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As a neurological disease with high morbidity, disability, and mortality, the pathological mechanism underlying stroke involves complex processes such as neuroinflammation, oxidative stress, apoptosis, autophagy, and excitotoxicity; but the related research on these molecular mechanisms has not been effectively applied in clinical practice. As a form of iron-dependent regulated cell death, ferroptosis was first discovered in the pathological process of cancer, but recent studies have shown that ferroptosis is closely related to the onset and development of stroke. Therefore, a deeper understanding of the relationship between ferroptosis and stroke may lead to more effective treatment strategies. Herein, we reviewed the mechanism(s) underlying the onset of ferroptosis in stroke, the potential role of ferroptosis in stroke, and the crosstalk between ferroptosis and other pathological mechanisms. This will further deepen our understanding of ferroptosis and provide new approaches to the treatment of stroke. [ABSTRACT FROM AUTHOR]

Background: Theabrownin (TB) is a bioactive component of tea and has been reported to exert effects against many human cancers, but its efficacy and mechanism on hepatocellular carcinoma (HCC) with different p53 genotypes remains unclarified. Methods: MTT assay, DAPI staining, flow cytometry and SA-β-gal staining were applied to evaluate the effects of TB on HCC cells. Quantitative real time PCR (qPCR) and Western blot (WB) were conducted to explore the molecular mechanism of TB. A xenograft model of zebrafish was established to evaluate the anti-tumor effect of TB. Results: MTT assays showed that TB significantly inhibited the proliferation of SK-Hep-1, HepG2, and Huh7 cells in a dose-dependent manner, of which SK-Hep-1 was the most sensitive one with the lowest IC50 values. The animal data showed that TB remarkably suppressed SK-Hep-1 tumor growth in xenograft model of zebrafish. The cellular data showed TB's pro-apoptotic and pro-senescent effect on SK-Hep-1 cells. The molecular results revealed the mechanism of TB that p53 signaling pathway (p-ATM, p-ATR, γ-H2AX, p-Chk2, and p-p53) was activated with up-regulation of downstream senescent genes (P16, P21, IL-6 and IL-8) as well as apoptotic genes (Bim, Bax and PUMA) and proteins (Bax, c-Casp9 and c-PARP). The p53-mediated mechanism was verified by using p53-siRNA. Moreover, by using JNK-siRNA, we found JNK as a bypass regulator in TB's mechanism. Conclusions: To sum up, TB exerted tumor-inhibitory, pro-senescent and pro-apoptotic effects on SK-Hep-1 cells through ATM-Chk2-p53 signaling axis in accompany with JNK bypass regulation. This is the first report on the pro-senescent effect and multi-target (p53 and JNK) mechanism of TB on HCC cells, providing new insights into the underlying mechanisms of TB's anti-HCC efficacy. [ABSTRACT FROM AUTHOR]

Reovirus infection induces dramatic changes in host mRNA expression. We utilized oligonucleotide microarrays to measure cellular mRNA decay rates in mock- or reovirus-infected murine L929 cells to determine if changes in host mRNA expression are a consequence of reovirus-induced alterations in cellular mRNA stability. Our analysis detected a subset of cellular transcripts that were coordinately induced and stabilized following infection with the reovirus isolates c87 and c8, strains that led to an inhibition of cellular translation, but not following infection with Dearing, a reovirus isolate that did not negatively impact cellular translation. The induced and stabilized transcripts encode multiple regulators of TGF- β signaling, including components of the Smad signaling network and apoptosis/survival pathways. The coordinate induction, through mRNA stabilization, of multiple genes that encode components of TGF-β signaling pathways represents a novel mechanism by which the host cell responds to reovirus infection. [ABSTRACT FROM AUTHOR]

