High Endoplasmic Reticulum Stress Research Articles

Prdx6 is required to protect human corneal epithelial cells against ultraviolet B injury.

The protective role of Prdx6 on rat corneal tissue against ultraviolet B injury in vivo has been confirmed previously. We further investigated the function and molecular mechanism of Prdx6 in human corneal epithelial cells under ultraviolet B radiation. The experimental groups were designed as follows: (1) Prdx6 RNAi, (2) Prdx6 RNAi + ultraviolet B radiation, (3) normal human corneal epithelial cells, (4) normal human corneal epithelial cells + ultraviolet B radiation, (5) wild-type Prdx6 overexpression, (6) wild-type Prdx6 overexpression + ultraviolet B radiation, (7) mutant-type Prdx6 overexpression, and (8) mutant-type Prdx6 overexpression + ultraviolet B radiation. The cell survival rate was detected by a Thiazolyl Blue Tetrazolium Bromide assay. Apoptosis, reactive oxygen species, and malondialdehyde were detected with a commercial kit. Gene expression was detected by real-time polymerase chain reaction. We found the following results. (1) Compared to normal cells, the survival rates were 32%, 87%, and 58% under ultraviolet B radiation in the Prdx6 interference, wild-type overexpression, and mutant-type overexpression groups, respectively. The survival rates were decreased to 50% at 24 h and 31% at 48 h when the phospholipase A2 activity of Prdx6 was inhibited after ultraviolet B radiation. (2) Apoptosis, reactive oxygen species content, and malondialdehyde levels were increased when Prdx6 was downregulated. This phenomenon became more severe under ultraviolet B radiation. (3) The expression levels of apoptosis-related and antioxidant genes all changed along with the changes in expression of Prdx6. (1) Both peroxidase and phospholipase A2 activities of Prdx6 are crucial for its protective role in corneal tissue. (2) Downregulated expression of Prdx6 resulted in high endoplasmic reticulum stress. (3) Apoptosis in human corneal epithelial cells with downregulated Prdx6 coupled with ultraviolet B radiation was related to the pathways of DNA damage and the death receptor. (4) Low levels of antioxidants are sufficient for maintaining homeostasis in human corneal epithelial cells without external stimuli. Under the condition that Prdx6 was downregulated, human corneal epithelial cells were more sensitive to ultraviolet B radiation.

Tauroursodeoxycholic acid (TUDCA) enhanced intracytoplasmic sperm injection (ICSI) embryo developmental competence by ameliorating endoplasmic reticulum (ER) stress and inhibiting apoptosis.

The objective of this study was to examine the effect of tauroursodeoxycholic acid (TUDCA) on intracytoplasmic sperm injection (ICSI) embryos by evaluating endoplasmic reticulum (ER) stress, apoptosis, and embryo developmental competence in vitro and in vivo. ER stress-associated genes and apoptosis-associated genes were measured and apoptosis index was analyzed. Embryo developmental competence was assessed in vitro and in vivo via the inner cell mass (ICM)/trophectoderm (TE) index, pregnancy and implantation rates, and birth rate. The relative mRNA and protein expression of binding immunoglobulin protein (BIP) was significantly higher in the ICSI embryo group without TUDCA treatment (ICSI-C) than in the in vitro fertilization (IVF) group and in the ICSI embryo group with TUDCA treatment (200 μM) (ICSI-T), while TUDCA ameliorated ER stress in ICSI embryos. Embryos in the ICSI-C group showed a higher apoptosis index than those in the IVF group and ICSI-T group, and there was no significant difference between the IVF group and ICSI-T group. TUDCA can significantly improve ICSI embryo developmental competence in vitro and in vivo based on the ICM/TE index, pregnancy and implantation rates, and birth rate. ICSI embryos manifested high ER stress and high apoptosis, while TUDCA ameliorated ER stress and reduced apoptosis in ICSI embryos. TUDCA can significantly improve the developmental competence of ICSI embryos in vitro and in vivo. This study provides a new idea for improving the efficiency of ICSI, and it will also have a positive effect on the development of assisted reproduction technologies for humans and other animals.

Single-Cell Mapping of Stress Response and Cell Death Pathways in Acute Myeloid Leukemia Reveals Stressor-Specific Alterations and Distinct Response Patterns

Single-Cell Mapping of Stress Response and Cell Death Pathways in Acute Myeloid Leukemia Reveals Stressor-Specific Alterations and Distinct Response Patterns

Myeloma Derived Extracellular Vesicles Containing Endoplasmic Reticulum Remodel the Bone Marrow Microenvironment Towards a Pro-Tumoral Senescent Phenotype

