Essential versus accessory aspects of cell death: recommendations of the NCCD 2015

PRC2 loss induces chemoresistance by repressing apoptosis in T cell acute lymphoblastic leukemia

The tendency of mitochondria to undergo or resist BCL2-controlled apoptosis (so-called mitochondrial priming) is a powerful predictor of response to cytotoxic chemotherapy. Fully exploiting this finding will require unraveling the molecular genetics underlying phenotypic variability in mitochondrial priming. Here, we report that mitochondrial apoptosis resistance in T cell acute lymphoblastic leukemia (T-ALL) is mediated by inactivation of polycomb repressive complex 2 (PRC2). In T-ALL clinical specimens, loss-of-function mutations of PRC2 core components (EZH2, EED, or SUZ12) were associated with mitochondrial apoptosis resistance. In T-ALL cells, PRC2 depletion induced resistance to apoptosis induction by multiple chemotherapeutics with distinct mechanisms of action. PRC2 loss induced apoptosis resistance via transcriptional up-regulation of the LIM domain transcription factor CRIP2 and downstream up-regulation of the mitochondrial chaperone TRAP1 These findings demonstrate the importance of mitochondrial apoptotic priming as a prognostic factor in T-ALL and implicate mitochondrial chaperone function as a molecular determinant of chemotherapy response.

Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?

The purpose of this paper was to investigate chondrocyte distribution and death in the cartilage in Kashin-Beck disease (KBD). Apoptotic chondrocytes were detected by TUNEL assay. Ultrastructural changes were examined by transmission electron microscope (TEM). Biochemical markers associated with apoptosis (eg, caspase-3) and necroptosis (eg, RIP3) were investigated by immunohistochemistry. In KBD cartilage chondrocyte death was characterized by paler staining of the cells. Multiple chondral cell clusters surrounded the areas lacking cells in the deep zone. The per cent of TUNEL-positive and RIP3-positive chondrocytes were higher in the middle zones of KBD samples; however, there was some positive staining for TUNEL but negative staining for caspase-3. Immunohistochemistry failed to detect significant differences in caspase-3 levels in KBD children compared to controls, suggesting that beside apoptosis necroptosis dominates as a cell death mechanism in the middle zone of cartilage from KBD children. To clarify further the presence of chondrocyte necroptosis in KBD, we performed TUNEL, caspase-3 and RIP3 staining in a rat KBD model which is based upon T-2 toxin treatment under selenium-deficient conditions. Apoptosis and necroptosis co-existed in the middle zone in this rat KBD model. Ultrastructural analysis of chondrocyte from deep cartilage revealed abnormal cells with numerous morphological changes, such as plasma membrane breakdown, generalized swelling of the cytoplasm and loss of identifiable organelles. Chondrocyte death by necrosis in the deep zone of cartilages in KBD may be a result of exposure to T-2 toxin from bone marrow or bloodstream under selenium-deficient nutrition status in KBD endemic areas. Chondrocyte death plays a key role in either the initiation or the progression of KBD pathogenesis.

Molecular Targeted Therapies Elicit Concurrent Apoptotic and GSDME-Dependent Pyroptotic Tumor Cell Death

PURPOSE

The induced death signals following oncogene inhibition underlie clinical efficacy of molecular targeted therapies against human cancer, and defects of intact cell apoptosis machinery often lead to therapeutic failure. Despite potential importance, other forms of regulated cell death triggered by pharmacologic intervention have not been systematically characterized.

EXPERIMENTAL DESIGN

Pyroptotic cell death was assessed by immunoblot analysis, phase-contrast imaging, scanning electron microscopy, and flow cytometry. Tumor tissues of patients with lung cancer were analyzed using IHC. Functional impact of pyroptosis on drug response was investigated in cell lines and xenograft models.

RESULTS

We showed that diverse small-molecule inhibitors specifically targeting KRAS-, EGFR-, or ALK-driven lung cancer uniformly elicited robust pyroptotic cell death, in addition to simultaneously invoking cellular apoptosis. Upon drug treatment, the mitochondrial intrinsic apoptotic pathway was engaged and the mobilized caspase-3 protease cleaved and activated gasdermin E (GSDME, encoded by DFNA5), which permeabilized cytoplasmic membrane and executed cell-lytic pyroptosis. GSDME displayed ubiquitous expression in various lung cancer cell lines and clinical specimens, including KRAS-mutant, EGFR-altered, and ALK-rearranged adenocarcinomas. As a result, cooccurrence and interplay of apoptosis and pyroptosis were widespread in lung cancer cells, succumbing to genotype-matched regimens. We further demonstrated that pyroptotic cell death partially contributed to the drug response in a subset of cancer models.

CONCLUSIONS

These results pinpoint GSDME-dependent pyroptosis as a previously unrecognized mechanism of action for molecular targeted agents to eradicate oncogene-addicted neoplastic cells, which may have important implications for the clinical development and optimal application of anticancer therapeutics.

Spontaneous Cancers, But Not Many Induced Ones in Animals, Resemble Semi-New Organisms that Possess a Unique Programmed Cell Death Mode Different from Apoptosis, Senescent Death, Necrosis and Stress-Induced Cell Death

There are four basic cell death modes in animals, i.e. physiological senescent death (SD) and apoptosis as well as pathological necrosis and stress-induced cell death (SICD). There have been numerous publications describing “apoptosis” in cancer, mostly focused on killing cancer cells using radio- or chemo-therapy, with few on exploring how cancer cells die naturally without such treatments. Spontaneous benign or malignant neoplasms are immortal and autonomous, but they still retain some allegiance to their parental tissue or organ and thus are still somewhat controlled by the patient's body. Because of these properties of immortality, semi-autonomy, and semi-allegiance to the patient's body, spontaneous tumors have no redundant cells and resemble “semi-new organisms” parasitizing the patients, becoming a unique tissue type possessing a hitherto unannotated cell death mode besides SD, apoptosis, necrosis and SICD. Particularly, apoptosis aims to expunge redundant cells, whereas this new mode does not. In contrast to spontaneous tumors, many histologically malignant tumors induced in experimental animals, before they reach an advanced stage, regress after withdrawal of the inducer. This mortal and non-autonomous nature disqualifies these animal lesions as authentic neoplasms and as semi-new organisms but makes them a good tissue type for apoptosis studies. Ruminating over cell death in spontaneous cancers and many inauthentic tumors induced in animals from these new slants makes us realize that “whether cancer cells undergo apoptosis” is not an easy question with a simple answer. Our answer is that cancer cells have an uncharacterized programmed cell death mode, which is not apoptosis.

Cell Death Patterns Due to Warm Ischemia or Reperfusion in Renal Tubular Epithelial Cells Originating from Human, Mouse, or the Native Hibernator Hamster

Ischemia⁻reperfusion injury contributes to the pathogenesis of many diseases, with acute kidney injury included. Hibernating mammals survive prolonged bouts of deep torpor with a dramatic drop in blood pressure, heart, and breathing rates, interspersed with short periods of arousal and, consequently, ischemia⁻reperfusion injury. Clarifying the differences under warm anoxia or reoxygenation between human cells and cells from a native hibernator may reveal interventions for rendering human cells resistant to ischemia⁻reperfusion injury. Human and hamster renal proximal tubular epithelial cells (RPTECs) were cultured under warm anoxia or reoxygenation. Mouse RPTECs were used as a phylogenetic control for hamster cells. Cell death was assessed by both cell imaging and lactate dehydrogenase (LDH) release assay, apoptosis by cleaved caspase-3, autophagy by microtubule-associated protein 1-light chain 3 B II (LC3B-II) to LC3B-I ratio, necroptosis by phosphorylated mixed-lineage kinase domain-like pseudokinase, reactive oxygen species (ROS) fluorometrically, and lipid peroxidation, the end-point of ferroptosis, by malondialdehyde. Human cells died after short periods of warm anoxia or reoxygenation, whereas hamster cells were extremely resistant. In human cells, apoptosis contributed to cell death under both anoxia and reoxygenation. Although under reoxygenation, ROS increased in both human and hamster RPTECs, lipid peroxidation-induced cell death was detected only in human cells. Autophagy was observed only in human cells under both conditions. Necroptosis was not detected in any of the evaluated cells. Clarifying the ways that are responsible for hamster RPTECs escaping from apoptosis and lipid peroxidation-induced cell death may reveal interventions for preventing ischemia⁻reperfusion-induced acute kidney injury in humans.

