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1.
Hydrogen peroxide (H2O2) has key signaling roles at physiological levels, while causing molecular damage at elevated concentrations. H2O2 production by mitochondria is implicated in regulating processes inside and outside these organelles. However, it remains unclear whether and how mitochondria in intact cells release H2O2. Here, we employed a genetically encoded high‐affinity H2O2 sensor, HyPer7, in mammalian tissue culture cells to investigate different modes of mitochondrial H2O2 release. We found substantial heterogeneity of HyPer7 dynamics between individual cells. We further observed mitochondria‐released H2O2 directly at the surface of the organelle and in the bulk cytosol, but not in the nucleus or at the plasma membrane, pointing to steep gradients emanating from mitochondria. Gradient formation is controlled by cytosolic peroxiredoxins, which act redundantly and with a substantial reserve capacity. Dynamic adaptation of cytosolic thioredoxin reductase levels during metabolic changes results in improved H2O2 handling and explains previously observed differences between cell types. Our data suggest that H2O2‐mediated signaling is initiated only in close proximity to mitochondria and under specific metabolic conditions.  相似文献   

2.
High intensity interval training (HIIT) is characterized by vigorous exercise with short rest intervals. Hydrogen peroxide (H2O2) plays a key role in muscle adaptation. This study aimed to evaluate whether HIIT promotes similar H2O2 formation via O2 consumption (electron leakage) in three skeletal muscles with different twitch characteristics. Rats were assigned to two groups: sedentary (n=10) and HIIT (n=10, swimming training). We collected the tibialis anterior (TA-fast), gastrocnemius (GAST-fast/slow) and soleus (SOL-slow) muscles. The fibers were analyzed for mitochondrial respiration, H2O2 production and citrate synthase (CS) activity. A multi-substrate (glycerol phosphate (G3P), pyruvate, malate, glutamate and succinate) approach was used to analyze the mitochondria in permeabilized fibers. Compared to the control group, oxygen flow coupled to ATP synthesis, complex I and complex II was higher in the TA of the HIIT group by 1.5-, 3.0- and 2.7-fold, respectively. In contrast, oxygen consumed by mitochondrial glycerol phosphate dehydrogenase (mGPdH) was 30% lower. Surprisingly, the oxygen flow coupled to ATP synthesis was 42% lower after HIIT in the SOL. Moreover, oxygen flow coupled to ATP synthesis and complex II was higher by 1.4- and 2.7-fold in the GAST of the HIIT group. After HIIT, CS activity increased 1.3-fold in the TA, and H2O2 production was 1.3-fold higher in the TA at sites containing mGPdH. No significant differences in H2O2 production were detected in the SOL. Surprisingly, HIIT increased H2O2 production in the GAST via complex II, phosphorylation, oligomycin and antimycin by 1.6-, 1.8-, 2.2-, and 2.2-fold, respectively. Electron leakage was 3.3-fold higher in the TA with G3P and 1.8-fold higher in the GAST with multiple substrates. Unexpectedly, the HIIT protocol induced different respiration and electron leakage responses in different types of muscle.  相似文献   

3.
Diabetes is a chronic disease associated to a cardiac contractile dysfunction that is not attributable to underlying coronary artery disease or hypertension, and could be consequence of a progressive deterioration of mitochondrial function. We hypothesized that impaired mitochondrial function precedes Diabetic Cardiomyopathy. Thus, the aim of this work was to study the cardiac performance and heart mitochondrial function of diabetic rats, using an experimental model of type I Diabetes. Rats were sacrificed after 28 days of Streptozotocin injection (STZ, 60 mg kg−1, ip.). Heart O2 consumption was declined, mainly due to the impairment of mitochondrial O2 uptake. The mitochondrial dysfunction observed in diabetic animals included the reduction of state 3 respiration (22%), the decline of ADP/O ratio (∼15%) and the decrease of the respiratory complexes activities (22–26%). An enhancement in mitochondrial H2O2 (127%) and NO (23%) production rates and in tyrosine nitration (58%) were observed in heart of diabetic rats, with a decrease in Mn-SOD activity (∼50%). Moreover, a decrease in contractile response (38%), inotropic (37%) and lusitropic (58%) reserves were observed in diabetic rats only after a β‐adrenergic stimulus. Therefore, in conditions of sustained hyperglycemia, heart mitochondrial O2 consumption and oxidative phosphorylation efficiency are decreased, and H2O2 and NO productions are increased, leading to a cardiac compromise against a work overload. This mitochondrial impairment was detected in the absence of heart hypertrophy and of resting cardiac performance changes, suggesting that mitochondrial dysfunction could precede the onset of diabetic cardiac failure, being H2O2, NO and ATP the molecules probably involved in mitochondrion-cytosol signalling.  相似文献   

