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PubMed2007

Chronological approach of diet-induced alterations in muscle mitochondrial functions in rats.

OBJECTIVE: Mitochondrial dysfunction might predispose individuals to develop insulin resistance. Our objective was to determine whether mitochondrial dysfunction or insulin resistance was the primary event during high-fat (HF) diet. RESEARCH METHODS AND PROCEDURES: Rats were fed an HF diet for 0, 3, 6, 9, 14, 20, or 40 days and compared with control. Soleus and tibialis muscle mitochondrial activity were assessed using permeabilized fiber technique. Insulin [area under the curve for insulin (AUC(I))] and glucose [area under the curve for glucose (AUC(G))] responses to intraperitoneal glucose tolerance test as well as fasting plasma non-esterified fatty acids (NEFAs), triglyceride, and glycerol concentrations were determined. RESULTS: AUC(I) and AUC(G) were altered from Day 6 (p < 0.01 vs. Day 0). In soleus, oxidative phosphorylation (OXPHOS) activity was transiently enhanced by 26% after 14 days of HF diet (p < 0.05 vs. Day 0) conjointly with 62% increase in NEFA concentration (p < 0.05 vs. Day 0). This was associated with normalized AUC(G) at Day 14 and with a decline of plasma NEFA concentration together with stabilization of intra-abdominal adiposity at Day 20. Prolongation of HF diet again caused an increase in plasma NEFA concentration, intra-abdominal adiposity, AUC(I), and AUC(G). At Day 40, significant decrease in OXPHOS activity was observed in soleus. DISCUSSION: Mitochondria first adapt to overfeeding in oxidative muscle limiting excess fat deposition. This potentially contributes to maintain glucose homeostasis. Persistent overfeeding causes insulin resistance and results in a slow decline in oxidative muscle OXPHOS activity. This shows that the involvement of mitochondria in the predisposition to insulin resistance is mainly due to an inability to face prolonged excess fat delivery.

Adaptation, Physiological↗

PubMed2002

Calpain upregulation and neuron death in spinal cord of MPTP-induced parkinsonism in mice.

Parkinson's disease (PD) is a neurodegenerative disorder resulting in slowness, tremors, and imbalance. Treatment of mice with 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) is one of several models used to mimic PD in humans. Administration of MPTP leads to the production of 1-methyl-4-phenyl-2,3 dihydropyridinium (MPP(+)). MPP(+) is taken up by dopaminergic neurons, causing mitochondrial dysfunction and cell death. Because calpain is involved in neuronal cell death and mitochondrial dysfunction, we examined the level of calpain in neurons in the substantia nigra (SN) and hippocampus of MPTP-treated C57BL/6 mice. Because of the interconnections between spinal cord and upper central nervous system neurons, we examined morphology, calpain activity, and calpain expression in neurons by double immunofluorescence using calpain and neuron marker (NeuN) antibodies. In controls, calpain expression was low in SN, hippocampus, and spinal cord NeuN(+) cells, and the NeuN stain was concentrated around the nucleus. In mice sacrificed 24 h after administration of three 20 mg/kg doses of MPTP, calpain expression was slightly increased in SN and hippocampal neurons and moderately increased in spinal cord neurons. In these animals, the NeuN stain was less concentrated around the nuclear membrane. One week after MPTP treatment, calpain content in NeuN(+) cells was greatly increased in SN, hippocampus, and spinal cord. Morphologically, SN and spinal cord neurons, treated for one week, were necrotic with a granular cytoplasmic NeuN content. Also, MPTP treatment upregulated calpain activity and mRNA level in spinal cord. These data suggest that following MPTP treatment, calpain causes neuronal death in SN as well as in spinal cord.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2006

Mitochondrial impairment is a critical event in anthrax lethal toxin-induced cytolysis of murine macrophages.

