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Introduction: In a previous retrospective study using postmortem human brain tissues, we demonstrated that loss of Cholinergic Receptor Muscarinic 1 (CHRM1) in the temporal cortex of a subset of Alzheimer's patients was associated with poor survival, whereas similar loss in the hippocampus showed no such association. Mitochondrial dysfunction underlies Alzheimer's pathogenesis. Therefore, to investigate the mechanistic basis of our findings, we evaluated cortical mitochondrial phenotypes in Chrm1 knockout (Chrm1-/-) mice. Cortical Chrm1 loss resulted in reduced respiration, reduced supramolecular assembly of respiratory protein complexes, and caused mitochondrial ultrastructural abnormalities. These mouse-based findings mechanistically linked cortical CHRM1 loss with poor survival of Alzheimer's patients. However, evaluation of the effect of Chrm1 loss on mouse hippocampal mitochondrial characteristics is necessary to fully understand our retrospective human tissue-based observations. This is the objective of this study. Methods: Enriched hippocampal and cortical mitochondrial fractions (EHMFs/ECMFs, respectively) derived from wild-type and Chrm1-/- mice were used to measure respiration by quantifying real-time oxygen consumption, supramolecular assembly of oxidative phosphorylation (OXPHOS)-associated proteins by blue native polyacrylamide gel electrophoresis, post-translational modifications (PTMs) by isoelectric focusing (IEF), and mitochondrial ultrastructure by electron microscopy. Results: In contrast to our previous observations in Chrm1-/- ECMFs, EHMFs of Chrm1-/- mice significantly increased respiration with a concomitant increase in the supramolecular assembly of OXPHOS-associated proteins, specifically Atp5a and Uqcrc2, with no mitochondrial ultrastructural alterations. IEF of ECMFs and EHMFs from Chrm1-/- mice showed a decrease and an increase, respectively in a negatively charged (pH∼3) fraction of Atp5a relative to the wild-type mice, with a corresponding decrease or increase in the supramolecular assembly of Atp5a and respiration indicating a tissue-specific signaling effect. Discussion: Our findings indicate that loss of Chrm1 in the cortex causes structural, and physiological alterations to mitochondria that compromise neuronal function, whereas Chrm1 loss in the hippocampus may benefit neuronal function by enhancing mitochondrial function. This brain region-specific differential effect of Chrm1 deletion on mitochondrial function supports our human brain region-based findings and Chrm1-/- mouse behavioral phenotypes. Furthermore, our study indicates that Chrm1-mediated brain region-specific differential PTMs of Atp5a may alter complex-V supramolecular assembly which in turn regulates mitochondrial structure-function.

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Osteomyelitis is a difficult-to-treat disease with high chronification rates. First studies suggest increases in mitochondrial fission and mitochondrial dysfunction as possible contributors to the accumulation of intracellular reactive oxygen species and thereby to the cell death of infected bone cells. The aim of the present study is to analyze the ultrastructural impact of bacterial infection on osteocytic and osteoblastic mitochondria. Human infected bone tissue samples were visualized via light microscopy and transmission electron microscopy. Osteoblasts, osteocytes and their mitochondria were analyzed histomorphometrically and compared with the control group of noninfectious human bone tissue samples. The results depicted swollen hydropic mitochondria including depleted cristae and a decrease in matrix density in the infected samples. Furthermore, perinuclear clustering of mitochondria could also be observed regularly. Additionally, increases in relative mitochondrial area and number were found as a correlate for increased mitochondrial fission. In conclusion, mitochondrial morphology is altered during osteomyelitis in a comparable way to mitochondria from hypoxic tissues. This gives new perspectives on the treatment strategies since the manipulation of mitochondrial dynamics may improve bone cell survival as a potential new target for the therapy of osteomyelitis.

