• The Korean Journal of Physiology and Pharmacology
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• v.23 no.2
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• pp.95-102
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• 2019

Endoplasmic reticulum (ER) stress is mediated by disturbance of $Ca^{2+}$ homeostasis. The store-operated calcium (SOC) channel is the primary $Ca^{2+}$ channel in non-excitable cells, but its participation in agent-induced ER stress is not clear. In this study, the effects of tunicamycin on $Ca^{2+}$ influx in human umbilical vein endothelial cells (HUVECs) were observed with the fluorescent probe Fluo-4 AM. The effect of tunicamycin on the expression of the unfolded protein response (UPR)-related proteins BiP and CHOP was assayed by western blotting with or without inhibition of Orai1. Tunicamycin induced endothelial dysfunction by activating ER stress. Orai1 expression and the influx of extracellular $Ca^{2+}$ in HUVECs were both upregulated during ER stress. The SOC channel inhibitor SKF96365 reversed tunicamycin-induced endothelial cell dysfunction by inhibiting ER stress. Regulation of tunicamycin-induced ER stress by Orai1 indicates that modification of Orai1 activity may have therapeutic value for conditions with ER stress-induced endothelial dysfunction.

• Korean Journal of Environmental Biology
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• v.26 no.3
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• pp.214-219
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• 2008

Changes in stress-associated biomolecules can be used as an important criterion for assessing the levels of environmental pollution because living organisms demonstrate contamination-stimulated stress responses. This study was conducted to determine the environmental status of Masan-Jinhae Bay, Korea, and its effects on marine organisms by investigating the endoplasmic reticulum (ER) dysfunction in the organs of the flat fish, Limanda yokohamae. ER dysfunction was evaluated via Western blot analysis of the ER stress proteins, immunoglobulin heavy chain binding protein (BiP) and C/EBP-homologous protein (CHOP), and the ER stress-associated protein caspase-12. The results showed that the amount of BiP and CHOP immunoreactivity in the flat fish from the bay area was much greater than that from the Gangneung, as a reference site. Similar to the ER stress proteins, the immunoreactivity of caspase-12 was also found to be elevated in the bay area when compared with that of Gangneung. These data suggest that the environmental status of Masan-Jinhae Bay induces the ER stress response, which is able to lead to phenotypic changes in marine organisms including fish.

• Parasites, Hosts and Diseases
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• v.59 no.6
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• pp.573-583
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• 2021

Toxoplasma gondii, an intracellular protozoan parasite that infects one-third of the world's population, has been reported to hijack host cell apoptotic machinery and promote either an anti- or proapoptotic program depending on the parasite virulence and load and the host cell type. However, little is known about the regulation of human FHs 74 small intestinal epithelial cell viability in response to T. gondii infection. Here we show that T. gondii RH strain tachyzoite infection or ESP treatment of FHs 74 Int cells induced apoptosis, mitochondrial dysfunction and ER stress in host cells. Pretreatment with 4-PBA inhibited the expression or activation of key molecules involved in ER stress. In addition, both T. gondii and ESP challenge-induced mitochondrial dysfunction and cell death were dramatically suppressed in 4-PBA pretreated cells. Our study indicates that T. gondii infection induced ER stress in FHs 74 Int cells, which induced mitochondrial dysfunction followed by apoptosis. This may constitute a potential molecular mechanism responsible for the foodborne parasitic disease caused by T. gondii.

• The Plant Pathology Journal
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• v.28 no.4
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• pp.401-408
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• 2012

Initial subcellular responses in susceptible (PI 274420) and resistant (cv. Hartwig) soybeans infected with the soybean cyst nematode (SCN) were examined 2 and 4 days after inoculation (DAI). Subcellular features common to both soybeans at 2 DAI included hypertrophied initial syncytial cells (ISCs) and syncytium-component cells (SCs) with a dense cytoplasm containing proliferated rough and smooth endoplasmic reticulum (RER and SER), a hypertrophied nucleolus, and reduced vacuoles, suggesting that the nematode-infected cells were dedifferentiated. In the resistant soybean, a striking initial subcellular difference from the susceptible soybean was the dilation of the RER, indicating ER dysfunction and leading to cell death. This disturbed nematode feeding, as evidenced by disrupted feeding tubes. In PI 274420, the ISC cytoplasm was depleted, with the exception of ER membranes, at 4 DAI, while the SC cytoplasm was dense with proliferation of starch-containing plastids around multiple nuclei that might be derived from the congregation of nuclei in the neighboring SCs and in part by nuclear division without cytokinesis. In cv. Hartwig, syncytia were necrotized with secondary cell wall thickening outside the plasma membrane and an extremely dense cytoplasm containing a nucleus with an electron-lucent nucleolus, accompanied by the proliferation of closely stacked parallel RER and ribosomes. These results suggest that syncytia develop continuously in PI 274420 to produce and store nutritional substances in SCs, providing for the nematode through ISC until maturation, but in cv. Hartwig, syncytia degenerate early due to excessive metabolism, blocking nematode feeding and cytoplasmic connections with adjacent intact cells.

