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PubMed1994

Canine mitochondrial myopathy associated with reduced mitochondrial mRNA and altered cytochrome c oxidase activities in fibroblasts and skeletal muscle.

Skeletal muscle and fibroblast biopsies obtained from a normal dog and an old English sheep dog with exertional myopathy and lactic acidosis were examined for mitochondrial enzyme activities and mitochondrially coded mRNAs. The fibroblast cultures of the affected dog showed reduced cytochrome c oxidase (COX) I+II mRNA content (25% of control) and COX enzyme activities (23% of control). The skeletal muscle of the affected dog was similarly affected and showed not only decreased COX I+II mRNA content, but also decreased ATPase6 mRNA level. Apart from COX enzyme activity (62% of control), the oligomycin sensitive ATPase and NADH-Ferricyanide reductase activities were also reduced in the skeletal muscle of the affected dog (12-20% of control). These results suggest that a mitochondrial dysfunction may be the causative factor of the exertional metabolic myopathy with lactic acidosis in this affected old English sheep dog. These animals may serve as an excellent model for mitochondrial myopathies.

Adenosine Triphosphatases↗
PubMed1995

Oxidative damage to mitochondrial DNA and its relationship to ageing.

Mitochondria are the most important intracellular source of reactive oxygen species and are protected against them by enzymatic and nonenzymatic antioxidants. Nevertheless, mitochondrial DNA (mtDNA) is subject to severe oxidative damage, and much more so than nuclear DNA (nDNA). Damage is indicated by the detection of various base modifications, particularly 8-hydroxydeoxyguanosine (8OHdG), which can lead to point mutations because of mispairing. MtDNA is also fragmented to some extent. Conceivably, such fragmentation relates to the deletions found in mtDNA. Several hypotheses suggest that defective mitochondria contribute to, or are responsible for, ageing. Recent observations indicate that mitochondria in an old organism differ in many respects from those in a young organism. Thus, with ageing there is an increased production of reactive oxygen species, a decrease in certain antioxidants, a decreased transcription, translation, and cytochrome oxidase content, and an increase in the extent of DNA modifications. Major unresolved questions concerning the role of mtDNA changes in ageing are addressed: is there a causal relationship; what is the true extent of DNA damage; what are significance and functional consequences of mtDNA oxidation; are reactive oxygen species the cause of the DNA modifications found in vivo; what is the relationship between DNA damage and alterations of RNAs and proteins? Future studies promise to clarify the possible causal relationship between mitochondrial dysfunction, reactive oxygen species production, mtDNA modifications, and ageing.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

A rapid and transient ROS generation by cadmium triggers apoptosis via caspase-dependent pathway in HepG2 cells and this is inhibited through N-acetylcysteine-mediated catalase upregulation.

Although reactive oxygen species (ROS) have been implicated in cadmium (Cd)-induced hepatotoxicity, the role of ROS in this pathway remains unclear. Therefore, we attempted to determine the molecular mechanisms relevant to Cd-induced cell death in HepG2 cells. Cd was found to induce apoptosis in the HepG2 cells in a time- and dose-dependent fashion, as confirmed by DNA fragmentation analysis and TUNEL staining. In the early stages, both rapid and transient ROS generation triggered apoptosis via Fas activation and subsequent caspase-8-dependent Bid cleavage, as well as by calpain-mediated mitochondrial Bax cleavage. The timing of Bid activation was coincided with the timing at which the mitochondrial transmembrane potential (MMP) collapsed as well as the cytochrome c (Cyt c) released into the cytosol. Furthermore, mitochondrial permeability transition (MPT) pore inhibitors, such as cyclosporin A (CsA) and bongkrekic acid (BA), did not block Cd-induced ROS generation, MMP collapse and Cyt c release. N-acetylcysteine (NAC) pretreatment resulted in the complete inhibition of the Cd-induced apoptosis via catalase upregulation and subsequent Fas downregulation. NAC treatment also completely blocked the Cd-induced intracellular ROS generation, MMP collapse and Cyt c release, indicating that Cd-induced mitochondrial dysfunction may be regulated indirectly by ROS-mediated signaling pathway. Taken together, a rapid and transient ROS generation by Cd triggers apoptosis via caspase-dependent pathway and subsequent mitochondrial pathway. NAC inhibits Cd-induced apoptosis through the blocking of ROS generation as well as the catalase upregulation.

