• Molecules and Cells
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• v.41 no.5
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• pp.401-412
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• 2018

Oxymatrine (OMT) often used in treatment for chronic hepatitis B virus infection in clinic. However, OMT-induced liver injury has been reported. In this study, we aim to investigate the possible mechanism of OMT-induced hepatotoxicity in human normal liver cells (L02). Exposed cells to OMT, the cell viability was decreased and apoptosis rate increased, the intracellular markers of oxidative stress were changed. Simultaneously, OMT altered apoptotic related proteins levels, including Bcl-2, Bax and pro-caspase-8/-9/-3. In addition, OMT enhanced the protein levels of endoplasmic reticulum (ER) stress makers (GRP78/Bip, CHOP, and cleaved-Caspase-4) and phosphorylation of c-Jun N-terminal kinase (p-JNK), as well as the mRNA levels of GRP78/Bip, CHOP, caspase-4, and ER stress sensors (IREI, ATF6, and PERK). Pre-treatment with Z-VAD-fmk, JNK inhibitor SP600125 and N-acetyl-l-cysteine (NAC), a ROS scavenger, partly improved the survival rates and restored OMT-induced cellular damage, and reduced caspase-3 cleavage. SP600125 or NAC reduced OMT-induced p-JNK and NAC significantly lowered caspase-4. Furthermore, 4-PBA, the ER stress inhibitor, weakened inhibitory effect of OMT on cells, on the contrary, TM worsen. 4-PBA also reduced the levels of p-JNK and cleaved-caspase-3 proteins. Therefore, OMT-induced injury in L02 cells was related to ROS mediated p-JNK and ER stress induction. Antioxidant, by inhibition of p-JNK or ER stress, may be a feasible method to alleviate OMT-induced liver injury.

• Journal of Microbiology and Biotechnology
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• v.16 no.9
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• pp.1453-1458
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• 2006

PKR-like endoplasmic reticulum (ER) kinase (PERK) is a type I transmembrane ER-resident protein containing a cytoplasmic catalytic domain with a Ser/Thr kinase activity, which is most closely related to the eukaryotic translation initiation factor-$2{\alpha}$ ($eIF2{\alpha}$) kinase PKR involved in the antiviral defense pathway by interferon. We cloned and expressed the PERK C-terminal kinase domain (cPERK) in Escherichia coli. Like PERK activation in cells under ER stress, wild-type cPERK underwent autophosphorylation when overexpressed in E. coli, whereas the cPERK(K621M) with a methionine substitution for the lysine at amino acid 621 lost the autophosphorylation activity. The activated form cPERK which was purified to near homogeneity, formed an oligomer and was able to trans-phosphorylate specifically its cellular substrate $eIF2{\alpha}$. Two-dimensional phosphoamino acids analysis revealed that phosphorylation of cPERK occurs at the Ser and Thr residues. The functionally active recombinant cPERK, and its inactive mutant should be useful for the analysis of biochemical functions of PERK and for the determination of their three-dimensional structures.

• Genomics & Informatics
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• v.7 no.2
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• pp.97-106
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• 2009

Epigallocatechin gallate (EGCG), a well-known antioxidant molecule, has been reported to cause hepatotoxicity when used in excess. However, the mechanism underlying EGCG-induced hepatotoxicity is still unclear. To better understand the mode of action of EGCG-induced hepatotoxicity, we examined the effect of EGCG on human hepatic gene expression in HepG2 cells using microarrays. Analyses of microarray data revealed more than 1300 differentially expressed genes with a variety of biological processes. Upregulated genes showed a primary involvement with protein-related biological processes, such as protein synthesis, protein modification, and protein trafficking, while downregulated genes demonstrated a strong association with lipid transport. Genes involved in cellular stress responses were highly upregulated by EGCG treatment, in particular genes involved in endoplasmic reticulum (ER) stress, such as GADD153, GADD34, and ATF3. In addition, changes in genes responsible for cholesterol synthesis and lipid transport were also observed, which explains the high accumulation of EGCG-induced lipids. We also identified other regulatory genes that might aid in clarifying the molecular mechanism underlying EGCG-induced hepatotoxicity.

