Exercise training decreases rat heart mitochondria free radical generation but does not prevent Ca2+-induced dysfunction

2007 ◽  
Vol 102 (5) ◽  
pp. 1793-1798 ◽  
Author(s):  
Joseph W. Starnes ◽  
Brian D. Barnes ◽  
Marissa E. Olsen
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Electron Flow ◽  
Respiratory Control ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Calcium Overload ◽  
Ros Generation ◽  
Ros Production ◽  
Ptp Opening

Exercise provides cardioprotection against ischemia-reperfusion injury, a process involving mitochondrial reactive oxygen species (ROS) generation and calcium overload. This study tested the hypotheses that isolated mitochondria from hearts of endurance-trained rats have decreased ROS production and improved tolerance against Ca2+-induced dysfunction. Male Fischer 344 rats were either sedentary (Sed, n = 8) or endurance exercise trained (ET, n = 11) by running on a treadmill for 16 wk (5 days/wk, 60 min/day, 25 m/min, 6° grade). Mitochondrial oxidative phosphorylation measures were determined with glutamate-malate or succinate as substrates, and H2O2 production and permeability transition pore (PTP) opening were determined with succinate. All assays were carried out in the absence and presence of calcium. In response to 25 and 50 μM CaCl2, Sed and ET displayed similar decreases in state 3 respiration, respiratory control ratio, and ADP:O ratio. Ca2+-induced PTP opening was also similar. However, H2O2 production by ET was lower than Sed ( P < 0.05) in the absence of calcium (323 ± 12 vs. 362 ± 11 pmol·min−1·mg protein−1) and the presence of 50 μM CaCl2 (154 ± 3 vs. 197 ± 7 pmol·min−1·mg protein−1). Rotenone, which blocks electron flow from succinate to complex 1, reduced H2O2 production and eliminated differences between ET and Sed. Mitochondrial superoxide dismutase and glutathione peroxidase were not affected by exercise. Catalase activity was extremely low but increased 49% in ET ( P < 0.05). In conclusion, exercise reduces ROS production in myocardial mitochondria through adaptations specific to complex 1 but does not improve mitochondrial tolerance to calcium overload.

scholarly journals Nutritional Preconditioning of Apigenin Alleviates Myocardial Ischemia/Reperfusion Injury via the Mitochondrial Pathway Mediated by Notch1/Hes1

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Huang Huang ◽  
Songqing Lai ◽  
Yong Luo ◽  
Qing Wan ◽  
Qicai Wu ◽  
...  
Keyword(s):  
Caspase 3 ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mitochondrial Pathway ◽  
Ros Generation ◽  
Antioxidant Power ◽  
Hes1 Expression

Apigenin (Api), a natural flavone found in high amounts in several herbs, has shown potent cardioprotective effects in clinical studies, although the underlying mechanisms are not clear. We hypothesized that Api protects the myocardium from simulated ischemia/reperfusion (SI/R) injury via nutritional preconditioning (NPC). Rats fed with Api-containing food showed improvement in cardiac functions; lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) activities; infarct size; apoptosis rates; malondialdehyde (MDA) levels; caspase-3, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities; and ferric reducing antioxidant power (FRAP) compared to those fed standard chow following SI/R injury. In addition, Api pretreatment significantly improved the viability, decreased the LDH activity and intracellular reactive oxygen species (ROS) generation, alleviated the loss of mitochondrial membrane potential (MMP), prevented the opening of the mitochondrial permeability transition pore (mPTP), and decreased the caspase-3 activity, cytochrome c (Cyt C) release, and apoptosis induced by SI/R in primary cardiomyocytes. Mechanistically, Api upregulated Hes1 expression and was functionally neutralized by the Notch1 γ-secretase inhibitor GSI, as well as the mPTP opener atractyloside (Atr). Taken together, Api protected the myocardium against SI/R injury via the mitochondrial pathway mediated by the Notch1/Hes1 signaling pathway.

