Circulating levels of peroxiredoxin 4 as a novel biomarker of oxidative stress in patients with sepsis

Molecular heterogeneity in pediatric sepsis: identification of oxidative stress-related subtypes and diagnostic biomarkers through integrated bioinformatics analysis

BACKGROUND

Pediatric sepsis is a life-threatening condition characterized by a dysregulated immune response to infection, often involving heightened oxidative stress. Understanding the molecular heterogeneity of sepsis can provide insights into potential therapeutic targets and diagnostic biomarkers.

METHODS

Machine learning approaches were employed to identify diagnostic biomarkers. Unsupervised clustering was performed to identify distinct sepsis subtypes. We conducted an integrative analysis combining Gene Set Variation Analysis (GSVA), Gene Set Enrichment Analysis (GSEA), differential gene expression, and functional enrichment to study oxidative stress-related subgroups in sepsis patients. Immune cell infiltration and immune-related pathway activities were analyzed using the ssGSEA algorithm. GSVA and GSEA indicated significant enrichment of oxidative stress-related pathways in sepsis patients compared to controls.

RESULTS

Differential expression analysis identified 371 upregulated and 304 downregulated genes in sepsis, with 34 genes linked to oxidative stress. LASSO and Random Forest analyses highlighted key diagnostic genes (GBA and MGST1), validated in independent datasets (GSE13904) with high diagnostic accuracy (AUC: GBA = 0.924, MGST1 = 0.857). Unsupervised clustering revealed two distinct sepsis subtypes with differential immune cell infiltration and pathway activities: Subtype 1 showed higher T cell and TFH infiltration, while Subtype 2 exhibited increased macrophage infiltration. Functional enrichment and GSEA identified key metabolic, oxidative stress, and immune pathways that were enriched in Subtype 2.

CONCLUSION

Our comprehensive bioinformatics analysis unveils significant oxidative stress-related molecular heterogeneity in sepsis, identifying potential diagnostic biomarkers and therapeutic targets. Personalized medicine approaches targeting specific oxidative stress pathways and immune responses could enhance sepsis management and patient outcomes.

A comprehensive review of peroxiredoxin 4, a redox protein evolved in oxidative protein folding coupled with hydrogen peroxide detoxification

Peroxiredoxin (PRDX) primarily employs electrons from thioredoxin in order to reduce peroxides. PRDX4 mainly resides either in the endoplasmic reticulum (ER) lumen or in extracellular spaces. Due to the usage of alternative promoters, a first exon is transcribed from different regions of the Prdx4 gene, which results in two types of mRNAs. The first type is designated as Prdx4. It is translated with a cleavable, hydrophobic signal sequence and is expressed in most cells throughout the body. The second type is designated as Prdx4t. The peroxidase activity of PRDX4 is involved in both the reduction of hydrogen peroxides and in the oxidative folding of nascent proteins in the ER. Prdx4 appears to have evolved from an ancestral gene in Eutherians simultaneously with the evolution of sperm protamine to cysteine-rich peptides, and, therefore, the testis-specific PRDX4t is likely involved in spermatogenesis through the oxidative folding of protamine. The dysfunction of PRDX4 leads to oxidative damage and ER stress, and is related to various diseases including diabetes and cancer. In this review article we refer to the results of biological and medical research in order to unveil the functional consequences of this unique member of the PRDX family.

Serum peroxiredoxin-4, a biomarker of oxidative stress, associates with new-onset chronic kidney disease: A population-based cohort study

BACKGROUND

Chronic Kidney Disease (CKD), is often detected late due to its asymptomatic nature in the early stage of the disease. Overproduction of reactive oxygen species contributes to various pathological processes through oxidative stress (OS), impacting on cellular structures and functions with previous studies suggesting a link between OS and CKD progression. This study investigated the association between serum peroxiredoxin-4 (Prx4), a biomarker of oxidative stress, and the development of CKD in the general population.

METHODS

This study featured data from the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) cohort, involving 5341 participants without CKD at baseline who underwent extensive prospective health evaluations. Serum Prx4 levels were quantified using an immunoluminometric assay. The primary outcome was new-onset CKD as defined by the composite of urinary albumin excretion (UAE) > 30 mg/24-h, an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, or both.

RESULTS

Baseline median Prx4 level was 0.65 [interquartile range (IQR): 0.42-1.04] U/L, median eGFR was 98 [IQR: 87-108] mL/min/1.73 m2, and median UAE was 8.1 [IQR: 6.0-12.1] mg/L. During a median follow-up of 10.4 [IQR: 6.3-11.4] years, 867 (16.2 %) patients developed new-onset CKD. Higher Prx4 levels were significantly associated with an increased risk of CKD (hazard ratio (HR) per doubling: 1.29 [95 % confidence interval (CI): 1.21-1.37], p < 0.001), also after adjustment for risk factors including sex, smoking status, systolic blood pressure, high-sensitive C-reactive protein, chronic heart failure, diabetes mellitus and dyslipidemia (HR per doubling: 1.16 [1.06-1.24], p < 0.001). Sensitivity analyses confirmed the robustness of these findings.

CONCLUSIONS

This study supports the hypothesis that systemic oxidative stress, reflected by higher serum Prx4 levels, is significantly associated with the risk of developing CKD in the general population. These findings suggest that Prx4 could be a valuable biomarker for early risk stratification and prevention strategies in CKD management.

Oxidative stress, defective proteostasis and immunometabolic complications in critically ill patients

Oxidative stress (OS) develops in critically ill patients as a metabolic consequence of the immunoinflammatory and degenerative processes of the tissues. These induce increased and/or dysregulated fluxes of reactive species enhancing their pro-oxidant activity and toxicity. At the same time, OS sustains its own inflammatory and immunometabolic pathogenesis, leading to a pervasive and vitious cycle of events that contribute to defective immunity, organ dysfunction and poor prognosis. Protein damage is a key player of these OS effects; it generates increased levels of protein oxidation products and misfolded proteins in both the cellular and extracellular environment, and contributes to forms DAMPs and other proteinaceous material to be removed by endocytosis and proteostasis processes of different cell types, as endothelial cells, tissue resident monocytes-macrophages and peripheral immune cells. An excess of OS and protein damage in critical illness can overwhelm such cellular processes ultimately interfering with systemic proteostasis, and consequently with innate immunity and cell death pathways of the tissues thus sustaining organ dysfunction mechanisms. Extracorporeal therapies based on biocompatible/bioactive membranes and new adsorption techniques may hold some potential in reducing the impact of OS on the defective proteostasis of patients with critical illness. These can help neutralizing reactive and toxic species, also removing solutes in a wide spectrum of molecular weights thus improving proteostasis and its immunometabolic corelates. Pharmacological therapy is also moving steps forward which could help to enhance the efficacy of extracorporeal treatments. This narrative review article explores the aspects behind the origin and pathogenic role of OS in intensive care and critically ill patients, with a focus on protein damage as a cause of impaired systemic proteostasis and immune dysfunction in critical illness.

Critical Role of the Sulfiredoxin-Peroxiredoxin IV Axis in Urethane-Induced Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC), the most common type of lung cancer, etiologically associates with tobacco smoking which mechanistically contributes to oxidative stress to facilitate the occurrence of mutations, oncogenic transformation and aberrantly activated signaling pathways. Our previous reports suggested an essential role of Sulfiredoxin (Srx) in promoting the development of lung cancer in humans, and was causally related to Peroxiredoxin IV (Prx4), the major downstream substrate and mediator of Srx-enhanced signaling. To further explore the role of the Srx-Prx4 axis in de novo lung tumorigenesis, we established Prx4-/- and Srx-/-/Prx4-/- mice in pure FVB/N background. Together with wild-type litter mates, these mice were exposed to carcinogenic urethane and the development of lung tumorigenesis was evaluated. We found that disruption of the Srx-Prx4 axis, either through knockout of Srx/Prx4 alone or together, led to a reduced number and size of lung tumors in mice. Immunohistological studies found that loss of Srx/Prx4 led to reduced rate of cell proliferation and less intratumoral macrophage infiltration. Mechanistically, we found that exposure to urethane increased the levels of reactive oxygen species, activated the expression of and Prx4 in normal lung epithelial cells, while knockout of Prx4 inhibited urethane-induced cell transformation. Moreover, bioinformatics analysis found that the Srx-Prx4 axis is activated in many human cancers, and their increased expression is tightly correlated with poor prognosis in NSCLC patients.

