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Results for “mitochondrial dysfunction”

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At least 199 records · Page 11Linked to original sources

PubMed2002

FKBP12-rapamycin-associated protein associates with mitochondria and senses osmotic stress via mitochondrial dysfunction.

FKBP12-rapamycin associated protein (FRAP, also known as mTOR or RAFT) is the founding member of the phosphatidylinositol kinase-related kinase family and functions as a sensor of physiological signals that regulate cell growth. Signals integrated by FRAP include nutrients, cAMP levels, and osmotic stress, and cellular processes affected by FRAP include transcription, translation, and autophagy. The mechanisms underlying the integration of such diverse signals by FRAP are largely unknown. Recently, FRAP has been reported to be regulated by mitochondrial dysfunction and depletion of ATP levels. Here we show that exposure of cells to hyperosmotic conditions (and to glucose-deficient growth medium) results in rapid and reversible dissipation of the mitochondrial proton gradient. These results suggest that the ability of FRAP to mediate osmotic stress response (and glucose deprivation response) is by means of an intermediate mitochondrial dysfunction. We also show that in addition to cytosolic FRAP a large portion of FRAP associates with the mitochondrial outer membrane. The results support the existence of a stress-sensing module consisting of mitochondria and mitochondrial outer membrane-associated FRAP. This module allows the cell to integrate a variety of stress signals that affect mitochondrial function and regulate a growth checkpoint involving p70 S6 kinase.

3T3 Cells↗

PubMed1997

Mitochondrial dysfunction after experimental and human brain injury and its possible reversal with a selective N-type calcium channel antagonist (SNX-111).

We have recently demonstrated in a rat model that traumatic brain injury induces perturbation of cellular calcium homeostasis with an overload of cytosolic calcium and excessive calcium adsorbed on the mitochondrial membrane, consequently the mitochondrial respiratory chain-linked oxidative phosphorylation was impaired. We report the effect of a selective N-type calcium channel blocker, SNX-111 on mitochondrial dysfunction induced by a controlled cortical impact. Intravenous administration of SNX-111 at varying times post injury was made. The concentration titration profile revealed SNX-111 at 4 mg kg-1 to be optimal, and the time window to be administration at 4 h post-injury, in line with that reported on the effect of SNX-111 in experimental stroke. Under optimal conditions, SNX-111 significantly improved the mitochondrial respiratory chain-linked functions, such as the electron transfer activities with both succinate and NAD-linked substrates, and the accompanied energy coupling capacities measured as respiratory control indices (RCI) and ATP synthesis (P/O ratio), and the energy linked Ca2+ transport. In order to assess the applicability of these data to the clinical setting, we have initiated studies with brain tissue which has to be resected during surgical treatment. Five patients suffered from brain trauma, one from intracranial hypertension due to stroke (noninfarcted tissue was taken), and one from epilepsy. Our data revealed that brain mitochondria derived from the patient with intracranial hypertension and the patient with epilepsy were tightly coupled with good respiratory rates with glutamate and malate as substrates, and high P/O ratios. The rates of respiration and ATP synthesis were severely impaired in the brain mitochondria isolated from traumatized patients. These results indicate that investigation of brain mitochondrial functions can be used as a measure for trauma-induced impairment of brain energy metabolism. The time window for the effect of SNX-111 in mitochondrial function and the (preliminary) similarity between mitochondrial dysfunction in experimental animals and humans make the drug appear to be well suited for clinical trials in severe head injury.

Animals↗

PubMed2004

Characterization of the role of glutathione in repin-induced mitochondrial dysfunction, oxidative stress and dopaminergic neurotoxicity in rat pheochromocytoma (PC12) cells.

