Pyrrolidine dithiocarbamate induces bovine cerebral endothelial cell death by increasing the intracellular zinc level

The antioxidant and metal-chelating effects of pyrrolidine dithiocarbamate (PDTC) have been extensively studied. PDTC prevents cell death induced by various insults. However, PDTC itself may cause cell death in selected experimental paradigms. PDTC induced bovine cerebral endothelial cell death. However, in serum-depleted medium, PDTC did not affect the cell viability, suggesting that certain factors in serum may mediate the cytotoxic effect of PDTC. The metal chelators bathocuproine disulfonic acid, o-phenanthroline, bathophenanthroline disulfonic acid, and N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine (TPEN) prevented the cell death induced by PDTC. In a serum-deprived condition, addition of exogenous metals, copper or zinc, restored the cytotoxic effect of PDTC. These data indicate that metals such as copper or zinc in serum may mediate the cytotoxic effect of PDTC. The potency of zinc for PDTC-induced endothelial cell death was greater than that of copper. Zn-EDTA did not block PDTC-induced cell death, whereas Ca-EDTA and Cu-EDTA were able to prevent this PDTC effect. PDTC increased the intracellular fluorescence of the zinc probe dye N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide, which was quenched by TPEN or various EDTA preparations but not by Zn-EDTA. Results suggest that an increase in intracellular zinc concentration is required in PDTC-induced cerebral endothelial cell death.     

Insights from Caenorhabditis elegans on the role of metals in neurodegenerative diseases

Neurodegeneration is characterized by the cell death or loss of structure and/or function of neurons. Many neurodegenerative diseases including Parkinson's disease (PD) and Alzheimer's disease (AD) are the result of neurodegenerative processes. Metals are essential for many life processes, but they are also culpable for several neurodegenerative mechanisms. In this review, we discuss the role of metals in neurodegenerative diseases with emphasis on the utility of Caenorhabditis elegans (C. elegans) genetic models in deciphering mechanisms associated with the etiology of PD and AD.     

The effects of 17beta-estradiol and ethanol on zinc- or manganese-induced toxicity in SK-N-SH cells

Serious neurodegenerative disorders are increasingly prevalent in our society and excessive oxidative stress may be a key mediator of neuronal cell death in many of these conditions. A variety of metals, such as manganese and zinc, are essential trace elements but can reach localized toxic concentrations through various disease processes or environmental exposures and have been implicated as having a role in neurodegeneration. Both manganese and zinc exist as bivalent cations and are essential cofactors/activators for numerous enzymes. Evidence suggests one action of these metals, when concentrated beyond physiological levels, may be to inhibit cellular energy production, ultimately leading to increased radical formation. Our studies were undertaken to directly investigate the toxic effects of manganese and zinc in an immortalized neuronal-like cell line (SK-N-SH) by testing interactions with the antioxidant, 17beta-estradiol, and the neurotoxin, ethanol. Employing undifferentiated SK-N-SH cells, we found that these metals caused biphasic effects, enhancing cell proliferation at low doses and inducing cell death at higher doses. Zinc was both more efficacious and more potent than manganese in enhancing growth and in causing cell death. 17beta-Estradiol and ethanol enhanced the proliferative actions of zinc and manganese across a wide concentration range. Furthermore, co-treatment with either 17beta-estradiol or ethanol afforded protection against manganese-, but not zinc-induced toxicity. Finally, combined administration of 17beta-estradiol and ethanol to SK-N-SH cells resulted in both a loss of growth enhancement and protective properties that were observed when these substances were administered individually. We also noted that the toxic effects occurred more rapidly from zinc than manganese exposure. Taken together, these data suggest that oxidative stress likely has a role in cell death resulting from toxic exposure to either zinc or manganese, but there is a difference in the precise mechanism of their effects.     

