Changes In Mitochondrial Structure Research Articles

Abstract 1259: c-Myc influences mitochondrial structure and function by regulating fusion and fission

Abstract Background: c-Myc (Myc) is a global transcription factor that controls the expression of a large part of the human genome. The numerous Myc target genes function in a variety of normal cellular processes whose collective expression of these processes is referred to as the “Myc phenotype”. One such cellular process is the regulation of mitochondrial biogenesis. Objectives: To understand the specific influence that Myc has on mitochondrial structure and function. We hypothesize that Myc is involved in the regulation of both the production and destruction of mitochondria, and that the ability of Myc to maintain this balance has an impact on cellular transformation. Design/Method: Various cell lines that allow for the manipulation of Myc levels have been used. These include cells that have been engineered to have inducible Myc over-expression as well as inducible expression of Myc shRNA. These strains were used in a series of assays that measured different aspects of the Myc effect on mitochondrial structure and function. Most notably, metabolic pathways were measured by an extracellular flux analyzer and electron and confocal microscopy was performed to examine the structure of the mitochondria in detail. Results: The induction of Myc results in dramatic increases in overall mitochondrial mass, as well as increasing individual mitochondrial size and cristae density. This increase in recognizable mitochondria correlates to increases in oxidative phosphorylation and decreased mitochondrial loss through mitophagy. Finally, Myc levels correlate to increased mitochondrial inter-connectivity. This appears to be related to the ability of Myc to influence the expression of the mitochondrial fusion protein, Opa1 and the fission protein, DLP1. Conclusions Reached: The changes in mitochondrial structure and function are directly influenced by the expression of Myc. There appear to be multiple pathways involved in maintaining a specific mitochondrial mass, which emphasizes the importance of this organelle in cellular homeostasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1259. doi:10.1158/1538-7445.AM2011-1259

Mitochondrial involvement in chronic chagasic cardiomyopathy

The pathogenesis of chronic chagasic cardiopathy is still under discussion; there is considerable evidence that inflammatory infiltrates and their mediators have a direct effect on cardiac cells. Here we studied the structure and function of cardiac mitochondria in chronic chagasic myocardiopathy. Cardiac mitochondrial structure and enzyme activity of citrate synthase and complexes I to IV of the respiratory chain were studied in albino Swiss mice infected with Trypanosoma cruzi (Tulahuen strain or SGO Z12 isolate) on 365 days post-infection (dpi). The presence of parasites in cardiac and skeletal muscle was also investigated. The activity of complexes I to IV was altered in different ways, according to the strain employed (P<0.0001), in relation to the cristae disorganisation and the parasite persistence found in the Tulahuen group, and the chronic inflammatory process described in both groups; citrate synthase activity also increased in both infected groups. Changes in mitochondrial structure were detected in 89% of Tulahuen- and 58% of SGO Z12-infected mice. In this paper we demonstrate that parasite persistence and inflammation are likely to be involved in the structural and functional alterations in cardiac mitochondria from chronically T. cruzi-infected mice, demonstrating that the parasite strain determines different mitochondrial changes in chagasic cardiopathy.

Cytochrome P450 2E1 and hyperglycemia-induced liver injury

Cytochrome P450 2E1 (CYP2E1), a microsomal enzyme involved in xenobiotic metabolism and generation of oxidative stress, has been implicated in promoting liver injury. The review deals with the changes in various cellular pathways in liver linked with the changes in regulation of CYP2E1 under hyperglycemic conditions. Some of the hepatic abnormalities associated with hyperglycemia-mediated induction of CYP2E1 include increased oxidative stress, changes in mitochondrial structure and function, apoptosis, nitrosative stress, and increased ketone body accumulation. Thus, changes in regulation of CYP2E1 are associated with the injurious effects of hyperglycemia in liver.

