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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. [ABSTRACT FROM AUTHOR]

High fidelity of biological systems is frequently achieved by duplication of the essential intracellular machineries or, removal of the entire cell, which becomes unnecessary or even harmful in altered physiological environments. Carefully controlled removal of these cells, without damaging normal cells, requires precise signaling, and is critical to maintaining homeostasis. This review describes how two anionic phospholipids - phosphatidylserine (PS) and cardiolipin (CL) - residing in distinct compartments of the cell, signal removal of “the unnecessary” using several uniform principles. One of these principles is realized by collapse of inherent transmembrane asymmetry and the externalization of the signal on the outer membrane surface - mitochondria for CL and the plasma membrane for PS – to trigger mitophagy and phagocytosis, respectively. Release from damaged cells of intracellular structures with externalized CL or externalized PS triggers their elimination by phagocytosis. Another of these principles is realized by oxidation of polyunsaturated species of CL and PS. Highly specific oxidation of CL by cytochrome c serves as a signal for mitochondria-dependent apoptosis, while oxidation of externalized PS improves its effectiveness to trigger phagocytosis of effete cells. [ABSTRACT FROM AUTHOR]

Significance: An ancient anionic phospholipid, cardiolipin (CL), ubiquitously present in prokaryotic and eukaryotic membranes, is essential for several structural and functional purposes. Recent Advances: The emerging role of CLs in signaling has become the focus of many studies. Critical Issues: In this work, we describe two major pathways through which mitochondrial CLs may fulfill the signaling functions via utilization of their (i) asymmetric distribution across membranes and translocations, leading to the surface externalization and (ii) ability to undergo oxidation reactions to yield the signature products recognizable by the executionary machinery of cells. Future Directions: We present a concept that CLs and their oxidation/hydrolysis products constitute a rich communication language utilized by mitochondria of eukaryotic cells for diversified regulation of cell physiology and metabolism as well as for inter-cellular interactions. Antioxid. Redox Signal. 22, 1667-1680. [ABSTRACT FROM AUTHOR]

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. Van Vlerken-Ysla et al. discuss that functional states of myeloid cells transcend single-cell omics-based cell clusters and outline factors involved in diversification of these cells in the bone marrow, periphery, and tumor microenvironment. They propose that lipid peroxidation represents a major mechanism governing their pathological state of activation, potentially providing a therapeutic vulnerability. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cardiolipin asymmetries. [•] Reduced trans-membrane asymmetry and externalization of CLs leads to mitophagy. [•] Translocation and peroxidation of CL in apoptosis. [•] Molecular asymmetry of cardiolipins and their oxidation products. [•] CL asymmetry as a new therapeutic target. [Copyright &y& Elsevier]

Abstract: Over the past two decades, nanotechnology has emerged as a key player in various disciplines of science and technology. Some of the most exciting applications are in the field of biomedicine – for theranostics (for combined diagnostic and therapeutic purposes) as well as for exploration of biological systems. A detailed understanding of the molecular interactions between nanoparticles and biological nano-machinery – macromolecules, membranes, and intracellular organelles – is crucial for obtaining adequate information on mechanisms of action of nanomaterials as well as a perspective on the long term effects of these materials and their possible toxicological outcomes. This review focuses on the use of structure-based computational molecular modeling as a tool to understand and to predict the interactions between nanomaterials and nano-biosystems. We review major approaches and provide examples of computational analysis of the structural principles behind such interactions. A rationale on how nanoparticles of different sizes, shape, structure and chemical properties can affect the organization and functions of nano-machinery of cells is also presented. [Copyright &y& Elsevier]

We have shown previously that single-walled carbon nanotubes can be catalytically biodegraded over several weeks by the plant-derived enzyme, horseradish peroxidase. However, whether peroxidase intermediates generated inside human cells or biofluids are involved in the biodegradation of carbon nanotubes has not been explored. Here, we show that hypochlorite and reactive radical intermediates of the human neutrophil enzyme myeloperoxidase catalyse the biodegradation of single-walled carbon nanotubes in vitro, in neutrophils and to a lesser degree in macrophages. Molecular modelling suggests that interactions of basic amino acids of the enzyme with the carboxyls on the carbon nanotubes position the nanotubes near the catalytic site. Importantly, the biodegraded nanotubes do not generate an inflammatory response when aspirated into the lungs of mice. Our findings suggest that the extent to which carbon nanotubes are biodegraded may be a major determinant of the scale and severity of the associated inflammatory responses in exposed individuals. [ABSTRACT FROM AUTHOR]

Engineered nanomaterials have unique physico-chemical properties that make them promising for many technological and biomedical applications, including tissue regeneration, drug and gene delivery and in vivo monitoring of disease processes. However, with the burgeoning capabilities to manipulate structures at the nanoscale, intentional as well as unintentional human exposures to engineered nanomaterials are set to increase. Nanotoxicology is an emerging discipline focused on understanding the properties of engineered nanomaterials and their interactions with biological systems, and may be viewed as the study of the undesirable interference between man-made nanomaterials and cellular nanostructures or nanomachines. In this review, we discuss recognition of engineered nanomaterials by the immune system, our primary defense system against foreign invasion. Moreover, as oxidative stress is believed to be one of the major deleterious consequences of exposure to nanomaterials, we explore triggering of pro- and antioxidant pathways as well as biomarkers of oxidauve stress. Finally, we highlight in vivo studies of the toxicological outcomes of engineered nanomaterials, including carbon nanotubes, with an emphasis on inflammation and genotoxic responses. [ABSTRACT FROM AUTHOR]

