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PubMed2005

Impaired mitochondrial response to simulated ischemic injury as a predictor of the development of atrial fibrillation after cardiac surgery: in vitro study in human myocardium.

OBJECTIVE: Atrial fibrillation occurs in 20% to 40% of patients after cardiac surgery, but its pathophysiology remains unclear. Recent studies demonstrated preexisting histologic markers that portend the development of postoperative atrial fibrillation. In this prospective study, we focused on mitochondrial dysfunction in response to ischemic stress as a potential predictor for postoperative atrial fibrillation. METHODS: Slices of right atrial trabeculae from 50 patients undergoing elective cardiac surgery were surperfused with oxygenated glucose-containing phosphate-buffered saline solution. After 30 minutes of stabilization, the sections were exposed to 90 minutes of simulated ischemia (nitrogenated phosphate-buffered saline solution without glucose) followed by 90 minutes of reoxygenation (reintroduction of the oxygenated solution). Mitochondrial viability and response were measured by staining with 3-[4.5 dimethylthiazol 2-yl]-2,5-diphenyltetrazolium bromide. The magnitudes of mitochondrial recovery after simulated ischemia and 28 possible risk factors for postoperative atrial fibrillation were entered into univariate and multivariate models. RESULTS: There were no deaths in this group of patients. Nineteen patients (38%) had postoperative atrial fibrillation. Interestingly, no difference in baseline (before simulated ischemia) mitochondrial function was documented between patients who had postoperative atrial fibrillation and those who did not. An independent predictor for postoperative atrial fibrillation was the degree of mitochondrial dysfunction in response to simulated ischemia, as measured by the intensity of the staining. CONCLUSION: This study has identified for the first time an association between mitochondrial dysfunction in response to ischemia and postoperative atrial fibrillation. This finding improves our understanding of the pathophysiology of postoperative atrial fibrillation and may eventually lead us to identify candidates for selective preoperative or early postoperative prophylactic treatment.

Aged↗
PubMed2006

A ketogenic diet as a potential novel therapeutic intervention in amyotrophic lateral sclerosis.

BACKGROUND: The cause of neuronal death in amyotrophic lateral sclerosis (ALS) is uncertain but mitochondrial dysfunction may play an important role. Ketones promote mitochondrial energy production and membrane stabilization. RESULTS: SOD1-G93A transgenic ALS mice were fed a ketogenic diet (KD) based on known formulations for humans. Motor performance, longevity, and motor neuron counts were measured in treated and disease controls. Because mitochondrial dysfunction plays a central role in neuronal cell death in ALS, we also studied the effect that the principal ketone body, D-beta-3 hydroxybutyrate (DBH), has on mitochondrial ATP generation and neuroprotection. Blood ketones were > 3.5 times higher in KD fed animals compared to controls. KD fed mice lost 50% of baseline motor performance 25 days later than disease controls. KD animals weighed 4.6 g more than disease control animals at study endpoint; the interaction between diet and change in weight was significant (p = 0.047). In spinal cord sections obtained at the study endpoint, there were more motor neurons in KD fed animals (p = 0.030). DBH prevented rotenone mediated inhibition of mitochondrial complex I but not malonate inhibition of complex II. Rotenone neurotoxicity in SMI-32 immunopositive motor neurons was also inhibited by DBH. CONCLUSION: This is the first study showing that diet, specifically a KD, alters the progression of the clinical and biological manifestations of the G93A SOD1 transgenic mouse model of ALS. These effects may be due to the ability of ketone bodies to promote ATP synthesis and bypass inhibition of complex I in the mitochondrial respiratory chain.

Amyotrophic Lateral Sclerosis↗
PubMed2004

Synergistic induction of oxidative injury and apoptosis in human multiple myeloma cells by the proteasome inhibitor bortezomib and histone deacetylase inhibitors.