Multiple myeloma (MM) is a tumor characterised by the generation of large quantities of immunoglobulin which undergoes protein folding and secretion through the endoplasmic reticulum (ER). Many studies have shown that primary MM cells have high ER stress (Lee et al, 2003 PNAS, Obeng et al 2006 Blood and Mimura et al, 2012 Blood,). Moreover, it has also been shown that serum from MM contains significantly more extracellular vesicles (EVs) than serum from normal patients (Caivano et al, 2015 Tumour Biol). Here we explore if these two observations are connected and determine whether primary MM cells export ER inside EVs and the impact this has on the tumor microenvironment. Primary MM and primary MM bone marrow stromal cells (BMSC) were isolated from the bone marrow of patients. To determine if MM secrete ER inside EV, patient derived MM and MM cell lines were transduced with rLV.EF.mCherry-ER lentivirus which fluorescently tags the ER. High-resolution imaging combined with image cytometry shows that CD38+ vesicles containing ER are formed by budding from the MM cell surface. Analysis of MM derived EVs using a combination of proteomics, confocal microscopy, image cytometry and dynamic light scattering shows that MM actively export ER in the large EVs, approximately 0.6micron-1.5micron in diameter. To track the recipient cell for large EV packaged ER in vivo, U266 MM cell line (transduced with rLV.EF.mCherry-ER9 lentivirus) was injected into the tail of NSG mice. BM was extracted from engrafted mice and various cell populations were analysed for increases in mCherry fluorescence, as evidence of MM derived ER uptake. Murine CD45-/CD31-Ter119-/CD105+/CD140a+ BMSC had increased mCherry fluorescence but not F4/80+/GR1-/CD115int BM macrophages or CD45-/Ter119-/CD31+ endothelial cells or CD45+ leukocytes. Two proteins detected at high levels in the proteomics analysis of large EV were endoplasmic reticulum oxidoreductin 1 (ERO1) and protein disulfide-isomerase (P4B4) which functionally catalyze the formation, breakage and rearrangement of disulfide bonds resulting in the production of superoxide. Next, we analysed large EVs containing ER for superoxide. MM derived ER+ and ER- large EVs were isolated by sorting for mCherry fluorescence (MM transduced with rLV.EF.mCherry-ER9 lentivirus) and Amplex Red assay confirmed that ER+ large EVs had increased levels of H2O2. In vivo analysis of the BMSC from MM engrafted NSG mice confirmed high oxidative stress as measured by increased H2DCFDA fluorescence. To determine the impact of MM derived ER containing EVs on the function of the BMSC isolated ER containing EVs were incubated with BMSC repeatedly for up to 7 days and senescent markers were assessed. Beta-galactosidase staining, p16ink4a gene expression and a senescence associated secretary phenotype (SASP) were all upregulated in BMSC cultured with MM derived ER+ large EV and not ER- large EV. To determine if MM induced BMSC senescence in vivo we injected U266 and primary MM into NSG mice, humanised NSG mice were used as a control. Post MM engraftment, animals were sacrificed and BMSC were isolated by cell sorting for CD45-/CD31-Ter119-/CD105+/CD140a+ cells and senescent markers were analysed by real-time PCR. p16ink4a and p21 were both upregulated in BMSC from U266 and primary MM engrafted NSG mice and not from humanised NSG mice. Knockdown of p16 in BMSC prevents ER+ large EV from inducing a SASP and conditioned media had no effect on MM proliferation compared to conditioned media from ER+ large EV treated BMSC. Finally, we used an NSG mouse model whereby we transplanted p16ink4a KD BMSC or control KD BMSC with MM cells subcutaneously into the flank. MM combined with p16ink4a KD BMSC has reduced tumor volume compared with animals with control KD BMSC. Data indicates that MM secrete ER in large EV and that MM derived EVs containing ER function as a signal which then changes the physiology of BMSC, towards a senescent phenotype which in turn promotes malignant plasma cell survival and proliferation. Disclosures Bowles: Janssen: Research Funding; Abbvie: Research Funding. Rushworth:Abbvie: Research Funding; Janssen: Research Funding.

