Blut-Hirn-Schrankenstörung und pharmakoresistente epileptische Anfälle

Sufficient seizure control can not be achieved in fifty to seventy percent of focal epilepsies, particularly in temporal lobe epilepsy, with present antiepileptic medications. Pharmacoresistance might result from changes in the properties of drug targets, augmented expression of drug efflux transporters, increased severity of seizures, network reorganization and / or development of drug tolerance. Recent studies indicated that blood-brain barrier (BBB) disruption is common among patients with pharmacoresistant focal epilepsies. Following BBB dysfunction, serum albumin can leak into the brain parenchyma, be taken up by astrocytes and / or neurons and trigger various transcriptional changes (e.g. reduction in inward rectifying potassium channel 4.1 (Kir 4.1), water channel 4 (AQP4) and gap junctions) via astrocytic TGFßR-II pathway, and lead to hyperexcitability. Serum albumin transports many hormones and drugs including some of the conventional antiepileptic drugs (AEDs), namely phenytoin (PHT), valproic acid (VPA), carbamazepine (CBZ), and phenobarbital (PHB) with variable binding affinities. We therefore hypothesized that following BBB disruption, albumin interferes with the action of these particular AEDs by binding to the drugs or by inducing transcriptional alterations of their targets. To test this hypothesis, we first induced seizure-like events (SLEs) by 4-aminopyridine, in acute entorhinal cortex- hippocampal slices from adult rats and investigated the efficacy of conventional AEDs in the presence of albumin by extracellular field recordings. Unbound AED concentrations were detected by ultrafiltration and high-performance liquid chromatography. Next, we applied albumin intracerebroventricularly (icv) 24 hrs prior to the experiments and analyzed the effects of CBZ on acute slices from these albumin-pretreated rats. Conventional AEDs failed to suppress SLEs in the entorhinal cortex in the presence of albumin. This effect was partially caused by buffering of PHT and CBZ by albumin. A two-fold increase of the maximal therapeutic concentration of CBZ resulted in SLE blockage. In slices obtained from animals pretreated with icv albumin, CBZ suppressed SLEs, similar to its effect in control slices. We also found that in the absence of albumin, application of serum- like electrolytes with increased potassium, decreased calcium and magnesium concentrations, transformed SLEs into late recurrent discharges that were resistant to CBZ. We therefore concluded that a dysfunctional BBB with acute extravasation of serum albumin into brain’s interstitial space and / or alterations in the extracellular electrolyte concentrations could cause pharmacoresistance. Thus, BBB monitoring can guide the treatment to control seizures in patients with BBB dysfunction using AEDs with low albumin binding affinity.Mit den derzeit verfügbaren Antiepileptika (AE), wird keine ausreichende Epilepsie-Anfallskontrolle in fünfzig bis siebzig Prozent der fokal Epilepsien, insbesondere der Temporalappenepilepsie, nicht erreicht. Pharmakoresistenz ist möglicherweise Folge von veränderten Eigenschaften der Wirkstoffziele, einer erhöhten Expression von Efflux-Transportern, massiver werdenden Anfällen, Reorganisation des Netzwerks oder / und der Entwicklung von Medikamententoleranz. Neueste Studien zeigen, dass eine Blut-Hirn- Schrankenstörung (BHS) häufig bei Patienten mit pharmakoresistenten fokal Epilepsien vorkommt. Nach BHS kann Albumin in das Hirnparenchym austreten und wird dort durch Astrozyten und ggfs. auch Neuronen aufgenommen. Der astrozytäre TGFßR-II-Signalweg wird aktiviert, woraus Transkriptionsänderungen (z.B. eine verminderte Expression einwärts gleichrichtender Kalliumkanäle 4.1 (Kir 4.1), Wasserkanäle 4 (AQP4) und Gap Junctions) mit nachfolgender Übererregbarkeit resultieren. Viel Hormone und Medikamente binden an Serumalbumin und werden so transportiert. Dazu gehören einige der konventionellen AE – Phenytoin (PHT), Valproinsäure (VPA), Carbamazepin (CBZ) und Phenobarbital (PHB). Wir haben daher die Hypothese aufgestellt, dass nach BHS, Albumin durch direkte Bindung an AE oder durch Induktion von Transkriptionsänderungen des AE-Targets, die Wirkweise der AE stören. Um diese Hypothese zu testen, wurden zuerst krampfähnliche Ereignisse durch 4-Aminopyridin in Akutschnitten des entorhinalen Kortex und Hippokampus der ausgewachsenen Ratte induziert. In diesen Schnitten haben wir die Wirksamkeit von konventionellen AE in der Gegenwart von Albumin durch extrazelluläre Feldpotenialableitungen untersucht. Die Konzentration ungebundener AE wurden durch Ultrafiltration und Hochleistungsflüssigkeitschromatographie detektiert. In weiteren Experimenten haben wir 24 Stunden vor dem ex-vivo Experiment Albumin intrazerebroventrikulär (izv) appliziert und die Wirkungen von CBZ auf die Akutschnitte aus diesen Albumin-vorbehandelten Ratten analysiert. Konventionelle AE konnten krampfähnliche Ereignisse im entorhinalen Kortex in Gegenwart von Albumin nicht unterdrücken. Dieser Effekt wurde teilweise durch die Pufferung von PHT und CBZ durch Albumin verursacht. In doppelter maximaler therapeutischer Konzentration, unterdrückte CBZ krampfähnliche Ereignisse. In Schnitten von Tieren, die mit izv Albumin vorbehandelt wurden, unterdrückt CBZ die krampfähnlichen Ereignisse ähnlich wie in den naiven Schnitten. Die Anwendung von serumartigen Elektrolytkonzentrationen mit erhöhter Kalium-, und verringerter Calcium- und Magnesiumkonzentration in der Abwesenheit von Albumin hat epileptische Entladungen in späte rezidivierende Entladungen umgewandelt, die CBZ-resistent waren. Wir kommen daher zu dem Schluss, dass eine BHS mit akuter Extravasation von Serumalbumin ins Hirnparenchym oder / und Veränderungen in den extrazellulären Elektrolytkonzentrationen der Pharmakoresistenz zugrunde liegen können. In Fällen von mehrfachem Versagen von AE, könnte die Überwachung der Permeabilität der Blut-Hirn-Schranke helfen erfolgreichere Behandlung zu leiten um mit einem AE mit niedriger Albuminbindungsaffinität Anfälle besser zu kontrollieren

