Showing papers on "Apoptosis published in 2008"
TL;DR: It is shown that the microRNA miR-34a regulates silent information regulator 1 (SIRT1) expression, which functions as a tumor suppressor, in part, through a SIRT1-p53 pathway.
Abstract: MicroRNA 34a (miR-34a) is a tumor suppressor gene, but how it regulates cell proliferation is not completely understood. We now show that the microRNA miR-34a regulates silent information regulator 1 (SIRT1) expression. MiR-34a inhibits SIRT1 expression through a miR-34a-binding site within the 3′ UTR of SIRT1. MiR-34 inhibition of SIRT1 leads to an increase in acetylated p53 and expression of p21 and PUMA, transcriptional targets of p53 that regulate the cell cycle and apoptosis, respectively. Furthermore, miR-34 suppression of SIRT1 ultimately leads to apoptosis in WT human colon cancer cells but not in human colon cancer cells lacking p53. Finally, miR-34a itself is a transcriptional target of p53, suggesting a positive feedback loop between p53 and miR-34a. Thus, miR-34a functions as a tumor suppressor, in part, through a SIRT1-p53 pathway.
1,238 citations
TL;DR: The regulation of LMP is perturbed in cancer cells, suggesting that specific strategies for LMP induction might lead to novel therapeutic avenues.
Abstract: Mitochondrial outer membrane permeabilization (MOMP) constitutes one of the major checkpoint(s) of apoptotic and necrotic cell death. Recently, the permeabilization of yet another organelle, the lysosome, has been shown to initiate a cell death pathway, in specific circumstances. Lysosomal membrane permeabilization (LMP) causes the release of cathepsins and other hydrolases from the lysosomal lumen to the cytosol. LMP is induced by a plethora of distinct stimuli including reactive oxygen species, lysosomotropic compounds with detergent activity, as well as some endogenous cell death effectors such as Bax. LMP is a potentially lethal event because the ectopic presence of lysosomal proteases in the cytosol causes digestion of vital proteins and the activation of additional hydrolases including caspases. This latter process is usually mediated indirectly, through a cascade in which LMP causes the proteolytic activation of Bid (which is cleaved by the two lysosomal cathepsins B and D), which then induces MOMP, resulting in cytochrome c release and apoptosome-dependent caspase activation. However, massive LMP often results in cell death without caspase activation; this cell death may adopt a subapoptotic or necrotic appearance. The regulation of LMP is perturbed in cancer cells, suggesting that specific strategies for LMP induction might lead to novel therapeutic avenues.
1,208 citations
TL;DR: The tumor suppressor protein Programmed Cell Death 4 (PDCD4) is regulated by miR-21 and it is demonstrated that PDCD4 is a functionally important target for mi R-21 in breast cancer cells.
1,107 citations
TL;DR: The evidence linking calcium homeostasis to the regulation of apoptotic, and more recently autophagic cell death is reviewed, as well as the discussion of mitochondria as a critical, although not unique checkpoint, and the molecular and functional elucidation of ER/mitochondria contacts.
Abstract: There is a growing consensus that the various forms of cell death (necrosis, apoptosis and autophagy) are not separated by strict boundaries, but rather share molecular effectors and signaling routes. Among the latter, a clear role is played by calcium (Ca2+), the ubiquitous second messenger involved in the control of a broad variety of physiological events. Fine tuning of intracellular Ca2+ homeostasis by anti- and proapoptotic proteins shapes the Ca2+ signal to which mitochondria and other cellular effectors are exposed, and hence the efficiency of various cell death inducers. Here, we will review: (i) the evidence linking calcium homeostasis to the regulation of apoptotic, and more recently autophagic cell death, (ii) the discussion of mitochondria as a critical, although not unique checkpoint and (iii) the molecular and functional elucidation of ER/mitochondria contacts, corresponding to the mitochondria-associated membrane (MAM) subfraction and proposed to be a specialized signaling microdomain.