Repin, a major constituent in extracts of the plant Centaurea repens is thought to be the active principal responsible for the development of equine nigropallidal encephalomalacia (ENE), a fatal Parkinson-like neurodegenerative disorder in horses. Although the exact mechanism by which ingestion of this weed causes ENE is uncertain, a limited body of experimental evidence suggests a critical role for the glutathione redox system. In the present study, the mechanism of repin neurotoxicity was examined in PC12 cells with a focus on determining the role of glutathione (GSH) in repin-induced mitochondrial dysfunction, oxidative stress and dopaminergic toxicity. The results demonstrate that repin reduced both cellular GSH levels and mitochondrial function in a manner that was time- and concentration-dependent. The repin-induced changes in GSH levels were found to precede the changes in mitochondrial function. Depletion of GSH with a potent GSH depletor (ethacrynic acid (EA)) and a GSH synthesis inhibitor (buthionine sulfoximine (BSO)) prior to repin treatment enhanced the repin-induced mitochondrial change. In addition, repin caused a concentration-dependent decrease in cellular dopamine levels in NGF-differentiated PC12 cells. Increases in intracellular GSH levels induced by pre-treatment with reducing agents (N-acetyl-L-cysteine or reduced glutathione) completely protected the cells from repin-induced mitochondrial and dopaminergic toxicity. Antioxidants, coenzyme-Q and ascorbic acid completely blocked repin-induced dopaminergic toxicity. These data suggest that GSH plays a critical role in repin-induced neurotoxicity and that the maintenance of neuronal redox status may prove to be a useful strategy for the prevention and/or treatment of ENE. The results support the view that GSH depletion, leading to oxidative damage and subsequent mitochondrial dysfunction, may serve as a trigger for neuronal cell death.

Animals↗

PubMed2001

Attenuation of staurosporine-induced apoptosis, oxidative stress, and mitochondrial dysfunction by synthetic superoxide dismutase and catalase mimetics, in cultured cortical neurons.

Neuronal apoptosis induced by staurosporine (STS) involves multiple cellular and molecular events, such as the production of reactive oxygen species (ROS). In this study, we tested the efficacy of two synthetic superoxide dismutase/catalase mimetics (EUK-134 and EUK-189) on neuronal apoptosis, oxidative stress, and mitochondrial dysfunction produced by STS in primary cortical neuronal cultures. Exposure of cultures to STS for 24 h increased lactate dehydrogenase (LDH) release, the number of apoptotic cells, and decreased trypan blue exclusion. Pretreatment with 20 microM EUK-134 or 0.5 microM EUK-189 significantly attenuated STS-induced neurotoxicity, as did pretreatment with the caspase-1 inhibitor, Ac-YVAD-CHO, but not the caspase-3 inhibitor, Ac-DEVD-CHO. Posttreatment (1-3 h following STS exposure) with 20 microM EUK-134 or 0.5 microM EUK-189 significantly reduced STS-induced LDH release, in a time-dependent manner. Exposure of cultures to STS for 1 h produced an elevation of ROS, as determined by increased levels of 2,7-dichlorofluorescein (DCF). This rapid elevation of ROS was followed by an increase in lipid peroxidation, and both the increase in DCF fluorescence and in lipid peroxidation were significantly blocked by pretreatment with EUK-134. STS treatment for 3-6 h increased cytochrome c release from mitochondria into the cytosol, an effect also blocked by pretreatment with EUK-134. These results indicate that intracellular oxidative stress and mitochondrial dysfunction are critically involved in STS-induced neurotoxicity. However, there are additional cellular responses to STS, which are insensitive to treatment with radical scavengers that also contribute to its neurotoxicity.

Animals↗

PubMed1981

Mechanism of chlorpromazine-induced arrhythmia -- arrhythmia and mitochondrial dysfunction.

In this study, we investigated the mechanism of the arrhythmogenic action of chlorpromazine (CPZ). Thirty-two anesthetized mongrel dogs were used. In each, the chest was opened and a stimulating electrode was attached to the apex of the left ventricle and the ventricular multiple response threshold (VMRT) was measured. The carotid artery was cannulated to measure aortic pressure. The dogs were divided into four groups, and the time course of VMRT, blood pressure, and heart rate were determined. All groups were placed under observation for 30 min after CPZ infusion. In the control group, only saline (2ml/kg) was infused; CPZ group: CPZ (Img/kg) was infused 10 min after saline (2ml/kg) infusion; CoQ10 group: Coenzyme Q10 (CoQ10) (5mg/kg) was infused 10 min before CPZ (Img/kg) infusion; FAD group: Flavin-adenine-dinucleotide (FAD) (2mg/kg) was infused 10 min before CPZ (Img/kg) infusion. In each group, myocardial mitochondria were prepared 30 min after CPZ infusion. The mitochondrial functions, respiratory control index, AdP/O, State III rate of oxygen consumption, and activities of two segments of the electron-transport chain (NADH leads to CoQ leads to cyt.c and cyt.c leads to cyt.a,a3 leads to O2) were measured separately. Ca++--binding activity of the mitochondria was also determined. CPZ administration decreased VMRT and blood pressure, and caused mitochondrial dysfunction which derived from a disturbance in the first segment of the electron transport chain. Decreased Ca++--binding activity was observed when mitochondrial function was disturbed. CoQ10 prevented significantly the decrease in VMRT and the disturbance of mitochondrial function induced by CPZ, but did not prevent the hypotensive effect of CPZ. FAD prevented not only the decrease in VMRT and the disturbance of mitochondrial function, but also the hypotensive effect of CPZ. These results suggest that the decrease in VMRT is closely related to mitochondrial dysfunction induced by CPZ. Moreover, it is suggested that the arrhythmogenic effect of CPZ is derived from the decreased mitochondrial Ca++--binding activity.

