Isoliensinine inhibits mitophagy and sensitizes T cell malignancies for STING-mediated NK clearance.

Inhibition of BCL11B Expression Leads to Apoptosis of Malignant T Cells but Not CD34+ Cells.

Increased production of reactive oxygen species (ROS) in mitochondria has been proposed as the pathogenic mechanism for chronic complications of diabetes. Mitochondrial DNA (mtDNA) is more vulnerable to reactive oxygen species. However, there are few data on the mitochondrial DNA damage in diabetes and these are available only from patients with different duration of the disease and tissues not relevant to the chronic complications of diabetes. We therefore proposed to study the stability of mitochondrial DNA under controlled experimental conditions, to understand its contribution to chronic complications of diabetes. The mitochondrial DNA damage was evaluated by long-fragment polymerase chain reaction in human dermal fibroblasts exposed to high glucose level and hypoxia (an additional source of reactive oxygen species) or in organs from diabetic animals (db/db mice) at different ages. Reactive oxygen species production was assessed in vitro by fluorescence and in vivo by nitrosylation of the proteins. The antioxidant enzymes were assessed by enzyme activity and by quantitative real-time polymerase chain reaction while the mitochondrial repair activity (base excision repair) was determined by using abasic site-containing oligonucleotides as substrates. Hyperglycaemia, when combined with hypoxia, is able to induce mitochondrial DNA damage in human dermal fibroblasts. The deleterious effect is mediated by mitochondrial reactive oxygen species, being abolished when the mitochondria electron transport is blocked. The accumulation of mitochondrial DNA damage in vivo is, however, decreased in 'old' diabetic animals (db/db) despite higher reactive oxygen species levels. This mitochondrial DNA protection might be conferred by an increased base excision repair activity. Increased base excision repair activity in tissues affected by the chronic complications of diabetes is a potential mechanism that can overcome mitochondrial DNA damage induced by hyperglycaemia-related reactive oxygen species overproduction.

DNA damage in brain mitochondria caused by aging and MPTP treatment

Lw-218, a New Flavonoid Compound, Exerts Anti-T-Cell Malignancies Effects Via Autophagy-Mediated Apoptosis

Bcl-2 Facilitates Recovery from DNA Damage after Oxidative Stress

Coronary atherosclerotic disease remains the leading cause of death in the Western world. Although the exact sequence of events in this process is controversial, reactive oxygen and nitrogen species (RS) likely play an important role in vascular cell dysfunction and atherogenesis. Oxidative damage to the mitochondrial genome with resultant mitochondrial dysfunction is an important consequence of increased intracellular RS. We examined the contribution of mitochondrial oxidant generation and DNA damage to the progression of atherosclerotic lesions in human arterial specimens and atherosclerosis-prone mice. Mitochondrial DNA damage not only correlated with the extent of atherosclerosis in human specimens and aortas from apolipoprotein E(-/-) mice but also preceded atherogenesis in young apolipoprotein E(-/-) mice. Apolipoprotein E(-/-) mice deficient in manganese superoxide dismutase, a mitochondrial antioxidant enzyme, exhibited early increases in mitochondrial DNA damage and a phenotype of accelerated atherogenesis at arterial branch points. Mitochondrial DNA damage may result from RS production in vascular tissues and may in turn be an early event in the initiation of atherosclerotic lesions.

Mitochondrial dysfunction in obesity and diabetes can be caused by excessive production of free radicals, which can damage mitochondrial DNA. Because mitochondrial DNA plays a key role in the production of ATP necessary for cardiac work, we hypothesized that mitochondrial dysfunction, induced by mitochondrial DNA damage, uncouples coronary blood flow from cardiac work. Myocardial blood flow (contrast echocardiography) was measured in Zucker lean (ZLN) and obese fatty (ZOF) rats during increased cardiac metabolism (product of heart rate and arterial pressure, i.v. norepinephrine). In ZLN increased metabolism augmented coronary blood flow, but in ZOF metabolic hyperemia was attenuated. Mitochondrial respiration was impaired and ROS production was greater in ZOF than ZLN. These were associated with mitochondrial DNA (mtDNA) damage in ZOF. To determine if coronary metabolic dilation, the hyperemic response induced by heightened cardiac metabolism, is linked to mitochondrial function we introduced recombinant proteins (intravenously or intraperitoneally) in ZLN and ZOF to fragment or repair mtDNA, respectively. Repair of mtDNA damage restored mitochondrial function and metabolic dilation, and reduced ROS production in ZOF; whereas induction of mtDNA damage in ZLN reduced mitochondrial function, increased ROS production, and attenuated metabolic dilation. Adequate metabolic dilation was also associated with the extracellular release of ADP, ATP, and H2O2 by cardiac myocytes; whereas myocytes from rats with impaired dilation released only H2O2. In conclusion, our results suggest that mitochondrial function plays a seminal role in connecting myocardial blood flow to metabolism, and integrity of mtDNA is central to this process.

