title: H(2)O(2) disposal in cardiolipin-enriched brain mitochondria is due to increased cytochrome c peroxidase activity.
abstract: The mitochondrial electron transport chain is a source of oxygen superoxide anion (O(2)(-)) that is dismutated to H(2)O(2). Although low levels of ROS are physiologically synthesized during respiration, their increase contributes to cell injury. Therefore, an efficient machinery for H(2)O(2) disposal is essential in mitochondria. In this study, the ability of brain mitochondria to acquire cardiolipin (CL), phosphatidylglycerol (PG), and phosphatidylserine (PS) in vitro through a fusion process was exploited to investigate lipid effects on ROS. MTT assay, oxygen consumption, and respiratory ratio indicated that the acquired phospholipids did not alter mitochondrial respiration and O(2)(-) production from succinate. However, in CL-enriched mitochondria, H(2)O(2) levels where 27% and 47% of control in the absence and in the presence of antimycin A, respectively, suggesting an increase in H(2)O(2) elimination. Concomitantly, cytochrome c (cyt c) was released outside mitochondria. Since free oxidized cyt c acquired peroxidase activity towards H(2)O(2) upon interaction with CL in vitro, a contribution of cyt c to H(2)O(2) disposal in mitochondria through CL conferred peroxidase activity is plausible. In this model, the accompanying CL peroxidation should weaken cyt c-CL interactions, favouring the detachment and release of the protein. Neither cyt c peroxidase activity was elicited by PS in vitro, nor cyt c release was observed in PS-enriched mitochondria, although H(2)O(2) levels were significantly decreased, suggesting a cyt c-independent role of PS in ROS metabolism in mitochondria.
authors.affiliation: Department of Internal Medicine, University of Perugia, 06122 Perugia, Italy.
authors.forename: Lara
authors.initials: L
authors.lastname: Macchioni
authors.forename: Magdalena
authors.initials: M
authors.lastname: Davidescu
authors.forename: Roberta
authors.initials: R
authors.lastname: Mannucci
authors.forename: Ermelinda
authors.initials: E
authors.lastname: Francescangeli
authors.forename: Ildo
authors.initials: I
authors.lastname: Nicoletti
authors.forename: Rita
authors.initials: R
authors.lastname: Roberti
authors.forename: Lanfranco
authors.initials: L
authors.lastname: Corazzi
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002308:Cardiolipins / Q000378:metabolism*; D003578:Cytochrome-c Peroxidase / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010715:Phosphatidylglycerols / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D051381:Rats; D013481:Superoxides / Q000378:metabolism
chemical_list: D002308:Cardiolipins; D045222:Electron Transport Chain Complex Proteins; D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; D010715:Phosphatidylglycerols; D010718:Phosphatidylserines; D013481:Superoxides; D006861:Hydrogen Peroxide; D003578:Cytochrome-c Peroxidase