Numerous early events in anthrax lethal toxin (LT)-mediated cell killing have been described, including uptake of LT and MAPKK cleavage. However, critical downstream events in LT killing remain to be identified. In this study we present evidence that LT causes mitochondrial dysfunction in murine J774A.1 macrophages, as indicated by a continuous drop in both mitochondrial membrane potential and SDH activity. This was further supported by ultrastructural analysis revealing LT-induced swelling of mitochondria. Mitochondrial impairment and cytolysis were controlled by proteasomes in LT-treated macrophages: proteasome inhibitors restored mitochondrial activity and rescued cells from cytolysis, even when added immediately prior to membrane perturbation. Similar to proteasome inhibitors, KCl also efficiently blocked LT-mediated cytolysis, even after late addition. However, KCl did not prevent mitochondrial impairment, though it precluded events linked to LT-induced cytolysis. These events included a precipitous drop in ATP levels and ubiquitinated proteins, revealing that they are epiphenomena in LT killing. Our studies suggest that proteasomes and potassium control LT-induced mitochondrial dysfunction and membrane perturbation, key events in LT killing.

Animals↗

PubMed2026

Simultaneously PYCR-1 and ALH-6 inhibition exacerbates 6-PPD quinone toxicity via disrupting proline and glutamate metabolisms and activating insulin signals in Caenorhabditis elegans.

Glutamate synthesized from the proline can serve as a precursor for key intermediate metabolites of citric acid cycle. Recently, we observed reduced glutamate content and expression of alh-6 controlling glutamate synthesis by 6-PPD quinone (6-PPDQ) in Caenorhabditis elegans. However, possible effect of 6-PPDQ on proline synthesis and the association with 6-PPDQ toxicity induction remain unclear. After 0.1-10 μg/L 6-PPDQ exposure, proline content was further reduced, and expression of pycr-1 governing proline biosynthesis was decreased. In 6-PPDQ exposed nematodes, RNA interference (RNAi) of pycr-1 decreased α-ketoglutarate content, enhanced mitochondrial dysfunction, reduced nicotinamide adenine dinucleotide (NADH) and reduced flavine adenine dinucleotide (FADH₂) contents, inhibited mitochondrial complex I/II activities, and decreased expressions of gas-1 and mev-1. Moreover, compared to single RNAi, double RNAi of pycr-1 and alh-6 exacerbated the 6-PPDQ toxicity in reducing α-ketoglutarate, NADH, and FADH₂ contents, and suppressing mitochondrial complex I/II activities and gas-1 and mev-1 expressions. Additionally, double RNAi of pycr-1 and alh-6 intensified toxicity of 6-PPDQ on longevity and caused upregulation of insulin ligand and receptor genes and downregulation of daf-16 and its targeted genes in 6-PPDQ exposed nematodes. Furthermore, after 6-PPDQ exposure, daf-16 RNAi suppressed pycr-1 and alh-6 expressions, suggesting formation of a regulatory feedback loop between pycr-1/alh-6 and daf-16. Our findings highlight involvement of disrupted proline and glutamate metabolisms in 6-PPDQ-induced mitochondrial dysfunction and reduced longevity.

Animals↗

PubMed2006

Neuron-specific conditional expression of a mitochondrially targeted fluorescent protein in mice.

Mitochondrial dysfunction contributes to the pathophysiology of both acute and chronic neurodegenerative disorders. Quantification of mitochondrial bioenergetic properties generally requires the use of isolated brain mitochondria. However, the involvement of neuronal mitochondrial dysfunction in these disorders is limited by the lack of markers, and therefore isolation procedures, that distinguish neuronal compared with astrocyte mitochondria. To address this and other issues concerning neuronal mitochondria in the CNS, transgenic mice were generated that express a fluorescent protein targeted specifically to neurons. A neuron-specific promoter, CaMKIIalpha (calcium/calmodulin-dependent kinase IIalpha) driven tTA (tetracycline transactivator) mice were crossed with TRE (tetracycline responsive element) driven mitochondrial targeted enhanced yellow fluorescent protein (eYFP) mice. Expression of eYFP in the bigenic mouse brain was observed only in neuronal mitochondria of striatum, forebrain, and hippocampus and was enhanced by the removal of the tetracycline analog doxycycline (Dox) in the diet. The respiratory control ratio of synaptic and nonsynaptic mitochondria isolated from eYFP-expressing mice was the same as control mice, suggesting that neuronal mitochondria expressing eYFP maintain normal bioenergetic functions. More importantly, the development of Dox-inducible, neuron targeted mito/eYFP transgenic mice offer a unique in vivo model for delineating the participation of neuronal mitochondria in neuronal survival and death.

