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I Activity (i + activity)
Kinds of I Activity Selected AbstractsS-Adenosyl-L-Methionine Co-administration Prevents the Ethanol-Elicited Dissociation of Hepatic Mitochondrial Ribosomes in Male RatsALCOHOLISM, Issue 1 2009Peter Sykora Background:, Chronic ethanol feeding to male rats has been shown to result in decreased mitochondrial translation, depressed respiratory complex levels and mitochondrial respiration rates. In addition, ethanol consumption has been shown to result in an increased dissociation of mitoribosomes. S-adenosyl-L-methionine (SAM) is required for the assembly and subsequent stability of mitoribosomes and is depleted during chronic ethanol feeding. The ability of dietary SAM co-administration to prevent these ethanol-elicited lesions was investigated. Methods:, Male Sprague-Dawley rats were fed a nutritionally adequate liquid diet with ethanol comprising 36% of the calories according to a pair-fed design for 28 days. For some animals, SAM was supplemented in the diet at 200 mg/l. Liver mitochondria were prepared and mitoribosomes isolated. Respiration rates, ATP levels, respiratory complex levels, and the extent of mitoribosome dissociation were determined. Results:, Twenty-eight days of ethanol feeding were found to result in decreased SAM content, depressed respiration, and increased mitoribosome dissociation. No changes in mitochondrial protein content; levels of respiratory complexes I, III, and V; complex I activities; and ATP levels were detected. Co-administration of SAM in the diet was found to prevent ethanol-induced SAM depletion, respiration decreases and mitoribosome dissociation. Conclusions:, Taken together, these findings suggest (1) that mitoribosome dissociation precedes respiratory complex depressions in alcoholic animals and (2) that dietary supplementation of SAM prevents some of the early mitochondrial lesions associated with chronic ethanol consumption. [source] 3241: Effect of glutaredoxin 2 gene knockout on lens epithelial cells against oxidative stressACTA OPHTHALMOLOGICA, Issue 2010M LOU Purpose The mitochondrial glutaredoxin 2 (Grx2) is known to possess both dethiolase and peroxidase activities, and has shown an ability to protect cells from oxidative stress-induced apoptosis in the human lens epithelial cells. In this study, we further studied the function of Grx2 by using Grx2 knockout mouse lens epithelial (MLE) cells as a model. Methods Primary culture of MLE cells was established from the lenses of wild-type (WT) and Grx2-knockout (Grx2 KO) mice. Cells were probed for ,A-crystallin and Grx2 by Western blot analysis while cell viability was examined by WST-8 assay. Glutathione (GSH) level, Grx2 and Complex I activities, and lactate dehydrogenase (LDH) release were determined by spectrophotometric assays. Reactive oxygen species was detected using DCF-DA fluorescein with a cell sorter. Apoptosis was quantified by flow cytometry. Results Both primary cell cultures were confirmed to be lens epithelial cells by the presence of ,A-crystallin. Western blotting showed normal expression of Grx2 in WT cells but absent in Grx2 KO cells. Both cell types showed similar morphology and growth rate with same level of GSH pool and complex 1 activity in the mitochondrial fraction. However, KO cells were more sensitive to oxidative stress (100 ,M H2O2 for 6 h) and exhibited lower cell viability and more LDH leakage in comparison with the WT cells. In addition, knockdown of Grx2 weakened the cell's ability to detoxify H2O2 and enhanced the H2O2-induced inactivation of complex I in the electron transport chain. Conclusion Grx2 can protect MLE cells from H2O2-induced cell injury, and the mechanism of this protection is likely associated with its ability to detoxify H2O2 and its preservation of complex I activity in the mitochondria. [source] Hypoxia induces complex I inhibition and ultrastructural damage by increasing mitochondrial nitric oxide in developing CNSEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008Sebastián Giusti Abstract NO-mediated toxicity contributes to neuronal damage after hypoxia; however, the molecular mechanisms involved are still a matter of controversy. Since mitochondria play a key role in signalling neuronal death, we aimed to determine the role of nitrative