Protein Levels Of CHOP Research Articles

CHOP mediates XBP1S-induced renal mesangial cell necrosis following high glucose treatment

High glucose (HG)-induced apoptosis in mesangial cells (MCs) is a critical determinant during the pathogenesis of diabetic nephropathy. The signaling cascade inducing MCs apoptosis by HG involves overproduction of reactive oxygen species. Our previous studies have demonstrated that HG-induced oxidative stress is mediated by suppression of spliced/active X-box binding protein 1 (XBP1S), suggesting the importance of XBP1S in HG-induced MCs apoptosis. CHOP, an endoplasmic reticulum stress-associated proapoptotic signal, is involved in downstream of XBP1S. In the present study, we explored the effect of XBP1S in modulating HG-induced apoptosis in renal MCs and then identified the role of CHOP in these processes. Apoptosis and necrosis were quantified by flow cytometry; protein levels of XBP1S, caspase3, Bax, Bcl2, BNIP3, and CHOP were analyzed by Western blotting. The cellular localization of XBP1S was determined by immunofluorescence histochemistry. The binding of XBP1 to CHOP promoter was determined by chromatin immunoprecipitation assays. In addition, adenoviruses harboring XBP1S gene (Ad-XBP1S) were used to overexpress XBP1S, whereas the knockdown of CHOP was achieved by small interference RNA. HG suppressed nuclear distribution of XBP1S and induced apoptosis and necrosis in MCs. Ad-XBP1S infection enhanced the nuclear translocation of XBP1S and reduced MCs apoptosis and necrosis. XBP1S bound to the promoter region of CHOP and upregulated CHOP expression. Conversely, CHOP expression was reduced upon HG exposure and knockdown of CHOP increased necrosis but not apoptosis in MCs. These results suggest that XBP1S protected MCs from HG-induced apoptosis and necrosis, and CHOP participates in XBP1S-regulated necrosis but not apoptosis.

The effects of NAD on glucose deprivation induced activation of protein O‐GlcNAcylation, ER stress and autophagy mediated by CD38 and cADPR

We have previously reported that exogenous nicotinamide adenine dinucleotide hydrate (NAD) decreases basal O-GlcNAc levels as well as attenuates the increase in O-GlcNAc that occurs in response to glucose deprivation (GD); however, the mechanism by which NAD regulates O-GlcNAcylation is unknown. Recent studies have shown that a major pathway for extracellular NAD metabolism is via the cell surface glycohydrolases, CD38 and the resulting formation of cADPR. Therefore, the goal of this study was to determine whether the effects of NAD on the cellular responses to GD were mediated via CD38 and cADPR. Consistent with earlier studies AC16 cardiomyocytes subjected to GD for up to 24hrs, demonstrated significant increases in O-GlcNAcylation as well as with increased protein levels of CHOP, BIP, P-PERK/T-PERK and LC3-II/LC3-I ratio; all of which were markedly attenuated with the addition of NAD (250µM). The addition of the CD38 inhibitor,Luteolinidin chloride (100µM), significantly blunted the effects of NAD on the cellular responses to GD. Conversely, the addition of cADPR (100µM) mimicked the effects of NAD, attenuating the GD-induced increase in O-GlcNAc and CHOP, BIP, P-PERK/T-PERK and LC3-II/LC3-I. These results demonstrate for the first time that NAD inhibits multiple cell survival pathways including increased protein O-GlcNAcylation, ER stress and autophagy through a CD38 and cADPR mediated pathway.

Rapamycin improves palmitate-induced ER stress/NF κ B pathways associated with stimulating autophagy in adipocytes.

