• Biomolecules & Therapeutics
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• v.11 no.2
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• pp.112-118
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• 2003

1-Methylated $\beta$-carbolines (harmaline and harmalol) and antioxidants (N-acetylcysteine and ascorbate) reduced the loss of cell viability in differentiated PC 12 cells treated with 5 mM glutamate. $\beta$-Carbolines prevented the glutamate-induced decrease in mitochondrial membrane potential, cytochrome c release and caspase-3 activation in PC 12 cells. $\beta$-Carbolines reduced the formation of reactive oxygen species and depletion of glutathione due to glutamate in PC12 cells. $\beta$-Carbolines revealed a scavenging action on hydrogen peroxide and reduced the iron and EDTA-mediated degradation of 2-deoxy-D-ribose. The results suggest that I-methylated $\beta$-carbolines attenuate the cytotoxic effect of glutamate on PC12 cells by reducing the alteration of mitochondrial membrane permeability that seems to be mediated by oxidative stress.

• Journal of Microbiology and Biotechnology
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• v.31 no.6
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• pp.875-881
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• 2021

The mitochondrial targeting domain (MTD) of Noxa contributes to its mitochondrial localization and to apoptosis induction. As a peptide, MTD fused with octa-arginine (R8), a CPP, induces necrosis related to intracellular calcium influx and destruction of mitochondria and endoplasmic reticulum. We searched for homologs of MTD, and compared their cell killing capability when fused with R8. Three of the seven peptides triggered cell death with similar mechanisms. The comparative analysis of peptide sequences showed that four amino acid sites of MTD are critical in regulating necrosis, suggesting the potential to generate artificial, adjustable cytotoxic peptides, which could be effective medicines for many diseases. Thus, homologs functionality could hint to the functions of their belonging proteins.

• Journal of Korean Neurosurgical Society
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• v.59 no.3
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• pp.259-268
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• 2016

Objective : Accumulation of advanced glycation end-products (AGE) and mitochondrial glycation is importantly implicated in the pathological changes of the brain associated with diabetic complications, Alzheimer disease, and aging. The present study was undertaken to determine whether sildenafil, a type 5 phosphodiesterase type (PDE-5) inhibitor, has beneficial effect on neuronal cells challenged with AGE-induced oxidative stress to preserve their mitochondrial functional integrity. Methods : HT-22 hippocampal neuronal cells were exposed to AGE and changes in the mitochondrial functional parameters were determined. Pretreatment of cells with sildenafil effectively ameliorated these AGE-induced deterioration of mitochondrial functional integrity. Results : AGE-treated cells lost their mitochondrial functional integrity which was estimated by their MTT reduction ability and intracellular ATP concentration. These cells exhibited stimulated generation of reactive oxygen species (ROS), disruption of mitochondrial membrane potential, induction of mitochondrial permeability transition, and release of the cytochrome C, activation of the caspase-3 accompanied by apoptosis. Western blot analyses and qRT-PCR demonstrated that sildenafil increased the expression level of the heme oxygenase-1 (HO-1). CoPP and bilirubin, an inducer of HO-1 and a metabolic product of HO-1, respectively, provided a similar protective effects. On the contrary, the HO-1 inhibitor ZnPP IX blocked the effect of sildenafil. Transfection with HO-1 siRNA significantly reduced the protective effect of sildenafil on the loss of MTT reduction ability and MPT induction in AGE-treated cells. Conclusion : Taken together, our results suggested that sildenafil provides beneficial effect to protect the HT-22 hippocampal neuronal cells against AGE-induced deterioration of mitochondrial integrity, and upregulation of HO-1 is involved in the underlying mechanism.