stress in hypoxia-induced mitochondrial damage. Therefore, we analysed the biochemical and ultrastructural impairment of these organelles in the optic lobe of chick embryos after in vivo hypoxia,reoxygenation. Also, we studied the NO-dependence of damage and examined modulation of mitochondrial nitric oxide synthase (mtNOS) after the hypoxic event. A transient but substantial increase in mtNOS content and activity was observed at 0,2 h posthypoxia, resulting in accumulation of nitrated mitochondrial proteins measured by immunoblotting. However, no variations in nNOS content were observed in the homogenates, suggesting an increased translocation to mitochondria and not a general de novo synthesis. In parallel with mtNOS kinetics, mitochondria exhibited prolonged inhibition of maximal complex I activity and ultrastructural phenotypes associated with swelling, namely, fading of cristae, intracristal dilations and membrane disruption. Administration of the selective nNOS inhibitor 7-nitroindazole 20 min before hypoxia prevented complex I inhibition and most ultrastructural damage. In conclusion, we show here for the first time that hypoxia induces NO-dependent complex I inhibition and ultrastructural damage by increasing mitochondrial NO in the developing brain. [source] Vitamins E and C prevent the impairment of retention of an inhibitory avoidance task caused by arginine administrationJOURNAL OF NEUROCHEMISTRY, Issue 2002E. A. Reis Hyperargininemia is an inherited metabolic disease of urea cycle caused by the deficiency of arginase I activity, resulting in tissue accumulation of arginine (Arg). Patients affected by this disease usually develop spasticity, epilepsy and mental retardation as principal symptoms. Previous studies from our laboratory have showed that acute administration of Arg impairs retention of the inhibitory avoidance task and that l -NAME (NOS inhibitor) prevents this effect. In the present study, we investigated the effect of chronic treatment with antioxidants (vitamins E and C) on the retrieval of the inhibitory avoidance task in adults rats subjected to experimental model of acute hyperargininemia in order to investigate the participation of oxidative stress on this phenomenon. Sixty-day-old-rats were treated for one week with i.p. injection of saline (0.9%) or vitamins E and C (vit E 40 mg/kg and vit C 100 mg/kg). Twelve hours after the last injection Arg (0.8 g/kg) or an equivalent volume of saline were administered 1 h before training, 1 h before testing or immediately after training sessions. Memory was significantly impaired in Arg-treated group, whereas the rats chronically treated with vitamins E and C had this effect prevented. Present data strongly indicate that Arg administration impairs memory, an effect probably mediated by oxidative stress since treatment with vitamins E and C prevented amnesia. Assuming the possibility that this might occur in the human condition, reported results may be relevant to explain, at least in part, neurologic dysfunction associated with hyperargininemia. [source] Bioenergetics in the pathogenesis of neurodegenerationJOURNAL OF NEUROCHEMISTRY, Issue 2001M. Flint Beal Evidence implicating both mitochondria and bioenergetics as playing a crucial role in necrotic and apoptotic cell death is rapidly accumulating. Mitochondria are essential in controlling specific apoptosis cell death pathways and they are the major source of free radicals in the cell. Direct evidence for a role of mitochondria in neurodegenerative diseases comes from studies in Friedreich's Ataxia. Mutations in frataxin lead to an accumulation of iron within mitochondria. We found a three-fold increase in a marker of oxidative damage to DNA in the urine of patients with Friedreich's Ataxia. There is evidence for mitochondrial defects in patients with amyotrophic lateral sclerosis (ALS). There are mitochondrial abnormalities in liver biopsies and muscle biopsies from individuals with sporadic ALS. Muscle biopsies have shown reduced complex I activity in patients with sporadic ALS. A study of ALS cybrids showed a significant decrease in complex I activity as well as trends towards reduced complex 3 and 4 activities. We found increased levels of 8-hydroxy-2-deoxyguanosine, a marker of oxidative damage to DNA in the plasma, urine and CSF of sporadic