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1.
The small GTPase Rac1 has emerged as an important regulator of cell survival and apoptosis, but the mechanisms involved are not completely understood. In this report, constitutively active Rac1 is shown to stimulate the phosphorylation of the Bcl-2 family member Bad, thereby suppressing drug-induced caspase activation and apoptosis in human lymphoma cells. Rac1 activation leads to human Bad phosphorylation specifically at serine-75 (corresponding to murine serine-112) both in vivo and in vitro. Inhibition of constitutive and activated Rac1-induced Bad phosphorylation by a cell-permeable competitive peptide inhibitor representing this Bad phosphorylation site sensitizes lymphoma cells to drug-induced apoptosis. The data show further that endogenous protein kinase A is a primary catalyst of cellular Bad phosphorylation in response to Rac activation, while Akt is not involved. These findings define a mechanism by which active Rac1 promotes lymphoma cell survival and inhibits apoptosis in response to cancer chemotherapy drugs.  相似文献   

2.
DNA damage responses to oxidative stress   总被引:12,自引:0,他引:12  
Barzilai A  Yamamoto K 《DNA Repair》2004,3(8-9):1109-1115
The DNA damage response is a hierarchical process. DNA damage is detected by sensor proteins such as the MRN complex that transmit the information to transducer proteins such as ATM and ATR, which control the damage response through the phosphorylation of effector proteins. The extent of the DNA damage determines cell fate: cell cycle arrest and DNA repair or the activation of apoptotic pathways. In aerobic cells, reactive oxygen species (ROS) are generated as a by-product of normal mitochondrial activity. If not properly controlled, ROS can cause severe damage to cellular macromolecules, especially the DNA. We describe here some of the cellular responses to alterations in the cellular redox state during hypoxia or oxidative stress. Oxidative damage in DNA is repaired primarily via the base excision repair (BER) pathway which appears to be the simplest of the three excision repair pathways. To allow time for DNA repair, the cells activate their cell cycle checkpoints, leading to cell cycle arrest and preventing the replication of damage and defective DNA.  相似文献   

3.
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 receptor- and 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.  相似文献   

4.
The purpose of our study was to investigate underlying basic mechanisms of hypothermia-induced cardioprotection during oxidative stress in a cardiomyocyte cell culture model. For hypothermic treatment we cooled H9c2 cardiomyocytes to 20 °C, maintained 20 min at 20 °C during which short-term oxidative damage was inflicted with 2 mM H2O2, followed by rewarming to 37 °C. Later on, we analyzed lactate dehydrogenase (LDH), caspase-3 cleavage, reactive oxygen species (ROS), mitochondrial activity, intracellular ATP production, cytoprotective signal molecules as well as DNA damage. Hypothermia decreased H2O2 damage in cardiomyocytes as demonstrated in a lower LDH release, less caspase-3 cleavage and less M30 CytoDeath staining. After rewarming H2O2 damaged cells demonstrated a significantly higher reduction rate of intracellular ROS compared to normothermic H2O2 damaged cardiomyocytes. This was in line with a significantly greater mitochondrial dehydrogenase activity and higher intracellular ATP content in cooled and rewarmed cells. Moreover, hypothermia preserved cell viability by up-regulation of the anti-apoptotic protein Bcl-2 and a reduction of p53 phosphorylation. DNA damage, proven by PARP-1 cleavage and H2AX phosphorylation, was significantly reduced by hypothermia. In conclusion, we could demonstrate that hypothermia protects cardiomyocytes during oxidative stress by preventing apoptosis via inhibiting mitochondrial dysfunction and DNA damage.  相似文献   

5.
Mitochondria are the major organelles that produce reactive oxygen species (ROS) and the main target of ROS-induced damage as observed in various pathological states including aging. Production of NADPH required for the regeneration of glutathione in the mitochondria is critical for scavenging mitochondrial ROS through glutathione reductase and peroxidase systems. We investigated the role of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm) in controlling the mitochondrial redox balance and subsequent cellular defense against oxidative damage. We demonstrate in this report that IDPm is induced by ROS and that decreased expression of IDPm markedly elevates the ROS generation, DNA fragmentation, lipid peroxidation, and concurrent mitochondrial damage with a significant reduction in ATP level. Conversely, overproduction of IDPm protein efficiently protected the cells from ROS-induced damage. The protective role of IDPm against oxidative damage may be attributed to increased levels of a reducing equivalent, NADPH, needed for regeneration of glutathione in the mitochondria. Our results strongly indicate that IDPm is a major NADPH producer in the mitochondria and thus plays a key role in cellular defense against oxidative stress-induced damage.  相似文献   

