Decrease In mtDNA Copy Number Research Articles

Quercetin protects human coronary artery endothelial cells against hypoxia/reoxygenation-induced mitochondrial apoptosis via the Nrf2/HO-1 axis.

Our study explored the therapeutic effect and the mechanism of quercetin against hypoxia/reoxygenation (H/R)-induced injury in human coronary artery endothelial cells (CAECs). Quercetin was selected as a potential component for the BuShenKangShuaiPian formula (BSKSP) treatment via the Network pharmacology analysis. Cell viability and reactive oxygen species (ROS) production were measured by CCK8 assay and immunofluorescence, respectively. The expression of Bax, Bcl-2, Cle-caspase-3, cytochrome c (Cyt-C), NF-E2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) protein was quantified by western blotting. The superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) activity, mtDNA copy number, and ATP production were measured via corresponding kits. Quercetin was selected from the BSKSP for its high degree value (Degree value: 22). Besides, quercetin protected CAECs against H/R-induced cytotoxicity and apoptosis. The H/R-induced increased ROS level, ATP production, Cyt-C release, and decreased mtDNA copy number were removed by the quercetin. Moreover, quercetin upregulated the Nrf2/ HO-1 axis, SOD, and CAT activity, and downregulated MDA levels in H/R treated CAECs, while knockdown Nrf2 reversed the protection of quercetin against H/R-induced oxidative stress, mitochondrial damage, and apoptosis. Quercetin protects CAECs against H/R-induced mitochondrial apoptosis via the Nrf2/HO-1 axis, which innovatively suggests the therapeutic potential of quercetin for coronary heart disease (CHD) treatment.

The dysregulation of mitochondrial homeostasis-related genes could be involved in the decrease of mtDNA copy number in systemic lupus erythematosus patients.

Systemic lupus erythematosus (SLE) is a chronic multifactorial autoimmune disease. It is now widely demonstrated that oxidative stress (OS) plays an important role in the modulation of the pathogenesis of this disease. Mitochondrial DNA (mtDNA) is highly vulnerable to OS and it is known a decrease of mtDNA copy number in SLE patients. However, to date, it has not been investigated if this decrease is associated with a dysregulation of mitochondrial homeostasis genes. Our aim is to evaluate the amount of mtDNA copy number and the expression of the genes more involved in the mitochondrial homeostasis pathways, in peripheral blood mononuclear cells (PBMCs) of SLE patients and healthy controls. We analysed the amount of mtDNA in PBMCs of 72 SLE patients and 61 healthy controls by qPCR. Then, we investigated the expression variability of TFAM and SIRT1 (biogenesis), MFN1 and MFF (fusion/fission) and PRKN2 (mitophagy) genes in a subgroup of SLE patients and healthy controls. Interestingly, we have observed a highly significant decrease in mtDNA copies in SLE patients compared to healthy controls (P < 0.0001). In addition, we have shown that the expression levels of SIRT1, MFN1 and PRKN2 genes were significantly decreased in SLE patients with respect to healthy controls (P = 0.00001 for SIRT1, P = 0.0150 for MFN1 and P = 0.0009 for PRKN2). Lastly, we have reported a positive correlation between PRKN2 expression level and mtDNA copy number (P = 0.019, r = 0.475). In conclusion, our data confirm the impairment of mtDNA copy number in the disease and show for the first time a dysregulation of the mitochondrial homeostasis genes. These results could provide additional support to the important role of mitochondria in SLE development.

Acute Cannabis Administration Transiently Reduces Mitochondrial DNA in Young Adults: Findings from a Secondary Analysis of a Double-Blind, Placebo-Controlled, Randomized Clinical Trial.