• Journal of Periodontal and Implant Science
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• v.48 no.5
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• pp.284-294
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• 2018

Purpose: Epithelial barrier dysfunction is involved in the pathophysiology of periodontitis and oral lichen planus. Estrogens have been shown to enhance the physical barrier function of intestinal and esophageal epithelia, and we aimed to investigate the effect of estradiol (E2) on the regulation of physical barrier and tight junction (TJ) proteins in human oral epithelial cell monolayers. Methods: HOK-16B cell monolayers cultured on transwells were treated with E2, an estrogen receptor (ER) antagonist (ICI 182,780), tumor necrosis factor alpha ($TNF{\alpha}$), or dexamethasone (Dexa), and the transepithelial electrical resistance (TER) was then measured. Cell proliferation was measured by the cell counting kit (CCK)-8 assay. The levels of TJ proteins and nuclear translocation of nuclear factor $(NF)-{\kappa}B$ were examined by confocal microscopy. Results: E2 treatment increased the TER and the levels of junctional adhesion molecule (JAM)-A and zonula occludens (ZO)-1 in a dose-dependent manner, without affecting cell proliferation during barrier formation. Treatment of the tight-junctioned cell monolayers with $TNF{\alpha}$ induced decreases in the TER and the levels of ZO-1 and nuclear translocation of $NF-{\kappa}B$. These $TNF{\alpha}-induced$ changes were inhibited by E2, and this effect was completely reversed by co-treatment with ICI 182,780. Furthermore, E2 and Dexa presented an additive effect on the epithelial barrier function. Conclusions: E2 reinforces the physical barrier of oral epithelial cells through the nuclear ER-dependent upregulation of TJ proteins. The protective effect of E2 on the $TNF{\alpha}-induced$ impairment of the epithelial barrier and its additive effect with Dexa suggest its potential use to treat oral inflammatory diseases involving epithelial barrier dysfunction.

• Journal of Embryo Transfer
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• v.32 no.4
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• pp.287-295
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• 2017

Mitochondrial dysfunction is found in oocytes and transmitted to offspring due to maternal obesity. Treatment of obese mothers with endoplasmic reticulum (ER) stress inhibitors such as salubrinal (SAL) can reverse the mitochondrial dysfunction and result in normal embryonic development. Pig oocytes have also shown ER stress mostly in metaphase II stage. ER stress in oocytes may hinder the in vitro production of pig embryos. This study investigated the effect of ER stress inhibition by SAL treatment during in vitro maturation (IVM) of porcine oocytes at 1, 10, 50 and 100 nM concentrations. Firstly, we tested various concentrations of SAL. SAL at 10 nM showed higher (P < 0.05) developmental competence to the blastocyst stage (55.6%) after parthenogenesis (PA) than control (44.2%) while not different from other concentrations (49.2, 51.6, and 50.8% for 1, 50, and 100 nM, respectively). Secondly, we performed time-dependent treatment at 10 nM of SAL for IVM of oocytes. It revealed that treatment with SAL during 22 to 44 h of IVM significantly improved PA embryonic development to the blastocyst stage compared to control (40.5, 46.3, 51.7 and 60.2% for control, 0 to 22 h, 22 to 44 h and 0 to 44 h of IVM, respectively, P < 0.05). Glutathione (GSH) content is an indicator of cytoplasmic maturation of oocytes. Reactive oxygen species (ROS) have a harmful effect on developmental competence of oocytes. For this, we determined the intraoocyte levels of GSH and ROS after 44 h of IVM. It was found that SAL increased intraoocyte GSH level and also decreased ROS level (P < 0.05). Finally, we performed somatic cell nuclear transfer (SCNT) after treating oocytes with 10 nM SAL during IVM. SAL treatment significantly improved blastocyst formation of SCNT embryos compared to control (39.6% vs. 24.7%, P < 0.05). Our results indicate that treatment of pig oocytes with ER stress inhibitor SAL during IVM improves preimplantation development PA and cloned pig embryos by influencing cytoplasmic maturation in terms of increased GSH content and decreased ROS level in IVM pig oocytes.

• Molecules and Cells
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• v.37 no.9
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• pp.672-684
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• 2014

