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© 2014, Springer Science+Business Media New York. The Fas receptor (FasR)/Fas ligand (FasL) system plays a significant role in the process of neuronal loss in neurological disorders. Thus, in the present study, we used a real-time PCR array focused apoptosis (Mouse Apoptosis RT 2 PCR Array) to study the role of the Fas pathway in the apoptotic process that occurs in a kainic acid (KA) mice experimental model. In fact, significant changes in the transcriptional activity of a total of 23 genes were found in the hippocampus of wild-type C57BL/6 mice after 12 h of KA treatment compared to untreated mice. Among the up-regulated genes, we found key factors involved in the extrinsic apoptotic pathway, such as tnf, fas and fasL, and also in caspase genes (caspase-4, caspase-8 and caspase-3). To discern the importance of the FasR/FasL pathway, mice lacking the functional Fas death receptor (lpr) were also treated with KA. After 24 h of neurotoxin treatment, lpr mice exhibited a reduced number of apoptotic positive cells, determined by the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) method in different regions of the hippocampus, when compared to wild-type mice. In addition, treatment of lpr mice with KA did not produce significant changes in the transcriptional activity of genes related to apoptosis in the hippocampus, either in the fas and fas ligand genes or in caspase-4 and caspase-8 and the executioner caspase-3 genes, as occurred in wild-type C57BL/6 mice. Thus, these data provide direct evidence that Fas signalling plays a key role in the induction of apoptosis in the hippocampus following KA treatment, making the inhibition of the death receptor pathway a potentially suitable target for excitotoxicity neuroprotection in neurological conditions such as epilepsy. ; Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CiberNed-Instituto de Salud Carlos III) and by grants fromMinisterio de Ciencia (MICINN, MINECO) SAF2009-08233 and SAF2012-34177 and Fundación Ramón Areces to JJL. Grant 2009/SGR00853 from the Generalitat de Catalunya (Autonomous Government of Catalonia) and grants BFU2010-19119/BFI to CA, SAF2011-23631 to AC, and SAF2012-39852-C02-01 to MP from the Spanish Ministerio de Ciencia (MICINN, MINECO) also supported the study. Grant 0177594 from CONACYT (Mexico) ; Peer Reviewed

Glycogen synthase kinase-3 (GSK-3) is ubiquitously expressed throughout the brain and involved in vital molecular pathways such as cell survival and synaptic reorganization and has emerged as a potential drug target for brain diseases. A causal role for GSK-3, in particular the brain-enriched GSK-3ß isoform, has been demonstrated in neurodegenerative diseases such as Alzheimer's and Huntington's, and in psychiatric diseases. Recent studies have also linked GSK-3 dysregulation to neuropathological outcomes in epilepsy. To date, however, there has been no genetic evidence for the involvement of GSK-3 in seizure-induced pathology. Status epilepticus (prolonged, damaging seizure) was induced via a microinjection of kainic acid into the amygdala of mice. Studies were conducted using two transgenic mouse lines: a neuron-specific GSK-3ß overexpression and a neuron-specific dominant-negative GSK-3ß (GSK-3ß-DN) expression in order to determine the effects of increased or decreased GSK-3ß activity, respectively, on seizures and attendant pathological changes in the hippocampus. GSK-3 inhibitors were also employed to support the genetic approach. Status epilepticus resulted in a spatiotemporal regulation of GSK-3 expression and activity in the hippocampus, with decreased GSK-3 activity evident in non-damaged hippocampal areas. Consistent with this, overexpression of GSK-3ß exacerbated status epilepticus-induced neurodegeneration in mice. Surprisingly, decreasing GSK-3 activity, either via overexpression of GSK-3ß-DN or through the use of specific GSK-3 inhibitors, also exacerbated hippocampal damage and increased seizure severity during status epilepticus. In conclusion, our results demonstrate that the brain has limited tolerance for