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At least 1,477 records · Page 82Linked to original sources
PubMed2000

Site of action of suramin and reactive blue 2 in preventing neuronal death induced by dequalinium.

Dequalinium (DQ, an anticancer drug) is a potent neurotoxicant in the cultured developing cerebellar granule neurons (CGNs) with an IC(50) of 1.31. M after 24 hr incubation. By utilizing fluorometric technique, we found that DQ initially induced apoptosis and then necrosis associated with a marked decrease in ATP contents. The purinergic P(2) receptor antagonists (suramin, and reactive blue 2) prevented DQ-cytotoxicity, although glutamate ionotropic receptor antagonists (MK 801 and NBQX) could not. Furthermore, we quantitatively determined a reduction of mitochondrial membrane potential and an increase of free radical production induced by DQ. Suramin abolished these detrimental events of DQ. This suggests that neuronal death induced by DQ is mediated, at least in part, through a signaling pathway of free radical production-mitochondrial dysfunction. Further evidence supporting this contention is that CGN progressively became more sensitive to both DQ-induced cytotoxicity and reduced mitochondrial membrane potential. This implies that neuronal mitochondria are apparently one of the target sites for DQ and suramin and directly or indirectly induce neurotoxicity and neuroprotection respectively. The alteration in mitochondrial membrane potential during neuronal maturation may be one of the determinants accounting for the increased susceptibility to neurotoxicants such as DQ.

Adenosine Triphosphate↗
PubMed2006

Role of mitochondria in multiple sclerosis.

This review presents inherited and acquired forms of mitochondrial dysfunction associated with oligodendrocytopathy and neurodegeneration in order to better understand the degenerative features of inflammatory demyelination. The recognition that various mitochondrial mechanisms are involved in the pathogenesis of multiple sclerosis leads to therapeutic considerations, re-emphasizing the importance of early neuroprotection in combination with the approved means of immune modulation.

DNA, Mitochondrial↗
PubMed2005

Interaction between yeast mitochondrial and nuclear genomes: null alleles of RTG genes affect resistance to the alkaloid lycorine in rho0 petites of Saccharomyces cerevisiae.

Some nuclear genes in Saccharomyces cerevisiae (S. cerevisiae) respond to signals from the mitochondria in a process called by Butow (Cell Death Differ. 9 (2002) 1043-1045) retrograde regulation. Expression of these genes is activated in cells lacking mitochondrial function by involvement of RTG1, RTG2 and RTG3 genes whose protein products bind to "R-boxes" in the promoter region; RTG2p is a cytoplasmic protein. Since S. cerevisiae rho0 strains, lacking the entire mitochondrial genome, are resistant to lycorine, an alkaloid extracted from Amaryllis plants, it could be hypothesized that in rho0 cells the dysfunctional mitochondrial status stimulates overexpression of nuclear genes very likely involved in both nuclear and mitochondrial DNA replication. In this report we show that the resistance of rho0 cells to lycorine is affected by the deletion of RTG genes.

Alleles↗
PubMed2026

Form and function of actin impacts actin health and aging.

The actin cytoskeleton is a fundamental and highly conserved structure that functions in diverse cellular processes, yet its direct contribution to organismal aging remains unclear. Here, we systematically interrogated how genetic and pharmacologic perturbations of actin structure and function influence lifespan and various hallmarks of aging in Caenorhabditis elegans. Whole-animal and tissue-specific knockdown of actin and key actin-binding proteins (ABPs)-arx-2 (Arp2/3), unc-60 (cofilin), and lev-11 (tropomyosin)-led to premature disruption of filament organization, reduced lifespan, and tissue-specific physiological defects. Actin dysfunction also displayed a more "aged" transcriptome using previously validated transcriptomics clocks, and broadly exacerbated many age-associated phenotypes, including mitochondrial dysfunction, lipid dysregulation, loss of proteostasis, impaired autophagy, and intestinal barrier failure. Pharmacological destabilization with Latrunculin A mirrored genetic knockdowns, while mild stabilization with Jasplakinolide modestly extended lifespan, emphasizing that optimal and finely tuned actin function is critical for healthy aging. Finally, analysis of human genome-wide association data revealed that common ACTB polymorphisms correlate with differences in age-related decline in gait speed, suggesting some links between aging and actin across organisms. Taken together, our results provide a comprehensive and publicly accessible resource that maps, for the first time, how changes in actin integrity correlate with diverse aging phenotypes across tissues. This descriptive framework is intended to enable future mechanistic discovery by offering a deep, unbiased dataset that can be integrated with emerging studies to define how actin dynamics can potentially influence aging.

actin↗
PubMed2005

Subcellular targeting of DISC1 is dependent on a domain independent from the Nudel binding site.

