Cell Death Paradigms Research Articles

RIPK4 promotes oxidative stress and ferroptotic death through the downregulation of ACSM1

One of the most critical axes for cell fate determination is how cells respond to excessive reactive oxygen species (ROS)-oxidative stress. Extensive lipid peroxidation commits cells to death via a distinct cell death paradigm termed ferroptosis. However, the molecular mechanism regulating cellular fates to distinct ROS remains incompletely understood. Through siRNA against human receptor-interacting protein kinase (RIPK) family members, we found that RIPK4 is crucial for oxidative stress and ferroptotic death. Upon ROS induction, RIPK4 is rapidly activated, and the kinase activity of RIPK4 is indispensable to induce cell death. Specific ablation of RIPK4 in kidney proximal tubules protects mice from acute kidney injury induced by cisplatin and renal ischemia/reperfusion. RNA sequencing revealed the dramatically decreased expression of acyl-CoA synthetase medium-chain (ACSM) family members induced by cisplatin treatment which is compromised in RIPK4-deficient mice. Among these ACSM family members, suppression of ACSM1 strongly augments oxidative stress and ferroptotic cell death with induced expression of ACS long-chain family member 4, an important component for ferroptosis execution. Our lipidome analysis revealed that overexpression of ACSM1 leads to the accumulation of monounsaturated fatty acids, attenuation of polyunsaturated fatty acid (PUFAs) production, and thereby cellular resistance to ferroptosis. Hence, knockdown of ACSM1 resensitizes RIPK4 KO cells to oxidative stress and ferroptotic death. In conclusion, RIPK4 is a key player involved in oxidative stress and ferroptotic death, which is potentially important for a broad spectrum of human pathologies. The link between the RIPK4-ASCM1 axis to PUFAs and ferroptosis reveals a unique mechanism to oxidative stress-induced necrosis and ferroptosis.

The different paradigms of NK cell death in patients with severe trauma

Lymphocyte decline, particularly the depletion of NK cells, is a prominent feature of immunosuppression following severe tissue injury, heightening the susceptibility of severe trauma patients to life-threatening infections. Previous research indicates that the reduction in the number of NK cells is closely associated with the process of cell death. Nonetheless, the precise mechanism of NK cell death remains unknown. Here, we discovered that following severe traumatic injury, NK cells undergo several cell death pathways, dominated by apoptosis and pyroptosis with coexistence of necrotic cell death, immunogenic cell death, ferroptosis, and autophagy. These NK cells with different paradigms of death have diverse cytokine expression profiles and diverse interactions with other immune cells. Further exploration revealed that hypoxia was strongly associated with this diverse paradigm of NK cell death. Detailed investigation of paradigms of cell death may help to enhance comprehension of lymphopenia post-severe trauma, to develop new strategy in preventing immunosuppression, and then to improve outcome for severe trauma population.

MST1 interactomes profiling across cell death in esophageal squamous cell carcinoma

Abstract Objectives Resistance to apoptosis in esophageal squamous cell carcinoma (ESCC) constitutes a significant impediment to treatment efficacy. Exploring alternative cell death pathways and their regulatory factors beyond apoptosis is crucial for overcoming drug resistance and enhancing therapeutic outcomes in ESCC. Methods Mammalian Ste 20-like kinase 1 (MST1) is implicated in regulating various cell deaths, including apoptosis, autophagy, and pyroptosis. Employing enhanced ascorbate peroxidase 2 (APEX2) proximity labeling coupled with immunoprecipitation-mass spectrometry (IP-MS), we elucidated the interactomes of MST1 across these three cell death paradigms. Results Proteomic profiling unveiled the functional roles and subcellular localization of MST1 and its interacting proteins during normal proliferation and various cell death processes. Notably, MST1 exhibited an expanded interactome during cell death compared to normal proliferation and chromosome remodeling functions consistently. In apoptosis, there was a notable increase of mitosis-associated proteins such as INCENP, ANLN, KIF23, SHCBP1 and SUPT16H, which interacted with MST1, alongside decreased expression of the pre-apoptotic protein STK3. During autophagy, the bindings of DNA repair-related proteins CBX8 and m6A reader YTHDC1 to MST1 were enhanced. In pyroptosis, LRRFIP2 and FLII which can inhibit pyroptosis increasingly binding to MST1. Conclusions Our findings delineate potential mechanisms through which MST1 and its interactomes regulate cell death, paving the way for further investigation to validate and consolidate these observations.

