Glutathione peroxidase 7 protects against oxidative DNA damage in oesophageal cells

Predicting the potential deterioration of Barrett's esophagus based on gut microbiota: a Mendelian randomization analysis

Esophageal adenocarcinoma (EAC) is one of the most malignant tumors in the digestive system. To make thing worse, the scarcity of treatment options is disheartening. However, if detected early, there is a possibility of reversing the condition. Unfortunately, there is still a lack of relevant early screening methods. Considering that Barrett's esophagus (BE), a precursor lesion of EAC, has been confirmed as the only known precursor of EAC. Analyzing which BE cases will progress to EAC and understanding the processes and mechanisms involved is of great significance for early screening of such patients. Considering the significant alterations in the gut microbiota of patients with BE and its potential role in the progression to EAC, this study aims to analyze the relationship between BE, EAC, and GM to identify potential diagnostic biomarkers and therapeutic targets. This study utilized comprehensive statistical data on gut microbiota from a large-scale genome-wide association meta-analysis conducted by the MiBioGen consortium (n = 18,340). Subsequently, we selected a set of single nucleotide polymorphisms (SNPs) that fell below the genome-wide significance threshold (1 × 10-5) as instrumental variables. To investigate the causal relationship between gut microbiota and BE and EAC, we employed various MR analysis methods, including Inverse Variance Weighting (IVW), MR-Egger regression, weighted median (WM), and weighted mean. Additionally, we assessed the level of pleiotropy, heterogeneity, and stability of genetic variations through MR-Egger intercept test, MR-PRESSO, Cochran's Q test, and "leave-one-out" sensitivity analysis. Furthermore, we conducted reverse MR analysis to identify the causal relationships between gut microbiota and BE and EAC. The results from the Inverse Variance-Weighted (IVW) analysis indicate that Alistipes (P = 4.86 × 10-2), Lactobacillus (P = 2.11 × 10-2), Prevotella 7 (P = 4.28 × 10-2), and RuminococcaceaeUCG004 (P = 4.34 × 10-2) are risk factors for Barrett's esophagus (BE), while Flavonifractor (P = 8.81 × 10-3) and RuminococcaceaeUCG004 (P = 4.99 × 10-2) are risk factors for esophageal adenocarcinoma (EAC). On the other hand, certain gut microbiota genera appear to have a protective effect against both BE and EAC. These include Eubacterium (nodatum group) (P = 4.51 × 10-2), Holdemania (P = 1.22 × 10-2), and Lactococcus (P = 3.39 × 10-2) in the BE cohort, as well as Eubacterium (hallii group) (P = 4.07 × 10-2) and Actinomyces (P = 3.62 × 10-3) in the EAC cohort. According to the results of reverse MR analysis, no significant causal effects of BE and EAC on gut microbiota were observed. Furthermore, no significant heterogeneity or pleiotropy was detected in the instrumental variables. We have established a causal relationship between the gut microbiota and BE and EAC. This study holds profound significance for screening BE patients who may be at risk of deterioration, as it can provide them with timely medical interventions to reverse the condition.

Alginate oligosaccharide alleviates vascular aging by upregulating glutathione peroxidase 7

Alginate oligosaccharide (AOS) may delay aging by decreasing oxidative stress, but the effects on vascular aging remain unclear. Here, we evaluate the effect of AOS on vascular aging and investigate the underlying mechanisms. Twenty-month-old rats acted as the natural aging model in vivo. Senescence of human aortic vascular smooth muscle cells (HA-VSMCs) was induced in vitro using angiotensin II (AngII). The aging rats and senescent cells were treated with AOS, followed by assessment of aging makers, oxidative stress, and aging-induced vascular remodeling. AOS treatment alleviated vascular aging and HA-VSMC senescence and decreased the levels of oxidative stress and vascular remodeling-associated indicators. AOS upregulated the expression of glutathione peroxidase 7 (GPX7) in aging rats and GPX7 depletion disrupted the geroprotective effect of AOS. AOS increased the nuclear translocation of nuclear factor erythroid-2-related factor (Nrf2) protein, which interacts with GPX7 protein to induce its expression. In conclusion, AOS alleviates vascular aging and HA-VSMC senescence and reduces aging-related vascular remodeling via the GPX7 antioxidant pathway, which may provide new avenues for treating aging-associated diseases.

Reflux conditions induce E-cadherin cleavage and EMT via APE1 redox function in oesophageal adenocarcinoma

OBJECTIVE

Chronic gastro-oesophageal reflux disease, where acidic bile salts (ABS) reflux into the oesophagus, is the leading risk factor for oesophageal adenocarcinoma (EAC). We investigated the role of ABS in promoting epithelial-mesenchymal transition (EMT) in EAC.

DESIGN

RNA sequencing data and public databases were analysed for the EMT pathway enrichment and patients' relapse-free survival. Cell models, pL2-IL1β transgenic mice, deidentified EAC patients' derived xenografts (PDXs) and tissues were used to investigate EMT in EAC.

RESULTS

Analysis of public databases and RNA-sequencing data demonstrated significant enrichment and activation of EMT signalling in EAC. ABS induced multiple characteristics of the EMT process, such as downregulation of E-cadherin, upregulation of vimentin and activation of ß-catenin signalling and EMT-transcription factors. These were associated with morphological changes and enhancement of cell migration and invasion capabilities. Mechanistically, ABS induced E-cadherin cleavage via an MMP14-dependent proteolytic cascade. Apurinic/apyrimidinic endonuclease (APE1), also known as redox factor 1, is an essential multifunctional protein. APE1 silencing, or its redox-specific inhibitor (E3330), downregulated MMP14 and abrogated the ABS-induced EMT. APE1 and MMP14 coexpression levels were inversely correlated with E-cadherin expression in human EAC tissues and the squamocolumnar junctions of the L2-IL1ß transgenic mouse model of EAC. EAC patients with APE1high and EMThigh signatures had worse relapse-free survival than those with low levels. In addition, treatment of PDXs with E3330 restrained EMT characteristics and suppressed tumour invasion.

CONCLUSION

Reflux conditions promote EMT via APE1 redox-dependent E-cadherin cleavage. APE1-redox function inhibitors can have a therapeutic role in EAC.

Lactobacillus sp. Facilitate the Repair of DNA Damage Caused by Bile-Induced Reactive Oxygen Species in Experimental Models of Gastroesophageal Reflux Disease

Gastroesophageal reflux disease (GERD) leads to the accumulation of bile-induced reactive oxygen species and oxidative stress in esophageal tissues, causing inflammation and DNA damage. The progression sequence from healthy esophagus to GERD and eventually cancer is associated with a microbiome shift. Lactobacillus species are commensal organisms known for their probiotic and antioxidant characteristics in the healthy esophagus. This prompted us to investigate how Lactobacilli survive in a bile-rich environment during GERD, and to identify their interaction with the bile-injured esophageal cells. To model human reflux conditions, we exposed three Lactobacillus species (L. acidophilus, L. plantarum, and L. fermentum) to bile. All species were tolerant to bile possibly enabling them to colonize the esophageal epithelium under GERD conditions. Next, we assessed the antioxidant potential of Lactobacilli and role in bile injury repair: we measured bile-induced DNA damage using the ROS marker 8-oxo guanine and COMET assay. Lactobacillus addition after bile injury accelerated repair of bile-induced DNA damage through recruitment of pH2AX/RAD51 and reduced NFκB-associated inflammation in esophageal cells. This study demonstrated anti-genotoxic and anti-inflammatory effects of Lactobacilli, making them of significant interest in the prevention of Barrett's esophagus and esophageal adenocarcinoma in patients with GERD.

P53 Deficiency Accelerate Esophageal Epithelium Intestinal Metaplasia Malignancy

Barrett’s esophagus (BE) is a precancerous lesion of esophageal adenocarcinoma (EAC). It is a pathological change in which the squamous epithelium distal esophagus is replaced by columnar epithelium. Loss of P53 is involved in the development of BE and is taken as a risk factor for the progression. We established a HET1A cell line with P53 stably knockdown by adenovirus vector infection, followed by 30 days of successive acidic bile salt treatment. MTT, transwell assay, and wound closure assay were applied to assess cell proliferation and migration ability. The expression of key factors was analyzed by RT-qPCR, western blotting and immunohistochemical staining. Our data show that the protein expression level of P53 reduced after exposure to acidic bile salt treatment, and the P53 deficiency favors the survival of esophageal epithelial cells to accommodate the stimulation of acidic bile salts. Furthermore, exposure to acidic bile salt decreases cell adhesions by repressing the JAK/STAT signaling pathway and activating VEGFR/AKT in P53-deficient esophageal cells. In EAC clinical samples, P53 protein expression is positively correlated with that of ICAM1 and STAT3 and negatively correlated with VEGFR protein expression levels. These findings elucidate the role of P53 in the formation of BE, explain the mechanism of P53 deficiency as a higher risk of progression for BE formation, and provide potential therapeutic targets for EAC.

