Modulation of Mitochondrial Respiration During Early Reperfusion Reduces Cardiac Injury in Donation After Circulatory Death Hearts

Donation after circulatory death (DCD) donors are a potential source for heart transplantation. The DCD process has unavoidable ischemia and reperfusion (I/R) injury, primarily mediated through mitochondria, which limits routine utilization of hearts for transplantation. Amobarbital (AMO), a transient inhibitor of the electron transport chain, is known to decrease cardiac injury following ex-vivo I/R. We studied whether AMO treatment during reperfusion can decrease injury in DCD hearts. Sprague Dawley rat hearts subjected to 25 minutes of in-vivo ischemia (DCD hearts), or control beating donor (CBD) hearts, were treated with AMO or vehicle for the first 5 minutes of reperfusion, followed by Krebs-Henseleit buffer reperfusion for 55 minutes (for mitochondrial isolation) or 85 minutes (for infarct size determination). Compared to vehicle, AMO treatment led to decreased infarct size (25.2 ± 1.5% vs. 31.5 ± 1.5%; p≤0.05), and troponin I release (4.5 ± 0.05 ng/ml vs. 9.3 ± 0.24 ng/ml, p≤0.05). AMO treatment decreased H2O2 generation with glutamate as complex I substrate in both subsarcolemmal mitochondria (SSM) (37± 3.7 pmol/mg/min vs. 56.9 ± 4.1 pmol/mg/min; p≤0.05), and interfibrillar mitochondria (IFM) (31.8 ± 2.8 pmol/mg/min vs. 46±4.8 pmol/mg/min; p≤0.05), and improved calcium retention capacity (CRC) in SSM (360 ±17.2 nmol/mg vs. 277 ± 13nmol/mg; p≤0.05), and IFM (483 ± 20nmol/mg vs. 377± 19 nmol/mg; p≤0.05) compared to vehicle treatment. SSM and IFM retained more cytochrome c with AMO treatment compared to vehicle. In conclusion, brief inhibition of mitochondrial respiration during reperfusion using amobarbital is a promising approach to decrease injury in DCD hearts.