A general strategy towards early endosome-stressed nanophotosensitizers for pyroptotic cancer therapy

Emerging evidence has revealed that induction of pyroptosis is a promising strategy for cancer therapy. However, it remains challenging to specifically evoke pyroptotic cancer cell death paradigm while sparing other programmed cell death pathways. Here, we report a general nanostrategy towards elicitation of precise oxidative stress in early endosomes (EE) by several nanosized photosensitizers (NPS) for robust pyroptotic cancer therapy. The spatiotemporally subcellular trafficking of NPS can regularly tune the pyroptosis-inducing activity of endocytic organelle stress. NPS-enabled EE oxidative stress (NPSee) initiates universal and robust gasdermin-E-mediated pyroptosis across different nanocarriers and cancer cell lines with up to 21.4-fold higher sensitivity, as compared with the traditional lysosomal stress. This EE-stressed nanostrategy achieves complete eradication of primary tumors with efficient immune response and long-lasting cancer prevention. This study provides guidelines for design of nanomedicines with pyroptosis-inducing activity for cancer therapy.

Zearalenone Induces Blood-Testis Barrier Damage through Endoplasmic Reticulum Stress-Mediated Paraptosis of Sertoli Cells in Goats.

Zearalenone (ZEA) is present worldwide as a serious contaminant of food and feed and causes male reproductive toxicity. The implication of paraptosis, which is a nonclassical paradigm of cell death, is unclear in ZEA-induced male reproductive disorders. In this study, the toxic effects of ZEA on the blood-testis barrier (BTB) and the related mechanisms of paraptosis were detected in goats. ZEA exposure, in vivo, caused a significant decrease in spermatozoon quality, the destruction of seminiferous tubules, and damage to the BTB integrity. Furthermore, ZEA exposure to Sertoli cells (SCs) in vitro showed similar dysfunction in structure and barrier function. Importantly, the formation of massive cytoplasmic vacuoles in ZEA-treated SCs corresponded to the highly swollen and dilative endoplasmic reticulum (ER), and paraptosis inhibition significantly alleviated ZEA-induced SC death and vacuolization, which indicated the important contribution of paraptosis in ZEA-induced BTB damage. Meanwhile, the expression of ER stress marker proteins was increased after ZEA treatment but decreased under the inhibition of paraptosis. The vacuole formation and SC death, induced by ZEA, were remarkably blocked by ER stress inhibition. In conclusion, these results facilitate the exploration of the mechanisms of the SC paraptosis involved in ZEA-induced BTB damage in goats.

Investigating the prognostic value of constructing disulfidptosis-related gene models for lung adenocarcinoma patients.

Disulfidptosis is a novel mode of cell death, a programmed mode of intracellular disulfide accumulation due to solute carrier family 7 member 11 (SLC7A11)-mediated abnormalities in the cell membrane cystine transport system. Numerous studies have confirmed the prominent role played by SLC7A11 in tumors, but the involvement of SLC7A11 as an important mediator of disulfidptosis in the death process of lung adenocarcinoma cells remains unclear. We obtained 4,107 SLC7A11-related genes and analyzed them using a total of 1,040 lung adenocarcinoma transcriptome sequencing data from The Cancer Genome Atlas (TCGA) cohort and GEO (Gene Expression Omnibus) cohort and 991 relevant clinical data. First, we screened for differential genes and identified molecular subtypes for assessing characteristic differences between lung adenocarcinoma subtypes under the influence of SLC7A11-associated genes. Then, risk score models were constructed to assess the prognosis, immune infiltration, tumor microenvironment, and drug treatment effects in lung adenocarcinoma patients. Finally, we also analyzed the distribution of cell types and expression of characteristic genes within the tumor using a single-cell database. In addition, relevant drug sensitivities were predicted. We screened 956 genes with significant differences and identified 2 molecular subtypes and found significant differences in their prognosis and that subtype B had a significantly better survival prognosis than subtype A. In addition, we found that pathways associated with cell proliferation division and DNA repair were enriched in the high-risk type A samples. Finally, we constructed a robust risk-scoring system, and our risk analysis revealed a general reduction of various immune cell components and tumor stromal components in the immune microenvironment of high-risk lung adenocarcinoma and a distinct immune infiltration pattern of immune cells, which was associated with a lower survival rate. Our comprehensive analysis of SLC7A11-related genes suggests that disulfidptosis has a potential value in the tumor microenvironment, immunity, clinical outcome, and prognosis of lung adenocarcinoma. These findings may increase our understanding of disulfidptosis as a novel cell death paradigm and provide ideas for assessing the prognosis of lung adenocarcinoma and developing new diagnostic and therapeutic strategies.