Mitochondrial Structure and Function Are Disrupted by Standard Isolation Methods

Mitochondria regulate critical components of cellular function via ATP production, reactive oxygen species production, Ca2+ handling and apoptotic signaling. Two classical methods exist to study mitochondrial function of skeletal muscles: isolated mitochondria and permeabilized myofibers. Whereas mitochondrial isolation removes a portion of the mitochondria from their cellular environment, myofiber permeabilization preserves mitochondrial morphology and functional interactions with other intracellular components. Despite this, isolated mitochondria remain the most commonly used method to infer in vivo mitochondrial function. In this study, we directly compared measures of several key aspects of mitochondrial function in both isolated mitochondria and permeabilized myofibers of rat gastrocnemius muscle. Here we show that mitochondrial isolation i) induced fragmented organelle morphology; ii) dramatically sensitized the permeability transition pore sensitivity to a Ca2+ challenge; iii) differentially altered mitochondrial respiration depending upon the respiratory conditions; and iv) dramatically increased H2O2 production. These alterations are qualitatively similar to the changes in mitochondrial structure and function observed in vivo after cellular stress-induced mitochondrial fragmentation, but are generally of much greater magnitude. Furthermore, mitochondrial isolation markedly altered electron transport chain protein stoichiometry. Collectively, our results demonstrate that isolated mitochondria possess functional characteristics that differ fundamentally from those of intact mitochondria in permeabilized myofibers. Our work and that of others underscores the importance of studying mitochondrial function in tissue preparations where mitochondrial structure is preserved and all mitochondria are represented.

Study of Mitochondrial Dynamics During Apoptosis by Optical Fourier Filtering Detection

Recent evidence shows that changes in mitochondrial structure are associated with programmed cell death (apoptosis), and dysregulation of these changes is associated with human diseases including cancer, Parkinsons' disease and amyotrophic lateral sclerosis. Detecting morphological changes such as mitochondrial fission during the beginning stages of apoptosis is therefore of great interest. We have developed a light-scatter measurement technique that is sensitive to changes in mitochondrial structure in living apoptotic cells. This technique uses a spatial light modulator to achieve Fourier filtering using optical Gabor filters of dark field signal from cells and can be used without fluorescent dyes. We monitor mitochondrial fission in whole cells by detecting changes in object shape using an aspect ratio parameter generated from the optical Gabor information. Using our Gabor filtering methodology, we detect an average 15% decrease (p < 0.05) in the aspect ratio parameter of subcellular organelles at 60-100 min following apoptosis induction concomitant mitochondrial fragmentation confirmed by fluorescence microscopy. We have demonstrated that this decrease can be spatially registered with regions closely associated with the fluorescently labeled mitochondria and is absent in regions dominated by other organelles. The measurements may be made at low image resolution (>0.6 µm/pixel) and the data acquisition has recently been automated (nominal analysis of 100 single cells per second), offering significant potential for high throughput measurements. We are currently using the automated platform to study changes in mitochondrial dynamics during apoptosis at high time resolution. We will also investigate changes in mitochondrial membrane potential and their association with changes in mitochondrial structure measured with our technique in apoptosis-competent and apoptosis-resistant cells.

Impact of 5-fluorouracil on glucose metabolism and pancreatic pathology in rats

To explore the impact of 5-fluorouracil (5-FU) on glucose metabolism and pancreatic pathology. Twenty Wistar rats were divided into 5-FU group(n=10, chemotherapy was administered intraperitoneally to animals at a dose of 20 mg/kg daily for continuous 5 days) and control group (n=10, sodium chloride was administered intraperitoneally to animals with the same dose at the same time ). Glucose tolerance was evaluated 2 and 7 days following 5-FU treatment by serial measurement of blood glucose before and after an oral glucose load. Plasma insulin concentration was determined by radioimmunoassay. Pancreatic pathology was examined with morphological method and the ultrastructural changes of β cells were observed by transmission electron microscope. Fasting blood glucose level was significantly higher in the 5-FU group than that in the control group [(7.6±0.9) mmol/L vs. (4.6±0.6) mmol/L at day 2; (8.9±1.0) mmol/L vs. (4.7±0.6) mmol/L at day 7, P<0.01]. Insulin releasing test indicated that the early phase insulin response to glucose load was significantly diminished in animals treated with 5-FU at day 2. Insulin level was significantly lower in the 5-FU group than that in the control group at 30 min (P<0.01). The peak secretion time of plasma insulin in 5-FU group was at 60 min, similar to the control group; and plasma insulin level decreased more slowly. Plasma insulin level was higher in 5-FU groups than in control groups on 120 min and 180 min. At day 7, Insulin level was lower in the 5-FU group than that in the control group on 60 min, and the peak secretion time of plasma insulin was delayed to 120 min. Plasma insulin level was significantly increased in 5-FU group than that in control group on 180 min(P<0.01). No gross histopathological damage to the pancreas was observed at day 2 and 7 following administration of 5-FU. The structural changes of mitochondria were mainly the quantities of secretory granule diminished at day 7 under transmission electron microscope. Dilated rough endoplasmic reticula, swollen mitochondria, and the presence of adipose drops in lysosomes were found in few cells. 5-FU-induced hyperglycemia appears to be mediated in part by a relatively deficient insulin secretion to glucose stimulation. A relative deficiency in insulin secretion following 5-FU treatment appears to be related to β cells function impairs with islet cell ultrastructural changes induced by 5-FU.