Background: Cannabis is one of the world's most commonly used substances; however, many questions remain unanswered as to how cannabis impacts the body. Recently, there has been a resurgence of research into the effects of plant-derived cannabinoids on mitochondrial health. In particular, a number of studies implicate mitochondrial-Δ9-tetrahydrocannabinol (Δ9-THC) interactions with altered memory, metabolism, and catalepsy in mice. Although the research in this field is expanding rapidly, there is little known about the effects of cannabis on mitochondria health in human subjects either in acute or chronic term use. Methods: Blood samples were obtained from a double-blind, placebo-controlled, parallel-group randomized clinical trial in which adults who regularly use cannabis (1-4 days/week) aged 19-25 years were randomized 2:1 to receive either an active (12.5% Δ9-THC) cigarette or placebo (<0.01% Δ9-THC) cigarette containing 750 mg of cannabis before driving simulator testing. DNA was extracted from whole blood using commercial spin columns, followed by measurement of mt-ND1, mt-ND4, and β2M using quantitative polymerase chain reaction. One-way repeated measures analysis of variance (ANOVA) followed by Dunnett's multiple comparisons test was used to observe changes in mitochondrial DNA (mtDNA) copy number over time. A two-tailed Pearsons R test was used to assess correlations between mtDNA copy number and cannabinoid levels (Δ9-THC and metabolites) in blood. Results: We found that exposure to active cannabis containing Δ9-THC, as opposed to placebo, was associated with an acute reduction in mitochondrial DNA copy number in whole blood at 15 min and 1 h after smoking. The observed decrease in mtDNA copy number negatively correlated with blood concentrations of 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) and 11-Nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH), the two primary metabolites of Δ9-THC, but not Δ9-THC itself. Further, the negative correlation between 11-OH THC and THC-COOH concentrations and mtDNA copy number was found in only a subgroup of participants who use cannabis infrequently, suggesting a tolerance effect. Conclusions: These results illuminate mitochondrial alterations attributed to Δ9-THC consumption, which may be mediated by metabolites. These results appear to suggest stronger effects in individuals who consume cannabis less frequently, suggesting some form of tolerance to the effects of Δ9-THC and its metabolites on mtDNA content in whole blood. Keywords: Mitochondria; mtDNA; cannabis; THC; THC metabolites; blood; THC-COOH; 11-OH-THC.

New insights from bidirectional Mendelian randomization: causal relationships between telomere length and mitochondrial DNA copy number in aging biomarkers.

Mitochondrial DNA (mtDNA) copy number and telomere length (TL) are dynamic factors that have been linked to the aging process in organisms. However, the causal relationship between these variables remains uncertain. In this research, instrumental variables (IVs) related to mtDNA copy number and TL were obtained from publicly available genome-wide association studies (GWAS). Through bidirectional Mendelian randomization (MR) analysis, we examined the potential causal relationship between these factors. The forward analysis, with mtDNA copy number as the exposure and TL as the outcome, did not reveal a significant effect (B=-0.004, P>0.05). On the contrary, upon conducting a reverse analysis, it was found that there exists a positive causal relationship (B=0.054, P<0.05). Sensitivity analyses further confirmed the reliability of these results. The outcomes of this study indicate a one-way positive causal relationship, indicating that telomere shortening in the aging process may lead to a decrease in mtDNA copy number, providing new perspectives on their biological mechanisms.

Dystonia, spastic tetraplegia, and ataxia due to a novel mutation in the dynamin domain of OPA1.

Movement disorders manifest in various hereditary neurodegenerative diseases. We reported a young man who presented with progressive upper limb dystonia, spastic tetraplegia, and ataxia. Whole-exome sequencing (WES) revealed a novel variant, c.2357A > G, in the dynamin domain of OPA1. No mtDNA deletion was detected in muscle by long-range PCR. Atrophy and decreased glucose metabolism of the basal ganglia were discovered. Decreased mtDNA copy number, fragmented mitochondria, slightly impaired oxidative phosphorylation, and increased autophagy were detected in mutant fibroblasts. Evident oxidative phosphorylation impairment and mtDNA deletions were not involved in the pathogenicity of this mutation unlike mutations in the GTPase domain of OPA1.

Lncrna Rmrp Regulate Mitochondrial Function in Relapsed and Refractory Acute Myeloid Leukemia