Peroxiredoxin 4 regulates tumor-cell-like characteristics of fibroblast-like synoviocytes in rheumatoid arthritis through PI3k/Akt signaling pathway

Peroxiredoxin-4 (PRDX4), a member of PRDX family, which played an important role in scavenging reactive oxygen species (ROS). The up-regulation of PRDX4 in synovial tissue and synovial fluid from rheumatoid arthritis (RA) patients has been reported. However, the biological functions of PRDX4 in fibroblast-like synoviocytes (RA-FLS) remains unclear. In this research, we reveal that expression of PRDX4 was notably increased in RA synovial tissue, especially in hyperplastic synovial tissue. PRDX4 silencing significantly inhibited the tumor cell-like behaviors and mRNA expression of matrix metalloproteinases (MMPs) in RA-FLS. Furthermore, overexpression of PRDX4 markedly activated PI3K/Akt signaling pathway, which can be reverted by Akt inhibitor MK-2206. These observations identified elevated PRDX4 may regulates the tumor cell-like biological characteristic of RA-FLS via Pi3k/Akt pathway. Targeting PRDX4 and its downstream signaling pathway might provide a potential diagnostic markers and therapeutic target for RA.

The Role of Peroxiredoxins in the Regulation of Sepsis

Oxidative stress, a result of a disturbance in redox homeostasis, is considered to be one of the main aggravating events in the pathogenesis of immune disorders. Peroxiredoxins (Prdxs) are an enzyme family that catalyzes the reduction of peroxides, including hydrogen peroxide, lipid peroxides, and nitrogen peroxides. Although the maintenance of cellular redox homeostasis through Prdxs is essential for surviving in adverse environments, Prdxs also participate in the regulation of cellular signal transduction by modulating the activities of a panel of molecules involved in the signal transduction process. Although Prdxs were discovered as intracellular anti-oxidative enzymes, recent research has revealed that Prdxs also play important roles in the extracellular milieu. Indeed, Prdxs have been shown to have the capacity to activate immune cells through ligation with innate immune receptors such as toll-like receptors (TLRs). In this review, we will summarize the intracellular as well as extracellular roles of Prdxs for and against the pathogenesis of inflammatory disorders including sepsis, hemorrhagic shock, and drug-induced liver injury.

De Novo Transcriptome Analysis Reveals Potential Thermal Adaptation Mechanisms in the Cicada Hyalessa fuscata

Simple Summary

In metropolitan Seoul and its vicinity, cicadas of the species Hyalessa fuscata living in warmer areas could tolerate the heat better than those living in cooler areas, but genetic mechanisms involved in better heat tolerance remained unclear. In this study, we examined differences in gene expression of cicadas living in a warm urban area, a cool urban area and a suburban area in three experimental treatments: no heating, 10 min heating and heating until the cicadas lost their mobility. Cicadas from the warm urban area changed their gene expressions the most. Activated genes were mostly related to heat shock, energy metabolism, and detoxification. These results suggested that under heat stress, cicadas inhabiting warm areas could differentially express genes to increase their thermal tolerance.

Abstract

In metropolitan Seoul, populations of the cicada Hyalessa fuscata in hotter urban heat islands (“high UHIs”) exhibit higher thermal tolerance than those in cooler UHIs (“low UHIs”). We hypothesized that heat stress may activate the expression of genes that facilitate greater thermal tolerance in high-UHI cicadas than in those from cooler areas. Differences in the transcriptomes of adult female cicadas from high-UHI, low-UHI, and suburban areas were analyzed at the unheated level, after acute heat stress, and after heat torpor. No noticeable differences in unheated gene expression patterns were observed. After 10 min of acute heat stress, however, low-UHI and suburban cicadas expressed more heat shock protein genes than high-UHI counterparts. More specifically, remarkable changes in the gene expression of cicadas across areas were observed after heat torpor stimulus, as represented by a large number of up- and downregulated genes in the heat torpor groups compared with the 10 min acute heat stress and control groups. High-UHI cicadas expressed the most differentially expressed genes, followed by the low-UHI and suburban cicadas. There was a notable increase in the expression of heat shock, metabolism, and detoxification genes; meanwhile, immune-related, signal transduction, and protein turnover genes were downregulated in high-UHI cicadas versus the other cicada groups. These results suggested that under heat stress, cicadas inhabiting high-UHIs could rapidly express genes related to heat shock, energy metabolism, and detoxification to protect cells from stress-induced damage and to increase their thermal tolerance toward heat stress. The downregulation of apoptosis mechanisms in high-UHI cicadas suggested that there was less cellular damage, which likely contributed to their high tolerance of heat stress.

Association of Prx4, Total Oxidant Status, and Inflammatory Factors with Insulin Resistance in Polycystic Ovary Syndrome

INTRODUCTION

Chronic inflammation and oxidative stress conditions have been reported in women with polycystic ovary syndrome (PCOS). Peroxiredoxin 4 (Prx4) is a related antioxidant in insulin synthesis. We hypothesized that insulin resistance in these women is associated with total oxidant status (TOS) and inflammatory factors.

MATERIALS AND METHODS

Two hundred three people including 104 PCOS patients and 99 healthy women, who were matched for age and body mass index (BMI), entered the study. Waist circumference of the participants was measured; serum glucose, lipid profile, insulin, Prx4, TOS, hs-CRP, and TNF-α were also evaluated.

RESULTS

The Prx4 level was significantly lower in PCOS than in the control group. In addition, marked increase was observed in the concentration of TOS, hs-CRP, and TNF-α in PCOS, compared to the healthy women. There was a positive correlation of TOS with hs-CRP, TNF-α, and HOMA-IR. The risk of PCOS for subjects with high hs-CRP was 60 times greater than those who had low serum hs-CRP concentration; after performing multiple logistic regression analyses with the backward method, TNF-α was considered as an effective biomarker to predict PCOS β = 49.087 (all p < 0.05).

CONCLUSION

This study identified increased oxidative stress and inflammation in PCOS; this may be due to decrease in the antioxidants, such as Prx4.

Acute Running and Coronary Heart Disease Risk Markers in Male Cigarette Smokers and Nonsmokers: A Randomized Crossover Trial

PURPOSE

Cigarette smoking is an independent risk factor for coronary heart disease and is associated with impaired postprandial metabolism. Acute exercise reduces postprandial lipemia and improves other coronary heart disease risk markers in nonsmokers. Less is known about responses in cigarette smokers.

METHODS

Twelve male cigarette smokers (mean ± SD; age = 23 ± 4 yr, body mass index = 24.9 ± 3.0 kg·m-2) and 12 male nonsmokers (age = 24 ± 4 yr, body mass index = 24.1 ± 2.0 kg·m-2) completed two, 2-d conditions (control and exercise) in a randomized crossover design. On day 1, participants rested for 9 h (0800-1700) in both conditions except a 60-min treadmill run (65% ± 7% peak oxygen uptake, 2.87 ± 0.54 MJ) was completed between 6.5 and 7.5 h (1430-1530) in the exercise condition. On day 2 of both conditions, participants rested and consumed two high-fat meals over 8 h (0900-1700) during which 13 venous blood samples and nine resting arterial blood pressure measurements were collected.

RESULTS

Smokers exhibited higher postprandial triacylglycerol and C-reactive protein than nonsmokers (main effect group effect size [Cohen's d] ≥ 0.94, P ≤ 0.034). Previous day running reduced postprandial triacylglycerol, insulin, and systolic and diastolic blood pressure (main effect condition d ≥ 0.28, P ≤ 0.044) and elevated postprandial nonesterified fatty acid and C-reactive protein (main effect condition d ≥ 0.41, P ≤ 0.044). Group-condition interactions were not apparent for any outcome across the total postprandial period (0-8 h; all P ≥ 0.089), but the exercise-induced reduction in postprandial triacylglycerol in the early postprandial period (0-4 h) was greater in nonsmokers than smokers (-21%, d = 0.43, vs -5%, d = 0.16, respectively; group-condition interaction P = 0.061).

CONCLUSIONS

Acute moderate-intensity running reduced postprandial triacylglycerol, insulin, and resting arterial blood pressure the day after exercise in male cigarette smokers and nonsmokers. These findings highlight the ability of acute exercise to augment the postprandial metabolic health of cigarette smokers and nonsmokers.

