Reactive oxygen species downregulate catalase expression via methylation of a CpG island in the Oct-1 promoter

Evaluation of Metabolic Dysfunction-Associated Fatty Liver Disease-Related Pathogenic Mechanisms in Human Steatotic Liver Cell-Based Model: Beneficial Effects of Prunus domestica L. subsp. syriaca Extract

Background/Objectives: Disrupted glucose uptake, oxidative stress, and increased de novo lipogenesis are some of the key features of metabolic dysfunction-associated fatty liver disease (MASLD). The modulation of these pathogenic mechanisms using extracts from natural and sustainable sources is a promising strategy to mitigate disease progression. This study aimed to evaluate the effects of Prunus domestica L. subsp. syriaca extract on these processes, taking advantage of a cell-based model of steatotic hepatocytes (HepG2-OA) that recapitulates some key pathophysiological features of MASLD. Methods: The HepG2-OA cell model was generated by treating cells for 7 days with 100 μM oleic acid (OA). The effect of different concentrations (0.01, 0.1, 0.5, and 1 mg/mL) of P. domestica extract was assessed through MTT assay (cell viability), flow cytometry (glucose uptake and reactive oxygen species, ROS, production), spectrophotometry (lipid accumulation), and qRT-PCR (expression of selected genes). Results: P. domestica extract exhibited no cytotoxicity at any tested concentration after 24 and 48 h in the HepG2-OA cells. The extract increased glucose uptake in a dose-dependent fashion after both 6 and 24 h. Additionally, the extract reduced lipid accumulation and downregulated the expression of key lipogenic genes (DGAT1 and FASN). Furthermore, in the HepG2-OA cells, P. domestica extract reduced ROS production and downregulated the expression of oxidative stress-related genes (SOD and CAT). Conclusions: P. domestica extract positively modulated some key molecular mechanisms associated with glucose metabolism, lipogenesis, and oxidative stress, supporting its potential as a nutraceutical candidate for MASLD management.

Crosstalk Between Oxidative Stress and Epigenetics: Unveiling New Biomarkers in Human Infertility

The correlation between epigenetic alterations and the pathophysiology of human infertility is progressively being elucidated with the discovery of an increasing number of target genes that exhibit altered expression patterns linked to reproductive abnormalities. Several genes and molecules are emerging as important for the future management of human infertility. In men, microRNAs (miRNAs) like miR-34c, miR-34b, and miR-122 regulate apoptosis, sperm production, and germ cell survival, while other factors, such as miR-449 and sirtuin 1 (SIRT1), influence testicular health, oxidative stress, and mitochondrial function. In women, miR-100-5p, miR-483-5p, and miR-486-5p are linked to ovarian reserve, PCOS, and conditions like endometriosis. Mechanisms such as DNA methylation, histone modification, chromatin restructuring, and the influence of these non-coding RNA (ncRNA) molecules have been identified as potential perturbators of normal spermatogenesis and oogenesis processes. In fact, alteration of these key regulators of epigenetic processes can lead to reproductive disorders such as defective spermatogenesis, failure of oocyte maturation and embryonic development alteration. One of the primary factors contributing to changes in the key epigenetic regulators appear to be oxidative stress, which arises from environmental exposure to toxic substances or unhealthy lifestyle choices. This evidence-based study, retracing the major epigenetic processes, aims to identify and discuss the main epigenetic biomarkers of male and female fertility associated with an oxidative imbalance, providing future perspectives in the diagnosis and management of infertile couples.

Targeting catalase in cancer

Healthy cells have developed a sophisticated network of antioxidant molecules to prevent the toxic accumulation of reactive oxygen species (ROS) generated by diverse environmental stresses. On the opposite, cancer cells often exhibit high levels of ROS and an altered levels of antioxidant molecules compared to normal cells. Among them, the antioxidant enzyme catalase plays an essential role in cell defense against oxidative stress through the dismutation of hydrogen peroxide into water and molecular oxygen, and its expression is often decreased in cancer cells. The elevation of ROS in cancer cells provides them proliferative advantages, and leads to metabolic reprogramming, immune escape and metastasis. In this context, catalase is of critical importance to control these cellular processes in cancer through various mechanisms. In this review, we will discuss the major progresses and challenges in understanding the role of catalase in cancer for this last decade. This review also aims to provide important updates regarding the regulation of catalase expression, subcellular localization and discuss about the potential role of microbial catalases in tumor environment. Finally, we will describe the different catalase-based therapies and address the advantages, disadvantages, and limitations associated with modulating catalase therapeutically in cancer treatment.

Correlation of High-Grade Osteosarcoma Response to Chemotherapy with Enhanced Tissue Immunological Response: Analysis of CD95R, IFN-γ, Catalase, Hsp70, and VEGF

High-grade osteosarcoma, a primary malignant bone tumour, is experiencing a global increase in reported incidence with varied prevalence. Despite advances in management, which include surgery and neoadjuvant chemotherapy often an unsatisfactory outcome is found due to poor or heterogeneous response to chemotherapy. Our study delved into chemotherapy responses in osteosarcoma patients and associated molecular expressions, focusing on CD95 receptor (CD95R), interferon (IFN)-γ, catalase, heat-shock protein (Hsp)70, and vascular endothelial growth factor (VEGF). Employing immunohistochemistry and Huvos grading of post-chemo specimens, we analysed formalin-fixed paraffin-embedded (FFPE) osteosarcoma tissue of resected post-chemotherapy specimens from Dr. Soetomo General Academic Hospital in Surabaya, Indonesia (DSGAH), spanning from 2016 to 2020. Results revealed varied responses (poor 40.38%, moderate 48.08%, good 11.54%) and distinct patterns in CD95R, IFN-γ, catalase, Hsp70, and VEGF expression. Significant differences among response groups were observed in CD95R and IFN-γ expression in tumour-infiltrating lymphocytes. The trend of diminishing CD95R expression from poor to good responses, accompanied by an increase in IFN-γ, implied a reduction in the count of viable osteosarcoma cells with the progression of Huvos grading. Catalase expression in osteosarcoma cells was consistently elevated in the poor response group, while Hsp70 expression was highest. VEGF expression in macrophages was significantly higher in the good response group. In conclusion, this study enhances our understanding of immune-chemotherapy interactions in osteosarcoma and identifies potential biomarkers for targeted interventions.

Carbon nanoparticles adversely affect CFTR expression and toxicologically relevant pathways

Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) that can lead to terminal respiratory failure. Ultrafine carbonaceous particles, which are ubiquitous in ambient urban and indoor air, are increasingly considered as major contributors to the global health burden of air pollution. However, their effects on the expression of CFTR and associated genes in lung epithelial cells have not yet been investigated. We therefore evaluated the effects of carbon nanoparticles (CNP), generated by spark-ablation, on the human bronchial epithelial cell line 16HBE14o- at air-liquid interface (ALI) culture conditions. The ALI-cultured cells exhibited epithelial barrier integrity and increased CFTR expression. Following a 4-h exposure to CNP, the cells exhibited a decreased barrier integrity, as well as decreased expression of CFTR transcript and protein levels. Furthermore, transcriptomic analysis revealed that the CNP-exposed cells showed signs of oxidative stress, apoptosis and DNA damage. In conclusion, this study describes spark-ablated carbon nanoparticles in a realistic exposure of aerosols to decrease CFTR expression accompanied by transcriptomic signs of oxidative stress, apoptosis and DNA damage.