Eosinophils play a central role in asthma. The present study was performed to investigate the effect of tumour necrosis factor-α (TNF-α) on longevity of isolated human eosinophils. In contrast to Fas, TNF-α inhibited eosinophil apoptosis as evidenced by a combination of flow cytometry, DNA fragmentation assay and morphological analyses. The effect of TNF-α on eosinophil apoptosis was reversed by a TNF-α neutralising antibody. The anti-apoptotic effect of TNF-α was not due to autocrine release of known survival-prolonging cytokines interleukins 3 and 5 or granulocyte-macrophage-colony-stimulating factor as their neutralisation did not affect the effect of TNF-α. The anti-apoptotic signal was mediated mainly by the TNF-receptor 1. TNF-α induced phosphorylation and degradation of IκB and an increase in NF-κB DNA-binding activity. The survival-prolonging effect of TNF-α was reversed by inhibitors of NF-κB pyrrolidinedithiocarbamate and gliotoxin and by an inhibitor of IκB kinase, BMS-345541. TNF-α induced also an increase in AP-1 DNA-binding activity and the antiapoptotic effect of TNF-α was potentiated by inhibitors of AP-1, SR 11302 and tanshinone IIA and by an inhibitor of c-jun-N-terminal kinase, SP600125, which is an upstream kinase activating AP-1. Our results thus suggest that TNF-α delays human eosinophil apoptosis via TNF-receptor 1 and the resulting changes in longevity depend on yin-yang balance between activation of NF-κB and AP-1. [ABSTRACT FROM AUTHOR]

Both nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases mediate production of proinflammatory cytokines in many types of cells. c-Jun N-terminal kinases (JNK) is a key regulator of many cellular events including cell inflammation and/or programmed cell death (apoptosis). In addition to mediating immune and inflammatory responses, NF-κB transcription factors control cell survival. It is reported that activation of NF-κB antagonizes apoptosis or programmed cell death by numerous triggers. It has been reported that NF-κB activation results in rapid inactivation of JNK in tumor necrosis factor alpha (TNFα)-treated murine embryonic fibroblasts. It is not clear about the relationship of JNK and NF-κB in the microglial cells induced by TLR4 activity. In the present study, we investigated the relationship of JNK and NF-κB in the highly aggressively proliferating immortalized microglial cell line treated with KDO2 (a TLR4 agonist). KDO2 treatment significantly induced the phosphorylation of JNK and NF-κB, and released TNFα. Knockdown of TLR4 with TLR4 siRNA significantly reduced phosphorylation of JNK (pJNK), phosphorylation of NF-κB, and release of TNFα. Inhibition of JNK reduced the release of TNFα, but not phosphorylation of NF-κB. Unexpectedly, inhibition of NF-κB enhanced pJNK and the release of TNFα. These results showed that TNFα induced by KDO2 was JNK-dependent, and that NF-κB negatively modulated both pJNK and TNFα in the cultured microglial cell line. The current study may provide a new insight in the modulation of TNFα in the microglial cell line. [ABSTRACT FROM AUTHOR]

Meningococcal invasive isolates of the ST-11 clonal complex are most frequently associated with disease and rarely found in carriers. Unlike carriage isolates, invasive isolates induce apoptosis in epithelial cells through the TNF-α signaling pathway. While invasive and non-invasive isolates are both able to trigger the TLR4/MyD88 pathway in lipooligosaccharide (LOS)- dependant manner, we show that only non-invasive isolates were able to induce sustained NF-κB activity in infected epithelial cells. ST-11 invasive isolates initially triggered a strong NF-κB activity in infected epithelial cells that was abolished after 9h of infection and was associated with sustained activation of JNK, increased levels of membrane TNFR1, and induction of apoptosis. In contrast, infection with carriage isolates lead to prolonged activation of NF-κB that was associated with a transient activation of JNK increased TACE/ADAM17-mediated shedding of TNFR1 and protection against apoptosis. Our data provide insights to understand the meningococcal duality between invasiveness and asymptomatic carriage. [ABSTRACT FROM AUTHOR]

Elevated levels of reactive oxygen species (ROS) are found in most oncogenically transformed cells and are proposed to promote cellular transformation through mechanisms such as inhibition of phosphatases. BCR-ABL, the oncoprotein associated with the majority of chronic myeloid leukemias (CMLs), induces accumulation of intracellular ROS, causing enhanced signaling downstream of PI3K. Previously we have shown that the transcription factor nuclear factor-kappa B (NF-κB) is activated by BCR-ABL expression and is required for BCR-ABL-mediated cellular transformation. Inhibition of IκB kinase (IKKβ) and NF-κB leads to cell death through an unknown mechanism. Here, we analyze the potential involvement of NF-κB in moderating BCR-ABL-induced ROS levels to protect from death. The data confirm that BCR-ABL promotes ROS and demonstrate that NF-κB prevents excessive levels. Inhibition of NF-κB leads to an increase in ROS levels and to cell death, which is at least partially controlled through ROS-induced c-Jun N-terminal kinase activity. The data demonstrate that one function for NF-κB in oncogenesis is the suppression of oncoprotein-induced ROS levels and that inhibition of NF-κB in some cancers, including CML, will increase ROS levels and promote cell death. [ABSTRACT FROM AUTHOR]