PURPOSE: The purpose of this study was to examine interactions between the proteasome inhibitor bortezomib (Velcade) and the histone deacetylase (HDAC) inhibitors sodium butyrate and suberoylanilide hydroxamic acid in human multiple myeloma (MM) cells that are sensitive and resistant to conventional agents. EXPERIMENTAL DESIGN: MM cells were exposed to bortezomib for 6 h before the addition of HDAC inhibitors (total, 26 h), after which reactive oxygen species (ROS), mitochondrial dysfunction, signaling and cell cycle pathways, and apoptosis were monitored. The functional role of ROS generation was assessed using the free radical scavenger N-acetyl-l-cysteine. RESULTS: Preincubation with a subtoxic concentration of bortezomib markedly sensitized U266 and MM.1S cells to sodium butyrate- and suberoylanilide hydroxamic acid-induced mitochondrial dysfunction; caspase 9, 8, and 3 activation; and poly(ADP-ribose) polymerase degradation; resulting in synergistic apoptosis induction. These events were associated with nuclear factor kappaB inactivation, c-Jun NH(2)-terminal kinase activation, p53 induction, and caspase-dependent cleavage of p21(CIP1), p27(KIP1), and Bcl-2, as well as Mcl-1, X-linked inhibitor of apoptosis, and cyclin D1 down-regulation. The bortezomib/HDAC inhibitor regimen markedly induced ROS generation; moreover, apoptosis and c-Jun NH(2)-terminal kinase activation were attenuated by N-acetyl-l-cysteine. Dexamethasone- or doxorubicin-resistant MM cells failed to exhibit cross-resistance to the bortezomib/HDAC inhibitor regimen, nor did exogenous interleukin 6 or insulin-like growth factor I block apoptosis induced by this drug combination. Finally, bortezomib/HDAC inhibitors induced pronounced lethality in primary CD138(+) bone marrow cells from MM patients, but not in the CD138(-) cell population. CONCLUSIONS: Sequential exposure to bortezomib in conjunction with clinically relevant HDAC inhibitors potently induces mitochondrial dysfunction and apoptosis in human MM cells through a ROS-dependent mechanism, suggesting that a strategy combining these agents warrants further investigation in MM.

Acetylcysteine↗
PubMed2002

Protective effects of rilmenidine and AGN 192403 on oxidative cytotoxicity and mitochondrial inhibitor-induced cytotoxicity in astrocytes.

Oxidative stress and mitochondrial dysfunction are important aspects of pathogenesis, particularly in the brain, which is highly dependent on oxygen, and the protection of astrocytes is essential for neuroprotection. In this context, imidazoline drugs have been reported to be neuroprotective. Our recent study showed that imidazoline drugs, including guanabenz, inhibit the naphthazarin-induced oxidative cytotoxicity associated with lysosomal destabilization. We now report on a study into the protective effects of rilmenidine and AGN 192403, which have affinity for imidazoline-1 receptors, on the cytotoxicity induced by naphthazarin and inhibitors of mitochondrial respiration in astrocytes. Cytotoxicity was measured grossly by LDH release and by measuring changes in lysosomal membrane stability and features of mitochondrial membrane permeabilization. Naphthazarin-induced cytotoxicity was evidenced by the ordered development of lysosomal acridine orange relocation, decrease in mitochondrial potential, cytochrome c release, and caspase-9 activation, and was inhibited by guanabenz, rilmenidine, and AGN 192403. Antimycin A and rotenone induced mitochondrial dysfunction primarily, and their cytotoxicities were inhibited only by AGN 192403. Rilmenidine and guanabenz may have a lysosomal stabilizing effect, which underlies their protective effects. AGN 192403 might affect the mitochondrial cell death cascades, and had a novel protective effect on the cytotoxicity associated with mitochondrial dysfunction.

Animals↗
PubMed2004

Apoptosis signaling triggered by the marine alkaloid ascididemin is routed via caspase-2 and JNK to mitochondria.

The marine alkaloid ascididemin (ASC) was shown to exert cytotoxicity even against multidrug-resistant cancer cells. Here, we address the signaling pathways utilized by ASC to trigger apoptosis in Jurkat leukemia T cells. We show that ASC (0.5-20 microM) induces a mitochondrial pathway that requires the activation of the initiator caspase-2 upstream of mitochondria. ASC-triggered apoptosis occurred independent of CD95, but required mitochondrial dysfunction. The activation of caspase-2 was shown to precede the processing of caspase-8, -9 and -3. The specific caspase-2 inhibitor zVDVADfmk abrogated ASC-induced DNA fragmentation almost completely. Overexpression of Bcl-x(L) blocked caspase-8 but not caspase-2 processing. Conversely, caspase-2 inhibition strongly reduced caspase-9 activation. As a possible link between caspase-2 and mitochondrial dysfunction, Bid was found to be cleaved by ASC. In addition, JNK was activated by ASC upstream of mitochondria via reactive oxygen species. The specific JNK inhibitor SP600125 partially inhibited caspase-2 and -9 processing as well as cytochrome c release and DNA fragmentation indicating that JNK contributes to, but is not necessary for ASC-mediated apoptosis. Thus, ASC triggers a pathway in which early activation of caspase-2 provides a possible link between its DNA-damaging activity and the induction of mitochondrial dysfunction. The activation of JNK contributes to this signaling upstream of mitochondria.

