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    Macrophage Death as a Pharmacological Target in Atherosclerosis. Martinet Wim,Coornaert Isabelle,Puylaert Pauline,De Meyer Guido R Y Frontiers in pharmacology Atherosclerosis is a chronic inflammatory disorder characterized by the gradual build-up of plaques within the vessel wall of middle-sized and large arteries. Over the past decades, treatment of atherosclerosis mainly focused on lowering lipid levels, which can be accomplished by the use of statins. However, some patients do not respond sufficiently to statin therapy and therefore still have a residual cardiovascular risk. This issue highlights the need for novel therapeutic strategies. As macrophages are implicated in all stages of atherosclerotic lesion development, they represent an important alternative drug target. A variety of anti-inflammatory strategies have recently emerged to treat or prevent atherosclerosis. Here, we review the canonical mechanisms of macrophage death and their impact on atherogenesis and plaque stability. Macrophage death is a prominent feature of advanced plaques and is a major contributor to necrotic core formation and plaque destabilization. Mechanisms of macrophage death in atherosclerosis include apoptosis, passive or accidental necrosis as well as secondary necrosis, a type of death that typically occurs when apoptotic cells are insufficiently cleared by neighboring cells via a phagocytic process termed efferocytosis. In addition, less-well characterized types of regulated necrosis in macrophages such as necroptosis, pyroptosis, ferroptosis, and parthanatos may occur in advanced plaques and are also discussed. Autophagy in plaque macrophages is an important survival pathway that protects against cell death, yet massive stimulation of autophagy promotes another type of death, usually referred to as autosis. Multiple lines of evidence indicate that a better insight into the different mechanisms of macrophage death, and how they mutually interact, will provide novel pharmacological strategies to resolve atherosclerosis and stabilize vulnerable, rupture-prone plaques. 10.3389/fphar.2019.00306
    CCL4 Inhibition in Atherosclerosis: Effects on Plaque Stability, Endothelial Cell Adhesiveness, and Macrophages Activation. Chang Ting-Ting,Yang Hsin-Ying,Chen Ching,Chen Jaw-Wen International journal of molecular sciences Atherosclerosis is an arterial inflammatory disease. The circulating level of the C-C chemokine ligand (CCL4) is increased in atherosclerotic patients. This study aimed to investigate whether CCL4 inhibition could retard the progression of atherosclerosis. In ApoE knockout mice, CCL4 antibody treatment reduced circulating interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α levels and improved lipid profiles accompanied with upregulation of the liver X receptor. CCL4 inhibition reduced the atheroma areas and modified the progression of atheroma plaques, which consisted of a thicker fibrous cap with a reduced macrophage content and lower matrix metalloproteinase-2 and -9 expressions, suggesting the stabilization of atheroma plaques. Human coronary endothelial cells (HCAECs) and macrophages were stimulated with TNF-α or oxidized LDL (ox-LDL). The induced expression of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were attenuated by the CCL4 antibody or CCL4 si-RNA. CCL4 inhibition reduced the adhesiveness of HCAECs, which is an early sign of atherogenesis. CCL4 blockade reduced the activity of metalloproteinase-2 and -9 and the production of TNF-α and IL-6 in stimulated macrophages. The effects of CCL4 inhibition on down-regulating adhesion and inflammation proteins were obtained through the nuclear factor kappa B (NFκB) signaling pathway. The direct inhibition of CCL4 stabilized atheroma and reduced endothelial and macrophage activation. CCL4 may be a novel therapeutic target for modulating atherosclerosis. 10.3390/ijms21186567
