The NKCC1 ion transporter modulates microglial phenotype and inflammatory response to brain injury in a cell-autonomous manner

Abstract

The NKCC1 ion transporter contributes to the pathophysiology of common neurological disorders, but its function in microglia, the main inflammatory cells of the brain, has remained unclear to date. Therefore, we generated a novel transgenic mouse line in which microglial NKCC1 was deleted. We show that microglial NKCC1 shapes both baseline and reactive microglia morphology, process recruitment to the site of injury, and adaptation to changes in cellular volume in a cell-autonomous manner via regulating membrane conductance. In addition, microglial NKCC1 deficiency results in NLRP3 inflammasome priming and increased production of interleukin-1β (IL-1β), rendering microglia prone to exaggerated inflammatory responses. In line with this, central (intracortical) administration of the NKCC1 blocker, bumetanide, potentiated intracortical lipopolysaccharide (LPS)-induced cytokine levels. In contrast, systemic bumetanide application decreased inflammation in the brain. Microglial NKCC1 KO animals exposed to experimental stroke showed significantly increased brain injury, inflammation, cerebral edema, and, worse, neurological outcome. Thus, NKCC1 emerges as an important player in controlling microglial ion homeostasis and inflammatory responses through which microglia modulate brain injury. The contribution of microglia to central NKCC1 actions is likely to be relevant for common neurological disorders.

Nanoformulated Bumetanide Ameliorates Social Deficiency in BTBR Mice Model of Autism Spectrum Disorder

“…Further understanding of the underlying molecular mechanisms of how bumetanide regulates microglia function remains to be elucidated. NKCC1 is expressed in glial cells, and a single-cell transcriptomic study (BRAIN-SAT database) has supported NKCC1 expression in microglia ( 21 ), which consisted of a recent study showing microglial NKCC1 expression in the brain ( 45 ), but its role in neurodevelopment conditions like ASD remains unknown. Researchers found that bumetanide attenuated LPS-induced acute lung injury by inhibiting NKCC1-mediated macrophage volume alteration and inflammatory function in a mouse model of LPS-induced lung injury ( 30 ).…”

“…This indicates that the beneficial actions of NP(bumetanide) may be based on the anti-inflammatory action caused by the inhibition of NKCC1 in the microglia. However, there is an intriguing finding that the direct administration of bumetanide into the brain in vivo displayed the opposite effect of a systemic administration and can be explained by changes in K + efflux mechanism in microglia ( 45 ). Therefore, the precise mechanism through the NKCC1 inhibitor bumetanide modulates the function of microglia in BTBR mice needs to be further investigated.…”

“…Therefore, the precise mechanism through the NKCC1 inhibitor bumetanide modulates the function of microglia in BTBR mice needs to be further investigated. We reasoned about several underlying mechanisms as follows: firstly, systemic treatment of bumetanide recently was reported to reduce inflammatory response in the brain of LPS-induced mice ( 45 ), and in the lung of LPS-induced lung injury mice ( 30 ), suggesting the therapeutic effects of systemic treatment of bumetanide in BTBR mice could be partially due to anti-inflammatory action. However, due to the non-selective action of bumetanide, neuronal and non-neuronal (both periphery and central) cells may be involved in this action; secondly, In this study, we used a nanoparticle system to deliver bumetanide, and the NP(bumetanide) would be easier to induce the phagocytosis function of microglia given the microglia are detector cells in the brain.…”

Microglia undergo rapid phenotypic transformation in acute brain slices but remain essential for neuronal synchrony

“…The extensive expression of P2Y12 receptors (P2Y12R) are widely considered to be a signature of microglia in the healthy brain (Bosco et al, 2018; Hickman et al, 2013; Peng et al, 2019), while downregulation of P2Y12R is generally observed in pathologies and associated with a reactive phenotype (Lin et al, 2021; Tóth et al, 2022; Zrzavy et al, 2017). Drastic downregulation of P2Y12Rs were observed in slice cultures as well, but changes were monitored in a longer timeframe (0, 8, 24 hours), and the extent has been shown to correlate strongly with microglia morphology (Haynes et al, 2006).…”

“…The extensive expression of P2Y12 receptors (P2Y12R) are widely considered to be a signature of microglia in the healthy brain (Bosco et al, 2018;Hickman et al, 2013;Peng et al, 2019), while downregulation of P2Y12R is generally observed in pathologies and associated with a reactive phenotype (Lin et al, 2021;Tóth et al, 2022;Zrzavy et al, 2017).…”