Oxidation of peroxiredoxin-4 induces oligomerization and promotes interaction with proteins governing protein folding and endoplasmic reticulum stress

Peroxiredoxins (PRDXs) catalyze the reduction of hydrogen peroxide (H₂O₂). PRDX4 is the only peroxiredoxin located within the endoplasmic reticulum (ER) and is the most highly expressed H₂O₂ scavenger in the ER. PRDX4 has emerged as an important player in numerous diseases, such as fibrosis and metabolic syndromes, and its overoxidation is a potential indicator of ER redox stress. It is unclear how overoxidation of PRDX4 governs its oligomerization state and interacting partners. Herein, we addressed these questions via nonreducing Western blots, mass spectrometry, and site-directed mutagenesis. We report that the oxidation of PRDX4 in lung epithelial cells treated with tertbutyl hydroperoxide caused a shift of PRDX4 from monomer/dimer to high molecular weight (HMW) species, which contain PRDX4 modified with sulfonic acid residues (PRDX4-SO₃), as well as of a complement of ER-associated proteins, including protein disulfide isomerases important in protein folding, thioredoxin domain-containing protein 5, and heat shock protein A5, a key regulator of the ER stress response. Mutation of any of the four cysteines in PRDX4 altered the HMW species in response to tertbutyl hydroperoxide as well as the secretion of PRDX4. We also demonstrate that the expression of ER oxidoreductase 1 alpha, which generates H₂O₂ in the ER, increased PRDX4 HMW formation and secretion. These results suggest a link between SO₃ modification in the formation of HMW PRDX4 complexes in cells, whereas the association of key regulators of ER homeostasis with HMW oxidized PRDX4 point to a putative role of PRDX4 in regulating ER stress responses.

Modulation of vascular integrity and neuroinflammation by peroxiredoxin 4 following cerebral ischemia-reperfusion injury

Ischemic stroke is a leading cause of morbidity and mortality worldwide, with oxidative stress playing a key role in the injury mechanism of thrombolytic therapy. There is increasing evidence that oxidative stress damages endothelial cells (ECs), degrades tight junction proteins (TJs), and contributes to increased blood-brain barrier (BBB) permeability. It has been demonstrated that the breakdown of BBB could increase the risk of intracerebral hemorrhagic transformation in ischemic stroke. And an episode of cerebral ischemia/reperfusion (I/R) also initiates oxidative stress-mediated inflammatory processes in ECs, which further promotes BBB disruption and the progression of brain injury. Previous studies have revealed that antioxidants could inhibit ROS generation and attenuate BBB disruption after cerebral I/R. Peroxiredoxin 4 (Prx4) is a member of the antioxidant enzymes family (Prx1-6) and has been characterized to be an efficient H₂O₂ scavenger. It should be noted that Prx4 may be directly involved in the protection of ECs from the effects of ROS and function in ECs as a membrane-associated peroxidase. This paper reviewed the implication of Prx4 on vascular integrity and neuroinflammation following a cerebral I/R injury.

Association of glutamate cystein ligase (GCL) activity Peroxiredoxin 4 (prxR4) and apelin levels in women with preeclampsia

INTRODUCTION

Preeclampsia is a common disease of pregnancy that is characterized by symptoms such as high blood pressure and proteinuria. Peroxiredoxin 4 (Prx4), is a protein with antioxidant properties which is produced in placenta and protects it from antioxidant stress and recurrent miscarriage. For regeneration of Peroxiredoxin 4 need to glutathione (GSH) and Glutamate-cysteine ligase (GCL) enzyme controls the pathway of glutathione regeneration. Apelin is a paired internal ligand with a G protein coupled receptor and is associated with angiotensin receptor (AT1) as a blood pressure regulator. This study was designed to evaluate GCL enzyme activity and Peroxiredoxin 4, glutathione and apelin levels in serum of women with preeclampsia.

MATERIAL AND METHODS

Thirty pregnant women with preeclampsia and 30 healthy pregnant women were enrolled in this study. All participants were diagnosed by clinical examination and confirmation by Obstetrician-Gynecologist. The GCL enzyme activity and concentration of Prx4 and apelin in serum samples were measured using ready-to-use non-competitive ELISA methods while glutathione level was determined using Ellman's reagent.

RESULTS

The GCL enzyme activity and Prx4 level were significantly lower in preeclampsia compared with control group (p < 0.05). In addition, marked reductions were observed in the concentrations of glutathione and apelin in preeclampsia compared to the healthy pregnant women (p < 0.05).

CONCLUSION

This study identified the role of the GCL and Prx4 system in preeclampsia disorder and may be one of the ways to prevent and reduce the risks of preeclampsia in high-risk women using diet control and stress reduction.

The overexpression of peroxiredoxin-4 affects the progression of idiopathic pulmonary fibrosis

BACKGROUND

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is life-threatening. Several serum biomarkers, such as Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D), are clinically used for evaluating AE-IPF, but these biomarkers are not adequate for establishing an early and accurate diagnosis of AE-IPF. Recently, the protective roles of the members of the peroxiredoxin (PRDX) family have been reported in IPF; however, the role of PRDX4 in AE-IPF is unclear.

METHODS

Serum levels of PRDX4 protein, KL-6, SP-D and lactate dehydrogenase (LDH) in 51 patients with stable IPF (S-IPF), 38 patients with AE-IPF and 15 healthy volunteers were retrospectively assessed using enzyme-linked immunosorbent assay. Moreover, as an animal model of pulmonary fibrosis, wild-type (WT) and PRDX4-transgenic (Tg) mice were intratracheally administered with bleomycin (BLM, 2 mg/kg), and fibrotic and inflammatory changes in lungs were evaluated 3 weeks after the intratracheal administration.

RESULTS

Serum levels of PRDX4 protein, KL-6, SP-D and LDH in patients with S-IPF and AE-IPF were significantly higher than those in healthy volunteers, and those in AE-IPF patients were the highest among the three groups. Using receiver operating characteristic curves, area under the curve values of serum PRDX4 protein, KL-6, SP-D, and LDH for detecting AE-IPF were 0.873, 0.698, 0.675, and 0.906, respectively. BLM-treated Tg mice demonstrated aggravated histopathological findings and poor prognosis compared with BLM-treated WT mice. Moreover, PRDX4 expression was observed in alveolar macrophages and lung epithelial cells of BLM-treated Tg mice.

CONCLUSIONS

PRDX4 is associated with the aggravation of inflammatory changes and fibrosis in the pathogenesis of IPF, and serum PRDX4 may be useful in clinical practice of IPF patients.

Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles

Inflammasomes are cytosolic protein complexes, which orchestrate the maturation of active IL‐1β by proteolytic cleavage via caspase‐1. Although many principles of inflammasome activation have been described, mechanisms that limit inflammasome‐dependent immune responses remain poorly defined. Here, we show that the thiol‐specific peroxidase peroxiredoxin‐4 (Prdx4) directly regulates IL‐1β generation by interfering with caspase‐1 activity. We demonstrate that caspase‐1 and Prdx4 form a redox‐sensitive regulatory complex via caspase‐1 cysteine 397 that leads to caspase‐1 sequestration and inactivation. Mice lacking Prdx4 show an increased susceptibility to LPS‐induced septic shock. This effect was phenocopied in mice carrying a conditional deletion of Prdx4 in the myeloid lineage (Prdx4‐ΔLysMCre). Strikingly, we demonstrate that Prdx4 co‐localizes with inflammasome components in extracellular vesicles (EVs) from inflammasome‐activated macrophages. Purified EVs are able to transmit a robust IL‐1β‐dependent inflammatory response in vitro and also in recipient mice in vivo. Loss of Prdx4 boosts the pro‐inflammatory potential of EVs. These findings identify Prdx4 as a critical regulator of inflammasome activity and provide new insights into remote cell‐to‐cell communication function of inflammasomes via macrophage‐derived EVs.

