Nuclear and mitochondrial DNA repair: similar pathways?

The effects and mechanisms of heat stress on mammalian oocyte and embryo development

The sum of nonspecific physiological responses exhibited by mammals in response to the disruption of thermal balance caused by high-temperature environments is referred to as heat stress (HS). HS affects the normal development of mammalian oocyte and embryos and leads to significant economic losses. Therefore, it is of great importance to gain a deep understanding of the mechanisms underlying the effects of HS on oocyte and embryonic development and to explore strategies for mitigating or preventing its detrimental impacts in the livestock industry. This article provides an overview of the negative effects of HS on mammalian oocyte growth, granulosa cell maturation and function, and embryonic development. It summarizes the mechanisms by which HS affects embryonic development, including generation of reactive oxygen species (ROS), endocrine disruption, the heat shock system, mitochondrial autophagy, and molecular-level alterations. Furthermore, it discusses various measures to ameliorate the effects of HS, such as antioxidant use, enhancement of mitochondrial function, gene editing, cultivating varieties possessing heat-resistant genes, and optimizing the animals'rearing environment. This article serves as a valuable reference for better understanding the relationship between HS and mammalian embryonic development as well as for improving the development of mammalian embryos and economic benefits under HS conditions in livestock production.

The impact of mitochondrial impairments on sperm function and male fertility: a systematic review

BACKGROUND

Besides adenine triphosphate (ATP) production for sustaining motility, the mitochondria of sperm also host other critical cellular functions during germ cell development and fertilization including calcium homeostasis, generation of reactive oxygen species (ROS), apoptosis, and in some cases steroid hormone biosynthesis. Normal mitochondrial membrane potential with optimal mitochondrial performance is essential for sperm motility, capacitation, acrosome reaction, and DNA integrity.

RESULTS

Defects in the sperm mitochondrial function can severely harm the fertility potential of males. The role of sperm mitochondria in fertilization and its final fate after fertilization is still controversial. Here, we review the current knowledge on human sperm mitochondria characteristics and their physiological and pathological conditions, paying special attention to improvements in assistant reproductive technology and available treatments to ameliorate male infertility.

CONCLUSION

Although mitochondrial variants associated with male infertility have potential clinical use, research is limited. Further understanding is needed to determine how these characteristics lead to adverse pregnancy outcomes and affect male fertility potential.

Emerging technology has a brilliant future: the CRISPR-Cas system for senescence, inflammation, and cartilage repair in osteoarthritis

Osteoarthritis (OA), known as one of the most common types of aseptic inflammation of the musculoskeletal system, is characterized by chronic pain and whole-joint lesions. With cellular and molecular changes including senescence, inflammatory alterations, and subsequent cartilage defects, OA eventually leads to a series of adverse outcomes such as pain and disability. CRISPR-Cas-related technology has been proposed and explored as a gene therapy, offering potential gene-editing tools that are in the spotlight. Considering the genetic and multigene regulatory mechanisms of OA, we systematically review current studies on CRISPR-Cas technology for improving OA in terms of senescence, inflammation, and cartilage damage and summarize various strategies for delivering CRISPR products, hoping to provide a new perspective for the treatment of OA by taking advantage of CRISPR technology.

A Review: Multi-Omics Approach to Studying the Association between Ionizing Radiation Effects on Biological Aging

Multi-omics studies have emerged as powerful tools for tailoring individualized responses to various conditions, capitalizing on genome sequencing technologies' increasing affordability and efficiency. This paper delves into the potential of multi-omics in deepening our understanding of biological age, examining the techniques available in light of evolving technology and computational models. The primary objective is to review the relationship between ionizing radiation and biological age, exploring a wide array of functional, physiological, and psychological parameters. This comprehensive review draws upon an extensive range of sources, including peer-reviewed journal articles, government documents, and reputable websites. The literature review spans from fundamental insights into radiation effects to the latest developments in aging research. Ionizing radiation exerts its influence through direct mechanisms, notably single- and double-strand DNA breaks and cross links, along with other critical cellular events. The cumulative impact of DNA damage forms the foundation for the intricate process of natural aging, intersecting with numerous diseases and pivotal biomarkers. Furthermore, there is a resurgence of interest in ionizing radiation research from various organizations and countries, reinvigorating its importance as a key contributor to the study of biological age. Biological age serves as a vital reference point for the monitoring and mitigation of the effects of various stressors, including ionizing radiation. Ionizing radiation emerges as a potent candidate for modeling the separation of biological age from chronological age, offering a promising avenue for tailoring protocols across diverse fields, including the rigorous demands of space exploration.

Mitophagy plays a "double-edged sword" role in the radiosensitivity of cancer cells

Mitochondria are organelles with double-membrane structure of inner and outer membrane, which provides main energy support for cell growth and metabolism. Reactive oxygen species (ROS) mainly comes from mitochondrial and can cause irreversible damage to cells under oxidative stress. Thus, mitochondrial homeostasis is the basis for maintaining the normal physiological function of cells and mitophagy plays a pivotal role in the maintenance of mitochondrial homeostasis. At present, to enhance the sensitivity of cancer cells to radiotherapy and chemotherapy by regulating mitochondria has increasingly become a hot spot of cancer therapy. It is particularly important to study the effect of ionizing radiation (IR) on mitochondria and the role of mitophagy in the radiosensitivity of cancer cells. Most of the existing reviews have focused on mitophagy-related molecules or pathways and the impact of mitophagy on diseases. In this review, we mainly focus on discussing the relationship between mitophagy and radiosensitivity of cancer cells around mitochondria and IR.

Dose-Dependent Effects of Radiation on Mitochondrial Morphology and Clonogenic Cell Survival in Human Microvascular Endothelial Cells

To better understand radiation-induced organ dysfunction at both high and low doses, it is critical to understand how endothelial cells (ECs) respond to radiation. The impact of irradiation (IR) on ECs varies depending on the dose administered. High doses can directly damage ECs, leading to EC impairment. In contrast, the effects of low doses on ECs are subtle but more complex. Low doses in this study refer to radiation exposure levels that are below those that cause immediate and necrotic damage. Mitochondria are the primary cellular components affected by IR, and this study explored their role in determining the effect of radiation on microvascular endothelial cells. Human dermal microvascular ECs (HMEC-1) were exposed to varying IR doses ranging from 0.1 Gy to 8 Gy (~0.4 Gy/min) in the AFRRI 60-Cobalt facility. Results indicated that high doses led to a dose-dependent reduction in cell survival, which can be attributed to factors such as DNA damage, oxidative stress, cell senescence, and mitochondrial dysfunction. However, low doses induced a small but significant increase in cell survival, and this was achieved without detectable DNA damage, oxidative stress, cell senescence, or mitochondrial dysfunction in HMEC-1. Moreover, the mitochondrial morphology was assessed, revealing that all doses increased the percentage of elongated mitochondria, with low doses (0.25 Gy and 0.5 Gy) having a greater effect than high doses. However, only high doses caused an increase in mitochondrial fragmentation/swelling. The study further revealed that low doses induced mitochondrial elongation, likely via an increase in mitochondrial fusion protein 1 (Mfn1), while high doses caused mitochondrial fragmentation via a decrease in optic atrophy protein 1 (Opa1). In conclusion, the study suggests, for the first time, that changes in mitochondrial morphology are likely involved in the mechanism for the radiation dose-dependent effect on the survival of microvascular endothelial cells. This research, by delineating the specific mechanisms through which radiation affects endothelial cells, offers invaluable insights into the potential impact of radiation exposure on cardiovascular health.