Obesity-induced endoplasmic reticulum (ER) stress and inflammation lead to adipocytes dysfunction. Autophagy helps to adapt to cellular stress and involves in regulating innate inflammatory response. In present study, we examined the activity of rapamycin, a mTOR kinase inhibitor, against endoplasmic reticulum stress and inflammation in adipocytes. An in vitro model was used in which 3T3-L1 adipocytes were preloaded with palmitate (PA) to generate artificial hypertrophy mature adipocytes. Elevated autophagy flux and increased number of autophagosomes were observed in response to PA and rapamycin treatment. Rapamycin attenuated PA-induced PERK and IRE1-associated UPR pathways, evidenced by decreased protein levels of eIF2α phosphorylation, ATF4, CHOP, and JNK phosphorylation. Inhibiting autophagy with chloroquine (CQ) exacerbated these ER stress markers, indicating the role of autophagy in ameliorating ER stress. In addition, cotreatment of CQ abolished the anti-ER stress effects of rapamycin, which confirms the effect of rapamycin on ERs is autophagy-dependent. Furthermore, rapamycin decreased PA-induced nuclear translocation of NFκB P65 subunit, thereby NFκB-dependent inflammatory cytokines MCP-1 and IL-6 expression and secretion. In conclusion, rapamycin attenuated PA-induced ER stress/NFκB pathways to counterbalance adipocytes stress and inflammation. The beneficial of rapamycin in this context partly depends on autophagy. Stimulating autophagy may become a way to attenuate adipocytes dysfunction.

ET-71 * THE ANTITUMOR EFFECTS OF WITHAFERIN A IN GLIOBLASTOMA STEM CELLS

INTRODUCTION: Glioblastoma Multiforme (GBM) is the most common and malignant primary brain tumors. Recent studies indicate that GBM stem cells (GSCs), are chemotherapy and radiotherapy resistant and are responsible for tumor cell invasion into normal brain, tumor growth and tumor reoccurrence following treatment. Withaferin A (WA), a steroidal lactone isolated from Withania somnifera, has demonstrated anti-tumor potential including inhibiting tumor growth, metastasis and angiogenesis. However, effects of WA in GSCs have not been previously explored. METHODS: GSCs were generated from patient's tumors and analyzed for stem cell markers CD133, CD44, GFAP, Nestin, Musashi, SOX2 and BMi1 by immunocytochemistry. Effect of WA on GSC viability was determined by MTS and/or LDH assay. Morphological effects of WA were evaluated by transmission electron microscopy. Effect of WA on cell signaling pathways was evaluated with flow cytometry, western blot analysis and fluorescent microscopy. ROS was detected using MitoSOX Red. RESULTS: WA induced both dose and time dependent increase in cell death in GSC lines (IC50 average 1.27+ 0.12uM for 6 GSC lines). In contrast, primary neurons were not affected by these concentrations and had a much higher IC50 (5.78uM). Treatment of GSCs with WA significantly increased the diameter of endoplasmic reticulum (ER) and western blot analysis confirmed ER stress demonstrating increased grp78, IRE1, and CHOP protein levels. WA treatment increased mitochondrial ROS production and induced apoptosis as indicated by increased levels of cleaved PARP, caspase 4/3/7/12, Bax, and bak. Pre-treatment with the antioxidant N-acetyl-L-cysteine (NAC) or caspase inhibitor (z-vad-fmk) attenuated WA-induced apoptosis. Lastly WA increased both velcade and NVP-BEZ235 induced cell death. CONCLUSION: Our data indicates that WA mediates anti-tumor effects via ROS generation, ER stress activation, and apoptosis induction in GSCs and potentially sensitizes these cells to additional chemotherapy. These findings warrant further investigation of WA as an adjuvant therapy for GBM.

ClC-3 deficiency protects preadipocytes against apoptosis induced by palmitate in vitro and in type 2 diabetes mice.

Palmitate, a common saturated free fatty acid (FFA), has been demonstrated to induce preadipocyte apoptosis in the absence of adipogenic stimuli, suggesting that preadipocytes may be prone to apoptosis under adipogenic insufficient conditions, like type 2 diabetes mellitus (T2DM). ClC-3, encoding Cl(-) channel or Cl(-)/H(+) antiporter, is critical for cell fate choices of proliferation versus apoptosis under diseased conditions. However, it is unknown whether ClC-3 is related with preadipocyte apoptosis induced by palmitate or T2DM. Palmitate, but not oleate, induced apoptosis and increase in ClC-3 protein expression and endoplasmic reticulum (ER) stress in 3T3-L1 preadipocyte. ClC-3 specific siRNA attenuated palmitate-induced apoptosis and increased protein levels of Grp78, ATF4, CHOP and phosphorylation of JNK1/2, whereas had no effects on increased phospho-PERK and phospho-eIF2α protein expression. Moreover, the enhanced apoptosis was shown in preadipocytes from high-sucrose/fat, low-dose STZ induced T2DM mouse model with hyperglycemia, hyperlipidemia (elevated serum TG and FFA levels) and insulin resistance. ClC-3 knockout significantly attenuated preadipocyte apoptosis and the above metabolic disorders in T2DM mice. These data demonstrated that ClC-3 deficiency prevent preadipocytes against palmitate-induced apoptosis via suppressing ER stress, and also suggested that ClC-3 may play a role in regulating cellular apoptosis and disorders of glucose and lipid metabolism during T2DM.

