Increased erythropoietin production after myocardial infarction in mice.
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Animals↗
Biomedical subjects
M Leist
Publications and source records attributed to M Leist.
Irradiation-induced progenitor cell death in the developing brain is resistant to erythropoietin treatment and caspase inhibition.
One hemisphere of postnatal day 8 (P8) rats or P10 mice was irradiated with a single dose of 4-12 Gy, and animals were killed from 2 h to 8 weeks after irradiation (IR). In the subventricular zone (SVZ) and the granular cell layer (GCL) of the dentate gyrus, harboring neural and other progenitor cells, nitrosylation and p53 peaked 2-12 h after IR, followed by markers for active caspase-3, apoptosis-inducing factor and TUNEL (6-24 h). Ki67-positive (proliferating) cells had disappeared by 12 h and partly reappeared by 7 days post-IR. The SVZ and GCL areas decreased approximately 50% 7 days after IR. The development of white matter was hampered, resulting in 50-70% less myelin basic protein staining. Pretreatment with erythropoietin did not confer protection against IR. Caspase inhibition by overexpression of XIAP prevented caspase-9 and caspase-3 activation but not cell death, presumably because of increased caspase-independent cell death.
Active Transport, Cell Nucleus↗
The fixation and leaching of cement stabilized arsenic.
The solidification/stabilization of sodium arsenite, sodium arsenate, arsenic trioxide and arsenic pentoxide at dosages of approximately 10% has been investigated using sequential batch leaching tests. The leaching of arsenic, which was found to be diffusion based, was clearly least effective for those formulations containing additional iron(II). Calcium was found to influence the leaching of cement immobilized arsenic: those formulations containing the greatest Ca:As mole ratios were generally the most successful. Analysis using both FTIR and SEM revealed substantial changes to the cement matrices of those formulations to which the ferrous sulfate had been added. Ettringite was identified in the cement+ferrous sulfate formulations.
Arsenic↗
Rapid, noninflammatory and PS-dependent phagocytic clearance of necrotic cells.
In pathological situations, different modes of cell death are observed, and information on the role and uptake of nonapoptotic corpses is scarce. Here, we modeled two distinct forms of death in human Jurkat T cells treated with staurosporine: classical apoptosis under normal culture conditions and programmed death with necrotic morphology under ATP-depleting conditions (necPCD). When offered to phagocytes, both types of cell corpses (but not heat-killed unscheduled necrotic cells) reduced the release of the proinflammatory cytokine TNF from the macrophages. The necPCD cells were efficiently engulfed by macrophages and microglia, and from mixtures of necPCD and apoptotic cells macrophages preferentially engulfed the necrotic cells. Using a newly developed assay, we demonstrated that phosphatidylserine is translocated to the surface of such necrotic cells. We demonstrate that this can occur independently of calcium signals, and that surface phosphatidylserine is essential for the uptake of necrotic cells by both human macrophages and murine microglia.
Animals↗
Disialoganglioside GD3 is released by microglia and induces oligodendrocyte apoptosis.
Increased brain ganglioside levels are a hallmark of various neuroinflammatory pathologies. Here, we provide evidence that murine microglia can secrete disialoganglioside GD3 upon exposure to inflammatory stimuli. Comparison of different neural cell types revealed a particular and specific sensitivity of oligodendrocytes towards exogenous GD3. Oligodendrocyte death triggered by GD3 was preceded by degeneration of cellular processes, and associated with typical features of apoptosis, such as chromatin condensation, exposure of phosphatidylserine, release of cytochrome c from mitochondria, and loss of mitochondrial membrane potential, followed by the loss of plasma membrane integrity and detachment of disintegrated oligodendrocytes. Overexpression of bcl-2 partially protected oligodendrocytes from death. In contrast, treatment with the pan-caspase inhibitor zVAD-fmk did not prevent phosphatidylserine exposure, chromatin margination at the nuclear periphery, and death, although caspase-3 was blocked. Thus, GD3 produced by microglia under neuroinflammatory conditions may function as a novel mediator triggering mitochondria-mediated, but caspase-independent, apoptosis-like death of oligodendrocytes.
Animals↗
Calpain inhibitors prevent nitric oxide-triggered excitotoxic apoptosis.