Acetylcysteine↗
PubMed1994

Isolated cerebral and cerebellar mitochondria produce free radicals when exposed to elevated CA2+ and Na+: implications for neurodegeneration.

The evidence is compelling that free radicals, plus increases in free cytosolic Ca2+ and Na+, figure prominently in neuronal death after exposure to glutamate and dicarboxylic excitotoxins such as NMDA and kainate. However, neither the source of these radicals nor the direct connection between Ca2+ mobilization and radical production has been well defined. Electron paramagnetic resonance studies reported here indicate that intact mitochondria isolated from adult rat cerebral cortex and cerebellum generate extremely reactive hydroxyl (.OH) radicals, plus ascorbyl and other carbon-centered radicals when exposed to 2.5 microM Ca2+, 14 mM Na+, plus elevated ADP under normoxic conditions, circumstances that prevail in the cytoplasm of neurons during excitotoxin-induced neurodegeneration. In a feed-forward cycle, exposure of isolated mitochondria to .OH significantly increases subsequent radical production five- to 16-fold (average = 8.8 +/- 1.6 SE, n = 6, p > 0.01) with succinate as substrate, and also selectively impairs function of NADH-CoQ dehydrogenase activity (electron transport complex 1). These effects are also reflected by respiration rates that are reduced 48% with complex 1 substrates, but increased 27% with complex 2 substrate, after .OH exposure. Comparable complex 1 dysfunction is observed in mitochondria isolated from the substantia nigra of Parkinson's disease patients, from platelets of Huntington's disease patients, and from neocortex of Alzheimer's disease patients. Mitochondrial radical production provides a testable model, based on oxyradical toxicity, oxidative enzyme inactivation, and mitochondrial dysfunction, for the final common pathway of neuronal necrosis during excitotoxicity, and in a host of neurodegenerative disorders.

Adenosine Diphosphate↗
PubMed2001

Unusual imaging findings in progressive myoclonus epilepsy.

We describe a patient with progressive myoclonus epilepsy (PME), white matter hyperintensities in the corpus callosum, cerebral hemispheres, and left cerebral peduncle on magnetic resonance imaging (MRI), and positive oligoclonal bands. A phosphorus magnetic resonance spectrum was compatible with mitochondrial dysfunction. Abnormal white matter signals are not a feature of the known PME syndromes, although they occur in Leber's hereditary optic neuropathy (LHON). These abnormalities oriented the diagnosis toward mitochondrial disease.

Adult↗
PubMed2003

In vivo assessment of the mitochondrial response to caloric restriction in obese women by the 2-keto[1-C]isocaproate breath test.

The 2-keto[1-(13)C]isocaproate breath test has been proposed as a tool to detect mitochondrial dysfunction in alcoholic liver disease. The aim of this study was to evaluate if the 2-keto[1-(13)C]isocaproate breath test could detect in vivo dynamic changes on mitochondrial activity due to caloric restriction in obese women. Fifteen obese women (body mass index [BMI] > 30 kg/m(2)) participated in the study at baseline. Ten of these women agreed to participate on a diet program to induce body weight loss. Fifteen lean women (BMI < 25 kg/m(2)) were included as a control group. The breath test was performed by the oral administration of the tracer measuring (13)CO(2) enrichment in breath before and after ingestion using isotope ratio mass spectrometry. Body composition, resting energy expenditure, and plasma levels of insulin and leptin were measured. There were no relationships observed between the 2-keto[1-(13)C]isocaproate breath test and the plasma insulin (before diet: P =.863; after diet: P =.879), or leptin (before diet: P =.500; after diet: P =.637). In obese women before treatment, kilograms of fat free mass (P =.108), resting energy expenditure adjusted for body composition (P =.312), and the 2-keto[1-(13)C]isocaproate breath test (P =.205) were similar in comparison to lean women. However, 2-keto[1-(13)C]isocaproate oxidation tended to increase after dieting and was significantly higher than in controls (P =.015). These data suggest that the 2-keto[1-(13)C]isocaproate breath test reflected the adaptive modifications in mitochondrial oxidation in response to caloric restriction in obese women.

Adolescent↗
PubMed1990

Mitochondrial metabolism following traumatic brain injury in rats.