An Epigenetic Role of Mitochondria in Cancer

Mitochondria are not only the main energy supplier but are also the cell metabolic center regulating multiple key metaborates that play pivotal roles in epigenetics regulation. These metabolites include acetyl-CoA, α-ketoglutarate (α-KG), S-adenosyl methionine (SAM), NAD⁺, and O-linked beta-N-acetylglucosamine (O-GlcNAc), which are the main substrates for DNA methylation and histone post-translation modifications, essential for gene transcriptional regulation and cell fate determination. Tumorigenesis is attributed to many factors, including gene mutations and tumor microenvironment. Mitochondria and epigenetics play essential roles in tumor initiation, evolution, metastasis, and recurrence. Targeting mitochondrial metabolism and epigenetics are promising therapeutic strategies for tumor treatment. In this review, we summarize the roles of mitochondria in key metabolites required for epigenetics modification and in cell fate regulation and discuss the current strategy in cancer therapies via targeting epigenetic modifiers and related enzymes in metabolic regulation. This review is an important contribution to the understanding of the current metabolic-epigenetic-tumorigenesis concept.

Coral Hydrate, a Novel Antioxidant, Improves Alcohol Intoxication in Mice

Alcohol-drinking culture may cause individuals to periodically experience unpleasant hangovers. In addition, ethanol catabolism stimulates the production of free radicals that may cause liver injury and further lead to the development of chronic alcoholic fatty liver disease. Although a number of studies have suggested that hydrogenated water may be consumed to act as free radical scavenger, its instability limits its application. In this study, we used coral hydrate (i.e., hydrogenated coral materials) as a more stable hydrogen source and evaluated its effects in a murine model of alcohol intoxication. In solution, coral hydrate exhibited much more stable redox potential than did hydrogenated water. Furthermore, administration of coral hydrate by oral gavage significantly prolonged the time to fall asleep and decreased the total sleep time in mice that received intraperitoneal injection of ethanol. The mice receiving coral hydrate also had lower plasma ethanol and acetaldehyde levels than controls. In line with this observation, hepatic expression of alcohol dehydrogenase, acetaldehyde dehydrogenase, catalase and glutathione peroxidase were all significantly increased by the treatment. Meanwhile, alcohol-induced upregulation of pro-inflammatory factors was attenuated by the administration of coral hydrate. Taken together, our data suggest that coral hydrate might be an effective novel treatment for alcohol intoxication.

Toxicological effects of hypoxanthine on Heterosigmaakashiwo: Mechanism of growth inhibition and change in hemolytic toxin content

Heterosigmaakashiwo is an algal species that causes harmful algal blooms (HABs) with strong hemolytic toxicity on coastal aquatic organisms. This study investigated the mechanism of growth inhibition and changes in hemolytic toxin contents in algal culture after exposure to hypoxanthine, a compound secreted by algicidal bacterium Bacillus sp.strain B1. An algal inhibition rate of 86% was observed with 1.0 mM hypoxanthine treatment on day 15. The levels of superoxide dismutase and catalase in algal cell culture increased while that of glutathione decreased during the treatment. In addition,the level of hemolytic toxin contents increased on day 3 under hypoxanthine treatment, and significantly decreased on days 6, 9, 12, and 15. Twelve fatty acids in H.akashiwo were detected by GC-MS, and the changes in the contents of C16, C18, C18:4ω3, and C20:5ω3 in the treatment group were consistent with the change in hemolytic toxin content. The four fatty acids were tested for hemolysis and it was observed that the hemolysis rate of 25 μg/mL C18:4ω3 and 5 μg/mL C20:5ω3 reached more than 80%, but C16 and C18 exhibited no hemolytic capability.Therefore, our results showed that hypoxanthine inhibited the growth of H. akashiwo through the changes of levels of antioxidants and hemolytic toxin content in the cultures, and fatty acids C18:4ω3 and C20:5ω3 were contributors to hemolytic toxins. The results confirmed that hypoxanthine is a potential algal inhibitor to prevent HABs.

Peroxisome proliferator-activated receptor-δ-mediated upregulation of catalase helps to reduce ultraviolet B-induced cellular injury in dermal fibroblasts

BACKGROUND

Previous studies suggested that the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-δ plays an essential role in cellular responses against oxidative stress.

OBJECTIVE

To investigate how PPAR-δ elicits cellular responses against oxidative stress in primary human dermal fibroblasts (HDFs) exposed to ultraviolet B (UVB).

METHODS

The present study was undertaken in HDFs by performing real-time polymerase chain reaction, gene silencing, cytotoxicity and reporter gene assay, analyses for catalase and reactive oxygen species, and immunoblot analyses.

RESULTS

The PPAR-δ activator GW501516 upregulated expression of catalase and this upregulation was attenuated by PPAR-δ-targeting siRNA. GW501516-activated PPAR-δ induced catalase promoter activity through a direct repeat 1 response element. Mutation of this response element completely abrogated transcriptional activation, indicating that this site is a novel type of PPAR-δ response element. In addition, GW501516-activated PPAR-δ counteracted the reductions in activity and expression of catalase induced by UVB irradiation. These recovery effects were significantly attenuated in the presence of PPAR-δ-targeting siRNA or the specific PPAR-δ antagonist GSK0660. GW501516-activated PPAR-δ also protected HDFs from cellular damage triggered by UVB irradiation, and this PPAR-δ-mediated reduction of cellular damage was reversed by the catalase inhibitor or catalase-targeting siRNA. These effects of catalase blockade were positively correlated with accumulation of reactive oxygen species in HDFs exposed to UVB. Furthermore, GW501516-activated PPAR-δ targeted peroxisomal hydrogen peroxide through catalase in UVB-irradiated HDFs.

CONCLUSION

The gene encoding catalase is a target of PPAR-δ, and this novel catalase-mediated pathway plays a critical role in the cellular response elicited by PPAR-δ against oxidative stress.

Browsing the oldest antioxidant enzyme: catalase and its multiple regulation in cancer

Aerobic organisms possess numerous antioxidant enzymatic families, including catalases, superoxide dismutases (SODs), peroxiredoxins (PRDXs), and glutathione peroxidases (GPXs), which work cooperatively to protect cells from an excess of reactive oxygen species (ROS) derived from endogenous metabolism or external microenvironment. Catalase, as well as other antioxidant enzymes, plays an important dichotomous role in cancer. Therefore, therapies aimed at either reverting the increased or further escalating catalase levels could be effective, depending on the metabolic landscape and on the redox status of cancer cells. This dichotomous role of catalase in cancers highlights the importance to deepen comprehensively the role and the regulation of this crucial antioxidant enzyme. The present review highlights the role of catalase in cancer and provides a comprehensive description of the molecular mechanisms associated with the multiple levels of catalase regulation.

A review of the phytochemical, pharmacological, pharmacokinetic, and toxicological evaluation of Quercus Infectoria galls

ETHNOPHARMACOLOGICAL RELEVANCE

Quercus Infectoria galls (QIG) have a long history of use in traditional Chinese medicine and traditional Uyghur medicine for the treatment of diarrhea, hemorrhage, skin disease, and many other human ailments. Medicinal applications of QIG have become increasingly popular in Greece, Asia Minor, Syria, and Iran.

AIM OF THE REVIEW

The present paper reviewed the ethnopharmacology, phytochemistry, analytical methods, biological activities, metabolism, pharmacokinetics, toxicology, and drug interactions of QIG to assess the ethnopharmacological uses, explore its therapeutic potential, and identify future opportunities for research.