Emerging treatment approaches for triple-negative breast cancer

Approximately, 15% of global breast cancer cases are diagnosed as triple-negative breast cancer (TNBC), identified as the most aggressive subtype due to the simultaneous absence of estrogen receptor, progesterone receptor, and HER2. This characteristic renders TNBC highly aggressive and challenging to treat, as it excludes the use of effective drugs such as hormone therapy and anti-HER2 agents. In this review, we explore standard therapies and recent emerging approaches for TNBC, including PARP inhibitors, immune checkpoint inhibitors, PI3K/AKT pathway inhibitors, and cytotoxin-conjugated antibodies. The mechanism of action of these drugs and their utilization in clinical practice is explained in a pragmatic and prospective manner, contextualized within the current landscape of standard therapies for this pathology. These advancements present a promising frontier for tailored interventions with the potential to significantly improve outcomes for TNBC patients. Interestingly, while TNBC poses a complex challenge, it also serves as a paradigm and an opportunity for translational research and innovative therapies in the field of oncology.

The Diagnostic, Prognostic, and Therapeutic Potential of Cell-Free DNA with a Special Focus on COVID-19 and Other Viral Infections

Cell-free DNA (cfDNA) in human blood serum, urine, and other body fluids recently became a commonly used diagnostic marker associated with various pathologies. This is because cfDNA enables a much higher sensitivity than standard biochemical parameters. The presence of and/or increased level of cfDNA has been reported for various diseases, including viral infections, including COVID-19. Here, we review cfDNA in general, how it has been identified, where it can derive from, its molecular features, and mechanisms of release and clearance. General suitability of cfDNA for diagnostic questions, possible shortcomings and future directions are discussed, with a special focus on coronavirus infection.

Sublethal Exposure to Plasma-Activated Water Influences the Morphological Characteristics, Phagocytic Ability, and Virulence of Acanthamoeba castellanii

PURPOSE

This study aimed to examine the ultrastructure, cytotoxicity, phagocytosis, and antioxidant responses of Acanthamoeba castellanii trophozoites exposed to sublethal plasma-activated water.

METHODS

Trophozoites were exposed to a sublethal treatment of PAW and compared to untreated viable trophozoites via adhesion assays on macrophage monolayers, osmo- and thermotolerance tests. Bacterial uptake was assessed in treated cells to evaluate their phagocytic characteristics. Oxidative stress biomarkers and antioxidant activities were compared in treated and untreated trophozoites. Finally, the expression of the mannose-binding protein (MBP), cysteine protease 3 (CP3), and serine endopeptidase (SEP) genes was determined in cells.

RESULTS

In PAW-treated trophozoites, cytopathic effects were more extensive and resulted in the detachment of macrophage monolayers. Treated trophozoites could not grow at high temperatures (43 °C). Moreover, they showed osmotolerance to 0.5 M D-mannitol but not to 1 M. Results demonstrated a higher bacterial uptake rate by PAW-treated trophozoites than untreated cells. Activities of superoxide dismutase and catalase and catalase were significantly greater in the treated trophozoites, and the glutathione and glutathione/glutathione disulfide were significantly lower in the PAW-treated cells. Exposure to PAW also significantly increased the malondialdehyde level and total antioxidant capacity. Treatment with PAW led to significantly higher expression of virulent genes like MBP, CP3, and SEP.

CONCLUSION

PAW is a double-edged sword against A. castellanii. PAW is an effective antiamoebic agent in proper usage, whereas its sublethal exposure may reduce its effectiveness and increase amoebas' pathogenicity. An agent's adequate concentration and exposure time are essential to achieve optimum results.

Peri-Operative Kinetics of Plasma Mitochondrial DNA Levels during Living Donor Kidney Transplantation

During ischemia and reperfusion injury (IRI), mitochondria may release mitochondrial DNA (mtDNA). mtDNA can serve as a propagator of further injury but in specific settings has anti-inflammatory capacities as well. Therefore, the aim of this study was to study the perioperative dynamics of plasma mtDNA during living donor kidney transplantation (LDKT) and its potential as a marker of graft outcome. Fifty-six donor-recipient couples from the Volatile Anesthetic Protection of Renal Transplants-1 (VAPOR-1) trial were included. Systemic venous, systemic arterial, and renal venous samples were taken at multiple timepoints during and after LDKT. Levels of mtDNA genes changed over time and between vascular compartments. Several donor, recipient, and transplantation-related variables significantly explained the course of mtDNA genes over time. mtDNA genes predicted 1-month and 24-month estimated glomerular filtration rate (eGFR) and acute rejection episodes in the two-year follow-up period. To conclude, mtDNA is released in plasma during the process of LDKT, either from the kidney or from the whole body in response to transplantation. While circulating mtDNA levels positively and negatively predict post-transplantation outcomes, the exact mechanisms and difference between mtDNA genes are not yet understood and need further exploration.

The Role of Retinal Pigment Epithelial Cells in Age-Related Macular Degeneration: Phagocytosis and Autophagy

Age-related macular degeneration (AMD) causes vision loss in the elderly population. Dry AMD leads to the formation of Drusen, while wet AMD is characterized by cell proliferation and choroidal angiogenesis. The retinal pigment epithelium (RPE) plays a key role in AMD pathogenesis. In particular, helioreceptor renewal depends on outer segment phagocytosis of RPE cells, while RPE autophagy can protect cells from oxidative stress damage. However, when the oxidative stress burden is too high and homeostasis is disturbed, the phagocytosis and autophagy functions of RPE become damaged, leading to AMD development and progression. Hence, characterizing the roles of RPE cell phagocytosis and autophagy in the pathogenesis of AMD can inform the development of potential therapeutic targets to prevent irreversible RPE and photoreceptor cell death, thus protecting against AMD.

The role of mitochondria in the resistance of melanoma to PD-1 inhibitors

Malignant melanoma is one of the most common tumours and has the highest mortality rate of all types of skin cancers worldwide. Traditional and novel therapeutic approaches, including surgery, targeted therapy and immunotherapy, have shown good efficacy in the treatment of melanoma. At present, the mainstay of treatment for melanoma is immunotherapy combined with other treatment strategies. However, immune checkpoint inhibitors, such as PD-1 inhibitors, are not particularly effective in the clinical treatment of patients with melanoma. Changes in mitochondrial function may affect the development of melanoma and the efficacy of PD-1 inhibitors. To elucidate the role of mitochondria in the resistance of melanoma to PD-1 inhibitors, this review comprehensively summarises the role of mitochondria in the occurrence and development of melanoma, targets related to the function of mitochondria in melanoma cells and changes in mitochondrial function in different cells in melanoma resistant to PD-1 inhibitors. This review may help to develop therapeutic strategies for improving the clinical response rate of PD-1 inhibitors and prolonging the survival of patients by activating mitochondrial function in tumour and T cells.

Bifenthrin disrupts cytochrome c oxidase activity and reduces mitochondrial DNA copy number through oxidative damage in pool barb (Puntius sophore)

Bifenthrin (BF), a synthetic pyrethroid is used worldwide for both agricultural and non-agricultural purposes due to its high insecticidal activity and low toxicity in mammals. However, its improper usage implies a possible risk to aquatic life. The Study was aimed to correlate the association of BF toxicity with mitochondrial DNA copy number variation in edible fish Punitus sophore. The 96-h LC 50 of BF in P. sophore was 3.4 μg/L, fish was treated with sub-lethal doses (0.34 μg/L,0.68 μg/L) of BF for 15 days. The activity and expression level of cytochrome c oxidase (Mt-COI) were measured to assess mitochondrial dysfunction caused by BF. Results showed BF reduced the level of Mt-COI mRNA in treated groups, hindered complex IV activity and increased ROS generation leading to oxidative damage. mtDNAcn was decreased in the muscle, brain and liver after BF treatment. Furthermore, BF induced neurotoxicity in brain and muscle cells through the inhibition of AchE activity. The treated groups showed elevated level of malondialdehyde (MDA) and an imbalance of antioxidant enzymes activity. Molecular docking and simulation analysis also predicted that BF binds to the active sites of the enzyme and restricts the fluctuation of active sites' residues. Hence, outcome of the study suggests reduction of mtDNAcn could be a potential biomarker to assess Bifenthrin induced toxicity in aquatic ecosystem.