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Mitochondria calcium is a double-edged sword. While low levels of calcium are essential to maintain optimal rates of ATP production, extreme levels of calcium overcoming the mitochondrial calcium retention capacity leads to loss of mitochondrial function. In moderate amounts, however, ATP synthesis rates are inhibited in a calcium-titratable manner. While the consequences of extreme calcium overload are well-known, the effects on mitochondrial function in the moderately loaded range remain enigmatic. These observations are associated with changes in the mitochondria ultrastructure and cristae network. The present mini review/perspective follows up on previous studies using well-established cryo-electron microscopy and poses an explanation for the observable depressed ATP synthesis rates in mitochondria during calcium-overloaded states. The results presented herein suggest that the inhibition of oxidative phosphorylation is not caused by a direct decoupling of energy metabolism via the opening of a calcium-sensitive, proteinaceous pore but rather a separate but related calcium-dependent phenomenon. Such inhibition during calcium-overloaded states points towards mitochondrial ultrastructural modifications, enzyme activity changes, or an interplay between both events.

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The effect of a single one-hour exposure to three modes of hypobaric hypoxia (HBH) differed in the content of O2 in inhaled air (FiO2-14%, 10%, 8%) in the development of mitochondrial-dependent adaptive processes in the myocardium was studied in vivo. The following parameters have been examined: (a) an urgent reaction of catalytic subunits of mitochondrial enzymes (NDUFV2, SDHA, Cyt b, COX2, ATP5A) in the myocardium as an indicator of the state of the respiratory chain electron transport function; (b) an urgent activation of signaling pathways dependent on GPR91, HIF-1α and VEGF, allowing us to assess their role in the formation of urgent mechanisms of adaptation to hypoxia in the myocardium; (c) changes in the ultrastructure of three subpopulations of myocardial mitochondria under these conditions. The studies were conducted on two rat phenotypes: rats with low resistance (LR) and high resistance (HR) to hypoxia. The adaptive and compensatory role of the mitochondrial complex II (MC II) in maintaining the electron transport and energy function of the myocardium in a wide range of reduced O2 concentrations in the initial period of hypoxic exposure has been established. The features of urgent reciprocal regulatory interaction of NAD- and FAD-dependent oxidation pathways in myocardial mitochondria under these conditions have been revealed. The data indicating the participation of GPR91, HIF-1a and VEGF in this process have been obtained. The ultrastructure of the mitochondrial subpopulations in the myocardium of LR and HR rats differed in normoxic conditions and reacted differently to hypoxia of varying severity. The parameters studied together are highly informative indicators of the quality of cardiac activity and metabolic biomarkers of urgent adaptation in various hypoxic conditions.

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Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) and are associated with thyroid diseases. Our previous study reported that 2,3',4,4',5-Pentachlorobiphenyl (PCB118) could induce thyroid dysfunction and the rat thyroid tissues exhibit abnormal mitochondrial ultrastructure. However, the more specific effects of PCB118 on mitochondria and the relationship between mitochondria and thyroid dysfunction remain unclear. In this study, Wistar rats were injected with PCB118 intraperitoneally at 0, 10, 100, and 1000 µg/kg/d for 13 weeks and FRTL-5 rat thyroid cells were treated with PCB118 (0, 0.25, 2.5, and 25 nM) for 24 hr, which did not influence the general conditions of rats and FRTL-5 cells viability. The detection of serum levels of thyroid hormones (THs) and the expression of sodium/iodide symporter (NIS) protein demonstrated that thyroid function was impaired after PCB118 exposure. Transmission electron microscopy showed mitochondrial damage in the thyroids of PCB118-treated rats. Biological processes analysis revealed that differentially expressed mRNAs in thyroid tissues induced by PCB118 were enriched in reactive oxygen species (ROS) metabolic process, hydrogen peroxide metabolic process, and hydrogen peroxide catabolic process. Moreover, mRNA expression of mitochondrial respiratory chain genes NDUFB3, UQCRC2, COX17, ATP5I and ATP5E decreased in PCB118-treated groups. In vivo and in vitro data showed that ROS production increased significantly after PCB118 exposure, accompanied by increased levels of phospho-c-Jun N-terminal kinase (P-JNK). Taken together, these results suggest that PCB118 could damage mitochondria by increasing oxidative stress and PCB118-induced thyroid dysfunction may be related to ROS-dependent activation of the JNK pathway.