Oroxylin A inhibits ATRA-induced IL-6 expression involved in retinoic acid syndrome by down-regulating CHOP

Production of IL-6 constituted the major cause of death in the ATRA trial called retinoic acid syndrome (RAS). LAP and LIP are active and inactive isoforms of C/EBPβ, respectively. Inactive LIP dimerized with LAP to eliminate its activity. Following treatment with ATRA, CHOP expression was increased and dimerized with LIP more preferentially than LAP to rescue function of LAP. Oroxylin A has been reported to activate CHOP, a key mediator of unfolded protein response (UPR) pathway, and resulted in apoptosis. Interestingly, we found that low concentration of oroxylin A (≦40μM) showed no apoptosis effect on NB4 and HL-60 cells and decreased the CHOP protein level via promoting its degradation. MG132 was utilized to conform the effect of oroxylin A on degrading CHOP. Our results showed that oroxylin A decreased the level of IL-6 secretion of NB4 cells with or without ATRA treatment while the effect was eliminated by C/EBPβ siRNA. We conclude that oroxylin A possessed abilities of inhibiting the ATRA-induced IL-6 production via modulation of LAP/LIP/CHOP in leukemia cell lines, which could providing a therapeutic strategy for RAS.

4-Phenylbutyric acid prevent cytotoxicity induced by thapsigargin in rat cardiac fibroblast

Cardiac fibroblast (CF) survival is important for the maintenance of the extracellular matrix homeostasis in the heart; providing a functional support to cardiomyocytes necessary for the correct myocardial function. Endoplasmic reticulum (ER) stress causes cellular dysfunction and cell death by apoptosis; and thapsigargin is a well-known ER stress inducer. On the other hand, the chemical chaperone, 4-phenylbutyric acid (4-PBA) had showed to prevent ER stress; however, in cardiac fibroblast both the ER stress induced by thapsigargin and prevention by 4-PBA, have not been studied in detail.Neonate rat CF were treated with thapsigargin in presence or absence of 4-PBA, and cell viability was evaluated by trypan blue exclusion and apoptosis by flow cytometry; whereas CHOP, BIP, PDI, ATF4 and procollagen protein levels were assessed by western blot.In CF, thapsigargin triggered the unfolded protein response detected by early increases in ATF4, CHOP, PDI and BIP protein levels as well as, the accumulation of intracellular procollagen. Thapsigargin also stimulated CF death in a time and concentration-dependent manner. ER stress, CF death and apoptosis induced by thapsigargin were prevented by 4-PBA.Conclusion our data suggest that 4-PBA prevent ER stress, intracellular procollagen accumulation, CF death and apoptosis induced by thapsigargin.

Neuregulin-1 protects myocardial cells against H2 O2 -induced apoptosis by regulating endoplasmic reticulum stress.

Neuregulin-1 (NRG-1) is a stress-mediated growth factor secreted by cardiovascular endothelial cells and provides the protection to myocardial cells, but the underlying mechanisms are not fully understood. This study aimed to demonstrate that NRG-1 protects myocardial cells exposed to oxidative damage by regulating endoplasmic reticulum (ER) stress. Neonatal rat cardiac myocytes (NRCMs) were isolated and treated with H2 O2 as a cellular model of ER stress. NRCMs were pretreated with different concentrations of NRG-1. We found that NRG-1 increased the viability and reduced the apoptosis of NRCMs treated by H2 O2 . Moreover, NRG-1 reduced lactate dehydrogenase level, increased superoxide dismutase activity and decreased malondialdehyde content in NRCMs treated by H2 O2 . Finally, we demonstrated that NRG-1 alleviated ER stress and decreased CHOP and GRP78 protein levels in NRCMs treated by H2 O2 . Taken together, these data indicate that NRG-1 relieves oxidative and ER stress in NRCMs and suggest that NRG-1 is a promising agent for cardioprotection.