    Rapamycin and FTY720 Alleviate Atherosclerosis by Cross Talk of Macrophage Polarization and Autophagy. Sun Rui-Zhen,Fan Ying,Liang Xiao,Gong Tian-Tian,Wang Qi,Liu Hui,Shan Zhi-Yan,Lei Lei BioMed research international Foam cell formation and macrophage polarization are involved in the pathologic development of atherosclerosis, one of the most important human diseases affecting large and medium artery walls. This study was designed to assess the effects of rapamycin and FTY720 (fingolimod) on macrophages and foam cells. Mouse peritoneal macrophages were collected and treated with rapamycin and FTY720 to study autophagy, polarization, and lipid accumulation. Next, foam cells were formed by oxidizing low-density lipoprotein to observe changes in lipid accumulation, autophagy, and polarization in rapamycin-treated or FTY720-treated foam cells. Lastly, foam cells that had been treated with rapamycin and FTY720 were evaluated for sphingosine 1-phosphate receptor (S1prs) expression. Autophagy microtubule-associated protein 1 light chain 3- (LC3-) II was increased, and classically activated macrophage phenotype markers interleukin- (IL-) 6, cyclooxygenase-2 (COX2), and inducible nitric oxide synthase (iNOS) were increased, whereas alternatively activated macrophage phenotype markers transforming growth factor- (TGF-) , arginase 1 (Arg1), and mannose receptor C-type 1 (Mrc1) were decreased by rapamycin in peritoneal macrophages. LC3-II was also obviously enhanced, though polarization markers were unchanged in rapamycin-treated foam cells. Moreover, lipid accumulation was inhibited in rapamycin-treated macrophage cells but was unchanged in rapamycin-treated foam cells. For FTY720, LC3-II did not change, whereas TGF-, Arg1 and Mrc1 were augmented, and IL-6 was suppressed in macrophages. However, LC3-II was increased, and TGF-, ARG1 and MRC1 were strikingly augmented, whereas IL-6, COX2 and iNOS could be suppressed in foam cells. Furthermore, lipid accumulation was alleviated in FTY720-treated foam cells. Additionally, S1pr1 was markedly decreased in foam cells ( < .05); S1pr2, S1pr3, S1pr4 and S1pr5 were unchanged in rapamycin-treated foam cells. In FTY720-treated foam cells, S1pr3 and S1pr4 were decreased, and S1pr1, S1pr2 and S1pr5 were unchanged. Therefore, we deduced that rapamycin stimulated classically activated macrophages and supressed early atherosclerosis. Rapamycin may also stabilize artery plaques by preventing apoptosis and S1PR1 in advanced atherosclerosis. FTY720 allowed transformation of foam cells into alternatively activated macrophages through the autophagy pathway to alleviate advanced atherosclerosis. 10.1155/2018/1010248
    Macrophage Apoptosis and Efferocytosis in the Pathogenesis of Atherosclerosis. Linton MacRae F,Babaev Vladimir R,Huang Jiansheng,Linton Edward F,Tao Huan,Yancey Patricia G Circulation journal : official journal of the Japanese Circulation Society Macrophage apoptosis and the ability of macrophages to clean up dead cells, a process called efferocytosis, are crucial determinants of atherosclerosis lesion progression and plaque stability. Environmental stressors initiate endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR). Unresolved ER stress with activation of the UPR initiates apoptosis. Macrophages are resistant to apoptotic stimuli, because of activity of the PI3K/Akt pathway. Macrophages express 3 Akt isoforms, Akt1, Akt2 and Akt3, which are products of distinct but homologous genes. Akt displays isoform-specific effects on atherogenesis, which vary with different vascular cell types. Loss of macrophage Akt2 promotes the anti-inflammatory M2 phenotype and reduces atherosclerosis. However, Akt isoforms are redundant with regard to apoptosis. c-Jun NH-terminal kinase (JNK) is a pro-apoptotic effector of the UPR, and the JNK1 isoform opposes anti-apoptotic Akt signaling. Loss of JNK1 in hematopoietic cells protects macrophages from apoptosis and accelerates early atherosclerosis. IκB kinase α (IKKα, a member of the serine/threonine protein kinase family) plays an important role in mTORC2-mediated Akt signaling in macrophages, and IKKα deficiency reduces macrophage survival and suppresses early atherosclerosis. Efferocytosis involves the interaction of receptors, bridging molecules, and apoptotic cell ligands. Scavenger receptor class B type I is a critical mediator of macrophage efferocytosis via the Src/PI3K/Rac1 pathway in atherosclerosis. Agonists that resolve inflammation offer promising therapeutic potential to promote efferocytosis and prevent atherosclerotic clinical events. (Circ J 2016; 80: 2259-2268). 10.1253/circj.CJ-16-0924
