scholarly journals Phlorotannins from Ecklonia cava Attenuates Palmitate-Induced Endoplasmic Reticulum Stress and Leptin Resistance in Hypothalamic Neurons

Marine Drugs ◽  
2019 ◽  
Vol 17 (10) ◽  
pp. 570 ◽  
Author(s):  
Seyeon Oh ◽  
Myeongjoo Son ◽  
Junwon Choi ◽  
Chang Hu Choi ◽  
Kook Yang Park ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Leptin Receptor ◽  
Saturated Fatty Acids ◽  
Receptor Expression ◽  
Leptin Resistance ◽  
Ecklonia Cava ◽  
Hypothalamic Neurons ◽  
Potent Effect ◽  
Stress Markers

Leptin resistance in the hypothalamus has an essential role in obesity. Saturated fatty acids such as palmitate bind to Toll-like receptor 4 (TLR4) and lead to endoplasmic reticulum (ER) stress and leptin resistance. In this study, we evaluated whether extracts of Ecklonia cava would attenuate the ER stress induced by palmitate and reduce leptin resistance in hypothalamic neurons and microglia. We added palmitate to these cells to mimic the environment induced by high-fat diet in the hypothalamus and evaluated which of the E. cava phlorotannins—dieckol (DK), 2,7-phloroglucinol-6,6-bieckol (PHB), pyrogallol-phloroglucinol-6,6-bieckol (PPB), or phlorofucofuroeckol-A (PFFA)—had the most potent effect on attenuating leptin resistance. TLR4 and NF-κB expression induced by palmitate was attenuated most effectively by PPB in both hypothalamic neurons and microglia. ER stress markers were increased by palmitate and were attenuated by PPB in both hypothalamic neurons and microglia. Leptin resistance, which was evaluated as an increase in SOCS3 and a decrease in STAT3 with leptin receptor expression, was increased by palmitate and was decreased by PPB in hypothalamic neurons. The culture medium from palmitate-treated microglia increased leptin resistance in hypothalamic neurons and this resistance was attenuated by PPB. In conclusion, PPB attenuated leptin resistance by decreasing ER stress in both hypothalamic neurons and microglia.

scholarly journals Palmitate Attenuates Insulin Signaling and Induces Endoplasmic Reticulum Stress and Apoptosis in Hypothalamic Neurons: Rescue of Resistance and Apoptosis through Adenosine 5′ Monophosphate-Activated Protein Kinase Activation

Endocrinology ◽  
2010 ◽  
Vol 151 (2) ◽  
pp. 576-585 ◽  
Author(s):  
Christopher M. Mayer ◽  
Denise D. Belsham
Keyword(s):  
Insulin Resistance ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Insulin Signaling ◽  
Caspase 3 ◽  
Saturated Fatty Acids ◽  
Amp Kinase ◽  
Hypothalamic Neurons ◽  
Peripheral Tissues ◽  
Short Term Exposure

Hypothalamic insulin signaling is essential to the maintenance of glucose and energy homeostasis. During pathological states, such as obesity and type 2 diabetes mellitus, insulin signaling is impaired. One key mechanism involved in the development of insulin resistance is lipotoxicity, through increased circulating saturated fatty acids. Although many studies have begun to determine the underlying mechanisms of lipotoxicity in peripheral tissues, little is known about the effects of excess lipids in the brain. We used a hypothalamic, neuronal cell model, mHypoE-44, to understand how the highly prevalent nonesterified fatty acid, palmitate, affects neuronal insulin signaling. Through Western blot analysis, we discerned that prolonged exposure to palmitate impairs insulin activation, as assessed by phosphorylation of Akt. We investigated the role of endoplasmic reticulum (ER) stress, which is known to promote cellular insulin resistance and apoptosis in peripheral tissues. Palmitate treatment induced ER stress through a c-Jun N-terminal kinase (JNK)-dependent pathway because a selective JNK inhibitor blocked palmitate activation of the ER stress pathways eIF2α and X-box binding protein-1. Interestingly, JNK inhibition did not prevent the palmitate-mediated cleaved caspase-3 increase, an apoptotic marker, or insulin signaling attenuation. However, pretreatment with the AMP kinase activator, aminoimidazole carboxamide ribonucleotide, blocked JNK phosphorylation and importantly prevented caspase-3 cleavage and restored insulin signaling during short-term exposure to palmitate. Thus, activation of AMP kinase prevents the deleterious effects of palmitate on hypothalamic neurons by inhibiting the onset of insulin resistance and apoptosis.

