title: An integrated mitochondrial ROS production and scavenging model: implications for heart failure.
abstract: It has been observed experimentally that cells from failing hearts exhibit elevated levels of reactive oxygen species (ROS) upon increases in energetic workload. One proposed mechanism for this behavior is mitochondrial Ca(2+) mismanagement that leads to depletion of ROS scavengers. Here, we present a computational model to test this hypothesis. Previously published models of ROS production and scavenging were combined and reparameterized to describe ROS regulation in the cellular environment. Extramitochondrial Ca(2+) pulses were applied to simulate frequency-dependent changes in cytosolic Ca(2+). Model results show that decreased mitochondrial Ca(2+)uptake due to mitochondrial Ca(2+) uniporter inhibition (simulating Ru360) or elevated cytosolic Na(+), as in heart failure, leads to a decreased supply of NADH and NADPH upon increasing cellular workload. Oxidation of NADPH leads to oxidation of glutathione (GSH) and increased mitochondrial ROS levels, validating the Ca(2+) mismanagement hypothesis. The model goes on to predict that the ratio of steady-state [H2O2]m during 3Hz pacing to [H2O2]m at rest is highly sensitive to the size of the GSH pool. The largest relative increase in [H2O2]m in response to pacing is shown to occur when the total GSH and GSSG is close to 1 mM, whereas pool sizes below 0.9 mM result in high resting H2O2 levels, a quantitative prediction only possible with a computational model.
authors.affiliation: Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland. Electronic address: laura.doyle@jhu.edu.
authors.forename: Laura D
authors.initials: LD
authors.lastname: Gauthier
authors.affiliation: Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Greenstein
authors.affiliation: Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore Maryland.
authors.forename: Brian
authors.initials: B
authors.lastname: O'Rourke
authors.affiliation: Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, Maryland.
authors.forename: Raimond L
authors.initials: RL
authors.lastname: Winslow
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006333:Heart Failure / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D008955:Models, Cardiovascular; D009243:NAD / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D009243:NAD; D012964:Sodium; D005978:Glutathione; D002118:Calcium