    Loss of 2 Akt (Protein Kinase B) Isoforms in Hematopoietic Cells Diminished Monocyte and Macrophage Survival and Reduces Atherosclerosis in Ldl Receptor-Null Mice. Babaev Vladimir R,Ding Lei,Zhang Youmin,May James M,Ramsey Stephen A,Vickers Kasey C,Linton MacRae F Arteriosclerosis, thrombosis, and vascular biology Objective- Macrophages express 3 Akt (protein kinase B) isoforms, Akt1, Akt2, and Akt3, which display isoform-specific functions but may be redundant in terms of Akt survival signaling. We hypothesize that loss of 2 Akt isoforms in macrophages will suppress their ability to survive and modulate the development of atherosclerosis. Approach and Results- To test this hypothesis, we reconstituted male Ldlr mice with double Akt2/Akt3 knockout hematopoietic cells expressing only the Akt1 isoform (Akt1). There were no differences in body weight and plasma lipid levels between the groups after 8 weeks of the Western diet; however, Akt1→ Ldlr mice developed smaller (57.6% reduction) atherosclerotic lesions with more apoptotic macrophages than control mice transplanted with WT (wild type) cells. Next, male and female Ldlr mice were reconstituted with double Akt1/Akt2 knockout hematopoietic cells expressing the Akt3 isoform (Akt3). Female and male Akt3→ Ldlr recipients had significantly smaller (61% and 41%, respectively) lesions than the control WT→ Ldlr mice. Loss of 2 Akt isoforms in hematopoietic cells resulted in markedly diminished levels of white blood cells, B cells, and monocytes and compromised viability of monocytes and peritoneal macrophages compared with WT cells. In response to lipopolysaccharides, macrophages with a single Akt isoform expressed low levels of inflammatory cytokines; however, Akt1 macrophages were distinct in expressing high levels of antiapoptotic Il10 compared with WT and Akt3 cells. Conclusions- Loss of 2 Akt isoforms in hematopoietic cells, preserving only a single Akt1 or Akt3 isoform, markedly compromises monocyte and macrophage viability and diminishes early atherosclerosis in Ldlr mice. 10.1161/ATVBAHA.118.312206
    Macrophage-Based Therapies for Atherosclerosis Management. Peng Renyi,Ji Hao,Jin Libo,Lin Sue,Huang Yijiang,Xu Ke,Yang Qinsi,Sun Da,Wu Wei Journal of immunology research Atherosclerosis (AS), a typical chronic inflammatory vascular disease, is the main pathological basis of ischemic cardio/cerebrovascular disease (CVD). Long-term administration was characterized with low efficacy and serious side effects, while the macrophages with attractive intrinsic homing target have great potential in the efficient and safe management of AS. In this review, we focused on the systematical summary of the macrophage-based therapies in AS management, including macrophage autophagy, polarization, targeted delivery, microenvironment-triggered drug release, and macrophage- or macrophage membrane-based drug carrier. In conclusion, macrophage-based therapies have great promise to effectively manage AS in future research and clinic translation. 10.1155/2020/8131754