Background: Abrogation of apoptosis for prolonged cell survival is essential in cancer progression. In our previous studies, we showed the MMP-2 downregulation induced apoptosis in cancer cell lines. Here, we attempt to investigate the exact molecular mechanism of how MMP-2 depletion leads to apoptosis in glioma xenograft cell lines. Methodology/Principal Findings: MMP-2 transcriptional suppression by MMP-2siRNA (pM) induces apoptosis associated with PARP, caspase-8 and -3 cleavage in human glioma xenograft cells 4910 and 5310. Western blotting and cytokine array showed significant decrease in the cellular and secreted levels of TNF-α with concomitant reduction in TNFR1, TRADD, TRAF2, RIP, IKKβ and pIκBα expression levels resulting in inhibition of p65 phosphorylation and nuclear translocation in pM-treated cells when compared to mock and pSV controls. In addition MMP-2 suppression led to elevated Fas-L, Fas and FADD expression levels along with increased p38 and JNK phosphorylation. The JNK-activity assay showed prolonged JNK activation in pM-transfected cells. Specific inhibition of p38 with SB203580 did not show any effect whereas inhibition of JNK phosphorylation with SP600125 notably reversed pM-induced cleavage of PARP, caspase-8 and -3, demonstrating a significant role of JNK in pM-induced cell death. Supplementation of rhMMP-2 counteracted the effect of pM by remarkably elevating TNF-α, TRADD, IKKβ and pIκBα expression and decreasing FADD, Fas-L, and phospho-JNK levels. The EMSA analysis indicated significant reversal of pM-inhibited NF-κB activity by rhMMP-2 treatment which rescued cells from pM-induced cell death. In vivo studies indicated that pM treatment diminished intracranial tumor growth and the immuno histochemical analysis showed decreased phospho-p65 and enhanced phospho-JNK levels that correlated with increased TUNEL-positive apoptotic cells in pM-treated tumor sections. Conclusion/Significance: In summary, our study implies a role of MMP-2 in the regulation of TNF-α mediated constitutive NF-κB activation and Fas-mediated JNK mediated apoptosis in glioma xenograft cells in vitro and in vivo. [ABSTRACT FROM AUTHOR]

The zinc-finger protein A20 has crucial physiological functions as a dual inhibitor of nuclear factor-κB (NF-κB) activation and apoptosis in tumor necrosis factor (TNF) receptor 1 signaling pathway. Although the molecular basis for the anti-NF-κB function of A20 has been well elucidated, the anti-apoptotic function of A20 is largely unknown. Here, we report a novel mechanism underlying the anti-apoptotic function of A20: A20 blocks TNF-induced apoptosis through suppression of c-jun N-terminal kinase (JNK) by targeting apoptosis signal-regulating kinase1 (ASK1). First, the ectopic expression of A20 drastically inhibits TNF-induced JNK activation and apoptosis in multiple cell types including those deficient of NF-κB activation. Unexpectedly, the blunting effect of A20 on TNF-induced JNK activation is not mediated by affecting the TNFR1 signaling complex formation. Instead, A20 interacts with ASK1, an important MAPKK kinase in the JNK signaling cascade. More importantly, overexpression of wild-type A20, but not of mutant A20 (ZnF4; C624A, C627A), promotes degradation of the ASK1 through the ubiquitin-proteasome system. Taken together, the results from this study reveal a novel anti-apoptotic mechanism of A20 in TNF signaling pathway: A20 binds to ASK1 and mediates ASK1 degradation, leading to suppression of JNK activation and eventually blockage of apoptosis. [ABSTRACT FROM AUTHOR]

The article presents a study on hepatocyte injury. It states that hepatocytes are especially vulnerable to cell injury because of several factors including its role in xenobiotic metabolism and in the enterohepatic circulation of bile acids. It explores the processes that contribute to hepatocyte injury such as endoplasmic reticulum stress and death ligands and receptors. It suggests that the mechanisms of the promotion of hepatic fibrosis by cell death are nuanced and multifaceted.