4.
It has been observed experimentally that cells from failing hearts exhibit elevated levels of reactive oxygen species (ROS) upon increases in energetic workload. One proposed mechanism for this behavior is mitochondrial Ca2+ mismanagement that leads to depletion of ROS scavengers. Here, we present a computational model to test this hypothesis. Previously published models of ROS production and scavenging were combined and reparameterized to describe ROS regulation in the cellular environment. Extramitochondrial Ca2+ pulses were applied to simulate frequency-dependent changes in cytosolic Ca2+. Model results show that decreased mitochondrial Ca2+uptake due to mitochondrial Ca2+ uniporter inhibition (simulating Ru360) or elevated cytosolic Na+, as in heart failure, leads to a decreased supply of NADH and NADPH upon increasing cellular workload. Oxidation of NADPH leads to oxidation of glutathione (GSH) and increased mitochondrial ROS levels, validating the Ca2+ mismanagement hypothesis. The model goes on to predict that the ratio of steady-state [H2O2]m during 3Hz pacing to [H2O2]m at rest is highly sensitive to the size of the GSH pool. The largest relative increase in [H2O2]m in response to pacing is shown to occur when the total GSH and GSSG is close to 1 mM, whereas pool sizes below 0.9 mM result in high resting H2O2 levels, a quantitative prediction only possible with a computational model.  相似文献   

5.
Calorie restriction (CR) has been shown to decrease H2O2 production in liver mitochondria, although it is not known if this is due to uniform changes in all mitochondria or changes in particular mitochondrial sub-populations. To address this issue, liver mitochondria from control and CR mice were fractionated using differential centrifugation at 1,000 g, 3,000 g and 10,000 g into distinct populations labeled as M1, M3 and M10, respectively. Mitochondrial protein levels, respiration and H2O2 production were measured in each fraction. CR resulted in a decrease in total protein (mg) in each fraction, although this difference disappeared when adjusted for liver weight (mg protein/g liver weight). No differences in respiration (State 3 or 4) were observed between control and CR mice in any of the mitochondrial fractions. CR decreased H2O2 production in all fractions when mitochondria respired on succinate (Succ), succ+antimycin A (Succ+AA) or pyruvate/malate+rotenone (P/M+ROT). Thus, CR decreased reactive oxygen species (ROS) production under conditions which stimulate mitochondrial complex I ROS production under both forward (P/M+ROT) and backward (Succ & Succ+AA) electron flow. The results indicate that CR decreases H2O2 production in all liver mitochondrial fractions due to a decrease in capacity for ROS production by complex I of the electron transport chain.  相似文献   

6.
《BBA》2020,1861(12):148290
We hypothesized that NO is generated in isolated cardiac mitochondria as the source for ONOO production during oxidative stress. We monitored generation of ONOO from guinea pig isolated cardiac mitochondria subjected to excess Ca2+ uptake before adding succinate and determined if ONOO production was dependent on a nitric oxide synthase (NOS) located in cardiac mitochondria (mtNOS). Mitochondria were suspended in experimental buffer at pH 7.15, and treated with CaCl2 and then the complex II substrate Na-succinate, followed by menadione, a quinone redox cycler, to generate O2•−. L-tyrosine was added to the mitochondrial suspension where it is oxidized by ONOO to form dityrosine (diTyr) in proportion to the ONOO present. We found that exposing mitochondria to excess CaCl2 before succinate resulted in an increase in diTyr and amplex red fluorescence (H2O2) signals, indicating that mitochondrial oxidant stress, induced by elevated mtCa2+ and succinate, increased mitochondrial ONOO production via NO and O2•−. Changes in mitochondrial ONOO production dependent on NOS were evidenced by using NOS inhibitors L-NAME/L-NNA, TEMPOL, a superoxide dismutase (SOD) mimetic, and PTIO, a potent global NO scavenger. L-NAME and L-NNA decreased succinate and menadione-mediated ONOO production, PTIO decreased production of ONOO, and TEMPOL decreased ONOO levels by converting more O2•− to H2O2. Electron microscopy showed immuno-gold labeled iNOS and nNOS in mitochondria isolated from cardiomyocytes and heart tissue. Western blots demonstrated iNOS and nNOS bands in total heart tissue, bands for both iNOS and nNOS in β-tubulin-free non-purified (crude) mitochondrial preparations, and a prominent iNOS band, but no nNOS band, in purified (Golgi and ER-free) mitochondria. Prior treatment of guinea pigs with lipopolysacharride (LPS) enhanced expression of iNOS in liver mitochondria but not in heart mitochondria. Our results indicate that release of ONOO into the buffer is dependent both on O2•− released from mitochondria and NO derived from a mtCa2+-inducible nNOS isoform, possibly attached to mitochondria, and a mtNOS isoform like iNOS that is non-inducible.  相似文献   