Expression Pattern and Molecular Mechanism of Oxidative Stress-Related Genes in Myocardial Ischemia-Reperfusion Injury

(1) Background: The molecular mechanism of oxidative stress-related genes (OSRGs) in myocardial ischemia-reperfusion injury (MIRI) has not been fully elucidated. (2) Methods: Differential expression analysis, enrichment analysis, and PPI analysis were performed on the MIRI-related datasets GSE160516 and GSE61592 to find key pathways and hub genes. OSRGs were obtained from the Molecular Signatures Database (MSigDB). The expression pattern and time changes of them were studied on the basis of their raw expression data. Corresponding online databases were used to predict miRNAs, transcription factors (TFs), and therapeutic drugs targeting common differentially expressed OSRGs. These identified OSRGs were further verified in the external dataset GSE4105 and H9C2 cell hypoxia-reoxygenation (HR) model. (3) Results: A total of 134 DEGs of MIRI were identified which were enriched in the pathways of "immune response", "inflammatory response", "neutrophil chemotaxis", "phagosome", and "platelet activation". Six hub genes and 12 common differentially expressed OSRGs were identified. A total of 168 miRNAs, 41 TFs, and 21 therapeutic drugs were predicted targeting these OSRGs. Lastly, the expression trends of Aif1, Apoe, Arg1, Col1a1, Gpx7, and Hmox1 were confirmed in the external dataset and HR model. (4) Conclusions: Aif1, Apoe, Arg1, Col1a1, Gpx7, and Hmox1 may be involved in the oxidative stress mechanism of MIRI, and the intervention of these genes may be a potential therapeutic strategy.

Altered genome‑wide hydroxymethylation analysis for neoadjuvant chemoradiotherapy followed by surgery in esophageal cancer

Esophageal cancer has high incidence rate in China. Neoadjuvant chemoradiotherapy (nCRT) has become the standard treatment for esophageal squamous cell carcinoma (ESCC). However, there are few reliable epigenetic parameters for patients with ESCC undergoing neoadjuvant therapy. Genomic extract from tumor tissue was amplified and sequenced using the Illumina HiSeq4000 to quantify genes associated methylation or hydromethylation in 12 patients with ESCC undergoing nCRT. The genome-wide hydroxymethylation were analyzed by methylated and hydroxymethylated DNA immunoprecipitation sequencing by MACS2 software and UCSC RefSeq database. Abnormal DNA methylation was statistically different between nCRT-well (showed a pathological complete response to nCRT) and nCRT-poor (showed incomplete pathological response to nCRT) patients. Levels of ten-eleven translocation 1, 2 and 3 mRNA and protein were higher in tumor tissue in nCRT-well group patients than in nCRT-poor group patients. Illumina HiSeq 4000 sequencing identified 2925 hypo-differentially hydroxymethylated region (DhMRs) and 292 hyper-DhMRs in promoter between nCRT-well and nCRT-poor patients. Biological processes associated with hyper-DhMRs included 'snRNA processing', 'hormone-mediated signaling pathway' and 'cellular response'. Metabolic processes were associated with hypo-DhMRs. These data may explain the functional response to nCRT in patients with abnormal promoter of methylation gene-associated mRNA expression. The present results implied that hyper-DhMRs and hypo-DhMRs affect molecular pathways, such as hippo and Notch signaling pathways, highlighting epigenetic modifications associated with clinical response to nCRT in patients with esophageal cancer.

Targeting NRF2 Sensitizes Esophageal Adenocarcinoma Cells to Cisplatin through Induction of Ferroptosis and Apoptosis

Esophageal adenocarcinoma (EAC), the predominant type of esophageal cancer in the United States, develops through Barrett's esophagus (BE)-dysplasia-carcinoma cascade. Gastroesophageal reflux disease, where acidic bile salts refluxate into the esophagus, is the main risk factor for the development of BE and its progression to EAC. The NFE2-related factor 2 (NRF2) is the master cellular antioxidant regulator. We detected high NRF2 protein levels in the EAC cell lines and primary tissues. Knockdown of NRF2 significantly enhanced acidic bile salt-induced oxidative stress, DNA damage, and inhibited EAC cell growth. Brusatol, an NRF2 inhibitor, significantly inhibited NRF2 transcriptional activity and downregulated the NRF2 target genes. We discovered that in addition to inducing apoptosis, Brusatol alone or in combination with cisplatin (CDDP) induced significant lipid peroxidation and ferroptosis, as evidenced by reduced xCT and GPX4 expression, two known ferroptosis markers. The combination of Brusatol and CDDP significantly inhibited EAC tumor xenograft growth in vivo and confirmed the in vitro data showing ferroptosis as an important mechanism in the tumors treated with Brusatol or Brusatol and CDDP combination. Our data support the role of NRF2 in protecting against stress-induced apoptosis and ferroptosis in EACs. Targeting NRF2 in combination with platinum therapy can be an effective strategy for eliminating cancer cells in EAC.

Simvastatin as an emerging pollutant on non-target aquatic invertebrates: effects on antioxidant-related genes in Daphnia magna

Simvastatin (SIM) is one of the most widely used lipid-lowering drugs and consequently has been frequently detected in various waters. However, its potential adverse effects and toxic mechanisms on non-target organisms such as Daphnia magna (D. magna) remain still unclear. In the present study, the expressions of Nrf2 and antioxidant genes including Keap1, HO-1, GCLC, GST, SOD, CAT, GPx5, GPx7, GRx, TRX, TrxR, and Prx1 in D. magna exposed to SIM for 24 h, 48 h, and 96 h were investigated. The changes of SOD, CAT, GST, and GPx enzymatic activities, and the GSH and MDA content under SIM for 48-h exposure were also addressed. Results showed that the expression of Nrf2 was inhibited at 24 h but induced at 96 h, displaying a time- and/or dose-dependent relationship under SIM exposure. In contrast, Keap1 exhibited induction at 24 h. HO-1 showed significant induction under SIM exposure for different time. SOD generally displayed an induction trend under SIM exposure for different periods. GPX5 expression showed significant induction under SIM exposure, particularly at 24 h in 5 µg L^-1 increasing 15 folds of the control. But GPX7 expression generally displayed inhibition except in 5 µg L^-1. Trx and TrxR showed different induction or inhibition, which was depended on the exposure time and concentration. Prx1 displayed significant induction in most SIM groups. In addition, the decreasing GSH and increasing MDA content also indicated oxidative stress of SIM exposure. Overall, SIM exposure affected the expression of Nrf2 and antioxidant-related genes and altered the redox homeostasis of D. magna, even may cause the morphological changes such as shorten spine and abnormal development eye.

A Bioinformatic Analysis: The Overexpression and Prognostic Potential of GPX7 in Lower-Grade Glioma

Purpose

Glutathione peroxidase-7 (GPX7) is a newly discovered non-selenium-containing protein with glutathione peroxidase activity, which mainly protects the organism from oxidative damage and is very important for basic biology studies. This study aims to reveal the expression pattern of GPX7 and its prognosis potential from a pan-cancer perspective.

Methods

Expression levels of GPX7 in human tumor tissues and normal tissues were evaluated using Human Protein Atlas (HPA), the Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx) and UALCAN databases. The prognostic potential of GPX7 for 33 TCGA tumors was evaluated by Kaplan–Meier analysis and Cox regression analysis. Subsequently, the Chinese Glioma Genome Atlas (CGGA) dataset was used to further verify the expression of GPX7 and its prognostic potential in glioma. We explored the correlation between GPX7 and immune infiltration, tumor mutational burden (TMB) and microsatellite instability (MSI). Furthermore, a nomogram lower-grade glioma (LGG) was constructed to verify the prognostic outcome of patients. Finally, the relationship between GPX7 and treatment regimens for LGG was also explored.

Results

GPX7 was overexpressed in multiple tumors. Elevated expression of GPX7 was associated with poor prognosis of LGG patients (OS hazard ratio (HR) = 1.044, P < 0.0001; DFS HR = 1.035, P < 0.0001; PFS HR = 1.045, P < 0.0001). GPX7 was proved to be an independent prognostic factor of LGG through univariate and multivariate Cox analysis. The nomogram confirmed a better predictability (Concordance index (C-index): 0.845; 95% CI, 0.825–0.865). GPX7 was positively correlated with TMB in LGG. GPX7 expression was negatively correlated with half-maximal inhibitory concentration (IC50) of temozolomide (TMZ) (\documentclass[12pt]{minimal} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \DeclareFontFamily{T1}{linotext}{} \DeclareFontShape{T1}{linotext}{m}{n} {linotext }{} \DeclareSymbolFont{linotext}{T1}{linotext}{m}{n} \DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext} \begin{document} $$\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}}\over \rho } $$ \end{document}_spearman= −0.59, P =1.3e-48).

Conclusion

GPX7 was upregulated in multiple tumors, and it was a potential prognostic biomarker in LGG. High-expressed GPX7 can predict the sensitivity of TMZ in LGG patients.

Global gene expression responses of Atlantic salmon skin to Moritella viscosa

Moritella viscosa is a Gram-negative pathogen that causes large, chronic ulcers, known as winter-ulcer disease, in the skin of several fish species including Atlantic salmon. We used a bath challenge approach to profile the transcriptome responses of M. viscosa-infected Atlantic salmon skin at the lesion (Mv-At) and away from the lesion (Mv-Aw) sites. M. viscosa infection was confirmed through RNA-based qPCR assays. RNA-Seq identified 5212 and 2911 transcripts differentially expressed in the Mv-At compared to no-infection control and Mv-Aw groups, respectively. Also, there were 563 differentially expressed transcripts when comparing the Mv-Aw to control samples. Our results suggest that M. viscosa caused massive and strong, but largely infection site-focused, transcriptome dysregulations in Atlantic salmon skin, and its effects beyond the skin lesion site were comparably subtle. The M. viscosa-induced transcripts of Atlantic salmon were mainly involved in innate and adaptive immune response-related pathways, whereas the suppressed transcripts by this pathogen were largely connected to developmental and cellular processes. As validated by qPCR, M. viscosa dysregulated transcripts encoding receptors, signal transducers, transcription factors and immune effectors playing roles in TLR- and IFN-dependent pathways as well as immunoregulation, antigen presentation and T-cell development. This study broadened the current understanding of molecular pathways underlying M. viscosa-triggered responses of Atlantic salmon, and identified biomarkers that may assist to diagnose and combat this pathogen.