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Our understanding of the regulation of respiration in C4 plants, where mitochondria play different roles in the different types of C4 photosynthetic pathway, remains limited. We examined how leaf dark respiration rates (Rdark ), in the presence and absence of added malate, vary in monocots representing the three classical biochemical types of C4 photosynthesis (NADP-ME, NAD-ME and PCK) using intact leaves and extracted bundle sheath strands. In particular, we explored to what extent rates of Rdark are associated with mitochondrial number, volume and ultrastructure. Based on examination of a single species per C4 type, we found that the respiratory response of NAD-ME and PCK type bundle sheath strands to added malate was associated with differences in mitochondrial number, volume, and/or ultrastructure, while NADP-ME type bundle sheath strands did not respond to malate addition. In general, mitochondrial traits reflected the contributions mitochondria make to photosynthesis in the three C4 types. However, despite the obvious differences in mitochondrial traits, no clear correlation was observed between these traits and Rdark . We suggest that Rdark is primarily driven by cellular maintenance demands and not mitochondrial composition per se, in a manner that is somewhat independent of mitochondrial organic acid cycling in the light.

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Ammonia nitrogen has been one of the key pollution indicators along the Chinese coastline for quite a few years. Our previous studies have proved that ammonia nitrogen is harmful for Ruditapes philippinarum clam in several aspects. Environmental concentrations of ammonia nitrogen were found to significantly decrease ATP contents and disturb ATP metabolism, in addition to reducing the potential across the mitochondrial membrane in clam gill tissues. Accordingly, mitochondrion is considered as one of the target organelles of ammonia nitrogen toxicity in clams. However, there is a lack of direct evidence to prove it. In order to reveal detail information of ammonia nitrogen toxicity on clam mitochondria and screen the related biomarker to indicate ammonia nitrogen pollution, mitochondrial parameters in gill tissues including swelling, mtDNA copy number and marker enzyme (succinic dehydrogenase, SDH) activity were measured after the clams were exposed to 0.1 mg/L and 0.5 mg/L ammonia nitrogen for 3 days and 21 days, respectively. Moreover, adverse effects of ammonia nitrogen exposure on clam mitochondrial ultra-structures, mitochondrial swelling and division were also discriminated under transmission electron microscope (TEM). Final results showed that ammonia nitrogen exposure to both concentrations significantly induced mitochondrial swelling, reduced the number of mitochondria and messed their normal structure, decreased the number of mtDNA copies and down-regulated SDH activity, all in a concentration and duration dependent manner. So, the present study helps us to better understand the structural damage of ammonia nitrogen on mitochondria in clam gill cells and provides fundamental data for ammonia nitrogen control in aquaculture.

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Mitochondrial supercomplexes form around a conserved core of monomeric complex I and dimeric complex III; wherein a subunit of the former, NDUFA11, is conspicuously situated at the interface. We identified nduf-11 (B0491.5) as encoding the Caenorhabditis elegans homologue of NDUFA11. Animals homozygous for a CRISPR-Cas9-generated knockout allele of nduf-11 arrested at the second larval (L2) development stage. Reducing (but not eliminating) expression using RNAi allowed development to adulthood, enabling characterisation of the consequences: destabilisation of complex I and its supercomplexes and perturbation of respiratory function. The loss of NADH dehydrogenase activity was compensated by enhanced complex II activity, with the potential for detrimental reactive oxygen species (ROS) production. Cryo-electron tomography highlighted aberrant morphology of cristae and widening of both cristae junctions and the intermembrane space. The requirement of NDUF-11 for balanced respiration, mitochondrial morphology and development presumably arises due to its involvement in complex I and supercomplex maintenance. This highlights the importance of respiratory complex integrity for health and the potential for its perturbation to cause mitochondrial disease. This article has an associated First Person interview with Amber Knapp-Wilson, joint first author of the paper.

