High extracellular concentrations of the excitatory neurotransmitter glutamate are observed in animal models of stroke, cardiac arrest, and head trauma, and are well established as a primary cause of neuronal death. The long-term goal of the research is to develop a method to prevent neuronal death by inhibiting the conversion of glutamine to glutamate by the enzyme glutaminase. The enzyme is abundant in neuronal mitochondria and the substrate, glutamine, is the most abundant amino acid in the brain extracellular fluid. The advantage of inhibiting the glutaminase is that it may be possible to selectively interfere with pathological glutamate production in damaged neural tissue, while leaving normal neurotransmission relatively intact. Our experiments show that neuronal damage in pure neuronal and mixed neuronal/glial cultures causes a large increase in the production of extracellular glutamate from glutamine. Neuroprotection can be achieved in pure neuronal cultures with a membrane impermeant glutaminase inhibitor. We propose to perform experiments which test the following hypotheses: (1) The glutaminase in damaged neurons is a biologically important source of glutamate in in- vitro and in-vivo models of anoxic neural damage, (2) That the enzyme in mixed cultures exposed to anoxia directly contributes to neuronal pathology, and (3) That it is possible to directly inhibit the glutaminase which contributes to neuronal pathology without interfering with the normal function of glutamatergic transmission. Positive outcomes will provide justification for the development, in Phase 2, of glutaminase inhibitors with optimal neuroprotective properties.Proposed commercial application:Glutaminase inhibitors may be commercially valuable as agents to lessen neuronal death after stroke, head trauma, and in chronic neurodegenerative disorders.National Institute of Neurological Disorders and Stroke (NINCDS)