MATERIALS AND METHODS

Information on QIG was gathered via the Internet (using Google Scholar, Baidu Scholar, Elsevier, ACS, Pubmed, Web of Science, CNKI, and EMBASE) and libraries. Additionally, information was also obtained from local books and PhD and MS dissertations.

RESULTS

QIG has played an important role in traditional Chinese medicine. The main bioactive metabolites of QIG include tannins, phenolic acids, flavonoids, triterpenoids, and steroids. Scientific studies on the QIG extract and its components have shown its wide range of pharmacological activities, such as cholinesterase- and monoamine oxidase-inhibitory, antitumor, anti-hypertension, antidiabetic, antimicrobial, insecticidal, antiparasitic, antioxidant, and anti-inflammatory.

CONCLUSIONS

The ethnopharmacological, phytochemical, pharmacological, and analytical methods of QIG were highlighted in this review, which provides information for future studies and commercial exploration. QIG has a huge potential for pharmaceutical and nutraceutical applications. Moreover, comprehensive toxicity studies of this plant must be conducted to ensure its safety. Additional investigations are recommended to transmute the ethnopharmacological claims of this plant in folklore medicines into scientific rationale-based information. Research on pharmacokinetics studies and potential drug interactions with standard-of-care medications is still limited, which calls for additional studies particularly on humans. Further assessments and clinical trials should be performed before it can be integrated into medicinal practices.

Oxidative Stress and Alterations in the Antioxidative Defense System in Neuronal Cells Derived from NPC1 Patient-Specific Induced Pluripotent Stem Cells

Oxidative stress (OS) represents a state of an imbalanced amount of reactive oxygen species (ROS) and/or a hampered efficacy of the antioxidative defense system. Cells of the central nervous system are particularly sensitive to OS, as they have a massive need of oxygen to maintain proper function. Consequently, OS represents a common pathophysiological hallmark of neurodegenerative diseases and is discussed to contribute to the neurodegeneration observed amongst others in Alzheimer’s disease and Parkinson’s disease. In this context, accumulating evidence suggests that OS is involved in the pathophysiology of Niemann-Pick type C1 disease (NPC1). NPC1, a rare hereditary neurodegenerative disease, belongs to the family of lysosomal storage disorders. A major hallmark of the disease is the accumulation of cholesterol and other glycosphingolipids in lysosomes. Several studies describe OS both in murine in vivo and in vitro NPC1 models. However, studies based on human cells are limited to NPC1 patient-derived fibroblasts. Thus, we analyzed OS in a human neuronal model based on NPC1 patient-specific induced pluripotent stem cells (iPSCs). Higher ROS levels, as determined by DCF (dichlorodihydrofluorescein) fluorescence, indicated oxidative stress in all NPC1-deficient cell lines. This finding was further supported by reduced superoxide dismutase (SOD) activity. The analysis of mRNA and protein levels of SOD1 and SOD2 did not reveal any difference between control cells and NPC1-deficient cells. Interestingly, we observed a striking decrease in catalase mRNA and protein levels in all NPC1-deficient cell lines. As catalase is a key enzyme of the cellular antioxidative defense system, we concluded that the lack of catalase contributes to the elevated ROS levels observed in NPC1-deficient cells. Thus, a restitution of a physiological catalase level may pose an intervention strategy to rescue NPC1-deficient cells from the repercussions of oxidative stress contributing to the neurodegeneration observed in NPC1.

The role of mitochondrial-related nuclear genes in age-related common disease

Mitochondria are critical organelles that provide energy as ATP to the cell. Besides 37 genes encoded by mitochondrial genome, it has been estimated that over 1500 nuclear genes are required for mitochondrial structure and function. Thus, mutations of many genes in the nuclear genome cause dysfunction of mitochondria that can lead to many severe conditions. Mitochondrial dysfunction often results in reduced ATP synthesis, higher levels of reactive oxygen species (ROS), imbalanced mitochondrial dynamics, and other detrimental effects. In addition to rare primary mitochondrial disorders, these mitochondrial-related genes are often associated with many common diseases. For example, in neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington disease, mitochondrialand energy metabolism abnormalities can greatly affect brain function. Cancer cells are also known to exhibit repressed mitochondrial ATP production in favor of glycolysis, which fuels the aggressive proliferation and metastasis of tumor tissues, leading many to speculate on a possible relationship between compromised mitochondrial function and cancer. The association between mitochondrial dysfunction and diabetes is also unsurprising, given the organelle's crucial role in cellular energy utilization. Here, we will discuss the multiple lines of evidence connecting mitochondrial dysfunction associated with mitochondria-related nuclear genes to many of the well-known disease genes that also underlie common disease.

Avian Stress-Related Transcriptome and Selenotranscriptome: Role during Exposure to Heavy Metals and Heat Stress

Selenium, through incorporation into selenoproteins, is one of the key elements of the antioxidant system. Over the past few years there has been increased interest in exploring those molecular mechanisms in chicken, responsible for the development of this protection system. In more detail, Cd/Pb poisoning and heat stress increase oxidation, mRNA levels of inflammatory proteins, and apoptotic proteins. Selenium seems to enhance the antioxidant status and alleviates these effects via upregulation of antioxidant proteins and other molecular effects. In this review, we analyze avian transcriptome key elements with particular emphasis on interactions with heavy metals and on relation to heat stress.

The POU-Domain Transcription Factor Oct-6/POU3F1 as a Regulator of Cellular Response to Genotoxic Stress

DNA damage and the generation of reactive oxygen species (ROS) are key mechanisms of apoptotic cell death by commonly used genotoxic drugs. However, the complex cellular response to these pharmacologic agents remains yet to be fully characterized. Several studies have described the role of transcription factor octamer-1 (Oct-1)/Pit-1, Oct-1/2, and Unc-86 shared domain class 2 homeobox 1 (POU2F1) in the regulation of the genes important for cellular response to genotoxic stress. Evaluating the possible involvement of other POU family transcription factors in these pathways, we revealed the inducible expression of Oct-6/POU3F1, a regulator of neural morphogenesis and epidermal differentiation, in cancer cells by genotoxic drugs. The induction of Oct-6 occurs at the transcriptional level via reactive oxygen species (ROS) and ataxia telangiectasia mutated- and Rad3-related (ATR)-dependent mechanisms, but in a p53 independent manner. Moreover, we provide evidence that Oct-6 may play a role in the regulation of cellular response to DNA damaging agents. Indeed, by using the shRNA approach, we demonstrate that in doxorubicin-treated H460 non-small-cell lung carcinoma (NSCLC) cells, Oct-6 depletion leads to a reduced G2-cell cycle arrest and senescence, but also to increased levels of intracellular ROS and DNA damage. In addition, we could identify p21 and catalase as Oct-6 target genes possibly mediating these effects. These results demonstrate that Oct-6 is expressed in cancer cells after genotoxic stress, and suggests its possible role in the control of ROS, DNA damage response (DDR), and senescence.