GPX7 Is Targeted by miR-29b and GPX7 Knockdown Enhances Ferroptosis Induced by Erastin in Glioma

Background

Glioma is a lethal primary tumor of central nervous system. Ferroptosis is a newly identified form of necrotic cell death. Triggering ferroptosis has shown potential to eliminate aggressive tumors. GPX7, a member of glutathione peroxidase family (GPXs), has been described to participate in oxidative stress and tumorigenesis. However, the biological functions of GPX7 in glioma are still unknown.

Methods

Bioinformatics method was used to assess the prognostic role of GPX7 in glioma. CCK8, wound healing, transwell and cell apoptosis assays were performed to explore the functions of GPX7 in glioma cells. In vivo experiment was also conducted to confirm in vitro findings. Ferroptosis-related assays were carried out to investigate the association between GPX7 and ferroptosis in glioma.

Results

GPX7 was aberrantly expressed in glioma and higher expression of GPX7 was correlated with adverse outcomes. GPX7 silencing enhanced ferroptosis-related oxidative stress in glioma cells and the loss of GXP7 sensitized glioma to ferroptosis induced by erastin. Furthermore, we found that miR-29b directly suppressed GPX7 expression post-transcriptionally. Reconstitution of miR-29b enhanced erastin sensitivity, partly via GPX7 suppression.

Conclusions

Our study clarified the prognostic role of GPX7 in glioma and preliminarily revealed the role of GPX7 in ferroptosis, which may be conducive to the exploration of therapeutic targets of glioma.

Genetically engineered mouse models of esophageal cancer

BACKGROUND

Esophageal cancer is the most common cause of cancer-related death worldwide with a diverse geographical distribution, poor prognosis, and diagnosis in advanced stages of the disease. Identification of the mechanisms involved in esophageal cancer development is evaluative to improve outcomes for patients. Genetically engineered mouse models (GEMMs) of cancer provide the physiologic, molecular, and histologic features of the human tumors to determine the pathogenesis and treatments for cancer, hence exhibiting a source of tremendous potential for oncology research. The advancement of cancer modeling in mice has improved to the extent that researchers can observe and manipulate the disease process in a specific manner. Despite the significant differences between mice and humans, mice can be great models for human oncology researches due to similarities between them at the molecular and physiological levels. Due to most of the existing esophageal cancer GEMMs do not propose an ideal system for pathogenesis of the disease, genetic risks, and microenvironment exposure, so identification of challenges in GEM modeling and well-developed technologies are required to obtain the most value for patients. In this review, we describe the biology of human and mouse, followed by the exciting esophageal cancer mouse models with a discussion of applicability and challenges of these models for generating new GEMMs in future studies.

Activation of NRF2 by APE1/REF1 is redox-dependent in Barrett's related esophageal adenocarcinoma cells

BACKGROUND

Chronic gastroesophageal reflux disease (GERD) is a major risk factor for the development of metaplastic Barrett's esophagus (BE) and its progression to esophageal adenocarcinoma (EAC). Uncontrolled accumulation of reactive oxygen species (ROS) in response to acidic bile salts (ABS) in reflux conditions can be lethal to cells. In this study, we investigated the role of APE1/REF1 in regulating nuclear erythroid factor-like 2 (NRF2), the master antioxidant transcription factor, in response to reflux conditions.

RESULTS

We found that APE1 protein was critical for protecting against cellular ROS levels, oxidative DNA damage, double strand DNA breaks, and cell death in response to conditions that mimic reflux. Analysis of cell lines and de-identified tissues from patients with EAC demonstrated overexpression of both APE1 and NRF2 in EAC cells, as compared to non-neoplastic esophageal cells. Using reflux conditions, we detected concordant and prolonged increases of APE1 and NRF2 protein levels for several hours, following transient short exposure to ABS (20 min). NRF2 transcription activity, as measured by ARE luciferase reporter, and expression of its target genes (HO-1 and TRXND1) were similarly increased in response to ABS. Using genetic knockdown of APE1, we found that APE1 was required for the increase in NRF2 protein stability, nuclear localization, and transcription activation in EAC. Using knockdown of APE1 with reconstitution of wild-type and a redox-deficient mutant (C65A) of APE1, as well as pharmacologic APE1 redox inhibitor (E3330), we demonstrated that APE1 regulated NRF2 in a redox-dependent manner. Mechanistically, we found that APE1 is required for phosphorylation and inactivation of GSK-3β, an important player in the NRF2 degradation pathway.

CONCLUSION

APE1 redox function was required for ABS-induced activation of NRF2 by regulating phosphorylation and inactivation of GSK-3β. The APE1-NRF2 network played a critical role in protecting esophageal cells against ROS and promoting cell survival under oxidative reflux conditions.

Endogenous aldehyde accumulation generates genotoxicity and exhaled biomarkers in esophageal adenocarcinoma

Volatile aldehydes are enriched in esophageal adenocarcinoma (EAC) patients' breath and could improve early diagnosis, however the mechanisms of their production are unknown. Here, we show that weak aldehyde detoxification characterizes EAC, which is sufficient to cause endogenous aldehyde accumulation in vitro. Two aldehyde groups are significantly enriched in EAC biopsies and adjacent tissue: (i) short-chain alkanals, and (ii) medium-chain alkanals, including decanal. The short-chain alkanals form DNA-adducts, which demonstrates genotoxicity and confirms inadequate detoxification. Metformin, a putative aldehyde scavenger, reduces this toxicity. Tissue and breath concentrations of the medium-chain alkanal decanal are correlated, and increased decanal is linked to reduced ALDH3A2 expression, TP53 deletion, and adverse clinical features. Thus, we present a model for increased exhaled aldehydes based on endogenous accumulation from reduced detoxification, which also causes therapeutically actionable genotoxicity. These results support EAC early diagnosis trials using exhaled aldehyde analysis.

GPx7 ameliorates non-alcoholic steatohepatitis by regulating oxidative stress

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases. NAFLD can further progress to irreversible liver failure such as non-alcoholic steatohepatitis (NASH) fibrosis and cirrhosis. However, specific regulator of NASH- fibrosis has yet to be established. Here, we found that glutathione peroxidase 7 (GPx7) was markedly expressed in NASH fibrosis. Although GPx7 is an antioxidant enzyme protecting other organs, whether GPx7 plays a role in NASH fibrosis has yet to be studied. We found that knockdown of GPx7 in transforming growth factor-β (TGF-β) and free fatty acids (FFA)- treated LX-2 cells elevated the expression of pro-fibrotic and pro-inflammatory genes and collagen synthesis. Consistently, GPx7 overexpression in LX-2 cells led to the suppression of ROS production and reduced the expression of pro-fibrotic and pro-inflammatory genes. Further, NASH fibrosis induced by choline-deficient amino acid defined, high fat diet (CDAHFD) feeding was significantly accelerated by knockdown of GPx7, as evidenced by up-regulated liver fibrosis and inflammation compared with CDAHFD control mice. Collectively, these results suggest that GPx7 might be a novel therapeutic target to prevent the progression and development of NAFLD.

Intracellular Sources of ROS/H2O2 in Health and Neurodegeneration: Spotlight on Endoplasmic Reticulum

Reactive oxygen species (ROS) are produced continuously throughout the cell as products of various redox reactions. Yet these products function as important signal messengers, acting through oxidation of specific target factors. Whilst excess ROS production has the potential to induce oxidative stress, physiological roles of ROS are supported by a spatiotemporal equilibrium between ROS producers and scavengers such as antioxidative enzymes. In the endoplasmic reticulum (ER), hydrogen peroxide (H2O2), a non-radical ROS, is produced through the process of oxidative folding. Utilisation and dysregulation of H2O2, in particular that generated in the ER, affects not only cellular homeostasis but also the longevity of organisms. ROS dysregulation has been implicated in various pathologies including dementia and other neurodegenerative diseases, sanctioning a field of research that strives to better understand cell-intrinsic ROS production. Here we review the organelle-specific ROS-generating and consuming pathways, providing evidence that the ER is a major contributing source of potentially pathologic ROS.

