Silencing Hyper-Excitable Neurons as a Treatment for Status Epilepticus and Temporal Lobe Epilepsy.

Abstract

Epilepsy is a neurological disorder affecting millions of people around the globe. It is characterized by recurrent, spontaneous seizures. Seizures are broadly classified into partial seizures and generalized seizures. Temporal lobe epilepsy (TLE) is the most common form of adult focal epilepsy. Almost one third of TLE suffering patients are non-responsive to anti-epileptic drugs. The last resort for these patients is surgery. Surgery comes with serious side effects and also does not promise complete cure from the disease. Status epilepticus (SE) is a medical emergency which is characterized by a seizure lasting for least 5 minutes. It affects 110,000 to 160,000 people annually in United States alone and results in 22,000-42000 deaths annually. Anti-epileptic drugs fail to treat status epilepticus in almost 23-43 % of suffering patients at some point. This thesis focused on finding an alternative gene therapy treatment to treat seizures focusing mainly on SE and TLE. Recombinant adeno-associated virus mediated gene have been in development for Alzheimer’s and Parkinson’s disease. Recently adeno-associated virus serotype 1 mediated gene therapy for lipoprotein lipase deficiency disorder has entered the European clinics. This study investigates the effect of adeno-associated virus mediated expression of constitutively-active potassium leak channel Trek-1 (Trek-M) on SE induced by intra-peritoneal injection of pilocarpine. The results have demonstrated that expression of a constitutively active potassium channel in rodent brain prior to pilocarpine insult causes a significant reduction in duration of SE. Significant less amount of neuronal death was observed in the brain regions like entorhinal cortex, CA3, CA1 in rats preinjected with TREK-M. This finding suggested that TREK-M preinjection prevented neuronal death in the brain regions where it was injected. We have made the first doxycycline regulated AAV targeting vector which can be turned on by addition of doxycycline in the diet. Doxycycline regulated expression of TREK-M showed promising results in significantly decreasing the normalized seizure frequency of chronic seizures in lithium pilocarpine rat model of epilepsy. This study of gene therapy approach to silence hyper-excitable neurons to treat seizures will pave the way for developing gene therapy to treat seizures in patients suffering from refractory convulsive status epilepticus and temporal lobe epilepsy.