GABAergic transmission regulates adult neurogenesis by exerting negative feedback on cell proliferation and enabling dendrite formation and outgrowth. Further, GABAergic synapses target differentiating dentate gyrus granule cells prior to formation of glutamatergic connections. GABAA receptors (GABAARs) mediating tonic (extrasynaptic) and phasic (synaptic) transmission are molecularly and functionally distinct, but their specific role in regulating adult neurogenesis is unknown. Using global and single-cell targeted gene deletion of subunits contributing to the assembly of GABAARs mediating tonic (α4, δ) or phasic (α2) GABAergic transmission, we demonstrate here in the dentate gyrus of adult mice that GABAARs containing α4, but not δ, subunits mediate GABAergic effects on cell proliferation, initial migration and early dendritic development. In contrast, α2-GABAARs cell-autonomously signal to control positioning of newborn neurons and regulate late maturation of their dendritic tree. In particular, we observed pruning of distal dendrites in immature granule cells lacking the α2 subunit. This alteration could be prevented by pharmacological inhibition of thrombospondin signaling with chronic gabapentin treatment, shown previously to reduce glutamatergic synaptogenesis. These observations point to homeostatic regulation of inhibitory and excitatory inputs onto newborn granule cells under the control of α2-GABAARs. Taken together, the availability of distinct GABAAR subtypes provides a molecular mechanism endowing spatiotemporal specificity to GABAergic control of neuronal maturation in adult brain.

The MTLE mouse model displays a differential sensitivity to AEDs with a greater efficacy of drug that facilitates GABAergic transmission. This model provides an efficient tool to identify new treatment for drug-resistant forms of focal epilepsies.

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O) and hydrogen peroxide (HO). However in the context of neuroinflammation, they present paradoxical features since O/HO generated by NOX and/or secondary reactive oxygen species (ROS) derived from O/HO can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.

Cajal-Retzius cells play a crucial role during ontogeny in regulating cortical lamination via release of reelin. In adult brain, they comprise small calretinin-positive interneurons located in the marginal zone of the cerebral cortex and in the hippocampal fissure. Alterations of reelin signaling or expression have been involved in major neurological disorders, and they underlie granule cell dispersion (GCD) in mesial temporal lobe epilepsy (TLE). Here, we investigated in a mouse model of TLE the contribution of Cajal-Retzius cells to reelin production in epileptic hippocampus and the molecular mechanisms underlying GCD. Following unilateral intrahippocampal Kainic acid injection in adult mice to induce an epileptic focus, we observed that Cajal-Retzius cells gradually became strongly immunopositive for reelin, due to intracellular accumulation. This phenotype resembled the morphology of Cajal-Retzius cells in reeler Orleans (reln (orl/orl) ) mice, which express a secretion-deficient 310-kDa reelin fragment. The possibility that GCD might result from abnormal reelin processing in Cajal-Retzius cells, leading to a lack of reelin secretion, was confirmed by KA injection in reln (orl/+) mice, which induced severe GCD. Furthermore, Western blot analysis in KA-treated wildtype mice revealed increased production of ∼300-kDa reelin fragments, confirming abnormal proteolytic processing. This effect was not seen upon treatment with Botulinum neurotoxin E (BoNT/E), which prevents GCD in KA-lesioned hippocampus by chronic blockade of synaptic transmission. Furthermore, BoNT/E blocked upregulation of TrkB in Cajal-Retzius cells, suggesting that production of truncated reelin in KA-treated hippocampus is activity-dependent and regulated by BDNF. Altogether, these data reveal that GCD results from abnormal reelin processing in Cajal-Retzius cells under the control of BDNF. Our findings highlight the critical role played by Cajal-Retzius cells for hippocampal neuronal reorganization in TLE.

Uncovering the molecular mechanisms of Mesial temporal lobe epilepsy (MTLE) is critical to identify therapeutic targets. In this study, we performed global protein expression analysis of a kainic acid (KA) MTLE mouse model at various time-points (1d, 3d, 30d post KA injection -dpi), representing specific stages of the syndrome.High resolution liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), in combination to label-free protein quantification, using three processing approaches for quantification, was applied. Following comparison of KA versus NaCl-injected mice, 22, 53 and 175 proteins were differentially (statistically significant) expressed at 1, 3 and 30dpi respectively, according to all 3 quantification approaches. Selected findings were confirmed by multiple reaction monitoring LC-MS/MS. As a positive control, the astrocyte marker GFAP was found to be upregulated (3dpi:1.9 fold; 30dpi:12.5 fold), also verified by IHC. The results collectively suggest that impairment in synaptic transmission occurs even right after initial status epilepticus (1dpi), with neurodegeneration becoming more extensive during epileptogenesis (3dpi) and sustained at the chronic phase (30dpi), where also extensive glial and astrocyte-mediated inflammation is evident. This molecular profile is in line with observed phenotypic changes in human MTLE, providing the basis for future studies on new molecular targets for the disease.