Changes of mitochondrial ultrastructures and function in central nervous tissue of hens treated with tri-ortho-cresyl phosphate (TOCP)

Tri-ortho-cresyl phosphate (TOCP), an organophosphorus ester, is capable of producing organophosphorus ester-induced delayed neurotoxicity (OPIDN) in humans and sensitive animals. The mechanism of OPIDN has not been fully understood. The present study has been designed to evaluate the role of mitochondrial dysfunctions in the development of OPIDN. Adult hens were treated with 750 mg/kg·bw TOCP by gavage and control hens were given an equivalent volume of corn oil. On day 1, 5, 15, 21 post-dosing, respectively, hens were anesthetized by intraperitoneal injection of sodium pentobarbital and perfused with 4% paraformaldehyde. The cerebral cortex cinerea and the ventral horn of lumbar spinal cord were dissected for electron microscopy. Another batch of hens were randomly divided into three experimental groups and control group. Hens in experimental groups were, respectively, given 185, 375, 750 mg/kg·bw TOCP orally and control group received solvent. After 1, 5, 15, 21 days of administration, they were sacrificed and the cerebrum and spinal cord dissected for the determination of the mitochondrial permeability transition (MPT), membrane potential (Δψ(m)) and the activity of succinate dehydrogenase. Structural changes of mitochondria were observed in hens' nervous tissues, including vacuolation and fission, which increased with time post-dosing. MPT was increased in both the cerebrum and spinal cord, with the most noticeable increase in the spinal cord. Δψ(m) was decreased in both the cerebrum and spinal cord, although there was no significant difference in the three treated groups and control group. The activity of mitochondrial succinate dehydrogenase assayed by methyl thiazolyl tetrazolium (MTT) reduction also confirmed mitochondrial dysfunctions following development of OPIDN. The results suggested mitochondrial dysfunction might partly account for the development of OPIDN induced by TOCP.

Mitochondrial-Associated Metabolic Changes and Neurodegeneration in Huntingtons Disease - from Clinical Features to the Bench

Huntington's disease (HD) is a genetic neurodegenerative disease selectively leading to striatal neurodegeneration, but also affecting the cortex and the hypothalamus. Although it is hard to predict the sequence of cell-damaging events occurring in HD patients, several pathological mechanisms have been proposed to explain HD selective neurodegeneration and disease symptomatology. Abnormalities in mitochondrial function and bioenergetics contribute to cell death and have been reported in HD-affected individuals, both in central and peripheral tissues. Moreover, the latter has been characterized in several HD models. Thus, this review describes the converging mechanisms that lead to mitochondrial and metabolic abnormalities in thoroughly studied in vivo and in vitro HD models, including excitotoxicity, altered calcium handling, changes in mitochondrial structure and dynamics and transcription deregulation, which may represent important disease therapeutic targets. Furthermore, the review describes the current evidences of metabolic disturbances in the brain of HD-affected humans and of peripheral metabolic and mitochondrial changes, weight loss and endocrine abnormalities operating in the whole HD body.