Background: The prognosis of relapsed and refractory acute myeloid leukemia (R/R AML) is extremely poor, primarily due to the development of chemotherapy resistance during the treatment, which leads to its relapse and refractory disease. Extensive studies have established that various dysfunctions in the mitochondria of AML cells play a significant role in promoting chemotherapy resistance and the recurrence of the disease. In our previous investigation, we successfully demonstrated the substantial enrichment of the long non-coding RNA (lncRNA) RMRP in the mitochondria. However, the specific function of RMRP in the mitochondria of R/R AML remains unexplored. The objective of this project is to uncover the function of RMRP in R/R AML mitochondria, aiming to provide innovative insights and a theoretical foundation for surmounting chemotherapy resistance in R/R AML. Methods: In order to investigate the factors that play a crucial role in R/R AML, we employed mass spectrometry (MS) to conduct a screening of factors associated with AML chemoresistance. We utilized quantitative real-time polymerase chain reaction (RT-qPCR) to assess the expression of lncRNA RMRP in both newly diagnosed AML (ND AML) and R/R AML patients. Furthermore, we knocked down the RMRP expression level by transfection with siRNA-NC and siRNA-RMRP. Additionally, we analyzed the correlation between lncRNA RMRP and mitochondria. To explore the involvement of lncRNA RMRP in regulating mitochondrial function in R/R AML, we performed mitochondrial oxidative phosphorylation metabolic function assays subsequent to the inhibition of lncRNA RMRP. Moreover, Western blot analysis was employed to evaluate the relative protein expression levels in AML cell lines. Results: We enrolled 23 AML patients (ND AML, n=12; R/R AML, n=11), and the result of MS shows that R/R AML group expressed higher level of mitochondria related protein. The qPCR results showed that R/R AML had higher expression level of RMRP ( P&amp;lt;0.0001) and mitochondrial genome genes ( P&amp;lt;0.0001) than ND AML patients. The result of co-cultured of BMSCs and AML suggests that mitochondrial transmission of BMSCs to AML existed in AML patients with high RMRP expression level( P&amp;lt;0.0001). The Seahorse metabolomics results suggest that RMRP knock down attenuated Spare Respiratory Capacity ( P=0.01) and Maximal Respiration ( P=0.01), increased the Cytarabine and Doxorubicin sensitivity, and induced alterations in the mitochondrial CpG1 and CpG9 methylation. Knockdown of RMRP is also accompanied by a decrease in mtDNA copy number ( P=0.10, 0.42, and 0.0074, respectively for mtDNA gene MT-ND2, MT-ND3, and MT-CO1), and mitochondrial genome transcription. Under transmission electron microscope (TEM), mitochondria were engulfed by lysosomes in RMRP knockdown AML cells. And results of Western blot showed that the autophagy markers such as LC3B, BNIP3L/Nix, NDP52 was upregulated, and SQSTM1, Parkin was downregulated in RMRP knockdown AML cells, suggesting that RMRP may induce mitophagy through the BNIP3L/Nix pathway, PINK1/Parkin pathway, and NDP52 pathway. Conclusion: In R/R AML, RMRP increased chemotherapy resistance and RMRP high expression was associated with multiple mitochondrial function abnormalities, including altered mitochondrial metabolism, reduced mitophagy, and altered mtDNA epigenetics.

CircRNA SCAR Improves High-Glucose-Induced Mitochondrial Dysfunction and Permeability Damage in Retinal Microvascular Endothelial Cells.

This study was designed to assess the role and mechanism of circRNA SCAR in human retinal microvascular endothelial cells (hRMVECs) treated with high glucose. Quantitative real-time polymerase chain reaction (qRT-PCR) and cell counting kit 8 (CCK-8) were used to detect the effects of different concentrations of glucose on circRNA SCAR expression and cell proliferation in hRMVECs. Cell viability, levels of oxygen species (ROS), malondialdehyde (MDA) and adenosine triphosphate (ATP), as well as activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in the transfected hRMVECs in each group were detected using CCK-8 and their corresponding detection kits. Changes in mtDNA copy number in high-glucose-induced hRMVECs were observed by qRT-PCR. Additionally, western blot was applied to detect effect of overexpressing circRNA SCAR on the expression levels of mitochondrial function-related proteins (Drp1 and Fis1) and cell permeability-related proteins (claudin-5, occludin and ZO-1) in hRMVECs under high-glucose concentration. According to experimental results, high glucose significantly downregulated circRNA SCAR expression and inhibited cell proliferation in hRMVECs. Instead, overexpression of this circRNA SCAR promoted cell proliferation, reduced levels of ROS, MDA and ATP, and increased SOD and CAT activities in hRMVECs under high-glucose concentration. Also, circRNA SCAR overexpression reversed the high-glucose-induced decrease in mtDNA copy number as well as, high-glucose-induced upregulation of Drp1 and Fis1 protein expression and downregulation of claudin-5, occludin and ZO-1 protein expression in hRMVECs. In summary, circRNA SCAR promotes the proliferation of hRMVECs under high-glucose concentration, alleviates oxidative stress induced by high glucose, and improves mitochondrial function and permeability damage.

Influence of different concentrations of ozone on the alteration of mitochondrial DNA copy numbers in human peripheral blood

