• Molecules and Cells
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• v.46 no.11
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• pp.675-687
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• 2023

Accumulation of pathogenic amyloid-β disrupts the tight junction of retinal pigment epithelium (RPE), one of its senescence-like structural alterations. In the clearance of amyloid-β, the autophagy-lysosome pathway plays the crucial role. In this context, mammalian target of rapamycin (mTOR) inhibits the process of autophagy and lysosomal degradation, acting as a potential therapeutic target for age-associated disorders. However, efficacy of targeting mTOR to treat age-related macular degeneration remains largely elusive. Here, we validated the therapeutic efficacy of the mTOR inhibitors, Torin and PP242, in clearing amyloid-β by inducing the autophagy-lysosome pathway in a mouse model with pathogenic amyloid-β with tight junction disruption of RPE, which is evident in dry age-related macular degeneration. High concentration of amyloid-β oligomers induced autophagy-lysosome pathway impairment accompanied by the accumulation of p62 and decreased lysosomal activity in RPE cells. However, Torin and PP242 treatment restored the lysosomal activity via activation of LAMP2 and facilitated the clearance of amyloid-β in vitro and in vivo. Furthermore, clearance of amyloid-β by Torin and PP242 ameliorated the tight junction disruption of RPE in vivo. Overall, our findings suggest mTOR inhibition as a new therapeutic strategy for the restoration of tight junctions in age-related macular degeneration.

• Applied Microscopy
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• v.24 no.1
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• pp.41-58
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• 1994

The present studies were designed to determine the feasibility of using the rat tracheal epithelium as models for induction of aging. The ultrastructural and cytochemical changes of tracheal epithelium were investigated in rats at ages of five, twelve and twenty four months. Some major changes in the tracheal epithelium with advancing age were observed by electron microscopy. The results were summarized as fellow: 1. With the advance of age, lysosome, vacuole and multivesicular bodies were increased in number and numerous myelinoid bodies were observed in cytoplasm of ciliated cells. 2. In goblet cell, serous cell and brush cell lysosome and myelinoid bodies were increased in number with the advance of age, and an myelinoid bodies was often found within the secretory granule. 3. Cytochemical studies showed that acid phosphatase activities was observed in multivesicular bodies and lysosome, strong activities with the advance of age. And alkaline phosphatase activity are observed in microvilli, granule and lateral membrane of secretory granule cells, and strong activities with age. Consequently suggest that with the advance of age, tracheal epithelium show ultrastructural and cytochemical alteration of some kind of cell organelles in all kind of cell.

• Journal of Life Science
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• v.31 no.5
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• pp.527-535
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• 2021

Lysosomes are organelles surrounded by membranes that contain acid hydrolases; they degrade proteins, macromolecules, and lipids. According to nutrient conditions, lysosomes act as signaling hubs that regulate intracellular signaling pathways and are involved in the homeostasis of cells. Therefore, the lysosomal dysfunction occurs in various diseases, such as lysosomal storage disease, neurodegenerative diseases, and cancers. Multiple forms of stress can increase lysosomal membrane permeabilization (LMP), resulting in the induction of lysosome-mediated cell death through the release of lysosomal enzymes, including cathepsin, into the cytosol. Here we review the molecular mechanisms of LMP-mediated cell death and the enhancement of sensitivity to anticancer drugs. Induction of partial LMP increases apoptosis by releasing some cathepsins, whereas massive LMP and rupture induce non-apoptotic cell death through release of many cathepsins and generation of ROS and iron. Cancer cells have many drug-accumulating lysosomes that are more resistant to lysosome-sequestered drugs, suggesting a model of drug-induced lysosome-mediated chemoresistance. Lysosomal sequestration of hydrophobic weak base anticancer drugs can have a significant impact on their subcellular distribution. Lysosome membrane damage by LMP can overcome resistance to anticancer drugs by freeing captured hydrophobic weak base drugs from lysosomes. Therefore, LMP inducers or lysosomotropic agents can regulate lysosomal integrity and are novel strategies for cancer therapy.

