Compartmentalized mitochondrial ferroptosis converges with optineurin-mediated mitophagy to impact airway epithelial cell phenotypes and asthma outcomes.

A stable mitochondrial pool is crucial for healthy cell function and survival. Altered redox biology can adversely affect mitochondria through induction of a variety of cell death and survival pathways, yet the understanding of mitochondria and their dysfunction in primary human cells and in specific disease states, including asthma, is modest. Ferroptosis is traditionally considered an iron dependent, hydroperoxy-phospholipid executed process, which induces cytosolic and mitochondrial damage to drive programmed cell death. However, in this report we identify a lipoxygenase orchestrated, compartmentally-targeted ferroptosis-associated peroxidation process which occurs in a subpopulation of dysfunctional mitochondria, without promoting cell death. Rather, this mitochondrial peroxidation process tightly couples with PTEN-induced kinase (PINK)-1(PINK1)-Parkin-Optineurin mediated mitophagy in an effort to preserve the pool of functional mitochondria and prevent cell death. These combined peroxidation processes lead to altered epithelial cell phenotypes and loss of ciliated cells which associate with worsened asthma severity. Ferroptosis-targeted interventions of this process could preserve healthy mitochondria, reverse cell phenotypic changes and improve disease outcomes.

Neutrophils and galectin-3 defend mice from lethal bacterial infection and humans from acute respiratory failure.

Respiratory infection by Pseudomonas aeruginosa, common in hospitalized immunocompromised and immunocompetent ventilated patients, can be life-threatening because of antibiotic resistance. This raises the question of whether the host's immune system can be educated to combat this bacterium. Here we show that prior exposure to a single low dose of lipopolysaccharide (LPS) protects mice from a lethal infection by P. aeruginosa. LPS exposure trained the innate immune system by promoting expansion of neutrophil and interstitial macrophage populations distinguishable from other immune cells with enrichment of gene sets for phagocytosis- and cell-killing-associated genes. The cell-killing gene set in the neutrophil population uniquely expressed Lgals3, which encodes the multifunctional antibacterial protein, galectin-3. Intravital imaging for bacterial phagocytosis, assessment of bacterial killing and neutrophil-associated galectin-3 protein levels together with use of galectin-3-deficient mice collectively highlight neutrophils and galectin-3 as central players in LPS-mediated protection. Patients with acute respiratory failure revealed significantly higher galectin-3 levels in endotracheal aspirates (ETAs) of survivors compared to non-survivors, galectin-3 levels strongly correlating with a neutrophil signature in the ETAs and a prognostically favorable hypoinflammatory plasma biomarker subphenotype. Taken together, our study provides impetus for harnessing the potential of galectin-3-expressing neutrophils to protect from lethal infections and respiratory failure.

Ferroptosis in health and disease.

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells' susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with - or caused by - ferroptosis.

Targeting LxCxE cleft pocket of retinoblastoma protein in M2 macrophages inhibits ovarian cancer progression.

Ovarian cancer remains a major health threat with limited treatment options available. It is characterized by immunosuppressive tumor microenvironment (TME) maintained by tumor- associated macrophages (TAMs) hindering anti-tumor responses and immunotherapy efficacy. Here we show that targeting retinoblastoma protein (Rb) by disruption of its LxCxE cleft pocket, causes cell death in TAMs by induction of ER stress, p53 and mitochondria-related cell death pathways. A reduction of pro-tumor Rb high M2-type macrophages from TME in vivo enhanced T cell infiltration and inhibited cancer progression. We demonstrate an increased Rb expression in TAMs in women with ovarian cancer is associated with poorer prognosis. Ex vivo, we show analogous cell death induction by therapeutic Rb targeting in TAMs in post-surgery ascites from ovarian cancer patients. Overall, our data elucidates therapeutic targeting of the Rb LxCxE cleft pocket as a novel promising approach for ovarian cancer treatment through depletion of TAMs and re-shaping TME immune landscape. Statement of significance: Currently, targeting immunosuppressive myeloid cells in ovarian cancer microenvironment is the first priority need to enable successful immunotherapy, but no effective solutions are clinically available. We show that targeting LxCxE cleft pocket of Retinoblastoma protein unexpectedly induces preferential cell death in M2 tumor-associated macrophages. Depletion of immunosuppressive M2 tumor-associated macrophages reshapes tumor microenvironment, enhances anti-tumor T cell responses, and inhibits ovarian cancer. Thus, we identify a novel paradoxical function of Retinoblastoma protein in regulating macrophage viability as well as a promising target to enhance immunotherapy efficacy in ovarian cancer.

