Background: Traumatic brain injury (TBI) is one of the major causes of mortality and morbidity among the active Iraqi-war military. It is also a major cause of morbidity and death in children and young adults. Loss of hippocampal neurons is a common sequela to a single traumatic brain insult. This loss can occur over a period of many days following the insult, yet despite improvements in surgical treatment of the primary insult, there are currently no therapies that provide neuroprotection to mitigate this secondary or delayed damage. Thus, even moderate brain injury is associated with poor prognosis and chronic cognitive impairment. We have a funded VA-based research project that is focused on developing neuroprotective drugs that target the nerve growth factor receptor TrkA. Neuroprotection and the development of therapeutic agents that can prevent neuronal injury is one of the identified research gaps in TBI. There is good reason to believe that neurotrophins may also be protective in traumatic brain injury, so we are proposing to extend and expand our research to develop neurotrophin mimics for TBI.

Objective/Hypothesis: The goal of this research program is to facilitate the discovery, development, and clinical evaluation of effective therapies for traumatic brain injury with emphasis on the development of lead compounds through preclinical in vitro and in vivo evaluation, and the conduct of pre-clinical "proof of concept" studies.

Our central hypothesis is that asterriquinone activators of the Trk receptors would prevent the neuronal cell death associated with traumatic brain injury and would improve cognitive and motor outcomes.

We propose to extend our current studies to develop better, more efficient TrkA activators, as well as new TrkB and TrkC agonists. These agonists will be tested in preclinical models of Alzheimers neurodegeneration, as an extension of our current program, and into models of traumatic brain injury with the hope of identifying lead drugs that can be taken into early trials in humans.

Specific Aims: The specific aims fall into three main areas reflecting the contributions of the three laboratories involved in this proposal. Professor Webster's group at the San Diego VA Hospital will provide the screening, mathematical modeling, and in vitro characterization of lead compounds. Professor Pirrung's group at the University of California, Riverside will provide the combinatorial library synthesis, targeted syntheses of modeled compounds, and large scale synthetic chemistry support. Professor Krajewski's lab at the Burnham Institute will provide the mouse model of TBI, and assessments of motor and cognitive function.

Aim 1: In vitro screening, modeling, and characterization. We will screen existing libraries against the BDNF receptor TrkB and the neurotrophin 3 receptor TrkC. Activity will be modeled mathematically and theoretical structure libraries screened in silico. Selected lead compounds will be tested for potency and selectivity for activation of Trk receptors and for the ability of compounds to support neuronal differentiation and neuronal survival using neuronal cells in culture.

Aim 2: Synthesis of combinatorial libraries and selected lead compounds. We will create new focused combinatorial libraries of asterriquinones and monoquinones, synthesize selected compounds based on in silico mathematical modeling for in vitro testing, and purify large quantities of selected compounds for animal testing.

Aim 3: Testing in traumatic brain injury and neurodegeneration models. We will test whether activators of the Trk receptors can lessen the long-term loss of neuronal cells that occurs in traumatic brain injury using a controlled cortical impact model, and in Alzheimers using the PDAPP mouse. We will evaluate blood brain barrier integrity, neuronal cell loss, functional motor activity, and cognitive loss. We will determine the pharmacokinetic properties of these compounds in rodents.

Study Design: The proposal combines targeted synthetic chemistry and combinatorial library construction, functional screening, and in-vitro evaluation, and, finally, functional testing in animal models of TBI and Alzheimers to provide complete preclinical development of neuroprotective agents. Overall coordination of the project will be provided by Professor Webster.