Mitochondrial Size Research Articles

The Effects of Chrysanthemum morifolium Flower Extract on Obesity-Induced Inflammation and Muscle AMPK/SIRT1 Activities in Obese Rats

ObjectivesThe objective of this study is to investigate the effects of hot water extract of Chrysanthemum morifolium Ramat flower (CE) on obesity-induced inflammation and skeletal muscle mitochondrial function in high-fat diet fed rats. MethodsMale Sprague-Dawley rats (3-week-old) were randomly divided into 4 groups, and fed with a normal diet (NOR), high fat diet (HF), HF containing 0.2% CE (CEL) or 0.4% CE (CEH) for 13 weeks. ResultsCE reduced body weight and total white adipose tissue weights. The levels of serum triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) significantly reduced in the CEL and CEH groups compared to the HF group. In white adipose tissue, CE attenuated HF-induced adipose tissue macrophage (ATM) infiltration and down-regulated F4/80 mRNA expression compared to the HF group. In addition, CE down-regulated the mRNA levels involved in inflammation and ATM polarization, such as tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), monocyte chemoattracted protein-1 (MCP1), inducible nitric oxide synthase (iNOS), and cluster of differentiation 11c (CD11c) compared to the HF group. On the other hand, gene expression of arginase 1 (Arg1), a M2 macrophage marker was significantly up-regulated in the CEL and CEH groups compared to the HF group. Nuclear factor-kappa B (NF-κB) activities and serum nitric oxide (NO) concentrations were significantly decreased by CE supplementation. In skeletal muscle, mitochondrial size and mitochondrial DNA (mtDNA) content were significantly increased in the CEL and CEH groups compared to the HF group. CE supplementation were also up-regulated the mRNA expression related to mitochondrial function, including sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), and carnitine palmitoyltransferase 1β (CPT-1β). Furthermore, activities of AMP-activated protein kinase (AMPK) and SIRT1 were increased by CE supplementation. ConclusionsThese results suggested that CE attenuates obesity-induced inflammation via regulating M1/M2 macrophage and increases the muscle mitochondria content and AMPK/SIRT1 activities. Funding SourcesThis research was supported by the BK21 FOUR (Fostering Outstanding Universities for Research) funded by the Ministry of Education (MOE, Korea) and National Research Foundation of Korea (NRF).

Metabolic evidence for distinct pyruvate pools inside plant mitochondria.

The majority of the pyruvate inside plant mitochondria is either transported into the matrix from the cytosol via the mitochondria pyruvate carrier (MPC) or synthesized in the matrix by alanine aminotransferase (AlaAT) or NAD-malic enzyme (NAD-ME). Pyruvate from these origins could mix into a single pool in the matrix and contribute indistinguishably to respiration via the pyruvate dehydrogenase complex (PDC), or these molecules could maintain a degree of independence in metabolic regulation. Here we demonstrate that feeding isolated mitochondria with uniformly labelled 13C-pyruvate and unlabelled malate enables the assessment of pyruvate contribution from different sources to intermediate production in the tricarboxylic acid cycle. Imported pyruvate was the preferred source for citrate production even when the synthesis of NAD-ME-derived pyruvate was optimized. Genetic or pharmacological elimination of MPC activity removed this preference and allowed an equivalent amount of citrate to be generated from the pyruvate produced by NAD-ME. Increasing the mitochondrial pyruvate pool size by exogenous addition affected only metabolites from pyruvate transported by MPC, whereas depleting the pyruvate pool size by transamination to alanine affected only metabolic products derived from NAD-ME. PDC was more membrane-associated than AlaAT and NAD-ME, suggesting that the physical organization of metabolic machinery may influence metabolic rates. Together, these data reveal that the respiratory substrate supply in plants involves distinct pyruvate pools inside the matrix that can be flexibly mixed on the basis of the rate of pyruvate transport from the cytosol. These pools are independently regulated and contribute differentially to organic acid export from plant mitochondria.