Prophylactic intervention of probiotics (L.acidophilus, L.rhamnosus GG) and celecoxib modulate Bax-mediated apoptosis in 1,2-dimethylhydrazine-induced experimental colon carcinogenesis

BACKGROUND

Colorectal cancer has been found to be attenuated either with prophylactic manipulation of gut microbiome with probiotics or celecoxib, a non-steroidal anti-inflammatory drug mainly by suppressing early pro-carcinogenic markers in various experimental studies. Therefore, the present study was designed to assess the prophylactic potential of combinatorial administration of probiotics (Lactobacillus rhamnosus GG, Lactobacillus acidophilus) and celecoxib in experimental colon carcinogenesis.

METHODS

Six groups of Spraugue Dawely rats received probiotics L.rhamnosus GG or/and L.acidophilus in combination with celecoxib one week prior to the inducement of tumor by 1,2-dimethylhydrazine (DMH) and the treatment continued for 18 weeks. Prophylactic potentials of probiotics and celecoxib were determined by employing various methods such as tumor incidence, tumor burden, tumor multiplicity, apoptosis, caspase activity, expression of proto-oncogene K-ras and tumor suppressor p53 gene in colonic tumors.

RESULTS

Interestingly, it was found that one week prior supplementation of both probiotics and celecoxib reduced tumor burden, tumor multiplicity, down-regulated the expression of anti-apoptotic Bcl-2, proto-oncogene K-ras and up-regulated pro-apoptotic Bax as well as tumor suppressor p53 in L.rhamnosus GG + celecoxib+DMH animals compared with counter controls and DMH-treated.

CONCLUSIONS

It can be concluded that such combinatorial approach may be useful in reducing the burden and severity of disease in highly susceptible individuals but needs to be validated clinically.

Induction of intracellular ferritin expression in embryo-derived Ixodes scapularis cell line (ISE6)

Iron is a very important nutrient for cells; however, it could also cause fatal effects because of its capability to trigger oxidative stress. Due to high exposure to iron from their blood diet, ticks make use of several mechanisms to cope up with oxidative stress. One mechanism is iron sequestration by ferritin and its control protein (IRP). Since the IRP activity is dependent on the ferrous iron concentration, we tried to induce intracellular ferritin (FER1) protein expression by exposing Ixodes scapularis embryo-derived cell line (ISE6) to different concentrations of ferrous sulphate at different time points. We were able to induce FER1 protein after exposure to 2 mM of ferrous sulphate for 48 h, as observed in both Western blotting and indirect immunofluorescent antibody tests. This could indicate that the FER1 produced could be a product of the release of IRPs from the FER1 mRNA leading to its translation. The RNA interference of FER1, through the transfection of dsRNA, led to an increase in mortality and decrease in the cellular proliferation of ISE6 cells. Overall, ISE6 cells could be a good tool in further understanding the mechanism of FER1 action, not just in Ixodes ticks but in other tick species as well.

Anthracyclines as Topoisomerase II Poisons: From Early Studies to New Perspectives

Mammalian DNA topoisomerases II are targets of anticancer anthracyclines that act by stabilizing enzyme-DNA complexes wherein DNA strands are cut and covalently linked to the protein. This molecular mechanism is the molecular basis of anthracycline anticancer activity as well as the toxic effects such as cardiomyopathy and induction of secondary cancers. Even though anthracyclines have been used in the clinic for more than 50 years for solid and blood cancers, the search of breakthrough analogs has substantially failed. The recent developments of personalized medicine, availability of individual genomic information, and immune therapy are expected to change significantly human cancer therapy. Here, we discuss the knowledge of anthracyclines as Topoisomerase II poisons, their molecular and cellular effects and toxicity along with current efforts to improve the therapeutic index. Then, we discuss the contribution of the immune system in the anticancer activity of anthracyclines, and the need to increase our knowledge of molecular mechanisms connecting the drug targets to the immune stimulatory pathways in cancer cells. We propose that the complete definition of the molecular interaction of anthracyclines with the immune system may open up more effective and safer ways to treat patients with these drugs.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Toxic effects of nickel oxide (NiO) nanoparticles on the freshwater alga Pseudokirchneriella subcapitata

Over the last decade, concerns have been raised regarding the potential health and environmental effects associated with the release of metal oxide nanoparticles (NPs) into ecosystems. In the present work, the potential hazards of nickel oxide (NiO) NPs were investigated using the ecologically relevant freshwater alga Pseudokirchneriella subcapitata. NiO NP suspensions in algal OECD medium were characterized with regard to their physicochemical properties: agglomeration, surface charge, stability (dissolution of the NPs) and abiotic reactive oxygen species (ROS) production. NiO NPs formed loose agglomerates and released Ni²⁺. NiO NPs presented a 72 h-EC₅₀ of 1.6 mg L^-1, which was evaluated using the algal growth inhibition assay and allowed this NP to be classified as toxic. NiO NPs caused the loss of esterase activity (metabolic activity), the bleaching of photosynthetic pigments and the intracellular accumulation of reactive oxygen species (ROS) in the absence of the disruption of plasma membrane integrity. NiO NPs also disturbed the photosynthetic process. A reduction in the photosynthetic efficiency (Φ_PSII) accompanied by a decrease in the flow rate of electrons through the photosynthetic chain was also observed. The leakage of electrons from the photosynthetic chain may be the origin of the ROS found in the algal cells. The exposure to NiO NPs led to the arrest of the cell cycle prior to the first cell division (primary mitosis), an increase in cell volume and the presence of aberrant morphology in the algal cells. In this work, the use of different approaches allowed new clues related to the toxicity mechanisms of NiO NPs to be obtained. This work also contributes to the characterization of the environmental and toxicological hazards of NiO NPs and provides information on the possible adverse effects of these NPs on aquatic systems.

I Spy in the Developing Fly a Multitude of Ways to Die

Cell proliferation and cell death are two opposing, yet complementary fundamental processes in development. Cell proliferation provides new cells, while developmental programmed cell death adjusts cell numbers and refines structures as an organism grows. Apoptosis is the best-characterized form of programmed cell death; however, there are many other non-apoptotic forms of cell death that occur throughout development. Drosophila is an excellent model for studying these varied forms of cell death given the array of cellular, molecular, and genetic techniques available. In this review, we discuss select examples of apoptotic and non-apoptotic cell death that occur in different tissues and at different stages of Drosophila development. For example, apoptosis occurs throughout the nervous system to achieve an appropriate number of neurons. Elsewhere in the fly, non-apoptotic modes of developmental cell death are employed, such as in the elimination of larval salivary glands and midgut during metamorphosis. These and other examples discussed here demonstrate the versatility of Drosophila as a model organism for elucidating the diverse modes of programmed cell death.