HKH40A downregulates GRP78/BiP expression in cancer cells.

HKH40A, the 8-methoxy analog of WMC79, is a synthetic agent with promising in vitro and in vivo antitumor activity, especially against solid tumors. However, molecular mechanisms underlying its antitumor effects are poorly understood. Here, we report that HKH40A markedly reduces the level of GRP78/BiP protein in cancer cell lines of various origin. In this study, we show that HKH40A not only downregulates transcription of GRP78 but also directly binds to the isolated protein and induces its proteosomal degradation. Knockdown of BiP increased the efficacy of the drug and overexpression of BiP diminished its activity. BiP is generally highly elevated in solid tumors having a pivotal role in cancer cell survival and chemoresistance, and has been suggested as a novel target for therapeutic intervention. We show that reduction of BiP level by HKH40A impairs its function and induces unfolded protein response as evidenced by the activation of IRE1α, ATF6 and PERK. This leads to a series of downstream events, including sustained eIF2α phosphorylation, increased abundance of spliced XBP1 mRNA and protein levels of ATF4 and CHOP. We also demonstrate that HKH40A inhibited tumor formation in an in vivo xenograft tumor model. Collectively, our data show that HKH40A reduces BiP levels and this could have an important role in the activity of HKH40A against cancer cells.

Contributions of Endoplasmic Reticulum Stress and Reactive Oxygen Species to Renal Injury in Aldosterone/Salt-Induced Rats

Background: Recent studies have suggested that aldosterone (Aldo) plays a key role in the pathogenesis of renal injury; however, the molecular mechanisms of Aldo-induced renal injury have not been characterized. This study was performed to test the hypothesis that reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress contribute to the pathogenesis of Aldo- and salt-induced renal injury. Methods: Rats were uninephrectomized and treated with one of the following for 4 weeks: (1) vehicle, (2) vehicle + NaCl, (3) Aldo + NaCl or (4) Aldo + NaCl + N-acetyl-<smlcap>L</smlcap>-cysteine (NAC). Following this treatment period, the extent of renal injury was assessed by periodic acid-Schiff staining and immunohistochemistry, and the expression levels of proteins related to ER stress, as well as p47phox and p67phox in the kidney, were measured by Western blot. Intracellular ROS generation was evaluated by 2′7′-dichlorofluorescin diacetate fluorescence and ELISA kits. Results: Rats that received Aldo + 1% NaCl exhibited severe renal injury. ROS levels were higher in Aldo-infused rats and were inhibited by NAC. Renal cortical protein levels of GRP78, GRP94, CHOP, ATF-4, p47phox and p67phox were significantly upregulated in rats that received Aldo + 1% NaCl. Treatment with NAC significantly ameliorated the increase in the expression of these proteins. Conclusion: These data suggest that ROS and ER stress play a role in the progression of Aldo- and salt-induced renal injury.

Enhanced Antitumor Effects of Adenoviral-Mediated siRNA against GRP78 Gene on Adenosine-Induced Apoptosis in Human Hepatoma HepG2 Cells

Our previous studies show that adenosine-induced apoptosis is involved in endoplasmic reticulum stress in HepG2 cells. In this study, we have investigated whether knockdown of GRP78 by short hairpin RNA (shRNA) increases the cytotoxic effects of adenosine in HepG2 cells. The adenovirus vector-delivered shRNA targeting GRP78 (Ad-shGRP78) was constructed and transfected into HepG2 cells. RT-PCR assay was used to determine RNA interference efficiency. Effects of knockdown of GRP78 on adenosine-induced cell viabilities, cell-cycle distribution and apoptosis, as well as relative protein expressions were determined by flow cytometry and/or Western blot analysis. The intracellular Ca2+ concentration was detected by laser scanning confocal microscope. Mitochondrial membrane potential (ΔΨm) was measured by a fluorospectrophotometer. The results revealed that GRP78 mRNA was significantly downregulated by Ad-shGRP78 transfection. Knockdown of GRP78 enhanced HepG2 cell sensitivity to adenosine by modulating G0/G1 arrest and stimulating Bax, Bak, m-calpain, caspase-4 and CHOP protein levels. Knockdown of GRP78 worsened cytosolic Ca2+ overload and ΔΨm loss. Knockdown of caspase-4 by shRNA decreased caspase-3 mRNA expression and cell apoptosis. These findings indicate that GRP 78 plays a protective role in ER stress-induced apoptosis and show that the combination of chemotherapy drug and RNA interference adenoviruses provides a new treatment strategy against malignant tumors.

