Redox Regulation of Apoptosis by Members of the TNF Superfamily (original) (raw)
Cancer Letters, 2002
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves as an extracellular signal triggering apoptosis in tumor cells. However, the molecular mechanisms leading to the apoptosis are largely unknown. To characterize the molecular events involved in TRAIL-induced apoptosis, we examined the association of reactive oxygen species (ROS) in human adenocarcinoma HeLa cells. In this study, we show strong ROS accumulation upon TRAIL induction, with activation of caspases, followed by apoptosis. The pre-treatment with g-glutamylcysteinylglycine or estrogen, both effective antioxidants, significantly attenuated TRAIL-induced apoptosis through the reduction of ROS accumulation and diminished caspases activity. Furthermore, zVAD-fmk, an inhibitor of pan-caspase, effectively inhibited the activation of caspases and prevented apoptosis by TRAIL, although TRAIL-induced ROS generation was not attenuated. These data indicate that ROS may play a role as an upstream mediator of caspases. Taken together, our results suggest that oxidative stress mediates TRAIL-induced apoptosis in HeLa cells.
TNF-Induced Signaling in Apoptosis
1999
Out of the almost 17 members of the TNF superfamily, TNF is probably the most potent inducer of apoptosis. TNF activates both cell-survival and cell-death mechanisms simultaneously. Activation of NF-kB-dependent genes regulates the survival and proliferative effects pf TNF, whereas activation of caspases regulates the apoptotic effects. TNF-induced apoptosis is mediated primarily through the activation of type I receptors, the death domain of which recruits more than a dozen different signaling proteins, which together are considered part of an apoptotic cascade. This cascade does not, however, account for the role of reactive oxygen intermediates, ceramide, phospholipases, and serine proteases which are also inplicated in TNF-induced apoptosis. This cascade also does not explain how type II TNF receptors which lack the death domain, induce apoptosis. Nevertheless, this review of apoptosis signaling will be limited to those proteins that makeup the cascade.
The American Journal of Pathology, 2000
Tumor necrosis factor (TNF) is a mediator of the acute phase response in the liver and can initiate proliferation and cause cell death in hepatocytes. We investigated the mechanisms by which TNF causes apoptosis in hepatocytes focusing on the role of oxidative stress, antioxidant defenses, and mitochondrial damage. The studies were conducted in cultured AML12 cells, a line of differentiated murine hepatocytes. As is the case for hepatocytes in vivo, AML12 cells were not sensitive to cell death by TNF alone, but died by apoptosis when exposed to TNF and a small dose of actinomycin D (Act D). Morphological signs of apoptosis were not detected until 6 hours after the treatment and by 18 hours ϳ50% of the cells had died. Exposure of the cells to TNF؉Act D did not block NFB nuclear translocation, DNA binding, or its overall transactivation capacity. Induction of apoptosis was characterized by oxidative stress indicated by the loss of NAD(P)H and glutathione followed by mitochondrial damage that included loss of mitochondrial membrane potential, inner membrane structural damage, and mitochondrial condensation. These changes coincided with cytochrome C release and the activation of caspases-8, -9, and -3. TNF-induced apoptosis was dependent on glutathione levels. In cells with decreased levels of glutathione, TNF by itself in the absence of transcriptional blocking acted as an apoptotic agent. Conversely, the antioxidant ␣-lipoic acid, that protected against the loss of glutathione in cells exposed to TNF؉Act D completely prevented mitochondrial damage, caspase activation, cytochrome C release, and apoptosis. The results demonstrate that apoptosis induced by TNF؉Act D in AML12 cells involves oxidative injury and mitochondrial damage. As injury was regulated to a larger extent by the glutathione content of the cells, we suggest that the combination of TNF؉Act D causes apoptosis be-cause Act D blocks the transcription of genes required for antioxidant defenses.
TNF-α activates at least two apoptotic signaling cascades
Oncogene, 1998
Apoptosis, the process whereby cells activate an intrinsic death program, can be induced in HeLa cells by TNF-a treatment. The aims of the present study were (i) to examine the precise role and the origin of Reactive Oxygen Species (ROS) in the TNF-a-induced programmed cell death, (ii) to characterize and order the morphological and mitochondrial changes associated with this process and (iii) to link these events with the activation of caspases. Analyses were performed on TNF-a-treated cells in the presence of an anti-oxidant, or of a general caspase inhibitor. To assess the role of mitochondria in the cell death signal transduction, these studies were also realized on HeLa-variant cell lines lacking functional mitochondrial respiratory chain. We show that at least two separate signaling cascades, both mediated by Z-VAD-sensitive caspase(s), contribute to the TNF-a-induced apoptosis of HeLa cells. One signaling pathway involves an early mitochondriadependent ROS production, the other being ROSindependent.
