Various Modes Of Cell Death Research Articles

Mitochondria as Therapeutic Targets for the Treatment of Malignant Disease

Mitochondria exert vital functions during normal physiology and are also centrally involved in the regulation of various modes of cell death. Thus, engaging the mitochondrial apoptosis pathway presents an attractive possibility to activate lethal effectors in cancer cells. Compounds that directly target mitochondria offer the advantage to initiate mitochondrial outer membrane permeabilization independently of upstream signal transduction elements that are frequently impaired in human cancers. As a consequence, mitochondrion-targeted agents may bypass some forms of drug resistance. An ever-increasing number of compounds, including natural compounds and rationally designed drugs, has been shown to directly act on mitochondria. Forthcoming insights into the fine regulation of mitochondrial apoptosis will likely open future perspectives for cancer drug development.

Cell death in mammalian cell culture: molecular mechanisms and cell line engineering strategies

Cell death is a fundamentally important problem in cell lines used by the biopharmaceutical industry. Environmental stress, which can result from nutrient depletion, by-product accumulation and chemical agents, activates through signalling cascades regulators that promote death. The best known key regulators of death process are the Bcl-2 family proteins which constitute a critical intracellular checkpoint of apoptosis cell death within a common death pathway. Engineering of several members of the anti-apoptosis Bcl-2 family genes in several cell types has extended the knowledge of their molecular function and interaction with other proteins, and their regulation of cell death. In this review, we describe the various modes of cell death and their death pathways at molecular and organelle level and discuss the relevance of the growing knowledge of anti-apoptotic engineering strategies to inhibit cell death and increase productivity in mammalian cell culture.

Pleiotropic effects of cadmium in mesangial cells

The mesangial cell of the renal glomerulus is exposed to circulating toxic substances and is a target involved in the glomerular component of chronic occupational and environmental exposure to cadmium. We review evidence for the involvement of cadmium in mesangial cell pathology, including effects on cell signaling, oncogene expression, and cell death. Previously we have shown that cadmium can inhibit apoptosis initiated through both the extrinsic (death ligand receptor) and intrinsic (mitochondrial) pathways, whereas exposure of mesangial cells to 10 μM CdCl 2 for 6 h initiates caspase-independent cell death through both apoptotic and apoptotic-like (annexin V positive, propidium iodide staining) mechanisms. Apoptotic death is dependent upon activation of Ca 2+/calmodulin-dependent protein kinase II (CaMK-II). In the present study we show that low level exposure of mesangial cells to Cd 2+ (0.5 μM) initiates cell survival signals including PI3 kinase/Akt signaling, also dependent on CaMK-II, that are eventually overcome resulting in caspase-dependent cell death. These studies underscore the roles of cell signaling in various modes of cell death, and in particular the central role of CaMK-II in cadmium toxicology of the mesangial cell.

Cryoablation Induces Necrosis and Apoptosis in Lung Adenocarcinoma in Mice

This study evaluated cryoablation on subcutaneously transplanted tumors of lung adenocarcinoma LA795 in T739 mice in vivo, in an effort to assess the feasibility of cryoablation in treatment of NSCLC. Subcutaneously transplanted lung adenocarcinoma LA795 was implanted into T739 mice yielding tumors of approximately 2.5 cm in diameter. Following cryoablation, the various modes of cell death were studied: necrosis in the central frozen zone by light microscopy and apoptosis in periphery of the frozen zone by in situ end labeling (TUNEL). Bc1-2 and bax expression were detected by immunohistochemical SABC procedures, and the cleavage and activation of Caspase 3 and PARP in peripheral zone by Western blot. We find that in central cryoablated zone, necrosis was the dominant mode of cell death occurring at three hours and four days post-thaw. The first three-hour necrosis peak involved approximately 47% of the tumor while the four-day peak increased in volume to 68% of the tumor. In peripheral cryoablation zone, definite cell apoptosis could be observed by morphological examination under light microscope and TUNEL staining, peaking at 8-16 h after cryoablation. Immunohistochemical results yielded little change in bcl-2 protein expression before and after cryoablation. However, bax protein expression was up-regulated significantly after cryoablation. In addition, cleavage and activation of Caspase-3 and PARP occurred in the peripheral freeze zone after the treatment. It indicated that Cryoablation efficiently induces cell death both by necrosis and apoptosis. Cryoablation appears to induce apoptosis in the peripheral freeze zone through the intrinsic mitochondrial caspase pathway based on bax upregulation. This observation allows us to suggest that cryoablation may be combined with chemotherapy to increase cancer destruction.