Oxidative stress induces damage and depletion of mitochondrial (mit) DNA and suppresses ATP production leading to defects in cell function and initiating cell death. 8‐oxoguanosine DNA glycosylase‐1 (OGG1) acts in the mitochondria to repair DNA damage. In this study H9C2 cells were infected with either adv‐ OGG1 or empty vector and, challenged with menadione, to induce mitochondrial DNA damage. The cells were used to evaluate the effects of OGG1 on mitochondrial DNA content and damage and on apoptotic events induced by oxidative stress. Levels of 8‐oxodG and AP‐sites, metrics of mitochondrial DNA damage, were decreased by 30% and 35%, respectively, in adv‐Ogg1 infected cells. Cells over‐expressing mitOgg1 showed increased membrane potential (p<0.05) and decreased mitochondrial fragmentation (p<0.005). mitOgg1 over‐expression preserved mitDNA content and lowered levels of fission and apoptotic factors such as DRP‐1, FIS1, cytoplasmic cytochrome c, caspase‐3 and caspase‐9. These observations suggest that mitOgg1 may be an alternative to protect cardiac cells against oxidative stress damage.

In experimental autoimmune uveitis (EAU), recent work has demonstrated that retinal damage involves oxidative stress early in uveitis, before macrophage cellular infiltration. The purpose of this study was to determine whether oxidative mitochondrial DNA damage occurs early in EAU, before leukocyte infiltration. Lewis rats were immunized with S-antigen mixed with complete Freund adjuvant (CFA) to induce EAU. Nonimmunized animals and animals injected with CFA served as controls. Animals were killed on days 3, 4, 7, and 12 after immunization. Damage to mitochondrial DNA and nuclear DNA was assessed using a novel long quantitative polymerase chain reaction technique. TUNEL staining to detect apoptosis and immunohistochemical detection of leukocyte infiltration in EAU retinas were also performed at these times. Mitochondrial DNA damage occurred early in EAU, from day 4 to day 12. In the early phase of EAU (days 4-7), there was no inflammatory cell infiltration. On day 12 inflammatory cells infiltrated the retina and uvea. Nuclear DNA damage occurred later in EAU at day 12. Neither mitochondrial nor nuclear DNA damage was detected in the controls. TUNEL-positive staining for apoptosis was detected only at day 12 in EAU retina. Oxidative mitochondrial DNA damage begins at day 4 in EAU, supporting the view that oxidative stress selectively occurs in the mitochondria in the early phase of EAU, before leukocyte infiltration. Such oxidative damage in the mitochondria may be the initial event leading to retinal degeneration in EAU.

Aging and male sex are major risk factors for abdominal aortic aneurysm (AAA), a disease characterized by vascular cell phenotypic switching and aortic wall remodeling. Mitochondrial oxidative stress has been implicated in these changes. We previously demonstrated that NOX4 (NADPH oxidase 4) expression and activity increase with age in cardiovascular cells, promoting mitochondrial oxidative stress and vascular dysfunction. This study investigates whether NOX4-driven mitochondrial oxidative stress and DNA damage promote AAA development through vascular cell reprogramming. We used mitochondria-targeted Nox4-overexpressing (Nox4TG) mice with an Apoe-/- background to model angiotensin II (Ang II)-induced AAA. AAA incidence, aortic morphology, reactive oxygen species levels, DNA damage markers, and wall remodeling parameters were assessed in Apoe-/-, Apoe-/-/Nox4TG, and Apoe-/-/Nox4-/- mice. Vascular cell populations were analyzed by spectral flow cytometry and gene expression profiling. Invitro, Ang II-treated smooth muscle cells (SMCs) from wild-type, Nox4TG, and Nox4-/- mice were evaluated for mitochondrial reactive oxygen species, DNA damage, and activation of inflammatory pathways. Apoe-/-/Nox4TG mice exhibited the highest AAA incidence, aortic dilation, reactive oxygen species levels, DNA damage, and inflammation, whereas Apoe-/-/Nox4-/- mice were most protected. Macrophage-like SMCs increased, and contractile SMCs decreased in Nox4TG aortas. Ang II-treated Nox4TG SMCs showed elevated mitochondrial reactive oxygen species, DNA damage, and cyclic GMP-AMP synthase-STING (stimulator of interferon genes) activation. Flow cytometry analysis confirmed the presence of aneurysmal SMC with reduced ACTA2 (actin alpha 2, smooth muscle), MYH11 (myosin heavy chain 11), TAGLN (transgelin), and increased CD68, CD11b, and LGALS3 expression. NOX4-dependent mitochondrial DNA damage and activation of DNA-sensing pathways promote SMC phenotypic switching, inflammation, and aortic wall remodeling in AAA. Targeting NOX4 and enhancing mitochondrial function may offer therapeutic strategies for AAA prevention.

