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ER Stress (er + stress)
Selected AbstractsA link between endoplasmic reticulum stress-induced , -cell apoptosis and the group VIA Ca2+ -independent phospholipase A2 (iPLA2,)DIABETES OBESITY & METABOLISM, Issue 2010X. Lei Endoplasmic reticulum (ER) stress is becoming recognized as an important contributing factor in various diseases, including diabetes mellitus. Prolonged ER stress can cause , -cell apoptosis; however, the underlying mechanism(s) that contribute to this process are not well understood. Early reports suggested that arachidonic acid metabolites and a Ca2+ -independent phospholipase A2 (iPLA2) activity play a role in , -cell apoptosis. The PLA2 family of enzymes catalyse the hydrolysis of the sn -2 substituent (i.e. arachidonic acid) of membrane phospholipids. In light of our findings that the pancreatic islet , -cells are enriched in arachidonate-containing phospholipids and express the group VIA iPLA2,, we considered the possibility that iPLA2, participates in ER stress-induced , -cell apoptosis. Our work revealed a novel mechanism, involving ceramide generation and triggering of mitochondrial abnormalities, by which iPLA2, participates in the , -cell apoptosis process. Here, we review our evidence linking ER stress, , -cell apoptosis and iPLA2,. Continued studies in this area will increase our understanding of the contribution of iPLA2, to the evolution of diabetes mellitus and will further our knowledge of factors that influence , -cell health in diabetes mellitus and identify potential targets for future therapeutic interventions to prevent , -cell death. [source] Increased stress protein ORP150 autoantibody production in Type 1 diabetic patientsDIABETIC MEDICINE, Issue 2 2006Y. Nakatani Abstract Aims Various genetic and environmental stresses interfere with protein folding in the endoplasmic reticulum (ER), which leads to the induction of ER stress. It has recently been reported that ER stress is involved in the development of diabetes in diabetic animal models. The aim of this study is to estimate ER stress levels in Type 1 diabetic patients. Methods We recruited Type 1 diabetic patients undergoing periodic follow-up examinations (n = 91) and healthy non-diabetic individuals (n = 37), and measured their serum anti-oxygen-related protein (ORP)150 autoantibody levels. Results Anti-ORP150 autoantibody levels in Type 1 diabetic patients were significantly higher compared with those in healthy non-diabetic subjects. Furthermore, the serum autoantibody levels in Type 1 diabetic patients correlated with HbA1c (F > 3.0, P = 0.079), indicating that hyperglycaemia itself induces ER stress in diabetes. Conclusions Anti-ORP150 autoantibody levels in Type 1 diabetic patients are higher compared with non-diabetic subjects, suggesting that ER stress is increased in Type 1 diabetes. [source] BimEL as a possible molecular link between proteasome dysfunction and cell death induced by mutant huntingtinEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2010Rebecca Leon Abstract Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an expanded polyglutamine repeat within the N-terminus of the huntingtin protein. It is characterized by a selective loss of medium spiny neurons in the striatum. It has been suggested that impaired proteasome function and endoplasmic reticulum (ER) stress play important roles in mutant huntingtin (mHtt)-induced cell death. However, the molecular link involved is poorly understood. In the present study, we identified the essential role of the extra long form of Bim (Bcl-2 interacting mediator of cell death), BimEL, in mHtt-induced cell death. BimEL protein expression level was significantly increased in cell lines expressing the N-terminus of mHtt and in a mouse model of HD. Although quantitative RT-PCR analysis indicated that BimEL mRNA was increased in cells expressing mHtt, we provided evidence showing that, at the post-translational level, phosphorylation of BimEL played a more important role in regulating BimEL expression. Up-regulation of BimEL facilitated the translocation of Bax to the mitochondrial membrane, which further led to cytochrome c release and cell death. On the other hand, knocking down BimEL expression prevented mHtt-induced cell death. Taken together, these findings suggest that BimEL is a key element in regulating mHtt-induced cell death. A model depicting the role of BimEL in linking mHtt-induced ER stress and proteasome dysfunction to cell death is proposed. [source] Autoregulation of the HAC1 gene is required for sustained activation of the yeast unfolded protein responseGENES TO CELLS, Issue 2 2004Naoki Ogawa