ABSTRACT
Photo-oxidized low-density lipoprotein is cytotoxic to bovine aortic endothelial cells in a concentration-dependent manner. Total cell killing occurs at a concentration of 600 mumol/l lipid hydroperoxide (LOOH). Selenium deficiency enhances the toxicity of LOOH such that 300 mumol/l LOOH is cytotoxic. This toxicity is inhibited by desferrioxamine, a transition metal ion chelator, and by butylatedhydroxytoluene, a potent inhibitor of lipid peroxidation. Toxicity is also inhibited by the nitric oxide donors S-nitrosoglutathione and spermine NONOate but not by reduced or oxidized glutathione and spermine. We propose that nitric oxide, released from these compounds, is inhibiting the toxicity of LOOH to selenium-deficient endothelial cells. Furthermore we hypothesize that the mechanism for this inhibition of toxicity is the scavenging of the propagatory peroxyl and alkoxyl free radicals, by nitric oxide, that are generated during peroxidation of cell membranes.
Subject(s)
Endothelium, Vascular/cytology , Glutathione/analogs & derivatives , Lipoproteins, LDL/pharmacology , Nitric Oxide/pharmacology , Nitroso Compounds/pharmacology , Spermine/pharmacology , Animals , Aorta, Thoracic , Butylated Hydroxytoluene/pharmacology , Cattle , Cell Survival/drug effects , Deferoxamine/pharmacology , Dose-Response Relationship, Drug , Endothelium, Vascular/drug effects , Glutathione/pharmacology , Glutathione Disulfide , Kinetics , Lipid Peroxides/pharmacology , Lipoproteins, LDL/antagonists & inhibitors , Platelet Aggregation Inhibitors/pharmacology , S-Nitrosoglutathione , Selenium/deficiency , Selenium/pharmacologyABSTRACT
The objective of this study was to determine whether inhibition of intracellular catalase would decrease the tolerance of the heart to ischemia-reperfusion and hydrogen peroxide-induced injuries. Isolated bicarbonate buffer-perfused rat hearts were used in the study. Intracellular catalase was inhibited with 3-amino-1,2,4-triazole (ATZ, 1.5 g/kg body weight, two hours prior to heart perfusion). In the ischemia-reperfusion protocol, hearts were arrested with St. Thomas'II cardioplegic solution, made ischemic for 35 min at 37 degrees C, and reperfused with Krebs-Henseleit buffer for 30 min. The extent of ischemic injury was assessed using postischemic contractile recovery and lactate dehydrogenase (LDH) leakage into reperfusate. In the hydrogen peroxide infusion protocol, hearts were perfused with increasing concentrations of hydrogen peroxide (inflow rates 0.05-1.25 mumol/min). Inhibition of catalase activity (30.4 +/- 1.8 mU/mg protein in control vs 2.4 +/- 0.3 mU/mg in ATZ-treated hearts) affected neither pre-ischemic aerobic cardiac function nor post-ischemic functional recovery and LDH release in hearts subjected to 35 min cardioplegic ischemic arrest. Myocardial contents of lipid hydroperoxides were similar in control and ATZ-treated animals after 20 min aerobic perfusion, ischemia, and ischemia-reperfusion. During hydrogen peroxide perfusion, there was an increase in coronary flow rate followed by an elevation in diastolic pressure and inhibition of contractile function in comparison with control hearts. The functional parameters between control and ATZ-treated groups remained unchanged. The concentrations of myocardial lipid hydroperoxides were the same in both groups. We conclude that inhibition of myocardial catalase activity with ATZ does not predispose the rat heart to ischemia-reperfusion and hydrogen peroxide-induced injury.