SAT-550 High Fat Diet-Induced ER Stress Affects Hypothyroidism

Recent studies revealed the emerging role of excess uptake of lipids in the development of hypothyroidism. Both dietary high-fat lard intake in rats and diet-induced obese mice displayed thyroid hypofunction (1,2). However, the underlying mechanism is largely unknown. We investigated the effect of high fat diet (HFD) on thyroid function and the role of endoplasmic reticulum (ER) in HFD induced hypothyroidism. Male Sprague Dawley rats were fed with HFD or control diet (CD) for 18 weeks. HFD rats showed increased serum TSH (n=15-16) and decreased T4 (n=15-16) compared to CD rats. Thyroid function was also evaluated by thyroid radioiodine uptake for 24 hours in vivo. Consistently, HFD decreased thyroid iodine uptake (-60%, n=5). To understand the molecular mechanism, we assessed the expression of proteins critical to thyroid production via Western blotting. Compared to CD, HFD rats showed significantly decreased thyroglobulin (Tg) (-40%, n=4), whereas TPO and NIS showed no difference. Meanwhile, luminal swelling of ER in thyroid epithelial cell of HFD rats was observed via transmission electron microscopy. Furthermore, We found PERK/eIF2a/ATF4 -- one of three traditional UPR pathways triggered under ER stress -- was activated in HFD rat thyroid glands compared to CD (n=4). In vitro, ER stress was induced in primary human thyrocytes by palmitate. Under the treatment of palmitate, Tg was degraded more rapidly than the control, indicating the activating of the ER-associated protein degradation pathway under ER stress. In addition, alleviation of ER stress by applying 4-phenyl butyric acid (4-PBA) in HFD rats or by the withdrawal of HFD improved the decrease of Tg (n=4-6) and thyroid function (n=3-6). In conclusion, we demonstrate that ER stress mediates the HFD induced hypothyroidism, probably by impairing the production of Tg, and attenuation of ER stress improves thyroid function. Reference: (1) Shao et al., Acta Pharmacol Sin 2014, 35: 1411-1420. (2) Lee et al., Endocrinology 2015, 156: 1181-1193. Conflict of interest: The authors declare they have no conflicts of interest. Sources of Research Support: National Natural Science Foundation of China (81430020, 81230018, 81600604, 81300644, and 81670720) and the Natural Science Foundation of Shandong Province (ZR2016HB07).

High Glucose Inhibits Neural Stem Cell Differentiation Through Oxidative Stress and Endoplasmic Reticulum Stress.

Maternal diabetes induces neural tube defects by suppressing neurogenesis in the developing neuroepithelium. Our recent study further revealed that high glucose inhibited embryonic stem cell differentiation into neural lineage cells. However, the mechanism whereby high glucose suppresses neural differentiation is unclear. To investigate whether high glucose-induced oxidative stress and endoplasmic reticulum (ER) stress lead to the inhibition of neural differentiation, the effect of high glucose on neural stem cell (the C17.2 cell line) differentiation was examined. Neural stem cells were cultured in normal glucose (5 mM) or high glucose (25 mM) differentiation medium for 3, 5, and 7 days. High glucose suppressed neural stem cell differentiation by significantly decreasing the expression of the neuron marker Tuj1 and the glial cell marker GFAP and the numbers of Tuj1+ and GFAP+ cells. The antioxidant enzyme superoxide dismutase mimetic Tempol reversed high glucose-decreased Tuj1 and GFAP expression and restored the numbers of neurons and glial cells differentiated from neural stem cells. Hydrogen peroxide treatment imitated the inhibitory effect of high glucose on neural stem cell differentiation. Both high glucose and hydrogen peroxide triggered ER stress, whereas Tempol blocked high glucose-induced ER stress. The ER stress inhibitor, 4-phenylbutyrate, abolished the inhibition of high glucose or hydrogen peroxide on neural stem cell differentiation. Thus, oxidative stress and its resultant ER stress mediate the inhibitory effect of high glucose on neural stem cell differentiation.

Endoplasmic Reticulum Stress Drives High Selenium‐Induced Endothelial Dysfunction

BackgroundSelenium is an essential trace element important to human health. Nonetheless, supra‐nutritional selenium intake is reported to be associated with insulin resistance and may therefore increase the risk of diabetes and disrupt endothelial function (ED), the initial step in atherosclerosis development. However, the underpinning molecular mechanisms are not clear. High selenium concentrations cause apoptosis in cancer cells through the induction of endoplasmic reticulum (ER) stress, a mechanism also involved in the pathogenesis of ED. Therefore, we hypothesised here that high selenium intake could cause ED through the activation of ER stress response.MethodsHuman Umbilical Vein Endothelial Cells (HUVECs) were cultured with selenite at either physiological (0.5μM) or supra‐nutritional concentrations (5–20μM) for 8 to 24 hours in the presence or absence of a chemical chaperone, 4‐phenylbutryic acid (PBA). Then, mRNA expression of key ER stress response markers was analysed by qPCR. To assess endothelial function, we evaluated NO (Griess assay) release and Reactive Oxygen Species (ROS, flow cytometry) production. Finally, apoptosis (flow cytometry) and caspases 3/7 activity were measured.ResultsHigh selenium concentrations (5–20μM of selenite) compared to physiological concentration (0.5μM) or control enhanced mRNA expression of several ER stress markers such as CAAA/enhanced‐binding homologous protein (CHOP) [control (2.25±0.88), 0.5 μM (3.9±0.85), 10μM (36.2±6); n=5]. The pre‐incubation of cells with PBA completely reversed high selenium‐mediated ER stress. High selenite (5–20μM) also reduced NO production [control (2.27±0.07), 0.5μM (2.4±0.04), 10μM (1.8±0.05); n=5] and enhanced ROS production [control (18.9±1.93), 0.5μM (21.7±2.14), 10μM (68±0.65); n=5] compared to physiological concentration of selenite while cells pre‐treated with PBA were fully protected. Finally, supra‐nutritional concentrations of selenite increased the percentage of apoptotic HUVECs [control (2.96%±0.94), 0.5μM (3.92%±0.85), 10μM (43.7%±5.1); n=7] and augmented caspases 3/7 activity [0.5μM (0.45±0.08), 5μM (1.92±0.3) fold of control; n=5] compared to physiological concentration. Importantly, pre‐treatment of cells with PBA completely reversed high selenium‐mediated cell death.ConclusionsWe show here that high selenium treatment causes ED and cell death through the activation of ER stress. These results highlight the importance of a balanced selenium intake in order to achieve maximal health benefits. These findings underscore the importance to monitor cardiovascular risk development in cancer patients supplemented with high amounts of selenium as part of their chemotherapeutic intervention.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Low dose Naltrexone for induction of remission in inflammatory bowel disease patients