• Archives of Pharmacal Research
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• v.10 no.1
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• pp.36-41
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• 1987

The conversion of xanthine dehydrogenase (type D) into xanthine oxidase (type D) was significantly increased in serum and liver of all $CCI_4$ treated rats on the necrosis and early cirrhosis stage of liver tissue. In the pretreatment of prednisolone, the ratio of type O per type O + D showed the decreasing tendency in serum, but the significant decrease in liver. In vitro, the conversion of liver xanthine oxidase from type D into type O was markedly increased by following preincubation with lysosomal fraction. The type conversion of xanthine oxidase may be caused by protelytic enzymes in lysosome.

• Applied Microscopy
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• v.21 no.2
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• pp.29-38
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• 1991

Ventral nephrocytes in the larva of the Lucilia illustris comprise ellipsoid cells situated onto the salivary glands. The cells are $60{\sim}100{\mu}m$ in diameter. Junctional complex beneath the basement membrane hold the plasma membrane in a even contour. Intracellular channels from the juntion complex are well developed at the cortex part of the cell. Coated vesicles pinched off from the channels seems to be connected with the ${\alpha}$-vacuoles via the tubular elements, which is regared as selective absorption system from the hemolymph. Two nuclei are sometimes observed in the medulla part of the cell. Ventral nephrocytes contain well-developed rough endoplasmic reticulum and Golgi complex, and numerous mitochondria. These cellular organelles synthesize lysosome. The lysosome not only digest some cell organells but also seems to be related with the ${\beta}$-vacuoles.

• BMB Reports
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• v.49 no.8
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• pp.424-430
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• 2016

Autophagy, an evolutionarily conserved cellular degradation pathway of the lysosome, is associated with many physiological and pathological processes. The hallmark of autophagy is the formation of the autophagosome that engulfs and degrades cytosolic components via its fusion with the lysosome, in either a selective or a non-selective manner. Autophagy is tightly regulated by proteins encoded by autophagy-related (atg) genes. Among these proteins, ATG8/LC3 is essential for autophagosome biogenesis/maturation and it also functions as an adaptor protein for selective autophagy. In mammalian cells, several homologs of yeast Atg8 such as MAP1LC3, GABARAP, and GABARAPL 1/2 have been identified. However, the biological relevance of this gene diversity in higher eukaryotes, and their specific roles, are largely unknown. In this review, we describe the mammalian ATG8/LC3 family and discuss recent advancements in understanding their roles in the autophagic process.

• BMB Reports
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• v.49 no.5
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• pp.247-248
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• 2016

Necroptosis is a well-known form of caspase-independent cell death. Necroptosis can be triggered by various extrinsic stimuli, including death ligands in the presence of receptorinteracting protein kinase 3 (RIPK3), a key mediator of necroptosis induction. Our recent studies have revealed that C-terminus HSC-70 interacting protein (CHIP), an E3 ligase, can function as an inhibitor of necroptosis. CHIP^−/− mouse embryonic fibroblast showed higher sensitivity to necrotic stimuli than wild-type mouse embryonic fibroblast cells. Deleterious effects of CHIP knockout MEFs were retrieved by RIPK3 depletion. We found that CHIP negatively regulated RIPK3 and RIPK1 by ubiquitylation- and lysosome- dependent degradation. In addition, CHIP^−/− mice showed postnatal lethality with intestinal defects that could be rescued by crossing with RIPK3^−/− mice. These results suggest that CHIP is a negative regulator of RIPK1 and RIPK3, thus inhibiting necroptosis.