Animals↗

PubMed2007

Cisplatin-induced nephrotoxicity is associated with oxidative stress, redox state unbalance, impairment of energetic metabolism and apoptosis in rat kidney mitochondria.

The clinical use of cisplatin (cis-diamminedichloroplatinum II) is highly limited by its nephrotoxicity. The precise mechanisms involved in cisplatin-induced mitochondrial dysfunction in kidney have not been completely clarified. Therefore, we investigated in vivo the effects of cisplatin on mitochondrial bioenergetics, redox state, and oxidative stress as well as the occurrence of cell death by apoptosis in cisplatin-treated rat kidney. Adult male Wistar rats weighing 200-220 g were divided into two groups. The control group (n = 8) was treated only with an intraperitoneal (i.p.) injection of saline solution (1 ml per 100 g body weight), and the cisplatin group (n = 8) was given a single injection of cisplatin (10 mg/kg body weight, i.p.). Animals were sacrificed 72 h after the treatment. The cisplatin group presented acute renal failure characterized by increased plasmatic creatinine and urea levels. Mitochondrial dysfunction was evidenced by the decline in membrane electrochemical potential and the substantial decrease in mitochondrial calcium uptake. The mitochondrial antioxidant defense system was depleted, as shown by decreased GSH and NADPH levels, GSH/GSSG ratio, and increased GSSG level. Moreover, cisplatin induced oxidative damage to mitochondrial lipids, including cardiolipin, and oxidation of mitochondrial proteins, as demonstrated by the significant decrease of sulfhydryl protein concentrations and increased levels of carbonylated proteins. Additionally, aconitase activity, which is essential for mitochondrial function, was also found to be lower in the cisplatin group. Renal cell death via apoptosis was evidenced by the increased caspase-3 activity. Results show the central role of mitochondria and the intensification of apoptosis in cisplatin-induced acute renal failure, highlighting a number of steps that might be targeted to minimize cisplatin-induced nephrotoxicity.

Aconitate Hydratase↗

PubMed2005

A hypomorphic allele of the first N-glycosylation gene, ALG7, causes mitochondrial defects in yeast.

The modification of proteins at asparagine residues with oligosaccharides (N-glycans) plays critical roles in diverse cell functions. N-glycans originate from a common lipid-linked oligosaccharide (LLO) precursor whose synthesis is initiated by the Dol-P-dependent GlcNAc-1-P transferase (GPT) encoded by an essential ALG7 gene. To identify cellular processes affected by ALG7 and N-glycosylation, we replaced the genomic copy of ALG7 with its hypomorphic allele in two genetically distinct haploid yeast cells. We show that ALG7 knockdown gave rise to an unexpected phenotype of mitochondrial dysfunction. The alg7 mutants did not grow on glycerol and DNA arrays revealed the absence of mitochondrial genes' expression. Accordingly, the alg7 mutants displayed no detectable mtDNA and respiratory activity. Both mutants exhibited diminished abundance of LLO and under-glycosylation of carboxypeptidase Y (CPY). Moreover, another N-glycosylation mutant with a LLO defect, alg6, was respiratory deficient. Collectively, our studies provide evidence that the dysregulation of N-glycosylation in haploid yeast cells leads to mitochondrial dysfunction.

3' Untranslated Regions↗

PubMed2002

Clostridium difficile toxin A triggers human colonocyte IL-8 release via mitochondrial oxygen radical generation.