BackgroundAround 30% of patients with inflammatory bowel disease (IBD) are refractory to current IBD drugs or relapse over time. Novel treatments are called for, and low dose Naltrexone (LDN) may provide a safe, easily accessible alternative treatment option for these patients. We investigated the potential of LDN to induce clinical response in therapy refractory IBD patients, and investigated its direct effects on epithelial barrier function.MethodsPatients not in remission and not responding to conventional therapy were offered to initiate LDN as a concomitant treatment. In total 47 IBD patients prescribed LDN were followed prospectively for 12 weeks. Where available, endoscopic remission data, serum and biopsies were collected. Further the effect of Naltrexone on wound healing (scratch assay), cytokine production and endoplasmic reticulum (ER) stress (GRP78 and CHOP western blot analysis, immunohistochemistry) were investigated in HCT116 and CACO2 intestinal epithelial cells, human IBD intestinal organoids and patient samples.ResultsLow dose Naltrexone induced clinical improvement in 74.5%, and remission in 25.5% of patients. Naltrexone improved wound healing and reduced ER stress induced by Tunicamycin, lipopolysaccharide or bacteria in epithelial barriers. Inflamed mucosa from IBD patients showed high ER stress levels, which was reduced in patients treated with LDN. Cytokine levels in neither epithelial cells nor serum from IBD patients were affected.ConclusionsNaltrexone directly improves epithelial barrier function by improving wound healing and reducing mucosal ER stress levels. Low dose Naltrexone treatment is effective and safe, and could be considered for the treatment of therapy refractory IBD patients.

NGF Attenuates High Glucose-Induced ER Stress, Preventing Schwann Cell Apoptosis by Activating the PI3K/Akt/GSK3β and ERK1/2 Pathways.

Diabetic peripheral neuropathy (DPN) is one of the most common and troublesome complications of diabetes mellitus. It has been demonstrated that nerve growth factor (NGF) exerts a pivotal role in the regulation of neuronal growth and the promotion of DPN recovery. However, the exact molecular mechanisms are not well understood. Recent studies have indicated that as a novel therapeutic target, endoplasmic reticulum (ER) stress participates in the onset and progression of DPN. In the present study, it has been demonstrated that NGF prevents the sciatic nerve from degeneration and demyelination in DPN rats. Thus, RSC 96 cells, which retain the characteristic features of Schwann cells (SCs), were cultured in medium containing 30mM glucose (high glucose, HG) to mimic SCs in DPN mice. The 50-ng/ml dose of NGF was identified to be the optimal concentration for treating an excessive ER stress level under HG conditions for 24h. We found that NGF treatment significantly inhibits HG-induced ER stress and subsequently suppresses ER-related apoptosis. Further, NGF administration also activates the upstream signaling pathway of ER stress, PI3K/Akt/GSK3β signaling and ERK1/2 signaling. Co-treatment with the PI3K inhibitor LY294002 or ERK1/2 inhibitor U0126 significantly reverses the protective role of NGF on HG-induced excessive ER stress and subsequent apoptosis. These observations suggest that the neuroprotective role of NGF in DPN is mediated by the inhibition of excessive ER stress via the activation of the PI3K/Akt/GSK3β and ERK1/2 signaling pathways.

Involvement of endoplasmic reticulum stress and neurite outgrowth in the model mice of autism spectrum disorder

