Glutathione peroxidases

The versatile utility of cysteine as a target for cancer treatment

Owing to its unique nucleophilicity, cysteine is an attractive sulfhydryl-containing proteinogenic amino acid. It is also utilized in various metabolic pathways and redox homeostasis, as it is used for the component of major endogenous antioxidant glutathione and the generation of sulfur-containing biomolecules. In addition, cysteine is the most nucleophilic amino acid of proteins and can react with endogenous or exogenous electrophiles which can result in the formation of covalent bonds, which can alter the cellular states and functions. Moreover, post-translational modifications of cysteines trigger redox signaling and affect the three-dimensional protein structure. Protein phosphorylation mediated by kinases and phosphatases play a key role in cellular signaling that regulates many physiological and pathological processes, and consequently, the modification of cysteine regulates its activities. The modification of cysteine residues in proteins is critically important for the design of novel types of pharmacological agents. Therefore, in cancer metabolism and cancer cell survival, cysteine plays an essential role in redox regulation of cellular status and protein function. This review summarizes the diverse regulatory mechanisms of cysteine bound to or free from proteins in cancer. Furthermore, it can enhance the comprehension of the role of cysteine in tumor biology which can help in the development of novel effective cancer therapies.

Biological Functions of Selenoprotein Glutathione Peroxidases (GPXs) and their Expression in Osteoarthritis

Purpose

In order to further study the biological functions of glutathione peroxidases (GPXs) and their expression level in patients with osteoarthritis (OA), we fully explored the potential relationship between GPXs and OA. This will provide new ideas for basic biological studies and therapeutic strategies for OA patients.

Patients and Methods

In this study, bioinformatics techniques were used to explore the biological functions of five GPXs. The core genes related to the biological functions of GPXs were identified by constructing a protein-protein interaction network (PPI). In addition, we utilized microarray data in public databases to analyze the expression levels of GPXs in OA patients and healthy controls. Finally, we used quantitative real-time polymerase chain reaction (qRT-PCR) to detect the expression of GPXs in OA patients and controls to validate our bioinformatic analysis results.

Results

Enrichment analysis showed GPXs were mainly enriched in the glutathione metabolic pathway and participate in the biological process of oxidative stress response, and further play an antioxidant role. The PPI network indicated that superoxide dismutase 1 (SOD1), superoxide dismutase 2(SOD2) and catalase (CAT) were the core proteins of this network. GPX1 was regulated by the greatest number of miRNAs. Experiments showed that the expression of GPX1 was elevated in OA patients compared with controls.

Conclusion

GPXs play an important antioxidant role in oxidative stress response. The expression of GPX1 was elevated in peripheral blood mononuclear cells (PBMCs) of OA patients. The changes of GPXs in OA patients may regulate the level of oxidative stress, which may influence synovial lesions and chondrocyte apoptosis.

Prospects for Anti-Tumor Mechanism and Potential Clinical Application Based on Glutathione Peroxidase 4 Mediated Ferroptosis

Ferroptosis, characterized by excessive iron accumulation and lipid peroxidation, is a novel form of iron-dependent cell death, which is morphologically, genetically, and biochemically distinct from other known cell death types, such as apoptosis, necrosis, and autophagy. Emerging evidence shows that glutathione peroxidase 4 (GPX4), a critical core regulator of ferroptosis, plays an essential role in protecting cells from ferroptosis by removing the product of iron-dependent lipid peroxidation. The fast-growing studies on ferroptosis in cancer have boosted a perspective on its use in cancer therapeutics. In addition, significant progress has been made in researching and developing tumor therapeutic drugs targeting GPX4 based on ferroptosis, especially in acquired drug resistance. Selenium modulates GPX4-mediated ferroptosis, and its existing form, selenocysteine (Sec), is the active center of GPX4. This review explored the structure and function of GPX4, with the overarching goal of revealing its mechanism and potential application in tumor therapy through regulating ferroptosis. A deeper understanding of the mechanism and application of GPX4-mediated ferroptosis in cancer therapy will provide new strategies for the research and development of antitumor drugs.

Review: Advances in the Accuracy and Traceability of Metalloprotein Measurements Using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

Advances in inductively coupled plasma mass spectrometry and the methods used to prepare isotopically enriched standards, allow for the high accuracy measurement of metalloproteins by isotope dilution mass spectrometry. This technique has now reached a level of maturity whereby a step change in the accuracy, precision, and traceability of, in particular, clinical, and biomedical measurements is achievable. Current clinical measurements, which require low limits of detection in the presence of complex sample matrices, use indirect methods based on immunochemistry for the study of human disease. However, this approach suffers from poor traceability, requiring comparisons based on provision of matrix-based reference materials, used as analytical standards. This leads to difficulty when changes in the reference material are required, often resulting in a lack of interlaboratory and temporal comparability in clinical results and reference ranges. In this review, we focus on the most important metalloproteins for clinical studies, to illustrate how the attributes of chromatography coupled to inorganic mass spectrometry can be used for the direct measurement of metalloproteins such as hemoglobin, transferrin, and ceruloplasmin. By using this approach, we hope to demonstrate how isotope dilution analysis can be used as a reference method to improve traceability and underpin clinical, biomedical, and other biological measurements.

"Multiomics" Analyses Combined with Systems Pharmacology Reveal the Renoprotection of Mangiferin Monosodium Salt in Rats with Diabetic Nephropathy: Focus on Improvements in Renal Ferroptosis, Renal Inflammation, and Podocyte Insulin Resistance

We explored the protection of mangiferin monosodium salt (MGM) on kidney injury in rats with streptozotocin (STZ)-induced diabetic nephropathy (DN) by "multiomics" analysis combined with systems pharmacology, with a specific focus on ferroptosis, inflammation, and podocyte insulin resistance (IR) signaling events in kidneys. MGM treatment afforded renoprotective effects on rats with STZ-induced DN by alleviating systemic IR-induced renal inflammation and podocyte IR. These mechanisms were correlated mainly with the MGM treatment-induced inhibition of the mitogen-activated protein kinase/nuclear factor-kappa B axis and activation of the phosphorylated insulin receptor substrate 1(Tyr608)/phosphorylated phosphatidylinositol 3-kinase/phosphorylated protein kinase B axis in the kidneys of DN rats. MGM had an ameliorative function in renal ferroptosis in rats with STZ-induced DN by upregulating mevalonate-mediated antioxidant capacities (glutathione peroxidase 4 and ferroptosis suppressor protein 1/coenzyme Q10 axis) and weakening acyl-CoA synthetase long-chain family member 4-mediated proferroptotic generation of lipid drivers in kidneys. MGM may be a promising alternative strategy for the treatment of DN.

Oxidants and Antioxidants in the Redox Biochemistry of Human Red Blood Cells

Red blood cells (RBCs) are exposed to both external and internal sources of oxidants that challenge their integrity and compromise their physiological function and supply of oxygen to tissues. Autoxidation of oxyhemoglobin is the main source of endogenous RBC oxidant production, yielding superoxide radical and then hydrogen peroxide. In addition, potent oxidants from other blood cells and the surrounding endothelium can reach the RBCs. Abundant and efficient enzymatic systems and low molecular weight antioxidants prevent most of the damage to the RBCs and also position the RBCs as a sink of vascular oxidants that allow the body to maintain a healthy circulatory system. Among the antioxidant enzymes, the thiol-dependent peroxidase peroxiredoxin 2, highly abundant in RBCs, is essential to keep the redox balance. A great part of the RBC antioxidant activity is supported by an active glucose metabolism that provides reducing power in the form of NADPH via the pentose phosphate pathway. There are several RBC defects and situations that generate oxidative stress conditions where the defense mechanisms are overwhelmed, and these include glucose-6-phosphate dehydrogenase deficiencies (favism), hemoglobinopathies like sickle cell disease and thalassemia, as well as packed RBCs for transfusion that suffer from storage lesions. These oxidative stress-associated pathologies of the RBCs underline the relevance of redox balance in these anucleated cells that lack a mechanism of DNA-inducible antioxidant response and rely on a complex and robust network of antioxidant systems.