Paraptosis: a non-classical paradigm of cell death for cancer therapy.

Due to the sustained proliferative potential of cancer cells, inducing cell death is a potential strategy for cancer therapy. Paraptosis is a mode of cell death characterized by endoplasmic reticulum (ER) and/or mitochondrial swelling and cytoplasmic vacuolization, which is less investigated. Considerable evidence shows that paraptosis can be triggered by various chemical compounds, particularly in cancer cells, thus highlighting the potential application of this non-classical mode of cell death in cancer therapy. Despite these findings, there remain significant gaps in our understanding of the role of paraptosis in cancer. In this review, we summarize the current knowledge on chemical compound-induced paraptosis. The ER and mitochondria are the two major responding organelles in chemical compound-induced paraptosis, which can be triggered by the reduction of protein degradation, disruption of sulfhydryl homeostasis, overload of mitochondrial Ca2+, and increased generation of reactive oxygen species. We also discuss the stumbling blocks to the development of this field and the direction for further research. The rational use of paraptosis might help us develop a new paradigm for cancer therapy.

The ε-Isozyme of Protein Kinase C (PKCε) Is Impaired in ALS Motor Cortex and Its Pulse Activation by Bryostatin-1 Produces Long Term Survival in Degenerating SOD1-G93A Motor Neuron-like Cells.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and ultimately fatal neurodegenerative disease, characterized by a progressive depletion of upper and lower motor neurons (MNs) in the brain and spinal cord. The aberrant regulation of several PKC-mediated signal transduction pathways in ALS has been characterized so far, describing either impaired expression or altered activity of single PKC isozymes (α, β, ζ and δ). Here, we detailed the distribution and cellular localization of the ε-isozyme of protein kinase C (PKCε) in human postmortem motor cortex specimens and reported a significant decrease in both PKCε mRNA (PRKCE) and protein immunoreactivity in a subset of sporadic ALS patients. We furthermore investigated the steady-state levels of both pan and phosphorylated PKCε in doxycycline-activated NSC-34 cell lines carrying the human wild-type (WT) or mutant G93A SOD1 and the biological long-term effect of its transient agonism by Bryostatin-1. The G93A-SOD1 cells showed a significant reduction of the phosphoPKCε/panPKCε ratio compared to the WT. Moreover, a brief pulse activation of PKCε by Bryostatin-1 produced long-term survival in activated G93A-SOD1 degenerating cells in two different cell death paradigms (serum starvation and chemokines-induced toxicity). Altogether, the data support the implication of PKCε in ALS pathophysiology and suggests its pharmacological modulation as a potential neuroprotective strategy, at least in a subgroup of sporadic ALS patients.