Mathematical Models of Cell Response Following Heating

The cells of the cardiovascular system can experience temperature excesses of a few degrees during a diseased state or of tens of degrees during a thermal therapy treatment. These raised temperatures may be acute or of long duration. The multiple cell lines that compose each tissue then react, in approximate order of increasing thermal insult, by expressing heat shock proteins, undergoing apoptosis, or suffering necrosis. Mathematical models of the response of cells could aid in planning and designing thermal therapies. The multi-factor nature of the cell response makes it challenging to develop such models. The models most used clinically are mathematically simple and based on the response of representative tissues. The model that might provide the most fundamental understanding of the biochemical response of cells requires many parameters, some of which are difficult to measure. None of the semi-empirical models that provide improved prediction of cell fate have been widely accepted to plan therapies. There remain great opportunities for developing mathematical models cell response.

Regulated Necrosis Orchestrates Microglial Cell Death in Manganese-Induced Toxicity

Microglia, the brain resident immune cells, play prominent roles in immune surveillance, tissue repair and neural regeneration. Despite these pro-survival actions, the relevance of these cells in the progression of several neuropathologies has been established. In the context of manganese (Mn) overexposure, it has been proposed that microglial activation contributes to enhance the neurotoxicity. However, the occurrence of a direct cytotoxic effect of Mn on microglial cells remains controversial. In the present work, we investigated the potential vulnerability of immortalized mouse microglial cells (BV-2) toward Mn²⁺, focusing on the signaling pathways involved in cell death. Evidence obtained showed that Mn²⁺ induces a decrease in cell viability which is associated with reactive oxygen species (ROS) generation. In this report we demonstrated, for the first time, that Mn²⁺ triggers regulated necrosis (RN) in BV-2 cells involving two central mechanisms: parthanatos and lysosomal disruption. The occurrence of parthanatos is supported by several cellular and molecular events: (i) DNA damage; (ii) AIF translocation from mitochondria to the nucleus; (iii) mitochondrial membrane permeabilization; and (iv) PARP1-dependent cell death. On the other hand, Mn²⁺ induces lysosomal membrane permeabilization (LMP) and cathepsin D (CatD) release into the cytosol supporting the lysosomal disruption. Pre-incubation with CatB and D inhibitors partially prevented the Mn²⁺-induced cell viability decrease. Altogether these events point to lysosomes as players in the execution of RN. In summary, our results suggest that microglial cells could be direct targets of Mn²⁺ damage. In this scenario, Mn²⁺ triggers cell death involving RN pathways.

Trial Watch: Toll-like receptor agonists in cancer immunotherapy

Toll-like receptor (TLR) agonists demonstrate therapeutic promise as immunological adjuvants for anticancer immunotherapy. To date, three TLR agonists have been approved by US regulatory agencies for use in cancer patients. Additionally, the potential of hitherto experimental TLR ligands to mediate clinically useful immunostimulatory effects has been extensively investigated over the past few years. Here, we summarize recent preclinical and clinical advances in the development of TLR agonists for cancer therapy.

Molecular Targets Modulated by Fangchinoline in Tumor Cells and Preclinical Models

Despite tremendous progress made during the last few decades in the treatment options for cancer, compounds isolated from Mother Nature remain the mainstay for therapy of various malignancies. Fangchinoline, initially isolated from the dried root of Stephaniae tetrandrine, has been found to exhibit diverse pharmacological effects including significant anticancer activities both in tumor cell lines and selected preclinical models. This alkaloid appears to act by modulating the activation of various important oncogenic molecules involved in tumorigenesis leading to a significant decrease in aberrant proliferation, survival and metastasis of tumor cells. This mini-review briefly describes the potential effects of fangchinoline on important hallmarks of cancer and highlights the molecular targets modulated by this alkaloid in various tumor cell lines and preclinical models.

Classification, Scoring, and Quantification of Cell Death in Tissue Sections

The analysis and description of the appearance of cell death in tissue sections can add valuable information to research studies. The scoring/grading and quantification of cell death can be used either as part of a larger scoring scheme or as the final end point of a study. The degree of precision needed is study dependent and will be determined by the question being addressed and the complexity of the model. The methods one uses to quantify cell death are often guided by the tissue of interest. For example, in the brain, it is sometimes necessary to examine death of specific neuronal populations, whereas in more homogeneous tissue such as a tumor xenograft, quantification can be done on a whole-slide basis. In addition to examination of hematoxylin and eosin (HE)–stained sections, immunohistochemistry can be employed to highlight areas of cell death or to identify specific types of cell death, for example, when differentiating apoptosis from necrosis. Automated quantification can be useful in generating statistically comparable data from HE-stained or immunolabeled samples. The rapidly expanding classification of cell death requires the use of multiple techniques to identify them in vivo. This article will provide examples of how different methods of examining and quantifying cell death are used in a variety of research areas, ranging from semiquantitative evaluation in HE-stained intestine to automated quantification of immunohistochemistry-immunolabeled brain and tumor xenografts. The recently described process of necroptosis will be discussed briefly, with the description and example of the methods used to differentiate this from apoptosis.

Iron and magnetic: new research direction of the ferroptosis-based cancer therapy

Ferroptosis is an iron depend cell death which caused by lipid peroxidation. Abnormal iron metabolism and high intracellular iron content are the characteristics of most cancer cells. Iron is a promoter of cell growth and proliferation. However, iron also could take part in Fenton reaction to produce reactive oxygen species (ROS). The intercellular ROS could induce lipid peroxidation, which is necessary for ferroptosis. Iron metabolism mainly includes three parts: iron uptake, storage and efflux. Therefore, iron metabolism-related genes could regulate intercellular iron content and status, which can be involved ferroptosis. In recent years, the application of nanoparticles in cancer therapy research has become more and more extensive. The iron-based nanoparticles (iron-based NPs) can release ferrous (Fe2+) or ferric (Fe3+) in acidic lysosomes and inducing ferroptosis. Magnetic field is widely used in the targeted concentration of iron-based NPs related disease therapy. Furthermore, multiple studies showed that magnetic fields can inhibit cancer cell proliferation by promoting intracellular ROS production. Herein, we focus on the relationship of between ferroptosis and iron metabolism in cancer cells, the application of nanoparticles and magnetic field in inducing ferroptosis of cancer cells, and trying to provide new ideas for cancer treatment research.

Dose- and time-dependent effects of triethylene glycol dimethacrylate on the proteome of human THP-1 monocytes

Triethylene glycol dimethacrylate (TEGDMA) is commonly used in polymer resin-based dental materials. This study investigated the molecular mechanisms of TEGDMA toxicity by identifying its time- and dose-dependent effects on the proteome of human THP-1 monocytes. The effects of different concentrations (0.07-5 mM) and exposure times (0-72 h) of TEGDMA on cell viability, proliferation, and morphology were determined using a real-time viability assay, automated cell counting, and electron microscopy, and laid the fundament for choice of exposure scenarios in the proteomic experiments. Solvents were not used, as TEGDMA is soluble in cell culture medium (determined by photon correlation spectroscopy). Cells were metabolically labeled [using the stable isotope labeled amino acids in cell culture (SILAC) strategy], and exposed to 0, 0.3 or 2.5 mM TEGDMA for 6 or 16 h before liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. Regulated proteins were analyzed in the STRING database. Cells exposed to 0.3 mM TEGDMA showed increased viability and time-dependent upregulation of proteins associated with stress/oxidative stress, autophagy, and cytoprotective functions. Cells exposed to 2.5 mM TEGDMA showed diminished viability and a protein expression profile associated with oxidative stress, DNA damage, mitochondrial dysfunction, and cell cycle inhibition. Altered expression of immune genes was observed in both groups. The study provides novel knowledge about TEGDMA toxicity at the proteomic level. Of note, even low doses of TEGDMA induced a substantial cellular response.