• BMB Reports
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• v.55 no.7
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• pp.354-359
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• 2022

MitoNEET, a mitochondrial outer membrane protein containing the Asn-Glu-Glu-Thr (NEET) sequence, controls the formation of intermitochondrial junctions and confers autophagy resistance. Moreover, mitoNEET as a mitochondrial substrate undergoes ubiquitination by activated Parkin during the initiation of mitophagy. Therefore, mitoNEET is linked to the regulation of autophagy and mitophagy. Mitophagy is the selective removal of the damaged or unnecessary mitochondria, which is crucial to sustaining mitochondrial quality control. In numerous human diseases, the accumulation of damaged mitochondria by impaired mitophagy has been observed. However, the therapeutic strategy targeting of mitoNEET as a mitophagy-enhancing mediator requires further research. Herein, we confirmed that mitophagy is indeed activated by mitoNEET inhibition. CCCP (carbonyl cyanide m-chlorophenyl hydrazone), which leads to mitochondrial depolarization, induces mitochondrial dysfunction and superoxide production. This, in turn, contributes to the induction of mitophagy; mitoNEET protein levels were initially increased before an increase in LC3-II protein following CCCP treatment. Pharmacological inhibition of mitoNEET using mitoNEET Ligand-1 (NL-1) promoted accumulation of Pink1 and Parkin, which are mitophagy-associated proteins, and activation of mitochondria-lysosome crosstalk, in comparison to CCCP alone. Inhibition of mitoNEET using NL-1, or mitoNEET shRNA transfected into RAW264.7 cells, abrogated CCCP-induced ROS and mitochondrial cell death; additionally, it activated the expression of PGC-1α and SOD2, regulators of oxidative metabolism. In particular, the increase in PGC-1α, which is a major regulator of mitochondrial biogenesis, promotes mitochondrial quality control. These results indicated that mitoNEET is a potential therapeutic target in numerous human diseases to enhance mitophagy and protect cells by maintaining a network of healthy mitochondria.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.40-49
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• 2018

We evaluated the antioxidant activity and neuronal cell-protective effect of fucoidan extract from Ecklonia cava (FEC) on hydrogen peroxide ($H_2O_2$)-induced cytotoxicity in PC-12 and MC-IXC cells to assess its protective effect against oxidative stress. Antioxidant activities were examined using the ABTS radical scavenging activity and malondialdehyde-inhibitory effect, and the results showed that FEC had significant antioxidant activity. Intracellular ROS contents and neuronal cell viability were investigated using the DCF-DA assay and MTT reduction assay. FEC also showed remarkable neuronal cell-protective effect compared with vitamin C as a positive control for both $H_2O_2$-treated PC-12 and MC-IXC cells. Based on the neuronal cell-protective effects, mitochondrial function was analyzed in PC-12 cells, and FEC significantly restored mitochondrial damage by increasing the mitochondrial membrane potential (${\Delta}{\Psi}m$) and ATP levels and regulating mitochondrial-mediated proteins (p-AMPK and BAX). Finally, the inhibitory effects against acetylcholinesterase (AChE), which is a critical hydrolyzing enzyme of the neurotransmitter acetylcholine in the cholinergic system, were investigated ($IC_{50}$ value = 1.3 mg/ml) and showed a mixed (competitive and noncompetitive) pattern of inhibition. Our findings suggest that FEC may be used as a potential material for alleviating oxidative stress-induced neuronal damage by regulating mitochondrial function and AChE inhibition.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.5
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• pp.1833-1837
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• 2015