Mitochondrial regulation of insulin action

Insulin resistance is the prodrome of many metabolic diseases and identifying ways to correct this pathological condition is a major goal for medical research. The foremost barrier to the development of new treatments is that the precise etiology of insulin resistance is uncertain. Recent studies suggest that changes in mitochondrial structure or function drive this condition, however much of this evidence is circumstantial. This Signaling Networks in Focus article provides a brief overview of known and speculative regulatory intersections whereby mitochondrial dysfunction at the levels of lipid oxidation, oxidative stress, calcium, adenine nucleotides, and protons may regulate insulin sensitivity. If mitochondrial dysfunction underlies the origins of metabolic disease then determining the precise molecular pathway will be essential for the development of new treatment and prevention strategies.

Quantifying subcellular dynamics in apoptotic cells with two-dimensional Gabor filters

We demonstrate an optical Fourier filtering method which can be used to characterize subcellular morphology during dynamic cellular function. In this paper, our Fourier filters were based on two-dimensional Gabor elementary functions, which can be tuned to sense directly object size and orientation. We utilize this method to quantify changes in mitochondrial and nuclear structure during the first three hours of apoptosis. We find that the technique is sensitive to a decrease in particle orientation consistent with apoptosis-induced mitochondrial fragmentation. The scattering signal changes were less pronounced in the nucleus and the remainder of the cytoplasm. Particles in these regions were less oriented than mitochondria and did not change orientation significantly.

Abnormalities in Mitochondrial Structure in Cells from Patients with Bipolar Disorder

Postmortem, genetic, brain imaging, and peripheral cell studies all support decreased mitochondrial activity as a factor in the manifestation of Bipolar Disorder (BD). Because abnormal mitochondrial morphology is often linked to altered energy metabolism, we investigated whether changes in mitochondrial structure were present in brain and peripheral cells of patients with BD. Mitochondria from patients with BD exhibited size and distributional abnormalities compared with psychiatrically-healthy age-matched controls. Specifically, in brain, individual mitochondria profiles had significantly smaller areas, on average, in BD samples (P = 0.03). In peripheral cells, mitochondria in BD samples were concentrated proportionately more within the perinuclear region than in distal processes (P = 0.0008). These mitochondrial changes did not appear to be correlated with exposure to lithium. Also, these abnormalities in brain and peripheral cells were independent of substantial changes in the actin or tubulin cytoskeleton with which mitochondria interact. The observed changes in mitochondrial size and distribution may be linked to energy deficits and, therefore, may have consequences for cell plasticity, resilience, and survival in patients with BD, especially in brain, which has a high-energy requirement. The findings may have implications for diagnosis, if they are specific to BD, and for treatment, if they provide clues as to the underlying pathophysiology of BD.

Rare genomic changes and mitochondrial sequences provide independent support for congruent relationships among the sea spiders (Arthropoda, Pycnogonida)

Pycnogonids, or sea spiders, are an enigmatic group of arthropods. Their unique anatomical features have made them difficult to place within the broader group Arthropoda. Most attempts to classify members of Pycnogonida have focused on utilizing these anatomical features to infer relatedness. Using data from mitochondrial genomes, we show that pycnogonids are placed as derived chelicerates, challenging the hypothesis that they diverged early in arthropod history. Our increased taxon sampling of three new mitochondrial genomes also allows us to infer phylogenetic relatedness among major pycnogonid lineages. Phylogenetic analyses based on all 13 mitochondrial protein-coding genes yield well-resolved relationships among the sea spider lineages. Gene order and tRNA secondary structure characters provide independent lines of evidence for these inferred phylogenetic relationships among pycnogonids, and show a minimal amount of homoplasy. Additionally, rare changes in three tRNA genes unite pycnogonids as a clade; these include changes in anticodon identity in tRNALys and tRNASer(AGN) and the shared loss of D-arm sequence in the tRNAAla gene. Using mitochondrial genome changes and tRNA structural changes is especially useful for resolving relationships among the major lineages of sea spiders in light of the fact that there have been multiple independent evolutionary changes in nucleotide strand bias among sea spiders. Such reversed nucleotide biases can mislead phylogeny reconstruction based on sequences, although the use of appropriate methods can overcome these effects. With pycnogonids, we find that applying methods to compensate for strand bias and that using genome-level characters yield congruent phylogenetic signals.