Emerging roles for non-selenium containing ER-resident glutathione peroxidases in cell signaling and disease

Maintenance of cellular redox control is pivotal for normal cellular functions and cell fate decisions including cell death. Among the key cellular redox systems in mammals, the glutathione peroxidase (GPX) family of proteins is the largest conferring multifaceted functions and affecting virtually all cellular processes. The endoplasmic reticulum (ER)-resident GPXs, designated as GPX7 and GPX8, are the most recently added members of this family of enzymes. Recent studies have provided exciting insights how both enzymes support critical processes of the ER including oxidative protein folding, maintenance of ER redox control by eliminating H₂O₂, and preventing palmitic acid-induced lipotoxicity. Consequently, numerous pathological conditions, such as neurodegeneration, cancer and metabolic diseases have been linked with altered GPX7 and GPX8 expression. Studies in mice have demonstrated that loss of GPX7 leads to increased differentiation of preadipocytes, increased tumorigenesis and shortened lifespan. By contrast, GPX8 deficiency in mice results in enhanced caspase-4/11 activation and increased endotoxic shock in colitis model. With the increasing recognition that both types of enzymes are dysregulated in various tumor entities in man, we deem a review of the emerging roles played by GPX7 and GPX8 in health and disease development timely and appropriate.

N-MYC Downstream Regulated Gene 4 (NDRG4), a Frequent Downregulated Gene through DNA Hypermethylation, plays a Tumor Suppressive Role in Esophageal Adenocarcinoma

Simple Summary

Esophageal adenocarcinoma has become a major clinical challenge in the western world due to its rapid increasing incidence and poor overall prognosis. Understanding the molecular events of its tumorigenesis is the key to better diagnosis and development of better therapeutic strategies. In the current study we aimed to identify epigenetic alteration targets in esophageal adenocarcinoma. We focused on a candidate gene, NDRG4 (N-myc downregulated gene 4). We found that NDRG4 was frequent downregulated in esophageal adenocarcinoma through DNA hypermethylation of its promoter region. Re-expression of NRDG4 in cancer cells significantly suppressed tumor growth via inhibition of cell proliferation. These results will improve our understanding on how dysfunction of NDRG4 contributes to esophageal adenocarcinoma. DNA hypermethylation of NDRG4 may be a useful biomarker in clinical monitoring of esophageal adenocarcinoma patients.

Abstract

The incidence of esophageal adenocarcinoma (EAC) has been rising dramatically in the past few decades in the United States and Western world. The N-myc downregulated gene 4 (NDRG4) belongs to the human NDRG family. In this study, we aimed to identify the expression levels, regulation, and functions of NDRG4 in EAC. Using an integrative epigenetic approach, we identified genes showing significant downregulation in EAC and displaying upregulation after 5-Aza-deoxycitidine. Among these genes, likely to be regulated by DNA methylation, NDRG4 was among the top 10 candidate genes. Analyses of TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus) data sets and EAC tissue samples demonstrated that NDRG4 was significantly downregulated in EAC (p < 0.05). Using Pyrosequencing technology for quantification of DNA methylation, we detected that NDRG4 promoter methylation level was significantly higher in EAC tissue samples, as compared to normal esophagus samples (p < 0.01). A strong inverse correlation between NDRG4 methylation and its gene expression levels (r = −0.4, p < 0.01) was observed. Treatment with 5-Aza restored the NDRG4 expression, confirming that hypermethylation is a driving force for NDRG4 silencing in EAC. Pathway and gene set enrichment analyses of TCGA data suggested that NDRG4 is strongly associated with genes related to cell cycle regulation. Western blotting analysis showed significant downregulation of Cyclin D1, CDK4 and CDK6 in EAC cells after overexpression of NDRG4. Functionally, we found that the reconstitution of NDRG4 resulted in a significant reduction in tumor cell growth in two-dimensional (2D) and three-dimensional (3D) organotypic culture models and inhibited tumor cell proliferation as indicated by the EdU (5-ethynyl-2′-deoxyuridine) proliferation assay.

Increased oxidative stress with substantial dysregulation of genes related to oxidative stress and DNA repair after laparoscopic colon cancer surgery

Surgical stress is followed by oxidative stress, where reactive oxygene species may act as regulators of pathways related to cancer cell survival and metastatic ability. Furthermore, reactive oxygene species may cause DNA and RNA damage. The aim of this study was to examine whether laparoscopic colon cancer surgery causes oxidative stress and dysregulation of related pathways.

METHODS

Patients undergoing elective laparoscopic surgery for colon cancer were included. Blood and urine samples were drawn on the day prior to surgery and on day 1 and 10 after surgery.

RESULTS

Twenty-six patients were included. Out of 140 genes previously identified as sensitive to regulation by reactive oxygene species, 46 were significantly differentially expressed on day 1 after surgery (FDR < 0.05). Upregulated genes were related to cellular immune suppression, proliferation, migration and epithelial to mesenchymal transition. Downregulated genes were related to IFN pathways and cytotoxic immunological reactions. Genes related to DNA repair were primarily downregulated on day one after surgery, and urinary excretion of 8oxdG was decreased on day two after (p = 0.004), and increased on day 10 after surgery (p = 0.01).

CONCLUSION

Laparoscopic colon cancer surgery causes oxidative stress, and impaired DNA repair. Gene expression profiling indicates that reactive oxygen species may act as regulators of pathways related to increased risk of metastasis and cellular immune suppression after surgery. Measures of intracellular oxidative stress, indicates impaired DNA repair on day two after surgery, and sustained oxidative stress on day 10 after surgery.

Characterization of the endoplasmic reticulum-resident peroxidases GPx7 and GPx8 shows the higher oxidative activity of GPx7 and its linkage to oxidative protein folding

Oxidative protein folding occurs primarily in the mammalian endoplasmic reticulum, enabled by a diverse network comprising more than 20 members of the protein disulfide isomerase (PDI) family and more than five PDI oxidases. Although the canonical disulfide bond formation pathway involving Ero1α and PDI has been well-studied so far, the physiological roles of the newly identified PDI oxidases, glutathione peroxidase-7 (GPx7) and -8 (GPx8), are only poorly understood. We here demonstrated that human GPx7 has much higher reactivity with H₂O₂ and hence greater PDI oxidation activity than human GPx8. The high reactivity of GPx7 is due to the presence of a catalytic tetrad at the redox-active site, which stabilizes the sulfenylated species generated upon the reaction with H₂O₂ Although it was previously postulated that GPx7 catalysis involved a highly reactive peroxidatic cysteine that can be sulfenylated by H₂O₂, we revealed that a resolving cysteine instead regulates the PDI oxidation activity of GPx7. We also determined that GPx7 formed complexes preferentially with PDI and P5 in H₂O₂-treated cells. Altogether, these results suggest that human GPx7 functions as an H₂O₂-dependent PDI oxidase in cells, whereas PDI oxidation may not be the central physiological role of human GPx8.

Proteome alterations associated with the oleic acid and cis-9, trans-11 conjugated linoleic acid content in bovine skeletal muscle

Oleic acid (OA) and cis-9, trans-11 conjugated linoleic acid (c9t11-CLA) are fatty acids found in beef with beneficial effects in human health. This study investigated differentially abundant proteins (DAPs) in skeletal muscle of bovines with extreme values of OA, and c9t11-CLA. For each one of the fatty acids, twenty muscle samples were divided into two groups (N = 10_High; N = 10_Low) and analyzed by high definition mass spectrometry. We identified 103 and 133 DAPs between the groups for each fatty acid. We found 64 and 45 up-regulated and 39 and 68 down-regulated proteins for OA and c9t11-CLA, respectively. Comparative analysis between proteomic and transcriptomic data revealed eight and ten genes with a consistent between mRNA expression levels and protein abundance for OA and c9t11-CLA, respectively. Unconventional myosin-Id (MYO1D), mineralocorticoid receptor (NR3C2), geranylgeranyl transferase type-2 subunit-alpha (RABGGTA), and uveal autoantigen with coiled-coil domains and ankyrin repeats (UACA) were found as putative candidate proteins for OA content. Fatty acid synthase (FASN), tubulin alpha-4A chain (TUBA4A), vinculin (VCL), NADH dehydrogenase 1 alpha subcomplex 5 (NDUFA5), and prefoldin subunit 6 (PFDN6) for c9t11-CLA. Our findings contribute to a deeper understanding of the molecular mechanisms behind the regulation of the OA and c9t11-CLA content in cattle skeletal muscle. SIGNIFICANCE: Questions about the association between meat intake and disease incidence in humans has driven animal scientist to pursue a better understanding of the biological processes associated with differences in the intramuscular fat composition. The beneficial effects of oleic acid and conjugated linoleic acid in human health have been demonstrated by improving the immune system and preventing atherosclerosis, different types of cancers, hypertension, and diabetes. Previous genome-wide association and gene expression studies identified genomic regions and differentially expressed genes associated with the fatty acid profile in skeletal muscle. In this work, differences were evaluated at the protein level. The use of a label-free quantitative proteomic approach, compared with muscle transcriptome results obtained by RNA-sequencing, allowed us to earn new insights into the variability in fatty acid deposition in skeletal muscle of farm animals. This study opens new avenues to explore the effect of the fatty acids in the skeletal muscle of livestock animals, which is associated with nutritional values of the meat, and perhaps to understand the mechanisms correlated with metabolic diseases in other species.

