Electron flow into cytochrome c coupled with reactive oxygen species from the electron transport chain converts cytochrome c to a cardiolipin peroxidase: Role during ischemia-reperfusion

摘要

Background Cytochrome c (Cyt c) is a mobile component of the electron transport chain (ETC.) which contains a tightly coordinated heme iron. In pathologic settings, a key ligand of the cyt c's heme iron, methionine (Met 80), is oxidized allowing cyt c to participate in reactions as a peroxidase with cardiolipin as a target. Myocardial ischemia (ISC) results in ETC. blockade and increased production of reactive oxygen species (ROS). We hypothesized that during ischemia-reperfusion (ISC-REP); ROS generation coupled with electron flow into cyt c would oxidize Met80 and contribute to mitochondrial-mediated ETC. damage. Methods Mitochondria were incubated with specific substrates and inhibitors to test the contributions of ROS and electron flow into cyt c. Subsequently, cyt c and cardiolipin were analyzed. To test the pathophysiologic relevance, mouse hearts that underwent ISC-REP were tested for methionine oxidation in cyt c. Results The combination of substrate/inhibitor showed that ROS production and electron flux through cyt c are essential for the oxidation of methionine residues that lead to cardiolipin depletion. The content of cyt c methionine oxidation increases following ISC-REP in the intact heart. Conclusions Increase in intra-mitochondrial ROS coupled with electron flow into cyt c, oxidizes cyt c followed by depletion of cardiolipin. ISC-REP increases methionine oxidation, supporting that cyt c peroxidase activity can form in the intact heart. General significance This study identifies a new site in the ETC. that is damaged during cardiac ISC-REP. Generation of a neoperoxidase activity of cyt c favors the formation of a defective ETC. that activates signaling for cell death.