Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes

Area of Science:

• Mitochondrial Physiology
• Cardiovascular Pharmacology
• Anesthesiology

Background:

• Cardiac ischemia-reperfusion (IR) injury is a significant clinical problem.
• Mitochondrial dysfunction is a key contributor to IR injury.
• Volatile anesthetics (VA) show potential for cardioprotection by modulating mitochondrial function.

Purpose of the Study:

• To investigate if the volatile anesthetic isoflurane (ISO) mediates cardioprotection by altering mitochondrial oxidative phosphorylation (OxPhos).
• To elucidate the specific effects of ISO on mitochondrial respiratory and transport proteins.

Main Methods:

• Fluorescence spectrophotometry was employed to measure mitochondrial bioenergetic variables.
• Experiments were conducted using pyruvate/malate (complex I) or succinate (complex II) substrates.
• Effects of ISO were compared to known inhibitors of electron transport chain complexes (rotenone, antimycin A).

Main Results:

• Isoflurane altered NADH oxidation, membrane potential (ΔΨm), and respiration in a substrate-dependent manner.
• ISO's effects on state 3 respiration resembled those of electron transport chain inhibitors, particularly rotenone.
• ISO reduced the magnitude of NADH oxidation and modulated the duration of depolarization and respiration.

Conclusions:

• Isoflurane alters mitochondrial function, specifically impacting oxidative phosphorylation.
• These alterations provide a mechanistic basis for the cardioprotective effects of isoflurane against IR injury.
• The study identifies potential targets within the mitochondrial electron transport chain for ISO's action.