The integrating theme of this PPG is to investigate the role of oxidative stress and reactive oxygen species (ROS) in mediating ischemic brain injury, focusing on detrimental effects involving neurons, astrocytes, microglia and endothelial cells, and the interactions between these various components in contributing to cerebral damage. Our initial PPG studied the role of SOD, Bcl-2 and HSP70 in protecting against necrotic and apoptotic neuronal and astroglial death. The current PPG represents an evolution in our approach based on results obtained in our labs over the last 5 years. It has become clear that ischemia/reperfusion induced ROS are also involved in inflammatory events mediated by microglia, leukocytes and astrocytes as well as causing endothelial cell death, in addition to direct neuronal and astroglial injury. It is also apparent that downstream apoptotic events precipitated by ROS are more complex and interrelated than previously assumed. We therefore propose to explore the delayed effects of ROS mediated injury on neurons, astrocytes, microglia and endothelial cells. The development of the 3 interrelated projects has benefited greatly from our ongoing collaboration during the first 5 years of this Program, and will continue to employ advanced molecular biology techniques, including gene transfer, transgenic/knockout technology and bone marrow transplant chimeras using in vivo and in vitro models of ischemic injury. Project by Giffard will examine ROS-related mechanisms of microglial exacerbation of ischemic injury, in vivo and in vitro. Project by Steinberg will study the role of ROS in initiating key apoptotic pathways leading to neuronal death using in vivo and in vitro models. Project by Chan will explore mechanisms of endothelial cell death in ROS-mediated brain damage utilizing in vivo models. The Transgenic Core will provide transgenic and knockout mice for use in each project, and the Vector Core will prepare viral vectors for gene transfer to be used in Projects by Giffard and Steinberg. The administrative Core will provide grant management, financial administration, centralized purchasing, seminar arrangement, statistical consulting, clerical and scientific consultation through the Advisory Committees.