scholarly journals Mitochondrial dysfunction in uremic cardiomyopathy

2015 ◽  
Vol 308 (6) ◽  
pp. F579-F587 ◽  
Author(s):  
David Taylor ◽  
Sunil Bhandari ◽  
Anne-Marie L. Seymour
Keyword(s):  
Cell Death ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Respiratory Control ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Oxidative Capacity ◽  
Mitochondrial Redox State ◽  
Uremic Cardiomyopathy

Uremic cardiomyopathy (UCM) is characterized by metabolic remodelling, compromised energetics, and loss of insulin-mediated cardioprotection, which result in unsustainable adaptations and heart failure. However, the role of mitochondria and the susceptibility of mitochondrial permeability transition pore (mPTP) formation in ischemia-reperfusion injury (IRI) in UCM are unknown. Using a rat model of chronic uremia, we investigated the oxidative capacity of mitochondria in UCM and their sensitivity to ischemia-reperfusion mimetic oxidant and calcium stressors to assess the susceptibility to mPTP formation. Uremic animals exhibited a 45% reduction in creatinine clearance ( P < 0.01), and cardiac mitochondria demonstrated uncoupling with increased state 4 respiration. Following IRI, uremic mitochondria exhibited a 58% increase in state 4 respiration ( P < 0.05), with an overall reduction in respiratory control ratio ( P < 0.01). Cardiomyocytes from uremic animals displayed a 30% greater vulnerability to oxidant-induced cell death determined by FAD autofluorescence ( P < 0.05) and reduced mitochondrial redox state on exposure to 200 μM H2O2 ( P < 0.01). The susceptibility to calcium-induced permeability transition showed that maximum rates of depolarization were enhanced in uremia by 79%. These results demonstrate that mitochondrial respiration in the uremic heart is chronically uncoupled. Cardiomyocytes in UCM are characterized by a more oxidized mitochondrial network, with greater susceptibility to oxidant-induced cell death and enhanced vulnerability to calcium-induced mPTP formation. Collectively, these findings indicate that mitochondrial function is compromised in UCM with increased vulnerability to calcium and oxidant-induced stressors, which may underpin the enhanced predisposition to IRI in the uremic heart.

Stress-induced opening of the permeability transition pore in the dystrophin-deficient heart is attenuated by acute treatment with sildenafil

2011 ◽  
Vol 300 (1) ◽  
pp. H144-H153 ◽  
Author(s):  
Alexis Ascah ◽  
Maya Khairallah ◽  
Frédéric Daussin ◽  
Céline Bourcier-Lucas ◽  
Richard Godin ◽  
...  
Keyword(s):  
Mitochondrial Permeability Transition ◽  
Contractile Function ◽  
Ex Vivo ◽  
Ischemia Reperfusion ◽  
Clinical Signs ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mdx Mice ◽  
Uptake Velocity ◽  
Ptp Opening

Susceptibility of cardiomyocytes to stress-induced damage has been implicated in the development of cardiomyopathy in Duchenne muscular dystrophy, a disease caused by the lack of the cytoskeletal protein dystrophin in which heart failure is frequent. However, the factors underlying the disease progression are unclear and treatments are limited. Here, we tested the hypothesis of a greater susceptibility to the opening of the mitochondrial permeability transition pore (PTP) in hearts from young dystrophic ( mdx) mice (before the development of overt cardiomyopathy) when subjected to a stress protocol and determined whether the prevention of a PTP opening is involved in the cardioprotective effect of sildenafil, which we have previously reported in mdx mice. Using the 2-deoxy-[3H]glucose method to quantify the PTP opening in ex vivo perfused hearts, we demonstrate that when compared with those of controls, the hearts from young mdx mice subjected to ischemia-reperfusion (I/R) display an excessive PTP opening as well as enhanced activation of cell death signaling, mitochondrial oxidative stress, cardiomyocyte damage, and poorer recovery of contractile function. Functional analyses in permeabilized cardiac fibers from nonischemic hearts revealed that in vitro mitochondria from mdx hearts display normal respiratory function and reactive oxygen species handling, but enhanced Ca2+ uptake velocity and premature opening of the PTP, which may predispose to I/R-induced injury. The administration of a single dose of sildenafil to mdx mice before I/R prevented excessive PTP opening and its downstream consequences and reduced tissue Ca2+ levels. Furthermore, mitochondrial Ca2+ uptake velocity was reduced following sildenafil treatment. In conclusion, beyond our documentation that an increased susceptibility to the opening of the mitochondrial PTP in the mdx heart occurs well before clinical signs of overt cardiomyopathy, our results demonstrate that sildenafil, which is already administered in other pediatric populations and is reported safe and well tolerated, provides efficient protection against this deleterious event, likely by reducing cellular Ca2+ loading and mitochondrial Ca2+ uptake.

