue repair activities, which were concentration-dependent. EaPrx1/pcDNA™ 3.1 (+)-transfected fathead minnow cells revealed high cell viability upon arsenic toxicity, indicating the heavy metal detoxification activity of EaPrx1. Taken together, the transcriptional and functional studies imply critical roles of EaPrx1 in innate immunity, redox regulation, apoptosis, and tissue-repair processes in E. akaara.

Peroxiredoxin 1 alleviates oxygen-glucose deprivation/ reoxygenation injury in N2a cells via suppressing the JNK/caspase-3 pathway

Objectives

Cerebral ischemia/reperfusion (I/R) injury inevitably aggravates the initial cerebral tissue damage following a stroke. Peroxiredoxin 1 (Prdx1) is a representative protein of the endogenous antioxidant enzyme family that regulates several reactive oxygen species (ROS)-dependent signaling pathways, whereas the JNK/caspase-3 proapoptotic pathway has a prominent role during cerebral I/R injury. This study aimed to examine the potential mechanism of Prdx1 in Neuro 2A (N2a) cells following oxygen-glucose deprivation and reoxygenation (OGD/R) injury.

Materials and Methods

N2a cells were exposed to OGD/R to simulate cerebral I/R injury. Prdx1 siRNA transfection and the JNK inhibitor (SP600125) were used to interfere with their relative expressions. CCK-8 assay, flow cytometry, and lactate dehydrogenase (LDH) assay were employed to determine the viability and apoptosis of N2a cells. The intracellular ROS content was assessed using ROS Assay Kit. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot analyses were conducted to detect the expression levels of Prdx1, JNK, phosphorylated JNK (p-JNK), and cleaved caspase-3.

Results

Firstly, Prdx1, p-JNK, and cleaved caspase-3 expression were significantly induced in OGD/R-exposed N2a cells. Secondly, the knockdown of Prdx1 inhibited cell viability and increased apoptosis rate, expression of p-JNK, and cleaved caspase-3 expression. Thirdly, SP600125 inhibited the JNK/caspase-3 signaling pathway and mitigated cell injury following OGD/R. Finally, SP600125 partially reversed Prdx1 down-regulation-mediated cleaved caspase-3 activation and OGD/R damage in N2a cells.

Conclusion

Prdx1 alleviates the injury to N2a cells induced by OGD/R via suppressing JNK/caspase-3 pathway, showing promise as a potential therapeutic for cerebral I/R injury.

Effects of M. oleifera leaf extract on the growth, physiological response and related immune gene expression of crucian carp fingerlings under Aeromonas hydrophila infection

We evaluated the effect of dietary supplementation with Moringa oleifera leaf extract on the resistance to Aeromonas hydrophila infection in crucian carp. The fish were randomly divided into five groups: the basal diet, the basal diet supplied with 0.25% (0.25 M), 0.5% (0.5 M), 0.75% (0.75 M) and 1.0% M. oleifera leaf extract (1.0 M) for 8 weeks. The growth, antioxidant capabilities, related immune genes as well as resistance to A. hydrophila infection were determined. The results showed that compared with the control group, the weight gain, specific growth rate in the group of 0.5% M. oleifera leaf extract, serum superoxide dismutase (SOD), albumin (ALB) and glutathione peroxidase (GSH-Px), the gene expression of hepatopancreas BTB and CNC homolog 1 (Bach1), NF-E2-related factor 2 (Nrf2), peroxidases (PRX) and NADPH oxidase (NOX) in the group of 0.5%-1.0% M. oleifera leaf extract increased, while feed conversion ratio, serum cortisol, red blood cell (RBC), alanine aminotransferase (ALT), malonaldehyde (MDA) decreased in the group of 0.5%-1.0% M. oleifera leaf extract before the stress. After the infection, the group of 0.5% or 0.75% M. oleifera leaf extract also could improve the serum ALB, hepatopancreas Kelch-like-ECH-associated protein 1 (Keap1), Bach1, Nrf2, TOR, PRX and NOX and reduce cortisol compared with the control group. In summary, this study suggested that 0.5% M. oleifera leaf extract inclusion increased the growth performance, even had positive effects on physiological and immune function, and enhanced resistance against pathogenic infections in crucian carp. The optimum level of M. oleifera leaf extract for crucian carp was estimated to be 0.35%-0.48% based on polynomial comparison with FCR and SGR.

The mechanism underlying the TC-G 1008 rescue of reactive oxygen species (ROS)-induced osteoblast apoptosis by the upregulation of peroxiredoxin 1

Osteoporosis is a common bone disease in the elderly with high morbidity and mortality. Previous studies have shown ROS-revulsive osteoblast apoptosis to be involved in the pathogenesis of osteoporosis. At present, a research hotspot exists on the topic of the ROS-targeted clinical treatment of osteoporosis. TC-G 1008, a potent and selective GPR39 agonist, exerts a conspicuous influence on a myriad of cellular processes, ranging from cellular redox status, to gene expression, to cell apoptosis. However, the underlying mechanism by which TC-G 1008 regulates osteoblast function under oxidative stress has not yet been elucidated. The purpose of this study was to investigate the effect and underlying mechanism of TC-G 1008 in the rescue of ROS-induced apoptosis by upregulating peroxiredoxin (Prx1). In this study, experimental results demonstrated that TC-G 1008 could activate GPR39, which then accelerated ROS obliteration and apoptosis inhibition in osteoblasts via Prx1 upregulation through the nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2). Interestingly, being regarded as an 'information' molecule rather than an anti-oxidase molecule, Prx1 was shown to restrict the dissociation of the apoptosis signal-regulating kinase 1 (ASK1)/thioredoxin (Trx) under oxidative stress, which signified the activation of the ASK1 pathway, thereby resulting in the suppression of apoptosis. In summary, this study explores the double mechanism of TC-G 1008 in osteoblast apoptosis amelioration under oxidative stress through (i) ROS elimination and (ii) ASK1/Trx signal suppression, both of which contribute to increased Prx1 expression, and the results suggest that TC-G 1008 has great potential in the clinical treatment of osteoporosis.

Comparative proteomics of adult Paragonimus kellicotti excretion/secretion products released in vitro or present in the lung cyst nodule

Paragonimus kellicotti is a zoonotic lung fluke infection, the agent of North American paragonimiasis, and an excellent model for other Paragonimus infections. The excretory/secretory proteins (ESP) released by parasites and presented at the parasite-host interface are frequently proposed to be useful targets for drugs and/or vaccines In vitro culture conditions may alter ESP compared to those produced in vivo. In order to investigate ESPs produced in vivo we took advantage of the fact that adult P. kellicotti reproduce in the lungs of experimentally infected gerbils in tissue cysts. We performed a mass-spectrometric analysis of adult P. kellicotti soluble somatic protein (SSPs) extracts, excreted/secreted proteins (ESPs) produced by adult worms during in vitro culture, and lung cyst fluid proteins (CFPs) from experimentally infected gerbils. We identified 2,137 P. kellicotti proteins that were present in at least two of three biological replicates and supported by at least two peptides. Among those were 1,914 proteins found in SSP, 947 in ESP and 37 in CFP. In silico analysis predicted that only 141 of the total 2,137 proteins were secreted via classical or non-classical pathways. The most abundant functional categories in SSP were storage and oxidative metabolism. The most abundant categories in ESP were proteins related to metabolism and signal transduction. The 37 parasite-related proteins in CFP belonged to 11 functional categories. The largest groups were proteins with unknown function, cytoskeletal proteins and proteasome machinery. 29 of these 37 proteins were shared among all three sample types. To our knowledge, this is the first study that compares in vitro and in vivo ESP for any Paragonimus species. This study has provided new insights into ESPs of food-borne trematodes that are produced and released in vivo. Proteins released at the host-parasite interface may help the parasite evade host immunity and may represent new targets for novel treatments or diagnostic tests for paragonimiasis.