Mitochondrial matrix-localized Src kinase regulates mitochondrial morphology

The architecture of mitochondria adapts to physiological contexts: while mitochondrial fragmentation is usually associated to quality control and cell death, mitochondrial elongation often enhances cell survival during stress. Understanding how these events are regulated is important to elucidate how mitochondrial dynamics control cell fate. Here, we show that the tyrosine kinase Src regulates mitochondrial morphology. Deletion of Src increased mitochondrial size and reduced cellular respiration independently of mitochondrial mass, mitochondrial membrane potential or ATP levels. Re-expression of Src targeted to the mitochondrial matrix, but not of Src targeted to the plasma membrane, rescued mitochondrial morphology in a kinase activity-dependent manner. These findings highlight a novel function for Src in the control of mitochondrial dynamics.

CYB5R3 overexpression preserves skeletal muscle mitochondria and autophagic signaling in aged transgenic mice

Cytochrome b5 reductase 3 (CYB5R3) overexpression activates respiratory metabolism and exerts prolongevity effects in transgenic mice, mimicking some of the salutary effects of calorie restriction. The aim of our study was to understand how CYB5R3 overexpression targets key pathways that modulate the rate of aging in skeletal muscle, a postmitotic tissue with a greater contribution to resting energy expenditure. Mitochondrial function, autophagy and mitophagy markers were evaluated in mouse hind limb skeletal muscles from young-adult (7 months old) and old (24 months old) males of wild-type and CYB5R3-overexpressing genotypes. Ultrastructure of subsarcolemmal and intermyofibrillar mitochondria was studied by electron microscopy in red gastrocnemius. CYB5R3, which was efficiently overexpressed and targeted to skeletal muscle mitochondria regardless of age, increased the abundance of complexes I, II, and IV in old mice and prevented the age-related decrease of complexes I, III, IV, and V and the mitofusin MFN-2. ATP was significantly decreased by aging, which was prevented by CYB5R3 overexpression. Coenzyme Q and the mitochondrial biogenesis markers TFAM and NRF-1 were also significantly diminished by aging, but CYB5R3 overexpression did not protect against these declines. Both aging and CYB5R3 overexpression upregulated SIRT3 and the mitochondrial fission markers FIS1 and DRP-1, although with different outcomes on mitochondrial ultrastructure: old wild-type mice exhibited mitochondrial fragmentation whereas CYB5R3 overexpression increased mitochondrial size in old transgenic mice concomitant with an improvement of autophagic recycling. Interventions aimed at stimulating CYB5R3 could represent a valuable strategy to counteract the deleterious effects of aging in skeletal muscle.Graphical abstract

The complete mitochondrial genome sequence of the karst-dwelling crab, Terrapotamon thungwa (Crustacea: Brachyura: Potamidae)

Terrapotamon thungwa is a new species of terrestrial long-legged crab discovered in a karst landscape of southern Thailand. Here, we report the first complete mitochondrial genome of this crab species. The mitochondrial genome size is 16,156 base-pairs (bp), including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA), and two ribosomal RNA (rRNA) genes. The AT and GC content of the mitochondrial genome sequence is 73.2% and 26.8%, respectively. Phylogenetic analysis with 26 crustacean species, based on 13 mitochondrial conserve genes, showed that T. thungwa was closely related to other freshwater crab species in the family Potamidae.

Mitochondrial Fusion, Fission, and Mitophagy in Cardiac Diseases: Challenges and Therapeutic Opportunities.