Docosanoids and elovanoids from omega-3 fatty acids are pro-homeostatic modulators of inflammatory responses, cell damage and neuroprotection

The functional significance of the selective enrichment of the omega-3 essential fatty acid docosahexaenoic acid (DHA; 22C and 6 double bonds) in cellular membrane phospholipids of the nervous system is being clarified by defining its specific roles on membrane protein function and by the uncovering of the bioactive mediators, docosanoids and elovanoids (ELVs). Here, we describe the preferential uptake and DHA metabolism in photoreceptors and brain as well as the significance of the Adiponectin receptor 1 in DHA retention and photoreceptor cell (PRC) survival. We now know that this integral membrane protein is engaged in DHA retention as a necessary event for the function of PRCs and retinal pigment epithelial (RPE) cells. We present an overview of how a) NPD1 selectively mediates preconditioning rescue of RPE and PR cells; b) NPD1 restores aberrant neuronal networks in experimental epileptogenesis; c) the decreased ability to biosynthesize NPD1 in memory hippocampal areas of early stages of Alzheimer's disease takes place; d) NPD1 protection of dopaminergic circuits in an in vitro model using neurotoxins; and e) bioactivity elicited by DHA and NPD1 activate a neuroprotective gene-expression program that includes the expression of Bcl-2 family members affected by Aβ42, DHA, or NPD1. In addition, we highlight ELOVL4 (ELOngation of Very Long chain fatty acids-4), specifically the neurological and ophthalmological consequences of its mutations, and their role in providing precursors for the biosynthesis of ELVs. Then we outline evidence of ELVs ability to protect RPE cells, which sustain PRC integrity. In the last section, we present a summary of the protective bioactivity of docosanoids and ELVs in experimental ischemic stroke. The identification of early mechanisms of neural cell survival mediated by DHA-synthesized ELVs and docosanoids contributes to the understanding of cell function, pro-homeostatic cellular modulation, inflammatory responses, and innate immunity, opening avenues for prevention and therapeutic applications in neurotrauma, stroke and neurodegenerative diseases.

Relationship of Autophagy and Apoptosis with Total Occlusion of Coronary Arteries

Background

The primary aim of this study was to evaluate the level of autophagy and apoptosis enzymes in patients with coronary artery disease (CAD). Furthermore, we investigated the role of autophagy and apoptosis in the progression of coronary collateral and coronary total occlusion (TO).

Material/Methods

We enrolled 115 patients in this prospective, observational, controlled study, who were categorized into 3 groups as follows: group 1, patients with chronic TO (n=49); group 2, patients with acute TO such as myocardial infarction (n=36); and group 3, healthy control patients (n=30). We used the enzyme-linked immunosorbent assay (ELISA) kit for autophagy-related protein 5 (ATG5) and apoptosis (M30) in the plasma for these 3 groups.

Results

Autophagy levels significantly varied among the groups (13.7±5.3 ng/mL, 11.7±3.4 ng/mL, and 7.5±3, respectively; P<0.001). In addition, apoptosis levels significantly varied among the groups (78.6±33.4 ng/mL, 64.9±30.6 ng/mL, and 47.6±18.2, respectively; P<0.001). The subgroup analysis revealed significant positive correlations between the autophagy level and the Rentrop score in contrast to apoptosis in group 1 (r=0.463; P<0.001).

Conclusions

This study determined that autophagy and apoptosis levels were higher in patients with CAD than in healthy controls. In contrast to the serum apoptosis level, serum autophagy levels demonstrated a significant positive correlation with the Rentrop score. Hence, an elevated autophagy level might be a potential activator and marker of the process by which the body protects itself in CAD.

Loperamide, pimozide, and STF-62247 trigger autophagy-dependent cell death in glioblastoma cells

Autophagy is a well-described degradation mechanism that promotes cell survival upon nutrient starvation and other forms of cellular stresses. In addition, there is growing evidence showing that autophagy can exert a lethal function via autophagic cell death (ACD). As ACD has been implicated in apoptosis-resistant glioblastoma (GBM), there is a high medical need for identifying novel ACD-inducing drugs. Therefore, we screened a library containing 70 autophagy-inducing compounds to induce ATG5-dependent cell death in human MZ-54 GBM cells. Here, we identified three compounds, i.e. loperamide, pimozide, and STF-62247 that significantly induce cell death in several GBM cell lines compared to CRISPR/Cas9-generated ATG5- or ATG7-deficient cells, pointing to a death-promoting role of autophagy. Further cell death analyses conducted using pharmacological inhibitors revealed that apoptosis, ferroptosis, and necroptosis only play minor roles in loperamide-, pimozide- or STF-62247-induced cell death. Intriguingly, these three compounds induce massive lipidation of the autophagy marker protein LC3B as well as the formation of LC3B puncta, which are characteristic of autophagy. Furthermore, loperamide, pimozide, and STF-62247 enhance the autophagic flux in parental MZ-54 cells, but not in ATG5 or ATG7 knockout (KO) MZ-54 cells. In addition, loperamide- and pimozide-treated cells display a massive formation of autophagosomes and autolysosomes at the ultrastructural level. Finally, stimulation of autophagy by all three compounds is accompanied by dephosphorylation of mammalian target of rapamycin complex 1 (mTORC1), a well-known negative regulator of autophagy. In summary, our results indicate that loperamide, pimozide, and STF-62247 induce ATG5- and ATG7-dependent cell death in GBM cells, which is preceded by a massive induction of autophagy. These findings emphasize the lethal function and potential clinical relevance of hyperactivated autophagy in GBM.

Phototoxicity of flavoprotein miniSOG induced by bioluminescence resonance energy transfer in genetically encoded system NanoLuc-miniSOG is comparable with its LED-excited phototoxicity

Photodynamic therapy (PDT) is a clinical, minimally invasive method for destroying cancer cells in the presence of a photosensitizer, oxygen, and a light source. The main obstacle for the PDT treatment of deep tumors is a strong reduction of the excitation light intensity as a result of its refraction, reflection, and absorption by biological tissues. Internal light sources based on bioluminescence resonance energy transfer can be a solution of this problem. Here we show that luciferase NanoLuc being expressed as a fusion protein with phototoxic flavoprotein miniSOG in cancer cells in the presence of furimazine (highly specific NanoLuc substrate) induces a photodynamic effect of miniSOG comparable with its LED-excited (Light Emitting Diode) phototoxicity. Luminescence systems based on furimazine and hybrid protein NanoLuc-miniSOG targeted to mitochondria or cellular membranes possess the similar energy transfer efficiencies and similar BRET-induced cytotoxic effects on cancer cells, though the mechanisms of BRET-induced cell death are different. As the main components of the proposed system for BRET-mediated PDT are genetically encoded (luciferase and phototoxic protein), this system can potentially be delivered to any site in the organism and thus may be considered as a promising approach for simultaneous delivery of light source and photosensitizer in deep-lying tumors and metastasis anywhere in the body.

