Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

https://biblio.ugent.be/publication/8555786/file/8555788.pdf

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

It has become increasingly difficult to find an area of cell biology in which lipids do not have important, if not key, roles as signalling and regulatory molecules. The rapidly expanding field of bioactive lipids is exemplified by many sphingolipids, such as ceramide, sphingosine, sphingosine-1-phosphate (S1P), ceramide-1-phosphate and lyso-sphingomyelin, which have roles in the regulation of cell growth, death, senescence, adhesion, migration, inflammation, angiogenesis and intracellular trafficking. Deciphering the mechanisms of these varied cell functions necessitates an understanding of the complex pathways of sphingolipid metabolism and the mechanisms that regulate lipid generation and lipid action.

Principles of bioactive lipid signalling: lessons from sphingolipids

In 2009, the Nomenclature Committee on Cell Death (NCCD) proposed a set of recommendations for the definition of distinct cell death morphologies and for the appropriate use of cell death-related terminology, including 'apoptosis', 'necrosis' and 'mitotic catastrophe'. In view of the substantial progress in the biochemical and genetic exploration of cell death, time has come to switch from morphological to molecular definitions of cell death modalities. Here we propose a functional classification of cell death subroutines that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic apoptosis, regulated necrosis, autophagic cell death and mitotic catastrophe. Moreover, we discuss the utility of expressions indicating additional cell death modalities. On the basis of the new, revised NCCD classification, cell death subroutines are defined by a series of precise, measurable biochemical features.

/pdf/molecular-definitions-of-cell-death-subroutines-q5g428rlyi.pdf

Molecular definitions of cell death subroutines: recommendations of the Nomenclature Committee on Cell Death 2012

Phosphatidic acid (PtdOH) is emerging as an important signalling lipid in abiotic stress responses in plants. The effect of cold stress was monitored using 32P-labelled seedlings and leaf discs of Arabidopsis thaliana. Low, non-freezing temperatures were found to trigger a very rapid 32P-PtdOH increase, peaking within 2 and 5 min, respectively. In principle, PtdOH can be generated through three different pathways, i.e. i) via de novo phospholipid biosynthesis (through acylation of lyso-PtdOH), ii) via phospholipase D hydrolysis of structural phospholipids or iii) via phosphorylation of diacylglycerol (DAG) by DAG kinase (DGK). Using a differential 32P-labelling protocol and a PLD-transphosphatidylation assay, evidence is provided that the rapid 32P-PtdOH response was primarily generated through DGK. A simultaneous decrease in the levels of 32P-PtdInsP, correlating in time, temperature dependency and magnitude with the increase in 32P-PtdOH, suggested that a PtdInsP-hydrolyzing PLC generated the DAG in this reaction. Testing T-DNA insertion lines available for the seven DGK genes, revealed no clear changes in 32P-PtdOH responses, suggesting functional redundancy. Similarly, known cold-stress mutants were analyzed to investigate whether the PtdOH response acted downstream of the respective gene products. The hos1, los1 and fry1 mutants were found to exhibit normal PtdOH responses. Slight changes were found for ice1, snow1, and the overexpression line Super-ICE1, however, this was not cold-specific and likely due to pleiotropic effects. A tentative model illustrating direct cold effects on phospholipid metabolism is presented.

/pdf/rapid-phosphatidic-acid-accumulation-in-response-to-low-3xktru1vuv.pdf

Rapid phosphatidic acid accumulation in response to low temperature stress in Arabidopsis is generated through diacylglycerol kinase

Autophagy is a mechanism by which cellular material is delivered to lysosomes for degradation, leading to the basal turnover of cell components and providing energy and macromolecular precursors. Autophagy has opposing, context-dependent roles in cancer, and interventions to both stimulate and inhibit autophagy have been proposed as cancer therapies. This has led to the therapeutic targeting of autophagy in cancer to be sometimes viewed as controversial. In this Review, we suggest a way forwards for the effective targeting of autophagy by understanding the context-dependent roles of autophagy and by capitalizing on modern approaches to clinical trial design.

/pdf/targeting-autophagy-in-cancer-2pjcn0h04a.pdf

Targeting autophagy in cancer

During the past several years there has been a dramatic increase in information on the role of ceramide in many cellular events. Many excellent and thorough reviews have been written on ceramide; therefore, the purpose of this chapter is to offer the reader a starting point in the body of literature focused on the role of ceramide in cell regulation. The field of ceramide signaling has rapidly expanded as studies reveal diverse roles for ceramide in cell biology and mechanisms of its regulation and action. Priorities for further study include determining the downstream actions of ceramide on protein targets that mediate specific cellular responses as well as determining the upstream events leading to ceramide production. Other key areas in need of further investigation include the subcellular localization of the substrates, enzymes, and protein targets of these sphingolipid signaling cascades.