Abstract: Effective regulation of highly compartmentalized production of reactive oxygen species and peroxidation reactions in mitochondria requires targeting of small molecule antioxidants and antioxidant enzymes into the organelles. This review describes recently developed approaches to mitochondrial targeting of small biologically active molecules based on: (i) preferential accumulation in mitochondria because of their hydrophobicity and positive charge (hydrophobic cations), (ii) binding with high affinity to an intra-mitochondrial constituent, and (iii) metabolic conversions by specific mitochondrial enzymes to reveal an active entity. In addition, targeted delivery of antioxidant enzymes via expression of leader sequences directing the proteins into mitochondria is considered. Examples of successful antioxidant and anti-apoptotic protection based on the ability of targeted cargoes to inhibit cytochrome c-catalyzed peroxidation of a mitochondria-specific phospholipid cardiolipin, in vitro and in vivo are presented. Particular emphasis is placed on the employment of triphenylphosphonium- and hemi-gramicidin S-moieties as two effective vehicles for mitochondrial delivery of antioxidants. [Copyright &y& Elsevier]

Abstract: Recently, phospholipid peroxidation products gained a reputation as key regulatory molecules and participants in oxidative signaling pathways. During apoptosis, a mitochondria-specific phospholipid, cardiolipin (CL), interacts with cytochrome c (cyt c) to form a peroxidase complex that catalyzes CL oxidation; this process plays a pivotal role in the mitochondrial stage of the execution of the cell death program. This review is focused on redox mechanisms and essential structural features of cyt c’s conversion into a CL-specific peroxidase that represent an interesting and maybe still unique example of a functionally significant ligand change in hemoproteins. Furthermore, specific characteristics of CL in mitochondria—its asymmetric transmembrane distribution and mechanisms of collapse, the regulation of its synthesis, remodeling, and fatty acid composition—are given significant consideration. Finally, new concepts in drug discovery based on the design of mitochondria-targeted inhibitors of cyt c/CL peroxidase and CL peroxidation with antiapoptotic effects are presented. [Copyright &y& Elsevier]

Manganese superoxide dismutase (MnSOD) provides the first line of defense against superoxide generated in mitochondria. SOD competes with nitric oxide for reaction with superoxide and prevents generation of peroxynitrite, a potent oxidant that can modify proteins to form 3-nitrotyrosine. Thus, sufficient amounts of catalytically competent MnSOD are required to prevent mitochondrial damage. Increased nitrotyrosine immunoreactivity has been reported after traumatic brain injury (TBI); however, the specific protein targets containing modified tyrosine residues and functional consequence of this modification have not been identified. In this study, we show that MnSOD is a target of tyrosine nitration that is associated with a decrease in its enzymatic activity after TBI in mice. Similar findings were obtained in temporal lobe cortical samples obtained from TBI cases versus control patients who died of causes not related to CNS trauma. Increased nitrotyrosine immunoreactivity was detected at 2 h and 24 h versus 72 h after experimental TBI and co-localized with the neuronal marker NeuN. Inhibition and/or genetic deficiency of neuronal nitric oxide synthase (nNOS) but not endothelial nitric oxide synthase (eNOS) attenuated MnSOD nitration after TBI. At 24 h after TBI, there was predominantly polymorphonuclear leukocytes accumulation in mouse brain whereas macrophages were the predominant inflammatory cell type at 72 h after injury. However, a selective inhibitor or genetic deficiency of inducible nitric oxide synthase (iNOS) failed to affect MnSOD nitration. Nitration of MnSOD is a likely consequence of peroxynitrite within the intracellular milieu of neurons after TBI. Nitration and inactivation of MnSOD could lead to self-amplification of oxidative stress in the brain progressively enhancing peroxynitrite production and secondary damage. [ABSTRACT FROM AUTHOR]

Programmed death (apoptosis) is turned on in damaged or unwanted cells to secure their clean and safe self-elimination. The initial apoptotic events are coordinated in mitochondria, whereby several proapoptotic factors, including cytochrome c, are released into the cytosol to trigger caspase cascades. The release mechanisms include interactions of B-cell/lymphoma 2 family proteins with a mitochondria-specific phospholipid, cardiolipin, to cause permeabilization of the outer mitochondrial membrane. Using oxidative lipidomics, we showed that cardiolipin is the only phospholipid in mitochondria that undergoes early oxidation during apoptosis. The oxidation is catalyzed by a cardiolipin-specific peroxidase activity of cardiolipin-bound cytochrome c. In a previously undescribed step in apoptosis, we showed that oxidized cardiolipin is required for the release of proapoptotic factors. These results provide insight into the role of reactive oxygen species in triggering the cell-death pathway and describe an early role for cytochrome c before caspase activation. [ABSTRACT FROM AUTHOR]

Studies in experimental traumatic brain injury (TBI) suggest both deleterious and protective effects of inducible nitric oxide synthase (iNOS). Early after injury, iNOS may be detrimental via formation of peroxynitrite and iNOS inhibitors are protective. In contrast, we reported impaired long-term functional outcome after TBI in iNOS knockout (ko) versus wild-type (wt) mice. To elucidate potential neuroprotective and neurotoxic mechanisms for iNOS, we studied nitric oxide formation by electron paramagnetic resonance (EPR) spectroscopy using diethyldithiocarbamate–iron (DETC–Fe) as a spin trap and markers of nitrosative (S-nitrosothiol (RSNO, Fluorescent assay); nitrotyrosine (3NT, ELISA)) and oxidative stress (ascorbate, HPLC) at 72 h after controlled cortical impact (CCI) in iNOS ko and wt and in uninjured iNOS ko and wt mice. 3NT immunostaining with macrophage and myeloperoxidase (MPO) dual labeling was also assessed in brain sections. Brain DETC–Fe–NO low-temperature EPR signal intensity was ∼2-fold greater in wt versus iNOS ko at 72 h after CCI. Ascorbate levels decreased in injured hemisphere in wt and iNOS ko versus uninjured —this decrease was more pronounced in iNOS ko. In wt mice, RSNO and 3NT levels were increased after CCI versus uninjured (50% and 400%, respectively, P<0.05). RSNO levels were not increased in iNOS ko after CCI. Nitrotyrosine levels increased after CCI in wt and ko versus respective uninjured —this increase was more pronounced in wt (2.34±0.95 versus 1.27±0.49 pmol/mg protein, P<0.05). Increased 3NT immunoreactivity was detected in wt versus iNOS ko at 72 h after CCI, and colocalized with macrophage marker and MPO. Our data support a role for iNOS-derived NO as an endogenous antioxidant after CCI. iNOS also contributes protein nitrosylation and nitration. Colocalization of 3NT with macrophages and MPO suggests generation of nitrating agents by macrophages and/or phagocytosis of nitrated proteins.Journal of Cerebral Blood Flow & Metabolism (2005) 25, 673–684. doi:10.1038/sj.jcbfm.9600068 Published online 16 February 2005 [ABSTRACT FROM AUTHOR]