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Mitochondria play a key role in cellular signalling, metabolism and energetics. Proper architecture and remodelling of the inner mitochondrial membrane are essential for efficient respiration, apoptosis and quality control in the cell. Several protein complexes including mitochondrial contact site and cristae organizing system (MICOS), F1 FO -ATP synthase, and Optic Atrophy 1 (OPA1), facilitate formation, maintenance and stability of cristae membranes. MICOS, the F1 FO -ATP synthase, OPA1 and inner membrane phospholipids such as cardiolipin and phosphatidylethanolamine interact with each other to organize the inner membrane ultra-structure and remodel cristae in response to the cell's demands. Functional alterations in these proteins or in the biosynthesis pathway of cardiolipin and phosphatidylethanolamine result in an aberrant inner membrane architecture and impair mitochondrial function. Mitochondrial dysfunction and abnormalities hallmark several human conditions and diseases including neurodegeneration, cardiomyopathies and diabetes mellitus. Yet, they have long been regarded as secondary pathological effects. This review discusses emerging evidence of a direct relationship between protein- and lipid-dependent regulation of the inner mitochondrial membrane morphology and diseases such as fatal encephalopathy, Leigh syndrome, Parkinson's disease, and cancer.

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Recent advancements in super-resolution nanoscopy allowed the study of mitochondrial biology at nanoscale and boosted the understanding its correlated cellular processes those were previously poorly understood. Nevertheless, studying mitochondrial ultrastructure remains a challenge due to the lack of probes that could target specific mitochondrial substances (e.g. cristae or mtDNA) and survive under harsh super-resolution optical conditions. Herein, in this work, we have rationally constructed a pyridine-BODIPY (Py-BODIPY) derivative that could target mitochondrial membrane in living cells without interfering its physiological microenvironments. Furthermore, we found Py-BODIPY is a membrane potential independent probe, hence it is not limit to live-cell staining but also showed a strong internalization into pre-fixed and stimulus disrupted sample. Importantly, its cristae specificity and superb photostability allow the observation of mitochondrial dynamic nano-structures with an unprecedented resolution, allow demonstrating how mitochondrial 3D ultrastructure evolved under oxidative phosphorylation condition.

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Cellular membranes can adopt a plethora of complex and beautiful shapes, most of which are believed to have evolved for a particular physiological reason. The closely entangled relationship between membrane morphology and cellular physiology is strikingly seen in membrane trafficking pathways. During clathrin-mediated endocytosis, for example, over the course of a minute, a patch of the more or less flat plasma membrane is remodeled into a highly curved clathrin-coated vesicle. Such vesicles are internalized by the cell to degrade or recycle plasma membrane receptors or to take up extracellular ligands. Other, steadier, membrane morphologies can be observed in organellar membranes like the endoplasmic reticulum or mitochondria. In the case of mitochondria, which are double membrane-bound, ubiquitous organelles of eukaryotic cells, especially the mitochondrial inner membrane displays an intricated ultrastructure. It is highly folded and consequently has a much larger surface than the mitochondrial outer membrane. It can adopt different shapes in response to cellular demands and changes of the inner membrane morphology often accompany severe diseases, including neurodegenerative- and metabolic diseases and cancer. In recent years, progress was made in the identification of molecules that are important for the aforementioned membrane remodeling events. In this review, we will sum up recent results and discuss the main players of membrane remodeling processes that lead to the mitochondrial inner membrane ultrastructure and in clathrin-mediated endocytosis. We will compare differences and similarities between the molecular mechanisms that peripheral and integral membrane proteins use to deform membranes.

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Deletion of mitochondrial uncoupling protein 2 (UCP2) has been shown to aggravate ischemic damage in the brain. However, the underlying mechanisms are not fully understood. The objective of this study is to explore the impact of homozygous UCP2 deletion (UCP2-/-) on mitochondrial fission and fusion dynamic balance in ischemic mice under normo- and hyperglycemic conditions. UCP2-/- and wildtype mice were subjected to a 60 min middle cerebral artery occlusion (MCAO) and allowed reperfusion for 6h, 24h and 72h. Our results demonstrated that deletion of UCP2 enlarged infarct volumes and increased numbers of cell death in both normo- and hyperglycemic ischemic mice compared with their wildtype counterparts subjected to the same duration of ischemia and reperfusion. The detrimental effects of UCP deletion were associated with increased ROS production, elevated mitochondrial fission markers Drp1 and Fis1 and suppressed fusion markers Opa1 and Mfn2 in UCP2-/- mice. Electron microscopic study demonstrated a marked mitochondrial swolling after 6h of reperfusion in UCP2-/- mice, contrasting to a mild mitochondrial swolling in wildtype ischemic animals. It is concluded that the exacerbating effects of UCP2-/- on ischemic outcome in both normo- and hyperglycemic animals are associated with increased ROS production, disturbed mitochondrial dynamic balance towards fission and early damage to mitochondrial ultrastructure.

