Phospholipid Hydroperoxide Research Articles

PRDX6 dictates ferroptosis sensitivity by directing cellular selenium utilization.

Selenium-dependent glutathione peroxidase 4 (GPX4) is the guardian of ferroptosis, preventing unrestrained (phospho)lipid peroxidation by reducing phospholipid hydroperoxides (PLOOH). However, the contribution of other phospholipid peroxidases in ferroptosis protection remains unclear. We show that cells lacking GPX4 still exhibit substantial PLOOH-reducing capacity, suggesting a contribution of alternative PLOOH peroxidases. By scrutinizing potential candidates, we found that although overexpression of peroxiredoxin 6 (PRDX6), a thiol-specific antioxidant enzyme with reported PLOOH-reducing activity, failed to prevent ferroptosis, its genetic loss sensitizes cancer cells to ferroptosis. Mechanistically, we uncover that PRDX6, beyond its known peroxidase activity, acts as a selenium-acceptor protein, facilitating intracellular selenium utilization and efficient selenium incorporation into selenoproteins, including GPX4. Its physiological significance was demonstrated by reduced GPX4 expression in Prdx6-deficient mouse brains and increased sensitivity to ferroptosis in PRDX6-deficient tumor xenografts in mice. Our study highlights PRDX6 as a critical player in directing cellular selenium utilization and dictating ferroptosis sensitivity.

Combined blockade of GPX4 and activated EGFR/HER3 bypass pathways inhibits the development of ALK-inhibitor-induced tolerant persister cells in ALK-fusion-positive lung cancer.

Cancers can develop resistance to treatment with ALK tyrosine kinase inhibitors (ALK-TKIs) via emergence of a subpopulation of drug-tolerant persister (DTP) cells that can survive initial drug treatment long enough to acquire genetic aberrations. DTP cells are thus a potential therapeutic target. We generated alectinib-induced DTP cells from a patient-derived ALK+ non-small-cell lung cancer (NSCLC) cell line and screened 3114 agents in the anticancer compounds library (TargetMol). We identified phospholipid hydroperoxide glutathione peroxidase GPX4 as being involved in promoting the survival of DTP cells. GPX4 was found to be upregulated in DTP cells and to promote cell survival by suppressing reactive oxygen species (ROS) accumulation; GPX4 inhibitors blocked this upregulation and facilitated ROS-mediated cell death. Activated bypass signals involving epidermal growth factor receptor (EGFR)/receptor tyrosine-protein kinase erbB-3 (HER3) were also identified in DTP cells, and co-treatment with EGFR-TKI plus ALK-TKI enhanced ROS levels. Triple combination with an ALK-TKI plus a bypass pathway inhibitor plus a GPX4 inhibitor suppressed cell growth and induced intracellular ROS accumulation more greatly than did treatment with each agent alone. The combined inhibition of ALK plus inhibition of activated bypass signals plus inhibition of GPX4 may be a potent therapeutic strategy for patients with ALK+ NSCLC to prevent the development of resistance to ALK-TKIs and lead to tumor eradication.

Targeting ferroptosis for improved radiotherapy outcomes in HPV‐negative head and neck squamous cell carcinoma

To enhance the efficacy of radiotherapy (RT) in human papillomavirus (HPV)‐negative head and neck squamous cell carcinoma (HNSCC), we explored targeting ferroptosis, a regulated cell death process. We developed a gene signature associated with ferroptosis using Cox proportional hazard modeling in HPV‐negative HNSCC patients who underwent RT. This ferroptosis‐related gene signature (FRGS) was a significant predictor of overall survival and recurrence‐free survival in HPV‐negative HNSCC patients who received RT. Subtype B of the FRGS, characterized by decreased expression of ferroptosis inducers [nuclear receptor coactivator 4 (NCOA4) and natural resistance‐associated macrophage protein 2 homolog/divalent metal transporter 1 (NRAMP2/DMT1)] and increased expression of suppressors [phospholipid hydroperoxide glutathione peroxidase (GPX4) and ferritin heavy chain (FTH1)], was associated with poorer prognosis, potentially indicating the inhibition of ferroptosis. Furthermore, our in vitro and in vivo studies demonstrated that treatment with statins, such as atorvastatin and simvastatin, induced ferroptosis and sensitized radioresistant HNSCC cells to irradiation, improving radiosensitivity and potentially enhancing the response to RT. Additionally, in xenograft models, the combination of statins and RT led to a significant reduction in tumor initiation. These findings provide valuable insights for enhancing treatment and improving prognosis in HPV‐negative HNSCC by targeting ferroptosis and utilizing statins to sensitize tumors to RT‐induced cell death.