Eukaryotic cells respond to the accumulation of unfolded proteins in the endoplasmic reticulum (ER) by activating a transcriptional induction program termed the unfolded protein response (UPR). The transcription factor Hac1p responsible for the UPR in Saccharomyces cerevisiae is tightly regulated by a post-transcriptional mechanism. HAC1 mRNA must be spliced in response to ER stress to produce Hac1p, which then activates transcription via direct binding to the cis -acting UPR element (UPRE) present in the promoter regions of its target genes. Here, we show that the HAC1 promoter itself responds to ER stress to induce transcription of its downstream gene, similarly to the KAR2 promoter; the KAR2 gene represents a major target of the UPR. Consistent with this observation, the HAC1 promoter contains an UPRE-like sequence, which is necessary and sufficient for the induction and to which Hac1p binds directly. Cells expressing the HAC1 gene from a mutant HAC1 promoter lacking the HAC1 UPRE could not maintain high levels of either unspliced or spliced HAC1 mRNA and became sensitive to ER stress when insulted for hours. Based on these results, we concluded that autoregulation of the HAC1 genes is required for sustained activation of the UPR and sustained resistance to ER stress. [source] Enhanced expression of vascular endothelial growth factor-A in ground glass hepatocytes and its implication in hepatitis B virus hepatocarcinogenesis,HEPATOLOGY, Issue 6 2009Jui-Chu Yang Ground glass hepatocytes (GGH) in chronic hepatitis B virus (HBV) infection harbor HBV pre-S deletion mutants in endoplasmic reticulum (ER) and exhibit complex biologic features such as ER stress, DNA damage, and growth advantage. The presence of pre-S mutants in serum has been shown to predict the development of hepatocellular carcinoma (HCC) in HBV carriers. GGHs hence represent a potentially preneoplastic lesion. Whether a specific growth factor is overexpressed and activated in GGHs remains to be clarified. In this study, growth factor(s) up-regulated by pre-S mutants was identified using a growth factor array in HuH-7 cells. Immunohistochemistry, reverse-transcriptase polymerase chain reaction, and Western blot analysis were performed to study the participation of these genes and their signal pathways in HuH-7 cells and liver tissues. We demonstrate that vascular endothelial growth factor-A (VEGF-A) was up-regulated by pre-S mutants in HuH-7 cells and further confirmed in GGHs by immunostaining. The VEGF-A up-regulation by pre-S mutants could be suppressed by vomitoxin, an ER stress inhibitor. Furthermore, pre-S mutants-expressed HuH-7 cells exhibited activation of Akt/mTOR (mammalian target of rapamycin) signaling and increased growth advantage, which could be inhibited by VEGF-A neutralization. Consistent with this notion, enhanced expression of VEGF-A and activation of Akt/mTOR signaling, comparable to the levels of paired HCC tissues, were also detected in HBV-related nontumorous livers. Conclusion: The enhanced expression of VEGF-A in GGHs provides potential mechanism to explain the progression from preneoplastic GGHs to HCC in chronic HBV infection. (HEPATOLOGY 2009;49:1962,1971.) [source] Effect of tauroursodeoxycholic acid on endoplasmic reticulum stress,induced caspase-12 activationHEPATOLOGY, Issue 3 2002Qing Xie Activation of death receptors and mitochondrial damage are well-described common apoptotic pathways. Recently, a novel pathway via endoplasmic reticulum (ER) stress has been reported. We assessed the role of tauroursodeoxycholic acid (TUDCA) in inhibition of caspase-12 activation and its effect on calcium homeostasis in an ER stress-induced model of apoptosis. The human liver-derived cell line, Huh7, was treated with thapsigargin (TG) to induce ER stress. Typical morphologic changes of ER stress preceded development of apoptotic changes, including DNA fragmentation and cleavage of poly (adenosine diphosphate-ribose) polymerase (PARP), as well as activation of caspase-3 and -7. Elevation of intracellular calcium levels without loss of mitochondrial membrane potential (MMP) was shown using Fluo-3/Fura-red labeling and flow cytometry, and confirmed by induction of Bip/GRP78, a calcium-dependent chaperon of ER lumen. These changes were accompanied by procaspase-12 processing. TUDCA abolished TG-induced markers of ER stress; reduced calcium efflux, induction of Bip/GRP78, and caspase-12 activation; and subsequently inhibited activation of effector caspases and apoptosis. In conclusion, we propose that mitochondria play a secondary role in ER-mediated apoptosis and that TUDCA prevents apoptosis by blocking a calcium-mediated apoptotic pathway as