Mitochondrial DNA Polymorphism in HV1 and HV2 Regions and 12S rDNA in Perimenopausal Hypertensive Women

Estrogens enhance cellular mitochondrial activity. The diminution of female hormones during menopause may have an effect on the mitochondrial genome and the expression of mitochondrial proteins. Hence, oxidative stress and the pro-inflammatory state contribute to the formation of systemic illnesses including arterial hypertension (AH). This study aimed to determine the types and frequency of mutations in the mitochondrial DNA (mtDNA) nucleotide sequence in the hypervariable regions 1 and 2 (HV1 and HV2) and the 12S RNA coding sequence of the D-loop in postmenopausal women with hypertension. In our study, 100 women were investigated, 53 of whom were postmenopausal and 47 of whom were premenopausal (53.9 ± 3.7 years vs. 47.7 ± 4.2 years, respectively). Of those studied, 35 premenopausal and 40 postmenopausal women were diagnosed with AH. A medical checkup with 24 h monitoring of blood pressure (RR) and heart rate was undertaken (HR). The polymorphism of the D-loop and 12S rDNA region of mtDNA was examined. Changes in the nucleotide sequence of mtDNA were observed in 23% of the group of 100 women. The changes were identified in 91.3% of HV1 and HV2 regions, 60.9% of HV1 segments, 47.5% of HV2 regions, and 43.5% of 12S rDNA regions. The frequency of nucleotide sequence alterations in mtDNA was substantially higher in postmenopausal women (34%) than in premenopausal women (10.6%), p = 0.016. A higher frequency of changes in HV1 + HV2 sections in postmenopausal women (30.2%) compared to the premenopausal group (10.6%) was detected, p = 0.011. Only postmenopausal women were found to have modifications to the HV2 segment and the 12S rDNA region. After menopause, polymorphism in the mtDNA region was substantially more frequent in women with arterial hypertension than before menopause (p = 0.030; 37.5% vs. 11.5%). Comparable findings were observed in the HV2 and HV1 regions of the AH group (35% vs. 11.5%), p = 0.015, in the HV1 segment (25% vs. 11.5%), p = 0.529, and in the HV2 segment, 12S rDNA (25% vs. 0%). More than 80% of all changes in nucleotide sequence were homoplasmic. The mtDNA polymorphisms of the nucleotide sequence in the HV1 and HV2 regions, the HV2 region alone, and the 12S RNA coding sequence were associated with estrogen deficiency and a more severe course of arterial hypertension, accompanied by symptoms of adrenergic stimulation.

Chronic Ionizing Radiation of Plants: An Evolutionary Factor from Direct Damage to Non-Target Effects

In present times, the levels of ionizing radiation (IR) on the surface of Earth are relatively low, posing no high challenges for the survival of contemporary life forms. IR derives from natural sources and naturally occurring radioactive materials (NORM), the nuclear industry, medical applications, and as a result of radiation disasters or nuclear tests. In the current review, we discuss modern sources of radioactivity, its direct and indirect effects on different plant species, and the scope of the radiation protection of plants. We present an overview of the molecular mechanisms of radiation responses in plants, which leads to a tempting conjecture of the evolutionary role of IR as a limiting factor for land colonization and plant diversification rates. The hypothesis-driven analysis of available plant genomic data suggests an overall DNA repair gene families' depletion in land plants compared to ancestral groups, which overlaps with a decrease in levels of radiation exposure on the surface of Earth millions of years ago. The potential contribution of chronic IR as an evolutionary factor in combination with other environmental factors is discussed.

Cell-free circulating mitochondrial DNA: An emerging biomarker for airborne particulate matter associated with cardiovascular diseases

The association of airborne particulate matter exposure with the deteriorating function of the cardiovascular system is fundamentally driven by the impairment of mitochondrial-nuclear crosstalk orchestrated by aberrant redox signaling. The loss of delicate balance in retrograde communication from mitochondria to the nucleus often culminates in the methylation of the newly synthesized strand of mitochondrial DNA (mtDNA) through DNA methyl transferases. In highly metabolic active tissues such as the heart, mtDNA's methylation state alteration impacts mitochondrial bioenergetics. It affects transcriptional regulatory processes involved in biogenesis, fission, and fusion, often accompanied by the integrated stress response. Previous studies have demonstrated a paradoxical role of mtDNA methylation in cardiovascular pathologies linked to air pollution. A pronounced alteration in mtDNA methylation contributes to systemic inflammation, an etiological determinant for several co-morbidities, including vascular endothelial dysfunction and myocardial injury. In the current article, we evaluate the state of evidence and examine the considerable promise of using cell-free circulating methylated mtDNA as a predictive biomarker to reduce the more significant burden of ambient air pollution on cardiovascular diseases.

Suitability of salivary leucocytes to assess DNA repair ability in human biomonitoring studies by the challenge-comet assay

The challenge-comet assay is a simple but effective approach that provides a quantitative and functional determination of DNA repair ability, and allows to monitor the kinetics of repair process. Peripheral blood mononuclear cells (PBMC) are the cells most frequently employed in human biomonitoring studies using the challenge-comet assay, but having a validated alternative of non-invasive biomatrix would be highly convenient for certain population groups and circumstances. The objective of this study was to validate the use of salivary leucocytes in the challenge-comet assay. Leucocytes were isolated from saliva samples and challenged (either in fresh or after cryopreservation) with three genotoxic agents acting by different action mechanisms: bleomycin, methyl methanesulfonate, and ultraviolet radiation. Comet assay was performed just after treatment and at other three additional time points, in order to study repair kinetics. The results obtained demonstrated that saliva leucocytes were as suitable as PBMC for assessing DNA damage of different nature that was efficiently repaired over the evaluated time points, even after 5 months of cryopreservation (after a 24 h stimulation with PHA). Furthermore, a new parameter to determine the efficacy of the repair process, independent of the initial amount of damage induced, is proposed, and recommendations to perform the challenge-comet assay with salivary leucocytes depending on the type of DNA repair to be assessed are suggested. Validation studies are needed to verify whether the method is reproducible and results reliable and comparable among laboratories and studies.

Mitochondrial DNA Repair in Neurodegenerative Diseases and Ageing

Mitochondria are the only organelles, along with the nucleus, that have their own DNA. Mitochondrial DNA (mtDNA) is a double-stranded circular molecule of ~16.5 kbp that can exist in multiple copies within the organelle. Both strands are translated and encode for 22 tRNAs, 2 rRNAs, and 13 proteins. mtDNA molecules are anchored to the inner mitochondrial membrane and, in association with proteins, form a structure called nucleoid, which exerts a structural and protective function. Indeed, mitochondria have evolved mechanisms necessary to protect their DNA from chemical and physical lesions such as DNA repair pathways similar to those present in the nucleus. However, there are mitochondria-specific mechanisms such as rapid mtDNA turnover, fission, fusion, and mitophagy. Nevertheless, mtDNA mutations may be abundant in somatic tissue due mainly to the proximity of the mtDNA to the oxidative phosphorylation (OXPHOS) system and, consequently, to the reactive oxygen species (ROS) formed during ATP production. In this review, we summarise the most common types of mtDNA lesions and mitochondria repair mechanisms. The second part of the review focuses on the physiological role of mtDNA damage in ageing and the effect of mtDNA mutations in neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. Considering the central role of mitochondria in maintaining cellular homeostasis, the analysis of mitochondrial function is a central point for developing personalised medicine.