992 citations
TL;DR: As well as its role in canonical intrinsic apoptosis, cytochrome c amplifies signals that are generated by other apoptotic pathways and participates in certain non-apoptotic functions.
Abstract: Cytochrome c is primarily known for its function in the mitochondria as a key participant in the life-supporting function of ATP synthesis. However, when a cell receives an apoptotic stimulus, cytochrome c is released into the cytosol and triggers programmed cell death through apoptosis. The release of cytochrome c and cytochrome-c-mediated apoptosis are controlled by multiple layers of regulation, the most prominent players being members of the B-cell lymphoma protein-2 (BCL2) family. As well as its role in canonical intrinsic apoptosis, cytochrome c amplifies signals that are generated by other apoptotic pathways and participates in certain non-apoptotic functions.
921 citations
TL;DR: A plethora of knowledge has been obtained on the mammalian caspases, the homologs of CED-3, with regard to their distinct physiological functions, their substrates, different activation mechanisms, the signal transduction pathways that lead to their activation as well as their involvement in the pathogenesis of diseases.
Abstract: The demonstration of protein sequence and functional homology of the Caenorhabditis elegans programmed cell death gene product, CED-3, with human caspase-1 in 1993 triggered an explosion of research activities toward the understanding of molecular mechanisms of apoptosis. During the past 15 years, a plethora of knowledge has been obtained on the mammalian caspases, the homologs of CED-3, with regard to their distinct physiological functions, their substrates, different activation mechanisms, the signal transduction pathways that lead to their activation as well as their involvement in the pathogenesis of diseases. Such knowledge is beginning to be translated into new therapies for the treatment of human diseases.
919 citations
TL;DR: Genome-wide RNA-interference screening is performed to identify 17 genes required for an activated BRAF oncogene (BRAFV600E) to block proliferation of human primary fibroblasts and melanocytes and finds a secreted protein, IGFBP7, has a central role in BRAFV 600E-mediated senescence and apoptosis.
848 citations
01 Jan 2008
TL;DR: Evidence is provided that the miR-106b-25 cluster, upregulated in a subset of human gastric tumors, is involved in E2F1 posttranscriptional regulation and may play a key role in the development of TGFbeta resistance in gastric cancer.
779 citations
TL;DR: A selection of techniques that can be used to identify necrosis and to discriminate it from apoptosis are presented and a recently developed approach based on the use of fluid phase tracers and different kind of microscopy, transmission electron and fluorescence microscopy is described to characterize the mechanisms used by phagocytes to internalize dying cells.
670 citations
TL;DR: KIM-1 is the first nonmyeloid phosphatidylserine receptor identified to the authors' knowledge that transforms epithelial cells into semiprofessional phagocytes and was directly responsible for phagocytosis in cultured primary rat tubule epithel cells and also porcine and canine epithelial cell lines.
Abstract: Following injury, the clearance of apoptotic and necrotic cells is necessary for mitigation and resolution of inflammation and tissue repair. In addition to macrophages, which are traditionally assigned to this task, neighboring epithelial cells in the affected tissue are postulated to contribute to this process. Kidney injury molecule-1 (KIM-1 or TIM-1) is an immunoglobulin superfamily cell-surface protein not expressed by cells of the myeloid lineage but highly upregulated on the surface of injured kidney epithelial cells. Here we demonstrate that injured kidney epithelial cells assumed attributes of endogenous phagocytes. Confocal images confirm internalization of apoptotic bodies within KIM-1-expressing epithelial cells after injury in rat kidney tubules in vivo. KIM-1 was directly responsible for phagocytosis in cultured primary rat tubule epithelial cells and also porcine and canine epithelial cell lines. KIM-1 was able to specifically recognize apoptotic cell surface-specific epitopes phosphatidylserine, and oxidized lipoproteins, expressed by apoptotic tubular epithelial cells. Thus, KIM-1 is the first nonmyeloid phosphatidylserine receptor identified to our knowledge that transforms epithelial cells into semiprofessional phagocytes.