Increased circulating peroxiredoxin-4 in sepsis model rats involves secretion from hepatocytes and is mitigated by GYY4137

Circulating peroxiredoxin-4 (Prx4) is suggested as a prognosis marker as well as a regulator of many diseases. We aimed to examine 1) whether Prx4 is secreted from the liver in an animal model of sepsis and 2) effects of GYY4137, a hydrogen sulfide donor molecule, on septic liver injury as well as the hepatic secretion of Prx4. Rats (Wistar, male, 6 weeks old) were administered lipopolysaccharide (LPS, 15 mg/kg body weight, i.p.) with or without pre-administration of GYY4137 (50 mg/kg body weight, i.p.) and sacrificed 24 h after LPS administration. Hematoxylin-eosin and Elastica Masson-Goldner stains were used to evaluate hepatic injuries. Cytokine expression levels were determined by qPCR, and the levels of Prx4 in the serum and liver were determined by immunoblotting. Hepatocytes were isolated from rat liver, and the levels of Prx4 in the medium as well as the cells were determined 24 h after the administrations of LPS (1 µg/ml), tumor necrosis factor-α (TNFα, 50 ng/ml), or interleukin-1β (IL-1β, 10 ng/ml), with or without GYY4137 (300 µM). Hepatic inflammation and damage in LPS-administered rats were suppressed by GYY4137. An increase in plasma Prx4 level caused by LPS was observed, but the increase was attenuated by pre-administration of GYY4137. Prx4 was secreted from isolated hepatocytes after stimulation with LPS, TNFα, or IL-1β. GYY4137 attenuated the IL-1β-induced Prx4 secretion from hepatocytes. Secretion from hepatocytes is likely involved in the increase in circulating Prx4 during sepsis. GYY4137 attenuates not only hepatic injury but also Prx4 secretion.

Organ-Specific Oxidative Events under Restrictive Versus Full Reperfusion Following Hemorrhagic Traumatic Shock in Rats

Background aim: Reperfusion after hemorrhagic traumatic shock (HTS) is often associated with complications that are partly ascribed to the formation of reactive oxygen species (ROS). The aim of our study was to compare the effects of restrictive reperfusion (RR) to rapid full reperfusion (FR) on ROS formation and/or oxidative events.

MATERIALS AND METHODS

Anesthetized male rats were randomly subjected to HTS followed by FR (75 mL/kg/h) or RR (30 mL/kg/h for 40 min, followed by 75 mL/kg/h) with Ringer's solution (n = 8/group). Compartment-specific ROS formation was determined by infusion of ROS scavenger 1-hydroxy-3-carboxy-2,2,5,5-tetramethyl-pyrrolidine hydrochloride (CP-H) during resuscitation, followed by electron paramagnetic resonance spectroscopy. Sham-operated animals (n = 8) served as controls. The experiment was terminated 100 min post-shock.

RESULTS

Mean arterial pressure was significantly higher in the FR compared to the RR group during early reperfusion. Only RR animals, not FR animals, showed significantly higher ROS concentrations in erythrocytes (1951 ± 420 vs. 724 ± 75 AU) and in liver (474 ± 57 vs. 261 ± 21 AU) compared to sham controls. This was accompanied by elevated alanine aminotransferase and creatinine levels in RR animals compared to both shams and FR animals, while lipid peroxidation products (thiobarbituric acid reactive substances) were significantly increased only in the kidney in the FR group (p < 0.05). RR animals showed significantly higher plasma peroxiredoxin-4 values when compared to the FR group (20 ± 2 vs. 14 ± 0.5 RLU).

CONCLUSION

Restrictive reperfusion after HTS is associated with increased ROS formation in erythrocytes and liver compared to sham controls. Moreover, the restrictive reperfusion is associated with a more pronounced injury to the liver and kidney, which is likely mediated by other than lipid peroxidation process and/or oxidative stress reactions.

Identification of key genes in Gram‑positive and Gram‑negative sepsis using stochastic perturbation

Sepsis is an inflammatory response to pathogens (such as Gram-positive and Gram-negative bacteria), which has high morbidity and mortality in critically ill patients. The present study aimed to identify the key genes in Gram-positive and Gram-negative sepsis. GSE6535 was downloaded from Gene Expression Omnibus, containing 17 control samples, 18 Gram-positive samples and 25 Gram-negative samples. Subsequently, the limma package in R was used to screen the differentially expressed genes (DEGs). Hierarchical clustering was conducted for the specific DEGs in Gram-negative and Gram-negative samples using cluster software and the TreeView software. To analyze the correlation of samples at the gene level, a similarity network was constructed using Cytoscape software. Functional and pathway enrichment analyses were conducted for the DEGs using DAVID. Finally, stochastic perturbation was used to determine the significantly differential functions between Gram-positive and Gram-negative samples. A total of 340 and 485 DEGs were obtained in Gram-positive and Gram-negative samples, respectively. Hierarchical clustering revealed that there were significant differences between control and sepsis samples. In Gram-positive and Gram-negative samples, myeloid cell leukemia sequence 1 was associated with apoptosis and programmed cell death. Additionally, NADH:ubiquinone oxidoreductase subunit S4 was associated with mitochondrial respiratory chain complex I assembly. Stochastic perturbation analysis revealed that NADH:ubiquinone oxidoreductase subunit B2 (NDUFB2), NDUFB8 and ubiquinol-cytochrome c reductase hinge protein (UQCRH) were associated with cellular respiration in Gram-negative samples, whereas large tumor suppressor kinase 2 (LATS2) was associated with G1/S transition of the mitotic cell cycle in Gram-positive samples. NDUFB2, NDUFB8 and UQCRH may be biomarkers for Gram-negative sepsis, whereas LATS2 may be a biomarker for Gram-positive sepsis. These findings may promote the therapies of sepsis caused by Gram-positive and Gram-negative bacteria.

Peroxiredoxin 6 overexpression attenuates lipopolysaccharide-induced acute kidney injury

Peroxiredoxin 6 (PRDX6) is a member of the PRDX family of antioxidant enzymes and correlated with inflammatory response. Therefore, we investigated the role of PRDX6 during lipopolysaccharide (LPS)-induced acute kidney injury. Both 3 months aged PRDX6-overexpressing transgenic mice (PRDX6 mice) and wild type (WT) mice had acute renal injury induced by intraperitoneal injection of LPS (10 mg/kg)., PRDX6 mice showed decreased mortality and renal injury following LPS challenge compared to WT mice. Furthermore, infiltration of macrophages, T-cells and neutrophils, and the number of apoptotic cells were more decreased by LPS treatment in PRDX6 mice than in WT mice. Because LPS induces reactive oxygen species (ROS) production which induces inflammation through c-Jun N-terminal Kinase (JNK) and p38 MAPK activation, we investigated ROS concentration and MAPK signaling pathway in the kidney of PRDX6 mice. As expected, LPS-induced oxidative stress was attenuated, and p38 MAPK and JNK activation was decreased in the kidney of PRDX6 mice. Inhibitory effect of PRDX6 on LPS-induced apoptosis and MAPK activation in the primary renal proximal tubular cells were overcome by treatment with PRDX6 inhibitor or hydrogen peroxide. These results suggest that PRDX6 overexpression inactivates p38 MAPK and JNK pathway through decrease LPS-induced ROS concentration in the kidney, resulting in inhibition of renal apoptosis and leukocyte infiltration and led to attenuation of LPS-induced acute kidney injury.

Biomarkers for diagnosis of sepsis in patients with systemic inflammatory response syndrome: a systematic review and meta-analysis

Background

Sepsis is one of the most common diseases that seriously threaten human health. Although a large number of markers related to sepsis have been reported in the last two decades, the diagnostic accuracy of these biomarkers remains unclear due to the lack of similar baselines among studies. Therefore, we conducted a large systematic review and meta-analysis to evaluate the diagnostic value of biomarkers from studies that included non-infectious systemic inflammatory response syndrome patients as a control group.

Methods

We searched Medline, Embase and the reference lists of identified studies beginning in April 2014. The last retrieval was updated in September 2016.

Results

Ultimately, 86 articles fulfilled the inclusion criteria. Sixty biomarkers and 10,438 subjects entered the final analysis. The areas under the receiver operating characteristic curves for the 7 most common biomarkers, including procalcitonin, C-reactive protein, interleukin 6, soluble triggering receptor expressed on myeloid cells-1, presepsin, lipopolysaccharide binding protein and CD64, were 0.85, 0.77, 0.79, 0.85, 0.88, 0.71 and 0.96, respectively. The remaining 53 biomarkers exhibited obvious variances in diagnostic value and methodological quality.

Conclusions

Although some biomarkers displayed moderate or above moderate diagnostic value for sepsis, the limitations of the methodological quality and sample size may weaken these findings. Currently, we still lack an ideal biomarker to aid in the diagnosis of sepsis. In the future, biomarkers with better diagnostic value as well as a combined diagnosis using multiple biomarkers are expected to solve the challenge of the diagnosis of sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-3591-5) contains supplementary material, which is available to authorized users.