ALS patients and increased numbers of point mutations in mtDNA of ALS spinal cord tissue. There is mitochondrial vacuolization in transgenic mouse models of ALS. We found substantial evidence for mitochondrial dysfunction in Huntington's Disease (HD). In HD postmortem brain tissue, there are significant reductions in complex 2, 3 activity. We also demonstrated increased brain lactate concentrations as well as reduced phosphocreatine to inorganic phosphate ratio in the resting muscle of patients with HD. More recent studies have demonstrated that there is abnormal depolarization of mitochondria of HD lymphoblasts, which directly correlates with CAG repeat length. There are reductions in ATP production in muscle are both presymptomatic and symptomatic HD patients. Transgenic mouse models of HD show significant reductions in N-acetylaspartate concentrations, which precede the onset of neuronal degeneration. We investigated a number of therapeutic interventions in both transgenic mouse models of ALS and HD. In transgenic ALS mice we found that oral administration of creatine dose-dependently extends survival and reduces the neuronal degeneration in the spinal cord. We found modest protection with ginkgo biloba and lipoic acid. In the HD mice we found significant improvement with oral administration of creatine in two different transgenic mouse models. Creatine not only extended survival but it also improved motor performance, delayed weight loss and attenuated striatal atrophy. Creatine significantly attenuated reductions in N-acetylaspartate concentrations as assessed using magnetic resonance spectroscopy. We also found significant neuroprotective effects with dichloroacetate, which stimulates pyruvate dehydrogenase. These findings implicate bioenergetic dysfunction in transgenic mouse models of both ALS and HD, and they suggest several novel therapeutic strategies aimed at energy replenishment. [source] Hexokinase II gene transfer protects against neurodegeneration in the rotenone and MPTP mouse models of Parkinson's disease,JOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2010Juan Carlos Corona Abstract A typical feature of Parkinson's disease is the progressive loss of dopaminergic neurons in the substantia nigra, in which inhibition of mitochondrial complex I activity may play an important role. Rotenone or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) inhibit the mitochondrial complex I and they cause the death of substantia nigra dopaminergic neurons, thereby providing acute murine models of Parkinson's disease. We have found that increasing mitochondrial hexokinase II activity can prevent cell death in neuronal cultures treated with rotenone. As a result, we have studied the effects of hexokinase II gene transfer in vivo using a herpes simplex virus type 1 (HSV-1) amplicon vector. The placHK2 amplicon vector was injected into substantia nigra of mice that were subsequently administered rotenone or MPTP. Overexpression of hexokinase II prevented both rotenone and MPTP-induced dopaminergic neuronal cell death, as well as reducing the associated motor defects. Our results provide the first proof-of-principle that hexokinase II protects against dopaminergic neurodegeneration in vivo, emphasizing the role of this enzyme in promoting neuronal survival. Thus, the increase of hexokinase II expression by gene transfer or other means represents a promising approach to treat Parkinson's and other neurodegenerative diseases. © 2010 Wiley-Liss, Inc. [source] A Mutation in Mitochondrial Complex I Increases Ethanol Sensitivity in Caenorhabditis elegansALCOHOLISM, Issue 4 2003Ernst-Bernhard Kayser Background: The gene gas-1 encodes the 49-kDa subunit of complex I of the mitochondrial electron transport chain in Caenorhabditis elegans. A mutation in gas-1 profoundly increases sensitivity to ethanol and decreases complex I-dependent metabolism in mitochondria. Methods: Mitochondria were isolated from wild-type and gas-1 strains of C. elegans. The effects of ethanol on complex I-, II-, and III-dependent oxidative phosphorylation were measured for mitochondria from each strain. Reversibility of the effects of ethanol was determined by measuring oxidative phosphorylation after removal of mitochondria from 1.5 M ethanol. The effects of ethanol on mitochondrial structure