    Loss of in Monocyte/Macrophages Suppresses Their Proliferation and Viability Reducing Atherosclerosis in LDLR Null Mice. Babaev Vladimir R,Huang Jiansheng,Ding Lei,Zhang Youmin,May James M,Linton MacRae F Frontiers in immunology Background:Rictor is an essential component of mammalian target of rapamycin (mTOR) complex 2 (mTORC2), a conserved serine/threonine kinase that may play a role in cell proliferation, survival and innate or adaptive immune responses. Genetic loss of inactivates mTORC2, which directly activates Akt S phosphorylation and promotes pro-survival cell signaling and proliferation. Methods and results:To study the role of mTORC2 signaling in monocytes and macrophages, we generated mice with myeloid lineage-specific deletion (M). These M mice exhibited dramatic reductions of white blood cells, B-cells, T-cells, and monocytes but had similar levels of neutrophils compared to control flox-flox () mice. M bone marrow monocytes and peritoneal macrophages expressed reduced levels of mTORC2 signaling and decreased Akt S phosphorylation, and they displayed significantly less proliferation than control cells. In addition, blood monocytes and peritoneal macrophages isolated from M mice were significantly more sensitive to pro-apoptotic stimuli. In response to LPS, M macrophages exhibited the M1 phenotype with higher levels of pro-inflammatory gene expression and lower levels of gene expression than control cells. Further suppression of LPS-stimulated Akt signaling with a low dose of an Akt inhibitor, increased inflammatory gene expression in macrophages, but genetic inactivation of reversed this rise, indicating that mTORC1 mediates this increase of inflammatory gene expression. Next, to elucidate whether mTORC2 has an impact on atherosclerosis , female and male null mice were reconstituted with bone marrow from M or mice. After 10 weeks of the Western diet, there were no differences between the recipients of the same gender in body weight, blood glucose or plasma lipid levels. However, both female and male M →  mice developed smaller atherosclerotic lesions in the distal and proximal aorta. These lesions contained less macrophage area and more apoptosis than lesions of control →  mice. Thus, loss of and, consequently, mTORC2 significantly compromised monocyte/macrophage survival, and this markedly diminished early atherosclerosis in mice. Conclusion:Our results demonstrate that mTORC2 is a key signaling regulator of macrophage survival and its depletion suppresses early atherosclerosis. 10.3389/fimmu.2018.00215
    Deficiency of the T cell regulator Casitas B-cell lymphoma-B aggravates atherosclerosis by inducing CD8+ T cell-mediated macrophage death. Seijkens Tom T P,Poels Kikkie,Meiler Svenja,van Tiel Claudia M,Kusters Pascal J H,Reiche Myrthe,Atzler Dorothee,Winkels Holger,Tjwa Marc,Poelman Hessel,Slütter Bram,Kuiper Johan,Gijbels Marion,Kuivenhoven Jan Albert,Matic Ljubica Perisic,Paulsson-Berne Gabrielle,Hedin Ulf,Hansson Göran K,Nicolaes Gerry A F,Daemen Mat J A P,Weber Christian,Gerdes Norbert,de Winther Menno P J,Lutgens Esther European heart journal Aims:The E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but their regulation in this disease remains largely unknown; thus, we studied the function of CBL-B in atherogenesis. Methods and results:The expression of CBL-B in human atherosclerotic plaques was lower in advanced lesions compared with initial lesions and correlated inversely with necrotic core area. Twenty weeks old Cblb-/-Apoe-/- mice showed a significant increase in plaque area in the aortic arch, where initial plaques were present. In the aortic root, a site containing advanced plaques, lesion area rose by 40%, accompanied by a dramatic change in plaque phenotype. Plaques contained fewer macrophages due to increased apoptosis, larger necrotic cores, and more CD8+ T cells. Cblb-/-Apoe-/- macrophages exhibited enhanced migration and increased cytokine production and lipid uptake. Casitas B-cell lymphoma-B deficiency increased CD8+ T cell numbers, which were protected against apoptosis and regulatory T cell-mediated suppression. IFNγ and granzyme B production was enhanced in Cblb-/-Apoe-/- CD8+ T cells, which provoked macrophage killing. Depletion of CD8+ T cells in Cblb-/-Apoe-/- bone marrow chimeras rescued the phenotype, indicating that CBL-B controls atherosclerosis mainly through its function in CD8+ T cells. Conclusion:Casitas B-cell lymphoma-B expression in human plaques decreases during the progression of atherosclerosis. As an important regulator of immune responses in experimental atherosclerosis, CBL-B hampers macrophage recruitment and activation during initial atherosclerosis and limits CD8+ T cell activation and CD8+ T cell-mediated macrophage death in advanced atherosclerosis, thereby preventing the progression towards high-risk plaques. 10.1093/eurheartj/ehy714