The exact causes of cell death in Parkinson's disease (PD) remain unknown despite extensive studies on PD.The identification of signaling and metabolic pathways involved in PD might provide insight into the molecular mechanisms underlying PD. The neurotoxin 1-methyl-4-phenylpyridinium ($MPP^+$) induces cellular changes characteristic of PD, and $MPP^+$-based models have been extensively used for PD studies. In this study, pathways that were significantly perturbed in $MPP^+$-treated human neuroblastoma SH-EP cells were identified from genome-wide gene expression data for five time points (1.5, 3, 9, 12, and 24 h) after treatment. The mitogen-activated protein kinase (MAPK) signaling pathway and endoplasmic reticulum (ER) protein processing pathway showed significant perturbation at all time points. Perturbation of each of these pathways resulted in the common outcome of upregulation of DNA-damage-inducible transcript 3 (DDIT3). Genes involved in ER protein processing pathway included ubiquitin ligase complex genes and ER-associated degradation (ERAD)-related genes. Additionally, overexpression of DDIT3 might induce oxidative stress via glutathione depletion as a result of overexpression of CHAC1. This study suggests that upregulation of DDIT3 caused by perturbation of the MAPK signaling pathway and ER protein processing pathway might play a key role in $MPP^+$-induced neuronal cell death. Moreover, the toxicity signal of $MPP^+$ resulting from mitochondrial dysfunction through inhibition of complex I of the electron transport chain might feed back to the mitochondria via ER stress. This positive feedback could contribute to amplification of the death signal induced by $MPP^+$.

• BMB Reports
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• v.51 no.10
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• pp.538-543
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• 2018

Pancreatic beta cell destruction and dysfunction induced by cytokines is a major cause of type 1 diabetes. Paraoxonase 1 (PON1), an arylesterase with antioxidant activity, has been shown to play an important role in preventing the development of diabetes in transgenic mice. However, no studies have examined the anti-diabetic effect of PON1 delivered to beta cells using protein transduction. In this study, we expressed the cell-permeable PON1 fused with PEP-1 protein transduction domain (PEP-1-PON1) to investigate whether transduced PEP-1-PON1 protects beta cells against cytokine-induced cytotoxicity. PEP-1-PON1 was effectively delivered to INS-1 cells and prevented cytokine-induced cell destruction in a dose-dependent manner. Transduced PEP-1-PON1 significantly reduced the levels of reactive oxygen species (ROS) and nitric oxide (NO), DNA fragmentation, and expression of inflammatory mediators, endoplasmic reticulum (ER) stress proteins, and apoptosis-related proteins in cytokine-treated cells. Moreover, transduced PEP-1-PON1 restored the decrease in basal and glucose-stimulated insulin secretion induced by cytokines. These data indicate that PEP-1-PON1 protects beta cells from cytokine-induced cytotoxicity by alleviating oxidative/nitrosative stress, ER stress, and inflammation. Thus, PEP-1-mediated PON1 transduction might be an effective method to reduce the extent of destruction and dysfunction of pancreatic beta cells in autoimmune diabetes.

• Molecules and Cells
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• v.37 no.11
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• pp.767-776
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• 2014

Alzheimer's disease (AD) is clinically characterized with progressive memory loss and cognitive decline. Synaptic dysfunction is an early pathological feature that occurs prior to neurodegeneration and memory dysfunction. Mounting evidence suggests that aggregation of amyloid-${\alpha}$ ($A{\alpha}$) and hyperphosphorylated tau leads to synaptic deficits and neurodegeneration, thereby to memory loss. Among the established genetic risk factors for AD, the ${\varepsilon}4$ allele of apolipoprotein E (APOE) is the strongest genetic risk factor. We and others previously demonstrated that apoE regulates $A{\alpha}$ aggregation and clearance in an isoform-dependent manner. While the effect of apoE on $A{\alpha}$ may explain how apoE isoforms differentially affect AD pathogenesis, there are also other underexplored pathogenic mechanisms. They include differential effects of apoE on cerebral energy metabolism, neuroinflammation, neurovascular function, neurogenesis, and synaptic plasticity. ApoE is a major carrier of cholesterols that are required for neuronal activity and injury repair in the brain. Although there are a few conflicting findings and the underlying mechanism is still unclear, several lines of studies demonstrated that apoE4 leads to synaptic deficits and impairment in long-term potentiation, memory and cognition. In this review, we summarize current understanding of apoE function in the brain, with a particular emphasis on its role in synaptic plasticity and the underlying cellular and molecular mechanisms, involving low-density lipoprotein receptor-related protein 1 (LRP1), syndecan, and LRP8/ApoER2.

• BMB Reports
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• v.47 no.2
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• pp.69-79
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• 2014

$Ca^{2+}$ release from intracellular stores and influx from extracellular reservoir regulate a wide range of physiological functions including muscle contraction and rhythmic heartbeat. One of the most ubiquitous pathways involved in controlled $Ca^{2+}$ influx into cells is store-operated $Ca^{2+}$ entry (SOCE), which is activated by the reduction of $Ca^{2+}$ concentration in the lumen of endoplasmic or sarcoplasmic reticulum (ER/SR). Although SOCE is pronounced in non-excitable cells, accumulating evidences highlight its presence and important roles in skeletal muscle and heart. Recent discovery of STIM proteins as ER/SR $Ca^{2+}$ sensors and Orai proteins as $Ca^{2+}$ channel pore forming unit expedited the mechanistic understanding of this pathway. This review focuses on current advances of SOCE components, regulation and physiologic and pathophysiologic roles in muscles. The specific property and the dysfunction of this pathway in muscle diseases, and new directions for future research in this rapidly growing field are discussed.