Peroxiredoxin 4 Interacts With Domeless and Participates in Antibacterial Immune Response Through the JAK/STAT Pathway

The JAK/STAT pathway plays an important role in the development and immune responses of animals. In vertebrates, families of cytokines or growth factors act as activators of the JAK/STAT pathway; however, the activators for the JAK/STAT signaling pathway in arthropods are largely unknown. Herein we report a new ligand, peroxiredoxin 4 (Prx4), for the Domeless in the JAK/STAT pathway of shrimp Marsupenaeus japonicus. Prx4 was induced to secrete into the extracellular surroundings upon Vibrio challenge, which then facilitated the anti-Vibrio activity of shrimp by activating the phosphorylation and nuclear translocation of STAT and the expression of STAT-responsive antimicrobial peptides. Blocking the expression of Prx4 in vivo abrogated the activation of the JAK/STAT pathway by Vibrio infection, while injection of Prx4 protein activated the pathway. The interaction between Prx4 and Domeless was proved by immuno-precipitation and protein pull-down assays. Moreover, two cysteine residues in Prx4 that are critical for the interaction and Prx4’s anti-Vibrio role were identified, and the binding site in Domeless for Prx4 was proved to be the cytokine-binding homology module fragment. Taken together, our study revealed a new function for Prx4 enzyme and established a new enzyme-type ligand for the activation of the JAK/STAT pathway in an aquatic arthropod.

Identification of ferroptosis-related genes for overall survival prediction in hepatocellular carcinoma

Ferroptosis is a novel type of cell death depending on iron and is strongly related to the development of tumors. Hepatocellular carcinoma (HCC) is a malignancy with high incidence. Despite some reports demonstrating the relation between ferroptosis-related genes and HCC, more details have not been excavated. In the present study, we collected and analyzed HCC patients' datasets from the TCGA-LIHC project and ICGC portal, respectively. Through the bioinformatic methods, we screened 126 differentially expressed genes. Then a prognostic model was established with four genes (GPX2, MT3, PRDX1, and SRXN1). PRDX1 is the hub gene of the prognosis model and has a high expression in hepatocellular carcinoma tumor tissue and cell lines. We further found that silencing PRDX1 increased the accumulation of ferrous ions and lipid peroxidation accumulation in HEPG2 cells and promoted ferroptosis in hepatocellular carcinoma. In conclusion, the study demonstrated the four-gene signature can be used to predict HCC prognosis. It also revealed the potential function of the ferroptosis-related gene PRDX1 in HCC, which can be a biomarker of the prediction for HCC outcome.

p66Shc in Cardiovascular Pathology

p66Shc is a widely expressed protein that governs a variety of cardiovascular pathologies by generating, and exacerbating, pro-apoptotic ROS signals. Here, we review p66Shc’s connections to reactive oxygen species, expression, localization, and discuss p66Shc signaling and mitochondrial functions. Emphasis is placed on recent p66Shc mitochondrial function discoveries including structure/function relationships, ROS identity and regulation, mechanistic insights, and how p66Shc-cyt c interactions can influence p66Shc mitochondrial function. Based on recent findings, a new p66Shc mitochondrial function model is also put forth wherein p66Shc acts as a rheostat that can promote or antagonize apoptosis. A discussion of how the revised p66Shc model fits previous findings in p66Shc-mediated cardiovascular pathology follows.

Peroxiredoxin 2 Inhibits Lipopolysaccharide Induced Mucin Expression and Reactive Oxygen Species Production in Human Airway Epithelial Cells

Background and Objectives Peroxiredoxin (Prx) is an antioxidant enzyme involved in signaling pathway. Prx2 is the most abundant in mammalian gray matter neurons and has protective role under oxidative stress. MUC5AC and MUC5B are typical mucin genes in human airway epithelial cells. Even if free radicals play a key role in chronic respiratory inflammatory diseases, the effects of the Prx2 on mucin expression and oxidative stress are not clearly known. The purpose of this study is to investigate the effect of Prx2 on lipopolysaccharide (LPS)-induced MUC5AC/5B expression and reactive oxygen species (ROS) in human airway epithelial cells.Subjects and Method In NCI-H292 cells and human nasal epithelial cells, the effects of Prx2 on LPS-induced MUC5AC/5B expression and ROS production were investigated using reverse transcriptase-polymerase chain reaction, real-time polymerase chain reaction, enzyme linked immunosorbent assay (ELISA) and flow cytometry analysis.Results MUC5AC, MUC5B mRNA expression and protein production were increased by LPS. ROS production was also increased by LPS. Prx2 suppressed the LPS-induced MUC5AC mRNA expression and protein production as well as ROS production. However, Prx2 did not inhibit MUC5B mRNA expression and protein production. N-acetylcysteine, diphenyleneiodonium, and apocynin also inhibited LPS-induced ROS production.Conclusion These results may show that Prx2 suppresses LPS-induced MUC5AC expression via ROS in human airway epithelial cells.

Antiviral Function of NKEF against VHSV in Rainbow Trout

Simple Summary

An antioxidant protein has been identified in a sample of erythrocytes exposed to a fish virus. We evaluated the role of this protein as an antiviral molecule in fish. Through silencing and overexpression assays we determined the antiviral effect of this protein in the infectivity of the virus. In conclusion, this antioxidant protein may be a potential target for new therapeutic strategies against viral infections.

Abstract

Natural killer enhancing factor (NKEF) belongs to the peroxiredoxin family of proteins, a group of antioxidants that has been extensively studied in mammals. Recently, we identified NKEF in the immunoprecipitated proteome of rainbow trout red blood cells (RBCs) exposed to viral hemorrhagic septicemia virus (VHSV). In the present study, we evaluated the role of NKEF in the antiviral response of rainbow trout against VHSV by examining the expression profile of NKEF in VHSV-exposed RBCs and rainbow trout gonad-2 (RTG-2) cell line. We found an in vitro correlation between decreased VHSV replication and increased NKEF expression after RBCs were exposed to VHSV, however this was not found in RTG-2 cells where the infection highly increased and nkef transcripts remained almost unchanged. In addition, siRNA silencing of the nkef gene in rainbow trout RBCs and RTG-2 cells resulted in increased VHSV replication. We also found a correlation between nkef gene silencing and a decrease in the expression of genes related to type 1 interferon (IFN1) pathway. These findings indicated that NKEF is involved in the antiviral mechanisms of rainbow trout RBCs against VHSV and thus support its antiviral role and implication in the modulation of their immune response. Finally, overexpression of NKEF in an EPC cell line significantly reduced VHSV infectivity and was coupled to an increment in IFN1-related genes. In conclusion, NKEF may be a potential target for new therapeutic strategies against viral infections.

The diterpenoid adenanthin upregulates the expression of natural killer group 2D receptor ligands in hepatocellular carcinoma cells

OBJECTIVE

The natural killer (NK) group 2D (NKG2D) receptor plays a crucial role in NK cell-mediated anti-tumor immunity. NKG2D anti-proliferative effect is mediated by direct interactions of the receptor with its ligands that may be considered as a potential target for NK-based immunotherapeutic strategy in cancer cells.