Peroxiredoxin 6 (Prx6) of Penaeus vannamei and effect of phenanthrene on Prx6 and glutathione peroxidase 4 expression, glutathione-dependent peroxidase activity and lipid peroxidation

Polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (PHE), are common pollutants found in coastal areas where shrimp farming is developed. Even though PAHs can have adverse effects on physiology, shrimp can detoxify and metabolize toxic compounds and neutralize the reactive oxygen species (ROS) produced during this process. This requires the activation of multiple antioxidant enzymes, including peroxiredoxin 6 (Prx6). Prx6 uses glutathione (GSH) to reduce phospholipid hydroperoxides, a function shared with GSH peroxidase 4 (GPx4). Prx6 has been scarcely studied in crustaceans exposed to pollutants. Herein, we report a novel Prx6 from the shrimp Penaeus vannamei that is abundantly expressed in gills and hepatopancreas. To elucidate the involvement of Prx6 in response to PAHs, we analyzed its expression in the hepatopancreas of shrimp sub-lethally exposed to PHE (3.3 μg/L) and acetone (control) for 24, 48, 72, and 96 h, along with GPx4 expression, GSH-dependent peroxidase activity, and lipid peroxidation (indicated by TBARS). We found that GPx4 expression is not affected by PHE, but Prx6 expression and peroxidase activity decreased during the trial. This might contribute to the rise of TBARS found at 48 h of exposure. However, maintaining GPx4 expression could aid to minimize lipid damage during longer periods of exposure to PHE.

Iron(III)-salophene catalyzes redox cycles that induce phospholipid peroxidation and deplete cancer cells of ferroptosis-protecting cofactors

Ferroptosis, a lipid peroxidation-driven cell death program kept in check by glutathione peroxidase 4 and endogenous redox cycles, promises access to novel strategies for treating therapy-resistant cancers. Chlorido [N,N′-disalicylidene-1,2-phenylenediamine]iron (III) complexes (SCs) have potent anti-cancer properties by inducing ferroptosis, apoptosis, or necroptosis through still poorly understood molecular mechanisms. Here, we show that SCs preferentially induce ferroptosis over other cell death programs in triple-negative breast cancer cells (LC50 ≥ 0.07 μM) and are particularly effective against cell lines with acquired invasiveness, chemo- or radioresistance. Redox lipidomics reveals that initiation of cell death is associated with extensive (hydroper)oxidation of arachidonic acid and adrenic acid in membrane phospholipids, specifically phosphatidylethanolamines and phosphatidylinositols, with SCs outperforming established ferroptosis inducers. Mechanistically, SCs effectively catalyze one-electron transfer reactions, likely via a redox cycle involving the reduction of Fe(III) to Fe(II) species and reversible formation of oxo-bridged dimeric complexes, as supported by cyclic voltammetry. As a result, SCs can use hydrogen peroxide to generate organic radicals but not hydroxyl radicals and oxidize membrane phospholipids and (membrane-)protective factors such as NADPH, which is depleted from cells. We conclude that SCs catalyze specific redox reactions that drive membrane peroxidation while interfering with the ability of cells, including therapy-resistant cancer cells, to detoxify phospholipid hydroperoxides.