    Macrophage-Enriched lncRNA RAPIA: A Novel Therapeutic Target for Atherosclerosis. Sun Changbin,Fu Yahong,Gu Xia,Xi Xiangwen,Peng Xiang,Wang Chuhan,Sun Qi,Wang Xueyu,Qian Fengcui,Qin Zhifeng,Qu Wenbo,Piao Minghui,Zhong Shan,Liu Shengliang,Zhang Maomao,Fang Shaohong,Tian Jiangtian,Li Chunquan,Maegdefessel Lars,Tian Jinwei,Yu Bo Arteriosclerosis, thrombosis, and vascular biology OBJECTIVE:Despite the current antiatherosclerotic and antithrombotic therapies, the incidence of advanced atherosclerosis-associated clinical events remains high. Whether long noncoding RNAs (lncRNAs) affect the progression of atherosclerosis and whether they are potential targets for the treatment of advanced atherosclerosis are poorly understood. Approach and Results: The progression of atherosclerotic lesions was accompanied by dynamic alterations in lncRNA expression, as revealed by RNA sequencing and quantitative polymerase chain reaction. Among the dynamically changing lncRNAs, we identified a novel lncRNA, lncRNA Associated with the Progression and Intervention of Atherosclerosis (RAPIA), that was highly expressed in advanced atherosclerotic lesions and in macrophages. Inhibition of RAPIA in vivo not only repressed the progression of atherosclerosis but also exerted atheroprotective effects similar to those of atorvastatin on advanced atherosclerotic plaques that had already formed. In vitro assays demonstrated that RAPIA promoted proliferation and reduced apoptosis of macrophages. A molecular sponge interaction between RAPIA and microRNA-183-5p was demonstrated by dual-luciferase reporter and RNA immunoprecipitation assays. Rescue assays indicated that RAPIA functioned at least in part by targeting the microRNA-183-5p/ITGB1 (integrin β1) pathway in macrophages. In addition, the transcription factor FoxO1 (forkhead box O1) could bind to the RAPIA promoter region and facilitate the expression of RAPIA. CONCLUSIONS:The progression of atherosclerotic lesions was accompanied by dynamic changes in the expression of lncRNAs. Inhibition of the pivotal lncRNA RAPIA may be a novel preventive and therapeutic strategy for advanced atherosclerosis, especially in patients resistant or intolerant to statins. 10.1161/ATVBAHA.119.313749
    Akt Signaling in Macrophage Polarization, Survival, and Atherosclerosis. Linton MacRae F,Moslehi Javid J,Babaev Vladimir R International journal of molecular sciences The PI3K/Akt pathway plays a crucial role in the survival, proliferation, and migration of macrophages, which may impact the development of atherosclerosis. Changes in Akt isoforms or modulation of the Akt activity levels in macrophages significantly affect their polarization phenotype and consequently atherosclerosis in mice. Moreover, the activity levels of Akt signaling determine the viability of monocytes/macrophages and their resistance to pro-apoptotic stimuli in atherosclerotic lesions. Therefore, elimination of pro-apoptotic factors as well as factors that antagonize or suppress Akt signaling in macrophages increases cell viability, protecting them from apoptosis, and this markedly accelerates atherosclerosis in mice. In contrast, inhibition of Akt signaling by the ablation of Rictor in myeloid cells, which disrupts mTORC2 assembly, significantly decreases the viability and proliferation of blood monocytes and macrophages with the suppression of atherosclerosis. In addition, monocytes and macrophages exhibit a threshold effect for Akt protein levels in their ability to survive. Ablation of two Akt isoforms, preserving only a single Akt isoform in myeloid cells, markedly compromises monocyte and macrophage viability, inducing monocytopenia and diminishing early atherosclerosis. These recent advances in our understanding of Akt signaling in macrophages in atherosclerosis may have significant relevance in the burgeoning field of cardio-oncology, where PI3K/Akt inhibitors being tested in cancer patients can have significant cardiovascular and metabolic ramifications. 10.3390/ijms20112703