The mitochondrial unfolded protein response (UPRmt): shielding against toxicity to mitochondria in cancer

Mitochondria are essential for tumor growth and progression. However, the heavy demand for mitochondrial activity in cancer leads to increased production of mitochondrial reactive oxygen species (mtROS), accumulation of mutations in mitochondrial DNA, and development of mitochondrial dysfunction. If left unchecked, excessive mtROS can damage and unfold proteins in the mitochondria to an extent that becomes lethal to the tumor. Cellular systems have evolved to combat mtROS and alleviate mitochondrial stress through a quality control mechanism called the mitochondrial unfolded protein response (UPR^mt). The UPR^mt system is composed of chaperones and proteases, which promote protein folding or eliminate mitochondrial proteins damaged by mtROS, respectively. UPR^mt is conserved and activated in cancer in response to mitochondrial stress to maintain mitochondrial integrity and support tumor growth. In this review, we discuss how mitochondria become dysfunctional in cancer and highlight the tumor-promoting functions of key components of the UPR^mt.

The Effect of High and Variable Glucose on the Viability of Endothelial Cells Co-Cultured with Smooth Muscle Cells

Diabetes mellitus causes endothelial dysfunction. The aim of this study was to investigate the effect of normal (5 mmol/L), high (20 mmol/L), and fluctuating (5 and 20 mmol/L changed every day) glucose concentration in the culture medium on the viability of human umbilical vein endothelial cells (HUVECs) co-cultured with human umbilical artery smooth muscle cells (HUASMCs). The cultures were conducted on semi-permeable flat polysulfone (PSU) fibronectin-coated membranes immobilized in self-made inserts. The insert contained either HUVECs on a single membrane or HUASMCs and HUVECs on two membranes close to each other. Cultures were conducted for 7 or 14 days. Apoptosis, mitochondrial potential, and the production of reactive oxygen species and lactate by HUVECs were investigated. The results indicate that fluctuations in glucose concentration have a stronger negative effect on HUVECs viability than constant high glucose concentration. High and fluctuating glucose concentrations slow down cell proliferation compared to the culture carried out in the medium with normal glucose concentration. In conclusion, HUASMCs affect the viability of HUVECs when both types of cells are co-cultured in medium with normal or variable glucose concentration.

Unusual evolution of tree frog populations in the Chernobyl exclusion zone

Despite the ubiquity of pollutants in the environment, their long-term ecological consequences are not always clear and still poorly studied. This is the case concerning the radioactive contamination of the environment following the major nuclear accident at the Chernobyl nuclear power plant. Notwithstanding the implications of evolutionary processes on the population status, few studies concern the evolution of organisms chronically exposed to ionizing radiation in the Chernobyl exclusion zone. Here, we examined genetic markers for 19 populations of Eastern tree frog (Hyla orientalis) sampled in the Chernobyl region about thirty years after the nuclear power plant accident to investigate microevolutionary processes ongoing in local populations. Genetic diversity estimated from nuclear and mitochondrial markers showed an absence of genetic erosion and higher mitochondrial diversity in tree frogs from the Chernobyl exclusion zone compared to other European populations. Moreover, the study of haplotype network permitted us to decipher the presence of an independent recent evolutionary history of Chernobyl exclusion zone's Eastern tree frogs caused by an elevated mutation rate compared to other European populations. By fitting to our data a model of haplotype network evolution, we suspected that Eastern tree frog populations in the Chernobyl exclusion zone have a high mitochondrial mutation rate and small effective population sizes. These data suggest that Eastern tree frog populations might offset the impact of deleterious mutations because of their large clutch size, but also question the long-term impact of ionizing radiation on the status of other species living in the Chernobyl exclusion zone.

Mitochondrial Genome Editing to Treat Human Osteoarthritis-A Narrative Review

Osteoarthritis (OA) is a severe, common chronic orthopaedic disorder characterised by a degradation of the articular cartilage with an incidence that increases over years. Despite the availability of various clinical options, none can stop the irreversible progression of the disease to definitely cure OA. Various mutations have been evidenced in the mitochondrial DNA (mtDNA) of cartilage cells (chondrocytes) in OA, leading to a dysfunction of the mitochondrial oxidative phosphorylation processes that significantly contributes to OA cartilage degeneration. The mitochondrial genome, therefore, represents a central, attractive target for therapy in OA, especially using genome editing procedures. In this narrative review article, we present and discuss the current advances and breakthroughs in mitochondrial genome editing as a potential, novel treatment to overcome mtDNA-related disorders such as OA. While still in its infancy and despite a number of challenges that need to be addressed (barriers to effective and site-specific mtDNA editing and repair), such a strategy has strong value to treat human OA in the future, especially using the groundbreaking clustered regularly interspaced short palindromic repeats (CRIPSR)/CRISPR-associated 9 (CRISPR/Cas9) technology and mitochondrial transplantation approaches.

Mini-Review: Mitochondrial dysfunction and chemotherapy-induced neuropathic pain

Chemotherapy-induced peripheral neuropathy (CIPN) is a somatosensory axonopathy in cancer patients receiving any of a variety of widely-use antitumor agents. CIPN can lead to long-lasting neuropathic pain that limits the dose or length of otherwise life-saving cancer therapy. Accumulating evidence over the last two decades indicates that many chemotherapeutic agents cause mitochondrial injury in the peripheral sensory nerves by disrupting mitochondrial structure and bioenergetics, increasing nitro-oxidative stress and altering mitochondrial transport, fission, fusion and mitophagy. The accumulation of abnormal and dysfunctional mitochondria in sensory neurons are linked to axonal growth defects resulting in the loss of intraepidermal nerve fibers in the hands and feet, increased spontaneous discharge and the sensitization of peripheral sensory neurons that provoke and promote changes in the central nervous system that establish a chronic neuropathic pain state. This has led to the propose mitotoxicity theory of CIPN. Strategies that improve mitochondrial function have shown success in preventing and reversing CIPN in pre-clinical animal models and have begun to show some progress toward translation to the clinic. In this review, we will review the evidence for, the causes and effects of and current strategies to target mitochondrial dysfunction in CIPN.

Neuroinflammatory Mechanisms of Mitochondrial Dysfunction and Neurodegeneration in Glaucoma

The exact mechanism of retinal ganglion cell loss in the pathogenesis of glaucoma is yet to be understood. Mitochondrial damage-associated molecular patterns (DAMPs) resulting from mitochondrial dysfunction have been linked to Leber's hereditary optic neuropathy and autosomal dominant optic atrophy, as well as to brain neurodegenerative diseases. Recent evidence shows that, in conditions where mitochondria are damaged, a sustained inflammatory response and downstream pathological inflammation may ensue. Mitochondrial damage has been linked to the accumulation of age-related mitochondrial DNA mutations and mitochondrial dysfunction, possibly through aberrant reactive oxygen species production and defective mitophagy. The present review focuses on how mitochondrial dysfunction may overwhelm the ability of neurons and glial cells to adequately maintain homeostasis and how mitochondria-derived DAMPs trigger the immune system and induce neurodegeneration.

Role of Oxidative DNA Damage and Repair in Atrial Fibrillation and Ischemic Heart Disease

Atrial fibrillation (AF) and ischemic heart disease (IHD) represent the two most common clinical cardiac diseases, characterized by angina, arrhythmia, myocardial damage, and cardiac dysfunction, significantly contributing to cardiovascular morbidity and mortality and posing a heavy socio-economic burden on society worldwide. Current treatments of these two diseases are mainly symptomatic and lack efficacy. There is thus an urgent need to develop novel therapies based on the underlying pathophysiological mechanisms. Emerging evidence indicates that oxidative DNA damage might be a major underlying mechanism that promotes a variety of cardiac diseases, including AF and IHD. Antioxidants, nicotinamide adenine dinucleotide (NAD⁺) boosters, and enzymes involved in oxidative DNA repair processes have been shown to attenuate oxidative damage to DNA, making them potential therapeutic targets for AF and IHD. In this review, we first summarize the main molecular mechanisms responsible for oxidative DNA damage and repair both in nuclei and mitochondria, then describe the effects of oxidative DNA damage on the development of AF and IHD, and finally discuss potential targets for oxidative DNA repair-based therapeutic approaches for these two cardiac diseases.