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Selective brain hypothermia is considered an effective treatment for neuronal injury after stroke, and avoids the complications of general hypothermia. However, the mechanisms by which selective brain hypothermia affects mitochondrial fission remain unknown. In this study, we investigated the effect of selective brain hypothermia on the expression of fission 1 (Fis1) protein, a key factor in the mitochondrial fission system, during focal cerebral ischemia/reperfusion injury. Sprague-Dawley rats were divided into four groups. In the sham group, the carotid arteries were exposed only. In the other three groups, middle cerebral artery occlusion was performed using the intraluminal filament technique. After 2 hours of occlusion, the filament was slowly removed to allow blood reperfusion in the ischemia/reperfusion group. Saline, at 4°C and 37°C, were perfused through the carotid artery in the hypothermia and normothermia groups, respectively, followed by restoration of blood flow. Neurological function was assessed with the Zea Longa 5-point scoring method. Cerebral infarct volume was assessed by 2,3,5-triphenyltetrazolium chloride staining, and apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. Fis1 and cytosolic cytochrome c levels were assessed by western blot assay. Fis1 mRNA expression was assessed by quantitative reverse transcription-polymerase chain reaction. Mitochondrial ultrastructure was evaluated by transmission electron microscopy. Compared with the sham group, apoptosis, Fis1 protein and mRNA expression and cytosolic cytochrome c levels in the cortical ischemic penumbra and cerebral infarct volume were increased after reperfusion in the other three groups. These changes caused by cerebral ischemia/reperfusion were inhibited in the hypothermia group compared with the normothermia group. These findings show that selective brain hypothermia inhibits Fis1 expression and reduces apoptosis, thereby ameliorating focal cerebral ischemia/reperfusion injury in rats. Experiments were authorized by the Ethics Committee of Qingdao Municipal Hospital of China (approval No. 2019008).

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The mitochondrial structure and the contents of subunits (NDUFV2, SDHA, Cyt b, COX1) of mitochondrial respiratory complexes I-IV as well as of the hypoxia-inducible factor (HIF-1α) in the brain cortex (BC) of rats with high resistance (HR) and low resistance (LR) to hypoxia were studied for the first time depending on the severity of hypoxia. Different regimes of 30-min hypobaric hypoxia (pO2 14, 10, and 8%) were used. It was found that cortical mitochondria responded to 30-min hypobaric hypoxia of different severity with typical and progressing changes in mitochondrial structure and function of mitochondrial enzymes. Under 14 and 10% hypoxia, animals developed compensatory structural and metabolic responses aimed at supporting the cell energy homeostasis. Consequently, these hypoxia regimes can be used for treatment in pressure chambers. At the same time, decreasing the oxygen concentration in the inhaled air to 8% led to the appearance of destructive processes in brain mitochondria. The features of mitochondrial ultrastructure and the function of respiratory enzymes in the BC of HR and LR rats exposed to normoxic and hypoxic conditions suggest that the two types of animals had two essentially distinct functional and metabolic patterns determined by different efficiency of the energy apparatus. The development of adaptive and destructive responses involved different metabolic pathways of the oxidation of energy substrates and different efficiency of the functioning of mitochondrial respiratory carriers.

