Browsing by Author "Fabel, Klaus"

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    Cannabinoid receptor CB1 mediates baseline and activity-induced survival of new neurons in adult hippocampal neurogenesis
    (2010) Wolf, Susanne A; Bick-Sander, Anika; Fabel, Klaus; Leal-Galicia, Perla; Tauber, Svantje; Ramírez-Rodríguez, Gerardo; Müller, Anke; Melnik, Andre; Waltinger, Tim P; Ullrich, Oliver; Kempermann, Gerd; Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, Berlin, Germany; gerd.kempermann@crt-dresden.de
    Background: Adult neurogenesis is a particular example of brain plasticity that is partially modulated by the endocannabinoid system. Whereas the impact of synthetic cannabinoids on the neuronal progenitor cells has been described, there has been lack of information about the action of plant-derived extracts on neurogenesis. Therefore we here focused on the effects of _9-tetrahydrocannabinol (THC) and Cannabidiol (CBD) fed to female C57Bl/6 and Nestin-GFP-reporter mice on proliferation and maturation of neuronal progenitor cells and spatial learning performance. In addition we used cannabinoid receptor 1 (CB1) deficient mice and treatment with CB1 antagonist AM251 in Nestin-GFP-reporter mice to investigate the role of the CB1 receptor in adult neurogenesis in detail. Results: THC and CBD differed in their effects on spatial learning and adult neurogenesis. CBD did not impair learning but increased adult neurogenesis, whereas THC reduced learning without affecting adult neurogenesis. We found the neurogenic effect of CBD to be dependent on the CB1 receptor, which is expressed over the whole dentate gyrus. Similarly, the neurogenic effect of environmental enrichment and voluntary wheel running depends on the presence of the CB1 receptor. We found that in the absence of CB1 receptors, cell proliferation was increased and neuronal differentiation reduced, which could be related to CB1 receptor mediated signaling in Doublecortin (DCX)-expressing intermediate progenitor cells. Conclusion: CB1 affected the stages of adult neurogenesis that involve intermediate highly proliferative progenitor cells and the survival and maturation of new neurons. The pro-neurogenic effects of CBD might explain some of the positive therapeutic features of CBD-based compounds.
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    The α Domain of Small Heat Shock Protein b8 (Hspb8) Acts as Survival and Differentiation Factor in Adult Hippocampal Neurogenesis
    (2013) Ramírez-Rodríguez, Gerardo; Babu, Harish; Klempin, Friederike; Krylyshkina, Olga; Baekelandt, Veerle; Gijsbers, Rik; Debyser, Zeger; Overall, Rupert; Nicola, Zeina; Fabel, Klaus; Kempermann, Gerd; Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz, Calz, México-Xochimilco 101, Col. Sn Lorenzo Huipulco 14370, México, D.F., Mexico; gerd.kempermann@crt-dresden.de
    Adult hippocampal neurogenesis is to a large degree controlled at the level of cell survival, and a number of potential mediators of this effect have been postulated. Here, we investigated the small heat shock protein Hspb8, which, because of its pleiotropic prosurvival effects in other systems, was considered a particularly promising candidate factor. Hspb8 is, for example, found in plaques of Alzheimer disease but exerts neuroprotective effects. We found that expression of Hspb8 increased during differentiation in vitro and was particularly associated with later stages (48–96 h) of differentiation. Gain-of-function and loss-of-function experiments supported the hypothesis that Hspb8 regulates cell survival of new neurons in vitro. In the dentate gyrus of adult mice in vivo, lentiviral overexpression of Hspb8 doubled the surviving cells and concomitantly promoted differentiation and net neurogenesis without affecting precursor cell proliferation. We also discovered that the truncated form of the crystallin domain of Hspb8 was sufficient to affect cell survival and neuronal differentiation in vitro and in vivo. Precursor cell experiments in vitro revealed that Hspb8 increases the phosphorylation of Akt and suggested that the prosurvival effect can be produced by a cell-autonomous mechanism. Analysis of hippocampal Hspb8 expression in mice of 69 strains of the recombinant inbred set BXD revealed that Hspb8 is a cis-acting gene whose expression was associated with clusters of transcript enriched in genes linked to growth factor signaling and apoptosis. Our results strongly suggest that Hspb8 and its _-crystallin domain might act as pleiotropic prosurvival factor in the adult hippocampus.