Significance: Mitochondria play a critical role in the physiology of the heart by controlling cardiac metabolism, function, and remodeling. Accumulation of fragmented and damaged mitochondria is a hallmark of cardiac diseases. Recent Advances: Disruption of quality control systems that maintain mitochondrial number, size, and shape through fission/fusion balance and mitophagy results in dysfunctional mitochondria, defective mitochondrial segregation, impaired cardiac bioenergetics, and excessive oxidative stress. Critical Issues: Pharmacological tools that improve the cardiac pool of healthy mitochondria through inhibition of excessive mitochondrial fission, boosting mitochondrial fusion, or increasing the clearance of damaged mitochondria have emerged as promising approaches to improve the prognosis of heart diseases. Future Directions: There is a reasonable amount of preclinical evidence supporting the effectiveness of molecules targeting mitochondrial fission and fusion to treat cardiac diseases. The current and future challenges are turning these lead molecules into treatments. Clinical studies focusing on acute (i.e., myocardial infarction) and chronic (i.e., heart failure) cardiac diseases are needed to validate the effectiveness of such strategies in improving mitochondrial morphology, metabolism, and cardiac function. Antioxid. Redox Signal. 36, 844-863.

Tomatidine-stimulated maturation of human embryonic stem cell-derived cardiomyocytes for modeling mitochondrial dysfunction.

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) have been reported to exhibit immature embryonic or fetal cardiomyocyte-like phenotypes. To enhance the maturation of hESC-CMs, we identified a natural steroidal alkaloid, tomatidine, as a new substance that stimulates the maturation of hESC-CMs. Treatment of human embryonic stem cells with tomatidine during cardiomyocyte differentiation stimulated the expression of several cardiomyocyte-specific markers and increased the density of T-tubules. Furthermore, tomatidine treatment augmented the number and size of mitochondria and enhanced the formation of mitochondrial lamellar cristae. Tomatidine treatment stimulated mitochondrial functions, including mitochondrial membrane potential, oxidative phosphorylation, and ATP production, in hESC-CMs. Tomatidine-treated hESC-CMs were more sensitive to doxorubicin-induced cardiotoxicity than the control cells. In conclusion, the present study suggests that tomatidine promotes the differentiation of stem cells to adult cardiomyocytes by accelerating mitochondrial biogenesis and maturation and that tomatidine-treated mature hESC-CMs can be used for cardiotoxicity screening and cardiac disease modeling.

Genetic Diversity, Heteroplasmy, and Recombination in Mitochondrial Genomes of Daphnia pulex, Daphnia pulicaria, and Daphnia obtusa.

Genetic variants of mitochondrial DNA at the individual (heteroplasmy) and population (polymorphism) levels provide insight into their roles in multiple cellular and evolutionary processes. However, owing to the paucity of genome-wide data at the within-individual and population levels, the broad patterns of these two forms of variation remain poorly understood. Here, we analyze 1,804 complete mitochondrial genome sequences from Daphnia pulex, Daphnia pulicaria, and Daphnia obtusa. Extensive heteroplasmy is observed in D. obtusa, where the high level of intraclonal divergence must have resulted from a biparental-inheritance event, and recombination in the mitochondrial genome is apparent, although perhaps not widespread. Global samples of D. pulex reveal remarkably low mitochondrial effective population sizes, <3% of those for the nuclear genome. In addition, levels of population diversity in mitochondrial and nuclear genomes are uncorrelated across populations, suggesting an idiosyncratic evolutionary history of mitochondria in D. pulex. These population-genetic features appear to be a consequence of background selection associated with highly deleterious mutations arising in the strongly linked mitochondrial genome, which is consistent with polymorphism and divergence data suggesting a predominance of strong purifying selection. Nonetheless, the fixation of mildly deleterious mutations in the mitochondrial genome also appears to be driving positive selection on genes encoded in the nuclear genome whose products are deployed in the mitochondrion.

Essential Oils Derived from Cistus Species Activate Mitochondria by Inducing SIRT1 Expression in Human Keratinocytes, Leading to Senescence Inhibition.