Neurodevelopmental disorders are congenital impairments, impeding the growth and development of the central nervous system. These disorders include autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder in Diagnostic and Statistical Manual of Mental Disorders-5. ASD is caused by a gene defect and chromosomal duplication. Despite numerous reports on ASD, the pathogenic mechanisms are not clear. The optimal methods to prevent ASD and to treat it are also not clear. Other studies have reported that endoplasmic reticulum (ER) stress contributes to the pathogenesis of neurodegenerative diseases. In this study, we have investigated ER stress condition and neuronal maturation in an ASD mice model employing male ICR mice.An ASD mice model was established by injecting with valproic acid (VPA) into pregnant mice. The offspring born from VPA-treated mothers were subjected to the experiments as the ASD model mice. The cerebral cortex and hippocampus of ASD model mice were found to be under high ER stress. The mRNA levels of Hes1 and Pax6 were decreased in the cerebral cortex of the ASD model mice, but not in the hippocampus. In addition, the mRNA level in Math1 was increased in the cerebral cortex. ER stress inhibited dendrite and axon extension in primary culture derived from the cerebral cortex of E14.5 mice. Furthermore, dendrite outgrowth was suppressed in primary culture derived from the cerebral cortex of ASD model mice by the same method.These results indicated the possibility that ER stress induces abnormal neuronal maturation in the embryonal cerebral cortex of ASD model mice employing male ICR mice. Therefore, ER stress may contribute to the pathogenesis of ASD.

Role of SEC62 in ER maintenance: A link with ER stress tolerance in SEC62-overexpressing tumors?

ABSTRACTAmplification of the candidate oncogene TLOC1/SEC62 in tumors correlates with reduced patient survival. The recently reported role of SEC62 as an autophagy receptor that controls endoplasmic reticulum (ER) size and function might open new scenarios for understanding the phenotypes and treat SEC62high tumors, which are characterized by high ER stress tolerance.

Heme oxygenase (HO)-1 induction prevents Endoplasmic Reticulum stress-mediated endothelial cell death and impaired angiogenic capacity

Most of diabetic cardiovascular complications are attributed to endothelial dysfunction and impaired angiogenesis. Endoplasmic Reticulum (ER) and oxidative stresses were shown to play a pivotal role in the development of endothelial dysfunction in diabetes. Hemeoxygenase-1 (HO-1) was shown to protect against oxidative stress in diabetes; however, its role in alleviating ER stress-induced endothelial dysfunction remains not fully elucidated. We aim here to test the protective role of HO-1 against high glucose-mediated ER stress and endothelial dysfunction and understand the underlying mechanisms with special emphasis on oxidative stress, inflammation and cell death.Human Umbilical Vein Endothelial Cells (HUVECs) were grown in either physiological or intermittent high concentrations of glucose for 5days in the presence or absence of Cobalt (III) Protoporphyrin IX chloride (CoPP, HO-1 inducer) or 4-Phenyl Butyric Acid (PBA, ER stress inhibitor). Using an integrated cellular and molecular approach, we then assessed ER stress and inflammatory responses, in addition to apoptosis and angiogenic capacity in these cells.Our results show that HO-1 induction prevented high glucose-mediated increase of mRNA and protein expression of key ER stress markers. Cells incubated with high glucose exhibited high levels of oxidative stress, activation of major inflammatory and apoptotic responses [nuclear factor (NF)-κB and c-Jun N-terminal kinase (JNK)] and increased rate of apoptosis; however, cells pre-treated with CoPP or PBA were fully protected. In addition, high glucose enhanced caspases 3 and 7 cleavage and activity and augmented cleaved poly ADP ribose polymerase (PARP) expression whereas HO-1 induction prevented these effects. Finally, HO-1 induction and ER stress inhibition prevented high glucose-induced reduction in NO release and impaired the angiogenic capacity of HUVECs, and enhanced vascular endothelial growth factor (VEGF)-A expression.Altogether, we show here the critical role of ER stress-mediated cell death in diabetes-induced endothelial dysfunction and impaired angiogenesis and underscore the role of HO-1 induction as a key therapeutic modulator for ER stress response in ischemic disorders and diabetes. Our results also highlight the complex interplay between ER stress response and oxidative stress.

P31 Endoplasmic reticulum stress drives high selenium induced endothelial dysfunction

Selenium is associated with insulin resistance and may therefore affect endothelial function, increasing type II diabetes and its associated cardiovascular-disease risk. However the molecular mechanisms underpinning this association are not clear. High selenium doses cause apoptosis in cancer cells through the induction of the endoplasmic reticulum (ER) stress response, a mechanism implicated in the pathogenesis of insulin resistance and endothelial dysfunction (ED). Thus we hypothesised that high selenium intake could cause ED via ER stress induction. Endothelial cells were treated with selenite (0.5–10 µM) in the presence or absence of the chemical chaperone, 4-phenylbutyric acid (PBA). Supra-nutritional concentrations (5–10 µM of selenite) but not physiological concentration (0.5 µM) of selenite induced expression of several pro-apoptotic ER stress markers; such as activating transcription factor-4 (ATF4) and X-binding box-1 (XBP–1). Griess assay showed that high selenite treatment (5–10 µM) reduced nitric oxide production. Moreover, high selenium induced the production of reactive oxygen species as shown by flow cytometry and impaired endothelial cell function as assessed by in-vitro angiogenesis assay. Interestingly, pre-incubation with PBA completely reversed these effects of high selenium suggesting ER stress drives the response to selenite. Overall, we hereby show that high selenium causes endothelial dysfunction and cell death through the activation of ER stress. These results highlight the importance of a balanced selenium intake for maximal health benefits and prevention of cardiovascular disease. These findings also indicate that cancer patients supplemented with high amounts of selenium as part of their chemotherapeutic regimen should be monitored for cardiovascular disease risk.