Animals↗

PubMed2001

Mitochondrial dysfunction associated with a mutation in the Notch3 gene in a CADASIL family.

BACKGROUND: Cerebral autosomal arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by recurrent subcortical ischemic strokes and dementia caused by mutations in the Notch3 gene. In Drosophila melanogaster, Notch signaling has a pleiotropic effect, affecting most tissues of the organism during development. OBJECTIVE: To characterize a potential mitochondrial dysfunction associated with mutations in the Notch3 gene. METHODS: Biochemical, histochemical, molecular, and genetic analyses were performed on muscle biopsy specimens and fibroblasts obtained from patients of a Spanish family with CADASIL. Additional biochemical and molecular analyses of the N(55e11) mutant of D. melanogaster were performed. RESULTS: In muscle biopsy specimens, a significant decrease was found in the activity of complex I (NADH [reduced form of nicotinamide adenine dinucleotide] dehydrogenase), and in one patient, histochemical analysis showed the presence of ragged-red fibers with abnormal cytochrome c oxidase staining. Reduced fibroblast activity of complex V (ATP synthase) was found. Supporting data on patients with CADASIL, it was found that the mutation N(55e11) in Drosophila decreases the activity of mitochondrial respiratory complexes I and V. CONCLUSIONS: Mitochondrial respiratory chain activity responds, directly or indirectly, to the Notch signaling pathway. Mitochondrial dysfunction in patients with CADASIL may be an epiphenomenon, but results of this study suggest that the pathophysiology of the disease could include a defect in oxidative phosphorylation.

Adult↗

PubMed2002

Neurolathyrism: mitochondrial dysfunction in excitotoxicity mediated by L-beta-oxalyl aminoalanine.

beta-N-Oxalyl amino-L-alanine (L-BOAA); synonym beta-N-oxalyl-alpha,beta-diaminopropionic acid (beta-ODAP) is a naturally occurring non-protein amino acid present in the chickling pea from the plant Lathyrus sativus grown in drought prone areas. Ingestion of L-BOAA as a staple diet results in a progressive neurodegenerative condition, neurolathyrism, a form of motor neuron disease which affects the upper motor neurons and anterior horn cells of the lumbar spinal cord. L-BOAA is an excitatory acid and acts as an agonist at the AMPA receptor. One of the primary effects of L-BOAA toxicity is the inhibition of mitochondrial complex I selectively in the motor cortex and lumbar spinal cord. Recent evidence has suggested that the mitochondrial dysfunction is a consequence of oxidation protein thiol groups as a result of generation of reactive oxygen species. Mitochondrial complex I is highly to vulnerable to inactivation through oxidation of vital sulfhydryl groups. Thiol antioxidants such as alpha-liopic acid offer a method of protecting mitochondrial function. A common mechanism involving oxidation of protein thiol groups may underlie neurodegeneration occurring through mitochondrial dysfunction induced by excitatory amino acid.

Amino Acids, Diamino↗

PubMed2005

Proteomics analysis provides insight into caloric restriction mediated oxidation and expression of brain proteins associated with age-related impaired cellular processes: Mitochondrial dysfunction, glutamate dysregulation and impaired protein synthesis.