6.
7.
Modulation of cerebral cell metabolism for improving the outcome of hypoxia-ischemia and reperfusion is a strategy yet to be explored. Because carbon monoxide (CO) is known to prevent cerebral cell death; herein the role of CO in the modulation of astrocytic metabolism, in particular, at the level of mitochondria was investigated. Low concentrations of CO partially inhibited oxidative stress-induced apoptosis in astrocytes, by preventing caspase-3 activation, mitochondrial potential depolarization, and plasmatic membrane permeability. CO exposure enhanced intracellular ATP generation, which was accompanied by an increase on specific oxygen consumption, a decrease on lactate production, and a reduction of glucose use, indicating an improvement of oxidative phosphorylation. Accordingly, CO increased cytochrome c oxidase (COX) enzymatic specific activity and stimulated mitochondrial biogenesis. In astrocytes, COX interacts with Bcl-2, which was verified by immunoprecipitation; this interaction is superior after 24 h of CO treatment. Furthermore, CO enhanced Bcl-2 expression in astrocytes. By silencing Bcl-2 expression with siRNA transfection, CO effects in astrocytes were prevented, namely: (i) inhibition of apoptosis, (ii) increase on ATP generation, (iii) stimulation of COX activity, and (iv) mitochondrial biogenesis. Thus, Bcl-2 expression is crucial for CO modulation of oxidative metabolism and for conferring cytoprotection. In conclusion, CO protects astrocytes against oxidative stress-induced apoptosis by improving metabolism functioning, particularly mitochondrial oxidative phosphorylation.  相似文献   

8.
Intrauterine growth restriction (IUGR) remains a significant obstacle in pig production; however, information regarding the relationship between reactive oxygen species (ROS)-induced placental dysfunction and IUGR is still unknown. This study aimed to explore the placental redox status, mitochondrial content, cellular progression, and mitogen-activated protein kinase (MAPK) pathways in IUGR. Placental tissues were collected from normal intrauterine gestation (NIUG) and IUGR fetuses at delivery. Compared with the NIUG, placental ROS production, lipid peroxidation, and DNA damage were increased in IUGR. Placental mitochondrial DNA (mtDNA) content and mtDNA-encoded gene expression decreased in IUGR. Moreover, p21 phosphorylation increased, cyclin E expression decreased in IUGR cases, which showed senescence characteristics. Analysis of signaling pathways showed that the ERK1/2 phosphorylation increased whereas the p38 and JNK phosphorylation decreased in IUGR. In cultured porcine trophectoderm (pTr) cells, exogenous H2O2 increased intracellular ROS production, decreased cell viability in a dose-dependent manner. Cell cycle distribution was found to arrest in S and G2/M phases. Our findings suggested that IUGR was associated with greater placental ROS and oxidative injury, which might be a factor that resulted in lower mitochondrial content, microvilli loss and senescence, and activation of MAPK pathways.  相似文献   

9.
Neurodegeneration can occur as a result of endogenous oxidative stress. Primary cerebellar granule cells were used in this study to determine if mitochondrial DNA (mtDNA) repair deficiencies correlate with oxidative stress-induced apoptosis in neuronal cells. Granule cells exhibited a significantly higher intracellular oxidative state compared with primary astrocytes as well as increases in reductants, such as glutathione, and redox sensitive signaling molecules, such as AP endonuclease/redox effector factor-1. Cerebellar granule cultures also exhibited an increased susceptibility to exogenous oxidative stress. Menadione (50 μM) produced twice as many lesions in granule cell mtDNA compared with astrocytes, and granule cell mtDNA repair was significantly less efficient. A decreased capacity to repair oxidative mtDNA damage correlates strongly with mitochondrial initiated apoptosis in these neuronal cultures. Interestingly, the mitochondrial activities of initiators for base excision repair (BER), the bifunctional glycosylase/AP lyases as well as AP endonuclease, were significantly higher in cerebellar granule cells compared with astrocytes. The increased mitochondrial AP endonuclease activity in combination with decreased polymerase γ activity may cause an imbalance in oxidative BER leading to an increased production and persistence of mtDNA damage in neurons when treated with menadione. This study provides evidence linking neuronal mtDNA repair capacity with oxidative stress-related neurodegeneration.  相似文献   