Abstract PS12-04: Inhibition of GPX4 enhances CDK4/6 inhibitor activity in breast cancer

Abstract Background: Cyclin D-dependent kinases 4 and 6 (CDK4/6) inhibitors (CDK4/6i) including palbociclib, ribociclib and abemaciclib in combination with endocrine therapy are the standard of care for patients with estrogen receptor-positive (ER+). Despite the success of these treatments, cytostasis is frequently observed, and novel strategies that enhance efficacy are required to eradicate residual cancer in the clinic. Methods: In the search of an effective drug combinations to enhance the efficacy of CDK4/6 inhibitors in breast cancer, we performed a whole genome CRISPR-Cas9 suppressor screen in MCF-7, an ER+ model. We also carried out transcriptomics, proteomics, and functional molecular biology analysis of breast cancer models treated with palbociclib to identify resistant mechanisms. Results: The whole genome CRISPR-Cas9 screen revealed that multiple genes involved in oxidative stress and ferroptosis modulated palbociclib sensitivity, being GPX4 the top sensitizing hit. GPX4 is a key glutathione peroxidase that protects again ferroptosis by catalysing the reduction of phospholipid and cholesterol hydroperoxides. CRISPR-depletion or drug inhibition of GPX4 increased sensitivity to palbociclib in ER+ breast cancer models, and in addition sensitised triple negative breast cancer models to palbociclib. Moreover, GPX4 null xenografts were highly sensitive to palbociclib in vivo. Transcriptomics and proteomics analysis showed that palbociclib upregulate pathways involved in oxidative stress and lipid metabolism promoting a redox-lipid imbalance. Palbociclib induced lipid peroxidation leading to a ferroptosis vulnerable state with GPX4 preventing cell death. Polyunsaturated fatty acids (PUFAs) are highly susceptible of lipid peroxidation, and pathways that regulate their abundance in membrane phospholipids were explored. Interestedly, in ER+ breast cancer models, lipid peroxidation relied on a peroxisome AGPAT3-dependent pathway rather than the classical ACSL4 pathway. Conclusion: Our studies demonstrate that quiescence induced by palbociclib results in a ferroptosis-vulnerable state that could be exploited through combination with GPX4 inhibitors to enhance sensitivity to CDK4/6 inhibition in breast cancer. Citation Format: Maria Teresa Herrera Abreu, Uzma Khalid, Jian Ning, Rosalind Cutts, Gemma Wilson, Christopher Lord, Amanda Swain, Nicholas Turner. Inhibition of GPX4 enhances CDK4/6 inhibitor activity in breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS12-04.

Metal-organic framework-mediated siRNA delivery and sonodynamic therapy for precisely triggering ferroptosis and augmenting ICD in osteosarcoma

The complex genomics, immunosuppressive tumor microenvironment (TME), and chemotherapeutic resistance of osteosarcoma (OS) have resulted in limited therapeutic effects in the clinic. Ferroptosis is involved in tumor progression and is regulated mainly by glutathione peroxidase 4 (GPX4). Small interfering RNA (siRNA)-based RNA interference (RNAi) can precisely target any gene. However, achieving effective siRNA delivery is highly challenging. Here, we fabricated a TME-responsive metal-organic framework (MOF)-based biomimetic nanosystem (mFeP@si) with siGPX4 delivery and sonodynamic therapy (SDT) to treat OS by targeting ferroptosis. Under ultrasound (US) irradiation, mFeP@si achieves lysosomal escape via singlet oxygen (1O2)-mediated lysosomal membrane disruption and then accelerates ROS generation and glutathione (GSH) depletion. Meanwhile, siGPX4 silences GPX4 expression by binding to GPX4 mRNA and leads to the accumulation of toxic phospholipid hydroperoxides (PL-OOH), further magnifying the ROS storm and triggering ferroptosis. Notably, synergistic therapy remarkably enhances antitumor effects, improves the immunosuppressive TME by inducing potent immunogenic cell death (ICD), and increases the sensitivity of chemotherapy-resistant OS cells to cisplatin. Overall, this novel nanosystem, which targets ferroptosis by integrating RNAi and SDT, exhibits strong antitumor effects both in vitro and in vivo, providing new insights for treating OS.