An aristolactam-type alkaloid, isolated from Orophea enterocarpa, is enterocarpam-III (10-amino-2,3,4,6-tetramethoxyphenanthrene-1-carboxylic acid lactam). It is cytotoxic to various human and murine cancer cell lines; however, the molecular mechanisms remain unclear. The aims of this study were to investigate cytotoxic effects on and mechanism (s) of human cancer cell death in human hepatocellular carcinoma HepG2 and human invasive breast cancer MDA-MB-231 cells compared to normal murine fibroblast NIH3T3 cells. Cell viability was determined by MTT assay to determine $IC_{10}$, $IC_{20}$ and $IC_{50}$ levels, reactive oxygen species (ROS) production with 2',7'-dichlorohydrofluorescein diacetate and the caspase-3, -8 and -9 activities using specific chromogenic (p-nitroaniline) tetrapeptide substrates, viz., DEVD-NA, IETD-NA and LEHD-NA and employing a microplate reader. Mitochondrial transmembrane potential (MTP) was measured by staining with 3, 3'-dihexyloxacarbocyanine iodide ($DiOC_6$) and using flow cytometry. The compound was cytotoxic to HepG2 and MDA-MB-231 cells with the $IC_{50}$ levels of $26.0{\pm}4.45$ and $51.3{\pm}2.05{\mu}M$, respectively. For murine normal fibroblast NIH3T3 cells, the $IC_{50}$ concentration was $81.3{\pm}10.1{\mu}M$. ROS production was reduced in a dose-response manner in HepG2 cells. The caspase-9 and -3 activities increased in a concentration-dependent manner, whereas caspase-8 activity did not alter, indicating the intrinsic pathway activation. Enterocarpam-III decreased the mitochondrial transmembrane potential (MTP) dose-dependently in HepG2 cells, suggesting that the compound induced HepG2 cell apoptosis via the mitochondrial pathway. In conclusion, enterocarpam-III inhibited HepG2 and MDA-MB-231 cell proliferation and induced human HepG2 cells to undergo apoptosis via the intrinsic (mitochondrial) pathway and induction of caspase-9 activity.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.4
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• pp.888-894
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• 2009

It has been reported that silibinin, a natural polyphenolic flavonoid, induces cell death in various cancer cell types. However, the underlying mechanisms by which silibinin induces apoptosis in human glioma cells are poorly understood. The present study was therefore undertaken to examine the effect of silibinin on glioma cell apoptosis and to determine its underlying mechanism in human glioma cells. Apoptosis was estimated by FACS analysis. Reactive oxygen species (ROS) generation and mitochondrial membrane potential (${\Psi}m$) were measured using fluorescence dyes DCFH-DA and $DiOC_6$(3), respectively. Cytochrome c release from mitochondria and caspase-3 activation were estimated by Western blot analysis using specific antibodies. Exposure of cells to 30 mM silibinin induced apoptosis starting at 6 h, with increasing effects after 12-48h in a time-dependent manner. Silibinin caused ROS generation and disruption of ym, which were associated with the silibinin-induced apoptosis. The silibinin-induced ROS generation and disruption in ym were prevented by inhibitors of mitochondrial electron transport chain. The hydrogen peroxide scavenger catalase blocked ROS generation and apoptosis induced by silibinin. Silibinin induced cytochrome c release into cytosolic fraction and its effect was prevented by catalase and cyclosporine A. Silibinin treatment caused caspase-3 activation, which was inhibited by DVED-CHO and cyclosporine A. Pretreatment of caspase inhibitors also protected against the silibinin-induced apoptosis. These findings indicate that ROS generation plays a critical role in the initiation of the silibinin-induced apoptotic cascade by mediation of the mitochondrial apoptotic pathway including the disruption of ${\Psi}m$, cytochrome c release, and caspase-3 activation.

• Clinical and Experimental Reproductive Medicine
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• v.45 no.1
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• pp.10-16
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• 2018

Objective: Placental oxidative stress is known to be a factor that contributes to pregnancy failure. The aim of this study was to determine whether selenium could induce antioxidant gene expression and regulate invasive activity and mitochondrial activity in trophoblasts, which are a major cell type of the placenta. Methods: To understand the effects of selenium on trophoblast cells exposed to hypoxia, the viability and invasive activity of trophoblasts were analyzed. The expression of antioxidant enzymes was assessed by reverse-transcription polymerase chain reaction. In addition, the effects of selenium treatment on mitochondrial activity were evaluated in terms of adenosine triphosphate production, mitochondrial membrane potential, and reactive oxygen species levels. Results: Selenium showed positive effects on the viability and migration activity of trophoblast cells when exposed to hypoxia. Interestingly, the increased heme oxygenase 1 expression under hypoxic conditions was decreased by selenium treatment, whereas superoxide dismutase expression was increased in trophoblast cells by selenium treatment for 72 hours, regardless of hypoxia. Selenium-treated trophoblast cells showed increased mitochondrial membrane potential and decreased reactive oxygen species levels under hypoxic conditions for 72 hours. Conclusion: These results will be used as basic data for understanding the mechanism of how trophoblast cells respond to oxidative stress and how selenium promotes the upregulation of related genes and improves the survival rate and invasive ability of trophoblasts through regulating mitochondrial activity. These results suggest that selenium may be used in reproductive medicine for purposes including infertility treatment.

