• Journal of Applied Biological Chemistry
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• v.66
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• pp.53-59
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• 2023

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has no effect on normal cells, but selectively can induce apoptosis in tumor cells. Gartanin, a xanthone compound in mangosteen, has been shown to inhibit cancer cell growth by arresting the cell cycle and inducing autophage. In this study, we revealed that gartanin can sensitize TRAIL-induced human liver cancer cell death. We also found that gartanin enhances DR5 expression, a death receptor for TRAIL. This effect appears to be related to CHOP activation associated with the response of endoplasmic reticulum stress. Gartanin treatment also inhibited p62 protein expression and cleaved LC3 to activate autophagy flux, which is related with TRAIL-induced cell death. Pretreatment with autophagy flux inhibitor, LY294002, inhibited gartanin-induced DR5 expression. In summary, our results reveal that the combined treatment of gartanin and TRAIL can be a valuable tool for cancer treatment.

• The Korean Journal of Physiology and Pharmacology
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• v.15 no.6
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• pp.345-351
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• 2011

High glucose leads to physio/pathological alterations in diabetes patients. We investigated collagen production in human gingival cells that were cultured in high concentrations of glucose. Collagen synthesis and secretion were increased when the cells were exposed to high concentrations of glucose. We examined endoplasmic reticulum (ER) stress response because glucose metabolism is related to ER functional status. An ER stress response including the expression of glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), inositol requiring enzyme alpha (IRE-$1{\alpha}$) and phosphoreukaryotic initiation factor alpha (p-eIF-$2{\alpha}$) was activated in the presence of high glucose. Activating transcription factor 4 (ATF-4), a downstream protein of p-eIF-$2{\alpha}$ as well as a transcription factor for collagen, was also phosphorylated and translocalized into the nucleus. The chemical chaperone 4-PBA inhibited the ER stress response and ATF-4 phosphorylation as well as nuclear translocation. Our results suggest that high concentrations of glucose-induced collagen are linked to ER stress and the associated phosphorylation and nuclear translocation of ATF-4.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.6
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• pp.1368-1378
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• 2009

Unfolded protein response (UPR) is an important genomic response to endoplasmic reticulum (ER) stress. The ER response is characterized by changes in specific proteins, induction of ER chaperones and degradation of misfolded proteins. Also, the pathogenesis of several diseases like Alzheimer's disease, neuronal degenerative diseases, and diabetes reveal the role of ER stress as one of the causative mechanisms. Borneolum has been used for neuronal disease in oriental medicine. In the present study, the protective effect of borneolum on thapsigargin-induced apoptosis in rat C6 glial cells. Treatment with C6 glial cells with 5 uM thapsigargin caused the loss of cell viability, and morphological change, which was associated with the elevation of intracellular $Ca^{++}$ level, the increase in Grp78 and CHOP and cleavage of pro-caspase 12 Furthermore, thapsigargin induced Grp98, XBP1, and ATF4 protein expression in C6 glial cells. Borneolum reduced thapsigargin-induced apoptosis through ER pathways. In the ER pathway, borneolum attenuated thapsigargin-induced elevations in Grp78, CHOP, ATF4, and XBP1 as well as reductions in pro-caspase 12 levels. Also, our data showed that borneolum protected thapsigargin-induced cytotoxicity in astrocytes from rat (P3) brain. Taken together, our data suggest that borneolum is neuroprotective against thapsigargin-induced ER stress in C6 glial cells and astrocytes. Accordingly, borneolum may be therapeutically useful for the treatment of thapsigargin-induced apoptosis in central nervous system.

• Journal of Life Science
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• v.34 no.1
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• pp.68-77
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• 2024

Airborne particulate matter (PM) is an environmentally hazardous pollutant that originates from various sources. PM is comprised of solid particles and liquid droplets of diverse composition and size. Hazardous chemical compositions of PM include elemental and organic carbon, organic compounds, biological compounds and metals. Upon acute and chronic PM exposure, toxic contaminants enter and accumulate within physiological systems and prompt cell structure changes accompanied with intracellular endoplasmic reticulum stress, mitochondrial dysfunction, oxidative stress, inflammation, lipid accumulation, and cell cycle arrest. Ultimately, these cellular response leads to the development of key characteristics of aging. In addition, PM internalization enhances autophagy reflux and lysosomal dysfunction, which is involved in cell aging. Previous studies have emphasized a positive association between PM and increased mortality or decreased lifespan, although these are evidenced mostly by observational studies. Direct evidence of the link between PM and aging is still limited. This review evaluates the evidence from not only observational studies but also in vitro and in vivo evidence of PM on aging progression and age-related diseases development. This evidence is based on age-associated cellular changes including endoplasmic reticulum stress, mitochondrial dysfunction, oxidative stress, inflammation, adipose accumulation, autophagy, which strengthen the association between PM exposure and aging. Understanding the underlying cellular responses under PM may allow for the development of new therapeutic targets for PM-induced aging.