We analyzed the survival responses and downstream signaling elicited by GDNF on sympathetic neurons from different Ret knockin mice. Lack of tyrosine 1062, a multidocking site in Ret, completely prevented GDNF-mediated survival. Importantly, lack of tyrosine 981, although abrogating Akt phosphorylation, had no effect on neuronal survival, indicating that the PI 3-K/Akt pathway is not necessary for survival of sympathetic neurons. In contrast, silencing of B-Raf completely prevented not only GDNF-mediated but also NGF-mediated cell survival, independently of MEK-1/2. We identified IKKs as the main effectors of the protective effects of B-Raf. First, B-Raf interacted with and activated IKKs. Second, knockdown of IKKs reversed the protection afforded by a constitutively active form of B-Raf. Third, knockdown of IKKs prevented both NGF- and GDNF-mediated survival. In conclusion, our data delineate a novel survival pathway for sympathetic neurons linking B-Raf to IKKs, independently of both PI 3-K and MEK-1/2 pathways.Cell Death and Differentiation (2008) 15, 1510–1521; doi:10.1038/cdd.2008.76; published online 23 May 2008 [ABSTRACT FROM AUTHOR]

Tumors that acquire resistance against death stimuli constitute a severe problem in the context of cancer therapy. To determine genetic alterations that favor the development of stress-resistant tumors in vivo, we took advantage of polyclonal tumors generated after retroviral infection of newborn Eλ-MYC mice, in which the retroviral integration acts as a mutagen to enhance tumor progression. Tumor cells were cultivated ex vivo and exposed to γ-irradiation prior to their transplantation into syngenic recipients, thereby providing a strong selective pressure for pro-survival mutations. Secondary tumors developing from stress-resistant tumor stem cells were analysed for retroviral integration sites to reveal candidate genes whose dysregulation confer survival. In addition to the gene encoding the antiapoptotic Bcl-xL protein, we identified the gadd45b locus to be a novel common integration site in these tumors, leading to enhanced expression. In accord with a thus far undocumented role of Gadd45β in tumorigenesis, we showed that NIH3T3 cells overexpressing Gadd45β form tumors in NOD/SCID mice. Interestingly and differently to other known ‘classical’ antiapoptotic factors, high Gadd45β levels did not protect against MYC-, UV- or γ-irradiation-induced apoptosis, but conferred a strong and specific survival advantage to serum withdrawal.Oncogene (2008) 27, 1429–1438; doi:10.1038/sj.onc.1210772; published online 24 September 2007 [ABSTRACT FROM AUTHOR]

Inhibition of NF-κB activation increases susceptibility to tumor necrosis factor (TNF)α-induced cell death, concurrent with caspases and prolonged c-Jun N-terminal kinase (JNK) activation, and reactive oxygen species (ROS) accumulation. However, the detailed mechanisms are unclear. Here we show that cellular FLICE-inhibitory protein (c-FLIP) is rapidly lost in NF-κB activation-deficient, but not wild-type fibroblasts upon TNFα stimulation, indicating that NF-κB normally maintains the cellular levels of c-FLIP. The ectopic expression of the long form of c-FLIP (c-FLIPL) inhibits TNFα-induced prolonged JNK activation and ROS accumulation in NF-κB activation-deficient fibroblasts. Conversely, TNFα induces prolonged JNK activation and ROS accumulation in c-Flip−/− fibroblasts. Moreover, c-FLIPL directly interacts with a JNK activator, MAP kinase kinase (MKK)7, in a TNFα-dependent manner and inhibits the interactions of MKK7 with MAP/ERK kinase kinase 1, apoptosis-signal-regulating kinase 1, and TGFβ-activated kinase 1. This stimuli-dependent interaction of c-FLIPL with MKK7 might selectively suppress the prolonged phase of JNK activation. Taken that ROS promote JNK activation and activation of the JNK pathway may promote ROS accumulation, c-FLIPL might block this positive feedback loop, thereby suppressing ROS accumulation. [ABSTRACT FROM AUTHOR]