Genome-wide surveillance of transcription errors in response to genotoxic stress

Mutagenic compounds are a potent source of human disease. By inducing genetic instability, they can accelerate the evolution of human cancers or lead to the development of genetically inherited diseases. Here, we show that in addition to genetic mutations, mutagens are also a powerful source of transcription errors. These errors arise in dividing and nondividing cells alike, affect every class of transcripts inside cells, and, in certain cases, greatly exceed the number of mutations that arise in the genome. In addition, we reveal the kinetics of transcription errors in response to mutagen exposure and find that DNA repair is required to mitigate transcriptional mutagenesis after exposure. Together, these observations have far-reaching consequences for our understanding of mutagenesis in human aging and disease, and suggest that the impact of DNA damage on human physiology has been greatly underestimated.

Radioprotective Agents and Enhancers Factors. Preventive and Therapeutic Strategies for Oxidative Induced Radiotherapy Damages in Hematological Malignancies

Radiation therapy plays a critical role in the management of a wide range of hematologic malignancies. It is well known that the post-irradiation damages both in the bone marrow and in other organs are the main causes of post-irradiation morbidity and mortality. Tumor control without producing extensive damage to the surrounding normal cells, through the use of radioprotectors, is of special clinical relevance in radiotherapy. An increasing amount of data is helping to clarify the role of oxidative stress in toxicity and therapy response. Radioprotective agents are substances that moderate the oxidative effects of radiation on healthy normal tissues while preserving the sensitivity to radiation damage in tumor cells. As well as the substances capable of carrying out a protective action against the oxidative damage caused by radiotherapy, other substances have been identified as possible enhancers of the radiotherapy and cytotoxic activity via an oxidative effect. The purpose of this review was to examine the data in the literature on the possible use of old and new substances to increase the efficacy of radiation treatment in hematological diseases and to reduce the harmful effects of the treatment.

Cilostazol ameliorates diabetic nephropathy by inhibiting highglucose- induced apoptosis

Diabetic nephropathy (DN) is a hyperglycemia-induced progressive development of renal insufficiency. Excessive glucose can increase mitochondrial reactive oxygen species (ROS) and induce cell damage, causing mitochondrial dysfunction. Our previous study indicated that cilostazol (CTZ) can reduce ROS levels and decelerate DN progression in streptozotocin (STZ)-induced type 1 diabetes. This study investigated the potential mechanisms of CTZ in rats with DN and in high glucose-treated mesangial cells. Male Sprague-Dawley rats were fed 5 mg/kg/day of CTZ after developing STZ-induced diabetes mellitus. Electron microscopy revealed that CTZ reduced the thickness of the glomerular basement membrane and improved mitochondrial morphology in mesangial cells of diabetic kidney. CTZ treatment reduced excessive kidney mitochondrial DNA copy numbers induced by hyperglycemia and interacted with the intrinsic pathway for regulating cell apoptosis as an antiapoptotic mechanism. In high-glucose-treated mesangial cells, CTZ reduced ROS production, altered the apoptotic status, and down-regulated transforming growth factor beta (TGF-β) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB). Base on the results of our previous and current studies, CTZ deceleration of hyperglycemia-induced DN is attributable to ROS reduction and thereby maintenance of the mitochondrial function and reduction in TGF-β and NF-κB levels.

The Role of Mitochondria in Systemic Lupus Erythematosus: A Glimpse of Various Pathogenetic Mechanisms

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a polysystem autoimmune disease that adversely affects human health. Various organs can be affected, including the kidney or brain. Traditional treatment methods for SLE primarily rely on glucocorticoids and immunosuppressors. Unfortunately, these therapeutic agents cannot prevent a high recurrence rate after SLE remission. Therefore, novel therapeutic targets are urgently required.

METHODS

A systematic search of the published literature regarding the abnormal structure and function of mitochondria in SLE and therapies targeting mitochondria was performed in several databases.

RESULTS

Accumulating evidence indicates that mitochondrial dysfunction plays important roles in the pathogenesis of SLE, including influencing mitochondrial DNA damage, mitochondrial dynamics change, abnormal mitochondrial biogenesis and energy metabolism, mitophagy, oxidative stress, inflammatory reactions, apoptosis and NETosis. Further investigation of mitochondrial pathophysiological roles will result in further clarification of SLE. Specific lupus-induced organ damage also exhibits characteristic mitochondrial changes.

CONCLUSION

This review aimed to summarize the current research on the role of mitochondrial dysfunction in SLE, which will necessarily provide potential novel therapeutic targets for SLE.

Mitochondrial DNA: Hotspot for Potential Gene Modifiers Regulating Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a prevalent and untreatable cardiovascular disease with a highly complex clinical and genetic causation. HCM patients bearing similar sarcomeric mutations display variable clinical outcomes, implying the involvement of gene modifiers that regulate disease progression. As individuals exhibiting mutations in mitochondrial DNA (mtDNA) present cardiac phenotypes, the mitochondrial genome is a promising candidate to harbor gene modifiers of HCM. Herein, we sequenced the mtDNA of isogenic pluripotent stem cell-cardiomyocyte models of HCM focusing on two sarcomeric mutations. This approach was extended to unrelated patient families totaling 52 cell lines. By correlating cellular and clinical phenotypes with mtDNA sequencing, potentially HCM-protective or -aggravator mtDNA variants were identified. These novel mutations were mostly located in the non-coding control region of the mtDNA and did not overlap with those of other mitochondrial diseases. Analysis of unrelated patients highlighted family-specific mtDNA variants, while others were common in particular population haplogroups. Further validation of mtDNA variants as gene modifiers is warranted but limited by the technically challenging methods of editing the mitochondrial genome. Future molecular characterization of these mtDNA variants in the context of HCM may identify novel treatments and facilitate genetic screening in cardiomyopathy patients towards more efficient treatment options.

Mitochondrial and Nuclear DNA Oxidative Damage in Physiological and Pathological Aging

Mitochondria play an important role in numerous processes, including energy generation, regulating ion homeostasis, and cell signaling. Mitochondria are also the main source of reactive oxygen species (ROS). Due to the oxidative environment within mitochondria, the macromolecules therein, for example, mtDNA, proteins, and lipids are more susceptible to sustaining damage. During aging, mitochondrial functions decline, partly as a result of an accumulation of mtDNA mutations, decreased mtDNA copy number and protein expression, and a reduction in oxidative capacity. The aim of this study was to summarize the knowledge on DNA oxidative damage in aging and age-related neurodegenerative diseases. It has been hypothesized that various ROS may play an important role not only in physiological senescence but also in the development of neurodegenerative diseases, for example, Alzheimer's disease and Parkinson's disease. Thus, mitochondria seem to be a potential target of novel treatments for neurodegenerative diseases.

Mitophagy and DNA damage signaling in human aging

Aging is associated with multiple human pathologies. In the past few years mitochondrial homeostasis has been well correlated with age-related disorders and longevity. Mitochondrial homeostasis involves generation, biogenesis and removal of dysfunctional mitochondria via mitophagy. Mitophagy is regulated by various mitochondrial and extra-mitochondrial factors including morphology, oxidative stress and DNA damage. For decades, DNA damage and inefficient DNA repair have been considered as major determinants for age-related disorders. Although defects in DNA damage recognition and repair and mitophagy are well documented to be major factors in age-associated diseases, interactivity between these is poorly understood. Mitophagy efficiency decreases with age leading to accumulation of dysfunctional mitochondria enhancing the severity of age-related disorders including neurodegenerative diseases, inflammatory diseases, cancer, diabetes and many more. Therefore, mitophagy is being targeted for intervention in age-associated disorders. NAD+ supplementation has emerged as one intervention to target both defective DNA repair and mitophagy. In this review, we discuss the molecular signaling pathways involved in regulation of DNA damage and repair and of mitophagy, and we highlight the opportunities for clinical interventions targeting these processes to improve the quality of life during aging.