By now, O3 pollution has become a main environmental problem. O3 is a prevalent risk factor for many diseases, but the regulatory factors linking O3 and diseases remain ambiguous. Mitochondrial DNA (mtDNA) is the genetic material in mitochondria, which plays a key role in the production of respiratory ATP. Due to a lack of histone protection, mtDNA is easily damaged by ROS, and O3 is an important source to stimulate the production of endogenous ROS in vivo. Therefore, we logically speculate that O3 exposure can alter mtDNA copy number by the induction of ROS. In the present study, we performed a panel study of 65 MSc students at the Chinese research academy of environmental sciences (CRAES) with 3 rounds of follow-up visits from August 2021 to January 2022. We examined the mtDNA copy numbers in the peripheral blood of subjects using quantitative polymerase chain reaction. Linear mixed-effect (LME) model and stratified analysis were used to investigate the association between O3 exposure and mtDNA copy numbers. We found a dynamic process of the association between the concentration of O3 exposure and the mtDNA copy number in the peripheral blood. The lower concentration of O3 exposure did not affect the mtDNA copy number. As the concentration of O3 exposure increased, the mtDNA copy number also increased. While, when O3 exposure reached a certain concentration, a decrease in mtDNA copy number was found. This correlation between the concentration of O3 and the mtDNA copy number could be ascribed to the severity of cellular damage induced by O3 exposure. Our results provide a new perspective for the discovery of a biomarker of O3 exposure and health response, as well as for the prevention and treatment of adverse health effects caused by different concentrations of O3.

Second International Pulmonary Hypertension/Heart Failure Symposium—Structural heart disease, right ventricular dysfunction, and stem cell therapy: The European Pediatric Pulmonary Vascular Disease Network

Second International Pulmonary Hypertension/Heart Failure Symposium—Structural heart disease, right ventricular dysfunction, and stem cell therapy: The European Pediatric Pulmonary Vascular Disease Network

The Large-scale Deletions and Copy Numbers of Mitochondrial DNA in Gout Patients Treated with Allopurinol

Allopurinol is now the first-line treatment for managing gout and its increasing usage has brought more gout patients at risk of developing allopurinol-induced hypersensitive reactions. Up to now, our attempts to identify the biomarkers for hypersensitivity to allopurinol are still finite. Besides, the association between drug-induced hypersensitive reactions and some mitochondrial DNA (mtDNA) alterations has been proved but remains unclear in gout patients. In this study, 41 blood samples of gout patients prescribed with allopurinol including 22 hypersensitive and 29 tolerant ones were used to analyze their mtDNA large-scale deletions through PCR and determine the mtDNA deletion level and the copy number by quantitative PCR. The results indicated that the mtDNA large-scale deletions and mtDNA copy number of the hypersensitive group were lower than that of the tolerant one (p &lt; 0.05). However, no association was found between the mtDNA deletion level and the appearance of hypersensitive reactions in gout patients. In addition, the study showed that the mtDNA deletion level and copy number were negatively correlated with the copy numbers of mitochondrial DNA in gout patients (R = -0.3495; p = 0.0119) and allopurinol hypersensitive group (R = -0.6744; p = 0.0005). Thus, a decrease in mtDNA copy number might serve as a potential biomarker for further investigation to assess the risk of hypersensitive reactions to allopurinol in gout patients.&#x0D;

Low mitochondrial DNA copy number induces chemotherapy resistance via epithelial-mesenchymal transition by DNA methylation in esophageal squamous cancer cells

BackgroundEsophageal squamous cell carcinoma (ESCC) is one of the most severe cancers and is characterized by chemotherapy resistance and poor prognosis associated with epithelial-mesenchymal transition (EMT). In a previous study, a low mitochondrial DNA (mtDNA) copy number was associated with poorer prognosis and induced EMT in ESCC. However, the detailed mechanism related to mtDNA copy number and EMT is unclear. The aim of this study was to clarify the mechanism by which a change in mtDNA copy number contributes to EMT and to examine treatment of chemotherapy resistance in ESCC.MethodsThe association between low mtDNA copy number and chemotherapy resistance was investigated using specimens from 88 patients who underwent surgery after neoadjuvant chemotherapy. Then, the mtDNA content of human ESCC cell lines, TE8 and TE11, was depleted by knockdown of mitochondrial transcription factor A expression. The present study focused on modulation of mitochondrial membrane potential (MMP) and DNA methylation as the mechanisms by which mtDNA copy number affects EMT. mRNA and protein expression, chemotherapy sensitivity, proliferation, MMP and DNA methylation were evaluated, and in vitro and in vivo assays were conducted to clarify these mechanisms.ResultsESCC patients with decreased mtDNA copy number who underwent R0 resection after neoadjuvant chemotherapy had significantly worse pathological response and recurrence-free survival. Additionally, low mtDNA copy number was associated with resistance to chemotherapy in vitro and in vivo. mtDNA controlled MMP, and MMP depolarization induced EMT. Depletion of mtDNA and low MMP induced DNA methylation via a DNA methylation transcription factor (DNMT), and a DNMT inhibitor suppressed EMT and improved chemotherapy sensitivity in mtDNA-depleted ESCC cells, as shown by in vitro and in vivo assays.ConclusionThis study showed that decreased mtDNA copy number induced EMT via modulation of MMP and DNA methylation in ESCC. Therapeutic strategies increasing mtDNA copy number and DNMT inhibitors may be effective in preventing EMT and chemosensitivity resistance.