10.
Reactive oxygen species (ROS) have been implicated as one of the agents responsible for many neurodegenerative diseases. A critical target for ROS is DNA. Most oxidative stress-induced DNA damage in the nucleus and mitochondria is removed by the base excision repair pathway. Apn1 is a yeast enzyme in this pathway which possesses a wider substrate specificity and greater enzyme activity than its mammalian counterpart for removing DNA damage, making it a good therapeutic candidate. For this study we targeted Apn1 to mitochondria in a neuronal cell line derived from the substantia nigra by using a mitochondrial targeting signal (MTS) in an effort to hasten the removal of DNA damage and thereby protect these cells. We found that following oxidative stress, mitochondrial DNA (mtDNA) was repaired more efficiently in cells containing Apn1 with the MTS than controls. There was no difference in nuclear repair. However, cells that expressed Apn1 without the MTS showed enhanced repair of both nuclear and mtDNA. Both Apn1-expressing cells were more resistant to cell death following oxidative stress compared with controls. Therefore, these results reveal that the expression of Apn1 in neurons may be of potential therapeutic benefit for treating patients with specific neurodegenerative diseases.  相似文献   

11.
Mitochondrial reactive oxygen species in cell death signaling   总被引:49,自引:0,他引:49  
Fleury C  Mignotte B  Vayssière JL 《Biochimie》2002,84(2-3):131-141
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.  相似文献   

12.
Although it is well known that Bcl-2 can prevent apoptosis, the Bcl-2's anti-apoptotic mechanism is not fully understood. Here, we investigate the mechanism of oxidant-induced cell death and to investigate the role of Bcl-2 in the tert-butyl hydroperoxide (t-BuOOH)-induced oxidant injury in Rat-1 fibroblasts and their bcl-2 transfected counterparts, b5 cells. Treatment with t-BuOOH causes mitochondrial disfunction and induced morphological features consistent with apoptosis more markedly in Rat-1 cells than in b5 cells. The hydroperoxide t-BuOOH at concentrations less than 100 nM for as long as 48 h or with higher concentrations (up to 100 microM) for only 3 h induces death in Rat-1 cells, whereas their bcl-2 transfectants were significantly resistant to cytotoxicity by both time and all concentration other than 100 microM. The similar results were obtained also for DNA strand cleavages as detected by TUNEL stain. The bcl-2 transfectants significantly suppressed t-BuOOH-induced increases in both lipid peroxidation and caspase-3 activation 3 and 1 h after t-BuOOH exposure, respectively, but failed to suppress either caspase-1 activation or an enhanced production of the intracellular reactive oxygen species (ROS). Intracellular uptake of [1-(14)C] ascorbic acid (Asc) into the bcl-2 transfectants was superior to that into the non-transfectants always under examined conditions regardless of serum addition to culture medium and cell density. Upregulation of Bcl-2 proteins was rapidly induced after t-BuOOH exposure in the transfectants, but not in non-transfectants, and restored till 24 h to the normal Bcl-2 level. Thus suppressions of both lipid peroxidation and the subsequent cell death events such as caspase-3 activation and DNA cleavage were concerned with the inhibitory effects of Bcl-2 on the t-BuOOH-induced cytotoxicity. And some of these events may correlate with Bcl-2 expression-induced partial enhanced anti-oxidant cellular ability including enrichment of intracellular Asc and oxidative stress-induced upregulation of Bcl-2 protein. On the other hand, ROS production and caspase-1 activation were not related to cytoprotection by Bcl-2.  相似文献   

13.
A growing body of evidence suggests that reactive oxygen species are critical components of cell signaling pathways, in particular regulating protein phosphorylation events. Here, we show that oxidative stress in response to hydrogen peroxide treatment of human epithelial cells induces robust tyrosine phosphorylation on multiple proteins. Using an anti-phosphotyrosine purification and liquid chromatography-tandem mass spectrometry approach, we have identified many of these H2O2-induced tyrosine-phosphorylated proteins. Importantly, we show that epidermal growth factor receptor (EGFR) and Src are the primary upstream kinases mediating these events through their redox activation. The finding that many of the identified proteins have functions in cell adhesion, cell-cell junctions, and the actin cytoskeleton prompted us to examine stress-induced changes in adhesion. Immunofluorescence analysis showed that H2O2 alters cell adhesion structures and the actin cytoskeleton causing loss of adhesion and apoptosis. Remarkably, these cellular changes could be attenuated by inhibition of EGFR and Src, identifying these kinases as targets to block oxidative damage. In summary, our data demonstrate that EGFR and Src together play a central role in oxidative stress-induced phosphorylation, which in turn results in loss of adhesion, morphological changes, and cell damage in epithelial cells. These data also provide a general model for redox signaling in other cell systems.  相似文献   