Mitochondrial-associated impairments of temozolomide on neural stem/progenitor cells and hippocampal neurons

Primary brain tumor patients often experience neurological, cognitive, and depressive symptoms that profoundly affect quality of life. The DNA alkylating agent, temozolomide (TMZ), along with radiation therapy forms the standard of care for glioblastoma (GBM) - the most common and aggressive of all brain cancers. Numerous studies have reported that TMZ disrupts hippocampal neurogenesis and causes spatial learning deficits in rodents; however, the effect of TMZ on mature hippocampal neurons has not been addressed. In this study, we examined the mitochondrial-mediated mechanisms involving TMZ-induced neural damage in primary rat neural stem/progenitor cells (NSC) and hippocampal neurons. TMZ inhibited mtDNA replication and transcription of mitochondrial genes (ND1 and Cyt b) in NSC by 24 h, whereas the effect of TMZ on neuronal mtDNA transcription was less pronounced. Transmission electron microscopy imaging revealed mitochondrial degradation in TMZ-treated NSC. Acute TMZ exposure (4 h) caused a rapid reduction in dendritic branching and loss of postsynaptic density-95 (PSD95) puncta on dendrites. Longer TMZ exposure impaired mitochondrial respiratory activity, increased oxidative stress, and induced apoptosis in hippocampal neurons. The presented findings suggest that NSC may be more vulnerable to TMZ than hippocampal neurons upon acute exposure; however long-term TMZ exposure results in neuronal mitochondrial respiratory dysfunction and dendritic damage, which may be associated with delayed cognitive impairments.

Pre-diagnostic leukocyte mitochondrial DNA copy number and colorectal cancer risk

Mitochondrial DNA (mtDNA) is susceptible to oxidative stress and mutation. Few epidemiological studies have assessed the relationship between mtDNA copy number (mtDNAcn) and risk of colorectal cancer (CRC), with inconsistent findings. In this study, we examined the association between pre-diagnostic leukocyte mtDNAcn and CRC risk in a case-control study of 324 female cases and 658 matched controls nested within the Nurses' Health Study (NHS). Relative mtDNAcn in peripheral blood leukocytes was measured by quantitative polymerase chain reaction-based assay. Conditional logistic regression models were applied to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for the association of interest. Results showed lower log-mtDNAcn was significantly associated with increased risk of CRC, in a dose-dependent relationship (P for trend < 0.0001). Compared to the fourth quartile, multivariable-adjusted OR [95% confidence interval (CI)] was 1.10 (0.69, 1.76) for the third quartile, 1.40 (0.89, 2.19) for the second quartile and 2.19 (1.43, 3.35) for the first quartile. In analysis by anatomic subsite of CRC, we found a significant inverse association for proximal colon cancer [lowest versus highest quartile, multivariable-adjusted OR (95% CI) = 3.31 (1.70, 6.45), P for trend = 0.0003]. Additionally, stratified analysis according to the follow-up time since blood collection showed that the inverse association between mtDNAcn and CRC remained significant among individuals with ≥ 5 years' follow-up, and marginally significant among those with ≥ 10 years' follow-up since mtDNAcn testing, suggesting that mtDNAcn may serve as a long-term predictor for risk of CRC. In conclusion, pre-diagnostic leukocyte mtDNAcn was inversely associated with CRC risk. Further basic experimental studies are needed to explore the underlying biological mechanisms linking mtDNAcn to CRC carcinogenesis.

Evaluation of mitochondria in oocytes following γ-irradiation

Standard cytotoxic cancer treatments, such as radiation, can damage and deplete the supply of oocytes stored within the ovary, which predisposes females to infertility and premature menopause later in life. The mechanisms by which radiation induces oocyte damage have not been completely elucidated. The objective of this study was to determine if γ-irradiation changes mitochondrial characteristics in oocytes, possibly contributing to a reduction in oocyte number and quality. Immature oocytes were collected from postnatal day (PN) 9–11 C57Bl6 mice 3, 6 and 24 hours after 0.1 Gy γ-irradiation to monitor acute mitochondrial changes. Oocytes were classified as small (>20 µm) or growing (40–60 µm). Mitochondrial membrane potential was lost in 20% and 44% of small oocytes (~20 µm) at 3 and 6 hours after γ-irradiation, respectively, consistent with the induction of apoptosis. However, mitochondrial mass, distribution and membrane potential in the surviving small oocytes were similar to the non-irradiated controls at both time points. At 24 hours after γ-irradiation, all mitochondrial parameters analysed within immature oocytes were similar to untreated controls. Mitochondrial parameters within growing oocytes were also similar to untreated controls. When mice were superovulated more than 3 weeks after γ-irradiation, there was a significant reduction in the number of mature oocytes harvested compared to controls (Control 18 ± 1 vs 0.1 Gy 4 ± 1, n = 6/16 mice, p < 0.05). There was a slight reduction in mitochondrial mass in mature oocytes after γ-irradiation, though mitochondrial localization, mtDNA copy number and ATP levels were similar between groups. In summary, this study shows that γ-irradiation of pre-pubertal mice is associated with loss of mitochondrial membrane potential in a significant proportion of small immature oocytes and a reduction in the number of mature oocytes harvested from adult mice. Furthermore, these results suggest that immature oocytes that survive γ-irradiation and develop through to ovulation contain mitochondria with normal characteristics. Whether the oocytes that survive radiation and eventually undergo meiosis can support fertility remains to be determined.

Mitochondrial DNA damage in the hair bulb: can it be used as a noninvasive biomarker of local exposure to low LET ionizing radiation?

Purpose: Our aim was to evaluate whether mitochondrial DNA (mtDNA) damage in hair bulbs could be a suitable biomarker for the detection of local exposure to ionizing radiation.Materials and methods: Mouse hair was collected 4 and 24 hours, 3 and 10 days after single whole-body exposure to 0, 0.1, and 2 Gy radiation. Pubic hair (treated area) and scalp hair (control area) were collected from 13 prostate cancer patients before and after fractioned radiotherapy with an average total dose of 2.7 Gy to follicles after five fractions. Unspecified lesion frequency of mtDNA was analyzed with long PCR, large mtDNA deletion levels were tested with real-time PCR.Results: Unspecified lesion frequency of mtDNA significantly increased in mouse hair 24 hours after irradiation with 2 Gy, but variance among samples was high. No increase in lesion frequency could be detected after 0.1 Gy irradiation. In prostate cancer patients, there was no significant change in either the unspecified lesion frequency or in the proportion of 4934-bp deleted mtDNA in pubic hair after radiotherapy. The proportions of murine 3860-bp common deletion, human 4977-bp common deletion and 7455-bp deleted mtDNA were too low to be analyzed reliably.Conclusions: Our results suggest that the unspecified lesion frequency and proportion of large deletions of mtDNA in hair bulbs are not suitable biomarkers of exposure to ionizing radiation.

Metabolic flexibility in melanoma: A potential therapeutic target

Cutaneous melanoma (CM) represents one of the most metastasizing and drug resistant solid tumors. CM is characterized by a remarkable metabolic plasticity and an important connection between oncogenic activation and energetic metabolism. In fact, melanoma cells can use both cytosolic and mitochondrial compartments to produce adenosine triphosphate (ATP) during cancer progression. However, the CM energetic demand mainly depends on glycolysis, whose upregulation is strictly linked to constitutive activation of BRAF/MAPK pathway affected by BRAF^V600E kinase mutant. Furthermore, the impressive metabolic plasticity of melanoma allows the development of resistance mechanisms to BRAF/MEK inhibitors (BRAFi/MEKi) and the adaptation to microenvironmental changes. The metabolic interaction between melanoma cells and tumor microenvironment affects the immune response and CM growth. In this review article, we describe the regulation of melanoma metabolic alterations and the metabolic interactions between cancer cells and microenvironment that influence melanoma progression and immune response. Finally, we summarize the hallmarks of melanoma therapies and we report BRAF/MEK pathway targeted therapy and mechanisms of metabolic resistance.