7.
H2O2 production by coupled mitochondrial fractions from the protozoan, Crithidia fasciculata, has been measured spectrophotometrically by the formation of the stable enzyme-substrate complex with yeast cytochrome c peroxidase. H2O2 formation was observed with succinate, l-α-glycerophosphate, l-proline, α-ketoglutarate, and with endogenous substrate. The maximum rate of H2O2 generation obtained with each substrate in the presence of antimycin A was about 10% of the state 4 rate of O2 respiration, and only 1–2% of the carbonylcyanide m-fluorophenylhydrazone-uncoupled respiratory rate. Therefore, excess O2 uptake due to the formation of H2O2 cannot satisfactorily account for the low ADP:O ratios previously reported.Cytochrome c peroxidase activity was measured in mitochondrial preparations by recording the decrease in absorbance at 550 nm during the oxidation of horse heart ferrocytochrome c which was observed after addition of H2O2. The distribution of activity after sonic disruption of mitochondrial preparations was that expected for a soluble enzyme. The activity was proportional to the amount of enzyme protein added, and was abolished by heating at 100 °C for 3 min. Total cytochrome c peroxidase activity in mitochondrial fractions isolated from C. fasciculata was calculated to be 0.3% that of isolated yeast mitochondria, but it is suggested that the in vivo activity may be considerably higher than this estimate.  相似文献   

8.
We compared the capacity of rat liver and heart mitochondria to remove exogenously produced H2O2, determining their ability to decrease fluorescence generated by H2O2 detector system. In the absence of substrates, liver and heart mitochondria removed H2O2 at similar rates. Respiratory substrate addition increased removal rates, indicating a respiration-dependent process. Moreover, the rates were higher with pyruvate/malate than with succinate and in heart than in liver mitochondria. Generally, the changes in H2O2 removal rates mirrored those of H2O2 release rates excluding the possibility that endogenous and exogenous H2O2 competed for the removing system. This idea was supported by the observation that the heaviest of three liver mitochondrial fractions exhibited the highest rates of both H2O2 release and removal. Pharmacological inhibition showed tissue-linked differences in antioxidant enzyme contribution to H2O2 removal which were consistent with the differences in antioxidant system activities. The enzymatic processes accounted only in part for net H2O2 removal and the non-enzymatic ones participated to H2O2 scavenging to a degree that was higher for heart than for liver mitochondria. The idea that non-enzymatic scavenging was due in great part to hemoproteins action was consistent with observation that the concentration of cytochromes, in particular cytochrome c, was higher in heart mitochondria. Indirect support was also obtained by a technique of enhanced luminescence, utilizing the capacity of cytochrome c/H2O2 to catalyze the luminol oxidation, which showed that luminescence response to an oxidative challenge was higher in heart mitochondria.  相似文献   

9.
Adequate methods to measure the rate of mitochondrial oxygen radical generation are needed since oxygen radicals are involved in many pathologies. A fluorometric method appropriate to measure the rate of generation of H2O2 in intact mitochondria is described. Just after isolation of functional mitochondria from fresh tissues, rates of generation of H2O2 are kinetically measured by fluorometry in the presence of homovanillic acid and horseradish peroxidase. The method is specific for H2O2 and is sensitive enough to assay mitochondrial H2O2 generation in the presence of respiratory substrate without inhibitors of the respiratory chain. Simultaneous measurement of mitochondrial oxygen consumption allows calculation of the free radical leak: the percentage of electrons out of sequence which reduce oxygen to oxygen radicals along the mitochondrial respiratory chain instead of reducing oxygen to water at the terminal cytochrome oxidase. The method shows instantaneous response to H2O2. This makes it appropriate to study the quick effects of different inhibitors and modulators on the rate of mitochondrial oxygen radical production. Its application to the localization of the sites where caloric restriction decreases mitochondrial oxygen radical generation in heart mitochondria is described.  相似文献   

