[unreadable] Stroke is the third leading cause of death in this country. Furthermore, perioperative neurologic dysfunction is one of the most feared complications of cardiac and neurosurgery. The goal of this work is to develop novel therapies to reduce the morbidity and mortality of stroke. A large body of literature demonstrates that overexpression of the protective protein heat shock protein 70 (Hsp70) reduces ischemic brain injury. Hsp70 is known to have many distinct functions, how many contribute to neuroprotection is unknown. This proposal seeks to better define the mechanisms of action of Hsp70 in 1) blocking protein aggregation, 2) improving mitochondrial function, and 3) modulating the astrocyte activation that accompanies ischemic brain injury. Protein aggregation likely contributes to stroke injury as it does to many chronic neurological degenerative diseases. Hsp70 is known to inhibit protein aggregation. Aim 1 will use molecular modeling to predict the minimum subdomain within Hsp70 that prevents aggregation. Expression of this subdomain will be used to test the prediction that it will reduce ischemia-like injury of astrocytes in vitro and reduce stroke damage in vivo. Aim 2 will test the ability of Hsp70 to preserve mitochondrial function in stressed astrocytes. Mitochondria provide energy for the cell, produce free radicals, and are central regulators of cell death. Mitochondrial membrane potential, free radical generation, and respiration will be assessed. In aim 3 astrocyte activation will be studied in vitro and in vivo. Astrocytes are essential for normal brain function. They maintain a tightly controlled extracellular environment, provide antioxidant and trophic support, and participate in the inflammatory response provoked by ischemia. The ability of Hsp70 to inhibit astrocyte inflammatory activation will be determined. Modulation of nuclear factor kB activation and the ensuing inflammatory cascade including cytokine release will be studied. These studies will identify new therapeutic strategies and lay the foundation for the development of Hsp70 mimetics for neuroprotection. [unreadable] [unreadable]