    Relationship between CCL22 Expression by Vascular Smooth Muscle Cells and Macrophage Histamine Receptors in Atherosclerosis. Kimura Satoshi,Noguchi Hirotsugu,Nanbu Uki,Wang Ke-Yong,Sasaguri Yasuyuki,Nakayama Toshiyuki Journal of atherosclerosis and thrombosis AIM:CCL22, mainly synthesized by monocyte-derived alternative (M2) macrophages, belongs to the CC family of chemokines and is involved in monocyte migration and recruitment. We have previously investigated CCL22 and histamine in atherosclerosis. Here, we investigated the hypothesis that CCL22 is involved in atherosclerosis, which is influenced by the differentiation of macrophage phenotypes via histamine. METHODS:CCL22 expression was investigated in human carotid arteries and coronary arteries with bare metal stents. Ligated carotid arteries of wild-type (C57BL/6J) and apolipoprotein E-deficient mice were also used as atherosclerotic models. The localization and expression of CCL22 and classical (M1)-like and M2-like macrophages in various human and mouse atherosclerotic lesions were investigated by immunohistochemical examination and quantitative real-time polymerase chain reaction. Histamine is expressed in atherosclerosis, and it induces inflammation and immunity. Human- and mice-derived monocytes and macrophages were used to examine the role of histamine in macrophage differentiation and CCL22-expression. Macrophages derived from histamine receptor 1 (H1R)- and 2 (H2R)-knockout (KO) mice were also examined. RESULTS:Atherosclerotic lesions showed a distribution of heterogeneous macrophage phenotypes with M1-like and M2-like macrophage dominant sites. CCL22 was distributed in sparse areas of vascular smooth muscle cells (VSMCs) and associated with M2-like macrophages. Moreover, H2R stimulation was associated with CCL22 expression via M2-like macrophage dominant differentiation. CONCLUSION:The expression of M1- or M2-like macrophages in atherosclerosis were observed to be dependent on the distribution of VSMCs owing to differences in causal stimuli and the switching of histamine receptors via Th1 or Th2 cytokines. These results suggest that CCL22 may control atherosclerosis. 10.5551/jat.44297
    Intracellular and Intercellular Aspects of Macrophage Immunometabolism in Atherosclerosis. Tabas Ira,Bornfeldt Karin E Circulation research Macrophage immunometabolism, the changes in intracellular metabolic pathways that alter the function of these highly plastic cells, has been the subject of intense interest in the past few years, in part because macrophage immunometabolism plays important roles in atherosclerosis and other inflammatory diseases. In this review article, part of the , we introduce the concepts of (1) intracellular immunometabolism-the canonical pathways of intrinsic cell activation leading to changes in intracellular metabolism, which in turn alter cellular function; and (2) intercellular immunometabolism-conditions in which intermediates of cellular metabolism are transferred from one cell to another, thereby altering the function of the recipient cell. The recent discovery that the metabolite cargo of dead and dying cells ingested through efferocytosis by macrophages can alter metabolic pathways and downstream function of the efferocyte is markedly changing the way we think about macrophage immunometabolism. Metabolic transitions of macrophages contribute to their functions in all stages of atherosclerosis, from lesion initiation to formation of advanced lesions characterized by necrotic cores, to lesion regression following aggressive lipid lowering. This review article discusses recent advances in our understanding of these different aspects of macrophage immunometabolism in atherosclerosis. With the increasing understanding of the roles of macrophage immunometabolism in atherosclerosis, new exciting concepts and potential targets for intervention are emerging. 10.1161/CIRCRESAHA.119.315939