Toxicity of environmental pollutants for mitochondrialDNA alteration

<p indent="0mm">Mitochondria, as the main site of cellular aerobic respiration, are organelles that provide energy for cells. The mitochondrial genomes are independent of the nuclear genome, known as mitochondrial DNA (mtDNA). mtDNA encodes 37 genes, including 13 respiratory chain-related polypeptides, 22 tRNAs and 2 rRNA genes. Mitochondrial abnormalities can directly reduce cellular ATP synthesis and thus generate insufficient cellular energy. The regulation of mtDNA copy number and epigenetics is crucial for the basic functions of mitochondria. After entering the cells of organisms, environmental pollutants elevate reactive oxygen species (ROS), causing oxidative stress in the organism and resulting in abnormal metabolism and various diseases. Compared with nuclear DNA, mtDNA is more susceptible to oxidative stress because of its proximity to the site of oxidative phosphorylation (OXPHOS) and lack of histone protection and sufficient DNA damage repair capacity. Exposure to various environmental pollutants can induce excessive accumulation of ROS, which leads to changes in mtDNA copy number and epigenetic modifications of mtDNA. An increasing number of studies focus on abnormal mtDNA as a possible biomarker for the exposure and toxicity of environmental pollutants. In this article, we briefly introduce the physiological functions and regulatory mechanisms of mitochondria and mtDNA copy number. Environment pollutant exposures often cause mitochondrial damage, which may alter mtDNA copy number, leading to mitochondrial abnormalities and impairing cell function. Studies have found that mitochondrial dysfunction is related to the occurrence and development of various diseases (e.g., cancer, diabetes, cardiovascular disease, neurodegenerative diseases, etc.). Noteworthily, decreased mtDNA copy number in germ cells blocks embryonic development. Next, along with the associated proteins found in recent studies, possible epigenetic modifications present on mtDNA (e.g., 5-methylcytosine, 5-hydroxymethylcytosine and N6-methyladenine) are also summarized. A study identified mtDNMT1 in the mitochondrial matrix, which was suggested to be a methyltransferase for mtDNA 5mC. Since 5hmC modification on mtDNA was first reported in 2011, the results of studies on mtDNA 5hmC have been conflicting. However, some research groups found that Tet1 and Tet2 may be involved in the formation of mtDNA 5hmC. A higher level of 6mA modification than nuclear DNA was suggested to be detected in mtDNA, and the METTL4 protein is a potential mtDNA 6mA methyltransferase. Nonetheless, the study on mtDNA methylation is of intensive interest. We reviewed the effects of multiple common environmental pollutants (e.g., PM, black carbon, nicotine, heavy metal particles, etc.) on mitochondrial DNA from two aspects: (1) Environmental pollutants exposure causes mtDNA copy number changes, which may increase disease risk; (2) environmental pollutant exposure alters methylation levels of certain genes in mtDNA. In the first aspect, exposure to different pollutants, or even the same pollutant, resulted in different changes in mtDNA copy number. It suggests that the same environmental pollutants may also affect mtDNA copy number through different mechanisms and pathways. In the second aspect, changes in the methylation levels of D-loop and gene regions on mtDNA caused by pollutant exposure can affect mitochondrial physiological function by affecting mitochondrial DNA replication and mitochondrial-encoded protein expression. We prospect and discuss how to perform further study on the effect of environmental pollutants on mtDNA and its molecular mechanism. The following two aspects should be improved in future pollutants-mtDNA studies: (1) Develop more convenient methods for the extraction of mtDNA from less than million cells to a high purity. This will facilitate the detection and sequencing of mtDNA for diverse purposes; (2) to achieve accurate identification of mtDNA methylation sites in small number of cells and eliminate the interference of mtDNA heterogeneity, the mtDNA methylation sequencing method should be further innovated.