Neurons and Microglia; A Sickly-Sweet Duo in Diabetic Pain Neuropathy

Diabetes is a common condition characterized by persistent hyperglycemia. High blood sugar primarily affects cells that have a limited capacity to regulate their glucose intake. These cells include capillary endothelial cells in the retina, mesangial cells in the renal glomerulus, Schwann cells, and neurons of the peripheral and central nervous systems. As a result, hyperglycemia leads to largely intractable complications such as retinopathy, nephropathy, hypertension, and neuropathy. Diabetic pain neuropathy is a complex and multifactorial disease that has been associated with poor glycemic control, longer diabetes duration, hypertension, advanced age, smoking status, hypoinsulinemia, and dyslipidemia. While many of the driving factors involved in diabetic pain are still being investigated, they can be broadly classified as either neuron -intrinsic or -extrinsic. In neurons, hyperglycemia impairs the polyol pathway, leading to an overproduction of reactive oxygen species and reactive nitrogen species, an enhanced formation of advanced glycation end products, and a disruption in Na⁺/K⁺ ATPase pump function. In terms of the extrinsic pathway, hyperglycemia leads to the generation of both overactive microglia and microangiopathy. The former incites a feed-forward inflammatory loop that hypersensitizes nociceptor neurons, as observed at the onset of diabetic pain neuropathy. The latter reduces neurons' access to oxygen, glucose and nutrients, prompting reductions in nociceptor terminal expression and losses in sensation, as observed in the later stages of diabetic pain neuropathy. Overall, microglia can be seen as potent and long-lasting amplifiers of nociceptor neuron activity, and may therefore constitute a potential therapeutic target in the treatment of diabetic pain neuropathy.

Ameliorative effect of Homalium zeylanicum against carbon tetrachloride-induced oxidative stress and liver injury in rats

Objective is to evaluate the ameliorative effects of Homalium zeylanicum in carbon tetrachloride-induced oxidative stress and liver injury in rats. To establish the nature of antioxidant principles in the bioactive ethyl acetate fractions of bark (HZEB) and leaf (HZEL); oxygen radical absorbance capacity (ORAC) and cell-based antioxidant protection in erythrocytes (CAP-e) assays were performed. From acute toxicity study, HZEB and HZEL at 200 and 300 mg/kg b.w., were relatively safe at their effective doses. The degree of protection was measured by using biochemical parameters such as serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), alkaline phosphatase (ALP), total bilirubin (TB) and total protein (TP) contents. Hepatic markers e.g. thiobarbituric acid reactive species (TBARS), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) were evaluated along with histopathological observations of liver tissues. Both fractions showed significant improvement in restoring SGOT, SGPT, ALP, TB and TP level. TBARS, SOD, CAT and GSH levels were significantly altered towards normal values. Both fractions at 300 mg/kg showed remarkable improvement in liver markers as compared to silymarin. Histopathological examinations showed reduction in hepatic necrosis and appeared normal hepatocellular architecture in HZEB and HZEL treated groups. In CAP-e assay, IC₅₀ of HZEB (54.66 mg/mL) was higher than HZEL (60.88 mg/mL) and in ORAC assay, AUC of HZEB and HZEL were 33.46, 21.29 respectively and results were comparable with trolox. GC-MS and LC-MS analysis identified a total no. of 44 compounds. Few compounds were identified as bioactive compounds e.g. catechol (7.23%), tetraacetyl-d-xylonic nitrile (3%), oleic acid (0.49%), 2,6-bis(1,1-dimethylethyl)-phenol (3.71%), 3,4,5-trimethoxy-phenol (0.31%), and conifer alcohol (7.41%). The presence of antioxidant principles in both fractions were responsible for hepatoprotective activities, however, the presence of catechol (7.23%) in the bark part imparted better activities in protecting liver than leaf of H. zeylanicum.

Catalase and nonalcoholic fatty liver disease

Obesity and insulin resistance are considered the main causes of nonalcoholic fatty liver disease (NAFLD), and oxidative stress accelerates the progression of NAFLD. Free fatty acids, which are elevated in the liver by obesity or insulin resistance, lead to incomplete oxidation in the mitochondria, peroxisomes, and microsomes, leading to the production of reactive oxygen species (ROS). Among the ROS generated, H₂O₂ is mainly produced in peroxisomes and decomposed by catalase. However, when the H₂O₂ concentration increases because of decreased expression or activity of catalase, it migrates to cytosol and other organelles, causing cell injury and participating in the Fenton reaction, resulting in serious oxidative stress. To date, numerous studies have been shown to inhibit the pathogenesis of NAFLD, but treatment for this disease mainly depends on weight loss and exercise. Various molecules such as vitamin E, metformin, liraglutide, and resveratrol have been proposed as therapeutic agents, but further verification of the dose setting, clinical application, and side effects is needed. Reducing oxidative stress may be a fundamental method for improving not only the progression of NAFLD but also obesity and insulin resistance. However, the relationship between NAFLD progression and antioxidants, particularly catalase, which is most commonly expressed in the liver, remains unclear. Therefore, this review summarizes the role of catalase, focusing on its potential therapeutic effects in NAFLD progression.

Determination of the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues: A comparison between two breeding seasons

The key prerequisite for successful insemination is sperm characterized to have positive values for morphological and biological variables which are determined by, among others, effective antioxidant protection during the lifespan of sperm cells. This study evaluated the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues during breeding (n = 5) and non-breeding (n = 5) seasons. The activity of superoxide dismutase (SOD) was greater (P < 0.05) during the breeding season, in particular in the testes and the caput epididymis, and SOD1 was the predominant isoform of the enzyme. The expression of the SOD3 gene was markedly less in the analyzed tissues, which indicates that this enzyme contributes to the antioxidant protection of the stallion reproductive tract. The activity of catalase (CAT) was less (P < 0.05) in the testes during both seasons while its relative abundances only during the breeding season. The greatest CAT activity was noted in the cauda epididymis during the breeding season. The activity of glutathione peroxidases (GPx) was greater (P < 0.05) in the testes than in other tissues and 10-fold greater during the breeding season. Similarly, relative abundance of GPx5 mRNA was greater (P < 0.05) in the caput epididymis than in the remaining tissues during both seasons. This study demonstrated that season has an ambiguous influence on the antioxidant defense system in stallion reproductive tissues. Seasonal differences in the present study, however, indicate that the reproductive system of stallions adapts well to environmental seasonal changes.

Regulation of tNOX expression through the ROS-p53-POU3F2 axis contributes to cellular responses against oxaliplatin in human colon cancer cells

BACKGROUND

Oxaliplatin belongs to the platinum-based drug family and has shown promise in treating cancer by binding to DNA to induce cytotoxicity. However, individual patients show diverse therapeutic responses toward oxaliplatin due to yet-unknown underlying mechanisms. We recently established that oxaliplatin also exert its anti-cancer activity in gastric cancer cell lines by targeting tumor-associated NADH oxidase (tNOX), attenuate NAD⁺ generation and reduce NAD⁺-dependent sirtuin 1 (SIRT1) deacetylase activity, which in turn enhances p53 acetylation and apoptosis.

METHODS

In this study, differential cellular outcomes in response to oxaliplatin exposure of p53-wild-type versus p53-null HCT116 human colon cancer cells were examined. Cell growth profile was determined by cell impedance measurements and apoptosis was analyzed by flow cytometry. The engagement between oxaliplatin and tNOX protein was studied by cellular thermal shift assay. Furthermore, western blot analysis revealed that p53 was important in regulating tNOX expression in these cell lines.

