Prevention of Oxidative Injury Associated with Thrombolysis for Ischemic Stroke

Although treatment of ischemic stroke focuses on re-establishing blood flow to the brain (e.g., thrombolysis), delayed reperfusion may be associated with oxidative damage to brain capillary endothelial cells, resulting in cerebral bleeding and death (hemorrhagic transformation). The goal of this study was to define cellular mechanisms responsible for reperfusion injury to brain capillaries, and to provide a rationale for more effective treatment of stroke. Mechanisms of oxidative injury to cerebral capillary endothelial cells were measured in the presence and absence of experimental inhibitors to define the roles of transport and metabolic pathways. In vitro experiments provided evidence that: (1) intracellular calcium is elevated in brain capillary endothelial cells following simulated transient ischemia and reperfusion, due to reverse movement of Na/Ca exchange; (2) a simultaneous increase of calcium and reactive oxygen species (ROS) during re-oxygenation causes mitochondrial dysfunction, thus initiating apoptosis and loss of brain capillary integrity. In vivo studies showed that γ-glutamylcysteine (an antioxidant precursor of glutathione) and the experimental compound KB-R7943 (inhibits reverse movement of Na/Ca exchange) protect brain capillary endothelial cells when co-administered just before reperfusion following transient ischemia. The data indicate that these agents may be useful in preventing oxidative injury associated with thrombolysis for ischemic stroke

A Glutathione Precursor Reduces Oxidative Injury to Cultured Embryonic Cardiomyocytes

BACKGROUND: Newborn infants are highly vulnerable to oxidative stress. Following birth asphyxia, oxidative injury due to ischemia-reperfusion can result in significant brain and heart damage, leading to death or long-term disability. STUDY QUESTION: The study objective was to evaluate the effectiveness of antioxidant gamma-L-glutamyl-L-cysteine (γGlu-Cys) in inhibiting oxidative injury to cultured embryonic cardiomyocytes (H9c2 cells). STUDY DESIGN: Control and γGlu-Cys-treated (0.5 mM) H9c2 cells were incubated under 6-hour ischemic conditions followed by 2-hour simulated reperfusion. MEASURES AND OUTCOMES: To quantify oxidative stress-induced apoptosis sustained by cardiomyocytes, lactate dehydrogenase (LDH) release and the presence of cytosolic cytochrome c were measured, as well as the number of secondary lysosomes visualized under electron microscopy. RESULTS: Compared to controls, H9c2 cells coincubated with γGlu-Cys during ischemia-reperfusion exhibited a significant reduction in both LDH release into the incubation medium [23.88 ± 4.08 (SE) vs. 9.95 ± 1.86% of total; P = 0.02] and the number of secondary lysosomes [0.070 ± 0.009 (SD) vs. 0.043 ± 0.004 per μm; P = 0.01]. Inhibition of LDH release with γGlu-Cys was the same (P = 0.67) as that of a caspase inhibitor. The significant increase in cytosolic cytochrome c (P = 0.01) after ischemia-reperfusion simulation further supports γGlu-Cys\u27s role in apoptosis prevention. CONCLUSIONS: It is concluded that the glutathione precursor γGlu-Cys protects cultured embryonic cardiomyocytes from apoptosis-associated oxidative injury