664 citations
TL;DR: MI-219 stimulates rapid but transient p53 activation in established tumor xenograft tissues, resulting in inhibition of cell proliferation, induction of apoptosis, and complete tumor growth inhibition.
Abstract: We have designed MI-219 as a potent, highly selective and orally active small-molecule inhibitor of the MDM2–p53 interaction. MI-219 binds to human MDM2 with a Ki value of 5 nM and is 10,000-fold selective for MDM2 over MDMX. It disrupts the MDM2–p53 interaction and activates the p53 pathway in cells with wild-type p53, which leads to induction of cell cycle arrest in all cells and selective apoptosis in tumor cells. MI-219 stimulates rapid but transient p53 activation in established tumor xenograft tissues, resulting in inhibition of cell proliferation, induction of apoptosis, and complete tumor growth inhibition. MI-219 activates p53 in normal tissues with minimal p53 accumulation and is not toxic to animals. MI-219 warrants clinical investigation as a new agent for cancer treatment.
TL;DR: It is found that glutathione depletion leads to hypercondensation and fragmentation of chromatin into spherical or irregular shapes, a morphologic signature of apoptosis, which suggests that oxidative stress can induce apoptosis in neurons.
Abstract: Glutamate-induced glutathione depletion in immature embryonic cortical neurons has been shown to lead to oxidative stress and cell death. We have used this in vitro model to investigate the mechanism(s) by which free radicals induce neuronal degeneration. We find that glutathione depletion leads to hyper-condensation and fragmentation of chromatin into spherical or irregular shapes, a morphologic signature of apoptosis. These morphologic changes are accompanied by laddering of DNA into multiple oligonucleosomal fragments and can be prevented by the antioxidants idebenone and butylated hydroxyanisole. Cell death induced by glutathione depletion can also be prevented by inhibitors of macromolecular synthesis. Taken together, these observations suggest that oxidative stress can induce apoptosis in neurons.
TL;DR: Two ROS-generating agents, hydrogen peroxide and 2-methoxyestradiol, induced autophagy in the transformed cell line HEK293 and the cancer cell lines U87 and HeLa but failed to induce autophagic cell death in non-transformed cells.
Abstract: Autophagy is a self-digestion process that degrades intracellular structures in response to stresses leading to cell survival. When autophagy is prolonged, this could lead to cell death. Generation of reactive oxygen species (ROS) through oxidative stress causes cell death. The role of autophagy in oxidative stress-induced cell death is unknown. In this study, we report that two ROS-generating agents, hydrogen peroxide (H(2)O(2)) and 2-methoxyestradiol (2-ME), induced autophagy in the transformed cell line HEK293 and the cancer cell lines U87 and HeLa. Blocking this autophagy response using inhibitor 3-methyladenine or small interfering RNAs against autophagy genes, beclin-1, atg-5 and atg-7 inhibited H(2)O(2) or 2-ME-induced cell death. H(2)O(2) and 2-ME also induced apoptosis but blocking apoptosis using the caspase inhibitor zVAD-fmk (benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone) failed to inhibit autophagy and cell death suggesting that autophagy-induced cell death occurred independent of apoptosis. Blocking ROS production induced by H(2)O(2) or 2-ME through overexpression of manganese-superoxide dismutase or using ROS scavenger 4,5-dihydroxy-1,3-benzene disulfonic acid-disodium salt decreased autophagy and cell death. Blocking autophagy did not affect H(2)O(2)- or 2-ME-induced ROS generation, suggesting that ROS generation occurs upstream of autophagy. In contrast, H(2)O(2) or 2-ME failed to significantly increase autophagy in mouse astrocytes. Taken together, ROS induced autophagic cell death in transformed and cancer cells but failed to induce autophagic cell death in non-transformed cells.
TL;DR: This review discusses what is known about granzyme-mediated pathways of cell death as well as recent studies that implicate granzymes in immune regulation and extracellular proteolytic functions in inflammation.