ADMINISTRATION OF SUNITINIB, AN ORAL ANGIOGENESIS INHIBITOR, IS ASSOCIATED WITH HYPERTENSION, BUT NOT WITH STRUCTURAL CARDIAC CHANGES OR CARDIOMYOCYTE MITOCHONDRIAL DYSFUNCTION: PP.22.363

Objectives: Inhibition of angiogenesis by blocking vascular endothelial growth factor (VEGF)-mediated signaling is an established treatment for various forms of cancer. This therapy is frequently associated with hypertension, but may also cause cardiac toxicity, mainly a decreased left ventricular ejection fraction (LVEF). Cardiomyocyte hypertrophy and changes in cardiac mitochondrial structure (swelling) have been reported in mice, suggesting that impaired adenosine triphosphate (ATP) generation secondary to mitochondrial dysfunction underlies the decrease in LVEF. We aimed to assess the effects of sunitinib on blood pressure (BP), cardiac structure and mitochondrial function in an ex-vivo rodent model. Methods: Normotensive male Wistar-Kyoto rats were administered sunitinib (n = 10) or vehicle (n = 6) by oral gavage and BP and heart rate (HR) were monitored telemetrically until a plateau in BP occurred at which time animals were euthanized. Blood and hearts were collected for determination of brain natriuretic peptide (BNP)-45 levels, heart weight, cardiomyocyte size and isolation of cardiomyocyte mitochondria for measurement of complex I- and II-dependent ATP production. Results: A plateau in BP rise was found after 6 days of treatment. At that time, mean arterial BP had increased from 98.3 ± 0.3mmHg to 126 ± 1.5mmHg and HR had decreased from 319.3 ± 1.4bpm to 271.6 ± 3.0bpm (both p < 0.001), while BP and HR did not change in the control group. Circulating BNP-45 levels were almost 2-fold (163.9 ± 33.9ng/ml vs 92.7 ± 15.0ng/ml; p = 0.03) and serum creatinine levels (28.8 ± 6.4 vs 8.0 ± 2.7 μmol/l; p = 0.03) almost threefold higher in the sunitinib compared to the control group. Heart weight-to-body weight ratio and cardiomyocyte area were not different between groups. Complex I-dependent ATP production between the sunitinib and control group (659.7 ± 88.1; vs 1028 ± 278 nmol/mg mitochondrial protein/30 min; p = 0.26) and complex II-dependent ATP-production (955.6 ± 93.3 vs 1409 ± 255 nmol/mg mitochondrial protein/30 min; p = 0.15) did not differ. Conclusions: Although circulating BNP-45 levels were increased in sunitinib-administered rats, no evidence for structural cardiac abnormalities or impaired cardiomyocyte mitochondrial ATP production was found. The rise in BNP-45 might be a consequence of the BP-rise and the decrease in renal function.

Curcumin induces mitochondria pathway mediated cell apoptosis in A549 lung adenocarcinoma cells

Several studies have shown that curcumin can induce apoptosis and inhibit growth in human tumor cell lines. However, the mechanism is not completely understood yet. The present studies were designed to investigate the effects of curcumin on human A549 lung adenocarcinoma cells lines to better understand its effect on apoptosis and apoptosis-related genes in vitro. Apoptosis induction, mitochondria membrane potential, mitochondria structure, and apoptotic associated gene expression were examined by flow cytometric assay, confocal microscopy, Western blotting and electron microscopy. After treatment with curcumin, percentage of apoptotic cells increased dose- and time-dependently, and morphology observation revealed typical apoptotic features. Our data further indicated that the expression of Bax proteins in A549 cells was increased in a dose-dependent manner, whereas the expression of Bcl-2 was significantly decreased, thus the ratio of Bax/Bcl-2 was increased. The apoptotic process was accompanied by the change of mitochondrial function and structure which led to release of the cytochrome c, and activation of caspase-9 and caspase-3. Furthermore, curcumin also induced a dose-dependent cleavage of PARP. Caspases activation during the course of curcumin-induced apoptosis was additionally confirmed by using a broad-spectrum caspases inhibitor, Z-VAD-fmk. As expected, the inhibitor was able to decrease curcumin-induced apoptosis on A549 cells. These results suggested that mitochondria played an important role in the curcumin-induced apoptosis, and mitochondria membrane potential loss initiated apoptosis via the activation of caspases.