Cistus L. is a genus of dicotyledonous perennial herbaceous plants. Cistus species have been commonly used in folk medicine in the Mediterranean region. In the present study, the biological activities of essential oils derived from Cistus species (Cistus laurifolius, C. monspeliensis, C. creticus, and C. salviifolius) were evaluated. Essential oils derived from C. laurifolius and C. monspeliensis were found to augment the expression of SIRT1, an anti-aging gene, in the normal culture of HaCaT cells. Furthermore, these essential oils increased the number and size of mitochondria and augmented their activity. These effects were thought to be caused by the up- and downregulated expression of MITOL and Drp1 in HaCaT cells, respectively, in response to the essential oil treatment. In addition, these essential oils were found to attenuate ultraviolet-B-induced mitochondrial damage and cellular senescence in HaCaT cells. These findings indicate that essential oils derived from C. laurifolius and C. monspeliensis may inhibit skin aging through mitochondrial regulation via SIRT1 activation.

Astragaloside-IV alleviates high glucose-induced ferroptosis in retinal pigment epithelial cells by disrupting the expression of miR-138-5p/Sirt1/Nrf2

ABSTRACT Astragaloside-IV (AS-IV) (C41H68O14) is a high-purity natural product extracted from Astragalus, which has demonstrated biological activities. However, the effect of AS-IV on retinal pigment epithelial (RPE) cells in diabetic retinopathy (DR) remains unclear. In this study, high glucose (HG) was shown to promote ARPE-19 RPE cell death, increase the contents of reactive oxygen species (ROS) and oxidized glutathione (GSSG), and enhance lipid peroxidation density of mitochondrial membrane. In contrast, AS-IV decreased glutathione (GSH) content, mitochondria size and ridge. Addition of ferroptosis inhibitor Ferrostatin-1 (Fer-1) to RPE cells decreased cell dead rate, thus indicating that HG-induced mitochondrial damage occurred due to ferroptosis. AS-IV alleviated HG-induced RPE cell damage. Furthermore, HG decreased levels of silent information regulator 1 (Sirt1) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in the nucleus of RPE cells; AS-IV could alleviate these effects and increased expression of glutathione peroxidase 4 (GPX4), glutamate cysteine ligase (GCLM) and glutamate cysteine ligase catalytic subunit (GCLC), which are Nrf2 downstream genes. Mechanistically, AS-IV was shown to alleviate the effects of HG by increasing mir-138-5p expression in RPE cells and promoting expression of Sirt1 and Nrf2 in the nucleus. Transfection of mir-138-5p agonist inhibited the regulatory effects of AS-IV on Sirt1 and Nrf2, accompanied by decreased GPX4, GCLM and GCLC levels, and restoration of ferroptosis-related changes. Collectively, HG increased ferroptosis rate in RPE cells. In addition, AS-IV inhibited miR-138-5p expression, subsequently increasing Sirt1/Nrf2 activity and cellular antioxidant capacity to alleviate ferroptosis, resulting decreased cell death, which potentially inhibits the DR pathological process.

Complex mitogenomic rearrangements within the Pectinidae (Mollusca: Bivalvia)

BackgroundScallops (Bivalvia: Pectinidae) present extraordinary variance in both mitochondrial genome size, structure and content, even when compared to the extreme diversity documented within Mollusca and Bivalvia. In pectinids, mitogenome rearrangements involve protein coding and rRNA genes along with tRNAs, and different genome organization patterns can be observed even at the level of Tribes. Existing pectinid phylogenies fail to resolve some relationships in the family, Chlamydinae being an especially problematic group.ResultsIn our study, we sequenced, annotated and characterized the mitochondrial genome of a member of Chlamydinae, Mimachlamys varia—a species of commercial interest and an effective bioindicator—revealing yet another novel gene arrangement in the Pectinidae. The phylogeny based on all mitochondrial protein coding and rRNA genes suggests the paraphyly of the Mimachlamys genus, further commending the taxonomic revision of the classification within the Chlamydinae subfamily. At the scale of the Pectinidae, we found that 15 sequence blocks are involved in mitogenome rearrangements, which behave as separate units.ConclusionsOur study reveals incongruities between phylogenies based on mitochondrial protein-coding versus rRNA genes within the Pectinidae, suggesting that locus sampling affects phylogenetic inference at the scale of the family. We also conclude that the available taxon sampling does not allow for understanding of the mechanisms responsible for the high variability of mitogenome architecture observed in the Pectinidae, and that unraveling these processes will require denser taxon sampling.