Disrupted in schizophrenia 1 (DISC1) has been identified as a putative risk factor for schizophrenia and affective disorders through study of a Scottish family with a balanced (1;11) (q42.1;q14.3) translocation, which results in the disruption of the DISC1 locus and cosegregates with major psychiatric disease. Several other reports of genetic linkage and association between DISC1 and schizophrenia in a range of patient populations have added credibility to the DISC1-schizophrenia theory, but the function of the DISC1 protein is still poorly understood. Recent studies have suggested that DISC1 plays a role in neuronal outgrowth, possibly through reported interactions with the molecules Nudel and FEZ1. Here we have analyzed the DISC1 protein sequence to identify previously unknown regions that are important for the correct targeting of the protein and conducted imaging studies to identify DISC1 subcellular location. We have identified a central coiled-coil region and show it is critical for the subcellular targeting of DISC1. This domain is independent from the C-terminal Nudel binding domain highlighting the multidomain nature/functionality of the DISC1 protein. Furthermore, we have been able to provide the first direct evidence that DISC1 is localized to mitochondria in cultured cortical neurons that are dependent on an intact cytoskeleton. Surprisingly, Nudel is seen to differentially associate with mitochondrial markers in comparison to DISC1. Disruption of the cytoskeleton results in colocalization of Nudel and mitochondrial markers-the first observation of such a direct relationship. Mitochondrial dysfunction has been implicated to play a role in schizophrenia so we speculate that mutations in DISC1 or Nudel may impair mitochondrial transport or function, initiating a cascade of events culminating in psychiatric illness.

Amino Acid Sequence↗
PubMed2004

Fulminant hepatic failure induced oxidative stress in nonsynaptic mitochondria of cerebral cortex in rats.

Fulminant hepatic failure (FHF) is a condition with sudden onset of necrosis of hepatocytes and degeneration of liver tissue without any established liver disease. FHF is associated with increased ammonia levels in blood and brain, which is supposed to be neurotoxic, ultimately leading to neuronal death. Evidences from previous studies suggest for mitochondrial dysfunctions under hyperammonemic conditions. In the present investigation, on thioacetamide-induced FHF rat models, studies were undertaken on cerebral nonsynaptic mitochondrial oxidative stress. The results of the present study reveal elevated lipid peroxidation along with reduced total thiol levels in the cerebral cortex mitochondria of experimental animals compared to saline treated control rats. In addition, the enzymatic activities of glutathione peroxidase and glutathione reductase were decreased, with an elevation in Mn-SOD activity. Overall, thioacetamide-induced FHF in rats enhanced the levels of lipid peroxidation coupled with impaired antioxidant defenses in the cerebral nonsynaptic mitochondria.

Animals↗
PubMed2000

Mitochondrial ultrastructure and density in a primate model of persistent tardive dyskinesia.

The use of neuroleptic drugs to treat schizophrenia is almost invariably associated with extrapyramidal movement disorders. One of these disorders, tardive dyskinesia (TD), can persist long after neuroleptic withdrawal suggesting that permanent neurological damage is produced. However, there appears to be no convincing pathology of TD and its pathogenesis remains unknown. Findings that neuroleptics interfere with normal mitochondrial function and produce mitochondrial ultrastructural changes in the basal ganglia of patients and animals suggest that mitochondrial dysfunction plays a role in TD. We have established a model for persistent TD in baboons that appears to involve compromised mitochondrial function. In this study, we evaluated two animals treated for 41 weeks with a derivative of haloperidol and two treated with vehicle only. Treatment was then withdrawn and the animals observed for a further 17-18 weeks. Treated animals developed abnormal orofacial signs that were consistent with TD. These symptoms persisted during the drug-free period. The animals were euthanased, the brains perfused-fixed then post-fixed in 4% paraformaldehyde and the caudate and putamen prepared for electron microscopy. Regardless of whether mitochondria were located in neural soma, excitatory terminals, glia or in non-somal neuropil there was no consistent difference either in size or number between treated and control animals. Thus, even if mitochondria in striatal neurons undergo ultrastructural alterations during neuroleptic therapy, these changes do not persist after drug withdrawal.