Integrated Bioinformatics Analysis Identifies Hub Genes Associated with the Pathogenesis and Prognosis of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) accounts for over 90% of all esophageal tumors. However, the molecular mechanism underlying ESCC development and prognosis remains unclear, and there are still no effective molecular biomarkers for diagnosing or predicting the clinical outcome of patients with ESCC. Here, using bioinformatics analyses, we attempted to identify potential biomarkers and therapeutic targets for ESCC. Differentially expressed genes (DEGs) between ESCC and normal esophageal tissue samples were obtained through comprehensive analysis of three publicly available gene expression profile datasets from the Gene Expression Omnibus database. The biological roles of the DEGs were identified by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Moreover, the Cytoscape 3.7.1 platform and subsidiary tools such as Molecular Complex Detection (MCODE) and CytoHubba were used to visualize the protein-protein interaction (PPI) network of the DEGs and identify hub genes. A total of 345 DEGs were identified between normal esophageal and ESCC samples, which were enriched in the KEGG pathways of the cell cycle, endocytosis, pancreatic secretion, and fatty acid metabolism. Two of the highest scoring models were selected from the PPI network using Molecular Complex Detection. Moreover, CytoHubba revealed 21 hub genes with a valuable influence on the progression of ESCC in these patients. Among these, the high expression levels of five genes-SPP1, SPARC, BGN, POSTN, and COL1A2-were associated with poor disease-free survival of ESCC patients, as indicated by survival analysis. Taken together, we identified that elevated expression of five hub genes, including SPP1, is associated with poor prognosis in ESCC patients, which may serve as potential prognostic biomarkers or therapeutic target for ESCC.

Peptidomics analysis of umbilical cord blood reveals potential preclinical biomarkers for neonatal respiratory distress syndrome

AIMS

The purpose of this study was to investigate the pathophysiology and discover novel predictors of neonatal respiratory distress syndrome (NRDS) from a peptidomics perspective.

MAIN METHODS

Comparative profiling of umbilical cord blood from NRDS and control patients was performed by liquid chromatography tandem mass spectrometry technology. The underlying biological functions of the differentially expressed peptides (DEPs) were predicted by Gene Ontology (GO) and KEGG pathway analyses. The interactions of DEPs and their precursor proteins were explored by ingenuity pathway analysis (IPA). The sources and stability of DEPs were determined by online databases, including UniProt, SMART and ProtParam tool.

KEY FINDINGS

A total of 251 DEPs were identified, of which 139 peptides were upregulated, and 112 peptides were downregulated (fold change ≥2.0, P < 0.05). These DEPs were predicted to be associated with respiratory failure, atelectasis, and morphogenesis of endothelial cells. These processes indicated that DEPs may play a role in NRDS. Among them, eleven stable DEPs might be used as preclinical biomarkers.

SIGNIFICANCE

Our findings improve our understanding of NRDS and facilitate the discovery of candidate diagnostic biomarkers for NRDS from the perspective of peptidomics.

Chronic restraint stress induces esophageal fibrosis with enhanced oxidative stress in a murine model

Although the underlying mechanism of stress remains unknown, it has been associated with the pathophysiology of gastroesophageal reflux diseases, the development of which appear to be accelerated by oxidative stress and fibrosis. The aim of the current study was to investigate the effect of chronic restraint stress on esophageal oxidative stress and fibrosis, as well as the impact of oxidative stress in a murine model whereby 8-week old C57BL/6J male mice were subjected to intermittent chronic restraint stress for a two-week period. The current study demonstrated that chronic restraint stress significantly reduced the body weight of mice compared with the control group. Although chronic restraint stress did not significantly alter the levels of triglycerides or cholesterol, free fatty acid concentration was significantly increased compared with the control group. Furthermore, chronic restraint stress significantly upregulated the expression levels of several fibrotic biomarkers including collagen type I, transforming growth factor β-1, α-smooth muscle actin and SMAD-3 compared with the control group. In addition, the expression levels of the reactive oxygen species (ROS) NADPH oxidase-4 and malondialdehyde were significantly increased, while the expression levels of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 were significantly decreased in esophageal tissue from mice in the chronic restraint stress group compared with the control group. In conclusion, chronic restraint stress may induce esophageal fibrosis by accumulating ROS and increasing fibrotic gene expression in a murine model.

Neural Differentiation of Mouse Neural Stem Cells as a Tool to Assess Developmental Neurotoxicity of Drinking Water in Taihu Lake

In this study, we used neural stem cells (NSCs) as a toxicology tool to assess the potential developmental neurotoxicity of drinking water from Taihu Lake. We found that the condensed drinking water could inhibit the proliferation and differentiation of NSCs, especially the tap water. Inductively coupled plasma mass spectrometry and high-performance liquid chromatography analysis showed that nickel was detected in the tap water with a high concentration. Our study revealed that nickel could inhibit NSCs proliferation and differentiation, which is induced not only by the intracellular reactive oxygen species generation, but also by the protein levels upregulation of p-c-Raf, p-MEK1/2 and p-Erk1/2 through the axon guidance signal pathways. These findings will provide a new way of research insight for investigation of nickel-induced neurotoxicity. Meanwhile, our test method confirmed the feasibility and reliability of stem cell assays for developmental neurotoxicity testing.

NRF2 antioxidant response protects against acidic bile salts-induced oxidative stress and DNA damage in esophageal cells

Gastroesophageal reflux disease (GERD) is the main risk factor for Barrett's tumorigenesis. In this study, we investigated the role of NRF2 in response to exposure to acidic bile salts (ABS), in conditions that mimic GERD, using Barrett's esophagus cell models. We detected an increase in NRF2 protein levels, following exposure to ABS. We found oxidization of cysteines (cysteines with oxidized thiol groups) in KEAP1 protein with a weaker interaction between NRF2 and KEAP1, following ABS exposure. Treatment with bile salts increased nuclear NRF2 levels, enhancing its transcription activity, as measured by an ARE (antioxidant response element) luciferase reporter assay. The mRNA expression levels of NRF2 target genes, HO-1 and GR, were increased in response to ABS exposure. Using genetic overexpression and knockdown of NRF2, we found that NRF2 has a critical role in suppressing ABS-induced ROS levels, oxidative DNA damage, DNA double strand breaks, and apoptosis. Collectively, our results suggest that transient induction of NRF2 in response to ABS plays a pivotal role in protecting esophageal cells by maintaining the levels of oxidative stress and DNA damage below lethal levels under GERD conditions.

Targeting the functional interplay between endoplasmic reticulum oxidoreductin-1α and protein disulfide isomerase suppresses the progression of cervical cancer

Background

Endoplasmic reticulum (ER) oxidoreductin-1α (Ero1α) and protein disulfide isomerase (PDI) constitute the pivotal pathway of oxidative protein folding, and are highly expressed in many cancers. However, whether targeting the functional interplay between Ero1α and PDI could be a new approach for cancer therapy remains unknown.

Methods

We performed wound healing assays, transwell migration and invasion assays and xenograft assays to assess cell migration, invasion and tumorigenesis; gel filtration chromatography, oxygen consumption assay and in cells folding assays were used to detect Ero1α-PDI interaction and Ero1α oxidase activity.

Findings

Here, we report that elevated expression of Ero1α is correlated with poor prognosis in human cervical cancer. Knockout of ERO1A decreases the growth, migration and tumorigenesis of cervical cancer cells, through downregulation of the H₂O₂-correlated epithelial-mesenchymal transition. We identify that the conserved valine (Val) 101 of Ero1α is critical for Ero1α-PDI complex formation and Ero1α oxidase activity. Val101 of Ero1α is specifically involved in the recognition of PDI catalytic domain. Mutation of Val101 results in a reduced ER, retarded oxidative protein folding and decreased H₂O₂ levels in the ER of cervical cancer cells and further impairs cell migration, invasion, and tumor growth.

Interpretation

Our study identifies the critical residue of Ero1α for recognizing PDI, which underlines the molecular mechanism of oxidative protein folding for tumorigenesis and provides a proof-of-concept for cancer therapy by targeting Ero1α-PDI interaction.

Fund

This work was supported by National Key R&D Program of China, National Natural Science Foundation of China, and Youth Innovation Promotion Association, CAS.

Activation of EGFR-DNA-PKcs pathway by IGFBP2 protects esophageal adenocarcinoma cells from acidic bile salts-induced DNA damage

Background

The incidence of esophageal adenocarcinoma (EAC) is rising rapidly in the US and Western countries. The development of Barrett’s esophagus (BE) and its progression to EAC have been linked to chronic gastroesophageal reflux disease (GERD). Exposure of BE and EAC cells to acidic bile salts (ABS) in GERD conditions induces high levels of oxidative stress and DNA damage. In this study, we investigated the role of insulin-like growth factor binding protein 2 (IGFBP2) in regulating ABS-induced DNA double-strand breaks.

Methods

Real-time RT-PCR, western blot, immunohistochemistry, immunofluorescence, co-immunoprecipitation, flow cytometry, and cycloheximide (CHX) chase assays were used in this study. To mimic GERD conditions, a cocktail of acidic bile salts (pH 4) was used in 2D and 3D organotypic culture models. Overexpression and knockdown of IGFBP2 in EAC cells were established to examine the functional and mechanistic roles of IGFBP2 in ABS-induced DNA damage.

Results

Our results demonstrated high levels of IGFBP2 mRNA and protein in EAC cell lines as compared to precancerous Barrett’s cell lines, and IGFBP2 is frequently overexpressed in EACs (31/57). Treatment of EAC cells with ABS, to mimic GERD conditions, induced high levels of IGFBP2 expression. Knocking down endogenous IGFBP2 in FLO1 cells (with constitutive high levels of IGFBP2) led to a significant increase in DNA double-strand breaks and apoptosis, following transient exposure to ABS. On the other hand, overexpression of exogenous IGFBP2 in OE33 cells (with low endogenous levels of IGFBP2) had a protective effect against ABS-induced double-strand breaks and apoptosis. We found that IGFBP2 is required for ABS-induced nuclear accumulation and phosphorylation of EGFR and DNA-PKcs, which are necessary for DNA damage repair activity. Using co-immunoprecipitation assay, we detected co-localization of IGFBP2 with EGFR and DNA-PKcs, following acidic bile salts treatment. We further demonstrated, using cycloheximide chase assay, that IGFBP2 promotes EGFR protein stability in response to ABS exposure.