were visualized with electron microscopy. Results: We found that ethanol inhibited complex I,, II,, and III,dependent oxidative phosphorylation in isolated wild-type mitochondria at concentrations that immobilize intact worms. It is important to note that the inhibitory effects of ethanol on mitochondria from either C. elegans or rat skeletal muscle were reversible even at molar concentrations. Complex I activity was lower in mitochondria from gas-1 animals than in mitochondria from wild-type animals at equal ethanol concentrations. Complex II activity was higher in gas-1 than in wild-type mitochondria at all concentrations of ethanol. No difference was seen between the strains in the sensitivity of complex III to ethanol. Conclusions: The difference in ethanol sensitivities between gas-1 and wild-type nematodes results solely from altered complex I function. At the respective concentrations of ethanol that immobilize whole animals, mitochondria from each strain of worms displayed identical rates of complex I-dependent state 3 respiration. We conclude that a threshold value of complex I activity controls the transition from mobility to immobility of C. elegans. [source] Salt- and glyphosate-induced increase in glyoxalase I activity in cell lines of groundnut (Arachis hypogaea)PHYSIOLOGIA PLANTARUM, Issue 4 2002Mukesh Jain Glyoxalase I (EC 4.4.1.5) activity has long been associated with rapid cell proliferation, but experimental evidence is forthcoming, linking its role to stress tolerance as well. Proliferative callus cultures of groundnut (Arachis hypogaea L. cv. JL24) showed a 3.3-fold increase in glyoxalase I activity during the logarithmic growth phase, correlating well with the data on FW gain and mitotic index. Inhibition of cell division decreased glyoxalase I activity and vice versa, thus further corroborating its role as a cell division marker enzyme. Cell lines of A. hypogaea selected in the presence of high salt (NaCl) and herbicide (glyphosate) concentrations, yielded 4.2- to 4.5-fold and 3.9- to 4.6-fold elevated glyoxalase I activity, respectively, in a dose dependent manner reflective of the level of stress tolerance. The stress-induced increase in enzyme activity was also accompanied by an increase in the glutathione content. Exogenous supplementation of glutathione could partially alleviate the growth inhibition of callus cultures induced by methylglyoxal and d -isoascorbic acid, but failed to recover the loss in glyoxalase I activity due to d -isoascorbic acid. The adaptive significance of elevated glyoxalase I activity in maintaining glutathione homeostasis has been discussed in view of our understanding on the role of glutathione in the integration of cellular processes with plant growth and development under stress conditions. [source] Ligand binding to the inhibitory and stimulatory GTP cyclohydrolase I/GTP cyclohydrolase I feedback regulatory protein complexesPROTEIN SCIENCE, Issue 4 2001Toshie Yoneyama BH4, 6R - l - erythro -5,6,7,8-tetrahydrobiopterin; GFRP, GTP cyclohydrolase I feedback regulatory protein Abstract GTP cyclohydrolase I feedback regulatory protein (GFRP) mediates feedback inhibition of GTP cyclohydrolase I activity by 6R - l - erythro -5,6,7,8-tetrahydrobiopterin (BH4), which is an essential cofactor for key enzymes producing catecholamines, serotonin, and nitric oxide as well as phenylalanine hydroxylase. GFRP also mediates feed-forward stimulation of GTP cyclohydrolase I activity by phenylalanine at subsaturating GTP levels. These ligands, BH4 and phenylalanine, induce complex formation between one molecule of GTP cyclohydrolase I and two molecules of GFRP. Here, we report the analysis of ligand binding using the gel filtration method of Hummel and Dreyer. BH4 binds to the GTP cyclohydrolase I/GFRP complex with a Kd of 4 ,M, and phenylalanine binds to the protein complex with a Kd of 94 ,M. The binding of BH4 is enhanced by dGTP. The binding stoichiometrics of BH4 and phenylalanine were estimated to be 10 molecules of each per protein complex, in other words, one molecule per subunit of protein, because GTP cyclohydrolase I is a decamer and GFRP is a pentamer. These findings were corroborated by data from equilibrium dialysis experiments. Regarding ligand binding to free proteins, BH4 binds weakly to GTP cyclohydrolase I but not