Potassium channel openers protect cardiac mitochondria by attenuating oxidant stress at reoxygenation

2002 ◽  
Vol 282 (2) ◽  
pp. H531-H539 ◽  
Author(s):  
Cevher Ozcan ◽  
Martin Bienengraeber ◽  
Petras P. Dzeja ◽  
Andre Terzic
Keyword(s):  
Cytochrome C ◽  
Structural Integrity ◽  
Oxidant Stress ◽  
Fatty Acid Derivative ◽  
Membrane Integrity ◽  
Radical Scavenger ◽  
Maximal Effect ◽  
Ros Production ◽  
Cytochrome C Release ◽  
Channel Opener

K+ channel openers have been recently recognized for their ability to protect mitochondria from anoxic injury. Yet the mechanism responsible for mitochondrial preservation under oxidative stress is not fully understood. Here, mitochondria were isolated from rat hearts and subjected to 20-min anoxia, followed by reoxygenation. At reoxygenation, increased generation of reactive oxygen species (ROS) was associated with reduced ADP-stimulated oxygen consumption, blunted ATP production, and disrupted mitochondrial structural integrity coupled with cytochrome c release. The prototype K+ channel opener diazoxide markedly reduced mitochondrial ROS production at reoxygenation with a half-maximal effect of 29 μM. Diazoxide also preserved oxidative phosphorylation and mitochondrial membrane integrity, as indicated by electron microscopy and reduced cytochrome c release. The protective effect of diazoxide was reproduced by the structurally distinct K+ channel opener nicorandil and antagonized by 5-hydroxydecanoic acid, a short-chain fatty acid derivative and presumed blocker of mitochondrial ATP-sensitive K+ channels. Opener-mediated mitochondrial protection was simulated by the free radical scavenger system composed of superoxide dismutase and catalase. However, the effect of openers on ROS production was maintained in nominally K+-free medium in the presence or absence of the K+ ionophore valinomycin and was mimicked by malonate, a modulator of the mitochondrial redox state. This suggests the existence of a K+ conductance-independent pathway for mitochondrial protection targeted by K+ channel openers. Thus the cardioprotecive mechanism of K+ channel openers includes direct attenuation of mitochondrial oxidant stress at reoxygenation.

Effect of chronic contractile activity on SS and IMF mitochondrial apoptotic susceptibility in skeletal muscle

2007 ◽  
Vol 292 (3) ◽  
pp. E748-E755 ◽  
Author(s):  
Peter J. Adhihetty ◽  
Vladimir Ljubicic ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Cytochrome C ◽  
Manganese Superoxide Dismutase ◽  
Mitochondrial Permeability Transition ◽  
Contractile Activity ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Ros Production ◽  
Cytochrome C Release ◽  
Apoptosis Inducing Factor

Chronic contractile activity of skeletal muscle induces an increase in mitochondria located in proximity to the sarcolemma [subsarcolemmal (SS)] and in mitochondria interspersed between the myofibrils [intermyofibrillar (IMF)]. These are energetically favorable metabolic adaptations, but because mitochondria are also involved in apoptosis, we investigated the effect of chronic contractile activity on mitochondrially mediated apoptotic signaling in muscle. We hypothesized that chronic contractile activity would provide protection against mitochondrially mediated apoptosis despite an elevation in the expression of proapoptotic proteins. To induce mitochondrial biogenesis, we chronically stimulated (10 Hz; 3 h/day) rat muscle for 7 days. Chronic contractile activity did not alter the Bax/Bcl-2 ratio, an index of apoptotic susceptibility, and did not affect manganese superoxide dismutase levels. However, contractile activity increased antiapoptotic 70-kDa heat shock protein and apoptosis repressor with a caspase recruitment domain by 1.3- and 1.4-fold ( P < 0.05), respectively. Contractile activity elevated SS mitochondrial reactive oxygen species (ROS) production 1.4- and 1.9-fold ( P < 0.05) during states IV and III respiration, respectively, whereas IMF mitochondrial state IV ROS production was suppressed by 28% ( P < 0.05) and was unaffected during state III respiration. Following stimulation, exogenous ROS treatment produced less cytochrome c release (25–40%) from SS and IMF mitochondria, and also reduced apoptosis-inducing factor release (≈30%) from IMF mitochondria, despite higher inherent cytochrome c and apoptosis-inducing factor expression. Chronic contractile activity did not alter mitochondrial permeability transition pore (mtPTP) components in either subfraction. However, SS mitochondria exhibited a significant increase in the time to Vmax of mtPTP opening. Thus, chronic contractile activity induces predominantly antiapoptotic adaptations in both mitochondrial subfractions. Our data suggest the possibility that chronic contractile activity can exert a protective effect on mitochondrially mediated apoptosis in muscle.