The nuclear factor-kappaB (NF-κB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-κB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-κB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-κB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-κB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-κB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-κB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-κB in many disease conditions including tumor development, tumor progression and anticancer treatment.Oncogene (2006) 25, 6800–6816. doi:10.1038/sj.onc.1209938 [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are emerging as key effectors in signal transduction. This role of ROS is especially evident in the pathways leading to programmed cell death (PCD) elicited in response to certain stress stimuli and cytokines. In these pathways, cytotoxic ROS signaling appears to be mediated in part by activation of the c-Jun-N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) cascade. Another pathway that is under ROS-mediated control in some systems is that leading to activation of transcription factor nuclear factor-kappa B (NF-κB), which is a central regulator of immunity, inflammation and cell survival. Remarkably, new evidence has unveiled the existence of a reciprocal, negative control that NF-κB exerts on ROS and JNK activities. This NF-κB-imposed restraint on ROS and JNK signaling is crucial for antagonism of PCD elicited by the proinflammatory cytokine tumor necrosis factor (TNF)α and likely other triggers. Effectors of this antagonistic cross-talk between NF-κB and ROS/JNK pathways have recently been identified. Because of the key roles that the prosurvival function of NF-κB plays in organismal physiology and disease, gaining a further mechanistic understanding of this cross-talk and NF-κB-dependent survival may be key to developing new therapies for the treatment of widespread human illnesses, such as cancer and chronic inflammatory conditions.Oncogene (2006) 25, 6731–6748. doi:10.1038/sj.onc.1209936 [ABSTRACT FROM AUTHOR]

NF-κB/Rel transcription factors have recently emerged as crucial regulators of cell survival. Activation of NF-κB antagonizes programmed cell death (PCD) induced by tumor necrosis factor-receptors (TNF-Rs) and several other triggers. This prosurvival activity of NF-κB participates in a wide range of biological processes, including immunity, lymphopoiesis and development. It is also crucial for pathogenesis of various cancers, chronic inflammation and certain hereditary disorders. This participation of NF-κB in survival signaling often involves an antagonism of PCD triggered by TNF-R-family receptors, and is mediated through a suppression of the formation of reactive oxygen species (ROS) and a control of sustained activation of the Jun-N-terminal kinase (JNK) cascade. Effectors of this antagonistic activity of NF-κB on this ROS/JNK pathway have been recently identified. Indeed, further delineating the mechanisms by which NF-κB promotes cell survival might hold the key to developing new highly effective therapies for treatment of widespread human diseases.Cell Death and Differentiation (2006) 13, 712–729. doi:10.1038/sj.cdd.4401865; published online 3 February 2006 [ABSTRACT FROM AUTHOR]

TNF-α activates several intracellular pathways to regulate inflammation, cell death, and proliferation. In the liver, TNF-a is not only a mediator of hepatotoxicity but also contributes to the restoration of functional liver mass by driving hepatocyte proliferation and liver regeneration. This review summarizes recent advances in TNF-α signaling mechanisms that demonstrate how the IKK, ROS, and JNK pathways interact with each other to regulate hepatocyte apoptosis and proliferation. Activation of these pathways is causatively linked to liver injury induced by concanavalin A, TNF-α, and ischemia-reperfusion and to liver regeneration and hepatocarcinogenesis. In light of recent findings, pharmacological inhibitors of JNK and IKK and antioxidants may be promising new tools for the treatment of hepatitis, ischemia-reperfusion injury, and hepatocellular carcinoma. [ABSTRACT FROM AUTHOR]