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OBJECTIVE: To study the impacts of aluminum chloride (AlCl3) on the sperm quality, sperm mitochondrial membrane potential (MMP) and sperm mitochondrial membrane permeability transition pore (MPTP) function of male rats, and the possible mechanisms of AlCl3 inducing the declination of sperm quality. METHODS: According to the median lethal dose (LD50) of AlCl3・6H2O in drinking water, we randomly assigned 96 male Wistar rats weighing 180－200 g to four groups of equal number and fed them with AlCl3 aqueous drinking water at 256.72 mg/kg/d (1/5 LD50, high-dose group), 128.36 mg/kg/d (1/10 LD50, medium-dose group), 64.18 mg/kg/d (1/20 LD50, low-dose group) and 0 mg/kg/d (control group), respectively, all for 16 weeks. Then, we examined the quality of the epididymal sperm of the rats, observed the morphology of the sperm mitochondria under the transmission electron microscope, and determined the MMP level of the sperm mitochondria and the function of the MPTP by flow cytometry. RESULTS: The percentage of progressively motile sperm was significantly decreased in the low-, medium- and high-dose AlCl3 groups as compared with that in the control group (ï¼»46.49 ± 5.37ï¼½%, ï¼»33.50 ± 8.75ï¼½% and ï¼»16.94 ± 5.00ï¼½% vs ï¼»66.28 ± 5.68ï¼½%, P < 0.01), that of dead sperm was remarkably increased (ï¼»19.73 ± 5.57ï¼½%, ï¼»35.80 ± 5.90ï¼½% and ï¼»55.19 ± 4.97ï¼½% vs ï¼»12.71 ± 4.84ï¼½%, P < 0.01), and so was that of morphologically abnormal sperm (ï¼»19.06 ± 2.44ï¼½%, ï¼»23.78 ± 3.29ï¼½% and ï¼»32.06 ± 4.65ï¼½% vs ï¼»14.56 ± 1.62ï¼½%, P < 0.01). Sperm mitochondrial swelling was aggravated in the AlCl3-exposed rats in a dose-dependent manner. The sperm MMP level was significantly lower in the low-, medium- and high-dose AlCl3 groups than in the control (ï¼»60.88 ± 7.37ï¼½%, ï¼»51.54 ± 6.12ï¼½% and ï¼»37.70 ± 7.44ï¼½% vs ï¼»74.35±4.67ï¼½%, P < 0.01), with a negative correlation to the dose of AlCl3 (rs = －0.819, P < 0.01), while the pathologically open MPTP was markedly higher in the former three than in the latter group (ï¼»27.80 ± 5.74ï¼½%, ï¼»36.58 ± 6.67ï¼½% and ï¼»64.95 ± 8.07ï¼½% vs ï¼»15.37 ± 7.13ï¼½%, P < 0.01), with a positive correlation to the dose of AlCl3 (rs = 0.867, P < 0.01). CONCLUSIONS: Exposure to aluminum can cause sperm mitochondrial swelling, decrease the sperm MMP level, induce pathological opening of the MPTP, and consequently reduce sperm quality in male rats.

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Aim To evaluate the role of fisson I (Fisl) in methamphetamine (METH)-induced injur)' of human neuroblastoma (SH-SY5Y) cells cultured in vitro. Methods SH-SY5Y cells cultured in vitro were divided into different groups by the group design method∗. unsilent groups, silent negative groups and silent groups. Different concentrations of METH induced SH-SY5 Y cells in each group for 24 hours. The expression level of Fisl was detected by Western blot. The effect of METH on the proliferative capacity of SH-SY5Y cells was analyzed by CCK-8 cytotoxicity proliferation assay. The MMP level of METH on SH-SY5Y cells was detected by mitochondrial membrane potential detection kit (JC-1). The effect of METH on the mitochondrial ultrastructure of SH-SY5Y cells was observed by transmission electron microscopy. Results In unsilent group, silent negative group and silent group, the expression level of Fisl increased (P < 0. 05) and the proliferative capacity decreased (P < 0. 05) , and the MMP levels decreased (P <0. 05) with the increase of the concentration of SH-SY5Y cells induced by METH. Compared with the same concentration in unsi-lent group and silent negative group, in silent group, the expression level of Fisl in SH-SY5Y cells de-creased (P < 0. 05) , the proliferative capacity increased (P<0. 05) , and the MMP level increased (P < 0. 05). Compared with control group, 2. 0 mmol • L"1 METH induced unsilent groups, silent negative groups and silent groups, and transmission electron microscopy showed the increase in the mitochondrial small globular structure (P < 0. 01). Conclusion Fisl may play a key role in METH-induced injury of SH-SY5Y cells cultured in vitro.