ObjectivePrior studies demonstrate mitochondrial dysfunction with increased reactive oxygen species generation in peripheral blood mononuclear cells in diabetes mellitus. Oxidative stress-mediated damage to mitochondrial DNA promotes atherosclerosis in animal models. Thus, we evaluated the relation of mitochondrial DNA damage in peripheral blood mononuclear cells s with vascular function in patients with diabetes mellitus and with atherosclerotic cardiovascular disease.Approach and resultsWe assessed non-invasive vascular function and mitochondrial DNA damage in 275 patients (age 57 ± 9 years, 60 % women) with atherosclerotic cardiovascular disease alone (N = 55), diabetes mellitus alone (N = 74), combined atherosclerotic cardiovascular disease and diabetes mellitus (N = 48), and controls age >45 without diabetes mellitus or atherosclerotic cardiovascular disease (N = 98). Mitochondrial DNA damage measured by quantitative PCR in peripheral blood mononuclear cells was higher with clinical atherosclerosis alone (0.55 ± 0.65), diabetes mellitus alone (0.65 ± 1.0), and combined clinical atherosclerosis and diabetes mellitus (0.89 ± 1.32) as compared to control subjects (0.23 ± 0.64, P < 0.0001). In multivariable models adjusting for age, sex, and relevant cardiovascular risk factors, clinical atherosclerosis and diabetes mellitus remained associated with higher mitochondrial DNA damage levels (β = 0.14 ± 0.13, P = 0.04 and β = 0.21 ± 0.13, P = 0.002, respectively). Higher mitochondrial DNA damage was associated with higher baseline pulse amplitude, a measure of arterial pulsatility, but not with flow-mediated dilation or hyperemic response, measures of vasodilator function.ConclusionsWe found greater mitochondrial DNA damage in patients with diabetes mellitus and clinical atherosclerosis. The association of mitochondrial DNA damage and baseline pulse amplitude may suggest a link between mitochondrial dysfunction and excessive small artery pulsatility with potentially adverse microvascular impact.

Look into any cell today, and you’ll see remnants of ancient bacteria by the thousands. These mitochondria—tiny organelles in the cell that each possess their own DNA—have come under a growing scientific spotlight; scientists increasingly believe they play a central role in many, if not most, human illnesses. Exquisitely sensitive to environmental threats, mitochondria convert dietary sugars into a high-energy molecule—adenosine triphosphate (ATP)—that cells use as fuel. And when mitochondria falter, cells lose power, just as a flashlight dims when its batteries weaken. Now scientists are linking environmental interactions with the mitochondria to an array of metabolic and age-related maladies, including cancer, autism, type 2 diabetes, Alzheimer disease, Parkinson disease, and cardiovascular illness.

Mitochondrial DNA (MtDNA) damage has generated much interest in recent years as a potential biomarker after ischemia/reperfusion and traumatic injury and in critical illness. MtDNA is particularly susceptible to damage due to is close proximity to the source of generation of reactive oxygen species during metabolism and its relatively low ability to repair DNA damage compared to nuclear repair mechanisms. Reduction in MtDNA damage appears to be a good indicator of a successful intervention. QRT‐PCR has been shown to be the most sensitive and accurate method to evaluate mtDNA damage requiring only nanogram amounts of DNA. While validated primer pairs for mtDNA damage for human and rodent mtDNA damage are available, comparable sets for pig have not previously been described, yet many studies in trauma and critical illness have utilized swine models. To select primer pairs for pigs, we aligned the pig mitochondrial DNA sequence to the pig genome in the UCSC Genome Browser and primers for regions not exhibiting overlap with the nuclear genome were selected with NCBI Primer3. Using the bleomycin injury model, porcine pulmonary artery endothelial cells obtained from Cell Biologics and cultivated in MCDB 131 medium were treated for 1 hr with bleomycin (10 μg/ml). Short and long sequences were tested with pig total DNA and demonstrated that one set detected specific induction of DNA lesions. The assay was able to detect 11 lesions per 10,000 base pairs. The short primer pairs also accurately predicted mitochondrial copy number DNA as corroborated for mtDNA by published results for the pig ND4 gene. We are currently employing this assay to detect mtDNA damage in a swine model of hemorrhagic shock.Support or Funding InformationFunded by US Army Medical Research Materiel Command