RESULTS

In p53-wild-type cells, we found that oxaliplatin inhibited cell growth by inducing apoptosis and concurrently down-regulating tNOX at both the transcriptional and translational levels. In p53-null cells, in contrast, oxaliplatin moderately up-regulated tNOX expression and yielded no apoptosis and much less cytotoxicity. Further experiments revealed that in p53-wild-type cells, oxaliplatin enhanced ROS generation and p53 transcriptional activation, leading to down-regulation of the transcriptional factor, POU3F2, which enhances the expression of tNOX. Moreover, the addition of a ROS scavenger reversed the p53 activation, POU3F2 down-regulation, and apoptosis induced by oxaliplatin in p53-wild-type cells. In the p53-null line, on the other hand, oxaliplatin treatment triggered less ROS generation and no p53 protein, such that POU3F2 and tNOX were not down-regulated and oxaliplatin-mediated cytotoxicity was attenuated.

CONCLUSION

Our results show that oxaliplatin mediates differential cellular responses in colon cancer cells depending on their p53 status, and demonstrate that the ROS-p53 axis is important for regulating POU3F2 and its downstream target, tNOX. Notably, the depletion of tNOX sensitizes p53-null cells to both spontaneous and oxaliplatin-induced apoptosis. Our work thus clearly shows a scenario in which targeting of tNOX may be a potential strategy for cancer therapy in a p53-inactivated system.

Low Oxidative Stress-Mediated Proliferation Via JNK-FOXO3a-Catalase Signaling in Transplanted Adult Stem Cells Promotes Wound Tissue Regeneration

Aims: Stem cells exposed to pathological levels of reactive oxygen species (ROS) at wound sites fail to regenerate tissue. The molecular mechanism underlying differential levels of ROS-mediated regulation of stem cells remains elusive. This study elucidates the mechanistic role of catalase at 10 μM H₂O₂-induced proliferation of mouse bone marrow stromal (BMSC) and hematopoietic (HSPC) stem/progenitor cells. Results: BMSCs and HSPCs depicted an increased growth rate and colony formation, in the presence of 10 μM but not 100 μM concentration of H₂O₂, an effect that was perturbed by Vit. C. Mechanistically, JNK activation-FOXO3a nuclear translocation and binding of FOXO3a to catalase promoter at 10 μM H₂O₂ led to an increased expression and activity of anti-oxidant gene, catalase. This was followed by an increased proliferative phenotype via the AKT-dependent pathway that was perturbed in the presence of catalase-inhibitor, 3-aminotriazole due to an increased ROS-mediated inactivation of AKT. Preclinically, 10 μM H₂O₂-mediated preconditioning of BMSCs/HSPCs transplantation accelerated wound closure, enhanced catalase expression, and decreased ROS levels at the wound site. Transplantation of male donor cells into female recipient mice or GFP-labeled BMSCs or HSPCs depicted an increased engraftment and proliferation in preconditioned cell transplanted groups as compared with the wound control. Wound healing occurred via keratinocyte generation and vascularization in preconditioned BMSCs, whereas only neo-vascularization occurred in the preconditioned HSPCs transplanted groups. Innovation and Conclusion: Our study suggests a distinct role of catalase that protects BMSCs and HSPCs from low ROS and promotes proliferation. Transplantation of preconditioned stem cells enhanced wound tissue regeneration with a better antioxidant defense mechanism-as a therapeutic approach in stem cell transplantation-mediated tissue regeneration. Antioxid. Redox Signal. 28, 1047-1065.

Expression of genes that encode cellular oxidant/antioxidant systems are affected by heat stress

Heat stress causes critical molecular dysfunction that affects productivity in chickens. Thus, the purpose of this study was to evaluate the effect of heat stress (HS) on the expression of select genes in the oxidation/antioxidation machinery in the liver of chickens. Chickens at 14 days of age were randomly assigned to two treatment groups and kept under either a constant normal temperature (25 °C) or high temperature (35 °C) in individual cages for 12 days. mRNA expression of Nrf2, oxidants NADPH(NOX): [NOX1, NOX2, NOX3, NOX4, NOX5 and DUOX2], and antioxidants [SOD1, CAT, GR, GPx1, NQO1] in the liver were analyzed at 1 and 12 days post-HS. We show that, HS changes the mRNA expression of oxidants thereby increasing cellular reactive oxygen species (ROS). Additionally, persistent HS up-regulates SOD which converts superoxides to hydrogen peroxide. We further demonstrated the dynamic relationship between catalase, GSH peroxidase (GPx) and NADPH under both acute and chronic heat stress. The pentose phosphate pathway could be important under HS since it generates NADPH which serves as a cofactor for GPx. Also, methionine, a precursor of cysteine has been shown to have reducing properties and thereby makes for an alternative fuel for redox processes. Genes in the ROS and antioxidant generation pathways may provide insight into nutritional intervention strategies, especially the use of methionine and/or cysteine when birds are suffering from heat stress.

Evaluation of Potential Mechanisms Controlling the Catalase Expression in Breast Cancer Cells

Development of cancer cell resistance against prooxidant drugs limits its potential clinical use. MCF-7 breast cancer cells chronically exposed to ascorbate/menadione became resistant (Resox cells) by increasing mainly catalase activity. Since catalase appears as an anticancer target, the elucidation of mechanisms regulating its expression is an important issue. In MCF-7 and Resox cells, karyotype analysis showed that chromosome 11 is not altered compared to healthy mammary epithelial cells. The genomic gain of catalase locus observed in MCF-7 and Resox cells cannot explain the differential catalase expression. Since ROS cause DNA lesions, the activation of DNA damage signaling pathways may influence catalase expression. However, none of the related proteins (i.e., p53, ChK) was activated in Resox cells compared to MCF-7. The c-abl kinase may lead to catalase protein degradation via posttranslational modifications, but neither ubiquitination nor phosphorylation of catalase was detected after catalase immunoprecipitation. Catalase mRNA levels did not decrease after actinomycin D treatment in both cell lines. DNMT inhibitor (5-aza-2′-deoxycytidine) increased catalase protein level in MCF-7 and its resistance to prooxidant drugs. In line with our previous report, chromatin remodeling appears as the main regulator of catalase expression in breast cancer after chronic exposure to an oxidative stress.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

Live or let die: Neuroprotective and anti-cancer effects of nutraceutical antioxidants

Diet sources are closely involved in the pathogenesis of diverse neuropsychiatric disorders and cancers, in addition to inherited factors. Currently, natural products or nutraceuticals (commonly called medical foods) are increasingly employed for adjunctive therapy of these patients. However, the potential molecular mechanisms of the nutrient efficacy remain elusive. In this review, we summarized the neuroprotective and anti-cancer mechanisms of nutraceuticals. It was concluded that the nutraceuticals exerted neuroprotection and suppressed tumor growth possibly through the differential modulations of redox homeostasis. In addition, the balance between reactive oxygen species (ROS) production and ROS elimination was manipulated by multiple molecular mechanisms, including cell signaling pathways, inflammation, transcriptional regulation and epigenetic modulation, which were involved in the therapeutic potential of nutraceutical antioxidants against neurological diseases and cancers. We specifically proposed that ROS scavenging was integral in the neuroprotective potential of nutraceuticals, while alternation of ROS level (either increase or decrease) or disruption of redox homeostasis (ROS addiction) constituted the anti-cancer property of these compounds. We also hypothesized that ROS-associated ferroptosis, a novel type of lipid ROS-dependent regulatory cell death, was likely to be a critical mechanism for the nutraceutical antioxidants. Targeting ferroptosis is advantageous to develop new nutraceuticals with more effective and lower adverse reactions for curing patients with neuropsychiatric diseases or carcinomas.

