Naphthoquinone Derivative PPE8 Induces Endoplasmic Reticulum Stress in p53 Null H1299 Cells

Endoplasmic reticulum (ER) plays a key role in synthesizing secretory proteins and sensing signal function in eukaryotic cells. Responding to calcium disturbance, oxidation state change, or pharmacological agents, ER transmembrane protein, inositol-regulating enzyme 1 (IRE1), senses the stress and triggers downstream signals. Glucose-regulated protein 78 (GRP78) dissociates from IRE1 to assist protein folding and guard against cell death. In prolonged ER stress, IRE1 recruits and activates apoptosis signal-regulating kinase 1 (ASK1) as well as downstream JNK for cell death. Naphthoquinones are widespread natural phenolic compounds. Vitamin K3, a derivative of naphthoquinone, inhibits variant tumor cell growth via oxygen uptake and oxygen stress. We synthesized a novel naphthoquinone derivative PPE8 and evaluated capacity to induce ER stress in p53 null H1299 and p53 wild-type A549 cells. In H1299 cells, PPE8 induced ER enlargement, GRP78 expression, and transient IER1 activation. Activated IRE1 recruited ASK1 for downstream JNK phosphorylation. IRE1 knockdown by siRNA attenuated PPE8-induced JNK phosphorylation and cytotoxicity. Prolonged JNK phosphorylation may be involved in PPE8-induced cytotoxicity. Such results did not arise in A549 cells, but p53 knockdown by siRNA restored PPE8-induced GRP78 expression and JNK phosphorylation. We offer a novel compound to induce ER stress and cytotoxicity in p53-deficient cancer cells, presenting an opportunity for treatment.

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Polyhexamethylene Guanidine Phosphate Induces Apoptosis through Endoplasmic Reticulum Stress in Lung Epithelial Cells

International Journal of Molecular Sciences ◽

10.3390/ijms22031215 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1215

Author(s):

Mi Ho Jeong ◽

Mi Seon Jeon ◽

Ga Eun Kim ◽

Ha Ryong Kim

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Epithelial Cell ◽

Er Stress ◽

Lung Fibrosis ◽

A549 Cells ◽

Polyhexamethylene Guanidine ◽

Lung Epithelial ◽

Epithelial Cell Death ◽

Guanidine Phosphate

Airway epithelial cell death contributes to the pathogenesis of lung fibrosis. Polyhexamethylene guanidine phosphate (PHMG-p), commonly used as a disinfectant, has been shown to be strongly associated with lung fibrosis in epidemiological and toxicological studies. However, the molecular mechanism underlying PHMG-p-induced epithelial cell death is currently unclear. We synthesized a PHMG-p–fluorescein isothiocyanate (FITC) conjugate and assessed its uptake into lung epithelial A549 cells. To examine intracellular localization, the cells were treated with PHMG-p–FITC; then, the cytoplasmic organelles were counterstained and observed with confocal microscopy. Additionally, the organelle-specific cell death pathway was investigated in cells treated with PHMG-p. PHMG-p–FITC co-localized with the endoplasmic reticulum (ER), and PHMG-p induced ER stress in A549 cells and mice. The ER stress inhibitor tauroursodeoxycholic acid (TUDCA) was used as a pre-treatment to verify the role of ER stress in PHMG-p-induced cytotoxicity. The cells treated with PHMG-p showed apoptosis, which was inhibited by TUDCA. Our results indicate that PHMG-p is rapidly located in the ER and causes ER-stress-mediated apoptosis, which is an initial step in PHMG-p-induced lung fibrosis.