A near-infrared GPX4 fluorescent probe for non-small cell lung cancer imaging

Glutathione peroxidase 4 (GPX4) is overexpressed in non-small cell lung cancer (H1299) cells. In this work, a near-infrared fluorescent probe ENBO-ML210 was developed. In vitro and in vivo imaging results showed that ENBO-ML210 could target and visualize GPX4 in H1299 cells, exhibiting potential for the diagnosis of non-small lung cancer.

Side-by-side comparison of recombinant human glutathione peroxidases identifies overlapping substrate specificities for soluble hydroperoxides

Five out of eight human glutathione peroxidases (GPXs) are selenoproteins, representing proteins that contain selenium as part of the amino acid selenocysteine. The GPXs are important for reducing hydroperoxides in a glutathione-consuming manner and thus regulate cellular redox homeostasis. GPX1, GPX2, and GPX4 represent the three main cytosolic GPXs, but they differ in their expression patterns with GPX1 and GPX4 being expressed ubiquitously, whereas GPX2 is mainly expressed in epithelial cells. GPX1 and GPX2 have been described to reduce soluble hydroperoxides, while GPX4 reduces complex lipid hydroperoxides, thus protecting cells from lipid peroxidation and ferroptosis. But most of these data are derived from cells that are devoid of one of the isoforms and thus, compensation or other cellular effects might affect the conclusions. So far, the use of isolated recombinant human selenoprotein glutathione peroxidases in pure enzyme assays has not been employed to study their substrate specificities side by side. Using recombinant GPX1, GPX2, and GPX4 produced in E. coli we here assessed their GPX activities by a NADPH-consuming glutathione reductase-coupled assay with 17 different peroxides (all at 50 μM) as substrates. GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide. In contrast, small soluble hydroperoxides such as H₂O₂, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms, but with approximately 10-fold higher efficiency for GPX1 in comparison to GPX2 and GPX4. Also, several fatty acid-derived hydroperoxides were reduced by all three isoforms and again GPX1 had the highest activity. Interestingly, the stereoisomerism of the fatty acid-derived hydroperoxides clearly affected the activity of the GPX enzymes. Overall, distinct substrate specificity is obvious for GPX4, but not so when comparing GPX1 and GPX2. Clearly GPX1 was the most potent isoform of the three GPXs in terms of turnover in reduction of soluble and fatty-acid derived hydroperoxides.

Glutathione: Pharmacological aspects and implications for clinical use in non-alcoholic fatty liver disease

Glutathione is a tripeptide synthesized at cytosolic level, that exists in cells in a reduced form (thiol-reduced-GSH-) and in an oxidized form (disulfide-oxidized). The antioxidant function of GSH has led to speculation about its therapeutic role in numerous chronic diseases characterized by altered redox balance and reduced GSH levels, including, for instance, neurodegenerative disorders, cancer, and chronic liver diseases. Among these latter, non-alcoholic fatty liver disease (NAFLD), characterized by lipid accumulation in hepatocytes, in the absence of alcohol abuse or other steatogenic factors, is one of the most prevalent. The umbrella term NAFLD includes the pure liver fat accumulation, the so-called hepatic steatosis or non-alcoholic fatty liver, and the progressive form with inflammation, also known as non-alcoholic steatohepatitis, which is related to the increase in oxidative stress and reactive oxygen species, eventually leading to liver fibrosis. Although the pathogenetic role of oxidative stress in these diseases is well established, there is still limited evidence on the therapeutic role of GSH in such conditions. Hence, the aim of this review is to depict the current molecular and pharmacological knowledge on glutathione, focusing on the available studies related to its therapeutic activity in NAFLD.

Targeting critical pathways in ferroptosis and enhancing antitumor therapy of Platinum drugs for colorectal cancer

Colorectal cancer (CRC) can be resistant to platinum drugs, possibly through ferroptosis suppression, albeit the need for further work to completely understand this mechanism. This work aimed to sum up current findings pertaining to oxaliplatin resistance (OR) or resistance to ascertain the potential of ferroptosis to regulate oxaliplatin effects. In this review, tumor development relating to iron homeostasis, which includes levels of iron that ascertain cells' sensitivity to ferroptosis, oxidative stress, or lipid peroxidation in colorectal tumor cells that are connected with ferroptosis initiation, especially the role of c-Myc/NRF2 signaling in regulating iron homeostasis, coupled with NRF2/GPX4-mediated ferroptosis are discussed. Importantly, ferroptosis plays a key role in OR and ferroptotic induction may substantially reverse OR in CRC cells, which in turn could inhibit the imbalance of intracellular redox induced by oxaliplatin and ferroptosis, as well as cause chemotherapeutic resistance in CRC. Furthermore, fundamental research of small molecules, ferroptosis inducers, GPX4 inhibitors, or natural products for OR coupled with their clinical applications in CRC have also been summarized. Also, potential molecular targets and mechanisms of small molecules or drugs are discussed as well. Suggestively, OR of CRC cells could significantly be reversed by ferroptosis induction, wherein this result is discussed in the current review. Prospectively, the existing literature discussed in this review will provide a solid foundation for scientists to research the potential use of combined anticancer drugs which can overcome OR via targeting various mechanisms of ferroptosis. Especially, promising therapeutic strategies, challenges ,and opportunities for CRC therapy will be discussed.

Destroying glutathione peroxidase improves the oxidative stress resistance and pathogenicity of Listeria monocytogenes

Introduction

Glutathione peroxidase is abundant in eukaryotes as an important antioxidant enzyme. However, prokaryotic glutathione peroxidase has not been thoroughly studied. Listeria monocytogenes is a facultative intracellular pathogen that is capable of causing listeriosis in animals as well as humans. Despite the fact that L. monocytogenes encodes a putative glutathione peroxidase, GSH-Px (encoded by lmo0983)), the functions of the enzyme are still unknown. Here we revealed the unusual roles of L. monocytogenes GSH-Px in bacterial antioxidants and pathogenicity.

Methods

L. monocytogenes Lm850658 was taken as the parental strain to construct the gsh-px deletion strain and related complement strain. The effect of the gsh-px gene on the resistance of L. monocytogenes to oxidative stress was determined by measuring the concentrations of glutathione and assaying the stress survival rates under different oxidative conditions. In addition, the pathogenicity of L. monocytogenes was determined by cellular adhesion and invasion assays and mice virulence tests, and the expression of virulence factors was determined by Western blot.

Results

Deficiency of GSH-Px not only increased glutathione concentrations in L. monocytogenes but also enhanced its resistance to oxidative stress when exposed to copper and iron ions. In addition, the absence of gsh-px significantly improved the adhesion and invasion efficiency of L. monocytogenes to Caco-2 cells. More importantly, L. monocytogenes lacking GSH-Px could colonize and proliferate more efficiently in mice livers and spleens, enhancing the pathogenicity of L. monocytogenes by increasing the expression of virulence factors like InlA, InlB, and LLO.

Discussion

Taken together, we confirmed that GSH-Px of L. monocytogenes has a counter-intuitive effect on the antioxidant capacity and pathogenicity.

Silencing lncRNA HCG18 regulates GPX4-inhibited ferroptosis by adsorbing miR-450b-5p to avert sorafenib resistance in hepatocellular carcinoma

Ferroptosis is potential to relieve drug resistance in hepatocellular carcinoma (HCC). Glutathione peroxidase 4 (GPX4) is a critical modulator of ferroptosis. This study discussed the mechanism of GPX4-inhibited ferroptosis in sorafenib resistance in HCC. HCG18 in HCC cells was detected. Sorafenib resistant (SR) cell line Huh7-SR cells were treated with sorafenib (0, 2.5, 5, 7.5, 10 μM). After silencing HCG18 in Huh7-SR cells, cell activity, proliferation and apoptosis were detected. The levels of iron, the concentration of MDA, GSH and lipid reactive oxygen species (ROS) were measured to evaluate the ferroptosis. The downstream mechanism of HCG18 was predicted and verified. Huh7-SR cells were infected with lentivirus sh-HCG18 to establish xenograft tumor model. HCG18 was elevated in HCC cells and associated with sorafenib resistance. Silencing HCG18 inhibited cell proliferation, promoted apoptosis, and impaired sorafenib resistance. Ferroptosis was inhibited in Huh7-SR cells, while silencing HCG18 inhibited sorafenib resistance by promoting ferroptosis. GPX4 overexpression averted the promotion of sh-HCG18 on ferroptosis, thereby reducing sorafenib resistance. HCG18 sponged miR-450b-5p to regulate GPX4. Collectively, Silencing HCG18 inhibits GPX4 by binding to miR-450b-5p, promotes GPX4-inhibited ferroptosis, and averts sorafenib resistance in HCC.