Ceramide induces cytochrome c release from isolated mitochondria

1999 ◽  
Vol 66 ◽  
pp. 27-31 ◽  
Author(s):  
Christoph Richter ◽  
Pedram Ghafourifar
Keyword(s):  
Cytochrome C ◽  
Membrane Integrity ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Cytochrome C Release ◽  
Mitochondrial Oxygen Consumption ◽  
Mitochondrial Functions ◽  
Cyt C ◽  
C6 Ceramide

This chapter addresses the role of mitochondria in apoptosis. Emphasis is put on the recently observed influence of ceramides on mitochondrial functions. We report here that N-acetylsphingosine (C2-ceramide), N-hexanoylsphingosine (C6-ceramide) and, to a much lesser extent, C2-dihydroceramide, induce cytochrome c (cyt c) release from isolated rat liver mitochondria. Ceramide-induced cyt c release is prevented by a low concentration of Bcl-2. The release takes place when cyt c is oxidized, but not when it is reduced. Upon cyt c release mitochondrial oxygen consumption, mitochondrial transmembrane potential (ΔΨm) and Ca2+ retention are diminished. Bcl-2 prevents, and addition of cyt c reverses, the alteration of these mitochondrial functions. In ATP-energized mitochondria ceramides do not alter ΔΨm, neither when cyt c is oxidized nor when it is reduced. This rules out a non-specific disturbance by ceramides of mitochondrial-membrane integrity. It is concluded that some of the apoptogenic properties of ceramides are mediated via their interaction with mitochondrial cyt c followed by its release.

Antioxidant MCI-186 inhibits mitochondrial permeability transition pore and upregulates Bcl-2 expression

2003 ◽  
Vol 285 (5) ◽  
pp. H2171-H2178 ◽  
Author(s):  
Katare Gopalrao Rajesh ◽  
Shiro Sasaguri ◽  
Ryoko Suzuki ◽  
Hironori Maeda
Keyword(s):  
Cytochrome C ◽  
Reperfusion Injury ◽  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Acute Ischemia ◽  
Radical Scavenger ◽  
Cytochrome C Release ◽  
Mitochondrial Permeability

Reperfusion after a period of ischemia is associated with the formation of reactive oxygen species (ROS) and Ca2+ overload resulting in the opening of a nonspecific pore in the inner membrane of the mitochondria, called the mitochondrial permeability transition pore (PTP), leading to cell damage. Although endogenous antioxidants are activated because of oxidative stress following ischemia, their levels are not high enough to prevent reperfusion injury. Hence there is always a need for exogenous supplement of antioxidants, especially after acute ischemia. Here we demonstrated the effects of the antioxidant 3-methyl-1-phenyl-2-pyrazolin-5-one (MCI-186) in preventing reperfusion injury of the heart by inhibition of PTP opening. Ischemia (30 min) by left coronary artery (LCA) occlusion and reperfusion (120 min) in Wistar rats after pretreatment with MCI-186 (10 mg/kg iv) infusion starting from 30 min before LCA occlusion resulted in 1) less area of myocardial infarction (19.2% vs. 61.6%), 2) well-maintained myocardial ATP content ( P < 0.03 vs. control), 3) decreased mitochondrial swelling and reduced cytochrome c release, 4) increased expression of BCl-2, 5) lower prevalence of apoptotic cells (14.3% vs. 2.9%), and 6) reduced DNA fragmentation in the MCI-186-treated group. These cytoprotective effects of MCI-186 were inhibited on opening PTP before MCI-186 treatment with the PTP activators lonidamine (10 mg/kg iv) or atractyloside (5 mg/kg iv) but failed to inhibit the protective effects exerted by another antioxidant, allopurinol, suggesting that the PTP inhibiting property is specific for MCI-186. These results demonstrate that the radical scavenger MCI-186, by inhibiting the opening of the PTP, prevents necrosis and cytochrome c release and hence pathological apoptosis.