Peroxiredoxin 6 suppresses ferroptosis in lung endothelial cells

Peroxiredoxin 6 (Prdx6) repairs peroxidized membranes by reducing oxidized phospholipids, and by replacing oxidized sn-2 fatty acyl groups through hydrolysis/reacylation by its phospholipase A2 (aiPLA2) and lysophosphatidylcholine acyltransferase activities. Prdx6 is highly expressed in the lung, and intact lungs and cells null for Prdx6 or with single-point mutations that inactivate either Prdx6-peroxidase or aiPLA2 activity alone exhibit decreased viability, increased lipid peroxidation, and incomplete repair when exposed to paraquat, hyperoxia, or organic peroxides. Ferroptosis is form of cell death driven by the accumulation of phospholipid hydroperoxides. We studied the role of Prdx6 as a ferroptosis suppressor in the lung. We first compared the expression Prdx6 and glutathione peroxidase 4 (GPx4) and visualized Prdx6 and GPx4 within the lung. Lung Prdx6 mRNA levels were five times higher than GPx4 levels. Both Prdx6 and GPx4 localized to epithelial and endothelial cells. Prdx6 knockout or knockdown sensitized lung endothelial cells to erastin-induced ferroptosis. Cells with genetic inactivation of either aiPLA2 or Prdx6-peroxidase were more sensitive to ferroptosis than WT cells, but less sensitive than KO cells. We then conducted RNA-seq analyses in Prdx6-depleted cells to further explore how the loss of Prdx6 sensitizes lung endothelial cells to ferroptosis. Prdx6 KD upregulated transcriptional signatures associated with selenoamino acid metabolism and mitochondrial function. Accordingly, Prdx6 deficiency blunted mitochondrial function and increased GPx4 abundance whereas GPx4 KD had the opposite effect on Prdx6. Moreover, we detected Prdx6 and GPx4 interactions in intact cells, suggesting that both enzymes cooperate to suppress lipid peroxidation. Notably, Prdx6-depleted cells remained sensitive to erastin-induced ferroptosis despite the compensatory increase in GPx4. These results show that Prdx6 suppresses ferroptosis in lung endothelial cells and that both aiPLA2 and Prdx6-peroxidase contribute to this effect. These results also show that Prdx6 supports mitochondrial function and modulates several coordinated cytoprotective pathways in the pulmonary endothelium.

Potential role and therapeutic implications of glutathione peroxidase 4 in the treatment of Alzheimer's disease.

Alzheimer's disease is an age-related neurodegenerative disorder with a complex and incompletely understood pathogenesis. Despite extensive research, a cure for Alzheimer's disease has not yet been found. Oxidative stress mediates excessive oxidative responses, and its involvement in Alzheimer's disease pathogenesis as a primary or secondary pathological event is widely accepted. As a member of the selenium-containing antioxidant enzyme family, glutathione peroxidase 4 reduces esterified phospholipid hydroperoxides to maintain cellular redox homeostasis. With the discovery of ferroptosis, the central role of glutathione peroxidase 4 in anti-lipid peroxidation in several diseases, including Alzheimer's disease, has received widespread attention. Increasing evidence suggests that glutathione peroxidase 4 expression is inhibited in the Alzheimer's disease brain, resulting in oxidative stress, inflammation, ferroptosis, and apoptosis, which are closely associated with pathological damage in Alzheimer's disease. Several therapeutic approaches, such as small molecule drugs, natural plant products, and non-pharmacological treatments, ameliorate pathological damage and cognitive function in Alzheimer's disease by promoting glutathione peroxidase 4 expression and enhancing glutathione peroxidase 4 activity. Therefore, glutathione peroxidase 4 upregulation may be a promising strategy for the treatment of Alzheimer's disease. This review provides an overview of the gene structure, biological functions, and regulatory mechanisms of glutathione peroxidase 4, a discussion on the important role of glutathione peroxidase 4 in pathological events closely related to Alzheimer's disease, and a summary of the advances in small-molecule drugs, natural plant products, and non-pharmacological therapies targeting glutathione peroxidase 4 for the treatment of Alzheimer's disease. Most prior studies on this subject used animal models, and relevant clinical studies are lacking. Future clinical trials are required to validate the therapeutic effects of strategies targeting glutathione peroxidase 4 in the treatment of Alzheimer's disease.

