The Potential Application of Mitochondrial Medicine in Toxicologic Poisoning

The advancement of biomolecular techniques has continued to advance in the area of mitochondrial medicine. This has allowed clinicians and researchers to more effectively study the bioenergetics of the mitochondria in various disease states. One potential technique in mitochondrial medicine is the generation of cytoplasmic hybrids. A cytoplasmic hybrid or cybrid are created by introducing mitochondrial DNA (mtDNA) of interest into cells depleted of mtDNA. A cybrid is therefore a hybrid cell that mixes the nuclear genome from one cell with the mitochondrial genes from another cell. Cybrids are currently utilized in mitochondrial research to demonstrate mitochondrial involvement in a wide range of diseases that include diabetes, Parkinson’s disease and inherited diseases. At this time the use of cybrids to study toxicologic poisoning is limited and offers a potential avenue of research in this area.     

母体肢体缺血预处理对宫内窘迫胎鼠复氧后海马神经元线粒体结构和功能的影响

目的:探索母体肢体缺血预处理(LIP)对宫内窘迫胎鼠复氧后海马神经元线粒体结构和功能的影响。方法:将孕20 d的40只SD大鼠随机分为假手术组(S组)、LIP对照组、胎鼠宫内窘迫组(FD组)和LIP+FD组。通过实验设计建立胎鼠宫内窘迫模型,观察各组胎鼠海马CA1区线粒体超微结构的变化;检测海马线粒体跨膜电位变化;测定海马组织活性氧簇(ROS)、三磷酸腺苷(ATP)、丙二醛(MDA)含量及锰-超氧化物歧化酶(MnSOD)活性变化。结果:(1)与S组比较,FD组和LIP+FD组电镜下观察胎鼠海马CA1区线粒体呈不同程度破坏,线粒体膜电位下降,ATP含量和Mn-SOD活性降低,ROS和MDA含量增加(P0.05)。(2)与FD组比较,LIP+FD组胎鼠海马CA1区线粒体的超微结构保持较好的完整性,线粒体膜电位明显提高,海马ATP含量和Mn-SOD活性显著增高,ROS和MDA含量减少(P0.05)。结论:母体肢体缺血预处理对宫内窘迫胎鼠复氧后海马神经元线粒体功能具有保护作用。     

Epigenetic dimension of oxygen radical injury in spermatogonial epithelial cells

The present work reports a direct role of mitochondrial oxidative stress induced aberrant chromatin regulation, as a central phenomenon, to perturbed genomic integrity in the testicular milieu. Oxygen-radical injury following N-succinimidyl N-methylcarbamate treatment in mouse spermatogonial epithelial (GC-1 spg) cells induced functional derailment of mitochondrial machinery. Mitophagy resulted in marked inhibition of mitochondrial respiration and reduced mtDNA copy number. Impaired cell cycle progression along with altered H3K9me1, H4K20me3, H3, AcH3 and uH2A histone modifications were observed in the treated cells. Dense heterochromatin foci and aberrant expression of HP1α in nuclei of treated cells implied onset of senescence associated secretory phenotype mediated through nuclear accumulation of NF-κB. Neoplastic nature of daughter clones, emerged from senescent mother phenotypes was confirmed by cytogenetic instability, aberrant let-7a and let-7b miRNA expression and anchorage independent growth. Together, our results provide the first insights of redox-dependent epigenomic imbalance in spermatogonia, a previously unknown molecular paradigm.     

Calcium,mitochondria and the initiation of acute pancreatitis

Acute pancreatitis is characterized by necrosis of its parenchymal cells and influx and activation of inflammatory cells that further promote injury and necrosis. This review is intended to discuss the central role of disorders of calcium metabolism and mitochondrial dysfunction in the mechanism of pancreatitis development. The disorders are placed in context of calcium and mitochondria in physiologic function of the pancreas. Moreover, we discuss potential therapeutics for preventing pathologic calcium signals that injure mitochondria and interventions that promote the removal of injured mitochondria and regenerate new and heathy populations of mitochondria.     

Recycle or die: the role of autophagy in cardioprotection

Autophagy is a highly conserved cellular process responsible for the degradation of long-lived proteins and organelles. Autophagy occurs at low levels under normal conditions, but is upregulated in response to stress such as nutrient deprivation, hypoxia, mitochondrial dysfunction, and infection. Upregulation of autophagy may be beneficial to the cell by recycling of proteins to generate free amino acids and fatty acids needed to maintain energy production, by removing damaged organelles, and by preventing accumulation of protein aggregates. In contrast, there is evidence that enhanced autophagy can contribute to cell death, possibly through excessive self-digestion. In the heart, autophagy has an essential role for maintaining cellular homeostasis under normal conditions and increased autophagy can be seen in conditions of starvation, ischemia/reperfusion, and heart failure. However, the functional significance of autophagy in heart disease is unclear and controversial. Here, we review the literature and discuss the evidence that autophagy can have both beneficial and detrimental roles in the myocardium depending on the level of autophagy, and discuss potential mechanisms by which autophagy provides protection in cells.     