The pathogenesis of some neurodegenerative disorders has been linked to excitotoxicity, excess generation of nitric oxide (NO) and apoptosis. Here, we used a model of NO-triggered neuronal apoptosis that was strictly dependent on autocrine NMDA receptor (NMDA-R) activation and intracellular Ca2+ increase. We investigated the efficiency and potentially beneficial effects of calpain inhibition. Three calpain inhibitors that prevented intracellular fodrin proteolysis also blocked apoptotic features such as decrease in mitochondrial membrane potential, chromatin breakdown, and subsequent death of cerebellar granule neurons exposed to NO donors (S-nitroso-L-glutathione, S-nitroso-N-acetyl-d,l-penicillamine, and diethylamino-diazenolate-2-oxide). Since inhibitors did not interfere with NMDA-R activation, we suggest that block of calpains blunts NO-triggered neuronal apoptosis by stopping the cascade downstream of primary autocrine excitotoxic events.
Animals↗
Caspase-3 activity is present in cerebrospinal fluid from patients with traumatic brain injury.
Loss of neurons after traumatic brain injury (TBI) might involve dysregulated apoptosis. Activation of caspase-3 is one hallmark of apoptosis. Therefore, caspase-3 activity (cleavage of DEVD-afc) was measured in cerebrospinal fluid (CSF) samples (n=113) from 27 patients with TBI at day 1 to 14 after trauma. Caspase-3 activity was detected in 31 (27.4%) CSF samples with highest values (> 5.5 microM/min) seen at day 2-5 after trauma. No caspase-3 activity was found in serum from patients or CSF from controls. The presence of activated caspase-3 in CSF suggests ongoing apoptotic processes during traumatic brain injury.
Adult↗
Cathepsin B acts as a dominant execution protease in tumor cell apoptosis induced by tumor necrosis factor.
Death receptors can trigger cell demise dependent or independent of caspases. In WEHI-S fibrosarcoma cells, tumor necrosis factor (TNF) induced an increase in cytosolic cathepsin B activity followed by death with apoptotic features. Surprisingly, this process was enhanced by low, but effectively inhibiting, concentrations of pan-caspase inhibitors. Contrary to caspase inhibitors, a panel of pharmacological cathepsin B inhibitors, the endogenous cathepsin inhibitor cystatin A as well as antisense-mediated depletion of cathepsin B rescued WEHI-S cells from apoptosis triggered by TNF or TNF-related apoptosis-inducing ligand. Thus, cathepsin B can take over the role of the dominant execution protease in death receptor-induced apoptosis. The conservation of this alternative execution pathway was further examined in other tumor cell lines. Here, cathepsin B acted as an essential downstream mediator of TNF-triggered and caspase-initiated apoptosis cascade, whereas apoptosis of primary cells was only minimally dependent on cathepsin B. These data imply that cathepsin B, which is commonly overexpressed in human primary tumors, may have two opposing roles in malignancy, reducing it by its proapoptotic features and enhancing it by its known facilitation of invasion.
Animals↗
In vivo and in vitro evidence for extracellular caspase activity released from apoptotic cells.
While caspases play an established role as intracellular executors of apoptosis, little is known about extracellular activities of this ubiquitously expressed family of proteases. We demonstrate here that recombinant caspase-3 retained enzymatic activity in various extracellular fluids. Experiments with cell lines, primary cells, and mice with fulminant CD95-triggered hepatitis showed that significant amounts of DEVD-aminofluoromethylcoumarine-cleaving activity, indicative of active effector caspases, were released into the medium/plasma during apoptosis. Furthermore, caspase activities were detected in liquor samples from human head trauma patients. These findings warrant closer investigation of DEVDase activity as a diagnostic marker, and of potential extracellular substrates for caspases.
Animals↗
Synthesis of ganglioside GD3 and its comparison with bovine GD3 with regard to oligodendrocyte apoptosis mitochondrial damage.
2,3-Dehydroneuraminic acid derivative 5 was transformed in five efficient steps into sialyl donor 2, which has a phenylthio group on the beta-side of the 3-position for anchimeric assistance and a diethyl phosphite residue as leaving group at the anomeric carbon. The known GM3 intermediate 10 was transformed into the 4b,4c,8c-O-unprotected acceptor 3, which was then allowed to react with 2 by using TMSOTf as catalyst and acetonitrile as solvent to afford the desired tetrasaccharide 12, which has an alpha(2-8)-linkage between two neuraminic acid residues. Removal of the phenylthio group gave intermediate 13, which was transformed into O-tetraosyl trichloroacetimidate 16 as glycosyl donor. Application of the azidosphingosine glycosylation procedure furnished GD3 (1) in high overall yield. Comparison of synthetic GD3 with bovine-brain-derived GD3 showed that there were similar effects in GD3-triggered uncoupling of mitochondrial respiration and in induction of apoptosis in oligodendrocytes.