Galangin inhibits proliferation of hepatocellular carcinoma cells by inducing endoplasmic reticulum stress

Prolonged endoplasmic reticulum (ER) stress may activate apoptotic pathways in cancer cells. It is suggested that ER stress has the potential of enhancing tumor death in cancer therapy. Galangin, a flavonol derived from Alpinia officinarum Hance, has been shown to suppress the proliferation of hepatocellular carcinoma cells (HCC). The aim of this study was to determine whether galangin was able to induce ER stress in HepG2, Hep3B and PLC/PRF/5 cells. The proliferation of HCC was tested by MTT method. Intracellular Ca2+ levels were measured with Fluo3-AM.The proteins levels of GRP94, GRP78 and CHOP were detected by Western blot. To further understand the anti-HCC mechanism of galangin, mitogen-activated protein kinases (MAPKs) were detected. The results showed that galangin treatment induced ER stress was evidenced by increased protein levels of GRP94, GRP78 and CHOP, as well as increased free cytosolic Ca2+ concentration. ER stress inhibitor 4-PBA and CHOP siRNA blocked significantly galangin-induced ER in all three cell lines. Furtherexperiments showed that MAPKs involved in ER stress induced by galangin. In summary, galangin is identified as a stimulator of ER stress to suppress the proliferation of HCC, and may be used as a potential anti-cancer agent.

Abstract 2129: Aplidin triggers the activation of molecular components of the UPR as part of its pro-apoptotic program in tumor cells.

Abstract Aplidin (APL), a cyclic depsipeptide originally isolated from the marine tunicate Aplidium albicans and currently under phase II/III clinical trials for cancer therapy, induces oxidative stress, activation of Rac1 and phosphorylation of JNK1, which together trigger a rapid apoptotic program in tumor cells. A previously generated APL-resistant HeLa cell line (APL-R) allowed us to find out differences in protein expression with the parental HeLa cells. Among the proteins differentially expressed, several endoplasmic reticulum (ER) stress-related proteins were observed. We found decreased basal levels of BiP in HeLa APL-R, while the levels of Ero1a and phospho-eIF2a were slightly increased when compared to parental HeLa cells, indicative of a higher basal ER stress. In this work, we investigated if APL was inducing a bona fide ER stress in HeLa cells and whether this process was essential in the mechanism of action of the compound. Similarly to that observed with thapsigargin and tunicamycin, two well known ER stress inducing agents, APL triggered the activation of several key molecular components of a classical ER stress induced unfolded protein response (UPR), including the phosphorylation of eIF2a and JNK1, the proteolitic processing of ATF6 and the alternative splicing of XBP1, but not others, such as the accumulation of noxa or the proteolitic activation of caspase 4. Interestingly, although the eIF2a phosphorylation induced by APL in HeLa wt cells correlated with a strong inhibition of protein synthesis, it did not elicit an increased expression of CHOP, a transcription factor involved in the launch of UPR mediated apoptosis. Actually, it was observed a clear reduction of CHOP protein levels after the treatment of HeLa cells with APL, most probably due to its rapid degradation by the proteasome machinery. In summary, as a part of the proapoptotic program triggered by APL in HeLa cells, we observed the induction of ER stress and the activation of several endpoint executioners of the UPR apoptotic branch. Citation Format: Alejandro Losada, Juan F. Martínez-Leal, Alberto Bejarano, Carmen Cuevas, Luis F. Garcia-Fernández, Carlos M. Galmarini. Aplidin triggers the activation of molecular components of the UPR as part of its pro-apoptotic program in tumor cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2129. doi:10.1158/1538-7445.AM2013-2129

P32 H2S post-conditioning protect rat myocardium from ischemia reperfusion injury involved in endoplasmic reticulum stress