N-arachidonylglycine causes ROS production and cytochrome c release in liver mitochondria

2009 ◽  
Vol 47 (5) ◽  
pp. 585-592 ◽  
Author(s):  
Patrizia Zaccagnino ◽  
Maddalena Saltarella ◽  
Susanna D'Oria ◽  
Angela Corcelli ◽  
Matilde Sublimi Saponetti ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Liver Mitochondria ◽  
Ros Production ◽  
Cytochrome C Release

Induction of apoptosis in rat lymphocytes by starvation

2006 ◽  
Vol 112 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Juliana Pires ◽  
Rui Curi ◽  
Rosemari Otton
Keyword(s):  
Fatty Acids ◽  
Cytochrome C ◽  
Dna Fragmentation ◽  
Ketone Bodies ◽  
Membrane Integrity ◽  
Diabetic Patients ◽  
Intermembrane Space ◽  
Cytochrome C Release ◽  
Phosphatidylserine Externalization ◽  
Fasted Rats

The aim of the present study was to investigate whether fasting for 24 and 48 h induces apoptosis of rat mesenteric lymph node lymphocytes similar to that observed previously in diabetic patients and alloxan-induced diabetic rats. Several features of lymphocyte death were evaluated by flow cytometry. Plasma levels of glucose, NEFAs (non-esterified fatty acids) and ketone bodies (acetoacetate and β-hydroxybutyrate) were determined in rats fasted for 24 and 48 h. Lymphocytes obtained from fasted rats had an increase in DNA fragmentation and phosphatidylserine externalization after 48 h of culture, although there was no loss of membrane integrity in lymphocytes even after 48 h of culture. Cytochrome c release from the mitochondrial intermembrane space into the cytosol was increased significantly in lymphocytes from fasted rats cultured for 24 h, whereas the levels of bcl-2 and bax proteins were not affected. Activities of caspases 3, 6, 8 and 9 were increased significantly in lymphocytes from rats fasted for 24 h, whereas only an increase in caspase 3 and 9 activities were observed in rats fasted for 48 h. In conclusion, fasting for 24 and 48 h caused a significant increase in the proportion of lymphocytes undergoing apoptosis. The occurrence of apoptosis was observed by DNA fragmentation, phosphatidylserine externalization, cytochrome c release from the mitochondria and activation of the caspase cascade. These findings support the hypothesis that conditions that raise plasma fatty acids levels (e.g. diabetes and starvation) may impair immune function by causing lymphocyte death.

scholarly journals Identification of a Novel Protein MICS1 that is Involved in Maintenance of Mitochondrial Morphology and Apoptotic Release of Cytochrome c

2008 ◽  
Vol 19 (6) ◽  
pp. 2597-2608 ◽  
Author(s):  
Toshihiko Oka ◽  
Tomoko Sayano ◽  
Shoko Tamai ◽  
Sadaki Yokota ◽  
Hiroki Kato ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Morphological Changes ◽  
Mitochondrial Protein ◽  
Membrane Integrity ◽  
Mitochondrial Morphology ◽  
Cytochrome C Release ◽  
Down Regulation ◽  
Inner Membrane ◽  
Inner Membrane Protein ◽  
Tight Association