Necroptosis mediates myofibre death in dystrophin-deficient mice

Duchenne muscular dystrophy (DMD) is a severe degenerative disorder caused by mutations in the dystrophin gene. Dystrophin-deficient muscles are characterised by progressive myofibre necrosis in which inflammation plays a deleterious role. However, the molecular mechanisms underlying inflammation-induced necrosis in muscle cells are unknown. Here we show that necroptosis is a mechanism underlying myofibre death in dystrophin-deficient muscle. RIPK1, RIPK3 and MLKL are upregulated in dystrophic mouse myofibres. In human DMD samples, there is strong immunoreactivity to RIPK3 and phospho-MLKL in myofibres. In vitro, TNFα can elicit necroptosis in C2C12 myoblasts, and RIPK3 overexpression sensitises myoblasts to undergo TNF-induced death. Furthermore, genetic ablation of Ripk3 in mdx mice reduces myofibre degeneration, inflammatory infiltrate, and muscle fibrosis, and eventually improves muscle function. These findings provide the first evidence of necroptotic cell death in a disease affecting skeletal muscle and identify RIPK3 as a key player in the degenerative process in dystrophin-deficient muscles.

Autophagy modulation: a prudent approach in cancer treatment?

Autophagy is a tightly controlled process comprising lysosomal degradation and recycling of cellular proteins and organelles. In cancer, its paradoxical dual role of cytoprotection and cytotoxicity is context-dependent and controversial. Autophagy primarily acts as a mechanism of tumour suppression, by maintenance of genomic integrity and prevention of proliferation and inflammation. This, combined with immune-surveillance capabilities and autophagy's implicated role in cell death, acts to prevent tumour initiation. However, established tumours exploit autophagy to survive cellular stresses in the hostile tumour microenvironment. This can lead to therapy resistance, one of the biggest challenges facing current anti-cancer approaches. Autophagy modulation is an exciting area of clinical development, attempting to harness this fundamental process as an anti-cancer strategy. Autophagy induction could potentially prevent tumour formation and enhance anti-cancer immune responses. In addition, drug-induced autophagy could be used to kill cancer cells, particularly those in which the apoptotic machinery is defective. Conversely, autophagy inhibition may help to sensitise resistant cancer cells to conventional chemotherapies and specifically target autophagy-addicted tumours. Currently, hydroxychloroquine is in phase I and II clinical trials in combination with several standard chemotherapies, whereas direct, deliberate autophagy induction remains to be tested clinically. More comprehensive understanding of the roles of autophagy throughout different stages of carcinogenesis has potential to guide development of novel therapeutic strategies to eradicate cancer cells.

A cell's agony of choice: how to cross the Styx? : From morphological to molecular approaches to disclose its decision

The original “apoptosis–necrosis” concept was based on morphology and (patho)physiological conditions of the occurrence of cell death: (1) apoptosis, with nuclear and cytoplasmic condensation/fragmentation prominent, exclusion of autolysis, considered to result from coordinated self-destruction of a cell; (2) necrosis, with cell lysis prominent, caused by violent environmental perturbation leading to collapse of internal homeostasis. This suggestion initiated a controversial discussion within the scientific community and it soon became clear that the “apoptosis–necrosis dichotomy” was not generally applicable. Nowadays, there is sufficient evidence that cells may activate diverse suicide pathways, thereby allowing a flexible response to environmental changes, either physiological or pathological. The present paper commemorates electron microscopic and cytochemical studies on cell death of cultured human mammary carcinoma cells performed by Adi Ellinger, adding a significant contribution to recognize that autophagy can be involved in regulated cell death, thereby challenging the apoptosis–necrosis dichotomy still predominant in the 1990s.

RIPK1-RIPK3-MLKL-Associated Necroptosis Drives Leishmania infantum Killing in Neutrophils

Necroptosis is a pro-inflammatory cell death, which happens in the context of caspase-8 inhibition, allowing activation of the receptor interacting protein kinase 1-receptor interacting protein kinase 3-mixed lineage kinase domain-like (RIPK1-RIPK3-MLKL) axis. Recently, necroptosis has emerged as a key component of resistance against pathogens including infected macrophage by Leishmania infantum, the ethiologic agent of Visceral leishmaniasis (VL). VL is the most severe form of Leishmaniasis, characterized by systemic inflammation and neutropenia. However, the role of neutrophil cell death in VL has not been characterized. Here, we showed that VL patients exhibited increased lactate dehydrogenase levels in the serum, a hallmark of cell death and tissue damage. We investigated the effect of necroptosis in neutrophil infection in vitro. Human neutrophils pretreated with zVAD-fmk (pan-caspase inhibitor) and zIETD-fmk (caspase-8 inhibitor) increased reactive oxygen species (ROS) level in response to Leishmania infection, which is associated with necroptotic cell death. MLKL, an important effector molecule downstream of necroptosis pathway, was also required for Leishmania killing. Moreover, in absence of caspases-8, murine neutrophils displayed loss of membrane integrity, higher levels of ROS, and decreased L. infantum viability. Pharmacological inhibition of RIPK1 or RIPK3 increased parasite survival when caspase-8 was blocked. Electron microscopy assays revealed morphological features associated with necroptotic death in L. infantum infected-neutrophils pretreated with caspase inhibitor, whereas infected cells pretreated with RIPK1 and RIPK3 inhibitors did not show ultra-structural alterations in membrane integrity and presented viable Leishmania within parasitophorous vacuoles. Taken together, these findings suggest that inhibition of caspase-8 contributes to elimination of L. infantum in neutrophils by triggering necroptosis. Thus, targeting necroptosis may represent a new strategy to control Leishmania replication.

Unconventional Ways to Live and Die: Cell Death and Survival in Development, Homeostasis, and Disease

Balancing cell death and survival is essential for normal development and homeostasis and for preventing diseases, especially cancer. Conventional cell death pathways include apoptosis, a form of programmed cell death controlled by a well-defined biochemical pathway, and necrosis, the lysis of acutely injured cells. New types of regulated cell death include necroptosis, pyroptosis, ferroptosis, phagoptosis, and entosis. Autophagy can promote survival or can cause death. Newly described processes of anastasis and resuscitation show that, remarkably, cells can recover from the brink of apoptosis or necroptosis. Important new work shows that epithelia achieve homeostasis by extruding excess cells, which then die by anoikis due to loss of survival signals. This mechanically regulated process both maintains barrier function as cells die and matches rates of proliferation and death. In this review, we describe these unconventional ways in which cells have evolved to die or survive, as well as the contributions that these processes make to homeostasis and cancer.

Differential Mechanisms of Septic Human Pulmonary Microvascular Endothelial Cell Barrier Dysfunction Depending on the Presence of Neutrophils

Sepsis is characterized by injury of pulmonary microvascular endothelial cells (PMVEC) leading to barrier dysfunction. Multiple mechanisms promote septic PMVEC barrier dysfunction, including interaction with circulating leukocytes and PMVEC apoptotic death. Our previous work demonstrated a strong correlation between septic neutrophil (PMN)-dependent PMVEC apoptosis and pulmonary microvascular albumin leak in septic mice in vivo; however, this remains uncertain in human PMVEC. Thus, we hypothesize that human PMVEC apoptosis is required for loss of PMVEC barrier function under septic conditions in vitro. To assess this hypothesis, human PMVECs cultured alone or in coculture with PMN were stimulated with PBS or cytomix (equimolar interferon γ, tumor necrosis factor α, and interleukin 1β) in the absence or presence of a pan-caspase inhibitor, Q-VD, or specific caspase inhibitors. PMVEC barrier function was assessed by transendothelial electrical resistance (TEER), as well as fluoroisothiocyanate-labeled dextran and Evans blue-labeled albumin flux across PMVEC monolayers. PMVEC apoptosis was identified by (1) loss of cell membrane polarity (Annexin V), (2) caspase activation (FLICA), and (3) DNA fragmentation [terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)]. Septic stimulation of human PMVECs cultured alone resulted in loss of barrier function (decreased TEER and increased macromolecular flux) associated with increased apoptosis (increased Annexin V, FLICA, and TUNEL staining). In addition, treatment of septic PMVEC cultured alone with Q-VD decreased PMVEC apoptosis and prevented septic PMVEC barrier dysfunction. In septic PMN-PMVEC cocultures, there was greater trans-PMVEC macromolecular flux (both dextran and albumin) vs. PMVEC cultured alone. PMN presence also augmented septic PMVEC caspase activation (FLICA staining) vs. PMVEC cultured alone but did not affect septic PMVEC apoptosis. Importantly, pan-caspase inhibition (Q-VD treatment) completely attenuated septic PMN-dependent PMVEC barrier dysfunction. Moreover, inhibition of caspase 3, 8, or 9 in PMN-PMVEC cocultures also reduced septic PMVEC barrier dysfunction whereas inhibition of caspase 1 had no effect. Our data demonstrate that human PMVEC barrier dysfunction under septic conditions in vitro (cytomix stimulation) is clearly caspase-dependent, but the mechanism differs depending on the presence of PMN. In isolated PMVEC, apoptosis contributes to septic barrier dysfunction, whereas PMN presence enhances caspase-dependent septic PMVEC barrier dysfunction independently of PMVEC apoptosis.