Although a number of studies of traumatic brain injury have implicated mitochondrial dysfunction as a cause of altered posttraumatic energy metabolism, no studies to date have isolated mitochondria and measured their respiratory capacity following trauma. The present study sought to determine whether mitochondrial capacity for oxidative phosphorylation is adversely affected by fluid-percussion-induced traumatic brain injury in rats. Prior to brain injury, the mitochondrial respiratory control ratio was 4.3 +/- 0.2 and the ratio of nmoles of ADP phosphorylated per natom oxygen consumed (ADP/O ratio) was 2.66 +/- 0.09. After injury (2.8 atm; t = 4 h), there were slight but not significant alterations in ADP/O ratio (2.41 +/- 0.07) and state 3 respiratory rate (ADP stimulated); however, there were no changes in the respiratory control ratio. These data suggest that traumatic brain injury, unlike ischemia, does not cause uncoupling of ATP synthesis from respiration, and that brain mitochondria are quite resistant to trauma-induced injury.

Adenosine Diphosphate↗
PubMed1999

GAS-1: a mitochondrial protein controls sensitivity to volatile anesthetics in the nematode Caenorhabditis elegans.

BACKGROUND: Mutations in several genes of Caenorhabditis elegans confer altered sensitivities to volatile anesthetics. A mutation in one gene, gas-1(fc21), causes animals to be immobilized at lower concentrations of all volatile anesthetics than in the wild-type, and it does not depend on mutations in other genes to control anesthetic sensitivity. gas-1 confers different sensitivities to stereoisomers of isoflurane, and thus may be a direct target for volatile anesthetics. The authors have cloned and characterized the gas-1 gene and the mutant allele fc21. METHODS: Genetic techniques for nematodes were as previously described. Polymerase chain reaction, sequencing, and other molecular biology techniques were performed by standard methods. Mutant rescue was done by injecting DNA fragments into the gonad of mutant animals and scoring the offspring for loss of the mutant phenotype. RESULTS: The gas-1 gene was cloned and identified. The protein GAS-1 is a homologue of the 49-kDa (IP) subunit of the mitochondrial NADH:ubiquinone-oxidoreductase (complex I of the respiratory chain). gas-1(fc21) is a missense mutation replacing a strictly conserved arginine with lysine. CONCLUSIONS: The function of the 49-kDa (IP) subunit of complex I is unknown. The finding that mutations in complex I increase sensitivity of C elegans to volatile anesthetics may implicate this physiologic process in the determination of anesthetic sensitivity. The hypersensitivity of animals with a mutation in the gas-1 gene may be caused by a direct anesthetic effect on a mitochondrial protein or secondary effects at other sites caused by mitochondrial dysfunction.

Amino Acid Sequence↗
PubMed2002

Is normal tension glaucoma actually an unrecognized hereditary optic neuropathy? New evidence from genetic analysis.

Normal tension glaucoma and dominant optic atrophy share many overlapping clinical features, and differentiating between these two diseases is often difficult. The gene responsible for dominant optic atrophy is the OPA1 gene located on chromosome 3. This gene encodes for a protein product that is involved in mitochondrial metabolic function. Recent genetic linkage analysis of patients with normal tension glaucoma has shown an association with polymorphisms of the OPA1 gene. This association suggests that normal tension glaucoma may actually be a hereditary optic neuropathy with a pathophysiology based in mitochondrial dysfunction.

Disease Progression↗
PubMed2002

[ Mutation of mtDNA and genetic background of hypertrophic cardiomyopathy].

The operation of the structural and functional units of the myocardial contractile apparatus relies on mutual myofilament movement, totally ATP dependent. As a consequence, cardiac action is integrally connected with the production of high energy ATP molecules, which are mainly synthesised in cellular mitochondrial structures. Mitochondrial dysfunction can lead to a reduced level of ATP, which is necessary to generate movement in the actino-myosin system. ATP insufficiencies may be a result of the genetic mitochondrial material (mtDNA) mutation, poorer expression of mitochondrial genes (at the transcription and/or translation stage), distorted import of proteins from the cytoplasm to the mitochondria or erroneous composition of mitochondrial breathing complexes. It has been proved that the efficacy of oxidative phosphorylation (mitochondrial ATP synthesis) is reduced with accumulated mutation of mitochondrial and/or nuclear DNA. The paper is a review of findings on the mutation of mitochondrial DNA discovered in patients with hypertrophy of the cardiac muscle. In many cases these changes accompany the mutations of the nuclear genes, but they may also be the only change discovered in the patient's genetic material.