METHODS

Here we report that a natural product adenanthin significantly promotes NKG2D ligands expression in hepatoma cells. The effect was determined using flow cytometry analysis. The activity of NK cell was evaluated by measuring its degranulation activity and cytotoxicity.

RESULTS

Our data indicates that the induction of NKG2D ligand binding to liver cancer cell surface receptors greatly improves the killing activity of NK cells against the cancer cells.

CONCLUSIONS

This is the first report of a new mechanism anti-cancer effects of adenanthin mediated by an indirect activation of NK cells. Our data suggests that adenanthin may be used to sensitize NK cells in tumor immunotherapy.

Epo-C12 inhibits peroxiredoxin 1 peroxidase activity

Epo-C12 is a synthetic derivative of epolactaene, isolated from Penicillium sp. BM 1689-P. Epo-C12 induces apoptosis in human acute lymphoblastoid leukemia BALL-1 cells. In our previous studies, seven proteins that bind to Epo-C12 were identified by a combination of pull-down experiments using biotinylated Epo-C12 (Bio-Epo-C12) and mass spectrometry. In the present study, the effect of Epo-C12 on peroxiredoxin 1 (Prx 1), one of the proteins that binds to Epo-C12, was investigated. Epo-C12 inhibited Prx 1 peroxidase activity. However, it did not suppress its chaperone activity. Binding experiments between Bio-Epo-C12 and point-mutated Prx 1s suggest that Epo-C12 binds to Cys⁵² and Cys⁸³ in Prx 1. The present study revealed that Prx 1 is one of the target proteins through which Epo-C12 exerts an apoptotic effect in BALL-1 cells.

Autonomous Non Antioxidant Roles for Fasciola hepatica Secreted Thioredoxin-1 and Peroxiredoxin-1

Trematode parasites of the genus Fasciola are the cause of liver fluke disease (fasciolosis) in humans and their livestock. Infection of the host involves invasion through the intestinal wall followed by migration in the liver that results in extensive damage, before the parasite settles as a mature egg-laying adult in the bile ducts. Genomic and transcriptomic studies revealed that increased metabolic stress during the rapid growth and development of F. hepatica is balanced with the up-regulation of the thiol-independent antioxidant system. In this cascade system thioredoxin/glutathione reductase (TGR) reduces thioredoxin (Trx), which then reduces and activates peroxiredoxin (Prx), whose major function is to protect cells against the damaging hydrogen peroxide free radicals. F. hepatica expresses a single TGR, three Trx and three Prx genes; however, the transcriptional expression of Trx1 and Prx1 far out-weighs (>50-fold) other members of their family, and both are major components of the parasite secretome. While Prx1 possesses a leader signal peptide that directs its secretion through the classical pathway and explains why this enzyme is found freely soluble in the secretome, Trx1 lacks a leader peptide and is secreted via an alternative pathway that packages the majority of this enzyme into extracellular vesicles (EVs). Here we propose that F. hepatica Prx1 and Trx1 do not function as part of the parasite’s stress-inducible thiol-dependant cascade, but play autonomous roles in defence against the general anti-pathogen oxidative burst by innate immune cells, in the modulation of host immune responses and regulation of inflammation.

The cytosolic tryparedoxin peroxidase from Trypanosoma cruzi induces a pro-inflammatory Th1 immune response in a peroxidatic cysteine-dependent manner

Trypanosoma cruzi cytosolic tryparedoxin peroxidase (c-TXNPx) is a 2-Cys peroxiredoxin (Prx) with an important role in detoxifying host cell oxidative molecules during parasite infection. c-TXNPx is a virulence factor, as its overexpression enhances parasite infectivity and resistance to exogenous oxidation. As Prxs from other organisms possess immunomodulatory properties, we studied the effects of c-TXNPx in the immune response and analysed whether the presence of the peroxidatic cysteine is necessary to mediate these properties. To this end, we used a recombinant c-TXNPx and a mutant version (c-TXNPxC52S) lacking the peroxidatic cysteine. We first analysed the oligomerization profile, oxidation state and peroxidase activity of both proteins by gel filtration, Western blot and enzymatic assay, respectively. To investigate their immunological properties, we analysed the phenotype and functional activity of macrophage and dendritic cells and the T-cell response by flow cytometry after injection into mice. Our results show that c-TXNPx, but not c-TXNPxC52S, induces the recruitment of IL-12/23p40-producing innate antigen-presenting cells and promotes a strong specific Th1 immune response. Finally, we studied the cellular and humoral immune response developed in the context of parasite natural infection and found that only wild-type c-TXNPx induces proliferation and high levels of IFN-γ secretion in PBMC from chronic patients without demonstrable cardiac manifestations. In conclusion, we demonstrate that c-TXNPx possesses pro-inflammatory properties that depend on the presence of peroxidatic cysteine that is essential for peroxidase activity and quaternary structure of the protein and could contribute to rational design of immune-based strategies against Chagas disease.

PRDX1 activates autophagy via the PTEN-AKT signaling pathway to protect against cisplatin-induced spiral ganglion neuron damage

Spiral ganglion neurons (SGNs) are auditory neurons that relay sound signals from the inner ear to the brainstem. The ototoxic drug cisplatin can damage SGNs and thus lead to sensorineural hearing loss (SNHL), and there are currently no methods for preventing or treating this. Macroautophagy/autophagy plays a critical role in SGN development, but the effect of autophagy on cisplatin-induced SGN injury is unclear. Here, we first found that autophagic flux was activated in SGNs after cisplatin damage. The SGN apoptosis and related hearing loss induced by cisplatin were alleviated after co-treatment with the autophagy activator rapamycin, whereas these were exacerbated by the autophagy inhibitor 3-methyladenine, indicating that instead of inducing SGN death, autophagy played a neuroprotective role in SGNs treated with cisplatin both in vitro and in vivo. We further demonstrated that autophagy attenuated reactive oxygen species (ROS) accumulation and alleviated cisplatin-induced oxidative stress in SGNs to mediate its protective effects. Notably, the role of the antioxidant enzyme PRDX1 (peroxiredoxin 1) in modulating autophagy in SGNs was first identified. Deficiency in PRDX1 suppressed autophagy and increased SGN loss after cisplatin exposure, while upregulating PRDX1 pharmacologically or by adeno-associated virus activated autophagy and thus inhibited ROS accumulation and apoptosis and attenuated SGN loss induced by cisplatin. Finally, we showed that the underlying mechanism through which PRDX1 triggers autophagy in SGNs was, at least partially, through activation of the PTEN-AKT signaling pathway. These findings suggest potential therapeutic targets for the amelioration of drug-induced SNHL through autophagy activation.

Abbreviations: 3-MA: 3-methyladenine; AAV : adeno-associated virus; ABR: auditory brainstem responses; AKT/protein kinase B: thymoma viral proto-oncogene; Baf: bafilomycin A₁; CAP: compound action potential; COX4I1: cytochrome c oxidase subunit 4I1; Cys: cysteine; ER: endoplasmic reticulum; H₂O₂: hydrogen peroxide; HC: hair cell; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; NAC: N-acetylcysteine; PRDX1: peroxiredoxin 1; PTEN: phosphatase and tensin homolog; RAP: rapamycin; ROS: reactive oxygen species; SGNs: spiral ganglion neurons; SNHL: sensorineural hearing loss; SQSTM1/p62: sequestosome 1; TOMM20: translocase of outer mitochondrial membrane 20; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling; WT: wild type.