Molecular and epigenetic markers as promising tools to quantify the effect of occupational exposures and the risk of developing non-communicable diseases

Non-communicable diseases (NCDs) are chronic diseases that are by far the leading cause of death in the world. Many occupational hazards, together with social, economic and demographic factors, have been associated to NCDs development. Genetic susceptibility or environmental exposures alone are not usually sufficient to explain the pathogenesis of NCDs, but can be integrated in a more complex scenario that can result in pathological phenotypes. Epigenetics is a crucial component of this scenario, as its changes are related to specific exposures, therefore potentially able to display the effects of environment on the genome, filling the gap between genetic asset and environment in explaining disease development. To date, the most promising biomarkers have been assessed in occupational cohorts as well as in case/control studies and include DNA methylation, histone modifications, microRNA expression, extracellular vesicles, telomere length, and mitochondrial alterations.

Mammalian Tyrosyl-DNA Phosphodiesterases in the Context of Mitochondrial DNA Repair

Mammalian mitochondria contain four topoisomerases encoded in the nuclear genome: TOP1MT, TOP2α, TOP2β, and TOP3α. They also contain the two known tyrosyl-DNA phosphodiesterases (TDPs): TDP1 and TDP2, including a specific TDP2^S isoform. Both TDP1 and TDP2 excise abortive topoisomerase cleavage complexes (TOPccs), yet their molecular structures and mechanisms are different. TDP1 is present across eukaryotes, from yeasts to humans and belongs to the phospholipase D family. It functions without a metal cofactor and has a broad activity range, as it also serves to cleanse blocking 3′-DNA ends bearing phosphoglycolate, deoxyribose phosphate, nucleoside, nucleoside analogs (zidovudine), abasic moieties, and with a lower efficiency, TOP2ccs. Found in higher vertebrates, TDP2 is absent in yeast where TDP1 appears to perform its functions. TDP2 belongs to the exonuclease/endonuclease/phosphodiesterase family and requires magnesium as a cofactor to excise TOP2ccs, and it also excises TOP1ccs, albeit with a lower efficiency. Here, we review TDP1 and TDP2 in the context of mitochondrial DNA repair and discuss potential new research areas centered on the mitochondrial TDPs.

The Role of Mitochondrial Dysfunction in the Progression of Alzheimer's Disease

The current molecular understanding of Alzheimer's disease (AD) has still not resulted in successful interventions. Mitochondrial dysfunction of the AD brain is currently emerging as a hallmark of this disease. One mitochondrial function often affected in AD is oxidative phosphorylation responsible for ATP production, but also for production of reactive oxygen species (ROS) and for the de novo synthesis of pyrimidines. This paper reviews the role of mitochondrial produced ROS and pyrimidines in the aetiology of AD and their proposed role in oxidative degeneration of macromolecules, synthesis of essential phospholipids and maintenance of mitochondrial viability in the AD brain.

The mitochondrial DNA 4977-bp deletion and copy number alteration in Han Chinese samples with uterine fibroids

Uterine fibroids (UFs) are the most common benign neoplasms, but their pathogenesis is not completely understood. Thus far, alterations in the mitochondrial DNA (mtDNA) content and the mtDNA 4977-bp deletion level in UFs, as well as the corresponding nontumorous tissue, have remained elusive. To test whether large mtDNA deletions and mtDNA content are involved in the pathogenesis of UFs, a total of 309 UF tissues and 28 paired adjacent myometrium from 270 UF patients were enrolled for the analysis of large mtDNA deletions and mtDNA content through the use of nested PCR and qPCR techniques, respectively. In our samples, a 4977-bp deletion was identified: 36 out of 309 UF tissues (11.56%) and 15 out of 28 (53.57%) paired adjacent myometrium were detected to harbor the 4977-bp deletion. In addition, a novel 4838-bp mtDNA deletion was identified in three UF tissues, and other different sizes of deleted fragments (4910, 4926, 5135-bp) were also found in UFs for the first time. Furthermore, older age was significantly associated with an mtDNA large deletion in the paired adjacent myometrium. We also found that increased mtDNA content and higher expression of ND1 occurred in solitary fibroids compared to adjacent myometrium. In conclusion, we identified a lower frequency of mtDNA large deletions and some novel large deletion in UFs for the first time. Furthermore, there was a general increase of mtDNA copy number during solitary UF development. Although the definite mechanism by which mtDNA was altered is supposed to be further confirmed, it will be helpful for further studies on the pathological mechanism of UFs.

Fruit and vegetable consumption, cigarette smoke, and leukocyte mitochondrial DNA copy number

Background

Mitochondrial dysfunction is an important component of the aging process and has been implicated in the development of many human diseases. Mitochondrial DNA copy number (mtDNAcn), an indirect biomarker of mitochondrial function, is sensitive to oxidative damage. Few population-based studies have investigated the impact of fruit and vegetable consumption and cigarette smoke (2 major sources of exogenous antioxidants and oxidants) on leukocyte mtDNAcn.

Objectives

We investigated the association between fruit and vegetable consumption, cigarette smoke, and leukocyte mtDNAcn based on data from the Nurses' Health Study (NHS).

Methods

Data from 2769 disease-free women in the NHS were used to examine the cross-sectional associations between dietary sources of antioxidants, cigarette smoke, and leukocyte mtDNAcn. In vitro cell-based experiments were conducted to support the findings from the population-based study.

Results

In the multivariable-adjusted model, both whole-fruit consumption and intake of flavanones (a group of antioxidants abundant in fruit) were positively associated with leukocyte mtDNAcn (P-trend = 0.005 and 0.02, respectively), whereas pack-years of smoking and smoking duration were inversely associated with leukocyte mtDNAcn (P-trend = 0.01 and 0.007, respectively). These findings are supported by in vitro cell-based experiments showing that the administration of naringin, a major flavanone in fruit, led to a substantial increase in mtDNAcn in human leukocytes, whereas exposure to nicotine-derived nitrosamine ketone, a key carcinogenic ingredient of cigarette smoke, resulted in a significant decrease in mtDNAcn of cells (all P < 0.05). Further in vitro studies showed that alterations in leukocyte mtDNAcn were functionally linked to the modulation of mitochondrial biogenesis and function.

Conclusions

Fruit consumption and intake of dietary flavanones were associated with increased leukocyte mtDNAcn, whereas cigarette smoking was associated with decreased leukocyte mtDNAcn, which is a promising biomarker for oxidative stress-related health outcomes.

Measuring radiation-induced DNA damage in Cryptococcus neoformans and Saccharomyces cerevisiae using long range quantitative PCR

DNA damage has been considered to be the universal critical lesion in cells after exposure to ionizing radiation. Measuring radiation-induced DNA damage is important to understand the mechanisms of radiation-induced toxicity and monitor DNA damage repairs. Currently the most widely used methods to measure DNA damage are pulsed-field gel electrophoresis (PFGF) and single-cell gel electrophoresis (also known as the comet assay), both of which are technically challenging and time consuming. Long range quantitative polymerase chain reaction (LR-QPCR) has been used successfully to measure nuclear and mitochondrial DNA damage in mammalian and several model organism cells. The principle of this assay is that DNA lesions will slow down or block the progression of DNA polymerase. Therefore, the amplification efficiency of DNA with fewer lesions will be higher than DNA with more lesions under the same reaction condition. Here, we developed the LR-QPCR assay primers and reaction conditions to quantify DNA damage in Cryptococcus neoformans (C. neoformans) and Saccharomyces cerevisiae (S. cerevisiae) after gamma ray exposure. Under these conditions, long DNA targets of C. neoformans H99 and S. cerevisiae BY4741 (17.6 and 16.4 kb for nuclear DNA and 15.3 and 14.6 kb for mitochondrial DNA) were quantitatively amplified using extracted DNA templates, respectively. Two short mitochondrial DNA targets of these two species (207 bp and 154 bp) were also quantitatively amplified and used to monitor the number of mitochondria. Using the LR-QPCR method, we showed that the frequency of radiation-induced mitochondrial and nuclear DNA lesions had a significant linear correlation with the radiation doses (from 500 Gy to 3000 Gy) in both species. Furthermore, the faster disappearance of DNA damage detected in C. neoformans H99S strain compared to H99 strain may help to explain the different radiation sensitivity of these two strains. In summary, we developed a simple, sensitive method to measure radiation-induced DNA damage, which can greatly facilitate the study of radiation-induced toxicity and can be widely used as a dosimetry in radiation-induced cell damage.

