Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA035

Poster Communications

Hearts subjected to ischemia-reperfusion benefit from adenine nucleotide translocase 1 overexpression

J. Heger1, O. Lynetskiy1, G. Euler1, U. Landmesser2,3, K. Schlueter1, R. Schulz1, A. Doener2,3

1. Institute of Physiology, Justus Liebig University, Giessen, Germany. 2. Medizinische Klinik für Kardiologie, Charité, Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany. 3. German Centre for Cardiovascular Research, Berlin, Germany.

The occlusion of coronary vessels blocks the supply of cells with oxygen, substrates and ATP and finally results in myocardial infarction. Oxygen deficiency during ischemia induces mitochondrial membrane depolarization and reperfusion provokes opening of the mitochondrial permeability transition pore (MPTP). The adenine nucleotide translocator 1 (ANT1) is a protein in the inner membrane of mitochondria that regulates the opening of the MPTP and has a physiologic key function in cellular energy metabolism. It was shown that I/R reduces the activity of ANT and thus inhibits oxidative phosphorylation. Overexpression of ANT1 should therefore have a protective effect. Therefore, we now analyzed whether ANT1-overexpressing hearts are protected against ischemia reperfusion (I/R) injury. Hearts of 5 - 8 month old wildtype (WT) and ANT1-TG rats were perfused retrogradely in Langendorff Apparatus with constant pressure of 50 mmHg and submitted to 45-minute global ischemia followed by 2-hour reperfusion. Hemodynamic parameters were measured continuously. Mitochondria were isolated and mitochondrial respiration, membrane potential and calcium retention capacity were measured. After I/R, ANT1-TG hearts showed a significant decrease in diastolic pressure (WT: 98.7 ± 4.3 mmHg; ANT1: 80.7 ± 3.4 mmHg, p<0.01) and aortic pressure (WT: 98.7 ± 4.3 mmHg; ANT1: 80.7 ± 3.4 mmHg, p<0.01). In accordance with better hemodynamics, ANT1-overexpressing mitochondria of I/R hearts showed a higher calcium retention capacity (WT: 50.0 ± 6.3 nM CaCl2; ANT1: 97.5 ± 8.5 nM CaCl2; p<0.01) and a weaker decrease in membrane potential than WT mitochondria (WT: 37.2 ±0.6 a.u.; ANT1: 25.5 ± 1.7 a.u.; p<0.01). In addition, ANT1-TG mitochondria from I/R rats are not restricted in their respiration (complex 1: WT 18.9 ± 1.4 basal vs 12.9 ± 1.7 I/R, p<0.05; ANT1 18.3 ± 1.2 basal vs 17.4 1.6 I/R; in nmol O2*min-1 *mg protein-1). Furthermore, mitofusin-2 (Mfn-2), a mitochondrial membrane protein contributing to the maintenance and operation of mitochondria, was downregulated in WT mitochondria after I/R, but was stable in ANT1-TG mitochondria (WT basal: 102.2 ± 1.2 %; WT I/R: 48.1 ± 3.4 %; ANT1 basal: 119.6 ± 9.4 %; ANT1 I/R: 102.9 ± 26.3 %). Optic atrophy protein 1 (OPA1) another mitochondrial fusion protein and critical regulator of mitochondrial respiration was significantly higher expressed in ANT1-TG hearts compared to WT hearts (WT: 100.0 ± 3.7 %; ANT1: 148.9 ± 1.7 %). ANT1-overexpressing rat hearts cope better with the consequences of I/R. This is reflected in better hemodynamics and greater stability of the mitochondria. This is indicated by the improved expression of mitochondrial proteins and results in a superior energy balance and improved calcium handling of mitochondria, which ultimately leads to a lower rigor of the surviving ANT1-TG cardiomyocytes.

Where applicable, experiments conform with Society ethical requirements