Age-related impairment of functionality of the central nervous system (CNS) is associated with increased susceptibility to develop many neurodegenerative diseases. Increased oxidative stress in the CNS of aged animals is manifested by increased protein oxidation, which is believed to contribute to the age-related learning and memory deficits. Glutamate dysregulation, mitochondrial dysfunction and impaired protein synthesis are observed in aged brains, along with increased protein oxidation. Interestingly, all of these age-related cellular alterations can be improved by caloric restriction (CR), which can also improve the plasticity and recovery of the CNS. Although the beneficial effects of CR on brains are well established, the mechanism(s) of its action remains unclear. In order to gain insight into the mechanism of CR in the brain, we located the brain regions that are benefited the most from reduced oxidative stress by CR. Along with other brain regions, striatum (ST) showed significantly decreased bulk protein carbonyl levels and hippocampus (HP) showed decreased bulk protein 3-nitrotyrosine (3-NT) levels in CR aged rats when compared to those of age matched controls. To determine which proteins were oxidatively modified in these brain regions, we used parallel proteomics approach to identify the proteins that are altered in oxidation and expression. The specific carbonyl levels of pyruvate kinase M2 (PKM2), alpha-enolase (ENO1), inositol monophosphatase (INSP1), and F1-ATPase Chain B (ATP-F1B) were significantly decreased in ST of aged CR rats. In contrast, the expression levels of phosphoglycerate kinase 1 (PKG1), inosine monophosphate cyclohydrolase (IMPCH) and F1-ATPase Chain A (ATP-F1A) were significantly increased in the ST of CR rats. In the hippocampus of CR rats, the specific 3-NT levels of malate dehydrogenase (MDH), phosphoglycerate kinase 1 (PKG1) and 14-3-3 zeta protein were significantly decreased and expression levels of DLP1 splice variant 1 (DLP1), mitochondrial aconitase (ACO2), dihydrolipoamide dehydrogenase (DLDH), neuroprotective peptide H3 (NPH3), and eukaryotic translation initiation factor 5A (eIF-5A) are increased. Moreover, an unnamed protein product (UNP1) with similar sequence to initiation factor 2 (IF-2) was decreased in the HP of CR rats. Our data support the hypothesis that CR induces a mild metabolic stress response by increasing the production of neurotrophic proteins, therefore, priming neurons against apoptosis. Moreover, our study shows that the improvement of glutamate dysregulation, mitochondrial dysfunction and protein synthesis by CR is, at least partially, due to the CR-mediated alteration of the oxidation or the expression of PKM2, ENO1, INSP1, ATP-F1B, PKG1, IMPCH, ATP-F1A MDH, PKG1 and 14-3-3 zeta protein, DLP1, ACO2, DLDH, NPH3, eIF-5A and UNP1. This study provides valuable insights into the mechanisms of the beneficial factors on brain aging by CR.

Aging↗

PubMed2006

Mitochondrial dysfunction in patients with severe sepsis: an EPR interrogation of individual respiratory chain components.

Electron paramagnetic resonance (EPR) spectra of complex biological systems contain information about the paramagnetic centres present. Retrieving such information is important since paramagnetic species are common intermediates of all redox reactions in both normal and abnormal metabolism. However, it is often difficult to determine the nature and content of all paramagnetic species present because the EPR signals from individual centres overlap. Here, we apply our deconvolution method based on spectra subtraction with variable coefficient to quantify individual paramagnetic components of human muscle biopsies taken from critically ill patients with severe sepsis. We use low temperature EPR spectroscopy to identify and quantify nine different paramagnetic species in the tissue. These include the majority of the mitochondrial iron-sulfur centres and the first in vivo report of a mitochondrial radical assigned to a spin-coupled pair of semiquinones (SQ*-SQ*). We have previously demonstrated in these same muscle biopsies that biochemical assays of mitochondrial dysfunction correlate with clinical outcomes (D. Brealey, M. Brand, I. Hargreaves, S. Heales, J. Land, R. Smolenski, N.A. Davies, C.E. Cooper, M. Singer, Association between mitochondrial dysfunction and severity and outcome of septic shock. Lancet 360 (2002) 219-223.). Analysis of the paramagnetic centres in the muscle confirms and extends these findings: the (SQ*-SQ*) radical species negatively correlates with the illness severity of the patient (APACHE II score) and a decreased concentration of mitochondrial Complex I iron-sulfur redox centres is linked to mortality.

Electron Spin Resonance Spectroscopy↗

PubMed1999

The antioxidant EPC-K1 attenuates NO-induced mitochondrial dysfunction, lipid peroxidation and apoptosis in cerebellar granule cells.