Adenosine Triphosphate↗
PubMed2004

Mitochondrial permeability transition in acetaminophen-induced necrosis and apoptosis of cultured mouse hepatocytes.

Acetaminophen overdose causes massive hepatic failure via mechanisms involving glutathione depletion, oxidative stress, and mitochondrial dysfunction. The ultimate target of acetaminophen causing cell death remains uncertain, and the role of apoptosis in acetaminophen-induced cell killing is still controversial. Our aim was to evaluate the mitochondrial permeability transition (MPT) as a key factor in acetaminophen-induced necrotic and apoptotic killing of primary cultured mouse hepatocytes. After administration of 10 mmol/L acetaminophen, necrotic killing increased to more than 49% and 74%, respectively, after 6 and 16 hours. MPT inhibitors, cyclosporin A (CsA), and NIM811 temporarily decreased necrotic killing after 6 hours to 26%, but cytoprotection was lost after 16 hours. Confocal microscopy revealed mitochondrial depolarization and inner membrane permeabilization approximately 4.5 hours after acetaminophen administration. CsA delayed these changes, indicative of the MPT, to approximately 11 hours after acetaminophen administration. Apoptosis indicated by nuclear changes, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and caspase-3 activation also increased after acetaminophen administration. Fructose (20 mmol/L, an adenosine triphosphate-generating glycolytic substrate) plus glycine (5 mmol/L, a membrane stabilizing amino acid) prevented nearly all necrotic cell killing but paradoxically increased apoptosis from 37% to 59% after 16 hours. In the presence of fructose plus glycine, CsA decreased apoptosis and delayed but did not prevent the MPT. In conclusion, after acetaminophen a CsA-sensitive MPT occurred after 3 to 6 hours followed by a CsA-insensitive MPT 9 to 16 hours after acetaminophen. The MPT then induces ATP depletion-dependent necrosis or caspase-dependent apoptosis as determined, in part, by ATP availability from glycolysis.

Acetaminophen↗
PubMed2004

Linoleic acid epoxide promotes the maintenance of mitochondrial function and active Na+ transport following hypoxia.

Low concentrations of arachidonic acid monoepoxides protect against ischemia/reperfusion injury. This study examined whether low concentrations of the linoleic acid monoepoxide, cis-12,13-epoxy-9-octadecenoic acid (12,13-EOA), protect renal cells against decreases in mitochondrial and transport functions induced by hypoxia/reoxygenation. Primary cultures of rabbit renal proximal tubular cells (RPTC) were pretreated with diluent or 1, 5, or 10 microM 12,13-EOA for 1 h and exposed to 2 h hypoxia/0.5 h reoxygenation in the absence of 12,13-EOA. Basal respiration, oligomycin-sensitive oxygen consumption (QO2), and ATP content decreased 31, 35 and 65%, respectively, following hypoxia/reoxygenation. Hypoxia/reoxygenation also increased mitochondrial membrane potential (DeltaPsi(m)). Pretreatment with 12,13-EOA prevented decreases in basal and oligomycin-sensitive QO2s and increases in DeltaPsi(m). Despite the protection against decreases in mitochondrial function, 12,13-EOA pretreatment did not prevent the initial decrease in intracellular ATP content following hypoxia. However, pretreatment did accelerate the recovery of intracellular ATP levels during reoxygenation. Pretreatment with 12,13-EOA also prevented hypoxia-induced decreases in active Na+ transport. Ouabain-sensitive QO2 (a marker of active Na+ transport) decreased 38% following hypoxia/reoxygenation but was maintained in RPTC pretreated with 1, 5 or 10 microM 12,13-EOA prior to hypoxia. Pretreatment of RPTC with the hydrolyzed product of 12,13-EOA, 12,13-dihydroxyoctadecenoic acid, did not have any protective effects against mitochondrial dysfunction and decreases in active Na+ transport. Thus, this is the first report demonstrating that preconditioning of RPTC with low concentrations of 12,13-EOA, but not its hydrolyzed product, maintains mitochondrial respiration, accelerates restoration of ATP levels, and prevents decreases in active Na+ transport following hypoxia/reoxygenation.

Adenosine Triphosphate↗
PubMed2001

Involvement of mitochondrial permeability transition and caspase-9 activation in dimethyl sulfoxide-induced apoptosis of EL-4 lymphoma cells.