Abstract: Mitochondria play a central role in the life and death of cells. These organelles serve as the major energy-producing powerhouse, whereby the generation of ATP is associated with the utilization of molecular oxygen. A significant fraction (2–3%) of molecular oxygen consumed by mitochondria may be reduced in a one-electron fashion to yield a series of reactive oxygen species (ROS) such as superoxide anion radical, hydrogen peroxide, and hydroxyl radical. ROS are capable of damaging components of the electron transport apparatus and can, in turn, disrupt mitochondrial functioning, limiting cellular ATP levels and ultimately resulting in cell death. ROS-induced disruption of electron transport can perpetuate production of deleterious ROS and propagate mitochondrial damage. Consequently, mitochondria are highly enriched with water-soluble and lipid-soluble antioxidants (glutathione, ascorbate, Vitamin E, and coenzyme Q) and antioxidant enzymes, such as superoxide dismutase, glutathione peroxidase, catalase, thioredoxins, and peroxiredoxin. Another important antioxidant acting as a very effective scavenger of reactive lipid (peroxyl, alkoxyl) radicals is nitric oxide (NO) generated by mitochondrial nitric oxide synthase. However, NO can also be very disruptive to mitochondria function, a process facilitated by its high reactivity with superoxide. This interaction results in the formation of peroxynitrite, an oxidant capable of causing oxidative/nitrosative stress, further aggravating mitochondrial dysfunction, causing ATP depletion and damage to cells. Thus, in the most general sense, the effects of NO in mitochondria may be either protective or deleterious depending on specific conditions of local redox environment (redox potential, ratio of oxidized to reduced glutathione, transition metals, and the presence of other oxygen- and nitrogen-centered radicals). [Copyright &y& Elsevier]

Abstract: The primary life-supporting function of cytochrome c (cyt c) is control of cellular energetic metabolism as a mobile shuttle in the electron transport chain of mitochondria. Recently, cyt c''s equally important life-terminating function as a trigger and regulator of apoptosis was identified. This dreadful role is realized through the relocalization of mitochondrial cyt c to the cytoplasm where it interacts with Apaf-1 in forming apoptosomes and mediating caspase-9 activation. Although the presence of heme moiety of cyt c is essential for the latter function, cyt c''s redox catalytic features are not required. Lately, two other essential functions of cyt c in apoptosis, that may rely heavily on its redox activity have been suggested. Both functions are directed toward oxidation of two negatively charged phospholipids, cardiolipin (CL) in the mitochondria and phosphatidylserine (PS) in the plasma membrane. In both cases, oxidized phospholipids seem to be essential for the transduction of two distinctive apoptotic signals: one is participation of oxidized CL in the formation of the mitochondrial permeability transition pore that facilitates release of cyt c into the cytosol and the other is the contribution of oxidized PS to the externalization and recognition of PS (and possibly oxidized PS) on the cell surface by specialized receptors of phagocytes. In this review, we present a new concept that cyt c actuates both of these oxidative roles through a uniform mechanism: its specific interactions with each of these phospholipids result in the conversion and activation of cyt c, transforming it from an innocuous electron transporter into a calamitous peroxidase capable of oxidizing the activating phospholipids. We also show that this new concept is compatible with a leading role for reactive oxygen species in the execution of the apoptotic program, with cyt c as the main executioner. [Copyright &y& Elsevier]

Inflammation is a beneficial host response to foreign challenge involving numerous soluble factors and cell types, including polymorphonuclear granulocytes or neutrophils. Programmed cell death (apoptosis) of neutrophils has been documented in vitro as well as in vivo, and is thought to be important for the resolution of inflammation, as this process allows for engulfment and removal of senescent cells prior to their necrotic disintegration. Studies in recent years have begun to unravel the mechanism of macrophage clearance of apoptotic cells, and evidence has accrued for a critical role of externalization and oxidation of plasma membrane phosphatidylserine, and its subsequent recognition by macrophage receptors, in this process. Activated neutrophils generate vast amounts of reactive oxygen species for the purpose of killing ingested micro-organisms, and these reactive metabolites may also modulate the life-span, as well as the clearance, of the neutrophil itself. This review aims to address the latter topic, as well as to summarize current knowledge on the molecular mechanisms of neutrophil apoptosis and macrophage clearance of these cells at the site of inflammation. [ABSTRACT FROM AUTHOR]