Abstract: The granzymes are cell death–inducing enzymes, stored in the cytotoxic granules of cytotoxic T lymphocytes and natural killer cells, that are released during granule exocytosis when a specific virus-infected or transformed target cell is marked for elimination. Recent work suggests that this homologous family of serine esterases can activate at least three distinct pathways of cell death. This redundancy likely evolved to provide protection against pathogens and tumors with diverse strategies for evading cell death. This review discusses what is known about granzyme-mediated pathways of cell death as well as recent studies that implicate granzymes in immune regulation and extracellular proteolytic functions in inflammation.
TL;DR: This review is devoted to the analysis of mitochondrial function in cancer cells, including the mechanisms underlying the upregulation of glycolysis, and how intervention with cellular bioenergetic pathways might make tumor cells more susceptible to anticancer treatment and induction of apoptosis.
TL;DR: It is proposed that enhanced activation of p53 by lack of Sirt7-mediated deacetylation contributes to the heart phenotype of SIRT7 mutant mice, suggesting a critical role of Sirts in the regulation of stress responses and cell death in the heart.
Abstract: Sirt7 is a member of the mammalian sirtuin family consisting of 7 genes, Sirt1 to Sirt7, which all share a homology to the founding family member, the yeast Sir2 gene. Most sirtuins are supposed to act as histone/protein deacetylases, which use oxidized NAD in a sirtuin-specific, 2-step deacetylation reaction. To begin to decipher the biological role of Sirt7, we inactivated the Sirt7 gene in mice. Sirt7-deficient animals undergo a reduction in mean and maximum lifespans and develop heart hypertrophy and inflammatory cardiomyopathy. Sirt7 mutant hearts are also characterized by an extensive fibrosis, which leads to a 3-fold increase in collagen III accumulation. We found that Sirt7 interacts with p53 and efficiently deacetylates p53 in vitro, which corresponds to hyperacetylation of p53 in vivo and an increased rate of apoptosis in the myocardium of mutant mice. Sirt7-deficient primary cardiomyocytes show a approximately 200% increase in basal apoptosis and a significantly diminished resistance to oxidative and genotoxic stress suggesting a critical role of Sirt7 in the regulation of stress responses and cell death in the heart. We propose that enhanced activation of p53 by lack of Sirt7-mediated deacetylation contributes to the heart phenotype of Sirt7 mutant mice.
TL;DR: It is suggested that caspase-orchestrated mitochondrial events determine the impact of apoptotic cells on the immune response and blocking sites of oxidation in HMGB1 prevented tolerance induction by apoptosis.
TL;DR: In this system, short-time inhibition of autophagy along with radiotherapy lead to enhanced cytotoxicity of radiotherapy in resistant cancer cells.
Abstract: Autophagy or "self eating" is frequently activated in tumor cells treated with chemotherapy or irradiation. Whether autophagy represents a survival mechanism or rather contributes to cell death remains controversial. To address this issue, the role of autophagy in radiosensitive and radioresistant human cancer cell lines in response to gamma-irradiation was examined. We found irradiation-induced accumulation of autophagosomes accompanied by strong mRNA induction of the autophagy-related genes beclin 1, atg3, atg4b, atg4c, atg5, and atg12 in each cell line. Transduction of specific target-siRNAs led to down-regulation of these genes for up to 8 days as shown by reverse transcription-PCR and Western blot analysis. Blockade of each autophagy-related gene was associated with strongly diminished accumulation of autophagosomes after irradiation. As shown by clonogenic survival, the majority of inhibited autophagy-related genes, each alone or combined, resulted in sensitization of resistant carcinoma cells to radiation, whereas untreated resistant cells but not sensitive cells survived better when autophagy was inhibited. Similarly, radiosensitization or the opposite was observed in different sensitive carcinoma cells and upon inhibition of different autophagy genes. Mutant p53 had no effect on accumulation of autophagosomes but slightly increased clonogenic survival, as expected, because mutated p53 protects cells by conferring resistance to apoptosis. In our system, short-time inhibition of autophagy along with radiotherapy lead to enhanced cytotoxicity of radiotherapy in resistant cancer cells.