modulation of GSK-3 activity in the setting of epileptic brain injury. These findings caution against targeting GSK-3 as a treatment strategy for epilepsy or other neurologic disorders where neuronal hyperexcitability is an underlying pathomechanism. ; Marie Curie International Mobility Fellowship, the Health Research Board (PD/2009/31 to T.E. and HRA_POR/2011/41 to D.C.H.); Science Foundation Ireland (13/SIRG/2098 and 17/CDA/4708 to T.E. and 16/RC/3948 to D.C.H.) and co-funded under the European Regional Development Fund and by FutureNeuro industry partners;); from the H2020 Marie Skłowdowksa-Curie Actions Individual Fellowship (753527 to E.B.); from the European Union's Horizon 2020 research and innovation programme under the Marie Sklowdowska-Cuire grant agreement (No. 766124 to T.E.); grants from Ministerio de Economía Industria y Competitividad of Spain SAF2009-08233 and SAF2015-65371-R to J.J.L., SAF2016-78603-R to M.M. and BFU2016-77885-P to F.H.; grant PI2015-2/06-3 from CIBERNED-ISCIII to J.J.L.; and institutional grants to CBMSO from Fundación Ramón Areces and Fundación Banco de Santander ; Peer Reviewed

14 p.-5 fig. ; Glycogen synthase kinase-3 (GSK-3) is ubiquitously expressed throughout the brain and involved in vital molecular pathways such as cell survival and synaptic reorganization and has emerged as a potential drug target for brain diseases. A causal role for GSK-3, in particular the brain-enriched GSK-3β isoform, has been demonstrated in neurodegenerative diseases such as Alzheimer's and Huntington's, and in psychiatric diseases. Recent studies have also linked GSK-3 dysregulation to neuropathological outcomes in epilepsy. To date, however, there has been no genetic evidence for the involvement of GSK-3 in seizure-induced pathology. Status epilepticus (prolonged, damaging seizure) was induced via a microinjection of kainic acid into the amygdala of mice. Studies were conducted using two transgenic mouse lines: a neuron-specific GSK-3β overexpression and a neuron-specific dominant-negative GSK-3β (GSK-3β-DN) expression in order to determine the effects of increased or decreased GSK-3β activity, respectively, on seizures and attendant pathological changes in the hippocampus. GSK-3 inhibitors were also employed to support the genetic approach. Status epilepticus resulted in a spatiotemporal regulation of GSK-3 expression and activity in the hippocampus, with decreased GSK-3 activity evident in non-damaged hippocampal areas. Consistent with this, overexpression of GSK-3β exacerbated status epilepticus-induced neurodegeneration in mice. Surprisingly, decreasing GSK-3 activity, either via overexpression of GSK-3β-DN or through the use of specific GSK-3 inhibitors, also exacerbated hippocampal damage and increased seizure severity during status epilepticus. In conclusion, our results demonstrate that the brain has limited tolerance for modulation of GSK-3 activity in the setting of epileptic brain injury. These findings caution against targeting GSK-3 as a treatment strategy for epilepsy or other neurologic disorders where neuronal hyperexcitability is an underlying pathomechanism. ; This work was supported by funding from the Sixth Framework Programme (MIRG-CT-2004-014567, to D.C.H.) a IRCSET-Marie Curie International Mobility Fellowship, the Health Research Board (PD/2009/31 to T.E. and HRA_POR/ 2011/41 to D.C.H.); Science Foundation Ireland (13/SIRG/2098 and 17/CDA/ 4708 to T.E. and 16/RC/3948 to D.C.H.) and co-funded under the European Regional Development Fund and by FutureNeuro industry partners;); from the H2020 Marie Skłowdowksa-Curie Actions Individual Fellowship (753527 to E.B.); from the European Union's Horizon 2020 research and innovation programme under the Marie Sklowdowska-Cuire grant agreement (No. 766124 to T.E.); grants from Ministerio de Economía Industria y Competitividad of Spain SAF2009-08233 and SAF2015-65371-R to J.J.L., SAF2016-78603-R to M.M. and BFU2016-77885-P to F.H.; grant PI2015-2/06-3 from CIBERNED-ISCIII to J.J.L.; and institutional grants to CBMSO from Fundación Ramón Areces and Fundación Banco de Santander. ; Peer reviewed