Conditional deletion of myeloid-specific mitofusin 2 but not mitofusin 1 promotes kidney fibrosis

Macrophages exert critical functions during kidney injury, inflammation, and tissue repair or fibrosis. Mitochondrial structural and functional aberrations due to an imbalance in mitochondrial fusion/fission processes are implicated in the pathogenesis of chronic kidney disease. Therefore, we investigated macrophage-specific functions of mitochondrial fusion proteins, mitofusin (MFN)1 and MFN2, in modulating macrophage mitochondrial dynamics, biogenesis, oxidative stress, polarization, and fibrotic response. MFN1 and MFN2 were found to be suppressed in mice after adenine diet-induced chronic kidney disease, in transforming growth factor-beta 1-treated bone marrow-derived macrophages, and in THP-1-derived human macrophages (a human leukemic cell line). However, abrogating Mfn2 but not Mfn1 in myeloid-lineage cells resulted in greater macrophage recruitment into the kidney during fibrosis and the macrophage-derived fibrotic response associated with collagen deposition culminating in worsening kidney function. Myeloid-specific Mfn1 /Mfn2 double knockout mice also showed increased adenine-induced fibrosis. Mfn2-deficient bone marrow-derived macrophages displayed enhanced polarization towards the profibrotic/M2 phenotype and impaired mitochondrial biogenesis. Macrophages in the kidney of Mfn2-deficient and double knockout but not Mfn1-deficient mice exhibited greater mitochondrial mass, size, oxidative stress and lower mitophagy under fibrotic conditions than the macrophages in the kidney of wild-type mice. Thus, downregulation of MFN2 but not MFN1 lead to macrophage polarization towards a profibrotic phenotype to promote kidney fibrosis through a mechanism involving suppression of macrophage mitophagy and dysfunctional mitochondrial dynamics.

The strange case of Drp1 in autophagy: Jekyll and Hyde?

There is a debate regarding the function of Drp1, a GTPase involved in mitochondrial fission, during the elimination of mitochondria by autophagy. A number of experiments indicate that Drp1 is needed to eliminate mitochondria during mitophagy, either by reducing the mitochondrial size or by providing a noncanonical mitophagy function. Yet, other convincing experimental results support the conclusion that Drp1 is not necessary. Here, we review the possible functions for Drp1 in mitophagy and autophagy, depending on tissues, organisms and stresses, and discuss these apparent discrepancies. In this regard, it appears that the reduction of mitochondria size is often required for mitophagy but not always in a Drp1-dependent manner. Finally, we speculate on Drp1-independent mitochondrial fission mechanism that may take place during mitophagy and on noncanonical roles, which Drp1 may play such as modulating organelle contact sites dynamic during the autophagosome formation.

Estrogen-related receptor is critical for testicular mitochondrial homeostasis and sperm motility: a Drosophila-based study

To study the role of estrogen-related receptors (ERRs) in testicular function, with particular emphasis on mitochondrial homeostasis, testicular steroidogenesis, and sperm motility using Drosophila as a model. Experimental study. Academic research laboratory. Wild-type and transgenic strains of Drosophila melanogaster. Using a ribonucleic acid interference-based approach, ERR was knocked down specifically in the testes to generate Drosophila males with reduced ERR levels in their testes. Genetically matched sibling males without the knockdown formed the controls. Analysis of the testicular mitochondrial structure and function in relation to energy production, steroidogenesis, and sperm motility in Drosophila. Depletion of ERR affects mitochondrial homeostasis (biogenesis, fission, fusion, mitophagy, and transport) and oxidative respiration in the testes. Consequently, ERR knockdown testes have significantly reduced mitochondrial size, mass, and depleted adenosine triphosphate levels resulting in testicular oxidative stress. Further, Halloween genes, associated with steroidogenesis in Drosophila, are misregulated in ERR knockdown testes, and knockdown of some of the steroidogenic genes in a testis-specific manner results in significantly reduced fertility. In addition, sperm from ERR knockdown testes have significantly reduced levels of glucose transporter, Na+K+ ATPase, Dynein heavy chain, and adenosine triphosphate-5α synthase essential for sperm function. Corroborating this, sperm from ERR knockdown males are significantly less motile compared with control. The ERR is crucial for meeting the cellular energy requirements of the testes and the generation of normal motile sperm and hormone synthesis/secretion in the testes. To our knowledge, this is the first report implicating ERR in these ultimate functions of the testes. These findings can potentially contribute to the etiologic understanding of asthenozoospermia or infertility at large in men.