Activation of apoptosis signalling pathways by reactive oxygen species
Biochimica et biophysica acta. Molecular cell research, 2016
Reactive oxygen species (ROS) are short-lived and highly reactive molecules. The generation of ROS in cells exists in equilibrium with a variety of antioxidant defences. At low to modest doses, ROS are considered to be essential for regulation of normal physiological functions involved in development such as cell cycle progression and proliferation, differentiation, migration and cell death. ROS also play an important role in the immune system, maintenance of the redox balance and have been implicated in activation of various cellular signalling pathways. Excess cellular levels of ROS cause damage to proteins, nucleic acids, lipids, membranes and organelles, which can lead to activation of cell death processes such as apoptosis. Apoptosis is a highly regulated process that is essential for the development and survival of multicellular organisms. These organisms often need to discard cells that are superfluous or potentially harmful, having accumulated mutations or become infected by pathogens. Apoptosis features a characteristic set of morphological and biochemical features whereby cells undergo a cascade of self-destruction. Thus, proper regulation of apoptosis is essential for maintaining normal cellular homeostasis. ROS play a central role in cell signalling as well as in regulation of the main pathways of apoptosis mediated by mitochondria, death receptors and the endoplasmic reticulum (ER). This review focuses on current understanding of the role of ROS in each of these three main pathways of apoptosis. The role of ROS in the complex interplay and crosstalk between these different signalling pathways remains to be further unravelled during the coming years.
Mitochondria-targeted antioxidants prevent TNFα-induced endothelial cell damage
Biochemistry (Moscow), 2014
Vascular endothelium performs numerous functions: it controls the blood clotting system, vascular tone, tissue perfusion, exchange of fluid and macromolecules between the blood and tissues, and immune system development and immune response [1]. Therefore, any damage or excessive activation of the endothelium leads to serious pathologies [2]. Various stimuli considered as cardiovascular risk factors (e.g. tumor necrosis factor alpha (TNFα)) cause apoptosis of endothelial cells in vitro [3]. Moreover, apoptosis of endothelial cells was observed in vivo in humans and other animals with various pathologies and in old animals [3, 4]. One of the significant risk factors for endothelial dysfunction is the increase in circulatory inflammatory cytokines, particularly TNFα [5]. TNFα binding to its receptors on the cell surface triggers a series of complex signaling cascades [6, 7] leading to different effects depending on the conditions and type of cell. In endothelial cells, TNFα activates secretion of blood coagulation factors, NO-synthase, expression of tissue factors, adhesion molecules, inflammatory cytokines and chemokines, transendothelial vesicular transport, cytoskeleton reorganization, disassembly of cell-cell contacts, and cell death [5]. TNFα can initiate endothelial cell apoptosis either due to direct activation of caspase cascades [8] or due to release of mitochondrial proapoptotic proteins (cytochrome c, AIF, DIABLO, etc.) [9].
Role of reactive oxygen species (ROS) in apoptosis induction
Apoptosis, 2000
Reactive oxygen species (ROS) and mitochondria play an important role in apoptosis induction under both physiologic and pathologic conditions. Interestingly, mitochondria are both source and target of ROS. Cytochrome c release from mitochondria, that triggers caspase activation, appears to be largely mediated by direct or indirect ROS action. On the other hand, ROS have also anti-apoptotic effects. This review focuses on the role of ROS in the regulation of apoptosis, especially in inflammatory cells.
Redox Regulation of Tumor Necrosis Factor Signaling
Antioxidants & Redox Signaling, 2009
Tumor necrosis factor-a (TNF) is a key cytokine that has been shown to play important physiologic (e.g., inflammation) and pathophysiologic (e.g., various liver pathologies) roles. In liver and other tissues, TNF treatment results in the simultaneous activation of an apoptotic pathway (i.e., TRADD, RIP, JNK) and a survival pathway mediated by NF-kB transcription of survival genes (i.e., GADD45b, Mn-SOD, cFLIP). The cellular response (e.g., proliferation versus apoptosis) to TNF is determined by the balance between the apoptotic signaling pathway and the NF-kB survival pathway stimulated by TNF. Reactive oxygen species (ROS) are important modulators of signaling pathways and can regulate both apoptotic signaling and NF-kB transcription triggered by TNF. ROS are important in mediating the sustained activation of JNK, to help mediate apoptosis after TNF treatment. In some cells, ROS are second messengers that mediate apoptosis after TNF stimulation. Conversely, ROS can cause redox modifications that inhibit NF-kB activation, which can lead to cell death triggered by TNF. Consequently, the redox status of cells can determine the biologic response that TNF will induce in cells. In many liver pathologies, ROS generated extrinsically (e.g., inflammation) or intrinsically (i.e., drugs, toxins) may act in concert with TNF to promote hepatocyte death and liver injury through redox inhibition of NF-kB. Antioxid. Redox Signal. 11, 2245-2263.