Animals↗
PubMed2004

Human hepatitis B virus-X protein alters mitochondrial function and physiology in human liver cells.

The hepatitis B virus-X protein (HBx) regulates fundamental aspects of mitochondrial physiology. We show that HBx down-regulates mitochondrial enzymes involved in electron transport in oxidative phosphorylation (complexes I, III, IV, and V) and sensitizes the mitochondrial membrane potential in a hepatoma cell line. HBx also increases the level of mitochondrial reactive oxygen species and lipid peroxide production. HBx does not activate apoptotic signaling, although it sensitizes hepatoma cells to apoptotic signaling, which is dependent on reactive oxygen species. Increased intrahepatic lipid peroxidation in HBx transgenic mice demonstrated that oxidative injury occurs as a direct result of HBx expression. Therefore, we conclude that mitochondrial dysfunction is a crucial pathophysiological factor in HBx-expressing hepatoma cells and provides an experimental rationale in the investigation of mitochondrial function in rapidly renewed tissues, as in hepatocellular carcinomas.

Animals↗
PubMed2004

Mitochondrial damage and DNA depletion in cord blood and umbilical cord from infants exposed in utero to Combivir.

OBJECTIVE: Although most uninfected infants born to women infected with HIV-1 show no clinical evidence of mitochondrial compromise, mitochondrial dysfunction has been reported in children born to women receiving zidovudine and/or lamivudine during pregnancy. In this pilot study we examined mitochondrial integrity in HIV-1-uninfected infants born to HIV-1-infected women receiving Combivir during pregnancy. DESIGN: : Samples of umbilical cord and cord blood were obtained from HIV-1-uninfected infants born to either HIV-1-infected women receiving Combivir therapy during pregnancy (n = 10) or HIV-1-uninfected women (n = 9). METHODS: Mitochondrial morphological integrity was examined in umbilical cords (n = 16) by electron microscopy and mtDNA quantity was determined in DNA from cord blood (n = 18) and umbilical cord (n = 18) by PCR-chemiluminescence immunoassay detection. RESULTS: In umbilical cords from six of nine infants born to HIV-1-infected mothers taking Combivir moderate to severe mitochondrial morphological damage was observed (P = 0.011), while none of seven unexposed infants showed similar damage. Compared to unexposed infants, statistically significant mtDNA depletion was observed in umbilical cord (P = 0.006) and cord blood (P = 0.003) from drug-exposed infants. CONCLUSIONS: A cohort of HIV-1-uninfected Combivir-exposed infants with no clinical symptoms showed morphological and molecular evidence of mitochondrial damage.

Anti-HIV Agents↗
PubMed2005

Mitochondrial function and mitochondria-induced apoptosis in an overstimulated rat ovarian cycle.

Female rats were treated with FSH (40 IU/kg) on the first and second diestrus days (D1 and D2) and with LH (40 IU/kg) on the proestrus (P) day to synchronize and maximize ovarian changes. Follicle area increased by 50% from D1 to P, and the estrus (E) phase showed multiple corpora lutea and massive apoptosis. Increased oxygen uptakes (42-102%) were determined in ovary slices and in isolated mitochondria in active state 3 along the proliferation phase (D1-D2-P) that returned to initial values in the E phase. Mitochondrial content and the electron transfer activities of complexes I and IV were also maximal in the P phase (20-79% higher than in D1). Production of NO by mitochondrial nitric oxide synthase (mtNOS), biochemically determined, and the mtNOS functional activity in regulating state 3 oxygen uptake were also maximal at P and 79-88% higher than at D1. The moderately increased rate of NO in the proliferative phase is associated with mitochondrial biogenesis, whereas the high rate of NO generation by mtNOS at phase P appears to trigger mitochondria-dependent apoptosis. The calculated fraction of ovary mitochondria in state 3 was at a minimal value at the P phase. Mitochondrial oxidative damage, with increased thiobarbituric acid-reactive substances and protein carbonyls, indicates progressive mitochondrial dysfunction between phases P and E. The roles of mitochondria as ATP provider, as a source of NO to signal for mitochondrial proliferation and mitochondria-dependent apoptosis, and as a source of O(2)(-) and H(2)O(2) appear well adapted to serve the proliferation-apoptosis sequence of the ovarian cycle.

