title: CNTF-mediated preactivation of astrocytes attenuates neuronal damage and epileptiform activity in experimental epilepsy.
abstract: Activated astrocytes display a broad spectrum of properties, ranging from neuroprotection to active contribution to demise of neural tissue. To investigate if activation of astrocytes by a single, defined stimulus enhances neuroprotective properties, we tested whether injection of ciliary neurotrophic factor (CNTF) can ameliorate epilepsy-related brain damage. Intrahippocampal CNTF injection in mice induced a rapid (within 2 days) and persistent (3 weeks) activation of astrocytes reflected by strong upregulation of glial fibrillary acidic protein (GFAP) mRNA synthesis and GFAP immunoreactivity. Moreover, CNTF signaling via phosphorylation and nuclear translocation of STAT3 (signal transducer and activator of transcription 3) was specifically activated in GFAP-positive astrocytes. CNTF-mediated activation of astrocytes 2 days prior to an epileptogenic intrahippocampal injection of kainate (KA) resulted in strongly reduced cell death in the hilus and CA3 region of the hippocampus, revealed by Fluoro-Jade B staining. Granule cell dispersion, the pathological widening of the granule cell layer, was also significantly reduced 16 days after KA injection. Importantly, intrahippocampal in vivo recordings 3 weeks after KA injection showed that the occurrence of high frequency oscillations (fast ripples, FR), a surrogate marker for epileptic activity, was significantly reduced in CNTF+KA-injected mice as compared to KA-injected animals. However, when CNTF was applied in the chronic epileptic phase at 3 weeks after KA injection, no reduction of FR activity was observed. In summary, our results indicate that the activation of astrocytes prior to an excitotoxic injury effectively reduces neuronal damage and the severity of epileptiform activity, whereas activation in the chronic phase is no longer protective.
authors.affiliation: Experimental Epilepsy Research, Department of Neurosurgery, University of Freiburg, Freiburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bechstein
authors.forename: Ute
authors.initials: U
authors.lastname: Häussler
authors.forename: Matthias
authors.initials: M
authors.lastname: Neef
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Hofmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Kirsch
authors.forename: Carola A
authors.initials: CA
authors.lastname: Haas
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000473:pathology*; D020934:Ciliary Neurotrophic Factor / Q000502:physiology*; D004195:Disease Models, Animal; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000473:pathology*; D018696:Neuroprotective Agents / Q000494:pharmacology
chemical_list: D020934:Ciliary Neurotrophic Factor; D018696:Neuroprotective Agents