Status epilepticus induces chronic silencing of burster and dominance of regular firing neurons during sharp wave-ripples in the mouse subiculum

Summary: Sharp wave-ripples (SWRs) are hippocampal oscillations associated with memory consolidation. The subiculum, as the hippocampal output structure, ensures that hippocampal memory representations are transferred correctly to the consolidating neocortical regions. Because patients with temporal lobe epilepsy often develop memory deficits, we hypothesized that epileptic networks may disrupt subicular SWRs. We therefore investigated the impact of experimentally induced status epilepticus (SE) on subicular SWRs and contributing pyramidal neurons using electrophysiological recordings in mouse hippocampal slices. Subicular SWRs expressed hyperexcitable features post-SE, including increased ripple and unit activity. While regular firing neurons normally remain silent during SWRs, selective disinhibition recruited more regular firing neurons for action potential generation during SWRs post-SE. By contrast, burster neurons generated fewer action potential bursts during SWRs post-SE. Furthermore, altered timing of postsynaptic and action potentials suggested distorted neuronal recruitment during SWRs. Distorted subicular SWRs may therefore impair information processing and memory consolidation in epilepsy

Four novel and two recurrent NHLRC1 (EPM2B) and EPM2A gene mutations leading to Lafora disease in six Turkish families

Lafora disease (LD) is a type of autosomal recessive, progressive myoclonus epilepsy resulting mostly from mutations in the EPM2A and NHLRC1 genes. Mutational analysis in both genes was initiated with the aim of establishing LD DNA diagnosis in Turkey. Four novel NHLRC1 (p.G131X, p.P69S and p.D82H) and EPM2A (p.V7A) and two recurrent NHLRC1 (p.D146N) and EPM2A (p.R241X) mutations were identified in six families. The delineation of causative mutations in patients provided early disease diagnosis for other family members and contributed to the knowledge of LD pathogenesis. (C) 2011 Elsevier B.V. All rights reserved

Four novel and two recurrent NHLRC1 (EPM2B) and EPM2A gene mutations leading to Lafora disease in six Turkish families

WOS: 000301316200027PubMed ID: 22047982Lafora disease (LD) is a type of autosomal recessive, progressive myoclonus epilepsy resulting mostly from mutations in the EPM2A and NHLRC1 genes. Mutational analysis in both genes was initiated with the aim of establishing LD DNA diagnosis in Turkey. Four novel NHLRC1 (p.G131X, p.P69S and p.D82H) and EPM2A (p.V7A) and two recurrent NHLRC1 (p.D146N) and EPM2A (p.R241X) mutations were identified in six families. The delineation of causative mutations in patients provided early disease diagnosis for other family members and contributed to the knowledge of LD pathogenesis. (C) 2011 Elsevier B.V. All rights reserved.Bogazici UniversityBogazici University [07HB101]; TUBITAK (Turkish Scientific and Technological Research Council)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)This study was financially supported by Bogazici University Research Fund Project Number 07HB101. SS was a recipient of TUBITAK (Turkish Scientific and Technological Research Council) graduate scholarship

