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Concept: Anoikis

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Whether responses of cells to extracellular environments affect the induction of apoptotic cell death is poorly understood. The current study aimed to unravel the different effects of culture media employed in vitro as extracellular environments on the susceptibility of cells to apoptosis. We found that apoptosis is stimulated to the higher levels by culturing human HeLa cells in Opti-MEM with unknown components, a medium that is specifically used for transfections, than by culturing cells in Dulbecco’s modified Eagle’s medium, a medium that is generally used for maintenance of cells. We showed that apoptosis is suppressed partially by culturing cells in heat-treated Opti-MEM, implicating a heat-sensitive component(s) in stimulating the apoptotic response of cells. Thus, different extracellular environments may contribute to different responses of cells to apoptosis, and this should be considered to evaluate the incidences of apoptotic cell death and could be applied to develop an efficient treatment for curing diseases such as cancer.

Concepts: Cancer, Death, Apoptosis, Cell culture, Programmed cell death, Vesicle, Caspase, Anoikis

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Synaptic activity increases the resistance of neurons to diverse apoptotic insults; however, the underlying mechanisms remain less well understood. Zinc promotes cell survival under varied conditions, but the role of synaptically released zinc in the activity-dependent anti-apoptotic effect is unknown. Using cultured hippocampal slices and primary neurons we show that a typical apoptosis inducer-staurosporine (STP) was able to cause concentration-dependent apoptotic cell death in brain slices; Enhanced synaptic activity by bicuculline (Bic)/4-Aminopyridine (AP) treatment effectively prevented neurons from STP-induced cell apoptosis, as indicated by increased cell survival and suppressed caspase-3 activity. Application of Ca-EDTA, a cell membrane-impermeable zinc chelator which can efficiently capture the synaptically released zinc, completely blocked the neuronal activity-dependent anti-apoptotic effect. Same results were also observed in cultured primary hippocampal neurons. Therefore, our results indicate that synaptic activity improves neuronal resistance to apoptosis via synaptically released zinc.

Concepts: Brain, Apoptosis, Membrane potential, Programmed cell death, Caspase, XIAP, Anoikis

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Hypoxia is known to induce pancreatic beta cell dysfunction and apoptosis. Changes in Programmed Cell Death Gene 4 (PDCD4) expression have previously been linked with beta cell neogenesis and function. Our aim was to investigate the effects of hypoxia on cell viability, PDCD4 expression and subcellular localisation.

Concepts: Gene, Cell, Apoptosis, Pancreas, Beta cell, Programmed cell death, Caspase, Anoikis

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NSCLC accounts for about 85% of all lung cancer cases. Absence of miR-103 has recently identified to be associated withmetastatic capacity of primary lung tumors. However, the exact role of miR-103 in NSCLC and the molecular mechanism is unclear. In the present study, we showed that miR-103 expression was reduced in NSCLC tissues and cells. miR-103 expression was negatively correlated with tumor size and stage. The overall survival was longer in patients with higher miR-103 level than in those with lower miR-103 expression. miR-103 inhibited cell proliferation in A549 cells, decreased tumor weight and volume and prolonged survival of tumor-implanted nude mice. miR-103 increased apoptotic cell death A549 cells. Furthermore, miR-103 decreased the invasion and migration ability in A549 cells, as evidenced by Transwell and Wound healing results. Downregualtion of miR-103 significantly reduced programmed cell death 10 (PDCD10) level. We found a significant decrease to the relative luciferase activity of the reporter gene in A549 cells co-transfected with miR-103 mimic and pGL3-PDCD10 WT 3'-UTR, but not pGL3-PDCD10 mut 3'-UTR. We showed that overexpression of PDCD10 significantly inhibited miR-103-induced inhibition of cell proliferation, increased of apoptosis and decrease of invasion and migration in A549 cells. Moreover, we found that PDCD10 expression was increased in NSCLC tissues and cells. PDCD10 expression was positively correlated with tumor size and stage. Overexpression of PDCD10 increased cell proliferation and inhibited apoptosis in A549 cells. The data demonstrated that dysregulation of miR-103/PDCD10 signal may be a novel therapeutic target for the treatment of NSCLC.

Concepts: Gene, Gene expression, Cancer, Lung cancer, Apoptosis, Programmed cell death, Caspase, Anoikis

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Apoptosis is a programmed cell death playing key roles in physiology and pathophysiology of multi cellular organisms. Its nuclear manifestation requires transmission of the death signals across the nuclear pore complexes (NPCs). In strategic sequential steps apoptotic factors disrupt NPCs structure, integrity and barrier ultimately leading to nuclear breakdown. The present review reflects on these steps.