Mitochondrial morphology dynamically changes in a balance of membrane fusion and fission in response to the environment, cell cycle, and apoptotic stimuli. Here, we report that a novel mitochondrial protein, MICS1, is involved in mitochondrial morphology in specific cristae structures and the apoptotic release of cytochrome c from the mitochondria. MICS1 is an inner membrane protein with a cleavable presequence and multiple transmembrane segments and belongs to the Bi-1 super family. MICS1 down-regulation causes mitochondrial fragmentation and cristae disorganization and stimulates the release of proapoptotic proteins. Expression of the anti-apoptotic protein Bcl-XL does not prevent morphological changes of mitochondria caused by MICS1 down-regulation, indicating that MICS1 plays a role in maintaining mitochondrial morphology separately from the function in apoptotic pathways. MICS1 overproduction induces mitochondrial aggregation and partially inhibits cytochrome c release during apoptosis, regardless of the occurrence of Bax targeting. MICS1 is cross-linked to cytochrome c without disrupting membrane integrity. Thus, MICS1 facilitates the tight association of cytochrome c with the inner membrane. Furthermore, under low-serum condition, the delay in apoptotic release of cytochrome c correlates with MICS1 up-regulation without significant changes in mitochondrial morphology, suggesting that MICS1 individually functions in mitochondrial morphology and cytochrome c release.

The warburg effect and tumour cell survival in human GBMs

2007 ◽  
Vol 30 (4) ◽  
pp. 97 ◽  
Author(s):  
A Wolf ◽  
J Mukherjee ◽  
A Guha
Keyword(s):  
Cytochrome C ◽  
Cell Survival ◽  
Expression Profile ◽  
Tumour Cell ◽  
Warburg Effect ◽  
Glycolytic Enzymes ◽  
Cytochrome C Release ◽  
Apoptotic Pathway ◽  
The Warburg Effect

Introduction: GBMs are resistant to apoptosis induced by the hypoxic microenvironment and standard therapies including radiation and chemotherapy. We postulate that the Warburg effect, a preferential glycolytic phenotype of tumor cells even under aerobic conditions, plays a role in these aberrant pro-survival signals. In this study we quantitatively examined the expression profile of hypoxia-related glycolytic genes within pathologically- and MRI-defined “centre” and “periphery” of GBMs. We hypothesize that expression of hypoxia-induced glycolytic genes, particularly hexokinase 2 (HK2), favours cell survival and modulates resistance to tumour cell apoptosis by inhibiting the intrinsic mitochondrial apoptotic pathway. Methods: GBM patients underwent conventional T1-weighted contrast-enhanced MRI and MR spectroscopy studies on a 3.0T GE scanner, prior to stereotactic sampling (formalin and frozen) from regions which were T1-Gad enhancing (“centre”) and T2-positive, T1-Gad negative (“periphery”). Real-time qRT-PCR was performed to quantify regional gene expression of glycolytic genes including HK2. In vitro functional studies were performed in U87 and U373 GBM cell lines grown in normoxic (21% pO2) and hypoxic (< 1%pO2) conditions, transfected with HK2 siRNA followed by measurement of cell proliferation (BrdU), apoptosis (activated caspase 3/7, TUNEL, cytochrome c release) and viability (MTS assay). Results: There exists a differential expression profile of glycolytic enzymes between the hypoxic center and relatively normoxic periphery of GBMs. Under hypoxic conditions, there is increased expression of HK2 at the mitochondrial membrane in GBM cells. In vitro HK2 knockdown led to decreased cell survival and increased apoptosis via the intrinsic mitochondrial pathway, as seen by increased mitochondrial release of cytochrome-C. Conclusions: Increased expression of HK2 in the centre of GBMs promotes cell survival and confers resistance to apoptosis, as confirmed by in vitro studies. In vivo intracranial xenograft studies with injection of HK2-shRNA are currently being performed. HK2 and possibly other glycolytic enzymes may provide a target for enhanced therapeutic responsiveness thereby improving prognosis of patients with GBMs.

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