• Biomolecules & Therapeutics
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• v.27 no.1
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• pp.41-47
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• 2019

The apoptotic effects of shikonin (5,8-dihydroxy-2-[(1R)-1-hydroxy-4-methylpent-3-enyl]naphthalene-1,4-dione) on the human colon cancer cell line SNU-407 were investigated in this study. Shikonin showed dose-dependent cytotoxic activity against SNU-407 cells, with an estimated $IC_{50}$ value of $3{\mu}M$ after 48 h of treatment. Shikonin induced apoptosis, as evidenced by apoptotic body formation, sub-G_1$ phase cells, and DNA fragmentation. Shikonin induced apoptotic cell death by activating mitogen-activated protein kinase family members, and the apoptotic process was mediated by the activation of endoplasmic reticulum (ER) stress, leading to activation of the $PERK/elF2{\alpha}/CHOP$ apoptotic pathway, and mitochondrial $Ca^{2+}$ accumulation. Shikonin increased mitochondrial membrane depolarization and altered the levels of apoptosis-related proteins, with a decrease in B cell lymphoma (Bcl)-2 and an increase in Bcl-2-associated X protein, and subsequently, increased expression of cleaved forms of caspase-9 and -3. Taken together, we suggest that these mechanisms, including MAPK signaling and the ER- and mitochondria-mediated pathways, may underlie shikonin-induced apoptosis related to its anticancer effect.

• Nutrition Research and Practice
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• v.11 no.6
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• pp.445-451
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• 2017

BACKGROUND/OBJECTIVES: Endoplasmic reticulum (ER) stress is positively associated with atherosclerosis via elevating macrophage cell death and plaque formation, in which oxidative stress plays a pivotal role. Antioxidative, lipid-lowering, and anti-atherogenic effects of kimchi, a Korean fermented vegetable, have been established, wherein capsaicin, ascorbic acid, quercetin, 3-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid, and lactic acids were identified. In this study, mechanisms of action of kimchi methanol extracts (KME) on fatty streak formation via suppression of ER stress and apoptosis in aorta were examined in low-density lipoprotein receptor knockout mice. MATERIALS AND METHODS: Mice fed a high cholesterol diet with an oral administration of KME (KME group, $200 mg{\cdot}kg-bw^{-1}{\cdot}day^{-1}$) or distilled water (control group) for 8 weeks (n = 20 for group). Plasma lipid and oxidative stress levels were evaluated. Protein expression was measured by western blot assay. Fatty streak lesion size and the degree of apoptosis were examined in the aorta. RESULTS: Compared to the control group, in the KME group, plasma lipids levels were decreased and oxidative stress was alleviated (P < 0.05). Protein expression levels of nuclear factor (erythroid-derived 2)-like 2-mediated antioxidants in aorta were increased whereas those for ER stress markers, glucose regulated protein 78, phospho-protein kinase RNA-like ER kinase, phospho-eukaryotic initiation factor 2 subunit ${\alpha}$, X-box binding protein 1, and C/EBP homologous protein were decreased in the KME group (P < 0.05). Moreover, apoptosis was suppressed via downregulation of phospho-c-Jun N-terminal kinase, bcl-2-associated X protein, caspases-9, and -3 with a concomitant upregulation of anti-apoptotic protein, B-cell lymphoma 2 (P < 0.05). Fatty streak lesion size was reduced and the degree of apoptosis was less severe in the KME group (P < 0.05). CONCLUSIONS: In conclusion, antioxidant activity of KME might prevent fatty streak formation through, in part, inhibition of ER stress and apoptosis in aortic sinus where macrophages are harbored.

• Journal of Life Science
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• v.25 no.4
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• pp.473-480
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• 2015

The endoplasmic reticulum (ER) in the eukaryotic cells is the first compartment in the secretory pathway. Almost secretory proteins and membrane proteins are secreted through the ER, in which post-translational modifications occur via diverse signals from the ER lumen to the cytoplasm and nucleus. Only then are correctly-folded proteins secreted to the outside cells. Unfolded proteins that accumulate in the ER cause a kind of intracellular stress, ER stress, and activate an unfolded protein response (UPR) system. The 3 major transducers of the UPR are inositol requiring 1 (IRE1), PKR-like ER kinase (PERK) and activating transcription factor 6 (ATF6), all of which are ER transmembrane proteins. Recently, novel types of a new ATF6 family have been identified. Those commonly have an ER-transmembrane domain, a transcription-activation domain and a basic leucine zipper (bZIP) domain―Luman, OASIS, BBF2H7, CREBH and CREB4. Each factor functions by regulating the UPR in specific organs and tissues. Although the detailed molecular mechanisms of OASIS family members are unknown, in this study we comprehensively introduce these molecular signals.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.4
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• pp.387-397
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• 2016