Research progress of glutathione peroxidase family (GPX) in redoxidation

Maintaining the balance of a cell's redox function is key to determining cell fate. In the critical redox system of mammalian cells, glutathione peroxidase (GPX) is the most prominent family of proteins with a multifaceted function that affects almost all cellular processes. A total of eight members of the GPX family are currently found, namely GPX1-GPX8. They have long been used as antioxidant enzymes to play an important role in combating oxidative stress and maintaining redox balance. However, each member of the GPX family has a different mechanism of action and site of action in maintaining redox balance. GPX1-4 and GPX6 use selenocysteine as the active center to catalyze the reduction of H₂O₂ or organic hydroperoxides to water or corresponding alcohols, thereby reducing their toxicity and maintaining redox balance. In addition to reducing H₂O₂ and small molecule hydroperoxides, GPX4 is also capable of reducing complex lipid compounds. It is the only enzyme in the GPX family that directly reduces and destroys lipid hydroperoxides. The active sites of GPX5 and GPX7-GPX8 do not contain selenium cysteine (Secys), but instead, have cysteine residues (Cys) as their active sites. GPX5 is mainly expressed in epididymal tissue and plays a role in protecting sperm from oxidative stress. Both enzymes, GPX7 and GPX8, are located in the endoplasmic reticulum and are necessary enzymes involved in the oxidative folding of endoplasmic reticulum proteins, and GPX8 also plays an important role in the regulation of Ca²⁺ in the endoplasmic reticulum. With an in-depth understanding of the role of the GPX family members in health and disease development, redox balance has become the functional core of GPX family, in order to further clarify the expression and regulatory mechanism of each member in the redox process, we reviewed GPX family members separately.

Role of Ferroptosis in Stroke

Stroke is a common and serious nervous system disease caused by the rupture or blockage of the cardiovascular system. It causes millions of deaths and disabilities every year, which is a huge burden on humanity. It may be induced by thrombosis, hypertension, hyperlipidemia, hyperglycemia, smoking, advanced age and so on. According to different causes, stroke can be generally divided into hemorrhagic stroke and ischemic stroke, whose pathogenesis and treatment are quite different. Ferroptosis is a new type of cell death first defined in 2012, which is characterized by non-apoptotic, iron-dependent, and over-accumulated lipid peroxides. Excess lipid reactive oxygen species produced during ferroptosis eventually leads to oxidative cell death. Ferroptosis has been shown to occur and play an important role in tumors, neurological diseases, kidney injury, and ischemia-reperfusion injury. Ferroptosis is also closely related to the pathogenesis of stroke. Moreover, scientists have successfully intervened in the process of stroke in animal models by regulating ferroptosis, indicating that ferroptosis is a new potential target for the treatment of stroke. This paper systematically summarizes the involvement and role of ferroptosis in the pathogenesis of stroke and predicts the potential of ferroptosis in the treatment of stroke. Ferroptosis in stroke. Stroke induces iron overload and lipid metabolism disorders. Elevated iron catalyzes lipid peroxidation and eventually triggers ferroptosis. Conversely, the GSH/GPX4 pathway, as well as CoQ10, Fer-1, and Lip-1, inhibits lipid peroxidation and, thus, alleviates ferroptosis. GSH glutathione; GPX4 glutathione peroxidase 4; CoQ10 coenzyme Q10; Lip-1 liproxstatin-1; Fer-1 ferostatin-1.

The complex role of inflammation and gliotransmitters in Parkinson's disease

Our understanding of the role of innate and adaptive immune cell function in brain health and how it goes awry during aging and neurodegenerative diseases is still in its infancy. Inflammation and immunological dysfunction are common components of Parkinson's disease (PD), both in terms of motor and non-motor components of PD. In recent decades, the antiquated notion that the central nervous system (CNS) in disease states is an immune-privileged organ, has been debunked. The immune landscape in the CNS influences peripheral systems, and peripheral immunological changes can alter the CNS in health and disease. Identifying immune and inflammatory pathways that compromise neuronal health and survival is critical in designing innovative and effective strategies to limit their untoward effects on neuronal health.

Modeling type 2 diabetes in rats by administering tacrolimus

The prevalence of diabetes is rapidly increasing. The current number of diagnosed cases is ~422 million, expected to reach ~640 million by 2040. Type 2 diabetes, which constitutes ~95% of the cases, is characterized by insulin resistance and a progressive loss of β-cell function. Despite intense research efforts, no treatments are yet able to cure the disease or halt its progression. Since all existing animal models of type 2 diabetes have serious drawbacks, one is needed that represents the complete pathogenesis, is low cost and non-obese, and can be developed relatively quickly. The aim of this study was to evaluate a low-cost, non-obese model of type 2 diabetes engendered by administering a daily high dose of tacrolimus (an immunosuppressant) to Wistar rats for 4 weeks. The biochemical and antioxidant markers were measured at basal and after the 4-week tacrolimus treatment. At week 4, the values of these parameters closely resembled those observed in human type 2 diabetes, including fasting blood glucose at 141.5 mg/dL, blood glucose greater than 200 mg/dL at 120 min of the glucose tolerance test, blood glucose at varied levels in the insulin tolerance test, and elevated levels of cholesterol and triglyceride. The tacrolimus treatment produced hypoinsulinemia and sustained hyperglycemia, probably explained by the alteration found in pancreatic β-cell function and morphology. This model should certainly be instrumental for evaluating possible type 2 diabetes treatments, and for designing new immunosuppressants that do not cause pancreatic damage, type 2 diabetes, or new-onset diabetes after transplantation (NODAT).

Ferroptosis As a Mechanism for Health Effects of Essential Trace Elements and Potentially Toxic Trace Elements

Ferroptosis is a unique form of programmed cell death driven by iron-dependent phospholipid peroxidation that was proposed in recent years. It plays an important role in processes of various trace element-related diseases and is regulated by redox homeostasis and various cellular metabolic pathways (iron, amino acids, lipids, sugars), as well as disease-related signaling pathways. Some limited pioneering studies have demonstrated ferroptosis as a mechanism for the health effects of essential trace elements and potentially toxic trace elements, with crosstalk among them. The aim of this review is to bring together research articles and identify key direct and indirect evidence regarding essential trace elements (iron, selenium, zinc, copper, chromium, manganese) and potentially toxic trace elements (arsenic, aluminum, mercury) and their possible roles in ferroptosis. Our review may help determine future research priorities and opportunities.

Glutathione and Its Metabolic Enzymes in Gliomal Tumor Tissue and the Peritumoral Zone at Different Degrees of Anaplasia

This research was aimed at investigating the features of free radical activity and the parameters of glutathione metabolism in tumor tissues and the peritumoral zone at different degrees of glial tumor anaplasia. We analyzed postoperative material from 20 patients with gliomas of different degrees of anaplasia. The greatest differences compared to adjacent noncancerous tissues were found in the tumor tissue: an increased amount of glutathione and glutathione-related enzymes at Grades I and II, and a decrease of these parameters at Grades III and IV. For the peritumoral zone of Grades I and II, the indices changed in different directions, while for Grades III and IV, they occurred synchronously with the tumor tissue changes. For Low Grade and High Grade gliomas, opposite trends were revealed regarding changes in the level of glutathione and the enzymes involved in its metabolism and in the free radical activity in the peritumoral zone. The content of glutathione and the enzymes involved in its metabolism decreased with the increasing degree of glioma anaplasia. In contrast, free radical activity increased. The glutathione system is an active participant in the antioxidant defense of the body and can be used to characterize the cell condition of gliomas at different stages of tumor development.