Prognostic Value of Peroxiredoxin-1 Expression in Patients with Solid Tumors: a Meta-Analysis of Cohort Study

Methods

We comprehensively searched electronic databases, namely, PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure (CNKI), and WanFang databases up to December 2019. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to evaluate the association between PRDX1 protein expression and the survival of patients with solid tumors. Odds ratios (ORs) with 95% CIs were pooled to estimate the correlation between PRDX1 protein expression and clinicopathologic characteristics in the patients.

Results

Seventeen cohort studies that involved 2,858 patients were included in this meta-analysis. The pooled results indicated that positive PRDX1 expression was related to poor overall survival (HR = 1.68, 95% CI: 1.24-2.27, P = 0.001) and disease-free survival (HR = 1.88, 95% CI: 1.31-2.70, P = 0.001). In addition, high PRDX1 expression was associated with large tumor size (OR = 1.69, 95% CI: 1.07-2.68, P = 0.025), advanced TNM stage (OR = 2.26, 95% CI: 1.24-4.13, P = 0.008), and poor tumor differentiation (OR = 0.59, 95% CI: 0.44-0.81, P = 0.001).

Conclusions

PRDX1 overexpression is associated with poor outcomes of cancers and may serve as a prognostic biomarker for malignant patients. Hence, PRDX1 could be a new target for antitumor therapy.

Overexpression of PRDX4 Modulates Tumor Microenvironment and Promotes Urethane-Induced Lung Tumorigenesis

Peroxiredoxin 4 (PRDX4), initially reported as an antioxidant, is overexpressed in lung cancer and participates in its progression. However, its role in the urethane-induced lung tumor model is undetermined. The aim of this study was to investigate the effect of PRDX4 overexpression on carcinogen-induced lung tumor development. Human PRDX4 overexpression transgenic (Tg) mice (hPRDX4^+/+) and non-Tg mice were intraperitoneally injected with urethane to induce lung tumor. After 6 months, tumor formation was compared between groups and possible mechanisms for the difference in tumor development were investigated. The serum and lung PRDX4 expressions were enhanced after urethane stimulation in Tg mice. Both the average number of tumors (≥0.5 mm) and tumor diameter per mouse in the Tg group were significantly larger than in non-Tg controls, while body weight was lower in the Tg group. Compared with non-Tg controls, tumor cell proliferation was enhanced, while tumor cell apoptosis was suppressed in Tg mice. Systemic oxidative stress and oxidative stress in lung tumors were inhibited by PRDX4 overexpression. The balance of prooxidant enzymes and antioxidant enzymes was also shifted to a decreased level in Tg tumor. In lung tumor tissue, the density of microvessel penetrated into tumor was higher in the Tg group; macrophage infiltration was enhanced in Tg tumors, while there was no difference in T lymphocyte infiltration; the expressions of cytokines, including interleukin-1 beta (IL-1β) and matrix metallopeptidase 9 (MMP9), were elevated in Tg tumors, which resulted from enhanced phosphorylation of nuclear factor-κB p65 (NF-κB p65) and c-Jun, respectively. In conclusion, PRDX4 overexpression modulated tumor microenvironment and promoted tumor development in the mouse urethane-induced lung cancer model.

Molecular profiling and functional delineation of peroxiredoxin 3 (HaPrx3) from the big-belly seahorses (Hippocampus abdominalis) and understanding their immunological responses

Peroxiredoxins (Prxs) are ubiquitously expressed antioxidant proteins that can protect aerobic organisms from oxidative stress. Here, we characterized the HaPrx3 homolog at the molecular level from big-belly seahorse (Hippocampus abdominalis) and analyzed its functional activities. The coding sequence of HaPrx3 consists of 726 bp, which encodes 241 amino acids. The predicted molecular weight and theoretical isoelectric point (pI) of HaPrx3 was 26.20 kDa and 7.04, respectively. Multiple sequence alignments revealed that the arrangements of domains, catalytic triads, dimers, and decamer interfaces of HaPrx3 were conserved among Prx sequences of other organisms. According to the phylogenetic analysis, HaPrx3 is clustered with the teleost Prx3 subclade. The highest transcript level of HaPrx3 was detected in the ovary tissue among fourteen healthy fish tissues. The mRNA levels of HaPrx3 in blood and liver tissues were significantly (P < 0.05) upregulated in response to lipopolysaccharide (LPS), polyinosinic-polycytidylic (poly I:C), Edwardsiella tarda, and Streptococcus iniae, suggesting its involvement in immune responses. Under functional properties, insulin disulfide reduction assay confirmed the oxidoreductase activity of recombinant HaPrx3. A cell viability assay and Hoechst staining indicated cell survival ability and reduction of apoptotic activity, respectively. Moreover, a peroxidase activity assay verified peroxidase activity, while a metal-catalyzed oxidation (MCO) assay indicated the DNA protection ability of HaPrx3. Collectively, it is concluded that HaPrx3 may play a significant role in oxidative stress and immune responses against pathogenic infections in big-belly seahorses.

Cloning and functional characterisation of natural killer enhancing factor-B (NKEF-B) gene of Labeo rohita: Anti-oxidant and antimicrobial activities of its recombinant protein

Natural killer enhancing factor (NKEF) of peroxiredoxin family is an important innate immune molecule with having anti-oxidant activity. Although this gene has already been studied in a few fish species, it is yet to be identified and functionally characterised in Indian major carps. In the present study, the complete NKEF-B cDNA of rohu, Labeo rohita was cloned that encoded a putative protein of 197 amino acids. The phylogenetic study showed that L. rohita NKEF-B (LrNKEF-B) is closely related to NKEF-B of Cyprinus carpio and Danio rerio species. Tissue-specific expression of LrNKEF-B gene revealed the highest transcript level in the liver tissue. In the ontogeny study, the highest level of the expression was observed in milt and at 18 h post-development. The expression pattern of this gene was also studied in various pathogen models viz., Gram-negative bacteria (Aeromonas hydrophila), ectoparasite (Argulus siamensis) and a dsRNA viral analogue (poly I:C) in the liver and anterior kidney tissues of L. rohita juveniles. During A. hydrophila infection, the increase in expression of transcripts was observed at 3 h post-infection in both liver (15-fold) and anterior kidney (8-fold). In A. siamensis infection, the expression gradually increased up to 3 d post-infection in the anterior kidney, whereas in liver 3-fold up-regulation was noticed at 12 h post-infection. Similarly, during poly I:C stimulation, up-regulation of NKEF-B transcript was observed in anterior kidney from 1 h to 24 h post-stimulation and down-regulated afterwards whereas, the transcript level increased gradually from 6 h to 15 d post-stimulation in liver tissue. In vitro exposure to concanavalin, A and formalin-killed A. hydrophila upregulated NKEF-B gene expression in anterior kidney and peripheral blood leukocytes of L. rohita, however, down-regulated the same in the splenic leukocytes. A recombinant protein of LrNKEF-B (rLrNKEF-B) of 22 kDa was produced and it showed anti-oxidant activity by protecting supercoiled DNA and reducing insulin disulfide bonds. The minimum bactericidal concentration of this recombinant protein was found to be 4.54 μM against A. hydrophila and Staphylococcus aureus. Interestingly, rLrNKEF-B showed relative percent survival of 72.6 % in A. hydrophila challenged L. rohita, and the survival was found to be associated with a high level of expression of different cytokines, anti-oxidant genes and perforin in the rLrNKEF-B treated L. rohita. An indirect ELISA assay for estimation of NKEF was developed in L. rohita, and the concentrations of NKEF-B increased with time periods post A. hydrophila challenge viz., 0 h (42.56 ng/mL), 12 h (174 ng/mL) and 48 h (370 ng/mL) in rohu serum. Our results suggest a crucial role of LrNKEF-B in innate immunity against biotic stress and oxidative damage and also having antibacterial activity.