International consensus guidelines for the definition, detection, and interpretation of autophagy-dependent ferroptosis.

Macroautophagy/autophagy is a complex degradation process with a dual role in cell death that is influenced by the cell types that are involved and the stressors they are exposed to. Ferroptosis is an iron-dependent oxidative form of cell death characterized by unrestricted lipid peroxidation in the context of heterogeneous and plastic mechanisms. Recent studies have shed light on the involvement of specific types of autophagy (e.g. ferritinophagy, lipophagy, and clockophagy) in initiating or executing ferroptotic cell death through the selective degradation of anti-injury proteins or organelles. Conversely, other forms of selective autophagy (e.g. reticulophagy and lysophagy) enhance the cellular defense against ferroptotic damage. Dysregulated autophagy-dependent ferroptosis has implications for a diverse range of pathological conditions. This review aims to present an updated definition of autophagy-dependent ferroptosis, discuss influential substrates and receptors, outline experimental methods, and propose guidelines for interpreting the results.Abbreviation: 3-MA:3-methyladenine; 4HNE: 4-hydroxynonenal; ACD: accidentalcell death; ADF: autophagy-dependentferroptosis; ARE: antioxidant response element; BH2:dihydrobiopterin; BH4: tetrahydrobiopterin; BMDMs: bonemarrow-derived macrophages; CMA: chaperone-mediated autophagy; CQ:chloroquine; DAMPs: danger/damage-associated molecular patterns; EMT,epithelial-mesenchymal transition; EPR: electronparamagnetic resonance; ER, endoplasmic reticulum; FRET: Försterresonance energy transfer; GFP: green fluorescent protein;GSH: glutathione;IF: immunofluorescence; IHC: immunohistochemistry; IOP, intraocularpressure; IRI: ischemia-reperfusion injury; LAA: linoleamide alkyne;MDA: malondialdehyde; PGSK: Phen Green™ SK;RCD: regulatedcell death; PUFAs: polyunsaturated fatty acids; RFP: red fluorescentprotein;ROS: reactive oxygen species; TBA: thiobarbituricacid; TBARS: thiobarbituric acid reactive substances; TEM:transmission electron microscopy.

PHLDA2-mediated phosphatidic acid peroxidation triggers a distinct ferroptotic response during tumor suppression.

Although the role of ferroptosis in killing tumor cells is well established, recent studies indicate that ferroptosis inducers also sabotage anti-tumor immunity by killing neutrophils and thus unexpectedly stimulate tumor growth, raising a serious issue about whether ferroptosis effectively suppresses tumor development in vivo. Through genome-wide CRISPR-Cas9 screenings, we discover a pleckstrin homology-like domain family A member 2 (PHLDA2)-mediated ferroptosis pathway that is neither ACSL4-dependent nor requires common ferroptosis inducers. PHLDA2-mediated ferroptosis acts through the peroxidation of phosphatidic acid (PA) upon high levels of reactive oxygen species (ROS). ROS-induced ferroptosis is critical for tumor growth in the absence of common ferroptosis inducers; strikingly, loss of PHLDA2 abrogates ROS-induced ferroptosis and promotes tumor growth but has no obvious effect in normal tissues in both immunodeficient and immunocompetent mouse tumor models. These data demonstrate that PHLDA2-mediated PA peroxidation triggers a distinct ferroptosis response critical for tumor suppression and reveal that PHLDA2-mediated ferroptosis occurs naturally in vivo without any treatment from ferroptosis inducers.

A guideline on the molecular ecosystem regulating ferroptosis.

Ferroptosis, an intricately regulated form of cell death characterized by uncontrolled lipid peroxidation, has garnered substantial interest since this term was first coined in 2012. Recent years have witnessed remarkable progress in elucidating the detailed molecular mechanisms that govern ferroptosis induction and defence, with particular emphasis on the roles of heterogeneity and plasticity. In this Review, we discuss the molecular ecosystem of ferroptosis, with implications that may inform and enable safe and effective therapeutic strategies across a broad spectrum of diseases.

Strikingly High Activity of 15-Lipoxygenase Towards Di-Polyunsaturated Arachidonoyl/Adrenoyl-Phosphatidylethanolamines Generates Peroxidation Signals of Ferroptotic Cell Death.

