Norman K. So

Bim regulation may determine hippocampal vulnerability after injurious seizures and in temporal lobe epilepsy

Programmed cell death pathways have been implicated in the mechanism by which neurons die following brief and prolonged seizures, but the significance of proapoptotic Bcl-2 family proteins in the process remains poorly defined. Expression of the death agonist Bcl-2-interacting mediator of cell death (Bim) is under the control of the forkhead in rhabdomyosarcoma (FKHR) transcription factors. This prompted us to examine the response of this pathway to experimental seizures and in hippocampi from patients with intractable temporal lobe epilepsy. A short period of status epilepticus in rats that damaged the hippocampus activated FKHR/FKHRL-1 and induced a significant increase in expression of Bim. Blocking of FKHR/FKHRL-1 dephosphorylation after seizures improved hippocampal neuronal survival in vivo, and Bim antisense oligonucleotides were neuroprotective against seizures in vitro. Inhibition of Akt increased the FKHR/Bim response and DNA fragmentation within the normally resistant cortex. Analysis of hippocampi from patients with intractable epilepsy revealed that Bim levels were significantly lower than in controls and FKHR was inhibited; we were able to reproduce these results experimentally in rats by evoking multiple brief, noninjurious electroshock seizures. We conclude that Bim expression may be a critical determinant of whether seizures damage the brain, and that its control may be neuroprotective in status epilepticus and epilepsy.

Acute Postictal Psychosis: A Stereo EEG Study

Summary An acute psychosis characterized by auditory hallucinations and paranoid delusions developed in a 19‐year‐old man with temporal lobe epilepsy after he had a cluster of seizures when antiepileptic drugs (AEDs) had been gradually discontinued. Continuous stereotactic depth and epidural EEG recordings confirmed that this was a postictal rather than an ictal event. Acute postictal psychosis is a self‐limited condition phenomenologically distinct from ictal or postictal confusion.

Progressive myoclonus epilepsies: clinical and neurophysiological diagnosis.

Diagnosis and management of the progressive myoclonus epilepsies (PMEs) provides a challenge to the clinician and neurophysiologist. Over 15 specific disorders can cause the PME syndrome; all are rare, and individual physicians are unlikely to have experience in all of them. Accurate diagnosis is essential to provide a prognosis, optimal therapy, and genetic counseling. The major causes are PME of the Unverricht-Lundborg type, Lafora disease, neuronal ceroid lipofuscinoses (three forms), MERRF (myoclonus epilepsy and ragged red fibers), and sialidoses (two forms), in addition to a number of even rarer disorders. Here we review the clinical aspects and neurophysiology of these disorders, which can now be diagnosed in life by relatively simple methods in the vast majority of cases.

Endoplasmic reticulum stress and apoptosis signaling in human temporal lobe epilepsy.

Apoptosis signaling pathways are implicated in the pathogenesis of temporal lobe epilepsy (TLE), but the role of endoplasmic reticulum (ER) stress and ER-localized apoptosis signaling components remains largely unexplored. Presently, we investigated ER stress and ER localization of proapoptotic Bcl-2 family members and initiator and effector caspases in resected hippocampus from patients with intractable TLE and compared findings with autopsy controls. Hippocampal immunoreactivity for KDEL (Lys-Asp-Glu-Leu), a motif in ER stress chaperones glucose-regulated proteins 78 and 94, and calnexin, was significantly higher in TLE hippocampus compared with controls. The ER-containing microsomal fraction in control brain contained Bid, Bim, and caspase 3, whereas Bad and caspases 6, 7, and 9 were very low or absent. In contrast, caspases 6, 7, and 9 were present within the microsomal fraction of TLE brain. Furthermore, cleaved caspases 7 and 9 were detected in TLE samples but not controls, and KDEL-expressing neurons coexpressed cleaved caspase 9. Potentially adaptive changes were also detected, including lowered Bim levels in this fraction, and binding of caspase 7 to the X-linked inhibitor of apoptosis protein. These data suggest seizures may induce ER stress and trigger proapoptotic signaling pathways in the ER that are counteracted by antiapoptotic signals in chronic human TLE.

Changes in seizure activity following anticonvulsant drug withdrawal

We retrospectively studied the effects of changing antiepileptic drug levels on patterns of seizure discharge in 8 patients investigated with intracerebral electrodes during presurgical evaluation. We compared seizures recorded at high levels of medication to seizures recorded at low levels for changes in seizure duration, duration from unilateral onset to contralateral spread, inter- and intrahemispheric coherence, and morphology of EEG discharges. Seizures were more frequent with low medication, as was secondary generalization. Reduction in medication did not affect the morphology of discharges at onset, duration to contralateral spread, and coherence between EEG discharges. Seizures of similar type (eg, complex partial seizures without secondary generalization) were not longer with low than with high medication. Whereas medication clearly affects seizure frequency and generalization, it has little effect on the pattern of early parts of seizures. In particular, we found no evidence that seizure discharges become bilateral or generalized more quickly when medication is reduced.