Mechanistic paradigms of cell death - revisited

Present review is the description of a journey that originates from Virchows' cell theory and terminates with the role of molecular switches in cell death recently proposed by Orrenius. Landmark discoveries made, in between, to characterize regulated as well as accidental cell death have also been documented. It embraces the studies that were made in early nineties to understand cellular homeostasis in health and disease. Furthermore, the effects of foreign chemicals on different cell types witnessed in late nineties have been classified into necrosis, apoptosis, autophagy etc. Since it is important to know how a cell dies, studies made in our own and other laboratories on the role of reactive oxygen species, oxidative stress, intracellular Ca2+ homeostasis, redox imbalance, mitochondrial and ER stress in cell death have also been reviewed. Possibility of a cross talk amongst these mechanisms has also been examined. It discusses the impact of wonder molecules like CYP450, GSH, metallothionein and melatonin together with enzymatic and non-enzymatic antioxidants on cell death. Understanding the cellular targets and molecular mechanisms activated by a variety of environmental xenobiotics is fundamental for human health risk assessment. It is expected that the contents of this article will answer the fundamental question- why and how cells die.

Radiation and adjuvant drug-loaded liposomes target glioblastoma stem cells and trigger in-situ immune response.

BackgroundThe radio- and chemo-resistance of glioblastoma stem-like cells (GSCs), together with their innate tumor-initiating aptitude, make this cell population a crucial target for effective therapies. However, targeting GSCs is hardly difficult and complex, due to the presence of the blood–brain barrier (BBB) and the infiltrative nature of GSCs arousing their dispersion within the brain parenchyma.MethodsLiposomes (LIPs), surface-decorated with an Apolipoprotein E-modified peptide (mApoE) to enable BBB crossing, were loaded with doxorubicin (DOXO), as paradigm of cytotoxic drug triggering immunogenic cell death (ICD). Patient-derived xenografts (PDXs) obtained by GSC intracranial injection were treated with mApoE-DOXO-LIPs alone or concomitantly with radiation.ResultsOur results indicated that mApoE, through the engagement of the low-density lipoprotein receptor (LDLR), promotes mApoE-DOXO-LIPs transcytosis across the BBB and confers target specificity towards GSCs. Irradiation enhanced LDLR expression on both BBB and GSCs, thus further promoting LIP diffusion and specificity. When administered in combination with radiations, mApoE-DOXO-LIPs caused a significant reduction of in vivo tumor growth due to GSC apoptosis. GSC apoptosis prompted microglia/macrophage phagocytic activity, together with the activation of the antigen-presenting machinery crucially required for anti-tumor adaptive immune response.ConclusionsOur results advocate for radiotherapy and adjuvant administration of drug-loaded, mApoE-targeted nanovectors as an effective strategy to deliver cytotoxic molecules to GSCs at the surgical tumor margins, the forefront of glioblastoma (GBM) recurrence, circumventing BBB hurdles. DOXO encapsulation proved in situ immune response activation within GBM microenvironment.

The role of necroptosis and apoptosis through the oxidative stress pathway in the liver of selenium-deficient swine.

Necroptosis is regarded as a new paradigm of cell death that plays a key role in the liver damage observed with selenium (Se) deficiency. Se deficiency has a significant impact on the livestock and poultry industries. Previous studies have confirmed that Se deficiency causes serious injury to the swine liver; however, it is unclear whether this liver damage is the result of necroptosis and apoptosis. To understand the damage induced by Se deficiency, swine were divided into a control group and Se-deficient group. The results showed that in the liver of swine, Se deficiency initiated apoptosis by increasing the expression of cysteinyl aspartate specific proteinase 3 (caspase-3), cysteinyl aspartate specific proteinase 9 (caspase-9) and BCL-2 antagonist/killer (BAK) at both the mRNA and protein levels and by decreasing the B cell lymphoma/leukemia 2 (BCL-2) levels compared with the levels in the control group. Meanwhile, compared with the control group, necroptosis was confirmed in the liver of Se-deficient swine through increased the expression of mixed lineage kinase domain like pseudokinase (MLKL) and receptor interacting serine/threonine kinase 1 (RIPK1) at both the mRNA and protein levels. In addition, the activities of catalase (CAT), nitric oxide (NO), and total antioxidative capacity (T-AOC) were clearly increased (P < 0.05), and the activities of OH- and total nitric oxide synthase (TNOS) were obviously decreased (P < 0.05), whereas in the Se-deficient group, the hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels were obviously increased (P < 0.05) compared with those in the control group. Moreover, the number of apoptotic cells was increased significantly in the Se-deficient group, and the liver tissues showed obvious necroptosis damage. These results show that Se deficiency induces apoptosis and necroptosis through the oxidative stress pathway in the swine liver.