In this study we investigated the effects of nitric oxide (NO) on cultured cerebellar granule cells. Exposure to NO donors, S-nitrosoglutathione (GSNO; 250 microM) or sodium nitroprusside (SNP; 500 microM), triggered apoptosis in immature cultures of cerebellar granule cells, which was characterized by chromatin condensation, nuclei fragmentation, and DNA laddering. Exposure of cerebellar granule cells to NO donors led to a decrease in the mitochondrial transmembrane potential and intracellular ATP content, which suggested that NO treatment caused mitochondrial dysfunction. NO treatment also induced oxidative stress in cerebellar granule cells as measured by thiobarbituric acid (TBA) assay. Pretreating cells with L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H -1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K1), a novel antioxidant, attenuated NO-induced mitochondrial dysfunction and oxidative stress to some extent, and prevented the cells from apoptosis. The results of the present investigation suggest that a superoxide/peroxynitrite-mediated oxidative stress may be an important pathway leading to NO-associated neuronal damage. Pretreating cells with the antioxidant EPC-K1 attenuated NO-induced neurotoxicity by scavenging superoxide/peroxynitrite and/or its breakdown products.

Animals↗

PubMed2006

Oxidative stress, mitochondrial dysfunction, and stress signaling in Alzheimer's disease.

Although oxidative stress and mitochondrial dysfunction have been linked to neurodegenerative diseases such as Alzheimer's disease (AD), it remains unclear how mitochondrial oxidative stress may induce neuronal death. In a variety of tissues, cumulative oxidative stress, disrupted mitochondrial respiration, and mitochondrial damage are associated with, and may indeed promote cell death and degeneration. In this review, we examine current evidence supporting the involvement of mitochondria and mitochondrially generated stress signaling in AD and discuss potential implications for the mechanism of pathogenesis of this disease. Mitochondria are pivotal in controlling cell life and death not only by producing ATP, and sequestering calcium, but by also generating free radicals and serving as repositories for proteins which regulate the intrinsic apoptotic pathway. Perturbations in the physiological function of mitochondria inevitably disturb cell function, sensitize cells to neurotoxic insults and may initiate cell death, all significant phenomena in the pathogenesis of a number of neurodegenerative disorders including AD.

Alzheimer Disease↗

PubMed2007

Mitochondrial dysfunction in human colorectal cancer progression.

The classic association between cancer and mitochondrial dysfunction is actually considered as a role of mitochondria in cellular signalling. It is understood that mitochondria, mitochondrial oxidative damage and NO and H2O2 diffusion are involved in the progression of human colorectal cancer. Mitochondria from human colorectal tumors and adjacent non-tumor colon tissues showed a markedly increased oxidative damage with increased contents of TBARS and protein carbonyls. Mitochondrial protein carbonyls was the most sensitive indicator. Oxidative stress and damage was also observed in adjacent non-tumor cells. Mitochondrial activities, as NADH-cytochrome c reductase and cytochrome oxidase, were observed decreased in tumor and in adjacent non-tumor tissue. Cu,Zn-SOD activity decreased by 42% in tumor tissue in the advanced stage as compared with the initial stage, whereas Mn-SOD activity did not change in tumor progression. An increased mtNOS activity (46%) was observed in tumor and non-tumor tissues in the advanced stage of cancer progression. A direct linear relationship between mtNOS and oxidative damage in tumor and non-tumor tissues supports the concept that mitochondrial NO and H2O2 diffuse from tumor to adjacent non tumor tissue signaling for cell death as the classic toxohormones.

Colorectal Neoplasms↗

PubMed2003

Tea catechins protect against lead-induced ROS formation, mitochondrial dysfunction, and calcium dysregulation in PC12 cells.