镉胁迫引起烟草悬浮细胞程序性死亡

镉胁迫会造成烟草悬浮细胞大规模死亡。通过TUNEL技术和琼脂糖凝胶电泳技术的检测发现,这种细胞死亡伴随有典型的DNA“梯形带”出现,表明这种由Cd胁迫引起的细胞死亡是一种程序性死亡。受胁迫细胞氧化性增强及细胞中丙二醛(MDA)水平升高,说明Cd胁迫时会在细胞中造成大量活性氧(ROS),暗示烟草细胞的程序性死亡可能与ROS有关。     

The role of phytochelates in plant growth and productivity

Plants require minimal amounts of certain metals (Zn,Fe,Cu,etc) for optimal growth and productivity, but excess of these metals leads to cell death. When growth is limited by metal excess or metal deficiency plants respond by synthesizing nonproteinogenic chelating substances. Phytosiderophores are secreted by roots of iron deficient grasses and are important in providing sufficient Fe for normal growth. In response to growth-inhibitory levels of heavy metals plants synthesize metal-binding phytochelatins which detoxify excess metals. Biostimulants such as humic substances and oligomers of lactic acid have properties in common with both phytosiderophores and phytochelatins. The word phytochelates is proposed as a generic term to cover substances that affect plant growth by acting as chelating agents.     

Ferroptosis: an iron-dependent form of nonapoptotic cell death

Nonapoptotic forms of cell death may facilitate the selective elimination of some tumor cells or be activated in specific pathological states. The oncogenic RAS-selective lethal small molecule erastin triggers a unique iron-dependent form of nonapoptotic cell death that we term ferroptosis. Ferroptosis is dependent upon intracellular iron, but not other metals, and is morphologically, biochemically, and genetically distinct from apoptosis, necrosis, and autophagy. We identify the small molecule ferrostatin-1 as a potent inhibitor of ferroptosis in cancer cells and glutamate-induced cell death in organotypic rat brain slices, suggesting similarities between these two processes. Indeed, erastin, like glutamate, inhibits cystine uptake by the cystine/glutamate antiporter (system x(c)(-)), creating a void in the antioxidant defenses of the cell and ultimately leading to iron-dependent, oxidative death. Thus, activation of ferroptosis results in the nonapoptotic destruction of certain cancer cells, whereas inhibition of this process may protect organisms from neurodegeneration.     

Two discrete events, human T-cell leukemia virus type I Tax oncoprotein expression and a separate stress stimulus, are required for induction of apoptosis in T-cells

Apoptosis, or programmed cell death, is a key event in biologic homeostasis but is also involved in the pathogenesis of many human diseases including human immunodeficiency virus (HIV) infection. Although multiple mechanisms contribute to the gradual T cell decline that occurs in HIV-infected patients, programmed cell death of uninfected bystander T lymphocytes, including CD4+ and CD8+ T cells, is an important event leading to immunodeficiency. The HIV envelope glycoproteins (Env) play a crucial role in transducing this apoptotic signal after binding to its receptors, the CD4 molecule and a coreceptor, essentially CCR5 and CXCR4. Depending on Env presentation, the receptor involved and the complexity of target cell contact, apoptosis induction is related to death receptor and/or mitochondria-dependent pathways. This review summarizes current knowledge of Env-mediated cell death leading to T cell depletion and clinical complications and covers the sometimes conflicting studies that address the possible mechanisms of T cell death.     

Toxic effect of heavy metals on cells isolated from the rat adrenal and testis

Summary Heavy metals including mercury, cadmium, cobalt, and copper (100 μM) exerted an adverse effect on the viability of isolated rat adrenal capsular (zona glomerulosa), adrenal decapsular (fasciculata and reticularis), and Leydig cells of the testis with mercury being the most potent. Due to the decreased cell viability there was a parallel reduction in corticotropin-stimulated, corticosterone production by adrenal decapsular cells and luteinizing hormone-stimulated testosterone production by Leydig cells. The results indicated a direct toxic action of these heavy metals on steroid-producing cell in the adrenal gland and the tectis. Other metals tested, including lead, zinc, aluminum, chromium, iron, nickel, and lithium, did not exert any deleterious effect on cell viability or hormone-induced steroidogenesis, in adrenal and Leydig cells when tested up to a concentration of 100 μM.     