Identification of differentially expressed genes associated with burn sepsis using microarray

The aim of the present study was to identify the potential target biomarkers associated with burn sepsis using microarray. GSE1781 was downloaded from Gene Expression Omnibus and included a collective of three biological replicates for each of the three conditions: Sham‑Sham, Sham‑cecal ligation and puncture (CLP) and Burn‑CLP. Subsequently, limma was applied to screen the differentially expressed genes (DEGs). Additionally, functional annotations were predicted by pathway enrichment. Furthermore, the transcription factors were screened according to the transcriptional regulation from patterns to profiles database. Furthermore, the interaction associations of the proteins were obtained from the STRING database and the protein‑protein interaction (PPI) network was constructed using Cytoscape. Finally, the gene co‑expression analysis was conducted using CoExpress. In total, compared with Sham‑Sham, a total of 476 DEGs and 682 DEGs were obtained in Sham‑CLP and Burn‑CLP, respectively. Additionally, 230 DEGs were screened in Burn‑CLP compared with Sham‑CLP. Acadm, Ehhadh and Angptl4 were significantly enriched in the PPAR signaling pathway. Additionally, Gsta3, Gstm2 and Gstt1 in Burn‑CLP were significantly enriched in glutathione metabolism. In the PPI network, the transcription factor Ppargc1a interacted with Angptl4, while Acadm interacted with Ehhadh. The gene co‑expression analysis showed that Ehhadh could be co‑expressed with Aqp8. In conclusion, Acadm, Ehhadh, Aqp8, Gsta3, Gstm2, Gstt1, Ppargc1a and Angptl4 may be potential target genes for the treatment of burn sepsis.

Total antioxidant and total oxidant states, and serum paraoxonase-1 in neonatal sepsis

BACKGROUND

Paraoxonase-1 (PON-1) is an enzyme with a glycoprotein structure that depends on calcium and which is located in serum high-density lipoprotein (HDL). The aim of this study was to evaluate PON-1, and oxidant/antioxidant state, before and after treatment for neonatal sepsis, and to determine the usability of PON-1 in neonatal sepsis treatment.

METHODS

A total of 35 neonatal sepsis patients and 35 healthy controls were included in the study. Activity of PON-1, total oxidant state (TOS) and total antioxidant state (TAS) were measured and oxidative stress index (OSI) was calculated.

RESULTS

In the neonatal sepsis patients, pre-treatment TAS, TOS and OSI were significantly higher than the post-treatment levels (P < 0.0001, P < 0.0001 and P < 0.0001, respectively), and PON-1 was significantly lower (P < 0.0001). Similarly, pre-treatment TAS, TOS and OSI in the sepsis group were also significantly higher than in the control group (P < 0.0001, P < 0.0001 and P < 0.0001, respectively) and PON-1 was significantly lower (P < 0.0001). Post-treatment TAS in the sepsis group was significantly higher than in the control group (P = 0.009), whereas post-treatment TOS, OSI and PON-1 in the sepsis group were not significantly different to the control group (P = 0.078, P = 0.597 and P = 0.086, respectively).

CONCLUSION

Low serum PON-1 was found in neonatal sepsis. Serum PON-1 is thought to be a useful biomarker to evaluate the effectiveness of treatment and recovery in neonatal sepsis.

Molecular characterization and functional analysis of a peroxiredoxin 1 cDNA from golden pompano (Trachinotus ovatus)

Peroxiredoxin 1 (Prx 1) is an important antioxidant protein that can protect organisms against the toxicity of reactive oxygen species. In this study, a full-length Prx 1 cDNA sequence (ToPrx 1) was identified from golden pompano (Trachinotus ovatus). The ToPrx 1 cDNA was 1049 base pairs (bp) long and contained a 5'-untranslated region (UTR) of 127 nucleotides, a 3'-UTR of 328 nucleotides, and a 594 bp open reading frame (ORF) encoding a 197 amino acid polypeptide. The ToPrx 1 protein showed strong homology (79-91%) with Prx 1 proteins from other species and contained the conserved Prx domain and the signature of the peroxidase catalytic center. Phylogenetic analysis revealed that ToPrx 1 was in the fish Prx 1 subgroup, which suggests that ToPrx 1 could belong to the 2-Cys Prx subgroup. ToPrx 1 mRNA was ubiquitously detected in all tested tissues, and its expression was comparatively high in the fin, spleen, kidney, intestine, eye, gill, and blood. The expression levels of ToPrx 1 mRNA were significantly up-regulated in liver, spleen, kidney, and intestine of golden pompano injected with Photobacterium damselae. The recombinant ToPrx 1 protein (rToPrx 1) was expressed and purified through affinity chromatography and refolded successfully using ion-exchange chromatography. The antioxidant activity assay of rToPrx 1 showed that it could reduce insulin in the presence of dithiothreitol, which suggests that the antioxidant function of rToPrx 1 is thiol dependent. This study provides useful information to help further understand the functional mechanism of Prx 1 in marine fish immunity.

Physiological and pathological views of peroxiredoxin 4

Peroxiredoxins (PRDXs) form an enzyme family that exhibits peroxidase activity using electrons from thioredoxin and other donor molecules. As the signaling roles of hydrogen peroxide in response to extracellular stimuli have emerged, the involvement of PRDX in the hydrogen peroxide-mediated signaling has become evident. Among six PRDX members in mammalian cells, PRDX4 uniquely possesses a hydrophobic signal peptide at the amino terminus, and, hence, it undergoes either secretion or retention by the endoplasmic reticulum (ER) lumen. The role of PRDX4 as a sulfoxidase in ER is now attracting much attention regarding the oxidative protein folding of nascent proteins. Contrary to this role in the ER, the functional significance of PRDX4 in the extracellular milieu is virtually unknown despite its implications as a biomarker under pathological conditions in some diseases. Other than its systemically expressed form, a variant form of PRDX4 is transcribed from the upstream promoter/exon 1 of the systemic promoter/exon 1 and is uniquely expressed in sexually matured testes. Circumstantial evidence, together with deduced functions from the systemic form, suggests that there are potential roles for testicular PRDX4 in the reproductive processes such as the regulation of hormonal signals and the oxidative packaging of sperm chromatin. Elucidation of these PRDX4 functions under in vivo situations is expected to show the whole picture of how PRDX4 has evolved in multicellular organisms.

Peroxiredoxin isoforms are associated with cardiovascular risk factors in type 2 diabetes mellitus

The production of oxygen free radicals in type 2 diabetes mellitus contributes to the development of complications, especially the cardiovascular-related ones. Peroxiredoxins (PRDXs) are antioxidant enzymes that combat oxidative stress. The aim of this study was to investigate the associations between the levels of PRDX isoforms (1, 2, 4, and 6) and cardiovascular risk factors in type 2 diabetes mellitus. Fifty-three patients with type 2 diabetes mellitus (28F/25M) and 25 healthy control subjects (7F/18M) were enrolled. We measured the plasma levels of each PRDX isoform and analyzed their correlations with cardiovascular risk factors. The plasma PRDX1, -2, -4, and -6 levels were higher in the diabetic patients than in the healthy control subjects. PRDX2 and -6 levels were negatively correlated with diastolic blood pressure, fasting blood sugar, and hemoglobin A1c. In contrast, PRDX1 levels were positively correlated with low-density lipoprotein and C-reactive protein levels. PRDX4 levels were negatively correlated with triglycerides. In conclusion, PRDX1, -2, -4, and -6 showed differential correlations with a variety of traditional cardiovascular risk factors. These results should encourage further research into the crosstalk between PRDX isoforms and cardiovascular risk factors.

Circulating peroxiredoxin 4 and type 2 diabetes risk: the Prevention of Renal and Vascular Endstage Disease (PREVEND) study

AIMS/HYPOTHESIS

Oxidative stress plays a key role in the development of type 2 diabetes mellitus. We previously showed that the circulating antioxidant peroxiredoxin 4 (Prx4) is associated with cardiometabolic risk factors. We aimed to evaluate the association of Prx4 with type 2 diabetes risk in the general population.

METHODS

We analysed data on 7,972 individuals from the Prevention of Renal and Vascular End-stage Disease (PREVEND) study (49% men, aged 28-75 years) with no diabetes at baseline. Logistic regression models adjusted for age, sex, smoking, waist circumference, hypertension and family history of diabetes were used to estimate the ORs for type 2 diabetes.