• Molecules and Cells
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• v.39 no.7
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• pp.566-572
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• 2016

Lysosomes are cellular organelles containing diverse classes of catabolic enzymes that are implicated in diverse cellular processes including phagocytosis, autophagy, lipid transport, and aging. Lysosome-associated membrane proteins (LAMP-1 and LAMP-2) are major glycoproteins important for maintaining lysosomal integrity, pH, and catabolism. LAMP-1 and LAMP-2 are constitutively expressed in Salmonella-infected cells and are recruited to Salmonella-containing vacuoles (SCVs) as well as Salmonella- induced filaments (Sifs) that promote the survival and proliferation of the Salmonella. LAMP-3, also known as DC-LAMP/CD208, is a member of the LAMP family of proteins, but its role during Salmonella infection remains unclear. DNA microarray analysis identified LAMP-3 as one of the genes responding to LPS stimulation in THP-1 macrophage cells. Subsequent analyses reveal that LPS and Salmonella induced the expression of LAMP-3 at both the transcriptional and translational levels. Confocal Super resolution N-SIM imaging revealed that LAMP-3, like LAMP-2, shifts its localization from the cell surface to alongside Salmonella. Knockdown of LAMP-3 by specific siRNAs decreased the number of Salmonella recovered from the infected cells. Therefore, we conclude that LAMP-3 is induced by Salmonella infection and recruited to the Salmonella pathogen for intracellular proliferation.

• Journal of Life Science
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• v.18 no.3
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• pp.344-349
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• 2008

Normal somatic cells proliferate for a limited number of doublings in culture and then enter an irreversible growth-arrest state called replicative senescence. Replicative senescence has been believed a reason for the limited cellular turnover and deterioration of tissue function in aged animals. However, there is no experimental evidence supporting this assumption. Furthermore, cells from aged person have been poorly characterized with an exception of the cases of T cells. In this study, we examined cell biological changes occurring in replicative senescence of fibroblast strains originated from a new-born (NHF-NB) and a 87 year old man (NHF-87). NHF-87 (and the cells from a 75-year old) proliferated to smaller population doublings and with longer doubling times than NHF-NB did. At early passages, NHF-87 exhibited a low senescence-associated ${\beta}-Gal$ (SA ${\beta}-Gal$) activity and lipofuscin level, typical markers for cellular senescence. Furthermore, they maintained low levels of lysosome and reactive oxygen species (ROS). All of these levels increased dramatically in the late passage NHF-87 quite similarly as those in the late passaged NHF-NB did. These results indicate that most cells originated from the aged maintain a phenotype of the cells originated from new-born donors and undergo replicative senescence with the same kinetics as that of the cells from new-born. It is also indicated that not SA ${\beta}-gal$ activity but cell proliferation rate may be qualified as a biomarker for cells aged in vivo.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.6
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• pp.664-672
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• 1993

The purpose of this study was to investigate the effect of alcohol administration on selenium concentration and cell morphology in tissurs of rats fed with the different levels of selenium (Se) and vitamin E. Seventy two male rats of Sprague-Dawley strain weighing about 58~62g were divided into 12 groups. The dietary Se levels were 0mg(L-), 0.4mg(C-) and 10mg(H-), and the dietary vitamin E levels were 0mg(-L) and 150mg(-C) per kg diet, respectively. Alcohol-adminstrated groups(--A) received the triple distilled potable water solution containing 10% of ethanol from the 3rd week of experimental periods. The obtained experimental results are summarized as follows. Se concentration in blood and urine made difference in accordance with Se level in diet and tended to be low in alcohol administrated groups. Se concentration in liver and kidney was also directly proportional to the dietary Se level, and it tended to be low in each alcohol group, but Se concentration in kidney tended to be increased by alcohol administration. Myocardium in rats showed lysosome increasing, fat droplet, mitochondrial swelling, and in particular, bad intracellular edema, in H-group fed with high Se and in L-group with low Se. It also showed such phenomena in the alcohol administrated group. In HC-group fed with excessive Se and normal vitamin E. there appeared no noticeable change in liver tissue. However, in the alcohol administrated HCA-group, there came out fat droplet. Especially, in the alcohol administrated LLA-group, not fed with sufficient Se and vitamin, E, there were found lysosome increasing and a number of fat droplet.