Animals↗
PubMed2005

Stimulation of mitochondrial activity by p43 overexpression induces human dermal fibroblast transformation.

Mitochondrial dysfunctions are frequently reported in cancer cells, but their direct involvement in tumorigenesis remains unclear. To understand this relation, we stimulated mitochondrial activity by overexpression of the mitochondrial triiodothyronine receptor (p43) in human dermal fibroblasts. In all clones, this stimulation induced morphologic changes and cell fusion in myotube-like structures associated with the expression of several muscle-specific genes (Myf5, desmin, connectin, myosin, AchRalpha). In addition, these clones displayed all the in vivo and in vitro features of cell transformation. This phenotype was related to an increase in c-Jun and c-Fos expression and extinction of tumor suppressor gene expression (p53, p21WAF1, Rb3). Lastly, reactive oxygen species (ROS) production was increased in positive correlation to the stimulation of mitochondrial activity. The direct involvement of mitochondrial activity in this cell behavior was studied by adding chloramphenicol, an inhibitor of mitochondrial protein synthesis, to the culture medium. This inhibition resulted in partial restoration of the normal phenotype, with the loss of the ability to fuse, a strong decrease in muscle-specific gene expression, and potent inhibition of the transformed phenotype. However, expression of tumor suppressor genes was not restored. Similar results were obtained by using N-acetylcysteine, an inhibitor of ROS production. These data indicate that stimulation of mitochondrial activity in human dermal fibroblasts induces cell transformation through events involving ROS production.

Animals↗
PubMed1988

Effect of extracellular Ca++ omission on isolated hepatocytes. II. Loss of mitochondrial membrane potential and protection by inhibitors of uniport Ca++ transduction.

Incubation of isolated rat hepatocytes in Ca++-free medium generates an oxidative stress which causes significant cell injury. Ruthenium red and La , which block Ca++ uptake through the mitochondrial uniport, totally prevented malondialdehyde formation, glutathione and protein thiol oxidation and vitamin E loss induced by Ca++ omission. Accordingly, these agents also prevented leakage of intracellular K+ and lactate dehydrogenase. Similar protective effects were provided by the Ca++ chelator ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. The absence of extracellular Ca++ resulted in a marked decline of the mitochondrial transmembrane potential which could be prevented by ruthenium red, ethylene glycol bis(beta-aminoethyl ether)-N,N'tetraacetic acid, the antioxidant vitamin E and the iron chelator, desferrioxamine. In contrast, oxidative stress induced by treatment with the redox active agent paraquat and 1,3-bis(2-chloroethyl)-1-nitrosourea had little effect on mitochondrial transmembrane potential and malondialdehyde formation and lactate dehydrogenase leakage were not affected by ruthenium red or La . These results indicate that the incubation of rat hepatocytes in the absence of extracellular Ca++ creates an unusual oxidative stress which markedly affects mitochondrial function. The ability of vitamin E and desferrioxamine to inhibit the loss of mitochondrial transmembrane potential indicates that oxidative damage is involved in producing mitochondrial dysfunction. Furthermore, the potent inhibitory effects of ruthenium red and La suggest that Ca++ movement through the uniport, perhaps indicative of mitochondrial Ca++ cycling, plays a major role in generating this oxidative stress and promoting cell injury.

Animals↗
PubMed1989

[The effect of flecainide on 2 hour occlusion-induced myocardial damages in dog].