Abstract 17188: Cryoem Analysis in Cardiac Isolated Mitochondria Reveals New Insights for CsA and mPTP Activation

Circulation ◽  
2018 ◽  
Vol 138 (Suppl_1) ◽  
Author(s):  
Jasiel O Strubbe ◽  
Jason Schrad ◽  
James F Conway ◽  
Kristin N Parent ◽  
Jason N Bazil
Keyword(s):  
Time Course ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Myocardial Necrosis ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Granule Formation ◽  
Membrane Rupture ◽  
Mptp Opening

Excessive Ca 2+ accumulation is the main source of cardiac tissue and cell death during myocardial ischemia-reperfusion injury (IR injury) and myocardial infarction. Calcium dysregulation and overload leads to mitochondrial dysfunction, excessive reactive oxygen species (ROS) production, catastrophic energy failure, and opening of the cyclosporine A-sensitive mitochondrial permeability transition pore (mPTP). Mitochondrial Ca 2+ accumulation also results in the formation of amorphous Ca 2+ -phosphate granules localized in the mitochondrial matrix. These amorphous electron-dense granules are main components of the mitochondrial Ca 2+ sequestration and buffering system by mechanisms not yet well understood. The two aims of the present study are to test the relationship of Ca 2+ -phosphate granule size and number in cardiac mitochondria 1) exposed to a bolus calcium sufficient to elicit permeabilization and 2) whether CsA-treated mitochondria alters granule formation and size. A time course series of CryoEM images was analyzed to follow the permeabilization process. CryoEM results showed that mitochondrial incubated for longer time-courses have increased number of small granules (40 - 110 nm), swelling, membrane rupture and induction of mPTP opening. Conversely, shorter incubation time resulted in less granules per mitochondrion yet of similar size (35 - 90 nm). CsA- treated mitochondria, on the other hand, showed bigger phosphate granules (120 - 160 nm), and both lower granules per mitochondria and mPTP opening susceptibility. These results suggest a novel mechanism for CsA in which Ca 2+ -phosphate granule sizes are enhanced while maintaining fewer per mitochondrion. This effect may explain why CsA-treated mitochondria have higher calcium tolerance, delayed Ca 2+ -dependent opening of the mPTP, and protects against reperfusion-induced myocardial necrosis.

Abstract P311: Blocking Succinate Release Enhances Mitochondrial Reactive Oxygen Species Generation And Worsens Ischemia-reperfusion Injury

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Alexander S Milliken ◽  
Sergiy M Nadtochiy ◽  
Paul S Brookes
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen Species Generation ◽  
Ros Generation ◽  
Ros Production ◽  
Succinate Oxidation ◽  
Fluorescence Measurements ◽  
Mitochondrial Ros ◽  
The Impact ◽  
Infarction Heart