Imaging Mitochondrial Functions: from Fluorescent Dyes to Genetically-Encoded Sensors.

Mitochondria are multifunctional organelles that are crucial to cell homeostasis. They constitute the major site of energy production for the cell, they are key players in signalling pathways using secondary messengers such as calcium, and they are involved in cell death and redox balance paradigms. Mitochondria quickly adapt their dynamics and biogenesis rates to meet the varying energy demands of the cells, both in normal and in pathological conditions. Therefore, understanding simultaneous changes in mitochondrial functions is crucial in developing mitochondria-based therapy options for complex pathological conditions such as cancer, neurological disorders, and metabolic syndromes. To this end, fluorescence microscopy coupled to live imaging represents a promising strategy to track these changes in real time. In this review, we will first describe the commonly available tools to follow three key mitochondrial functions using fluorescence microscopy: Calcium signalling, mitochondrial dynamics, and mitophagy. Then, we will focus on how the development of genetically-encoded fluorescent sensors became a milestone for the understanding of these mitochondrial functions. In particular, we will show how these tools allowed researchers to address several biochemical activities in living cells, and with high spatiotemporal resolution. With the ultimate goal of tracking multiple mitochondrial functions simultaneously, we will conclude by presenting future perspectives for the development of novel genetically-encoded fluorescent biosensors.

Drug-induced PD-L1 expression and cell stress response in breast cancer cells can be balanced by drug combination

The impact of chemotherapy on tumor-immune system interaction can be either beneficial or harmful, which is represented by the immunogenic cell death (ICD) paradigm or overexpression of the immunosuppressive protein – programmed death ligand 1 (PD-L1). In this study we explore the impact of steroid receptor coactivator inhibitor, other targeted anti-cancer compounds and traditional chemotherapeutic agents on the expression of PD-L1 in four breast cancer (BC) cell lines. Our results show that these agents induce PD-L1 expression, yet the magnitude of this induction varies substantially across the different compounds. In addition, we utilized the E0771 ER + BC cells as a model to examine in greater detail the relationship between pharmacological pressure, cell stress and the induction of PD-L1. Our results imply that drug induced PD-L1 expression occurs in the broader context of cell-stress, without conferring acquired drug-resistance. Furthermore, a balance between BC cytotoxicity, induction of cell-stress and the overexpression of PD-L1 can be achieved through the selection of appropriate combinations of anti-cancer compounds. Therefore, we propose that drug combination can be employed not only for increasing the direct kill of cancer cells, but also as a strategy to minimize the activation of immunosuppressive and cancer cell pro-survival program responses during drug treatment.

The regulatory effects of miR-138-5p on selenium deficiency-induced chondrocyte apoptosis are mediated by targeting SelM.

Apoptosis is a common paradigm of cell death and plays a key role in cartilage damage and selenium (Se) deficiency. Selenoproteins play major roles in determining the biological effects of Se, and are potentially involved in the pathophysiological processes in bone tissue. MicroRNAs (miRNAs) play important roles in cell proliferation, differentiation, apoptosis and tumorigenesis. Based on the preliminary results, the expression of selenoprotein M (SelM) was significantly decreased (69%) in chicken cartilage tissues with Se deficiency, and we subsequently screened and verified that SelM is one of the target genes of miR-138-5p in chicken cartilage using a dual luciferase reporter assay and real-time quantitative PCR (qRT-PCR). The expression of miR-138-5p was increased in response to Se deficiency, and the overexpression of miR-138-5p increased caspase-3, caspase-9, BAX and BAK levels, while the BCL-2 level was decreased, suggesting that miR-138-5p induced apoptosis via the mitochondrial pathway in vivo and in vitro. We explored whether oxidative stress, mitochondrial fission and fusion, and energy metabolism might trigger apoptosis to obtain an understanding of the mechanisms underlying the effects of miR-138-5p on Se deficiency-induced apoptosis in cartilage. The levels of indicators of oxidative stress, mitochondrial dynamics and energy metabolism were changed as well. This study confirmed that SelM is one of the target genes of miR-138-5p, and the overexpression of miR-138-5p induced by Se deficiency triggered oxidative stress, an imbalance in mitochondrial fission and fusion, and energy metabolism dysfunction. Therefore, miR-138-5p is involved in the mitochondrial apoptosis pathway via targeting SelM in chicken chondrocytes.

