• Journal of Ginseng Research
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• 제46권1호
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• pp.138-146
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• 2022

Background: Red Ginseng has been used for many years to treat diseases. Ginsenoside Rg3 has documented therapeutic effects, including anticancer and anti-inflammatory activities. However, the anticancer effect of Rg3-enriched red ginseng extract (Rg3-RGE) and its underlying mechanisms have not been fully explored. We investigated whether Rg3-RGE plays an anti-tumor role in lung cancer cells. Methods: To examine the effect of Rg3-RGE on lung cancer cells, we performed cell viability assays, flow cytometry, western blotting analysis, and immunofluorescence to monitor specific markers. Results: Rg3-RGE significantly inhibited cell proliferation and induced mitochondria-dependent apoptosis. Furthermore, Rg3-RGE also increased expression of mitophagy-related proteins such as PINK1 and Parkin. In addition, treatment with Rg3-RGE and mitophagy inhibitors stimulated cell death by inducing mitochondria dysfunction. Conclusions: Rg3-RGE could be used as a therapeutic agent against lung cancer.

• Journal of Ginseng Research
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• 제46권5호
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• pp.646-656
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• 2022

Background: In addition to its use as a health food, ginseng is used in cosmetics and shampoo because of its extensive health benefits. The ginsenoside, Rh2, is a component of ginseng that inhibits tumor cell proliferation and differentiation, promotes insulin secretion, improves insulin sensitivity, and shows antioxidant effects. Methods: The effects of Rh2 on cell survival, extracellular matrix (ECM) protein expression, and cell differentiation were examined. The antioxidant effects of Rh2 in UV-irradiated normal human dermal fibroblast (NHDF) cells were also examined. The effects of Rh2 on mitochondrial function, morphology, and mitophagy were investigated in UV-irradiated NHDF cells. Results: Rh2 treatment promoted the proliferation of NHDF cells. Additionally, Rh2 increased the expression levels of ECM proteins and growth-associated immediate-early genes in ultraviolet (UV)-irradiated NHDF cells. Rh2 also affected antioxidant protein expression and increased total antioxidant capacity. Furthermore, treatment with Rh2 ameliorated the changes in mitochondrial morphology, induced the recovery of mitochondrial function, and inhibited the initiation of mitophagy in UV-irradiated NHDF cells. Conclusion: Rh2 inhibits mitophagy and reinstates mitochondrial ATP production and membrane potential in NHDF cells damaged by UV exposure, leading to the recovery of ECM, cell proliferation, and antioxidant capacity.

• Molecules and Cells
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• 제40권11호
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• pp.864-870
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• 2017

The uncoupling protein 4 (ucp-4) gene is involved in age-dependent neurodegeneration in C. elegans. Therefore, we aimed to investigate the mechanism underlying the association between mitochondrial uncoupling and neurodegeneration by examining the effects of uncoupling agents and ucp-4 overexpression in C. elegans. Treatment with either DNP or CCCP improved neuronal defects in wild type during aging. Uncoupling agents also restored neuronal phenotypes of ucp-4 mutants to those exhibited by wild type, while ucp-4 overexpression attenuated the severity of age-dependent neurodegeneration. Neuronal improvements were further associated with reductions in mitochondrial membrane potentials. However, these age-dependent neuroprotective effects were limited in mitophagy-deficient mutant, pink-1, background. These results suggest that membrane uncoupling can attenuate age-dependent neurodegeneration by stimulating mitophagy.

• Molecules and Cells
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• 제40권7호
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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.

• Journal of Korean Neurosurgical Society
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• 제65권2호
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• pp.236-244
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• 2022

Objective : To evaluate the interactions among differentially expressed autophagy and mitophagy markers in subarachnoid hemorrhage (SAH) patients with delayed cerebral ischemia (DCI). Methods : The expression data of autophagy and mitophagy-related makers in the cerebrospinal fluid (CSF) cells was analyzed by real-time reverse transcription-polymerase chain reaction and Western blotting. The markers included death-associated protein kinase (DAPK)-1, BCL2 interacting protein 3 like (BNIP3L), Bcl-1 antagonist X, phosphatase and tensin homolog-induced kinase (PINK), Unc-51 like autophagy activating kinase 1, nuclear dot protein 52, and p62. In silico functional analyses including gene ontology enrichment and the protein-protein interaction network were performed. Results : A total of 56 SAH patients were included and 22 (38.6%) of them experienced DCI. The DCI patients had significantly increased mRNA levels of DAPK1, BNIP3L, and PINK1, and increased expression of BECN1 compared to the non-DCI patients. The most enriched biological process was the positive regulation of autophagy, followed by the response to mitochondrial depolarization. The molecular functions ubiquitin-like protein ligase binding and ubiquitin-protein ligase binding were enriched. In the cluster of cellular components, Lewy bodies and the phagophore assembly site were enriched. BECN1 was the most connected gene among the differentially expressed markers related to autophagy and mitophagy in the development of DCI. Conclusion : Our study may provide novel insight into mitochondrial dysfunction in DCI pathogenesis.