Oxidative DNA damage induces hypomethylation in a compromised base excision repair colorectal tumourigenesis

Background:

A compromised base excision repair (BER) promotes carcinogenesis by accumulating oxidative DNA-damaged products as observed in MUTYH-associated polyposis, a hereditary colorectal cancer syndrome marked by adenomas and cancers with an accumulation of 8-oxoguanine. Remarkably, DNA global demethylation has been shown to be mediated by BER, suggesting a relevant interplay with early colorectal tumourigenesis. To check this hypothesis, we investigated a cohort of 49 adenomas and 10 carcinomas, derived from 17 MUTYH-associated polyposis patients; as adenoma controls, we used a set of 36 familial adenomatous polyposis and 24 sporadic polyps.

Methods:

Samples were analysed for their mutational and epigenetic status, measured as global LINE-1 (long interspersed nuclear element) and gene-specific LINE-1 MET methylation by mass spectrometry and pyrosequencing.

Results:

MUTYH-associated polyposis adenomas were strikingly more hypomethylated than familial adenomatous and sporadic polyps for both DNA demethylation markers (P=0.032 and P=0.007 for LINE-1; P=0.004 and P<0.0001 for LINE-1 MET, respectively) with levels comparable to those of the carcinomas derived from the same patients. They also had mutations due mainly to KRAS/NRAS p.G12C, which was absent in the controls (P<0.0001 for both sets).

Conclusions:

Our results show that DNA demethylation, together with specific KRAS/NRAS mutations, drives the early steps of oxidative damage colorectal tumourigenesis.

Chromatin remodeling regulates catalase expression during cancer cells adaptation to chronic oxidative stress

Regulation of ROS metabolism plays a major role in cellular adaptation to oxidative stress in cancer cells, but the molecular mechanism that regulates catalase, a key antioxidant enzyme responsible for conversion of hydrogen peroxide to water and oxygen, remains to be elucidated. Therefore, we investigated the transcriptional regulatory mechanism controlling catalase expression in three human mammary cell lines: the normal mammary epithelial 250MK primary cells, the breast adenocarcinoma MCF-7 cells and an experimental model of MCF-7 cells resistant against oxidative stress resulting from chronic exposure to H₂O₂ (Resox), in which catalase was overexpressed. Here we identify a novel promoter region responsible for the regulation of catalase expression at -1518/-1226 locus and the key molecules that interact with this promoter and affect catalase transcription. We show that the AP-1 family member JunB and retinoic acid receptor alpha (RARα) mediate catalase transcriptional activation and repression, respectively, by controlling chromatin remodeling through a histone deacetylases-dependent mechanism. This regulatory mechanism plays an important role in redox adaptation to chronic exposure to H₂O₂ in breast cancer cells. Our study suggests that cancer adaptation to oxidative stress may be regulated by transcriptional factors through chromatin remodeling, and reveals a potential new mechanism to target cancer cells.

Regulation of catalase expression in healthy and cancerous cells

Catalase is an important antioxidant enzyme that dismutates hydrogen peroxide into water and molecular oxygen. The catalase gene has all the characteristics of a housekeeping gene (no TATA box, no initiator element sequence, high GC content in promoter) and a core promoter that is highly conserved among species. We demonstrate in this review that within this core promoter, the presence of DNA binding sites for transcription factors, such as NF-Y and Sp1, plays an essential role in the positive regulation of catalase expression. Additional transcription factors, such as FoxO3a, are also involved in this regulatory process. There is strong evidence that the protein Akt/PKB in the PI3K signaling pathway plays a major role in the expression of catalase by modulating the activity of FoxO3a. Over the past decade, other transcription factors (PPARγ, Oct-1, etc.), as well as genetic, epigenetic, and posttranscriptional processes, have emerged as crucial contributors to the regulation of catalase expression. Altered expression levels of catalase have been reported in cancer tissues compared to their normal counterparts. Deciphering the molecular mechanisms that regulate catalase expression could, therefore, be of crucial importance for the future development of pro-oxidant cancer chemotherapy.

Peroxisome biogenesis in mammalian cells: The impact of genes and environment

The initiation and progression of many human diseases are mediated by a complex interplay of genetic, epigenetic, and environmental factors. As all diseases begin with an imbalance at the cellular level, it is essential to understand how various types of molecular aberrations, metabolic changes, and environmental stressors function as switching points in essential communication networks. In recent years, peroxisomes have emerged as important intracellular hubs for redox-, lipid-, inflammatory-, and nucleic acid-mediated signaling pathways. In this review, we focus on how nature and nurture modulate peroxisome biogenesis and function in mammalian cells. First, we review emerging evidence that changes in peroxisome activity can be linked to the epigenetic regulation of cell function. Next, we outline how defects in peroxisome biogenesis may directly impact cellular pathways involved in the development of disease. In addition, we discuss how changes in the cellular microenvironment can modulate peroxisome biogenesis and function. Finally, given the importance of peroxisome function in multiple aspects of health, disease, and aging, we highlight the need for more research in this still understudied field.

Mechanisms of superoxide signaling in epigenetic processes: relation to aging and cancer

Superoxide is a precursor of many free radicals and reactive oxygen species (ROS) in biological systems. It has been shown that superoxide regulates major epigenetic processes of DNA methylation, histone methylation, and histone acetylation. We suggested that superoxide, being a radical anion and a strong nucleophile, could participate in DNA methylation and histone methylation and acetylation through mechanism of nucleophilic substitution and free radical abstraction. In nucleophilic reactions superoxide is able to neutralize positive charges of methyl donors S-adenosyl-L-methionine (SAM) and acetyl-coenzyme A (AcCoA) enhancing their nucleophilic capacity or to deprotonate cytosine. In the reversed free radical reactions of demethylation and deacetylation superoxide is formed catalytically by the (Tet) family of dioxygenates and converted into the iron form of hydroxyl radical with subsequent oxidation and final eradication of methyl substituents. Double role of superoxide in these epigenetic processes might be of importance for understanding of ROS effects under physiological and pathological conditions including cancer and aging.

Oxidative stress levels are correlated with P15 and P16 gene promoter methylation in myelodysplastic syndrome patients

Oxidative stress and abnormal DNA methylation have been implicated in some types of cancer, namely in myelodysplastic syndromes (MDS). Since both mechanisms are observed in MDS patients, we analyzed the correlation of intracellular levels of peroxides, superoxide anion, and glutathione (GSH), as well as ratios of peroxides/GSH and superoxide/GSH, with the methylation status of P15 and P16 gene promoters in bone marrow leukocytes from MDS patients. Compared to controls, these patients had lower GSH content, higher peroxide levels, peroxides/GSH and superoxide/GSH ratios, as well as higher methylation frequency of P15 and P16 gene promoters. Moreover, patients with methylated P15 gene had higher oxidative stress levels than patients without methylation (peroxides: 460 ± 42 MIF vs 229 ± 25 MIF, p = 0.001; superoxide: 383 ± 48 MIF vs 243 ± 17 MIF, p = 0.022; peroxides/GSH: 2.50 ± 0.08 vs 1.04 ± 0.34, p < 0.001; superoxide/GSH: 1.76 ± 0.21 vs 1.31 ± 0.10, p = 0.007). Patients with methylated P16 and at least one methylated gene had higher peroxide levels as well as peroxides/GSH ratio than patients without methylation. Interestingly, oxidative stress levels allow the discrimination of patients without methylation from ones with methylated P15, methylated P16, or at least one methylated (P15 or P16) promoter. Taken together, these findings support the hypothesis that oxidative stress is correlated with P15 and P16 hypermethylation.

