• Proceedings of the Botanical Society of Korea Conference
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• 2001.04a
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• pp.5-5
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• 2001

• Biomolecules & Therapeutics
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• v.27 no.6
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• pp.530-539
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• 2019

Brain aging is an inevitable process characterized by structural and functional changes and is a major risk factor for neurodegenerative diseases. Most brain aging studies are focused on neurons and less on astrocytes which are the most abundant cells in the brain known to be in charge of various functions including the maintenance of brain physical formation, ion homeostasis, and secretion of various extracellular matrix proteins. Altered mitochondrial dynamics, defective mitophagy or mitochondrial damages are causative factors of mitochondrial dysfunction, which is linked to age-related disorders. Etoposide is an anti-cancer reagent which can induce DNA stress and cellular senescence of cancer cell lines. In this study, we investigated whether etoposide induces senescence and functional alterations in cultured rat astrocytes. Senescence-associated ${\beta}$-galactosidase (SA-${\beta}$-gal) activity was used as a cellular senescence marker. The results indicated that etoposide-treated astrocytes showed cellular senescence phenotypes including increased SA-${\beta}$-gal-positive cells number, increased nuclear size and increased senescence-associated secretory phenotypes (SASP) such as IL-6. We also observed a decreased expression of cell cycle markers, including PhosphoHistone H3/Histone H3 and CDK2, and dysregulation of cellular functions based on wound-healing, neuronal protection, and phagocytosis assays. Finally, mitochondrial dysfunction was noted through the determination of mitochondrial membrane potential using tetramethylrhodamine methyl ester (TMRM) and the measurement of mitochondrial oxygen consumption rate (OCR). These data suggest that etoposide can induce cellular senescence and mitochondrial dysfunction in astrocytes which may have implications in brain aging and neurodegenerative conditions.

• International Journal of Oral Biology
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• v.32 no.1
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• pp.35-43
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• 2007

Tooth loss in elderly is mainly caused by alveolar bone loss via severe periodontitis. Although the severity of periodontitis is known to be affected by age, the aging process or the genetic changes during the aging of periodontal tissue cells are not well characterized. In this study, we investigated the effect of in vitro aging on the change of gene expression pattern in periodontal fibroblasts. Gingival fibroblasts (GF) and periodontal ligament fibroblasts (PDL) were obtained from two young patients and replicative senescence was induced by sequential subcultivation. When more than 90% cells were positively stained with senescence-associated ${\beta},-galactosidase$, those cells were regarded as aged cells. In aged GF and PDL, the level of phosphorylated retinoblastoma (RB) and $p16^{INK4A}$ protein was significantly decreased and increased, respectively. However, the protein level of p53 and p21, well known senescence-inducing genes, did not increase in aged GF and PDL. Although $p27^{Kip1}$ and $p15^{INK4B}$, another cyclin-dependent kinase inhibitors, were reported to be involved in replicative senescence of human cells, they were decreased in aged GF and PDL. Because senescent cells showed flattened and enlarged cell shape and are known to have increased focal adhesion, we examined the protein level of several integrins. Aged GF and PDL showed increased protein level of integrin ${\alpha}2$, ${\alpha}v$, and ${\beta}1$. When the gene expression profiles of actively proliferating young cells and aged cells were compared by cDNA microarray of 3,063 genes and were confirmed by reverse transcription-polymerase chain reaction, 7 genes and 15 genes were significantly and commonly increased and decreased, respectively, in aged GF and PDL. Among them, included are the genes that were known to be involved in the regulation of cell cycle, gene transcription, or integrin signaling. The change of gene expression pattern in GF and PDL was minimally similar to that of oral keratinocyte. These results suggest that $p16^{INK4A}/RB$ might be involved in replicative senescence of periodontal fibroblasts and the change of gene expression profile during aging process is cell type specific.