• BMB Reports
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• v.53 no.6
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• pp.311-316
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• 2020

Cholestasis is a condition in which the bile duct becomes narrowed or clogged by a variety of factors and bile acid is not released smoothly. Bile acid-induced liver injury is facilitated by necrotic cell death, neutrophil infiltration, and inflammation. Metformin, the first-line treatment for type 2 diabetes, is known to reduce not only blood glucose but also inflammatory responses. In this study, we investigated the effects of metformin on liver injury caused by cholestasis with bile acid-induced hepatocyte injury. Static bile acid-induced liver injury is thought to be related to endoplasmic reticulum (ER) stress, inflammatory response, and chemokine expression. Metformin treatment reduced liver injury caused by bile acid, and it suppressed ER stress, inflammation, chemokine expression, and neutrophil infiltration. Similar results were obtained in mouse primary hepatocytes exposed to bile acid. Hepatocytes treated with tauroursodeoxycholic acid, an ER stress inhibitor, showed inhibition of ER stress, as well as reduced levels of inflammation and cell death. These results suggest that metformin may protect against liver injury by suppressing ER stress and inflammation and reducing chemokine expression.

• Journal of Life Science
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• v.23 no.8
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• pp.1050-1056
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• 2013

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia throughout the world. The bacteria invade through lung tissue and cause sepsis, shock, and serious sequelae, including rheumatic fever and acute glomerulonephritis. However, the molecular mechanism associated with pneumonia's penetration of lung tissue and invasion of the blood stream are still unclear. We attempted to investigate the host cell response at protein levels to S. pneumoniae D39 invasion using human lung cancer epithelial cells, A549. Streptococcus pneumoniae D39 began to change the morphology of A549 cells to become round with filopodia at 2 hours post-infection. A549 cell proteins obtained at each infection time point were separated by SDS-PAGE and analyzed using MALDI-TOF. We identified several endoplasmic reticulum (ER) resident proteins such as Grp94 and Grp78 and mitochondrial proteins such as ATP synthase and Hsp60 that increased after S. pneumoniae D39 infection. Cytosolic Hsc70 and Hsp90 were, however, identified to decrease. These proteins were also confirmed by Western blot analysis. The identified ER resident proteins were known to be induced during ER stress signaling. These/ data, therefore, suggest that S. pneumoniae D39 infection may induce ER stress.

• BMB Reports
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• v.44 no.11
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• pp.735-740
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• 2011

Tunicamycin, an endoplasmic reticulum (ER) stress inducer, specifically inhibits N-glycosylation. The cyclic AMP (cAMP) response element-binding protein H (CREBH) was previously shown to be regulated by UPR-dependent proteolytic cleavage in the liver. On the other hand, the role of CREBH in other tissues is unknown. In the present study, tunicamycin increased the level of CREBH activation (cleavage) as well as mRNA expression in osteoblast cells. Adenoviral (Ad) overexpression of CREBH suppressed BMP2-induced expression of alkaline phosphatase (ALP) and osteocalcin (OC). Interestingly, the BMP2-induced OASIS (structurally similar to CREBH, a positive regulator of osteoblast differentiation) expression was also inhibited by CREBH overexpression. In addition, inhibition of CREBH expression using siRNA reversed the tunicamycin-suppressed ALP and OC expression. These results suggest that CREBH inhibited osteoblast differentiation via suppressing BMP2-induced ALP, OC and OASIS expression in mouse calvarial derived osteoblasts.

• Animal Bioscience
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• v.34 no.7
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• pp.1210-1220
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• 2021