Gallic acid induces necroptosis via TNF-α signaling pathway in activated hepatic stellate cells

Gallic acid (3, 4, 5-trihydroxybenzoic acid, GA), a natural phenolic acid widely found in gallnuts, tea leaves and various fruits, possesses several bioactivities against inflammation, oxidation, and carcinogenicity. The beneficial effect of GA on the reduction of animal hepatofibrosis has been indicated due to its antioxidative property. However, the cytotoxicity of GA autoxidation causing cell death has also been reported. Herein, we postulated that GA might target activated hepatic stellate cells (aHSCs), the cell type responsible for hepatofibrosis, to mitigate the process of fibrosis. The molecular cytotoxic mechanisms that GA exerted on aHSCs were then analyzed. The results indicated that GA elicited aHSC programmed cell death through TNF–α–mediated necroptosis. GA induced significant oxidative stress through the suppression of catalase activity and the depletion of glutathione (GSH). Elevated oxidative stress triggered the production of TNF–α facilitating the undergoing of necroptosis through the up-regulation of key necroptotic regulatory proteins TRADD and receptor-interacting protein 3 (RIP3), and the inactivation of caspase–8. Calmodulin and calpain–1 activation were engaged, which promoted subsequent lysosomal membrane permeabilization (LMP). The TNF–α antagonist (SPD–304) and the RIP1 inhibitor (necrostatin–1, Nec–1) confirmed GA-induced TNFR1–mediated necroptosis. The inhibition of RIP1 by Nec–1 diverted the cell death from necroptosis to apoptosis, as the activation of caspase 3 and the increase of cytochrome c. Collectively, this is the first report indicating that GA induces TNF signaling–triggered necroptosis in aHSCs, which may offer an alternative strategy for the amelioration of liver fibrosis.

Cell line-specific oxidative stress in cellular toxicity: A toxicogenomics-based comparison between liver and colon cell models

Imbalance between high reactive oxygen species formation and antioxidant capacity in the colon and liver has been linked to increased cancer risk. However, knowledge about possible cell line-specific oxidative stress-mechanisms is limited. To explore this further, gene expression data from a human liver and colon cell line (HepG2/Caco-2), both exposed to menadione and H2O2 at six time points (0.5-1-2-4-8 and 24h) were compared in association with cell cycle distribution. In total, 3164 unique- and 1827 common genes were identified between HepG2 and Caco-2 cells. Despite the higher number of unique genes, most oxidative stress-related genes such as CAT, OGG1, NRF2, NF-κB, GCLC, HMOX1 and GSR were differentially expressed in both cell lines. However, cell-specific regulation of genes such as KEAP1 and GCLM, or of the EMT pathway, which are of pathophysiological importance, indicates that oxidative stress induces different transcriptional effects and outcomes in the two selected cell lines. In addition, expression levels and/or -direction of common genes were often different in HepG2 and Caco-2 cells, and this led to very diverse downstream effects as confirmed by correlating pathways to cell cycle changes. Altogether, this work contributes to obtaining a better molecular understanding of cell line-specific toxicity upon exposure to oxidative stress-inducing compounds.

Epigenetic modifiers of islet function and mass

Type 2 diabetes (T2D) is associated with insulin resistance in target tissues including the β-cell, leading to significant β-cell loss and secretory dysfunction. T2D is also associated with aging, and the underlying mechanisms that increase susceptibility of an individual to develop the disease implicate epigenetics: interactions between susceptible loci and the environment. In this review, we discuss the effects of aging on β-cell function and adaptation, besides the significance of mitochondria in islet bioenergetics and epigenome. We highlight three important modulators of the islet epigenome, namely: metabolites, hormones, and the nutritional state. Unraveling the signaling pathways that regulate the islet epigenome during aging will help to better understand the development of disease progression and to design novel therapies for diabetes prevention.

Causes and Consequences of Age-Related Changes in DNA Methylation: A Role for ROS?

Recent genome-wide analysis of C-phosphate-G (CpG) sites has shown that the DNA methylome changes with increasing age, giving rise to genome-wide hypomethylation with site‑specific incidences of hypermethylation. This notion has received a lot of attention, as it potentially explains why aged organisms generally have a higher risk of age-related diseases. However, very little is known about the mechanisms that could cause the occurrence of these changes. Moreover, there does not appear to be a clear link between popular theories of aging and alterations in the methylome. Some of the most fruitful of these theories attribute an important role to reactive oxygen species, which seem to be responsible for an increase in oxidative damage to macromolecules, such as DNA, during the lifetime of an organism. In this review, the connection between changes in DNA methylation and these reactive oxygen species is discussed, as well as the effect of these changes on health. Deeper insights into the nature, causes and consequences of the aging methylome might provide a deeper understanding of the molecular mechanisms of aging and eventually contribute to the development of new diagnostic and therapeutic tools.

Catalase expression in MCF-7 breast cancer cells is mainly controlled by PI3K/Akt/mTor signaling pathway

Catalase is an antioxidant enzyme that catalyzes mainly the transformation of hydrogen peroxide into water and oxygen. Although catalase is frequently down-regulated in tumors the underlying mechanism remains unclear. Few transcription factors have been reported to directly bind the human catalase promoter. Among them FoxO3a has been proposed as a positive regulator of catalase expression. Therefore, we decided to study the role of the transcription factor FoxO3a and the phosphatidylinositol-3 kinase (PI3K) signaling pathway, which regulates FoxO3a, in the expression of catalase. To this end, we developed an experimental model of mammary breast MCF-7 cancer cells that acquire resistance to oxidative stress, the so-called Resox cells, in which catalase is overexpressed as compared with MCF-7 parental cell line. In Resox cells, Akt expression is decreased but its phosphorylation is enhanced when compared with MCF-7 cells. A similar profile is observed for FoxO3a, with less total protein but more phosphorylated FoxO3a in Resox cells, correlating with its higher Akt activity. The modulation of FoxO3a expression by knockdown and overexpression strategies did not affect catalase expression, neither in MCF-7 nor in Resox cells. Inhibition of PI3K and mTOR by LY295002 and rapamycin, respectively, decreases the phosphorylation of downstream targets (i.e. GSK3β and p70S6K) and leads to an increase of catalase expression only in MCF-7 but not in Resox cells. In conclusion, FoxO3a does not appear to play a critical role in the regulation of catalase expression in both cancer cells. Only MCF-7 cells are sensitive and dependent on PI3K/Akt/mTOR signaling.

Human catalase, its polymorphisms, regulation and changes of its activity in different diseases

Catalase (CAT) is a well-studied enzyme that plays an important role in protecting cells against the toxic effects of hydrogen peroxide. In human, it has been implicated in different physiological and pathological conditions. This review summarizes the information available on the function and role of CAT polymorphisms in pathogenesis of various pathophysiological states as well as on the regulation of CAT gene expression. Numerous studies have described the CAT polymorphisms and their link with various diseases. Changes in the CAT levels were reported in many different diseases and polymorphisms in the CAT gene were shown to be associated with different pathophysiological states, e.g. hypertension, diabetes mellitus, insulin resistance, dyslipidaemia, asthma, bone metabolism or vitiligo. Regulation of the CAT gene expression plays an important role in the levels of CAT. The catalase gene expression is regulated by various mechanisms involving e.g. peroxisome proliferator-activated receptor γ (PPARγ), tumour necrosis factor α (TNF-α), p53 protein and hypermethylation of CpG islands in the catalase promoter. Transcription of the CAT gene is mainly influenced by the -262 C/T and -844 A/G polymorphisms. A common polymorphism -262 C/T in the promoter region has been found to be associated with altered CAT activities. Apart from genetic factors, the activities of CAT may be affected by age, seasonal variations, physical activity, or a number of chemical compounds. Future investigations are necessary to elucidate the role of CAT in pathogenesis of oxidative stress-related diseases.