Reactive oxygen species, cellular redox systems, and apoptosis
ROS and apoptosis GSH and thioredoxin redox systems GSH redox signaling and apoptosis Pyridine nucleotide redox couples and apoptosis Mitochondria and apoptosis Redox control of caspases Reactive oxygen species (ROS) are products of normal metabolism and xenobiotic exposure, and depending on their concentration, ROS can be beneficial or harmful to cells and tissues. At physiological low levels, ROS function as "redox messengers" in intracellular signaling and regulation, whereas excess ROS induce oxidative modification of cellular macromolecules, inhibit protein function, and promote cell death. Additionally, various redox systems, such as the glutathione, thioredoxin, and pyridine nucleotide redox couples, participate in cell signaling and modulation of cell function, including apoptotic cell death. Cell apoptosis is initiated by extracellular and intracellular signals via two main pathways, the death receptorand the mitochondria-mediated pathways. Various pathologies can result from oxidative stress-induced apoptotic signaling that is consequent to ROS increases and/or antioxidant decreases, disruption of intracellular redox homeostasis, and irreversible oxidative modifications of lipid, protein, or DNA. In this review, we focus on several key aspects of ROS and redox mechanisms in apoptotic signaling and highlight the gaps in knowledge and potential avenues for further investigation. A full understanding of the redox control of apoptotic initiation and execution could underpin the development of therapeutic interventions targeted at oxidative stress-associated disorders.
Cell Death and Differentiation, 2003
The role of reactive oxygen species (ROS) production in death receptor-mediated apoptosis is ill-defined. Here, we show that ROS levels play a role in moderating Fas-dependent apoptosis. Treatment of Jurkat T cells with oligomycin (ATP-synthase inhibitor) or (mitochondrial uncoupler) and Fas-activating antibody (CH11) facilitated rapid cell death that was not associated with decreased ATP production or increased DEVDase activity and cytochrome c release. However, a decrease in cellular ROS production was associated with CH11 treatment, and combinations of CH11 with oligomycin or FCCP further inhibited cellular ROS production. Thus, decreased ROS production is correlated with enhanced cell death. A transition from state 3 to state 4 mitochondrial respiration accounted for the attenuated ROS production and membrane potential. Similar observations were demonstrated in isolated rat liver mitochondria. These data show that ROS production is important in receptor-mediated apoptosis, playing a pivotal role in cell survival.
Reactive oxygen species and the mitochondrial signaling pathway of cell death
Histology and histopathology
Reactive oxygen species (ROS) are produced as a by-product of cellular metabolic pathways and function as a critical second messenger in a variety of intracellular signaling pathways. Thus, a defect or deficiency in the anti-oxidant defense system on the one hand and/or the excessive intracellular generation of ROS on the other renders a cell oxidatively stressed. As a consequence, direct or indirect involvement of ROS in numerous diseases has been documented. In most of these cases, the deleterious effect of ROS is a function of activation of intracellular cell-death circuitry. To that end, involvement of ROS at different phases of the apoptotic pathway, such as induction of mitochondrial permeability transition and release of mitochondrial death amplification factors, activation of intracellular caspases and DNA damage, has been clearly established. For instance, the ROS-induced alteration of constitutive mitochondrial proteins, such as the voltage-dependent anion channel (VDAC) a...
Mitochondrial reactive oxygen species in cell death signaling
Biochimie, 2002
During apoptosis, mitochondrial membrane permeability (MMP) increases and the release into the cytosol of pro-apoptotic factors (procaspases, caspase activators and caspase-independent factors such as apoptosis-inducing factor (AIF)) leads to the apoptotic phenotype. Apart from this pivotal role of mitochondria during the execution phase of apoptosis (documented in other reviews of this issue), it appears that reactive oxygen species (ROS) produced by the mitochondria can be involved in cell death. These toxic compounds are normally detoxified by the cells, failing which oxidative stress occurs. However, ROS are not only dangerous molecules for the cell, but they also display a physiological role, as mediators in signal transduction pathways. ROS participate in early and late steps of the regulation of apoptosis, according to different possible molecular mechanisms. In agreement with this role of ROS in apoptosis signaling, inhibition of apoptosis by anti-apoptotic Bcl-2 and Bcl-x L is associated with a protection against ROS and/or a shift of the cellular redox potential to a more reduced state. Furthermore, the fact that active forms of cell death in yeast and plants also involve ROS suggests the existence of an ancestral redox-sensitive death signaling pathway that has been independent of caspases and Bcl-2.
