Selective role for superoxide in InsP3 receptor-mediated mitochondrial dysfunction and endothelial apoptosis

Abstract

Reactive oxygen species (ROS) play a divergent role in both cell survival and cell death during ischemia/reperfusion (I/R) injury and associated inflammation. In this study, ROS generation by activated macrophages evoked an intracellular Ca2+([Ca2+]i) transient in endothelial cells that was ablated by a combination of superoxide dismutase and an anion channel blocker. [Ca2+]i store depletion, but not extracellular Ca2+ chelation, prevented [Ca2+] i elevation in response to O2.- that was inositol 1,4,5-trisphosphate (InsP3) dependent, and cells lacking the three InsP3 receptor (InsP3R) isoforms failed to display the [Ca2+]i transient. Importantly, the O 2.- -triggered Ca2+ mobilization preceded a loss in mitochondrial membrane potential that was independent of other oxidants and mitochondrially derived ROS. Activation of apoptosis occurred selectively in response to O2.- and could be prevented by [Ca 2+]i buffering. This study provides evidence that O 2.- facilitates an InsP3R-linked apoptotic cascade and may serve a critical function in I/R injury and inflammation. © The Rockefeller University Press.