CHAPTER 165 – The Role of Ceramide in Cell Regulation


 MYCN is amplified in 20% to 25% of neuroblastoma, and MYCN-amplified neuroblastoma contributes to a large percent of pediatric cancer-related deaths. Therapy improvements for this subtype of cancer are a high priority. Ferroptosis is an iron-dependent, oxidative form of cell death that is counteracted mainly by the production of Glutathione Peroxidase 4 (GPX4), a phospholipid hydroperoxidase that is produced through the glutathione pathway. The identification of cancers that may benefit from ferroptosis inducers are just emerging. Here we uncover a MYCN-dependent therapeutic vulnerability in neuroblastoma. Namely, amplified MYCN rewires the cell through expression of key receptors, ultimately enhancing iron influx through increased expression of the iron import transferrin receptor 1 (TFR1). Accumulating iron causes reactive oxygen species (ROS) production, and MYCN-amplified neuroblastomas show enhanced reliance on the system Xc- cystine/glutamate antiporter for ROS detoxification through increased transcription of this receptor. By performing metabolomics, we demonstrate that the transsulfuration pathway is also activated by MYCN. The increased activation of both pathways leads to cysteine accumulation that results in inhibition of lipid peroxidation. Utilizing drugs that target the main components of the glutathione and transsulfuration pathway we sensitize the MYCN neuroblastomas to ferroptotic cell death. These data provide novel insights into how MYCN alters the transcriptome in neuroblastoma to confer growth and survival advantages and simultaneously sheds light on the mechanism of action of ferroptosis inducers with potential application in other types of cancer.
 Citation Format: Konstantinos V. Floros, Mia O. Johnson-Berro, Richard Kurupi, Carter K. Fairchild, Krista Dalton, Bin Hu, Madhavi Puchalapalli, Mikhail G. Dozmorov, Jennifer E. Koblinski, James A. Olzmann, Lauren A. Cowart, Anthony C. Faber. MYCN-amplified neuroblastoma is addicted to iron and vulnerable to ferroptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 362.

Abstract 362: MYCN-amplified neuroblastoma is addicted to iron and vulnerable to ferroptosis

Lack of significant advancements in early detection and treatment of heart failure have precipitated the need for discovery of novel biomarkers and therapeutic targets. Over the past decade, circulating sphingolipids have elicited promising results as biomarkers that premonish adverse cardiac events. Additionally, compelling evidence directly ties sphingolipids to these events in patients with incident heart failure. This review aims to summarize the current literature on circulating sphingolipids in both human cohorts and animal models of heart failure. The goal is to provide direction and focus for future mechanistic studies in heart failure, as well as pave the way for the development of new sphingolipid biomarkers.

/pdf/circulating-sphingolipids-in-heart-failure-1jenbm21.pdf

Circulating sphingolipids in heart failure

Saccharomyces cerevisiae has been an invaluable tool for the dissection of sphingolipid metabolic pathways and cloning of enzymes involved in sphingolipid metabolism. Due to the biochemical conservation of these pathways in mammalian cells, information gained in yeast has greatly contributed to the understanding of sphingolipid formation and function in mammals. Sphingolipids are involved in diverse cellular processes in yeast including cell cycle control, stress responses, and various steps of intracellular protein transport. Importantly, yeast systems are allowing the characterization of mechanisms of sphingolipid involvement. In addition to sphingolipid signaling via interaction with direct protein targets, sphingolipids are involved in protein transport as components of lipid rafts, and also allow correct protein anchoring to membrane as components of GPI anchors. Novel methods and strategies are beginning to allow the placement of sphingolipids within broader cellular contexts.

