Blood-brain barrier function in epilepsy: new targets for therapy

There is a lack in understanding the mechanism responsible for blood-brain barrier dysfunction in epilepsy. This is a significant clinical challenge since it prevents development of a therapy to overcome antiepileptic drug (AED) resistance and reduce seizure burden. Our long-term goal is to elucidate the mechanisms that regulate blood-brain barrier function, which may lead to new strategies to treat epilepsy and other neurological diseases. The objectives in this application are to identify the mechanism(s) by which seizures trigger barrier dysfunction, and map key signaling proteins that can potentially serve as targets to repair the blood-brain barrier in epilepsy. Accomplishing these objectives is expected to increase AED brain uptake and reduce seizure burden. Our central hypothesis is that 1) glutamate activates the two-arm LOX/COX pathway, thereby decreasing expression and activity of influx transporters, and upregulating expression and activity of efflux transporters through the COX arm, that 2) glutamate triggers development of barrier leakage through the LOX arm; and that 3) inhibiting cPLA2 to block both arms of the LOX/COX pathway reverses barrier dysfunction and thereby reduces seizure burden. The rationale for this research is that identifying the mechanism(s) responsible for changes in transporter expression and activity, and barrier leakage will potentially provide new targets to improve epilepsy treatment and better control seizures. To accomplish the objectives of this application, our hypothesis will be tested by pursuing three specific aims: 1) Determine the mechanism of seizure-induced changes of transporter expression and activity; 2) Determine the mechanism of seizure-induced blood-brain barrier leakage; and 3) Develop a therapeutic strategy to reduce seizures in chronic epileptic rats. In Aim 1, we will block cPLA2 and COX-2 to reverse seizure- induced changes in transporter expression and activity. We will monitor influx and efflux transporter expression and activity, and determine AED brain uptake. In Aim 2, we will inhibit cPLA2 and 5-LOX to map the signaling pathway causing seizure-induced barrier leakage. We will determine expression of tight junction proteins and matrix metalloproteases, and assess barrier leakage. In Aim 3, we will evaluate the therapeutic benefit of cPLA2 inhibition on seizure burden in a rat chronic epilepsy model by determining influx and efflux transporter expression and activity, assessing barrier leakage, and monitoring seizure frequency, duration and severity. The proposed research is innovative because it is focused on a new, integrated strategy that considers blood-brain barrier transporters, as well as barrier leakage, and it is designed specifically to repair the barrier to overcome AED resistance and reduce seizures. The proposed research is significant because the expected outcomes will potentially provide a new strategy to improve pharmacotherapy in patients with resistant epilepsy. The proposed research is translational because cPLA2 inhibitors are under development, and our strategy has potential to be translated into the clinic.