RESULTS

During a median follow up of 7.7 years, 496 individuals (288 men; 58%) developed type 2 diabetes. The median (Q1-Q3) Prx4 level was 0.84 (0.53-1.40) U/l in individuals who developed type 2 diabetes and 0.68 (0.43-1.08) U/l in individuals who did not develop type 2 diabetes. For every doubling of Prx4 levels, the adjusted OR (95% CI) for type 2 diabetes was 1.16 (1.05-1.29) in the whole population; by sex, it was 1.31 (1.14-1.50) for men and 1.03 (0.87-1.21) for women. Further adjustment for other clinical measures did not materially change the results. The addition of Prx4 to a validated diabetes risk score significantly improved the prediction of type 2 diabetes in men (p = 0.002 for reclassification improvement).

CONCLUSIONS/INTERPRETATION

Our findings suggest that elevated serum Prx4 levels are associated with a higher risk of incident type 2 diabetes. For men, taking Prx4 into consideration can improve type 2 diabetes prediction over a validated diabetes risk score; in contrast, there is no improvement in risk prediction for women.

Peroxiredoxin VI oxidation in cerebrospinal fluid correlates with traumatic brain injury outcome

Traumatic brain injury (TBI) patients would benefit from the identification of reliable biomarkers to predict outcomes and treatment strategies. In our study, cerebrospinal fluid (CSF) from patients with severe TBI was evaluated for oxidant stress-mediated damage progression after hospital admission and subsequent ventriculostomy placement. Interestingly, substantial levels of peroxiredoxin VI (Prdx6), a major antioxidant enzyme normally found in astrocytes, were detected in CSF from control and TBI patients and were not associated with blood contamination. Functionally, Prdx6 and its associated binding partner glutathione S-transferase Pi (GSTP1-1, also detected in CSF) act in tandem to detoxify lipid peroxidation damage to membranes. We found Prdx6 was fully active in CSF of control patients but becomes significantly inactivated (oxidized) in TBI. Furthermore, significant and progressive oxidation of "buried" protein thiols in CSF of TBI patients (compared to those of nontrauma controls) was detected over a 24-h period after hospital admission, with increased oxidation correlating with severity of trauma. Conversely, recovery of Prdx6 activity after 24h indicated more favorable patient outcome. Not only is this the first report of an extracellular form of Prdx6 but also the first report of its detection at a substantial level in CSF. Taken together, our data suggest a meaningful correlation between TBI-initiated oxidation of Prdx6, its specific phospholipid hydroperoxide peroxidase activity, and severity of trauma outcome. Consequently, we propose that Prdx6 redox status detection has the potential to be a biomarker for TBI outcome and a future indicator of therapeutic efficacy.

CT-proAVP (copeptin), MR-proANP and Peroxiredoxin 4 after cardiac arrest: release profiles and correlation to outcome

BACKGROUND

Further characterization of the post-cardiac arrest syndrome (PCAS) is essential to better understand the mechanisms resulting in injury and death. We investigated serial serum concentrations of the stress hormone c-terminal provasopressin (CT-proAVP or copeptin), the cardiac biomarker MR-proANP and a biomarker of oxidation injury, Peroxiredoxin 4 (Prx4) in patients treated with mild hypothermia (MHT) after cardiac arrest, and studied their association to the PCAS and long-term outcome.

METHODS

Serum samples from cardiac arrest patients were collected serially: at admission, 2, 6, 12, 24, 36, 48 and 72 h after cardiac arrest. CT-proAVP, MR-proANP and Prx4 concentrations were determined and tested for association with two surrogate markers of PCAS (time to return of spontaneous circulation and circulation-SOFA score) and with cerebral performance category (CPC) at 6 months. Good outcome was defined as CPC 1 to 2.

RESULTS

Eighty-four patients were included. CT-proAVP, MR-proANP and Prx4 were early biomarkers with maximum concentrations soon after cardiac arrest and with a significant discriminatory ability between good and poor long-term outcome at most time points. CT-proAVP predicted a poor outcome with the highest accuracy, followed by MR-proANP and Prx4 (area under the receiving operating characteristics curve at 12 h of 0.85, 0.77 and 0.76 respectively). CT-proAVP and MR-proANP showed best correlation to the PCAS.

CONCLUSION

In 84 resuscitated patients receiving MHT after cardiac arrest, there is a significant difference in concentrations of CT-proAVP, MR-proANP and Prx4 between patients with good and poor outcome. CT-proAVP and MR-proANP have a significant correlation to surrogate markers of the PCAS.

Maternal obesity induces gut inflammation and impairs gut epithelial barrier function in nonobese diabetic mice

Impairment of gut epithelial barrier function is a key predisposing factor for inflammatory bowel disease, type 1 diabetes (T1D) and related autoimmune diseases. We hypothesized that maternal obesity induces gut inflammation and impairs epithelial barrier function in the offspring of nonobese diabetic (NOD) mice. Four-week-old female NOD/ShiLtJ mice were fed with a control diet (CON; 10% energy from fat) or a high-fat diet (HFD; 60% energy from fat) for 8 weeks to induce obesity and then mated. During pregnancy and lactation, mice were maintained in their respective diets. After weaning, all offspring were fed the CON diet. At 16 weeks of age, female offspring were subjected to in vivo intestinal permeability test, and then ileum was sampled for biochemical analyses. Inflammasome mediators, activated caspase-1 and mature forms of interleukin (IL)-1β and IL-18 were enhanced in offspring of obese mothers, which was associated with elevated serum tumor necrosis factor α level and inflammatory mediators. Consistently, abundance of oxidative stress markers including catalase, peroxiredoxin-4 and superoxide dismutase 1 was heightened in offspring ileum (P<.05). Furthermore, offspring from obese mothers had a higher intestinal permeability. Morphologically, maternal obesity reduced villi/crypt ratio in the ileum of offspring gut. In conclusion, maternal obesity induced inflammation and impaired gut barrier function in offspring of NOD mice. The enhanced gut permeability in HFD offspring might predispose them to the development of T1D and other gut permeability-associated diseases.

Novel links among peroxiredoxins, endothelial dysfunction, and severity of atherosclerosis in type 2 diabetic patients with peripheral atherosclerotic disease

Peroxiredoxins, a group of antioxidant protein enzymes (PRDX1 to 6), are reported as antiatherogenic factors in animals; however, human studies are lacking. The present work aims to provide baseline data regarding the phenotype of PRDX1, 2, 4, and 6 in diabetic patients with peripheral atherosclerosis disease (PAD) and their relation to endothelial dysfunction (ED) and disease severity. Plasma levels of PRDX1, 2, 4, and 6 and markers of endothelial dysfunction (ICAM-1 and VCAM-1) were measured using ELISA in 55 type 2 diabetic patients having PAD and 25 healthy subjects. Ankle-brachial index (ABI), body mass index (BMI), triglycerides (TG), total cholesterol, HbA1c, and insulin resistance (HOMA IR) were measured. PRDX1, 2, 4, and 6 levels were significantly higher in patients compared to controls (PRDX1 21.9 ± 5.71 vs 16.8 ± 3.9 ng/ml, P < 0.001, PRDX2 36.5 ± 14.83 vs 20.4 ± 8.61 ng/ml, P < 0.001, PRDX4 3,840 ± 1,440 vs 2,696 ± 1,972 pg/ml, P < 0.005, PRDX6 311 ± 110 vs 287.9 ± 114 pg/ml, P < 0.05). PRDX1 and PRDX4 correlated negatively with ABI (r = -0.273, P < 0.05 and r = -0.28, P < 0.05, respectively), while PRDX1 and PRDX2 correlated positively with HOMA/IR and TG (r = 0.276, P < 0.01 and r = 0.295, P < 0.01, respectively). ICAM-1 was associated with PRDX2 and log PRDX6 (r = 0.345, P = 0.0037 and r = 0.344, P = 0.0038). Our results provide strong links among PRDXs, ED, and severity of PAD in diabetic patients which warrants further evaluation to clarify whether high circulating levels of PRDXs are a consequence of chronic atherosclerotic disease or a predisposing factor for later cardiovascular events.

Serum peroxiredoxin 4: a marker of oxidative stress associated with mortality in type 2 diabetes (ZODIAC-28)

Background

Oxidative stress plays an underlying pathophysiologic role in the development of diabetes complications. The aim of this study was to investigate peroxiredoxin 4 (Prx4), a proposed novel biomarker of oxidative stress, and its association with and capability as a biomarker in predicting (cardiovascular) mortality in type 2 diabetes mellitus.