    FSP1 is a glutathione-independent ferroptosis suppressor. Doll Sebastian,Freitas Florencio Porto,Shah Ron,Aldrovandi Maceler,da Silva Milene Costa,Ingold Irina,Goya Grocin Andrea,Xavier da Silva Thamara Nishida,Panzilius Elena,Scheel Christina H,Mourão André,Buday Katalin,Sato Mami,Wanninger Jonas,Vignane Thibaut,Mohana Vaishnavi,Rehberg Markus,Flatley Andrew,Schepers Aloys,Kurz Andreas,White Daniel,Sauer Markus,Sattler Michael,Tate Edward William,Schmitz Werner,Schulze Almut,O'Donnell Valerie,Proneth Bettina,Popowicz Grzegorz M,Pratt Derek A,Angeli José Pedro Friedmann,Conrad Marcus Nature Ferroptosis is an iron-dependent form of necrotic cell death marked by oxidative damage to phospholipids. To date, ferroptosis has been thought to be controlled only by the phospholipid hydroperoxide-reducing enzyme glutathione peroxidase 4 (GPX4) and radical-trapping antioxidants. However, elucidation of the factors that underlie the sensitivity of a given cell type to ferroptosis is crucial to understand the pathophysiological role of ferroptosis and how it may be exploited for the treatment of cancer. Although metabolic constraints and phospholipid composition contribute to ferroptosis sensitivity, no cell-autonomous mechanisms have been identified that account for the resistance of cells to ferroptosis. Here we used an expression cloning approach to identify genes in human cancer cells that are able to complement the loss of GPX4. We found that the flavoprotein apoptosis-inducing factor mitochondria-associated 2 (AIFM2) is a previously unrecognized anti-ferroptotic gene. AIFM2, which we renamed ferroptosis suppressor protein 1 (FSP1) and which was initially described as a pro-apoptotic gene, confers protection against ferroptosis elicited by GPX4 deletion. We further demonstrate that the suppression of ferroptosis by FSP1 is mediated by ubiquinone (also known as coenzyme Q, CoQ): the reduced form, ubiquinol, traps lipid peroxyl radicals that mediate lipid peroxidation, whereas FSP1 catalyses the regeneration of CoQ using NAD(P)H. Pharmacological targeting of FSP1 strongly synergizes with GPX4 inhibitors to trigger ferroptosis in a number of cancer entities. In conclusion, the FSP1-CoQ-NAD(P)H pathway exists as a stand-alone parallel system, which co-operates with GPX4 and glutathione to suppress phospholipid peroxidation and ferroptosis. 10.1038/s41586-019-1707-0
    Posttranslational Modifications in Ferroptosis. Wei Xiang,Yi Xin,Zhu Xue-Hai,Jiang Ding-Sheng Oxidative medicine and cellular longevity Ferroptosis was first coined in 2012 to describe the form of regulated cell death (RCD) characterized by iron-dependent lipid peroxidation. To date, ferroptosis has been implicated in many diseases, such as carcinogenesis, degenerative diseases (e.g., Huntington's, Alzheimer's, and Parkinson's diseases), ischemia-reperfusion injury, and cardiovascular diseases. Previous studies have identified numerous targets involved in ferroptosis; for example, acyl-CoA synthetase long-chain family member 4 (ACSL4) and p53 induce while glutathione peroxidase 4 (GPX4) and apoptosis-inducing factor mitochondria-associated 2 (AIFM2, also known as FSP1) inhibit ferroptosis. At least three major pathways (the glutathione-GPX4, FSP1-coenzyme Q (CoQ), and GTP cyclohydrolase-1- (GCH1-) tetrahydrobiopterin (BH4) pathways) have been identified to participate in ferroptosis regulation. Recent advances have also highlighted the crucial roles of posttranslational modifications (PTMs) of proteins in ferroptosis. Here, we summarize the recently discovered knowledge regarding the mechanisms underlying ferroptosis, particularly the roles of PTMs in ferroptosis regulation. 10.1155/2020/8832043