• Molecules and Cells
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• v.37 no.3
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• pp.189-195
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• 2014

The NF-${\kappa}B$ pathway transcriptionally controls a large set of target genes that play important roles in cell survival, inflammation, and immune responses. While many studies showed anti-tumorigenic and pro-survival role of NF-${\kappa}B$ in cancer cells, recent findings postulate that NF-${\kappa}B$ participates in a senescence-associated cytokine response, thereby suggesting a tumor restraining role of NF-${\kappa}B$. In this review, we discuss implications of the NF-${\kappa}B$ signaling pathway in cancer. Particularly, we emphasize the connection of NF-${\kappa}B$ with cellular senescence as a response to chemotherapy, and furthermore, present examples how distinct oncogenic network contexts surrounding NF-${\kappa}B$ produce fundamentally different treatment outcomes in aggressive B-cell lymphomas as an example.

• Development and Reproduction
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• v.21 no.1
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• pp.1-10
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• 2017

The use of human mesenchymal stem cells (hMSCs) in cell-based therapy has attracted extensive interest in the field of regenerative medicine, and it shows applications to numerous incurable diseases. hMSCs show several superior properties for therapeutic use compared to other types of stem cells. Different cell types are discussed in terms of their advantages and disadvantages, with focus on the characteristics of hMSCs. hMSCs can proliferate readily and produce differentiated cells that can substitute for the targeted affected tissue. To maximize the therapeutic effects of hMSCs, a substantial number of these cells are essential, requiring extensive ex vivo cell expansion. However, hMSCs have a limited lifespan in an in vitro culture condition. The senescence of hMSCs is a double-edged sword from the viewpoint of clinical applications. Although their limited cell proliferation potency protects them from malignant transformation after transplantation, senescence can alter various cell functions including proliferation, differentiation, and migration, that are essential for their therapeutic efficacy. Numerous trials to overcome the limited lifespan of mesenchymal stem cells are discussed.

• Korean Journal of Plant Tissue Culture
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• v.27 no.4
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• pp.259-268
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• 2000

Senescence is a sequence of biochemical and physiological events that lead to death of a cell, organ, or whole organism. Senescence is now clearly regarded as a genetically determined and evolutionarilly acquired developmental process comprising the final stage of development. However, in spite of the biological and practical importance, genetic mechanism of senescence has been very limited. Through forward and reverse genetic approaches, we are trying to reveal the molecular and genetic mechanism of senescence in plants, employing leaf organs of Arabidopsis as a model system. Using forward genetic approach, we have initially isolated several delayed senescence mutants either from T-DNA insertional lines or chemical-mutagenized lines. In the case of ore 4 and ore 9 mutants, the mutated genes were identified. The recent progress on characterization of mutants and identification of the mutated genes will be reported. We are also screening mutations from other various sources of mutant pools, such as activation tagging lines and promoter trap lines. Two dominant senescence-delayed mutants were isolated from the activation tagging pool. Cloning of the genes responsible for this phenotype is in progress. For reverse genetic approach, the genes that induced during leaf senescence were first isolated by differential screening method. We are currently using PCR-based suppression subtractive hybridization, designed to enrich a cDNA library for rare differentially expressed transcripts. Using this method, we have identified over 35 new sequences that are upregulated at leaf senescence stage. We are investigating the function of these novel genes by systemically generating antisense lines.

• Toxicological Research
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• v.23 no.4
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• pp.311-319
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• 2007

Elevated blood levels of homocysteine (a sulfur-containing amino acid) have been linked to increased risk of cerebrovascular disease including Alzheimer's disease. A recent study suggests that elevated homocysteine levels may lead to replicative senescence in vitro called 'permanent arrest of cell cycle' caused by oxidative stress. In this study, serum homocysteine level in rat was reduced by Lentinus edodes-powder diet, resulting in the reduced level of oxidative stress in rat brain. In addition, homocysteine-induced replicative senescence treated with or without Lentinus edodes-powder was analyzed by population doubling in vitro. The Lentinus edodes-powder induced a increased number of population doubling in primary neuron cell isolated from rat-cerebral cortex. This indicates that Lentinus edodes-powder would delay a homocysteine-induced aging of neuron cells in brain, showing a possible role in preventing cerebrovascular diseases including Alzheimer's disease.

