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Glucocorticoids decrease cytochrome c oxidase activity of isolated rat kidney mitochondria
1Départment de Pharmacologie, Faculté de Médecine de Paris XII, Créteil, France.
Abstract:
The importance of mitochondria is rising as a target in pathologic processes such as ischemia. We have investigated the effects of hydrocortisone, prednisolone, dexamethasone and triamcinolone on oxidative phosphorylation, Ca2+ fluxes, swelling and membrane potentials in isolated kidney mitochondria. The measurement of respiration state 3 showed a significant decrease in presence of glucocorticoids whereas the other respiration states were not modified. When mitochondria were uncoupled and either the complexes III and IV or the complex IV were stimulated, the O2 consumption was decreased by glucocorticoids. These results suggest the cytochrome c oxidase is a target of the glucocorticoid effect on the respiratory chain. Indeed, the other mitochondrial functions investigated were unchanged, ruling out a direct effect on Ca2+ fluxes or swelling. A regulation of cytochrome c oxidase activity by glucocorticoids will be of particular interest in pathology involving metabolic insult.
Insights
Glucocorticoids significantly decrease mitochondrial respiration state 3 and O2 consumption, suggesting cytochrome c oxidase is a key target. This finding is crucial for understanding metabolic insults in diseases like ischemia.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Mitochondria are increasingly recognized as critical targets in pathological conditions, particularly ischemia.
- Glucocorticoids are potent anti-inflammatory drugs with known effects on cellular metabolism.
Purpose of the Study:
- To investigate the impact of specific glucocorticoids (hydrocortisone, prednisolone, dexamethasone, triamcinolone) on isolated kidney mitochondria functions.
- To identify the specific mitochondrial targets affected by glucocorticoid treatment.
Main Methods:
- Isolated kidney mitochondria were used to assess oxidative phosphorylation, calcium (Ca2+) fluxes, swelling, and membrane potentials.
- Respiration states (state 3) and oxygen (O2) consumption were measured in the presence and absence of glucocorticoids.
- Mitochondrial complexes III, IV, and V were stimulated under uncoupled conditions to evaluate specific respiratory chain activities.
Main Results:
- Glucocorticoids significantly reduced mitochondrial respiration state 3.
- Oxygen consumption decreased when complexes III and IV, or complex IV alone, were stimulated, indicating an effect on the respiratory chain.
- Other mitochondrial functions, including Ca2+ fluxes and swelling, remained unaffected, suggesting a specific interaction with the respiratory chain.
Conclusions:
- The results strongly suggest that cytochrome c oxidase is a primary target of glucocorticoid action within the mitochondrial respiratory chain.
- Glucocorticoids do not directly affect mitochondrial Ca2+ fluxes or swelling.
- Understanding this regulation of cytochrome c oxidase by glucocorticoids is vital for addressing pathologies involving metabolic insult, such as ischemia.