10.
Mitochondrial dysfunction and heart disease   总被引:1,自引:0,他引:1  
Rosenberg P 《Mitochondrion》2004,4(5-6):621-628
  相似文献   

11.
This study employed confocal laser scanning microscopy to monitor the effect of H2O2 on cytosolic as well as mitochondrial calcium (Ca2+) concentrations, mitochondrial inner membrane potential (m) and flavine adenine dinucleotide (FAD) oxidation state in isolated mouse pancreatic acinar cells. The results show that incubation of pancreatic acinar cells with H2O2, in the absence of extracellular Ca2+ ([Ca2+]o) led to an increase either in cytosolic and in mitochondrial Ca2+ concentration. Additionally, H2O2 induced a depolarization of mitochondria and increased oxidized FAD level. Pretreatment of cells with the mitochondrial inhibitors rotenone or cyanide inhibited the response induced by H2O2 on mitochondrial inner membrane potential but failed to block oxidation of FAD in the presence of H2O2. However, the H2O2-evoked effect on FAD state was blocked by pretreatment of cells with the mitochondrial uncoupler, carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP). On the other hand, perfusion of cells with thapsigargin (Tps), an inhibitor of the SERCA pump, led to an increase in mitochondrial Ca2+ concentration and in oxidized FAD level, and depolarized mitochondria. Pretreatment of cells with thapsigargin inhibited H2O2-evoked changes in mitochondrial Ca2+ concentration but not those in membrane potential and FAD state. The present results have indicated that H2O2 can evoke marked changes in mitochondrial activity that might be due to the oxidant nature of H2O2. This in turn could represent the mechanism of action of ROS to induce cellular damage leading to cell dysfunction and generation of pathologies in the pancreas. (Mol Cell Biochem 269: 165–173, 2005)  相似文献   

12.
Scavenger enzyme activities in subcellular fractions under polyethylene glycol (PEG)-induced water stress in white clover (Trifolium repens L.) were studied. Water stress decreased ascorbic acid (AA) content and catalase (CAT) activity and increased the contents of hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) (measure of lipid peroxidation), and activities of superoxide dismutase (SOD), its various isozymes, ascorbate peroxidase (APOX), and glutathione reductase (GR) in cellular cytosol, chloroplasts, mitochondria, and peroxisomes of Trifolium repens leaves. In both the PEG-treated plants and the control, chloroplastic fractions showed the highest total SOD, APOX, and GR activities, followed by mitochondrial fractions in the case of total SOD and GR activities, whereas cytosolic fractions had the second greatest APOX activity. However, CAT activity was the highest in peroxisomes, followed by the cytosol, mitochondria, and chloroplasts in decreasing order. Although Mn-SOD activity was highest in mitochondrial fractions, residual activity was also observed in cytosolic fractions. Cu/Zn-SOD and Fe-SOD were observed in all subcellular fractions; however, the activities were the highest in chloroplastic fractions for both isoforms. Total Cu/Zn-SOD activity, the sum of activities observed in all fractions, was higher than other SOD isoforms. These results suggest that cytosolic and chloroplastic APOX, chloroplastic and mitochondrial GR, mitochondrial Mn-SOD, cytosolic and chloroplastic Cu/Zn-SOD, and chloroplastic Fe-SOD are the major scavenger enzymes, whereas cellular CAT may play a minor role in scavenging of O2 and H2O2 produced under PEG-induced water stress in Trifolium repens.  相似文献   

13.
14.
Syu GD  Chen HI  Jen CJ 《PloS one》2011,6(9):e24385
Neutrophil spontaneous apoptosis, a process crucial for immune regulation, is mainly controlled by alterations in reactive oxygen species (ROS) and mitochondria integrity. Exercise has been proposed to be a physiological way to modulate immunity; while acute severe exercise (ASE) usually impedes immunity, chronic moderate exercise (CME) improves it. This study aimed to investigate whether and how ASE and CME oppositely regulate human neutrophil apoptosis. Thirteen sedentary young males underwent an initial ASE and were subsequently divided into exercise and control groups. The exercise group (n = 8) underwent 2 months of CME followed by 2 months of detraining. Additional ASE paradigms were performed at the end of each month. Neutrophils were isolated from blood specimens drawn at rest and immediately after each ASE for assaying neutrophil spontaneous apoptosis (annexin-V binding on the outer surface) along with redox-related parameters and mitochondria-related parameters. Our results showed that i) the initial ASE immediately increased the oxidative stress (cytosolic ROS and glutathione oxidation), and sequentially accelerated the reduction of mitochondrial membrane potential, the surface binding of annexin-V, and the generation of mitochondrial ROS; ii) CME upregulated glutathione level, retarded spontaneous apoptosis and delayed mitochondria deterioration; iii) most effects of CME were unchanged after detraining; and iv) CME blocked ASE effects and this capability remained intact even after detraining. Furthermore, the ASE effects on neutrophil spontaneous apoptosis were mimicked by adding exogenous H2O2, but not by suppressing mitochondrial membrane potential. In conclusion, while ASE induced an oxidative state and resulted in acceleration of human neutrophil apoptosis, CME delayed neutrophil apoptosis by maintaining a reduced state for long periods of time even after detraining.  相似文献   