Alkaloids↗
PubMed2000

Nucleoside exposure in the children of HIV-infected women receiving antiretroviral drugs: absence of clear evidence for mitochondrial disease in children who died before 5 years of age in five United States cohorts.

BACKGROUND: Nucleoside reverse transcriptase inhibitors (NRTIs) have been associated with mitochondrial toxicity in individuals receiving treatment. A report of two deaths in Europe attributed to mitochondrial dysfunction in HIV-uninfected infants with perinatal NRTI exposure prompted a review of five U.S. cohorts. METHODS: Deaths in HIV-exposed children <60 months of age and HIV-uninfected or indeterminate were reviewed. Review included birth history; perinatal antiretroviral drug exposure; hospital, laboratory, and clinic records; death reports; autopsy results; and local physician queries. Deaths were classified as unrelated (Class 1), unlikely related (Class 2), possibly related (Class 3), or highly suggestive or proven relationship (Class 4), to mitochondrial dysfunction; sudden infant death syndrome (SIDS) was categorized separately. RESULTS AND CONCLUSIONS: Among over 20,000 children of HIV-infected women, over half of whom had been exposed to NRTIs, 223 died. In HIV-uninfected children, 26 deaths were attributed to Class 1, and 4 were attributed to SIDS. In HIV-indeterminate children, 141, 10, 3, and 0 were Classes 1, 2, 3, and 4, respectively; 33 were due to SIDS and 6 could not be classified. There was no indication that antiretroviral exposure was associated with Class 2 or 3 deaths, or deaths from SIDS. A search for mitochondrial dysfunction among living children in these cohorts is ongoing.

Anti-HIV Agents↗
PubMed2006

Molecular neuropathology of MELAS: level of heteroplasmy in individual neurones and evidence of extensive vascular involvement.

Mitochondrial DNA (mtDNA) disease is an important genetic cause of neurological disability. A variety of different clinical features are observed and one of the most common phenotypes is MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis and Stroke-like episodes). The majority of patients with MELAS have the 3243A>G mtDNA mutation. The neuropathology is dominated by multifocal infarct-like lesions in the posterior cortex, thought to underlie the stroke-like episodes seen in patients. To investigate the relationship between mtDNA mutation load, mitochondrial dysfunction and neuropathological features in MELAS, we studied individual neurones from several brain regions of two individuals with the 3243A>G mutation using dual cytochrome c oxidase (COX) and succinate dehydrogenase (SDH) histochemistry, and Polymerase Chain Reaction Restriction Fragment Lenght Polymorphism (PCR-RFLP) analysis. We found a low number of COX-deficient neurones in all brain regions. There appeared to be no correlation between the threshold level for the 3243A>G mutation to cause COX deficiency within single neurones and the degree of pathology in affected brain regions. The most severe COX deficiency associated with the highest proportion of mutated mtDNA was present in the walls of the leptomeningeal and cortical blood vessels in all brain regions. We conclude that vascular mitochondrial dysfunction is important in the pathogenesis of the stroke-like episodes in MELAS patients. As migraine is a commonly encountered feature in MELAS, we propose that coupling of the vascular mitochondrial dysfunction with cortical spreading depression (CSD) might underlie the selective distribution of ischaemic lesions in the posterior cortex in these patients.

Adult↗
PubMed2006

Poly(ADP-ribose) polymerase-1 signaling to mitochondria in necrotic cell death requires RIP1/TRAF2-mediated JNK1 activation.