Peri/Epicellular Thiol Oxidoreductases as Mediators of Extracellular Redox Signaling

Significance: Supracellular redox networks regulating cell-extracellular matrix (ECM) and organ system architecture merge with structural and functional (catalytic or allosteric) properties of disulfide bonds. This review addresses emerging evidence that exported thiol oxidoreductases (TORs), such as thioredoxin, protein disulfide isomerases (PDIs), quiescin sulfhydryl oxidases (QSOX)1, and peroxiredoxins, composing a peri/epicellular (pec)TOR pool, mediate relevant signaling. pecTOR functions depend mainly on kinetic and spatial regulation of thiol-disulfide exchange reactions governed by redox potentials, which are modulated by exported intracellular low-molecular-weight thiols, together conferring signal specificity. Recent Advances: pecTOR redox-modulates several targets including integrins, ECM proteins, surface molecules, and plasma components, although clear-cut documentation of direct effects is lacking in many cases. TOR catalytic pathways, displaying common patterns, culminate in substrate thiol reduction, oxidation, or isomerization. Peroxiredoxins act as redox/peroxide sensors, contrary to PDIs, which are likely substrate-targeted redox modulators. Emerging evidence suggests important pecTOR roles in patho(physio)logical processes, including blood coagulation, vascular remodeling, mechanosensing, endothelial function, immune responses, and inflammation. Critical Issues: Effects of pecPDIs supporting thrombosis/platelet activation have been well documented and reached the clinical arena. Roles of pecPDIA1 in vascular remodeling/mechanosensing are also emerging. Extracellular thioredoxin and pecPDIs redox-regulate immunoinflammation. Routes of TOR externalization remain elusive and appear to involve Golgi-independent routes. pecTORs are particularly accessible drug targets. Future Directions: Further understanding mechanisms of thiol redox reactions and developing assays for assessing pecTOR redox activities remain important research avenues. Also, addressing pecTORs as disease markers and achieving more efficient/specific drugs for pecTOR modulation are major perspectives for diagnostic/therapeutic improvements.

PRDX4 overexpression is associated with poor prognosis in gastric cancer

Peroxiredoxin IV (PRDX4) is a multifunctional protein that is involved in cell protection against oxidative injury, regulation of cell proliferation, modulation of intracellular signaling, and the pathogenesis of tumors. We previously conducted a proteomic analysis to investigate tumor-specific protein expression in gastric cancer. The aim of the present study was to investigate whether PRDX4 could be a marker of poor prognosis in patients with gastric cancer. Immunohistochemistry was used to validate PRDX4 as a prognostic marker for gastric cancer. Short hairpin RNA (shRNA)-mediated knockdown of PRDX4 expression in AGS cells and MKN28 cells was used for functional studies, and PRDX4 overexpression in PRDX4-depleted cells was used for knock-in studies. Based on immunohistochemistry data, TNM stage and PRDX4 were independent prognostic factors in the Cox proportional hazard model (P<0.05). In the survival analysis, the PRDX4-overexpressing group demonstrated significantly worse survival than the PRDX4-underexpression group (P<0.01). In vitro, knockdown of PRDX4 expression by shRNA caused a significant decrease in cancer invasion. Conversely, overexpression of PRDX4 in PRDX4-depleted cancer cells promoted migration and invasion. By measuring the expression of EMT-related genes, we found that E-cadherin was increased in shPRDX4 cells compared with control shMKN28 cells, and snail and slug were decreased in shPRDX4-1 cells compared with sh-control cells. Furthermore, the expression levels of these genes could be recovered in rescue experiments. In conclusion, the results of the present study suggested that PRDX4 is a marker of poor prognosis in gastric cancer and that PRDX4 is associated with cancer cell migration and invasion via EMT.

Peroxiredoxin 1 as an inflammatory marker in diarrhea-predominant and postinfectious irritable bowel syndrome

BACKGROUND

Low-grade inflammation occurs in some patients with irritable bowel syndrome (IBS). However, the exact inflammatory markers of IBS and the relationship of these markers with IBS subtypes and symptoms are poorly defined. Peroxiredoxin 1 (PRDX1) plays an important role in inflammatory responses, including intestinal inflammation. We investigated whether PRDX1 is associated with the diagnosis, subtypes, and symptom severity of IBS.

METHODS

A total of 177 IBS patients and 174 sex- and age-matched healthy controls (HCs) were recruited. The PRDX1 levels in the sera and colonic mucosa of the participants were detected by enzyme-linked immunosorbent assays and immunohistochemistry. The severity of IBS symptoms was assessed using the IBS Severity Scoring System (SSS) questionnaire.

RESULTS

The PRDX1 levels in the sera (F = 71.81, P < .001) and colonic mucosa (F = 5.359, P < .001) of postinfectious (PI-IBS) and diarrhea-predominant IBS (IBS-D) groups were significantly higher than those of the other three IBS subtypes and HC group. The PRDX1 level in the serum and colonic mucosa of IBS-D (serum, P < .01, mucosa, P < .001) and PI-IBS (serum, P < .05, mucosa, P < .001) groups with the most severe symptoms was significantly higher than that in the groups with mild and moderate symptoms. Correlation analysis revealed that in patients with IBS-D (P < .001) and PI-IBS (P < .05), the levels of PRDX1 and TNF-α in sera had a significant positive correlation with IBS-SSS.

CONCLUSION

Elevated PRDX1 in the serum and colon mucosa may be closely related to the progression of IBS (especially IBS-D and PI-IBS) and the expression of gastrointestinal symptoms.

A Peroxiredoxin From the Haemaphysalis longicornis Tick Affects Langat Virus Replication in a Hamster Cell Line

Ticks are hematophagous arthropods, and their blood feeding on vertebrate hosts is essential for their development. The vertebrate blood contains high levels of free iron that can react with oxygen in ticks, resulting in the production of hydrogen peroxide (H₂O₂), one of the reactive oxygen species. Peroxiredoxins (Prxs), H₂O₂-scavenging enzymes, take on an important role in the ticks' oxidative stress coping mechanism. Ticks also transmit several disease-causing pathogens, including tick-borne encephalitis virus (TBEV), in animals and humans. Therefore, the control of ticks and tick-borne pathogens is a key issue that needs to be addressed. Infection with an arthropod-borne flavivirus is known to induce oxidative stress in insect cells. We hypothesize that vector-derived Prxs could have an effect on the infection and/or replication of flaviviruses in the hosts, since ticks Prxs are possibly transmitted from ticks to their hosts. In this study, we established stable strains of baby hamster kidney (BHK) cells expressing two types of H₂O₂-scavenging Prxs from the hard tick Haemaphysalis longicornis (BHK-HlPrx and BHK-HlPrx2 cells). Although the infection of TBEV surrogate Langat virus (LGTV) did not induce H₂O₂ production in normal BHK cells, the mortality rate and the virus titer of LGTV infected BHK-HlPrx cells increased. In addition, HlPrx proteins in BHK cells can facilitate LGTV replication in cells, while HlPrx2 proteins in BHK cells cannot. The results also demonstrated that this facilitation of LGTV replication by the 1-Cys Prx in the BHK cells is not by scavenging H₂O₂ but by an unknown mechanism. In order to understand this mechanism, more studies using tick-derived cells and ticks are necessary.