• Journal of Pharmacopuncture
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• v.20 no.3
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• pp.213-219
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• 2017

Objectives: Based on data from Chinese and Indian traditional herbal medicines, gum resin of Ferula assa-foetida (sometimes referred to asafetida or asafoetida) has several therapeutic applications. The authors of various studies have claimed that asafetida has cytotoxic, antiulcer, anti-neoplasm, anti-cancer, and anti-oxidative effects. In present study, the anti-aging effect of asafetida on senescent human dermal fibroblasts was evaluated. Methods: Senescence was induced in in vitro cultured human dermal fibroblasts (HDFs) through exposure to $H_2O_2$, and the incidence of senescence was recognized by using cytochemical staining for the activity of ${\beta}$-galactosidase. Then, treatment with oleo gum resin of asafetida was started to evaluate its rejuvenating effect. The survival rate of fibroblasts was evaluated by using methyl tetrazolium bromide (MTT) assays. Real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot assays were performed to evaluate the expressions of apoptotic and anti-apoptotic markers. Results: Our experiments show that asafetida in concentrations ranging from $5{\times}10^{-8}$ to $10^{-7}g/mL$ has revitalizing effects on senescent fibroblasts and significantly reduces the ${\beta}$-galactosidase activity in these cells (P < 0.05). Likewise, treatment at these concentrations increases the proliferation rate of normal fibroblasts (P < 0.05). However, at concentrations higher than $5{\times}10^{-7}g/mL$, asafetida is toxic for cells and induces cell death. Conclusion: The results of this study indicate that asafetida at low concentrations has a rejuvenating effect on senescent fibroblasts whereas at higher concentrations, it has the opposite effect of facilitating cellular apoptosis and death.

• Molecules and Cells
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• v.38 no.3
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• pp.229-235
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• 2015

Nicotinamide (NAM) has been shown to suppress reactive oxygen species (ROS) production in primary human fibroblasts, thereby extending their replicative lifespan when added to the medium during long-term cultivation. Based on this finding, NAM is hypothesized to affect cellular senescence progression by keeping ROS accumulation low. In the current study, we asked whether NAM is indeed able to reduce ROS levels and senescence phenotypes in cells undergoing senescence progression and those already in senescence. We employed two different cellular models: MCF-7 cells undergoing senescence progression and human fibroblasts in a state of replicative senescence. In both models, NAM treatment substantially decreased ROS levels. In addition, NAM attenuated the expression of the assessed senescence phenotypes, excluding irreversible growth arrest. N-acetyl cysteine, a potent ROS scavenger, did not have comparable effects in the tested cell types. These data show that NAM has potent antioxidative as well as anti-senescent effects. Moreover, these findings suggest that NAM can reduce cellular deterioration caused by oxidative damage in postmitotic cells in vivo.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.4
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• pp.297-305
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• 2021

Luteolin, a sort of flavonoid, has been reported to be involved in neuroprotective function via suppression of neuroinflammation. In this study, we investigated the protective effect of luteolin against oxidative stress-induced cellular senescence and its molecular mechanism using hydrogen peroxide (H₂O₂)-induced cellular senescence model in House Ear Institute-Organ of Corti 1 cells (HEI-OC1). Our results showed that luteolin attenuated senescent phenotypes including alterations of morphology, cell proliferation, senescence-associated 𝛽-galactosidase expression, DNA damage, as well as related molecules expression such as p53 and p21 in the oxidant challenged model. Interestingly, we found that luteolin induces expression of sirtuin 1 in dose- and time-dependent manners and it has protective role against H₂O₂-induced cellular senescence by upregulation of sirtuin 1 (SIRT1). In contrast, the inhibitory effect of luteolin on cellular senescence under oxidative stress was abolished by silencing of SIRT1. This study indicates that luteolin effectively protects against oxidative stress-induced cellular senescence through p53 and SIRT1. These results suggest that luteolin possesses therapeutic potentials against age-related hearing loss that are induced by oxidative stress.