Anti-apoptosis and cell survival: A review

Type I programmed cell death (PCD) or apoptosis is critical for cellular self-destruction for a variety of processes such as development or the prevention of oncogenic transformation. Alternative forms, including type II (autophagy) and type III (necrotic) represent the other major types of PCD that also serve to trigger cell death. PCD must be tightly controlled since disregulated cell death is involved in the development of a large number of different pathologies. To counter the multitude of processes that are capable of triggering death, cells have devised a large number of cellular processes that serve to prevent inappropriate or premature PCD. These cell survival strategies involve a myriad of coordinated and systematic physiological and genetic changes that serve to ward off death. Here we will discuss the different strategies that are used to prevent cell death and focus on illustrating that although anti-apoptosis and cellular survival serve to counteract PCD, they are nevertheless mechanistically distinct from the processes that regulate cell death.     

动物细胞培养过程中的细胞自然凋亡

细胞培养过程中的细胞自然凋亡是细胞受环境压力的影响而发生的现象。随着细胞自然凋亡的分子生物学和生物化学研究的深入,对以动物细胞产品生产为目的的细胞培养产业将产生极有价值的影响。采用DNA重组技术把预防细胞自然凋亡的基因导入细胞和在培基中加入具有抗细胞自然凋亡的化合物等手段已用于预防或减缓细胞培养过程中的细胞自然凋亡。这些技术将大大延长细胞达到饱和密度后的培养时间,从而使细胞培养系统的生产效率得以显著提高。     

p38 MAPK and MSK1 mediate caspase-8 activation in manganese-induced mitochondria-dependent cell death

Heavy metals are important regulators of cell apoptosis. Manganese (Mn(2+)) is a potent inducer of apoptosis in different cell types, but the precise mechanisms that mediate such effects are not well defined. We previously reported that Mn(2+) was a potent apoptotic agent in human B cells, including lymphoma B cell lines. We show here that Mn(2+)-induced cell death in human B cells is associated with caspase-8-dependent mitochondrial activation leading to caspase-3 activity and apoptosis. We used specific caspase-8 interfering shRNAs to reduce caspase-8 expression, and this also reduced Mn(2+)-induced caspase-3 activation and apoptosis. Mn(2+)-triggered caspase-8 activation is associated with a specific pathway, which is independent of Fas-associated death domain protein, and dependent on the sequential activation of p38-mitogen-activated protein kinase (p38 MAPK) and mitogen- and stress-response kinase 1 (MSK1). Inhibition of p38 activity using either pharmacological inhibitors or dominant-negative mutant forms of p38 blocked Mn(2+)-mediated phosphorylation of MSK1 and blocked subsequent caspase-8 activation. However, specific inhibitors and the expression of a dominant-interfering mutant of MSK1 only inhibited caspase-8 activation, but not p38 activity. These findings suggest a novel model for the regulation of caspase-8 during Mn(2+)-induced apoptosis based on the sequential activation of p38 MAPK, MSK1, caspase-8 and mitochondria, respectively.     

胞外三磷酸腺苷通过一氧化氮调节镉诱导的氧化压力和细胞死亡

采用液体悬浮培养方法,研究胞外三磷酸腺苷(ATP)通过一氧化碳(NO)调节镉诱导对烟草(Nicotiana tabacum L.)悬浮细胞氧化压力和死亡水平的影响。结果显示,镉离子(Cd^2+)可以以剂量依赖的模式引起烟草悬浮细胞氧化压力和死亡水平的上升,而施加外源ATP可有效缓解Cd^2+诱导的氧化压力和细胞死亡。进一步研究发现,和外源ATP的缓解作用相似,NO的供体硝普钠(SNP)同样可以缓解Cd^2+诱导的氧化压力和细胞死亡水平的上升;且NO合成抑制剂(L-NAME)可部分解除外源ATP的缓解作用。研究结果表明外源ATP可通过NO调节镉诱导的氧化压力和细胞死亡。     

Protease Activity of Procaspase-8 Is Essential for Cell Survival by Inhibiting Both Apoptotic and Nonapoptotic Cell Death Dependent on Receptor-interacting Protein Kinase 1 (RIP1) and RIP3

