NKCC1 modulates microglial phenotype, cerebral inflammatory responses and 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 not been studied 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 and inflammatory responses. As opposed to systemic NKCC1 blockade, which decreased intracortical lipopolysaccharide (LPS)-induced cytokine levels, neuroinflammation was potentiated by both intracortically administered bumetanide and in the absence of microglial NKCC1, suggesting a considerable role for microglia to influence central NKCC1 actions. Correspondingly, 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 to shape microglial responses and brain inflammation after CNS injury, which is likely to be relevant for common neurological disorders.

Dysregulation of GABAergic Signaling in Neurodevelomental Disorders: Targeting Cation-Chloride Co-transporters to Re-establish a Proper E/I Balance

“…However, such deletion only slightly affects the in vivo network dynamics or hippocampal-dependent behavioral tasks, suggesting that most of the effects observed in NKCC1 knock-out mice or after pharmacological blockade of the transporter, may be attributed to the loss of the protein from non-neuronal cells or from cells localized outside the brain (Graf et al, 2021 ). In the brain, NKCC1 has been found to be expressed in several non-neuronal cell types such as choroid plexus epithelial cells, astrocytes, oligodendrocytes and microglia (Tóth et al, 2021 ). In particular NKCC1 is highly expressed in microglia (DePaula-Silva et al, 2019 ) ( Figure 1 ) where it plays a fundamental role in neuro-inflammation.…”

“…In particular NKCC1 is highly expressed in microglia (DePaula-Silva et al, 2019 ) ( Figure 1 ) where it plays a fundamental role in neuro-inflammation. Thus, the selective deletion of NKCC1 on microglia affects their cell volume and baseline morphology and boosts cytokines production in response to inflammatory stimuli (Tóth et al, 2021 ). Interestingly, it has been recently reported that long-term potentiation triggers in potentiated synapses withdrawal of perisynaptic astrocytic processes, which involves the NKCC1 transporter and the actin-controlling protein cofilin.…”

“…Overall, bumetanide has been shown to exert a symptomatic action mitigating, at least in a subpopulation of autistic children, the severity of symptoms, which reappear after interruption of the treatment. A limitation however in using bumetanide for treating Neurodevelopmental Disorders lies on the fact that this drug has poor pharmacokinetic properties and low capability to cross the blood brain barrier (BBB) to reach either neuronal or non-neuronal targets (Puskarjov et al, 2014a ; Virtanen et al, 2020 ; Löscher and Kaila, 2021 ; Tóth et al, 2021 ). Moreover, an active efflux of bumetanide from the brain to the blood, which involves several transporters expressed at the BBB, including organic anion ones, would contribute to maintain a very low concentration of the drug in the brain (Römermann et al, 2017 ).…”

Reply to the commentary by Ben‐Ari and Delpire: Bumetanide and neonatal seizures: Fiction versus reality

“…Interestingly, systemic administration of bumetanide has an anti‐inflammatory action outside the brain, whereas direct application into the brain in vivo has the opposite effect 44 . There are also intriguing findings obtained using low systemic doses of bumetanide and other diuretics in rodents (e.g., Krystal et al, 45 and Marguet et al 46 ) that point to beneficial actions, based on unidentified mechanisms outside the brain.…”

NKCC1 and KCC2: Structural insights into phospho-regulation

“…NKCC1 is also expressed in mature neurons, but the mRNA expression developmentally changes from a neuronal pattern at birth to a glial pattern (esp. oligodendrocytes and their precursors, endothelial cells, astrocytes and microglia) in adult mouse brain (Hübner et al, 2001a;Su et al, 2001;Wang et al, 2003;Zhang et al, 2014;Henneberger et al, 2020;Virtanen et al, 2020;Tóth et al, 2022). In glia cells, NKCC1 regulates for instance the proliferation and maturation of oligodendrocyte precursor cells in the adult mouse cerebellar white mater (Zonouzi et al, 2015) and modulates the microglial phenotype and inflammatory response (Tóth et al, 2022).…”