Focal cerebral ischemia induces the neurogenic potential of mouse Dach1-expressing cells in the dorsal part of the lateral ventricles.

The mouse Dach1 gene, involved in the development of the neocortex and the hippocampus, is expressed by neural stem cells (NSCs) during early neurogenesis, and its expression also continues in a subpopulation of cells in the dorsal part of the lateral ventricles (LV) of the adult mouse brain. In this study we aimed to elucidate the role of Dach1-expressing cells in adult neurogenesis/gliogenesis under physiological as well as post-ischemic conditions, employing transgenic mice in which the expression of green fluorescent protein (GFP) is controlled by the D6 promotor of the mouse Dach1 gene. A neurosphere-forming assay of GFP⁺ cells isolated from the dorsal part of the LV was carried out with subsequent differentiation in vitro. To elucidate the neurogenic/gliogenic potential of GFP⁺ cells in the dorsal part of the LV, in situ immunohistochemical/electrophysiological analyses of GFP⁺ cells in adult sham-operated brains (controls) and those after middle cerebral artery occlusion (MCAo) were performed. The GFP⁺ cells isolated from the dorsal part of the LV of controls formed neurospheres and differentiated solely into a glial phenotype, while those isolated after MCAo also gave rise to cells with the properties of neuronal precursors. In situ analyses revealed that GFP⁺ cells express the phenotype of adult NSCs or neuroblasts in controls as well as following ischemia. Following MCAo we found a significantly increased number of GFP⁺ cells expressing doublecortin as well as a number of GFP⁺ cells migrating through the rostral migratory stream into the olfactory bulb, where they probably differentiated into calretinin⁺ interneurons. Collectively, our results suggest the involvement of the mouse Dach1 gene in adult neurogenesis; cells expressing this gene exhibit the properties of adult NSCs or neuroblasts and respond to MCAo by enhanced neurogenesis.

The inhibitor of volume-regulated anion channels DCPIB activates TREK potassium channels in cultured astrocytes.

BACKGROUND AND PURPOSE: The ethacrynic acid derivative, 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) is considered to be a specific and potent inhibitor of volume-regulated anion channels (VRACs). In the CNS, DCPIB was shown to be neuroprotective through mechanisms principally associated to its action on VRACs. We hypothesized that DCPIB could also regulate the activity of other astroglial channels involved in cell volume homeostasis. EXPERIMENTAL APPROACH: Experiments were performed in rat cortical astrocytes in primary culture and in hippocampal astrocytes in situ. The effect of DCPIB was evaluated by patch-clamp electrophysiology and immunocytochemical techniques. Results were verified by comparative analysis with recombinant channels expressed in COS-7 cells. KEY RESULTS: In cultured astrocytes, DCPIB promoted the activation of a K(+) conductance mediated by two-pore-domain K(+) (K(2P) ) channels. The DCPIB effect occluded that of arachidonic acid, which activates K(2P) channels K(2P) 2.1 (TREK-1) and K(2P) 10.1 (TREK-2) in cultured astrocytes. Immunocytochemical analysis suggests that cultured astrocytes express K(2P) 2.1 and K(2P) 10.1 proteins. Moreover, DCPIB opened recombinant K(2P) 2.1 and K(2P) 10.1 expressed in heterologous system. In brain slices, DCPIB did not augment the large background K(+) conductance in hippocampal astrocytes, but caused an increment in basal K(+) current of neurons. CONCLUSION AND IMPLICATIONS: Our results indicate that the neuroprotective effect of DCPIB could be due, at least in part, to activation of TREK channels. DCPIB could be used as template to build new pharmacological tools able to increase background K(+) conductance in astroglia and neuronal cells.