We observed that dimethyl sulfoxide (DMSO) induced apoptotic changes in the EL-4 murine lymphoma cell line and that effect was dependent on the concentration and time period. Incubating cells over a period of 18 h, 2.5% DMSO was found to induce sub-G1 peak in DNA histograms analyzed by flowcytometer and nucleosomal ladder formation in DNA gel electrophoresis. We also found down-regulation of Bcl-2, collapse of mitochondrial membrane potential (delta psi m) occurred following DMSO treatment, and release of cytochrome c from the mitochondria to cytosol. These observations suggest that DMSO converted its pro-apoptotic signal at the mitochondria. In the involvement of caspases, caspase-9 and -3, but not caspase-8, were found to be activated responding to DMSO treatment. Inhibitory experiments demonstrated that caspase cascade of mitochondrial apoptotic pathway was indispensable for DMSO-induced apoptosis. In the caspase cascade, caspase-9 was an upstream initiator and its primary signal could be transduced and amplified by caspase-3, -6 and -7. Kinetic study of these data showed mitochondrial dysfunction and caspase activation occurred at 12 h and apoptotic change of nuclear DNA at 18 h, providing another support for the transduction of DMSO pro-apoptotic signal via the mitochondrial pathway.

Animals↗
PubMed1999

Mitochondrial DNA determines the cellular response to cancer therapeutic agents.

Mutations in the mitochondrial genome leading to mitochondrial dysfunction have been reported in a variety of cancers. However, the potential implication of these findings in the cellular response to cancer therapeutic agents is unclear. To examine the importance of mitochondrial DNA (mitDNA) encoded functions in cancer therapeutic response, we determined the clonogenic survival of HSL2 (Rho+, HeLa subline), and its derivative cell line lacking mitDNA (Rho0) after exposure to different anticancer agents. We found that isogenic Rho0 cells lacking mitDNA were extremely resistant to adriamycin and photodynamic therapy (PDT) induced cell death, whereas the Rho+ cell line was sensitive. However, there was no measurable difference in the responses of these cell lines to either alkylating agent or gamma-radiation. We show that the development of resistance to adriamycin was not due to changes in apoptotic cell death, cell cycle response or to the uptake of adriamycin in isogenic Rho0 cells. We also demonstrate that exposure of HeLa cells to adriamycin leads to mutations in mitDNA. These studies provide direct evidence that mitDNA plays an important role in cellular sensitivity to cancer therapeutic agents.

Antineoplastic Agents↗
PubMed2006

Signaling of mitochondrial biogenesis following oxidant injury.

Mitochondrial dysfunction is a common consequence of ischemia-reperfusion and drug injuries. For example, sublethal injury of renal proximal tubular cells (RPTCs) with the model oxidant tert-butylhydroperoxide (TBHP) causes mitochondrial injury that recovers over the course of six days. Although regeneration of mitochondrial function is integral to cell repair and function, the signaling pathway of mitochondrial biogenesis following oxidant injury has not been examined. A 10-fold overexpression of the mitochondrial biogenesis regulator PPAR-gamma cofactor-1alpha (PGC-1alpha) in control RPTCs resulted in a 52% increase in mitochondrial number, a 27% increase in respiratory capacity, and a 30% increase in mitochondrial protein markers, demonstrating that PGC-1alpha mediates mitochondrial biogenesis in RPTCs. RPTCs sublethally injured with TBHP exhibited a 50% decrease in mitochondrial function and increased mitochondrial autophagy. Compared with the controls, PGC-1alpha levels increased 12-fold on days 1, 2, and 3 post-injury and returned to base line on day 4 as mitochondrial function returned. Inhibition p38 MAPK blocked the up-regulation of PGC-1alpha following oxidant injury, whereas inhibition of calcium-calmodulin-dependent protein kinase, calcineurin A, nitric-oxide synthase, and phosphoinositol 3-kinase had no effect. The epidermal growth factor receptor (EGFR) was activated following TBHP exposure, and the EGFR inhibitor AG1478 blocked the up-regulation of PGC-1alpha. Additional inhibitor studies revealed that the sequential activation of Src, p38 MAPK, EGFR, and p38 MAPK regulate the expression of PGC-1alpha following oxidant injury. In contrast, although Akt was activated following oxidant injury, it did not play a role in PGC-1alpha expression. We suggest that mitochondrial biogenesis following oxidant injury is mediated by p38 and EGFR activation of PGC-1alpha.