Lidocaine Enhances Apoptosis and Suppresses Mitochondrial Functions of Human Neutrophil In Vitro

Neutrophils play an essential role in innate immunity and against infection. Mitochondria are organelles that produce energy in the form of adenosine triphosphate (ATP), which is required for maintaining the function and structure of cells and organs. Although local anesthetics (LAs) are widely used in clinical practice, it remains unclear whether LAs such as lidocaine, ropivacaine, and bupivacaine affect neutrophil mitochondrial functions. The aim of this study was to examine whether LAs have any effects on human neutrophil mitochondrial functions. Freshly isolated human neutrophils were incubated with lidocaine, ropivacaine, or bupivacaine. The oxidative burst and phagocytic activity of neutrophils and apoptotic rate of neutrophils were measured to assess the effect of LAs on neutrophil functions. The ATP concentration, mitochondrial transmembrane potential (Deltapsim), and neutrophil mitochondrial morphology were also measured to evaluate the effect of LAs on mitochondrial functions. Lidocaine (400 microm) induced a reduction in the oxidative burst and phagocytosis activity of neutrophils by approximately 20%. The ATP concentration was significantly lower in lidocain-treated neutrophils compared with control neutrophils (876 +/- 25 vs. 1,332 +/- 76 pmol/10(6) neutrophils; p < 0.05). Mitochondrial transmembrane potential (Deltapsim) was also significantly lower in lidocaine-treated neutrophils compared with control neutrophils (p < 0.05). Lidocaine also induced mitochondrial structural changes and induced apoptosis of neutrophils. Ropivacaine and bupivacaine had no effect on neutrophil functions including mitochondrial function. Furthermore, the study of mitochondrial function depletion demonstrated that neutrophil function requires active mitochondrial function. Although ropivacaine and bupivacaine had no effect on neutrophil and mitochondrial functions, lidocaine suppressed neutrophil function, inhibited ATP synthesis, reduced mitochondrial membrane potential, and induced apoptosis.

Oxidative stress causes reversible changes in mitochondrial permeability and structure

Mitochondria are a primary source as well a principal target of reactive oxygen species within cells. Using immunofluorescence microscopy, we have found that a number of mitochondrial matrix proteins are normally undetectable in formaldehyde-fixed cells permeabilized with the cholesterol-binding detergent saponin. However, exogenous or endogenous oxidative stress applied prior to fixation altered the permeability of mitochondria, rendering these matrix proteins accessible to antibodies. Electron microscopy revealed a loss of matrix density and disorganization of inner membrane cristae upon oxidative stress. Notably, the changes in permeability and in structure were rapidly reversed when the oxidative stress was relieved. The ability of reactive oxygen species to reversibly alter the permeability of the mitochondrial membrane provides a potential mechanism for communication within the cell such as between nucleus and mitochondria.

Mitochondrial Damage in Nasopharyngeal Carcinoma Cells Induced by Ultrasound Radiation in the Presence of Hypocrellin B

The mitochondrion is an important target of ultrasound-induced cell death. This study aimed to investigate the mitochondrial damage in nasopharyngeal carcinoma (NPC) cells induced by ultrasound radiation in the presence of hypocrellin B (HB). The NPC cell line CNE2 was used to investigate the effect of HB on ultrasonic action with an HB concentration of 2.5 mumol/L and ultrasound exposure for 15 seconds at an intensity of 0.65 W/cm(2). Cytotoxicity was investigated 24 hours after ultrasound exposure. Mitochondrial structure changes were observed by transmission electron microscopy. The mitochondrial membrane potential was evaluated by confocal laser-scanning microscopy with rhodamine 123 staining. The mean death rates of the CNE2 cells +/- SD were 25.14% +/- 1.50% after ultrasound radiation alone and 76.72% +/- 1.13% after ultrasound radiation in the presence of HB. Transmission electron microscopy showed that slightly enlarging mitochondria were found in the ultrasound-treated cells. After treatment with ultrasound and HB together, some cells had seriously damaged mitochondria, namely, obvious swollen mitochondria and mitochondria in which cristae had almost completely disappeared. The mitochondrial membrane potential was more significantly collapsed when the CNE2 cells were exposed to HB for 5 hours and then ultrasound at 0.65 mW/cm(2) than with ultrasound radiation alone (P < .05). Hypocrellin B significantly enhanced the cytotoxicity of ultrasound radiation in the CNE2 cells. The damage to the mitochondrial structure and function might be an important cause of death in the CNE2 cells induced by treatment with ultrasound radiation and HB together.

