Alexander Grote

Lack of P2X receptor mediated currents in astrocytes and GluR type glial cells of the hippocampal CA1 region

Purinergic signalling plays a major role in intercellular communication between neurons and glial cells. Glial cells express metabotropic receptors for ATP and adenosine, the latter being activated after ATP cleavage through extracellular ecto‐ATPase activity. Ionotropic receptors for extracellular ATP, so called P2X receptors, might contribute to neuron–glia signalling. However, experimental evidence for the presence of these receptors in glial cells is less convincing so far. In a previous study, immunohistochemistry was used to identify P2X1–4,6,7 receptor protein in S100β‐positive hippocampal glial cells. Applying patch clamp and fast application techniques, here we challenged the question of the functional expression of these receptors. Time correlated membrane currents served as test criterion for receptor function, since P2X receptor activation leads to the opening of unspecific cation channels in a millisecond time scale. Agonists were applied via short pressure puffs, with a fast concentration clamp method and through UV flash triggered photolysis of caged ATP. Two types of murine hippocampal macroglial cells, both labelled by the expression of green fluorescence protein driven by the human glial fibrillary acid protein promoter, were analysed in acute brain slices and in freshly dissociated cell suspensions. Surprisingly, ATP or related agonists completely failed to activate currents. Additionally, changes in spontaneously occurring glial postsynaptic currents were never observed. These results have been verified using rat and human hippocampal tissue as well as investigating cells from P2X7 knock out mice. It is concluded that in acute preparations, astroglial cells of the hippocampal CA1 subfield do not express functional P2X receptors.

Systems genetics identifies a convergent gene network for cognition and neurodevelopmental disease

Genetic determinants of cognition are poorly characterized, and their relationship to genes that confer risk for neurodevelopmental disease is unclear. Here we performed a systems-level analysis of genome-wide gene expression data to infer gene-regulatory networks conserved across species and brain regions. Two of these networks, M1 and M3, showed replicable enrichment for common genetic variants underlying healthy human cognitive abilities, including memory. Using exome sequence data from 6,871 trios, we found that M3 genes were also enriched for mutations ascertained from patients with neurodevelopmental disease generally, and intellectual disability and epileptic encephalopathy in particular. M3 consists of 150 genes whose expression is tightly developmentally regulated, but which are collectively poorly annotated for known functional pathways. These results illustrate how systems-level analyses can reveal previously unappreciated relationships between neurodevelopmental disease–associated genes in the developed human brain, and provide empirical support for a convergent gene-regulatory network influencing cognition and neurodevelopmental disease.

Cliniconeuropathologic correlations show astroglial albumin storage as a common factor in epileptogenic vascular lesions

Purpose:  Intracerebral vascular malformations including cavernous angiomas (CAs) and arteriovenous malformations (AVMs) are an important cause of chronic pharmacoresistant epilepsies. Little is known about the pathogenetic basis of epilepsy in patients with vascular malformations. Intracerebral deposits of iron‐containing blood products have been generally regarded as responsible for the strong epileptogenic potential of CAs. Here, we have analyzed whether blood–brain barrier (BBB) dysfunction and subsequent astrocytic albumin uptake, recently described as critical trigger of focal epilepsy, represent pathogenetic factors in vascular lesion–associated epileptogenesis.

TLR4, ATF-3 and IL8 inflammation mediator expression correlates with seizure frequency in human epileptic brain tissue