The effects of tamoxifen on radiation-induced pulmonary fibrosis in Wistar albino rats: Results of an experimental study

This study was performed to evaluate the effects of tamoxifen on pulmonary fibrosis, given concurrently with or after irradiation in Wistar albino rats. Twenty-one female Wistar albino rats were randomized into three groups. The first group (Group A) had tamoxifen, which was started after the completion of irradiation. The second group (Group B) had tamoxifen concomitant with irradiation. The third group (Group C) had only thoracic irradiation and did not receive tamoxifen. Whole lungs were irradiated to a total dose of 30 Gy in ten fractions with Co60. Tamoxifen was continued until the animals were sacrificed 16 weeks after the start of irradiation. As an end point the percentage of lung with fibrosis for each rat was quantified with image analysis of histological sections of the lung. Groups were compared using the one-way ANOVA method and Bonferroni post hoc test. The mean percentage values of fibrosis were 10.03 for Group A, 36.81 for Group B, and 3.87 for group C (P < 0.001). When the percentages of fibrosis were compared for each group, the difference was statistically significant between Group A and Group B (P < 0.001) and between Group B and Group C (P < 0.001). Concomitant use of tamoxifen appears to increase radiation-induced pulmonary fibrosis and it seems more convenient to delay tamoxifen until the completion of irradiation. (C) 2005 Elsevier Ltd. All rights reserved

Atorvastatin has cardiac safety at intensive cholesterol-reducing protocols for long term, yet its cancer-treatment doses with chemotherapy may cause cardiomyopathy even under Coenzyme-Q10 protection

Statins provide strong clinical benefits via reducing stroke deaths, and they are also considered for tumor reduction and chemo-sensitization. High dose atorvastatin in adults (80 mg daily, approx. 1 mg/kg) is proven to afford greater protection against cardiac deaths than does a standard lipid-lowering dose in coronary syndrome. For cancer trials, mega doses up to 30 mg/kg have been used for short term treatments but neither a high nor a mega-dose of atorvastatin has been tested for long term cardiac safety. This may be of special concern, since some animal studies showed deleterious effects of statins on cardiac tissue, which may be related with coenzymeQ (CoQ) depletion. We performed an electron microscopic analysis of rat hearts after low, high-or mega-dose atorvastatin therapy and with or without MNU (methyl-nitrosourea)- stress. MNU + daily high dose atorvastatin treatment for 13 months did not produce severe cardiac toxicity with CoQ. However, at mega doses (30 mg/kg) and with MNU, mitochondrial damage and myofibrillary disintegration was obvious. Strong proliferation of mitochondria under high dose atorvastatin therapy with CoQ may explain the lack of cardiotoxicity; and this finding seems to parallel recent data that statins induce HNF-4 and PPAR-alpha, both responsible for mitochondria-proliferation. Employment of statins for tumor chemo-sensitization at high-dosage and for long term treatments may require strategies to direct the mevalonate-entry differentially into cardiac and tumor cells and to develop a protocol analogous to folic acid salvage of methotrexate toxicity. Copyright (C) 2006 John Wiley & Sons, Ltd

SCN1A gene sequencing in 46 Turkish epilepsy patients disclosed 12 novel mutations

Yalçın Çapan, Özlem (Arel Author)Purpose: The SCN1A gene is one of the most commonly mutated human epilepsy genes associated with a spectrum of phenotypes with variable degrees of severity. Despite over 1200 distinct mutations reported, it is still hard to draw clear genotypephenotype relationships, since genetic and environmental modifiers contribute to the development of a particular disease caused by an SCN1A mutation. We aimed to initiate mutational screening of the SCN1A gene in Turkey and advance further our understanding of the relationship between the SCN1A sequence alterations and disease phenotypes such as GEFS+, DS and related epileptic encephalopathies. Methods: Mutational analysis of the SCN1A gene was carried out in 46 patients with DS, late-onset DS, GEFS+ and unspecified EE using either direct Sanger sequencing of the coding regions and exon/intron boundaries or massively parallel sequencing. Results: Nineteen point mutations, 12 of which were novel were identified, confirming the clinical diagnosis of the patients. Patients with a mutation (either truncating or missense) on linker regions had significantly later disease onset than patients with mutations in homology regions. The presence of SCN1A mutations in two clinically unclassified patients supported the association of SCN1A mutations with a wide range of phenotypes. Conclusion: The conventional Sanger sequencing method was successfully initiated for the detection of SCN1A point mutations in Turkey in epilepsy patients. Furthermore, a modified strategy of massively parallel pyro-sequencing was also established as a rapid and effective mutation detection method for large genes as SCN1A