Death-associated protein kinase expression in human temporal lobe epilepsy

Experimental and human data suggest programmed (active) cell death may contribute to the progressive hippocampal atrophy seen in patients with refractory temporal lobe epilepsy. Death‐associated protein (DAP) kinase is a novel calcium/calmodulin‐activated kinase that functions in apoptosis mediated by death receptors. Because seizure‐induced neuronal death involves both death receptor activation and calcium, we examined DAP kinase expression, localization, and interactions in hippocampal resections from patients with intractable temporal lobe epilepsy (n = 10) and autopsy controls (n = 6). Expression and phosphorylation of DAP kinase was significantly increased in epilepsy brain compared with control. DAP kinase and DAP kinase–interacting protein 1 (DIP‐1) localized to mitochondria in control brain, whereas levels of both were increased in the cytoplasm and microsomal (endoplasmic reticulum) fraction in epilepsy samples. Coimmunoprecipitation analysis showed increased DAP kinase binding to calmodulin, DIP‐1, and the Fas‐associated protein with death domain (FADD) in epilepsy samples. Finally, immunohistochemistry determined DAP kinase was coexpressed with DIP‐1 in neurons. This study provides the first description of DAP kinase and DIP‐1 in human brain and suggests DAP kinase is a novel molecular regulator of neuronal death in epilepsy. Ann Neurol 2004;55:000–000

Caspase-3 cleavage and nuclear localization of caspase-activated dnase in human temporal lobe epilepsy

Programmed cell death (apoptosis) signaling pathways have been implicated in seizure-induced neuronal death and the pathogenesis of human temporal lobe epilepsy (TLE). End-stage DNA fragmentation during cell death may be mediated by nucleases including caspase-activated DNase (CAD), apoptosis-inducing factor (AIF) and endonuclease G. In the present study, we investigated the subcellular localization of these nucleases in resected hippocampus from TLE patients and autopsy controls. Subcellular fractionation determined levels of CAD were significantly higher in the nuclear fraction of TLE samples compared with controls, and semiquantitative immunohistochemistry revealed cleaved caspase-3 positive cells in TLE sections but not controls. While mitochondrial levels of AIF and endonuclease G were higher in TLE samples than controls, nuclear localization of AIF was limited and restricted to cells that were negative for cleaved caspase-3. Nuclear accumulation of endonuclease G was not found in TLE samples. These data support ongoing caspase-dependent apoptosis signaling in human TLE and suggest that interventions targeting such pathways may have potential as adjunctive neuroprotective therapy in epilepsy.

Ictal asystole and SUDEP

The most frightening consequence of uncontrolled epilepsy is sudden unexplained death (SUDEP). Population studies suggest a risk in the range of 1 to 5 per 1,000 patient-years,1,2 and in high risk populations with neurologic impairments this rate is even higher. How seizures cause sudden death is still debated. Respiratory mechanisms such as suffocation, pulmonary edema, and centrally mediated respiratory arrest may each play a role, but best documented is the effect of seizures on the heart, either directly or secondary to apnea. A variety of potentially serious arrhythmias have been observed during or immediately after seizures, with ictal bradycardia and asystole the most striking. These ictally mediated bradyarrhythmias may be a point of differentiation from sudden unexplained death in young people with structurally normal hearts and no known cardiac conduction disease. In people without epilepsy, underlying conditions such as congenital long QT syndrome, Brugada syndrome, or catecholaminergic polymorphic ventricular tachycardia may also predispose to ventricular tachyarrhythmias. The experimental literature supports a direct CNS effect on heart rhythm. Stimulation of …

Evidence of tumor necrosis factor receptor 1 signaling in human temporal lobe epilepsy

Seizures, particularly when prolonged, may cause neuronal loss within vulnerable brain structures such as the hippocampus, in part by activating programmed (apoptotic) cell death pathways. Experimental modeling suggests that seizures activate tumor necrosis factor receptor 1 (TNFR1) and engage downstream pro- and anti-apoptotic signaling cascades. Whether such TNFR1-mediated signaling occurs in human temporal lobe epilepsy (TLE) is unknown. Presently, we examined this pathway in hippocampus surgically obtained from refractory TLE patients and contrasted findings to matched autopsy controls. Western blotting established that total protein levels of the TNFR1 proximal signaling adaptor TNFR-associated protein with death domain (TRADD), cleaved initiator caspase-8 and apoptosis signal-regulating kinase 1 (ASK1) were higher in TLE samples than controls. Intracellular distribution analyses revealed raised cytoplasmic levels of TNFR1, TRADD and the caspase-8 recruitment adaptor Fas-associated protein with death domain (FADD), and higher levels of TRADD and cleaved caspase-8 in the microsomal fraction, in TLE samples. Immunoprecipitation studies detected TRADD-FADD binding, and fluorescence microscopy revealed TRADD co-localization with FADD in TLE hippocampus. These data suggest that TNFR1 signaling is engaged in the hippocampus of patients with refractory temporal lobe epilepsy.

Quantitative EEG analysis of carbamazepine effects on amygdaloid kindled seizures in cats

We studied the effects of carbamazepine (CBZ) on seizure behaviour and electroencephalographic (EEG) activity in 6 amygdala kindled cats. CBZ reduced the behavioural severity of kindled seizures and prolonged the earlier seizure stages (latency to stage 4). These effects were not always paralleled by a reduction in the duration of seizure activity. EEG activity paradoxically increased in amplitude during early and mid-seizure, then fell in late seizure after CBZ. CBZ also caused an overall decrease in EEG coherence during mid and late seizure. These observations represent a first attempt to use quantitative EEG analysis to investigate the effects of anticonvulsants on electrographic seizure activity. The duration of postictal EEG suppression was reduced after CBZ treatment. The results support the view that CBZ has a major effect on limiting the spread of seizure discharges.