well as caspase-12 activation. This novel mechanism of TUDCA action suggests new intervention methods for ER stress-induced liver disease. [source] From HLA-B27 to spondyloarthritis: a journey through the ERIMMUNOLOGICAL REVIEWS, Issue 1 2010Robert A. Colbert Summary:, Almost four decades of research into the role of human leukocyte antigen-B27 (HLA-B27) in susceptibility to spondyloarthritis has yet to yield a convincing answer. New results from an HLA-B27 transgenic rat model now demonstrate quite convincingly that CD8+ T cells are not required for the inflammatory phenotype. Discoveries that the HLA-B27 heavy chain has a tendency to misfold during the assembly of class I complexes in the endoplasmic reticulum (ER) and to form aberrant disulfide-linked dimers after transport to the cell surface have forced the generation of new ideas about its role in disease pathogenesis. In transgenic rats, HLA-B27 misfolding generates ER stress and leads to activation of the unfolded protein response, which dramatically enhances the production of interleukin-23 (IL-23) in response to pattern recognition receptor agonists. These findings have led to the discovery of striking T-helper 17 cell activation and expansion in this animal model, consistent with results emerging from humans with spondyloarthritis and the discovery of IL23R as an additional susceptibility gene for ankylosing spondylitis. Together, these results suggest a novel link between HLA-B27 and the T-helper 17 axis through the consequences of protein misfolding and open new avenues of investigation as well as identifying new targets for therapeutic intervention in this group of diseases. [source] Nerve growth factor blocks thapsigargin-induced apoptosis at the level of the mitochondrion viaregulation of BimJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6a 2008E. Szegezdi Abstract This study examined how the neurotrophin, nerve growth factor (NGF), protects PC12 cells against endoplasmic reticulum (ER) stress-induced apoptosis. ER stress was induced using thapsigargin (TG) that inhibits the sarcoplasmic/ER Ca2+ -ATPase pump (SERCA) and depletes ER Ca2+ stores. NGF pre-treatment inhibited translocation of Bax to the mitochondria, loss of mitochondrial transmembrane potential, cytochrome c release, activation of caspases (,3, ,7 and ,9) and apoptosis induction by TG. Notably, TG also caused a marked induction of Bimel mRNA and protein, and knockdown of Bim with siRNA protected cells against TG-induced apoptosis. NGF delayed the induction and increased the phosphorylation of Bimel. NGF-mediated protection was dependent on phosphatidylinositol-3 kinase (PI3K) signalling since all above apoptotic events, including expression and phosphorylation status of Bimel protein, could be reverted by the PI3K inhibitor LY294002. In contrast, NGF had no effect on the TG-mediated induction of the unfolded protein response (increased expression of Grp78, GADD34, splicing of XBP1 mRNA) or ER stress-associated pro-apoptotic responses (induction of C/EBP homologous protein [CHOP], induction and processing of caspase-12). These data indicate that NGF-mediated protection against ER stress-induced apoptosis occurs at the level of the mitochondria by regulating induction and activation of Bim and mitochondrial translocation of Bax. [source] Changes in endoplasmic reticulum stress proteins and aldolase A in cells exposed to dopamineJOURNAL OF NEUROCHEMISTRY, Issue 1 2008April A. Dukes Abstract In Parkinson's disease, oxidative stress is implicated in protein misfolding and aggregation, which may activate the unfolded protein response by the endoplasmic reticulum (ER). Dopamine (DA) can initiate oxidative stress via H2O2 formation by DA metabolism and by oxidation into DA quinone. We have previously shown that DA quinone induces oxidative protein modification, mitochondrial dysfunction in vitro, and dopaminergic cell toxicity in vivo and in vitro. In this study, we used cysteine- and lysine-reactive fluorescent dyes with 2D difference in-gel electrophoresis, mass spectrometry, and peptide mass fingerprint analysis to identify proteins in PC12 cell mitochondrial-enriched fractions that were altered in abundance following DA exposure (150 ,M, 16 h). Quantitative changes in proteins labeled with fluorescent dyes indicated increases in a subset of proteins after DA exposure: calreticulin, ERp29, ERp99, Grp58, Grp78, Grp94 and Orp150 (149,260%), and decreased levels of aldolase A (39,42%). Changes in levels of several proteins detected by 2D difference in-gel electrophoresis were confirmed by western blot. Using this unbiased proteomics approach, our findings demonstrated that in PC12 cells, DA