Prospecting for candidate molecules from Conus virgo toxins to develop new biopharmaceuticals

Background

A combination of pharmacological and biomedical assays was applied in this study to examine the bioactivity of Conus virgo crude venom in order to determine the potential pharmacological benefit of this venom, and its in vivo mechanism of action.

Methods

Two doses (1/5 and 1/10 of LC₅₀, 9.14 and 4.57 mg/kg) of the venom were used in pharmacological assays (central and peripheral analgesic, anti-inflammatory and antipyretic), while 1/2 of LC₅₀ (22.85 mg/kg) was used in cytotoxic assays on experimental animals at different time intervals, and then compared with control and reference drug groups.

Results

The tail immersion time was significantly increased in venom-treated mice compared with the control group. Also, a significant reduction in writhing movement was recorded after injection of both venom doses compared with the control group. In addition, only the high venom concentration has a mild anti-inflammatory effect at the late inflammation stage. The induced pyrexia was also decreased significantly after treatment with both venom doses. On the other hand, significant increases were observed in lipid peroxidation (after 4 hours) and reduced glutathione contents and glutathione peroxidase activity, while contents of lipid peroxidation and nitric oxide (after 24 hours) and catalase activity were depleted significantly after venom administration.

Conclusion

These results indicated that the crude venom of Conus virgo probably contain bioactive components that have pharmacological activities with low cytotoxic effects. Therefore, it may comprise a potential lead compound for the development of drugs that would control pain and pyrexia.

The Role of rs713041 Glutathione Peroxidase 4 (GPX4) Single Nucleotide Polymorphism on Disease Susceptibility in Humans: A Systematic Review and Meta-Analysis

Aim: The single-nucleotide polymorphism (SNP) rs713041, located in the regulatory region, is required to incorporate selenium into the selenoprotein glutathione peroxidase 4 (GPX4) and has been found to have functional consequences. This systematic review aimed to conduct a meta-analysis to determine whether there is an association between GPX4 (rs713041) SNP and the risk of diseases in humans and its correlation with selenium status. Material and methods: A systematic search for English-language manuscripts published between January 1990 and November 2022 was carried out using six databases: CINAHL, Cochrane, Medline, PubMed, Scopus and Web of Science. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to assess a relationship between GPX4 (rs713041) SNP and the risk of different diseases based on three genetic models. Review Manager 5.4 and Comprehensive Meta-Analysis 4 software were used to perform the meta-analysis and carry out Egger’s test for publication bias. Results: Data from 21 articles were included in the systematic review. Diseases were clustered according to the physiological system affected to understand better the role of GPX4 (rs713041) SNP in developing different diseases. Carriers of the GPX4 (rs173041) T allele were associated with an increased risk of developing colorectal cancer in additive and dominant models (p = 0.02 and p = 0.004, respectively). In addition, carriers of the T allele were associated with an increased risk of developing stroke and hypertension in the additive, dominant and recessive models (p = 0.002, p = 0.004 and p = 0.01, respectively). On the other hand, the GPX4 (rs713041) T allele was associated with a decreased risk of developing pre-eclampsia in the additive, dominant and recessive models (p < 0.0001, p = 0.002 and p = 0.0005, respectively). Moreover, selenium levels presented lower mean values in cancer patients relative to control groups (SMD = −0.39 µg/L; 95% CI: −0.64, −0.14; p = 0.002, I2 = 85%). Conclusion: GPX4 (rs713041) T allele may influence colorectal cancer risk, stroke, hypertension and pre-eclampsia. In addition, low selenium levels may play a role in the increased risk of cancer.

Male guanine-rich RNA sequence binding factor 1 knockout mice (Grsf1-/-) gain less body weight during adolescence and adulthood

The guanine-rich RNA sequence binding factor 1 (GRSF1) is an RNA-binding protein of the heterogenous nuclear ribonucleoprotein H/F (hnRNP H/F) family that binds to guanine-rich RNA sequences forming G-quadruplex structures. In mice and humans there are single copy GRSF1 genes, but multiple transcripts have been reported. GRSF1 has been implicated in a number of physiological processes (e.g. embryogenesis, erythropoiesis, redox homeostasis, RNA metabolism) but also in the pathogenesis of viral infections and hyperproliferative diseases. These postulated biological functions of GRSF1 originate from in vitro studies rather than complex in vivo systems. To assess the in vivo relevance of these findings, we created systemic Grsf1^-/- knockout mice lacking exons 4 and 5 of the Grsf1 gene and compared the basic functional characteristics of these animals with those of wildtype controls. We found that Grsf1-deficient mice are viable, reproduce normally and have fully functional hematopoietic systems. Up to an age of 15 weeks they develop normally but when male individuals grow older, they gain significantly less body weight than wildtype controls in a gender-specific manner. Profiling Grsf1 mRNA expression in different mouse tissues we observed high concentrations in testis. Comparison of the testicular transcriptomes of Grsf1^-/- mice and wildtype controls confirmed near complete knock-out of Grsf1 but otherwise subtle differences in transcript regulations. Comparative testicular proteome analyses suggested perturbed mitochondrial respiration in Grsf1^-/- mice which may be related to compromised expression of complex I proteins. Here we present, for the first time, an in vivo complete Grsf1 knock-out mouse with comprehensive physiological, transcriptomic and proteomic characterization to improve our understanding of the GRSF1 beyond in vitro cell culture models.

Baicalein Relieves Ferroptosis-Mediated Phagocytosis Inhibition of Macrophages in Ovarian Endometriosis

Iron overload and oxidative stress have been reported to contribute to ferroptosis in endometriotic lesions. However, the possible roles of iron overload on macrophages in endometriosis (EMs) remain unknown. Based on recent reports by single-cell sequencing data of endometriosis, here we found significant upregulations of ferroptosis-associated genes in the macrophage of the endometriotic lesion. Additionally, there was an elevated expression of HMOX1, FTH1, and FTL in macrophages of peritoneal fluid in EMs, as well as iron accumulation in the endometriotic lesions. Notably, cyst fluid significantly up-regulated levels of intracellular iron and ferroptosis in Phorbol-12-myristate-13-acetate (PMA)-stimulated THP-1 cells. Additionally, high iron-induced ferroptosis obviously reduced PMA-stimulated THP-1 cells' phagocytosis and increased the expression of angiogenic cytokines, such as vascular endothelial growth factor A (VEGFA) and interleukin 8 (IL8). Baicalein, a potential anti-ferroptosis compound, increased GPX4 expression, significantly inhibited ferroptosis, and restored phagocytosis of THP-1 cells in vitro. Collectively, our study reveals that ferroptosis triggered by high iron in cyst fluid promotes the development of EMs by impairing macrophage phagocytosis and producing more angiogenic cytokines (e.g., IL8 and VEGFA). Baicalein displays the potential for the treatment of EMs, especially in patients with high ferroptosis and low phagocytosis of macrophages.

Iron and liver cancer: an inseparable connection

Iron is an essential element for all organisms. Iron-containing proteins play critical roles in cellular functions. The biological importance of iron is largely attributable to its chemical properties as a transitional metal. However, an excess of 'free' reactive iron damages the macromolecular components of cells and cellular DNA through the production of harmful free radicals. On the contrary, most of the body's excess iron is stored in the liver. Not only hereditary haemochromatosis but also some liver diseases with mild-to-moderate hepatic iron accumulation, such as chronic hepatitis C, alcoholic liver disease and nonalcoholic steatohepatitis, are associated with a high risk for liver cancer development. These findings have attracted attention to the causative and promotive roles of iron in the development of liver cancer. In the last decade, accumulating evidence regarding molecules regulating iron metabolism or iron-related cell death programmes such as ferroptosis has shed light on the relationship between hepatic iron accumulation and hepatocarcinogenesis. In this review, we briefly present the current molecular understanding of iron regulation in the liver. Next, we describe the mechanisms underlying dysregulated iron metabolism depending on the aetiology of liver diseases. Finally, we discuss the causative and promotive roles of iron in cancer development.