Poly(ADP-ribose) polymerase-1 (PARP-1) hyperactivation-induced necrosis has been implicated in several pathophysiological conditions. Although mitochondrial dysfunction and apoptosis-inducing factor translocation from the mitochondria to the nucleus have been suggested to play very important roles in PARP-1-mediated cell death, the signaling events downstream of PARP-1 activation in initiating mitochondria dysfunction are not clear. Here we used the DNA alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine, a potent PARP-1 activator, to study PARP-1 activation-mediated cell death. We found, based on genetic knockouts and pharmacological inhibition, that c-Jun N-terminal kinase (JNK), especially JNK1, but not the other groups of mitogen-activated protein kinase, is required for PARP-1-induced mitochondrial dysfunction, apoptosis-inducing factor translocation, and subsequent cell death. We reveal that receptor-interacting protein 1 (RIP1) and tumor necrosis factor receptor-associated factor 2 (TRAF2), are upstream of JNK in PARP-1 hyperactivated cells, because PARP-1-induced JNK activation was attenuated in RIP1-/- and TRAF2-/- mouse embryonic fibroblast cells. Consistently, knockouts of RIP1 and TRAF2 caused a resistance to PARP-1-induced cell death. Therefore, our study uncovers that RIP1, TRAF2, and JNK comprise a pathway to mediate the signaling from PARP-1 overactivation to mitochondrial dysfunction.

Animals↗
PubMed2002

Alterations in mitochondrial function in a mouse model of hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy (HCM) is an autosomal dominant disease characterized by varying degrees of ventricular hypertrophy and myofibrillar disarray. Mutations in cardiac contractile proteins cause HCM. However, there is an unexplained wide variability in the clinical phenotype, and it is likely that there are multiple contributing factors. Because mitochondrial dysfunction has been described in heart disease, we tested the hypothesis that mitochondrial dysfunction contributes to the varying HCM phenotypes. Mitochondrial function was assessed in two transgenic models of HCM: mice with a mutant myosin heavy chain gene (MyHC) or with a mutant cardiac troponin T (R92Q) gene. Despite mitochondrial ultrastructural abnormalities in both models, the rate of state 3 respiration was significantly decreased only in the mutant MyHC mice by approximately 23%. Notably, this decrease in state 3 respiration preceded hemodynamic dysfunction. The maximum activity of alpha-ketogutarate dehydrogenase as assayed in isolated disrupted mitochondria was decreased by 28% compared with isolated control mitochondria. In addition, complexes I and IV were decreased in mutant MyHC transgenic mice. Inhibition of beta-adrenergic receptor kinase, which is elevated in mutant MyHC mouse hearts, can prevent mitochondrial respiratory impairment in mutant MyHC mice. Thus our results suggest that mitochondria may contribute to the hemodynamic dysfunction seen in some forms of HCM and offer a plausible mechanism responsible for some of the heterogeneity of the disease phenotypes.

Animals↗
PubMed2002

Mitochondrial DNA deletions/rearrangements in parkinson disease and related neurodegenerative disorders.

Inhibition of mitochondrial respiratory chain function may contribute to dopaminergic neurodegeneration in the substantia nigra (SN) of patients with Parkinson disease (PD). Since large-scale structural changes (e.g. deletions and rearrangements in mitochondrial DNA [mtDNA]) have been associated with mitochondrial dysfunction, we tested the hypothesis that increased total mtDNA deletions/rearrangements are associated with neurodegeneration in PD. This study employed a well-established technique, long-extension polymerase chain reaction (LX-PCR), to detect the multiple mtDNA deletions/rearrangements in the SN of patients with PD, multiple system atrophy (MSA), dementia with Lewy bodies (DLB), Alzheimer disease (AD), and age-matched controls. We also compared the total mtDNA deletions/rearrangements in different brain regions of PD patients. The results demonstrated that both the number and variety of mtDNA deletions/rearrangements were selectively increased in the SN of PD patients compared to patients with other movement disorders as well as patients with AD and age-matched controls. In addition, increased mtDNA deletions/rearrangements were observed in other brain regions in PD patients, indicating that mitochondrial dysfunction is not just limited to the SN of PD patients. These data suggest that accumulation of total mtDNA deletions/rearrangements is a relatively specific characteristic of PD and may be one of the contributing factors leading to mitochondrial dysfunction and neurodegeneration in PD.

Aged↗
PubMed2004

The small-molecule Bcl-2 inhibitor HA14-1 interacts synergistically with flavopiridol to induce mitochondrial injury and apoptosis in human myeloma cells through a free radical-dependent and Jun NH2-terminal kinase-dependent mechanism.