15.
Oxidative stress is a crucial factor inducing cardiomyocyte apoptosis due to cardiac hypertrophy. Additional evidence has revealed that H2S plays an antioxidant role and is cytoprotective. Hence, we aimed to elucidate whether H2S prevents cardiomyocyte apoptosis due to cardiac hypertrophy via its antioxidant function. The cardiac hypertrophy model was obtained by injecting a high dose of isoproterenol (ISO) subcutaneously, and the hemodynamic parameters were measured in groups that received either ISO or ISO with the treatment of NaHS. TUNEL (terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling) and EM (electron microscopy) experiments were performed to determine the occurrence of apoptosis in heart tissues. The expression of caspase-3 protein in the cytoplasm and NADPH oxidase 4 (NOX4), and cytochrome c (cyt c) proteins in the mitochondria were analyzed using Western blotting. In contrast, to determine whether ISO-induced apoptosis in the cultured cardiomyocytes may be related to oxidative stress, JC-1 and MitoSOX assays were performed to detect the mitochondrial membrane potential and reactive oxygen species (ROS) production in the mitochondria. Exogenous H2S was found to ameliorate cardiac function. The histological observations obtained from TUNEL and EM demonstrated that treatment with NaHS inhibited the occurrence of cardiac apoptosis and improved cardiac structure. Moreover, H2S reduced the expression of the cleaved caspase-3, NOX4 and the leakage of cyt c from the mitochondria to the cytoplasm. We also observed that exogenous H2S could maintain the mitochondrial membrane potential and reduce ROS production in the mitochondria. Therefore, H2S reduces oxidative stress due to cardiac hypertrophy through the cardiac mitochondrial pathway.  相似文献   

16.
The present study was designed to investigate ex vivo the protective mechanisms of heat-shock response against H2O2-induced oxidative stress in peripheral blood mononuclear cells (PBMCs) of rats. Twenty-four hours later, heat-shock treatment was executed in vivo; rat PBMCs were collected and treated with H2O2. The accumulation of reactive oxygen species and the mitochondrial membrane potential were evaluated by intracellular fluorescent dHE and JC-1 dye staining, respectively, and expression of HSP72 and cytochrome c was detected by Western blot analysis. Cellular apoptosis was assayed by TUNEL staining and double staining of Annexin V and PI. The results showed that H2O2-induced oxidative stress leads to intracellular superoxide accumulation and collapse of the mitochondrial membrane potential in rat PBMCs. Moreover, cellular apoptosis was detected after H2O2 treatment, and the release of mitochondrial cytochrome c from mitochondria to cytosol was significantly enhanced. Heat-shock pretreatment decreases the accumulation of intracellular superoxide in PBMCs during H2O2-induced oxidative stress. Moreover, heat-shock treatment prevents the collapse of the mitochondrial membrane potential and cytochrome c release from mitochondria during H2O2-induced oxidative stress. In conclusion, mitochondria are critical organelles of the protective effects of heat-shock treatment. Cellular apoptosis during H2O2-induced oxidative stress is decreased by heat-shock treatment through a decrease in superoxide induction and preservation of the mitochondrial membrane potential.  相似文献   