exposure leads to a cellular response indicative of ER stress prior to the onset of cell death, providing a potential link between DA and the unfolded protein response in the pathogenesis of Parkinson's disease. [source] Involvement of Gadd153 in the pathogenic action of presenilin-1 mutationsJOURNAL OF NEUROCHEMISTRY, Issue 3 2002Ollivier Milhavet Abstract Mutations in the presenilin-1 (PS1) gene cause early onset familial Alzheimer's disease (FAD) by a mechanism believed to involve perturbed endoplasmic reticulum (ER) function and altered proteolytic processing of the amyloid precursor protein. We investigated the molecular mechanisms underlying cell death and ER dysfunction in cultured cells and knock-in mice expressing FAD PS1 mutations. We report that PS1 mutations cause a marked increase in basal protein levels of the pro-apoptotic transcription factor Gadd153. PS1 mutations increase Gadd153 protein translation without affecting mRNA levels, while decreasing levels of the anti-apoptotic protein Bcl-2. Moreover, an exaggerated Gadd153 response to stress induced by ER stress agents was observed in PS1 mutant cells. Cell death in response to ER stress is enhanced by PS1 mutations, and this endangering effect is attenuated by anti-sense-mediated suppression of Gadd153 production. An abnormality in the translational regulation of Gadd153 may sensitize cells to the detrimental effects of ER stress and contribute to the pathogenic actions of PS1 mutations in FAD. [source] Endoplasmic reticulum-associated degradation of the NR1 but not the NR2 subunits of the N-methyl-D-aspartate receptor induced by inhibition of the N-glycosylation in cortical neuronsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2007Sergio Gascón Abstract The N-methyl-D-aspartate receptor (NMDAR) is fundamental to normal and pathological functioning of neurons. The receptor subunits are N-glycosylated proteins synthesized in the endoplasmic reticulum (ER) that fold, mature, and oligomerize as they transit through the secretory pathway. Although the early processes of biogenesis are fundamental to NMDAR expression and function, our knowledge of them is nevertheless limited. Additionally, the investigation of NMDAR synthesis is highly relevant, in that ER dysfunction, frequently associated with acute and degenerative brain diseases, might alter this process. We characterize here the effect of ER stress produced by inhibition of N-glycosylation on NMDAR synthesis and function. We use first heterologous systems of NMDAR expression in which NR1 and NR2A subunits are synthesized in nonneuronal cells. The function of these NMDARs as Ca2+ channels is repressed by tunicamycin, because of the inhibition of NR1, but no NR2A, synthesis. The regulation of NR1 is relevant to the central nervous system, in that a dramatic decrease in synthesis of this subunit and assembly of NMDARs is observed in cortical neurons treated with tunicamycin. The inhibition of NR1 synthesis is not due to changes in levels of mRNA but associated with the earliest stages in NMDAR biogenesis. The inhibition of N-glycosylation activates ER-specific stress responses in neurons, which include the ER-associated degradation (ERAD) mechanism responsible for differential and extremely efficient degradation of nonglycosylated NR1 by the proteasome after ubiquitination. Because this is an obligatory NMDAR component, the significant sensitivity of NR1 to ER stress will have important consequences on receptor function. © 2007 Wiley-Liss, Inc. [source] Melatonin suppresses cyclosporine A-induced autophagy in rat pituitary GH3 cellsJOURNAL OF PINEAL RESEARCH, Issue 3 2010Yeong-Min Yoo Abstract:, Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the induction of chronic nephrotoxicity including endoplasmic reticulum (ER) stress in tubular cells. Recently, it was reported that autophagy is induced by ER stress and serves to alleviate the associated deleterious effects. In the current study, CsA treatment (0,100 ,m) decreased cell survival of rat pituitary GH3 cells in a dose-dependent manner. At concentrations ranging from 1.0 to 10 ,m, CsA induced a dose-dependent increase in the expression of microtubule-associated protein 1 light chain 3 (LC3)-I and LC3-II. Cells treated with 2.5 ,m CsA exhibited cytoplasmic vacuolation, indicating that CsA induces autophagy in rat pituitary GH3 cells. In the presence of 1.0,10 ,m CsA, the expression of catalase decreased while that of the ER stress markers, ER luminal binding protein (BiP) and inositol-requiring enzyme 1 alpha (IRE1,), increased as compared those levels in untreated cells. These results suggested that CsA-induced autophagy is dependent on ER