Conclusions

IGFBP2 protects EAC cells against ABS-induced DNA damage and apoptosis through stabilization and activation of EGFR - DNA-PKcs signaling axis.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-1021-y) contains supplementary material, which is available to authorized users.

GPx3-mediated redox signaling arrests the cell cycle and acts as a tumor suppressor in lung cancer cell lines

Glutathione peroxidase 3 (GPx3), a major scavenger of reactive oxygen species (ROS) in plasma, acts as a redox signal modulator. However, the mechanism underlying GPx3-mediated suppression of cancer cell growth is unclear. The aim of this study was to identify these mechanisms with respect to lung cancer. To enhance the redox modulating properties of GPx3, lung cancer cells were subjected to serum starvation for 12 h, resulting in ROS generation in the absence of oxidant treatment. We then investigated whether suppression of tumorigenesis under conditions of oxidative stress was dependent on GPx3. The results showed that GPx3 effectively suppressed proliferation, migration, and invasion of lung cancer cells under oxidative stress. In addition, GPx3 expression led to a significant reduction in ROS production by cancer cells and induced G2/M phase arrest. We also found that inactivation of cyclin B1 significantly suppressed by nuclear factor-κB(NF-κB) inactivation in lung cancer cells was dependent on GPx3 expression. To further elucidate the mechanism(s) underlying GPx3-medited suppression of tumor proliferation, we next examined the effect of GPx3-mediated redox signaling on the ROS-MKP3-extracellular signal-regulated kinase (Erk)-NF-κB-cyclin B1 pathway and found that GPx3 strongly suppressed activation of the Erk-NF-κB-cyclin B1 signaling cascade by protecting MKP3 (an Erk-specific phosphatase) from the effects of ROS. Thus, this study demonstrates for the first time that the GPx3 suppresses proliferation of lung cancer cells by modulating redox-mediated signals.

Metformin alleviates human cellular aging by upregulating the endoplasmic reticulum glutathione peroxidase 7

Metformin, an FDA-approved antidiabetic drug, has been shown to elongate lifespan in animal models. Nevertheless, the effects of metformin on human cells remain unclear. Here, we show that low-dose metformin treatment extends the lifespan of human diploid fibroblasts and mesenchymal stem cells. We report that a low dose of metformin upregulates the endoplasmic reticulum-localized glutathione peroxidase 7 (GPx7). GP×7 expression levels are decreased in senescent human cells, and GPx7 depletion results in premature cellular senescence. We also indicate that metformin increases the nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2), which binds to the antioxidant response elements in the GPX7 gene promoter to induce its expression. Moreover, the metformin-Nrf2-GPx7 pathway delays aging in worms. Our study provides mechanistic insights into the beneficial effects of metformin on human cellular aging and highlights the importance of the Nrf2-GPx7 pathway in pro-longevity signaling.

Exposure of Barrett's and esophageal adenocarcinoma cells to bile acids activates EGFR-STAT3 signaling axis via induction of APE1

The development of Barret’s esophagus (BE) and its progression to esophageal adenocarcinoma (EAC) is highly linked to exposure to acidic bile salts due to chronic gastroesophageal reflux disease (GERD). In this study, we investigated the role of Apurinic/apyrimidinic endonuclease 1 /redox effector factor-1 (APE-1/REF-1) in STAT3 activation in response to EAC. Our results indicate that APE1 is constitutively overexpressed in EAC whereas its expression is transiently induced in response to acidic bile salts in non-neoplastic BE. Using overexpression or shRNA knockdown of APE1, we found that APE1 is required for phosphorylation, nuclear localization, and transcription activation of STAT3. By using an APE1 redox-specific mutant (C65A) and APE1 redox inhibitor (E3330), we demonstrate that APE1 activates STAT3 in a redox-dependent manner. By using pharmacologic inhibitors and genetic knockdown systems, we found that EGFR is a required link between APE1 and STAT3. EGFR phosphorylation (Y1068) was directly associated with APE1 levels and redox function. Co-immunoprecipitation and proximity ligation assays indicated that APE-1 coexists and interacts with the EGFR-STAT3 protein complex. Consistent with these findings, we demonstrated a significant induction in mRNA expression levels of STAT3 target genes (IL-6, IL-17A, BCL-xL, Survivin and c-Myc) in BE and EAC cells, following acidic bile salts treatment. ChIP assays indicated that acidic bile salts treatment enhances binding of STAT3 to the promoter of its target genes, Survivin and BCL-xL. Inhibition of APE1/REF-1 redox activity using E3330 abrogated STAT3 DNA binding and transcriptional activity. The induction of APE-1 - STAT3 axis in acidic bile salts conditions provided a survival advantage and promoted cellular proliferation. In summary, our study provides multiple pieces of evidence supporting a critical role for APE1 induction in activating the EGFR-STAT3 signaling axis in response to acidic bile salts, the main risk factors for Barrett’s carcinogenesis.

Reprogramming human A375 amelanotic melanoma cells by catalase overexpression: Upregulation of antioxidant genes correlates with regression of melanoma malignancy and with malignant progression when downregulated

Reactive oxygen species (ROS) are implicated in tumor transformation. The antioxidant system (AOS) protects cells from ROS damage. However, it is also hijacked by cancers cells to proliferate within the tumor. Thus, identifying proteins altered by redox imbalance in cancer cells is an attractive prognostic and therapeutic tool. Gene expression microarrays in A375 melanoma cells with different ROS levels after overexpressing catalase were performed. Dissimilar phenotypes by differential compensation to hydrogen peroxide scavenging were generated. The melanotic A375-A7 (A7) upregulated TYRP1, CNTN1 and UCHL1 promoting melanogenesis. The metastatic A375-G10 (G10) downregulated MTSS1 and TIAM1, proteins absent in metastasis. Moreover, differential coexpression of AOS genes (EPHX2, GSTM3, MGST1, MSRA, TXNRD3, MGST3 and GSR) was found in A7 and G10. Their increase in A7 improved its AOS ability and therefore, oxidative stress response, resembling less aggressive tumor cells. Meanwhile, their decrease in G10 revealed a disruption in the AOS and therefore, enhanced its metastatic capacity.

These gene signatures, not only bring new insights into the physiopathology of melanoma, but also could be relevant in clinical prognostic to classify between non aggressive and metastatic melanomas.

Relationships between the genes expressed in the mesenteric adipose tissue of beef cattle and feed intake and gain

Mesenteric fat, a depot within the visceral fat, accumulates in cattle during maturation and finishing and may be a potential source of production inefficiency. The aim of this study was to determine whether the genes expressed in the mesenteric fat of steers were associated with body weight gain and feed intake. Sixteen steers chosen by their rank of distance from the bivariate mean for gain and feed intake were used for this study. Mesenteric fat was obtained and evaluated for differences in gene expression. A total of 1831 genes were identified as differentially expressed among steers with variation in feed intake and gain. Many of these genes were involved with metabolic processes such as proteolysis, transcription and translation. In addition, the Gene Ontology annotations including transport and localization were both over-represented among the differentially expressed genes. Pathway analysis was also performed on the differentially expressed genes. The superoxide radical degradation pathway was identified as over-represented based on the differential expression of the genes GPX7, SOD2 and TYRP1, suggesting a potential role for oxidative stress or inflammatory pathways among low gain-high intake animals. GPX7 and SOD2 were in lower transcript abundance, and TYRP1 was higher in transcript abundance among the low gain-high feed intake animals. The retinoate biosynthesis pathway was also enriched due to the differential expression of the genes AKR1C3, ALDH8A1, RDH8, RDH13 and SDR9C7. These genes were all more highly expressed in the low gain-high intake animals. The glycerol degradation and granzyme A signaling pathways were both associated with gain. Three glycerol kinase genes and the GZMA gene were differentially expressed among high vs. low gain animals. Mesenteric fat is a metabolically active tissue, and in this study, genes involved in proteolysis, transcription, translation, transport immune function, glycerol degradation and oxidative stress were differentially expressed among beef steers with variation in body weight gain and feed intake.