Background In the process of myocardial ischemia and reperfusion (I/R), hypoxia, deficient glucose, ATP depletion, calcium overload and a large number of free radicals can induce endoplasmic reticulum stress (ERS), and excessive endoplasmic reticulum stress will induce apoptosis and increase the myocardial I/R injury. Recent studies have found that the new endogenous gaseous signal molecule hydrogen sulfide (H 2 S) was involved in myocardial ischemia postconditioning and alleviated ischemia/reperfusion injury, and that exogenous H 2 S postconditioning has a protective effect on the isolated heart ischemia–reperfusion injury. However, the precise mechanism that hydrogen sulfide protect heart from myocardial I/R injury remain unclear. Our study aimed to investigate whether hydrogen sulfide protect myocardium from I/R injury by inhibiting the I/R-induced excessive endoplasmic reticulum stress in rat heart. Methods Sprague–Dawley rats were randomly divided into 5 groups ( n = 12 in each): Sham group, I/R group, I/R + NaHS (sodium hydrosulfide, an H 2 S donor) groups (H 2 S post-conditioning group), I/R + TUDCA (Tauro Ursodesoxy Cholic Acid, an endoplasmic reticulum stress blocker) group and I/R + TUDCA + NaHS group. NaHS 14 μmol/kg and TUDCA 25 mg/kg were injected i.p. after 30 min of myocardial ischemia and within reperfusion 10 min. The myocardial I/R rats were subjected to ischemia by 30 min of coronary artery branch of left anterior descending occlusion followed by 2 h of reperfusion. During myocardial I/R, electrocardiogram (ECG, lead II) was monitored continuously, arrhythmias rating was assessed according to the standard of Lambeth meeting. At the end of the reperfusion, myocardial infarct size was examined by triphenyltetrazolium chloride (TTC) staining, serum concentration of H 2 S was determined with a spectrophotometer, myocardial apoptosis was detected by TUNEL and the protein levels of GRP78, CHOP were assayed by Western blotting. Results Compared with the Sham group, the H 2 S concentration in the serum of the I/R group was significantly decrease ( p p p 2 S concentrations of I/R + NaHS group were significantly increased ( p 2 S into rat/H 2 S post-conditioning could decrease the arrhythmia score and reduce myocardial infarct size significantly. The apoptotic rate was also decreased by exogenous H 2 S post-conditioning. The decrease of GRP78 and CHOP protein level in I/R could be partly reversed by H 2 S post-conditioning ( p Conclusions NaHS postconditioning could protect rat myocardiocytes from myocardial ischemia–reperfusion injury partly by inhibition of H 2 S on excessive endoplasmic reticulum stress induced by myocardiac ischemia/reperfusion.

Abstract 22: Calpain-Dependent Induction of Endoplasmic Reticulum Stress in Cardiomyocyte Apoptosis and Post--Myocardial Infarction Remodeling

Background: Calpain is up-regulated and implicated in cardiomyocyte apoptosis and myocardial remodelling post myocardial infarction. Endoplasmic reticulum (ER) stress is induced and contributes to myocardial injury in a variety of cardiac diseases. This study was to investigate whether calpain plays a role in ER stress, thereby mediating apoptosis in cardiomyocytes and myocardial remodelling after infarction. Methods and Results: In rat cardiomyoblasts H9C2 cells, over-expression of calpain-1 increased the protein levels of Bip and CHOP, indicative of ER stress, and induced apoptosis determined by a decrease in Bcl-2 and increases in caspase-3 activation and DNA fragmentation. Inhibition of calpain activity or ER stress prevented apoptosis induced by calpain-1 over-expression. In contrast, over-expression of calpain-2 failed to induce apoptosis. The induction of ER stress by calpain-1 might be mediated through SERCA2a/Calcium signaling as up-regulation of calpain-1 reduced SERCA2a protein and elevated intracellular free Calcium in H9C2 cells. In a mouse model of myocardial infarction induced by coronary artery ligation, calpain activity was increased and ER stress was induced in the infracted heart. Up-regulation of calpastatin, the endogenous calpain inhibitor, inhibited calpain activation, prevented ER stress and apoptosis, reduced myocardial remodelling and improved myocardial function after infarction in calpastatin transgenic mice compared with their wild-type littermates. Conclusion: Calpain-1 induces ER stress through the proteolysis of SERCA2a, thereby mediating apoptosis in cardiomyocytes. Inhibition of calpain prevents ER stress and apoptosis, reduces myocardial remodelling and dysfunction after infarction. Thus, ER stress may represent a novel mechanism by which calpain mediates myocardial injury in the infracted heart.