AT 101 induces early mitochondrial dysfunction and HMOX1 (heme oxygenase 1) to trigger mitophagic cell death in glioma cells

In most cases, macroautophagy/autophagy serves to alleviate cellular stress and acts in a pro-survival manner. However, the effects of autophagy are highly contextual, and autophagic cell death (ACD) is emerging as an alternative paradigm of (stress- and drug-induced) cell demise. AT 101 ([-]-gossypol), a natural compound from cotton seeds, induces ACD in glioma cells as confirmed here by CRISPR/Cas9 knockout of ATG5 that partially, but significantly rescued cell survival following AT 101 treatment. Global proteomic analysis of AT 101-treated U87MG and U343 glioma cells revealed a robust decrease in mitochondrial protein clusters, whereas HMOX1 (heme oxygenase 1) was strongly upregulated. AT 101 rapidly triggered mitochondrial membrane depolarization, engulfment of mitochondria within autophagosomes and a significant reduction of mitochondrial mass and proteins that did not depend on the presence of BAX and BAK1. Conversely, AT 101-induced reduction of mitochondrial mass could be reversed by inhibiting autophagy with wortmannin, bafilomycin A₁ and chloroquine. Silencing of HMOX1 and the mitophagy receptors BNIP3 (BCL2 interacting protein 3) and BNIP3L (BCL2 interacting protein 3 like) significantly attenuated AT 101-dependent mitophagy and cell death. Collectively, these data suggest that early mitochondrial dysfunction and HMOX1 overactivation synergize to trigger lethal mitophagy, which contributes to the cell killing effects of AT 101 in glioma cells.

ABBREVIATIONS

ACD, autophagic cell death; ACN, acetonitrile; AT 101, (-)-gossypol; BAF, bafilomycin A₁; BAK1, BCL2-antagonist/killer 1; BAX, BCL2-associated X protein; BH3, BCL2 homology region 3; BNIP3, BCL2 interacting protein 3; BNIP3L, BCL2 interacting protein 3 like; BP, Biological Process; CCCP, carbonyl cyanide m-chlorophenyl hydrazone; CC, Cellular Component; Con, control; CQ, chloroquine; CRISPR, clustered regularly interspaced short palindromic repeats; DMEM, Dulbecco's Modified Eagle Medium; DTT, 1,4-dithiothreitol; EM, electron microscopy; ER, endoplasmatic reticulum; FACS, fluorescence-activated cell sorting; FBS, fetal bovine serum; FCCP, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone; GO, Gene Ontology; HAcO, acetic acid; HMOX1, heme oxygenase 1; DKO, double knockout; LC-MS/MS, liquid chromatography coupled to tandem mass spectrometry; LPL, lipoprotein lipase, MEFs, mouse embryonic fibroblasts; mPTP, mitochondrial permeability transition pore; MTG, MitoTracker Green FM; mt-mKeima, mito-mKeima; MT-ND1, mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 1; PBS, phosphate-buffered saline; PE, phosphatidylethanolamine; PI, propidium iodide; PRKN, parkin RBR E3 ubiquitin protein ligase; SDS, sodium dodecyl sulfate; SQSTM1/p62, sequestome 1; STS, staurosporine; sgRNA, single guide RNA; SILAC, stable isotope labeling with amino acids in cell culture; TFA, trifluoroacetic acid, TMRM, tetramethylrhodamine methyl ester perchlorate; WM, wortmannin; WT, wild-type.

Pyroptosis Induction and Detection

Pyroptosis is a form of programmed pro-inflammatory cell death that plays a protective role in the host response to infection, but can also promote pathogenic inflammation. Pyroptosis is mediated by the cysteine protease, caspase-1. Caspase-1 cleaves gasdermin D, releasing the N-terminal pore-forming domain, which inserts into the plasma membrane and drives osmotic lysis. Caspase-1 also proteolytically activates the inflammatory cytokines interleukin 1β (IL-1β) and IL-18. This unit describes methods for stimulating pyroptosis and assessing subsequent loss of plasma membrane integrity. We also describe an ELISA to quantify released IL-1β. These methods can be applied to many different types of experiments. © 2018 by John Wiley & Sons, Inc.

Inhibiting autophagy reduces retinal degeneration caused by protein misfolding

Mutations in the genes necessary for the structure and function of vertebrate photoreceptor cells are associated with multiple forms of inherited retinal degeneration. Mutations in the gene encoding RHO (rhodopsin) are a common cause of autosomal dominant retinitis pigmentosa (adRP), with the Pro23His variant of RHO resulting in a misfolded protein that activates endoplasmic reticulum stress and the unfolded protein response. Stimulating macroautophagy/autophagy has been proposed as a strategy for clearing misfolded RHO and reducing photoreceptor death. We found that retinas from mice heterozygous for the gene encoding the RHOP23H variant (hereafter called P23H) exhibited elevated levels of autophagy flux, and that pharmacological stimulation of autophagy accelerated retinal degeneration. In contrast, reducing autophagy flux pharmacologically or by rod-specific deletion of the autophagy-activating gene Atg5, improved photoreceptor structure and function. Furthermore, proteasome levels and activity were reduced in the P23H retina, and increased when Atg5 was deleted. Our findings suggest that autophagy contributes to photoreceptor cell death in P23H mice, and that decreasing autophagy shifts the degradation of misfolded RHO protein to the proteasome and is protective. These observations suggest that modulating the flux of misfolded proteins from autophagy to the proteasome may represent an important therapeutic strategy for reducing proteotoxicity in adRP and other diseases caused by protein folding defects.

Toxic Effects of Trichloroethylene on Rat Neuroprogenitor Cells

Trichloroethylene (TCE) is a common volatile organic solvent which is considered as an ubiquitous environmental pollutant. It is claimed to be a developmental neurotoxicant. Our group evaluated previously its impact on three-dimensional neurospheres in vitro. The current work aims to investigate the neurotoxic effects of a lower concentration of TCE on the same system. To perform the experiment, neural progenitor cells were obtained from the brains of nine newborn rats. Afterward, these cells were cultured in both growth and differentiation media to get the neurospheres. Cell cultures were divided into two groups: group 1 (control), group 2 (exposed to 0.25 μM TCE). Neurospheres were photographed at different durations and assessment of the morphological changes such as proliferation and differentiation of neurospheres was done. In addition, cell viability, apoptosis, and necrosis were analyzed using flow cytometry to clarify the mechanism of involved cytotoxicity. The results revealed that TCE-treated neurospheres showed significantly decreased proliferation on days 7 and 14. These cells failed to show the neurogenic differentiation seen in the neurospheres of the control group. Furthermore, a highly significant decrease in viability and a significant increase in the number of apoptotic cells were observed in the treated cells in comparison to the control group. The present work confirmed that TCE, at very low doses relevant to daily life exposure in humans, caused neurotoxic effects in 3D neurosphere model through the affection of neural proliferation and differentiation as well as disturbance of cell viability and apoptosis.