to GFRP, and phenylalanine binds weakly to GFRP but not to GTP cyclohydrolase I. These results suggest that the overall structure of the protein complex contributes to binding of BH4 and phenylalanine but also that each binding site of BH4 and phenylalanine may be primarily composed of residues of GTP cyclohydrolase I and GFRP, respectively. [source] Neuroprotective effects of zonisamide target astrocyteANNALS OF NEUROLOGY, Issue 2 2010Masato Asanuma MD Objective Recent double-blind, controlled trials in Japan showed that the antiepileptic agent zonisamide (ZNS) improves the cardinal symptoms of Parkinson's disease. Glutathione (GSH) exerts antioxidative activity through quenching reactive oxygen species and dopamine quinone. GSH depletion within dopaminergic neurons impairs mitochondrial complex I activity, followed by age-dependent nigrostriatal neurodegeneration. This study examined changes in GSH and GSH synthesis-related molecules, and the neuroprotective effects of ZNS on dopaminergic neurodegeneration using 6-hydroxydopamine,injected hemiparkinsonian mice brain and cultured neurons or astrocytes. Methods and Results ZNS increased both the cell number and GSH levels in astroglial C6 cells, but not in dopaminergic neuronal CATH.a cells. Repeated injections of ZNS (30mg/kg intraperitoneally) for 14 days also significantly increased GSH levels and S100,-positive astrocytes in mouse basal ganglia. Repeated ZNS injections (30mg/kg) for 7 days in the hemiparkinsonian mice increased the expression of cystine/glutamate exchange transporter xCT in activated astrocytes, which supply cysteine to neurons for GSH synthesis. Treatment of these mice with ZNS also increased GSH levels and completely suppressed striatal levodopa,induced quinone formation. Reduction of nigrostriatal dopamine neurons in the lesioned side of hemiparkinsonian mice was significantly abrogated by repeated injections of ZNS with or without adjunctive levodopa starting 3 weeks after 6-hydroxydopamine lesioning. Interpretation These results provide new pharmacological evidence for the effects of ZNS. ZNS markedly increased GSH levels by enhancing the astroglial cystine transport system and/or astroglial proliferation via S100, production or secretion. ZNS acts as a neuroprotectant against oxidative stress and progressive dopaminergic neurodegeneration. ANN NEUROL 2010;67:239,249 [source] Is the mitochondrial complex I ND5 gene a hot-spot for MELAS causing mutations?ANNALS OF NEUROLOGY, Issue 1 2003Danae Liolitsa PhD We identified two novel heteroplasmic mitochondrial DNA point mutations in the gene encoding the ND5 subunit of complex I: a 12770A,G transition identified in a patient with MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) and a 13045A,C transversion in a patient with a MELAS/Leber's hereditary optic neuropathy/Leigh's overlap syndrome. Biochemical analysis of muscle homogenates showed normal or very mildly reduced complex I activity. Histochemistry was normal. Our observations add to the evidence that mitochondrial ND5 protein coding gene mutations frequently associate with the MELAS phenotype, and it highlights the role of complex I dysfunction in MELAS. Ann Neurol 2003 [source] Novel heteroplasmic mutation in the anticodon stem of mitochondrial tRNALys associated with dystonia and stroke-like episodesACTA NEUROLOGICA SCANDINAVICA, Issue 4 2010A. Gal Gal A, Pentelenyi K, Remenyi V, Pal Z, Csanyi B, Tomory G, Rasko I, Molnar MJ. Novel heteroplasmic mutation in the anticodon stem of mitochondrial tRNALys associated with dystonia and stroke-like episodes. Acta Neurol Scand: 2010: 122: 252,256. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objectives,,, We report a novel heteroplasmic mitochondrial tRNALys mutation associated with dystonia, stroke-like episodes, sensorineural hearing loss and epilepsy in a Hungarian family. Material and methods,,, A 16-year-old boy, his brother and mother were investigated. Thorough clinical investigation as well as electrophysiological, neuroradiological and myopathological examinations were performed. Molecular studies included the analysis of the DYT1, DDP1/TIMM8A (deafness-dystonia peptid-1) genes and mitochondrial DNA (mtDNA). Results,, The mtDNA analysis of the proband revealed a heteroplasmic A8332G substitution in the anticodon stem of the