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BBF2H7, a Novel Transmembrane bZIP Transcription Factor, Is a New Type of Endoplasmic Reticulum Stress Transducer

Molecular and Cellular Biology ◽

10.1128/mcb.01552-06 ◽

2006 ◽

Vol 27 (5) ◽

pp. 1716-1729 ◽

Cited By ~ 105

Author(s):

Shinichi Kondo ◽

Atsushi Saito ◽

Shin-ichiro Hino ◽

Tomohiko Murakami ◽

Maiko Ogata ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Transcription Factor ◽

Er Stress ◽

Target Genes ◽

Transmembrane Protein ◽

Late Phase ◽

Neuroblastoma Cell ◽

Bzip Transcription Factor ◽

Unfolded Proteins

ABSTRACT Endoplasmic reticulum (ER) stress transducers IRE1 (inositol requiring 1), PERK (PKR-like endoplasmic reticulum kinase), and ATF6 (activating transcription factor 6) are well known to transduce signals from the ER to the cytoplasm and nucleus when unfolded proteins accumulate in the ER. Recently, we identified OASIS (old astrocyte specifically induced substance) as a novel ER stress transducer expressed in astrocytes. We report here that BBF2H7 (BBF2 human homolog on chromosome 7), an ER-resident transmembrane protein with the bZIP domain in the cytoplasmic portion and structurally homologous to OASIS, is cleaved at the membrane in response to ER stress. The cleaved fragments of BBF2H7 translocate into the nucleus and can bind directly to cyclic AMP-responsive element sites to activate transcription of target genes. Interestingly, although BBF2H7 protein is not expressed under normal conditions, it is markedly induced at the translational level during ER stress, suggesting that BBF2H7 might contribute to only the late phase of unfolded protein response signaling. In a mouse model of focal brain ischemia, BBF2H7 protein is prominently induced in neurons in the peri-infarction region. Furthermore, in a neuroblastoma cell line, BBF2H7 overexpression suppresses ER stress-induced cell death, while small interfering RNA knockdown of BBF2H7 promotes ER stress-induced cell death. Taken together, our results suggest that BBF2H7 is a novel ER stress transducer and could play important roles in preventing accumulation of unfolded proteins in damaged neurons.

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The aryl hydrocarbon receptor reduces LC3II expression and controls endoplasmic reticulum stress

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00122.2020 ◽

2020 ◽

Author(s):

Necola Guerrina ◽

Noof Aloufi ◽

Fangyi Shi ◽

Kashmira Prasade ◽

Caitlin Mehrotra ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Aryl Hydrocarbon Receptor ◽

Cigarette Smoke ◽

A549 Cells ◽

Lung Fibroblasts ◽

Lung Cells ◽

Autophagic Flux ◽

Aryl Hydrocarbon

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor whose physiological function is poorly understood. The AhR is highly expressed in barrier organs such as the skin, intestine and lung. The lungs are continuously exposed to environmental pollutants such as cigarette smoke (CS) that can induce cell death mechanisms such as apoptosis, autophagy and endoplasmic reticulum (ER) stress. CS also contains toxicants that are AhR ligands. We have previously shown that the AhR protects against apoptosis, but whether the AhR also protects against autophagy or ER stress is not known. Using cigarette smoke extract (CSE) as our in vitro surrogate of environmental tobacco exposure, we first assessed the conversion of LC3I to LC3II, a classic feature of both autophagic and ER stress-mediated cell death pathways. LC3II was elevated in CSE-exposed lung structural cells (mouse lung fibroblasts [MLFs], MLE12 and A549 cells) when AhR was absent. However, this heightened LC3II expression could not be explained by increased expression of key autophagy genes (Gabarapl1, Becn1, Map1lc3b), upregulation of upstream autophagic machinery (Atg5-12, Atg3) or by impaired autophagic flux, suggesting that LC3II may be autophagy-independent. This was further supported by the absence of autophagosomes in Ahr-/- lung cells. However, Ahr-/- lung cells had widespread ER-dilation, elevated expression of the ER stress markers CHOP and GADD34 and an accumulation of ubiquitinated proteins. These findings collectively illustrate a novel role for the AhR in attenuating ER stress by a mechanism that may be autophagy-independent.