Objective. To test the hypothesis that enhanced oxidative stress during pregnancies complicated by preeclampsia is associated with improper copper (Cu) binding by plasma albumin, resulting in enhanced Cu redox-cycling activity and that altered Cu binding, in turn, is caused by interactions of excessive amounts of free fatty acids with albumin. Study Design. We studied binding and redox-cycling activity of Cu in 17 normal pregnancy and 17 preeclampsia plasma samples. Binding of exogenous Cu in plasma samples was quantified indirectly using spectrophotometric measurements of its complex with a specific chelator of Cu(I), bathocuproine disulfonate. Redox-cycling activity of Cu in plasma samples was estimated by electron paramagnetic resonance (EPR) spectroscopy of ascorbate radicals formed during one-electron oxidation of ascorbate by redox-active catalytic Cu. Formation of Cu/albumin complexes in model systems in the presence and absence of fatty acids was studied using EPR spectroscopy of Cu(II)/albumin. Results. We found that preeclampsia plasma (as compared to normal pregnancy plasma) (1) displays elevated endogenous ascorbate redox-cycling that is normalized by a Cu(II) chelator, cuprizone I, (2) has lowered capacity to bind and redox-regulate exogenously added Cu, and (3) responds to treatment with fatty-acid-free albumin by diminished ascorbate oxidizing activity. Conversely, addition of free fatty acid (oleic acid) to normal pregnancy plasma sample yields increased ascorbate redox-cycling activity. Our model experiments showed that Cu-dependent redox-cycling activity of purified human serum albumin is significantly increased by excess free fatty acids. Conclusion. Mishandling of Cu by albumin contributes to oxidative stress in preeclampsia. Cu chelators may represent promising mechanism-based antioxidants to attenuate oxidative stress in preeclampsia. [ABSTRACT FROM AUTHOR]

Tests the hypothesis that the toxicity of 6-hydroxydopamine is caused by its interaction with serum ferric transferrin resulting in release of iron. Additional hypothesis that this iron triggers generation of reactive oxygen species; Emphasis on the physiological and pharmacological relevance of 6-hydroxydopamine-mediated iron release from ferric transferrin.

Reports on the interactions of ascorbate throls (glutathione, dihydrolipoic acid, and metallothioneins), and its combinations with the phenoxyl radical generated by tyrosynase-catalyzed oxidation of VP-16, a phenol widely used as an anti tumor drug. Description of materials and methods; Results of the report; Discussion of results.

Explores the role of lipid peroxidation in live cells as a potential molecular target for apoptotic signaling and Bcl-2 action. Oxidative stress; Apoptosis in mouse 32D cells caused by paraquat; Anti-apoptotic action of Bcl-2 early after oxidant stress; Inhibition of lipid peroxidation.

Investigates the influence of Bcl-2 on selective oxidation and externalization of phosphatidylserine (PS) during paraquat-induced apoptosis. Overexpression of Bcl-2; Deoxyribonucleic acid fragmentation; Lipid peroxidation and apoptosis; Role of lipid peroxidation in apoptosis during oxidative stress.

Examines the physiological characteristics of the paraquat-induced phosphatidylserine oxidation and apoptosis in connection with the independent-activation of phospholipase A2 (PLA2). Definition of paraquat; Information on the potential of the activation of phospholipid hydrolysis; Reference to the procedures used for cells.

Presents a study which examines whether myocardial ischemic reperfusion injury is mediated by apoptotic cell death, isolated perfused rat hearts were subjected to minutes of ischemia as well as reperfusion. Methodology used to conduct the study; Discussion based on the results of the study.

The intrinsic fluorescence of tocopherol homologues with hydrocarbon chains ranging from 1 carbon (C1) to 16 carbons (α-tocopherol, C16) and their ability to quench the fluorescence of 9-anthroyloxy derivatives of fatty acids with the fluorophore located at different positions in the hydrophobic domain of phospholipid bilayers has been used to model the interaction of tocopherol with lipid bilayer membranes. All the tocopherol homologues used, C1, C6, C11 and α-tocopherol, showed a similar fluorescence emission intensity at 325 nm in cyclohexane but were almost completely self-quenched by aggregation in water. Fluorescence was restored when dispersions of dimyristoylglycerophosphocholine were added but the maximum intensity was lower with the longer-chain homologues. Full intensity was observed in all homologues on addition of the detergent Triton X-100. Studies using 9-anthracenecarboxylic acid and 9-anthracenecarboxymethyl ester, 6-(9-anthroyloxy)stearic acid and 16-(9anthroyloxy)palmitelaidic acid showed that the tocopherol homologues partitioned into the hydrophobic domain of phospholipid dispersions composed of dimyristoylglycerophosphocholine at 40°C and dioleoylglycerophosphocholine at 40°C. The 9-anthroyloxy fatty acids and 1,6-diphenyl-1,3.5-hexatriene were quenched by all the homologues and Stern-Volmer plots of the concentration dependence of the quenching indicated that this was predominantly via dynamic processes. No fluorescence energy transfer was observed between diphenylhexatriene and tocopberols but efficient transfer was recorded to the 9-anthroyloxy fatty acid probes. The results are consistent with a model in which the chromanol nucleus of tocopherol is oriented towards the lipid-water interface of the phospholipid bilayer. As the phytol chain length increases there is an increasing tendency for the chromanol nucleus to reside in the hydrophobic interior of the structure. α-Tocopherol appears to form clusters within the phospholipid dispersion which are not fluorescent and do not quench the fluorescence of the different fluorescent probes nor transfer fluorescence energy to them. It is suggested that the monomeric form is responsible for the vitamin effects of tocopherol and the aggregated form acts as a reservoir that does not markedly perturb bilayer stability. [ABSTRACT FROM AUTHOR]

Examines whether myocardial ischemic reperfusion injury is mediated by apoptotic cell death. Effect of ischemia-reperfusion on DNA fragmentation; Phospholipid distribution of cardiomyocytes obtained from control, ischemic and ischemic reperfused hearts.

Investigates the potential role of paraquat-induced phosphatidylserine oxidation and apoptosis in the activation of phospholipase (PLA). Analysis of mechanisms of cellular damage caused by paraquat; Potential effect of lipid peroxidation on membrane fluidity; Linkage of tumor necrosis factor in the induction of apoptosis.