The vast majority of membrane phospholipids (PLs) include two asymmetrically positioned fatty acyls: oxidizable polyunsaturated fatty acids (PUFA) attached predominantly at the sn2 position, and non-oxidizable saturated/monounsaturated acids (SFA/MUFA) localized at the sn1 position. The peroxidation of PUFA-PLs, particularly sn2-arachidonoyl(AA)- and sn2-adrenoyl(AdA)-containing phosphatidylethanolamines (PE), has been associated with the execution of ferroptosis, a program of regulated cell death. There is a minor subpopulation (≈1-2 mol %) of doubly PUFA-acylated phospholipids (di-PUFA-PLs) whose role in ferroptosis remains enigmatic. Here we report that 15-lipoxygenase (15LOX) exhibits unexpectedly high pro-ferroptotic peroxidation activity towards di-PUFA-PEs. We revealed that peroxidation of several molecular species of di-PUFA-PEs occurred early in ferroptosis. Ferrostatin-1, a typical ferroptosis inhibitor, effectively prevented peroxidation of di-PUFA-PEs. Furthermore, co-incubation of cells with di-AA-PE and 15LOX produced PUFA-PE peroxidation and induced ferroptotic death. The decreased contents of di-PUFA-PEs in ACSL4 KO A375 cells was associated with lower levels of di-PUFA-PE peroxidation and enhanced resistance to ferroptosis. Thus, di-PUFA-PE species are newly identified phospholipid peroxidation substrates and regulators of ferroptosis, representing a promising therapeutic target for many diseases related to ferroptotic death.

Vitamin E/Coenzyme Q-Dependent "Free Radical Reductases": Redox Regulators in Ferroptosis.

Significance: Lipid peroxidation and its products, oxygenated polyunsaturated lipids, act as essential signals coordinating metabolism and physiology and can be deleterious to membranes when they accumulate in excessive amounts. Recent Advances: There is an emerging understanding that regulation of polyunsaturated fatty acid (PUFA) phospholipid peroxidation, particularly of PUFA-phosphatidylethanolamine, is important in a newly discovered type of regulated cell death, ferroptosis. Among the most recently described regulatory mechanisms is the ferroptosis suppressor protein, which controls the peroxidation process due to its ability to reduce coenzyme Q (CoQ). Critical Issues: In this study, we reviewed the most recent data in the context of the concept of free radical reductases formulated in the 1980-1990s and focused on enzymatic mechanisms of CoQ reduction in different membranes (e.g., mitochondrial, endoplasmic reticulum, and plasma membrane electron transporters) as well as TCA cycle components and cytosolic reductases capable of recycling the high antioxidant efficiency of the CoQ/vitamin E system. Future Directions: We highlight the importance of individual components of the free radical reductase network in regulating the ferroptotic program and defining the sensitivity/tolerance of cells to ferroptotic death. Complete deciphering of the interactive complexity of this system may be important for designing effective antiferroptotic modalities. Antioxid. Redox Signal. 40, 317-328.

Anomalous peroxidase activity of cytochrome c is the primary pathogenic target in Barth syndrome.

Barth syndrome (BTHS) is a life-threatening genetic disorder with unknown pathogenicity caused by mutations in TAFAZZIN (TAZ) that affect remodeling of mitochondrial cardiolipin (CL). TAZ deficiency leads to accumulation of mono-lyso-CL (MLCL), which forms a peroxidase complex with cytochrome c (cyt c) capable of oxidizing polyunsaturated fatty acid-containing lipids. We hypothesized that accumulation of MLCL facilitates formation of anomalous MLCL-cyt c peroxidase complexes and peroxidation of polyunsaturated fatty acid phospholipids as the primary BTHS pathogenic mechanism. Using genetic, biochemical/biophysical, redox lipidomic and computational approaches, we reveal mechanisms of peroxidase-competent MLCL-cyt c complexation and increased phospholipid peroxidation in different TAZ-deficient cells and animal models and in pre-transplant biopsies from hearts of patients with BTHS. A specific mitochondria-targeted anti-peroxidase agent inhibited MLCL-cyt c peroxidase activity, prevented phospholipid peroxidation, improved mitochondrial respiration of TAZ-deficient C2C12 myoblasts and restored exercise endurance in a BTHS Drosophila model. Targeting MLCL-cyt c peroxidase offers therapeutic approaches to BTHS treatment.