The selenium-independent phospholipid hydroperoxide glutathione peroxidase from Theobroma cacao (TcPHGPX) protects plant cells against damages and cell death

Proteins from the glutathione peroxidase (GPX) family, such as GPX4 or PHGPX in animals, are extensively studied for their antioxidant functions and apoptosis inhibition. GPXs can be selenium-independent or selenium-dependent, with selenium acting as a potential cofactor for GPX activity. However, the relationship of plant GPXs to these functions remains unclear. Recent research indicated an upregulation of Theobroma cacao phospholipid hydroperoxide glutathione peroxidase gene (TcPHGPX) expression during early witches' broom disease stages, suggesting the use of antioxidant mechanisms as a plant defense strategy to reduce disease progression. Witches' broom disease, caused by the hemibiotrophic fungus Moniliophthora perniciosa, induces cell death through elicitors like MpNEP2 in advanced infection stages. In this context, in silico and in vitro analyses of TcPHGPX's physicochemical and functional characteristics may elucidate its antioxidant potential and effects against cell death, enhancing understanding of plant GPXs and informing strategies to control witches' broom disease. Results indicated TcPHGPX interaction with selenium compounds, mainly sodium selenite, but without improving the protein function. Protein-protein interaction network suggested cacao GPXs association with glutathione and thioredoxin metabolism, engaging in pathways like signaling, peroxide detection for ABA pathway components, and anthocyanin transport. Tests on tobacco cells revealed that TcPHGPX reduced cell death, associated with decreased membrane damage and H2O2 production induced by MpNEP2. This study is the first functional analysis of TcPHGPX, contributing to knowledge about plant GPXs and supporting studies for witches' broom disease control.

Slowly progressive cell death induced by GPx4-deficiency occurs via MEK1/ERK2 activation as a downstream signal after iron-independent lipid peroxidation.

Glutathione peroxidase 4 (GPx4) is an antioxidant enzyme that reduces phospholipid hydroperoxide. Studies have reported that the loss of GPx4 activity through anticancer drugs leads to ferroptosis, an iron-dependent lipid peroxidation-induced cell death. In this study, we established Tamoxifen-inducible GPx4-deficient Mouse embryonic fibroblast (MEF) cells (ETK1 cells) and found that Tamoxifen-inducible gene disruption of GPx4 induces slow cell death at ~72 h. In contrast, RSL3- or erastin-induced ferroptosis occurred quickly within 24 h. Therefore, we investigated the differences in these mechanisms between GPx4 gene disruption-induced cell death and RSL3- or erastin-induced ferroptosis. We found that GPx4-deficiency induced lipid peroxidation at 24 h in Tamoxifen-treated ETK1 cells, which was not suppressed by iron chelators, although lipid peroxidation in RSL3- or erastin-treated cells induced ferroptosis that was inhibited by iron chelators. We revealed that GPx4-deficient cell death was MEK1-dependent but RSL3- or erastin-induced ferroptosis was not, although MEK1/2 inhibitors suppressed both GPx4-deficient cell death and RSL3- or erastin-induced ferroptosis. In GPx4-deficient cell death, the phosphorylation of MEK1/2 and ERK2 was observed 39 h after lipid peroxidation, but ERK1 was not phosphorylated. Selective inhibitors of ERK2 inhibited GPx4-deficient cell death but not in RSL3- or erastin-induced cell death. These findings suggest that iron-independent lipid peroxidation due to GPx4 disruption induced cell death via the activation of MEK1/ERK2 as a downstream signal of lipid peroxidation in Tamoxifen-treated ETK1 cells. This indicates that GPx4 gene disruption induces slow cell death and involves a different pathway from RSL3- and erastin-induced ferroptosis in ETK1 cells.

Discovery of GPX4 inhibitors through FP-based high-throughput screening

Ferroptosis is a form of non-apoptotic cell death, regulated by phospholipid hydroperoxide glutathione peroxidase 4 (GPX4), a selenoprotein with a selenocysteine residue (sec) in the active site. GPX4 is a promising target for cancer cells in therapy-resistant conditions via ferroptosis, which can reduce the level of lipid reactive oxygen species (ROS). So far, all existing GPX4 inhibitors covalently bind to GPX4 via a reactive alkyl chloride moiety or masked nitrile-oxide electrophiles with poor selectivity and pharmacokinetic properties and most were obtained by cell phenotype-based screening. Lacking of effective high-throughput screening methods for GPX4 protein limits the discovery of GPX4 inhibitors. Here, we report a fluorescence polarization (FP)-based high throughput screening (HTS) assay for GPX4-U46C-C10A-C66A in vitro, and found Metamizole sodium from our in-house compound library inhibits GPX4-U46C-C10A-C66A enzyme activity. Structure-activity relationships (SAR) demonstrated the importance of sulfonyl group on interaction between Metamizole sodium and GPX4-U46C-C10A-C66A. Our FP assay could be an effective tool for discovery of GPX4 inhibitors and Metamizole sodium was a potential inhibitor for GPX4 in vitro.