TL;DR: The observations provide a molecular basis for the different phenotypes seen in mice lacking either caspase and indicate that these proteases occupy nonredundant roles within the cell death machinery.
Abstract: Members of the caspase family of cysteine proteases play central roles in coordinating the stereotypical events that occur during apoptosis. Because the major executioner caspases, caspase-3 and caspase-7, exhibit almost indistinguishable activity toward certain synthetic peptide substrates, this has led to the widespread view that these proteases occupy functionally redundant roles within the cell death machinery. However, the distinct phenotypes of mice deficient in either of these caspases, as well as mice deficient in both, is at odds with this view. These distinct phenotypes could be related to differences in the relative expression levels of caspase-3 and caspase-7 in vivo, or due to more fundamental differences between these proteases in terms of their ability to cleave natural substrates. Here we show that caspase-3 and caspase-7 exhibit differential activity toward multiple substrate proteins, including Bid, XIAP, gelsolin, caspase-6, and cochaperone p23. Caspase-3 was found to be generally more promiscuous than caspase-7 and appears to be the major executioner caspase during the demolition phase of apoptosis. Our observations provide a molecular basis for the different phenotypes seen in mice lacking either caspase and indicate that these proteases occupy nonredundant roles within the cell death machinery.
TL;DR: This review summarizes recent cellular and molecular advances in the understanding of the injury mechanisms leading to end-stage liver disease and indicates activated stellate cell apoptosis leads to slowing and resolution of apoptosis.
TL;DR: Although elevated PUma expression elicits profound chemo- and radiosensitization in cancer cells, inhibition of PUMA expression may be useful for curbing excessive cell death associated with tissue injury and degenerative diseases.
Abstract: PUMA (p53 upregulated modulator of apoptosis) is a Bcl-2 homology 3 (BH3)-only Bcl-2 family member and a critical mediator of p53-dependent and -independent apoptosis induced by a wide variety of stimuli, including genotoxic stress, deregulated oncogene expression, toxins, altered redox status, growth factor/cytokine withdrawal and infection. It serves as a proximal signaling molecule whose expression is regulated by transcription factors in response to these stimuli. PUMA transduces death signals primarily to the mitochondria, where it acts indirectly on the Bcl-2 family members Bax and/or Bak by relieving the inhibition imposed by antiapoptotic members. It directly binds and antagonizes all known antiapoptotic Bcl-2 family members to induce mitochondrial dysfunction and caspase activation. PUMA ablation or inhibition leads to apoptosis deficiency underlying increased risks for cancer development and therapeutic resistance. Although elevated PUMA expression elicits profound chemo- and radiosensitization in cancer cells, inhibition of PUMA expression may be useful for curbing excessive cell death associated with tissue injury and degenerative diseases. Therefore, PUMA is a general sensor of cell death stimuli and a promising drug target for cancer therapy and tissue damage.
TL;DR: An overview of the function of the tumor suppressor gene product p53 in the c-MYC-mediated apoptotic response and how c- MYC amplifies the intrinsic mitochondrial pathway and triggers and/or amplifying the death receptor pathways is provided.
Abstract: c-MYC has a pivotal function in growth control, differentiation and apoptosis, and its abnormal expression is associated with many tumors. Overexpression of c-MYC sensitizes cells to apoptosis by a variety of stimuli. The decision of a cell to undergo apoptosis and how this apoptotic response is regulated by c-MYC depends on the specific cell type and the physiological status of the cell. Multiple cooperating molecular pathways of cell survival and apoptosis determine whether a cell lives or dies, and understanding how c-MYC interfaces with these pathways to influence the survival of cells is important to understand normal and abnormal development, tumor initiation and progression, and response of tumors to different treatment regimens. This article will provide an overview of the function of the tumor suppressor gene product p53 in the c-MYC-mediated apoptotic response and how c-MYC amplifies the intrinsic mitochondrial pathway and triggers and/or amplifies the death receptor pathways. Finally, a model for how deregulated c-MYC prematurely triggers the normal apoptotic response associated with terminal myeloid differentiation while also blocking the differentiation program is presented.