Methods

Prx4 was assessed in baseline serum samples of 1161 type 2 diabetes patients. Cox proportional hazard models were used to evaluate the relationschip between Prx4 and (cardiovascular) mortality. Risk prediction capabilities of Prx4 for (cardiovascular) mortality were assessed with Harrell’s C statistic, the integrated discrimination improvement and net reclassification improvement.

Results

Mean age was 67 and the median diabetes duration was 4.0 years. After a median follow-up period of 5.8 years, 327 patients died; 137 cardiovascular deaths. Prx4 was associated with (cardiovascular) mortality. The Cox proportional hazard models added the variables: Prx4 (model 1); age and gender (model 2), and BMI, creatinine, smoking, diabetes duration, systolic blood pressure, cholesterol-HDL ratio, history of macrovascular complications, and albuminuria (model 3). Hazard ratios (HR) (95% CI) for cardiovascular mortality were 1.93 (1.57 – 2.38), 1.75 (1.39 – 2.20), and 1.63 (1.28 – 2.09) for models 1, 2 and 3, respectively. HR for all-cause mortality were 1.73 (1.50 – 1.99), 1.50 (1.29 – 1.75), and 1.44 (1.23 – 1.67) for models 1, 2 and 3, respectively. Addition of Prx4 to the traditional risk factors slightly improved risk prediction of (cardiovascular) mortality.

Conclusions

Prx4 is independently associated with (cardiovascular) mortality in type 2 diabetes patients. After addition of Prx4 to the traditional risk factors, there was a slightly improvement in risk prediction of (cardiovascular) mortality in this patient group.

Gene structure, immune response and evolution: comparative analysis of three 2-Cys peroxiredoxin members of miiuy croaker, Miichthys miiuy

Peroxiredoxin family was a superfamily of selenium independent peroxidases. It was divided into six subtypes: Prx1-4 (typical 2-Cys), Prx5 (atypical 2-Cys) and Prx6 (1-Cys). This study reports the isolation and characterization three 2-Cys peroxiredoxin members of full cDNA and genomic clones from miiuy croaker (Miichthys miiuy). The genetic structure analysis showed that the C-terminal catalytic Cys positioned within GEVCPAXW. This sequence was different between Prx3 and Prx4, but was conservative in different species of the same gene, the X base was S in Prx3 but G in Prx4. Tissues expression analysis showed that the expressions of Prx3 in liver and brain were much higher than other tissues; the values of Prx4 in spleen, intestine and kidney were significantly higher than others; and the expression of Prx5 in muscle was higher than that of other tissues. Real-time PCR results showed that there were highest values of these three Prxs emerging with the time post challenge of Vibrio anguillarum in liver, spleen and kidney although the highest value time differed from each other and the expression of these three genes also changed with the change of infection time. These results indicated that expression analysis of these three genes play some positive function against pathogenic bacteria infection in miiuy croaker.

Stress markers predict mortality in patients with nonspecific complaints presenting to the emergency department and may be a useful risk stratification tool to support disposition planning

OBJECTIVES

To the authors' knowledge, no prospectively validated, biomarker-based risk stratification tools exist for elderly patients presenting to the emergency department (ED) with nonspecific complaints (NSCs), such as generalized weakness, despite the fact that an acute serious disease often underlies nonspecific disease presentation. The primary purpose for this study was to validate the retrospectively derived model for outcome prediction using copeptin and peroxiredoxin 4 (Prx4), in a different group of patients, in a prospective fashion, in a multicenter setting. The secondary goals were to evaluate the potential contribution of the midregional portion of the precursor of adrenomedullin (MR-proADM) for outcome prediction and to investigate whether disposition decisions show promise for potential improvement by using biomarker levels in addition to a clinical assessment.

METHODS

The Basel Nonspecific Complaints (BANC) study is a delayed-type cross-sectional diagnostic study, carried out in three EDs in Switzerland, with a prospective 30-day follow-up. Patients presenting to the ED with NSCs, as defined previously, were included if their vital signs were within predefined limits. Measurement of biomarkers was performed in serum samples with sandwich immunoluminometric assays. To examine the disposition process, the final disposition was compared with a combination of the first clinical disposition decision and the risk assessment, which included the biomarker MR-proADM in a retrospective simulation. Patients were divided into three groups according to MR-proADM concentration, defining three risk classes with three disposition possibilities (admission to tertiary care, transfer to geriatric hospital, discharge).

RESULTS

Thirty-three 30-day nonsurvivors were observed from among 504 study patients with NSCs. Biomarker levels were significantly greater in nonsurvivors than survivors (p < 0.0001 for all three biomarkers). Univariate Cox models reveal a C-index of 0.732 for MR-proADM, 0.719 for Prx4, and 0.723 for copeptin. The incremental added value for chi-square obtained via multivariate modeling showed that models inclusive of MR-proADM, copeptin, or Prx4 are superior to and independent of models limited to sex and age. The incrementally added chi-square for MR-proADM, beyond the chi-square of a base model consisting of age and sex, was 29.79 (p < 0.00001). In a multimarker approach, only Prx4 provided additional information to MR-proADM alone (C-index = 0.77). Applying an algorithm combining physicians' first clinical assessment plus biomarker information to derive a modified risk assessment, reassignment would lead to a potential decrease of 48 admissions to acute care, seven additional transfers to geriatric care, and 41 additional discharges (negative likelihood ratio [-LR] = 0.13). Analysis of 30-day mortality reveals that our algorithm is not inferior in terms of safety.

CONCLUSIONS

In this study the authors confirm that these new stress biomarkers permit reliable prognostication of adverse outcomes in a heterogeneous group of patients with NSCs. A simulation showed that this prognostic information could be useful to enhance the appropriateness of disposition decisions of ED patients with NSC. The use of biomarkers for risk stratification in this patient group should be evaluated with prospective intervention studies.

Correlation of the oxygen radical activity and antioxidants and severity in critically ill surgical patients - study protocol

BACKGROUND

Surgical patients who require an emergent operation commonly have severe sepsis or septic shock, followed by high morbidity and mortality rates.Despite advances in treatment however, no predictable markers are available. In severe sepsis, many pathophysiologic mechanisms are involved in progression to organ failure, and oxygen free radical and antioxidants are known to contribute to this process. Oxygen free radical and antioxidants contribute to progression of organ failure in severe sepsis. In fact, oxygen radical activity has been reported to be correlated with disease severity and prognosis in patients with severe sepsis or septic shock. Accordingly, we aim to assess the usefulness of oxygen free radical and antioxidant concentrations to predict the disease severity and mortality in a cohort of critically ill surgical patients.

METHODS/DESIGN

This is a prospective observation study including patient demographic characteristics, clinical information, blood sampling/serum oxygen radical activity, serum antioxidant activity, serum antioxidant concentrations (zinc, selenium and glutamate), disease severity scores, outcomes, lengths of stay in intensive care unit, hospital 30-day mortality.

Prognostic value of serum paraoxonase and arylesterase activity in patients with sepsis

Objective

To determine whether serum paraoxonase (PON) and arylesterase (ARE) activity might predict sepsis mortality.

Methods

Patients with sepsis and healthy control subjects were enrolled in this retrospective study. Serum PON and ARE activity levels were measured. Patients were stratified according to 30-day mortality rates.

Results

Serum PON and ARE activity levels were significantly lower in patients with sepsis ( n = 61) than in healthy controls ( n = 32), and were significantly lower in nonsurviving patients ( n = 22) than in surviving patients ( n = 39). Low PON and ARE activity levels were significantly correlated with poor overall survival in patients with sepsis.

Conclusions

Decreased serum PON and ARE activity is related to poor prognosis in patients with sepsis. Measuring the activity of PON and ARE may represent a new method for evaluating the prognosis of sepsis. In addition, both PON and ARE are potential molecular treatment targets for sepsis.

Peroxiredoxin 4, a novel circulating biomarker for oxidative stress and the risk of incident cardiovascular disease and all-cause mortality

BACKGROUND

Oxidative stress has been suggested to play a key role in the development of cardiovascular disease (CVD). The aim of our study was to investigate the associations of serum peroxiredoxin 4 (Prx4), a hydrogen peroxide-degrading peroxidase, with incident CVD and all-cause mortality. We subsequently examined the incremental value of Prx4 for the risk prediction of CVD compared with the Framingham risk score (FRS).