http://link.springer.com/content/pdf/10.1007%2F978-3-540-40999-1_13.pdf

12 Baker’s Yeast: a rising foundation for eukaryotic sphingolipid-mediated cell signaling

Asthma is a chronic inflammatory disease affecting the airways which is characterized by reversible airflow obstruction, bronchial hyperresponsiveness, and airway remodeling. In allergic asthma, this airway pathology is mediated by Type 2 cytokines (IL-4, IL-5, and IL-13) and allergen-specific IgE. IL-4, IL-5, and IL-13 are predominantly produced by lung resident T helper 2 (Th2) cells and Type 2 innate lymphoid cells. The production of allergen-specific IgE from B cells is driven by a subset of IL-4 and IL-13 producing T follicular helper cells termed T follicular helper 13 (Tfh13) cells.1, 2 The initiation of these T-cell responses is mediated by dendritic cells (DCs). The mechanisms by which DCs regulate Th2 and Tfh13 polarization, however, are unclear. Several genome-wide association studies have identified that single-nucleotide polymorphisms (SNPs) in the D2HGDH locus are associated with allergic asthma and allergic rhinitis risk, with the G allele of rs34290285 associated with a lower risk of disease.3 The D2HGDH gene encodes the enzyme D-2-hydroxyglutarate dehydrogenase (D2HGDH), which converts D-2-hydroxyglutarate (D2HG) to α-ketoglutarate (α-KG). To elucidate the functional consequences of these SNPs, the regulatory landscape of the D2HGDH locus was analyzed using the ENCODE database. We found that the sentinel SNP, rs34290285, resides within a candidate cis-regulatory element (cCRE) with distal enhancer-like features in human monocytes (Figure 1A). Previously described lung eQTL analysis of the 10 most significant SNPs revealed that these asthma risk alleles are associated with reduced expression of D2HGDH mRNA in the lung (Figure 1B).3 As the lead SNP, rs34290285 is also associated with GAL3ST2, the effects of GAL3ST2 cannot be excluded.3 The downregulation of D2HGDH expression suggests that these SNPs may promote accumulation of D2HG, which is a potent endogenous inhibitor of α-KG-dependent dioxygenases, a group of histone demethylase and prolyl hydroxylase enzymes.4 Recent studies demonstrate that inhibition of these α-KG dependent histone demethylases in DCs results in a tolerogenic DC phenotype.5 D-2HG and α-KG, therefore, reciprocally regulate these dioxygenase enzymes to dynamically regulate gene expression via epigenetic mechanisms. Thus, we performed metabolomic analysis of murine bone marrow-derived dendritic cells following stimulation with LPS or the allergen Alternaria which revealed a significant increase in the ratio of α-KG to hydroxyglutarate following Alternaria treatment (Figure 1C). Therefore, we predicted that D-2HG may modulate DC function to alter allergic sensitization in a murine model of allergic airway inflammation. We found that intranasal administration of octyl-D-2HG, a cell permeable form of D-2HG, prior to intranasal exposure to Alternaria significantly reduced mediastinal lymph node (mLN) Th2, Tfh13, and Tfh2 cell polarization, but overall Tfh priming was unimpaired (Figure 2A–D. Figure S1A,B). Further, octyl-D2HG impaired mLN IgE+ germinal center B cell (GCBC) and IgE+ plasma cell (PC) differentiation (Figure 2E,F). IgG1+ GCBC and PC differentiation, however, was unaffected by octyl-D2HG administration (Figure S1C,D). Additionally, octyl-D-2HG administration promoted T follicular regulatory (Tfr) cell polarization, which act to restrain IgE production in allergic asthma (Figure 2G).6 Intranasal treatment of octyl-D2HG in a model of established murine allergic asthma resulted in a durable suppression of airway hyperreactivity for 4 days following treatment (Figure 2H,I) Additionally, mice treated with octyl-D2HG exhibited reduced levels of airway antigen-specific IgE and MCPT-1, indicating suppression of airway mast cell degranulation (Figure 2J,K). Overall, these data demonstrate that D2HG critically regulates allergic sensitization and the polarization of Th2 and Tfh13 cells following allergen exposure. Further, we demonstrate that D-2HG induces Tfr cell differentiation in response to allergens in a murine model of allergic asthma, but it is not clear if this is the mechanism by which D2HG reduces allergic airway inflammation. Octyl-D2HG treatment in allergen-sensitized mice demonstrated significant attenuation of airway hyperreactivity and may therefore be a potential therapeutic approach for the treatment of allergic asthma and other IgE-mediated diseases. A.T. and R.K.M. made substantial contributions to concept and design. A.T., A.K., J.A., and R.K.M. made substantial contributions to analysis and/or interpretation of data. All authors were involved in drafting and/or critically revising the manuscript. None. This work was supported by funding from VCU's CTSA (UL1TR002649 from the National Center for Advancing Translational Sciences) to R.K.M. and the CCTR Endowment Fund of VCU. Services and products in support of the research project were generated by the Virginia Commonwealth University (VCU) Massey Cancer Center Flow Cytometry Shared Resource and Metabolomics and Lipidomics Shared Resource supported, in part, with funding from NIH-NCI Cancer Support Grant P30 CA016059. Rebecca K. Martin and Anuj Tharakan own stock in Pleros Therapeutics Inc. which is currently of no value. The rest of the authors have no conflicts of interest to declare. The data that support the findings of this study are available from the corresponding author upon reasonable request. Data S1 Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/all.15809

L. Ashley Cowart

Papers

CHAPTER 165 – The Role of Ceramide in Cell Regulation

Abstract 362: MYCN-amplified neuroblastoma is addicted to iron and vulnerable to ferroptosis

Circulating sphingolipids in heart failure

12 Baker’s Yeast: a rising foundation for eukaryotic sphingolipid-mediated cell signaling

D-2-hydroxyglutarate suppresses allergic sensitization in a murine model of experimental asthma.