Marine teleost ortholog of catalase from rock bream (Oplegnathus fasciatus): molecular perspectives from genomic organization to enzymatic behavior with respect to its potent antioxidant properties

Catalases are well known antioxidant enzymes that can mainly dismutate hydrogen peroxide into water and oxygen in order to prevent oxidative stress. The complete genomic DNA (gDNA) sequence of the catalase gene from rock bream (Oplegnathus fasciatus) was identified from our custom-constructed BAC genomic DNA library and designated as RbCat. RbCat consists of 13 exons, separated by 12 introns, within a 13,722-bp gDNA sequence. The complete cDNA sequence (3303 bp) of RbCat is comprised of a 1581-bp coding region, encoding a peptide of 527 amino acids (aa) in length, with a predicted molecular mass of 60 kDa and a theoretical isoelectric point of 8.34. The anticipated promoter region of RbCat contains several transcription factor-binding sites, including sites that bind with immune- and antioxidant-responsive signaling molecules, suggesting its substantial transcriptional regulation. RbCat resembles the typical catalase family signature, i.e., it is composed of the catalase proximal active site motif along with a catalase proximal heme-ligand signature motif and shares great homology with its fish counterparts. According to multiple sequence alignment, functionally important amino acids present in RbCat were thoroughly conserved among its vertebrate counterparts. Phylogenetic analysis revealed that RbCat evolved from a vertebrate origin, and further positioned it in the fish clade. Recombinant RbCat had noticeable peroxidase activity against its substrate, hydrogen peroxide, in a dose-dependent manner. However, it demonstrated substantial peroxidase activity within a broad range of temperatures and pH values. Constitutive RbCat mRNA expression of different magnitudes was detected in a tissue-specific manner, suggesting its diverse role in physiology with respect to the tissue type. Moreover, immune challenge experiments using Edwardsiella tarda and rock bream iridovirus (RBIV) as live pathogens and polyinosinic:polycytidylic acid and lipopolysaccharide as mitogens revealed that the transcription of RbCat can be modulated by immune stimulation. Collectively, the results obtained in this study suggest that RbCat can function as a potent antioxidant enzyme in rock bream and may play a role in post-immune responses with respect to its peroxidase activity.

Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD)

Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.

Global DNA methylation screening of liver in piperonyl butoxide-treated mice in a two-stage hepatocarcinogenesis model

Disruptive epigenetic gene control has been shown to be involved in carcinogenesis. To identify key molecules in piperonyl butoxide (PBO)-induced hepatocarcinogenesis, we searched hypermethylated genes using CpG island (CGI) microarrays in non-neoplastic liver cells as a source of proliferative lesions at 25 weeks after tumor promotion with PBO using mice. We further performed methylation-specific polymerase chain reaction (PCR), real-time reverse transcription PCR, and immunohistochemical analysis in PBO-promoted liver tissues. Ebp4.1, Wdr6 and Cmtm6 increased methylation levels in the promoter region by PBO promotion, although Cmtm6 levels were statistically non-significant. These results suggest that PBO promotion may cause altered epigenetic gene regulation in non-neoplastic liver cells surrounding proliferative lesions to allow the facilitation of hepatocarcinogenesis. Both Wdr6 and Cmtm6 showed decreased expression in non-neoplastic liver cells in contrast to positive immunoreactivity in the majority of proliferative lesions produced by PBO promotion. These results suggest that both Wdr6 and Cmtm6 were spared from epigenetic gene modification in proliferative lesions by PBO promotion in contrast to the hypermethylation-mediated downregulation in surrounding liver cells. Considering the effective detection of proliferative lesions, these molecules could be used as detection markers of hepatocellular proliferative lesions and played an important role in hepatocarcinogenesis.

Balancing reactive oxygen species in the epigenome: NADPH oxidases as target and perpetrator

SIGNIFICANCE

NADPH oxidases are important sources for regulated generation of reactive oxygen species (ROS). The main ROS produced are superoxide and hydrogen peroxide, both of which are redox signaling molecules in the context of various cellular functions. Redox imbalance due to excessive or insufficient ROS is a hallmark of pathophysiological aspects, including cancer development and progression.

RECENT ADVANCES

Epigenetic silencing of NADPH oxidases by hypermethylation of their promoter region or of the genes required for their assembly and activity occurs in diseases, such as lung cancer, and may represent an early stage of neoplastic transformation.

CRITICAL ISSUES

Loss of ROS-mediated signaling by epigenetic silencing may promote tumorigenesis. Conversely, increased oxidative stress caused by oncogene-induced overexpression of NADPH oxidases may also drive epigenetic instability. Thus, the cellular redox balance is likely vital in carcinogenesis.

FUTURE DIRECTIONS

NADPH oxidases may serve as prognostic tumor biomarker, especially when their individual expression is confined to accessible tissues, such as mucosal epithelia or blood. Further validation of NADPH oxidase/dual oxidase enzymes as candidate markers will require well controlled, large-scale clinical data sets. This review is focused on NADPH oxidases as targets of epigenetic changes in cancer and on the emerging role of ROS as inducers of epigenetic changes.

Role of the hypothalamic-pituitary-adrenal axis in developmental programming of health and disease

Adverse environments during the fetal and neonatal development period may permanently program physiology and metabolism, and lead to increased risk of diseases in later life. Programming of the hypothalamic-pituitary-adrenal (HPA) axis is one of the key mechanisms that contribute to altered metabolism and response to stress. Programming of the HPA axis often involves epigenetic modification of the glucocorticoid receptor (GR) gene promoter, which influences tissue-specific GR expression patterns and response to stimuli. This review summarizes the current state of research on the HPA axis and programming of health and disease in the adult, focusing on the epigenetic regulation of GR gene expression patterns in response to fetal and neonatal stress. Aberrant GR gene expression patterns in the developing brain may have a significant negative impact on protection of the immature brain against hypoxic-ischemic encephalopathy in the critical period of development during and immediately after birth.

Epididymis response partly compensates for spermatozoa oxidative defects in snGPx4 and GPx5 double mutant mice

We report here that spermatozoa of mice lacking both the sperm nucleaus glutathione peroxidase 4 (snGPx4) and the epididymal glutathione peroxidase 5 (GPx5) activities display sperm nucleus structural abnormalities including delayed and defective nuclear compaction, nuclear instability and DNA damage. We show that to counteract the GPx activity losses, the epididymis of the double KO animals mounted an antioxydant response resulting in a strong increase in the global H₂O₂-scavenger activity especially in the cauda epididymis. Quantitative RT-PCR data show that together with the up-regulation of epididymal scavengers (of the thioredoxin/peroxiredoxin system as well as glutathione-S-transferases) the epididymis of double mutant animals increased the expression of several disulfide isomerases in an attempt to recover normal disulfide-bridging activity. Despite these compensatory mechanisms cauda-stored spermatozoa of double mutant animals show high levels of DNA oxidation, increased fragmentation and greater susceptibility to nuclear decondensation. Nevertheless, the enzymatic epididymal salvage response is sufficient to maintain full fertility of double KO males whatever their age, crossed with young WT female mice.