Fluoxetine inhibited the activation of A1 reactive astrocyte in a mouse model of major depressive disorder through astrocytic 5-HT2BR/β-arrestin2 pathway

Abstract

Background Fluoxetine, a selective serotonin reuptake inhibitor, has been reported to directly bind with 5-HT2B receptor (5-HT2BR), but the precise mechanisms, whereby fluoxetine confers the anti-depressive actions via 5-HT2BR is not fully understood. Although neuroinflammation-induced A1 astrocytes are involved in neurodegenerative diseases, the role of A1 astrocyte in the pathogenesis and treatment of major depressive disorder (MDD) remains unclear. Methods Mice were subjected to chronic mild stress (CMS) for 6 weeks and subsequently treated with fluoxetine for 4 weeks. The depressive-like and anxiety-like behaviors and the activation of A1 reactive astrocyte in hippocampus and cortex of mice were measured. Primary astrocytes were stimulated with A1 cocktail (tumor necrosis factor (TNF)-α, interleukin (IL)-1α and C1q), activated (LPS) microglia-conditioned medium (MCM) or IL-6 for 24 h and the expression of A1-special and A2-special markers were determined using RT-qPCR and western blot. The role of 5-HT2BR in the effects of fluoxetine on A1 reactive astrocyte was measured using 5-HT2BR inhibitor and siRNA in vitro and AAVs in vivo. The functions of downstream signaling Gq protein and β-arrestins in the effects of fluoxetine on the activation of A1 astrocyte were determined using pharmacological inhibitor and genetic knockout, respectively. Results In this study, we found that fluoxetine inhibited the activation of A1 reactive astrocyte and reduced the abnormal behaviors in CMS mice, as well as ameliorated A1 astrocyte reactivity under three different stimulators in primary astrocytes. We also showed that astrocytic 5-HT2BR was required in the inhibitory effects of fluoxetine on A1 reactive astrocyte in MDD in vivo and in vitro. We further found that the functions of fluoxetine in the activation of A1 astrocyte were independent of either Gq protein or β-arrestin1 in vitro. β-arrestin2 pathway was the downstream signaling of astrocytic 5-HT2BR mediated the inhibitory effects of fluoxetine on A1 astrocyte reactivity in primary astrocytes and CMS mice, as well as the improved roles of fluoxetine in behavioral impairments of CMS mice. Conclusions These data demonstrate that fluoxetine restricts reactive A1 astrocyte via astrocytic 5-HT2BR/β-arrestin2 pathway in a mouse model of MDD and provide a novel therapeutic avenue for MDD.

Hippocampal astrocytes modulate anxiety-like behavior

“…In this regard, it is of note that hippocampal astrocytes express oxytocin receptor 27 , and oxytocin released in amygdala activate astrocyte Ca 2+ signal through oxytocin receptor and mediate its anxiolytic effects 11 . Besides, astrocytes express receptors for dopamine and serotonin, key neuropeptides regulating mood and emotion 28,29 . Therefore, it can be speculated that these neuropeptides exert their effects by regulating hippocampal astrocyte activity, in addition to their direct effects on neuronal dopamine/serotonin receptors.…”

Prospective study on Maresin-1 and cytokine levels in medication-naïve adolescents with first-episode major depressive disorder

“…On the other hand, fluoxetine treatment reversed depression and anxiety-like behavior and inhibited the activation of NF-κB and cytosolic IL-6 protein expression in CSIS rats. Fang et al ( 49 ) Also, Fluoxetine might restrict the activation of reactive A1 astrocytes through the astrocyte 5-HT2BR/β-arrestin2 pathway and decrease IL-6 levels in the central nervous system.…”

Seeing Neurodegeneration in a New Light Using Genetically Encoded Fluorescent Biosensors and iPSCs

“…Experimentally, R-iGluSnFR1, a red fluorescent indicator alternative to iGluSnFR, created via the replacement of cpEGFP with cpmApple [ 206 ], could be utilised in neurons exhibiting excitotoxic pathological features. In addition, a co-culture with iGluSnFR astrocytes and microglia would help to visualise loss of homeostatic function in glia [ 207 ], when exposed to various pathological hallmarks such as alpha-synuclein oligomers [ 208 ]. Glutamate dynamics monitored in real-time using fluorescent imaging could then be juxtaposed upon the targeted delivery of exosomes expressing beneficial microRNA, e.g., miR-124-3p and antioxidants such as catalase [ 209 , 210 , 211 , 212 , 213 ].…”