Objective: Unlike mammals, goose fatty liver shows a strong tolerance to fatty acids without obvious injury. Stearyl-coenzyme A desaturase 1 (SCD1) serves crucial role in desaturation of saturated fatty acids (SAFs), but its role in the SAFs tolerance of goose hepatocytes has not been reported. This study was conducted to explore the role of SCD1 in regulating palmitic acid (PA) tolerance of goose primary hepatocytes. Methods: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide was examined to reflect the effect of PA on hepatocytes viability, and quantitative polymerase chain reaction was used to detect the mRNA levels of several genes related to endoplasmic reticulum (ER) stress, inflammation, and apoptosis, and the role of SCD1 in PA tolerance of goose hepatocytes was explored using RNA interfere. Results: Our results indicated that goose hepatocytes exhibited a higher tolerant capacity to PA than human hepatic cell line (LO2 cells). In goose primary hepatocytes, the mRNA levels of fatty acid desaturation-related genes (SCD1 and fatty acid desaturase 2) and fatty acid elongate enzyme-related gene (elongase of very long chain fatty acids 6) were significantly upregulated with 0.6 mM PA treatment. However, in LO2 cells, expression of ER stress-related genes (x box-binding protein, binding immunoglobulin protein, and activating transcription factor 6), inflammatory response-related genes (interleukin-6 [IL-6], interleukin-1β [IL-1β], and interferon-γ) and apoptosis-related genes (bcl-2-associated X protein, b-cell lymphoma 2, Caspase-3, and Caspase-9) was significantly enhanced with 0.6 mM PA treatment. Additionally, small interfering RNA (siRNA) mediated downregulation of SCD1 significantly reduced the PA tolerance of goose primary hepatocytes under the treatment of 0.6 mM PA; meanwhile, the mRNA levels of inflammatory-related genes (IL-6 and IL-1β) and several key genes involved in the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT), forkhead box O1 (FoxO1), mammalian target of rapamycin and AMPK pathways (AKT1, AKT2, FoxO1, and sirtuin 1), as well as the protein expression of cytochrome C and the apoptosis rate were upregulated. Conclusion: In conclusion, our data suggested that SCD1 was involved in enhancing the PA tolerance of goose primary hepatocytes by regulating inflammation- and apoptosis-related genes expression.

• Molecules and Cells
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• v.42 no.11
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• pp.783-793
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• 2019

When endoplasmic reticulum (ER) functions are perturbed, the ER induces several signaling pathways called unfolded protein response to reestablish ER homeostasis through three ER transmembrane proteins: inositol-requiring enzyme 1 (IRE1), PKR-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Although it is important to measure the activity of ATF6 that can indicate the status of the ER, no specific cell-based reporter assay is currently available. Here, we report a new cell-based method for monitoring ER stress based on the cleavage of $ATF6{\alpha}$ by sequential actions of proteases at the Golgi apparatus during ER stress. A new expressing vector was constructed by using fusion gene of GAL4 DNA binding domain (GAL4DBD) and activation domain derived from herpes simplex virus VP16 protein (VP16AD) followed by a human $ATF6{\alpha}$ N-terminal deletion variant. During ER stress, the GAL4DBD-VP16AD(GV)-$hATF6{\alpha}$ deletion variant was cleaved to liberate active transcription activator encompassing GV-$hATF6{\alpha}$ fragment which could translocate into the nucleus. The translocated GV-$hATF6{\alpha}$ fragment strongly induced the expression of firefly luciferase in HeLa Luciferase Reporter cell line containing a stably integrated 5X GAL4 site-luciferase gene. The established double stable reporter cell line HLR-GV-$hATF6{\alpha}$(333) represents an innovative tool to investigate regulated intramembrane proteolysis of $ATF6{\alpha}$. It can substitute active pATF6(N) binding motif-based reporter cell lines.

• Biomolecules & Therapeutics
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• v.17 no.2
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• pp.162-167
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• 2009

Adipocytes undergo adipocyte stress in the excessive presence of lipid. Adipocyte stress accompanies the typical signs of endoplasmic reticulum (ER) stress: unfolded protein response and overexpression of molecular chaperones. Apoptotic induction in adipocytes is known as a good strategy for treating obesity. The drug "tunicamycin" was tested for its therapeutic potential in inducing apoptosis on differentiating adipocytes of 3T3-L1. When the 3T3-L1 cells, stimulated for adipogenesis, were treated with tunicamycin, they showed typical ER stress symptoms. Despite progression in ER stress, however, the differentiated 3T3-L1 hardly proceeded to apoptosis based on the CHOP protein expression and FACS analysis. This is very different from C2C12, the myogenic counterpart of 3T3-L1, which showed significant apoptosis along with ER stress. This study also characterizes a potential mechanism whereby adipocyte may avoid apoptosis to sustain the pathological state of obesity. The level of GRP94 expression significantly upholds in 3T3-L1 under tunicamycin treatment compared to preadipocytes and C2C-12. When GRP94 expression was inhibited by siRNA, 3T3-L1 showed a higher level of CHOP expression compared to C2C12 cells. In conclusion, adipocytes exert an anti-apoptotic mechanism under ER stress caused by tunicamycin; thus, apoptotic induction in adipocyte is not a viable anti-obesity option. The unusual level of GRP94 may serve as a key role whereby adipocytes reach to the obesity level circumventing the apoptosis.