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Aim To evaluate the influence of METH on MMP, mitochondrial ultrastructure, and the expression levels of mitochondrial proteins, Mfnland Fisl, in human neuroblastoma SH-SY5Y cells in vitro. Methods A stable and feasible culture method of SH-SY5Y cells in vitro was established with different concentrations of METH(0. 0, 1. 0, 1. 5 and 2. 0 mmol L-1), and for various periods of exposure for 3, 6, 12, 24 h, the MMP of SH-SY5Y cells was stained by MMP assay kit (JC-1) , the mitochondrial ultrastructure of SH-SY5Y cells exposed to METH was observed by transmission electron microscope, and the expression levels of Mfnl and Fisl proteins were detected by Western blot. Results Compared with control group for various periods of exposure(3,6,12,24 h), the red/green fluorescence ratios of MMP and the expression levels of Mfn1 protein decreased significantly in METH groups (P<0. 05) , while the expression levels of Fisl pro-tein increased significantly (P <0.05). SH-SY5Y cells were treated with METH for 24 h prior to observation under transmission electron microscope ( TEM ). The mitochondria of SH-SY5Y cells in unprocessed group showed the oval, rodlike and double-layer membrane structure, along with clear normal mitochondrial cristae. However, the oval and rodlike structure of mitochondria in SH-SY5Y cells of METH treatment groups had been split into small ball structures. Moreover , mitochondrial autophagosome and autophagic iyso-some could also be found. Conclusions METH could induce a decrease in MMP, mitochondrial ultrastruc-tural changes, and changes in the expression levels of Mfnl and Fisl in SH-SY5Y cells, which might be associated with nerve cell damage caused by METH.

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Electroacupuncture preconditioning at acupoint Baihui (GV20) can reduce focal cerebral ischemia/reperfusion injury. However, the precise protective mechanism remains unknown. Mitochondrial fission mediated by dynamin-related protein 1 (Drp1) can trigger neuronal apoptosis following cerebral ischemia/reperfusion injury. Herein, we examined the hypothesis that electroacupuncture pretreatment can regulate Drp1, and thus inhibit mitochondrial fission to provide cerebral protection. Rat models of focal cerebral ischemia/reperfusion injury were established by middle cerebral artery occlusion at 24 hours after 5 consecutive days of preconditioning with electroacupuncture at GV20 (depth 2 mm, intensity 1 mA, frequency 2/15 Hz, for 30 minutes, once a day). Neurological function was assessed using the Longa neurological deficit score. Pathological changes in the ischemic penumbra on the injury side were assessed by hematoxylin-eosin staining. Cellular apoptosis in the ischemic penumbra on the injury side was assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling staining. Mitochondrial ultrastructure in the ischemic penumbra on the injury side was assessed by transmission electron microscopy. Drp1 and cytochrome c expression in the ischemic penumbra on the injury side were assessed by western blot assay. Results showed that electroacupuncture preconditioning decreased expression of total and mitochondrial Drp1, decreased expression of total and cytosolic cytochrome c, maintained mitochondrial morphology and reduced the proportion of apoptotic cells in the ischemic penumbra on the injury side, with associated improvements in neurological function. These data suggest that electroacupuncture preconditioning-induced neuronal protection involves inhibition of the expression and translocation of Drp1.

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Mitochondria are organelles with a highly dynamic ultrastructure maintained by a delicate equilibrium between its fission and fusion rates. Understanding the factors influencing this balance is important as perturbations to mitochondrial dynamics can result in pathological states. As a terminal site of nutrient oxidation for the cell, mitochondrial powerhouses harness energy in the form of ATP in a process driven by the electron transport chain. Contemporaneously, electrons translocated within the electron transport chain undergo spontaneous side reactions with oxygen, giving rise to superoxide and a variety of other downstream reactive oxygen species (ROS). Mitochondrially-derived ROS can mediate redox signaling or, in excess, cause cell injury and even cell death. Recent evidence suggests that mitochondrial ultrastructure is tightly coupled to ROS generation depending on the physiological status of the cell. Yet, the mechanism by which changes in mitochondrial shape modulate mitochondrial function and redox homeostasis is less clear. Aberrant mitochondrial morphology may lead to enhanced ROS formation, which, in turn, may deteriorate mitochondrial health and further exacerbate oxidative stress in a self-perpetuating vicious cycle. Here, we review the latest findings on the intricate relationship between mitochondrial dynamics and ROS production, focusing mainly on its role in malignant disease.