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. [Display omitted] • Association with membrane triggers an opening in the 15LOX-1/PEBP1 complex that enables substrate (SAPE) access to the catalytic site. • SAPE binding induces tight interactions and conformational changes in 15LOX-1/PEBP1 to facilitate the hydroperoxidation reaction. • Two products, 15- and 12-HpETE-PE, are produced upon hydroperoxidation of SAPE in the ratio 5:1. • PEBP1 plays a significant role in the generation of 15-HpETE-PE. • The PEBP1 mutation P112E impairs the generation of the ferroptotic cell death signal. [ABSTRACT FROM AUTHOR]

From the very early stages since the emergence of life on our planet, phospholipids played a very essential role by fulfilling two major functions: 1) as structural building blocks of membranes, and 2) as communication signals. Among many different mechanisms, oxygenation of polyunsaturated lipids played an essential role in coordinating numerous metabolic reactions and pathways, including death programs. Cells overpowered by viruses or bacterial pathogens or overburdened with genotoxic material are destined to die through one of the strictly coordinated death pathways. As several new programs of cell death have been discovered, they turned to be closely interconnected and failure of one of them inevitably triggers another one such the ultimate goal - elimination of the damaged cell representing high risk for the multicellular community - is achieved. This paramount role of oxygenated polyunsaturated lipids in regulation is also associated with a risk of their involvement in aberrant injury reactions due to lipid peroxidation and the production of secondary reactive lipid electrophiles. In this talk, we will discuss how redox lipidomics discovered specific predictive oxygenated phospholipid biomarkers acting as signals in two important death programs - apoptosis and ferroptosis. We will present mechanistic data describing the enzymatic machinery that generates highly specific oxygenated phospholipids - cardiolipins and phosphatidylethanolamines in apoptosis and ferroptosis, respectively. [ABSTRACT FROM AUTHOR]

Since the emergence of life on our planet, phospholipids played a very essential role by fulfilling two major functions as: 1) structural components of membranes, and 2) as signaling molecules. The latter is mostly associated with oxygenation of polyunsaturated (phospho)lipids. In this talk, I will focus on the role, mechanisms and regulation of phospholipid oxidation in ferroptosis, the latest addition to the list of regulated cell death pathways. The data will be presented linking ferroptosis with catalytic activity of 15-lipoxygenases and their allosteric regulation by a scaffold-protein, PEBP1, resulting in the generation of 15-hydro-peroxy-arachidonoyl(adrenoyl)-phosphatidylethanolamines. Examples illustrating the contribution of ferroptosis in vivo will be presented such as asthma exacerbations, acute renal injury and traumatic brain injury. Potential role of bacterial lipoxygenases will be considered in lieu of their propensity to oxidize membrane phospholipids. [ABSTRACT FROM AUTHOR]

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. Ferroptosis is an iron-dependent mechanism of regulated necrosis that is driven by the robust oxidation of polyunsaturated fatty acid-containing phospholipids. This Review describes the fundamental mechanisms of ferroptosis, the potential contribution of ferroptosis to kidney disease and therapeutic strategies for targeting ferroptosis. Key points: Multiple cell death pathways contribute to the pathogenesis of acute and chronic kidney injury; ferroptosis is one such mechanism of regulated necrotic cell death, characterized by marked oxidation of phospholipids containing polyunsaturated fatty acids. Ferroptotic death programs are triggered in cells with dysregulated iron and thiol redox metabolism, leading to robust but selective lipid peroxidation, which is propagated through enzymatic and non-enzymatic mechanisms. The excessive accumulation of hydroperoxy-derivatives of arachidonoyl- and adrenoyl-phosphatidylethanolamines is catalysed by a complex of 15-lipoxygenase with phosphatidylethanolamine-binding protein 1 and represents a potential therapeutic target. GPX4 detoxifies phospholipid hydroperoxides to non-toxic phospholipid alcohols using glutathione as a source of reducing equivalents, thus preventing ferroptotic cell death. iNOS, NO•, Ca2+-independent phospholipase A2β and FSP1 can eliminate ferroptotic lipid peroxidation products and prevent ferroptosis in cells that lack GPX4 catalytic activity. Increased levels of urinary ferroptotic phospholipid hydroperoxides are associated with non-recovery of kidney function in patients with acute kidney injury. [ABSTRACT FROM AUTHOR]

Necroptosis is one the best-characterized forms of regulated necrosis. Necroptosis is mediated by the kinase activities of receptor interacting protein kinase-1 and receptor interacting protein kinase-3, which eventually lead to the activation of mixed lineage kinase domain-like. Necroptosis is characterized by rapid permeabilization of the plasma membrane, which is associated with the release of the cell content and subsequent exposure of damage-associated molecular patterns ( DAMPs) and cytokines/chemokines. This release underlies the immunogenic nature of necroptotic cancer cells and their ability to induce efficient anti-tumor immunity. Triggering necroptosis has become especially important in experimental cancer treatments as an alternative to triggering apoptosis because one of the hallmarks of cancer is the blockade or evasion of apoptosis. In this review, we discuss recent advances in necroptosis research and the functional consequences of necroptotic cancer cell death, with focus on its immunogenicity and its role in the activation of anti-tumor immunity. Next, we discuss the molecular mechanisms of phosphatidylserine exposure during necroptosis and its role in the recognition of necroptotic cells. We also highlight the complex role of the necroptotic pathway in tumor promotion and suppression and in metastasis. Future studies will show whether necroptosis is truly a better strategy to overcome apoptosis resistance and provide the insights needed for development of novel treatment strategies for cancer. [ABSTRACT FROM AUTHOR]