17.
A recent report (Radi et al., J. Biol. Chem. 266:22028–22034, 1991) showed that rat heart mitochondria contain catalase. The protective role of mitochondrial catalase was tested by exposing heart or kidney mitochondria and mitoplasts to two oxidants (H2O2) or tert-butyl hydroperoxide, t-BOOH), estimating lipid peroxidation (as thiobarbituric acid-reactive substances, TBARS) and overall oxidative stress (as chemiluminescence). Additional controls included heart and kidney preparations from aminotriazole-treated (catalase-depleted) rats. Both oxidants increased TBARS in catalase-free preparations to similar extents over their respective controls (between 200 to 350%). In catalase-containing preparations, H2O2 lipid peroxidation increased by only 40 to 96% over controls. Similar qualitative results were obtained when measuring chemiluminescence. The catalytic role of cytochrome c in mitochondrial lipid peroxidation was investigated by exposing either control or cytochrome-c-depleted kidney mitoplasts (catalase free) to either H2O2 or t-BOOH. Hydrogen-peroxide-dependent mitochondrial lipid peroxidation varied with cytochrome c concentrations, remaining close to controls when cytochrome c concentration decreased by 66%, even though there was no catalase present. Tert-butyl hydroperoxide-dependent lipid peroxidation was less affected by cytochrome c remaining 2.3-fold above controls under the same conditions, suggesting that organic peroxides are more likely to remain in the less polar membrane environment being decomposed by heme or nonheme iron imbedded in the inner mitochondrial membrane. Chemiluminescence was less affected by cytochrome c depletion. Comparing control and cytochrome-c-deficient mitochondria, chemiluminescence was 1.7-fold and 2.8-fold higher when control preparations were challenged with t-BOOH or H2O2, respectively.  相似文献   

18.
Recent evidence highlights monoamine oxidases (MAO) as another prominent source of oxidative stress. MAO are a class of enzymes located in the outer mitochondrial membrane, deputed to the oxidative breakdown of key neurotransmitters such as norepinephrine, epinephrine and dopamine, and in the process generate H2O2. All these monoamines are endowed with potent modulatory effects on myocardial function. Thus, when the heart is subjected to chronic neuro-hormonal and/or peripheral hemodynamic stress, the abundance of circulating/tissue monoamines can make MAO-derived H2O2 production particularly prominent. This is the case of acute cardiac damage due to ischemia/reperfusion injury or, on a more chronic stand, of the transition from compensated hypertrophy to overt ventricular dilation/pump failure. Here, we will first briefly discuss mitochondrial status and contribution to acute and chronic cardiac disorders. We will illustrate possible mechanisms by which MAO activity affects cardiac biology and function, along with a discussion as to their role as a prominent source of reactive oxygen species. Finally, we will speculate on why MAO inhibition might have a therapeutic value for treating cardiac affections of ischemic and non-ischemic origin. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.  相似文献   

19.
《Free radical research》2013,47(9):1085-1094
Abstract

Mitochondrial superoxide flash (mitoflash) reflects quantal and bursting superoxide production and concurrent membrane depolarization triggered by transient mitochondrial permeability transition in many types of cells, at the level of single mitochondria. Here we investigate reactive oxygen species (ROS)-mediated modulation of mitoflash activity in cardiac myocytes and report a surprising finding that hypochlorite ions potently and preferentially triggered mitoflashes in the subsarcolemmal mitochondria (SSM), whereas hydrogen peroxide (H2O2) elicited mitoflash activity uniformly among SSM and interfibrillar mitochondria (IFM). The striking SSM mitoflash response to hypochlorite stimulation remained intact in cardiac myocytes from NOX2-deficient mice, excluding local NOX2-mediated ROS as the major player. Furthermore, it occurred concomitantly with SSM Ca2+ accumulation and local Ca2+ and CaMKII signaling played an important modulatory role by altering frequency and unitary properties of SSM mitoflashes. These findings underscore the functional heterogeneity of SSM and IFM and the oxidant-specific responsiveness of mitochondria to ROS, and may bear important ramifications in devising therapeutic strategies for the treatment of oxidative stress-related heart diseases.  相似文献   

20.
We have examined the substrate specificity and inhibitor sensitivity of H2O2 formation by rat heart mitochondria. Active H2O2 production requires both a high fractional reduction of Complex I (indexed by NADH/NAD+ + NADH ratio) and a high membrane potential, . These conditions are achieved with supraphysiological concentrations of succinate. With physiological concentrations of NAD-linked substrates, rates of H2O2 formation are much lower (less than 0.1% of respiratory chain electron flux) but may be stimulated by the Complex III inhibitor antimycin A, but not by myxothiazol. Addition of Mn2+ to give 10 nmol/mg of mitochondrial protein enhances H2O2 production with all substrate combinations, possibly by repleting mitochondrial superoxide dismutase with this cation. Contrary to previously published work, no increased activity of H2O2 production was found with heart mitochondria from senescent (24 month) rats, relative to young adults (6 month).  相似文献   

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