• BMB Reports
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• 제53권1호
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• pp.56-63
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• 2020

The ubiquitin-proteasome system (UPS) and autophagy are two major degradative pathways of proteins in eukaryotic cells. As about 30% of newly synthesized proteins are known to be misfolded under normal cell conditions, the precise and timely operation of the UPS and autophagy to remove them as well as their tightly controlled regulation, is so important for proper cell function and survival. In the UPS, target proteins are labeled by small proteins called ubiquitin, which are then transported to the proteasome complex for degradation. Alternatively, many greatly damaged proteins are believed to be delivered to the lysosome for autophagic degradation. Although these autophagy and UPS pathways have not been considered to be directly related, many recent studies proposed their close link and dynamic interconversion. In this review, we'll focus on the several regulatory molecules that function in both UPS and autophagy and their crosstalk. Among the proposed multiple modulators, we will take a closer look at the so-called main connector of UPS-autophagy regulation, p62. Last, the functional role of p62 in the mitophagy and its implication for the pathogenesis of Parkinson's disease, one of the major neurodegenerative diseases, will be briefly reviewed.

• Molecules and Cells
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• 제39권2호
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• pp.87-95
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• 2016

Sirt1 is the most prominent and extensively studied member of sirtuins, the family of mammalian class III histone deacetylases heavily implicated in health span and longevity. Although primarily a nuclear protein, Sirt1's deacetylation of Peroxisome proliferator-activated receptor Gamma Coactivator-$1{\alpha}$ (PGC-$1{\alpha}$) has been extensively implicated in metabolic control and mitochondrial biogenesis, which was proposed to partially underlie Sirt1's role in caloric restriction and impacts on longevity. The notion of Sirt1's regulation of PGC-$1{\alpha}$ activity and its role in mitochondrial biogenesis has, however, been controversial. Interestingly, Sirt1 also appears to be important for the turnover of defective mitochondria by mitophagy. I discuss here evidences for Sirt1's regulation of mitochondrial biogenesis and turnover, in relation to PGC-$1{\alpha}$ deacetylation and various aspects of cellular physiology and disease.

• Journal of Microbiology and Biotechnology
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• 제26권10호
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• pp.1790-1799
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• 2016

Matrix assisted laser desorption ionization (MALDI)-time of flight/mass spectrometry (TOF/MS) was applied to investigate alterations in phospholipids in mitophagic cancer cells. Several phospholipids, including phosphatidylcholines (PCs), sphingomyelins (SMs), and phosphatidylinositols (PIs), were successfully analyzed in control and mitophagy-induced H460 cells in the positive and negative ion modes. Principal component analysis was applied to differentiate the two groups. The upregulated and downregulated phospholipid species in the mitophagic cells were also represented in a heatmap. In the volcano plot (fold change > 1.3 and p value < 0.01), individual species of seven PCs, two SMs, and three PIs were selected as differentially regulated phospholipids. In particular, almost all the molecular species of PC, SM, and PI were downregulated in the mitophagic cells. Quantification of these lipids indicated that mitophagy induces altered metabolism of phospholipids. Therefore, phospholipid alterations during the mitophagic process of lung cancer cells were well characterized by MALDI-TOF/MS.

• The Korean Journal of Physiology and Pharmacology
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• 제21권6호
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• pp.567-577
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• 2017

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all associated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dynamic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochondria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in $O_2$ respiration and increase in oxidative stress) in skeletal muscle. The balance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mitochondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal muscle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle.

• Journal of Yeungnam Medical Science
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• 제41권2호
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• pp.61-73
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• 2024

Acute kidney ischemia-reperfusion (IR) injury is a life-threatening condition that predisposes individuals to chronic kidney disease. Since the kidney is one of the most energy-demanding organs in the human body and mitochondria are the powerhouse of cells, mitochondrial dysfunction plays a central role in the pathogenesis of IR-induced acute kidney injury. Mitochondrial dysfunction causes a reduction in adenosine triphosphate production, loss of mitochondrial dynamics (represented by persistent fragmentation), and impaired mitophagy. Furthermore, the pathological accumulation of succinate resulting from fumarate reduction under oxygen deprivation (ischemia) in the reverse flux of the Krebs cycle can eventually lead to a burst of reactive oxygen species driven by reverse electron transfer during the reperfusion phase. Accumulating evidence indicates that improving mitochondrial function, biogenesis, and dynamics, and normalizing metabolic reprogramming within the mitochondria have the potential to preserve kidney function during IR injury and prevent progression to chronic kidney disease. In this review, we summarize recent advances in understanding the detrimental role of metabolic reprogramming and mitochondrial dysfunction in IR injury and explore potential therapeutic strategies for treating kidney IR injury.