Recent studies have shown that lead causes oxidative stress by inducing the generation of reactive oxygen species (ROS) and reducing the antioxidant defense system of cells, which suggests that antioxidants may play an important role in the treatment of lead poisoning. The present study was designed to elucidate whether tea catechins had any protective effects on altered oxidative stress parameter in PC12 cells exposed to lead. The experimental results showed that lead decreased PC12 cell viability and induced a rapid elevation of [Ca(2+)](i), which was followed by an accumulation of ROS and a decrease of mitochondrial membrane potential (MMP). Treatment by tea catechins significantly increased cell viability, decreased intracellular Ca(2+) levels and ROS formation, and improved MMP in PC12 cells exposed to lead. The galloylated catechins showed a greater effect on ROS formation and mitochondrial dysfunction than that of nongalloylated catechins, which was similar to the result of their scavenging ability on free radical. In view of the time course of ROS formation and mitochondrial dysfunction and their correlation, our results also suggested that the beneficial effects of tea catechins on MMP are related, at least in part, to its ability to scavenge ROS in PC12 cells exposed to 100 microM Pb(2+). The present results suggest that tea catechins supplementation may play a role for modulating oxidative stress in PC12 cells exposed to lead.

Animals↗

PubMed1999

Altered calcium homeostasis and mitochondrial dysfunction in cortical synaptic compartments of presenilin-1 mutant mice.

Alzheimer's disease is characterized by amyloid beta-peptide deposition, synapse loss, and neuronal death, which are correlated with cognitive impairments. Mutations in the presenilin-1 gene on chromosome 14 are causally linked to many cases of early-onset inherited Alzheimer's disease. We report that synaptosomes prepared from transgenic mice harboring presenilin-1 mutations exhibit enhanced elevations of cytoplasmic calcium levels following exposure to depolarizing agents, amyloid beta-peptide, and a mitochondrial toxin compared with synaptosomes from nontransgenic mice and mice overexpressing wild-type presenilin-1. Mitochondrial dysfunction and caspase activation following exposures to amyloid beta-peptide and metabolic insults were exacerbated in synaptosomes from presenilin-1 mutant mice. Agents that buffer cytoplasmic calcium or that prevent calcium release from the endoplasmic reticulum protected synaptosomes against the adverse effect of presenilin-1 mutations on mitochondrial function. Abnormal synaptic calcium homeostasis and mitochondrial dysfunction may contribute to the pathogenic mechanism of presenilin-1 mutations.

Alzheimer Disease↗

PubMed2005

Insulin resistance in the HIV-infected population: the potential role of mitochondrial dysfunction.

Insulin resistance is accepted as the underlying fundamental defect that predates and ultimately leads to the development of type 2 (adult onset) diabetes mellitus in the general non-human immunodeficiency virus (HIV)-infected population. Insulin resistance is also a major component of the metabolic syndrome that, in association with other factors such as hypertension, hypercholesterolemia, and central obesity, defines a pre-diabetic atherogenic state that leads to adverse cardiovascular events. Growing evidence now suggests that mitochondrial dysfunction in skeletal muscle may be the mechanism whereby insulin resistance is induced. The prevalence of insulin resistance, glucose intolerance, and diabetes in the HIV-infected population has dramatically increased following the common use of highly active antiretroviral therapy (HAART). The development of insulin resistance in the HIV-infected population is likely to be multifactorial reflecting genetic predisposition, direct and indirect effects of both the protease inhibitor (PI) and nucleoside reverse transcriptase inhibitor (NRTI) class of antiretroviral therapy, and a possible contribution from chronic inflammatory changes induced by HIV. Indirect effects of antiretroviral therapy on insulin resistance may be mediated through both the visceral adiposity and peripheral fat depletion components of lipodystrophy as well as through fatty infiltration in liver and muscle. Based on current knowledge, mitochondrial dysfunction can be hypothesized to play a key role in each of these components.

Acquired Immunodeficiency Syndrome↗

PubMed2003

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) promotes mitochondrial dysfunction and apoptosis induced by 7-hydroxystaurosporine and mitogen-activated protein kinase kinase inhibitors in human leukemia cells that ectopically express Bcl-2 and Bcl-xL.

