Role of Adenosine Kinase Inhibitor in Adenosine Augmentation Therapy for Epilepsy: A Potential Novel Drug for Epilepsy

Abstract

Epilepsy, an ancient disease, is defined as an enduring predisposition to generate epileptic seizures and by the neurobiological, cognitive, psychological, and social consequences of this condition. Antiepileptic drugs (AEDs) are currently used as first-line treatment for patients with epilepsy; however, around 36% of patients are diagnosed with refractory epilepsy, which means two or more AEDs have been considered as failed after sufficiently correct usage. Unfortunately, it is unlikely that the improvement of the efficacy of AEDs will be easily achieved, especially since no AEDs show efficacy in ceasing epileptogenesis. Consequently, several endogenous anticonvulsants attract investigators and epileptologists, such as galanin, cannabis, and adenosine. Astrogliosis is a neuropathological hallmark of epilepsy, whatever the etiology is, and astrogliosis is frequently associated with overexpression of adenosine kinase, which means downregulation of synaptic levels of adenosine. Consequently, adenosine is negatively regulated by adenosine kinase through the astrocyte-based cycle. On the other hand, focal adenosine augmentation therapy, using adenosine kinase inhibitor, has been proved to be effective for reducing seizures in both animal models and in vitro human brain tissue resected from a variety of etiology of refractory epilepsy patients. In addition to reducing seizures, adenosine augmentation therapy can also palliate co-morbidities, like sleep, cognition, or depression. Of importance, transgenic mice with reduced ADK were resistant to epileptogenesis induced by acute brain injury. In terms of translation, based on findings of adenosinerelated epileptogenic mechanisms, the application into clinical practice seems to be feasible by molecular strategies that have been already experimentally implemented, including gene and RNA interference. In the present review, we will focus on the evidence of ADK dysfunction in the epileptic brain from human beings and animals, and review the role of ADK inhibitor in adenosine augmentation therapy and the underlying mechanism of prevention of epileptogenesis.