GPx4, Lipid Peroxidation, and Cell Death: Discoveries, Rediscoveries, and Open Issues

SIGNIFICANCE

Iron-dependent lipid peroxidation is a complex oxidative process where phospholipid hydroperoxides (PLOOH) are produced in membranes and finally transformed into a series of decomposition products, some of which are endowed with biological activity. It is specifically prevented by glutathione peroxidase 4 (GPx4), the selenoenzyme that reduces PLOOH by glutathione (GSH). PLOOH is both a product and the major initiator of peroxidative chain reactions, as well as an activator of lipoxygenases. α-Tocopherol both specifically breaks peroxidative chain propagation and inhibits lipoxygenases. Thus, GPx4, GSH, and α-tocopherol are integrated in a concerted anti-peroxidant mechanism. Recent Advances: Ferroptosis has been recently identified as a cell death subroutine that is specifically activated by missing GPx4 activity and inhibited by iron chelation or α-tocopherol supplementation. Ferroptosis induction may underlie spontaneous human diseases, such as major neurodegeneration and neuroinflammation, causing an excessive cell death. The basic mechanism of ferroptosis, therefore, fits the features of activation of lipid peroxidation.

CRITICAL ISSUES

Still lacking are convincing proofs that lipoxygenases are involved in ferroptosis. Also, unknown are the molecules eventually killing cells and the mechanisms underlying the drop of the cellular anti-peroxidant capacity.

FUTURE DIRECTIONS

Molecular events and mechanisms of ferroptosis to be unraveled and validated on animal models are GPx4 inactivation, role of GSH concentration, increased iron availability, and membrane structure and composition. This is expected to drive drug discovery that is aimed at halting cell death in degenerative diseases or boosting it in cancer cells. Antioxid. Redox Signal. 29, 61-74.

Alterations in the nucleocytoplasmic transport in apoptosis: Caspases lead the way

Apoptosis is a mode of regulated cell death that is indispensable for the morphogenesis, development and homeostasis of multicellular organisms. Caspases are cysteine-dependent aspartate-specific proteases, which function as initiators and executors of apoptosis. Caspases are cytosolic proteins that can cleave substrates located in different intracellular compartments during apoptosis. Many years ago, the involvement of caspases in the regulation of nuclear changes, a hallmark of apoptosis, was documented. Accumulated data suggest that apoptosis-associated alterations in nucleocytoplasmic transport are also linked to caspase activity. Here, we aim to discuss the current state of knowledge regarding this process. Particular attention will be focused on caspase nuclear entry and their functions in the demolition of the nucleus upon apoptotic stimuli.

Fusogenic Viruses in Oncolytic Immunotherapy

Oncolytic viruses are under intense development and have earned their place among the novel class of cancer immunotherapeutics that are changing the face of cancer therapy. Their ability to specifically infect and efficiently kill tumor cells, while breaking immune tolerance and mediating immune responses directed against the tumor, make oncolytic viruses highly attractive candidates for immunotherapy. Increasing evidence indicates that a subclass of oncolytic viruses, which encodes for fusion proteins, could outperform non-fusogenic viruses, both in their direct oncolytic potential, as well as their immune-stimulatory properties. Tumor cell infection with these viruses leads to characteristic syncytia formation and cell death due to fusion, as infected cells become fused with neighboring cells, which promotes intratumoral spread of the infection and releases additional immunogenic signals. In this review, we discuss the potential of fusogenic oncolytic viruses as optimal candidates to enhance immunotherapy and initiate broad antitumor responses. We provide an overview of the cytopathic mechanism of syncytia formation through viral-mediated expression of fusion proteins, either endogenous or engineered, and their benefits for cancer therapy. Growing evidence indicates that fusogenicity could be an important feature to consider in the design of optimal oncolytic virus platforms for combinatorial oncolytic immunotherapy.

Response to Comment on "Sterilizing immunity in the lung relies on targeting fungal apoptosis-like programmed cell death"

Aouacheria et al question the interpretation of contemporary assays to monitor programmed cell death with apoptosis-like features (A-PCD) in Aspergillus fumigatus Although our study focuses on fungal A-PCD for host immune surveillance and infectious outcomes, the experimental approach incorporates multiple independent A-PCD markers and genetic manipulations based on fungal rather than mammalian orthologs to circumvent the limitations associated with any single approach.

AG-1031 and AG-1503 improve cognitive deficits by promoting apoptosis and inhibiting autophagy in C6 glioma model rats

High-grade gliomas (HGGs; grades III and IV) are the most common and aggressive adult primary brain tumors, and their invasive nature ranks them the fourth in the incidence of cancer death. In our previous study, we found that AG-1031 and AG-1503 showed inhibitory effects on several cancer cell lines. In this study, C6 glioma-bearing rats were treated with AG-1031 or AG-1503. Western blot results of autophagy-associated protein (LC3 II/I, Beclin-1) and apoptosis-associated proteins (caspase-3, Bcl-2, Bax) revealed that AG-1031 could activate apoptotic signal pathway via inhibiting autophagy process in cancer cells. HE staining indicated that the tumor volumes were significantly decreased in AG-1031 and AG-1503 treated rats compared to non-treated C6 glioma-bearing rats. Meanwhile, AG-1031 and AG-1503 significantly decreased the expression of VEGF, a marker of invasion ability of tumor, in tumor tissue. The novel object recognition test showed that cognitive functions in C6 glioma-bearing rats were considerably damaged, whereas AG-1031 and AG-1503 significantly impeded the cognitive impairment. AG-1031 and AG-1503 efficiently alleviated the glioma-induced impairments of long-term potentiation (LTP), which was damaged in C6 glioma-bearing rats. Furthermore, AG-1031 and AG-1503 augmented the expression of synaptophysin (SYP), which were decreased in glioma rats. In conclusion, our results suggest that AG-1031 and AG-1503 can inhibit the expansion of glioma, and improve the cognitive impairment caused by glioma in glioma-bearing rats.

Chitosan gold nanoparticles induce cell death in HeLa and MCF-7 cells through reactive oxygen species production

Background

Nanotechnology has gained important interest, especially in the development of new therapies; the application of gold nanoparticles (AuNPs) in the treatment and detection of diseases is a growing trend in this field. As cancer represents a serious health problem around the world, AuNPs are studied as potential drugs or drug carriers for anticancer agents. Recent studies show that AuNPs stabilized with chitosan (CH) possess interesting biological activities, including potential antitumor effects that could be selective to cancer cells.

Materials and methods

In this study, we synthesized sodium citrate-AuNPs and CH-capped AuNPs of 3-10 nm, and analyzed their cytotoxicity in cervical (HeLa) and breast (MCF-7) cancer cells, and in peripheral blood mononuclear cells (PBMCs). Then, we evaluated the clonogenic potential, cell cycle, nuclear alterations, caspase dependence, and reactive oxygen species (ROS) production in HeLa and MCF-7 cells after chitosan gold nanoparticles (CH-AuNPs) exposure.