Ultrastructural changes in mitochondria during oogenesis in two phylogenetically close fish species.

The ultrastructure of oocyte mitochondria and their contribution to the endogenous autosynthesis of the yolk was investigated in two clupeoid species, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus. The structure and abundance of mitochondria differ in secondary growth oocytes of the two species, whereas they are similar in chromatin nucleolus and primary growth oocytes. Sardine oocytes show a higher percentage of mitochondria in the cytoplasm as they develop. However, the individual size of each mitochondrion decreases, becoming smaller than those observed in anchovy oocytes. The volume fraction of cristae in mitochondria of sardine oocytes gradually increased throughout the oocyte developmental phases up to the early secondary growth phase and then slightly decreased during the mid-secondary growth phase. In the cytoplasm of early secondary growth oocytes of anchovy, the percentage of mitochondria is larger than in mid-secondary growth oocytes. As oocytes develop, the size of mitochondria diminishes as well. In contrast to the volume fraction of cristae in mitochondria of sardine oocytes, the volume fraction of cristae in anchovy was decreased in early secondary growth oocytes and then it was increased during the mid-secondary growth phase. As a result, based on both cytoplasmic dynamics of each species and mitochondrial alterations, it was assumed that mitochondria in sardine play a role in the formation of yolk granules, whereas mitochondria in anchovy play a role in the lipid synthesis pathway. Both species showed exogenous heterosynthesis of yolk, through the process of pinocytosis in the zona radiata of oocytes.

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.

Morphological Changes in Endothelial Cell Organelles in a No-Touch Saphenous Vein Graft.

IntroductionImproved long-term patency of the no-touch (NT) saphenous vein graft has been reported to result from the preservation of a healthy vascular microstructure, especially endothelial cells. However, the precise morphology of endothelial cells and their organelles in NT saphenous vein graft has not been fully investigated. In this study, we assessed the ultrastructure of preserved endothelial cells in saphenous vein graft using transmission electron microscopy.MethodsIntact control (IC) vein, NT saphenous vein graft, and conventional (CT) saphenous vein graft were harvested from a patient. After observation by light microscopy, the nuclei and mitochondria in the preserved endothelial cells were compared among IC, NT, and CT using transmission electron microscopy, and the endothelial organelles were assessed quantitatively.ResultsLight microscopy showed that the preservation of endothelial cells was comparable in IC, NT, and CT. Subsequent transmission electron microscopy observation showed that the nuclei in preserved endothelial cells appeared more swollen in CT than that in NT. Quantitative analysis revealed that nuclear size and circularity of preserved endothelial cells in NT and IC were similar, but those in CT were larger and higher, respectively, than those in IC and NT. In addition, the mitochondrial size in preserved endothelial cells in CT was larger than that in IC and NT.ConclusionNecrotic changes in endothelial organelles characterized by swelling of nuclei and mitochondria were prominent in CT saphenous vein graft. The normally maintained ultrastructure of preserved endothelial cells in NT saphenous vein graft could contribute to long-term patency.

Interfering with mitochondrial dynamics sensitizes glioblastoma multiforme to temozolomide chemotherapy.