All-trans retinoic acid (ATRA) significantly improves the survival of patients with acute promyelocytic leukemia (APL) by inducing granulocytic differentiation of leukemia cells. Since an activation of the transcription factor NF-κB occurs during ATRA-induced maturation of APL cells, a mechanistic link between these two processes was investigated. Using an in vitro model for APL, we report that ectopic overexpression of a repressor of NF-κB activation did not affect granulocytic differentiation. Importantly, NF-κB inhibition markedly resulted in a decreased viability of the differentiated cells, which correlated with increased apoptosis. Apoptosis was accompanied by a sustained activation of the c-Jun N-terminal kinase (JNK). Inhibition of JNK by the specific inhibitor SP600125 or by transfection of a dominant-negative mutant of JNK1 reduced the percentage of apoptotic cells, thus showing that JNK activation constitutes a death signal. Furthermore, impairment of NF-κB activation resulted in increased levels of reactive oxygen species (ROS) upon ATRA treatment. ROS accumulation was suppressed by the antioxidant butylated hydroxyanisol, which also abolished ATRA-induced JNK activation and apoptosis. Altogether, our results demonstrate an antiapoptotic effect of NF-κB activation during ATRA-induced differentiation of NB4 cells and identify repression of ROS-mediated JNK activation as a mechanism for this effect. Our observations also suggest that NF-κB signalling may contribute to an accumulation of mature APL cells and participate in the development of ATRA syndrome.Oncogene (2005) 24, 7145–7155. doi:10.1038/sj.onc.1208889; published online 25 July 2005 [ABSTRACT FROM AUTHOR]

Tumor necrosis factor-a(TNFa) activates both cell death and cell survival pathways, which render most cancer cells resistant to its cytotoxicity. In this study, we found that pretreatment with luteolin, a plant flavonoid, greatly sensitized TNFa-induced apoptotic cell death in a number of human cancer cell lines; including colorectal cancer COLO205, HCT116 cells and cervical cancer HeLa cells. In the search of the molecular mechanisms responsible for the sensitization effect of luteolin, we discovered that luteolin inhibited TNFa-induced activation of nuclear transcription factor-kappa B (NF-?B), the main survival factor in TNFasignaling. As a result, luteolin suppressed the expression of NF-?B-targeted antiapoptotic genes, including A20 and cellular inhibitor of apoptosis protein-1 (c-IAP1). The role of A20 and c-IAP1 was further confirmed by ectopic expression of these two genes, which significantly protected cell death induced by luteolin followed by TNFa. In addition, inhibition of NF-?B by luteolin led to augmentation and prolongation of c-Jun N-terminal kinase (JNK) activation induced by TNFa. Suppression of JNK activation, either by a synthetic JNK inhibitor (SP600125) or by overexpression of the dominant negative forms of JNK kinase 1 (JNKK1) and JNK kinase 2 (JNKK2), conferred significant protection against apoptotic cell death induced by luteolin and TNFa, suggesting that NF-?B and JNK are closely associated with the sensitization effect of luteolin. Data from this study reveal a novel function of luteolin and enhance the value of luteolin as an anticancer agent.Oncogene (2004) 23, 7712-7721. doi:10.1038/sj.onc.1208046 Published online 30 August 2004 [ABSTRACT FROM AUTHOR]

Recent studies strongly suggest an active involvement of the c-Jun N-terminal kinase (JNK) signaling pathway in tumor necrosis factor (TNF)-induced apoptosis. The direct evidence for the role of JNK and its isoforms has been missing and the mechanism of how JNK actually could facilitate this process has remained unclear. In this study, we show that Jnk2-/- primary mouse embryonic fibroblasts (pMEFs) exhibit resistance towards TNF-induced apoptosis as compared to corresponding wild-type and Jnk1-/- pMEFs. JNK2-deficient pMEFs could be resensitized to TNF via retroviral transduction of any of the four different JNK2 splicing variants. Jnk2-/- pMEFs displayed deficient and delayed effector caspase activation as well as impaired cytosolic cystein cathepsin activity: processes that both were needed for efficient TNF-induced apoptosis in pMEFs. Our work demonstrates that JNK has a central role in the promotion of TNF-induced apoptosis in pMEFs, and that the JNK2 isoform can regulate both mitochondrial and lysosomal death pathways in these cells.Cell Death and Differentiation (2004) 11, 301-313. doi:10.1038/sj.cdd.4401353 Published online 12 December 2003 [ABSTRACT FROM AUTHOR]