    MDM2 and MDMX promote ferroptosis by PPARα-mediated lipid remodeling. Venkatesh Divya,O'Brien Nicholas A,Zandkarimi Fereshteh,Tong David R,Stokes Michael E,Dunn Denise E,Kengmana Everett S,Aron Allegra T,Klein Alyssa M,Csuka Joleen M,Moon Sung-Hwan,Conrad Marcus,Chang Christopher J,Lo Donald C,D'Alessandro Angelo,Prives Carol,Stockwell Brent R Genes & development MDM2 and MDMX, negative regulators of the tumor suppressor p53, can work separately and as a heteromeric complex to restrain p53's functions. MDM2 also has pro-oncogenic roles in cells, tissues, and animals that are independent of p53. There is less information available about p53-independent roles of MDMX or the MDM2-MDMX complex. We found that MDM2 and MDMX facilitate ferroptosis in cells with or without p53. Using small molecules, RNA interference reagents, and mutant forms of MDMX, we found that MDM2 and MDMX, likely working in part as a complex, normally facilitate ferroptotic death. We observed that MDM2 and MDMX alter the lipid profile of cells to favor ferroptosis. Inhibition of MDM2 or MDMX leads to increased levels of FSP1 protein and a consequent increase in the levels of coenzyme Q, an endogenous lipophilic antioxidant. This suggests that MDM2 and MDMX normally prevent cells from mounting an adequate defense against lipid peroxidation and thereby promote ferroptosis. Moreover, we found that PPARα activity is essential for MDM2 and MDMX to promote ferroptosis, suggesting that the MDM2-MDMX complex regulates lipids through altering PPARα activity. These findings reveal the complexity of cellular responses to MDM2 and MDMX and suggest that MDM2-MDMX inhibition might be useful for preventing degenerative diseases involving ferroptosis. Furthermore, they suggest that MDM2/MDMX amplification may predict sensitivity of some cancers to ferroptosis inducers. 10.1101/gad.334219.119
    The CoQ oxidoreductase FSP1 acts parallel to GPX4 to inhibit ferroptosis. Bersuker Kirill,Hendricks Joseph M,Li Zhipeng,Magtanong Leslie,Ford Breanna,Tang Peter H,Roberts Melissa A,Tong Bingqi,Maimone Thomas J,Zoncu Roberto,Bassik Michael C,Nomura Daniel K,Dixon Scott J,Olzmann James A Nature Ferroptosis is a form of regulated cell death that is caused by the iron-dependent peroxidation of lipids. The glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4) prevents ferroptosis by converting lipid hydroperoxides into non-toxic lipid alcohols. Ferroptosis has previously been implicated in the cell death that underlies several degenerative conditions, and induction of ferroptosis by the inhibition of GPX4 has emerged as a therapeutic strategy to trigger cancer cell death. However, sensitivity to GPX4 inhibitors varies greatly across cancer cell lines, which suggests that additional factors govern resistance to ferroptosis. Here, using a synthetic lethal CRISPR-Cas9 screen, we identify ferroptosis suppressor protein 1 (FSP1) (previously known as apoptosis-inducing factor mitochondrial 2 (AIFM2)) as a potent ferroptosis-resistance factor. Our data indicate that myristoylation recruits FSP1 to the plasma membrane where it functions as an oxidoreductase that reduces coenzyme Q (CoQ) (also known as ubiquinone-10), which acts as a lipophilic radical-trapping antioxidant that halts the propagation of lipid peroxides. We further find that FSP1 expression positively correlates with ferroptosis resistance across hundreds of cancer cell lines, and that FSP1 mediates resistance to ferroptosis in lung cancer cells in culture and in mouse tumour xenografts. Thus, our data identify FSP1 as a key component of a non-mitochondrial CoQ antioxidant system that acts in parallel to the canonical glutathione-based GPX4 pathway. These findings define a ferroptosis suppression pathway and indicate that pharmacological inhibition of FSP1 may provide an effective strategy to sensitize cancer cells to ferroptosis-inducing chemotherapeutic agents. 10.1038/s41586-019-1705-2