scholarly journals EGFRvIII Promotes Cell Survival during Endoplasmic Reticulum Stress through a Reticulocalbin 1-Dependent Mechanism

Cancers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1198
Author(s):  
Juliana Gomez ◽  
Zammam Areeb ◽  
Sarah F. Stuart ◽  
Hong P. T. Nguyen ◽  
Lucia Paradiso ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Viability ◽  
Er Stress ◽  
Cell Survival ◽  
Glioblastoma Cells ◽  
Over Expression ◽  
Stress Markers ◽  
Apoptotic Protein ◽  
Novel Association ◽  
Reduced Activity

Reticulocalbin 1 (RCN1) is an endoplasmic reticulum (ER)-residing protein, involved in promoting cell survival during pathophysiological conditions that lead to ER stress. However, the key upstream receptor tyrosine kinase that regulates RCN1 expression and its potential role in cell survival in the glioblastoma setting have not been determined. Here, we demonstrate that RCN1 expression significantly correlates with poor glioblastoma patient survival. We also demonstrate that glioblastoma cells with expression of EGFRvIII receptor also have high RCN1 expression. Over-expression of wildtype EGFR also correlated with high RCN1 expression, suggesting that EGFR and EGFRvIII regulate RCN1 expression. Importantly, cells that expressed EGFRvIII and subsequently showed high RCN1 expression displayed greater cell viability under ER stress compared to EGFRvIII negative glioblastoma cells. Consistently, we also demonstrated that RCN1 knockdown reduced cell viability and exogenous introduction of RCN1 enhanced cell viability following induction of ER stress. Mechanistically, we demonstrate that the EGFRvIII-RCN1-driven increase in cell survival is due to the inactivation of the ER stress markers ATF4 and ATF6, maintained expression of the anti-apoptotic protein Bcl-2 and reduced activity of caspase 3/7. Our current findings identify that EGFRvIII regulates RCN1 expression and that this novel association promotes cell survival in glioblastoma cells during ER stress.

The effect of baicalein on endoplasmic reticulum stress and autophagy on liver damage

2021 ◽  
pp. 096032712110036
Author(s):  
MC Üstüner ◽  
C Tanrikut ◽  
D Üstüner ◽  
UK Kolaç ◽  
Z Özdemir Köroğlu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Er Stress ◽  
Liver Damage ◽  
Albino Rats ◽  
Tem Analysis ◽  
Stress Markers ◽  
Activating Transcription Factor 4 ◽  
Activating Transcription Factor ◽  
Wistar Albino Rats

Carbon tetrachloride (CCl4) is a toxic chemical that causes liver injury. CCl4 triggers endoplasmic reticulum (ER) stress and unfolded protein response (UPR). UPR triggers autophagy to deal with the damage. The aim of this study was to investigate the effect of baicalein, derived from Scutellaria baicalensis, on CCl4-induced liver damage concerning ER stress and autophagy. Two groups of Wistar albino rats (n = 7/groups) were treated with 0.2 ml/kg CCl4 for 10 days with and without baicalein. Histological and transmission electron microscopy (TEM) analysis, autophagy, and ER stress markers measurements were carried out to evaluate the effect of baicalein. Histological examinations showed that baicalein reduced liver damage. TEM analysis indicated that baicalein inhibited ER stress and triggered autophagy. CCl4-induced elevation of C/EBP homologous protein (CHOP), glucose-regulating protein 78 (GRP78), activating transcription factor 4 (ATF4), activating transcription factor 6 (ATF6), inositol requiring enzyme 1 (IRE1), pancreatic ER kinase (PERK), and active/spliced form of X-box-binding protein 1 (XBP1s) ER stress markers were decreased by baicalein. Baicalein also increased the autophagy-related 5 (ATG5), Beclin1, and Microtubule-associated protein 1A/1B-light chain 3-phosphatidylethanolamine-conjugated form (LC3-II) autophagy marker levels. In conclusion, baicalein reduced the CCl4-induced liver damage by inhibiting ER stress and the trigger of autophagy.