stress. To determine whether melatonin would protect cells against CsA-induced autophagy, we treated rat pituitary GH3 cells with melatonin in the presence of CsA. Melatonin treatment (100 and 200 ,m) suppressed autophagy induced by 2.5 and 5 ,m CsA. Furthermore, co-treatment with 100 ,m melatonin inhibited LC3-II expression, and increased catalase and phosphorylated p-ERK levels in the presence of 2.5 and 5 ,m CsA. BiP and IRE1, expression in melatonin-co-treated cells was superior to that in cells treated with 2.5 and 5 ,m CsA alone. Thus, melatonin suppresses CsA-mediated autophagy in rat pituitary GH3 cells. [source] Proteomics reveals lowering oxygen alters cytoskeletal and endoplasmatic stress proteins in human endothelial cellsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 19 2009Louise Østergaard Abstract A proteomic approach was applied to explore the signalling pathways elicited by lowering O2 in endothelial cells. Endothelial cells isolated from native umbilical cords were subjected to 21, 5, or 1% O2 for 24,h. 2-D PAGE was performed and candidate proteins were identified using LC-MS/MS. Lowering of O2 from 21 to 5% induced upregulation of cofilin-1, cyclophilin A, tubulin and tubulin fragments, a fragment of glucose-regulated protein 78 (Grp78) and calmodulin. The upregulation of Grp78 suggested that ER stress proteins were altered and indeed Grp94 and caspase 12 expression were increased in cells exposed to 5% O2. The presence of ER stress is also supported by findings of blunted caffeine-evoked ER calcium release in cells exposed to 5 and 1% O2. Exposure to 1% O2 caused increases in cofilin-1, cyclophilin A, and caspase 12 as well as a decrease of ,-actin, but it did not alter the expression of calmodulin, tubulin, Grp78, and Grp94. Incubation with CoCl2, a stabilizer of the hypoxia-inducible factor, increased the expression of several of the proteins. The present investigations reveal that lowering O2, probably in part through hypoxia-inducible factor, alter the expression of a series of proteins mainly involved in cytoskeletal changes (e.g. cofilin-1, tubulin, and ,-actin) and in ER stress/apoptosis (e.g. Grp78/94, caspase 12, and cyclophilin A). [source] Proteomic and transcriptomic study on the action of a cytotoxic saponin (Polyphyllin D): Induction of endoplasmic reticulum stress and mitochondria-mediated apoptotic pathwaysPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 15 2008Fung-Ming Siu Abstract Polyphyllin D (PD) is a potent cytotoxic saponin found in Paris polyphylla. In the present study, bioinformatic, proteomic and transcriptomic analyses were performed to study the mechanisms of action of PD on human nonsmall cell lung cancer (NSCLC) cell line (NCI-H460). Using a gene expression-based bioinformatic tool (connectivity map), PD was identified as a potential ER stress inducer. Our proteomic and transcriptomic analyses revealed that PD treatment led to upregulation of typical ER stress-related proteins/genes including glucose-regulated protein 78 (BiP/GRP78) and protein disulfide isomerase (PDI). In particular, elevated expression of C/EBP homologous transcription factor (chop) and activation of caspase-4 occurred at early time point (8,h) of PD treatment, signifying an initial ER stress-mediated apoptosis. Induction of tumor suppressor p53, disruption of mitochondrial membrane, activation of caspase-9 and caspase-3 were detected upon prolonged PD treatment. Collectively, these data revealed that PD induced the cytotoxic effect through a mechanism initiated by ER stress followed by mitochondrial apoptotic pathway. The ability of activating two major pathways of apoptosis makes PD an attractive drug lead for anticancer therapeutics. [source] Dopamine D2 receptor knockout mice develop features of Parkinson disease,ANNALS OF NEUROLOGY, Issue 4 2009Rogan B. Tinsley PhD Objective This study questions whether increased dopamine (DA) turnover in nigral neurons leads to formation of Lewy bodies (LBs), the characteristic ,-synuclein,containing cytoplasmic inclusion of Parkinson disease (PD). Methods Mice with targeted deletion of the dopamine D2 receptor gene (D2R[,/,]) have higher striatal and nigral dopamine turnover and elevated oxidative stress. These mice were examined for evidence of histological, biochemical, and gene expression changes consistent with a synucleinopathy. Results LB-like cytoplasmic inclusions containing ,-synuclein and ubiquitin were present in substantia nigra pars compacta (SNpc) neurons of older D2R(,/,) mice, and were also occasionally seen in aged wild-type mice. These inclusions displaced the nucleus of affected cells and were eosinophilic. Diffuse cytosolic ,-synuclein immunoreactivity in SNpc neurons increased with age in both wild-type and D2R(,/,) mice, most likely because of redistribution of ,-synuclein from striatal terminals to SNpc cell bodies. Gene and protein expression studies indicated endoplasmic reticulum (ER) stress and changes in trafficking and autophagic pathways in D2R(,/,) SNpc. These changes were accompanied by a loss of DA terminals in the dorsal striatum, although there was no evidence of progressive cell death in the SNpc. Interpretation Increased sprouting and DA turnover, as observed in PD and D2R(,/,) mice, augments LB-like inclusions and axonal degeneration of dopaminergic neurons. These changes are associated with ER stress and autophagy. Ann Neurol 2009;66:472,484 [source] Nitric oxide selectively depletes macrophages in atherosclerotic plaques via induction of endoplasmic reticulum stressBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2007W Martinet Background and purpose: Macrophages in atherosclerotic plaques have a tremendous impact on atherogenesis and plaque destabilization. We previously demonstrated that treatment of plaques in cholesterol-fed rabbits with the nitric oxide (NO) donor molsidomine preferentially eliminates macrophages, thereby favouring features of plaque stability. In this study, we investigated the underlying mechanism. Experimental approach: Macrophages and smooth muscle cells (SMCs) were treated in vitro with the NO donors, spermine NONOate or S -nitroso- N -acetylpenicillamine (SNAP) as well as with the well-known endoplasmic reticulum (ER) stress inducers thapsigargin, tunicamycin, dithiothreitol or brefeldin A. Cell viability was analysed by Neutral Red viability assays. Cleavage of caspase-3, DNA fragmentation and ultrastructural changes were examined to characterize the type of macrophage death. Induction of ER stress was evaluated by measuring C/EBP homologous protein (CHOP) expression, phosphorylation of eukaryotic initiation factor 2, (eIF2a), splicing of X-box binding protein 1 (XBP1) and inhibition of protein synthesis. Key results: Macrophages and SMCs treated with spermine NONOate or SNAP showed several signs of ER stress, including upregulation of CHOP expression, hyperphosphorylation of eIF2,, inhibition of de novo protein synthesis and splicing of XBP1 mRNA. These effects were similar in macrophages and SMCs, yet only macrophages underwent apoptosis. Plaques from molsidomine-treated atherosclerotic rabbits showed a 2.7-fold increase in CHOP expression as compared to placebo. Beside NO, selective induction of macrophage death could be initiated with thapsigargin and tunicamycin. Conclusions and implications: Induction of ER stress explains selective depletion of macrophages in atherosclerotic plaques by a NO donor, probably via inhibition of protein synthesis. British Journal of Pharmacology (2007) 152, 493,500; doi:10.1038/sj.bjp.0707426; published online 13 August 2007 [source] Hepatitis B virus pre-S mutants, endoplasmic reticulum stress and hepatocarcinogenesisCANCER SCIENCE, Issue 8 2006Hui-Ching Wang Although hepatitis B virus (HBV) has been documented to cause hepatocellular carcinoma (HCC), the exact role of HBV in the development of HCC remains enigmatic. Several hypotheses have been proposed to explain the potential mechanism, including insertional mutagenesis of HBV genomes and transcriptional activators of HBV gene products such as hepatitis B x protein (HBx) and truncated middle S mutants. In the past few years, we have identified two types of large HBV surface antigens (LHBs) with deletions at the pre-S1 (,S1-LHBs) and pre-S2 (,S2-LHBs) regions in ground glass hepatocytes. The pre-S mutant LHBs are retained in the endoplasmic reticulum (ER) and escape from immune attack. The pre-S mutants, particularly ,S2-LHBs, are increasingly prevalent in patients with hepatitis B e antigen (HBeAg)-positive chronic HBV infection, ranging from 6% before the 3rd decade to 35% in the 6th decade. In HCC patients, the two pre-S mutants were detected in 60% of HCC patients, in the serum and in HCC tissues. Pre-S mutant LHBs can initiate ER stress to induce oxidative DNA damage and genomic instability. Furthermore, pre-S mutant LHBs can upregulate cyclooxygenase-2 and cyclin A to induce cell cycle progression and proliferation of hepatocytes. In transgenic mice, the pre-S mutants can induce dysplasia of hepatocytes and development of HCC. In a nested control study, the presence of pre-S mutants carried a high risk of developing HCC in HBV carriers. In summary, the findings we describe in this review suggest a potential role for HBV pre-S mutants in HBV-related hepatocarcinogenesis, providing a model of viral