Effect of auranofin on oxidative and endoplasmic reticulum stress as well as anti-CLL activity with proteasome inhibitor.

e13568 Background: The gold-containing compound auranofin (AF) (Ridaura), is a treatment of rheumatoid arthritis. Recently, AF was shown to inhibit thioredoxin reductase (TRR), increase reactive oxygen species (ROS) and induce apoptosis in cancer cells. Methods: We determined the ability of AF (250 to 1000 nM) to induce oxidative, proteotoxic and lethal endoplasmic reticulum (ER) stress in CD19+ primary CLL cells, including those with deletion of chromosome 17p. Results: Treatment with AF induced 20 to 40% increase in ROS levels, decreased TRR activity (mean of 45%), but not its protein expression, in CLL cells. AF-mediated oxidative stress induced NRF2 activity with increase in hemeoxygenase-1 (HO-1) and glutamate cysteine ligase modifier (GCLM) levels. AF induced ER stress, associated with increase in GRP78 and the pro-apoptotic transcription factor CHOP protein levels. AF also induced the pro-apoptotic BH3-only domain protein BIM. Exposure to AF increased the intracellular levels of misfolded polyubiquitylated proteins. This disrupted the binding of heat shock protein (hsp) 90 with histone deacetylase 6 (HDAC6), resulting in hyperacetylation and inhibition of the chaperone function of hsp90. This led to proteasomal degradation of CLL-relevant hsp90 client proteins, including ZAP70, c-Raf and AKT. Nuclear STAT3 levels also declined. Exposure to AF induced significantly more apoptosis (range 40 to 60%) in primary CLL cells, as compared to CD19+ normal B cells and CD34+ human cord blood and bone marrow progenitor cells (&lt; 15% apoptosis) (p &lt; 0.01). AF treatment also induced apoptosis in CD19+ cells from patients with poor prognosis CLL with deletion of 17p or with deletion of 13q. Co-treatment with AF and the proteasome inhibitor carfilzomib or the GCLM antagonist buthionine sulfoximine (BSO) synergistically induced apoptosis in primary CLL cells. A FDA IND-supported phase II clinical trial of AF (6 to 9 mg PO/day) with correlative biomarker analysis (as above) is underway and three patients are enrolled. Conclusions: These findings support the full evaluation of clinical activity and predictive biomarkers of response to the re-purposed AF in patients with CLL.

Autophagy regulates endoplasmic reticulum stress in ischemic preconditioning

Recent studies have suggested that autophagy plays a prosurvival role in ischemic preconditioning (IPC). This study was taken to assess the linkage between autophagy and endoplasmic reticulum (ER) stress during the process of IPC. The effects of IPC on ER stress and neuronal injury were determined by exposure of primary cultured murine cortical neurons to 30 min of OGD 24 h prior to a subsequent lethal OGD. The effects of IPC on ER stress and ischemic brain damage were evaluated in rats by a brief ischemic insult followed by permanent focal ischemia (PFI) 24 h later using the suture occlusion technique. The results showed that both IPC and lethal OGD increased the LC3-II expression and decreased p62 protein levels, but the extent of autophagy activation was varied. IPC treatment ameliorated OGD-induced cell damage in cultured cortical neurons, whereas 3-MA (5–20 mM) and bafilomycin A1 (75–150 nM) suppressed the neuroprotection induced by IPC. 3-MA, at the dose blocking autophagy, significantly inhibited IPC-induced HSP70, HSP60 and GRP78 upregulation; meanwhile, it also aggregated the ER stress and increased activated caspase-12, caspase-3 and CHOP protein levels both in vitro and in vivo models. The ER stress inhibitor Sal (75 pmol) recovered IPC-induced neuroprotection in the presence of 3-MA. Rapamycin 50–200 nM in vitro and 35 pmol in vivo 24 h before the onset of lethal ischemia reduced ER stress and ischemia-induced neuronal damage. These results demonstrated that pre-activation of autophagy by ischemic preconditioning can boost endogenous defense mechanisms to upregulate molecular chaperones, and hence reduce excessive ER stress during fatal ischemia.

