Pyridine-nucleotide oxidation, Ca2+ cycling and membrane damage during tert-butyl hydroperoxide metabolism by rat-liver mitochondria

Epigallocatechin gallate (EGCG) is a green tea antioxidant with adverse effects on rat liver mitochondria and hepatocytes at high doses. Here, we assessed whether low doses of EGCG would protect these systems from damage induced by tert-butyl hydroperoxide (tBHP). Rat liver mitochondria or permeabilized rat hepatocytes were pretreated with EGCG and then exposed to tBHP. Oxygen consumption, mitochondrial membrane potential (MMP), and mitochondrial retention capacity for calcium were measured. First, 50 μM EGCG or 0.25 mM tBHP alone increased State 4 Complex I-driven respiration, thus demonstrating uncoupling effects; tBHP also inhibited State 3 ADP-stimulated respiration. Then, the coexposure to 0.25 mM tBHP and 50 μM EGCG induced a trend of further decline in the respiratory control ratio beyond that observed upon tBHP exposure alone. EGCG had no effect on MMP and no effect, in concentrations up to 50 μM, on mitochondrial calcium retention capacity. tBHP led to a decline in both MMP and mitochondrial retention capacity for calcium; these effects were not changed by pretreatment with EGCG. In addition, EGCG dose-dependently enhanced hydrogen peroxide formation in a cell- and mitochondria-free medium.Conclusion. Moderate nontoxic doses of EGCG were not able to protect rat liver mitochondria and hepatocytes from tBHP-induced mitochondrial dysfunction.

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Modification of calcium retention capacity of rat liver mitochondria by phosphate and tert-butyl hydroperoxide

Physiological Research ◽

10.33549/physiolres.933912 ◽

2019 ◽

pp. 59-65 ◽

Cited By ~ 5

Author(s):

R. Endlicher ◽

Z. Drahota ◽

Z. Červinková

Keyword(s):

Rat Liver ◽

Cyclosporine A ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Retention Capacity ◽

Butyl Hydroperoxide ◽

Calcium Retention ◽

Tert Butyl ◽

Tert Butyl Hydroperoxide ◽

Calcium Retention Capacity

By determining the calcium retention capacity (CRC) of rat liver mitochondria, we confirmed and extended previous observations describing the activation of mitochondrial swelling by phosphate and tert-butyl hydroperoxide (t-BHP). Using CRC measurements, we showed that both phosphate and t-BHP decrease the extent of calcium accumulation required for the full mitochondrial permeability transition pore (MPTP) opening to 35 % of control values and to only 15 % when both phosphate and t-BHP are present in the medium. When changes in fluorescence were evaluated at higher resolution, we observed that in the presence of cyclosporine A fluorescence values return after each Ca(2+) addition to basal values obtained before the Ca(2+) addition. This indicates that the MPTP remains closed. However, in the absence of cyclosporine A, the basal fluorescence after each Ca(2+) addition continuously increased. This increase was potentiated both by phosphate and t-BHP until the moment when the concentration of intramitochondrial calcium required for the full opening of the MPTP was reached. We conclude that in the absence of cyclosporine A, the MPTP is slowly opened after each Ca(2+) addition and that this rate of opening can be modified by various factors such as the composition of the media and the experimental protocol used.

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Tert-butyl hydroperoxide-induced radical production in rat liver mitochondria

Free Radical Biology and Medicine ◽

10.1016/0891-5849(92)90087-w ◽

1992 ◽

Vol 12 (5) ◽

pp. 381-387 ◽

Cited By ~ 54

Author(s):

Christopher H. Kennedy ◽

Daniel F. Church ◽

Gary W. Winston ◽

William A. Pryor

Keyword(s):

Rat Liver ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Butyl Hydroperoxide ◽

Tert Butyl ◽

Radical Production ◽

Tert Butyl Hydroperoxide

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Inhibition of Palmityl Carnitine Oxidation in Rat Liver Mitochondria by Tert-Butyl Hydroperoxide

Physiological Research ◽

10.33549/physiolres.931198 ◽

2008 ◽

pp. 133-136

Author(s):

Z Červinková ◽

H Rauchová ◽

P Křiváková ◽

Z Drahota

Keyword(s):

Oxidative Damage ◽

Respiratory Chain ◽

Respiratory Control ◽

Atp Synthesis ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Respiratory Chain Complexes ◽

Butyl Hydroperoxide ◽

Tert Butyl ◽

Tert Butyl Hydroperoxide

Mitochondria as an energy generating cell device are very sensitive to oxidative damage. Our previous findings obtained in hepatocytes demonstrated that Complex I of the respiratory chain is more sensitive to oxidative damage than other respiratory chain complexes. We present additional data on isolated mitochondria showing that palmityl carnitine oxidation is strongly depressed at a low (200 µM) tert-butyl hydroperoxide (tBHP) concentration, while oxidation of the flavoproteindependent substrate – succinate is not affected and neither is ATP synthesis inhibited by tBHP. In the presence of tBHP, the respiratory control index for palmityl carnitine oxidation is strongly depressed, but when succinate is oxidized the respiratory control index remains unaffected. Our findings thus indicate that flavoprotein-dependent substrates could be an important nutritional factor for the regeneration process in the necrotic liver damaged by oxidative stress.

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Energy dependence of pyridine nucleotide-linked dismutations in rat liver mitochondria

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(63)90273-0 ◽

1963 ◽

Vol 10 (1) ◽

pp. 85-90 ◽

Cited By ~ 14

Author(s):

Lennart Danielson ◽

Lars Ernster

Keyword(s):

Energy Dependence ◽

Rat Liver ◽

Pyridine Nucleotide ◽

Liver Mitochondria ◽

Rat Liver Mitochondria

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THE INHIBITION OF OXIDATIVE AND PHOSPHORYLATIVE ENZYMES IN RAT LIVER MITOCHONDRIA BY AMINOAZOBENZENE DERIVATIVES

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y60-001 ◽

1960 ◽

Vol 38 (1) ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

W. C. McMurray

Keyword(s):

Cytochrome C ◽

Rat Liver ◽

Pyridine Nucleotide ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Succinate Oxidation ◽

Metabolic Block ◽

Liver Carcinogen ◽

Mitochondrial Dehydrogenase Activity

The liver carcinogen, dimethylaminoazobenzene, inhibited in vitro the oxidation of a variety of pyridine nucleotide linked substrates of rat liver mitochondria without affecting the process of oxidative phosphorylation. Cytochrome c oxidase activity was not inhibited by the carcinogen, nor was the succinoxidase activity, but the phosphorylation accompanying succinate oxidation was uncoupled. Similar effects were noted with other aminoazobenzene derivatives, but did not appear to be correlated with the ability of the compounds to evoke tumors.The site of the respiratory inhibition by dimethylaminoazobenzene appears to be at the level between reduced pyridine nucleotide and cytochrome c in the respiratory chain. Mitochondrial dehydrogenase activity was not inhibited, while the oxidation of reduced diphosphopyridine nucleotide was markedly decreased. The reduction of the electron acceptor, ferricyanide, by pyridine nucleotide linked substrates was also strongly inhibited but the reduction of tetrazolium compounds was not affected. The latter observations suggest that dimethylaminoazobenzene produces a metabolic block between reduced flavin and cytochrome c in the mitochondrial electron transport system.

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