Glioblastoma multiforme (GBM) is a primary tumour of the central nervous system (CNS) that exhibits the highest degree of malignancy. Radiotherapy and chemotherapy are essential to prolong the survival time of patients. However, clinical work has demonstrated that sensitivity of GBM to chemotherapy decreases with time. The phenomenon of multi‐drug resistance (MDR) reminds us that there may exist some fundamental mechanisms in the process of chemo‐resistance. We tried to explore the mechanism of GBM chemo‐resistance from the perspective of energy metabolism. First, we found that the oxidative phosphorylation (OXPHOS) level of SHG44 and U87 cells increased under TMZ treatment. In further studies, it was found that the expression of PINK1 and mitophagy flux downstream was downregulated in GBM cells, which were secondary to the upregulation of TP53 in tumour cells under TMZ treatment. At the same time, we examined the mitochondrial morphology in tumour cells and found that the size of mitochondria in tumour cells increased under the treatment of TMZ, which originated from the regulation of AMPK on the subcellular localization of Drp1 under the condition of unbalanced energy supply and demand in tumour cells. The accumulation of mitochondrial mass and the optimization of mitochondrial quality accounted for the increased oxidative phosphorylation, and interruption of the mitochondrial fusion process downregulated the efficiency of oxidative phosphorylation and sensitized GBM cells to TMZ, which was also confirmed in the in vivo experiment. What is more, interfering with this process is an innovative strategy to overcome the chemo‐resistance of GBM cells.

The effects of Acyclovir administration to NCI-H1975 non-small cell lung cancer cells

The biochemical mechanisms by which the antiviral drug Acyclovir (ACV) may induce anticancer effects even without detecting human herpesviruses (HHVs) are still poorly understood. Herein, we investigated for the first time how NCI-H1975 non-small cell lung cancer cells responded in vitro to ACV administration by exploring mitochondrial damage and apoptosis induction. We confirmed ACV ability to cause the inhibition of cancer cell growth even without detecting intracellular HHVs; the drug also significantly inhibited the colony formation capacity of NCI-H1975 cells. Cell cycle analysis revealed an increase of the sub-G1 hypodiploid peak after ACV treatment; the activation of caspase-3 and the presence of DNA laddering sustained the capacity of the drug to induce apoptotic cell death. Regarding mitochondrial toxicity, a reduction of mitochondrial membrane potential, altered mitochondrial size and shape, and mtDNA damage were found after ACV administration. Furthermore, an increment of intracellular reactive oxygen species levels as well as the upregulation of NudT3 involved in DNA repair mechanisms were observed. Altogether, these findings suggest that mitochondria may be possible initial targets and/or sites of ACV cytotoxicity within cancer cells in the absence of intracellular HHVs.

Assembly of the Complete Mitochondrial Genome of Chinese Plum (Prunus salicina): Characterization of Genome Recombination and RNA Editing Sites.

Despite the significant progress that has been made in the genome sequencing of Prunus, this area of research has been lacking a systematic description of the mitochondrial genome of this genus for a long time. In this study, we assembled the mitochondrial genome of the Chinese plum (Prunus salicina) using Illumina and Oxford Nanopore sequencing data. The mitochondrial genome size of P. salicina was found to be 508,035 base pair (bp), which is the largest reported in the Rosaceae family to date, and P. salicina was shown to be 63,453 bp longer than sweet cherry (P. avium). The P. salicina mitochondrial genome contained 37 protein-coding genes (PCGs), 3 ribosomal RNA (rRNA) genes, and 16 transfer RNA (tRNA) genes. Two plastid-derived tRNA were identified. We also found two short repeats that captured the nad3 and nad6 genes and resulted in two copies. In addition, nine pairs of repeat sequences were identified as being involved in the mediation of genome recombination. This is crucial for the formation of subgenomic configurations. To characterize RNA editing sites, transcriptome data were used, and we identified 480 RNA editing sites in protein-coding sequences. Among them, the initiation codon of the nad1 gene confirmed that an RNA editing event occurred, and the genomic encoded ACG was edited as AUG in the transcript. Combined with previous reports on the chloroplast genome, our data complemented our understanding of the last part of the organelle genome of plum, which will facilitate our understanding of the evolution of organelle genomes.