Activation of caspase-3-dependent and -independent pathways during 7-ketocholesterol- and 7β-hydroxycholesterol-induced cell death: A morphological and biochemical study

On treatment with 7-ketocholesterol (7-keto) or 7beta-hydroxycholesterol (7beta-OH), which are major oxysterols in atherosclerotic plaques, the simultaneous identification of oncotic and apoptotic cells suggests that these compounds activate different metabolic pathways leading to various modes of cell death. With U937, MCF-7 (caspase-3 deficient), MCF-7/c3 cells (stably transfected with caspase-3), we demonstrate that caspase-3 is essential for caspase-9, -7, -8 activation, for Bid degradation mediating mitochondrial cytochrome c release, for cleavage of poly(ADP-ribose) polymerase and inhibitor of the caspase-activated deoxyribonuclease, and, at least in part, for internucleosomal DNA fragmentation. The crucial role of caspase-3 was supported by the use of z-VAD-fmk and z-DEVD-fmk, which abolished apoptosis and the associated events. However, inactivation or lack of caspase-3 did not inhibit 7-keto- and 7beta-OH-induced cell death characterized by staining with propidium iodide, loss of mitochondrial potential. The mitochondrial release of apoptosis-inducing factor and endonuclease G was independent of the caspase-3 status, which conversely played major roles in the morphological aspects of dead cells. We conclude that caspase-3 is essential to trigger 7-keto- and 7beta-OH-induced apoptosis, that these oxysterols simultaneously activate caspase-3-dependent and/or -independent modes of cell death.

Hydrogen Peroxide Induces Necrosis, Apoptosis, Oncosis and Apoptotic Oncosis of Mouse Terminal Proximal Straight Tubule Cells

Hydrogen peroxide (H₂O₂) has been shown to be an important mediator of ischemic and toxic tubular damage. The purpose of this study was to identify the mode of cell death observed in H₂O₂-exposed cultures of mouse terminal proximal straight tubule (S₃) cells. H₂O₂ induced a dose- and time-dependent decrease in viability of S₃ cells. Morphologically, S₃ cells exposed to H₂O₂ (0.05–0.1 mM) showed features of necrosis, apoptosis, oncosis and apoptotic oncosis, whereas necrosis occurred most frequently in every experimental condition tested. On the other hand, agarose gel electrophoresis of DNA extracted from S₃ cells exposed to H₂O₂ revealed a typical DNA ladder pattern. These data suggest that H₂O₂-induced proximal tubule damages are associated with the induction of various modes of cell death including necrosis, apoptosis, oncosis and apoptotic oncosis, and with the activation of endonuclease.

Analysis of Apoptotic Cells in Surgical Pathology Materials.

Analysis of tissue turnover, the balance between cell proliferation and cell death, can provide important information about our understanding of the biological characteristics of various tissues and their functions. Especially it is very important to study apoptosis, one of the modes of cell death, in surgical pathology specimens. It is very important to note that the whole concept of cell death including apoptosis and oncosis is based on the morphological findings. Therefore, an analysis of morphological features of the cells undergoing the processes of various modes of cell death is very important. DNA fragmentation can be detected in situ by labeling 3′-OH ends with biotinylated deoxyuridine triphosphate (dUTP) through the action of terminal deoxynucleotidyl transferase (TdT).Since then, this method, subsequently termed 3′-OH nick end labeling, or TdT-mediated dUTP-biotin nick end labeling (TUNEL), has been widely used to detect cells with DNA fragmentation, especially in surgical pathology materials of human disorders. This TUNEL method is now being incorporated into many pathology laboratories throughout the world. However, increasing evidence suggest that TUNEL method is by no means specific for the detection of apoptosis and this method may also detect cells which are committed to, but not yet in the process of apoptosis. Therefore, it is very important to correlate the findings of TUNEL with morphological features of surgical pathology specimens. In addition, it is also important to note that over-fixation is associated with false negative results and insufficient fixation is likely to be associated with false positive results. Therefore, the processing of the specimens including fixation and others is critical in performing TUNEL and its interpretation.