Animals↗
Differential effects of bcl-2 on cell death triggered under ATP-depleting conditions.
The intracellular ATP concentration decides on the onset of either apoptosis or necrosis in Jurkat cells exposed to death stimuli. Bcl-2 can block apoptotic demise, which occurs preferably under conditions of high cellular ATP levels. Here, we investigated the effects of Bcl-2 on the necrotic type of cell demise that prevails under conditions of energy loss. ATP levels were modulated by using mitochondrial inhibitors, such as rotenone or S-nitrosoglutathione, in medium either lacking glucose or supplemented with glucose to stimulate glycolytic ATP generation. Under conditions of ATP depletion, staurosporine (STS) induced >90% necrosis in vector control-transfected cells, whereas bcl-2-transfected cells were protected. Thus, the antiapoptotic protein Bcl-2 can reduce the overall amount of cell death in ATP-depleted cells regardless whether it occurs by apoptosis or necrosis. Cytochrome c release, normally preceding STS-induced necrosis, was also inhibited by Bcl-2. However, Bcl-2 did not prevent an initial STS-induced drop of the mitochondrial membrane potential (DeltaPsi(m)). Therefore, the mechanisms whereby Bcl-2 prevents cell death and favors retention of cytochrome c in the mitochondria require neither the maintenance of mitochondrial DeltaPsi nor the maintenance of normal ATP levels.
Adenosine Triphosphate↗
Cascade of caspase activation in potassium-deprived cerebellar granule neurons: targets for treatment with peptide and protein inhibitors of apoptosis.
Cerebellar granule neurons (CGN) cultured in the presence of serum and depolarizing potassium concentrations undergo apoptosis when switched to serum-free medium containing physiological potassium concentrations. Here we show that processing of the key protease, caspase-3, depends on the activation of caspase-9, but not of caspase-8. Selective peptide inhibitors of caspase-9 block processing of caspase-3 and caspase-8 and inhibit apoptosis, whereas a selective inhibitor of caspase-8 blocks neither processing of caspase-3 nor cell death. The data obtained with peptide inhibitors were confirmed by adenovirally mediated ectopic expression of the cytokine response modifier A (crmA), the baculovirus protein p35, and the X chromosome-linked inhibitor of apoptosis (XIAP). Further, caspase-8-activating death receptors do not mediate apoptosis in CGN and potassium withdrawal-induced apoptosis evolves unaltered in gld or lpr mice, which harbor mutations in the CD95/CD95 ligand system. Thus, neuronal apoptosis triggered by potassium deprivation is death receptor-independent but involves the mitochondrial pathway of caspase activation.
Animals↗
Four deaths and a funeral: from caspases to alternative mechanisms.
A single family of proteases, the caspases, has long been considered the pivotal executioner of all programmed cell death. However, recent findings of evolutionarily conserved, caspase-independent controlled death mechanisms have opened new perspectives on the biology of cell demise, with particular implications for neurobiology, cancer research and immunological processes.
Animals↗
Triggering of apoptosis by cathepsins.
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Animals↗
Apoptosis in caspase-inhibited neurons.
BACKGROUND: There is growing evidence of apoptosis in neurodegenerative disease. However, it is still unclear whether the pathological manifestations observed in slow neurodegenerative diseases are due to neuronal loss or whether they are related to independent degenerative events in the axodendritic network. It also remains elusive whether a single, caspase-based executing system involving caspases is responsible for neuronal loss by apoptosis. MATERIALS AND METHODS: Long-term exposure to the microtubule-disassembling agent, colchicine, was used to disrupt the axodendritic network and eventually trigger caspase-3-mediated apoptosis in cultures of cerebellar granule cells. For this model, we investigated the role of Bcl-2 and caspases in neurite degeneration and death of neuronal somata. RESULTS: Early degeneration of the axodendritic network occurred by a Bcl-2 and caspase-independent mechanism. Conversely, apoptosis of the cell body was delayed by Bcl-2 and initially blocked by caspase inhibition. However, when caspase activity was entirely blocked by zVAD-fmk, colchicine-exposed neurons still underwent delayed cell death characterized by cytochrome c release, chromatin condensation to irregularly shaped clumps, DNA-fragmentation, and exposure of phosphatidylserine. Inhibitors of the proteasome reduced these caspase-independent apoptotic-like features of the neuronal soma. CONCLUSION: Our data suggest that Bcl-2-dependent and caspase-mediated death programs account only partially for neurodegenerative changes in injured neurons. Blockage of the caspase execution machinery may only temporarily rescue damaged neurons and classical apoptotic features can still appear in caspase-inhibited neurons.