Results

Our data showed that CH-AuNPs are cytotoxic in a dose-dependent manner in the cancer cell lines tested, while they induce low cytotoxicity in PBMCs. Sodium citrate gold nanoparticles did not show cytotoxic effects. In both HeLa and MCF-7 cell lines, CH-AuNPs inhibit clonogenic potential without inducing cell cycle arrest or nuclear alterations. The cell death mechanism is specific for the type of cancer cell line tested, as it depends on caspase activation in HeLa cells, whereas it is caspase independent in MCF-7 cells. In all cases, ROS production is mandatory for cell death induction by CH-AuNPs, as ROS inhibition with N-acetyl cysteine inhibits cell death.

Conclusion

Our results show that CH-AuNPs are selective for HeLa and MCF-7 cancer cells, rather than normal PBMCs, and that ROS production seems to be a conserved feature of the cell death mechanism induced by CH-AuNPs. These results improve the knowledge of CH-AuNPs and open the way to the design of new pharmacological strategies using these agents against cancer.

Cell death and immunity in cancer: From danger signals to mimicry of pathogen defense responses

The immunogenicity of cancer cells is an emerging determinant of anti-cancer immunotherapy. Beyond developing immunostimulatory regimens like dendritic cell-based vaccines, immune-checkpoint blockers, and adoptive T-cell transfer, investigators are beginning to focus on the immunobiology of dying cancer cells and its relevance for the success of anticancer immunotherapies. It is currently accepted that cancer cells may die in response to anti-cancer therapies through regulated cell death programs, which may either repress or increase their immunogenic potential. In particular, the induction of immunogenic cancer cell death (ICD), which is hallmarked by the emission of damage-associated molecular patterns (DAMPs); molecules analogous to pathogen-associated molecular patterns (PAMPs) acting as danger signals/alarmins, is of great relevance in cancer therapy. These ICD-associated danger signals favor immunomodulatory responses that lead to tumor-associated antigens (TAAs)-directed T-cell immunity, which paves way for the removal of residual, treatment-resistant cancer cells. It is also emerging that cancer cells succumbing to ICD can orchestrate "altered-self mimicry" i.e. mimicry of pathogen defense responses, on the levels of nucleic acids and/or chemokines (resulting in type I interferon/IFN responses or pathogen response-like neutrophil activity). In this review, we exhaustively describe the main molecular, immunological, preclinical, and clinical aspects of immunosuppressive cell death or ICD (with respect to apoptosis, necrosis and necroptosis). We also provide an extensive historical background of these fields, with special attention to the self/non-self and danger models, which have shaped the field of cell death immunology.

Immune recognition of irradiated cancer cells

Ionizing irradiation has been extensively employed for the clinical management of solid tumors, with therapeutic or palliative intents, for decades. Until recently, radiation therapy (RT) was believed to mediate antineoplastic activity mostly (if not only) as a consequence of cancer cell-intrinsic effects. Indeed, the macromolecular damage imposed to malignant cells by RT initiates one or multiple signal transduction cascades that drive a permanent proliferative arrest (cellular senescence) or regulated cell death. Both these phenomena show a rather linear dose-response correlation. However, RT also mediates consistent immunological activity, not only as an "on-target effect" originating within irradiated cancer cells, but also as an "off-target effect" depending on the interaction between RT and stromal, endothelial, and immune components of the tumor microenvironment. Interestingly, the immunological activity of RT does not exhibit linear dose-response correlation. Here, we discuss the mechanisms whereby RT alters the capacity of the immune system to recognize and eliminate irradiated cancer cells, either as an "on-target" or as on "off-target" effect. In particular, we discuss the antagonism between the immunostimulatory and immunosuppressive effects of RT as we delineate combinatorial strategies to boost the former at the expenses of the latter.

Fate of nuclear material during subsequent steps of the kinetin-induced PCD in apical parts of Vicia faba ssp. minor seedling roots

In animals during apoptosis, the best examined type of programmed cell death (PCD), three main phases are distinguished: (i) specification (signaling), (ii) killing and (iii) execution one. It has bean postulated that plant PCD also involves three subsequent phases: (i) transmission of death signals to cells (signaling), (ii) initiation of killing processes and (iii) destruction of cells. One of the most important hallmarks of animal and plant PCD are those regarding nucleus, not thoroughly studied in plants so far. To study kinetin-induced PCD (Kin-PCD) in the context of nuclear material faith, 2-cm apical parts of Vicia faba ssp. minor seedling roots were used. Applied assays involving spectrophotometry, transmission electron microscopy, fluorescence and white light microscopy allowed to examine metabolic and cytomorphologic hallmarks such as changes in DNA content, ssDNA formation and activity of acidic and basic nucleases (DNases and RNases) as well as malformations and fragmentation of nucleoli and nuclei. The obtained results concerning the PCD hallmarks and influence of ZnSO₄ on Kin-PCD allowed us to confirmed presence of specification/signaling, killing and execution/degradation phases of the process and broaden the knowledge about processes affecting nuclei during PCD.

Repeated exposure of epithelial cells to apoptotic cells induces the specific selection of an adaptive phenotype: Implications for tumorigenesis

The consequences of apoptosis extend beyond the mere death of the cell. We have shown that receptor-mediated recognition of apoptotic target cells by viable kidney proximal tubular epithelial cells (PTECs) inhibits PTEC proliferation, growth, and survival. Here, we tested the hypothesis that continual exposure to apoptotic targets can induce a phenotypic change in responding PTECs, as in other instances of natural selection. In particular, we demonstrate that repeated exposure to apoptotic targets leads to emergence of a PTEC line (denoted BU.MPT^SEL) resistant to apoptotic target-induced death. Resistance is exquisitely specific. Not only are BU.MPT^SEL responders fully resistant to apoptotic target-induced death (∼85% survival versus <10% survival of nonselected cells) but do so while retaining sensitivity to all other target-induced responses, including inhibition of proliferation and growth. Moreover, the resistance of BU.MPT^SEL responders is specific to target-induced apoptosis, as apoptosis in response to other suicidal stimuli occurs normally. Comparison of the signaling events induced by apoptotic target exposure in selected versus nonselected responders indicated that the acquired resistance of BU.MPT^SEL cells lies in a regulatory step affecting the generation of the pro-apoptotic protein, truncated BH3 interacting-domain death agonist (tBID), most likely at the level of BID cleavage by caspase-8. This specific adaptation has especial relevance for cancer, in which the prominence and persistence of cell death entail magnification of the post-mortem effects of apoptotic cells. Just as cancer cells acquire specific resistance to chemotherapeutic agents, we propose that cancer cells may also adapt to their ongoing exposure to apoptotic targets.

Till Death Do Us Part: The Marriage of Autophagy and Apoptosis

Autophagy is a widely conserved catabolic process that is necessary for maintaining cellular homeostasis under normal physiological conditions and driving the cell to switch back to this status quo under times of starvation, hypoxia, and oxidative stress. The potential similarities and differences between basal autophagy and stimulus-induced autophagy are still largely unknown. Both act by clearing aberrant or unnecessary cytoplasmic material, such as misfolded proteins, supernumerary and defective organelles. The relationship between reactive oxygen species (ROS) and autophagy is complex. Cellular ROS is predominantly derived from mitochondria. Autophagy is triggered by this event, and by clearing the defective organelles effectively, it lowers cellular ROS thereby restoring cellular homeostasis. However, if cellular homeostasis cannot be reached, the cells can switch back and choose a regulated cell death response. Intriguingly, the autophagic and cell death machines both respond to the same stresses and share key regulatory proteins, suggesting that the pathways are intricately connected. Here, the intersection between autophagy and apoptosis is discussed with a particular focus on the role ROS plays.