METHODS AND RESULTS

We performed Cox regression analyses in 8141 participants without history of CVD (aged 28 to 75 years; women 52.6%) from the Prevention of Renal and Vascular End-stage Disease (PREVEND) study in Groningen, The Netherlands. Serum Prx4 was measured by an immunoluminometric assay in baseline samples. Main outcomes were: (1) incident CVD events or CVD mortality and (2) all-cause mortality during a median follow-up of 10.5 years. In total, 708 participants (7.8%) developed CVD events or CVD mortality, and 517 participants (6.3%) died. Baseline serum Prx4 levels were significantly higher in participants with incident CVD events or CVD mortality and in those who died than in participants who remained free of outcomes (both P<0.001). In multivariable models with adjustment for Framingham risk factors, hazard ratios were 1.16 (95% CI 1.06 to 1.27, P<0.001) for incident CVD events or CVD mortality and 1.17 (95% CI 1.06 to 1.29, P=0.003) for all-cause mortality per doubling of Prx4 levels. After the addition of Prx4 to the FRS, the net reclassification improvement was 2.7% (P=0.01) using 10-year risk categories of CVD.

CONCLUSIONS

Elevated serum Prx4 levels are associated with a significantly higher risk of incident CVD events or CVD mortality and all-cause mortality after adjustment for clinical risk factors. The addition of Prx4 to the FRS marginally improved risk prediction of future CVD.

Procalcitonin as a predictive biomarker for total body irradiation-induced bacterial load and lethality in mice

Sepsis is the leading cause of mortality in intensive care units. Early detection and intervention are critical to prevent death. The acute radiation syndrome is characterized by damage of the gastrointestinal and hematopoietic systems. Translocation of intestinal microflora combined with immune system compromise may lead to septicemia and death. This work examined the utility of procalcitonin, a clinical sepsis biomarker, in a mouse model of radiation toxicity. C57/BL6 mice were exposed to total body irradiation (TBI). Intestinal mucosal permeability was measured in vivo, and liver bacterial load and plasma levels of procalcitonin (PCT), lipopolysaccharide (LPS), and LPS-binding protein were measured at baseline and at 3.5, 7, and 10 days after TBI. The value of early PCT in predicting subsequent lethality was determined by receiver operating characteristic analysis. Four days after TBI, a dose-dependent increase in permeability of the intestinal mucosa was observed, whereas bacterial translocation was present from day 7 onward. There was a high positive correlation between bacterial translocation and all sepsis biomarkers, with PCT exhibiting the strongest correlation. Moreover, plasma PCT levels were elevated already from day 3.5 onward, whereas LPS was elevated from day 7 and LPS-binding protein only 10 days after TBI. Receiver operating characteristic analysis revealed that PCT levels measured 3.5 days after TBI predicted lethality at 10 days. These data demonstrate the value of PCT as an early biomarker in radiation-induced bacteremia for mouse studies and suggest that clinical results from other septic conditions may apply to postradiation septicemia in humans.

Distinct responses of lung and liver macrophages to acute endotoxemia: role of toll-like receptor 4

Exposure to excessive quantities of bacterial-derived lipopolysaccharide (LPS) is associated with injury to the lung and the liver. Macrophages are thought to play a key role in the pathogenic response to LPS by releasing proinflammatory/cytotoxic mediators. Macrophage responses to LPS are mediated in large part by toll-like receptor 4 (TLR4). In the present studies we used C3H/HeJ mice, which possess a mutated nonfunctional TLR4, to examine its role in lung and liver macrophage responses to acute endotoxemia induced by LPS administration. Treatment of control C3H/HeOuJ mice with LPS (3 mg/ml, i.p.) was associated with a significant increase in the number of macrophages in both the lung and the liver. This was most prominent after 48 h, and was preceded by expression of proliferating cell nuclear antigen (PCNA), suggesting that macrophage proliferation contributes to the response. In liver, but not lung macrophages, LPS administration resulted in a rapid (within 3 h) increase in mRNA expression of Mn superoxide dismutase (SOD) and heme oxygenase-1 (HO-1), key enzymes in antioxidant defense. In contrast, HO-1 protein expression decreased 3 h after LPS administration in liver macrophages, while in lung macrophages it increased. mRNA expression of enzymes mediating the biosynthesis of eicosanoids, including cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1), but not 12/15-lipoxygenase (LOX), was upregulated in liver macrophages 3-24 h after LPS, with no effect on lung macrophages. However, COX-2 protein expression increased in both cell types. Loss of functional TLR4 significantly blunted the effects of LPS. Thus, no major changes were observed after LPS administration in the number of lung and liver macrophages recovered from TLR4 mutant mice, or on expression of PCNA. Increases in HO-1, MnSOD, COX-2 and PGES-1 mRNA expression in liver macrophages were also reduced in these mice. Conversely, in lung macrophages, loss of functional TLR4 resulted in increased expression of COX-2 protein and 12/15-LOX mRNA. These results demonstrate distinct lung and liver macrophage responses to acute endotoxemia are mediated, in part, by functional TLR4.

Peroxiredoxin 4: a multifunctional biomarker worthy of further exploration

Currently, there is much interest in identifying clinically relevant biomarkers, as they have the potential to be high utility non-invasive tools for early diagnosis and reliable patient monitoring in numerous conditions. Since its discovery almost 15 years ago, research on the ubiquitous antioxidant enzyme peroxiredoxin 4 (Prx4) has culminated in the recognition that Prx4 levels are different in blood drawn from the healthy general population and patients with acute or chronic diseases. In this commentary, the most striking research data from different in vitro approaches, animal models and human observational studies are discussed collectively, highlighting the clinical importance of Prx4 as a multifunctional staging and prognosis biomarker. In this context, the oxidative state of patients may be reflected by intra- and extracellular Prx4 levels, redox state, oligomerization and nitro-oxidative modifications of the enzyme. A consolidated model of the potential role and origin of circulating Prx4 is presented to stimulate further investigations in light of the current biomarker situation.

Copeptin and peroxiredoxin-4 independently predict mortality in patients with nonspecific complaints presenting to the emergency department

OBJECTIVES

Patients presenting to emergency departments (ED) with nonspecific complaints (NSCs) such as "not feeling well,""feeling weak,""being tired,""general deterioration," or other similar chief complaints that do not have a readily identifiable probable etiology are a common patient group at risk for adverse outcomes. Certain biomarkers, which have not yet been tested for prognostic value when applied to ED patients with NSCs, have emerged as useful tools for predicting prognosis in patients with a variety of diseases. This study tested the hypothesis that two of these novel markers, copeptin (a C-terminal portion of provasopressin) and/or peroxiredoxin-4 (Prx4), an enzyme that degrades hydrogen peroxide, singly or together are helpful in predicting death in the near term among patients presenting to the ED with NSCs.

METHODS

The Basel Non-specific Complaints (BANC) study is a delayed type cross-sectional diagnostic study with a prospective 30-day follow-up. ED patients with NSCs were consecutively enrolled. Patients with vital parameters out of the normal range were excluded. The primary endpoint of this study was the predictive value of copeptin and Prx4 for 30-day mortality in patients with NSCs. Measurement of both copeptin and Prx4 was performed in serum samples with sandwich immunoluminometric assays.

RESULTS

On follow-up at 30 days after ED presentation, 28 of 438 patients with NSC had died. Copeptin and Prx4 concentrations were significantly higher in nonsurvivors than in survivors (Kruskal-Wallis test, p = 0.0001 and p < 0.0001, respectively). In univariate models, Prx4 (likelihood ratio [LR] χ(2) = 22.24, p < 0.00001, concordance index [C-index] = 0.749) and copeptin (LR χ(2) = 16.98, p = 0.00004, C-index = 0.724) were both predictive of 30-day mortality, and elevated levels were associated with an increased mortality. The bivariable model, which included both Prx4 and copeptin (LR χ(2) = 28.22, p < 0.00001, C-index = 0.783), allows a significantly better prediction than the univariate Prx4 (p = 0.00025) and copeptin models (p = 0.00099), respectively. Both biomarkers provided independent and additional information to clinical risk scores (Katz Activities of Daily Living [ADL] and Charlson Comorbidity Index [CCI], all p < 0.0005).

CONCLUSIONS

Copeptin and Prx4 are new prognostic markers in patients presenting to the ED with NSCs. Copeptin and Prx4 might be valuable tools for risk stratification and decision-making in this patient group.