Amino Acid Chloromethyl Ketones↗
Age-related macular degeneration. The lipofusion component N-retinyl-N-retinylidene ethanolamine detaches proapoptotic proteins from mitochondria and induces apoptosis in mammalian retinal pigment epithelial cells.
10-20% of individuals over the age of 65 suffer from age-related macular degeneration (AMD), the leading cause of severe visual impairment in humans living in developed countries. The pathogenesis of this complex disease is poorly understood, and no efficient therapy or prevention exists to date. A precondition for AMD appears to be the accumulation of the age pigment lipofuscin in lysosomes of retinal pigment epithelial (RPE) cells. In AMD, these cells seem to die by apoptosis with subsequent death of photoreceptor cells, and light may accelerate the disease process. Intracellular factors leading to cell death are not known. Here we show that the lipophilic cation N-retinyl-N-retinylidene ethanolamine (A2E), a lipofuscin component, induces apoptosis in RPE and other cells at concentrations found in human retina. Apoptosis is accompanied by the appearance of the proapoptotic proteins cytochrome c and apoptosis-inducing factor in the cytoplasm and the nucleus. Biochemical examinations show that A2E specifically targets cytochrome oxidase (COX). With both isolated mitochondria and purified COX, A2E inhibits oxygen consumption synergistically with light. Inhibition is reversed by the addition of cytochrome c or cardiolipin, a negatively charged phospholipid that facilitates the binding of cytochrome c to membranes. Succinate dehydrogenase activity is not altered by A2E. We suggest that A2E can act as a proapoptotic molecule via a mitochondria-related mechanism, possibly through site-specific targeting of this cation to COX. Loss of RPE cell viability through inhibition of mitochondrial function might constitute a pivotal step toward the progressive degeneration of the central retina.
Aging↗
Apoptosis in the dorsal lateral geniculate nucleus after monocular deprivation involves glutamate signaling, NO production, and PARP activation.
In mammals, visual experience during early postnatal life is critical for normal development of the visual system. Here we report that monocular deprivation for 2, 7, and 14 consecutive days causes p53 accumulation, cell death, and progressive loss of neurones in the dorsal lateral geniculate nucleus (dLGN) of newborn rats and these are prevented by NMDA and non-NMDA glutamate receptor antagonists, and by L-NAME, an inhibitor of nitric oxide synthesis. Monocular deprivation also increases dLGN levels of citrulline, the coproduct of nitric oxide synthesis, and this, as well as cell death and neuronal loss, is abolished by antagonists of glutamate receptors and by L-NAME. Finally, poly-(ADP-ribose) polymerase (PARP) knock-out mice appear to be protected from monocular deprivation-induced cell death. In conclusion, during early postnatal development of the rat visual system monocular deprivation causes excitotoxic, nitric oxide-mediated, cell death in the dLGN that appears to be apoptotic and also requires activation of PARP.
Animals↗
The management of arsenic wastes: problems and prospects.
Arsenic has found widespread use in agriculture and industry to control a variety of insect and fungicidal pests. Most of these uses have been discontinued, but residues from such activities, together with the ongoing generation of arsenic wastes from the smelting of various ores, have left a legacy of a large number of arsenic-contaminated sites. The treatment and/or removal of arsenic is hindered by the fact that arsenic has a variety of valence states. Arsenic is most effectively removed or stabilized when it is present in the pentavalent arsenate form. For the removal of arsenic from wastewater, coagulation, normally using iron, is the preferred option. The solidification/stabilization of arsenic is not such a clear-cut process. Factors such as the waste's interaction with the additives (e.g. iron or lime), as well as any effect on the cement matrix, all impact on the efficacy of the fixation. Currently, differentiation between available solidification/stabilization processes is speculative, partly due to the large number of differing leaching tests that have been utilized. Differences in the leaching fluid, liquid-to-solid ratio, and agitation time and method all impact significantly on the arsenic leachate concentrations. This paper reviews options available for dealing with arsenic wastes, both solid and aqueous through an investigation of the methods available for the removal of arsenic from wastewater as well as possible solidification/stabilization options for a variety of waste streams.
Arsenic↗