Decrease of MtDNA copy number affects mitochondrial function and involves in the pathological consequences of ischaemic stroke

The mtDNA copy number can affect the function of mitochondria and play an important role in the development of diseases. However, there are few studies on the mechanism of mtDNA copy number variation and its effects in IS. The specific mechanism of mtDNA copy number variation is still unclear. In this study, mtDNA copy number of 101 IS patients and 101 normal controls were detected by qRT‐PCR, the effect of D‐loop variation on mtDNA copy number of IS patients was explored. Then, a TFAM gene KD‐OE PC12 cell model was constructed to explore the effect of mtDNA copy number variation on mitochondrial function. The results showed that the mtDNA copy number level of the IS group was significantly lower than that of the normal control group (p < 0.05). The relative expression of TFAM gene mRNA in the cells of the OGD/R treatment group was significantly lower than that of the control group (p < 0.05). In addition, after TFAM gene knockdown and over‐expression plasmids were transfected into HEK 293T cells, mtDNA copy number and ATP production level of Sh‐TFAM transfection group was significantly decreased (p < 0.05), while mtDNA copy number and ATP production level of OE‐TFAM transfected group were significantly higher than that of blank control group and OE‐ctrl negative control group (p < 0.01). Our study demonstrated that mitochondrial D‐loop mutation and TFAM gene dysfunction can cause the decrease of mtDNA copy number, thus affecting the mitochondrial metabolism and function of nerve cells, participating in the pathological damage mechanism of IS.

Mitochondrial DNA Efflux Maintained in Gingival Fibroblasts of Patients with Periodontitis through ROS/mPTP Pathway.

Mitochondria have their own mitochondrial DNA (mtDNA). Aberrant mtDNA is associated with inflammatory diseases. mtDNA is believed to induce inflammation via the abnormal mtDNA release. Periodontitis is an infectious, oral inflammatory disease. Human gingival fibroblasts (HGFs) from patients with chronic periodontitis (CP) have shown to generate higher reactive oxygen species (ROS) that cause oxidative stress and have decreased mtDNA copy number. Firstly, cell-free mtDNA was identified in plasma from CP mice through qRT-PCR. Next, we investigated whether mtDNA efflux was maintained in primary cultures of HGFs from CP patients and the possible underlying mechanisms using adenovirus-mediated transduction live cell imaging and qRT-PCR analysis. Here, we reported that mtDNA was increased in plasma from the CP mice. Additionally, we confirmed that CP HGFs had significant mtDNA efflux from mitochondria compared with healthy HGFs. Furthermore, lipopolysaccharide (LPS) from Porphyromonas gingivalis can also cause mtDNA release in healthy HGFs. Mechanistically, LPS upregulated ROS levels and mitochondrial permeability transition pore (mPTP) opening by inhibition of pyruvate dehydrogenase kinase (PDK)2 expression, resulting in mtDNA release. Importantly, mtDNA efflux was even persistent in HGFs after LPS was removed and cells were passaged to the next three generations, indicating that mtDNA abnormalities were retained in HGFs in vitro, similar to the primary hosts. Taken together, our results elucidate that mtDNA efflux was maintained in HGFs from periodontitis patients through abnormal ROS/mPTP activity. Therefore, our work indicates that persistent mtDNA efflux may be a possible diagnostic and therapeutic target for patients with periodontitis.

Effects of Antiviral Nucleoside Analogues on the Maintenance of the Mitochondrial Genome

The outbreak of the COVID‐19 pandemic prompted the search for effective antivirals. Remdesivir (Gilead Sciences) was the first nucleoside analogue approved by the FDA for COVID‐19 treatment, and currently the FDA considers authorization for the use of another analogue, molnupiravir (Merck). Mitochondrial toxicity, resulting from the interference with mitochondrial DNA (mtDNA) replication, is the most common side effect of nucleoside analogues treatment. In addition, defects to the mtDNA synthesis may give rise to heritable mutations, which may be carried undetected for generations before populating mitochondria to the level that onsets a mitochondrial disease. Therefore, nucleoside analogues need to be thoroughly investigated for their impact on the maintenance and integrity of the mitochondrial genome.We recently assessed the effect of remdesivir on the maintenance of the mitochondrial genome. We observed that in in vitro DNA synthesis assays, its triphosphate metabolite may impede the synthetic activity of the mitochondrial replicative polymerase, Pol γ, when in excess over nucleotides. Prompted by this finding, we tested the effect of the nucleoside metabolite of remdesivir on the maintenance and integrity of the mitochondrial genome in proliferating fibroblasts. However, we found no evidence for deleterious effects on the integrity of the mitochondrial genome.We are currently performing an analogical assessment of the effects of molnupiravir on the integrity of the mitochondrial genome. Thus far, we have observed that, unlike remdesivir, molnupiravir is cytotoxic for proliferating fibroblasts and results in a decrease in mtDNA copy number. We are currently testing the impact of molnupiravir on the activity of Pol γ in vitro, and its potential to elicit mutations in the mitochondrial genome in vivo.