Excessive Lipid Peroxidation in Uterine Epithelium Causes Implantation Failure and Pregnancy Loss.

The uterine epithelium undergoes a dramatic spatiotemporal transformation to enter a receptive state, involving a complex interaction between ovarian hormones and signals from stromal and epithelial cells. Redox homeostasis is critical for cellular physiological steady state; emerging evidence reveals that excessive lipid peroxides derail redox homeostasis, causing various diseases. However, the role of redox homeostasis in early pregnancy remains largely unknown. It is found that uterine deletion of Glutathione peroxidase 4 (GPX4), a key factor in repairing oxidative damage to lipids, confers defective implantation, leading to infertility. To further pinpoint Gpx4's role in different cell types, uterine epithelial-specific Gpx4 is deleted by a lactotransferrin (Ltf)-Cre driver; the resultant females are infertile, suggesting increased lipid peroxidation levels in uterine epithelium compromises receptivity and implantation. Lipid peroxidation inhibitor administration failed to rescue implantation due to carbonylation of major receptive-related proteins underlying high lipid reactive oxygen species. Intriguingly, superimposition of Acyl-CoA synthetase long-chain family member 4 (ACSL4), an enzyme that promotes biosynthesis of phospholipid hydroperoxides, along with uterine epithelial GPX4 deletion, preserves reproductive capacity. This study reveals the pernicious impact of unbalanced redox signaling on embryo implantation and suggests the obliteration of lipid peroxides as a possible therapeutic approach to prevent implantation defects.

Proteomic and metabolomic analysis of ageing beef exudate to determine that iron metabolism enhances muscle protein and lipid oxidation

The study aimed to assess differences in proteomic and metabolite profiles in ageing (1, 2, 4, and 6 days at 4 °C) beef exudates and determine their relationship with beef muscle iron metabolism and oxidation. Proteomic and metabolomic analyses identified 877 metabolites and 1957 proteins. The joint analysis identified 24 differential metabolites (DMs) and 56 differentially expressed proteins (DEPs) involved in 15 shared pathways. Ferroptosis was identified as the only iron metabolic pathway, and 4 DMs (l-glutamic acid, arachidonic acid, glutathione and gamma-glutamylcysteine) and 5 DEPs (ferritin, phospholipid hydroperoxide glutathione peroxidase, heme oxygenase 1, major prion protein, and acyl-CoA synthetase long chain family member 4) were involved in iron metabolism by regulating heme and ferritin degradation, Fe2+ and Fe3+ conversion, arachidonic acid oxidation and inactivation of glutathione peroxidase (GPX) 4, leading to increased levels of free iron, ROS, protein and lipid oxidation (P < 0.05). Overall, abnormal iron metabolism during ageing induced oxidative stress in muscle tissue.

Impact of IGF3 stimulation on spotted scat (Scatophagus argus) liver: Implications for a role in ovarian development

Insulin-like growth factor 3 (IGF3) plays an essential role in the reproductive system and influences the liver of teleosts. However, the mechanism of IGF3 action on the liver remains unknown. In this study, we analyzed the transcriptome patterns and enzymatic activities in the liver of Scatophagus argus following IGF3 injection. We identified 155 differentially expressed genes (DEGs), which were enriched in terms ‘retinol metabolism’, ‘steroid hormone biosynthesis’, ‘epidermal growth factor receptor tyrosine kinase inhibitor resistance’, and ‘one carbon pool by folate’ in Kyoto Encyclopedia of Genes and Genomes pathway analysis. Notable DEGs included inhbb, shmt2, slc2a5, cyp1a1, got1, mid1ip1, sstr5, hnf6, slc39a14, and hspa1a. The activities of amylase, lipase, malic enzyme, fatty acid synthase, and lipoprotein lipase increased significantly, whereas those of phospholipid hydroperoxide glutathione peroxidase and pyruvate kinase decreased significantly. The combined analysis of transcriptome patterns and enzyme activities suggests IGF3 may promote energy storage and protein synthesis by the liver. These findings indicate IGF3 may support the liver to promote ovarian development and maturation in S. argus.