PURPOSE Data from animal models has nicely shown that inflammatory processes in the central nervous system (CNS) can modulate seizure frequency. However, a potential relationship between the modulation of seizure frequency and gene expression of key inflammatory factors in human epileptic tissue is still unresolved. Brain tissue from pharmacoresistant patients with mesial temporal lobe epilepsy (mTLE) provides a unique prerequisite for clinico-neuropathological correlations. Here, we have concentrated on gene expression of the human key inflammatory mediators, TLR4, ATF-3 and IL8, in correlation to seizure frequency and additional clinical parameters in human epileptic brain tissue of pharmacoresistant mTLE patients. Furthermore, we characterized the cell types expressing the respective proteins in epileptic hippocampi. METHODS Total RNAs were isolated from n=26 hippocampi of pharmacoresistant mTLE patients using AllPrep DNA/RNA Mini Kit. cRNA was used for hybridization on Human HT-12 v3 Expression BeadChips with Illumina Direct Hybridization Assay Kit and resulting gene expression data was normalized based on the Illumina BeadStudio software suite by means of quantile normalization with background subtraction. Corresponding human hippocampal sections for immunohistochemistry were probed with antibodies against TLR4, ATF-3, IL8 and glial fibrillary acidic protein (GFAP), neuronal nuclear protein (NeuN) and the microglial marker HLA-DR. RESULTS We observed abundant TLR4 gene expression to relate to seizure frequency per month. For ATF-3, we found an inverse correlation of expression to seizure frequency. Lower expression of IL8 was significantly associated with high seizure frequency. Further, we detected TLR4 expression in neurons and GFAP-positive astrocytes of pharmacoresistant mTLE patients. Only neurons of human epileptic hippocampi express ATF-3. IL8 was expressed in microglia and reactive astrocytes. CONCLUSION Our results suggest a differential correlation of key inflammatory factor expression in epileptic hippocampi and seizure frequency in patients. The modulation of such processes may open new therapeutic perspectives for treating seizures.

Presence of human herpes virus 6 DNA exclusively in temporal lobe epilepsy brain tissue of patients with history of encephalitis.

Temporal lobe epilepsy (TLE) is frequently associated with mesial temporal sclerosis (MTS). Many etiologic aspects of TLE are still unresolved. Here, we aimed to analyze the presence of human herpes virus 6 (HHV‐6) DNA in distinct TLE pathologies. Nested polymerase chain reaction (PCR) in surgical tissue from 38 pharmacoresistant TLE patients and 10 autopsy controls revealed HHV‐6 DNA in 55.6% of the TLE patients with a history of encephalitis, involving MTS and gliotic hippocampi without substantial neurodegeneration, but not in lesion‐associated TLE or nonlesional MTS with or without a history of complex febrile seizures (CFS). HHV‐6 protein was present in only one patient’s tissue. Our data argue against HHV‐6 as a major local pathogenetic factor in MTS hippocampi after CFS. The high detection rate of HHV‐6 DNA suggests a potential pathogenetic role of HHV‐6 in TLE patients with a history of encephalitis.

Melanotic Tumors of the Nervous System are Characterized by Distinct Mutational, Chromosomal and Epigenomic Profiles

Melanotic tumors of the nervous system show overlapping histological characteristics but differ substantially in their biological behavior. In order to achieve a better delineation of such tumors, we performed an in‐depth molecular characterization. Eighteen melanocytomas, 12 melanomas, and 14 melanotic and 14 conventional schwannomas (control group) were investigated for methylome patterns (450k array), gene mutations associated with melanotic tumors and copy number variants (CNVs). The methylome fingerprints assigned tumors to entity‐specific groups. Methylation groups also showed a substantial overlap with histology‐based diagnosis suggesting that they represent true biological entities. On the molecular level, melanotic schwannomas were characterized by a complex karyotype with recurrent monosomy of chromosome 22q and variable whole chromosomal gains and recurrent losses commonly involving chromosomes 1, 17p and 21. Melanocytomas carried GNAQ/11 mutations and presented with CNV involving chromosomes 3 and 6. Melanomas were frequently mutated in the TERT promoter, harbored additional oncogene mutations and showed recurrent chromosomal losses involving chromosomes 9, 10 and 6q, as well as gains of 22q. Together, melanotic nervous system tumors have several distinct mutational and chromosomal alterations and can reliably be distinguished by methylome profiling.