Interactions between the cyclin-dependent kinase inhibitor flavopiridol and the small-molecule Bcl-2 antagonist HA14-1 were examined in human multiple myeloma cells. Whereas individual treatment of U266 myeloma cells with 10 micromol/L HA14-1 or 100 nmol/L flavopiridol had little effect, exposure of cells to flavopiridol (6 hours) followed by HA14-1 (18 hours) resulted in a striking increase in mitochondrial dysfunction (cytochrome c and Smac/DIABLO release; loss of mitochondrial membrane potential), activation of the caspase cascade, apoptosis, and diminished clonogenic survival. Similar findings were noted in other myeloma cell lines (e.g., MM.1S, RPMI8226, and NCI-H929) as well as in those resistant to dexamethasone and cytotoxic agents (e.g., MM.1R, 8226/Dox40, and 8226/LR5). Combined exposure to flavopiridol and HA14-1 was associated with down-regulation of Mcl-1 and Bcl-xL, Bid cleavage, and mitochondrial translocation of Bax. Flavopiridol/HA14-1-treated cells also exhibited a pronounced activation of Jun NH2-terminal kinase, a modest activation of p38 mitogen-activated protein kinase, and down-regulation of cyclin D1. Flavopiridol/HA14-1-induced apoptosis was associated with a marked increase in reactive oxygen species generation; moreover,both events were attenuated by the antioxidant N-acetyl-l-cysteine. Finally, in contrast to dexamethasone, flavopiridol/HA14-1-induced lethality was unaffected by exogenous interleukin-6 or insulin-like growth factor-I. Together, these findings indicate that flavopiridol and the small-molecule Bcl-2 antagonist HA14-1 cooperate to trigger oxidant injury, mitochondrial dysfunction, caspase activation, and apoptosis in human multiple myeloma cells and suggest that this approach may warrant further evaluation as an antimyeloma strategy.

Antineoplastic Agents↗
PubMed2006

Overexpression of mitochondrial superoxide dismutase in mice protects the retina from diabetes-induced oxidative stress.

The retina experiences mitochondrial dysfunction in diabetes, superoxide levels are elevated, and mitochondrial superoxide dismutase (MnSOD) activity is decreased. Inhibition of superoxide accumulation in diabetes prevents mitochondrial dysfunction, apoptosis of retinal capillary cells, and the development of retinal histopathology. The purpose of this study is to examine the effect of overexpression of MnSOD on oxidative stress, DNA damage, and nitrative stress in the retina of diabetic mice. After 7 weeks of diabetes in MnSOD overexpressing (hemizygous) mice (MnSOD-Tg) and in their age-matched nontransgenic mice, parameters of oxidative stress and nitrative stress were measured in the retina. Overexpression of MnSOD prevented diabetes-induced decreases in retinal GSH levels and the total antioxidant capacity. In the same retina, MnSOD overexpression also inhibited diabetes-induced increases in the levels of 8-OHdG and nitrotyrosine. This suggests that MnSOD could be implicated in the pathogenesis of retinopathy by protecting the retina from increased oxidative damage experienced in diabetic conditions. Thus, understanding how changes in mitochondrial function result in the development of diabetic retinopathy could help identify SOD mimics to inhibit its development.

Animals↗
PubMed2004

Mitochondrial complex I subunits expression is altered in schizophrenia: a postmortem study.

BACKGROUND: Several independent lines of evidence indicate mitochondrial dysfunction in schizophrenia in the brain and periphery, including mitochondrial hypoplasia, dysfunction of the oxidative phosphorylation system, and altered mitochondrial-related gene expression. METHODS: In this study, three subunits of mitochondrial complex I were analyzed at the level of mRNA and protein in postmortem brain specimens from the prefrontal and the ventral parietooccipital cortex of patients with schizophrenia, major depression, bipolar disorder, and normal control subjects. RESULTS: Both mRNA and protein levels of the 24-kDa and 51-kDa subunits of complex I were significantly decreased in the prefrontal cortex, but increased in the ventral parietooccipital cortices of schizophrenia patients compared with normal control subjects. In the latter region, protein levels of both subunits were increased in bipolar patients as well, being in line with the significant overlap in clinical symptoms between schizophrenia and bipolar patients. No change was observed in the 75-kDa subunit expression in the prefrontal cortex. CONCLUSIONS: The schizophrenia-specific reduction in complex I subunits in the prefrontal cortex is consistent with one of schizophrenia's most prominent deficits, namely, hypofrontality, thus further supporting the hypothesis of mitochondrial dysfunction in this disorder. The abnormal, bidirectional expression of complex I in various brain regions, rather than in a circumscribed area, supports the idea of impaired cerebral circuitry in schizophrenia.