Caspase selective reagents for diagnosing apoptotic mechanisms.

Apical caspases initiate and effector caspases execute apoptosis. Reagents that can distinguish between caspases, particularly apical caspases-8, 9, and 10 are scarce and generally nonspecific. Based upon a previously described large-scale screen of peptide-based caspase substrates termed HyCoSuL, we sought to develop reagents to distinguish between apical caspases in order to reveal their function in apoptotic cell death paradigms. To this end, we selected tetrapeptide-based sequences that deliver optimal substrate selectivity and converted them to inhibitors equipped with a detectable tag (activity-based probes-ABPs). We demonstrate a strong relationship between substrate kinetics and ABP kinetics. To evaluate the utility of selective substrates and ABPs, we examined distinct apoptosis pathways in Jurkat T lymphocyte and MDA-MB-231 breast cancer lines triggered to undergo cell death via extrinsic or intrinsic apoptosis. We report the first highly selective substrate appropriate for quantitation of caspase-8 activity during apoptosis. Converting substrates to ABPs promoted loss-of-activity and selectivity, thus we could not define a single ABP capable of detecting individual apical caspases in complex mixtures. To overcome this, we developed a panel strategy utilizing several caspase-selective ABPs to interrogate apoptosis, revealing the first chemistry-based approach to uncover the participation of caspase-8, but not caspase-9 or -10 in TRAIL-induced extrinsic apoptosis. We propose that using select panels of ABPs can provide information regarding caspase-8 apoptotic signaling more faithfully than can single, generally nonspecific reagents.

MiR-200a-5p regulates myocardial necroptosis induced by Se deficiency via targeting RNF11

Necroptosis has been discovered as a new paradigm of cell death and may play a key role in heart disease and selenium (Se) deficiency. Hence, we detected the specific microRNA (miRNA) in response to Se-deficient heart using microRNAome analysis. For high-throughput sequencing using Se-deficient chicken cardiac tissue, we selected miR-200a-5p and its target gene ring finger protein 11 (RNF11) based on differential expression in cardiac tissue and confirmed the relationship between miR-200a-5p and RNF11 by dual luciferase reporter assay and real-time quantitative PCR (qRT-PCR) in cardiomyocytes. We further explored the function of miR-200a-5p and observed that overexpression of miR-200a-5p spark the receptor interacting serine/threonine kinase 3 (RIP3)-dependent necroptosis in vivo and in vitro. To understand whether miR-200a-5p and RNF11 are involved in the RIP3-dependent necroptosis pathway, we presumed that oxidative stress, inflammation response and the mitogen-activated protein kinase (MAPK) pathway might trigger necroptosis. Interestingly, necroptosis trigger, z-VAD-fmk, failed to induce necroptosis but enhanced cell survival against necrosis in cardiomyocytes with knockdown of miR-200a-5p. Our present study provides a new insight that the modulation of miR-200a-5p and its target gene might block necroptosis in the heart, revealing a novel myocardial necrosis regulation model in heart disease.

SK2 channels regulate mitochondrial respiration and mitochondrial Ca2+ uptake.

