Mitochondrial depolarization underlies delay in permeability transition by preconditioning with isoflurane: roles of ROS and Ca2+.
During reperfusion, the interplay between excess reactive oxygen species (ROS) production, mitochondrial Ca(2+) overload, and mitochondrial permeability transition pore (mPTP) opening, as the crucial mechanism of cardiomyocyte injury, remains intriguing. Here, we investigated whether an induction of a partial decrease in mitochondrial membrane potential (DeltaPsi(m)) is an underlying mechanism of protection by anesthetic-induced preconditioning (APC) with isoflurane, specifically addressing the interplay between ROS, Ca(2+), and mPTP opening. The magnitude of APC-induced decrease in DeltaPsi(m) was mimicked with the protonophore 2,4-dinitrophenol (DNP), and the addition of pyruvate was used to reverse APC- and DNP-induced decrease in DeltaPsi(m). In cardiomyocytes, DeltaPsi(m), ROS, mPTP opening, and cytosolic and mitochondrial Ca(2+) were measured using confocal microscope, and cardiomyocyte survival was assessed by Trypan blue exclusion. In isolated cardiac mitochondria, antimycin A-induced ROS production and Ca(2+) uptake were determined spectrofluorometrically. In cells exposed to oxidative stress, APC and DNP increased cell survival, delayed mPTP opening, and attenuated ROS production, which was reversed by mitochondrial repolarization with pyruvate. In isolated mitochondria, depolarization by APC and DNP attenuated ROS production, but not Ca(2+) uptake. However, in stressed cardiomyocytes, a similar decrease in DeltaPsi(m) attenuated both cytosolic and mitochondrial Ca(2+) accumulation. In conclusion, a partial decrease in DeltaPsi(m) underlies cardioprotective effects of APC by attenuating excess ROS production, resulting in a delay in mPTP opening and an increase in cell survival. Such decrease in DeltaPsi(m) primarily attenuates mitochondrial ROS production, with consequential decrease in mitochondrial Ca(2+) uptake.
Department of Anesthesiology and Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin53226, USA. fsedlic@mcw.edu
Filip
F
Sedlic
Ana
A
Sepac
Danijel
D
Pravdic
Amadou K S
AK
Camara
Martin
M
Bienengraeber
Anna K
AK
Brzezinska
Tetsuro
T
Wakatsuki
Zeljko J
ZJ
Bosnjak
D000818:Animals; D002118:Calcium / Q000502:physiology*; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology*; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors
D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; D007530:Isoflurane; D002118:Calcium