Haplotype distribution in a forensic full mtDNA genome database of admixed Southern Brazilians and its association with self-declared ancestry and pigmentation traits

Background:The advent of massively parallel sequencing (MPS) applications focused on the generation of forensic-quality full mitochondrial genome sequences led to a popularization of the technique on a global scale. However, the lack of forensic-graded population databases has refrained a wider adoption of full genome sequences as the industry standard, despite its better discrimination capacity of individual maternal lineages.Purpose:This work describes a forensic-oriented full mtDNA genome database comprised of 480 samples from a Southern Brazilian population.Methods:A collection of mitochondrial sequences were obtained from low-pass, full genome DNA sequencing results. The complete sample set was evaluated regarding haplotype composition and distribution. Summary statistics and forensic parameters were calculated and are presented for the database, with detailed information concerning the impact of removing genetic information in the form of specific variants or increasingly larger genomic regions. Interpopulational analysis comparing haplotypical diversity in Brazilian and 26 worldwide populations was also performed. The association between mitochondrial genetic variability and phenotypic diversity was also evaluated in populations, with self-declared ancestry and three distinct phenotypic pigmentation traits (eyes, skin and hair colors) as parameters.Results:The presented database can be used to evaluate mitochondrial-related genetic evidence, providing LR values of up to 20,465 for unobserved haplotypes. Haplotype distribution in Southern Brazil seems to be different than the remaining of the country, with a larger contribution of maternal lines with European origin. Despite association can be found between lighter and darker phenotypes or self-declared ancestry and haplotype distribution, prediction models cannot be reliably proposed due to the admixed nature of the Brazilian population.Conclusions:The proposed database provides a basis for statistical calculation and frequency estimation of full mitochondrial genomes, and can be part of an integrated, representative, national database comprising most of the genetic diversity of maternal lineages in the country.     

叠氮钠对SH—SYT6人神经母细胞瘤细胞膜电位和胞内β—淀粉样蛋白表达的影响

目的：观察线粒体呼吸链复合体Ⅳ抑制剂叠氮钠对SH－SY5Y细胞的细胞膜电位及胞内β－淀粉样蛋白（Aβ）表达水平的影响，以探讨用叠氮钠建立模拟Alzheimer病（AD）脑中神经细胞能量代谢障碍的细胞模型的可能性。方法：不同浓度的叠氮钠损伤细胞后，用激光共聚焦显微镜观察细胞膜膜电位；用免疫细胞化学法检测细胞内β－淀粉样蛋白前体蛋白（APP）和Aβ的表达水平。结果：叠氮钠在浓度25－100mmol/L时，与细胞共孵育，可使细胞膜电位去极化程度明显增高，并引起胞内Aβ表达显著增高，但对胞内APP表达水平影响不明显。结论：叠氮钠致神经细胞损伤模型可能是模拟AD患者及脑中与线粒体复合体Ⅳ损伤相关的病理改变的较好模型。     

Prolongation of tension on reoxygenation following myocardial hypoxia: a possible role for mitochondria in muscle relaxation.

The mechanism for tension prolongation during reoxygenation following myocardial hypoxia was investigated. It was found that prior addition of isoproterenol, reserpine, quinidine, lidocaine and insulin or a change in pH, temperature, stimulation rate, preload or duration of hypoxia did not qualitatively alter the appearance of the phenomenon. On reoxygenating hypoxic preparations in the presence of 5, 10 or 20% oxygen, tension prolongation was clearly present when little increase in isometric tension was evident. Inhibition of glycolysis by iodoacetate did not alter the appearance of the phenomenon during reoxygenation. Three respiratory inhibitors, antimycin A, rotenone and cyanide, at concentrations which did not prevent an increase in isometric tension during recovery from myocardial hypoxia, all completely prevented the appearance of tension prolongation. Two uncouplers of oxidative phosphorylation, 2–4 dinitrophenol and carbonyl cyanide m-chlorophenyl hydrazone at concentrations large enough to lead to mechanical deterioration despite the presence of oxygen, failed to prevent the appearance of tension prolongation upon reoxygenation. It is concluded that myocardial respiratory activity, independent of ability to generate high energy phosphate, appears capable of altering the duration of mechanical events during reoxygenation of hypoxic heart muscle.     

Phosphorylative respiratory activity of mitochondria isolated from the left and right ventricles of rabbit hearts following partial pulmonary trunk occlusion

Right ventricular hypertrophy was produced by placing a spiral Monel metal clip around the pulmonary trunks of rabbits causing a sustained 67% occlusion of the vessel. The operation produced a doubling of right ventricular weight, by 13 days post-surgery, which persisted throughout the post-operative period studied (13 to 84 days); only a slight increase in left ventricular free wall weight was observed. Isolated mitochondria exhibited region-specific changes with time in state 3 Qo₂. Thirteen days after operation, the state 3 Qo₂ of right ventricular mitochondria was depressed to about 85% of controls. Thereafter, respiration increased fairly sharply, peaking at just above control values by 40 days post-operation. Finally, it declined abruptly to about 70% of controls by 84 days. A very different pattern of change was observed when left ventricular mitochondrial respiratory activities were examined. Thirteen days after the operation, state 3 Qo₂ was elevated somewhat above controls. Thereafter, it declined linearly and gradually, dropping to about 85% of controls by 84 days.     

Scanning Electron Microscopy of the Interior of Cells in Hürthle Cell Tumors

Four cases of Hurthle cell tumor were examined by scanning electron microscopy after being macerated to remove all soluble components. By all morphological criteria, Hurthle cells are oncocytes with their usual augmented complement of mitochondria. The Hurthle cell mitochondria either are ovate with central stacks of cristae or elliptical or rod-like with cristae that often are finger-like. As in salivary gland oncocytes, the shelf-like cristae are anchored to the inner boundary membrane by tubular necks. In some Hurthle cells, all of the mitochondria exhibit reticulate cristae. A few mitochondria harbor a globular inclusion in their inner compartment. The Golgi apparatuses are relatively simple, consisting of imbricated saccules that are edged by small, bud-like structures. The rare lumina in the midst of clusters of Hurthle cells are lined by numerous microvilli. Thus, scanning electron microscopy of macerated Hurthle cell tumors has revealed a number of features, especially of their mitochondria, that have escaped detection by transmission electron microscopy.