This study was designed to clarify whether or not flecainide have cardioprotective effect on ischemic myocardium. Nineteen dogs anesthetized and subjected to 2 h coronary occlusion, were divided into 2 groups. In the control group, physiological saline was infused, and in the flecainide group, 2 mg/kg of flecainide acetate and followed by 100 micrograms/kg/min continuous infusion. To assess the cardioprotective effect, mitochondrial function and lysosomal enzyme activities were measured. Two hours after occlusion, mitochondria were prepared from both ischemic and non-ischemic areas in each group, and their function (respiratory control index, and the rate of oxygen consumption in state III respiration) were measured polarographically with succinate as substrate. Fractionation of myocardial tissue from both non-ischemic and ischemic areas was performed according to the method of Weglicki et al, and the activities of lysosomal enzymes (N-acetyl-beta-glucosaminidase, and beta-glucuronidase) were measured. In the control group, mitochondrial dysfunction and leakage of lysosomal enzymes induced by 2 h occlusion were observed. On the contrary, administration of flecainide maintained significantly mitochondrial function, and prevented significantly leakage of lysosomal enzymes. These results indicated that flecainide had cardioprotective effect as well as antiarrhythmic effects in ischemic myocardium.

Animals↗
PubMed1997

Mitochondrial DNA mutations in multiple symmetric lipomatosis.

Multiple symmetric lipomatosis (MSL) is a rare disorder of middle life characterized by large subcutaneous fat masses around the neck, shoulders and other parts of the trunk. Peripheral neuropathy is a common finding in these predominantly male patients. Employing electrophysiological measures, we found additional signs of central nervous system involvement in a majority of patients. Etiologically, there is an association with mitochondrial dysfunction. In muscle biopsy, we found ragged red fibers in 8 of 12 patients. Molecular genetic analysis revealed multiple deletions of mitochondrial DNA in one patient and the MERRF mutation at nucleotide 8344 in another. In this review, we summarize our clinical, electrophysiological morphological, biochemical and molecular genetic findings in 17 MSL patients, and give a survey of the literature.

Adult↗
PubMed2003

Mitochondrial complex I mutations in Caenorhabditis elegans produce cytochrome c oxidase deficiency, oxidative stress and vitamin-responsive lactic acidosis.

Mitochondrial dysfunction, with an estimated incidence of 1 in 10 000 live births, is among the most common genetically determined conditions. Missense mutations in the human NDUFV1 gene, which encodes the 51 kDa active site subunit of the NADH-ubiquinone oxidoreductase or complex I, can lead to severe neurological disorders. Owing to the rare and often sporadic nature of mitochondrial disorders, the mechanisms of pathogenesis of most mutations remain poorly understood. We have generated transgenic strains of Caenorhabditis elegans that express disease-causing mutations in the nuo-1 gene, the C. elegans homolog of the NDUFV1 gene. The transgenic strains demonstrate hallmark features of complex I dysfunction such as lactic acidosis and decreased NADH-dependent mitochondrial respiration. They are also hypersensitive to exogenous oxidative stress, suggesting that cellular defense mechanisms against reactive oxygen species are already taxed by an endogenous stress. The lactic acidosis induced by the NDUFV1 mutations could be partially corrected with the vitamins riboflavin and thiamine or with sodium dichloroacetate, an activator of the pyruvate dehydrogenase complex, resulting in significant increases in animal fitness. Surprisingly, cytochrome c oxidase activity and protein levels were reduced, establishing a connection between complexes I and IV. Our results indicate that complex I mutations exert their pathogenic effects in multiple ways: by impeding the metabolism of NADH, by increasing the production of reactive oxygen species, and by interfering with the function or assembly of other mitochondrial respiratory chain components.

Acidosis, Lactic↗
PubMed2006

Compensated volume overload increases the vulnerability of heart mitochondria without affecting their functions in the absence of stress.