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5-Aminolevulinic Acid Attenuates Glucose-Regulated Protein 78 Expression and Hepatocyte Lipoapoptosis via Heme Oxygenase-1 Induction

International Journal of Molecular Sciences ◽

10.3390/ijms222111405 ◽

2021 ◽

Vol 22 (21) ◽

pp. 11405

Author(s):

Takaaki Hashimoto ◽

Takaaki Sugihara ◽

Tsutomu Kanda ◽

Tomoaki Takata ◽

Hajime Isomoto

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Heme Oxygenase ◽

Caspase 3 ◽

Aminolevulinic Acid ◽

Therapeutic Potential ◽

B Cell Lymphoma ◽

Heme Oxygenase 1 ◽

Glucose Regulated Protein

Endoplasmic reticulum (ER) stress plays a pivotal role in the progression of steatohepatitis. 5-aminolevulinic acid (5-ALA), a precursor in the heme biosynthetic pathway, has recently been reported to induce heme oxygenase (HO)-1. HO-1 exerts important cytoprotective actions. In this study, we aimed to explore the therapeutic potential of 5-ALA on palmitate-induced ER stress and lipoapoptosis. Huh-7 cells were treated with palmitic acid (PA) (800 μM) to induce steatosis for eight hours. Steatosis was evaluated by Lipi-green staining. 5-ALA (200 μM) was added with PA. The gene expression levels of the nuclear factor erythroid 2–related factor 2 (NRF2), HO-1, Glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), PKR-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1), C/EBP homologous protein (CHOP), and B-cell lymphoma 2 (BCL-2) were evaluated by RT-PCR. Caspase-3/7 activity was evaluated by fluorescein active Caspase-3/7 staining. Cell death was evaluated by Annexin V/SYTOX green staining. PA significantly induced steatosis and increased GRP78 expression in Huh-7 cells. 5-ALA significantly induced HO-1 and decreased GRP78 expression. ATF6 was subsequently decreased. However, NRF2 and CHOP expression were not altered. Anti-apoptotic BCL-2 expression significantly increased, and Caspase 3/7 activity and cell death also decreased. 5-ALA has a therapeutic potential on hepatic steatosis by suppressing ER stress and lipoapoptosis by attenuating GRP78 via HO-1 induction.

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Inhibition of Autophagy Potentiated Hippocampal Cell Death Induced by Endoplasmic Reticulum Stress and its Activation by Trehalose Failed to be Neuroprotective

Current Neurovascular Research ◽

10.2174/1567202616666190131155834 ◽

2019 ◽

Vol 16 (1) ◽

pp. 3-11

Author(s):

Luisa Halbe ◽

Abdelhaq Rami

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Cell Damage ◽

Protective Mechanism ◽

Unfolded Proteins ◽

Neuronal Viability ◽

Hippocampal Cell ◽

Trigger Cell Death ◽

Autophagy Inhibition

Introduction: Endoplasmic reticulum (ER) stress induced the mobilization of two protein breakdown routes, the proteasomal- and autophagy-associated degradation. During ERassociated degradation, unfolded ER proteins are translocated to the cytosol where they are cleaved by the proteasome. When the accumulation of misfolded or unfolded proteins excels the ER capacity, autophagy can be activated in order to undertake the degradative machinery and to attenuate the ER stress. Autophagy is a mechanism by which macromolecules and defective organelles are included in autophagosomes and delivered to lysosomes for degradation and recycling of bioenergetics substrate. Materials and Methods: Autophagy upon ER stress serves initially as a protective mechanism, however when the stress is more pronounced the autophagic response will trigger cell death. Because autophagy could function as a double edged sword in cell viability, we examined the effects autophagy modulation on ER stress-induced cell death in HT22 murine hippocampal neuronal cells. We investigated the effects of both autophagy-inhibition by 3-methyladenine (3-MA) and autophagy-activation by trehalose on ER-stress induced damage in hippocampal HT22 neurons. We evaluated the expression of ER stress- and autophagy-sensors as well as the neuronal viability. Results and Conclusion: Based on our findings, we conclude that under ER-stress conditions, inhibition of autophagy exacerbates cell damage and induction of autophagy by trehalose failed to be neuroprotective.