TL;DR: It is reported that B7-H1 on cancer cells receives a signal from PD-1 to rapidly induce resistance against T cell-mediated killing, a new mechanism by which cancer cells use a receptor on immune cells as a ligand to induce resistance to therapy.
TL;DR: Early clinical trial data suggest that rhApo2L/TRAIL is generally safe and provide preliminary evidence for potential antitumor activity, and clinical studies are ongoing to assess the safety and efficacy of this novel agent in combination with established anticancer therapies.
Abstract: Cancer is a leading cause of premature human death and commands considerable research attention. Apoptosis (type 1 programmed cell death) is critical in maintaining tissue homeostasis in metazoan organisms, and its dysregulation underpins the initiation and progression of cancer. Conventional chemotherapy and radiotherapy can induce apoptosis as a secondary consequence of inflicting cell damage. However, more direct and selective strategies to manipulate the apoptotic process in cancer cells are emerging as potential therapeutic tools. Genetic and biochemical understanding of the cellular signaling mechanisms that control apoptosis has increased substantially during the last decade. These advances provide a strong scientific framework for developing several types of targeted proapoptotic anticancer therapies. One promising class of agents is the proapoptotic receptor agonists. Of these, recombinant human apoptosis ligand 2/tumor necrosis factor-related apoptosis-inducing ligand (rhApo2L/TRAIL)-an optimized soluble form of an endogenous apoptosis-inducing ligand-is unique in that it activates two related proapoptotic receptors, DR4 and DR5. Preclinical data indicate that rhApo2L/TRAIL can induce apoptosis in a broad range of human cancer cell lines while sparing most normal cell types. In vitro, and in various in vivo tumor xenograft models, rhApo2L/TRAIL exhibits single-agent antitumor activity and/or cooperation with certain conventional and targeted therapies. Preclinical safety studies in nonhuman primates show rhApo2L/TRAIL to be well tolerated. Moreover, early clinical trial data suggest that rhApo2L/TRAIL is generally safe and provide preliminary evidence for potential antitumor activity. Clinical studies are ongoing to assess the safety and efficacy of this novel agent in combination with established anticancer therapies.
TL;DR: New molecular insights have inspired the development of pro-apoptotic receptor agonists (PARAs), including the recombinant human protein apoptosis ligand 2/TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) and agonistic monoclonal antibodies to its signalling receptors.
Abstract: Each day, the human body eliminates billions of unwanted cells by apoptotic suicide. Apoptosis provides an important barrier against cancer; however, specific mutations enable some tumour cells to escape apoptotic death and become more malignant. Two signalling pathways initiate apoptosis: one acts through intracellular Bcl-2 proteins, the other through cell-surface pro-apoptotic receptors. New molecular insights have inspired the development of pro-apoptotic receptor agonists (PARAs), including the recombinant human protein apoptosis ligand 2/TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) and agonistic monoclonal antibodies to its signalling receptors. Acting alone, or in concert with other agents, PARAs may overcome key apoptosis blocks and direct cancer cells to self-destruct.
TL;DR: This study reveals that non-canonical autophagy induced by resveratrol can act as a caspase-independent cell death mechanism in breast cancer cells.
Abstract: Resveratrol, a polyphenol found in grapes and other fruit and vegetables, is a powerful chemopreventive and chemotherapeutic molecule potentially of interest for the treatment of breast cancer The human breast cancer cell line MCF-7, which is devoid of caspase-3 activity, is refractory to apoptotic cell death after incubation with resveratrol Here we show that resveratrol arrests cell proliferation, triggers death and decreases the number of colonies of cells that are sensitive to caspase-3-dependent apoptosis (MCF-7 casp-3) and also those that are unresponsive to it (MCF-7vc) We demonstrate that resveratrol (i) acts via multiple pathways to trigger cell death, (ii) induces caspase-dependent and caspase-independent cell death in MCF-7 casp-3 cells, (iii) induces only caspase-independent cell death in MCF-7vc cells and (iv) stimulates macroautophagy Using BECN1 and hVPS34 (human vacuolar protein sorting 34) small interfering RNAs, we demonstrate that resveratrol activates Beclin 1-independent autophagy in both cell lines, whereas cell death via this uncommon form of autophagy occurs only in MCF-7vc cells We also show that this variant form of autophagic cell death is blocked by the expression of caspase-3, but not by its enzymatic activity In conclusion, this study reveals that non-canonical autophagy induced by resveratrol can act as a caspase-independent cell death mechanism in breast cancer cells
TL;DR: The findings indicate that the fission-mediated fragmentation of mitochondrial tubules is causally associated with enhanced production of mitochondrial ROS and cardiovascular cell injury in hyperglycaemic conditions.