Ferroptosis is a form of regulated cell death characterized by the iron-dependent accumulation of lipid hydroperoxides to lethal levels. Emerging evidence suggests that ferroptosis represents an ancient vulnerability caused by the incorporation of polyunsaturated fatty acids into cellular membranes, and cells have developed complex systems that exploit and defend against this vulnerability in different contexts. The sensitivity to ferroptosis is tightly linked to numerous biological processes, including amino acid, iron, and polyunsaturated fatty acid metabolism, and the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q 10 . Ferroptosis has been implicated in the pathological cell death associated with degenerative diseases (i.e., Alzheimer’s, Huntington’s, and Parkinson’s diseases), carcinogenesis, stroke, intracerebral hemorrhage, traumatic brain injury, ischemia-reperfusion injury, and kidney degeneration in mammals and is also implicated in heat stress in plants. Ferroptosis may also have a tumor-suppressor function that could be harnessed for cancer therapy. This Primer reviews the mechanisms underlying ferroptosis, highlights connections to other areas of biology and medicine, and recommends tools and guidelines for studying this emerging form of regulated cell death. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) have been incorporated in many emerging applications in the biomedical field including chemical sensing, biological imaging, drug delivery, and photothermal therapy. To overcome inherent hydrophobicity and improve their biocompatibility, pristine SWCNTs are often coated with surfactants, polymers, DNA, proteins, or lipids. In this paper, we report the effect of polyunsaturated fatty acids (PUFAs) on SWCNT photoluminescence. A decrease in the SWCNT bandgap emission (E11) and a new red-shifted emission (E11–) were observed in the presence of PUFAs. We attribute the change in SWCNT photoluminescence to the formation of oxygen-containing defects by lipid hydroperoxides through photo-oxidation. The observed changes in near-infrared emission of SWCNTs are important for understanding the interaction between SWCNTs and lipid biocorona. Our results also indicate that photoexcited SWCNTs can catalyze lipid peroxidation similarly to lipoxygenases. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ferroptosis is a regulated, non-apoptotic form of cell death, characterized by hydroxy-peroxidation of discrete phospholipid hydroperoxides, particularly hydroperoxyl (Hp) forms of arachidonoyl- and adrenoyl-phosphatidylethanolamine, with a downstream cascade of oxidative damage to membrane lipids, proteins and DNA, culminating in cell death. We recently showed that human trophoblasts are particularly sensitive to ferroptosis caused by depletion or inhibition of glutathione peroxidase 4 (GPX4) or the lipase PLA2G6. Here, we show that trophoblastic ferroptosis is accompanied by a dramatic change in the trophoblast plasma membrane, with macro-blebbing and vesiculation. Immunofluorescence revealed that ferroptotic cell-derived blebs stained positive for F-actin, but negative for cytoplasmic organelle markers. Transfer of conditioned medium that contained detached macrovesicles or co-culture of wild-type target cells with blebbing cells did not stimulate ferroptosis in target cells. Molecular modeling showed that the presence of Hp-phosphatidylethanolamine in the cell membrane promoted its cell ability to be stretched. Together, our data establish that membrane macro-blebbing is characteristic of trophoblast ferroptosis and can serve as a useful marker of this process. Whether or not these blebs are physiologically functional remains to be established. [ABSTRACT FROM AUTHOR]

Abstract: As a result of their unique electronic, optical, and mechanical properties, carbon nanotubes (CNTs) have been implemented in therapeutic and imaging applications. In an idealized situation, CNTs would be disposed of after they transport their theranostic payloads. Biodegradation represents an attractive pathway for the elimination of CNT carriers post-delivery and may be integral in catalyzing the release of the cargo from the delivery vehicle. Accordingly, recent research efforts have focused on peroxidase-driven biodegradation of CNTs. In this review, we not only summarize recent efforts to biodegrade CNTs in the test tube, in vitro, and in vivo, but also attempt to explore the fundamental parameters underlying degradation. Encouraged by the in vivo results obtained to date, we envision a future, where carbon-based nano-containers, which are specifically designed to target organs/cells, deliver their cargo, and biodegrade via peroxidase-driven mechanism, will represent an attractive therapeutic delivery option in nanomedicine. [Copyright &y& Elsevier]

Altered redox biology challenges all cells, with compensatory responses often determining a cell's fate. When 15 lipoxygenase 1 (15LO1), a lipid-peroxidizing enzyme abundant in asthmatic human airway epithelial cells (HAECs), binds phosphatidylethanolamine-binding protein 1 (PEBP1), hydroperoxy-phospholipids, which drive ferroptotic cell death, are generated. Peroxidases, including glutathione peroxidase 4 (GPX4), metabolize hydroperoxy-phospholipids to hydroxy derivatives to prevent ferroptotic death, but consume reduced glutathione (GSH). The cystine transporter SLC7A11 critically restores/maintains intracellular GSH. We hypothesized that high 15LO1, PEBP1, and GPX4 activity drives abnormal asthmatic redox biology, evidenced by lower bronchoalveolar lavage (BAL) fluid and intraepithelial cell GSH:oxidized GSH (GSSG) ratios, to enhance type 2 (T2) inflammatory responses. GSH, GSSG (enzymatic assays), 15LO1, GPX4, SLC7A11, and T2 biomarkers (Western blot and RNA-Seq) were measured in asthmatic and healthy control (HC) cells and fluids, with siRNA knockdown as appropriate. GSSG was higher and GSH:GSSG lower in asthmatic compared with HC BAL fluid, while intracellular GSH was lower in asthma. In vitro, a T2 cytokine (IL-13) induced 15LO1 generation of hydroperoxy-phospholipids, which lowered intracellular GSH and increased extracellular GSSG. Lowering GSH further by inhibiting SLC7A11 enhanced T2 inflammatory protein expression and ferroptosis. Ex vivo, redox imbalances corresponded to 15LO1 and SLC7A11 expression, T2 biomarkers, and worsened clinical outcomes. Thus, 15LO1 pathway-induced redox biology perturbations worsen T2 inflammation and asthma control, supporting 15LO1 as a therapeutic target. [ABSTRACT FROM AUTHOR]