Ferroptosis in heart failure

With its complicated pathobiology and pathophysiology, heart failure (HF) remains an increasingly prevalent epidemic that threatens global human health. Ferroptosis is a form of regulated cell death characterized by the iron-dependent lethal accumulation of lipid peroxides in the membrane system and is different from other types of cell death such as apoptosis and necrosis. Mounting evidence supports the claim that ferroptosis is mainly regulated by several biological pathways including iron handling, redox homeostasis, and lipid metabolism. Recently, ferroptosis has been identified to play an important role in HF induced by different stimuli such as myocardial infarction, myocardial ischemia reperfusion, chemotherapy, and others. Thus, it is of great significance to deeply explore the role of ferroptosis in HF, which might be a prerequisite to precise drug targets and novel therapeutic strategies based on ferroptosis-related medicine. Here, we review current knowledge on the link between ferroptosis and HF, followed by critical perspectives on the development and progression of ferroptotic signals and cardiac remodeling in HF.

Selenoprotein GPX1 is a prognostic and chemotherapy-related biomarker for brain lower grade glioma

OBJECTIVE

Glutathione peroxidase 1 (GPX1) is a major selenoprotein in most animal tissues, primarily expressed in the cytoplasm and mitochondria of cells and peroxidase structures of certain cells. GPX1 expression is highly correlated with carcinogenesis and disease progression. The goal of the study was to determine the association between GPX1 expression and tumor therapy, and to identify GPX1 prognostic value in various malignancies.

METHODS

The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Human Protein Atlas (HPA) databases were used to detect the levels of GPX1 expression in human tumor tissues and normal tissues. Indeed, correlations between GPX1 and tumor purity, tumor mutation burden (TMB), microsatellite instability (MSI), and DNA mismatch repair genes (MMRs) were explored using the TCGA cohort. Functional and enrichment analyses were performed by the GeneMANIA database and Gene Set Enrichment Analysis (GSEA), respectively. Cox regression models and Kaplan - Meier curves were used to screen for independent risk factors and estimate brain lower-grade glioma (LGG) survival probability. The Chinese Glioma Genome Atlas (CGGA) database was used to determine whether GPX1 had a race-specific effect on overall survival (OS) in LGG. The cross-interaction between GPX1 and chemoradiotherapy on LGG OS was determined by Kaplan - Meier curves. Logistic regression models of multiplicative interactions were constructed. Furthermore, the relationship between GPX1 and LGG treatment regimens was also explored through the Genomics of Drug Sensitivity in Cancer (GDSC) database.

RESULTS

GPX1 was highly expressed in various tumors, GPX1 overexpression was significantly correlated with the poor prognosis of LGG. GPX1 was found to be an independent predictive factor for LGG in both univariate and multivariate Cox models. The nomogram showed a high predictive accuracy (C-index: 0.804, 95% CI: 0.74-0.86). In addition, GPX1 was significantly associated with TMB, MSI, and MMRs in diverse cancers. GPX1 was involved in IL6/JAK/STAT3, inflammatory response, and apoptosis signaling pathways. Besides, non-radiotherapy, chemotherapy, and low GPX1 expression were important factors affecting the better prognosis of LGG. GPX1 acted as a tumor promoter, which has taken the worst effect on LGG survival, but a multiplicative interaction of GPX1*chemoradiotherapy may improve the poor clinical outcome. GPX1 was negatively correlated with the half inhibition concentration (IC50) of temozolomide (TMZ) (Spearman = -0.44, P = 4.52 ×10^-26).

CONCLUSION

In LGG patients, high GPX1 expression was linked to a shorter OS. The interaction between GPX1 and chemoradiotherapy exhibits a beneficial clinical effect and chemotherapy was recommended for LGG patients, especially for those with high GPX1 expression. Besides, high GPX1 expression can predict TMZ sensitivity in LGG, providing potential evidence for chemotherapy. On the whole, this study presents a wealth of biological as well as clinical significance for the roles of GPX1 in human tumors, particularly in LGG.

Melatonin as an Antioxidant Agent in Stroke: An Updated Review

Stroke is a devastating disease associated with high mortality and disability worldwide, and is generally classified as ischemic or hemorrhagic, which share certain similar pathophysiological processes. Oxidative stress is a critical factor involved in stroke-induced injury, which not only directly damages brain tissue, but also enhances a series of pathological signaling cascades, contributing to inflammation, brain edema, and neuronal death. To alleviate these serious secondary brain injuries, neuroprotective agents targeting oxidative stress inhibition may serve as a promising treatment strategy. Melatonin is a hormone secreted by the pineal gland, and has various properties, such as antioxidation, anti-inflammation, circadian rhythm modulation, and promotion of tissue regeneration. Numerous animal experiments studying stroke have confirmed that melatonin exerts considerable neuroprotective effects, partially via anti-oxidative stress. In this review, we introduce the possible role of melatonin as an antioxidant in the treatment of stroke based on the latest published studies of animal experiments and clinical research.

Glutathione peroxidase 4 expression predicts poor overall survival in patients with resected lung adenocarcinoma

This study aimed to evaluate the protein expression of glutathione peroxidase 4 (GPX4) in resected non-small cell lung cancer (NSCLC). The clinical relevance and prognostic significance of GPX4 expression were analyzed. We reviewed patients with resected NSCLCs at Taipei Veterans General Hospital between September 2002 and January 2018. Available paraffin-embedded specimens were retrieved for immunohistochemistry (IHC) staining to detect GPX4 expression. The cutoff value for defining GPX4 positivity was determined according to the percentage of tumor stained in the microscopic field. The correlation between immune expression, clinicopathologic data, overall survival (OS), and disease-free survival (DFS) were analyzed. A total of 265 NSCLC specimens were retrieved for IHC staining. GPX4 expression positive was in 192 (72.5%) according to a cutoff value of 5%. GPX4 was a significant prognostic factor for OS and DFS on multivariate analysis at both 5% and 25% cutoff values. GPX4 expression was associated with poor OS and DFS, especially in lung adenocarcinoma (p = 0.008, and 0.027, respectively). In conclusions, IHC analysis revealed that GPX4 expression was associated with poor survival outcomes in patients with resected lung adenocarcinoma. Further research is needed to understand the role of GPX4 in tumorigenesis and the underlying mechanism responsible for survival outcomes in patients with resected lung adenocarcinoma.

Nrf2 and Oxidative Stress: A General Overview of Mechanisms and Implications in Human Disease

Organisms are continually exposed to exogenous and endogenous sources of reactive oxygen species (ROS) and other oxidants that have both beneficial and deleterious effects on the cell. ROS have important roles in a wide range of physiological processes; however, high ROS levels are associated with oxidative stress and disease progression. Oxidative stress has been implicated in nearly all major human diseases, from neurogenerative diseases and neuropsychiatric disorders to cardiovascular disease, diabetes, and cancer. Antioxidant defence systems have evolved as a means of protection against oxidative stress, with the transcription factor Nrf2 as the key regulator. Nrf2 is responsible for regulating an extensive panel of antioxidant enzymes involved in the detoxification and elimination of oxidative stress and has been extensively studied in the disease contexts. This review aims to provide the reader with a general overview of oxidative stress and Nrf2, including basic mechanisms of Nrf2 activation and regulation, and implications in various major human diseases.