Metabolic Reprogramming in Response to Alterations of Mitochondrial DNA and Mitochondrial Dysfunction in Gastric Adenocarcinoma

We used gastric cancer cell line AGS and clinical samples to investigate the roles of mitochondrial DNA (mtDNA) alterations and mitochondrial respiratory dysfunction in gastric adenocarcinoma (GAC). A total of 131 clinical samples, including 17 normal gastric mucosa (N-GM) from overweight patients who had received sleeve gastrectomy and 57 paired non-cancerous gastric mucosae (NC-GM) and GAC from GAC patients who had undergone partial/subtotal/total gastrectomy, were recruited to examine the copy number and D310 sequences of mtDNA. The gastric cancer cell line AGS was used with knockdown (KD) mitochondrial transcription factor A (TFAM) to achieve mitochondrial dysfunction through a decrease of mtDNA copy number. Parental (PT), null-target (NT), and TFAM-KD-(A/B/C) represented the parental, control, and TFAM knocked-down AGS cells, respectively. These cells were used to compare the parameters reflecting mitochondrial biogenesis, glycolysis, and cell migration activity. The median mtDNA copy numbers of 17 N-GM, 57 NC-GM, and 57 GAC were 0.058, 0.055, and 0.045, respectively. The trend of decrease was significant (p = 0.030). In addition, GAC had a lower mean mtDNA copy number of 0.055 as compared with the paired NC-GM of 0.078 (p < 0.001). The mean mtDNA copy number ratio (mtDNA copy number of GAC/mtDNA copy number of paired NC-GM) was 0.891. A total of 35 (61.4%) GAC samples had an mtDNA copy number ratio ≤0.804 (p = 0.017) and 27 (47.4%) harbored a D310 mutation (p = 0.047), and these patients had shorter survival time and poorer prognosis. After effective knockdown of TFAM, TFAM-KD-B/C cells expressed higher levels of hexokinase II (HK-II) and v-akt murine thymoma viral oncogene homolog 1 gene (AKT)-encoded AKT, but lower levels of phosphorylated pyruvate dehydrogenase (p-PDH) than did the NT/PT AGS cells. Except for a higher level of p-PDH, the expression levels of these proteins remained unchanged in TFAM-KD-A, which had a mild knockdown of TFAM. Compared to those of NT, TFAM-KD-C had not only a lower mtDNA copy number (p = 0.050), but also lower oxygen consumption rates (OCR), including basal respiration (OCRBR), ATP-coupled respiration (OCRATP), reserve capacity (OCRRC), and proton leak (OCRPL)(all with p = 0.050). In contrast, TFAM-KD-C expressed a higher extracellular acidification rate (ECAR)/OCRBR ratio (p = 0.050) and a faster wound healing migration at 6, 12, and 18 h, respectively (all with p = 0.050). Beyond a threshold, the decrease in mtDNA copy number, the mtDNA D310 mutation, and mitochondrial dysfunction were involved in the carcinogenesis and progression of GACs. Activation of PDH might be considered as compensation for the mitochondrial dysfunction in response to glucose metabolic reprogramming or to adjust mitochondrial plasticity in GAC.

Hypermethylation of mitochondrial DNA facilitates bone metastasis of renal cell carcinoma.

Kidney cancers including clear cell carcinoma (RCC) are identified with very vulnerable mitochondria DNA (mtDNA) and frequent epigenetic aberrations. Bone metastasis from RCC is prevalent and destructive. Bone marrow contains a quite hypoxic microenvironment that usually insitigate 50% of hypermethylation events in conferring a selective advantage for tumor growth. We hypothesized that hypermethylation of mtDNA in RCC cells would significantly contribute to bone metastatic tumor progression. Methylation-specific polymerase chain reaction assay (MSP) was adopted to measure the methylation status of D-loop region of mtDNA in 15 pairs of bone metastatic and primary RCC as well as tumor adjescent normal kidney tissues. mtDNA copy number was examined by the real-time quantitative polymerase chain reaction (qPCR). Western blotting analysis was used to measure the accumulation of several DNA methyltransferases (DNMTs) in the mitochondria and nucleus fractions of bone metastatic RCC cells. mRNA expression of mitochondria encoded genes was examined by RT-PCR. Reactive oxygen species (ROS), mitochondrial membrane potential and ATP content were measured using in vitro cells treated with de-methylation drug 5-Azacytidine (5-Aza). Non-invasive bioluminescent imaging was performed to monitor tumor occurrence in skeleton in mice. Our results showed that the D-loop region in bone metastatic tumor cells was markedly hypermethylated than those in primary RCC tumor cells, that is associated with a decreased mtDNA copy number and accumulation of DNMT1 in the mitochondria. The bone-tropism tumor colonization and progression of RCC cells was significantly suppressed by demethylating the D-loop region of mtDNA and reducing the intracellular level of ROS and ATP by 5-Aza treatment. In conclusion, our study provided a direct association between hypermethylation of mtDNA in RCC with bone metastastic tumor growth.

