Jong M. Rho - US grants

This application is for a Mentored Clinical Scientist Development Award (K08). The candidate obtained clinical training in Child Neurology at UCLA, and then completed a two-year fellowship in neuropharmacology at the National Institutes of Health (Epilepsy Research Branch, NINDS) prior to taking his current faculty appointment in 1994 at the University of Washington. The long- term career goal of the candidate is to study the relationship between ion channels and epileptogenesis, to identify potentially novel treatments for developmental epilepsies that have a rational molecular basis, and to explore the relationship between genetic susceptibility and environmental influence in the pathogenesis of the developmental epilepsies. The university medical center and Children's Hospital possess complementary strengths in the basic neurosciences and clinical pediatric epileptology, respectively. Laboratory space, equipment, and specialized consultants are available to the candidate on a collaborative basis provided by several academic departments. This environment is ideally suited for supporting and fostering the candidate's long-term professional goals. We have chosen as our experimental model the mKv1.1 potassiumchannel single gene mouse mutant which exhibits spontaneous seizures early in development. First, we hypothesize that loss of a specific potassium channel subunit in the CA 3 region of the hippocampus results in a functional alteration in physiological properties of pyramidal neurons such that they became hyperexcitable and prone to excessive synchronization of discharge. Second, we postulate that pharmacological treatment can alter the natural course of the epilepsy and may protect the animal from neuronal injury as a consequence of repeated seizures. Finally, we will explore whether partial expression of the mKv1.1 gene in plus/minus mice, resulting in an enhanced susceptibility to seizures, can be modified by secondary exposure to kainic acid (a potent convulsant and neurotoxin) early in development. Initial efforts will involve electrophysiological recordings from CA3 pyramidal neurons in hippocampal slices taken from null mutants at different ages; intrinsic and synaptic properties of these cells, as well as whole-cell potassium currents, will be measured with extracellular, intracellular and patch-clamp recording techniques. Video-EEG monitoring (with depth electrodes) will be employed to document epileptiform or seizure activity in the hippocampus, and histochemical analysis of neuronal damage and/or plasticity will be made with routine and special (e.g., Timm) stains. The results of these studies may lead to an improved understanding of the role ion channels play in epileptogenesis, may shed light on the controversial issue of whether chronic seizures can cause brain damage, and will provide a framework for further studies examining genetic and environmental interactions in the developing brain.

[unreadable] DESCRIPTION (provided by applicant): This application is for an Independent Scientist Award (K02). The candidate is a pediatric neurologist with a specialty interest in childhood epilepsy, and is currently in the final year of K08 (MCSDA) funding. He recently relocated to the University of California at Irvine (UCI). UCI hosts an internationally recognized basic neuroscience research community, and is well suited to the career development needs of the candidate, especially at this critical time when he has just established an independent laboratory. During the early period of K08 funding, the candidate performed detailed studies of a developmental animal model of epilepsy, the Kv1.1 potassium channel knockout mouse (i.e., the Kcna1-null mutant). Later, the applicant pursued research into the mechanisms underlying the anticonvulsant efficacy of the ketogenic diet (KD), an established but still poorly understood treatment for intractable epilepsy. The KD is a high-fat, low carbohydrate and low-protein diet designed to mimic the early biochemical changes seen upon fasting. The hallmark feature of the KD is the production of the ketone bodies by the liver. The fundamental goal of the proposed studies is to assess the potential role of the GABAergic system in contributing to seizure control by the KD, and in the process establish and validate a clinically relevant animal model of the KD. As a secondary goal, it will be determined whether chronic ketone body exposure can enhance GABAergic inhibition in the brain. Further, the question of whether the KD can exert a lasting antiepileptic effect, beyond the duration of therapy, will be addressed, thereby setting the stage for future studies aimed at determining a mechanistic basis for an anti-epileptogenic effect of the KD. Toward these goals, the effects of the KD on the Kcna1-null mutant will be investigated. In addition, the long-term impact of ketone bodies in hippocampal organotypic slice cultures prepared from these mice will be studied. Neuroanatomical (i.e., histological, immunocytochemical, in situ hybridization) and functional (i.e., video-EEG monitoring, cellular electrophysiological) techniques will be employed in the proposed studies. It is expected that the results of these investigations will shed light on the potential role of the KD in epileptogenesis, especially as it relates to effects on GABAergic inhibition