Inducing ferroptosis has the potential to overcome therapy resistance in breast cancer

Breast cancer is the most common type of malignancy among women. Due to the iron-dependent character of breast cancer cells, they are more sensitive to ferroptosis compared to normal cells. It is possible to reverse tumor resistance by inducing ferroptosis in breast cancer cells, thereby improving tumor treatment outcomes. Ferroptosis is highly dependent on the balance of oxidative and antioxidant status. When ferroptosis occurs, intracellular iron levels are significantly increased, leading to increased membrane lipid peroxidation and ultimately triggering ferroptosis. Ferroptotic death is a form of autophagy-associated cell death. Synergistic use of nanoparticle-loaded ferroptosis-inducer with radiotherapy and chemotherapy achieves more significant tumor suppression and inhibits the growth of breast cancer by targeting cancer tissues, enhancing the sensitivity of cells to drugs, reducing the drug resistance of cancer cells and the toxicity of drugs. In this review, we present the current status of breast cancer and the mechanisms of ferroptosis. It is hopeful for us to realize effective treatment of breast cancer through targeted ferroptosis.

The Importance of Dietary Antioxidants on Oxidative Stress, Meat and Milk Production, and Their Preservative Aspects in Farm Animals: Antioxidant Action, Animal Health, and Product Quality-Invited Review

The biological effects of oxidative stress and associated free radicals on farm animal performance, productivity, and product quality may be managed via dietary interventions-specifically, the provision of feeds, supplements, and forages rich in antioxidants. To optimize this approach, it is important first to understand the development of free radicals and their contributions to oxidative stress in tissue systems of farm animals or the human body. The interactions between prooxidants and antioxidants will impact redox homeostasis and, therefore, the well-being of farm animals. The impact of free radical formation on the oxidation of lipids, proteins, DNA, and biologically important macromolecules will likewise impact animal performance, meat and milk quality, nutritional value, and longevity. Dietary antioxidants, endogenous antioxidants, and metal-binding proteins contribute to the 'antioxidant defenses' that control free radical formation within the biological systems. Different bioactive compounds of varying antioxidant potential and bio-accessibility may be sourced from tailored feeding systems. Informed and successful provision of dietary antioxidants can help alleviate oxidative stress. However, knowledge pertaining to farm animals, their unique biological systems, and the applications of novel feeds, specialized forages, bioactive compounds, etc., must be established. This review summarized current research to direct future studies towards more effective controls for free radical formation/oxidative stress in farm animals so that productivity and quality of meat and milk can be optimized.

Protective effect of fermented aloe extract on glutamate-induced cytotoxicity in HT22 cells

Excessive glutamate can cause oxidative stress in neuronal cells and this can significantly contribute to the etiology of neurodegenerative disease. The present study mainly aims to investigate that aloe extract (AE) and fermented aloe extract (FAE) could protect against glutamate-induced cytotoxicity by modulating oxidative stress. In this study, both AE and FAE showed potent neuroprotective activity by inhibiting ROS and Ca²⁺ concentration, increasing mitochondria membrane potential, and activating glutathione-related enzymes against glutamate-insulted neurotoxicity in HT22 cells. In addition, the neuroprotective activity of FAE was more potent than that of AE. HPLC analysis reveals that the chemical composition of FAE is different from that of AE. Especially, the contents of aloin A, aloin B and aloenin were higher in FAE than in AE. In conclusion, this study indicates that both AE and FAE may have effective neuroprotective activity in glutamate-insulted pathological conditions such as Alzheimer's disease by managing oxidative stress.

Selenium and Redox Enzyme Activity in Pregnant Women Exposed to Methylmercury

Selenium (Se) is a micronutrient with essential physiological functions achieved through the production of selenoproteins. Adequate Se intake has health benefits and reduces mercury (Hg) toxicity, which is important due to its neurotoxicity. This study determined the Se status and redox enzyme, including selenoproteins', activity in pregnant women highly exposed to Hg (between 1 to 54 µg Hg/L blood) via fish consumption. A cross-sectional study enrolling 513 women between the first and third trimester of pregnancy from Madeira, Portugal was conducted, encompassing collection of blood and plasma samples. Samples were analyzed for total Se and Hg levels in whole blood and plasma, and plasma activity of redox-active proteins, such as glutathione peroxidase (GPx), thioredoxin reductase (TrxR) and thioredoxin (Trx). Enzyme activities were related to Se and Hg levels in blood. Se levels in whole blood (65.0 ± 13.1 µg/L) indicated this population had a sub-optimal Se status, which translated to low plasma GPx activity (69.7 ± 28.4 U/L). The activity of TrxR (12.3 ± 5.60 ng/mL) was not affected by the low Se levels. On the other hand, the decrease in Trx activity with an increase in Hg might be a good indicator to prevent fetal susceptibility.

Ferroptosis-A New Dawn in the Treatment of Organ Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) is a common pathological phenomenon that occurs in numerous organs and diseases. It generally results from secondary damage caused by the recovery of blood flow and reoxygenation, followed by ischemia of organ tissues, which is often accompanied by severe cellular damage and death. Currently, effective treatments for I/R injury (IRI) are limited. Ferroptosis, a new type of regulated cell death (RCD), is characterized by iron overload and iron-dependent lipid peroxidation. Mounting evidence has indicated a close relationship between ferroptosis and IRI. Ferroptosis plays a significantly detrimental role in the progression of IRI, and targeting ferroptosis may be a promising approach for treatment of IRI. Considering the substantial progress made in the study of ferroptosis in IRI, in this review, we summarize the pathological mechanisms and therapeutic targets of ferroptosis in IRI.

Anticancer Effects of Thymoquinone through the Antioxidant Activity, Upregulation of Nrf2, and Downregulation of PD-L1 in Triple-Negative Breast Cancer Cells

The variety of therapies available for treating and preventing triple-negative breast cancer (TNBC) is constrained by the absence of progesterone receptors, estrogen receptors, and human epidermal growth factor receptor 2. Nrf2 (nuclear factor-erythroid 2-related factor), and PD-L1 (program cell death ligand 1), a downstream signaling target, have a strong correlation to oxidative stress and inflammation, major factors in the development and progression of TNBC. In this study, the genetically distinct MDA-MB-231 and MDA-MB-468 TNBC cells were treated with the natural component thymoquinone (TQ). The results show that TQ exhibits considerable antioxidant activity and decreases the generation of H₂O₂, at the same time increasing catalase (CAT) activity, superoxide dismutase (SOD) enzyme, and glutathione (GSH). Additionally, the results show that TQ treatment increased the levels of the different genes involved in the oxidative stress-antioxidant defense system PRNP, NQO1, and GCLM in both cell lines with significant large-fold change in MDA-MB-468 cells (+157.65 vs. +1.7, +48.87 vs. +2.63 and +4.78 vs. +2.17), respectively. Nrf2 mRNA and protein expression were also significantly increased in TQ-treated TNBC cells despite being higher in MDA-MB-468 cells (6.67 vs. 4.06). Meanwhile, TQ administration increased mRNA levels while decreasing PD-L1 protein expression in both cell lines. In conclusion, TQ modifies the expression of multiple oxidative-stress-antioxidant system genes, ROS, antioxidant enzymes, Nrf2, and PD-L1 protein, pointing to the therapeutic potential and chemopreventive utilization of TQ in TNBC.

GPX4 regulates cellular necrosis and host resistance in Mycobacterium tuberculosis infection

Cellular necrosis during Mycobacterium tuberculosis (Mtb) infection promotes both immunopathology and bacterial dissemination. Glutathione peroxidase-4 (Gpx4) is an enzyme that plays a critical role in preventing iron-dependent lipid peroxidation-mediated cell death (ferroptosis), a process previously implicated in the necrotic pathology seen in Mtb-infected mice. Here, we document altered GPX4 expression, glutathione levels, and lipid peroxidation in patients with active tuberculosis and assess the role of this pathway in mice genetically deficient in or overexpressing Gpx4. We found that Gpx4-deficient mice infected with Mtb display substantially increased lung necrosis and bacterial burdens, while transgenic mice overexpressing the enzyme show decreased bacterial loads and necrosis. Moreover, Gpx4-deficient macrophages exhibited enhanced necrosis upon Mtb infection in vitro, an outcome suppressed by the lipid peroxidation inhibitor, ferrostatin-1. These findings provide support for the role of ferroptosis in Mtb-induced necrosis and implicate the Gpx4/GSH axis as a target for host-directed therapy of tuberculosis.