carcinogenesis associated with ER stress. (Cancer Sci 2006; 97: 683,688) [source] Subtilase cytotoxin, produced by Shiga-toxigenic Escherichia coli, transiently inhibits protein synthesis of Vero cells via degradation of BiP and induces cell cycle arrest at G1 by downregulation of cyclin D1CELLULAR MICROBIOLOGY, Issue 4 2008Naoko Morinaga Summary Subtilase cytotoxin (SubAB) is a AB5 type toxin produced by Shiga-toxigenic Escherichia coli, which exhibits cytotoxicity to Vero cells. SubAB B subunit binds to toxin receptors on the cell surface, whereas the A subunit is a subtilase-like serine protease that specifically cleaves chaperone BiP/Grp78. As noted previously, SubAB caused inhibition of protein synthesis. We now show that the inhibition of protein synthesis was transient and occurred as a result of ER stress induced by cleavage of BiP; it was closely associated with phosphorylation of double-stranded RNA-activated protein kinase-like ER kinase (PERK) and eukaryotic initiation factor-2, (eIF2,). The phosphorylation of PERK and eIF2, was maximal at 30,60 min and then returned to the control level. Protein synthesis after treatment of cells with SubAB was suppressed for 2 h and recovered, followed by induction of stress-inducible C/EBP-homologous protein (CHOP). BiP degradation continued, however, even after protein synthesis recovered. SubAB-treated cells showed cell cycle arrest in G1 phase, which may result from cyclin D1 downregulation caused by both SubAB-induced translational inhibition and continuous prolonged proteasomal degradation. [source] 2233: Endoplasmic reticulum stress and inflammation signaling in RPE cellsACTA OPHTHALMOLOGICA, Issue 2010A SALMINEN Pathogenesis of AMD is linked to augmentation of cellular stress, e.g. oxidative and proteotoxic stress, hypoxia and inflammation. All these conditions trigger stress in endoplasmic reticulum (ER) and in that way can disturb the protein quality control in retinal pigment epithelial (RPE) cells. ER stress stimulates the unfolded protein response (UPR) via the activation of IRE1, PERK and ATF6 transducers. The UPR signaling can restore cellular homeostasis but chronic and overwhelming stress can induce inflammatory response via different UPR signaling pathways and lead to apoptotic cell death. Moreover, ER stress is a well-known inducer of vascular endothelial growth factor (VEGF) expression and in AMD, ER stress could provoke neovascularization and the conversion of dry form to wet counterpart. ER stress has a fundamental role in the pathogenesis of several diseases, e.g. in diabetes and neurodegenerative diseases. This lecture will review the recent advance in understanding the inducers of ER stress, present in RPE cells during AMD, and the possible role of ER stress in evoking inflammation and neovascularization during the pathogenesis of AMD. [source] 3244: The significance of ER stress in cataractogenesisACTA OPHTHALMOLOGICA, Issue 2010T SHINOHARA [source] Neuroprotective effects of pramipexole against tunicamycin-induced cell death in PC12 cellsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2009Hitoshi Nakayama Summary 1Pramipexole (PPX), a dopamine D2 and D3 receptor agonist, exerts neuroprotective effects via both dopamine receptor-mediated and non-dopaminergic mechanisms. In the present study, we demonstrate that PPX reduces the toxicity of tunicamycin, a typical endoplasmic reticulum (ER) stressor, in PC12h cells, a subline of PC12 cells. 2The PC12h cells were treated with 300 ,mol,/,L PPX in the presence of 0.5 ,mol,/,L tunicamycin for 24 h. The neuroprotective effects of PPX against tunicamycin-induced cell death were evaluated using 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays, Hoechst 33258 staining and western blot analysis. 3Tunicamycin (0.2, 0.3 and 0.5 ,g,/,mL) dose-dependently decreased MTT activity and increased LDH release from PC12h cells. Treatment with 300 ,mol,/,L PPX rescued the tunicamycin-induced decrease in cell viability. 4Spiperone (10 ,mol,/,L), a dopamine D2 and D4 receptor antagonist, had no effect on PPX neuroprotection against tunicamycin in these cells. Marker proteins of ER stress and apoptosis are known to be upregulated by tunicamycin, but we detected no significant effects of PPX on these factors. 5In conclusion, we speculate that a combination of several mechanisms may be involved in PPX-induced neuroprotection. [source] ENDOPLASMIC RETICULUM STRESS INVOLVED IN HEART AND LIVER INJURY IN IRON-LOADED RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 7 2009Li-Xia Lou SUMMARY 1Iron overload contributes to the pathogenesis of various diseases and directly induces tissue injury. In the present study, we investigated the relationship between heart and liver injury induced by iron overload and cellular endoplasmic reticulum (ER) stress to explore the molecular mechanism of iron overload-induced cellular injury. 