Glutathione peroxidase 7 suppresses cancer cell growth and is hypermethylated in gastric cancer

Gastric cancer (GC) is one of the most common cancers in the world, and remains the third leading cause of cancer-related deaths worldwide. Glutathione peroxidase 7 (GPX7) is a member of GPX family which is downregulated in some cancer types. In this study, we investigated the expression, regulation, and molecular function of GPX7 in gastric cancer using 2D and 3D in vitro models and de-identified human tissue samples. Quantitative real-time RT-PCR, immunofluorescence, Western blot, 3D organotypic cultures, and pyrosequencing assays were used. We detected downregulation of GPX7 in all 7 gastric cancer cell lines that we tested and in approximately half (22/45) of human gastric cancer samples, as compared to histologically normal gastric tissues. Quantitative bisulfite pyrosequencing methylation analysis demonstrated DNA hypermethylation (> 10% methylation level) of GPX7 promoter in all 7 gastric cancer cell lines and in 56% (25/45) of gastric cancer samples, as compared to only 13% (6/45) in normal samples (p < 0.0001). Treatment of AGS and SNU1 cells with 5-Aza-2′-deoxycytidine led to a significant demethylation of GPX7 promoter and restored the expression of GPX7. In vitro assays showed that reconstitution of GPX7 significantly suppressed gastric cancer cell growth in both 2D and 3D organotypic cell culture models. This growth suppression was associated with inhibition of cell proliferation and induction of cell death. We detected significant upregulation of p27 and cleaved PARP and downregulation of Cyclin D1 upon reconstitution of GPX7. Taken together, we conclude that epigenetic silencing of GPX7 could play an important role in gastric tumorigenesis and progression.

Redox signaling in the gastrointestinal tract

Redox signaling regulates physiological self-renewal, proliferation, migration and differentiation in gastrointestinal epithelium by modulating Wnt/β-catenin and Notch signaling pathways mainly through NADPH oxidases (NOXs). In the intestine, intracellular and extracellular thiol redox status modulates the proliferative potential of epithelial cells. Furthermore, commensal bacteria contribute to intestine epithelial homeostasis through NOX1- and dual oxidase 2-derived reactive oxygen species (ROS). The loss of redox homeostasis is involved in the pathogenesis and development of a wide diversity of gastrointestinal disorders, such as Barrett's esophagus, esophageal adenocarcinoma, peptic ulcer, gastric cancer, ischemic intestinal injury, celiac disease, inflammatory bowel disease and colorectal cancer. The overproduction of superoxide anion together with inactivation of superoxide dismutase are involved in the pathogenesis of Barrett's esophagus and its transformation to adenocarcinoma. In Helicobacter pylori-induced peptic ulcer, oxidative stress derived from the leukocyte infiltrate and NOX1 aggravates mucosal damage, especially in HspB+ strains that downregulate Nrf2. In celiac disease, oxidative stress mediates most of the cytotoxic effects induced by gluten peptides and increases transglutaminase levels, whereas nitrosative stress contributes to the impairment of tight junctions. Progression of inflammatory bowel disease relies on the balance between pro-inflammatory redox-sensitive pathways, such as NLRP3 inflammasome and NF-κB, and the adaptive up-regulation of Mn superoxide dismutase and glutathione peroxidase 2. In colorectal cancer, redox signaling exhibits two Janus faces: On the one hand, NOX1 up-regulation and derived hydrogen peroxide enhance Wnt/β-catenin and Notch proliferating pathways; on the other hand, ROS may disrupt tumor progression through different pro-apoptotic mechanisms. In conclusion, redox signaling plays a critical role in the physiology and pathophysiology of gastrointestinal tract.

Expression of Reactive Oxygen Species-Related Transcripts in Egyptian Children With Autism

The molecular basis of the pathophysiological role of oxidative stress in autism is understudied. Herein, we used polymerase chain reaction (PCR) array to analyze transcriptional pattern of 84 oxidative stress genes in peripheral blood mononuclear cell pools isolated from 32 autistic patients (16 mild/moderate and 16 severe) and 16 healthy subjects (each sample is a pool from 4 autistic patients or 4 controls). The PCR array data were further validated by quantitative real-time PCR in 80 autistic children (55 mild/moderate and 25 severe) and 60 healthy subjects. Our data revealed downregulation in GCLM, SOD2, NCF2, PRNP, and PTGS2 transcripts (1.5, 3.8, 1.2, 1.7, and 2.2, respectively;P < .05 for all) in autistic group compared with controls. In addition, TXN and FTH1 exhibited 1.4- and 1.7-fold downregulation, respectively, in severe autistic patients when compared with mild/moderate group (P = .005 and .0008, respectively). This study helps in a better understanding of the underlying biology and related genetic factors of autism, and most importantly, it presents suggested candidate biomarkers for diagnosis and prognosis purposes as well as targets for therapeutic intervention.

Esophageal cancer: Risk factors, genetic association, and treatment

The poor prognosis and rising incidence of esophageal cancer highlight the need for improved detection and prediction methods that are essential prior to treatment. Esophageal cancer is one of the most fatal malignancies worldwide, with a dramatic increase in incidence in the Western world occurring over the past few decades. Despite improvements in the management and treatment of esophageal cancer patients, the general outcome remains very poor for overall 5-year survival rates (∼10%) and 5-year postesophagectomy survival rates (∼15-40%). Esophageal cancer is often diagnosed during its advanced stages, the main reason being the lack of early clinical symptoms. In an attempt to improve the outcome of patients after surgery, such patients are often treated with neoadjuvent concurrent chemoradiotherapy (CCRT) in order to decrease tumor size. However, CCRT may enhance toxicity levels and possibly cause a delay in surgery for patients who respond poorly to CCRT. Thus, precise biomarkers that could predict or identify patients who may or may not respond well to CCRT can assist physicians in choosing the appropriate therapy for patients. Identifying susceptible gene and biomarkers can help in predicting the treatment response of patients while improving their survival rates.

Chronic Inhibition of STAT3/STAT5 in Treatment-Resistant Human Breast Cancer Cell Subtypes: Convergence on the ROS/SUMO Pathway and Its Effects on xCT Expression and System xc- Activity

Pharmacologically targeting activated STAT3 and/or STAT5 has been an active area of cancer research. The cystine/glutamate antiporter, system x_c^-, contributes to redox balance and export of intracellularly produced glutamate in response to up-regulated glutaminolysis in cancer cells. We have previously shown that blocking STAT3/5 using the small molecule inhibitor, SH-4-54, which targets the SH2 domains of both proteins, increases xCT expression, thereby increasing system x_c^- activity in human breast cancer cells. The current investigation demonstrates that chronic SH-4-54 administration, followed by clonal selection of treatment-resistant MDA-MB-231 and T47D breast cancer cells, elicits distinct subtype-dependent effects. xCT mRNA and protein levels, glutamate release, and cystine uptake are decreased relative to untreated passage-matched controls in triple-negative MDA-MB-231 cells, with the inverse occurring in estrogen-responsive T47D cells. This “ying-yang” effect is linked with a shifted balance between the phosphorylation status of STAT3 and STAT5, intracellular ROS levels, and STAT5 SUMOylation/de-SUMOylation. STAT5 emerged as a definitive negative regulator of xCT at the transcriptional level, while STAT3 activation is coupled with increased system x_c^- activity. We propose that careful classification of a patient’s breast cancer subtype is central to effectively targeting STAT3/5 as a therapeutic means of treating breast cancer, particularly given that xCT is emerging as an important biomarker of aggressive cancers.

Differential genotoxicity mechanisms of silver nanoparticles and silver ions

In spite of many reports on the toxicity of silver nanoparticles (AgNPs), the mechanisms underlying the toxicity are far from clear. A key question is whether the observed toxicity comes from the silver ions (Ag⁺) released from the AgNPs or from the nanoparticles themselves. In this study, we explored the genotoxicity and the genotoxicity mechanisms of Ag⁺ and AgNPs. Human TK6 cells were treated with 5 nM AgNPs or silver nitrate (AgNO₃) to evaluate their genotoxicity and induction of oxidative stress. AgNPs and AgNO₃ induced cytotoxicity and genotoxicity in a similar range of concentrations (1.00-1.75 µg/ml) when evaluated using the micronucleus assay, and both induced oxidative stress by measuring the gene expression and reactive oxygen species in the treated cells. Addition of N-acetylcysteine (NAC, an Ag⁺ chelator) to the treatments significantly decreased genotoxicity of Ag⁺, but not AgNPs, while addition of Trolox (a free radical scavenger) to the treatment efficiently decreased the genotoxicity of both agents. In addition, the Ag⁺ released from the highest concentration of AgNPs used for the treatment was measured. Only 0.5 % of the AgNPs were ionized in the culture medium and the released silver ions were neither cytotoxic nor genotoxic at this concentration. Further analysis using electron spin resonance demonstrated that AgNPs produced hydroxyl radicals directly, while AgNO₃ did not. These results indicated that although both AgNPs and Ag⁺ can cause genotoxicity via oxidative stress, the mechanisms are different, and the nanoparticles, but not the released ions, mainly contribute to the genotoxicity of AgNPs.

Transit of H2O2 across the endoplasmic reticulum membrane is not sluggish

Cellular metabolism provides various sources of hydrogen peroxide (H2O2) in different organelles and compartments. The suitability of H2O2 as an intracellular signaling molecule therefore also depends on its ability to pass cellular membranes. The propensity of the membranous boundary of the endoplasmic reticulum (ER) to let pass H2O2 has been discussed controversially. In this essay, we challenge the recent proposal that the ER membrane constitutes a simple barrier for H2O2 diffusion and support earlier data showing that (i) ample H2O2 permeability of the ER membrane is a prerequisite for signal transduction, (ii) aquaporin channels are crucially involved in the facilitation of H2O2 permeation, and (iii) a proper experimental framework not prone to artifacts is necessary to further unravel the role of H2O2 permeation in signal transduction and organelle biology.