Effect of rosuvastatin on high glucose-induced endoplasmic reticulum stress in human umbilical vein endothelial cells.

It is well established that endothelial injury plays an essential role in atherosclerotic plaque formation. Accumulating evidence has shown that high glucose levels may detrimentally affect cultured endothelial cells through endoplasmic reticulum (ER) stress. In this study, we investigated the effect of rosuvastatin on high glucose-induced ER stress in human umbilical vein endothelial cells (HUVECs). HUVECs treated with 30 mM glucose were used to simulate high-glucose conditions, and rosuvastatin concentrations ranging from 0.1 to 10 nM were used. Cell viability was analyzed by thiazolyl blue tetrazolium bromide assay, and apoptosis rate was measured using flow cytometry. Expression of GRP78, IRE1α, XBP1s, and CHOP was quantified using western blot and real-time polymerase chain reaction. Compared to cells treated with high glucose alone, cell viability increased and apoptosis rate decreased significantly in the rosuvastatin + high-glucose groups. Furthermore, GRP78, IRE1α, XBP1s, and CHOP expression was downregulated as a result of rosuvastatin administration. These results suggest that rosuvastatin may protect HUVECs from injury induced by high glucose levels, through alleviation of ER stress.

Losing p53 loosens up ER-stress.

The endoplasmic reticulum (ER) is the central intracellular organelle responsible for proper folding, localization, and post-translational modifications of proteins in eukaryotic cells. During conditions of cellular stress, incorrectly folded proteins can accumulate in the ER and trigger the unfolded protein response (UPR), which involves the activation of signal transduction pathways designed to restore correct protein folding and recovery from ER stress [1]. In rapidly dividing tumor cells, UPR can become constitutively activated, presumably because higher levels of proliferation require increased protein synthesis [1, 2]. In addition, the tumor micro-environment is often host to additional adverse conditions including nutrient and oxygen deprivation, leading to further perturbations of ER function. Therefore, it may come as no surprise that UPR has been shown to play a crucial cytoprotective role in tumor cells [2]. We have recently unveiled an unexpected role for the tumor suppressor p53 in regulating ER function via the IRE1α/XBP1 pathway [3]. IRE1α is an ER stress sensor that activates the UPR to restore ER function and maintain cellular homeostasis. It was observed that wild-type p53 suppresses IRE1α expression and activation, while the loss of active p53 potentiates the IRE1α/XBP1 pathway, enhancing ER function [3]. This finding suggests a survival benefit for cancer cells that can inactivate p53. Because cancer cells with high protein load on the ER would need enhanced ER function to cope with constant ER stress, losing p53 function would assist tumors to grow in adverse conditions by increasing IRE1α/XBP1 pathway activation. In addition, we found that a p53 target, CDIP1, acts as a proapototic signal mediator in conditions of ER stress [4]. The CDIP1/BAP31 complex was shown to transduce ER stress-mediated apoptotic signaling to the mitochondria and activate the intrinsic apoptosis pathway, suggesting that loss of p53 function may contribute to the survival of cancer cells by enhancing ER function as well as hindering ER stress-mediated apoptosis signaling. The loss of p53 function in relation to ER stress is likely to have important consequences for the sustenance of cancer cell proliferation. Previous studies have demonstrated that the activation of p53 suppresses mTOR activity and consequently inhibits protein translation [5, 6]. The elimination of wild-type p53 function may therefore provide an opportunity for cancer cells to further promote unregulated proliferation, via elevated protein synthesis and a subsequent increase in ER function. We have revealed that wild-type p53 directly interacts with synoviolin (SYVN1) and can thereby stimulate SYVN1-dependent degradation of IRE1α. The loss of p53 disrupts SYVN1-mediated IRE1α downregulation, producing an ER stress-resistant phenotype by increased IRE1α/XBP1 pathway activity [3]. However, although the loss of p53 function facilitates enhanced ER function to manage high ER stress, this also generates an overreliance on IRE1α in cancer cells with p53 mutations. Indeed, we have found that pharmacological inhibition of IRE1α strongly suppresses protein secretion and potently induces cell death in such p53-deficient cancer cells [3]. Importantly, the IRE1α inhibitor exhibited significant inhibitory effects against p53-deficient human tumors in vivo compared to those with wild-type p53. These results illuminate an important proof-of-concept for targeting tumors with mutant p53 via inhibition of the IRE1α/XBP1 pathway. Malignant transformation occurs through a combination of oncogenic pathway activation and the loss of tumor suppression. Understanding the consequences and identifying vulnerabilities caused by such changes can provide promising opportunities to selectively target cancer cells. Mutation in the p53 gene is the most frequent genetic alteration found in human cancer and inactivation of p53 is known as one of the strongest driving factors in cancer development and chemoresistance [7]. The new finding that loss of p53 activates the IRE1α/XBP1 pathway leading to enhanced ER function broadens our understanding of how cancer cells with mutant p53 survive, and also highlights a possibility for the development of novel therapeutic strategies.