Adult↗
PubMed1989

2-Bromohydroquinone-induced toxicity to rabbit renal proximal tubules: the role of biotransformation, glutathione, and covalent binding.

2-Bromohydroquinone (BHQ) is a model toxic hydroquinone and plays an important role in bromobenzene-induced nephrotoxicity. Proximal tubules isolated to contain decreased glutathione (GSH) levels were at least twice as sensitive to the GSH depleting effects of BHQ and BHQ-induced mitochondrial dysfunction as were tubules with "normal" (i.e., in vivo) GSH content. The decrease in tubular GSH content resulted from BHQ-GSH conjugate formation. A mono-GSH conjugate (2-bromo-3-(glutathion-S-yl)hydroquinone) and a di-GSH conjugate (2-bromo-3,5- or 6-(diglutathion-S-yl)hydroquinone) were identified. In addition, a glucuronide conjugate was identified (2-bromo-1- or 4-O-glucuronylhydroquinone). BHQ-GSH conjugates were not responsible for BHQ-induced toxicity since (1) tubules with normal levels of GSH were more resistant to BHQ-induced toxicity even though they formed more BHQ-GSH conjugates than tubules with decreased GSH levels and (2) inhibition of gamma-glutamyltranspeptidase did not prevent BHQ-induced toxicity. BHQ-equivalents bound covalently to tubular protein in a concentration-, time-, and temperature-dependent manner with the majority of the binding (61%) occurring during the first 15 min after exposure to 0.2 mM BHQ. Tubules pretreated with GSH underwent less BHQ-protein alkylation and mitochondrial dysfunction, and the amount of BHQ recovered and BHQ-di-GSH conjugate formed increased. These data suggest that BHQ is biotransformed to a reactive intermediate (2-bromoquinone and/or 2-bromosemiquinone) and that this intermediate can react with GSH to form BHQ-GSH conjugates and/or bind covalently to tubular protein which may result in mitochondrial dysfunction and tubular death.

Animals↗
PubMed2000

18. PET for Diagnosis of Mytochondrial Cardiomyopathy in Children.

Purpose: To study the capability of positron emission tomography for mitochondrial dysfunction diagnosis on basis of oxidative metabolism evaluation.Methods: PET studies were carried out in 13 patients (pts.) aged from 2 to 13 years (7,5+3,1) with CMP: hypertopic (HCMP) - 4, dilated (DCMP) - 9.The dynamic study with [C-11]-acetate was performed for evaluation of Krebs cycle activity. Rate constant (k(mono)) and [C-11]-activity clearance half-time (t(1/2)) were calculated using myocardial time-activity curve (from 3 to 10 min.). Myocardial perfusion was assessed with [N-13]-ammonia, glucose metabolism - with [F-18]-fluorodeoxylucose (FDG).Results: Perfusion was normal in hypertohic parts of left ventricle (LV) in patients with HCMP. Krebs cycle activity was reduced (k(mono) = 0,077 +/- 0,013 min(-1)). Glucose utilisation was increased in comparison with norm. Thus, Krebs cycle activity reduction (mitochondrial dysfunction) was compensated by increasing glycolysis activity. Perfusion was normal in all children with DCMP. Krebs cycle activity was reduced in LV in 6 pts. (k(mono) = 0,065 +/- 0,029 min(-1)), normal - in 3 (k(mono) = 0,104 +/- 0,010 min(-1)). All children had normal oxidative metabolism in right ventricle (k(mono) = 0,129 +/- 0,203 min(-1)).Focal perfusion defects were noted in 2 pts. with CMP. In this region the Krebs cycle activity was decreased more then another LV parts. It means that ischemic injuries were. Glucose utilisation reduction in this field means that injuries were irreversible.Conclusion: PET study showed Krebs cycle activity reduction in children with cardiomyopathy was noted despite in normal perfusion (mitochondrial dysfunction) vs. ischemic injuries of myocardium.

Journal Article↗
PubMed1997

Calcium homeostasis and reactive oxygen species production in cells transformed by mitochondria from individuals with sporadic Alzheimer's disease.