SUMMARY: The identification of genes differentially regulated by ischemia will lead to an improved understanding of cell death pathways such as those involved in the neuronal loss observed following a stroke. Furthermore, the characterization of such pathways could facilitate the identification of novel targets for stroke therapy. We have used a novel approach to amplify differential gene expression patterns in a primary neuronal model of stroke by employing a lentiviral vector system to specifically bias the transcriptional activation of hypoxically regulated genes. Overexpression of the hypoxia-induced transcription factor subunits HIF-1α and HIF-2α elevated hypoxia-mediated transcription of many known HIF-regulated genes well above control levels. Furthermore, many potentially novel HIF-regulated genes were discovered that were not previously identified as hypoxically regulated. Most of the novel genes identified were activated by a combination of HIF-2α overexpression and hypoxic insult. These included several genes with particular importance in cell survival pathways and of potential therapeutic value. Hypoxic induction of HIF-2α may therefore be a critical factor in mediating protective responses against ischemic injury. Further investigation of the genes identified in this study may provide increased understanding of the neuronal response to hypoxia and may uncover novel therapeutic targets for the treatment of cerebral ischemia. [ABSTRACT FROM AUTHOR]

During their lifetime, cells encounter many life or death situations that challenge their very own existence. Their survival depends on the interplay within a complex yet precisely orchestrated network of proteins. The Rel/NF-?B signaling pathway and the transcription factors that it activates have emerged as critical regulators of the apoptotic response. These proteins are best known for the key roles that they play in normal immune and inflammatory responses, but they are also implicated in the control of cell proliferation, differentiation, apoptosis and oncogenesis. In recent years, there has been remarkable progress in understanding the pathways that activate the Rel/NF-?B factors and their role in the cell's decision to either fight or surrender to apoptotic challenge. Whereas NF-?B is most commonly involved in suppressing apoptosis by transactivating the expression of antiapoptotic genes, it can promote programmed cell death in response to certain death-inducing signals and in certain cell types. This review surveys our current understanding of the role of NF-?B in the apoptotic response and focuses on many developments since this topic was last reviewed in Oncogene 4 years ago. These recent findings shed new light on the activity of NF-?B as a critical regulator of apoptosis in the immune, hepatic, epidermal and nervous systems, on the mechanisms through which it operates and on its role in tissue development, homoeostasis and cancer.Oncogene (2003) 22, 8961-8982. doi:10.1038/sj.onc.1207230 [ABSTRACT FROM AUTHOR]

Interactions between proteasome and cyclin-dependent kinase inhibitors have been examined in human leukemia cells in relation to induction of apoptosis. Simultaneous exposure (24?h) of U937 myelomonocytic leukemia cells to 100?nM flavopiridol and 300?nM MG-132 resulted in a marked increase in mitochondrial injury (cytochrome c, Smac/DIABLO release, loss of ??m), caspase activation, and synergistic induction of cell death, accompanied by a marked decrease in clonogenic potential. Similar effects were observed with other proteasome inhibitors (e.g., Bortezomib (VELCADE™ bortezomib or injection), lactacystin, LLnL) and cyclin-dependent kinase inhibitors (e.g., roscovitine), as well as other leukemia cell types (e.g., HL-60, Jurkat, Raji). In U937 cells, synergistic interactions between MG-132 and flavopiridol were associated with multiple perturbations in expression/activation of signaling- and survival-related proteins, including downregulation of XIAP and Mcl-1, activation of JNK and p34cdc2, and diminished expression of p21CIP1. The lethal effects of MG-132/flavopiridol were not reduced in leukemic cells ectopically expressing Bcl-2, but were partially attenuated in cells ectopically expressing dominant-negative caspase-8 or CrmA. Flavopiridol/proteasome inhibitor-mediated lethality was also significantly diminished by agents and siRNA blocking JNK activation. Lastly, coadministration of MG-132 with flavopiridol resulted in diminished DNA binding of NF-?B. Notably, pharmacologic interruption of the NF-?B pathway (e.g., by BAY 11-7082, PDTC, or SN-50) or molecular dysregulation of NF-?B (i.e., in cells ectopically expressing an I?Ba super-repressor) mimicked the actions of proteasome inhibitors in promoting flavopiridol-induced mitochondrial injury, JNK activation, and apoptosis. Together, these findings indicate that proteasome inhibitors strikingly lower the apoptotic threshold of leukemic cells exposed to pharmacologic CDK inhibitors, and suggest that interruption of the NF-?B cytoprotective pathway and JNK activation both play key roles in this phenomenon. They also raise the possibility that combining proteasome and CDK inhibitors could represent a novel antileukemic strategy.Oncogene (2003) 22, 7108-7122. doi:10.1038/sj.onc.1206863 [ABSTRACT FROM AUTHOR]