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

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.

scholarly journals Attenuation of endoplasmic reticulum stress by caffeine ameliorates hyperoxia-induced lung injury

2017 ◽  
Vol 312 (5) ◽  
pp. L586-L598 ◽  
Author(s):  
Ru-Jeng Teng ◽  
Xigang Jing ◽  
Teresa Michalkiewicz ◽  
Adeleye J. Afolayan ◽  
Tzong-Jin Wu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Lung Injury ◽  
Er Stress ◽  
Saline Control ◽  
Sprague Dawley ◽  
Chemical Chaperone ◽  
Stress Markers ◽  
Rat Pups ◽  
Caffeine Treatment ◽  
Downstream Effectors

Rodent pups exposed to hyperoxia develop lung changes similar to bronchopulmonary dysplasia (BPD) in extremely premature infants. Oxidative stress from hyperoxia can injure developing lungs through endoplasmic reticulum (ER) stress. Early caffeine treatment decreases the rate of BPD, but the mechanisms remain unclear. We hypothesized that caffeine attenuates hyperoxia-induced lung injury through its chemical chaperone property. Sprague-Dawley rat pups were raised either in 90 (hyperoxia) or 21% (normoxia) oxygen from postnatal day 1 (P1) to postnatal day 10 (P10) and then recovered in 21% oxygen until P21. Caffeine (20 mg/kg) or normal saline (control) was administered intraperitoneally daily starting from P2. Lungs were inflation-fixed for histology or snap-frozen for immunoblots. Blood caffeine levels were measured in treated pups at euthanasia and were found to be 18.4 ± 4.9 μg/ml. Hyperoxia impaired alveolar formation and increased ER stress markers and downstream effectors; caffeine treatment attenuated these changes at P10. Caffeine also attenuated the hyperoxia-induced activation of cyclooxygenase-2 and markers of apoptosis. In conclusion, hyperoxia-induced alveolar growth impairment is mediated, in part, by ER stress. Early caffeine treatment protects developing lungs from hyperoxia-induced injury by attenuating ER stress.

scholarly journals 12/15-Lipoxygenase signaling in the endoplasmic reticulum stress response

2012 ◽  
Vol 302 (6) ◽  
pp. E654-E665 ◽  
Author(s):  
Banumathi K. Cole ◽  
Norine S. Kuhn ◽  
Shamina M. Green-Mitchell ◽  
Kendall A. Leone ◽  
Rebekah M. Raab ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Er Stress ◽  
Pancreatic Islets ◽  
High Fat Diet ◽  
Wild Type ◽  
High Fat ◽  
Stress Markers ◽  
Deficient Mice

Central obesity is associated with chronic inflammation, insulin resistance, β-cell dysfunction, and endoplasmic reticulum (ER) stress. The 12/15-lipoxygenase enzyme (12/15-LO) promotes inflammation and insulin resistance in adipose and peripheral tissues. Given that obesity is associated with ER stress and 12/15-LO is expressed in adipose tissue, we determined whether 12/15-LO could mediate ER stress signals. Addition of 12/15-LO lipid products 12(S)-HETE and 12(S)-HPETE to differentiated 3T3-L1 adipocytes induced expression and activation of ER stress markers, including BiP, XBP-1, p-PERK, and p-IRE1α. The ER stress inducer, tunicamycin, upregulated ER stress markers in adipocytes with concomitant 12/15-LO activation. Addition of a 12/15-LO inhibitor, CDC, to tunicamycin-treated adipocytes attenuated the ER stress response. Furthermore, 12/15-LO-deficient adipocytes exhibited significantly decreased tunicamycin-induced ER stress. 12/15-LO action involves upregulation of interleukin-12 (IL-12) expression. Tunicamycin significantly upregulated IL-12p40 expression in adipocytes, and IL-12 addition increased ER stress gene expression; conversely, LSF, an IL-12 signaling inhibitor, and an IL-12p40-neutralizing antibody attenuated tunicamycin-induced ER stress. Isolated adipocytes and liver from 12/15-LO-deficient mice fed a high-fat diet revealed a decrease in spliced XBP-1 expression compared with wild-type C57BL/6 mice on a high-fat diet. Furthermore, pancreatic islets from 12/15-LO-deficient mice showed reduced high-fat diet-induced ER stress genes compared with wild-type mice. These data suggest that 12/15-LO activity participates in ER stress in adipocytes, pancreatic islets, and liver. Therefore, reduction of 12/15-LO activity or expression could provide a new therapeutic target to reduce ER stress and downstream inflammation linked to obesity.

