Oxidative stress in the mitochondrial matrix underlies ischemia/reperfusion-induced mitochondrial instability

• Published in: The Journal of biological chemistry Vol. 299; no. 1; p. 102780
• Main Authors: Solhjoo, Soroosh, Liu, Ting, Sidor, Agnieszka, Lee, Dong I., O’Rourke, Brian, Steenbergen, Charles
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2023; American Society for Biochemistry and Molecular Biology
• Subjects: Calcium - metabolism; calcium imaging; cardiac monolayers; coverslip-induced ischemia; GSH redox potential; Humans; inner membrane potential oscillations; Ischemia - metabolism; Membrane Potential, Mitochondrial; Mitochondria, Heart - metabolism; Myocytes, Cardiac - metabolism; neonatal rat ventricular myocytes; optical mapping; Oxidative Stress; reactive oxygen species; Reactive Oxygen Species - metabolism; reentry arrhythmias; Reperfusion; reentry arrhythmias; neonatal rat ventricular myocytes; IR; RIRR; cardiac monolayers; TMRM; GSH redox potential; coverslip-induced ischemia; GSH-MEE; reactive oxygen species; ROS; optical mapping; inner membrane potential oscillations; reperfusion; calcium imaging; GSH; NRVM
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/j.jbc.2022.102780

Ischemia and reperfusion affect multiple elements of cardiomyocyte electrophysiology, especially within the mitochondria. We previously showed that in cardiac monolayers, upon reperfusion after coverslip-induced ischemia, mitochondrial inner membrane potential (ΔΨ) unstably oscillates between polarized and depolarized states, and ΔΨ instability corresponds with arrhythmias. Here, through confocal microscopy of compartment-specific molecular probes, we investigate the mechanisms underlying the postischemic ΔΨ oscillations, focusing on the role of Ca2+ and oxidative stress. During reperfusion, transient ΔΨ depolarizations occurred concurrently with periods of increased mitochondrial oxidative stress (5.07 ± 1.71 oscillations/15 min, N = 100). Supplementing the antioxidant system with GSH monoethyl ester suppressed ΔΨ oscillations (1.84 ± 1.07 oscillations/15 min, N = 119, t test p = 0.027) with 37% of mitochondrial clusters showing no ΔΨ oscillations (versus 4% in control, odds ratio = 14.08, Fisher’s exact test p < 0.001). We found that limiting the production of reactive oxygen species using cyanide inhibited postischemic ΔΨ oscillations (N = 15, t test p < 10−5). Furthermore, ΔΨ oscillations were not associated with any discernable pattern in cell-wide oxidative stress or with the changes in cytosolic or mitochondrial Ca2+. Sustained ΔΨ depolarization followed cytosolic and mitochondrial Ca2+ increase and was associated with increased cell-wide oxidative stress. Collectively, these findings suggest that transient bouts of increased mitochondrial oxidative stress underlie postischemic ΔΨ oscillations, regardless of Ca2+ dynamics.