A second chance—reoperation in patients with failed surgery for intractable epilepsy: long-term outcome, neuropsychology and complications

Object Resective surgery is a safe and effective treatment of drug-resistant epilepsy. If surgery has failed reoperation after careful re-evaluation may be a reasonable option. This study was to summarise the risks and benefits of reoperation in patients with epilepsy. Methods This is a retrospective single centre study comprising clinical data, long-term seizure outcome, neuropsychological outcome and postoperative complications of patients, who had undergone a second resective epilepsy surgery from 1989 to 2009. Results A total of 66 patients with median follow-up of 10.3 years were included into the study. Fifty-one patients (77%) had surgery for temporal lobe epilepsy, the remaining 15 cases for extra-temporal lobe epilepsies. The most frequent histological findings were tumours (n=33, 50%), followed by dysplasia, gliosis (n=11, each) and hippocampus sclerosis (n=9). The main reasons for seizure recurrence were incomplete resection (59.1%) of the putative epileptogenic lesion. After reoperation 46 patients (69.7%) were completely seizure-free International League Against Epilepsy 1 (ILAE 1) at the last available follow-up. The neuropsychological evaluation demonstrated that repeated losses in the same cognitive domain, that is, successive changes from better to worse performance categories, were rare and that those losses after first surgery were followed by improvement rather than decline. However, reoperations lead to an increased rate of permanent neurological deficits (9%), overall surgical complications (9%) and visual field deficits (67%). Conclusions Reoperation after failed resective epilepsy surgery led to approximately 70% long-time seizure freedom and reasonable neuropsychological outcome. There is an increased risk of permanent postoperative neurological deficits, which should be taken into consideration when counselling for reoperation.

Management and outcome in adult intramedullary spinal cord tumours: a 20-year single institution experience

BackgroundSeveral uncertainties remain concerning the management of intramedullary spinal cord tumours (IMSCTs). These include the timing and extent of resection, its interrelated functional outcome, and the adequate use and timing of radiation therapy and/or chemotherapy. In this retrospective study we report on all adult cases involving IMSCTs treated from 1987 to 2007 in our institution to validate our treatment strategy for IMSCTs. Pre- and post-operative functional performance was classified according to the McCormick scale.ResultsA total of 70 adult cases with IMSCTs consisting of ependymoma (39), astrocytoma (11), carcinoma metastasis (8), haemangioblastoma (5), cavernoma (3) and others (4) were reviewed. Mean age was 46.8 years (range, 18-79 years), and mean follow-up was 4.5 years (range, 1-195 months). The proportion of localisation in descending order was thoracic (36%), cervical (33%), cervicothoracic (19%) and conus region (13%), with 45 gross total resections, 22 partial resections and three biopsies. Surgery-related morbidity with worsening postoperative symptoms occurred immediately in 13 patients (18.6%). The preoperative McCormick grade correlated significantly with the early postoperative grade and the grade at follow-up (χ2-test; p = 0.001). None of the patients with preserved intraoperative evoked potentials exhibited significant postoperative deterioration. The degree of resection was correlated with progression-free survival (Duncan test; p = 0.05). Most patients with malignant tumours, namely anaplastic ependymoma (3), astrocytoma (2) or metastatic lesions (5), underwent postoperative radiation therapy. Six patients (one anaplastic ependymoma, two anaplastic astrocytomas and three metastatic lesions) received postoperative chemotherapy.ConclusionsIMSCTs should be operated on when symptoms are mild. We recommend evoked potential-guided microsurgical total resection of ependymomas and other benign lesions; partial resection or biopsy followed by adjuvant therapy should be confined to patients with high-grade astrocytomas, whereas resection or biopsy with adjuvant therapy is the best option for metastatic lesions.

Epilepsy surgery of the rolandic and immediate perirolandic cortex: Surgical outcome and prognostic factors

Herein we present a single‐center retrospective study of patients who underwent epilepsy surgery for seizures arising from the sensorimotor (rolandic) cortex. The goal was to find prognostic factors associated with better seizure outcome and to evaluate both surgical and neurologic outcomes.

Large-scale analysis of viral nucleic acid spectrum in temporal lobe epilepsy biopsies.

Chronic inflammatory processes are important promotors of temporal lobe epilepsy (TLE) development. Based on human herpesvirus 6 (HHV‐6) DNA detection in brain tissue from patients with TLE, an association of persistent viral infection with TLE has been discussed. Individual studies reported increased HHV‐6 DNA in patients with clinical signs of previous inflammatory brain reaction, that is, febrile seizures or meningoencephalitis. However, detection rates vary considerably between different studies. Here we performed a large‐scale analysis of viral DNA/RNA spectrum in high‐quality TLE biopsies. In addition to all Herpesviridae, we addressed potentially relevant neurotropic RNA viruses.