Mitochondrial membrane potential regulates production of reactive oxygen species and opening of mitochondrial permeability transition pore
Anesthetic preconditioning (APC) protects the heart from ischemia/reperfusion injury. We hypothesized that APC by isoflurane protects the heart by attenuating generation of reactive oxygen species (ROS) that delays opening of mitochondrial permeability transition pore (mPTP) via mild decrease in mitochondrial membrane potential (Δψm). ROS and Δψm were measured in rat cardiomyocytes by real‐time confocal microscopy using TMRE and CM‐H2DCFDA fluorescent dyes, respectively. Opening of mPTP, which initiates cell death, was detected as rapid and complete loss of TMRE fluorescence from mitochondria. APC by isoflurane (0.5 mM) decreased TMRE fluorescence (88±5% of control) and increased flavoprotein fluorescence (109±3% of control), indicating decrease in Δψm and mitochondrial uncoupling, respectively. Low dose of protonophore DNP (100 nM) produced similar effect. Pyruvate (25 μM) increased respiration and reversed mitochondrial depolarization and uncoupling. When exposed to oxidative stress, myocytes with partly decreased Δψm produced less ROS (62±5% of control) and exhibited a delay in mPTP opening (162±7% of control). Increase in Δψm by pyruvate increased production of ROS and shortened the time of mPTP opening. In conclusion, APC protects cardiomyocytes in part via mild decrease in Δψm that attenuates ROS production under stress and leads to the delay in mPTP opening.