• Journal of Applied Biological Chemistry
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• v.57 no.3
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• pp.259-265
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• 2014

Mitochondrial DNA (mtDNA)-depleted (${\rho}^0$) cells are often used as mtDNA recipients to study the interaction between the nucleus and mitochondria in mammalian cells. Therefore, it is crucial to obtain mtDNA-depleted cells with many different nuclear backgrounds for the study. Here, we demonstrate a rapid and reliable method to isolate mammalian mtDNA-depleted cells involving treatment with the antimitochondrial agents ethidium bromide (EtBr) and 2',3'-dideoxycytidine (ddC). After a short exposure to EtBr or ddC, followed by rapid clonal isolation, we were able to generate viable mtDNA-depleted cells from mouse and human cells and were able to successfully repopulate them with exogenous mitochondria from platelets isolated from mouse and human blood samples. These mtDNA-depleted cells can be used to characterize the nuclear mitochondrial interactions and to study mtDNA-associated defects in mammalian cells. Our method of isolating mtDNA-depleted cells is practical and applicable to a variety of cell types.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.6
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• pp.519-528
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• 2019

Mitochondrial dysfunction is closely associated with reactive oxygen species (ROS) generation and oxidative stress in cells. On the other hand, modulation of the cellular antioxidant defense system by changes in the mitochondrial DNA (mtDNA) content is largely unknown. To determine the relationship between the cellular mtDNA content and defense system against oxidative stress, this study examined a set of myoblasts containing a depleted or reverted mtDNA content. A change in the cellular mtDNA content modulated the expression of antioxidant enzymes in myoblasts. In particular, the expression and activity of glutathione peroxidase (GPx) and catalase were inversely correlated with the mtDNA content in myoblasts. The depletion of mtDNA decreased both the reduced glutathione (GSH) and oxidized glutathione (GSSG) slightly, whereas the cellular redox status, as assessed by the GSH/GSSG ratio, was similar to that of the control. Interestingly, the steady-state level of the intracellular ROS, which depends on the reciprocal actions between ROS generation and detoxification, was reduced significantly and the lethality induced by $H_2O_2$ was alleviated by mtDNA depletion in myoblasts. Therefore, these results suggest that the ROS homeostasis and antioxidant enzymes are modulated by the cellular mtDNA content and that the increased expression and activity of GPx and catalase through the depletion of mtDNA are closely associated with an alleviation of the oxidative stress in myoblasts.

• BMB Reports
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• v.51 no.6
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• pp.296-301
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• 2018

Mitochondrial DNA (mtDNA) mutations are often observed in various cancer types. Although the correlation between mitochondrial dysfunction and cancer malignancy has been demonstrated by several studies, further research is required to elucidate the molecular mechanisms underlying accelerated tumor development and progression due to mitochondrial mutations. We generated an mtDNA-depleted cell line, ${\rho}^0$, via long-term ethidium bromide treatment to define the molecular mechanisms of tumor malignancy induced by mitochondrial dysfunction. Mitochondrial dysfunction in ${\rho}^0$ cells reduced drug-induced cell death and decreased the expression of pro-apoptotic proteins including p53. The p53 expression was reduced by activation of nuclear $factor-{\kappa}B$ that depended on elevated levels of free calcium in $HCT116/{\rho}^0$ cells. Overall, these data provide a novel mechanism for tumor development and drug resistance due to mitochondrial dysfunction.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.6
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• pp.697-703
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• 2018

Myoblast fusion depends on mitochondrial integrity and intracellular $Ca^{2+}$ signaling regulated by various ion channels. In this study, we investigated the ionic currents associated with $[Ca^{2+}]_i$ regulation in normal and mitochondrial DNA-depleted(${\rho}0$) L6 myoblasts. The ${\rho}0$ myoblasts showed impaired myotube formation. The inwardly rectifying $K^+$ current ($I_{Kir}$) was largely decreased with reduced expression of KIR2.1, whereas the voltage-operated $Ca^{2+}$ channel and $Ca^{2+}$-activated $K^+$ channel currents were intact. Sustained inhibition of mitochondrial electron transport by antimycin A treatment (24 h) also decreased the $I_{Kir}$. The ${\rho}0$ myoblasts showed depolarized resting membrane potential and higher basal $[Ca^{2+}]_i$. Our results demonstrated the specific downregulation of $I_{Kir}$ by dysfunctional mitochondria. The resultant depolarization and altered $Ca^{2+}$ signaling might be associated with impaired myoblast fusion in ${\rho}0$ myoblasts.