HEK293T Cells with TFAM Disruption by CRISPR-Cas9 as a Model for Mitochondrial Regulation.

The mitochondrial transcription factor A (TFAM) is considered a key factor in mitochondrial DNA (mtDNA) copy number. Given that the regulation of active copies of mtDNA is still not fully understood, we investigated the effects of CRISPR-Cas9 gene editing of TFAM in human embryonic kidney (HEK) 293T cells on mtDNA copy number. The aim of this study was to generate a new in vitro model by CRISPR-Cas9 system by editing the TFAM locus in HEK293T cells. Among the resulting single-cell clones, seven had high mutation rates (67–96%) and showed a decrease in mtDNA copy number compared to control. Cell staining with Mitotracker Red showed a reduction in fluorescence in the edited cells compared to the non-edited cells. Our findings suggest that the mtDNA copy number is directly related to TFAM control and its disruption results in interference with mitochondrial stability and maintenance.

A Case-control Study on the Association of Mitochondrial Transcription Factor a Gene +35G/C Polymorphism and Mitochondrial DNA Copy Number with the Risk of Endometriosis in Indian Women

Aim: The Mitochondrial transcription factor A (TFAM) and mitochondrial (mt) DNA copy number variations are known to contribute in disease development. Genetic factors play an important role in the development of endometriosis. Therefore, this case–control study aimed to analyze the association of TFAM+35G/C polymorphism and mitochondrial copy number with the risk of endometriosis in Indian women.&#x0D; Study Design: This study was carried out on 418 subjects including 200 endometriosis cases and 218 controls.&#x0D; Methodology: Genotyping of TFAM +35G/C polymorphism (rs1937) was carried out by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Quantification of mtDNA copy number was carried out using a real time quantitative polymerase chain reaction (qRT-PCR).&#x0D; Place and Duration of Study: Department of Biochemistry, Osmania University, 2014 to 2020.&#x0D; Results: TFAM genotype as well as allele distributions were all in Hardy-Weinberg equilibrium. The results indicated a significant reduction of GG genotype frequency (P=0.009), high ‘C’ allele frequency (P=0.017) and significantly decreased mtDNA copy number in endometriosis cases compared to controls (P= 0.0001).&#x0D; Conclusion: Present study revealed a statistically significant association of decreased GG genotype of TFAM +35G/C polymorphism and mtDNA copy number with the risk of developing endometriosis in Indian women.

Decreased mitochondrial DNA copy number in nerve cells and the hippocampus during nicotine exposure is mediated by autophagy

Cigarette smoke is a harmful air pollutant and nicotine dependence is the essential cause of the tobacco epidemic. Since mitochondrial abnormalities are associated with substance addiction, in this work we used mitochondrial DNA (mtDNA) copy number as an indicator of mitochondrial function to investigate whether nicotine addicts also exhibit mitochondrial abnormalities. We found significantly lower mtDNA copy number in the peripheral blood of healthy nicotine addicts than in non-smokers, indicating that long-term nicotine exposure through smoking has detrimental effects on mitochondria. We also examined the effects of nicotine on mtDNA levels in a rat conditioned place preference (CPP) model of addiction and in cultured neuron cells, which revealed that the mtDNA copy number was significantly reduced in the hippocampus of CPP rats, in human neuroblastoma SH-SY5Y cells, and in rat pheochromocytoma PC12 cells, suggesting that significantly reduced mtDNA copy number is a potential biomarker of nicotine addiction. In SH-SY5Y cells, nicotine treatment induced several mitochondrial defects, such as increased mtDNA damage, increased reactive oxygen species (ROS) levels, decreased mitochondrial membrane potential (△Ψm), and stimulation of autophagic flux via transcriptional up-regulation of several autophagy-related genes and elevated marker protein accumulation, although genes controlling mtDNA replication were unaffected. In addition, pretreatment with the autophagy inhibitor Bafilomycin A1 led to accumulation of microtubule-associated protein 1 light chain 3b-II (LC3B-II) and counteracted the nicotine-induced decrease in mtDNA copy number. These results were recapitulated in PC12 cells, which also showed significant down-regulation of the marker SQSTM1/P62, suggesting that the decrease in mtDNA copy number is mediated by autophagy. This study shows that prolonged nicotine exposure, such as that in nicotine addicts, leads to a decrease of mtDNA copy number in neurons due to enhanced induction of autophagy. CapsuleIt was found that smoking or nicotine exposure decreased mtDNA copy number based on population, animal, and cell models, and these effects appear to be mediated by autophagy.