Caspase-8 has an important role as an initiator caspase during death receptor-mediated apoptosis. Moreover, it has been reported to contribute to the regulation of cell fate in various types of cells including T-cells. In this report, we show that caspase-8 has an essential role in cell survival in mouse T-lymphoma-derived L5178Y cells. The knockdown of caspase-8 expression decreased the growth rate and increased cell death, both of which were induced by the absence of protease activity of procaspase-8. The cell death was associated with reactive oxygen species (ROS) accumulation, caspase activation, and autophagosome formation. The cell death was inhibited completely by treatment with ROS scavengers, but only partly by treatment with caspase inhibitors, expression of Bcl-xL, and knockdown of caspase-3 or Atg-7 which completely inhibits apoptosis or autophagosome formation, respectively, indicating that apoptosis and autophagy-associated cell death are induced simultaneously by the knockdown of caspase-8 expression. Further analysis indicated that RIP1 and RIP3 regulate this multiple cell death, because the cell death as well as ROS production was completely inhibited by not only treatment with the RIP1 inhibitor necrostatin-1, but also by knockdown of RIP3. Thus, in the absence of protease activity of procaspase-8, RIP1 and RIP3 simultaneously induce not only nonapoptotic cell death conceivably including autophagic cell death and necroptosis but also apoptosis through ROS production in mouse T-lymphoma cells.     

Protection of mature oligodendrocytes by inhibitors of caspases and calpains

Mature mouse oligodendrocytes (OLs) are susceptible to death in demyelinating diseases such as multiple sclerosis and in brain injury following neurotrauma, ischemia, or stroke. To understand mechanisms leading to death of mature OLs and develop strategies for protection, we utilized cultures of mature mouse OLs to investigate the role of caspases and calpains in OL cell death mediated by different mechanisms. The agents used were (i) staurosporine, which induces apoptotic death via inhibition of protein kinases; (ii) kainate, which activates non-NMDA glutamate receptors; (iii) thapsigargin, which releases intracellular calcium stores; and (iv) SNAP, which releases active NO species and causes necrotic cell death. Inhibitors blocking primary effector caspases (including caspase 3), the FAS (death receptor)-mediated initiator caspases (including caspase 8), and stress-induced caspases (including caspase 9), were tested for their protective effects. Inhibition of caspases 3, 8, and 9 each robustly protected OLs following insult with staurosporine, thapsigargin, or kainate when added at optimal times. The time of addition of the inhibitors for maximal protection varied with the agent, from 1 h of preincubation before addition of staurosporine to 6 h after addition of kainate. Much less protection was seen for the NO generator SNAP under any condition. The role of calcium in OL death in each model was investigated by chelating extracellular Ca⁺⁺ with EGTA, and by inhibiting the Ca⁺⁺-activated calpain proteases. Calcium chelation did not protect against staurosporine, but decreased OL death initiated by kainate, thapsigargin, or NO. The calpain inhibitors PD150606 and calpain inhibitor I protected from cell death initiated by staurosporine, kainate, and thapsigargin, but not from cell death initiated by the NO donor SNAP.     

Systems biology of yeast cell death

Programmed cell death (PCD) (including apoptosis) is an essential process, and many human diseases of high prevalence such as neurodegenerative diseases and cancer are associated with deregulations in the cell death pathways. Yeast Saccharomyces cerevisiae, a unicellular eukaryotic organism, shares with multicellular organisms (including humans) key components and regulators of the PCD machinery. In this article, we review the current state of knowledge about cell death networks, including the modeling approaches and experimental strategies commonly used to study yeast cell death. We argue that the systems biology approach will bring valuable contributions to our understanding of regulations and mechanisms of the complex cell death pathways.     

Flexibility exists in the region of [A6-A11, A7-B7] disulfide bonds during insulin precursor folding

Programmed cell death or apoptosis is the regulatory mechanism for removing unneeded cells during animal development and in tissue homeostasis. Perturbation of the cell death mechanisms leads to various disorders, including neurodegenerative diseases, immunodeficiency diseases, and tumors. c-Jun N-terminal kinase (JNK) has crucial roles in the regulation of cell death in response to many stimuli. Since JNK is highly conserved from yeast to mammals, genetic studies using model animals are helpful in understanding the principal cell death mechanisms regulated by JNK. For example, loss-of-function studies using the targeted disruption of murine genes have established the genetic framework of the mechanisms of the cell death induced by UV radiation. Also, in Drosophila, many cell death-related genes have been identified by genetics. Genetic studies of JNK-dependent cell death mechanisms should shed light on the regulation of both physiological and pathological cell death.