BACKGROUND & AIMS: Clostridium difficile toxin A causes mitochondrial dysfunction resulting in generation of oxygen radicals and adenosine triphosphate (ATP) depletion. We investigated whether mitochondrial dysfunction is involved in nuclear factor kappaB (NF-kappaB) activation and interleukin (IL)-8 release from toxin A-exposed enterocytes. METHODS: NF-kappaB activation and IL-8 release in response to toxin A were correlated with reactive oxygen intermediate (ROI) generation and ATP production in HT-29 monolayers or HT-29 cells exposed to ethidium bromide (EB) to inhibit mitochondrial function. RESULTS: HT-29 cells exposed to EB showed damaged mitochondria and diminished resting levels of ATP. ROI production in EB-treated cells exposed to toxin A for 30 minutes was significantly reduced. Exposure of wild-type HT-29 cells to toxin A resulted in increased oxygen radical generation and IL-8 production (P < 0.01 vs. control) that was inhibited by antioxidant pretreatment. Degradation of IkappaB was observed within 30 minutes of toxin exposure, before ras homologue (Rho) glucosylation, and was followed by nuclear translocation of NF-kappaB. Toxin A did not increase IL-8 levels in EB-treated cells, whereas IL-8 release in response to IL-1beta was not affected. CONCLUSIONS: Our data support an early role for mitochondria-derived ROIs in stimulation of IL-8 release from colonocytes by toxin A. ROI generation is independent of Rho inactivation and involves nuclear translocation of NF-kappaB before release of IL-8.

Adenosine Triphosphate↗

PubMed1995

Gonadal dysfunction in mitochondrial encephalomyopathies.

To understand endocrine function and to determine which endocrine systems are likely to be affected, 6 patients with mitochondrial encephalomyopathies were studied. Three patients had myoclonus epilepsy and ragged-red fibers, and the other 3 patients had mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes. Clinically, short stature (5/6), amenorrhea (2/3), impotency (3/3), and poor development of secondary sexual characteristics (4/6) were noted. The endocrinological studies including triiodothyronine, tetraiodothyronine, thyrotropin, adrenocorticotropin, cortisol, parathyroid hormone and blood sugar were normal. However, there were low serum concentrations of estradiol (2), and progesterone (2) in 3 female patients. Two patients (1 man and 1 woman) had growth hormone deficiency and 1 had low testosterone level. Hypothalamopituitary dysfunction was confirmed after a series of stimulation tests. We conclude that patients with mitochondrial encephalomyopathies are common to have gonadal dysfunction. Although target organ may play a role, hypothalamopituitary lesion may be responsible for this abnormality.

Adolescent↗

PubMedDate not supplied

Antenatal and neonatal antiretroviral therapy in HIV-infected women and their infants: a review of safety issues.

Specific interventions to prevent mother-to-child transmission (MTCT) include antiretroviral therapy, elective caesarean section and avoidance of breastfeeding. Rates of MTCT below 1-2% are now achievable in developed country settings. However, although the vast majority of infants born to HIV infected mothers are protected from acquisition of infection, most are exposed to antiretroviral drugs for which there is only limited information on toxicity. Increasing use of complex and potent combinations of antiretroviral drugs in pregnancy, particularly during the period of organogenesis, has raised many questions relating to pregnancy outcome and safety issues for the exposed children, both in the short and longer term. A shorter duration of pregnancy has been reported to be associated with taking protease inhibitors in pregnancy, particularly prolonged and early use, but this has been an inconsistent finding. Risk of congenital abnormalities may be increased with exposure to specific antiretroviral drugs, such as efavirenz, and certain combinations of Pneumonia Pneumocystis Carinii (PCP) prophylaxis and antiretroviral drugs, but there is no evidence of an excess of congenital malformations associated with exposure to zidovudine prophylaxis. Although data from observational studies and follow-up of children enrolled in clinical trials have not shown uninfected, zidovudine-exposed children to be at increased risk of adverse events including cancer in the short- to medium-term, the possibility that they may be at risk of cancer at older ages cannot be excluded. Concerns regarding mitochondrial dysfunction in children with foetal/neonatal exposure to zidovudine have arisen following a report from France of eight uninfected children with mitochondrial dysfunction, of whom two died. However, there is limited additional evidence of clinically evident mitochondrial disease in children exposed to antiretroviral therapy in utero or neonatally, and the absence of any excess mortality in large observational cohort studies of children born to HIV infected women and exposed to antiretroviral drugs is reassuring.