tRNALys gene. The mutation segregated in all affected family members. Besides this mutation 16 further mtDNA polymorphisms were detected. Complex I activity of the patient's fibroblast cultures showed decreased activity confirming mitochondrial dysfunction. Conclusion,, The novel A8332G heteroplasmic mutation is most likely a new cause of dystonia and stroke-like episodes due to mitochondrial encephalopathy. The synergistic effect of the G8697A, A11812G and T10463C single nucleotide polymorphisms may modify the phenotype. [source] 3241: Effect of glutaredoxin 2 gene knockout on lens epithelial cells against oxidative stressACTA OPHTHALMOLOGICA, Issue 2010M LOU Purpose The mitochondrial glutaredoxin 2 (Grx2) is known to possess both dethiolase and peroxidase activities, and has shown an ability to protect cells from oxidative stress-induced apoptosis in the human lens epithelial cells. In this study, we further studied the function of Grx2 by using Grx2 knockout mouse lens epithelial (MLE) cells as a model. Methods Primary culture of MLE cells was established from the lenses of wild-type (WT) and Grx2-knockout (Grx2 KO) mice. Cells were probed for ,A-crystallin and Grx2 by Western blot analysis while cell viability was examined by WST-8 assay. Glutathione (GSH) level, Grx2 and Complex I activities, and lactate dehydrogenase (LDH) release were determined by spectrophotometric assays. Reactive oxygen species was detected using DCF-DA fluorescein with a cell sorter. Apoptosis was quantified by flow cytometry. Results Both primary cell cultures were confirmed to be lens epithelial cells by the presence of ,A-crystallin. Western blotting showed normal expression of Grx2 in WT cells but absent in Grx2 KO cells. Both cell types showed similar morphology and growth rate with same level of GSH pool and complex 1 activity in the mitochondrial fraction. However, KO cells were more sensitive to oxidative stress (100 ,M H2O2 for 6 h) and exhibited lower cell viability and more LDH leakage in comparison with the WT cells. In addition, knockdown of Grx2 weakened the cell's ability to detoxify H2O2 and enhanced the H2O2-induced inactivation of complex I in the electron transport chain. Conclusion Grx2 can protect MLE cells from H2O2-induced cell injury, and the mechanism of this protection is likely associated with its ability to detoxify H2O2 and its preservation of complex I activity in the mitochondria. [source] NOVEL MITOCHONDRIAL DNA MUTATIONS ASSOCIATED WITH CHINESE FAMILIAL HYPERTROPHIC CARDIOMYOPATHYCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2009Yan-Ling Wei SUMMARY 1Hypertrophic cardiomyopathy (HCM) is a genetic disorder that has a complex set of symptoms and potentially devastating consequences. Increasing evidence indicates that mitochondrial DNA (mtDNA) mutations are responsible for the development of HCM, but the mtDNA mutations appear to differ considerably among different populations and regions. 2In the present study, three families with HCM were found and investigated: one in Shandong province and two in the Chongqing region of China. The entire mtDNA genome from the 18 affected and 66 unaffected family members was sequenced directly and the mtDNA mutations were determined. 3The frequency of haplogroup M10 was significantly higher in family members with HCM (HCM group) than in unaffected family members (normal group). Three mtDNA mutations were found with a significantly higher frequency in affected individuals than in unaffected family individuals, namely G7697A in the cytochrome c oxidase subunit II gene (P < 0.0001; odds ratio (OR) 227.5; 95% confidence interval (CI) 23.6,2194.8) and T12477C (P = 0.0037; OR 5.6; 95% CI 1.8,17.6) and G13135A in the NADH dehydrogenase 5 gene (P < 0.0001; OR 26.0; 95% CI 6.9,98.3), suggesting that these mutations are probably associated with susceptibility to HCM. In addition, mitochondrial Complex I activity was markedly decreased in the HCM group, suggesting that these mutations most likely affect mitochondrial respiratory function. 4In conclusion, the results of the present study imply that mtDNA mutations G7697A, T12477C and G13135A are genetic factors that indicate a susceptibility to HCM and that could be used for the large-scale screening of genetic markers as well as the early diagnosis of HCM. [source] | |||||||||||||