Oxytocin Receptor-Mediated Signaling in Astrocytes

Especially in higher vertebrates, astrocytes are an indispensible part of signal processing within the brain. Thus, the mode of action of a neuroactive peptide such as OXT cannot be fully understood without this integral part of the CNS. The effects of OXT on neuronal cells have been well characterized, while its effects on astrocytic cells, specifically on OXTR-coupled signaling and its resulting cellular consequences, are poorly understood and might very well differ. To characterize the effect of OXT on astrocytic gene expression, intracellular signaling, as well as astrocyte-specific proteins, synthetic OXT was either administered icv in male Wistar rats or applied to cultured rat primary cortical astrocytes. Due to the results of this analysis implying an acute OXT-induced cytoskeletal remodeling and alterations to gap-junction coupling, I next examined the underlying molecular mechanisms and cellbiological consequences of these alterations. Here I found that OXT led to rapid elongation and formation of astrocytic processes in vitro and in vivo, while simultaneously impairing astrocytic intercellular connectivity. Mechanistically, both of these effects were OXTR-specific, conveyed via PKC and, to a lesser extent, MEK1/2 signaling. Notably, OXT-induced cytoskeletal remodeling and impairment of gap-junctions were characteristic for OXT, since its closely related sister-peptide AVP did not affect the examined parameters. CLSM and STED-microscopy following icv or ex vivo administration of OXT furthermore revealed changes to astrocyte-neuron spatial relationships in two brain regions associated with high responsiveness of astrocytic markers to OXT, i.e. PVN and hippocampus. In depth in vitro studies identified the previously undescribed Sp1-Gem signaling axis to be at the base of these effects. A combination of knockdown, knockout and overexpression experiments revealed that OXT drives Gem expression via the transcription factor Sp1 and that Gem is required and sufficient for the effects of OXT on astrocytes. The Sp1-Gem axis was differentially regulated by OXT in neuronal cells, identifying it as key driver in the cell type-specific response of astroglial cells to OXT. Based on these findings, astrocyte-specific AAV-mediated Gem or Oxtr shRNA knockdown vectors were established as tools for a targeted manipulation of astrocytic OXTR signaling and future assessment of astrocytic contribution to the physiological and behavioral effects of OXT. To this end, shRNA oligonucleotides were screened for knockdown efficiency in vitro and subsequently packaged into viral vectors providing astrocyte-specific expression via transcriptional control of shRNA expression under the hGFAP promoter

Modellhafte Schadensanalyse und Entwicklung eines Restaurierungskonzeptes zur Beseitigung der Umweltschaeden an den mittelalterlichen Glasfenstern der St. Marienkirche in Frankfurt (Oder) Abschlussbericht

SIGLEAvailable from TIB Hannover: F04B1645 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman

De Novo Protein Synthesis Mediated by the Eukaryotic Elongation Factor 2 Is Required for the Anxiolytic Effect of Oxytocin.

The neuropeptide oxytocin (OXT) mediates its actions, including anxiolysis, via its G protein-coupled OXT receptor. Within the paraventricular nucleus of the hypothalamus (PVN), OXT-induced anxiolysis is mediated, at least in part, via activation of the mitogen-activated protein kinase pathway following calcium influx through transient receptor potential cation channel subfamily V member 2 channels. In the periphery, OXT activates eukaryotic elongation factor 2 (eEF2), an essential mediator of protein synthesis. In order to study whether OXT activates eEF2 also in neurons to exert its anxiolytic properties in the PVN, we performed in vivo and cell culture experiments. We demonstrate that OXT, in a protein kinase C-dependent manner, activates eEF2 both in a hypothalamic cell line and in vivo within the PVN. Next, we reveal that OXT stimulates de novo protein synthesis, while inhibition of protein synthesis within the PVN prevents the anxiolytic effect of OXT in male rats. Moreover, activation of eEF2 within the PVN conveyed an anxiolytic effect supporting a role of OXT-induced eEF2 activation and protein synthesis for its anxiolysis. Finally, we show that one of the proteins that is upregulated by OXT is the neuropeptide Y receptor 5. Infusion of a specific neuropeptide Y receptor 5 agonist into the PVN consequently led to decreased anxiety-related behavior, while pretreatment with a neuropeptide Y receptor 5 antagonist prevented the anxiolytic effect of OXT. Taken together, these results show that OXT recruits several intracellular signaling cascades to induce protein synthesis, which mediates the anxiolytic effects of OXT within the PVN and suggests that eEF2 represents a novel target for anxiety-related disorders