scholarly journals Possible involvement of 4-hydroxy-2-nonenal in the pathogenesis of leptin resistance in obesity

2019 ◽  
Vol 316 (5) ◽  
pp. C641-C648 ◽  
Author(s):  
Toru Hosoi ◽  
Ayaka Kuwamura ◽  
Mina Thon ◽  
Kyoji Tsuchio ◽  
Amer Ali Abd El-Hafeez ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Leptin Receptor ◽  
Neuroblastoma Cell ◽  
Initiation Factor ◽  
Leptin Resistance ◽  
Human Neuroblastoma Cell ◽  
Human Neuroblastoma ◽  
Stat3 Phosphorylation ◽  
Induced Signal

Insensitivity to the antiobesity hormone, leptin, has been suggested to be involved in the pathogenesis of obesity. However, the pathological mechanisms underlying the development of leptin resistance are not well-understood. This study aimed to examine the pathological mechanisms of leptin resistance in obesity. In the present study, we found that 4-hydroxy-2-nonenal (4-HNE), an aldehyde, may be involved in the development of leptin resistance. The SH-SY5Y-Ob-Rb human neuroblastoma cell line, transfected to express the Ob-Rb leptin receptor stably, was treated with 4-HNE, and leptin-induced signal transduction was analyzed. We found that 4-HNE dose- and time-dependently inhibited leptin-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation, a major antiobesity signal of leptin. On the other hand, 4-HNE did not affect tyrosine phosphorylation of broad cellular proteins, suggesting that the inhibitory effect may be selective to leptin signaling. Mechanistically, 4-HNE induced the eukaryotic initiation factor 2α-CCAAT/enhancer-binding protein homologous protein arm of endoplasmic reticulum stress signaling, which may be involved in the pathogenesis of leptin resistance. Overall, these results suggest that 4-HNE may partly affect endoplasmic reticulum stress-induced unfolded protein response signaling and may be involved in the pathogenesis of leptin resistance.

Modulation of palmitate-induced endoplasmic reticulum stress and apoptosis in pancreatic β-cells by stearoyl-CoA desaturase and Elovl6

2011 ◽  
Vol 300 (4) ◽  
pp. E640-E649 ◽  
Author(s):  
Christopher D. Green ◽  
L. Karl Olson
Keyword(s):  
Type 2 Diabetes ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Neutral Lipids ◽  
Saturated Fatty Acids ◽  
Mrna Levels ◽  
Β Cells ◽  
Fatty Acid Elongase ◽  
Stearoyl Coa Desaturase

Induction of endoplasmic reticulum (ER) stress and apoptosis by elevated exogenous saturated fatty acids (FAs) plays a role in the pathogenesis of β-cell dysfunction and loss of islet mass in type 2 diabetes. Regulation of monounsaturated FA (MUFA) synthesis through FA desaturases and elongases may alter the susceptibility of β-cells to saturated FA-induced ER stress and apoptosis. Herein, stearoyl-CoA desaturase (SCD)1 and SCD2 mRNA expression were shown to be induced in islets from prediabetic hyperinsulinemic Zucker diabetic fatty (ZDF) rats, whereas SCD1, SCD2, and fatty acid elongase 6 (Elovl6) mRNA levels were markedly reduced in diabetic ZDF rat islets. Knockdown of SCD in INS-1 β-cells decreased desaturation of palmitate to MUFA, lowered FA partitioning into complex neutral lipids, and increased palmitate-induced ER stress and apoptosis. Overexpression of SCD2 increased desaturation of palmitate to MUFA and attenuated palmitate-induced ER stress and apoptosis. Knockdown of Elovl6 limited palmitate elongation to stearate, increasing palmitoleate production and attenuating palmitate-induced ER stress and apoptosis, whereas overexpression of Elovl6 increased palmitate elongation to stearate and palmitate-induced ER stress and apoptosis. Overall, these data support the hypothesis that enhanced MUFA synthesis via upregulation of SCD2 activity can protect β-cells from elevated saturated FAs, as occurs in prediabetic states. Overt type 2 diabetes is associated with diminished islet expression of SCD and Elovl6, and this can disrupt desaturation of saturated FAs to MUFAs, rendering β-cells more susceptible to saturated FA-induced ER stress and apoptosis.

