Age-associated differences in the inhibition of mitochondrial permeability transition pore opening by cyclosporine A

Background: Inhibiting mitochondrial permeability transition pore (mPTP) opening is a key protection of the myocardium from ischemia/reperfusion (I/R) injury. Here, we investigated age‐associated differences in the ability of cyclosporine A (CsA) to protect the heart and to modulate mPTP opening during I/R injury in vivo and its opening induced by reactive oxygen species (ROS) in vitro. Methods: Fischer 344 male rats were assigned from their respective age groups, young or old groups, to (1) I/R or (2) I/R+CsA. All animals were subjected to 30 min of ischemia following 120 min of reperfusion to determine myocardial infarct size in vivo. To measure mPTP opening in vivo, left ventricular tissues were collected 10 min after reperfusion and nicotinamide adenine dinucleotide (NAD⁺) levels were measured. In parallel experiments, rat ventricular myocytes were prepared from young and old hearts, loaded with tetramethylrhodamine ethylester and then subjected to oxidative stress in the presence or absence of CsA, and the mPTP opening time was measured using laser scanning confocal microscopy. Results: CsA reduced myocardial infarct size in young I/R rats. Whereas CsA failed to significantly affect myocardial infarct size in old I/R rats, NAD⁺ levels were better preserved in young CsA‐treated rats, but this relative improvement was not observed in old rats. CsA also significantly prolonged the time necessary to induce mPTP opening in young cardiomyocytes, but not in cardiomyocytes isolated from the old rats. Conclusions: mPTP regulation is dysfunctional in the aged myocardium and this could account for loss of cardioprotection with aging.