Rottlerin induces apoptosis of HT29 colon carcinoma cells through NAG-1 upregulation via an ERK and p38 MAPK-dependent and PKC δ-independent mechanism

Rottlerin, a selective inhibitor of novel isoforms of protein kinase C δ (PKC δ), has been shown to exert multiple effects on cancer cells, including inhibition of cell proliferation and migration. However, the molecular mechanisms responsible for these effects are not fully understood. We found that rottlerin dramatically induced non-steroidal anti-inflammatory drug activated gene-1 (NAG-1) expression in both p53 wild-type and p53-null cancer cell lines, suggesting that NAG-1 upregulation is a common response to rottlerin that occurs independently of p53 in multiple cell lines. Although rottlerin is known to inhibit PKC δ, PKC δ siRNA and overexpression of dominant-negative (DN)-PKC δ did not affect rottlerin-mediated induction of NAG-1. These results suggest that rottlerin induces NAG-1 upregulation via a PKC δ-independent pathway. We also observed that CHOP protein levels were significantly increased by rottlerin, but CHOP siRNA did not affect rottlerin-induced NAG-1 expression. In addition, we demonstrated the involvement of the mitogen-activated protein kinase (MAP kinase) signal transduction pathway in rottlerin-induced NAG-1 expression. Inhibitors of MEK (PD98059) and p38 MAP kinase (SB203580) prevented rottlerin-induced NAG-1 expression. Furthermore, we found that down-regulation of NAG-1 attenuated rottlerin-induced apoptosis. Collectively, the results of this study demonstrate, for the first time, that upregulation of NAG-1 contributes to rottlerin-induced apoptosis in cancer cells.

Valproate protects the retina from endoplasmic reticulum stress-induced apoptosis after ischemia–reperfusion injury

Valproate (VPA) is commonly used in the treatment of bipolar disorder and epilepsy. The mechanism underlying its clinical efficacy is complicated, including its ability to inhibit histone deacetylase (HDAC). Here, we show that VPA promoted endoplasmic reticulum (ER) chaperone expression and attenuated ER-induced apoptosis after ischemia/reperfusion (I/R) injury in retina. Male Wistar rats were randomly divided into four groups: sham (group A), sham+VPA (group B), I/R+vehicle (group C), and I/R+VPA (group D). VPA was administered subcutaneously at 300mg/kg twice daily before insult. Morphological changes were analyzed on stained histological sections and flat-mounted retinas labeled by Fluoro-gold. Western blot analysis was used to determine protein levels of GRP78, CHOP, caspase-12 and acetylation of histone H3 in each group. In group C, the severe retinal damage was shown in histological sections, however, the damage was reduced by VPA in group D. Significant loss of retinal ganglion cells (RGCs) was observed in group C, whereas, the density of RGCs was significantly higher in group D at 7days post-insult. VPA increased GRP78 expression and acetylation of histone H3, attenuated upregulation of CHOP and activation of caspase-12 in group D. Our results suggest that VPA can protect ischemic retinas from ER stress-induced apoptosis by mechanisms that may involve HDAC inhibition.

Contrasting apoptotic responses of conjugated linoleic acid in the liver of obese Zucker rats fed palm oil or ovine fat

We hypothesized that reducing weight properties of conjugated linoleic acid (CLA) are due to adipocyte apoptosis and that CLA differentially modulates the apoptotic responses in hepatic lipotoxicity from rats fed saturated fat diets. Obese Zucker rats were fed atherogenic diets (2% w/w of cholesterol) formulated with high (15% w/w) saturated fat, from vegetable or animal origin, supplemented or not with 1% of a mixture (1:1) of cis-9, trans-11 and trans-10, cis-12 CLA isomers for 14 weeks. CLA induced no changes on retroperitoneal fat depot weight, which was in line with similar levels of apoptosis. Interestingly, CLA had a contrasting effect on cell death in the liver according to the dietary fat. CLA increased hepatocyte apoptosis, associated with upregulation of Fas protein in rats fed palm oil, compared to rats receiving palm oil alone. However, rats fed ovine fat alone displayed the highest levels of hepatic cell death, which were decreased in rats fed ovine fat plus CLA. This reducing effect of CLA was related to positively restoring endoplasmic reticulum (ER) ATF-6α, BiP and CHOP protein levels and increasing phosphorylated c-Jun NH 2-terminal kinase (JNK) and c-Jun, thus suggesting an adaptive response of cell survival. These findings reinforce the role of CLA as regulator of apoptosis in the liver. Moreover, the dietary fat composition is a key factor in activation of apoptosis.