Membrane regulation of 15LOX-1/PEBP1 complex prompts the generation of ferroptotic signals, oxygenated PEs.

Ferroptosis is a regulated form of cell death, the mechanism of which is still to be understood. 15-lipoxygenase (15LOX) complex with phosphatidylethanolamine (PE)-binding protein 1 (PEBP1) catalyzes the generation of pro-ferroptotic cell death signals, hydroperoxy-polyunsaturated PE. We focused on gaining new insights into the molecular basis of these pro-ferroptotic interactions using computational modeling and liquid chromatography-mass spectrometry experiments. Simulations of 15LOX-1/PEBP1 complex dynamics and interactions with lipids revealed that association with the membrane triggers a conformational change in the complex. This conformational change facilitates the access of stearoyl/arachidonoyl-PE (SAPE) substrates to the catalytic site. Furthermore, the binding of SAPE promotes tight interactions within the complex and induces further conformational changes that facilitate the oxidation reaction. The reaction yields two hydroperoxides as products, 15-HpETE-PE and 12-HpETE-PE, at a ratio of 5:1. A significant effect of PEBP1 is observed only on the predominant product. Moreover, combined experiments and simulations consistently demonstrate the significance of PEBP1 P112E mutation in generating ferroptotic cell death signals.

Discovering selective antiferroptotic inhibitors of the 15LOX/PEBP1 complex noninterfering with biosynthesis of lipid mediators.

Programmed ferroptotic death eliminates cells in all major organs and tissues with imbalanced redox metabolism due to overwhelming iron-catalyzed lipid peroxidation under insufficient control by thiols (Glutathione (GSH)). Ferroptosis has been associated with the pathogenesis of major chronic degenerative diseases and acute injuries of the brain, cardiovascular system, liver, kidneys, and other organs, and its manipulation offers a promising new strategy for anticancer therapy. This explains the high interest in designing new small-molecule-specific inhibitors against ferroptosis. Given the role of 15-lipoxygenase (15LOX) association with phosphatidylethanolamine (PE)-binding protein 1 (PEBP1) in initiating ferroptosis-specific peroxidation of polyunsaturated PE, we propose a strategy of discovering antiferroptotic agents as inhibitors of the 15LOX/PEBP1 catalytic complex rather than 15LOX alone. Here we designed, synthesized, and tested a customized library of 26 compounds using biochemical, molecular, and cell biology models along with redox lipidomic and computational analyses. We selected two lead compounds, FerroLOXIN-1 and 2, which effectively suppressed ferroptosis in vitro and in vivo without affecting the biosynthesis of pro-/anti-inflammatory lipid mediators in vivo. The effectiveness of these lead compounds is not due to radical scavenging or iron-chelation but results from their specific mechanisms of interaction with the 15LOX-2/PEBP1 complex, which either alters the binding pose of the substrate [eicosatetraenoyl-PE (ETE-PE)] in a nonproductive way or blocks the predominant oxygen channel thus preventing the catalysis of ETE-PE peroxidation. Our successful strategy may be adapted to the design of additional chemical libraries to reveal new ferroptosis-targeting therapeutic modalities.

The lipase cofactor CGI58 controls placental lipolysis.

In eutherians, the placenta plays a critical role in the uptake, storage, and metabolism of lipids. These processes govern the availability of fatty acids to the developing fetus, where inadequate supply has been associated with substandard fetal growth. Whereas lipid droplets are essential for the storage of neutral lipids in the placenta and many other tissues, the processes that regulate placental lipid droplet lipolysis remain largely unknown. To assess the role of triglyceride lipases and their cofactors in determining placental lipid droplet and lipid accumulation, we assessed the role of patatin like phospholipase domain containing 2 (PNPLA2) and comparative gene identification-58 (CGI58) in lipid droplet dynamics in the human and mouse placenta. While both proteins are expressed in the placenta, the absence of CGI58, not PNPLA2, markedly increased placental lipid and lipid droplet accumulation. These changes were reversed upon restoration of CGI58 levels selectively in the CGI58-deficient mouse placenta. Using co-immunoprecipitation, we found that, in addition to PNPLA2, PNPLA9 interacts with CGI58. PNPLA9 was dispensable for lipolysis in the mouse placenta yet contributed to lipolysis in human placental trophoblasts. Our findings establish a crucial role for CGI58 in placental lipid droplet dynamics and, by extension, in nutrient supply to the developing fetus.