14.
Lee JH  Park JW 《Free radical research》2005,39(12):1325-1333
Ionizing radiation induces the production of reactive oxygen species (ROS), which play an important causative role in apoptotic cell death. alpha-Phenyl-N-t-butylnitrone (PBN) is one of the most widely used spin-trapping compounds for investigating the existence of free radicals in biological systems. We investigated the effects of PBN on ionizing radiation-induced apoptosis in U937 cells. Upon exposure to 2 Gy of gamma-irradiation, there was a distinct difference between the control cells and the cells pre-treated with 2 mM PBN for 2 h in regard to apoptotic parameters, cellular redox status, mitochondria function and oxidative damage to cells. PBN effectively suppressed morphological evidence of apoptosis and DNA fragmentation in U937 cells exposed to ionizing radiation. The [GSSG]/[GSH+GSSG] ratio and the generation of intracellular ROS were higher and the [NADPH]/[NADP+ +NADPH] ratio was lower in control cells compared to PBN-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of ROS, and the reduction of ATP production were significantly higher in control cells compared to PBN-treated cells. PBN pre-treated cells showed significant inhibition of apoptotic features such as activation of caspase-3, up-regulation of Bax and p53, and down-regulation of Bcl-2 compared to control cells upon exposure to ionizing radiation. This study indicates that PBN may play an important role in regulating the apoptosis induced by ionizing radiation presumably through scavenging of ROS.  相似文献   

15.
Globular adiponectin (gAd), a truncated form of adipocyte-derived cytokine, stimulates RAW 264 cells to produce reactive oxygen species (ROS), which trigger an apoptotic cascade. In this study, we investigated the generation of intracellular and mitochondrial ROS in gAd-stimulated RAW 264 cells. Treatment with gAd efficiently induced the generation of intracellular and mitochondrial ROS, as detected by dichlorodihydrofluorescein diacetate and MitoSOX fluorescence, respectively. Furthermore, gAd treatment significantly increased 8-oxoguanine, a specific indicator of oxidative DNA damage. The transfection of RAW 264 cells with iNOS- and gp91phox-specific small interfering RNA reduced markedly the generation of intracellular, but not mitochondrial, ROS. Quantitative PCR revealed that the expression ratio of Bcl-2 to Bax was reduced in a time-dependent manner in gAd-treated RAW 264 cells. The overexpression of Bcl-2 markedly inhibited gAd-induced apoptosis in RAW 264 cells and also reduced both the intracellular and the mitochondrial ROS generation induced by gAd treatment. Moreover, the overexpression of Bcl-2 significantly suppressed gAd-induced NO secretion and NOS activity. In addition, the inhibition of NOS activity partially reduced the oxidative DNA damage induced by gAd. Taken together, these results demonstrate that the gAd-induced apoptotic pathway acting via ROS/RNS generation involves Bcl-2.  相似文献   

16.
Oxidative stress plays an important role in neurodegenerative diseases. Reactive oxygen species (ROS)-mediated stress in microglia in vivo could result in cellular injuries and preferentially induces neuronal injury. Corilagin, a novel member of the phenolic tannin family, has been shown to possess antioxidant properties. In this study, we investigated the effects of corilagin on tert-butyl hydroperoxide (TBHP)-induced injury in cultured N9 murine microglial cells and the underlying mechanisms by a methyltetrazolium assay and oxidative damage assay. We found that exposure of N9 cells to TBHP induced cytotoxicity as demonstrated by cell shrinkage, loss of cell viability, increased lactate dehydrogenase (LDH) leakage, and increased intracellular levels of ROS. By contrast, TBHP reduced both superoxide dismutase activity and total cell anti-oxidation capacity, but glutathione was not reduced. Moreover, TBHP treatment was associated with the loss of mitochondrial membrane potential, and it induced cell apoptosis through the mitochondrial-mediated pathway involving the down-regulation of Bcl-2 expression and up-regulation of the Bax/Bcl-2 ratio. Interestingly, pre-treatment with corilagin reversed these reactions. These data collectively indicated that corilagin could attenuate TBHP-induced oxidative stress injury in microglial cells, and its protective effects may be ascribed to its antioxidant and antiapoptotic properties. Our findings suggest that corilagin should be a potential candidate for the treatment of oxidative stress-induced neurodegenerative diseases.  相似文献   