Oxytosis/Ferroptosis in Neurodegeneration: the Underlying Role of Master Regulator Glutathione Peroxidase 4 (GPX4).

Oxytosis/ferroptosis is an iron-dependent oxidative form of cell death triggered by lethal accumulation of phospholipid hydroperoxides (PLOOHs) in membranes. Failure of the intricate PLOOH repair system is a principle cause of ferroptotic cell death. Glutathione peroxidase 4 (GPX4) is distinctly vital for converting PLOOHs in membranes to non-toxic alcohols. As such, GPX4 is known as the master regulator of oxytosis/ferroptosis. Ferroptosis has been implicated in a number of disorders such as neurodegenerative diseases (amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), etc.), ischemia/reperfusion injury, and kidney degeneration. Reduced function of GPX4 is frequently observed in degenerative disorders. In this study, we examine how diminished GPX4 function may be a critical event in triggering oxytosis/ferroptosis to perpetuate or initiate the neurodegenerative diseases and assess the possible therapeutic importance of oxytosis/ferroptosis in neurodegenerative disorders. These discoveries are important for advancing our understanding of neurodegenerative diseases because oxytosis/ferroptosis may provide a new target to slow the course of the disease.

Study on the Properties and Synergistic Antioxidant Effects of Novel Bifunctional Fusion Proteins Expressed Using the UTuT6 System.

Important antioxidant enzymes, glutathione peroxidase (GPx) and superoxide dismutase (SOD), are involved in maintaining redox balance. They can protect each other and result in more efficiently removing excessive reactive oxygen species (ROS), protecting cells against injury, and maintaining the normal metabolism of ROS. In this study, human cytosolic GPx (hGPx1) and human phospholipid hydroperoxide GPx (hGPx4) genes were integrated into the same open reading frame with human extracellular SOD active site (SOD3-72P) genes, respectively, and several novel fusion proteins were obtained by using the UTuT6 expression system for the first time. Among them, Se-hGPx1UAG-L4-SOD3-72P is the bifunctional fusion protein with the highest GPx activity and the best anti-hydrogen peroxide inactivation ability thus far. The Se-hGPx4UAG-L3-SOD3-72P fusion protein exhibits the strongest alkali and high temperature resistance and a greater protective effect against lipoprotein peroxidation damage. Se-hGPx1UAG-L4-SOD3-72P and Se-hGPx4UAG-L3-SOD3-72P fusion proteins both have good synergistic and antioxidant abilities in H2O2-induced RBCs and liver damage models. We believe that this research will help with the development of novel bifunctional fusion proteins and the investigation of the synergistic and catalytic mechanisms of GPx and SOD, which are important in creating novel protein therapeutics.

Emerging Role of Ferroptosis in Breast Cancer: Characteristics, Therapy, and Translational Implications for the Present and Future.

Ferroptosis is a nonapoptotic, iron-dependent form of cell death that can be actuated in disease cells by expected improvements and manufactured specialists. Different studies have recently resurrected the role of this newly discovered cell death pathway and demonstrated its efficacy in treating breast cancer. Breast cancer is the most well-known type of cancer among women worldwide. Despite many years of research focusing on cell death in breast cancer, counting apoptosis, clinical treatment leftovers are difficult due to the high likelihood of recurrence. Ferroptosis is defined by a lack of lipid peroxide repair capacity by phospholipid hydroperoxides GPX4, accessibility of redox-active iron, and followed oxidation of polyunsaturated fatty acids acid-containing phospholipids signalling, amino acid and iron metabolism, ferritinophagy, epithelial-tomesenchymal transition, cell adhesion, and mevalonate and phospholipid biosynthesis can all be factors that influence ferroptosis susceptibility. Ferroptosis, an iron-dependent controlled cell death caused by excessive lipid peroxidation, has been entwined in breast cancer development and therapeutic response for the past decade. Advances in enhancing clinical drugs targeting ferroptosis are developing silver linings to treat breast cancer. Ferroptosis is influenced by metabolism and the expression of certain genes, making it a prospective therapeutic target for monitoring malignant growth and an appealing target for precision cancer medication disclosure. In the coming years, research into biomarkers to follow ferroptosis in patients with breast cancer and the course of events and the subsequent use of novel ferroptosis-based treatments will be captious. We present a fundamental analysis of the actual understanding of molecular mechanisms along with regulatory networks associated with ferroptosis, expected physiological functions in growth concealment, ferroptosis-associated differentially expressed genes, treatment targeting potential, and recent advances in the development of therapeutic strategies in this review.