Ultrastructural observation on genesis and morphology of cortical granules in Macrobrachium nipponense (Crustacea, Caridea)

Cortical granules are secretory vesicles in oocytes that develop from the Golgi complex. In the freshwater shrimp, Macrobrachium nipponense, mitochondria participates in the formation of cortical granules. We investigated the structural changes of mitochondria and the distribution cortical granules in different stages of oocyte development. Transmission electron microscopy provided evidence for the involvement of mitochondria and a particular spiral lamellar organization and an electron-lucent area in internal cortical granules. The ooplasm provided material for the cortical granules in early oocyte development. We demonstrated that mitochondria play a role in coalescence and maturation of cortical granules in this species. Additionally, a concept of cortical granules regarded as a functional integration is put forward. The genesis of shrimp cortical granules exhibited a particular pathway of maturation. The outer shape and inner organization considering different taxa suggested general as well as specific features of the development of cortical granules.

Leptin-mediated changes in hepatic mitochondrial metabolism, structure, and protein levels.

Leptin reduces body weight in ob/ob mice by decreasing food intake and increasing energy expenditure; however, the mechanisms by which it does the latter are not known. Here we report that 30% of the weight loss induced by leptin treatment of ob/ob mice is due to changes in energy expenditure. In assessing leptin's effects on specific tissues, we found that hepatic basal metabolic rate was paradoxically decreased 1.7-fold with leptin treatment, which was the result of a 1.6-fold reduction in mitochondrial volume density and altered substrate oxidation kinetics. The altered kinetics were associated with a decrease in protein levels of 2 mitochondrial respiratory chain components--cytochrome c oxidase subunit VIa and cytochrome c oxidase subunit IV. In addition to reduced hepatic metabolism, there was reduced long chain fatty acid production and a 2.5-fold increase in hepatic lipid export, both of which explain the reduced steatosis in leptin-treated animals. These data help clarify the role of the liver in leptin-mediated weight loss and define the mechanisms by which leptin alters hepatic metabolism and corrects steatosis.

Esculetin Restores Mitochondrial Dysfunction and Reduces Allergic Asthma Features in Experimental Murine Model

We recently showed that IL-4-dependent oxidative stress and mitochondrial dysfunction are associated with allergic asthma. IL-4 also induces a prooxidant enzyme, 15-lipoxygenase, which predominantly expresses in asthmatic bronchial epithelium and degrades mitochondria. Esculetin (6,7-dihydroxy-2H-1-benzopyran-2-one), a plant-derived coumarin and immunomodulator, was found to have potent bronchodilating property in carbachol-induced bronchoconstriction and also reduces mitochondrial dysfunction in neurological diseases. In this study, we evaluated its potential in restoring mitochondrial dysfunction and structural changes and anti-asthma property in a mouse model of experimental asthma. In this study, we found that esculetin treatment reduced airway hyperresponsiveness, Th2 response, lung eotaxin, bronchoalveolar lavage fluid eosinophilia, airway inflammation, and OVA-specific IgE. It also reduced the expression and metabolites of 15-lipoxygenase and lipid peroxidation which is an essential prerequisite for mitochondrial dysfunction. Interestingly, esculetin treatment restored the activity of cytochrome c oxidase of electron transport chain in lung mitochondria and expression of the third subunit of cytochrome c oxidase of electron transport chain in bronchial epithelium. It reduced the cytochrome c level and caspase 9 activity in lung cytosol and restored mitochondrial structural changes and lung ATP levels. In addition, esculetin reduced subepithelial fibrosis and TGF-beta1 levels in the lung. These results suggest that esculetin not only restores mitochondrial dysfunction and structural changes but also alleviates asthmatic features.