Animals↗
PubMed1995

High levels of mitochondrial DNA with an unstable 260-bp duplication in a patient with a mitochondrial myopathy.

Other investigators reported the presence of low levels of a 260-bp heteroplasmic duplication of mitochondrial DNA in patients with mitochondrial DNA deletions and their asymptomatic mothers. In this study, we were not able to detect this polymorphism in 30 patients with mitochondrial DNA deletions, but the 260-bp duplication was detected in relatively high levels (32% in muscle) in a patient with a slowly progressive mitochondrial myopathy. The duplication was also present in cultured fibroblasts (10%) and in WBC (< 1%). Mitochondrial dysfunction in this patient was evidenced in muscle by the presence of ragged-red fibers and a partial decrease in cytochrome c oxidase activity. We also detected low levels of mitochondrial DNA harboring a triplication of the 260-bp region, indicating that this polymorphism is unstable. Taken together, our results suggest that an unstable 260-bp duplication, which includes important mitochondrial DNA cis-acting regulatory sequences, may be pathogenic per se, if present at high levels.

Base Sequence↗
PubMed2004

[Mechanism of specific dopaminergic neuronal death in Parkinson's disease].

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic (DAergic) neurons of the nigrostriatal system, with resulting reduction in striatal dopamine (DA) concentration. Various mechanisms have been implicated in the pathogenesis and progression of PD. Among them, mitochondrial dysfunction, inflammation and oxidative stress had been accepted as the most plausible mechanism of disease progression. The free radicals/oxidative stress produced by MPTP, 6-hydroxydopamine, rotenone, activated microglias, and disturbances in mitochondrial respiratory enzymes provide a common pathway for the progression of all kinds of neurons. On the other hand, numerous studies on DA-induced neurotoxicity have been reported recently, and DA itself exerts cytotoxicity in DAergic neurons mainly due to the generation of highly reactive DA -quinones which are DAergic neuron-specific cytotoxic molecules. DA quinones may irreversibly alter protein function through the formation 5-cysteinyl-dopamine on the protein. For example, the formation of DA quinone-alpha-synuclein complex consequently increases cytotoxic protofibrils and covalent modification of functional enzymes. Thus, DA quinones play an important role in 'specific' DAergic neuro-degeneration of PD.

Brain↗
PubMed1990

Altered calcium homeostasis in irreversibly injured P388D1 macrophages.

Sequestration of calcium by mitochondria is an important mechanism to maintain normal intracellular calcium homeostasis. Anoxic or toxic damage to these organelles has been postulated to disrupt intracellular calcium compartmentalization, leading to cell death. The authors examined the potential relationship between mitochondrial dysfunction, altered calcium homeostasis, and irreversible injury in a model system of silica-induced toxicity to P388D1 cells. Exposure to toxic silica particles, but not to nontoxic latex heads, disrupted mitochondrial membrane potential, increased membrane-associated calcium, elevated free cytosolic calcium, and killed 50% to 60% of the cell population after 6 to 8 hours. To test whether disruption of the mitochondrial membrane potential was sufficient to cause irreversible injury, P388D1 cells were exposed to either the proton ionophore, carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or to the mitochondrial inhibitor, antimycin A. Over 90% of the treated cells showed depolarization of the mitochondrial membrane as indicated by the fluorescent probe rhodamine 123. Carbonyl cyanide p-trifluoromethoxyphenylbydrazone also caused an elevation in free cytosolic calcium as monitored by fura-2. However, even after 6 hours of exposure to these proton ionophores or mitochondrial inhibitors, P388D1 cells did not show increased chlorotetracycline (CTC)-induced fluorescence or loss of viability. P388D1 cells exposed to silica have been shown previously to lose 80% of their adenosine triphosphate (ATP) content. The effect of reduced ATP levels on intracellular calcium homeostasis and viability was assessed by exposing P338D1 cells to FCCP in the presence of sodium azide and 2-deoxyglucose, which reduced ATP content by more than 90%. Under these conditions, none of the cells were killed, and only 5.5% showed increased CTC-induced fluorescence after 6 hours. These data indicate that disruption of the mitochondrial membrane potential, even in combination with reduced ATP content, is not sufficient to kill P388D1 cells.

Adenosine Triphosphate↗