Cell-autonomous metabolic reprogramming and oxidative stress underlie endothelial dysfunction in acute myocardial infarction

Abstract

Compelling evidence has accumulated for the role of oxidative stress on the endothelial cell (EC) dysfunction underlying acute coronary syndromes. However, understanding the metabolic determinants of EC dysfunction has been hampered by the scarcity of appropriate cell models. Here, we have generated and phenotypically characterized EC derived from thrombectomy specimens in patients with acute myocardial infarction (AMI). We have found that AMI-derived endothelial cells (AMIECs), but not control EC from health coronary arteries, display impaired growth, migration and tubulogenesis. These phenotypic abnormalities were accompanied with metabolic abnormalities including augmentation of reactive oxygen species (ROS) and glutathione intracellular content, along with diminished glucose consumption coupled to increased lactate production. In AMIECs, the protein levels of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase type 3, PFKFB3, were downregulated, while those of PFKFB4 were upregulated, suggesting a shunting of glycolysis towards the pentose phosphate pathway (PPP) in the pathological ECs. PPP overactivation was further supported by upregulation of G6PD in AMIECs, the key enzyme in the oxidative branch of the PPP, which supplies the bulk of NADPH reducing equivalents necessary for the reduction/turnover and lipid synthesis.. Further, the glutaminolytic enzyme glutaminase (GLS) was upregulated in AMIECs, providing a mechanistic explanation for the observed increase in glutathione content. Finally, AMIECs had higher mitochondrial membrane potential than control ECs, which, together with high ROS levels, suggest a highly coupled mitochondrial activity in patient ECs. We suggest that high proton coupling underlies the abnormally high production of ROS, balanced by PPP-driven glutathione turnover, as a primary, cell-autonomous abnormality driving EC dysfunction in AMI.