We previously noted an important signaling role for decreased labile intracellular zinc ([Zn]i) in LPS-induced apoptosis in cultured sheep pulmonary artery endothelial cells (SPAEC) (Tang ZL, Wasserloos KJ, Liu X, Stitt MS, Reynolds IJ, Pitt BR, St Croix CM. Mol Cell Biochem 234-235: 211-217, 2002; Thambiayya K, Wasserloos KJ, Huang Z, Kagan VE, St Croix CM, Pitt BR. Am J Physiol Lung Cell Mol Physiol 300: L624-632, 2011). In the present study, we used small interfering RNA (siRNA) to important contributors of zinc homeostasis [SLC39A14 or Zrt/Irt-like protein 14 (ZIP14), a zinc importer; metallothionein (MT), a zinc binding protein] to define molecular pathways by which extracellular zinc or nitric oxide (NO) increase labile [Zn]i [e.g., zinc-sensitive fluorophore (FluoZin-3) detectable and/or chelatable by N,N,N'=,N'=-tetrakis(2-pyridylmethyl)ethylenediamine] and reduce the sensitivity of SPAEC to LPS. Addition of 10 μM zinc to serum-free medium of SPAEC increased [Zn]i and abolished LPS-induced apoptosis (e.g., increased annexin V binding). The increase in [Zn]i and the protective effect of extracellular zinc were sensitive to reduction in ZIP14 expression (by siRNA), but not affected by collectively knocking down major isoforms of sheep MT (sMT-Ia, -Ib, -Ic, and -II). Pretreatment of wild-type SPAEC with 250 μM of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) increased labile zinc in a relatively similar fashion to addition of extracellular zinc and reduced sensitivity of SPAEC to LPS-induced apoptosis (e.g., caspase-3/7 activation) in a N,N,N'=,N'=-tetrakis(2- pyridylmethyl)ethylenediamine-sensitive fashion. The antiapoptotic effects of SNAP were insensitive to siRNA knockdown of ZIP14, but were abolished (along with SNAP-induced increase in [Zn]i) when SPAEC were pretreated with siRNA to sheep MT. Zinc was able to directly inhibit recombinant caspase-3 activity in an in vitro assay. Collectively, these data show that increases in labile [Zn]i are an important component of ZIP14- or NO-mediated resistance to LPSinduced apoptosis. Cytoprotection via ZIP14 appeared to be secondary to transcellular movement of extracellular zinc, whereas NOmediated protection was secondary to S-nitrosation of MT and redistribution of [Zn]i. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we report that nitric oxide (NO) and the thioredoxin/thioredoxin reductase system affect the activity of caspase 8 in HepG2 cells. Exposure of cells to NO resulted in inhibition of caspase 8, while a subsequent incubation of the cells in NO-free medium resulted in spontaneous reactivation of the protease. The latter process was inhibited in thioredoxin reductase-deficient HepG2 cells, in which, however, lipoic acid markedly reactivated caspase 8. The data obtained suggest that extrinsic apoptosis can be subjected to redox regulation before induction of proteolytic damage by caspase 3. [Copyright &y& Elsevier]

Single-walled carbon nanotubes (SWCNT) are being produced in increasing quantities and the application of these materials in a large number of new technologies and consumer products necessitates studies of their potential impact on human health and the environment. To determine whether SWCNT affect viability or function of macrophages, important components of the innate immune system, we performed in vitro studies using primary human monocyte-derived macrophages (HMDM). Our findings show that SWCNT with a low content of metal impurities do not exert direct cytotoxic effects on HMDM. However, SWCNT suppressed chemotaxis of primary human monocytes in a standard chemotaxis assay. Moreover, macrophage engulfment of apoptotic target cells was significantly impaired following pre-incubation of HMDM with SWCNT at non-cytotoxic concentrations. These results are in line with previous studies showing that ultrafine carbon particles and carbon nanotubes may impair alveolar macrophage ingestion of microorganisms, and suggest that tissue homeostasis may be compromised by SWCNT due to suppressive effects on macrophages. [ABSTRACT FROM AUTHOR]

F2-isoprostanes are produced during free radical oxidation of cell phospholipids and are considered reliable biomarkers of oxidative stress. Currently, mass spectroscopy is the method of choice to detect F2-isoprostanes. However, due to numerous isomeric forms, analysis of F2-isoprostanes using MS detectors requires preliminary chromatographic separation. The current study was undertaken to develop a method of HPLC separation and quantification of different isomers of prostaglandin F2α, including 8-iso-PGF2α, following derivatization with 1-pyrenyldiazomethane (PDAM) to a highly fluorescent 1-pyrenylmethyl ester. HPLC separation and quantification of 1-pyrenylmethyl esters of PGF2α isomers at picogram level are complicated by numerous interfering products of the degradation of 1-pyrenyldiazomethane. A procedure of derivatization and purification was developed to reduce these interfering contaminants. The procedure of derivatization includes sorption of PGF2α isomers from solution in a hexane:ethyl acetate mixture (10:1) on a cellulose support prepared in the form of small (4×4 mm) filter paper squares. Bound PGF2α isomers are derivatized by 1-pyrenyldiazomethane dissolved in the same hexane:ethyl acetate mixture. During subsequent washing of the cellulose squares by the hexane:ethyl acetate mixture (10:1), fluorescent derivatives of PGF2α remain bound to cellulose while a significant portion of the contaminants are washed out. The 1-pyrenylmethyl esters of PGF2α can be quantitatively extracted from cellulose by an ethyl acetate:methanol (1:1) mixture. The next step in eliminating interference is a solid-phase extraction on silica cartridges using ethyl acetate for application of the sample and an ethyl acetate:methanol (1:1) mixture for elution. Final purification is achieved by normal-phase HPLC with wet ethyl acetate as the mobile phase. This chromatographic method displays remarkable resolution in the separation of different PGF2α isomers and can be used not only for sample purification but also for pre-MS separation. The purified 1-pyrenylmethyl esters of PGF2α were quantitatively analyzed by reverse-phase HPLC with fluorescent detection, with a detection limit of 5–10 pg. [Copyright &y& Elsevier]