Neurofibrillary tangles (NFTs) of microtubule-associated protein tau are a pathological hallmark of Alzheimer's disease (AD). Endoplasmic reticulum (ER) stress has been known to be involved in the pathogenesis of AD. However, the exact role of ER stress in tau pathology has not yet been clearly elucidated. In present study, the possible relationship between tau pathology and ER stress was examined in terms of sorcin, which is a calcium binding protein and plays an important role in calcium homeostasis. Our previous yeast two hybrid study showed that sorcin is a novel tau interacting protein. Caspase-3-cleaved tau (T4C3) showed significantly increased tau-sorcin interaction compared to wild type tau (T4). Thapsigargin-induced ER stress and co-expression of constitutively active $GSK3{\beta}$ ($GSK3{\beta}-S9A$) also exhibited significantly increased tau-sorcin interactions. T4C3-expressing cells showed potentiated thapsigargin -induced apoptosis and disruption of intracellular calcium homeostasis compared to T4-expressing cells. Overexpression of sorcin significantly attenuated thapsigargin-induced apoptosis and disruption of calcium homeostasis. In contrary, siRNA-mediated knock-down of sorcin showed significantly increased thapsigargin-induced apoptosis and disruption of calcium homeostasis. These data strongly suggest that sequestration of sorcin by aberrant forms of tau compromises the function of sorcin, such as calcium homeostasis and cellular resistance by ER stress, which may consequently result in the contribution to the progression of AD.

• BMB Reports
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• v.47 no.10
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• pp.563-568
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• 2014

Human genome projects have enabled whole genome mapping and improved our understanding of the genes in humans. However, many unknown genes remain to be functionally characterized. In this study, we characterized human chromosome 4 open reading frame 34 gene (hC4orf34). hC4orf34 was highly conserved from invertebrate to mammalian cells and ubiquitously expressed in the organs of mice, including the heart and brain. Interestingly, hC4orf34 is a novel ER-resident, type I transmembrane protein. Mutant analysis showed that the transmembrane domain (TMD) of hC4orf34 was involved in ER retention. Overall, our results indicate that hC4orf34 is an ER-resident type I transmembrane protein, and might play a role in ER functions including $Ca^{2+}$ homeostasis and ER stress.

• The Korean Journal of Pain
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• v.35 no.4
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• pp.383-390
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• 2022

Background: The treatment of trigeminal neuralgia remains a challenging issue. Stem cells from human exfoliated deciduous teeth (SHED) provide optimized therapy for chronic pain. This study aimed to investigate the mechanisms underlying the attenuation of trigeminal neuralgia by SHED. Methods: Trigeminal neuralgia was induced by chronic constriction injury of the infraorbital nerve. The mechanical threshold was assessed after model establishment and local SHED transplantation. Endoplasmic reticulum (ER) morphology and Caspase12 expression in trigeminal ganglion (TG) was evaluated as well. BiP expression was observed in PC12 cells induced by tunicamycin. Results: The local transplantation of SHED could relieve trigeminal neuralgia in rats. Further, transmission electron microscopy revealed swelling of the ER in rats with trigeminal neuralgia. Moreover, SHED inhibited the tunicamycin-induced up-regulated expression of BiP mRNA and protein in vitro. Additionally, SHED decreased the up-regulated expression of Caspase12 mRNA and protein in the TG of rats caused by trigeminal neuralgia after chronic constriction injury of the infraorbital nerve mode. Conclusions: This findings demonstrated that SHED could alleviate pain by relieving ER stress which provide potential basic evidence for clinical pain treatment.

• Journal of Life Science
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• v.23 no.9
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• pp.1104-1108
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• 2013

Ethylene glycol (EG) is the most commonly used for automotive antifreeze, and it's easily misuseful for human. EG poisoning occurs in suicide attempts and infrequently, either intentionally through misuse or accidentally because of sweet taste. Though EG itself is mild toxic to the human body, it becomes higher toxic organic acids by in vivo broken down that are responsible for extensive cellular damage in various tissues caused principally by the metabolites. It is already well known that various cellular stresses induce gene expression of endoplasmic reticulum (ER) chaperones and ER stress sensors. This study demonstrated that regulation of gene expression of ER chaperones and ER stress sensors was induced by EG in rat tissues, and in tissues histological changes are also detected by both staining H&E and immunofluorescent.