Decreased expression of microRNA-510 in intestinal tissue contributes to post-infectious irritable bowel syndrome via targeting PRDX1

OBJECTIVE

Post-infectious irritable bowel syndrome (PI-IBS) is a common functional gastrointestinal (GI) disorder that occurs after acute GI infection. Recent studies showed that microRNAs were involved in the occurrence and development of IBS. Here, we elaborated the role of miR-510 in the occurrence of PI-IBS and analyzed its mechanism.

METHODS

We detected the expressions of miR-510 and PRDX1 in colonic mucosal tissues by qRT-PCR, Western blot and immunohistochemistry. Furthermore, we transfected Caco-2 cells with miR-510 mimic, anti-miR-510, si-PRDX1, and control, then evaluated the cell viability and apoptosis by CCK8 assay and flow cytometry, assessed expression levels of PRDX1 by qRT-PCR and Western blot analysis, and pro-inflammatory cytokines by qRT-PCR and ELISA.

RESULTS

MiR-510 expression was downregulated and negatively correlated with TNF-α, whereas PRDX1 expression was upregulated in PI-IBS colonic mucosal tissues. LPS at concentrations of 5 and 10 μg/ml can significantly induce inflammatory injury in Caco-2 cells. MiR-510 overexpression aggravated the injury induced by LPS, as reflected by increased cell viability, decreased apoptosis, and less production of pro-inflammatory cytokines. miR-510 mimic transfection in cells significantly suppressed the mRNA and protein expression levels of PRDX1. Furthermore, the inflammatory injury induced by LPS was exacerbated by upregulating PRDX1 expression when miR-510 was knocked down.

CONCLUSION

MiR-510 downregulation in intestinal tissue might contribute to PI-IBS via targeting PRDX1. The results of this study will not only enrich the pathogenesis of PI-IBS but also make us understand the biological activity of miR-510 and provide important experimental basis for PI-IBS clinical treatment targeting miR-510.

Prdx2 Upregulation Promotes the Growth and Survival of Gastric Cancer Cells

Peroxiredoxins (Prdxs) play important roles in cell proliferation, differentiation, and the mediation of intracellular signalling pathways. Prdx2 is an important member of the peroxiredoxin family and is upregulated in many cancers. Until now, the biological functions of Prdx2 in gastric cancer have not been completely understood, and the underlying mechanisms remain elusive. The aim of this study was to identify the role of Prdx2 on the growth of gastric cancer cells and the underlying mechanisms. We demonstrated that Prdx2 was highly expressed in gastric cancer tissues and cell lines and that the over-expression of Prdx2 correlated with the progression of gastric cancer. Further, Prdx2 was silenced with a specific, lentiviral vector-mediated shRNA, and this suppressed the proliferation of gastric cancer cells and promoted the apoptosis of gastric cancer cells. Finally, the knockdown of Prdx2 contributed to the attenuated gastric cancer growth in BALB/c nude mice. In conclusion, these findings demonstrate that Prdx2 may participate in the carcinogenesis and development of gastric cancer.

Characterization of a classical 2-cysteine peroxiredoxin1 gene from Chinese soft-shelled turtle Pelodiscus sinensis with its potent antioxidant properties and putative immune response

Peroxiredoxin family members could function in host defense against oxidative stress, and modulate immune response. In the present study, a 2-cysteine peroxiredoxin gene named PsPrx1 was isolated from Chinese soft-shelled turtle Pelodiscus sinensis. The PsPrx1 cDNA was composed of 1130 bp, consisted of 199 amino acid residues and included a Redoxin and AphC-TSA domain. As detected by qPCR, PsPrx1 was ubiquitously expressed in the examined tissues with the higher levels in liver and spleen. Upon the immune challenge with A. jandaei bacteria and oxidative stress with ammonia pressure, both mRNA and protein expression level in liver could be significantly enhanced. The results of immunohistochemical examinations showed PsPrx1 was mainly distributed at the junction between the hepatic cells. The general functional properties of PsPrx1 were confirmed using purified rPsPrx1 protein. From the results, rPsPrx1 protein was confirmed to exhibit antioxidant activity and antibacterial properties. The potential for scavenging extracellular H₂O₂ was evidenced by the purified rPsPrx1 protein in vitro system. In the mixed-function oxidase assay, rPsPrx1 also exhibited a dose-dependent inhibition of DNA damage. These results suggest that rPsPrx1 was implicated defense against microbial pathogens and oxidants, and would provide important information to further understand the functional mechanism of Prx1 in P. sinensis immunity.

Identification and molecular characterization of peroxiredoxin 2 in grass carp (Ctenopharyngodon idella)

Peroxiredoxin (Prx), also named thioredoxin peroxidase (TPx), is a selenium independent antioxidant enzyme that can protect organisms from oxidative damage caused by reactive oxygen species (ROS) and is important for immune responses. In this study, the molecular cloning and characterization of a Prx2 homologue (CiPrx2) were described from grass carp (Ctenopharyngodon idella). The full-length cDNA of CiPrx2 was 1163 bp containing 5'-untranslated region (UTR) of 52 bp, a 3'-UTR of 517 bp with the putative polyadenylation consensus signal (AATAAA), an open reading frame (ORF) of 594 bp encoding polypeptides of 197 amino acids with a predicted molecular mass of 21.84 kDa and theoretical isoelectric point of 5.93. The analysis results of multiple sequence alignment and phylogenetic tree confirmed that CiPrx2 belong to the typical 2-Cys Prx subfamily. The CiPrx2 mRNA was ubiquitously expressed in all tested tissues. The temporal expression of CiPrx2 were differentially induced infected with grass carp reovirus (GCRV), polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharide (LPS) in liver and spleen. Subcellular localization of CiPrx2-GFP fusion proteins were only distributed in the cytoplasm. The purified recombinant CiPrx2 possessed an apparent antioxidant activity and could protect DNA against oxidative damage. Finally, CiPrx2 proteins could obviously inhibit H₂O₂ and heavy metal toxicity. However, further researches are needed to better understand the regulation of CiPrx2 under oxidative stresses.

Role of Cytosolic 2-Cys Prx1 and Prx2 in Redox Signaling

Peroxiredoxins (Prxs), a family of peroxidases, are reactive oxygen species scavengers that hydrolyze H₂O₂ through catalytic cysteine. Mammalian Prxs comprise six isoforms (typical 2-Cys Prxs; Prx1–4, atypical 2-Cys Prx; Prx5, and 1-Cys Prx; Prx6) that are distributed over various cellular compartments as they are classified according to the position and number of conserved cysteine. 2-Cys Prx1 and Prx2 are abundant proteins that are ubiquitously expressed mainly in the cytosol, and over 90% of their amino acid sequences are homologous. Prx1 and Prx2 protect cells from ROS-mediated oxidative stress through the elimination of H₂O₂ and regulate cellular signaling through redox-dependent mechanism. In addition, Prx1 and Prx2 are able to bind to a diversity of interaction partners to regulate other various cellular processes in cancer (i.e., regulation of the protein redox status, cell growth, apoptosis, and tumorigenesis). Thus, Prx1 and Prx2 can be potential therapeutic targets and it is particularly important to control their level or activity. This review focuses on cytosolic 2-Cys Prx1 and Prx2 and their role in the regulation of redox signaling based on protein-protein interaction.