Concepts: Cell nucleus, Organism, Apoptosis, Nuclear pore, Prokaryote, Programmed cell death, Caspase, Anoikis

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Apoptosis has been implicated in compensatory proliferation signaling (CPS), whereby dying cells induce proliferation in neighboring cells as a means to restore homeostasis. The nature of signaling between apoptotic cells and their neighboring cells remains largely unknown. Here we show that a fraction of apoptotic cells produce and release CrkI-containing microvesicles (distinct from exosomes and apoptotic bodies), which induce proliferation in neighboring cells upon contact. We provide visual evidence of CPS by videomicroscopy. We show that purified vesicles in vitro and in vivo are sufficient to stimulate proliferation in other cells. Our data demonstrate that CrkI inactivation by ExoT bacterial toxin or by mutagenesis blocks vesicle formation in apoptotic cells and inhibits CPS, thus uncoupling apoptosis from CPS. We further show that c-Jun amino-terminal kinase (JNK) plays a pivotal role in mediating vesicle-induced CPS in recipient cells. CPS could have important ramifications in diseases that involve apoptotic cell death.

Concepts: Immune system, Signal transduction, Death, Apoptosis, Programmed cell death, Vesicle, Caspase, Anoikis

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Cancer cells are continuously challenged by adverse environmental factors including hypoxia, metabolite restriction, and immune reactions, and must adopt diverse strategies to survive. Heat shock protein (Hsp) 70 plays a central role in protection against stress-induced cell death by maintaining protein homeostasis and interfering with the process of programmed cell death. Recent findings have suggested that Hsp70 acetylation is a key regulatory modification required for its chaperone activity, but its relevance in the process of programmed cell death and the underlying mechanisms involved are not well understood. In this study, we sought to investigate mechanisms mediated by Hsp70 acetylation in relation to apoptotic and autophagic programmed cell death. Upon stress-induced apoptosis, Hsp70 acetylation inhibits apoptotic cell death, mediated by Hsp70 association with apoptotic protease-activating factor (Apaf)-1 and apoptosis-inducing factor (AIF), key modulators of caspase-dependent and -independent apoptotic pathways, respectively. Hsp70 acetylation also attenuated autophagic cell death associated with upregulation of autophagy-related genes and autophagosome induction. Collectively, these results suggest that the acetylation of Hsp70 plays key regulatory roles in cell death pathways as well as in its function as a chaperone, together enabling cellular protection in response to stress.

Concepts: Immune system, Cancer, Apoptosis, P53, Programmed cell death, Caspase, Heat shock protein, Anoikis

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Apoptosis has been regarded to mediate intervertebral disc degeneration (IDD); however, the basic question of how the apoptotic bodies are cleared in the avascular intervertebral disc without phagocytes, which are essential to apoptosis, remains to be elucidated. Our goals were to investigate the ultrastructure of nucleus pulposus (NP) cells undergoing chondroptosis, a variant of apoptotic cell death, in a rabbit annular needle-puncture model of IDD. Experimental IDD was induced by puncturing discs with a 16-G needle in New Zealand rabbits. At 4 and 12 weeks after puncture, progressive degeneration was demonstrated by X-ray, magnetic resonance imaging and histological staining. TUNEL staining suggested a significant increase in the apoptosis index in the degenerated NP. However, the percentage of apoptotic cells with the classic ultrastructure morphology was much less than that with chondroptotic ultrastructure morphology under transmission electron microscopy (TEM). The chondroptotic cells from the early to late stage were visualized under TEM. In addition, the percentage of chondroptotic cells was significantly enhanced in the degenerated NP. Furthermore, ‘paralyzed’ cells were found in the herniated tissue. Western blotting revealed an increase in caspase3 expression in the degenerated NP. The expression of the Golgi protein (58K) was increased by the fourth week after puncture but decreased later. These findings indicate that chondroptosis is a major type of programmed cell death in the degenerated rabbit NP that may be related to the progressive development of IDD.

Concepts: Golgi apparatus, Apoptosis, Microscope, Necrosis, Transmission electron microscopy, Programmed cell death, Caspase, Anoikis

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Apoptosis is a carefully orchestrated and tightly controlled form of cell death, conserved across metazoans. As the executioners of apoptotic cell death, cysteine-dependent aspartate-directed proteases (caspases) are critical drivers of this cellular disassembly. Early studies of genetically programmed cell death demonstrated that the selective activation of caspases induces apoptosis and the precise elimination of excess cells, thereby sculpting structures and refining tissues. However, over the past decade there has been a fundamental shift in our understanding of the roles of caspases during cell death-a shift precipitated by the revelation that apoptotic cells actively engage with their surrounding environment throughout the death process, and caspases can trigger a myriad of signals, some of which drive concurrent cell proliferation regenerating damaged structures and building up lost tissues. This caspase-driven compensatory proliferation is referred to as apoptosis-induced proliferation (AiP). Diverse mechanisms of AiP have been found across species, ranging from planaria to mammals. In this review, we summarize the current knowledge of AiP and we highlight recent advances in the field including the involvement of reactive oxygen species and macrophage-like immune cells in one form of AiP, novel regulatory mechanisms affecting caspases during AiP, and emerging clinical data demonstrating the critical importance of AiP in cancer.Cell Death and Differentiation advance online publication, 31 March 2017; doi:10.1038/cdd.2017.47.

Concepts: Immune system, Signal transduction, Mitochondrion, Apoptosis, Programmed cell death, Caspase, Cisplatin, Anoikis