Although mitochondrial dysfunction has often been associated to heart failure, it has been suggested that it may represent only a late phenomenon in the disease process. We hypothesized that mitochondrial vulnerability to stress could be impaired in hypertrophied but non-decompensated hearts at a time when overt mitochondrial defects are not yet apparent. In the present study, hypertrophic remodeling was induced by means of an aorto-caval fistula (ACF) in WKHA rats and experiments were performed 12 weeks post surgery. At this time, ACF animals displayed normal contractile function, tissue oxidative capacity as well as mitochondrial membrane potential and respiratory function. However, compared to sham, mitochondria from ACF animals were more vulnerable to anoxia-reoxygenation injury in vitro as indicated by a greater impairment of oxidative phosphorylation and a greater dependence of respiration on exogenous NADH. Addition of the PTP inhibitor CsA restored respiratory function to the level observed in mitochondria from sham animals. Likewise, mitochondria from ACF displayed a greater sensitivity to Ca(2+)-induced PTP opening in vitro compared to their sham counterparts. In addition to the greater vulnerability of mitochondria in vitro, mitochondrial PTP opening measured in situ in perfused hearts was greater following ischemia-reperfusion in ACF animals than in their sham counterparts. This was associated with a more impaired functional recovery and greater tissue damage during reperfusion in hearts from ACF vs sham. Taken together, these results indicate that, in response to volume overload, mitochondria may display increased vulnerability in the absence of any sign of dysfunction under baseline unstressed conditions, at a time when adverse ventricular remodelling is observed but systolic dysfunction and decompensation have not occurred yet.

Animals↗
PubMed2004

A novel NOTCH3 frameshift deletion and mitochondrial abnormalities in a patient with CADASIL.

BACKGROUND: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), which leads to strokes and dementia, is caused by single missense mutations or, in a few cases, small deletions in the NOTCH3 gene. These mutations result in a gain or a loss of 1 (or, rarely, 3) cysteine residue in 1 of 34 epidermal growth factor-like repeats in the extracellular amino-terminal region of NOTCH3. OBJECTIVE: To describe a patient with a novel NOTCH3 mutation in whom clinical and laboratory findings of mitochondrial abnormalities were associated with a diagnosis of CADASIL. Patient A patient with a history of migraines, repeated transient ischemic attacks, and generalized fatigue underwent muscle biopsy, brain magnetic resonance spectroscopic imaging, and screening of mitochondrial DNA and NOTCH3. RESULTS: Molecular genetic analysis showed a NOTCH3 mutation (the first documented frameshift deletion in a patient with CADASIL) in exon 4. Although the screening of mitochondrial DNA did not show mitochondrial mutations, findings from muscle biopsy and brain magnetic resonance spectroscopic imaging showed signs of mitochondrial impairment (ultrastructural mitochondrial abnormalities and increased parenchymal brain lactate, respectively). CONCLUSIONS: A patient with CADASIL and a 5-base pair deletion leading to a frameshift mutation showed clinical and laboratory evidence of mitochondrial dysfunction. This adds to the previously reported hypothesis of a pathogenetic role of NOTCH3 or, less specifically, a microvascular pathologic effect on mitochondrial energy metabolism.

Base Sequence↗
PubMed2007

Iron chelation study in a normal human hepatocyte cell line suggests that tumor necrosis factor receptor-associated protein 1 (TRAP1) regulates production of reactive oxygen species.

Iron is an essential component of many proteins, and has crucial roles in the proper functioning of proteins involved in cellular respiration, proliferation, and differentiation. It has been recently reported that the deferoxamine (DFO), an iron chelator, induces mitochondrial dysfunction, characterized by an attenuation of oxidative phosphorylation, as well as senescence-like cellular morphology. However, the effects of DFO on mitochondrial heat shock proteins (HSPs) remain poorly understood. In this study, we examined the effect of DFO on tumor necrosis factor receptor-associated protein 1 (TRAP1), a representative mitochondrial HSP, in a normal human hepatocyte cell line, Chang cells. DFO specifically decreased TRAP1 levels, increasing reactive oxygen species (ROS) and caveolin-1 (Cav-1), a marker protein of senescence. To examine whether these effects of DFO are reversed, we established TRAP1-overexpressing Chang cells. DFO treatment to TRAP1-overexpressing cells resulted in decreases in levels of ROS, Cav-1, glutathione peroxidase (GPX), and manganese superoxide dismutase (MnSOD) levels as well as senescence-associated beta-galactosidase (SA beta-gal) activity. These results suggest that TRAP1 might play a role in protecting mitochondria against damaging stimuli via decrease of ROS generation.

Cell Line↗