Effects of Moringa oleifera leaf extract on growth performance, physiological and immune response, and related immune gene expression of Macrobrachium rosenbergii with Vibrio anguillarum and ammonia stress

In order to study the effects of Moringa oleifera leaf extract on Macrobrachium rosenbergii under high ammonia exposure, freshwater prawns were randomly divided into five groups: a control group was fed with basal diet, and four treatment groups fed with basal diet supplemented with 0.25%, 0.5% and 1.0% M. oleifera leaf extract and 0.025% Enrofloxacin for 60 days, respectively. Then, freshwater prawns were exposed to high ammonia stress for 72 h and Vibro anguillarum infection. The growth, antioxidant capabilities, related immune genes as well as resistance to infection by V. anguillarum were determined. The results showed that compared with the control group, the weight gain, specific growth rate and protein efficiency rate, haemolymph catalase (CAT), superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) increased while feed conversion ratio, haemolymph aspartate aminotransferase, alanine aminotransferase, nitrogen oxide (NO), hepatopancreas heat shock proteins (HSP70), immune deficiency (IMD) expression levels decreased in the group of 0.5% M. oleifera leaf extract before the stress. After ammonia stress, the group of 0.5% M. oleifera leaf extract also could improve the haemolymph SOD, glutathione peroxidase, NO, iNOS, hepatopancreas HSP70 expression levels and reduce haemolymph CAT, hepatopancreas peroxiredoxin 5 and NF kappa B inhibitor alpha expression level compared with the control group. The rate of mortality of the prawns challenged with V. anguillarum was lower in the supplemented groups in comparison with the control group with the lowest being in the group of 0.5% M. oleifera leaf extract. Antioxidant activities as well as biochemical parameters in the enrofloxacin group (0.025%E) were not significantly enhanced both pre and post challenge in comparison with the M. oleifera leaf extract groups, showing the superiority of the natural herb over the synthetic antibiotic. In summary, this study suggested that at an inclusion rate of 0.5%, M. oleifera leaf extract could increase the growth performance, even has positive effects on physiological and immune function and prevents high ammonia stress in the Freshwater prawn, M.rosenbergii.

Elevated ER stress exacerbates dextran sulfate sodium-induced colitis in PRDX4-knockout mice

BACKGROUND AND AIMS

Peroxiredoxin 4 (PRDX4), a secretory protein that is preferentially retained in the endoplasmic reticulum (ER), is encoded by a gene located on the X chromosome and highly expressed in colonic tissue. In this study, we investigated the role of PRDX4 by means of male PRDX4-knockout (PRDX4^-/y) mice in the development of intestinal inflammation using a dextran sulfate sodium (DSS)-induced colitis model.

MATERIALS AND METHODS

Acute colitis was induced with DSS (2.5% in drinking water) in wild-type (WT) and PRDX4^-/y male C57BL/6 mice. Histological and biochemical analyses were performed on the colonic tissues.

RESULTS

PRDX4 was mainly localized in the colonic epithelial cells in WT mice. The disease activity index (DAI) scores of PRDX4^-/y mice were significantly higher compared to those of WT mice. Specifically, PRDX4^-/y mice showed marked body weight loss and shortening of colon length compared to WT mice, whereas the myeloperoxidase levels were increased in PRDX4^-/y compared to WT mice. In addition, the mRNA expression levels of TNF-α and IFN-γ were significantly higher in the colonic mucosa of PRDX4^-/y compared to WT mice. Moreover, the levels of CHOP and activated caspase 3 were higher in the colonic tissues of PRDX4^-/y compared to WT mice following treatment with DSS. The ER also showed greater expansion in PRDX4^-/y than WT mice, which was consistent with severe ER stress under PRDX4 deficiency.

CONCLUSION

Our results demonstrated that the lack of PRDX4 aggravated the colonic mucosal damage induced by DSS. Because PRDX4 functions as an ER thiol oxidase as well as an antioxidant, DSS induced oxidative damage and ER stress to a greater degree in PRDX4^-/y than WT mice. These findings suggest that PRDX4 may represent a novel therapeutic molecule in intestinal inflammation.

In-depth proteomic analysis of Boleophthalmus pectinirostris skin mucus

Fish skin mucus serves as the first line of defence against pathogens and external stressors. The mudskipper Boleophthalmus pectinirostris inhabits intertidal mudflats containing abundant and diverse microbial populations; thus, the skin and mucus of B. pectinirostris are very important for immune defence. However, the molecules involved in the immune response and mucus secretion in the skin of this fish are poorly understood. To explore the proteomic profile of the skin mucus and understand the molecular mechanisms underlying B. pectinirostris adaption to amphibious environments, the microstructure of B. pectinirostris skin was analysed, and a series of histochemical procedures were employed for mucous glycoprotein localization and characterization. In addition, the antibacterial activity of B. pectinirostris skin mucus was studied, and the transcriptome of the skin and in-depth proteome of the mucus were determined. These studies revealed the hierarchical structure of B. pectinirostris skin and different types of glycoproteins (GPs) in the dermal bulge (DB) of the B. pectinirostris skin epidermis. The mucus has a broad antimicrobial spectrum and significant effects on the bacterial morphology. Furthermore, 93,914 unigenes were sequenced from B. pectinirostris skin tissue, and a total of 559 proteins were identified from B. pectinirostris skin mucus. SIGNIFICANCE.

Peroxiredoxin 1, a Novel HBx-Interacting Protein, Interacts with Exosome Component 5 and Negatively Regulates Hepatitis B Virus (HBV) Propagation through Degradation of HBV RNA

Hepatitis B virus (HBV) infection is a major risk factor for the development of chronic liver diseases, including cirrhosis and hepatocellular carcinoma (HCC). A growing body of evidence suggests that HBV X protein (HBx) plays a crucial role in viral replication and HCC development. Here, we identified peroxiredoxin 1 (Prdx1), a cellular hydrogen peroxide scavenger, as a novel HBx-interacting protein. Coimmunoprecipitation analysis coupled with site-directed mutagenesis revealed that the region from amino acids 17 to 20 of the HBx, particularly HBx Cys¹⁷, is responsible for the interaction with Prdx1. Knockdown of Prdx1 by siRNA significantly increased the levels of intracellular HBV RNA, HBV antigens, and extracellular HBV DNA, whereas knockdown of Prdx1 did not increase the activities of HBV core, enhancer I (Enh1)/X, preS1, and preS2/S promoters. Kinetic analysis of HBV RNA showed that knockdown of Prdx1 inhibited HBV RNA decay, suggesting that Prdx1 reduces HBV RNA levels posttranscriptionally. The RNA coimmunoprecipitation assay revealed that Prdx1 interacted with HBV RNA. The exosome component 5 (Exosc5), a member of the RNA exosome complexes, was coimmunoprecipitated with Prdx1, suggesting its role in regulation of HBV RNA stability. Taken together, these results suggest that Prdx1 and Exosc5 play crucial roles in host defense mechanisms against HBV infection.IMPORTANCE Hepatitis B virus (HBV) infection is a major global health problem. HBx plays important roles in HBV replication and viral carcinogenesis through its interaction with host factors. In this study, we identified Prdx1 as a novel HBx-binding protein. We provide evidence suggesting that Prdx1 promotes HBV RNA decay through interaction with HBV RNA and Exosc5, leading to downregulation of HBV RNA. These results suggest that Prdx1 negatively regulates HBV propagation. Our findings may shed new light on the roles of Prdx1 and Exosc5 in host defense mechanisms in HBV infection.