Visualizing Cardiolipin In Situ with HKCL-1M, a Highly Selective and Sensitive Fluorescent Probe.

Reliable probing of cardiolipin (CL) content in dynamic cellular milieux presents significant challenges and great opportunities for understanding mitochondria-related diseases, including cancer, neurodegeneration, and diabetes mellitus. In intact respiring cells, selectivity and sensitivity for CL detection are technically demanding due to structural similarities among phospholipids and compartmental secludedness of the inner mitochondrial membrane. Here, we report a novel "turn-on" fluorescent probe HKCL-1M for detecting CL in situ. HKCL-1M displays outstanding sensitivity and selectivity toward CL through specific noncovalent interactions. In live-cell imaging, its hydrolyzed product HKCL-1 efficiently retained itself in intact cells independent of mitochondrial membrane potential (Δψm). The probe robustly co-localizes with mitochondria and outperforms 10-N-nonyl acridine orange (NAO) and Δψm-dependent dyes with superior photostability and negligible phototoxicity. Our work thus opens up new opportunities for studying mitochondrial biology through efficient and reliable visualization of CL in situ.

Redox phospholipidomics discovers pro-ferroptotic death signals in A375 melanoma cells in vitro and in vivo.

Growing cancer cells effectively evade most programs of regulated cell death, particularly apoptosis. This necessitates a search for alternative therapeutic modalities to cause cancer cell's demise, among them - ferroptosis. One of the obstacles to using pro-ferroptotic agents to treat cancer is the lack of adequate biomarkers of ferroptosis. Ferroptosis is accompanied by peroxidation of polyunsaturated species of phosphatidylethanolamine (PE) to hydroperoxy- (-OOH) derivatives, which act as death signals. We demonstrate that RSL3-induced death of A375 melanoma cells in vitro was fully preventable by ferrostatin-1, suggesting their high susceptibility to ferroptosis. Treatment of A375 cells with RSL3 caused a significant accumulation of PE-(18:0/20:4-OOH) and PE-(18:0/22:4-OOH), the biomarkers of ferroptosis, as well as oxidatively truncated products - PE-(18:0/hydroxy-8-oxo-oct-6-enoic acid (HOOA) and PC-(18:0/HOOA). A significant suppressive effect of RSL3 on melanoma growth was observed in vivo (utilizing a xenograft model of inoculation of GFP-labeled A375 cells into immune-deficient athymic nude mice). Redox phospholipidomics revealed elevated levels of 18:0/20:4-OOH in RSL3-treated group vs controls. In addition, PE-(18:0/20:4-OOH) species were identified as major contributors to the separation of control and RSL3-treated groups, with the highest variable importance in projection predictive score. Pearson correlation analysis revealed an association between tumor weight and contents of PE-(18:0/20:4-OOH) (r = -0.505), PE-18:0/HOOA (r = -0.547) and PE 16:0-HOOA (r = -0.503). Thus, LC-MS/MS based redox lipidomics is a sensitive and precise approach for the detection and characterization of phospholipid biomarkers of ferroptosis induced in cancer cells by radio- and chemotherapy.

Functional states of myeloid cells in cancer.

Myeloid cells, comprised of macrophages, dendritic cells, monocytes, and granulocytes, represent a major component of the tumor microenvironment (TME) and are critically involved in regulation of tumor progression and metastasis. In recent years, single-cell omics technologies have identified multiple phenotypically distinct subpopulations. In this review, we discuss recent data and concepts suggesting that the biology of myeloid cells is largely defined by a very limited number of functional states that transcend the narrowly defined cell populations. These functional states are primarily centered around classical and pathological states of activation, with the latter state commonly defined as myeloid-derived suppressor cells. We discuss the concept that lipid peroxidation of myeloid cells represents a major mechanism that governs their pathological state of activation in the TME. Lipid peroxidation is associated with ferroptosis mediating suppressive activity of these cells and thus could be considered an attractive target for therapeutic intervention.

Oxoglutarate dehydrogenase complex controls glutamate-mediated neuronal death.