Palmitic Acid Increases Endothelin-1 Expression in Vascular Endothelial Cells through the Induction of Endoplasmic Reticulum Stress and Protein Kinase C Signaling

Cardiology ◽  
2018 ◽  
Vol 140 (3) ◽  
pp. 133-140 ◽  
Author(s):  
Juan Zhang ◽  
Wen-Shu Zhao ◽  
Xin Wang ◽  
Lin Xu ◽  
Xin-Chun Yang
Keyword(s):  
Endothelial Cells ◽  
Endoplasmic Reticulum ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Palmitic Acid ◽  
Er Stress ◽  
Statistical Significance ◽  
Saturated Fatty Acids ◽  
Endothelin 1 ◽  
Kinase C

Objective: We investigated the regulation of endothelin-1 (ET-1) expression in in vivo high-fat diet (HFD)-fed mice and in vitro cultured human aortic endothelial cells (HAECs). Methods: Male C57BL/6 mice were fed on standard chow, serum was prepared, and ET-1 levels were analyzed using an ELISA kit. Quantitative PCR was performed using iQ SYBR Green Supermix. Statistical significance was assessed using SPSS, with p < 0.05 considered significant. Results: The serum ET-1 content and endothelial expression of ET-1 mRNA were increased in the HFD-fed mice compared to the chow-fed control mice. Moreover, the mRNA expression of ET-1 was significantly increased in cultured HAECs in response to acute (< 24 h) and chronic (12–16 days) treatments with palmitic acid (PA), one of the most abundant saturated fatty acids in obesity. We found that the induction of ET-1 expression by PA was abolished by pretreating the cells with the endoplasmic reticulum (ER) stress inhibitor 4-phenylbutyric acid or the protein kinase C (PKC) inhibitor Gö 6850. Conclusion: Our findings demonstrate for the first time that PA increases ET-1 expression in endothelial cells through the induction of ER stress and the activation of PKC, providing novel mechanistic insights into the pathogenesis of obesity-associated hypertension and cardiovascular diseases.

114 ENDOPLASMIC RETICULUM (ER) STRESS IN HYPOXIA-INDUCED DIABETES MELLITUS MODEL

2016 ◽  
Vol 28 (2) ◽  
pp. 187
Author(s):  
C. Ahn ◽  
D. Lee ◽  
K. P. Kim ◽  
M. H. Lee ◽  
E.-B. Jeung
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Er Stress ◽  
Pancreatic Beta Cells ◽  
Hypoxic Condition ◽  
Protein Translation ◽  
Ion Concentration ◽  
Cellular Stress Response ◽  
Stress Markers ◽  
Calbindin D9k

Endoplasmic reticulum (ER) regulates calcium ion concentration as a reservoir in the cell. ER stress is a cellular stress response related to the endoplasmic reticulum. At the initial stage of ER stress, ER tries to restore normal function by halting protein translation, degrading misfolded proteins, and increasing production of chaperones involved in protein folding. If ER fails to restore ER stress, ER stress can lead cells to apoptosis. To study the signaling between ER stress and calcium channels under ER-stressed circumstances, we designed a hypoxia-induced diabetic model. Nine-week-old male mice were chosen, maintained under hypoxic condition under 10% O2, 5% CO2 for 10 days, and the expression of ER stress markers and calcium channel gene expression were examined by real-time PCR. By maintaining hypoxic condition, the mice showed high glucose levels. Under this diabetic condition, in pancreatic beta cells, ER stress markers were elevated. This tendency showed an increase in calbindin-D9k KO mice. Chaperones such as calreticulin and calnexin were decreased, but in calbindin-D9k KO mice chaperone calnexin was not decreased. Interestingly, the calbindin-D9k KO normoxia mice showed increased glucose level compared with wild-type normoxia mice. Also, calnexin expression of pancreas was decreased in calbindin-D9k KO normoxia mice. This result indicates that pancreas cells were under endoplasmic reticulum stress. Taken together, calbindin may play an important role in endoplasmic reticulum stress in pancreas. This work was supported by the National Research Foundation of Korea (NRF) grant of Korean government (MEST) (No. 2013-010514).

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