Mitochondrial calcium ([Ca2+]m) overload and changes in mitochondrial metabolism are key players in neuronal death. Small conductance calcium-activated potassium (SK) channels provide protection in different paradigms of neuronal cell death. Recently, SK channels were identified at the inner mitochondrial membrane, however, their particular role in the observed neuroprotection remains unclear. Here, we show a potential neuroprotective mechanism that involves attenuation of [Ca2+]m uptake upon SK channel activation as detected by time lapse mitochondrial Ca2+ measurements with the Ca2+-binding mitochondria-targeted aequorin and FRET-based [Ca2+]m probes. High-resolution respirometry revealed a reduction in mitochondrial respiration and complex I activity upon pharmacological activation and overexpression of mitochondrial SK2 channels resulting in reduced mitochondrial ROS formation. Overexpression of mitochondria-targeted SK2 channels enhanced mitochondrial resilience against neuronal death, and this effect was inhibited by overexpression of a mitochondria-targeted dominant-negative SK2 channel. These findings suggest that SK channels provide neuroprotection by reducing [Ca2+]m uptake and mitochondrial respiration in conditions, where sustained mitochondrial damage determines progressive neuronal death.

BID links ferroptosis to mitochondrial cell death pathways

Ferroptosis has been defined as an oxidative and iron-dependent pathway of regulated cell death that is distinct from caspase-dependent apoptosis and established pathways of death receptor-mediated regulated necrosis. While emerging evidence linked features of ferroptosis induced e.g. by erastin-mediated inhibition of the Xc- system or inhibition of glutathione peroxidase 4 (Gpx4) to an increasing number of oxidative cell death paradigms in cancer cells, neurons or kidney cells, the biochemical pathways of oxidative cell death remained largely unclear. In particular, the role of mitochondrial damage in paradigms of ferroptosis needs further investigation.In the present study, we find that erastin-induced ferroptosis in neuronal cells was accompanied by BID transactivation to mitochondria, loss of mitochondrial membrane potential, enhanced mitochondrial fragmentation and reduced ATP levels. These hallmarks of mitochondrial demise are also established features of oxytosis, a paradigm of cell death induced by Xc- inhibition by millimolar concentrations of glutamate. Bid knockout using CRISPR/Cas9 approaches preserved mitochondrial integrity and function, and mediated neuroprotective effects against both, ferroptosis and oxytosis. Furthermore, the BID-inhibitor BI-6c9 inhibited erastin-induced ferroptosis, and, in turn, the ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 prevented mitochondrial dysfunction and cell death in the paradigm of oxytosis. These findings show that mitochondrial transactivation of BID links ferroptosis to mitochondrial damage as the final execution step in this paradigm of oxidative cell death.

IAPs and Cell Death.

IAPs were named as inhibitors of apoptosis, programmed cell death, but it has become apparent that they are regulators of other types of cell death too. Because they inhibit cell death in cancer cells there has been an intense interest in developing inhibitors of these proteins to induce or sensitise cancer cells to death. In this article, we will discuss the involvement of IAPs in the apoptosis, necroptosis and pyroptosis programmed cell death paradigms. All these types of cell death are intimately involved with causing or repressing inflammation and it should perhaps therefore come as no surprise that IAPs are also involved in regulating inflammation directly. To come full circle, the IAP antagonist drugs that were developed to sensitise cancer cells to apoptosis have led to some of these insights.

Cell death by autophagy: emerging molecular mechanisms and implications for cancer therapy.

Autophagy is a tightly-regulated catabolic process of cellular self-digestion by which cellular components are targeted to lysosomes for their degradation. Key functions of autophagy are to provide energy and metabolic precursors under conditions of starvation and to alleviate stress by removal of damaged proteins and organelles, which are deleterious for cell survival. Therefore, autophagy appears to serve as a pro-survival stress response in most settings. However, the role of autophagy in modulating cell death is highly dependent on the cellular context and its extent. There is an increasing evidence for cell death by autophagy, in particular in developmental cell death in lower organisms and in autophagic cancer cell death induced by novel cancer drugs. The death-promoting and -executing mechanisms involved in the different paradigms of autophagic cell death (ACD) are very diverse and complex, but a draft scenario of the key molecular targets involved in ACD is beginning to emerge. This review provides an up-to-date and comprehensive report on the molecular mechanisms of drug-induced autophagy-dependent cell death and highlights recent key findings in this exciting field of research.