Galangin inhibited ferroptosis through activation of the PI3K/AKT pathway in vitro and in vivo

Ferroptosis is an iron-dependent form of nonapoptotic cell death characterized by the accumulation of lipid peroxides in cells. In recent years, extensive attention has been dedicated to exploring safe and effective natural ferroptosis regulators which can provide novel treatment strategies for ferroptosis-related diseases. This study identified galangin, a natural flavonoid, as an effective inhibitor of ferroptosis, which could increase cell viability in RSL3-inhibited HT1080 cells, decrease levels of lipid ROS and MDA, improve PTGS2 mRNA expression, and enhance the expression of glutathione peroxidase 4 (GPX4). Ferroptosis is widely present in ischemia-reperfusion (IR) injury. This study found that galangin significantly ameliorated the pathological damage of liver tissue in mice with IR, reduced levels of serum ALT, AST, and MDA, and increased the expression of GPX4. The results of RNA-seq exhibited ferroptosis was significant and the PI3K/AKT pathway deserved to explore the inhibition effects of galangin on ferroptosis. Indeed, galangin treatment significantly rescued RSL3-inhibited phosphorylation levels of PI3K, AKT, and CREB proteins, and the ferroptosis inhibitory effects of galangin were counteracted by PI3K inhibitor LY294002. These findings indicated that galangin may exert its anti-ferroptosis effects via activating the PI3K/AKT/CREB signaling pathway and it will hopefully serve as a promising effective measure to attenuate IR injury by inhibiting ferroptosis.

Bromodomain-containing protein 4 (BRD4) as an epigenetic regulator of fatty acid metabolism genes and ferroptosis

Reprogramming lipid metabolism is considered a fundamental step in tumourigenesis that influences ferroptosis. However, molecular mechanisms between lipid metabolism and ferroptosis remain largely unknown. Results from the drug screening of 464 inhibitors (for 164 targets) applied to ferroptosis cells indicated that 4 inhibitors targeted bromodomain-containing protein 4 (BRD4) significantly inhibiting erastin-induced ferroptosis. Functional studies proved that the loss of BRD4 weakened oxidative catabolism in mitochondria, protecting cells from the excessive accumulation of lipid peroxides. Mechanism research revealed that the transcriptional levels of fatty acid metabolism-related genes (HADH, ACSL1 and ACAA2) participating in the β-oxidation of fatty acids (FAO) and polyunsaturated fatty acids (PUFAs) synthesis depended on the activity of super-enhancers (SEs) formed by BRD4 and HMGB2 in their promoter regions. Conclusively, this study demonstrated that BRD4 was indispensable for fatty acid metabolism based on its epigenetic regulatory mechanisms and affecting erastin-induced ferroptosis, providing a new theoretical reference for understanding the relationship between lipid metabolism and ferroptosis deeply.

Metabolism of Selenium, Selenocysteine, and Selenoproteins in Ferroptosis in Solid Tumor Cancers

A potential target of precision nutrition in cancer therapeutics is the micronutrient selenium (Se). Se is metabolized and incorporated as the amino acid selenocysteine (Sec) into 25 human selenoproteins, including glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs), among others. Both the processes of Se and Sec metabolism for the production of selenoproteins and the action of selenoproteins are utilized by cancer cells from solid tumors as a protective mechanism against oxidative damage and to resist ferroptosis, an iron-dependent cell death mechanism. Protection against ferroptosis in cancer cells requires sustained production of the selenoprotein GPX4, which involves increasing the uptake of Se, potentially activating Se metabolic pathways such as the trans-selenation pathway and the TXNRD1-dependent decomposition of inorganic selenocompounds to sustain GPX4 synthesis. Additionally, endoplasmic reticulum-resident selenoproteins also affect apoptotic responses in the presence of selenocompounds. Selenoproteins may also help cancer cells adapting against increased oxidative damage and the challenges of a modified nutrient metabolism that result from the Warburg switch. Finally, cancer cells may also rewire the selenoprotein hierarchy and use Se-related machinery to prioritize selenoproteins that are essential to the adaptations against ferroptosis and oxidative damage. In this review, we discuss both the evidence and the gaps in knowledge on how cancer cells from solid tumors use Se, Sec, selenoproteins, and the Se-related machinery to promote their survival particularly via resistance to ferroptosis.

ROS: Basic Concepts, Sources, Cellular Signaling, and its Implications in Aging Pathways

Reactive oxygen species (ROS) are bioproducts of cellular metabolism. There is a range of molecules with oxidizing properties known as ROS. Despite those molecules being implied negatively in aging and numerous diseases, their key role in cellular signaling is evident. ROS control several biological processes such as inflammation, proliferation, and cell death. The redox signaling underlying these cellular events is one characteristic of the new generation of scientists aimed at defining the role of ROS in the cellular environment. The control of redox potential, which includes the balance of the sources of ROS and the antioxidant system, implies an important target for understanding the cells' fate derived from redox signaling. In this review, we summarized the chemical, the redox balance, the signaling, and the implications of ROS in biological aging.

Iron metabolism, ferroptosis, and lncRNA in cancer: knowns and unknowns

Cancer cells undergo substantial metabolic alterations to sustain increased energy supply and uncontrolled proliferation. As an essential trace element, iron is vital for many biological processes. Evidence has revealed that cancer cells deploy various mechanisms to elevate the cellular iron concentration to accelerate proliferation. Ferroptosis, a form of cell death caused by iron-catalyzed excessive peroxidation of polyunsaturated fatty acids (PUFAs), is a promising therapeutic target for therapy-resistant cancers. Previous studies have reported that long noncoding RNA (lncRNA) is a group of critical regulators involved in modulating cell metabolism, proliferation, apoptosis, and ferroptosis. In this review, we summarize the associations among iron metabolism, ferroptosis, and ferroptosis-related lncRNA in tumorigenesis. This information will help deepen understanding of the role of lncRNA in iron metabolism and raise the possibility of targeting lncRNA and ferroptosis in cancer combination therapy.

Short-chain L-3-hydroxyacyl-CoA dehydrogenase: A novel vital oncogene or tumor suppressor gene in cancers

The reprogramming of cellular metabolism is frequently linked to tumorigenesis. Glucose, fatty acids, and amino acids are the specific substrates involved in how an organism maintains metabolic equilibrium. The HADH gene codes for the short-chain L-3-hydroxyacyl-CoA dehydrogenase (HADH), a crucial enzyme in fatty acid oxidation that catalyzes the third phase of fatty acid oxidation in mitochondria. Increasing data suggest that HADH is differentially expressed in various types of malignancies and is linked to cancer development and progression. The significance of HADH expression in tumors and its potential mechanisms of action in the onset and progression of certain cancers are summarized in this article. The possible roles of HADH as a target and/or biomarker for the detection and treatment of various malignancies is also described here.

Mitochondrial event as an ultimate step in ferroptosis

In ferroptosis, the roles of mitochondria have been controversial. To explore the role of mitochondrial events in ferroptosis, we employed mitochondrial DNA-depleted ρ⁰ cells that are resistant to cell death due to enhanced expression of antioxidant enzymes. Expression of mitochondrial-type GPx4 (mGPx4) but no other forms of GPx4 was increased in SK-Hep1 ρ⁰ cells. Likely due to high mGPx4 expression, SK-Hep1 ρ⁰ cells were resistant to ferroptosis by erastin inhibiting xCT channel. In contrast, SK-Hep1 ρ⁰ cells were susceptible to cell death by a high concentration of RSL3 imposing ferroptosis by GPx4 inhibition. Accumulation of cellular ROS and oxidized lipids was observed in erastin- or RSL3-treated SK-Hep1 ρ⁺ cells but not in erastin-treated SK-Hep1 ρ⁰ cells. Mitochondrial ROS and mitochondrial peroxidized lipids accumulated in SK-Hep1 ρ⁺ cells not only by RSL3 but also by erastin acting on xCT on the plasma membrane. Mitochondrial ROS quenching inhibited SK-Hep1 ρ⁺ cell death by erastin or a high dose of RSL3, suggesting a critical role of mitochondrial ROS in ferroptosis. Ferroptosis by erastin or RSL3 was inhibited by a more than 20-fold lower concentration of MitoQ, a mitochondrial ROS quencher, compared to DecylQ, a non-targeting counterpart. Ferroptosis of SK-Hep1 ρ⁺ cells by erastin or RSL3 was markedly inhibited by a VDAC inhibitor, accompanied by significantly reduced accumulation of mitochondria ROS, total peroxidized lipids, and mitochondrial peroxidized lipids, strongly supporting the role of mitochondrial events in ferroptotic death and that of VDAC in mitochondrial steps of ferroptosis induced by erastin or RSL3. SK-Hep1 ρ⁺ cell ferroptosis by sorafenib was also suppressed by mitochondrial ROS quenchers, accompanied by abrogation of sorafenib-induced mitochondrial ROS and mitochondrial peroxidized lipid accumulation. These results suggest that SK-Hep1 ρ⁰ cells are resistant to ferroptosis due to upregulation of mGPx4 expression and mitochondrial events could be the ultimate step in determining final cell fate.

