Cell Type-Specific Gene Expression and Editing Responses to Chronic Fluoxetine Treatment in the In Vivo Mouse Brain and Their Relevance for Stress-Induced Anhedonia

Abstract

Recently developed methods for fluorescence-activated cell sorting (FACS) of freshly-isolated brain cells from transgenic mice combining fluorescent signals with cell type-specific markers allow cell-type separation. Based upon previous observations in primary cultures of mouse astrocytes we treated transgenic mice tagged with a neuron-specific or an astrocyte-specific marker with fluoxetine, either acute (10 mg/kg for 2 h) or chronic (10 mg/kg daily for 2 weeks). Acute treatment upregulated cfos and fosB mRNA expression in astrocytes and neurons. Chronic effects on astrocytes replicated those demonstrated in cultures, i.e., upregulation of mRNA and/or protein expression of 5-HT(2B) receptors (5-HT(2B)R), and GluK2 receptors, and of cPLA(2a) and ADAR2, together with increased GluK2 and 5-HT(2B)R editing. Neurons showed increased GluK4 and 5-HT(2C) receptor expression. To further correlate these findings with major depression we compared the changes in gene expression with those in a mouse model of anhedonia. Three out of 4 genes up-regulated in astrocytes by fluoxetine were down-regulated, whereas the neuronally upregulated 5-HT(2C) receptor gene showed no change. References are made to recent review papers discussing potential relations between observed fluoxetine effects and clinical effects of SSRIs, emphasizing that all 5 clinically used SSRIs have identical and virtually equipotent effects on cultured astrocytes.

Fluoxetine induces alkalinization of astroglial cytosol through stimulation of sodium-hydrogen exchanger 1: dissection of intracellular signaling pathways

“…Characteristics, usage and advantages of these cultures has recently been authoritatively reviewed (Lange et al, 2012). Ontogenetic similarity with freshly isolated astrocytes in gene development has been reported by ourselves (Li et al, 2012b); similarly there is evidence for identical drug-induced changes in gene expression between in vitro and in vivo assessed astrocytes (Li et al, 2012a; Song et al, 2012). …”

Astrocytic and neuronal accumulation of elevated extracellular K+ with a 2/3 K+/Na+ flux ratio—consequences for energy metabolism, osmolarity and higher brain function

“…Nor are our cultures similar to those used previously by Harold Kimelberg (Hertz et al, 1985). Recently we have compared expression of genes of interest in specific studies in freshly isolated astrocytes and these cultured astrocytes and consistently shown similar expression of several different genes for acid extruders, other transporters and glutamate receptor subtypes (Fu et al, 2012; Li et al, 2012a,b; Song et al, 2012). The gene expression of Na + ,K + ATPase subtypes in freshly isolated cells which was shown in Figure 5 is also identical to that previously shown in these cultures (Peng et al, 1997, Under revision).…”

Role of Glycogenolysis in Stimulation of ATP Release from Cultured Mouse Astrocytes by Transmitters and High K+ Concentrations

“…Use of astrocyte cultures has recently been authoritatively reviewed (Lange et al, 2012), and in our own cultures drug-induced changes in gene expression and editing have recently been confirmed in freshly isolated cells from mice treated with the same drugs (Li et al, 2012b; Song et al, 2012; Peng et al, 2013). Moreover the development of the glutamate/aspartate exchanger component aralar shows similar developmental patterns in the two preparations, with an increase in the cultured cells after dBcAMP administration (Li et al, 2012a). …”

“…MPEP is generally known as an inhibitor of mGluR5, a metabotropic glutamate receptor, but this receptor is only functioning in astrocytes during very early development (Sun et al, 2013). MPEP appears also to inhibit the kainate receptor GluK2, present in mature astrocytes in vivo (Li et al, 2012a) and active in culture (Li et al, 2011). GluK2 is equally distributed in freshly isolated neurons and astrocytes (Li et al, 2012a).…”

“…MPEP appears also to inhibit the kainate receptor GluK2, present in mature astrocytes in vivo (Li et al, 2012a) and active in culture (Li et al, 2011). GluK2 is equally distributed in freshly isolated neurons and astrocytes (Li et al, 2012a). The signaling pathway for the GluK2 receptor in astrocytes has not been determined, but glutamate increases [Ca 2+ ] i in the presently used astrocytes (Li et al, 2011).…”