Oleanolic acid and N-acetylcysteine ameliorate diabetic nephropathy through reduction of oxidative stress and endoplasmic reticulum stress in a type 2 diabetic rat model.

Hyperglycemia-induced endoplasmic reticulum (ER) stress and oxidative stress could be causes of renal fibrosis in diabetes. Oleanolic acid (OA) naturally occurs in fruits and vegetables. It has anti-inflammatory, antihyperlipidemic and antioxidant effects. N-acetylcysteine (NAC) is a precursor of glutathione, which has a strong antioxidant effect in the body. In this study, we investigated the therapeutic effects of OA and NAC in diabetic nephropathy (DN). Otsuka Long-Evans Tokushima Fatty rats were treated with OA (100 mg/kg/day) or NAC (300 mg/kg/day) for 20 weeks by oral gavage. The OA or NAC administration increased blood insulin secretion and superoxide dismutase levels, and decreased triglycerides and urinary albumin/creatinine levels. In the kidney, the damaged renal structure recovered with OA or NAC administration, through an increase in nephrin and endothelial selective adhesion molecules and a decrease in transforming growth factor-β/p-smad2/3 and ER stress. Reactive oxygen species and ER stress were increased by high glucose and ER stress inducers in cultured mesangial cells, and these levels recovered with OA (5.0 μM) or NAC (2.5 mM) treatment. The findings in this study suggest that OA and NAC have therapeutic effects for DN through an antioxidant effect and ER stress reduction.

Reduction of p53 by knockdown of the UGT1 locus in colon epithelial cells causes an increase in tumorigenesis.

Background & AimsThe UDP-glucuronosyltransferases (UGTs) are a part of the cell machinery that protects the tissues from a toxicant insult by environmental and host cell metabolites. We investigated the mechanism behind tumor growth and UGT repression.MethodsWe initially silenced the Ugt1 locus in human colon cell lines and investigated markers and responses linked to p53 activation. To examine the role of the Ugt1 locus in p53-directed apoptosis and tumorigenesis, experiments were conducted to induce acute colon inflammation and chemically induced colon cancer in mice where we have selectively deleted the Ugt1 locus in the intestinal epithelial cells (Ugt1ΔIEC mice).ResultsKnockdown of the UGT1A proteins by RNAi in human colon cancer cells and knockout of the Ugt1 locus in intestinal crypt stem cells reduces phosphorylated p53 activation and compromises the ability of p53 to control apoptosis. Targeted deletion of intestinal Ugt1 expression in Ugt1ΔIEC mice represses colon inflammation-induced p53 production and proapoptotic protein activation. When we induced colon cancer, the size and number of the tumors were significantly greater in the Ugt1ΔIEC mice when compared with wild-type mice. Furthermore, analysis of endoplasmic reticulum (ER) stress-related markers indicated that lack of UGT1A expression causes higher ER stress in intestinal epithelial cells and tissue, which may account for the lower expression of p53.ConclusionsOur results demonstrate that UGT1A expression is required to maintain and sustain p53 activation in stress-induced colon epithelial cells and has a significant impact on p53-mediated apoptosis and tumor suppression, thus protecting the colon tissue from neoplastic transformation.

Dominant negative FADD dissipates the proapoptotic signalosome of the unfolded protein response in diabetic embryopathy.

Endoplasmic reticulum (ER) stress and caspase 8-dependent apoptosis are two interlinked causal events in maternal diabetes-induced neural tube defects (NTDs). The inositol-requiring enzyme 1α (IRE1α) signalosome mediates the proapoptotic effect of ER stress. Diabetes increases tumor necrosis factor receptor type 1R-associated death domain (TRADD) expression. Here, we revealed two new unfolded protein response (UPR) regulators, TRADD and Fas-associated protein with death domain (FADD). TRADD interacted with both the IRE1α-TRAF2-ASK1 complex and FADD. In vivo overexpression of a FADD dominant negative (FADD-DN) mutant lacking the death effector domain disrupted diabetes-induced IRE1α signalosome and suppressed ER stress and caspase 8-dependent apoptosis, leading to NTD prevention. FADD-DN abrogated ER stress markers and blocked the JNK1/2-ASK1 pathway. Diabetes-induced mitochondrial translocation of proapoptotic Bcl-2 members mitochondrial dysfunction and caspase cleavage were also alleviated by FADD-DN. In vitro TRADD overexpression triggered UPR and ER stress before manifestation of caspase 3 and caspase 8 cleavage and apoptosis. FADD-DN overexpression repressed high glucose- or TRADD overexpression-induced IRE1α phosphorylation, its downstream proapoptotic kinase activation and endonuclease activities, and apoptosis. FADD-DN also attenuated tunicamycin-induced UPR and ER stress. These findings suggest that TRADD participates in the IRE1α signalosome and induces UPR and ER stress and that the association between TRADD and FADD is essential for diabetes- or high glucose-induced UPR and ER stress.