Evaluation of the immune response against Trypanosoma cruzi cytosolic tryparedoxin peroxidase in human natural infection

Trypanosoma cruzi, the aetiological agent of Chagas disease, has a highly efficient detoxification system to deal with the oxidative burst imposed by its host. One of the antioxidant enzymes involved is the cytosolic tryparedoxin peroxidase (c-TXNPx), which catalyses the reduction to hydrogen peroxide, small-chain organic hydroperoxides and peroxynitrite. This enzyme is present in all parasite stages, and its overexpression renders parasites more resistant to the oxidative defences of macrophages, favouring parasite survival. This work addressed the study of the specific humoral and cellular immune response triggered by c-TXNPx in human natural infection. Thus, sera and peripheral blood mononuclear cells (PBMC) were collected from chronically infected asymptomatic and cardiac patients, and non-infected individuals. Results showed that levels of IgG antibodies against c-TXNPx were low in sera from individuals across all groups. B-cell epitope prediction limited immunogenicity to a few, small regions on the c-TXNPx sequence. At a cellular level, PBMC from asymptomatic and cardiac patients proliferated and secreted interferon-γ after c-TXNPx stimulation, compared with mock control. However, only proliferation was higher in asymptomatic patients compared with cardiac and non-infected individuals. Furthermore, asymptomatic patients showed an enhanced frequency of CD19⁺ CD69⁺ cells upon exposure to c-TXNPx. Overall, our results show that c-TXNPx fails to induce a strong immune response in natural infection, being measurable only in those patients without any clinical symptoms. The low impact of c-TXNPx in the human immune response could be strategic for parasite survival, as it keeps this crucial antioxidant enzyme activity safe from the mechanisms of adaptive immune response.

Dual function of peroxiredoxin I in lipopolysaccharide-induced osteoblast apoptosis via reactive oxygen species and the apoptosis signal-regulating kinase 1 signaling pathway

Lipopolysaccharide (LPS)-induced osteoblast apoptosis is a prominent factor to the defect in periodontal tissue repair in periodontal disease. LPS challenge contributes to the production of reactive oxygen species (ROS) in periodontitis, and peroxiredoxin 1 (Prx1) is an antioxidant protein that protect cells against oxidative damage from ROS. Without LPS stimulation, apoptotic rates were higher in both Prx1 knockout (Prx1^KO) and Prx1 overexpression (Prx1^OE) cells compared with wild type. After LPS stimulation, intracellular ROS in Prx1^KO cells showed the highest level and Prx1^OE cells showed the least. Treatment with LPS significantly elevated the expression of Bax, Cyto-c, and caspase 3 in Prx1^KO cells compared with wild type, although this could be completely abolished by NAC. In Prx1^OE cells, the expression and activation of ASK1 were significantly increased, and this was slightly reduced by LPS stimulation. NQDI-1 completely abolished the increased phosphorylation of JNK and p38 and the expression of caspase 3 in LPS-stimulated cells. These results indicate that Prx1 eliminates intracellular ROS and exhibits a cytoprotective role in LPS-induced apoptosis. However, under physiological conditions, Prx1 overexpression acts as a H₂O₂ messenger, triggering the expression of ASK1 and its downstream cascades.

Specific Interactions Measured by AFM on Living Cells between Peroxiredoxin-5 and TLR4: Relevance for Mechanisms of Innate Immunity

Inflammation is a pathophysiological response of innate immunity to infection or tissue damage. This response is among others triggered by factors released by damaged or dying cells, termed damage-associated molecular pattern (DAMP) molecules that act as danger signals. DAMPs interact with pattern recognition receptors (PRRs) to contribute to the induction of inflammation. However, how released peroxiredoxins (PRDXs) are able to activate PRRs, such as Toll-like receptors (TLRs), remains elusive. Here, we used force-distance curve-based atomic force microscopy to investigate the molecular mechanisms by which extracellular human PRDX5 can activate a proinflammatory response. Single-molecule experiments demonstrated that PRDX5 binds to purified TLR4 receptors, on macrophage-differentiated THP-1 cells, and on human TLR4-transfected CHO cells. These findings suggest that extracellular PRDX5 can specifically trigger a proinflammatory response. Moreover, our work also revealed that PRDX5 binding induces a cellular mechanoresponse. Collectively, this study provides insights into the role of extracellular PRDX5 in innate immunity.

FGF1 improves functional recovery through inducing PRDX1 to regulate autophagy and anti-ROS after spinal cord injury

Fibroblast growth factor 1 (FGF1) is thought to exert protective and regenerative effects on neurons following spinal cord injury (SCI), although the mechanism of these effects is not well understood. The use of FGF1 as a therapeutic agent is limited by its lack of physicochemical stability and its limited capacity to cross the blood‐spinal cord barrier. Here, we demonstrated that overexpression of FGF1 in spinal cord following SCI significantly reduced tissue loss, protected neurons in the ventricornu, ameliorated pathological morphology of the lesion, dramatically improved tissue recovery via neuroprotection, and promoted axonal regeneration and remyelination both in vivo and in vivo. In addition, the autophagy and the expression levels of PRDX1 (an antioxidant protein) were induced by AAV‐FGF1 in PC12 cells after H₂O₂ treatment. Furthermore, the autophagy levels were not changed in PRDX1‐suppressing cells that were treated by AAV‐FGF1. Taken together, these results suggest that FGF1 improves functional recovery mainly through inducing PRDX1 expression to increase autophagy and anti‐ROS activity after SCI.

Peroxiredoxin-1 promotes cell proliferation and metastasis through enhancing Akt/mTOR in human osteosarcoma cells

Osteosarcoma is characterized by high propensity for metastasis, especially to the lung, which is the main cause of death. Peroxiredoxin-1 (PRDX1) plays significant roles in multiple processes of initiation and progression of tumorogenesis. However, whether PRDX1 participates in metastasis of osteosarcoma remains unknown. Here, we demonstrate that PRDX1 overexpressed in osteosarcoma tissues comparing to adjacent non-tumor tissues. Two independent cohorts of patients showed high level of PRDX1 correlated with clinicopathological features such as larger tumor size and advanced tumor metastasis stage. While patients with high PRDX1 level have poor prognosis. Notably, expression level of PRDX1 especially increased in lung lesion of osteosarcoma patients, indicating that PRDX1 may promote lung metastasis. Ectopic expression of PRDX1 promotes osteosarcoma cell migration and metastasis in vitro and in vivo, whereas knockdown of PRDX1 expression suppresses cell metastatic behaviors such as invasion and migration. Furthermore, we found that PRDX1 promotes cells metastasis through enhancing Akt/mTOR signal pathway. Taken together, our findings prove the important role of PRDX1 in the molecular etiology of osteosarcoma and suggest that PRDX1 may be a novel prognostic biomarker and therapeutic target for osteosarcoma.