17.
Ionizing radiation induces the production of reactive oxygen species (ROS), which play an important causative role in apoptotic cell death. α-Phenyl-N-t-butylnitrone (PBN) is one of the most widely used spin-trapping compounds for investigating the existence of free radicals in biological systems. We investigated the effects of PBN on ionizing radiation-induced apoptosis in U937 cells. Upon exposure to 2 Gy of γ-irradiation, there was a distinct difference between the control cells and the cells pre-treated with 2 mM PBN for 2 h in regard to apoptotic parameters, cellular redox status, mitochondria function and oxidative damage to cells. PBN effectively suppressed morphological evidence of apoptosis and DNA fragmentation in U937 cells exposed to ionizing radiation. The [GSSG]/[GSH+GSSG] ratio and the generation of intracellular ROS were higher and the [NADPH]/[NADP++NADPH] ratio was lower in control cells compared to PBN-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of ROS, and the reduction of ATP production were significantly higher in control cells compared to PBN-treated cells. PBN pre-treated cells showed significant inhibition of apoptotic features such as activation of caspase-3, up-regulation of Bax and p53, and down-regulation of Bcl-2 compared to control cells upon exposure to ionizing radiation. This study indicates that PBN may play an important role in regulating the apoptosis induced by ionizing radiation presumably through scavenging of ROS.  相似文献   

18.
19.
p66Shc, a redox enzyme that enhances reactive oxygen species (ROS) production by mitochondria, promotes T cell apoptosis. We have addressed the mechanisms regulating p66Shc-dependent apoptosis in T cells exposed to supraphysiological increases in [Ca2+]c. p66Shc expression resulted in profound mitochondrial dysfunction in response to the Ca2+ ionophore A23187, as revealed by dissipation of mitochondrial transmembrane potential, cytochrome c release and decreased ATP levels. p66Shc expression also caused a dramatic alteration in the cells' Ca2+-handling ability, which resulted in Ca2+ overload after A23187 treatment. The impairment in Ca2+ homeostasis was ROS dependent and caused by defective Ca2+ extrusion due at least in part to decreased plasma membrane ATPase (PMCA) expression. Both effects of p66Shc required Ca2+-dependent serine-36 phosphorylation. The mitochondrial effects of p66Shc were potentiated by but not strictly dependent on the rise in [Ca2+]c. Thus, Ca2+-dependent p66Shc phosphorylation causes both mitochondrial dysfunction and impaired Ca2+ homeostasis, which synergize in promoting T cell apoptosis.  相似文献   

20.
BackgroundHuman Adenovirus (HAdV) can cause severe respiratory symptoms in people with low immunity and there is no targeted treatment for adenovirus infection. Anti-adenoviral drugs have high clinical significance for inhibiting adenovirus infection. Selenium (Se) plays an important role in anti-oxidation, redox signal transduction, and redox homeostasis. The excellent biological activity of Se is mainly achieved by being converted into selenocystine (SeC). Se participates in the active sites of various selenoproteins in the form of SeC. The ability of SeC to resist the virus has raised high awareness due to its unique antioxidative activity in recent years. The antiviral ability of the SeC was determined by detecting the infection rate of the virus in the cells.MethodsThe experiment mainly investigated the antiviral mechanism of SeC by locating the virus in the cell, detecting the generation of ROS, observing the DNA status of the cell, and monitoring the mitochondrial membrane potential.ResultsIn the present study, SeC was designed to resist A549 cells infections caused by HAdV-14. SeC could prevent HAdV-14 from causing cell apoptosis-related to DNA damage. SeC significantly inhibited ROS generation and protect the cells from oxidative damage induced by ROS against HAdV-14. SeC induced the increase of antiviral cytokines such as IL-6 and IL-8 by activating the Jak2 signaling pathway, and repaired DNA lesions by suppressing ATR, p53, and PARP signaling pathways.ConclusionSeC might provide an effective selenium species with antiviral properties for the therapies against HAdV-14.  相似文献   

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