Brain injury is accompanied by neuroinflammation, accumulation of extracellular glutamate and mitochondrial dysfunction, all of which cause neuronal death. The aim of this study was to investigate the impact of these mechanisms on neuronal death. Patients from the neurosurgical intensive care unit suffering aneurysmal subarachnoid hemorrhage (SAH) were recruited retrospectively from a respective database. In vitro experiments were performed in rat cortex homogenate, primary dissociated neuronal cultures, B35 and NG108-15 cell lines. We employed methods including high resolution respirometry, electron spin resonance, fluorescent microscopy, kinetic determination of enzymatic activities and immunocytochemistry. We found that elevated levels of extracellular glutamate and nitric oxide (NO) metabolites correlated with poor clinical outcome in patients with SAH. In experiments using neuronal cultures we showed that the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme of the glutamate-dependent segment of the tricarboxylic acid (TCA) cycle, is more susceptible to the inhibition by NO than mitochondrial respiration. Inhibition of OGDHC by NO or by succinyl phosphonate (SP), a highly specific OGDHC inhibitor, caused accumulation of extracellular glutamate and neuronal death. Extracellular nitrite did not substantially contribute to this NO action. Reactivation of OGDHC by its cofactor thiamine (TH) reduced extracellular glutamate levels, Ca2+ influx into neurons and cell death rate. Salutary effect of TH against glutamate toxicity was confirmed in three different cell lines. Our data suggest that the loss of control over extracellular glutamate, as described here, rather than commonly assumed impaired energy metabolism, is the critical pathological manifestation of insufficient OGDHC activity, leading to neuronal death.

Melanoma-associated repair-like Schwann cells suppress anti-tumor T-cells via 12/15-LOX/COX2-associated eicosanoid production.

Peripheral glia, specifically the Schwann cells (SCs), have been implicated in the formation of the tumor microenvironment (TME) and in cancer progression. However, in vivo and ex vivo analyses of how cancers reprogram SC functions in different organs of tumor-bearing mice are lacking. We generated Plp1-CreERT/tdTomato mice which harbor fluorescently labeled myelinated and non-myelin forming SCs. We show that this model enables the isolation of the SCs with high purity from the skin and multiple other organs. We used this model to study phenotypic and functional reprogramming of the SCs in the skin adjacent to melanoma tumors. Transcriptomic analyses of the peritumoral skin SCs versus skin SCs from tumor-free mice revealed that the former existed in a repair-like state typically activated during nerve and tissue injury. Peritumoral skin SCs also downregulated pro-inflammatory genes and pathways related to protective anti-tumor responses. In vivo and ex vivo functional assays confirmed immunosuppressive activities of the peritumoral skin SCs. Specifically, melanoma-reprogrammed SCs upregulated 12/15-lipoxygenase (12/15-LOX) and cyclooxygenase (COX)-2, and increased production of anti-inflammatory polyunsaturated fatty acid (PUFA) metabolites prostaglandin E2 (PGE2) and lipoxins A4/B4. Inhibition of 12/15-LOX or COX2 in SCs, or EP4 receptor on lymphocytes reversed SC-dependent suppression of anti-tumor T-cell activation. Therefore, SCs within the skin adjacent to melanoma tumors demonstrate functional switching to repair-like immunosuppressive cells with dysregulated lipid oxidation. Our study suggests the involvement of the melanoma-associated repair-like peritumoral SCs in the modulation of locoregional and systemic anti-tumor immune responses.

Ferroptotic mechanisms and therapeutic targeting of iron metabolism and lipid peroxidation in the kidney.

Ferroptosis is a mechanism of regulated necrotic cell death characterized by iron-dependent, lipid peroxidation-driven membrane destruction that can be inhibited by glutathione peroxidase 4. Morphologically, it is characterized by cellular, organelle and cytoplasmic swelling and the loss of plasma membrane integrity, with the release of intracellular components. Ferroptosis is triggered in cells with dysregulated iron and thiol redox metabolism, whereby the initial robust but selective accumulation of hydroperoxy polyunsaturated fatty acid-containing phospholipids is further propagated through enzymatic and non-enzymatic secondary mechanisms, leading to formation of oxidatively truncated electrophilic species and their adducts with proteins. Thus, ferroptosis is dependent on the convergence of iron, thiol and lipid metabolic pathways. The kidney is particularly susceptible to redox imbalance. A growing body of evidence has linked ferroptosis to acute kidney injury in the context of diverse stimuli, such as ischaemia-reperfusion, sepsis or toxins, and to chronic kidney disease, suggesting that ferroptosis may represent a novel therapeutic target for kidney disease. However, further work is needed to address gaps in our understanding of the triggers, execution and spreading mechanisms of ferroptosis.