Mitochondrial proteomic response to post-conditioning: a network-assisted systems biology analysis in a preclinical model
Authors: Gallinat A , Vilahur G , Padro T , Badimon L 
Published: June 2022

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Agencia Estatal de Investigación - PID 2019-107160RB-I00;
Instituto de Salud Carlos III - CiberCV

Background
The discovery of the conditioning phenomena evidenced the existence of an endogenous cardioprotective program. However, most cardioprotective strategies have failed in translation to clinical studies. The understanding of the myocardium response to ischemic conditioning is a need both to explore novel cardioprotective strategies and to improve translation.

Purpose
To characterize the effects of ischemic post-conditioning in the mitochondrial proteome, in a preclinical model of acute myocardium infarction.

Methods
21 regular farm pigs were randomized into 4 groups: (I) closed-chest 90min left anterior descending (LAD) coronary artery balloon occlusion with no reperfusion (ischemia group; N=7); (II) closed-chest 90min LAD occlusion followed by 2.5h of reperfusion (ischemia-reperfusion group – I/R; N=5); (III) closed-chest 90 min LAD occlusion followed by post-conditioning and 2.5 h of reperfusion (post-conditioning group; N=5); and (IV) sham-operated animals (sham group; N=4). After experimental procedure, hearts were arrested, and all animals sacrificed. Infarct size was then measured and samples from the area at risk were collected and further processed for proteomic analysis by two-dimensional gel electrophoresis and mass spectrometry. Differentially regulated mitochondrial proteins were employed to build a protein-protein interaction (PPI) network, and functional enrichments were analyzed.

Results
The application of post-conditioning resulted in a 52% infarct size reduction, compared to the I/R group (p&lt;0.05). 22 mitochondrial proteins were identified to be differentially regulated in the myocardium at risk of the post-conditioned pigs compared to the I/R group. The resulting PPI network revealed a functional enrichment for the electron transport chain (FDR&lt;0.01), and the tricarboxylic acid cycle (FDR&lt;0.01). The strongest changes were found for the mitochondrial complex I and III, and for the oxoglutarate dehydrogenase complex, all of them up-regulated following post-conditioning. Amongst the proteins not belonging to the functional classification, the mitochondrial inner membrane protein (OXA1L), the voltage-dependent anion-selective channel 2 (VDAC2), and protein DJ-1, exhibited the strongest up-regulation. OXA1L is required for the insertion and correct assembly of inner mitochondrial membrane integral proteins, suggesting de novo synthesis of the identified electron transport chain members, and both VDAC2 and DJ-1 have been previously related to cardioprotection.

Conclusion
Collectively, our results highlight cardiac metabolism regulation as the driver for cardioprotection and suggest a dual role for post-conditioning promoting a metabolic reprogramming of the myocardium, and a protective response potentially mediated by VDAC2 and DJ-1 in the mitochondria.