Essential Roles of Peroxiredoxin IV in Inflammation and Cancer

Peroxiredoxin IV (Prx4) is a 2-Cysteine peroxidase with ubiquitous expression in human tissues. Prx4 scavenges hydrogen peroxide and participates in oxidative protein folding in the endoplasmic reticulum. In addition, Prx4 is secreted outside the cell. Prx4 is upregulated in several cancers and is a potential therapeutic target. We have summarized historical and recent advances in the structure, function and biological roles of Prx4, focusing on inflammatory diseases and cancer. Oxidative stress is known to activate pro-inflammatory pathways. Chronic inflammation is a risk factor for cancer development. Hence, redox enzymes such as Prx4 are important players in the crosstalk between inflammation and cancer. Understanding molecular mechanisms of regulation of Prx4 expression and associated signaling pathways in normal physiological and disease conditions should reveal new therapeutic strategies. Thus, although Prx4 is a promising therapeutic target for inflammatory diseases and cancer, further research needs to be conducted to bridge the gap to clinical application.

Changes in the Oxidative Status of Dual-Purpose Hens Rearing in the Free-Range System during Cold, Thermoneutral and Hot Period

This study aimed to assess the changes in the oxidative status of six genotypes of free-range laying hens during cold, thermoneutral, and hot periods by measuring the levels of lipid peroxidation (LPO), total glutathione (tGSH), and the activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in erythrocyte suspension, in relation with their egg production. Two identical experiments were conducted in two consecutive years. Thermal stress adversely affected the oxidative status of hens. The induced OS is expressed by an increase in LPO and the activities of antioxidant enzymes SOD and GPx during cold and hot periods and a decrease in CAT and tGSH during the cold period in both years. The factor “temperature period”, compared to “year” and “genotype”, had the most significant influence on all biochemical parameters (p < 0.001). Significant phenotypic correlations (p < 0.05) were detected among studied biochemical parameters, except between SOD and tGSH. The chicken genotypes showed differences in their susceptibility to OS and this had an effect on egg production—from 37.87% to 74.93%. The OS is genotypically specific and can play a significant role in determining welfare and egg production in free-range systems.

1H, 13C, and 15N resonance assignments of human glutathione peroxidase 4

Glutathione peroxidase 4 (GPx4) behaves as an antioxidant enzyme capable of directly reducing peroxidized phospholipids within cell membranes. Recently, GPx4 has attracted attention as a target molecule for cancer therapy because it induces the immortalization of cancer cells suppressing ferroptosis. In this study, to analyze the function and structure of GPx4 by solution NMR, we performed resonance assignments of GPx4 and assigned almost all backbone ¹H, ¹³C, and ¹⁵N resonances and most of the side chain ¹H and ¹³C resonances. Using these assignments, the secondary structure of GPx4 was analyzed by the TALOS + program. GPx4 has six helices and seven strands. Then, the backbone dynamics were examined by the {¹H}-¹⁵N heteronuclear NOE experiment. GPx4 was found to be rigid except for a short loop region. These results will provide basis for functional analysis and the first solution structure determination of GPx4.

Mechanisms underlying Nrf2 nuclear translocation by non-lethal levels of hydrogen peroxide: p38 MAPK-dependent neutral sphingomyelinase2 membrane trafficking and ceramide/PKCζ/CK2 signaling

Hydrogen peroxide is an aerobic metabolite playing a central role in redox signaling and oxidative stress. H₂O₂ could activate redox sensitive transcription factors, such as Nrf2, AP-1 and NF-κB by different manners. In some cells, treatment with non-lethal levels of H₂O₂ induces rapid activation of Nrf2, which upregulates expression of a set of genes involved in glutathione (GSH) synthesis and defenses against oxidative damage. It depends on two steps, the rapid translational activation of Nrf2 and facilitation of Nrf2 nuclear translocation. We review the molecular mechanisms by which H₂O₂ induces nuclear translocation of Nrf2 in cultured cells by highlighting the role of neutral sphingomyelinase 2 (nSMase2), a GSH sensor. H₂O₂ enters cells through aquaporin channels in the plasma membrane and is rapidly reduced to H₂O by GSH peroxidases to consume cellular GSH, resulting in nSMase2 activation to generate ceramide. H₂O₂ also activates p38 MAP kinase, which enhances transfer of nSMase2 from perinuclear regions to plasma membrane lipid rafts to accelerate ceramide generation. Low levels of ceramide activate PKCζ, which then activates casein kinase 2 (CK2). These protein kinases are able to phosphorylate Nrf2 to stabilize and activate it. Notably, Nrf2 also binds to caveolin-1 (Cav1), which protects Nrf2 from Keap1-mediated degradation and limits Nrf2 nuclear translocation. We propose that Cav1serves as a signaling hub for the control of H₂O₂-mediated phosphorylation of Nrf2 by kinases, which results in release of Nrf2 from Cav1 to facilitate nuclear translocation. In summary, H₂O₂ induces GSH depletion which is recovered by Nrf2 activation dependent on p38/nSMase2/ceramide signaling.

Silencing TRPM2 enhanced erastin- and RSL3-induced ferroptosis in gastric cancer cells through destabilizing HIF-1α and Nrf2 proteins

Ferroptosis is a regulated form of cell death driven by small molecules or conditions that induce lipid-based reactive oxygen species (ROS) accumulation. Cation channel transient receptor potential melastatin-2 (TRPM2) is crucial for cancer cell survival. Our bioinformatic analysis revealed that TRPM2 is associated with cellular responses to chemical stimulus and oxidative stress, implying the potential role of TRPM2 in ferroptosis. Gastric cancer cells were treated with the ferroptosis-inducer, Erastin and RSL3. siRNA transfection was used to silence TRPM2. The levels of GSH, Fe2+, ROS and lipid peroxidation, and the activity of GPx activity were evaluated by flow cytometry and spectrophotometer. The effect of TRPM2 on ubiquitination of HIF-1α and Nrf2 were evaluated by co-immunoprecipitation. Erastin and RSL3 induced the up-regulation of TRPM2 in gastric cancer cell lines, especially in SGC7901 and MGC803. These two cells also showed stronger resistance to Erastin and RSL3 than the other cell lines. TRPM2 knockdown reduced the concentration of GSH and GPx activity, but enhanced the concentration of Fe2+, ROS and lipid peroxidation, which are significant indicators of ferroptosis. Importantly, silencing TRPM2 enhanced the inhibitory effects of Erastin and RSL3 on gastric cancer cell viability, migration, and invasion. TRPM2 stabilized and finally elevated the abundance of HIF-1α and Nrf2 in SGC7901 and MGC803 cells upon Erastin and RSL3. Activation of HIF-1α impaired Erastin- and RSL3-induced ferroptosis after TRPM2 knockdown. Collectively, silencing TRPM2 enhanced Erastin- and RSL3-induced ferroptosis in gastric cancer cells through destabilizing HIF-1α and Nrf2 proteins.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00545-z.