Adult↗

PubMed1993

Mitochondrial disease and reduced sperm motility.

Mitochondrial dysfunction reduces aerobic energy production and results in symptoms from various tissues, depending on metabolic demands. Mitochondrial adenosine triphosphate (ATP) is essential for sperm motility. Sperm motility was investigated in a patient with a mitochondrial disease caused by reduced activity of the mitochondrial enzyme complexes I and IV, and in two control subjects. Spermatozoa were cultured in media containing various energy substrates. Motility was judged by light microscopy, and ultrastructure by transmission electron microscopy. In the patient with mitochondrial disease, 12% of the spermatozoa were motile in the medium containing only glucose. There was a three-fold increase in motile spermatozoa when pyruvate and succinate were present together with glucose. In contrast, the spermatozoa of both control subjects had best motility in the presence of substrates for complex I, and no further increase was observed when succinate was added. Glucose and pyruvate enter the respiratory chain at complex I, and succinate at complex II. Electron microscopy of spermatozoa from the patient with mitochondrial disease revealed mitochondria with increased matrix, thickening of membranes, parallelization of cristae and lipid inclusions, which are characteristic findings in mitochondrial disorders. Abnormal mitochondria were also found in a spermatid, suggesting that the ultrastructural changes of mitochondria are primary rather than secondary to degeneration of the spermatozoa. The results indicate that mitochondrial dysfunction causes reduced sperm motility in some men.

Adenosine Triphosphate↗

PubMed2001

Differential induction of apoptosis and MAP kinase signaling by mitochondrial toxicants in drug-sensitive compared to drug-resistant B-lineage lymphoid cell lines.

A panel of human B-lineage lymphoma cell lines differing in cancer drug-resistance status and Bcl-2/Bax expression were used to study the contribution of mitochondrial-based perturbations and regulation in differential induction of apoptosis. Mitochondrial dysfunction was induced in cells by the uncoupler carbonyl cyanide m-chlorophenylhydrazone (mClCCP) and the respiratory chain inhibitor antimycin A. Cells were then assayed for early changes in MAP kinase signaling and subsequent induction of apoptosis. The cancer drug-resistant cell lines EW36 and CA46, overexpressing Bcl-2 and deficient in Bax, respectively, were both resistant to mitochondrial toxicant-induced cleavage of poly(ADP-ribose) polymerase (PARP) and morphologically detectable apoptotic cell death. In contrast, cancer drug-sensitive ST486 cell line, with low Bcl-2 expression, was sensitive to PARP cleavage and apoptosis engagement. Interestingly, mClCCP induced twofold more apoptosis than antimycin A in the ST486 cells. Exposure to the mitochondrial toxicants resulted in the early and preferential activation of the ERK and p38 MAP kinase pathways in only the drug-sensitive ST486 cell line, with mClCCP more potent than antimycin A. Specific inhibition of the p38 pathway augmented baseline and mClCCP-induced apoptosis. These results show that multi-drug-resistant and -sensitive B-lineage cells are also resistant and sensitive to compounds inducing mitochondrial dysfunction. The differential sensitivity to mitochondrial toxicant effects involved regulation by MAP kinases, since ERK and p38 were found to be preferentially activated only in the drug-sensitive B-lineage cells. Modulation of the p38 signaling pathway altered the sensitivity of cells to mitochondrial stress and may play a more general role in regulating the sensitivity of B-lineage cells to drugs and environmental toxicants.