Abstract: Aims One of the main causes of cardiovascular complications in diabetes is the hyperglycaemia-induced cell injury, and mitochondrial fission has been implicated in the apoptotic process. We investigated the role of mitochondrial fission in high glucose-induced cardiovascular cell injury. Methods and results We used several types of cultured mouse, rat, and bovine cells from the cardiovascular system, and evaluated mitochondrial morphology, reactive oxygen species (ROS) levels, and apoptotic parameters in sustained high glucose incubation. Adenoviral infection was used for the inhibition of the fission protein DLP1. We found that mitochondria were short and fragmented in cells incubated in sustained high glucose conditions. Under the same conditions, cellular ROS levels were high and cell death was increased. We demonstrated that the increased level of ROS causes mitochondrial permeability transition (MPT), phosphatidylserine exposure, cytochrome c release, and caspase activation in prolonged high glucose conditions. Importantly, maintaining tubular mitochondria by inhibiting mitochondrial fission in sustained high glucose conditions normalized cellular ROS levels and prevented the MPT and subsequent cell death. These results demonstrate that mitochondrial fragmentation is an upstream factor for ROS overproduction and cell death in prolonged high glucose conditions. Conclusion These findings indicate that the fission-mediated fragmentation of mitochondrial tubules is causally associated with enhanced production of mitochondrial ROS and cardiovascular cell injury in hyperglycaemic conditions.
TL;DR: Two proapoptotic receptor agonists, recombinant human Apo2-ligand/TNF-related apoptosis-inducing ligand and Apomab, which activate death receptor (DR) 4 and/or DR5, thus stimulating the cell-extrinsic pathway are focused on.
TL;DR: Using a combination of live-cell reporters, flow cytometry, and immunoblotting, it is found that initiator caspases are active during the long and variable delay that precedes mitochondrial outer membrane permeabilization (MOMP) and effector caspase activation.
TL;DR: The observations further validate the use of the HL‐60 cell line as a model system for the study of human granulopoiesis in vitro and conclude that this model system may be useful for gaining insight into the underlying mechanisms involved in apoptosis.
Abstract: SUMMARY
The human promyelocytic HL-60 cell line can be induced to differentiate to neutrophil-like cells in response to a variety of chemical stimuli. We have found that retinoic acid-treatment of HL-60 cells over a period of 6–8 days resulted in a progressive increase in the proportion of cells with mature neutrophil morphologies and was closely followed by an increase in the proportion of cells exhibiting the morphological characteristics of apoptosis, the non-pathological mode of cell death. Using Percoll step-density gradients we have demonstrated a marked increase in the buoyant density of these cells and have used this density difference to obtain enriched fractions of cells for more detailed study. Degradation of the nuclear DNA of these cells into integer multiples of about 200 base pairs, indicative of endogenous endonuclease activation a major characteristic of programmed cell death, was also demonstrated. From these observations we conclude that the mode of cell death in cultures of terminally differentiated HL-60 cells is that of apoptosis. These results parallel those of a recent report which has shown apoptosis to be the mode of cell death of ageing peripheral blood neutrophils. Because of this, we believe that our observations further validate the use of the HL-60 cell line as a model system for the study of human granulopoiesis in vitro and further, that this model system may be useful for gaining insight into the underlying mechanisms involved in apoptosis.