Succinate is a metabolite that plays a central role in ischemia-reperfusion (IR) injury,which is relevant to myocardial infarction (heart attack) and stroke. Succinateaccumulates during ischemia and is rapidly consumed at reperfusion driving reactiveoxygen species (ROS) generation at complex-I (Cx-I) and III of the mitochondrial electrontransport chain. This ROS production triggers cell-death, leading to tissue necrosis.Although succinate oxidation has been extensively studied and exploited as a noveltherapeutic target, only 1/3 of the succinate accumulated in ischemia is oxidized atreperfusion, with the remaining 2/3 being released from the cell via monocarboxylatetransporter 1 (MCT1). Extracellular succinate is thought to be pro-inflammatory, and ithas been proposed that preventing succinate release may be therapeutically beneficial.To determine the impact of preventing succinate release on IR injury, we comparedfunctional recovery (i.e. rate x pressure product, RPP) and infarction (i.e. tissue necrosis)of Langendorff perfused mouse hearts treated with an MCT1 inhibitor, AR-C155858,versus vehicle control. This revealed that succinate retention worsens IR injury (i.e.increased infarction and decreased functional recovery) likely due to increased ROS. Totest this hypothesis, we utilized a Langendorff apparatus positioned within aspectrofluorimeter, which permits real-time fluorescence measurements in beatingmouse hearts. Using the mitochondria targeted superoxide probe, MitoSOX red tomeasure ROS production at reperfusion + AR-C155858, demonstrated that succinateretention leads to enhanced mitochondrial ROS generation at the onset of reperfusion.Overall, these results suggest that inhibiting succinate release in the context of IR injurymay not be a viable therapeutic approach, regardless of any downstream anti-inflammatory effects.

Abstract MP124: De-palmitoylation of Cysteine 202 of Cyclophilin-D by Calcium is Important for the Activation of the Permeability Transition Pore

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Georgios Amanakis ◽  
Junhui Sun ◽  
Maria Fergusson ◽  
Chengyu Liu ◽  
Jeff D Molkentin ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Cyclophilin D ◽  
Perfused Heart ◽  
Knock Out

Cyclophilin-D (CypD) is a well-known regulator of the mitochondrial permeability transition pore (PTP), the main effector of cardiac ischemia/reperfusion (I/R) injury characterized by oxidative stress and calcium overload. However, the mechanism by which CypD activates PTP is poorly understood. Cysteine 202 of CypD (C202) is highly conserved across species and can undergo redox-sensitive post-translational modifications, such as S-nitrosylation and oxidation. To study the importance of C202, we developed a knock-in mouse model using CRISPR where CypD-C202 was mutated to a serine (C202S). Hearts from these mice are protected against I/R injury. We found C202 to be abundantly S-palmitoylated under baseline conditions while C202 was de-palmitoylated during ischemia in WT hearts. To further investigate the mechanism of de-palmitoylation during ischemia, we considered the increase of matrix calcium, oxidative stress and uncoupling of ATP synthesis from the electron transport chain. We tested the effects of these conditions on the palmitoylation of CypD in isolated cardiac mitochondria. The palmitoylation of CypD was assessed using a resin-assisted capture (Acyl-RAC). We report that oxidative stress (phenylarsenide) and uncoupling (CCCP) had no effect on CypD palmitoylation (p>0.05, n=3 and n=7 respectively). However, calcium overload led to de-palmitoylation of CypD to the level observed at the end ischemia (1±0.10 vs 0.63±0.09, p=0.012, n=9). To further test the hypothesis that calcium regulates S-palmitoylation of CypD we measured S-palmitoylation of CypD in non-perfused heart lysates from global germline mitochondrial calcium uniporter knock-out mice (MCU-KO), which have reduced mitochondrial calcium and we found an increase in S-palmitoylation of CypD (WT 1±0.04 vs MCU-KO 1.603±0.11, p<0.001, n=6). The data are consistent with the hypothesis that C202 is important for the CypD mediated activation of PTP. Ischemia leads to increased matrix calcium which in turn promotes the de-palmitoylation of CypD on C202. The now free C202 can further be oxidized during reperfusion leading to the activation of PTP. Thus, S-palmitoylation and oxidation of CypD-C202 possibly target CypD to the PTP, making them potent regulators of cardiac I/R injury.

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