DNA hypermethylation of the vimentin gene inversely correlates with vimentin expression in intestinal- and diffuse-type gastric cancer

The vimentin gene is a hallmark of epithelial-to-mesenchymal transition and has been observed to be overexpressed in various types of tumor cell line and tissue. Previous studies have reported correlations between vimentin DNA methylation levels and subsequent vimentin expression levels in solid tumors, including breast and colorectal cancer; however, to the best of our knowledge, such a correlation has not been reported for gastric cancer (GC) using Lauren classification. Therefore, the present study aimed to quantify DNA methylation levels of the vimentin gene using quantitative (q) methylation-specific polymerase chain reaction (PCR) in intestinal-type GC cell lines (MKN-28, AGS and MKN-1), diffuse-type GC cell lines (SGC-7901, SNU-5 and KATO III), the GES-1 immortalized human non-neoplastic gastric epithelial cell line, as well as in tumor and paratumor normal tissue samples. Furthermore, the present study analyzed the messenger RNA expression of the vimentin gene in these cell lines and tissues by reverse transcription-qPCR. A comparison of the clinicopathological features was conducted between patients, grouped according to the Lauren classification. The present study identified that the vimentin promoter region was hypermethylated in all GC cell lines and tumor tissue samples when compared with immortalized normal gastric epithelial cells and paratumor normal tissues. In addition, vimentin promoter methylation levels were observed to be higher in intestinal-type cell lines when compared with those of diffuse-type lines and tissues. Correspondingly, vimentin expression levels were lower in intestinal-type gastric cell lines compared with those of diffuse-type cell lines and tissues, and were lowest in the non-neoplastic gastric cell line and paratumor normal tissues. Patients with diffuse-type GC were on average younger (P=0.023), and exhibited higher tumor (P=0.020), node (P=0.032) and TNM classification of malignant tumor stage (P=0.039) than those with intestinal-type GC. Following treatment of AGS cells (which demonstrated the highest methylation level of the vimentin gene) with 5-aza-2'-deoxycytidine, vimentin expression was restored significantly. Thus, the present study revealed that vimentin promoter methylation levels are inversely correlated with vimentin expression levels in GC (according to Lauren classification). High levels of methylation in the vimentin gene promoter region may be involved in carcinogenesis and the development of GC, and may provide a novel molecular classification for GC.

NPGPx modulates CPEB2-controlled HIF-1α RNA translation in response to oxidative stress

Non-selenocysteine-containing phospholipid hydroperoxide glutathione peroxidase (NPGPx or GPx7) is an oxidative stress sensor that modulates the antioxidative activity of its target proteins through intermolecular disulfide bond formation. Given NPGPx's role in protecting cells from oxidative damage, identification of the oxidative stress-induced protein complexes, which forms with key stress factors, may offer novel insight into intracellular reactive oxygen species homeostasis. Here, we show that NPGPx forms a disulfide bond with the translational regulator cytoplasmic polyadenylation element-binding protein 2 (CPEB2) that results in negative regulation of hypoxia-inducible factor 1-alpha (HIF-1α) RNA translation. In NPGPx-proficient cells, high oxidative stress that disrupts this bonding compromises the association of CPEB2 with HIF-1α RNA, leading to elevated HIF-1α RNA translation. NPGPx-deficient cells, in contrast, demonstrate increased HIF-1α RNA translation under normoxia with both impaired induction of HIF-1α synthesis and blunted HIF-1α-programmed transcription following oxidative stress. Together, these results reveal a molecular mechanism for how NPGPx mediates CPEB2-controlled HIF-1α RNA translation in a redox-sensitive manner.

The effects of microRNA on the absorption, distribution, metabolism and excretion of drugs

The importance of genetic factors (e.g. sequence variation) in the absorption, distribution, metabolism, excretion (ADME) and overall efficacy of therapeutic agents is well established. Our ability to identify, interpret and utilize these factors is the subject of much clinical investigation and therapeutic development. However, drug ADME and efficacy are also heavily influenced by epigenetic factors such as DNA/histone methylation and non-coding RNAs [especially microRNAs (miRNAs)]. Results from studies using tools, such as in silico miRNA target prediction, in vitro functional assays, nucleic acid profiling/sequencing and high-throughput proteomics, are rapidly expanding our knowledge of these factors and their effects on drug metabolism. Although these studies reveal a complex regulation of drug ADME, an increased understanding of the molecular interplay between the genome, epigenome and transcriptome has the potential to provide practically useful strategies to facilitate drug development, optimize therapeutic efficacy, circumvent adverse effects, yield novel diagnostics and ultimately become an integral component of personalized medicine.

The antioxidant machinery of the endoplasmic reticulum: Protection and signaling

Cellular metabolism is inherently linked to the production of oxidizing by-products, including reactive oxygen species (ROS) hydrogen peroxide (H2O2). When present in excess, H2O2 can damage cellular biomolecules, but when produced in coordinated fashion, it typically serves as a mobile signaling messenger. It is therefore not surprising that cell health critically relies on both low-molecular-weight and enzymatic antioxidant components, which protect from ROS-mediated damage and shape the propagation and duration of ROS signals. This review focuses on H2O2-antioxidant cross talk in the endoplasmic reticulum (ER), which is intimately linked to the process of oxidative protein folding. ER-resident or ER-regulated sources of H2O2 and other ROS, which are subgrouped into constitutive and stimulated sources, are discussed and set into context with the diverse antioxidant mechanisms in the organelle. These include two types of peroxide-reducing enzymes, a high concentration of glutathione derived from the cytosol, and feedback-regulated thiol-disulfide switches, which negatively control the major ER oxidase ER oxidoreductin-1. Finally, new evidence highlighting emerging principles of H2O2-based cues at the ER will likely set a basis for establishing ER redox processes as a major line of future signaling research. A fundamental problem that remains to be solved is the specific, quantitative, time resolved, and targeted detection of H2O2 in the ER and in specialized ER subdomains.

Characterization of a novel chicken muscle disorder through differential gene expression and pathway analysis using RNA-sequencing

Background

Improvements in poultry production within the past 50 years have led to increased muscle yield and growth rate, which may be contributing to an increased rate and development of new muscle disorders in chickens. Previously reported muscle disorders and conditions are generally associated with poor meat quality traits and have a significant negative economic impact on the poultry industry. Recently, a novel myopathy phenotype has emerged which is characterized by palpably “hard” or tough breast muscle. The objective of this study is to identify the underlying biological mechanisms that contribute to this emerging muscle disorder colloquially referred to as “Wooden Breast”, through the use of RNA-sequencing technology.

Methods

We constructed cDNA libraries from five affected and six unaffected breast muscle samples from a line of commercial broiler chickens. After paired-end sequencing of samples using the Illumina Hiseq platform, we used Tophat to align the resulting sequence reads to the chicken reference genome and then used Cufflinks to find significant changes in gene transcript expression between each group. By comparing our gene list to previously published histology findings on this disorder and using Ingenuity Pathways Analysis (IPA®), we aim to develop a characteristic gene expression profile for this novel disorder through analyzing genes, gene families, and predicted biological pathways.

Results

Over 1500 genes were differentially expressed between affected and unaffected birds. There was an average of approximately 98 million reads per sample, across all samples. Results from the IPA analysis suggested “Diseases and Disorders” such as connective tissue disorders, “Molecular and Cellular Functions” such as cellular assembly and organization, cellular function and maintenance, and cellular movement, “Physiological System Development and Function” such as tissue development, and embryonic development, and “Top Canonical Pathways” such as, coagulation system, axonal guidance signaling, and acute phase response signaling, are associated with the Wooden Breast disease.

Conclusions

There is convincing evidence by RNA-seq analysis to support localized hypoxia, oxidative stress, increased intracellular calcium, as well as the possible presence of muscle fiber-type switching, as key features of Wooden Breast Disease, which are supported by reported microscopic lesions of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1623-0) contains supplementary material, which is available to authorized users.

Comparison of the deleterious effects of binge drinking-like alcohol exposure in adolescent and adult mice

A major cause of alcohol toxicity is the production of reactive oxygen species generated during ethanol metabolism. The aim of this study was to compare the effect of binge drinking-like alcohol exposure on a panel of genes implicated in oxidative mechanisms in adolescent and adult mice. In adolescent animals, alcohol decreased the expression of genes involved in the repair and protection of oxidative DNA damage such as atr, gpx7, or nudt15 and increased the expression of proapoptotic genes such as casp3. In contrast, in the adult brain, genes activated by alcohol were mainly associated with protective mechanisms that prevent cells from oxidative damage. Whatever the age, iterative binge-like episodes provoked the same deleterious effects as those observed after a single binge episode. In adolescent mice, multiple binge ethanol exposure substantially reduced neurogenesis in the dentate gyrus and impaired short-term memory in the novel object and passive avoidance tests. Taken together, our results indicate that alcohol causes deleterious effects in the adolescent brain which are distinct from those observed in adults. These data contribute to explain the greater sensitivity of the adolescent brain to alcohol toxicity. The effects of alcohol exposure were investigated on genes involved in oxidative mechanisms. In adolescent animals, alcohol decreased the expression of genes involved in DNA repair, a potential cause of the observed decrease of neurogenesis. In contrast, in the adult brain, alcohol increased the expression of genes associated with antioxidant mechanisms. Apoptosis was increase in all groups and converged with other biochemical alterations to enhance short-term memory impairment in the adolescent brain. These data contribute to explain the greater sensitivity of the adolescent brain to alcohol toxicity.