Extracellular vesicle-based bumetanide delivery alleviates depression-like behaviors of male mice by restoring chloride homeostasis.

Major depressive disorder (MDD), the most prevalent psychiatric disorder worldwide, is often linked to changes in GABAergic neurotransmission. K(+)/Cl(-) cotransporter 2 (KCC2) plays a key role in maintaining proper chloride levels within neurons, influencing the hyperpolarization caused by GABA(A) receptor (GABA(A)R) activation in mature neurons. However, the impact of KCC2-modulated GABAergic neurotransmission on depressive behaviors remains unclear. In this study, we investigated the role of KCC2 in a mouse model of depression. Our findings revealed a significant decrease in KCC2 expression in the dorsal hippocampus (dHip), accompanied by a depolarizing shift of the GABA reverse potential and a reduction in the amplitude of miniature inhibitory postsynaptic currents (mIPSCs). Knockdown of KCC2 expression increased the susceptibility to stress in mice. Conversely, overexpression of KCC2 or treatment with bumetanide reversed the chronic social defeat stress (CSDS)-induced changes in E(GABA) and deficits of GABAergic neurotransmission, contributing to the improvement of depression-like behaviors. Additionally, extracellular vesicles (EVs) derived from bumetanide-treated HEK293T cells and engineered with acetylcholine receptor (AChR)-specific rabies virus glycoprotein (RVG) peptides, when injected via the tail vein, were found to alleviate depression symptoms. These results suggest that KCC2-mediated chloride homeostasis plays a key role in depression pathology and that bumetanide can be used to treat depression.