β-arrestin 2 is essential for fluoxetine-mediated promotion of hippocampal neurogenesis in a mouse model of depression

Over the last decade, the roles of beta-arrestins in the treatment of neuropsychological diseases have become increasingly appreciated. Fluoxetine is the first selective serotonin reuptake inhibitor developed and is approved for the clinical treatment of depression. Emerging evidence suggests that fluoxetine can directly combine with the 5-HT receptor, which is a member of the G protein-coupled receptor (GPCR) family, in addition to suppressing the serotonin transporter. In this study, we prepared a chronic mild stress (CMS)-induced depression model with beta-arrestin2(-/-) mice and cultured adult neural stem cells (ANSCs) to investigate the involvement of the 5-HT receptor-beta-arrestin axis in the pathogenesis of depression and in the therapeutic effect of fluoxetine. We found that beta-arrestin2 deletion abolished the fluoxetine-mediated improvement in depression-like behaviors and monoamine neurotransmitter levels, although beta-arrestin2 knockout did not aggravate CMS-induced changes in mouse behaviors and neurotransmitters. Notably, the beta-arrestin2(-/-) mice had a shortened dendritic length and reduced dendritic spine density, as well as decreased neural precursor cells, compared to the WT mice under both basal and CMS conditions. We further found that beta-arrestin2 knockout decreased the number of proliferating cells in the hippocampal dentate gyrus and suppressed the proliferative capability of ANSCs in vitro. Moreover, beta-arrestin2 knockout aggravated the impairment of cell proliferation induced by corticosterone and further blocked the fluoxetine-mediated promotion of mouse hippocampal neurogenesis. Mechanistically, we found that the 5-HT2BR-beta-arrestin2-PI3K/Akt axis is essential to maintain the modulation of hippocampal neurogenesis in depressed mice. Our study may provide a promising target for the development of new antidepressant drugs.

Automated summary

The study highlights the crucial role of beta-arrestin2 in the therapeutic effects of fluoxetine on depression, potentially through the modulation of neurogenesis via the 5-HT receptor-beta-arrestin axis. Deletion of beta-arrestin2 affected mouse behaviors and neurotransmitter levels, without exacerbating changes induced by chronic mild stress, and also impacted dendritic morphology and proliferating cells.