Metabolomic Profile of Ferroptosis in Cardiac Cells

Abstract

Ferroptosis, a novel iron-dependent programmed cell death mechanism, has emerged to play an important role in various human diseases including coronary heart diseases such as myocardial infarction/ischemia-reperfusion. Ferroptosis is characterized by the accumulation of iron and an excessive oxygenation of polyunsaturated fatty acid residues of phospholipids, particularly phosphatidylethanolamine. Different intracellular antioxidant enzymes, such as glutathione peroxidase 4 (GPX4), prevent the accumulation of oxidized lipids. Reduced glutathione (GSH), a tripeptide generated from cysteine, glycine, and glutamic acid, is required for GPX4 activity. In addition to GSH/GPX4, ferroptosis affects different metabolic pathways in the cell. However, the effects of ferroptosis on the metabolome remain uncovered. In this study, we elucidated the effect of ferroptosis on the metabolome in cardiac cells. Ferroptosis was induced in H9c2 cardioblast cells by RSL3, a pro-ferroptotic compound - GPX4 inhibitor, in the presence of ferrostatin (Fer-1), a lipid antioxidant that inhibits ferroptosis. Experiments were performed in the following 4 groups: i) control, ii) Fer-1, iii) RSL3, and iv) RSL3+Fer-1. Each group contained 6 independent experiments (n=6). RSL3 (0.5 µM) and Fer-1 (1 µM) were added simultaneously to the culture medium. The cells were incubated for 3 h, then harvested and processed for gas chromatography-mass spectrometry (GC/MS). MetaboAnalyst online platform was used for bioinformatic analysis. A total of 50 metabolites across experimental groups were identified by GC/MS. Principal component analysis showed an excellent separation of RSL3 group from the others, thus, indicating significant differences between them. The total 95% confidence ellipses of samples in Control, Fer-1, RSL3+Fer-1 groups were overlapped suggesting no differences found between their respective metabolomes. RSL3 reduced the levels of 4 metabolites (cysteine, glutamic acid, glutamine, and glycine), known as ferroptotic markers involved in GSH synthesis. However, Fer-1 prevented RSL3-induced reduction of the metabolites. In addition, 5-oxoproline, a GSH degradation marker, was reduced in RSL3-treated cells indicating that GSH does not degrade which maybe as a compensatory response of the cells to ferroptosis. Moreover, TCA cycle-related metabolites (citrate, malate, oxoglutarate and succinate levels were reduced in the presence of RSL3. Saturated fatty acids (FA) levels were not affected, whereas changes were observed in unsaturated FA, particularly, palmitoleic acid. Furthermore, aminoacids related to energy metabolism and FA oxidation like leucine, isoleucine, lysine, tryptophan, alanine, and proline, were decreased after the ferroptosis induction. As expected, aminoacids with antioxidant capacity, like methionine and serine, important for GSH synthesis and protection against oxidative damage, were reduced in the presence of RSL3. In conclusion, our study demonstrates that RSL3-induced ferroptosis impairs the H9c2 cardioblasts metabolome, particularly affecting GSH production and redox status.