BACKGROUND: Various environmental factors that can affect the stability of the genetic material in humans, using a range of cytological and molecular genetic methods, are being studied actively. AIM: This work aimed to identify and analyze the associations between the buccal epithelial micronucleus assay results and mitochondrial DNA damage detected using real-time polymerase chain reaction (RT-PCR). METHODS: The study was conducted in Voronezh; 25 and 10 men and women, respectively, aged 20–24 years, were selected as participants. The buccal epithelial micronucleus assay and mitochondrial DNA damage assessment using RT-PCR were applied. In each sample, ≥2000 cells were examined to determine the number of cells with micronuclei, perinuclear vacuoles, notches, and protrusions. DNA repair and cytogenetic damage accumulation indices were calculated. The DNA was extracted using the CTAB buffer. RT-PCR employing the Encyclo polymerase and selected primers amplified two fragments (short and long) within the D-loop region of mitochondrial DNA. The number of DNA lesions was calculated based on the Ct values by applying a specific formula. Statistical analysis of the data was conducted with the Stadia software package. RESULTS: The frequency of mitochondrial DNA damage and the occurrence of nuclear abnormalities in the buccal epithelial cells of the study groups were determined. A higher degree of variation in the parameters studied was observed in females compared to males. Correlations were established between mitochondrial DNA damage and the frequency of nuclear abnormalities. Similar patterns of change were observed in mitochondrial DNA damage frequencies and nuclear aberrations. CONCLUSION: The common patterns of variation identified in the cytogenetic and molecular genetic indicators of genomic stability, as well as the correlations between the frequency of nuclear abnormalities in buccal epithelial cells and mitochondrial DNA damage, suggest a shared etiology of molecular and cell genetic lesions. These findings indicate the potential of utilizing these parameters to predict and refine the values of each other.

Each mitochondrion consists of 16,569 base pairs which encodes 37 genes, all of which are essential for normal mitochondrial function (Anderson et al., 1981). Each human cell contains several hundred copies of mitochondrial DNA, encoding 13 genes that are required for oxidative phosphorylation, 22 transfer RNAs and 2 ribosomal RNAs (Anderson et al., 1981). Mitochondria are vital organelles, which generate the majority of the cells energy through oxidative phosphorylation (Wallace, 2005). During this process, reactive oxygen species (ROS) are produced, that can leak out and react with a range of cellular components, including the mitochondrial genome (Richter et al., 1988). Therefore, it has been suggested that levels of oxidative DNA damage are higher in mitochondrial DNA than in nuclear DNA, with mitochondrial DNA accumulating mutations at a 10to 50fold higher rate (Hudson et al., 1998; Michikawa et al., 1999; Pakendorf and Stoneking, 2005; Yakes and Van Houten, 1997). If this mitochondrial DNA damage is not repaired, it can lead to disruption of the electron transport chain and increased generation of ROS, possibly resulting in vicious cycle of ROS production and mitochondrial DNA damage, leading to energy depletion and ultimately cell death (Harman, 1972; Miquel et al., 1980). Therefore suggesting that mitochondria must employ some form of repair or defence mechanism against such forms of deleterious damage. The integrity of mitochondrial DNA repair plays a central role in maintaining homeostasis in the cell and thus the efficient repair of mitochondrial DNA damage serves as an essential function in cellular survival. In comparison to nuclear DNA repair, our knowledge regarding mitochondrial DNA repair is limited. In fact, it was originally believed that mitochondria employed no repair mechanisms and damaged DNA was not repaired, but was merely degraded. This was primarily based on a study published in 1974, which demonstrated the inability of mitochondria to remove cyclobutyl pyrimidine dimers after exposure to ultraviolet light (Clayton et al., 1974). This theory remained for many years, but now it is abundantly clear that multiple DNA repair pathways and the controlled degradation of mitochondrial DNA, work together to maintain the integrity of the mitochondrial genome (Berneburg et al., 2006; Liu and Demple, 2010). Initially the repair of most mitochondrial DNA damage was thought to be limited to short-patch base excision repair (BER) (Stierum et al., 1999). However, the complex range of DNA lesions inflicted on mitochondrial DNA by ROS and potential replication errors indicated that such a restricted repair mechanism would be insufficient. Our knowledge of mitochondrial DNA repair has recently witnessed a rapid expansion and it is now evident that mitochondria also employ