Peroxidized phosphatidylethanolamine (PEox) species have been identified by liquid chromatography mass spectrometry (LC‐MS) as predictive biomarkers of ferroptosis, a new program of regulated cell death. However, the presence and subcellular distribution of PEox in specific cell types and tissues have not been directly detected by imaging protocols. By applying gas cluster ion beam secondary ion mass spectrometry (GCIB‐SIMS) imaging with a 70 keV (H2O)n+ (n>28 000) cluster ion beam, we were able to map PEox with 1.2 μm spatial resolution at the single cell/subcellular level in ferroptotic H9c2 cardiomyocytes and cortical/hippocampal neurons after traumatic brain injury. Application of this protocol affords visualization of physiologically relevant levels of very low abundance (20 pmol μmol−1 lipid) peroxidized lipids in subcellular compartments and their accumulation in disease conditions. [ABSTRACT FROM AUTHOR]

Peroxidized phosphatidylethanolamine (PEox) species have been identified by liquid chromatography mass spectrometry (LC‐MS) as predictive biomarkers of ferroptosis, a new program of regulated cell death. However, the presence and subcellular distribution of PEox in specific cell types and tissues have not been directly detected by imaging protocols. By applying gas cluster ion beam secondary ion mass spectrometry (GCIB‐SIMS) imaging with a 70 keV (H2O)n+ (n>28 000) cluster ion beam, we were able to map PEox with 1.2 μm spatial resolution at the single cell/subcellular level in ferroptotic H9c2 cardiomyocytes and cortical/hippocampal neurons after traumatic brain injury. Application of this protocol affords visualization of physiologically relevant levels of very low abundance (20 pmol μmol−1 lipid) peroxidized lipids in subcellular compartments and their accumulation in disease conditions. [ABSTRACT FROM AUTHOR]

The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)- phosphatidylethanolamine (Hp-PE). The seleniumdependent glutathione peroxidase 4 (GPX4) inhibits ferroptosis, converting unstable ferroptotic lipid hydroperoxides to nontoxic lipid alcohols in a tissue-specificmanner. While placental oxidative stress and lipotoxicity are hallmarks of placental dysfunction, the possible role of ferroptosis in placental dysfunction is largely unknown. We found that spontaneous preterm birth is associated with ferroptosis and that inhibition of GPX4 causes ferroptotic injury in primary human trophoblasts and during mouse pregnancy. Importantly, we uncovered a role for the phospholipase PLA2G6 (PNPLA9, iPLA2beta), known to metabolize Hp-PE to lyso-PE and oxidized fatty acid, in mitigating ferroptosis induced by GPX4 inhibition in vitro or by hypoxia/ reoxygenation injury in vivo. Together, we identified ferroptosis signaling in the human and mouse placenta, established a role for PLA2G6 in attenuating trophoblastic ferroptosis, and provided mechanistic insights into the ill-defined placental lipotoxicity that may inspire PLA2G6-targeted therapeutic strategies. [ABSTRACT FROM AUTHOR]

Lysocardiolipin acyltransferase (LYCAT), a cardiolipin (CL)- remodeling enzyme, is crucial for maintaining normal mitochondrial function and vascular development. Despite the well-characterized role for LYCAT in the regulation of mitochondrial dynamics, its involvement in lung cancer, if any, remains incompletely understood. In this study, in silico analysis of TCGA lung cancer data sets revealed a significant increase in LYCAT expression, which was later corroborated in human lung cancer tissues and immortalized lung cancer cell lines via indirect immunofluorescence and immunoblotting, respectively. Stable knockdown of LYCAT in NSCLC cell lines not only reduced CL and increased monolyso-CL levels but also reduced in vivo tumor growth, as determined by xenograft studies in athymic nude mice. Furthermore, blocking LYCAT activity using a LYCAT mimetic peptide attenuated cell migration, suggesting a novel role for LYCAT activity in promoting NSCLC. Mechanistically, the pro-proliferative effects of LYCAT were mediated by an increase in mitochondrial fusion and a G1/S cell cycle transition, both of which are linked to increased cell proliferation. Taken together, these results demonstrate a novel role for LYCAT in promoting NSCLC and suggest that targeting LYCAT expression or activity in NSCLC may provide new avenues for the therapeutic treatment of lung cancer. [ABSTRACT FROM AUTHOR]

Temporally harmonized elimination of damaged or unnecessary organelles and cells is a prerequisite of health. Under Type 2 inflammatory conditions, human airway epithelial cells (HAECs) generate proferroptotic hydroperoxy-arachidonoyl-phosphatidylethanolamines (HpETE-PEs) as proximate death signals. Production of 15-HpETE-PE depends on activation of 15-lipoxygenase-1 (15LO1) in complex with PE-binding protein-1 (PEBP1). We hypothesized that cellular membrane damage induced by these proferroptotic phospholipids triggers compensatory prosurvival pathways, and in particular autophagic pathways, to prevent cell elimination through programmed death. We discovered that PEBP1 is pivotal to driving dynamic interactions with both proferroptotic 15LO1 and the autophagic protein microtubule-associated light chain-3 (LC3). Further, the 15LO1-PEBP1-generated ferroptotic phospholipid, 15-HpETE-PE, promoted LC3-I lipidation to stimulate autophagy. This concurrent activation of autophagy protects cells from ferroptotic death and release of mitochondrial DNA. Similar findings are observed in Type 2 Hi asthma, where high levels of both 15LO1-PEBP1 and LC3-II are seen in HAECs, in association with low bronchoalveolar lavage fluid mitochondrial DNA and more severe disease. The concomitant activation of ferroptosis and autophagy by 15LO1-PEBP1 complexes and their hydroperoxy-phospholipids reveals a pathobiologic pathway relevant to asthma and amenable to therapeutic targeting. [ABSTRACT FROM AUTHOR]