Free Radical Biology and Medicine, 2009
Fas-mediated caspase-dependent cell apoptosis has been well investigated. However, recent studies have shown that Fas can induce nonapoptotic caspase-independent cell death (CICD) when caspase activity is inhibited. Currently, the molecular mechanism of this alternative cell death mediated by Fas remains unclear. In this study, we investigated the signaling pathway of Fas-induced CICD in mouse embryonic fibroblasts (MEFs) whose caspase function was disrupted by the pan-caspase inhibitor Z-VAD-FMK and its coupling to inflammatory responses. Our results revealed that receptor-interacting protein 1 and tumor necrosis factor receptor-associated factor 2 play important roles in FasL-induced CICD. This death is associated with intracellular reactive oxygen species (ROS) production from mitochondria, as a ROS scavenger (BHA), antioxidants (trolox, NAC), and a mitochondrial respiratory chain uncoupler (rotenone) could prevent this event. Furthermore, delayed and sustained JNK activation, mitochondrial membrane potential breakdown, and loss of intracellular GSH were observed. In addition to CICD, FasL also induces cyclooxygenase-2 and MIP-2 gene upregulation, and both responses are attributed to ROS-dependent JNK activation. Taken together, these results demonstrate alternative signaling pathways of Fas upon caspase inhibition in MEFs that are unrelated to the classical apoptotic pathway, but steer cells toward necrosis and an inflammatory response through ROS production.
TNFα and reactive oxygen species in necrotic cell death
Cell Research, 2008
Death receptors, including the TNF receptor-1 (TNF-RI), have been shown to be able to initiate caspase-independent cell death. This form of "necrotic cell death" appears to be dependent on the generation of reactive oxygen species. Recent data have indicated that superoxide generation is dependent on the activation of NADPH oxidases, which form a complex with the adaptor molecules RIP1 and TRADD. The mechanism of superoxide generation further establishes RIP1 as the central molecule in ROS production and cell death initiated by TNFα and other death receptors. A role for the sustained JNK activation in necrotic cell death is also suggested. The sensitization of virus-infected cells to TNFα indicates that necrotic cell death may represent an alternative cell death pathway for clearance of infected cells.
More Than One Way to Die: Methods to Determine TNF-Induced Apoptosis and Necrosis
Tumor Necrosis Factor, 2004
In most cellular systems tumor necrosis factor (TNF) induces apoptotic cell death. However, in some particular cell lines, such as the L929sA fibrosarcoma, TNF induces necrotic cell death. This effect is not the result of an inability to die apoptotically, because triggering of Fas in L929sAhFas cells leads to apoptosis. Moreover, TNFR-1-induced necrosis can be reverted to apoptosis when cells are pretreated with geldanamycin, an Hsp90 inhibitor. In contrast, addition of caspase-inhibitors (zVAD-fmk) prevents Fas-induced apoptosis and switches it to necrosis. These results demonstrate that depending on the cellular context, the same stimulus can induce either apoptosis or necrosis. Apoptosis and necrosis are clearly distinguished by their morphology, although in the absence of phagocytosis, the late stage of apoptosis is associated with secondary necrotic cell death, which is hard to distinguish from necrotic cell death. Necrosis is described mostly in negative terms as cell death that is characterized by the absence of apoptotic parameters, such as caspase activation, cytochrome c release, and DNA fragmentation. Here we describe a selection of techniques used to distinguish both modes of TNFR-1induced cell death, namely apoptotic or necrotic cell death.
Biochemical Journal, 2005
ROS (reactive oxygen species) from mitochondrial and non-mitochondrial sources have been implicated in TNFα (tumour necrosis factor α)-mediated signalling. In the present study, a new class of specific mitochondria-targeted antioxidants were used to explore directly the role of mitochondrial ROS in TNF-induced apoptosis. MitoVit E {[2-(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)ethyl]triphenylphosphonium bromide} (vitamin E attached to a lipophilic cation that facilitates accumulation of the antioxidant in the mitochondrial matrix) enhanced TNF-induced apoptosis of U937 cells. In time course analyses, cleavage and activation of caspase 8 in response to TNF were not affected by MitoVit E, whereas the activation of caspase 3 was significantly increased. Furthermore, there was an increased cleavage of the proapoptotic Bcl-2 family member Bid and an increased release of cytochrome c from mitochondria, in cells treated with TNF in the presence of MitoVit E. We conside...