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Acute Tissue Injury Caused by Subcutaneous Fat Biopsies Produces Endoplasmic Reticulum Stress

Endocrine Reviews ◽

10.1210/edrv.30.7.9995 ◽

2009 ◽

Vol 30 (7) ◽

pp. 928-928

Author(s):

Guenther Boden ◽

Matthew Silviera ◽

Brian Smith ◽

Peter Cheung ◽

Carol Homko

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Tissue Injury ◽

Subcutaneous Fat ◽

Whole Body ◽

Monocyte Chemoattractant Protein 1 ◽

Homologous Protein ◽

Stress Markers ◽

Acute Tissue Injury ◽

Glucose Regulated Protein

Abstract Background It is not known whether acute tissue injury is associated with endoplasmic reticulum (ER) stress. Objective Our objective was to determine whether open, sc fat biopsies cause ER stress. Approach Five healthy subjects underwent three open sc fat biopsies. The first biopsy, taken from the lateral aspect of a thigh, was followed 4 h later by a second biopsy from the same incision site and a third biopsy from the contralateral leg. Expression markers of ER stress, inflammation, hypoxia, and adipokines were measured in these fat biopsies. In addition, we tested for signs of systemic ER stress and inflammation in plasma and in circulating monocytes. Results mRNA/18s ratios of IL-6, monocyte chemoattractant protein-1, CD-14, hypoxia-induced factor 1-α, the spliced form of Xbox protein-1, glucose-regulated protein 78, CEBP homologous protein, and activating factor-4 were all severalfold higher, whereas mRNA/18s ratios of adiponectin and leptin were lower in fat biopsies taken from the same site 4 h after the first biopsy but were unchanged in the second biopsy that was taken from the contralateral site. The biopsies were not associated with changes in plasma and monocyte IL-6 concentrations or in monocyte ER stress markers. Also, whole-body insulin-stimulated glucose uptake was the same in 15 subjects who had biopsies compared with 15 different subjects who did not. Conclusion Open, sc fat biopsies produced inflammation, hypoxia, ER stress, and decreased expression of adiponectin and leptin. These changes remained confined to the biopsy site for at least 4 h.

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c-Jun Inhibits Thapsigargin-Induced ER Stress Through Up-Regulation of DSCR1/Adapt78

Experimental Biology and Medicine ◽

10.3181/0803-rm-84 ◽

2008 ◽

Vol 233 (10) ◽

pp. 1289-1300 ◽

Cited By ~ 25

Author(s):

Peng Zhao ◽

Xiaoyan Xiao ◽

Agnes S. Kim ◽

M. Fatima Leite ◽

Jinxia Xu ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Wild Type Mouse ◽

Mouse Fibroblast ◽

Expression Levels ◽

Mouse Fibroblasts ◽

The Unfolded Protein Response ◽

Calcineurin Activity

The endoplasmic reticulum (ER) is exquisitely sensitive to changes in its internal environment. Various conditions, collectively termed “ER stress”, can perturb ER function, leading to the activation of a complex response known as the unfolded protein response (UPR). Although c-Jun N-terminal kinase (JNK) activation is nearly always associated with cell death by various stimuli, the functional role of JNK in ER stress-induced cell death remains unclear. JNK regulates gene expression through the phosphorylation and activation of transcription factors, such as c-Jun. Here, we investigated the role of c-Jun in the regulation of ER stress-related genes. c-Jun expression levels determined the response of mouse fibroblasts to ER stress induced by thapsigargin (TG, an inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase). c-jun−/− mouse fibroblast cells were more sensitive to TG-induced cell death compared to wild-type mouse fibroblasts, while reconstitution of c-Jun expression in c-jun−/− cells (c-Jun Re) enhanced resistance to TG-induced cell death. The expression levels of ER chaperones Grp78 and Gadd153 induced by TG were lower in c-Jun Re than in c-jun−/− cells. Moreover, TG treatment significantly increased calcineurin activity in c-jun−/− cells, but not in c-Jun Re cells. In c-Jun Re cells, TG induced the expression of Adapt78, also known as the Down syndrome critical region 1 (DSCR1), which is known to block calcineurin activity. Taken together, our findings suggest that c-Jun, a transcription factor downstream of the JNK signaling pathway, up-regulates Adapt78 expression in response to TG-induced ER stress and contributes to protection against TG-induced cell death.

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