Antimycin A↗

PubMed1997

Cytotoxicity of linoleic acid diols to renal proximal tubular cells.

Monoepoxides of linoleic acid (leukotoxin and isoleukotoxin) have been associated with a variety of pathophysiological diseases in humans including multiple organ failure. They also have been shown to be toxic when injected into experimental animals. Because leukotoxin and isoleukotoxin are excellent substrates for epoxide hydrolases, we tested the hypothesis that the diol metabolites are less toxic than the parent monoepoxides using the rabbit renal proximal tubule (RPT) suspension model. An equimolar mixture of the positional isomers of the methyl esters of leukotoxin and isoleukotoxin did not cause cell death to RPT cells at concentrations up to 1 mm using lactate dehydrogenase release as the endpoint. The corresponding diols, however, caused cell death in a time- and concentration-dependent manner beginning at 4 hr and reaching 42% cell death in 6 hr at 1 mm. Cell death was not due to oxidative stress since malondialdehyde content did not increase and the iron chelator deferoxamine and the antioxidant N,N'-diphenyl-1, 4-phenylenediamine were not cytoprotective. In contrast, cell death was associated with mitochondrial dysfunction with respiration decreasing 54% prior to the onset of cell death. Secondary to the mitochondrial dysfunction, the diols completely inhibited active Na+ transport within 30 min of addition. These results suggest that the in vivo toxicity and pathophysiology previously attributed to the monoepoxides of linoleic acid may be due to the diol metabolites.

Animals↗

PubMed2003

The mitochondria-regulated death pathway mediates asbestos-induced alveolar epithelial cell apoptosis.

The mechanisms underlying asbestos-induced pulmonary toxicity are not fully understood. Alveolar epithelial cell (AEC) apoptosis by iron-derived reactive oxygen species (ROS) is one important mechanism implicated. The two major pathways regulating apoptosis include (i) the mitochondrial death (intrinsic) pathway caused by DNA damage, and (ii) the plasma-membrane death receptor (extrinsic) pathway. However, it is unknown whether asbestos activates either death pathway in AEC. We determined whether asbestos triggers AEC mitochondrial dysfunction by exposing cells (A549 and rat alveolar type II) to amosite asbestos and assessing mitochondrial membrane potential changes (deltapsi(m)) using a fluorometric technique involving tetremethylrhodamine ethyl ester (TMRE) and mitotracker green. Unlike inert particulates (titanium dioxide and glass beads), amosite asbestos caused dose- and time-dependent reductions in deltapsi(m). Asbestos-induced deltapsi(m) was associated with the release of cytochrome c from the mitochondria to the cytoplasm as well as activation of caspase 9, a mitochondrial-activated caspase. In contrast, a lower level of caspase 8, the death receptor-activated caspase, was detected in asbestos-exposed AEC. An iron chelator (phytic acid or deferoxamine) or a hydroxyl radical scavenger (sodium benzoate) each blocked asbestos-induced reductions in deltapsi(m) and caspase 9 activation, suggesting a role for iron-derived ROS. Finally, Bcl-X(L), a mitochondrial antiapoptotic protein that prevents cell death by preserving the outer mitochondrial membrane integrity, blocked asbestos-induced decreases in A549 cell deltapsi(m) and reduced apoptosis as assessed by DNA fragmentation. We conclude that asbestos-induced AEC apoptosis results from mitochondrial dysfunction, in part due to iron-derived ROS, which is followed by the release of cytochrome c and caspase 9 activation. Our findings suggest an important role for the mitochondria-regulated death pathway in the pathogenesis of asbestos-associated pulmonary toxicity.

Animals↗

PubMed2004

Effect of streptozotocin-induced diabetes on rat brain mitochondria.