• Molecules and Cells
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• v.40 no.7
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• pp.503-514
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• 2017

Nicotinamide (NAM) plays essential roles in physiology through facilitating $NAD^+$ redox homeostasis. Importantly, at high doses, it protects cells under oxidative stresses, and has shown therapeutic effectiveness in a variety of disease conditions. In our previous studies, NAM lowered reactive oxygen species (ROS) levels and extended cellular life span in primary human cells. In the treated cells, levels of $NAD^+/NADH$ and SIRT1 activity increased, while mitochondrial content decreased through autophagy activation. The remaining mitochondria were marked with low superoxide levels and high membrane potentials (${\Delta}_{{\Psi}m}$); we posited that the treatment of NAM induced an activation of mitophagy that is selective for depolarized mitochondria, which produce high levels of ROS. However, evidence for the selective mitophagy that is mediated by SIRT1 has never been provided. This study sought to explain the mechanisms by which NAM lowers ROS levels and increases ${\Delta}_{{\Psi}m}$. Our results showed that NAM and SIRT1 activation exert quite different effects on mitochondrial physiology. Furthermore, the changes in ROS and ${\Delta}_{{\Psi}m}$ were not found to be mediated through autophagy or SIRT activation. Rather, NAM suppressed superoxide generation via a direct reduction of electron transport, and increased ${\Delta}_{{\Psi}m}$ via suppression of mitochondrial permeability transition pore formation. Our results dissected the effects of cellular $NAD^+$ redox modulation, and emphasized the importance of the $NAD^+/NADH$ ratio in the mitochondria as well as the cytosol in maintaining mitochondrial quality.

• The Korea Journal of Herbology
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• v.36 no.5
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• pp.125-133
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• 2021

Objectives : Thymus quinquecistatus var. japonica (H.Hara) is a member of the genus Thymus of perennial aromatic herb, and it's designated as a natural monument of South Korea. It has traditionally been known to have protective or therapeutic effects on various human disease including cerebrovascular and neurological disease. Recently it was suggested that essential oil extracted from thyme has anti-fungal and anti-bacterial effect. The aim of this study is to investigate anti-inflammatory effect of Thymus quinquecistatus var. japonica in Raw 264.7 macrophage cell line. Methods : The cytotoxic effects of water and 70% ethanol extracts from Thymus quinquecistatus var. japonica, was tested using MTT assay. Inhibitory effects of the extracts to nitric oxide production and mRNA expression of inflammatory cytokines were examined by RT-PCR. Also, MitoSOX-red assay and JC-1 assay were performed to determine if the extracts can inhibit mitochondrial ROS accumulation and maintain mitochondrial membrane potential. Results : In LPS-induced inflammatory response, the extracts efficiently reduced nitric oxide NO production through inhibiting mRNA expression of iNOS enzyme. In addition, expression of the proinflammatory cytokines, IL-1𝛽 and IL-6, was also down-regulated by the extract treatments. Excessive accumulation of mitochondrial ROS induced by LPS was inhibited in the extract treated cells, which finally protected mitochondrial membrane potential. Conclusions : These results showed that water and 70% ethanol extracts from Thymus quinquecistatus var. japonica have anti-inflammatory effect through down regulation of IL-1𝛽, IL-6, and iNOS, and also have antioxidative effect against mitochondrial ROS accumulation that promote inflammatory response.