In the last few years, the ubiquitin(Ub)/proteasome system has become increasingly recognized as a controller of numerous physiological processes, including signal transduction, DNA repair, chromosome maintenance, transcriptional activation, cell cycle progression, cell survival, and certain immune cell functions. This is in addition to its more established roles in the removal of misfolded, damaged, and effete proteins. This review examines the role of the Ub/proteasome system in processes underlying the classical effects of irradiation on cells, such as radiation-induced gene expression, DNA repair and chromosome instability, oxidative damage, cell cycle arrest, and cell death. Furthermore, recent evidence suggests that the proteasome is a redox-sensitive target for ionizing radiation and other oxidative stress signals. In other words, the Ub/proteasome system may not simply be a passive player in radiation-induced responses, but may modulate them. The extent of the modulation will be influenced by the functional and structural diversity that is expressed by the system. Cell types vary in the Ub/proteasome structures they possess and the level at which they function, and this changes as they go from the normal to the cancerous condition. Cancer-related functional changes within the Ub/proteasome system may therefore present unique targets for cancer therapy, especially when targeting agents are used in combination with radio- or chemotherapy. The peptide boronic acid compound PS-341, which was designed to inhibit proteasome chymotryptic activity, is in clinical trials for the treatment of solid and hematogenous tumors. It has shown some efficacy on its own and in combination with chemotherapy. Preclinical studies have shown that PS-341 will also potentiate the cytotoxic effects of radiation therapy. In addition, other drugs in common clinical use have been shown to affect proteasome function, and their activities may be valuably reconsidered from this perspective.Oncogene (2003) 22, 5755-5773. doi:10.1038/sj.onc.1206676 [ABSTRACT FROM AUTHOR]

Apoptosis is an important phenomenon in cytotoxicity induced by anticancer drugs. Here, we review the current status of the molecular mechanisms of anticancer drug-induced apoptosis in order to assess the contribution of molecular-level analysis to cancer chemotherapy. It is apparent that the molecular mechanisms by which anticancer drugs induce apoptosis are mediated by death receptor-dependent and -independent pathways, which are related to the release of cytochrome c through voltage-dependent anion channels in the mitochondrial inner membrane. The release of cytochrome c is the central gate in turning on/off apoptosis, and is regulated by the interaction of proapoptotic proteins, including Bid, Bax and Bak, and antiapoptotic proteins including Bcl-2 and Bcl-XL, and a specific class of inhibitors of apoptosis proteins (IAPs) including Akt, survivin, and heat-shock proteins. The caspase cascade is activated by the release of cytochrome c, which is initiated by the formation of apoptosomes consisting of procaspase-9, Apaf-1 and cytochrome c in the presence of dATP, and results in the activation of caspase-9 and caspase-3, thereby leading to apoptosis. Drug sensitivity can be enhanced by the introduction of proapoptotic genes and the inhibition of antiapoptotic proteins. The latter process is mediated by antisense oligonucleotides and is associated with apoptosis. The signal transduction pathways that are triggered by the central gate in mitochondria play a critical role in anticancer drug-induced apoptosis. The modulation of signal transduction pathways targeting the proteins involved in these signal transduction pathways using antisense IAPs, and growth factor antibodies may be a good strategy for enhancing therapeutic efficacy of anticancer drugs in cancer chemotherapy. [ABSTRACT FROM AUTHOR]

Examines the survival and cell death signaling by tumor necrosis factor (TNF)-alpha and the role of caspases in turning off nuclear factor-kappaB survival signal. Role of DAP kinase in TNF-induced apoptosis; Molecular basis of the effect of age on TNF-alpha-induced apoptosis in human T cells.

This article reports that reactive oxygen species connect nuclear factor-kB and c-Jun amino-terminal kinase. Numerous studies have shown that nuclear factor-kB inhibits various types of cell death by upregulating anti-apoptotic genes, such as cellular FADD-like interleukin-1-converting enzyme-inhibitory protein, X-chromosome-linked inhibitor of apoptosis, A1 and B-cell leukaemia/lymphoma-XL. Recently, two groups reported an essential role of ROS in longlasting JNK stimulation in NF-kB activation-deficient cells.