Previous studies have demonstrated that cotreatment with mitogen activated-protein kinase kinase (MEK) 1/2 inhibitors (e.g., PD184352) and the checkpoint abrogator 7-hydroxystaurosporine (UCN-01) dramatically induces apoptosis in a variety of human leukemia and multiple myeloma cell types. The purpose of this study was to evaluate the roles of Bcl-2 family members and the relative contribution of the intrinsic mitochondrial versus the extrinsic receptor-related apoptotic pathways to MEK inhibitors/UCN-01-induced leukemic cell death. Cotreatment of U937 cells with PD184352 and UCN-01 resulted in the activation of procaspase-3, -9, and -8 as well as Bid cleavage. PD184352/UCN-01-induced mitochondrial dysfunction and apoptosis were both substantially attenuated in cells ectopically expressing Bcl-2, an N-terminal phosphorylation loop-deleted mutant Bcl-2, or Bcl-xL, but not in cells expressing dominant-negative (DN) caspase-8, cytokine response modifier A (cowpox virus-encoded antiapoptotic protein), or DN Fas-associated death domain. Coadministration of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) or TNF-alpha substantially increased MEK inhibitors (e.g., PD184352 or U0126)/UCN-01-induced mitochondrial dysfunction, activation of procaspase-8 and Bid, and apoptosis in Bcl-2- and Bcl-xL-overexpressing cells but not in those in which the extrinsic pathway was interrupted. Together, these findings suggest that the MEK inhibitors/UCN-01 regimen primarily induces leukemic cell apoptosis by engaging the intrinsic, mitochondrial apoptotic pathway and that resistance to these events conferred by increased expression of certain antiapoptotic Bcl-2 family members can be overcome, at least in part, by coadministration of TRAIL and other agents that activate the extrinsic apoptotic cascade.

Apoptosis↗

PubMed2005

Physiologic progesterone reduces mitochondrial dysfunction and hippocampal cell loss after traumatic brain injury in female rats.

Growing literature suggests important sex-based differences in outcome following traumatic brain injury (TBI) in animals and humans. Progesterone has emerged as a key hormone involved in many potential neuroprotective pathways after acute brain injury and may be responsible for some of these differences. Many studies have utilized supraphysiologic levels of post-traumatic progesterone to reverse pathologic processes after TBI, but few studies have focused on the role of endogenous physiologic levels of progesterone in neuroprotection. We hypothesized that progesterone at physiologic serum levels would be neuroprotective in female rats after TBI and that progesterone would reverse early mitochondrial dysfunction seen in this model. Female, Sprague-Dawley rats were ovariectomized and implanted with silastic capsules containing either low or high physiologic range progesterone at 7 days prior to TBI. Control rats received ovariectomy with implants containing no hormone. Rats underwent controlled cortical impact to the left parietotemporal cortex and were evaluated for evidence of early mitochondrial dysfunction (1 h) and delayed hippocampal neuronal injury and cortical tissue loss (7 days) after injury. Progesterone in the low physiologic range reversed the early postinjury alterations seen in mitochondrial respiration and reduced hippocampal neuronal loss in both the CA1 and CA3 subfields. Progesterone in the high physiologic range had a more limited pattern of hippocampal neuronal preservation in the CA3 region only. Neither progesterone dose significantly reduced cortical tissue loss. These findings have implications in understanding the sex-based differences in outcome following acute brain injury.

Animals↗

PubMed1995

Nitric oxide mediates mitochondrial dysfunction in hepatoma cells induced by non-activated Kupffer cells: evidence implicating ICAM-1-dependent process.

The metabolic changes in a rat hepatoma cell line, AH70 cells, after co-culture with rat Kupffer cells (KC) were visualized and analysed using a fluorescence microscope equipped with a silicon intensified target camera and a laser scanning confocal microscopic system. Kupffer cells were isolated from male Wistar rats, and cultured without any stimuli. The non-activated KC reduced the mitochondrial energization in the cocultured AH70 cells within 2 h, which was indicated by decreased rhodamine 123 (Rh123) fluorescence. Either NG-monomethyl-L-arginine or dexamethasone significantly attenuated the KC-induced mitochondrial dysfunction in AH70 cells, suggesting the involvement of nitric oxide (NO) derived from inducible-type nitric oxide synthase (iNOS). Administration of monoclonal antibody (mAb) directed against rat ICAM-1 also prevented the decrease in Rh123 fluorescence. Electron microscopy revealed that the membrane-to-membrane attachment between KC and AH70 cells occurred within 2 h. A laser scanning confocal microscopic observation using mAb against ICAM-1 presented that the ICAM-1 expression on AH70 cells and KC increased after the co-culture. It is therefore concluded that the KC-mediated mitochondrial dysfunction of hepatoma cells largely depends on NO production by iNOS. Furthermore, the present study supports a scenario that the NO production and release from KC is triggered by the close contact with hepatoma cells through adhesion molecules such as ICAM-1.

Animals↗