PLA(2) dependence of diaphragm mitochondrial formation of reactive oxygen species.
Contraction-induced respiratory muscle fatigue and sepsis-related reductions in respiratory muscle force-generating capacity are mediated, at least in part, by reactive oxygen species (ROS). The subcellular sources and mechanisms of generation of ROS in these conditions are incompletely understood. We postulated that the physiological changes associated with muscle contraction (i.e., increases in calcium and ADP concentration) stimulate mitochondrial generation of ROS by a phospholipase A(2) (PLA(2))-modulated process and that sepsis enhances muscle generation of ROS by upregulating PLA(2) activity. To test these hypotheses, we examined H(2)O(2) generation by diaphragm mitochondria isolated from saline-treated control and endotoxin-treated septic animals in the presence and absence of calcium and ADP; we also assessed the effect of PLA(2) inhibitors on H(2)O(2) formation. We found that 1) calcium and ADP stimulated H(2)O(2) formation by diaphragm mitochondria from both control and septic animals; 2) mitochondria from septic animals demonstrated substantially higher H(2)O(2) formation than mitochondria from control animals under basal, calcium-stimulated, and ADP-stimulated conditions; and 3) inhibitors of 14-kDa PLA(2) blocked the enhanced H(2)O(2) generation in all conditions. We also found that administration of arachidonic acid (the principal metabolic product of PLA(2) activation) increased mitochondrial H(2)O(2) formation by interacting with complex I of the electron transport chain. These data suggest that diaphragm mitochondrial ROS formation during contraction and sepsis may be critically dependent on PLA(2) activation.
Nethery
D
D
Pulmonary Division, Department of Medicine, Case Western Reserve University, and MetroHealth Medical Center, Cleveland, Ohio 44109, USA.
Callahan
L A
LA
Stofan
D
D
Mattera
R
R
DiMarco
A
A
Supinski
G
G
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology; D003964:Diaphragm / Q000378:metabolism*; D042967:Electron Transport Complex I; D003576:Electron Transport Complex IV / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008297:Male; D008555:Melitten / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012402:Rotenone / Q000494:pharmacology; D018805:Sepsis / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D003486:Cyanides; D004791:Enzyme Inhibitors; D008293:Malates; D009861:Onium Compounds; D010726:Phosphodiesterase Inhibitors; D017382:Reactive Oxygen Species; D013729:Terpenes; D014475:Uncoupling Agents; D012402:Rotenone; D008555:Melitten; D016718:Arachidonic Acid; D000244:Adenosine Diphosphate; C007517:diphenyleneiodonium; C030298:malic acid; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; C045673:manoalide; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D003576:Electron Transport Complex IV; D010741:Phospholipases A; D042967:Electron Transport Complex I; D002118:Calcium