[unreadable] DESCRIPTION (provided by applicant): While most neurological disorders have traditionally been treated with pharmacological agents, there is growing evidence that dietary interventions can also exert beneficial clinical effects comparable to, or perhaps exceeding, drug therapy. This is especially true for the epilepsies which respond favorably to a high-fat low-carbohydrate diet known as the ketogenic diet. Indeed, following historical observations that fasting was effective for seizure control, clinicians formulated the ketogenic diet in the 1920's to mirror the biochemical changes seen in the fasted state. And although the ketogenic diet has been available since then in medical centers throughout the United States, it was not until this past decade that widespread international acceptance of this non-pharmacological intervention as an effective treatment for medically refractory epilepsy had been achieved. Scientific interest in the ketogenic diet has also paralleled the growth of clinical centers throughout the world, with the goal of understanding its underlying mechanisms of action - important information that is necessary to improve upon its clinical implementation. In the past several years, variations of the ketogenic diet have emerged as efficacious and better tolerated options in the treatment of epilepsy in both pediatric and adult patients. Additionally, there is a small but growing interest in treating other neurological disorders with dietary interventions - such as calorie restriction - that share some biochemical similarities with the KD. These conditions include Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, traumatic brain & spinal cord injury, and even brain tumors. That dietary factors should influence brain function is not altogether surprising, but it is important to note that such treatments can exert such profound clinical effects, where in many instances drugs have failed to produce lasting effects. A greater fundamental understanding of dietary and metabolic effects of brain function and disease processes is required to develop novel and effective strategies for what are often considered neurodegenerative and/or debilitating disorders. This symposium is aimed at neurologists, epileptologists, research scientists, nurses, dietitians, and other allied health professionals, with the fundamental goal of sharing up-to-date information on this rapidly expanding topic, and defining the important clinical and research questions that should be pursued in the future. Additionally, this symposium will provide a forum for extended discussions regarding practical clinical implementation, surveillance of adverse effects, and importantly, a critical look at basic cellular and molecular mechanisms that could account for the anticonvulsant and neuroprotective effects of the ketogenic diet. This symposium will be held over three full days, and will consist of both plenary sessions and mini- symposia, as well as poster and break-out sessions devoted to specific groups of healthcare professionals and researchers. While much of the focus of the symposium will be on dietary treatments for epilepsy, the final day will review our clinical and experimental experience with dietary therapies for other neurological disorders (including Alzheimer's and Parkinson's diseases, brain tumors and neurotrauma), paving the way toward a greater understanding of how dietary substrates, and the biochemical and metabolic consequences of their administration, can protect the diseased brain. An additional practical short-term goal will be to have attendees share information and establish clinical and research collaborations. It takes a multidisciplinary team to successfully implement the ketogenic diet, study it appropriately, and improve upon it. This spirit of cooperation constitutes the core rationale for this international symposium. PUBLIC HEALTH RELEVANCE: The fundamental goal of this symposium is to share up-to-date information on the rapidly expanding topic of dietary therapies for epilepsy, and to define the important clinical and research questions that should be pursued in the future. While there have been a few international meetings devoted to the topic of the KD, none have comprehensively examined both clinical and basic science aspects of this time-honored treatment. As such, we believe that this symposium may be the first landmark scientific meeting devoted to this long-neglected area of medicine. [unreadable] [unreadable] [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): The hypothalamic hamartoma (HH) is a rare congenital human brain malformation associated with gelastic (or laughing) seizures that are difficult to diagnosis early in life and are notoriously refractory to medical therapy. Despite increasing clinical recognition of this condition, the mechanisms of epileptogenesis are largely unknown. Importantly, seizures have previously been shown to originate from the hamartoma itself. At the Barrow Neurological Institute, we have treated over 100 patients with this condition over the past several years, constituting the largest single-center series ever; we are currently the only multidisciplinary program for HH management in the United States, and the most active HH program in the world. Thus, we are uniquely positioned to study the mechanisms of epileptogenesis in HH. The major goal of the proposed studies is to determine the mechanisms of seizure genesis in surgically resected HH tissue using a combination of cellular electrophysiological, fluorescence imaging, immunocytochemical and gene expression techniques. Our preliminary data demonstrate that HH tissue contains two distinct populations of neurons; small HH neurons exhibit intrinsic pacemaker-like activity, whereas large HH neurons are quiescent. We have demonstrated that a subpopulation of large HH neurons depolarize when perfused with the GABAA-receptor agonist muscimol. Based on these intriguing findings, we hypothesize that such GABAA-receptor mediated depolarization may be a consequence of decreased expression of the cation-chloride co-transporter KCC2 (relative to its cousin, NKCC1), and that such responses may contribute to seizure genesis. Specifically, we hypothesize that muscimol will increase intracellular calcium levels, an effect that can be blocked by the NKCC1 antagonist bumetanide. Further, we hypothesize that HH tissue will demonstrate decreased expression of KCC2 relative to NKCC1 using immunocytochemical and single-cell RT-PCR expression techniques. Although HH itself is uncommon with an estimated prevalence of 1 in 50,000-100,000 it is perhaps the best human model for subcortical epilepsy, and one of the most intriguing models for understanding the consequences of catastrophic epilepsy in childhood. As such, a detailed scientific understanding of this disorder has major ramifications for expediting translational research focused on the developmental epilepsies. PUBLIC HEALTH RELEVANCE: Epilepsy is a common neurological disorder that afflicts more than 3 million people in the United States alone, and many newly diagnosed patients are infants and children. There is a substantial need to understand how epilepsy develops in the pediatric population in order to develop newer, more effective treatments. This research proposal, while focused on a rare brain tumor that causes uncontrolled seizures, may provide novel insights into the mechanisms of seizure propagation and progression. [unreadable] [unreadable] [unreadable]