This study evaluated several parameters related to mitochondrial function and oxidative stress in streptozotocin (STZ)-treated rats, a model of type 1 diabetes. For this purpose, the respiratory indexes (RCR and ADP/O ratio), mitochondrial transmembrane potential (DeltaPsim), repolarization lag phase, repolarization level, mitochondrial enzymatic activities, ATP and malondialdehyde (MDA) levels, reduced glutathione (GSH), vitamin E and cardiolipin contents were determined in rat brain mitochondria isolated after 4 and 9 weeks after STZ treatment. Brain mitochondria isolated from citrate (vehicle)-treated Wistar rats were used as control. We observed that STZ-induced diabetes did not substantially affect brain mitochondrial function. Instead, 4-week diabetic rats presented higher mitochondrial respiratory chain enzymatic activities, especially succinate-cytochrome C reductase activity, compared to 4-week control rats. In 9-week diabetic rats, only a significant decrease in cardiolipin content was observed; however, a significant increase in mitochondrial GSH content occurred. All other parameters analysed remained statistically unchanged. From these results, we conclude that STZ-induced diabetes did not promote brain mitochondrial dysfunction, suggesting that oxidative stress associated with type 1 diabetes is not directly related to mitochondrial dysfunction, but probably is related to extramitochondrial factor(s).

Animals↗

PubMed2006

Mitochondria in Parkinson disease: back in fashion with a little help from genetics.

Parkinson disease is a devastating neurodegenerative disorder with no known cure. Impairment in mitochondrial dysfunction is thought to play a major role in the pathogenesis. Recent genetic advances suggest that mitochondrial dysfunction may be the primary defect. Drugs that target the mitochondria may therefore represent the best hope for disease-modifying therapies in Parkinson disease.

Humans↗

PubMed2005

Emodin induces apoptosis in human lung adenocarcinoma cells through a reactive oxygen species-dependent mitochondrial signaling pathway.

Emodin, a natural anthraquinone derivative isolated from Rheum palmatum L., has been reported to exhibit anti-cancer effect on several human cancers such as liver cancers and lung cancers. However, the molecular mechanisms of emodin-mediated tumor regression have not been fully defined. In this study, we show that treatment with 50 microM emodin resulted in a pronounced release of cytochrome c, activation of caspase-2, -3, and -9, and apoptosis in human lung adenocarcinoma A549 cells. These events were accompanied by the inactivation of ERK and AKT, generation of reactive oxygen species (ROS), disruption of mitochondrial membrane potential ((Delta)psi(m)), decrease of mitochondrial Bcl-2, and increase of mitochondrial Bax content. Ectopic expression of Bcl-2, or treatment with aurintricarboxylic acid, furosemide or caspase inhibitors markedly blocked emodin-induced apoptosis. Conversely, pharmacologic ERK and AKT inhibition promoted emodin-induced apoptosis. Furthermore, the free radical scavenger ascorbic acid and N-acetylcysteine attenuated emodin-mediated ROS production, ERK and AKT inactivation, mitochondrial dysfunction, Bcl-2/Bax modulation, and apoptosis. Take together, these findings suggest that in A549 cells, emodin-mediated oxidative injury acts as an early and upstream change in the cell death cascade to antagonize cytoprotective ERK and AKT signaling, triggers mitochondrial dysfunction, Bcl-2 and Bax modulation, mitochondrial cytochrome c release, caspase activation, and consequent leading to apoptosis.

Adenocarcinoma↗

PubMed2006

Mitochondria: dynamic organelles in disease, aging, and development.

Mitochondria are the primary energy-generating system in most eukaryotic cells. Additionally, they participate in intermediary metabolism, calcium signaling, and apoptosis. Given these well-established functions, it might be expected that mitochondrial dysfunction would give rise to a simple and predictable set of defects in all tissues. However, mitochondrial dysfunction has pleiotropic effects in multicellular organisms. Clearly, much about the basic biology of mitochondria remains to be understood. Here we discuss recent work that suggests that the dynamics (fusion and fission) of these organelles is important in development and disease.

Aging↗