Structural and Functional Diversity of the Peroxiredoxin 6 Enzyme Family.

Significance: Peroxiredoxins (Prdxs) with a single peroxidative cysteine (CP) in a conserved motif PXXX(T/S)XXCP within its thioredoxin fold, have been classified as the peroxiredoxin 6 (Prdx6 ) family. All Prdxs can reduce H2O2 and short chain hydroperoxides while Prdx6 in addition, can reduce phospholipid hydroperoxides (PLOOH) due to its ability to interact with peroxidized phospholipid substrate. The single CP of Prdx6 uses various external electron donors including glutathione thioredoxin, and ascorbic acid for resolution of its peroxidized state and, therefore, its peroxidase activity. Prdx6 proteins also exhibit Ca2+-independent phospholipase A2 (PLA2), lysophosphatidylcholine acyltransferase (LPCAT), and chaperone activities that depend on cellular localization and the oxidation and oligomerisation states of the protein. Thus, Prdx6 is a "moonlighting" enzyme. Recent Advance: Physiologically, Prdx6s have been reported to play an important role in protection against oxidative stress, repair of peroxidized cell membranes, mammalian lung surfactant turnover, activation of some NADPH oxidases, the regulation of seed germination in plants, as an indicator of cellular levels of reactive O2 species through Nrf-Klf9 activation, and possibly in male fertility, regulation of cell death through ferroptosis, cancer metastasis, and oxidative stress-related signalling pathways. Critical Issues: This review outlines Prdx6 enzyme unique structural features and explores its wide range of physiological functions. Yet, existing structural data falls short of fully revealing all of human Prdx6 multifunctional roles. Further endeavour is required to bridge this gap in its understanding. Although there are wide variations in both the structure and function of Prdx6 family members in various organisms, all Prdx6 proteins show the unique a long C-terminal extension that is also seen in Prdx1, but not in other Prdxs. Future Directions: As research data continues to accumulate, the potential for detailed insights into the role of C-terminal of Prdx6 in its oligomerisation and activities. There is a need for thorough exploration of structural characteristics of the various biological functions. Additionally, uncovering the interacting partners of Prdx6 and understanding its involvement in signalling pathways will significantly contribute to a more profound comprehension of its role.

Gene deletion of long-chain acyl-CoA synthetase 4 attenuates xenobiotic chemical-induced lung injury via the suppression of lipid peroxidation

Long-chain acyl-CoA synthetase (ACSL) 4 converts polyunsaturated fatty acids (PUFAs) into their acyl-CoAs and plays an important role in maintaining PUFA-containing membrane phospholipids. Here we demonstrated decreases in various kinds of PUFA-containing phospholipid species in ACSL4-deficient murine lung. We then examined the effects of ACSL4 gene deletion on lung injury by treating mice with two pulmonary toxic chemicals: paraquat (PQ) and methotrexate (MTX). The results showed that ACSL4 deficiency attenuated PQ-induced acute lung lesion and decreased mortality. PQ-induced lung inflammation and neutrophil migration were also suppressed in ACSL4-deficient mice. PQ administration increased the levels of phospholipid hydroperoxides in the lung, but ACSL4 gene deletion suppressed their increment. We further found that ACSL4 deficiency attenuated MTX-induced pulmonary fibrosis. These results suggested that ACSL4 gene deletion might confer protection against pulmonary toxic chemical-induced lung injury by reducing PUFA-containing membrane phospholipids, leading to the suppression of lipid peroxidation. Inhibition of ACSL4 may be promising for the prevention and treatment of chemical-induced lung injury.