Urolithin-A mitigates synaptic dysfunctions associated with epilepsy through VDAC1 inhibition: A novel therapeutic approach

Abstract

Urolithin-A mitigates synaptic dysfunctions associated with epilepsy through VDAC1 inhibition: A novel therapeutic approach Epilepsies are a group of neurological disorders with a prevalence of 70 million people worldwide and are characterized by spontaneous, unprovoked, and variably synchronized seizures. Despite being presented with distinct aetiologies, epileptic seizures occur due to imbalances in excitation/inhibition (E/I) activity that disrupts neuronal ensemble activity. A large group of anti-epileptic medications (AEMs) available in the market constitutes a symptomatic approach by targeting the E/I imbalance involved in seizure generation and propagation, mediated by ion channels and neurotransmitter receptors. However, these drugs produce undesirable secondary effects and are ineffective in treating 30% of patients. Therefore, the development of new adjuvant drugs is required that act on other novel components of underlying pathogenesis: oxidation, mitochondrial dysfunctions, inflammation, apoptosis, and activity-dependent synaptic modifications. Such novel approaches might provide a homeostatic boost to the neuronal network and restore physiological imbalances. Recently, interest in compounds of natural origin for anti-epileptic potential has renewed, owing to less toxicity, safer profiles, and the probability of finding novel targets. Thus, identifying safer and tolerable natural products targeting the novel downstream mediators represents a promising treatment approach against epilepsy. While the pathogenesis of epilepsy is highly complex, with multiple stage-specific levels of anatomic, transcriptomic, and circuitry changes, aberrations in the synaptic transmission represent an essential common hallmark of initiation, epileptogenesis, and chronic illness phases of epilepsy. Studies on the protein-protein interactions have identified Punica granatum (Pomegranate) as one of the several natural products targeting synaptic proteins with anti-epileptic treatment potential. Additionally, ellagic acid (the primary polyphenolic precursor of UA found in Pomegranate) has been shown to exert anti-epileptic effects in epileptic models of mice. However, parental extracts undergo reduced bioavailability in the plasma; therefore, several studies have shown that the beneficial effects of the precursors are primarily mediated by gut microbial catabolite product, Urolithin-A (UA). UA supplementation has been shown to benefit central nervous system (CNS) disorders such as Parkinson’s and Alzheimer’s disease, attenuating oxidative stress in neuronal cells; however, its effects on epilepsy remain elusive. In this study, we show that the UA exerts anti-epileptic effects with disease-modifying potential resulting in fewer seizure-susceptible neuronal activity in different experimental models of epilepsy with diverse aetiologies. Anti-epileptic results were scored based on behavioral paradigms and studies of synaptic transmission at both structural and functional levels in the sub-acute picrotoxin-induced chemoconvulsive and chronic genetic models with a gain of function in sodium channel bang senseless (bss1). UA administration had no effects on the epileptiform firing induced in acute brain slices of mice, indicating that the anti-epileptic effects of UA are, indeed, through target mediators of the underlying pathogenesis of seizures; therefore, slow in action. Furthermore, the results were validated in the Pentylenetetrazol (PTZ)-induced chronic kindling mouse model. Extracellular and whole-cell patch clamp electrophysiology studies have shown that the effects mediated by UA were restricted to the post-synaptic level without affecting pre-synaptic functions. Using a combination of affinity purification with synthesized UA-attached beads and molecular-docking studies, we identified a complex of voltage-dependent anion channel-1 (VDAC-1) and β-Tubulin as the direct interactor of UA in the mouse brain. Transcriptomics studies in Drosophila and mice revealed disruption in the regulation of several downstream targets hinting at VDAC-1 inhibition. Finally, VDAC-1 knockdown in the sub-acute epileptic model of Drosophila mimics the effects of UA. Thus, our study provides an exciting and novel platform for developing effective and potent anti-epileptic therapy of Urolithin-A mediated modulation of VDAC1.