Abstracts

Rationale: Temporal lobe epilepsy (TLE) affects roughly 50 million people and is often treatment-refractory. Understanding mechanisms of epileptogenesis during the latent phase following a neurological insult has long been a goal, as this represents a critical window during which effective intervention could prevent epileptic network development. There is currently no treatment available to prevent or modify this process in TLE. Previous research has demonstrated that LOFU can alter epileptiform neuronal activities after the development of spontaneous seizures. In the present study, we aim to prevent the development of an epileptic network, using a kainic acid (KA)-induced TLE model to investigate the functional, tissue, and molecular-level impact of LOFU.


Methods: All animal procedures followed institutional guidelines and were approved by the University of Maryland Institutional Animal Care and Use Committee (Protocol Number 00000032). In adult male rats, KA (500ng) was stereotactically injected into the right dorsal hippocampus to induce initial status epilepticus (SE). Critically, this method yields a 2-4 week latent period after resolution of SE prior to the development of spontaneous seizures, representing the period of epileptogenesis. Rats were treated with LOFU early in this latent period, 48 hours after KA injection. Seizure counts were quantified by blinded observers through an 8-week observation period, using the modified Racine scale. Multiple behavioral tests were performed to study the impact of LOFU on overall cognitive health. To study critical alterations in epileptic pathology in the hippocampus, we used Timm’s staining to assess mossy fiber sprouting and immunohistochemistry to examine c-FOS expression co-labeled with excitatory (vGLUT) and inhibitory (GAD1/67) neuronal markers, as well as GFAP, caspase, PS6, and NeuN in hippocampal sub-regions.


Results: KA-injected animals developed spontaneous seizures, with widespread activation of hippocampal mossy fiber sprouting (Fig 1), and both excitatory and inhibitory neurons (Fig 2) in hippocampal sub-regions. Seizure frequency and hippocampal histopathological effects measured at the 4- and 8-week timepoints were attenuated with LOFU. LOFU decreased cell death (caspase), astrogliosis (GFAP), and mechanistic target of rapamycin (mTOR) activity (PS6), and increased neurogenesis (NeuN) in KA-injected animals. This correlated with decreased excitatory (vGLUT, c-FOS) and increased inhibitory (GAD1/67, c-FOS) neuronal activity. Moreover, LOFU alone did not significantly alter the animals’ behavioral performance.


Conclusions: LOFU modulates the development of an epileptic network in TLE through the activation of inhibitory neurons and downregulation of excitatory and inflammatory pathways, without causing tissue damage in the hippocampus. Early intervention with LOFU offers a promising non-invasive anti-epileptogenic strategy for the prevention of TLE and other forms of epilepsy.


Funding: This study is funded by the Department of Neurosurgery of the University of Maryland, Baltimore.