Investigation of whole mitochondrial genome variation in normal tension glaucoma

Glaucoma is one of the leading causes of visual impairment and blindness worldwide. However, the cause of retinal ganglion cell loss and damage of the optic nerve in its pathogenesis is largely unknown. The high energy demands of these cells may reflect their strong dependence on mitochondrial function and thus sensitivity to mitochondrial defects. To address this issue, we studied whole mitochondrial genome variation in normal tension glaucoma patients and control individuals from the Polish population using next generation sequencing. Our findings indicate that few features of mitochondrial DNA variation are different for glaucoma patients and control subjects. New insights into normal tension glaucoma development are discussed. We provide also a comprehensive approach for mitochondrial DNA analysis and variant evaluation.

Mitochondrial Morphologies Driven by Energy-Consuming Cell Sites in a Spatially and Time-Resolved Quality Model

Mitochondria are the energy plants of eukaryotic cells. Mitochondrial network morphologies are essential for the energy supply of eukaryotic cells. However, the associated dynamics are not yet fully understood. They behave as a dynamic network that adapts to the cell's environment and its energetic needs. Various processes such as mitochondrial fission and fusion, mitochondrial recycling, repair mechanisms, and oxidative stress influence the state of the mitochondrial network. Here, we introduce a novel time-dependent and spatially resolved quality model on mitochondrial morphology. The interplay between the mitochondrial network and energy-consuming cell sites is modeled by biophysical interactions of quality-dependent mitochondrial clusters in the presence of adenosine triphosphate (ATP) consumers represented by Mie potentials. Mitochondria are modeled as simplified ballistic particles that move within the cytoplasm of a virtual cell, and connect and divide by inelastic collisions. With this model, we investigate the coupling of mitochondrial dynamics with oscillating cell functions, representing diverse global states of the energetic architecture in the cell. Our simulations based on a generalized cell reveal a perinuclear condensation of mitochondria during phases of high-energy demand. Furthermore, quality-increasing mechanisms disclose the benefits of high mitochondrial masses. Simulations reveal that varying energy demands modeled by oscillations of ATP consumers alter the morphology of the network. Phases of high-energy consumption lead to interconnected network structures and perinuclear condensation of mitochondria. The model explains quality-increasing benefits of high mitochondrial masses.

Relationship between cardiovascular diseases and circulating cell-free nucleic acids in human plasma

Cardiovascular diseases (CVDs) are the main cause of human morbidity and mortality worldwide. Early diagnosis could improve the efficiency of treatments. New biomarkers are needed for the identification of high-risk populations in order to make accurate diagnosis and therapy monitoring. Circulating cell-free nucleic acids (cf-NAs) offer a promising new noninvasive tool. These have a role in the regulation of normal physiological functions and in the development of pathological alterations. There is extended research on the clinical application and utilization of cell-free genomic DNA, mtDNA, mRNA, miRNA and long noncoding RNA in CVDs. These molecules could serve as components of new generation therapeutics. Our review focuses on the role of cf-NAs in the pathogenesis of CVDs and we are discussing also possible diagnostic applications and therapeutic implications.

A Ketogenic Diet Improves Mitochondrial Biogenesis and Bioenergetics via the PGC1α-SIRT3-UCP2 Axis

A ketogenic diet (KD; high-fat, low-carbohydrate) can benefit refractory epilepsy, but underlying mechanisms are unknown. We used mice inducibly expressing a mutated form of the mitochondrial DNA repair enzyme UNG1 (mutUNG1) to cause progressive mitochondrial dysfunction selectively in forebrain neurons. We examined the levels of mRNAs and proteins crucial for mitochondrial biogenesis and dynamics. We show that hippocampal pyramidal neurons in mutUNG1 mice, as well as cultured rat hippocampal neurons and human fibroblasts with H₂O₂ induced oxidative stress, improve markers of mitochondrial biogenesis, dynamics and function when fed on a KD, and when exposed to the ketone body β-hydroxybutyrate, respectively, by upregulating PGC1α, SIRT3 and UCP2, and (in cultured cells) increasing the oxygen consumption rate (OCR) and the NAD⁺/NADH ratio. The mitochondrial level of UCP2 was significantly higher in the perikarya and axon terminals of hippocampus CA1 pyramidal neurons in KD treated mutUNG1 mice compared with mutUNG1 mice fed a standard diet. The β-hydroxybutyrate receptor GPR109a (HCAR2), but not the structurally closely related lactate receptor GPR81 (HCAR1), was upregulated in mutUNG1 mice on a KD, suggesting a selective influence of KD on ketone body receptor mechanisms. We conclude that progressive mitochondrial dysfunction in mutUNG1 expressing mice causes oxidative stress, and that exposure of animals to KD, or of cells to ketone body in vitro, elicits compensatory mechanisms acting to augment mitochondrial mass and bioenergetics via the PGC1α-SIRT3-UCP2 axis (The compensatory processes are overwhelmed in the mutUNG1 mice by all the newly formed mitochondria being dysfunctional).

Circulating cell-free mitochondrial DNA, but not leukocyte mitochondrial DNA copy number, is elevated in major depressive disorder

Major depressive disorder (MDD) has been linked to mitochondrial defects, which could manifest in mitochondrial DNA (mtDNA) polymorphisms or mutations. Additionally, copy number of mtDNA (mtDNA-cn) can be quantified in peripheral blood mononuclear cells (PBMC)s, indirectly reflecting cellular energetics, or in the circulating cell-free mtDNA (ccf-mtDNA) levels, which may reflect a fraction of the mitochondrial genome released during cellular stress. Few studies have examined ccf-mtDNA in MDD, and no studies have tested its relationship with intracellular mtDNA-cn or with antidepressant treatment response. Here, mtDNA levels were quantified in parallel from: (i) PBMCs and (ii) cell-free plasma of 50 unmedicated MDD subjects and 55 controls, in parallel with PBMC telomere length (TL) and antioxidant enzyme glutathione peroxidase (GpX) activity. MtDNA measures were repeated in 19 MDD subjects after 8 weeks of open-label SSRI treatment. In analyses adjusted for age, sex, BMI, and smoking, MDD subjects had significantly elevated levels of ccf-mtDNA (F = 20.6, p = 0.00002). PBMC mtDNA-cn did not differ between groups (p > 0.4). In preliminary analyses, we found that changes in ccf-mtDNA with SSRI treatment differed between SSRI responders and non-responders (F = 6.47, p = 0.02), with the non-responders showing an increase in ccf-mtDNA and responders not changing. Baseline ccf-mtDNA was positively correlated with GpX (r = 0.32, p = 0.001), and PBMC mtDNA correlated positively with PBMC TL (r = 0.38, p = 0.0001). These data suggest that plasma ccf-mtDNA and PBMC mtDNA-cn reflect different cellular processes and that the former may be more reflective of certain aspects of MDD pathophysiology and of the response to SSRI antidepressants.