183 Heme Oxygenase (HO)-1 Induction Prevents Endoplasmic Reticulum Stress-Mediated Endothelial Cell Death and Dysfunction

<h3></h3> Diabetes is a widely spread metabolic disorder and is intimately associated with major micro- and macro-vascular complications. Several previous studies including ours highlight the complex interplay between Endoplasmic Reticulum (ER) stress and oxidative stress in the pathogenesis of cardiovascular complications associated with obesity and diabetes. Hemeoxygenase-1 (HO-1) induction has been shown to protect against oxidative stress in diabetes, however the underlying molecular mechanisms have not yet been fully elucidated. We aim in this project to test the hypothesis that HO-1 induction will protect against high glucose-mediated ER stress and oxidative stress in endothelial cells and will enhance cell survival. Endothelial cells, EA.hy926 cell line and Human Umbilical Vein Endothelial cells (HUVECs), were cultured in physiological or high concentrations of glucose to mimic diabetic environment in the presence of cobalt protoporphyrin IX (CoPP, HO-1 inducer), 4-phenylbutyrate (PBA, chemical chaperone to inhibit ER stress), Tauroursodeoxycholic acid (TUDCA, another chemical chaperone to inhibit ER stress) or vehicle. Then, ER stress response was assessed (PCR and western blot). The productions of reactive oxygen species (ROS) and Nitric Oxide (NO) were analysed by flow cytometer and Griess assay, respectively. Furthermore, we analysed apoptosis and caspase 3/7activity in endothelial cells. Expression of inflammatory cytokines was also assessed by PCR. High glucose treatment in endothelial cells induced an increase of mRNA expression of several ER stress response markers (BIP, CHOP, ATF4) in addition to an increase in ROS production and a reduction in NO release. Interestingly, the pre-treatment of cells with TUDCA/PBA or CoPP significantly reduced high glucose-mediated ER stress and oxidative stress in cells. In addition, endothelial cells incubated with high glucose exhibited enhanced cell death and increased caspase 3/7 activity while cells pre-treated with either PBA or CoPP were partially or totally protected. The mRNA expression of inflammatory cytokine IL-6 was significantly enhanced in cells incubated with high glucose while this was completely reversed in cells pre-treated with TUDCA or CoPP. Overall, these results highlight the importance of oxidative stress both in initiating or maintaining ER stress response and in mediating ER stress-induced damage and cell death in endothelial cells. This work also underscores the therapeutic potential of HO-1 induction against hyperglycaemia-mediated endothelial dysfunction.

Toll-like Receptor 4-mediated Endoplasmic Reticulum Stress in Intestinal Crypts Induces Necrotizing Enterocolitis

The cellular cues that regulate the apoptosis of intestinal stem cells (ISCs) remain incompletely understood, yet may play a role in diseases characterized by ISC loss including necrotizing enterocolitis (NEC). Toll-like receptor-4 (TLR4) was recently found to be expressed on ISCs, where its activation leads to ISC apoptosis through mechanisms that remain incompletely explained. We now hypothesize that TLR4 induces endoplasmic reticulum (ER) stress within ISCs, leading to their apoptosis in NEC pathogenesis, and that high ER stress within the premature intestine predisposes to NEC development. Using transgenic mice and cultured enteroids, we now demonstrate that TLR4 induces ER stress within Lgr5 (leucine-rich repeat-containing G-protein-coupled receptor 5)-positive ISCs, resulting in crypt apoptosis. TLR4 signaling within crypts was required, because crypt ER stress and apoptosis occurred in TLR4(ΔIEC-OVER) mice expressing TLR4 only within intestinal crypts and epithelium, but not TLR4(ΔIEC) mice lacking intestinal TLR4. TLR4-mediated ER stress and apoptosis of ISCs required PERK (protein kinase-related PKR-like ER kinase), CHOP (C/EBP homologous protein), and MyD88 (myeloid differentiation primary response gene 88), but not ATF6 (activating transcription factor 6) or XBP1 (X-box-binding protein 1). Human and mouse NEC showed high crypt ER stress and apoptosis, whereas genetic inhibition of PERK or CHOP attenuated ER stress, crypt apoptosis, and NEC severity. Strikingly, using intragastric delivery into fetal mouse intestine, prevention of ER stress reduced TLR4-mediated ISC apoptosis and mucosal disruption. These findings identify a novel link between TLR4-induced ER stress and ISC apoptosis in NEC pathogenesis and suggest that increased ER stress within the premature bowel predisposes to NEC development.