Alzheimer's disease (AD) is associated with defects in mitochondrial function. Mitochondrial-based disturbances in calcium homeostasis, reactive oxygen species (ROS) generation, and amyloid metabolism have been implicated in the pathophysiology of sporadic AD. The cellular consequences of mitochondrial dysfunction, however, are not known. To examine these consequences, mitochondrially transformed cells (cybrids) were created from AD patients or disease-free controls. Mitochondria from platelets were fused to rho0 cells created by depleting the human neuroblastoma line SH-SY5Y of its mitochondrial DNA (mtDNA). AD cybrids demonstrated a 52% decrease in electron transport chain (ETC) complex IV activity but no difference in complex I activity compared with control cybrids or SH-SY5Y cells. This mitochondrial dysfunction suggests a transferable mtDNA defect associated with AD. ROS generation was elevated in the AD cybrids. AD cybrids also displayed an increased basal cytosolic calcium concentration and enhanced sensitivity to inositol-1,4, 5-triphosphate (InsP3)-mediated release. Furthermore, they recovered more slowly from an elevation in cytosolic calcium induced by the InsP3 agonist carbachol. Mitochondrial calcium buffering plays a major role after this type of perturbation. beta-amyloid (25-35) peptide delayed the initiation of calcium recovery to a carbachol challenge and slowed the recovery rate. Nerve growth factor reduced the carbachol-induced maximum and moderated the recovery kinetics. Succinate increased ETC activity and partially restored the AD cybrid recovery rate. These subtle alterations in calcium homeostasis and ROS generation might lead to increased susceptibility to cell death under circumstances not ordinarily toxic.

Adenine Nucleotides↗
PubMed2006

Investigation of drug-induced mitochondrial toxicity using fluorescence-based oxygen-sensitive probes.

Mitochondrial dysfunction is a common mechanism of drug-induced toxicity. Early identification of new chemical entities (NCEs) that perturb mitochondrial function is of significant importance to avoid attrition in later stages of drug development. One of the most informative ways of assessing mitochondrial dysfunction is by measuring mitochondrial oxygen consumption. However, the conventional polarographic method of measuring oxygen consumption is not amenable to high sample throughput or automation. We present an alternative, low-bulk, high-throughput approach to the analysis of isolated-mitochondrial oxygen consumption using luminescent oxygen-sensitive probes. These probes are dispensable and are analyzed in standard microtitre plates on a fluorescence plate reader. Respiratory substrate and adenosine diphosphate (ADP) dependencies of mitochondrial oxygen consumption were assessed using the fluorescence-based method, and results compared favourably to conventional polarographic analysis. To assess assay performance, the method was then applied to the analysis of a panel of classical modulators of oxidative phosphorylation. The effect of uncoupler concentration was analyzed in detail to identify factors which would be important in applying this method to large scale NCE screening and mechanistic investigations. Results demonstrate that the 96-well format can accommodate up to approximately 200 compounds/day at a single concentration or alternatively IC(50) values can be generated for approximately 25 compounds. Throughput may be increased by moving to a 384-well plate format.

Animals↗
PubMed2003

Mitochondrial DNA dysfunction in oncocytic hepatocytes.

Hepatic oncocytes with abundant granular, eosinophilic cytoplasm due to mitochondrial hyperplasia are seen in various chronic liver diseases, particularly chronic hepatitis and cirrhosis. Increased mitochondria in oncocytes are thought to be a compensatory mechanism for deficiencies in the hepatocellular respiratory chain, although the pathogenesis of these deficiencies has been uncertain. We selected seven cases of cirrhosis (six with oncocytes, one without) for the following analysis: histoenzymatic and immunohistochemical staining of several mitochondrial DNA (mtDNA)- and nuclear DNA (nDNA)-encoded respiratory chain enzymes; immunostaining using antibodies against double-strand-DNA (anti-DNA) and against Ki-67 (a cell proliferation marker); and Southern blot analysis for mtDNA and nDNA. Eighty percent of oncocytes showed histoenzymatic and immunohistochemical deficiencies of cytochrome c oxidase and the mtDNA-encoded subunit I of complex IV, with preserved expression of nDNA-encoded succinate dehydrogenase and the iron-sulfur subunit of complex III (FeS). Cytoplasmic (but not nuclear) anti-DNA staining was partially or completely absent in approximately 50% of oncocytes. Three cases with oncocytes studied by Southern blot showed mtDNA reductions of 66%, 71%, and 85%. In conclusion, hepatic oncocytes demonstrate significant deficiencies of mtDNA and mtDNA-encoded respiratory chain enzymes. We propose that mtDNA depletion plays an important role in hepatocellular oncocytic transformation.

Adult↗