2Iron overload in rats was generated by intraperitoneal injection of iron,dextran chronically (30 mg/kg per day for 9 weeks) or acutely (300 mg/kg once). Tissue injury was assessed by determining serum lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, as well as malondialdehyde (MDA) content in the heart and liver. The ER stress response was analysed by expression of glucose-response protein 78 (GRP78) and activation of caspase 12. 3In chronic iron-loaded rats, iron levels in the heart and liver were higher, by approximately 2-and 7.8-fold, respectively (P < 0.01), compared with control. Serum LDH, ALT and AST activity, as well as MDA content, GRP78 expression and caspase 12 activity in the heart and liver, were upregulated in chronically iron-loaded rats. In acute iron-loaded rats, iron content in the heart and liver was 51% and 63% higher than in controls (both P < 0.01). Serum LDH, ALT and AST activity, MDA content in the heart and liver and levels of ER stress markers were all increased in acute iron-loaded rats. N -Acetylcysteine (150 mg/kg, s.c.) lowered the levels of these parameters in acute iron-loaded rats. 4The results of the present study indicate that ER stress may play an important role in iron-induced tissue injury and that reactive oxygen species may mediate the ER stress response in the pathogenesis of iron-overload cellular injury. [source] INVOLVEMENT OF BOTH ENDOPLASMIC RETICULUM- AND MITOCHONDRIA-DEPENDENT PATHWAYS IN CARDIOTOXIN III-INDUCED APOPTOSIS IN HL-60 CELLSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2008Ching-Ming Chien SUMMARY 1Cardiotoxin (CTX) III, a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. In the present study, we investigated the mechanisms underlying the anticancer activity of CTX III in human leukaemia (HL-60 cells). 2Cardiotoxin III activated the endoplasmic reticulum (ER) pathway of apoptosis in HL-60 cells, as indicated by increased levels of calcium and glucose-related protein 78 (Grp78), and triggered the subsequent activation of µ-calpain and caspase 12. 3In addition, CTX III initiated the mitochondrial apoptotic pathway in HL-60 cells, as evidenced by an increased Bax/Bcl-2 ratio, the release of cytochrome c and activation of caspase 9. 4In the presence of 50 µmol/L Z-ATAD-FMK (a caspase 12 inhibitor) and 100 µmol/L Z-LEHD-FMK (a caspase 9 inhibitor), the CTX III-mediated activation of caspase 9 and caspase 3 was significantly reduced. There was no significant effect of the caspase 12 inhibitor Z-ATAD-FMK on mitochondrial cytochrome c release. 5Cardiotoxin III-mediated activation of caspase 12 was not abrogated in the presence of the caspase 9 inhibitor Z-LEHD-FMK, indicating that caspase 12 activation was not downstream of caspase 9. 6These results indicate that CTX III induces cell apoptosis via both ER stress and a mitochondrial death pathway. [source] Proteomics reveals lowering oxygen alters cytoskeletal and endoplasmatic stress proteins in human endothelial cellsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 19 2009Louise Østergaard Abstract A proteomic approach was applied to explore the signalling pathways elicited by lowering O2 in endothelial cells. Endothelial cells isolated from native umbilical cords were subjected to 21, 5, or 1% O2 for 24,h. 2-D PAGE was performed and candidate proteins were identified using LC-MS/MS. Lowering of O2 from 21 to 5% induced upregulation of cofilin-1, cyclophilin A, tubulin and tubulin fragments, a fragment of glucose-regulated protein 78 (Grp78) and calmodulin. The upregulation of Grp78 suggested that ER stress proteins were altered and indeed Grp94 and caspase 12 expression were increased in cells exposed to 5% O2. The presence of ER stress is also supported by findings of blunted caffeine-evoked ER calcium release in cells exposed to 5 and 1% O2. Exposure to 1% O2 caused increases in cofilin-1, cyclophilin A, and caspase 12 as well as a decrease of ,-actin, but it did not alter the expression of calmodulin, tubulin, Grp78, and Grp94. Incubation with CoCl2, a stabilizer of the hypoxia-inducible factor, increased the expression of several of the proteins. The present investigations reveal that lowering O2, probably in part through hypoxia-inducible factor, alter the expression of a series of proteins mainly involved in cytoskeletal changes (e.g. cofilin-1, tubulin, and ,-actin) and in ER stress/apoptosis (e.g. Grp78/94, caspase 12, and cyclophilin A). [source] | |||||||||||||||||||||||||